How is carbon dioxide to be removed from flue gases?
Carbon dioxide arising from coal combustion can be precipitated from flue gas and stored underground (or recycled). Technical CO2 precipitation processes are known of from the chemical industry. But no plants have been forthcoming to date able to precipitate the climate-noxious carbon dioxide in coal power plants. Both power plant operators and plant constructors across the world are researching intensively into the appropriate processes. Basically they are pursuing three different approaches:
- CO2 pre-combustion capture:
Here the coal is gasified prior to combustion and by the addition of water vapor is transferred into hydrogen and carbon dioxide. This carbon dioxide can then be captured.
- CO2 capture during combustion (Oxyfuel variant):
The coal is combusted with pure oxygen rather than with the ambient air. The CO2 can then be more easily precipitated from the flue gas.
- CO2 Post-Combustion Capture (PCC) – downstream-arranged flue gas scrubber:
Here the carbon dioxide in the flue gas is scrubbed out with the help of chemical solutions at the end of the power plant operation and trapped.
Hitachi Power Europe is, in particular, actively pursuing the line with the oxyfuel process and the downstream-arranged flue gas scrubber (PCC). Together with a power plant operator, we have developed a mobile pilot unit for CO2 capture based on the PCC process – a pilot unit which is being tested at various power plant sites. We anticipate commercial deployment of CCS for 2020.