What is Coal ?

 Coal 

Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is the leading mineral fuel.  It is burn to produce heat which is used to generate electric power. The term coal is generally carbonaceous character that is derived from vegetable matter involving set of process such as burial, compaction and biochemical transformation.

Types or ranks of coal are determined by carbon content. There are four types of coal, ordered from lowest to highest rank below.

Type (From Lowest to Highest)	Properties
Peat	It’s our first stage of transformation to coal. Peat is a brown porous mass of partly decomposed vegetable material. It contains about 85% moisture, 10.4% volatile matter and 4.6 % carbon. Type : 2 type  a)     Big peat :  Bob peat, which is evolved out of lower type of vegetation, like mosses (plant) b)    Mountain Peat:  that is composed and partially altered form of higher types of trees. This type of Peat is found in sub mountainous regions. It's calorific value is very low
Lignite	Lignite is the lowest rank of coal. It is a peat that has been transformed into a rock, and that rock is a brown-black coal. Lignite is also called brown coal as it color is often dark brown. The lignite is composed of finely divided plant tissues. It contain about 25-45% moisture, 60—70% carbon and 20-25% oxygen. It's calorific value is very low (11000—12500 B.T.U)
Bituminous	It's also known as common coal. The original vegetable material has been fully transformed into carbonaceous material. It burns with a yellow flame. Types : sub-bituminous, bituminous and semi-bituminous Bituminous coal is formed when a sub bituminous coal is subjected to increased levels of organic metamorphism. It's contains 63-95% carbon, 8-15% moisture and 10-40% volatile matter. It's calorific value range between 13500—16000 B.T.U.
Anthracite	Anthracite is the highest rank of coal. It is a hard coal with an iron -black color and submatallic lustre. It is often subdivided into semi-anthracite, anthracite, and meta-anthracite on the basis of carbon content. The Anthracite contains about 90–94% carbon and 3–4% volatile matter. Burns with a short blue flame and give little smoke. calorific value ranges between 15000—15600 B.T.U