The Catalytic Effect of Fe on Char-NO Reactions at High-Temperatures

The reduction of NO over coal-derived chars and the catalytic effect of Fe on NO-char reaction during char combustion were investigated in a drop-tube furnace in a temperature range of 1323-1523K. The catalytic characteristics of Fe in the NO–char reaction were studied in detail. The results show that iron (Fe) is an effective catalyst for the NO reduction by char derived from de-ashed coal at a high temperature, i.e., the chars with catalysts have high activity in the NO-char reaction. Furthermore, the stoichiometric ratio (SR) in the reaction zone has a significant influence on the catalytic activity of Fe-catalysts, which will be more effective in SR=0.7-0.9. The catalytic activity of Fe depends slightly on its loading amount, while the specific activity of the catalyst obviously decreased with the increasing of the Fe-loading amount. The effect of the temperatures used in the experiments on the NO reduction is small, which suggests the NO-char reaction mainly depends on the diffusion of reactants to char, the reactants' surface adsorption, and the desorption of products under high temperature. However, the effect of the temperature on NO reduction by metal-free char is much more important than that of NO reduction by Fe-loaded char.