Thermal power plant

1. Thermal Power Plants
(Steam Power Plants(
Instructor:
Engr. Intisar Ali Sajjad

2. Lecture Outlines
 Thermal Energy
 Energy conversion process
 Principle and Working
 Efficiency
 Merits & Demerits
 Parts of steam power plant
 Numerical Examples

3. Thermal Energy
1.The kinetic energy of the molecules in a
solid, liquid or gas
2.The more kinetic energy, the more thermal
energy the object possesses
3.Physicists also call this the internal energy of
an object

4. Heat
 Touch something hot and thermal energy
enters your hand
 Touch something cold and thermal energy
leaves your hand
 Direction of energy flow is from hot to cold
 Heat is the thermal energy transferred due to
a temperature difference

5. Equilibrium
 Thermal energy transfers between two
objects until the reach the same temperature
 This means until the average kinetic energy
of the atoms and molecules is the same

6. STEAM POWER PLANTS

7. Steam Power Plants
 Electricity generation in thermal power plants
if characterized by the main source of
generation being firing of coal, gas etc.
 Steam is produced in a boiler, and it drives a
turbine connected to an alternator. Heat
energy is converted to electric energy within
the so-called steam cycle.

9. Energy Conversion Process in Steam
Power Plants
Chemical Energy is
Converted into Thermal
Energy by Combustion
In Boiler
Thermal Energy is
Converted into
Mechanical Energy
In Turbine
Mechanical Energy is
Converted into
Electrical Energy
In Generator
Chemical
Energy
Fuel
Thermal
Energy
Mechanical
Energy
Electrical
Energy

10. Energy Conversion. . .
 Fuel, Air and water produce steam in the boiler by
combustion
 Steam of high temperature and pressure is
expended from high pressure to low pressure in the
turbine
 Thermal energy is converted into kinetic energy and
finally mechanical energy
 This mechanical energy derives the generator to
produce electricity

11. Steam Power Plant can work in two
Manners
1. Production of electricity
2. Production of electricity with production of
steam for the use in industry e.g. paper
mills, textile mills, sugar mills, refineries

12. Processing of Power Plant
Turbine Grid
Water
Fuel
Steam
Waste Gases
Exhaust Steam
Generator
Boiler

13. Types of Steam Power Plant w.r.t.
Stem Exhaust
1. Condensing
2. Non- Condensing

14. Efficiency
Efficiency = Heat Equivalent of Electrical output / Heat of Combustion
 Normally η = 29%
Losses:
1. Boiler House Losses:
a. To Dry Fuel Gases 5%
b. To moisture in gases 5%
c. To ash and unburnt carbon 1%
d. To radiation and leakage 2.5%
e. Unknown losses 2.5%
TOTAL 16%

15. Efficiency. . .
2. Turbine Losses:
a. Heat rejection to Condenser 54%
3. Alternator or Generator Loss 1%
TOTAL 55%
Grand Total 71%
So Efficiency = (100% - Losses)
= 100% - 71% = 29%

16. Merits of Steam Power Plant
 Fuel is cheaper*
 Less space is required
 The initial cost is less
 Plant can be located near the load centre
 Turbine can work at 25% overload continuously
 A portion of steam can be used in various industries

17. Demerits of Steam Power Plant
 Maintenance and operating costs are high
 Pollution of atmosphere is one of the major
problems
 Water is required in huge quantity
 Handling of coal and disposal of ash are
difficult tasks
 It requires long time for installation
 Efficiency falls quickly below 75%

18. Site Selection
 Availability of Coal (Fuel)
 Proper arrangement for ash disposal
 Nature of the land
 Location from load centre
 Availability of water
 Transport facilities
 Availability of labor

19. Principle of conversion of Heat Energy
to Kinetic Energy in Gases
Think………. ?

20. Main Circuits of Thermal Power Plant
 Coal and Ash Circuit
 Air and Gas circuit
 Feed Water and Steam circuit
 Cooling Water circuit

21. Coal and Ash Circuit
 Coal from the storage is fed to the boiler
through coal handling equipment for the
generation of steam.
 Ash produced due to combustion of coal is
removed to ash storage through ash-
handling system

22. Air and Gas Circuit
 Air is supplied to the combustion chamber of the
boiler either through forced draught or induced
draught fan or by using both.
 The dust from the air is removed before supplying to
the combustion chamber.
 The exhaust gases carrying sufficient quantity of
heat and ash are passed through the air-heater.
 Here the exhaust heat of the gases is given to the air
 then it is passed through the dust collectors where
most of the dust is removed before exhausting the
gases to the atmosphere

23. Feed Water and Steam Circuit
 The steam generated in the boiler is fed to the steam prime
mover to develop the power
 The steam coming out of the prime mover is condensed in the
condenser and then fed to the boiler with the help of pump
 The condensate is heated in the feed-heaters using the steam
tapped from different points of the turbine
 The feed water supplied from external source is passed
through the purifying plant to reduce to reduce dissolve salts to
an acceptable level
 This purification is necessary to avoid the scaling of the boiler
tubes

24. Cooling Water Circuit
 The quantity of cooling water required to
condense the steam is considerably high and
it is taken from a lake, river or sea
 . The water is pumped in by means of pumps
and the hot water after condensing the steam
is cooled before sending back into the pond
by means of cooling towers

25. Major Parts of Steam Power Plant
1. Boilers 2. Superheater
3. Turbine 4. Condenser
5. Economizer 6. Air preheater
7. Induced Draft Fan 8. Forced Draft Fan
9. Chimney 10. Coal Handling Plant
11. Ash Handling Plant 12. Cooling Tower
13. Alternator 14. Evaporator
15. Pumps

26. 1.Boiler
Purpose: To produce steam under pressure
Types:
1. Fire Tube Boiler: Hot gases of combustion are
inside the tubes and the tubes are surrounded by
water
2. Water Tube Boiler: Water is inside the tube and
hot gases are outside the tube
One of these are used according to the requirements
(See advantages and disadvantages of both in text)

28. Fire Tube Boiler

29. Water Tube Boiler

30. Boiler Furnace
 It is like a chamber in which fuel is burnt to produce
heat energy
 Furnace walls are made of refractory materials
such as fire clay, silica etc.
Types:
1. Plain refractory Walls: Used where furnace
temperature is not very high
2. Hollow Refractory Walls: Through which air is
circulated and used for quite high temperatures
3. Partially Water Cooled Walls: Similar to plain but a
potion of surface is covered by water tubes. It is
used for high temperature applications

32. Superheater
 Device used to remove the traces of moisture from saturated
steam leaving boiler tubes.
 It also increase the temperature above saturation temperature
Classes:
1. Radiant Superheater: Located in the furnace between the
furnace water walls and absorbs heat from the burning fuel
through radiation
2. Convection Superheater: Located well back in boiler tube
bank. It receives its heat from flue gases through convection.
(Advantages and disadvantages on text)

33. Economizer
 It absorbs heat from outgoing flue gases and
used for raising the temperature of feed
water coming from condenser
 Economizer raises efficiency of boiler by 10
-12 % thus 5 – 15 % of fuel consumption is
saved

35. Air Preheater
 Air preheater is used to recover heat from
flue gases since entire heat can’t be
extracted by economizer
 Boiler Efficiency is increased by 1% if the
avg. air temp. is increased by 20°C

37. Steam Turbines
 There are two types of steam turbines
1. Impulse type: Steam expands completely in
the stationary nozzles, the pressure over
the moving blades remains constant.
2. Reaction Type: Steam is expanded both in
fixed blades (nozzles) and moving blades.
(More detail on text)

40. Coal Handling
1. Coal shouldn’t be exposed to air
 It pollutes the air and releases poisonous gases like
carbon monoxide
2. The coal from the heaps is moved into the plant by
means of long conveyors that are electrically
operated
 There are many different types of conveyors and
coal-handling devices like screwing conveyors,
bucket elevators, grabbing bucket conveyors etc.

43. Coal Crusher
 Before the coal is sent to the plant it has to
be ensured that the coal is of uniform size so
it is passed through the crushers
 Rotary crushers are very commonly used for
this purpose as they can provide a
continuous flow of coal to the pulverizer

45. Coal Crusher. . .

46. Pulverizer
 Are used to smash materials into tiny
granular.
 Most commonly used pulverizer is the Boul
Mill
 The arrangement consists of 2 stationary
rollers and a power driven baul in which
pulverization takes place as the coal passes
through the sides of the rollers and the baul

49. STEAM POWER PLANT
LAYOUT

51. Numerical Examples