Coking coal and carbonization

Coke production connects coal mining to metal production and has a significant share in coal distribution. In metallurgy, coke is not used only as a fuel. Is is primarily a reducing agent participating in chemical reactions during the conversion of raw ore to metal. In connection with the reduction of metal production, coke production has also been reduced. However, the current world-wide demand for metal again sets favourable conditions for the development of the coke sector.

What is coke in real terms?

Coke is solid carbon residue produced from low-ash, low-sulphur hard coal, from which the volatile components are removed in ovens with limited oxygen inlet and temperatures around 1000 °C. During this process bituminous coal tar, ammoniac, light oils and coal-gas are produced. It has an outstanding calorific value of 29,6 MJ/kg, its other properties are also important in metallurgy, in particular high carbon content and little residue of combustion.

Owing to its high calorific value and 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 metal production in the rest of the world as well as in the Ostrava region 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 produced also in the processing of oil (the so-called petroleum coke), however, due to its high percentage of debris it is not suitable for metal production.

Natural coke

Conversion of hard coal to coke also took place without human intervention by means of natural processes. 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.