SPECIFICATION:

PARAMETER Penalty/Rejection
Total Moisture 35% (As received)            >35%
Inherent Moisture 16% Max(ADB)
Ash 4% (ADB) Max
Total Sulfur Content 0.60% (ADB) Max
Volatiles Matter 39-44%(ADB) Max
Calorie Value 5500 (ADB)                     5300 Reject
HGI 45-55
Fixed Carbon 39-45%
Physical Size 0 to 50 MM

Coal is a fossil fuel and is classified into four types--anthracite, bituminous, sub-bituminous, and lignite.  Coal is found in seams (veins/coal beds) which vary from a few inches to 100' or more in thickness.  Depending on the amount of ground cover or overburden, the coal can be mined by the surface method (complete removal of overburden) or the deep (underground) method.  In some circumstances, the auger method was used; the perimeter of a hilltop was surface mined and the interior coal was bored using an auger, a large horizontal drilling machine.  The deep mine method originated with miners using picks and shovels to dig the coal (room and pillar method) and then loading it into small carts.  At one time, horses and mules pulled the carts from the miner (who worked at the face of the mine) to the adit (the entry portal of the mine.)  If a surface adit could not be made due to the depth of the mine, then a large elevator or a skip bucket brought the coal to the surface.
The individual coal miner in the deep mine was replaced by machines in the mid-20th century.  The continuous mining machine uses a rotary cutting drum to dig the coal from the face and convey it to a tram car (a motorized cart.)  Another machine using a large cutter bar (similar to a chain saw) makes horizontal cuts at the top and bottom of the coal seam.  

Mining methods are always changing as machinery and technology improve.  Today, huge draglines and power shovels remove entire hilltops to uncover coal seams.  Gigantic bucket excavators standing several stories high mine thick seams in some coal fields.  And underground, the longwall mining machine needs just three miners to cut a 500' wide swath through the coal seam.  With this system, there is no need to even prop up the mine roof--it is allowed to cave in behind the machinery.  Such advances in productivity are the reason why more tonnage of coal is mined in the USA today with fewer than 10% of the coal miners employed in 1940-50. 

Since coal was first mined in earnest some 150 years ago, the industry has been plagued with problems.  Thousands of miners have died in accidents, roof falls, and methane gas explosions.  With the advent of the continuous mining machine, many believe that the coal dust it generated is what is primarily responsible for black lung disease.  And there continue to be environmental concerns for the air, the surface and sub-surface waters, and the landscape.  But, coal has been and will continue to be indispensable for electric power generation and steel manufacturing for the foreseeable future.  Concerns about acid-mine water drainage, the greenhouse effect, or the disappearing horizon, will continue to occupy our environmental debates.

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