Supercritical Fluid Extraction of Flavoring Material - American

Chapter 32

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on August 25, 2015 | http://pubs.acs.org Publication Date: August 29, 1989 | doi: 10.1021/bk-1989-0406.ch032

Supercritical Fluid Extraction of Flavoring Material Design and Economics Richard A. Novak and Raymond J. Robey Supercritical Processing, Inc., 966 Postal Road, Allentown, PA 18103 A battery limits capital cost of $2.8 million and an operating cost of $1.10 per kilogram of feed are estimated for a supercritical extraction plant with a capacity of 0.8 million kg/year of feed spices. Production cost declines significantly as plant size increases, reaching $0.50 per kilogram for a 3.1 million kg/year plant. Process costs for 12 spices and 8 herbs are estimated, ranging from $0.60 to $4.30 per kilogram feed. Costs are based on a factored estimate with probable accuracy of +/- 50%. A preliminary process design for a multiproduct plant i s described, based on proprietary p i l o t plant data. The advantages of supercritical extraction over conventional solvent extraction are discussed, including: natural, nontoxic solvent; control of flavor profile; mild process temperatures; high quality products.

Plant materials, such as spices and herbs, can be supercritically extracted for flavor, fragrance, and pharmaceutical applications. Using nontoxic carbon dioxide as a solvent, supercritical extraction (SCE) leaves no harmful residues. Food materials produced with SCE are viewed as natural and have been shown to be of high quality, often with superior properties not obtainable with other separation techniques. the purpose of this paper i s to discuss the advantages of SCE for flavor applications, to describe a preliminary design for a commercial plant, and to present economics for this application. Background SCE i s a powerful separation tool for many applications i n the chemical, food, and pharmaceutical fields (1-7). The process has proven economical i n large scale catmercial application. For 0097-6156/89/Ό406-0511$06.00/0 © 1989 American Chemical Society

In Supercritical Fluid Science and Technology; Johnston, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


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example, General Foods i s new operating a 50 m i l l i o n pound per year (23 m i l l i o n kg) c o f f e e decaff e i n a t i o n p l a n t using SCE ( 8 ) . Some of the advantages of SCE w i t h carbon d i o x i d e are: - No Harmful Residue - Carbon d i o x i d e i s odorless, t a s t e l e s s , i n e r t and nontoxic. I t i s e a s i l y and completely removed from the e x t r a c t s and processed m a t e r i a l s . - Low Temperature Process - SCE temperatures are lew enough t o prevent degradation o f s e n s i t i v e m a t e r i a l s , o f t e n important i n flavor applications. - High Q u a l i t y - E x t r a c t s prepared by SCE r e t a i n more top and back notes, w i t h no o f f f l a v o r s . Flavors and fragrances are c l o s e r t o the n a t u r a l m a t e r i a l , and are o f t e n judged superior t o conventional e x t r a c t s (5. 9. 11). - F l e x i b l e Process - The s e l e c t i v i t y o f SCE can be adjusted by proper choice o f operating conditions and procedures. Hie process can be f i n e tuned t o achieve a d e s i r e d f l a v o r o r fragrance p r o f i l e . E x t r a c t s o f a wide v a r i e t y o f spices and herbs have been prepared w i t h l i q u i d and s u p e r c r i t i c a l carbon d i o x i d e (5. 10). The techniques o f f r a c t i o n a l e x t r a c t i o n and f r a c t i o n a l separation (5. 11) allow the separation o f f l a v o r from aroma components during SCE. C o n t r o l l e d blending can then be used f o r standardization o f extracted product. S u p e r c r i t i c a l Processing, Inc. 's technology includes both f r a c t i o n a l e x t r a c t i o n and f r a c t i o n a l separation. The choice o f approach depends on the feed m a t e r i a l and product requirements. I n f r a c t i o n a l e x t r a c t i o n , the feed m a t e r i a l i s extracted i n two o r more stages. The s e l e c t i v i t y f o r e s s e n t i a l o i l s , f a t t y o i l s , and r e s i n s i s c o n t r o l l e d i n each stage through s e l e c t i o n o f e x t r a c t i o n pressure, temperature, o r cosolvent a d d i t i o n . With the f i r s t e x t r a c t i o n stage a t s u b c r i t i c a l temperatures, s e n s i t i v e e s s e n t i a l o i l s are removed a t m i l d conditions and a t short processing times. A second stage e x t r a c t i o n a t higher temperatures can then i s o l a t e f l a v o r components. For example, i n the e x t r a c t i o n o f black pepper (11), a f i r s t stage e x t r a c t i o n a t 300 bar, 30 C (31 MPa, 303 K) produces an e s s e n t i a l o i l y i e l d of 2.1% and a p i p e r i n e (hot f l a v o r component) y i e l d o f 0.6%. The second stage e x t r a c t i o n a t 312 bar, 58°C (32 MPa, 331 K) produces a lower e s s e n t i a l o i l y i e l d (0.7%) but a much higgler p i p e r i n e y i e l d (5.2%). Conversely, conditions i n the e x t r a c t o r may be h e l d constant and the extracted components separated i n stages. Optimized e x t r a c t i o n and separation conditions f o r a v a r i e t y o f s p i c e s and herbs have a l s o been developed using f r a c t i o n a l separation technology (Herikel KGaA, Ηίφ-pressure ifttr^çfrjqn Qf ffpioeg Py tfefrps of Carbon Dioxide Dusseldorf, 1982, p r o p r i e t a r y technology package. ). The consistent e x t r a c t o r conditions o f f r a c t i o n a l separation s i m p l i f i e s p l a n t operation where m u l t i p l e batch e x t r a c t o r s are used. A l s o , the s u p e r c r i t i c a l e x t r a c t i o n f l u i d i s always f u l l y loaded w i t h extracted m a t e r i a l , making a more e f f i c i e n t process. e

P


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Supercritical Fluid Extraction of Flavoring Material 513


Design P r i n c i p l e s The design o f cxximercial SCE p l a n t s has been discussed by s e v e r a l authors (1-2. 5. 7 ) . The f o l l o w i n g u n i t operations and design s p e c i f i c a t i o n s a r e important f o r SCE o f f l a v o r m a t e r i a l s : - Raw m a t e r i a l preparation - p a r t i c l e s i z e , moisture content, c e l l disruption - E x t r a c t i o n c o n d i t i o n s - pressure, tea^erature, time, s o l v e n t t o feed r a t i o , s o l v e n t f l e w - E x t r a c t o r operation - batch o r continuous, constant c o n d i t i o n s o r staged ( f r a c t i o n a l e x t r a c t i o n ) - Separation c o n d i t i o n s - pressure, temperature, disengagement design, v o l a t i l e s recovery, water removal - Separator operation - batch o r cxmtinuous, s i n g l e stage o r m u l t i p l e c o n d i t i o n s ( f r a c t i o n a l separation) - S u p e r c r i t i c a l solvent r e c y c l e and treatment, i f any - E x t r a c t recovery and treatment, i n c l u d i n g degassing, f i l t r a t i o n , t e s t i n g , dehydration, homogenization, and blending Appropriate values o f these parameters must be determined f o r each raw m a t e r i a l t o achieve optimum y i e l d and q u a l i t y o f e x t r a c t . Lab and p i l o t p l a n t o p t i m i z a t i o n s t u d i e s a r e required. The f o l l o w i n g f a c t o r s must a l s o be considered i n the design o f SCE p l a n t s f o r n a t u r a l m a t e r i a l s : - Equipment must be designed f o r pressures between 80-400 b a r (8-40 MPa), as w e l l as f o r the s t r e s s o f repeated c y c l e s . - Food p l a n t design procedures must be used. Surfaces i n contact w i t h food must be c o r r o s i o n r e s i s t a n t , smooth, and easy t o c l e a n and decontaminate. Equipment and p i p i n g must be designed w i t h no "dead ends" where m a t e r i a l may c o l l e c t and stagnate, p o s s i b l y causing œntamination. - The d i f f i c u l t y and expense o f continuous feed o f s o l i d s i n t o h i g h pressure v e s s e l s means t h a t batch operation i s probable (except, perhaps, f o r v e r y l a r g e , s i n g l e product p l a n t s ) . low b u l k d e n s i t y , o f t e n d i f f i c u l t t o handle s o l i d feeds may r e q u i r e use o f pre-loaded baskets. F u l l bore openings a r e used on v e s s e l s w i t h quick, h i g h pressure c l o s u r e s . - Heat t r a c i n g must be used where e x t r a c t e d m a t e r i a l may deposit i n l i n e s and v a l v e s . - Appropriate alarms, i n t e r l o c k s , and emergency systems must be used t o a l l o w s a f e operation a t h i g h pressure. Preliminary P l a n t Pesign Design B a s i s . A p r e l i m i n a r y design f o r a multiproduct s p i c e e x t r a c t i o n p l a n t was prepared, based on SCP's p r o p r i e t a r y process (Henkel KGaA, op. c i t . ) and p l a n t design data (Stearns C a t a l y t i c Corporation, Tolling/Demo SCE P l a n t . P h i l a d e l p h i a , PA, 1984, p r o p r i e t a r y data.). Key parameters i n the "base case" design are: Feedstock: Spices and herbs ( s o l i d ) E x t r a c t o r volume: T o t a l 974 L, Basket 695 L, S o l i d s l e v e l 90%


514

SUPERCRITICAL FLUID SCIENCE AND TECHNOLOGY Number o f e x t r a c t o r s : Extraction:

2 Pressure 60-300 bar (6-30 MPa) Temperature 20-80 C (293-353 K) Pressure 45-150 bar (4-15 MPa) Temperature 15-40 C (288-313 K) S u p e r c r i t i c a l carbon d i o x i d e 10,000 l b / h r (4,550 kg/hr) For an average s p i c e , 1.7 i f f l b (0.8 m i l l i o n kg). 24 hr/day, 7 days/week, a t 85% e

Separation:

e

E x t r a c t i o n solvent: Solvent flew r a t e : Annual capacity:


Operation:

m is Li Bam The assumed 85% a v a i l a b i l i t y i s probably a maximum. For a raultiproduct p l a n t , a d d i t i o n a l cleaning time may be needed, depending on feed mix. Process Description. A s i m p l i f i e d flowsheet f o r the process i s shewn i n Figure 1. Feed w i l l be placed i n e x t r a c t i o n baskets and loaded i n t o the e x t r a c t i o n v e s s e l s ( R - l ) . The two e x t r a c t o r s w i l l operate batchwise and i n a staggered c y c l e , so t h a t solvent c i r c u l a t i o n and e x t r a c t removal i s c a r r i e d out continuously. Except the case o f f r a c t i o n a l e x t r a c t i o n , solvent w i l l flew through the e x t r a c t o r s i n s e r i e s , so t h a t the e x t r a c t o r containing the most depleted charge always receives the freshest solvent. The e x t r a c t i o n conditions and c y c l e times w i l l vary, depending on the feed. When f r a c t i o n a l e x t r a c t i o n i s d e s i r e d , the e x t r a c t o r s w i l l operate batchwise, i n p a r a l l e l , a t d i f f e r e n t conditions. Each would feed a d i f f e r e n t separator, i n p a r a l l e l . When an e x t r a c t o r has reached the d e s i r e d e x t r a c t i o n time, i t w i l l be taken o f f l i n e , depressurized, the baskets unloaded, and the processed m a t e r i a l sent on t o d i s p o s a l o r by-product s a l e . A basket containing f r e s h feed w i l l be loaded, and the e x t r a c t o r repressurized and returned t o operation. The s u p e r c r i t i c a l solvent l e a v i n g the e x t r a c t o r s w i l l flew through a f i l t e r (F-l) t o capture entrained s o l i d s . One o r two separation stages w i l l be used, i n s e r i e s ( f r a c t i o n a l separation) o r i n p a r a l l e l ( f r a c t i o n a l e x t r a c t i o n ) . For each stage, the pressure of the s u p e r c r i t i c a l f l u i d w i l l be reduced by flow through a t h r o t t l i n g v a l v e (PCV-1, PCV-2) and the temperature adjusted i n a heat exchanger ( E - l , E-2) t o the conditions d e s i r e d f o r the stage o f separation. Any extracted m a t e r i a l which p r e c i p i t a t e s i n each stage w i l l be c o l l e c t e d i n separator v e s s e l s ( V - l , V-2). Gaseous solvent from the separators w i l l flow through a f i l t e r (F-2), an a i r c o o l e r (E-3), and a molecular s i e v e d r i e r (Χ-1) t o remove moisture. The d r i e d solvent w i l l be condensed t o a l i q u i d i n a heat exchanger (E-4), and sent t o a holding tank (V-5). L i q u i d carbon d i o x i d e w i l l be maintained i n the h o l d tank a t about 900 PSIG (6.3 MPa) and ambient temperature. Solvent w i l l be added t o the h o l d i n g tank t o make up f o r process l o s s e s . Α Ιύφ pressure r e c i p r o c a t i n g pump (P-3) w i l l compress the l i q u i d solvent t o e x t r a c t i o n pressure, and a heat exchanger (E-5) w i l l heat i t t o e x t r a c t i o n temperature, before i t flows back t o the e x t r a c t o r vessels.


Supercritical Fluid Extraction ofFlavoring Material


32. NOVAK AND ROBEY


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Extracted m a t e r i a l w i l l be continuously withdrawn from the pressurized separators ( V - l , V-2) t o atmospheric h o l d i n g tanks (V-3, V-4). Gaseous solvent t h a t f l a s h e s out o f the extracted m a t e r i a l i n the h o l d tanks w i l l be sent t o the vent system f o r d i s p o s a l . Pumps ( P - l , P-2) w i l l t r a n s f e r the degassed e x t r a c t s t o product f i n i s h i n g and storage.


Economics Scope. Based on the p r e l i m i n a r y process design, b a t t e r y l i m i t s c a p i t a l and operating c o s t s were estimated f o r mid-1988. Hie b a t t e r y l i m i t s p l a n t comprises equipment and systems d i r e c t l y associated w i t h the s u p e r c r i t i c a l e x t r a c t i o n operation, as shown i n the process flowsheet (Figure 1). Offs i t e s , such as m a t e r i a l shipping and handling, b u i l d i n g s , land, e t c . , were not included. For a s u p e r c r i t i c a l p l a n t i n s t a l l e d a t an e x i s t i n g f a c i l i t y , these s e r v i c e s may already be a v a i l a b l e . For a new o r "grassroots p l a n t , a d d i t i o n a l c a p i t a l investment, perhaps 25% t o 75% o f b a t t e r y l i m i t s c a p i t a l , w i l l be needed f o r o f f s i t e s . 11

C a p i t a l Cost. The estimated c a p i t a l c o s t f o r the base case p l a n t i s $2.8 m i l l i o n , as shown i n Table I . A l l equipment i n contact w i t h process f l u i d s i s 300 s e r i e s s t a i n l e s s s t e e l , o r s t a i n l e s s s t e e l l i n e d where appropriate. Heat exchangers are s h e l l and tube, w i t h s t a i n l e s s s t e e l tubes f o r process f l u i d s and carbon s t e e l s h e l l s f o r heat t r a n s f e r f l u i d s . The c a p i t a l c o s t includes c o s t o f equipment, i n s t a l l a t i o n m a t e r i a l s and l a b o r , and engineering and c o n s t r u c t i o n c o s t s . The c a p i t a l c o s t excludes c o s t s o f land, b u i l d i n g s , u t i l i t i e s (e.g., steam o r e l e c t r i c a l supply equipment and d i s t r i b u t i o n ) , feed and product storage, feed preparation and handling, r e c e i v i n g and shipping, other o f f s i t e s , contingencies, e s c a l a t i o n , working c a p i t a l , and r o y a l t i e s . Operating Cost. The estimated operating c o s t f o r the base case p l a n t i s about $ 115 per hour o f e x t r a c t i o n time, as shown i n Table II. Included i n the operating c o s t are the c o s t s o f u t i l i t i e s supplied t o the b a t t e r y l i m i t s , such as power, f u e l , and water (excluding any c a p i t a l charges f o r the u t i l i t i e s investment), makeup s u p e r c r i t i c a l solvent, l a b o r (operating and production s u p e r v i s i o n ) , maintenance m a t e r i a l and labor, d e p r e c i a t i o n on b a t t e r y l i m i t s c a p i t a l , and c a p i t a l r e l a t e d taxes and insurance. Operating c o s t s f o r p l a n t equipment outside the b a t t e r y l i m i t s (such as feed preparation) are excluded. A l s o excluded from the operating c o s t are the c o s t s o f raw m a t e r i a l s , p l a n t overhead and support s e r v i c e s , financing, corporate fees (sales, general and a d m i n i s t r a t i v e , research and development), contingencies, p r o f i t , and r o y a l t i e s . Production Costs. Data on e x t r a c t i o n times and y i e l d s were used t o estimate production c o s t s f o r e x t r a c t s o f twelve s p i c e s and e i g h t herbs, as shown i n Tables I I I and IV ( S u p e r c r i t i c a l Processing,


Supercritical Fluid Extraction ofFlavoring Material

NOVAK AND ROBEY

Table I. Battery Limits Capital Cost, Base Case Design


Tag # Description R-1A R-1B X-2 E-1 V-1 V-3 P-1 E-2 V-2 V-4 P-2 F-1 F-2 E-3 X-1 E-4 V-5 VP-1 P-3 E-5

Design Pressure PSIG

Extractor Extractor Ext. Baskets (10) 1st Sep. Preheater 1st Separator 1st Prod. Rec. 1st Prod. Trans. 2nd Sep. Preheater 2nd Separator 2nd Prod. Rec. 2nd Prod. Trans. Ovhd F i l t e r Recyc. F i l t e r Solv. Cooler Solv. Drier Solv. Condenser Solv. Hold Tank Vacuum Pump Solv. Recyc. Solv. Preheater

4800 4800 3500 3500 15 3500 3500 15 4800 1000 1000 1000 1000 1000 4800 4800

Size

units

973 973 695 43 208 757 10 117 208 757 10 20 30 1100 25 600 600 30 20 137

L L L FT2 L L GPH FT2 L L GPH CFM CFN FT2 PPH FT2 GAL PPH GPN FT2

Total, Equipment Cost ($1000) Installation Factor

Estimated Cost $1000 166.9 166.9 10.0 11.0 74.0 7.5 1.3 20.0 74.0 7.5 1.3 3.8 3.4 28.0 60.0 28.0 60.0 6.1 38.1 24.6 792.4

3.5

TOTAL, Battery Limits Capital ( M i l l i o n )

2.8

Table I I . Battery Limits Operating Cost, Base Case Design Item

Comments

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Labor 287 72

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33 8

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Supercritical Fluid Extraction of Flavoring Material - American

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