Coal is a combustible rock characterized by extensive deposits of crystalline solid matter composed of carbon, hydrogen, oxygen and nitrogen. It is found in almost every part of the world, and it is a major source of energy for many countries. Over the last century, coal has been widely used for the generation of electricity and has become the single most important source of primary energy for industry and home heating.
Coal is classified according to its degree of hardness, which is related to the amount of carbon, volatile matter and minerals or impurities present. The classification of coal is an important way of identifying coal resources. Generally, hard coal is represented by 2 grades of coal: anthracite, which has the highest carbon content, and bituminous coal, which has the lowest carbon content. In between the two grades is a range of intermediate steps, each grade having different characteristics and uses.
Anthracite coal is a type of hard coal with a high carbon content and very little volatile matter. It is often referred to as ‘black diamond’ because of its lustre and is one of the most valued combustible fuels. Because of its low oxygen and sulfur content, anthracite is often used as a domestic heating fuel, particularly in Europe and the eastern United States. It is also used in heat generation for industry, in blast furnaces and other applications.
Bituminous coal is the most common type of hard coal and is made up of various amounts of reactive carbon, volatile matter and minerals, depending on the region. Bituminous coal has a higher heating value than anthracite, but it also contains more polluting components such as sulfur and nitrogen. In addition, bituminous coal tends to produce more smoke and ash when burned. Bituminous coal is usually found in seams below the surface and is more expensive to mine due to its depth. Bituminous coal is mainly used for power generation and industrial applications, such as iron and steel making.
Sub-bituminous coal is a softer, less dense, and lower quality coal than bituminous coal. It has a higher moisture content, higher ash content, and a lower heat value. Sub-bituminous coal is mainly used for power generation and by-product industries. It is usually found at shallow depths and can be mined either by open-pit or underground methods.
Lignite is a type of soft coal that is composed mainly of elements of the woody structure of the peat. It has a higher moisture content and a low degree of carbonization, and it is mainly used as a fuel in power plants. Lignite is also used in some cases to make charcoal or briquettes as fuel for domestic or industrial use.
Finally, peat is the softest and least combustible form of coal. It is made up of partially decomposed organic matter that has been compressed over millions of years. The content can vary from region to region, but it is mainly composed of hydrogen, oxygen, nitrogen, and carbon. Peat has a low calorific value and is mainly used for horticultural and industrial purposes.
In conclusion, coal is a combustible rock found in almost every part of the world, and it is a major source of energy for many countries. Coal is classified according to its degree of hardness and its content of carbon, volatile matter and minerals or impurities. The four major types of coal are anthracite, bituminous, sub-bituminous and lignite, and each has a different use due to its composition and characteristics. Coal has played a major role in the development of modern industries, and it will continue to be an important energy source in the future.
