Coal

stone coal

Coal is a solid fossil fuel plant, a kind of fossil coals with higher carbon content and higher density than that of brown coal . Coal is a dense black rock, sometimes grayish-black with a shiny, semi-matt or matt finish.

Coal contains 75-97% or more of carbon, 1,5-5,7% hydrogen 1.5-15% oxygen, 0.5-4% sulfur and 1.5% nitrogen, 45-2% of volatile substances , the amount of moisture varies from 4 to 14% ash - usually from 2-4% to 45%. Higher heating value, calculated on a wet weight of ash-free coal, not less than 23.8 MJ / kg (5700 kcal / kg). Coal is formed from the decomposition products of organic residues of higher plants have undergone changes in conditions of high pressure surrounding crustal rocks and the relatively high temperature. With increasing degree of metamorphism in the combustible mass of coal has consistently increased carbon content and a simultaneous decrease in the amount of oxygen, hydrogen, volatile substances also change the heat of combustion, the ability to sinter and other properties.
The change in these qualities, determined by the results of thermal decomposition of coal (volatile matter, fixed residue characteristic), adopted in Russia is based industrial classification of coals by brand:
- Long-flame (A)
- Gas (G)
- Gas Fatty (GJ)
- Fat (F)
- Coke fatty (QOL)
- Coke (R)
- Otoschennye caking (OS)
- Thin (T)
- Slabospekayuschiesya (CC)
- Poluantratsity (PA)
- Anthracite (A)

Approximately on the same principles as in Russia, a classification of coal in some Western European countries. In the U.S., the most common classification of coal based on volatile content and calorific value at which they are divided into sub-bituminous to high volatile matter (meets Russian brands D and F), with an average tar yield of volatile matter (corresponding to Make RV and K) , bituminous low volatile matter (OS and T) and anthracite coals, separated by semiantratsity (part of T and A), the actual anthracite and metaantratsity (A).
In addition, there is an international classification of coal based on the content of volatile substances, sintering, coking, and displays of technological properties of coals.