Effect of dilution of fuel in CO2 on the conversion of NH3 to NOx during oxy-fuel combustion

Abstract

The indirect chemical effects of fuel dilution by CO2 on NO formation were investigated numerically in this paper. CH4 doped with NH3 was used as fuel, while CO2 and O2 were mixed as oxidant. The dilution effect of CO2 was then investigated through adding extra CO2 to the reaction system. An isothermal plug flow reactor was used. An unbranched chain reaction mechanism is proposed to illustrate the chemical effects of CO2 on the H/O/OH radical pool and NOx. Due to the reaction between CO2 and H, extra NO will be formed in fuel-rich conditions, while NO will be inhibited in fuel-lean conditions and high CO2 dilution conditions. The reaction affected the radical pools of OH, H, and O of the branched chain reaction, and then the formation and reduction of NO. The pool of H had the greatest effect on NO reduction. The results suggest that the indirect chemical effects on NO formation differ between diluted fuel oxy-fuel combustion conditions and normal oxy-fuel conditions.