Question

state the main type of mineral coal. Explain any one of them in brief. ​

Answer 1

There are four major types (or “ranks”) of coal. Rank refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon rich, and harder material. The four ranks are:

Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.

Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. Bituminous usually has a high heating (Btu) value and is the most common type of coal used in electricity generation in the United States. Bituminous coal appears shiny and smooth when you first see it, but look closer and you may see it has layers.

Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has a higher heating value than lignite.

Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon.

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Answer 2

Types of Coal

The four types of coal are peat, lignite, bituminous, and anthracite. Peat is often not listed as a type of coal since the use of it as an energy source is limited today. However, it's still a type of coal and can be used as an energy source.

Peat is the first step in coal formation. Peat is composed of over 60% organic matter; typically, ferns and vegetation found in swamps or bogs. As a result of the high water content of this environment, peat contains a lot of water, which limits its heat content or the amount of energy it contains. It's a very soft brown coal.

Eventually over time, with increasing pressures and temperatures, peat is 'cooked' into coal's next stage, lignite. Lignite is a soft brown coal that still contains a high amount of water. Lignite has a higher heat content than peat but is still not the most desired form of coal. However, lignite makes up almost half of our known coal reserves.

Bituminous coal is formed as more pressure is applied to lignite coal. The greater the pressure applied, the more water is expelled, which increases the amount of pure carbon present and increases the heat content of the coal. Bituminous coal is often classified as sub-bituminous or bituminous. The difference is that sub-bituminous is the transition stage from lignite to bituminous coal. Bituminous coal is widely used in the United States and across Europe.

Anthracite coal is a metamorphic rock and is considered the highest grade coal. It's hard and dark black in color. It has a very light weight when compared to other forms of coal, as there is very little water present in anthracite. As a result, anthracite has the highest heat content. Anthracite is formed when bituminous coal is subjected to great pressures, such as those associated with the folding of rock during the creation of mountain ranges.

Formation of Coal

As mentioned earlier, coal is formed from ancient swamps and bogs. The vegetation found in these areas eventually become buried beneath sediment and rock called overburden. As more and more overburden is added, the buried vegetation becomes compressed. The temperature and pressure are also increasing as a result of the overburden. Under these conditions, the buried vegetation is kept free of oxygen by the presence of mud and acidic water. Slowly over time, the buried vegetation is 'cooked' to coal. The process of turning dead carbon-rich vegetation to coal is called carbonization.