SIC 1231 Anthracite Mining
SIC 1231
This category covers establishments primarily engaged in producing anthracite or in developing anthracite mines. All establishments in the United States that are classified in this industry are located in Pennsylvania. This industry includes mining by owners or lessees, or by establishments that have complete responsibility for operating anthracite mines for others on a contract or fee basis. Also included are anthracite preparation plants, whether or not operated in conjunction with a mine.
212113
Anthracite Mining
Anthracite is a hard coal containing a high percentage of fixed carbon and a low percentage of volatile matter, such as sulfur and ash, containing more than 90 percent of fixed carbon, less than 5 percent of volatile matter (gases), and a very small percentage of moisture (usually less than 5 percent). With these desirable qualities, anthracite coal is ranked higher than other, more commonly used coals like bituminous and lignite because it has more than twice the energy content of these other coals. Thus, it provides a longer burning potential and is, accordingly, a higher energy fuel.
Almost all of the U.S. supply of anthracite coal is located in eastern Pennsylvania and is often referred to as Pennsylvania anthracite. Pennsylvania has about 7 billion tons of minable anthracite coal reserves. In 2003, anthracite mined in Pennsylvania totaled 1.3 million short tons. Showing a steady and significant decline, anthracite production was 4.8 million short tons in 1999, 4.6 million short tons in 2000, and 1.5 million short tons in 2001. Most of the original markets for anthracite were relinquished long ago to natural gas, fuel oil, and other coals, such as bituminous and lignite coal. Anthracite maintains a small share of a niche market, consisting primarily of coal-fired home-heating units. In fact, anthracite mining has been declining steadily for many years, from peak production in 1918, when anthracite mines produced 99.6 million short tons.
During 2004 the demand for anthracite coal increased to 1.7 million short tons, or 32.8 percent over 2003. Despite the increase, numerous mines in Pennsylvania, the nation's leading producer of anthracite coal, were "steadily dwindling." However, with the rising cost of coking and metallurgical coals some analysts forecast an increased demand for anthracite coal. This was particularly the case with the Pulverised Coal Injection (PCI) methods used within the steelmaking sector. According to a spokesperson at the Coal Trans World Anthracite and PCI conference, "tight coke availability and high prices have certainly stimulated interest in anthracite as a partial replacement, and this can only continue as met coal prices remain high."
Both surface and underground methods were used in the extraction of anthracite. In 1995 some 270,000 short tons were produced by underground mines and 4.1 million tons by surface mines. Surface mining is usually practiced on relatively flat ground; the coal is recovered from a depth of less than 200 feet. To reach coal deposits, miners must first remove the overburden, or strata, that covers the coal bed. Between 1 and 30 cubic yards of strata must be excavated for each ton of coal recovered. Dragline excavators, power shovels, bulldozers, front-end loaders, scrapers, and other heavy pieces of equipment are used to move the strata and extract the coal.
The two common methods of surface mining are strip and auger. At strip mines, large drills bore holes in the strata. Explosives are placed in these cavities and detonated. Power shovels or draglines operating at surface level then move the broken strata, while power shovels below dig up the coal and load it into trucks. The strata and coal are removed in long strips. This is done so that the debris from the newest strip can be dumped into an adjacent strip, from which the coal has already been recovered.
Auger mining consists of boring a series of holes that are 2 feet to 5 feet in diameter and 300 or more feet deep. This parallel and horizontal pattern is carved into a seam of coal that has already been exposed by an outcropping or by strip mining methods. No blasting takes place, and the overburden is left intact. The coal is simply removed and loaded into waiting trucks. Auger mining is frequently used in open-pit mines, where the strata is too thick to economically remove the coal using strip methods.
Underground mines consist of a series of parallel and interconnecting tunnels from which the coal is cut and removed with special machinery. The process is complex and sometimes dangerous. The mine must be adequately ventilated to protect miners from dust and explosive methane gas that is released by the coal. In addition, careful ground control must be practiced to prevent the roof of the mine from collapsing on workers and equipment.
Three types of underground operations are distinguished by the method used to access the coal mine. Drift mines are characterized by the use of a level tunnel leading into the mine, while slope mines have an inclined tunnel, and shaft mines utilize a vertical tunnel. The primary methods of extracting coal from all of these mines are room-and-pillar, longwall, and shortwall, but no anthracite mines used longwall systems.
Room-and-pillar mining is often the least efficient method. It allows recovery of only about 50 percent of the coal, although there are occasions when this methodology can achieve a much greater recovery percentage. In comparison, longwall and shortwall mining extract up to 80 percent of the usable...
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