The tests of pulverized coal combustion have been carried out at different temperatures(600 ℃~1 300 ℃)

different oxygen concentrations(3%~21%)

and different water vapor volume(0%~12%) respectively in a fixed bed reactor

and the influence of water vapor upon formation of NO in combustion of pulverized coal being studied.Results of study show that as follows:(1) when water vapor of 4% is added into the air

formation of NO is suppressed at a temperature being lower than 950 ℃

but the time of burnout being extended

and the formation of NO being promoted at a temperature higher than 950 ℃

whereas the time of burnout being shortened;(2) at a temperature of 1 200 ℃ and with water vapor of 4% being added into the gas mixture

the formation of NO is suppressed at the oxygen concentration being lower than 8.5%

and the time of burnout can be shortened

and the formation of NO is promoted at an oxygen concentrition higher than 8.5%

whereas the time of burnout being also shorted;(3) at a temperature of 1 200 ℃ and oxygen concentration of 3%

the formation of NO decreases firstly along with the volume change of water vapor

and afterwards it increases along with the volume change of water vapor

and the minimum formation of NO is obtained at the volume of water vapor to be 6%

the time of burnout can be shortened at various volume of water vapor.Therefore

both low formation of NO and accelerated combustion of pulverized coal can be achieved with a certain amount of water vapor to be added under condition of both high temperature and low oxygen concentration.