type of coal

As geological processes apply pressure to dead biotic matter over time, under suitable conditions it is transformed successively into
Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland.
Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
Bituminous coal, dense mineral, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil, as from the deposits in Pennsylvania.
Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.
The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:[2]
Name
Volatiles %
C Carbon %
H Hydrogen %
O Oxygen %
S Sulfur %
Heat content kJ/kg
Braunkohle (Lignite)
45-65
60-75
6.0-5.8
34-17
0.5-3
<28470
Flammkohle (Flame coal)
40-45
75-82
6.0-5.8
>9.8
~1
<32870
Gasflammkohle (Gas flame coal)
35-40
82-85
5.8-5.6
9.8-7.3
~1
<33910
Gaskohle (Gas coal)
28-35
85-87.5
5.6-5.0
7.3-4.5
~1
<34960
Fettkohle (Fat coal)
19-28
87.5-89.5
5.0-4.5
4.5-3.2
~1
<35380
Esskohle (Forge coal)
14-19
89.5-90.5
4.5-4.0
3.2-2.8
~1
<35380
Magerkohle (Non baking coal)
10-14
90.5-91.5
4.0-3.75
2.8-3.5
~1
35380
Anthrazit (Anthracite)
7-12
>91.5
<3.75
<2.5
~1
<35300
Percent by weight