Experimental and Numerical Study of the Effects of Steam Addition on NO Formation during Methane and Ammonia Oxy-Fuel Combustion

Abstract

The effect of H2O addition on the oxidation of methane and ammonia during oxy-fuel combustion was investigated both experimentally and numerically. Comparison experiments between O2/CO2 and O2/CO2/H2O atmospheres were conducted in a flow reactor at atmospheric pressure with equivalence ratios ranging from fuel-rich to fuel-lean and temperature from 973 to 1773 K. The experimental results indicate that the effects of H2O addition shift the onset temperature of oxidation to the lower values, inhibit CO formation significantly, and enhance NO formation remarkably. The chemical kinetic mechanism, which was hierarchically structured and updated in our previous work, captured the main characteristics of CO and NO formation satisfactorily. The presence of H2O leads to far higher OH radical concentrations in the CO2/H2O atmospheres. The ultrahigh OH radical concentrations dramatically enhance the reactions between OH and amine radicals, resulting in the significant enhancement of pathways NH2 → NH → HNO → NO and ...