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

Abstract

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.