The kinetics of C1 to C4 hydrocarbons/NO interactions in relation with reburning

A study of the reduction of nitric oxide (NO) by C-1 to C-4 hydrocarbons, in simulated conditions of die reburning zone, was undertaken in a fused-silica jet-stirred reactor (JSR) operating at 1 atm. The tem temperatures ranged from 1000 to 1450 K; the initial mole fractions of NO were 750-1000 ppm, and the initial mole fraction of reburn fuel corresponded to 8800 ppm of carbon. The equivalence ratio varied from 0.7 to 2.5. It was demonstrated that the reduction of NO increases as the temperature rises, 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. A detailed chemical kinetic modeling of the present experiments was performed using a single updated and improved kinetic scheme (892 reversible reactions and 113 species). An overall reasonable agreement between the experimental data and the modeling was obtained. Furthermore, the proposed kinetic mechanism was successfully used to model the JSR neat oxidation of the fuels considered here, HCN oxidation in a JSR, C-1 to C-2 flames, and NO reduction by CH4 in a JSR at 1580-1800 K. According to this study, NO reduction by the hydrocarbons mainly proceeds via reaction with the ketenyl radical: fuel --> C2H2 --> HCCO, CH; HCCO + NO --> HCNO + CO and HCN + CO2; CH2 + 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.