Coal Classification

Coal is classified according to the nature of the original vegetation, the duration of its formation and – importantly – the depths and temperatures to which it has been subjected. There are several classifications; we use the ASTM classification by rank, which is based on fixed carbon and gross calorific value. The higher-rank coals are classified according to fixed carbon on a dry basis; the lower-rank coals are classified according to the gross calorific value on a moist basis.

Coal layers
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  • 2
  • 3
  • 4

Coal is one of the most
important energy sources
in the world

Lignite*

Calorific value

<4,600
kcal/kg

Moisture content

30-75%

Fixed carbon content

No limit

Volatile matter

No limit

Sub-bituminous*

Calorific value

4,600-6,400
kcal/kg

Moisture content

10-30%

Fixed carbon content

No limit

Volatile matter

No limit

Bituminous*

Calorific value

5,800-8,300
kcal/kg

Moisture content

1-10%

Fixed carbon content

<86%

dry
basis

Volatile matter

>14%

dry
basis

Anthracite

Calorific value

No specific limit
under ASTM

Moisture content

<5%

Fixed carbon content

>86%

dry
basis

Volatile matter

>14%

dry
basis

* - Produced by SUEK Group

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