Some coals can be used to produce coke, an important raw material used in steel making. These coals are referred to as metallurgical coal, met coal, or coking coal.These can be considered grade terms. Coke (not the soft drink) is a hard, porous, carbon-rich compound. Only coals with specific quality characteristics can be used to make coke. Metallurgical grade coals for steel production must be very low in ash (generally less than 10 percent) and sulfur (less than 1 percent), have volatile matter contents from 20 to 30 percent (medium- to high-volatile bituminous rank), and have a favorable balance of reactive and inert components. Grade terms in the coking industry include low-ash, low-sulfur, and low-volatile, based on the requirements to make coke. Element concentrations are important as well, because certain elements (for example, phosphorous) can cause problems in the resulting steel (Zimmerman, 1979; Stach and others, 1982).
Are any Kentucky coals metallurgical grade coals?
Because the ideal coal for making coke rarely occurs in a single bed, it is common practice to blend several coals together to achieve the quality parameters needed to make coke for steel. Coals from western Kentucky are typically not used for steel production (e.g., met coal), because of their high sulfur content. Several coal beds in eastern Kentucky meet the low-ash and sulfur requirements of metallurgical-grade coal feedstock, but unfortunately they typically have volatile matter contents (in the mid to high 30’s) that are too high for use in steel production. As such, most eastern Kentucky coals are not used by themselves to produce coke. Rather, they can be blended with low-volatile bituminous coals to form very high-quality coke. Low-volatile bituminous coals are mined in adjacent West Virginia and Virginia and have volatile matter contents below 20 percent.