Coal Mining Technique
Coal Mining Technique
Coal Mining Technique
As was the case 50 years ago, most coal is produced from two major types of mines--
underground and surface. But the methods for recovering coal from the earth have
undergone drastic changes in the past 25 years, as a consequence of technological
advances.
Fifty years ago when most coal mining was done manually, underground mines accounted
for 96 percent of the coal produced each year. Today, almost 60 percent is produced from
surface mines. Most underground mines in the United States are located east of the
Mississippi River, although there are some in the West, particularly in Utah and Colorado.
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mining coal
to 600 foot long face (longwall) of the
coal seam. This machine has a
revolving cylinder with tungsten bits that
shear off the coal. The coal falls into a
conveyor system which carries it out of
the mine. The roof is supported by large
steel supports, attached to thelongwall
machine. As the machine moves
forward, the roof supports are
advanced. The roof behind the
supports is allowed to fall. Nearly 80
percent of the coal can be removed
using this method. The remaining 11
percent of underground production is
produced by conventional mining which
uses explosives to break up the coal for
removal.
Half of the minable surface coal in the
United States is located in the West, but
significant amounts are also present in
Appalachia and Midwestern states.
Surface mining is used when the coal
seam is located relatively close to the
surface, making underground mining
impractical.
Most surface mines follow the same basic steps to produce coal. First, bulldozers clear and
level the mining area. The topsoil is removed and stored for later use in the reclamation
process. Many small holes are drilled through the overburden (dirt and rock above the coal
seam) to the coal seam. Each is loaded with explosives which are discharged, shattering
the rock in the overburden. Giant power shovels or draglines clear away the overburden
until the coal is exposed. Smaller shovels then scoop up the coal and load it onto trucks,
which carry the coal to the preparation plant.
Once the coal is removed, the land is returned to the desired contour and the topsoil is
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mining coal
replaced. Native vegetation and/or trees are planted. Coal companies operating surface
mines must comply with strict requirements and regulations of the Federal Surface Mining
Control and Reclamation Act. A crucial part of the surface mining process is restoring a
mined site to acceptable ecological conditions, which means it must be made as productive
as it was prior to mining. There are farms, parks, wilderness and recreation areas on what
was once surface mines.
The major stigma associated with the coal industry today is the abandoned or "orphan"
mines of the early coal mining years. These orphan mines are systematically being
reclaimed under the Surface Mining Act taxes coal producers at the rate of 35 cents a ton for
surface mined coal, 10 cents a ton for lignite mined coal, and 15 cents a ton for underground
mined coal. The tax is paid to the government and is used to reclaim the orphaned mines.
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