With oxyfuel combustion fossil fuels are burnt in pure oxygen instead of normal air. Virtually all the gas that’s emitted is composed of CO2 and water vapour. The vapour is condensed out and the CO2 is then captured.
Conventional boilers combust coal in air, which consists of 78% nitrogen, 21% oxygen, and trace gases including CO2. This results in a flue gas stream that’s rich in nitrogen and dilute in CO2, (around 12 - 15%) making CO2 capture more challenging. By removing the nitrogen first and combusting the coal in nearly pure oxygen, it produces a much more concentrated stream of CO2 (around 90%), which allows for much easier CO2 capture.
Oxyfuel combustion with CO2 storage is currently in demonstration phase.
In 2008, the world’s first pilot project to demonstrate oxyfuel technology at a coal-fired power plant commenced. The Schwarze Pumpe project in western Germany is owned by the European energy company, Vattenfall, and it is successfully demonstrating the capture of CO2 emissions with a purity of over 99%.
In Biloela, Queensland, a low-emissions oxyfuel demonstration project is being established at the Callide Power Station. Oxyfuel combustion capture applies a new technology to conventional power plant boilers to capture CO2 emissions. This has the advantage in that it can be retrofitted (‘bolted on’) to the thousands of power plants already in operation around the world, as well as being applied to new power plants. It has the potential to be one of the most cost-effective methods of capturing CO2 emissions from coal-fired power plants. Research is being carried out to reduce costs and improve efficiency.