Serious slagging occurred on three 300 MW unit boilers with low ash fusion point bituminous and lignite as the fuel.Six factors such as installation error of the burner

air leakage of the furnace

primary air speed imbalance under thermal state

unreasonable combustion air distribution and the bad fuel quality were considered as the main reason.Thus

several measures were proposed as following:improving the installation quality of boiler combustion equipment;carrying out the thermal state leveling test of primary air regularly;clearing the hanging slagging in furnace and the burner nozzle timely;considering blending coals with high ash melting point and similar quality when burning the coals with ash melting point that below 1 100 ℃;controlling the oxygen concentration at the outlet of furnace or economizer by adjusting the supply air volume.