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18 T h e Syngas Process
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HERMAN F. FELDMANN Battelle-Columbus Laboratories, 505 King Ave., Columbus, OH 43201 JOSEPH K. ADLERSTEIN Syngas, Inc., Suite 1260 East, First National Center, Oklahoma City, OK 73102 The Syngas Process concept and experimental data used i n its development have been published.(1,2) The intent of this paper i s to present additional information on calculated material b a l ances for an integrated process, projected oxygen consumption, as w e l l as to present preliminary projections of the economics of producing an intermediate-Btu gas by the Syngas Process. B r i e f l y , the Syngas Process, Figure 1, consists of a two-stage reactor system with a zone between the two stages where separation of metal and glass from organic char is accomplished by e l u t r i a t i n g the r e l a t i v e l y l i g h t carbonaceous char from the dense metal and glass phase. In the first stage, incoming s o l i d waste contacts a hydrogen-rich synthesis gas generated from the gasification of residual carbonaceous char. In this first stage, the incoming waste is devolatilized and hydrogasified and the residual char is then gasified to produce the hot synthesis gas. Our experimental studies suggest that the product d i s t r i b u t i o n (namely CH4 versus organic liquids) is influenced by the hydrogen/ s o l i d waste feed r a t i o more than by the hydrogen p a r t i a l pressure and, therefore, there i s considerable flexibility i n the selection of the system pressure. Overall Material Balances Overall material balances for the Syngas Process utilize experimental data generated i n our small process development unit (PDU) to determine the key factors influencing carbon conversion and product d i s t r i b u t i o n i n the first stage methane production reactor (MPR). The char produced in the MPR is then fed to a second stage entrained g a s i f i e r where it is completely gasified with oxygen and steam. Because the char fed to the second stage is mostly devolatilized, the performance of the entrained gasifiers was simulated using published data for entrained systems feeding coal or coal char.(3) Figure 2 shows a material balance calculated on the above basis. By separation of the MPR from the gasification zone, the 0-8412-0434-9/78/47-076-359$05.00/0 © 1978 American Chemical Society In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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SOLID WASTES AND RESIDUES
Shredded Waste
Product Gas Lock Hopper (Drying) System
Quench
W
Recovery
Ash Slurry to Settling
Methane Production Reactor Hot Syn Gas Char + Metal/Glass -
Char-Metal/Glass Separation Zone
Char Gasifierl
Char Oxygen
|Metal/Glass Water Quench Metal/Glass
-
Figure 1.
txH
Simplified block diagram—Syngas reactor system
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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18.
F E L D M A N
AND
ADLERSTEIN
The
StjngdS
361
PrOCeSS
Shredded S o l i d Waste
Product Gas
70 l b s "Organics" 30 l b s Moisture —
Constituent H
=
2
CH4
Methane Production Reactor
CO C02
C H C6H 2
H2O
6
= = = = =
6
=
Amount (lb-moles)
1.134 0.612 0.567 1.394 0.034 0.011 2.771 6.523 T o t a l lb-mol
Metal/Glass 17.8 l b s Char
Steam 23.8 l b s -
Steam Oxygen [Gasification
2700 F Synthesis Gas C o n s t i t u e n t - Amount (lb-moles) CO H C0 H2O 2
2
= = = =
0.795 0.512 0.243 0.899 2.449
Oxygen 13.24 l b s
Total
Ash Figure 2.
Material balance for the Syngas process
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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f o l l o w i n g key advantages c r i t i c a l to the o v e r a l l process economics are achieved. (1) M e t a l and g l a s s can be recovered i n a r e s a l a b l e s t a t e without b e i n g slagged or without r e q u i r i n g a complex f r o n t end s e p a r a t i o n and c l e a n i n g system. I f the metal and g l a s s entered the g a s i f i e r , f u s i o n and p o s s i b l e o x i d a t i o n of metal would r e s u l t . (2) Methane y i e l d s are i n c r e a s e d because the methane i s prevented from e n t e r i n g the g a s i f i e r where i t would be reformed or combusted. (3) Oxygen requirements are minimized because only the char from the MPR, a s m a l l f r a c t i o n of the o r i g i n a l s o l i d feed, i s g a s i f i e d and because the char e n t e r s the g a s i f i e r a t a temperature of 1000 to 1200 F. In a d d i t i o n , the o v e r a l l process heat requirements are minimized because of the h i g h methane y i e l d p o s s i b l e from t h i s type of staged system. As mentioned, the balances shown i n F i g u r e 2 are based upon experimental data generated i n the PDU s t u d y i n g the MPR. Ci) For the steam/oxygen g a s i f i e r , experimental data presented by Von F r e d e r s d o r f f and E l l i o t t Q ) f o r an IGT e n t r a i n e d g a s i f i e r was used. A comparison of the IGT e n t r a i n e d g a s i f i e r data w i t h that from o t h e r e n t r a i n e d g a s i f i e r s i n d i c a t e d e x c e l l e n t c o n s i s t e n c y and i t i s t h e r e f o r e f e l t that the r e s u l t s are t y p i c a l . Because the char from the MPR enters the g a s i f i e r at 1000 to 1200 F, oxygen consumption should be l e s s than t h a t c a l c u l a t e d based on the above g a s i f i e r t e s t s because the c o a l used i n these t e s t s was not preheated. I t should be s t r e s s e d t h a t experimental data f o r an e n t r a i n e d g a s i f i e r was used and the g a s i f i e r was s m a l l compared to commercial s i z e . Thus, these r e s u l t s i n c l u d e the e f f e c t s of heat l o s s e s and c o n s e r v a t i v e l y represent the performance of a l a r g e r system. A f t e r c o o l i n g and quenching, the product gas from the Syngas r e a c t o r w i l l have the approximate composition and the y i e l d shown below. F u e l Gas Y i e l d and Composition from Syngas Reactor System F u e l Gas Composition, volume percent H2 = 30.3 CH4 = 16.4 Heating Value = 329 Btu/SCF CO =15.1 Y i e l d , SCF/lb-dry " o r g a n i c s " =20.3 37.3 CO2 C H 0.9 100.0 2
6
The major u n c e r t a i n t y i n the above gas composition i s the d i s t r i b u t i o n between H2, CO and CO2 which i s determined by the water gas s h i f t . The composition above i s based on assuming an H2/CO r a t i o approximately 2 because of the h i g h steam content of
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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the gas. However, the Purox process r e p o r t s an H2/CO r a t i o s l i g h t l y l e s s than 1 i n s p i t e of h i g h steam c o n c e n t r a t i o n s i n the gas. A lower v a l u e f o r the H2/CO r a t i o w i l l i n c r e a s e the h e a t i n g value of the d r i e d product gas because the l e s s water-gas s h i f t o c c u r r i n g the lower the CO2 content of the gas and the h i g h e r the H2O content which i s removed by d r y i n g w h i l e CO2 i s not. Because oxygen consumption i s important i n determining gas p r o d u c t i o n c o s t s , the oxygen consumption p r o j e c t e d f o r the Syngas Process should be compared w i t h those r e p o r t e d f o r other g a s i f i c a t i o n processes. A comparison between p r o j e c t e d oxygen consumption f o r the Syngas P r o c e s s , the Purox P r o c e s s , and the L u r g i Process (for c o a l g a s i f i c a t i o n ) i s given i n Table 1. TABLE 1. OXYGEN REQUIREMENTS PER MILLION BTU OF RAW PRODUCT GAS
Process Syngas Purox(l>2) Lurgi(3)
Oxygen Requirements (tons oxygen/MM B t u , raw product
gas)
0.014 0.029 0.019 (For a high-oxygen western c o a l )
(1) S o l i d Waste D i s p o s a l Resource Recovery, Brochure P u b l i s h e d by Union C a r b i d e s Environmental Systems. (2) Anderson, J.E., "The Oxygen Refuse Converter A System f o r Producing F u e l Gas, O i l , Molten M e t a l and S l a g from Refuse, 1974 N a t i o n a l I n c i n e r a t o r Conference, Miami, F l o r i d a (May 12-14, 1974). (3) E l g i n , D.C. and H. R. P e r k s , " R e s u l t s of American Coals i n L u r g i Pressure G a s i f i c a t i o n P l a n t at W e s t f i e l d , S c o t l a n d " , Proceedings of the S i x t h S y n t h e t i c P i p e l i n e Gas Symposium, pp 247-265, American Gas A s s o c i a t i o n , Chicago, I l l i n o i s (October 1974). 1
Thus, the Syngas Process o f f e r s the p o t e n t i a l of a very subs t a n t i a l r e d u c t i o n i n oxygen requirements over the Purox P r o c e s s , which employs a f i x e d - b e d s l a g g i n g g a s i f i e r . Reactor Design Concepts. E x p e r i m e n t a l l y , we operated the MPR as both a f r e e - f a l l and moving-bed r e a c t o r . However, these t e s t s e s t a b l i s h e d t h a t the conversion r a t e was l i m i t e d o n l y by heat t r a n s f e r t o the p a r t i c l e and t h a t the conversion l e v e l was d e t e r mined by the H2 "seen" by the waste. Thus, there i s c o n s i d e r a b l e f l e x i b i l i t y i n r e a c t o r design. For the purposes of e s t i m a t i n g r e a c t o r throughput, a f r e e f a l l system i s assumed. One major advantage of a f r e e - f a l l MPR i s t h a t there should be no problems w i t h b r i d g i n g of s o l i d waste. (For example, we were able t o operate even our 2.8 i n c h I.D. MPR
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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i n the f r e e - f a l l mode without b r i d g i n g problems.) The presence of metal and g l a s s should provide a d d i t i o n a l impetus f o r m a i n t a i n i n g f l o w through the f r e e - f a l l zone. Another advantage of the f r e e - f a l l system i s the i n c r e a s e d u t i l i z a t i o n of s e n s i b l e heat i n the product gases, which a l l o w feeding higher moisture content waste. Crude measurements of the f r e e - f a l l v e l o c i t y of shredded paper, which w i l l have the lowest t e r m i n a l v e l o c i t y of any s i g n i f i c a n t f r a c t i o n of s o l i d waste, i n d i c a t e that i t s f r e e - f a l l v e l o c i t y i s about 4 f t / s e c . Operating t h i s system i n the f r e e - f a l l mode a t a gas v e l o c i t y l i m i t e d t o 3 f t / s e c a l l o w s a gas p r o d u c t i o n r a t e i n the MPR e q u i v a l e n t t o about 7 m i l l i o n B t u / h r - f t 2 (1100 l b s dry organic material/hr-ft2). This s p e c i f i c Btu p r o d u c t i o n r a t e i s q u i t e h i g h compared t o most c o a l g a s i f i c a t i o n processes e s p e c i a l l y f i x e d or moving-bed systems. For example, the s p e c i f i c Btu output of a WellmanGalusha c o a l g a s i f i e r has been reported t o be about 1.5 m i l l i o n B t u / f t 2 - h r . d) A f t e r the char/metal/glass mixture f a l l s through the f r e e f a l l zone, the char w i l l be s t r i p p e d from the metal/glass mixture by a stream of steam and the char w i l l be blown i n t o an e n t r a i n e d g a s i f i e r i n t o which oxygen i s i n j e c t e d t o complete g a s i f i c a t i o n of the char. Before a d e t a i l e d design of the system i s p o s s i b l e , a d d i t i o n a l data w i l l have t o be generated. For example, i t w i l l be necessary to make more accurate measurements of entrainment v e l o c i t i e s of v a r i o u s s o l i d waste c o n s t i t u e n t s a f t e r primary shredding. I n a d d i t i o n , the d r y i n g r a t e s of s o l i d waste w i l l have to be d e t e r mined i n order to evaluate whether p r e d r y i n g i s necessary of i f f l a s h d r y i n g can be c a r r i e d out i n the top of the MPR i t s e l f . I n t e g r a t i o n of the MPR and g a s i f i e r should provide no t e c h n i c a l problem but w i l l r e q u i r e more d e t a i l e d engineering a n a l y s i s . P r e l i m i n a r y Cost Estimates. Because we do not y e t have a d e t a i l e d r e a c t o r d e s i g n , i t i s i m p o s s i b l e t o do a d e t a i l e d cost estimate. By u t i l i z i n g p u b l i s h e d c o s t s f o r s i m i l a r c o a l g a s i f i c a t i o n processes, i t i s p o s s i b l e t o determine a reasonable estimate of what gas c o s t s are l i k e l y t o be. U n f o r t u n a t e l y , most of the p u b l i s h e d cost data on c o a l g a s i f i c a t i o n i s f o r base load p i p e l i n e gas p l a n t s which a r e f a r l a r g e r than i s p r a c t i c a l f o r a p l a n t u t i l i z i n g m u n i c i p a l s o l i d wastes. However, the C u l b e r t s o n , Kasper d i s c u s s i o n on the economics of s m a l l c o a l gasifiers(£) provides a means of examining cost f e a s i b i l i t y f o r p l a n t s i z e s of g r e a t e s t i n t e r e s t i n g a s i f y i n g m u n i c i p a l s o l i d waste as w e l l as other biomass feeds. Economic f e a s i b i l i t y was evaluated f o r a c a t t l e manure feeds t o c k i n a d d i t i o n to the s o l i d waste. Chemically, both a r e s i m i l a r except that c a t t l e manure i s probably more r e a c t i v e , more homogeneous, and, i n many areas, a v a i l a b l e a t a p r i c e that makes i t s
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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u t i l i z a t i o n f o r conversion t o gas economically a t t r a c t i v e . The cost p r o j e c t i o n s a r e the u t i l i z a t i o n of commercially a v a i l a b l e Wellman-Galusha a g i t a t o r type g a s i f i e r s 10 f e e t i n diameter. Though the Syngas system i s d i f f e r e n t than the WellmanGalushaR g a s i f i e r , the higher throughput p o s s i b l e w i t h the Syngas system makes the u t i l i z a t i o n of Wellman-Galusha cost data reasonable and probably c o n s e r v a t i v e . Included i n the t o t a l c a p i t a l requirements are: (1) Estimated i n s t a l l e d cost of both o n - s i t e and off-site facilities, (2) P r o j e c t contingency of 15 percent of f a c i l i t y c o s t , (3) I n i t i a l charge o f c a t a l y s i s and chemicals, (4) Paid-up r o y a l t i e s , (5) Allowance f o r funds used during c o n s t r u c t i o n , (6) Start-up c o s t s , and (7) Working c a p i t a l . The estimated gas p r i c e i s the average p r i c e based on the f o l l o w i n g assumptions o u t l i n e d i n the ERDA Gas Cost G u i d e l i n e s . (1) 20-year p r o j e c t d u r a t i o n . (2) 20-year s t r a i g h t - l i n e d e p r e c i a t i o n on p l a n t investment, allowance f o r funds used d u r i n g c o n s t r u c t i o n , and c a p i t a l i z e d p o r t i o n of start-up costs. (3) Debt/equity r a t i o o f 75/25. (4) 15 percent r e t u r n on e q u i t y . (5) 9 percent i n t e r e s t on debt. (6) F e d e r a l income tax r a t e o f 48 percent. The major s e c t i o n s o f the p l a n t a r e : (1) Coal storage and h a n d l i n g , (2) Coal g a s i f i c a t i o n , (3) P a r t i c u l a t e removal, (4) Tar removal and d i s p o s a l , (5) Water treatment and d i s p o s a l , (6) Ash d i s p o s a l , and (7) Oxygen p l a n t ( f o r the intermediate-Btu gas case). The only m o d i f i c a t i o n s o f the above cost p r o j e c t i o n s that were made were the f o l l o w i n g . (1) The e x t e r n a l oxygen consumption f o r producing intermediate-Btu gas from manure was adjusted f o r the d i f f e r e n c e i n oxygen consumption between s o l i d waste and c o a l . (2) The d i f f e r e n c e i n h e a t i n g value between manure and s o l i d waste and c o a l was compensated f o r i n determining the manure requirements t o produce an e q u i v a l e n t B t u output. (3) The c o a l cost c o n t r i b u t i o n was i s o l a t e d t o a l l o w separate assessment o f the e f f e c t of f u e l c o s t . R
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R
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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Manure Case. No advantage was taken of the much h i g h e r react i v i t y of s o l i d waste and manure compared to c o a l , the f a c t that these feeds do not agglomerate, the h i g h e r ethane y i e l d s r e s u l t ing from t h e i r p y r o l y s i s and the h i g h e r throughputs a n t i c i p a t e d f o r the Syngas Reactor System. Thus, these cost p r o j e c t i o n s summarized below should be regarded as c o n s e r v a t i v e .
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Comparison of Average Gas P r i c e s Produced from Manure and Coal from a S i n g l e 1 0 f t I.D. Fixed-Bed G a s i f i e r
T o t a l C a p i t a l Requirements, m i l l i o n s Manure or C o a l Requirement, tons/day Gas P r o d u c t i o n , 109 Btu/day Cost C o r r e c t i o n f o r Reduced Manure Oxygen Requirements, $/MM Btu Average Gas P r i c e without Coal or Manure Cost, $/MM Btu Average Gas P r i c e Coal = $35/ton, Manure = $2.50/ton, $/MM Btu
Coal
Manure
5.44 132 2.27
5.44 254 2.27 -0.32
2.49
2.17
4.53
2.45
These cost f i g u r e s e s t a b l i s h that an i n t e r m e d i a t e - B t u gas can be produced from manure at a cost that i s c u r r e n t l y competitive w i t h imported LNG ( p r i c e d at 2.50 to 3.50/MM Btu) and No. 2 h e a t i n g o i l ( p r i c e d at $2.70/MM Btu as of Summer 1977) and at a c o n s i d e r a b l y lower p r i c e than i t can be produced from c o a l . Wherever manure can be combined w i t h s o l i d wastes, the c o s t s w i l l be even more a t t r a c t i v e because of the lower cost to the p l a n t of s o l i d waste compared to manure and the l a r g e r p l a n t s i z e . Of course, other biomass can a l s o be combined to a l l o w l a r g e r p l a n t s . The q u a n t i t a t i v e e f f e c t of combining other forms of b i o mass w i l l depend on i t s cost r e l a t i v e to manure. Solid-Waste Case. Conversion of m u n i c i p a l s o l i d waste to e i t h e r an intermediate or low-Btu gas w i l l be extremely cost e f f e c t i v e because a nominal l a n d - f i l l fee can be charged to d i s pose of the s o l i d waste and the contained metal and g l a s s can be recovered i n r e s a l a b l e form by the Syngas Process. In the p r o d u c t i o n of i n t e r m e d i a t e - B t u gas, another important f a c t o r i n costs i s oxygen consumption. As p r e v i o u s l y pointed out, the Syngas Process should a l l o w a r e d u c t i o n of approximately $0.32/MM Btu compared to c o a l (because of the h i g h e r oxygen content of c e l l u l o s i c type m a t e r i a l s compared to c o a l ) . As mentioned, a g r a v i t a t i n g , f i x e d - b e d , s l a g g i n g bottom g a s i f i e r such as the Purox w i l l r e q u i r e s u b s t a n t i a l l y more oxygen a c c o r d i n g to publ i s h e d oxygen consumption data.(5) In a d d i t i o n to the increased oxygen consumption, the f u s i o n of metal and g l a s s to s l a g reduces the revenue that could o t h e r wise be obtained from t h e i r s a l e . For the s l a g g i n g g a s i f i e r case,
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
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The Syngas Process
367
i t i s assumed that t h e i r i s no net value f o r the s l a g and f o r the Syngas Process a net value of $3.00 MM/Btu i s assumed because metal and g l a s s a r e recovered i n r e s a l a b l e form. In order t o maintain these cost p r o j e c t i o n s on as common a b a s i s as p o s s i b l e , the same investment costs were assumed f o r the s l a g g i n g g a s i f i e r and the Syngas Process w i t h an adjustment made i n oxygen consumption, which f o r the c o a l case i s estimated by Culbertson and K a s p e r ( i ) t o c o n t r i b u t e about $1.00/MM B t u of product gas. The o v e r a l l thermal e f f i c i e n c y of both the Syngas Process and the s l a g g i n g g a s i f i e r i s assumed the same (approximately 72 percent) as estimated by Culbertson and Kasper f o r the c o a l g a s i f i c a t i o n case. No low-Btu gas cost p r o j e c t i o n s a r e made f o r the s l a g g i n g g a s i f i e r because i t i s impossible t o achieve s l a g g i n g temperatures w i t h an air-blown g a s i f i e r unless e x c e s s i v e l y high a i r preheat temperatures a r e employed. A c h i e v i n g these temperatures r e q u i r e s a u x i l i a r y f i r i n g of the a i r preheater w i t h a c l e a n f u e l . A l s o , f o r the solid-waste cases, i t was a r b i t r a r i l y decided to i n c r e a s e the investment cost by 20 percent over the c o a l case to account f o r the greater hetrogeneity of s o l i d waste compared to c o a l or manure. The gas p r i c e s presented i n the f o l l o w i n g t a b l e are: (1) The average gas p r i c e w i t h c o a l as a feedstock. (2) A base case gas p r i c e f o r both the Syngas and Slagging G a s i f i e r Systems which assumes that waste, already shredded a t v a r i o u s t r a n s f e r s t a t i o n s , i s d e l i v e r e d t o the g a s i f i c a t i o n p l a n t s . The d i s p o s a l charge f o r t h i s waste i s assumed t o be $2.00/ton. For both Syngas and the s l a g g i n g g a s i f i e r a 20 percent i n c r e a s e i n p l a n t i n v e s t ment was assumed f o r the same Btu output. (3) A gas p r i c e assuming a net r e c y c l e value of $3.00/ton f o r recovered metal and g l a s s i s c a l c u l a t e d f o r the Syngas Process. The j u s t i f i c a t i o n i s that the Syngas Process recovers the metal and g l a s s i n a r e s a l a b l e form as p a r t of the g a s i f i c a t i o n process. (4) P r i c e s f o r low-Btu gas are presented only f o r the Syngas Process because i t can operate a i r blown as w e l l as oxygen blown. These cost p r o j e c t i o n s i n d i c a t e : (1) That e i t h e r s o l i d wastes or manure can produce intermediate and low-Btu gas a t p r i c e s that are e i t h e r c u r r e n t l y competitive or substant i a l l y cheaper than other c l e a n f u e l s and, i n the case of a solid-waste feedstock, even cheaper than c o a l ( c o a l a t $35/ton i s a p p r o x i mately $1.46/MM B t u ) .
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
No. of Gasif1er8
8.20
390
11.35
660
1.64
2.27
132
78
Gas Output 109 Btu/day
Coal Reg. tpd
Oxygen Blown
COST PROJECTIONS FOR INTERMEDIATE AND LOW-BTU GAS FROM SOLID WASTES
2.62
3.44
3.75
4.53 1420
284
839
168
0.86
1.68
0.55
1.37
1.99
0.52
1.47
Air Blown
2.77 1.30
Slagging Gasifier $2/ton Solid Waste Fee No additional Value for Metal and Glass
2.25
Syngas Gas Price $3/ton Metal and Glass Value $/MM Btu
Coal Cost Contribution - $1.66/MM Btu Gas Heating Value - 158 Btu/SCF
Gas Price Coal Feed $/MM Btu
Equivalent Solid Waste Requirements tpd
Syngas Base Case Gas Price g $2.00/ton Solid Waste fee $/MM Btu
Coal Cost Contribution - $2.03/MM Btu Gas Heating Value - 285 Btu/SCF for coal; about 400 Btu/SCF from solid waste
Table II.
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18.
FELDMAN AND ADLERSTEIN
The SyrigOS PfOCeSS
369
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(2)
That the oxygen reduction made possible by the Syngas Process allows a very significant reduction i n gas price over a slagging g a s i f i e r . (3) The additional net revenue because of the separation of metal and glass that accrues to the Syngas Process i s an extremely important factor i n process economics. (4) That a plant producing low or intermediateBtu gas from manure or s o l i d waste need not be a giant to be economic. In fact, i f lowBtu gas i s produced, plant sizes capable of serving small communities (170 tpd) are economically very attractive. This greatly increases the s o l i d waste and manure that i s economically available for gasification. (5) Because one can produce a low-Btu gas from s o l i d waste at a lower price per Btu than i s available for coal, at an overall thermal efficiency of 88 percent, one should seriously examine the option of s e l l i n g this gas as supplementary fuel to a larger f o s s i l fuel power plant rather than c o - f i r i n g waste and refuse. Obviously the combination of attractive economics, an a b i l i t y to u t i l i z e a currently wasted resource, and the solution of a growing envionmental problem make the Syngas Process attractive for commercialization. These economic projections also indicate that gasification of waste and transportation of the gas to end users who can u t i l i z e the gas i s probably a much more attractive option than using the s o l i d waste d i r e c t l y . For example, the option of gasifying the waste and using the intermediate-Btu gas i n u t i l i t y boilers w i l l probably be a more attractive option than f i r i n g waste d i r e c t l y . For larger plants (^-3000 tpd), the production of SNG from the raw product gas may also present an attractive option i n many locales. Literature Cited (1)
Feldmann, H. F., G. W. Felton, H. Nack and J. Adlerstein, (Pipeline Gas from Solid Wastes by the Syngas Recycling Process", paper presented at Fuel Division Symposium, American Chemical Society New York Meeting (April 4-9, 1976). (2) Feldmann, H. F., G. W. Felton, H. Nack and J . Adlerstein, "Syngas Process Converts Waste to SNG", Hydrocarbon Processing, p 201-204 (November 1976). (3) VonFredersdorff, C. G. and M. A. Elliott, "Coal Gasification", Chemistry of Coal U t i l i z a t i o n , Chapter 20, pp 892-1022 (1963). (4) Culbertson, R. W., and S. Kasper, "Economic Advantages and Areas of Application of Small Gasifiers", Presented at 4th Internat'l Conf. on Coal Gasification, Liquefaction and
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
370
SOLID WASTES AND RESIDUES
Conversion to Electricity, University of Pittsburgh (August 2-4, 1977). (5) Anderson, J.E., "The oxygen Refuse Converter - A System for Producing Fuel Gas, Oil, Molten Metal and Slag from Refuse", National Incinerator Conference, Miami (May 12-14, 1974). 1978
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MARCH 3,
In Solid Wastes and Residues; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
