To greatly enhance the efficiency of coal-fired power units and make the net efficiency of 700 ℃advanced ultra supercritical(A-USC) unit higher than 50%

the conceptual design scheme of the 700 ℃ A-USC unit is studied. The initial steam parameters

unit capacity

reheat times

main engine selection scheme

thermal system formulation

main auxiliary equipment selection and plant layout scheme are analyzed. A primary reheat unit with capacity of 660 MW and initial parameters of 35 MPa/700 ℃/720 ℃ is recommended as the conceptual design scheme for the 700 ℃ A-USC unit. The boiler is planned to use the spiral tube coil once-through furnace with ultra-supercritical parameters and variable pressures. It is a tower boiler with all steel suspension structure

which has single furnace

single reheat system

circular combustion mode

balanced ventilation

solid slag discharge and open layout. The steam turbine is supposed to have single shaft

single intermediate reheat system

four cylinders and four steam rows. It is recommended to use the BEST steam turbine heat regenerative system with variable frequency generator. 12-stage non-adjusted steam extraction system is applied in the unit. The main plant house is recommended to adopt the layout scheme with two-row

side coal bunker and high level arranged steam turbine.The conceptual design scheme of the 700 ℃ A-USC unit is an important reference for the construction of more efficient and clean thermal power plants in China.