May 25, 2009 | Siemens and the Norwegian power utility Statkraft are researching methods for removing carbon dioxide (CO2) from the exhaust gases of combined cycle power plants. Siemens is already working on technologies for separating CO2 from the flue gas of coal-fired power plants.

Now this process is to be adapted to the special conditions of combined cycle plants. The more efficient combined cycle facilities emit only about half as much CO2 as coal-fired power plants. They are the most environmentally friendly of today’s power plants that burn fossil fuels. Until now there have not been any systems for CO2-separation in combined cycle power plants. Nevertheless, operators are preparing for planned EU directives that will require further reductions in the CO2 emissions of large plants. A pilot facility for the underground storage of CO2 is currently being built in Germany. With this step, the politicians have established a legal framework for this technology, which is also important for the power utility companies.

Siemens and Statkraft are now trying to adapt the post-combustion process developed for coal-fired power plants to use with combined cycle plants. The method mixes the flue gas created during combustion with a cleaning solution that absorbs the CO2 in the gas. Now containing about ten percent residual CO2, the purified exhaust gas is emitted into the atmosphere. The absorbing solution is then heated to remove the CO2, Left behind is pure CO2, which can be compressed for transportation to storage sites. The cleaning solution, which is not consumed, is then returned to the process for reuse.

Unlike with coal-fired power plants, which are operated at base load, the load in combined cycle power plants changes frequently, so the quantity of gas also fluctuates. What’s more, the flue gas has a lower CO2 content, but it contains a lot of oxygen, which is highly reactive and affects the stability of the cleaning solutions. The process created by the experts at Siemens Fossil Power relies on stable cleaning solutions specially developed for this purpose. Now what remains to be seen is how the cleaning process will develop under the more demanding conditions in the combined cycle power plant. This technology could play an important role in the Siemens environmental portfolio. In fiscal year 2008 the company generated turnover of nearly €19 billion with its green products and solutions.
 
Reference Number: IRN 2009.05.05.e