Underground coal gasification (UCG)

[brooki]

I raised this in another thread which seems to have sunk down the main board unread, so please feel free to delete as appropriate.

 

See this link for a general definition of UCG

http://www.coal.gov.uk/resources/cleanerco...es/ucgintro.cfm

 

and this for a more general explanation:

http://en.wikipedia.org/wiki/Gasification

 

Basically, oxygen and steam is pumped underground down a horizontal well (used in Azebaijan, also with pilot tests in Oz, Spain and UK). This burns the coal in-situ in a controlled manner, and the 'syngas':

 

http://www.syngasrefiner.com/

http://en.wikipedia.org/wiki/Syngas

 

is piped to the surface where it can be burnt in a power plant. This is essentially the same as normal gasification introduced in the 1800s to produce Town gas, except it is performed in-situ, which obviates the need for surface gasifiers, and makes CO2 sequestration (obviously a big deal in current global warming discussions) much easier. There's some reference to UK UCG work by a company called UCG Engineering Ltd which seems to have connections with Tullow oil, (their website was lat updated Jan '06):

 

http://www.coal-ucg.com/index.html

http://www.ucgp.com/

 

which seems to imply the UK is leading the way here, with possible exports of technology to China and India. The concept isn't new, though having been developed in the 1960s.

 

This is different to 'coal bed methane' production

 

http://en.wikipedia.org/wiki/Coal_bed_methane_extraction

 

whereby the depressurization caused by removing the water from a coal seam causes methane in the surrounding coal to move into solution in the water which is pumped to the surface. Big problems are the numbers of wells required, heavy contamination of the fluid/gas mixture and lowering of the water table. There doesn't seem to be quite the geological/technical hurdles with UCG, as there are with coal bed methane.

 

I thought this was interesting from the UCG Engineering ltd website

The possibility of gasification of the vast reserves of coal that lie offshore would eliminate still further the environmental impact of power generation by UCG. The UK, which has large reserves in the shallow waters of the North Sea, has included a pre-feasibility study of offshore UCG as part of its current programme.

and here's their general conclusions:

1. As the UCG process becomes better developed, UCG has a very good chance of succeeding as the modern method of exploiting and winning the energy stored in the massive coal resources of the world.

2. In- seam will only become more attractive for UCG if the currently high costs of specialist drilling can be substantially reduced. This has to be addressed as a priority.

3. Environmental considerations will pre-dominate in any future development of UCG, eventually, even those located away from populated areas.

4. Onshore UCG in populated areas, like the UK and other parts of Europe, will be permitted only at considerable depth, where the possibility of endangering aquifers and the leakage of gas can be virtually eliminated.

5. The combination of UCG and CO2 sequestration offers an interesting possibility for the sustainable consumption of coal resources, particularly those beyond mineable depth. Further research is required.

6. It is unlikely that a single coal producing country has the resources or incentive to fully develop UCG. International collaboration is the only realistic means of developing a major commercial UCG industry.

 

I don't have any background in this, so you'll have to do your own research, but the topic looked interesting to me.

 

TLM