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Underground Coal Mine Fires
And some ideas on how to put them out! Extinguish mine fires that have been burning for years?!
Amazing as it may seem, coal fires can burn underground for a long time. If a seam of coal in a mine catches fire, it can go on burning, and that produces various problems. For one thing, it's a waste of coal, and for another, it pollutes the environment (it's bad enough burning coal for useful purposes, but for it to burn without doing any good is appalling), and also it can result in the nearby above-ground area becoming uninhabitable, both because of toxic fumes and also because the ground tends of collapse unpredictably.
I first heard about the coal mine fire problem when I was looking into an anomaly I had found to do with the movie SILENT HILL. There was something funny about the date and age of the film, and I seem to remember seeing it many years before 2006 when it was supposed to have been made! Anyway, it turns out that the town of Silent Hill was based on a real town, Centralia, which is in Pennsylvania. Admittedly the real town didn't have such severe problem with ghosts, demons, fanatical religious cults, anomalous radio interference problems, and people disappearing, but it did have an underground coal mine fire. The fire started in 1962 during a controlled burning of the rubbish dump, but then the fire got into underground coal seams, and it went on burning during the 1960s, 1970s, and 1980s, and a few people left the town because of the poisonous emissions from underground, and the collapsing ground, and then the US Government paid people to leave, and that caused a difference of opinion between those who wanted to accept the offer and those who wanted to stay. Despite some brave expensive attempts to put the underground coal fire out, it still burned on during the later decades, and the place became a ghost town.
Here are a few Centralia references and resources to help with research:
www.pahighways.com/features/centralia.html - includes some interesting aerial photography
http://technology.infomine.com/enviromine/case_hist/centralia/fire.html - including underground temperature map!
Further investigation into the problem of mine fires shows that there are a great many of them, burning around the world, in various different places. There are some very large underground fires in China, and some notable coal fires in India, Australia, Canada, and now that there is infra-red imaging, it's possible to see the problem is widespread.
Here are a some global resources:
Practical solutions towards extinguishing mine fires... See www.libertygasturbine.nl and www.steamexfire.com for more info.
Underground coal mine fires are an ecological disaster and a dreadful waste of fuel. Also, they are difficult to extinguish. It's impractical to have the fire brigade going down a mine to extinguish a fire which is approximately "unreachable". Any air fills with poisonous fumes, and it's unsafe to dig tunnels to reach a fire as the whole structure is at risk of subsidence.
Although it's tempting just to mourn a mine fire and stick a few signs up to make it a tourist attraction and make wild guesses about how many centuries it's going to burn for, there is a set of more practical solutions. As with the problem of how to get a spider out of the bath, once you look at the situation a different way, solutions come to mind.
A fire underground can't go on burning just because it's got plenty of fuel and because no-one can get at it to put it out. It needs another vital ingredient: Oxygen. (There's an absence of mine fires under the sea, even though there's plenty of fuel such as North Sea Oil, gas, etc). So, an underground fire has to get some air down there by sneaking it down when no-one is looking. In practice this is usually gone by first setting up a distraction such as an outgassing of noxious fumes, possibly the destruction of some buildings, etc, and then, in some unobtrusive location, a crafty crack can be opened up in the road or on a bit of ground where no-one's looking, as all the people are distracted by the outgassing, smoke, fire coming up out of the ground, etc somewhere else. No-one notices the air being sucked into the ground where the fire is "breathing in", and their attention is drawn to where it is "breathing out".
If you wanted to seek out the air inlets to the fire, you could go poking around with something smoking on the end of a stick, like they have in aerodynamics labs. Upon finding such air inlets, it would be possible to put up cloches (plastic sheet suspended on an array of sticks), and then fill the area under the cloches with either nitrogen (from liquid nitrogen) or de-oxygenated air (which, strange as it may seem, can be made by using FIRE to take the oxygen out of the air). The unsuspecting underground fire will then suck in the no-oxygen gas or nitrogen, and will go out.
That's not the end of the problem, because there's a lot of residual heat remaining underground from where the fire has been burning for a long time. So, either the entire ground has got to be sealed up (which could be expensive if it's acres and acres of land!), or the heat has got to be extracted. Fortunately, there are people who are in the business of finding and using underground heat. They are in the geothermal heat business. Usually they are on the lookout for geological energy, but the leftover embers of an underground coal fire will do just as well! A nice touch to this is the fact that energy can be won back from the fire which had already burned the coal. It's a kind of retrospective recovery of energy.
Other points of note:
* No, the cloches will not burn, as they are over the air INLETS, not the hot exhaust gas outlets!
* Yes, you do have to make sure the fire is out and the ground has cooled down. If there's still some hot bits underground, the fire can re-light spontaneously if it gets any air again.
* I am willing to enter into affiliate arrangements with folks in the nitrogen business. Links and reciprocal links are also a possibility, but affiliate programs are even better as this produces dedicated pages like the disc drive recovery business.
* If you're worried that your house might be over a mineral resource which could catch fire, make sure your home insurance covers you for such an eventuality. Chances are, you won't be the first person in the town to find out there's a problem. Also see volcano insurance