OT Coal Gasification

[Adam Aglionby]

Its not underground fires honest:

"The process of gasification involves drilling horizontally into a seam and then injecting air and oxygen to produce syngas"

[harryagain]

The problems are that where the fire runs can't be controlled. The fire often can't be extinguished. The land above subsides. Guaranteed eakage of gases and other contaminants into ground water and to the surface. Cunningly invisible under the sea. But nevertheless still causing pollution.

Hence eminently suitble for the home counties and othe whinging leafy surburban NIMBYs. Ten times worse than fracking. The gas produced is low quality and filled with pollutants.

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[Chris Hogg]

A sort of underground old-fashioned gas-works! Bearing in mind the amount of tar and other nasties those gas-works produced, I can't imagine the pipework drawing off the gas produced like that, staying un-clogged for long!

[Tim Streater]

The old method of gas from coal was what we all used until North Sea gas came on stream. It was make by heating coal in the absence of air. And indeed this produced gas, as harry so wittily puts it, of "low quality and filled with pollutants". But that was not what was piped around the place. It went through a purification process which removed all these pollutants, simply because the removed stuff made excellent feedstock for the chemical industry.

Where d'ye think coal tar came from, eh? What d'ye think the likes of Perkin were using when they discovered aniline dyes? Coal tar from the coal gas production process.

One of my brother's school prize books had an article detailing this process, which I read when I was about 10.

[Chris Hogg]

Well, yes, I know all that; every little town had a gas-works, including ours. But I was referring to the pipework that takes the gas from the..er..'combustion face', to the clean-up plant, which would presumably be on the surface, and a whole mine-depth's distance away.

[Tim Streater]

Hard to say, since I don't know what has been proposed to be done.

[Nightjar]

I was under the impression that underground gasification works best with very deep seams, which can't be reached by conventional means. Those contain very hard coal, which has relatively little in the way of unwanted by-products.

[newshound]

And also, I doubt if you have a single pipe from the, er, coal face. Rather that once you get the seam burning (which presumably means having an air injection route?) you will seek to tap off gas heading upwards through natural fissures and voids which will tend to condense (filter) the tarry volatiles.

[harryagain]

Not the same at all. The coal is heated by burning it, (ie adding air). This means as well as fuel gases (H, CH4, CO), all the combustion products are present. ie CO2, N, NOX, SO2. So gas quality is very low. Expensive to clean up, if it were to be used domestically. I expect it would be used in power stations but there would be a lot of issues and problems to overcome.