New insights into energy conversion mechanism, optimal absorbent selection criteria, and operation strategies of absorption carbon capture systems

Absorption carbon capture is currently the most commercialized technology and deemed as the vital solution to balance continued use of fossil fuels and carbon emission reduction. Nevertheless, its high energy cost remains the major concern for wide-scale application. Consequently, it is of great significance to address this issue by analyzing the underlying energy conversion mechanism, answering the pivotal question "What characteristics lead to a superior absorbent?", and developing more efficient absorbent. In this paper, an irreversible decoupling model of absorption carbon capture system, consisting of a heat engine and a chemical pump, is innovatively established. Accordingly, key performance indicators are analytically derived and the optimal operation strategies of the system are explicitly determined. Notably, the matching of two subsystems leads to a novel insight into the heat and mass transfer interaction of absorbent, according to which the simulated results and the question concerning the best absorbent are thermodynamically interpreted and addressed, respectively. Additionally, the comparisons between the calculated optimal energy conversion efficiencies with experimental and simulated results are presented and discussed. Our findings may indicate the efficient pathway for developing advanced absorbent and provide instructing information for the design and operation of practical carbon capture systems.