System design for 700 °C power plants: Integration scheme and performance evaluation

Abstract

With the increase of steam parameters, how to improve the available energy proportion from high-temperature flue gas and realize efficient utilization of low-grade flue gas heat are two key issues that limit the efficiency improvement of power plants. In this study, a base scheme for the 700 °C single reheat power plant is proposed by the design of flue gas and steam regenerative systems for solving the above issues. However, large cold end loss in boiler and turbine and imperfect thermodynamic processes in flue gas and steam regenerative systems are bottlenecks for further improvement of energy efficiency. An integration scheme of flue gas and steam regenerative systems is proposed, and a comprehensive evaluation is performed from the perspectives of energy, exergy, CO2 emission reduction, and economy. The analysis results indicate that the net efficiency of the integration scheme reaches 50.3%. The exergy loss is reduced by 56.9 MW compared with the base scheme. The increased investment can be recovered within 4.7 years. In the design of the 700 °C power plant, special attention should be paid to perfecting the thermodynamic processes of its flue gas and steam regenerative systems.