Flash evaporation and thermal vapor compression aided energy saving CO2 capture systems in coal-fired power plant

Abstract

In this paper, flash evaporation and thermal vapor compression are used to reduce heat consumption of CO2 capture processes and two improved capture systems are proposed. One is the flash evaporator (FE) and thermal vapor compressor (TVC)-aided system, the other is the heated flash evaporator (HFE) and thermal vapor compressor (TVC)-aided system. Analyses are carried out to verify their effectiveness in reducing heat consumption. Compared with the base CO2 capture system of 108.76t/h CO2 capture capacity from a 660 MW coal-fired power unit, the FE-TVC-aided capture system reduces the specific heat consumption from 4.421GJ/tCO2 to 4.161GJ/tCO2, and the specific exergy consumption from 1.368GJ/tCO2 to 1.275GJ/tCO2, the corresponding energy saving and exergy saving are 10.3%, and the plant electric efficiency penalty is decreased from 11.83% to 11.02%, on condition that the CO2 recovery ratio is set at 90%. Compared with the base CO2 capture system, the HFE-TVC-aided capture system reduces the heat consumption from 4.421GJ/tCO2 to 4.057GJ/tCO2, and the specific exergy consumption from 1.368GJ/tCO2 to 1.243GJ/tCO2, the corresponding energy saving and exergy saving are 12.5%, and the plant electric efficiency penalty is decreased from 11.83% to 10.80%.