2. • A steam power plant converts the chemical energy of the
fossil fuel (Coal) into mechanical energy/electrical energy.
• This is done by raising the steam in the boilers, expanding
it through the turbines and coupling the turbines to the
generators which converts mechanical energy to electrical
energy.
• Purposes of Steam Power Plant
1. to produce electric power
2. to produce steam for industrial processes like textile,
food manufacturers, paper mills etc.
Introduction
3.
4.
5.
6. LAW OF CONSERVATION OF
ENERGY
Chemical energy of fuel
Heat energy in furnace
Heat energy of medium water
Kinetic energy of turbine rotor
Electromotive force
Electricity generation
7. Division of a Steam power plant
Coal Handling Plant
Water Treatment Plant
Fuel and Ash Plant
Feed Water and Steam Plant
Cooling Water Plant
8. Coal and Ash handling plant:
Coal arrives at the storage yard and after necessary handling passes
to the furnace through fuel feeding device. Ash after combustion
collects at the back of the boiler and is removed to the ash storage
yard.
Air and Gas handling plant:
Air is taken in from the atmosphere through the action of a forced
or induced draught fan and passes on to the furnace through the air
preheater, where it has been preheated by the flue gases which pass
to the chimney via preheater.
Feed water and Steam flow plant:
Condensate leaving the condenser is first heated in a closed feed
water heater through extracted steam from the lowest pressure
extraction point of turbine. -deaerator- economiser -boiler.
11. ASH HANDLING PLANT
The Ash from the boiler is collected in two forms:
1. Bottom Ash(Slurry) It’s a waste which is dumped into a Ash Pond
2. Fly ash: Fly ash is separated from Flue Gases in ESP(Electro static
Precipitator).
Fly Ash &
Flue
Gases
Economizer ESP
Bottom
ash(wet ash)
Ash Pond
Boiler
Cylo
Chimney
Fly ash
Flue Gases
Cement Factory
12. In Boiler the water circulates due to difference in density of
water in the lower temp. and higher temperatures of boiler
Wet steam from boiler is heated up in Superheater----
Prime mover---HP turbine---Superheater----LP turbine----
-condenser ---hot well.
Cooling water circuit:
The cooling water supply to the condenser helps in
maintaining a low pressure in it. Water may be taken from
a natural source.
13. Components of Steam Power Plant
1. Boiler 7. Boiler feed pump
• Superheater 8. Wagon Tippler
• Reheater 9. Crusher house
• Economiser 10. Coal Mill
• Air-heater 11. Induced draught fan
2. Steam Turbine 12. Ash Precipitators
3. Generator 13. Boiler Chimney
4. Condenser 14. Forced draught fan
5. Cooling Tower 15. Water treatment plant
6. Circulating Water Pump 16. Control room
17. Switch yard
14. Steam generating plant
The steam generating plant consists of a boiler for the
production of steam and other auxiliary equipment for
the utilization of flue gases
1) Boiler: The heat of combustion
in the boiler is utilized
to convert water into steam at
high temperature and pressure
16. Steam generating plant
2) Super heater: The steam produced in boiler is wet
and is passed through a super heater where it is dried
and superheated. Hence Increases efficiency
17. Steam generating plant
3) Economizer:
It’s essentially a feed
water heater and
derives heat from the
flue gases
18. Steam generating plant
4) Air Preheater: Increases the temperature of the air
supplied for coal burning by deriving heat from flue
gases. Air is drawn from the atmosphere by a forced
drought fan and is passed through air preheater before
supplying to the boiler furnace.
19. Steam Turbine
Dry and superheated steam from superheater is fed to
the steam turbine.
The heat energy of steam when passing over the blades
of turbine is converted into mechanical energy.
After giving energy to the turbine, the steam is
exhausted to the condenser which condenses the
exhausted steam by means of cold water circulation
20. ‘Turbo Machine’ is defined as a device that extracts
energy from a continuously flowing fluid by the dynamic
action of one or more rotating elements .
The prefix ‘turbo’ is a Latin word meaning ‘spin’ or ‘whirl’
implying that turbo machines rotate in some way.
22. A steam turbine is mainly used as an ideal prime mover in
which heat energy is transformed into mechanical energy in
the form of rotary motion.
A steam turbine is used in
1. Electric power generation in thermal power plants.
2. Steam power plants.
3. To propel the ships, submarines.
In steam turbines, the heat energy of the steam is first
converted into kinetic (velocity) energy which in turn is
transformed into mechanical energy of rotation and then
drives the generator for the power generation.
23. Based on action of steam or type of expansion:
1. Impulse or velocity or De Laval turbine
2. Reaction or pressure or Parson’s turbine
3. Combination turbine
Based on number of stages:
1. Single stage turbine 2. Multi-stage turbine
Based on type of steam flow:
1. Axial flow turbine 2. Radial flow turbine
24.
25.
26. The steam is made to fall
in its pressure by
expanding in a nozzle. Due
to this fall in pressure, a
certain amount of heat
energy is converted into
kinetic energy, which sets
the steam to flow with a
greater velocity.
The rapidly moving particles of the steam enter the
rotating part of the turbine, where it undergoes a
change in the direction of motion, which gives rise to
a change of momentum and therefore a force. This
constitutes the driving force of the turbine.
27. Impulse Turbines (De Laval
Turbine)
In this type of turbine, steam is initially expanded in a nozzle from high
pressure to low pressure. High velocity jet of steam coming out of the nozzle
is made to glide over a curved vane, called ‘Blade’.
The jet of steam gliding over the blade gets deflected very closely to
surface. This causes the particles of steam to suffer a change in the
direction of motion, which gives rise to a change of momentum and
therefore a force, which will be centrifugal in nature.
Resultant of all these centrifugal forces acting on the entire curved
surface of the blade causes it to move.
28. Reaction steam Turbine
Principle of working -
In this type of turbine, the high
pressure steam does not
initially expand in the nozzle as
in the case of impulse turbine,
but instead directly passes onto
the moving blades.
Blade shapes of reaction
turbines are designed in such a
way that the steam flowing
between the blades will be
subjected to the nozzle effect.
Hence, the pressure of the
steam drops continuously as it
flows over the blades causing,
simultaneous increase in the
velocity of the steam.
29. Impulse Turbine Reaction Turbine
The steam expands (pressure drops)
completely in nozzles or in the fixed
blades
The steam expands both in the fixed
and moving blades continuously as it
flows over them
The blades have symmetrical profile
of uniform section
The blades have converging (aerofoil)
profile
The steam pressure while passing
over the blades remains constant
The steam pressure while passing
over the blades gradually drops
Because of large initial pressure drop,
the steam and turbine speeds are
very high
Because of gradual pressure drop,
the steam and turbine speeds are low
The nozzles are fitted to the
diaphragm (the partition disc between
the stages of the turbine)
The fixed blades attached to the
casing serve as nozzles
Difference between Impulse & Reaction Turbines
30. Impulse Turbine Reaction Turbine
Power is obtained only due to the
impulsive force of the incoming
steam
Power is obtained due to impulsive
force of incoming steam as well as
reaction of exit steam
Suitable for small capacity of power
generation & occupies less space per
unit power
Suitable for medium & high
capacity power generation and
occupies more space per unit
power
Efficiency is lesser Efficiency is higher
Compounding is necessary to reduce
speed
Compounding is not necessary
31. Compounding of Impulse Turbines
As the complete expansion of steam takes in one stage (i.e., the entire pressure drop from
high pressure to low pressure takes place in only one set of nozzles), the turbine rotor
rotates at very high speed of about 30,000 rpm (K.E. is fully absorbed).
High speed poses number of technical difficulties like destruction of machine by the large
centrifugal forces developed, increase in vibrations, quick overheating of blades,
impossibility of direct coupling to other machines, etc.
To overcome the above difficulties, the expansion of steam is performed in several stages.
Utilization of the high pressure energy of the steam by expanding it in successive stages
is called Compounding.
Methods of Compounding:
Velocity compounding (Curtis Impulse Turbine)
Pressure compounding
Pressure-velocity compounding
32. Velocity compounding
Comprise of nozzles and two or more rows of moving blades arranged in
series. In between two rows of moving blades, one set of guide (fixed)
blades are suitably arranged.
Guide (fixed) blades are fixed to casing and are stationary.
39. Alternator
Steam turbine is coupled to an alternator which
converts the mechanical energy to electrical energy
The electrical output of the alternator is delivered to
the bus bars through transformer, circuit breakers and
isolators.
40. Feed Water
The condensate from the condenser is used as feed
water to the boiler.
The water that may be lost in the cycle is made up
from the external source
The feed water on its way to boiler gets heated up by
water heaters and economiser.
This helps to improve the overall efficiency of the plant
41. Selection of Site
1. Availability of raw material.
2. Nature of land.
3. Cost of land.
4. Availability of water.
5. Transport facilities
6. Ash disposal facilities
7. Availability of labour
8. Size of plant
9. Load centre
10. Public Problems
11. Future Extension
