Abstract: In order to further improve the utilization of the bottom slag residual heat of the drum slag cooler and increase the revenue of the circulating fluidized bed boiler unit,the energy efficiency calculation model of the drum slag cooler and the unit system were established and calculated based on a 350 MW supercritical CFB boiler unit.The calculation results show that for the present drum slag cooler,the bulk thermal efficiency will decrease after controlling the cooling water flow and increasing the outlet water temperature,while the unit power generation increases.When the outlet water temperature increases to 150 ℃,although the efficiency of the drum slag cooler reduces to less than 90%,the power generation capacity of the unit can increase exceed 1.1 MW since drum slag cooler can directly enter the deaerator.For the new unit,the thermal efficiency can be maintained while reducing the cooling water flow of the drum slag cooler.Further,the power generation value of the unit increases close to 1.2 MW when the outlet water temperature is also 150 ℃.Therefore,continuously increasing the outlet temperature is the most important technical development direction of the drum slag cooler.