(4b) Critical Review of Separation Technologies for Co2 Capture from Post-Combustion Flue Gases

The existing processes for capturing CO2 from flue gases on coal-fired power plants are expensive and account for about 80% of the total cost of an integrated carbon sequestration process. The high capture cost results from both high energy consumption and high capital cost.

In this review, four CO2 separation technologies, absorption, adsorption, membrane and cryogenic processes, were critically reviewed. In-depth process engineering analyses of these separation processes along with the heat and mass flows in the steam cycle of pulverized coal power plants provided many insights into the potential applications of these separation technologies for CO2 capture from post-combustion flue gases. The results indicate that adsorption processes with fixed-bed configurations are not suitable for CO2 capture even when a sorbent with extremely high capacity is available. Membrane separation processes, on the other hand, are limited by the performance of the current available membranes and cryogenic processes are not realistic for CO2 capture due to the physical and chemical properties of the post-combustion flue gases. Absorption-based processes are the most promising options for CO2 capture from post-combustion flue gases at the present time.