Calculation and analysis of influence of coal gas on selective non-catalytic reduction of nitric oxide by ammonia

Coal gas was added to Selective Non-Catalytic Reduction(SNCR) process to change the temperature window for NO reduction. The effective composition of coal gas is the mixture of H-2, CO and CH4 for SNCR process. Its influence on NO reduction and by-products emission was investigated through chemical kinetics calculation with detailed reaction mechanism. The results indicate that coal gas additive could shift the NO reduction temperature window to lower temperatures as much as 150K, and raise the maximum NO removal efficiency slightly. These effects are enhanced when the fraction of H-2 in coal gas rises, and not affected by the initial NO concentration when the concentration ratio of coal gas additive and the initial NO keeps constant. Coal gas does not elevate NO2 emission, but it elevates N2O emission. Analysis through chemical kinetics mechanism indicates that coal gas affects NO reduction by promoting OH, O and H radicals production, and the critical reaction path is founded out.