17 E P A ' s R & D P r o g r a m i n P y r o l y t i c Conversion of Wastes to F u e l Products
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GEORGE L. HUFFMAN and WALTER W. LIBERICK, JR. U. S. Environmental Protection Agency, Industrial Environmental Research Laboratory, Cincinnati, OH 45268
Only in recent years have we become properly concerned about the f i n a l disposition or utilization of the large volumes of wastes generated by our everyday a c t i v i t i e s . Many environmental insults have resulted from improper disposal; for example, the obvious insults from open burning, leaching from dumps, and improper discharges to surface and groundwaters. These insults l e d to passage of the 1965 S o l i d Waste Disposal Act and the subsequent Amendments that mandate the Federal Government (EPA) to support research, development, and demonstrations and applications of new and improved technologies for processing and recovering materials and energy from s o l i d wastes. This mandate, coupled with recent concerns about our dwindling energy supply, has focused our attent i o n on the utilization of these wastes as sources of energy. Although recovering energy-from-waste has been practiced i n Europe for many years, this technology has not been pursued in the United States u n t i l recently. Many options to utilize these wastes as an energy resource have been investigated. Options have varied from combustion i n waterwall incinerators, to c o - f i r i n g of prepared wastes with coal i n utility b o i l e r s , to the thermochemical conversion of wastes into usable fuel products.
0-8412-0434-9/78/47-076-323$09.00/0 This chapter not subject to U.S. copyright. Published 1978 American Chemical Society Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
324
SOLID
WASTES
AND
RESIDUES
This paper focuses on c u r r e n t e f f o r t s being supported by EPA to develop new concepts o f thermochemical (or p y r o l y t i c ) convers i o n o f wastes t o energy. More s p e c i f i c a l l y , t h i s paper discusses f o u r EPA p r o j e c t s t h a t are i n v e s t i g a t i n g b a s i c r e a c t i o n k i n e t i c s and ways t o enhance the y i e l d and q u a l i t y o f p y r o l y s i s end-products; these are: •
S u b p i l o t - s c a l e p y r o l y s i s of mixed wastes t o f u e l gas, f u e l o i l and char i n a 500 l b / h o u r f l u i d i z e d bed r e a c t o r (by the Energy Resources Company, ERCO);
•
Bench-scale steam g a s i f i c a t i o n o f a g r i c u l t u r a l and f e e d l o t wastes t o energy products (by P r i n c e t o n University);
•
Laboratory t e s t s on a process t h a t converts a troublesome waste, d i s c a r d e d t i r e s , i n t o f u e l s and other products by u t i l i z a t i o n of a molten s a l t c a t a l y t i c technique (by the U n i v e r s i t y o f Tennessee); and,
•
I n t e g r a t e d bench-scale development o f a nonc a t a l y t i c process t h a t transforms p y r o l y s i s off-gases i n t o polymer g a s o l i n e ( r e s e a r c h b e i n g conducted v i a Interagency Agreement w i t h China Lake, C a l i f o r n i a , Naval Weapons Center).
S u b n i l o t - S c a l e Conversion o f Mixed Wastes t o F u e l (ERCO) The o b j e c t i v e s o f t h i s p r o j e c t are t o i n v e s t i g a t e the k i n e t i c s o f the p y r o l y s i s o f s o l i d wastes and t o develop a data base t h a t w i l l a l l o w design engineers t o s e l e c t p y r o l y s i s system operat i n g c o n d i t i o n s f o r commercial systems t h a t w i l l p r o v i d e a p r e determined mix o f f u e l product y i e l d s . To accomplish these object i v e s , t h i s p r o j e c t i s d i v i d e d i n t o the f o l l o w i n g t a s k s : 1.
P l a n and Experimental Study. The i n i t i a l t a s k i n c l u d e d a l i t e r a t u r e study t o determine the p h y s i c a l and chemical p r o p e r t i e s of the wastes t o be u t i l i z e d and t o determine the r e a c t o r v a r i ables which would have a s i g n i f i c a n t i n f l u e n c e on product q u a l i t y and y i e l d s . From t h i s study, the p r o j e c t team determined the experiments t o be run and the data necessary t o model the r e s u l t s . This t a s k i n c l u d e d r e a c t o r and support equipment design.
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
17.
H U F F M A N
2.
AND
LiBERiCK
Pyrolytic Conversion of Wastes
325
Equipment Procurement, Assembly and Check-Out. This task i n c l u d e d the f a b r i c a t i o n of the t e s t apparatus (a f l u i d i z e d bed r e a c t o r ) and i t s check-out. During t h i s t a s k , s e v e r a l m o d i f i c a t i o n s were made t o i n c r e a s e system operating r e l i a b i l i t y .
3.
Subpilot Plant Testing. This task i n c l u d e d a c q u i s i t i o n o f data on s e v e r a l waste components, some of which were taken during t e s t s run i n d i f f e r e n t o p e r a t i n g modes. These data were comp i l e d f o r use i n modeling the t e s t r e s u l t s of t h i s project.
k.
Development of the P r e d i c t i o n Model. Based on the data c o l l e c t e d i n Task 3 , a mathematic a l model was developed to p r e d i c t the y i e l d s t o be expected from a known waste composition under v a r i o u s pyr o l y s i s o p e r a t i n g c o n d i t i o n s . The t h e o r e t i c a l model was then v e r i f i e d w i t h the experimental data.
5.
Chemical Conversion. In a d d i t i o n t o the v a r i a b l e p y r o l y s i s o p e r a t i n g modes i n v e s t i g a t e d , an e f f o r t was undertaken t o l o o k at p a r t i a l o x i d a t i o n and steam g a s i f i c a t i o n e f f e c t s .
6.
Product C h a r a c t e r i z a t i o n . D e t a i l e d product c h a r a c t e r i z a t i o n t e s t s were conducted on samples of the o i l and char products.
7.
Trace Metals I n v e s t i g a t i o n . A m a t e r i a l balance f o r t r a c e metals was completed f o r s e v e r a l of the runs on d i f f e r e n t waste components.
An extensive l i t e r a t u r e search was conducted t o : ( l ) p h y s i c a l l y and chemically c h a r a c t e r i z e s o l i d waste; (2) determine the parameters which would a f f e c t p y r o l y s i s y i e l d s ; and (3) determine the t h e o r e t i c a l k i n e t i c s t o be used i n modeling the r e a c t i o n s . The l i t e r a t u r e search provided the data contained i n Table I . These average chemical compositions of m u n i c i p a l s o l i d waste were s e l e c t e d as a b a s e - l i n e f o r t h i s study {l). A c t u a l analyses were of course used i n the m a t e r i a l balances throughout the work.
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
326
SOLID WASTES AND RESIDUES
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Tenr>?ratnres ( Man. i i o l i d M i x t u r e 1: Waste 1 P a c e r and Sawdust
PARAMETERS AND TESTS ON MATERIALS REQUIRING COMPLETE
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Feed Rate Low Kighl
TABLE VI TEST PLAN
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ml
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g s
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17.
H U F F M A N A N D LiBERiCK
333
Pyrolytic Conversion of Wastes
TABLE V I I
TEST
PLAN
S C R E E N I N G RUNS USING A D D I T I O N A L
MATERIALS
FLUIDIZATIONS MATERIAL
Manure
Low High
Tires,
Small
Low High
Tires,
Large
Low High
Wood C h i p s
{1%
TEMPERATURES
VELOCITY/^
Moisture)
Fixed
(°c)
UT5 723
6l8
809
8ÔT
921
500 ii5i
h^h 630
810
930
5I46 517
6ll* 595
727
932"
610
671
825
866
7^0
8U7
856
916
550
92c
935 Wood C h i p s
(17%
Moisture)
Fixed
57-1
Wood C h i p s
{2k%
Moisture)
Fixed
Ghi
Textiles
Fixed
Plastics
Fixed
863
781
6ho
690
706
770
800
Mixt.
H2 ( P a p e r
+
Textiles)
Fixed
Mixt.
/Π ( P a p e r
+
Plastics)
Fixed
620
650
715
760
765
Mixt.
f/U ( C o r n c o b s
Fixed
550
675
757
875
2ÏL
Mixt.
#5
(Paper
+
+ Manure) Plastics
Fixed
+ Sawdust) Mun.
Solid
Sludge
H2
Waste
tl2
Fixed Fixed
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
877
334
SOLID WASTES AND RESIDUES
VAULT vu τ ΉΜΤ
PLAN
PARTIAL OXTDAITOK, ST?AM CAST Π CATION AND CATALYTIC iSFFJSCT RIKS
PALTIAL OXIDATION Run Conditions Oxygen/Feed Ratio Material
Low Vrlr.h
O.xy.'ron Content Low High
m
Β Δ
ν
Δ
ν
0
Fesd Rate Low Kif-)-
Temperatures, °C Δ V
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•
Δ
668
0
V
0
Τ 30
•
Δ
6k0
0
Τ
0
790
ο
Α
650
7
•
—
827
•
Λ
1*23
•
•
0
8Ô5 —
Sawdust ϋ Δ
• Δ *
0 0 A
• A V
ν
·
•
88ο
670
Pape r •
Δ
Τ
t
a Δ τ
t
1*76
lits. 1*73
705
833
STEAM GASIFICATION AT 35-50/0 STEAM CONTENT Material
Oxygen
Content
Sawdust
•
τ
è
•
g
ν
Paper
•
τ
à
•
g
γ
Teed Rate Low High a
a
9 a υ
?
1
7 α
τ i γ
α
ν
ά
Temperatures, °c φ Q γ
556 5 3 8 667 61*3 6 0 0 5
