Teach PA History
Edible Coal Mining
Background Information for Teachers

Uses of Coal and Coal By-Products

The uses of coal are numerous and varied. Some may even surprise you. Coal is used in the production of steel, for electricity generation, and for other industrial uses. Bituminous coal is also called coking coal and is considered to be high-quality black coal which is converted to coke for the manufacture of steel. When heated in large, airless ovens, virtually all the coal's volatile matter is driven off in the form of gases and vapors, while the material left behind forms hard, thin-walled bubbles. This remaining material, coke, is composed almost entirely of carbon. Coke is used in blast furnaces to provide a consistent, high, clean heat which converts iron oxide (iron ore) into metallic iron. Coke also supplies the carbon required in steel manufacturing. Even the by-products of this process are valuable. These by-products include refined coal tar used in plastics, explosives, dyes, pitch, and also ammonia and other chemicals used in fertilizers, cement, bricks, and tiles.

Methods of Extraction

There are two main methods of mining coal: surface and underground mining. The method ultimately used is determined by the depth of the coal deposit. When the coal seam lies close to the surface, surface mining techniques are used. Different types of surface mining include: strip mining, open-pit mining, and mountain top removal. In surface mining the rock and soil lying on top of the coal seam (also known as overburden) is first broken up by explosives. It is then removed by excavators, or, if only a small amount of overburden exists, by truck and shovel. Once the coal seam is exposed, it is drilled, fractured, or systematically mined in strips. The loosened coal is then loaded by electric power shovels onto a fleet of large trucks for transport to the coal preparation plant.

In underground mining, the coal seam can be reached from the surface in two ways–(1) either through a vertical hole called a 'shaft' sunk down to the seam or (2) by means of inclined tunnels driven from the surface to the seam. Both entryways provide access, ventilation, power, water pipes (for spraying the coal face to prevent airborne dust) and means of communications for the miners. The sloping tunnel is generally preferred, as coal can be transported by conveyor straight to the surface in a continuous operation and miners can walk to the surface in an emergency.

Once the miners have reached their destination, there are a few different ways or systems developed to get the coal out. One is called the Room and Pillar System. With the Room and Pillar System, large parallel tunnels are drilled into the coal seam with pillars left behind to support the ceiling. These tunnels eventually form rooms underneath the ground. There are two types of room and pillar mining–one uses conventional mining techniques and the other continuous mining. In continuous mining a machine cuts away the coal from the coal seam by moving back and forth across the seam. [See image of a continuous miner in the Teacher Resource section.] The coal is automatically gathered up by steel arms and dumped into shuttle cars which transport the coal to a conveyor system for removal from the mine. This machine can clear more coal in a minute than a miner used to in an entire day. Remote control machines are now being used in particularly difficult seams and conditions. In conventional mining, an older practice, workers use dynamite to loosen coal seams after which the coal is gathered and loaded onto shuttle cars for removal.

Another system for coal removal is called the Longwall System. The Longwall System is two tunnels cut into the coal seams at a distance of 100 to 200 meters apart. The headings are joined by a third connecting tunnel at the farther end. The third tunnel becomes the coal face, and the block of coal lying in between the two main headings is mined away. The coal is cut by a rotating shearer, which shaves it off the long face. A steel conveyor running along the whole face takes the coal away. This system is the safest for miners because large, hydraulic, steel jacks hold up the face to give continuous support to the roof while the coal is removed. When the shearer has completed a traverse of the entire coal face, all the long wall equipment (shearer, conveyor, and roof supports) moves forward closer to the coal face. This provides continuous support to miners and machinery. The mine is allowed to collapse behind the supports. Long wall running achieves very high rates of output and allows almost total extraction of the seam.

For additional simple explanations of different types of coal mining with helpful images see the "Types of Coal Mining" website listed below.

In addition, it would be helpful before the lesson to review the Teacher Guide to Student Worksheet 1-Basics of Mining.

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