Heat Integration and Optimization of Supercritical CO2 Recompression Cycle Coupled with Oxy-Coal Combustion

Abstract

This study proposes a supercritical CO2 recompression cycle based on external oxy-coal combustion. It aims to evaluate and improve the performance of the system guided by energetic and exergetic analyses. The influence of the heat integration of the air separation unit (ASU) on performance is initially assessed and sensitivity analyses of cycle variables are then conducted. The system parameters are thermodynamically optimized using a genetic algorithm. Results show that the net efficiency of the base case is 42.13%. If ASU heat integration is considered, then the net efficiency increases to 45.1%, showing an efficiency increment of 2.97%. The comparison of the layouts reveals that the intercooled reheat cycle has the maximum net efficiency that can reach 47.73% when the optimal inlet and outlet pressures are 4 and 7.6 MPa, respectively. Finally, the proposed optimized system is compared with an ultra-supercritical pulverized coal (USC-PC) plant, and the economic performance is evaluated. Results show that the proposed optimized system is economically suitable, the net efficiency is comparable to that of the USC-PC plant, and the net efficiency with carbon capture is 4.27% higher than that of the USC-PC plant.