Numerical simulation of NO_x emission characteristics for a supercritical 660 MW unit wall type tangentially fired pulverized coal boiler were carried out. The influence of temperature field and NOxconcentration in the furnace were studied by using the method of oxy-fuel combustion in the air staged combustion technology. The results show that

under oxy-fuel conditions with oxygen content of 25%

28% and 30%

the operation situation of the boiler under 30% oxy-fuel condition shows good agreement with that under the actual air condition in the power plant

and the flame fullness and combustion stability is better than that using the air staged combustion. The reaction between the high concentration CO_2 in flue gas recirculation and the char exacerbated the reducing atmosphere

and the increase of residence time of the pulverized coal flow in the reduction zone improves the transformation of NO_x to N_2

thus the NO_x generation is reduced. After the staged oxy-fuel combustion technology is apllied

the NO_x concentration at the furnace outlet reduces by 47.03%

which is from 236 mg/m~3 to 125 mg/m~3.