One of the fields of geological sciences is coal petrology, i.e. the science of the origin, transforming, methods of coalification and technological properties of coal. Its basic branch is coal petrography, which studies concentrated accumulations of organic matter, usually in the form of the coal seam. The method of description and classification are currently standardized by ICCP (International Committee for Coal and Organic Petrology) and used in about 50 associated countries.

Macerals are an elementary petrographic component of fossilized organic matter, distinguished based on its characteristic morphology within 3 groups, in which macerals exhibit similar optical and chemical properties. The division into 3 groups is based on the technological properties of macerals. There are macerals with good sintering and dilatation properties (vitrinite group), intermediate (liptinite group) and not having such properties (inertinite group). The coking properties of macerals are justified mainly by the intensity of light reflection, which is measured by the value of the average random reflectance of vitrinite, Rr, or in the case of high-rank coals – vitrinite anisotropy determined by the maximum reflectance, Rmax.

The main differences between macerals are:

  • origin – various tissues and plant elements, i.e. cuticle, resin, spores;
  • the way of coalification – wet and dry peat environment, possibly a peat bog fire;
  • C / H ratio.

The main component that forms the coke matrix in the coking process is vitrinite, therefore its major content is required in the petrographic composition of the coal blend (min. 65%). The liptinite macerals contain a lot of hydrogen and have a plasticizing effect on vitrinite grains. The highly coalified macerals from the inertinite group behave inertly or partially inert in the pyrolysis process. Their significant content in the coal blend will deteriorate the quality of the obtained coke, mainly in mechanical terms. They do not sinter with the coke matrix, weakening its structure, that is why their content should not exceed 35%.

The analysis of the maceral composition is extremely important for composing of the coal blend for coking. The composition of the macerals groups is one of the key parameters for coke quality prediction. The Department of Coking Technologies carries out an extended petrographic analysis of coals in the entire coal rank, both for single coals and coal blends. Tests are performed by a qualified certified petrographer – ICCP Accreditation Certificate ICCP / SCAP / – 127 / AB; ICCP / CBAP – 127.

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Contact person for petrographic analysis:
Małgorzata Wojtaszek-Kalaitzidi
mwojtaszek@ichpw.pl  |  tel: 48 32 621 06 20 41.