Page 35 - New Trends In Coal Conversion

4 New Trends in Coal Conversion

Figure 1.2 (Left) Bukit Asam coalfield in Sumatra. Coal rank is variable ranging from subbi-
tuminous to semianthracite coal, the latter due to local heating by igneous intrusions. (Right)
Visonta open-pit mine of lignite in Northern Hungary which supplies the M atrai power station.
Photocredits: D. Flores, University of Porto, Portugal.

Formation conditions
Chemical changes
Pressure
temperature Volatile
Swamp time Rank C H O matter
Increasing burial depth Lignite Increasing metamorphism
Peat

Bituminous

Anthracite

Figure 1.3 Scheme of the formation of coal in terms of rank (coalification series).
Modified from Pajares, J.A., Díez, M.A., 2014. Coal and coke. Encyclopedia reference module
in chemistry, molecular sciences and chemical engineering. In: Reedijk, J. (Ed.). Elsevier,
Waltham, MA, 22 pp.

these three primary factors, heat is considered to be the most important. There is little
doubt that time does play a role in coalification, with the amount of time necessary to
achieve the coal rank varying from less than a year in contact metamorphism to 106e
107 years for regional metamorphism. The role of pressure has been the subject of dis-
cussion for many years, although it is well known that pressure causes physico-
structural coalification, which influences the physical properties of coals.