Thermodynamic analysis and life cycle assessment of supercritical pulverized coal-fired power plant integrated with No.0 feedwater pre-heater under partial loads

With ever increasing share of renewable energy sources in the electricity mix, pulverized coal-fired power plants (PCPP) have to participate in peak load regulations frequently and thus, they regularly operate under partial loads. The energy efficiency and eco-efficiency are both significantly affected by such operating patterns. Therefore, the present work aims to establish an overall concept for the estimation of environmental impacts from PCPP under nominal and partial loads with combined thermodynamic analysis and life cycle assessment (LCA) methodology. A 1000 MW supercritical PCPP was modeled using commercial simulation software (GSE for thermodynamic simulation and SimaPro for LCA analysis). Results indicated that global warming was the predominant environmental impact of PCPP, while ozone formation, acidification and eutrophication were also serious concerns attributed to NO_x emissions in electricity generation process. The mechanisms of formation, migration and removal of different kinds of pollutant emissions significantly influenced the LCA results. Particularly, the total environmental impact potential considerably increased by approximately 90% under partial/low loads due to reductions in the plant thermal efficiency and NO_x removal efficiency. A novel partial load No.0 feedwater preheating system driven by steam ejector was thus proposed for NO_x reduction improvement. Operation optimization was carried out based on the guidelines of the LCA framework. It was found that the total environmental impact could be effectively reduced by up to 27.3%. Therefore, the implementation of the No.0 feedwater pre-heater was favorable for environmental performance improvement under partial/low loads.