Experimental study on the impact of adding NH3 on NO production in coal combustion and the effects of char, coal ash, and additives on NH3 reducing NO under high temperature

In the past, few studies were reported on advanced air-staged combustion (AASC) for achieving deep NO reduction in furnaces. Therefore, a fixed-bed reactor was employed to uncover the role of injecting NH3 on NO reduction in the reduction zone of the AASC process. Four types of coal, char and ash from furnaces were used as samples. First, the effect of ammonia injected into the coal combustion process on NO formation was investigated. Then, the NO reduction characteristics of the ammonia injection were investigated as well as the coupling effect of char and ash or certain additives (Fe2O3, Fe3O4, CuO, Cu2O, MnO, etc.) joined together under a reductive atmosphere. The presence of O2 is not conducive to NO reduction by ammonia. The heterogeneous reducing NO efficiencies of the different chars are higher than that of NH3 when reducing NO using the pure gas. Ammonia addition can further strengthen the reaction of char and NO. Coal ash can obviously increase the ability of ammonia to reduce NO. The promotion of the denitrification effects by the various ashes follows the same sequence as the Fe2O3, CaO and MgO contents in the four coal ashes. Fe2O3, Fe3O4 and Cu2O have certain promoting effects on NO reduction with ammonia addition. However, MnO and CuO show negative effects.