Focus on Coal
New life for old coal
A proposed scheme to use coal in a greenersand safer way involves burning it underground to generate energy.
Una innovadora propuesta conlleva la combustión subterránea de carbón para generar energía.
Ein vorgeschlagenes System involviert die Verbrennung von Kohle im Untergrund zur Energieerzeugung.
R
esearchers at the University of Leeds in the UK are exploring a greener, safer and cheaper way of using coal from deep underground seams as an energy source.
Under the proposed scheme coal would be burned underground to generate energy, offering a new lease of life to coal seams that are too expensive to mine. Waste greenhouse gases would also be stored in the rock, making the process virtually carbon neutral.
Profile scanners Coal-fired power plants still have a sizeable carbon footprint, despite advances in technology that have made them ‘greener’. Many of the world’s coal reserves are also lying unused because the seams are simply too deep to dig out. University of Leeds engineers, together with colleagues from across Europe, hope to solve both of these problems in a €3 million project funded by the European Commission. “Te potential environmental impact of this scheme is enormous,” said Dr Yong Sheng, who is leading the University of Leeds part of the project. “By 2020, all power plants across Europe will have to incorporate some system of carbon capture and storage to meet EU targets on greenhouse gas emissions. Tis two-step process makes it easy to meet these targets, whilst making the most of coal seams that might otherwise be impossible to exploit.”
Underground coal gassification During the first step – a process known as underground coal gasification (UCG) – oxygen or enriched air are injected into the un-mined seam together with water and the coal is burned underground at high pressure. Tis produces streams of combustible gas, rich in hydrogen- and/or methane and CO2
into the rock. Te proposed two-step process consequently provides a source of clean energy with a near-zero carbon footprint. UCG has been tested in numerous small-scale trials worldwide. Te technology was applied on an industrial scale in the former Soviet Union and is still operating in Uzbekistan. Te
proposed scheme for on-site, underground CO2 storage is, however, completely new. “Tere is a lot of talk about the need for carbon capture and storage, but nearly every suggested system has the same problem: the high cost of capturing and transporting carbon dioxide to the storage site. Tis scheme would be much more cost-effective – as well as virtually carbon neutral - because we wouldn’t need to move the gas anywhere,” said Dr Sheng.
Potential hazards Researchers will assess the viability of the scheme at a test site in Bulgaria where coal is buried more than 1200m underground. Te international team, including the Leeds engineers, will use data from this site to model the complete process – including combustion, gas extraction and CO2
storage. Tey will pay particular attention
to potential environment hazards, such as the chance of stored CO2
the rock. Te project is being co-ordinated by the
, which can
be extracted from underground through long boreholes. Once above ground, the hydrogen- and/ or methane-rich gas stream could be used to generate power in conventional turbines or fuel cells, or for industrial heating. Meanwhile, the CO2
-rich stream of gas would be compressed and injected back into the rock, filling the space where the coal had previously been. In other words, most of the carbon produced by the underground burning would be locked
Bulgarian company Overgas Inc AD. Te other partners are the Geological Institute of the Bulgarian Academy of Sciences (BAN), Institute for Solid and Fuels Technology Applications (Greece), Instituto Superior Técnico of Technical University of Lisbon (Portugal), DMT GmbH &Co KG (Germany), Geo- ForschungsZentrum Potsdam (Germany) and UCG Engineering Ltd (UK). Te project is funded by the European Commission’s Research Fund for Coal and Steel, grant agreement number RFCR- CT-2010-00003. More details about the project will be available at
http://www.ucg-co2.eu. Te Faculty of Engineering at the University of Leeds is ranked seventh in the UK for the quality of its research, according to the 2008 Research Assessment Exercise). Te university is one of the largest higher education institutions in the UK. ●
For more information, visit
www.leeds.ac.uk www.engineerlive.com 63 leaking through cracks in
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