The formation of coal is a long
process. The coal around the Appalachian region has formed from the remains of
swamp plants that used to cover the area 300-400 million years ago. The plants
became buried in the swamp, but didn’t rot due to the lack of oxygen. Instead
of rotting, the dead plants formed into peat over very long periods of time.
Peat doesn’t have a very high heat value and
isn’t as valuable. Peat is not coal, but a precursor to it. Lignite is the next
type of coal in the process. The carbon concentration is only at 30% and has a
low heat value, yet it is still used to generate electrical power. Over time with heat and pressure, the peat is
converted into lignite and then into bituminous coal, the most common form. This
type of coal has a highly variable carbon value and is coked for use in the
steel industry. Bituminous coal can be used in factories to create electrical
energy as well. Anthracite coal is different in regards to rock type: it’s
metamorphic instead of sedimentary. It has the highest carbon content (85-95%)
and the highest heat value. Finally, metallurgical coke is bituminous coal
heated up to a temperature around 2,000 degrees Celsius in the absence of
oxygen. With the extreme heat affecting it, water, tar, gas and other volatiles
are taken away to leave a higher carbon fuel.
That is
how coal forms and the different types and stages of coal.
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