Post-combustion carbon capture by, for example, amine absorption, is a technology fit for both power plants and industrial CO2 emissions, including new builds and retrofits. The retrofitting possibility and the technology's ability to capture emissions from industrial sources is quite unique compared to the main alternatives (pre-combustion and oxyfuel). For these reasons, post-combustion will probably survive as a major technology, even though it will most likely not end up as the preferred technology for newly built power plants.
Extracting CO2 from atmospheric flue gas is relatively energy-intensive. Nebb has developed Cesam, an oxyfuel process that supplies heat and power to a post-combustion absorption unit (amine or other technology).
In the amine post-combustion process, CO2 is chemically bound to a solvent at relatively low temperatures in an absorber tower and released from the solvent at relatively high temperatures in a stripper tower. Atmospheric CO2 capture requires heat transfer to the solvent and power to drive fans and solvent circulation pumps.
For an atmospheric absorption process, it is normal to extract 80-90% of the CO2 in the inlet flue gas stream.
Cesam is an oxyfuel process that supplies heat and power to the absorption process. The process is illustrated below (bottom of page).
The figure below shows a conventional natural gas combined power cycle with an absorption unit and an oxyfuel process that supplies heat to the stripper tower. Cesam may, however, be applied to any post-combustion absorption unit.
In the illustration below, a steam turbine is used in the oxyfuel process. This is an existing unit, that can be applied with minor modifications. In the long run, an oxyfuel gas turbine may be used to improve overall process efficiency. A highly efficient oxyfuel gas turbine will take some years to develop.
Applying Cesam technology to post-combustion installation has several advantages:
Nebb is currently performing a concept study of a Cesam process solution for a full scale 430 MW combined cycle gas power plant and a test plant at Technology Centre Mongstad (TCM). Both studies are with public funding from Climit/Gassnova. A fact sheet can be found here, and a news article about the project can be found here.