Integrated optimization of coal-fired power plant and CO2 capture system coupled with membrane condenser for recovering flue gas hydrothermal energy

CCS can effectively solve the problem of large-scale carbon emissions from coal-fired units, but at a considerable expense in terms of high energy and water consumption. In this paper, the conventional MEA-based CO2 capture system process is improved and integrated optimization with coal-fired power plant. An MEA-based CO2 capture system coupled with membrane condenser and an improved integrated decarbonization system are proposed based on the recovery potential of waste heat from flue gas and CO2 capture system. Besides, an MEA-based CO2 capture system coupled with membrane condenser is proposed. The membrane condenser is added to exchange heat with the rich solvent flowing from the bottom of the absorber before the flue gas into the absorber for recovering the flue gas hydrothermal energy. The regeneration duty of the CO2 capture system is reduced from 4.341 MJ/kg CO2 to 4.275 MJ/kg CO2. The extraction steam is further utilized by a small steam turbine before being sent to the reboiler. And the heat released by CO2 condensation at the top of stripper and CO2 cooling in the middle of multi-stage compression is used to heat the condensate of coal-fired system. Compared with the simple integration scheme which adopts the same CO2 capture system, the output power of the integrated decarbonization system increases from 510.719 MW to 593.850 MW. Correspondingly, the thermal efficiency increases by 6 %, the exergy efficiency increases by 5.86 % and the cooling water saves 1497.12 kg/s. Moreover, the variation of output power and saving cooling water with the membrane condenser parameters of the improved integrated system is analyzed.