Enhancing Reactive Absorption in Lithium-Based Looping Systems: Energy Integration and Compression Strategies for Efficient CO 2 Capture

Abstract

Natural gaspower plants require efficient and compact carbon capture systems to achievenear-net-zero CO2 emissions whileminimizing energy penalties and investment costs. Postcombustion CO2 captureusing lithium orthosilicate as a reactive solid absorbent emerges as apromising solution due to its ease of integration into existing thermal powerplants, high cyclic and thermal stability, significant CO2 loading capacity,and low environmental impact. However, the CO2 separation process is highlydependent on gas−solid thermodynamic equilibrium, making flue gas recirculationstrategies essential to improving capture yields and reducing the size of thecarbon capture plant. Thisstudy evaluates the performance of a CO2 capture process under varyingcompression conditions, combining precompressed flue gas through an exhaust gasrecirculation strategy with the expansion of low-CO2 gases in a recuperativeturbine. This approach enhances the reactive absorption stage, addressing atopic that has remained underexplored in the literature. Furthermore, aninnovative cold-shot flue gas strategy in the absorption stage is integratedwith conventional multistream heat exchangers, optimizing energy recovery andsignificantly reducing the external energy demand. Energy integrationdemonstrates substantial reductions in heating and cooling requirements, withauxiliary fuel savings exceeding 50%. Lower operating pressures yield greaterenergy savings, achieving CO2 capture rates close to 85%, albeit with anassociated energy penalty of 11%.