Антрацит: Қара көмірдің ең жоғары сапалы түрі

Hard, compact variety of coal

Anthracite, also known as hard coal and black coal, is a hard, compact variety of coal that has a submetallic lustre. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals. The Coal Region of Northeastern Pennsylvania in the United States has the largest known deposits of anthracite coal in the world with an estimated reserve of seven billion short tons. China accounts for the majority of global production; other producers include Russia, Ukraine, North Korea, South Africa, Vietnam, Australia, Canada, and the United States. Total production in 2020 was 615 million tons. Anthracite is the most metamorphosed type of coal, but still represents low grade metamorphism, in which the carbon content is between 86% and 97%. The term is applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition. Anthracite is difficult to ignite, and burns with a short, blue, and smokeless flame. Anthracite is categorized into several grades. Standard grade is used predominantly in power generation, and high grade (HG) and ultra high grade (UHG), are used predominantly in the metallurgy sector. Anthracite accounts for about 1% of global coal reserves, and is mined in only a few countries around the world.

Anthracite derives from the Greek anthrakítēs (ἀνθρακίτης), literally "coal like". Other terms which refer to anthracite are black coal, hard coal, stone coal, dark coal, coffee coal, blind coal (in Scotland), Kilkenny coal (in Ireland), crow coal or craw coal, and black diamond. "Blue Coal" is the term for a once popular and trademarked brand of anthracite, mined by the Glen Alden Coal Company in Pennsylvania, and sprayed with a blue dye at the mine before shipping to its Northeastern U. S. markets to distinguish it from its competitors. Culm has different meanings in British and American English. In British English, culm is the imperfect anthracite, located predominantly north Devon and Cornwall, which was used as a pigment. The term is also used to refer to some carboniferous rock strata found in both Britain and in the Rhenish hill countries, also known as the Culm Measures. In Britain, it may also refer to coal exported from Britain during the 19th century. In American English, "culm" refers to the waste or slack from anthracite mining, mostly dust and small pieces not suitable for use in home furnaces.

Anthracite is similar in appearance to the mineraloid jet and is sometimes used as a jet imitation. Anthracite differs from ordinary bituminous coal by its greater hardness (2.75–3 on the Mohs scale), its higher relative density of 1.3–1.4, and luster, which is often semi metallic with a mildly green reflection. It contains a high percentage of fixed carbon and a low percentage of volatile matter. It is also free from included soft or fibrous notches and does not soil the fingers when rubbed. Anthracitization is the transformation of bituminous coal into anthracite. The moisture content of fresh mined anthracite generally is less than 15 percent. The heat content of anthracite ranges from 26 to 33 MJ/kg (22 to 28 million Btu/short ton) on a moist, mineral matter free basis. The heat content of anthracite coal consumed in the United States averages 29 MJ/kg (25 million Btu/ton), on the as received basis, containing both inherent moisture and mineral matter. Since the 1980s, anthracite refuse or mine waste has been used for coal power generation in a form of recycling. The practice known as reclamation is being applied to culm piles antedating laws requiring mine owners to restore lands to their approximate original condition. Chemically, anthracite may be considered as a transition stage between ordinary bituminous coal and graphite, produced by the more or less complete elimination of the volatile constituents of the former, and it is found most abundantly in areas that have been subjected to considerable stresses and pressures, such as the flanks of great mountain ranges. Anthracite is associated with strongly deformed sedimentary rocks that were subjected to higher pressures and temperatures (but short of metamorphic conditions) just as bituminous coal is generally associated with less deformed or flat lying sedimentary rocks. The compressed layers of anthracite that are deep mined in the folded Ridge and Valley Province of the Appalachian Mountains of the Coal Region of East central Pennsylvania are extensions of the same layers of bituminous coal that are mined on the generally flat lying and undeformed sedimentary rocks further west on the Allegheny Plateau of Kentucky and West Virginia, Eastern Ohio, and Western Pennsylvania. In the same way the anthracite region of South Wales is confined to the contorted portion west of Swansea and Llanelli, the central and eastern portions producing steam coal, coking coal and domestic house coals. Anthracite shows some alteration by the development of secondary divisional planes and fissures so that the original stratification lines are not always easily seen. The thermal conductivity is also higher; a lump of anthracite feels perceptibly colder when held in the warm hand than a similar lump of bituminous coal at the same temperature. Anthracite has a history of use in blast furnaces for iron smelting; however, it lacked the pore space of metallurgical coke, which eventually replaced anthracite.

In southwest Wales, anthracite has been burned as a domestic fuel since at least medieval times, when it was mined near Saundersfoot. More recently, large scale mining of anthracite took place across the western part of the South Wales Coalfield until the late 20th century. In the United States, anthracite coal history began in 1790 in Pottsville, Pennsylvania, with the discovery of coal made by the hunter Necho Allen in what is now known as the Coal Region. Legend has it that Allen fell asleep at the base of Broad Mountain and woke to the sight of a large fire because his campfire had ignited an outcrop of anthracite coal. By 1795, an anthracite fired iron furnace had been built on the Schuylkill River. Anthracite was first experimentally burned as a residential heating fuel in the US on 11 February 1808, by Judge Jesse Fell in Wilkes Barre, Pennsylvania, on an open grate in a fireplace. Anthracite differs from wood in that it needs a draft from the bottom, and Judge Fell proved with his grate design that it was a viable heating fuel. In spring 1808, John and Abijah Smith shipped the first commercially mined load of anthracite down the Susquehanna River from Plymouth, Pennsylvania, marking the birth of commercial anthracite mining in the United States. From that first mine, production rose to an all time high of over 100 million tons in 1917. The difficulty of igniting anthracite inhibited its early use, especially in blast furnaces for smelting iron. The development of the hot blast in 1828, which used waste heat to preheat combustion air, anthracite became a preferred fuel, accounting for 45% of US pig iron production within 15 years. Anthracite iron smelting was later displaced by coke. From the late 19th century until the 1950s, anthracite was the most popular fuel for heating homes and other buildings in the northern US, until it was supplanted by oil burning systems, and more recently natural gas systems. Many large public buildings, such as schools, were heated with anthracite burning furnaces through the 1980s. During the American Civil War, Confederate blockade runners used anthracite as a smokeless fuel for their boilers to avoid revealing their position to the blockaders. The invention of the Wootten firebox enabled locomotives to directly burn anthracite efficiently, particularly waste culm. In the early 20th century US, the Delaware, Lackawanna and Western Railroad started using only the more expensive anthracite coal in its passenger locomotives, dubbed themselves "The Road of Anthracite", and advertised widely that travelers on their line could make railway journeys without getting their clothing stained with soot. The advertisements featured a white clad woman named Phoebe Snow and poems containing lines like "My gown stays white / From morn till night / Upon the road of Anthracite". Similarly, the Great Western Railway in the UK was able to use its access to anthracite (it dominated the anthracite region) to earn a reputation for efficiency and cleanliness unmatched by other UK companies. Internal combustion motors driven by the so called "mixed", "poor", "semi water" or "Dowson gas" produced by the gasification of anthracite with air (and a small proportion of steam) were at one time the most economical method of obtaining power, requiring only , or less. Large quantities of anthracite for power purposes were formerly exported from South Wales to France, Switzerland and parts of Germany. as of 2013, widespread commercial anthracite mining in Wales has now ceased, although a few large open cast sites remain, along with some relatively small drift mining operations.

Anthracite generally costs two to six times as much as regular coal. In June 2008, the wholesale cost of anthracite was US$150/short ton, falling to $107/ton in 2021; it makes up 1% of U. S. coal production. The principal use of anthracite today is for a domestic fuel in either hand fired stoves or automatic stoker furnaces. It delivers high energy per its weight and burns cleanly with little soot, making it ideal for this purpose. Its high value makes it prohibitively expensive for power plant use. Other uses include the fine particles used as filter media, and as an ingredient in charcoal briquettes. Anthracite was an authorised fuel in terms of the United Kingdom's Clean Air Act 1993, meaning that it could be used within a designated Smoke Control Area such as the central London boroughs.

China today mines by far the largest share of global anthracite production, accounting for more than three quarters of global output. Current U. S. anthracite production averages around five million tons per year. Of that, about 1.8 million tons were mined in the state of Pennsylvania. Mining of anthracite coal continues to this day in eastern Pennsylvania, and contributes up to 1% to the gross state product. More than 2,000 people were employed in the mining of anthracite coal in 1995. Most of the mining as of that date involved reclaiming coal from slag heaps (waste piles from past coal mining) at nearby closed mines. Some underground anthracite coal is also being mined. Countries producing HG and UHG anthracite include Russia and South Africa. HG and UHG anthracite are used as a coke or coal substitute in various metallurgical coal applications (sintering, PCI, direct BF charge, pelletizing). It plays an important role in cost reduction in the steel making process and is also used in production of ferroalloys, silicomanganese, calcium carbide and silicon carbide. South Africa exports lower quality, higher ash anthracite to Brazil to be used in steel making.

On the opposite end from high grade anthracite coal, semianthracite coal is defined as a coal which is intermediate between anthracite coal and bituminous coal, and particularly a coal which approaches anthracite in nonvolatile character.

Historically, from time to time, underground seams of coal have caught fire, often from careless or unfortunate mining activities. The pocket of ignited coal is fed oxygen by vent paths that have not yet been discovered. These can smolder for years. Commonly, exhaust vents in populated areas are soon sensed and are sealed while vents in uninhabited areas remain undiscovered. Occasionally, vents are discovered via fumes sensed by passers by, often in forested areas. Attempts to extinguish those remaining have at times been futile, and several such combustion areas exist today. The existence of an underground combustion site can sometimes be identified in the winter where fallen snow is seen to be melted by the warmth conducted from below. Proposals for harnessing this heat as geothermal energy have not been successful. A vein of anthracite that caught fire in Centralia, Pennsylvania, in 1962 has been burning ever since, turning the once thriving borough into a ghost town.

Geologically, the largest most concentrated anthracite deposit in the world is found in the Lackawanna Coal Mine in northeastern Pennsylvania, United States in and around Scranton, Pennsylvania. Locally called the Coal Region, the deposit contains 480 square miles (1,243 km2) of coal bearing rock which originally held 22.8 billion short tons (20.68 billion tonnes) of anthracite. The geographic region is roughly 100 miles (161 km) in length and 30 miles (48 km) in width. Because of historical mining and development of the lands overlying the coal, it is estimated that 7 billion short tons (6.3 billion tonnes) of minable reserves remain. The United States also contains several smaller deposits of anthracite, such as those historically mined in Crested Butte, Colorado. Among current producers, Russia, China, Poland, and Ukraine have the largest estimated recoverable reserves of anthracite. Other countries with substantial reserves include Vietnam and North Korea. The Groundhog Anthracite Deposit in British Columbia, Canada, is the world's largest previously undeveloped anthracite deposit. It is owned by the Australian publicly traded company Atrum Coal and has 1.57 billion tonnes of high grade anthracite. Anthracites of newer Tertiary or Cretaceous age are found in the Crowsnest Pass part of the Rocky Mountains in Canada and at various places in the Andes in Peru.

Report of the United states coal commission (5 vol in 3; 1925) Official US government investigation. online vol 1 2
Tryon, Frederick Gale, and Joseph Henry Willits, eds. What the Coal Commission Found: An Authoritative Summary by the Staff (1925). General policies committee of anthracite operators. The anthracite coal strike of 1922: A statement of its causes and underlying purposes (1923); Official statement by the operators. online