Coal dust

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

Explosions

Le Petit Journal illustration of the Courrières mine disaster

Coal 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.

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,^[1] 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.^[2] 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 boiler
• Pulverised fuel firing

Notes

References

• "Occupational Safety and Health Guideline for Coal Dust (Less than 5 percnet SiO(2))". Occupational Safety & Health Administration, U.S. Department of Labor. http://www.osha.gov/SLTC/healthguidelines/coaldust-less5percentsio2/recognition.html. Retrieved 2008-08-28. 

• "Technology News 515 - Float Coal Dust Explosion Hazards". Technology News. NIOSH Publication No. 2006-125, Mining Safety and Health, National Institute for Occupational Safety and Health, CDC. April 2006. http://www.cdc.gov/niosh/mining/pubs/pubreference/outputid1717.htm. Retrieved 2008-08-28.