| Carbon Capture |
| Wednesday, 26 April 2006 | |
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Paul Fennell and Stuart Scott discuss underground storage of CO2 In the UK we use 50 million tonnes of coal a year for electricity generation. This figure is dwarfed by use in China, where 1582 million tonnes of coal are burnt. Global reserves of coal exceed those of oil and gas combined, but if all the coal in the world were burnt it would be impossible to stabilise atmospheric carbon dioxide at an acceptable level. If we are to cut carbon dioxide emissions we must limit emissions from fossil fuels long before they run out.The development of carbon capture technology—to which both the EU and China are committed—is a key factor in limiting future emissions.
Our research in the Combustion Group at the Department of Chemical Engineering focuses on two technologies which could be used to produce pure carbon dioxide, ready for sequestration. One technology utilizes limestone (CaCO3) rocks to shuttle carbon dioxide from a dilute stream of carbon dioxide in a power station exhaust to a separate reactor where pure carbon dioxide is driven off.The solid CaO is recycled to react with the exhaust stream, and carbon dioxide is produced at a pressure and concentration suitable for sequestration. An alternative uses a solid carrier such as iron to transfer oxygen from the air to react with a fuel: this technology produces a pure stream of CO2 because the oxygen reacting with the fuel has been separated from the air to start with. The time-scale over which these technologies could become commercially viable is, in essence, set by the nominal value of CO2 emissions. Enhanced oil recovery via CO2 injection is already a reality. Given reasonable political will (and sufficient funding), the technologies we are investigating could be working at full scale within 10 years. Other technologies which are able to produce a pure stream of CO2 are closer to market, for example oxy-fuel combustion, where the fuel is combusted in pure (and expensive) oxygen rather than air, and the scrubbing of CO2 from the gases produced from a power station using an amine. However, these latter two methods reduce power station efficiency, and so development of the full potential of carbon sequestration will require continued research. Paul Fennell is Post-Doctoral Researcher at the Department of Chemical Engineering Stuart Scott is a Lecturer at the Department of Engineering |
Carbon capture aims to recover the carbon dioxide released from burning fossil
fuels, ready for storage underground. Suggested storage sites include saline
aquifers (vast underground watercontaining rock formations) and depleted oil
and gas wells. The Intergovernmental Panel on Climate Change suggests that that
full carbon capture facilities could decrease emissions of a typical modern
coal-burning power plant by up to 90%, making development of this technology
an attractive prospect. The sequestration of CO2 does, however, have difficulties:
it requires the identification of stable areas for disposal on a geological
time-frame, and has substantial infrastructure costs. Additionally, there are
concerns over the possibility of leakage back into the atmosphere and of unpredictable
environmental effects. In the UK we could sequester large quantities of CO2
in depleted oil and gas wells using the existing infrastructure. Injecting CO2
into these fields can also increase the amount of oil recovered. | < Prev | Next > |
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