This document describes the key components and processes in a coal-based thermal power plant. There are four main circuits: 1) the coal and ash circuit which includes coal delivery, preparation, combustion in the boiler, and ash handling; 2) the air and flue gas circuit which includes fans that move air and exhaust gases through the plant; 3) the water and steam circuit where water is turned into steam to power the turbines; and 4) the cooling water circuit which condenses the exhaust steam and cools the plant. The document also discusses fluidized bed combustion boilers, steam turbines, condensers, and other important systems within a coal power plant.

1. Coal based Thermal Power Plant
( Steam turbine Power Plant )

2. Steam turbine Power Plant

3. Layout of Steam (Thermal) Power Plant

4. Coal Based Thermal Power Plant

6. Four circuits in the PP
1. Fuel (coal) and ash circuit
2. Air and flue gas circuit
3. Feed water and steam flow circuit
4. Cooling water flow circuit

7. Coal and Ash Circuit

8. Coal and Ash circuit
• This includes coal delivery, preparation, coal handling,
boiler furnace, ash handling and ash storage.
• The coal from coal mines is delivered by ships, rail or by
trucks to the power station. This coal is sized by
crushers, breakers etc.
• The sized coal is then stored in coal storage (stock yard).
From the stock yard, the coal is transferred to the boiler
furnace by means of conveyors, elevators etc.
• The coal is burnt in the boiler furnace and ash is formed
by burning of coal, Ash coming out of the furnace will be
too hot, dusty and accompanied by some poisonous
gases.

9. Coal and Ash circuit
• The ash is transferred to ash storage. Usually, the
ash is quenched to reduced temperature
corrosion and dust content. There are different
methods employed for the disposal of ash.
• They are hydraulic system, water jetting, ash
sluice ways, pneumatic system etc. In large power
plants hydraulic system is used. In this system,
ash falls from furnace grate into high velocity
water stream. It is then carried to the slumps.

10. Working principle-Coal Circuit
• In a coal based thermal power plant, coal is
transported from coal mines to the generating
station.
• Generally, bituminous coal or brown coal is used as
fuel. The coal is stored in either 'dead storage' or in
'live storage'.
• Dead storage is generally 40 days backup coal storage
which is used when coal supply is unavailable. Live
storage is a raw coal bunker in boiler house.
• The coal is cleaned in a magnetic cleaner to filter out
if any iron particles are present which may cause
wear and tear in the equipment.

11. Working principle-Coal Circuit
• The coal from live storage is first crushed in
small particles and then taken into pulverized to
make it in powdered form.
• Fine powdered coal undergoes complete
combustion, and thus pulverized coal improves
efficiency of the boiler.
• The ash produced after the combustion of coal
is taken out of the boiler furnace and then
properly disposed.
• Periodic removal of ash from the boiler furnace
is necessary for the proper combustion.

12. Air and Flue Gas Circuit

13. Water and Steam circuit
• It consists of feed pump, economizer, boiler
drum, super heater, turbine condenser etc.
• Feed water is pumped to the economizer from
the hot well.
• This water is preheated by the flue gases in the
economizer.
• This preheated water is then supplied to the
boiler drum. Heat is transferred to the water by
the burning of coal. Due to this, water is
converted into steam

14. Water and Steam Circuit

15. Air and Flue gas circuit
• It consists of forced draught fan, air pre heater,
boiler furnace, super heater, economizer, dust
collector, induced draught fan, chimney etc. Air is
taken from the atmosphere by the action of a forced
draught fan.
• It is passed through an air pre-heater. The air is pre-
heated by the flue gases in the pre-heater. This pre-
heated air is supplied to the furnace to aid the
combustion of fuel. Due to combustion of fuel, hot
gases (flue gases) are formed

16. Air and Flue gas circuit
• The flue gases from the furnace pass over boiler
tubes and super heater tubes. (In boiler, wet steam
is generated and in super heater the wet steam is
superheated by the flue gases.)
• Then the flue gases pass through economizer to
heat the feed water. After that, it passes through
the air pre-heater to pre-heat the incoming air. It is
then passed through a dust catching device (dust
collector). Finally, it is exhausted to the atmosphere
through chimney.

17. Cooling Water Circuit

18. Cooling water circuit
• The circuit includes a pump, condenser, cooling
tower etc. the exhaust steam from the turbine is
condensed in condenser.
• In the condenser, cold water is circulated to
condense the steam into water. The steam is
condensed by losing its latent heat to the
circulating cold water
• Thus the circulating water is heated. This hot
water is then taken to a cooling tower, In cooling
tower, the water is sprayed in the form of
droplets through nozzles

19. Cooling water circuit
• The atmospheric air enters the cooling tower from the
openings provided at the bottom of the tower. This air
removes heat from water. Cooled water is collected in
a pond (known as cooling pond).
• This cold water is again circulated through the pump,
condenser and cooling tower. Thus the cycle is
repeated again and again. Some amount of water may
be lost during the circulation due to vaporization etc.
• Hence, make up water is added to the pond by means
of a pump. This water is obtained from a river or lake.

20. Advantages and Disadvantages of steam power plant

26. FBC Boilers
• Fluidization is a method of mixing fuel and air in a
specific proportion, for obtaining combustion.
• A fluidized bed is defined as the bed of solid
particles behaving as a fluid.
• If the distributed air is passed upward through a
finely divided bed of solid particles at low velocity.
• The velocity of air flow is steadily increased, a
stage is reached when the individual particles are
suspended in the air stream.
• If the air velocity is further increased, the bed
becomes highly turbulent and rapid mixing of
particles occur which appear like formation of
bubbles in a boiling liquid and the process of
combustion as a result is known as fluidized bed
combustion.

28. Types of FBC System
1. Atmospheric FBC System
a. Overfeed system
b. Underfeed system
2. Pressurized FBC System

29. Atmospheric FBC System

30. Pressurized FBC System

31. Commercial Layout of FBC system

32. Advantages of FBC Boiler
1.High thermal efficiency.
2.Easy ash removal system, to be transferred
for made cement.
3.Short commissioning and erection period.
4.Fully automated and thus ensures safe
operation, even at extreme temperatures.
5.Efficient operation at temperatures down to
150oC ( i.e. well below the ash fusion
temperature).
6.Reduced coal crushing etc. (pulverized coal is
not a necessity here).

33. 7.The system can respond rapidly to
changes in load demand, due to quick
establishment of thermal equilibrium
between air and fuel particles in the bed.
8.The operation of fluidized bed furnace
at lower temperature helps in reducing
air pollution. The low temperature
operation also reduces the formation of
nitrogen oxides.

34. Disadvantages
• The fan power has to be maintained at a
considerably high value, since the air has
to be supplied continuously at a very high
pressure for supporting the bed.
• This in turn increases the operating cost
of the auxiliary units of the plant.

35. Steam Turbines
• Types Steam Turbine
Impulse Turbine
Reaction Turbine

40. Compounding of steam turbines is the method in which energy from the steam is
extracted in a number of stages rather than a single stage in a turbine. A compounded
steam turbine has multiple stages i.e. it has more than one set of nozzles and rotors, in
series, keyed to the shaft or fixed to the casing, so that either the steam pressure or
the jet velocity is absorbed by the turbine in number of stages.
1. Velocity Compounding of Impulse Turbine:
The velocity compounded impulse turbine has moving and fixed blades.
The moving blades are keyed to turbine shaft and fixed blades are fitted to casing.
The high pressure steam from boiler is expander in nozzle where pressure energy is
converted into kinetic energy.
2. Pressure Compounding of Impulse Turbine(Rateau turbine):
This is used to solve the problem of high blade velocity in the single-stage
impulse turbine.
It consists of alternate rings of nozzles and turbine blades. The nozzles are
fitted to the casing and the blades are keyed to the turbine shaft. In this type of
compounding, steam is expanded more than once(as in velocity compounding).

46. Condenser

47. Steam Condensers

48. Classification of condensers
• Jet Condensers
 Parallel flow type
Counter flow type
(i) Low level (ii) High level
 Ejector type
• Surface Condensers
(i) Down flow type
(ii) Central flow type
(iii)Inverted flow type
(iv) Regenerative type
(v) Evaporative type

49. Parallel flow –Low level jet condenser

50. Counter flow–Low level jet condenser

51. Counter flow –High level jet condenser

52. Ejector Condenser

53. Surface Condenser-Down flow type

54. Surface Condenser-Central flow type

55. Surface Condenser-Evaporative flow

60. Coal Unloading

61. • Preparation
– Breakers
– Crushers
– Sizers
– Dryers
– Magnetic separators
• Transfer
Belt conveyors Screw conveyors
Vee bucket elevator Pivoted bucket conveyors
Grab bucket conveyors Flight conveyors
Skip hosts Mass flow conveyors

68. Storage of coal

76. Draught System
• Types
Natural draught
Artificial draught
Mechanical Draught
 Forced Draught
 Induced Draught

80. Feed water treatment
Classification of impurities
Visible impurities
Microbiological growth
Turbidity and sediments
Dissolved gases
CO2,O2,N2,H2S
Minerals and salts
Fe, Mn, NaCl, KCl, Fluorides, Silica
 Mineral acids
Hardness

81. Causes of Impurities
Scale formation
Corrosion
Carryover
Embrittlement

82. Methods of Feed water treatment
1.Mechanical treatment
(i) Sedimentation (ii) Coagulation
(iii) Filtration (iv) Interior painting
2. Thermal treatment
(i) Deaeration
(ii) Distillation by evaporators

83. 3. Chemical treatment
(i) Cold lime soda softening process
(ii) Hot lime soda softening process
(iii) Lime phosphate softening process
(iv) Ion exchange process
4. Demineralization
(i) Hot lime soda and hot zeolite process
(ii) Adding acid to control alkalinity and vice versa
5.Blow down

84. Mechanical treatment

85. Thermal treatment

86. Chemical Treatment
• Lime soda softening process

87. Hot process softening process

88. Ion Exchange process
• Sodium zeolite process

89. Hydrogen zeolite process

91. Demineralization

92. Binary Vapor Cycle

93. Topping Cycle

94. Cogeneration

96. Bottoming cycle Power plant

97. Rankine cycle

98. Rankine cycle improvisations
Effect of Operating Conditions on
Rankine Cycle Efficiency
The Rankine cycle efficiency can be improved by
• Increasing the average temperature at which
heat is supplied.
• Decreasing/reducing the temperature at
which heat is rejected

99. Rankine cycle improvisations
This can be achieved by making suitable changes in the conditions of steam
generation or condensation, as discussed below :
Increasing boiler pressure. It has been observed that by
increasing the boiler pressure (other factors remaining the
same) the cycle tends to rise and reaches a maximum value at
a boiler pressure of about 166 bar
Superheating. All other factors remaining the same, if the steam
is superheated before allowing it to expand the Rankine cycle
efficiency may be increased. The use of superheated steam
also ensures longer turbine blade life because of the absence
of erosion from high velocity water particles that are
suspended in wet vapour.
Reducing condenser pressure. The thermal efficiency of the
cycle can be amply improved by reducing the condenser
pressure (hence by reducing the temperature at which heat is
rejected), especially in high vacuums. But the increase in
efficiency is obtained at the increased cost of condensation
apparatus

100. Improvisations of Rankine Cycle
• Reheating
• Regeneration
• Combined reheating and regeneration

108. Steam is the working fluid in an ideal Rankine cycle with
superheat and reheat. Steam enters the first-stage
turbine at 8.0 MPa, 480ºC, and expands to 0.7 MPa. It is
then reheated to 440ºC before entering the second-
stage turbine, where it expands to the condenser
pressure of 0.008 MPa. The net power output is 100
MW. Determine
(a) the thermal efficiency of the cycle, (b) the mass flow
rate of steam, in kg/h, (c) the rate of heat transfer from
the condensing steam as it passes through the
condenser, in MW. Discuss the effects of reheat on the
vapor power cycle.
Rankine reheat cycle

110. • Starting at the inlet to the first turbine stage, the
pressure is 8.0 MPa and the temperature is
480°C, so the steam is a superheated vapor. h1=
3348.4 kJ/kg and s1= 6.6586 kJ/kg .K.
• State 2 is fixed by p2 = 0.7 MPa and s2 = s1 for the
isentropic expansion. Using saturated liquid and
saturated vapor data from table, the quality at
state 2 is

111. • The specific enthalpy is then ,
• State 3 is superheated vapor with p3 = 0.7 MPa and
T3 = 440o
C, so from table, h3 =3353.3 kJ/kg and s3 =
7.7571 kJ/kg .K.
• To fix state 4, use p4 = 0.008 MPa and s4 = s3 for the
isentropic expansion through the second-stage
turbine.

112. • The specific enthalpy is
• h4 = 173.88 + (0.9382)2403.1 = 2428.5 kJ/kg
• State 5 is saturated liquid at 0.008 MPa, so h5
=5173.88 kJ/kg. Finally, the state at the pump
exit h6 = 181.94 kJ/kg.
• The net power developed by the cycle is
Mass and energy rate balances for the two
turbine stages and the pump reduce to give,
respectively

113. • Where ṁ is the mass flow rate of the steam.
• The total rate of heat transfer to the working fluid
as it passes through the boiler–superheater and
reheater is
•

114. • Using these expressions, the thermal efficiency is
• The mass flow rate of the steam can be obtained by

115. • The rate of heat transfer from the condensing steam
to the cooling water is

116. Consider a regenerative vapor power cycle with one
open feed water heater. Steam enters the turbine at 8.0
MPa, 480°C and expands to 0.7 MPa, where some of
the steam is extracted and diverted to the open feed
water heater operating at 0.7 MPa. The remaining steam
expands through the second-stage turbine to the
condenser pressure of 0.008 MPa. Saturated liquid exits
the open feed water heater at 0.7 MPa. The isentropic
efficiency of each turbine stage is 85% and each pump
operates isentropic ally. If the net power output of the
cycle is 100 MW, determine
• (a) the thermal efficiency and (b) the mass flow rate
of steam entering the first turbine stage, in kg/h.

118. • In summary, h1 = 3348.4 kJ/kg, h2 = 2832.8 kJ/kg,
• s2 = 6.8606 kJ/kg . K, h4 = 173.88 kJ/kg.
• The specific enthalpy at state 3 can be determined
using the isentropic efficiency of the second-stage
turbine
• State 6 is saturated liquid at 0.7 MPa. Thus,
• h6 = 697.22 kJ/kg.
• Since the pumps operate isentropically.

119. The specific enthalpy values at states 5 and 7 can be
determined as
Applying mass and energy rate balances to a control
volume enclosing the open heater, we find the
fraction y of the flow extracted at state 2 from

120. • On the basis of a unit of mass passing through the
first-stage turbine, the total turbine work output is