Comparative analysis of optimized double-pressure, triple-pressure, and quadruple-pressure heat recovery steam generators

Heat recovery steam generator is a component of Rankine cycle in combined cycle power plant. Conventionally, heat recovery steam generators are classified based on the number of pressure levels. Heat recovery steam generator with two and three pressure levels are double-pressure and triple-pressure heat recovery steam generators. Generally, power plants of large capacities use triple-pressure heat recovery steam generator, whereas power plants of small capacities use double-pressure heat recovery steam generator. However, no power plants use quadruple-pressure heat recovery steam generator, which has four pressure levels, despite the fact that net power output of Rankine cycle increases with the number of pressure levels. In this paper, performances of double-pressure, triple-pressure, and quadruple-pressure heat recovery steam generators are compared. All heat recovery steam generators are optimized with respect to their steam pressures and temperatures. Simulation results show that the net power output of Rankine cycle with quadruple-pressure heat recovery steam generator is between 0.4 % and 0.9 % higher than that of Rankine cycle with triple-pressure heat recovery steam generator depending on inlet gas temperature and total heating surface area.