Bituminous coal

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Bituminous coal

Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite coal but of poorer quality than anthracite. Formation is usually the result of high pressure being exerted on lignite. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. These distinctive sequences, which are classified according to either "dull, bright-banded" or "bright, dull-banded", is how bituminous coals are stratigraphically identified.


Bituminous coal is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. Its primary constituents are macerals: vitrinite, and liptinite. The carbon content of bituminous coal is around 60–80%; the rest is composed of water, air, hydrogen, and sulfur, which have not been driven off from the macerals. Bank density is approximately 1,346 kilograms per cubic metre (84.0 lb/cu ft). Bulk density typically runs to 833 kilograms per cubic metre (52.0 lb/cu ft). The heat content of bituminous coal ranges from 24 to 35 megajoules per kilogram (21 to 30 million British thermal units per short ton) on a moist, mineral-matter-free basis.

Within the coal mining industry, this type of coal is known for releasing the largest amounts of firedamp, a dangerous mixture of gases that can cause underground explosions. Extraction of bituminous coal demands the highest safety procedures involving attentive gas monitoring, good ventilation and vigilant site management.


Bituminous coals are graded according to vitrinite reflectance, moisture content, volatile content, plasticity and ash content. Generally, the highest value bituminous coals have a specific grade of plasticity, volatility and low ash content, especially with low carbonate, phosphorus, and sulfur.

Plasticity is vital for coking as it represents its ability to gradually form specific plasticity phases during the coking process, measured by coal dilatation tests. Low phosphorus content is vital for these coals, as phosphorus is a highly damaging element in steel making.

Coking coal is best if it has a very narrow range of volatility and plasticity. This is measured by the free swelling index test. Volatile content and swelling index are used to select coals for coke blending as well.

Volatility is also critical for steel-making and power generation, as this determines the burn rate of the coal. High volatile content coals, while easy to ignite often are not as prized as moderately volatile coals; low volatile coal may be difficult to ignite although it contains more energy per unit volume. The smelter must balance the volatile content of the coals to optimize the ease of ignition, burn rate, and energy output of the coal.

Low ash, sulfur, and carbonate coals are prized for power generation because they do not produce much boiler slag and they do not require as much effort to scrub the flue gases to remove particulate matter. Carbonates are deleterious as they readily stick to the boiler apparatus.

Smithing coal

Smithing coal is a type of high-quality bituminous coal ideally suited for use in a coal forge. It is as free from ash, sulfur, and other impurities as possible. [1] The constituents of the coal should be as follows: [2]

SulfurNot over 1%
AshNot over 7%
CarbonNot less than 70%
MoistureNot over 12%

Cannel coal

Cannel coal is a coal which ignites easily producing a bright flame. The name derives from the Scottish pronunciation of candle coal. It contains a high volatile content, is non-coking and was a source for coal oil in West Virginia during the mid-1800s. [3] While the use of Cannel has greatly diminished over the past century, it is still valued by artists for its ability to be carved and polished into sculptures and jewelry.[ citation needed ] "Cannel coal is a terrestrial type of hydrogen sulfide rich oil shale that is technically called sapropelic coal." [4]

Coking coal

When used for many industrial processes, bituminous coal must first be "coked" to remove volatile components. Coking is achieved by heating the coal in the absence of oxygen, which drives off volatile hydrocarbons such as propane, benzene and other aromatic hydrocarbons, and some sulfur gases. This also drives off a considerable amount of the contained water of the bituminous coal.

Coking coal (metallurgical coal) is used in the manufacture of steel, where carbon must be as volatile-free and ash-free as possible.

Coking coal is heated to produce coke, a hard, grey, porous material which is used to blast in furnaces for the extraction of iron from the iron ore.

Bituminous coal by geologic period

Bituminous coal in the United States is between 100 and 300 million years old. [5]

Cretaceous coals

In the United States, Cretaceous bituminous coals occur in Wyoming, Colorado and New Mexico. [6] [7]

In Canada, the Western Canada Sedimentary Basin of Alberta and British Columbia hosts major deposits of bituminous coal that formed in swamps along the western margin of the Western Interior Seaway. They range in age from latest Jurassic or earliest Cretaceous in the Mist Mountain Formation, to Late Cretaceous in the Gates Formation. [8] The Intermontane and Insular Coalfields of British Columbia also contain deposits of Cretaceous bituminous coal. [9]

Jurassic coals

Extensive but low-value coals of Jurassic age extend through the Surat Basin in Australia, formed in an intracratonic sag basin, and contain evidence of dinosaur activity in the numerous ash plies. These coals are exploited in Queensland from the Walloon Coal Measures, which are up to 15 m thick of sub-bituminous to bituminous coals suited for coking, steam-raising and oil cracking.

Triassic coals

Coals of Triassic age are known from the Clarence-Moreton and Ipswich Basins, near Ipswich, Australia and the Esk Trough. Coals of this era are rare, and many contain fossils of flowering plants. Some of the best coking coals are Australian Triassic coals, although most economic deposits have been worked out.

Permian coals

The second largest deposits of the world's bituminous coal are contained within Permian strata in Russia. Australian deposits in the Bowen Basin in Queensland, the Sydney Basin and Perth Basin are Permian coal, where thicknesses in excess of 300 m are known. Current reserves and resources are projected to last for over 200 years.

Australia exports the vast majority of its coal for coking and steel making in Japan. Certain Australian coals are the best in the world for these purposes, requiring little to no blending. Some bituminous coals from the Permian and Triassic in Australia are also the most suitable for cracking into oil.

Carboniferous coals

Much North American coal was created in subsiding areas adjacent to the Appalachian Mountains during the Pennsylvanian subperiod. A vast network of swamps covered large parts of North America at this time and much of the organic material created in these wetlands accumulated to form thick layers of peat (the precursor to coal) that were buried faster than they could decay.

Bituminous coal is mined in the Appalachian region, primarily for power generation. Mining is done via both surface and underground mines. Pocahontas bituminous coal at one time fueled half the world's navies and today stokes steel mills and power plants all over the globe.

See also

Related Research Articles

Coal A combustible sedimentary rock composed primarily of carbon

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 is formed when dead plant matter decays into peat and 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.

Lignite soft, brown, combustible, sedimentary rock

Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content. It has a carbon content around 60–70 percent. It is mined all around the world, is used almost exclusively as a fuel for steam-electric power generation, and is the coal which is most harmful to health.

Coke (fuel) A grey, hard and porous fuel with high carbon content and few impurities.

Coke is a grey, hard, and porous fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air — a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

Anthracite A hard, compact variety of coal that has a submetallic luster

Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. 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.

Vitrinite is one of the primary components of coals and most sedimentary kerogens. Vitrinite is a type of maceral, where "macerals" are organic components of coal analogous to the "minerals" of rocks. Vitrinite has a shiny appearance resembling glass (vitreous). It is derived from the cell-wall material or woody tissue of the plants from which coal was formed. Chemically, it is composed of polymers, cellulose and lignin.

A maceral is a component, organic in origin, of coal or oil shale. The term 'maceral' in reference to coal is analogous to the use of the term 'mineral' in reference to igneous or metamorphic rocks. Examples of macerals are inertinite, vitrinite, and liptinite.

Sub-bituminous coal is a type of coal whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation.

Cannel coal type of bituminous coal

Cannel coal or candle coal is a type of bituminous coal, also classified as terrestrial type oil shale. Due to its physical morphology and low mineral content cannel coal is considered to be coal but by its texture and composition of the organic matter it is considered to be oil shale. Although historically the term cannel coal has been used interchangeably with boghead coal, a more recent classification system restricts cannel coal to terrestrial origin, and boghead coal to lacustrine environments.

Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel.

Western Canadian Sedimentary Basin

The Western Canada Sedimentary Basin (WCSB) is a vast sedimentary basin underlying 1,400,000 square kilometres (540,000 sq mi) of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock extending from the Rocky Mountains in the west to the Canadian Shield in the east. This wedge is about 6 kilometres (3.7 mi) thick under the Rocky Mountains, but thins to zero at its eastern margins. The WCSB contains one of the world's largest reserves of petroleum and natural gas and supplies much of the North American market, producing more than 16,000,000,000 cubic feet (450,000,000 m3) per day of gas in 2000. It also has huge reserves of coal. Of the provinces and territories within the WCSB, Alberta has most of the oil and gas reserves and almost all of the oil sands.

Oil shale geology

Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale formation takes place in a number of depositional settings and has considerable compositional variation. Oil shales can be classified by their composition or by their depositional environment. Much of the organic matter in oil shales is of algal origin, but may also include remains of vascular land plants. Three major type of organic matter (macerals) in oil shale are telalginite, lamalginite, and bituminite. Some oil shale deposits also contain metals which include vanadium, zinc, copper, and uranium.

According to the United States Energy Information Administration (EIA), Pakistan may have over 9 billion barrels (1.4×109 cubic metres) of petroleum oil and 105 trillion cubic feet (3.0 trillion cubic metres) in natural gas (including shale gas) reserves.

The Zonguldak basin of northwestern Turkey is the only basin in Turkey with mineable coal deposits. It has been mined for coal since the late 1800s. The basin takes its name after Zonguldak, Turkey, and is approximately 41° N. Geographically, the Zonguldak is roughly elliptical in shape with its long axis oriented roughly SW to NE, and is adjacent to the Black Sea. Three main regions have been recognized in the Zonguldak basin. These are the Armutcuk, the Zonguldak, and the Amasra, from west to east respectively.

Metallurgical coal or coking coal is a grade of coal that can be used to produce good-quality coke. Coke is an essential fuel and reactant in the blast furnace process for primary steelmaking. The demand for metallurgical coal is highly coupled to the demand for steel. Primary steelmaking companies often have a division that produces coal for coking, to ensure a stable and low-cost supply.

The geology of North Dakota includes thick sequences oil and coal bearing sedimentary rocks formed in shallow seas in the Paleozoic and Mesozoic, as well as terrestrial deposits from the Cenozoic on top of ancient Precambrian crystalline basement rocks. The state has extensive oil and gas, sand and gravel, coal, groundwater and other natural resources.

The geology of Kazakhstan includes extensive basement rocks from the Precambrian and widespread Paleozoic rocks, as well as sediments formed in rift basins during the Mesozoic.

The geology of Laos includes poorly defined oldest rocks. Marine conditions persisted for much of the Paleozoic and parts of the Mesozoic, followed by periods of uplift and erosion. The country has extensive salt, gypsum and potash, but very little hydrocarbons and limited base metals.

The geology of Croatia includes Precambrian rocks, covered over by younger sedimentary rocks and deformed or superimposed by tectonic activity.

Geology of Italy

The Geology of Italy includes mountain ranges such as the Alps, the Dolomites and the Apennines formed from the uplift of igneous and primarily marine sedimentary rocks all formed since the Paleozoic.. Some active volcanoes are located in Insular Italy.

Funginite Coal mineral based on fossilized fungus

Funginite is a maceral that exhibits several different physical properties and characteristics under particular conditions, and its dimensions are based upon its source and place of discovery. Furthermore, it is primarily part of a group of macerals that naturally occur in rocks containing mostly carbon constituents, specifically coal. Due to its nature, research into the chemical structure and formula of funginite is considered limited and lacking. According to Chen et al. referencing ICCP, 2001, alongside the maceral secretinite, they "are both macerals of the inertinite group, which is more commonly known as fossilized charcoal, and were previously jointly classified as the maceral sclerotinite". In the scientific community, the discernment between the two does not remain entirely clear, but there are slight particular and specific differences in regards to the composition between both. It is also the product of fungal development on these carbon rich sedimentary rocks.


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