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Combustion principle
1. MEHRAN UNIVERSITY OF
ENGINEERING AND TECHNOLOGY
Jamsher Khan 16CH44 (GL)
Sagar Khan 16CH56
Affaque Bhatti 16CH51
Abdul Manan 16CH15
Waqar Amin 16Ch110
Topic
Combustion Principle
Submitted To
Pro. Dr Shaheen
Department Of Chemical Engineering MUET
2. COMBUSTION PRINCIPLE
Combustion is a chemical reaction between a
Fuel and Oxygen Which is accompanied by the
production of considerable amount of Heat
Usually Its an Endothermic Reaction
The reaction has to be initiated By some Source
Of High Temperature Energy (ignition) l
Combustion refers to the rapid oxidation results
in large amount of heat is released
Solid and liquid fuels must be changed to a gas
before they will burn
3. COMBUSTION PRINCIPLE
Combustion plants are fired by wide
variety of fuels from natural gas
But common to all is the combustion of
fuels containing the elements are
CARBON and HYDROGEN generally
known as Hydrocarbon Fuels
5. COMBUSTION PROCESSES
o There are several processes of combustion Of
Fuel
1. Bringing together the fuel and air
2. Ignition the reaction
3. Ensuring that the flame burns in a stable
manner
4. Extracting useful heat from the process
5. Arranging for the Safe disposal of the products
of combustion
6. BASIC ELEMENT OF COMBUSTION
The fire triangles or combustion triangles
or ″fire diamond″ are simple models for
understanding the necessary ingredients
for most fires.
The triangle illustrates the three
elements a fire needs to ignite: heat, fuel,
and an oxidizing agent (usually oxygen
9. PHASES OF COMBUSTION
2. Ignition
Process Where A rapid Exothermic reaction
is initiated Which Causes The material to
undergo Changes producing temperature
greatly in excess of ambiet
10. PHASES OF COMBUSTION
3. Combustion
Flaming =Volatiles that produced in the
preheating phase ignite to form a visible
flame
Smoldering =The remaining carbon may
burn as a solid surfaces oxidation
11. PHASES OF COMUSTION
4. Extinction
Opposite of ignition
(termination of combustion)
Moisture Content of fuel can play a large
role
12. FACTORS THAT WHICH INCREASES THE
COMBUSTION PROCESS
Flames are brought closer to the Fuel to
Slope
The wind Pushes The Flames Over wind
The amount Of time the fire has burnt
The ventilation characteristic Of the
Confining Structure
The Amount and Type Of Combustible
Present
14. PRINCIPLE OF FIRE/ COMBUSTION
Breaking
Of Chain
Reaction
(It Is the
chemical
reaction)
Smotherin
g
(Cutting off The
supply Of oxygen
from Fire Area )
Starvation
(Removal of
un burnt
Material from
Fire Area)
Cooling
(Removal of heat
from the burning
material Fire)
16. INDUSTRIAL COMBUSTION
1. General definition
combustion is defined as the oxidation of fuels,
typically, but not exclusively, through the rapid
combination of hydrogen and carbon contained
in the fuel with the oxygen contained in
atmospheric air
This rapid combination releases heat at
relatively high temperature, which may then be
used for the heating of industrial processes,
including the generation of steam and high-
pressure hot water
17. INDUSTRIAL COMBUSTION
This may be very simplistically represented
as:
2C + O2 2CO + Heat
2CO + O2 2CO2 + Heat
2H2 + O2 2H2O + Heat
18. INDUSTRIAL COMBUSTION
2. Industrial Fuels
An industrial fuel may be a regular fossil fuel
such as coal, crude oil, or natural gas.
These may be processed from their raw “as
found” state to produce a wide variety of
refined fuels such as blended pulverised coal,
desulphurised coal gas, Liquified Petroleum
Gases (LPGs), liquid fuels ranging from
gasoline through to residual oils and so forth.
Alternatively the fuel may be derived from
biomass material.
19. INDUSTRIAL COMBUSTION
Traditional firewood is arguably the
“original fuel” used by mankind.
Alternatively fuels may be derived from
wastes to produce so-called 'Refuse Derived
Fuels”' or RDFs.
20. INDUSTRIAL COMBUSTION
3. Industrial Comburents
An industrial Comburent may range from
regular atmospheric air containing
approximately 21% v/v O2,
The remainder being almost exclusively
molecular nitrogen - N2, through oxygen
enriched air to relatively pure oxygen - Oxygen
containing a very small quantity of impurities.
Alternatively oxygen depleted (vitiated) air - for
example Gas Turbine or Diesel exhaust gases -
may also be used as a comburent.
21. INDUSTRIAL COMBUSTION
4. Industrial Combustion Modes
Traditional industrial combustion processes were
primarily based on the concept of the comburent -
almost always, regular atmospheric air - being
encouraged to rise through a bed of fuel
Originally containing wood but later various forms of
lump coal and most recently, domestic solid waste.
Such a system is described as a stoker fired boiler of
which there a several basic types. Figure 1 shows an
example of a stoker fired boiler.
24. CLASSIFICATION OF INDUSTRIAL
COMBUSTION
1. Solids
In recent decades such solid fuel combustion
modes, have given way, at least in relatively large
coal fired scale boilers, to pulverised coal burners,
where the coal is milled to a very fine powder -
typically 75% by mass < 75mm
passed through a burner in suspension in an
atmosphere derived from the coal dryer. This
produces a turbulent diffusion flame, an example
of which is shown in Figure Arrays of such flames
are used to fire boilers of various designs.
26. CLASSIFICATION OF INDUSTRIAL
COMBUSTION
2. Liquids
Liquid fuels have been traditionally burned in
various forms of pot burners
Modern liquid fuel burners employ atomising
devices to produced fine droplets of the fuel
Which initially are evaporated in the throat of a
burner which gives rise to a turbulent diffusion
flame, an example of which is shown in Figure
28. CLASSIFICATION OF INDUSTRIAL
COMBUSTION
3. Gaseous
Finally gaseous fuels are exclusively fired in
burners which give rise to flames.
These may be produced by premixing the
gaseous fuel and the comburent to give a
'premixed' flame.
Alternatively the gaseous fuel and the
comburent may be mixed in the burner to give a
regular turbulent diffusion flame, as shown in
Figure
30. CONCLUSION
It is clear from the various examples of
combustion given above, that there is a
variety of combustion modes used in
industry.
Flames are of considerable importance in
industrial process heating and have formed
the basis of the research of the International
Flame Research Foundation for over 50 years
(Ref to Spirit of IJmuiden)
31. CONCLUSION
However the various form of bed stokers,
particularly fluidized beds, are also of
particular importance in industry.