Study On Coordination Control Technology For 1000-MW Double Reheat Ultra-Supercritical Units

The second phase of Guodian Taizhou Power Generation Co.,Ltd.as a science and technology demonstration project,adopts the two reheat technology for the first time in China.The main steam pressure is 31 MPa,the main steam temperature is 600 degrees,and the reheat temperature is 610 degrees.The single parameter of the unit is the leading level of the world,meanwhile,it is the largest capacityof the two reheat unitin the world.The unit is designed to generate electricity for 256.2 g / kW,which is 6 g / kWh lower than the best level in the present world.But the two reheat modewill lead to the units more complex: there are two reheater--boiler complicated structure;adding a super high pressure cylinder,increase a reheat steam tube and reheat heat pipe,adding a set of ultra high pressure main steam regulating valve.At the same time,it has a great influence on the boiler,and the requirement of control is higher in operation.In this paper,the coordinated control technology of the 1000 MW super supercritical two reheat unit is studied in depth.Whether the output power of the unit is consistent with the load requirement reflects the balance between the energy supply and demand between the unit and the external power grid,while the main steam pressure reflects the balance between the energy supply and demand between the boiler and the steam turbine inside the unit.The basic task of regulating the combustion process is to make the heat supplied by the combustion of fuel adapt to the demand of the steam turbine load,and to ensure the economic combustion and safe operation.A main task of feedwater control is to maintain steam temperature stability,strictly control the ratio of fuel to water,and ensure the outlet enthalpy of separator is fixed value,making the first level temperature reduction control and two stage temperature reduction control in the adjustable range,and achieve the coarse adjustment of superheated steam temperature control.After the completion of the water supply coarse adjustment of steam temperature control,a fine controlof steam temperature is executed by the spray desuperheating system.According to the design of reheater system boiler plant,reheat steam temperature is adjustedby the burner nozzle angle as the main means,supplemented by regulating gas baffle.When reheat temperature adjustment is normal,and desuperheating water volume is zero,if the reheat steam temperature is higher than the set value of a certain amount,add little or accident spray desuperheatingto control steam temperature,the boiler reheat steam temperature is controlled in safe range at the end.