COAL

Coal is a fossil fuel formed by the breakdown of vegetable material trapped underground without access to air.

Technically, Coal is a naturally occurring combustible rock containing 70% (by Vol) carbonaceous material including moisture.

Classification based on level of Maturity : Depending upon the level of maturity/metamorphism, coal is classified under 3 main categories namely, Lignite/Brown Coal, Bituminous Coal, Anthracite Coal.

Grouping based on Property : Coals are grouped according to particular properties as defined by their Rank (which is a measure of degree of maturity/metamorphism), Type (Vitrinite, Liptinite and Inertinite which are the 3 main groups of materials that constitute coal) and Grade ( ( depending on Impurities and Calorific Value).

Use of Coal : Natural coal in general is too dense and/or fragile and has limited use as a fuel/reductant in metallurgical plants like Blast Furnace. However, some specific varieties of natural coal (crushed and screened in specified size ranges) find direct application in other metallurgical operations (such as Corex Plant, Coal Dust Injection/Pulverised Coal Injection in Blast Furnace etc.).

Coking/Non-coking Coal : Based on coking property, coals are broadly classified into two categories namely, Coking Coal and Non-coking Coal. Steam coal used for steam/power generation falls under the broad group of Non-coking coal.

Coal is formed from vegetable matter burried under the earth. About 300 million years ago, the earth was covered with dense forests, marshlands and rivers. The forests grew and died and fell into the waters of the surrounding swamps. These plants were covered with tons of earth over a period of millions of years. Due to the huge pressure and temperature inside the earth, this vegetable matter got converted into coal.

Coal is obtained from dead plant matter which consists primarily of carbon, hydrogen and oxygen.

On dry land, this matter rots away by bacterial action in presence of atmospheric oxygen to form carbon dioxide and water. But in swampy locations , the dead plant matter is covered with water and is, therefore, protected from the oxidising action of air. Instead, it is attacked by bacteria. In this process oxygen and hydrogen of the dead plant matter gradually escape and the residue, therefore, becomes richer and richer in carbon. The end product of the bacterial action is a soggy, carbon-rich substance called peat. As peat gets compressed and heated further due to geological changes, more gases are forced out and therefore the proportion of carbon continues to increase. In this way, peat is gradually converted into various forms of coal such as lignite, bituminous and anthracite.

Some of the main coal-producing countries of the world are China, USA, UK, Germany, Poland, Australia and India.