The coal is the most abundant fossil fuel on earth. It is estimated that there are reserves for another 200 years of human consumption. Generally, it is black and shiny, although this characteristic may vary.
Origin and formation of coal
Mineral coal comes from the decomposition of the forests that occurred in the Carboniferous period, of the primary era, being one of the forms in which the carbon element is found in the Terrestrial Globe, in the formation of the mineral coal occurs a process in which there is transformation of the cellulose, with the output of hydrogen and oxygen ions and an increase in carbon enrichment.
This process can be originated by the decomposition of forests in the local place, or by the sedimentation of vegetal debris brought by the waters. Thus, coal deposits represent the remains of plants that have been transformed or transported over long distances, where the cellulose has been decomposed by bacteria, such as Micrococus carbo , an anaerobic bacterium.
Types of coal
There are distinct types of mineral coal, each formed in a different geological period. They can be classified according to the percentage of carbon they present, which increases with the passage of time, so that the most carbon rich are also the oldest.
- The anthracite is the coal with the highest carbon content, around 90%. It is the oldest and the most powerful energy.
- The coal has a carbon content ranging from 75% to 90% and has a high calorific value. It is the coal most used in thermal power plants.
- The lithium has approximately 70% carbon, and its calorific value is not very high. It is the youngest of the coals and has a dark brown color.
- The peat is coal class that has the lowest carbon content in 50 atom%. It is therefore less profitable, in addition to fuel, peat is considered one of the best natural fertilizers.
The good quality of the coal depends on the small amount of minerals in its composition, because these minerals do not burn and still steal heat.
Extraction and treatment of coal
Mineral coal can be mined from underground or underground mines. Nowadays, there are few open-air deposits because they are already running out, so the most common thing now is to extract the coal from underground, from very deep mines.
When opening a mine, it is important to first prospect the land to see if it will be profitable. Sometimes the coal is so deep that the cost of extraction exceeds the final sale price or it is a coal with such a low carbon content that its extraction will not result in a profitable product.
The coal, as it leaves the mines, should be washed to eliminate sulfur residues. It is then milled and ground until pulverized. Finally, it is classified and separated into different types of coal.
The chemical energy contained in the coal extracted from the mines transforms into electrical energy in the thermal power plants. In this process, sulfur dioxide is released into the air, a dangerous substance that must be filtered in the same plants.
Uses of coal
The use of coal has been known for more than 2,000 years, but it was only in the Middle Ages that it began to be used to produce heat. Its most intense use, however, came with the Industrial Revolutionin the late eighteenth century.
The first steam engines, the main engine of industrialization, were based on coal energy. It has now been replaced by oil. Its use happens mainly in thermal power plants, where its chemical energy is used to obtain electricity.
In the mills, coal is burned to heat the water, which turns into steam and is capable of moving a turbine. The motion of the turbine drives a generator, and the mechanical energy is then transformed into electricity.
Coal is also an important component in the production of iron and steel as well as in the chemical industry.