The denitrification effect of coal-water slurry pyrolysis gas is investigated by numerical simulation in a 330 MW power station pulverized coal boiler

focusing on the influence law of excess air coefficient α_1 in the primary combustion zone(PCZ) and pyrolysis gas ratio β on the combustion characteristics and NO_x emission in the furnace. The results show that

when β is kept constant

the temperature of the PCZ decreases and the temperature of over-fire air(OFA) zone and furnace outlet increases as α_1 decreases. Meanwhile

the decrease of α_1 enhances the reducing atmosphere in the PCZ

which is beneficial to improve the denitrification rate of pyrolysis gas and thus to reduce the NO_x mass concentration at the furnace outlet. But the decrease of α_1 will affect the combustion performance of the pulverized coal and increase the CO concentration at the furnace outlet. With the increase of β

the center of the furnace flame moves up and the reduction rate of NO_x by pyrolysis gas increases. When β increases from 5% to 20%

the overall mass concentration of NO_x in the furnace shows a trend of first decreasing and then increasing

and when β=15%

the NO_x mass concentration reaches the lowest and the NO_x reduction efficiency of the pyrolysis gas reaches 44.35%.