Postcombustion

Postcombustion refers to processes and technologies that operate on exhaust gases after the combustion of fuel has occurred. It is most commonly discussed in the context of removing carbon dioxide and other pollutants from flue gases prior to release to the atmosphere, enabling emissions control and, in many cases, carbon capture and storage or utilization.

The most widely studied post-combustion CO2 capture technology uses liquid solvents, particularly aqueous amines such as monoethanolamine. In a typical setup, flue gas contacts the solvent in an absorber, CO2 is captured, and a rich solvent is regenerated in a stripper by heating to release CO2 for compression and storage or utilization. Alternative approaches include solid sorbents, membranes, and other retrofit-friendly concepts. Some mineral-based methods, such as calcium looping, operate on the flue gas stage as well, capturing CO2 as part of a cycling process.

Postcombustion methods are applied in coal-fired and gas-fired power plants and in various industrial facilities, including cement production, where retrofitting existing plants is a common motivation. They enable decarbonization without altering the primary combustion technology.

Key challenges include the energy penalty associated with regenerating absorbents, equipment costs, solvent degradation and corrosion, and water usage. Impurity management, especially from sulfur oxides and nitrogen oxides, adds complexity. Ongoing research aims to improve solvent stability, develop advanced solid sorbents and membranes, reduce energy consumption, and optimize integration with existing plants.

As part of broader carbon management strategies, postcombustion capture forms a central pillar of carbon capture and storage (CCS) and carbon capture, utilization and storage (CCUS) efforts, facilitating decarbonization of fossil-fuel systems and certain industrial processes.