The investigation of this quarter focuses on the rates of NO reactions with chars in various gaseous environments. The results have revealed significant insights into the NO reduction mechanisms on char surface, particularly when the oxidants, O{sub 2} and CO{sub 2}, are introduced into the feed. Indeed, evidences suggest that the formation of stable oxygen complexes is the major cause of differences in NO reactivity on chars of different origins. The oxidants retard the reactivity of char derived fro the bituminous coal more seriously than they affect the char derived from lignite. Furthermore, additions of these oxidants into the reacting stream produce additional yields of CO and CO{sub 2} during NO reaction with lignite char, suggesting gasification of carbon from lignite char. No excess CO and CO{sub 2} were observed when the bituminous coal char was used. These yields of CO and CO{sub 2} also imply that desorption of stable surface oxygen complex is a rate-limiting step which may be catalyzed by the mineral matters during reactions involving lignite char. Surface area evaluated by CO{sub 2} and Dubinin-Radushkevich (D-R) equation is not a normalization factor of char reactivity during reburning. In the absence of oxidants, the bituminous coal char shows …