On Saturday night, about 9 p.m., a short, sharp explosion rattled one of Russia's largest coal mines, a deep maze of underground tunnels located in Siberia. About 370 miners were working at the time.
Most of them came hurrying out of mine entrances. But not all. Managers organized rescue teams and sent about 50 people back into the Raspadskaya mine to hunt for survivors - and bodies. In the best of circumstances - which would not be in the panic of an emergency, in the middle of the night - this would be a daunting task. The mine's tunnels (an estimated 200 miles worth) plunge steeply downward, to a depth of some 1,650 below the surface and safety.
The rescuers were, apparently, near the bottom of the mine when the second - much larger - explosion occurred some four and a half hours after the first. The blast ripped apart the mine's main shaft and shattered a five-story building near the entrance. As of today, sixty workers are known dead in the explosions, thirty are still missing, and Russian Prime Minister Vladamir Putin is raising angry questions about safety standards and decisions at the mine.
Sound familiar? It should because we in the U.S. just went through a very similar disaster only last month, at the Upper Big Branch Mine in West Virginia. Twenty-nine mine workers died in that fire and explosion; it was the highest death toll at a U.S. mine in 40 years. The track record is worse in Russia; this week's tragedy - even if all 90 are dead - will not match the death toll at another Siberian mine two years ago. One hundred and eight miners died in that inferno.
But all have the same cause in common - a lack of careful safety procedures which led to a build up of highly flammable methane gas. Coal mines always contain methane; it's just another fossil fue, another useful chemical bundle of carbon and hydrogen, trapped underground. It's often in the same seams where coal is located. It naturally seeps out during excavation and it can be managed to a fair degree with a combination of venting devices, monitors and alarms, and rigorous training. Because if methane builds up, a single spark from a machine can ignite it, turning it into a torch-like fuse for the explosive coal dust that also builds up in those tunnels.
This was the scenario at Upper Big Branch, which has led to a federal investigation of the mine's manager, Massey Energy. This was the scenario at Russia's Ulyanovskaya mine three years ago. This is the suspected scenario at Raspadskaya. And, just to repeat myself, as I I wrote in my first methane calculation post, it was the cause of the 1812 disaster at Britain's Spelling Mine, which killed 93 miners and prompted the invention of safety lamps for miners (which got rid of open-flame lighting). The standard formula for mining disasters - methane build up, coal dust build up, fire, boom - has been known to generations of miners and regulators.
Are dead miners somehow considered just collateral damage in our drive for energy resources? Is mine safety so difficult after more than two hundred years we still can't get it right? As we calculate the risks of methane-fed mine fires against expenditures on safety, why haven't we reached the obvious conclusion?
Because the only correct answer to the methane calculation is that lives are the most valuable of all resources - yes, even the lives of the unheralded workers who toil more than 1,000 feet below to surface to feed our mills, our homes, and our fuel addictions.
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Methane in air has a clear lower explosive limit and a clear upper explosive limit. Between those limits it is explosive and outside those limits it is not. When a combustible dust is added, things get more complicated. Dust lowers the explosive limit, but dust is usually pretty hard to ignite. Combustible dust plus a combustible gas is a lot easier to ignite, even when the gas is below its lower explosive limit. There is no upper explosive limit for a combustible dust plus air mixture.
The usual practice is to dilute coal dust with rock dust which is pulverized calcium carbonate (limestone). The problem is it takes 3 parts limestone to one part coal dust to make it non-explosive and that is a lot of limestone. Limestone which has to be hauled into the mine and costs about as much as the coal is worth (most of that cost is shipping and handling).
The problem is that coal contains methane, and when coal is broken from the mine face, methane is released along with coal dust. The initial mixture of coal, air and methane is extremely likely to be explosive, and there isn't much that can be done to make it non-explosive except to dilute the air with an inert gas, but then the O2 level isn't high enough for people to breathe (according to regs, people can survive in atmospheres that are low enough so that a flame won't propagate (~12% O2) but then asphyxiation is another risk).
Once an explosion starts, the pressure wave moves out at the speed of sound, the combustion front moves much more slowly, perhaps 10 feet per second. The pressure wave can kick up dust that is on the floor of the shaft, or on any horizontal surface. Then there is a dust cloud to propagate the flame front when the flame front reaches it. In a confined space, like a mine shaft, the pressure behind the flame front increases which accelerates the flame velocity.
The pressure wave kicking up dust when can then propagate the flame front is the reason that so much rock dust needs to be used and used frequently. The whole depth of the dust layer needs to have 75% limestone or it can propagate an explosion. There are better inerting solids, but they are a lot more expensive than limestone and not that much better. Keeping everything wet helps a lot, but increases the risk of electrical problems, makes things slippery, and increases the corrosion of the equipment (by a lot). If you let things dry out, then the risk is right back where it was. You can âfloodâ mines with firefighting foam, a person can move and breath in a foam that will not support a fire.
It is a tough problem to extract coal safely under the best of conditions. When you cut corners, it becomes impossible.
I am loving you here on ScienceBlogs!! How fierce are you?
hi, isis! glad to be keeping you company on Scienceblogs. loved your post today.
so, fierce? mama lion but only when i have to be. deborah
Yes. Always have been. Ordinary working people are merely regarded as expendable assets. Now, expensive machinery on the other hand, that's an investment which must be protected... It's exactly the same reasoning which concludes that "the economic logic behind dumping a load of toxic waste in the lowest wage country is impeccable". People are only considered to be "worth" as much as they earn.
Yes, it sucks. Welcome to capitalism.
"Are dead miners somehow considered just collateral damage in our drive for energy resources? Is mine safety so difficult after more than two hundred years we still can't get it right? As we calculate the risks of methane-fed mine fires against expenditures on safety, why haven't we reached the obvious conclusion?
"
I realize the questions are rhetorical, really, but the answers are: Yes, No, and Money repectively.
The simple fact is, it's more profitable (and, pretty much, always has been) to risk someone else's life than to install proper safety gear unless the Bad Ol'gubmint moves in and distorts the pricing relationship with regulations.
As an added bonus. the poor sods who do the being blown up part are usually so poor, ignorant & codependent that they see no other choice.
@Dunc:
Which is cheaper to insure?
@Stephen: I think the cost of installing and maintaining safety equipment is actually pretty trivial. The expense comes when your safety equipment is telling you to shut the mine down until you make it safe again, at which point you sabotage or ignore the safety equipment, as Massey is alleged to have done.