Conventional and Advanced Exergy Analysis of Post-combustion CO₂ Capture in the Context of Supercritical Coal-Fired Power Plant

Post-combustion CO₂ capture (PCC) is one of the strategic technologies identified to reduce emissions of greenhouse gases (GHG) in an existing power plant. CO₂ capture incurs serious energy penalty due to the energy use for solvent regeneration in the capture process and subsequent increase in cost of electricity. Reducing the energy/exergy use in the process can lead to a reduction in energy penalties. Beyond demonstrating this lower level of actual energy/exergy consumption, it is important to increase the efficiency of the CO₂ capture system. This study includes steady-state simulation and conventional and advanced exergy analyses of PCC with solvents for emission reduction. It focuses on (1) steady-state simulation of the closed-loop PCC system, (2) conventional and advanced exergy analyses of the CO₂ capture process, and (3) strategies to reduce exergy destruction and losses in the capture process. A detailed exergy destruction analysis is performed in this study, both for the absorber and the desorber columns of the system. These analyses allow for a better understanding of the exergy destruction due to a component’s own inefficiency and/or the remaining components’ inefficiencies. The analyses show improvement in reducing exergetic losses in the system without incurring additional penalties. The results show that the energy/exergy destruction in the monoethanol-based (MEA-based) CO₂ capture system (and hence the energy penalty) and the efficiency can be improved by recovering the avoidable exergy destructions in the system.