Assessment of Thermodynamic Efficiency of Carbon Dioxide Separation in Capture Plants by Using Gas–Liquid Absorption

Typical carbon capture plants include CO₂ separation and compression steps. CO₂ separation from diluted flue gases may be achieved by using gas-liquid absorption. This process requires work input for e.g. separating CO₂ from flue gases and regenerating the CO₂ loaded solvent. Hence, CO₂ capture plants involving gas-liquid absorption consume a remarkable part of power and thermal energy generated by power plants. By increasing the thermodynamic efficiency of capture plants one can increase the produced power and save fossil fuels. Therefore, this study provides a quantitative assessment of the thermodynamic efficiency of CO₂ separation in capture plants. To this aim the minimum work required for CO₂ separation and actual work input in realistic carbon capture plants are estimated. The results reveal that for the state-of-the-art MEA solvent the thermodynamic efficiency of the capture plant is about 16%, for state-of-the-art advanced solvent based capture process (ASBCP) is about 25%, while given the progress in developing ASBCPs in near future it may reach about 30%. Additional measures to reduce the energy requirement of the capture plant such as heat pumps are also discussed. This all means that CO₂ separation by gas-liquid absorption is still a relatively inefficient process and remarkable potential for further improvements with step change innovations in gas-liquid absorption exist and may be beneficially used for optimising CO₂ capture plants.