Research On Process And Parameter Optimization Of Double Reheat Ultra-Supercritical Unit

In 2019,China’s total thermal power generation capacity reached 5220.148 billion kWh,accounting for 69.57%of the total power generation.During the "14th Five-Year Plan" period,coal power generation will continue to be the main power source.With the proposal of China’s "carbon neutral" plan in 2060,the theme of low-carbon energy development and transformation will become more vivid,and it is necessary to continue to promote the energy saving of thermal power units.This paper takes a 660MW ultra-supercritical double reheat unit as the research object,uses Ebsilon Professional software to establish simulation modeling,conducts thermal performance analysis and exergy analysis of the system under all working conditions,and reveals the energy-saving potential of the system.Aiming at the problem of large exergy losses caused by high superheat degree of the regenerative extraction steam in the system,this paper proposes a double reheat coal-fired power generation system that integrates external steam cooler and regenerative turbine at the same time.Thermal performance analysis and exergy analysis of the new system under all working conditions conduct are made in this paper.Research results show that the new system can reduce coal consumption by 4.03g/(kW·h)under 100%THA working condition,3.62g/(kW·h)under 40%THA working condition,and the coal consumptions under all working conditions of the new system are lower than those of the benchmark system.At the same time,technical economic analysis result shows that the new system’s new investment cost is 26.82 million China Yuan,the annual net income is 5.11 million China Yuan,and the payback period is about 5.25 years,the new system is an implementable and low-energy double reheat system.Based on the genetic algorithm,this paper optimizes the reheating and regenerative extraction parameters of the benchmark system,and the coal consumption is reduced by 0.89g/(kW·h)after optimization.Then,the reheating and regenerative extraction parameters of the double reheat system with regenerative steam turbines are optimized under design conditions,and the back pressure of the regenerative steam turbines are optimized under variable load work conditions.The results show that coal consumptions are reduced by 1.19g/(kW·h)under design condition,0.99g/(kW·h)under 75%THA working condition,1.19g/(kW·h)under 50%THA working condition,and 1.27g/(kW·h)under 40%THA working condition,respectively.