COAL CLASSIFICATION
HARD COAL:
Hard coal is a hard fossil coal intermediate between lignite and anthracite. It is formed under increased pressure and temperature from brown coal at depths of about three kilometres.
It is black in colour.
It contains 75-95 % of carbon, up to 12 % (3-4 % internal) of moisture (water) and up to 32 % of volatile substances. It is highly flammable.
As the moisture content is low, it has a higher calorific value than lignite - more than 24 MJ/kg.
ANTRACITE:
Anthracite is a hard fossil coal, coal of the highest degree of carbonification (metamorphism). It is formed under increased pressure and temperature from hard coal at depths of about six kilometres. It is a transitional form from hard coal to graphite.
It has a deep black or black-grey colour and a metallic lustre.
It contains 95% carbon, 1-3% moisture (water) and up to 8% volatile matter. It burns quickly, without smoke or flame.
Anthracite reserves account for only three per cent of the world's total coal reserves. It is actively used in the production of ferrous and non-ferrous metals, electrodes, microphone powder, various kinds of adsorbents, in paint and varnish, chemical, pharmaceutical industries and other spheres. Anthracite coal is the most efficient among all types of coals in terms of burning time and heat dissipation. Such coal is very hard to ignite, but in the process of combustion it releases a very large amount of heat (6300-8300 kcal/kg), and practically does not sinter.