Why is coal mine explosion?

Methane explosions occur in mines when a buildup of methane gas, a byproduct of coal, comes into contact with a heat source, and there is not enough air to dilute the gas to levels below its explosion point, said Yi Luo, an associate professor of mining engineering at West Virginia University.

Are explosives used in coal mining?

Explosives used in coal mines have to be efficient in blasting rock and coal but at the same time should not ignite the flammable atmosphere that can sometimes be encountered underground. When used, the explosives are placed in drilled holes and shot in rounds, with a short delay between each shot.

Why does coal dust forms an explosive mixture with air?

Coal dust suspended in air is explosive—coal dust has far more surface area per unit weight than lumps of coal, and is more susceptible to spontaneous combustion. As a result, a nearly empty coal store is a greater explosion risk than a full one.

Is a mine a bomb?

A mine is an explosive placed underground or underwater that explodes when disturbed, or when remotely triggered. Mines, unlike bombs, are placed in situ and then require some other stimulus from a target before they will detonate.

What explosives do they use in mines?

Dynamite, a nitroglycerin-based explosive, is rarely used today for blasting at surface mines in Illinois. Blasting agents account for almost 99\% of the explosive materials used. ANFO, ammonium nitrate and fuel oil, is the most common explosive.

How do you stop explosions in mines?

Research strategies include eliminating ignition sources, minimizing methane concentrations and coal dust accumulations, applying proper dispersible rock dust in sufficient quantity at all locations, using supplemental protection such as passive and active barriers to suppress propagating explosions, understanding the …

How do you stop coal dust explosion?

Coal dust explosions in underground coal mines are prevented by generous application of rock dust (usually limestone). If an explosion should occur, the rock dust disperses, mixes with the coal dust and prevents flame propagation by acting as a thermal inhibitor or heat sink.

Why does dust explode violently if ignited?

Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials.

How does dust explode?

Dust explosions are the result of high concentrations of combustible dust particles rapidly combusting inside an enclosed space. This will mix the dust with the oxygen in the air, which will make the explosion bigger, and potentially fuel a second dust explosion – or even several.

What happens when a coal mine explode?

The pressure wave or wind forces created by a small methane explosion can scour the mine entry, blowing coal dust up into the air. Once this dust is ignited, a chain reaction effect can occur and flame propagation can continue to spread over long distances consuming available fuel and oxygen and generating large volumes of toxic gases.

How can we prevent methane explosions in coal mines?

Ventilation is the most common method to avoid such methane explosions in coal mines. Large fans are used to blow air out or draw air into mines, but Luo stated that mine ventilation is still a complicated science. “In coal mines, we are required to control the concentration [of methane to] less than 1 percent,” he said.

Is methane or coal dust more explosive?

While methane is easier to ignite, the explosion pressure and heat value of methane is not as high as coal dust. In most cases, dust explosions are first caused by methane explosions, said Luo.

What was the worst mine explosion in the United States?

The worst disaster caused by a coal mine explosion in the U.S. occurred in 1907 when 362 miners were killed in Monongah, WV. How is methane controlled from mined-out areas? Coal mines generally have active mining zones and areas that were previously mined.