Reduction of Recycled NOx by Simulated Coal Volatiles in Oxy-Fuel Combustion

The reduction of recycled NO by simulated coal volatiles (CH4 and NH3) during oxy-fuel combustion has been studied in a flow reactor. Special emphasis was given to the effects of different variables on the reduction of recycled NO, and to the comparison with results obtained in air-fired combustion. The experiments were conducted in a temperature range of 873-1273 K The stoichiometries varied from fuel-rich to fuel-lean. The results showed higher temperature favored the reduction of recycled NO under fuel-rich conditions, and the recycled NO reduction obtained in CO2 was much lower than that obtained in N-2. However, under stoichiometric and fuel-lean conditions, the recycled NO reduction decreased with increasing temperature, and a slightly higher recycled NO reduction was obtained in CO2 compared to that in N-2. Higher recycled NO concentration accelerated its reduction. The recycled NO reduction decreased with increasing CO2 concentration under fuel-rich conditions, while it increased under fuel-lean conditions. Higher CO maximum concentration was obtained in the CO2 case due to the CO2 + H double left right arrow CO + OH reaction. But a decrease in the CO concentration was observed when the CO2 concentration reached a certain level. This indicates there are other important reactions responsible for the effect of a high concentration of CO2 besides CO2 + H reaction.