In order to reduce the NOx emission of cyclone combustion

suitable air staging method on the premise of ensuring stable liquid slagging should be researched. Combined with the viscous-temperature characteristics of Zhundong coal

the liquid slagging model for cyclone furnace was established in this paper

and the excess air coefficient in main combustion zone was determined. Moreover

the air staging combustion test was carried out on a cyclone furnace. The results show that

when the Zhundong coal with good rheology was burned in cyclone furnace

the excess air coefficient in the main combustion zone can be reduced to 0.8. The tangential secondary air was divided into three layers

and the ratio was larger in the upper part and smaller in the lower part

which was 20%

10% and 10% respectively. The over fire air ratio was 30%～35%

and the residence time from the main combustion zone to the over fire air spout should be longer than 0.62 s. When the air supply was deeply staged in the cyclone combustion

the NOx emission mass concentration can be reduced by more than 30%

while the boiler thermal efficiency decreased by 0.22%

which was mainly caused by the increase of unburned carbon content in the slag.