Kinetic Modeling of the Thermal Decomposition of Ammonia

Abstract

A detailed N/H reaction mechanism has been developed and validated in comparison with experimental data for ammonia pyrolysis in shock waves (Davidson et al., Int. J. Chem. Kinet, 1990, 22:513). It has been shown that incorporation of the reactions with N₂H₃ and N₂H₄ into the mechanism significantly influences calculated rise-time and peak concentrations of the NH and NH₂ radicals if the currently adopted rate constant of the reaction is employed. A sensitivity analysis reveals which reactions are critical for the quality of the modeling in particular experimental conditions. The choice of the rate constants for these reactions is discussed. It has been found that only significant decrease of the reaction (22) rate constant can improve the agreement between the modeling and experimental data. The best fit in the range 2200 - 2800 K is met with the rate constant k₂₂ = 1.0E+11 T^0.5 exp(-21600/RT).