Effects of Heterogeneous Reaction and Slow/Rapid Volatilization Process on N2O Formation During the Combustion of Pulverized Biomass

The purpose of this study is to clarify the fundamental and general features of N2O formation during the combustion of pulverized biomass under low temperature. First, the effect of various important factors, i.e., volatilization process (i.e., either slow or rapid dispersion), oxygen concentration, and solid-gas reaction on N2O formation were investigated by theoretical analysis. The analysis of the effect of the slow/rapid volatilization process on the formation of nitrous oxide showed that the conversion ratio of biomass-N to N2O increases with the decrease in the dispersion of volatile matter per unit time; it means that biomass-N is effectively converted to N2O during slow volatilization. The analysis of the effect of initial oxygen concentration on the formation of nitrous oxide showed that at low temperature (T = 1100K), the level of N2O emission increases, while that of NO emission decreases, with the decrease in initial oxygen concentration. In other words, there is a trade-off relationship between the formation of NO and that of N2O. With respect to the effect of solid-gas reaction, the gasification reactions between CO2, O2, and C(s) occur simultaneously on the surface of biomass particles during combustion. Further, the N2O emission level increases with the increase in N-content of the biomass, while the NO emission level remains constant during low-temperature combustion.