Abstract: After the 1000MW unit of Zouxian Power Plant of Huadian Power International Corporation Limited was put in operation, there were problems of incomplete combustion existed in normal operation of the burning system, which includes the black coking piece like carbon and particles of coal found in the slag. At the boiler overhaul, it is fund that there were dust deposit in the burner and the cannel of primary air was clogged by slag block etc. through follow surveillance, it is found that the slag increased, slag block fallen became big in the boiler No.7 after overhaul at may 2008, and the combustible dust in slag was increased abnormally. From angles of boiler design, installation, overhaul, operation and maintenance, the influence of heat leakage was analyzed, and some aimed measures were put forward. It is expected that the measures would be useful for energysaving and emission reducing.

Key words: pulverized fuel boiler, incomplete combustion, slag coking, energy saving