Coal mining

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Coal mining is the extraction or removing of coal from the earth for use as fuel. A coal mine and its accompanying structures are collectively known as a colliery. For the world history see History of coal mining. See also world coal reserves and major coal exporters.

Contents 1 Methods of extraction 1.1 Surface and mountaintop mining 1.2 Underground mining 2 History 3 Modern mining in the United States of America 4 Dangers to miners 5 Safer times in modern mining 6 Environmental impacts and mitigation 7 See also 8 Notes 9 References 10 External links

[edit] Methods of extraction

The most economical method of coal extraction from coal seams depends on the depth and quality of the seams, and also the geology and environmental factors of the area being mined. Coal mining processes are generally differentiated by whether they operate on the surface or underground. Many coals extracted from both surface and underground mines require washing in a coal preparation plant.

[edit] Surface and mountaintop mining

If the coal seams are near the surface, the coal is extracted by strip mining. Strip mining exposes the coal by the advancement of an open pit or strip. As the coal is exposed and extracted, the overburden from the still-covered coal fills the former pit, and the strip progresses. Most open cast mines in the United States extract bituminous coal. In South Wales open casting for steam coal and anthracite is practiced.

Mountaintop removal is a form of surface mining that takes place at the topmost portion of a mountain, and is a technique that is commonly applied in Appalachia. Utilized for the past 30 years, mountaintop mining involves removing the highest part of the mountain for the maximum recovery of coal. The process is highly controversial for the drastic changes in topography, the practice of hollow fills, or filling in valleys with mining debris, and for covering streams and disrupting ecosystems.^[1]

[edit] Underground mining

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It has been suggested that Sub-surface mining be merged into this article or section. (Discuss)

Main article: Sub-surface mining

Most coal seams are too deep underground for open cast mining and thus this type of mining is called underground mining. In deep mining, the room and pillar or board and pillar method progresses along the seam, while pillars and timber are left standing to support the coal mine roof. Once room and pillar mines have been developed to a stopping point(limited by geology, ventilation, or economics), a supplementary version of room and pillar mining referred to as second mining or retreat mining is commonly started. This is when miners remove the coal in the pillars, thereby recovering as much coal from the coal seam as possible. A work area that is involved in pillar extraction is called a pillar section. Modern pillar sections use remote controlled equipment, including large hydraulic mobile roof supports, which can prevent cave ins until the miners and other equipment have left a work area. The mobile roof supports are similar to a large dining room table, but with hydraulic jacks for legs. After the large pillars of coal have been mined away, the mobile roof support legs shorten, and the mobile roof supports travel out to a safe area. The mine roof typically collapses once the mobile roof supports leave an area.

There are four major underground mining methods:

• Longwall mining – accounts for about 50% of underground production. The longwall shearer has a face of 1000 feet or more. It is a sophisticated machine with a rotating drum that moves mechanically back-and-forth across a wide coal seam. The loosened coal falls onto a pan line that takes the coal to the conveyor belt for removal from the work area. Longwall systems have their own hydraulic roof supports for overlying rock that advance with the machine as mining progresses. As the longwall mining equipment moves forward, overlying rock that is no longer supported by the coal that has been removed is allowed to fall behind the operation in a controlled manner. The supports make possible high levels of production and safety. Sensors detect how much coal remains in the seam while robotic controls enhance efficiency. Longwall systems allow a 60-to-100% coal recovery rate where the surrounding geology allows their use.

• Continuous mining– Utilize a machine with a large rotating steel drum equipped with tungsten carbide teeth that scrape coal from the seam. Operating in a “room and pillar” system – where the mine is divided into a series of 20-to-30 foot “rooms” or work areas cut into the coalbed – it can mine as much as five tons of coal a minute – more than a miner of the 1920s would produce in an entire day. Continuous miners account for about 45% of underground coal production, and also utilize conveyors to transport the removed coal from the seam. Remote controlled continuous miners are used to work in a variety of difficult seams and conditions and robotic versions controlled by computers are becoming increasingly common.

• Blast mining – An older practice that uses explosives such as dynamite to break up the coal seam, after which the coal is gathered and loaded onto shuttle cars or conveyors for removal to a central loading area. This process consists of a series of operations that begins with “cutting” the coalbed so it will break easily when blasted with explosives. This type of mining accounts for less than 5% of total underground production in the U.S. today.

• Shortwall mining– A method that accounts for less than 1% of deep coal production, shortwall involves the use of a continuous mining machine with moveable roof supports, similar to longwall. The continuous miner shears coal panels 150-200 feet wide and more than a half-mile long, depending on other things like the strata of the Earth and the transverse waves.

[edit] History

Main article: History of coal mining

The oldest continuously worked deep-mine in the UK and possibly the world is Tower Colliery at the northern end of the south Wales valleys. This colliery was started in 1805 and at the end of the 20th century it was bought out by its miners rather than being allowed to be closed.

The World Championships in coal-carrying take place every Easter Monday, at Ossett in West Yorkshire, UK The race starts from the site of the old Savile & Shaw Cross colliery.

The first commercial coal mines in the United States were started in 1748 in Midlothian, Virginia, near Richmond, Virginia.^[2]

In the 1880s, Coal-cutting machines became available (prior to that, coal was mined underground by hand.)

By 1912, surface mining was underway with steam shovels specifically designed for coal mining.

[edit] Modern mining in the United States of America

Technological advancements have made coal mining today more productive than it has ever been. To keep up with technology and to extract coal as efficiently as possible modern mining personnel must be highly skilled and well trained in the use of complex, state-of-the-art instruments and equipment. Future coal miners have to be highly educated and many jobs require four-year college degrees. Computer knowledge has also become greatly valued within the industry as most of the machines and safety monitors are computerized.

The increase in technology has significantly decreased the mining workforce from 335,000 coal miners working at 7,200 mines fifty years ago to 104,824 miners working in fewer than 2,000 mines today. As some might see this as a sign that coal is a declining industry its advances has reported an 83% increase of production from 1970 to 2004. These statistics are provided by the National Mining Association.

[edit] Dangers to miners

Historically, coal mining has been a very dangerous activity. Open cut hazards are principally slope failure, underground mining roof collapse and gas explosions. Most of these risks can be greatly reduced in modern mines, and multiple fatality incidents are now rare in some parts of the developed world.^[3]

However, in lesser developed countries and some developed countries, many miners continue to die annually, either through direct accidents in coal mines or through adverse health consequences from working under poor conditions. China, in particular, has the highest number of coal mining related deaths in the world, with official statistic 6,027 deaths in 2004.^[4] To compare, the USA reported 28 deaths in the same year.^[5] Coal production in China is twice that of the United States^[6], while the number of coal miners is around 50 times that of the USA, making deaths in coal mines in China 4 times as common per worker (50 times as common per unit output) as in the USA.

When compared to industrial countries such as China, the U.S. fatality rate is low. However in 2006 fatal work injuries among U.S. miners doubled from the previous year, totaling 47.^[7] These figures can in part be attributed to the Sago Mine disaster. The recent mine accident in Utah's Crandall Canyon Mine, where nine miners were killed and six entombed, speaks to the increase in occupational risks faced by U.S. miners.^[8]

Chronic lung diseases, such as pneumoconiosis (black lung) were once common in miners, leading to reduced life expectancy. In some mining countries black lung is still common, with 4000 new cases of black lung every year in the USA (4% of workers annually) and 10 000 new cases every year in China (0.2% of workers). ^[9] Rates may be higher than reported in some regions.

Build-ups of a hazardous gas are known as damps, possibly from the German word "Dampf" which means steam or vapor:

• Black damp: a mixture of carbon dioxide and nitrogen in a mine can cause suffocation.
• After damp: similar to black damp, an after damp consists of carbon dioxide and nitrogen and forms after a mine explosion.
• Fire damp: consists of mostly methane, a flammable gas.
• Stink damp: so named for the rotten egg smell of the sulfur, a stink damp can explode.
• White damp: mainly carbon monoxide, suffocates like black damp [also, Carbon monoxide is very toxic, even at low concentrations]

(See: Mining accidents)

[edit] Safer times in modern mining

Improvements in mining methods (e.g. longwall mining), hazardous gas monitoring (such as safety-lamps or more modern electronic gas monitors), gas drainage, and ventilation have reduced many of the risks of rock falls, explosions, and unhealthy air quality. Statistical analyses performed by the U.S. Department of Labor’s Mine Safety and Health Administration (MSHA) show that between 1990 and 2004, the industry cut the rate of injuries by more than half and fatalities by two-thirds. However according to the Bureau of Labor Statistics, mining remains the second most dangerous occupation in America.^[10]

[edit] Environmental impacts and mitigation

Coal mining causes adverse environmental impacts. These include:

1. Release of methane, a greenhouse gas
2. Interference with groundwater and water table levels
3. Impact of water use on flows of rivers and consequential impact on other land-uses
4. Dust
5. Subsidence above tunnels, sometimes damaging infrastructure (e.g., roads in the Lake Macquarie area in NSW, Australia).
6. Rendering land unfit for the common usage of the area.

In addition, burning of coal, mainly for power generation, introduces a large amount of carbon dioxide into the atmosphere.

Strip mining severely alters the landscape, which damages environmental value in the surrounding land. Mountaintop removal to remove coal is a large negative change to the environment. While there are sometimes requirements for remediation of the strip mined area, the remediation is often delayed for decades. One of the legacies of coal mining is the low coal content waste forming boney piles.

In response to negative land effects of coal mining and the abundance of abandoned mines in the USA, the federal government enacted the Surface Mining Control and Reclamation Act of 1977 (SMCRA), which requires reclamation plans for future coal mining sites. Reclamation plans must be approved and permitted by federal or state authorities before mining begins. As of 2003, over 2 million acres (8,000 km²) of previously mined lands have been reclaimed in the United States.

Coal mining can cause a water pollution called Acid mine drainage (AMD); a metal-rich water formed from the chemical reaction between water and rocks containing sulfur-bearing minerals. While AMD usually forms in areas where coal mining has taken place, metal-rich drainage can also occur in mineralized areas that have not been mined. AMD happens when the pyrite reacts with air and water to form sulfuric acid and dissolves iron. This acid run-off dissolves heavy metals such as copper, lead and mercury into ground and surface water. Through effective mine management methods AMD can be minimized. Also a good mine design can keep water away from acid generating materials and help prevent AMD from occurring. There are two ways to get rid of AMD. One way is to install a water treatment plant. First the AMD is dosed with lime to neutralize the acid and then it is passed through a settling tank to remove the sediment and particulate metals. The second way is to develop a self-operating system that can treat the effluent without constant human intervention^[11].

All forms of mining are likely to generate areas where coal is stacked and where the coal has significant sulfur content, such coal heaps generate highly acidic, metal-laden drainage when exposed to rainfall. These liquors can cause severe environmental damage to receiving water-courses^[12]. Coal mining releases approximately twenty toxic release chemicals, of which 85% is said to be managed on site.^{[citation needed]} In modern mining, operations must, under federal and state law, meet standards for protecting surface and ground waters from contamination, including acid mine drainage (AMD). To mitigate these problems, water is continuously monitored at coal mines. The five principal technologies used to control water flow at mine sites are: diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems, and subsurface barriers. In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants. Still, AMD remains a large problem, emanating from coal mines abandoned in the United States prior to SMCRA.

Coal mining produces methane a potent greenhouse gas. Methane is the naturally occurring product of the decay of organic matter as coal deposits are formed with increasing depths of burial, rising temperatures, and rising pressures over geological time. A portion of the methane produced is adsorbed by the coal and later released from the coal seam and surrounding disturbed strata during the mining process ^[13]. Methane accounts for 9% of greenhouse gas emissions created through human activity ^[14]. According to the Inter-Governmental Panel on Climate Change, methane has a global warming potential 21 times greater than that of carbon dioxide on a 100 year time line. While burning coal in power plants is most harmful to air quality, due to the emission of dangerous gases, the process of mining can release pockets of hazardous gases. These gases may pose a threat to coal miners as well as a source of air pollution. This is due to the relaxation of pressure and fracturing of the strata during mining activity, which gives rise to serious safety concerns for the coal miners if not managed properly. The buildup of pressure in the strata can lead to explosions during or after the mining process if prevention methods, such as "methane draining", are not taken. ^[15]

[edit] See also

• History of coal mining
• Coal-mining region
• Acid mine drainage
• Anthracite Coal Region of Pennsylvania
• Bevin Boys
• Black lung disease
• Coal Measures
• Coal Mine Safety and Health Act of 1969 (in the US)
• Coal mining in Australia
• Coal mining debate
• El Cerrejon
• Hurrying
• Mine fire
• Mining accidents
• Mining in Limburg
• Category:Mining in the United Kingdom
• The Stars Look Down
• The Citadel
• Powder River Basin
• Problems in coal mining
• World Coal Institute
• Australian Coal Alliance
• Category:Coal mines in the United States

[edit] Notes

[edit] References

• Daniel Burns. The modern practice of coal mining (1907)
• Hughes. Herbert W, A Text-Book of Mining: For the Use of Colliery Managers and Others (London, many editions 1892-1917), the standard British textbook for its era.
• James Tonge. The principles and practice of coal mining (1906)
• Charles V. Nielsen and George F. Richardson. 1982 Keystone Coal Industry Manual (1982)
• Hayes, Geoffrey. Coal Mining (2004), 32 pp
• A.K. Srivastava. Coal Mining Industry in India (1998) (ISBN 81-7100-076-2)
• Chirons, Nicholas P. Coal Age Handbook of Coal Surface Mining (ISBN 0-07-011458-7)
• Saleem H. Ali. Minding our Minerals, 2006. [1]
• National Energy Information Center, Greenhouse Gases, Climate Change, Energy, <http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html>. Retrieved on 2007-10-16

• The Department of Trade and Industry, The Coal Authority, <http://www.coal.gov.uk/resources/cleanercoaltechnologies/CoalMineandbedmethane.cfm>. Retrieved on 2007-10-16

[edit] External links

• Photos of Mining from Eastern PA
• Abandoned Mine Research
• [2]. Excellent educational resource on longwall mining, provided by the University of Wollongong.
• National Coal Mining Museum for England
• World Coal Institute - Coal Mining
• World Coal Institute - Environmental Impacts of Coal Mining
• West Virginia (USA) Coal Mining
• A short historical account of the coal seams and mining industry of North Staffordshire, UK.
• Old photographs and historic ephemera relating to the mining industry and related labour struggles in North Staffordshire, UK.
• NIOSH Coal Workers' Health Surveillance Program
• The Powder and Bulk Channel
• The Virtual Museum of Coal Mining in Western Pennsylvania
• Aerial photographs of coal mines in Wales
• [[3]]

• [[4]]bg:Въгледобив

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