Experimental and kinetic modeling study of the reduction of NO by hydrocarbons and interactions with SO_2 in a JSR at 1 atm

摘要

The reduction of nitric oxide (NO) by a mixture of methane, ethylene and acetylene with and without addition of SO_2 has been studied in a fused silica jet-stirred reactor operating at 1 atm in simulated conditions of the reburning zone. The temperatures were ranging from 800 to 1400 K. In these experiments, the initial mole fractions of NO and SO_2 were 0 or 1000 ppm, that of methane, ethylene and acetylene were, respectively, 2400, 1200 and 600 ppm. The equivalence ratio has been varied from 0.5 to 2.5. 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. The addition of SO_2 inhibited the process of reduction of NO under the present conditions. The present results generally 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 an updated and improved kinetic scheme (1006 reversible reactions and 145 species). An overall reasonable agreement between the present data and the modeling was obtained. Also, 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). The kinetic modeling indicates that the reduction of NO proceeds via the following sequence of reactions: HCCO + NO = HCNO + CO; HCCO + NO = HCN + CO_2; HCN + O = NCO + H; HCN + O = NH + CO; HCN + H = CN + H_2; HCNO + H = HCN + OH; CN + O_2 = NCO + O; NCO + H = NH + CO; NCO + NO = N_2O + CO; NCO + NO = CO_2 + N_2; NH + NO = N_2O + H; NH + NO = N_2 + OH. The inhibition of this process by SO_2 is explained by the sequence of reactions H + SO_2 + M = HOSO + M and HOSO + H = SO_2 + H_2 that acts as a termination process: H + H + M = H_2 + M.