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Lignite (derived from Latin lignum meaning 'wood'), often referred to as brown coal, [1] is a soft, brown, combustible sedimentary rock formed from naturally compressed peat.It has a carbon content around 25–35% [1] [2] and is considered the lowest rank of coal due to its relatively low heat content.
Peat, a precursor of coal; Lignite, or brown coal, the lowest rank of coal, most harmful to health when burned, [7] used almost exclusively as fuel for electric power generation; Sub-bituminous coal, whose properties range between those of lignite and those of bituminous coal, is used primarily as fuel for steam-electric power generation.
As a fossil fuel burned for heat, coal supplies about a quarter of the world's primary energy and two-fifths of its electricity. [4] The largest consumer and importer of coal is China. China mines almost half the world's coal, followed by India with about a tenth. Australia accounts for about a third of world coal exports, followed by Indonesia ...
Its bank density (the density of a coal seam prior to breaking up during mining) is about 1346 kg/m 3 (84 lb/ft 3) while the bulk density of extracted coal is up to 833 kg/m 3 (52 lb/ft 3). [12] Bituminous coal characteristically burns with a smoky flame and softens and swells during combustion. [13]
Coal plies and particles have different relative densities, determined by vitrinite content, rank, ash value/mineral content and porosity. Coal is usually washed by passing it over a bath of liquid of known density. This removes high-ash value particle and increases the saleability of the coal as well as its energy content per unit volume.
The coal industry is one of the most controversial industries in the world, which may not be as big as it once was, but […] Click to skip ahead and jump to the 5 largest coal companies in the world.
Sub-bituminous coal is a lower grade of coal that contains 35–45% carbon. The properties of this type are between those of lignite, the lowest grade of coal, and those of bituminous coal, the second-highest grade of coal. [1] Sub-bituminous coal is primarily used as a fuel for steam-electric power generation.
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 tons . [ 2 ]