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Show at temperatures well below 300F to preclude volatilization of captured species. In addition, fly ash hold-up in heat recovery equipment (economizers, air heaters, etc) and ducting operating in the critical temperature range will result in PCDD/PCDF formation. 2. Reduce entrainment of fly ash and promote burnout of carbonaceous compounds in flue gas particulate. These studies show a direct correlation between emissions of fly ash carbon and PCDD/PCDF, suggesting organic compounds in the fly ash are precursors for PCDD/PCDF formation in the furnace. Lessening of fly ash entrainment is best accomplished by reducing flue gas velocity. Combustion air staging can reduce flue gas velocities in the lower reaches of the furnace allowing solids to settle. Improved air/fuel mixing, ample excess air levels and sufficient fly ash residence time at temperature will increase burnout of fly ash carbon compounds. 3. Reduce RDF load and avoid fluctuations in RDF feed rate and incinerator operation. Results from these tests indicate reductions in RDF load can substantially decrease PCDD/PCDF emissions. The studies also show unsteady furnace operation leading to periods of low excess air will increase emissions. Natural gas co-firing can be used to compensate for heat input loss from an RDF load reduction. The unit can be operated at full heat load with reduced PCDD/PCDF emissions from operation at 1 OOo~ RDF feed. The natural gas can be injected to smooth temporal and spatial fluctuations in full scale units that lead to poor combustion and formation of PCDD/PCDF. ACKNOWLEDGMENTS Special acknowledgement to D. G. Linz of the Gas Research Institute without whose technical and financial support this research would not have been possible. Thanks to l. Ho and J. S. Johnsen for design and operational assistance. REFERENCES 1. Olie K., P.l. Vermulen, O. Hutzinger, Chemosphere ~ 455 (1977) 2. Seeker, W. R., W. S. Lanier, and M. P. Heap, "Municipal Waste Combustion Study: Combustion Control of MSW Combustors to Minimize Emission of Trace Organics," EPA Contract 68-02-4247, May 1987. 3. Vogg, H., Metzger, M., and Stieglitz, l., "Recent Findings on the Formation and Decomposition of PCDD/PCDF in Solid Waste Incineration," Proceedings: Emission of Trace Organics from Municipal Solid Waste Incinerators, Copenhagen 20-22 January 1987. 4. Hagenmaier, H, H. Brunner, R. Haag, and M. Kraft, "Copper-Catalyzed Dechlorination/Hydrogenation of Polychorinated Dibenzo-p-dioxins, Polychlorinated Dibenzofurans, and Other Chlorinated Aromatic Compounds," Environmental Science and Technology, 11, 11 (1987) 5. Barton, R. G., W. D. Clark, W. S. Lanier, and W. R. Seeker, "Dioxin Emissions From Waste Incinerators." Dioxin 89, Toronto, September 1989. 8 |