Combustion of fuels under enhanced oxygen atmospheres has been well investigated over the past decades in various types of combustors, varying from diesel engines to coal-fired boilers. Most studies have found significantly lower NOx emissions during Oxy-coal combustion. In this paper, NOx combustion chemistry under O-2/CO2 atmosphere as well as air atmosphere was studied using detailed kinetic model. A suitable reaction mechanism was chosen based on the comparison between the calculation result and the experimental data. The influence of various parameters (temperature, CO2 concentration) on NO conversion was investigated. The chemical effects of high CO2 concentration on NO formation and destruction process was studied. On the basis of investigations through elementary chemical reactions, it can be concluded that high CO2 concentration play a pronounced role on NOx conversion process. Moreover, the dominant reaction steps contribution to production and destruction of NO as well as the most important reactions for NO reduction under different atmospheres were discussed. (c) 2010 Elsevier By. All rights reserved.