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1 Overview of Solid Waste and Residue Generation,

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Disposition, and Conversion Technologies JERRY L . JONES SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025

This discussion of s o l i d wastes and residues is restricted to the materials that are predominantly organic i n nature. I n cluded are municipal refuse, scrap t i r e s , a g r i c u l t u r a l residues, and forestry residues as well as organic sludges (mainly from wastewater treatment). The d i s t i n c t i o n between the terms " s o l i d waste" and "residue" may be made precise by d e f i n i t i o n . Residues are defined here as s o l i d by-products that have some positive value or represent no cost for disposal. These materials that represent a disposal cost are defined as solid wastes. These definitions, however, do not allow simple c l a s s i f i c a t i o n . For many types of materials, l o c a l market conditions are quite v a r i able and the material may fall into both categories depending on the specific s i t e , the season of the year, or the state of the economy. The conversion processes to be discussed at this symposium are those that may be described as pyrolysis, thermal g a s i f i c a tion, or liquefaction processes. The products from these so-called advanced thermal processes may be gaseous or l i q u i d fuels, a synthesis gas for use as a chemical feedstock, or a carbon char. In some cases, a gaseous fuel generated from p a r t i a l combustion containing condensible tars may be immediately combusted i n a second stage. In others, a fuel product may be transported o f f s i t e for use. The process types included i n the advanced processes category are not a l l necessarily new, but their application to the conversion of s o l i d wastes and residues i s new or has been l i t t l e used i n the past. This paper provides some background on the types, quantities, and current disposition of wastes and residues as well as some information on other existing and developing processing options that are not included i n this symposium. The method used to c l a s s i f y the processes to be discussed by the symposium speakers w i l l also be described.

0-8412-0434-9/78/47-076-003$05.00/0 © 1978 A m e r i c a n C h e m i c a l Society

Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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SOLID WASTES AND RESIDUES

SOLID WASTE AND RESIDUE QUANTITIES GENERATED AND DISPOSITION More than 500 m i l l i o n tons (dry b a s i s ) of organic s o l i d wastes and r e s i d u e s are c u r r e n t l y generated y e a r l y i n the United S t a t e s . These m a t e r i a l s represent a p o t e n t i a l energy resource equivalent to more than 5 quads.* Estimates of the q u a n t i t i e s of these m a t e r i a l s by type are summarized i n Table I . The f i g u r e s have been presented on a dry b a s i s to a l l o w comparison i n cons i s t e n t u n i t s . In f a c t , these m a t e r i a l s vary g r e a t l y i n moisture content and other p h y s i c a l and chemical p r o p e r t i e s (bulk d e n s i t y , p a r t i c l e s i z e , p a r t i c l e s i z e d i s t r i b u t i o n , i n o r g a n i c ash c o n t e n t ) . The use of a s p e c i f i c m a t e r i a l as a feedstock to an energy recovery process depends on many f a c t o r s r e l a t e d to the cost to c o l l e c t and d e l i v e r the m a t e r i a l to the s i t e of the conversion r e a c t o r , and the p h y s i c a l and chemical p r o p e r t i e s of the m a t e r i a l that a f f e c t the conversion c o s t . The homogeneity of the m a t e r i a l , f o r i n s t a n c e , o f t e n determines the extent of preprocessing r e q u i r e d . A major cost i n c e r t a i n m u n i c i p a l r e f u s e processing systems i s the f r o n t end processing to reduce the p a r t i c l e s i z e and to separate out metals and g l a s s before the thermal conversion step. By-product wood bark, a pulp and paper m i l l s r e s i d u e , on the other hand i s o f t e n q u i t e homogeneous and r e q u i r e s minimal preprocessing. Such a d i f f e r e n c e i n preprocessing cost may be p a r t i a l l y o f f s e t , however, by the dumping fee paid to the conv e r s i o n p l a n t f o r the r e f u s e or by s a l e of the recovered m a t e r i a l s such as f e r r o u s metals and aluminum. The moisture content of m a t e r i a l s may a l s o a f f e c t the c o s t s of the preprocessing (dewatering and drying) or f u e l product s e p a r a t i o n (dehydration of a f u e l gas). Where a r e a c t o r product gas contains condensible organics and r e q u i r e s dehydration, the dehydration o p e r a t i o n can represent a major cost because of poss i b l e t a r fog removal and water p o l l u t i o n problems. The moisture contents of some common s o l i d wastes and residues are shown i n Table I I . I t may be p r e f e r a b l e to predry r a t h e r than to attempt to process a wet m a t e r i a l i n the r e a c t o r . (See reference 8 f o r a more extensive d i s c u s s i o n of t h i s t o p i c . ) The d i s p o s i t i o n of the s e v e r a l c a t e g o r i e s of m a t e r i a l s l i s t e d i n Table I has been estimated i n Tables I I I and IV. The estimates shown i n Table I are based on an exhaustive study by SRI I n t e r n a t i o n a l , whereas those shown i n Table IV are merely crude a p p r o x i mations. One t h i n g i s obvious from a l l these estimates: A l a r g e

A quad i s 1015 Btu. more than 75 quads.

Current y e a r l y U.S.

energy consumption i s


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Overview of Solid Waste and Residue

Table I APPROXIMATE TONNAGES OF SELECTED ORGANIC RESIDUES AND SOLID WASTES IN THE UNITED STATES IN 1975 (Dry Weight B a s i s )

Type of M a t e r i a l " Agricultural crop manures

Quantity Generated ( m i l l i o n s of dry tons)

Data Sources (references)

residues ^ 278* 2>26*

1 1

Forestry residues

2>125*

1

M u n i c i p a l refuse

-100

2

Industrial sludges

wastewater

treatment 5,6

(Food p r o c e s s i n g , pulp and paper, p l a s t i c s and s y n t h e t i c s , organic chemicals, t e x t i l e s and petroleum r e f i n i n g ) M u n i c i p a l wastewater sludges Scrap t i r e s

treatment

-5.3

3,4

3 £546

Quantity c o l l e c t e d during normal operations or r e a l i s t i c a l l y collectible.


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Table I I MOISTURE CONTENT OF SELECTED SOLID WASTES AND RESIDUES

S o l i d Waste or Residue Wood r e s i d u e s Fresh manure (with u r i n e ) Rice h u l l s

Moisture Content (wt %) ^45 85 5-10

Bagasse

~ 50

Municipal refuse

20-35

Wastewater treatment sludges G r a v i t y thickened Centrifuged Vacuum f i l t e r e d F i l t e r pressed ( p l a t e and frame f i l t e r )

95 80-85 75-80 60-70

Scrap t i r e s

Negligible



Source:

To s o i l

Reference 1

12.3

12.2

52,389,318

52,636,074

Total

Percent of t o t a l

52,142,254 — 247,064

11,266,626 37,449,165 3,920,283

Fed

Crop Forestry Manure

Sold

4.9

21,060,223

1,741,990 19,301,797 16,436

Fuel

52.1

223,445,115

205,599,417 — 17,845,698

Returned

18.5

79,150,181

6,810,630 67,909,684 4,429,867

Wasted

T o n s — D r y Weight

100.0%

428,680,911

277,560,917 124,660,646 26,459,348

Total

CROP, FORESTRY, AND MANURE RESIDUE DISPOSITION—COTERMINOUS UNITED STATES (1975)

Table I I I

100.0%

64.7% 29.1 6.2

Percent of T o t a l

I

Co

ο

CO

Ο

M

Ο

8


Table IV ORGANIC SLUDGE AND MUNICIPAL REFUSE DISPOSITION IN THE UNITED STATES

D i s p o s a l Technique

Municipal Sludges

Landfill

25-30

Land a p p l i c a t i o n

25-30

Onsite lagoons

small

Thermal conversion

25-30

Ocean Dumping

Percent of T o t a l Industrial Refuse Sludges

15

85 £90

small small

4-5

Recycled

Quantity ( m i l l i o n s of d r y tons/year)

10

5-6

9

Small number of u n i t s w i t h energy recovery. Sources: References J2_, 3> 4,, _5..


100

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amount of s o l i d waste and r e s i d u e m a t e r i a l i s s t i l l p o t e n t i a l l y a v a i l a b l e ( a t some p r i c e ) as feedstock to energy recovery processes. I n the case of sludge d i s p o s a l , a primary c o n s i d e r a t i o n i s not to recover energy, but r a t h e r , to dispose of the m a t e r i a l f o r the lowest cost p o s s i b l e w i t h minimal energy use.

ENERGY RECOVERY OPTIONS The major process o p t i o n s f o r energy recovery from s o l i d wastes and r e s i d u e s have been described p r e v i o u s l y (see F i g ure 1 ) . ^The most w i d e l y used processes f o r energy recovery from wastes and r e s i d u e s have been d i r e c t combustion i n a furnace or c o f i r i n g of the m a t e r i a l s w i t h a f o s s i l f u e l f o r steam generat i o n . A recent use of s o l i d wastes and r e s i d u e s i s as f u e l f o r cement k i l n s . I t has been p r e d i c t e d that by 1980, 90% of the k i l n s i n the United States w i l l be a b l e to burn c o a l . v i ' I n many of these u n i t s , r e f u s e - d e r i v e d f u e l (RDF) and a g r i c u l t u r a l or f o r e s t r y r e s i d u e s can be s u b s t i t u t e d f o r the c o a l . The more advanced thermal processes of p y r o l y s i s , thermal g a s i f i c a t i o n , and l i q u e f a c t i o n (PTGL)* may produce l i q u i d , gaseous, or s o l i d char products. I n some i n s t a n c e s , the gases l e a v i n g the r e a c t o r a r e immediately combusted f o r steam generation. One advantage of t h i s approach over c o n v e n t i o n a l i n c i n e r a t i o n i s that the s o l i d waste or r e s i d u e can be burned w i t h l e s s excess a i r , which means lower gas volumes f o r c l e a n i n g (and perhaps lower p a r t i c u l a t e l o a d i n g i n the combustor f l u e gas) and a higher thermal e f f i c i e n c y ( l e s s heat l o s s out o f the s t a c k ) . Biochemical conversion processes i n c l u d e methane fermentation (anaerobic d i g e s t i o n ) f o r p r o d u c t i o n of a f u e l gas (up to 70% C H 4 and the remainder mostly C O 2 ) and fermentation of sugars to e t h y l a l c o h o l . The fermentable sugars may be produced by a c i d o r enzymatic h y d r o l y s i s of c e l l u l o s e . T h i s paper focuses on the advanced thermal processes; however, to provide a p e r s p e c t i v e on the a p p l i c a t i o n s f o r the newer processes, i t a l s o presents some i n f o r m a t i o n on the use of combustion and biochemical conversion t e c h n o l o g i e s .

For d e f i n i t i o n of terms see reference 8.


Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978. ' Solid Waste

Unprocessed

r - — — - · > Use as Aggregate

DISPOSAL

LAND

Steam

a

WITH S T E A M GENERATION^

BOILER

INCINERATION

INDUSTRIAL

UTILITY OR

—ι

a

Η

ι

·>

JL

Soil Conditioner

PROCESSES*

CONVERSION

BIOCHEMICAL

Fuel

Gaseous

R D F may be used as a supplemental fuel for sludge incineration

Char

Liquid Fuel

•

I I

PROCESSES*

PTGL

!

F o r district heating, industrial process heating, electric power production, water desalting

6

1 1
14) had a combined process c a p a c i t y of l e s s than 10% of the t o t a l m u n i c i p a l r e f u s e generated. By the mid-1970s, only about 160 of these r e f u s e i n c i n e r a t o r s were o p e r a t i n g i n the United States.(15) Since 1970 at l e a s t s i x w a t e r - w a l l furnaces f o r r e f u s e have been i n s t a l l e d i n the United States (16) f o r energy recovery.* The combined c a p a c i t y of these u n i t s i s approximately 1 m i l l i o n tons/year. These water w a l l u n i t s were i n i t i a l l y developed i n Europe and r e q u i r e only 50 to 100% excess a i r f o r combustion compared w i t h 150 to 200% f o r r e f r a c t o r y w a l l furnaces. This f a c t o r makes a s u b s t a n t i a l d i f f e r e n c e i n f l u e gas volume and improves thermal e f f i c i e n c y . Whereas the o l d e r i n c i n e r a t o r s r e c e i v e d a great d e a l of adverse p u b l i c i t y concerning a i r p o l l u t i o n problems, the modern u n i t s , which are equipped w i t h high energy scrubbers, e l e c t r o s t a t i c p r e c i p i t a t o r s , o r f a b r i c f i l t e r s , have been a b l e t o meet s t r i n g e n t p a r t i c u l a t e standards. (17, 18) Even though r e f u s e combustion w i l l probably continue to p l a y a r o l e i n the s o l i d waste management f i e l d , p r o d u c t i o n of RDF f o r c o f i r i n g i n b o i l e r s i s c u r r e n t l y r e c e i v i n g a great d e a l of a t t e n t i o n i n regions where c o a l i s f i r e d i n u t i l i t y b o i l e r s . Of the 47 e l e c t r i c u t i l i t y f e a s i b i l i t y s t u d i e s ( i n v o l v i n g r e f u s e use) under way i n the United States during 1976, 29 (62%) were concerned w i t h the use of shredded waste; 4 ( 8 % ) , the combustion of raw waste i n i n c i n e r a t o r s ; 3 ( 6 % ) , the use of a p e l l e t i z e d f u e l ; 6 (13%), the use of a powdered f u e l ; and 5 (11%), the use of a pyrolysis fuel,(i?) A number of p r o j e c t s based s o l e l y on m a t e r i a l s recovery (not f u e l ) from m u n i c i p a l r e f u s e are now being planned. Nevertheless, most a c t i v i t y i n the f u t u r e w i l l focus on systems that i n c l u d e energy recovery. Energy s a l e s account f o r 50% of the revenues f o r a system t h a t a l s o recovers aluminum and f e r r o u s metals. The d i s p o s a l fee may represent about 25% of the u n i t ' s revenue.


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Another s o l i d waste problem f o r many c i t i e s i s the d i s p o s a l of sludges from wastewater treatment p l a n t s . Sludges from wastewater treatment p l a n t s i n the United States have been combusted i n m u l t i p l e hearth furnaces s i n c e the 1930s and i n f l u i d i z e d bed u n i t s s i n c e the 1960s. C u r r e n t l y , about 25 to 30 percent or more of the sludge generated i s i n c i n e r a t e d . ( 3 , 4) Energy recovery from the i n c i n e r a t o r f l u e gases by use of waste heat b o i l e r s has only r e c e n t l y become common p r a c t i c e , however. Co-disposal of m u n i c i p a l r e f u s e and sludge i n thermal conversion processes i s c u r r e n t l y a t o p i c of great i n t e r e s t to m u n i c i p a l i t i e s . An EPA c o n t r a c t o r r e c e n t l y reported that c o - i n c i n e r a t i o n of sludge and r e f u s e " w i l l have lower o v e r a l l cost than separate i n c i n e r a t i o n of sludge and r e f u s e " (^0); although t h i s approach has met w i t h v a r i e d degrees of t e c h n i c a l and economic success i n the p a s t , i t may represent a f u t u r e s o l u t i o n f o r c e r t a i n s i t e s where r e f u s e d i s p o s a l by thermal conversion processes can be econ o m i c a l l y j u s t i f i e d . I t i s probably not going to be w i d e l y used i n the near term, however, unless some form of government subs i d i e s a r e o f f e r e d to l o c a l government agencies. For a f u r t h e r d i s c u s s i o n of t h i s t o p i c , see reference 21. As mentioned e a r l i e r , cement k i l n s o f f e r another o p p o r t u n i t y for use of RDF because many a r e near l a r g e p o p u l a t i o n c e n t e r s . Government-supported p r o j e c t s are under way i n the United S t a t e s , Canada and the United Kingdom to determine the e f f e c t of u s i n g RDF on cement q u a l i t y . ( 2 2 . > 2 3 ) A g r i c u l t u r a l r e s i d u e s a l s o r e p r e sent a f u e l source f o r these k i l n s . At S t u t t g a r t , Arkansas, r i c e h u l l s , which have a h i g h s i l i c a content, a r e now being used as a f u e l f o r a cement k i l n . While use of organic r e s i d u e s as a f u e l by a nonproducer of the r e s i d u e s may be new, the use of r e s i d u e s as f u e l i s n o t . Combustion of wood wastes and bagasse f o r steam production c u r r e n t l y represents a major energy source f o r the pulp and paper i n d u s t r y , lumber m i l l s , and sugar cane processors.(^5) The combined consumption of these r e s i d u e s f o r f u e l s represents c l o s e to one quad of energy f o r these i n d u s t r i e s . D i r e c t combustion of whole scrap t i r e s f o r energy recovery has not been w i d e l y p r a c t i c e d i n the United States but use of a Lucas C y c l o n i c Furnace f o r t h i s purpose was reported i n 1974 f o r a Goodyear T i r e and Rubber Company P l a n t i n Jackson, M i c h i gan. (^6, 27) Use of shredded scrap t i r e s as a supplemental f u e l i n c o a l f i r e d i n d u s t r i a l b o i l e r s has been p r a c t i c e d a t s e v e r a l sites.(27) Biochemical Conversion Anaerobic d i g e s t i o n of sludges from wastewater treatment p l a n t s has been p r a c t i c e d i n the United States f o r over 50 years. According to the EPA, (?§) there are c u r r e n t l y approximately 6000 anaerobic d i g e s t i o n f a c i l i t i e s a t treatment p l a n t s i n the United S t a t e s . I n the p a s t , a p o r t i o n of the f u e l gas produced by these u n i t s has been f l a r e d and the main purpose of the process was t o s t a b i l i z e the p u t r e s c i b l e s o l i d s . Now, more and more %


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p l a n t s are u s i n g the product gas as a f u e l f o r i n t e r n a l combust i o n engines to d r i v e pumps and compressors. Such d i g e s t e r s , however, do not produce l a r g e q u a n t i t i e s of f u e l gas. The amount of energy i n the product gas ranges from 300 to 600 Btu/day per person served by the treatment p l a n t (approximately 2000 B t u / l b of dry s o l i d s processed). Since the e a r l y 1970s, research has been under way t o develop an anaerobic d i g e s t i o n process to produce methane from a mixture of m u n i c i p a l r e f u s e and sludge.(29) The f i r s t demonstrat i o n p l a n t w i l l process about 100 tons per day of r e f u s e and sludge and i s scheduled to begin o p e r a t i o n during 1978 i n Pompano Beach, F l o r i d a , under Department of Energy sponsorship.(^0) p r o j e c t e d net gas y i e l d w i l l be about 1700 B t u / l b of dry s o l i d s processed or more than 5000 Btu/day per person served by the plant. P r o j e c t s to tap the methane produced from the i n s i t u ana e r o b i c d i g e s t i o n a t l a n d f i l l s i t e s have a l s o been under way during t h i s decade. Reserve S y n t h e t i c Fuels Company and the Los Angeles County S a n i t a t i o n D i s t r i c t are r e c o v e r i n g methane a t the Palos Verdes l a n d f i l l , and the P a c i f i c Gas and E l e c t r i c Company i s r e c o v e r i n g gas from the Mountain View, C a l i f o r n i a , l a n d f i l l . ( 3 1 ) Numerous p r o j e c t s are a l s o under way to produce methane from c a t t l e manure by anaerobic d i g e s t i o n . Net gas y i e l d s are equival e n t to as high as 2000 B t u / l b of dry s o l i d s processed. A l a r g e p l a n t (processing 1000 dry tons of manure s o l i d s / d a y ) can produce approximately 4 m i l l i o n s c f of methane per day.(32) A process development program p a r t i a l l y funded by the United States Department of Energy i s c u r r e n t l y under way a t Kaplan I n d u s t r i e s , Incorporated, o f Bartow, F l o r i d a , under the d i r e c t i o n of Hamilton Standard (Windsor Locks, C o n n e c t i c u t ) . The process development u n i t w i l l a n a e r o b i c a l l y d i g e s t the manure from an environmental f e e d l o t w i t h 10,000 head of c a t t l e . Other a c t i v e Department of Energy-sponsored anaerobic d i g e s t i o n programs are under way a t C o r n e l l U n i v e r s i t y , the U n i v e r s i t y of I l l i n o i s , the U.S. Department of A g r i c u l t u r e , and Stanford U n i v e r s i t y . Carbohydrate c o n t a i n i n g m a t e r i a l s can a l s o be used as a feedstock to fermentation f o r the p r o d u c t i o n of ethanol f o r use as a t r a n s p o r t a t i o n f u e l . Ethanol production from g r a i n i s being a c t i v e l y i n v e s t i g a t e d by the S t a t e of Nebraska.(33) One of the economic problems w i t h the use of c e l l u l o s i c wastes and r e s i d u e s as a feedstock f o r ethanol production i s the cost f o r h y d r o l y s i s of the c e l l u l o s e to fermentable sugars. The conversion of carbohydrates to sugars by h y d r o l y s i s i s a very a c t i v e area of r e s e a r c h , which i n c l u d e s enzymatic h y d r o l y s i s . Enzymatic h y d r o l y s i s has been s t u d i e d a c t i v e l y by the U.S. Army Laboratory i n N a t i c k , Massachusetts, L o u i s i a n a S t a t e U n i v e r s i t y , the U n i v e r s i t y of C a l i f o r n i a a t Berkeley, Rutgers U n i v e r s i t y , the U n i v e r s i t y of Pennsylvania, the General E l e c t r i c Company, and the Massachusetts I n s t i t u t e of Technology. U n l i k e enzymatic h y d r o l y s i s technology, h y d r o l y s i s of c e l l u l o s e i n


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d i l u t e a c i d has been known f o r w e l l over a hundred years and has been p r a c t i c e d commercially. Some b e l i e v e that a c i d h y d r o l y s i s o f f e r s a more economical approach than does enzymatic h y d r o l y s i s . (_34) A c i d h y d r o l y s i s i s c u r r e n t l y under study a t Dartmouth C o l l e g e , New York U n i v e r s i t y , and Purdue U n i v e r s i t y . ADVANCED THERMAL CONVERSION PROCESSES Reasons f o r Development Based on the previous d i s c u s s i o n of a v a i l a b l e conversion t e c h n o l o g i e s , the f i r s t q u e s t i o n one might ask about the advanced thermal processes (PTGL processes) i s — w h y do we need them? Numerous answers a r e given but the most common ones a r e : (1) PTGL processes can produce gaseous or l i q u i d f u e l products that can be burned more e f f i c i e n t l y (low excess a i r ) i n secondary combustion chambers or used as f u e l f o r e x i s t i n g combustion equipment designed to burn f u e l o i l or n a t u r a l gas w i t h only minor m o d i f i c a t i o n s r e q u i r e d . ( 2 ) U n l i k e steam generated from a combustion process, l i q u i d or char f u e l products a r e s t o r a b l e — a medium Btu gas may a l s o be s t o r a b l e a t a reasonable cost. This second answer i s important because a t many s i t e s , no market e x i s t s f o r steam, and e l e c t r i c power cannot be generated economically because of the s m a l l s i z e of the e l e c t r i c a l generator. In other cases, i t i s uneconomical to s h i p the s o l i d waste or residue and the area where the m a t e r i a l i s l o c a t e d o f f e r s no market f o r the product f u e l s . Thus, the o n l y way to u t i l i z e the m a t e r i a l i s to produce a h i g h v a l u e shippable f u e l . The products a l s o may a l s o f i n d nonfuel uses. The char m a t e r i a l produced from some processes can be used as feedstock to produce a low cost adsorbent f o r wastewater treatment. This may be a t t r a c t i v e to both m u n i c i p a l i t i e s and i n d u s t r y . The r e a c t o r product gas (which i s mainly CO and H 2 from an oxygen blow r e a c t o r ) can be used as s y n t h e s i s gas to produce s t o r a b l e h i g h v a l u e products l i k e methanol or ammonia. Product o i l s may r e p r e sent a source of chemicals, but because of the h i g h l y oxygenated nature of the compounds (organic a c i d s ) , the o i l s may not be suitable f o r processing i n conventional r e f i n i n g u n i t s . Another reason o f t e n c i t e d f o r developing PTGL t e c h n o l o g i e s i s t h a t they may r e q u i r e lower investments f o r environmental cont r o l equipment. This statement may not be v a l i d i n a l l cases, as was discussed p r e v i o u s l y by t h i s author i n r e f e r e n c e 8.


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15

C a t e g o r i z a t i o n of Processes Numerous ways are a v a i l a b l e to c a t e g o r i z e PTGL processes, such as by: * Feedstock Type Refuse, t i r e s , sludge, a g r i c u l t u r a l and f o r e s t r y residues, etc. * Product D i s t r i b u t i o n Maximized char y i e l d Maximized f u e l gas y i e l d Maximized l i q u i d o r g a n i c s y i e l d * Product Use D i r e c t combustion of gases from r e a c t o r ( i . e . , furnaces o p e r a t i n g i n a s t a r v e d a i r o r p a r t i a l combustion mode to supply gas to a boiler) Clean f u e l gas f o r i n d u s t r i a l uses Synthesis gas f o r methanol or ammonia O i l f o r o f f s i t e use * S p e c i f i c Process Operating C h a r a c t e r i s t i c s Slagging versus nonslagging A i r blown versus oxygen blown * Fundamental Process Reactor C h a r a c t e r i s t i c s Solids flow d i r e c t i o n Conditions of s o l i d s i n r e a c t o r Type of r e a c t o r v e s s e l Heat t r a n s f e r method Relative gas/solid flow d i r e c t i o n The l a s t o p t i o n appears to be the most l o g i c a l approach t o analyze conversion processes and i s the approach used i n previous work.(8, 35) The b a s i c process c a t e g o r i e s are l i s t e d i n Table 5. (Reference j$ i n c l u d e s drawings showing the d i f f e r e n t types o f r e a c t o r s ). SYMPOSIUM PAPERS The other 22 speakers scheduled to p a r t i c i p a t e i n t h i s sym posium w i l l d e s c r i b e a wide v a r i e t y of thermal conversion process development and demonstration programs w i t h * Equipment s i z e s ranging from bench s c a l e to commercial scale. * Many types and q u a l i t i e s of f e e d s t o c k s . Numerous product types, q u a l i t i e s and uses, and * More than a dozen r e a c t o r types. Most of the papers w i l l i n c l u d e not only t e c h n i c a l d e t a i l s concerning process design and t e s t i n g , but a l s o estimates of the investment and o p e r a t i n g c o s t s . The papers have been organized f o r p r e s e n t a t i o n by process r e a c t o r type as p r e v i o u s l y d e s c r i b e d . The e x c e l l e n t response o f process developers to p a r t i c i p a t e i n t h i s symposium i s g r a t i f y i n g . β


16


Table V PTGL PROCESS CATEGORIES* I

VERTICAL FLOW REACTORS D i r e c t Heat Transfer • Moving packed bed (shaft furnaces) • Moving staged s t i r r e d bed ( m u l t i p l e hearth furnaces) • Entrained bed (transport reactors)

II

III

FLUIDIZED BED REACTORS D i r e c t Heat Transfer

V VI

I n d i r e c t Heat Transfer ( r e c i r c u l a t i n g heat carrier)

HORIZONTAL OR INCLINED FLOW REACTORS D i r e c t Heat Transfer * Tumbling s o l i d s bed (rotary k i l n s ) * A g i t a t e d s o l i d s bed (on conveyer)

IV

I n d i r e c t Heat Transfer * Moving packed bed ( s h a f t furnaces) * Entrained bed ( r e c i r c u l a t i n g heat carrier)

I n d i r e c t Heat Transfer •Tumbling s o l i d s bed - Rotary c a l c i n e r s - Rotary v e s s e l s (recirculating heat c a r r i e r ) • A g i t a t e d s o l i d s bed (on conveyer) • S t a t i c s o l i d s bed (on conveyer)

MOLTEN METAL OR SALT BATH REACTORS Numerous flow and mixing options MULTIPLE REACTOR SYSTEMS Numerous flow and mixing options BACK-MIX FLOW REACTORS For s l u r r i e s and melts

Some r e a c t o r s may be designed w i t h numerous s o l i d s and gas f l o w regimes (countercurrent, cocurrent, s p l i t flow, c r o s s f l o w ) . A l s o known as f i x e d bed r e a c t o r s .


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With few e x c e p t i o n s , the e n t i r e range of the technology i s represented. Every type of process r e a c t o r l i s t e d i n Table V (except the two that are checkmarked) w i l l be d i s c u s s e d . The r o t a r y k i l n r e a c t o r ( d i r e c t l y f i r e d ) i s the type being used a t the demonstration p l a n t i n B a l t i m o r e , Maryland. Information on that process may be obtained from many sources, such as r e f e r ences 36 and 37. The h o r i z o n t a l f l o w , s t a t i c s o l i d s bed r e a c t o r i s now being proposed o n l y f o r t i r e p y r o l y s i s and has not been described i n the open l i t e r a t u r e .


17

18


LITERATURE CITED 1.

SRI International, Menlo Park, California, "Crop, Forestry and Manure Residue Inventory--Continental United States" (June 1976), report prepared for the U.S. Energy Research and Development Administration, Contract Ε(04-3)-115.

2.

"Fourth Report to Congress--Resource Recovery and Waste Reduction" (1977), U.S. Environmental Protection Agency, Report SW-600.

3.

Jones, J. L., Bomberger, D. C., and Lewis, F. Μ., "Energy Usage and Recovery i n Sludge Disposal," Water and Sewage Works (July 1977) 124(7), 44-47.

4.

Jones, J . L., et al., "Municipal Sludge Disposal Economics" (October 1977), Environmental Science and Technology 11(10), 968-972.

5.

Jones, J . L., unpublished SRI International data (October 1977).

6.

Moore, J . G., J r . , "Wastewater Requirements Multiply Solids Problems, Hydrocarbon Processing (October 1976), 55(10), 98-101.

7.

Beckman, J. Α., et al., "Scrap Tire Disposal," Rubber Reviews--Rubber Chemistry and Technology (July 1974) 47, 597-627.

8.

Jones, J . L., "Converting s o l i d wastes and residues to fuel," Chemical Engineering (January 2, 1978), 85(1), 87-94.

9.

"Conversion to Coal F i r i n g Picks Up Steam" (February 14, 1977), Chemical Engineering, 84(4), 40, 42, 44.

10.

Venable, Ν. Μ., "Burning Refuse for Steam Production," Garbage Crematories in America, John Wiley and Sons, New York, 1906.

11.

Venable, E., "Burning Issues--Letter to the Editor," Chemical Engineering Progress (January 1977).

12.

Stephenson, J . Ν., and Cafeiro, S. Α., "Municipal Incinera tor Design Practices and Trends," Paper presented at the 1966 National Incinerator Conference (ASME) at New York, New York, May 1966.

13.

Combustion Engineering, Inc., Techno-Economic Study of Solid Waste Disposal Needs and Practices, U.S. Department of Health, Education and Welfare, Public Health Service (1969), SW-7c, PHS 1886.


1.

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19

14.

"Nationwide Inventory of A i r Pollutant Emissions," 1968, U.S. National A i r Pollution Control Administration (1970), AP-73.

15.

"Present Status of Municipal Refuse Incinerators," American Society of Mechanical Engineers (January 1975).

16.

"Refuse to Energy Plant Uses F i r s t Von R o l l Incinerators i n United States," Environmental Science and Technology (August 1974) 8(8), 692-694.

17.

"Hard Road Ahead of City Incinerators," Environmental Science and Technology (November 1972), 6(12), 992-993.

18.

Weinstein, N. J . , and Toro, R. F., "Control Systems on Municipal Incinerators," Environmental Science and Tech nology (June 1976), 10(6), 545-547.

19.

" E l e c t r i c Utilities Actively Study Solid Waste Use, Resource Recovery and Energy Review, (1976), 3(5), 4.

20.

Niessen, W., et al., "A Review of Techniques for Incineration of Sewage Sludge with Solid Wastes (December 1976), EPA-600/2 EPA-600/2-76-288.

21.

Jones, J. L., "The Costs for Processing Municipal Refuse and Sludge" (1978), paper presented at the F i f t h National Conference on Acceptable Sludge Disposal Techniques, Orlando, Florida (January 31 to February 2, 1978). Pro ceedings to be published by Information Transfer, Inc., Rockville, Maryland, Spring 1978.

22.

"Garbage: New Fuel for Making Cement," Business Week (April 12, 1976), 720.

23.

News Release of the Ontario Ministry of the Environment, Toronto, Ontario, Canada (December 1976).

24.

"A Rice Hull Foundation for Cement," Business Week (April 12, 1976), 72Q.

25.

Tillman, D. Α., "Combustible Renewable Resources," Chemtech (1977), 7(10), 611-615.

26.

Gaunt, A. R., and Lewis, F. Μ., "Solid Waste Incineration i n a Rotary Hearth, Cyclonic Furnace," paper presented at the 67th Annual Meeting of the American Institute of Chemical Engineers, Tulsa, Oklahoma (March 1974).

27.

"Decision-Makers Guide i n Solid Waste Management" (1976), Environmental Protection Agency Report SW-500.

28.

Cost Estimates for Construction of Publicly Owned Wastewater Treatment Facilities--Summaries of Technical Data, Cate gories I-IV, 1976 Needs Survey(February 1977), Environmental Protection Agency Report 430/9-76-011.


20


29.

Pfeffer, J. T., "Reclamation of Energy from Organic Waste, U. S. Environmental Protection Agency, EPA-670/2-74-016 (1974).

30.

"Refuse Conversion to Methane-Pompano Beach, Florida"(1977), Waste Management Inc., Oak Brook, Illinois.

31.

Parkinson, G., "Short on Gas? Use L a n d f i l l " (February 13, 1978), Chemical Engineering, 85(4), 68, 70.

32.

Varani, F. T., Burford, J . , and Arber, R. P., "The Design of Large-Scale Manure/Methane Facility" (June 1977), Report from Bio Gas of Colorado, Inc., Arvada, Colorado.

33.

Scheller, W. Α., and Mohr, B. J . , "Gasoline Does, too, Mix with Alcohol" (1977), Chemtech, 7 (10), 616-623.

34.

Klee, J . , and Rogers, C. J . , "Biochemical Routes to Energy Recovery from Municipal Wastes" (1977) Proceedings of the Second P a c i f i c Chemical Engineering Congress, AIChE.

35.

Jones, J . L., et al., "Worldwide Status of Pyrolysis, Thermal Gasification, and Liquefaction Processes for Solid Wastes and Residues (as of September 1977)," paper to be presented at the 1978 ASME National Solid Waste Processing Conference, Chicago, Illinois (May 1978).

36.

"Baltimore Demonstrates Gas Pyrolysis" (1974), U. S. Environ mental Protection Agency Report EPA/530/SW-75d.i.

37.

Weinstein, N. J . , Municipal Scale Thermal Processing of Solid Wastes, Environmental Protection Agency Report EPA/530/SW-133e (1977), available through NTIS, PB-263 396.

MARCH 3,

1978.


Overview of Solid Waste and Residue Generation ... - ACS Publications

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