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1
National Thermal Power Corporation
Badarpur,New Delhi
TRAINING REPORT
Name: Bhanu Pratap Singh (615/MP/08)
Branch: MANUFACTURING PROCESS AND AUTOMATION
ENGINEERING
College: NETAJI SUBHAS INSTITUTE OF TECHNOLOGY(NSIT)
Duration:12 December, 2011 to 28th January, 2012
2
CONTENTS
1.0 Introduction
1.1 NTPC
1.2 Power Generation in India
1.3 Overall Power Generation
1.4 Badarpur Thermal Power Station (BTPS)
2.0 Objective
3.0 Work Done During The Training Period
3.1 Electricity From Coal
3.2 Boiler Maintenance Division (BMD)
3.3 Plant Auxiliary Maintenance (PAM)
3.4 Turbine Maintenance Division (TMD)
3.5 Pollution Control and Waste Management
4.0 Inference
5.0 Bibliography
3
ACKNOWLEDGEMENT
With profound respect and gratitude, I take the opportunity to convey my thanks to
complete the training here. I do extend my heartfelt thanks to Mr. H.S. Bhatia for providing
me this opportunity to be a part of this esteemed organization. I am extremely grateful to all
the technical staff of National Thermal Power Corporation for their co-operation and
guidance that helped me a lot during the course of training. I have learnt a lot working under
them and I will always be indebted of them for this value addition in me. I would also like
to thank the training in charge of NETAJI SUBHAS INSTITUTE OF TECHNOLOGY,
DWARKA and all the faculty member of Manufacturing Process And Automation
Department for their effort of constant co-operation. Which have been significant factor in
the accomplishment of my industrial training.
4
1.0 INTRODUCTION
1.1 NTPC
NTPC Limited is the largest thermal power generating company of India. A public sector
company, it was incorporated in the year 1975 to accelerate power development in the
country as a wholly owned company of the Government of India. At present, Government of
India holds 89.5% of the total equity shares of the company and FIIs, Domestic Banks, Public
and others hold the balance 10.5%. Within a span of 35 years, NTPC has emerged as a truly
national power company, with power generating facilities in all the major regions of the
country.
1.2 POWER GENERATION IN INDIA
NTPC‟s core business is engineering, construction and operation of power generating plants.
It also provides consultancy in the area of power plant constructions and power generation to
companies in India and abroad. As on date the installed capacity of NTPC is 27,904 MW
through its 15 coal based (22,895 MW), 7 gas based (3,955 MW) and 4 Joint Venture
Projects (1,054 MW). NTPC acquired 50% equity of the SAIL Power Supply Corporation
Ltd. (SPSCL). This JV Company operates the captive power plants of Durgapur (120 MW),
Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33% stake in Ratnagiri Gas &
Power Private Limited (RGPPL) a joint venture company between NTPC, GAIL, Indian
Financial Institutions and Maharashtra SEB Co Ltd. NTPC has set new benchmarks for the
power industry both in the area of power plant construction and operations. Its providing
power at the cheapest average tariff in the country.
1.3 OVERALL POWER GENERATION
Unit 1997-98 2006-07 % of increase
Installed Capacity MW 16,847 26,350 56.40
Generation MUs 97,609 1,88,674 93.29
No. of employees No. 23,585 24,375 3.34
Generation/employee MUs 4.14 7.74 86.95
5
The table below shows the detailed operational performance of coal based stations over the
years.
The energy conservation parameters like specific oil consumption and auxiliary power
consumption have also shown considerable improvement over the years.
1.4 BADARPUR THERMAL POWER STATION (BTPS)
Badarpur thermal power plant produces 705MW of power. In total there are 5 units in BTPS,
3 are 95MW each and 2 of 210MW each.95MW units were installed in early 70‟s and
210MW in late 70‟s to early 80‟s.Coal Requirements ( Depends On the Calorific Value Of
the Fuel):
95 MW -60 tonnes/hour
210MW-105 to 110 tonnes/hour 65MW of power is
consumed in company while rest (640MW) is provided to states of northern
region like UP, Delhi, Haryana, Rajasthan.There are 11 feeders in use at
present, 2-Okhla, 2-Sarita Vihar, 2-Mahroli, 2-Noida, 2-Ballabhgarh, 1-
Alwar.
OPERATIONAL PERFORMANCE OF COAL BASED NTPC STATIONS
Unit 97-98 98-99 99-00 00-01 01-02 02-03 03-04 04-05 05-06 06-07
Generation BU 106.2 109.5 118.7 130.1 133.2 140.86 149.16 159.11 170.88 188.67
PLF % 75.20 76.60 80.39 81.8 81.1 83.6 84.4 87.51 87.54 89.43
Availability
Factor
% 85.03 89.36 90.06 88.54 81.8 88.7 88.8 91.20 89.91 90.09
6
OBJECTIVE
I was appointed to do four-week training at this esteemed organization from 12th
Dec 2011 to
28 th
Jan, 2012. In these four weeks I was assigned to visit various division of the plant which
were
1. Boiler Maintenance Division I (BMD-I)
2. Boiler Maintenance Division II (BMD-II)
3. Boiler Maintenance Division III (BMD-III)
4. Plant Auxillary Maintenance (PAM)
5. Turbine Maintenance Division(TMD)
The objective of the training at NTPC is to gain experience of eight weeks on field, and to
gain practical knowledge in the field of thermal power generation.
WORK DONE DURING THE TRAINING PERIOD 3.1 ELECTRICITY FROM COAL
Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P. (Coal
Handling Plant) this coal is taken to the raw coal bunkers with the help of conveyor belts.
Coal is then transported to bowl mills by coal feeders where it is pulverized and ground in the
powered form.
This crushed coal is taken away to the furnace through coal pipes with the help of hot and
cold mixture P.A fan. This fan takes atmospheric air, a part of which is sent to pre heaters
while a part goes to the mill for temperature control. Atmospheric air from F.D fan in the air
heaters and sent to the furnace as combustion air.
Water from boiler feed pump passes through economizer and reaches the boiler drum . Water
from the drum passes through the 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 density
difference the water rises up in the water wall tubes. This steam and water mixture is again
taken to the boiler drum where the steam is sent to super heaters for super heating. The super
heaters are located inside the furnace and the steam is super heated (540 degree Celsius) and
finally it goes to the turbine.
7
Fuel gases from the furnace are extracted from the induced draft fan, which maintains
balance draft in the furnace with F.D fan. These fuel gases heat energy to the various super
heaters and finally through air pre heaters and goes to electrostatic precipitators where the ash
particles are extracted. This ash is mixed with the water to from slurry is pumped to ash
period. The steam from boiler is conveyed to turbine through the steam pipes and through
stop valve and control valve that automatically regulate the supply of steam to the turbine.
Stop valves and controls valves are located in steam chest and governor driven from main
turbine shaft operates the control valves the amount used. Steam from controlled valves enter
high pressure cylinder of turbines, where it passes through the ring of blades fixed to the
cylinder wall. These act as nozzles and direct the steam into a second ring of moving blades
mounted on the disc secured in the turbine shaft. The second ring turns the shaft as a result of
force of steam on the stationary and moving blades together.
Typical components of a coal fired thermal power station
1. Cooling water pump
2. Three-phase transmission line
3. Step up transformer
4. Electrical Generator
5. Low pressure steam
6. Boiler feed water pump
7. Surface condenser
8. Intermediate pressure steam turbine
9. Steam control valve
10. High pressure steam turbine
11. Deaerator Feed water heater
12. Coal conveyor
13. Coal hopper
14. Coal pulverizer
15. boiler steam drum
16. Bottom ash hoper
17. Super heater
18. Forced draught (draft) fan
19. Reheater
20. Combustion air intake
8
21. Economizer
22. Air preheater
23. Precipitator
24. Induced draught (draft) fan
25. Fuel gas stack
The description of some of the components written above is described as follows:
1. Cooling towers
Cooling Towers are evaporative coolers used for cooling water or other working
medium to near the ambivalent web-bulb air temperature. Cooling tower use
evaporation of water to reject heat from processes such as cooling the circulating
water used in oil refineries, Chemical plants, power plants and building cooling, for
example. The tower vary in size from small roof-top units to very large hyperboloid
structures that can be up to 200 meters tall and 100 meters in diameter, or rectangular
structure that can be over 40 meters tall and 80 meters long. Smaller towers are
normally factory built, while larger ones are constructed on site. The primary use of
large , industrial cooling tower system is to remove the heat absorbed in the
circulating cooling water systems used in power plants , petroleum refineries,
petrochemical and chemical plants, natural gas processing plants and other industrial
facilities . The absorbed heat is rejected to the atmosphere by the evaporation of some
of the cooling water in mechanical forced-draft or induced draft towers or in natural
draft hyperbolic shaped cooling towers as seen at most nuclear power plants.
2. Electrical generator
An Electrical generator is a device that converts kinetic energy to electrical energy,
generally using electromagnetic induction. The task of converting the electrical energy
into mechanical energy is accomplished by using a motor. The source of mechanical
energy may be a reciprocating or turbine steam engine, , water falling through the turbine
are made in a variety of sizes ranging from small 1 hp (0.75 kW) units (rare) used as
mechanical drives for pumps, compressors and other shaft driven equipment , to
2,000,000 hp(1,500,000 kW) turbines used to generate electricity.
3. TurbinesThere are several classifications for modern steam turbines.
Steam turbines are used in all of our major coal fired power stations to drive the generators or
9
alternators, which produce electricity. The turbines themselves are driven by steam generated
in „Boilers‟ or „steam generators‟ as they are sometimes called.
Electrical power station use large steam turbines driving electric generators to produce most
(about 86%) of the world‟s electricity. These centralized stations are of two types: fossil fuel
power plants and nuclear power plants. The turbines used for electric power generation are
most often directly coupled to their-generators .As the generators must rotate at constant
synchronous speeds according to the frequency of the electric power system, the most
common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for 60 Hz systems. Most
large nuclear sets rotate at half those speeds, and have a 4-pole generator rather than the more
common 2-pole one.
Energy in the steam after it leaves the boiler is converted into rotational energy as it passes
through the turbine. The turbine normally consists of several stage with each stages
consisting of a stationary blade (or nozzle) and a rotating blade. Stationary blades convert the
potential energy of the steam into kinetic energy into forces, caused by pressure drop, which
results in the rotation of the turbine shaft. The turbine shaft is connected to a generator, which
produces the electrical energy.
4. Boiler feed water pump
A Boiler feed water pump is a specific type of pump used to pump water into a steam boiler.
The water may be freshly supplied or retuning condensation of the steam produced by the
boiler. These pumps are normally high pressure units that use suction from a condensate
return system and can be of the centrifugal pump type or positive displacement type.
Construction and operation:
Feed water pumps range in size up to many horsepower and the electric motor is usually
separated from the pump body by some form of mechanical coupling. Large industrial
condensate pumps may also serve as the feed water pump. In either case, to force the water
into the boiler; the pump must generate sufficient pressure to overcome the steam pressure
developed by the boiler. This is usually accomplished through the use of a centrifugal pump.
Feed water pumps usually run intermittently and are controlled by a float switch or other
similar level-sensing device energizing the pump when it detects a lowered liquid level in the
boiler is substantially increased. Some pumps contain a two-stage switch. As liquid lowers to
the trigger point of the first stage, the pump is activated. I f the liquid continues to drop
10
(perhaps because the pump has failed, its supply has been cut off or exhausted, or its
discharge is blocked); the second stage will be triggered. This stage may switch off the boiler
equipment (preventing the boiler from running dry and overheating), trigger an alarm, or
both.
5. Steam-powered pumps
Steam locomotives and the steam engines used on ships and stationary applications such
as power plants also required feed water pumps. In this situation, though, the pump was
often powered using a small steam engine that ran using the steam produced by the boiler.
A means had to be provided, of course, to put the initial charge of water into the
boiler(before steam power was available to operate the steam-powered feed water
pump).the pump was often a positive displacement pump that had steam valves and
cylinders at one end and feed water cylinders at the other end; no crankshaft was required.
In thermal plants, the primary purpose of surface condenser is to condense the exhaust
steam from a steam turbine to obtain maximum efficiency and also to convert the turbine
exhaust steam into pure water so that it may be reused in the steam generator or boiler as
boiler feed water. By condensing the exhaust steam of a turbine at a pressure below
atmospheric pressure, the steam pressure drop between the inlet and exhaust of the
turbine is increased, which increases the amount heat available for conversion to
mechanical power. Most of the heat liberated due to condensation of the exhaust steam is
carried away by the cooling medium (water or air) used by the surface condenser.
6. Control valves
Control valves are valves used within industrial plants and elsewhere to control
operating conditions such as temperature,pressure,flow,and liquid Level by fully
partially opening or closing in response to signals received from controllers that
compares a “set point” to a “process variable” whose value is provided by sensors that
monitor changes in such conditions. The opening or closing of control valves is done
by means of electrical, hydraulic or pneumatic systems
11
7. Deaerator
A Dearator is a device for air removal and used to remove dissolved gases (an
alternate would be the use of water treatment chemicals) from boiler feed water to
make it non-corrosive. A deaerator typically includes a vertical domed deaeration
section as the deaeration boiler feed water tank. A Steam generating boiler requires
that the circulating steam, condensate, and feed water should be devoid of dissolved
gases, particularly corrosive ones and dissolved or suspended solids. The gases will
give rise to corrosion of the metal. The solids will deposit on the heating surfaces
giving rise to localized heating and tube ruptures due to overheating. Under some
conditions it may give to stress corrosion cracking.
Deaerator level and pressure must be controlled by adjusting control valves- the level
by regulating condensate flow and the pressure by regulating steam flow. If operated
properly, most deaerator vendors will guarantee that oxygen in the deaerated water
will not exceed 7 ppb by weight (0.005 cm3/L)
8. Feed water heater
A Feed water heater is a power plant component used to pre-heat water delivered to a
steam generating boiler. Preheating the feed water reduces the irreversible involved in
steam generation and therefore improves the thermodynamic efficiency of the
system.[4] This reduces plant operating costs and also helps to avoid thermal shock to
the boiler metal when the feed water is introduces back into the steam cycle.
In a steam power (usually modeled as a modified Ranking cycle), feed water heaters
allow the feed water to be brought up to the saturation temperature very gradually.
This minimizes the inevitable irreversibility‟s associated with heat transfer to the
working fluid (water). A belt conveyor consists of two pulleys, with a continuous loop
of material- the conveyor Belt – that rotates about them. The pulleys are powered,
moving the belt and the material on the belt forward. Conveyor belts are extensively
used to transport industrial and agricultural material, such as grain, coal, ores etc.
9. Pulverizer :A pulverizer is a device for grinding coal for combustion in a furnace in
a fossil fuel power plant.
10. Boiler Steam Drum
Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam
12
at the top end of the water tubes in the water-tube boiler. They store the steam
generated in the water tubes and act as a phase separator for the steam/water mixture.
The difference in densities between hot and cold water helps in the accumulation of
the “hotter”-water/and saturated –steam into steam drum. Made from high-grade steel
(probably stainless) and its working involves temperatures 390‟C and pressure well
above 350psi (2.4MPa). The separated steam is drawn out from the top section of the
drum. Saturated steam is drawn off the top of the drum. The steam will re-enter the
furnace in through a super heater, while the saturated water at the bottom of steam
drum flows down to the mud-drum /feed water drum by down comer tubes
accessories include a safety valve, water level indicator and fuse plug. A steam drum
is used in the company of a mud-drum/feed water drum which is located at a lower
level. So that it acts as a sump for the sludge or sediments which have a tendency to
the bottom.
11. Super Heater
A Super heater is a device in a steam engine that heats the steam generated by the
boiler again increasing its thermal energy and decreasing the likelihood that it will
condense inside the engine. Super heaters increase the efficiency of the steam engine,
and were widely adopted. Steam which has been superheated is logically known
as superheated steam; non-superheated steam is called saturated steam or wet steam;
Super heaters were applied to steam locomotives in quantity from the early 20th
century, to most steam vehicles, and so stationary steam engines including power
stations.
12. Economizers
Economizer, or in the UK economizer, are mechanical devices intended to reduce
energy consumption, or to perform another useful function like preheating a fluid. The
term economizer is used for other purposes as well. Boiler, power plant, and heating,
ventilating and air conditioning. In boilers, economizer are heat exchange devices that
heat fluids , usually water, up to but not normally beyond the boiling point of the
fluid. Economizers are so named because they can make use of the enthalpy and
improving the boiler‟s efficiency. They are a device fitted to a boiler which saves
energy by using the exhaust gases from the boiler to preheat the cold water used the
13
fill it (the feed water). Modern day boilers, such as those in cold fired power stations,
are still fitted with economizer which is decedents of Green‟s original design. In this
context they are turbines before it is pumped to the boilers. A common application of
economizer is steam power plants is to capture the waste hit from boiler stack gases
(flue gas) and transfer thus it to the boiler feed water thus lowering the needed energy
input , in turn reducing the firing rates to accomplish the rated boiler output .
Economizer lower stack temperatures which may cause condensation of acidic
combustion gases and serious equipment corrosion damage if care is not taken in their
design and material selection.
13. Air Preheater
Air preheater is a general term to describe any device designed to heat air before
another process (for example, combustion in a boiler). The purpose of the air
preheater is to recover the heat from the boiler flue gas which increases the thermal
efficiency of the boiler by reducing the useful heat lost in the fuel gas. As a
consequence, the flue gases are also sent to the flue gas stack (or chimney) at a lower
temperature allowing simplified design of the ducting and the flue gas stack. It also
allows control over the temperature of gases leaving the stack.
14. Precipitator
An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device
that removes particles from a flowing gas (such As air) using the force of an induced
electrostatic charge. Electrostatic precipitators are highly efficient filtration devices,
and can easily remove fine particulate matter such as dust and smoke from the air
steam.
ESP‟s continue to be excellent devices for control of many industrial particulate
emissions, including smoke from electricity-generating utilities (coal and oil fired),
salt cake collection from black liquor boilers in pump mills, and catalyst collection
from fluidized bed catalytic crackers from several hundred thousand ACFM in the
largest coal-fired boiler application.
The original parallel plate-Weighted wire design (described above) has evolved as
more efficient ( and robust) discharge electrode designs were developed, today
14
focusing on rigid discharge electrodes to which many sharpened spikes are attached ,
maximizing corona production. Transformer –rectifier systems apply voltages of 50-
100 Kilovolts at relatively high current densities. Modern controls minimize sparking
and prevent arcing, avoiding damage to the components. Automatic rapping systems
and hopper evacuation systems remove the collected particulate matter while on line
allowing ESP‟s to stay in operation for years at a time.
15. Fuel gas stack
A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure
through which combustion product gases called fuel gases are exhausted to the
outside air. Fuel gases are produced when coal, oil, natural gas, wood or any other
large combustion device. Fuel gas is usually composed of carbon dioxide (CO2) and
water vapor as well as nitrogen and excess oxygen remaining from the intake
combustion air. It also contains a small percentage of pollutants such as particulates
matter, carbon mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are
often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the exhaust
pollutants over a greater aria and thereby reduce the concentration of the pollutants to
the levels required by governmental environmental policies and regulations.
When the fuel gases exhausted from stoves, ovens, fireplaces or other small sources
within residential abodes, restaurants , hotels or other stacks are referred to as
chimneys.
3.2 BOILER MAINTENANCE DIVISION I/II/III (BMD-I/II/III)
As the name suggests this unit maintains the boiler and checks out its proper functioning.
There are 5 boilers 3 of 95 MW and 2 of 210 MW each. Each boiler is considered as one unit.
Structure of units 1,2,3 is same and so is of unit 4,5
Units 1/2/3 (95 MW each)
1. I.D Fans 2 in no.
2. F.D Fans 2 in no.
3. P.A.Fans 2 in no.
4. Mill Fans 3 in no.
15
5. Ball mill fans 3 in no.
6. RC feeders 3 in no.
7. Slag Crushers 5 in no.
8. DM Make up Pump 2 in no.
9. PC Feeders 4 in no.
10. Worm Conveyor 1 in no.
11. Turnikets 4 in no.
Units 4/5 (210 MW each)
1. I.D Fans 2 in no.
2. F.D Fans 2 in no.
3. P.A Fans 2 in no.
4. Bowl Mills 6 in no.
5. R.C Feeders 6 in no.
6. Clinker Grinder 2 in no.
7. Scrapper 2 in no.
8. Seal Air Fans 2 in no.
9. Hydrazine and
Phosphorous Dozing
2 in no.
2/3 in no.
16
Coal Handling Plant and New Coal Handling Plant (CHP/ NCHP)
The old coal handling plant caters to the need of units 2,3,4,5 and 1 whereas the latter
supplies coal to units 4 and V.O.C.H.P. supplies coal to second and third stages in the
advent coal to usable form to (crushed) form its raw form and send it to bunkers, from
where it is send to furnace.
17
Major Components
1. WAGON TIPPLER: - Wagons from the coal yard come to the tippler and are emptied
here. The process is performed by a slip –ring motor of rating: 55 KW, 415V, 1480 RPM.
This motor turns the wagon by 135 degrees and coal falls directly on the conveyor
through vibrators. Tippler has raised lower system which enables is to switch off motor
when required till is wagon back to its original position. It is titled by weight balancing
principle. The motor lowers the hanging balancing weights, which in turn tilts the
18
conveyor. Estimate of the weight of the conveyor is made through hydraulic weighing
machine.
2. CONVEYOR: - There are 14 conveyors in the plant. They are numbered so that their
function can be easily demarcated. Conveyors are made of rubber and more with a speed of
250-300m/min. Motors employed for conveyors has a capacity of 150 HP. Conveyors have a
capacity of carrying coal at the rate of 400 tons per hour. Few conveyors are double belt, this
is done for imp. Conveyors so that if a belt develops any problem the process is not stalled.
The conveyor belt has a switch after every 25-30 m on both sides so stop the belt in case of
emergency. The conveyors are 1m wide, 3 cm thick and made of chemically treated
vulcanized rubber. The max angular elevation of conveyor is designed such as never to
exceed half of the angle of response and comes out to be around 20 degrees.
3. ZERO SPEED SWITCH:-It is safety device for motors, i.e., if belt is not moving and the
motor is on the motor may burn. So to protect this switch checks the speed of the belt and
switches off the motor when speed is zero.
4. METAL SEPERATORS: - As the belt takes coal to the crusher, No metal pieces should go
along with coal. To achieve this objective, we use metal separators. When coal is dropped to
the crusher hoots, the separator drops metal pieces ahead of coal. It has a magnet and a belt
and the belt is moving, the pieces are thrown away. The capacity of this device is around 50
kg. .The CHP is supposed to transfer 600 tons of coal/hr, but practically only 300-400 tons
coal is transferred.
5. CRUSHER: - Both the plants use TATA crushers powered by BHEL motors. The crusher
is of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed to crush the pieces
to 20 mm size i.e. practically considered as the optimum size of transfer via conveyor.
6. ROTARY BREAKER: - OCHP employs mesh type of filters and allows particles of 20mm
size to go directly to RC bunker, larger particles are sent to crushes. This leads to frequent
clogging. NCHP uses a technique that crushes the larger of harder substance like metal
impurities easing the load on the magnetic separators.
19
Milling System
1. RC Bunker: - Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4
& ½ tons of coal are fed in 1 hr. the depth of bunkers is 10m.
2. RC Feeder: - It transports pre crust coal from raw coal bunker to mill. The quantity of
raw coal fed in mill can be controlled by speed control of aviator drive controlling
damper and aviator change.
3. Ball Mill: - The ball mill crushes the raw coal to a certain height and then allows it to
fall down. Due to impact of ball on coal and attraction as per the particles move over each
other as well as over the Armor lines, the coal gets crushed. Large particles are broken by
impact and full grinding is done by attraction. The Drying and grinding option takes place
simultaneously inside the mill.
4. Classifier:- It is an equipment which serves separation of fine pulverized coal particles
medium from coarse medium. The pulverized coal along with the carrying medium
strikes the impact plate through the lower part. Large particles are then transferred to the
ball mill.
5. Cyclone Separators: - It separates the pulverized coal from carrying medium. The
mixture of pulverized coal vapour caters the cyclone separators.
6. Turniket: - It serves to transport pulverized coal from cyclone separators to pulverized
coal bunker or to worm conveyors. There are 4 turnikets per boiler.
7. Worm Conveyor: - It is equipment used to distribute the pulverized coal from bunker
of one system to bunker of other system. It can be operated in both directions.
8. Mills Fans: - It is of 3 types
Six in all and are running condition all the time.
(a) ID Fans: - Located between electrostatic precipitator and chimney.
Type-radical
Speed-1490 rpm
20
Rating-300 KW
Voltage-6.6 KV
Lubrication-by oil
(b) FD Fans: - Designed to handle secondary air for boiler. 2 in number and
provide ignition of coal.
Type-axial
Speed-990 rpm
Rating-440 KW
Voltage-6.6 KV
(c) Primary Air Fans: - Designed for handling the atmospheric air up to 50
degrees Celsius, 2 in numbers,and they transfer the powered coal to
burners to firing.
Type-Double suction radial
Rating-300 KW
Voltage-6.6 KV
Lubrication-by oil
Type of operation-continuous
9. Bowl Mill: - One of the most advanced designs of coal pulverizes presently
manufactured.
Motor specification –squirrel cage induction motor
Rating-340 KW
Voltage-6600KV
Curreen-41.7A
Speed-980 rpm
Frequency-50 Hz
No-load current-15-16 A
New Coal Handling Plant (NCHP)- Flow
1. Wagon Tippler:-
Motor Specification
(i) H.P 75 HP
(ii) Voltage 415, 3 phase
(iii) Speed 1480 rpm
(iv) Frequency 50 Hz
21
(v) Current rating 102 A
2. Coal feed to plant:-
Feeder motor specification
(i) Horse power 15 HP
(ii) Voltage 415V,3 phase
(iii) Speed 1480 rpm
(iv) Frequency 50 Hz
3. Conveyors Nomenclature:-
10A, 10B/11A, 11B/12A, 12B/13A, 13B/14A, 14B/15A, 15B/16A, 16B/17A, 17B/18A, 18B.
4. Transfer Point 6
5. Breaker House
6. Rejection House
7. Reclaim House
8. Transfer Point 7
9. Crusher House
10. Exit
The coal arrives in wagons via railways and is tippled by the wagon tipplers into the hoppers.
If coal is oversized (>400 mm sq) then it is broken manually so that it passes the hopper
mesh. From the hopper mesh it is taken to the transfer point TP6 by conveyor 12A ,12B
which takes the coal to the breaker house , which renders the coal size to be 100mm sq. the
stones which are not able to pass through the 100mm sq of hammer are rejected via
conveyors 18A,18B to the rejection house . Extra coal is to sent to the reclaim hopper via
conveyor 16. From breaker house coal is taken to the TP7 via Conveyor 13A, 13B. Conveyor
17A, 17B also supplies coal from reclaim hopper, From TP7 coal is taken by conveyors 14A,
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14B to crusher house whose function is to render the size of coal to 20mm sq. now the
conveyor labors are present whose function is to recognize and remove any stones moving in
the conveyors . In crusher before it enters the crusher. After being crushed, if any metal is
still present it is taken care of by metal detectors employed in conveyor 10.
3.3 PLANT AUXILIARY MAINTENANCE (PAM)
This unit of the plant mainly dealt with the auxiliary or helping parts in the plant eg: water
treatment, ash treatment, pump division etc.
This two week of training in this division were divided as follows:
1. Control Structure Pump House (CSPH)
2. Water Treatment Plant (WTP)
3. Ash Pump House (APH)
4. Compressed Air Systems
The details of the above sub units are as follows:
a. Control Structure Pump House (CSPH)
This unit consists of all types of pumps used in plants for purposes like water supply,
ash slurry flow etc. The various types of pumps are :
Sr.No Types No.
1 CRW Pump 3
2 Fire Fighting Pump 2
3 Diesel Fire Pump 1
4 Low Pressure Pump 3
5 High Pressure Pump 6
6 TWS Pump 3
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CRW pump is raw water pump used in CSPH, through which raw water is sent into
water treatment plant to get demineralised water.
Fire Fighting Pump are used to pacify fire, which occurs most of the time in Coal
Handling Plant. These pumps direct the screened or strained water into the areas
where fire has started.
Diesel Fire Pump is an alternative to Fire fighting pump. It acts as spare.
Low Pressure Pump is used to direct treated water into turbines and cooling lines of
units 1, 2, 3, 4, 5.
In case LP pump is not able to send water up to unit 4 or 5, HP pumps are used. High
Pressure Pumps are also used in ash lines, where the ash is directed into slurry pond.
Travelling Water Strainer or TWS pump is used to screen the catchable impurities,
plastics, dirt through screens placed in the inlet of the agra canal channel.
b. Water Treatment Plant (WTP)
The raw water from CSPH is sent to WTP where it is processed and converted into
DM water. This unit has 8 pumps in all, of which 3 pumps are of 210 MW and are
used in running plant, whereas other 5 are 100 MW pumps used in cooling water
circulation. Here, initially raw water is mixed with alum and chlorine, and then passed
through chambers of carbon filter to convert it to clarified water. This water is passed
through resin filter and then mixed with 30 % HCL solution, to form ions. Then it is
passed through cation chamber to separate cations, and similarly anions are removed
through anion chamber. Thus we get carbonated water, this water is passed through
the process of decarbonation, and thus we get DM or Demineralised water.
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The layout of water treatment plant is shown in the below figure:
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c. Ash Pump House (APH)
In the bottom ash system the ash slag discharged from furnace bottom is collected in
two water impounded scraper troughs installed below bottom ash hoppers. The ash is
continuously transported by means of scrapper chain conveyor, on to the respective
cinker grinders which reduces the lump size to required fineness. The crushed ash
from clinker grinders falls into the ash sluice trench provided below bottom ash
hopper from where ash slurry is further transported to ash slurry sump aided by the
ash sluice channel. If the clinker grinder is not in operation , bottom ash can be
discharged directly into the sluice channel through bifurcating chute bypass the
grinder.
The Main types of hoppers used in power plants are:
Water Filter Hoppers
Quencher Cooled Ash Hopper
The various ash disposal systems are:
Fly Ash System
The fly ash collected in these hoppers drop continuously to flushing apparatus
where fly ash gets mixed with flushing water and the resulting slurry drops
into the ash sluice channel. Low pressure water is applied through the nozzle
directing tangentially yto the section of pipe to create turbulence and proper
mixing of ash with water. For the maintenance of flushing apparatus plate
valve is provided between apparatus and connecting chute.
Ash Water System
High pressure water required for B.A. hopper quenching nozzles, B.A.
hoppers window spraying, clinker grinder sealing scrapper bars, cleaning
nozzles, B.A. hopper seal through flushing, Economizer hoppers flushing
nozzles and sluicing trench jetting nozzles is tapped from the high pressure
water ring main provided in the plant area.
Low pressure water required for bottom ash hopper seal through make up,
scrapper conveyor makeup, flushing apparatus jetting nozzles for all..
F.A.hoppers excepting economiser hoppers, is tapped from low pressure water
ring mains provided in the plant area.
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Ash Slurry System
Bottom ash and fly ash slurry of the system is sluiced upto ash slurry pump
along the channel with the aid of high pressure water jets located at suitable
intervals along the channel.
Slurry pump suction line consisting of reducing elbow with drain valve
reducer and butterfly valve and portion of slurry pump delivery line consisting
of butterfly valve, pipe and fittings has also been provided.
d. Compressed Air Systems
Instrument air is required for operating various dampers , burner tilting devices,
diaphragm valves etc., in the 210 MW units. Station air meets the general requirement
of the power statin such as light oil atomising air, for cleaning filters and for various
maintenance works. The control air compressors have been housed separately with
separate receivers and supply headers and their tappings.
Control Air System
These have been installed for supplying moisture free dry air required for instrument
used. The output from the compressor is fed to air receivers via non return valves.
From the receiver air is passed through the dryers to the main instrument air line
which runs alongwith the boiler house and turbine house of 210 MW unit.
There is one interconnection between service air and instrument air headers just at the
inlet of drying units. This connection has been provided as an emergency provision to
meet the requirement of instrument air in case of non-availability of instrument air
compressor. The line connecting the service air header with instrument air header is
provided with two isolating valves , one oil separator, one activated carbon filter, one
non return valve and one regulating valve. Oil and dust free air is supplied to the
instrument air header which is then passed through air drier units. Instrument air
compressor are of double acting horizontal cross head type of two opposed cylinder.
The compressors are driven by electric motor through V belts. Gear wheel type
lubricating oil pump is provided to feed the main bearing. Connecting rod bearing and
cross heads of one side ie. to the opposite side of crank shaft rotation piston. The
compressor is equipped with water cooled inter cooler or header, pressure regulator to
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load and unload the compressor and safety valves for first and second stages. The
suction air filter is at the middle of the cylinder so that air can enter at both ends of the
piston. After compression the air passes through the delivery valves to the intercooler
where the air is cooled and enters the HP cylinder. The entrapped air in HP side is
compressed in a similar manner as in LP cylinder to the required pressure and enters
the header connected to the HP cylinders through the delivery valves and then finally
to the air receiver.
Air Drying Unit
Air contains moisture which tends to condense, and cause trouble in operation of
various devices by compressed air. Therefore drying of air is accepted widely in case
of instrument air. Air drying unit consists of dual absorption towers with embedded
heaters for reactivation. The absorption towers are adequetly filled with specially
selected silica gel and activated alumina .While one tower is drying the air , the other
tower is under reactivation. Thus the unit maintains continuous supply of dry air for
plant requirement. Thus the system is completely automatic.
3.4 TURBINE MAINTENANCE DIVISION (TMD)
A turbine, being a form of engine, requires in order to function a suitable working fluid, a
source of high grade energy and a sink for low grade energy. When the fluid flows through
the turbine, part of the energy content is continuously extracted and converted into useful
mechanical work.
The data about the turbine of 210 MW is shown below:
MAIN TURBINE DATA
Rated output of Turbine 210 MW
Rated speed of turbine 3000 rpm
Rated pressure of steam before emergency 130 kg/cm^2
Stop valve rated live steam temperature 535 degree Celsius
Rated steam temperature after reheat at inlet to receptor
valve
535 degree Celsius
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The thermal (steam) power plant uses a dual (vapour + liquid) phase cycle. It is a closed cycle
to enable the working fluid(water) to be used again and again. The cycle used is “Rankine
Cycle” modified to include super heating of steam, regenerative feed water heating and
reheating of steam as shown in figure.
Factors Affecting Thermal Cycle Efficiency
Thermal cycle efficiency is affected by following :
Initial Steam Pressure
Initial Steam Temperature
Steam flow at valve wide open condition 670 tons/hour
Rated quantity of circulating water through condenser 27000 cm/hour
1. For cooling water temperature (degree Celsius) 24,27,30,33
1.Reheated steam pressure at inlet of interceptor valve
in kg/cm^2 ABS
23,99,24,21,24,49,24.82
2.Steam flow required for 210 MW in ton/hour 68,645,652,662
3.Rated pressure at exhaust of LP turbine in mm of Hg 19.9,55.5,65.4,67.7
Operating Principles
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Whether reheat is used or not, and if used reheat pressure and temperature
Condenser Pressure
Regenerative feed water heating
Turbine Components
The Main Turbine
The 210 MW turbine installed in our power stations is predominantly of condensing-
tandom - compound, three cylinder, horizontal, disc and diaphragm, reheat type with
nozzle governing and regenerative system of feed water heating and is coupled
directly with A.C. generator
The various main components of the steam turbine are as follows :
Turbine casings
I. High Pressure Casing
II. Intermediate Pressure Casing
III. Low Pressure Casing
Rotors
I. High Pressure Rotor
II. Intermediate Pressure Rotor
III. Low Pressure Rotor
Blades
Blades fitted in stationary part are called guide blades or nozzles and those fitted in
the rotor are called moving or working blades. The following are three main types of
blades.
I. Cylindrical (or constant profile) blade (fig A)
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II. Tapered cylindrical (Tapered but similar profile)
III. Twisted and varying profile
Sealing glands
To eliminate the possibility of steam leakage to atmosphere from the inlet and exhaust
ends of the cylinder, labyrinth glands of the radial clearance type are provided which
provide a trouble free frictionless sealing.
Emergency Stop Valves and Control Valves
ESV‟s are provided to cut off steam supply and with control valves regulate steam
supply.
Couplings
Since the shaft is made in small parts due to forging limitations and other
technological and economic reasons , the couplings are required between any two
rotors. It permits angular misalignment, transmits axial thrust and ensures axial
location.In 210 MW turbines, coupling between HPT and IPT is of rigid type and
between IPT and LPT is of semi flexible lens type.
Bearings
Barring Gear
Arrangement Of Turbine Auxiliaries
The turbine cycle can be viewed in the form of different systems as given in following
paragraphs
Vacuum System
I. Condenser- 2 per 210 MW unit at the exhaust of LP turbine
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II. Ejectors- One starting and two main ejectors connected to the condenser
located near the turbine
III. C.W. pumps – Normally two per unit of 50 % capacity
Condensate System
I. Condensate Pumps- 3 per unit of 50% capacity each located near the
condenser hot well.
II. LP heaters- Normally 4 in number with no.1 located at ther upper part of the
condenser and nos 2,3,4 around 4m level
III. Deaerator- One per unit located around 18 M level in CD bay
Feed Water System
I. Boiler Feed Pump- 3 per unit of 50% capacity each located in the „0‟ meter
level in TG bay
II. High Pressure Heaters- Normally 3 in number and are situated in the TG bay
Drip Pumps
Generally two in number of 100% capacity each situated beneath the LP heaters
Turbine Lub Oil system
This consists of Main Oil Pump(MOP), Starting Oil Pump(SOP), AC standby oil
pumps and emergency DC oil pump and Jacking Oil Pump (JOP) (one each per unit)
Auxiliary Steam System
The main 16 ata header runs parallel to BC bay at the level of around 18‟M‟.
The arrangement of turbine auxiliaries is shown in the following figure:
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3.5 POLLUTION CONTROL AND WASTE MANAGEMENT
NTPC is committed to the environment, generating power at minimal environmental cost and
preserving the ecology in the vicinity of the plants.Harmony between man and environment is
the essence of healthy life and growth. Therefore, maintenance of ecological balance and a
pristine environment has been of utmost importance to NTPC. It has been taking various
measures discussed below for mitigation of environment pollution due to power generation.
Pollution Control systems:
While deciding the appropriate technology for its projects, NTPC integrates many
environmental provisions into the plant design. In order to ensure that NTPC comply with all
the stipulated environment norms, various state-of-the-art pollution control systems / devices
as discussed below have been installed to control air and water pollution.
Electrostatic Precipitators (ESP):
The ash left behind after combustion of coal is arrested in high efficiency Electrostatic
Precipitators (ESP‟s) and particulate emission is controlled well within the stipulated norms.
The ash collected in the ESP‟s is disposed to Ash Ponds in slurry form.
Flue Gas Stacks:
Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions (SOX,
NOX etc) into the atmosphere.
Low-NOX Burners:
In gas based NTPC power stations, NOx emissions are controlled by provision of Low-NOx
Burners (dry or wet type) and in coal fired stations, by adopting best combustion practices.
Neutralisation Pits:
Neutralisation pits have been provided in the Water Treatment Plant (WTP) for pH correction
of the effluents before discharge into Effluent Treatment Plant (ETP) for further treatment
and use.
Coal Settling Pits / Oil Settling Pits:
In these Pits, coal dust and oil are removed from the effluents emanating from the Coal
Handling Plant (CHP), coal yard and Fuel Oil Handling areas before discharge into ETP.
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DE & DS Systems:
Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in all coal fired
power stations in NTPC to contain and extract the fugitive dust released in the Coal Handling
Plant (CHP).
Cooling Towers:
Cooling Towers have been provided for cooling the hot Condenser cooling water in closed
cycle Condenser Cooling Water (CCW) Systems. This helps in reduction in thermal pollution
and conservation of fresh water.
Ash Dykes & Ash Disposal systems:
Ash ponds have been provided at all coal based stations except Dadri where Dry Ash
Disposal System has been provided. Ash Ponds have been divided into lagoons and provided
with garlanding arrangements for change over of the ash slurry feed points for even filling of
the pond and for effective settlement of the ash particles. Ash in slurry form is discharged
into the lagoons where ash particles get settled from the slurry and clear effluent water is
discharged from the ash pond. The discharged effluents conform to standards specified by
CPCB and the same is regularly monitored.
At its Dadri Power Station, NTPC has set up a unique system for dry ash collection and
disposal facility with Ash Mound formation. This has been envisaged for the first time in
Asia which has resulted in progressive development of green belt besides far less requirement
of land and less water requirement as compared to the wet ash disposal system.
Ash Water Recycling System:
Further, in a number of NTPC stations, as a proactive measure, Ash Water Recycling System
(AWRS) has been provided. In the AWRS, the effluent from ash pond is circulated back to
the station for further ash sluicing to the ash pond. This helps in savings of fresh water
requirements for transportation of ash from the plant.The ash water recycling system has
already been installed and is in operation at Ramagundam, Simhadri, Rihand, Talcher
Kaniha, Talcher Thermal, Kahalgaon, Korba and Vindhyachal. The scheme has helped
stations to save huge quantity of fresh water required as make-up water for disposal of ash.
Dry Ash Extraction System (DAES):
Dry ash has much higher utilization potential in ash-based products (such as bricks, aerated
autoclaved concrete blocks, concrete, Portland pozzolana cement, etc.). DAES has been
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installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon, Farakka,
Talcher Thermal, Korba, Vindhyachal, Talcher Kaniha and BTPS.
Liquid Waste Treatment Plants & Management System:
The objective of industrial liquid effluent treatment plant (ETP) is to discharge lesser and
cleaner effluent from the power plants to meet environmental regulations. After primary
treatment at the source of their generation, the effluents are sent to the ETP for further
treatment. The composite liquid effluent treatment plant has been designed to treat all liquid
effluents which originate within the power station e.g. Water Treatment Plant (WTP),
Condensate Polishing Unit (CPU) effluent, Coal Handling Plant (CHP) effluent, floor
washings, service water drains etc. The scheme involves collection of various effluents and
their appropriate treatment centrally and re-circulation of the treated effluent for various plant
uses.
NTPC has implemented such systems in a number of its power stations such as
Ramagundam, Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, Jhanor
Gandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. These plants have helped to
control quality and quantity of the effluents discharged from the stations.
Sewage Treatment Plants & Facilities:
Sewage Treatment Plants (STPs) sewage treatment facilities have been provided at all NTPC
stations to take care of Sewage Effluent from Plant and township areas. In a number of NTPC
projects modern type STPs with Clarifloculators, Mechanical Agitators, sludge drying beds,
Gas Collection Chambers etc have been provided to improve the effluent quality. The
effluent quality is monitored regularly and treated effluent conforming to the prescribed limit
is discharged from the station. At several stations, treated effluents of STPs are being used for
horticulture purpose.
Waste Management
Various types of wastes such as Municipal or domestic wastes, hazardous wastes, Bio-
Medical wastes get generated in power plant areas, plant hospital and the townships of
projects. The wastes generated are a number of solid and hazardous wastes like used oils &
waste oils, grease, lead acid batteries, other lead bearing wastes (such as garkets etc.), oil &
clarifier sludge, used resin, used photo-chemicals, asbestos packing, e-waste, metal scrap,
C&I wastes, electrical scrap, empty cylinders (refillable), paper, rubber products, canteen
(bio-degradable) wastes, buidling material wastes, silica gel, glass wool, fused lamps &
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tubes, fire resistant fluids etc. These wastes fall either under hazardous wastes category or
non-hazardous wastes category as per classification given in Government of India‟s
notification on Hazardous Wastes (Management and Handling) Rules 1989 (as amended on
06.01.2000 & 20.05.2003). Handling and management of these wastes in NTPC stations have
been discussed below.
Advanced / Eco-friendly Technologies
NTPC has gained expertise in operation and management of 200 MW and 500 MW Units
installed at different Stations all over the country and is looking ahead for higher capacity
Unit sizes with super critical steam parameters for higher efficiencies and for associated
environmental gains. At Sipat, higher capacity Units of size of 660 MW and advanced Steam
Generators employing super critical steam parameters have already been implemented as a
green field project.
Higher efficiency Combined Cycle Gas Power Plants are already under operation at all gas-
based power projects in NTPC. Advanced clean coal technologies such as Integrated
Gasification Combined Cycle (IGCC) have higher efficiencies of the order of 45% as
compared to about 38% for conventional plants. NTPC has initiated a techno-economic study
under USDOE / USAID for setting up a commercial scale demonstration power plant by
using IGCC technology. These plants can use low-grade coals and have higher efficiency as
compared to conventional plants.
With the massive expansion of power generation, there is also growing awareness among all
concerned to keep the pollution under control and preserve the health and quality of the
natural environment in the vicinity of the power stations. NTPC is committed to provide
affordable and sustainable power in increasingly larger quantity. NTPC is conscious of its
role in the national endeavour of mitigating energy poverty, heralding economic prosperity
and thereby contributing towards India‟s emergence as a major global economy.
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4.0 INFERENCE
In these 6 weeks in NTPC/ BTPS, I gained practical experience and earned quite a lot of
information regarding thermal power engineering.
The thermal plant consists of various units. All the main plant running equipments were
divided into units, which were further sub divided into more specific units for their
maintenance and efficient working.
For my four week training, I was assigned the work of three units, which were BMD, PAM
and TMD. These 3 units are explained above in chapter 3, of this report.
Boiler and turbine are the most important part of the power plant, without which the power
plant cannot run. This plant produces 705 MW of electricity, with the help of its 5 units. 3
units of 95 MW each and 2 units of 210 MW each. The 95 MW units were the first ones to be
established followed by the 210 MW units in the later years.
As for the unit PAM, it is equally important. It takes care of all the auxiliary processes going
on in the plant. It provides water to all the parts of the plant with the help of pumps present in
CSPH. Also it produces DM water from raw water by passing it through water treatment
plant. The ash or the waste produced on burning is taken care of, by Ash handling plant. The
compressed air required in any part of the plant is provided by the unit comprising of the
compressor, also known as compressor house.
The fuel used was coal which was pulverized with the help of bowl and ball mills. These
pulverized coal was the fuel burnt in the furnace to produce heat, which then heated the
water to superheated steam. This superheated steam was passed into the turbine rotor, thus
rotating the turbine shafts. To ensure the quality of steam generated a process named as
reheating is taken into account, which increases the dryness fraction of steam or makes it
superheated. Thus as the rotor rotates, it also runs the generator, which produces electricity.
This electricity is then sent to GT junction (Generator- Transformer), through which the
electricity is passed into the switching yard. After which it is distributed into various grids.
The coal is basically brought from Bihar and Jharkhand coal mines, by rail wagons. The
plant has special facility or technique to unload the coal from wagon and include it in
generation process. Thus i learned a lot during my training and hope to use this knowledge
in the future.
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5.0 BIBLIOGRAPHY
NTPC Trainer Manual , By Training Department
Senior Student Training Report , NTPC Nalanda Library
Power Plant Engineering, By- N.V.Ramaswamy
NTPC slides , By- NTPC training Department