Coal
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Also called black gold.
Found in sedimentary strata [layers of soil].
Contains carbon, volatile matter, moisture and ash [in some
cases Sulphur and phosphorous]
Mostly used for power generation and metallurgy.
Coal reserves are six times greater than oil and petroleum reserves.
Composition
Almost by definition, coal consists mostly of carbon. The plant materials from
which coal is derived are largely carbohydrates of various kinds, only the most
resistant of which (mainly cellulose and lignin) remain after partial decomposition
after death of the plants. The initial plant residues that are buried to become coal
therefore consist largely of carbon even at the very beginning. But coals—even
lignites—contain appreciable percentages of other constituents as well. Here’s a
list:
nitrogen: a couple of percent; doesn’t vary much. Probably from the organic
matter itself, not from entrapped air.
sulfur: small percentages, a couple of percent, but undesirable because of
production of sulfuric acid (the main constituent of acid rain) upon combustion.
water: varies with rank from a few percent to as much as 90%
(conventionally measured after drying at a temperature a little greater than 100 °C,
to get rid of liquid water in pore spaces).
gases: CO2, O2, N2, CH4, variable percentages.
“ash”: the solid residue upon combustion: sand, silt, and clay in variable
proportions, either carbonate or siliciclastic (mostly the latter). From fractions of a
percent in the cleanest coal to such large values that the rock should be called a
carbonaceous shale or a carbonaceous sandstone rather than coal. Very impure
coal is called bone coal.
Figure 12-3 shows one segment of a composition triangle whose end members are
percent of carbon, hydrogen, and oxygen. Only the area nearest the carbon corner
is occupied by rocks we would call coal. You can see that the increase in rank is
associated with a progressive decrease in the percentages of hydrogen and oxygen,
presumably owing to driving off of the volatile constituent water.
The plant constituents of coal have been classified both macroscopically and
microscopically. The basic idea is that all coal is composed of a small number of
kinds of fragments of plant debris called macerals, which are analogous to the
minerals of an ordinary sedimentary rock.
Macerals represent such things as branches, twigs, leaves, bark, interior tissue of
various kinds, and pollen or spores, among many others. Study and classification
of coal macerals is highly botanical and can be done only with the aid of a
microscope.
The macroscopic study and classification of coals, on the other hand, while not as
fundamental, is easier to deal with. Coal has long been recognized to consist of just
a few macroscopic constituents, usually interlaminated. These constituents form
strata that are typically from fractions of a millimeter to tens of millimeters thick.
vitrain: brilliant, vitreous (glassy-looking), jetlike coal with conchoidal
(shell-like) fracture
clarain: coal layers that appear silky from the presence of very delicate
internal lamination
durain: dull, lusterless, matte layers of coal with a close or dense texture,
without internal lamination
fusain: friable and highly porous coal, usually appearing as irregular chips
and wedges lying along the bedding; often called mineral charcoal.
Origin
Coal can form wherever growth of vegetation is abundant enough, and
accumulation of the sediment is scanty enough, that plant material can accumulate
in high concentrations and large quantities before complete decomposition. For
this, one has to appeal to extensive swamps, usually termed coal swamps, either
fresh water or sea water (probably mainly fresh water) in climatic conditions
conducive to lush growth of vegetation and far from sources of siliciclastic
sediments.
Most coal seems to have formed in place, by gradual accumulation of plant
material right where it grew. You can imagine thick accumulations of earlier plant
material into which the present crop puts down its roots, only to succumb
eventually and form the substrate for yet another crop. Such coal is said to be
autochthonous. Some coal, however, seems to consist of plant fragments that were
transported far from where they grew, presumably by flowing water, and deposited
in some rather different sedimentary environment—but again one without an
abundance of “ordinary” siliciclastic sediment. SZCuch coal is said to be
allochthonous.
The overall association of other sedimentary facies with coals—mainly shallow
marine and fluvial sediments—tells us that, broadly, coal accumulates in coastal
environments of one kind or other. Perhaps the most common kind of environment
of this kind could be termed deltaic. Imagine a broad river carrying mud and sand
to the shoreline. The river flow in deltas tends to be well channelized, with strong
flows carrying sand to the channel mouths. Mud carried by such channels is either
spilled widely over the banks of the channels along the way or disgorged into the
sea at the mouths of the channels. In certain settings, in between the channels are
low-lying areas that receive little fluvial sediment and are conducive to dense
vegetation. Such areas tend to experience slow subsidence, from compaction of
earlier-deposited sediments; this subsidence makes room for further accumulation
of plant materials. (Keep in mind that there must be great compaction of the plant
material as it's buried.)
Carboniferous Coal
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Most of the world’s coal was formed in Carboniferous age [350 million
years ago][Best quality coal].
Carboniferous age: In terms of absolute time, the Carboniferous
Period began approximately 358.9 million years ago and ended
298.9 million years ago. Its duration is approximately 60 million
years.
The name Carboniferous refers to coal-bearing strata.
Formation of Coal
Amount of oxygen, nitrogen and moisture content decreases with
time while the proportion of carbon increases [The quantity of carbon
doesn’t increase, only its proportion increases due to the loss of other
elements].
Capacity of coal to give energy depends upon the percentage or carbon
content [Older the coal, much more is its carbon content].
Percentage of carbon in coal depends upon the duration and intensity of
heat and pressure on wood. [carbon content also depends on depth of
formation. More depth == more pressure and heat == better
carbon content].
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Coal formed millions of years ago when the earth was covered with huge
swampy [marshy] forests where plants – giant ferns and mosses – grew.
As the plants grew, some died and fell into the swamp waters. New plants
grew up to take their places and when these died still more grew.
In time, there was thick layer of dead plants rotting in the swamp. The surface
of the earth changed and water and dirt washed in, stopping the decaying
process.
More plants grew up, but they too died and fell, forming separate layers. After
millions of years many layers had formed, one on top of the other.
The weight of the top layers and the water and dirt packed down the lower
layers of plant matter.
Heat and pressure produced chemical and physical changes in the plant layers
which forced out oxygen and left rich carbon deposits. In time, material that
had been plants became coal.
Coals are classified into three main ranks, or types: lignite, bituminous coal,
and anthracite.
These classifications are based on the amount of carbon, oxygen, and
hydrogen present in the coal.
Coals other constituents include hydrogen, oxygen, nitrogen, ash, and
sulfur.
Some of the undesirable chemical constituents include chlorine and sodium.
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In the process of transformation (coalification), peat is altered to lignite,
lignite is altered to sub-bituminous, sub-bituminous coal is altered to
bituminous coal, and bituminous coal is altered to anthracite.
Types of Coal
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Peat, Lignite, Bituminous & Anthracite Coal.
This division is based on carbon, ash and moisture content.
Peat
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First stage of transformation.
Contains less than 40 to 55 per cent carbon == more impurities.
Contains sufficient volatile matter and lot of moisture [more smoke and more
pollution].
Left to itself, it burns like wood, gives less heat, emits more smoke and leaves
a lot of ash.
Lignite
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Brown coal.
Lower grade coal.
40 to 55 per cent carbon.
Intermediate stage.
Dark to black brown.
Moisture content is high (over 35 per cent).
It undergoes SPONTANEOUS COMBUSTION [Bad. Creates fire accidents
in mines]
Bituminous Coal
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Soft coal; most widely available and used coal.
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Derives its name after a liquid called bitumen.
40 to 80 per cent carbon.
Moisture and volatile content (15 to 40 per cent)
Dense, compact, and is usually of black colour.
Does not have traces of original vegetable material.
Calorific value is very high due to high proportion of carbon and low
moisture.
Used in production of coke and gas.
Anthracite Coal
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Best quality; hard coal.
80 to 95 per cent carbon.
Very little volatile matter.
Negligibly small proportion of moisture.
Semi-metallic lustre.
Ignites slowly == less loss of heat == highly efficient.
Ignites slowly and burns with a nice short blue flame. [Complete combustion
== Flame is BLUE == little or no pollutants. Example: LPG]
In India, it is found only in Jammu and Kashmir and that too in small quantity.
Distribution of Coal in India
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Gondwana coal fields [250 million years old]
Tertiary coal fields [15 – 60 million years old]
Gondwana Coal
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Gondwana coal makes up to 98 per cent of the total reserves and 99 per
cent of the production of coal in India. Satpuras, denudation [weathering +
erosion] has exposed coal bearing Gondwana strata.
The carbon content in Gondwana coal [250 million years old] is less
compared to the Carboniferous coal [350 million years old][Almost Absent
in India] because of its much younger age.
Gondwana coal forms India’s metallurgical grade as well as superior quality
coal.
The Damuda series (i.e. Lower Gondwana) possesses the best worked
coalfields accounting for 80 per cent of the total coal production in India. 80
out of 113 Indian coalfields are located in the rock systems of the Damuda
series [lower Gondwana Age].
Coking as well as non-coking and bituminous as well as sub-bituminous coal
are obtained from Gondwana coal fields.
Anthracite is generally not found in the Gondwana coal fields.
The volatile compounds and ash (usually 13 – 30 per cent) and doesn’t allow
Carbon percentage to rise above 55 to 60 per cent. [It requires few million
years more if the quality has to get better. Remember Gondwana coal is 100
million years younger than Carboniferous coal].
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Gondwana coal is free from moisture, but it
contains Sulphur and Phosphorous.
These basins occur in the valleys of certain rivers viz., the Damodar
(Jharkhand-West Bengal); the Mahanadi (Chhattisgarh-Odisha); the Son
(Madhya Pradesh Jharkhand); the Godavari and the Wardha (MaharashtraAndhra Pradesh); the Indravati, the Narmada, the Koel, the Panch, the Kanhan
and many more.
Distribution of Gondwana Coal in India
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First coal mine was opened in 1774 at Raniganj in West Bengal.
Coal industry was nationalized in 1973-74. [The present government made
some serious changes during the last year [2015] by allowing private sector to
play a bigger role in coal production].
India is now the third largest coal producer in the world after China and the
USA.
Coal industry provides employment to nearly seven lakh persons.
Gondwana Coalfields == exclusively found in the Peninsular plateau of India.
Gondwana Coalfields in Chhattisgarh
Coalfield
Extent
Korba coalfield
Korba district.
Birampur coalfield
Hasdo-Arand coalfield
Surguja district.
Chirmiri coalfield
Lakhanpur coalfield
Jhilmili coalfield
Shandol district & Koriya district
Johilla coalfield
Johilla valley
Sonhat coalfield
Surguja district
Tatapani-Ramkota coalfields
Surguja district
Gondwana Coalfields in Jharkhand
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1st in reserves [28%].
2nd in production [20%].
Most of the coal fields are located in a narrow belt running in east-west
direction.
Major coalfields are present in Dumka (Santhal Parganas), Hazaribagh,
Dhanbad and Palamu.
Jharia, Bokaro, Girdih and Karanpura are the major coal fields
Jharia coalfield
Danbad district
Jayanti coalfields
One of the oldest and the richest coalfields of India;
store house of the best metallurgical coal [coking coal]
inferior quality and has high ash content
Bokaro coalfield
West Bokaro [900
m deep]
It is a long but narrow strip in the catchment area of
the Bokaro river.
East Bokaro [600
m deep]
Girdih
(Karharbari)
coalfield
Hazaribagh
district
Gives out of the finest coking coal in India for
metallurgical purposes.
Karanpura and
Ramgarh
coalfields
Auranga coalfield
Hutar coalfield
Palamu district
inferior quality; used in cement furnaces and brick kilns
Deltenganj
coalfield
Devgarh coalfields Dumka district
inferior quality
Rajmahal coalfield Rajmahal hills
inferior quality
Coalfield locations can be asked in Prelims.
Gondwana Coalfields in Odisha
Ranks second in reserves (24,374 million tonnes)
after Raniganj;
Talcher field
Talcher town to
Rairkhol in Dhenkanal
and Sambalpur districts
Coal from this field is most suitable for steam and
gas production.
Most of the coal is utilised in thermal power and
fertilizer plants at Talcher.
Rampur-Himgir
coalfields
Sambalpur and
Sundargarh
Coal occurs here in middle and lower Barakar
seams.
inferior quality
Ib river coalfield
Sambalpur and
Jharsuguda district
Much of the coal is of inferior quality.
Gondwana Coalfields in Madhya Pradesh
largest coalfield of Madhya Pradesh
Singrauli
(Waidhian)
coalfield
Sidhi and Shandol
districts
Jhingurda, Panipahari, Khadia, Purewa and Turra
are important coal seams
Jhingurda with a total thickness of 131 m is the
richest coal seam of the country.
thermal power plants at Singrauli and Obra
Pench-Kanhan-
Chhindwara district
Ghoravari seam in Kanhan field is 4.6 m thick and
Tawa
contains coking coal
Sohagpur coalfield
Shandol district
Umaria coalfield
Umaria district
inferior quality with high percentage of moisture
and ash.
Gondwana Coalfields in Andhra Pradesh
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6th in reserves [7.07 %].
5th in production [9.69 %].
Most of the coal reserves are in the Godavari valley.
Adilabad, Karimnagar, Warangal, Khammam, East Godavari, and West
Godavari.
The actual workable collieries are situated at Singareni and Kothagudam.
Almost the entire coal is of non-coking variety.
These are the southern most coalfields of India and a source of coal supply to
most of south India.
Gondwana Coalfields in Maharashtra
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3 per cent reserves.
7 per cent of the production.
Gondwana Coalfields in West Bengal
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4 % of India’s coal.
11 % of the coal reserves.
Darjeeling and Jalpaiguri are the chief producing districts.
RANIGANJ is the largest coalfield of West Bengal.
Raniganj == Barddhaman, Bankura and Purulia districts; Small part of this
field is in Jharkhand state.
The coal here is non-coking steam coal.
Dalingkot coalfield == Darjeeling district.
Gondwana Coalfields in Uttar Pradesh
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Do not possess coal reserves.
A small portion of the Singrauli field of Madhya Pradesh falls within Mirzapur
district.
A high grade coal seam, about 1 to 1.5 m thick occurs near Kotah.
Tertiary Coal
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Tertiary coal 15 to 60 million years old. Carbon content is very low.
Mainly confined to the extra-Peninsula [Jammu and Kashmir, Himachal
Pradesh, Assam, Arunachal Pradesh etc.]
Coal generally has low carbon and high percentage of
moisture and Sulphur.[It takes few hundred million years for the carbon
content to improve].
Important areas of Tertiary coal include parts of Assam, Meghalaya,
Arunachal Pradesh, Nagaland, Himalayan foothills of Darjeeling in West
Bengal, Jammu and Kashmir, Uttar Pradesh, Rajasthan, Kerala,
Tamil Nadu and the union territory of Pondicherry also bear tertiary coal
reserves [exceptions].
Tertiary Coalfields in Assam
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Makum, Nazira, Mikir Hills, Dilli-Jeypore and Lakhuni.
Makum coalfield in Sibsagar district is the most developed field.
Assam coals contain very low ash and high coking qualities but the sulphur
content is high, as a result of which this coal is not suitable for metallurgical
purposes.
But these coals are best suited for hydrogenation process and are used
for making liquid fuels.
Tertiary Coalfields in Arunachal Pradesh
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Upper Assam Coal belt extends eastwards as Namchick-Namrup coalfield.
High in volatiles and in sulphur.
Tertiary Coalfields in Meghalaya
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Garo, Khasi and Jaintia hills.
Darrangiri field == Garo hills.
Siju, Cherrapunji, Liotryngew, Maolong and Langrin coalfields == Khasi and
Jaintia hills.
Tertiary Coalfields in Jammu and Kashmir, Himachal Pradesh
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Kalakot and surrounding regions in Jammu, south of Pirpanjal.
Himachal Pradesh == Chamba district.
Tertiary Coal – Lignite
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Tamil Nadu, Gujarat, Jammu and Kashmir, Kerala, Rajasthan, West Bengal
and Puducherry.
Tamil Nadu excels all other states regarding reserves and production of lignite.
Lignite in Tamil Nadu
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90 per cent of the reserves.
57 per cent of the production.
Neyveli Lignite fields of Cuddalore district.
These are the largest deposits of lignite in south – east Asia.
Neyveli mines suffer from the artesian structure [mining goes deep and deep].
Mining in Lignite coalfields is risky due to SPONTANEOUS
COMBUSTION of lignite.
Lignite in Gujarat and Rajasthan
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Kachchh district and Dharuch district; poor quality.
Rajasthan == Palana in Bikaner district; The 250 MW thermal plant
at Bikaner wholly depends upon lignite as the basic fuel.
Tertiary Coal – Peat
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Confined to a few areas only.
Occurs in Nilgiri hills.
Kashmir valley, peat occurs in the alluvium of the Jhelum.
In West Bengal peat beds are noted in Kolkata and its suburbs.
In the Ganga delta, there are layers of peat which are composed of forest and
rice plants.
Problems of Coal Mining in India
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The distribution of coal is uneven.
High ash content and low caloric value.
Large percentage of coal is taken out from underground mines. [Very few
open cast mines]
Heavy losses due to fires in the mines.
Pilferage at several stages also adds to losses – bad transportation
infrastructure.
Serious problem of environmental pollution. High ash, moisture == more
smoke.
Safety measures against environmental pollution are very costly. Clean coal
technology == Complex technology.
Misuse of good quality coal for burning into transport and industries.
Short life of metallurgical coal.
Selective mining leading to large scale wastage of raw coal
Unscientific method of extraction of coal.
Measures to be taken
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Coking coal should be used for metallurgical industry only.
Low grade coal should be washed and blended with superior quality coal in
requisite proportion and used in industries. [Clean Coal Technology]
Selective mining should be discouraged and all possible coal from the mines
should be taken out.
New reserves should be discovered and new techniques should be adopted.
Alternative energy sources should be encouraged.
Coking Coal vs. Non-Coking Coal
Coking Coal or Metallurgical Coal
Thermal Coal or Non-Coking Coal or
Steaming coal
High carbon content, less moisture, less
Sulphur content is high and hence
cannot be used in iron and steel
sulphur, less ash.
industry.
Sulphur is very bad for iron and steel
industry.
Used to create coke.
Creating coke using this coal is not
Coke is produced by heating bituminous
economical.
coal without air to extremely high
temperatures.
Moreover traces of sulphur will remain
even after coking.
Coking == flushing out impurities and
improving the concentration of carbon.
Coking coal is an essential ingredient in
steel production.
Major producers: Australia, Canada,
United States.
Major exporters: Australia, Canada,
United States.
China imports huge amount of coking
coal from Australia.
India also imports coking coal.
Coal Reserves in India by State
Thermal coal is used to generate
power.
Major producers: China, Australia,
USA, Russia.
Major exporters: Australia, South
Africa.
Name of the state
Reserves in billion tonne
% of total reserves
1. JHARKHAND
80.71
26.76
2. ODISHA
75.07
24.89
3. CHATTISHGARH
52.53
17.42
4. WEST BENGAL
31.31
10.38
5. MADHYA PRADESH
25.67
8.51
6. ANDHRA PRADESH
22.48
7.45
7. MAHARASTRA
10.98
3.64
8. OTHERS
2.81
0.95
Coal Production in India by State
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All data from 2013-2014. For latest data you must follow newspapers or
Reports published by Ministry of Coal.
Remember top 3 positions in all data below.
Coking Coal Production by State
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Jharkhand [More than 90% of India’s Coking coal comes from Jharkhand]
West Bengal
Madhya Pradesh
Non Coking Coal Production By State
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Chhattisgarh
Odisha
Madhya Pradesh
Jharkhand
Andhra Pradesh
Total Coal Production By State
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Chhattisgarh
Jharkhand
Odisha
Madhya Pradesh
Andhra Pradesh
India’s Coal Imports and Exports
Major Coalfields in India
Major Coalfields in India
1. Singrauli
2. Karanpura Bokaro
3. Jharia
4. Raniganj
5. Ib & Talcher
6. Pench & Kanhan
7. Singareni – Godavari Velley
8. Lignite: TN, Gujrat And Rajasthan