for students coal and its types

1. COAL and TYPES

3.  The natural solid fuels are wood, peat,
lignite or brown coal, bituminous coal and
anthracite coal.
 The prepared solid fuels are wood
charcoal, coke, briquette coal and
pulverized coal.

5.  At once it was extensively used as fuel. It
consists of mainly carbon and hydrogen.

 Wood has been the main source of the fuel
until the recent times on account of its
relatively rapid growth and production
and ease of obtaining and supplies.
 The large scale deforestation and the
increasingly large demand of energy by
industries lead to more extensive use of
other types of fuel.

6.  Freshly cut wood contains greater content
of the water which is 25-30% then dry
which has 15% of water content.
 Its heating value is directly proportional
to the water content.
 Wood mainly consists of cellulose and
lingo-cellulose as well as some cell sap
associated with traces of mineral ash.

7.  On the dry and ash free basis the average
composition of the wood is 50% carbon,
43% Oxygen,, 6% Hydrogen and 1%
nitrogenous and resinous material.
 As a rule, the dry wood is very
combustible and easily kindled and
burned with a long non-smoky flame.
 It give maximum heat intensity very
quickly.

8.  However the calorific value of the wood is
only 19.7 to 21.3 MJ/Kg, (4710 to 5085
Kcal/Kg).
 The calorific value of wood varies with its
kind and moisture content.
 The ash content of the wood is very low
and lies in the range of 0.3% to 0.6%.
 Wood is largely used as domestic fuel.

9.  It is rarely used in industry except where
dirt and smoke are undesirable.
 Due to its high flame emissive, it is
preferentially used for space heating.
 The wood is converted into coal when
burnt in the absence of air.
 Wood charcoal is obtained by it
destructive distillation of the wood.

11.  The carbonization is performed usually in
closed retort. The charcoal is not pure
carbon because even when the
carbonization is conducted at high
temperature, it rapidly absorbs some gas
and moisture.
 It also contains some inorganic residues
derived from the from the wood.
 Charcoal was widely used for
metallurgical operations formerly. But it
has been replaced by coke excepting for
some special application.

12.  The major use of the charcoal today is for
producing the activated carbon which find
extensive application in the
decolonization (e.g. in sugar industry).,
adsorption of gasses and vapors and
recovery of solvent from the gases and air.
 Charcoal is used in the production of
CaC2, Ferro Alloys and especially quality
pig iron in small furnaces.

16.  It is a spongy humid substance found in
boggy land.
 It has a characteristic odor.
 Peat is considered as the first step in the
conversion of vegetable debris to coal and
is produced under water-logged areas
under the action of fungi and anaerobic
reaction.

17.  It founds in high altitudes.
 Three main types UPLAND TYPE consisting
mainly of decomposed heath (a low
evergreen shrub of the family Ericaceae; has
small bell-shaped pink or purple flowers)
and mosses (tiny leafy-stemmed flowerless
plants), LOWLAND TYPE derived from
sedges (grass like trees), grasses and willows
(shedding foliage of trees) and FOREST PEAT
formed from accumulation of leaves, twigs (a
small branch or division of a branch) etc.

18.  It is mostly found in the tropical
countries.
 USSR (42% of world peat), Ireland, UK,
Canada, Finland, Siberia, France,
Germany and Italy.
 Freshly cut peat may contain up to 90%
water, which is reduced to 15-20% by air
drying.
 Most peat blocks contains 20-25% of
moisture.

19.  Utilization of peat depends upon its
economical drying.
 Calorific value of the dry peat is 23000
KJ/Kg. or almost 5450 Kcal/Kg.
 Peat as such is only used as local fuel, and is
not considered as economical fuel because of
cost of drying and handling and
transportation as it is voluminous, relatively
low calorific value and because of its
property of getting powdered during
burning.

20.  It is mostly used by briquette with other
substances, as domestic fuel.
 Carbonization of peat at low temperatures
(500-600 o
C) produces char oils and light
spirit, and under proper condition it may
yield coke and gasses.
 It is used as domestic fuel mostly in Europe
as fuel for domestic appliances (Cooker and
Space Heaters), for steam raising for thermal
insulation, packing, gas purification, and soil
conditioning, Russia use it for power
generation as well due to shortage of coal.

23.  Intermediate stage between peat and
black coal
 Moisture content ranges from 35 to 50%.
 Carbon content on dry and ash free bases
ranges from 60 to 75%. While oxygen is
over 20%.
 They have high volatile matters from 48%
to 50% and ash content up to 4% or more.

24.  Occurs at shallow depths and obtained by
open cast mining.
 Because of large volatile matters they
burn with long smoky flame.
 They tend to break in small pieces on
drying.
 Their calorific value is only in the range of
24.3 to 29.3 MJ/Kg (5800-7000 Kcal/Kg
on dry ash free basis.

25.  Lignite’s absorbs oxygen readily on exposure to
air and get spontaneous ignition.
 Not considered as good fuel but better then peat.
 They are made in briquettes after dehydration
and marketed as such or after carbonization.
 They are used in power plants and in production
of producer gas.

26.  Maximum carbonization gives tar and
Ammonium Sulfate, tar on further
hydrogenation gives motor sprit and
Ammonium Sulfate is used as fertilizer.
 On basis of maturity and external
characteristics they are classified as
 Australian Morewel Brown Coal
 Wood Brown Coal (e.g Italian Valderno Brown Coal)
 Laminated Lignite’s which are rather black.

27. Brown varieties tends to darken on
exposure to the air.
Large amount is used in Russia and
Germany for steam raising.
Coal in Thar Pakistan is also lignite
but with greater content of water.

30.  Forms a group in between lignite and
bituminous coal
 They are harder and denser than lignite.
 Black in colour with dull waxy luster.
 Moisture content is 12-25%.

31. Calorific value 7000 Kcals/Kg.
Carbon content 75-83%
Oxygen 10-20%.

34.  These coals burn with smoky yellow flame
like bitumen.
 Product of distillation is coal tar which is
bituminous in nature.
 Black in color with banded appearance,
laminated structure and cubical fracture.
 Calorific value 8000-8500 Kcals/Kg.

35.  Carbon content 78-90%
 Volatile matter 20-45%
 Oxygen 10-20%.

36. Easy to handle and good in heating
values.
They are widely used in the world for
domestic, industrial, steam raising,
coke and gas production and by
product manufactures.

39. Forms a group in between anthracite
and bituminous coal.
Characterized to have low volatile
matters (9-20)
Calorific value 8600 Kcals/Kg.

40. Carbon content 90-93%
Used for manufacture of coke.

43.  Considered higher rank of coal.
 Maximum percentage of carbon (92-96%).
 Are black hard and lustrous and have
conchoidal fracture.
 Low volatile matters (about 6%) so very
little flame produced which is non smoky
and blue in color.

44.  Calorific value is 8600 Kcal/kg.
 They burn with intense local heating.
 Due to smokeless combustion they used for
domestic heating
 Used in metallurgical purposes, naval purposes,
slow combustion stoves, central heating
furnaces, producer gas production etc.

47.  The different stages of coalification are
called as Peat-Anthracite series.
 Each stage in the above series is
considered to belong to higher rank of
maturity then their respective preceding
member in the series.
 As coalification progresses, the
percentage of carbon and hardness
increases.

49. While the percentage of Hydrogen,
Oxygen, Moisture and volatile
matter generally decreases.
The calorific value generally
increases from peat to Semi
bituminous coal, there is slight fall
in the calorific value of the
anthracite because the percentage of
hydrogen decreases.