Through measurement of NOx emission concentration from a supercritical 1100 t/h boiler in one power plant

it has discovered that the facts are listed as in the following:under same load of unit

if the oxygen content in flue gas from outlet of the air preheater is increasing

the concentration of NOx emission is also increasing

if the open-degree of over-fired air gate is decreased

the variation of formation rate for the thermal type NOx isn't large

the formation rate of fuel type NOx is gradually increased

the cotent of unburnt combustible in fly ash is gradually reduced

the boiler efficiency is gradually enhanced

the concentration of NOx emission is basically not changed.The property of coal quality has greater influence upon the concentration of NOx emission

the ratio between fixed carbon and volatile matters as well as nitrogen content in the fuel play a decisive role.During the time of decreasing load of unit

the concentration of thermal type NOx emission is gradually reduced.