Gas-Fired Power Plants to Be More Climate-Friendly

Siemens and the Norwegian power utility Statkraft are researchingmethods for removing carbon dioxide (CO2) from the exhaustgases of combined cycle power plants. Siemens is already workingon technologies for separating CO2 from the flue gas of coalfiredpower plants. Now this process is to be adapted to the specialconditions of combined cycle plants.

The more efficient combined cycle facilities emit only abouthalf as much CO2 as coal-fired power plants. They are the mostenvironmentally friendly of today's power plants that burn fossilfuels. Until now there have not been any systems for CO2-separation in combined cycle power plants. Nevertheless, operatorsare preparing for planned EU directives that will require furtherreductions in the CO2 emissions of large plants. A pilot facilityfor the underground storage of CO2 is currently being built inGermany. With this step, the politicians have established a legalframework for this technology, which is also important for thepower utility companies.

Siemens and Statkraft are now trying to adapt the postcombustionprocess developed for coal-fired power plants to usewith combined cycle plants. The method mixes the flue gas createdduring combustion with a cleaning solution that absorbs theCO2 in the gas. Now containing about ten percent residual CO2, the purified exhaust gas is emitted into the atmosphere. Theabsorbing solution is then heated to remove the CO2, Left behindis pure CO2, which can be compressed for transportation to storagesites. The cleaning solution, which is not consumed, is thenreturned to the process for reuse.

Unlike with coal-fired power plants, which are operated at baseload, the load in combined cycle power plants changes frequently,so the quantity of gas also fluctuates. What's more, theflue gas has a lower CO2 content, but it contains a lot of oxygen,which is highly reactive and affects the stability of the cleaningsolutions. The process created by the experts at Siemens FossilPower relies on stable cleaning solutions specially developed forthis purpose. Now what remains to be seen is how the cleaningprocess will develop under the more demanding conditions in thecombined cycle power plant. This technology could play an importantrole in the Siemens environmental portfolio. In fiscal year2008 the company generated turnover of nearly €19 billion withits green products and solutions.

Photo: http://www.siemens.com/ct-pictures/in20090505