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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. Is a type of fossil fuel, 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. Is used primarily as a fuel. 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.General Characteristics

It is derived from plants that once formed lush vegetation in swamps or lagoons. The plants, when they died, were partially decomposed by microorganisms and buried by other sediment that protected them from total destruction. At the volatile components were released, the carbon became concentrated and the plant accumulations successively passed through the stages of tuba, lignite (hard coal) and eventually, graphite if geological conditions favored their metamorphism.

Classification of Carbon


Lignite or brown coal


Sub-bituminous coal


Bituminous coal

Anthracite coal


Cannel coal

Carbon ComponentsComposition of coal

The main components of coal are macerals and ashes. The are macerated but still recognizable plant remains, which make up the organic part of the charcoal.

Three types are distinguished: 

Huminite, is the main group in most coals and comes from the woody tissues of plants.

Liptinite, appears in smaller proportion than the previous group and comes from resinous and waxy parts of plants.

Inertinite is the scarcest component in coals and is practically inert throughout the carbonization process.

The composition of coal is reported either as a proximate analysis (moisture, volatile matter, fixed carbon, and ash) or an ultimate analysis (ash, carbon, hydrogen, nitrogen, oxygen, and sulfur).The “volatile matter” does not exist by itself (except for some adsorbed methane) but designates the volatile compounds that are produced and driven off by heating the coal.

A typical bituminous coal may have an ultimate analysis on a dry, ash-free basis of 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis.

Ash Composition, Weight percentWhile the molten metal is in the mould, the coal burns slowly, releasing reducing gases at pressure, and so preventing the metal from penetrating the pores of the sand. It is also contained in ‘mould wash’, a paste or liquid with the same function applied to the mould before casting. Sea coal can be mixed with the clay lining (the “bod”) used for the bottom of a cupola furnace. When heated, the coal decomposes and the bod becomes slightly friable, easing the process of breaking open holes for tapping the molten metal.








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