How is coal produced?
Geology and occurrence generally determine which of the two primary methods of coal production will be used. For relatively continuous coal seams close to the surface, surface mining is used. Where the coal is deeper, underground mining is used.
The first stage in surface mining is to clear the topsoil from the area and stockpile it for reclamation. The overburden, material between the top soil and the coal seams, is removed next by huge draglines, and also stockpiled. With strip mining, the coal is removed next by power shovels or wheel excavators and transported by enormous dump trucks or high-capacity conveyor belts. As the production area moves along the coal seams, the area already mined is reclaimed by replacing overburden and soil, recontouring the land to its original topography and replanting. With open pit mining, coal is produced from large excavations which are deepened and widened as mining progresses. Surface methods generally recover a greater proportion of the coal in place. Approximately 95 per cent of Canada’s coal is mined using surface methods.
Underground mining uses two methods to recover coal deposits. With room-and-pillar mining, large rooms are cut into the coal face leaving large pillars of coal to support the mine roof. This method may leave up to 50 per cent of the coal in place, although some of the pillars can be removed later in the mining operation. Longwall mining uses machines to cut and remove coal from the coal face. The roof is held in place by hydraulic supports. Once the coal face is mined out, the machinery and supports are withdrawn and the roof is allowed to collapse.
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