Experimental and modeling study for the effect of methanol blending on ammonia oxidation and NOx formation at high pressure

To investigate the kinetic of ammonia-methanol mixtures oxidation and NOx formation under low-to- intermediate-temperature and high-pressure conditions, the mole fractions of key intermediates and products in NH3/CH3OH 3 /CH 3 OH were measured in a flow reactor, at 5.0 MPa, 650-1250 K. A comprehensive kinetic model was proposed with the modification of C-N interaction mechanism. The present model can adequately predict the species concentration, laminar flame speed and ignition delay time of ammonia-methanol mixture. The study indicated that under current conditions NO and N2O 2 O change non-monotonic with temperature. There is a tradeoff between NO and N2O 2 O at intermediate temperature range. NO increases as N2O 2 O begins to decrease with temperature. Based on a kinetic analysis aided by the developed model, the HO2 2 content is identified as the key factor influencing the overall reactivity at high pressure. H-elimination reactions of CH3OH 3 OH and CH2O 2 O by NH2 2 enhances the consumption of methanol and further promotes ammonia oxidation. However, with higher methanol content, this reaction transforms NH2 2 to NH3 3 at the same time and exhibits an inhibition effect. As to NO formation, H2NO 2 NO plays a crucial role, acting as chain carrier and converts NH2 2 to NO. The competition of NO formation and reduction results in the non-monotonic trend of NO concentration, while the further decomposition of N2O 2 O at high temperature leads to the decrease of N2O 2 O concentration. The above trend can be enhanced by methanol addition, as the dominant reactions involved in the rate production of NO, such as NH2 2 + NO2 2 = H2NO 2 NO + NO, followed by HONO (+M) +M) = NO + OH (+M) +M) and HNO+O2 +O 2 = HONO + NO, are strengthened with more methanol addition.