The gas predominantly occurs as a consequence of burning fossil fuels (coal, oil and gas). CO2 capture means cleaning (capturing) CO2 from this flue gas on a major scale. In order to do this, capture technology is required.
The technologies are normally divided into three main groups:
- CO2 is separated from the flue gas after combustion in the power plant ("post-combustion"). The capture facility treats the flue gas from the power plant and is separated from the power plant.
- CO2 is captured from the fuel before combustion in the power plant ("pre-combustion"). The fuel could be gasified coal or natural gas that is reformed to synthesis gas (H2, CO2/CO). CO2 is captured before the hydrogen-rich fuel is burned in a gas turbine. In this case, the capture facility is part of the power plant.
- Natural gas or coal is burned with pure oxygen ("oxy-fuel"). This means that the flue gas contains only CO2 and water vapour, thus allowing both smaller and simpler capture facilities. However, the oxygen must first be separated from the air in a separate, energy-intensive plant.
Today, post-combustion capture using amine-based processes is a relatively mature technology and is ready for use in full-scale plants. Other mature technologies in this group are based on amino acid salts and carbonate-based solvents. Other promising concepts are also being developed, but are not expected to be commercially available until after 2020.
Work is in progress on several potential technologies for pre-combustion capture. The most mature technologies available today are "Combined Cycle Gas Turbine" (CCGT) combined with reformation of natural gas or gasification of coal, as well as "Integrated Gasification Combined Cycle" (IGCC). These technologies use physical solvents to remove CO2 from the synthesis gas.
As regards the combustion method with pure oxygen, research is under way on both new and less power-intensive methods of separating oxygen from air, and new concepts involving other special oxygen carriers such as Chemical Looping Combustion.
We need more research, development and demonstration of CO2 capture. Gassnova does not believe there will be only one winning technology when it comes to capture. Multiple technologies are needed to meet various needs.