An experimental and modeling study on the oxidation of ammonia-methanol mixtures in a jet stirred reactor

Abstract

Methanol and liquid ammonia can form a mixture with better combustion quality. In order to investigate the ammonia (NH3)/methanol (CH3OH) mixture oxidation process, jet-stirred reactor (JSR) oxidation experiments were conducted at atmospheric pressure and temperature of 700–1200 K. The concentration of NH3 in the NH3/CH3OH mixture was 80%, 60%, and 40%, respectively, for equivalent ratios of 0.8, 1.0, and 1.2. By using synchronous vacuum ultraviolet photoionization mass spectrometry, important species (such as CH2O, CO, NO, NO2, N2O) involved in the oxidation reaction were identified and quantified. The original chemical kinetic model was validated and optimized based on experimental data, which improved the model's ability to predict NH3/CH3OH oxidation process (the overall improvement is approximately 81.3% compared to the original mechanism). The results demonstrated that methanol accelerated the rate of ammonia oxidation,and methanol was rapidly oxidized at high methanol content. The sensitivity analysis of reaction pathways with varying equivalent ratios revealed that HO2 generated a substantial amount of OH radicals and facilitated the oxidation of methanol and ammonia. During the oxidation of ammonia, nearly half of the NO produced NO2 through NO + HO2 = NO2 + OH, and about 60% of the NO came from the reduction reaction of NO2. More than 80% of the N2O was produced by NH2 + NO2 = N2O + H2O, and most of the N2O was converted to N2, while NH2 promoted the conversion of NOx to N2.