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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 ton. China accounts for the majority of global production; other producers include Russia, Ukraine, North Korea, South Africa, Vietnam, Australia, Canada, and the United States. The total production of anthracite worldwide in 2023 was 632 million short tons.
Anthracite is the most metamorphism 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 coal tar or other hydrocarbon vapours when heated below their point of Combustion. Anthracite is difficult to ignite, and burns with a short, blue, and smokeless flame.
Anthracite is categorized into several grades. Standard grade anthracite 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.
Culm has different meanings in British English 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 Stratum 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 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 mine 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 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 for iron smelting; however, it lacked the pore space of metallurgical coke, which eventually replaced anthracite.
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 the late 18th century, it was known in the United States that anthracite could be burnt, but the techniques required to do so were unknown. Anthracite differs from wood and bituminous coal in that it has a higher ignition temperature and needs a fresh air draft from the bottom to burn. Several claims are made about who "first" burnt anthracite coal in the United States around this time, and all such claims originate from Pennsylvania. The city of Pottsville, Pennsylvania claims that their town was founded around an anthracite-fired blast furnace purchased by John Potts in 1806, which was built on the Schuylkill River in 1795. Pennsylvanian Charles V. Hagner recalls in his 1869 book that an unnamed employee of Josiah White and Erskine Hazard accidentally burnt anthracite in their rolling mill at the Schuylkill River (after much failed experimentation with burning anthracite) at some point between 1812 and 1815. Judge Jesse Fell is claimed to be the first person to burn anthracite for the purposes of residential heating in the USA in Wilkes-Barre, Pennsylvania on 11 February 1808. Judge Fell used an open grate in his fireplace to burn anthracite, as an experiment to prove that it was a viable residential 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 for smelting iron. With 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 steam locomotive 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.
Commercial anthracite mining in Wales ceased in 2013, although a few large open cast sites remain, along with some relatively small drift mining operations. Commercial anthracite mining is still ongoing in Pennsylvania; the state produced a "total of 4,614,391 tons of anthracite coal, predominately from surface coal mines" in 2015.
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.
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 blast furnace charge, pelletizing). It plays an important role in cost reduction in the steel making process and is also used in production of , silicomanganese, calcium carbide and silicon carbide. South Africa exports lower-quality, higher-ash anthracite to Brazil to be used in steel-making.
Anthracite is classified into three grades, depending on its carbon content. Standard grade is used as a domestic fuel and in industrial power-generation. The rarer higher grades of anthracite are purer – i.e., they have a higher carbon content – and are used in steel-making and other segments of the metallurgical industries. Technical characteristics of the various grades of anthracite are as follows:
| 5% |
| 14% |
| 2% |
| 84% |
| 0.8% |
The common American classification by size is as follows:
Lump, steamboat, egg and stove coals, the latter in two or three sizes, all three being above in (38 mm) size on round-hole screens.
High grade and ultra high grade anthracite are harder than standard grade anthracite, and have a higher relative density. An example of a chemical formula for high-grade anthracite would be C240H90O4NS, representing 94% carbon. UHG anthracite typically has a minimum carbon content of 95%.
They also differ in usage from standard grade anthracite (used mainly for power generation), being employed mainly in metallurgy as a cost-efficient substitute for coke in processes such as sintering and Pelletizing, as well as pulverised coal injection (PCI) and direct injection into . They can also be used in water purification and domestically as a smokeless fuel.
HG and UHG anthracite account for a small percentage of the total anthracite market. The major producing countries are Russia, Ukraine, Vietnam, South Africa and the US.
| +Standard classifications by size !Name !!Imperial (inches) !!Metric (mm) |
The primary sizes used in the United States for domestic heating are Chestnut, Pea, Buckwheat and Rice, with Chestnut and Rice being the most popular. Chestnut and Pea are used in hand fired furnaces while the smaller Rice and Buckwheat are used in automatic stoker furnaces. Rice is currently the most sought-after size due to the ease of use and popularity of that type of furnace.
In South Wales, a less elaborate classification is adopted, but great care is exercised in hand-picking and cleaning the coal from particles of pyrites in the higher qualities known as best malting coals, which are used for kiln-drying malt.
Anthracite dust can be made into coal briquette and is sold in the United Kingdom under trade names such as Phurnacite, Ancit and Taybrite.
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.Bellows, Alan (2006) "The Smoldering Ruins of Centralia" DamnInteresting.com (accessed August 29, 2006)
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 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.
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