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Studies on DEA and MDEA degradation Chakma, Amitabha 1987

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STUDIES ON DEA AND MDEA DEGRADATION b y AMITABHA CHAKMA D i p l . I n g . , A l g e r i a n Petro leum I n s t i t u t e , 1982 M . A . S c . , U n i v e r s i t y of B r i t i s h Co lumbia , 1984 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Department Of Chemical E n g i n e e r i n g We accept t h i s t h e s i s as conforming to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA June 1987 © AMITABHA CHAKMA, 198 7 4 6 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. AMITABHA CHAKMA Department of Chemical Engineering The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date June 2 9, 1987 DE-6(3/81) ABSTRACT Aqueous d i e t h a n o l a m i n e ("DEA") i s w i d e l y used f o r the removal of a c i d gases such as C0 2 and H 2S w h i l e aqueous meth y l diethanoamine("MDEA") i s p r i m a r i l y used f o r the s e l e c t i v e removal of H 2S i n t h e presence of C0 2 from l i g h t h y d r ocarbon gases. In a d d i t i o n t o normal a b s o r p t i o n and d e s o r p t i o n r e a c t i o n s , some s i d e r e a c t i o n s o ccur between C 0 2 , DEA and MDEA r e s u l t i n g i n t h e f o r m a t i o n of d e g r a d a t i o n compounds. D e g r a d a t i o n not o n l y r e p r e s e n t s a l o s s of v a l u a b l e s o l v e n t , but may a l s o l e a d t o o p e r a t i o n a l problems such as c o r r o s i o n , foaming and f o u l i n g . C 0 2 e q u i l i b r i u m s o l u b i l i t y i n aqueous MDEA s o l u t i o n s as w e l l as i n aqueous N,N-bis h y d r o x y e t h y l p i p e r a z i n e ("BHEP"), a major DEA and MDEA d e g r a d a t i o n p r o d u c t , were measured and m a t h e m a t i c a l models t o p r e d i c t e q u i l i b r i u m C 0 2 s o l u b i l i t y i n aqueous MDEA and aqueous BHEP s o l u t i o n s were d e v e l o p e d . DEA d e g r a d a t i o n e x p e r i m e n t s under f l o w c o n d i t i o n s were c a r r i e d out i n a c o i l e d heat exchnager tube h e a t e d by means of a c o n s t a n t t e m p e r a t u r e heat t r a n s f e r f l u i d . A M a t h e m a t i c a l model p r e d i c t i n g DEA d e g r a d a t i o n i n heat t r a n s f e r tubes was d e v e l o p e d . C a r e f u l l y c o n t r o l l e d MDEA d e g r a d a t i o n e x p e r i m e n t s w i t h C 0 2 were c a r r i e d out i n a 600 mL s t a i n l e s s s t e e l a u t o c l a v e t o study the e f f e c t of temperature, MDEA c o n c e n t r a t i o n and C 0 2 p a r t i a l p r e s s u r e . MDEA was found t o degrade f a i r l y r a p i d l y a t e l e v a t e d temperature. The major MDEA degradation compounds were i d e n t i f i e d by gas chromatography and mass spectrometry. A k i n e t i c model d e s c r i b i n g MDEA degradation was developed. S o l u t i o n p u r i f i c a t i o n s t u d i e s c o n s i s t i n g of a c t i v a t e d carbon a d s o r p t i o n of degradation compounds and r e v e r s a l of degradation r e a c t i o n s by a l k a l i a d d i t i o n were a l s o s t u d i e d . While a c t i v a t e d carbon a d s o r p t i o n was found i n e f f e c t i v e , a l k a l i a d d i t i o n was found to be q u i t e e f f e c t i v e i n r e v e r s i n g some of the major DEA degra d a t i o n r e a c t i o n s . A p u r i f i c a t i o n p rocess based on degradation r e a c t i o n r e v e r s a l technique was developed. i i i Table of Contents ABSTRACT i i LIST OF TABLES ix LIST OF FIGURES x i i i ACKNOWLEDGEMENTS xxvi 1. INTRODUCTION 1 1.1 The Amine process 2 1.2 Amine degr a d a t i o n 5 1.3 O b j e c t i v e s of the pr e s e n t study 8 2. LITERATURE REVIEW 9 2.1 A b s o r p t i o n of C0 2 i n aqueous DEA AND MDEA s o l u t i o n s 9 2.1.1 C0 2 Reactions with water ....10 2.1.2 C0 2 Reactions w i t h DEA 10 2.1.3 C0 2 Reactions w i t h MDEA 12 2.2 Amine degradation 13 2.2.1 DEA degradation 13 2.2.2 DEA degradation mechanism 18 2.2.3 K i n e t i c models f o r DEA degradation 22 2.2.4 MDEA degra d a t i o n 25 2.3 A n a l y s i s of amine s o l u t i o n s 26 2.4 S o l u t i o n p u r i f i c a t i o n 26 2.4.1 HEOD r e v e r s a l 29 2.4.2 THEED r e v e r s a l 30 2.4.3 BHEP r e v e r s a l 32 2.5 S o l u b i l i t y of C0 2 i n DEA and MDEA s o l u t i o n s 33 3. C0 2 SOLUBILITY STUDIES IN DEA, MDEA AND BHEP SOLUTIONS 35 3.1 Experimental apparatus and procedure 35 3.2 C0 2 s o l u b i l i t y d e t e r m i n a t i o n 37 3.3 Mathematical model f o r C0 2 s o l u b i l i t y i n DEA, MDEA and BHEP 38 3.3.1 S o l u b i l i t y i n DEA 38 3.3.2 S o l u b i l i t y i n MDEA 41 3.3.3 S o l u b i l i t y i n BHEP 44 3.3.4 S o l u t i o n of model equations 45 3.4 R e s u l t s and d i s c u s s i o n 47 4. DEA DEGRADATION IN HEAT TRANSFER TUBES ....62 4.1 Experimental equipment and procedure 62 4.2 Mathematical model 65 4.2.1 Model without r a d i a l temperature v a r i a t i o n s 68 4.2.2 Model with r a d i a l temperature v a r i a t i o n s .72 4.3 DEA degradation k i n e t i c s 75 4.4 Reactions i n heat t r a n s f e r tube 78 4.5 Autoclave 80 4.6 P i p i n g 81 4.7 Model p r e d i c t i o n s 81 5. MDEA STUDIES 91 5.1 Experimental equipment and procedure 91 5.1.1 Autoclave 91 5.1.2 S o l u t i o n p r e p a r a t i o n 94 5.1.3 Loading the au t o c l a v e 94 5.1.4 Sampling 96 5.1.5 Experimental procedure f o r degradation experiments 97 5.2 P r e l i m i n a r y experiments 99 5.2.1 Thermal deg r a d a t i o n 100 v 5.2.2 J u s t i f i c a t i o n f o r the use of e l e v a t e d temperatures 103 5.2.3 E f f e c t of s t i r r e r speed and r e a c t a n t volume 103 5.2.4 R e p r o d u c i b i l i t y 104 5.3 Experimental c o n d i t i o n s 107 5.4 I d e n t i f i c a t i o n of MDEA degradation compounds ...109 5.4.1 I d e n t i f i c a t i o n u s i n g GC/MS 109 5.4.2 Molecular mass d e t e r m i n a t i o n by CIMS ....139 5.4.3 Hydroxyl group number d e t e r m i n a t i o n 145 5.5 Experimental r e s u l t s 153 5.5.1 E f f e c t of temperature 159 5.5.2 E f f e c t of i n i t i a l MDEA c o n c e n t r a t i o n ....181 5.5.3 E f f e c t of C0 2 p a r t i a l p r e ssure 184 5.6 MDEA degra d a t i o n mechanism 198 5.6.1 Degradation of DMAE 198 5.6.2 Formation of DMAE 200 5.6.3 Formation of TMA 202 5.6.4 Proof of the presence of DEA and MAE ....204 5.6.5 Formation of TEA 213 5.6.6 Formation of TEHEED 213 5.6.7 Formation of HEOD 214 5.6.8 Formation of HMP 215 5.6.9 Formation of BHEP 216 5.6.10 Summary of the degradation r e a c t i o n s ....217 5.7 K i n e t i c model f o r MDEA degradation 217 ACTIVATED CARBON PURIFICATION OF DEGRADED AMINE SOLUTIONS 225 6.1 B a t c h a d s o r p t i o n and r e g e n e r a t i o n e x p e r i m e n t a l equipment and p r o c e d u r e s 225 6.1.1 M a t e r i a l s 227 6.1.2 E x p e r i m e n t a l p r o c e d u r e 229 6.1.3 A c t i v a t e d c a r b o n r e g e n e r a t i o n 229 6.1.4 R e s u l t s and d i s c u s s i o n 231 6.2 Column a d s o r p t i o n e x p e r i m e n t s 261 6.2.1 E x p e r i m e n t a l equipment and p r o c e d u r e ....261 6.2.2 M a t h e m a t i c a l m o d e l l i n g 265 6.2.3 B r e a k t h r o u g h c u r v e s and model p r e d i c t i o n s 269 7. CHEMICAL PURIFICATION OF DEGRADED DEA SOLUTIONS ....275 7.1 E x p e r i m e n t a l m a t e r i a l s and proced u r e 275 7.1.1 A l k a l i a d d i t i o n e x p e r i m e n t s 276 7.1.2 Ion exchange e x p e r i m e n t s 277 7.1.3 C a t i o n removal e x p e r i m e n t s 277 7.2 R e s u l t s and d i s c u s s i o n 278 7.2.1 A l k a l i t r e a t m e n t of i n d u s t r i a l samples ..278 7.2.2 HEOD and THEED r e v e r s a l 283 7.2.3 R e s i n t r e a t m e n t 297 7.2.4 Sodium i o n remo v a l e x p e r i m e n t s 299 7.3 I n d u s t r i a l a p p l i c a t i o n s 300 7.3.1 C h o i c e of a l k a l i 300 7.3.2 I n t e g r a t i o n i n t o an e x i s t i n g p l a n t 301 8. CONCLUSIONS. 305 8.1 S o l u b i l i t y s t u d i e s ..305 8.2 DEA d e g r a d a t i o n i n hea t t r a n s f e r t u b e s 305 8.3 MDEA d e g r a d a t i o n 306 v i i 8.4 A c t i v a t e d carbon a d s o r p t i o n 307 8.5 DEA degradation r e a c t i o n r e v e r s a l 308 9. RECOMMENDATIONS FOR FURTHER WORK 309 9.1 Degradation with COS and CS 2 309 9.1.1 Degradation w i t h C0 2, COS, CS 2 i n the presence of H 2S 309 9.1.2 Measurement of C0 2 s o l u b i l i t y 310 NOMENCLATURE 311 REFERENCES 318 APPENDICES A. SYNTHESIS OF SELECT DEA AND MDEA DEGRADATION COMPOUNDS 331 B. GAS CHROMATOGRAPHIC TECHNIQUE 337 C. COMPUTER PROGRAM LISTINGS 353 D. COMPARISON OF MDEA DEGRADATION MODEL PREDICTIONS WITH EXPERIMENTAL DATA 371 L I S T O F T A B L E S Table 3.1 S o l u b i l i t y of C0 2 i n 4.28 M MDEA 49 3.2 S o l u b i l i t y of C0 2 i n 1.69 M MDEA 50 3.3 S o l u b i l i t y of C0 2 i n 0.287 M BHEP 51 3.4 S o l u b i l i t y of C0 2 i n 0.115 M BHEP 52 4.1 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t temp.: 60°C; O u t l e t temp.: 205°C; Heating F l u i d temp.: 225°C; Flow r a t e : 0.011 L/s; C0 2 p a r t i a l p r e s s u r e : 5.5 MPa) 84 4.2 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t temp.: 60°C; O u t l e t temp.: 205°C; Heating F l u i d temp.: 225°C; Flow r a t e : 0.011 L/s; C0 2 p a r t i a l p r e s s u r e : 4.14 MPa)... 85 4.3 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t temp.: 60°C; O u t l e t temp.: 205°C; Heating F l u i d temp.: 225°C; Flow r a t e : 0.011 L/s; C0 2 p a r t i a l p r e s s u r e : 2.76 MPa) 86 4.4 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t i x temp.: 60°C; O u t l e t temp.: 190°C; Heating F l u i d temp.: 225°C; Flow r a t e : 0.015 L/s; C0 2 p a r t i a l p r e s s u r e : 4.14 MPa) 87 4.5 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t temp.: 60°C; O u t l e t temp.: 180°C; Heating F l u i d temp.: 225°C; Flow r a t e : 0.018 L/s; C0 2 p a r t i a l p r e s s u r e : 4.14 MPa) 188 4.6 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 4.93 mm; I n l e t temp.: 60°C; O u t l e t temp.: 185°C; Heating F l u i d temp.: 200°C; Flow r a t e : 0.011 L/s; C0 2 p a r t i a l p r e s s u r e : 4.14 MPa) 89 4.7 Comparison of e x p e r i m e n t a l l y determined and c a l c u l a t e d c o n c e n t r a t i o n s . ( I n i t i a l DEA c o n c e n t r a t i o n : 3 mol/L; Tube ID: 2.03 mm; I n l e t temp.: 60°C; O u t l e t temp.: 195°C; Heating F l u i d temp.: 250°C; Flow r a t e : 0.011 L/s; C0 2 p a r t i a l p r e s s u r e : 4.14 MPa).. 90 5.1 Comparison of MDEA degradation experiments conducted with d i f f e r e n t s t i r r e r speed and re a c t a n t volume. (Temperature: 200°C; I n i t i a l MDEA c o n c e n t r a t i o n : 4.28 mol/L; C0 2 p a r t i a l p r e s s u r e : 2.59 MPa) 105 5.2 Comparison of MDEA degradation experiments x conducted a year apart.(Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 106 5.3 Summary of experimental conditions used for the MDEA degradation experiments 108 5.4 Results of hydroxyl group calculation 149 6.1 Properties of SGL and Darco carbons 228 6.2 Concentrations of laboratory degarded DEA solutions as a function of SGL carbon added to 20 mL of solution 233 6.3 Constants of the Freundlich equation at 25°C for SGL carbon 239 6.4 Constants of the Freundlich equation at 25°C for DARCO carbon 248 6.5 Constants of the Freundlich equation at 40°C for SGL carbon 248 6.6 Constants of the Freundlich equation at"80°C for SGL carbon 248 6.7 Adsorptive capacities of fresh and water washed SGL carbons 249 6.8 Adsorptive capacities of fresh and thermally regenerated SGL carbons . . . .249 6.9 Adsorptive capacities of fresh and 1 M HCl washed SGL carbons 251 6.10 Adsorptive capacities of fresh and 1 M HN03 washed SGL carbons 251 6.11 Adsorptive capacities of HCl regenerated carbons. 253 6.12 Adsorptive capacities of HN03 regenerated carbon. 253 6.13 Concentrations of amine samples taken from the inlet and outlet of activated carbon beds in Plant #1 256 7.1 HEOD to DEA conversion resulting from contacting aqueous HEOD samples ( i n i t i a l concentration 0.31 mol/L HEOD; 0.12 mol/L DEA) with 15 M NaOH solutions under different conditions for 5 min. ..289 7.2 HEOD to DEA conversion resulting from contacting aqueous HEOD samples ( i n i t i a l concentration 0.31 mol/L HEOD; 0.12 mol/L DEA) with 20 M KOH solutions under different conditions of NaOH are required 289 7.3 THEED to DEA conversion resulting from contacting aqueous THEED samples also containing DEA and HEOD with 15 M NaOH solutions under different conditions for 5 min 293 7.4 Results showing the effect of a lka l i strength on HEOD reversal 296 7.5 Results showing a lka l i strength on THEED reversal 296 7.6 Results of batch resin reversal experiments 298 7.7 Results of column resin reversal experiments 298 7.8 Results of Na* ion removal experiments 299 x i i LIST OF FIGURES Figure 1.1 Simplified flowsheet of an amine unit 4 3.1 Comparison of the present C0 2 so lubi l i ty data in 4.28 M MDEA solutions with Jou et a l . ' s data [8] and model predictions as function of C0 2 part ia l pressure (temperature 100°C) 53 3.2 Present experimental and predicted (solid lines) C0 2 so lubi l i t i es in 4.28 M MDEA solutions as function of C0 2 part ia l pressure and temperature 54 3.3 Present experimental and predicted (solid lines) C0 2 so lubi l i t i es in 1.69 M MDEA solutions as function of C0 2 part ia l pressure and temperature 55 3.4 CO2 so lubi l i ty data in 4.28 M MDEA solutions reported by Jou et a l . [8] and present model predictions as function of C0 2 part ia l pressure and temperature 56 3.5 C0 2 so lubi l i ty data in 2.00 M MDEA solutions reported by Jou et a l . [8] and present model predictions as function of C0 2 part ia l pressure and temperature 57 3.6 Present experimental and predicted (solid lines) C0 2 so lubi l i t i es in 0.287 M BHEP solutions as function of C0 2 part ia l pressure and temperature 58 x i i i 3.7 Present experimental and predicted (solid lines) C0 2 so lubi l i t i e s in 0.115 M BHEP solutions as function of C0 2 part ia l pressure and temperature 59 3.8 Solubi l i ty of C0 2 in 5 wt% DEA and 5 wt% BHEP solutions as a function of C0 2 part ia l pressure at 100°C 60 3.9 Solubi l i ty of C0 2 in 30 wt% DEA and 25 wt% DEA plus 5 wt% BHEP solutions as a function of C0 2 part ia l pressure at 40°C 61 4.1 Flowsheet of the equipment for DEA degradation in heat exchanger tubes 63 4.2 Simplified flowsheet of the equipment for DEA degradation in heat exchanger tubes 67 4.3 Schematic diagram of an idealized temperature profi le across the metal tube wall 69 5.1 Sketch of the autoclave used for MDEA degradation studies 93 5.2 Sketch of the autoclave loading system 95 5.3 Chromatogram of a part ia l ly degraded MDEA solution at the end of 54 h. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 101 5.4 Chromatogram of a part ia l ly degraded MDEA solution at the end of 316 h. (Temperature: 140°C; I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 101 xiv 5.5 MDEA c o n c e n t r a t i o n as f u n c t i o n s of time and blanket gas. (Temperature: 200°C; I n i t i a l MDEA c o n c e n t r a t i o n : 4.28 mol/L; Blanket gas p a r t i a l p r e s s u r e : 2.59 MPa) 102 5.6 Chromatogram of a p a r t i a l l y degraded MDEA s o l u t i o n of 4.28 M i n i t i a l c o n c e n t r a t i o n , degraded at 180°C under a C0 2 p a r t i a l p r e s s u r e of 2.59 MPa f o r 144 h 110 5.7 Comparison of EI mass spectrum of peak #1 with l i b r a r y spectrum of methanol 113 5.8 Comparison of EI mass spectrum of peak #2 with l i b r a r y spectrum of EO 114 5.9 Comparison of EI mass spectrum of peak #3 with l i b r a r y spectrum of TMA. 115 5.10 Comparison of EI mass spectrum of peak #4 with l i b r a r y spectrum of N,N-dimethyl ethanamine 116 5.11 Comparison of EI mass spectrum of peak #5 with l i b r a r y spectrum of EG 117 5.12 Comparison of EI mass spectrum of peak #6 with l i b r a r y spectrum of DMAE 118 5.13 Comparison of EI mass spectrum of peak #7 with l i b r a r y spectrum of 4-methyl morpholine 119 5.14 Comparison of EI mass spectrum of peak #8 with l i b r a r y spectrum of DMP 120 5.15 EI mass spectrum of peak #9 i d e n t i f i e d as MDEA...121 5.16 EI mass spectrum of peak #13 i d e n t i f i e d as BHEP 122 xv 5.17 EI mass spectrum of peak #14 i d e n t i f i e d as HEOD 123 5.18 EI mass spectrum of peak #15 i d e n t i f i e d as THEED 124 5.19 EI mass spectrum of peak #12 125 5.20 Comparison of EI mass spectrum of peak #12 and TEA 127 5.21 Comparison of EI mass spectrum of peak #12 and BHG .128 5.22 Chromatogram of a degraded MDEA s o l u t i o n (a) before and (b) a f t e r TEA a d d i t i o n 129 5.23 Fragmentation mechanism of the EG molecule 130 5.24 Fragmentation mechanism of the DMAE molecule. ..130 5.25 Fragmentation mechanism of the DMP molecule. ...131 5.26 Fragmentation mechanism of the MDEA molecule. ..132 5.27 Fragmentation mechanism of the HEOD molecule. ..133 5.28 Fragmentation mechanism of the BHEP molecule. ..134 5.29 Fragmentation mechanism of the THEED molecule. .137 5.30 EI Mass Spectrum of peak #10 138 5.31 Comparison of EI and methane CI mass s p e c t r a of MDEA 141 5.32 Comparison of EI and methane CI mass s p e c t r a of BHEP 142 5.33 Comparison of EI and methane CI mass s p e c t r a of HEOD 143 5.34 Comparison of EI and methane CI mass s p e c t r a of peak #10 144 x v i 5.35 Methane CI mass spectra of MDEA (a) before and (b) after s i ly la t ion with TSIM 148 5.36 Methane CI mass spectra of BHEP (a) before and (b) after s i ly la t ion with TSIM 150 5.37 Methane CI mass spectra of TEA (a) before and (b) after s i ly la t ion with TSIM 151 5.38 Methane CI mass spectra of peak #10 (a) before and (b) after s i ly la t ion with TSIM 152 5.39 EI Mass spectra of peak #10 and HMP synthesized in the laboratory 155 5.40 Chromatograms of a solution which contained 4.28 mol/L MDEA and which was degraded at 200°C under a C0 2 part ia l pressure: 2.59 MPa 156 5.41 Chromatograms of a solution which contained 4.28 mol/L MDEA and which was degraded at 200°C under a C0 2 part ia l pressure of 2.59 MPa 157 5.42 Concentration of MDEA and its major degradation compounds as functions of time. (Temperature: 230°C; I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 158 5.43 MDEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure 2.59 MPa) 160 5.44 MDEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 161 5.45 MDEA concentration as functions of time and xvi i temperature. ( In i t ia l MDEA concentration: 3.40 mol/L; C0 2 part ia l pressure: 2.59 MPa) 162 5.46 MDEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.00 mol/L; C0 2 part ia l pressure: 2.59 MPa) 163 5.47 Arrhenius plot of the overall MDEA degradation rate constant. (C02 part ia l pressure: 2.59 MPa).164 5.48 DMAE concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 166 5.49 DMAE concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 3.4 mol/L; C0 2 part ia l pressure: 2.59 MPa) 167 5.50 DMAE concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.0 mol/L; CO2 part ia l pressure: 2.59 MPa) 168 5.51 TEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 169 5.52 TEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 3.4 mol/L; C0 2 part ia l pressure: 2.59 MPa) 170 5.53 TEA concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.0 mol/L; C0 2 part ia l pressure: 2.59 MPa) 171 5.54 EG concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 xvi i i mol/L; C0 2 part ia l pressure: 2.59 MPa) 172 5.55 EG concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 3.4 mol/L; C0 2 part ia l pressure: 2.59 MPa) 173 5.56 EG concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.0 mol/L; C0 2 part ia l pressure: 2.59 MPa) 174 5.57 HMP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 175 5.58 HMP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 3.4 mol/L; C0 2 part ia l pressure: 2.59 MPa) 176 5.59 HMP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.0 mol/L; C0 2 part ia l pressure: 2.59 MPa).. 177 5.60 BHEP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) 178 5.61 BHEP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 3.4 mol/L; C0 2 part ia l pressure: 2.59 MPa) 179 5.62 BHEP concentration as functions of time and temperature. ( In i t ia l MDEA concentration: 2.0 mol/L; C0 2 part ia l pressure: 2.59 MPa) 180 5.63 MDEA concentration as functions of time and i n i t i a l MDEA concentration. (Temperature: xix 200°C; C0 2 part ia l pressure: 2.59 MPa) 182 5.64 Overall MDEA degradation rate constant as a function of i n i t i a l MDEA concentration. (Temperature: 200°C; C0 2 part ia l pressure: 2.59 MPa) 183 5.65 MDEA concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 185 5.66 MDEA concentration as functions of C0 2 part ia l pressure and time. (Temperature: 180°C; I n i t i a l MDEA concentration 4.28 mol/L) 186 5.67 Overall MDEA degradation rate constant as functions of temperature and C0 2 part ia l pressure. ( In i t ia l MDEA concentration: 4.28 mol/L) 187 5.68 DMAE concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 188 5.69 DMAE concentration as functions of time and C0 2 part ia l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 189 5.70 TEA concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 190 5.71 TEA concentration as functions of time and C0 2 part ia l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 191 xx 5.72 EG concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 192 5.73 EG concentration as functions of time and C0 2 part ia l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 193 5.74 HMP concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 194 5.75 HMP concentration as functions of time and C0 2 part ia l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 195 5.76 BHEP concentration as functions of time and C0 2 part ia l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 196 5.77 BHEP concentration as functions of time and C0 2 part ia l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 197 5.78 Chromatogram of a part ia l ly degraded DMAE solution of 1 M i n i t i a l concentration, degraded at 200°C under a C0 2 part ia l pressure of 2.59 MPa for 72 h. 199 5.79 Methane CI mass spectrum of part ia l ly s i ly lated DEA carbamate 205 5.80 Methane CI mass spectra of part ia l ly s i ly lated MAE carbamate 206 5.81 EI mass spectra of s i ly lated MAE carbamate 207 xxi 5.82 Chromatogram of a part ia l ly degraded MDEA solution used in the test for DEA's presence, before DEA addition 209 5.83 Chromatogram of a part ia l ly degraded MDEA solution used in the test for DEA's presence, after addition of 1 uL of DEA 210 5.84 Chromatogram of a part ia l ly degraded MDEA solution used in the test for DEA's presence, after addition of 2 uL of DEA 212 6.1 Chromatograms of amine samples (20 mL) from Plant #1 (a) before and (b) after treatment with 6 g of SGL carbon at 2 5 ° C . . 232 6.2 Experimental and predicted (solid lines) adsorption isotherm of DEA and i t s major degradation compounds at 25°C for SGL carbon 235 6.3 Experimental and predicted (solid lines) adsorption isotherms of EG, HEI and HMP at 25°C for SGL carbon 236 6.4 Experimental and predicted (solid lines) adsorption isotherms of DMAE and DMP at 25°C for SGL carbon 237 6.5 Experimental and predicted (solid lines) adsorption isotherms of DEA, MDEA and TEA at 25°C for SGL carbon 238 6.6 Experimental and predicted (solid lines) adsorption isotherms of DEA at 25°C for SGL and DARCO carbons 241 xxi i 6.7 Experimental and p r e d i c t e d ( s o l i d l i n e s ) a d s o r p t i o n isotherms of BHEP at 25°C f o r SGL and DARCO carbons 242 6.8 Experimental and p r e d i c t e d ( s o l i d l i n e s ) a d s o r p t i o n isotherms of DEA as a f u n c t i o n of temperature f o r SGL carbon 244 6.9 Experimental and p r e d i c t e d ( s o l i d l i n e s ) a d s o r p t i o n isotherms of BHEP as a f u n c t i o n of temperature f o r SGL carbon 245 6.10 Experimental and p r e d i c t e d ( s o l i d l i n e s ) a d s o r p t i o n isotherms of HEOD as a f u n c t i o n of temperature f o r SGL carbon 246 6.11 Experimental and p r e d i c t e d ( s o l i d l i n e s ) a d s o r p t i o n isotherms of THEED as a f u n c t i o n of temperature f o r SGL carbon 247 6.12 Chromatograms of amine samples taken (a) upstream and (b) downstream of the carbon adsorber i n U n i t I of P l a n t #1 255 6.13 Chromatograms of amine samples taken upstream and downstream of the carbon bed i n Pl a n t #1, 6 h a f t e r the bed was loaded with f r e s h carbon. ..257 6.14 Chromatograms of amine samples taken downstream of the carbon bed i n Pl a n t #1, a) 10 and b) 20 days a f t e r the bed was loaded with f r e s h carbon..259 6.15 Chromatograms of amine samples taken a) upstream and b) downstream of the carbon bed i n Pla n t #2 260 x x i i i 6.16 Simplified flowsheet of the equipment for column carbon adsorption experiments 264 6.17: Experimental and calculated breakthrough curves of a part ia l ly degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. (Solution velocity 1.7 mm/s) 271 6.18 Experimental and calculated breakthrough curves of a part ia l ly degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. (Solution velocity 2.54 mm/s) 272 6.19 Experimental and calculated breakthrough curves of a part ia l ly degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. (Solution velocity 3.0 mm/s) 273 6.20 Experimental and calculated breakthrough curves of a solution containing 2.0 mol DEA/L and 0.10 mol BHEP/L. (Solution velocity: 1.7 mm/s) 274 7.1 Chromatograms of 20 mL samples from Plant # 1 (a) before and (b) after addition of 0.02 mole of 15 M NaOH solution at 20°C for 5 min 279 7.2 Chromatograms of 20 mL samples from Plant # 1 (a) before and (b) after addition of 0.02 mole of 20 M KOH solution at 20°C for 5 min 280 7.3 Chromatograms of 20 mL samples from Plant # 2 xxiv (a) before and (b) after addition of 0.02 mole of 15 M NaOH solution at 20°C for 5 min 281 7.4 Chromatograms of 20 mL samples from Plant # 2 (a) before and (b) after addition of 0.02 mole of 20 M KOH solution at 20°C for 5 min 282 7.5 Chromatograms of 20 mL samples from Plant # 2 treated with 0.02 mole of 15 M NaOH solution at different time intervals 284 7.6 Chromatograms of 20 mL samples from Plant # 1 treated with 0.02 mole of 15 M NaOH solution at (a) 25°C and (b) 100°C for 5 min 285 7.7 Chromatograms of 20 mL samples (0.12 M DEA, 0.31 M HEOD) showing conversion of HEOD to DEA (a) before and (b) after addition of 0.0125 mole of 15 M NaOH solution at 20°C for 5 min 287 7.8 Chromatograms of 20 mL samples (0.12 M DEA, 0.31 M HEOD) showing conversion of HEOD to DEA (a) before and (b) after addition of 0.0125 mole of 20 M KOH solution at 20°C for 5 min 288 7.9 Chromatograms of 20 mL samples (1 M DEA, 0.06 M BHEP, 0.12 M HEOD, 0.40 M THEED) showing conversion of HEOD and THEED to DEA (a) before and (b) after addition of 0.03 mole of 15 M NaOH solution at 25°C for 5 min 291 7.10 Simplified flowsheet of a DEA plant showing the incorporation of the resin bed 302 X X V ACKNOWLEDGEMENTS I would l i k e t o thank the f o l l o w i n g : Dean Ax e l Meisen f o r h i s s u p e r v i s i o n , guidance, wise suggestions and encouragements; P r o f e s s o r L a r r y W e i l e r of Chemistry Department f o r h i s immense h e l p i n s o l v i n g the p u z z l e s of the r e a c t i o n mechanisms; - P r o f e s s o r Chi T i e n and Mr. John E. C e r e s i , J r . of Syracuse U n i v e r s i t y f o r p r o v i d i n g a copy of t h e i r computer program f o r multicomponent a d s o r p t i o n ; My parents and my wife Meena f o r t h e i r l o v e , understanding and encouragements. The f i n a n c i a l support p r o v i d e d by the N a t u r a l Sciences and E n g i n e e r i n g Research C o u n c i l of Canada and Imp e r i a l O i l L t d . are g r a t e f u l l y acknowledged. xxv i D E D I C A T I O N To the memory of my beloved father, who would have been the happiest person on this earth to see the successful completion of this work had he lived 46 more days Ionger. Chapter 1 INTRODUCTION N a t u r a l gas produced from g e o l o g i c a l formations f r e q u e n t l y c o n t a i n s carbon d i o x i d e and/or hydrogen s u l p h i d e . These a c i d gases must be removed from the n a t u r a l gas p r i o r to i t s t r a n s p o r t a t i o n i n order to a v o i d c o r r o s i o n i n p i p e l i n e s and to minimise h e a l t h and p o l l u t i o n problems upon subsequent use. The degree of removal of these c o n s t i t u e n t s v a r i e s a c c o r d i n g t o end use. The aqueous diethanolamine (DEA) p r o c e s s , which belongs to the amine process group, was developed by Bottoms [1,2] i n 1930 t o remove a c i d gases (C0 2 and H 2S) from h i g h volume, high p ressure n a t u r a l gas streams. I t has long been favoured f o r the removal of a c i d gases from r e f i n e r y or manufactured gases because DEA r e a c t s only slowly with carbon d i s u l p h i d e (CS 2) and c a r b o n y l s u l p h i d e (COS), which are t y p i c a l contaminants of r e f i n e r y or manufactured gases. However, i n recent years DEA has a l s o become i n c r e a s i n g l y popular with n a t u r a l gas p r o c e s s o r s and i s widely used i n Western Canada f o r n a t u r a l gas sweetening. Although d i f f i c u l t i e s are sometimes encountered with reducing H 2S c o n c e n t r a t i o n s t o p i p e l i n e s p e c i f i c a t i o n s , the SNPA m o d i f i c a t i o n of the DEA process i s c l a i m e d to be able to reduce H 2S c o n c e n t r a t i o n s to about 1.15 t o 3.45 mg/std m3 [ 3 ] . 1 2 While the DEA process and other c o n v e n t i o n a l amine processes simultaneously remove H 2S and C0 2, i n some cases i t i s d e s i r a b l e to remove H 2S s e l e c t i v e l y with minimal removal of C0 2. T h i s i s p a r t i c u l a r l y the case when the H 2S needs to be converted to elemental sulphur and the presence of C0 2 impairs the co n v e r s i o n e f f i c i e n c y . In a d d i t i o n , i n recent years C0 2 i n j e c t i o n i n t o l i q u i d hydrocarbon r e s e r v o i r s f o r enhanced o i l recovery has proven to be very s u c c e s s f u l . In t h i s case too, i t i s necessary to remove H 2S s e l e c t i v e l y t o be ab l e to produce C0 2. Aqueous methyl diethanolamine (MDEA) s o l u t i o n s are f i n d i n g wide acceptance i n i n d u s t r y f o r the s e l e c t i v e removal of H 2S from l i g h t hydrocarbon gases c o n t a i n i n g C0 2 [4-6]. The s e l e c t i v e removal of H 2S by MDEA i s achieved because MDEA r e a c t s f a s t e r with H 2S than with C0 2. 1.1 THE AMINE PROCESS Amines absorb a c i d gases mostly by means of chemical r e a c t i o n s . The o v e r a l l C0 2-DEA [7] and C02-MDEA [8] r e a c t i o n s can be represented by the f o l l o w i n g equations : C0 2-DEA : 2 R 2NH + H 20 + C0 2 .. * (R 2NH 2 * ) 2C0 3"" (1.1) ( R 2 N H 2 + ) 2 C 0 3 " - + H 20 + C0 2 «. 2R 2NH 2 + + 2HC0 3' (1.2) C02-MDEA : R 2NCH 3 + H 20 + C0 2 «. HC0 3" + R 2NHCH 3 * (1.3) Where R stands f o r -C2H,OH. 3 The e q u i l i b r i u m of the above r e a c t i o n s l i e s to the r i g h t at low temperatures and high p r e s s u r e s and to the l e f t at high temperatures and low p r e s s u r e s . For t h i s reason, i n d u s t r i a l absorbers are operated at low temperatures ( t y p i c a l l y 40°C) and at h i g h p r e s s u r e s ( t y p i c a l l y above 4 MPa). A s i m p l i f i e d flow sheet of an i n d u s t r i a l amine sweetening u n i t i s shown i n F i g . 1.1. The raw sour gas, which e n t e r s the u n i t through an i n l e t s eparator where e n t r a i n e d hydrocarbon l i q u i d s and s o l i d p a r t i c u l a t e s are removed, flows from the bottom of the absorber upwards a g a i n s t a c o u n t e r - c u r r e n t stream of aqueous amine s o l u t i o n . The a c i d gases are absorbed by the amine and the sweetened gas l e a v e s the top of the absorber. The r i c h amine s o l u t i o n c o n t a i n i n g C0 2 and H 2S flows from the bottom of the absorber and passes through the l e a n - r i c h heat exchanger where i t i s heated by the hot, lean amine s o l u t i o n . I t then e n t e r s the top of the s t r i p p e r column. In some cases a f l a s h tank i s i n s t a l l e d upstream of the l e a n - r i c h heat exchanger to desorb hydrocarbons from the s o l u t i o n by l e t t i n g down the pressure of the r i c h amine stream. SWEET GAS 0-H CONDENSER ABSORBER ACID GASES SEPARATOR FLASH TANK REBOILER Figure 1.1: Simplified flowsheet of an amine un i t . 5 Upon entry i n t o the s t r i p p e r , some of the absorbed a c i d gases are f l a s h e d . The s o l u t i o n then flows downward a g a i n s t a c o u n t e r - c u r r e n t flow of vapour generated i n the r e b o i l e r . The s t r i p p i n g vapour, which c o n s i s t s mainly of steam, removes most of the remaining a c i d gases from the r i c h amine s o l u t i o n . The overhead mixture passes through a condenser where most of the steam i s condensed. The a c i d gases are separated from the condensate i n a separator and the condensate i s r e t u r n e d to the top of the s t r i p p e r as r e f l u x . The lean s o l u t i o n , which l e a v e s the bottom of the s t r i p p e r , exchanges heat with the r i c h s o l u t i o n i n the l e a n - r i c h heat exchanger and then passes through a c o o l e r to r e t u r n i t to the o p e r a t i n g temperature of the absorber. In the case of DEA, a small s i d e stream of lean s o l u t i o n i s u s u a l l y passed through an a c t i v a t e d carbon f i l t e r to prevent the b u i l d - u p of contaminants. 1.2 AMINE DEGRADATION In s p i t e of DEA's a l l e g e d r e s i s t a n c e t o d e g r a d a t i o n , c e r t a i n s i d e r e a c t i o n s may occur and r e s u l t i n the formation of u n d e s i r a b l e compounds. The l a t t e r are termed "degradation compounds" and the phenomenon i s termed 6 "degradation". Most p l a n t o p e r a t o r s experience some l o s s of DEA due to degradation, but the s e v e r i t y of degradation v a r i e s widely and depends on raw gas composition and p l a n t o p e r a t i o n . Degradation of DEA i s u n d e s i r a b l e not onl y because i t re p r e s e n t s a l o s s of v a l u a b l e DEA, but a l s o because accumulation of degradation compounds may r e s u l t i n f o u l i n g of p r ocess equipment and may i n c r e a s e the foaming tendency of the s o l u t i o n i n the absorber and s t r i p p e r . Furthermore, some of the degradation compounds are c o r r o s i v e towards m i l d s t e e l [9-12]. U n l i k e monoethanolamine (MEA), degraded DEA s o l u t i o n s cannot be p u r i f i e d by d i s t i l l a t i o n a t atmospheric p r e s s u r e . The reason f o r t h i s i s that DEA and i t s degradation compounds have very s i m i l a r vapour p r e s s u r e s . A c t i v a t e d carbon f i l t e r s are claimed t o be able t o remove major degr a d a t i o n compounds and are widely used i n DEA p l a n t s [11, 13-15]. However, Meisen and Kennard's [16] l i m i t e d l a b o r a t o r y t e s t s as w e l l as chromatographic a n a l y s i s of i n d u s t r i a l DEA s o l u t i o n s taken upstream and downstream of a c t i v a t e d carbon f i l t e r s i n d i c a t e d that a c t i v a t e d carbon f i l t e r s do not remove any s i g n i f i c a n t q u a n t i t y of major degradation compounds. In l i g h t of these c o n t r a d i c t i o n s there i s a need to examine the e f f e c t i v e n e s s of a c t i v a t e d carbon f o r removing major DEA degradation p r o d u c t s . 7 No i n f o r m a t i o n on MDEA degradation i s p r e s e n t l y a v a i l a b l e i n the l i t e r a t u r e . I t i s widely b e l i e v e d that MDEA does not degrade with C0 2. Blanc et a l . [17] s t a t e d t h a t MDEA s o l u t i o n s used i n i n d u s t r i a l p l a n t s f o r s e v e r a l years d i d not show any sign of deg r a d a t i o n . However, our p r e l i m i n a r y experiments i n d i c a t e d t h a t MDEA can a l s o degrade with C0 2 [18]. Although MDEA i s mainly used f o r the s e l e c t i v e removal of H 2S, i t a l s o absorbs some C0 2 which may be s u f f i c i e n t t o cause MDEA degra d a t i o n . Although MDEA's r e s i s t a n c e towards degradation i s g r e a t e r than t h a t of DEA, i t s c o s t i s higher than DEA's. Consequently, t h e r e i s a need to examine degradation of MDEA as a f u n c t i o n of temperature, C0 2 p a r t i a l p r e s s u r e and i n i t i a l MDEA c o n c e n t r a t i o n . 8 1.3 OBJECTIVES OF THE PRESENT STUDY The two p r i n c i p a l o b j e c t i v e s of the present study a r e : * E l u c i d a t e and develop a p r e d i c t i v e model f o r MDEA degradation; * Examine p u r i f i c a t i o n techniques ( i n c l u d i n g a c t i v a t e d carbon a d s o r p t i o n ) s u i t a b l e f o r r e g e n e r a t i n g degraded DEA and MDEA s o l u t i o n s . In a d d i t i o n , the s o l u b i l i t y of C0 2 i n v a r i o u s amine and r e l a t e d s o l u t i o n s was determined and r e s u l t s are presented on DEA degradation i n heat t r a n s f e r tubes. The t h e s i s i s d i v i d e d i n t o s e v e r a l , s e l f - c o n t a i n e d c hapters d e s c r i b i n g the v a r i o u s i n d i v i d u a l s t u d i e s and a s s o c i a t e d r e s u l t s . Chapter 2 LITERATURE REVIEW S e v e r a l papers on the performance of DEA p l a n t s have been p u b l i s h e d [19-22]. S e l e c t i v e H 2S removal by MDEA has a l s o been r e p o r t e d by s e v e r a l authors [4-6, 23]. Operating data of an MDEA u n i t has been r e p o r t e d by Ammons and S i t t o n [24]. Daviet et a l . [25] r e p o r t e d s u c c e s s f u l c o n v e r s i o n of a gas t r e a t i n g p l a n t from DEA to MDEA to accommodate changes in feed gas C0 2 c o n c e n t r a t i o n . In a d d i t i o n , s e v e r a l textbooks [6,7,26,27] and handbooks [28,29] are a v a i l a b l e which review n a t u r a l gas p r o c e s s i n g i n g e n e r a l . V a r i o u s a n a l y t i c a l methods f o r r o u t i n e a n a l y s i s of gas t r e a t i n g s o l u t i o n s are d e s c r i b e d i n the Gas C o n d i t i o n i n g Fact Book [30]. 2.1 ABSORPTION OF CO, IN AQUEOUS DEA AND MDEA SOLUTIONS The chemistry of C0 2 r e a c t i o n s with aqueous DEA s o l u t i o n s i s f a i r l y complex and not yet f u l l y understood. The l i t e r a t u r e on C0 2-DEA r e a c t i o n s i s ex t e n s i v e [31-46] with Blauwhoff et a l . [47] p r o v i d i n g an e x c e l l e n t review of the works r e p o r t e d up t o 1982. Two more a r t i c l e s have been p u b l i s h e d s i n c e then [48,49]. U n t i l r e c e n t l y , C02-MDEA r e a c t i o n s have not r e c e i v e d much a t t e n t i o n . Although 9 10 several reaction mechanisms have been postulated [4,50], only those proposed by Barth et a l . [51,52] and Yu et a l . [53] are supported by experimental work. Savage et a l . [54] recently published a thermodynamic analysis of the se lect iv i ty of MDEA. 2.1.1 CO, REACTIONS WITH WATER When C0 2 dissolves in water, i t f i r s t hydrolyses to form carbonic acid, H 2 C0 3 which then s l ight ly dissociates to form H* and HC03" ions. The following reactions are pertinent for the aqueous phase: H* + OH" (2.1) H 2 C0 3 (2.2) H* + HC03" (2.3) H 20 ^ C0 2 + H 20 ^ H 2 C0 3 ^ 2.1.2 CQ2 REACTIONS WITH DEA The following acid-base reactions take place in aqueous DEA solutions: R2NH + H 20 R 2NH 2 * + OH" R2NH + H* R 2NH 2 * R 2 NH 2 + + HC03" [R 2 NH 2 + ] [HCO3-] (2.4) (2.5) (2.6) 11 DEA is protonated according to Egs. 2.4 and 2.5. The protonated molecules then react with bicarbonate ions to form DEA bicarbonate complexes according to Eg. 2.6. In addition, the following carbamate reactions, which involving the labi le hydrogen atom of the DEA molecule, take place: R2NH + C0 2 ^ZZ± R2NH*COO- (2.7) R2NH+COO- + H 20 ^  ^ R2NCOO" + H 3*0 (2.8) R2NH + COO" + OH- ^  R2NCOO" + H 20 (2.9) R2NH*COO- + R2NH R2NCOO* + R 2NH 2*0 (2.10) R2NCOO" + H* + H2Q ^ s R 2NH 2 * + HC03" (2.11) C0 2 reacts d irect ly with DEA according to Eq. 2.7 to form an extremely unstable dipole known as a zwitterion complex [38]. The zwitterion is then rapidly deprotonated by water, hydroxyl ions or DEA (see Eqs. 2.8 to 2.10) to form DEA carbamate, R2NCOO'. The carbamate formation reactions are much faster then the acid-base reactions and therefore C0 2 absorption in aqueous DEA solutions mostly takes place via carbamate formation [38]. 12 2.1.3 CO2 REACTIONS WITH MDEA MDEA is a tertiary amine and therefore cannot form carbamate with C 0 2 . It has been suggested that, in addition to C02-water reactions, the following simple proton transfer reaction takes place in aqueous MDEA solutions: R2NCH3 + H + ^ ^ R2NH*CH3 (2.12) Barth et a l . [51,52] confirmed experimentally that this reaction mechanism is val id for very low C0 2 concentrations. At C0 2 concentrations in excess of 0.007 M, the theoretical predictions of C0 2 absorption were lower than the experimental results. They suggested a catalytic effect of MDEA on C0 2 hydrolysis (see Eq. 2.2) and were able to improve the agreement between the theoretical predictions and experimental results by replacing Eq. 2.12 with R2NCH3 + H 20 + C0 2 ^ R 2N +HCH 3 + HC03" (2.13) Such a catalytic effect was also reported by Donaldson and Nguyen [39] for another tert iary amine, triethanolamine (TEA). Yu et a l . [53] recently suggested the poss ibi l i ty of zwitterion formation on the nitrogen atom as an intermediate in the catalytic path according to: R2NCH3 + C0 2 R 2CH 3N COO (2.14) 1 3 R 2CH 3N COO + H 20 R2CH3NH+ + HC03" (2.15) 2.2 AMINE DEGRADATION In his exploratory work on organic bases for gas sweetening, which led to the discovery of amine processes, Bottoms [2] observed that ethanolamines (including DEA), were stable at low temperatures. However, when the pure compounds or their aqueous solutions were heated above 150°C, some decomposition was noticed. This was probably the f i r s t reported indication of amine degradation. 2.2.1 DEA DEGRADATION In addition to the main reactions (see Eqs. 2.4 to 2.11), DEA and DEA carbamate undergo further changes resulting in the formation of DEA degradation compounds. DEA degradation is a complex phenomenon. Smith and Younger [11,19] reported that degradation apparently depends on temperature, pressure, gas composition, amine concentration, solution pH and the presence of metal ions. The f i r s t major work on DEA degradation was published by Polderman and Steele [9] in 1956. Their work consisted of saturating a 25 wt% DEA solution with C0 2 at 25°C inside 14 a stainless steel autoclave, sealing and and heating the autoclave to a temperature ranging from 100 to 175°C. The pressure inside the autoclave varied from 1.26 to 4.14 MPa. After 8 h the autoclave was cooled to 25°C and the part ia l ly degraded solutions were analysed by fractional d i s t i l l a t i o n and crys ta l l i zat ion . DEA losses ranged from 0% at 100°C and 1.26 MPa to 97% at 175°C and 4.14 MPa. They identified N,N-bis(hydroxyethyl) piperazine (BHEP) as a degradation compound. However, the authors did not identify other degradation compounds due to the lack of suitable analytical techniques. They suggested that BHEP was formed via an intermediate compound 3-(2-hydroxyethyl)-2-oxazolidone (HEOD). In a follow-up study, Hakka et a l . [55] were able to detect N,N,N'- tr is (2-hydroxyethyl) ethylenediamine (THEED) in degraded DEA solutions by using more sophisticated analytical procedures. According to the authors, THEED occurred frequently at concentrations of 0.5 to 2 wt% in the DEA solution and should be regarded as a major degradation compound. Choy [56] performed several carefully controlled degradation experiments and found that DEA degradation appears to be governed by a f i r s t order reaction at temperatures and C0 2 part ia l pressures ranging from 165 185°C and 1.2 to 4.14 MPa, respectively. He also found that 15 the rate of degradation was affected by the i n i t i a l DEA concentration. This clearly contradicts the simple f i r s t order reaction concept. Furthermore, several unidentifiable degradation compounds were detected and their concentration changes with time suggested a series of simultaneous and consecutive degradation reactions. Blanc et a l . [17] reacted C0 2 separately with DEA and HEOD solutions in a sealed autoclave. The temperature of the autoclave was varied from 90 to 130°C. They proposed various mechanisms for the formation of HEOD, THEED, BHEP and other degradation compounds. However, no quantitative data were presented in support of these reaction mechanisms. Kennard [57] as well as Kennard and Meisen [58] undertook a comprehensive study of the reaction mechanisms and kinetics of DEA degradation. Their work consisted of reacting C0 2 with DEA in a 600 mL st irred stainless steel autoclave. The temperature, pressure and i n i t i a l DEA concentration were varied from 90 to 205°C, 0.4 to 6.9 MPa and 5 to 100 wt%, respectively. They found the reactions between C0 2 and DEA to be complex and consisting of a combination of equilibrium, p a r a l l e l , series and ionic steps. They proposed a pseudo-first order mechanism to describe the overall degradation reaction of DEA. 16 They were able to detect 12 degradation compounds but found HEOD, THEED and BHEP to be the major ones. HEOD and THEED appeared to be produced direct ly from DEA whereas BHEP was formed from THEED. They also found that C0 2 was neither consumed nor produced during degradation of DEA; this suggested that C0 2 acts as a catalyst. Kim and Sartori [59] have also studied DEA degradation with C0 2 and observed the same catalytic effect of C0 2 on the degradation reactions. They also found BHEP, HEOD and THEED to be the major DEA degradation products, but found degradation to occur in successive steps, i . e . DEA degraded to HEOD, which then formed THEED and subsequently produced BHEP. Kennard [57] has, however, presented evidence that THEED is not produced from HEOD; consequently, the val id i ty of Kim and Sartori 's [59] reaction scheme is questionable. Apart from BHEP, HEOD and THEED, other types of degradation compounds known as "heat stable salts" may also form in the presence of any acidic constituents stronger than H 2S and C 0 2 . Such strong acids, reported by Henry and Grennert [60,61] in 1955, were later identified by Blanc et a l . [17] as formic, acetic, propionic and oxalic acids. These acids react with the amine by proton transfer mechanisms. However, the anions of these acids are not capable of accepting protons back from the protonated amine molecules during stripping. Amine molecules which have been 17 protonated by strong acids thus become neutralized. Formation of these acids has been attributed to the presence of oxygen, but the mechanism of their formation is not clearly understood. Waterman et a l . [62] reported the presence of heat stable anions such as acetate, formate, oxalate and thiosulphate in gas treating DEA solutions. Industrial grade DEA solutions usually contain small amounts of MEA. MEA can also degrade to form oxazolidone ("OZD"), 1-(2-hydroxyethyl) imidazolidone ("HEI"), N,N'-bis(hydroxyethyl) urea ("BHEU") and N-(hydroxyethyl) ethylenediamine ("HEED") [63,64]. Degradation compounds of higher molecular weight have also been suggested [9]. Hsu and Kim [65] later identified them as 3-(2-(bis(2-hydroxyethyl) amino) ethyl) 2 oxazolidone ("HAO"), N-(2-(N,N-bis(2-hydroxyethyl) amino) ethyl) N' (2-hydroxyethyl) piperazine ("HAP") and N,N,N",N"-tetrakis(2-hydroxyethyl) diethylenetriamine ("THEDT"). In a follow-up study of Kennard and Meisen's work [58], Chakma and Meisen [66] performed carefully controlled degradation experiments on DEA solutions passing through a coiled heat transfer tube (2.032 mm ID, 3.175 mm OD, 4.8 m long) immersed in a constant temperature bath. The operating conditions were: DEA flow rate 0.011 to 0.0172 18 L / s , DEA concentration 20 to 40 wt%, DEA temperature 60 to 200°C and C02 part ia l pressure 1.38 to 4.18 MPa. They found the degradation rate to increase with temperature, DEA concentration and C0 2 part ia l pressure and to decrease with solution flow rate. They also found degradation to be accompanied by the formation of a fouling deposit. 2.2.2 DEA DEGRADATION MECHANISM DEA reacts with C0 2 to form DEA carbamate as folows: HO-C 2H, HO-C2H« y.0 HO-C2H„ N-H + CO2 (2.16) "DEA" "DEA carbamate" The dotted and dashed lines represent ionic complexes. 19 According to Kennard [57], the DEA carbamate then dehydrates to form HECD according to the following equation: HO-CH 0 N-C -/ \ HO-CzH,, o; 'DEA carbamate' HO-C 2H,-N 0 + H 20 H + CH 2 C H 2 "HEOD" (2.17) As shown in the above equation, HEOD formation is par t ia l ly reversible. The DEA carbamate can also react with DEA to form THEED. HO~C 2H, y0 C 2H,-OH \ S / N-C + HO-C 2Hn-N HO-C 2H, H *H + "DEA carbamate" "DEA" HO-C 2H f t C 2 H a -OH \ / N-C 2 H,-N HO-C 2H, H "THEED" + H + + HCO,- (2.18) 20 DEA carbamate can also react with i t se l f to form THEED carbamate. HO-C 2H f t .0 C2Hfl-OH N-C + HO-C 2H«-N «^ / \ \ HO-CzH, o ; c = o / H + 0" H + "DEA carbamate" "DEA carbamate' H0-C 2H„ C 2H„-0H N-C 2H 4-N + H + + HC0 3- (2.19) HO-CzHft^^ C = 0 / H* "THEED carbamate' 21 THEED carbamate can either revert to THEED or form BHEP according to the following equation. HO-C 2H 4 C 2H 4-OH \ / N-C 2H f l-N / \ HO-C 2H» C = 0 / o-'THEED carbamate" H + C 2 H a / \ HO-C 2H 4-N N-C 2H,-0H + H* + HC0 3" (2.20) C 2 H 4 "BHEP" BHEP may also be formed by the direct dehydration of THEED as follows: HO-C 2H 4 C 2H 4-OH "^N-CzH.-N HO~C 2H 4 H "THEED" C 2 H 4 / \ H 0 - C 2 H 4 - N ^ ^ ^ N - C 2 H 4 - O H + H 20 C 2 H 4 (2.21 ) "BHEP" The overall DEA degradation with C0 2 may therefore be written in simplified form as: BHEP + H + + H C O 3 -It THEED carbamate + H + + HC03" II DEA carbamate + DEA + C0 2 ~ DEA carbamate ^ HEOD + H 20 + DEA If THEED + H + + HC0 3 ' I t BHEP + H 20 2.2.3 KINETIC MODELS FOR DEA DEGRADATION Although several models have been proposed to describe DEA degradation, only two are based on systematic laboratory studies. One is due to Kim and Sartori [59] who postulated that THEED is formed from the reaction of HEOD and DEA, i . e . DEA + C0 2 > HEOD + H 20 HEOD + DEA > THEED (2.22) (2.23) THEED > BHEP 23 (2.24) They provided rate constants for the above model at 120°C. The second detailed model for DEA degradation is due to Kennard and Meisen [58], Their simplified reaction scheme can be summarized as follows: or DEA + CO2 DEA + CO2 THEED HEOD HEOD + H 20 THEED BHEP (2.25) (2.26) (2.27) DEA (2.28) THEED BHEP The conditions covered by their model are: temperature, 90 to 175°C; DEA concentration, 0 to 100 wt% ;C0 2 loading, > 0.48 mol C0 2/mol DEA. They plotted the rate constants as a function of temperature and DEA concentration only. C0 2 loading, which is affected by solution concentration, temperature and C0 2 part ia l pressure, had some eaffect on the rate constants below 0.48 mol C0 2/mol DEA. By restr ict ing the model to C0 2 loadings above this l imi t , they 24 in effect eliminated the effect of C0 2 part ia l pressure on the rate constants. Although, in industrial units, the C0 2 loading of the amine solution in the absorber may be above or close to this l imi t , in the regenerator and reboiler, where the solution experiences the highest temperatures, the C0 2 loading is considerably less than 0.48 mol C0 2/mol DEA. In an effort to overcome this l imitation of the model, Chakma and Meisen [66] modified i t by introducing a C0 2 term as follows: HEOD k, DEA + C0 2 (2.29) THEED BHEP + C0 2 They re-evaluated Kennard and Meisen's [58] rate * * constants by dividing k, and k 2 by the total C0 2 loading, [ C 0 2 T ] . Since the G02 loading is affected by solution concentration and C0 2 part ia l pressure for a given temperature, they were able to lump the effects of solution concentration and C0 2 part ia l pressure into [ C 0 2 T ] . Thus i t became possible to correlate the rate constants as a function of temperature alone. The rate constants are given by the following equations: 25 ln{k,*} = 1 1 .924 - 6421/T ln{k2*} = 8.450 - 5580/T ln{k3*} = 32.643 - 15650/T (2.32) (2.30) (2.31) where T denotes the absolute temperature in kelvins. The * * * units of k, and k 2 are L/(mol h); the units of k 3 are 2.2.4 MDEA DEGRADATION In the case of DEA, the major degradation products are formed primarily from DEA carbamate. Unlike DEA, MDEA cannot form carbamate with C0 2 and this suggests that the degradation of MDEA as a result of reaction with C0 2 is unlikely. Blanc et a l . [17] have stated that "No one has been able to show any degradation products in solutions having been used for several years in industrial units". The val id i ty of this statement is questionable because few gas plants have used MDEA extensively and accurate analytical techniques for detecting degradation compounds may not have been employed. In addition, our i n i t i a l laboratory tests indicated that MDEA degrades in the presence of C0 2 at elevated temperatures and pressures [18]. 26 2.3 ANALYSIS OF AMINE SOLUTIONS Kennard and Meisen [67] developed a simple, rel iable and direct gas chromatographic technique for the analysis of DEA and its degradation compounds. They used Tenax G.C. as the column packing and were able to detect 14 compounds in degraded DEA solutions. They later identified them by using combined gas chromatography and mass spectrometry. They were able to detect DEA and known degradation products at concentrations as low as about 0.5 wt%. The reproducibilty was typical ly ±5% Hsu and Kim [65] used chemical ionization (CI) mass spectral analysis for the accurate determination of molecular weight of unknown degradation compounds. They also used selective hydroxyl group s i ly la t ion techniques to determine the number of hydroxyl groups present in the individual degradation compounds. The information on the molecular weight and the number of hydroxyl groups present, along with mass spectral data thus enabled them to identify previously unidentified high molecular weight degradation compounds. 2.4 SOLUTION PURIFICATION Purification of part ia l ly degraded DEA solutions has proven to be rather d i f f i c u l t . Most of the degradation 27 compounds are high boiling compounds having vapour pressures similar to that of DEA. Therefore, they can not be reclaimed by atmospheric d i s t i l l a t i o n . Activated carbon f i l t e r s are widely used in DEA plants for the purification of contaminated DEA solutions. Although various authors [11,13,14] have claimed that activated carbon can remove major DEA degradation products from amine solutions, no experimental evidence has been presented. In fact no systematic study on the adsorptive capacity of activated carbons for major DEA degradation products has been reported in the open l i terature . Meisen and Kennard's [16] limited laboratory tests as well as chromatographic analyses of industrial DEA solutions taken upstream and downstream of activated carbon beds [57,68] suggested that activated carbon does not remove significant quantities of major degradation compounds. This was rather surprising because activated carbons are known to be capable of adsorbing various organic compounds including amines [69,70]. Therefore the a b i l i t y of activated carbon to remove major DEA degradation products from DEA solutions remains unclear and controversial . Several other techniques for the purif ication of degraded DEA solutions have been patented. They mostly deal with the removal of heat stable salts . 28 One of the techniques (U.S. Patent 2,701,750) involves withdrawal of a small side stream of amine solution, addition of sodium or potassium hydroxide and removal of most of the water by d i s t i l l a t i o n . Sodium and potassium hydroxide, being stronger bases than DEA can then break up the heat stable salts by forming their own salts and thus freeing the DEA. An alcohol is then added, which causes the sodium and potassium salts to precipitate. The precipitate can then be removed by f i l t ra t ion and the alcohol is separated from the DEA solution by d i s t i l l a t i o n [71], Another patented technique (US patents 2,892,775 and 2,914,469) for the removal of heat stable salts involves addition of a 48% solution of potassium hydroxide to the degraded solution which lowers the melting point of the salt mixture suff ic iently to permit DEA separation by atmospheric d i s t i l l a t i o n . [72] Morgan and Klare [73] describe the use of a highly basic anion exchange resin (Amberlite IRA-910) for treating sodium chloride contaminated DEA solutions. Hydroxide ions replace the chloride ions and sodium hydroxide thus formed reacts with C0 2 to form sodium bicarbonate. The latter precipitates and can be separated by f i l t r a t i o n . Another way of purifying degraded amine solutions is to reverse the degradation reactions. Chakma [68] reported 29 some preliminary studies on the ab i l i ty of NaOH to reverse some of the degradation reactions. He found that HEOD can be completely converted back to DEA. While THEED was also found to disappear as a result of NaOH addition, i t is unclear whether i t was converted back to DEA. 2.4.1 HEOD REVERSAL The HEOD formation is known to be reversible [58] which probably results from the instabi l i ty of the HEOD ring. Hydroxyl ions attack the electron deficient carbonyl group so that the addition of strong a l k a l i , such as NaOH, to a degraded solution causes HEOD to break up: 0 II HO -C2H f l -N 0 + OH" + Na+ CH2 CH2 "HEOD" H 20 HO-C2H„ N-H + Na+ + HC0 3-HO-C 2H, "DEA" (2.33) 30 or, C HO-C2H« .0 / \ \ V H0-C2H,,-N 0 + OH"+H+ + 2NaOH > N-C + 2NaOH CH 2 C H 2 "HEOD" HO-C 2H f l 0-H + 'DEA carbamate' HO-C2H„ \ HO-C 2H, "DEA" N-H + Na2 + + C 0 3 - - + H 20 (2.34) DEA is therefore reformed, but i t occurs at the expense of sodium hydroxide which stays in solution either as sodium bicarbonate, Na +HC0 3", or possibly sodium carbonate, N a 2 + C 0 3 - _ , i f the conditions in the stripper are severe. 2.4.2 THEED REVERSAL THEED is formed directly as a result of reactions between DEA carbamate and DEA (see Eq. 2.18) or via THEED carbamate formation which arises from the combination of two DEA carbamate molecules (see Eq. 2.19). Although these two reactions do not appear to be reversible under normal industrial conditions, i t may be possible to reverse them by 31 increasing the H + and HC03~ concentrations in solution. When NaOH is added to degraded DEA solutions containing THEED, i t is l ike ly that NaOH increases the concentration of HC03" ions in solution by reacting with C0 2 and thus helping to reverse the THEED formation. It may also be possible that, as a result of an increase in the OH" concentration, THEED simply breaks up to form DEA according to the following equation: R R R R \ / \ / , . N-C 2H«-N + OH* + H + > N-H + HO-CzH^-N (2.35) R ^ H R ^ ^ H "THEED" "DEA" "DEA" THEED carbamate may also be attacked by OH" ions to form DEA and DEA carbamate. R R R R > S V N - C 2 H , - N ^ + OH" + H + J ^ N - H + HO-C 2H,-N (2.36) / \ / \ R C - 0 ' . . . H + R C-O-.H* II II 0 0 "THEED carbamate" "DEA" "DEA carbamate" Alternatively, NaOH can direct ly react with THEED as follows: 32 R R R R ^ N - C 2 H „ - N ^ + NaOH » N+Na + HO-C2H,~N (2.37) R H R ^ ^ H "THEED" "Na-salt Of DEA" "DEA" THEED carbamate may also react with NaOH directly to form the Sodium salt of DEA and DEA carbamate. R R R R •^N-CzHft -N,^ + NaOH • ^ N r t N a * " * H O - C 2 H f l - N ^ (2.38) R C - 0 - . . . H * R C - 0 - . . . H + II H 0 o "THEED carbamate" "Na-salt" "DEA carbamate" 2.4.3 BHEP REVERSAL The BHEP ring is quite stable. Therefore, i t is very d i f f i c u l t to reverse i ts formation to THEED. For practical purposes, BHEP formation may therefore be considered irrevers ible . However, since BHEP is formed from THEED, the reversal of THEED should prevent BHEP from being formed. 33 2.5 SOLUBILITY OF CQ2 IN DEA AND MDEA SOLUTIONS Data on C0 2 so lubi l i ty in aqueous DEA solutions for DEA concentrations of 5 - 80 wt%, C0 2 part ia l pressures of 0.0098 - 5.7 MPa and temperatures of 20° - 140°C have been reported by several researchers [2,74-80]. Kennard and Meisen [81] published C0 2 so lubi l i ty data for high temperatures (up to 205°C) . Therefore, adequate data on C0 2 so lubi l i ty in DEA solutions are available in the l i terature . On the other hand, only limited data on C0 2 so lubi l i ty in aqueous MDEA solutions are available. In fact only Jou et. a l . [8] have reported C0 2 so lubi l i t i es in aqueous MDEA solutions up to 120°C. No data on C0 2 so lubi l i ty in aqueous solutions containing DEA degradation products are available in the l i terature . A number of researchers have attempted to correlate C0 2 so lubi l i ty in aqueous ethanolamine solutions [82-84] by obtaining pseudo equilibrium constants from experimental data [82-84]. Among them the Kent and Eisenberg model [84] (for a detailed description refer to Chapter 3) appears to be the most popular. 34 Deshmukh and Mather [85] have developed a rigourous thermodynamic model requiring calculation of act iv i ty and fugacity coefficients. While the fugacity coefficients were calculated from the Peng-Robinson [86] equation of state, the act iv i ty coefficients were calculated using the extended Debye-Huckel expression given by Guggenheim [87]. The use of the extended Debye-Huckel expression requires the knowledge of interaction parameters for a l l pairs of species in solution. Since these parameters are not readily available, this model is d i f f i c u l t to use, although it is theoretically sound. Chapter 3 CO2 SOLUBILITY STUDIES IN DEA, MDEA AND BHEP SOLUTIONS Since the DEA and MDEA degradation rates depend on C0 2 so lubi l i ty in aqueous amine solutions, some knowledge of C0 2 so lubi l i ty was required. Unfortunately data on C0 2 so lubi l i ty in MDEA solutions at elevated temperatures (above 120°C) were not available in the l i terature . Similarly, no information on C0 2 so lubi l i ty in solutions containing degradation compounds was available. Among the major DEA and MDEA degradation compounds, BHEP was known to be a primary degradation compound. Therefore, information on the so lubi l i ty of C0 2 in aqueous BHEP solutions was also of interest. Experiments were conducted to determine C0 2 so lubi l i ty in aqueous MDEA solutions at temperatures ranging from 100 to 200°C and in aqueous BHEP solutions at temperatures ranging from 40 to 180°C. 3.1 EXPERIMENTAL APPARATUS AND PROCEDURE The experimental apparatus and procedures are similar to those described by Kennard and Meisen [81], Aqueous MDEA and BHEP solutions of the desired concentration were prepared by mixing d i s t i l l e d water with 99% + pure MDEA and 35 36 BHEP (supplied by Aldrich Chemicals, Milwaukee, WI). The purity of MDEA and BHEP was confirmed by gas chromatography (see Appendix A). A 500 mL, high pressure, stainless steel bomb was f i l l e d with C0 2 and weighed with an electronic balance (Type P2000, Mettler, Switzerland) to within ± 0.1g. A 600 mL stainless steel autoclave (Model 4560, Parr Instrument Co. , 111., see F ig . 5.1, page 93) was charged with 200 mL of the prepared MDEA or BHEP solution and closed. The autoclave was then heated to the desired temperature. Its contents were constantly st irred and the temperature was kept at the desired value by means of a controller (Model 4831EB, Parr Instrument Co. , IL) . The pressure of the solution was read from the gauge attached to the autoclave. The C0 2 f i l l e d bomb was then connected to the autoclave. Usually 20 - 50 g of C0 2 were introduced into the autoclave. Equilibrium was usually reached within less than half an hour as noted from any changes in the pressure reading. However, the system was allowed to equilibrate for at least 4 h before the 500 mL bomb was disconnected from the autoclave. The equilibrium pressure was then recorded. The bomb was reweighed and the mass of C0 2 introduced into the autoclave was calculated from the weight change. 37 3.2 CO, SOLUBILITY DETERMINATION The so lubi l i ty of C0 2 was calculated as follows. F i r s t , the amount of C0 2 in the vapour phase was determined by assuming that the phase obeyed Dalton's law, i . e . the total pressure exerted by the vapour phase equals the sum of part ia l pressures of the individual components. The part ia l pressure of C0 2 in the vapour phase was therefore calculated from the difference between the f inal equilibrium pressure and the solution pressure before the C0 2 was introduced. The number of moles of C0 2 in the vapor phase was then found by using the B-W-R equation of state [88], the part ia l pressure of C0 2 , the volume of the vapour phase (determined from the known internal volume of the autoclave and the volume of the MDEA or BHEP solution) and the temperature. The B-W-R constants for C0 2 were obtained from Reid et a l . [89], The mass of C0 2 dissolved in the MDEA or BHEP solution was then found by subtracting the mass of C0 2 in the vapour phase from the mass of C0 2 fed to the autoclave. 38 3.3 MATHEMATICAL MODEL FOR CO, SOLUBILITY IN DEA, MDEA AND BHEP 3.3.1 SOLUBILITY IN DEA In the absence of degradation reactions, the equilibrium in the DEA-C0 2-H 20 system is governed by the following ionic reactions: R 2NH 2* * R2NH + H + (3.1) R2NCOO" + H 20 % R2NH + HC03" (3.2) H 20 + C0 2 ^ ~* H + + HC0 3- (3.3) H 20 ^ H + + OH" (3.4) H C O 3 - v H + + C O 3 - - (3.5) Henry's Law may be written as: Pco2 = Hco 2[C0 2] (3.6) where Pco 2 and Hco 2 denote the part ia l pressure of carbon dioxide in the gas phase and Henry's law constant, respectively. Molar concentrations in the l iquid phase are indicated by square brackets, i . e . [ ]. The corresponding equilibrium expressions are: [R2NH] [H+] K, = (3.7) [R 2 NH 2 + ] [R2NH] [ H C O 3 - ] K 2 = (3.8) [R2NCOO"] 39 [H+] [ H C O 3 - ] K 3 = (3.9) [C0 2] K„ = [H+] [0H-] (3.10) [H+] [ C O 3 " ] K 5 = (3.11) [HC .O3-] In addition, the total molar and charge balances must be satisf ied: [DEA] = [R2NH] + [R 2 NH 2 + ] + [R2NCOO"] (3.12) [DEA] 7 = [C0 2] + [ H C O 3 - ] + [ C O 3 " ] + [R2NCOO-] (3.13) [R2NCH3H*]+[H+] = [OH-] + [ H C O 3 - ] + 2[C0 3 "] + [R2NCOO"] (3.14) where [DEA] and 7 denote the total DEA concentration and C0 2 loading in the solution, respectively. Equations 3.7 through 3.14 can be rewritten to express the C0 2 part ia l pressure as a function of acid gas loading in the solution. ([DEA]7 - Pco 2 /Hco 2 )[H*] 2 Hco2 Pco2 = ( ) (3.15) K 3 Rs [ H + ] [DEA] [H+] 1 + + K 5 Rj R 5 R™ 40 [DEA] + K K" [H+] = ( — ) (([DEA] T -Pco 2 /Hco 2 )[H + ] 2 ( 1 + K 1 K •) K c K A ) + r-^r ) K 2 K 5 + K 2 [H + ] + [DEA][H+]/K" [H+] (3.16) [H+] Pco 2 K 3 K" = 1 + + (3.17) K, K 2 Hco2 [H*] Provided the C0 2-DEA-H 2O system behaves ideal ly , the Henry's law and equilibrium constants defined by Eqs. 3.7 to 3.11 should only be functions of temperature. Kent and Eisenberg [84], who investigated the C0 2-MEA-H 20 and C0 2-DEA-H 20 systems, found this to be the case. They f irs t f i t ted published data to obtain empirical expressions for the Henry's coefficient, Hco 2 , and ionisation constants, K 3 - K 5 . Then they f i t ted H2S-amine equilibrium data to obtain an expression for K 1 f which represented the simple proton transfer reaction, and C02-amine equilibrium data to obtain a similar expression for K 2 . Their empirical expressions for the equilibrium constants are given below in SI units: K, = exp{-2.55l0 - 5652/T} (3.18) K 2 = exp{ 4.825 - 1885/T} (3.19) K 3 = exp{-241.8l8 + 298.253E3/T - 148.528E6/T2 + 332.648E8/T3 - 282.394E10/T*} (3.20) K„ = exp{39.5554 - 987.9E2/T + 568.828E5/T2 - 146.451E8/T3 + 136.146E10/T"} (3.21) 41 K 5 = exp{-294.74 + 364.385E3/T - 184.158E6/T2 + 415.793E8/T3 - 354.291E10/T"} (3.22) Hco2 = exp{22.28l9 - 138.306E2/T + 691.346E4/T2 - 155.895E7/T3 + 120.037E9/T"}/7.50061 (3.23) Although the Kent and Eisenberg [84] model is able to predict C0 2 so lubi l i ty in aqueous solutions under normal operating temperatures and pressures, predictions deviate considerably from the experimental data at elevated temperatures. This was understandable, as they did not use high temperature so lubi l i ty data in evaluating the constants of their empirical equations. Therefore, i t was decided to reevaluate the coefficients of the expression for K 2 using available C0 2 so lubi l i ty data, including the high temperature C0 2 so lubi l i ty data of Kennard and Meisen [81]. The following expression for K 2 was thus obtained: K 2 = exp{ 1.0343898 +2.92236989E-2 T + 26.207099/T 10.394767 x ln{T} + 3.7497158 [C0 2] + 0.19297775 x ln{[C02]} + 9.00067215E-3 x [DEA] + 74.282674 x ln{[DEA]}} (3.24) 3.3.2 SOLUBILITY IN MDEA Since MDEA does not form a carbamate with C0 2 , the carbamate formation reaction is not required. With this exception and in the absence of degradation reactions, the 42 equi l ibr ia in the MDEA-C02-H20 system are similar to . those in the DEA-C0 2-H 20 system represented by Eqs. 3.1 to 3.5. Equation 3.1 needs to be replaced by: R2NCH3 + C0 2 + H 20 ^ZZ±T R2NCH3H* + HC0 3- (3.25) Equation 3.7 becomes: [R 2NCH 3H+] [HC03-] Km, = (3.26) [R2NCH3] [C0 2] The mass and charge balance equations are: [MDEA] = [R2NCH3] + [R 2NCH 3H+] (3.27) [MDEA]7 = [C0 2] + [HC03-] + [C0 3"-] (3.28) [R 2NCH 3H+] + [H*] = [OH"] + [HC03"] +2[C03"-] (3.29) where [MDEA] and y denote the total MDEA concentration and C0 2 loading in the solution, respectively. The following equations can then be derived to express the C0 2 part ia l pressure as a function of acid gas loading at a given temperature and MDEA concentration. 43 [MDEA]7 " Pco 2/Hco 2 PC02 = Hco2 [ H + ] 2 (3.30) K 3 ( K S + [H+]) K K ( ( [MDEA]7 - Pco 2 /[Hco 2 ] ) ( 1 + ) + — K 5 + [H+] [H+] [H*] = Km,[MDEA] 1 + K 3 + Km,[H+] (3.31) For the C02-MDEA-H20 system, Jou et al . [8] were only able to predict their experimental measurements sat is factori ly by assuming that Hco 2 , K 3 , K„ and K 5 depended on temperature. (They used Kent and Eisenberg's [84] empirical expressions to calculate these constants.) However, for the equilibrium constant governing the main amine reaction ( i . e . for Km,) they had to postulate a dependence on temperature, acid gas loading and total amine concentration. This modification is equivalent to including a l l system non-idealities in the expression for Km,. A method similar to that of Jou et a l . [8] was developed for this work. In particular, Kent and Eisenberg's [84]'expressions for Hco 2 , K 3 , K„ and K 5 were chosen and Km, was expressed as a function of temperature, [C0 2] and [MDEA]. Using [C0 2] is preferable to 7 since the former can be calculated directly from Pco2 and Hco 2 . Thus the equilibrium constant expression for Km, is : 44 Km, = exp{92.421453 - 1.49081486E-2 T + 40.847708/T -14.031652 x ln{T} - 9.8778738E-2 [C0 2] + 0.18275505 x ln{[C02]} + 3.9862282 x [MDEA] - 12.715421 x ln{[MDEA]}} (3.32) 3.3.3 SOLUBILITY IN BHEP The equi l ibr ia for the C0 2-BHEP-H 20 system are similar to those of the C02-MDEA-H20 system. Equation 3.25 needs to be replaced by: [BHEPH +] ^ [H\] + [BHEP] (3.33) and Equation 3.26 becomes: [H+][BHEP] Kb, = . (3.34) [BHEPH +] The mass and charge balance equations are: B = [BHEP] + [BHEPH*] (3.35) B 7 = [C0 2] + [HC0 3-] + [C0 3 --] (3.36) [BHEPH *] + [H+] = [OH"] + [HC0 3-] + 2[C0 3-"] (3.37) The following equations can then be derived to relate the C0 2 part ia l pressure to the acid gas loading at a given temperature and BHEP concentration: 45 Pco, = Hco 2 [H + ] 2 B7 - Pco 2 /Hco 2 K 3 (K 5 + [H +]) (3 .38) [H+] = Kb, [H+] Kb,+[H+]+B ((B 7 -Pco 2 /Hco 2 ) ( 2K5+[H+] K 5+[H+] ) + K, ) [H+] (3.39) The following empirical correlation for Kb, was obtained by f i t t ing the experimental data: Kb, = exp{-63.263099 - 2.8134775 E-2 T + 35.949793/T + 10.472318 ln{T} + 2.6761498 [C0 2] - 0.75472578 ln{[C02]} - 7.3049642 B) (3.40) 3.3.4 SOLUTION OF MODEL EQUATIONS Equations 3.15 to 3.17 together with Eqs. 3.24, 3.18 and 3.20 to 3.23 can be solved by using non-linear equation solvers to calculate the so lubi l i ty of carbon dioxide, 7, provided the DEA concentration, solution temperature and C0 2 part ia l pressure are given. For MDEA Eqs. 3.30 and 3.31 together with Eqs. 3.32 and 3.20 to 3.23 can be solved to calculate the so lubi l i ty of C0 2 in MDEA solutions. Unlike the procedure of Jou et a l . [8], the present model allows the so lubi l i ty calculations to be performed directly without an i n i t i a l estimate of so lubi l i ty for the calculation of Km,. Furthermore, i t is not restricted to any particular solution concentration within the range of 1.69 to 4.28 kmol 46 MDEA/m3. Similarly Eqs. 3.38 and 3.39 together with Eq. 3.40 and Eqs. 3.20 to 3.23 can be solved to calculate the C0 2 so lubi l i ty in aqueous BHEP solutions. A non linear equation solver routine, NDINVT, which is available at The University of B.C. Computing Centre Library [90], was used to solve Eqs. 3.15 to 3.17, 3.30 to 3.31, and 3.38 to 3.39. This routine is based on the generalized secant method. The two unknowns to be determined are [H*] and 7. I n i t i a l values of [H+] and 7 need to be provided for the iterative calculations, but, they need not be very close to the f inal value. Typical i n i t i a l values of [H*] and 7 are 10' 6 to 10~B and 1.5, respectively. No serious convergence problems were encountered. 47 3.4 RESULTS AND DISCUSSION Tables 3.1,3.2 and 3.3,3.4 summarize the C0 2 so lubi l i ty data for aqueous MDEA and BHEP solutions, respectively. The data are presented as a function of temperature, C0 2 part ia l pressure and MDEA or BHEP concentration. The present experimental method for determining the so lubi l i ty is somewhat simple and approximate. To check the accuracy of the present method, experiments were also performed with a solution containing 4.28 kmol MDEA/m3 at 100°C and various C0 2 part ia l pressures. As seen from F ig . 3.1, the present experimental so lubi l i t i es are s l ight ly lower (average 8%) than those reported by Jou et a l . [8]. The small discrepancies may be due to the inaccuracy in Dalton's law. The present solubi l i ty data as well as those of Jou et a l . [8] are compared with the model predictions in Figs. 3.2 to 3.7. Good agreement was found over wide ranges of temperature and C0 2 part ial pressure. In order to compare the so lubi l i ty of C0 2 in aqueous BHEP solutions with that in aqueous DEA solutions of similar concentrations, experiments were carried out with 5 wt% BHEP and 5 wt% DEA solutions at 100 °C. The results are presented in F i g . 3.8 and the solubi l i ty of C02 in BHEP is 48 seen to be less than that in DEA. Experiments were also carried out with 30 wt% DEA solutions and mixtures containing 25 wt% DEA and 5 wt% BHEP at 40°C. These experiments were performed to establish whether DEA degradation and the formation of BHEP reduce the C0 2 absorption capacity of the solution. The results are plotted in F ig . 3.9. It is clear, that formation of BHEP as a result of DEA degradation reduces the effective absorptive capacity of the solution. As described ear l i er , two sets of non-linear equations have to be solved in order to calculate the C0 2 so lubi l i ty in the C02-MDEA-H20 and C0 2-BHEP-H 20 systems. The f i r s t equation ( i . e . Eq. 3.15, 3.30 or 3.38) relates the C0 2 part ia l pressure to the acid gas loading and the hydrogen ion concentration, [H*], whereas the second equation ( i . e . Eq. 3.16, 3.31 or 3.39) gives the hydrogen ion concentration as a function of acid gas loading. If one could measure the hydrogen ion concentration direct ly and accurately, then the second equations would not be needed. Although pH electrodes capable of operating at high temperature and pressure are not readily available, they have been produced [91]. Such electrodes might therefore provide a convenient way of determining acid gas loading provided the Pco 2 , Hco 2 , temperature and the equilibrium constants are known. It appears worthwhile to explore this matter further in future. 3.1: S o l u b i l i t y of C 0 2 i n 4.28 M MDEA Temp. C02 p a r t i a l C02 s o l u b i l i t y C p r e s s u r e ( k P a ) mol C02/mol MDEA 100 4929.7 0.9504 3171.6 0.7919 2102.9 0.6427 1413.4 0.4973 896.32 0.3844 586.05 0.3138 275.79 0.2129 137.90 0.1385 140 4516.1 0.3372 3619.7 0.2876 2516.6 0.2261 1413.4 0.1568 723.95 0.1055 310.26 0.0660 137.90 0.0396 160 4136.8 0.2101 3033.7 0.1661 1516.8 0.1064 689.48 0.0640 275.79 0.0377 137.90 0.0251 180 4550.5 0.1635 3930.0 0.1475 3240.5 0.1266 2488.1 0.1041 1516.8 0.0731 792.9 0.0491 413.68 0.0347 137.90 0.0170 200 3558.3 0.1071 2733.4 0.0867 2033.9 0.06916 1344.5 0.05048 620.53 0.0311 344.73 0.0214 172.37 0.01344 T a b l e 3 . 2 : S o l u b i l i t y o f C 0 2 i n 1.69 M MDEA Temp. C02 p a r t i a l C02 s o l u b i l i t y C p r e s s u r e ( k P a ) mol C02/mol MDEA 100 4929.7 1.3044 3930.0 1.2329 2757.9 1.1198 1999.5 1.0164 1310.0 0.9042 758.42 0.6941 517.1 1 0.5226 275.79 0.3781 137.90 0.2738 140 4309.2 1.0030 2689.0 0.6786 1827.1 0.4843 1172.1 0.3549 930.79 0.3007 723.95 0.2606 448.16 0.2041 206.84 0.1406 103.42 0.0950 160 4274.7 0.7102 2964.7 0.4945 2068.4 0.3799 1516.8 0.3046 999.74 0.2362 689.48 0.1877 413.69 0.1470 137.90 0.0844 180 4136.8 0.5042 2895.8 0.3643 2068.4 0.2831 1378.9 0.2183 827.37 0.1581 551.58 0.1271 275.79 0.0885 137.90 0.0655 200 3585.3 0.3494 2482.1 0.2595 1792.6 0.2128 1103.2 0.1560 689.48 0.1178 413.68 0.0960 3.3: S o l u b i l i t y o f C 0 2 i n 0. 287 M BHEP Temp. C02 p a r t i a l C02 s o l u b i l i t y C p r e s s u r e ( k P a ) mol C02 /mol BHEP 40 3861.10 3.6169 3137.10 3.0065 2757.90 2.6692 2137.40 2.1157 1585.80 1.5917 1137.40 1.1783 620.53 0.6395 275.79 0.2919 137.90 0.1681 100 3999.00 1.8559 3550.80 1.6640 2689.00 1.2859 2033.90 0.9862 1413.40 0.7018 758.42 0.4132 344.74 0.1778 172.37 0.0905 140 3654.20 1.2345 2689.00 0.9592 2378.70 0.8406 1516.80 0.5475 896.32 0.3382 448.16 0.1760 172.37 0.0708 180 3999.00 1.0642 3068.20 0.8472 2620.00 0.7104 1689.20 0.4701 999.74 0.2726 517.11 0.1478 193.05 0.0633 3 . 4 : S o l u b i l i t y of C 0 2 i n 0.115 M BHEP Temp. C02 p a r t i a l C p r e s s u r e ( k P a ) C02 s o l u b i l i t y mol C02/mol BHEP 40 4067.90 8.2602 3447.40 6.9918 2428.10 5.1314 2206.30 4.5985 1792.60 3.7458 1378.90 2.8411 999.74 2.1240 482.63 1.1219 172.37 0.4700 100 3826.60 3.8898 3447.40 3.4904 3171.60 3.2168 2757.90 2.8506 2102.90 2.2171 1378.90 1.4748 896.32 0.9872 586.05 0.6855 206.84 0.2707 140 3516.30 2.7120 3102.60 2.4744 2551.10 2.0039 2137.40 1.6876 1792.60 1.4486 1378.90 1.0737 896.32 0.7457 482.63 0.4233 206.84 0.1910 180 3586.00 2.2270 3206.10 2.0337 2585.50 1.6520 1620.30 1.0722 655.00 0.4889 241.32 0.1229 53 1 1 1—I I I I I I ° • This work * A Jou et al. MODEL i — i — i i 111 i i i i i i i -t A D I i I i I i i 102 3 5 7 108 3 5 7 104 C02 PARTIAL PRESSURE (kPa) Figure 3.1: Comparison of the present C0 2 s o l u b i l i t y data in 4.28 M MDEA solutions with Jou et al . ' s data [8] and model predictions as function of C0 2 p a r t i a l pressure (temperature 100°C). 54 " F 1 1 I I I I I I I 1 1 1 | | | | L -Q o <L> l _ I I I I I 1 1 1 1 I I . 1 I 1 . 1 " " l O 8 3 5 7 1 0 3 3 5 7 1 0 4 C02 PARTIAL PRESSURE (kPa) Figure 3.2: Present experimental and predicted ( s o l i d l i n e s ) CO2 s o l u b i l i t i e s i n 4.28 M MDEA solutions as function of C0 8 p a r t i a l pressure and temperature. 55 O i—i—i i i i 11 1 1—I I I I Ll 1 I I I I I I IO2 3 5 7 10s 3 5 7 104 C02 PARTIAL PRESSURE (kPa) Figure 3.3: Present experimental and predicted ( s o l i d l i n e s ) C0 2 s o l u b i l i t i e s i n 1.69 M MDEA solutions as function of C0 2 p a r t i a l pressure and temperature. 5 6 2 b I HUH" Mlllllll lllllllll lllllllll lllllllll lllllllll IIIIIHj IT) - -<J CO -C02 PARTIAL PRESSURE (kPa) Figure 3.4: CO, solubility data in 4.28 M MDEA solutions reported by Jou et a l . [8] and present model predictions as function of COa partial pressure and temperature. 57 t- i 11nun 11mini i 11min i imini i imini i i i n <C co W i~ ! CO »-—< CO o o C/3 " T o I I IIIHti 11 mill 111 mill i i i "itnil i i mini i 11 mill n m 10~8 10"8 lO"1 10° 101 108 103 10* C02 PARTIAL PRESSURE (kPa) Figure 3.5: C0 2 s o l u b i l i t y data i n 2.00 M MDEA solutions reported by Jou et a l . [8] and present model predictions as function of C0 2 p a r t i a l pressure and temperature. 58 O y—i w ffi co PQ i—i o So c\2 ^  O 00 O O CO i o T I 1 I I I I I I T 1 I I I I U I I I I I I I I 108 3 5 7 103 3 5 7 10* C02 PARTIAL PRESSURE (kPa) Figure 3.6: Present experimental and predicted ( s o l i d l i n e s ) CO 2 s o l u b i l i t i e s i n 0.287 M BHEP solutions as function of C0 2 p a r t i a l pressure and temperature. 59 ID CO PL, W K PQ •—i o a \ o o w • — i O o ^ i—i PQ o CO o i—i—IIII i—i—IIII J i l i l i 11 I i I i I i i 102 3 5 7 108 3 5 7 104 C02 PARTIAL PRESSURE (kPa) Figure 3.7: Present experimental and predicted ( s o l i d l i n e s ) C0 2 s o l u b i l i t i e s i n 0.115 M BHEP solutions as function of C0 2 p a r t i a l pressure and temperature. 60 o CO CD _ XI o O CO 6° \ O o O too E -H o I-t—H o CO -1 o o 1 I 1 1 11 III 1 1 1 1 11 III - o o DEA 5 WT% 1 1 1 1 1 111 • _ A A BHEP 5 WT% — A -• A — A _ • A • A -• — CD — A A . 1 . 1 . l u l . 1 . 1 i l u l 1 1 1 1 l l l l 10' 3 5 710s 3 5 710» 3 5 7104 C02 PARTIAL PRESSURE (kPa) Figure 3.8: S o l u b i l i t y of C0 2 i n 5 wt% DEA and 5 wt% BHEP solutions as a function of C0 2 p a r t i a l pressure at 100°C. 61 CO d c2 CD j > O I D w 6 8 I D \ ° C\2 O O * o o >-1 o 13 ID o ° CO CVJ d 1 1 I 1 1 i 1 1 1 1 1 1 1 1 I 1 1 _ • n DEA 30 WT% — A DEA 25WT%+ BHEP 5 WT% _ — • ° A • A • — • D A • A A • A — A — A — i 1 i 1 . 1 . i 1 . 1 , 1 , 1 , , 102 3 5 7 10s 3 5 7 10' C02 PARTIAL PRESSURE (kPa) Figure 3.9: Solubi l i ty of C0 2 in 30 wt% DEA and 25 wt% DEA plus 5 wt% BHEP solutions as a function of C0 2 part ia l pressure at 40°C. Chapter 4 DEA DEGRADATION IN HEAT TRANSFER TUBES 4.1 EXPERIMENTAL EQUIPMENT AND PROCEDURE In the p r e v i o u s work on DEA degradation i n heat t r a n s f e r equipment [68], a heat exchanger tube of 3.175 mm OD and 2.032 mm ID was used. Since t h i s tube was c o n s i d e r e d to be too small i n diameter compared with i n d u s t r i a l heat exchanger tubes, i t was decided to perform s i m i l a r c a r e f u l l y c o n t r o l l e d DEA degradation experiments i n tubes of l a r g e r diameter. The equipment i s e s s e n t i a l l y the same as that d e s c r i b e d by Chakma [68] c o n s i s t i n g of a heat exchanger tube, a hi g h p r e s s u r e a u t o c l a v e , a pump, a water c o o l e r and a s s o c i a t e d i n s t r u m e n t a t i o n . A s i m p l i f i e d flowsheet of the equipment i s shown i n F i g . 4.1. Since the DEA degradation i n a s i n g l e pass through the heat t r a n s f e r tube was too sm a l l to r e s u l t i n s i g n i f i c a n t c o n c e n t r a t i o n changes, a r e c i r c u l a t i n g system had to be employed. A DEA s o l u t i o n s a t u r a t e d with C0 2 i n an autoclave ( c a p a c i t y 4 L, max. pressure 34.5 MPa) was t r a n s f e r r e d by means of a gear pump (Micropump, Concord, CT, Model 210-513) i n t o a c o i l e d , 316 s t a i n l e s s s t e e l heat t r a n s f e r tube (4.93 mm ID, 6.35 mm OD, 4.8 m lon g , 0.41 m t u r n i n g r a d i u s ) . The s o l u t i o n flow r a t e through the heat exchanger tube was a d j u s t e d by means of v a l v e s FCV1 and FCV2. 62 STIRRER© 1 SAFETY RELIEF FCVI HEAT TRANSFER TUBE ELECTRIC HEATER FC V 3 PUMP AUTOCLAVE C0 2 SUPPLY Figure 4.1: Flowsheet of the equipment used for DEA degradation in heat exchanger tubes. OJ 64 The flow rate was determined with a calibrated, custom built capi l lary flowmeter (1.75 mm ID, 3.17 mm OD, 50.8 mm long). The heat transfer tube was immersed in an insulated aluminum tank (0.7 m ID, 0.75m high) f i l l e d with approximately 150 L Shell Thermia O i l - C , which is a petroleum based heat transfer f l u i d . The tank was f i t ted with a 1/3 HP variable speed (100 - 1625 rpm) motor (Model NS-1 (EVS), Greey Mixing equipment, Toronto, ON) and s t irrer (0.914 m long, 12.7 mm d i a . , 304 stainless steel) attached to a single 0.1016 m diameter marine propeller type blade. A 10 kW over-the 1side immersion heater (Model KTLO-310-1, Chromalox Canada, Rexdale, ON) was used to heat the heat transfer f l u i d . A simple vapour recovery system consisting of a vacuum pump and water condenser was provided to reduce entry of heat transfer f lu id into the laboratory atmosphere. After leaving the heat transfer tube, the DEA solution was cooled in a water cooler (12.2 m long, 10.9 mm ID, 12.7 mm OD, 316 stainless steel c o i l immersed in a 0.51 m ID, 0.91 m high PVC tank) and returned to the autoclave. Flu id temperatures were measured with J-type, iron-constantan thermocouples and displayed on a d ig i ta l indicator (Trendicator 410 A, Doric) . 65 The temperature of the heat transfer f luid was maintained at the desired value with a proportional controller (Omega Inc. , Stamford, CT, Model 49). The system was designed for unattended operation and was capable of functioning without shut-down for several days. A pressure re l ie f valve and e lectr ica l power shut-off were incorporated for safety reasons. In addition, the entire equipment was placed into an aluminum trough capable of containing a l l l iquids in case a leak developed during unattended operation. Prior to conducting the experiments, the equipment was throughly rinsed with d i s t i l l e d water and flushed with C0 2 to expel any residual contaminants such as previously formed degradation compounds and oxygen. DEA solution samples (approx. 20 mL) were taken every 24 h, or more frequently i f necessary. The samples were then analysed by gas chromatography. 4.2 MATHEMATICAL MODEL Chakma and Meisen [66] developed a simple mathematical model to predict DEA degradation in heat transfer tubes. Their model neglected temperature variations in the radial direction of the heat transfer tube. Since radial temperature variation may be significant in industrial heat 66 exchangers, i t is presently incorporated into their model. The suggestion of von Karman [92] was followed by dividing the solution inside the heat transfer tube into a laminar sublayer, a buffer layer and a turbulent core. The resultant model may be described as follows: The experimental apparatus shown in F i g . 4.1 is represented by the simplified flowsheet depicted in F ig . 4.2. The latter consists essentially of the heat transfer tube in which the DEA solution is heated and simultaneously degraded. At the tube outlet, the solution temperature is rapidly lowered thereby effectively stopping the reactions. The autoclave (see F ig . 4.1) is represented by a wel l -st irred tank (see F ig . 4.2) and no reactions take place in i t . The solution then returns to the inlet of the heat transfer tube. The simplified flowsheet therefore consists essentially of a tubular reactor, a wel l -st irred tank and connecting piping. 67 T. HEAT TRANSFER TUBE T • 1 «o [DEA], FT VA]F [DEA]. [DEA]P AUTOCLAVE Figure 4.2: S i m p l i f i e d flowsheet of the equipment used for DEA degradation i n heat transfer tubes. 68 4.2.1 MODEL WITHOUT RADIAL TEMPERATURE VARIATIONS For the purpose of mathematical modelling, the tubular reactor was notionally divided into a number of segments (typically 48) of short, equal lengths. Each segment was treated as a small exchanger in which the f luid properties could be taken as constant. Since the temperature (T n) of the outside heat transfer f lu id was kept constant, i t is easy to show that the outlet f luid bulk temperature of a segment is given by: - UffD-x T 0 = T , - ( T h - T . ) exp{ i - } ( 4 . D n n i w c ^ where T^ and x denote the bulk temperature of the DEA solution at the inlet of the segment and the segment length, respectively. It may be noted that Eq. 4.1 is based on the assumptions that the DEA solution moves in plug flow and that the heats of reaction are small compared with the sensible heat transfer. Figure 4.3 shows an idealized temperature profi le in the v i c in i ty of the wall of the tubular reactor. The resistance to heat transfer arises in the tube wall as well as in the two f luid films located on either side of the wall . It follows from simple heat balances that: 69 Figure 4.3: Schematic diagram of an i d e a l i z e d temperature p r o f i l e across the metal tube w a l l . 70 T h~ T _ T h~ Two _ Two~ Twi _ T wi- T (1/U) ( l / h 0 ) ( D i / D 0 ) ( x ^ X D j / D ^ ) ( l /hj) (4.2) Hence T h " Two = ( l / h ° } ( V Do) T ) u or, Two = T h " ( T h ~ T ) < 1/ ho) (Dj/Do) U (4.3) and V Twi - <V km> ^ i ^ l m V ( V T> U or, Twi = T « o " ( T h " T> (*mAn.J ( Di/ Dlm> u ( 4 - 4 ) The outside and inside wall temperatures can therefore be found from Eqs. 4.3 and 4.4, respectively, provided U, h Q , h^, km and the physical dimensions of the tube are known. However, as shown below, U, h Q and h^ depend on T W Q and T w ^ . Consequently, an iterative procedure had to be developed to find T w o and T w i . The overall heat transfer coefficient U for the coiled heat exchanger tube was calculated from [93]: U = Ui(^ + 3 . 5 ^ / 0 ^ ) (4.5) where is the overall heat transfer coefficient for a straight tube. Furthermore, ( l /Uj) = ( l /hj) + ( l /h 0 ) (Dj/Do) + (Di ln{D 0 /D i }/(2 km) 71 (4.6) The inside [94] and the outside [95] heat transfer coefficients were calculated from: hi = 0.023 (k/Dj) ( R e c ) 0 - 8 ( P r c ) 1 / 3 ( m /M w ) 0 ' 1 4 (4.7) h Q = 0.17 (k h /D 0 )(Re 0 ) 0 - 6 7 ( P r o ) ° - 3 7 ( D b / D t ) 0 • 1 ( d 0 / D f c ) 0 • 5 K/*hw>m (4.8) where, m= 0.714 uh~°'2] The f luid properties were determined at the mean inside and outside film temperatures for each tube segment. Semi-empirical expressions developed by Chakma and Meisen [96] were used to calculate the f lu id properties as a function of temperature and solution concentration. By setting the outlet f lu id bulk temperature of one segment equal to the inlet f lu id bulk temperature of the next segment and repeating the calculations, the f luid temperature at the outlet of the entire heat exchanger tube could be found. 72 4.2.2 MODEL WITH RADIAL TEMPERATURE VARIATIONS As in the previous case the heat transfer tube is notionally divided into segments of short and equal lengths and the f lu id is assumed to be well mixed at the exit of each segment. If one can also assume that the properties of the f lu id in individual segments are also constant, the following momentum and energy equations may be written for steady state conditions: = 0 (4.9) 9u 9u 1 3 { r ( v + e ) 9u } 1 9P u — + v„ — — — — — + — — 9x r 9r r 9r m 9r P 9x 9T 9T 1 9 {r(a+eh) 9T } u — + v„ — — — — — = 0 9x r 9r r 9r n 9r (4.10) For fu l ly developed flow the radial velocity component, v f = 0 and also 9u/9x = 0. Therefore, the momentum and energy equations become: 1 9 9u 1 9P {rU+e m ) — } = (4.11) r 9r m 9r p 9x 1 9 9T 9T {r(a+e.) — } = u — (4.12) r 9r n 9r 9x These two equations must be solved in order to find the temperature variation in the radial direct ion. 73 As mentioned i n the i n t r o d u c t o r y s e c t i o n , the f l u i d i s d i v i d e d i n t o three r e g i o n s . M a r t i n e l l i [97] s o l v e d Eqs. 4.11 and 4.12 f o r the three d i f f e r e n t regions by making s i m p l i f y i n g assumptions and obtained the f o l l o w i n g equations which d e s c r i b e the temperature d i s t r i b u t i o n : Laminar sublayer'. T w-T £Pr(y/y 1) T w - T c £Pr + In (1 + 5£Pr) + 0.5 In(Re/60)/(f/2) Buffer I ayer: T w-T £Pr + ln{1+£Pr(y/y 1 -1)} T -TV. £Pr + In (1 + 5$Pr) + 0.5 In (Re/60)/(f/2) Turbulent core: T w-T $Pr + ln{l+5$Pr} + 0.5 ln ( R e / 6 0 ) / ( f / 2 ) ( y / R ) T w - T c " £Pr + In (1 + 5£Pr) + 0.5 In(Re/60)/(f/2) (4.13) (4.14) (4.15) The f o l l o w i n g equation g i v e s the temperature drop between the w a l l and the ce n t r e of the tube: T = T - (5.0 q u ) U C _ p /( — ^ ) ) U P r + ln(l+5$Pr) + c w w y p Re f 0.5 In — / - ) (4.16) 60 2 74 The thickness of the laminar sublayer from the wall is defined as y + = 5, where y + is the dimensionless distance parameter defined as: y+= /( I* ) y / „ ( 4 . 1 7 ) P Therefore the thickness of the laminar sublayer, y^, is given by: y1 = 5v/ V( — ) (4.18) P The distance of the edge of the buffer layer from the wall is defined as y + = 30; Hence y b = 30i>/ •( I* ) (4.19) P Equations 4.13 to 4.16 can be solved provided q w , T w , Pr, Re, f, £ and the solution properties are known. £ was assumed to be unity. Only q w and the fr ic t ion factor, f, are unknown. The fr ic t ion factor can be calculated using the Colebrook formula [98]: e 4.67 -4.0 log( — + ) + 2.28 Di Rev/f (4.20) 75 The solution of Eq. 14.20 requires an i n i t i a l estimate of the fr ic t ion factor followed by a t r i a l and error solution. The i n i t i a l estimate of the fr ic t ion factor was obtained from the following equation: f = 0.04 ( R e ) - 0 ' 1 6 (4.21) For the present experimental equipment, the surface roughness factor "e" was found to be 0.012 mm from pressure drop measurements of water flowing through a 0.5 m long section of the heat exchanger tube. The heat transfer rate through the wall q w , . can be calculated as follows: q w = TT Di x h- ( T w i - T x ) (4.22) 4.3 DEA DEGRADATION KINETICS Chakma and Meisen's [66] modification of Kennard and Meisen's [58] model for DEA degradation was used in the present work. As described in Chapter 2, they used the total carbon dioxide loading in solution, [C0 2 T ] , which includes chemically absorbed and physically dissolved C 0 2 . 76 Since major DEA degradation products are formed from DEA carbamate, which contains chemically absorbed C 0 2 , this approach appears reasonable. However, from mass transfer considerations, C0 2 must f i r s t diffuse into the DEA solution as free C0 2 before it can react with DEA to form DEA carbamate and subsequently degradation compounds. Therefore, i t was decided to use free C0 2 , denoted by [C0 2] rather than [C0 2 T 1 to describe the DEA degradation reactions. Since [C02] is related directly to the C0 2 part ia l pressure via the Henry's law constant, this approach should describe the effect of C0 2 part ia l pressure on DEA degradation better than the previous approach. Furthermore, in the previous model [66] the C0 2 loading was assumed to be constant throughout the heat exchanger tube and the poss ib i l i ty of C0 2 breakout resulting from heating was not taken into account. In the present work, this effect was accounted for as follows. The vapour pressure of the aqueous DEA solution was calculated by assuming ideal solution behaviour as suggested by Maddox [7]: P soln = PDEAXDEA + P H 2 0 ( 1 ~ XDEA ) (4.23) The vapour pressures of DEA and H 20 (expressed in terms of kPa) were calculated from Antoine type equations [7]: PDEA = ° - 1 3 3 3 2 exp{8.12303 - 2315.46/T} (4.24) P H 2 0 = ° - 1 3 3 3 2 exp{7.96681 - 1668.21/T} (4.25) The C0 2 part ia l pressure and the concentration of free C0 2 77 in solution is then given by: Pco2 = P T 0 T - P s o l n (4.26) [C0 2] = Pco 2/Hco 2 (4.27) The new rate constant expressions, based on "free C0 2" in solution, are: k,* = 3.27 x 1011exp{-104546/RT} (4.28) k 2* = I.08 x I01*exp{-125375/RT} (4.29) k 3* = 4.90 x 1013exp{-129803/RT} (4.30) If diffusional effects are negligible, the concentration changes are given by: d[DEA] i t d[HEOD] dt = -(k 1*+k 2*)[DEA][C0 2] (4.31) = k,*[DEA][C0 2] (4.32) d[THEED] * * = k 2 [DEA][C02] - k 3 [THEED] (4.33) dt d[BHEP] dt = k 3 *[THEED] (4.34) The above di f ferent ia l equations (Eqs. 4.31 - 4.34) can be integrated analytical ly provided the solution temperature and C0 2 concentration are assumed to be constant. In addition, the i n i t i a l concentrations (indicated by subscript 0 ) must be known. 78 [DEA] = [DEA]0 exp{-(k,*+ k 2*)[C0 2]t} (4.35) k,* [ HEOD ] = [ HEOD ] 0 + [ DEA ] 0 w ( 1 -ki + k 2 exp{-(k,*+ k 2*)[C0 2]t}) (4.36) k 2 *[C0 2 ][DEA] 0 , , * , * , [THEED] = — , -— (exp{-(k1 + k 2 ) x k3 - (k, + k 2 )[C0 2] [C0 2]t}-exp{-k 3*t}) + [THEED]0exp{-k3t} (4.37) k 2 *k 3 *[C0 2 ][DEA] 0 exp{-(k,*+ k 2*)[C0 2]t} L BHEP J = x x — ( x x k 3 - (k, + k 2 *)[C0 2 ] (k, + k 2 )[C0 2] exp{-k 3*t) k 2 *[DEA] 0 * + ) + * * - + [THEED] o (1 ~ exp{-k3 t}) k 3 (k, + k2 ) + [BHEP]0 (4.38) 4.4 REACTIONS IN HEAT TRANSFER TUBE As in the case of heat transfer, the chemical changes in the heat transfer tube were modelled by dividing the reactor into a number (typically 48) segments of equal length. The residence time in each segment is given by: r r = TT D ^ x/4QF (4.39) Each segment was further divided into three regions, v i z . a laminar sublayer, a buffer layer and a turbulent core. Degradation rates and concentrations of different 79 components were c a l c u l a t e d s e p a r a t e l y f o r each of t h e s e r e g i o n s a t t h e i r r e s p e c t i v e mean tem p e r a t u r e s and c o n c e n t r a t i o n s . The average c o n c e n t r a t i o n i n each segment was c a l c u l a t e d by assuming t h a t d e g r a d a t i o n r e a c t i o n s t a k e p l a c e i n each r e g i o n and t h a t the c o n t e n t s of a l l t h r e e r e g i o n s a r e mixed t h o r o u g h l y a t the e x i t of the segment. The average DEA c o n c e n t r a t i o n i n a segment i s c a l c u l a t e d from: The above e q u a t i o n s r e p r e s e n t s a major s i m p l i f i c a t i o n of the a c t u a l s i t u a t i o n but l e d t o a s t a b l e c o m p u t a t i o n a l scheme and good agreement w i t h e x p e r i m e n t a l measurements. S i m i l a r e q u a t i o n s can a l s o be w r i t t e n f o r BHEP, HEOD and THEED. The volume of each r e g i o n can be c a l c u l a t e d as f o l l o w s : [ D E A ] i V T = [ D E A ] i f l V i f + f ° E A h , b V i , b + t D E A ^ i , t V i , t ( 4 . 4 0 ) v i , l = x {R 2 - ( R 2 - y x 2 ) } ( 4 . 4 1 ) i , b = 7r x {(R - Y l ) 2 - (R - y b ) 2 ) } ( 1 4 . 4 2 ) v i , t - » x (R - y b > 2 ( 4 . 4 3 ) 80 After time r r , the f lu id is considered to be moved into the next downstream segment and the calculation is repeated. The dynamic behaviour of the tubular reactor was therefore modelled by regarding i t as a number of small, well s t irred batch reactors. 4.5 AUTOCLAVE The material balance for DEA across the autoclave, which was modelled as a wel l -st irred tank,in which no reaction occur, is given by: d[DEA]• V T — — i- = Qp[DEA]F - Qp [ DEA ] ^ (4.44) The concentration changes for a single pass through the tubular reactor are very small, i . e . of the order of 0.0001 mol/L. In addition, the quantity of DEA inside the tubular reactor is only about 0.6% of the total l iquid inventory inside the autoclave. Consequently, the rates of overall concentration changes are very small; i . e . of the order of 0.005 mol/h or 1.4 x 10"6 mol/sec. It is therefore reasonable to assume that, for a short period of time, (e.g. a few minutes) the outlet concentration from the heat transfer tube, [DEA]p, remains constant. This also implies that the transportation lag is negligible. Under these conditions Eq. 4.44 can be solved: 81 [DEA]i = [DEA]F - ([DEA] p - [DEA]0) e x p { - t / T r > T } (4.45) where [DEA]0 and r r T denote the DEA concentration in the tank at t=0 and the residence time in the tank, respectively. Equations similar to Eq. 4.45 may be written for BHEP, HEOD and THEED. The time elements chosen for solving Eq. 4.45 were the same as those selected for the heat transfer tube. 4.6 PIPING The piping leading into and out of the reactor was modelled by assuming the f lu id to be in plug flow and neglecting axial mixing. In addition, transportation lag between the various pieces of equipment in the heat transfer loop was neglected. 4.7 MODEL PREDICTIONS A computer program describing the model is l i s ted in Appendix C. The present as well as the previous model predictions and experimental results (obtained under various conditions of temperature, C0 2 part ia l pressure, solution concentration and flow rate) may be compared by examining Tables 4.1 to 4.6. The present model in general predicts the experimental concentrations of a l l the compounds better 82 than the previous model [66], The present model predicts DEA concentrations better than the previous model at high temperatures (see Tables 4.1 to 4.4). At such temperatures the DEA concentrations predicted by the previous model are higher than the experimental results. This was so in spite of the fact that the tube wall temperature rather than the bulk solution temperature was used to calculate the rate constants. At lower temperatures, the DEA concentration predictions of the two models are similar (see Tables 4.5 to 4.6). Both models predict higher BHEP concentrations than the experimental results. However, the predictions of the present model are closer to the experimental values. The present model s l ight ly overpredicts HEOD concentration whereas the previous model tends to underpredict them. The THEED concentrations predicted by both the models are similar and are in good agreement with the experimental data. Typical comparisons of model predictions and previously obtained experimental results using a thinner tube (2.03 mm ID) [66] are shown in Table 4.7. Both models predict 83 similar concentrations of DEA, HEOD and THEED. The present model overpredicts BHEP concentrations. It may therefore be concluded that the radial temperature variations give rise to significant concentration differences. This effect would be expected to increase with the diameter of the heat transfer tube. Unfortunately i t was not possible to examine this aspect using industrial size tubes due to limitations of the experimental equipment. 84 Table 4.1: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inlet temp.: 60°C; Outlet temp.: 205°C; Heating F l u i d temp.: 225°C; Flow rate: 0.011 L/s; C0 2 p a r t i a l pressure: 5.5 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.81 2.79 2.83 0.02 0.04 0.05 48.0 2.62 2.59 2.67 0.07 0.10 0.12 72.0 2.43 2.40 2.51 0.15 0.16 0.20 96.0 2.25 2.23 2.37 0.20 0.22 0.28 120.0 2.10 2.07 2.23 0.25 0.28 0.35 144.0 1.90 1 .92 2.10 0.29 0.33 0.42 168.0 1.80 1 .78 1.98 0.35 0.36 0.49 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0. 0 0.00 0.00 0.00 0.00 0.00 0.00 24. 0 0.05 0.07 0.06 0.08 0.07 0.07 48. 0 0.10 0.14 0.11 0.12 0.09 0.09 72. 0 0.16 0.20 0.16 0.13 0.09 0.09 96. 0 0.21 0.26 0.20 0.13 0.08 0.09 120. 0 0.27 0.31 0.25 0.12 0.08 0.08 144. 0 0.35 0.36 0.29 0.10 0.07 0.08 168. 0 0.37 0.41 0.33 0.10 0.07 0.07 85 Table 4.2: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inlet temp.: 60°C; Outlet temp.: 205°C; Heating F l u i d temp.: 225°C; Flow rate: 0.011 L/s; C0 2 p a r t i a l pressure: 4.14 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.85 2.84 2.87 0.02 0.03 0.04 48.0 2.70 2.68 2.74 0.05 0.08 0.10 72.0 2.55 2.54 2.62 0.11 0.13 0.16 96.0 2.42 2.40 2.50 0.15 0.18 0.23 120.0 2.30 2.27 2.39 0.20 0.23 0.29 144.0 2.15 2.14 2.28 0.25 0.28 0.34 168.0 2.06 2.03 2.18 0.30 0.32 0.40 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24.0 0.02 0.05 0.04 0.05 0.05 0.05 48.0 0.08 0.11 0.08 0.05 0.07 0.07 72.0 0.10 0.15 0.12 0.08 0.07 0.07 96.0 0.15 0.20 0.16 0.10 0.06 0.07 120.0 0.20 0.24 0.19 0.11 0.06 0.07 144.0 0.25 0.28 0.23 0.10 0.06 0.06 168.0 0.28 0.32 0.26 0.08 0.06 0.06 B6 Table 4.3: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inlet temp.: 60°C; Outlet temp.: 205°C; Heating F l u i d temp.: 225°C; Flow rate: 0.011 L/s; C0 2 p a r t i a l pressure: 2.76 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0. 00 24.0 2.92 2.89 2.91 0.01 0.02 0. 04 48.0 2.80 2.78 2.82 0.05 0.06 0. 08 72.0 2.70 2.68 2.73 0.08 0.10 0. 14 96.0 2.61 2.58 2.65 0.11 0.14 0. 19 120.0 2.50 2.49 2.57 0.15 0.17 0. 25 144.0 2.42 2.40 2.49 0.21 0.24 0. 30 168.0 2.25 2.22 2.41 0.25 0.28 0. 34 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0. 00 0.00 0.00 0.00 24.0 0.02 0.04 0. 03 0.03 0.04 0.03 48.0 0.04 0.07 0. 06 0.05 0.05 0.04 72.0 0.08 0.11 0. 08 0.07 0.05 0.05 96.0 0.12 0.14 0. 11 0.08 0.05 0.05 120.0 0.14 0.17 0. 13 0.06 0.04 0.05 144.0 0.20 0.23 0. 16 0.05 0.04 0.05 168.0 0.22 0.26 0. 18 0.05 0.04 0.04 87 Table 4.4: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inlet temp.: 60°C; Outlet temp.: 190°C; Heating F l u i d temp.: 225°C; Flow rate: 0.015 L/s; C0 2 p a r t i a l pressure: 4.14 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.95 2.93 2.94 0.01 0.02 0^04 48.0 2.87 2.86 2.87 0.05 0.06 0.10 72.0 2.81 2.79 2.81 0.08 0.10 0.16 96.0 2.73 2.72 2.75 0.12 0.15 0.23 120.0 2.65 2.65 2.69 0.19 0.21 0.31 144.0 2.60 2.59 2.64 0.23 0.26 0.38 168.0 2.55 2.52 2.58 0.27 0.31 0.46 TIME CONCENTRATION (mol/L) (h) HEOD . THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24.0 0.02 0.03 0.02 0.01 0.03 0.03 48.0 0.04 0.05 0.04 0.06 0.05 0.04 72.0 0.06 0.06 0.06 0.08 0.06 0.06 96.0 0.09 0.10 0.08 0.10 0.07 0.06 120.0 0.10 0.13 0.09 0.08 0.07 0.07 144.0 0.11 0.15 0.11 0.07 0.07 0.07 168.0 0.12 0.17 0.13 0.06 0.07 0.07 88 Table 4.5: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inlet temp.: 60°C; Outlet temp.: 180°C; Heating F l u i d temp.: 225°C; Flow rate: 0.018 L/s; C0 2 p a r t i a l pressure: 4.14 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.97 2.96 2.96 0.00 0.02 0.05 48.0 2.94 2.92 2.92 0.03 0.05 0.10 72.0 2.90 2.89 2.86 0.07 0.09 0.15 96.0 2.85 2.84 2.84 0.11 0.14 0.22 120.0 2.80 2.80 2.80 0.17 0.19 0.29 144.0 2.78 2.76 2.76 0.22 0.25 0.36 168.0 2.74 2.72 2.72 0.26 0.30 0.42 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24.0 0.01 0.02 0.01 0.01 0.02 0.02 48.0 0.02 0.03 0.02 0.02 0.04 0.03 72.0 0.03 0.05 0.03 0.04 0.05 0.04 96.0 0.05 0.06 0.05 0.05 0.06 0.05 120.0 0.06 0.08 0.06 0.08 0.06 0.05 144.0 0.08 0.09 0.07 0.07 0.07 0.06 168.0 0.10 0.11 0.08 0.06 0.07 0.06 89 Table 4.6: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 4.93 mm; Inl e t temp.: 60°C; Outlet temp.: 185°C; Heating F l u i d temp.: 200°C; Flow rate: 0.011 L/s; C0 2 p a r t i a l pressure: 4.14 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.96 2.94 2.94 0.01 0.02 0.03 48.0 2.90 2.88 2.89 0.03 0.05 0.08 72.0 2.83 2.82 2.83 0.07 0.10 0.14 96.0 2.78 2.76 2.78 0.12 0.15 0.20 120.0 2.71 2.70 2.73 0.18 0.20 0.26 144.0 2.65 2.65 2.68 0.24 0.26 0.33 168.0 2.60 2.59 2.63 0.28 0.31 0.40 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24.0 0.01 0.02 0.02 0.01 0.03 0.02 48.0 0.02 0.05 0.04 0.03 0.05 0.04 72.0 0.05 0.07 0.05 0.06 0.05 0.05 96.0 0.08 0.09 0.07 0.08 0.07 0.06 120.0 0.10 0.11 0.09 0.06 0.07 0.07 144.0 0.11 0.13 0.10 0.06 0.07 0.07 168.0 0.11 0.15 0.12 0.05 0.07 0.07 90 Table 4.7: Comparison of experimentally determined and calculated concentrations. ( I n i t i a l DEA concentration: 3 mol/L; Tube ID: 2.03 mm; Inlet temp.: 60°C; Outlet temp.: 195°C; Heating F l u i d temp.: 250°C; Flow rate: 0.011 L/s; C0 2 p a r t i a l pressure: 4.14 MPa) TIME CONCENTRATION (mol/L) (h) DEA BHEP EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 3.00 3.00 3.00 0.00 0.00 0.00 24.0 2.89 2.90 2.88 0.00 0.01 0.01 48.0 2.75 2.77 2.76 0.00 0.02 0.02 72.0 2.68 2.69 2.64 0.00 0.03 0.02 96.0 2.57 2.59 2.53 0.00 0.04 0.02 120.0 2.46 2.45 2.42 0.00 0.06 0.03 144.0 2.35 2.36 2.32 0.00 0.06 0.03 168.0 2.25 2.23 2.22 0.02 0.07 0.03 192.0 2.13 2.14 2.13 0.02 0.08 0.03 TIME CONCENTRATION (mol/L) (h) HEOD THEED EXP MODEL CALC. EXP MODEL CALC. NEW OLD NEW OLD 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24 .0 0.05 0.08 0 .09 0.00 0.01 0.02 48 .0 0.14 0.15 0.17 0.00 0.02 0.03 72.0 0.20 0.22 0.25 0.00 0.04 0.05 96.0 0.28 0.30 0.32 0.05 0.04 0.06 120.0 0.35 0.37 0.40 0 .05 0.06 0.08 144.0 0.44 0.45 0.47 0.07 0.07 0.09 168.0 0.52 0.53 0.53 0.08 0.08 0.10 192.0 0.58 0.57 0.60 0.10 0.09 0.11 Chapter 5 MDEA STUDIES To study MDEA degradation, carefully controlled MDEA degradation experiments were performed under different conditions of C0 2 part ia l pressure, solution temperature and solution concentration. A high pressure autoclave, previously used by Kennard [57] for DEA degradation, was used as the reactor. The progress of the reactions was followed by withdrawing and analysing samples periodical ly . Degradation compounds could then be identified by using various analytical techniques (see section 5.4 and Appendix B). 5.1 EXPERIMENTAL EQUIPMENT AND PROCEDURE 5.1.1 AUTOCLAVE A 600 mL stainless steel autoclave (Model 4560, Parr Instrument Co. , Moline, IL) was used as the reactor. The autoclave was rated up to a maximum temperature and pressure of 350°C and 13.8 MPa, respectively. 91 92 The autoclave was equipped with the following accessories: (see F ig . 5.1) 1. A close f i t t i n g , quartz fabric heating mantle in an insulated aluminum housing. 2. A J-type thermocouple in a 316 stainless steel well placed inside the autoclave for measuring the reactor temperature. 3. An automatic on/off temperature controller (Model 4831EB, Parr Instrument Co. , Moline, IL) capable of holding the temperature to within ± 0.5°C of the set value. The output from the temperature controller is monitored by a d ig i ta l temperature indicator (Model 410A, Doric) and recorded on a s tr ip chart recorder (Model 840, Corning) 4. A 316 stainless steel internal cooling c o i l . 5. A variable speed s t i rrer (0-600 rpm) driven by a variable speed drive assembly. 6. A 0-2000 psi bourdon type pressure gauge, accurate to ± 5 ps i . 7. A safety rupture disc . 8. Two inlet and outlet ports f i t ted with valves. The autoclave could also be f i t ted with a pyrex l iner , so that the reactants do not come into contact with the metal surface of the autoclave. 93 F i g u r e 5.1: S k e t c h of t h e a u t o c l a v e used f o r MDEA d e g r a d a t i o n s t u d i e s . 94 The main problem w i t h the a u t o c l a v e was gas leakage around the p a c k i n g g land of the s t i r r e r s h a f t . The p a c k i n g g l a n d c o n s i s t s of 4 g l a s s f i l l e d t e f l o n p a c k i n g cones wi th 3 t e f l o n O - r i n g s p l a c e d between s u c c e s s i v e cones . I t was s e l f - s e a l i n g , u t i l i z i n g p r e s s u r e from w i t h i n the a u t o c l a v e to f o r c e the p a c k i n g cones a g a i n s t the r o t a t i n g s h a f t . The cones and the O - r i n g s of the p a c k i n g g l a n d wore out p e r i o d i c a l l y and had to be r e p l a c e d . Repacking the p a c k i n g g l a n d was a s imple o p e r a t i o n and c o u l d be done i n about 15 m i n . 5 . 1 .2 SOLUTION PREPARATION Aqueous MDEA s o l u t i o n s of the d e s i r e d c o n c e n t r a t i o n were p r e p a r e d s i m p l y by m i x i n g d i s t i l l e d water w i t h 99%+ pure MDEA ( s u p p l i e d by A l d r i c h C h e m i c a l s , Mi lwaukee , WI) . The p u r i t y of the MDEA was c o n f i r m e d by gas chromatography. 5 .1 .3 LOADING THE AUTOCLAVE B e f o r e l o a d i n g the a u t o c l a v e , i t s t emperature was r a i s e d t o the d e s i r e d l e v e l . The aqueous MDEA s o l u t i o n was then i n j e c t e d from a l o a d i n g c y l i n d e r (see F i g . 5 . 2 ) . The l o a d i n g c y l i n d e r c o n s i s t e d of a m o d i f i e d 500 mL s t a i n l e s s s t e e l p r e s s u r e c y l i n d e r . The c y l i n d e r was f i r s t purged e i t h e r w i t h C 0 2 or N 2 depending on the run b e i n g conducted i n o r d e r to remove any oxygen which might r e a c t w i t h MDEA. Figure 5.2: Sketch of the autoclave loading system. vo 96 I t was then f i l l e d with about 250 mL of aqueous MDEA s o l u t i o n and connected t o the aut o c l a v e i n j e c t i o n p o r t at one end and to the C0 2 or N 2 c y l i n d e r at the other end. The o u t l e t p r essure of the C0 2 or N 2 pressure r e g u l a t o r was set to the d e s i r e d o p e r a t i n g p r e s s u r e of the a u t o c l a v e . The contents were then d i s c h a r g e d i n t o the a u t o c l a v e simply by opening the a u t o c l a v e i n l e t p ort v a l v e and the C0 2 or N 2 p r e s s u r e r e g u l a t o r o u t l e t v a l v e . 5.1.4 SAMPLING L i q u i d phase samples were obtained by means of a 5 mL c o i l e d sampling tube f i t t e d with i n l e t and o u t l e t v a l v e s . One end of the sampling tube was connected to the l i q u i d sampling port of the a u t o c l a v e . The a u t o c l a v e sampling p o r t v a l v e , f o l l o w e d by the sampling tube i n l e t v a l v e , were opened thus f o r c i n g a l i q u i d sample i n t o the tube under r e a c t o r p r e s s u r e . The sampling tube o u t l e t v a l v e was then opened to bleed o f f a l i t t l e sample. A l l the v a l v e s were then c l o s e d and the sampling tube d i s c o n n e c t e d from the a u t o c l a v e and p l a c e d i n water f o r r a p i d c o o l i n g . The sample was then removed from the tube and s t o r e d i n screw cap g l a s s v i a l s f o r a n a l y s i s . The sampling tube was then thoroughly r i n s e d with d i s t i l l e d water and d r i e d by pa s s i n g a i r f o r subsequent use. 97 Vapour phase samples were only c o l l e c t e d o c c a s i o n a l l y . T h i s was done simply by t a k i n g a sample with a s y r i n g e from the gas sampling p o r t . 5.1.5 EXPERIMENTAL PROCEDURE FOR DEGRADATION EXPERIMENTS In a t y p i c a l degradation experiment, an aqueous MDEA s o l u t i o n was r e a c t e d with C0 2 i n the auto c l a v e at the d e s i r e d temperature and pr e s s u r e f o r a s p e c i f i c p e r i o d . Samples were withdrawn and anal y s e d at r e g u l a r i n t e r v a l s . In a l l experiments the f o l l o w i n g g e n e r a l procedure was f o l l o w e d : 1. The aut o c l a v e was f i r s t s e a l e d . 2. I t was purged with e i t h e r C0 2 or N 2. 3. The s t i r r e r was s t a r t e d and the au t o c l a v e heated to the d e s i r e d temperature. .4. The l o a d i n g c y l i n d e r was connected to the auto c l a v e i n l e t port a t one end and to the C0 2/N 2 c y l i n d e r at the other end. 5. The au t o c l a v e i n l e t p o r t v a l v e and the C0 2/N 2 c y l i n d e r r e g u l a t o r o u t l e t v a l v e were opened thus f o r c i n g the aqueous MDEA s o l u t i o n i n t o the a u t o c l a v e . 6. The aut o c l a v e i n l e t p o r t v a l v e and the C0 2/N 2 c y l i n d e r r e g u l a t o r v a l v e were l e f t open f o r about 30 min. T h i s compensated f o r the C0 2 a b s o r p t i o n by the MDEA s o l u t i o n and maintained a constant p r e s s u r e . Although a b s o r p t i o n of C0 2 i s an exothermic r e a c t i o n , the temperature i n s i d e 98 the autoclave did not change noticebly. This is probably due to fact that the entering C0 2 was cold and compensated for the heat of absorption. 7. After 30 min the autoclave inlet port valve and the C 0 2 / N 2 cylinder regulator valve were closed and the loading cylinder disconnected from the autoclave. 8. The loading cylinder was thoroughly rinsed with d i s t i l l e d water and dried with air for subsequent use. 9. Liquid samples were removed at regular intervals during the run using the coiled sampling tube. After transferring a sample to the glass v i a l , the sampling tube was throughly rinsed with d i s t i l l e d water and dried with a i r . 10. After the completion of a run, the heating element of the autoclave was switched off and the autoclave removed. Water was passed through the cooling c o i l to cool the autoclave and i ts contents to room temperature. 11. When the autoclave reached room temperature, the pressure was reduced to atmospheric. The autoclave was opened, the contents removed, throughly rinsed with d i s t i l l e d water and wiped dry. Most of the runs were conducted with 250 mL of solution to ensure that removal of several samples did not have a significant effect on the reactant volume and that excess C0 2 was available for the experiment. However, for longer runs, when i t was necessary to remove more than 12 samples, 99 350 mL of solution were used. The duration of the experiments depended on the time required for significant degradation to take place. 5.2 PRELIMINARY EXPERIMENTS In order to determine whether or not MDEA degrades with C 0 2 , 250 mL of a 50 wt% (4.28 mol/L) aqueous MDEA solution were transferred into the autoclave which was kept at a temperature of 200°C, under a C0 2 part ia l pressure of 2.59 MPa. Samples were withdrawn at regular intervals. Over a period of 54 h, the MDEA concentration f e l l from 4.28 mol/L to 1.21 mol/L. A chromatogram of the part ia l ly degraded MDEA solution at the end of 54 h is shown in F ig . 5.3. Another run was performed at 140°C also using a C0 2 part ia l pressure of 2.59 MPa. Under these conditions, MDEA was also found to degrade, but the change in MDEA concentration was much lower than in the previous run. At the end of 316 h, the MDEA concentration had fallen to 3.15 mol/L. The chromatogram of a sample taken after 316 h is shown in F ig . 5.4. A comparison of Figs. 5.3 and 5.4 shows that the degradation products formed during the two experiments are s imilar. 100 5.2.1 THERMAL DEGRADATION Once i t was established that MDEA degrades with C0 2 at elevated temperatures, one experiment was performed at 200°C and 4.24 MPa using N 2 as the blanket gas to determine whether the degradation was due to thermal breakdown. Thermal degradation was found to be very slow since after 240 h, the MDEA concentration had merely declined from 4.28 mol/L to 4.1 mol/L. F ig . 5.5 shows the MDEA concentration as functions of time and blanket gas. These results indicate that the thermal decomposition of MDEA in the presence of nitrogen is v ir tual ly negligible, at least up to 240 h at 200°C. Figure 5.3: Chromatogram of a p a r t i a l l y degraded MDEA solution at the end of 54 h. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.26 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) Figure 5.4: Chromatogram of a p a r t i a l l y degraded MDEA solution at the end of 316 h. (Temperature: 140°C; I n i t i a l MDEA concentration: 4.28 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) 102 . CM o LO O gco 55 O < E-& W O o o < o l O CO e o t—1 i> l O CO -~l 1 1 1 I 1 1 1 T~ • NITROGEN A CARBON DIOXIDE 1 1 1—3 V - S J I I ! I I L I I 1 0.0 40.0 80.0 120.0 160.0 200.0 240.0 TIME (h) Figure 5.5: MDEA concentration as functions of time and blanket gas. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L; Blanket gas p a r t i a l pressure: 2.59 MPa) 1 03 5.2.2 JUSTIFICATION FOR THE USE OF ELEVATED TEMPERATURES Degradation was found to be low at temperatures below 120°C. In gas treating units the maximum average solution temperatures are generally kept below 120°C. However, temperatures well above this l imit had to be employed in this study in order to speed up the degradation reactions so that experiments could be carried out in a matter of days rather than months. The use of higher temperatures, can be just i f ied for the following reasons: 1. In industrial units, temperatures in the immediate v ic in i ty of heat transfer surfaces can be considerably higher than 120°C. 2. Degradation products formed at elevated temperatures are similar to those formed at lower temperatures, suggesting a similar reaction mechanism. 3. Thermal degradation is negligible at temperatures up to 200°C for the typical duration (50 h) of the present experiments. 5.2.3 EFFECT OF STIRRER SPEED AND REACTANT VOLUME St irrer speeds ranging from 20 to 200 rpm and reactant volumes ranging from 100 to 400 mL were used to determine whether mass transfer of C0 2 from the vapour phase into the solution affected degradation. As seen from Table 5.1, no significant effects on the degradation were observed. 1 04 5.2.4 REPRODUCIBILITY In order to check reproducibility of the experiments several runs were repeated over a one year period and the results were found to agree within ± 5%. Results of two such runs performed under similar conditions are given in Table 5.2. The reproducibil ity of determining the concentrations of major degradation products was very good. However, when the samples were not analysed right away, the more reactive and volat i le degradation compounds, notably ethylene oxide, could no longer be detected. Since the concentration of these compounds in the degraded solution is very small, this does not affect the concentration of MDEA and other major degradation products. 105 Table 5.1: Comparison of MDEA degradation experiments conducted with d i f f e r e n t s t i r r e r speed and reactant volume. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L? C0 2 p a r t i a l pressure: 2.59 MPa) MDEA concentration (mol/L) Time (h) 100 rpm 20 rpm 100 rpm 250 mL 250 mL 100 mL 0 4.28 2 4.04 4 3.80 6 3.56 6 3.35 12 2.96 20 2.40 24 2.22 28 2.02 32 1.84 40 1.49 42 1.42 46 1.30 50 1.22 54 1.14 4.28 4.28 4.03 4.04 3.81 3.83 3.54 3.55 3.32 3.33 2.95 2.94 2.38 2.40 2.21 2.23 2.03 2.00 1.82 1.81 1.50 1.48 1.43 1.41 1.31 1.29 1.20 1.20 1.14 1.13 106 Table 5.2: Comparison of MDEA degradation experiments conducted a year apart.(Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 part ia l pressure: 2.59 MPa) MDEA concentration (mol/L) Time (h) Original Repeat 0 4.28 4.28 2 4.04 4.02 4 3.80 3.82 6 3.56 3.55 6 3.35 3.31 12 2.96 2.94 20 2.40 2.38 24 2.22 2.20 28 2.02 2.00 32 1 .84 1 .81 40 1 .49 1 .52 42 1 .42 1 .40 46 1 .30 1 .29 50 1 .22 1.21 54 1.14 1.15 107 5.3 EXPERIMENTAL CONDITIONS Since the solution temperature, i n i t i a l solution concentration and C 0 2 part ia l pressure are the important process operating variables, an experimental program was devised to study the effect of these variables on MDEA degradation. The experiments were designed to provide sufficient data to develop a simple kinetic model describing MDEA degradation. Table 5.3 summarizes the experiments carried out for this purpose. 108 T a b l e 5 . 3 : Summary of e x p e r i m e n t a l c o n d i t i o n s used for the MDEA d e g r a d a t i o n e x p e r i m e n t s . A . C 0 2 p a r t i a l p r e s s u r e = 2585 kPa MDEA cone . Temperature °C (mo l /L) 100 120 140 160 180 200 210 220 230 2.00 x x x x x x x 3.00 x 3.40 x x x x x x x 4.00 x 4.28 x x x x x x x x x 5.00 x 6.00 x B . I n i t i a l MDEA c o n c e n t r a t i o n = 4.28 m o l / L T e m p . r ° C C 0 2 p a r t i a l p r e s s u r e , kPa 345 517 1206 1896 3965 4654 140 X X X X X X 160 X X X X X X 180 X X X X X X 200 X X X X X X 220 X X X X X X 109 5.4 IDENTIFICATION OF MDEA DEGRADATION COMPOUNDS Once i t was established that MDEA degrades in the presence of C0 2 , identif ication of the degradation compounds was attempted. When a 4.28 M MDEA solution was degraded for 144 h under 2.59 MPa C0 2 part ia l pressure at 180°C, 22 peaks (see F ig . 5.6) were detected by the gas chromatographic technique described in Appendix B. Except for the MDEA peak (peak 9), a l l other peaks were i n i t i a l l y unknown. In order to identify these unknown compounds, a combined gas chromatograph and mass spectrometer (GC/MS) was used. 5.4.1 IDENTIFICATION USING GC/MS In GC/MS the gas chromatograph vapourizes and separates the compounds while the mass spectrometer produces ions by bombarding the neutral vapour molecules with a beam of electrons. The energy required to form molecular ions from organic molecules is typical ly of the order of 10 eV. Additional energy is provided to break the bonds of the molecular ion. The various ions thus generated are accelerated through a strong electromagnetic f i e l d , forced into a c ircular path and separated according to their mass to charge rat io . 9 110 3 I 4 ' I 1 T 8 I 10 1 13 11 12 14 15 16 Figure 5.6: Chromatogram of a p a r t i a l l y degraded MDEA solution of 4.28 M i n i t i a l concentration, degraded at 180°C under a C0 2 p a r t i a l pressure of 2.59 MPa for 144 h. 111 The ions normally carry only one e lec tr ica l charge. The movement of these charges is equivalent to an electric current which is detected by an electrometer. The output from the electrometer is recorded as ion current versus mass number and represents the mass spectrogram. Each peak in the mass spectrum is due to a different ion. Since molecules fragment in the same manner under similar conditions, the mass spectrum provides a characteristic "thumbprint" for each compound. The process described above is called electron impact (EI) mass spectrometry. A compound may be identified by matching its mass spectrum against that of a known compound. Mass spectra may also provide information on the molecular mass of the compounds, provided the molecular ion is present in abundance. The knowledge of molecular mass and fragmentation pattern of molecular ions can also give considerable insight into molecular stucture. A microprocessor based Gas Chromatograph/Mass Spectrometer (Model 5985B, Hewlett Packerd, Palo Alta , CA) was used to produce the mass spectra of the compounds in the degraded MDEA sample. The EPA/NIH mass spectral data base [99] was stored in the memory disk of the microprocessor. Peaks 1 to 7 were identified to be methanol, ethylene oxide (EO), trimethylamine(TMA), N,N-dimethylethanamine, 1,2 1 12 ethanediol or ethylene glycol (EG), 2-dimethylamino ethanol (DMAE) and 4-methyl morpholine, respectively, by matching their mass spectra with the l ibrary spectra. The mass spectra obtained from the degraded samples and the corresponding l ibrary spectra are shown in Figs. 5.7 to 9.13. Peak 8 was identified to be 1,4 dimethyl piperazine(DMP) by matching i ts mass spectrum given in the Eight Peak Index of Mass Spectra [100]. The mass spectrum of this compound is shown in F i g . 5.14. The MDEA (peak 9) mass spectrum is shown in F ig . 5.15. Mass spectra of peaks 13,14 and 15, which are shown in Figs. 5.16 to 5.18, were suspected to be those of N,N-bis-(2-hydroxyethyl)-piperazine (BHEP), 3-(hydroxyethyl) 2-oxazolidone(HEOD), and N,N,N-tris-(hydroxyethyl) ethylenediamine (THEED) respectively. This supposition arose by comparing their mass spectra with the ones reported by Kennard [57]. The mass spectrum of peak 12 is shown in F ig . 5.19. By noting the fragmentation pattern i t was suspected to be either N,N-bis-(hydroxyethyl) glycine (BHG) or triethanolamine (TEA). For positive identif ication, these compounds were either purchased or synthesized in pure form (see Appendix A) and their standard mass spectra produced. 100-80-60-40-20-0 11 n i 11 i i i | • i II | i SAMPLE SPECTRUM PEAR #1 10 20 30 i I »» I I | i i i i ! i i • • i i i i i i i i i I • [ i i i i | • i i i ! 40 50 60 70 80 90 r [ 69.4'* 'I " II" « 1 LFRN 3002 SPECT .7107 M e t h a n o l ( 8 C I 9 C I ) 15 MUI» 32 CH40 Figure 5.7: Comparison of EI mass spectrum of peak #1 with l i b r a r y spectrum of methanol. 100 8 0 -6 0 -4 0 -2 0 - ..1 SAMPLE SPECTRUM PEAR #2 10 20 i . . . . . . . 30 40 50 60 i i i 1 **• * i i 70 80 90 r 65.3'< « 1 LFRN 3002 S P E C T . 9 7 8 0 O x i r a n e (9C1) 38 M N 44 C2H40 1 0 0 -8 0 -6 0 -LIBRARY SPECTRUM 4 0 -2 0 - 1 • , 1 0 - 1 1 1 1 • i • 111 10 20 i 11 1 1 1 30 1 1 1 11 111 40 1 1 1 1 1 1 1 i • 11 50 . . . . . . . . 60 1 1 1 1 1 1 1 1 1 1 1 1 70 80 90 Figure 5.8: Comparison of EI mass spectrum of peak #2 with l i b r a r y spectrum of ethylene oxide, EO. 100-80-60 40-20-0 -^n i i | i 11 i | i i 11 | i i i i | I I I I | 1  i i | i 1  I | I I 11 | i i i 11 I I i I | 11 I I | i n i | i i 11 j i i i 11 I i i i [ 11 i i | i 11 i | i i 11 | i 10 20 30 40 50 60 70 80 90 SAMPLE SPECTRUM PEAK #3 r L 62.7'< • l .11 • 1 LFRN 3002 SPECT 102 MU= 59 C3H9N .7053 Methanamine, N,N-dimethyl- (9CI) 1001 80 60 40-20-0 - ^ i r r T i i 11 11 i T r r | i T - r i | i i ( i 10 20 I 11 I 11 I I I I I I 30 40 59 LIBRARY SPECTRUM i • i • 11 • 111111111 60 70 I | II I I | HI I | • I M | I 80 90 Figure 5.9: Comparison of EI mass spectrum of peak #3 with l i b r a r y spectrum of trimethyl amine, TMA. 100-80-60-40-20-SAMPLE SPECTRUM PEAK #4 1 l [ > l 1 ll ill 11111111. i . 11» 111 I I 111 I I • • i • • • • 11 • • i 10 20 38 40 50 60 70 80 90 r L 11 .6'<C i h i . « 1 LFRN 3002 SPECT 269 MW= 73 C4H11N .9734 Ethanamine, N,N-dimethy1- (9CI) 100-80-60- LIBRARY SPECTRUM 40-20- . 1 I || 0- 1 1 1 • 11 i • i i 10 20 I I 30 1 1 1 11 i 40 50 i 11 111 i 68 1111111 i 70 • 1111111 • • 11 80 • 111 • 111 90 Figure 5.10: Comparison of EI mass spectrum of peak #4 with l i b r a r y spectrum of N rN-dimethyl ethanamine. 100-80- SAMPLE SPECTRUM 60-48- PEAK #5 20- 1 , 0- i i • i • i 20 40 60 80 100 120 140 160 180 , i r — i — 200 I—i— r—r-220 r 1 1 1 ' - ~ » 1 LFRN 3002 SPECT 128 HU= 62 C2H602 .8386 1,2-Ethanediol (9C1) 100-88-60-40-20-0 V I —1—r-y 20 LIBRARY SPECTRUM 40 —r-~ 60 •>—I—r—r 100 1—'—I—' 140 80 120 160 180 200 220 Figure 5.11: Comparison of EI mass spectrum of peak #5 with l i b r a r y spectrum of 1,2 ethanediol, EG. 1 66 n 86 66 H 46 26 6 SAMPLE SPECTRUM PEAK #6 -.—.—.—• ill,.... . , 1 ll. i - 1.— _ >6 46 6© 89 100 120 r 14 .Q'< l ll I » 1 LFRH 3662 SPECT 632 MW= 89 C4H11N0 ,9769 E t h a n o l , 2-(d iiii* thy 1 ami no) - (8CI9CI) . . I I . 100 -i 80 -60 - LIBRARY SPECTRUM 40 -26 -1 | 6 - • i • i • i 26 40 i 60 i i • i 80 ..... , ,. , .... 100 120 Figure 5.12: Comparison of EI mass spectrum of peak #6 with l ibrary spectrum of DMAE. 100-1 80-60-40-20-0-20 SAMPLE SPECTRUM PEAK #7 40 60 i "• 80 100 120 r i L 19.2''. • i t . . H I I.. « 1 LFRN 3002 SPECT 1218 MW= 101 C5H11N0 .9765 Morpholine, 4-methyl- (8CI9CI) 100-80-60-40-20-0-LIBRARY SPECTRUM i " 1 — i • i '"' 1 f—r 20 40 68 - i — i — T — i r — i i •—r— 80 100 120 Figure 5.13: Comparison of EI mass spectrum of peak #7 with l i b r a r y spectrum of 4-methyl morpholine. 100 80 60 40 20 H 0 28 lb 30 43 56 40 I" 50 it 60 71 SAMPLE SPECTRUM PEAK #8 85 Il I" 78 80 • i •1 90 99 100 1 8 . 7 114 • • I ' " 110 Figure 5.14: EI mass spectrum of peak #8 i d e n t i f i e d as 1,4 dimethyl piperazine, DMP. 100-1 8 0 -6 0 -40 2 0 -0 -31 44 58 A 78 l 88 40 1—c 60 ''•-1 30 •31 . 8 SAMPLE SPECTRUM PEAR #9 100 119 132 147 189 2 1 7 100 1 1 120 140 160 130 2 0 0 Figure 5.15: EI mass spectrum of peak #9 i d e n t i f i e d as MDEA. ro 1001 80 60 40-20-0 31 42 40 56 I 70 60 82 lllllll, 100 f 80 113 SAMPLE SPECTRUM PEAK #13 143 14.9 125 I. • ll i - i — * 156 173 183 -r—t-100 120 140 160 180 >00 Figure 5.16: EI mass spectrum of peak #13 i d e n t i f i e d as BHEP. to to 1100-80-60 40-20-0 J J29 42 40 56 70 60 88 100 119 131 i • "I1" • SAMPLE SPECTRUM PEAK #14 80 100 120 140 160 180 1-17.7 200 Figure 5.17: EI mass spectrum of peak #14 i d e n t i f i e d as HEOD. 100 T 80 60 H 40 20 0 100 80 -60 -40 -20 -0 -40 SAMPLE SPECTRUM PEAK #15 I 18 70 60 88 I till at too I J _ 130 i l l i l i l 80 IOC 120 143 140 156 174 i 187 1 60 180 199 207 200 :17 24 3 24 0 Figure 5.18: E I m a s s spectrum of peak #15 identif ied as THEED. ro |100-80-60-40 20-j 0-1 29 42 40 56 74 88 60 80 118 100 r SAMPLE SPECTRUM PEAK #12 128 143 157 170 ' i - r 100 120 -I""1 140 169 188 13.3 207 >00 Figure 5.19: EI mass spectrum of peak #12. 126 The mass spectrum corresponding to peak 12 is similar to the BHG and TEA spectra as can be seen from Figs. 5.20 and 5.21. Therefore, identification was not possible based on the mass spectra. However, peak 12 had a retention time in the GC column of 20.1 to 20.3 min which is similar to that of TEA. By contrast BHG had a retention time of 22.1 to 22.2 min. To provide further evidence that peak 12 is due to TEA, TEA was added to a part ia l ly degraded MDEA sample. The chromatograms of the sample before and after TEA addition are shown in F i g . 5.22. As can be seen, the addition of TEA resulted in the area increase of peak 12. When a similar experiment was performed with BHG, a new peak resulted. Therefore i t was concluded that peak 12 is produced by TEA. As stated earl ier molecules have characteristic fragmentation patterns which are helpful in the elucidation of structures. The fragmentation mechanism of the molecules of the major complex compounds identified so far are shown in Figs. 5.23 to 5.29. The fragmentation reactions explain the occurence of various peaks in the mass spectrograms. Among the major degradation compounds, peak 10 whose EI mass spectrum is given in F i g . 9.30, s t i l l needed to be identif ied. Although the fragmentation pattern suggested the compound to be some kind of a piperazine, no satisfactory match with a l ibrary mass spectrum was found. 100 -30 60 ^ 40 20 0 29 42 40 I 56 74 88 68 88 100 100 118 I I I 128 4U. 120 SAMPLE SPECTRUM PEAK #12 143 157 178 148 168 130 13.3 20; 200 100 - j 8 0 -6 0 -4 0 -2 0 -31 . 0 - 4U TEA SPECTRUM 4 5 5 6 LL 74 4 0 l 1— 6 0 + ~T-~ 80 88 1 1 0 0 100 118 132 120 Figure 5.20: Comparison of EI mass spectra of peak #12 and TEA. 29 42 40 I 56 74 88 60 80 100 118 111 128 SAMPLE SPECTRUM PEAK #12 14? 157 170 13.3 100 120 •• "I 140 T 207 160 180 200 Figure 5.21: Comparison of EI mass spectra of peak #12 and BHG. td : Chromatogram of a degraded MDEA solution (a) before and (b) after TEA addition. 130 CH2 - CH2 + e I I OH OH I CH2 - CH2 m/e=62 I I 0 + H OH - CH2-OH loss, CH2 0 +H m/e=31 Figure 5.23: Fragmentation mechanism of the EG molecule. CH-CH, CH-N-CH 2-CH 2-OH + e" CH-N +CH 2-CH 2-OH m/e=89 - CH2-OH loss, CH: CH-N+= CH2 m/e=58 Figure 5.24: Fragmentation mechanism of the DMAE molecule, 131 Figure 5.25: Fragmentation mechanism of the DMP molecule 1 32 CH 3-N \ CH 2-CH 2-OH CH 3-N* I CH 2-CH 2-OH CH 2-CH 2-OH CH 2-CH 2-OH + e m/e=119 - CH2OH loss, CH,-N + CH-CH 2-CH 2-OH m/e=88 - C2H«,OH loss, CH 3-N-CH 2 loss, CH3-N*=CH2 m/e=43 CH 2 ™"H 2 C \ / 0 + m/e=45 1 H 1 CH 2 -H 2 C m/e=44 Figure 5.26: Fragmentation mechanism of the MDEA molecule. 133 0 II HO-CH 2-CH 2-N 0 + e + I I CH2 CH2 0 * II / C \ HO-CH 2-CH 2-N + 0 I I CH 2 ——"™~" CH 2 m/e=131 - CH2-OH loss, 0 II CH2=N+ 0 I I CH 2 CH 2 m/e=100 - C0 2 loss, CH2=NT CH 2 ™" CH 2 m/e=56 Figure 5.27: Fragmentation mechanism of the HEOD molecule. 134 HO-CH 2-CH 2-N CH 2 - CH 2 ,N -CH 2 -CH 2 -OH + e' H O - C H 2 - C H 2 - N ; CH 2 ~~ CH 2 1 , CH 2 CH 2 , *N*CH2-CH2-OH m/e=l74 CH 2 CH 2 - CH2-OH loss, a) C H 2 = N ; CH 2 - CH 2 . CH 2 — CH2 N +CH 2-CH 2-OH m/e=143 or, - H 20 loss, b) CH2=CH-N' CH 2 — CH 2 N*-CH 2-CH 2-OH m/e=156 CH 2 ~~ CH 2 Figure 5.28: Fragmentation mechanism of the BHEP molecule. 135 After -CH 2-OH loss from BHEP: a) ^ ^ C H 2 - C H 2 < ^ CH 2=N <^^ ^ ^ N + CH 2-CH 2-OH m/e=143 CH 2 ~" CH 2 CH2=N / CH-CH: CH 2=N+-CH 3 CH2 \ H N + -CH,-CH 2 -OH i / CH CH2 I CH 2 =CH-N+ CH 2 -CH 2-OH m/e=43 m/e=100 - H loss, - CH 3-0 loss, CH*-N-CH3 CH2 I CH2=CH-N+-CH3 m/e=42 m/e=70 Figure 5.28: Fragmentation mechanism of the BHEP molecule, After H,0 loss from BHEP: 136 CH, - CH: b) CH2=CH-N 'N + -CH 2 -CH 2 -OH \ ^ CH 2 ~ CH 2 CH2=CH-N CH: / CH2=CH-N-CH3 CH2 - CH CH2 H N + -CH 2 -CH 2 -OH \ CH2 I CH 2 =CH-N + CH 2 -CH 2"OH m/e=156 m/e=56 m/e=100 - CH30 loss, CH2 I CH2=CH-N+-CH3 m/e=70 Figure 5.28: Fragmentation mechanism of the BHEP moleclue, 137 HO-CjH, HO-C2H, HO-C2H, HO-C2H,' ; N - C H 2 - C H 2 - N C2H,-OH \ + e H *N*CH2-CH2-N HO-C2H4 V ^ N + =CH2 HO-C 2H,^ m/e=118 C2H,-OH m/e=l89 H / C H 2 = N * \ C2H,-OH H m/e=7l - H 20 loss -H20 loss CH2=CH HO-C2H, m/e100 y - H 20 loss , CH2=CH ^^N*=CH 2 CH2=CH m/e=82 CH=CH2 N*=CH2 CH2=N* H m/e=56 Figure 5.29: Fragmentation mechanism of the THEED molecule. 1 0 0 - | I 70 8 0 - 42 SAMPLE SPECTRUM 6 0 -PEAK #10 4 0 -56 113 2 0 - 29 di 1 if 1 88 9 8 126 1 , 144 0 - llll, •, .1-. 1—r** 1—i—•—i—>—i—>—i—i—r—i—i—i—r—'-40 60 80 100 120 140 160 180 200 Figure 5.30:. EI Mass spectrum of peak #10 139 Based on F ig . 5.30 the molecular peak was suspected to be 126 mu. However, no plausible piperazine compound with a molar mass of 126 could be formulated. In EI mass spectra i t is possible for molecular ions to be absent. This happens when the c r i t i c a l energy required for fragmentation of the molecular ion is extremely low. In this case fragmentation is easy and quick so that no molecular ions survive before impact on the current detector. It was therefore decided to determine molecular masses in a different manner. Chemical ionization mass spectrometry (CIMS) was found to be an excellent technique for this purpose. 5.4.2 MOLECULAR MASS DETERMINATION BY CIMS In chemical ionization mass spectroscopy, abundant pseudomolecular ions can be generated by reacting the sample molecules with ions of a suitable reagent gas. Pseudomolecular ions may be produced by various reactions including proton transfer, hydrogen abstraction, electron attachment and cluster ion formation [101]. The proton transfer reaction is most commonly used in positive chemical ionization mass spectrometry. Thus from the mass to charge ratios of the protonated ions as well as other pseudomolecular ions, the molecular mass of the compound can be determined. For oxygen and nitrogen bearing compounds, 140 either methane or isobutane are frequently used as reagent gases [65]. Chemical ionization mass spectra of peak 10 and some other major compounds were obtained using methane as the reagent gas. The methane CI mass spectra of MDEA, BHEP and HEOD are compared with their respective EI mass spectra in Figs. 5.31 to 5.33. As can be seen, the peaks of the protonated molecular ion (M + H + ) , are very dist inct in the methane CI spectra compared with the molecular ion peaks in the EI spectra. Similarly, the methane CI and EI mass spectra of peak 10 are compared in F ig . 5.34. Although the molecular ion peak appears to be 126 from the EI spectrum, the methane CI spectrum shows a protonated molecular ion peak of 145 mu thus indicating a molecular mass of 144. Careful inspection of the EI spectrum also shows a very small peak at 144 mu which was previously disregarded in favour of the more dist inct peak at 126 mu. This clearly shows that molecular mass determination from EI spectra may sometimes be erroneous. 1 0 0 -8 0 -6 0 -40 20 -0 -120 • 4 0 . 8 102 M+H+ MDEA METHANE CI SPECTRUM 83 61 i—'—i 76 •1 !• — f - —4- '• , .'I 130 ' • •• i 1 4 9 160 • ' • • ! • 175 —i " ' , — i—>—i 60 80 100 120 140 160 180 Figure 5.31: Comparison of EI and methane CI mass spectra of MDEA. 100-1 80-60-40-20-0 -31 42 40 56 I 70 60 "I'lll, 82 188 r 88 113 125 143 BHEP EI SPECTRUM 156 I 173 183 - r 100 120 140 160 130 r l 4 . 9 280 F i g u r e 5.32: Comparison of EI and methane CI mass s p e c t r a of BHEP 109 80 -\ 60 40 20 0 29 42 40 56 70 t — i 60 38 80 160 119 131 HEOD EI SPECTRUM r l 7 . 7 100 120 140 160 ' I ' I 180 200 100 80 H 60 40 H 20 0 J 72 88 •I— 80 100 114 132 M+H+ r 3 3 .6 HEOD METHANE CI SPECTRUM 160 144 172 . i . . . 181 191 100 120 140 160 180 200 Figure 5 .33 : Comparison of EI and methane CI mass spectra of HEOD. 100 -I 80 6 0 - | 40 20 H 0 40 I 70 60 80 100 120 140 160 r22.3 42 PEAK #10 EI SPECTRUM 56 113 29 M r-4 . 88 9 8 III , . . . | . . l . t .,11,1.1, i—fJ 126 u 144 1 i —'—i—•—i—•—i—'—i—•- i •—i • i—»-180 200 100-1 8 8 -6 0 -40 2 0 -0 J 70 145 M+H • 4 0 . 7 127 88 102 I — ' — i r 88 113 PEAK #10 METHANE CI SPECTRUM 173 157 185 100 120 140 160 188 200 Figure 5 .34: Comparison of EI and methane CI mass spectra of peak #10. 145 5.4.3 HYDROXYL GROUP NUMBER DETERMINATION Many of the compounds identified so far contain hydroxyl groups. A selective hydroxyl group s i ly la t ion technique described by Hsu and Kim [65] and Hsu [102] was used to determine the number of hydroxyl groups present in a compound for further confirmation of a compound's identity. Since the presence of water may interfere with the s i ly la t ion process, water was removed from a l l degraded MDEA samples. The samples were saturated with potassium carbonate and extracted with isopropyl alcohol. The alcohol was later separated simply by vapourization. Selective s i ly la t ion results in the addition of s i l y l groups to the hydroxyl groups of the compounds in the sample. This, increases the mass to charge ratio of the pseudomolecular ions in a CI spectrum in proportion to the number of hydroxyl groups present. Thus by comparing the mass to charge ratios of the pseudomolecular ions of CI spectra obtained before and after s i ly la t ion one can calculate the number of hydroxyl groups present. Two s i ly lat ion reagents were tested. The f i r s t one was a mixture of hexamethyldisilazane (HMDS), trimethylchlorosilane (TMCS) and anhydrous pyridine used by Hsu and Kim [65]. A mixture of 1 mL HMDS, 0.5 mL TMCS and 2 1 46 mL pyridine were added to 5 mL of the previously dehydrated sample in a 10 mL screw-cap v i a l . The v i a l was then shaken vigorously for about 5 min and then allowed to stand at least 10 min at room temperature to ensure complete s i l y la t i on . However, i t was found that in some cases s i ly lat ion of hydroxyl and amino groups occurred. The second reagent, as suggested by Hsu [102], was N-trimethylsi lyl imidazole (TSIM). 5 mL of TSIM were added to 5 mL of the sample in a 20 mL screw-cap v i a l . The mixture was then reacted following the same procedure described above. TSIM was found to s i ly late the hydroxyl groups only while leaving amino groups unreacted. Consequently, TSIM is the preferred reagent for selective hydroxyl group s i ly lat ion in this study. In a typical s i ly lat ion reaction, the active hydrogen is replaced by the s i l y l group, which in this case is the trimethyl s i l y l group -Si(CH 3 ) or TMS. For example MDEA forms the following TMS derivative upon s i ly la t ion with TSIM: TSIM C H a - N - t C z H f l O H ) 2 +• C H 3 - N - ( C 2 H » 0 - S i - ( C H 3 ) 3 ) 2 ( 5 . 1 ) m/e(M + H +) = 120 m/e(M + H +) = 264 Methane CI spectra of MDEA before and after s i ly la t ion are 147 shown in F ig . 5.35. The formula mass of the TMS group is 73 and i t replaces one active hydrogen atom. Therefore, the addition of each TMS group increases the mass to charge ratio of the pseudomolecular ion by 72. As seen from F i g . 5.35, the m/e of the pseudomolecular ions of unsilylated and s i ly lated MDEA are 120 and 264 respectively. The TMS group replaces two active hydrogen atoms in the two hydroxyl groups of MDEA. Therefore, the m/e of the pseudomolecular ion increases by 72 x 2 =144, and becomes 120 + 144 = 264. The number of hydroxyl groups can simply be calculated from the difference in the mass to charge ratios of the pseudomolecular ions before and after s i ly la t ion as follows: Number of OH groups = {m/e(M+H+,silylated - m/e(M+H+,unsilylated)}/72. (5.2) In the case of MDEA, Number of OH groups = (264 - 120)/72 = 2. 100-80-60-40-28-0 X 61 —r~ 60 88 76 102 120 M * H * M - CH.-N CiH,-OH C,H,-OH 130 148 -1 160 175 80 100 120 140 -«—r 160 130 43.8 a) before 100-88-60-40-20-160 248 174 191 218 232 i • I" 160 180 i 1— i — | — i —T 1 | I—• 200 228 240 M - - C H , M - CH. -N >64 C , H , - 0 - S l - ( C H , ) , C , H , - 0 - S l - ( C H , ) , M * H 292 304 -.—i - i — i— i — i— i - — " — i * '" " i—•—i—'—i—'— i 260 280 300 320 340 30.1 b) after Figure 5 .35 : Methane CI mass spectra of MDEA (a) before and (b) after s i l y l a t i o n with TSIM. CD 149 The methane CI spectra of BHEP, TEA and peak 10 before and after s i ly la t ion are shown in Figs. 5.36 to 5.38, respectively. The results of the hydroxyl group calculation for MDEA, BHEP, TEA and peak 10 are presented in Table 5.4. Table 5.4: Results of the hydroxyl group calculation. Compound M + H* M + H + Number of unsilylated s i ly lated OH groups mu mu MDEA 120 264 2 TEA 150 366 3 BHEP 175 319 2 Peak 10 145 217 1 The val id i ty of this method is demonstrated by the accurate hydroxyl group determination of known compounds such as MDEA, TEA and BHEP. Peak 10 having a molecular weight of 144 carries one OH group. Based on this information and i ts fragmentation pattern, which suggested the presence of a piperazine ring, i t was identif ied to be 1-(2-hydroxyethyl)-4-methyl piperazine (HMP). As a further check, HMP was synthesized in the laboratory (see Appendix A). Its retention time in the GC column and i ts mass spectrum were determined and compared with those of peak 10. 1 0 0 -8 0 -6 0 -4 0 -2 0 -175 M * H * • 3 6 . 2 M - H O - C , H , - N M-C,H, -OH 157 88 100 113 127 143 0 '-| i|il..|...|..li|i.l.|....|iiint.. 100 120 140 160 203 189 215 >30 247 180 200 -i—•—r 220 1 — i — 240 a) before 100 80 60 4 0 . 2 0 -0-"r 3Q3 M - ' C H , C , H . X N - ( C H , ) , - S l - 0 - C , H , - M ^ M - C H . - O - S i - J C H , ) , C,H , 215 201 • 1" ' ' 200 229 243 — T — i " i 1 • — r * 1 220 248 T ' I ' 260 319 M * H 333 347 359 T—< 1 1 —I ' 1' " ' " I 280 300 320 T ^ 1 — I — 1 340 ->—1 360 • 2 6 . 8 b) after Figure 5.36: Methane CI mass spectra of BHEP (a) before and (b) after s i l y l a t i o n with TSIM. o 1 0 0 -8 0 " 60 4 0 ' 20-1 150 M * H * 102 118 132 88 JJLL. ..•••ll 80 100 M - H O - C , H , - M X ,CtH t-CW C , H , - O H 158 178 189 1 2 . 4 120 140 ', ,n.l| 193 286 217 229 160 180 200 220 a) before 100-1 8 0 -6 0 -4 0 -2 0 -0 -M - ( C H , ) , - S l - 0 - C , H , - M C , H , - 0 - S l - ( C H , ) , 350 M _ ' C H » C , H , - 0 - S l - ( C H , ) , 262 276 334 260 i i—•—r 280 '—i—>—i—1—i— 300 320 366 M * H * 394 340 360 1 — i — • — r 380 400 2 7 . 8 b) after Figure 5 . 3 7 : Methane CI mass spectra of TEA (a) before and (b) after s i l y l a t i o n with TSIM. tn a) before 1 0 0 - M-'CH i 21 . 5 201 M+H* 8 0 - 2 6 0 -4 0 -113 127 2 0 -146 234 245 98 160 174 183 1 1 l l i 2 5 7 278 0 - II Ii 1. .. f i—p-i r~ ,, ••, | •)••• | , ., 1 1 1 I I 1 1 i 1 i • i 100 120 140 160 180 208 220 240 260 288 b) after Figure 5.38: Methane CI mass spectra of peak #10 a)before and b)after s i ly lat ion with TMS. 1 53 A good match was found in a l l cases and Lts identif ication as HMP was thus confirmed. The mass spectra of peak 10 and synthesized HMP are shown in F i g . 5.39. 5.5 EXPERIMENTAL RESULTS During the degradation experiments, i t was noticed from visual inspection of the samples taken that the colour of the solution gradually turned brown as degradation progressed. The odour of the solution also became more pungent with time. During the high temperature runs (above 200 °C) , an increase in the autoclave pressure was also noticed. At 230°C, this increase was about 10 p s i . This suggests the formation of vo lat i le compounds as a result of MDEA degradation. Figures 5.40 and 5.41 show chromatograms of samples of 4.28 M MDEA solution degraded at 200°C, under a C0 2 part ia l pressure of 2.59 MPa taken at different time intervals. As can be seen from the chromatograms, the MDEA peak decreases with time indicating a loss of MDEA. It is also worth noting that DMAE is the f i r s t degradation compound to be formed. Concentrations of MDEA and its major degradation compounds, obtained at 230 °C, but otherwise identical conditions are shown in F ig . 5.42. The decrease in MDEA concentration is again evident from this figure. It can 154 also be seen that the DMAE and TEA concentrations i n i t i a l l y increase and then decrease again, which suggests that they are intermediate compounds. By contrast the EO, EG, DMP, HMP and BHEP concentrations increase and level off with time. EO and TMA are very volat i le and most probably contribute to the pressure rise in the autoclave. Therefore i t was not possible to determine their formation quantitatively from the analysis of the solution. 100-1 80 60 H 40 JUL 42 40 56 I 70 60 83 1 (1.1.-98 PEAK #10 E l SPECTRUM 113 126 I 144 •22.3 80 100 i—T—^ 120 1 I •"' 140 160 130 200 1 O 0 T 50 I 42 I 70 r 15.3 56 0 J 40 100-50-0-V 60 85 lk 98 114 126 I. 144 80 207 188 2O0 220 - i — 1 r** 1O0 120 140 HMP EI SPECTRUM —i 1 — | 1 i 1——i—> i— 240 260 160 15.3 281 280 Figure 5.39: EI Mass spectra of peak #10 and HMP synthesized in the laboratory. 156 Figure 5.40: Chromatograms of a solution which contained 4.28 mol/L MDEA and which was degraded at 200°C under a C0 2 p a r t i a l pressure: 2.59 MPa. 157 24 h < w 55 h F i g . 5.41: Chromatograms of a solution which contained 4.28 mol/L MDEA and which was degraded at 200°C under a C0 2 p a r t i a l pressure of 2.59 MPa. 158 o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.42: Concentration of MDEA and i t s major degradation compounds as functions of time. (Temperature: 230°C; I n i t i a l MDEA concentration: 4.28 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) 159 5.5.1 EFFECT OF TEMPERATURE Figures 5.43 to 5.46 are typical plots of MDEA concentration versus time at different temperatures, C0 2 part ia l pressures and i n i t i a l MDEA concentrations. It is evident that MDEA degradation is a strong function of temperature and is v ir tua l ly negligible below about 120°C. At lower temperatures, the data shown in Figs. 5.43 to 5.46 f a l l , at least approximately on straight l ines . However, at higher temperatures they deviate from the straight l ine behaviour. In an effort to examine the reaction order, the overall MDEA degradation reaction was assumed to be governed by a simple f i r s t order reaction. Based on this hypothesis, the i n i t i a l overall rate constant, k, was determined from the slope of the lines using f i r s t three data points and the corresponding Arrhenius plots are shown in F ig . 5.47. As can be seen, the plots are linear at temperatures ranging from about 100°C to 170°C. However, at higher temperatures, they deviate from the straight l ine behaviour. The rate constants are also affected by the i n i t i a l MDEA concentration. 160 i 1 1 1 1 1 1 — i 1 1 1 1 r o < « h W o «< w Q CO * • + . x O + ° O • X • o _ + O o X • + + + + D X « + + X * x ^ • X ° • • X X • x X o 180 C D + 200 C • 210 C • x 220 C ° D • 230 C n i ' I I I I I I I I I I L X • 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.43: MDEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; CO2 p a r t i a l pressure 2.59 MPa) • 160 C a 140 C o 120 C o 100 c I I I I I I I I I I I I I I I I I 0.0 40.0 80.0 120.0 160.0 200.0 240.0 280.0 320 TIME (h) Figure 5.44: MDEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 162 i 1 1 1 1 1 1 1 1 1 1 1 r 1(3 -\ r—I o B Jz; . o E -< tt b Jz; W CJ r-$5 o v„ <j w o 2.gxx * • • + + + + + * D x A • • X X X * • m x v • x * X * • + • 180 C 160 C A * * x A Q A * • o 140 C A * o x 200 C * * • 210 C A A * * 220 C A 230 C J 1 1 1 1 I I I I I I I A 0.0 8.0 16.0 84.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.45: MDEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.40 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) 163 — i 1 1 1 1 1 1 1 1 1 1 1 r o 140 C *• h + 160 c • 180 C * h x 200 C • 210 C * 220 C A 230 C CO O E, o t—t < E - -55 W 55 o < w Q CO A * * * X * * * • X x • • A * A * A J I I I I I I I i » A A 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.46: MDEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.00 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 164 2 F ~ i — i — i — r CO H o H CO 55 O O CO W H <J ID O T o 1—I—I—I—I—I—I—I—• o 4.28 M A 3.40 U o 2.00 M J I I L J I I I I I L 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 1000/T (1/K) Figure 5.47: Arrhenius plot of the o v e r a l l MDEA degradation rate constant. (C0 2 p a r t i a l pressure: 2.59 MPa) 165 Furthermore, as described previously, MDEA f irs t degrades to form DMAE which contains two methyl groups. Since MDEA contains only one methyl group, two MDEA molecules must react to form DMAE. Therefore, the MDEA degradation should not be f i r s t order with respect to MDEA concentration. Figures 5.48 to 5.50 and 5.51 to 5.53 show the DMAE and the TEA concentration as functions of time and temperature for different i n i t i a l MDEA concentrations. As can be seen from these figures both the DMAE and the TEA concentrations rise sharply, especially at higher temperature and then decrease before they level off. This indicates that DMAE and TEA are intermediate compounds. Figures 5.54 to 5.56, 5.57 to 5.59 and 5.60 to 5.62 show the EG, HMP and BHEP concentrations, respectively, as functions of time and temperature for different i n i t i a l MDEA concentrations. As can be seen from these figures, the EG, HMP and BHEP concentrations increase steadily with time. 166 \ »—i O S w o o ® *° o u W co Q CM 6 I 1 1 1 1 1 1 1 1 1 i 1 1 -LD • X -X - — - X X « x --• X + • + • + + X + + - • + • X + + — ID X - X o X 8-+ • o o - o o o • • D + o • -X • -1 o 180 C -<J> 0 + 200 C • 210 C — x 220 C o • 230 C o I 1 1 1 1 1 1 1 i i i 1 i i o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.48: DMAE concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 167 O tt °* W O O o O T — i — i 1—i—i 1 1 1 1 — i 1—r o 140 C + 160 C o 180 C L x 200 C A * * • 210 C A * K D S • m * 220 C 1 3 ... A 230 C A * X • 3K X A I H w -* • V ^ • O * A X° -A • • A X • h • • * X + ++ + + • * + + + + + 0 o 00 00-0 _ + 1 Hi t m 1 I O 9 S I I I 1 I I I 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.49: DMAE concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.4 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 168 \ -o 6, Z ~ O »—« < z w z® o © o w § 2 CM 6 1 1 1 1 1 i i 1 1 1 1 1 1 o 200 C + 210 c — * 220 c — - x 230 c -X X X - — X X - v X — X • + + o + + + + X -+_ o -o o ° - X • + - -+ - X o + CD -± O CD i 1 1 1 • • • 1 t 1 1 1 • 1 o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.50: DMAE concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.0 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 169 32 O S5 O • — i H < «q K © E-55 W O < CM © 1 1 1 1 1 1 1 1 1 1 1 I i o 180 C + 200 C — * 210 x 220 c c • 230 c • X - X • X • ' • x - • • + X J • X + + • + + + + X • o x » • ©-- • • + o • X X . + O i o 1 o 1 I o 1 1 1 1 • i • • i •_ 1 o 0.0 8.0 18.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.51: TEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 170 C4 5 5 » o ( D-H H O E -< E - ^ W ° O 55 o o o < E -ci ~-T 1—i 1—i 1 1—i—i—i—i—i—r o o 180 C + + 200 C • • 210 C x x 220 C • • 230 C • • • • • V K X X Q • + + X • x + X % x o • o ° ¥ g-o x ^ * xx • • + O • A X -o + + ° 0 . B i ffi i J i i i i i i i i i 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.52: TEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.4 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 171 ci ci 10 ci 26 O °3 1—4 O < « W ° CJ CJ o < w E -IO o T 1 1 1 r o 200 C + 210 C * 220 C x x 230 C • X + + X • X • + + (D O + O X • + X + X O X CD d „ i i i » i t I I I I I I I 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.53: TEA concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.0 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) 172 O ~ O *i t-H E -«< E-1 co 2 6 W o o ^ o § o w © T 1 1 1 1 1 1 1 1 1 1 1 r o 180 C + 200 C o 210 C x 220 C ru • • 230 C x • • + • X • + X • • X + + XX • • + o • X + Q • o © 0 CD ID • X x +H • o + + J I I I I I I » « I I » o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.54: EG concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 173 01 O -* 55 CD O d l-H « E - • to 55© W O 55 o 2^ o w CM © T 1 1 1 1 1 1 1 1 1 1 1 CD 180 C D . + 200 C • • 210 C x ' x 220 C X . • 230 C n • x * -• x • x + X • a X + • + a * * o ° ° . • X ^ + X • + * + ^ CD ° CD • K t i + ° n v + CD + CD 1 I I I I I I I I ' I o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.55: EG concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.4 mol/L; CO2 p a r t i a l pressure: 2.59 MPa) 174 CO ci © *1 °* O E 10 v — d 55 O M £ 2 E-« 55 W O co 55 ° O O W d o d l l l l 1 1 1 1 1 1 1 1 1 CD 200 C + 210 C o 220 C v x 230 C X X X — X -+ -+ + — X CD + CD — CD x o + — X + — + CD CD -CD + _ CD » x ffi CD * ^ Tn 1— 1 <P 1 1 l I i 1 1 l l 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.56: EG concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.0 >1/L; C0 2 p a r t i a l pressure: 2.59 MPa) mo. 175 t-3 O ° S5 O cq h ° Z * W ° o o 01 ci 1 1 1 1 1 1 1 1 1 1 1 1 1 o 180 C + 200 C • 210 C x 220 C • 230 C • • • x • X • X • v o • * +H • x • + • x • + x o + + o + • * + • OH • + o ° o « I <D l I I I I I I o • 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.57: HMP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.2B mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 176 b 3 ^ •ST o O s a 6 o •—I K b E-W o a, i—i 1 1 1 — i 1 1 i — i — r — i — r o o 180 C CD CO X O • • • + + 200 C • o 210 C x x 220 C • • 230 C • x x CD O • X • X x • + CO • + • + K + + O • X + CD CD • CD ° m i 5Jl] i i 2 i i i i i ' i 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.58: HMP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.4 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 177 oo b • J \ r—< O l b o E- 1 < ° E-§ 2 U 6 O o co P H P o b o 1 1 1 I I I I 1 1 1 1 1 1 - o + 200 210 C c --• X 220 230 c c X X X -- X — - X • -- +--X + -CD — CD - X + CD — - + --X CD -— CD — CD • • 1 i CD l l l l l ! t i 0.0 6.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.59: HMP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.0 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 178 03 O O E ^ O eo EH ° < P4 EH 2 CD W 6 O O °* CU °* w CQ oi 6 1 I 1 1 1 1 1 1 1 1 1 1 CD 180 C + 200 C • • 210 C a m • x 220 C • 230 C • • • • • x x • x X • X X X o. • X • X x o + + + + • • + X I" D x o + CD CD' o _ " * O $ t I I CD l CD I CD i i i i 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.60: BHEP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 4.28 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 179 CM O o O co E - ° < E -Z c o W d O 55 O °* a,© W CQ CM d T 1 1 1 1 1 1 1 1 1 1 1 1 o 180 C + 200 C • 210 C x 220 C • 230 C D • v X X • X * D X • • X + + • + + X • X . + ID m m m D • • x X X • + + + P m O O C P * O t + I • • i I (DO I O i i i i o © o 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.61: BHEP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 3.4 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 180 CD d d \ ° 'o E . o EH h ° W o O © o Cu ffid PQ 1 1 1 1 o 200 C + 210 C * 220 C x 230 C 2 ± ± + CD I I (D CD CD J I L 0.0 8.0 16.0 24.0 32.0 TIME (h) 40.0 + (D CD CD J L 48.0 56.0 Figure 5.62: BHEP concentration as functions of time and temperature. ( I n i t i a l MDEA concentration: 2.0 mol/L; C0 2 p a r t i a l pressure: 2.59 MPa) 181 5.5.2 EFFECT OF INITIAL MDEA CONCENTRATION Figure 5.63 is a semi logarithmic plot of the MDEA concentration as a function of time and i n i t i a l MDEA concentration at 200°C. It has already been shown that the rate constants are affected by i n i t i a l MDEA concentration as shown by F ig . 5.47. The rate constants appear to increase with i n i t i a l solution concentration for the concentration ranges shown. When the rate constants corresponding to F i g . 5.63, which cover a wider MDEA concentration range of 2.0 M to 6.0 M, are plotted as a function of i n i t i a l MDEA concentration (see F ig . 5.64), a somewhat different trend is noticed. The rate increases with i n i t i a l solution concentration up to about 3.5 M; above this level i t starts to decrease, suggesting a complex reaction mechanism. The i n i t i a l increase in the degradation rate with concentration can be explained by noting the C0 2 concentration in solution (for a given C0 2 part ia l pressure in the vapour phase) increases with MDEA concentration. At elevated MDEA concentrations water becomes l imiting and, as a result , the concentration of protonated MDEA ( i . e . MDEAH*) decreases (see Chapter 2, Eq. 2.13). Since the f i r s t step in MDEA degradation is the reaction between MDEA and MDEAH* (see next section, Eq. 5.3), the decrease in MDEAH* concentration reduces the overall MDEA degradation rate. 182 r - l — r r — H o 6 [3-D • 00 (p~, O EH 0 1 h o o o CO <c w Q o • A O i i — r • A • n A . CD CD * CD • 6 M A 5 M CD 4 M • 3 M * 2 M J J I ! J I L • n • CD * ft • • CD * w CD * * CD J I I L 0.0 8.0 16.0 24.0 32.0 40.0 TIME (h) 48.0 56.0 Figure 5.63: MDEA concentration as functions of time and i n i t i a l MDEA concentration. (Temperature: 200°C; CO, p a r t i a l pressure: 2.59 MPa) 1B3 i O < H CO O co O W < W > o 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 INITIAL MDEA CONCENTRATION (mol/L) Figure 5 .64: Overall MDEA degradation rate constant as a function of i n i t i a l MDEA concentration. (Temperature: 200°C; C0 2 p a r t i a l pressure: 2.59 MPa) 184 5.5.3 EFFECT OF CO, PARTIAL PRESSURE Typical plots of MDEA concentration as functions of time and C02 part ia l pressure at 200 and 180°C, are shown in Figs. 5.65 and 5.66, respectively. The overall rate constants are plotted as functions of C0 2 part ia l pressure and temperature in F ig . 5.67. As can be seen from this figure the overall MDEA degradation rate is affected by the C0 2 part ia l pressure. The rate of degradation increases s l ight ly with C0 2 part ia l pressure. The higher degradation rate with C0 2 part ia l pressure can be explained in terms of the increase in C0 2 so lubi l i ty in MDEA solutions as the C0 2 part ia l pressure is raised. Figures 5.68 to 5.77 show the DMAE, TEA, EG, HMP and BHEP concentrations as functions of time and C02 part ia l pressure at different temperatures. While the DMAE and TEA concentration i n i t i a l l y increase and then decrease with C0 2 part ia l pressure, the concentration of EG, HMP and BHEP increase steadily with time. 185 to o -3 <? CO O 6 Z " O E -c\i E -W O O w o •< d e CD + • + CD X + CD + CD X • ± T CD 0.34 MPa + 0.52 MPa * 1.21 MPa x 1.90 MPa • 3.96 MPa * 4.76 MPa CD CD CD • * • H _L CD CD + -X _ 0.0 8.0 18.0 24.0 32.0 TIME (h) 40.0 48.0 56.0 Figure 5.65: MDEA concentration as functions of time and CO2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 1B6 to «o i 1 1 r o 0.34 MPa + 0.52 MPa « r * 1.21 MPa x 1.90 MPa J i q i n 3.96 MPa [ * 4.76 MPa o o n + P x • «< ^ x H w • S * x + ° f n -9 CD + CD X + CD • X  * • * X o n o < o oi • " I T 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.66: MDEA concentration as functions of C0 2 p a r t i a l pressure and time. (Temperature: 180°C; I n i t i a l MDEA concentration 4.28 mol/L) 187 O 1-1 •ID CO ID T o z o -~ i — i — i — i — r Q o 220 C i — i — r 1 I 1 1 I—3 * 200 C * 180 C * 160 C * 140 C — i — i — i i i i i i i i i i i i 32 0.91 1.51 2.11 2.70 3.30 3.9 4.5 C02 PARTIAL PRESSURE (MPa) Figure 5.67: Overall MDEA degradation rate constant as functions of temperature and C0 2 p a r t i a l pressure. ( I n i t i a l MDEA concentration: 4.28 mol/L) 188 O CM 2P EH ~ < E- 1 55 co W 6 O o CD W 6 Q CM 6 o ci • JK • - o © -© i_ 0.0 Figure 5.68: T 1 1 1 1 1 1 1 1 r JK CD X 0 X X • JK O + X CD CD CD CD CD JK • JK • JK CD JK CD 0.34 MPa + 0.52 MPa • 1.21 MPa x 1.90 MPa CD 3.96 MPa JK 4.65 MPa i r + • CD CD-X X • -J I I I I I I I I I I 8.0 16.0 24.0 32.0 40.0 TIME (h) 48.0 56.0 DMAE concentration as functions of time and CO2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 189 CO <£> O E w o < 1 — I E -53 W m * ° o o W CO < d Q d CM d 1 1 1 i i i 1 1 i i i 1 - e> 0.34 + 0.52 MPa MPa -— o 1.21 MPa — - x 1.90 • 3.96 MPa MPa --* 4.65 MPa -_ • --* * • o B X * X • X • + o -- • x 3 - • • X + -- * CD — - • + ° -- * X 0 -! • 6" -.1, 1 1 1 l •i I l I 1 o 0.0 6.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.69: DMAE concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 190 CO © d 55 O I - H O O 55 O U co o < E -cv d o d ID • * X • X • + o + o • K K -I 1 L + CD • + (D CD CD (D 0.34 MPa + 0.52 MPa • 1.21 MPa x 1.90 MPa • 3.96 MPa * 4.65 MPa 0 0 8.0 16.0 24.0 32.0 TIME (h) X I' 40.0 48.0 56.0 Figure 5.70: TEA concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 191 © co d 2 d 8 5 -O t • o E -< tt w ° u 55 O U OJ o < W o d 1 I I I I 1 1 1 1 1 1 1 1 - o 0.34 MPa + 0.52 MPa -— • 1.21 MPa — - x 1.90 MPa • 3.96 MPa • JK 4.65 MPa • -JK • JK • JK X X • JK *_ - JK • X ffi-e JK • X + — X G CD -- • JK X • + CO -- JK $ O -• i B CD I I I I 1 1 1 1 1 1 i i 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.71: TEA concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 192 O ^ 6 Z CD 2 ° < E-H CD W O w d o d 1 l l l l 1 1 l l l l 1 1 - 0 0.34 MPa + 0.52 MPa -— • 1.21 MPa *-* - x 1.90 MPa • 3.96 MPa * 4.65 MPa • - K -* • 0 — • X 0 -* X • • X 0 0 <p (D _ • X X $ 0 • CD — • * 10 — I I I I 1 1 I I I I 1 1 0.0 6.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.72: EG concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 193 ci CD O O o 55 ^ 2 ° EH < tt EH co 2 d W O o d 1 1 1 1 1 1 1 1 1 1 1 1 1 o 0.34 MPa + 0.52 MPa — • 1.21 MPa JK x 1.90 MPa • 3.96 MPa JK 4.65 MPa • JK X-• JK o -JK • X X • • X -• © --• * X © -+ * * ^ O -¥ B3 . O 1 I i i i 1 1 T i i i i 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.73: EG concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 194 OB d CO d d ° d 55 O « W ° u o O co 0 , ° ' d o d 1 1 1 1 1 I 1 1 1 1 1 1 1 m • -o 0.52 + 1.21 MPa MPa • 1.90 MPa X -x 3.96 MPa X • 4.65 MPa • - • X - X --- X • G - B G + - + -+ — - + + CD-CD X . , ? r ( + 1 1 CD 1 1 O 1 1 I i 0.0 8.0 40.0 48.0 16.0 24.0 32.0 TIME (h) Figure 5 .74 : HMP concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 56.0 195 ta ci ci ta CO ci E ° O w P H E-53 N W 6 O o d ta © ci o d I I I I I I I i i i 1 1 1 o 1.21 MPa + 1.90 MPa x" o 3.96 MPa X -- x 4.65 MPa — X — X X -+ X — x • — + + CD - x • -+ o x o o • I i i i i i i 1 1 1 1 1 1 0.0 8.0 18.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.75: HMP concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 196 1 l l l l i i l l l l 1 1 o 0.34 MPa + 0.52 MPa — o 1.21 MPa * •-• x 1.90 MPa • 3.96 MPa * 4.65 MPa m -B * • X X -X B X * X • 1 c • * x x f • t 1 X • » 1 x o • . • * 6B l l l l +-+ o 1 1 o 0.0 8.0 18.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.76: BHEP concentration as functions of time and C0 2 p a r t i a l pressure. (Temperature: 200°C; I n i t i a l MDEA concentration: 4.28 mol/L) 1 97 to CD d d o 55 O ^ i— i E- ° <J W d o 55 O u § O H 6 w 09 O d T 1 1 1 1 1 1 1 r o 1.90 MPa + 3.96 MPa o 4.65 MPa + CD-• + CD CD • + CD + J I I I I I I t i l l ! O 0.0 8.0 16.0 24.0 32.0 40.0 48.0 56.0 TIME (h) Figure 5.77: BHEP concentration as functions of time and C 0 2 p a r t i a l pressure. (Temperature: 180°C; I n i t i a l MDEA concentration: 4.28 mol/L) 198 5.6 MDEA DEGRADATION MECHANISM Once the major MDEA degradation compounds were identif ied and the effects of the main operating variables established, efforts were directed towards formulating the degradation mechanism. It was possible to obtain some preliminary information by observing the concentration changes of various compounds and their sequence of formation with time. As stated earl ier and as seen from Figs. 5.40 and 5.41, DMAE is the f i r s t compound to be formed. This is followed by HMP and TMA. The EG, BHEP and DMP peaks then appear almost simultaneously. The EO, HEOD and TEA peaks appear along with THEED and TEHEED peaks. 5.6.1 DEGRADATION OF DMAE Since DMAE was found to be the f i r s t compound to be formed and was also an intermediate compound, it was decided to degrade DMAE with C0 2 in order to find out which compounds are formed from DMAE. The degradation experiments were carried out following the same procedures described for the MDEA degradation experiments. A chromatogram of a 1 M DMAE solution degraded at 200°C, under a C0 2 part ia l pressure of 2.59 MPa for 72 h is shown in F ig . 5.78. 199 Figure 5.78: Chromatogram of a p a r t i a l l y degraded DMAE solution of 1 M i n i t i a l concentration, degraded at 200°C under a C0 2 p a r t i a l pressure of 2.59 MPa for 72 h. 200 Methanol,EO, EG, TMA, DMP, HMP and BHEP, which are a l l MDEA degradation products were detected by GC/MS analysis of the degraded sample. While TMA, EG, DMP and and HMP were found to be present in large quantities, only small quantities of BHEP were detected. After studying the formation of the major degradation compounds formed as a result of C0 2 reactions with MDEA and DMAE, the following observations were made: MDEA degrades to DMAE which in turns degrades to TMA. EO, EG, DMP, HMP and BHEP are at least partly formed from DMAE. 5.6.2 FORMATION OF DMAE On the basis of the above observations the following i n i t i a l reaction scheme was postulated: HO-C 2H f t HO-C 2H, H* N-CH3 + C0 2 + H 20 ^ N-CH3 + H C O 3 - (5.3) HO-CjH, HO-C 2H, "MDEA" 201 HO-C 2H f t H + C 2H,-OH \ I / N-CH 3 + CH 3-N > / \ HO-C2H» C 2H f l-OH CH, 1 N ,C 2H,-OH 'C 2H 4-OH CH 3 \ N-CaHa-OH + CH2 - CH2 X \ / CH 3 0 "DMAE" H H-N I \ C2H»-OH C 2H,-OH + C0 2 (5 .4) H + . , -OOC-N / \ C 2H,-OH C 2H f l-OH "DEA CARBAMATE" CH2 - CH-I I OH OH "EG" MDEA is protonated as a result of i t s reaction with C0 2 (see Chapter 2). The protonated molecule then reacts with a neutral molecule by transferring the methyl group and forming a methylated MDEA molecule and a DEA molecule. The latter then quickly reacts with C0 2 to form DEA carbamate. The methylated MDEA then forms DMAE by simply losing a hydroxyl group which in turns forms EG via EO. 202 5.6.3 FORMATION OF TMA DMAE is believed to degrade with C0 2 as follows: CH 3 CH3 H* N-C 2H,-OH + C0 2 + H 20 N-C2H„-OH + HC0 3' (5.5) "DMAE" CH, N-C2H»-OH + CH, CH-H + I N-C2H,,-OH CH3 CH 3 ^ ^ N - C 2 H f t - O H CH 3 CH-,N-CH 3 + CH2 - CH2 C H 3 ^ O ^ I H "TMA" CH 2 ~~ CH 2 I I OH OH "EG" I H I + CH3-N-C2H„-OH "MAE" + C 0 2 COO"...H* I CH 3-N-C 2H,,-OH 'MAE CARBAMATE' (5.6) 203 Like MDEA, DMAE also is protonated as a result of its reaction with C0 2 according to Eq. 5.5. The protonated molecules then react with neutral DMAE by transferring a methyl group and, according to Eq. 5.6, form methylated DMAE and methyl amino ethanol (MAE). The MAE then quickly reacts with C0 2 to form MAE carbamate. The methylated DMAE loses i ts hydroxyl group, which then forms EG via EO formation. The above reaction mechanism appears plausible and is able to explain the formation of EO, EG, DMAE and TMA. However, i t also postulates DEA and MAE formation which have not been detected in the degraded samples by gas chromatographic analysis. Since the major DEA degradation compounds, i . e . BHEP, HEOD and THEED, are present in the degraded MDEA solution, DEA's presence seems l i k e l y . It is possible that DEA is an intermediate compound and disappears very quickly to form other compounds and occurs in very low concentrations. DEA's retention time in the GC column is very close to that of MDEA. When the DEA concentration is relat ively small as compared to the MDEA concentration, the separation in the GC column becomes d i f f i c u l t . MAE's retention time is also very close to that of DMAE. Again, when the MAE concentration is relatively small compared with the DMAE concentration, separation in the GC column is d i f f i c u l t . In addition, MAE is more reactive' due to its labi le H atom and therefore i t is possible that i t reacts to form other compounds as soon as i t is formed and thus occurs 204 i n low c o n c e n t r a t i o n s . As a r e s u l t i t a l s o remains u n d e t e c t e d . However, at t h i s p o i n t DEA's e x i s t e n c e i s more e v i d e n t than MAE's because of the presence of the major DEA d e g r a d a t i o n compounds. 5 .6 .4 PROOF OF THE PRESENCE OF DEA AND MAE In o r d e r to v a l i d a t e the proposed i n i t i a l r e a c t i o n scheme, i t was n e c e s s a r y to e s t a b l i s h the e x i s t e n c e of DEA and MAE. I t was e a r l i e r s u s p e c t e d t h a t both of them r e a c t q u i c k l y to form o ther compounds. S i n c e s i l y l a t i o n can i n c r e a s e the s t a b i l i t y of a molecu le by r e p l a c i n g the a c t i v e hydrogen by the s i l y l g r o u p , i t was d e c i d e d to s i l y l a t e a f r e s h l y degraded MDEA s o l u t i o n and a n a l y s e i t by GC/MS. In t h i s case the sample was o b t a i n e d by opening the sampl ing v a l v e of the a u t o c l a v e (see F i g . 5.1) w i thout f o l l o w i n g the u s u a l c o o l i n g p r o c e d u r e . The sample was then immediate ly s i l y l a t e d w i t h HMDS-TMCS-pyr id ine and a n a l y s e d by GC/MS. Both DEA and MAE were d e t e c t e d as DEA and MAE carbamates and t h e i r mass s p e c t r a are shown i n F i g s . 5.79 to 5 . 8 1 . A l t h o u g h both DEA and MAE were d e t e c t e d in t h e i r carbamate forms, they o c c u r r e d i n low c o n c e n t r a t i o n s . A c c o r d i n g to the proposed r e a c t i o n scheme, the r e a c t i o n s by Figure 5.79: Methane CI mass spectrum of p a r t i a l l y s i l y l a t e d DEA carbamate 100 80 60 40 20 0 J M - CH.-N 102 C - O - O - S l - t C H , ) , 192 M*H •21 .8 C,H, -OH 176 75 88 160 61 130 116 . 145 220 204 ' 1 T ' ' " T "' 80 i | . . . P . i |».., J 100 120 140 232 160 T 180 >00 220 Figure 5.80: Methane CI mass spetrum of p a r t i a l l y s i l y l a t e d MAE carbamate M , - C H , - M , 1C,H, -OH C - 0 - 0 - S i - ( C H , ) , M ] • CH,-H. C - 0 -0 - S l - < C H , ) , C - O - O - S l - I C H , ) , 100-1 0 1 0 0 -5 0 -73 102 117 1 0 . 5 61 L U 80 91 I I ill L l - ,1.1 I I • 111 111 80 191 100 : i 9 147 125 131 137 l•I • • i • •• 153 163 120 140 175 0 2 0 7 2 3 5 180 2 0 0 220 — i — 2 4 0 V • M , 2 6 3 _L_ i* ' 160 - r r 1 0 . 5 275 — r 2 6 0 Figure 5.81: EI mass spectra of s i l y l a t e d MAE carbamate. 208 which DEA and MAE are formed are molecular reactions (see Eqs. 5.3 and 5.5). For every degrading mole of MDEA one mole of DEA should be formed; similarly for every degrading mole of DMAE one mole of MAE should be formed. If the reaction mechanisms were to be correct, both DEA and MAE must be intermediate compounds and therefore must produce other degradation compounds. In order to test this hypothesis, 1 uL of DEA was added to a 1 mL sample of freshly degraded MDEA solution in a screw cap v i a l . The glass v i a l was shaken vigorously for about 1 min. DEA was expected to react with EO to form TEA. The sample was then analysed by GC. The DEA peak did not appear in the chromatogram. However, the peak area of ethylene oxide decreased from 900 to 690 units and the TEA peak area increases from 2780 to 3160 units as calculated by the GC integrator. This was in accordance with expectations. The HMP and TEHEED peak areas increased s l ight ly which suggests that DEA also plays a role in the formation of HMP and TEHEED. In addition, the TMA peak also increased but the reason this increase was unclear. The chromatograms of the samples before and after DEA addition are shown in Figs. 5.82 and 5.83. The decrease in the EO peak area is quite obvious, while the increase in TEA and HMP peak areas are not because of their relat ively larger peak areas. 209 Figure 5.82: Chromatogram of a p a r t i a l l y degraded MDEA solution used in the test for DEA's presence, before. DEA addition. 210 Figure 5.83: Chromatogram of a p a r t i a l l y degraded MDEA solution used in the test for DEA's presence, afte r addition of 1 ui* of DEA. 21 1 When an additional 2 uL DEA were added to the same sample, the DEA peak appeared on the chromatogram (see F ig . 5.84). As a result , the EO peak decreased further to 440 units. The TEA peak this time has decreased to 1200 units suggesting a reaction between TEA and DEA while the TEHEED peak increased to 4800 units. Similarly , when 1 uL of MAE was added to 1 mL of a degraded MDEA sample, the peak areas of DMP and HMP increased s l ight ly , indicating that MAE is at least partly responsible for the formation of DMP and HMP. These findings conclusively prove the existence of DEA and MAE in degraded MDEA solutions and provides an explanation why they are not detected by GC analysis. It is now clear that DEA plays a major role in the degradation process affecting ethylene oxide, TEA, HMP and TEHEED. It is also l ike ly to be responsible for the formation of HEOD and BHEP. Similarly, MAE plays a role in the formation of DMP and HMP. Figure 5.84: Chromatogram of a p a r t i a l l y degraded MDEA solution used i n the test for DEA's presence, afte r addition of 2 yL of DEA. 213 5 . 6 . 5 FORMATION OF TEA I t i s suggested tha t TEA i s formed as a r e s u l t of a r e a c t i o n between DEA and EO a c c o r d i n g t o : HO-C 2 H„ H O - C 2 H , H O - C 2 H f l N-H + C H ^ - ^ C H j HO-C 2 H„ N - C 2 H 4 - O H (5.7) "DEA" 'EO' "TEA" T h i s r e a c t i o n i s w e l l known and i s w i d e l y used f o r the manufacture of T E A . 5 . 6 . 6 FORMATION OF TEHEED TEA was found to be an i n t e r m e d i a t e compound, whose c o n c e n t r a t i o n i n i t i a l l y i n c r e a s e d and then decreased a g a i n . The TEA peak of a degraded sample was a l s o found to i n c r e a s e w i t h the i n i t i a l a d d i t i o n of DEA and to decrease wi th f u r t h e r a d d i t i o n wh i l e the TEHEED peak was found to i n c r e a s e . On the b a s i s of these o b s e r v a t i o n s , i t i s sugges ted tha t TEHEED i s formed from TEA and DEA a c c o r d i n g t o : 214 H O - C 2 H f t CzH^-OH N - C 2 H » - O H + HN H O - C 2 H 4 C 2 H , , - O H "TEA" "DEA" HO-C 2 H» C 2 H 8 - O H N - C 2 H , - N + H* + H C O 3 - (5 .8) H O - C 2 H , C 2 H 4 - O H "TEHEED" 5 . 6 . 7 FORMATION OF HEOD HEOD was found to occur i n s m a l l c o n c e n t r a t i o n s i n the degraded MDEA s o l u t i o n . I t s f o r m a t i o n can be a t t r i b u t e d to DEA and the r e a c t i o n by which i t i s formed i s known [ 5 7 , 5 8 ] . HEOD i s produced by the d e h y d r a t i o n of DEA carbamate (see E q . 2 . 1 7 ) . 215 5 .6 .8 FORMATION OF HMP DEA a l s o p l a y s a r o l e i n the f o r m a t i o n of HMP. I t f i r s t r e a c t s w i t h C 0 2 t o form DEA carbamate . The DEA carbamate then r e a c t s w i t h MAE t o form N ,N ( h y d r o x y e t h y l ) N' methyl e t h y l e n e d i a m i n e (HEMED) which then dehydrate s to g i v e HMP a c c o r d i n g t o : H O - C 2 H 4 H O - C 2 H » O \ ^ \ II N - H + C 0 2 y N - C - 0 " . . H + H O - C 2 H 4 H O - C 2 H , "DEA" "DEA CARBAMATE" H O - C 2 H , 0 ^ N - C - O " H O - C 2 H , . H + + H O - C 2 H a - N I CH. H HO-C 2 H„ CH: N - C 2 H , - N + H C 0 3 - + H< / X HO-C 2 H« H "HEMED" 1 / C j H , \ H O - C 2 H , - N N - C H 3 C 2 H , (5 .9) (5.10) 'HMP' 216 5.6.9 FORMATION OF BHEP BHEP may be produced from THEED or THEED carbamate (see Eqs. 2.20 and 2.21). However, due to the presence of highly reactive ethylene oxide, BHEP is also produced as a result of ethylene oxide reacting with: N-CH 3 + CH 2 - CH 2 + H++ OH-HO-C 2 H 4 -N "HMP" "EO" C 2 H 4 CH 3 HO-C 2H,-N + OH" \ C2H« (5.11 ) HO-C2H«-N N-C 2H,-OH + CH3-OH C 2 H ; "BHEP" 217 5.6.10 SUMMARY OF THE DEGRADATION REACTIONS The MDEA degradation reactions can be summarized as follows: MDEA + C0 2 + H 20 MDEAH* (5.12) MDEA + MDEA* —> DMAE + EO + DEA (5.13) DMAE + DMAE* —> TMA + EO + MAE (5.14) MAE + C0 2 ^ ~ MAECOOH (5.15) MAE + MAECOOH —> DMP (5.16) EO + H 20 —=> EG (5.17) DEA + C0 2 ^ - DEACOOH (5.18) DEACOOH + MAE —> HMP (5.19) DEA + EO — TEA (5.20) HMP + EO —>• BHEP (5.21 ) DEA + C0 2 — —>• HEOD (5.22) DEA + C0 2 — — THEED (5.23) THEED — —>• BHEP (5.24) 5.7 KINETIC MODEL FOR MDEA DEGRADATION Based on the reaction mechanism postulated in the previous section, i t is possible to propose a kinetic model to describe MDEA degradation with C 0 2 . Since MDEA degradation is rather complex involving several equilibrium, paral le l and series reactions, i t is d i f f i c u l t to obtain the kinetic rate constants for such a model from the 218 experimental data obtained for this study. For example, the concentrations of various ionic species and some minor molecular species were not detected. The gas chromatographic technique employed could not distinguish between MDEA and protonated MDEA, DEA and DEA carbamate, MAE and MAE carbamate, etc. As a result , some simplifications were necessary. With the exception of Eq. 5.12, a l l reactions were assumed to be irrevers ible . Equation 5.12 was regarded as an equilibrium reaction. This also assumes that C0 2 absorption into MDEA is not mass transfer l imit ing . The resultant simplified equations are as follows: [MDEA] + [C0 2] + [H20] Ke 2 ^ J -«c- [MDEA* ] +[HC03"] (5.25) k <, " [MDEA] + [MDEA*] > [DMAE] + [EO] + [DEA] (5.26) 2 [DMAE] + [C0 2] -> [TMA] + [EO] + [MAE] (5.27) 2 [MAE] + [C0 2] k 6 -» [DMP] (5.28) [EO] k 7 -> [EG] (5.29) [DEA] + [C0 2] + [MAE] -> [HMP] (5.30) [DEA] + [EO] -> [TEA] (5.31) [HMP] + [EO] H » [BHEP] [TEA] + [DEA] + [C0 2] k 1 2 [DMP] + [EO] > [DEA] + [C0 2] > k 2 [DEA] + [C0 2] > k 3 [THEED] 219 (5.32) [TEHEED] (5.33) [HMP] [HEOD] [THEED] [BHEP] (5.34) (5.35) (5.36) (5.37) It may be noted that water is omitted from being included exp l i c i t l y in Eq. 5.29 since i t is generally present in excess compared with the EO concentration. The following rate equations can then be written: d[MDEA] = - k,"[MDEA][MDEAH*] dt [MDEA] [C0 2] But, [MDEAH*] = Ke! [ H C O 3 - ] Therefore, d[MDEA] [CO,] = - k«"[MDEA] Ke,[MDEA] dt [ H C O 3 - ] 220 Where, k a = k „ " x Ke d[BHEP] dt = k 3 [THEED] + k 1 0 [ H M P ] [ E O ] (5 .39) d[DEA] [ C 0 2 ] = k „ [ M D E A ] 2 - k 8 [ D E A ] [ M A E ] [ C 0 2 ] dt [ H C O 3 - ] - k 9 [ D E A ] [ E O ] - k j D E A ] [ C 0 2 ] - k 2 [ D E A ] [ C 0 2 ] - k , , [ D E A ] [ T E A ] [ C 0 2 ] (5 .40) d[DMAE] [ C 0 2 ] = k , [ M D E A ] 2 - k 5 [ D M A E ] 2 [ C 0 2 ] (5 .41) dt [ H C O 3 - ] d[DMP] = k 6 [ M A E ] 2 [ C 0 2 ] - k , 2 [ D M P ] [ E O ] (5 .42) dt d[EG] = k 7 [EO] (5 .43) dt d[EO] [ C 0 2 ] = k„ [MDEA] 2 + k 5 [ D M A E ] 2 [ C 0 2 ] - k 9 [ D E A ] [EO] dt [ H C O 3 - ] - k 1 0 [ H M P ] [EO] - k 1 2 [ D M P ] [EO] (5.44) 221 d [ HEOD ] dt d[HMP] dt = kjDEA] [C0 2] (5.45) kB[MAE][DEA][C02] + k12[DMP][EO] - k10[HMP][EO] (5.46) d[MAE] dt k 5[DMAE] 2[C0 2] - k 6[MAE] 2[C0 2] -k 8[MAE][DEA][C02] (5.47) d[TEA] dt = k9[DEA] [EO] - k, ,[TEA][DEA][C0 2] d[TEHEED] dt = k,,[TEA] [DEA] [C0 2] d[THEED] dt = k 2[DEA][C0 2] - k3[THEED] d[TMA] dt = k 5[DMAE] 2[C0 2] (5.48) (5.49) (5.50) (5.51) The values of [C0 2] and [HC03~] can be calculated from the so lubi l i ty model described in Chapter 3. Although i t would have been more desirable to evaluate the other rate constants individually from the experimental data, the complex inter-relationship between various species makes this impractical. Therefore, i t was decided to search by means of an optimization routine [103] the set of rate constants which gave the best agreement with a l l 222 experimental data for a given temperature. The search was then repeated for different temperatures. A l l together 649 data points were used. By plotting the rate constants as functions of temperature and assuming the appl icabi l i ty of Arrhenius law, the following expressions were obtained. k, • = 5.39 x 10s exp{-75215/RT} (5.52) k 2 ' = 2.00 x 107 exp{-79447/RT} (5.53) k 3 • = 3.80 x 101 1 exp{-12843/RT} (5.54) k« • = 2.34 x 10" exp{-57407/RT} (5.55) k 5 • = 4.77 x 10* exp{-50927/RT} (5.56) k 6 • = 2.42 x 105 exp{-60583/RT} (5.57) k 7 -= 2.60 x 10" exp{-56l93/RT} (5.58) k 8 -= 5.82 x 105 exp{-52429/RT] (5.59) k 9 • = 2.70 x 106 exp{-65405/RT} (5.60) k 1 o = 2.28 x 10 4 exp{-544l8/RT} (5.61) k,, = 6.13 x 10 • exp{-56316/RT} (5.62) k , 2 = 3.47 x 10 * exp{-79447/RT} (5.63) Equations 5.38 to 5.51 were then solved simultaneously. A double precision Runge-Kutta subroutine RKC, which is available at the University of Bri t i sh Columbia Computing Centre [104], was used for this purpose. The model predictions and the experimental data are presented in Appendix D. 223 The values of activation energy in Eqs. 5.52 to 5.63 ranged from approximately 50 to 100 kcal per mole. These values are somewhat higher than those typical ly encountered for l iquid phase reactions [105], However, since the degradation reactions are slow, more activation energy may be required for the reactions to proceed. This may explain the high values of activation energy for the present system. The frequency factors exibit a wide variation in magnitude ranging from 10" to 10 1 0 . However, in most of the cases, they are of the order of 10". The simplifications inherent in the reaction scheme and also the manner in which constants were determined, are probably responsible for these wide variations. Therefore, the activation energies and frequency factors presented in Eqs. 5.52 to 5.63, may not be truly representative of the actual reactions. They are probably better described as "pseudo frequency factors" and "pseudo activation energies". Nevertheless, the kinetic model using the stated values predicts MDEA degradation quite well. Unfortunately, due to time constraint no s ta t i s t i ca l analysis was carried out. However, some general observations could be made by comparing the model predictions and the experimental results which are given in Appendix D. 224 The MDEA c o n c e n t r a t i o n s c a l c u l a t e d wi th the model are i n e x c e l l e n t agreement w i t h the e x p e r i m e n t a l r e s u l t s . The DMAE, DMP, HEOD and HMP c o n c e n t r a t i o n s are a l s o p r e d i c t e d w e l l by t h i s mode l . The model p r e d i c t i o n of the BHEP and EG c o n c e n t r a t i o n s are not as s a t i s f a c t o r y . The model p r e d i c t s h i g h e r EG c o n c e n t r a t i o n s a t e l e v a t e d temperatures and lower BHEP c o n c e n t r a t i o n s at lower i n i t i a l MDEA c o n c e n t r a t i o n s . O v e r a l l , the s u c c e s s f u l p r e d i c t i o n of c o n c e n t r a t i o n s of MDEA and o ther compounds, f or w i d e l y rang ing t e m p e r a t u r e s , C 0 2 p a r t i a l p r e s s u r e s and i n i t i a l MDEA c o n c e n t r a t i o n s , c o n f i r m s the g e n e r a l v a l i d i t y of the model p r e s e n t e d e a r l i e r . Chapter 6 ACTIVATED CARBON PURIFICATION OF DEGRADED AMINE SOLUTIONS To examine the effectiveness of activated carbon for removing major DEA and MDEA degradation products, experiments were undertaken with activated carbon. The experiments included analyses of DEA samples taken upstream and downstream of activated carbon beds in different amine plants, batch and column adsorption tests. Experiments were also conducted to regenerate saturated activated carbon. The latter included thermal regeneration and acid washing. 6.1 BATCH ADSORPTION AND REGENERATION EXPERIMENTAL EQUIPMENT  AND PROCEDURES Adsorption of compounds from a solution by activated carbon depends on the characteristics of the carbon as well as the physical and chemical properties of the solutes. Among the carbon properties affecting adsorption are the specific surface area, pore volume and surface characterist ics . On the other hand, the molecular structure of the solutes, their solubi l i ty in the solvent and solution temperature affect adsorption. In the case of multicomponent systems, the factors determining the adsorption are the molecular size and structure as well as concentrations of the solutes. 225 226 Batch adsorption tests can be used for the preliminary evaluation of activated carbon for commercial purification processes. The equilibrium adsorptive capacity of pure compounds, which can be determined from batch tests, may be represented by adsorption isotherms. The Freundlich isotherm [106] is widely used to represent adsorption isotherms: q = A C 1 / " where q - adsorptive capacity (mmol of compound adsorbed/ g of carbon) C - equilibrium concentration of solute in solution (mmol/L) A and n - constants characteristic of the carbon and solute When the equation is rewritten in logarithmic form, a plot of log{q} versus log{C} should place the experimental data on a straight l ine provided the Freundlich equation is obeyed. The coefficients A and n are readily determined from the plots. 227 6.1.1 MATERIALS Two different types of activated carbon were examined in this study. A bituminous-coal based carbon (commercially known as SGL carbon), which is widely used in DEA plants, was obtained from Calgon Corporation, Pittsburg, PA. A l igni te coal based carbon (commercially known as DARCO carbon), manufactured by ICI Americas Inc. , was purchased from Aldrich Chemicals, Milwaukee, WI. The physical properties and specifications of the two carbons are given in Table 6.1. A comparison of the properties indicates that the total surface area of the SGL carbon is higher than that of the DARCO carbon. Similarly the iodine number, which is a measure of the quantity of iodine adsorbed per gram of carbon, is also higher for the SGL carbon. In order to minimise the effect of part ic le size on adsorptive capacity, only pulverized carbon, 95*% of which could pass through a 325 mesh screen, was used. Pulverized SGL carbon was obtained direct ly from the supplier and the DARCO carbon was pulverized in the laboratory using a mortar and pestle. Before use, the pulverized carbon was oven-dried for at least 6 h at a temperature of 150°C to eliminate moisture. 228 Table 6.1: Properties of SGL and DARCO carbons Carbon Property SGL DARCO Total surface area (N 2, BET method), ma/g 950 - 1050 600 - 650 Apparent density, g/mL (bulk density) 0.48 0.43 Real density, g/mL (He displacement) 2.10 2.00 Pore volume, mL/g (within p a r t i c l e ) 0.85 0.95 Mean p a r t i c l e diameter mm 1.5 - 1.7 1.60 Iodine number, min. 900 650 229 6.1.2 EXPERIMENTAL PROCEDURE For the batch adsorption experiments, the following procedure was followed: Different, precisely weighed, quantities of activated carbon (e.g. 1 - 6 g) were added to stoppered 100 mL flasks each containing 20 mL of solution of known concentration. The stoppered flasks were then shaken in a temperature controlled shaker (Controlled Environment Incubator Shaker, New Brunswick Scient i f ic Co. , New Brunswick, NJ) at 250 rpm for at least 48 h. The solutions were then analysed by gas chromatography (see Appendix B). The experiments were repeated for solutions of different i n i t i a l concentrations and containing different compounds. 6.1.3 ACTIVATED CARBON REGENERATION Saturated activated carbon samples were prepared by contacting 40 mL of part ia l ly degraded DEA solutions of known concentration with 7 g of activated carbon samples. The quantities of various compounds adsorbed were determined by gas chromatographic analysis of the i n i t i a l and f inal equilibrium concentrations of the solution. The saturated carbon samples were then separated from the solution by 230 f i l t r a t i o n . They were subsequently washed several times with d i s t i l l e d water unti l the effluent water showed no trace of adsorbed compounds. The washing operation was carefully performed to avoid loss of activated carbon with the wash water. The carbon was then allowed to dry at room temperature. The dried samples were subsequently contacted again with 40 mL of the same part ia l ly degraded solution to check whether the washing operation had removed any of the adsorbed compounds. The washing and drying sequence was repeated again. The saturated carbon samples were then used in the thermal and acid wash regeneration experiments. In the thermal regeneration experiments, the saturated carbon samples were dried in an oven either at 150°C or 300°C for 10 h. The regenerated carbon was then contacted with 40 mL of the same batch of part ia l ly degraded solution to determine whether i t could adsorb any further compounds. In the acid wash experiments, 20 mL of hydrochloric or n i t r i c acid of known concentration were added to the carbon and placed in the shaker for 48 h followed by washing and drying. The acids were expected to react with the adsorbed compounds, which are alkaline in nature, and possibly dislodge them from the carbon surface. The acid washed carbon was then contacted with the same part ia l ly degraded solution and the equilibrium concentration determined. The quantities of compounds adsorbed by the acid washed carbon 231 were found from the differences in the i n i t i a l and f inal concentrations. The entire sequence was repeated twice to determine whether the adsorption capacity deteriorated with subsequent reuse. A l l contacting operations were carried out in the shaker for 48 h at room temperature. 6.1.4 RESULTS AND DISCUSSION PRELIMINARY ADSORPTION TESTS When 20 mL of an industrial DEA sample was contacted with 6 g of SGL carbon following the procedures described ear l ier , the yellow solution turned colourless and the concentrations of a l l the major compounds decreased somewhat. This suggested that SGL carbon is indeed capable of removing DEA and i ts major degradation products. The chromatograms of the sample before and after activated carbon treatment are shown in F ig . 6.1. Similar results were also obtained with DEA samples degraded in the laboratory (see Table 6.2.) These findings suggest that SGL carbon does indeed remove DEA and i ts major degradation products and that industrial carbon adsorbers had become ineffective due to saturation. 232 Figure 6.1: Chromatograms of amine samples (20 mL) from Plant #1 (a) before and (b) a f t e r treatment with 6 g of SGL carbon at 25°C. 233 Table 6.2: Concentrations of laboratory degraded DEA solutions as a function of SGL carbon added to 20 mL of solution. Carbon Added Concentration (m mol/L) (g) DEA BHEP HEOD THEED 0 1500 12 220 425 i 1420 1 1 200 375 2 1400 10 175 325 3 1380 8 165 275 4 1360 7 130 240 5 1350 6 112.5 150 6 1330 5 95 120 7 1310 - 80 100 234 ADSORPTION ISOTHERMS FOR SGL CARBON The equilibrium isotherms of DEA and its major degradation compounds at 25 °C are shown in F ig . 6.2. The isotherms of other impurities are shown in Figs. 6.3 and 6.4. The DEA, MDEA and TEA isotherms for wider concentration ranges are presented in F i g . 6.5. The corresponding constants of the Freundlich equation are summarized in Table 6.3. The results c learly show that, although DEA, MDEA and their major degradation compounds are adsorbed by SGL carbon, i ts adsorptive capacity is extremely low; in most cases i t is less than 3 mmol/g carbon. Oda and Yokokawa [107] report similar adsorptive capacities for aromatic amines and phenol derivatives. To gain insight into the quantities of activated carbon required for industrial applications, let us consider removing BHEP from 5,000 L of DEA solution containing 100 mmol of BHEP/L. At that concentration, the adsorptive capacity of SGL carbon is about 1.4 mmol of BHEP/g of carbon at 25°C. 235 CD ri ri C O U CD (0 CM o o d • • DEA A A BHEP o o HEOD o o THEED 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m m o l / L ) Figure 6.2: Experimental and f i t t e d ( s o l i d l i n e s ) adsorption isotherm of DEA and i t s major degradation compounds at 25°C for SGL carbon. 236 co I 1 1 1 1 1 1 1 1 i i i i r O l l l l l l l l l I I 1 J I 1 o 0 20 0 40 0 80 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) Figure 6.3: Experimental and f i t ted (solid lines) adsorption isotherms of EG, HEI and HMP at 25°C for SGL carbon. 237 E i g u r e 6 . 4 : E x p e r i m e n t a l and f i t t e d ( s o l i d l i n e s ) a d s o r p t i o n i so therms of DMAE and DMP at 2 5 ° C f o r SGL c a r b o n . 238 co ri I 1 1 i 1 I I I I T i P I L_ I I ! I I ! I I I l l l l o 0 40 0 80 0 120 0 160 0 200 0 240 0 280 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) Figure 6.5: Experimental and f i t ted adsorption isotherms of DEA, 25°C for SGL carbon. (sol id lines) MDEA and TEA at 239 -T a b l e 6 . 3 : C o n s t a n t s of the F r e u n d l i c h e q u a t i o n at 2 5 ° C f o r SGL c a r b o n . Compound A n Max. cone , (m m o l / L ) BHEP 0.815 10.000 1000 DEA 1 .058 7.390 3000 DMAE 0.018 1 .371 1000 DMP 0.272 3.596 1000 EG 0.073 1 .798 1000 HE I 0.695 4.919 1000 HEOD 0.335 3.861 1000 HMP 0.476 5.239 1000 MDEA 0.400 3.885 3000 TEA 0.385 3.681 3000 THEED 0.570 4.720 1000 240 To remove the BHEP completely, a minimum of 5000 L x 100 (m mol BHEP/L)/1.4 (m mol BHEP/g Carbon) = 357,000 g of carbon are required. This simple calculation assumes that only BHEP is adsorbed by activated carbon, which is certainly not the case since DEA and other degradation compounds are also simultaneously adsorbed. Therefore, the carbon requirement would be much higher in practice. COMPARISON OF SGL AND DARCO CARBONS The adsorption isotherms of DEA and BHEP on SGL and DARCO carbons are shown in Figs . 6.6 and 6.7. It is clear that the adsorptive capacity of the DARCO carbon is much lower than that of SGL carbon. This effect is probably due to the higher total surface area and iodine number of the SGL carbon (see Table 6.1). Therefore, the DARCO carbon was excluded from further tests. The constants of the Freundlich equation for DARCO carbon are presented in Table 6.4. 241 co CO CO — i i 1 1 1 r o o SGL + + DARCO o U to cd CVJ o &0 f-4 O o i s • o 03 < > CD CD°CD CD CD O H CD CD CD CD CD o d CD 40 0 80 0 120 0 160 0 200 0 240 0 280 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) Figure 6.6: Experimental and f itted (sol id lines) adsorption isotherms of DEA at 25°C for SGL and DARCO carbons. 242 N co I i ~i i i i i i i i i i r _ o o SGL ^ + + DARCO O N ,0 i-i (0 O t—t O S o a " " 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) Figure 6.7: Experimental and f i t ted (solid lines) adsorption isotherms of BHEP at 25°C for SGL and DARCO carbons. 243 EFFECT OF TEMPERATURE In order to investigate the effect of temperature on adsorption, additional experiments were conducted at 40°C and 80°C. The results are plotted in Figs. 6.8 to 6.9 and the constants for the Freundlich equation are shown in Tables 6.5 and 6.6. The adsorptive capacity was, in general, found to decrease with temperature. However, the change was not major between 25°C and 40°C. At 80°C the difference was significant in the lower concentration ranges. REGENERATION OF SGL CARBON The adsorptive capacities of fresh and water-washed saturated carbons are shown in Table 6.7. The data indicate that removal due to the water wash is v ir tua l ly negligible. The results of the thermal regeneration experiments are presented in Table 6.8. They are given in terms of adsorptive capacities of fresh and thermally regenerated carbon. It can be concluded that the regeneration efficiency increases with temperature. However, even at 300°C, the carbon was only part ia l ly regenerated. The boil ing points of DEA and BHEP are 217°C at 150mm Hg and 210 to 220°C at 50mm Hg, respectively. Therefore, i t is 244 40 0 80 0 120 0 160 0 200 0 240 0 280 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) F i g u r e 6 . 8 : E x p e r i m e n t a l and f i t t e d ( s o l i d l i n e s ) a d s o r p t i o n i so therms of DEA as a f u n c t i o n of temperature f o r SGL c a r b o n . 245 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) F i g u r e 6 . 9 : E x p e r i m e n t a l and f i t t e d ( s o l i d l i n e s ) a d s o r p t i o n i sotherms of BHEP as a f u n c t i o n of t emperature for SGL c a r b o n . 246 _ • • 25 C ^ A A 40 C fn CO o ci ~ o o 80 C cd o bj)cv» ~ o P I I I ! I I I I I I I I I I I o 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) ire 6.10: Experimental and f i t ted (sol id lines) adsorption isotherms of HEOD as a function of temperature for SGL carbon. 247 d I 1 1 1 — T 1 i i i i i i i r _ • • 25 C 0 A A 40 C O oi " o o 80 C u O d ° . I i i i i i i i i i i i i i i o 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 EQUILIBRIUM CONCENTRATION, C (m mol/L) Figure 6.11: Experimental and f i t ted (solid lines) adsorption isotherms of THEED as a function of temperature for SGL carbon. 248 T a b l e 6 .4 : C o n s t a n t s of the F r e u n d l i c h e q u a t i o n at 2 5 ° C f o r DARCO c a r b o n . Compound A n Max. cone , (m m o l / L ) DEA 0.210 5.983 3000 BHEP 0.015 2.019 1000 T a b l e 6 .5 : C o n s t a n t s of the F r e u n d l i c h e q u a t i o n at 4 0 ° C f o r SGL c a r b o n . Compound A n Max. cone , (m m o l / L ) DEA 1 .020 7.151 3000 BHEP 0.566 6.340 1000 HEOD 0.280 3.552 1000 THEED 0.460 4.237 1000 6: C o n s t a n t s of the f o r SGL c a r b o n . F r e u n d l i c h e q u a t i o n a t 8 0 ° C Compound A n Max. cone . (m m o l / L ) DEA 0.482 4.345 3000 BHEP 0.327 4.250 1000 HEOD 0.144 2.675 1000 THEED 0.270 3.208 1000 249 Table 6.7: Adsorptive capacities of fresh and water washed SGL carbons. Adsorptive capacity (m mol/g carbon) DEA BHEP HEOD THEED Fresh Carbon 1.143 0.057 0.257 1.371 Water Washed Carbon 0 0 0 0.057 Table 6.8: Adsorptive capacities of fresh and thermally regenerated SGL carbons. Adsorptive capacity (m mol/g carbon) DEA BHEP HEOD THEED Fresh Carbon 1. 143 0.057 0. 257 1 . 371 Carbon Regenerated at 150 C 0. 343 0.029 0. 057 0. 171 Carbon Regenerated at 300 C 0. 514 0.034 0. 086 0. 400 250 unlikely that most of the adsorbed BHEP or DEA would be volatized at 300°C. 0 The results of regeneration using HC1 and HN03 are presented in Tables 6.9 and 6.10, respectively. Some interesting observation may be made. After HC1 treatment, the carbon was able to re-adsorb equal amounts of THEED and roughly half the amounts of BHEP and HEOD adsorbed by virgin carbon. Furthermore, the regenerated carbon did not adsorb DEA any further. The reason why the HC1 treated carbon did not regain i ts DEA adsorptive capacity is not entirely c lear. It is possible that the DEA-HC1 reaction product is less soluble in water than the DEA-HN03 reaction product and therefore d i f f i cu l t to dislodge from the carbon surface. The phenomenon of preferential adsorption of larger molecules is demonstrated by the fact that the carbon adsorbs more THEED than the other compounds and that i t re-adsorbs equal amounts of THEED after the acid wash. Ideally, one would l ike to adsorb the undesirable compounds ( i . e . BHEP, HEOD and THEED) without adsorbing any DEA. Unfortunately this does not appear to be possible under normal conditions. However, i f one can prevent further DEA adsorption, while adsorbing other undesirable compounds, this would be advantageous. Further investigation into this matter is required. Repeated acid washes showed no significant deterioration in adsorptive capacity. 251 Table 6.9: Adsorptive capacities of fresh and 1 M HCl washed SGL carbons. Adsorptive capacity (m mol/g carbon) DEA BHEP HEOD THEED Fresh Carbon 1.143 0 .057 0. 257 1 .371 Acid Washed Carbon 0 0 .029 0. 143 1 .371 Acid Washed Carbon 0 0 .034 0. 143 1 .371 Acid Washed Carbon 0 0 .029 0. 200 1 .314 Table 6.10: Adsorptive capacities of fresh and 1 M HNO, washed SGL carbons. Adsorptive capacity (m mol/g carbon) DEA BHEP HEOD THEED Fresh Carbon 1.143 0.057 0.257 1.371 Acid Washed Carbon 0.571 0.057 0.229 1.371 Acid Washed Carbon 0.571 0.057 0.246 1.371 Acid Washed Carbon 0.457 0.057 0.200 1.314 252 D i f f e r e n t a c i d c o n c e n t r a t i o n s r a n g i n g from 5 M to 0.1 M were u s e d . A d s o r p t i v e c a p a c i t i e s of a c i d t r e a t e d carbon as a f u n c t i o n of a c i d c o n c e n t r a t i o n are shown i n T a b l e s 6.11 and 6 .12 . Very s i m i l a r r e s u l t s were o b t a i n e d p r o v i d e d the carbon remained i n an a c i d i c medium. In most c a s e s , the pH d u r i n g the a c i d wash ranged from 2 to 4. A f t e r HN0 3 a c i d wash (see T a b l e 6 . 1 0 ) , the carbon was a b l e to r e g a i n i t s o r i g i n a l a d s o r p t i v e c a p a c i t y f o r THEED and BHEP. I t s a d s o r p t i v e c a p a c i t y for HEOD was a l s o c l o s e to i t s o r i g i n a l v a l u e . C o n t r a r y to the H C l e x p e r i m e n t s , i t was a l s o a b l e to p a r t l y r e g a i n i t s a d s o r p t i v e c a p a c i t y for DEA. The s u p e r i o r performance of HN0 3 may be e x p l a i n e d by the f a c t t h a t HN0 3 i s a s t r o n g o x i d i z i n g a g e n t . I t i s p o s s i b l e t h a t HN0 3 was r e s p o n s i b l e for p a r t i a l o x i d a t i o n of the adsorbed s p e c i e s , t h e r e f o r e making room f o r the compounds to be r e a d s o r b e d on the c a r b o n . The a p p l i c a b i l i t y of a c i d treatment w i l l however depend on economics and waste d i s p o s a l . 253 Table 6.11: Adsorptive capacities of HC1 regenerated carbon. HC1 concentration used for regeneration Adsorptive capacity (m mol/g carbon) (M) DEA BHEP HEOD THEED 5 0 0.034 0.143 1.371 1 0 0.029 0.143 1.371 0.1 0 0.034 0.137 1.314 Table 6.12: Adsorptive capacities of HN03 regenerated carbon. HN03 concentration Adsorptive capacity used for (m mol/g carbon) regeneration (M) DEA BHEP HEOD THEED 5 0.571 0.057 0.229 1 .371 1 0.571 0.057 0.229 1.371 0.1 0.514 0.063 0.217 1.371 254 INDUSTRIAL SAMPLES Amine samples were obtained from two gas plants located in Western Canada and analysed by gas chromatography. Typical chromatograms of samples taken upstream and downstream of activated carbon beds in Plant #1 are shown in F i g . 6.12. The chromatograms indicate the presence of substantial quantities of impurities including BHEP, HEOD, THEED, EG, HEI and TEA. The detailed results are summarized in Table 6.13. A comparison of the inlet and outlet concentrations of the amine solutions indicates that, with the exception of a minor reduction in BHEP and THEED concentrations in Units II and I, respectively, the carbon adsorbers were ineffective in removing degradation compounds. It should also be noted that the carbon in Unit II had been in service for only 4 months and did not perform any better than the carbon in Units I and III which is about 4 years old. A second set of samples were later obtained from Plant #1 just after the adsorbers were loaded with fresh carbon. The chromatograms of samples taken upstream and downstream of the bed at different time intervals are shown in Figs. 6.13 to 6.14. As can be seen from F ig . 6.13, even after 6 hours, the carbon bed was only removing degradation compounds part ia l ly along with some DEA. 255 Figure 6.12: Chromatograms of amine samples taken (a) upstream and (b) downstream of the carbon adsorber i n Unit I of Plant #1. 256 Table 6.13: Concentrations of amine samples taken from the i n l e t and outlet of activated carbon beds in Plant #1. COMPOUND UNIT 1 I UNIT II UNIT III IN OUT IN OUT IN OUT Concentration i r (m mol/L) DEA 2300 2300 2400 2400 2450 2450 BHEP 80 80 94 93 87 87 HEOD 23 23 50 50 24 24 THEED 104 102 99 99 99 99 EG 20 20 40 40 66 66 HEI 50 50 40 40 60 60 TEA 40 40 35 35 50 50 257 (a) upstream (b) downstream Figure 6.13: Chromatograms of amine samples taken upstream and downstream of the carbon bed in Plant #1, 6 h aft e r the bed was loaded with fresh carbon. 258 The chromatograms of samples taken after 10 and 20 days, (see F i g . 6.14) show no removal at a l l . Therefore i t can be definitely concluded that the carbon bed had become saturated in less than 10 days. Figure 6.15 shows the chromatograms of the samples taken upstream and downstream of the activated carbon beds in Plant #2. The only important difference between the samples from Plant #1 and #2 is that the sample from Plant #2 did not contain TEA. As in the case of Plant #1, the bed in Plant #2 did not remove significant quantities of degradation compounds. 259 10 days 20 days Figure 6.14: Chromatograms of amine samples taken downstream of the carbon bed i n Plant #1, a) 10 and b) 20 days after the bed was loaded with fresh carbon. 260 W o td Q O W (a) upstream 3 Q U L i r o o w a. s u s Q H U (b) downstream 1 r Figure 6.15: Chromatograms of amine samples taken a) upstream and b) downstream of the carbon bed in Plant #2. 261 6.2 COLUMN ADSORPTION EXPERIMENTS It is clear from the results of the batch adsorption tests that activated carbon is not part icularly effective for removing amine degradation compounds. However, many gas plants use carbon adsorbers. Since no information on the breakthrough characteristics of these carbon adsorbers are available in the open l i terature , gas plant operators appear to regenerate or change the carbon somewhat a r b i t r a r i l y . For example in Plant # 1, which consists of three paral le l units, carbon in one of the adsorbers was changed after four months while that of a second adsorber was changed only after four years. In order to obtain some information on the breakthrough characteristics of the activated carbon adsorbers used in gas plants, dynamic adsorption tests were conducted using part ia l ly degraded industrial amine solutions. 6.2.1 EXPERIMENTAL EQUIPMENT AND PROCEDURE A simplified flowsheet of the experimental equipment is shown in F i g . 6.17. The major components of the equipment are a plexiglass column (50.8 mm ID, 1.524 m long) f i l l e d with granular activated carbon, the solution pump (Model 210-513, Micropump, Concord, CT) and associated instrumentation and piping. 262 Granular SGL carbon particles (8x30 _ mesh, 1.5-1.7 mm mean particle diameter, 0.48 g/mL particle bulk density) were packed into the column and confined by fine stainless steel screens at the both end of the column. D i s t i l l e d water was pumped through the column at the same rate as the solution for a particular run prior to the start of the experiment. This was done in order to f i l l the carbon particles with water and prevent sudden movement of the particles at the beginning of the experiment due to sudden flow of solution. The flow rate was monitored by a custom-built capi l lary flow meter (1.75 mm ID, 3.17 mm OD, 50.8 mm long). In order to reduce channeling, the column was operated in the upflow mode. Solutions of known concentration were pumped from the solution tank at a constant flow rate through the column. Samples were withdrawn at appropriate intervals from the outlet of the column and analysed by gas chromatography. After the end of each experiment, the used carbon was discarded and the column was f i l l e d with fresh carbon. Only the effect of flow rate was studied. Although relative concentrations of various compounds may also affect the performance of the column, i t was impractical to prepare large quantities of degraded samples required for column 263 exper iments i n the l a b o r a t o r y . S ince the s o l u t i o n used was o b t a i n e d from a gas p r o c e s s i n g p l a n t , i t was c o n s i d e r e d to be r e p r e s e n t a t i v e of t y p i c a l i n d u s t r i a l DEA s o l u t i o n s and the r e s u l t s shou ld t h e r e f o r e be u s e f u l to i n d u s t r y . 264 COLUMN SAMPLING PORT 2 : PUMP SOLUTION TANKS Figure 6.16: S i m p l i f i e d flowsheet of the equipment for the study of dynamic activated carbon adsorption of amine degradation products. 265 6.2.2 MATHEMATICAL MODELLING Mathematical modelling of multicomponent adsorption systems is quite complex due to interactions between the components during diffusion and competitive adsorption onto the available s i tes . The complexity increases with the number of components present. Furthermore, considerable effort and time are required for the determination of interaction parameters between the adsorbing compounds. In order to overcome these complexities, attempts have been made to use single component isotherm data to describe multicomponent adsorption. Myers and Prausnitz [108] developed the "Ideal Adsorbed Solution" or IAS theory for calculating adsorption equi l ibr ia for multicomponent gas mixtures using pure component adsorption isotherms. Radke and Prausnitz [109] later extended this theory to multicomponent adsorption from dilute l iquid solutions. The IAS theory has been successfully applied to describe multicomponent fixed bed adsorption from dilute solutions [110 -111]. However, no such model is available for multicomponent adsorption of concentrated solutions such as amine solutions. Higher solution concentration increases the non-ideality of the system by increasing component interaction. In such cases, the IAS theory would probably f a i l . The alternative is to determine the interaction parameters experimentally and then develop equations for the isotherm. This approach was not taken here due to the 266 c o n s i d e r a b l e t ime and e f f o r t r e q u i r e d . However, an attempt was made to a p p l y the IAS t h e o r y us ing the Wang and T i e n model [110]. For a system c o n t a i n i n g N components i n s o l u t i o n and i n the adsorbed phase , the f o l l o w i n g e q u a t i o n s may be w r i t t e n [110]: c i = c ^ C n ^ T l z j z • = S i q T = 1 (6.1) (6.2) (6.3) C i ° o RT q-0 lb = — / - i - d C i ° (6.4) A o c i where, c^ = c o n c e n t r a t i o n of s o l u t e i i n the l i q u i d phase , C j ° { } - c o n c e n t r a t i o n of s i n g l e s o l u t e i n l i q u i d phase , q^ = c o n c e n t r a t i o n of the s o l u t e i n the adsorbed phase , q T = t o t a l a d s o r b a t e c o n c e n t r a t i o n i n the adsorbed phase , z^ = mole f r a c t i o n i n the adsorbed phase , X = s u r f a c e a r e a of the a d s o r b e n t , and 267 = s p r e a d i n g p r e s s u r e . The a c t i v a t e d carbon p r o c e s s may be d e s c r i b e d as f o l l o w s . A s o l u t i o n c o n t a i n i n g N a d s o r b a b l e s p e c i e s f lows through a f i x e d bed packed w i t h g r a n u l a r a c t i v a t e d carbon under p l u g flow c o n d i t i o n s . N e g l e c t i n g a x i a l d i s p e r s i o n , assuming no c h e m i c a l r e a c t i o n s and a l i n e a r d r i v i n g f o r c e for mass t r a n s f e r , the f o l l o w i n g e q u a t i o n s may be w r i t t e n : 6c- 8q-u — ^ + p K —i- = 0 (6 .5) 6x D 60 6q. 3 k , . T 7 1 = — ( c i " c s i ) = k s i ( < a s i - 5 i ) ( 6 ' 6 ) g 0 1 5 1 5 1 1 P P Wang and T i e n [110] r e - w r o t e E q s . 6.5 and 6.6 i n d i m e n s i o n l e s s form as f o l l o w s : u —i- + = 0 (6 .7) 8x A , 56* A- 6q ; * k n • r _ k _ • p _ - ± = ( c - + - c ^ * ) = A- P 5 1 P ( q s i * - q i * ) (6 .8) A , 66* k X l 1 5 1 1 3 k u p b 5 1 1 where, C i * = ^ i - (6 .9) c i o q i * = ^ i - (6.10) q 10 268 A- = _ "b^i 10 i - L f b k  A i r p "p l i e = t - xc . /u (6.11) (6.12) (6.13) (6.14) The corresponding i n i t i a l and boundary conditions are: qj* = 0 at x* £ 0 and 8*<0 c ^ = 1 at x+ = 0 and 8+ Z 0 The relationship between c^ and q^ is expressed by means of the Freundlich equation [106] as follows: Si = A i ( c i > l / n (15.15) The l iquid phase and pore mass transfer coefficients were estimated using the following equations [112]: 3k-,, 2.62 ( D H u ) 0 , 5 — l i - [ 1 1 . b ] (6.16) r p 1 - 0.4 ( 2 r p ) 1 - t > 15 Dpore•X:(1 - fK) = _ L l ! b_ (6.17) R s i A r p The pore d i f fus iv i ty Dpore^ was calculated as follows: 269 Dpore^ = ( 6 . 1 8 ) 2 where, D - ^ i s the l i q u i d phase d i f f u s i v i t y and \p i s the i n t e r n a l p o r o s i t y of the a d s o r b e n t . X i n E q . 6.17 i s d e f i n e d as f o l l o w s : c a l c u l a t i o n , x^ was taken to be u n i t y . The l i q u i d d i f f u s i v i t i e s f o r DEA was o b t a i n e d from [113] and the d i f f u s i v i t y of o ther compounds were taken to be e q u a l to D E A ' s . 6 . 2 . 3 BREAKTHROUGH CURVES AND MODEL PREDICTIONS The breakthrough c u r v e s f o r a p a r t i a l l y degraded DEA s o l u t i o n (2 .6 mol D E A / L ; 0.10 mol B H E P / L ; 0. 043 mol HEOD/L; 0.13 mol T H E E D / L ) , were de termined f o r t h r e e d i f f e r e n t f low r a t e s and c o r r e s p o n d i n g model p r e d i c t i o n s are shown i n F i g s . 6.17 to 6 .19 . As can be seen from these f i g u r e s , DEA and THEED breakthroughs occur e a r l y . T h i s i s f o l l o w e d by HEOD and BHEP. P r o b a b l y the most important c o n c l u s i o n t h a t can be drawn i s tha t the b r e a k t h r o u g h t imes are v e r y s h o r t and t h a t complete removal of d e g r a d a t i o n compounds i s t h e r e f o r e Xi = 0.775/(1 - 0.225 r c 0 ' 4 ) (6.19) where, r g i s the s e p a r a t i o n f a c t o r . For the presen t 270 v i r t u a l l y i m p o s s i b l e . A computer program f o r the IAS a d s o r p t i o n model deve loped at the Syracuse U n i v e r s i t y was used i n the p r e s e n t work [114] . As can be seen, the p r e d i c t e d breakthrough t ime i s somewhat h i g h e r than the e x p e r i m e n t a l v a l u e s . T h i s i s p r o b a b l y due to the presence of o ther minor d e g r a d a t i o n compounds i n the s o l u t i o n which were not i n c l u d e d i n the model as the i n c l u s i o n of a d d i t i o n a l compounds c r e a t e s severe convergence p r o b l e m s . Another p r o b a b l e reason i s t h a t the IAS t h e o r y , which i s a p p l i c a b l e to d i l u t e s o l u t i o n s , has been a p p l i e d to h i g h l y c o n c e n t r a t e d DEA s o l u t i o n s which may have i n c r e a s e d the n o n - i d e a l i t i e s i n the sys tem. The p r e d i c t i o n s were much b e t t e r when a aqueous s o l u t i o n c o n t a i n i n g o n l y 2.0 mol D E A / L and 0.10 mol BHEP/L was passed through the bed. The breakthrough c u r v e s and the model p r e d i c t i o n s are shown i n F i g . 6 .20 . T h i s suggests t h a t d e v i a t i o n of the model p r e d i c t i o n from e x p e r i m e n t a l r e s u l t s i n c r e a s e s w i t h the number of compounds. 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 TIME (h) TIME (h) Figure 6.17: Experimental and calculated breakthrough curves of a p a r t i a l l y degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. (Solution v e l o c i t y : 1.7 mm/s) ro - j TIME (h) TIME (h) Figure 6.18: Experimental and calculated breakthrough curves of a p a r t i a l l y degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. " to (Solution v e l o c i t y : 2.54 mm/s) oi CO 6 O C J CD O ci o b 01 0.0 o 6 T— i 1—i—i 1 — r o THEED o HEOD MODEL ± 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 TIME (h) TIME (h) Figure 16.19: Experimental and calculated breakthrough curves of a p a r t i a l l y degraded solution containing 2.6 mol DEA/L, 0.10 mol BHEP/L, 0.043 mol HEOD/L and 0.13 mol THEED/L. (Solution v e l o c i t y : 3.0 mm/s) 2.0 U> 274 CM o O co CD © o d o d — i — i — i 1 r a • DEA A A BHEP MODEL i — r 0.0 0.5 1.0 1.5 TIME (h) 2.0 Figure 16.20: Experimental and calculated breakthrough curves of a solution containing 2.0 mol DEA/L and 0.10 mol BHEP/L. (Solution v e l o c i t y : 1.7 mm/s) Chapter 7 CHEMICAL PURIFICATION OF DEGRADED DEA SOLUTIONS I n s t e a d of removing d e g r a d a t i o n compounds from the s o l u t i o n s , r e c o v e r i n g the DEA by r e v e r s i n g the d e g r a d a t i o n r e a c t i o n s appears more a t t r a c t i v e . T h e r e f o r e i t was d e c i d e d to conduct s y s t e m a t i c t e s t s to s tudy the r e v e r s a l of DEA d e g r a d a t i o n r e a c t i o n s . The r e v e r s a l exper iments i n c l u d e d c o n t a c t i n g a l k a l i s such as NaOH, KOH, NH„OH and b a s i c a n i o n exchange r e s i n s e i t h e r w i t h degraded DEA s o l u t i o n s or m i x t u r e s p r e p a r e d from pure d e g r a d a t i o n compounds. The a l k a l i s and r e s i n were expec ted to p r o v i d e h y d r o x y l ions f o r the r e v e r s a l of HEOD and THEED to DEA. S i n c e d i r e c t a d d i t i o n of a l k a l i s to the s o l u t i o n would i n c r e a s e the c o n c e n t r a t i o n of c a t i o n s ( N a + , K + e t c . ) i n the DEA s o l u t i o n s , i t was f e l t neces sary to remove them a l s o from the system. A s t r o n g l y a c i d i c c a t i o n i c exchange r e s i n was used f o r t h i s p u r p o s e . 7.1 EXPERIMENTAL MATERIALS AND PROCEDURE NaOH and KOH s o l u t i o n s of a p p r o x i m a t e l y 22 M s t r e n g t h were p r e p a r e d s i m p l y by d i s s o l v i n g NaOH/KOH p e l l e t s in d i s t i l l e d water . The s o l u t i o n s were then s t a n d a r d i s e d a g a i n s t 10 M H C l and d i l u t e d to 15 M NaOH and 20 M KOH s t r e n g t h by adding d i s t i l l e d water . 275 276 A b a s i c g e l type r e s i n w i t h q u a t e r n a r y ammonium f u n c t i o n a l i t y , c o m m e r c i a l l y known as A m b e r l i t e IRA-400(OH) was used f o r r e v e r s a l exper iments u s i n g r e s i n . A s t r o n g l y a c i d i c g e l type r e s i n w i t h s u l f o n i c a c i d f u n c t i o n a l i t y , c o m m e r c i a l l y known as A m b e r l i t e IR-120 p l u s ( H ) , was used for c a t i o n removal e x p e r i m e n t s . Both of the r e s i n s were purchased from Chemica l Dynamics C o r p o r a t i o n , South P l a i n s f i e l d , N J . 7 .1 .1 ALKALI ADDITION EXPERIMENTS For the exper iments i n v o l v i n g d i r e c t a l k a l i a d d i t i o n , the f o l l o w i n g pr oc e dur e was f o l l o w e d : P r e c i s e l y known q u a n t i t i e s of a l k a l i s o l u t i o n s of known c o n c e n t r a t i o n were added to s t o p p e r e d 100 mL f l a s k s each c o n t a i n i n g 20 mL of degraded s o l u t i o n . E q u a l amounts of d i s t i l l e d water were added to a 100 mL f l a s k c o n t a i n i n g 20 mL of the degraded s o l u t i o n in o r d e r to compensate for the water i n t r o d u c e d w i t h the a l k a l i d u r i n g the gas chromatograph ic a n a l y s i s of b lank samples . The s toppered f l a s k s were then shaken in a temperature c o n t r o l l e d m e c h a n i c a l shaker ( C o n t r o l l e d Environment I n c u b a t o r Shaker , New Brunswick S c i e n t i f i c C o . , New B r u n s w i c k , NJ) at 250 rpm for d i f f e r e n t t ime i n t e r v a l s r a n g i n g from 1 min to 1 h . 277 The s o l u t i o n s were then a n a l y s e d by gas chromatography . 7 . 1 . 2 ION EXCHANGE EXPERIMENTS For exper iments i n v o l v i n g ion exchange r e s i n s , degraded s o l u t i o n s were e i t h e r c o n t a c t e d w i t h known q u a n t i t i e s of the r e s i n i n 100 mL f l a s k s f o l l o w i n g the p r e v i o u s l y d e s c r i b e d p r o c e d u r e or passed throu gh a 20 mm d i a m e t e r , 0.5 m long g l a s s column packed w i t h r e s i n at a flow r a t e of 0.5 mL/min . The s o l u t i o n s were then a n a l y s e d by gas chromatography . 7 . 1 . 3 CATION REMOVAL EXPERIMENTS For the c a t i o n removal e x p e r i m e n t s , NaOH t r e a t e d DEA samples were s imply c o n t a c t e d w i t h known q u a n t i t i e s of A m b e r l i t e IR-120 p l u s ( H ) r e s i n f o l l o w i n g the p r e v i o u s l y d e s c r i b e d p r o c e d u r e . The Na* content was de termined by atomic a b s o r p t i o n s p e c t r o m e t r y (Model 303, P e r k i n E l m e r , N o r w a l k , C T ) . 278 7.2 RESULTS AND DISCUSSION 7.2 .1 ALKALI TREATMENT OF INDUSTRIAL SAMPLES Amine samples were o b t a i n e d from two gas p l a n t s l o c a t e d i n Western Canada and s u b j e c t e d to a l k a l i t r e a t m e n t . U n l i k e NH„0H (15 M ) , both NaOH and KOH were a b l e to cause the d i s a p p e a r e n c e of HEOD and THEED from the degraded s o l u t i o n s . Chromatograms of the degraded samples from P l a n t #1 b e f o r e and a f t e r NaOH and KOH treatment are shown i n F i g s . 7.1 and 7 . 2 , r e s p e c t i v e l y . As can be seen , both the HEOD and THEED peaks d i s a p p e a r e d w h i l e the BHEP peak remained unchanged. A new minor peak, which c o u l d not be i d e n t i f i e d , a p p e a r e d . The DEA peak area as de termined by the gas chromatograph' s i n t e g r a t o r i n c r e a s e d , thereby r a i s i n g the DEA c o n c e n t r a t i o n from 2.3 m o l / L to about 2.4 m o l / L , a l t h o u g h t h i s may not be e v i d e n t from the chromatograms. T h i s suggests that at l e a s t p a r t of the d e g r a d a t i o n p r o d u c t s were r e c o n v e r t e d to DEA. Chromatograms of the samples from P l a n t #2 b e f o r e and a f t e r NaOH and KOH treatment are shown i n F i g s . 7.3 and 7 . 4 , r e s p e c t i v e l y . S i m i l a r t r e n d s can be seen . EFFECTS OF CONTACT TIME AND TEMPERATURE To e v a l u a t e the e f f e c t of c o n t a c t t ime on the r e v e r s a l r e a c t i o n s , 0.02 mole NaOH ( or KOH) was c o n t a c t e d wi th 20 mL samples of degraded s o l u t i o n f o r t ime p e r i o d s rang ing from 1 279 a) before b) after Figure 7.1: Chromatograms of 20 mL samples from Plant # 1 (a) before and (b) aft e r addition of 0.02 mole of 15 M NaOH solution at 20°C for 5 min. 280 Figure 7.2 Chromatograms of 20 mL samples from Plant # 1 (a) before and (b) aft e r addition of 0.02 mole of 20 M KOH solution at 20°C for 5 min. < u o (a) before ( b ) a f t e r Figure 7.3: Chromatograms of 20 mL samples from Plant # 2 (a) before and (b) after addition of 0.02 mole of 15 M.NaOH solution at 20°C for 5 min. 282 Figure 7 .4: Chromatograms of 20 mL samples from Plant # 2 (a) before and (b) after addition of 0.02 mol of 20 M KOH solution at 20°C for 5 min. 283 min to 1 h . The chromatograms of the samples taken a f t e r 1 min and 1 h a r e shown i n F i g . 7 . 5 . A l l the HEOD and a lmost a l l the THEED d i s a p p e a r e d a f t e r 1 m i n ; v e r y l i t t l e change o c c u r r e d d u r i n g the next h o u r . The e f f e c t of temperature on the r e v e r s a l r e a c t i o n s was s t u d i e d by c o n d u c t i n g exper iments at t emperatures r a n g i n g from 25 to 1 0 0 ° C . The c o r r e s p o n d i n g chromatograms are shown i n F i g . 7 . 6 . As can be seen from the chromatograms, w i t h i n t h i s temperature range , there appears to be no a p p r e c i a b l e e f f e c t on the r e v e r s a l r e a c t i o n s . H i g h e r temperatures were a v o i d e d due to the f a c t tha t d e g r a d a t i o n r a t e s i n c r e a s e s u b s t a n t i a l l y w i t h t e m p e r a t u r e . T h i s r e s u l t t o g e t h e r w i t h the n e g l i g i b l e e f f e c t of c o n t a c t t ime beyond 1 min suggests t h a t the r e v e r s a l r e a c t i o n s a r e f a s t and go to c o m p l e t i o n i n a mat ter of s econds . 7 .2 .2 HEOD AND THEED REVERSAL A l t h o u g h both HEOD and THEED peaks d i s a p p e a r e d as a r e s u l t of NaOH and KOH t r e a t m e n t , i t remained to be d e t e r m i n e d which r e a c t i o n p r o d u c t s were formed and what p r o p o r t i o n r e v e r t e d to DEA. T h e r e f o r e , exper iments were conducted w i t h pure aqueous HEOD, THEED and DEA s o l u t i o n s . 284 Figure 7.5: Chromatograms of 20 mL samples from Plant # 2 treated with 0.02 mole of 15 M NaOH solution at d i f f e r e n t time i n t e r v a l s . Figure 7.6: Chromatograms of 20 mL samples from Plant # 1 treated with 0.02 mole - of 15 M NaOH solution at (a) 25°C and (b) 100°C for 5 min. 286 When a 10 mL s o l u t i o n c o n t a i n i n g 0.12 M DEA and 0.31 M HEOD was c o n t a c t e d wi th C 0 1 2 5 mol of NaOH, the HEOD r e v e r t e d almost e n t i r e l y to DEA as c o n f i r m e d by gas chromatography . The chromatograms of t h i s sample be fore and a f t e r NaOH a d d i t i o n a r e shown i n F i g . 7 . 7 . S i m i l a r r e s u l t s were a l s o o b t a i n e d w i t h KOH (see F i g . 7 . 8 ) . A d d i t i o n a l exper iments to de termine the e f f e c t s of temperature on the NaOH/KOH a d d i t i o n were a l s o p e r f o r m e d . The q u a n t i t y of NaOH (or KOH) r e q u i r e d to c o n v e r t one mole of HEOD to DEA was c a l c u l a t e d and the r e s u l t s are summarized i n T a b l e s 7.1 and 7 . 2 . From the r e s u l t s i t i s c l e a r that r o u g h l y 2 moles of NaOH (or KOH) are r e q u i r e d to c o n v e r t 1 mole of HEOD to DEA. T h i s i s due to the f a c t that C 0 2 generated i n the p r o c e s s of THEED r e v e r s a l r e a c t s wi th 2 moles of NaOH to form N a 2 C 0 3 and water (see E q . 2 . 3 4 ) . When NaOH was added to aqueous THEED s o l u t i o n s , no s i g n i f i c a n t change o c c u r r e d . A 0.5 M THEED s o l u t i o n was then s a t u r a t e d w i t h C 0 2 at room temperature and a tmospher ic p r e s s u r e in o r d e r to produce THEED carbamate as w e l l as H C 0 3 _ and thus make the sample more r e p r e s e n t a t i v e of i n d u s t r i a l gas t r e a t i n g s o l u t i o n s . Once a g a i n , NaOH a d d i t i o n r e s u l t e d i n no change. S u b s e q u e n t l y , a mixture of 1 M DEA and 0.5 M THEED was p r e p a r e d and s a t u r a t e d wi th C 0 2 p r i o r to NaOH a d d i t i o n . Aga in no change took p l a c e . 287 a o w « I < Id Q (a) before < w O (b) af t e r Figure 7 . 7 : Chromatograms of 20 mL samples (0.12 M DEA, 0.31 M HEOD) showing conversion of HEOD to DEA (a) before and (b) after addition of 0.0125 mole of 15 M NaOH solution at 20°C for 5 min. (b) a f t e r Figure 7.8: Chromatograms of 20 mL samples (0.12 M DEA, 0.31 M HEOD) showing conversion of HEOD to DEA (a) before and (b) after addition of 0.0125 mole of 20 M KOH solution at 20°C for 5 min. 289 Table 7.1: HEOD to DEA conversion r e s u l t i n g from contacting aqueous HEOD samples ( i n i t i a l concentration 0.31 mol/L HEOD; 0.12 mol/L DEA) with 15 M NaOH solutions under d i f f e r e n t conditions for 5 min. Temp. (C) Sample size (mL) NaOH added (mol) DEA cone. (mol/L) HEOD cone. (mol/L) NaOH/HEOD converted (mol/mol) 25 10 0.0125 0.42 0.00 40 20 0.0125 0.40 0.01 2.08 80 20 0.0125 0.40 0.01 2.08 100 20 0.0125 0.40 0.01 2.08 25 30 0.0125 0.30 0.12 2.19 25 30 0.0188 0.40 0.02 2.16 25 30 0.0250 0.44 0.00 2.69 Table 7.2: HEOD to DEA conversion r e s u l t i n g from contacting aqueous HEOD samples ( i n i t i a l concentration 0.31 mol/L HEOD; 0.12 mol/L DEA) with 20 M KOH solutions under d i f f e r e n t conditions for 5 min. Temp. Sample KOH DEA HEOD KOH/HEOD size added cone. cone. converted (C) (mL) (mol) (mol/L) (mol/L) (mol/mol) 25 10 0.009 0.43 0.00 -25 20 0.009 0.33 0.08 1.96 25 20 0.0125 0.39 0.02 2.16 40 20 0.0125 0.39 0.02 2.16 80 20 0.0125 0.40 0.02 2.16 100 20 0.0125 0.39 0.02 2.16 25 20 0.0160 0.44 0.00 2.58 290 I t was then d e c i d e d to degrade DEA i n the l a b o r a t o r y under c o n d i t i o n s maximiz ing THEED p r o d u c t i o n . Three d i f f e r e n t degraded s o l u t i o n s were p r e p a r e d and l a t e r t r e a t e d w i t h NaOH. For example, one s o l u t i o n was p r e p a r e d by d e g r a d i n g 4 m o l / L DEA at 1 7 5 ° C under a C 0 2 p a r t i a l p r e s s u r e of 2.19 MPa for 6 h . The s o l u t i o n o b t a i n e d was d i l u t e d by a dd i ng d i s t i l l e d water and a s o l u t i o n c o n t a i n i n g 0.6 m o l / L DEA, 0.05 m o l / L BHEP, 0.10 m o l / L HEOD and 0.20 m o l / L THEED was o b t a i n e d . When 0.0075 mol of NaOH were added to a 20 mL of the p r e p a r e d s o l u t i o n , a l l the HEOD r e v e r t e d to DEA thus i n c r e a s i n g the DEA c o n c e n t r a t i o n to 0.68 m o l / L w h i l e the THEED c o n c e n t r a t i o n f e l l s l i g h t l y to 0.18 m o l / L . When 0.015 mol of NaOH were added, the THEED peak d i s a p p e a r e d c o m p l e t e l y . The DEA c o n c e n t r a t i o n i n c r e a s e d to 0.9 m o l / L i n d i c a t i n g at l e a s t 50% c o n v e r s i o n of THEED to DEA. The BHEP peak remained i n t a c t and a new minor peak a p p e a r e d . The chromatograms of the samples be fore and a f t e r NaOH treatment are shown i n F i g . 7 . 9 . S i n c e a l l of the HEOD r e v e r t e d to DEA, one can de termine the q u a n t i t y of THEED which formed DEA. I f THEED were to f o l l o w the r e v e r s a l r e a c t i o n s r e p r e s e n t e d by E q s . 2 .35 and 2 .36 , each mole of THEED s h o u l d produce two moles of DEA. T h e r e f o r e , i n t h i s p a r t i c u l a r c a s e , the d i s a p p e a r a n c e of 0.2 m o l / L of THEED s h o u l d i n c r e a s e the DEA c o n c e n t r a t i o n by 0.4 m o l / L , i . e . r a i s e i t from 0.68 m o l / L to 1.08 m o l / L . (a) before • r J - r ! i i 2 Q 291 (b) a f t e r W-^-C ' r ' i ' \ J Q U W Figure 7.9: Chromatograms of 20 mL samples (1 M DEA, 0.06 M BHEP, 0.12 M HEOD, 0.40 M THEED) showing conversion of HEOD and THEED to DEA (a) before and (b) af t e r addition of 0.03 mole of 15 M NaOH solution at 25°C for 5 min. 292 However, the DEA c o n c e n t r a t i o n o n l y i n c r e a s e d by 0.22 m o l / L to 0.9 m o l / L . T h i s suggests t h a t o n l y about a h a l f of the THEED r e v e r t e d to DEA. The r e s u l t s of these experiments are summarized i n T a b l e 7 . 3 . They a l l show tha t a p p r o x i m a t e l y h a l f the THEED r e v e r t e d to DEA; the remainder p r o b a b l y formed some k i n d of sodium (or potass ium) s a l t w i t h NaOH (or KOH) as shown i n E q s . 2.37 and 2 .38 . The q u a n t i t y of NaOH (or KOH) r e q u i r e d to cause the d i s a p p e r e n c e of one mole of THEED was de termined as shown i n the f o l l o w i n g sample c a l c u l a t i o n . C o m p o s i t i o n of i n i t i a l sample: DEA-0 .60 m o l / L , BHEP-0.05 m o l / L , HEOD-0.10 m o l / L , THEED-0 .20 m o l / L . Sample s i z e = 20 mL NaOH added : 0.015 mol HEOD i n i n i t i a l sample = 0.1 (20/1000) = 0.002 mol THEED i n i n i t i a l sample = 0.1 (20/1000) = 0.004 mol mol NaOH NaOH used f o r HEOD r e v e r s a l = 0.002 mol x 2 mol HEOD = 0.004 m o l . NaOH used f o r THEED r e v e r s a l = 0.015 - 0.004 = 0.011 mol . mol NaOH 0.011 T h e r e f o r e , = = 2.75 mol THEED 0.004 F o r each mole of THEED to d i s a p p e a r , 0 .011/0 .004 or 2.75 moles of NaOH are r e q u i r e d . 293 Table 7 . 3(a): THEED to DEA conversion r e s u l t i n g from contacting aqueous THEED samples also containing DEA and HEOD with 15 M NaOH solutions under d i f f e r e n t conditions for 5 min. Sample # 1 NaOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 0.0075 0.0150 0.60 0.68 0.90 0.05 0.10 0.05 0.00 0.05 0.00 0.20 0.18 0.00 Sample # 2 NaOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 0.0075 0.0150 0.0300 1.00 1.11 1.15 1.34 0.06 0.12 0.06 0.00 0.06 0.00 0.06 0.00 0.40 0.38 0.35 0.00 Sample # 3 NaOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 1.50 0.15 0.25 0.35 0.015 1.74 0.15 0.00 0 .35 0.030 2.00 0.15 0.00 0.01 294 Table 7.3(b): THEED to DEA conversion r e s u l t i n g from contacting aqueous THEED samples also containing DEA and HEOD with 20 M KOH solutions under d i f f e r e n t conditions for 5 min. Sample # 1 KOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 0.0010 0.0150 0.60 0.70 0.91 0.05 0.05 0.05 0.10 0.00 0.00 0.20 0.17 0.00 Sample # 2 KOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 0.010 0.015 0.025 1 .00 1.12 1.16 1 .32 0.06 0.06 0.06 0.06 0.12 0.00 0.00 0.00 0.40 0.38 0.34 0.05 Sample # 3 KOH added (mol) DEA CONCENTRATION (mol/L) BHEP HEOD THEED 0.00 0.015 0.030 1 .50 1 .74 2.02 0.15 0.15 0.15 0.25 0.00 0.00 0.35 0.35 0.00 295 T h i s r e s u l t can be e x p l a i n e d i n terms of E q . 2 .46 , which suggests t h a t one mole of NaOH (or KOH) i s needed to r e a c t w i th the THEED carbamate molecu le and two a d d i t i o n a l moles of NaOH (or KOH) are r e q u i r e d to r e a c t wi th the C 0 2 r e l e a s e d from the carbamate . EFFECT OF NaOH (KOH) STRENGTH A l t h o u g h most of the exper iments were c a r r i e d out w i t h 15 M NaOH and 20 M KOH s o l u t i o n s , NaOH and KOH s o l u t i o n s of 5 M and 1 M s t r e n g t h , r e s p e c t i v e l y , were a l s o used i n some of the exper iments to determine whether the NaOH (or KOH) c o n c e n t r a t i o n had any s i g n i f i c a n t e f f e c t on the r e v e r s a l e f f i c i e n c y . The r e s u l t s of these exper iments are shown i n T a b l e s 7.4 and 7 . 5 . As can be seen from the t a b l e s , the NaOH (or KOH) s t r e n g t h does not have any s i g n i f i c a n t e f f e c t on the r e v e r s a l e f f i c i e n c y as i n d i c a t e d by the moles of NaOH (or KOH) r e q u i r e d to r e v e r s e one mole of HEOD or THEED. 296 Table 7 . 4 : Results showing the effect of a l k a l i strength on HEOD reversal (temperature 25°C). A l k a l i A l k a l i strength (M) Reversal e f f i c i e n c y (mol a l k a l i /mol HEOD) NaOH 15 2.08 NaOH 5 2.01 NaOH 1 2.03 KOH 20 2.16 KOH 5 2.11 KOH 1 2.17 Table 7.5: Results showing a l k a l i strength on THEED reversal (temperature 25°C). A l k a l i Reversal A l k a l i strength e f f i c i e n c y (M) (mol a l k a l i /mol THEED) NaOH 15 3.15 NaOH 5 3.10 NaOH 1 3.15 KOH 20 2.89 KOH 5 2.95 KOH 1 2.95 297 7 . 2 . 3 RESIN TREATMENT When a 20 mL sample of a degraded s o l u t i o n c o n t a i n i n g 2 mol D E A / L , 0.032 mol B H E P / L , 0.135 mol HEOD/L and 0.25 mol THEED/L was c o n t a c t e d w i t h 5 g of A m b e r l i t e IRA-400(OH) r e s i n , the c o n c e n t r a t i o n s of a l l compounds d e c r e a s e d . (see T a b l e 7 . 6 ) . THEED e x p e r i e n c e d the h i g h e s t decrease i n c o n c e n t r a t i o n f o l l o w e d by BHEP, DEA and HEOD. The decrease i n c o n c e n t r a t i o n may be e x p l a i n e d as f o l l o w s . S i n c e the d e g r a d a t i o n compounds e x i s t i n i o n i c forms, t h e i r r e s p e c t i v e c a t i o n s r e a c t w i t h the r e s i n and t h i s r e s u l t s i n the c o n c e n t r a t i o n d r o p . For example , i n the case of DEA, the DEA carbamate r e a c t s w i th the r e s i n i n the f o l l o w i n g manner: R R R ( C H 3 ) 3 N - O H + N - C - 0 - . . . H * > R ( C H 3 ) 3 N - 0 ~ C - N + H , 0 / I I H \ R O O R (7. 1 ) "DEA carbamate" The r e s u l t s of flow exper iments o b t a i n e d by p a s s i n g degraded DEA s o l u t i o n through a f r e s h l y r e g e n e r a t e d r e s i n bed are summarized i n T a b l e 7 . 7 . 298 Table 7.6: Results of batch Resin reversal experiments. Resin added (gm) DEA cone. (mol/L) BHEP cone. (mol/L) HEOD cone. (mol/L) THEED cone. (mol/L) 2.00 0.032 0.135 0.25 5 1.70 0.026 0.1175 0.20 % Reduction 15 18.75 12.96 20 Tbale 7.7: Results of Column Resin reversal experiments. Time CONCENTRATION !min) DEA BHEP HEOD (mol/L) THEED EG HE I TEA 0 2.40 0.094 0.05 0.10 0.04 0.04 0.035 1 0.80 0.030 - - - - -5 2.20 0.075 - 0.01 0.005 - 0.00.5 20 2.45 0.090 - 0.085 0.04 0.035 0.030 40 2.40 0.094 0.05 0.10 0.04 0.04 0.035 60 2.40 0.094 0.05 0.10 0.04 0.04 0.035 7.2.4 SODIUM ION REMOVAL EXPERIMENTS 299 Three 20 mL samples of degraded DEA solutions with d i f f e r e n t Na* content were contacted with various p r e c i s e l y measured quantities of Amberlite IR-120 plus(H) r e s i n . The r e s u l t s of these experimets are summarized i n Table 7.8. As can be seen from the table, the resin was very e f f e c t i v e i n removing Na* ions from the s o l u t i o n . The average Na* removal capacity was calculated to be approximately 57 mg Na*/g of r e s i n . I t should be noted that, i f other cations are a l s o present in the s o l u t i o n , they may also react with the r e s i n . Table 7.8: Results of Na* ion removal experiments. Resin Na+ concentration added (mg/L) (g) Sample #1 Sample #2 Sample #3 0 6210 7800 12770 1 3335 4900 8980 2 450 2010 6995 3 5 5 4070 4 1245 5 4 Average Na+ removal capacity = 58 mg/g of r e s i n . Removal capacity c a l c u l a t i o n , example: Removal capacity, mg/g of resin = (6210-3335)/l000 mL x 20 mL = 57.7 300 7.3 INDUSTRIAL APPLICATIONS I t has been shown tha t i t i s p o s s i b l e to r e v e r s e the HEOD and THEED f o r m a t i o n r e a c t i o n s by a d d i t i o n of e i t h e r NaOH or KOH. S i n c e BHEP i s formed v i a THEED, r e v e r s i n g the THEED f o r m a t i o n .would m i n i m i s e , i f not p r e v e n t , the f o r m a t i o n of BHEP. A l t h o u g h some THEED i s p r o b a b l y l o s t i n the form of s a l t s , about h a l f of i t can be c o n v e r t e d back to DEA. S i n c e HEOD was found to be c o r r o s i v e towards m i l d s t e e l [12 ] , the r e v e r s a l of HEOD not o n l y r e c o v e r s DEA but a l s o m i n i m i s e s c o r r o s i o n . The problem of e x c e s s i v e a c c u m u l a t i o n of N a + or K + c a t i o n s and t h e i r s a l t s can be c o n t r o l l e d by i n s t a l l i n g r e s i n beds . T h e r e f o r e , t h i s p u r i f i c a t i o n p r o c e s s s h o u l d be h e l p f u l to gas p l a n t s e x p e r i e n c i n g s o l u t i o n d e g r a d a t i o n and c o r r o s i o n p r o b l e m s . 7 .3 .1 CHOICE OF ALKALI Both NaOH and KOH can r e v e r s e c e r t a i n d e g r a d a t i o n r e a c t i o n s . The o n l y major d i f f e r e n c e l i e s i n the s o l u b i l i t i e s of N a 2 C 0 3 and K 2 C 0 3 which are formed upon r e a c t i o n w i t h C 0 2 (see E q . 2 . 3 4 ) . The l a t t e r i s more s o l u b l e than the former . T h i s means tha t N a 2 C 0 3 , i f present i n e x c e s s , p r e c i p i t a t e s out of s o l u t i o n thereby p o s s i b l y c r e a t i n g o p e r a t i o n a l p r o b l e m s . However, i f t h i s p r e c i p i t a t i o n takes p l a c e i n the surge t a n k , which i s the 301 p r e f e r r e d p l a c e f o r a l k a l i a d d i t i o n , the p r e c i p i t a t i o n may be of b e n e f i t , because i t would minimise the work l o a d of the c a t i o n exchange r e s i n bed . N a 2 C 0 3 i s a l s o known to be a b l e to break up so c a l l e d "heat s t a b l e s a l t s " which are formed due to D E A ' s r e a c t i o n wi th c a r b o x y l i c a c i d s such as formic and a c e t i c a c i d s , which have been d e t e c t e d i n i n d u s t r i a l s o l u t i o n s . A l t h o u g h heat s t a b l e s a l t s are not c o v e r e d i n t h i s s t u d y , i t i s a l s o l i k e l y tha t K 2 C 0 3 breaks up these s a l t s . T h e r e f o r e , t h e r e i s no need to remove a l l the N a + or K* i o n s . The c a t i o n exchange r e s i n can then be p l a c e d on a s l i p stream of the s o l u t i o n to c o n t r o l the N a + or K + c o n c e n t r a t i o n . 7 .3 .2 INTEGRATION INTO AN EXISTING PLANT The i n t e g r a t i o n of a l k a l i p u r i f i c a t i o n p r o c e s s e s i n t o an e x i s t i n g p l a n t can e a s i l y be acompl i shed wi th l i t t l e c a p i t a l i n v e s t m e n t . A t y p i c a l f lowsheet of a DEA p l a n t i s shown i n F i g . 7 .10 . NaOH (or KOH) s o l u t i o n s i s added to the surge tank u s i n g the condensate a d d i t i o n pump e i t h e r by i t s e l f or a l o n g wi th the condensate which i s o c c a s i o n a l l y added to the surge tank to m a i n t a i n the d e s i r e d s o l u t i o n c o n c e n t r a t i o n . The c o n t i n u o u s flow of DEA s o l u t i o n s i n and out of the surge tank s h o u l d p r o v i d e adequate m i x i n g of the NaOH (or KOH) Figure 7.10: Simplified flowsheet of a DEA plant showing the incorporation of the resin bed. 303 s o l u t i o n w i t h the DEA s o l u t i o n . The c a t i o n exchange r e s i n bed can be p l a c e d i n p a r a l l e l w i th the e x i s t i n g a c t i v a t e d carbon adsorber on a s l i p s tream taken from the o u t l e t of the surge tank . The s o l u t i o n p a s s i n g through the c a t i o n exchange r e s i n bed can then j o i n the stream from the carbon a d s o r b e r p r i o r to i t s e n t r a n c e i n t o the surge t a n k . The b l e n d i n g of the f i l t e r e d s o l u t i o n w i t h the tank s o l u t i o n s h o u l d a l s o p r o v i d e some a d d i t i o n a l m i x i n g . A l t h o u g h the c a r b o n adsorber i s u s u a l l y o p e r a t e d on a c o n t i n u o u s b a s i s , the c a t i o n exchange r e s i n bed may have to be opera ted on ly o c c a s i o n a l l y depending on the Na*( or K + ) c o n c e n t r a t i o n s . As mentioned b e f o r e , the r e v e r s a l r e a c t i o n r a t e s are v e r y f a s t and appear to go to c o m p l e t i o n i n l e s s than a m i n u t e . The r e s i d e n c e t imes i n s i d e the surge tank are u s u a l l y of the o r d e r of 5 to 10 m i n u t e s . C o n s e q u e n t l y , the r e v e r s a l r e a c t i o n s s h o u l d come to c o m p l e t i o n i n s i d e the surge t a n k . Thus the o n l y major c a p i t a l c o s t i n v o l v e d i s the i n s t a l l a t i o n of the c a t i o n exchange bed . 304 To o b t a i n an e s t i m a t e of the q u a n t i t i e s of NaOH (or KOH) r e q u i r e d for t y p i c a l i n d u s t r i a l a p p l i c a t i o n s , l e t us c o n s i d e r a gas p l a n t w i th a DEA s o l u t i o n i n v e n t o r y of 50,000 L c o n t a i n i n g 0.05 mol HEOD/L and 0.10 mol THEED/L as i m p u r i t i e s . To r e v e r s e a l l the HEOD and THEED c o m p l e t e l y , the q u a n t i t y of NaOH (or KOH) r e q u i r e d i s mol HEOD mol NaOH(KOH) 50,000 L (0.05 x 2 + L mol HEOD mol THEED mol NaOH(KOH) 0. 10 X 3 ) = 20,000 m o l . L mol THEED 20,000 mols are e q u i v a l e n t to about 800 kg of NaOH or 1120 kg of KOH. A l t h o u g h these are s u b s t a n t i a l q u a n t i t i e s of c a u s t i c , i n p r a c t i c e t h i s can be reduced s u b s t a n t i a l l y i f the s o l u t i o n i s s u b j e c t e d to NaOH (KOH) treatment b e f o r e the c o n c e n t r a t i o n l e v e l s of HEOD and THEED become t h i s h i g h . Chapter 8 CONCLUSIONS 8.1 SOLUBILITY STUDIES The f o l l o w i n g p r i n c i p a l c o n c l u s i o n s may be drawn: * M a t h e m a t i c a l models have been deve loped t o c a l c u l a t e the e q u i l i b r i u m C 0 2 s o l u b i l i t y in aqueous MDEA and BHEP s o l u t i o n s . * The C 0 2 s o l u b i l i t y i n aqueous BHEP s o l u t i o n s was found to be lower than t h a t i n DEA s o l u t i o n s of s i m i l a r c o n c e n t r a t i o n on a weight b a s i s . C o n s e q u e n t l y , f o r m a t i o n of BHEP as a r e s u l t of d e g r a d a t i o n reduces the s o l v e n t c a p a c i t y . 8.2 DEA DEGRADATION IN HEAT TRANSFER TUBES * R a d i a l temperature v a r i a t i o n s as w e l l as v a r i a t i o n s of C 0 2 c o n c e n t r a t i o n i n the s o l u t i o n were i n c o r p o r a t e d i n t o the p r e v i o u s l y d e v e l o p e d model f o r the p r e d i c t i o n of DEA d e g r a d a t i o n . The r e s u l t a n t model gave b e t t e r agreement w i t h e x p e r i m e n t a l r e s u l t s . 305 306 8.3 MDEA DEGRADATION * MDEA can degrade i n the presence of C 0 2 . * The o v e r a l l MDEA d e g r a d a t i o n r a t e i n c r e a s e s w i th s o l u t i o n temperature and C 0 2 p a r t i a l p r e s s u r e . Whi le the r a t e a l s o i n c r e a s e s w i t h s o l u t i o n c o n c e n t r a t i o n up to about 3 .5 mol MDEA/L, water becomes r a t e l i m i t i n g above t h i s l e v e l . *. The major MDEA d e g r a d a t i o n compounds are BHEP, DMAE, EO, E G , HMP, and T E A . * Minor d e g r a d a t i o n compounds which c o u l d be d e t e c t e d are DMP, HEOD, M e t h a n o l , TEHEED, THEED and TMA. * MDEA d e g r a d a t i o n proceeds v i a the format ion of MDEAH*, which then r e a c t s wi th MDEA to form DMAE, EO and DEA. C 0 2 p l a y s a r o l e i n the p r o t o n a t i o n of MDEA as w e l l as i n the f o r m a t i o n of DEA carbamate from DEA. * DMAE r e a c t s w i t h C 0 2 to form DMAEH*, which then r e a c t s w i t h DMAE to form TMA, EO and MAE. MAE a l s o r e a c t s w i th C 0 2 t o form MAE carbamate . * DEA and MAE are i n t e r m e d i a t e compounds which r e a c t q u i c k l y to form o t h e r d e g r a d a t i o n compounds and t h e r e f o r e can not be d e t e c t e d e a s i l y . * The presence of r e a c t i v e EO r e s u l t s i n the f o r m a t i o n of o t h e r d e g r a d a t i o n compounds. * EO may s i m p l y h y d r o l y s e to form E G . I t may a l s o r e a c t w i t h DEA to form TEA as w e l l as HMP to form BHEP. 307 * DEA carbamate r e a c t s w i th MAE to form the i n t e r m e d i a t e HEMED which dehydrate s to form HMP. * A l t h o u g h BHEP may be produced from DEA carbamate v i a THEED, the major route of BHEP f o r m a t i o n i s b e l i e v e d to be the r e a c t i o n between HMP and EO in the presence of water . * TEA can r e a c t w i t h DEA carbamate to form TEHEED. * HEOD and THEED are a l s o produced from DEA carbamate as i n the case of DEA d e g r a d a t i o n . However, because DEA r e a d i l y forms TEA w i t h EO, o n l y s m a l l amounts of HEOD and THEED are p r o d u c e d . * A s i m p l i f i e d k i n e t i c model was deve loped to p r e d i c t MDEA d e g r a d a t i o n as f u n c t i o n s of s o l u t i o n t e m p e r a t u r e , C 0 2 p a r t i a l p r e s s u r e and i n i t i a l MDEA c o n c e n t r a t i o n . The model covered the f o l l o w i n g c o n d i t i o n s : temperature 100 - 2 3 0 ° C , C 0 2 p a r t i a l p r e s s u r e 344.7 to 4654 kPa and i n i t i a l s o l u t i o n c o n c e n t r a t i o n 2 m o l / L to 6 m o l / L . 8.4 ACTIVATED CARBON ADSORPTION Whi l e DARCO carbon was found to be v i r t u a l l y i n e f f e c t i v e , SGL carbon was found to adsorb DEA, MDEA and t h e i r major d e g r a d a t i o n compounds. However, i t s a d s o r p t i v e c a p a c i t y i s low ( a p p r o x i m a t e l y 2 m m o l / g of c a r b o n ) . As a r e s u l t , the SGL carbon beds used i n gas p l a n t s become q u i c k l y s a t u r a t e d . 308 * A d s o r p t i o n i so therms f o r DEA and MDEA and t h e i r major d e g r a d a t i o n compounds were d e t e r m i n e d . They can be used to e v a l u a t e the performance of e x i s t i n g SGL carbon beds . * S a t u r a t e d SGL carbon can not be r e g e n e r a t e d a d e q u a t e l y by h e a t i n g to 3 0 0 ° C . * S a t u r a t e d SGL carbon can be p a r t i a l l y r e g e n e r a t e d by t r e a t i n g i t w i t h H C l or H N 0 3 . * The Wang and T i e n model [110] was a p p l i e d to p r e d i c t b r e a k t h r o u g h of carbon a d s o r b e r s . The p r e d i c t e d r e s u l t s were i n good agreement w i t h the e x p e r i m e n t a l r e s u l t s . 8 .5 DEA DEGRADATION REACTION REVERSAL At l e a s t two of the major DEA d e g r a d a t i o n r e a c t i o n s can be r e v e r s e d by the a d d i t i o n of s t r o n g a l k a l i s such as NaOH or KOH. HEOD can be t o t a l l y c o n v e r t e d back to DEA w h i l e about a h a l f of THEED can be c o n v e r t e d back to DEA. In the case of e x c e s s i v e N a * ( K + ) b u i l d up , a s t r o n g l y a c i d i c c a t i o n exchange r e s i n can be used to remove these i o n s . A p u r i f i c a t i o n p r o c e s s based on r e v e r s i n g the d e g r a d a t i o n r e a c t i o n s was d e v e l o p e d . T h i s p r o c e s s can be e a s i l y i n t e g r a t e d i n t o an e x i s t i n g p l a n t w i t h l i t t l e c a p i t a l inves tment . Chapter 9 RECOMMENDATIONS FOR FURTHER WORK 9.1 DEGRADATION WITH COS AND C S , C o n s i d e r a b l e work has been done on DEA and MDEA d e g r a d a t i o n wi th C 0 2 . However, no s u b s t a n t i a l work has been r e p o r t e d on amine d e g r a d a t i o n w i t h COS and C S 2 , which are a l s o common contaminants p r e s e n t i n the l i g h t hydrocarbon g a s e s . I t would t h e r e f o r e be worthwhi le to conduct d e g r a d a t i o n exper iments by c o n t a c t i n g d i f f e r e n t amines w i th COS and C S 2 . 9 .1 .1 DEGRADATION WITH C 0 2 , COS, C S , IN THE PRESENCE OF H,S A l t h o u g h v e r y l i m i t e d a v a i l a b l e e x p e r i m e n t a l data suggest t h a t H 2 S i n h i b i t s DEA d e g r a d a t i o n w i t h C 0 2 , more work needs to be done to e x p l o r e t h i s f u r t h e r . H 2 S u s u a l l y o c c u r s a l o n g w i t h C 0 2 and o t h e r c o n t a m i n a n t s . The work conduc ted so f a r has been concerned o n l y wi th C 0 2 . The d e g r a d a t i o n models deve loped a r e p r o b a b l y o n l y v a l i d for s i t u a t i o n s where C 0 2 i s the o n l y major c o n t a m i n a n t . T h e r e f o r e , i t would be u s e f u l to determine the e f f e c t of H 2 S , i f any , on DEA, MDEA d e g r a d a t i o n wi th C 0 2 . 309 310 9 .1 .2 MEASUREMENT OF C Q 2 SOLUBILITY -The e q u a t i o n s d e s c r i b i n g C 0 2 s o l u b i l i t y i n aqueous amine s o l u t i o n s can be s o l v e d i f the hydrogen ion c o n c e n t r a t i o n [ H + ] i s known. T h e r e f o r e , i f one c o u l d measure [ H + ] a c c u r a t e l y by us ing a h i g h p r e s s u r e pH e l e c t r o d e , i t would be v e r y easy to c a l c u l a t e the C 0 2 s o l u b i l i t y from s imple pH measurements. I t appears worthwhi le to e x p l o r e t h i s f u r t h e r . 311 NOMENCLATURE A Constant i n F r e u n d l i c h e q u a t i o n A w W a l l s u r f a c e area of a segment of the heat exchanger tube (m 2 ) BHEP N , N - B i s ( h y d r o x y e t h y l ) p i p e r a z i n e C E q u i l i b r i u m c o n c e n t r a t i o n of s o l u t e i n s o l u t i o n , (m m o l / L ) [ C 0 2 ] P h y s i c a l l y d i s s o l v e d C 0 2 c o n c e n t r a t i o n (mol /L) [ C 0 2 T ] T o t a l d i s s o l v e d C 0 2 c o n c e n t r a t i o n (mol /L) Cp S p e c i f i c heat of aqueous DEA s o l u t i o n ( J / g ° C ) C p Q S p e c i f i c heat of the heat t r a n s f e r f l u i d ( J / g ° C ) C T C o n c e n t r a t i o n i n s i d e the s o l u t i o n tank (mol /L) c^ C o n c e n t r a t i o n of s o l u t e i i n the l i q u i d phase (m m o l / L ) c ^ ° C o n c e n t r a t i o n of s i n g l e s o l u t e i i n the l i q u i d phase (m m o l / L ) c^* D i m e n s i o n l e s s c o n c e n t r a t i o n parameter as d e f i n e d i n E q . 6 .9 (-) D^ S t i r r e r b lade d iameter (m) D c T u r n i n g d iameter of the heat t r a n s f e r tube (m) D^ I n s i d e d iameter of the heat t r a n s f e r tube (m) D ^ m Log mean d iameter (m) D^ Diameter of the f l u i d c o n t a i n i n g heat t r a n s f e r f l u i d DEA D i e t h a n o l a m i n e 312 [DEA]p DEA c o n c e n t r a t i o n at the o u t l e t of the t u b u l a r r e a c t o r (mol /L) [DEA]^ DEA c o n c e n t r a t i o n at the i n l e t of the t u b u l a r r e a c t o r (mol /L) [DEA]o I n i t i a l DEA c o n c e n t r a t i o n (mol /L) DMAE 2 - (d imethy lamino) e t h a n o l DMP 1,4 d i m e t h y l p i p e r a z i n e EO E t h y l e n e ox ide EG E t h y l e n e g l y c o l D L A x i a l d i s p e r s i o n c o e f f i c i e n t D R R a d i a l d i s p e r s i o n c o e f f i c i e n t D ^ D i f f u s i v i t y of component i (m 2 / s ) Dpore^ Pore d i f f u s i v i t y of the adsorbent ( m 2 / s ) f F a n n i n g f r i c t i o n f a c t o r HEI H y d r o x y e t h y l i m i n e HEOD 3 - ( h y d r o x y e t h y l ) - 2 - o x a z o l i d o n e HMP N - ( h y d r o x y e t h y l ) methyl p i p e r a z i n e H c o 2 H e n r y ' s law c o n s t a n t h^ I n s i d e heat t r a n s f e r c o e f f i c i e n t ( J / m 2 s ° C ) h 0 O u t s i d e heat t r a n s f e r c o e f f i c i e n t ( J / m 2 s ° C ) K , - K 5 E q u i l i b r i u m c o n s t a n t s K e , E q u i l i b r i u m c o n s t a n t Km, Kb E q u i l i b r i u m c o n s t a n t k O v e r a l l MDEA d e g r a d a t i o n r a t e cons tant (1/h) k 1 f k 2 MDEA d e g r a d a t i o n r a t e c o n s t a n t s ( L / m o l h) k 3 , k 7 MDEA d e g r a d a t i o n r a t e c o n s t a n t s (1/h) k„ MDEA d e g r a d a t i o n r a t e c o n s t a n t s (L i o n / m o l 2 h) 313 k 5 , k 6 MDEA d e g r a d a t i o n r a t e c o n s t a n t s ( L 2 / m o l 2 h) k 8 i k 1 i MDEA d e g r a d a t i o n r a t e c o n s t a n t s ( L2 / m o l 2 h) kg MDEA d e g r a d a t i o n r a t e c o n s t a n t s ( L / m o l h) k i 2 MDEA d e g r a d a t i o n r a t e c o n s t a n t s ( L / m o l h) k, * * - k 2 DEA d e g r a d a t i o n r a t e c o n s t a n t s ( L / m o l h) k 3 * DEA d e g r a d a t i o n r a t e c o n s t a n t (1/h) k d Thermal c o n d u c t i v i t y of DEA s o l u t i o n (W/m°C) k h Thermal c o n d u c t i v i t y of the heat t r a n s f e r k l i m k s i MAE MDEA MEA n P P c o 2 P D E A P H 2 0 p s o l n P T 0 T Q F (W/m°C) L i q u i d phase mass t r a n s f e r c o e f f i c i e n t of component i Thermal c o n d u c t i v i t y of the tube meta l (W/m°C) S o l i d phase mass t r a n s f e r c o e f f i c i e n t of component i M e t h y l - a m i n o e t h a n o l M e t h y l - d i e t h a n o l a m i n e Monoethanolamine Constant i n the F r e u n d l i c h e q u a t i o n (-) P r e s s u r e (kPa) C 0 2 p a r t i a l p r e s s u r e (kPa) Vapour p r e s s u r e of pure DEA, (kPa) Vapour p r e s s u r e of water , (kPa) Vapour p r e s s u r e of the aqueous DEA s o l u t i o n , (kPa) T o t a l p r e s s u r e , (kPa) V o l u m e t r i c f low r a t e , ( m 3 / s ) A d s o r p t i v e c a p a c i t y or c o n c e n t r a t i o n of the s o l u t e i i n the s o l i d phase (m mol of s o l u t e i a d s o r b e d / g 314 of carbon) q^o C o n c e n t r a t i o n of the s i n g l e s o l u t e i n the s o l i d phase (m mol of s o l u t e a d s o r b e d / gm of carbon) q ^ + D i m e n s i o n l e s s s o l i d phase c o n c e n t r a t i o n parameter as d e f i n e d i n E q . 6.10 q w Heat f l u x a c r o s s u n i t c r o s s s e c t i o n a l area of the heat t r a n s f e r tube (W/m 2) q T T o t a l c o n c e n t r a t i o n i n the s o l i d phase (m mol /g of carbon) R Radius of the heat exchanger tube (m) RPS S t i r r e r r e v o l u t i o n s per second Rg U n i v e r s a l gas c o n s t a n t r Radius of a s e c t i o n i n s i d e the tube (m) r c Rate e x p r e s s i o n ( d C / d t ) Tp Radius of adsorbent p a r t i c l e (m) r s S e p a r a t i o n f a c t o r (-) T Temperature ( ° C or K) T ^ Temperature of the b u f f e r l a y e r ( ° C ) T c Temperature a t the c e n t e r l i n e of the heat t r a n s f e r tube ( ° C ) T^ Heat t r a n s f e r f l u i d temperature ( ° C ) T^ Heat t r a n s f e r tube i n l e t temperature ( ° C ) T 0 Heat t r a n s f e r tube o u t l e t t emperature ( ° C ) T t Temperature of the t u r b u l e n t core ( ° C ) T w Temperature of the tube w a l l ( ° C ) T w ^ Heat t r a n s f e r tube i n s i d e w a l l t emperature ( ° C ) T Heat t r a n s f e r tube o u t s i d e w a l l t emperature ( ° C ) 315 TEA TEHEED THEED TMA t U m + u u u u v T V F w x x DEA m x + y v b v i + y Zi T r i e t h a n o l a m i n e T e t r a - ( h y d r o x y e t h y l ) e t h y l e n e d i a m i n e N , N , N - t r i s - ( h y d r o x y e t h y l ) e t h y l e n e d i a m i n e T r i m e t h y l amine Time (h or s) O v e r a l l heat t r a n s f e r c o e f f i c i e n t f o r the c o i l e d heat t r a n s f e r tube ( J / m 2 s ° C ) O v e r a l l heat t r a n s f e r c o e f f i c i e n t based on i n s i d e s u r f a c e of the s t r a i g h t heat t r a n s f e r tube ( J / m 2 s ° C ) S o l u t i o n l i n e a r v e l o c i t y (m/s) Mean s o l u t i o n l i n e a r v e l o c i t y (m/s) V e l o c i t y i n the r a d i a l d i r e c t i o n (m/s) D i m e n s i o n l e s s v e l o c i t y parameter (-) Volume of the tank o c c u p i e d by the s o l u t i o n (m 3 ) V o l u m e t r i c f low r a t e ( m 3 / s ) Mass f low r a t e (kg / s ) D i s t a n c e a l o n g the tube l e n g t h (m) DEA f r a c t i o n i n aqueous DEA s o l u t i o n . T h i c k n e s s of the heat t r a n s f e r tube w a l l (m) D i m e n s i o n l e s s d i s t a n c e parameter as d e f i n e d i n E q . 6.13 (-) D i s t a n c e from the w a l l (m) T h i c k n e s s of the b u f f e r l a y e r (m) T h i c k n e s s of the l a m i n a r s u b l a y e r (m) D i m e n s i o n l e s s d i s t a n c e parameter (-) Mole f r a c t i o n (-) 316 DIMENSIONLESS GROUPS Pr P r a n d t l Number P r c P r a n d t l Number f o r DEA s o l u t i o n , C p u / k ^ P r 0 P r a n d t l Number for heat t r a n s f e r f l u i d , C p 0 M n / k 0 Re Reynolds Number R e c Reynolds Number f o r DEA s o l u t i o n , puD^/p R e 0 Reynolds Number f o r heat t r a n s f e r f l u i d , D b 2 R P S p 0 / M h GREEK LETTERS a Thermal d i f f u s i v i t y of the s o l u t i o n ( m 2 / s ) 7 A c i d gas l o a d i n g (mol C 0 2 / m o l s o l v e n t ) X S u r f a c e a r e a of the adsorbent (m 2 ) 8 E l a p s e d t ime as d e f i n e d i n E q . 6.14 (h or s) d* D i m e n s i o n l e s s t ime parameter as d e f i n e d i n E q . 6.12 (-) p D e n s i t y of DEA s o l u t i o n (kg /m 3 ) p 0 D e n s i t y of the heat t r a n s f e r f l u i d (kg /m 3 ) P b Bu lk d e n s i t y of the a c t i v a t e d carbon bed (kg /m 3 ) Pp P a r t i c l e d e n s i t y of the adsorbent (kg /m 3 ) u V i s c o s i t y of DEA s o l u t i o n ( P a . s ) M n V i s c o s i t y of the heat t r a n s f e r f l u i d (Pa . s ) nv V i s c o s i t y a t the w a l l ( P a . s ) v K i n e m a t i c v i s c o s i t y of the s o l u t i o n ( m 2 / s ) S p r e a d i n g p r e s s u r e of the of s o l u t e i as d e f i n e d i n E q . 6.4 317 P a r t i t i o n c o e f f i c i e n t as d e f i n e d in E q . 6.11 (-) \p I n t e r n a l p o r o s i t y of the adsorbent (-) X Parameter used to c a l c u l a t e s o l i d phase mass t r a n s f e r c o e f f i c i e n t as d e f i n e d i n E q . 6.19 (-) V o i d f r a c t i o n of the a c t i v a t e d carbon bed (-) Eddy d i f f u s i v i t y for heat ( m 2 / s ) e m Eddy d i f f u s i v i t y f o r momentum ( m 2 / s ) * £ h / e m p D e n s i t y of the s o l u t i o n ( k g / m 3 ) T R Res idence t ime i n s i d e an element of the t u b u l a r r e a c t o r (s) T W Shear s t r e s s at the w a l l (N/m 2 ) T R Res idence t ime i n s i d e the tank (s) AH Heat of r e a c t i o n SUBSCRIPTS b B u f f e r r e g i o n c C e n t r e of the tube f O u t l e t of the tube i I n l e t of the tube 1 Laminar sub l a y e r t T u r b u l e n t r e g i o n w W a l l of the tube 318 REFERENCES Bottoms, R. 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Chem. , 22, 849-851, 1957. 331 A P P E N D I X - A SYNTHESIS OF SELECT DEA AND MDEA DEGRADATION COMPOUNDS In order to i d e n t i f y the MDEA d e g r a d a t i o n compounds, the s u s p e c t e d compounds had to be o b t a i n e d i n t h e i r pure form f o r mass s p e c t r a l a n a l y s i s . Once the compounds were p o s i t i v e l y i d e n t i f i e d , i t was necessary to c a l i b r a t e the gas chromatograph wi th s t a n d a r d s of v a r i o u s d e g r a d a t i o n compounds for the q u a n t i t a t i v e a n a l y s i s of the degraded samples . DEA d e g r a d a t i o n compounds were r e q u i r e d not on ly f o r the c a l i b r a t i o n of the gas chromatograph, but a l s o for s t u d i e s on p u r i f y i n g degraded DEA s o l u t i o n s . A.1 DEA DEGRADATION COMPOUNDS Among the major DEA d e g r a d a t i o n compounds BHEP was p u r c h a s e d from A l d r i c h Chemica l s C o . , M i l w a k e e , WI. A l t h o u g h HEOD c o u l d be purchased from ICN P h a r m a c e u t i c a l s , I n c . , NY, i t s p u r i t y was found to be too low f o r c a l i b r a t i n g the gas chromatograph . THEED was not a v a i l a b l e from any commerc ia l s o u r c e . T h e r e f o r e , both HEOD and THEED had to be s y n t h e s i z e d in the l a b o r a t o r y . 332 HEOD s y n t h e s i s Kennard [57] at tempted v a r i o u s methods of HEOD s y n t h e s i s , but was not s u c c e s s f u l in o b t a i n i n g the h i g h p u r i t y neces sary f o r the c a l i b r a t i o n . Kim and S a r t o r i [59] s u c c e s s f u l l y s y n t h e s i z e d HEOD of 95%* p u r i t y by f o l l o w i n g the procedure d e s c r i b e d by. D r e c h s e l [115] . A s i m i l a r procedure was f o l l o w e d f o r the s y n t h e s i s of HEOD i n t h i s s t u d y . 210 g of DEA, 260 g of d i e t h y l c a r b o n a t e and 2 g of sodium methoxide were p l a c e d i n t o a 316 s t a i n l e s s s t e e l a u t o c l a v e (see F i g . 5 . 1 ) . The a u t o c l a v e temperature was g r a d u a l l y r a i s e d to 1 3 0 ° C w h i l e c o n t i n u o u s l y s t i r r i n g the c o n t e n t s at a tmospher ic p r e s s u r e . The f o l l o w i n g r e a c t i o n was expected to take p l a c e : f H O - C 2 H , C 2 H s O C ^ N - H + \ = 0 > H O - C 2 H 0 - N ^ ^ 0 + 2 C 2 H 5 ~ 0 H / / I I H 0 - C 2 H 4 C 2 H 5 0 C H 2 - C H 2 "DEA" " D i e t h y l carbonate" "HEOD" (A.1) A f t e r 2 hours about 250 mL of e t h a n o l was c o l l e c t e d and the e t h a n o l p r o d u c t i o n r a t e was a lmost n i l . The a u t o c l a v e was then c o o l e d down to room temperature by p a s s i n g c o o l i n g water through the c o o l i n g c o i l . The a u t o c l a v e was opened 333 and the c o n t e n t s a n a l y z e d . The p r o d u c t was found to be HEOD of 90%+ p u r i t y as de termined by GC a n a l y s i s . I t was then f u r t h e r p u r i f i e d to 95%* by add ing SGL type a c t i v a t e d carbon (Calgon C o r p . P i t t s b u r g , PA) to the sample. THEED s y n t h e s i s THEED was s y n t h e s i z e d a c c o r d i n g to K e n n a r d ' s procedure [ 5 7 ] , i . e . r e a c t i n g DEA w i t h N - ( 2 - h y d r o x y e t h y l ) e t h y l i m i n e (HEM). The f o l l o w i n g r e a c t i o n was expected to o c c u r : „ 0 - C , H CH ; N-H + H O - C 2 H « - N HO-C 2 H„ C H 2 "DEA" "HEM" HO-C 2 H„ C 2 H « - O H N - C 2 H « - N + H 2 0 (A.2) H O - C 2 H , ^ H "THEED" 105 g of DEA, 87 g of HEM and 5 g of aluminum c h l o r i d e were p l a c e d i n s i d e the a u t o c l a v e f i t t e d wi th the pyrex l i n e r (see F i g . 3 . 1 ) . The a u t o c l a v e was then s e a l e d and p r e s s u r i z e d to 0.7 MPa w i t h n i t r o g e n . The c o n t e n t s were c o n s t a n t l y s t i r r e d and m a i n t a i n e d a t 1 2 0 ° C f o r 24 h . Upon r a p i d c o o l i n g , THEED of 80%* p u r i t y was o b t a i n e d . T h i s p r o d u c t was f u r t h e r 334 p u r i f i e d by d i l u t i n g i t w i t h water and then p a s s i n g i t at a f low r a t e of 0.5 mL/min through a 20 mm ID, 0.40 m l o n g g l a s s column f i l l e d w i t h 60-200 mesh s i l i c a g e l and t r a c e amounts of aluminum h y d r o x i d e . The p r o d u c t was c o n c e n t r a t e d by b o i l i n g to d r i v e o f f the water . THEED of 98%+ p u r i t y was o b t a i n e d . A . 2 MDEA DEGRADATION PRODUCTS Most of the MDEA d e g r a d a t i o n compounds, w i t h the e x c e p t i o n of HMP, c o u l d be o b t a i n e d c o m m e r c i a l l y . The s o u r c e s of these compounds a r e l i s t e d in T a b l e A . l . HEOD and THEED which were p r e s e n t i n s m a l l q u a n t i t i e s were a v a i l a b l e from p r e v i o u s s y n t h e s i s . T h e r e f o r e , o n l y HMP needed to be s y n t h e s i z e d . HMP s y n t h e s i s HMP was s y n t h e s i z e d by r e a c t i n g 1-methyl p i p e r a z i n e (MP) w i t h e t h y l e n e o x i d e . The f o l l o w i n g r e a c t i o n was expec ted to o c c u r : C2H1, C 2 H f t C H 3 - N N-H + C H , - CH N - C 2 H , - O H "MP" "EO" "HMP" (A.3) 335 About 20 g of 1 -methyl p i p e r a z i n e was p l a c e d i n a b e a k e r . E t h y l e n e ox ide was g r a d u a l l y bubbled through the s o l u t i o n . Samples were a n a l y z e d f r e q u e n t l y and the g r a d u a l f o r m a t i o n of HMP was n o t i c e d . B u b b l i n g was c o n t i n u e d u n t i l a l l the MP was c o n v e r t e d to HMP. A p r o d u c t p u r i t y of 97%* was o b t a i n e d . T a b l e A.1: Sources of c h e m i c a l s . Chemica l s Source BHEP A l d r i c h Chemica l C o . , Mi lwaukee , WI. C 0 2 Union C a r b i d e , V a n c o u v e r , B C . DEA A l d r i c h C h e m i c a l C o . , Mi lwaukee , WI. DMAE A l d r i c h C h e m i c a l C o . , Mi lwaukee , WI. DMP A l d r i c h C h e m i c a l C o . , Mi lwaukee , WI. D i e t h y l carbonate A l d r i c h C h e m i c a l C o . , Mi lwaukee , WI. EG A l d r i c h C h e m i c a l C o . , Mi lwaukee , WI. EO Matheson of Canada L t d . HCl A l l i e d C h e m i c a l s Canada L t d . , St C l a i r e , PQ. HEI F r i n t o n L a b o r a t o r i e s , V i n e l a n d , NS. HEM A l d r i c h Chemica l C o . , Mi lwaukee , WI. HN0 3 A l l i e d C h e m i c a l s Canada L t d . , S t . C l a i r e , PQ. K 2 C 0 3 BDH C h e m i c a l s , T o r o n t o , ON. MDEA A l d r i c h Chemica l C o . , Mi lwaukee , WI. MP A l d r i c h Chemica l C o . , Mi lwaukee , WI. 336 NaOH F i s h e r S c i e n t i f i c C o . , F a i r l a w n , N J . TEA A l d r i c h Chemica l C o . , Mi lwaukee , WI. TEHEED A l d r i c h Chemica l C o . , Mi lwaukee , WI. 337 APPENDIX - B GAS CHROMATOGRAPHIC TECHNIQUE The gas chromatographic t e c h n i q u e d e s c r i b e d by Kennard and Meisen [67] has proven to be very e f f e c t i v e f o r the a n a l y s i s of degraded DEA s o l u t i o n s . T h i s t e c h n i q u e was a l s o used f o r the a n a l y s i s of the degraded MDEA s o l u t i o n s . B,1 OPERATING CONDITIONS P r e v i o u s e x p e r i e n c e showed tha t amine d e g r a d a t i o n compounds v a r y c o n s i d e r a b l y in m o l e c u l a r weight and p o l a r i t y . An i n i t i a l a n a l y s i s of a degraded MDEA s o l u t i o n a l s o i n d i c a t e d the presence of compounds wi th v a r y i n g m o l e c u l a r we ight . In o r d e r to a c h i e v e good s e p a r a t i o n of a l l d e g r a d a t i o n compounds, temperature programming was u s e d . A f t e r s e v e r a l i n i t i a l t r i a l s , optimum o p e r a t i n g c o n d i t i o n s were found which are summarized i n T a b l e B . 1 . 338 T a b l e B.1 O p e r a t i n g c o n d i t i o n s of the gas chromatograph Gas Chromatograph M a n u f a c t u r e r Model D e t e c t o r Chromatographic Column M a t e r i a l Dimens ions P a c k i n g O p e r a t i n g c o n d i t i o n s C a r r i e r gas C a r r i e r gas f low r a t e I n j e c t i o n p o r t temp. D e t e c t o r p o r t temp. Column temperature S y r i n g e M a n u f a c t u r e r Model I n j e c t e d sample s i z e Hewlet t P a c k a r d 5830A H 2 f lame i o n i z a t i o n S t a i n l e s s s t e e l 1/8" O . D . , 9' l o n g Tenax G . C . , 60/80 mesh N i t r o g e n 25 mL/min 3 0 0 ° C 3 0 0 ° C I s o t h e r m a l a t 1 0 0 ° C for 0.5 m i n . , then temperature r a i s e d a t 8 ° C / m l n to 3 0 0 ° C . H a m i l t o n C o . , Reno, Nevada. 701, 10/xL, w i t h f i x e d need le and Chaney a d a p t e r . 1ML 339 B.2 SAMPLE INJECTION A p r e c i s i o n s y r i n g e f i t t e d w i t h a Chaney adapter (Model 701, Hami l ton C o . , Reno, NV) was used for i n j e c t i n g samples i n t o the co lumn. The column i n j e c t i o n p o r t was equipped w i t h a needle guide which not o n l y p r o t e c t e d the f r a g i l e s y r i n g e needle but a l s o s e r v e d as a spacer f o r the needle p e n e t r a t i o n and h e l p e d l eng then the septum l i f e . 1 M L samples were i n j e c t e d and the a n a l y s i s took about 40 m i n u t e s . A f t e r each r u n , the column had to be c o o l e d from 3 0 0 ° C to 1 0 0 ° C which took about 10 m i n u t e s . B . 3 COLUMN PERFORMANCE Two columns (1.524 m and 2.286 m long) were used . The 2.286 m l o n g column gave b e t t e r s e p a r a t i o n and was c o n s e q u e n t l y used f o r a l l the a n a l y s i s . Performance of the column was v e r y good. Sharp peaks were o b t a i n e d i n d i c a t i n g a good s e p a r a t i o n . However, when two compounds h a v i n g very s i m i l a r r e t e n t i o n t imes were p r e s e n t , d i f f i c u t i e s were e n c o u n t e r e d , e s p e c i a l l y when one of the compounds o c c u r r e d i n v e r y low c o n c e n t r a t i o n s r e l a t i v e to the o ther compound. T h i s was the case w i t h MDEA and DEA, where DEA o c c u r r e d in v e r y low c o n c e n t r a t i o n s as compared to MDEA. A s i m i l a r case was d i m e t h y l amino e t h a n o l ("DMAE") and methyl amino e t h a n o l ("MAE") where the l a t t e r o c c u r r e d in low c o n c e n t r a t i o n s . 340 Peak t a i l i n g and b a s e l i n e d r i f t d i d not cause any s i g n i f i c a n t prob lems . B.4 G . C . CALIBRATION A d i r e c t method was used to c a l i b r a t e the G . C . T h i s was done by i n j e c t i n g known amounts of v a r i o u s DEA and MDEA d e g r a d a t i o n compounds i n t o the chromatograph and n o t i n g the peak a r e a which was a u t o m a t i c a l l y i n t e g r a t e d by the chromatograph' s computer . At l e a s t f i v e i n j e c t i o n s were made f o r each amount and the peak area a v e r a g e d . The c a l i b r a t i o n p l o t s showing c o n c e n t r a t i o n v s . peak area were produced f o r d i f f e r e n t compounds and they are shown i n F i g s . B.1 to B.11. The r e t e n t i o n t imes of d i f f e r e n t compounds i n the gas chromatographic co lumn, under the c o n d i t i o n s l i s t e d i n T a b l e B.1, are summarized i n T a b l e B.2 T a b l e B . 2 : G . C . r e t e n t i o n time of d i f f e r e n t compounds. Compound R e t e n t i o n t ime m i n . EO 1.3 - 1.4 TMA 1 .9 - 2 . 0 EG 7.2 - 7 . 3 DMAE 8.4 - 8.6 MAE 8.5 - 8.6 DMP 11.5 - 11.6 MDEA 14.7 - 14.8 DEA 14.8 - 14.9 HMP 16.5 - 16.7 TEA 20. 1 - 20.3 BHEP 21 .4 - 2 1 . 6 HEOD 22.2 - 22.4 THEED 25.5 - 25.7 TEHEED 27.8 - 28.0 DEA CONCENTRATION (mol /L) Z9Z MDEA CONCENTRATION (mol/L) o 20.0 40.0 60.0 60.0 100.0 120.0 BHEP PEAK AREA (X101 ) 140.0 160.0 Figure B .3 : Calibration plot for BHEP. 2 | — , — | — | — i — | — | — | — | — | — | — | — | — | — j — | — r 0.0 20.0 40.0 60.0 60.0 100.0 120.0 140.0 160.0 DMAE PEAK AREA (XlO 1 ) F i g u r e B.4: C a l i b r a t i o n p l o t f o r DMAE. F i g u r e B . 5 : C a l i b r a t i o n p l o t f o r DMP F i g u r e B . 6 : C a l i b r a t i o n p l o t f o r E G . LO HEI CONCENTRATION (mol/L) o o 8 * e F i g u r e B.8: C a l i b r a t i o n p l o t f o r HEOD. *» I D Figure B.9: Calibration plot for HMP * oi I— i 1 — i — i — i — i — i 1 — i 1 1 1 1 1 1 r 0.0 40.0 80.0 120.0 160.0 200.0 240.0 280.0 320.0 THEED PEAK AREA (X101 ) Figure B .11: Calibration plot for THEED. 353 APPENDIX - C C.1: Program for the ca l c u l a t i o n of C0 2 s o l u b i l i t y in aqueous DEA solutions, c C PROGRAM TO CALCULATE ACID GAS LOADING. ALPHA C (GM-MOLE C02/GM-M0LE MDEA) FOR THE FOLLOWING C REACTION SCHEME :[BHEPJ • (H]+ « [BHEPH+] C C INPUT VARIABLES : TEMPEPARTURE (K) C C02 PARTIAL PRESSURE (kPa) C BHEP CONCENTRATION (moles/L) C c IMPLICIT REAL*8(A - H.O - 2) DIMENSION X ( 2 ) . F ( 2 ) . ACCEST(2) COMMON CN1, CN2, CN3. CN4. HC02. B COMMON AM. T. PC02 DATA A2. B2 . C2 /-241.818DO, 298.253D3. -148.528D6/ DATA D2. E2 /332.648D8, -282.394D10/ DATA A3. B3 . C3 / 39.5554DO, -987.9D2, 568.82805/ DATA D3. E3 /-14G.451D8. 136.146010/ DATA A4. B4, C4 / -294.74D0, 364.385D3. -184.158D6/ DATA D4. E4 /415.793D8. -354.291D10/ DATA A5. B5 . C5 /22.2819DO. -138.306D2. 691.346D4/ DATA D5. E5 / -155.895D7. 120.03709/ AM - 4.28000000D0 NE" 2 READ (5 .10) NP. T 10 FORMAT (12. F8 .2 ) WRITE (6 .30) AM. T 30 FORMAT ( I X . ' A M - ' . F12 .B . 2X. ' T E M P ( K ) - ' . F10 .2 . / / ) WRITE (6 .40) 40 FORMAT (2X. 'C02 P R E S ' . 4X, 'FREE C02 CONC, 3 X , ' ALPHA' , 1 4X. ' A L P H A - C A L ' . 9X. 'HPLUS ' . / / ) C C SET INPUT VARIABLES C C X(1)-ALPHA CALC. X(2)«HPLUS C X (1 ) - 1.2D0 X (2 ) - 0.1D-6 DO 60 U • 1. NP READ (5 .20) PC02.ALPHA 20 FORMAT (2F10.5) PC02 - PC02 * 7.500610D0 C C CALCULATE CONSTANTS C CN2 - DEXP(A2 + B2/T + (C2/(T**2)) • (D2/(T**3)) + (E2/(T**4))) CN3 • DEXP(A3 + B3/T • ( C 3 / ( T » * 2 ) ) + (D3/(T**3)) • (E3/(T**4))) CN4 - DEXP(A4 + B4/T + (C4/(T**2)) • (D4/(T**3)) • (E4/(T**4))) HC02 " DEXP(A5 + B5/T • (C5/(T**2)) + (D5 / (T»*3) ) • (E5/(T**4))) C02 - PC02/HC02 CN1 - DEXP(-363.83161D0 - O.13080603D0*T + 11.570746D0/T • 1 66.508132D0*(DL0G(T)) •»• 2.2209994D0*C02 - 0.27008433D0*(DL0G( 1 C02)) - 4.2510361D0*AM + 13.06430800*(DLOG(AM))) C C SET INPUT PARAMETERS FOR NDINVT C ERR • .1D-10 MAXIT » 10000 EXTERNAL FCN C 354 C NDINVT IS CALLED C CALL N O I N V T ( N E , X , F . A C C E S T . MAXIT, ERR. F C N . &70) C C THE SOLUTION IS PRINTED C PC02 • PC02 / 7 .500610OD0 WRITE ( 6 , 5 0 ) P C 0 2 . C02 . ALPHA. ( X ( I ) . I - 1 . N E ) 50 FORMAT ( 5 G 1 3 . 5 ) X ( 1 ) « X ( I ) 6 0 CONTINUE STOP 70 STOP 1 END C C SUBROUTINE C SUBROUTINE F C N ( X . F ) IMPLICIT R E A L * 8 ( A - H ,0 - 2) DIMENSION X ( 1 ) , F ( 1 ) COMMON C N I . CN2, CN3 , CN4. HC02. B COMMON AM, T . PC02 F ( 1 ) « P C 0 2 - H C 0 2 * X ( 2 ) * X ( 2 ) * ( X ( 1 ) » A M - P C 0 2 / H C 0 2 ) / ( C N 2 * C N 4 ) * * ( 1 . 0 0 / ( 1 . D 0 + X ( 2 ) / C N 4 ) ) F ( 2 ) « X ( 2 ) - ( X ( 1 ) * A M - P C 0 2 / H C 0 2 ) * ( 1 . D 0 + C N 4 / ( C N 4 + X ( 2 ) ) ) / $ ( 1 . D O + A M / ( C N 1 + X ( 2 ) ) ) - C N 3 / ( X ( 2 ) * ( 1 . D 0 + A M / ( C N 1 * X ( 2 ) ) ) ) RETURN END 355 C.2: Program for the calculation of C0 2 so lubi l i ty in aqueous MDEA solution. c C PROGRAM TO CALCULATE ACID GAS LOADING. ALPHA C (GM-MOLE C02/GM-M0LE MDEA) FOR THE FOLLOWING C REACTION SCHEME :[MDEAH+] • HC03- « [MDEA] + H20 +C02 C C INPUT VARIABLES : TEMPEPARTURE (K) C C02 PARTIAL PRESSURE (kPa) C MDEA CONCENTRATION ( m o l e s / L ) C C IMPLICIT R E A L * 8 ( A - H.O - Z ) DIMENSION X ( 5 ) . F ( 5 ) . A C C E S T ( S ) COMMON CN1 . CN2. CN3 . CN4, HC02. B COMMON AM. ALPHA, T . PC02 DATA A 2 , B 2 , C2 / - 2 4 1 . 8 1 B D O . 2 9 8 . 2 5 3 D 3 , - 1 4 8 . 5 2 8 D 6 / DATA D 2 . E2 / 3 3 2 . 6 4 8 D 8 , - 2 8 2 . 3 9 4 D 1 0 / DATA A 3 . B 3 . C3 / 3 9 . 5 5 5 4 D 0 , - 9 8 7 . 9 0 2 , 5 6 8 . 8 2 8 0 5 / DATA D 3 . E3 / - 1 4 6 . 4 5 1 D 8 , 136 .146D10 / DATA A 4 . B 4 , C4 / - 2 9 4 . 7 4 D 0 . 364 .385D3 , - 1 8 4 . 1 5 8 D 6 / DATA D4 , E4 / 4 1 5 . 7 9 3 D 8 , - 3 5 4 . 2 9 1 D 1 0 / DATA A 5 . B 5 , C5 / 2 2 . 2 B 1 9 D 0 . - 1 3 8 . 3 0 6 D 2 . 6 9 1 . 3 4 6 D 4 / DATA D 5 . E5 / - 1 5 5 . B 9 5 D 7 . 120 .037D9 / AM - 4 . 2 8 0 D 0 NE - 5 READ ( 5 . 1 0 ) NP . T 10 FORMAT ( 1 2 . F 8 . 2 ) WRITE ( 6 , 2 0 ) AM. T 20 FORMAT (1X . ' A M = ' , F 1 2 . 8 . 2X . ' T E M P ( K ) - ' , F 1 0 . 2 . / / ) WRITE ( 6 , 3 0 ) 30 FORMAT ( 2 X . 'C02 P R E S ' . 4X , ' F R E E C02 C O N C ' . 3X. ' A L P H A ' , 4X, 1 ' A L P H A - C A L ' . 9X . ' H P L U S ' . / / ) C C SET INPUT VARIABLES C C X ( 1 ) - A L P H A CALC ; X ( 2 ) - H P L U S ; X ( 3 ) - H C 0 3 - ; X ( 4 ) « M D E A H ; C X (5 ) -MDEA C X ( 1 ) - 0 . 2 D 0 X ( 2 ) - O . 1 0 0 - 6 X ( 3 ) • O . 1 0 0 0 X ( 4 ) - O . 1 0 0 0 X ( 5 ) - 4 . 0 0 0 DO 60 J « 1. NP READ ( 5 , 4 0 ) P C 0 2 . ALPHA 40 FORMAT ( 2 F 1 0 . 5 ) PC02 » PC02 • 6 .894757D0 C C CALCULATE CONSTANTS C CN2 » DEXP(A2 + B 2 / T + ( C 2 / ( T * * 2 ) ) • ( D 2 / ( T * » 3 ) ) + ( E 2 / ( T * * 4 ) ) ) CN3 » DEXP(A3 + B 3 / T + ( C 3 / ( T * » 2 ) ) + ( D 3 / ( T « » 3 ) ) + ( E 3 / ( T * * 4 ) ) ) CN4 - DEXP(A4 + B 4 / T + ( C 4 / ( T * * 2 ) ) + ( D 4 / ( T » * 3 ) ) + ( E 4 / ( T * » 4 ) ) ) HC02 - DEXP(A5 + B 5 / T + ( C 5 / ( T » * 2 ) ) + ( D 5 / ( T * * 3 ) ) + ( E 5 / ( T « * 4 ) ) ) C02 » PC02 / HC02 C CN1 • DEXP( -380 .36530OD0-0 .12111467D0*T • 25 .771837D0 /T + 7 1 . C 1 2 5 O 3 5 7 D O » ( D L 0 G ( T ) ) - 1.0898470DO*C02 - 8 . 7 2 1 8 5 7 4 4 D - 2 * ( D L 0 G ( C 0 2 ) ) C 2 +3.9333975D0*AM - 13 .713722D0*(DLOG(AM)) • 2 .0471742DO*(DLOG(AM) C 3 » * 2 ) ) C N 1 - 3 . 356 C SET INPUT PARAMETERS FOR NDINVT C ERR - . 1 0 - 1 0 MAXIT • 10000 EXTERNAL FCN C C NDINVT IS CALLED C CALL NDINVT(NE, X , F . A C C E S T . MAXIT. ERR. F C N , &70) C C THE SOLUTION IS PRINTED C PC02 - PC02 / 6 .B947570D0 WRITE ( 6 , 5 0 ) P C 0 2 . ( X ( I ) . I - 1 , N E ) 50 FORMAT ( 6 G 1 3 . 5 ) X ( 1 ) - X ( I ) 60 CONTINUE STOP 70 STOP 1 END C C SUBROUTINE C SUBROUTINE FCN(X . F ) IMPLICIT R £ A L * 8 ( A - H.O - Z ) DIMENSION X ( 1 ) , F ( 1 ) COMMON CN1 . CN2, CN3, CN4. HC02, B COMMON AM, ALPHA. T , PC02 F ( 1 ) • PC02 - HC02 * X (2 ) » X (2 ) * (X (1 ) *AM - PC02/HC02) / (CN2* 1CN4) • ( 1 . D 0 / ( 1 . D 0 + X ( 2 ) / C N 4 ) ) F ( 2 ) « X ( 2 ) - ( X ( 1 ) » A M - PC02 /HC02) * (1 .D0+CN4/(CN4 • X ( 2 ) ) ) / ( 11.D0+AM/(CN2*CN1 + X ( 2 ) ) ) - C N 3 / ( X ( 2 ) » ( 1 . D 0 + A M / ( C N 2 » C N 1 + X ( 2 ) ) ) ) F ( 3 ) • X (3 ) - ( X ( 2 ) / ( X ( 2 ) + 2 . * C N 4 ) ) * ( X ( 2 ) + X ( 4 ) - C N 3 / X ( 2 ) ) F ( 4 ) - X ( 4 ) - C N 1 » X ( 5 ) » P C 0 2 / ( H C 0 2 * X ( 3 ) ) F ( 5 ) « X ( 5 ) - AM + X ( 4 ) RETURN END 357 C . 3 : Program f o r the c a l c u l a t i o n of C 0 2 s o l u b i l i t y i n aqueous BHEP s o l u t i o n . c c c c c c c c c c PROGRAM TO CALCULATE ACID GAS LOADING. ALPHA (GM-MOLE C02/GM-MOLE DEA) FOR THE FOLLOWING REACTION SCHEME : [DEA] + [H] + " [DEAH+] + [DEACOO-] MODIFIED KENT EISENBERG VERSION INPUT VARIABLES : TEMPEPARTURE (K) C02 PARTIAL PRESSURE (kPa) BHEP CONCENTRATION ( r a o l e s / L ) IMPLICIT R E A L * 8 ( A - H.O - Z ) DIMENSION X ( 3 ) . F ( 3 ) . ACCEST(3 ) COMMON CN1 . CN2, CN3. CN4. CN5 . HC02 COMMON AM, T , P C 0 2 , ALPHA DATA A 1 . B1 / - 2 . 5 5 1 0 D O . - 0 . 5 6 5 2 0 4 / DATA A 2 , B2 / 4 . 8 2 5 D 0 . - 0 . 1 8 B 5 D 4 / DATA A 3 . 8 3 . C3 / - 2 4 1 . 8 1 8 D 0 , 298 .253D3 . - 1 4 8 . 5 2 8 D 6 / DATA 0 3 . E3 / 3 3 2 . 6 4 8 D 8 . - 2 8 2 . 3 9 4 D 1 0 / DATA A 4 . B 4 . C4 / 3 9 . 5 5 5 4 D 0 . - 9 8 7 . 9 0 2 . 5 6 8 . B 2 B D 5 / DATA D4 . E4 / - 1 4 6 . 4 5 1 D 8 , 136 .146D10 / DATA A 5 , B 5 , C5 / - 2 9 4 . 7 4 D 0 , 364 .385D3 , - 1 8 4 . 1 5 8 D 6 / DATA D 5 . E5 / 4 1 5 . 7 9 3 0 8 . - 3 5 4 . 2 9 1 D 1 0 / DATA A 6 , B 6 . C6 / - 0 . 3 0 4 7 D 3 , 0 . 3 8 7 2 1 0 6 . - 0 . 1 9 4 7 5 5 0 9 / DATA D6 . E6 / 0 . 4 3 8 1 1 7 D 1 1 . - O . 3 7 3 1 8 7 D 1 3 / DATA A 7 . B 7 . C7 / - 6 5 7 . 9 6 5 D 0 . 9 1 . 6 3 1 1 D 6 . - 4 . 9 0 6 2 9 6 D 8 / DATA D 7 , E7 / 1 . 1 5 3 0 7 2 7 D 1 1 , - 1 . 0 1 0 1 6 4 2 D 1 3 / DATA A 8 . B 8 . C8 / 2 2 . 2 8 1 9 D 0 . - 1 3 8 . 3 0 6 D 2 . 6 9 1 . 3 4 6 D 4 / DATA D8 . E8 / - 1 5 5 . B 9 5 D 7 . 120 .037D9 / C C C C c DATA A 9 . B 9 . C9 / 1 0 4 . 5 1 8 D 0 , DATA D 9 . E9 / - O . 1 7 4 7 2 2 2 D 1 1 , NE - 3 H2S - 0 . D 0 SUM - O.DO ERR - O.DO READ ( 5 . 1 0 ) NP 10 FORMAT (13) WRITE ( 6 . 2 0 ) 20 FORMAT (2X . 'DEA C O N C . 3X, 1 ' A L P H A - C A L ' . / / ) SET INPUT VARIABLES - 0 . 1 3 6 8 0 7 7 8 D 6 . 0 .7377438D8 / 0 . 1521624D13/ 'TEMP K ' . 6X . ' P C 0 2 ' , BX . ' A L P H A ' . 6X , 30 C C C X ( 1 ) - A L P H A C A L C . X ( 2 ) - H P L U S . X ( 3 ) « K ' X ( 1 ) « 1 .000 X ( 2 ) • 0 . 1 D - B X ( 3 ) - 5 .DO DO 50 J • 1. NP X ( 1 ) - 0 .12002 X ( 2 ) - 0 . 1 0 - 7 X ( 3 ) - 5 .DO READ ( 5 . 3 0 ) AM. T . P C 0 2 , ALPHA FORMAT ( 4 F 1 0 . 4 ) PC02 - PC02 • 7 .50061000 CALCULATE CONSTANTS CNI - DEXP(A1 «• B 1 / T ) CN3 - DEXP(A3 + B 3 / T + ( C 3 / ( T * » 2 ) ) + ( D 3 / ( T * » 3 ) ) • ( E 3 / ( T * * 4 ) ) ) CN4 • DEXP(A4 • B 4 / T + ( C 4 / ( T * * 2 ) ) + ( D 4 / ( T * * 3 ) ) • ( E 4 / ( T » * 4 ) ) ) 358 CN5 « DEXP(A5 + B 5 / T + ( C 5 / ( T * » 2 ) ) * ( D 5 / ( T - * 3 ) ) + ( E 5 / ( T * » 4 ) ) ) HC02 « DEXP(A8 + B 8 / T + ( C 8 / ( T » * 2 ) ) + ( D 8 / ( T » » 3 ) ) • ( E B / ( T » * 4 ) ) ) C02 - PC02 / HC02 CN2 - DEXP(1 .0343898DO+2.92236989D-2*T + 2 6 . 2 0 7 0 9 9 0 0 / T - 10. 1 3 9 4 7 6 7 * ( D L 0 G ( T ) ) • 3 . 7 4 9 7 1 5 8 D 0 » C 0 2 + 0 .19297775D0* (DL0G(C02) ) * 2 9 .00067215D-3*AM + 7 4 . 2 8 2 6 7 4 » ( D L 0 G ( A M ) ) ) C C SET INPUT PARAMETERS FOR NOINVT C ERR « . 1 D - 1 0 MAXIT « 20000 EXTERNAL FCN C C NDINVT IS CALLED C CALL NDINVT(NE. X . F . A C C E S T . MAXIT, ERR. F C N , &70) C C THE SOLUTION IS PRINTED C PC02 - PC02 / 7 .5O06100D0 WRITE ( 6 . 4 0 ) AM. T . P C 0 2 . ALPHA. X ( 1 ) 4 0 FORMAT ( 3 X . F 6 . 3 . 4X . F 6 . 2 . 4X . F 8 . 3 . 4 X . F 8 . 4 . 4X . F 8 . 4 . / ) SUM « SUM • (DABS(ALPHA - X ( 1 ) ) ) * * 2 ERR - ERR + ( D A B S ( ( X ( 1 ) - A L P H A ) / A L P H A ) * 1 C O . D O ) • * 2 . 0 X ( 1 ) - X ( 1 ) 50 CONTINUE RMS » (ERR/NP) * » 0 . 5 WRITE ( 6 . 6 0 ) SUM. RMS 60 FORMAT { IX . ' S U M - ' . E 1 5 . 5 , 5 X , ' R M S - ' . E 1 5 . 5 . / ) STOP 70 STOP 1 END C C SUBROUTINE C SUBROUTINE FCN(X . F ) IMPLICIT REAL»8(A - H.O - Z ) DIMENSION X ( 1 ) , F ( 1 ) COMMON CN1. CN2. CN3 , CN4. CN5 , HC02 COMMON AM, T . P C 0 2 , ALPHA F ( 1 ) - PC02 - ( ( H C 0 2 / C N 3 / C N 5 ) * ( A M * X ( 1 ) - P C 0 2 / H C 0 2 ) * X ( 2 ) * X ( 2 ) / ( ( 1 . 1 • X ( 2 ) / C N 5 ) + ( A M » X ( 2 ) / C N 2 / C N 5 / X ( 3 ) ) ) ) F ( 2 ) • X ( 2 ) - ( (AM*X(1 ) - P C 0 2 / H C 0 2 ) * ( 1 . + (CN2*CN5/ (CN2*CN5 + 1 C N 2 » X ( 2 ) • A M * X ( 2 ) / X ( 3 ) ) ) ) / ( 1 . + A M / C N 1 / X ( 3 ) ) + C N 4 / ( X ( 2 ) * ( 1 . • 2 A M / C N 1 / X ( 3 ) ) ) ) F ( 3 ) » X ( 3 ) - ( 1 . • X ( 2 ) / C N 1 + P C 0 2 » ( C N 3 / C N 2 ) » H C 0 2 * X ( 2 ) ) RETURN END 359 C.4: Program for the c a l c u l a t i o n of DEA, BHEP, HEOD and THEED concentration in heat transfer tubes. C PROGRAM TO PREDICT TEMPERATURE P R O F I L E , PRESSURE DROP. C F ILM THICKNESS, DEA, HEOD, THEED AND BHEP CONCENTRATIONS C IN THE HEAT TRANSFER TUBE OF THE DEA DEGRADATION EXPT. C C TH-TEMPERATURE OF THE HEATING MEDIUM (C) C TS'TEMPERATURE OF THE AUTOCLAVE (C) C TWIN-INSIDE WALL TEMPERATURE OF THE COIL (C) C T C L - T O T A L COIL LENGTH (M) C TLV«TOTAL LIQUID INVENTORY (CU.M) C RVOL-REACTOR VOLUME (CU.M) C WCVOL-WATER COOLER VOLUME (CU.M) C S P T - S P A C E TIME INSIDE THE REACTOR ( « e c ) C WCT-WATER COOLER RESIDENCE TIME ( s e c ) C R T T - R E S . TIME INSIDE THE TANK C RXT-T IME REOD. FOR LIQUID TO REACH THE TANK C T S P S - T I M E FOR A SINGLE PASS THRU HEX. (SEC) C D E A L - Q N T Y . OF OEGRAOED DEA IN 1 PASS C DEANP-DEA CONC. AFTER NP PASSES C HEONP«HEDD CONC. " C THENP-THEED CONC. " C TOTHR«TOTAL TIME (HR) C NPT-TOTAL NO. OF PASSES C NPHR'NO. OF PASSES PER HOUR C X - C O I L LENGTH (M) C D E A L T - L O S S OF DEA AT THE END OF EACH INCREMENT C HEODT-HEOD CONC. . . . C THEEDT" THEED C O N C * • C DEACT«DEA CONC. . . . C F F T - F R I C T I O N FACTOR TOLERANCE C EPS-COLEBROOK CONST. C DELP-PRESSURE DROP ( P A . ) C A L P H A - E n i / E h DIMENSION T ( 1 0 0 ) . TWIN(100) , TW0(1OO), TW(100) . TWOUT(IOO), 1 V E L T ( 1 0 0 ) , THR( IOO) . T W I N C O O O ) . T R ( 1 0 0 , 3 ) . A ( 1 0 0 . 3 ) , 2 B O 0 0 . 3 ) . C O C O . 3 ) . D O 0 0 . 3 ) . D 2 ( 1 0 0 , 3 ) , E ( 1 0 0 , 3 ) . 3 F ( 1 0 0 , 3 ) . G ( 1 0 0 , 3 ) . D E A ( 1 0 0 , 3 ) . B H E P ( 1 0 0 , 3 ) . 4 H E 0 D O 0 0 . 3 ) . T H E E D ( 1 0 O , 3 ) , C 0 2 O 0 O . 3 ) . V L ( 1 0 0 , 3 ) . 5 D E A X ( 1 0 0 ) . HEODX( IOO) . THEEDX( IOO) . BHEPX( IOO) . 6 A B ( 1 0 0 . 3 ) REAL K ( 1 0 O , 3 ) . K 1 ( 1 0 0 . 3 ) . K 2 ( 1 0 0 , 3 ) . K 3 ( 1 0 0 . 3 ) REAL NPT, NPHR, NPNHR DATA A 1 , A2 / 2 5 . 0 1 3 4 . - 1 2 . 5 9 6 4 / DATA A 3 . A4 / 3 1 . 0 1 0 6 . - 1 5 . 1 0 5 5 / DATA A 5 , A6 / 3 4 . S 2 1 9 . - 1 5 . 6 3 9 5 / C DATA A l . A2 / 1 1 . 9 2 4 , - 6 . 4 2 1 / C DATA A 3 , A4 / 8 . 4 5 0 . - 5 . 5 8 0 / C DATA A 5 , A6 / 3 2 . 6 4 3 , - 1 5 . 6 5 0 / OATA DOT, D B . RPH / 0 . 7 1 1 2 . 0 . 1 0 1 6 . 5 . / DATA VOLS / O . 0 0 0 0 1 1 0 0 / DATA D I , DO, D C , XW / O . 0 0 4 9 3 0 . 0 . 0 0 6 3 5 . 0 . 4 0 6 4 . 0 .O0O715 / DATA DIWC, TLWC / 0 . 0 1 0 2 , 1 2 . 1 9 / DATA TOTHR. T C L , TLV / 1 9 3 . . 4 . 8 . . 0 0 2 5 / DATA T I N C , T E P S , X INC, FFT / I . . . 0 0 1 , . 1 . 0 . 0 0 1 / PI " 4 . • A T A N ( 1 . ) EPS - 0 .O00O12 AM « 3 . 0 ALPHA • 1.0 PTOT « 4 1 2 9 . RI • DI / 2 . NI - 12. 360 ICOUNT » 1 .0 DX - TCL / 12. DEAO - 3 . 0 0 0 BHEPO - O . O HEODO - 0 . 0 THEEDO » 0 . 0 DEAOT « DEAO DEAT - DEAO HEODT - 0 . 0 THEEDT » 0 . 0 BHEPT « 0 . 0 SUMDP " 0 . 0 C IN IT IAL WALL TEMPERATURE TS - 6 0 . 0 TO • 6 0 . 0 T ( 1 ) - 6 0 . 0 TOLD » TS TT - T ( 1 ) TI - TS TH • 2 2 5 . 0 TH2 - 2 2 5 . O - 1 0 . 0 T W O U T O ) - TH TW0(1) - T W O U T O ) TWOT - T W O O ) T W I N O ) - TH - 1 0 . 0 TWIOLD - T W I N O ) TWINT • TWIN(1) T W O ) - TWIN(I ) TWT - T W O ) TWOLD - T W O ) XT • 0 . 0 0 TIME - 0 . 0 DT - 3 0 . 0 X - 0 . 0 5 HR - 24 . RVOL - PI * ( D I * * 2 ) / 4 . * TCL WCVOL " P I * ( D I W C » » 2 ) I A. * TLWC VOLX - PI • ( D I * - 2 ) / 4 . • DX RTT - TLV / VOLS CONST - E X P ( - D T / R T T ) C * * » » WRITE ( 6 . 1 0 ) V O L S . TH 10 FORMAT ( 2 X . ' V O L . FLOW R A T E - ' . F 1 0 . 7 . 4X . 'HOT FLUIO T E M P . - ' . 1 F 8 . 2 . / / ) WRITE ( 6 , 2 0 ) DEAO 20 FORMAT ( 1 X , ' I N I T I A L DEA CONC. - ' , F 6 . 2 . / ) WRITE ( 6 . 3 0 ) 30 FORMAT ( I X . ' L E N G T H ( m ) ' , 2X. 'WALL T ( C ) ' . 2X. ' S O L . T ( C ) ' . 5X. 1 ' V E ' . 6 X . 'DEA C O N C . 6X . ' D E L X * E 5 ' . / / ) WRITE ( 6 . 4 0 ) 40 FORMAT ( 1 X . ' T I M E - H ' , 3X , ' O E A ' . 3X. ' B H E P ' . 3X , ' H E O D ' . 3X, 1 ' T H E E D ' , / / ) C C CALL SUBROUTINE THERM TO CALCULATE PROPERTIES OF SHELL THERIMA C CALL THERM(TH, CPO. TKO. RHOO. VISO) CALL DPROP(TS. OEAO. RHOS. V I S S . T K S , CPS) C C 361 DO 270 I - 1. NI TWIN(I ) « TWINT C C CALL DPROP TO CALCULATE DEA PROPERTIES C 50 CALL DPROP(TT. DEAO. RHO. V I S . T K , CP) CALL DPROP(TWINT. DEAO. RHOW, VISW. TKW. CPW) CALL THERM(TH2. CPOW. TKOW. RHOOW. VISOW) C C CALL SUBROUTINE SSPROP TO CALCULATE T H . COND. OF METAL C CALL SSPROP(TWT. TKM) C C CALCULATE PROCESS SIDE HEAT TRANSFER COEFFICIENT C VOLT • VOLS * (RHOS/RHO) WT - VOLS • RHOS V E L T ( I ) - ( 4 . * W T ) / ( R H 0 * P I * D I * * 2 . ) THR( I ) - DX / V E L T ( I ) / 3600. C THR( I ) « D T / 3 6 0 0 . GF - ( 4 . » W T ) / ( P I * D I * * 2 . ) REC « ( D I * G F ) / V IS PRC • ( C P « V I S ) / TK HI • 0 . 0 2 3 * ( T K / D I ) * ( R E C * * 0 . 8 ) * ( P R C * * ( 1 . / 3 . ) ) • (V IS /V ISW) 1 * * O .14 C C CALCULATE THE OUTSIDE HEAT TRANSFER COEFFICIENT C RED • DB * * 2 . * RPH * RHOO / VISO PRO • CPO * VISO / TKO VISEX » 0 .1 * ( V I S 0 * 8 . 6 2 1 E - O 5 ) * * ( - 0 . 2 1 ) HO - 0 . 1 7 * (TKO/DO) * ( R E 0 * * 0 . 6 6 7 ) • ( P R O * ( 1 . / 3 . ) ) * (DB/DOT) 1 * • 0 .1 * (DO/DOT) * * 0 . 5 * (VISO/VISOW) * * VISEX C C CALCULATE THE LOG MEAN DIAMETER C DL - (DO - D I ) / (ALOG(DO/D I ) ) C C CALCULATE THE OVERALL HEAT TRANSFER COEFFICIENT C U • 1. / ( ( 1 . / H I ) • ( ( 1 . / H 0 ) * ( D I / D 0 ) ) + ( ( X W / T K M ) * ( D I / D L ) ) ) UC • U * (1 • 3 . 5 * ( D I / D C ) ) C C CALCULATE THE BULK TEMPERATURE OF THE SOLUTION C T ( I ) - TH - (TH - T I ) * E X P ( ( - U C * P I * D I * D X ) / ( W T * C P ) ) C C CALCULATE THE INSIDE WALL TEMPERATURE AND CHECK WITH ASSUMED VALUE C TWOUT(I) - TH - ( ( T H - T ( I ) ) • ( 1 . / H O ) * ( D I / D O ) * U C ) TWINC(I ) - TWOUT(I) - ( ( T H - T ( I ) ) * ( X W / T K M ) * ( D O / D L ) * U C ) C WRITE ( 6 . 6 0 ) TWOUT( I ) , TWINC( I ) . TWIN( I ) . T ( I ) 60 FORMAT ( I X . ' T W O U T - ' . F B . 2 , 2X, ' T W I N C - ' , F 8 . 2 , 2X. ' T W I N « ' . 1 F 8 . 2 . 2X . ' T ( I ) - ' . F 8 . 2 , / ) IF ( (TWINC( I ) - T ( I ) ) . L T . 0 .0000001 ) GO TO 80 IF (ABS(TWINC( I ) - TWIN( I ) ) . L T . TEPS) GO TO 90 IF (ABS(TWINC( I ) - TWIN( I ) ) . G T . TEPS) GO TO 70 70 TWIN(I ) • TWINC(I ) TW(I) • (TWIN( I ) • TWOUT(I ) ) / 2 . 362 TT - ( T ( I ) + T1 ) / 2 . TWINT - TWIN(I ) TWT - TW(I) TWOT - TWOUT(I) GO TO 50 8 0 TWIN( I ) - T ( I ) 9 0 CONTINUE C C CALCULATE FANNING FRICTION FACTOR C C IN IT IAL ESTIMATE C F l - 0 . 0 4 * REC * * ( - 0 . 1 6 ) C C COLEBROOKE FORMULA C 100 FC - ( 1 . / ( - 4 . 0 * A L O G 1 0 ( ( E P S / D I ) • ( 4 . 6 7 / ( R E C * F I * * 0 . 5 ) ) ) + 2 . 2 8 ) ) 1 * » 2 IF ( A B S ( F C - F l ) . L T . F F T ) GO TO 120 IF ( A B S ( F C - F l ) . G T . F F T ) GO TO 110 110 F l - FC GO TO 100 120 CONTINUE C C CALCULATE SORT(TOWO/RHO). SORTR C SORTR « V E L T ( I ) • S 0 R T ( F C / 2 . ) C C CALCULATE THICKNESS OF LAMINAR AND BUFFER LAYERS C YLMAX • 5 . • VIS / (RHO'SORTR) YBMAX - 3 0 . * VIS / (RHO'SORTR) C WRITE ( 6 . 1 3 0 ) YLMAX, YBMAX 130 FORMAT (1X , ' Y L M A X - ' . E 1 2 . 7 . 2X. ' Y B M A X - ' . E 1 2 . 7 , / ) C C CALCULATE HEAT TRANSFER RATE THROUGH THE WALL, OW C OW • PI • DI • DX • HI • (TWIN(I ) - T ( I ) ) C C CALCULATE BIGO (MARTINELLI ) C BIGO - OW / ( A L P H A * C P * R H O * P I » D I » D X * S Q R T R ) C C CALCULATE RESISTANCES C RLAM - ALPHA • PRC RBUF - A L 0 G ( 1 . • 5 . * A L P H A * P R C ) RTUR - 0 . 5 0 * A L 0 G ( R E C / 6 0 . ) * S Q R T ( F C / 2 ) RTOT > RLAM + RBUF + RTUR C WRITE ( 6 , 1 4 0 ) OW, BIGO, RTOT 140 FORMAT ( I X . ' O W - ' . E 1 0 . 4 . 2X, ' B I G O - ' . E 1 0 . 4 , 2X. ' R T O T - ' , 1 E 1 0 . 4 ) C C CALCULATE TEMPERATURE AT THE CENTRE. T c C TC - TWIN(I ) - 5 . * BIGO * RTOT C WRITE ( 6 , 1 5 0 ) T C . T W I N ( I ) , T ( I ) 150 FORMAT ( I X , ' T C - ' . F 6 . 2 . 2X , ' T W I N ( I ) - ' , F 6 . 2 , 2X. ' T ( I ) - ' , 1 F 6 . 2 ) C 363 c c 160 170 180 1 190 1 2 0 0 C 210 210 1 220 230 C C C 240 CALCULATE RADIAL TEMPERATURE DISTRIBUTION Y - 0 . 0 TLAM - TC TBUF - TC TTUR - TC DY - RI / 2 0 . DO 230 L - 1, 20 IF (Y . L E . YLMAX) GO TO 170 IF (Y . G T . YLMAX .AND. Y . L E . YBMAX) GO TO 180 IF (Y . G T . YBMAX .AND. Y . L E . R I ) GO TO 190 TLAM - TWIN(I ) - (TWIN(I ) - TC) • (RLAM/RTOT) * (Y /YLMAX) GO TO 200 TBUF - TWIN(I ) - (TWIN(I ) - T C ) * (RLAM • ALOG(1 . * R L A M * ( ( Y / YLMAX) - 1. ) ) ) / RTOT GO TO 200 TTUR - TWIN(I ) - (TWIN(I ) - T C ) * (RLAM + RBUF • R T U R » ( Y / R I ) ) / RTOT IF (Y . G E . R I ) GO TO 240 WRITE ( 6 . 2 2 0 ) Y , TLAM, TBUF, TTUR FORMAT (1X . ' Y - ' , E 8 . 3 , 2X, ' T L A M - ' , F 6 . 2 . 2X. ' T B U F - ' . F 6 . 2 . 2X . ' T T U R - ' . F 6 . 2 ) Y • Y • DY CONTINUE 250 1 C C C C C C C C C c CALCULATE AVERAGE TEMPERATURE FOR THE LAYERS T R ( 1 , 1 ) - TLAM T R ( I , 2 ) - TBUF T R ( I , 3 ) - TTUR WRITE ( 6 . 2 6 0 ) T R ( I . 1 ) . T R ( I , 2 ) . T R ( I , 3 ) FORMAT ( 1 X , ' T R I . 1 - ' . F 8 . 2 . 2X. ' T R I . 2 - ' . F 8 . 2 . 2X. ' T R I , 3 « F 8 . 2 , / ) CALCULATE VOL OF EACH LAYER V L ( I . 1 ) - PI * DX * ( R I * * 2 . - (RI - Y L M A X ) * * 2 . ) V L U . 2 ) - PI * DX * ( (R I - Y L M A X ) * * 2 . - ( R l - Y B M A X ) » » 2 . ) V L ( I . 3 ) - PI * DX * (RI - YBMAX) * * 2 . C A L C U L A T E FREE C02 CONCENTRATION OF EACH LAYER C 0 2 ( I , 1 ) - F C 0 2 ( A M . T L A M , P T 0 T . P C 0 2 ) C 0 2 U . 2 ) - F C 0 2 ( A M , T B U F , P T 0 T , P C 0 2 ) C 0 2 ( 1 . 3 ) - F C 0 2 ( A M . T T U R . P T 0 T . P C 0 2 ) CALCULATE RATE CONSTANTS FOR EACH LAYER DO 260 J - 1. 3 K K I . J ) « EXP(A1 • A 2 * ( 1 0 0 0 . / ( T R ( I . J ) + 2 7 3 . ) ) ) K 2 ( I . J ) - EXP(A3 • A 4 * ( 1 0 O 0 . / ( T R ( I . J ) + 2 7 3 . ) ) ) K 3 ( I , J ) - EXP(A5 + A 6 » ( 1 0 O 0 . / ( T R ( I . J ) + 2 7 3 . ) ) ) A ( I . J ) • E X P ( - ( ( K 1 ( I , J ) + K 2 ( I , J ) ) * C 0 2 ( I . J ) * T H R ( I ) ) ) A B ( I . U ) - E X P ( ( K 3 ( I . d ) - ( ( K K I . J ) • K 2 ( I . J ) ) * C 0 2 ( I . J ) ) * T H R ( I ) )) B ( I , J ) - K K I . J ) / ( K I ( I . J ) + K 2 ( I . J ) ) C ( I . J ) - K 2 ( I . J ) * C 0 2 ( I . J ) / ( K 3 ( I . J ) - ( K I ( I . J ) • K 2 ( I . J ) ) * C 0 2 ( I . J ) ) D ( I . J ) • K 2 ( I . J ) / ( K K I . J ) + K 2 ( I . J ) ) D 2 ( I . d ) « 1. / ( ( K l ( I . d ) + K 2 ( I . d ) ) * C 0 2 ( I . d ) ) E ( I , J ) • K 3 ( I . d ) / ( K 3 ( I . d ) - ( K l ( I . d ) • K 2 ( I , d ) ) * C 0 2 ( I . d ) ) F ( I . d ) - ( K I ( I . J ) + K 2 ( I . d ) ) * C 0 2 ( I . d ) / ( K 3 ( I . J ) - ( K l ( I . d ) 1 • K 2 ( I . d ) ) * C 0 2 ( I , d ) ) G ( I . d ) - E X P ( - K 3 ( I . d ) * T H R ( I ) ) 260 CONTINUE T T - ( T ( I ) * T I ) / 2 . T I - T ( I ) TWINT - TWIN( I ) TWT - TW(I ) TWOT • TWOUT(I) C 00 280 d « 1. 3 C 280 WRITE ( 6 . 2 9 0 ) I. d . T ( I ) . T H R ( I ) , C 0 2 ( I . d ) . K 1 ( I . d ) . K 2 ( I . d ) . C 1 A ( I . d ) C 290 FORMAT ( 1 X . 2 1 3 . 2X. 6 F 1 2 . 6 . / ) ICOUNT • ICOUNT • 10. 270 CONTINUE C C C A L C U L A T E CONCENTRATIONS ALONG THE REACTOR LENGTH C DEAT - 3 . 0 0 0 280 DO 30O I - 1. NI DO 290 d • 1. 3 D E A ( I . d ) • DEAT • A ( I . d ) H E O D ( I . d ) • DEAT • B ( I . d ) * ( 1 . - A ( I . d ) ) • HEODT T H E E D ( I . d ) - DEAT • C ( I . d ) * ( A ( I . d ) - G ( I . d ) ) • THEEDT • G ( I . 1 d ) B H E P ( I . d ) » DEAT * K 3 ( I , d ) * C ( I . d ) * ( G ( I . d ) / K 3 ( I . d ) - A ( I . d ) 1 • 0 2 ( 1 . 0 ) ) • ( T H E E D T / K 3 ( I , d ) ) * ( 1 . - G ( I . d ) ) • DEAT • D ( I . d ) + 2 BHEPT 290 CONTINUE D E A X ( I ) - ( V L ( I . 1 ) / V 0 L X ) * D E A ( I . I ) + ( V L ( I . 2 ) / V O L X ) • D E A ( I , 2 ) 1 • ( V L ( I . 3 ) / V 0 L X ) * D E A ( I . 3 ) H E O D X ( I ) • ( V L ( I . D / V O L X ) • H E 0 D ( I . 1 ) + ( V L ( I , 2 ) / V O L X ) * HEOD( I . 1 2 ) + ( V L ( I , 3 ) / V 0 L X ) * H E O D ( I . S ) T H E E D X ( I ) - ( V L ( I . D / V O L X ) • T H E E D ( I , 1 ) + ( V L ( I . 2 ) / V O L X ) » 1 T H E E D ( 1 , 2 ) + ( V L ( I , 3 ) / V 0 L X ) * T H E E D ( I . S ) B H E P X ( I ) - ( V L ( I . D / V O L X ) • B H E P ( I . I ) • ( V L ( I . 2 ) / V O L X ) * B H E P ( I . 1 2 ) + ( V L ( I . 3 ) / V 0 L X ) * B H E P ( I , 3 ) DEAT - D E A X ( I ) HEODT - HEODX( I ) THEEDT - THEEDX( I ) BHEPT - B H E P X ( I ) C WRITE ( 6 . 3 2 5 ) I . D E A X ( I ) . B H E P X ( I ) , HEODX( I ) .THEEDX( I ) C 325 FORMAT ( 1 X . 1 3 . 4 X . F 8 . 3 . 2X. F 1 0 . 2 . 3X, F B . 4 . 3X. C 1 F 1 2 . 6 . / ) 300 CONTINUE C C - C A L C U L A T E CONC. INSIDE THE TANK* C 310 DEAF - DEAT * ( 1 . - CONST) • DEAO * CONST BHEPF - BHEPT * ( 1 . - CONST) • BHEPO * CONST HEODF • HEODT * ( 1 . - CONST) + HEODO * CONST THEEDF - THEEDT * ( 1 . - CONST) • THEEDO * CONST TIMEHR • TIME / 3600 . IF (TIMEHR . G T . HR) GO TO 320 TIME - TIME • DT DEAO - DEAF BHEPO • BHEPF HEODO » HEODF THEEDO • THEEDF DEAT - DEAF BHEPT • BHEPF HEODT • HEODF THEEDT - THEEDF GO TO 280 320 WRITE ( G . 3 3 0 ) TIMEHR, D E A F , BHEPF . HEODF. THEEDF 330 FORMAT (1X . F 1 0 . 4 , 1X. F 1 0 . 4 . 2X, F 1 0 . 4 . 3X, F 1 0 . 4 , 4 X . F 1 2 . 6 , / / HR » HR • 2 4 . IF (HR . G E . TOTHR) GO TO 340 IF (HR . L T . TOTHR) GO TO 280 340 WRITE ( 6 . 3 5 0 ) T 1 . TLAM, T B U F . TTUR 350 FORMAT ( 1 X . ' T 1 - ' . F 8 . 2 , 2X . ' T L A M " , F 8 . 2 . 2X , ' T B U F - ' . F 8 . 2 . 2X 1 ' T T U R - ' . F 8 . 2 , / ) STOP , END C C SUBROUTINE DPROP CALCULATES DEA PROPPERTIES C SUBROUTINE DPROP(TT . DEAO, RHO, V I S , T K , CP) DEAO - DEAO • 10. RHO - 9 8 8 . 0 - 0 . 0 0 4 0 3 * TT • * 2 • DEAO * ( 3 . 4 - 0 . 0 0 0 2 5 * T T » * 1 . 4 5 ) 1- DEAO * * 1.19 VIS1 - ( 0 . 0 6 7 6 6 6 * D E A 0 - 6 . 820867 ) / ( 1 . - 0 .004395*DEA0) V IS2 - TT * ( ( 0 . 0 1 4 0 6 6 • 0 . 0 0 0 0 1 0 5 * D E A 0 ) / ( 1 . - 0 . 004965*DEA0) ) V IS - EXP(VIS1 - V IS2 ) TK - ( 0 . 4 6 7 5 - O . O O 6 2 * D E A 0 * * O . B 5 3 8 ) • TT * * 0 . 0 8 CP - 4 . 1 7 6 • 0 . 0 0 0 4 6 * TT - 0 .01837 * DEAO * 0 .000054 * DEAO * TT CP - CP • 100O. DEAO - DEAO / 10. RETURN END C C SUBROUTINE THERM CALCULATES THE PROPERTIES OF SHELL THERMIA C SUBROUTINE THERM(TH. CPO. TKO, RHOO, VISO) CPO - ( 0 . 3 8 8 + O . O 0 0 4 5 * ( T H * ( 9 . / 5 . ) • 3 2 . ) ) / 0 .9352 CPO - CPO • 4164 TKO - ( 0 .821 - 0 . 0 0 0 2 4 4 » ( T H - ( 9 . / S . ) • 3 2 . ) ) / 0 .6742 TKO - TKO * O.1441314 RHOO - 0 . 8 8 6 6 6 2 - 0 . 0 0 0 7 5 0 • TH RHOO - RHOO • 1000. VISO - E X P ( - ( 2 . 2 1 7 7 • 0 . 0 1 8 8 * T H ) ) RETURN END C C SUBROUTINE SSPROP CALCULATES THE PROPERTIES OF SS STEEL C SUBROUTINE SSPROP(TW. TKM) TKM • 1 5 . 6 0 + 0 . 006289 * TW RETURN END C C FUNCTION FC02 EVALUATES FREE C02 CONCENTRATION C FUNCTION FC02(AM, T . PTOT. PC02) TEK - T + 2 7 3 . 15 PH20 - EXP(7 .96681 - 1 6 6 8 . 2 1 / T E K ) 366 PDEA • EXP(B.12303 - 2315.46/TEK) DEAFR • AM * 105.14 / 10OO.O PMIX - PDEA * DEAFR + PH20 * (1. - DEAFR) PMIX - PMIX / 7.50061 PC02 • PTOT - PMIX HC02 - EXP(22.2819 - 138.306E2/TEK + 691.346E4/(TEK**2) - 155. 1895E7/(TEK**3) + 120.037E9/(TEK**4)) / 7.50061 FCD2 • PC02 / HC02 RETURN END 367 C.5: Program for the ca l c u l a t i o n of MDEA and i t s major degradation products concentration in a batch reactor. C KINETIC MODEL FOR MDEA DEGRADATION C C THIS PROGRAM USES TWO UBC SUBROUTINES WITH C TWO DIFFERENT FUNCTIONS TO CALCULATE THE C CONCENTRATIONS OF MDEA AND ITS DEGRADATION C PRODUCTS AS A FUNCTION OF TIME IN A BATCH C REACTOR. C C LIBRARY ROUTINE NDINVT WITH EXTERNAL FUNCTION C FCN PERFORMS EQUILIBRIUM CALCULATIONS WHEN C C02 IS DISSOLVED IN AQUEOUS MDEA SOLUTIONS C AND THUS CALCULATES CONCENTRATION OF VARIOUS C SPECIES IN EQUILIBRIUM INCLUDING PROTONATED C MDEA USING REACTION SCHEME PROPOSED BY C BARTH ET AL. C C LIBRARY ROUTINE RKC WITH EXTERNAL FUNCTION C FUNC SOLVES THE DIFFERENTIAL EQUATIONS C DESCRIBING CHANGE IN CONCENTRATION OF MDEA C AND ITS DEGRADATION PRODUCTS. C C c C INPUT DATA : TEMPERATURE (TK) K e l v i n C MDEA CONCENTRATION (AM) mole/L C C02 PARTIAL PRESSURE (PC02K) kPa C C INPUT DATA FOR R-K SUBROUTINE : C C TIME INTERVAL : TINIT (X) » 0.0 h C TFINAL(Z) « ??? h C IMPLICIT REAL*8(A - H.O - 2) DIMENSION Y(20). F(20) . T(20) . S(20). G(20) DIMENSION FE(5) , ACCEST(S) COMMON / C / CN1. CN2. CN3. CN4, HC02. HC03 COMMON AM, TK, PC02 COMMON / C N / C02. C(13), XE(5) EXTERNAL FCN. FUNC DATA A2, B2. C2 /-241.818D0. 298.25303. -148.52806/ DATA D2, E2 /332.648D8. -282.394D10/ DATA A3. B3. C3 /39.5554D0. -987.9D2. 568.828D5/ DATA 03. E3 /-146.451D8, 136.146D10/ DATA A4, B4, C4 / -294.74D0, 364.385D3, -184.158D6/ DATA D4, E4 /415.793D8, -354.291010/ DATA A5. B5, C5 /22.2819D0, -138.306D2. 691.346D4/ DATA D5. E5 /-155.B95D7, 120.037D9/ DATA NE. N / 5 . 15/ AM - 3.00D0 TK - 473.15DO PC02K « 2588.0000 PC02 - PC02K • 7.5CO61D0 C C CALCULATE EQUILIBRIUM CONSTANTS C CN2 « DEXP(A2+B2/TK+(C2/(TK»»2)) + (D2/(TK**3)) • (E2/(TK**4 ) ) ) CN3 - DEXP(A3+B3 /TK+(C3 / (TK»*2 ) )+ (D3 / (TK»*3 ) ) + ( E 3 / ( T K » » 4 ) ) ) CN4 « DEXP(A4+B4 /TK+(C4 / (TK»*2 ) )+ (D4 / (TK*»3 ) ) • ( E 4 / ( T K » » 4 ) ) ) 368 HC02 - DEXP(A5+B5/TK+(C5/(TK**2))+(D5/(TK**3))+ (E5/ (TK**4) ) ) C02 » PC02 / HC02 CN1 « DEXP(92.421453D0-1.49081486D-2*TK+ 40.84770BD0/TK- 14. 1O31652DO*(DL0G(TK))- 9.8778738D-2*C02+0.18275505D0*(0L0G(C02)) + 2 3.98G2282D0*AM - 12.71542100*(DL0G(AM))) WRITE(6.11) AM. TK. PC02K 11 FORMAT(IX,'MDEA C O N C . « ' , F 5 . 3 , 2 X . ' T E M P ( K ) « ' . F 6 . 2 . 2 X , ' C 0 2 PP(kPa) 1 « ' . F 7 . 2 . / / ) C C SET INITIAL GUESSES FOR EQUILIBRIUM CALCULATION C C XE(1)«ALPHA CALC ; XE(2)«HPLUS : XE(3)»HC03- : C XE(4)-MDEAH+ ; XE(5)-MDEA C XE(1) « 0.10D0 XE(2) - 0.500-7 XE(3) - 0.1000 XE(4) - 0.2000 XE(5) - 3.00D0 C C SET INPUT PARAMETERS FOR LIBRARY ROUTINE NDINVT C ERR » .10-10 MAXIT - 10000 C C PARAMETERS FOR RATE CALCULATION WITH LIBRARY ROUTINE RKC C C TIME INTERVALS X-TINIT, Z-TFIN C X - 0.000 Z - 60.0000 C C CALCULATE H, HMIN AND SET E C H - (Z - X) / 64.DO HMIN • 1.D-3 » H ZH - 2. • (Z - X) / Z Z « X + ZH E « 1.D-5 C C SET INITIAL CONCENTRATIONS C Y(1) - 4.28D0 00 40 J • 2.N.1 Y(d) - 0.000 40 CONTINUE C C CALCULATE RATE CONSTANTS C C(4) » DEXPO0.0614D0-6916.48D0/TK) C(5) - DEXP(1O.7719900-6135.78D0/TK) C(6) - DEXP(12.39755DO-7299.12D0/TK) C(7) • DEXP(10.16495DO-6770.19D0/TK) C(8) • OEXP(13.2750D0-6316.73D0/TK) C(9) - DEXP(14.80872D0-7880.14D0/TK) C(10) • DEXPO0.0337D0-6556.43D0/TK) C(11) - DEXPO1.0243D0-6785.03D0/TK) 369 C(12) » DEXP(10.4539D0-6562.04D0/TK) C(1) • DEXPO5.5D0-9062.D0/TK) C(2) • DEXP(16.8116D0-9571.9/TK) C(3) • DEXP(24.3607D0-12843.4D0/TK) WRITE (6.50) 50 FORMAT (1X. 'T IME' . 1X, 'MDEAT' ,1X. 'MDEA' .1X. 'MDEH' .1X. 'BHEP' . 1 2X. ' D E A ' . IX, 'OMEA', 1X, 'DMP'. 2X, ' E G ' . 4X, ' E O ' . 2X. 2 'HEOD', 2X, 'HMP'. 2X. 'MAE' . IX, ' T E A ' . IX, 'TEHEED'. 1X. 3 'THEED' . 1X, 'TMA' , / / ) C C NDINVT IS CALLED C DO 60 JJ= 1.28 CALL NDINVT(NE, XE, F E . ACCEST, MAXIT. ERR, FCN. &80) C C ASSIGN NEW VALUES OF MDEA AND MDEAH C Y(1) - XE(5) Y(2) - XE(4) C WRITE(6,58) XE(3) C 58 FORMAT(1X. 'XE(3) • ' .F12 .6 , / ) C C CALL RKC TO CALCULATE Y 'S EVERY 2 HOURS C C DO 60 J J • 1.28 CALL DRKC(N. X. Z . Y. F, H, HMIN. E. FUNC. G. S. T) Y(2) - ((CN1*C02)/HC03) * Y(1) AM=Y(1) • Y(2) WRITE (6.70) X. AM, ( Y ( d ) , J « 1 , N ) Z - Z • 2H 60 CONTINUE 70 FORMAT (IX. F5.1.16F5.2) STOP 80 STOP 1 END C C SUBROUTINE C SUBROUTINE FCN(XE. FE) IMPLICIT REAL*8(A - H.O - Z) DIMENSION XE(1) . F E O ) COMMON ICI CN1. CN2. CN3. CN4. HC02. HC03 COMMON AM. TK, PC02 F E O ) »PC02- HC02 * XE(2) * XE(2) • (XE(1)*AM - PC02/HC02) / ( 1CN2»CN4) * (1.DO/O.D0+XE(2)/CN4)) FE(2)=XE(2) - (XE(1)*AM - PC02/HC02) • (1.D0+CN4/(CN4 + XE(2))) / 1 (1 .D0+CN1»AM/(CN2+CN1*XE(2) ) ) -CN3/ (XE(2)»(1 .D0+CN1*AM/(CN2+CN1* 2XE(2)))) FE(3) - XE(3) - (XE(2)/(XE(2) • 2.*CN4)) • (XE(2) • XE(4) - CN3/XE( 12)) FE(4 ) - XE(4) - CN1 * XE(5) * PC02 / (HC02*XE(3)) FE(5 )« XE(5) - AM + XE(4) RETURN END C C FUNCTION FC02 EVALUATES FREE C02 CONCENTRATION C FUNCTION FC02(AM. T. PTOT, PC02) 370 TEK « T + 273.15 PH20 - EXP(7.96681 - 1668.21/TEK) PDEA * EXP(8.12303 - 2315.46/TEK) DEAFR » AM»105.14/100O.0 PMIX • PDEA*DEAFR + PH20*(1.-DEAFR) PMIX « PMIX/7.50061 PC02 • PT07 - PMIX HC02 « EXP(22.2819 - 138.306E2/TEK + 691 .346E4 / (TEK*«2 ) - 155. 1895E7/(TEK»»3) + 1 2 0 . 0 3 7 E 9 / ( T E K » * 4 ) ) / 7.50061 FC02 « PC02 / HC02 RETURN END C C SUBROUTINE FUNC C SUBROUTINE FUNC(X. Y, F) IMPLICIT REAL*8(A - H.O - Z) DIMENSION Y(1) , F(1) COMMON /RKC$/ OK COMMON / C N / C02, C(13). XE(5) COMMON / C / CN1. CN2. CN3. CN4, HC02, HC03 LOGICAL OK IF ( .NOT. OK) STOP 2 C ' HC03 • XE(3) + Y(6) • Y(10) • Y(13) + Y(15)/2.D0 HC03 - XE(3) F(1) — C ( 4 ) * Y ( 1 ) » * 2 . 0 *C02/HC03 F(3) - C(10) • Y(8) • Y(10) + C(3) • Y(14) F(4) • C(4) * Y(1)"*2.0 *C02/HC03 - C(8) * Y(4) • Y(11) * C02 1 - C(9) * Y(4) * Y(8) - C(11) * Y(4) » Y(12) * C02 2 - C(1) • Y(4) • C02 - C(2) * Y(4) • C02 F(5) « C(4) * Y(1)**2 .0 *C02/HC03 - C(5) * Y(5) » Y(5) * C02 F(6) «= C(6) * Y(11) » Y(11) • C02 - C(12) * Y(6) » Y(8) F(7) • C(7) • Y(B) F(8) « C(4) • Y(1)**2 .0 *C02/HC03 + C(5) * Y(5) * Y(5)*C02 1 - C ( 7 ) » Y ( 8 ) - C ( 9 ) » Y ( 4 ) » Y ( 8 ) - C ( 1 0 ) » Y ( 1 0 ) * Y ( 8 ) - C(12)*Y(6)*Y(8) F(9) « C O ) » Y U ) * C02 F(10) " C(8) * Y(4) * Y(11) • C02 * C(12) » Y(6) * Y(8) 1 - C O O ) * Y(8) • Y(10) F(11) • C(5) * Y(5) • Y(5) » C02 - C(6) * Y(11) » V(11) • C02 - C( 18) * Y(4) * Y(11) * C02 F(12) - C(9) • Y(4) * Y(8) - C(11) * Y(12) F(13) • C(11) * Y(4) • Y(2) * C02 F(14) « C(2) * Y(4) * C02 - C(3) * Y(14) F(15) - C(5) * Y(5) • Y(5) * C02 RETURN E N D APPENDIX-D J / 1 COMPARISON OF MDEA DEGRADATION MODEL PREDICTION WITH EXPERIMENTAL DATA TIME CONCENTRATION (mol/L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4.28 2.0 3 . 30 3.27 4 .0 2 . 57 2.57 6.0 2. 12 2.07 8.0 1. 75 1 .71 12.0 1. 25 1 .21 20.0 0. 74 0.70 24 .0 0. 58 0.56 26 .0 0. 47 0.51 30 .0 0. 38 0.42 32 .0 0. 35 0.38 40 .0 0. 24 0.28 44 .0 0. 21 0.24 48 .0 0. 19 0.21 50 .0 0. 17 0.20 54 .0 0. 14 0.17 0.00 0.00 0.00 0.04 0.00 0.65 0.10 0.02 1.20 0.20 0.04 1.40 0.30 0.08 1.76 0.43 0.16 1.80 0.60 0.38 1.50 0.74 0.50 1.40 0 .65 0.55 1.30 0.72 0.66 1.15 0 .75 0.71 1.08 0.84 0.89 0.85 0.92 0.97 0.75 0.96 1.03 0.70 1.01 1.06 0.65 1.05 1.11 0.60 0.00 0.00 0.00 0.96 0.00 0.00 1.51 0.00 0.00 1.79 0.01 0.00 1.88 0.01 0.00 1.83 0.02 0.03 1.49 0.07 0.12 1.32 0.08 0.18 1.25 0.10 0.20 1.12 0.12 0.26 1.07 0.14 0.28 0.88 0.20 0.37 0.81 0.23 0.41 0.74 0.27 0.45 0.72 0.31 0.48 0.66 0.35 0.52 TIME CONCENTRATION (mol/L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 2 .0 0.03 0.03 0. 00 0.01 0.00 0.00 0.08 0.21 4 .0 0.08 0.06 0. 01 0.03 0.02 0.03 0.28 0.71 6.0 0.14 0.17 0. 05 0.05 0.05 0.10 0.62 1.09 8.0 0.20 0.25 0. 05 0.06 0.11 0.18 0.90 1.29 12.0 0.30 0.43 0. 08 0.07 0.24 0.29 1.25 1.33 20 .0 0.58 0.88 0. 10 0.08 0.40 0.34 1.05 0.93 24 .0 0 .75 1 .12 0. 10 0.08 0.46 0.36 0.82 0.73 26 .0 0.80 1 .23 0. 10 0.08 0.50 0.37 0.75 0.65 30 .0 0.92 1.43 0. 10 0.08 0.54 0.39 0.58 0.50 32.0 1.10 1.52 0. 10 0.08 0.58 0.41 0.50 0.44 40 .0 1.35 1.83 0. 10 0.08 0.70 0.48 0.30 0.25 44 .0 1.42 1 .48 0. 10 0.08 0.80 0.51 0.25 0.19 48 .0 1.50 2.04 0. 10 0.09 0.85 0.54 0.20 0.15 50.0 1.50 2.08 0. 10 0.09 0.90 0.56 0.16 0.13 54 .0 1.55 2.14 0. 10 0.09 0.95 0.59 0.12 0.10 372 TABLE D.2 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 220 C . TIME CONCENTRATION (mol /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0 .00 0 .00 0.00 0.00 2.0 3.66 3.59 0.00 0.00 0 .60 0 .66 0.00 0.00 4.0 3.12 3.06 0.02 0.01 1 .00 1 .12 0.00 0.00 6.0 2.70 2.63 0.08 0.02 1 .35 1 .43 0.00 0.00 8.0 2.34 2.29 0.15 0.03 1 .55 1 .61 0.01 0.00 12.0 1 .82 1.78 0.30 0.08 1 .76 1 .75 0.01 0.01 20.0 1.15 1.16 0.42 0.22 1 .68 1 .62 0.03 0.04 24.0 0.96 0.97 0.50 0.31 1 .55 1 .51 0.05 0.08 26.0 0.85 0.89 0.51 0.35 1 .50 1 .45 0.06 0.10 30.0 0.73 0.76 0.55 0.44 1 .40 1 .33 0.08 0.13 34.0 0.61 0.65 0.63 0.52 1 .30 1 .23 0.10 0.17 40.0 0.44 0.53 0.69 0.64 1 .15 1 .09 0.16 0.23 44.0 0.39 0.47 0.73 0.72 1 .10 1 .02 0.20 0.26 50.0 0.33 0.39 0.80 0.83 0 .95 0 .91 0.25 0.31 54.0 0.31 0.35 0.84 0.90 0 .90 0 .85 0.28 0.34 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2 .0 0.00 0.02 0.00 0.01 0.00 0.00 0.00 0.08 4 .0 0.02 0.06 0.01 0.02 0.00 0.01 0.15 0.36 6.0 0.05 0.11 0.01 0.03 0.00 0.04 0.40 0.67 8.0 0.10 0.16 0.02 0.04 0.02 0.09 0.58 0.93 12.0 0.20 0.27 0.04 0.06 0.06 0.20 0.90 1.19 20.0 0.42 0.56 0.06 0.07 0.25 0.33 1 .00 1.12 24.0 0.55 0.73 0.07 0.08 0.35 0.34 1.05 0.98 26.0 0.54 0.81 0.08 0.08 0.40 0.35 0.92 0.91 30.0 0.70 0.99 0.08 0.08 0.45 0.36 0.80 0.77 34.0 0.80 1.16 0.09 0.08 0.52 0.37 0.65 0.65 40.0 1 .00 1.39 0.10 0.08 0.60 0.39 0.45 0.49 44.0 1.10 1.53 0.10 0.08 0.70 0.41 0.40 0.40 50.0 1 .25 1.71 0.10 0.08 0.75 0.45 0.30 0.30 54.0 1 .34 1.82 0.11 0.08 0.85 0.47 0.25 0.25 373 TABLE D.3 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 210 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4.28 0.00 0.00 0 .00 0 .00 0.00 0.00 2.0 3 .86 3.83 0.00 0.00 0 .43 0 .43 0.00 0.00 4.0 3 .50 3 .45 0.00 0.00 0 .70 0 .77 0.00 0.00 6.0 3 .20 3.13 0.02 0.01 0 .95 1 .04 0.00 0.00 8.0 2 .91 2.84 0.04 0.01 1 .10 1 .25 0.01 0.00 10.0 2 .68 2 .60 0.08 0.02 1 .30 1 .39 0.01 0.00 18.0 1 .92 1 .88 0.18 0.08 1 .50 1 .61 0.02 0.01 20.0 1 .76 1 .74 0.22 0.10 1 .60 1 .61 0.02 0.01 24.0 1 .55 1 .52 0.31 0.15 1 .52 1 .57 0.03 0.02 28.0 1 .38 1 .33 0.35 0.21 1 .45 1 .51 0.05 0.04 32.0 1 .15 1.18 0.40 0.27 1 .38 1 .44 0.06 0.05 36.0 1 .01 1 .05 0.45 0.34 1 .35 1 .36 0.10 0.08 44.0 0 .82 0.85 0.50 0.47 1 .15 1 .22 0.15 0.13 50.0 0 .76 0.74 0.56 0.56 1 .00 1 .12 0.16 0.17 54.0 0 .65 0.67 0.61 0.62 0 .90 1 .06 0.18 0.20 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 2.0 0. 00 0.01 0.00 0. 00 0.00 0. 00 0.00 0. 03 4.0 0. 01 0.03 0.00 0. 01 0.00 0. 00 0.08 0. 14 6.0 0. 03 0.06 0.01 0. 02 0.02 0. 01 0.17 0. 33 8.0 0. 06 0 .09 0.02 0. 03 0.03 0. 03 0.30 0. 53 10.0 0. 09 0.13 0.05 0. 04 0.04 0. 06 0.42 0. 70 18.0 0. 24 0.29 0.08 0. 06 0.20 0. 22 0.90 1. 08 20.0 0. 30 0.34 0.08 0. 06 0.25 0. 25 0.94 1. 10 24.0 0. 38 0.44 0.08 0. 07 0.29 0. 30 0.94 1. 07 28.0 0. 45 0.55 0.09 0. 07 0.34 0. 33 0.85 1. 01 32.0 0. 62 0.67 0.10 0. 07 0.40 0. 35 0.81 0. 92 36.0 0. 70 0.80 0.10 0. 07 0.45 0. 35 0.68 0. 83 44.0 0. 95 1 .04 0.10 0. 08 0.55 0. 37 0.50 0. 66 50.0 1 . 10 1 .22 0.10 0. 08 0.60 0. 38 0.40 0. 54 54.0 1. 20 1 .33 0.10 0. 08 0.65 0. 39 0.35 0. 47 374 TABLE D.4 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4 .28 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 4.04 4 .00 0.00 0.00 0 .20 0.26 0.00 0.00 4.0 3.80 3 .75 0.00 0.00 0 .46 0.50 0.00 0.00 6.0 3.56 3 .52 0.00 0.00 0 .65 0.70 0.00 0.00 8.0 3 .35 3 .31 0.02 0.00 0 .82 0.87 0.00 0.00 12.0 2.96 2 .94 0.04 0.01 1 .15 1.14 0.00 0.00 20.0 2.40 2 .38 0.10 0.04 1 .32 1.41 0.01 0.00 24.0 2.22 2 .15 0.12 0.06 1 .30 1 .45 0.01 0.00 28.0 2.02 1 .96 0.18 0.09 1 .32 1 .47 0.01 0.01 32.0 1 .84 1 .79 0.21 0.12 1 .30 1 .45 0.02 0.01 40.0 1 .49 1 .51 0.28 0.20 1 .26 1 .39 0.05 0.03 42.0 1 .42 1 .45 0.30 0.22 1 .25 1 .37 0.06 0.04 46.0 1 .30 1 .34 0.33 0.26 1 .20 1.33 0.08 0.05 50.0 1 .22 1 .25 0.34 0.31 1 .15 1.28 0.08 0.07 54.0 1.14 1 .16 0.36 0.36 1 .00 1 .24 0.08 0.08 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 0.01 4.0 0.02 0.02 0. 00 0.00 0.00 0.00 0.02 0.05 6.0 0.04 0.03 0. 00 0.01 0.00 0.00 0.06 0.12 8.0 0.06 0.05 0. 00 0.01 0.02 0.01 0.12 0.23 12.0 0.11 0.10 0. 02 0.03 0.04 0.03 0.30 0.47 20.0 0.20 0.20 0. 08 0.05 0.10 0.13 0.60 0.83 24.0 0.30 0.26 0. 08 0.05 0.15 0.19 0.70 0.92 28.0 0.34 0.32 0. 08 0.06 0.25 0.24 0.75 0.96 32.0 0.46 0.39 0. 08 0.06 0.30 0.28 0.78 0.96 40.0 0.62 0.55 0. 10 0.07 0.35 0.33 0.70 0.90 42.0 0.68 0.59 0. 10 0.07 0.36 0.34 0.65 0.87 46.0 0.75 0.67 0. 10 0.07 0.40 0.35 0.62 0.82 50.0 0.90 0.76 0. 10 0.07 0.45 0.36 0.56 0.76 54.0 1 .00 0.84 0. 10 0.07 0.50 0.36 0.50 0.70 375 TABLE D . 5 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION • 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 4.0 4.10 4.09 0.00 0.00 0.15 0.18 0.00 0.00 6.0 4.00 3.99 0.00 0.00 0.22 0.26 0.00 0.00 10.0 3.80 3.82 0.00 0.00 0.40 0.42 0.00 0.00 18.0 3.52 3.50 0.00 0.00 0.65 0.68 0.00 0.00 24.0 3.30 3.29 0.01 0.00 0.72 0.83 0.00 0.00 30.0 3.03 3.09 0.02 0.01 0.75 0.95 0.00 0.00 34.0 2.92 2.97 0.02 0.01 0.80 1.01 0.00 0.00 44.0 2.65 2.70 0.06 0.03 0.86 1.11 0.01 0.00 48.0 2.50 2.61 0.07 0.03 0.90 1.14 0.01 0.00 54.0 2.45 2.47 0.08 0.05 0.92 1 .17 0.01 0.00 58.0 2.35 2.39 0.09 0.06 0.95 1.18 0.01 0.00 64.0 2.20 2.27 0.10 0.07 0.96 1.18 0.02 0.01 72.0 2.10 2.12 0.10 0.10 0.90 1.18 0.02 0.01 100.0 1 .65 1 .71 0.24 0.23 0.80 1.10 0.05 0.04 120.0 1.41 1 .49 0.30 0.34 0.76 1.02 0.09 0.07 TIME CONCENTRATION ( m o l / L ) (h) : EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0 .00 0 .00 0.00 0.00 0.00 0.00 0. 00 4.0 0.00 0 .00 0 .00 0.00 0.00 0.00 0.00 0. 00 6.0 0.02 0 .01 0 .00 0.00 0.00 0.00 0.02 0. 01 10.0 0.05 0 .02 0 .00 0.00 0.00 0.00 0.05 0. 04 18.0 0.10 0 .05 0 .00 0.01 0.00 0.01 0.10 0. 15 24.0 0.14 0 .08 0 .01 0.02 0.02 0.02 0.20 0. 26 30.0 0.15 0 . 1 1 0 .02 0.03 0.06 0.04 0.30 0. 38 34\ 0 0.18 0 .13 0 .02 0.03 0.10 0.06 ,0.35 0. 45 44.0 0.27 0 .19 0 .05 0.04 0.12 0.12 0.42 0. 59 48.0 0.32 0 .22 0 .05 0.04 0.16 0.15 0.46 0. 63 54.0 0.38 0 .26 0 .06 0.05 0.20 0.18 0.50 0. 67 58.0 0.45 0 .29 0 .06 0.05 0.22 0.21 0.45 0. 69 64.0 0.55 0 .33 0 .07 0.05 0.30 0.24 0.42 0. 71 72.0 0.60 0 .40 0 .07 0.06 0.32 0.27 0.40 0. 71 100.0 1 .00 0 .65 0 .06 0.06 0.45 0.34 0.26 0. 61 120.0 1.20 0 .85 0 .06 0.07 0.55 0.36 0.20 0. 51 376 TABLE D . 6 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP • 160 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 4 .28 4.28 0.00 0 .00 0.00 0.00 0.00 0.00 24. 0 4 .00 3.92 0.00 0 .00 0.22 0.30 0.00 0.00 48. 0 3 .71 3.61 0.00 0 .00 0.42 0.54 0.00 0.00 72. 0 3 .25 3.34 0.00 0 .01 0.60 0.70 0.00 0.00 96. 0 3 .00 3 .09 0.00 0 .01 0.65 0.81 0.00 0.00 120. 0 2 .85 2.87 0.01 0 .03 0.69 0.87 0.00 0.00 144. 0 2 .64 2.68 0.02 0 .05 0.64 0.90 0.01 0.00 168. 0 2 .48 2.50 0.05 0 .07 0.60 0.91 0.01 0.01 192. 0 2 .32 2.35 0.07 0 . 11 0.52 0.90 0.01 0.01 216. 0 2 .15 2.20 0.11 0 .15 0.50 0.88 0.02 0.02 240. 0 2 .00 2.07 0.15 0 .20 0.46 0.86 0.05 0.03 264. 0 1 .90 1 .95 0.18 0 .24 0.44 0.83 0.06 0.04 288. 0 1 .80 1 .85 0.20 0 .29 0.41 0.81 0.08 0.05 312. 0 1 .72 1 .75 0.22 0 .35 0.39 0.78 0.09 0.06 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 0.00 0.00 0.00 0.00 0. 00 0.00 0.00 0. 00 24. 0 0.02 0.01 0.00 0.00 0. 00 0.00 0.02 0. 02 48. 0 0.08 0.05 0.00 0.01 0. 00 0.01 0.10 0. 1 1 72. 0 0.17 0.10 0.01 0.02 0. 03 0.03 0.18 0. 24 96 . 0 0.29 0.16 0.01 0.03 0. 08 0.08 0.22 0. 35 120. 0 0.44 0.22 0.02 0.04 0. 18 0.14 0.25 0. 43 144. 0 0.55 0.29 0.05 0.04 0. 25 0.19 0.28 0. 47 168. 0 0.76 0.36 0.06 0.05 0. 35 0.24 0.33 0. 48 192. 0 0.88 0.44 0.07 0.05 0. 42 0.28 0.29 0. 47 216. 0 0.93 0.53 0.08 0.05 0. 46 0.31 0.26 0. 44 240. 0 1 .06 0.62 0.08 0.06 0. 45 0.32 0.23 0. 41 264. 0 1.15 0.72 0.08 0.06 0. 43 0.34 0.20 0. 37 288. 0 1 .24 0.81 0.08 0.06 0. 42 0.34 0.18 0. 33 312. 0 1 .36 0.91 0.09 0.06 0. 42 0.35 0.18 0. 30 377 TABLE D . 7 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 140 C . TIME CONCENTRATION ( m o l / L ) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4.28 0.00 0.00 0.00 0. 00 0.00 0.00 24.0 4. 22 4.17 0.00 0.00 0.05 0. 08 0.00 0.00 48.0 4. 14 4.07 0.00 0.00 0.12 0. 16 0.00 0.00 72.0 4. 10 3.98 0.00 0.00 0.18 0. 23 0.00 0.00 96.0 3 . 86 3.88 0.00 0.00 0.23 0. 30 0.00 0.00 120.0 3 . 75 3.79 0.00 0.00 0.29 0. 36 0.00 0.00 144.0 3 . 68 3.70 0.00 0.00 0.33 0. 41 0.00 0.00 168.0 3 . 58 3.62 0.00 0.00 0.35 0. 46 0.00 0.00 192.0 3 . 50 3.54 0.00 0.00 0.38 0. 50 0.00 0.00 216.0 3 . 42 3.46 0.00 0.01 0.38 0. 53 0.00 0.00 240.0 3 . 37 3.38 0.01 0.01 0.34 0. 56 0.00 0.00 264.0 3 . 26 3.31 0.01 0.01 0.33 0. 58 0.00 0.00 288.0 3 . 20 3.24 0.01 0.02 0.33 0. 60 0.00 0.00 312.0 3 . 15 3.17 0.01 0.02 0.32 0. 62 0.00 0.00 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0. 00 0.00 0.00 0.00 0. 00 0. 00 0. 00 24.0 0. 00 0. 00 0.00 0.00 0.00 0. 00 0. 02 0. 00 48.0 0. 01 0. 01 0.00 0.00 0.00 0. 00 0. 00 0. 01 72.0 0. 03 0. 02 0.00 0.00 0.00 0. 00 0. 01 0. 02 96.0 0. 05 0. 03 0.00 0.01 0.00 0. 00 0. 03 0. 03 120.0 0. 06 0. 04 0.00 0.01 0.02 0. 00 0. 05 0. 05 144.0 0. 08 0. 06 0.01 0.01 0.05 0. 01 0. 07 0. 08 168.0 0. 12 0. 07 0.01 0.01 0.08 0. 02 0. 09 0. 1 1 192.0 0. 18 0. 09 0.02 0.02 0.10 0. 03 0. 13 0. 14 216.0 0. 21 0. 11 0.02 0.02 0.14 0. 04 0. 18 0. 16 240.0 0. 33 0. 13 0.03 0.02 0.15 0. 05 0. 22 0. 19 264.0 0. 25 0. 15 0.04 0.03 0.18 0. 07 0. 20 0. 21 288.0 0. 27 0. 17 0 .05 0.03 0.20 0. 09 0. 19 0. 23 312.0 0. 29 0. 19 0.05 0.03 0.20 0. 11 0. 18 0. 25 378 TABLE D .8 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 120 C . TIME CONCENTRATION (mol /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4. 28 0.00 0.00 0. 00 0.00 0.00 0.00 24.0 4. 27 4. 25 0.00 0.00 0. 01 0.02 0.00 0.00 48.0 4. 25 4. 23 0.00 0.00 0. 02 0.03 0.00 0.00 72.0 4. 21 4. 20 0.00 0.00 0. 04 0.05 0.00 0.00 96.0 4. 17 4. 18 0.00 0.00 0. 06 0.07 0.00 0.00 120.0 4. 15 4. 15 0.00 0.00 0. 09 0.08 0.00 0.00 144.0 4. 13 4. 12 0.00 0.00 0. 10 0.10 0.00 0.00 168.0 4. 08 4. 10 0.00 0.00 0. 12 0.1 1 0.00 0.00 192.0 4. 06 4. 07 0.00 0.00 0. 14 0.13 0.00 0.00 216.0 4. 05 4. 05 0.00 0.00 0. 16 0.14 0.00 0.00 240.0 4. 03 4. 03 0.00 0.00 0. 15 0.16 0.00 0.00 264.0 4. 01 4. 00 0.01 0.00 0. 15 0.17 0.00 0.00 288.0 4. 00 3 . 98 0.01 0.00 0. 14 0.19 0.00 0.00 312.0 3. 94 3. 95 0.01 0.00 0. 13 0.20 0.00 0.00 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 24.0 0. 00 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 48.0 0. 00 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 72.0 0. 00 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 96.0 0. 01 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 120.0 0. 01 0 .00 0.00 0. 00 0.00 0. 00 0.00 0. 00 144.0 0. 01 0 .01 0.00 0. 00 0.00 0. 00 0.00 0. 00 168.0 0. 01 0 .01 0.00 0. 00 0.00 0. 00 0.00 0. 00 192.0 0. 02 0 .01 0.00 0. 00 0.00 0. 00 0.00 0. 01 216.0 0. 02 0 .01 0.00 0. 00 0.00 0. 00 0.01 0. 01 240.0 0. 04 0 .02 0.00 0. 00 0.01 0. 00 0.01 0. 01 264.0 0. 05 0 .02 0.00 0. 00 0.02 0. 00 0.01 0. 01 288.0 0. 06 0 .02 0.00 0. 00 0.02 0. 00 0.01 0. 01 312.0 0. 06 0 .03 0.00 0. 00 0.02 0. 00 0.02 0. 01 379 TABLE D . 9 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 100 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 24.0 4.28 4.27 0.00 0.00 0.00 0.00 48.0 4.28 4.27 0.00 0.00 0.00 0.01 72.0 4.27 4.26 0.00 0.00 0.00 0.01 96.0 4.27 4.26 0.00 0.00 0.01 0.01 120.0 4.27 4.27 0.00 0.00 0.01 0.01 144.0 4.26 4.25 0.00 0.00 0.01 0.01 168.0 4.26 4.24 0.00 0.00 0.01 0.02 192.0 4.26 4.24 0.00 0.00 0.02 0.02 216.0 4.26 4.23 0.00 0.00 0.02 0.02 240.0 4.24 4.23 0.00 0.00 0.02 0.02 264.0 4.24 4.23 0.00 0.00 0.02 0.03 288.0 4.23 4.21 0.00 0.00 0.03 0.03 312.0 4.22 4.21 0.00 0.00 0.03 0.03 TIME CONCENTRATION ( m o l / L ) (h) : EG HMP TEA EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 24.0 0.00 0.00 0.00 0.00 0.00 0.00 48.0 0.00 0.00 0.00 0.00 0.00 0.00 72.0 0.00 0.00 0.00 0.00 0.00 0.00 96.0 0.00 0.00 0.00 0.00 0.00 0.00 120.0 0.00 0.00 0.00 0.00 0.00 0.00 144.0 0.00 0.00 0.00 0.00 0.00 0.00 168.0 0.00 0.00 0.00 0.00 0.00 0.00 192.0 0.01 0.00 0.00 0.00 0.00 0.00 216.0 0.01 0.00 0.00 0.00 0.00 0.00 240.0 0.01 0.00 0.00 0.00 0.00 0.00 264.0 0.01 0.00 0.00 0.00 0.00 0.00 288.0 0.01 0.00 0.00 0.00 0.00 0.00 312.0 0.01 0.00 0.00 0.00 0.00 0.00 380 TABLE D.10 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 230 C . TIME CONCENTRATION (mol/D (h) ~ MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3 . 40 3.40 0.00 0.00 0 .00 0.00 0. 00 0.00 2.0 2. 60 2.48 0.02 0.03 0 .80 0.88 0. 00 0.00 4.0 2. 00 1 .89 0.08 0.02 1 .25 1 .36 0. 00 0.00 8.0 1 . 25 1.19 0.30 0.06 1 .62 1 .68 0. 00 0.00 10.0 1 . 10 0.98 0.40 0.10 1 .70 1 .66 0. 00 0.01 18.0 0. 56 0.52 0.60 0.25 1 .75 1 .39 0. 02 0.05 20.0 0. 50 0.45 0.64 0.28 1 .50 1 .31 0. 05 0.08 24.0 0. 38 0.35 0.71 0.36 1 .35 1.17 0. 08 0.13 28.0 0. 32 0.29 0.75 0.43 1 .30 1 .05 0. 12 0.17 36.0 0. 21 0.20 0.84 0.56 1 .00 0.86 0. 18 0.25 40.0 0. 19 0.17 0.87 0.62 0 .95 0.79 0. 22 0.29 44.0 0. 15 0.14 0.90 0.68 0 .90 0.72 0. 26 0.33 52.0 0. 10 0.1 1 1 .00 0.76 0 .84 0.62 0. 30 0.40 54.0 0. 09 0.10 1 .05 0.78 0 .75 0.60 0. 30 0.42 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0 .00 0.00 0. 00 0. 00 0.00 0.00 0. 00 0.00 2.0 0 .01 0.03 0. 00 0. 01 0.00 0.00 0. 04 0.18 4.0 0 .04 0.09 0. 01 0. 03 0.02 0.03 0. 20 0.60 6.0 0 .10 0.22 0. 03 0. 06 0.05 0.14 0. 70 1 .09 10.0 0 .15 0.29 0. 05 0. 06 0.10 0.20 0. 90 1.14 18.0 0 .35 0.64 0. 05 0. 07 0.26 0.28 0. 95 0.85 20.0 0 .40 0.74 0. 05 0. 07 0.30 0.28 1 . 00 0.76 24.0 0 .50 0.93 0. 06 0. 08 0.35 0.29 0. 90 0.59 28.0 0 .65 1.11 0. 07 0. 08 0.40 0.30 0. 75 0.45 36.0 0 .85 1.41 0. 08 0. 08 0.52 0.34 0. 40 0.26 40.0 0 .96 1 .53 0. 10 0. 08 0.58 0.36 0. 30 0.20 44.0 1 .05 1 .64 0. 10 0. 08 0.62 0.39 0. 20 0.15 52.0 1 .25 1 .80 0. 10 0. 08 0.72 0.43 0. 12 0.08 54.0 1 .30 1 .83 0. 10 0. 08 0.74 0.44 0. 10 0.07 381 TABLE D.11 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.4 MOL/L, C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 220 C. TIME CONCENTRATION ( m o l / D (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 3 .40 3. 40 2. 0 2 .84 2. 77 4. 0 2 .35 2. 29 6. 0 2 .00 1 . 93 8. 0 1 .70 1 . 65 16. 0 1 .00 0. 97 20. 0 0 .80 0. 78 24. 0 0 .65 0. 64 32. 0 0 .45 0. 45 34. 0 0 .40 0. 42 38. 0 0 .35 0. 36 42. 0 0 .30 0. 31 50. 0 0 .25 0. 24 52. 0 0 .23 0. 23 54. 0 0 .21 0. 22 0. 00 0. 00 0 .00 0. 00 0. 00 0 .50 0. 02 0. 01 0 .90 0. 08 0. 01 1 .35 0. 12 0. 03 1 .50 0. 30 0. 12 1 .60 0. 40 0. 17 1 .70 0. 50 0. 23 1 .65 0. 60 0. 35 1 .45 0. 62 0. 38 1 .30 0. 65 0. 44 1 .20 0. 68 0. 49 1 .10 0. 73 0. 59 1 .00 0. 75 0. 61 0 .90 0. 75 0. 64 0 .85 0 .00 0. 00 0. 00 0 .61 0. 00 0. 00 1 .02 0. 00 0. 00 1 .29 0. 00 0. 00 1 .45 0. 00 0. 00 1 .53 0. 00 0. 01 1 .44 0. 02 0. 03 1 .34 0. 03 0. 05 1 .14 0. 06 0. 11 1 .09 0. 09 0. 13 1 .01 0. 12 0. 1 6 0 .94 0. 1 5 0. 19 0 .81 0. 18 0. 24 0 .79 0. 19 0. 26 0 .76 0. 22 0. 27 TIME CONCENTRATION (mol/L) (h) ~~ EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.02 0.00 0.01 0.00 0.00 0.02 0.07 4.0 0.05 0.05 0.01 0.02 0.00 0.01 0.18 0.31 6.0 0.08 0.10 0.01 0.03 0.01 0.03 0.30 0.58 8.0 0.10 0.14 0.02 0.04 0.02 0.07 0.50 0.79 16.0 0.30 0.36 0.04 0.06 0.10 0.24 0.75 1 .03 20.0 0.35 0.48 0.05 0.07 0.20 0.27 0.78 0.94 24.0 0.42 0.62 0.06 0.07 0.30 0.29 0.80 0.81 32.0 0.64 0.90 0.08 0.07 0.43 0.30 0.55 0 .57' 34.0 0.70 0.97 0.08 0.07 0.45 0.30 0.50 0.52 38.0 0.75 1.10 0.10 0.08 0.48 0.31 0.45 0.43 42.0 0.88 1 .22 0.10 0.08 0.50 0.32 0.36 0.35 50.0 1 .00 1 .44 0.10 0.08 0.60 0.35 0.25 0.23 52.0 1.15 1 .49 0.10 0.08 0.62 0.36 0.22 0.21 54.0 1 .20 1 .53 0.10 0.08 0.64 0.37 0.20 0.19 382 TABLE D.12 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 210 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3.40 3.40 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 3.10 2.98 0.00 0.00 0 .30 0.40 0.00 0.00 4.0 2 .75 2.64 0.00 0.00 0 .60 0.71 0.00 0.00 6.0 2.40 2.35 0.02 0.00 0 .90 0.96 0.00 0.00 8.0 2.15 2.11 0.05 0.01 1 .10 1.14 0.00 0.00 18.0 1 .35 1 .32 0.15 0.07 1 .50 1 .44 0.00 0.00 20.0 1 .20 1.21 0.18 0.08 1 .55 1 .44 0.00 0.01 24.0 1 .00 1 .04 0.24 0.12 1 .50 1 .40 0.01 0.02 28.0 0.92 0.90 0.28 0.17 1 .40 1 .35 0.03 0.03 36.0 0.71 0.69 0.35 0.26 1 .25 1 .22 0.05 0.06 40.0 0.60 0.62 0.40 0.30 1 .15 1.15 0.06 0.08 44.0 0.55 0.55 0.45 0.35 1 .10 1 .09 0.08 0.10 52.0 0.46 0.45 0.50 0.44 1 .00 0.97 0.13 0.12 54.0 0.40 0.43 0.52 0.46 0 .94 0.95 0.15 0.15 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 2.0 0.00 0.01 0.00 0.00 0.00 0.00 0. 00 0.02 4.0 0.02 0.03 0.00 0.01 0.00 0.00 0. 05 0.13 6.0 0.05 0.06 0.01 0.02 0.00 0.01 0. 15 0.29 8.0 0.10 0.09 0.01 0.03 0.01 0.03 0. 20 0.46 18.0 0.26 0.12 0.03 0.03 0.15 0.18 0. 80 0.61 20.0 0.30 0.30 0.04 0.06 0.20 0.21 0. 84 0.94 24.0 0.36 0.39 0.05 0.06 0.25 0.25 0. 80 0.92 28.0 0.45 0.48 0.06 0.07 0.30 0.28 0. 75 0.85 36.0 0.60 0.68 0.08 0.07 0.40 0.30 0. 62 0.69 40.0 0.70 0.78 0.09 0.07 0.44 0.30 0. 55 0.61 44.0 0.80 0.89 0.08 0.07 0.50 0.31 0. 48 0.54 52.0 1 .02 1.08 0.08 0.07 0.58 0.32 0. 35 0.41 54.0 1 .05 1.13 0.08 0.07 0.60 0.32 0. 32 0.38 3 8 3 TABLE D.13 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION « 3.4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3.40 3.40 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 3.10 3.00 0.00 0.00 0 .15 0.25 0.00 0.00 4.0 3.00 2.91 0.00 0.00 0 .50 0.47 0.00 0.00 6.0 2.80 2.70 0.00 0.00 0 .70 0.65 0.00 0.00 8.0 2.55 2.51 0.02 0.00 0 .85 0.81 0.00 0.00 10.0 2.38 2.34 0.02 0.01 1 .00 0.94 0.00 0.00 20.0 1 .75 1 .71 0.08 0.03 1 .30 1 .28 0.01 0.00 24.0 1 .55 1 .53 0.10 0.05 1 .35 1 .32 0.01 0.00 28.0 1 .40 1 .38 0.14 0.07 1 .28 1 .32 0.01 0.01 30.0 1 .30 1 .31 0.15 0.08 1 .25 1 .32 0.01 0.01 38.0 1.10 1 .08 0.25 0.14 1 .20 1 .27 0.02 0.02 42.0 1 .00 0.99 0.28 0.17 1 .15 1 .23 0.04 0.03 44.0 0.94 0.95 0.30 0.19 1 .10 1.21 0.05 0.03 52.0 0.79 0.80 0.34 0.26 1 .00 1.13" 0.08 0.06 54.0 0.75 0.77 0.35 0.27 0 .96 1.11 0.09 0.06 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 0.00 0. 00 0.00 0.00 0. 00 0.00 0.00 0.00 2. 0 0.00 0. 00 0.00 0.00 0. 00 0.00 0.00 0.01 4. 0 0.00 0. 01 0.00 0.00 0. 00 0.00 0.02 0.04 6. 0 0.02 0. 03 0.00 0.01 0. 00 0.00 0.05 0.11 8. 0 0.05 0. 05 0.00 0.01 0. 00 0.01 0.10 0.20 10. 0 0.06 0. 07 0.01 0.02 0. 02 0.01 0.20 0.31 20. 0 0.18 0. 18 0.05 0.04 0. 10 0.11 0.50 0.72 24. 0 0.25 0. 24 0.06 0.05 0. 15 0.16 0.60 0.80 28. 0 0.30 0. 33 0.08 0.05 0. 18 0.20 0.65 0.83 30. 0 0.36 0. 32 0.08 0.06 0. 20 0.22 0.70 0.83 38. 0 0.50 0. 45 0.10 0.06 0. 30 0.27 0.65 0.79 42. 0 0.60 0. 51 0.09 0.06 0. 35 0.29 0.60 0.74 44. 0 0.64 0. 55 0.09 0.07 0. 38 0.29 0.51 0.72 52. 0 0.75 0. 69 0.08 0.07 0. 40 0.31 0.40 0.61 54. 0 0.80 0. 73 0.08 0.07 0. 44 0.31 0.38 0.59 384 TABLE D.14 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP - 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3.40 3 .40 0.00 0.00 0.00 0. 00 0.00 0.00 2.0 3 .35 3 .31 0.00 0.00 0.10 0. 09 0.00 0.00 4.0 3 .25 3 .22 0.00 0.00 0.15 0. 17 0.00 0.00 6.0 3 .15 3 .13 0.00 0.00 0.20 0. 25 0.00 0.00 8.0 3 .05 3 .05 0.00 0.00 0.28 0. 33 0.00 0.00 16.0 2.80 2 .75 0.00 0.00 0.60 0. 58 0.00 0.00 20.0 2.60 2 .61 0.00 0.00 0.70 0. 69 0.00 0.00 24.0 2.50 2 .49 0.00 0.00 0.80 0. 77 0.00 0.00 32.0 2.25 2 .27 0.02 0.01 0.88 0. 91 0.00 0.00 34.0 2.20 2 .21 0.02 0.01 0.90 0. 94 0.00 0.00 38.0 2.10 2 .12 0.02 0.01 0.90 0. 98 0.00 0.00 42.0 2.00 2 .03 0.03 0.02 0.85 1 . 01 0.01 0.00 50.0 1 .90 1 .86 0.05 0.03 0.80 1 . 06 0.01 0.00 52.0 1 .80 1 .82 0.06 0.04 0.78 1 . 07 0.01 0.00 54.0 1 .75 1 .79 0.07 0.04 0.75 1. 07 0.01 0.00 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 2.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 4.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 6.0 0. 00 0.01 0.00 0. 00 0.00 0. 00 0.00 0. 01 8.0 0. 02 0.01 0.00 0. 00 0.00 0. 00 0.01 0. 02 16.0 0. 05 0.04 0.00 0. 01 0.00 0. 00 0.08 0. 11 20.0 0. 10 0.05 0.00 0. 01 0.00 0. 01 0.15 0. 17 24.0 0. 12 0.07 0.01 0. 02 0.02 0. 02 0.20 0. 24 32.0 0. 20 0.11 0.05 0. 03 0.05 0. 04 0.30 0. 37 34.0 0. 22 0.12 0.05 0. 03 0.06 0. 05 0.35 0. 40 38.0 0. 24 0.15 0.06 0. 03 0.08 0. 07 0.40 0. 46 42.0 0. 26 0.17 0.07 0. 04 0.10 0. 09 0.42 0. 50 50.0 0. 40 0.21 0.07 0. 04 0.14 0. 14 0.45 0. 57 52.0 0. 42 0.23 0.06 0. 04 0.16 0. 15 0.42 0. 59 54.0 0. 44 0.24 0.06 0. 04 0.18 0. 16 0.40 0. 60 385 TABLE D.15 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3 . 4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 160 C . TIME CONCENTRATION (mol /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 3. 40 3. 40 2. 0 3 . 38 3. 37 6. 0 3. 30 3. 31 10. 0 3. 25 3. 25 18. 0 3. 15 3. 1 4 20. 0 3. 1 3 3. 12 24. 0 3. 05 3. 06 28. 0 3. 00 3. 01 38. 0 2. 90 2. 89 42. 0 2. 85 2. 84 44. 0 2. 80 2. 82 52. 0 2. 75 2. 73 54. 0 2. 70 2. 71 0. 00 0. 00 0. 00 0. 00 0. 00 0. 02 0. 00 0. 00 0. 05 0. 00 0. 00 0. 10 0. 00 0. 00 0. 20 0. 00 0. 00 0. 25 0. 00 0. 00 0. 30 0. 00 0. 00 0. 35 0. 00 0. 00 0. 45 0. 00 0. 00 0. 48 0. 00 0. 00 0. 50 0. 00 0. 00 0. 45 0. 00 0. 00 0. 44 0. 00 0. 00 0 .00 0. 03 0. 00 0 .00 0. 08 0. 00 0 .00 0. 13 0. 00 0 .00 0. 22 0. 00 0 .00 0. 25 0. 00 0 .00 0. 29 0. 00 0 .00 0. 33 0. 00 0 .00 0. 43 0. 00 0 .00 0. 47 0. 00 0 .00 0. 48 0. 00 0 .00 0. 55 0. 00 0 .00 0. 56 0. 00 0 .00 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 2.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 6.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 10.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 18.0 0. 00 0.01 0.00 0.00 0.00 0.00 0. 00 0.01 20.0 0. 02 0.01 0.00 0.00 0.00 0.00 0. 00 0.01 24.0 0. 05 0.01 0.00 0.00 0.00 0.00 0. 02 0.02 28.0 0. 06 0.02 0.00 0.00 0.00 0.00 0. 04 0.03 38.0 0. 10 0.03 0.00 0.01 0.00 0.00 0. 10 0.06 42.0 0. 12 0.04 0.00 0.01 0.00 0.00 0. 12 0.08 44.0 0. 1 4 0.04 0.00 0.01 0.00 0.01 0. 14 0.09 52.0 0. 18 0.06 0.00 0.01 0.01 0.01 0. 18 0.12 54.0 0. 20 0.06 0.01 0.01 0.01 0.01 0. 18 0.13 386 TABLE D.16 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.4 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 140 C . TIME CONCENTRATION ( m o l / L ) (h) " : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3 . 40 3.40 0. 00 0.00 0. 00 0. 00 0.00 0.00 2.0 3 . 40 3.39 0. 00 0.00 0. 00 0. 01 0.00 0.00 6.0 3 . 38 3.37 0. 00 0.00 0. 02 0. 02 0.00 0.00 10.0 3 . 37 3.36 0. 00 0.00 0. 02 0. 03 0.00 0.00 18.0 3 . 34 3.32 0. 00 0.00 0. 05 0. 06 0.00 0.00 20.0 3 . 32 3.32 0. 00 0.00 0. 06 0. 07 0.00 0.00 24.0 3. 30 3.30 0. 00 0.00 0. 08 0. 08 0.00 0.00 28.0 3 . 27 3.28 0. 00 0.00 0. 10 0. 10 0.00 0.00 38.0 3 . 25 3.24 0. 00 0.00 0. 15 0. 13 0.00 0.00 42.0 3 . 22 3.23 0. 00 0.00 0. 16 0. 14 0.00 0.00 44.0 3 . 20 3.22 0. 00 0.00 0. 17 0. 15 0.00 0.00 52.0 3 . 18 3.19 0. 00 0.00 0. 19 0. 17 0.00 0.00 54.0 3 . 15 3.18 0. 00 0.00 0. 20 0. 18 0.00 • 0.00 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 2.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 6.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 10.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 18.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 20.0 0. 00 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 24.0 0. 01 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 28.0 0. 01 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 38.0 0. 01 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 42.0 0. 02 0.01 0.00 0.00 0.00 0.00 0. 00 0.00 44.0 0. 02 0.01 0.00 0.00 0.00 0.00 0. 01 0.00 52.0 0. 02 0.01 0.00 0.00 0.00 0.00 0. 01 0.01 54.0 0. 02 0.01 0.00 0.00 0.00 0.00 0. 01 0.01 387 TABLE D.17 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2 . 0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 230 C . TIME CONCENTRATION ( m o l / L ) (h) " MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 2.00 2 .00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 1 .80 1 .73 0.00 0.00 0.20 0.26 0.00 0.00 4.0 1.55 1 .51 0.00 0.00 0.40 0.45 0.00 0.00 6.0 1 .38 1 .33 0.02 0.01 0.60 0.60 0.00 0.00 8.0 1 .25 1 .18 0.05 0.02 0.78 0.71 0.00 0.00 10.0 1.15 1 .06 0.07 0.03 0.85 0.79 0.00 0.00 20.0 0.65 0 .65 0.15 0.09 1 .05 0.88 0.00 0.01 24.0 0.55 0 .55 0.23 0.12 1.15 0.86 0.00 0.01 28.0 0.50 0 .47 0.27 0.14 0.95 0.82 0.01 0.02 36.0 0.35 0 .36 0.32 0.18 0.85 0.74 0.02 0.04 40.0 0.30 0 .32 0.36 0.20 0.80 0.70 0.03 0.05 42.0 0.28 0 .30 0.38 0.21 0.76 0.68 0.04 0.06 50.0 0.24 0 .24 0.42 0.25 0.72 0.61 0.06 0.09 54.0 0.21 0 .22 0.44 0.27 0.70 0.58 0.08 0.10 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0 .00 0.00 0. 00 0. 00 0.00 2.0 0.00 0.01 0.00 0 .00 0.00 0. 00 0. 00 0.02 4.0 0.01 0.03 0.00 0 .01 0.00 0. 00 0. 02 0.09 6.0 0.02 0.06 0.01 0 .02 0.00 0. 01 0. 05 0.18 8.0 0.05 0.09 0.01 0 .03 0.00 0. 01 0. 10 0.27 10.0 0.06 0.12 0.02 0 .04 0.00 0. 03 0. 16 0.34 20.0 0.22 0.29 0.03 0 .06 0.05 0. 11 0. 40 0.40 24.0 0.26 0.37 0.04 0 .07 0.10 0. 14 0. 35 0.35 28.0 0.32 0.45 0.05 0 .07 0.15 0. 15 0. 30 0.30 36.0 0.45 0.61 0.06 0 .08 0.20 0. 17 0. 20 0.20 40.0 0.50 0.69 0.06 0 .08 0.22 0. 17 0. 18 0.16 42.0 0.55 0.73 0.05 0 .08 0.23 0. 18 0. 16 0.15 50.0 0.65 0.88 0.06 0 .08 0.25 0. 19 0. 10 0.09 54.0 0.68 0.95 0.06 0 .08 0.26 0. 19 0. 08 0.08 388 TABLE D.18 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 220 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 2.00 2.00 0.00 0. 00 0.00 0.00 0.00 0. 00 2.0 1 .85 1 .82 0.00 0. 00 0.15 0.16 0.00 0. 00 4.0 1 .70 1 .67 0.00 0. 00 0.30 0.30 0.00 0. 00 6.0 1 .55 1 .54 0.00 0. 00 0.45 0.42 0.00 0. 00 8.0 1 .40 1.42 0.02 0. 01 0.60 0.52 0.00 0. 00 16.0 1 .00 1 .06 0.05 0. 04 0.80 0.75 0.00 0. 00 18.0 0.95 0.99 0.08 0. 04 0.85 0.77 0.00 0. 00 22.0 0.85 0.87 0.1 1 0. 06 0.90 0.81 0.00 0. 00 26.0 0.75 0.77 0.16 0. 08 0.82 0.81 0.00 0. 00 36.0 0.60 0.59 0.25 0. 12 0.80 0.78 0.00 0. 01 40.0 0.55 0.54 0.29 0. 14 0.76 0.76 0.01 0. 02 42.0 0.50 0.51 0.30 0. 14 0.74 0.75 0.01 0. 02 50.0 0.40 0.43 0.35 0. 18 0.70 0.69 0.02 0. 04 54.0 0.36 0.39 0.36 0. 19 0.66 0.67 0.02 0. 04 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 2.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 01 4.0 0. 00 0.02 0.00 0. 01 0.00 0. 00 0.00 0. 03 6.0 0. 02 0.03 0.01 0. 01 0.00 0. 00 0.02 0. 08 8.0 0. 05 0.05 0.01 0. 02 0.00 0. 00 0.05 0. 14 16.0 0. 10 0.14 0.02 0. 04 0.02 0. 04 0.25 0. 32 18.0 0. 1 2 0.16 0.03 0. 04 0.03 0. 05 0.27 0. 34 22.0 0. 18 0.21 0.05 0. 05 0.04 0. 08 0.30 0. 36 26.0 0. 25 0.26 0.05 0. 06 0.08 0. 10 0.32 0. 36 36.0 0. 35" 0.40 0.08 0. 07 0.13 0. 15 0.35 0. 29 40.0 0. 38 0.46 0.08 0. 07 0.16 0. 16 0.20 0. 26 42.0 0. 40 0.49 0.08 0. 07 0.17 0. 16 0.18 0. 24 50.0 0. 50 0.60 0.07 0. 07 0.18 0. 17 0.15 0. 18 54.0 0. 52 0.66 0.07 0. 07 0.18 0. 18 0.13 0. 16 389 TABLE D.19 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 210 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 2.00 2.00 0. 00 0. 00 0.00 0. 00 0.00 0.00 2.0 1 .92 1 .89 0. 00 0. 00 0.08 0. 10 0.00 0.00 4.0 1 .80 1 .79 0. 00 0. 00 0.06 0. 19 0.00 0.00 6.0 1 .70 1 .70 0. 00 0. 00 0.25 0. 28 0.00 0.00 8.0 1 .60 1 .61 0. 02 0. 00 0.35 0. 35 0.00 0.00 18.0 1 .25 1 .26 0. 04 0. 02 0.65 0. 60 0.00 0.00 22.0 1.15 1.16 0. 07 0. 03 0.70 0. 66 0.00 0.00 24 .0 1.10 1.11 0. 08 0. 03 0.72 0. 68 0.00 0.00 34 .0 0.90 0.91 0. 12 0. 06 0.70 0. 74 0.00 0.00 38.0 0.80 0.84 0. 15 0. 07 0.70 0. 74 0.00 0.00 40 .0 0.78 0.81 0. 16 0. 08 0.68 0. 74 0.01 0.00 48.0 0.68 0.71 0. 19 0. 10 0.65 0. 73 0.01 0.01 50.0 0.65 0.68 0. 20 0. 1 1 0.63 0. 72 0.01 0.01 54.0 0.62 0.64 0. 22 0. 12 0.62 0. 71 0.01 0.01 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0. 00 0. 00 0.00 0.00 2.0 0.00 0.00 0. 00 0.00 0. 00 0. 00 0.00 0.00 4.0 0.00 0.01 0. 00 0.00 0. 00 0. 00 0.00 0.01 6.0 0.00 0.02 0. 00 0.01 0. 00 0. 00 0.00 0.03 8.0 0.01 0.03 0. 00 0.01 0. 00 0. 00 0.02 0.05 18.0 0.05 0.10 0. 01 0.03 0. 00 0. 02 0.10 0.21 22.0 0.06 0.13 0. 02 0.04 0. 02 0. 03 0.16 0.26 24.0 0.08 0.15 0. 03 0.04 0. 03 0. 04 0.21 0.28 34.0 0.12 0.23 0. 06 0.05 0. 08 0. 08 0.25 0.31 38.0 0.14 0.27 0. 07 0.06 0. 10 0. 10 0.28 0.31 40.0 0.15 0.28 0. 07 0.06 0. 12 0. 11 0.30 0.30 48.0 0.28 0.36 0. 08 0.06 0. 15 0. 14 0.26 0.27 50.0 0.30 0.38 0. 08 0.06 0. 16 0. 14 0.24 0.26 54.0 0.32 0.42 0. 08 0.07 0. 18 0. 15 0.21 0.24 390 TABLE D.20 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2 . 0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CAL EXP CALC EXP CALC 0.0 2 .00 2.00 0.00 0.00 0.00 0. 00 0.00 0.00 2 .0 1 .95 1 .93 0.00 0.00 0.05 0. 06 0.00 0.00 4.0 1 .90 1.87 0.00 0.00 0.10 0. 11 0.00 0.00 6.0 1 .80 1 .81 0.00 0.00 0.15 0. 17 0.00 0.00 8.0 1 .75 1 .75 0.00 0.00 0.20 0. 22 0.00 0.00 18.0 1 .50 1 .50 0.02 0.01 0.48 0. 42 0.00 0.00 22.0 1 .40 1 .42 0.03 0.01 0.50 0. 48 0.00 0.00 26.0 1 .35 1 .34 0.04 0.01 0.52 0. 53 0.00 0.00 34.0 1 .20 1 .20 0.07 0.03 0.64 0. 60 0.00 0.00 36.0 1 .15 1.17 0.08 0.03 0.61 0. 61 0.00 0.00 40.0 1 .10 1.11 0.10 0.04 0.56 0. 64 0.00 0.00 50.0 1 .00 0.98 0.13 0.05 0.52 0. 66 0.00 0.00 52.0 0 .95 0.96 0.14 0.06 0.50 0. 67 0.00 0.00 • 54.0 0 .92 0.94 0.15 0.06 0.48 0. 67 0.00 0.00 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 2 .0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 4 .0 0. 00 0.00 0.00 0. 00 0.00 0. 00 0.00 0. 00 6.0 0. 00 0.01 0.00 0. 00 0.00 0. 00 0.00 0. 01 8.0 0. 01 0.01 0.00 0. 00 0.00 0. 00 0.00 0. 02 18.0 0. 05 0.05 0.03 0. 02 0.00 0. 00 0.04 0. 10 22.0 0. 06 0.07 0.04 0. 02 0.00 0. 01 0.08 0. 14 26.0 0. 08 0.09 0.04 0. 03 0.01 0. 02 0.15 0. 17 34.0 0. 12 0.14 0.06 0. 04 0.02 0. 03 0.18 0. 23 36.0 0. 14 0.15 0.06 0. 04 0.04 0. 04 0.20 0. 24 40.0 0. 15 0.17 0.07 0. 04 0.06 0. 05 0.24 0. 25 50.0 0. 28 0.23 0.08 0. 05 0.10 0. 08 0.26 0. 26 52.0 0. 30 0.24 0.08 0. 05 0.11 0. 09 0.27 0. 26 54.0 0. 32 0.25 0.08 0. 05 0.13 0. 10 0.29 0. 26 391 TABLE D.21 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2 . 0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 2.00 2 .00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 1 .98 1 .98 0.00 0.00 0.01 0.02 0.00 0.00 4.0 1 .96 1 .95 0.00 0.00 0.02 0.04 0.00 0.00 8.0 1 .90 1 .91 0.00 0.00 0.05 0.08 0.00 0.00 12.0 1 .85 1 .87 0.00 0.00 0.10 0.11 0.00 0.00 24.0 1 .75 1 .75 0.00 0.00 0.20 0.21 0.00 0.00 28.0 1.70 1 .71 0.00 0.00 0.25 0.23 0.00 0.00 32.0 1 .66 1 .68 0.00 0.00 0.30 0.26 0.00 0.00 40.0 1 .60 1 .61 0.00 0.00 0.35 0.31 0.00 0.00 44.0 1 .58 1 .58 0.01 0.00 0.30 0.33 0.00 0.00 52.0 1 .50 1 .51 0.01 0.01 0.30 0.37 0.00 0.00 54.0 1 .48 1 .50 0.02 0.01 0.28 0.38 0.00 0.00 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0.00 2.0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0.00 4.0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0.00 8.0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0.00 12.0 0.00 0.01 0. 00 0.00 0. 00 0.00 0.00 0.00 24.0 0.02 0.02 0. 00 0.01 0. 00 0.00 0.00 0.01 28.0 0.03 0.03 0. 00 0.01 0. 00 0.00 0.00 0.03 32.0 0.04 0.03 0. 00 0.01 0. 00 0.00 0.00 0.04 40.0 0.06 0.05 0. 00 0.01 0. 00 0.00 0.00 0.06 44.0 0.07 0.05 0. 01 0.01 0. 02 0.01 0.00 0.07 52.0 0.12 0.07 0. 01 0.02 0. 02 0.01 0.01 0.09 54.0 0.14 0.08 0. 01 0.02 0. 01 0.01 0.01 0.10 392 TABLE D.22 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 2.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 160 C . TIME CONCENTRATION (mol/D (h) = MDEA DMAE EG EXP CALC EXP CALC EXP CALC 0.0 2.00 2.00 0.00 0.00 0.00 0.00 2.0 1 .99 1 .99 0.01 0.01 0.00 0.00 4.0 1 .98 1 .99 0.01 0.01 0.00 0.00 8.0 1.96 1 .97 0.01 0.02 0.00 0.00 12.0 1 .95 1 .96 0.02 0.03 0.00 0.00 24.0 1.91 1 .92 0.05 0.06 0.00 0.00 28.0 1.90 1 .90 0.06 0.07 0.00 0.00 30.0 1 .89 1 .90 0.07 0.08 0.00 0.01 38.0 1 .85 1 .87 0.10 0.09 0.00 0.01 42.0 1 .84 1 .86 0.08 0.10 0.02 0.01 50.0 1 .81 1 .84 0.08 0.12 0.02 0.01 54.0 1 .79 1 .82 0.07 0.13 0.02 0.01 TABLE D.23 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION • 2.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa, TEMP = 140 C . TIME CONCENTRATION (mol /L) (h) MDEA BHEP DMAE EXP CALC EXP CALC EXP CALC 0.0 2.00 2.00 0.00 0.00 0.00 0.00 4.0 2.00 2.00 0.00 0.00 0.00 0.00 10.0 1 .99 1 .99 0.00 0.00 0.01 0.01 20.0 1 .98 1 .98 0.00 0.00 0.01 0.01 32.0 1 .97 1 .97 0.00 0.00 0.01 0.02 44.0 1 .95 1 .96 0.00 0.00 0.01 0.03 54.0 1 .94 1 .95 0.00 0.00 0.02 0.03 393 TABLE D.24 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 4654 kPa , TEMP = 220 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CAL EXP CALC EXP CALC 0.0 4 .28 4. 28 2.0 3 .50 3. 44 4.0 2 .90 2. 83 8.0 2 .05 2. 00 10.0 1 .75 1. 72 .18.0 1 .00 1 . 03 24.0 0 .76 0. 75 28.0 0 .66 0. 63 38.0 0 .45 0. 42 42.0 0 .40 0. 37 50.0 0 .32 0. 29 54.0 0 .30 0. 26 0.00 0. 00 0. 00 0.02 0. 00 0. 60 0.10 0. 01 1 . 10 0.25 0. 07 1 . 50 0.35 0. 12 1 . 60 0.60 0. 38 1. 46 0.68 0. 59 1. 30 0.82 0. 73 1. 20 1.05 1 . 02 0. 80 1.10 1 . 12 0. 74 1 .20 1 . 28 0. 62 1 .26 1. 35 0. 58 0.00 0. 00 0. 00 0.78 0. 00 0. 00 1 .24 0. 00 0. 00 1 .56 0. 00 0. 01 1 .55 0. 00 0. 01 1 .29 0. 05 0. 10 1 .08 0. 11 0. 24 0.97 0. 16 0. 24 0.75 0. 22 0. 34 0.68 0. 26 0. 37 0.58 0. 32 0. 43 0.54 0. 35 0. 46 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0 .00 0.00 0. 00 0. 00 0.00 0.00 0. 00 0. 00 2 .0 0 .02 0.02 0. 00 0. 01 0.00 0.00 0. 02 0. 11 4.0 0 .05 0.07 0. 01 0. 04 0.02 0.04 0. 18 0. 46 8.0 0 .10 0.20 0. 05 0. 08 0.10 0.24 0. 50 1 . 05 10.0 0 .16 0.27 0. 07 0. 09 0.20 0.33 0. 70 1 . 16 18.0 0 .42 0.65 0. 10 0. 10 0.50 0.45 0. 95 1 . 04 24.0 0 .64 0.97 0. 10 0. 10 0.70 0.46 0. 81 0. 82 28.0 0 .80 1.17 0. 10 0. 1 1 0.76 0.48 0. 70 0. 68 38.0 1 .20 1.59 0. 10 0. 11 1 .00 0.54 0. 42 0. 42 42.0 1 .30 1.72 0. 10 0. 1 1 1.10 0.56 0. 35 0. 34 50.0 1 .50 1.92 0. 10 0. 11 1.20 0.61 0. 25 0. 22 54.0 1 .60 2.00 0. 10 0. 11 1 .25 0.63 0. 20 0. 18 394 TABLE D.25 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 3964.4 kPa , TEMP = 220 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4.28 0.00 0.00 0 .00 0 .00 0.00 0.00 2.0 3. 55 3 .49 0.02 0.00 0 .60 0 .74 0.00 0.00 4.0 2. 95 2.89 0.10 0.01 1 .10 1 .21 0.00 0.00 8.0 2. 15 2.08 0.25 0.06 1 .50 1 .59 0.01 0.00 18.0 1 . 10 1 .09 0.56 0.32 1 .70 1 .40 0.05 0.07 24.0 0. 80 0.81 0.70 0.50 1 .65 1 .19 0.10 0.15 28.0 0. 70 0.67 0.75 0.62 1 .52 1 .07 0.14 0.20 36.0 0. 50 0.49 0.90 0.85 1 .30 0 .88 0.21 0.29 40.0 0. 45 0.43 0.96 0.95 1 .10 0 .81 0.26 0.32 44.0 0. 40 0.37 1 .05 1 .04 0 .90 0 .74 0.28 0.36 52.0 0. 30 0.30 1 .25 1.19 0 .70 0 .63 0.35 0.42 54.0 0. 27 0.28 1 .28 1 .22 0 .64 0 .61 0.37 0.43 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0.00 0. 00 0. 00 0.00 0.00 0.00 0.00 2.0 0. 00 0.02 0. 00 0. 01 0.00 0.00 0.02 0.10 4.0 0. 05 0.07 0. 01 0. 03 0.02 0.03 0.15 0.43 8.0 0. 10 0.18 0. 05 0. 07 0.10 0.19 0.54 1 .02 18.0 0. 50 0.60 0. 08 0. 09 0.50 0.41 1.10 1 .09 24.0 0. 65 0.90 0. 09 0. 10 0.60 0.43 1 .00 0.87 28.0 0. 72 1.10 0. 09 0. 10 0.65 0.44 0.82 0.73 36.0 0. 94 1.45 0. 10 0. 10 0.84 0.48 0.52 0.50 40.0 1 . 10 1 .59 0. 10 0. 10 0.92 0.51 0.46 0.41 44.0 1 . 24 1 .72 0. 10 0. 10 1 .00 0.53 0.40 0.33 52.0 1 . 45 1 .92 0. 10 0. 10 1.10 0.58 0.25 0.22 54.0 1 . 52 1 .96 0. 10 0. 10 1.15 0.59 0.22 0.19 395 TABLE D.26 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 1896 kPa , TEMP = 220 C . TIME CONCENTRATION ( m o l / L ) (h) :  MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4.28 0.00 0. 00 0.00 0.00 0. 00 0.00 2.0 3 .75 3.66 0.00 0. 00 0.50 0.60 0. 00 0.00 4.0 3 .25 3.17 0.02 0. 00 1 .00 1.04 0. 00 0.00 8.0 2 .52 2.44 0.10 0. 02 1 .50 1.59 0. 00 0.00 18.0 1 .50 1 .43 0.30 0. 12 2.00 1.84 0. 00 0.01 24.0 1 .12 1 .09 0.40 0. 20 1 .90 1.73 0. 02 0.04 28.0 0 .95 0.93 0.45 0. 27 1 .80 1.63 0. 04 0.07 36.0 0 .72 0.70 0.50 0. 40 1 .60 1.43 0. 08 0.13 38.0 0 .65 0.66 0.55 0. 43 1 .48 1 .38 0. 10 0.14 42.0 0 .60 0.58 0.60 0. 49 1 .40 1.29 0. 12 0.17 50.0 0 .45 0.46 0.65 0. 62 1 .24 1.14 0. 15 0.23 54.0 0 .40 0.42 0.70 0. 67 1.18 1.07 0. 16 0.26 TIME CONCENTRATION" ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0 .00 0. 00 0.00 0. 00 0 .00 0.00 0.00 0.00 2.0 0 .00 0. 02 0.00 0. 00 0 .00 0.00 0.00 0.07 4.0 0 .02 0. 05 0.00 0. 01 0 .00 0.00 0.10 0.31 8.0 0 .08 0. 14 0.01 0. 03 0 .02 0.05 0.45 0.84 18.0 0 .28 0. 41 0.03 0. 06 0 .20 0.23 0.62 1.20 24.0 0 .42 0. 61 0.04 0. 06 0 .25 0.28 0.85 1.05 28.0 0 .54 0. 76 0.04 0. 06 0 .30 0.29 0.95 0.91 36.0 0 .82 1 . 07 0.05 0. 07 0 .40 0.31 0.90 0.66 38.0 0 .85 1 . 14 0.05 0. 07 0 .46 0.31 0.72 0.60 42.0 0 .96 1 . 29 0.05 0. 07 0 .50 0.33 0.60 0.51 50.0 1 .20 1 . 55 0.06 0. 07 0 .62 0.36 0.48 0.35 54.0 1 .30 1. 66 0.06 0. 07 0 .65 0.38 0.36 0.29 396 TABLE D.27 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 1206 kPa , TEMP = 220 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 3.90 3.76 0.00 0.00 0 .30 0.51 0.00 0.00 4.0 3.40 3.32 0.02 0.00 0 .70 0.93 0.00 0.00 8.0 2.75 2.65 0.05 0.01 1 .20 1 .49 0.00 0.00 18.0 1 .70 1 .65 0.16 0.06 1 .80 1 .99 0.00 0.00 24.0 1 .35 1 .30 0.24 0.10 1 .90 1 .99 0.00 0.01 28.0 1.15 1.12 0.30 0.14 2 .00 1 .94 0.00 0.02 36.0 0.92 0.87 0.35 0.22 1 .85 1 .79 0.03 0.06 38.0 0.85 0.82 0.38 0.24 1 .82 1 .75 0.04 0.07 42.0 0.76 0.73 0.42 0.28 1 .76 1 .67 0.06 0.09 50.0 0.65 0.59 0.46 0.37 1 .65 1 .51 0.08 0.13 54.0 0.62 0.53 0.48 0.41 1 .62 1.44 0.09 0.15 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0. 00 0.00 0.00 0. 00 2.0 0.00 0.01 0.00 0.00 0. 00 0.00 0.00 0. 05 4.0 0.02 0.05 0.00 0.01 0. 00 0.00 0.10 0. 24 8.0 0.05 0.13 0.00 0.02 0. 02 0.02 0.30 0. 72 18.0 0.25 0.34 0.02 0.04 0. 10 0.13 0.92 1 . 17 24.0 0.40 0.48 0.03 0.05 0. 14 0.19 0.95 1 . 10 28.0 0.45 0.60 0.03 0.05 0. 18 0.21 1 .00 0. 99 36.0 0.60 0.84 0.04 0.05 0. 24 0.23 0.78 0. 75 38.0 0.65 0.90 0.04 0.05 0. 26 0.24 0.75 0. 70 42.0 0.72 1 .03 0.04 0.05 0. 34 0.24 0.65 0. 60 50.0 0.90 1 .27 0.05 0.05 0. 35 0.26 0.45 0. 43 54.0 0.96 1 .39 0.05 0.05 0. 38 0.27 0.40 0. 36 397 TABLE D.28 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 517 kPa , TEMP = 220 C . TIME CONCENTRATION ( m o l / L ) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 4 .28 4.28 2. 0 4 .00 3.89 4. 0 3 .70 3.55 8. 0 3 .10 3.00 10. 0 2 .90 2.76 20 . 0 2 .10 1 .93 24. 0 1 .80 1 .70 28. 0 1 .60 1 .51 36. 0 1 .30 1 .21 40 . 0 1 .25 1 .09 44. 0 1 .12 0.99 52. 0 0 .95 0.83 54. 0 0 .92 0.79 0. 00 0. 00 0.00 0. 00 0. 00 0.25 0. 00 0. 00 0.50 0. 00 0. 00 0.95 0. 02 0. 01 1 .25 0. 06 0. 02 1 .60 0. 10 0. 03 1 .80 0. 12 0. 04 2.00 0. 14 0. 06 2.05 0. 15 0. 07 1 .84 0. 16 0. 09 1 .80 0. 18 0. 12 1.75 0. 19 0. 13 1 .72 0 .00 0. 00 0.00 0 .38 0. 00 0.00 0 .71 0. 00 0.00 1 .24 0. 00 0.00 1 .44 0. 00 0.00 2 .07 0. 00 0.00 2 .18 0. 00 0.00 2 .25 0. 00 0.00 2 .29 0. 00 0.01 2 .28 0. 00 0.01 2 .25 0. 01 0.02 2 .17 0. 01 0.03 2 .15 0. 01 0.03 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0.00 0. 00 0.00 0.00 2.0 0.00 0.01 0. 00 0.00 0.00 0. 00 0.00 0.03 4.0 0.02 0.04 0. 00 0.00 0.00 0. 00 0.05 0.15 8.0 0.05 0.10 0. 00 0.01 0.00 0. 00 0.25 0.51 10.0 0.08 0.13 0. 00 0.01 0.00 0. 00 0.45 0.66 20.0 0.25 0.29 0. 00 0.02 0.02 0. 03 0.86 1 .01 24.0 0.30 0.35 0. 01 0.02 0.03 0. 05 0.90 1 .02 28.0 0.34 0.41 0. 01 0.02 0.04 0. 07 0.95 0.98 36.0 0.48 0.53 0. 02 0.03 0.05 0. 1 1 0.82 0.85 40.0 0.50 0.60 0. 02 0.03 0.07 0. 12 0.75 0.77 44.0 0.55 0.67 0. 02 0.03 0.08 0. 13 0.70 0.69 52.0 0.70 0.83 0. 02 0.03 0.10 0. 14 0.62 0.53 54.0 0.74 0.87 0. 02 0.03 0.12 0. 15 0.50 0.50 398 TABLE D.29 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 344.7 kPa , TEMP = 220 C . TIME CONCENTRATION (mo l /L) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4 .28 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 4.10 3 .95 0.00 0.00 0 .25 0.33 0.00 0.00 6.0 3 .75 3 .36 0.00 0.00 0 .50 0.88 0.00 0.00 8.0 3.25 3 .23 0.00 0.00 1 .00 1.11 0.00 0.00 10.0 3.05 2 .95 0.02 0.00 1 .10 1.31 0.00 0.00 20.0 2.25 2 .15 0.05 0.01 1 .65 1 .98 0.00 0.00 24.0 2.00 1 .92 0.06 0.02 1 .75 2.14 0.00 0.00 28.0 1 .85 1 .73 0.07 0.02 1 .80 2.25 0.00 0.00 38.0 1 .43 1 .33 0.14 0.04 2 .00 2.40 0.00 0.00 42.0 1 .30 1 .24 0.15 0.04 2 .10 2.42 0.00 0.01 46.0 1 .20 1 . 1 1 0.16 0 .05 2 .15 2.42 0.01 0.01 54.0 1.10 0 .94 0.18 0.07 2 .20 2.40 0.01 0.01 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.01 0. 00 0.00 0.00 0.00 0.00 0.02 4 .0 0.02 0.03 0. 00 0.00 0.00 0.00 0.05 0.12 8.0 0.05 0.09 0. 00 0.00 0.00 0.00 0.20 0.42 10.0 0.08 0.12 0. 00 0.01 0.00 0.00 0.30 0.57 20.0 0.20 0.26 0. 00 0.01 0.00 0.01 0.65 0.91 24.0 0.25 0.31 0. 00 0.01 0.00 0.02 0.70 0.93 28.0 0.30 0.36 0. 00 0.02 0.02 0.03 0.72 0.92 38.0 0.40 0.48 0. 01 0.02 0.03 0.07 0.62 0.80 42.0 0.45 0.53 0. 01 0.02 0.04 0.08 0.60 0.74 46.0 0.50 0.58 0. 01 0.02 0.05 0.09 0.56 0.68 54.0 0.58 0.69 0. 01 0.02 0.10 0.10 0.45 0.55 399 TABLE D.30 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 4654 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4.28 0.00 0.00 0 .00 0 .00 0.00 0.00 2 .0 3.98 3.93 0.00 0.00 0 .25 0 .32 0.00 0.00 4.0 3.70 3.63 0.00 0.00 0 .50 0 .59 0.00 0.00 8.0 3.20 3.11 0.02 0.01 1 .00 0 .97 0.00 0.00 12.0 2.55 2.70 0.06 0.02 1 .20 1 .18 0.00 0.00 20.0 2.15 2.09 0.22 0.09 1 .25 1 .29 0.01 0.01 24.0 1 .92 1 .86 0.26 0.14 1 .20 1 .26 0.01 0.02 28.0 1 .70 1 .67 0.30 0.20 1 .10 1 .22 0.02 0.03 36.0 1 .40 1 .36 0.42 0.34 1 .05 1 . 1 1 0.05 0.07 40.0 1 .25 1 .24 0.45 0.41 0 .90 1 .05 0.07 0.09 44.0 1.15 1.14 0.52 0.48 0 .85 1 .00 0.10 0.12 52.0 1 .00 0.96 0.60 0.62 0 .75 0 .89 0.14 0.17 54.0 0.90 0.92 0.64 0.66 0 .72 0 .87 0.15 0.18 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 0.00 0.00 0.00 0.00 0.00 0. 00 0.00 0.00 2. 0 0.00 0.01 0.00 0.00 0.00 0. 00 0.00 0.01 4. 0 0.02 0.02 0.00 0.01 0.00 0. 00 0.02 0.07 8. 0 0.05 0.06 0.01 0.03 0.02 0. 03 0.15 0.30 12. 0 0.10 0.12 0.03 0.05 0.08 0. 1 1 0.35 0.57 20 . 0 0.25 0.26 0.06 0.08 0.25 0. 30 0.70 0.89 24. 0 0.35 0.34 0.07 0.08 0.30 0. 37 0.72 0.92 28. 0 0.45 0.43 0.08 0.09 0.38 0. 41 0.68 0.91 36. 0 0.70 0.63 0.10 0.09 0.60 0. 44 0.60 0.83 40. 0 0.80 0.74 0.10 0.09 0.65 0. 45 0.55 0.77 44. 0 0.90 0.84 0.10 0.10 0.70 0. 46 0.50 0.71 52. 0 1.15 1 .05 0.10 0.10 0.85 0. 47 0.38 0.59 54. 0 1.20 1.10 0.1 1 0.10 0.88 0. 47 0.35 0.57 400 TABLE D.31 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 3964.4 kPa , TEMP = 200 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4.28 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 4 .05 3.95 0.00 0.00 0 .25 0.30 0.00 0.00 4.0 3 .75 3.66 0.00 0.00 0 .60 0.56 0.00 0.00 8.0 3 .25 3.17 0.02 0.01 1 .00 0.95 0.00 0.00 10.0 3 .05 2.96 0.05 0.01 1 .10 1 .08 0.00 0.00 20.0 2 .15 2.17 0.15 0.07 1 .35 1 .33 0.01 0.01 24.0 2 .00 1 .94 0.25 0.11 1 .20 1 .33 0.01 0.01 28.0 1 .80 1.75 0.30 0.16 1 .15 1 .30 0.01 0.02 36.0 1 .50 1 .44 0.40 0.28 1 .10 1 .20 0.03 0.05 40.0 • 1 .35 1.31 0.45 0.34 1 .00 1.14 0.04 0.07 44.0 1 .20 1 .20 0.50 0.41 0 .95 1 .09 0.06 0.09 52.0 1 .00 1 .02 0.58 0.53 0 .80 0.99 0.10 0.14 54.0 0 .95 0.99 0.60 0.57 0 .74 0.97 0.1 1 0.15 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0 .0 0.00 0.00 0.00 0 .00 0. 00 0.00 0.00 0.00 2 .0 0.00 0.00 0.00 0 .00 0. 00 0.00 0.00 0.01 4 .0 0.02 0.02 0.00 0 .01 0. 00 0.00 0.02 0.06 8 .0 0.05 0.06 0.01 0 .02 0. 02 0.02 0.20 0.28 10 .0 0.10 0.08 0.02 0 .03 0. 04 0.05 0.30 0.42 20 .0 0.30 0.24 0.04 0 .07 0. 25 0.25 0.75 0.88 24 .0 0.35 0.31 0.05 0 .07 0. 30 0.32 0.80 0.93 28 .0 0.40 0.40 0.06 0 .08 0. 40 0.36 0.72 0.94 36 .0 0.60 0.58 0.07 0 .08 0. 50 0.41 0.62 0.86 40 .0 0.65 0.68 0.08 0 .09 0. 60 0.42 0.55 0.81 44 .0 0.72 0.78 0.09 0 .09 0. 66 0.43 0.50 0.75 52 .0 0.94 0.98 0.10 0 .09 0. 76 0.44 0.37 0.63 54 .0 1 .02 1.03 0.10 0 .09 0. 80 0.44 0.34 0.61 401 TABLE A.32 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 1896 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4.28 0.00 0. 00 0.00 0 .00 0.00 0.00 2.0 4 .10 4.03 0.00 0. 00 0.25 0 .24 0.00 0.00 4.0 3 .90 3.80 0.00 0. 00 0.50 0 .45 0.00 0.00 8.0 3 .30 3.40 0.02 0. 00 0.75 0 .81 0.00 0.00 16.0 2 .80 2.77 0.05 0. 01 1 .30 1 .28 0.00 0.00 20.0 2 .50 2.52 0.06 0. 02 1 .35 1 .41 0.00 0.00 24.0 2 .25 2.30 0.08 0. 04 1 .40 1 .49 0.01 0.00 34.0 1 .90 1 .87 0.15 0. 08 1.30 1 .56 0.01 0.01 38.0 1 .75 1 .73 0.20 0. 1 1 1 .25 1 .55 0.01 0.01 42.0 1 .62 1 .60 0.25 0. 14 1 .20 1 .53 0.02 0.02 50.0 1 .40 1 .39 0.32 0. 20 1.16 1 .47 0.03 0.04 52.0 1 .32 1 .34 0.35 0. 22 1.15 1 .45 0.03 0.04 54.0 1 .28 1 .30 0.37 0. 24 1.12 1 .43 0.03 0.05 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0. 00 0.00 0.00 0.00 0. 00 0.00 0.00 2.0 0. 00 0. 00 0.00 0.00 0.00 0. 00 0.00 0.01 4.0 0. 00 0. 01 0.00 0.00 0.00 0. 00 0.02 0.04 8.0 0. 00 0. 05 0.00 0.01 0.00 0. 00 0.10 0.20 16.0 0. 10 0. 13 0.02 0.03 0.02 0. 04 0.40 0.61 20.0 0. 22 0. 18 0.02 0.03 0.05 0. 08 0.55 0.76 24.0 0. 25 0. 23 0.03 0.04 0.10 0. 12 0.70 0.87 34.0 0. 40 0. 37 0.04 0.05 0.20 0. 22 0.80 0.96 38.0 0. 50 0. 43 0.04 0.05 0.25 0. 25 0.72 0.95 42.0 0. 60 0. 50 0.05 0.06 0.30 0. 27 0.68 0.91 50.0 0. 74 0. 64 0;06 0.06 0.40 0. 30 0.55 0.82 52.0 0. 77 0. 68 0.07 0.06 0.42 0. 30 0.53 0.79 54.0 0. 80 0. 71 0.07 0.06 0.45 0. 30 0.50 0.77 402 TABLE D.33 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION • 4.28 M O L / L , C02 PARTIAL PRESSURE = 1206 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 4.28 4.28 0. 00 0.00 0.00 0.00 0.00 0.00 2. 0 4.15 4.07 0. 00 0.00 0.20 0.20 0.00 0.00 4. 0 3.95 3.88 0. 00 0.00 0.40 0.39 0.00 0.00 8. 0 3.60 3.53 0. 00 0.00 0.65 0.71 0.00 0.00 16. 0 3.00 2.96 0. 02 0.01 1.10 1.19 0.00 0.00 20. 0 2.75 2.72 0. 03 0.01 1 .30 1 .36 0.00 0.00 24. 0 2.50 2.52 0. 04 0.02 1 .50 1 .48 0.00 0.00 32. 0 2.15 2.17 0. 10 0.04 1 .60 1 .64 0.00 0.00 36. 0 2.00 2.02 0. 12 0.05 1 .64 1 .68 0.00 0.00 40. 0 1 .85 1 .89 0. 14 0.06 1 .66 1 .70 0.00 0.01 50. 0 1 .60 1 .61 0. 18 0.10 1 .54 1 .70 0.01 0.01 54. 0 1 .54 1 .51 0. 20 0.12 1 .48 1 .68 0.01 0.02 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0. 00 0. 00 0. 00 0.00 2.0 0.00 0.00 0. 00 0.00 0. 00 0. 00 0. 00 0.00 4.0 0.00 0.01 0. 00 0.00 0. 00 0. 00 0. 02 0.03 8.0 0.02 0.04 0. 00 0.01 0. 00 0. 01 0. 10 0.15 16.0 0.10 0.12 0. 01 0.02 0. 00 0. 01 0. 30 0.51 20.0 0.15 0.16 0. 01 0.02 0. 01 0. 03 0. 40 0.66 24.0 0.20 0.20 0. 02 0.03 0. 05 0. 05 0. 50 0.77 32.0 0.28 0.28 0. 02 0.03 0. 10 0. 10 0. 65 0.90 36.0 0.40 0.33 0. 03 0.04 0. 15 0. 13 0. 70 0.92 40.0 0.45 0.37 0. 04 0.04 0. 18 0. 15 0. 65 0.93 50.0 0.60 0.50 0. 05 0.04 0. 25 0. 20 0. 55 0.87 54.0 0.65 0.56 0. 05 0.04 0. 28 0. 22 0. 50 0.83 403 TABLE D.34 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 517 kPa , TEMP = 200 C . TIME CONCENTRATION (mo l /L) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4 .28 4. 28 2 .0 4 .20 4. 13 4 .0 4 .10 3. 99 8.0 3 .80 3. 72 16.0 3 .30 3. 27 20 .0 3 .10 3. 07 24.0 2 .90 2. 89 34.0 2 .50 2. 50 38 .0 2 .40 2. 37 42.0 2 .30 2. 25 52.0 2 .00 1 . 98 54.0 1 .90 1. 93 0.00 0. 00 0 .00 0.00 0. 00 0 .10 0.00 0. 00 0 .20 0.00 0. 00 0 .40 0.00 0. 00 0 .95 0.00 0. 00 1 .10 0.00 0. 01 1 .20 0.02 0. 01 1 .36 0.03 0. 01 1 .52 0.05 0. 02 1 .60 0.08 0. 03 1 .75 0.10 0. 03 1 .80 0.00 0. 00 0. 00 0.15 0. 00 0. 00 0.29 0. 00 0. 00 0.54 0. 00 0. 00 0.97 0. 00 0. 00 1.14 0. 00 0. 00 1 .30 0. 00 0. 00 1 .59 0. 00 0. 00 1 .68 0. 00 0. 00 1 .75 0. 00 0. 00 1 .88 0. 00 0. 00 1 .90 0. 01 0. 00 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0 .00 2 .0 0.00 0.00 0. 00 0.00 0. 00 0.00 0.00 0 .00 4 .0 0.00 0.01 0. 00 0.00 0. 00 0.00 0.00 0 .02 8 .0 0.05 0.03 0. 00 0.00 0. 00 0.00 0.05 0 .09 16.0 0.10 0.10 0. 00 0.01 0. 00 0.00 0.20 0 .35 20.0 0.14 0.12 0. 01 0.01 0. 00 0.00 0.30 0 .47 24.0 0.20 0.16 0. 01 0.01 0. 00 0.01 0.40 0 .57 34.0 0.25 0.23 0. 02 0.01 0. 00 0.02 0.58 0 .73 38.0 0.30 0.26 0. 02 0.02 0. 02 0.03 0.62 0 .77 42.0 0.35 0.29 0. 03 0.02 0. 03 0.04 0.55 0 .79 52.0 0.45 0.37 0. 03 0.02 0. 07 0.06 0.50 0 .80 54.0 0.48 0.38 0. 03 0.02 0. 08 0.07 0.46 0 .79 404 TABLE D.35 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 344.7 kPa , TEMP = 200 C . TIME CONCENTRATION (mol/D (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0 .00 0.00 0.00 0.00 2.0 4.25 4.15 0.00 0.00 0 .10 0.13 0.00 0.00 4.0 4.10 4.03 0.00 0.00 0 .20 0.25 0.00 0.00 8.0 3 .90 3.80 0.00 0.00 0 .40 0.47 0.00 0.00 18.0 3.30 3.30 0.00 0.00 0 .90 0.95 0.00 0.00 22.0 3.10 3.13 0.00 0.00 1 .12 1.10 0.00 0.00 26.0 2.90 2.97 0.00 0.00 1 .20 1 .24 0.00 0.00 34.0 2 .65 2.69 0.02 0.01 1 .50 1 .48 0.00 0.00 38.0 2 .55 2.56 0.03 0.01 1 .52 1 .58 0.00 0.00 42.0 2 .45 2.45 0.04 0.01 1 .46 1 .67 0.00 0.00 52.0 2 .15 2.18 0.06 0.02 1 .40 1 .84 0.00 0.00 54.0 2.10 2.14 0.07 0.02 1 .40 1 .87 0.00 0.00 TIME CONCENTRATION (mol/D (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.0 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 8.0 0.02 0.03 0.00 0.00 0.00 0.00 0.05 0.07 18.0 0.10 0.10 0.00 0.00 0.00 0.00 0.20 0.34 22.0 0.15 0.13 0.00 0.01 0.00 0.00 0.30 0.44 26.0 0.20 0.15 0.00 0.01 0.00 0.00 0.40 0.52 34.0 0.30 0.24 0.01 0.01 0.00 0.01 0.50 0.64 38.0 0.34 0.24 0.01 0.01 0.00 0.01 0.45 0.68 42.0 0.36 0.26 0.01 0.01 0.00 0.01 0.42 0.70 52.0 0.42 0.32 0.01 0.01 0.02 0.03 0.38 0.72 54.0 0.45 0.34 0.01 0.01 0.02 0.03 0.35 0.72 405 TABLE D.36 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 4654 kPa , TEMP = 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 2.0 4.20 4.16 0.00 0.00 0.05 0.11 0.00 0.00 4.0 4.10 4.04 0.00 0.00 0.15 0.21 0.00 0.00 8.0 3.90 3.82 0.00 0.00 0.30 0.40 0.00 0.00 12.0 3.70 3.61 0.00 0.00 0.48 0.56 0.00 0.00 20.0 3.30 3 .25 0.00 0.01 0.70 0.79 0.00 0.00 24.0 3.10 3 .09 0.00 0.01 0.80 0.87 0.00 0.00 28.0 3.00 2.94 0.02 0.02 0.90 0.93 0.00 0.00 36.0 2.70 2.68 0.05 0.04 0.82 1 .00 0.00 0.00 40.0 2.60 2.56 0.07 0.05 0.80 1.01 0.00 0.00 44.0 2.50 2 .45 0.10 0.06 0.78 1 .02 0.00 0.01 52.0 2.20 2.24 0.15 0.10 0.74 1.01 0.01 0.01 54.0 2.17 2.20 0.17 0.11 0.72 1 .00 0.01 0.01 TIME CONCENTRATION ( m o l / L ) (h) : EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 0.00 0.00 0. 00 0.00 0.00 0. 00 0. 00 0.00 2. 0 0.00 0.00 0. 00 0.00 0.00 0. 00 0. 00 0.00 4. 0 0.00 0.00 0. 00 0.00 0.00 0. 00 0. 00 0.00 8. 0 0.02 0.01 0. 00 0.01 0.00 0. 00 0. 05 0.03 12. 0 0.05 0.03 0. 00 0.01 0.02 0. 01 0. 10 0.08 18. 0 0.10 0.06 0. 01 0.02 0.05 0. 03 0. 20 0.20 24. 0 0.15 0.09 0. 04 0.04 0.10 0. 07 0. 30 0.33 28. 0 0.16 0.12 0. 05 0.04 0.15 0. 11 0. 35 0.41 36. 0 0.30 0.18 0. 06 0.06 0.25 0. 19 0. 42 0.55 40. 0 0.35 0.21 0. 07 0.06 0.30 0. 23 0. 45 0.59 44. 0 0.40 0.24 0. 08 0.07 0.34 0. 27 0. 40 0.63 52. 0 0.55 0.32 0. 08 0.07 0.40 0. 33 0. 38 0.66 54. 0 0.58 0.32 0. 08 0.07 0.42 0. 33 0. 36 0.66 406 TABLE D.37 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 3964.4 kPa , TEMP = 180 C . TIME CONCENTRATION (mol/D (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4. 28 0. 00 0. 00 0.00 0. 00 0.00 0.00 2.0 4. 20 4. 16 0. 00 0. 00 0.05 0. 10 0.00 0.00 4.0 4. 10 4. 05 0. 00 0. 00 0.15 0. 20 0.00 0.00 10.0 3. 85 3. 74 0. 00 0. 00 0.40 0. 47 0.00 0.00 18.0 3 . 40 3. 38 0. 00 0. 00 0.60 0. 73 0.00 0.00 22.0 3 . 20 3 . 22 0. 00 0. 01 0.70 0. 83 0.00 0.00 26.0 3 . 10 3. 07 0. 01 0. 01 0.74 0. 90 0.00 0.00 36.0 2. 75 2. 74 0. 02 0. 03 0.80 1 . 02 0.00 0.00 40.0 2. 60 2. 63 0. 05 0. 04 0.85 1 . 04 0.00 0.00 50.0 2. 35 2. 37 0. 08 0. 07 0.82 1 . 06 0.01 0.01 54.0 2. 25 2. 27 0. 10 0. 09 0.80 1 . 06 0.01 0.01 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0. 00 0. 00 0. 00 0.00 0.00 0.00 0.00 2.0 0. 00 0. 00 0. 00 0. 00 0.00 0.00 0.00 0.00 4.0 0. 00 0. 00 0. 00 0. 00 0.00 0.00 0.00 0.00 10.0 0. 02 0. 02 0. 00 0. 01 0.00 0.00 0.02 0.05 18.0 0. 10 0. 05 0. 01 0. 02 0.02 0.02 0.12 0.19 22.0 0. 12 0. 08 0. 02 0. 03 0.05 0.04 0.20 0.27 26.0 0. 14 0. 10 0. 02 0. 03 0.11 0.06 0.30 0.36 36.0 0. 25 0. 17 0. 04 0. 05 0.16 0.15 0.40 0.53 40.0 0. 30 0. 20 0. 05 0. 05 0.20 0.19 0.45 0.59 50.0 0. 50 0. 28 0. 05 0. 06 0.30 0.27 0.50 0.66 54.0 0. 54 0. 31 0. 05 0. 07 0.32 0.30 0.52 0.68 407 TABLE D.38 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 1896 kPa, TEMP = 180 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0 .00 0.00 0.00 2.0 4.25 4.19 0.00 0.00 0.05 0 .08 0.00 0.00 4.0 4.15 4.11 0.00 0.00 0.12 0 .16 0.00 0.00 10.0 3.95 3.87 0.00 0.00 0.30 0 .38 0.00 0.00 18.0 3.60 3.58 0.00 0.00 0.56 0 .63 0.00 0.00 22.0 3.46 3 .45 0.00 0.00 0.68 0 .73 0.00 0.00 28.0 3.55 3.63 0.00 0.00 0.75 0 .87 0.00 0.00 38.0 3.00 2.98 0.02 0.01 0.90 1 .04 0.00 0.00 42.0 2.90 2.88 0.03 0.01 0.94 1 .09 0.00 0.00 48.0 2.80 2.79 0.04 0.02 0.90 1 .16 0.00 0.00 54.0 2.60 2.61 0.06 0.03 0.84 1 .20 0.00 0.00 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10.0 0.00 0.02 0.00 0.00 0.00 0.00 0.02 0.03 18.0 0.04 0.04 0.00 0.01 0.00 0.00 0.10 0.13 22.0 0.10 0.06 0.00 0.01 0.00 0.01 0.15 0.20 28.0 0.15 0.09 0.01 0.02 0.00 0.02 0.25 0.30 38.0 0.25 0.14 0.02 0.02 0.04 0.05 0.32 0.46 42.0 0.28 0.16 0.02 0.03 0.06 0.06 0.37 0.52 46.0 0.31 0.18 0.03 0.03 0.08 0.08 0.40 0.56 54.0 0.40 0.23 0.05 0.04 0.16 0.11 0.45 0.62 408 TABLE D.39 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 1206 kPa , TEMP = 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 2.0 4.26 4.21 0.00 0.00 0.02 0.07 0.00 0.00 4.0 4.18 4.13 0.00 0.00 0.08 0.14 0.00 0.00 8.0 4.06 4.00 0.00 0.00 0.18 0.27 0.00 0.00 18.0 3.70 3.68 0.00 0.00 0.50 0.56 0.00 0.00 22.0 3.60 3.56 0.00 0.00 0.60 0.66 0.00 0.00 28.0 3.40 3.40 0.00 0.00 0.80 0.79 0.00 0.00 36.0 3.20 3.20 0.00 0.00 0.86 0.95 0.00 0.00 40.0 3.10 3.10 0.00 0.01 0.90 1.01 0.00 0.00 44.0 3.00 3.01 0.00 0.01 0.96 1 .07 0.00 0.00 52.0 2.90 2.89 0.02 0.01 1.10 1.18 0.00 0.00 54.0 2.80 2.81 0.02 0.01 1.14 1 .20 0.00 0.00 TIME CONCENTRATION ( m o l / L ) ' (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 0.00 4.0 0.00 0. 00 0.00 0.00 0.00 0.00 0.00 0.00 8.0 0.00 0. 01 0.00 0.00 0.00 0.00 0.00 0.01 18.0 0.02 0. 04 0.00 0.00 0.00 0.00 0.05 0.10 22.0 0.05 0. 05 0.00 0.01 0.00 0.00 0.10 0.15 28.0 0.10 0. 08 0.00 0.01 0.00 0.01 0.16 0.24 36.0 0.20 0. 1 1 0.01 0.01 0.00 0.01 0.25 0.36 40.0 0.24 0. 13 0.01 0.02 0.02 0.02 0.30 0.41 44.0 0.28 0. 15 0.01 0.02 0.03 0.03 0.35 0.46 52.0 0.35 0. 19 0.02 0.02 0.06 0.04 0.42 0.55 54.0 0.38 0. 20 0.02 0.02 0.08 0.05 0.44 0.56 409 TABLE D.40 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE » 517 kPa, TEMP = 180 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 2.0 4.26 4.23 0.00 0.00 0.02 0.05 0.00 0.00 4.0 4.22 4.18 0.00 0.00 0.08 0.10 0.00 0.00 10.0 4.07 4.03 0.00 0.00 0.20 0.25 0.00 0.00 18.0 3.85 3.84 0.00 0.00 0.40 0.43 0.00 0.00 22.0 3.76 3 .75 0.00 0.00 0.50 0.51 0.00 0.00 28.0 3.60 3.62 0.00 0.00 0.55 0.63 0.00 0.00 36.0 3.45 3.46 0.00 0.00 0.62 0.77 0.00 0.00 44.0 3.30 3.31 0.00 0.00 0.75 0.90 0.00 0.00 52.0 3.18 3.20 0.00 0.00 0.86 1 .02 0.00 0.00 54.0 3.12 3.14 0.00 0.00 0.95 1 .05 0.00 0.00 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10.0 0.02 0.01 0.00 0.00 0.00 0.00 0.00 0.01 18.0 0.04 0.03 0.00 0.00 0.00 0.00 0.04 0.06 22.0 0.05 0.04 0.00 0.00 0.00 0.00 0.08 0.10 28.0 0.08 0.06 0.00 0.00 0.00 0.00 0.12 0.16 36.0 0.10 0.09 0.00 0.00 0.00 0.00 0.20 0.24 44.0 0.16 0.12 0.00 0.01 0.00 0.00 0.24 0.32 52.0 0.20 0.15 0.01 0.01 0.00 0.01 0.28 0.40 54.0 0.22 0.15 0.01 0.01 0.00 0.01 0.30 0.41 410 TABLE D.41 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 344.7 k P a , TEMP = 180 C . TIME CONCENTRATION (mo l /L) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0. 00 0.00 0.00 0.00 0.00 0.00 2.0 4.26 4.23 0. 02 0.04 0.00 0.00 0.00 0.00 4.0 4.22 4.19 0. 08 0.09 0.00 0.00 0.00 0.00 10.0 4.10 4.06 0. 18 0.21 0.00 0.01 0.00 0.01 18.0 3 .95 3.94 0. 30 0.37 0.02 0.03 0.02 0.05 22.0 3.80 3.82 0. 42 0.44 0.05 0.04 0.05 0.07 28.0 3.70 3.71 0. 50 0.55 0.06 0.05 0.10 0.12 36.0 3.60 3.57 0. 62 0.68 0.10 0.08 0.15 0.20 44.0 3.40 3.43 0. 74 0.81 0.15 0.11 0.22 0.27 52.0 3.31 3.31 0. 86 0.92 0.20 0.13 0.28 0.33 54.0 3 .25 3.28 0. 90 0.95 0.22 0.14 0.30 0.35 41 1 TABLE D.42 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 4654 kPa , TEMP = 160 C . TIME CONCENTRATION (mol/D (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 4.0 4.25 4.20 0.00 0.00 0.02 0.06 0.00 0.00 8.0 4.16 4.13 0.00 0.00 0.08 0.12 0.00 0.00 12.0 4.10 4.05 0.00 0.00 0.14 0.18 0.00 0.00 22.0 3.90 3.88 0.00 0.00 0.28 0.32 0.00 0.00 26.0 3.80 3.81 0.00 0.00 0.30 0.36 0.00 0.00 30.0 3 .75 3.75 0.00 0.00 0.35 0.41 0.00 0.00 38.0 3.60 3.62 0.00 0.00 0.40 0.49 0.00 0.00 42.0 3 .55 3.56 0.00 0.00 0.45 0.52 0.00 0.00 46.0 3.50 3.50 0.00 0.00 0.48 0.56 0.00 0.00 54.0 3.40 3.39 0.00 0.00 0.53 0.61 0.00 0.00 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0. 00 4.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0. 00 8.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0. 00 12.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0. 00 22 .0 0.02 0.01 0.00 0.01 0.00 0.00 0.00 0. 02 26.0 0.04 0.02 0.00 0.01 0.00 0.01 0.05 0. 03 30.0 0.06 0.03 0.00 0.01 0.00 0.01 0.08 0. 05 38.0 0.10 0.04 0.00 0.02 0.02 0.01 0.15 0. 09 42.0 0.12 0.05 0.01 0.02 0.04 0.02 0.17 0. 11 46.0 0.14 0.06 0.01 0.02 0.06 0.02 0.19 0. 13 54.0 0.22 0.07 0.01 0.03 0.10 0.04 0.24 0. 18 412 TABLE D.43 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 3964.4 kPa , TEMP = 160 C . TIME CONCENTRATION (mo l /L) (h) : MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0. 00 0. 00 0.00 0. 00 0.00 4.0 4.24 4.21 0.00 0. 00 0. 04 0.06 0. 00 0.00 8.0 4.16 4.14 0.00 0. 00 0. 10 0.12 0. 00 0.00 12.0 4.10 4.07 0.00 0. 00 0. 15 0.18 0. 00 0.00 22.0 3.90 3.90 0.00 0. 00 0. 30 0.31 0. 00 0.00 26.0 3.85 3.84 0.00 0. 00 0. 35 0.35 0. 00 0.00 30.0 3.80 3.77 0.00 0. 00 0. 40 0.40 0. 00 0.00 38.0 3.66 3.65 0.00 0. 00 0. 45 0.48 0. 00 0.00 42.0 3.60 3.60 0.00 0. 00 0. 48 0.52 0. 00 0.00 46.0 3.55 3.54 0.00 0. 00 0. 50 0.55 0. 00 0.00 54.0 3.45 3.43 0.00 0. 00 0. 55 0.61 0. 00 0.00 TIME CONCENTRATION (mo l /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0.00 0.00 0.00 0. 00 0.00 0. 00 0. 00 4.0 0.00 0.00 0.00 0.00 0. 00 0.00 0. 00 0. 00 8.0 0.00 0.00 0.00 0.00 0. 00 0.00 0. 00 0. 00 12.0 0.00 0.00 0.00 0.00 0. 00 0.00 0. 00 0. 00 22.0 0.02 0.01 0.00 0.00 0. 00 0.00 0. 02 0. 02 26.0 0.05 0.02 0.00 0.01 0. 00 0.00 0. 04 0. 03 30.0 0.06 0.03 0.00 0.01 0. 00 0.00 0. 06 0. 05 38.0 0.08 0.04 0.00 0.01 0. 01 0.01 0. 10 0. 08 42.0 0.10 0.05 0.00 0.01 0. 01 0.02 0. 12 0. 10 46.0 0.12 0.05 0.01 0.02 0. 02 0.02 0. 14 0. 12 54.0 0.15 0.07 0.01 0.02 0. 04 0.07 0. 20 0. 17 413 TABLE D.44 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 1896 kPa , TEMP = 160 C . TIME CONCENTRATION (mo l /L) (h) — MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0. 00 0.00 0. 00 0.00 0. 00 0.00 4.0 4.24 4.22 0. 02 0.05 0. 00 0.00 0. 00 0.00 8.0 4.20 4.17 0. 08 0.10 0. 00 0.00 0. 00 0.00 12.0 4.15 4.12 0. 15 0.14 0. 00 0.00 0. 00 0.00 20.0 4.00 4.01 0. 50 0.24 0. 02 0.01 0. 00 0.01 24.0 3 .95 3.96 0. 28 0.28 0. 03 0.01 0. 02 0.02 28.0 3.90 3.91 0. 30 0.32 0. 04 0.02 0. 03 0.03 36.0 3.80 3.82 0. 36 0.40 0. 08 0.03 0. 05 0.05 44.0 3.70 3.72 0. 45 0.47 0. 12 0.04 0. 10 0.08 52.0 3.60 3.63 0. 50 0.54 0. 15 0.05 0. 15 0.12 54.0 3.58 3.61 0. 53 0.56 0. 16 0.06 0. 16 0.13 TABLE D.45 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE - 1206 kPa , TEMP = 160 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 4 .28 4.28 0. 00 0. 00 0. 00 0.00 0.00 0.00 4. 0 4 .26 4.23 0. 02 0. 04 0. 00 0.00 0.00 0.00 8. 0 4 .24 4.19 0. 06 0. 08 0. 00 0.00 0.00 0.00 12. 0 4 .16 4.14 0. 10 0. 13 0. 00 0.00 0.00 0.00 22. 0 4 .05 4.03 0. 20 0. 23 0. 02 0.01 0.00 0.01 26. 0 4 .00 3 .99 0. 24 0. 26 0. 04 0.01 0.00 0.02 30. 0 3 .95 3.95 0. 30 0. 30 0. 06 0.02 0.02 0.03 38. 0 3 .85 3.86 0. 34 0. 37 0. 10 0.03 0.05 0.05 42. 0 3 .80 3.82 0. 40 0. 41 0. 12 0.03 0.08 0.06 46. 0 3 .75 3.78 0. 45 0. 44 0. 15 0.04 0.10 0.07 54. 0 3 .68 3.71 0. 50 0. 50 0. 18 0.05 0.14 0.10 414 TABLE D.46 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 517 kPa , TEMP = 160 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0. 00 0.00 0. 00 0 .00 0.00 0.00 6.0 4.25 4.23 0. 02 0.05 0. 00 0 .00 0.00 0.00 12.0 4.20 4.18 0. 06 0.09 0. 00 0 .00 0.00 0.00 22.0 4.08 4.10 0. 14 0.17 0. 00 0 .01 0.00 0.01 26.0 4.05 4.07 0. 20 0.20 0. 00 0 .01 0.00 0.01 30.0 4.00 4.04 0. 22 0.23 0. 02 0 .01 0.01 0.01 38.0 3.95 3.97 0. 30 0.29 0. 04 0 .02 0.02 0.03 42.0 3.90 3.94 0. 35 0.32 0. 05 0 .03 0.04 0.04 46.0 3.86 3.91 0. 31 0.34 0. 06 0 .03 0.04 0.04 54.0 3.81 3.86 0. 40 0.40 0. 10 0 .04 0.08 0.06 TABLE D.47 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 344.7 kPa , TEMP - 160 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0. 00 0. 00 0. 00 0.00 0. 00 0.00 4.0 4.28 4.25 0. 02 0. 03 0. 00 0.00 0. 00 0.00 8.0 4.25 4.22 0. 05 0. 05 0. 00 0.00 0. 00 0.00 12.0 4.20 4.19 0. 08 0. 08 0. 00 0.00 0. 00 0.00 22.0 4.10 4.12 0. 14 0. 15 0. 00 0.01 0. 00 0.00 26.0 4.07 4.10 0. 16 0. 17 0. 00 0.01 0. 00 0.01 30.0 4.05 4.07 0. 18 0. 20 0. 00 0.01 0. 00 0.01 38.0 4.00 4.06 0. 23 0. 25 0. 02 0.02 0. 02 0.02 42.0 3.96 3.99 0. 24 0. 28 0. 04 0.02 0. 04 0.03 46.0 3.94 3.96 0. 28 0. 30 - 0. 06 0.03 0. 06 0.03 54.0 3.90 3.91 0. 30 0. 35 0. 10 0.03 0. 10 0.05 415 TABLE D.48 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 4654 kPa , TEMP = 140 C . TIME CONCENTRATION (mol/D (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4.28 0.00 0.00 0.00 0.00 0.00 0.00 4.0 4.26 4.26 0.00 0.02 0.00 0.00 0.00 0.00 8.0 4.25 4.24 0.01 0.03 0.00 0.00 0.00 0.00 12.0 4.24 4.22 0.03 0.05 0.00 0.00 0.00 0.00 20.0 4.18 4.17 0.05 0.08 0.00 0.00 0.00 0.00 24.0 4.15 4.15 0.10 0.09 0.00 0.00 0.00 0.00 28.0 4.12 4.13 0.12 0.10 0.00 0.00 0.00 0.00 36.0 4.10 4.09 0.15 0.13 0.00 0.00 0.00 0.00 40.0 4.05 4.07 0.16 0.15 0.02 0.01 0.00 0.00 44.0 4.02 4.05 0.18 0.16 0.03 0.01 0.01 0.00 54.0 3.96 4.00 0.20 0.19 0.05 0.01 0.01 0.01 TABLE D.49 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION • 4.28 M O L / L , C02 PARTIAL PRESSURE = 3964 kPa , TEMP - 160 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4.28 0.00 0. 00 0.00 0.00 0.00 0.00 4.0 4. 26 4.26 0.01 0. 02 0.00 0.00 0.00 0.00 8.0 4. 25 4.24 0.02 0. 03 0.00 0.00 0.00 0.00 12.0 4. 21 4.22 0.02 0. 04 0.00 0.00 0.00 0.00 20.0 4. 16 4.18 0.05 0. 07 0.00 0.00 0.00 0.00 24.0 4. 15 4.16 0.07 0. 09 0.00 0.00 0.00 0.00 28.0 4. 13 4.14 0.10 0. 10 0.01 0.00 0.00 0.00 36.0 4. 10 4.10 0.1 1 0. 13 0.01 0.00 0.00 0.00 40.0 4. 06 4.08 0.1 1 0. 14 0.02 0.01 0.00 0.00 44.0 4. 02 4.06 0.12 0. 15 0.02 0.01 0.00 0.00 54.0 3 . 98 4.01 0.14 0. 19 0.03 0.01 0.00 0.01 416 TABLE D.50 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 1896 kPa , TEMP = 140 C . TIME CONCENTRATION ( m o l / L ) (h) " : MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4.28 0.00 0. 00 0.00 0.00 0.00 0.00 4.0 4. 26 4.26 0.01 0. 01 0.00 0.00 0.00 0.00 8.0 4. 25 4.25 0.02 0. 03 0.00 0.00 0.00 0.00 12.0 4. 24 4.23 0.02 0. 04 0.00 0.00 0.00 0.00 20.0 4. 21 4.20 0.05 0. 06 0.00 0.00 0.00 0.00 24.0 4. 20 4.19 0.06 0. 08 0.00 0.00 0.00 0.00 28.0 4. 18 4.17 0.07 0. 09 0.00 0.00 0.00 0.00 36.0 4. 15 4.14 0.09 0. 11 0.01 0.00 0.00 0.00 40.0 4. 13 4.12 0.10 0. 13 0.01 0.00 0.00 0.00 44.0 4. 10 4.1 1 0.11 0. 14 0.02 0.01 0.00 0.00 54.0 4. 05 4.07 0.11 0. 17 0.02 0.01 0.01 0.01 TABLE D.51 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 1206 k P a , TEMP = 140 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4. 28 4. 28 0.00 0. 00 0.00 0 .00 0.00 0 .00 4 .0 4. 28 4. 27 0.01 0. 01 0.00 0 .00 0.00 0 .00 8.0 4. 26 4. 25 0.02 0. 02 0.00 0 .00 0.00 0 .00 12.0 4. 25 4. 24 0.02 0. 03 0.00 0 .00 0.00 0 .00 22.0 4. 22 4. 21 0.05 0. 06 0.00 0 .00 0.00 0 .00 26.0 4. 20 4. 19 0.05 0. 07 0.00 0 .00 0.00 0 .00 30.0 4. 18 4. 18 0.06 0. 08 0.01 0 .00 0.00 0 .00 38.0 4. 16 4. 15 0.07 0. 11 0.01 0 .00 0.00 0 .00 42.0 4. 15 4. 14 0.09 0. 12 0.01 0 .00 0.00 0 .00 46.0 4. 12 4. 13 0.11 0. 13 0.02 0 .01 0.00 0 .00 54.0 4. 11 4. 10 0.12 0. 15 0.02 0 .01 0.00 0 .01 417 TABLE D.52 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4 . 2 8 M O L / L , C02 PARTIAL PRESSURE = 517 kPa , TEMP = 140 C . TIME CONCENTRATION (mol/D (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.28 4. 28 0.00 0. 00 0.00 0. 00 0.00 0.00 4.0 4.28 4. 27 0.00 0. 01 0.00 0. 00 0.00 0.00 8.0 4 .27 4. 26 0.00 0. 02 0.00 0. 00 0.00 0.00 10.0 4 .26 4. 26 0.01 0. 02 0.00 0. 00 0.00 0.00 20.0 4.24 4. 23 0.02 0. 04 0.00 0. 00 0.00 0.00 24.0 4.23 4. 22 0.03 0. 05 0.00 0. 00 0.00 0.00 28.0 4.22 4. 21 0.05 0. 06 0.00 0. 00 0.00 0.00 36.0 4.20 4. 19 0.06 0. 08 0.01 0. 00 0.00 0.00 40.0 4 .19 4. 18 0.07 0. 09 0.01 0. 00 0.00 0.00 44.0 4.18 4. 17 0.08 0. 10 0.01 0. 00 0.00 0.00 54.0 4 .15 4. 15 0.10 0. 12 0.02 0. 01 0.00 0.00 TABLE D.53 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 4.28 M O L / L , C02 PARTIAL PRESSURE = 344.7 kPa , TEMP = 140 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA DMAE EG TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 4.28 4.28 0.00 0. 00 0.00 0.00 0. 00 0.00 4. 0 4 .28 4.27 0.00 0. 01 0.00 0.00 0. 00 0.00 8. 0 4 .27 4.26 0.00 0. 02 0.00 0.00 0. 00 0.00 10. 0 4 .27 4.26 0.01 0. 02 0.00 0.00 0. 00 0.00 20. 0 4 .25 4.24 0.01 0. 04 0.00 0.00 0. 00 0.00 24. 0 4.24 4.23 0.02 0. 05 0.00 0.00 0. 00 0.00 28. 0 4.23 4.22 0.02 0. 05 0.00 0.00 0. 00 0.00 36. 0 4.22 4.20 0.03 0. 07 0.00 0.00 0. 00 0.00 40. 0 4.21 4.20 0.04 0. 08 0.00 0.00 0. 00 0.00 44. 0 4.20 4.19 0.06 0. 09 0.01 0.00 0. 00 0.00 54. 0 4.20 4.17 0.09 0. 10 0.01 0.01 0. 00 0.00 418 TABLE D.54 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 6 . 0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 6. 00 6. 00 0. 00 0. 00 0.00 0 .00 0.00 0.00 2.0 5. 90 5. 87 0. 00 0. 00 0.06 0 . 11 0.00 0.00 4.0 5. 78 5. 75 0. 00 0. 00 0.15 0 .21 0.00 0.00 8.0 5. 55 5. 51 0. 00 0. 00 0.34 0 .41 0.00 0.00 16.0 5. 10 5. 08 0. 02 0. 01 0.65 0 .72 0.00 0.00 20.0 4. 90 4. 89 0. 02 0. 01 0.75 0 .83 0.00 0.00 24.0 4. 73 4. 70 0. 04 0. 02 0.86 0 .93 0.00 0.00 34.0 4. 30 4. 29 0. 10 0. 05 0.95 1 .08 0.00 0.00 38.0 4. 16 4. 14 0. 12 0. 07 1 .00 1 . 11 0.00 0.00 42.0 4. 01 3. 99 0. 15 0. 09 0.98 1 .13 0.00 0.01 50.0 3. 75 3. 73 0. 18 0. 13 0.96 1 .14 0.01 0.01 54.0 3. 62 3. 61 0. 19 0. 16 0.94 1 .14 0.01 0.02 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0. 00 0. 00 0 .00 0.00 0.00 0. 00 0.00 0. 00 2.0 0. 00 0. 00 0 .00 0.00 0.00 0. 00 0.00 0. 00 4.0 0. 00 0. 01 0 .00 0.00 0.00 0. 00 0.00 0. 01 8.0 0. 02 0. 02 0 .00 0.01 0.00 0. 00 0.05 0. 05 16.0 0. 05 0. 08 0 .01 0.02 0.00 0. 01 0.12 0. 23 20.0 0. 10 0. 1 1 0 .02 0.03 0.01 0. 03 0.19 0. 33 24.0 0. 15 0. 14 0 .02 0.04 0.02 0. 05 0.25 0. 42 34.0 0. 22 0. 24 0 .03 0.05 0.08 0. 13 0.36 0. 56 38.0 0. 30 0. 29 0 .04 0.06 0.10 0. 16 0.40 0. 59 42.0 0. 35 0. 34 0 .05 0.06 0.12 0. 19 0.40 0. 61 50.0 0. 43 0. 44 0 .05 0.07 0.20 0. 25 0.40 0. 60 54.0 0. 52 0. 50 0 .05 0.07 0.22 0. 27 0.40 0. 59 419 TABLE D.55 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION - 5.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION (mol /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 5.00 5 .00 0.00 0.00 0.00 0.00 0. 00 0.00 2.0 4.80 4 .77 0.00 0.00 0.15 0.21 0. 00 0.00 4.0 4.60 4 .56 0.00 0.00 0.32 0.40 0. 00 0.00 8.0 4.22 4 .18 0.00 0.00 0.65 0.73 0. 00 0.00 16.0 3.56 3 .54 0.02 0.02 1 .03 1.16 0. 00 0.00 20.0 3.30 3 .28 0.05 0.03 1 .00 1.29 0. 00 0.00 24.0 3.05 3 .04 0.08 0.05 0.97 1.36 0. 00 0.00 34.0 2.55 2 .56 0.15 0.1 1 0.95 1.42 0. 00 0.01 38.0 2.40 2 .39 0.19 0.15 0.92 1.41 0. 01 0.02 42.0 2.24 2 .25 0.20 0.19 0.88 1.39 0. 01 0.03 50.0 2.00 1 .99 0.25 0.27 0.80 1.33 0. 03 0.05 54.0 1 .85 1 .88 0.27 0.32 0.78 1.29 0. 04 0.07 TIME CONCENTRATION (mol /L) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0.0 0.00 0. 00 0. 00 0.00 0.00 0.00 0 .00 0.00 2.0 0.00 0. 00 0. 00 0.00 0.00 0.00 0 .00 0.00 4.0 0.00 0. 01 0. 00 0.00 0.00 0.00 0 .00 0.03 8.0 0.02 0. 04 0. 00 0.01 0.00 0.00 0 .05 0.16 16.0 0.09 0. 13 0. 02 0.03 0.02 0.05 0 .32 0.54 20.0 0.15 0. 18 0. 03 0.04 0.06 0.10 0 .45 0.70 24.0 0.22 0. 23 0. 04 0.05 0.10 0.15 0 .57 0.80 34.0 0.36 0. 38 0. 05 0.06 0.21 0.27 0 .60 0.90 38.0 0.42 0. 45 0. 06 0.07 0.24 0.30 0 .62 0.89 42.0 0.51 0. 53 0. 07 0.07 0.31 0.33 0 .58 0.86 50.0 0.65 0. 69 0. 08 0.07 0.37 0.36 0 .55 0.78 54.0 0.70 0. 78 0. 08 0.07 0.43 0.36 0 .48 0.74 420 TABLE D.56 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION - 4.0 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION ( m o l / L ) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 4.00 4.00 0.00 0.00 0.00 0 .00 0.00 0.00 2.0 3.74 3.71 0.00 0.00 0.18 0 .27 0.00 0.00 4.0 3.50 3.46 0.00 0.00 0.45 0 .51 0.00 0.00 8.0 3.05 3.02 0.00 0.00 0.76 0 .88 0.00 0.00 18.0 2.25 2.23 0.05 0.03 0.98 1 .36 0.00 0.00 22.0 2.02 2.00 0.13 0.05 1 .24 1 .42 0.00 0.00 26.0 1 .84 1 .80 0.16 0.07 1.18 1 .44 0.00 0.01 36.0 1 .45 1 .42 0.23 0.15 0.96 1 .40 0.01 0.02 40.0 1 .35 1 .30 0.25 0.19 0.94 1 .36 0.01 0.03 44.0 1 .23 1 .20 0.28 0.23 0.91 1 .31 0.02 0.04 54.0 1.01 0.99 0.35 0.34 0.88 1 .20 0.04 0.08 TIME CONCENTRATION ( m o l / L ) (h) EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0 .0 0.00 0.00 0.00 0.00 0.00 0. 00 0. 00 0.00 2 .0 0.00 0.00 0.00 0.00 0.00 0. 00 0. 00 0.00 4 .0 0.00 0.02 0.00 0.00 0.00 0. 00 0. 01 0.05 8 .0 0.02 0.05 0.00 0.01 0.00 0. 01 0. 10 0.24 18 .0 0.15 0.17 0.02 0.04 0.05 0. 1 1 0. 50 0.76 22 .0 0.23 0.23 0.03 0.05 0.10 0. 16 0. 60 0.87 26 .0 0.30 0.29 0.04 0.06 0.15 0. 22 0. 73 0.93 36 .0 0.48 0.46 0.06 0.06 0.24 0. 30 0. 68 0.91 40 .0 0.58 0.54 0.07 0.07 0.30 0. 32 0. 65 0.87 44 .0 0.63 0.62 0.08 0.08 0.35 0. 33 0. 50 0.82 54 .0 0.78 0.83 0.10 0.07 0.42 0. 35 0. 45 0.67 421 TABLE D.57 COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED CONCENTRATIONS. MDEA CONCENTRATION = 3.00 M O L / L , C02 PARTIAL PRESSURE = 2585 kPa , TEMP = 200 C . TIME CONCENTRATION (mo l /L) (h) MDEA BHEP DMAE DMP EXP CALC EXP CALC EXP CALC EXP CALC 0.0 3.00 3.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 2.80 2.78 0.00 0.00 0.15 0.21 0.00 0.00 4.0 2.62 2.59 0.00 0.00 0.30 0.39 0.00 0.00 8.0 2.28 2.25 0.00 0.00 0.55 0.68 0.00 0.00 16.0 1 .76 1 .75 0.04 0.01 0.96 1 .03 0.00 0.00 20.0 1 .60 1 .57 0.06 0.03 1 .05 1.12 0.00 0.00 24.0 1 .40 1 .41 0.09 0.04 1 .00 1.17 0.00 0.00 32.0 1.17 1.15 0.12 0.07 0.94 1.18 0.00 0.01 40.0 1 .00 0.96 0.20 0.12 0.90 1.15 0.00 0.01 44.0 0.91 0.88- 0.22 0.14 0.85 1.12 0.01 0.02 46.0 0.80 0.85 0.23 0.16 0.82 1.10 0.01 0.02 54.0 0.71 0.73 0.28 0.21 0.80 1 .03 0.02 0.04 TIME CONCENTRATION (mo l /L) (h) : EG HEOD HMP TEA EXP CALC EXP CALC EXP CALC EXP CALC 0. 0 0. 00 0.00 0.00 0.00 0. 00 0.00 0 .00 0.00 2. 0 0. 00 0.00 0.00 0.00 0. 00 0.00 0 .00 0.00 4. 0 0. 00 0.01 0.00 0.00 0. 00 0.00 0 .01 0.03 8. 0 0. 02 0.04 0.00 0.01 0. 00 0.00 0 .08 0.15 16. 0 0. 10 0.12 0.01 0.03 0. 01 0.04 0 .40 0.46 20. 0 0. 15 0.16 0.02 0.04 0. 05 0.08 0 .43 0.58 24. 0 0. 20 0.20 0.03 0.05 0. 10 0.12 0 .45 0.65 36. 0 0. 31 0.35 0.05 0.06 0. 15 0.22 0 .50 0.69 40. 0 0. 45 0.41 0.06 0.06 0. 20 0.24 0 .42 0.67 44. 0 0. 49 0.47 0.06 0.06 0. 26 0.25 0 .40 0.63 46. 0 0. 55 0.50 0.07 0.06 0. 27 0.26 0 .38 0.61 54. 0 0. 72 0.62 0.08 0.07, 0. 25 0.27 0 .33 0.52 

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