TransAlta Corporation and Alstom will work together to develop a large scale carbon capture and storage (CCS) facility in Alberta, Canada.
The project will use Alstom’s proprietary Chilled Ammonia Process (earlier post) for carbon capture. TransAlta considers the Chilled Ammonia Process as one of the more promising and potentially lowest cost solutions for CCS. TransAlta plans to test the technology at one of its coal-fired generating stations west of Edmonton and reduce current CO2 emissions by one million tonnes per year.
Our project with TransAlta is a key part of our objectives for the early deployment of the technology. There will be no CCS without storage, and we are aware of the favorable geological conditions in Alberta, Canada. That is why we have set this region as a priority for our development efforts.—Philippe Joubert, Alstom Executive Vice President and President of Alstom Power Systems
The first phase of the overall project, aimed at advancing and improving understanding of CO2 capture and storage technology, will begin this year with engineering, stakeholder relations and regulatory work at a cost of approximately C$12 million. This, and subsequent phases, are subject to partner and government funding, and will continue over the next five years with testing expected to commence in 2012.
TransAlta has also partnered with experts at the Institute for Sustainable Energy, Environment and Economy (ISEEE), part of the University of Calgary, to quantify CO2 sequestration potential in the Wabamum area west of Edmonton. The results, due in January 2009, will provide a scientific assessment of potential sequestration sites in the area surrounding several power plants including their capacity and security.
In the chilled ammonia capture system, flue gas is cooled to 0-10°C, condensing water and removing residual contaminants. This also reduces flue gas volume, increasing the concentration of CO2. This cooled gas then flows to the absorber, which operates at 0-10°C for high CO2 capture and low ammonia emission.
There, the ammonia reacts with CO2 and water to form ammonia carbonate or bicarbonate. Raising the temperature to 120°C or more and pressure to above 20 bar reverses the reaction, generating a high pressure CO2 stream with low moisture and ammonia concentration. The CO2 can then be processed for sequestration.
Alstom’s chilled ammonia process is one of several new processes being explored for post-combustion capture. Research suggests that chilled ammonia-based CO2 capture can remove up to 90% of the CO2 from flue gases. Although there are several proposed techniques that can separate carbon dioxide from the other gases (such as MEA, Mono-Ethanol Amine scrubbing), Alstom’s chilled ammonia process reduces the amount of energy used to capture CO2 (energy loss). Studies by EPRI have indicated that ammonia scrubbing results in a 10% energy loss, while the older MEA (amine scrubbing) cuts generated power by 29%.