By taking a subcritical 350 MW unit in Huaneng Dandong Power Plant as an example

the operation schemes of the steam-driven feedwater pump group of which the booster pump and small steam turbine are driven coaxially were investigated.Moreover

the calculated economy of three schemes was compared.The results show that

the Scheme III has the optimum economy and safety

in which the motor-driven feedwater pumps were adopted during water feeding

boiler washing and furnace temperature enhancing until the steam turbine speed increases to 2 900r/min in the initial stage of unit cold state startup

then the first steam-driven feedwater pump was put into service when the unit load reached 30%.Therefore

not all units are fitted for using steam-driven turbine to accomplish cold state startup.The reasonable startup schemes should be proposed by considering the actual situation of each unit comprehensively.