Coal: Do you know that there was no electricity or no trains running on engines in earlier days? Imagine how would people perform tasks in the dark or travel to father places. It was only possible because of the energy that could be obtained from a natural resource, Coal. This article will explore a little more about this natural resource, its type, and its modern-day uses.

Coal

Coal is a hard rock that may be burned to generate various types of energy. Carbon is the most abundant element in coal. However, it also contains hydrogen, sulphur, oxygen, and nitrogen. It is a sedimentary rock created from peat under the pressure of later-deposited rocks.

Where Is Coal Found?

Rich coal deposits are found in Russia, China, the USA, UK, Africa and Australia. In India, coal deposits are found in abundance in Chhattisgarh, Jharkhand and West Bengal.
Anthracite, which is the best variety of coal, is found at greater depth. It has the maximum carbon content and a very high calorific value. Other varieties of coal, in increasing order of their carbon content, are peat, lignite and bituminous coal.

Formation of Coal

Coal was formed from large plants or trees that grew in swampy areas millions of years ago. Due to some natural phenomena like earthquakes and volcanic eruptions, the tress got buried inside the Earth. As they sat deep inside the earth’s surface, the intense heat of the core of the Earth and the soil pressure above drove out the moisture and gases from the remains of trees and increased the carbon content. Together with this, the bacteria action slowly converted the cellulose present in the wood into coal. This process of conversion of wood into coal in the absence of the air is known as carbonisation. Thus, coal found at greater depth is rich in carbon and lacking in moisture content.

Types of Coal

There are four main varieties of coal: peat, lignite, bituminous, and anthracite, all of which are formed through the carbonisation process.

i. Peat – It is a light brown spongy material that contains \(55 – 65\% \) carbon. It is formed as a piling up of dead plants and animals and is the most inferior variety of coal.
ii. Lignite – It is soft brown coal that contains \(65 – 75\% \) carbon.
iii. Bituminous – It is the most commonly found variety of coal, which is black in colour. It contains about \(75 – 90\% \) carbon. It is used as household fuel and industry.
iv. Anthracite – It is hard, black and contains up to \(90\% \) carbon. It cannot be lit quickly, but when ignited, it burns slowly with very little smoke.

Burning of Coal

Coal burns to produce a large amount of heat and gives off carbon dioxide and a small amount of sulphur dioxide and nitrogen dioxide gases. These gases are a source of air pollution and affect the Earth’s atmosphere in numerous ways.

How can Coal be Obtained?

The coal is produced or obtained from the underground by the process of mining.

Coal Mining

Surface or underground mining can be used to extract coal from coal mines. Coal can be used directly for heating and industrial processes or as a fuel for coal based thermal power plants to generate energy once it has been extracted.

Surface Mining

Surface mining is done to extract coal that is less than 61 metres (\(200\) feet) deep.
Surface miners remove any overburden, which includes mud, plants, and rocks. It is a cost-effective method of extracting coal as compared to the underground mining process. It helps extract two and a half times more coal per worker per hour than done using traditional methods.

Strip mining, open-pit mining, and mountaintop removal (MTR) mining are the three basic methods of surface coal mining.

Underground Mining

Underground mining, often known as deep mining, is a method of extracting coal from a depth of up to \(300\) metres beneath the surface of the Earth (\(1,000\) feet) Miners descend a mine shaft via an elevator to reach the mine’s depths. They operate heavy machinery that removes coal and transports it above ground.
Longwall mining, room-and-pillar mining, and retreat mining are the three primary forms of underground coal mining.

Coal Power Plant

A coal-fired power station, often known as a coal power plant, is a thermal power plant that generates electricity by burning coal. Coal-fired power plants generate a third of the world’s electricity. Coal-fired power plants are one form of the fossil-fuel power plant.  In a pulverised coal-fired boiler, the coal is generally pulverised before being burned. The heat from the furnace turns boiler water into steam, which is then used.

Mainland China has the most coal-fired power stations in the world. There were \(1,082\) operational coal power stations in the country as of \(2021.\) India, which came in second, had nearly four times the number of such power stations. China generates more than half of all coal-fired electricity worldwide.

Uses of Coal

The important uses/ importance of coal are as follows:

i. Its primary functions are to generate heat and power.
ii. It is utilised in both homes and businesses to do a variety of activities.
iii. It is the most cost-effective source of energy.
iv. Face packs and cosmetics contain activated charcoal.
v. Activated carbon is found in water and air purification filters, as well as renal dialysis devices. Activated carbon is made from coal.
vi. Coal is used in the production of paper.
vii. Coal is used in the production of alumina refineries.

Destructive Distillation of Coal

Destructive distillation of coal involves heating coal to high temperatures (about \(1000\,^\circ {\rm{C}}\)) in the absence of air. The process causes its decomposition into different products- solid and gaseous. Some of the gases condense while some dissolve in water. Some of the products obtained in the process are coke, coal, coal tar, and coal gas.

Coke – It is a solid residue left at the end of the process. It consists mainly of carbon.

1. Coke is a fairly clean fuel and is therefore used as an industrial fuel.
2. It is also used in iron extraction.

The essential features of coke are its ash and sulphur content, both linearly proportional to the coal used in its manufacture. Coke with lower ash and sulphur levels is very expensive.

Coal tar – It is a complex liquid mixture of carbon compounds. Earlier, it was used to prepare organic compounds such as benzene and phenol. However, these are now obtained mainly from petroleum.

Coal tar is used as a production material for various everyday and industrial products, including synthetic colours, medicines, explosives, fragrances, polymers, road surfacing, waterproofing roofs, and paints.

Ammoniacal liquor – It is an impure solution of ammonia used to make nitrogen fertilisers and ammonia gas.

Coal gas – It is a mixture of hydrogen, methane, carbon monoxide and other gases. It was used as fuel earlier but now has been replaced by natural gas.

Many companies near coal processing plants use it as a source of energy.

Below given is the diagram of destructive distillation of coal in the laboratory:

Summary

In this article, we studied the details of coal- its formation and types according to the content of the carbon present in it. We also learned that the burning of coal causes air pollution by releasing gases into the atmosphere. We looked at how coal can be used in households and industrial purposes to produce various products. The destructive distillation of coal is used to produce coke, coal gas, and coal tar.

Frequently Asked Questions (FAQs) on Coal

Q.1. How is coal formed?
Ans: Over hundreds of millions of years, dead plant matter immersed in wetland conditions is subjected to heat and pressure of geological forces, resulting in the coal formation. Coal is an energy source, and carbon compounds of dense black or brownish-black sedimentary rock form over time from damp, low-carbon peat.

Q.2. Is coal renewable or non-renewable?
Ans: Coal is a non-renewable source of energy as it takes millions of years for its formation.

Q.3. What are the uses of coal?
Ans: The uses of coal are as follows:
i. It is widely used as a fuel in industries and household and thermal power stations.
ii. It is also used to make products such as coke, coal tar and coal gas.

Q.4. Is coal a mineral?
Ans: A mineral is a naturally occurring inorganic solid (containing metals) having a crystalline structure and a specific chemical composition. Coal is not a mineral because it does not meet the criteria.

Q.5. How many types of coal are there?
Ans: Four main varieties of coal are formed through the carbonisation process, and according to the carbon content, they are as follows-
i. Peat
ii. Lignite
iii. Bituminous
iv. Anthracite