Mechanism of decay of ammonia in flame gases from an NH3/O2 flame

Measurements are reported on the decay of NH₃, NH, NO, and OH in the flame gases from an NH₃/O₂ flame burning on a flat flame burner at atmospheric pressure. Cold gas velocity was 7.8 cm/sec and the measured temperature was 2010°K; concentrations were determined by optical absorption. The data are interpreted in terms of a relatively complete mechanism containing 12 species by simplifying the mechanism into a set of 6 pseudo-first-order reactions. Analysis was carried out with an electrical analog of the system. It is concluded that the decay occurs through the combination of one set of reversible reactions that convert the various NH_i(NH_i --- NH₃, NH₂, NH, or N) into each other, and another set of irreversible reactions that remove one or more of the NH_i permanently. The behavior of NO is accounted for. It is proposed that the observation that OH] is below equilibrium can be accounted for by the fact that some dissociation process, which produces radicals, cannot keep up with the consumption of radicals required by the mechanism.