Study on the N2O Formation under Low Temperature Condition in Pulverized Biomass Combustion

概要

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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., combustion temperature, volatilization process (i.e., either slow or rapid dispersion), and nitrogen content in biomass on N2O formation were investigated by numerical analysis. The analysis of the effect of combustion temperature on the formation of nitrous oxide showed that N2O emission level increases with the decrease in combustion temperature, and both N2O and NO levels are strongly dependent on the combustion temperature. In other words, there is a trade-off relationship between the formation of NO and that of N2O. 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. Further, the gasification reactions among CO2, O2, and C occur simultaneously on the surface of biomass particles during combustion. With respect to the effect of nitrogen content in biomass, 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.