IMPORTANT READING MATERIAL FROM COAL DIRECTORY OF INDIA

IMPORTANT READING  MATERIAL FROM COAL DIRECTORY OF INDIA 
http://www.coalcontroller.gov.in  

Concepts, Definitions and Practices

1.7 Coal: Coal is a combustible sedimentary

rock formed from ancient vegetation which

has been consolidated between other rock

strata and transformed by the combined

effects of microbial action, pressure and

heat over a considerable time period. This

process is commonly called ‘coalification’.

Coal occurs as layers or seams, ranging in

thickness from millimeters to many tens of

metres. It is composed mostly of carbon

(50–98 per cent), hydrogen (3–13 per cent)

and oxygen, and smaller amounts of

nitrogen, Sulphur and other elements. It

also contains water and particles of other

inorganic matter. When burnt, coal releases

energy as heat which has a variety of uses.

1.8 Classification of Coal

1.8.1 Coal refers to a whole range of

combustible sedimentary rock materials

spanning a continuous quality scale. For

convenience, this continuous series is often

divided into two main categories, namely

Hard Coal and Brown Coal. These are

further divided into two subcategories as

given below.

· Hard Coal

· Anthracite

· Bituminous coal

· Coking coal

· Other bituminous coal

· Brown coal

· Sub-bituminous coal

· Lignite

1.8.2 In practice, hard coal is calculated as

the sum of anthracite and bituminous coals.

Anthracite is a high-rank, hard coal used

mainly for industrial and residential heat

raising. Bituminous coal is a medium-rank

coal used for gasification, industrial coking

and heat raising and residential heat raising.

Bituminous coal that can be used in the

production of a coke capable of supporting a

blast furnace charge is known as coking

coal. Other bituminous coal, not included

under coking coal, is also commonly known

as thermal coal. This also includes

recovered slurries, middling and other lowgrade,

higher-rank coal products not further

classified by type.

1.8.3 Classifying different types of coal into

practical categories for use at an

international level is difficult because

divisions between coal categories vary

between classification systems, both

national and international, based on calorific

value, volatile matter content, fixed carbon

content, caking and coking properties, or

some combination of two or more of these

criteria.

1.8.4 Although the relative value of the coals

within a particular category depends on the

degree of dilution by moisture and ash and

contamination by sulphur, chlorine,

phosphorous and certain trace elements,

these factors do not affect the divisions

between categories.

1.8.5 The International Coal Classification of

the Economic Commission for Europe

(UNECE) recognizes two broad categories of

coal:

i) Hard coal – Coal of gross calorific value

not less than 5700 kcal/kg (23.9 GJ/t) on

an ash-free but moist basis and with a

mean random reflectance of vitrinite of at

least 0.6.

ii) Brown coal - Non-agglomerating coal

with a gross calorific value less than

5700 kcal/kg (23.9 GJ/t) containing

more than 31% volatile matter on a dry

mineral matter free basis.

1.8.6 It should be stressed that the above

classification system is based on the

inherent qualities of the coal in question and

not on the final use of the coal. In this way

the classification system attempts to be

objective and simple to apply.

1.9 Classification of Coal in India

1.9.1 In India coal is broadly classified into

two types – Coking and Non-Coking. The

former constitute only a small part of the

total coal resources of the country. These

two are further subdivided as follows on the

basis of certain physical and chemical

parameter as per the requirement of the

industry.

1.9.2 Coking Coal: Coking coal, when

heated in the absence of air, form coherent

beads, free from volatiles, with strong and

porous mass, called coke. Coking coal has

coking properties and is mainly used in steel

making and metallurgical industries.

1.9.3 Semi Coking Coal: Semi Coking

Coal, when heated in the absence of air,

form coherent beads not strong enough to

be directly fed into the blast furnace. Such

coal is blended with coking coal in adequate

proportion to make coke. Clearly, Semi

Coking Coal has comparatively less coking

properties than coking coal. It is mainly used

as blendable coal in steel making, merchant

coke manufacturing and other metallurgical

industries.

1.9.4 Non-Coking Coal: Non-Coking Coal

does not have coking properties and is

mainly used for power generation. It is also

used for cement, fertilizer, glass, ceramic,

paper, chemical and brick manufacturing,

and for other heating purposes.

1.9.5 Washed Coal: Processing of coal

through water separation mechanism to

improve the quality of coal by removing

denser material (rocks) and high ash

produces washed coal which has less ash,

higher moisture, better sizing, better

consistency, less abrasive, etc. The washed

coking coal is used in manufacturing of hard

coke for steel making. Washed non-coking

coal is used mainly for power generation but

is also used by cement, sponge iron and

other industrial plants.

1.9.6 Middlings and Rejects: In the

process of coal washing, apart from Clean

Coal we also get two by-products, namely,

Middlings and Rejects. Clean coal has low

density whereas rejects have high density.

Middlings have intermediate density. Rejects

contain high ash, mineral impurities, fraction

of raw coal feed, etc. and are used for

Fluidized Bed Combustion (FBC) Boilers for

power generation, road repairs, briquette

(domestic fuel) making, land filling, etc.

Middlings are fraction of raw coal feed

having values of classificatory parameters

between that of clan coals and rejects. It is

used for power generation. It is also used by

domestic fuel plants, brick manufacturing

units, cement plants, industrial plants, etc.

1.9.7 Hard Coke: Solid product obtained

from carbonaisation of coal, used mainly in

the iron & steel industry.

1.10 Categorisation of Coal in India

1.10.1 In India, coking coal has been

categorized or graded on the basis of ash

content as per following scheme:

Grade Ash Content

Steel Gr I Ash content < 15%

Steel Gr II 15%<=Ash content<18%

WasheryGrI 18%<=Ash content<21%.

WasheryGr.II 21%<=Ash content<24%

Washery Gr. III 24%<=Ash content<28%

Washery Gr. IV 28%<=Ash content<35%

1.10.2 In India, semi coking coal has been

categorized or graded on the basis of ash

and moisture content as per following

scheme:

Grade Ash + Moisture content

Semi coking Gr. I less than 19%

Semi coking Gr. II Between 19% and 24%

1.10.3 In India, non-coking coal had been

categorized or graded on the basis of Useful

Heat Value (UHV) as per following scheme:

Grade Useful Heat Value

A UHV.> 6200 kCal/Kg

B 6200 >=UHV(KCal/Kg)>5600

C 5600 >=UHV(KCal/Kg)>4940

D 4940 >=UHV(KCal/Kg)>4200

E 4200 >=UHV(KCal/Kg)>3360

F 3360 >=UHV(KCal/Kg)>2400

G 2400 >=UHV(KCal/Kg)>1300

N.B:

1. "Useful heat value" is defined as:

UHV = 8900- 138 (A + M)

Where UHV = Useful heat value in kCal/kg,

A = Ash content (%),

M = Moisture content (%).

2. In the case of coal having moisture less

than 2 percent and volatile content less than

19 percent the useful heat value shall be the

value arrived as above reduced by 150 kilo

calories per kilogram for each 1 percent

reduction in volatile content below 19

percent fraction pro-rata.

3. Both moisture and ash is determined after

equilibrating at 60 percent relative humidity

and 40 degree C temperature.

4. Ash percentage of coking coals and hard

coke shall be determined after air drying as

per IS1350 -1959. If the moisture so

determined is more than 2 per cent, the

determination shall be after equilibrating at

60 percent relative humidity at 40 degree C

temperature as per IS : 1350 - 1959.

1.10.4 In order to adopt the best

international practices, India decided to

switch over from the grading based on

Useful Heat Value (UHV) to the grading

based on Gross Calorific Value (GCV) and

therefore on 16.01.2011 the Ministry of Coal

notified the switch over. As per the new

system, following nomenclature has been

introduced for gradation of non-coking

coal.

Grades GCV Range (Kcal/Kg)

G1 GCV exceeding 7000

G2 GCV between 6701 & 7000

G3 GCV between 6401 & 6700

G4 GCV between 6101 & 6400

G5 GCV between 5801 & 6100

G6 GCV between 5501 & 5800

G7 GCV between 5201 &5500

G8 GCV between 4901 & 5200

G9 GCV between 4601 & 4900

G10 GCV between 4301 & 4600

G11 GCV between 4001 & 4300

G12 GCV between 3700 & 4000

G13 GCV between 3400 & 3700

G14 GCV between 3101 & 3400

G15 GCV between 2801 & 3100

G16 GCV between 2501 & 2800

G17 GCV between 2201 & 2500

1.10.5 Based on the GCV ranges of proposed

gradation and erstwhile gradation, a

concordance table is generated for better

understanding. However, it may be noted that this concordance does not depict exact

to-one relation between the two systems.

 Table 5: Concordance Table
Old Grading based             New Grading based
on GCV                                 on UHV

A                                               G1
                                                  G2
                                                  G3
B
                                                 G4
                                                 G5
C                                               G6
D
                                                     G7
                                                          G8
E
                                                          G9
                                                     G10
F
                                                    G11
                                                              G12
G
                                                      G13
                                                      G14
Non-coking Coal
Ungraded                                    G15
                                                   G16
                                                     G17
1.11 Some General C

1.11 Some General Concepts

1.11.1 Run-of-mine (ROM) coal: The coal

delivered from the mine to the Coal

Preparation Plant (CPP) is called run-of-mine

(ROM) coal. This is the raw material for the

CPP and consists of coal, rocks, middlings,

minerals and contamination. Contamination

is usually introduced by the mining process

and may include machine parts, used

consumables and parts of ground engaging

tools. ROM coal can have a large variability

of moisture and particle size.

1.11.2 Opencast Mining: Open-pit mining,

open-cut mining or opencast mining is a

surface mining technique of extracting rock

or minerals from the earth by their removal

from an open pit or borrow. This form of

mining differs from extractive methods that

require tunneling into the earth such as long

wall mining. Open-pit mines are used when

deposits of commercially useful minerals or

rock are found near the surface; that is,

where the overburden(surface material

covering the valuable deposit) is relatively

thin or the material of interest is structurally

unsuitable for tunneling (as would be the

case for sand, cinder, and gravel). For

minerals that occur deep below the surface -

where the overburden is thick or the mineral

occurs as veins in hard rock - underground

mining methods extract the valued material.

1.11.3 Underground Mining of Coal: It

refers to a group of underground mining

techniques such as Longwall Mining, Room-

And-Pillar Mining, etc. used to extract coal

from sedimentary ("soft") rocks in which the

overlying rock is left in place, and the

mineral(coal) is removed through shafts or

tunnels.

1.11.4 Stripping Ratio : In mining,

stripping ratio or strip ratio refers to the

ratio of the volume of overburden (waste

materials) required to be handled in order

to extract some tonnage of coal. For

example, a 3:1 stripping ratio means that

mining one tonne of coal will require mining

three tonnes of waste materials. This is a

phenomenon related to mainly Opencast

(OC) mining which requires removal of

overburden prior to extraction of coal.

Underground mining operations tend to

have lower stripping ratio due to increased

selectivity.

1.11.5 Output per Man Shift (OMS) :

Productivity means ratio between input and

output and can be interpreted in different

ways by different people. To some people, it

is output per man shift (OMS). To the

production people, it is actual return from

plants, machineries of productivity of

machineries.

1.11.6 Despatch and Off-take: The term

"Despatch" (say, of raw coal) is used in this

compilation to mean all the despatch of coal

to different sectors but exclude collieries'

own consumption (boiler coal used in

collieries and supply to employees). On

the other hand "Off-take" means total

quantity of raw coal used/ lifted for

consumption and naturally includes collieries

own consumption. Therefore,

Off-take = Despatch + Colliery Consumption

1.11.7 Change of Stock: Change of Stock

means the difference between opening and

closing stock of an item.

1.11.8 Pit-Head Stock: The term "Pithead

Closing Stock" of raw coal is used in

this compilation to mean all the raw coal

stock at pit- head of collieries.

1.11.9 Pit-head Value: Pit-head Value of

coal is the value of coal at pit-head of the

colliery. It is computed on the basis of base

price and therefore it does not involve any

cost of loading, transportation from pithead,

Cess, Royalty, Sales tax, Stowing

Excise Duty etc. This approach is followed

by all non-captive coal companies, viz., CIL

Subsidiaries, The Singareni Collieries

Companies Ltd. (SCCL), Jharkhand State

Mineral Development Corporation Ltd.

(JSMDCL) and Jammu & Kashmir Mineral

Ltd. (JKML).

1.11.9.1 In case of captive collieries, pithead

value of coal depends upon their

accounting policy. If the costing of coal is

done on no-profit-no-loss basis then pithead

value is calculated accordingly. This

practice is found to be followed in captive

collieries of public sector units.

1.11.9.2 On the other hand, if the captive

colliery is treated as independent

commercial unit then pit-head value is

calculated on the basis of unit value of

realisation, which includes cost price and

profit/loss per unit but excludes any

transportation cost from pit-head, Cess,

Royalty, Sales tax, Stowing Excise Duty etc.

This is particularly followed in private captive

colliery which is in contract to supply coal to

any priority sector for which captive colliery

is permitted (Steel, Iron, Power, Cement, etc.).