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Municipal Waste Combustion
The municipal waste combustion (MWC) program supports the development of revised rules for air pollutant emissions from the MWC source category. Basic research is performed on MWC pollutant formation and control mechanisms for acid gas, trace organic, and trace metal emissions. The program also supports field tests, regulation development, and laboratory research for medical waste incinerators (MWI). Much of the MWC regulatory support effort has involved the development of good combustion practice and field evaluations of the performance of air pollution control (flue gas cleaning) systems. This effort has encompassed field evaluations of five mass burn combustors, two refuse-derived fuel units, and a mass burn refractory (rotary kiln) unit. Air pollution controls on these units include: lime spray dryer absorber [SD/fabric filter (SD/FF)], lime SD/electrostatic precipitator (SD/ESP), and dry sorbent (limestone) injection into a furnace and duct sorbent (hydrated lime) injection, both followed by an ESP.
In-house MWC research includes supporting the development and operation of an organics laboratory specializing in analysis of polychlorinated dibenzo dioxins and furans (PCDD/PCDF), research on in-furnace injection of additives to control acid gases and the formation/destruction of organic pollutants, and evaluation of the formation and control of metal vapors in furnaces.
Technology assessment and technology transfer activities Canada, and Niiogaz (a gas cleaning institute in Russia). Researchers have traveled to Canada, Europe, Russia, a nd Japan to evaluate foreign technology and participate in international conferences and workshops.
Multi-Fuel Stoker Combustor
This unique facility gives EPA much needed capability for solid fuel combustion research. Most of the commercial solid waste incinerators and biomass combustors are of stoker designs. The combustor is capable of burning a wide variety of solid fuels including municipal solid waste (MSW) refuse-derived fuel (RDF), biomass fuel, and coal. Three interchangeable, alternative stoker grate systems were designed for the combustor to be operated under mass burn, spreader stoker, and batch feed firing modes. The combustor is designed to have 0.58 MW (2,000,000 BTU/hr) maximum thermal output, which is sufficient to simulate the full range of conditions that might be encountered in practical systems. The processes controlling pollutant formation and destruction can be studied during combustion on the fuel bed which may be thin or thick, in the radiant furnace, or the convective section, a swell as a variety of air control devices such as baghouses and scrubbers. The facility's modular design allows it to be used to study and control pollutant emissions from solid fuels for which the characteristics are presently unknown. A solid fuel preparation system is also installed as part of the research facility for preparing simulated MSW, RDF, and biomass fuels with controlled composition and particle size.
Pilot-Scale Innovative Furnace Reactor (IFR) Studies on Dioxin Formation
APPCD has conducted cooperative studies to examine the effect of combustion variables which include O2 concentration, temperature, and residence time. In addition, flue gas cleaning parameters have been examined, such as the injection of calcium-based sorbents on low temperature formation of PCDD/PCDF. These experiments were performed while injecting municipal waste combustion (MWC) flyash samples into the horizontal duct section of the IFR. The metal catalyzed PCDD/PCDF formation reactions that occur on the surface of the MWC flyash are of concern to EPA's Office of Air Quality Planning and Standards (OAQPS).