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Show AFRC90 Paper 5 PILOT SCALE STUDIES ON PCDD/PCDF FORMATION AND CONTROL USING THE STRATEGIC COFIRING OF NATURAL GAS IN MUNICIPAL WASTE COMBUSTION SYSTEMS ABSTRACT T. P. McGrath, W. R. Seeker and S. L. Chen Energy and Environmental Research Corporation 18 Mason Irvine, California 92718 D. G. Linz Gas Research Institute 8600 West Bryn Mawr Avenue Chicago, Illinois 60631 This test program was designed to study the formation and emission of PCDD/PCDF during Refuse Derived Fuel combustion. Tests were conducted in a pilot scale RDF incinerator. Incinerator fly ash hold up for one hour at a temperature of 570F resulted in an 8 to 20 fold increase in PCDD/PCDF content. Reductions in RDF load were found to decrease PCDD/PCDF emissions. Fluctuations in RDF feed rate produced increases in PCDD/PCDF emissions. Test results suggest the dominant PCDD/PCDF formation mechanism(s) in the incinerator involve organic compounds in entrained fly ash. A combustion strategy for PCDD/PCDF emissions control has been developed. Natural gas co-firing allows RDF load reduction while smoothing temporal and spatial fluctuations in the furnace. INTRODUCTION Increasing regulatory pressure and limitations on landfill capacity have expanded interest in the incineration of municipal solid waste (MSW). During the combustion of MSW incomplete destruction of organic compounds in the waste can lead to the formation and emission of polychlorinated dibenzo (p) dioxins and dibenzofurans (PCDD/PCDF). These chlorinated trace organics are considered to be highly toxic and regulatory agencies are moving towards strict control of their emissions. Therefore control of PCDD/PCDF emissions is essential for successful operation of a MSW incineration system. The highly variable nature of MSW can lead to a number of operational and emissions problems in mass burn systems. To overcome this problem refuse derived fuel (RDF) is frequently used. RDF combustion systems process the MSW before incineration to produce a more homogeneous feed stock. Processing includes removal of large objects, separation of metals and size reduction. RDF generally has a top size of three to four inches. Despite increased ease of operation with RDF, available data indicate that the emissions of PCDD/PCDF from RDF fired systems can be significantly higher than those from mass-burn MSW systems. This may be because RDF incinerator operating procedures and waste size reduction result in higher fly ash emissions than from mass- 1 ~~ liV/"', ~i l/,O .. &~O"f ~ ~~~) |
