Metallurgical coal or coking coal is a grade of

coal Coal 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. Coal is formed when ...

that can be used to produce good-quality coke. Coke is an essential fuel and reactant in the blast furnace process for primary

steelmaking Steelmaking is the process of producing steel from iron ore and carbon/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon (the most important impurity) are removed from the sourced iron, and alloy ...

. The demand for metallurgical coal is highly coupled to the demand for steel. Primary steelmaking companies often have a division that produces coal for coking, to ensure a stable and low-cost supply. Metallurgical coal comes mainly from Canada, the United States, and Australia, with Australia exporting 58% of seaborne trade, mostly going to China. In the United States, the electric power sector used "93% of total U.S. coal consumption between 2007 and 2018"; only 7% of the total was metallurgical coal and coal for other uses such as heating.

Characteristics

Metallurgical coal is low in ash, moisture, sulfur and phosphorus content, and its

rank Rank is the relative position, value, worth, complexity, power, importance, authority, level, etc. of a person or object within a ranking, such as: Level or position in a hierarchical organization * Academic rank * Diplomatic rank * Hierarchy * ...

is usually

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

. Some grades of anthracite coal are used for

sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...

, pulverized coal injection, direct blast furnace charge, pelletizing, and in production of ferro-alloys, silicon-manganese, calcium-carbide and silicon-carbide. Metallurgical coal produces strong, low-density coke when it is heated in a low-oxygen environment. On heating, the coal softens, and volatile components evaporate and escape through pores in the mass. During coking, the material swells and increases in volume. The coking ability of coal is related to its physical properties such as its rank, but laboratory testing is required to completely evaluate the coking ability of a coal. The strength and density of coke are particularly important when it is used in a blast furnace, as the coke supports part of the ore and flux burden inside the furnace. Metallurgical coal contrasts with

thermal coal Coal 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. Coal is formed when de ...

, which does not produce coke when heated. Because of their different end-uses, prices for the two types of coal are usually quite different. The suitability of coal for conversion to coke is also referred to as the ''caking ability''.

Types

There are several types of metallurgical coal: * Hard coking coals (HCC) * Medium coking coal (MCC) * Semi-soft coking coal (SSCC) * Pulverized coal for injection (PCI) coal

References

{{geology-stub Coal

Characteristics

Types

See also

References