00/00994 Prediction of NOx control by basic and advanced gas reburning using the Two-Stage Lagrangian model

Abstract

The reduction of nitric oxide (NO) by acetylene in simulated conditions of the reburning zone has been undertaken in a fused silica jet-stirred reactor operating at 1 atm, at temperatures ranging from 1050 to 1300 K. In the present experiment, the initial mole fraction of NO was 1000 ppm, and that of acetylene was 4400 ppm. The equivalence ratio has been varied from 0.75 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. Thus, operating in optimal NO-reburning conditions is possible for particular combinations of equivalence ratio and temperature. The present results generally follow those obtained with previous studies involving simple hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiment was performed using an updated and improved kinetic scheme (877 reversible reactions and 122 species). An overall reasonable agreement between the present data and the modeling was obtained although improvements of the model are still necessary. 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) and HCN, and the low temperature interactions between NO and simple alkanes. According to this study, the main route to NO-reduction by acetylene involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: C2H2+O→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→N2; NH+NO→N2O followed by N2O+H→N2.