Post-combustion Capture

In post-combustion capture, fuel is burned as usual in a (more-or-less) unmodified power plant. Currently the commercialised technology for post combustion capture is chemical absorption. It is the most advanced method due to considerable industrial experience with similar processes. CO2 is absorbed from the flue gas in a separation tower using a solvent and regenerated by heating in a recovery column at temperatures over 100˚C. Post combustion is advantageous because it can be applied to already constructed plants (retrofit), where components can be replaced, developed and upgraded without fundamental impacts on the power plant. This also allows for staged introduction of carbon capture onto a plant, which reduces disruption to the plant as well as investment risk. The fact that post-combustion can be retrofitted to existing power plants means that such demonstration projects have thus far been more common than for other capture technologies. The major disadvantage of chemical absorption for post combustion capture is the large energy penalty associated with thermal solvent regeneration. Other research challenges include large equipment requirements due to high volumes of flue gas, corrosion of equipment in the presence of oxygen and other impurities, solvent degradation due to reaction with oxygenated impurities, potential releases of harmful solvent degradation products and disposal requirements of expired solvent. Future development of second and third generation capture technologies to improve efficiency and reduce cost may include better liquid solvents and novel membranes or microporus solids.