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.