Thermal-economy optimization for single/dual/triple-pressure HRSG of gas-steam combined cycle by multi-objective genetic algorithm

This investigation proposed the RBF-NSGA-II optimization algorithm and explored the thermal economy of different bottom combined cycles under 16 design parameters. The maximum efficiency, minimum exergy loss and minimum unit investment of different gas-water system combined cycles under various design factors were compared with traditional optimization, NSGA-II optimization and RBF-NSGA-II optimization. The results indicated that the combined cycle efficiency optimized by NSGA-II and RBF-NSGA-II increased by 25.2%, the exergy loss was reduced by 32%, and the specific investment was reduced by 38% compared with the traditional optimization. This investigation showed that the convergence speed of the newly proposed RBF-NSGA-II optimization algorithm is increased by three times compared to the NSGA-II optimization algorithm. Furthermore, through single-parameter sensitivity analysis, the relationship between compressor outlet pressure, gas turbine inlet temperature, pinch point temperature difference, approach point temperature difference, waste heat boiler pressure and combined cycle efficiency, exergy loss, and specific investment costs were investigated. The paper provided a new way for combined cycle design and guided the operation of combined cycle power plants.