Courtesy of the World Coal Institute www.worldcoal.org
Over 5540Mt of hard coal is currently produced ? 97% growth over the past 25 years. Coal production has grown fastest in Asia, while Europe has actually seen a decline in production.
The largest coal producing countries are not confined to one region ? the top five producers are China, the USA, India, Australia and South Africa. Much of global coal production is used in the country in which it was produced, only around 15% of hard coal production is destined for the international coal market.
Brown coal production was 945Mt in 2007. Germany remains the world?s biggest producer of brown coal.
Mining Methods Coal is mined by two methods: surface or ?opencast? mining and underground or ?deep? mining. The choice of mining method is largely determined by the geology of the coal deposit. Underground mining currently accounts for about 60% of world coal production; although in several important coal producing countries surface mining is more common. Surface mining accounts for around 80% of production in Australia, while in the USA it is used for about 67% of production. 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; and The overburden of soil and rock is first broken up by explosives; it is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured and systematically mined in strips. The coal is loaded for transport to either the coal preparation plant or direct to where it will be used.
Underground 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 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. The choice of mining technique is site specific but always based on economic considerations; differences even within a single mine can lead to both methods being used.