Post-Combustion Capture

Post-combustion capture involves removing the dilute CO2 from flue gases after hydrocarbon combustion. It can be typically built in to existing industrial plants and power stations (known as retro-fitting) without significant modifications to the original plant. This is the type of technology favoured by teh UK Government in its competition for state support.

There are several methods that can be used to capture the CO2. The most common method is passing the CO2 through a solvent and adsorbing it and amine solvents are typically used. A change in temperature and/or pressure will then release the CO2. Another process in development is calcium cycle capture where quicklime is used to capture the CO2 to produce limestone, which can then be heated to drive off the CO2 and quicklime which can then be recycled. All of these require additional energy input to drive off the CO2 from the solvent - this typically results in extra energy costs of 20-30% compared to plants with no capture. New solvents are under development to reduce these penalties to 10%.

Other post-combustion possibilities, currently being researched, include cryogenically solidifying the CO2 from the flue gases, or removing CO2 with an adsorbent solid, or by passing CO2 through a membrane.