User:Pmorley1/Anthracite

Anthracite (Greek aνθρακίτης (anthrakítes), "coal-like," from άνθραξ (ánthrax), coal) is a hard, compact variety of mineral coal that has a high luster. It has the highest carbon count, the fewest impurities, and the highest calorific content of all types of coals, which also include bituminous coal and lignite.

Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%. 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 ignites with difficulty and burns with a short, blue, and smokeless flame.

Anthracite is categorized into standard grade (SG), which is used mainly in power generation, and high grade (HG) and ultra high grade (UHG), the principal uses of which are in the metallurgy sector. Anthracite accounts for about 1% of global coal reserves, and is mined in only a few countries around the world. China accounts for the lion’s share of production; other producers are Russia, Ukraine, North Korea, Vietnam, the UK, Australia and the US. Total production in 2010 was 670 million tons.

Terminology
Other terms which refer to anthracite are black coal, hard coal, stone coal (not to be confused with the German Steinkohle or Dutch steenkool which are broader terms meaning all varieties of coal of a stonelike hardness and appearance, like bituminous coal and often anthracite as well, as opposed to lignite, which is softer), blind coal (in Scotland), Kilkenny coal (in Ireland), crow coal (or craw coal from its shiny black appearance), 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. The imperfect anthracite of north Devon and north Cornwall (around Bude) in England, which is used as a pigment, is known as culm. Culm is also the term used in geological classification to distinguish the strata in which it is found and similar strata in the Rhenish hill countries are known as the Culm Measures. In America, culm is used as an equivalent for waste or slack in anthracite mining.

Properties
Anthracite differs from ordinary bituminous coal by its greater hardness, its higher relative density of 1.3–1.4, and lustre, which is often semi-metallic with a mildly brown 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 into anthracite.

The moisture content of fresh-mined anthracite generally is less than 15 percent. The heat content of anthracite ranges from 22 to 28 million Btu per short ton (26 to 33 MJ/kg) on a moist, mineral-matter-free basis. The heat content of anthracite coal consumed in the United States averages 25 million Btu/ton (29 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter). Since the 1980s, anthracite refuse or mine waste has been used for steam electric power generation.

Anthracite may be considered to be a transition stage between 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 earth-movements, such as the flanks of great mountain ranges. Anthracite is a product of metamorphism and is associated with metamorphic rocks, just as bituminous is associated with sedimentary rocks. For example, the compressed layers of anthracite that are deep mined in the folded (metamorphic) Appalachian Mountains of the Coal Region of northeastern Pennsylvania are extensions of the layers of bituminous coal that are strip mined on the (sedimentary) Allegheny Plateau of Kentucky and West Virginia, 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.

Structurally, it 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 feeling perceptibly colder when held in the warm hand than a similar lump of bituminous at the same temperature. The chemical composition of some typical anthracites is given in the article coal.

Anthracite is similar in appearance to the mineraloid jet and is sometimes used as a jet imitation.

Classifications
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:

Anthracite is divided by size mainly into applications that need lumps (typically larger than 10mm) - various industrial processes where it replaces metallurgical coke, and domestic fuel - and those that need fines (less than 10mm), such as sintering and pelletising.

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 1½ in (38 mm) size on round-hole screens.

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 briquettes and is sold in the United Kingdom under trade names such as Phurnacite, Ancit and Taybrite.

Production and uses


China today mines by far the largest share of global anthracite production, accounting for more than three-quarters of global output. Most Chinese production is of standard-grade anthracite, which is used in power generation. Increased demand in China has made that country into a net importer of the fuel, mostly from Vietnam, another major producer of anthracite for power generation, although increasing domestic consumption in Vietnam means that exports may be scaled back.

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 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 ferro-alloys, silicon-manganese, calcium-carbonate and silicon-carbide. South Africa exports lower-quality, higher-ash anthracite to Brazil to be used in steel-making.

Current U.S. anthracite production averages around 5 million tons per year. Of that, about 1.8 million tons were mined in the state of Pennsylvania. Mining of anthracite coal contributes up to 1% to Pennsylvania's gross state product; the state has the largest anthracite market in the nation at about $150 million. 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. As petroleum and natural gas have become more expensive, anthracite coal may grow in its importance as an energy source.

Anthracite is processed into different sizes by what is commonly referred to as a breaker (see coal). The large coal is raised from the mine and passed through breakers with toothed rolls to reduce the lumps to smaller pieces. The smaller pieces are separated into different sizes by a system of graduated sieves, placed in descending order. Sizing is necessary for different types of stoves and furnaces.

An important application has been developed in the extended use of 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. This is probably the most economical method of obtaining power known; with an engine as small as 15 horsepower the expenditure of fuel is at the rate of only 1 pound per horsepower-hour, and with larger engines it is proportionately less.

Major reserves
Among current producers, Russia, China and Ukraine have the largest estimated recoverable reserves of anthracite. Other countries with substantial reserves include Vietnam and North Korea.

The largest fields of anthracite coal in the United States are found in northeastern Pennsylvania called the Coal Region, where there are 7 billion short tons (6.3 billion tonnes) of minable reserves. Deposits at Crested Butte, Colorado were mined historically.

Anthracites of newer, Tertiary or Cretaceous age, are found in the Crow's Nest part of the Rocky Mountains in Canada, and at various places in the Andes in Peru.

Anthracite mining in the US and UK
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 outcropping 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 USA 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.

From the late 19th century until the 1950s, anthracite was the most popular fuel for heating homes and other buildings in the northern United States, until it was supplanted first by oil burning systems and more recently by natural gas systems as well. 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 giving away their position to the blockaders.

In the early 20th century United States, the Lackawanna 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.

In southwest Wales, anthracite was burned as a domestic fuel since at least medieval times. It was mined near Saundersfoot.

Anthracite is an authorised fuel in terms of the United Kingdom's Clean Air Act 1993, meaning that it can be used within a designated Smoke Control Area such as the central London boroughs.