Power plants are the biggest source of CO2 and any attempt to mitigate these emissions must address CO2 capture from combustion systems. The challenge here is the large volume of the flue gas due to essentially atmospheric pressure and the presence of N2. The CO2 levels are also relatively small which leads to very large equipment for the capture section.
Post-Combustion Flue Gas Clean-up
In post-combustion capture, a chemical solvent is used to separate CO2 from the flue gas stream produced by combustion of fuels in air. The typical application of an amine process would be for a pulverized coal (PC) or natural gas combined cycle (NGCC) power plant. The CO2 concentration in the flue gas ranges from 3% for NG to about 15% for PC.
The Post-Combustion CO2 Capture Unit can be viewed as a retrofit or add-on to the existing power plant. The flue gas from the boiler would have to still be cleaned up for NOx (SCR), particulate matter (ESP), and SOx (FGD) before it would be routed to the CO2 Capture Unit and finally out through the stack.
Typical Post-Combustion Capture Unit
The Post-Combustion CO2 Capture process is by itself quite simple. It comprises an absorber where CO2 is captured using a chemical solvent like an amine and a regenerator where the captured CO2 is released from the solvent.
KBR has undertaken several post-combustion CO2 capture studies at our M.W. Kellogg London office. The first one was for the Norwegian Water Authority (NVE) in 2006. The CO2 was captured from a 420 MW natural gas fired power plant in Karsto, Norway. In 2007, we worked for Statoil on the European CO2 Test Centre at Mongstad, Norway. Also in the same year, we did an independent study of the same gas fired power plant at Karsto for Norsk Hydro.