The carbon capture and storage (CCS) discussion has focused on pre-combustion capture of CO2, since it has long been assumed that is easier and cheaper than trying to capture the CO2 post-combustion from the flue gas (exhaust stream). The problem is 1) that approach limits CCS to new coal plants and 2) that requires utilities to build integrated gasification combined cycle (IGCC) plants, which are more expensive to build and more expensive to maintain.
Post-combustion capture would allow CCS to be retrofitted on existing coal plants. If it proves practical and affordable, that would be a major breakthrough in efforts to control greenhouse gas emissions. Last week brought us this announcement:
More details on this potentially important technology below:
In May 2004, Powerspan and the DOE’s National Energy Technology Laboratory entered into a cooperative research and development agreement to develop a cost effective CO2 removal process for coal-fired power plants. The regenerative process is readily integrated with Powerspan’s ECO process for multi-pollutant control, and uses an ammonia-based solution to capture CO2 in flue gas and release it for enhanced oil recovery or other form of geological storage. The CO2 capture takes place after the NOx, SO2, mercury and fine particulate matter are captured. Once the CO2 is captured, the ammonia-based solution is regenerated to release CO2 and ammonia. The ammonia is recovered and sent back to the scrubbing process, and the CO2 is in a form that is ready for geological storage. Ammonia is not consumed in the scrubbing process, and no separate by-product is created. The process can be applied to both existing and new coal-fired power plants and is particularly advantageous for sites where ammonia-based scrubbing of power plant emissions is employed.