Mechanisms of N2O formation from char combustion

This paper describes an experimental study on N2O and NOx emission from char combustion. Experiments have been carried out in a fixed bed reactor in the temperature range of 973-1323 K. Oxygen concentrations for combustion, temperature, and char type have been found to have strong effects on both N2O and NOx emissions. With an increasing temperature, N2O reaches a peak at 1073 K and then decreases with temperature. At the same time NOx remains nearly the same. When oxygen concentration increases, the concentration of N2O increases and NO, first increases and then decreases. The char with higher nitrogen content emits;more N2O, indicating that nitrogen oxides come from char-N. When NO is included in the inlet gases, much more N2O is produced from char combustion. This suggests that the reaction of NO + O-2 + char is the main pathway for N2O formation. Another pathway, i.e., the homogeneous oxidation of HCN from the gasfication of char, seems to be important as well.