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Basic Concept of FuelCourse - 3131 : Fuel Technology
3rd Year : Odd Semester
Chapter : 1
4 May 2016 1
Course Outline
6. Role of fixed C, N, S, O and ash content on calorific value in fuels.
1. Definition, classification and essential requirements of fuel
2. Primary and secondary fuel
3. Solid, liquid and gaseous fuel, advantages and disadvantages.
4. Classification of gaseous fuel, composition and calorific value of fuel.
5. Determination of calorific value (Direct and indirect method)
4 May 2016 2
Fuel
A fuel is anything that can produce energy/power.
A substance that produces useful energy when it undergoes a chemical or
nuclear reaction. Fuel such as coal, wood, oil, or gas provides energy when
burned. Compounds in the body such as glucose are broken down into
simpler compounds to provide energy for metabolic processes. Some
radioactive substances, such as plutonium and tritium, provide energy by
undergoing nuclear fission or fusion.
4 May 2016 3
Basic Concept of Fuel
4 May 2016 4
A fuel is any combustible substances which may be burnt to supply heat forpractical applications without the formation of excessively objectionable
byproducts.
Example- Petroleum, coal, wood, peat, dung, natural gas,
gasoline, kerosene, LPG, gas oil etc.
Modern Concept of Fuel
It is now well established that combustion is not necessary for a fuel to give
out energy. For example electrical energy when used as a source of heat is
also called fuel. Nuclear energy may also be used as source of heat. Chemical
compounds, such as power alcohol, ammonia etc. are used as fuels.
According to the modern concept-
A fuel is any fissionable material, chemical or reactant which produces energy
in a form that can be used for producing power. Example- Electrical E, Nuclear
E, Fuel cell etc.
A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity
4 May 2016 5Source: E-books
Composition of Fuel
Solid Fuel:
Carbon, Hydrogen, Oxygen, Sulfur, Moisture, Ash
Wood Coal Straw
4 May 2016 6
Composition of FuelLiquid/Gaseous Fuel:Carbon mono-oxide, Hydrogen, Methane, Ethane, Propane Ethylene, Butane,
Hydrogen Sulfide, Nitrogen, Sulfur, Carbon Di-Oxide
4 May 2016 7
Primary Fuel: Fuels that directly produce heat energy on ignition.
Ex: Wood, Coal, Petroleum, Natural Gas, Animal Dung etc.
Secondary Fuel: Fuels that processed & prepared from primary
fuel. Ex: Charcoal, Coke, Petrol, Diesel, Kerosene etc.
Classification of Fuel
According to Origin
4 May 2016 8
Classification of Fuel
According to physical state
4 May 2016 9
Type of Fuel Primary (natural) Secondary (artificial)
Solid fuelswood, coal, peat, dung,
etc.coke, semi-coke, charcoal
Liquid fuels petroleumdiesel, gasoline, kerosene, LPG, gas oil,
coaltar, naphtha, ethanol
Gaseous fuels natural gashydrogen, propane, coal gas, water gas, producer
gas, blast furnace gas, coke oven gas, CNG
Essential Requirements of Fuel
1. Reasonably high velocity of combustion
2. Release high value of thermal energy
7. Safe to transport or in case of accident
3. Proper ignition temperature
4. Low percentage of non-combustibles
5. Reasonable cost
6. Low toxicity with contact
4 May 2016 10
Solid Fuel: Advantage & DisadvantageAdvantages
1. Solid fuel can be very conveniently stored due to their high ignition temp.
2. They are comparatively cheap
3. Safe to transfer
4. Easy to handle
5. Their cost of production is low
Disadvantages
1. Large portion of heat is wasted due to lack of proper surface contact
2. A large amount of unburnt fuel is also wasted along with clinker, cinder etc.
3. Cannot stored in open area
4. Large area need for store.
5. Also produce smoke and ash
6. Their combustion operation cannot be controlled easily.
7. Their cost of handling is high
4 May 2016 11
Liquid Fuel: Advantage & DisadvantageAdvantages
1. Handling of liquid fuel is easy and they require less storage space
2. Liquid fuels can be fired easily and maximum temperature is attained in time.
3. Can use directly to produce energy.
4. Does not produce smoke and ash.
5. Easily burn and mixed with air.
Disadvantages1. They can pollute our environment during burning.
2. They require special type of burners
3. Costly special storage tanks are required for storing liquid fuels
4. Ignition temperature is low
5. The cost of liquid fuel is relatively much higher as compared to solid fuel
4 May 2016 12
Gaseous Fuel: Advantage & DisadvantageAdvantages
1. It contains no ash
2. There is no smoke/ash problem and hence much less labor
3. They are burned easily and readily mixed with air
4. Much higher fuel economy because of regenerative heating
5. Easy to transport
6. Everywhere can use (Industrial furnace, domestic use, internal combustion of engine etc.
Disadvantages
1. Comparatively dangerous to store due to their low ignition temperature
2. Need container to store
3. Handling is not so easy
4. Extra care need to take during storing, transferring and also using.
5. Danger of explosion and large scale of fire it may cause.
4 May 2016 13
Properties of Fuels1. Calorific Value
2. Specific Heat of Combustion
3. Ignition Temperature
4. Flame Temperature
5. Flash Point
6. Fire Point
7. Aniline Point
8. Knocking
9. Specific Gravity
10. Pour Point
11. Cloud Point
12. Coke Number
13. Viscosity
4 May 2016 14
Reference: Industrial Chemistry- by- B.K. Sharma
Properties of liquid fuels
Density
• Ratio of the fuel’s mass to its volume at 15 oC,
• kg/m3
• Useful for determining fuel quantity and quality
Viscosity
• Measure of fuel’s internal resistance to flow
• Most important characteristic for storage and use
• Decreases as temperature increases
4 May 2016 15Source: E-books
Flash point
• Lowest temperature at which a fuel can be heated so that the vapour gives
off flashes when an open flame is passes over it
• Flash point of furnace oil: 66oC
Pour point
• Lowest temperature at which fuel will flow
• Indication of temperature at which fuel can be pumped
Properties of liquid fuels
4 May 2016 16
Calorific value
• Heat or energy produced
• Gross calorific value (GCV): vapour is fully condensed
• Net calorific value (NCV): water is not fully condensed
Specific gravity
• Ratio of weight of oil volume to weight of same water volume at a given temperature
• Specific gravity of water is 1
• Hydrometer used to measure
Properties of liquid fuels
4 May 2016 17
Sulphur content
• Depends on source of crude oil and less on the refining process
• Furnace oil: 2-4 % sulphur
• Sulphuric acid causes corrosion
Ash content
• Inorganic material in fuel
• Typically 0.03 - 0.07%
• Corrosion of burner tips and damage to materials /equipments at high
temperatures
Properties of liquid fuels
4 May 2016 18
Carbon residue
• Tendency of oil to deposit a carbonaceous solid residue on a hot surface
• Residual oil: >1% carbon residue
Water content
• Normally low in furnace oil supplied (<1% at refinery)
• Free or emulsified form
• Can damage furnace surface and impact flame
Properties of liquid fuels
4 May 2016 19
Ignition Temperature
Factors affecting the Ignition Temperature
1. Nature of Fuel
2. Combustion environment
3. Presence of moisture
4. Pressure over the Fuel
5. Size and shape of burning unit
6. Particle size of Fuel
7. Presence of foreign matter
The lowest temperature at which a combustible substance will spontaneously ignite in a
normal atmosphere and continues to burn without an external source of ignition —called
also autogenous ignition temperature
4 May 2016 20
Reference: Industrial Chemistry- by- B.K. Sharma
Calorific ValueCalorific Value:
The quantity of heat produced by the complete combustion of a given mass of a fuel.
It is usually expressed in J/Kg.
Method for determining calorific value:
a) Direct Method
b) Indirect Method
4 May 2016 21
Calorific Value
The calorific value of solid fuels is expressed as British Thermal Units per Pound (B.T.U. per 1b)
or Kilogram Centigram Unit per Kilogram (K.C.U. per kg.).
Taking both above definitions of these units, a correlation between them can be written as;
1 B.T.U = 252 cals
4 May 2016 22
a) Direct Method
A calorimeter is used to measure the calorific value of a fuel called bomb calorimeter. The principle is
look like a bomb that is why the calorimeter is known as bomb calorimeter.
4 May 2016 23
Reference: E-Books
a) Direct Method
Procedure of bomb calorimeter experiment
1. A known quantity of fuel sample is taken in a crucible.
2. The stirrer is then started and note the initial temperature of water is noted down.
3. Current flow is started through crucible and let fuel sample to burn in presence of oxygen.
4. Heat release during combustion of fuel is taken by water and temperature of it rises.
5. Final steady state temperature of water is noted down.
Calorific Value =M
1+M
2X Tc+T
2−T
1X Cw
Mf
Where,
M1 and M2 are mass of water & water equivalent of
bomb calorimeter
Mf is mass of fuel sample.
T2 and T1 are final and initial temperature of water
sample.
Tc is temperature correction for radiation losses.
Cw is specific heat of water
4 May 2016 24
b) Indirect Method
Calorific value can be determined from the elements of the fuels. It is
assumed that the heating value of a fuel is equal to the sum of the heating value
of the elements present in fuel at free state.
Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur
Reference: Applied Chemistry-Volume-2, by V.M. Balsaraf (Google Books)
4 May 2016 25
b) Indirect Method
Calorific value: According to Dulong, the calorific value of a fuel is the sum
total of calorific values of its constituents elements. The calorific values of
some elements are as follows:
Total Calories/gm. =% 𝐶 𝑋 8080 + %𝐻 −
%𝑂
8𝑋 34500+% 𝑆 𝑋 2240
100
C + O2 CO2 + 96960 Calories ( 96960/12 = 8080 Cals.)
H2 + 1/2O2 H2O + 69000 Calories (69000/2 = 34500 Cals.)
Reference: Applied Chemistry-Volume-2, by V.M. Balsaraf (Google Books)
S + O2 SO2 + 71680 Calories (71680/32 = 2240 Cals.)
Dulong Equation
4 May 2016 26
Calorific Value
The quantity known as lower heating value (LHV) (net calorific value or lower calorific value -
LCV) is determined by subtracting the heat of vaporization of the water vapor from the higher
heating value.
NCV = GCV- Heat of vaporization of water
[Heat of vaporization of water = 0.09 H X 587 cal/gm.]
Reference: Applied Chemistry-Volume-2, by V.M. Balsaraf (Google Books)
4 May 2016 27
Criteria for Selecting a Fuel
There are some important criteria that are to be considered for a particular
type of purpose.
1. Suitability to process
2. Supply position
3. Cost of fuel
4. Calorific value
5. Transportation and labor
4 May 2016 28
Role of Different Element on CV
Different element/content present in a fuel plays an important role on
calorific value. Such as:
1. Fixed Carbon
2. Sulfur
3. Nitrogen
4. Oxygen
5. Ash content
4 May 2016 29
Role of Fixed Carbon on Calorific Value
It indicates the organic matter that does not undergo volatilization When a
known weight of the powdered solid fuel is combusted at a fixed
Temperature (950° ± 20° ) for a fixed period (7 Mins.)
The percentage of fixed carbon can be calculated by subtracting the weight
of ash from the residue. Suppose the weight of residue left after
subtracting the weight of ash is ‘a’ grams then-
Fixed carbon increases the calorific value of fuels.
% of fixed carbon =𝒂
𝐖𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐅𝐮𝐞𝐥X 100
4 May 2016 30
Role of Nitrogen on Calorific Value
Actually nitrogen does not have any calorific value. Nitrogen act as a
detergent in fuel engine and thus increases the calorific value indirectly.
Reference: Applied Chemistry-Volume-2, by V.M. Balsaraf (Google Books)
4 May 2016 31
Role of Sulfur on Calorific Value1. High sulfur levels in fuel, when combined with water vapor can also cause corrosive wear
on valve guides and cylinder lines, which can lead to premature engine failure.
2. Sulfur reduces catalytic efficiency in modern vehicles.
3. Sulfur in gasoline may degrade the performance of oxygen sensors, which may also result
high emissions.
4. High sulfur level in gasoline may also impair the performance of some vehicles.
5. Low sulfur level can reduces the natural lubricating properties of the diesel fuel.
6. Reduction of sulfur level can changes the overall chemical composition of the fuel and it
can affect fuel pump seals, engine seals etc.
4 May 2016 32
Role of Oxygen on Calorific Value
Oxygen present in the fuel normally as moisture or some oxygen is used to
burn the combustibles of the fuel. Heat will lose for burning. As a result low
amount of heat will be produced, because oxygen combine with hydrogen
to form water. So higher the oxygen level lowers the calorific value of fuel.
4 May 2016 33
Role of Ash Content on Calorific Value
% Ash =𝐖𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐀𝐬𝐡
𝐖𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐅𝐮𝐞𝐥X 100
Ash is non-combustibles materials and reduce the calorific value of fuel. Ash
also cause hindrance to flow of air and heat. Ash reduce the rate of
combustion. Hence lower the ash content, better the grade of fuel.
4 May 2016 34
Conclusion
Fuel crisis in Bangladesh and it’s remedy……..
4 May 2016 35