In order to explore the way of high efficiency and low nitrogen combustion in oxy-fuel combustion

the experimental study on oxy-fuel staged combustion characteristics of Shenfu bituminous coal and Yunnan inferior bituminous coal was carried out on the down-draft furnace of Dongfang Boiler Test Center

and the burnout characteristics and nitrogen oxide emission characteristics of two kinds of coal under oxy-fuel staged combustion conditions were explored. The experimental results show that under the condition of oxy-fuel combustion

the combustion efficiency of Shenfu bituminous coal can reach more than 99%

and the NO_x emission concentration in flue gas can be controlled within 19.10 mg/MJ by using over-fire air staged combustion and reasonable control of oxygen staged feeding. The combustion efficiency of Yunnan inferior bituminous coal is slightly lower due to the delay of ignition and the long enough residence time required for burnout. However

the combustion efficiency can reach more than 90 % with reasonable oxygen classification

and the NO_x emission concentration in flue gas can be controlled within 16.83 mg/MJ. The effect of furnace temperature of oxy-fuel combustion on the cumulative formation and release curve of NO_x is consistent with that of air combustion. The higher the furnace temperature

the faster the heating rate of pulverized coal particles. The higher combustion efficiency and lower NO_x emission concentration can be found by adopting oxy-fuel staged combustion and reasonably controlling the timing and position of oxygen staged injection

so as to achieve high efficiency and low NO_x emission of oxy-fuel combustion.