KINETICS OF THE GAS-PHASE REACTION BETWEEN NITRIC-OXIDE, AMMONIA AND OXYGEN

For the purpose of developing a simple and quantitative description of the rate of reactions occurring in the Thermal DeNOx process, the kinetics of the homogeneous reaction between NO and NH3 with excess of O2 has been studied in an isothermal plug flow reactor. Temperature windows of NO reduction were observed with the optimum temperature decreasing with increasing residence time. The degree of reduction of NO increases with residence time at lower temperatures but is sensitive to residence time only at very short residence times at higher temperatures. The degree of conversion of NH3 increases with both temperature and residence time. A simple model has been proposed to describe the reaction rates: r(NO) = k(ox) [NH3] - k(r) [NH3] [NO] r(NH3) = -k(ox) [NH3] - k(r) [NH3] [NO] The two rate constants in the model were estimated based on the experimental data obtained in the present plug flow reactor at about 4% (vol.) oxygen: k(ox) = (2.21 +/- 0.33) x 10(14) exp {-(38160 +/- 170)/T}, l/s k(r) = (2.45 +/- 0.49) x 10(14) exp {-(29400 +/- 250)/T}, m3/mol . s It is verified that the kinetic model can give a satisfactory prediction of the experimental results under different conditions.