The Effects of LBG Composition and Combustor Characteristics on Fuel NO_x Formation

The low Btu gas (LBG) combined gas and steam turbine power cycle is a potentially attractive alternative to the direct coal fired steam cycle because of the potential for low sulfur emissions and high overall cycle efficiency. However, LBG may contain ammonia (NH₃) which could be converted to nitrogen oxides (NO_x) under typical combustion conditions. This paper examines the effects of LBG composition and combustor design on NO_x emissions. Low Btu gases of varying compositions were synthesized from bottled gases and fired in three atmospheric pressure flame reactors: diffusion flame reactor, flat flame reactor and catalytic reactor. Nitrogen oxide emissions were found to be most sensitive to the concentrations of NH₃ and hydrocarbon fuel gas in the synthetic LBG. Lowest NO_x emissions were produced by the diffusion flame reactor operating at near stoichiometric conditions and the catalytic reactor operating fuel rich.