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 VINDYACHAL THERMAL
POWER PLANT,

SINGRAULI, MADHYA
PRADESH

1982

LARGEST IN INDIA

4760 MW
VAPOUR POWER CYCLES COAL-BASED

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Taichung Power Plant, Taiwan

Worlds biggest thermal power station (1992);
5788 MW POWER

Mundra Thermal Power Plant, Gujarat (2008), Second

largest in India, 4620 MW, Coal based 7 8

GUJARAT

2008
 Furnace
Components of a steam power plant
Components Turbine
and working of Generator
a steam power
plant

Condenser
Pump
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View of turbine Pressure and

and generator Generator temperature
reduces here

High pressure and high temperature steam

flow through turbine blades
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 Way to condenser

LP

IP
HP
View of high pressure (HP), Intermediate View of steam flowing through HP, IP and
pressure (IP) and low Pressure (LP) turbine 13 LP turbines 14

View of View of
condenser condenser
where the where the
steam is steam is
cooled 15
cooled 16
View of Boiler

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Combustion in boiler 18

Why are turbine

blades curved?
View of turbine in a
19 Power Plant 20
 Super-critical carnot cycle
In-dome Carnot Cycle
Carnot cycle is the most efficient
cycle operating between two
Carnot cycle specified temperature limits
Can we use the carnot cycle as an ideal cycle for
vapour power plants???

Answer: No

Why is it so??

T-S diagram of two Carnot Power Cycles

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What are the issues with the Super-critical carnot cycle What are the issues with
In-dome Carnot Cycle
in-dome Carnot Cycle?? the supercritical Carnot
1. Process 1-2: Limits the Cycle??
maximum temperature below
the critical point (which is 374oC 1. Process 1-2: Requires
for water Isothermal heat transfer at
2. Process 2-3: Turbine cannot variable pressures.
handle steam with high
moisture contents (erosion 2. Process 4-1: Requires
occurs) isentropic compression to
3. Process 4-1: Not practical to extremely high pressures
design a pump that handles two
phase fluids

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 The steady flow energy equation per unit mass of steam
Simple ideal Rankine Cycle
1-2 Isentropic compression in Pump
2-3 Constant Pressure heat addition in boiler
3-4 Isentropic expansion in turbine
4-1 Constant pressure heat rejection in condenser

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Problem Solving
Deviation of
1. Consider a steam power plant
operating on the simple ideal actual power
Rankine cycle.
cycles from the
Steam enters the turbine at 3MPa idealized ones
and 350oC and is condensed in
the condenser at a pressure of 75
kPa.

Determine the thermal efficiency

of this cycle.

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 Deviation of actual vapor power cycle The effect of pump and turbine
from the ideal Rankine cycle irreversibilities on the ideal Rankine
cycle Problem Solving
2. A steam power plant
operates on the cycle shown
in figure here.

determine

(a) the thermal efficiency of

the cycle and

(b) the net power output of

the plant for a mass flow rate
of 15 kg/s.
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How to increase the efficiency of Rankine Cycle?

Clue:
Increase Wnet or decrease qin

Steam power plants are responsible for the

production of most electric power in the world,
and even small increases in thermal efficiency
can mean large savings from the fuel How to Increase Wnet?
requirements Clue:
See what modifications you can
do in the TS diagram. There are
three possible ways?
Steam power plants have How to increase the efficiency,
low efficiency (35 - 49%) then?
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 Superheat the steam to a higher
Lower the condenser pressure (one of temperature (second way of improving the
the ways to increase efficiency) efficiency of Rankine cycle)
● Decreases the average lower temperature of
the cycle.
● increases the work output as shown by the ● Additional heat needs to be added.
shaded region, which in turn results in ● Results in a increase in wnet,output
increase in thermal efficiency
● Compared to the heat added, the work
Usually the pressure is slightly less than the output is more. Hence, the cycle has higher
atmospheric pressure (A disadvantage is that air efficiency compared to the normal Rankine
can leave inside the condenser if not properly cycle
sealed) ● Limitation: You cannot superheat the steam
to very high temperature (why? - Because
Moisture content also increases at the final stages the blades may not be able to withstand
of the turbine. such high temperatures)

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Increase the boiler pressure (third way of

improving the efficiency of Rankine cycle)

● Pressure in the boiler is increased.

Damage by
● Results in a increase (green shaded) as well
as decrease (orange shaded) in wnet,output erosion in the
● Compared to the decrease in wnet,output, the working blades
increase in wnet,output is more. Therefore, the
efficiency of the cyle is higher. of the last
● Limitation: Moisture content of the steam stage in a
exiting the turbine is more (see the state 4 )
steam turbine
of 300 MW

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3. Consider a steam power
plant operating on the ideal What is the need for this
Rankine cycle. Steam enters
the turbine at 3 MPa and (reheat cycle)?
350oC and is condensed in
the condenser at a pressure Increasing Pboiler increases efficiency but
of 10 kPa. also increases the moisture content of
steam to unacceptable levels.
Determine
(a) the thermal efficiency of this
power plant, THE IDEAL Then how to take the advantage of
increased efficiencies at a higher Pboiler
(b) the thermal efficiency if steam is
superheated to 600oC instead of REHEAT without facing excessive moisture ??
350oC, and
(c) the thermal efficiency if the RANKINE CYCLE Answer:
boiler pressure is raised to 15 MPa Reheat the steam (i.e., heat the steam
while the turbine inlet temperature
is maintained at 600oC.
again)
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Option 1: Superheat the

Ideal ‘reheat’ rankine cycle
steam to very high
temperatures.

Option 2: Use different stages

of turbine and reheat the
steam in between.

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Numerical problem on Reheat Rankine Q4. Consider a steam power plant operating on
Is there any other way to improve the efficiency by using any
the ideal reheat Rankine cycle. Steam enters
Cycle technique other than the following?
the high-pressure turbine at 15 MPa and 600oC
and is condensed in the condenser at a
pressure of 10 kPa. 1. Increase boiler pressure
2. Lower the condenser pressure
If the moisture content of the steam at the 3. Superheat the steam
exit of the low-pressure turbine is not to Further 4. Take a part of the steam from HP turbine, heat it again
exceed 10.4 percent, in the boiler and send it to the LP turbine (i.e.,
improvement in Reheating)
Determine
(a) The pressure at which the steam should be
Vapour power Answer:
reheated and cycles... Take a part of the steam from the turbine (only one turbine) and
use it for heating the water that exits the pump.
(b) The thermal efficiency of the cycle. Assume
the steam is reheated to the inlet temperature
of the high-pressure turbine.
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Some part of hot steam is expanded in the turbine and sent to

feedwater heater ;and the remain is expanded and sent to pump

For example: For each 1 kg of steam leaving the boiler, y kg of

steam is sent to FWH and (1-y) is sent to the pump after expansion in
the turbine

Feedwater heater
Steam mixed with water here

1-y

Additional pump Regular pump 47 48