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1. Self Introduction.
• Name: Muhammad Shozab Mehdi
• Qualifications:
– BSc. Chemical Engineering (2003), NFC Institute of Engineering
and Technology (IET), Multan, Pakistan.
– MS leading to PhD in Chemical Engineering (2013), Pakistan
Institute of Engineering and Technology, Islamabad, Pakistan.
– Research in Chemical Engineering Laboratory (LGC), Toulouse,
France.
• Research Interest: Hydrodynamics and Mass Transfer in
Multiphase flows.
• Office: FMSE-xxx, Ext: xxxx, Email: xxxxx@giki.edu.pk
• Teaching Assistant: Mr. Jahanzaib Ahmad Ansari, Ext:
xxxx, Email: xxxxxxxxxxxx@giki.edu.pk

2. CH 212: Fuel and Combustion
Spring – 2014

3. Introduction
Fuel: Anything which burn to
give heat in presence of oxygen.
Combustion: The process of
burning fuel.
• Burning is the intense
chemical reaction with the
emission of heat and other
exhaust gases when fuel reacts
with oxygen.

4. Introduction (contd.)
• Where does the energy comes from the combustion reactions?
• The energy stored in the chemical bonds that hold the carbon and
hydrogen atoms together, releases when bonds are broken and
atoms are rearranged.
• How does this energy stored in fuel?
• This energy stores in fuel by the process of photosynthesis which
converts sunlight into chemical energy and storing it in the bond of
sugar. Plants needs Carbon dioxide, Water and sunlight to make
sugar. The overall reaction is:
6CO2 + 6H2O + Sunlight -----> C6H12O6 + 6O2
• These plants when became dead, buried under the soil, as more and
more soil deposited over them for thousands of years, they became
compressed and then under high temperature and pressure
converted into fossil fuel.

5. Introduction (contd.)

6. Importance
• Almost 70% of energy used in the world came
from combustion sources.

7. Importance (contd.)
• Heat for homes comes directly from combustion.
• Electricity for homes generated by burning fossil fuel.
• Our transportation system relies almost entirely on combustion.
– Air craft are entirely powered by fuel burning.
– Most trains are powered by diesel engine.
– Most of the domestic vehicles use gasoline.
• Industrial process rely heavily on combustion.
– Iron, steel, aluminum and other metal refining industries employ
furnaces for producing raw products.
– Cement industry is the heavy user of heat energy delivered by
combustion.
– Other example of industrial combustion devices are boiler, refinery,
glass melters and solid dryers etc.

8. Course Description
• Various conventional and non-conventional fuels; their
characterization and processing including refining, coal
gasification and natural gas treatment.
• Various aspect of combustion and related balances.
• Fuel economy, burners classification and design.
• Flame analysis and its various regimes and
temperatures; Interface energy balances and heat
distribution; oxygen diffusion and flame front;
flammability limits and flame quenching.
• Furnaces, boilers and engines (I.C & G.T).
• Emission control (SOx & NOx).

9. Books (Text & Reference)
• Flame and Combustion by J. F. Griffiths and J.
A. Barnard, 3rd Ed. 1995
• An Introduction to Combustion; Concept and
Applications by Stephen R. Turns, 2nd Ed. 2000
• Elements of Fuel, Furnaces and Refractories by
O. P. Gupta 4th Ed. 1997

10. Before Mid
Solid Fuel Liquid Fuel Gaseous Fuel
•Introduction and
•Origin and composition
classification of fuels.
of petroleum.
•Fundamentals /
•Classification of
Definitions.
petroleum and their
•Solid fuel [Wood,
characteristics.
Charcoal, Peat].
•Constituents of
•Origin of coal
petroleum and their
•Solid fuel [Lignite,
uses.
Bituminous coal,
•Processing of crude oil
Anthracite].
[Distillation, Cracking,
•Constituents of coal.
Reforming].
•Testing of coal.
•Properties of
•Carbonization of coal.
petroleum products.
•Methane from coal
mines.
•Wood gas.
•Bio gas.
•Gas from underground
gasification of coal.
•Natural gas.
•Liquified petroleum
gas.
•Refinery gases.
•Producer gas.
•Water gas.
•Blast furnace gas.
•Coke oven gas.
• Various aspect of combustion and related balances.

11. After Mid
• Various aspect of combustion and related
balances.
• Fuel economy, burners classification and design.
• Flame analysis and its various regimes and
temperatures; Interface energy balances and heat
distribution; oxygen diffusion and flame front;
flammability limits and flame quenching.
• Furnaces, boilers and engines (I.C & G.T).
• Emission control (SOx & NOx).

12. Marks Distribution
• Assignments (Nos?): ?%
• Quizzes (Nos?): ?%
• Midterm exam: ?%
• Final Exam: ?%
• Attendance: ?%

13. Classification of Fuels

14. General Classification of Fuels
• Fossil fuels:
Those which have been derived from fossil remains of plants and
animal life and are found in crust of earth. For example coal,
petroleum and natural gas etc.
• By-product fuels:
Those which are co-product of regular manufacturing process and
of secondary in nature. For example coke oven gas from
manufacturing of coke and blast furnace gas from making of iron.
• Chemical fuels:
Those which are of an toxic in nature and normally not used in
conventional processes. For examples hydrazine, ammonium nitrate
etc.
• Nuclear fuels:
Those which release heat by fission (uranium, plutonium etc.) or by
fusion (deuterium, tritium etc.)

15. Classification based on Occurrence
• Solid Fuels:
Wood, charcoal, coal, coke etc.
• Liquid Fuels:
petroleum and its products (gasoline,
kerosene, diesel, furnace oil, lubricating oil
etc), Liquid fuel from coal liquefaction etc.
• Gaseous Fuels:
Natural gas, refinery gas, gas from coal
gasification, wood gas, bio gas etc.

16. Classification based on Nature of Fuel
• Primary Fuels:
Those which occurred in nature i.e. wood, coal, natural gas and
petroleum.
• Secondary Fuels:
Those which are derived from primary fuels e.g. fuel oil and
kerosene derived from petroleum, coke oven gas derived from coal
etc.
Secondary fuels are further classified into:
– Manufactured:
Those which are manufactured for some specific purpose e.g. coke
made for iron making, gasoline made for internal combustion engine,
producer gas made for industrial heating etc.
– By-Product:
Those which are co-product of regular manufacturing process e.g. tar,
refinery gas etc.

17. Fundamentals / Definitions

18. • Rank of Coal: It denote the maturity of coal. So peat the most
immature coal has a lowest rank while the anthracite the most
mature coal has highest rank.
• Metamorphism of coal: The process of conversion of lignite to
anthracite is called metamorphism of coal or coalification.
• Carbonization of coal: Heating of coal in absence of air at high
temperature to produce coke, tar and gases is called carbonization
of coal.
• Gasification of coal: Heating of coal in insufficiently less amount of
air plus steam to produce a gas rich in CO and H2 is called
gasification of coal.
• Proximate analysis of coal: Finding out the weight percent of
moisture, volatile matter, fixed carbon and ash content in coal. The
analysis is useful in deciding the utilization for a particular purpose.
• Ultimate analysis: Finding out the weight percent of carbon,
hydrogen, nitrogen, oxygen and sulphur of pure coal free from
moisture and inorganic constituents. The analysis is useful in
designing of coal burning equipments.

19. • Calorific value: The quantity of heat liberated by combustion of unit
quantity of fuel is called its calorific value.
– Gross calorific value: Where the heat obtained from condensation of
water vapours in the flue gases is also include.
– Net calorific value: Where the heat obtained from condensation of
water vapours in the flue gases is not include.
• Flue gas: The gaseous product of combustion of a fuel.
• Heat capacity: Amount of heat required to raise the unit weight of
substance by one degree.
• Specific heat: It is the ratio of heat capacity of a substance to the
heat capacity of water (Cp > Cv).
• Ignition temperature: It is the minimum temperature at which the
fuel ignites.
• Flash point: It is the minimum temperature at which the fuel give
enough vapours which produces a momentary flash when exposes
to flame.
• Pour point: It is the minimum temperature at which fuel keeps its
flowing nature when cooled under specific conditions.

20. Solid Fuel

21. Wood
Domestic fuel used in tropical countries
where forest are abundant and other
fuels are not easily and cheaply
available.

22. • Main combustible components: cellulose and
lignin (compounds of carbon, hydrogen and
oxygen)
• Minor combustible components: resin and
waxes.
• Non combustible components: Water (25-50% in
freshly cut and 10-15% in air dried)
• Ash content: very low (<1%) but because oxygen
content is very high (upto 45%) therefore its
calorific value is very low.
• Calorific value: 4000-5000 kcal/kg.
• Density: 650 kg/m3.

23. Composition of Air-dried Wood
Proximate Analysis
• Cellulose: 50%
• Lignin: 30%
• Moisture: 15%
• Water soluble: 2.5%
• Resin & Wax: 2%
• Ash: 0.5%
Ultimate Analysis
• Carbon: 50%
• Hydrogen: 6%
• Oxygen: 44%

24. Properties of wood
• It is clean, readily ignites, burn with long clean
flame in excess air and leaves only small
amount of ash.
• Wood is a solid fuel as dense as coal but to
obtain same amount of heat as any given
weight of coal can produce, you have to burnt
wood, four times the weight of coal.
• It is used to produce charcoal.

25. Charcoal
Carbonization of wood at 600oC

26. Stages Involved in Carbonization of
Wood
Stage 1: At 100-120oC ---> moisture expelled results in
moisture free wood.
Stage 2: At 275oC ---> initial decomposition takes place
results in formation of little distillate gas containing
acetic acid and water.
Stage 3: At 350oC ---> active distillation of wood takes
place results in emission of liquid (acetic acid, methyl
alcohol, tar etc) and gases (CO, CO2, N2, H2, CnHn).
Stage 4: At 350-600oC ---> slow evolution of residual
volatile matters from the wood charcoal left in 3rd
stage.

27. Products of Carbonization of Wood
• Charcoal: Solid product left after the
carbonization of coal.
• Hot gases: Cooled to separate
– Wood gas
– Liquid in two layer
• Upper layer is Pyrolignious acid (mixture of acetic acid,
acetone and water).
• Lower layer is wood tar (fractionated to separate many
chemicals).

28. Uses and Composition of Charcoal
• Used for removal of obnoxious and coloring
material from solution, gases, vapors and
petroleum products by adsorption on its surface.
• Used as a feed stock for gasification to make
producer gas which is used as a fuel for domestic
and industrial use.
• Used as raw material for production of carbon
sulfide.
• Charcoal contains 80% carbon, 15% oxygen and
nitrogen, 2% hydrogen and 3% ash.

29. Merits and Demerits
• Because of porous in nature it has high
specific surface area as compared to coal.
• Ash content is very low.
• Calorific value is high as compared to wood.
• Mechanical strength is very poor.

30. Peat
First stage in formation of coal from
wood (cellulose)
The most immatured coal

31. Formation of Peat
• Peat is the first stage in the formation of coal
from wood (cellulose).
• It is not strictly a coal or else can be termed as
the most immatured coal.
• It is formed by gradual decaying (action of
bacteria under high pressure and
temperature) of remains of plants in moist
places.

32. Properties of Peat
• Peat is light brown in color.
• Highly fibrous in nature.
• With increase in depth the color becomes darker and
fibrous structure disappeared.
• Composition of peat varies from nature of plants,
depth in deposit and age.
• Freshly mined peat contains about 90% water and 10%
solid. Therefore cannot be used unless air dried.
• Calorific value is 650 kcal/kg for freshly mined peat and
5000 kcal/kg for air dried peat.

33. Composition of Peat
Proximate Analysis
• Moisture: 20%
• Volatile matter: 50%
• Fixed carbon: 25%
• Ash: 5%
Ultimate Analysis
• Carbon: 55%
• Hydrogen: 6%
• Oxygen: 33%
• Nitrogen: 3%
• Sulfur: 1%

34. Gasification of Peat
• Peat is gasified in presence of steam and air to produce
producer gas.
• Steam requirement is very low because peat itself contain
sufficient moisture.
• Typical composition of gas is:
• CO2 – 13%
• CO – 18%
• H2 – 11%
• CH4 – 2.5%
• N2 – 55.5%
• Caloric value is 1000 kcal/kg
• Gas yield is 2500 Nm3/ton of peat

35. Other non Fossil Domestic Fuel

36. Origin of coal
• Coal is a complex mixture of plant substances altered in varying degree by
physical and chemical processes.
• These processes which changed plant substances into coal has taken
million of years and has been accomplished by bacteria, heat and pressure
inside the earth’s crust.
• Two theories namely “in-situ” theory and “drift theory” have been
suggested by geologists regarding mechanism of formation of coal from
plant substances.
• In situ theory: According to this theory, coal seam occupies the same site
where the original plants grew and where their remains accumulated
several million years ago to produce coal under the action of heat,
pressure and bacteria.
• Drift theory: According to this theory plants, tree etc were uprooted and
drifted by rivers to lakes and deposited there to form coal during the
course of time after they got buried underground.
• Stages information of coal: plants/trees  peat  lignite  sub-bituminous
coal  bituminous coal  anthracite coal  graphite.

37. • Points in favor of “in-situ” theory:
– In the existing peat deposits; the decayed plant substances had
accumulated at the place of origin.
– Large quantity of fossil fuel have been found under the coal seam.
– Composition of coal seam is generally constant over a wide area. If the
original decaying plants and tree had been drifted from their original
place then they would have a great variation in composition of coal.
• Points in favor of “drift” theory:
– In coal seam, the percentage of inclined trunks of fossil is much more
than the vertical position. It the coal had been formed at the same
place where the plants substances decayed then fossil trunks would
have been vertical.
– To form one meter thick coal seam, ten meter thick seam of peat is
required, So for the formation of ten meter thick coal seam should
have resulted from hundred meter thick seam of peat, which occur no
where.
– Seams of coal are made up of different layers separated by layers of
clay or sandstone which vary in thickness from merely a film to several
meters. As the plants accumulated under water some slits also settled
along with them. Thus at later stage some mineral mater got mixed
with coal as it formed.

39. • Stages for transformation of wood to coal:
• The initial transformation of wood to coal is due to the action of
bacteria (aerobic or anaerobic) causing degradation of organic
matters (e.g. cellulose, lignin etc. present in wood) and removal
of oxygen.
• The bacterial action produced acidity which if accumulated
prevented further action and coal formation could not proceed.
• In some cases the soil was alkaline which neutralized the acidity
and bacterial action continued to take place further degradation
of organic matter. This explain why coal is found along with
certain types of rocks.
• Bacterial action takes place in initial stage breaks up organic
matters into simpler molecules.
• The degraded organic matters, as time passed, gave rise to peat.
• Beyond this stage heat, pressure and time became the chief
factors for further conversion of peat into different rank of coal.

40. Lignite
• It is the second stage product in the formation of coal from wood.
• It is friable and occurs in thick seams (up to 30 meter thick) near the
surface of earth.
• It moisture content is up to 60 % and calorific value is around 5000
kcal/kg.
• On exposes to air the brown color darkens and moisture content reduces
to equilibrium value of 10 – 20 %.
• On drying lignite shrinks and break up in irregular manner.
• It is likely to ignite spontaneously as it adsorbs oxygen readily and must
not be stored in open without care.
• Composition and property of lignite varies widely. The carbon content is
70 – 75 % and oxygen content is 20 – 25 %.
• In large number of cases the ratio of volatile matter to fixed carbon is 1:1.
• Raw Lignite is inferior fuel due to high moisture content, low calorific
value, small size and bad weathering properties.
• Lignite is of economic importance where it is readily available and other
fuels do not occur in abundance.

41. Composition of Lignite
Proximate Analysis
• Moisture: 10 – 30 %
• Volatile matter: 40 – 45 %
• Fixed carbon: 30 – 35 %
• Ash: 3.5 – 7.5 %
Ultimate Analysis
• Carbon: 70 – 73 %
• Hydrogen: 4.6 – 5.5 %
• Oxygen: 22 – 26 %
• Nitrogen: 0.6 – 1.0 %
• Sulfur: 0.6 – 1.5 %

42. Bituminous Coal
• It is the most common variety of coal.
• It is black and brittle which burns and ignites readily with
yellow smoky flame.
• It has low moisture content i.e. less than 10 % and carbon
content varies from 75 – 90 % where as volatile matter
content is 20 – 45 %.
• Depending upon the volatile matter content, it is termed as
low volatile, medium volatile and high volatile coal.
• Its calorific value based on dry mineral free basis goes up to
9000 kcal/kg.
• It is used for power generation, coke making, gasification
and domestic use.

43. Composition of Bituminous coal
Proximate Analysis
• Moisture: 3.5 – 8 %
• Volatile matter: 16 – 36 %
• Fixed carbon: 49 – 72 %
• Ash: 7 – 8.5 %
Ultimate Analysis
• Carbon: 68.5 – 79.5 %
• Hydrogen: 4.5 – 5.5 %
• Oxygen: 4.5 – 16.5 %
• Nitrogen: 1 – 1.4 %
• Sulfur: 0.5 – 1 %

44. Anthracite coal
• It is most matured coal hence of highest rank.
• It is hard and burns without smoke with a short non-luminous
flame.
• It has high carbon content i.e. 85 – 95 % and low volatile matter
content i.e. less than 10 %.
• It ignite with difficulty due to low volatile matter content.
• Its calorific value may be up to 8000 to 8500 kcal/kg which is less
than bituminous coal de to its lower hydrogen and volatile matter
content.
• It has sub-metallic lustre and sometime even a graphitic
appearance.
• The chief use of anthracites are in boilers and metallurgical
furnaces.
• On calcining it gives thermo-anthracite which is a raw material for
the production of carbon electrode.

45. Composition of Anthracite coal
Proximate Analysis
• Moisture: 2.5 – 3 %
• Volatile matter: 3 – 8.5 %
• Fixed carbon: 79 – 87.5 %
• Ash: 7 – 9.5 %
Ultimate Analysis
• Carbon: 80 – 86.5 %
• Hydrogen: 2.5 – 3.5 %
• Oxygen: 3 – 4.5 %
• Nitrogen: 0.5 – 1.5 %
• Sulfur: 0.5 %

46. Significance of constituents of coal
Proximate analysis
• Moisture
• Volatile matter
• Fixed carbon
• Ash
Ultimate analysis
• Carbon
• Hydrogen
• Nitrogen
• Sulphur
• Oxygen

47. Moisture
• In general high moisture content in coal is undesirable because:
– it reduces the caloric value of fuel
– it increases the consumption of coal for heating purpose
– it lengthens the time of heating
– it increases the cost for purchase and transportation.
• Owing to its nature, origin and occurrence, coal is always associated
with moisture.
• When coal is exposed to atmosphere its external moisture (free
moisture) evaporates but apparently dry coal still contain some
moisture (inherent moisture).
• Air-dried moisture content of coal is determined by observing loss
in weight of coal sample on heating at 105 degree centigrade.
• Air-dried moisture of coal decreases with increasing rank from a
value of 25% for lignite to a minimum value of 0.5% for low volatile
bituminous coal.

48. Volatile matter
• Certain gases like CO, CO2, CH4, H2, N2, O2, CXHY etc, are present in
coal which comes out during its heating in absence of air.
• These gases are called volatile matter of coal.
• Coal with high volatile matter content:
– Ignites easily i.e. it has low ignition temperature
– Burns with long smoky yellow flame
– Give more quantity of coke oven gas when it is heated in absence of
air.
• Volatile matter does not include moisture of coal but it contain
moisture that is formed from oxygen and hydrogen of coal during
the decomposition.
• Volatile matter expressed as per cent on dry mineral matter free
basis.
• Higher the volatile matter, lower the fixed carbon.

49. Ash content
• Ash is the combustion product of mineral matters presents in the
coal.
• It is comprises mainly of silica, alumina and ferric oxide with varying
amount of other oxide such as calcium and magnesium.
• High ash content in coal is undesirable in general.
• A coal with high ash content is harder and stronger and has lower
calorific value.
• Ash content of coal is reduced by its washing.
• Coal contains inorganic mineral substance which are converted into
ash by chemical reaction during combustion. Ash and coal are
therefore not the same.
• The bulk of mineral matter of coal is due to clay or shale consisting
of alumino-silicates of different composition. Other major
constituents may be calcite and pyrites.
• When coal burns these mineral matter decomposed resulting loss
in weight hence the ash of coal is always less than the mineral
matter content.

50. Fixed carbon
• It is the pure carbon present in coal.
• Higher the fixed carbon, higher will be the
calorific value.
• In anthracite where the value of volatile
matter is very small, fixed carbon and total
carbon are almost same.
• In other coals, fixed carbon is always less then
total carbon.

51. Total Carbon
• Its mean fixed carbon plus the carbon present
in the volatile matters.
• Total carbon is always more than fixed carbon
in any coal.
• High total carbon coal will have high calorific
value.

52. Hydrogen
• It increases the calorific value of coal. It is
associated with volatile matter of coal.
• The content of coal from peat to bituminous
varies between 4.5 and 6.5 and is not related
to the rank of coal.
• Beyond the bituminous stage the hydrogen
content sharply decreases to a value of 1 – 2%
in anthracite.

53. Nitrogen
• Nitrogen in coal is present up to 1 – 3% and
comes from the protein matter presents in plant.
• Presence of inert nitrogen decreases the calorific
value of coal.
• However when coal is carbonized, its hydrogen
and nitrogen combined thereby producing NH3
which is recovered as (NH4)2SO4 (by reacting it
with H2SO4) which is a valuable fertilizer.
• Nitrogen content does not have any relation with
rank of coal.
• In most coal it is between 1 – 2%.

54. Sulphur
• Though its presence increases the calorific value
of coal but has several undesirable effects.
• The oxidation product of sulphur i.e. SO2 in
presence of moisture cause corrosion of the
equipment and cause atmospheric pollution.
• Sulphur is highly undesirable in metallurgical coal
used for iron and steel making as it badly effect
the properties of iron and steel.
• The sulphur content of coal has no relation to its
rank or composition.

55. Oxygen
• Less the oxygen content better the coal as it
reduces its calorific value.
• It decreases from lignite to anthracite.
• As the oxygen content of coal increases it
moisture holding property increases.
Phosphorus & Chlorine

56. Washing of coal
• Most of the coal when mined contain impurities associated with it
which must be removed before the coal is used.
• These impurities are removed from coal by washing.
• Coal contain two types of impurities.
– Fixed or inherent impurities which are derived from coal forming
plants and cannot be removed by washing.
– Free impurities which are adhering to the surface of coal and
comprise mainly of dirt and rock particles which can be removed by
washing.
• Washing of coal:
– Reduces its ash content
– Reduces its sulphur content
– Increase its heating value
– Improves its coking property

57. Principle of washing of coal
• Specific gravity of pure coal varies from 1.2 to 1.7
and that of free impurities from 1.7 to 4.9.
• The coal can be separated by its impurities by
utilizing difference in specific gravity.
• If the average specific gravity of pure coal is 1.3
and it is suspended in liquid of specific gravity 1.5
then the impurities being heavier will sink in it
whereas the pure coal will float.
• Washing medium used in industrial coal washing
is a slurry of sand and water or that of water and
iron ore.

58. Properties and testing of coal
• Determination of moisture content: A known amount of finely
powdered coal sample is kept in a silica crucible and heated in a
muffle furnace at 105 – 110 degree centigrade for one hour. The
process of heating, cooling and weighing is repeated for number of
times until the constant weight of anhydrous coal is achieved.
• Determination of volatile matter: It is the loss in weight of
moisture free powdered coal when heated in crucible fitted with
cover in a muffle furnace at 950 degree centigrade for 7 minutes.
• Determination of ash content: It is the weight of residue obtained
after burning a weighed quantity of coal in an open crucible at 750
degree centigrade in a muffle furnace until a constant weight is
achieved.
• Determination of fixed carbon: It is determined indirectly by
deducting the sum total of moisture, volatile matter and ash
percentage from 100

59. • Determination of carbon and hydrogen:
– A known amount of coal is burnt in a current of dry oxygen
thereby converting Carbon and hydrogen of coal into
Carbon dioxide and water respectively.
– The product of combustion are then passed over weighed
tubes of anhydrous calcium chloride and potassium
hydroxide, which absorb water and carbon dioxide
respectively.
– The increase in weight of calcium chloride tube represent
the weight of water formed while increase in weight of
potassium hydroxide tube represent the weight of carbon
dioxide formed.
– The percentage of carbon and hydrogen then can easily be
calculated.
• Determination of Nitrogen in coal:
• Determination of Sulphur in coal:

60. • Determination of Calorific Value by bomb calorimeter:
• Strong stainless
steel vessel (25 – 30
atm).
• Provided with
electrode, crucible,
and oxygen inlet
valve.
• Bomb placed in
copper calorimeter.
• Calorimeter is
surrounded by
water and air jacket
provided with
electrical stirrer.

61. Carbonization of Coal
Low temperature carbonization
(LTC)
• It carried out at 700 degree C.
• It produces semi coke which is used as
smokeless domestic fuel.
• Yield of coke oven gas is less due to less
cracking of hydrocarbons.
• Yield of tar is high i.e. about 10% of dry
coal.
• Ammonia yield is low.
• Calorific value of coke oven gas is high
(6000 – 6500 kcal/kg) due to higher
percentage of methane and
unsaturated hydrocarbon in it.
• The tar produce is aliphatic in nature.
• Coke produced is weaker, bigger in size
and more reactive.
• Volatile matter content in coke is more.
• Hydrogen content in coke oven gas is
less i.e. 35 – 40%.
High temperature carbonization
(HTC)
• It carried out at 1000 degree C.
• It produces metallurgical coke for use in
blast furnace.
• Yield of coke oven gas is more due to
more cracking of hydrocarbon.
• Yield of tar is less i.e. about 3% of dry
coal.
• Ammonia yield is more.
• Calorific value of coke oven gas is less
(4200 – 4400 kcal/kg) due to lesser
percentage of hydrocarbon resulting
from cracking.
• The tar produce is aromatic in nature.
• Coke produced is stronger, smaller is
size and less reactive.
• Volatile matter content in coke is less.
• Hydrogen content in coke oven gas is
more i.e. 55 – 60%).