Page 149 - Synthetic Fuels Handbook

FUELS FROM COAL 135

Time

Swamp
Pressure

Heat

Peat
Lignite
Coal
FIGURE 5.6 Formation of coal. (Reproduced with permission. Copyright 2000. Kentucky
Geological Survey, University of Kentucky).

water, in the absence of oxygen, the carbon content increases. The initial product of this
decomposition process is known as peat. The transformation of peat to lignite is the result
of pressure exerted by sedimentary materials that accumulate over the peat deposits. Even
greater pressures and heat from movements of the Earth’s crust (as occurs during mountain
building), and occasionally from igneous intrusion, cause the transformation of lignite to
bituminous and anthracite coal.

5.2.2 Coal Types
Coal occurs in different forms or types (Fig. 5.7). Variations in the nature of the source
material and local or regional variations in the coalification processes cause the vegetal
matter to evolve differently. Thus, various classification systems exist to define the different
types of coal.

Burial pressure, heat, and time

Peat Lignite
Bituminous
Subbituminous Anthracite

FIGURE 5.7 Coal types. (Reproduced with permission. Copyright 2000. Kentucky
Geological Survey, University of Kentucky).