Effects of methanol and its cracked gas on ammonia consumption and NOx emission under high pressure

Abstract

The mole fraction profiles for NH₃/syngas were measured at 5.0 MPa and different blending ratios and compared with NH₃/methanol to understand the effects of methanol and its cracked gas on ammonia oxidation and micro-species behavior. A kinetic model proposed in our previous work is validated against the measured data. The model demonstrates remarkable accuracy in predicting the concentration profiles of NH₃ and NO_x under all conditions. Moreover, a superior performance of methanol control is found at low temperatures, while syngas has a better performance at high temperatures. The onset temperature of methanol is lower than that of syngas. When the temperature reaches 950 K, H₂ can provide more active OH than methanol and accelerate the ammonia consumption through the reaction cycle. Moreover, methanol triggers NO formation at 50 K lower than syngas, and the peak molar concentration of NO is lower than that of syngas at high blending ratios. At a substitution ratio of 50 %, NO generated by an ammonia-methanol mixture exhibits an “N”-shaped trend, while it monotonically increases with temperature with syngas blending. The peak concentrations of N₂O with methanol are higher than those from syngas, especially at substitution ratios of 10 % and 25 %.