Grade of Coal

The grade of coal refers to the amount of mineral matter that is present in the coal and is a measure of coal quality. Sulfur content, ash fusion temperatures (i.e., measurement of the behavior of ash at high temperatures), and the quantity of trace elements in coal are also used to grade coal. Formal classification systems have not been developed with regard to the grading of coal; however, grade is important to the coal user. Mineral matter may occur as finely dispersed or in discrete partings in the coal. Some of the inorganic matter and trace elements are derived from the original vegetation, but the majority is introduced during coalification by wind or water to the peat swamp or through movement of solutions in cracks, fissures, and cavities [15]. Coal mineralogy can affect the ability to remove minerals during coal preparation/cleaning, the coal combustion and conversion (i.e., production of liquid fuels or chemicals) characteristics, and metallurgical coke properties.

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