Nearly 250 million years ago, the temperature of the atmosphere was high and the humidity was excessive. Rainfall was so high that very dense forests grew on the earth. Along with it, big marshes and great lakes developed.
The vegetation continued depositing in them and they were later covered with sand, clay, etc. These layers were again deposited with decayed vegetation including big stems and branches of trees. This process continued for millions of years.
The upper layers put pressure upon the lower ones, increasing their temperature. The high temperature and pressure reduced the moisture content of the remnants of trees. The trees were transformed into masses of carbon and impurities. The burning of these tree remnants (called Fossils) produced large amount of heat.
The greater the concentration of carbon, the higher is the amount of energy locked in them. The first formation is called ‘peat’. The fossils having higher content of carbon, according to their grade are called Lignite, Bituminous and Anthracite.
Naturally, the upper layers mostly consist of Peat as their transformation started recently. The lower the layers, the greater are the carbon or energy content. In this way lignite, bituminous and lastly anthracite coal is formed.
Coal formation started in Carboniferous times about 285 millions years ago. Again in Jurassic times the conditions for the formation of coal set in. The third was Cretaceous and fourth or the last started 50 million years ago.
Coal is principal energy which accounts for nearly 67% of the country’s commercial requirement. It is an essential input in steel and carbo-chemical industries.
Types of Coal
The purer the coal, the greater is the amount of carbon present in it. The purer the form, the harder it looks. On the basis of the carbon content, coal can be divided into four types:
This is the first coal forming stage and its life is about 50 million years.
Its colour ranges from light grey to black. It has about 90% moisture. When burnt, it produces clouds of smoke. It has little heat and energy. This is the poorest type of coal. Economically, it has little use.
Its storage entails big space; its transport is costly because of large volume. This type of coal is commonly found in Scandinavian countries, Russia, Iceland and N. America.
It belongs to a stage later than that of Peat.
It is estimated that lignite started forming nearly 100 million years ago.
It has brown colour. It is, therefore, also called ‘brown coal’. It contains about 40% moisture. It has carbon content range between 45-60%. It produces a lot of smoke when burnt. It has some useful chemical compounds.
It is, therefore, used as a raw material in the chemical industry. In Russia and eastern part of Germany lignite coal is also used as fuel. Due to its large volume it needs more space for storage. The Geological Survey of India has estimated the following coal reserves in India as on 1 January, 2001.
It is better than lignite in quality. It took about 150 million years to form. Its colour is usually black. Moisture and other impurities constitute 15-40% bituminous. Its carbon content ranges from 50-80%.
On burning, it does give smoke but it has lot of heat and leaves behind some ash. It is largely used in the industries for producing heat. It is usually used in Iron and Steel, Textile, Cement and in a large number of industrial units. Bituminous is about 80% of the total coal produced in the world.
It started forming about 250 million years ago. It is considered to be the best type of coal. It has shining black colour. It is very hard. It is almost free from moisture. It, therefore, gives no smoke or ash on burning.
It has very high (95%) carbon content. Hence it produces intense heat. In cold countries it is used to keep houses warm. It is also used as household fuel. It is also used for industrial purposes.
The by-products of coal are very useful for manufacturing a variety of products such as:
It is a by-product of coal and is widely used in metalling roads and water proofing.
Dyes are obtained from coal-tar and find ready utilization in chemicals, printing, textiles and other industries.
(3) Ammonium Sulphate.
The chemical obtained from coal is used in chemical explosives and refrigeration industries. It is used as reagent in laboratories.
(4) Benzol, sulphur, naphtha, methanol, rayon and plastics are coal products.
The following conditions are helpful in coal exploitation:
If the coal is near to the consumption areas, transport cost is minimized as such exploitation is profitable.
(2) The Quantity of Deposits.
If the coal deposits are enormous and roads, rails etc. are constructed, the exploitation of coal is accelerated. Industries are set up close to the coal fields.
(3) The Richness of Deposits.
If the coal deposits are of good quality, exploitation is more. Poor quality coal does not attract much attention.
(4) The Thickness of Deposits.
The commercially exploitable coal thickness should be at least 2 metres. Coal deposits less than this thickness are exploited provided it is of high grade.
(5) The Depth of Coal Layers.
The nearer the coal deposit to the surface, the greater is the possibility of its exploitation. Coal at greater depth is expensive to mine. Coal mining is done by two methods.
(i) Open pit mining
(ii) Shaft tunnel method
Coal is a major source of energy. It accounts for 67% of country’s Commercial requirement. Coal is an essential output in steel and carbo-chemical industries. 98% of Indian coal occurs in the Gondwana rocks. 2% in the Tertiary rocks.
Gondwana coal: out of 113 coalfields in India, 80 are situated in the rock system relating to lower Gondwana age. These fields are in the river valleys of the Damodar, the Sone, the Godavari and the Wardha.
It is found in the rocks pertaining to post Oligocene times of the geological era. Such states are Assam, Nagaland, Arunachal, and Rajasthan, Jammu and Kashmir.
Coal is the primary source of energy in India. The country is fairly rich in coal reserves and these can meet country’s demand for decades. Coal reserves are estimated at 211594 million tonnes.
In 2001, production was nearly 309-63 million tonnes. Coal is mined in a number of states of India but West Bengal, Jharkhand and Chhattisgarh are the coal states of India because they have more than one half of the coal reserves of the country and also produce more than 50% coal of India.
This coal is largely coking coal, ideal for smelting purposes, thus very useful for the development of iron and steel and metallurgical industries. This coal occurs in Raniganj, Western Jharia, Bokaro, Ramgarh, Northern Karanpura (Damodar Valley) and in the kanhan Valley in Madhya Pradesh. 75% of the coal mined in India is consumed in generating thermal power, railways, chemicals, fertilizers, domestic purposes and iron and steel industries.
The non-coking coal occurs in Eastern parts of Raniganj, parts of Bokaro, north and south Karanpura and Rajmahal (Damodar river valley area), Talcher coalfields (Mahanadi river valley area) ; Singrauli, Korba, Bisrampur, Sohagpur, Lakhanpur, Mand Rajgarh (Sone Valley area); Kamptee, Chanda, Wardha (Maharashtra) and the Godavari valley coalfields (Andhra Pradesh). All these above mentioned coal fields belong to Gondwana land.
The tertiary coal fields of Makum (Assam); Namchick, Nampherk (Arunachal Pradesh), Garo, Khasi, Jaintia hills (Meghalaya) are of lignite, a poor quality coal, not of much economic use.
Moreover, rough topography, forests, lack of means of transport and shortage of labour and lack of industrial development, restrict coal mining in these areas. Manufacturing is least developed in north-eastern states.
In India, Lignite coal deposits are there at Neyveli in South Arcot district of Tamil Nadu; Palana and Khari in Bikaner district of Rajasthan; Nichahom in Jammu and Kashmir and Kutchch and Bharuch districts in Gujarat.
Statewise distribution and production of coal in India is as under:
1. Jharkhand rank first in coal production in India. The major coal producing districts are Dhanbad, Palamau and Hazaribagh.
Jharia in Dhanbad district leads in production. Another field is Chandrapura in the same district. Coal is for thermal power generation. Jharia fields cover 450 sq km area.
East and West Bokaro, Giridih, north and south Karanpura and Ramgarh coal fields lie in Hazaribagh district. Raurkela Steel Plant depends upon coal which is mined at Kargali in East Bokaro.
In Palamau district mines are located at Auranga, Daltonganj and Hutar.
Orissa is the second largest producer of coal in India. The deposits are in Dhenkanal, Sambalpur and Sundergarh districts.
Talcher coal field in Dhenkanal is the third largest coal mine in India as far as coal reserves are concerned. Coal is used by the Talcher Power Plant and the fertilizer factory. In Samalpur district Rampur-Himgir coal fields are significant.
3. Madhya Pradesh.
It is the third largest coal mining state. Shahdol, Sindhi, Chindwara, Umaria, Rewa, Hoshangabad districts have rich resources of coal. Singrauli in Shahdol and Sidhi districts are the largest coal mining area in the state. Mirzapur power
plant in U.P. utilizes this coal. Sohagpur in Shahdol district is the second important coal field. Patherkhera coal field is located in Betul district of M.P. This inferior coal is used for generating power at Patherkhera.
Coal fields are in the districts of Surguja, Bilaspur, Bastar and Durg. The Bhalai steel plant draws coal from Korba (Bilaspur district). Bisrampur, kharsia, Sonehat and Koreagarh coal mines are in Surguja district.
5. West Bengal .
Raniganj is the most outstanding coal field in the state. It is situated in Burdwan, Birbhum, Bankura and Pruilia districts. Durgapur steel plant uses coal of Raniganj. It is used for generating thermal electricity at Durgapur and in other power plants. Darjeeling, Jalapaiguri districts also have coal.
6. Andhra Pradesh.
Coal is found in the
(i) Godavari Valley :
Adilabad, Warangal, Karimnagar and West Godavari districts. Singareni, Kothgudem and Tandur are major mines. Coal is used mainly for thermal power and railway.
7. Maharashtra .
In Chandrapur district, the Wardha valley has rich coal deposits. Kamptee in Nagpur and Wun fields in Yavantamal district are also rich sources of coal.
Assam, Arunachal Pradesh, Nagaland, J&K states also have coal
The coal fields are Metka, Ladda Kalakot and Mohogala.