Analysis of the effect of sliding pressure operation on the efficiency of a 610 MW subcritical steam power plant

The 610 MW subcritical steam power plant is designed to operate at a fixed load with constant steam pressure. Due to the electricity demand, the power plant needs to be operated at partial load. The inefficiency of the power plant increases due to increasing throttle losses in the control valves, particularly at minimum load. This research investigates the impact of the sliding pressure operating mode on the power plant's efficiency compared to the constant pressure operating mode. The computer simulation program was used to simulate the effect of the sliding pressure operating mode at three loads: 50%, 75%, and 100%. Following the computer simulation, the sliding pressure operating mode was then tested directly at the plant to analyze its performance. The computer simulation results show that the sliding pressure operating mode has an improvement in the plant's heat rate (the amount of heat energy required to produce one kilowatt-hour of electricity) at 50% load of 23.6 kcal/kWh compared to the constant pressure mode. For loads from 75% to 100%, there is no significant difference. The testing at the steam power plant at 55% load revealed that the sliding pressure operating mode resulted in a 57 kcal/kWh improvement in heat rate, which is equivalent to coal savings of 11.87 kg/MWh compared to the constant pressure operating mode at the same load condition.