thermal power plants help meet almost
half of the world's power demand
they use water as the working fluid
today's thermal power plants are capable
to run under great efficiency by
conforming to stringent environmental
standards
in this video we will see how a
coal-based thermal power plant achieves
this in a detailed step-by-step manner
by turning the shaft of this generator
we will be able to generate electricity
the generator derives motion from a
steam turbine the heart of the power
plant
in order to turn the steam turbine you
have to supply a high pressure and high
temperature steam at the inlet of the
turbine
as the turbine absorbs energy from the
high energy fluid its pressure and
temperature drop toward the outlet
you can take a closer look at the
uniquely shaped steam turbine rotor
blades
high capacity power plants often use
different stages of steam turbines
such as high pressure turbine
intermediate pressure turbine
and low pressure turbines
so now we have met our objective we have
produced electricity from the generator
if we can bring the low pressure and low
temperature steam back to their original
states which were of a much higher
pressure and temperature we can repeat
the process
the first step is to raise the pressure
you can use a compressor for this
purpose
but compressing steam is a highly energy
intensive process
and such a power plant will not be
efficient at all
the easy way is to convert the steam
into liquid and boost the pressure
for this purpose we'll introduce
condenser heat exchangers which sit
beneath the low pressure turbine
in the condenser a stream of cold water
flows through the tubes
the steam rejects heat to this liquid
stream and becomes condensed
now we can use a pump to increase the
pressure of this feed water
typically multi-stage centrifugal
pumping is used for this purpose
that way the pressure will revert to its
original state
the next task is to bring the
temperature back to its original value
for this purpose heat is added to the
exit of the pump with the help of a
boiler
high capacity power plants generally use
a type of boiler called a water tube
boiler
pulverized coal is then burned inside
the boiler
the incoming water initially passes
through an economizer session here the
water will capture energy from the flue
gas
the water flows through a down comer
and then through water walls where it
transforms into steam
the pure steam is separated at a steam
drum
now the working fluid is back to its
original state high pressure and high
temperature
this steam can be fed back into the
steam turbine
and the cycle can be repeated over and
over again for continuous power
production
but a power plant working on this basic
rankine cycle will have a very low
efficiency and a low capacity
we can increase the performance of the
power plant considerably with the help
of a few simple techniques
in case of superheating even after the
liquid has been converted into steam
even more heat is added
and with that the steam becomes
superheated
the higher the temperature of the steam
the more efficient the cycle
just remember the carnot's theorem of
maximal thermal efficiency possible
but the steam turbine material will not
withstand temperatures of more than 600
degrees celsius so superheating is
limited to that threshold
the temperature of the steam decreases
as it flows along the rows of the blade
consequently a great way to increase the
efficiency of the power plant is to add
more heat after the first turbine stage
this is known as reheating and it will
increase the temperature of the steam
again leading to a high power output and
greater efficiency
the low pressure sides of the power
plant are prone to suck the atmospheric
air even with sophisticated sealing
arrangements
the dissolved gases in the feed water
will spoil the boiler material over time
to remove these dissolved gases an open
feed water heater is introduced
hot steam from the turbine is mixed into
the feed water steam bubbles so
generated will absorb the dissolved
gases
the mixing also preheats the feed water
which helps improve the efficiency of
the power plant to an even greater
extent
all these techniques make the modern
power plant work under an efficiency
range of 40 to 45 percent
now we'll take a look at how heat
addition
and heat rejection are executed in an
actual power plant
cold liquid is supplied at the condenser
with the help of a cooling tower
the heated up water from the condenser
outlet is sprayed in the cooling tower
which induces a natural air draft and
the sprayed water loses heat
this is how a colder liquid is always
provided at the condenser inlet
at the heat addition side the burning
coal produces many pollutants
we cannot release these pollutants
directly into the atmosphere
so before transferring them to a stack
the exhaust gas is cleaned in an
electrostatic precipitator
the esp uses plates with high voltage
static electricity to absorb the
pollutant particles
[Music]
we hope that we've given you new
insights into the inner workings of
thermal power plants
thank you for watching the video