74-461: Agglestone Rock , also known as the Devil's Anvil , is a sandstone block of about 400 tonnes weight, perched on a conical hill, approximately 1-mile (1.6 km) from the village of Studland , south Dorset . Formerly an 'anvil' shape with a flat top, it fell onto one end and side in 1970, leaving the top at an angle of approximately 45°. Legend has it that the devil threw the rock from The Needles on
148-512: A cyclothem . Cyclothems are thought to have their origin in glacial cycles that produced fluctuations in sea level , which alternately exposed and then flooded large areas of continental shelf. The woody tissue of plants is composed mainly of cellulose, hemicellulose, and lignin. Modern peat is mostly lignin, with a content of cellulose and hemicellulose ranging from 5% to 40%. Various other organic compounds, such as waxes and nitrogen- and sulfur-containing compounds, are also present. Lignin has
222-470: A thin section using a method like the Gazzi-Dickinson Method . This yields the relative percentages of quartz, feldspar, and lithic grains and the amount of clay matrix. The composition of a sandstone can provide important information on the genesis of the sediments when used with a triangular Q uartz, F eldspar, L ithic fragment ( QFL diagrams ). However, geologist have not been able to agree on
296-487: A fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution . With the invention of the steam engine , coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity . Some iron and steel -making and other industrial processes burn coal. The extraction and burning of coal damages
370-417: A process called carbonization . Carbonization proceeds primarily by dehydration , decarboxylation , and demethanation. Dehydration removes water molecules from the maturing coal via reactions such as Decarboxylation removes carbon dioxide from the maturing coal: while demethanation proceeds by reaction such as In these formulas, R represents the remainder of a cellulose or lignin molecule to which
444-478: A sandstone goes through as the degree of kinetic processing of the sediments increases. Dott's (1964) sandstone classification scheme is one of many such schemes used by geologists for classifying sandstones. Dott's scheme is a modification of Gilbert's classification of silicate sandstones, and it incorporates R.L. Folk's dual textural and compositional maturity concepts into one classification system. The philosophy behind combining Gilbert's and R. L. Folk's schemes
518-459: A set of boundaries separating regions of the QFL triangle. Visual aids are diagrams that allow geologists to interpret different characteristics of a sandstone. For example, a QFL chart can be marked with a provenance model that shows the likely tectonic origin of sandstones with various compositions of framework grains. Likewise, the stage of textural maturity chart illustrates the different stages that
592-464: A switch in fuels happened in London in the late sixteenth and early seventeenth centuries. Historian Ruth Goodman has traced the socioeconomic effects of that switch and its later spread throughout Britain and suggested that its importance in shaping the industrial adoption of coal has been previously underappreciated. The development of the Industrial Revolution led to the large-scale use of coal, as
666-549: A tenth. Indonesia and Australia export the most, followed by Russia . The word originally took the form col in Old English , from reconstructed Proto-Germanic * kula ( n ), from Proto-Indo-European root * g ( e ) u-lo- "live coal". Germanic cognates include the Old Frisian kole , Middle Dutch cole , Dutch kool , Old High German chol , German Kohle and Old Norse kol . Irish gual
740-445: A twofold classification: Cement is what binds the siliciclastic framework grains together. Cement is a secondary mineral that forms after deposition and during burial of the sandstone. These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite. Sandstone that becomes depleted of its cement binder through weathering gradually becomes friable and unstable. This process can be somewhat reversed by
814-403: A weight basis. This composition reflects partly the composition of the precursor plants. The second main fraction of coal is ash, an undesirable, noncombustable mixture of inorganic minerals. The composition of ash is often discussed in terms of oxides obtained after combustion in air: Of particular interest is the sulfur content of coal, which can vary from less than 1% to as much as 4%. Most of
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#1733084854483888-406: A weight composition of about 54% carbon, 6% hydrogen, and 30% oxygen, while cellulose has a weight composition of about 44% carbon, 6% hydrogen, and 49% oxygen. Bituminous coal has a composition of about 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis. The low oxygen content of coal shows that coalification removed most of the oxygen and much of the hydrogen
962-439: Is a stub . You can help Misplaced Pages by expanding it . This article about a specific United Kingdom geological feature is a stub . You can help Misplaced Pages by expanding it . Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks . Most sandstone
1036-837: Is a distinction that can be recognized in the field . In turn, the distinction between an orthoquartzite and a metaquartzite is the onset of recrystallization of existing grains. The dividing line may be placed at the point where strained quartz grains begin to be replaced by new, unstrained, small quartz grains, producing a mortar texture that can be identified in thin sections under a polarizing microscope. With increasing grade of metamorphism, further recrystallization produces foam texture , characterized by polygonal grains meeting at triple junctions, and then porphyroblastic texture , characterized by coarse, irregular grains, including some larger grains ( porphyroblasts .) Sandstone has been used since prehistoric times for construction, decorative art works and tools. It has been widely employed around
1110-449: Is a type of fossil fuel , formed when dead plant matter decays into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous ( Pennsylvanian ) and Permian times. Coal is used primarily as
1184-577: Is also a cognate via the Indo-European root. The conversion of dead vegetation into coal is called coalification . At various times in the geologic past, the Earth had dense forests in low-lying areas. In these wetlands, the process of coalification began when dead plant matter was protected from oxidation , usually by mud or acidic water, and was converted into peat . The resulting peat bogs , which trapped immense amounts of carbon, were eventually deeply buried by sediments. Then, over millions of years,
1258-429: Is burned in a turbine). Hot exhaust gases from the turbine are used to raise steam in a heat recovery steam generator which powers a supplemental steam turbine . The overall plant efficiency when used to provide combined heat and power can reach as much as 94%. IGCC power plants emit less local pollution than conventional pulverized coal-fueled plants. Other ways to use coal are as coal-water slurry fuel (CWS), which
1332-498: Is composed of quartz or feldspar , because they are the most resistant minerals to the weathering processes at the Earth's surface. Like uncemented sand , sandstone may be imparted any color by impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Because sandstone beds can form highly visible cliffs and other topographic features, certain colors of sandstone have become strongly identified with certain regions, such as
1406-594: Is entirely vertical; however, metamorphism may cause lateral changes of rank, irrespective of depth. For example, some of the coal seams of the Madrid, New Mexico coal field were partially converted to anthracite by contact metamorphism from an igneous sill while the remainder of the seams remained as bituminous coal. The earliest recognized use is from the Shenyang area of China where by 4000 BC Neolithic inhabitants had begun carving ornaments from black lignite. Coal from
1480-523: Is likely formed during eogenesis. Deeper burial is accompanied by mesogenesis , during which most of the compaction and lithification takes place. Compaction takes place as the sand comes under increasing pressure from overlying sediments. Sediment grains move into more compact arrangements, ductile grains (such as mica grains) are deformed, and pore space is reduced. In addition to this physical compaction, chemical compaction may take place via pressure solution . Points of contact between grains are under
1554-455: Is made when metallurgical coal (also known as coking coal ) is baked in an oven without oxygen at temperatures as high as 1,000 °C, driving off the volatile constituents and fusing together the fixed carbon and residual ash. Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace . The carbon monoxide produced by its combustion reduces hematite (an iron oxide ) to iron. Pig iron , which
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#17330848544831628-409: Is more abundant, and anthracite. The % carbon in coal follows the order anthracite > bituminous > lignite > brown coal. The fuel value of coal varies in the same order. Some anthracite deposits contain pure carbon in the form of graphite . For bituminous coal, the elemental composition on a dry, ash-free basis of 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on
1702-431: Is redeposited in the unstrained pore spaces. Mechanical compaction takes place primarily at depths less than 1,000 meters (3,300 ft). Chemical compaction continues to depths of 2,000 meters (6,600 ft), and most cementation takes place at depths of 2,000–5,000 meters (6,600–16,400 ft). Unroofing of buried sandstone is accompanied by telogenesis , the third and final stage of diagenesis. As erosion reduces
1776-443: Is that it is better able to "portray the continuous nature of textural variation from mudstone to arenite and from stable to unstable grain composition". Dott's classification scheme is based on the mineralogy of framework grains, and on the type of matrix present in between the framework grains. In this specific classification scheme, Dott has set the boundary between arenite and wackes at 15% matrix. In addition, Dott also breaks up
1850-452: Is used as fuel. 27.6% of world energy was supplied by coal in 2017 and Asia used almost three-quarters of it. Other large-scale applications also exist. The energy density of coal is roughly 24 megajoules per kilogram (approximately 6.7 kilowatt-hours per kg). For a coal power plant with a 40% efficiency, it takes an estimated 325 kg (717 lb) of coal to power a 100 W lightbulb for one year. In 2022, 68% of global coal use
1924-691: The Bronze Age (3000–2000 BC), where it formed part of funeral pyres . In Roman Britain , with the exception of two modern fields, "the Romans were exploiting coals in all the major coalfields in England and Wales by the end of the second century AD". Evidence of trade in coal, dated to about AD 200, has been found at the Roman settlement at Heronbridge , near Chester ; and in the Fenlands of East Anglia , where coal from
1998-530: The Dorset Echo as one of the "25 Things To Do In Dorset Before You Die". In his 1927 book Downland Man , H.J. Massingham wrote: A musing stroll across the heath from Studland, brings you to the Aggllestone, the holy stone (Helig - Anglo-Saxon for holy) hurled by the devil on to the crest of a hillock rising above the peaty waste. Fiends often do dress like angels, and it is certainly hard to detect anything of
2072-512: The Fushun mine in northeastern China was used to smelt copper as early as 1000 BC. Marco Polo , the Italian who traveled to China in the 13th century, described coal as "black stones ... which burn like logs", and said coal was so plentiful, people could take three hot baths a week. In Europe, the earliest reference to the use of coal as fuel is from the geological treatise On Stones (Lap. 16) by
2146-550: The Global Heritage Stone Resource . In some regions of Argentina, the orthoquartzite-stoned facade is one of the main features of the Mar del Plata style bungalows. Coal Coal is a combustible black or brownish-black sedimentary rock , formed as rock strata called coal seams . Coal is mostly carbon with variable amounts of other elements , chiefly hydrogen , sulfur , oxygen , and nitrogen . Coal
2220-506: The Isle of Wight with the intention of hitting either Corfe Castle , Bindon Abbey or Salisbury Cathedral . "Aggle" was taken into the old Dorset dialect as meaning "to wobble". The rock is an "eroded relic of iron-cemented, Tertiary sandstone, the Agglestone Grit". It used to be anvil -shaped, but has since changed form due to erosion and been toppled. Visiting the rock was listed by
2294-590: The Midlands was transported via the Car Dyke for use in drying grain. Coal cinders have been found in the hearths of villas and Roman forts , particularly in Northumberland , dated to around AD 400. In the west of England, contemporary writers described the wonder of a permanent brazier of coal on the altar of Minerva at Aquae Sulis (modern day Bath ), although in fact easily accessible surface coal from what became
Agglestone Rock - Misplaced Pages Continue
2368-702: The Somerset coalfield was in common use in quite lowly dwellings locally. Evidence of coal's use for iron -working in the city during the Roman period has been found. In Eschweiler , Rhineland , deposits of bituminous coal were used by the Romans for the smelting of iron ore . No evidence exists of coal being of great importance in Britain before about AD 1000, the High Middle Ages . Coal came to be referred to as "seacoal" in
2442-491: The coal gap in the Permian–Triassic extinction event , where coal is rare. Favorable geography alone does not explain the extensive Carboniferous coal beds. Other factors contributing to rapid coal deposition were high oxygen levels, above 30%, that promoted intense wildfires and formation of charcoal that was all but indigestible by decomposing organisms; high carbon dioxide levels that promoted plant growth; and
2516-444: The steam engine took over from the water wheel . In 1700, five-sixths of the world's coal was mined in Britain. Britain would have run out of suitable sites for watermills by the 1830s if coal had not been available as a source of energy. In 1947 there were some 750,000 miners in Britain, but the last deep coal mine in the UK closed in 2015. A grade between bituminous coal and anthracite
2590-407: The 13th century; the wharf where the material arrived in London was known as Seacoal Lane, so identified in a charter of King Henry III granted in 1253. Initially, the name was given because much coal was found on the shore, having fallen from the exposed coal seams on cliffs above or washed out of underwater coal outcrops, but by the time of Henry VIII , it was understood to derive from the way it
2664-578: The Carboniferous, and suggested that climatic and tectonic factors were a more plausible explanation, reconstruction of ancestral enzymes by phylogenetic analysis corroborated a hypothesis that lignin degrading enzymes appeared in fungi approximately 200 MYa. One likely tectonic factor was the Central Pangean Mountains , an enormous range running along the equator that reached its greatest elevation near this time. Climate modeling suggests that
2738-587: The Central Pangean Mountains contributed to the deposition of vast quantities of coal in the late Carboniferous. The mountains created an area of year-round heavy precipitation, with no dry season typical of a monsoon climate. This is necessary for the preservation of peat in coal swamps. Coal is known from Precambrian strata, which predate land plants. This coal is presumed to have originated from residues of algae. Sometimes coal seams (also known as coal beds) are interbedded with other sediments in
2812-563: The Greek scientist Theophrastus (c. 371–287 BC): Among the materials that are dug because they are useful, those known as anthrakes [coals] are made of earth, and, once set on fire, they burn like charcoal [anthrakes]. They are found in Liguria ;... and in Elis as one approaches Olympia by the mountain road; and they are used by those who work in metals. Outcrop coal was used in Britain during
2886-491: The application of tetraethyl orthosilicate (Si(OC 2 H 5 ) 4 ) which will deposit amorphous silicon dioxide between the sand grains. The reaction is as follows. Pore space includes the open spaces within a rock or a soil. The pore space in a rock has a direct relationship to the porosity and permeability of the rock. The porosity and permeability are directly influenced by the way the sand grains are packed together. Sandstones are typically classified by point-counting
2960-468: The common minerals most resistant to weathering processes at the Earth's surface, as seen in the Goldich dissolution series . Framework grains can be classified into several different categories based on their mineral composition: Matrix is very fine material, which is present within interstitial pore space between the framework grains. The nature of the matrix within the interstitial pore space results in
3034-456: The depositional environment, older sand is buried by younger sediments, and it undergoes diagenesis . This mostly consists of compaction and lithification of the sand. Early stages of diagenesis, described as eogenesis , take place at shallow depths (a few tens of meters) and are characterized by bioturbation and mineralogical changes in the sands, with only slight compaction. The red hematite that gives red bed sandstones their color
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3108-407: The depth of burial, renewed exposure to meteoric water produces additional changes to the sandstone, such as dissolution of some of the cement to produce secondary porosity . Framework grains are sand-sized (0.0625-to-2-millimeter (0.00246 to 0.07874 in) diameter) detrital fragments that make up the bulk of a sandstone. Most framework grains are composed of quartz or feldspar , which are
3182-629: The devil when the Madonna-blue chalices of that visionary flower, Gentiana pneumonanthe, are open on the heath. But devils did traffic with holy stones in archaic England, for devils were once gods themselves fallen from heaven upon evil days, the days when the usurping Celts looked with dread upon the works of their predecessors. For the Agglestone is a menhir . 50°38′42″N 1°58′05″W / 50.645083°N 1.968125°W / 50.645083; -1.968125 This Dorset location article
3256-446: The different types of framework grains that can be present in a sandstone into three major categories: quartz, feldspar, and lithic grains. When sandstone is subjected to the great heat and pressure associated with regional metamorphism , the individual quartz grains recrystallize, along with the former cementing material, to form the metamorphic rock called quartzite . Most or all of the original texture and sedimentary structures of
3330-571: The environment , causing premature death and illness, and it is the largest anthropogenic source of carbon dioxide contributing to climate change . Fourteen billion tonnes of carbon dioxide were emitted by burning coal in 2020, which is 40% of total fossil fuel emissions and over 25% of total global greenhouse gas emissions . As part of worldwide energy transition , many countries have reduced or eliminated their use of coal power . The United Nations Secretary General asked governments to stop building new coal plants by 2020. Global coal use
3404-430: The evolution of the first trees . But bacteria and fungi did not immediately evolve the ability to decompose lignin, so the wood did not fully decay but became buried under sediment, eventually turning into coal. About 300 million years ago, mushrooms and other fungi developed this ability, ending the main coal-formation period of earth's history. Although some authors pointed at some evidence of lignin degradation during
3478-512: The factors involved in coalification, temperature is much more important than either pressure or time of burial. Subbituminous coal can form at temperatures as low as 35 to 80 °C (95 to 176 °F) while anthracite requires a temperature of at least 180 to 245 °C (356 to 473 °F). Although coal is known from most geologic periods , 90% of all coal beds were deposited in the Carboniferous and Permian periods. Paradoxically, this
3552-498: The form of iron pyrite (FeS 2 ). Being a dense mineral, it can be removed from coal by mechanical means, e.g. by froth flotation . Some sulfate occurs in coal, especially weathered samples. It is not volatilized and can be removed by washing. Minor components include: As minerals, Hg, As, and Se are not problematic to the environment, especially since they are only trace components. They become however mobile (volatile or water-soluble) when these minerals are combusted. Most coal
3626-433: The greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as the mineral dissolved from strained contact points
3700-442: The hardness of individual grains, uniformity of grain size and friability of their structure, some types of sandstone are excellent materials from which to make grindstones , for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone . A type of pure quartz sandstone, orthoquartzite, with more of 90–95 percent of quartz, has been proposed for nomination to
3774-475: The heat and pressure of deep burial caused the loss of water, methane and carbon dioxide and increased the proportion of carbon. The grade of coal produced depended on the maximum pressure and temperature reached, with lignite (also called "brown coal") produced under relatively mild conditions, and sub-bituminous coal , bituminous coal , or anthracite coal (also called "hard coal" or "black coal") produced in turn with increasing temperature and pressure. Of
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#17330848544833848-431: The increasing tendency of the anthracite to break with a conchoidal fracture , similar to the way thick glass breaks. As geological processes apply pressure to dead biotic material over time, under suitable conditions, its metamorphic grade or rank increases successively into: There are several international standards for coal. The classification of coal is generally based on the content of volatiles . However
3922-453: The morphology and some properties of the original plant. In many coals, individual macerals can be identified visually. Some macerals include: In coalification huminite is replaced by vitreous (shiny) vitrinite . Maturation of bituminous coal is characterized by bitumenization , in which part of the coal is converted to bitumen , a hydrocarbon-rich gel. Maturation to anthracite is characterized by debitumenization (from demethanation) and
3996-405: The most important distinction is between thermal coal (also known as steam coal), which is burnt to generate electricity via steam; and metallurgical coal (also known as coking coal), which is burnt at high temperature to make steel . Hilt's law is a geological observation that (within a small area) the deeper the coal is found, the higher its rank (or grade). It applies if the thermal gradient
4070-493: The much lower temperatures and pressures associated with diagenesis of sedimentary rock, but diagenesis has cemented the rock so thoroughly that microscopic examination is necessary to distinguish it from metamorphic quartzite. The term orthoquartzite is used to distinguish such sedimentary rock from metaquartzite produced by metamorphism. By extension, the term orthoquartzite has occasionally been more generally applied to any quartz-cemented quartz arenite . Orthoquartzite (in
4144-464: The narrow sense) is often 99% SiO 2 with only very minor amounts of iron oxide and trace resistant minerals such as zircon , rutile and magnetite . Although few fossils are normally present, the original texture and sedimentary structures are preserved. The typical distinction between a true orthoquartzite and an ordinary quartz sandstone is that an orthoquartzite is so highly cemented that it will fracture across grains, not around them. This
4218-407: The nature of Carboniferous forests, which included lycophyte trees whose determinate growth meant that carbon was not tied up in heartwood of living trees for long periods. One theory suggested that about 360 million years ago, some plants evolved the ability to produce lignin , a complex polymer that made their cellulose stems much harder and more woody. The ability to produce lignin led to
4292-455: The number of double bonds between carbon). As carbonization proceeds, aliphatic compounds convert to aromatic compounds . Similarly, aromatic rings fuse into polyaromatic compounds (linked rings of carbon atoms). The structure increasingly resembles graphene , the structural element of graphite. Chemical changes are accompanied by physical changes, such as decrease in average pore size. The macerals are coalified plant parts that retain
4366-456: The pre-combustion treatment, turbine technology (e.g. supercritical steam generator ) and the age of the plant. A few integrated gasification combined cycle (IGCC) power plants have been built, which burn coal more efficiently. Instead of pulverizing the coal and burning it directly as fuel in the steam-generating boiler, the coal is gasified to create syngas , which is burned in a gas turbine to produce electricity (just like natural gas
4440-638: The product of physical and chemical weathering of bedrock. Weathering and erosion are most rapid in areas of high relief, such as volcanic arcs , areas of continental rifting , and orogenic belts . Eroded sand is transported by rivers or by the wind from its source areas to depositional environments where tectonics has created accommodation space for sediments to accumulate. Forearc basins tend to accumulate sand rich in lithic grains and plagioclase . Intracontinental basins and grabens along continental margins are also common environments for deposition of sand. As sediments continue to accumulate in
4514-427: The reacting groups are attached. Dehydration and decarboxylation take place early in coalification, while demethanation begins only after the coal has already reached bituminous rank. The effect of decarboxylation is to reduce the percentage of oxygen, while demethanation reduces the percentage of hydrogen. Dehydration does both, and (together with demethanation) reduces the saturation of the carbon backbone (increasing
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#17330848544834588-704: The red rock deserts of Arches National Park and other areas of the American Southwest . Rock formations composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs . Quartz-bearing sandstone can be changed into quartzite through metamorphism , usually related to tectonic compression within orogenic belts . Sandstones are clastic in origin (as opposed to either organic , like chalk and coal , or chemical , like gypsum and jasper ). The silicate sand grains from which they form are
4662-417: The sandstone are erased by the metamorphism. The grains are so tightly interlocked that when the rock is broken, it fractures through the grains to form an irregular or conchoidal fracture. Geologists had recognized by 1941 that some rocks show the macroscopic characteristics of quartzite, even though they have not undergone metamorphism at high pressure and temperature. These rocks have been subject only to
4736-399: The sulfur and most of the nitrogen is incorporated into the organic fraction in the form of organosulfur compounds and organonitrogen compounds . This sulfur and nitrogen are strongly bound within the hydrocarbon matrix. These elements are released as SO 2 and NO x upon combustion. They cannot be removed, economically at least, otherwise. Some coals contain inorganic sulfur, mainly in
4810-612: The world in constructing temples, churches, homes and other buildings, and in civil engineering . Although its resistance to weathering varies, sandstone is easy to work. That makes it a common building and paving material, including in asphalt concrete . However, some types that have been used in the past, such as the Collyhurst sandstone used in North West England , have had poor long-term weather resistance, necessitating repair and replacement in older buildings. Because of
4884-415: The world's coal-generated electricity. Efforts around the world to reduce the use of coal have led some regions to switch to natural gas and renewable energy . In 2018 coal-fired power station capacity factor averaged 51%, that is they operated for about half their available operating hours. Coke is a solid carbonaceous residue that is used in manufacturing steel and other iron-containing products. Coke
4958-574: Was 8.3 billion tonnes in 2022, and is set to remain at record levels in 2023. To meet the Paris Agreement target of keeping global warming below 2 °C (3.6 °F) coal use needs to halve from 2020 to 2030, and "phasing down" coal was agreed upon in the Glasgow Climate Pact . The largest consumer and importer of coal in 2020 was China , which accounts for almost half the world's annual coal production, followed by India with about
5032-574: Was based on the trading of this commodity. Coal continues to arrive on beaches around the world from both natural erosion of exposed coal seams and windswept spills from cargo ships. Many homes in such areas gather this coal as a significant, and sometimes primary, source of home heating fuel. Coal consists mainly of a black mixture of diverse organic compounds and polymers. Of course, several kinds of coals exist, with variable dark colors and variable compositions. Young coals (brown coal, lignite) are not black. The two main black coals are bituminous, which
5106-504: Was carried to London by sea. In 1257–1259, coal from Newcastle upon Tyne was shipped to London for the smiths and lime -burners building Westminster Abbey . Seacoal Lane and Newcastle Lane, where coal was unloaded at wharves along the River Fleet , still exist. These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground extraction by shaft mining or adits
5180-602: Was developed in the Soviet Union , or in an MHD topping cycle . However these are not widely used due to lack of profit. In 2017 38% of the world's electricity came from coal, the same percentage as 30 years previously. In 2018 global installed capacity was 2 TW (of which 1TW is in China) which was 30% of total electricity generation capacity. The most dependent major country is South Africa, with over 80% of its electricity generated by coal; but China alone generates more than half of
5254-408: Was developed. The alternative name was "pitcoal", because it came from mines. Cooking and home heating with coal (in addition to firewood or instead of it) has been done in various times and places throughout human history, especially in times and places where ground-surface coal was available and firewood was scarce, but a widespread reliance on coal for home hearths probably never existed until such
5328-490: Was during the Late Paleozoic icehouse , a time of global glaciation . However, the drop in global sea level accompanying the glaciation exposed continental shelves that had previously been submerged, and to these were added wide river deltas produced by increased erosion due to the drop in base level . These widespread areas of wetlands provided ideal conditions for coal formation. The rapid formation of coal ended with
5402-606: Was once known as "steam coal" as it was widely used as a fuel for steam locomotives . In this specialized use, it is sometimes known as "sea coal" in the United States. Small "steam coal", also called dry small steam nuts (DSSN), was used as a fuel for domestic water heating . Coal played an important role in industry in the 19th and 20th century. The predecessor of the European Union , the European Coal and Steel Community ,
5476-430: Was used for electricity generation. Coal burnt in coal power stations to generate electricity is called thermal coal . It is usually pulverized and then burned in a furnace with a boiler . The furnace heat converts boiler water to steam , which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process varies between about 25% and 50% depending on
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