is a fine powdered
form of coal
, which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle
nature of coal, coal dust can be created during mining
, or by mechanically handling coal.
Coal dust suspended in air
. Coal dust has far more surface area
per unit weight
than chunks 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. The worst mining accidents
in history have been caused by coal dust explosions
, such as the disaster at Senghenydd
in South Wales
in 1914. Such mining accidents
were usually initiated by firedamp
ignitions, the shock wave
of which raised dust from the floor of the mine galleries to make an explosive mixture. The problem was investigated by Michael Faraday
and Charles Lyell
in the explosion at the colliery situated at Haswell County Durham
of 1844, but their conclusions ignored at the time.
The Luisenthal Mine Disaster and the explosion at Benxihu Colliery are two examples of this type of explosion caused by coal dust.
The main attempts at prevention include using safety lamps, adding stone dust coffers to mine galleries, and watering workings.
Lung and skin problems
Coal workers' Pneumoconiosis
, or black lung disease, is caused by inhaling
coal dust, typically dust produced in coal mining
According to George Orwell, coal miners could develop characteristic tattoos owing to coal dust getting into wounds. This can also occur with substances like gunpowder.
Coal dust in energy generation
For use in thermal power plants
, coal is ground into dust using a device called a powdered coal mill
. The resulting product, called powdered coal
or pulverized coal
, is then generally used in a fossil fuel power plant
for electricity generation
Pulverised coal is a significant dust explosion hazard, as large quantities are suspended in air for transfer from the mill to the power plant. Explosions have occurred when the flow drops and flames in the burning chamber pass back along the ductwork delivering fuel.