Coal

From MoxyWiki

Classification of coal

Coal is classified by its type and rank.

1. Type is related to the particular plant origin of the coal.
2. Rank, the more important property,because it is an indicator of fixed carbon is related to the geochemical process of coal formation, or coalification, which simplistically may be expressed as:

peat -> lignite -> sub-bituminous -> bituminous -> anthracite

Lignite is the coal of lowest rank and anthracite the highest. Low rank usually implies low calorific value and low fixed carbon and high moisture and high volatile matter.

Analysis of coal

1. There are three analytical processes^[1] used to classify coal:
   • chemical analysis called proximate analysis - to define the moisture, volatile matter, ash and - indirectly - fixed carbon
   • chemical analysis called ultimate analysis - to give amounts of carbon, hydrogen, nitrogen, sulphur and, often indirectly, 'by difference', oxygen
   • calorific determination
2. Basis of analytical data

Figure 1 gives the most commonly used bases for classification of coal.

Figure 1: Relationship of different analytical bases to various coal components^[2]

References

1. ↑ [Miller, Bruce G. "Coal energy systems," Elsevier Inc, London, 2005]
2. ↑ [Ward, C. R. "Coal geology and coal technology", Blackwell Scientific Publishers, Melbourne, 1984 ]