This work examined the effects of CO2 gasification in the reduction layer on NO emissions during subsequent char combustion in the oxidation layer during a grate-fired process. In experimental trials, the pyrolysis char of Shenhua bituminous coal was initially gasified in CO2, employing different conversion rates so as to vary the residence time of the char in the reduction layer. The pore structure and degree of graphitization of the char were monitored and the effects of CO2 gasification on NO emissions were ascertained. In this manner, the relationship between the transformation of char nitrogen and the physicochemical characteristics of the char was clarified. The effects of CO2 gasification on the properties of the char and NO emissions in the subsequent oxidation layer were determined. The results show that CO2 gasification can improve the pore structure and degree of graphitization of the char, such that NO emissions are reduced in an inert atmosphere. However, the conversion rate of char nitrogen will increase in conjunction with oxidative combustion. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.