Reduction of NO by n-butane in a JSR:: Experiments and kinetic modeling

A study of the reduction of nitric oxide (NO) by n-butane, in simulated conditions of a reburning zone, has been undertaken in a fused silica jet-stirred reactor operating at 1 atm. The temperatures ranged from 1100 to 1450 K, the initial mole fraction of NO was 1000 ppm,and that of n-butane was 2000-2200 ppm. The equivalence ratio (phi = [fuel%/O-2%]/[fuel%/O-2%](at phi=1)) was varied from 0.68 to 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 above stoichiometric conditions. Generally, the present results follow those obtained in previous studies involving simple hydrocarbons or natural gas as reburn-fuel. The oxidation of n-butane was also studied without NO in the same conditions of temperature, pressure, and residence time. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (892 reversible reactions and 113 species). An overall reasonable agreement between the present data and the modeling was obtained. Furthermore, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethane, ethylene, a natural gas blend (methane-ethane 10:1), acetylene, propene, and propane. According to this study, NO reduction by n-butane mainly occurs via reaction with ketenyl radical (HCCO): n-C4H10 --> C3H6, C2H4 --> C2H2 --> HCCO, CH; HCCO + NO --> HCNO + CO, and HCN + CO2; CH + NO --> HCN; HCNO + H --> HCN + OH; HCN + O --> NCO --> NH; NH + H -->N; N + NO --> N-2; NH + NO --> N2O followed by N2O + H --> N-2.