Effects of H₂O Dilution on NO _x Emissions of Methane-Added Ammonia Oxidation

For the NH3/CH4 combustion in a furnace, the reactant jets entrain the combustion products containing H2O, and the combustion occurs with H2O dilution. Previous literature indicates that the effect of H2O on NOx emissions from NH3/CH4 oxidation is significant. This study systematically compares the oxidation of NH3/CH4 using a jet-stirred reactor (JSR) with N2 and H2O dilution. The impacts of temperature (T), equivalence ratio (Phi), H2O volume fraction (XH2O), and the CH4/NH3 ratio (by volume) are experimentally and numerically investigated. The NO generation is enhanced as the T or CH4/NH3 ratio elevates, while it is hindered with higher Phi or XH2O. The concentration of N2O is comparable to NO concentration with T < 1375 K. At XH2O = 20%, the maximum N2O concentration is observed when T = 1325 K, Phi = 0.5, and CH4/NH3 ratio = 0.33. The presence of 20% H2O leads to a reduction of 54.6% in NO and 47.3% in CO at T = 1375 K and Phi = 0.9. To minimize the NOx formation and NH3 slip, the suggested conditions for NH3/CH4 oxidation are identified. The presence of H2O significantly influences NOx formation in NH3/CH4 oxidation, and this work provides new insights into NH3/CH4 oxidation in the dilution of H2O.