3. Factors involve in the selection of fuels
Number of factors are to be considered
when fuel is chosen for a particular purpose.
The main factors are:
The type of heating w. r. t. size or whether a continuous
or intermittent (irregular) operation is involved.
The availability and reliability of supply of fuels.
The price of the fuel delivered to the place where it is
required, as some fuels need storage and feeding
The efficiency of the heating operation with selected
The ratio of the cost of heating operation to the cost of the
finished product. If the ratio is low then a high grade expensive
fuel need to be considered.
The adverse effect of fuel on the quantity/quality of finished
Adequate storage space for the fuels should be available.
The degree of closed technical control necessary to ensure a
high quality of finished product.
The clean and hygiene of working conditions
The fuel chosen should achieve smokeless combustion
5. Solid Fuels
It is a readily combustible black or brownish-black sedimentary
It is composed primarily of carbon along with variable quantities of
other elements, chiefly sulfur, hydrogen, oxygen and nitrogen.
Coal was formed from plant remains that were protected by water
and mud against oxidization and biodegradation, thus trapping
atmospheric carbon in the ground.
Over time, the chemical and physical properties of the remains
were changed by geological action to create a solid material.
Coal, a fossil fuel, is the largest source of energy for the
generation of electricity worldwide, as well as one of the largest
worldwide source of carbon dioxide emissions.
6. Types of Coal
Peat, considered to be a precursor of coal, has industrial
importance as a fuel in some regions, for example, Ireland and
Lignite, also referred to as brown coal, is the lowest rank of coal
and used almost exclusively as fuel for electric power generation.
Sub-bituminous coal, whose properties range from those of
lignite to those of bituminous coal and are used primarily as fuel
for steam-electric power generation.
Bituminous coal, dense mineral, black but sometimes dark
brown, used primarily as fuel in steam-electric power generation,
with substantial quantities also used for heat and power
applications in manufacturing and to make coke.
Anthracite, the highest rank; a harder, glossy, black coal used
primarily for residential and commercial space heating.
Graphite, technically the highest rank, but difficult to ignite and is
not so commonly used as fuel: it is mostly used in pencils and,
when powdered, as a lubricant.
7. Solid fuels
Coke is a solid carbonaceous residue derived from low-ash, low-
sulfur bituminous coal from which the volatile constituents are
driven off by baking in an oven without oxygen at temperatures
as high as 1,000 °C (1,832 °F) so that the fixed carbon and
residual ash are fused together.
Metallurgical coke is used as a fuel and as a reducing agent in
smelting iron ore in a blast furnace. The product is too rich in
dissolved carbon, and must be treated further to make steel
A briquette (or briquet) is a
block of flammable matter
which is used as fuel to start
and maintain a fire.
Common types of briquettes
are charcoal briquettes and
Some briquettes are
compressed and dried brown
coal extruded into hard blocks.
This is a common technique
for low rank coals.
They are typically dried to 12-
18% moisture, and are
primarily used in household
Pitch is the name for any of a
number of highly viscous
liquids which appear solid.
Pitch can be made from
Pitch was traditionally used to
help the seams of wooden
It was heated, Pitch was also
used to waterproof wooden
containers, and is sometimes
still used in the making of
It is black in color, hence the
adjectival phrase, "pitch-
10. Properties and testing of Coal
Proximate analysis of Coal
Determination of moisture, volatile matter,
ash and fixed carbon in coal comprises its
Determination of moisture content in coal
% Moisture in Coal =
Loss in weight of coal/ wt of coal in initially
Determination of volatile matter
It is the loss in weight of moisture free
powdered coal when heated in a crucible
fitted with cover in a muffle furnace at 950
degree C for 7 minutes.
% Volatile Matter =
Loss in weight of moisture free coal/ Wt of
moisture free coal * 100
Determination of ash in coal
It is the weight of residue obtained after burning a weighed
quantity of coal in open crucible (i.e. in presence of air) at
750 degree C in a muffle furnace.
% Ash in Coal =
Wt of residue ash formed / wt of coal initially taken * 100
13. Modern Theory
According to the this theory petroleum is
formed by the decay and decomposition of
marine animals as well as the vegetable
organism of the pre historic forests.
Due to action of prolonged action of high
temperature and pressure in the interior of
the earth, the biological matter decomposed
into the petroleum.
This theory explain the following facts:
Presence of brine & Coal in the vicinity of the
Presence of N & S compounds.
Presence of chlorophyll & optically active
Gasoline is the most widely used liquid fuel.
Gasoline, as it is known in United States and
Canada, or petrol in India, Britain, Australia, New
Zealand, South Africa and many English speaking
countries, is made of hydrocarbon molecules
forming aliphatic compounds, or chains of carbons
with hydrogen atoms attached.
Production of gasoline is achieved by distillation of
crude oil at the temperature of 30 - 200o
Kerosene once used in kerosene lamps as an alternative to
whale oil, is today mainly used in fuel for jet engines (more
technically Avtur, Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7 or JP-8).
One form of the fuel known as RP-1 is burned with liquid oxygen
as rocket fuel.
Kerosene is sometimes used as an additive in diesel fuel to
prevent gelling or waxing in cold temperatures.
Kerosene is obtain at the temperature of 140 – 290o
Diesel is similar to gasoline in that it is a
mixture of aliphatic hydrocarbons extracted
Diesel may cost more or less than gasoline,
but generally costs less to produce because
the extraction processes used are simpler.
Diesel is obtain at the temperature of 140 –
22. Flash Point
According to ASTM, which first standardized the test
in 1924, the flash point is the lowest temperature at
which an ignition source causes the vapors of the
specimen to ignite under specified conditions.
Flash point gives the idea about:
Nature of boiling point diagram
Amount of low boiling point fraction present in the liquid fuel
Volatility of liquid fuels
25. Fire Point
It is the lowest temperature at which vapors given off by oil
ignites and continues to burn for at least 5 seconds.
The fire-point, the test is continued until the application of the
test flame causes the test specimen to ignite and sustain burning
for a minimum of 5s.
In most cases the fire point is 5 - 40o
C higher than flash point
It gives the idea about:
Fire hazards during storage
Use of oil
26. Cloud Point
The temperature at which oil becomes cloudy
or hazy is called cloud point.
This haziness is due to the separation of
crystals of wax or increase of viscosity at low
28. Pour Point
The temperature at which the oil just ceases
to flow is called pour point.
It determines the temperature below which,
an oil can not be use as lubricant.
31. Smoke Point
Smoke point is an indicator of the
combustion qualities of aviation turbine
fuels and kerosene.
The fuel sample is burned in the Smoke
Point Lamp, and the maximum flame
height obtainable without smoking is
33. Aniline Point
Aniline point is defined as
the temperature at which
equal volumes of aniline
and diesel oil are
The value gives an
indication of the aromatic
content of diesel oil, since
aniline is an aromatic
compound which is
dissolved on heating by the
aromatics in diesel oil.
34. Diesel Index
An alternative method of expressing the
quality of diesel oil by the use of the diesel
index . It is given by
DIESEL INDEX = (ANILINE POINT of) (API
35. Calorific Value
It is defined as the quantity of heat librated by
the combustion of unit quantity of fuel.
There are two types of calorific value
Higher gross CV
Lower or net CV
36. Higher or Gross C.V.
It is defined as the total amount of heat librated
when one unit of fuel is burnt completely and the
combustion products are cooled to room
Lower or net C.V.
It is defined as the amount of heat librated when one
unit of the fuel is burnt completely and the
combustion product are allowed to escape.
37. Advantages of Liquid fuels
It can be stored more compactly than solid
It occupies much less space for equal heating
It can handle easily with little labor.
It has no ash and clinkering problems.
It is not liable to spontaneous combustion
and deterioration during storage.
It can be used in I.C. engine.
38. Disadvantages of liquid fuel
Special provision for storage in the way of
tanks, heaters, lagging and pipelines is to be
Sulphur content in the most of the petroleum
oils is high compared to coal .
Vanadium compound present on oils form
corrosive deposits on the hot pressure parts
40. Gaseous Fuels
Gaseous fuels are those which are burnt is
gaseous state in air or oxygen to give heat or
utilization in domestic/commercial sector.
41. Natural gas
Natural gas is a
means it is made up of
hydrogen and carbon.
methane; it contains
one carbon atom and
four hydrogen atoms.
Natural gas can be found by itself or in association
with oil. It is both colorless and odorless and is in
fact a mixture of hydrocarbons.
While mainly methane, the other hydrocarbons
include ethane, propane, and butane.
Water, oil, Sulphur, carbon dioxide, nitrogen, and
other impurities may be mixed with the gas when it
comes out of the ground.
These impurities are removed before the natural gas
is delivered to our homes and businesses.
Natural gas can be measured in a variety of
ways, although the most common unit of
measurement is the Giga joule (GJ), which
signifies one billion joules, the metric
measure for heat or energy. Other measures
are Mcf (thousand cubic feet) and Btu (British
45. Natural Gas - Sources
Natural gas is a fossil fuel. This means it originates
from the remains of plants and animals that lived
many millions of years ago.
These organisms were buried and exposed to heat
as a result of being highly compressed underneath
thousands of metres of soil and rock.
These forces transformed the once living organisms
into natural gas.
46. Natural Gas - Transportation
The transportation of natural gas from a gas well to our homes and businesses requires an
extensive network of interconnected pipelines, designed to move natural gas quickly and
effectively, sometimes over great distances.
The pipeline system moves the natural gas from the point of origin to areas of high
There are essentially three main types of transportation pipelines:
Gathering pipelines transport raw natural gas directly from the wellhead to the gas
The highly pressurized natural gas is gathered into increasingly larger pipelines, almost
always underground, until it reaches the large transmission pipelines where it is often
transported over large distances.
The gas flows into a low-pressure distribution system. As a safety precaution, utility
companies add an odorant to the gas (so we can smell it in the unlikely event of a leak)
and then send it to us through a network of smaller pipelines.
49. Liquefied Petroleum Gas (LPG)
Liquefied petroleum gas (also called LPG, GPL,
LP Gas, or autogas) is a mixture of hydrocarbon
gases used as a fuel in heating appliances and
vehicles, and increasingly replacing
chlorofluorocarbons as an aerosol propellant and a
refrigerant to reduce damage to the ozone layer.
It is prepared by the wet natural gas and gases.
51. Producer Gas
The mixture of flammable gases (principally carbon monoxide
and hydrogen) and nonflammable gases (mainly nitrogen and
carbon dioxide) made by the partial combustion of carbonaceous
substances, usually coal, in an atmosphere of air and steam.
A combustible mixture of nitrogen, carbon monoxide, and
hydrogen, generated by passing air with steam over burning
coke or coal in a furnace and used as fuel.
Producer gas has lower heating value than other gaseous fuels,
but it can be manufactured with relatively simple equipment; it is
used mainly as a fuel in large industrial furnaces.
53. Fuels for producer gas
Producer gas can be made form practically
any solid fuel:
Coals of all ranks
Nature of fuel
High volatile bituminous coal gives a richer gas
containing small proportion of methane. Tar vapors
also enriches the gas when is used hot. Coke gives
a gas free of tar vapor.
Low temperature favors high production of CO2.
High temperature favors high production of CO.
Effect of steam
Water in the coal feed or steam in air blast
increase the proportion of H2 and CO in the
gas. If steam is not added there are chance
of clinker formation.
57. Impurities in Producer Gas
Steam: Lower the flame temperature.
Tar: Increase the flame temperature
Dust: It would foul and choke the gas mains
Sulphur: It can cause corrosion & pollution
Ammonia: It cause the endothermic water
It is used as fuel in furnace.
It is used as the source of hydrogen for the
synthesis in fertilizer plants.
61. Blast Furnace Gas
Blast furnace gas is a by-product of blast
furnaces that is generated when the iron ore
is reduced with coke to metallic iron.
63. Properties & Uses of B.F. Gas
It is very poisonous gas due to the presence of CO.
B.F. gas pipes and vessels should be leak proof.
Under some conditions mixture of gas and air forms
an explosive mixture which explodes when coming
in contract with any source of fire.
64. Coke Oven Gas
It is produced during high temperature carbonization of coal. It is
the most important fuel in an integrated steel plants.
In a by-product coke oven the evolved coke oven gas leaves the
coke oven chambers at high temperatures approaching 2000o
This hot gas is immediately quenched by direct contact with a
spray of aqueous liquor.
The resulting cooled gas is water saturated and has a
temperature of 176o
This gas is collected in the coke oven battery gas collecting
66. Factors Effecting Composition of
Coke Oven Gas
Effect of temperature
With increase in the temperature of carbonization ,
hydrogen content of the coke oven gas increase
because of cracking of hydro carbons.
Effect of time
With increase in the time of carbonization at a given
temperature, the hydrogen and the hydrocarbons
content decreases resulting in the greatly reduced
C.V. of the gas.
67. Advantages of Gaseous Fuels
It has no ash or clinker trouble. Burning is
quite clean without any smoke.
It is easier to maintain oxidizing or reduction
atmosphere inside the furnace with gaseous
Gaseous fuel may be prepared at a central
place and distributed over wide area through