ABOUT NTPC
NTPC, India's largest power company, was set up in 1975 to
accelerate power development in India. It is emerging as an'
Integrated Power Major’, with a significant presence in the entire
value chain of power generation business.
With a current generating capacity of 34,854 MW, NTPC has
embarked on plans to become a 75,000 MW company by 2017.
Presently, NTPC generates power from Coal and Gas. With
an installed capacity of 34,854 MW, NTPC is the largest
power generating major in the country.
NTPC BADARPUR
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Badarpur thermal power plant started working
with a single 95 MW unit. There were two more
units installed in next two consecutive years. Now
it has total 5 units with total capacity of 720
MW.
UNIT NUMBER
INSTALLED
CAPACITY(MW)
1
95 MW
2
95 MW
3
95 MW
4
210 MW
5
210 MW
Coal to electricity
The basic steps in generation of electricity from coal is carried out in
three stages:
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Coal to steam
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Steam to mechanical power
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Mechanical power to electrical power
RANKINE CYCLE
Rankine cycle is a basic thermodynamic cycle
that converts heat into work.
Rankine cycle describes a model of operation
of steam heat engines most commonly found in
power generation plants.
T-s diagram of a Rankine cycle operating between pressures 0-06 bar and 50 bar. there
are 4 stages in rankine cycle each changing the state of fluid.

Process 1-2: The working fluid is pumped from low pressure to high pressure, as the fluid
is in liquid state at this stage it requires more input.
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Process 2-3:The high pressure liquid enters the boiler where it is heated at constant
pressure by an external heat source to become a dry saturated vapor.
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Process 3-4: The dry saturated vapor expands through a turbine, generating power. This
decreases the temperature and pressure of the vapor, and some condensation may occur
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Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant
pressure and temperature to become a saturated liquid.
In an ideal Rankine cycle the pump and turbine would be isentropic i.e. the pump and
turbine would generate no entropy and hence maximize the net work output.
Coal Handling Plant
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This plant transfers the coal to the boiler
and also stores the coal in the bunker.
Wagon tipplers are employed to unload
the coal wagons into coal hopper.
Vibrating screen are used for controlled
removal of coal from coal hopper.
We receive coal in the form of odd lumps.
These lumps are to be crushed to required
sizes which is done by the coal crusher.
Electromagnetic separator performs the
function of separation of iron and magnetic
impurities from the coal.
Wagon tippler
Vibrating screen
Conveyor belt
Electromagnetic
separator
Coal crusher
Coal bunker
Coal wagons containing coal
Wagon tippler
There are three operational cycles working in CHP:
1.
Normal Bunkering Cycle: Shifting of the coal received from coal wagons
directly to coal bunkers
2.
Coal stacking: when there is no requirement of coal in the coal bunker even then
CHP has to unload the received coal which is stacked at open ground called
yard.
3.
Coal reclaiming: as and when coal wagons are not available, the requirement
of the coal bunker is fulfilled from the stacked coal. this is called reclaiming
cycle.
Boiler Maintenance Department
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Coal from the coal wagons are unloaded in the coal handling plant. This coal is
transported up to the coal bunker with the help of conveyor belts. coal is taken to
the bowl mill by coal feeders. The coal is pulverized in the bowl mill and ground to
powdered form.
The mill consists of the round metallic table on which coal particles fall. The table is
rotated with the help of motor. There are three large steel rollers which are spaced
120° apart.
When there is no coal, The rollers do not rotate but when but when the coal is fed to
the table it packs up between roller and the table and these forces the rollers to
rotate. Coal is crushed by the crushing action between the rollers and the rotating
table.
This crushed coal is taken away to the furnace through coal pipes with the help of
hot and cold air mixture from P.A. fan. P.A. Fan takes atmospheric air, a part of
which is sent to air-pre heaters for heating while a part goes directly to the mill for
temperature control. Atmospheric air from F.D. Fan is heated in the air heaters and
sent to the furnace as combustion air.
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Water from the boiler feed pump passes through economizer and reaches the boiler drum. Water from the
drum passes through down comers and goes to the bottom ring header. Water from the bottom ring header
is divided to all the four sides of the furnace
Due to heat and density difference, the water rises up in the water wall tubes. Water is partly converted to
steam as it rises up in the furnace. This steam and water mixture is again taken to thee boiler drum where
the steam is separated from water.
Water follows the same path while the steam is sent to super heaters for superheating and finally goes to
the turbine.
Flue gases from the furnace are extracted by induced draft fan .These flue gases emit their heat energy to
various super heaters in the pent house and finally pass through air-preheater and goes to electrostatic
precipitators where the ash particles are extracted.
Steam Boiler
Turbine maintainence department
A steam turbine has two main parts:
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Stator:it contains fixed blades ,vanes and nozzles that directs the steam into the
moving blades carried by rotor.
Rotor : a rotor is a rotating shaft that carries the moving blades on the outer edges
on either discs or drum. The blade rotates as the rotor revolves.
As the steam passes through the fixed blades or nozzles, it expands and its
velocity increases.
The high velocity jet of stream strikes the first set of
moving blades. The K.E of the steam changes to
mechanical energy causing the shaft to rotate. The
steam that enters the next row of moving blades.
As the steam flows through the turbine, its pressure
and temperature decreases while its volume
increases.
The path of steam
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Superheated steam
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H.P turbine
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Reheater
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I.P turbine
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L.P turbine
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Condenser
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Condensate Extraction Pump
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Ejector
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GSC-1
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LPH- 1
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GSC-2
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LPH-2
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LPH-3
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LPH-4
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Deareator
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Boiler Feed Pump
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HPH-5
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HPH-6
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HPH-7
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Feed Regulating Station
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Condenser: To condense the steam.
Condensate extraction pump: The condensate water is drawn from the condenser
by the extraction pump.
Gland steam cooler: The seals around the rotating shaft on steam turbines are
many in several ways but all leak a small amount of steam to the atmosphere. To
capture this steam, many of the seals have small condensers to capture this steam.
Deareator: A deaerator is a device that is widely used for the removal of air and
other dissolved gases from the feed water to steam-generating boilers.
Main Turbine
The 210 MW turbine comprises of H.P, I.P and L.P
cylinders. The superheated steam from the boiler
passes through the emergency stop valve and
control valve before entering the H.P turbine.
After expanding in the 12 stages in the H.P
turbine the steam returns to the boiler for
reheating. The reheated steam from the boiler
enters the I.P turbine via control valves and after
expanding enters the I.P turbine in the l.P stage
the steam expands in opposite direction to
counteract the trust and then enters the condenser.
The cooling water flowing through the condenser
tubes condenses the steam and the condensate is
collected in the hot well of the condenser
.
Plant Auxiliary Maintenance
Water circulation system: The water is
circulated from the drum and then comes back
to the drum where the water is separated
from the steam and directed to the super
heater.
Types of water circulation system:
1.
Natural circulation system
2.
Forced circulation system
Ash handling Plant
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Hydraulic Ash Handling System: The hydraulic system carries the ash with the flow of
water with high velocity through a channel and finally dumps into a sump. The hydraulic
system is divided into:
Low velocity system
High velocity system
In the low velocity system the ash from the boilers falls into a stream of water flowing
into the sump. The ash is carried along with the water and they are separated at the
sump. In the high velocity system a jet of water is sprayed to quench the hot ash. Two
other jets force the ash into a trough in which they are washed away by the water into
the sump .Hydraulic Ash handling system is used at the Badarpur Thermal Power station.
Bottom Ash Collection and Disposal
At the bottom of every boiler, a hopper has been provided for collection of the bottom
ash from the bottom of the furnace. This hopper is always filled with water to quench the
ash and clinkers falling down from the furnace. Some arrangement is included to crush the
clinkers and for conveying the crushed clinkers and bottom ash to a storage site.
WATER TREATMENT PLANT
Water treatment plants used in thermal power plants used in thermal power plants
are designed to process the raw water to water with a very low content of dissolved
solids known as ‘demineralized water’.
Pretreatment Section: Pretreatment plant removes the suspended solids such as clay,
silt, organic and inorganic matter, plants and other microscopic organism. The
suspended solids can either be separable solids or non-separable solids(colloids).
The coarse components, such as sand, silt, etc: can be removed from the water by
simple sedimentation. Finer particles, however, will not settle in any reasonable time
and must be flocculated to produce the large particles, which are settleable.
demineralisation
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This filter water is now used for demineralizing purpose and is fed
to cation exchanger bed. But before that it needs to be
dechorinated. This can be done in the following ways:
by passing through activated carbon filter
injecting along the flow of water an equivalent amount of sodium
sulphite through some stroke pumps.
The residual chlorine should be remove as it interferes with the
resin.
A DM plant generally consists of cation, anion and mixed bed
exchangers. The final water from this process consists essentially of
hydrogen ions and hydroxide ions which is the chemical composition
of pure water. The DM water, being very pure, becomes highly
corrosive once it absorbs oxygen from the atmosphere because of its
very high affinity for oxygen absorption. Some storage is essential
as the DM plant may be down for maintenance. For this purpose, a
storage tank is installed from which DM water is continuously used.
Compressor house
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Instrument air is required for operating various burners and other devices etc in the
210 MW units.
INSTUMENT AIR SYSTEM:
Control air compressors have been installed for supplying moisture free dry air
required for instrument.
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Air-Drying Unit
Air contains moisture which tends to condense, and causes trouble in operation of
various devices by compressed air. Therefore drying of air is accepted widely in
case of instrument air. The absorption towers are adequately filled with specially
selected silica gel and activated alumina while one tower is drying the air.
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