Microscopic mechanism for the effect of potassium on heterogeneous NO–char(N) interaction: A theoretical account

Abstract

Reburning is an effective way for the clean and efficient utilization of biomass with low nitrogen oxides (NOx) emission. During the reburning process, the heterogeneous reaction between NOx and char nitrogen (char(N)) obviously affects the removal efficiency of NOx, and the abundant K species in biomass can inevitably affect the NOx–char(N) reaction. In the present study, char(N) models of Zigzag(N) and Armchair(N) configurations were adopted, abbreviated as ZN and AN. The effects of K on heterogeneous NO–char(N) reactions were investigated by density functional theory (DFT) and wave function analysis, and the rate constants for all reaction rate-determining steps in the temperature range from 800 to 1800 K were calculated by conventional transition state theory. The results show that NO can react with ZN and AN to generate N2 easily. The presence of K changes the reaction path of NO–char(N) by facilitating the heterogeneous reduction of NO and inhibiting the migration of char(N). According to kinetics calculation, K can inhibit the occurrence of NO–ZN in the low temperature while it inhibits NO–AN along all the investigated temperatures. The heterogeneous migration mechanism of nitrogen can provide theoretical guidance for NOx emission control during biomass reburning.