What are four major types of coal?
Coal is a versatile energy source. Its compositions vary even within the same deposit. Basically, there are four different types of coals with differences in energy output resulting from the effects of pressure, heat and time.
This is a brownish-black coal sometimes labeled as “brown coal” which has high moisture and ash content. Lignite has the lowest heating value in comparison to three other types of coal. Lignite has a heat value that ranges between 4,000 and 8.300 BTUs-per-pound. It is considered an “immature” coal that is still soft and is used almost exclusively for electric power generation.
This rank of coal is found and mostly mined in Texas, Montana, North Dakota and some states in the Gulf Coast.
Lignite ranks fourth in heat and carbon content compared to other types of coal.
This is a dull black coal with a higher heating value than lignite and is used for electricity and space heating. The reserves for this particular form of coal are located in Western states as well as in Alaska. Its heat value brings in only 8,300 to 13,000 BTUs-per pound. However, it is often viewed as a cleaner coal as it has low sulfur content to go along with its slightly lower heat value. Subbituminous coal is commonly used for steam-electric power generation.
Sub-bituminous ranks 3rd in heat and carbon content compared to other types of coal.
This is the most common type of coal in the United States, accounting for over 50% of the demonstrated reserve base. It is part of the fastest growing market for coal which is used to supply heat for industrial processes.
Bituminous coal is a dark, hard coal that has a higher heating value than lignite and subbituminous coal, but a lower heating value than anthracite. This coal has a carbon content ranging from 45-86 percent carbon and a heat value of 10,500 to 15,500 BTUs-per-pound. It is also the most commonly used type of coal for electric power generation in the United States and is mainly used to generate electricity and make coke for the steel industry.
Bituminous coal ranks second in heat and carbon content compared to other types of coal.
This is also known as "hard coal" which is formed from bituminous coal under increased pressure in rock during the creation of mountain ranges. This type of coal is the most compact and therefore, has the highest energy content of the four levels of coal. Anthracite is used for space heating and generating electricity. In the United States, it is found primarily in the Appalachian region of Pennsylvania and makes up only 1.5% of the demonstrated reserve base for coal in the United States.
Anthracite ranks first in heat and carbon content compared to other types of coal.
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