Evaluation of Near-Isothermal Phase-Change CO₂ Capture Technology with Heat Pump

Developing low-energy decarbonization technology is crucial for achieving large-scale CO2 capture from industrial flue gas. During the absorption of CO2, phase-change solvents (PCSs) can be separated into a CO2-rich phase and a CO2-lean phase. By exclusively supplying the CO2-rich phase to the desorber for solvent regeneration, the need for sensible heat is eliminated as a result of the reduction of the amount of solvent. However, the heat absorbed by the CO2-lean phase remains unrecovered. This study proposes a near-isothermal CO2 capture technology utilizing phase-change solvents (NI-PCSs-TCC) to recover the reaction heat absorbed by the CO2-lean phase to compensate for regeneration heat through a heat pump system. A Solvent-Technology Matching Method (STMM) is proposed, which helps to co-optimize the solvent concentration and process operation parameters. The optimal operating range for the MEA/sulfolane/water solvent concentration and process parameters within the NI-PCSs-TCC is evaluated. NI-PCSs-TCC can achieve an energy consumption of 2.16 GJ/t CO2 between the temperature ranges of 338.15–341.15 K for absorption and 379.15–383.15 K for desorption. This energy reduction is possible while maintaining a capture efficiency of over 90% and a lean loading of 0.2540 mol of CO2/mol of amine.