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DEA degradation in heat exchanger tubes Chakma, Amitabha 1984

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DEA  DEGRADATION  IN  HEAT EXCHANGER  TUBES  by  \  A M I T A B H A CHAKMA Dipl.Ing.,  A  THESIS THE  Algerian  SUBMITTED  Petroleum  IN  REQUIREMENTS MASTER  Institute,  PARTIAL  FULFILMENT  FOR T H E D E G R E E  OF A P P L I E D  OF  SCIENCE  in THE  F A C U L T Y OF G R A D U A T E  Department  We  accept to  THE  Of  Chemical  this  thesis  the  required  UNIVERSITY  OF  June  ©  Amitabha  STUDIES  Engineering  as  conforming  standard  BRITISH  COLUMBIA  1984  Chakma,  1984  1982  OF  In p r e s e n t i n g requirements  this thesis f o r an  of  British  it  freely available  agree that for  understood that for  Library  shall  for reference  and  study.  I  f o r extensive copying of  h i s or  her  copying or  f i n a n c i a l gain  be  shall  g r a n t e d by  not  be  of  The U n i v e r s i t y o f B r i t i s h 1956 Main Mall V a n c o u v e r , Canada V6T 1Y3  Date  of  Columbia  make  further this  thesis  head o f  this  my  It is thesis  a l l o w e d w i t h o u t my  permission.  Department  the  representatives. publication  the  University  the  p u r p o s e s may by  the  I agree that  permission  department or  f u l f i l m e n t of  advanced degree a t  Columbia,  scholarly  in partial  written  ABSTRACT  Aqueous acid  diethanolamine  gases  refinery  such  Degradation also  lead  and  in  Carefully  mm  in a  OD a n d 4 . 8  heat to  out  transfer  4137  solution  The  flow  temperature, decrease severe  fouling foaming  is  heat heated  a  to  between  degradation  complex  process  C02  and  compounds. DEA, but  may  foaming  and  and depends  solution  degradation  by means  on  flow  rate  experiments  were  flow  of  constant  to  200  to  m/s  3.175  temperature  covered  ° C , 20  (3.4  was  rate.  the  DEA  are:  1379  40 wt%  to  DEA  5.3  m/s)  to  increase  with  concentration  Degradation tube.  solutions  degradation i i  found  and  exchanger  of  of  a  mm I D ,  60 ° C .  rate  the heat  (2.032  L/s  pressure  solution  tendency  at  tube  conditions  60  0.0172  measured  the concentration  occur  composition,  pressure,  L/s  with  and  corrosion,  The o p e r a t i n g  as  absorption  as  exchanger  well  desired  such  degradation  of  as  as  problems  C02 partial  with  well  gas  temperature.  m long)  DEA  of  valuable  coiled  rate  removal  of  DEA  and 0.011  the  loss  raw g a s  kPa C 0 2 p a r t i a l  solutions  of  controlled  fluid.  for  a  degradation  importantly)  the  reactions  represents  concentration,  (most  side  used  natural  to  formation  operational  DEA  carried  some  widely  from  addition  the  not only  to  fouling. solution  In  reactions,  resulting  is  C 0 2 and H 2 S  gases.  desorption DEA  as  ("DEA")  The  were  products.  resulted viscosity  found  to  and in as  increase  The of  following  simple  DEA d e g r a d a t i o n  in  mathematical  heat  exchangers  +  rate  constants  loss  tests  found  to  be  k,,  k2  and  k3  11 . 9 2 4  -  ln(k2)  =  8.450  -  5580/T  ln(k3)  =  39.813  -  15160/T  corrosion  were  as  out  and  towards  components.  steel  analysis.  by  Minor  HEOD  given  (  by  prediction :  '  .  '  of  as  the  3-  one  AISI-SAE  electron  were  steel.  identified  in  weight  DEA s o l u t i o n s  pitting  noticed  :  C02  carbon  was  by  +  conventional  1020  detected also  as  degraded  "HEOD")  Severe  was  well  AISI-SAE  was  pitting  BHEP  6421/T  studies  carried  corrosive  corrosive  carbon  are  =  (hydroxyethyl)-2-oxazolidone the  developed  •  ln(k, )  Potentiodynamic  the  C02 THEED  The  was  for  HEOD  ^ Y y ^ , DEA  model  of 1020  micrographic  case  of  BHEP  and DEA.  Use both  of  found  products. was  activated to  be  carbon  incapable  A purification  developed  and  filters  found  of  method to  be  and  conversion  presence  of  other  of  HEOD  degradation  to  consisting effective  DEA  ash  removing  N,N,N-tris-(hydroxyethyl)ethylenediamine However,  soda  major of  in  NaOH  ("THEED")  were  degradation  converting  apparently  compounds.  treatment  back  depends  injection HEOD  and  to DEA. on  the  TABLE  ABSTRACT  OF CONTENTS  .  LIST  OF T A B L E S  LIST  OF F I G U R E S  .  i i ..  viii x  ACKNOWLEDGEMENTS  xiv  Chapter 1  2  INTRODUCTION  1  1.1  T h e DEA p r o c e s s  2  1.2  DEA d e g r a d a t i o n  5  1.3  Objectives  LITERATURE  present  7  8  A b s o r p t i o n of  2.2  DEA d e g r a d a t i o n  2.3  study  REVIEW  2.1  2.2.1  3  of  Other  C02  i n DEA  8 10  degradation  products  C o r r o s i o n i n DEA s o l u t i o n s 2.3.1 . C o r r o s i v i t y of DEA products  2.4  Role  of  2.5  Fouling  2.6  Analysis  EXPERIMENTAL DESCRIPTION  heat of of  exchanger  heat  14  degradation  variables  17 22  exchangers  23  DEA s o l u t i o n s  EQUIPMENT  15  24  AND  PROCESS. 28  3.1  Equipment d e s i g n  28  3.2  Process  38  3.3  Equipment d e s c r i p t i o n  32  3.3.1 3.3.2  32 33  description  Autoclave Heat exchanger i v  3.3.3 3.3.4 3.3.5 3.3.6 3.3.7 3.3.8 3.4  S o l u t i o n pump Water c o o l e r Flow meter Temperature c o n t r o l l e r Temperature measurements Vapor recovery system  System  preparation  3.5 S y s t e m 3.6 S t a r t  4  37  loading  .37  up  ANALYTICAL 4.1  34 34 34 36 36 36  39  PROCEDURE  42  C a l i b r a t i o n o f Gas C h r o m a t o g r a p h  4.2 O p e r a t i n g  conditions  42  4.3 E r r o r s  5  CORROSION 5.1  46  STUDIES  of c o r r o s i o n  5.3 E x p e r i m e n t a l  7  47  P r i n c i p l e s of potentiodynamic  5.2 C a l c u l a t i o n  6  .42  technique  current  procedure  47 51 54  MISCELLANEOUS TESTS  55  6.1  V i s c o s i t y measurements  55  6.2  Foaming  tests  57  MODEL DEVELOPMENT  59  7.1  Heat e x c h a n g e r model 7.1.1 Temperature p r o f i l e determination 7.1.2 DEA t r a n s p o r t p r o p e r t i e s 7.1.3 H e a t t r a n s f e r f l u i d p r o p e r t i e s 7.1.4 T h e r m a l conductivity of 316 stainless steel 7.1.5 P r e s s u r e d r o p d e t e r m i n a t i o n 7.1.6 F i l m t h i c k n e s s d e t e r m i n a t i o n 7.1.7 H e a t e x c h a n g e r m o d e l p e r f o r m a n c e  v  ..59 59 67 68 72 73 74 75  7.2  8  RESULTS AND EXPERIMENTS 8.1  8.2  8.3  9  K i n e t i c model 7.2.1 Determination 7.2.2 Determination  of of  DISCUSSION  OF  DEGRADATION 84  Comparison of experimental model p r e d i c t i o n Effects of degradation 8.2.1 Effect 8.2.2 Effect 8.2.3 Effect 8.2.4 Effect  operating of of of of  Effect of viscosity  8.4  Effect foaming  8.5  Effect  77 81 83  rate constants inlet conditions  with 84  variables  on  flow r a t e .temperature solution concentration C02 p a r t i a l pressure  degradation  on  90 90 97 97 101  solution 103  of  of  data  degradation  degradation  on  on  solution  solution  pH  103 105  8 . 6 "Heat e x c h a n g e r fouling 8.6.1 E f f e c t of temperature 8.6.2 Electron microprobe analysis 8.6.3 Apparent deposit thickness  108 108 110 110  8.7  111  Experiment  RESULTS 9.1  with a  new  tube  AND D I S C U S S I O N OF CORROSION  Corrosion  rate  in  STUDIES  undegraded  DEA  solutions  116  9.2  Corrosion  rate  9.3  Effect  C02  9.4  on c o r r o s i o n Effect of corrosion  9.5  Effect  9.6  Effect products  of  of  116  in  dissolved  in  DEA s o l u t i o n s DEA  ....116  solutions 119  solution  solution of on  degraded  concentration  pH o n  individual corrosion v i  on  corrosion  120 120  degradation 121  10  9.7  Effect  9.8  Passivity  124  9.9  Pitting  125  PURIFICATION  metal  complexing  OF DEGRADED  123  DEA S O L U T I O N S  Use  of  activated  10.2  Use  of  chemicals  10.3  Removal  of  HEOD  133  10.4  Removal  of  THEED  133  10.5  Purification  10.6  NaOH  10.7  of  carbon  131  10.1  HEOD a n d  11  of  filters  131 133  industrial  treatment  of  a  sample  mixture  135  of DEA,  THEED  Soda  CONCLUSION  ash  138 treatment  138  AND RECOMMENDATIONS  142  11.1  Conclusions  142  11.2  Recommendations  145  11.3  Recommendations  for  further  work-  148  NOMENCLATURE  149  REFERENCES  153  APPENDIX A  L i s t i n g of the computer program for calculation of DEA d e g r a d a t i o n rate in heat t r a n s f e r tube  vii  the the  162  LIST  OF T A B L E S  Table 4.1  Operating conditions chromatograph '  4.2  G.C. retention compounds  major  gas  43  degradation 44  Density  7.2  Viscosity  7.3  Comparison of pressure drop  and initial runs  76  8.1  Comparison of DEA, HEOD, THEED and BHEP c o n c e n t r a t i o n s of run 1 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.190°C, heating fluid temp.250°C, flow rate 0.0124 L/s, C02 p a r t i a l p r e s s u r e 4137 kPa)  85  Comparison of DEA, HEOD, THEED and BHEP c o n c e n t r a t i o n s of run 2 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.170°C heating fluid temp.250°C, flow rate 0.0124 L/s, C02 p a r t i a l p r e s s u r e 4137 kPa)  ...85  Comparison of DEA, HEOD, THEED and BHEP c o n c e n t r a t i o n s of run 3 w i t h the theoretical model prediction • (30 wt% DEA, inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C, f l o w r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 4137 k P a )  86  Comparison of DEA, HEOD, THEED a n d BHEP c o n c e n t r a t i o n s of run 4 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.l65°C, heating fluid temp.250°C, flow rate 0.0172 L/s, C02 p a r t i a l p r e s s u r e 4137 kPa)  86  Comparison of DEA, HEOD, THEED a n d BHEP c o n c e n t r a t i o n s of run 5 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.l65°C, heating fluid temp.250°C, flow r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 4137 k P a )  87  8.3  8.4  8.5  Shell  of  the  7.1  8.2  of  time  of  of  Thermia O i l - C  Shell  69  Thermia O i l - C  outlet temperature data for d i f f e r e n t  viii  70  8.6  8.7  8.8  8.9  8.10  8.11  C o m p a r i s o n , of DEA, HEOD, THEED and BHEP c o n c e n t r a t i o n s of run 6 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.140°C, heating fluid temp.l90°C, f l o w r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 4137 k P a )  87  Comparison of DEA, HEOD, THEED a n d BHEP c o n c e n t r a t i o n s of run 7 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C, f l o w r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 2758 k P a )  88  C o m p a r i s o n of DEA, HEOD, THEED and BHEP c o n c e n t r a t i o n s of run 8 w i t h the theoretical model prediction (30 wt% DEA, inlet temp.60°C, outlet t e m p . l 9 5 ° C , heating fluid temp.250°C, f l o w r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 1379 k P a )  88  Comparison of DEA, HEOD, THEED a n d BHEP c o n c e n t r a t i o n s of run 9 w i t h the theoretical model prediction (40 wt% DEA, inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C, flow r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 41 37 k P a )  89  Comparison of DEA, HEOD, THEED and BHEP concentrations of run 10 with the t h e o r e t i c a l model p r e d i c t i o n (20 wt% D E A , inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C, f l o w r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 4137 k P a )  89  Average DEA degradation rates. temp.60°C, outlet temp.l95°C, heating temp.250°C, f l o w r a t e 0.011 L/s)  9.1  Effect  9.2  Effect rates  of of  C02  on c o r r o s i o n  DEA  (Inlet fluid  rates  concentration  101 ...119  on  corrosion 121  ix  LIST  OF F I G U R E S  Figure 1.1 1.2  Typical  flowsheet  of  Typical  flowsheet  of  areas 2.2  3.1  where  DEA p l a n t a  corrosion  DEA  3  paint  usually  for  3.3  Photograph equipment  of  overall  showing  view main  of  16  the  iron19  Flowsheet of the equipment f o r the DEA d e g r a d a t i o n i n h e a t e x c h a n g e r s Photograph  showing  occurs  Pourbaix p o t e n t i a l - p H diagram water system  3.2  3.4  a  the  study  of 29  equipment  components  of  30  the 31  C a l i b r a t i o n curve  for  the  capillary  flow  meter  35  3.5  Schematic  4.1  Chromatogram  5.1  run 3 a f t e r 192 Typical anodic important zones  5.2  diagram of  of a  the  feed  degraded  tank  DEA s a m p l e  hr polarization and t r a n s i t i o n  Typical anodic polarization the effect of environment a d d i t i o n upon the c u r v e  5.3  Cathodic corroding  polarization metal  6.1  Schematic  diagram  6.2  Schematic apparatus  diagram  of  the of  system  38  from  , plot showing points curve showing and inhibitor  diagram  for  a  viscosimeter the  foam  45 49  50  52 56  testing 58  7.1  Schematic diagram of the temperature profile a c r o s s a segment of the heat e x c h a n g e r tube  7.2  Schematic a c r o s s the  diagram of temperature metal tube w a l l  x  .62  profile 65  8.1  8.2  8.3  8.4  8.5  8.6  8.7  8.8  DEA c o n c e n t r a t i o n a s a f u n c t i o n o f a n d flow rate. (30 wt% D E A , i n l e t t e m p . 6 0 ° C , heating oil temp.250°C, C02 p a r t i a l pressure 4.14 MPa)  91  Temperature of the DEA solution as a function of the distance from the tube e n t r a n c e and flow r a t e . (30 wt% D E A , inlet temp.60°C, outlet temp.l70°C, heating oil temp. 2 5 0 ° C , C 0 2 p a r t i a l p r e s s u r e 4 . 1 4 MPa)  94  DEA c o n c e n t r a t i o n a s a f u n c t i o n o f t i m e and flow rate. (30 wt% D E A , i n l e t temp.60°C, outlet t e m p . 1 7 0 ° C , C02 p a r t i a l pressure 4.14 MPa)  95  Theoretical model prediction of DEA c o n c e n t r a t i o n as a f u n c t i o n of time and flow rate (single pass). (30 wt% DEA, i n l e t temp.60°C, outlet temp.l70°C, C02 partial p r e s s u r e 4 . 1 4 MPa)  96  Theoretical model prediction of the film t h i c k n e s s as a f u n c t i o n of the d i s t a n c e from • the tube e n t r a n c e and flow rate. (30 wt% DEA, inlet temp.60°C, outlet temp.170°C, C02 p a r t i a l p r e s s u r e 4 . 1 4 MPa)  97  DEA c o n c e n t r a t i o n a s a f u n c t i o n o f t i m e a n d heating f l u i d temperature. (30 wt% D E A , inlet temp.60°C, flow r a t e 0.011 L/s, C02 p a r t i a l p r e s s u r e 4 . 1 4 MPa)  99  DEA c o n c e n t r a t i o n a s a f u n c t i o n o f t i m e and initial DEA concentration. (Inlet temp.60°C, outlet temp.l95°C, flow rate 0.011 L / s , C 0 2 p a r t i a l p r e s s u r e 4 . 1 4 MPa)  100  DEA c o n c e n t r a t i o n as a f u n c t i o n of time and C02 partial pressure (30 wt% DEA, inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C,)  102  8.9  S o l u t i o n v i s c o s i t y as a f u n c t i o n of degradation product concentration  104  8.10  T y p i c a l pH c h a n g e o f p a r t i a l l y d e g r a d e d DEA solution a s a f u n c t i o n o f t i m e (30 wt% D E A , inlet temp.60°C, outlet temp.l95°C, heating fluid temp.250°C, flow r a t e 0.011 L/s)  xi  time  and  107  8.11  8.12  8.13  8.14  8.15  9.1  9.2  9.3  9.4  9.5  9.6  Pressure drop as a function heating fluid temp. (30 wt% temp.60°C, f l o w r a t e 0.011 L/s)  of time and DEA, inlet  Electron micrographic . photos of u n c o n t a m i n a t e d and c o n t a m i n a t e d s u r f a c e s t h e h e a t e x c h a n g e r t u b e (20 x )  the of  109  112  Electron micrographic p h o t o s of the fouled s u r f a c e of the heat exchanger tube (20 x) and a magnified view ( 4 0 0 x ) o f t h e same surface  113  Electron microprobe plots uncontaminated and c o n t a m i n a t e d the heat exchanger tube  114  of the s u r f a c e s of  Apparent deposit t h i c k n e s s as a f u n c t i o n of time and heating f l u i d temperature (30 wt% DEA, i n l e t t e m p . 6 0 ° C , f l o w r a t e 0.011 L/s)  115  P o t e n t i o d y n a m i c a n o d i c p o l a r i z a t i o n c u r v e of 30 wt% u n d e g r a d e d DEA s o l u t i o n ( t e m p . 25°C)  ....117  Potentiodynamic anodic p o l a r i z a t i o n 30 wt% partially degraded DEA containing 8.7 wt% degradation (temp. 25°C) • E l e c t r o n micrographic photo AISI 1020 c a r b o n s t e e l t e s t  c u r v e of solution products  118  o f an u n c o r r o d e d c o u p o n ( 4 0 0 x)  126  Electron micrographic photo of AISI 1020 carbon steel test coupon after 120 h r . i m m e r s i o n i n 15 wt% DEA solution at 100°C (400x)  127  Electron micrographic photo of AISI 1020 carbon s t e e l test coupon after 120 hr. immersion in 15 wt% BHEP s o l u t i o n a t 100°C (400x)  128  Electron micrographic photo of AISI 1020 carbon steel test coupon after 120 h r . i m m e r s i o n i n 15 wt% HEOD s o l u t i o n at 100°C (400x)  .129  9.7  10.1  10.2  10.3  10.4  10.5  E l e c t r o n m i c r o g r a p h i c p h o t o of a p i t a r e a of A I S I 1020 c a r b o n s t e e l c o u p o n a f t e r 120 h r . immersion in 15 wt% HEOD s o l u t i o n a t 100°C (2000x)  130  Chromatograms of partially degraded DEA samples t a k e n u p s t r e a m a n d d o w n s t r e a m o f an a c t i v a t e d carbon f i l t e r located in a gas plant in Alberta  132  Chromatograms of a p a r t i a l l y d e g r a d e d DEA sample of run 3 before and after NaOH treatment  136  Chromatograms of a p a r t i a l l y d e g r a d e d DEA sample from a gas processing plant before a n d a f t e r NaOH t r e a t m e n t  137  Chromatograms o f l a b o r a t o r y made 30 wt% D E A , 12 wt% HEOD and 8 b e f o r e a n d a f t e r NaOH t r e a t m e n t  139  Chromatograms of sample from a gas and a f t e r soda a s h  m i x t u r e of wt% THEED  a p a r t i a l l y d e g r a d e d DEA processing . plant before treatment  xi i i  141  1  CHAPTER 1  INTRODUCTION  Natural  gas  saturated  produced with  dioxide  and/or  must  removed  and  be  problems  water  from use  pipelines  upon  subsequent  Water gas  to  use.  hydrate  minimise  The degree  according  to  aqueous  diethanolamine  the  amine  process  group,  was d e v e l o p e d  to  remove  gases  (C02  pressure  natural  processes  were  proscessors natural  using  sweetening  processes  thirties,  the  of  one k i n d  The  very  have  majority  of  of  carbon  acid  gases  transportation  formation health  of  H2S)  ,  prevent  and p o l l u t i o n  removal  only of  from many  choice  (removal  solvents.  been  its  of  these  belongs  [1,2]  in  volume,  years,  the  acid  Although since  processing  to  1930  high  available  of  developed  the gas  which  by B o t t o m s  For  the  chemical  high amine  to  gases  gas  from)  n u m e r o u s new the  plants  nineteen use  amines  another.  DEA s w e e t e n i n g  sweetening only  or  and  the sweetening  and  (DEA) p r o c e s s ,  streams.  virtually  for  gas  gas  usually  end u s e .  The  acid  to  is  contains  vapor  prior  to avoid  and  formations  frequently  sulphide.  in order  varies  and  the natural  in  constituents  geological  vapor  hydrogen  subsequent  corrosion  from  refinery  slowly  with  process  has  long  or manufactured  carbon  disulphide  been gases and  favoured  for  the  because  DEA r e a c t s  carbonyl  sulphide,  2  i.e.  typical  contaminants  However, popular been to  1.  with  in  natural  converted  the  to  following  Low  solvents;  2.  Low  solvent  3.  Less  corrosion.  4.  Low  rate  reactions  is  due  are  1.1  shown  through and  to  increasingly plants be  have  attributed  and  lower,  with  specific  most heat  H2S.  vapor  a  compared  pressure  result  of  of DEA.  irreversible  side  the  0.15  encountered  to  pipeline  DEA p r o c e s s  is  grains  per  100  to  SCF)  reducing  specifications,  claimed  concentration  with  to  about  be 1.15  able to  the to 3.45  [10].  T h e DEA P r o c e s s  A typical is  as  concentration  sulphide  (0.05  lower  DEA's  sometimes  reduce  m3  can  gases.  C02.  of  hydrogen  C02  degradation  SNPA m o d i f i c a t i o n  mg/std  to  to  sulphide  MEA  popularity  due  loss  difficulties  hydrogen  many  regeneration  with  with  become  for  reaction  of  also  and  DEA's  manufactured  :  this  heat  or  DEA h a s  processors  DEA [ 3 - 9 ] .  and  Although  gas  requirement,  of  refinery  years,  factors  energy  other  recent  of  an  solid  in  flow  sheet  Figure  inlet  1.1.  separator  particulates  of  are  an  industrial  The where  raw  sour  entrained  removed.  DEA gas  sweetening enters  hydrocarbon  unit  the  unit  liquids  SWEET  GAS  0-H  CONDENSER  ACID  GASES  ABSORBER  F E E D GAS  REBOILER  Figure  1.1  Typical  flow  sheet  of  a  DEA  plant  4  The  gas  against are  then a  enters  the bottom  counter-current  absorbed  with  water  is  sent  to a  The bottom  rich  of  then  solution  then  DEA  entry  are  the the  down  into  upstream  the s t r i p p e r ,  in of  the  steam,  lean  gases  which  is  the absorber  and  some  top tray  of  counter  reboiler. removes  of  from  lean-rich  the heat  DEA s o l u t i o n . In  of  the  hydrocarbons  a  gas,  the  column.  the pressure  downward a g a i n s t  The a c i d  C 0 2 and H 2 S flows  through  stripper  on t h e  upward  unit.  by t h e h o t ,  the absorbed  flashed  mainly  are  some  It  cases  lean-rich desorbed  heat  from  the  the  rich  DEA s t r e a m .  of  the  absorbed  the column. current  flow  The of  The s t r i p p i n g  the a c i d  gases  from  a  acid  solution stripping  vapor,which the  rich  where  most  solution.  The of  the  DEA.  the top of  containing  heated  and flows  The sweetened  leaves  installed  generated  consists  is  by l e t t i n g  flows  vapor  is  where  Upon gases  it  aqueous  and passes  the t o p of  tank  exchanger,  of  dehydration  DEA s o l u t i o n  where  enters  flash  vapour,  the absorber  exchanger  stream  the absorber  b y t h e DEA s o l u t i o n .  saturated usually  of  overhead  t h e steam  is  condensate top of  The exchanges exchanger  the  lean  products  condensed. in a  pass  The a c i d  separator  stripper  reflux.  DEA s o l u t i o n  leaving  with  and then  the  passes  a condenser  gases  are  and the condensate  as  heat  through  rich through  the bottom solution a  cooler,  of  i n the where  separated is  from  returned  the  stripper,  lean-rich it  to  is  heat  cooled  5  to  the  stream  operating of  lean  activated  1.2  DEA  carbon  spite  react  of  Most  to  degradation  on  raw  to  the  is  absorber.  usually  prevent  gas  DEA's  supposed  carbon  dioxide  plant  but  represents  a  the  increases  absorber  and  compounds  are  Plant  of  loss  degradation  of  the  A small  passed  b u i l d - u p of  the  side  through  an  contaminants.  limited filters  are  along  can  filters  are  believed with  laboratory  compounds  not  from  in  try  be  of  to  some  process  variables  be  the  such  in  able  the  degradation  in to  absorb  removing  DEA some  [13,15,16]. that  any  solutions  DEA  solution Unlike  economically.  most  indicated  as  of  etc.  reclaimed  have  degraded  equipment  solution of  it  accumulation  minimise degradation  tests  partially  because  [11-14].  contaminants  of  of  the  other  capable  DEA d u e  depending  only  because  fouling  installed  to  of  varies  pressure not  undesireable loss  not  also  corrosive  operating  DEA  some  DEA  operation.  DEA, but  temperature,  carbon  are  be  degradation,  some  degradation  tendency  usually  changing  form  Furthermore,  to  to  undesireable  results  foaming  monoethanolamine,  compounds  is  to  of  plant  valuable  believed  by  and  DEA  stripper.  concentration,  plants  and  resistance  experience  severity  compounds  operators  solutions  Activated  operators  composition  Degradation  and  solution  filter  with  products.  of  of  DEA D e g r a d a t i o n  In can  temperature  sweetening degradation However,  activated  major [17].  carbon  degradation  6  The  strong  been o b s e r v e d laboratory expected  temperature  in i n d u s t r i a l  studies to  temperatures  such  as  bulk  in  the  solution  control.  In  design  The  fluid  greatest  the  adjacent  lean-rich  and  temperature  to the heat  transfer  i n c r e a s e and  t h e h e a t i n g medium but  temperature  No  temperature  i n t h e DEA  information  degradation important  skin  In a d d i t i o n ,  profile  is presently  r a t e on DEA  have  the  some  degradation  the  available. over  control,  the  i n heat important  units.  Usually,  used  for  process as  well  importance.  surface experiences  the  depends not also  flow  on  rate  only  the  flow  on  the  r a t e of  determines  the  solution.  concerning  operating variable  operators  and  i s t h e r e f o r e most s u s c e p t i b l e  temperature  solution.  and  is  most  i s of g r e a t e s t  The  t h e DEA  the  by  at e l e v a t e d  degradation  o p e r a t i o n of DEA  to d e g r a d a t i o n . of  DEA  exchanger  minimise  a r e measured  of  operated  heat  has  been c o n f i r m e d  the p o i n t of view of d e g r a d a t i o n  skin  temperature  to  degradation  degradation  i s c o n s i d e r e d t o be  However, from  corrosion,  has  equipment  order  temperatures  as  in  the  temperature  variable  Therefore,  mostly  stripper-reboiler. exchangers,  o p e r a t i o n s and  [17].  occur  dependence of DEA  effect  flow  which d e s i g n e r s as w e l l as  the  of  rate  DEA an  study  flow  r a t e on is  the  Since  of  the e f f e c t  i s of c o n s i d e r a b l e i n d u s t r i a l  of  flow  interest.  7  1.3  Objectives  of  present  The  objectives  of  this  1.  and 2.  simulate  controlled  the  simple  degradation  obtained Study  the  • corrosion  The  may be  summarized as  DEA  conditions  in  follows:  degradation  industrial  experiments  heat  exchangers  reboilers;  Develop a of  3.  study  Perform c a r e f u l l y which  study  present  in  of  work  DEA i n  previous  effect of  mathematical  mild  is  of  heat  model  exchangers  batch-wise DEA a n d  which  its  predicts using  the  rate  kinetic  data  experiments; degradation  products  steel.  restricted  to  C02  as  the  acid  gas.  on  the  8  CHAPTER  LITERATURE  Several have  been  process,  conventional and  In  25],  Book"  2.1  The  performance  [18-21].'  which  which  REVIEW  uses  of  DEA  sweetening  T h e SNPA m o d i f i c a t i o n higher  concentrations  processes,  has  been  text  books  of of  units t h e DEA  DEA t h a n  reported  by  [10].  there  review  are  natural-gas  analytical  solutions  are  several  methods  described  in  processing for the  in  handbooks  general  routine "Gas  and  [2 2  analysis  of  Conditioning  gas Fact  [26].  ABSORPTION  chemistry  fairly C02-DEA [40]  Dailey  Various  treating  the  DEA s w e e t e n i n g  addition,  available  on  published  sweetening  Wendt  papers  2  complex  OF CARBON D I O X I D E  of  C02  and  not  reactions  is  p r o v i d i n g an  IN DEA  reactions yet  fully  extensive  excellent  with  aqueous  understood. [27-39],  recent  review.  with  DEA s o l u t i o n s  The  literature  Blauwhoff  et  is on al.  9  The  C0 -DEA  overall  following  2  =s=as.  (R NH ) C0  + H 0  + C0  2  equilibrium  temperature  2  2  3  2  represented  by  the  (R NH ) C0 2  2  2  [2.1]  3  2R NH HC0  2  2  2  3  [2.2]  f o r - C H„OH. 2  o f t h e above  and high pressure  pressure.  be  :  + C0  Where, R s t a n d s  operated  can  2R NH + H 0 2  low  [3]  equations  2  The  reactions  2  For  reactions lies and l e f t  this  reason,  a t low temperature  and high  to the right  at high industrial  pressure.  a t low  temperature  and  absorbers  are  10  2.2  DEA DEGRADATION  Besides  the  irreversible  side  compounds;  In  the  his  sweetening, Bottoms stable their  reactions  latter  which  indication  amine  of  well  is  composition;  amine  first  published  by  consisted  bases  amine  for  gas  processes,  ( i n c l u d i n g D E A ) , were the  heated  was  complex Nonhebel depends  pure  compounds  above  probably  the  phenomenon. [14] on  concentration,  comprehensive  saturating  stainless to  a  inside  psi).  partially  This  Polderman and  of  autoclave  600  of  However,when were  compounds."  nitrogen  ethanolamines  undesireable  150°C, first  or some  reported  Smith and Younger  have  reported  temperature,  solution  that  pressure,  pH a n d  the  gas  presence  ions.  The  pressure  a  as  apparently  a  discovery  in  certain  degradation.  degradation  inside  result  "degradation  the  that  reactions,  and  on o r g a n i c  noticed.  degradation as  occur  work  solutions  was  metal  may  temperatures.  decomposition  of  absorption  termed  to  observed  low  [7,13,18]  are  led  aqueous  DEA  C02  exploratory  [2] at  main  steel  After degraded  distillation  and  Steele a  25  vessel 8 hr  the  DEA in  degradation  1956.  wt% DEA s o l u t i o n  ranging  varied  from  autoclave  solutions  on  [12]  autoclave,  temperature the  work  were  crystallization.  sealing from 1257 was  with and  100 to  to  4137  cooled  analysed  Their  to by  C02  was work  at  25°C  heating  the  175°C.  The  kPa 25°C  (180  to  and  the  fractional  11  DEA and  losses 4137  ranged  kPa.  from  They  ("BHEP")  as  a  reaction  scheme  0% a t  100°C  identified  degradation for  its  and  1257  N,N-bis  compound and  kPa  to  97% a t  (hydroxyethyl) postulated  175°C  piperazine  the  following  formation:  0 HO-C2Ha  II  \  / N-H  + C02  HO-C2Ha  5»  -  HO-C2H„ "DEA"  C  \  N  0  + H20  CH2  CH2  [2.3]  "HEOD" 0  II  C  / 2 HO-C2H«  -  \  N  0  CH 2  1  "HEOD"  The  authors  compounds  In  a  due  to  HO-C2Ha-N^  •"* CH 2  the  did  lack  of  study,  DEA s o l u t i o n s According  concentrations  be  regarded  as  a  of  ^N-C2Ha-OH  "BHEP"  not  Hakka  major  +  2C02  using  to  the to  et  [2.4]  other  analytical  al.[4l]  were  more  authors,  2 wt%  degradation  in  degradation  techniques.:  able  ethylenediamine  by  0.5  identify  suitable  (2-hydroxyethyl)  at  \  CH 2 — C H 2  '  follow-up  procedures.  >  however,  N,N,N'-tris degraded  /  CH2-CH2  to  detect  ("THEED")  in  sophisticated  analytical  THEED  frequently  the  occurred  DEA s o l u t i o n  compound.  and  should  1 2  These THEED to  can  authors absorb  that  of  industrial in.  the  gases.  and  acid  others  gases  and  triethanolamine  operating or  THEED  Hence,  on  a  of  the  that  their  only  molecule  molecular  DEA  found  ("TEA").  conditions,  BHEP  capacity  [8,9,12]  basicity  of  the  likely  basis,  the  falls  with  solution  both  However,  one  is  that  to  BHEP  is  and  similar  under  normal  nitrogen  atoms  react  acid  with  acid  gas  removal  increasing  solution  degradation.  Smith  and  degradation reported  Younger  and  by  compounds  to  be  (175  600  degradation clearly  was  found  to  ("TEA")  in  detected series  experiments by a  of  and  first  the  found  from  several  165  that  -  first  unidentifiable  and  retention  time  as  analysis.  controlled appears  at  and  temperatures and  1207  found  to  that  order  the  reaction  degradation with  C02  4137  kPa  rate  DEA c o n c e n t r a t i o n .  changes  consecutive  compounds  DEA d e g r a d a t i o n  185°C  He a l s o  DEA  degradation  carefully  initial  concentration  simultaneous  these  same  reaction  the  simple  the  discussed  degradation of  several  order  by  other  have  chromatographic  respectively.  affected  their  and  ranging  psi), was  gas  [42]  One  have  performed  contradicts  Furthermore,  several  operators.  pressures  to  others  plant  governed  partial  mentioned  [42,43]  degradation  and  gas  triethanolamine  Choy  [13]  of  This  concept.  compounds  were  time  suggested  degradation  reactions.  a  1 3  Kennard on  the  Their  reaction  work  stirred the  and Meisen  autoclave.  They  found  consisting  and  ionic  the  of  DEA  be  to  THEED HEOD,  unstable  scheme  which  temperatures  of  to  and  could  90  of  DEA  DEA  varied  kPa  and  study  degradation.  in  from  a 90  the  a  C02  be  and  600 to  mL  250°C,  initial  pseudo-first reaction  the  nor  DEA  the  back  Kennard also  the  that  f r o m DEA a n d  to  found  degradation  C02  C02,  [51]  acts was  as  a  shown  to DEA.  following  DEA c o n c e n t r a t i o n s  to  175°C  C02  series  equation  He  during  for  and  order  ones.  suggested  converted  complex  parallel,  compounds  main  be  of DEA.  produced  this  simplified of  loading  gC02/gDEA.  THEED  DEA t o  equilibrium,  produced  proposed  valid  was  between  BHEP;  be  of  with  degradation  consumed  [51] is  BHEP  although  and  C02  degradation  and  comprehensive  wt%.  proposed  detectable  neither  Kennard  100  a  kinetics  6895  combination  They  is  catalyst. to  12  to  reactions  overall  HEOD,THEED C02  5 to  a  steps.  Among  that  of  and  temperature  413.7  the  undertook  reacting  The  from  and  describe  of  from  concentration  found  mechanisms  consisted  pressure  [17,44]  BHEP  0  to  greater  reaction 100 than  wt%, 0.2  1 4  In  a  separately The  recent with  Blanc  DEA a n d HEOD  temperature  They  study,  proposed  of  the  various  HEOD,THEED,  BHEP  quantitative  data  and  al.  solutions  autoclave  in  was  mechanisms other  were  et  in  a  for  reacted  sealed  varied  degradation  presented  [45]  from  the  autoclave.90  to  130°C.  formation  compounds.  support  C02  of  of  However,  these  no  reaction  mechanisms.  2.2.1  Other  degradation  Other salts"  may a l s o  stronger and  types  than  acids  as  with  protonated  The  DEA m o l e c u l e  C02. in  Such  which  has  not  reported  the  chloride,  formate,  and  been  of  oxygen,  of  of  oxalate  heat and  stable  the  by  a  the  et  These  back  of  from  process. acid  thus  acids  has  been  mechanism of  their  anions in  Blanc  strong  Waterman  thiosulphate  Henry  anions  proton  these  but  understood.  by  regeneration  protonated  by  acids.  However, the  stable  constituents  reported  oxalic  the  "heat  identified  accepting  during  as  acidic  acids,  later  Formation  clearly  presence  of  known  any  transfer.  capable  presence  is  of  strong  were  proton  DEA m o l e c u l e  the  presence  1955,  neutralized. to  products  acetic,propionic.  not  formation  solutions.  the  DEA b y  are  the  attributed  in  [46,47]  acids  becomes  degradation  and  formic,  react  these  form  H2S  Grennert  al.[45]  of  products  et such  gas  al. as  [50]  acetate,  treating  DEA  15  Industrial-grade amounts  of  DEA  monoethanolamine  [48,49]  to  form  been  suggested  believed amine  2.3  to  treating  units  analysis  acid  gas  recognised  (HEED)  molecular  [4,12].  1-(2-  hydroxyethy1)urea [48,49].  weight  These  have  also  compounds  are  containing  the  by  the  loading  the  rich  2.1  shows  to  occur.  the the  polyalkylene  [52].  Hall  in  have  and  been  Barron  problems  at  the  on  higher  the  high heat  regenerator a  are  temperature the  acid  rate  of  most  prone  DEA u n i t  where  such the to  industrial by  presented  Ram R i v e r The  a  Gas  effects  corrosion  are  well  loading  and  the  corrosion.  temperatures, exchanger,  gas  in  reported  [53]  and  high  reported  some  Canada.  The h i g h e r  of  widely  A q u i t a i n e Company o f  DEA a t  areas  been  Canada  corrosion  l e a n - r i c h amine  of  have  C o r r o s i o n problems  Western  of  [3,54].  temperature, processing  in  Richardson  operated  plants  [11-14].  detailed  trays  identified  i n DEA t r e a t i n g  and  of  high  degrade  ("OZD"),  ethylenediamine  of  also  small  I N DEA S O L U T I O N S  Fitzerald  of  can  N,N'-bis  1inear-polycarbamides  literature  Plant  not  MEA  contain  stuctures.  Corrosion  DEA  be  CORROSION  the  compounds  but  ("MEA").  ("HEI"),  and N - ( h y d r o x y e t h y l )  Degradation  usually  oxazolidone  hydroxyethyl)imidazolidone (BHEU),  solutions  as  The the  reboiler  equipment rich  and  corrosion.  corrosion  is  most  side  the  top  Figure likely  SWEET GAS  0-H CONDENSER  CD  ABSORBER  WATER COOLER  REGENERATOR  _l  FEED GAS  ACID GASES  J  AMINE-AMINE HEAT EXCHANGER  REBOILER  i  FLASH TANK Where  Figure  2.1  T y p i c a l flow s h e e t of a where c o r r o s i o n u s u a l l y  DEA p l a n t occurs.  corrosion  showing  occurs.  areas  1 7  2.3.1  Corrosivity  Polderman degradation ("HEI")  and  the  Their  findings  corrosiveness  probably  that  the  m a j o r MEA  1 -(2-hydroxyethyl)imidazolidone  were  to of  et  products  the  first  DEA s y s t e m s . rate  later  of  date the  MEA  ("HEED")  confirmed  by  degradation  [56-59],  degradation  of  al.  [12]  were  corrosive.  to  publish  The a u t h o r corrosion  products,  reaching  1  corrosive  nature  the  in  publications  various  However, of  the They  range  o f . 20  to  11.5  and  10  of  Blanc  corrosive.  products.  reported  are  Lang  products  However,in products  the is  and has  case  of  still  a  controversy.  degradation  support  have  (i.e.  accepted  Polderman  the  [48]  Corrosiveness  been  matter.of  in  al.  products  N-(hydroxyethyl)ethylenediamine  [55].  generally DEA,  et  DEA d e g r a d a t i o n  products  corrosive. Mason  of  Moore  in  the  a  DEA  in  1960  was  substantial  mpy).  degradation  that  data  concentration  (40  1956  [11]  industrial  reported  with  products  corrosion  increase of  Since has  on  in  degradation then,  been  the  described  [13,14].  al.  claim suggest  100°C,  some  mm/year  et  reported  the  depending  [45]  recently  that  DEA  that,  within  pH o f on  30  the  published  degradation the  products  operating  wt% DEA s o l u t i o n concentration  of  data  in  are  not  temperature lies  between  degradation  18  They  proposed  steel  are  Pourbaix  that,  either  diagram the  or  A  iron  water  for  Pourbaix  potential-pH  iron  passive  [60].  diagram  indication  on  conditions,  they  to  conditions,  and  carbon  according  schematic system  to  the  Pourbaix is  given  in  2.2.  Although  obtain  these  non-corrosive  potential-pH  potential-pH Figure  under  an  resort  the do  accurate to  potentiodynamic consideration  feasibility not  prove  picture  of  experimental polarization [60].  diagrams of  that what  corrosion it  curves  under  takes  studies, for  provide  actually  actually  kinetic  can  the  some  certain  occurs. place,  such  as  system  To  one  has  plotting under  19  Figure  2.2  Pourbaix potential-pH diagram for the i r o n - w a t e r system.  20  The p o t e n t i a l - p H diagram to which Blanc et a l . [ 4 4 ] r e f e r r e d (see  Figure  2.2)  However, the DEA  i s r e p r e s e n t a t i v e of the iron-water system.  system, in g e n e r a l ,  i s f a r more complex  the f o l l o w i n g reasons :  1.  The  system  to  ^  consists  s u l p h i d e , water and 2.  due  of  iron,  carbon  dioxide,  hydrogen  DEA.  The shape of the p o t e n t i a l - p H curve  changes  substantially  with temperature; i n the case of the iron-water system, the region  of  corrosion  widens  and  the region of p a s s i v i t y  narrows. 3.  Degraded stable  industrial salts.  complexes  DEA  These  with the  solutions salts  metal  usually  (such  thus  contain  as cyanides) may  invalidating  the  use  heat form of  Pourbaix p o t e n t i a l - p H diagram [60].  Blanc  et  al.  [45]  immersing  mild  steel  solutions  at  psi).  c a r r i e d out t h e i r c o r r o s i o n experiment by coupons  80°C with a H S 2  in  3N  (30  wt%)  aqueous  DEA  p a r t i a l pressure of 2000 kPa  (290  A f t e r 500 hours of immersion, the weight l o s s measurement  of the coupons y i e l d e d a c o r r o s i o n rate of 0.05  Choy [43], i n h i s work on DEA sulphide  to  i n h i b i t DEA  degradation.  the r e s u l t s of Blanc et a l . s o l u t i o n d i d not degrade  degradation,  mm/year (2 mpy).  found  hydrogen  In l i g h t of Choy's work,  [45] are understandable, as the DEA  noticeably.  21  In  another  corrosion  aqueous  mixture  of-DEA  0.02 Fe  mm/year system.  presence is  in  (0.8  of  BHEP,  conducted  immersed  in  THEED a n d  HEED.  case  of  Blanc  BHEP  less  and  than  attributed which  contradiction  latter  and  mpy),  They  test,  is  to  the  corrosion  boiling, They  aqueous  to  a  in of  with  weight  loss  of  0.4  to  the this  [41].  carbon  6 wt.% 1.8 mg  of  DEA-H2S-  rate  al.  low  of  loss of  the  an  rate  However,  et  SAE1010  weight  for  nature. Hakka  used  corrosion  corrosion  solutions a  a  [45]  obtained  lower  findings  reported  BHEP c o m p a r e d  that  basic  tests  al.  obtained  the  also  et  in  The steel  DEA,  BHEP,  mg  in  the  the  case  of  DEA.  Recent Kennard  [10]  degradation  extensive  work  on  revealed  that  HEOD,THEED and  products.  DEA d e g r a d a t i o n as  proven  examined  in  products  since their  not  all  The  DEA  statement  are  not  the  major  corrosion  degradation  by  BHEP Blanc  corrosive  tests.  can  by are et not  DEA d e g r a d a t i o n  Meisen the  al. be  and  m a j o r DEA [45]  that  regarded  products  were  22  2.4  R O L E OF H E A T  To' d a t e , the  heat  However,  no  it  is  heat  has  to  been  operation  recognised  and  temperature  in  the in  the  and  directed  towards  regarding  that  degradation  exchanger  elevated  VARIABLES  research  exchanger  susceptible rich  EXCHANGER  degradation  DEA s o l u t i o n  the  rich  reboiler.  dissolved  the  is  of  of DEA.  particularly  solution  side  This  be  acid  role  may  gas  of  due  level  leanto  the  in  the  for  the  solution.  Ballard proper  design  corrosion *  [61]  steam  *  the  operation  problems  and  excessive  to  partial  flooding  prevent  skin  prevent  high  of  amine  above  maximum a l l o w a b l e  (260°F)  comprehensive  suggested  temperatures  prevent *  and  published  He  emphasized  :  140°C  temperatures  amine of  reboilers.  that  reboiler  guidelines  (285°F) on  the  temperature  be  avoided  to  tubes; be  kept  at  127°C  degradation;  the  reboiler in  the  tubes  heat  loads  top  bundle  always  be  kept  liquid  to  prevent  be  avoided  section  of  the  to tube  bundle; *  the m  reboiler  (6  -  8  inches)  of  covered  with  localised  0.15  -  0.20  drying  and  overheating.  These also  guidelines  degradation  temperatures).  should  by p r e v e n t i n g  minimise local  hot  not  only  spots  corrosion  (or  high  but skin  23  McMin metal  and  skin  are  on  metal  general and  pipes  to  breakout  low.  in  to  to In  of  of  (10-20  also  act  keep  as  0.6  ft/sec)  For  solution  higher from  Ballard  [61]  in  (2  pipes  and  in  -  and  may  thus  maximum  heat  is  lead cause  solution  exchangers,  6 m/sec  (15  a  exchangers  velocities  recommends  4.5  of  forming  there  heat  solution  in  by  reason,  solution  ft/sec)  importance  inhibitors this  the  the  corrosion.  velocities  gases  m/sec  with  corrosion  [61].  addition, acid  emphasize  connection  surfaces  [ 53,62,63].  velocities m/sec  known  tendency  corrosio.n  [54]  temperatures  Amines films  in  Farmer  -20  3 - 6 ft/sec)  valves.  2.5  FOULING  OF H E A T  Although the  fouling  attention Barron  and  in  exponentially Epstein  [65]  wall  decrease  in  with  such  they  rate  no  heat  did  increases particular  exchangers. exchangers  mention  Temperature and  and with  is  the  most  effects  fouling  Hall  and  did  not  but  existence  heat  tend  [64].  increases flux.  increasing  likely  therefore  temperature  exponential  temperatures  exchangers,  exchangers  absolute  reported  fouling  of  heat  rates  usually  of  products.  fouling.  reaction  impurities  o n DEA h e a t  However,  DEA  of  heat  fouling  degradation  reaction  chemical  in  focused  cause.  Fouling chemical  been  reported  its  corrosion  accumulation  resistance  has  [53]  identify  with  the  EXCHANGERS  in They  flow  caused  to  by  dominate increases  Watkinson and fouling also  rate.  rates  reported Shah  et.  a  24  al.  [66]  small  reported  diameter.  that  These  in  2.6  OF DEA S O L U T I O N S  Quantitative proven  to  be  degradation at  fouling  analysis  compounds  elevated  of  rather  rates  were  higher  may  also  have  findings  implications  ANALYSIS  the  fouling  of  DEA h e a t  partially  difficult have  temperatures,  degraded to  of  important  highly  DEA s o l u t i o n s  the  low v a p o r  are  tubes  exchangers.  due  fairly  in  fact  that  pressures,  polar  and  the  first  has the  decompose  occur  in  low  concentrations.  Henry  and G r e n n e r t  interested  in  salts  refinery  in  acidic  the  also  other  methods  alkalinity the  samples.  titration  They acids;  for  for  the  total  presence  of  chlorides;  the  sodium.  However,  DEA d e g r a d a t i o n  researchers heat  four  of  determination) total  cyanide,  their  study  compounds.  types  used  acids.  (such as  of and  They  organic  c h e m i c a l methods  of  stable  cyanides  thiosulphates.  detection  nitrogen  determination  of  investigated  and  sulphate,thiocyanate, and  among  measurements  c o n v e n t i o n a l wet  and K j e l d a h l  mercaptide,  and  organic  discussed  titration  were  sulphites,sulphates,  potentiometric They  detection  materials:  thiocyanates;  [46,47]  well  aS as  sulphur,  sulphide,  chloride,  carbonate,  failed  to  detect  25  Conventional solution  are  methods  wet  also  are  chemical  described  not  in  capable  methods  reference of  for  analysing  [26].  Again  identifying  DEA  DEA these  degradation  compounds.  Polderman  and  degradation  Steele  [12]  compounds  crystallization  and  were  by  thin  of  spectroscopy,  layer  chromatography  Gough  [67]  provided  DEA s o l u t i o n s .  a)  b)  a  detect  scheme  for  information  on  a  scheme  quality  routine However,  procedures  and  were  Persinger  using  solutions. volatile  distillation and  gas  identify et  al.  and N,N'-  [41]  used  chromatography  and  study  on  analytical component  the  analysis  schemes:  analysis,  to  obtain  composition,  individual degradation  Brydia technique,  DEA  evaluation,  appropriate  not  for  for  analysis.  these  identifying  for  the  THEED.  two  detailed simple  analyse  Hakka  comprehensive  He d e s c r i b e d  comprehensive  isolate  spectroscopy,  to  a  to  ("BHEP").  mass  to  fractional  able  bis(hydroxyethyl)piperazine infrared  attempted  [68]  derivatization  Trifluoroacetyl  amines  prior  to  fairly  simple  into  chromatographic and  reproducibility,  rapid,  the  precision,  described  for  amine  the  authors the  a  or  chromatographic  analysis  of  was  to  used  ethanolamine convert  trifluoroacetyl  separation.  and  detecting  compounds.  anhydride  volatile  suitable  Although  reported presence  derivatives  the  method  difficulties of  non-  water.  was with  26  Piekos by  et  Brydia  al.  et  [69]  al.  eliminated  [68]  by  trimethylsilyl  derivatives.  was  a  used  amino  and  produces and  as  fairly  stable  identified  by  trimethylsilyl alkanolamines are  more  sites.  groups  group and  and  be  provided  tolerated  Saha of  et  amines  and  prior  to  column  based  on  packing  separate eight ft  an  minutes  long)  required  with  the  using  probability  stainless  found  the  that  Tenax  and  the  3.175  column  oxide,  of  mm O . D . ,  not  1.2192 No  affected  a was  They  MEA,DEA  and  TEA could  excess.  Among  the of  derivatization long  periods.  polymer  porous able  beads  polymer  to  separate  were  able  to  TEA i n  less  than  m long  sample by  in  process  organic  G.C.,  results.  column. was  of  and  derivatization  incomplete  use  the  reactive  5% w a t e r  of  a  compounds  of  present  for  of  of  analysis.  derivatives  mixture  steel  is  to  consuming  of  separated  MEA,DEA  up  the  method  addition  reduction  problems  time  both  This  Silylated  of  agent  the  were:  the  with  polarity  chromatographic  excellent  a  to  to  acetamide  easily  The  the  presence  silylation  gas  aqueous  more  separate  2, 6 * - d i p h e n y l p a r a p h e n y l e n e  alkanolamines  are  due  to  investigated and  alkanolamines  reacts  bonding.  stable  described  of  they  which  able  mentioned  instability  which  decreases  that  preparation,  experienced  alkanolamines.  hydrogen  the  [70]  Consequently, as  found  al.  inconveniences derivative  . also  were  derivatives  the  chromatography.  a n d more  The a u t h o r s  the  compounds  reduces  volatile  converting  reagent,  of  gas  shortcomings  N,0-bis(trimethylsilyl)  silylation  hydroxyl  the  (1/8"  O.D., 4  preparation  water.  was  27  Choy  and  specifically They  the  adopted  degraded  Meisen analysis  a  of  were  which  by a i r  formamide  using  a  stainless  steel  column  chromosorb used  as  reliable, during  3.175  followed the it  was  it  Kennard  degradation packing. solutions  gas.  was  and  chromatography  able later  and  with  identified  mass  and  known  degradation  0.5  wt%.  The  14  reproducibility  at was  method  was  6  long)  80/100  mesh  Nitrogen  was  accurate  and  removal  plant  analysis  and  of  by  as in  able  concentrations ±  5%.  gas  and  the  its  column  degraded  using  He was  typically  water.  direct  DEA  G.C.  compounds them  of  care  use.  reliable  Tenax  then  ft  regard  to  N,0-  were  considerable  spectrometry.  products  (1/8",  the in  with  compounds  on  it  required  the  detect  drying  it  detection.  simple,  used  products.  first  OV17  the  for  a  for He  to  8%  Although  investigate  dissolving  m long  ionization  developed  compounds.  He was  1.8288  suitable  technique  then  silylated  consuming,  not  of  silylating  with  particularly  [51]  chromatographic  flame  time  silylation  Consequently,  mm O . D . , packed  by  carrier  The  to  degradation  consisted  finally  bis(trimethylsilyl)acetamide.  first  its  stripping,  and  separated  the  DEA a n d  technique  DEA s a m p l e  dimethyl  [42]  as  DEA  combined to  detect  low as  gas DEA  about  28  CHAPTER  EXPERIMENTAL  3.1  EQUIPMENT  A principal  EQUIPMENT  objective controlled  conditions  typically  equipment  s u c h as  in  of  Figure  exchanger cooler  main  the  tube, and  of DEA  The high  of  the  the  DESCRIPTION  The  aqueous  DEA s o l u t i o n  heater.  kept  uniform  instrumentation. equipment  is  heat  immersion  of  first  is  then  transfer  purpose  is of  pump,  Figure  whereas  Figure  saturated  with  filtered  exchanger  the  The h e a t  of  a  transfer  The t e m p e r a t u r e of  a  tube.  equipment  by means  by means  this  flow  reboilers.  a  through the  tank.  and  heat  autoclave,  pressure  aluminum  exchangers  perform  under  pressure  It  temperature  experiments  industrial  for  to  consists  autoclave.  heart  was  essentially  pressure  the  heat  work  shown a  a  heat water  3.2  3.3  The  is  shows  a the  equipment.  PROCESS  desired  DESCRIPTION  equipment  entire  of  in  developed  associated  components  is  degradation  equipment  a  present  encountered  3.2  tube  the  lean-rich  3.1.  photograph  AND PROCESS  DESIGN  carefully  flowsheet  3  stirrer.  the  high  pumped u n d e r  high  The  fluid the  transfer itself heat  in  heat  w h e r e DEA i s  heat  of  and  C02  is  exchanger  heated  to  the  fluid  in  an  heated  transfer  by  fluid  an is  Figure  3.1  Flow sheet of the equipment f o r t h e s t u d y o f DEA d e g r a d a t i o n i n h e a t exchangers.  30  Figure  3.2  Photograph  of  overall  view  of  the  equipment.  31  Figure  3.3  Photograph  showing  main  components  of  the  equipment.  32  Degradation The  reactions  temperature  autoclave  of  take  the  temperature  autoclave  place  DEA s o l u t i o n by h e a t  temperature, and  measured  thermocouples.  exchanger Bourdon  water  inlet  and  pressure  the  DEA s o l u t i o n  of  time  gauges. is  (typically  about  in a  water  exchanger inlet The  out 120  by  gas. c h r o m a t o g r a p h y .  to  hours  240  and  and  The outlet  temperatures pressure,  are heat  m o n i t o r e d by m e a n s heating for  hr).  analyzed  and a  cooling  long  of  period  10 mL s a m p l e s for  of  are  degradation  Autoclave  Engineers,  Erie,  34.5  (5000  MPa as  to  desired which  the  relief  is  can  a  as  streams.  autoclave valve.  the  and  used  316  stainless  ) capable  psi).  saturate  be  4 L,  PA.  pressure  outgoing of  of  the  DESCRIPTION  autocalve  well  are  continuously  compounds  The  outlet  to  cooler.  inlet  autoclave  process  least  3.3.1  and  pressures  at  EQUIPMENT  24  tube.  exchange  withdrawn  3.3  'every  transfer  lowered again  This  carried  heat  then  cooler  outlet  the  is  heat  temperatures, by  inside  It  is  of  and  To p r e v e n t  ports  is  as  with  temperature. inlet  vessel  (Autoclave  withstanding pressures  used  solution  steel  It  outlet  the  carbon is  to  an  container  dioxide  provided with  ports  excessive  connected  solution  up  for  pressure  at 6  to as the  ports,  incoming  and  build  one  adjustable  up,  pressure  33  3.3.2  Heat  exchanger  The . heat tube, and  an  an  coil  150  aluminum tank  4.80  m  of  made  of  long, tube  316  stainless  m ID,  0.75  transfer -  fluid. 1625  Model  recovery  system  a  was type  0.914  steel,  was  The  tank  Thermia tank  NS-1 (see  to  12.7 a  was  a  (Greey  The  was  mm d i a . , single  304  0.1016  with  1/3  Stirrer  3.3.8).  helical  The  turning  which  was  aluminum  tank  approximately  petroleum-based  with  tank  the  stirrer  a  tube,  in  filled  exchanger a  is  mm I D .  The  immersed  heat  fluid,  tube  2.032  inch).  fitted  (EVS)). Section  single  exchanger  Oil-C,  was  Lightnin  m long,  connected  The  heat  HP v a r i a b l e Mixing  Equipment,  connected  stirrer  stainless m diameter  to  was  steel  speed  a  vapor  attached  shaft  marine  which  propeller  blade.  A  10  Rexdale, transfer tubular was  The  rpm)  Toronto,  to  Shell  m (16  a  transfer  mm O D , a n d  0.4064  m high).  of  heat  The heat  3.175  is  consists  containing  the  L commercial  (100  set-up  immersion heater.  radius  (0.7  exchanger  kw o v e r - t h e - s i d e  immersion  Ontario,  K T L O - 3 1 0 - 1 ) was  fluid. heating  fitted  inside  the  provided  Model  The h e a t e r elements  with  three  welded 0.1016  aluminum t a n k .  the  required  is  A  made into m long  3  heater  up a  used of  sludge 240  to  heat  3  junction  phase,  electricity.  (Chromalox  Canada, the  heat  steel-sheathed box.  legs  and  volts  The  heater  was  placed  power  line  34  3.3.3  The  Solution  solution  pump  pump  is  a  magnetically  Concord,  C T . , Model  210-513  motor.  The  parts  pump to  is  capable  10.3  3.3.4  The  water  3.3.5  the  meter  mm  (0.069  function Figure  made  under  by of  a  1/6  316  high  temperature  m (40  mm ( 0 . 4 3 0 a  0.508  The  is  PVC  pump  HP  (Micropump,  explosion-proof  stainless  pressure  and  of  (275  135°C  steel. is  The  rated  up  ° F ) .  hot  cooled  ft)  long  helical  inch)  ID,  316  m (20  inch)  an  upward  12.7  stainless  diameter,  DEA s o l u t i o n by  coil,  steel  0.9144  m  passes  downwards  flow  water,  of  mm  (3 in  flowing  shell.  meter  used  to  inch)  measure  at  the  ID,-3.17  tube  Research  measured  tube.  a  12.19  inside  capillary  (Orange  at  a  10.92  and  The  long  is  PVC s h e l l .  Flow  were  operating psi)  driven  gear  cooler  OD,  coil  through  was  (1500  placed  high  the  of  cooler  inch)  tube, ft)  MPa  Water  (0.5  wetted  )  driven  60  mm ( 0 . 1 2 5  connected  Inc., ° C at  to  Milford, the  The  pressure  gauge  of  pressure  drop.  3.4.  DEA f l o w  a  The  inch)  consists  OD, 50.8  differential  C T . , Model  inlet  was  rate  of  the  calibrated  to  calibration  1502  of  mm (2  1.75 inches)  pressure DG).  the  heat  give  flow  curve  a  is  gauge  Flow  rate  transfer rate shown  as  a in  se  36  The  calibration  solution of  a  stop  least  3.3.6  a  given  watch  10  minimise  The  for  was  and  a  temperature  Stamford,  were  about  Model  compares  measured  3.3.7  the  the  the  heat  each  30  wt% DEA  reading  by  average  flow  rate  means of  in  at  order  to  were  proportional  It  controller  was  connected  heating  elements  transfer  measured  41 OA) b y m e a n s  3.3.8  recovery  fluid.  with by  the  to  a  to  (Omega,  thermocouple measure  the  The c o n t r o l l e r  then  set  point  c o n t r o l l i n g the  and  takes  electricity  tank  and  to  a  by  thermocouples  digital of  a  temperature  multiple  (J-type, indicator  Iron(Doric,  rotary  switch.  of  condenser,  system  recovery  transfer  a  measurements  Trendicator  heat  for  action  connected  collection  The  temperature  constantan)  vapor  cylinder.  of  heater.  Temperature  Temperatures  The  meter  is  the  proportional  Vapor  particular  49).  10 mm f r o m of  to  a  taken  flow  controller  temperature  supply  the  graduated  controller  CT.,  corrective  at  by m e a s u r i n g  error.  Temperature  placed  time  readings the  done  system a  water  fluid  tank  consisted ejector. was  a  Vapor  condensed  generated in  a  water  in  a  2L the  condenser  37  placed was  at  top  connected  transfer vapor a  the  to  fluid  from  water  of  is  the  the a  tank, which  passed  through  tank  3.4  SYSTEM  PREPARATION  In  order  to  solution,  the  prevent heat  2  pressure  order  exclude  3.5  A  to  SYSTEM  feed  tank  loading  the  the  valves  to  order  to  that  all  of  the  the  condensed  prevent  system the  was  vapor  condenser heat  leakage  of  connected  .to  generated  in  condenser.  from  239  kPa  possibility  coming is  in  purged  run. (15 of  air  contact with  After 20  with  t h e DEA  carbon  dioxide  purging,  psig)  is  a  slight  maintained  re-entering  the  in  system.  LOADING  of  4L c a p a c i t y ,  system.  psig)  autoclave.  the  oxygen  205  The  pressure,  feed  ensured  end  where  recovery  each  positive  the  vapor  before  DEA s o l u t i o n  (10  In  tube  aqueous  kPa  tank,  transfer  min  positive  collector  the  ejector,  about  The o t h e r  collected.  the  for  tank.  by  tank The  of  shown  feed the  slightly  in  tank, desired  higher  then  system  VA01 a n d V A 0 2  (see  could  than  Figure  be  was  filled  concentration that  of  dioxide.  connected  then  3.5  usually  introducing carbon was  Figure  to loaded  3.5).  used  with was  the  2.5 put  inlet  simply  L  port by  of  under  system  The o u t l e t  the  for  170  port  of  of  the  opening  FEED  TANK  V A 0 2  CO,  AUTOCLAVE  SUPPLY  HXH VA01  F i g u r e 3.5  Schematic diagram of the feed tank  system. oo  39  This air  method into  min.  allowed  the  After  valve  was  loading  of  the  solution  system.  Loading  usually  solution  loading  was  shut  off,  and  the  required  completed,  feed  without  tank  introducing  about  the  10  -  autoclave  disconnected  15  inlet  from  the  system.  The total  total  time  inventory system  required was  as  well  inventory  3.6  liquid  was  inventory  for  provided as  for  found  each for  be  kept  run.  small  2.5  The  minimise  enough  circulation  sampling.  about  to  However,  adequate  solution  to  was  the  liquid  throughout minimum  the  liquid  L.  S T A R T UP  After  loading  the  system  were  taken  1.  The water  inlet  condenser  was  2.  The  3.  The the  w i t h DEA s o l u t i o n ,  the  following  steps  :  stirrer  to  the  heat  exchanger  tank  overhead  opened.  speed  temperature electric  valve  was  raised  controller  heater  was  to  set  switched  about  point on.  200  was  rpm.  set  to  50  °C  and  40  The  temperature  raised by  to  the desired  gradually  point  of the heat  The  solution  by-pass  The  system  pressure  opening  The  the carbon  pump  was This  pump,  but a l s o  The  flow  temperature  gradually  about  250°C)  controller  set  speed.  valve  FCV2  was  with  not  was  fully  raised supply  the  only  opened.  t o 791 valve  by  by  FCV3.  pass  required  kPa ( l O O p s i g )  valve  FCV2  fully  f o r the startup  of the  the  pressure  was g r a d u a l l y  increased  supply  DEA  solution  with  the heat  increased up t o t h e  by o p e n i n g valve  valve  FCV3  by o p e n i n g t h e  to the desired  value, i . e .  kPa (600 p s i g ) .  through  temperature  by-pass  (typically  in saturating  4238  gradually  °C),  was  helps  dioxide  typically  The  fluid  dioxide.  system  carbon  is  the  dioxide  started  open.  carbon  temperature  increasing  and the s t i r r e r  transfer  t o i t s maximum desired  t h e flow  FCV2.  exchanger  control  tube  was  to bring  temperature valve  started the  and  autoclave  (typically  60  FCV1 a n d c l o s i n g t h e  41  10.  11.  Maximum in  the  60  ° C ) .  The  flow  autoclave  adjusting  cooler  temperature  12.  The  order  to  (about  and  temperature within  to  the  The water  set  temperature  to  (typically  5 min.  desired inlet  obtain  value  valve  a  by  to  DEA  the  outlet  150  -  were  steady was  200  hr)  carefully  steady  state  state  was  monitored operation  reached  in  and  of  the  about  15  then  continued  for  extended  while  monitoring  all  variables  required.  A 1OmL s a m p l e  At  valve.  achieve  experiment  (or  reduced  variables  min.  The  desired  solution  60°C."  Usually,  as  14.  of  the  achieveable  was  opened  equipment.  periods  13.  was  in  rate  until  the  was  by-pass  operating  regulated  this  flow  the  continued  reached  Usually  solution  water  was  more  the  the  frequently)  end  distilled  of  of water  each in  DEA s o l u t i o n  was  and  by  analysed  run,  order  to  the  withdrawn gas  system  prepare  it  every  24  hr  chromatography.  was for  the  flushed next  with  run.  42  CHAPTER  ANALYTICAL  The  gas  chromatographic  adopted this  4.1  for  the  of  developed  DEA a n d  its  by K e n n a r d  degradation  [51]  products  was in  work.  CALIBRATION  Calibration from  that  OF GAS CHROMATOGRAPH  curves  Kennard's  ensure  the  for  DEA,HEOD,THEED  thesis  OPERATING  CONDITIONS  The  operating  conditions  Table  4.1.  [51]  calibration  4.2  in  PROCEDURE  technique  analysis  4  of  and  curves  the  Gas  and  checked were  BHEP from  still  were time  obtained to  time  to  applicable.  Chromatograph are  summarized  43  Table  Gas  4.1  Operating  conditions  of  the  gas  chromatograph,  Chromatograph Manufacturer  Hewlett  Model  5830A  Detector  Hydrogen  Chromatographic  Packard  Stainless  Dimensions  1/8"  Packing  Tenax  steel  O.D., G.C.,  6'  long  60/80  mesh  conditions  Carrier  Ni trogen  gas  Carrier  gas  Injection Detector Column  ionization  Column  Material  Operating  flame  25ml/min  flow  port port  temp. temp.  300°C 300°C Isothermal  temp.  then to  at  150°C  temperature  for  raised  0.5 at  min., 8°C/min  300°C.  Syringe Manufacturer  Hamilton  Model  701, and  Injected  sample  size  1  ML  Co.,  Reno,  10M1, w i t h Chaney  Nevada.  fixed  adapter  needle  44  Typically  1 LIL s a m p l e s  directly  into  Chaney  adapter.  volume was  of  used  and  major  min. order  run  the  to  in  but  column had  to  be  in  elution cooled  not as  could  from  that  heavy  a  with  constant  A needle  guide  protected  spacer  a  the  for  needle  in  about  life.  be  carried  of  a  injected  fitted  only  septum  products was  syringe  column.  served  the  were  ensuring  the  which  also  analysis  solution  precision  into  lengthen  the  DEA  helped  port,  degradation  ensure  detected  out  for  about  compounds.  300°C  to  150°C  from  run  30  min.  After  each  which  took  5 min.  A chromatogram Figure  helped  the  a  injected  needle  However,  in  was  injection  syringe  The  about  The a d a p t e r  the  penetration  degraded  column with  sample  at  fragile  20  the  of  4.1.  degraded  Table  4.2  of  a  Table DEA  degraded 4.2  gives  DEA s o l u t i o n the  GC r e t e n t i o n  times  3  is of  shown  compounds  solutions.  Retention  time  Compound  of  major  degradation  Retent ion  compounds.  t ime  (min)  7.80  -  7 . 95  BHEP  14.30  -  1 4 . 40  HEOD  1 4.90 -  15. 1 0  THEED  17.80  1 8 . 00  DEA  -  in  DEA  gure  4.1  Chromatogram of a from run 3 after  degraded 192 h r .  DEA s a m p l e  46  4.3  ERRORS  The  major  time  of  the  source the  column  time  vaporization  error  sample port  injection  needle.  of  of  The  in  (i.e.  the  G.C.  the  time  injection).  result  in  the  small  extent  amount  of  this  of  this  error,  the  same  sample  made  and  for  the  determination  flow  flow  daily  This rate  gas.  the  least  six areas by  by  automatic  then  means  overcome  the  the  skill  were  became  necessary  in  of  column  the  the  injections  As  making  to  the  of  was  error  in  of  source  problem and  due  normally held  average  inside  increases  on  the  injection  needle  areas  concentrations  Another  carrier  flow  error  areas the  deciding  error  compared  was by  to  associated  the  to  integrator  begin  associated curves. that  with  chromatograph.  automatic  where  calibration  time.  of  the  the  depends  at  the  was  used  of  the  the  change  clogged,  in the  checking  the  adjustments  on  a  basis.  bunch,  some  of  fell. gas  Another peak  charts.  rate  rate  carrier  were  peak  liquid  error  by  is  Slight  larger  To m i n i m i s e  the  spent  during  operator.  calibration  analysis-  and  end  with  by  may  the  peaks  make  the  this  variation  of in  to  there  reading error  sample  of  t a i l .or  errors  Finally, and  form  tend  small  integration.  establishing  However,  produced  If  integration  is  in is the  minor  injection  -  47  CHAPTER  CORROSION  5.1  PRINCIPLES  When  a  and  Typically,  the  reduced anode  with and  STUDIES  OF P O T E N T I O D Y N A M I C TECHNIQUE  metal  oxidation  5  specimen  is  reduction metal  the  immersed reactions  corrodes  liberation  cathode.  in a  due  of  occur  to  on  oxidation  hydrogen.  Corrosion  corrosive its and  is  a  both  surface.  the  The m e t a l  usually  medium,  medium  acts  result  as  of  is  both  anodic  currents.  To  get  advantageous or  as  a  better  understanding  tomake  the  a  cathode  (but  corrosive  liquid,  it  "free  corrosion  [71].  At  cathodic no  net  the made  to  have  and  current.  predominate  relative  can  the  be  anodic  shifting  processes,  either  metal  to  a  as  is  Ecorr,  known  both  current the  anodic  then  in  as  electrode  and  and  there  use  of  predominates  cathodic  a  the  anodic  by  is  anode  immersed  same m a g n i t u d e  made m o r e  it  an  reference  potential,  Similarly, by  a  potential  exactly  the  act  When  corrosion  The m e t a l  voltage  cathodic  a  corrosion  specimen  both).  assumes  free  currents  external  not  potential"  this  current.  metal  of  current the  an over  can  the  potential  in  of  a  specimen  is  be  negative  direction.  The given  corrosion  environment  characteristics can  be  studied  by  metal  plotting  the  in  a  current  48  response as  as  a  function  "Potentiodynamic  anodic  of  applied  potential.  Polarization  polarization  plot  can  This  Plot."  yield  A  plot  is  known  potentiodynamic  important  information  such  as: 1.  The the  ability  of  the  particular  medium;  transformation  of  electrochemical active 2.  The  or  3.  noble  A typical  rate  anodic  zones  reaches  begins.  From  due  the  remains break  Figure polarization temperature, complexes and  a  B to  in  in  over  is  in  that  defined  the of  which  5.2  the of  At  Emf  an  in  as  the  series  in  appreciably  less  the  specimen  remains  a  shows  current  acidity the  addition  can  of  the  shown  are  At  point  current  from  E,  the  metal C  in  Figure  labelled.  formation  protective  the  As  B.  is  is  points  and  point  region.  plot  corrosion  potential  curve.  passive  A to  maximum  corrosion  the  the  from  formation  increase  inhibitor  to  transition  C,  passive.  down a s  metal  polarization  and  current  no c h a n g e  active  region  increasingly  is  (Passivation  passivate  metal)  corrodes  to  spontaneously  ,  The c o r r o s i o n  Important  an  to  behaviour  potential  passive;  material  to  B  The  the  of  a  D  passive  There  the  film  film  rapidly  layer.  and  protective  metal  corrosion  decreases oxide  5.1.'  metal  starts  to  increased.  effect be  seen  of from  solution  corrosion decrease  and  current. the  environment Figure the  5.2,  upon raising  formation  By c o n t r a s t ,  corrosion  the  current.  of  the  metal  alloying  49  CURRENT (Log s c a l e )  Figure  5.1  T y p i c a l anodic p o l a r i z a t i o n plot showing important zones and t r a n s i t i o n points.  50  CA  >o Increasing temperature, acidity or metal c o m p l e x i n g increases t h e minimum p a s s i v e current.  HI  IO  Increasing temperature i n c r e a s e s the c r i t i c a l current.  Q.  Minimum  passive  Inhibitor decreases corrosion  current  addition the current.  Critical  current  CURRENT (Log scale) Figure  5.2  T y p i c a l anodic p o l a r i z a t i o n curve showing theeffect of e n v i r o n m e n t and i n h i b i t o r a d d i t i o n upon the c u r v e .  51  5.2  C A L C U L A T I O N OF CORROSION  The by  corrosion using  As  the  seen  to  0',  following  can  calculated  equation  from  5.3,  Figure  by the  raising cathodic  relationship  :  Ic  +  Similarly,  be  Stern-Geary  cathodically 0cor  current  CURRENT  for  =  la  anodic la  =  a  corroding  externally  current  I  polarization  data  [71].  if  an  from  (Ic)  metal  applied  increases  applied  is  polarized  potential  according  from  to  the  expressed  as  [5.1]  polarization;  Ic  -  I  applied  [5.2]  where la  -  Anodic  Ic  -  cathodic  Iapplied The  change  follows  in  -  potential  current current  applied due  to  current.  polarization  can  be  : For  cathodic  polarization; Ic  0cor  -  4>' = A<£ =  Similarly  for  /3c  log  anodic  L\<J> = -  /3a  Icor  polarization;  log  la Icor  Where /3a  -  /3c Icor  -  anodic  Tafel  cathodic corrosion  [5.3]  constant,  Tafel  constant,  current.  [5.4]  52  Figure  5.3  Cathodic  polarization  diagram  for  a  corroding metal.  53  From  equations I  5.1  applied  and  = Ic  5.2;  -  Ia  Therefore,  Iapplied  =  (A0/0c)  10  (A0/0c)  Icor  and  [10  (A</>//3a) 10  (A0//3a).  -  can  10  be  ]  [5.5]  expressed  as  series  as  follows  2 (Atf>//3c) 10 and  (A0/0c) +  = 1 + 2 . 3  -(A0/0a)  10  (-2.3(A0//3c)  = 1 - 2 . 3  (Atf>//3a)  ) +  . . .  [5.6]  -  . . .  [5.7]  2!  (-2.3(A0//5a) )  +  2  2! Assuming  A#//3c  neglected  and  and  A</>//3a t o  equation  Iapplied  =  2.3  be  5.5  small,  can  Icor  A0  Iapplied —  (  be  ( 1 //3c  the  higher  approximated +  terms by  :  l/0a)  or, Icor  1 = —  &<j>  2.3  Equation  5.8  is  the  Stern  /3a /3b /3a  Geary  +  )  /3c  equation.  [5.8]  can  be  54  5.3  EXPERIMENTAL  Polished cm2  were  solution. used  as  connected  mild  PROCEDURE  steel  immersed  in  A calomel  electrode  the to  Research,  a  a  was  determined  The  experiments  corrosion with  with a cell  surface  saturated  KC1  The c o r r o s i o n  corrosion  measurement  system  NJ,  Model  Potentiodynamic 1 mv/sec via  scanning  Tafel  were  slope  conducted  350A),  and  the  determination at  25°C.  of  6.44  a q u e o u s DEA  solution cell  was  (Princeton equipped  polarization  rate  area  containing  electrode.  Princeton,  at  each  reference  microcomputer. obtained  specimens,  was then  Applied with  curves  a  were  free  corrosion  rate  and  extrapolation.  55  CHAPTER  6  MISCELLANEOUS  6.1  VISCOSITY  MEASUREMENTS  The  viscosity  of  by  means  Germany,  of  partially  a  Model  rotoviscometer  RV12)  combination(NV). given  in  constant  using  A  Figure  maintained  the  The  water  the  cup's  inner  core.  At  least  three  readings  and  the  instrumental  The was  2  cp.  order  above  and  minimum  the  the  to  all  viscosity  minimum  the  of  by  through  readings  measured  Berlin, bob  and  was  the  solution  tempering,  used  cup  viscosimeter  c i r c u l a t i n g water the  West  speeds to  is was  from  bath  were  minimise  a  and  taken the  errors.  which  could  limit  of  be  determined  decreases  measurements  viscosity  readable  the  rotational  viscosity  viscosity  keep  temperature  various  three  the  of  value  experimental  Since  temperature, in  of  Rotovisco,  diagram  bath  at  were  small-gap-clearance  desired  temperature  average  a  DEA s o l u t i o n s  (Haake  schematic  6.1.  at  degraded  TESTS  of  were  the  the  with  carried  degraded  accurately increasing out  at  25°C  DEA s o l u t i o n s  Rotoviscometer.  © Basic instrument ROTOVISCO RV 12 © Recorder: xy/t ® Speed programmer PG 142 & Measuring-drive-units: M 150, M 500, M 1500 - choose one or more to cover the full range of your samples. ® Stand d Temperature vessel © Thermal liquid constant temperature circulator. A refrigerated circulator model is best suited for viscosity measurements at or below room temperature. @ Sensor system: 40 alternatives to choose from for optimal test conditions and results. SENSOR SYSTEM  NV  Rotor (BOB) 17.85; 20.1 60  radius R 2 ; R3 (mm) height I (mm) STAT0R (CUP) radius  ; R  4  (mm)  17.5 ; 20.5  RADII RATIO R /Rj  1.02  4  SAMPLE VOLUME V (cm )  9  3  TEMPERATURE: max. (°C) min. (°C)  150 -30  CALCULATION FACTORS A ( P a / s c i l e grad.) M (min/s) G (mPa-s/scale grad.-min)  Figure  6.1  Schematic  diagram  of  the  0,5356 5,41  98,65 •  viscosimeter.  57  6.2  A  FOAMING  TEST  standard  industrial  determination  of  technique  foaming  [26]  was  used  characteristics  of  for  degraded  the DEA  solut ions.  The  foaming  apparatus  graduated  cylinder,  tube  mm d i a m e t e r ,  (8  dispersion  tube  passed  through  200mL  of  air  supply  oil-free supply foam  to  then  consisted  fritted  mm l o n g )  and  inside  the  connected  was a  rate  of  stopped  this  method  products  accumulation foaming.  of  to  the  were  a  of  glass  wet  gas  a  1000  gas  mL  dispersion  meter.  graduated  the  poured  the was  foam  The  cylinder  gas and  into  gas  the  cylinder.  dispersion  passed height  for and  tube  5 min. the  time  An and  The  air  for  the  noted.  does  foaming in  was  4 L/min  and  completely  degradation  on  coarse  tube at  6.2)  stopper.  between  effect  20  placed  relationship  the  extra  DEA s a m p l e  break  Although  a  an  Figure  degraded  air  was  was  (see  not  tendency  provide and  solution,  degradation  the  it  products  a  quantitative  concentration  does has  indicate a  of  whether  significant  58  AIR  IM  No. 12 Stopper  1000  GAS DISPERSION TUBE  900  CYUINDER-  Gas Dispersion  :oo  Tube  Cylindrical, Fritted  Glass  Extra Coarse. 8 x 5 5 0 - m m .  Figure  6.2  Schematic  diagram  of  the  foam  testing  apparatus.  59  CHAPTER  MODEL  A theoretical of  DEA  consists  7.1  model  was  inside  of  parts  two m a j o r  1.  Heat  2.  Kinetic  A successive  The  small  and  segments  heat  exchanger  bulk  solution the  heat each  unit.  error the  temperature  order, to  to  calculate  segment  average and  used  for  tube.  rate  The  model  thus  tube  was  length  treated  properties each with  bulk  the  heat was  as  were  the  into  individual  evaluated This  evaluating  allows  divided  an  segment.  solution  exchanger  the  the  approach transport  temperature  p r e d i c t i o n of  at  for a  the more  profile.  profile  determine the  of  associated  exchanger  In  transfer  exchanger  temperature  Temperature  heat  the  model,  Transport  entire  7.1.1  predict  MODEL  at  accurate  to  model.  properties heat  the  s u m m a t i o n m e t h o d was  calculation.  minimises  in order  :  exchanger  H E A T EXCHANGER  DEVELOPMENT  developed  degradation  7  determination  the  overall  temperature  heat  transfer  profile,  it  was  co-efficient.  necessary  60  The  inside  equation  film  [72]  co-efficient  =  0.023  (  )  the  by  the  following  )  (Re  Do  [7.1]  MW  film  0.67  = 0 . 1 7 (.  0.14 )  co-efficient  was  calculated  Db 0 . 1  0.37  )  (Pr  ) o  O  (  )  do (  Dt  0.5 )  Dt  M  m  (  ) MW  where  -0.21 m =  and  the  0.714  outside  M  Reynolds  Db2x Re  RPS x  number  is  defined  as  :  po  = o  M O  where Db  =  blade  Dt  =  tank  RPS  =  stirrer  po  = density  diameter  MO  = viscosity  diameter  (m) (m)  speed of  by  [73]:  Tk ho  M  (  c  outside  equation  1/3 )  (Pr  c  corresponding following  0.8 )  (Re  Di  The  calculated  :  Tk hi  was  the of  heat  the  transfer  heat  transfer  fluid fluid  (kg/m3) (pa.s).  [7.2]  6-1  The  overall  diameter)  TJi  heat  for  straight  coefficient  tube,  Since  the  transfer coiled  +  calculated  on  from  the  tube  had  equation  +  [72]:  (xm/Tkm)(Di/Dlm)  experimental overall  heat  to  found.  be  work  This  :  = Ui  (1 +  3.5(Di/Dc))  exchanger  tube  was  exchanger  considered  as  calculations  an  segments  assumed of  individual  were  then  involved  transfer  [74]  Uc  heat  the  inside  [7.3]  (1/ho)(Di/Do)  present  tube,  following  heat  was  (based  1  = (1/hi)  The  a  transfer  to  coefficient done  consist "x".  exchanger  performed  coiled  heat  for  by means  the  of  the  [7.4]  length  heat  was  a  on  of  "n"  Each unit.  successive  of  small  segment  was  Heat  transfer  heat  exchanger  segments.  The  schematic  small  heat  diagram  exchanger  of  the  segment  temperature is  shown  profile  in Figure  7.1  across  any  62  Th To  Ti  X  o  Figure  The  heat  "x",  may b e  7.1  Schematic diagram of the temperature p r o f i l e a c r o s s a segment of t h e heat e x c h a n g e r t u b e .  balance  for  written  as  a  small  heat  exchanger  segment  of  :  W C p d T = Uc d A  (Th -  T)  [7.5]  Where flow  W  = Mass  Cp  =  specific  rate  dT  =  temperature  Th  = hot  T  = bulk  dA  = elemental  Uc  = overall  heat  fluid  length  of of  the the  DEA s o l u t i o n , DEA s o l u t i o n ,  difference  of  the  DEA s o l u t i o n ,  temperature,  solution  temperature,  heat  heat  transfer  transfer  area,  coefficient.  63  We  can w r i t e  dA = IT D i d x , s o t h a t  W C p dT = Uc ff D i d x  Assuming  where,  that  x = 0,  ( T h -T)  the i n l e t  !  temperature.  ir D i x j > + I n (Th - T i ) W Cp } Uc !  s o l u t i o n temperature be  gives,  the integration constant.  Uc  therefore  [7.6]  I n (Th - T i ) = IC  where, T i denotes  The b u l k  becomes :  Uc a n d C p a r e c o n s t a n t a n d i n t e g r a t i n g  IC denotes  At,  E q u a t i o n 7.5  found  TT D i  W Cp  in  each  x) / )  [7.7]  individual  p r o v i d e d Th a n d T i a r e known.  segment  can  64  Since the  heat  the  exchager  information, calculated segment segment  temperature  easily.  The  so  temperature  of  forth. a  =  To  j  outlet  temperature  The  Figure  an 7.2  exchanger  the  inlet  ; 1 <  inlet  be  first  T i , of  the  second  relates  the  outlet of  the  the  exit  [7.8]  temperature  - outlet  temperature  n  - number  of  temperature t h e DEA  of  shows wall.  segments.  of the l a s t  solution  the outside  analysis  tube  can  the  temperature  j < n  To  of  of  of  pertinent  segment  To,  equation  inlet  j-1  Ti -  calculations  require  to  other  the f i r s t  temperature,  following  at the  :  Ti  where  of  with  temperature,  the i n l e t The  solution  along  temperature  segment  segment  t h e DEA  known  outlet  becomes  and  The  is  the o u t l e t  then  following  tube  of  the  of  segment  leaving  and  individual temperature  represents  the heat  inside heat  transfer  wall  transfer  profile  tube.  temperatures resistances.  across  the  heat  65  Heat transfer f l u i d Th  DEA Solution Twi  Two  T —  Figure  7.2  Schematic diagram of temperature a c r o s s the metal tube w a l l .  profile  66  Considering across  each  written  of  the  resistances  resistances,  T h - Two : ; (1/ho)(Di/Do)  = (1/Uc)  equation  Th  individual  the  and  following  temperature equation  drops  can  be  :  Th-T  From  the  -  7.8  Two =  it  Two -  Twi  Twi  =  -  T  =  [7.9]  (xm/Tkm)(Di/Dlm)  follows  (1/hi)  that  (1/ho)(Di/Do)(Th  -  T)  Uc  or Two  = Th -  (Th  -  T)(1/ho)(Di/Do)  [7.10]  Uc  Similarly, Two  -  Twi  =  Twi  = Two -  (xm/Tkm)(Di/Dlm)(Th  -  T)  Uc  or  From  equation  temperatures However,  to  inside  wall  a  and  trial  this  (Th  purpose  -T)(xm/Tkm)(Di/Dlm)  7.10  can  be  and  calculated  determine  U , h and  temperatures error (see  7.11,  method; Appendix  both  Two a n d a  we  need  Twi.  computer A).  the  provided T,  [7.11]  Uc  outside  and  U,h,T etc. to The  are  know, t h e latter  program  was  inside  wall  known.  outside  were  found  written  and by for  67  7.1.2  DEA t r a n s p o r t  properties  Transport  properties  the  transfer  heat  properties form  was  The  used  to  to  the  specific  heat  a  perform the  simple  aqueous  have  the  T2  In**'  =  (0.067666  6.820867)/(1  k  Cp where  =  (0.4675  = 4.176  +  -  +  0.0062  0.00046  p = density = viscosity  k  =  thermal  0.000105  c  a 8 5 3 8  T -  )  -  C)/(1  T  a  0.001837  conductivity  Cp=  specific  o  graphical summation  calculation, of  it  equations.  developed  conductivity  T  =  temperature  C  = DEA c o n c e n t r a t i o n  (°C) (wt%)  -  -  C1-19  to and  C +  [7.12]  C)  0.004965))  [7.13]  [7.14]  8  (W/m°C)  (J/g°C)  T 1 , a5 )  0.004395  (Pa.s)  heat  physical  in  successive  therefore  + C ( 3 .-4-0 . 0 0 0 2 5  (kg/m3)  M  published  thermal  calculate  DEA s o l u t i o n s :  998.0-0.00403  (T(0.014066  to  the  by m e a n s  were  viscosity,  on  exchanger  properties  =  -  been  heat  ' p  C -  required  Data  equations  density, of  are  computer-based  predict  following  predict  solutions  Since  preferable  DEA s o l u t i o n s  co-efficients.  DEA  [26,75].  method was  of  of  0.000054  C T  [7.15]  68  In a l l c a s e s predicted than  t h e p e r c e n t a g e d i f f e r e n c e between  values  2%  for  concentrations  7.1.3  Heat  The o n l y was  i s less  between  0 and  transfer fluid  provided  5% and i n most c a s e s  temperatures  information  information  than  between  100  20  and  is  100  °C  less and  properties  Shell  provided,  it  and  wt%.  on t h e p r o p e r t i e s of  by  the p u b l i s h e d  Canada  Shell  [76].  Thermia  Using  the  i t s p r o p e r t i e s were e v a l u a t e d  Oil-C limited  as f o l l o w s :  Density Density  a t 15°C was  equation Engineering  was  po T  as 874.6  developed  D a t a Book  1000  where  given  from  kg/m  3  Figure  [76]. 16-11  of t h e heat  temperature  of  following G.P.S.A.  [77] u s i n g d e n s i t y a t 15°C.  ( 0.886662 - 0.000750 T )  density  The  (°C)  transfer fluid  [7.16]  (kg/m ) 3  69  Density values Table  was  determined  predicted 7.1.  by e q u a t i o n  The a c c u r a c y  Table  experimentally  7.1  was  Density  Temp  (C)  of  7.15. found  The comaprison to  Shell  Density Measured  and compared  be  within  Thermia  Predicted  5  874.6  875.4  20  872.0  871 . 7  40  852.5  .856.7  1 00  808.5  811.7  1 40  780.0  781 . 7  1 60  764.8  766.7  200  732.5  736.7  1  is  ±1% .  Oil-C  (kg/m3)  with  the  the  shown  in  70  Viscosity ASTM v i s c o s i t y petroleum  oils  two d i f f e r e n t Thermia  Chapter  any  were  and  7.2  = -(2.2177  experimentally accuracy  of  temperature  provides  is  Table  a  and  within  7.2  are  +  obtain  provided  known.  the  viscosities  of  viscosities  at  The v i s c o s i t i e s  experimentally procedure  equation  0.0188  the  was  for  is  then  of  Shell  different  described  obtained  for  in the  heat  T)  [7.17]  transfer  fluid  (Pa.s)  (°C)  comparison  between  predicted  viscosities by  equation  10%.  Viscosity  Temp(C)  to  :  those ±  used  temperature  following  MO = v i s c o s i t y  be  experimental  determination  =  can  determined  the  The  In(MO)  T  [78],  temperatures  6.  viscosity  Table  at  Oil-C  temperatures  where  charts  of  Shell  Viscosity Measured  Thermia  (pa.s) Predicted  40  0.0514  0.0514  1 00  0.0154  0.0167  1 50  0.0070  0.0065  200  0.0025  0.0026  Oil-C  determined 7.17.  The  71  Thermal No  conductivity  data  on  Canada; of  the  but  thermal  i t was  Standards  Where;  The  and  at  [0.821  =  temperature  d  =  specific  to  Specific  be  U.S.  Shell Bureau  [7.18]  gravity  can  2  60/60°F  then  be  by  a  specific  between  (BTU/ft /hr/°F/inch),  converted  conversion  gravity  -17.8  to  to  range  426  °C  of the  S.I.  units  factor  of  0.740 a n d  1.00  accuracy  is  +10%.  heat  Specific  heat  Bureau  Standards  of  specific  following  by  (°F),  multiplying the  the  conductivity  conductivity  Within  use  provided  0.000244]/d  T  temperatures  claimed  -  thermal  by  to  were  :  =  simply  0.1441314.  [79]  Tk  thermal  (W/m°C)  recommended  equation  Tk  conductivity  heat  Where;  data  were  also  equation  unavailabale.  [79]  was  used  The  folowing  to  calculate  :  Cp  =  [0.388  +  0.00045  Cp  =  specific  T  =  temperature  d  =  specific  heat  T]/d  0 5  [7.19]  (BTU/lb/°F),  (°F),  gravity.  U.S. the  72  The  specific  units The  (j/kg°C)  stated  7.1.4  heat by  thus  multiplying  accuracy  Thermal  o b t a i n e d can by  i s within  conductivity  of  of  dependent  on  between  transfer  from  the  km  where  km T  The  the  =  accuracy  150  +  equation Book  0.006289  conductivity  temperature  i s within  in  ±0.5%.  factor  to  of  S.I. 4184.  (°C)  steel and  to was  is  not  250°C, to  strongly  the  perform  predict developed  [80].  T  of  steel  order  especially  Reference  15.60  = -thermal = metal  and  following  Metals  stainless  However,  calculations  temperature, data  range.  converted  conversion  stainless  conductivity  experimental  be  ±4%.  Thermal  temperature  a  then  the by  present the  tube fitting  heat wall the  :  [7.20]  316  stainless  steel  (W/m°C)  73  7.1.5  Pressure  The  drop  Colebrook  determination  equation  was  used  to  calculate  friction  factors  [81] :  1  e =  -4.0  log  solution  the  of  friction  + Di  Re  equation  7.21  y i  The  4.67  (  factor  "  f  yr  )  +  2.28  requires "  [7.21]  an  initial  followed  by  a  estimate  trial  and  of  error  solut ion.  The  initial  equation  friction  [81]  factor  0.012  initial mm  through  0.5  After drop  for  surface  from  a  the  APst  estimated  by  the  following  : f  The  was  =  drop  section  calculating  the  straight  pipe  =  f  2 p v2  (Re)'  roughness  pressure m long  0.04  L/D  of  factor  "  e  "  measurements the  heat  friction  was  [7.22]  0 1 6  of  determined water  exchanger  factor  calculated  was  by  "  f  ",  as  flowing  tube.  the  [81]:  [7.23]  pressure  74  The  pressure  APc  This  drop  = APst  equation  relates  heat  straight  tube  7.1.6  The  Film  heat  was  (see  the  tube  was  determined  3.5(Di/Dc))  by  Equation  analogy  7.4)  from  :  [7.24]  coefficient  with of  a  equation coiled  7.4  tube  to  which that  of  [74].  determination  film  thickness  conductive  and  "  6L  convective  "  was  terms  calculated in  the  by  heat  flow  term,  the  : =  6L =  equation  k dA d T / 6 L  7.1  and  equation  "  "  as  diameter  and  a mass  k =  h  can  [7.25]  neglecting be  flow  the  derived  function rate  43.478 =  = h dA d T  k/h  following  5L  +  thickness  Hence,  5L  (1  coiled  transfer  dQ  From  the  chosen  transfer  equating equation  +  in  of of  d1-8  to  fluid the  viscosity give  the  ratio film  transport  thickness  properties,  solution.  [7.26]  tube  75  7.1.7  The  Heat  exchanger  performance  comparing predicted pressure  the by  the  close  considering the  the  model.  model  to  the  fact  with  fact  that  experimentally 7.3  shows  pressure  can  a  one  the  the  initial  various  of  by those  initial  found is  some  at  be  were  included  with  these  in  good  extent.  were  also  This  is  probably  was  ambient  outlet  runs.  to  surprising,  associated  roughness  water  comparisons  were  correlations  results.  surface  using  for  to  with  Similarly,  This  predictions  experimental  drops  ones.  another  evaluated  compared.  errors  the  the  be  of  be  temperatures  temperatures  drop  (albeit  may  runs.  also  number  Probably  pressure  initial  various  measured  that  Initial  Table  for  model  outlet  outlet  cancelled  agreement  exchanger  experimental  correlations  the  heat  predicted  extremely  to  performance  drop measurements  The  in  the  of  model  due  determined  temperature).  temperatures  and  76  Table  7.3  Comparison of pressure drop  outlet temperature data for d i f f e r e n t  and initial runs.  Run No.  Outlet Expt.  1  1.90  1 92  690  718  2  1 70  174  1 207  1 237  3  195  200  552  572  4  1 65  171  552  1 339  5  1 65  171  552  574  6  1 40  141  552  581  7  195  200  552  572  8  1 95  200  552  572  9  1 95  200  552  602  1 0  1 95  200  552  548  temp.(C) Model  Initial Expt.  AP  (kPa) Model  77  7.2  KINETIC  Kennard's written  MODEL  [51]  as  simplified  follows  model  for  DEA  degradation  may  be  by  C02  :  BHEP  Kennard  reported  partial  pressures  solution  of  k2  as  found  a  k3  the  industrial be a  as  as  Both the  the  of  the  take  into  partial  than  which  takes  C02  of  solubilty  account  the  on  first  order  and the  pressure  0.2  in in  account  is  unaffected  the  DEA  also  reported  the  the  initial  in  rate  DEA  constants  k,  concentration.  He  concentration  but  he  did  model.  reboilers),  gC02/gDEA.  into  a  DEA  his  not  include  However,  under  the  C02  loading  Therefore,  the  need  the  C02  partial  to  pressure  clear.  and  DEA  i n DEA s o l u t i o n s is  DEA  Consequently,  pressure  C02  He  rate  of  (especially  lower  is  concentration  temperature  temperature.  partial  solubility  Hence  of  rate  DEA.  pseudo  DEA c o n c e n t r a t i o n  C02  C02  gC02/g  plotted  conditions  term  the  independent  C02  much  include well  be  degradation  degradation  function  on  effect  may  and  to  dependent  0.2  the  concentration  the  provided  exceeds  dependency  and  that  parameter  variation  in  C02  concentration at  a  which  determine  given  temperature.  should  be  partial  pressure  able as  to well  78  I t was t h e r e f o r e decided to i n c l u d e a C 0  as DEA c o n c e n t r a t i o n . solubility that  term  DEA  in  the r a t e equations.  degradation  changes  with  2  Kennard [51] reported  DEA  concentration.  He  i d e n t i f i e d three regions :  1.  0 - 1 0 wt% DEA, where the main degradation route i s i o n i c .  2.  10  -  30  wt%  DEA,  where  combination of molecular 3.  30 - 100 wt% DEA,  the degradation  and i o n i c  where  route  is a  routes.  the main  degradation  route  is  molecular.  Recognising that i t was i m p r a c t i c a l to develop a s i n g l e for  equation  p r e d i c t i n g the rate constants f o r a DEA c o n c e n t r a t i o n range  of 0 - 100 wt%, i t was decided to develop an intermediate industrial  range  of  20  to  40  wt%  equation  which  f o r the  i s of g r e a t e s t  importance.  Kennard's model [51] was m o d i f i e d as f o l l o w s :  THEED  The  k  3  >  BHEP  + C0  f o l l o w i n g equations represent the above k i n e t i c model  d[DEA]  = - kjDEA][C02]  - k [DEA][C02] 2  [7.27]  dt d[HEOD] =  dt  2  k,[DEA][C02]  [7.28]  79  d[THEED] dt d[BHEP]  =  k2[DEA][C02] "  =  k3[THEED]  k3[THEED]  [7.29]  [7.30]  dt d[C02] Assuming  = 0,  integration  of  equation  7.27  yields,  dt [DEA]  =  [DEA]o  Equation  d[HEOD]  7.28  exp{-(k1+k2)[C02]t}  on s u b s t i t u t i o n  =  k.[C02][DEA]o  =  [DEA]o  [7.31]  and i n t e g r a t i o n  yields,  exp{-(k1+k2)[C02]t}  dt  [HEOD]  k, (k,+k2)  (1-  exp{-(k,+k2)[C02]t})  + Equation  7.29  c a n be w r i t t e n  as  [HEOD]0  follows  [7.23]  :  d[THEED] dt  =  kz[C02][DEA]o  +  k3 [ T H E E D ]  exp{-(k,+k2)[C02]t}-k3[THEED]  d[THEED] dt  = k2 [ C 0 2 ] [ D E A ] 0  exp{-(k,+k2)[C02]t} [7.34]  The  above  equation factor [THEED]  equation a n d c a n be  is  a  first  solved  order  linear  by m u l t i p l y i n g  differential by an  integration  exp{k3t} exp{k3t}  =  Jk [C0 ][DEA] exp{(k -(k,+k )[C0 ])t}dt 2  2  0  3  2  2  k2[C02][DEA]0 =  (  : —) e x p { ( k 3 - ( k , + k 2 ) [ C 0 2 ] ) t } k3-(k ,+k2)[C02] w h e r e IC1 d e n o t e s i n t e g r a t i o n constant.  + IC1  [7.35]  80  At  t = 0,  [THEED]  =  [THEED]0  k2[C02][DEA]0 [ THEED ] o =  + IC1 k3-(k,+k2)[C02]  k2[C02][DEA]0 Therefore, Equation  IC1 ,=  [THEED]0  7.35 can then  -  k3-(k,+k2)[C02]  be w r i t t e n  as  :  k2[C02][DEA]0 [THEED]  =  (  )(exp{-(k,+k2)[C02]t}-exp{-k3t}) k3-(k,+k2)[C02] +  Equation  d[BHEP] dt  7.30  =  can then  be  [THEED]0exp{-k3t}  solved  as  [7.36]  follows  k3[THEED] k2k3[C02][DEA]0 k3-(k,+k2)[C02]  (exp{-(k,+k2)[C02]t}-exp{-k3t}) + [THEED]0exp{-k3t}  [BHEP]  [BHEP]  =/ J  /*k2k3[C02][DEA]0 K3-(k,+k2)[C02]  k2k3[CO2][DEA]o  =  k 3 - ( k ,-+k 2 ) [ C 0 2 ] •  +  where  1 k3  exp{-k3t})  IC2 d e n o t e s  (exp{-(k1+k2)[C02]t}-exp{-k3t})dt r  +/[THEED]0exp{-k3t}dt  (-  -  integration  exp{-(k,+k2)[C02]t (k,+k2) [C02]  1 k,  [THEED]0  constant.  exp{-k3t}  + IC2  81  At  t=0,  [BHEP]=[BHEP]0  k2 k 3 [ C O 2 ] [ D E A ] 0 [BHEP]0  k3-(k.+k2)[C02]  =  )  k3-(k,+k2)[C02]  IC2  k2[DEA]o  =  k3  +  k2k3[C02][DEA]0  exp{-(k,+k2)[C02]t}  =  +  +  ( 1 - exp{-k3t})  +  were the  to  of  determine  needed. limited  In  data  rate  the  the  of  Lee  was  desireable  accurate  rate  et  constants, of  al.  needed.  any  [82] This  prediction  unavoidable.  New  values  Kennard's  rate  constants  [51]  +  [BHEP]0  [7.37]  constants  absence  interpolation for  k3  k3  Determination  order  )  (k,+k2)[C02]  [THEED]0  (k,+k2)  In  exp{-k3t}  (  k2[DEA]0  IC2  k3  [BHEP]0  k3-(k,+k2)[C02]  7.2.1  +  k3(k1+k2)[C02]  [THEED]0  +  (k.+k2)  [BHEP]  [THEED]  (  of  k,  C02  reliable were  kind of  rate  In  some  approach  were  by  an  is  data model, cases,  not  very  it  was  generated  from  constants k2  (identified  solubility  used. of  and  solubility  but  asterisk)  as  follows:  The  k,  =  k,*/[C02]  k2  =  k2*/[C02]  values  temperatures.  of  k,  Values  and of  k3  k2 were  were  calculated  obtained  from  for  Kennard's  various thesis.  82  It  should  obtained  at  be  C02  noted partial  some  u n c e r t a i n t y when  The  following  function  of  that  most  of  pressures  the  C02  equations  temperature  Kennard's  of  4137  partial  for  kPa a n d  pressure  predicting  were  then  rate  k  1 f  obtained  data  thus  were  there  is  is  different.  k2  and  by  k3  least  as  a  square  fitting:  where Bulk rate  T  ln(k, )  =  11.924  -  6421/T  [7.38]  ln(k2)  =  8.450  -  5580/T  [7.39]  ln(k3)  =  39.813  -  15160/T  [7.40]  denotes  solution  the  absolute  temperature  was  used  for  the  in degrees  Kelvin.  calculation  of  the  for  the  constants.  Attempts  were  made  to  prediction  of  C02  solubility  mainly  due  to  the  lack  It  therefore  was  initial possible  to  partial of  20  covering  to  40  develop  adequate to  range wt%.  the the of  an  i n aqueous  use  conditions  predict  pressure  of  decided  saturation  accurately,  range  temperature  in  rate  to  it  C02  was  not  solubility  successful. under  autoclave.  of  DEA  degradation  range  of  4137  60  It  However,  the  temperature 1379  model  DEA s o l u t i o n s .  data,  the  empirical  to  then  200  the  became fairly ° C , C02  k P a a n d DEA c o n c e n t r a t i o n  83  7.2.2  Determination  For  the computer  the  residence  flow  rate  volume the  the  residence the  time  once  is  as  for  a  the heat  to  total  transfer  tube  residence is  then  result  =  heat  compared  mixing  transfer small.  solution occurs  time  of  given  by:  to  tube  to  no.  be  This  the heat  well  solution tube  time  is  required  for  exchanger  passes  as  known.  transfer  The time  of  as  and  one h e a t  rt.  through  the  tube  N can then  be  with  through autoclave  is  not  predictions  solution  a  single  pass  DEA s o l u t i o n  the  partially  tube  the  for  of  DEA  total  DEA  was  DEA  and  expected  heat  the to  significantly.  affect  transfer  change  as  from  that tube  pass  a l l  the  a  the  i n the autoclave  transfer next  low.  inventory  solution  assumed  heat  very  solution  the c o n c e n t r a t i o n  degraded  the  are  i n the heat  t h e DEA s o l u t i o n it  in the  x N  Therefore,  Consequently,  approximation computer  of  passes in  transfer  at  t/tsp  changes  the autoclave. of  need  pass,  The t o t a l  the q u a n t i t y  small  inside  very  concentration  addition, is  tube  process  RT = r t  In  conditions  time  follows:  tube  The  and residence  c a n be d e t e r m i n e d .  pass  N The  to  single  by t s p .  inlet  transfer  required  solution  denoted  determined  of  conditions  the  DEA s o l u t i o n  time  DEA  inlet  i n the heat  the volume  equivalent  all  tube  calculations  time  Knowing  of  is  DEA  before  mixing  begins.  This  the accuracy  of  the  84  CHAPTER  RESULTS  AND D I S C U S S I O N  OF DEGRADATION  8.1  COMPARISON OF T H E E X P E R I M E N T A L  The  comparisons  model  are  agreement are  quite  are  not  experimental  given  in  will  also  predictions graphical  of  form  later  between good  fully  Table be  in  but  not  known  DATA  data  8.1  perfect. may  The  be  those  Table  chapter.  predictions  but  with  to  EXPERIMENTS  WITH MODEL  compared with the  the  8  and  the  PREDICTION  predicted  8.10.  The  experimental  As  can  the  experimental  reasons  for  attributed  to  be  the the  by  the  model data  seen,  in the  values  differences following  factors:  *  Inaccuracies  *  The s i m p l i f i c a t i o n  *  Inaccuracies  *  Inaccuracies the  low  BHEP  in  in in  the  rate  constants,  involved  the  C02  the  in  the  solubility  experimental  concentrations.  reaction  scheme,  data, measurements,  especially  85  TABLE  8.1  RUN N O . 1 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 9 0 C , T 0 U T C = 1 9 2 . 4 C FLOW R A T E = 0 . 0 1 2 4 L / s , D E L P = 6 9 0 k P a , C A L D P = 7 1 7 . 9 kPa C 0 2 P A R T I A L P R E S S U R E = 4137 k P a , TH=250C TIME hr  00.0 24.0 48.0 72.0 96.0 1 20.0 144.0 168.0 192.0  TABLE  EXP  DEA  3.00 2.92 2.83 2.73 2.64 2.56 2.50 2.41 2.27  CONCENTRATION HEOD CALC EXP CALC  3.00 2.91 2.82 2.72 2.63 2.54 2.45 2.35 2.26  (MOLES/L) THEED EXP CALC  BHEP EXP C A L C  _ 0.05 0.11 0.16 0.22 0.30 0.35 0.40 0.47  0.06 0.12 0.18 0.24 0.30 0.36 0.42 0.49  -  0.05 0.06 0.07 0.09 0.11 0.13  0.01 0.03 0.04 0.05 0.06 0.08 0.09 0.10  -  -  -  0.05 0.05  0.01 0.01 0.01 0.01 0.01  8.2  RUN N O . 2 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 7 0 C , T O U T C = 1 7 3 . 7 C FLOW R A T E = 0 . 0 1 6 5 L / s , D E L P = 1 2 0 7 k P a , CALDP=1237 kPa C 0 2 P A R T I A L P R E S S U R E = 4137 k P a TH=250C TIME hr  00.0 24.0 48.0 72.0 96.0 120.0 144.0 168.0 1 92.0  DEA EXP CALC  3.00 2.94 2.87 2.81 2.76 2.69 2.63 2.55 2.50  3.00 2.93 2.87 2.80 2.74 2.67 2.61 2.54 2.48  CONCENTRATION HEOD EXP CALC  (MOLES/L) THEED EXP CALC  BHEP EXP CALC —  -  0.06 0.10 0.12 0.16 0.19 0.22 0.2jS  0.03 0.07  o. to  0.14 0.17 0.20 0.24 0.27  0.02 0.04 0.04 0.05 0.06  0.01 0.02 0.02 0.03 0.04 0.05 0.06 0.07  0.01  0.02 0.02 0.03 0.03  •0 -. 0 1  0.01 0.02 0 .02 0.02 0.03  86  TABLE  8.3  RUN N O . 3 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 9 5 C , T O U T C = 2 0 0 C FLOW R A T E = 0 . 0 1 1 0 l / s , D E L P = 5 5 2 k P a , C A L D P = 5 7 1.9 kPa C O 2 P A R T I A L P R E S S U R E = 4 1 3 7 k P a , TH=2 50 C TIME hr  00.0 24.0 48.0 72.0 96.0 120.0 144.0 168.0 1 92.0  TABLE  EXP  CONCENTRATION HEOD EXP CALC CALC  3.00 2.89 2.75 2.68 2.57 2.46 2.35 2.25 2.13  3.00 2.89 2.78 2.67 2.57 2.46 2.35 2.24 2.13  DEA  (MOLES/L) THEED EXP CALC  EXP  BHEP CALC  _ 0.05 0.14 0.20 0.28 0.35 0.44 0 . 52 0.58  0.08 0.15 0.23 0.30 0.38 0.46 0.53 0.61  -  0.05 0.05 • 0.07 0.08 0.10  0.02 0.03 0.05 0.06 0.08 0.10 0.11 0.12  -  0.02 0.02  0.01 0.01 0.01 0.02 0.02 0.02  8.4  RUN N O . 4 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 6 5 C , T O U T C = 1 7 0 . 9 C FLOW R A T E = 0 . 0 1 7 2 L / s , D E L P = 1 . 3 1 M P a , C A L D P = 1 . 3 4 MPa C 0 2 P A R T I A L P R E S S U R E = 4 1 3 7 k P a , TH=250C TIME hr  00.0 24.0 48.0 72.0 96.0 120.0 144.0 168.0 192.0  DEA EXP CALC  3.00 2.94 2.88 2.84 2.78 2.72 2.64 2.57 2.51  3.00 2.94 2.87  2.81 2.75 2.69 2.62 2.56 2.50  CONCENTRATION HEOD EXP CALC _  _  -  0.03 0.06 0.09 0.13 0.16 0.19 0.22 0.25  0.06 0.10 0.12 0.15 0.18 0.21 0.26  (MOLES/L) THEED EXP CALC  0.02 0.04 0.04 0.05 0.06  0.01 0.02 0.02 0.03 0.04 0.05 0.05 0.06  BHEP EXP CALC  0.01 0.02 0.02 0.03 0.04  -  0.01 0.01 0.01 0.02 0.02 0.02  87  TABLE  8.5  RUN N O . 5 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 6 5 C , T O U T C = 1 7 1 . 5 C FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 kPa, CALDP=573.2kPa C 0 2 P A R T I A L P R E S S U R E = 4137 k P a , T H = 2 2 5 C TIME hr  00.0 24.0 48.0 72.0 96.0 120.0 1 44.0 1 68.0 192.0  TABLE  DEA EXP CALC  3.00 2.95 2.90 2.84 2.79 2.74 2.67 2.61 2.54  3.00 2.94 2.88  2.81 2.75 2.69 2.63 2.57 2.50  CONCENTRATION HEOD EXP CALC  0.07 0.11 0.12 0.16 0.21 0.24 0.28  0.04 0.07 0..1 1 0.15 0.19 0.22 0.26 0 . 30  (MOLES/L) THEED EXP CALC  0.02 0.04 0.04 0.05 0.06  0.01 0.02 0.03 0.03 0.04 0.05 0.06 0.07  BHEP EXP CALC  -  -0.01 0.02 0.02 0.03 0.03  0.01 0.01 0.01 0.01  8.6  RUN N O . 6 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 4 0 C , T O U T C = 1 4 2 . 1 C FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 k P a , CALDP=581 kPa C 0 2 P A R T I A L P R E S S U R E = 4137 k P a , TH=190C TIME hr  00.0 24.0 48.0 72.0 96.0 120.0 1 44.0 168.0 192.0  DEA EXP CALC  3.00 2.98 2.94 2.92 2.87 2.82 2.80 2.77 2.72  3.00 2.97 2.93 2.90 2.86 2.8 3 2.79 2.76 2.72  CONCENTRATION HEOD EXP CALC  0.05 0.05 0.05 0.06 0.07 0.09  0.01 0.03 0.04 0.06 0.07 0.08 0.10 0.11  (MOLES/L) THEED EXP CALC  -  -  0.02 0.02 0.04 0.04  0.01 0.01 0.15 0.02 0.02 0.03 0.03  BHEP EXP CALC  0.02 0.03 0.04 0.04  0.01 0.01  88  TABLE 8.7 RUN N O . 7 : 30WT% D E A , T I N = 6 0 C , T O U T = 1 9 5 C , T O U T C = 2 0 0 C FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 kPa, CALDP=572 kPa C 0 2 P A R T I A L PRESSURE = 2758 k P a , TH=250C TIME DEA EXP CALC  i  00.0 24.0 48.0 72.0 96.0 120.0 144.0 168.0 192.0  TABLE  3.00  2.91  2.82 2.71 2.60 2.50 2.40 2.30 2.20  3.00 2.91 2.80 2.69 2 . 59 2.49 2.39 2.29  2.18  CONCENTRATION HEOD EXP CALC _ 0.05 0.15 0.20 0.30 0.35 0.45 0.50 0.58  _ 0 . 07 0.14 0.21 0.29 0.36 0.43 0.50 0 . 57  00.0 24.0 48.0 72.0 96.0 120.0 144.0 168.0 192.0  BHEP EXP CALC  —  -0.05 0.06 0.08 0.10 0.10  0.01 0.03 0.04 0.06 0.07 0.09 0.10 0.11  -  --  0.01 0.02 0.03 0.03  -0.01 0.01 0.01 0.01 0.01 0.01  8.8  RUN N O . 8 : 30WT% D E A , T I N = 6 0 C , FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 C 0 2 P A R T I A L P R E S S U R E =1379 k P a TIME hr  (MOLES/L) THEED EXP CALC  DEA EXP CALC  3.00 2.94 2.83 2.74 2.64 2.56 2.47 2.38 2.28  3.00 2.91 2.81 2.72 2.63 2 . 53 2.44 2.35 2.25  CONCENTRATION HEOD EXP CALC  0.10 0.16 0.25 0.30 0.40 0.46 0.50  0 . 07 0.13 0.19 0.26 0 . 32 0 . 39 0.45 0.52  TOUT=195C,TOUTC=200 C kPa, CALDP= 572 k P a , TH=250C (MOLES/L) THEED EXP CALC  0.05 0.05 0.07 0.10 0.10  0.01 0.03 0.04 0.05 0.07 0.08 0.09 0.10  BHEP EXP CALC  0.01 0.01  0.01 0.01 0.01 0.01 0.02 0.02  89  TABLE  8.9  RUN N O . 9 : 40WT% D E A , T I N = 6 0 C , TOUT= 1 95C , TOUTC = 20 0' C FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 k P a , CALDP= 602 k P a C 0 2 P A R T I A L P R E S S U R E = 4137 k P a , TH=250C TIME hr  00.0 24.0 48.0 72.0 96.0 1 20.0 144.0 168.0 192.0  TABLE  DEA EXP CALC  4.00 3.84 2.66 2 . 52 2.36 2.21 2.10 2.89 2.72  CONCENTRATION HEOD EXP CALC  4.00 3.84 3.68 3.52 3.35 3.19 3.03 2.87 2.71  0.10 0.20 0.34 0.50 0.60 0.70 0.80 0.92  0.12 0.24 0.36 0.48 0.60 0.72 0.83 0.95  (MOLES/L) THEED EXP CALC  0.05 0.07 0.10 0.12 0.16 0.20 0.20  0.02 0.05 0.07 0.10 0.12  0.15  0.17  0.19  BHEP EXP CALC  0.01 0.02 0.03 0.03 0.04  0.01 0.01 0.01 0.02 0.02 0.02 ,  8.10  RUN N O . 1 0 : 20WT% D E A , T I N = 6 0 C , T O U T = 1 9 5 C , T O U T C = 2 00 C FLOW R A T E = 0 . 0 1 1 0 L / s , D E L P = 5 5 2 k P a , CALDP= 572 k P a C 0 2 P A R T I A L PRESSURE = 4 1 3 7 kPa , TH=250C TIME hr  00.0 24.0 48.0 72. 0 96.0 120.0 144.0 168.0 192.0  DEA EXP CALC  2.00 1 .94 1 .89 1 .82 1 .76 1 . 70 1 .64 1 . 57 1 . 52  2.00 1 . 94 1 .88 1.81 1 .75 1 .69 1 .63 1 .57 1 .50  CONCENTRATION HEOD EXP CALC  (MOLES/L) THEED EXP CALC  BHEP EXP CALC  _ 0-.06 0.10 0.15 0.20 0.22 0.25 0.28  0.04 0.08 0.11 0.15 0.19 0.23 0.26 0 . 30  - 0.01 0 . 02 0.02 0.03 0.05 0.05 0.06  0.01 0.02 0.02 0.03 0".04 0.05 0.05 0.06  --0.01 0.01  -  0.01 0.01 0.02 0.02 0.02 0.03 0.03  90  8.2  EFFECTS  OF O P E R A T I N G V A R I A B L E S  The  effects  of  pressure were  temperature,  and e s p e c i a l l y  of  ON DEGRADATION  solution solution  concentration, flow  rate  C02  partial  on DEA d e g r a d a t i o n  studied.  8.2.1  Effect  In  order  two  sets  flow  of  to of  flow  examine  rate  was  leaving  the heat  plotted  constant.  in  resulted  degradation residence  8.1.  for  temperature,  the  In second  exert  order set  of  to  single  keeping  the  As might  to  temperature  in  the predominating  elucidate  the  first  set,  temperature  of  the  DEA  to vary.  of  lower  i n the tube  effect and the  rate  increases  the  outlet  flow  i n DEA of  the  solution  rapidly  section  the  results  The i n c r e a s e  combined  the  solution  The  be e x p e c t e d ,  rates.  the  pass  on D E A d e g r a d a t i o n , In  was a l l o w e d  the degradation  experiments  rate  out.  degradation  c a n be a t t r i b u t e d time  flow  The temperature  Figure  Since  to  while  coil  in higher  of  carried  transfer  temperature.  assumed  were  varied  fluid  rates  the effect  experiments  heating  are  rate  with c a n be  influence.  effect  was c a r r i e d  of out.  flow  rate  only,  a  91  3  |  '  i  1  •  -  0.0165  L/s  •  - 0.0124  L/s  A - 0.0110  L/s  1  1  r  CM co  "  Model  o  »  I  I-  0  40  '  I  80  120  I 160  i 200  ' 240  TIME (Hours) Figure  8.1  DEA c o n c e n t r a t i o n a s a f u n c t i o n of time and flow rate. (30 wt% D E A , i n l e t t e m p . 60°C, heating oil temp. 250 °C, C02 partial p r e s s u r e 4 . 1 4 MPa)  92  The  flow  rates  constant  by  were  varied  regulating  rates  were  chosen,  one  0.011  L/s  (3.4  m/s).  the  two  they  flow  are  time  are  the  same  rates  almost  in  for  both  8.4.  As  rate  higher  when flow is  fluids This  same  The  in  for  two  in  is  both  temperature.  (5.3  Figure  m/s)  and  8.2.  the  flow a  The  two for  rates  single  pass  rates  recirculated) to  the  "  a  at from  be  seen,  function  are the  of  almost of  the  plotted  in  degradation  Although  lower given  almost  total  flow  predictions  the  for  are  a  L/s).  at  Two  remains  pass,  (0.011  kept  other  can as  rates  single  was  resulting  As  model  flow a  the  profiles  DEA d e g r a d a t i o n  rates.  seen,  due  flow  the  rate  period  the  same  residence  time  (and  for ",  is  both which  cases.  of  flow  w, ==l o w e r w == h i g h e r 2  L/s  8.3.  degradation  are  effect  considering  be  fluid  temperature  DEA c o n c e n t r a t i o n s  for  lower  overall  rates.  the  at  rate  the  the  can  hot  outlet  temperature  shown  flow  Figure  higher,  The  Figure  profiles  the  0.0172  identical.  plotted  degradation  the  at  are  concentration  is  while  residence  rates flow  W, a n d  time W2  (W,  can < W2)  be  explained  and  defining  by :  rate  flow  rate  N,  == t o t a l  no.  of  passes  at  flow  r a t e W,  N2  == t o t a l  no.  of  passes  at  flow  r a t e W2  R T , == t o t a l  residence  time  at  flow  r a t e W,  RT2  ••= t o t a l  residence  time  at  flow  r a t e W2  rt,  == r e s i d e n c e  time  for  single  pass  at  flow  r a t e W,  rt  == r e s i d e n c e  time  for  single  pass  at  flow  rate  2  W2  93  The W,  residence is  higher  W2.  than  However,  through We c a n  If  time  rt,  tube  write  :  same  for  rates  of  be  the  layer  is  2  flow L/s  with  consequently,  at  the  higher  given than  x N,  ,  rates  (3.4  to  that  Figure  Film  tube  experiments.  the  higher  and  the  is  the  heat  in  RT2  =  total W2.  rt  This  0.0172  one  of  the  rates  thicknesses  are  very  the  the bulk  exchangers, metal rate  wall  Reynolds  solution the  film  constants.  for  flow  factor  has  film", The  liquid  film film  is  in  exchanger  because  rate  are of  used could  be  temperature.  may  i.e.  A large  model  thicknesses  temperature  case  wall.  number  degradation  the  and,  degradation.  theoretical  N,  rate.  more  heat  thin  passes  m/s).  the  of  rate  is  rate.  the  higher  the  tube  proportion  higher  is  flow  flow  time  "boundary  exchanger  rate  N2  L/s(5.3  so-called  of  x  2  flow  of  flow  residence  increasing  higher  Therefore,  therefore,  the  of  number  by  and  heat  N2  considerations,  predicted  using  the  surface  results as  T,  and  with  the  2  time  W, a n d  m/s)  the  a  ,  then  This  thicknesses  calculating  tr  hydrodynamic  contact  and  time  N2  means  industrial  residence  lower  decreases  accurately  lower  x  thickness  diameter  the  rt  adjacent  8.5.  at  a  examined.  thickness  tr,  rt,  0.011  to  pass  =  =  on  single  RT,  both  Based  a  the  for  the  x N,  for  have  shown  in  the  small  in  the  predicted However  may to  Film  be be  in  large  used  for  94  O •  -  0.0172  L/s  -  0.0110  L/s  JL X ±2 1 3 4 5 DISTANCE FROM TUBE ENTRANCE (m)  o  Figure  r  r-  oo  8.2  Temperature o f t h e DEA s o l u t i o n a s a f u n c t i o n of the d i s t a n c e from the tube entrance and flow rate. (30 wt% D E A , i n l e t t e m p . 60°C, o u t l e t temp. 170°C, C02 p a r t i a l pressure 4.14 MPa)  95  co  CM CO  r  I  • •  - 0JD110 L/s - 0.0172 L/s  E Z co  o  eg  r<  I-  Z CO UJ OJ  o z  O O  < CM o  UJ  CM CM  O CM  Figure  8.3  40  X 80  X  120  TIME (Hours)  160  200  240  DEA c o n c e n t r a t i o n a s a f u n c t i o n of time and flow rate. (30 wt% D E A , i n l e t t e m p . 60°C, o u t l e t temp. 170°C, C02 p a r t i a l pressure 4.14 MPa)  96  Figure  8.4  Model p r e d i c t i o n of DEA c o n c e n t r a t i o n as a f u n c t i o n of t i m e and f l o w r a t e ( s i n g l e p a s s ) . (30 wt% D E A , i n l e t t e m p . 60°C, outlet temp. 1 7 0 ° C , C 0 2 p a r t i a l p r e s s u r e 4 . 1 4 MPa)  97  — r  -  r  T - 0.0110 L/s • - 0.0172 L/s CO  h  o  '  0 Figure  8.5  »  J  I  I  I  1 2 3 4 5 DISTANCE FROM TUBE ENTRANCE (m)  Model p r e d i c t i o n of the f i l m thickness as a function of ' the distance from the tube e n t r a n c e and flow r a t e . (30 wt% DEA, inlet temp. 6 0 ° C , o u t l e t temp. 170°C, C02 partial p r e s s u r e 4 . 1 4 Mpa)  98  8.1.2  The  Effect  rate  of  of  DEA d e g r a d a t i o n  temperature. a  of  temperatures.  8.6,  the  This  time The  tube  temperature  is  of  Three  experiments  solutions  of  at  conditions.  time the  rate  heat  of  purposes,  these  the  transfer  degradation  using  initial  Table  8.11.  and  in  heat  allowed can  dependent  Figure  8.6.  and to  seen  increasing  fluid  the  vary  heat  with  from  on as  transfer  constant  As  the  Figure  temperature.  findings.  flow to  shows  with  20,  rate  of  30  and  0.011  L/s.  concentration  DEA  rate  It  is  increases  with  the  tube,  not  possible  was  DEA c o n c e n t r a t i o n s  rates and  as  from the  to  a this  solution  solution  However  degradation  industrial  clear  of  DEA These  the  temperature  of  wt%  typical  experiments.  it  40  reflect  accurately.  values final  was  with  out  degradation  average  kept  falls  carried  8.7  Since  plotted  fluid.  chosen  for  strongly  concentration  constant  Figure  that  the  were  be  different  was  previous  solution  to  are  temperature  transfer  were  concentration.  the  rate  with  a  concentrations  of  known  three  DEA c o n c e n t r a t i o n  Effect  along  flow  heat  8.2.2  figure  for  outlet  consistent  function  is  DEA c o n c e n t r a t i o n s  function  transfer  temperature  varied  calculate  for  comparison  were  calculated  are  presented  in  99  0  Figure  8.6  40  80  120  160  200  240  TIME (Hours) of time, and DEA c o n c e n t r a t i o n a s a f u n c t i o n wt% D E A , f l ow heating f l u i d temperature. (30 6 0 ° C , c 0 2 p a r t i al r a t e 0.011 L/s, i n l e t temp, p r e s s u r e 4 . 1 4 Mpa)  1 00  CD  r  1 — —  1  1  1  r  - 40 wt% • - 30 wt% m - • - 20 wt% Model o> o A  o  I  0 Figure  8.7  I  40  1  1  80 120 TIME (Hours)  1  160  1  1  200  DEA c o n c e n t r a t i o n a s a f u n c t i o n of time and initial DEA c o n c e n t r a t i o n . (Inlet temp. 6 0 ° C , o u t l e t temp. 195°C, heating f l u i d temp. 250°C, flow rate 0.011 L/s, C02 partial p r e s s u r e 4 . 1 4 MPa)  101  1  Table  8.11  Average degradation rates. (Inlet o u t l e t t e m p . 195 C , h e a t i n g f l u i d f l o w r a t e 0.011 L/s)  Solution  cone.  Degradation  wt%  The  increase  higher The  in  solution  higher  the  For  at  of  2  more  C02  (20 is  degradation  8.2.4  Effect  Experiments  100°C  and  in  wt%)  rate  of  rate  C02  C02  using  on  explained in  higher  dissolved partial  N (30  wt%)  1.290 At  the  be  hr)  the  DEA i s  higher solution  of  solution. and  690  kPa,  N (0.538  mole  and  of  DEA s o l u t i o n .  1.883  solution  terms  alkalinity  the  pressure  N (0.490  DEA  the  in  in  the mole  C02/mole  DEA)  concentrations,  this  causes  the  kPa  C02  rise.  partial  30 were  in  the  C02  to  in  pressure  wt% DEA a t carried  degradation.  plotted  a  may  dissolved  C02  DEA [ 8 2 ] .  to  effect  of  3.5  dissolved  pressures  are  and  compared  partial  runs  0.0065  quantity  DEA) as  N  40  degradation  concentration  C02/mole  0.0045  DEA c o n c e n t r a t i o n ,  the  C02  30 -  strength  consequently example,  0.0025  60 C , 250 C ,  rate  moles/(L  20  temp. temp.  Figure  4137, out  2758, in  and  order  The DEA c o n c e n t r a t i o n s 8.8  as  a  function  of  1379 to  study  for time.  these  of  their three  1 02  T"  CO  r  MPa 2.76 MPa 4.14 MPa — Model 1.38  A  CO  o  JL  co  0  40  80  TIME Figure  8.8  120  160  (Hours)  200  240  DEA concentration as a f u n c t i o n of time and C02 partial pressure. (30 wt% DEA, inlet temp. 60°C, outlet temp. 195°C, heating f l u i d temp. 250°C, f l o w r a t e 0.011 L/s)  1 03  As  expected,  partial  the  pressure.  •increase partial  in  The  accumulation  very  on  was  in  of  this  increase  C02  in  the  left  degradation  can  to be  increase  with  C02  attributed  to  the  DEA s o l u t i o n s  at  higher  C02  8.9. to  12% o f  unattended,  it  might  plant  performance  power  consumption  the  heat  by  such the  transfer  as  the have  some  Therefore,  viscosity  increases  performance  of  absorber  will in  EFFECT  OF D E G R A D A T I O N ON S O L U T I O N  In  order  to  solution  determine  foaming, out.  The  is  not  consequences  operation It  the  decrease likely  or  also  heat  higher  decreases exchangers.  with  viscosity.  result  in  poor  facilities.  FOAMING  whether  degradation  foaming  tests  described  results  are  as  increase  are  serious  industrial  8.4  runs  viscosity),  pumps.  co-efficients  viscosity  solution  very  of  the  typical  viscosity  initial  coefficient  mass  C02  of  unsatisfactory  Furthermore  the  the  DEA s o l u t i o n  transfer  increases  changes  Although  (4  VISCOSITY  products  The v i s c o s i t y  Figure  significant  carried  found  OF D E G R A D A T I O N ON S O L U T I O N  DEA s o l u t i o n s .  shown  rate  pressures.  EFFECT  if  Again  dissolved  8.3  of  degradation  presented  has  in  in Table  any  Chapter 8.12.  effect 6  on were  Figure  8.9  S o l u t i o n v i s c o s i t y as a and d e g r a d a t i o n p r o d u c t  f u n c t i o n of time concentration.  1 05  Table  8.12  Sample  As  Results  of  Foam  description  30  wt% DEA  Foam b r e a k d o w n time (s)  height mL  DEA  40  5  5.0  wt% d e g r a d e d  DEA  50  30  7.3  wt% d e g r a d e d  DEA  80  70  8.7  wt% d e g r a d e d  DEA  1 00  100  be  seen  from  the  increases  However,  results,  the  foaming  it  was  not  compound(s)  are  primarily  EFFECT  DEA  degrades, and  increases. compounds  the  The  to  of  tendency  the  to  solution  degradation in  the  for  concentration  THEED)  TEA [ 4 1 ] .  is  compounds pH o f  the  the  DEA  also  of  two  as  Furthermore, is  which  degradation  partly  solution.  DEA i n  the  solution  degradation  than  Therefore,  decreases.  solution.  pH  of  lower  degradation  foaming  concentration  of  of  determine  responsible  alkalinity  (BHEP a n d  equivalent  decrease  possible  accumulation  OF D E G R A D A T I O N ON S O L U T I O N  decreases  the  with  wt% d e g r a d e d  products  When  tests  0.0  can  8.5  foaming  principal that  of  degradation DEA  DEA d e g r a d e s , formation  and  and  the of  responsible Hall  products  is  pH o f other  for  Barron  the [53]  106  presented solution stable  industrial pH w i t h  salts  carboxylic the  are acids  showing  formation  formed with  as  a  of  heat  a  result  DEA [ 4 5 ]  gradual  stable  thereby  .reduction  salts.  of  These  in heat  neutralization  reducing  the  basicity  of of  solution.  These obtained was  the  data  findings from  measured  8.10)  The  are  degradation  as  a  function  initial  sharp  absorption  of  C02.  the  of  basicity  loss  formation  of  confirmed  less  basic  the  experiments of  time.  drop  The g r a d u a l due  by  to  in  in  for  pH c a n  loss  degradation  which  (see,  decrease  the  experimental  of  be  the  results  solution  example, attributed  thereafter  BHEP a n d  Figure to  the  represents  DEA a c c o m p a n i e d  products  pH  by  THEED.  the  1 07  80 Figure  8.10  120 160 TIME (Hours)  200  240  T y p i c a l pH c h a n g e o f p a r t i a l l y degraded DEA s o l u t i o n a s a f u n c t i o n o f t i m e . (30 wt% D E A , i n l e t t e m p . 6 0 C , o u t l e t temp.l95C, h e a t i n g f l u i d temp. 250C, flow r a t e 0.011 L/s)  108  8.6  HEAT  Heat  EXCHANGER  exchanger  results  in  the  8.6.1  The  of  the  same  varied  of  time  the  fouling  constant the  attributed  rate  rate in  rises  mostly  may  tube  increasing  the  heat  pressure  drop  In  order of  to  heat  exchanger  coil  fluid  seems  of  to  different  L/s),  the  temperature shows  the  runs.  As c a n  A l l these  where v i s c o u s slight the  hot was  be  was  increase  temperature  drop  as  from  temperature runs  were  play  increases in  to a  function  minor  pressure  a  8.11,  reaches  carried  as  was  change  Figure and  a  to  performed  allowed  seen  forces  viscosity  runs  fluid  pressure  increasing  case.  out  in  role.  result  drop  a  can  of be  fouling.  increase diameter  surface  three  (0.011  with  each  spite  effective  the  which  fouling  transfer  In  three  degradation,  Fouling  on  heat  rate.  8.11  region,  in  across  flow  fouling.  degradation  hot  outlet  these  turbulent  solution  the  Figure  value  Therefore,  of  the  for  Therefore  i n f o r m a t i o n on  drop  to  temperature  flow  accordingly.  resistance  drops.  solution  fouling  and  a  run.  temperature the  pressure  pressure  each  Effect  creates  provide of  the  for  influence at  can  effect  exchangers, recorded  fouling  increased  measurements study  FOULING  the  pressure  due  roughness  to of  drop  scale the  by  reducing  f o r m a t i o n and  tube.  also  the by  109  O  o  • - 250 °C • - 225 °C o o o - 4-190 °C •  A  4  O  o m o o  Figure  8.11  -L  4 6 TIME (Days)  8  10  Pressure drop as a function of time and heating fluid temperature. (30 wt% D E A , inlet temp. 60°C, heating fluid temp. 250°C, flow rate 0.011 L/s, C02 partial p r e s s u r e 4 . 1 4 MPa)  1 10  Electron  micrographic  uncontaminated 8.12.  Figure  cross  section,  x),  of  8.6.2  the  surface  contaminated  show  the  fouling  the be  Electron  noted  Apparent It  was  due  to  the  result  of  of  Figure  8.15  as  are  micrographic and  of  the  a  of  shown  an  Figure  photos  magnified  fouled  aluminum not  no a l u m i n u m was  used  are  of  view  a (400  of  the  shown  in  in  heat  the be  in  exchanger  fouling  determined. the  flow  contaminated  Figure  scale. It  circuit. and  un-  8.14.  thickness  thickness  assumed  that  was  calculated  the  increase  decrease  formation. a  section  aluminum c o u l d  plots  deposit  scale  tube  tube  of  presence  that  the  surfaces  analysis  analysis  surfaces  deposit  the  electron  contaminated  microprobe  Apparent  of  scale.  source  contaminated  the  microprobe  revealed  should  only  of  a  microprobe  However,  data.  8.13  Electron  Electron  8.6.3  and  photos  function  in  the  Deposit of  time.  in  from  the  the  effective  pressure  pressure tube  thicknesses  are  drop  diameter plotted  drop was as  a in  111  8.7  E X P E R I M E N T WITH  Run  1  (30  rate  0.0124  pressure of  same  drop  wt% D E A , i n l e t  temp.  60°C,  L/s,  fluid  temp.250°C  4137  data  heating  kPa)  dimension  turning  A NEW T U B E  radius matched  was  (4.80 of  repeated m long,  0.4064  accurately  using 3.175  m). with  a  outlet  and  C02  mm O D , 2 . 0 3 2 as  previous  mm ID  well  as  results.  flow  partial  new u n c o n t a m i n a t e d  Degradation the  temp.190°C,  tube  and  a  pressure  b)  Fiqure  8.12  Contaminated  E l e c t r o n m i c r o g r a p h i c p h o t o s of u n c o n t a m i n a t e d and c o n t a m i n a t e d of t h e h e a t e x c h a n g e r t u b e . (20  the surfaces x)  113  Figure  8.13  Electron micrographic p h o t o s of the fouled s u r f a c e o f t h e h e a t e x c h a n g e r t u b e (20 x ) a n d a m a g n i f i e d v i e w (400 x) o f t h e same s u r f a c e  Fe  Cr Al Fe  Mn + Cr  *•  •  a)  Contaminated  Ni  Ni  • •**" • •  • . •  surface  Fe  Cr  Mn +  Fe  Ni  Cr  Al ••••••  b)  Figure  8.14  y  Uncontaminated  Ni  .  surface  E l e c t r o n microprobe p l o t s of the c o n t a m i n a t e d and uncontaminated s u r f a c e s of the heat exchanger tube.  11 5  CM  TIME (Days) Figure  8.15  Apparent deposit thickness as a f u n c t i o n of time and h e a t i n g f l u i d t e m p e r a t u r e . (30 wt% D E A , i n l e t t e m p . 6 0 C , f l o w r a t e 0.011  L/s)  11 6  CHAPTER  RESULTS  9  AND D I S C U S S I O N OF CORROSION S T U D I E S  9.1  CORROSION  RATE  I N UNDEGRADED DEA S O L U T I O N S  The  corrosion  rate  of  as  determined  mm/year  by  (2.46  0.05  mm/year  their  tests  (2  using  practically  used  in  DEA  degradation  only  with H2S,  9.2  their  CORROSION  A degraded  (16.1  HEOD, steel  obtained  the  same.  tests. their  not  degrade  (see to  Blanc  system. should Since  un-degraded Figure the et  H2S  al.  DEA s o l u t i o n ,  was  [45]  in  corrosion  noted is  9.1),  corrosion  The  be  -solution,  that  known which  0.06  rate  of  one  of  rates  C02  was  to  inhibit  was  not  saturated  noticeably.  I N DEGRADED DEA S O L U T I O N S  of  DEA  6.5  solution  yielded times  indicates  thereby  the  close by  Fe~H2S-DEA  RATES  and  quite  It  in  test  the  did  This  is  [43],  about  THEED and  mpy)  products  mpy),  solution.  This  corrosion  sample  degradation  steel  potentiodynamic  mpy),  are  carbon  BHEP  contradicts  corrosion  higher  that are,  a  containing  than  about  rate  that  of of  degraded  DEA s o l u t i o n s  in  corrosive  fact,  earlier  claims  0.4  8.7  %  mm/year  un'-degraded containing  towards  carbon  [45].  I  RRER  E . HH I - I .5DD I I  MI//SEC  C0RR  E  - • . S O D  CTC  RESULTS D.53H  RTC  a.oas  J-CBRRC  S.7SIE3  MPY  2.ESH  C0RR  - • . 3 3 7  :  •• . I DO -  -•.SHD  -  ID Figure  9.1  5  ID NR/CM  Potentiodynamic anodic p o l a r i z a t i o n curve o f 30 wt% u n d e g r a d e d DEA s o l u t i o n . ( t e m p . 2 5  3  C)  2  2  SRMPLE DRTE RRER  • 2 . • I E .HH I - I . E D O I I - • . 7 B D  I?  NI//SEC  C0RR RESULTS CTC • . I 77 RTC N07 F0UND I C0RRC 3.H3DEH E  MPY E  I  - 0 . 0 3 2  C0RR V  - • . S H d  -  .3B0  -  N R / C M 2 3.3BHES 5.BI I EH 2.HSSEH 2 . E 7 0 E H  - • . S D H - • . 2 3 0 • . 2HH • . 332  • Figure  9.2  9  N R / C l i  P o t e n t i o d y n a m i c a n o d i c p o l a r i z a t i o n c u r v e o f 30 wt% p a r t i a l l y d e g r a d e d DEA s o l u t i o n c o n t a i n i n g 8 . 7 wt% degradation products. (Temp. 25C)  .EIDEI  2  oo  1 19  9.3  EFFECT  DEA  solutions  when can  they be  OF C Q 2  in  are  concluded  obtained initially  with  40  DISSOLVED  the  saturated from  of  C02  with C 0 2 ,  Table  9.1  by  wt% DEA s o l u t i o n s  saturated  Table  absence  IN DEA S O L U T I O N S  9.1  with C02  Effect  Sample  at  of  are they  not  corrosive.  become  This  corrosion  rates  the  which  either  are  on  rates  mm/year  mi l s / y e a r  wt% DEA  0.003  0. 1  40 wt% DEA + CO 2  1 .840  72.32  40  free  of  or  and  100  °C.  pressure  corrosion  Corrosion  However,  corrosive.  comparing  atmospheric  C02  ON CORROSION  rates  1 20  9.4  When  E F F E C T OF S O L U T I O N  DEA c o n t a i n s  concentration.  C02,  the  Weight  concentrations indicate  CONCENTRATION  are  that  corrosion  loss  results  presented  the  rate  in  corrosion  increases  conducted  with  at  Table  9.2.  rate  increases  t h e DEA  various  They  DEA  clearly with  DEA  concentration.  Table  9.2  Effect  of  DEA c o n c e n t r a t i o n  Corrosion  Sample  9.5  30 wt% DEA + C02  1 .60  63. 1  40 wt% DEA + C02  1 .840  72.32  60 wt% DEA + C02  2.070  81.60  pH ON CORROSION  diagram  qualitative  information  seen  Figure  corrosion, than  9.  minimal  one At  due  at  on  2.2,  the  for  the  Fe-H20  effect  there  pH g r e a t e r  intermediate to  rates  rates  mils/year  potential-pH  from  corrosion  mm/year  E F F E C T OF S O L U T I O N  Pourbaix  on  exist  than  13  pH v a l u e s ,  formation  of  of  metal  system pH two  on  [60]  distinct  the  other  the  corrosion on  provide  corrosion.  and  oxide  can  regions  at rate the  As  pH  of  lower  would  be  surface.  121  Therefore, gradually the  any  decrease  towards  corrosion  the  initially  absorption  and  degradation become  more  9.6 E F F E C T  After was  loss  decrease  thereafter  rapidly  drop  gradually  to  identify  responsible were  for  corrosion  carried BHEP  HEOD  and  these  weight  which  the  formation  of  are  expected  to  out  with  separately  DEA  plus  loss  carbon  different as  well  as  Table  of  C02  DEA s a m p l e s ,  degradation  BHEP.  tests.  degraded  of  pH o f DEA  to  PRODUCTS  of  the  due  DEGRADATION  nature  increases  result  OF I N D I V I D U A L  corrosive  8,  system  a  occurs.  the  the  as  degradation  DEA  of  Chapter  as  corrosive  HEOD a n d  results  in  lead  therefore  solutions  containing plus  and  to  Therefore,  desireable  tests  pH, tends  region  As d i s c u s s e d  products.  noticing  primarily  solution  corrosion  rate.  solutions  in  products steel.  aqueous with  it are  Weight solutions  mixtures  of  9.3 s u m m a r i z e s  the  . 1 22  Table  9.3  Effect  of  individual degradation  Corrosion  Sample  mm/year  The  5.1  15 wt% + C02  BHEP  0 . 16  6.3  15 wt% HEOD + C02  1 .95  76.6  30 wt% D E A + C02  1 .60  63. 1  30 wt% D E A + 5 wt% BHEP + C02  1 .57  62.0  30 wt% DEA + 5 wt% HEOD + C02  1 .91  75.0  lower  than  corrosive  nature  with  findings  the  solutions  (on  DEA  own.  on  data This  its for  is  15  also  a  in  the  that of  of  of  Blanc  et  weight be  seen  wt% D E A a n d  15  wt  agreement  with  This  DEA s o l u t i o n s  can  in  containing  DEA a l o n e .  BHEP.in  constant This  solution  al.  the  are  is  the  and  agreement  is  more  BHEP  corrosive  than  the  of  in  non-  However,  weight  solutions,  findings  BHEP,  indicates  comparing  % BHEP  DEA a n d  [45].  basis) by  corrosion  mils/year  0.13  rate  on  rates  15 wt% DEA + C02  corrosion  slightly  compound  loss  respectively. Hakka  et  al.  DEA  plus  [41].  The HEOD w e r e BHEP.  corrosion higher  This  than  indicates  rates  in  those the  the  solution  containing  corrosive  containing  DEA a l o n e  nature  of  and  HEOD.  DEA  plus  1 23  9.7  EFFECT  Aqueous  OF M E T A L  DEA  species  in  solutions  as  mentioned  species,  forming  metal  degradation  well  forming  C02  Other etc.,  ligands.  Comeaux  with  THEED a r e  [57]  polyamines  such etc.  agent  which  ion  Hall  and  which  tie  presence degraded of  one  Barron up of  DEA  kind  or  in  of  The  corrosion  the  +  are  effect  is  also the  very  DEA form  hydrazine,  act  as  complex  ethylenediamine,  N-  is  than of  complexing  iron  point). chelates,  Considering  that  the  abilities  metal  metal  equilibrium  a one  forming  the is  to  of  iron  likely  complexing  Major  formation  presence  with  ,  above  capable  as  3 -  of  more  w i t h complex  the  likely  (A c h e l a t e  the  produced of  may  HCO  the in  complexes  ions  in  the  reduction  of  the  represented  by  the  :  2e'  in  regions  it  are  such  ionised  OH",  steel.  also  as  at  ,  of  Among  DEA s o l u t i o n s .  metal-ion/metal  reaction  reduction  species  another  potential  2 +  reported  solutions,  The main  Fe  metal  industrial  these  solution.  following  a  [53]  iron, all  to  +  R2NH+  reported  (Hydroxyethyl)-Ethylenediamine attaches  and  carbon  present,  H  [51].  contaminants, if  mixtures  of  R2NH+  with  HEOD a n d  as  mainly  R2NCOO"  complexes  sulphides,  regarded  and  OH", HC03~,  products,  chelates  be  consisting  as  complexes.  cyanides,  can  equilibria,  R2NCOO~,  metal  COMPLEXING  in  -  Fe  this  equilibrium  the  potential-pH  [9.1]  potential diagram.  enlarges  the  1 24  Formation  of  solution,  and  solubility passive  metal  therefore,  of  the  films;  the  concentration  of  9.8  PASSIVITY  An  examination  and  the  over  a  film  seem  extent  in to  polarization  the  case  be  very  adequate  protection.  other this  in  velocities, metal  factors, respect.  the  as  curves  they  unstable.  and  order is acid  to  promote  for  both  in  the the  breakdown on  are  of the  of  Figure  important  is  very  protect  9.1),  the  that  the  to  the  is  close does  not  maintaining  the  protective  However, to  be  do  stable.  of  out,  9.2,  passivity  DEA ( s e e  idea  break  and  quite  consequently the  undegraded  not  More  region  the  9.1  regions  questionable. gas  in  depends  Figure  undegraded  passive  increase  breakdown  although  Therefore, in  an  ions  solution.  range,  current  surface such  of  metal  also  (see,  that  potential  corrosion  the  in  samples  critical  on  the  of  current  film  of  indicates  in  may  complexes  corrosion  solution  It  the  wide  Particularly  stabilises  results  metal.  degraded  respectively), exist  complexes  provide lower passive  there  considered  are in  125  9.9  PITTING  The  pitting  to  be  very  degraded  distinct  DEA  visible. might  potential  different  corrosion  the  9.3  to  case  the  test  corrosion is  shown  is in  also Figure  9.6  9.7.  in  However,  of fact  that  degraded  under the  test  A 2000  the  Pitting HEOD.  x magnification  found case  is  of  clearly  DEA  solutions  conditions.  coupons  pitting  in  not  in  certain  show  immersed  was  potential  respectively).  coupon  evident.  9.1).  indicate  photos  tests,  DEA s o l u t i o n s  pitting  corrosion  Figures of  Figure the  to  pitting  micrographic  in  (see  seems  Electron  (see  undegraded  solutions,  This  induce  of  used  very is  in  clearly  most  severe  Intragranular of  a  pit  area  Figure  9.3  E l e c t r o n m i c r o g r a p h i c photo A I S I 1020 c a r b o n s t e e l t e s t  o f an u n c o r r o d e d coupon. (400x)  1 27  Figure 9.4  E l e c t r o n micrographic photo of AISI 1020 carbon s t e e l t e s t coupon a f t e r 120 hr immersion in in 15 wt% DEA s o l u t i o n at 100 C. (400x)  1 28  Figure  9.5  Electron micrographic photo s t e e l t e s t coupon a f t e r 120 wt% BHEP s o l u t i o n a t 100 C .  o f A I S I 1020 c a r b o n h r . i m m e r s i o n i n 15 UOOx)  Figure  9.6  E l e c t r o n micrographic photo s t e e l t e s t coupon a f t e r 120 wt% HEOD s o l u t i o n a t 100 C .  o f A I S I 1020 c a r b o n h r . i m m e r s i o n i n 15 UOOx)  Figure  9.7  E l e c t r o n m i c r o g r a p h i c photo of a p i t a r e a of A I S I 1020 c a r b o n s t e e l t e s t c o u p o n a f t e r 120 h r . i m m e r s i o n i n 15 wt% HEOD s o l u t i o n a t 100 C . ( 2 0 0 0 x )  131  CHAPTER  PURIFICATION  Unlike  MEA, d e g r a d e d  distillation that  DEA  at  and  OF DEGRADED  DEA  solutions  atmospheric its  10  DEA S O L U T I O N S  can  pressure.  degradation  not The  products  be  purified  reason  have  for  this  similar  by is  vapor  pressures.  10.1  U S E OF CARBON  Activated  carbon  solutions. and  They  probably  successful  some  DEA  treating These  can  that  and  of  degradation  heat  carbon  of  products  salts  Alberta that  removed  purify  d e g r a d e d DEA  heavy  hydrocarbons  [51]. by  limited do  not  Chromatograms  confirm  were  to  solids,  filters  activated in  used  reported  Kennard's  compounds.  also  stable  been  and  located  widely  suspended  has  activated  chromatograms  filter.  the  downstream  plant  are  remove  Meisen  degradation  upstream  filters  operation  [12,15,16], indicated  FILTERS  of  carbon are  by  the  several  of  their  authors  laboratory  tests  remove  major  any  DEA s a m p l e s  filters  shown  none  Although  in  taken a  in Figure the  10.1.  major  activated  gas  DEA  carbon  1 32  HEM  a)  b)  Figure  10.1  Sample  Sample  taken  taken  upstream  downstream  of  of  filter  filter  C h r o m a t o g r a m s o f p a r t i a l l y d e g r a d e d DEA s a m p l e s t a k e n u p s t r e a m a n d d o w n s t r e a m o f an activated c a r b o n f i l t e r l o c a t e d i n a gas p l a n t i n A l b e r t a .  1 33  10.2  U S E OF C H E M I C A L S  Scheirman removal  [15] of  use  of  of  soda  salt  heat  the  stable  sodium h y d r o x i d e  activated They  reported  Hall  carbon  filters  content  Since present  as  a  were  and  tests  NaOH  [53] in a  these  (Na2C03)  suggested  the  possible  compounds  instead  the  Ram R i v e r  reduction  for  the  reported  the  in  use Gas  the  of  both  Plant.  heat  stable  treatments.  indicated  directed  ash  potassium  Barron  and  of  soda He a l s o  indicating  result  corrosion  efforts  and  data  of  salts.  (NaOH)  ash.  presented  use  that  towards  the  BHEP  is  not  removal  of  corrosive, HEOD  and  THEED.  10.3  REMOVAL OF HEOD  According DEA  to  Kennard  [51],"HEOD  is  formed  by  the  dehydration  carbamate.  0  II  0 R-N-C-jO"  I C2H„-0-iH DEA C a r b a m a t e  H* i  *• N CH2  0 - CH2 HEOD  +  H20  [10.1 ]  of  1 34  Kennard  [51]  suggested  convert  most  the  ring  atom  HEOD of  the  of is  the  that  HEOD t o  unstable  ring  is  NaOH  easily  and  addition  DEA.  This  the  to is  elec-tron  attacked  HEOD s o l u t i o n s due  to  the  deficient  fact  can that  carbonyl  by O H " .  0 + OH' + H +  II  ->  [10.2]  R-N-C-OH  I  C2H,-OH HEOD  When  NaOH  DEA c a n upon  be  DEA  is  added,  HEOD  regenerated  applying  is  Carbamate  c o n v e r t e d back  by d r i v i n g  off  C02  to  DEA c a r b a m a t e  from  the  carbamate  heat.  0  II  R-N-C-OH  >  R2NH  I C2H4-OH DEA  Carbamate  DEA  + C02  and  [10.3]  135  10.4  REMOVAL OF T H E E D  NaOH  is  also  Although to  be  capable  the  as  of  removing  mechanism  follows  is  THEED  unclear,  R  \ C2Ha  -  /  + OH'  of  this  Figure  was  10.2.  HEOD was to  appear.  As  also  processing  at  can  plant  H  to  and  are  Figure  completely,  the  HEOD was  about  after  seen,  a  was  has  a  The  treatment  retention  a  shown  in  completely  and  new  time  the  chromatograms are  removed  However,  and  peak  seems  similar  to  N-  a  gas  SAMPLE  heated  DEA s a m p l e  at  DEA s a m p l e  removed  solution  ("HEI").  degraded  10.3.  DEA 2 min.  NaOH  completely. peak  DEA  T H E E D was  OF I N D U S T R I A L  of  in  be  imidazolidone  added  [10.4]  \  degraded  C for  and  new  chromatograms shown  80  almost  This  PURIFICATION  NaOH was  typical  before  removed  (hydroxyethyl)  10.5  a  heated  solution  N  / DEA  to  -  R  THEED  mixture  /  N-H +OH-C2H«  H  added  appears  R  ^  \  was  reaction  \  N  R  NaOH  overall  solutions.  R  / -  the  degraded  :  R N  from  80  C for  before  Once  about  and  after  again,  partially  and  obtained  THEED a  2  from min.  NaOH was  new p e a k  The  treatment removed appeared.  136  a) B e f o r e  NaOH  treatment  DEA  New  peak  -L  b) A f t e r Figure  10.2  NaOH  treatmet  C h r o m a t o g r a m s o f a p a r t i a l l y d e g r a d e d DEA o f r u n 3 b e f o r e a n d a f t e r NaOH t r e a t m e n t .  sample  1 37  DEA  HEM  Yr—T-  a)  Before  NaOH  treatment  DEA  New  HEM  b)  Figure  10.3  After  NaOH  Chromatograms of p l a n t b e f o r e and  peak  treatment  a degraded a f t e r NaOH  from a gas treatmet.  processing  1 38  Once  again,  partially  was  removed  a n d a new p e a k  This may  THEED  partial  have  laboratory  10.6  to  decided of  and  absence  to  especially  to prepare  DEA,  -HEOD a n d THEED, of other solution  a p p r o p r i a t e chromatograms  was  Consequently, appears  from  of  N-  was n o t p r e s e n t i n  complete the  HEOD  HEOD  completely  the i n d u s t r i a l  from  sample,  o f 30 w t % , 12 w t % a n d i n the laboratory  was h e a t e d  a r e shown  removal and  THEED  2 mL o f 1 N NaOH was t h e n  and the mixture  complete  t o depend  remove  contaminants.  The  removal  presence  which  respectively,  the  almost  ("HEM"),  a 20 mL m i x t u r e  to  time,  the  OF A M I X T U R E OF DEA, HEOD AND  of the i n a b i l i t y  laboratory  removed  sample.  NaOH T R E A T M E N T  Because  was  o f HEOD was s o m e w h a t s u r p r i s i n g a n d  due  (hydroxyethyl)ethyleneamine the  HEOD  appeared.  removal  been  completely,  the  removal  on t h e p r e s e n c e  of new  in  HEOD  a t 80°C Figure  i t was 8  wt%  in  the  added  f o r 2 min. 10.4.  This  was a c h i e v e d .  THEED  peak  appeared  efficiency of other  the  b y NaOH  again. treatment  contaminants.  1 39  DEA  HEOD  i—r  a)  Before  NaOH  treatment  DEA  b) Figure  10.4  After  NaOH  treatment  C h r o m a t o g r a m s o f l a b o r a t o r y made m i x t u r e 30 wt % D E A , 12 wt% HEOD a n d 8 wt% T H E E D b e f o r e a n d a f t e r NaOH t r e a t m e n t .  of  1 40  10.7  SODA A S H TREATMENT  Soda  ash  (Na2C03)  degradation  is  occasionally  compounds,  degraded  DEA s o l u t i o n s .  addition  upon  was  added  was  to  an  heated  sample  As  was  removed.  the  same  and  can  the  In  assess  removal  80  be  seen,  On t h e  retention  order  of  C for  after  Na2C03 none  the  heat  sample  2 min.  the  "new"  are  major  another  the  removal  stable  salts  effect  peak  from  Na2C03  compounds,  Na2C03  and  the  shown  mixture  in  degradation  peak  of  of  The chromatograms  treatment of  the  degradation  DEA s o l u t i o n about  as  to  major  contrary,  time  for  especially  industrial  at  before  10.5.  the  used  appears  mentioned  of  the  Figure  compounds which  above.  has  141  HEM  Figure  10.5  a)  Before  b)  After  soda  soda  ash  ash  treatment  treatment  C h r o m a t o g r a m s o f a d e g r a d e d DEA s a m p l e from a gas p r o c e s s i n g p l a n t b e f o r e and a f t e r soda ash t r e a t m e n t .  1 42  CHAPTER 11  CONCLUSION  11.1  CONCLUSIONS;  1.  Degradation  2.  DEA i n  temperature,  C02  Accumulation  of  solution  3.  of  DEA  AND RECOMMENDATIONS  heat  partial  DEA  exchangers  pressure  mainly  depends  on  a n d DEA c o n c e n t r a t i o n .  degradation  compounds,  increases  the  viscosity.  degradation  results  in  severe  fouling  of  process  equipment.  4.  DEA  degradation  also  increases  the  foaming  and  not  bulk  tendency  of  the  solut ion.  5  Skin  temperature  largely  6.  determines  Solution  flow  minimising minimise thickness  rate  skin  the of  the  of  solution  DEA d e g r a d a t i o n  be  used  temperature.  rate the  can  the  as  Higher  degradation  solution  an  adjacent  by to  temperature  rate.  operating solution  flow  decreasing the  variable  metal  rate the  wall.  in can film  143  7.  Kennard's  simplified  DEA d e g r a d a t i o n  k i n e t i c model was n o t a b l e t o p r e d i c t  under v a r i a b l e C 0  partial  2  model p r o v i d e s d i f f e r e n t r a t e c o n s t a n t s concentration degradation DEA  ranges.  In  order  r a t e under v a r i a b l e C 0  concentrations,  Kennard's  pressures.  f o r three d i f f e r e n t  to  predict  partial  2  His  model  was  the  pressure modified  DEA and as  follows:  ^ J ^ ^ DEA + C 0  HEOD  2  k  3  THEED  >•  + C0  The p s e u d o r a t e c o n s t a n t s  k,,k  a function  by u s i n g t h e f o l l o w i n g  of temperature  3  6451/T(K)  ln(k )  =  5580/T(K)  ln(k )  = 39.813 - 15160/T(K)  3  8.450 -  t h e above m o d e l , i t was p o s s i b l e  of DEA d e g r a d a t i o n °C, t h e C 0  2  partial  f o r the temperature pressure.range  2  c a n be c a l c u l a t e d a s  l n ( k , ) = 11.924 2  Using  2  and k  BHEP  equations:  to predict r a n g e o f 60  the rate to  200  o f 1379 t o 4137 k P a , a n d  DEA s o l u t i o n c o n c e n t r a t i o n r a n g e o f 20 t o 40 w t % .  1 44  8.  HEOD, to  9.  be  HEOD, be  10.  The  THEED  some  and  any  back  to  removal  Industrially  from  major  towards  presence  Na2C03  the  corrosive  HEOD  remove  12.  of  converted  the  11.  one  of  major  treatment  degraded  mild  other  minor  DEA b y  adding  not  DEA s o l u t i o n s .  was  found  to  and  compounds applying  apparently  can  heat.  depends  on  compounds.  carbon  able  NaOH  by NaOH  DEA d e g r a d a t i o n  is  degradation  degradation  activated  products  steel.  efficiency  other  used  DEA d e g r a d a t i o n  filters  are  not  able  to  products.  remove  BHEP,  HEOD o r  THEED  1 45  11.2  a)  RECOMMENDATIONS  The e f f e c t  of  Temperature  is  controlled  in  temperatures, hot  spots,  heat be  temperature  the  should  to  Metal 120°C  thermocouples, should  be  purpose.  are  met  skin be  the  heat  either  metal  during  the the  by  skin  plant  temperature  control  rate  would  than  This  the  transfer  the  should  lowering  a  should  done that  At  skin  least  at  the  be  due  medium.  swifter  temperature  of  two  for  rate  be  outlet this to  brought  flow  by heat  preferably  increases  heating  provide  local  metal  surface  solution the  such  other  be  designing  be  high  should  it  In  can  creating  and  and  consideration  temperature  of  plant.  carefully.  operation,  increasing  flow  the  temperatures monitored  to  Elevated  temperatures  resistances  without  to  variable  degradation.  plants,  transfer  attached  control  temperature  heat  inlet  the  skin  temperature.  the  upset  increasing  treating  at  If  decreasing  and  DEA  throughout  one  process  medium.  skin  requirements  temperature.  high metal  amine  individual  operating  minimise  avoided  for  metal  selecting  limited  be  :  important  to  especially  to  transfer  most  order  exchangers  given  :  any  under or  by  However,  and  better  the  heating  .1 46  b)  Effect  C02  of  dissolved  catalyses  DEA  all  the  the  is  the  reboiler the  C02  C02  efficiency  of  done  regenerator  and  The C 0 2  the  by  to  be  should  be  by  out  higher  taken  to  This  increasing  the  the  the  In all  the  entering both  samples  that  increase  the  stripping  should  done  by  the  temperature.  the  lean  only to  be  the  C02,  in the the  checked.  This  leaving  the  should the  for be  dissolved the  efficiency the  same.  reboiler  DEA s o l u t i o n ,  increasing  to  strip  whether  dissolved  entering  in  entering  see  reboiler  than  be  of  solution  degradation  samples  the  DEA s o l u t i o n  to  should  DEA  reboiler,  not  then  C02,  highest  serve  but  order  operation lean  the  should  C02,  of  the  DEA s o l u t i o n  dissolved  in  of  regeneration, If  absence  regenerator  out  reboiler  almost  stipping  of  stripped  minimal.  concentrations  found  not  be  DEA s a m p l e s  content  regenerator.  little  analysing  C02  be  reboiler.  stripping the  DEA i n  for  the  Since,  by  The  steam  very  would  is  C02.  the  contains  regenerator  be  trays.  in  In  appreciable.  should  necessary  reboiler  can  not  reactions.  experienced  regenerator  dissolved  If  is  dissolved  provide  :  DEA d e g r a d a t i o n  degradation  temperature  C02  of  reflux  is  steps the rate,  147  c)  Corrosion  control  Solution  pH  has  Therefore  the  pH o f  absorber  should  meter.  The  Corrosive from  the  d)  be  solution by  effect  rich  pH s h o u l d  not  solution  be  as  of  mild  leaving with  allowed  such  formation oxygen  corrosion  preferably  compounds  and  on  DEA  monitored,  preventing  Purification  activated means  purposes: helps  of  system.  carbon  to  HEOD  of  organic  from  coming  NaOH  injection  steel. the  an  C02  on-line  go  below  9.  should  be  acids  should  in  pH  removed be  contact  with  the  may  employed  suspended it  DEA products the  present),  particles.  the  salts  if  solutions and  NaOH  ,  be  slightly of  be  be  salt  should  removal should  the  HEOD,  added.  THEED  pH a b o v e  would  might  The a c t i v a t e d  NaOH  HEOD a n d  solution  A reclaimer  DEA s o l u t i o n  and  purification.  removes  sodium  :  filter  solution  maintain  addition  for  the  solution  Solution  removes  the  strong  solution.  Both as  a  degradation  minimised DEA  :  be  carbon  injection to  some  9.  As  gradually  serves  extent  and  it  a  result  of  build  up  inside  used  to  separate  build  up  becomes  routinely  filter  these  also NaOH the from  excessive.  analysed  for  above  stoichiometric  THEED  and  other  salts  two  organic  degradation requirement acids  (if  1 48  11.3  a) The  RECOMMENDATIONS  Kinetic  Model  kinetic  The  developed  following  concentration in  for  prediction  be  the  developed  Kinetic range  data of  at  40  then  be  lower  This,  used  to  to  b)  to  study  Purification Although  of  NaOH  have  some  degradation  adverse  regenerator.  information  on  equilibria  conditions.  the of  affect  in  DEA-C02  purpose  :  on  of  this  is  kinetic  the  the it NaOH  needs  from  batchwise data,  be  carried  can  out  compounds  in and  solution.  regeneration its  of  addition the  use  efficiency  desireable  under  DEA  excessive  stripping is  to  constants.  degradation DEA  model  temperature  solubility  should  system  important  model.  and  obtained  in  an  thermodynamic  compounds,  Therefore, effect  for  pseudo-rate  mechanisms  aid  the  the  be  corrosive  can  some  pressure  studies  addition  might  liquid  the  needs  DEA s o l u t i o n  with C02  :  of  some  C should  DEA s o l u t i o n  some  the  other  in  with  partial  combined  corrosion  from  of  120  corrosion  identify the  solubility  C02  thesis  solution  A theoretical  calculate  Potentiodynamic order  DEA  incorporated  C to  experiments.  of  this  recommended  the  model.  and  in  is  in  parameter the  WORK:  :  model  improvement.  C02  FOR F U R T H E R  on  to  have  vapor-  regenerator  149  NOMENCLATURE  A  Heat  BHEP  N,N-Bis(hydroxyethyl)  piperazine  BHEU  N,N-Bis(hydroxyethyl)  urea  C  DEA c o n c e n t r a t i o n  Cp  Specific  heat  Cpo  Specific  of  d  Specific  Db  Stirrer  blade  Dc  Turning  diameter  Di  Inside  Dim  Log  Do  Outside  Dt  Diameter  DEA  Diethanolamine  Ecorr  Free  f  Friction  hi  Inside  HEED  N-(hydroxyethyl)  ethylenediamine  HEI  N-(hydroxyethyl)  imidazolidone  HEM  N-(hydroxyethyl)  ethylenimine  HEOD  transfer  surface  of  area  (m2)  (wt%) DEA s o l u t i o n  heating  fluid  (J/g°C)  (J/g°C)  gravity diameter of  diameter  mean  of  diameter diameter of  corrosion  the  heat heat  transfer transfer  tube tube  (m) (m)  (Do-Di)/In[Do/Di] the  tank  heat  equation  transfer  transfer  containing  potential  factor,  heat  the  of  the  (m)  heat  tube  transfer  (Volts) 7.22  coefficient  (J/m2s°C)  3-(hydroxyethyl)-2-oxazolidone  ho  Outside  heat  Ia  Anodic  Ic  Cathodic  Icorr  Corrosion  transfer  current  coefficient  (Amps)  current current  (Amps) (Amps)  (m)  (J/m2s°C)  fluid  (m)  1 50  k  Thermal  Ki,K ,k 2  3  Rate  conductivity  constants  degradation  of  of  used  aqueous in  DEA s o l u t i o n  the  DEA ( L / m o l e s  kinetic  model  Thermal  L  Length  MEA  Monoethanolamine  N  No.  OZD  Oxazolidone  P  Pressure  Q  Heat  R  -C2Ha-OH  RPS  Revolutions  rt  Residence  RT  Total  t  Time  (hr)  T  Bulk  solution  TEA  Triethanolamine  THEED  N,N,N-Tris(hydroxyethyl)  ethylenediamine  Ti  Heat  temperature ( ° C )  Tk  Thermal  To  Heat  transfer  tube  Th  Heat  transfer  fluid  tsp  Time  r e q u i r e d to pass  heat  transfer  of  of  the heat  passes  of  the  transfer  through  for  the  hr)  km  conductivity  (W/m°C)  tube  metal  tube  (m)  the heat  (W/m°C)  transfer  tube  (kPa)  duty  (kJ/s)  per  time  for a  residence  transfer  second single  time  pass  (hr)  (hr)  temperature ( ° C )  tube  inlet  conductivity  tube  of  heating  outlet  o i l  (W/m°C)  temperature ( ° C )  temperature ( ° C ) total  in a  DEA i n v e n t o r y  single  pass  (hr)  through  the  151  Twi  Inside  Two  Outside  wall  temperature  wall  of the heat  temperature  of  transfer  the heat  tube  (°C)  transfer  tube  (°C) Ui  Uc  Overall  heat  transfer  surface  of the s t r a i g h t  Overall  heat  transfer  tube  w  Mass  x  Length  xm  Heat  DIMENSIONLESS  flow  transfer  heat  based  transfer  coefficient  tube  on  inside  (J/m s°C) 2  f o r the c o i l e d  2  (kg/s)  small  transfer  segment  tube  wall  of the heat  thickness  transfer  tube  (m)  GROUPS  Nu  Nusselt  Number,  Pr  P r a n d t l . Number , C p n / k  Re  Reynolds  hD/k  Number,  pvD/y  GREEK L E T T E R S  Tafel  heat  (J/m s°C)  rate  of a  coefficient  /3a  Anodic  constant, equation  /3c  Cathodic  e  Surface  0  Potential  (Volts)  0corr  Corrosion  potential  p  D e n s i t y o f DEA  po  D e n s i t y of the h e a t i n g  u  Viscosity  Tafel  5.4  constant, equation  roughness  factor, of t h e heat  (Volts)  solution  o f DEA  5.3  (kg/m ) 3  fluid  solution  (kg/m )  (Pa.s)  3  transfer  tube  1 52  MW  Viscosity  of  DEA  solution  at  the  wall  temperature  (Pa.s) u.o  Viscosty  MOW  Viscosity (Pa . s)  SUBSCRIPTS  i  Inside  o  Outside  of of  the the  heating heating  fluid fluid  (Pa.s) at  the wall  temperature  1 53  REFERENCES  Bottoms,  R.R.,  U.S.  Bottoms,  R.R.,  "Organic  Eng.  Chem.,  23  501,  "Gas  and  R.N.,  Campbell  Petroleum  Carbon  and  Dioxide  into  Chemical Swaim,  Engineer,  C D . ,  Hydrocarbon Jones,  Treating," Younger, Symp.  Proc.  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TH=TEMPERATURE TS=TEMPERATURE  OF OF  THE H E A T I N G MEDIUM THE AUTOCLAVE  T W I N = I N S I O E WALL T E M P E R A T U R E TCL=TOTAL COIL LENGTH (M)  (C) (C)  OF T H E C O I L  TLV=TOTAL L I O U I O INVENTORY (CU.M) T S P S = T I M E FOR A S I N G L E P A S S THRU H E X . DEAL'ONTY. OF D E G R A D E D D E A I N 1 P A S S DEANP=DEA C O N C . A F T E R NP P A S S E S HEONP=HEOD C O N C . THENP=THEED CONC. " TOTHR=TOTAL TIME (HR) N P T = T O T A L N O . OF P A S S E S N P H R = N O . O F P A S S E S P E R HOUR X =COIL LENGTH (M) D E A L T = L O S S OF D E A AT T H E ENO OF HEODT = HEOD C O N C . THEEDT= THEED C O N C . " DEACT=DEA CONC.  EACH  (SEC)  INCREMENT  F F T = F R I C T I O N FACTOR TOLERANCE K=COLEBROOK CONST. 0ELP=PRESSURE DROP (PA.) REAL NPRC. NPRO, N P T , NPHR, NPNHR DATA D O T , D B , RPH / 0 . 7 1 1 2 , 0.101G 8./ DATA VOLS / O . 0 0 0 0 1 1 0 0 / D A T A 0 1 , 0 0 . D C , XW / 0 . 0 0 2 0 3 2 . O . 0 0 3 1 7 5 TLV / 2 0 0 . . 4 .8, DATA TOTHR. T C L .0025/ XINC, F F T /1 . . DATA T I N C , TEPS .001, . C02 = 3.200 OEAO = 3 0 . 0 0 DEAOT = DEAO DEALT = DEAO HEODT = 0 . 0 THEEDT = 0 . 0 BHEPT = 0 . 0 SUMOP = 0 . 0 REAL K, K 1 , K 2 , K 3 , LNK1. LNK2, LNK3 K = 0.000012 PI = 4 . * ATAN( 1 . ) INITIAL WALL T E M P E R A T U R E TS = 6 0 . 0 T = 60.0 T1 = TS TH = 2 5 0 . 0 TWOUT = TH TWIN = TH - 1 0 . 0 TW • T W I N X = 0.00 DX = 0.1 WRITE (6.10) ' L E N G T H ( m ) ' , 2X . 10 F O R M A T ( 1X , 1 ' ' R E ' , 6X , ' D E A C O N C . '  (C)  0.4064.  0.0007  15/  0.001/  ' W A L L T ( C ) ' , 2X 6X , ' D E L X * E 5 ' ,  'SOL.T(C)'. //)  5X,  of DEA  1 63  c C C  CALL CALL  SUBROUTINE THERM(TH,  THERM  CPO.  TO  TKO,  CALCULATE RHOO.  PROPERTIES  OF  SHELL  THERMIA  VISO)  C C C  CALL  SUBROUTINE  DPROP  TO  CALCULATE  DEA  CALL DPROP(TS. DEAO, RHOS. V I S S . TKS, CALL DPROP(T, DEAO, RHO, V I S , TK, CP) GO T O 30 20 30  CALL CALL CALL  C C C  CALL  CPS)  DPROP(T, D E A O . RHO, V I S , TK, CP) D P R O P ( T W I N , D E A O . RHOW, V I S W , TKW, THERM(TWO, CPO, TKO, VISOW)  CALL  SUBROTINE  SSPROP  SSPROP(TW,  TO  CALCULATE  PROPERTIES  TH.  CPW)  COND.  OF  METAL  WALL  TKM)  C C C  CALCULATE  PROCESS  SIDE  HEAT  TRANSFER  COEFFICIENT  VOLT = VOLS * (RHOS/RHO) WT = V O L S * RHOS VELT = (4.*WT) / (RH0*PI*DI**2. ) G = (4.*WT) / (PI*DI**2. ) REC = ( D I * G ) / VIS NPRC = ( C P * V I S ) / TK HI  = 0.023 * (TK/DI) * (REC**0.8) * (NPRC**0.3333333) * (VIS/VISW) ** 0.14 DELX = 4 3 . 5 * DI ** 1.8 / (((4.*WT )/(PI*VIS))**0.8*(NPRC * *0. 1333333)) DELX = DELX * 100000. 1  C C C  CALCULATE  THE  OUTSIDE  HEAT  TRANSFER  COEEFFICIENT  R E O = DB * * 2 . * R P H * RHOO / VISO NPRO = CPO * V I S O / TKO VISEX = 0.1 * (VIS0*8.621E-05) ** (-0.21) HO = 0 . 1 7 * (TKO/DO) * (REO**0.S667) * (NPRO**0.3333) 1** 0.1 * (DO/DOT) * * .5 * ( V I S O / V I S O ) ** VISEX C C C  CALCULATE DL  C C C  =  (DO  -  CALCULATE U » 1. UC = U  C C C  / *  =  TH  -  MEAN  DI)  /  THE  OVERALL  THE  (TH  -  (ALOG(DO/DI))  BULK TI)  (DB/OOT)  01AMETER  HEAT  TRANSFER  ( ( 1 . / H I ) + (( 1 . / H O ) * ( D I / D O ) ) ( 1 + 3.5*(DI/DC) )  CALCULATE T  LOG  *  TEMPERATURE *  OF  DEA  COEFFICIENT +  ((XW/TKM)*(OI/DL)) )  SOLN.  EXP((-UC*PI*DI*0X)/(WT"CP ) )  C C  CALCULATE  INSIDE  WALL  TEMPERATURE  AND  CHECK  WITH  40  TWOUT = T H ((TH - T ) * ( 1 . / H O ) *.( D I / D O ) * U C ) T W I N C = TWOUT ((TH - T ) *(XW/TKM)*(DO/DL)*UC) IF ((TWINC - T) .LT. 0 . 0 0 0 0 0 0 1 ) GO T O 50 IF ( A B S ( T W I N C - TWIN) . LT. TEPS) GO T O 60 IF ( A B S ( T W I N C - TWIN) .GT. T E P S ) GO T O 40 TWIN = TWINC  50 60  TW = ( T W I N GO T O 20 TWIN = T THR = X I N C THR  =  THR  +  TWOUT)  /  /  ASSUMED  VALUE  2.  VELT  /  3600.  C C C C C  PRESSURE ININIAL FI  =  DROP  CALCULATION  ESTIMATE  0.04  *  REC  OF  **  FRICTION  FACTOR  (-0.16)  C C  CALCULATION  OF  FRICTION  FACTOR  BY  COLEBROOK  FORMULA  C 70  80 90  C  F = ( 1./(-4,0*AL0G10((K/DI) + (4.67/(REC*FI **0.5))) IF (ABS(F - FI) . L T . -FFT) GO T O 90 IF (ABS(F - FI) .GT. FFT) GO T O 80 FI = F GO T O 70 DELP = ( 2 . * R H 0 * V E L T * * 2 . * F * X I N C ) / DI DELP = DELP * (1. + 3.5*(DI/DC)) DELP = DELP / 1000. SUMDP = SUMDP + D E L P CALL  SUBROUTINE  RATE  TO  CALCULATE  CONC.  PROFILE  FOR  +  2.28))  1  **  PASS  C CALL  RATE(T,  DEALT  =  HEODT  =  THEEDT  =  THR.  DEAOT.  DEALT  -  DEAX  HEODT  +  HEODX  C02,  DEAX,  X = X + 0.100 IF (X .GE. TCL) IF (X .LT. TCL) DEAOT = DEAX T1 = T GO  TO  20  THEEDX,THEEDT.  BHEPX )  THEEDX  BHEPT = BHEPX DEACT = DEAOT DEALT WRITE ( 6 , 1 0 0 ) X, TWIN. T, REC, DEAX, 100 FORMAT ( 1 X . F5.2. 4X, F8.3, 4X, F8.3. 1 F10.4, /)  110  HEODX,  GO GO  TO TO  120 110  DELX 2X,  F10.2.  3X.  F8.4,  3X.  2.  1 65  c C C  *CALCULATE 120 130  140  -150  160  C C C  TIME  FOR T O T A L  180  PASS*  & THEED  CONC.  F O R NP P A S S E S  WRITE (6,170) FORMAT ( ' 1 ' , 2 X , ' T I M E ( h r ) ' , 4X. 'RT ( s e c ) ' , 4 X , ' D E AC O N C . ' , 1 'HEOO C O N C , 4X, 'THEED C O N C . ' . 4X, 'BHEP C O N C . //) HR = 0 . NPHR = 3 6 0 0 . / TSPS N P N H R = N P H R * HR R T S = T H R * NPNHR * 3 6 0 0 . DEAL = DEAO - DEAX DEANP = DEAO - (OEAO - OEAX) HEONP = H E O D T * NPNHR T H E N P = T H E E D T * NPNHR B H E N P = B H E P T * NPNHR  WRITE ( 6 . 1 9 0 ) HR, R T S . DEANP. FORMAT ( 1 X . F 1 0 . 4 . 1X, F 1 0 . 4 , 1 F10.4, //) HR = HR + 2 4 . IF (HR . G E . TOTHR) GO T O 2 0 0 IF (HR . L T . TOTHR) GO T O 1 8 0 200 STOP END 190  C C C  VOL.TO  TSPS = T L V / VOLS WRITE ( 6 , 1 3 0 ) TSPS FORMAT ( 1 X , ' T S P S = ' . F12.S, //) T O T S = TOTHR * 3 6 0 0 . PSI = SUMDP / 6.894757 WRITE ( 6 , 1 4 0 ) SUMDP, P S I FORMAT ( 1 X , ' T O T A L P R E S . D R O P , k P a = ' , F12.4, 2X, 'PSI='. F12.4, //) NPT = TOTS / TSPS WRITE ( 6 . 1 5 0 ) V O L S , TH F O R M A T ( 2 X , ' V O L . FLOW R A T E = ' , F 1 0 . 7 , 4 X , 'HOT FLUID TEMP. = ' , 1 F 8 . 2 . //) WRITE ( 6 . 1 6 0 ) DEAO, C 0 2 F O R M A T ( 1'X, ' I N I T I A L D E A C O N C . = ' , F 6 . 2 . 4 X . ' [ C O ] L = ' . F 6 . 2 , / / 1 )  CALCULATE OEA.HEOO  170  LIQUID  SUBROUTINE  DPROP  *  4X,  NPNHR  HEONP, THENP. BHENP 2X. F10.4. 3X, F10.4.  4X. F10.4.  4X.  TO C A L C U L A T E DEA P R O P E R T I E S  SUBROUTINE DPROP(T, DEAO, RHO, V I S , T K ,C P ) RHO = 9 9 8 . 0 - 0 . 0 0 4 0 3 * T * * 2 + D E A O * ( 3 . 4 - 0 . 0 0 0 2 5 * T * * 1 . 4 5 ) 1DEA0 * * 1 . 1 9 VIS1 = (0.067666*DEA0 - 6.820867) / ( 1 . - 0.004 395*DEAO) VIS2 = T * ((0.014066 + 0.OOOO105*DEAO)/( 1 . - 0.004965*DEAO)) VIS = EXP(VIS1 - VIS2) TK = ( 0 . 4 6 7 5 - 0 . 0 0 6 2 * D E A O * * 0 . 8 5 3 8 ) * T * * 0.08 CP * 4 . 1 7 6 + 0 . 0 0 0 4 6 * T - 0 . 0 1 8 3 7 * DEAO + 0 . 0 0 0 0 5 4 * DEAO * T CP = C P * 1 0 0 0 . RETURN END  -  166  SUBROUTINE RATE(T, THR,DEAO.C02,DEAX,HEODX,THEEDX,THE EOT.BHEPX) REAL K 1 . K 2 . K 3 , L N K 1 , LNK2, LNK3 DATA A 1 , A2 / 1 1 . 9 2 4 , -6.451/ DATA A 3 , A4 / 8 . 4 5 , -5.58/ DATA A 5 . A6 / 2 0 . 6 4 0 . -6.52/ L N K 1 = A1 + A 2 * ( 1 0 0 0 . / ( T + 273.)) K1 = EXP(LNK1) L N K 2 = A 3 +• A 4 ( 1 0 0 0 . / ( T + 2 7 3 . )) EXP(LNK2) K2 A5 + A6 LNK3 (1000./(T + 273.)) K3 = EXP(LNK3) A = EXP(-(K1 K2)*C02*THR) B = K 1 / (K1 + K2) C = K2 * C02 / (K3 (K1 K2)*C02) D = K2 / (K1 + K 2 ) D1=K2*K3*C02*DEA0/(K3-(K1+K2)*C02) D2= 1 . / ( ( K 1 + K 2 ) * C 0 2 ) 03 = 1 . / K 3 ( K 3 - (K1 + K 2 ) * C 0 2 ) E = K3 / F = ((K1 + K 2 ) * C 0 2 ) / ( K 3 - (K1 + K 2 ) * C 0 2 ) G = EXP(-K3*THR) C2= THEEDT*G C3= (THEEDT/K3)*(1.-G) CALCULATES  DEA  CONCENTRATION  DEAX = DEAO * A HEODX = DEAO * B * ( 4 . T H E E D X = DEAO * C * (A BHEPX = RETURN END  -  A) G)  +  D1*((-A«D2)+(D3*G))-C3  SUBROUTINE  SSPROP  C2 +  CALCULATES TH.  (DEAO*D)  COND.  +  OF  BHEPT  METAL  SUBROUTINE SSPROP(TW, TKM) TKM = 1 5 . 6 0 + 0 . 0 0 6 2 8 9 * TW RETURN END SUBROUTINE  THERM  C A L C U L A T E S THE PROPERTIES  SUBROUTINE THERM(TH, C P O , T K O , RHOO, CPO = ( 0 . 3 8 8 + 0.00045*(TH*(9./5.) + C P O = C P O * 4 184 TKO = " ( 0 . 8 2 1 - 0 . 0 0 0 2 4 4 * ( T H * ( 9 . / 5 . ) TKO = TKO * 0 . 1 4 4 1 3 1 4 RHOO = 0 . 8 8 6 6 6 2 - 0 . 0 0 0 7 5 0 * TH R H O O = RHOO * 1000. VI SO = - ( 2 . 2 1 7 7 + 0.0188*TH) V I SO = E X P ( V I S O ) RETURN END  VISO) 32.)) +  32.))  OF S H E L L  /  0.9352 /  0.8742  THERMIA  PUBLICATIONS  , -  Chakma,A. and Meisen,A., "Predicting Density, V i s c o s i t y , Thermal C o n d u c t i v i t y and Specific Heat of A q u e o u s DEA S o l u t i o n s " , H y d r o c a r b o n P r o c e s s i n g , in p r e s s . Chakma,A. and M e i s e n , A . , "Degradation of Aqueous DEA Solutions in Heat Transfer Tubes", to be p r e s e n t e d a t t h e 1984 A n n u a l M e e t i n g o f A.I.Ch.E., San F r a n c i s c o , N o v . , 1984. Chakma,A. and Meisen,A., "Corrosivity of DEA S o l u t i o n s and t h e i r D e g r a d a t i o n Products", to be p r e s e n t e d at the 34th Canadian C h e m i c a l E n g i n e e r i n g C o n f e r e n c e , Quebec C i t y , C a n a d a , O c t . 1984.  


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