According to survey of equipment code and practical operation state of axial-flow forced draft fan with adjustable rotating blades in some 600MW units

such problems as overlarge type selection

mismatch between the electric motor capacity and the fan capacity were found

which may increase the unit initial investment

decrease the actual operation efficiency of the axial-flow forced draft fan

and raise the electricity consumption.It suggested that the flow margin during type selection of the forced draft fan should be controlled at about 5%

and the motor power be within 1 500kW.Besides

the economical benefit comparison between capacity-decreasing speedreduction retrofit and frequency conversion retrofit was performed.For reconstruction of the axial flow forced draft fan

the capacity-decreasing speed-reducing retrofit was suggested.