The emission of NOx when coal was burning in O2/CO2 was compared with the case of burning in air

and the effects of temperature and excess air ratio on NOx formation were analyzed by using a one-dimensional drop-tube furnace. The formation and reduction mechanisms of NOx in O2/CO2 were studied.There was a NOx peak in both two atmospheres

and the peak of high volatile matter coal appeared much earlier than the peak of low volatile matter coal.The peak in O2/CO2 atmosphere appeared earlier than the peak in air and the peak value was lower than that in air.The amount of NOx increased quickly with temperature in air

but the amount of NOx changed slowly with temperature in O2/CO2 atmosphere.In both atmospheres the NOx peak value increased with excess air ratio.The peak value of high volatile matter coal in O2/CO2 was lower than that in air but the low volatile matter coal was less affected.