Energy, Exergy, and Economic Analysis of a Low-Energy Consumption CO₂ Capture System with Ionic Liquid [DEME][TF₂N]

This study aimed to reduce the energy consumption of the CO2 capture system by coupling the CO2 capture process with an energy recovery element and screening for a solvent with a better CO2 capture performance. The high-pressure N2 and O2 mixture, which was not absorbed by the ionic liquid during the absorption process, expanded in the turbine to output work in the energy recovery element. The heat-transfer fluid in the heat exchangers between the compressors and turbines transferred compression heat from the flue gas to the N2 and O2 mixture to increase the amount of energy recovered. Subsequently, the heat-transfer fluid flowed into the desorber to utilize the remaining heat to facilitate desorption. In addition, the COSMO-RS method was used to screen for the best CO2 capture solvent, diethylmethyl(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([DEME][TF2N]). We measured the solubilities of N2, O2, and CO2 in [DEME][TF2N] and the specific heat capacity of [DEME][TF2N] for system analysis. Energy, exergy, and economic analyses were conducted to comprehensively evaluate the performance of the proposed system. The analysis results indicated that the total energy consumption was 0.703 GJ/tCO2 at an absorption pressure of 1000 kPa and a heat-transfer fluid rate of 1800 kg/h.