Analysis of a cooling system of the ultra-supercritical coal-fired power unit integrated with CO2 capture

Highlights: • Analyses of the cooling system of power unit with CO₂ capture were done. • Water demand ratio of the capture and compression unit is 99.8 kg/kgCO₂. • In nominal conditions, 21% more heat goes to the cooling tower. • Approx. 77% bigger CCU coolers area due to variable ambient temperature. • Higher nominal cooling water temperature and condenser pressure by 0.3 kPa. The subject of this paper is analysis of the cooling system of a conceptual advanced ultra-supercritical coal-fired power unit integrated with a CO₂ capture and compression unit (CCU). The capture unit, based on wet chemical absorption using MEA (monoethanolamine), was modelled in Aspen PLUS. The obtained results were used in the power unit model developed in Ebsilon Professional. The aim of the calculations was to determine the cooling demand of the CCU and to define the impact of the integration on the power unit operation under nominal and variable ambient conditions. Performed analyses show that, in nominal conditions, CO₂ separation and compression involve an increase in the cooling demand by about 21%. In higher ambient temperatures it is not possible to keep the assumed cooling parameters in the CCU. One of the solutions, is an increase in the area of the heat exchangers. Obtained results showed, that the total surface of all heat exchangers in the CCU has to be increased by 77% (48–89% for individual coolers). The need to collect a considerable amount of extra heat results in a rise in the cooling water temperature and in higher pressure in the steam turbine condenser by 0.3 kPa.