Coke is the name given to the solid carbonaceous material derived from the destructive distillation of coal.
Coke is produced from low-ash, low-sulphur hard coal, from which volatile components are removed in ovens with limited oxygen inlet and temperatures of around 1000°C. During this process bituminous coal tar, ammoniac, light oils and coal-gas are produced. Coke has an outstanding calorific value of 29.6 MJ/kg, and its other properties are also important in metallurgy, in particular, high carbon content and little residue of combustion.
Owing to its high calorific value, favourable combustion products (in fact only carbon dioxide is produced during burning) and low dust formation, coke is the only fuel allowed in certain city centres.
Originally, in global metal production, charcoal was used as the source of heat and a reducing agent. It started to be replaced by coal coke in the first half of the 19th century.
It is notable that coke is also produced in the processing of oil (so-called petroleum coke), however, due to its high percentage of debris it is not suitable for metal production.
Year ended 31 December 2008
Natural coke
Conversion of hard coal to coke also been taking place by means of natural processes without human intervention. Volcanic activity in the Bohemian part of the coal basin resulted in local coking of certain coal seam areas through which the hot volcanic materials passed. Such natural coke can be found, for example, in the Ostrava and Odra mines and in the boreholes at Frenštát.
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