Coal is a non-renewable energy source formed by dead plants that have been compressed and heated and it is a solid but brittle, carbonaceous black sedimentary rock that burns. It is made up of carbon, hydrogen, oxygen, nitrogen, and lesser amounts of sulfur and other trace elements. Coal has lots of energy in it. When it is burned, it makes heat and ligh enargy.
Coal is divided into four classes:lignite, subbituminous coal, bituminous, and anthracite. Of the commonly minable coals, anthracite is the hardest and has the most carbon, giving it a higher heat value.
Lignite is the softest coal and has the least amount of carbon. By definition, coal is a combustible rock containing more than 50 percent by weight carbonaceous material formed from compaction of variously altered plant remains originally derived from peat.
Subbituminous Coal: Under still more pressure, some lignite was changed into the next rank of coal subbituminous. This is a dull black coal with a higher heating value than lignite that is used primarily for generating electricity and for space heating. Most subbituminous reserves are located in Montana, Wyoming, Colorado, New Mexico, Washington and Alaska.
Bituminous Coal: Bituminous coal is the most abundant and most widely used coal. This is the type of coal found in the Appalachian region. It has a higher heating potential and is used for making coke. It has a higher percentage of fixed carbon, greater heat value and better weathering characteristics than lignite and sub-lignite coals. This is the type most commonly used for electric power generation in the U.S. It has a higher heating value than either lignite or subbituminous coal, but less than that of anthracite. Bituminous coal is mined chiefly in Appalachia and the Midwest. Also used to make coke.
Anthracite: anthracite forms from bituminous coal when great pressures developed in folded rock strata during the creation of mountain ranges. This occurs only in limited geographic areas - primarily the Appalachian region of Pennsylvania. Anthracite has the highest energy content of all coals and is used for space heating and generating electricity. This type of coal has the highest percentage of fixed carbon and a lower percentage of volatile material than all other coals, making it harder to ignite. However, when it is ignited, it burns relatively smokeless.
What Is Coal Used For?
Coal is used primarily as an energy source, either for heat or electricity. It was once heavily used to heat homes and power locomotives and factories. Bituminous coal is also used to produce coke for making steel and other industrial process heating. Coal gasification and coal liquefaction (coal-to-liquids) are also possible uses of coal for producing synthetic fuel. Approximately 4% of the coal mined in the United States is exported, and most of the exported coal is used for making steel.
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