Experimental and kinetic modeling of nitric oxide reduction by acetylene in an atmospheric pressure jet-stirred reactor

The reduction of nitric oxide (NO) by acetylene in simulated conditions of the reburning zone has been undertaken in a fused silica jet-stirred reacto r operating at 1 atm, at temperatures ranging from 1050 to 1300 K. In the p resent experiment, the initial mole fraction of NO was 1000 ppm, and that o f acetylene was 4400 ppm. The equivalence ratio has been varied from 0.75 t o 2. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO reduction occurs slightly a bove stoichiometric conditions. Thus, operating in optimal NO-reburning con ditions is possible for particular combinations of equivalence ratio and te mperature. The present results generally follow those obtained with previou s studies involving simple hydrocarbons or natural gas as reburn fuel. A de tailed chemical kinetic modeling of the present experiment was performed us ing an updated and improved kinetic scheme (877 reversible reactions and 12 2 species). An overall reasonable agreement between the present data and th e modeling was obtained although improvements of the model are still necess ary. Also, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethane, ethylene, a natural gas blend (methane-etha ne 10:1) and HCN, and the low temperature interactions between NO and simpl e alkanes. According to this study, the main route to NO-reduction by acety lene involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: C2H2 + O --> HCCO, CH; HCCO + NO --> H CNO -t CO and HCN +; CO, CH + NO +/- HCN; HCNO + H --> HCN + OH; HCN + O -- > NCO +/- NH; NH + H +/- N; N + NO -t N,; NH + NO +/- N,O followed by N2O H -t Nz. (C) 1999 Elsevier Science Ltd. All rights reserved.