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Improvement of venting procedures and energy consumption by modification of conventional steam retorts Bennett, Lee 1986

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IMPROVEMENT OF VENTING PROCEDURES AND ENERGY CONSUMPTION BY MODIFICATION OF CONVENTIONAL STEAM RETORTS by Lee Bennett B.Sc. (Agr.) Honours, U n i v e r s i t y of B r i t i s h Columbia, 1970. A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Food Science) We accept t h i s t h e s i s as conforming to the requ i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1986 © Lee Bennett, 1986 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of C V £TrJ C J F The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date /HI 1 i i SUMMARY The s t e r i l i z a t i o n process f o r low a c i d canned foods requires a c c u r a t e d e t e r m i n a t i o n o f the food product thermal c h a r a c t e r i s t i c s as well as knowledge of the process equipment environment. Establishment o f the r e t o r t vent schedule ensures that the temperature d i s t r i b u t i o n w i t h i n the r e t o r t i s uniform through complete removal of a i r by purging with l i v e steam. This has proven to be a s u c c e s s f u l procedure but i s not without c o s t i m p l i c a t i o n s . Therefore i n v e s t i g a t i o n to qu a n t i f y energy r e q u i r e -ments and m i n i m i z e energy c o s t s a s s o c i a t e d with r e t o r t venting were st u d i e d . Energy u t i l i z a t i o n by a 4-crate v e r t i c a l steam r e t o r t was i n v e s t i g a t e d . B a l l a s t loads of white beans i n brine were processed i n 300x407 cans to simulate production c o n d i t i o n s . The steam energy use with a vent schedule of 7 minutes a f t e r the r e t o r t reached 107°C averaged 902 MJ per load. Losses due to venting accounted f o r about 16.0% of the t o t a l energy. The other major energy l o s s e s included 45.0% to heat the product, 13.9% f o r bleeders and blowdown and 9.34% to heat the r e t o r t s h e l l and c r a t e s . These approximate percentages f o r each category would vary due to f a c t o r s such as can s i z e , process time and product c h a r a c t e r i s t i c s . I n i t i a l l y , the recommended minimum g u i d e l i n e s p e r t a i n i n g to the steam spreader c o n f i g u r a t i o n and number of steam ports were followed. Later t h e s e were modified i n an e f f o r t to enhance venting e f f i c a c y . These i i i changes proved not to be su c c e s s f u l as i n d i c a t e d i n the temperature d i s t r i b u t i o n p l o t s and required come-up times i n the t e s t r e t o r t . The f i n a l m o d i f i c a t i o n focused on an increase i n the steam supply l i n e and steam c o n t r o l valve dimensions. I t was hoped that the r e s i d u a l a i r i n the r e t o r t vessel could be purged more e f f e c t i v e l y i n terms of ach i e v i n g a minimum vent schedule and come-up time. The l a r g e s t spreader of 1.5 inches (38.1 mm) diameter s i g n i f i c a n t l y reduced venting and come-up times; however, an excessive amount of steam was e x p e l l e d to the atmosphere through the vent o u t l e t . An intermediate spreader dimension of 1.25 inch (31.7 mm) diameter proved to maintain the optimum c o n d i t i o n s f o r steam u t i l i z a t i o n and v e n t i n g e f f i c a c y as compared to the 1.0 and 1.5 inch spreaders. I n v e s t i g a t i o n s to determine the minimum vent schedule and come-up time were a l s o c a r r i e d o u t . Examination of the temperature d i s t r i b u t i o n p r o f i l e and energy balance e q u a t i o n r e v e a l e d t h a t the p r e s e n t vent schedule could be reduced. A reduction of the vent o u t l e t port s i z e was proposed i n an attempt to increase back pressure i n the r e t o r t system. I t was b e l i e v e d that higher steam pressure would a c c e l e r a t e e q u i l i b r a t i o n of temperature by reducing the amount of steam escaping with a i r . Experiments revealed that neither energy s a v i n g nor temperature d i s t r i b u t i o n p r o f i l e s were s u f f i c i e n t l y improved to warrant f u r t h e r i n v e s t i g a t i o n . i v TABLE OF CONTENTS PAGE SUMMARY 1 i LIST OF TABLES vi LIST OF FIGURES . ... v i i ACKNOWLEDGEMENTS v i i i INTRODUCTION 1 LITERATURE REVIEW 2 EXPERIMENT 9 I. EQUIPMENT AND MATERIALS . 5 i. Steam Flow Measurement 5 i i . Temperature Measurement 6 i i i . Data Recording 6 i v . Retort Equipment 6 I I . STEAM SUPPLY MEASUREMENT 9 i ) Steam Q u a l i t y 9 i i ) Method of A n a l y s i s 9 i i i ) C a l c u l a t i o n of Steam Q u a l i t y 10 i v ) Steam Flow to Retort 11 v) D i f f e r e n t i a l Pressure C e l l s 14 v i ) Pressure Transducers 14 v i i ) Temperature Measurement 15 I I I . EQUIPMENT INSTALLATION 15 i ) Steam I n l e t Monitor 15 i i ) Steam Spreader Design and I n s t a l l a t i o n 16 i i i ) Equipment C a l i b r a t i o n - d i f f e r e n t i a l pressure c e l l s , pressure transducers and thermocouples 18 IV. ENERGY BALANCE CALCULATIONS 20 i ) Steam I n l e t Flow Rate 20 i i ) Steam Energy Flow 20 i i i ) Energy Sinks 21 a) Vent o u t l e t flow r a t e 21 b) Convection l o s s 21 c) R a d i a t i v e l o s s 22 d) Product heating 22 e) Bleeder l o s s 22 f ) Blowdown l o s s 23 g) Energy to heat metal 23 h) Condensate l o s s 24 V TABLE OF CONTENTS (Continued) V. DATA COLLECTION 24 i ) Temperature Measurements 24 i i ) Thermocouple C a l i b r a t i o n 25 i i i ) A n a l y s i s of Temperature D i s t r i b u t i o n 25 RESULTS AND DISCUSSION 27 I. ENERGY BALANCE ANALYSIS 27 I I . SAMPLE CALCULATIONS 33 I I I . STEAM SPREADERS 38 i ) E f f e c t of Number of P e r f o r a t i o n s i n the Steam Spreader 38 i i ) Steam Spreader C o n f i g u r a t i o n 41 a) Vent f o r seven minutes a f t e r 107°C with a 1.0 inch (25.4 mm) diameter steam spreader 47 b) Vent to 104°C with a 1.0 inch (25.4 mm) and a 1.25 inch (31.7 mm) diameter steam spreader ... 53 i i i ) Steam spreader pipe dimension 62 a) Establishment of the minimum vent schedule . . . . 65 b) The p o t e n t i a l f o r energy savings 68 c) Minimum come-up time 68 d) Steam spreader dimension 70 IV. NOVEL VENTING PROCEDURES . . . . 73 CONCLUSIONS . 76 REFERENCES 78 v i L I S T OF TABLES PAGE Table 1. Summary of steam spreader s p e c i f i c a t i o n s 19 Table 2. Energy balance summary! f o r 1.0 inch (25.4 mm) diameter steam spreader with a vent schedule of 104°C 29 Table 3. Energy balance c a l c u l a t i o n f o r a r e t o r t b a l l a s t load with the Annubar flow device 34 Table 4. A t y p i c a l energy balance c a l c u l a t i o n f o r a r e t o r t b a l l a s t load without the steam input Annubar device 37 Table 5. Summary of energy balances f o r b a l l a s t load of white beans i n b r i n e (300 x 407) to measure the e f f e c t of steam port number 42 Table 6. S t a t i s t i c a l summary to compare the e f f e c t of steam port t o t a l area to cross s e c t i o n a l area o f c r o s s b a r steam spreader 43 Table 7. A computer a n a l y s i s f o r steam i n p u t and vent steam output . 45 Table 8. Computerized format of environmental thermocouple data f o r cross bar steam spreader 46 Table 9. Summary of energy balances f o r b a l l a s t load of white beans i n b r i n e , to measure the e f f e c t of steam spreader con-f i g u r a t i o n 48 Table 10. Summary o f a n a l y s i s f o r a 1.0 i n (25.4 mm) diameter s t r a i g h t spreader and cross bar steam spreader to compare energy consumption and temperature d i s t r i b u t i o n 50 Table 11. Summary o f a n a l y s i s f o r a 1.25 i n (31.7 mm) s t r a i g h t spreader and cross bar spreader to compare energy consump-t i o n and temperature d i s t r i b u t i o n 52 Table 12. Summary o f a n a l y s i s f o r a 1.0 i n (25.4 mm) diameter s t r a i g h t spreader and cross bar steam spreader to compare energy consumption and temperature d i s t r i b u t i o n with a vent schedule of 104°C 54 Table 13. Summary o f a n a l y s i s f o r a 1.25 i n (31.7 mm) diameter s t r a i g h t spreader and cross bar steam spreader to compare energy consumption and temperature d i s t r i b u t i o n with a minimum vent schedule 55 v i i LIST OF TABLES (Continued) Table 14. Steam spreader performance and energy consumption f o r a 1.0 i n (25.4 mm) diameter pipe 66 Table 15. Steam spreader performance and energy consumption f o r a 1.25 i n (31.7 mm) diameter pipe 67 Table 16. Energy use and r e t o r t come-up times f o r 1.0 inch (25.4 mm) and 1.5 inch (38.1 mm) diameter steam spreaders 71 Table 17. Temperature d i s t r i b u t i o n a n a l y s i s to compare 1.0, 1.25 and 1.5 inch steam spreader dimensions 72 Table.18. Summary of energy balances f o r b a l l a s t load of white beans i n b r i n e with a 1.5 inch (38.1 mm) steam spreader 74 v i i i L I S T OF FIGURES PAGE Figure 1. Schematic diagram of a v e r t i c a l steam r e t o r t 8 Figure 2. Annubar flow meter device i n s t a l l e d i n the steam supply l i n e 13 Figure 3. Accutube flow device to monitor venting steam 17 Figure 4. Instantaneous energy flow p r o f i l e using a 1.0 inch (25.4 mm) diameter cross bar spreader with r e t o r t venting to 104°C 30 Figure 5. Steam demand p l o t using a 1.0 inch (25.4 mm) diameter c r o s s bar spreader with r e t o r t venting to 104°C 31 Figure 6. Temperature d i s t r i b u t i o n p l o t using a 1.0 inch (25.4 mm) diameter c r o s s bar spreader with r e t o r t venting to 104°C . 32 Figure 7. Temperature d i s t r i b u t i o n p r o f i l e s to compare the e f f e c t of the number of steam ports i n a cross bar spreader with a vent schedule o f 104°C 39 Figure 8. Temperature d i s t r i b u t i o n p r o f i l e s to compare the e f f e c t o f the number of steam ports i n a cross bar spreader with a vent schedule o f 7 min a f t e r 107°C 40 Figure 9. Temperature d i s t r i b u t i o n p r o f i l e to compare spreader pipe c o n f i g u r a t i o n e f f e c t between a 1.0 i n (25.4 mm) diameter s t r a i g h t spreader versus a 1.0 i n (25.4 mm) diameter c r o s s bar spreader 51 Figure 10. Slowest h e a t i n g zone numbers 7 to 12 i n a 4 c r a t e r e t o r t f i t t e d with a 1.25 inch (31.7 mm) steam spreader 58 Figure 11. Reto r t c o n t r o l l e r temperature charts f o r the r e t o r t with a 1.25 i n (31.7 mm) diameter steam spreader 59 Figure 12. Temperature d i s t r i b u t i o n p r o f i l e when using a 1.25 i n (31.7 mm) diameter steam c o n t r o l valve 61 Figure 13. Temperature d i s t r i b u t i o n p r o f i l e s when using 1.0, 1.25 and 1.5 inch diameter steam con t r o l valves with a vent schedule to 104°C 64 Figure 14. Temperature d i s t r i b u t i o n p r o f i l e s when using a cr o s s - b a r steam spreader with venting f o r 7 minutes a f t e r 107°C and vented to 104°C 69 ACKNOWLEDGEMENTS ix The author wishes to express h i s s i n c e r e a p p r e c i a t i o n to Dr. Marvin A. Tung f o r h i s i n t e r e s t , advice and encouragement throughout the course o f t h i s p r o j e c t . The author i s a p p r e c i a t i v e o f the a s s i s t a n c e and cooperation o f Trudi Smith, Agnes Papke and A l l a n T. Paulson a t the U n i v e r s i t y of B r i t i s h Columbia, Food Science Department and strong support of h i s employer T.J. Lipto n Inc. Thanks are extended to the members o f his committee: Drs: W i l l i a m D. Powrie and John Vanderstoep of the Department of Food Science and Dr. K. V i c t o r Lo, Department o f Bio-resource Engineering f o r t h e i r i n t e r e s t i n these studies and review of t h i s t h e s i s . He i s extremely g r a t e f u l to h i s w i f e , Laurel Bennett f o r her patience, encouragement, understanding and support without which t h i s study would not have been p o s s i b l e . INTRODUCTION 1 In recent years there has been an increased a t t e n t i o n on the expenditure and conservation of energy d e r i v e d from non-renewable energy sources. I t has been reported in Canada that approximately 15% of the energy consumed i s used by the food and a g r i c u l t u r a l i n d u s t r i e s (Finn, 1979). Energy use improvements are being adopted i n some segments of the food i n d u s t r y ; however, documentation of the engineering and operating d e t a i l s remain p r o p r i e t a r y i n f o rmation. P r e v i o u s i n v e s t i g a t o r s have f o c u s e d on i d e n t i f y i n g s p e c i f i c energy consumption processes (Chhinnan e t a l . , 1980 and Mayou et a l . , 1980) as well as the methodology to measure and a u d i t energy u t i l i z a t i o n (Singh, 1977 and 1980). As w e l l , Davis e t a l . (1980), compared d i f f e r e n t product processes and the energy r e q u i r e d per u n i t output. The dominant energy i n t e n s i v e o p e r a t i o n i n the manufacture of canned foods i s the thermal s t e r i l i z a t i o n process t h a t may consume up to 80% of the p l a n t energy demand (Carroad e t a l . , 1980 and Singh, 1980). Most of the c u r r e n t thermal s t e r i l i z a t i o n processes and procedures were developed decades ago when energy costs were not considered i n the equipment design. Today, the r a p i d e s c a l a t i o n o f energy c o s t s are i m p a c t i n g on the manufacturer's production c o s t s and the p r i c e to consumers. For these reasons, i t i s important to understand the energy use i m p l i c a t i o n s of our present thermal processing operations with the o b j e c t i v e of implementing improvements which may r e s u l t i n greater energy e f f i c i e n c y . LITERATURE REVIEW 2 The p r e s e r v a t i o n of food by thermal p r o c e s s i n g has d e v e l o p e d from a r e l a t i v e l y s i m p l i s t i c methodology to a complex science i n v o l v i n g p r i n c i -p l e s of microbiology and engineering. One of the important aspects i n the research i s the establishment of the thermal s t e r i l i z a t i o n process. B i g e l o w and co-workers (1920) f i r s t e s t a b l i s h e d the general method that combined information on b a c t e r i a l spore d e s t r u c t i o n with the temperature h i s t o r y i n the c o l d spot of a food c o n t a i n e r . This was followed by the development of methods to charac-t e r i z e the heat penetration curve which was then organized with the r a t e of b a c t e r i a l d e s t r u c t i o n with temperature using a formula method ( B a l l , 1928; B a l l and Olson, 1957). I n t e r e s t i n c o n d i t i o n s that could a l t e r the heat penetration curve would a l s o tend to change the s t e r i l i z a t i o n value. Improper venting of the r e t o r t would a l t e r the processing medium to a mixture of a i r and steam r a t h e r than pure steam and s u b s t a n t i a l l y a f f e c t the r a t e of heat t r a n s f e r of the food c o n t a i n e r (Hemler et a l . , 1952). Basic s p e c i f i c a t i o n s and design c r i t e r i a f o r r e t o r t systems were described by Lopez (1975) f o r c o n v e n t i o n a l b a t c h - t y p e steam r e t o r t s used f o r processing with a pure steam atmosphere. At the s t a r t of the process, a i r i s purged from the r e t o r t by venting with steam. Upon completion of venting the vent valve i s c l o s e d , the r e t o r t temperature r i s e s to the process temperature, and the process i s timed. P f l u g (1975) o u t l i n e d procedures f o r conducting temperature d i s t r i b u t i o n s t u d i e s and described some of the problems a s s o c i a t e d with development o f 3 the temperature p r o f i l e when opera t i n g the r e t o r t under commercial con-d i t i o n s . Determination of the temperature p r o f i l e i s a necessary step i n e v a l u a t i n g the r e t o r t performance i n terms of the time to reach the s p e c i f i e d r e t o r t temperature and v a r i a t i o n i n temperature throughout the r e t o r t . I t has been s u g g e s t e d t h a t c o n v e n t i o n a l s t i l l cook r e t o r t s are r e l a t i v e l y i n e f f i c i e n t as compared to other types processing equipment (Ferrua and C o l , 1975). Sampson (1934) reported that only 16.7% of the steam s u p p l i e d to a conventional s t i l l r e t o r t f o r a two hour cook was used to heat the cans and contents, with 16.4% to heat r e t o r t and c r a t e s , 11.2% f o r condensate l o s s , 19.5% f o r r a d i a t i o n l o s s from the r e t o r t s u r f a c e , and 36.4% l o s t due to steam through vents. To improve the e f f i c i e n c y , Ecklund and Benjamin (1942) studied steam consumption i n v e r t i c a l r e t o r t s with bottom vents versus conventional top venting r e t o r t s and reported that the bottom vent systems were more e f f i c i e n t i n steam use and come-up time r e d u c t i o n . However, i t was not u n t i l the mid 1970's and e a r l y 1980 that the issue of energy conservation i n the canning i n d u s t r y prompted the need f o r r e v i -sions of i n d u s t r y p r a c t i c e s and equipment m o d i f i c a t i o n s (Jacob e t a l . , 1980). The need to improve energy accounting to generate r e l i a b l e data was a l s o recognized (Singh, 1978). Research should also focus on mea-su r i n g energy flow to separate p r o c e s s i n g o p e r a t i o n s . A l t h o u g h the methodology i s well documented, few i n v e s t i g a t o r s have q u a n t i f i e d the steam used during the vent c y c l e of r e t o r t processes. I t was reported by Pedersen et a l . (1980) that there were very high steam flow rates due to ve n t i n g and more than 50% of the energy used f o r the e n t i r e cook c y c l e was 4 u t i l i z e d d u r ing the venting p e r i o d . In a more recent study, Smith e t a l . (1983) i n v e s t i g a t e d the p o s s i b i l i t y o f reductions i n the vent schedules and i n doing so, developed energy balance equations to account f o r a l l energy l o s s e s from the system. The o b j e c t i v e s of t h i s p r o j e c t were to modify the steam spreader and steam i n l e t supply l i n e i n a commonly used conventional s t i l l - c o o k v e r t i c a l r e t o r t i n order to observe the e f f e c t s on the temperature d i s t r i b u t i o n , the r e t o r t come-up time and energy consumption. The p o t e n t i a l b e n e f i t s o f these changes would be to provide valuable information f o r implementation i n t o e x i s t i n g i n s t a l l a t i o n s and new f a c i l i t i e s to improve energy consump-t i o n and p r o d u c t i v i t y . EQUIPMENT AND MATERIALS 5 I. STEAM FLOW MEASUREMENT: 1. Annubar Flow Meter S t a t i o n Model No. ASR-61 (1 inch) D i e t r i c h Standard Corp., Boulder, CO 2. Accutube Flow Meter Element Model No. 20 (1.5 inch) Miriam Instrument, Cleveland, OH 3. D i f f e r e n t i a l Pressure C e l l s (2) Model No. 1DP4J12-B1 83560A-A2 D i e t r i c h Standard Corp., Boulder, CO 4. Pressure Transducers (3) Model No. AB with options 2 & 7 Data Instruments Inc., Lexington, MA 5. Sub-Miniature Thermocouple Probes (2) Model No. SCPSS-U62E-6 (Copper/constantan with exposed j u n c t i o n ) Omega Engineering Inc., Stamford, CT 6. Omegalok Compression F i t t i n g s Model No. SSLK-116-18 ( S t a i n l e s s S t e e l , 1/16 inch) p r o t e c t i o n tube, 1/8 inch NPT thread) Omega Engineering Inc., Stamford, CT 7. Pressure C a l i b r a t o r Model No. 153S19 T a y l o r Instruments L t d . , Toronto, ON 8. "Deadweight" Pressure C a l i b r a t o r Chandler Engineering Co., T u l s a , OK 9. Vacuum B o t t l e s " F l i p V Pour" Thermos Model No. 2421 Canadian Thermos Products, Toronto, ON 10. D i g i t a l Thermometer Doric Microtemp 450 Model 450AET Doric S c i e n t i f i c , San Diego, CA 11. D i g i t a l Top-loading Balance Model No. 1303MP Sartorius-Werke GmbH, Gottingen, West Germany 6 I I . TEMPERATURE MEASUREMENT 12. Thermocouple Wire Model No. TT-T-24 (Teflon Coated, 24 AWG) Omega Engineering Inc., Stamford, CT 13. Quick-Disconnect Thermocouple Connectors Model No. NMP-T-MF Omega Engineering Inc., Stamford, CT 14. Thermocouple Assemblies for Heat Penetration Tests. Type C - l and CNS thermocouple probes, type CS thermocouple receptacles, and type C6 thermocouple connectors, O.F. Ecklund L t d . , Cape Coral , FL I I I . DATA RECORDING 15. Datalogger Model: Digitrend 235 Doric Sc i ent i f i c , San Diego, CA 16. Digital Cartridge Tape Recorder Model No. 300D Columbia Data Products Inc., Columbia, MD IV. RETORT EQUIPMENT 17. Retort (See Figure 1) 4 basket v e r t i c a l with a volume 2.45 m3 and straight pipe spreader (1 inch diameter with 1/4 inch diameter holes on opposing sides (switch at center); 29 holes total) 18. Baskets Busse vertical s lat retort crates Busse Bros. , Randolph, WI 19. Divider Sheets 90 mil thick polypropylene with 3/8 inch holes on 9/16 inch centers. 20. Boiler 10,000 l b / h r . natural gas f ired Cleaver-Brooks, Milwaukee, WI P i p i n g 6 inch header, 1 i n c h i n l e t pipe, 1.5 inch vent pipe 1 inch i n l e t cross bar 1.5 inch s t r a i g h t bar 1.25 inch s t r a i g h t bar 1.25 inch cross bar 8 Adapted from American Can Co. s p e c i f i c a t i o n s Figure 1. Schematic diagram of a v e r t i c a l steam r e t o r t EXPERIMENTAL METHODS 9 I. STEAM SUPPLY MEASUREMENT i) Steam Quality D e t e r m i n a t i o n o f steam q u a l i t y i s an important step i n developing an understanding of energy flow to a system. The c o n d i t i o n s e x i s t i n g between satu r a t e d l i q u i d and saturated vapor mixtures can be expressed i n terms o f "steam q u a l i t y " . Steam of 100% q u a l i t y would have no water present i n the l i q u i d phase; however, f o r example, 80% q u a l i t y steam would have 20% by weight i n the l i q u i d phase. Measurement of steam q u a l i t y i s e s s e n t i a l f o r two reasons. F i r s t l y , as i t a f f e c t s energy content per u n i t mass. For example, 0.454 kg o f dry saturated steam w i l l y i e l d 1023.8 kJ compared to 819.0 kJ f o r 80% steam q u a l i t y . Secondly, steam q u a l i t y s i g n i f i c a n t l y a f f e c t s the density of flowing steam. The devices f o r measuring flow r a t e monitor d i f f e r e n t i a l pressure between the s t a t i c and impact pressure of the f l u i d moving i n the p i p e . The p r e s s u r e i s p a r t i a l l y a f u n c t i o n o f l i n e a r v e l o c i t y and de n s i t y . i i ) Method of Analysis Steam samples were c o l l e c t e d from both the steam i n l e t pipe and vent l i n e of the system. Sampling ports were i n s t a l l e d and f i t t e d with a 1/4 inch (6.35 mm) b a l l valve and copper tubing attachment. The tubing was shaped to f i t down the spout of the " F l i p ' n Pour" Thermos b o t t l e . An i n s u l a t i n g 10 cover on the tubing was f i t t e d to minimize heat l o s s along the tubing to the Thermos b o t t l e opening during sampling. The sampling tube was purged f o r 5 to 15 seconds before each steam sample was drawn to remove conden-sate i n the c o l l e c t i o n system. Using t h i s technique, steam q u a l i t y was measured by the c a l o r i m e t r i c method o f Si n g h (1980). T a r e d sample c o l l e c t i o n v e s s e l s c o n t a i n i n g 600 mL of c o l d water a t 6-10°C were prepared f o r each experiment. The weight of water i n the f l a s k was determined to a p r e c i s i o n of 0.1 gram using a top - l o a d i n g d i g i t a l balance. The f l a s k was sealed and shaken gently and temperature measured to a p r e c i s i o n of 0.1°C. Three to s i x steam q u a l i t y analyses f o r the incoming steam were made and a s i m i l a r number taken f o r the vent l i n e . The spout of the Thermos b o t t l e was opened f o r i n s e r t i o n of the copper tubing u n t i l the tubing was below the l e v e l of c o l d water i n the f l a s k . The sampling valve was opened s u f f i c i e n t l y to provide a s u i t a b l e steam flow to ensure complete condensa-t i o n w i t h i n the Thermos. When measuring steam q u a l i t y i n the vent pipe, sample times ranged from one minute a t the s t a r t to 30 seconds near the end of the venting c y c l e due to c o n s i d e r a b l y lower temperature and pressure than i n the steam l i n e . A f t e r gently shaking the f l a s k the temperature was measured and wei g h t d e t e r m i n e d . The optimum f i n a l temperature was between 50 and 70°C with a weight gain from 30 to 80 grams f o r condensed steam. i i i ) Calculation of Steam Quality Steam q u a l i t y was expressed i n percent and was c a l c u l a t e d as o u t l i n e d by Singh (1980) and Smith et a l . (1983). 11 100(Es - E.) Steam Q u a l i t y = —rr F — t — u v " tl' Es = enthalpy of steam, J/g E i = enthalpy of l i q u i d water, J/g E v = enthalpy of water vapor, J/g iv) Steam Flow to Retort The t e s t r e t o r t was a four-basket v e r t i c a l r e t o r t system designed to operate with steam cooks below i t s rated pressure of 239.1 kPa. The energy a u d i t i n t h i s study was intended to include the contents and s h e l l of the r e t o r t as well as any flows i n and out of the r e t o r t w i t h i n the time boundaries o f the experiment. The r e t o r t was f i t t e d with d i f f e r e n t steam spreader c o n f i g u r a t i o n s and steam i n l e t pipe s i z e s . Busse v e r t i c a l s l a t r e t o r t baskets with p l a s t i c d i v i d e r sheets were used to c o n t a i n the b a l l a s t cans o f blanched white beans w i t h i n the r e t o r t . In order to q u a n t i f y energy inputs and outputs due to steam, i t i s neces-sary to measure steam flow through the steam i n l e t and through the vent l i n e . The steam l i n e to the system was r e l o c a t e d to b r i n g the s e c t i o n of p i p i n g above the f l o o r l e v e l to f a c i l i t a t e i n s t a l l a t i o n and operation of the flow-metering equipment and d e v i c e s . An "Annubar" averaging pi t o t -type flow device was welded i n t o a ho r i z o n t a l s e c t i o n of the incoming steam l i n e with the a p p r o p r i a t e valves and f i t t i n g s . By measuring the d i f f e r e n t i a l pressure between impact and s t a t i c ports of the Annubar flow sensor, l i n e temperature, l i n e pressure and steam q u a l i t y , the steam flow was determined. 12 Steam l o s t during the venting c y c l e was measured by means of an Accutube sensor i n s t a l l e d on the vent l i n e . O r i f i c e p l a t e s would not be a p p l i c a b l e since the vent l i n e was subject to unsteady flow c o n d i t i o n s t h a t can a f f e c t the thermal expansion of an o r i f i c e p l a t e and would be d i f f i c u l t to account f o r . This was not a major f a c t o r i n p i t o t - t y p e "Annubar" or "Accutube" sensors. The p i t o t - t y p e sensors could a l s o be f i t t e d i n t o s h o r t e r runs o f s t r a i g h t pipe and were th e r e f o r e more s u i t a b l e f o r cramped c o n d i t i o n s . The c o m m e r c i a l l y a v a i l a b l e Accutube and Annubar operate on the same p r i n c i p l e but d i f f e r i n c o n s t r u c t i o n and d u r a b i l i t y . The Accutube was formed from a t h i n walled tube that was mounted through the wall of the steam pipe at r i g h t angles to the flow. The tube extended outside past the wall of the pipe to allow f o r connection to the d i f f e r e n t i a l pressure (D.P.) c e l l . Therefore, i t was s u s c e p t i b l e to external damage whereas the Annubar was welded i n t o the pipe i n the same plane as the flow media and was constructed of much heavier material (see Figure 2 ). The Annubar was more expensive but could cope with higher flow rates t h a t occurred i n the steam i n l e t pipe as well as much greater d i f f e r e n t i a l pressures without damage. Therefore the Annubar was chosen f o r the steam i n l e t l i n e and Accutube f o r the vent l i n e where i t would be exposed to lower flow r a t e s . 13 F i g u r e 2. Annubar flow meter d e v i c e i n s t a l l e d i n the steam supply l i n e . 14 v) Differential Pressure Cells Since p i t o t - t y p e devices provide a pressure d i f f e r e n c e between the impact and s t a t i c pressure p o r t s , a d i f f e r e n t i a l pressure (D.P.) c e l l may be employed t o measure t h i s s i g n a l . T h i s technique simply r e q u i r e s a s e n s i t i v e manometer or e l e c t r o n i c d i f f e r e n t i a l pressure transducer. The frequency of data c o l l e c t i o n and non-steady flow r a t e s n e c e s s i t a t e d the use of an e l e c t r o n i c t r a n s d u c e r . A D i e t r i c h S t a n d a r d d i f f e r e n t i a l pressure transducer was s e l e c t e d because i t had a good performance record f o r these types of a p p l i c a t i o n s and i t provided the c a p a b i l i t y t o be co n n e c t e d to a datalogger. In order to operate i n t h i s manner, the D i e t r i c h Standard D.P. c e l l r equired a reg u l a r power source with an output c u r r e n t of 4 to 20 mA. The s i g n a l s from the D.P. c e l l s and other pressure transducers r e q u i r e d c o n d i t i o n i n g to convert the c u r r e n t to a v o l t a g e output. vi) Pressure Transducers Data I n s t r u m e n t s Inc. Model AB transducers were i n s t a l l e d to measure s t a t i c pressure. Both s t a t i c pressure, temperature of the flowing steam and d i f f e r e n t i a l pressure across the flow sensor were needed to c a l c u l a t e flow r a t e . The transducers were i n s t a l l e d i n both the steam i n l e t on the s t a t i c side of the Annubar flow sensor and downstream side of the Accutube flow sensor i n the vent system. 15 v i i ) Temperature Measurement Temperature of the flowing steam was monitored using a thermocouple probe i n s t a l l e d i n the pipe downstream of the flow sensor. Since the exposed j u n c t i o n of the thermocouple was a f i n e wire, response to temperature changes was r a p i d . I I . EQUIPMENT INSTALLATION i ) Steam In l e t Monitor The i n s t a l l a t i o n of the Annubar sensor i n the steam i n l e t pipe required s i g n i f i c a n t changes to the t e s t r e t o r t equipment. The use of a f l e x i b l e high pressure steam l i n e from the main steam supply header enabled the equipment to be i n s t a l l e d above the r e t o r t p i t . This was necessary f o r two r e a s o n s : due to s a f e t y o f the p e r s o n n e l i n the workplace and s e n s i t i v i t y of the e l e c t r o n i c equipment to humidity i n the presence of steam and c o o l i n g water in the r e t o r t p i t . The steam i n l e t pipe was secured and f i t t e d with the Annubar flow sensor, sampling port f o r steam q u a l i t y and pressure and temperature f i t t i n g s ( F igure 2). I t was important to i n s t a l l the flow measuring device i n the steam l i n e ahead of the steam c o n t r o l valve to the r e t o r t since the i n t e r m i t t e n t operation of the steam c o n t r o l l e r valve produced p u l s a t i o n s in the l i n e pressure and d i f f e r e n t i a l pressure. 16 Normally the vent pipe e x i t s from the r e t o r t near the top of the side wall w i t h a s h o r t c o u p l i n g and elbow f a c i n g downward to a v e r t i c a l pipe s e c t i o n . The v e r t i c a l pipe c o n t a i n s a c o n t r o l v a l v e and c o n t i n u e s downward to discharge d i r e c t l y i n t o the r e t o r t p i t . The m o d i f i c a t i o n o f the vent l i n e provided the necessary length to f a c i l i t a t e i n s t a l l a t i o n o f the Accutube on a h o r i z o n t a l plane, along with the pressure and tempera-ture sensors and steam sampling port (Figure 3). i i ) Steam Spreader Design and I n s t a l l a t i o n Steam to be d i s t r i b u t e d w i t h i n the r e t o r t flows through a steam d i s t r i b u -t i o n pipe commonly r e f e r r e d to as the steam spreader. Aside from i t s primary use f o r steam entry, i t was designed to perform a second f u n c t i o n that w i l l i n f l u e n c e the steam flow pattern i n the r e t o r t . The spreader was constructed from standard s t e e l pipe f i t t e d with a threaded cap end and p e r f o r a t i o n s e q u a l i n g 1 to 1.5 times the c r o s s - s e c t i o n a l area of the steam i n l e t pipe (Townsend e t a l . , 1956) or 1.5 to 2 times according to Lopez (1975). Several types of spreaders have been used i n v e r t i c a l r e t o r t s , such as the s t r a i g h t bar and the more commonly used cross bar. The cross bar c o n s i s t s of fou r stub pipes r a d i a t i n g out from a threaded c a s t f i t t i n g o f the same s i z e as the steam l i n e . The four arms of the c r o s s have t h e steam p o r t s on one side opposing each other to form a l t e r n a t e l i v e and dead quadrants under the bottom of the r e t o r t basket. I t i s b e l i e v e d t h i s c o n f i g u r a t i o n produces a s w i r l i n g motion i n the steam and f a c i l i t a t e s the purging o f the a i r from the r e t o r t . 18 For each s e r i e s of experiments, the b a l l a s t l o a d o f c o n t a i n e r s were removed and the appropriate steam spreader and a i r a c t i v a t e d steam c o n t r o l valve i n s t a l l e d i n the system. The steam spreader s p e c i f i c a t i o n s are o u t l i n e d i n T a b l e 1 which i n d i c a t e s steam pipe dimension, spreader c o n f i g u r a t i o n , number of steam ports and the r a t i o of steam port t o t a l area to i n s i d e c r o s s - s e c t i o n a l area of the steam spreader pipe. i i i ) Equipment Calibration D i f f e r e n t i a l pressure c e l l s , pressure transducers and thermocouples The c a l i b r a t i o n of the three major sensor devices was followed as o u t l i n e d by Smith et a l . (1983). The pressure transducers were c a l i b r a t e d using a dead weight c a l i b r a t o r that produced a pressure which was r e l a t e d to the v o l t a g e output from the transducers. C a l i b r a t i o n of the d i f f e r e n t i a l pressure c e l l was accomplished using a Tay l o r Instruments bulb c a l i b r a t o r . The span and zero s e t p o i n t were adjusted by tur n i n g set screws f i t t e d d i r e c t l y on to the d i f f e r e n t i a l pressure c e l l body. F u l l s c a l e a d j u s t -ments were e q u i v a l e n t to 3-4 p . s . i . g . or 20.7-27.6 kPa. The thermocouple measurement of steam l i n e and vent l i n e temperatures were c a l i b r a t e d i n a c i r c u l a t i n g o i l bath a g a i n s t an ASTM c e r t i f i e d mercury i n glass thermometer. 19 Table 1. Summary of steam spreader specifications Steam supply nominal diameter Spreader c o n f i g u r a t i o n Number of ports Total area of spreader ports (mm2) Area r a t i o ports/supply 1.0 inch (25.4 mm i n s i d e diameter) S t r a i g h t Bar 29* 91.7 1.65 1.0 inch Cross Bar 28* 88.5 1.90 1.0 inch Cross Bar 60* 189.6 4.00 1.25 inch (31.7 mm i n s i d e diameter) S t r a i g h t Bar 45** 142.4 1.48 1.25 inch Cross Bar 45* 142.2 1.48 1.5 inch (38.1 mm i n s i d e diameter) S t r a i g h t Bar 20** 262.5 2.00 * 6.35 mm diameter p o r t 12.70 mm diameter port 20 I I I . ENERGY BALANCE CALCULATIONS i ) Steam In l e t Flow Rate The general equations which describe flow rate f o r steam were based on methods i n the Annubar Flow Handbook by D i e t r i c h Standard Corp. and Smith et a l . (1983). Energy flow r a t e was c a l c u l a t e d from the mass flow r a t e , steam q u a l i t y and enthalpy of water vapor and l i q u i d water a t the steam temperature. The steam mass flow rate (W) was c a l c u l a t e d using: h w - d i f f e r e n t i a l pressure across Annubar Fna = u n i t s conversion f a c t o r K - flow c o e f f i c i e n t D - i n t e r n a l diameter of pipe Fra = Reynold's number f a c t o r Y a = expansion f a c t o r f o r flowing gas Faa = thermal expansion f o r Annubar Pf = d e n s i t y of flowing gas [ ( S p e c i f i c volume of vapor) (Steam q u a l i t y ) ] " 1 i i ) Steam Energy Flow Energy flow r a t e s f o r incoming steam and vent steam l o s s e s were c a l c u l a t e d by m u l t i p l y i n g the mass flow rate by energy content per k i l o g r a m as es t a b l i s h e d from temperature and q u a l i t y of the flowing steam. W C where W 21 E = Steam Q u a l i t y • V + (1 - Steam Q u a l i t y ) • L where V = enthalpy of water vapor L = enthalpy of l i q u i d waste E = energy content i n kJ/kg i i i ) Energy Sinks a) Vent o u t l e t flow r a t e : The c a l c u l a t i o n f o r steam l e a v i n g the system through the vent o u t l e t using the Accutube sensor was s i m i l a r to the Annubar f o r incoming steam. Hence: W = F n a . K . D 2 . Y a . F ^ V ^ b) Convection l o s s Singh (1977) c a l c u l a t e d values f o r convection and r a d i a t i v e heat l o s s e s f o r a long v e r t i c a l c y l i n d e r : Qc = hcA(T R - T J where Qc = convective heat l o s s , W he = surfac e heat t r a n s f e r c o e f f i c i e n t , W/m2 K A = s u r f a c e area of r e t o r t , m2 TR = r e t o r t temperature, ° K T = temperature of surroundings, ° K 22 c) R adiative l o s s The t h e o r e t i c a l assumptions f o r c a l c u l a t i o n of the r a d i a t i v e l o s s e s were discussed in Harper (1976) and K r e i t h and Black (1980). Qr = EA (T R4-T 04) where = Stefan-Boltzmann constant = 5.67 x 10-8 w/m2K4 E = e m i s s i v i t y = 0.94 (roughly o x i d i z e d s t e e l ) d) Product heating Another important component of the energy balance was the amount of energy absorbed by the product b a l l a s t load from an average i n i t i a l temperature (IT) to r e t o r t temperature (RT). The product mass was c a l c u l a t e d as the product of the number of c o n t a i n e r s , the mass i n each c o n t a i n e r , t h e a p p a r e n t s p e c i f i c h eat c a p a c i t y o f the product and the increase i n temperature of the product. The apparent s p e c i f i c heat c a p a c i t y was assumed to be equal to t h a t of water (4.186 kJ/kg). e) Bleeder l o s s Steam l o s t through 1/8 inch (3 mm) and 1/4 inch (6 mm) bleeders were estimated from data t a b l e s d e s c r i b i n g the mass of steam escaping through an o r i f i c e as a f u n c t i o n of o r i f i c e diameter and steam pressure s u p p l i e d by the B.C. Hydro Energy Management Seminar, B.C. Hydro, Vancouver, B.C. Bleeder l o s s estimates were timed a f t e r the r e t o r t vessel reached 100-23 104°C. Steam l o s s p r i o r to the 100-104°C temperature was ignored due to the low steam pressure i n the vessel and the d i f f i c u l t y i n determining enthalpy i n unknown compositions of a i r and steam. Bleeders must be open and emit steam continuously and f r e e l y during the e n t i r e process. From steam on to blowdown to provide steam c i r c u l a t i o n i n the r e t o r t and thermometer w e l l s . In any case, l o s s e s through the bleeders p r i o r to p r e s s u r i z a t i o n of the r e t o r t would be expected to be r e l a t i v e l y s m all. f ) Blowdown l o s s Blowdown l o s s e s were i n c u r r e d at the end of the cook c y c l e when the incoming steam was shut o f f and the p r e s s u r i z e d vessel was reduced to atmospheric pressure. The high pressure steam which was present at the end of the cook c y c l e represents the energy l o s s a t blowdown. Blowdown steam volume was determined from the known volume of the r e t o r t minus the volume occupied by the baskets and b a l l a s t l o a d . The blowdown energy l o s s e s were c a l c u l a t e d as the steam volume m u l t i p l i e d by the s a t u r a t i o n steam enthalpy at the r e t o r t temperature. g) Energy to heat metal The q u a n t i t y of metal i n the system included the r e t o r t s h e l l , four baskets and metal of the food c o n t a i n e r s . To c a l c u l a t e the s e n s i b l e heat gain of the metal, a heat c a p a c i t y of 0.4730 kJ/kgC° f o r ordinary s t e e l was used to m u l t i p l y the t o t a l weight and temperature change. 24 h) Condensate l o s s The amount of steam condensate was estimated by the d i f f e r e n c e o f the t o t a l steam e n t e r i n g the system and the cumulative amounts l e a v i n g through the bleeders, blowdown and vent l i n e . Thermal energy l o s t with condensate was d e r i v e d from the enthalpy of l i q u i d water a t the r e t o r t temperature. IV. DATA COLLECTION A l l data from d i f f e r e n t pressure c e l l s , steam temperatures i n the vent and supply l i n e s and temperatures from d i s t r i b u t i o n s t u d i e s were logged every t h i r t y seconds from steam on to the end of the cook c y c l e using a Doric D i g i t r e n d 235 datalogger connected to a Columbia d i g i t a l tape recorder. That d a t a were t r a n s f e r r e d to the U.B.C. mainframe computer (Amdahl 470/V8) which was programmed to c a l c u l a t e and p l o t mass and energy flows through steam and vent l i n e s , convection and r a d i a t i o n energy l o s s e s as well as temperature d i s t r i b u t i o n w i t h i n the b a l l a s t load. 1) Temperature Measurements The b a l l a s t loads o f 2,200 cans were prepared under commercial processing c o n d i t i o n s . Each 425 g co n t a i n e r (300 x 407) was f i l l e d with 225 g of blanched white beans and 205 g of 2% sodium c h l o r i d e b r i n e . Temperature throughout the b a l l a s t was monitored with 24-gauge c o p p e r / c o n s t a n t a n thermocouples. At the sensing end o f each thermocouple the copper and constantan wires were s t r i p p e d of i n s u l a t i o n , twisted together and secured with s o l d e r to ensure intimate c o n t a c t between the wires. To ensure that the thermocouples d i d not produce erroneous readings by touching metal or 25 cans, the t i p s were f i t t e d and secured i n t o the center of a p r o t e c t i v e c o l l a r . The c o l l a r was formed from a compression s p r i n g of 3 inches (76.2 mm) long by 5/8 inch (15.8 mm) diameter which allowed f o r fr e e c i r c u l a t i o n of the steam to the thermocouple j u n c t i o n . The other end of the thermocouples passed through the wall of the r e t o r t by means of a packing gland and were connected to the Doric datalogger. Each thermocouple was i d e n t i f i e d and placed with 6 thermocouples per basket with a t l e a s t one thermocouple at the center of each l a y e r of c o n t a i n e r s . i i ) Thermocouple C a l i b r a t i on For the purpose of temperature d i s t r i b u t i o n measurements the accuracy o f the absolute temperature was not v i t a l . Therefore, c o r r e c t i o n f a c t o r s f o r each thermocouple were determined from the d e v i a t i o n of each thermocouple from the mean temperature measured by a l l the t h e r m o c o u p l e s . Three readings f o r each thermocouple were used during each s e r i e s o f t e s t s a f t e r the r e t o r t s t a b i l i z e d a t process temperature. i i i ) Analysis of Temperature Di s t r i b u t i o n The generated standard d e v i a t i o n f o r each thermocouple p o s i t i o n per 30 second time i n t e r v a l was used as an i n d i c a t o r of acceptable or unaccep-t a b l e temperature d i s t r i b u t i o n during the r e t o r t come-up time. Upon reaching process temperature f o l l o w i n g the r e t o r t come-up time, the mean and standard d e v i a t i o n f o r each thermocouple reading was c a l c u l a t e d over t i m e . Good temp e r a t u r e s t a b i l i t y was i n d i c a t e d by a small standard 26 d e v i a t i o n . Temperature d i s t r i b u t i o n data were al s o analyzed g r a p h i c a l l y with various f e a t u r e s between treatments being i d e n t i f i e d . S t a b i l i t y of temperatures during the cook c y c l e were assessed by the v a r i a t i o n o f t hermocouple r e a d i n g s at a given l o c a t i o n throughout the e n t i r e cook c y c l e . RESULTS AND DISCUSSION 27 I. ENERGY BALANCE ANALYSIS To i n v e s t i g a t e a number of v a r i a b l e s which can a f f e c t venting e f f i c i e n c y , a b a l l a s t load was prepared to simulate a production model. This pro-cedure permitted the load to be recooked under commercial c o n d i t i o n s , with a v a r i e t y of vent schedules and m o d i f i c a t i o n s to the r e t o r t system. The energy balance concept was used f o r i d e n t i f y i n g and monitoring energy e n t e r i n g and l e a v i n g the system boundary. The steam flow c a l c u l a t i o n was an i n t e g r a l p a r t of the a n a l y s i s and required monitoring of the d i f f e r e n -t i a l pressure across the flow measuring device, s t a t i c pressure, steam l i n e temperature and steam q u a l i t y . I t a l s o provided both a q u a n t i t a t i v e value and q u a l i t a t i v e measure to compare the e f f e c t of m o d i f y i n g the r e t o r t equipment. As w e l l , when inputs and l o s s e s were i n c l o s e agree-ment, i t provided g r e a t e r confidence t h a t a major heat sink or heat source had not been omitted i n the system. For each s e r i e s o f experiments, the equipment was operated i n the same manner from the time of steam on to completion of the cook c y c l e . At the beginning o f a t e s t the r e t o r t l i d was secured, the vent valve was i n the open p o s i t i o n and the bottom d r a i n cracked tt> allow steam condensate to leave the system. The sampling o f the incoming steam and vent steam was c o l l e c t e d f o r a n a l y s i s as the system followed the p r e s c r i b e d schedule. At 100°C the manual d r a i n valve was c l o s e d and the vent valve c l o s e d at completion of the a p p r o p r i a t e vent c y c l e . The c r i t i c a l times throughout the process were recorded both manually and aut o m a t i c a l l y by the data l o g g e r . 28 Energy r e l e a s e d from the system was c a t e g o r i z e d as vent l o s s , bleeder l o s s , condensate l o s s as well as losses due to r a d i a t i o n and convection at the r e t o r t s h e l l . S e n s i b l e heat gains were measured i n terms of increased temperature of the r e t o r t s h e l l , baskets and product. The energy balance data f o r 13 t r i a l runs were c a r r i e d out with a one-inch diameter bar spreader with venting u n t i l the r e t o r t thermometer reached 104°C. Since t h i s was probably the s h o r t e s t vent c y c l e that could be used s a f e l y f o r the e x i s t i n g system, a r e l a t i v e l y small amount of energy was l o s t though the vent l i n e as represented by an average of 3.28%. Thus, approximately 50.05% of the a v a i l a b l e energy was used to heat the product, 10.17% was l o s t through bleeders and blowdown, 10.90% from r a d i a t i o n and convection, 10.34% to metal and 15.26% with condensate. These percentages would be expected to change as f a c t o r s r e l a t e d to types of product, l e n g t h o f process, i n i t i a l temperature and can s i z e s . In a d d i t i o n to the c a l c u l a t i o n of the energy b a l a n c e , p l o t s o f the instantaneous energy flow, steam flow and temperature d i s t r i b u t i o n are presented from a t y p i c a l experimental run using a 1.0 inch (25.4 mm) diameter c r o s s - b a r spreader with venting to a temperature of 104°C and a process of 60 minutes at 121°C (Figures 4,5,6). 29 Table 2. Energy balance summary1 for 1.0 inch (25.4 mm) diameter steam spreader with a vent schedule of 104°C. Component Energy per load (MJ) Average Range(+/-) Energy out (%) Product 373.6 98.8 50.05 Vent 24.5 14.3 3.28 Bleeders and blowdown 75.9 10.5 10.17 Radia t i o n and convection 81.4 6.3 10.90 Metal (baskets, containers & r e t o r t s h e l l ) 77.2 20.1 10.34 Condensate 113.9 30.3 15.26 Summation of energy out 746.5 148.4 100.00 ^Results are the average of 13 t r i a l runs. 30 2400-2000-sz T i m e , m i n F i g u r e 4. Instantaneous energy flow p r o f i l e u s i n g a 1.0 i n c h (25.4mm) diameter c r o s s bar spreader w i t h r e t o r t v e n t i n g to 10 4°C; a) 'showing steam i n p u t b) showing vent, r a d i a t i o n and c o n v e c t i o n c) vent 31. 0 10 20 30 40 50 60 70 80 Time, min Figure 5. Steam demand p l o t using a 1.0 inch (25,4mm) diameter cross bar spreader with r e t o r t venting to 10 4 C. F i g u r e 6. Temperature d i s t r i b u t i o n p l o t u s i n g a 1.0 i n c h (25.4mm) d i a m e t e r c r o s s b a r s p r e a d e r w i t h r e t o r t v e n t i n g t o 104 C. 33 During the f i r s t f i f t e e n minutes, the steam demand was r e l a t i v e l y constant at 1500-1580 MJ per hour, but was reduced d r a m a t i c a l l y at 15-18 minutes a f t e r steam on. During the 60 minute process, there were some sporadic steam flow periods to provide steam to replace l o s s e s from bleeders, l o s s from condensate formed on the product load as well as con v e c t i v e and r a d i a t i v e l o s s e s . The g r e a t e s t p r o p o r t i o n was used to heat the product, r e t o r t vessel and b a s k e t s w i t h a s m a l l e r amount l o s t t o b l e e d e r s , convection and r a d i a t i o n a t the r e t o r t s u r f a c e . II. SAMPLE CALCULATIONS An o u t l i n e of the f a c t o r s and c a l c u l a t i o n s to determine the energy balance f o r experiments with the steam input Annubar measuring device are pre-s e n t e d i n T a b l e 3. The t h e o r e t i c a l c a l c u l a t e d t o t a l steam use was normally w i t h i n 5-10% of the measured value derived from the Annubar flow device. For the t r i a l runs with the 1.5 inch (38.1 mm) diameter steam l i n e , there was no steam flow measurement because a s u i t a b l e Annubar was not a v a i l a b l e f o r i n s t a l l a t i o n i n the steam l i n e . For these energy balance estimates, computations were made as shown i n the sample c a l c u l a -t i o n p r o v i d e d i n Table 4. F i r s t , a c a l c u l a t e d condensate value was determined from the product heat, metal energy and r a d i a t i o n and convec-t i o n heat summation. From steam t a b l e s the thermal energy i n the vapor st a t e of 121°C was used to estimate the weight of condensate and the enthalpy of l i q u i d of 121°C, thus the energy content of the condensate was determined. The t o t a l steam input was then c a l c u l a t e d as the summation of a l l energy sources as o u t l i n e d . 34 Table 3. Energy balance calculation for a retort ballast load with the Annubar flow device, tr ial 4-4. Product D e s c r i p t i o n : 300 x 407 cans o f White beans i n sodium c h l o r i d e b r i n e I n i t i a l temperature: 36.0°C Vent schedule: Vent to 104°C Come-up time: 13 min Cook time: 60 min Steam spreader: 1.0 inch diameter (25.4 mm) Energy in Steam mass = 274.8 kg Steam energy = 738.7 MJ Energy out  1) Vent steam mass = 10.7 kg Vent steam l o s s =27.2 MJ 2) Radiation and convection = 82.6 MJ 3) Product: mass = 0.447 kg/canx2200 cans = 983.4 kg Energy content = 983.4 kg x 4.186 kJ/kg°C x 85°C = 349.9 MJ Table 3 (Continued) 4) Metal heat: (Retort s h e l l , Retort s h e l l Retort baskets Metal c o n t a i n e r s I n i t i a l temperature: 36.0°C Thermal energy 5) Bleeder l o s s : a t 15 p s i g Two bleeders combined Process time Thermal energy Retort baskets (4), Metal c o n t a i n e r s ) = 1047.2 kg = 544.4 kg = 181.4 kg 1773.0 kg = 1773 kg x 85°C x 0.4730 kJ/kg C° = 71.2 MJ = 45 Ib/h = 77 min = 77 min/60 min/h x 1224 k J / l b = 70.6 MJ 6) Bl owdown Void volume of the r e t o r t c o n t a i n i n g a f u l l load of 2200 cans, 300 x 407 assuming both cans and r e t o r t were p e r f e c t c y l i n d e r s . Approximate volume of r e t o r t = 2.45 m3 Approximate volume of cans = 1.12 m3 Approximate volume of baskets = 0.07 m3 Approximate f r e e volume of r e t o r t = 1.26 m3 At 121°C s p e c i f i c volume of steam = 0.862 m3/kg Mass of steam i n void volume = 1.46 kg Energy l o s s a t blowdown = 1.46 kg x 2.707 MJ/kg = 4.0 MJ Table 3 (Continued) 7) Condensate: Qcond. = ( t o t a l steam i n - vent l o s s - bleeder l o s s ) x enthalpy of l i q u i d water a t T r Total steam = 274.8 kg Vent l o s s = 10.7 kg Bleeder l o s s = 26.2 kg Condensate mass = 36.9 kg Enthalpy of l i q u i d water a t r e t o r t temperature = 483.3 kJ/kg Enthalpy of condensate = (237.9)(483.3 kJ/kg) = 114.9 MJ 37 Table 4. A typical energy balance calculation for a retort ballast load without the steam input Annubar device, tr ial 5-5. Product D e s c r i p t i o n : 300 x 407 cans of White beans i n sodium c h o r l i d e b r i n e I n i t i a l temperature: 33°C Vent schedule: 5 min and 107°C Come-up time: 6 min Cook time: 60 min Steam spreader: 1.5 inch diameter (38.1 mm) Energy out  1) Vent steam l o s s = 94.6 MJ 2) Radiation and convection = 75.6 MJ 3) Product energy = 362.2 MJ 4) Metal heat ( r e t o r t s h e l l , r e t o r t baskets, metal c o n t a i n e r s ) = 71.2 MJ 5) Bleeder l o s s and blowdown = 66.3 MJ 6) Condensate c a l c u l a t e d value: Product energy = 362.2 MJ Metal energy = 71.2 MJ Radiati o n & convection = 75.6 MJ Total 509.0 MJ From steam t a b l e s at 121°C enthalpy of vapor = 996 MJ/lb Therefore, weight of condensate = 509.0 MJ / 996 MJ/lb = 0.51 l b From steam t a b l e s at 121°C = (232.7 MJ/lb)(0.51 lb) enthalpy of l i q u i d = 118.6 MJ Total i n (estimated) Summation of steps (1-6) = 788.5 MJ 38 I I I . STEAM SPREADERS i ) E f f e c t of Number of Perforations i n the Steam Spreader A steam spreader i s an extension of the steam i n l e t pipe that i s normally l o c a t e d a t the bottom of a v e r t i c a l r e t o r t . In p r i n c i p l e , i t i s designed to i n f l u e n c e the steam flow pattern and optimize the purging of a i r from the system. Lopez (1975) s t a t e d that steam spreaders are necessary i n a l l i n s t a l l a t i o n s except f o r v e r t i c a l r e t o r t s vented at the bottom, where the steam enters through top of the r e t o r t . The simple cross bar spreader i s the most common design c o n s i s t i n g of four c a p p e d - o f f s t u b p i p e s r a d i a t i n g o u t from a c e n t r a l pipe cross with p e r f o r a t i o n s only on one s i d e . The pipes are arranged with t h e i r holes opposing one another, thereby forming a l t e r n a t i n g l i v e and dead quadrants. Several experiments were conducted to determine whether the number o f pe r f o r a t i o n s c o u l d a f f e c t r e t o r t come-up times and temperature d i s t r i -b u t i o n . A cr o s s bar design was chosen with p e r f o r a t i o n s equal to 1.9 and 4.0 times the c r o s s - s e c t i o n a l area of the steam l i n e . F igure 7 i s a r e p r e s e n t a t i v e example of temperature d i s t r i b u t i o n p r o f i l e s f o r one inch c r o s s bar spreaders to demonstrate p o s s i b l e e f f e c t s of the number o f p e r f o r a t i o n s . The temperature p r o f i l e s appeared to be s i m i l a r i n terms o f the time f o r the r e t o r t to achieve process temperature, as well as f o l l o w i n g the same temperature p a t t e r n . I t appears t h a t extension of the vent schedule d i d not improve the temperature d i s t r i b u t i o n as shown i n F i g u r e 8. These r e s u l t s were c o n s i s t e n t from run to run. 39 123 122 121 120 119 O o CD 118 1_ 3 2 117 cu Q. | 122 1-120 119-118 117 A B 10 20 30 40 50 60 70 80 T i m e , m i n Figure 7. Temperature d i s t r i b u t i o n P r o f i l e A i s a cross bar steam spreader with steam port t o t a l area equal to 4 times the pipe area. P r o f i l e B i s the same spreader at 1.9 times the pipe area. Vent to 10 4 C. Figure 8 0 Temperature d i s t r i b u t i o n P r o f i l e A i s a 25.4mm diameter cross bar spreader with steam port t o t a l area equal to 4.0 times the pipe area. P r o f i l e B i s the same spreader at 1.9 times the pipg area. Vent 7 minutes a f t e r 10 7 C. 41 To measure the performance c h a r a c t e r i s t i c s o f the steam s p r e a d e r the t e m p e r a t u r e d i s t r i b u t i o n c u r v e was reviewed and the c o e f f i c i e n t s of v a r i a t i o n of the 24 environmental thermocouples were computed every 30 seconds u n t i l the process reached a s t a b i l i z e d c o n d i t i o n at twenty-five minutes a f t e r steam on. The c o e f f i c i e n t of v a r i a t i o n was derived from the mean and s t a n d a r d d e v i a t i o n o f tem p e r a t u r e f o r a l l e n v i r o n m e n t a l thermocouples at each time. Tables 5 and 6 summarize the e f f e c t of the number of p e r f o r a t i o n s . I t can be seen that the f i n a l mean temperature d i d not d i f f e r , however the experiments with the lower i n i t i a l temperature had a l a r g e r c o e f f i c i e n t of v a r i a t i o n . Retort t e s t s run at the 104°C vent schedule i n d i c a t e d t h a t the come-up time was not s i g n i f i c a n t l y d i f f e r e n t between the 1.9 or 4.0 times the r a t i o of the t o t a l steam p o r t area to the steam spreader pipe c r o s s -s e c t i o n a l area. The c o e f f i c i e n t of v a r i a t i o n values f o r the 104°C vent schedule had comparable values, from 4.70% to 8.99% f o r the 1.9 x area and 4.98 to 5.56% f o r the 4.0 x area of the pipe c r o s s - s e c t i o n . l"i) Steam Spreader C o n f i g u r a t i o n The steam spreader performs another important f u n c t i o n in a d d i t i o n to the d i s t r i b u t i o n of steam. This second f u n c t i o n i s that of i n f l u e n c i n g the flow pattern of the heating medium w i t h i n the system. The cross s t y l e spreader i s thought to give a s w i r l i n g motion to f a c i l i t a t e i n the purging of a i r from the pressure vessel s u p p l i e d with 100% steam. P f l u g and Borrero (1965) reported that c i r c u l a r or f i s h nozzle type spreaders were more a p p l i c a b l e to steam-air and water heating media in v e r t i c a l r e t o r t s . Table 5. Smeary or energy balances for ballast load of white beans in brine (300 x 407) to Measure the effect of steaa port nunber. D e s c r i p t i o n Steam input IT Energy ainka (MJ) T o t a l Accounted (kg) (MJ) CC) Vent Radiation 4 Bleeders & S e n s i b l e Heat l o s s Convection Blowdown Condensate Metal Product (MJ) (%) Vent 7 min a f t e r 107*C 1.0 i n (25.A mm) cross bar spreader (1.9 x area) 3-1 355.6 941.4 25.0 175.3 93.6 86.4 123.1 83.9 395.1 957.0 101.2 (4.0 x area) 4-1 338.6 895.0 24.0 143.8 101.7 86.4 127.6 81.3 399.3 940.0 104.0 (4.0 x area) 4-2 296. B 791.3 43.0 150.1 89.8 76.0 107.2 65.4 321.0 813.0 102.0 Vent to 104-C 1.0 i n (25.4 mm) cross bar spreader (1.9 x area) 3-2 276.2 717.2 40.0 28.1 84.7 83.5 113.9 67.9 333.4 711.5 99.2 (1.9 x area) 3-3 282.9 725.3 36.0 24.8 82.1 83.0 116.4 71.2 349.9 727.4 100.2 (1.9 x area) 3-5 251.3 670.0 34.0 26.3 82.4 83.0 108.1 72.9 358.1 730.8 109.0 (4.0 x area) 4-3 266.7 705.8 38.0 26.5 83.1 74.6 111.2 69.6 341.6 706.6 100.1 (4.0 x area) 4-4 274.8 738.7 36.0 27.2 82.6 74.6 114.9 71.2 349.9 720.4 97.5 (4.0 x area) 4-5 259.9 691.7 35.0 47.3 84.6 81.6 102.8 72.1 354.0 742.0 107.0 (4.0 x area) 4-6 303.1 815.2 30.0 26.0 85.4 77.8 128.2 76.3 374.6 768.3 94.2 (4.0 x area) 4-7 271.7 729.7 31.0 37.2 82.4 74.9 111.4 75.4 370.4 751.7 103.0 Note: 1.9 or 4.0 times the area r e f e r s to the t o t a l of the steam port area compared t o the c r o s s s e c t i o n a l area of the steam spreader. Table 6. Statistical suaaary to coapare the effect of steaa port total area to cross sectional area of cross bar steaa spreader. 25.4 mm Steam spreader Test Vent Schedule IT 'Temperature Distribution Coefficient of variation Come-up time diameter ID CC) CC) (min) Steam port = 1.9 X area 3-1 7 min after 107"C 25 92.1 5.98 25.0 Steam port = 4.0 X area 4-1 7 min after 107*C 24 87.8 7.68 24.5 Steam port = 4.0 X area 4-2 7 min after 107'C 43 94.2 3.67 21.5 Steam port = 1.9 X area 3-2 Vent to 104*C 40 92.5 4.70 17.0 Steam port 1.9 X area 3-3 Vent to 104*C 36 95.1 5.32 15.0 Steam port = 1.9 X area 3-4 Vent to 104*C 24 84.9 8.99 22.0 Steam port = 1.9 X area 3-5 Vent to 104"C 34 95.2 5.14 16.0 Steam port = 4.0 X area 4-3 Vent to 104*C 38 95.2 4.98 15.5 Steam port = 4.0 X area 4-4 Vent to 104*C 36 94.1 5.56 15.5 * Temperature distribution as mean temperature per min from time zero to twenty-five min. 44 To study the e f f e c t o f steam spreader c o n f i g u r a t i o n s , a s t r a i g h t bar spreader was s e l e c t e d s i n c e the e x i s t i n g r e t o r t s i n t h i s p l a n t were of t h i s design. For comparison o f performance c h a r a c t e r i s t i c s , the cross bar spreader was chosen s i n c e i t i s the spreader design most widely reported i n the l i t e r a t u r e . Assessment of t h e i r performance was determined by an a l y z i n g the amount of steam consumed during the r e t o r t come-up time from steam on (time=zero) to 25 minutes, and the amount of steam l o s t during v e n t i n g . The mean t e m p e r a t u r e s and standard d e v i a t i o n s between the thermocouples l o c a t e d w i t h i n the b a l l a s t load were als o considered. A smal l s t a n d a r d d e v i a t i o n i n d i c a t e d good temperature d i s t r i b u t i o n . In a d d i t i o n the amount of steam used by the system was monitored during the same peri o d from time zero to the completion of the venting procedure. The temperature d i s t r i b u t i o n p r o f i l e s suggested that the system was s t a b l e a t t h e c o m p l e t i o n o f v e n t i n g . Two d i f f e r e n t venting schedules were studied f o r t h i s s e r i e s of experiments: a) vent f o r seven minutes a f t e r reaching 107°C and b) vent to a temperature of 104°C. Table 7 i s a copy of the data used f o r the a n a l y s i s of steam flow r a t e , the t o t a l steam used and the amount o f steam consumed during the venting c y c l e f o r a t y p i c a l run. The environmental temperatures recorded over time f o r the same t e s t c o n d i t i o n s are di s p l a y e d i n Table 8. The mean temperature standard d e v i a t i o n s were c a l c u l a t e d as the data were processed i n the computer system. Thus, to evaluate spreader c o n f i g u r a t i o n p e r f o r -mance, a n a l y s i s of variance i n the t o t a l steam used and amount of steam used during the venting c y c l e were c a r r i e d out. Table 7 0 A computer analysis for steam input and vent steam output. FIOW R A I F S II1H V F R I I C A L REIOHI • • ' • • I 3 - I CROSS BAR FIOW R A I E S FOR S I E A M INPUI ANO VENT OUIPUI l i m e S t e a m P r e s s S t e a m I einp S t e a m OP S t e a m F l o w Cwtnul S t e a m V e n t P r e s s V e n t I ernp V e n t OP V e n t L o s s C u m u l V e n t ( M ' a l d l u g C ) <M>a» ( k g / h i ) ( k g ) (t<Pa> ' d<-'U C I I k P a l ( f c g / h r ) (Wij) 20 35 43 906 0 177 2 19 57 878 5 7 .321 129 4 17 . BO 0 . 5 0 2 6 E 01 4 .111 0 3426F - O l 20 36 13 774 6 J67 3 9 . 7 30 553 6 1 1 93 128 7 2 5 . 2 0 6 7 306F - d i 6 . 105 0 8 513E d i 20 36 43 805 2 167 4 9 . 734 553 a 16 55 128 7 2 9 . 4 0 0 . 8 I 3 5 E 01 7 275 0 1458 20 37 13 8 15 7 168 6 10 53 584 2 2 1 . 4 1 128 7 3 7 . 8 0 0 B549E 01 9. 137 0 2219 20 37 43 8 14 9 168 3 10 77 588 6 2 6 . 3 2 128 6 46 . 20 0 917 IE -01 1 1 47 0 3 175 20 38 13 804 3 167 7 10 98 590 3 31 24 128 6 5 5 . 2 0 0 9534E -01 14 22 0 4360 20 38 43 806 6 167 B 1 1 07 593 4 3 6 . 18 128 5 6 5 . 10 0 3523E -01 10. 59 0 5212 20 39 13 806 i 167 8 i d B4 587 2 41 08 128 4 77 . 0 0 0 30571 -01 12 39 0 . 6 2 7 4 20 39 43 8 1 1 a 168 2 11 06 596 0 4 6 . 0 4 128 1 8 4 . 9 0 0 . 1 0 8 3 26 . 91 0 . 8 5 17 20 40 13 8 19 3 168 7 10 75 590 9 5 0 . 9 7 127 6 8 9 . 4 0 0 . 1 5 1 3 34 . 42 1 . 139 20 •to 43 8 17 a 168 6 i i 06 598 6 5 5 . 9 6 126 9 9 1 40 6.1767 38 . 50 1 159 20 4 1 13 8 17 2 168 7 10 86 594 1 6 0 . 9 1 126 5 9 2 . 9 0 0 . 1 8 8 6 4 0 . 8 1 1 799 20 4 t 43 809 8 269 4 11 02 1561. 7 3 . 9 1 126 3 2 0 3 . 6 0 1938 175 . 1 3 . 258 20 42 13 808 2 168 1 i o 92 591 3 7 8 8 4 12G i 95 10 6. 1933 42; 87 3 6 i 6 20 42 43 802 4 167 B 10 79 585 9 8 3 . 7 2 126 i 96 20 0 . 1782 4 1 93 3 965 20 43 13 805 7 168 0 10 86 589 1 8 8 . 6 3 126 i 97 . 0 0 0 . 17 15 4 t . 69 4 312 20 43 43 8 11 6 168 3 i d 95 593 7 93 .58 126 i 97 . BO 0 . 1 6 7 4 41: 73 4 6 6 0 20 44 13 8 15 2 16B 4 to 95 594 3 9 8 . 5 3 126 i 98 . 6 0 0 . 1 7 3 1 43 00 5 . 0 1 8 20 44 43 8 16 6 168 8 10 95 597 1 103 .5 126 7 9 9 . 4 0 0 . 3 6 7 9 6 3 . 5 1 5 518 20 45 13 8 15 5 168 6 i o 97 596 4 i 0 8 . 5 i 2 7 6 i d o . i 6 . 5694 7 9 . 91 6 2 14 20 45 43 B 16 1 168 4 10 94 594 0 113.4 129 4 100.7 0 . 7 4 5 6 92 . 33 6 983 20 46 13 a 16 9 168 6 11 07 599 0 118.4 131 5 101 3 1 . 225 1 19 . 5 7 . 979 20 46 43 8 19 a 168 7 i d 98 597 4 123.4 134 6 i d i .9 i . 654 J40 2 9 147 20 47 13 8 19 a 168 7 10 97 597 1 128.4 137 2 102 .6 2 172 162 3 10 50 20 47 43 819 4 168 7 11 01 598 t 133.4 139 5 103 . 1 2 6 IO 179 4 1 1 99 20 •18 13 820 6 168 8 i o 94 596 8 i 3 8 . 3 142 6 i d - i . i 3 I20 199 2 i 3 65 20 48 43 825 9 169 | 10 98 600 2 143.3 144 3 104 7 3 .585 2 15 .5 15 45 20 49 13 823 9 16B 9 11 01 599 4 148 . 3 146 4 105.3 3 . 9 5 5 228 .5 17 35 20 49 4 3 824 6 169 i i o 98 600 i i 5 3 . 3 149 i i d s i 4 474 242 . 2 J9 37 20 50 13 823 6 168 9 10 92 597 1 158 3 151 5 106 . 4 4 673 252 6 2 1 4 8 20 50 43 8 17 6 168 6 10 94 595 4 163 3 153 a 106 .9 4 946 26 1 9 23 66 20 5 i 13 8 16 2 168 6 i d 88 593 a i e a 2 156 2 J06 . 3 5 275 267 9 25 .89 20 51 43 8 18 4 168 7 10 88 594 5 173 2 158 0 106 .7 5 850 283 8 28 26 20 52 13 822 6 168 8 10 93 596 7 178 . 1 160 2 108 . 1 5 .828 289 . 6 30 67 20 52 43 824 7 169 6 i d 87 596 5 183. i 162 2 108 .5 6 . 0 4 5 296 . 7 33 i 4 20 53 13 B22 6 168 9 10 8 1 594 0 188. 1 164 2 108 9 6 291 304 6 35 68 20 53 43 825 1 169 0 10 89 596 8 193 .0 165 9 109 . 3 6 545 3 12 . 6 38 . 29 20 54 13 8 17 8 168 7 i d 7 5 59 1 1 198 0 i 6 7 5 IOD 6 6 911 322 7 40 98 20 54 43 8 IB 5 168 7 10 90 595 1 202 9 169 2 109 9 7 034 327 0 4 3 70 20 55 13 8 17 4 t6B 6 10 80 59 1 6 207 .9 170 B 1 10 3 7 2 14 333 2 46 IB 20 55 43 8 17 7 168 7 i d 79 592 d 2 12 8 172 4 i 10 7 7 . 405 339 6 4 9 . 3 1 20 56 13 8 19 7 168 7 10 93 596 0 217 8 174 1 1 1 1 . 0 7 539 344 . 3 52 18 20 56 43 8 17 3 I6B 6 10 78 59 1 i 222 . 7 175 9 1 1 1 2 7 645 347 7 5 5 . 0 7 20 57 13 822 6 168 8 i o 86 594 6 227 6 17 7 4 1 1 1 5 7 999 357 . 3 58 0 5 20 57 43 823 8 168 9 10 85 595 2 232 6 178 9 1 1 1 8 8 115 362 . 2 6 1 07 20 58 13 822 4 I6B 9 10 87 595 7 237 6 ISO 2 112 1 8 3 18 367 6 64 13 20 58 43 823 i 168 9 10 78 593 3 242 . 5 18 I 4 112 .3 8 420 37 i 0 67 22 20 59 13 822 2 168 7 10 80 592 3 247 4 1B2 5 112 6 8 576 3 76 1 70 36 20 59 43 8 19 1 168 6 10 6 1 586 5 252 3 2 13 1 118 2 0 . 0 0 0 70 36 T a b l e 8. C o m p u t e r i z e d format o f e n v i r o n m e n t a l thermocouple d a t a f o r c r o s s b a r s p r e a d e r . L 3 - 1 C H O S S B A R T l t e r m o c o u p 1 e n u m b e r a n d c o r r e c t I o n f a c t o l 1 2 3 4 5 6 7 B 9 10 1 1 12 13 14 15 1G 17 18 2 4 3 32 3 3 3 4 3 5 T l i n e 0 4 0 0 -6. 1 -6 i - O 1 - O i -6 1 - 0 1 - O 1 -6 i -6 4 -6 . 1 -6 2 -6 2 - o . 2 ( M e a n , S 0 . 1 - 0 2 - 0 2 - 0 2 0 0 - 0 1 0 0 0 0 0 1 0 0 - . — — 0 0 19 8 2 0 8 2 2 6 21 3 2 3 3 2 2 5 2 2 1 2 5 3 2 3 6 2 4 8 2 6 4 2 6 .8 2 6 4 2 6 5 2 7 . 7 ..< 2 5 6 1 . 1 0 ) 2 4 1 2 9 2 2 9 6 2 6 3 2 8 7 3 0 4 2 9 3 2 9 3 27 B 3 0 5 2 3 3 2 4 6 2 5 5 3 8 3 2 8 8 3 0 7 2 5 6 2 7 4 2 6 2 2 6 4 2 6 a 2 7 6 2 6 9 2 7 6 2 8 7 8 9 I 2 5 1 2 8 7 2 8 4 2 6 1 2 7 2 3 0 1 2 9 4 2 9 3 2 7 8 ( 2 7 7 5 . 2 1 0 2 6 6 3 0 4 3 0 4 5 0 1 37 0 4 1 1 2 8 2 3 0 6 • 2 9 5 2 9 9 2 8 9 31 1 2 7 2 2 8 1 2 8 7 ( 3 0 3 8 ) 2 5 5 2 8 6 2 8 3 2 5 9 2 6 5 2 9 5 2 9 3 2 9 4 2 7 7 3 2 . 5 1 5 3 1 6 3 9 4 4 0 5 6 5 2 5 0 8 5 2 8 3 3 8 3 5 9 3 5 6 3 4 . 1 3 3 3 3 7 8 2 7 .6 2 8 6 2 8 . 7 < 3 4 5 6 , ??) 2 6 0 2B 6 2 8 9 2 6 1 2 7 9 2 9 6 2 9 6 2 9 4 27 7 9 2 6 3 8 3 4 9 9 4 9 8 7 4 6 6 0 3 6 6 7 4 5 S 4 4 i 4 5 3 " 4 4 .2 4 1 7 4 8 i s 2 8 . 5 2 9 . 6 2 9 . 0 3 0 ) 2 6 7 2 8 9 3 0 2 2 6 4 3 3 3 3 0 B 3 0 3 2 9 5 2 7 8 ( 3 9 9 7 , 13 2 5 4 7 6 6 0 7 5 9 B BO 0 6 8 9 7 4 5 5 7 6 5 8 9 5 9 9 5 8 0 5 3 8 5 9 . 0 3 0 2 3 1 . 5 2 9 . 4 ( 4 6 8 5 ) 2 7 9 2 9 2 3 1 . 9 2 7 6 4 7 6 3 5 5 3 2 3 2 9 9 2 7 9 6 2 ! 16 3 0 5 5 5 6 8 7 6 6 7 8 3 5 7 3 7 8 2 0 6 7 7 6 9 3 6 9 1 7 1 1 6 5 8 6 8 . 1 3 2 7 3 4 4 3 0 . 1 7 0 ) 2 9 1 2 9 7 3 5 0 3 0 4 5 8 2 4 1 7 3 4 7 3 0 7 2 8 2 < .52 34 , 19 3 5 6 1 9 7 3 7 7 2 6 8 6 2 78 2 8 5 2 7 5 3 7 6 3 7 6 5 7 8 . 3 7 2 8 7 4 . 7 3 8 . 1 4 0 6 3 1 . 2 ( 5 7 14 . 2 0 9 3 ) 3 0 9 3 0 5 3 9 3 37 7 6 4 9 4 9 1 3 7 6 3 1 6 2 8 7 4 0 7 0 0 7 8 9 77 2 8 8 3 B 2 3 8 7 5 BO 4 8 1 5 8 1 6 8 3 1 7 8 2 7 9 .2 4 4 5 4 6 5 3 3 . 7 " 3 5 4 3 2 6 4 5 4 ' 5 1 4 7 i 6 5 4 3 4 1 0 3 2 6 2 9 8 9 3 . 2 1 1 4 ) 4 5 7 4 6 8 3 1 8 2 0 8 9 7 8 5 6 8 9 7 8 4 3 8 5 5 8 5 2 B 6 0 8 2 5 8 3 . 0 5 3 7 5 5 . 1 3 5 . 3 ( 6 6 2 5 , 2 0 9 9 ) 3 9 7 34 0 4 5 7 5 9 9 7 8 7 6 0 9 4 8 2 3 5 0 3 2 6 5 6 7 8 9 8 6 4 8 4 3 9 1 3 8 8 2 9 1 6 8 7 2 8 7 8 8 7 7 8 8 6 8 5 5 8 5 6 6 0 ' 5 6 1 3 3 8 . 7 9 9 ) 4 5 9 38 1 5 0 3 6 9 5 8 2 3 6 8 1 5 3 1 3 7 0 3 8 8 ( 7 0 2 8 . 19 5 5 B 2 7 8 9 1 8 7 5 9 2 6 9 0 2 9 2 9 8 9 5 9 0 t 8 9 6 ?9 .6 88 2 8 8 . 1 6 5 . 5 6 7 .8 4 1 •? . " " ( 74 2 5 . IB 4 5 ) 5 3 9 4 2 5 5 5 2 7 7 i 8 4 9 7 3 4 5 7 9 4 1 7 4 8 B 6 0 8 5 7 9 0 8 8 9 5 9 3 6 9 1 7 9 4 1 9 1 5 9 1 8 9 1 7 9 2 .2 9 0 0 9 0 .8 7 5 2 7 4 2 4 7 .2 ( 1 0 6 4 7 . 4 7 5 6 ) 5 9 1 4 7 4 6 1 4 1 9 3 B 197 4 1 8 9 1 1 7 7 4 1 6 3 5 1 7 6 1 6 5 8 9 4 9 2 9 9 1 5 9 4 5 9 3 3 9 5 0 9 2 7 9 3 3 9 3 2 9 3 3 9 1 9 9 2 . 3 8 0 7 7 9 2 5 4 . 0 ( 8 1 14 5 6 ) 6 5 1 5 3 9 6 7 . 5 8 6 6 8 9 8 8 0 8 6 8 8 5 0 5 7 0 6 7 0 . 7 0 9 1 7 9 4 3 9 3 6 9 5 6 9 4 5 9 5 8 9 4 1 9 4 6 9 4 5 9 4 6 9 3 5 9 4 1 8 4 4 8 1 8 6 1 . 9 < 8 5 1 7 , 12 7 0 4 6 2 4 7 3 5 8 9 6 9 1 9 8 4 9 7 3 7 5 7 6 s i 7 2 1 ) 7 5 9 3 3 9 5 4 9 4 . 9 9 6 4 9 5 6 9 6 7 9 5 5 9 5 6 9 5 5 9 5 7 9 5 0 9 5 3 8 9 5 8 7 7 7 0 .6 I 8 8 6 0 . 4 8 ) 7 6 2 72 2 7 9 5 9 2 6 9 3 5 8 8 7 7 9 1 6 5 4 8 6 4 9 8 6 9 5 1 9 6 6 9 6 d 9 7 3 9 6 6 9 7 4 9 6 6 9 6 B 9 6 8 9 6 . 7 " 9 6 2 9 6 . 5 9 3 . 2 9 1 . i 7 9 . 9 1 3 . 3 8 ) 8 1 4 8 6 1 8 6 3 9 4 7 9 6 0 9 2 4 8 6 B 7 4 6 9 0 0 ( 9 2 6 8 5 9 G 7 9 7 7 9 7 3 98 1 9 7 6 98 3 9 7 7 9 7 9 97 a 9 8 0 9 7 6 9 7 . a 9 5 6 9 4 6 8 7 . 2 ( 9 4 2 9 ) 8 2 7 9 2 i 9 i 9 9 6 4 9 7 1 9 5 i 9 1 i 8 6 6 94 9 8 8 . 4 9 0 9 8 5 9 8 8 9 8 6 9 9 1 9 8 7 9 9 2 9 8 8 9 8 9 9 8 8 9 8 9 9 8 7 9 8 . 8 9 7 7 9 7 5 9 4 . 0 1 6 ) 9 2 2 9 5 8 9 6 1 9 7 8 9 8 6 9 6 9 9 4 8 9 1 8 9 7 1 ( 9 7 3 4 . 2 9 5 9 9 7 9 9 6 9 9 5 9 9 a 9 9 6 9 9 9 9 9 6 9 9 7 9 9 6 9 9 7 9 9 5 9 9 . 6 9 9 1 9 9 i 9 8 . 1 0 3 . 8 4 ) 9 8 0 9 8 2 9 8 3 9 9 t 9 9 6 98 5 9 7 4 9 G 8 9 8 a ( 9 9 0 10 0 1 0 0 8 1 0 0 5 1 0 0 4 1 0 0 6 1 0 0 4 1 0 0 6 1 0 0 5 1 0 0 5 1 0 0 5 1 0 0 . 5 1 0 0 4 1 0 0 . 4 1 0 0 3 1 0 0 . 2 9 9 8 2 3 . O 9 9 B i o o b 1 0 0 6 1 0 0 2 1 0 0 4 99 9 9 9 3 9 9 3 1 0 0 2 ( i o b 3 9 ) 10 5 101 8 101 4 101 3 101 4 101 2 101 A 101 3 101 3 101 3 101 . 3 101 2 101 . 3 1 0 1 . 3 1 0 1 . 3 101 . 1 ( 101 2 0 ) 1 0 1 0 101 0 101 2 101 2 101 3 101 2 1 0 0 7 101 0 101 2 2 4 , 0 1 i 6 1 0 2 7 1 0 2 3 102 1 1 0 2 2 1 0 2 1 102 2 1 0 2 2 102 i 102 i 1 0 2 . 1 " 1 0 2 6 1 0 2 '. i 1 0 2 . 2 1 0 2 . 2 1 0 2 . 1 1 5 ) 1 0 2 0 102 1 1 0 2 1 1 0 2 1 102 2 102 2 101 8 102 2 102 2 ( 102 1 5 , 0 1 1 5 1 0 3 6 1 0 3 1 1 0 3 0 103 1 1 0 3 0 1 0 3 0 1 0 3 1 1 0 3 0 1 0 3 0 102 . 9 102 9 102 . 9 1 0 3 . 0 1 0 3 . 0 1 0 3 0 CTi 47 A summary of the energy balances f o r b a l l a s t load runs i s provided i n Table 9. a) Vent f o r seven minutes a f t e r 107°C with a 1.0 inch (25.4 mm)  diameter steam spreader Table 10 summarizes the a n a l y s i s of treatments with two steam spreader c o n f i g u r a t i o n s : the s t r a i g h t spreader and the cross bar spreader f a b r i -cated from one inch s t e e l pipe. Increased v a r i a b i l i t y among thermocouples i s r e f l e c t e d by the l a r g e r value f o r the c o e f f i c i e n t o f v a r i a t i o n , 100 cr/X, i n p e r c e n t , where Y i s the a r i t h m e t i c average of the mean temperature o f the thermocouple and a i s the a r i t h m e t i c average o f the temperature standard d e v i a t i o n s . The t o t a l steam consumption and steam use f o r venting were not s i g n i f i c a n t l y d i f f e r e n t (p>0.05) between the two spreader designs. The steam f l o w v a l u e s were somewhat d i s a p p o i n t i n g with s i g n i f i c a n t l y higher values f o r the 6-31, 6-29 and 6-33 t e s t s e r i e s . P o s s i b l y the higher values were due to some abnormal s e n s i t i v i t y i n the mechanical or e l e c t r i c a l components of the D i f f e r e n t i a l pressure c e l l or Annubar devices measuring the input steam to the system. T h i s c o n d i t i o n r e s u l t e d i n a c a l c u l a t e d F r a t i o of 58.1 as compared to a tabulated F r a t i o of 6.61 (p=0.05) and are t h e r e f o r e s i g n i f i c a n t l y d i f f e r e n t . However, the o v e r a l l steam consumption (MJ) between the two spreaders was not s i g n i f i c a n t l y d i f f e r e n t (p>0.05). Fol l o w i n g t h i s s e r i e s of experiments the D i f f e r e n t i a l pressure c e l l which r e c e i v e s s i g n a l s from the steam flow Annubar malfunc-t i o n e d due to an e l e c t r i c a l f a u l t . Table 9. Summary of energy balances for ballast load of white beana in brine, to measure the effect of steam spreader configuration. D e s c r i p t i o n Steam input IT Energy s i n k s (MJ) T o t a l Accounted (kg) (MJ) C O Vent R a d i a t i o n & Bleeders & S e n s i b l e Heat l o s s Convection Blowdown Condensate M e t a l P r o d u c t (MJ) (%) Vent 7 min a f t e r 107'C 1.0 i n (25.4 mm) s t r a i g h t 6-31 spreader 6-29 6-33 333.4 327.6 379.3 851.9 860.1 966.2 18.1 17.8 21.3 129.1 167.5 122.7 87.7 88.1 106.5 79.7 82.1 81.1 122.0 111.8 146.5 86.2 86.5 83.6 423.5 424.8 410.4 928.2 960.8 950.8 108.9 111.7 98.4 1.0 i n c r o s s bar 3-1 4-1 355.6 338.6 941.4 395.0 25.0 24.0 175.3 143.8 93.6 101.7 86.4 86.4 123.1 127.6 83.8 81.3 395.1 399.3 957.0 940.0 101.2 104.0 1.25 i n (31.7 mm) s t r a i g h t 6-8 spreader 6-9 297.7 290.5 787.8 781.4 20.0 29.0 106.7 114.0 84.1 85.4 78.7 76.8 109.8 105.5 84 .7 77 .1 415.7 378.7 879.7 837.5 111.0 107.0 1.25 i n cross bar 6-19 6-20 6-22 312.0 307.1 297.5 826.0 795.3 786.9 20.6 17.9 23.0 128.9 89.8 116.5 83.9 83.8 84.5 77.8 78.7 71.5 114.4 115.1 109.2 78.8 86.4 82.1 386.9 424.4 403.4 870.7 878.3 866.9 105.0 110.0 110.0 Vent to 104"C 1.0 i n (25.4 mm) 6-34 283.9 715.1 20.4 18.5 81.7 73.9 121.1 84.3 414.1 793.6 110.9 s t r a i g h t spreader 6-35 — 763.6 28.0 20.3 83.1 73.5 126.0 77.9 382.8 — — 6-36 — 780.3 25.5 26.6 81.4 72.5 128.9 77 .3 393.1 — — 1-1 250.0 667.2 24.0 28.3 79.7 73.9 103.7 83.8 333.4 702.9 105.0 1.0 i n c r o s s bar 3-2 276.2 717.2 40.0 28.1 84.7 83.5 113.9 67 .9 333.4 711.5 99.2 3-3 282.9 725.3 36.0 24.8 82.1 83.0 116.4 71.2 349.9 727.4 100.2 3-5 251.3 670.0 34.0 26.3 82.4 83.0 108.1 72.9 358.1 730.8 109.0 4-3 266.7 705.8 38.0 26.5 83.1 74.6 111.2 69.6 341.6 706.6 100.1 4-4 274.8 738.7 36.0 27.2 82.6 74.6 114.9 71.2 349.9 720.4 97.5 1.25 i n (31.7 mm) 6-11 264.7 703.0 24.0 20.0 78.4 73.0 111.0 81.3 399.3 763.0 108.5 s t r a i g h t spreader 6-12 260.2 690.9 27.0 13.8 90.2 73.0 110.6 78.8 386.9 744.2 107.0 6-13 265.8 704.7 26.0 24.9 79.9 73.5 111.2 79.6 382.8 751.8 106.0 6-14 281.3 718.9 16.0 33.3 80.0 75.9 116.1 88.0 432.2 825.3 114.0 1.25 i n c r o s s bar 6-23 231.4 613.7 35.0 26.9 80.5 73.9 94.2 72.1 354.0 701.6 114.0 6-24 274.2 726.7 19.0 19.4 82.1 77.4 115.5 84.5 419.4 798.0 109.0 6-25 259.2 685.1 27.0 21.2 82.1 78.7 107.6 78.8 386.9 755.3 110.0 6-26 270.7 702.5 20.2 27.2 80.1 75.0 112.7 84.7 415.7 795.8 113.0 Note: Steam spreader dimensions represent diameters of the s p r e a d e r . co 49 C a l c u l a t i o n of the c o e f f i c i e n t of v a r i a t i o n was the r e s u l t o f averaging the mean and S.D. values that were taken every 30 seconds during the f i r s t t wenty-five minutes of the process and expressing the r a t i o (S.D./mean) i n terms of percent. The c o e f f i c i e n t s of v a r i a t i o n f o r temperature d i s t r i -bution were comparable, ranging from 6.37-11.41% f o r the s t r a i g h t spreader and 5.96-7.68% f o r the cross bar spreader (Table 10). However, experiment 6-29 had an abnormally l a r g e c o e f f i c i e n t v a l u e f o r the te m p e r a t u r e d i s t r i b u t i o n which could be due to an uneven i n i t i a l temperature of the b a l l a s t load a t the beginning of the t e s t . The i n i t i a l temperature of the r e t o r t l o a d was a l s o of i n t e r e s t as i t had an i n f l u e n c e on the c o e f f i c i e n t of v a r i a t i o n value c a l c u l a t e d f o r the temperature d i s t r i b u t i o n p r o f i l e . The higher i n i t i a l temperature con-d i t i o n s were a s s o c i a t e d with smaller standard d e v i a t i o n values and higher mean temperatures of the r e t o r t load as i n d i c a t e d by the values of 3.6% and 4.1%, r e s p e c t i v e l y (Table 10). Figure 9 shows a t y p i c a l temperature d i s t r i b u t i o n p r o f i l e f o r a 1.0 inch (25.4 mm) diameter s t r a i g h t spreader and cross bar spreader of the same dimension with a vent schedule of 7 minutes a f t e r 107°C. Table 11 contains a s i m i l a r a n a l y s i s of data as t h a t found i n Table 10. T h i s s e r i e s o f t r i a l s employed a 1.25 inch (37.4 mm) diameter steam spreader f o r both the s t r a i g h t spreader and cross bar spreader. The steam f l o w r a t e , v e n t l o s s and steam use were not s i g n i f i c a n t l y d i f f e r e n t between the two spreader designs (p>0.05). The c o e f f i c i e n t of v a r i a t i o n values f o r the temperature d i s t r i b u t i o n s i n d i c a t e s that performance of the steam spreader i n the venting process are comparable. Table 10. Stimnary of analysis for a 1.0 i n (25.4 on) diameter straight spreader and cross bar steam spreader to compare energy consump-tion and teaperature distribution. Energy Flows Temperature D i s t r i b u t i o n C h a r a c t e r i s t i c s Vent 7 min a f t e r 107'C IT C C ) Steam Input (MJ) Steam Flow (kg/h) Vent Loss (MJ) X C C ) a ( C ) C o e f f i c i e n t of V a r i a t i o n (30 1 i n s t r a i g h t spreader run no. 6-31 18.1 674 749 129 93.5 5.96 6.37 6-29 17.8 698 725 167 86.8 9.90 11.41 6-33 21.3 668 680 122 92.0 6.44 7.00 1 i n cro s s bar spreader run no. 3-1 25.0 667 591 175 92.1 5.49 5.96 4-1 24.0 668 582 143 87.8 6.75 7.68 Steam input F - r a t i o = 0.27 Steam flow F - r a t i o = 58.1 Vent l o s s F - r a t i o = 1.94 Tabulated F - r a t i o = 6.61 E f f e c t of high i n i t i a l temperature IT X (7 C o e f f i c i e n t of V a r i a t i o n C C ) C C ) ( C ) (30 1 i n s t r a i g h t spreader 35 99.5 4.109 4.12 run no. 6-32 1 i n c r o a 3 bnr spreader 43 94.5 3.46 3.66 run no. 4-2 note X = mean temp per min C O from time zero to 25 min. O = a r i t h m e t i c mean of standard d e v i a t i o n s of thermocouple temperatures per min. 51 I23n F i g u r e 9. T e m p e r a t u r e d i s t r i b u t i o n p r o f i l e s t o c o m p a r e s p r e a d e r p i p e c o n f i g u r a -t i o n s e f f e c t b e t w e e n a 1 . 0 i n c h ( 2 5 . 4 m m ) d i a m e t e r s t r a i g h t s p r e a d e r v e r s u s a 1 . 0 i n c h ( 2 5 . 4 m m ) d i a m e t e r c r o s s b a r s p r e a d e r . Table 11. Suzzaary of analysis for a 1.25 in (31.7 mat) straight spreader and cross bar spreader to compare energy consumption and tetsperature distribution. Energy F l o w s T e m p e r a t u r e D i s t r i b u t i o n C h a r a c t e r i s t i c s Vent 7 min a f t e r 107°C IT Steam I n p u t Steam F l o w Vent L o s s X <J C o e f f i c i e n t o f V a r i a t i o n CC) (MJ) ( k g / h ) (MJ) CC) (C) {%) 1.25 i n s t r a i g h t s p r e a d e r r u n no. 6-8 20 787 747 6-9 29 781 768 1.25 i n c r o s s b a r s p r e a d e r r u n no. 6-19 20 826 773 6-20 17 795 729 6-22 23 786 717 106 92.6 7.33 7.9 114 98.0 4.66 4.7 128 90.3 6.66 7.3 89 86.3 6.98 8.0 116 89.4 6.65 7.4 Steam i n p u t F - r a t i o = 1.346 Vent l o s s F - r a t i o = 0.004 T a b u l a t e d F - r a t i o = 10.13 Steam f l o w F - r a t i o = 0.63 T a b u l a t e d F - r a t i o = 7.71 N o t e : X = mean t e m p e r a t u r e p e r min (*C) fr o m t i m e z e r o t o 25 min. O - a r i t h m e t i c mean o f s t a n d a r d d e v i a t i o n s o f t h e r m o c o u p l e t e m p e r a t u r e s p e r m i n . 53 b) Vent to 104°C w i t h a 1.0 i n c h (25.4 mm) and a 1.25 inch  (31.7 mm) diameter steam spreader Table 12 shows a summary of r e s u l t s f o r a schedule o f v e n t i n g t o a t e m p e r a t u r e o f 104°C w i t h one i n c h diameter s t r a i g h t and cross bar spreaders. A n a l y s i s of variance f o r t o t a l steam use and vent steam d i d not i n d i c a t e any s i g n i f i c a n t d i f f e r e n c e between spreader c o n f i g u r a t i o n s (p>0.05). The c o e f f i c i e n t of v a r i a t i o n derived from the t e m p e r a t u r e d i s t r i b u t i o n curves a l s o confirmed t h a t the performance of the spreaders were s i m i l a r with values ranging from 4.66-6.00% f o r the one inch s t r a i g h t spreader and 4.70-6.21% f o r the one inch cross bar spreader. Steam energy a v a i l a b l e to s e r v i c e the system was v e r i f i e d by the uniform flow r a t e values. T h i s was a concern since a r e s t r i c t i o n i n the a v a i l a b l e steam supply c o u l d be an i n f l u e n t i a l f a c t o r i n a s s e s s i n g the spreader performance from treatment to treatment. S i m i l a r r e s u l t s f o r a 1.25 inch s t r a i g h t spreader and 1.25 inch cross bar s p r e a d e r are p r e s e n t e d i n T a b l e 13. The steam use, steam l o s t due to venting and temperature d i s t r i b u t i o n c o e f f i c i e n t s were not s i g n i f i c a n t l y d i f f e r e n t (p>0.05). Table 12. Susssary of analysis for a 1.0 in (25.4 pa) diameter straight spreader and cross bar steam spreader to compare energy con-sumption and temperature distribution with a vent schedule of 104*C. Energy Flows Temperature D i s t r i b u t i o n C h a r a c t e r i s t i c s Vent to 104°C IT Steam Input Steam Flow Vent Loss X O C o e f f i c i e n t of V a r i a t i o n C O (MJ) (kg/h) (MJ) C O (C°) (SS) 1.0 i n s t r a i g h t spreader run no. 6-34 6-35 6-36 1-1 20 28 25 24 568 N/A N/A 495 769 599 18 20 26 28 95.1 99.2 100.6 101.4 5.47 5.49 6.03 4.73 5.75 5.55 6.00 4.66 1.0 i n cross bar spreader run no. 3-2 3-3 3- 5 4- 3 4-4 40 36 34 38 36 491 417 490 515 533 568 568 567 567 585 27 24 26 26 27 92.5 95.1 95.2 95.3 94.1 4.35 5.06 4.89 5.92 5.23 4.70 5.32 5.14 6.21 5.56 Steam input F - r a t i o = 1.05 Vent l o s s F - r a t i o = 1.53 Steam flow F - r a t i o = 6.65 Tabulated F - r a t i o = 6.61 Note: X = mean temperature per min C O from time zero to 25 min. CT = a r i t h m e t i c mean of standard d e v i a t i o n s of thermocouple temperatures per min. Table 13. Susamry of analysis Tor a 1.25 in (31.7 na) diameter straight spreader and cross bar steam spreader to compare energy consumption and tenperature distribution with a nininua vent schedule. Energy Flows Temperature D i s t r i b u t i o n C h a r a c t e r i s t i c s Vent to 104*C IT CC) Steam Input (MJ) Steam Flow (kg/h) Vent Loss (MJ) X Cc) a (c-) C o e f f i c i e n t of V a r i a t i o n (30 1.25 i n s t r a i g h t spreader run no. 6-11 24 632 6-12 27 691 6-13 26 704 6-14 16 718 757 799 772 734 20 13 25 33 98.0 98.1 95.5 88.1 5.15 5.66 4.61 8.49 5.20 5.77 4.83 9.63 1.25 i n cross bar spreader run no. 6-23 35 613 6-24 19 726 6-25 27 685 6-26 20 702 733 729 647 744 26 19 21 27 96.2 85.7 86.4 88.1 5.13 9.02 7.706 8.23 5.33 10.53 8.91 9.35 Steam input F - r a t i o = 0.02 Vent l o s s F - r a t i o = 1.94 Steam flow F - r a t i o = 3.99 Tabulated F - r a t i o = 5.99 Note: X = mean temperature per min (°C) from time zero to 25 min. O = a r i t h m e t i c mean of standard d e v i a t i o n s of thermocouple temperatures per min. U l 56 b ( l ) Temperature d i s t r i b u t i o n p r o f i l e s f o r a 1.25 in (31.7 mm) steam  spreader S i m i l a r analyses to f u r t h e r compare the e f f e c t of spreader c o n f i g u r a t i o n s were conducted using a l a r g e r steam supply l i n e of 1.25 inches. However, some i n c r e a s e d v a r i a b i l i t y i n the c o e f f i c i e n t v a r i a t i o n values were apparent as seen on Table 13 and the temperature d i s t r i b u t i o n p r o f i l e s . Changing the steam s p r e a d e r i n v o l v e d d i s c o n n e c t i n g the environmental thermocouples and removing the four c r a t e s of b a l l a s t c o n t a i n e r s . The steam c o n t r o l valve was a l s o disconnected from the input steam l i n e and replaced with the a p p r o p r i a t e s i z e d v a l v e . The steam spreader was removed from the bottom o f the v e r t i c a l r e t o r t and the d e s i r e d spreader con-s t r u c t e d on s i t e and i n s t a l l e d . Reassembly req u i r e d great care to ensure a l l components i n the system would f u n c t i o n p r o p e r l y . The permanently i n s t a l l e d temperature sensor and temperature co n t r o l system t h a t modulated the a i r operated steam valve on the energy input l i n e to open and c l o s e on demand was not changed i n each s e t of experiments. The r e t o r t temperature r e c o r d e r was not designed to monitor d e v i a t i o n s i n temperature throughout the r e t o r t s i n c e i t only records the temperature at one l o c a t i o n i n the system a t the perimeter of the load and not i n the center of the r e t o r t basket. Temperature d i s t r i b u t i o n p r o f i l e s f o r the 1.0 and 1.25 inch steam spreader were reviewed to a s c e r t a i n an explanation f o r questionable temperature d i s t r i b u t i o n curves on the 1.25 inch s i z e . I t was found t h a t s e v e r a l thermocouples were f a l l i n g well below the s p e c i f i e d process temperature f o l l o w i n g the vent s c h e d u l e , a t 15-20 minutes a f t e r steam was turned on. I t i s noteworthy that not a l l tempera-57 ture d i s t r i b u t i o n curves f o r the runs with 1.0 and 1.5 inch spreaders d i s p l a y e d t h i s c h a r a c t e r i s t i c temperature f l u c t u a t i o n a f t e r the r e t o r t process temperature was reached. Both sets of runs with 1.0 and 1.25 inch spreaders had s i m i l a r heating p r o f i l e c h a r a c t e r i s t i c s from the time steam was turned on u n t i l t h i s p o i n t . The slowest heating zone was found to be i n the second r e t o r t basket and part of the t h i r d counting from the bottom of the r e t o r t up. As much as 1-2C° below p r o c e s s temperature were observed (Figure 10). b(2) A i r operated steam valve, diameter 1.25 i n (31.7 mm) The steam c o n t r o l valve i n s t a l l e d on the input steam l i n e serves to meter steam to the r e t o r t on demand. I t i s designed to respond to a signal from the temperature c o n t r o l l e r and to operate when compressed a i r exerts a fo r c e on the rubber diaphragm i n the valve body to open and permit steam to flow i n t o the r e t o r t . This type of valve i s g e n e r a l l y r e f e r r e d to as an "air-to-open v a l v e " . The a u t o m a t i c steam c o n t r o l l e r should be capable of maintaining the s p e c i f i e d r e t o r t temperature w i t h i n + 1 F° (Figure 11). The Vancouver, B.C. r e p r e s e n t a t i v e f o r the Ta y l o r Instrument steam c o n t r o l l e r equipment was contacted to v e r i f y the operating a i r pressure requirements. The valve s u p p l i e r s p e c i f i c a t i o n required a c t i v a t i o n pressures from 3 p . s . i . g . (20.7 kPa) to 15 p . s . i . g . (103.4 kPa). 58 F i g u r e 10. Slowest h e a t i n g zone numbers 7 to 12 i n a 4 c r a t e r e t o r t f i t t e d with a 1.25 i n c h (31.7mm) steam spreader. i g u r e 11. R e t o r t c o n t r o l l e r t e m p e r a t u r e c h a r t s f o r t h e r e t o r t w i t h a 1.25 i n c h (31.7mm) d i a m e t e r s t e a m s p r e a d e r . vo 60 The valve in question was removed from the system and thoroughly examined and bench tested by a q u a l i f i e d T a y l o r Instrument t e c h n i c i a n upon comple-t i o n of the t r i a l runs and computer analyses. I t was observed that the valve would not begin to be a c t i v a t e d u n t i l 11 p . s . i . g . (75.8 kPa) a i r pressure was a p p l i e d . The valve s u p p l i e r advised that a number of mechanical f a c t o r s could cause r e s i s t a n c e i n the valve and prevent i t from b e i n g a c t i v a t e d a t the s p e c i f i e d a i r pressure. The p o t e n t i a l f a u l t s are: a) the valve seat could be too t i g h t b) the valve stem could be bent and t h e r e f o r e not a l i g n i t s e l f i n the valve body c) the valve stem packing may be out adjustment d) the valve springs may not be properly matched to the s p e c i f i e d valve body e) the maintenance personnel may have adjusted the valve to the i n c o r r e c t a i r pressure range Based on the experimental c o n d i t i o n s at the time, i t was reasonable to assume the abnormal temperature d i s t r i b u t i o n p r o f i l e s were due to the steam c o n t r o l l e r v a l v e . During the time lapse u n t i l adequate c o n t r o l l e r a i r pressure was present the steam was condensing w h i l e h e a t i n g the product which would i n d i c a t e a p o s s i b l e c o l d spot as i l l u s t r a t e d on the computer p r i n t o u t of the temperature d i s t r i b u t i o n (Figure 12). This non-uniform temperature environment could a l s o a f f e c t the ultimate product s a f e t y of the thermal process as i t impinges on the product heating rate index and hence the thermal process determination. 122-121-0 10 20 30 40 50 60 70 80 T i m e , m i n Figure 12. Temperature d i s t r i b u t i o n p r o f i l e when using a 1.25 inch (31.7mm) diameter steam control valve. 62 Perhaps t h i s was only an abnormal event; however, i t suggests t h a t f u r t h e r i n v e s t i g a t i o n i n t o v a r i a b i l i t y w i t h i n the system may be warranted i n terms of a) design, l o c a t i o n and number of the r e t o r t temperature sensors i n the system, b) t y p e o f temperature sensor, thermocouple, versus RTD versus mercury-in-glass type sensors, and c) the n e c e s s i t y to conduct temperature d i s t r i b u t i o n e v a l u a t i o n s by competent thermal process a u t h o r i t i e s to v e r i f y the e f f e c t o f equipment m o d i f i c a t i o n and annual maintenance to the equipment components i n c l u d i n g v e n t , h e a t i n g and c o o l i n g c o n t r o l d e v i c e s . i i i ) Steam spreader pipe dimension The t h i r d phase of t h i s research p r o j e c t was d i r e c t e d to study the e f f e c t of the s i z e of the steam supply l i n e on the r e t o r t come-up time and vent schedule. Establishment of a safe s t e r i l i z a t i o n process must c o n s i d e r a number of f a c t o r s , o f which the f o l l o w i n g are important: a) the come-up t i m e , b) p o i n t - t o - p o i n t temperature v a r i a t i o n i n the r e t o r t , and c) temperature c y c l i n g a t a s p e c i f i c p o i n t with time. P f l u g (1975) recommended t h a t a l l r e t o r t c o n t r o l systems should u l t i m a t e l y provide a minimum come-up time, maintain zero p o i n t - t o - p o i n t temperature d i f f e r e n c e and minimize temperature c y c l i n g . In the f i n a l a n a l y s i s , the performance of the r e t o r t i s governed by the i n t e r a c t i o n of many elements in the r e t o r t system. I t has been suggested that c e r t a i n elements e x h i b i t g r eater e f f e c t on s p e c i f i c v a r i a b l e s , such as the steam supply design, p i p e d i m e n s i o n , c o n t r o l v a l v e s i z e and incoming steam pressure t h a t determine come-up time. Whereas, r e t o r t geometry, steam spreader design, 63 vent l o c a t i o n and dimension v a r i a b l e s i n f l u e n c e p o i n t - t o - p o i n t temperature v a r i a t i o n . R e t o r t temperature c y c l i n g i s reported to be a t t r i b u t a b l e to the c o n t r o l system s p e c i f i c a t i o n s i n c l u d i n g c o n t r o l v a l v e s . N e v e r t h e l e s s , i t i s e s s e n t i a l f o r safe thermal processing of the product that the r e t o r t environment i s uniform i n order to guarantee r e p r o d u c i b l e s t e r i l i z a t i o n c o n d i t i o n s . Steam l o s s from the vent l i n e while a i r i s being purged from the r e t o r t can account f o r a s i g n i f i c a n t p o r t i o n of the o v e r a l l r e t o r t energy demand, p a r t i c u l a r l y when a long vent c y c l e i s needed. Lopez (1975) described i n general terms, r e t o r t design g u i d e l i n e s t h a t recommended maximizing both the steam l i n e and steam spreader pipe dimensions. In l i g h t o f these comments and knowledge that no s i n g l e vent method i s e n t i r e l y a p p l i c a b l e to a l l r e t o r t s , the f o l l o w i n g items were i n v e s t i g a t e d : a) the establishment of the minimum vent schedule, and b) the establishment of the maximum steam i n l e t pipe s i z e . Temperature d i s t r i b u t i o n p r o f i l e s were s t u d i e d with 1.0, 1.25 and 1.5 inch diameter steam supply l i n e s as shown i n F i g u r e 13. During the thermal p r o c e s s i n g phase, the 1.5 inch diameter t r i a l s experienced a s i g n i f i c a n t amount of r e t o r t c y c l i n g i n excess of 1C°. T h i s c o n d i t i o n would not be acceptable f o r commercial p r a c t i c e and would n e c e s s i t a t e t u n i n g and m o d i f i c a t i o n of the temperature c o n t r o l l e r system to reduce the c y c l i n g to an acceptable temperature range. T e m p e r a t u r e , °C O CM *3 H" c 0) O r t (D H 0) O 3 OO n o • 3 rt H 0 t-3 fD 3 TJ fD i - l 0) rt c h 0) < H < ID ui rr rr < fD 3 rt Bl o rr ro QJ G H fD • a ro H " u i UJ - r t H 0) H-3 cr Qi r t I—1 H-• O on 3 H-TJ 3 i-i O O 3* H i M-Qi H H* fD OJ cn 3 fD S rt 3-fD fD H 3 O CD CM o 3 *. o cn O o-v O T e m p e r a t u r e , °C T e m p e r a t u r e , °C U l o »-3 a> CM * o 3 o O o o N J M K) CM 65 The 1.5 Inch diameter l i n e was very r a p i d and almost u n c o n t r o l l a b l e i n reaching the s p e c i f i e d vent temperature, whereas the 1.0 and 1.25 inch diameter pipe s i z e s were much more c o n t r o l l e d . a) Establishment of the minimum vent schedule According to P f l u g (1975), the i n d u s t r y vent c y c l e standard was a vent per i o d o f four minutes or u n t i l the heating medium i n the r e t o r t reached 104°C, or whichever was greater. The present vent schedule used at the l o c a t i o n of these s t u d i e s was 7 minutes a f t e r a temperature of 107°C was obtained. Normally, a r e t o r t would not begin purging steam out though the vent l i n e u n t i l a temperature of 100-102°C. Based on the observation and published v e n t s c h e d u l e s t o as low as 102°C, a t a r g e t of 104°C was s e l e c t e d . Figure 13 confirms t h a t the come-up p o r t i o n of the temperature d i s t r i b u -t i o n p r o f i l e s f o r the three r e s p e c t i v e pipe diameters were s i m i l a r with a vent p e r i o d to 104°C. The steam l o s s f o r the vent c y c l e and t o t a l process consumption f o r a 1.0 inch diameter pipe s i z e are shown i n Table 14. For a vent schedule of 7 minutes a f t e r 107°C the steam consumption averaged 895.0 MJ, with 147.6 MJ used f o r venting as compared to 743.7 MJ f o r t o t a l steam and 21.9 MJ f o r vent l o s s using a vent schedule of 104°C. This represents a dramatic r e d u c t i o n of steam f o r venting from 16.0% to 3.0% of the t o t a l consump-t i o n . S i m i l a r t r i a l s f o r a 1.25 inch diameter spreader are presented i n Table 15. Table 14. Steaa spreader performance and energy consunption for a 1.0 in (25.4 rnrni) diaaeter pipe. Teat D e t a i l s CUT IT Steam Use Vent Loss (min) CC) (MJ) (MJ) Vent 7 min a f t e r 107°C 1 i n s t r a i g h t spreader run no. 6-31 6-33 6-29 19.0 20.5 20.5 18.1 21.3 17.8 851.9 926.2 860.1 129.1 122.7 167.5 1 i n cro s s bar spreader run no. 3-1 4-1 Average Range 25.0 24.5 21.9 6.0 25.0 24.0 21.2 7.2 941.4 895.0 895.0 89.5 175.3 143.8 147.6 52.6 Smith et a l . (1983) Average Range 23.0 5.0 36.0 8.0 846.0 146.0 134.0 37.0 Vent to 104*C 1 i n s t r a i g h t spreader run no. 6-34 6-35 6-36 1-1 13.0 11.5 11.5 14.0 20.4 28.0 25.5 24.0 715.1 763.6 780.3 667.2 18.0 20.3 26.6 28.3 1 i n cross bar spreader run no. 3-6 Average Range 17.0 13.4 5.5 25.2 25.2 7.6 792.5 743.7 125.3 16.4 21.9 11.4 Table 15. Steaa spreader perfoarance and energy consuaption for a 1.25 in (31.7 mm) diaaeter pipe. Teat Details CUT IT Steam Use Vent loss (min) (*C) (MJ) (MD) Vent 7 min after 107'C 1.25 in Straight Spreader run no. 6-8 16.0 20.0 787.8 106.7 6-9 16.0 29.0 781.4 114.0 1.25 in cross bar spreader run no. 6-19 17.5 20.6 826.0 128.0 6-20 18.5 17.9 795.0 89.0 6-22 17.5 23.0 786.0 116.0 Average 17.1 22.1 795.2 110.7 Range 2.5 11.1 44.6 39.0 Vent to 104 *C 1.25 in straight spreader run no. 6-11 11.0 24.0 631.9 20.0 6-12 11.5 27.0 690.9 13.8 6-13 12.5 26.0 704.7 24.9 6-14 15.0 16.0 718.9 33.3 1.25 in cross bar spreader run no. 6-23 13.5 35.0 613.7 26.9 6-24 16.5 19.1 726.7 19.4 6-25 18.0 27.0 685.1 21.2 6-26 15.0 20.2 702.5 27.2 Average 14.1 24.2 684.3 23.3 Range 7.0 19.0 113.0 19.5 68 b) The p o t e n t i a l f o r energy savings I t would c l e a r l y be d e s i r a b l e to omit the venting process completely i n terms of minimizing energy consumption, but t h i s i s not f e a s i b l e . Venting f u n c t i o n s to e s t a b l i s h a uniform temperature d i s t r i b u t i o n w i t h i n the r e t o r t by c r e a t i n g a pure steam atmosphere w i t h i n the r e t o r t . L i t t l e i f any improvement i n the temperature d i s t r i b u t i o n p r o f i l e can be gained by e x t e n s i o n o f ven t i n g ; moreover, i t i s necessary to co n s i d e r the high energy c o s t t h a t w i l l be i n c u r r e d as shown i n Figure 14. On the basis o f these r e s u l t s , i t i s evident that a s i g n i f i c a n t reduction of vent l o s s should be p o s s i b l e . Therefore, assuming a p l a n t throughput of 40 r e t o r t loads processed per day f o r 250 days y e a r , a savings of $5000 could be r e a l i z e d . T h is c a l c u l a t i o n was based on a b o i l e r e f f i c i e n c y of 70% with energy c o s t a t $0.35 per 100 MJ. c) Minimum come-up time In a d d i t i o n to the concern f o r minimizing steam consumption, the length of time to achieve the d e s i r e d process temperature i s important i n terms of m a x i m i z i n g p r o d u c t i o n t h r o u g h p u t and m i n i m i z i n g p r o d u c t i o n c o s t s . Table 14 summarizes the dramatic reduction i n the vent c y c l e t h a t can be achieved with proper temperature d i s t r i b u t i o n s t u d i e s . The come-up time f o r the 1 inch steam spreader on average was reduced from 21.9 minutes with a vent schedule of 7 minutes a f t e r 107°C as compared to 13.4 minutes with a vent schedule of 104°C. 1 2 3 -1 2 2 121 1 2 0 119-118 117-ffliflTOlprftr" 1 2 2 - B 1 2 1 -1 2 0 -119-118 -117 T -10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 T i m e , m i n Figure 14. Temperature d i s t r i b u t i o n p r o f i l e s for a cross bar steam spreader with venting for 7 minutes a f t e r 107 C (bottom) and to 10 4°C (top) . 70 The 1.0 inch diameter steam spreader was considered to comply with the minimum standards f o r r e t o r t i n s t a l l a t i o n as compared to the 1.25 and 1.50 inch spreaders. The reduction of come-up time i n the 1.25 inch diameter steam l i n e was l e s s dramatic with 17.1 minutes f o r a vent schedule of 7 minutes a f t e r 107°C and 14.1 minutes with a vent c y c l e of 104°C as shown i n Table 15. This e f f e c t was most l i k e l y caused by the increase in steam l i n e dimension. d) Steam spreader dimension One of the most important v a r i a b l e s which can s i g n i f i c a n t l y a f f e c t the r e t o r t come-up time and venting e f f i c a c y i s the steam spreader pipe s i z e . To evaluate the e f f e c t of the steam spreader dimension, the steam use, vent steam l o s s , come-up time and c o e f f i c i e n t of v a r i a t i o n values were compared. Table 16 i s a c o n s o l i d a t i o n of t r i a l s with 1.0 and 1.5 inch steam spreaders employing s i m i l a r vent c y c l e s . The 1.0 inch steam system r e q u i r e d a 15.0 minute come-up time, used 715.9 MJ of steam and vented 28.9 MJ of steam. In comparison, the 1.5 inch l i n e had a 5.9 minute come-up time, consumed 836.1 MJ of steam and vented 82.6 MJ of steam. However, the vent l o s s with 1.5 inch steam spreader would not be acceptable and t h e r e f o r e the 1.25 inch diameter spreader would be more s u i t a b l e . The temperature v a r i a b i l i t y between the 24 environmental thermocouples was remarkably low f o r the 1.5 inch diameter steam spreader of with +1.13% compared to 5.43% f o r the 1.0 inch and 7.4% f o r the 1.25 inch as taken from Table 17. I t was d i s a p p o i n t i n g t h a t the c o e f f i c i e n t of v a r i a t i o n values f o r the 1.25 inch diameter steam l i n e were not somewhat lower, but Table 16. Energy use and re tor t come-up times For 1.0 inch (25.4 ma) and 1.5 inch (38.1 en) diasteter steam spreaders. Test Conditions CUT (min) IT CC) Steam Use (MJ) Vent Loss (MJ) Vent to 104'C, higher IT 1 i n s t r a i g h t spreader run no. 6-37 9.0 45.0 650.2 16.9 1 i n cro s s bar spreader run no. 4-7 3-2 3-3 3- 5 4- 3 4-4 4-5 4-6 13.0 17.0 15.0 16.0 15.5 15.5 19.0 16.0 31.0 40.0 36.0 34.0 38.0 36.0 35.0 30.3 729.7 717.2 725.3 670.0 705.8 738.7 691.7 815.2 37.2 28.1 24.3 26.3 26.5 27.2 47.3 26.0 Average Range 15.0 6.0 36.1 14.7 715.9 164.8 28.9 30.4 Vent 5 minutes and 107 °C 1.5 i n s t r a i g h t spreader run no. 5-5 5-6 5-7 5-9 5-10 6.0 6.5 5.4 6.0 6.0 33.0 40.0 18.0 18.0 14.0 788.6 739.1 881.4 872.3 899.1 94.6 65.0 94.0 79.2 80.2 Average Range 5.9 0.6 24.6 26.0 836.1 160.0 82.6 29.6 Table 17. Temperature distribution analysis to compare 1.0, 1.25 and 1.5 inch steaa spreader dimensions. Temperature D i s t r i b u t i o n C h a r a c t e r i s t i c Test Conditions X C C ) (C°) C o e f f i c i e n t of V a r i a t i o n Vent 5 min - 1.5 i n s t r a i g h t spreader run no. 5-5 5-6 5-7 5-9 5- 10 Vent to 104*C - 1 i n s t r a i g h t spreader run no. 6-34 6- 35 6-36 1-1 Vent to 104 °C - 1 i n cross bar spreader run no. 3-2 3-3 3- 5 4- 3 4-4 Vent to 104°C - 1.25 i n s t r a i g h t spreader run no. 6-11 6-12 6-13 6-14 Vent to 104*C - 1.25 i n cross bar spreader run no. 6-23 6-24 6-25 6-26 114.1 112.6 114.5 112.6 114.4 95.1 99.2 100.6 101.4 92.5 95.1 95.2 95.3 94.1 98.0 98.1 95.5 88.1 96.2 85.7 86.4 88.1 1.57 1.48 1.06 0.66 1.68 5.47 5.49 6.03 4.73 4.35 5.06 4.89 5.92 5.23 5.15 5.66 4.61 8.49 5.13 9.02 7.70 8.23 Average Average Average 1.38 1.31 0.93 0.58 1.47 1.13 5.75 5.55 6.00 4.66 4.70 5.32 5.14 6.21 5.55 5.43 5.20 5.77 4.83 9.63 5.33 10.52 8.91 9.35 7.40 Note: X = mean temperature per min (°C) from time zero to 25 min. = a r i t h m e t i c mean of standard d e v i a t i o n s of thermocouple temperatures per min. 73 as mentioned p r e v i o u s l y , the steam c o n t r o l valve was found to be malfunc-t i o n i n g . The energy balances f o r the 1.5 inch diameter spreader are presented in Table 18. IV. NOVEL VENTING PROCEDURES Smith et a l . (1983) reported on two novel techniques f o r reducing vent l o s s e s and minimizing r e t o r t come-up time. The f i r s t concept involved a p p l i c a t i o n of vacuum to the loaded r e t o r t by mechanical means to remove a i r at the s t a r t of the cook. The system was capable of drawing 25 inches vacuum (84.7 kPa). The r e t o r t was s t a r t e d and the vent and d r a i n valves were c l o s e d . I t was found that vacuum a s s i s t a n c e used about the same amount of steam with no n o t i c e a b l e improvement i n the temperature d i s t r i -b u t i o n . The second m o d i f i e d vent procedure i s r e f e r r e d to as "reverse-purge" venting. Hickman and Robinson (1973) i n d i c a t e d t h a t t h i s p r o c e d u r e provided no great advantage over conventional venting. Since a i r i s more dense than steam, steam flowing from the top down should therefore a s s i s t i n d i s p l a c i n g the a i r . The r e s u l t s i n d i c a t e d that reverse-purge venting was more e f f e c t i v e and r e l i a b l e than conventional venting without d r a i n i n g of condensate; however, i t was not as e f f e c t i v e as conventional venting with d r a i n i n g . Table 18. Suoaary of energy balances for ballast load of white beans in brine with a 1.5 inch (38.1 na) steam spreader. Vent 5 min and 107°C Run no. Steam input IT Energy s i n k s (MJ) T o t a l Accounted (MO) CC) Vent l o s s Radiation 4 Convection Bleeders & Blowdown Condensate S e n s i b l e Heat Metal Product (MJ) (30 1.5 inch s t r a i g h t 5-5 788.6 33.0 94.6 75.6 66.3 118.6 71.2 362.2 — — spreader 5-6 739.1 40.0 65.0 76.7 68.2 127.9 67.9 333.4 — — 5-7 881.4 18.0 94.0 75.0 66.3 135.8 86.3 424.0 — 5-9 872.3 18.0 79.2 77.1 69.1 136.6 86.3 424.0 — — 5-10 899.1 14.0 80.2 77.8 69.1 141.9 89.7 440.0 — — 4=. 75 In view of the s t u d i e s to date to minimize r e t o r t come-up and steam consumption, i t was hypothesized that i t may be p o s s i b l e to improve the purge e f f e c t i f the pressure within the r e t o r t vessel were more r a p i d l y achieved upon t u r n i n g on the steam. In order to accommodate t h i s condi-t i o n , a 1 inch diameter r e s t r i c t i o n was secured i n the 1 1/4 inch vent l i n e . The r e t o r t was operated in the same manner as a l l other t r i a l s i n c l u d i n g d r a i n i n g condensate up to 100°C. The r e s u l t s revealed there was no n o t i c e a b l e improvement i n the steam consumption or come-up time. This c o n c l u s i o n was based on examination of the temperature d i s t r i b u t i o n come-up time and steam vent l o s s e s of the experimental runs as compared with the c o n t r o l runs. CONCLUSIONS 76 The f i n d i n g s i n t h i s study have i d e n t i f i e d some p o t e n t i a l methodologies whereby to improve energy e f f i c i e n c y and production c a p a b i l i t y during thermal processing i n batch-type v e r t i c a l r e t o r t s f o r low-acid canned food products. F i n a n c i a l o p p o r t u n i t i e s f o r energy saving through adjustment of the venting p r a c t i c e and m o d i f i c a t i o n of the steam p i p i n g show promise. In a d d i t i o n , energy l o s s e s i n the steam condensate, and r a d i a t i o n and convection have been i d e n t i f i e d i n the energy balance equation and appear to be worthwhile f o r fu t u r e c o n s i d e r a t i o n i n energy recovery a n a l y s i s . Three major changes to the r e t o r t system were examined to measure t h e i r impact on energy consumption, venting e f f i c a c y and r e t o r t come-up time. The f i r s t changes to the design of the steam spreader involved an i n c r e a s e in the number of steam ports and secondly the c o n f i g u r a t i o n of the steam spreader. Both were found not to improve the venting of a i r from the system nor energy c o n s u m p t i o n . The f i n a l m o d i f i c a t i o n i n v o l v e d an increase i n the s i z e of the steam c o n t r o l valve and steam l i n e . The steam l i n e was increased from 1.0 to 1.25 to 1.5 inch pipe diameters. I t was found that the l a r g e s t steam l i n e d i s p l a y e d the most s i g n i f i c a n t impact on r e t o r t come-up time and u n i f o r m i t y of environmental temperatures throughout the r e t o r t . A 1.0 inch (25.4 mm) diameter steam l i n e venting to 104°C consumed 715 MJ of steam energy, l o s t 28.9 MJ i n venting and achieved the process s e t p o i n t temperature i n 15.0 minutes. The 1.5 inch (38.1 mm) diameter steam l i n e used 836 MJ of steam l o s t 32.9 MJ i n venting and achieved process temperature i n 5.9 min. 77 Tests with a b a l l a s t load of white beans i n brine i n d i c a t e d that i t was f e a s i b l e to reduce the come-up time by 8 minutes. This reduction in the venting schedule r e s u l t e d i n a 13% savings in energy. I t i s apparent from t h i s study that f u r t h e r i n v e s t i g a t i o n s p e r t a i n i n g to the accuracy of the automatic time and temperature control systems and condensate removal are needed to f u r t h e r assure the s a f e t y of the thermal process. Perhaps i t i s f e a s i b l e to economically upgrade the p r e s e n t equipment w i t h a d d i t i o n a l temperature sensors. However, i t must be recognized that such s t u d i e s and recommendations should be undertaken only by thermal process a u t h o r i t i e s . REFERENCES 78 B a l l , C O . 1928. Mathematical S o l u t i o n of Problems on Thermal Processing of Canned Foods. Univ. C a l i f . Publ. Pu b l i c Health 1, 230 pp. B a l l , C O . and Olson, F.C.W. 1957 S t e r l i z a t i o n i n Food Technology, McGraw-H i l l Book Company, Inc. New York, NY. Bigelow, W.D., Bohart, G.S., Richardson, A.C., and B a l l , C O . 1920. Heat penetration i n processing canned foods. B u l l e t i n N0.I6-L. Res. Lab. N a t l . Canners Ass'n., Washington, D C Carroad, P.A., Singh, R.P., Chhinnan, M.S., Jacob, N.L. and Rose, W.W. 1980. Energy use q u a n t i f i c a t i o n i n the c a n n i n g of c l i n g s t o n e peaches. J . Food S c i . 45:723. Chhinnan, M.S., Singh, R.P., Pedersen, L.D., Rose, W.W. and Jacob, N.L. 1980. A n a l y s i s o f energy u t i l i z a t i o n i n s p i n a c h p r o c e s s i n g . Transactions of the ASAE 23:503. Davis, D.S., Romberger, J.S., Pettibone, C A . and Kranzer, G.A. 1980. Waste heat from Food Processing Plants in the P a c i f i c Northwest. Transactions of the ASAE 23:498. Ecklund, O.F. and Benjamin, H.A. 1942. Bottom vents f o r v e r t i c a l r e t o r t s . Food I n d u s t r i e s , American Can Co., Maywood, IL. Ferrua, J.P. and C o l , M.H. 1975. Energy consumption rates f o r s t e r i l i z i n g equipment. Canner Packer. January: 44. Finn, P.J. 1979. Energy use i n Canadian food and beverage manufacturing and the impact of energy c o s t s on food p r i c e s , i n Proceedings of the Work Planning Meeting on Energy i n the Food System. P.W. Voisey, e d i t o r , Engineering and S t a t i s t i c a l Research I n s t i t u t e , R e s e a r c h Branch, A g r i c u l t u r e Canada, Ottawa, ON. Harper, J.C. 1976. Elements of Food Engineering. AVI P u b l i s h i n g Co., Westport, CT. Hemler, V.H., A l s t r a n d , D.V., Ecklund, O.F. and Benjamin, H.F. 1952. Processing and c o o l i n g of canned foods. Ind. and Eng. Chem. 44:1459. Hickman, A. and Robinson, D.J. 1973. Batch s t e r i l i z i n g cans. Process Biochem. 8(7):21. K r e i t h , F. and Black, W.Z. 1980. Basic Heat T r a n s f e r . Harper and Row, New York, NY. Lopez, A. 1975. A Complete Course i n Canning. Book I - Basic Information on Canning. The Canning Trade, Baltimore, MD. 79 Mayou L. and Singh, P. 1980. Energy use p r o f i l e s i n c i t r u s packing plants i n C a l i f o r n i a . Transactions of the ASAE 23:234. Pedersen, L.D., Rose, W.W. Jacob, N.L., and Singh, R.P. 1980. ASAE Energy Symposium 1980, Energy c o n s e r v a t i o n i n the c a n n i n g i n d u s t r y . T r a n s a c t i o n s of the ASAE 23:598. P f l u g , I . J . , and Borrero, C. 1965 Evaluation of the Heating Media For Processing S h e l f Stable Foods i n F l e x i b l e Packages i n Commercial P r o c e s s i n g Equipment. F i n a l Report of Part II of Quartermaster P r o j e c t No. IK64332D587. US Army Natick L a b o r a t o r i e s , Natick, MA. P f l u g , I . J . 1975. Procedures f o r C a r r y i n g Out Heat Penetration Tests and Analyses of the R e s u l t i n g Data. Department of Food S c i e n c e and N u t r i t i o n , U n i v e r s i t y of Minnesota, Minneapolis, MN. Sampson, D.F. 1934. Some A s p e c t s o f the T e c h n o l o g y o f P r o c e s s i n g . American Can Company, Maywood, IL. Singh, R.P. 1977. Energy consumption and conservation i n food s t e r i l i z a -t i o n . Food Technol. 31:57. Singh, R.P. 1978. Energy accounting i n food process operations. Food Technol. 32:40. S i n g h , R.P. 1980. Methods f o r determining steam u t i l i z a t i o n i n food processing p l a n t s . American Society of A g r i c u l t u r a l Engineers, Paper 80-6552, ASAE. S t . Joseph, MI. Smith, T., Tung, M.A. and Bennett, L. 1983. Saving Energy In Conventional Steam Retorts With Emphasis on Venting Procedures. F i n a l report f o r E n g i n e e r i n g and S t a t i s t i c a l R esearch I n s t i t u t e , C o n t r a c t F i l e 09SU.01843-1-EP08. A g r i c u l t u r e Canada, Ottawa, ON. Townsend, C.T., Somers, I . I . , Lanb, F.C. and Olson, N.A. 1956. A Laboratory Manual For the Canning Industry. 2nd Ed. National Canners A s s o c i a t i o n , Washington, DC. 

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