The transformation rule of volatile nitrogen and coke nitrogen during preheating process was analyzed.The XPS analyzer was employed to investigate the variation of nitrogen functional groups in the tested coals.Moreover

the TGA was used to study the emission characteristics of NOxprecursors during the preheating process of the tested coal.The results show that:the preheating process was contribute to decreasing the NOxgeneration

and the higher the temperature

the better the reduction effect;the effect of preheating process on Jincheng anthracite was better than that on Shaanxi bituminous coal.