Coal dust 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, transportation, or by mechanically handling coal.
Risks
ExplosionsCoal dust suspended in air is explosive -- 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 1913 in which 439 miners died, the
Courrières mine disaster in Northern France which killed 1099 miners, the
Luisenthal Mine disaster in Germany, which claimed 299 lives in 1962, and the worst: the explosion at
Benxihu Colliery, China, which killed 1549 in 1942. Such 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 at
Haswell County Durham of 1844, but their conclusions were ignored at the time. The main attempts at prevention include using
safety lamps, adding stone dust coffers to mine galleries, watering workings and ensuring efficient
ventilation of all the workings.
Coal dust in energy generationFor use in thermal
power plants, coal is ground into dust using a device called a
powdered coal mill.
[1] 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.
See also
Pulverized coal-fired boilerNotes
^"Powdered Coal Mill".
Engineering Dictionary. EngNet.
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