Coal Mining
Mining Methods
Coal is mined by two methods:- surface or 'opencast' mining
- underground or 'deep' mining
Surface Mining
Surface mining - also known as opencast or opencut mining - is only economic when the coal seam is near the surface. This method recovers a higher proportion of the coal deposit than underground mining as all coal seams are exploited - 90% or more of the coal can be recovered.Large opencast mines can cover an area of many square kilometres and use very large pieces of equipment, including:
- draglines, which remove the overburden
- power shovels
- large trucks, which transport overburden and coal
- bucket wheel excavators
- conveyors
Underground Mining
There are two main methods of underground mining: room-and-pillar and longwall mining.Room & Pillar Mining
In room-and-pillar mining, coal deposits are mined by cutting a network of 'rooms' into the coal seam and leaving behind 'pillars' of coal to support the roof of the mine. These pillars can be up to 40% of the total coal in the seam - although this coal can sometimes be recovered at a later stage.Longwall Mining
Longwall mining involves the full extraction of coal from a section of the seam, or 'face' using mechanical shearers. A longwall face requires careful planning to ensure favourable geology exists throughout the section before development work begins. The coal 'face' can vary in length from 100-350m. Self-advancing, hydraulically-powered supports temporarily hold up the roof while coal is extracted. When coal has been extracted from the area, the roof is allowed to collapse. Over 75% of the coal in the deposit can be extracted from panels of coal that can extend 3km through the coal seam.Technological advancements have made coal mining today more productive than it has ever been. To keep up with technology and to extract coal as efficiently as possible modern mining personnel must be highly skilled and well-trained in the use of complex, state-of-the-art instruments and equipment.
Top Ten Hard Coal Producers (2011e) | |||
---|---|---|---|
PR China | 3471Mt | Russia | 334Mt |
USA | 1004Mt | South Africa | 253Mt |
India | 585Mt | Germany | 189Mt |
Australia | 414Mt | Poland | 139Mt |
Indonesia | 376Mt | Kazakhstan | 117Mt |
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