Coal Power to Become More Climate-friendly
Mar 11, 2009 – Siemens and E.ON are building a pilot facility for sequestering carbon dioxide (CO2). Starting in summer 2009, the facility is expected to remove around 90% of the CO2 from a part of the exhaust gases emitted by the Staudinger coal-fired power plant near Hanau, Germany. Thanks to a special CO2-scrubbing process from Siemens, the sequestration of the greenhouse gas will consume comparatively little energy and have no adverse impact on the environment. The technology has been tested in the lab and is also suited for retrofitting in conventional power plants. According to experts, coal will remain an important energy source, with forecasts even pointing to an increase in coal use, particularly in India and China. Because coal-fired power plants emit relatively large amounts of CO2, researchers are working to make such power generation more climate-friendly. The procedure used for this is known as “post-combustion capture” and involves mixing the flue gas from combustion with a solution that absorbs the CO2 contained in the gas. The purified exhaust gas is emitted into the atmosphere with a minimal amount of residual CO2. The absorbing solution is then heated to remove the CO2, which is compressed for transport to storage sites. Research is still underway on how CO2 can be stored underground. After the carbon dioxide has been removed from the solution, the process starts over again from the beginning. The energy consumed in sequestering the CO2 still poses a major challenge because it reduces a power plant’s efficiency by more than 10%. The most energy-consuming process is the heating of the solution for releasing the absorbed CO2. The experts at Siemens Energy have therefore chosen an absorbing solution that consumes less energy than is the norm and for which many process parameters have been improved in the lab. Among the important factors to be considered here are the effect of associated gases such as oxygen and sulfur dioxide. The result is a CO2-scrubbing process that 
consumes far less energy than previous procedures and therefore reduces efficiency by only 9.2%. The new solution is also very stable, so it hardly reacts with trace substances in the flue gas. As a result, it is almost fully retained in the cycle without escaping with the residual gas, unlike many other absorbing solutions. The pilot facility will test the new technology under everyday conditions encountered in power plant operation. Among the factors to be studied are the solution’s long-term chemical stability and the effectiveness of the process. In addition, the researchers will aim to further reduce energy consumption.
Photo courtesy & © Siemens
