A detailed chemical kinetic model for methanol and ammonia co-oxidation under hydrothermal flames: Reaction mechanism and flame characteristics

Abstract

A detailed chemical kinetic model for ammonia and methanol co-oxidation under hydrothermal flames was established with pressure and thermodynamic corrections. Simulation model was validated by comparing with experimental temperature rise, and methanol and ammonia removal efficiencies. Species evolutions, reaction paths, and reaction sensitivities for pure ammonia combustion, and ammonia and methanol co-oxidation under hydrothermal flames were analyzed. Ammonia concentration begins to decrease only when methanol is consumed in a certain amount in the ammonia and methanol co-oxidation under hydrothermal flames, indicating the addition of methanol promotes the degradation of ammonia. Moreover, reaction heat is more conductive to ignition and the conversion of ammonia to nitrogen than active free radicals provided from methanol. The ignition delay time presents a minimum as a function of ammonia/methanol concentration ratio, with the minimum values of ignition delay time present at approximately ω_NH3/ω_CH3OH = 1 for different methanol concentrations. Higher preheating temperatures favor more NO_X but less N₂O formation, while higher ammonia concentrations favor both NO_X and N₂O formations. The presence of ammonia increases the laminar flame speed and permits a lower extinction temperature, indicating the mixture of methanol and ammonia can improve the stability of hydrothermal flames.