Underground Coal Combustion

UPDATE BELOW

An article in the Wall Street Journal reports on a technology it says is getting a lot of attention in China, which itâ''misleadingly, I believeâ''refers to as underground coal gasification. That makes it sound as if coal is gasified, as in IGCC, creating a syngas thatâ''s burned. But actually the technology seems to more closely resemble oxyfiring, a technology Vattenfall is just now demonstrating for the first time at larger-than-laboratory scale at a plant in East Germany. In the approach described in the Journal, coal is ignited underground and fed a piped-down stream of pure oxygen; the combustion yields nitrogen-free gases including carbon dioxide, which can be separated and kept underground.

The Journal says this technology was invented in the Soviet Union in the 1930s and demonstrated at a large scale in Uzbekistan.

Coal combustion in China and India is the biggest single aspect of the long-term climate problem, and was the subject of a two-issue special report in IEEE Spectrum, in November and December 1999.

UPDATE, 9/18/08:

My fellow energy writer and editor Peter Fairley has alerted me to an accuracy in this blog. From the cryptic Wall Street Journal description of the technology, I came away with the impression that it was closely analogous to oxyfiring, where coal is burned in an atmosphere of pure oxygen. Underground coal gasification is in fact more closely analogous to IGCC, inasmuch as a syngas consisting of carbon monoxide and hydrogen is created, as well as methane and carbon dioxide. The combustible gases can be burned at the surface to drive turbines; in some situations at least, the carbon dioxide can be stored in the subsurface voids left by the gasified coal.

A basic description of the process and its variants can be found at:

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

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