Exergoenvironmental analysis of a ultra-supercritical coal-fired power plant

Abstract

This paper presents an exergoenvironmental analysis for a coal-fired ultra-supercritical technology. The study was carried out for a generating unit of 800 MWe of power, which uses bituminous coal as fuel. The environmental impact rates associated with: the destruction of exergy, to the life cycle of the components, to pollutants formation, besides the indicator of relative difference and the exergoenvironmental factor for each of the components of the system are evaluated. It was identified that the flow of cooling water and exhaust gas has a significant environmental impact rate (349.39 mPts/s and 702.26 mPts/s, respectively), which represents an impact rate per kWh of generated electricity of 1.57 and 3.16 mPts/kWh, respectively. The impact rate for the electricity generated by the ultra-supercritical system is 40.78 mPts/kWh. The environmental impact rate associated with the component (production, operation and maintenance, and disposal) is not significant in the analysis of this system. The environmental impact rate related to the destruction of exergy is representative in system (35.36%), together with the formation of pollutants which is the main source of environmental impact of system (64.55%) due to the large contribution of emissions provided by the combustion of coal. The system with ultra-supercritical technology presents itself as an alternative to less efficient coal generation systems, such as subcritical and even supercritical, but it promotes a high environmental impact rate when compared to other generation systems. The incorporation of exhaust gas treatment equipment, such as to particulate removal, gas desulphurisation, and removal of nitrogen oxides, can significantly reduce the environmental impact of the system.