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SUMMER TRAINING
REPORT
AT
NTPC, TANDA
Submitted To: Submitted By:
Mr. Sandhya Srivastava Arpit Tripathi
Manager [HR-EDE] Mechanical Engineering Pro.
NTPC, Tanda Govt. Polytechnic Ayodhya
Ambedkar Nagar 224001
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ACKNOWLEDGEMENT
I hereby take this opportunity to thank NTPC Tanda for giving me this
opportunity to conduct my training in NTPC Tanda. I am grateful to Mr.
A.P. Pandey Sir for allowing me to conduct my training . I am heartily
indebted to my guide Mr. S.C. Dwivedi Sir for providing me with detailed
in depth knowledge and very useful information about the process and
system used in the plant. His support was instrumental in my training being
fruitful. I am also thankful to the entire officers and staff of NTPC
Tanda for extending a helping hand whenever I need it.
``WITH REGARDS
Arpit Tripathi
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BRIEF DESCRIPTION OF TANDA THERMAL
PROJECT
Geographical location:-The TANDA Thermal Power Project is located
about 185kms from Lucknow. It is nearly 55kms from Faizabad. The nearest rail ahead
is Akbarpur (now called as Ambedkar Nagar). The project lies in the Ambedkar Nagar
district and is about 22 km from the nearest railway station.
The complete project is situated on the bank of Saryu River. The climate conditions are
quite favourable with greenery all around.
Features:- The plant has been designed by M/s. Desein. The installed capacity is
4 X 110 MW.
The water requirement of the station is met from the Saryu River through Mehripur
pumping Station constructed for feeding Mehripur Pump Canal. The coal linkages for
the station have been provided from North Karnpura & BCCL. The power generation
is evacuated through 220kV feeders connected to Sultanpur (2 feeders), Basti &
Gorakhpur (1 each) 220kV substations.
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PRODUCTION OF ELECTRICITY
The means and steps involved in the production of electricity in a coal-fired power
station are described below.
The coal, brought to the station by train or other means, travels from the coal handling
plant by conveyer belt to the coal bunkers, from where it is fed to the pulverizing mills
which grinds it as fine as face powder. The finely powdered coal mixed with pre-heated
air is then blown into the boiler by fan called Primary Air Fan where it burns, more
like a gas than as a solid in convectional domestic or industrial grate, with additional
amount of air called secondary air supplied by Forced Draft Fan. As the coal has been
grounded so finely the resultant ash is also a fine powder. Some of this ash binds
together to form lumps which fall into the ash pits at the bottom of the furnace. The
water quenched ash from the bottom of the furnace is conveyed to pits for subsequent
disposal or sale. Most of ash, still in fine particles form is carried out of the boiler to
the precipitators as dust, where it is trapped by electrodes charged with high voltage
electricity. The dust is then conveyed by water to disposal areas or to bunkers for sale
while the cleaned flue gases pass on through ID Fan to be discharged up the chimney.
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Meanwhile he heat released from the coal has been absorbed by the many kilometres
of tubing which line the boiler walls. Inside the tubes the boiler feed water which is
transformed by the heat into the steam at high pressure and temperature. The steam
super-heated in further tubes (Super Heater) passes to the turbine where it is discharged
through the nozzles on the turbine blades. Just the energy of the wind turns the sail of
the wind-mill, so the energy of the steam.
Coupled to the end of the turbine is the rotor of the generator – a large cylindrical
magnet, so that when the turbine rotates the rotor turns with it. The rotor is housed
inside the stator having heavy coils of copper bars in which electricity is produced
through the movement of the magnetic field created by the rotor. The electricity passes
from the stator winding to the step-up transformer which increases its voltage so that
it can be transmitted efficiently over the power lines of the grid.
The steam which has given up its heat energy is changed back into water in the
condenser so that it is ready for re-use. The condenser contains many kilometres of
tubing through which the colder is constantly pumped. The steam passing around the
tubes looses the heat and is rapidly changed back to water. But the two lots of water
(i.e. boiler feed water & cooling water) must NEVER MIX. The cooling water is drawn
from the river, but the boiler feed water must be absolutely pure, far purer than the
water we drink, if it is not to damage the boiler tubes. Chemistry at the power station
is largely the chemistry of water.
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To condense the large quantities of steam, huge and continuous volume of cooling
water is essential. In most of the power stations the same water is to be used over and
over again. So the heat which the water extracts from the steam in the condenser is
removed by pumping the water out to the cooling towers. The cooling towers are
simply concrete shells acting as huge chimneys creating a draught
(natural/mechanically assisted by fans) of air. The water is sprayed out at the top of
towers and as it falls into the pond beneath it is cooled by the upward draught of air.
The cold water in the pond is then circulated by pumps to the condensers. Inevitably,
however, some of the water is drawn upwards as vapours by the draught and it is this
which forms the familiar white clouds which emerge from the towers seen sometimes.
Why bother to change stem from the turbine back into water if it has to be heated up
again immediately? The answer lies in the law of physics which states that the boiling
point of water is related to pressure. The lower the pressure, the lower the temperature
at which water boils. The turbine designer want as low boiling point of water as
possible because he can only utilize the energy of the steam – when the steam changes
back into water he can get NO more work out of it. So a condenser is built, which by
rapidly changing the steam back into water creates a vacuum. This vacuum results in
a much lower boiling point which, in turns, means he can continue getting work out of
the stem well below 100 degree Celsius at which it would normally change into water.
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DESCRIPTION OF THERMAL PLANT
The plant is in fact designed on the modern concept of unit system. Each of the
turbogenerator is connected to its individual steam generating plant. The steam turbine
has inlet steam pressure of about 130kg/cm2 and super heat type with a reheat
temperature of 540 0C. Regenerative feed heating with 8 stages heaters have been
adopted. There are two high pressure feed water heaters connected with the exhaust of
the H.P cylinder and the second one from an extraction of I.P cylinder.
Constant pressure de-aeration is adopted for de-aeration and is fed from auxiliary
system header of the plant which maintains the de-aeration pressure of 6kg/cm2 under
all load conditions.
There are five low pressure heaters – two connected to the IP (Intermediate Pressure)
heaters. The heat input from the grand steam condenser and the ejector condenser is
also recovered to improve the cycle efficiency. Drip pump is also used to pump the
drain from the 3rd LP (Low Pressure) heater back to the condensate system. This also
adds to the efficiency of the system. Drains from various stages of steam turbine are
treated so that the maximum thermodynamics benefit is derived.
The plant is also provided with automatic control features. The operation of the Coal
Handling, Ash Handling, Water treatment Plant, River water Intake pump is provided
with remote as well as local manual control features to cope with the requirements of
such large units.
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BASIC CYCLE OF A POWER PLANT
For proper functioning of a power plant, its working operation has been divided into
following main operation cycles.
• Steam cycle
• Feed water cycle
• Condensate water cycle
• Primary air cycle
• Flue gas cycle
• Secondary air cycle
IMPORTANT EQUIPMENTS OF PLANT
1.Mechanical Equipments:-
Steam generating unit
Mechanical Dust Collector & Electrostatic Precipitators
Turbine Generator Unit
Condensing Equipments
De-aerating heater & Closed heaters
Boiler
A steam generator is a complex integration of following accessories:
1. Economiser 7. Div panels
2. Boiler drums 8. Platen SH
3. Down comers 9. Reheater
4. CCW pumps 10. Burners
5. Bottom ring header 11. APHs
6. Water walls
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1. Economizer:- Boiler Economiser is feed-water heaters in which the heat from
waste gases is recovered to raise the temperature of feed-water supplied to the
boiler.
2. Boiler Drum:- It is an enclosed Pressure Vessel. Heat generated by Combustion
of Fuel is transferred to water to become steam.
3. Boiler drum level control:- Important for both plant protection and equipment
safety. Maintain drum up to level at boiler start-up and maintain the level at
constant steam load.
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4. Down comers:- It carries water from boiler drum to the ring header.
5. Water wall:- These are membrane walls, no. of tubes are joined.
2. Electrical Equipments:-
a.) Generator:- The generator is directly coupled with its respective turbine
normally rated for 110 MW at 0.88 power factor (i.e. 125 MVA), 11kV, 3 phases,
50Hz. The hydrogen cooling mechanism is used for the generator. The neutral
point of the generator is earthed through a single phase Distribution Transformer,
the secondary of which is shunted through a suitable resistance. The excitation
system consists of high frequency AC mains and pilot exciters directly driven
from the main shaft, silicon rectifying unit and associated control gears.
b.) Generator Transformer:- The generation voltage of 11kV is stepped up to
220kV by generator-transformer (in short GT) whose low voltages side is
directly connected with the generator through an isolated phase bus duct. The
rating of generator-transformer is 125MVA, 11/220kV, 3 phase, 50 Hz having an
ON/OFF cooling. The high voltage side of the transformer is connected to the
220kV system in 220kV switchyard.
c.) Unit Transformer:- The bus-duct leading from the generator to the GT is tapped
off conveniently for connection to high voltage side of Unit Auxiliary
Transformer used for stepping down the voltage to 6.6kV for supplying power
to the unit auxiliary loads of the power station. The rating of the UAT is 15MVA,
11/6.6kV, 3-phase, 50 Hz.
d.) Start-up cum Reserve Transformer:- Each of the four units draw its start up
power from the 220kV system through two/three windings common start-up cum
reserve transformer rated for 30/10/20 MVA, 220/33/6.6 kV, 3 phase, 50Hz. The
transformer supplies the 33kV load requirements. This transformer also meets
the requirement of station loads like coal & ash handling, compressed air and
water treatment plant, station lightening and other common services as well as
act as a standby source of power to unit auxiliaries.
e.) L.T Auxiliary Transformer:- For further step down of 6.6kV power from the
reserve system for utilization at medium voltage 16 nos. 1000kVA, 6.6kV/415V,
3-phase, 50Hz transformers have been envisaged. The actual requirement is
assessed after detail design of the system. Power for station illumination, unit
wise is provided by five 300kVA, 6.6kV/415V, 3-phase, 4 wire transformers.
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f.) DC Supply System:- A station battery unit, complete with battery charger and
control & distribution system is installed as required for supply to all loads either
for normal operation or during any emergency conditions.
g.) Switchgear:- The drives for auxiliary equipment rated 150kW and above are
operated at 6.6kV and drives having a rating below 150kW are operated at 415V,
3-phase, and 4-wire system having a provision for single phase 230V. For
starting up of these motors suitable switchgears/starters are provided.
h.) 220kV Switch Yard: Generator Transformer step-up the 11 kV voltage
generated by the Generator to 220 kV. This voltage is used to charge the three
buses in the Switch yard which follows Double Bus Bar with Transfer Bus
Scheme. Switch yard provides protection between generator transformer and
transmission lines.
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3. Auxiliary systems: The following auxiliary systems for the 4X110 MW as
envisaged is described below:-
a.) Coal Handling System:- Railway is only the means of transport of coal to this
power station. Annual coal requirement for 4X110 MW units is estimated to be
approximately 13.70 lakhs mega tonnes. The coal yard in the layout is adequate
for about 30 days storage with two coal stock piles and considering 3800 MT of
coal requirement daily.
b.) Fuel Oil System:- The fuel oil is made available to the power station in tank
wagon. The lighter grade oil such as light diesel oil is made available for starting
of boiler from cold condition & furnace oil is made available for flame
stabilisation purpose during low load operation and during any other period
when flame stability is not satisfactory. The oil received from the tank wagon is
pumped into the storage tank. The railway siding facilities provided is able to
accommodate on the rake of tank wagons.
c.) Ash Handling System:- The ash disposal area is within the distance of 4~5kms
from the power station and this is a low lying area. The ash from the boiler
hoppers is conveyed to the ash disposal area either by direct sluicing or hydro-
pneumatic system. Boilers manufactured by M/s. BHEL or AVB are so designed
that it was possible to adopt either of the system for both fly as well as bottom
ash.
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d.) Cooling Water Management:-
Water from the raw water
reservoir is pumped through
clariflocculators. The clarified
water from these clarifloccolator
flows to the cooling water basin
by gravity. A clarified pump is
present which pumps the clarified
water to the DM plant. For this,
three pumps are involved. The
outlets from the cooling water
tower basins are connected to the
common tunnel which takes the
water back to the power house.
e.) Water Treatment Plant:- A
demineralising plant is provided
for supplying make-up water for
the heat cycle. Clarified water is
pumped from the clarified water
storage pit which passes through
pressure filter, activated carbon
filter, caution exchanger,
degassifier, anion exchanger and
mixed bed exchanger. There are
four streams each rated 30m3/hr.
Adequate facilities are provided
for unloading, handling and
storage of chemicals. Waste
effluent is neutralised before it is
discharged to outside drain.
