Chapter 8
Liquids from Municipal Solid Waste 1
James E. Helt and Ravindra K. Agrawal
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Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 The pyrolysis of municipal solid waste (MSW) is a promising method of producing useful fuels. However, the reaction mechanisms are not well understood. Current DOE/ANL research is directed at gaining a better understanding of the basic thermokinetic mechanisms associated with the pyrolytic conversion of MSW. Initial results are given for determinations of pyrolytic reactivity for MSW components in a nonisοthermal bench -scale reactor. The effects of heating rate and sample weight on overall degradation and product formation over the temperature range 300-475°C were determined. Gas chromatographic and gas chromatographic/mass spectrometric analyses of both the gaseous and liquid products are being performed. Tentative identifications were made of some liquid components from pyrolysis of MSW. Municipal s o l i d waste (MSW) i s a highly variable "raw m a t e r i a l , " by both season and l o c a t i o n . However, i t i s generally accepted to have a composition within the ranges shown i n Table I (jL). C e l l u l o s i c materials, including paper, newsprint, packaging materials, wood wastes, and yard c l i p p i n g s , constitute over 50% of MSW. A basic understanding of the p y r o l y t i c reactions i s important and relevant to both combustion and conversion of MSW. As MSW i s heated the different components react d i f f e r e n t l y at different temperatures. The v o l a t i l e species can evaporate without major change, while the rest of the c e l l u l o s i c . components p a r t i a l l y break down to v o l a t i l e components leaving a carbonaceous char Current address: K R W Energy Systems, Inc., P.O. Box 334, Madison, P A 15663-0334
c
0097-6156/88A)376-0079$06.00/0 1988 American Chemical Society
Soltes and Milne; Pyrolysis Oils from Biomass ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
PYROLYSIS OILS FROM BIOMASS
80 Table I.
Composition Ranges for Several MSW Samples
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Component
Paper Glass Metals Plastics Rubber-Leather Wood Textiles Food Wastes Yard Wastes Other
Composition Range, wt %
30-50 8-10 7-10 1-5 1-3 1-4 1-5 10-20 5-20 1-4
Source: Reprinted with permission from réf. 1. Copyright 1983 Argonne National Laboratory. containing i n addition the ash and noncombustibles. One f r a c t i o n of the v o l a t i l e pyrolysis products i s a noncondensable gaseous f r a c t i o n comprising CO, C O 2 » some hydrocarbons, and Η 2 · Another f r a c t i o n i s a l i g h t condensable f r a c t i o n containing H 2 O , v o l a t i l e hydrocarbons and low molecular weight degradation products such as aldehydes, acids, ketones, and alcohols. F i n a l l y , there i s a t a r f r a c t i o n containing higher molecular weight sugar residues, furan derivatives, and phenolic compounds. The proportion and composition of these products are highly dependent on the c e l l u l o s i c composition of the MSW, the pyrolysis temperature and the presence of inorganic compounds that could influence (catalyze) the pyrolysis reactions. Pyrolysis of c e l l u l o s e at temperatures below 300°C results mainly i n char formation. Any l i g n i n present i n the MSW (Kraft paper, cardboard, and wood waste contain s i g n i f i c a n t proportions) tends to char, even at higher temperatures. On the other hand, the c e l l u l o s e and hemicelluloses readily decompose to v o l a t i l e products at temperatures above 300*C. Most of the p l a s t i c s present thermally degrade at a s i g n i f i c a n t l y higher temperature (400-450°C) (2). BASIC MECHANISMS RESEARCH The ANL/DOE program on pyrolysis of municipal s o l i d waste (MSW) has two o v e r a l l objectives: (1) to understand the basic thermokinetic mechanisms associated with the p y r o l y t i c conversion of MSW and (2) to seek new processing schemes or methods of producing a l i q u i d or gaseous f u e l from MSW feedstock. To meet these objectives, we are performing laboratory experiments with the aim of determining the effects of d i f f e r e n t operating parameters on the pyrolysis-product compositions and deriving an a n a l y t i c a l model of the p y r o l y t i c process that describes the chemical k i n e t i c s .
Soltes and Milne; Pyrolysis Oils from Biomass ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
Downloaded by CORNELL UNIV on August 23, 2016 | http://pubs.acs.org Publication Date: September 30, 1988 | doi: 10.1021/bk-1988-0376.ch008
8.
HELT & AGRAWAL
Liquids from Municipal Solid Waste
This DOE-sponsored research involves both ANL a c t i v i t i e s and subcontracted work. Argonne i s performing closely controlled laboratory-scale parametric t e s t s . The work i s being performed on two experimental f a c i l i t i e s : (1) a TGA to study the thermal degradation versus temperature, and (2) a bench-scale reactor to produce s i g n i f i c a n t quantities of products to permit characterization. The goal i s to determine how different operating parameters influence the product compositions. Subcontracted a c t i v i t i e s are being performed at the Solar Energy Research I n s t i t u t e (SERI) and the Chemical Engineering Department at the University of Arizona. SERI has used t h e i r d i r e c t high-pressure molecular beam mass spectrometric sampling system to c o l l e c t q u a l i t a t i v e "fingerprints" and experimental data on the p y r o l y s i s products generated from components of MSW and various refuse derived fuel (RDF) samples (3). They are also using the same experimental apparatus to d i s t i n g u i s h between the primary and secondary reactions leading to the formation of the p y r o l y s i s products (4). This data w i l l be part of an o v e r a l l data base to describe the influence of sample properties and reaction conditions on the s o l i d phase and gas phase processes of lowtemperature (
