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Sub-bituminous coal

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.

Sub-bituminous coal may be dull, dark brown to black, soft and crumbly at the lower end of the range, to bright, jet-black, hard, and relatively strong at the upper end. It contains 20-30% inherent moisture by weight. The heat content of sub-bituminous coal ranges from 17 to 24 million British thermal units (Btu) per short ton (20 to 28 megajoules per kilogram) on a moist, mineral-matter-free basis. The heat content of sub-bituminous coal consumed in the United States averages 17 to 18 million Btu per short ton (20 to 21 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter). A major source of sub-bituminous coal in the United States is the Powder River Basin in Wyoming.

Its relatively low density and high water content renders some types of sub-bituminous coal susceptible to spontaneous combustion if not packed densely during storage in order to exclude free air flow.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Sub-bituminous_coal". A list of authors is available in Wikipedia.
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