For a 600 MW and two 300 MW units pulverized coal boilers

the burners tilt down

and the temperature in reheater and the amount of desuperheater spray exceed their design value.Too much heating surface area caused heat deviation in the reheater was considered as the major reason

according to the coal characteristics(low heat calorific value

high moisture and ash content).Therefore

it is proposed to cut part of the heating area.The actual operation results show that the desuperheater spray amount decreased markedly and the burner tilt can also be placed in a horizontal position at low loads after the retrofitting.The retrofitting improved the loading capacity of boiler when high pressure heaters are separated and coal mills are stopped.The hidden troubles of heating surface corrosion were be reduced.The boilers' safety and economy is enhanced.