Turbine Circulating Water System Operating Mode Optimization

Circulating water system is one of important auxiliary systems in power plant. It is very important in power plant operation. The variation of circulating water flow directly affects the vacuum of condenser and the efficiency of steam turbine. But many important factors are neglected during calculating the optimum vacuum and the circulating water flow at present. In addition, there is not a general method for calculating the change of power with back pressure. So the calculation results of the optimum vacuum and the optimum circulating water flow can't reflect the actual optimum value, and can not direct the optimizing operation of power plant.Therefore, firstly, several methods which are used to calculate the change of steam turbine power with back pressure are analyzed in this paper, and the conclusion is obtained that the equivalent enthalpy drop method is the best. Secondly, the calculation methods of the optimum vacuum and the optimum circulating water flow are improved. That is, the circulating water cost, the exhaust resistance of steam turbine, the make-up water of boiler, the standby venting equipment, the dissolved oxygen in condensate, the condenser cleanliness, the extreme pressure, the lowest flow rate of the circulating water and the subcooling degree of condensate are taken into account during calculation. At last, a new method of calculating the optimum vacuum and the optimum circulating water flow is put forward. So the calculating result that is very close to the actual optimum value is obtained.