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Show 10/79 RECENT NO RESEARCH AT IGT Richard T. Waibel Institute of Gas Technology IIT Center Chicago, Illinois 60616 Introduction During the past several years, IGT has conducted research programs for the EPA and others which included the objective of characterizing the N0X emissions of a variety of industrial burners under various operating conditions and using several fuels. The most extensive results were obtained using a forward-flow baffle burner, a rotary kiln fuel injector, and an industrial boiler burner. These burners are shown schematically in Figures 1 through 3. The operating conditions investigated were excess air, air preheat, furnace temperature, firing rate, furnace size, fuel injector design, combustion air swirl, flue gas recirculation, and combustion air staging. The primary fuel used in these investigations was natural gas with both cleaned and uncleaned low- and medium-Btu gases used in some of the trials. The trials were conducted in a pilot-scale furnace with either internally cooled walls or water tubes to simulate the furnace load. This paper discusses the factors affecting N0X emissions and gives the data from IGT research programs illustrating these effects. N0X emissions from combustion can be formed by thermal oxidation of the nitrogen in the combustion air, commonly termed thermal N0X, or by oxidation of nitrogen in the fuel, termed fuel N0X. For liquid fuels the nitrogen is generally chemically bound in heterocyclic aromatic2 structures. Natural gas and cleaned low-Btu gases contain no fuel nitrogen and thus only produce thermal N0X. Low-Btu gases that are not subject to post-gasifier cleaning will contain ammonia and other fuel nitrogen compounds and thus produce fuel N0X. Thermal N0X Formation Thermal N0X strongly depends on the time/temperature history of the flame gases and the availability of oxygen. The oxygen concentration is affected by the availability of excess air and the rate of fuel/air mixing. The mixing rate also affects the time/temperature relation or combustion intensity. Thermal N0X will generally increase with excess air and rate of fuel/air mixing. Burner parameters that control mixing include fuel/air momentum ratio, air swirl and fuel injection angle for gaseous fuels, plus degree of atomization for liquid fuels. In general, any set of conditions that raises the peak flame 6-1 I N S T I T U T E OF GAS T E C H N O L O GY |