New Energy-Saving Absorption Configurations with Heat Exchange Between Partial Lean and Semi-Lean Solutions for CO2 Capture

Post-combustion CO2 capture from coal-fired power plant flue gas remains constrained by the low material performance and high energy consumption of solvent regeneration. Advancement needs to be made on two fronts: the development of improved solvents and materials, and the design of more efficient capture process configurations. Among the configurations developed to lower the energy penalty, lean solution vaporization and compression (LVC) effectively reduces reboiler duty; however, it introduces a vapor compressor that raises capital cost and consumes electricity, which is unfavorable given the adverse price ratio between electricity and low-grade steam in many carbon capture facilities. This study proposes a compression-free configuration based on heat exchange between partial lean and semi-lean solutions (HPS) to decrease energy consumption for CO2 capture. Three HPS design configurations are proposed: no heat exchange, merged heat exchange, and separate heat exchange. These three configurations are implemented in a partial-to-full split ratio of the lean solutions to achieve the lowest specific reboiler duty for the aqueous AMP + PZ solvent CO2 capture system eliminating the vapor compression requirement. Relative to the standard configuration with absorber inter-cooling and a rich solution split, the HPS design configurations with no heat exchange, merged heat exchange, and separate heat exchange effectively reduce specific reboiler duty by 9.47%, 7.34%, and 12.94%, respectively, with the dual advantage of avoiding both the compressor and the compression electricity penalty inherent to lean vapor compression configurations. The results indicate that the HPS configurations provide a compression-free route to energy reduction for amine-based CO2 capture, with the potential for economic benefits where electricity is costly relative to steam.