the slagging on the heating surface reduces the heat absorption of the steam-water mixture in the tube, increases the flue gas temperature and increases the heat loss of the smoke exhaust. if there is slag at the outlet of the furnace, the flue gas passage is blocked, the ventilation is limited, and the air supply in the furnace is insufficient; if the slag is formed at the outlet of the furnace, the normal injection flow rate is affected, which will increase the heat loss of chemical incomplete combustion and mechanical incomplete combustion, and reduce the boiler working efficiency. When the slagging is serious or the slag discharging time is long, the water wall tube is damaged easily.