Anthracite is the highly coalified form of hard coal. It is characterized by a high content of elemental carbon (>90%). It was formed in deep layers, mainly Carboniferous, often as a result of presence of additional thermal factors, i.e. igneous intrusions.
Anthracite is mined all over the world, but mainly in Ukraine, Russia, USA, Canada, East Asia, Australia and Indonesia. It is widely used as a special fuel, in metallurgy and the electrode industry. In order to improve thermal parameters and qualitative stabilization, anthracite is processed by calcination.
Calcination is the treatment of solid carbon raw materials in an inert or reducing atmosphere in the temperature range of 1000-3000°C. The purpose of calcination is to remove impurities, improve conductivity and thus increase the amount of graphite-like structures. Calcination also makes it possible to test the thermal resistance and volume changes of anthracite in the processes of further heat treatment. This operation is carried out in gas-fired rotary and retort furnaces or electric furnaces.
Although anthracite is the highly coalified form of hard coal, it still remains significant structural diversity. It is not so much about the maceral composition of anthracite, as about the structure of the vitrinite itself.
Depending on the structure of vitrinite, anthracites show different thermal resistance, which is associated with the formation of porosity, cracks and expansion of the material.
In Institute has been developed a number of methods allowing for a broad description of anthracite optical properties, both in its raw (green) and calcined form. Both, standard petrographic tests (reflectance Rr, Rmin, Rmax, Rbi, maceral composition) and more complex tests of vitrinite structure (uniform, lamellar, etc.) and level of thermal degradation of anthracite are performed. The analysis of thermal degradation, or in other words thermal resistance of anthracite, consists in the image analysis of specially processed microscopic images of both green and calcined anthracite.
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At the Institute of Energy and Fuel Processing Technology, the contact person for microscopic analysis of anthracite and other carbon materials is dr Małgorzata Wojtaszek-Kalaitzidi (mwojtaszek@itpe.pl; tel: +48 32 621062041) Department of Cokemaking Technologies.