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Coal mining,underground coal mining machinery

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Coal mining,underground coal mining machinery

April 15, 2023 nflg 0 Comments

Coal fields in Arkansas are located in the Arkansas River Valley between the western border of the state and Russellville (Pope County) an area only about thirty-three miles wide and sixty miles long. Until about 1880, most coal mined in Arkansas was used near its original location, often to fuel the fires of blacksmiths. Between 1880 and 1920, coal was Arkansas’s first mineral/fuel output, used especially for locomotives and steam-powered machines, as well as for heating homes and businesses. After 1920, oil and oil byproducts pushed aside the popularity of coal as a fuel, and mining of coal decreased. Much of the coal mined in Franklin County and Sebastian County around the year 2000 was used in the manufacture of charcoal briquettes for outdoor cooking. However, rising oil prices in the twenty-first century have led to increased interest in burning coal to generate electricity.

The thickness of the coal beds in Arkansas rarely exceeds nine feet. The fields are often small because the coal beds are lenticular and may have been folded, faulted, or eroded during or after deposition. Arkansas River Valley coals vary from low-volatile bituminous coal in the western portion of the area to semianthracite in the eastern portion. One of the principal advantages of Arkansas coal is that it gives off little smoke when it burns. Another advantage is low sulfur content as compared to many coals mined in the United States. Because of its high carbon content, Arkansas coal is a more efficient fuel than coal from other parts of the country—Arkansas coal has been rated at 13,000 to 15,000 BTU, as compared to 7,500 BTU for Pennsylvania.

The first recorded mine output in the state was 220 tons in 1848. A coal mine operating in Spadra (Johnson County) in 1840 filled eleven barges to be shipped to Louisiana; however, all eleven barges sank in the high water of the Arkansas River, and the coal was lost. By 1880, eighty percent of the coal mined in Arkansas came from Johnson County. Railroad installations and extensions in the late 1800s encouraged shipping of the coal, and this resulted in extensive coal mine development. In 1907, coal mined in Arkansas reached a peak of 2.6 million tons. Over 106 million tons of coal were produced from 1880 to 2006.

Coal may have first been mined from strip mines or open pits. As production increased, it became difficult to mine the remaining coals near to the surface, and therefore underground methods were developed.One underground method was the use of slope mines, whereby the mining followed the slope of the natural coal bed, gathering and extracting the coal as the slope shaft continued to follow the coal bed. Steel tracks could be laid and the coal removed by coal carts pulled from the mine.If the use of a slope mine was ineffective, a vertical shaft might be dug from the surface to the coal bed; coal would then be extracted from rooms out from this shaft and removed by lifting it upward. All significant coal mining was by underground methods until 1918, when surface mining produced substantial amounts.

Among the dozens of coal mining companies formed in Arkansas in the nineteenth and twentieth centuries, several were owned by Franklin Backe and Heber Denman, including the Mammoth Vein Coal Mining Company of Sebastian County. Central Coal & Coke Corporation and the Southern Anthracite Coal Company were two other significant coal-mining companies.

Coal is mined by two methods:

* surface or ‘opencast’ mining
* underground or ‘deep’ mining

The choice of mining method is largely determined by the geology of the coal deposit. Underground mining currently accounts for a bigger share of world coal production than opencast; although in several important coal producing countries surface mining is more common. For example, surface mining accounts for around 80% of production in Australia; while in the USA it is used for about 67% of production.
Surface Mining

Surface mining – also known as opencast or opencut mining – is only economic when the coal seam is near the surface. This method recovers a higher proportion of the coal deposit than underground mining as all coal seams are exploited – 90% or more of the coal can be recovered.

Large opencast mines can cover an area of many square kilometres and use very large pieces of equipment , including:

* draglines, which remove the overburden
* power shovels
* large trucks, which transport overburden and coal
* bucket wheel excavators
* conveyors

The overburden of soil and rock is first broken up by explosives; it is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured and systematically mined in strips. The coal is then loaded on to large trucks or conveyors for transport to either the coal preparation plant or direct to where it will be used.
Underground Mining

There are two main methods of underground mining: room-and-pillar and longwall mining.

Room & Pillar Mining

In room-and-pillar mining, coal deposits are mined by cutting a network of ‘rooms’ into the coal seam and leaving behind ‘pillars’ of coal to support the roof of the mine. These pillars can be up to 40% of the total coal in the seam – although this coal can sometimes be recovered at a later stage.

Longwall Mining

Longwall mining involves the full extraction of coal from a section of the seam, or ‘face’ using mechanical shearers. A longwall face requires careful planning to ensure favourable geology exists throughout the section before development work begins. The coal ‘face’ can vary in length from 100-350m. Self-advancing, hydraulically-powered supports temporarily hold up the roof while coal is extracted. When coal has been extracted from the area, the roof is allowed to collapse. Over 75% of the coal in the deposit can be extracted from panels of coal that can extend 3km through the coal seam.

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.

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