Metallurgical Coal

Metallurgical Coal Metallurgical coal is also called ‘met coal’ or ‘coking coal. It is a bituminous coal which allows the production of a coke suitable to support a blast furnace (BF) charge. It is distinguished by the strong low-density coke produced when the coal is heated in a low oxygen (O2) environment or in absence of air to reduce mineral impurities (e.g. less sulphur, phosphorus). On heating, the coal softens, and volatile components evaporate and escape through pores in the mass. On cooling, the resultant coke has swollen, becoming a larger volume. The strength and density of coke is particularly important when it is used in a BF, as the coke supports part of the ore and flux burden inside the BF. Metallurgical coal possesses the ability to soften and re-solidify into a coherent, porous mass, when heated from 300 deg C to 550 deg C in the absence of air in a confined space. The conversion from coal to coke occurs in chambers called coke ovens where the volatiles from the coal escape, leaving behind what is referred to as metallurgical coke, which reaches a temperature of around 1,000 deg C to 1200 deg C before being removed from the ovens. The coking cycle is normally dependent on several parameters. Coke is used primarily as a fuel and a reducing agent in a BF. The gross calorific value (CV) of the metallurgical coal is greater than 5700 kcal/kg on an ash?free but moist basis. It presents unique plastic properties during carbonization which in turn produces a porous solid, high in carbon (C) coke. Metallurgical coals, when heated at a moderate rate in the absence of air, undergo complex and continuous changes in chemical composition and physical character. During carbonization, most bituminous coals, except those bordering...

Bituminous coal

Bituminous coal Bituminous coal is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. It is also called as black coal. It is often referred to as soft coal. However, this designation is a layman’s term and has little to do with the hardness of the rock. Bituminous coal is by far the largest group and is characterized as having lower fixed carbon (C) and higher volatile matter than anthracite coals. It is the type of coal which is most widely used in the world today. Bituminous coal is the second highest quality of coal (below anthracite) and the most abundant type. Usually, bituminous coal comes from fairly old coal deposits (around 300 million years old).The energy density of this coal is relatively high, therefore, releases a significant amount of energy when burned. Bituminous coal is defined as a medium?rank coal with either a gross calorific value (CV) on a moist, ash?free basis of not less than 24 mega joules per kilogram (MJ/kg) and with a Vitrinite mean Random Reflectance less than 2.0 %, or with a gross CV on a moist, ash?free basis of less than 24 MJ/kg provided that the Vitrinite mean random reflectance is equal to, or greater than 0.6 %. Bituminous coals are agglomerating and have a higher volatile matter (VM) and lower C content than anthracite coal. This coal is originated by coalification of plant matter deposited in sequences dominated by clastic sediments under diagenetic conditions (thermal and pressure mode) of a given coal basin. Coalification proceeded under geologic time scale. In various coal basins (coal seams) coal matter differs in regard of different primary composition of plant matter and sedimentary environment. Composition of coal (e.g. elemental composition, VM etc.) and mean reflectance of vitrinite reflect final stage of coal metamorphism of a given sedimentary basin. Bituminous...