Engineers plan to set fire to a coal seam deep underground in the first in a series of subterranean blazes around Britain that, they claim, will provide clean fossil fuel energy for generations.

There are fears that the technology, which has only ever been used on a large scale in the former Soviet republic of Uzbekistan, will lead to greater greenhouse gas emissions and could poison fresh water.

Underground coal gasification (UCG) involves drilling two shafts down to a coal seam and igniting the coal. Oxygen and water are then pumped down one shaft, causing the coal to burn in such a way that gas that can be used as fuel streams out through the other shaft. In June a government-funded environmental review of UCG will begin, prior to the choice of a site for the first UK trial. This follows Department of Trade and Industry funding of a trial in Spain.

Proponents say it will be possible to scrub the gas clean of greenhouse gases like carbon dioxide once it reaches the surface, so that it will burn as cleanly as natural gas. It could lead to the exploitation of the huge coalfields under the North Sea.

Engineers and geologists hunting for a suitable test site are looking for an area with a coal seam more than 2 metres thick, between 600m and 1,200m underground, with at least 60,000 tonnes of coal, and 500m or more from any old mine workings.

The technology would enable coal to be used as fuel without miners and without slag heaps. Above ground, a full scale installation would feature silos for oxygen and water, two well heads, plants for treating the gas, and a power station.

UGC power generation would produce less CO2 than conventional coal burning, but no less than natural gas.

An investigation into UGC in today's New Scientist warns: "Under the guise of offering a 'clean' technique for unlocking the energy from coal reserves, engineers are actually concocting a way to increase massively the amount of coal the world can get its hands on."

The Soviet Union pioneered UGC in the 1930s, and a plant in Uzbekistan is still in use. A small project in Derbyshire began and ended in the 1950s. More recently, Uzbek experts have had success in trials in Australia and Spain, where gas was extracted from 500m underground.

New Scientist reported that an initial list of 10 possible sites for the British trial had been whittled down to four.

Tests in the US have shown that combustion produces carcinogenic chemicals. One of the biggest problems for the British pilot will be to keep these away from underground aquifers.

LONDON - Britain's Energy Minister Brian Wilson invited yesterday companies to bid for up to 15 million pounds of government funding for the research and development of renewable energy technologies.

"The challenge of climate change is global, and the UK now has the chance to contribute to world-size solutions", he said in a statement.

"But the opportunity is now - others will seize the advantage if we do not."

The 15 million pounds available forms part of a previously announced 260-million-pound package of government support for renewables over three years.

Britain wants to raise renewable power output to 10 percent of its electricity supply by 2010.

At present less than three percent of UK energy supply is classed as renewable.

Researchers at the University of Warwick's Warwick Process Technology Group have devised a process that turns wet waste from sewage farms and paper mills into a source of power.

University of Warwick researcher Dr Ashok Bhattacharya and his team are part of a Europe wide consortium that have cracked the problem of how to extract very pure levels of hydrogen from wet bio-matter, such as sewage or paper mill waste. This very pure hydrogen can then be used in "fuel cells" to power homes, factories and cars. The research consortium have now received GBP2.5million in European funding to work up their lab based solution into larger prototypes. Eventually the research team's "plated membrane reactors" could be built as small industrial units, no bigger than a large room in some cases, and added directly to the sites of sewage plants or paper mills.

Previous attempts to extract pure hydrogen from bio-matter to power fuel cells have only met with limited success, even with dry material.

The new process extracts very pure hydrogen from the more difficult but exceedingly abundant wet bio-matter and even makes a virtue of the water content of the material to generate even more pure hydrogen.

First the waste biomass is gasified breaking it down into its Methane CH₄, water H₂O, Carbonmonoxide CO, and carbondioxide CO₂ and some hydrogen. All these gases are then fed into a reactor which uses them in a chemical reaction which extracts the hydrogen from both the methane and the water. In normal circumstances this reaction would reach an equilibrium and simply stop once a certain amount of hydrogen had been generated. However the research team uses a palladium coated ceramic semi permeable membrane as part of the reactor which only lets hydrogen pass through. This allows the researchers to both harvest very pure hydrogen from the system (it can be over 95% pure) and to keep the reaction going as long as it is fed with the waste biomass as the hydrogen never builds up to the point where a chemical equilibrium would be reached thus stopping the reaction.

The hydrogen produced by this very energy efficient method can then be used to power hydrogen fuel cells. This process is also much cleaner than traditional production of H2 as it does not use up fossil fuels, thus it produces no more CO₂ than would be produced naturally from the material biodegrading and it produces no other emissions such as nitrous oxides.

Other novel engineering in the process includes the use of a coated nanocrystaline catalyst to accelerate the reaction, and particular methods to manage heat transfer and pressure.

The research project brings together the University of Warwick's Warwick Process Technology Group team with Dutch, German and UK firms.

In particular the Dutch firm BTG and the University of Twente have contributed to the gasification process and the Sheffield firm Dytech have contributed to the highly engineered porous ceramics used in the reactor.

For more information contact: ashok.bhattacharya@warwick.ac.uk

  

Akersloot TOTeMs 2002 –11th-12th June 2002; Final calls for registration to participate: Contributed by Peter Roberts Eurotherm Seminar Nr 73: Contributed by Patricia Evrard Post-Doctoral Position – Combustion; Ecole des Mines d’Albi, France: Contributed by Peter Roberts Environmental News: Contributed by Aristide Mbiock World Energy News: Contributed by Aristide Mbiock

 

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Edited: Peter Roberts
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