CHAPTER: 1 INTRODUCTION Kanti bijlee utpadan nigam limited (Muzaffarpur thermal power station) is a joint venture of National thermal power corporation (N.T.P.C) and Bihar State Electricity Board (B.S.E.B). It is situated in Muzaffarpur district of bihar across National highway. It has a installed capacity of 220 MW (2 X 110 MW).Another two units of 2 X 195 MW is proposed and the work is already started. The coal required for power generation comes from raniganj and mugma.The source of water is old bagmati river and canal. The ash as a result of combustion of coal is deposited at ash dike across the river. 1.1) INTRODUCTION TO THERMAL POWER PLANT 1
Project Training Report of NTPC Thermal Plant, Kanti (Bihar)
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CHAPTER: 1
INTRODUCTION
Kanti bijlee utpadan nigam limited (Muzaffarpur thermal power station) is a joint venture of
National thermal power corporation (N.T.P.C) and Bihar State Electricity Board (B.S.E.B). It is
situated in Muzaffarpur district of bihar across National highway.
It has a installed capacity of 220 MW (2 X 110 MW).Another two units of 2 X 195 MW is
proposed and the work is already started. The coal required for power generation comes from
raniganj and mugma.The source of water is old bagmati river and canal. The ash as a result of
combustion of coal is deposited at ash dike across the river.
1.1) INTRODUCTION TO THERMAL POWER PLANT
FIG-1 THERMAL POWER PLANT
A thermal power plant is a power plant in which the prime mover is steam driven. Water is
heated, turns in to steam and spins a steam turbine which drives an electrical generator. After it
passes through the turbine, the steam is condensed in a condenser; this is known as Rankine
cycle .such power stations are most usually constructed on a very large scale and designed for
continuous operation.
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Reciprocating steam engines have been used for mechanical power sources since the 18 century,
with notable improvements being made by James watt. The very first commercial central
electrical generating stations in New York and London in 1882 also used reciprocating steam
engines. By the 1920s any central station larger than a few thousands kilowatt would use a
turbine prime mover.
1.2) EFFICIENCY
The efficiency of a conventional thermal power station considered as energy produced at the
plant bus bars compared with the heating value of the fuel consumed ,is typically 33% to 48%
efficient.
1.3) COMPONENTS OF A TYPICAL THERMAL POWER PLANT
1. Cooling tower
2. Cooling water pump
3. Three phase transmission line
4. Step up transformer
5. Electrical generator
6. Boiler feedwater pump
7. Low pressure steam turbine
8. Surface condenser
9. Intermediate pressure steam turbine
10. Steam control valve
11. High pressure steam turbine
12. Feed water heater
13 .Coal conveyor
14.Coal pulverizer
15.Boiler steam drum
16. Bottom ash hopper
17. Superheater
18. Forced draught fan.
19. Reheater
20. Economiser
21. Air preheater
22. Precipitator
23. Induced Draught fan
24. Ash dike
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CHAPTER: 2
FUEL & FUEL HANDLING SPECIFICATIONS
The fuel (coal) used at MTPS comes from two sourses, that are Raniganj and Mugma.The grade
of coal is BCD.
Type of fuel = Pulverized coal, heavy oil & L.D.O.
Number of mills = 06
Type of mills = Pressurized type bowl mill.
Number of PA fan = 02 Number of F.D fan= 02
Number of I.D fan = 03 (1 standby)
2.1) Fuel preparation system:
In coal-fired power stations, the raw feed coal is brought through railway wagons to the coal
storage area. Wagon triplers are used to empty the rail wagons and coal from here are directly
sent to coal conveyer units from where coal is to be forwarded to crusher house for pulverization
and from there further forwarded to coal bunkers beside the boiler through conveyer belts.
Manual coal feeding is carried out through crane.
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FIG-2 WAGON TRIPLER
Conveyer belt arrangement is accompanied by pull cord switch which operates at 16A & 440 V
A.C. It urgently stops the conveyer belt system in case of fault. A number of pull cord switch is
connected in series.
A suspended magnet (16 KVA Electromagnetic separators) is lifted above conveyer belts to
attract metal pieces from the coal passing above the conveyer belts.
FIG-3 CONVEYOR BELTS
2.2) CRUSHER HOUSE:
From the hopper coal reaches to surge hopper through conveyer belts and from there it get
divided in two parts called as vibrating screen 1 and vibrating screen 2. From there fine particles
bypass to number three belt and large pieces of coal goes to the crusher. Shaft of the crusher is
connected to foot coupling drive (FCUI) drive which contains oil at 45 degree empty. More
speed of FCUI drive more speed of crusher so, more crushing of coal. From here pulverized coal
fall on conveyer belt arrangement as shown in figure.
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FIG-4 PULVERIZER
Inside the crusher house there is an induction motor to move the conveyer belts over the rollers.
The specifications of the induction motor are as follows:
Power = 100 KW
Volts = 415
Rpm = 1480
Amperes = 169
Phase = 3
Frequency = 50 Hz
Horse power = 133
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CHAPTER:3
GENERATION OF STEAM
3.1) BOILER:
Type of boiler- single drum, tangential firing & reheat type.
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid
exits the boiler for use in various processes or heating applications.
The pressure vessel in a boiler is usually made of steel, stainless steel or wrought iron. Copper
was often used for fireboxes (particularly for steam locomotives), because of its better thermal
conductivity; however, in recent times, the high price of copper often makes this an uneconomic
choice and cheaper substitutes (such as steel) are used instead.
3.2) BOILER FITTINGS AND ACCESSORIES:
Safety valve: It is used to relieve pressure and prevent possible explosion of a boiler.
Water level indicators: They show the operator the level of fluid in boiler, also known as a
sight
glass, water gauge or water column is provided.
Bottom blow down valves: They provide a means for removing solid particulates that condense
and lay on the bottom of a boiler. As the name implies, this valve is usually located directly on
the bottom of the boiler, and is occasionally opened to use the pressure in the boiler to push
these particulates out.
Continuous blow down valves: This allows a small quantity of water to escape continuously.
Its purpose is to prevent the water in the boiler becoming saturated with dissolved salts.
Saturation will lead to foaming and cause water droplets to be carried over with steam, a
condition known as priming.
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Low water cutoff: It is a mechanical means (usually a float switch) that is used to turn off the
burner or shut off fuel to the boiler to prevent it from running once the water goes below a
certain point ,thus preventing boiler from rupture on account of dry firing.
Surface blow down line: It provides a means for removing foam or other light weight non-
condensable substances that tend to flow on top of the water inside the boiler.
Circulating pump: It is designed to circulate water back to the boiler after it has expelled some
of its heat.
Feed water check valve or clack valve: A no return stop valve in the feed water line. This may
be fitted to the side of the boiler, just below the water level or to the top of the boiler. A top
mounted check valve is called a top feed and is intended to reduce the nuisance of Hme scale. It
doesn't prevent lime scale formation but causes it to be precipitated in a powdery form which is
easily washed out of the boiler.
Chemical injection line: A connection to add chemicals for controlling feed water pH.
3.3) STEAM GENERATION:
After the coal reaches bunkers which are at a height of 53m above the ground ,coal reaches
bunkers through conveyer belts. The bottom of the bunker is coupled to motor which extracts
coal from bunker.
At a height of 15m from the ground there is coal mill or pulverizer. Below the pulverizer there is
a bowl like structure which is movable and a roller is placed at the top of the bowl like structure
which crushes the coal and pulverized coal comes out of the bowl by virtue of centrifugal force.
Now this pulverized coal is brought to the boiler through primary air fan.
There are four mills and corresponding to each mill there is six elevations (A,B,C,D,E,F) and for
each mill the pulverized coal is brought by primary air fan is fed to boiler through six elevations
as given corresponding to each mill.
Inside the boiler pulverized coal is now fed and there are water walls in the boiler which gets
heated on account of combustion of coal & hence steam is generated.
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The generated steam reaches the boiler drum which is above the boiler and it is maintained at
constant pressure such that high temperature steam comes out of the drum. The steam generated
which is not suitably heated is again sent to boiler for further heating where there is ring header
(a small area of heating), inside boiler & steam after getting heated reaches boiler drum due to
density difference & comes out of it.
Air path: External fans are provided to give sufficient air for combustion. The forced draught
fan takes air from the atmosphere and, first warming it in the air preheater for better combustion,
injects it via the air nozzles on the furnace wall.
The induced draught fan assists the FD fan by drawing out combustible gases from the furnace,
maintaining a slightly negative pressure in to avoid backfiring through any opening. At the
furnace outlet and before the furnace gases are handled by the ID fan, fine dust carried by outlet
gases is removed to avoid atmospheric pollution. This is an environmental limitation prescribed
by law, and additionally minimizes erosion of the ID fan.
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CHAPTER:4
COOLING TOWERS
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere.
Cooling towers may either use the evaporation of water to remove process heat and cool the
working fluid or rely solely on air to cool the working fluid.
FIG-5 COOLING TOWER
Common applications include cooling the circulating water used in power plants and achieve
cooling. The towers vary in size from small roof top units to very large hyperboloid structure
that can be up to 200 meters tall and 100 meters in diameter, or rectangular structures that can be
over 40 meters tall and 80 meters long. Smaller towers are normally factory built, while larger
ones are constructed on site.
4.1) D.M. PLANT:
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The water is treated in this portion such that it is free of all the mineral impurities. Hence the
name demineralization plant. Thus the water becomes fit for further use in the boiler drum with
high value of steam formation and least damage to the turbine. This leads to the increases life of
the boiler and an improvement in efficiency.
4.2) BOILER FEED PUMP:
It is a specific type of pump used to pump feed water in to a steam boiler. The water may be
freshly supplied or returning condensate produced as a result of the 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.
4.3) CONDENSER:
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated
through the tubes. The exhaust steam from the low pressure turbine enter the shell where it is
cooled and converted to water by flowing over the tubes as shown in the adjacent diagram. Such
condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air
and gases from the steam side to maintain vacuum.
FIG-6 CONDENSER
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For best efficiency, the temperature in the condenser must be kept as low as practical in order to
achieve lowest possible pressure in the condensing steam. The condenser generally uses either
circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once
through water from a river, lake or ocean.
CHAPTER:5
ASH HANDLING
Coal burnt in the boiler produces a large amount of ash, out of these only 20% of ash settles at
the bottom of the boiler and through ash slurry pumps these are sent to ash dike across river
bagmati. Still 80% of the ash is now with the flue gases. The pressure maintained within the
boiler is negative on account of the reason that-
(a.) Flue gases can be ejected from the boiler easily.
(b.) A cylindrical flame is required in boiler.
(c.) To ensure that there is no backfiring through any of the nozzles.
After the flue gases are ejected from the boiler flue gases passes through superheater, reheater &
economizer. The flue gases coming out of economizer has a temperature of 275-325 degree
Celsius before it enters air preheater. After coming out of the air preheater flue gases get divided
in to two paths-
(a.) First accompanied by induced draught fan.
(b.) Path leading to electrostatic precipitator (E.S.P).
Electrostatic precipitator: Electrostatic precipitator consists of pair of seven plates in which of
a pair first plate is negatively charged and second is positively charged & as a result field is
created. The ash get deposited on the positive plate of the pair of seven plates on all the seven
pair of plates and by continuous hammering , it is removed from the plates and from here it is
deposited at ash dike across river by the use of slurry pumps.
The flue gases consist of carbon dioxide, nitrogen di oxide and sulphur dioxide. Induced draught
fan extract these gases and forward it to chimney from where it is exhausted. The flue gases
coming out of the chimney has a temperature of at least 120 degree Celsius.11
CHAPTER:6
TURBINE: SPECIFICATIONS & OPERATION
Type of turbine: Reheat type
Number of cycles: 3(HP, IP, LP)
Temperature of hp turbine inlet: 535 degree Celsius
Pressure at hp turbine inlet: 130 atm
Temperature at IP turbine inlet: 535 degree Celsius
Turbine speed: 3000 rpm
Condenser vacuum pressure: 0.1 kg/cm^2
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FIG-7 TURBINE
6.1) INTRODUCTION:
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and
converts it in to useful mechanical work.
It has almost completely replaced the reciprocating piston steam engine (invented by Thomas
Newcomen and greatly improved by James watt) primarily because of its greater thermal
efficiency and high power to weight ratio. Because the turbine generates rotary motion, it is
particularly suited to be used to drive an electrical generator -about 80% of all electric
generation in the world is by the use of steam turbines. The steam turbine is a form of heat
engine that derives much of its improvement in thermodynamic efficiency through the use of
multiple stages in the expansion of the steam, which results in a closer approach to the ideal
reversible process.
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6.2) OPERATION OF TURBINE IN UNIT:
There are three stages of operation:
(a.) High pressure (H.P)
(b.) Intermediate pressure (LP)
(c.) Low pressure (L.P)
The three stages of expansion of the steam is used because of the large shaft length. In the first
stage the high pressure steam from the output of the boiler is given to the first turbine unit .The
steam expands on the blades in this stage and sent to the next stage and so on.
NOTE: A special operation motor is mounted on the shaft of the turbine in order to keep it
rotating even in non-generating condition. This is done in order to keep the coupled shaft of the
turbine and the alternator from bending.
From superheater steam divided in two parts, left and right then after they pass through oil
operated control valve. When the pressure of the oil increase up to suitable level plunger above
rises and steam enters the HP turbine. To increase oil pressure we have arrangement in control
room and manual arrangement near HP turbine which when rotated in anti clockwise direction
increases the pressure of oil and plunger rises.
Control valves start opening at 0.7 and get fully opened at 1.5 units of pressure.
After passing through HP turbine steam again enters boiler and after getting heated it enters the
LP
turbine through valves present on left and right positions of the turbine.
Another valve present on LP turbine that is low pressure control valve (L.P.C.L) that is on the
adjacent positions.
L.P.C.L valves starts opening at a pressure of 0.5 units and get fully opened at pressure of 1 unit
of pressure. Steam then enters low pressure turbine, having definite arrangement, when steam
enters inside it gas expands and this in turn rotates the blades of the turbine. The L.P turbine is
coupled to generator which produces electricity.
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Three phase supply is obtained from the stator of the generator through hexagonal pipes which is
connected to generating transformer.
FIG-8 GENERATING TRANSFORMER
CHAPTER:7
GENERATION UNIT/ALTERNATOR
The generation unit consists of the following sub-parts:
(a.) Turbine assembly
(b.) Alternator
(c.) Excitation Transformer.
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FIG-9 GENERATOR
7.1) GENERATOR RATING/SPECIFICATIONS:
MW Rating = 110MW
MVA Rating = 137.5 MVA
KV Rating =11KV (+/- 5 %)
Frequency = 50 Hz
Power Factor = 0.8 lagging
7.2) ALTERNATOR:
An alternator is an electromechanical device that converts mechanical energy to electrical energy
in the form of alternating current.
Most alternators use a rotating magnetic field but linear alternators are occasionally used. In
principle, any AC electrical generator can be called an alternator, but usually the word refers to
small rotating machines driven by automotive and other internal combustion engines. Alternators
in power stations driven by steam turbines are called turbo-alternators.
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Basic principle:
Alternators generate electricity using the same principle as DC generators, namely, when the
magnetic field around a conductor changes, a current is induced in the conductor. Typically, a
rotating magnet, called the rotor turns within a stationary set of conductors wound in coils on an
iron core, called the stator. The field cuts across the conductors, generating an induced emf
(electromotive force), as the mechanical input causes the rotor to turn.
The rotating magnetic field induces an AC voltage in the stator windings. Often there are three
sets of stator windings, physically offset so that the rotating magnetic field produces a three
phase current, displaced by one-third of a period with respect to each other.
The rotors magnetic field may be produced by induction (as in a "brush-less" alternator), by
permanent magnets (as in very small machines), or by a rotor winding energized with direct
current through slip rings and brushes. The rotors magnetic field may even be provided by
stationary field winding, with moving poles in the rotor. Automotive alternators invariably use a
rotor winding, which allows control of the alternators generated voltage by varying the current in
the rotor field winding. Permanent magnet machines avoid the loss due to magnetizing current in
the rotor, but are restricted in size, owing to the cost of the magnet material. Since the permanent
magnet field is constant, the terminal voltage varies directly with the speed of the generator.
Brushless AC generators are usually larger machines than those used in automotive applications.
An automatic voltage control device controls the field current to keep output voltage constant. If
the output voltage from the stationary armature coils drops due to an increase in demand, more
current is fed into the rotating field coils through the Automatic Voltage Regulator or AVR.
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CHAPTER:8
TRANSFORMERS
A transformer is a static device that transfers power from one circuit to another through
inductively coupled electrical conductors without change in frequency.
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FIG-10 TRANSFORMER
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductors—the transformer's coils. A varying current in the first or primary
winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic
field through the secondary winding this varying magnetic field induces a varying electromotive
force (EMF), or "voltage", in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding
and electrical energy will be transferred from the primary circuit through the transformer to the
load. In an ideal transformer, the induced voltage in the secondary winding (V s ) is in proportion
to the primary voltage (V p ) , and is given by the ratio of the number of turns in the secondary (N s )
to the number of turns in the primary (N p ) as follows:
By appropriate selection of the ratio of turns, a transformer thus allows an alternating current
(AC) voltage to be "stepped up" by making N s greater than N p , or "stepped down" by making N s
less than N p .
In the vast majority of transformers, the windings are coils wound around a ferromagnetic core,
air-core transformers being a notable exception.19
Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage
microphone to huge units weighing hundreds of tons used to interconnect portions of power
grids. All operate with the same basic principles, although the range of designs is wide. While
new technologies have eliminated the need for transformers in some electronic circuits,
transformers are still found in nearly all electronic devices designed for household ("mains")
voltage. Transformers are essential for high-voltage electric power transmission, which makes