Continuous Mining

This mobile machine has a series of metal-studded rotating drums that gouge coal from the face of the coal seam (known as the wall face). One continuous miner can mechanically break apart approximately 2 tons of coal per hour. After a wall face has been mined to a certain depth, miners stabilize the adjacent roof by bolting long rods into the mine ceiling, advance the ventilation, and begin a new continuous mining cycle. 

In the method, the mine is divided into a series of 20-30 ft (6-9 m) rooms or work areas cut into the coal bed, and coal production can be as much as 5 tons of coal a minute. In fact, continuous mining is not necessarily continuous since room and pillar coal mining is cyclical. Conveyors transport the removed coal from the seam. 

The weak link in this system was often the method of secondary transportation located immediately behind the continuous miner. The high rate of advance and loading of the mining equipment meant that normal secondary haulage systems were inadequate and mobile belt conveyors had to be introduced. These high-capacity conveyors have self-propelled drive and tail sections and sufficient belt storage to permit advances of up to 100 ft (30.5 m) without stopping the conveyor. 

Cornering devices were also developed to carry coal around a series of right angle turns thereby removing the need for transference to another conveyor. 

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The mechanical equipment used in room-and-pikar underground mining usuaky involves a series of specific operations with continuous mining equipment. Continuous miners use rotating heads equipped with bits to pick or cut through the coal without blasting and load it into a shuttle car for conveying to a belt system. 

One significant advantage of pulverized coal boilers is the ability to use any kind of coal, including mn-of-mine or uncleaned coals. However, with the advent of continuous mining equipment, the ash content frequently is ca 25%, and some preparation is frequently practiced. There were 931 coal preparation plants in the United States in 1988, mainly in Kentucky, West Virginia, and Peimsylvania. 

Both conventional and continuous mining methods use a room-and-pillar system in which the coal is mined by extracting a scries of rooms into the coalbed, and leaving pillars, or columns, of coal to help support the mine roof (Figure 1). Depending on the location, the rooms are generally 20 to 30 ft. wide... 

As a rule of thumb, 50 to 55 percent of coal can be extracted using continuous mining. To improve this extraction ratio, a pillar-recovery process usually is applied when mining reaches the end of the panel and the direction of the mining is reversed. The continuous miner mines into the pillars, recovering as much coal as possible, as the roof is allowed to systematically collapse. Usually this can increase the extraction ratio by up to 5 percent. 

Although the development of the continuous mining system in the 1950s consolidated several opera-... 

Shortwall Mining. This method is used in relatively few underground mines. It involves the use of a continuous mining machine and movable... 

Fig. 10. Continuous mining machine used in underground mine. As coal accumulates on the mine flixir. the helical screw effect of the culling head constantly moves the pile toward the center of the head, contributing to fast loading and improved productivity and cleanup. Two powerful motors handle all motions of the machine. Safety provisions are incorporated in the design. (National Coal Association)...

Respirable Dust—with the objective of providing improvements for protecting miners from exposure to respirable coal mine dust. Study areas have included (a) dust formation fb) dust control, and (c) dust measurement. Tests have included the infusion of water into coal beds for control of respirable dust the use of water-based, high-expansion foaming systems in conjunction with continuous mining machines, to reduce dust at the face the use of roam systems for dust suppression on conveyors and transfer points and the use of prototype dust meters. See also Pneumokonioses. 

A modification of this method, using a continuous mining machine on faces up to 150 ft long, is known as shortwall mining. It uses the roof support system of self-advancing chocks developed for longwall operations. 

That region which according to the geographers, is the first of all Britain, and... was in ancient times inhabited by those Britains, whom Solinas called, Dunmonii, Ptolomy (called) Damnonii, or (as we find in some other copies), more truly Danmonil which name. .. derived from the ever-continuing mines of tin in this tract, which Britains call mania. 

V Short-wall continuous water preservation continuous mining class The bedrock thickness is usually bigger than 35 to 40 m, having the features of single key strata, and long-waU mining is not suitable. 

Miners use two processes, known as conventional mining and continuous mining, to remove coal from room and pillar underground mines. Conventional coal mining replaced hand mining (mining with pick and shovel) in the 1930s. 

The shortwall mining system originated in Australia and is, in essence, a combination of the continuous mining and longwall mining concepts. 

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