Effect of volatile-char interaction on the NO emission from coal combustion

To clarify the effects of volatile-char interaction on the redistribution of fuel-N to N₂ during devolatilization and the reduction of NO through gas-solid reactions during combustion, two types of experiments were performed on a novel reactor. The separate combustion of volatile and char and the combustion of entrained pulverized coal, and the formation of NO was examined between 800 and 1100°C by using four typical Chinese coals with different ranks. The effect of volatile-char interaction on fuel-N conversion to NO during combustion was elucidated through comparing the NO emissions from the two types of combustion experiments. The results show that the volatile-char interaction is more important in the redistribution of fuel-N to N₂ during devolatilization than in the reduction of NO over 900°C, and a contrary conclusion is obtained below 850°C for all used coals. A specific parameter has been proposed to characterize the relative importance of the volatile-char interaction in the redistribution of fuel-N to N₂ during devolatilization to the interaction in the reduction of NO to N ₂ during simulataneous combustion of volatile and char. The results are of significance for minimizing the NO formation in industrial combustion processes.