Thermodynamic cycle analysis and optimization to improve efficiency in a 700 °C ultra-supercritical double reheat system

Abstract

When increasing steam parameters, the incomplete thermodynamic cycle and large irreversible system losses are bottlenecks in improving thermal efficiency in ultra-supercritical power plants. In this study, a comprehensive analysis of both parameter optimization and system cycle analysis is carried out for a 1000-MW double reheat ultra-supercritical thermal power plant. First, the genetic algorithm is used to optimize the primary and double thermal pressure, as well as the steam extraction parameters of the steam turbine. Then, a thermodynamic optimization model is proposed to analyze performance. Moreover, the exergy analysis method is applied to reveal the irreversibility mechanism in the thermodynamic cycle. In order to further solve the energy-grade mismatch problem, the performance of a regenerative steam turbine thermal system is improved based on the optimized system. The results indicate that the power generation efficiency of the optimized system is 0.31% higher than that of the prototype system, and the heat consumption rate is decreased by 43.67 kJ (kW h)−1. The power generation efficiency in the regenerative steam turbine system is up to 52.42%, which is 1.44% higher than that of the optimized system. Therefore, an effective method to improve the thermal efficiency is obtained through the thermodynamic cycle analysis and optimization for 700 °C ultra-supercritical double reheats systems.