Unit 3 Power Plant Engineering
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Transcript of Unit 3 Power Plant Engineering
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Power Plant EngineeringUnit 3
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Sources of Energy
Conventional Energy Sources
Non-Conventional Energy Sources Renewable Energy sources
Non-Renewable Energy sources
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Energy Sources
Conventional Energy Source: thermal, nuclearenergy sources.
Non-Conventional Energy Source: Hydel, Wind,solar, Geo-thermal energy sources.
Renewable Energy Source: the sources of energywhich are inexhaustible. Available in abundant
quantity in the earth and they are continuouslyrestore in nature.
Non-Renewable Energy Sources: The energysources which are exhaustible. Fossil fuel &
nuclear power are the example of it.
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Classification of Power Plants
Thermal Power Plant
Hydro-Electrical Power Plant
Nuclear Power Plant
Diesel Power Plant
Gas Power Plant
Solar Energy Power Plant
Wind Energy Power Plant
Tidal Power Plant
Geo Thermal Power Plant
Bio Mass Energy Power Plant
Ocean Thermal Energy Conversion
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Thermal (Steam) Power Plants
Thermal power plant is to convert energy contained
in the fossil fuel into mechanical or electrical energy.
Coal is used as a fossil fuel for thermal power plant
2000 to 3000 tonnes of coal per day are required forthe 200MW capacity power plant.
Layout of thermal power plant
Coal & Ash circuit
Air & Gas circuit
Feed water & steam circuit
Cooling Water circuit.
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Thermal Power Plant
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Coal & Ash Circuit
Coal delivered by ships, trains or trucks to power station
Received in coal storage yard
Sized by crushers, breakers, etc.
Stored in stock yard(coal storage)
Transferred to the boiler furnace by conveyors, elevators
Ash is produced due to the combustion of coal in the furnace
of the boiler.
It is separated in ash precipitator and is mechanically removed.
Ash disposal is a serious problem because ash is coming out in
hot condition and it is highly corrosive
Thermal Power Plant
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Air & Gas Circuit
Air is essential for combustion of coal in the furnace.Atmospheric air is supplied to the furnace either induced draught (I.D) fan or
forced draught (F.D).
The air enters the pre-heater where the temperature of air slightly increased
due to the heat of exhaust gases.
The heated air is supplied to the combustion chamber in the furnace of the
boiler.
The hot flue gases leaving the furnace of the boiler flow over boiler tubes
where water is converted into steam and it passes through the dust
collector.
The hot flue gases pass through the economiser where feed water is pre-
heated.
The hot flue gases pass through the air-preheater where air is pre-heated.
Finally hot flue gases leaves to the atmosphere through chimeny.
Thermal Power Plant
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Feed Water and steam flow circuit
The feed water enters the boiler tubes in which water evaporates
into steam with the application of heat.
The steam is further heated in the super heaters.
The high pressure & temperature steam passes through the steam
turbine where thermal energy of steam is converted into mechanicalenergy and thus to electrical energy.
The exhaust steam flows into condenser. Steam is cooled and
condensed into water by the circulation of cooling water.
The condense water is pumped to the low pressure feed heater andhigh pressure feed heater thus the temperature of feed water get
increased.
The feed water passes through the economiser is further heated up
by the hot flue gases leaving the boiler.
The heated feed water is fed into the boiler.
Thermal Power Plant
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Cooling water circuit
cooling water is required to condense the steam in the condenser. Large quantities of water is required for the purpose.
Water is either taken from river or lake.
When the adequate water supply is not available, the water coming out
from the condenser is cooled either in cooling tower or in the cooling
pond.
Working Principle
It is known as steam power plant
The main element of power plant are boiler, turbine, condenser, feed
pump. Coal is burnt in the furnace of the boiler where hot flue gases flows
over the boiler and water is converted into superheated steam.
The high pressure & temperature steam passes through the steam turbine
where thermal energy of steam is converted into mechanical energy and
thus to electrical energy.
Thermal Power Plant
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Working Principle
The condense water is pumped to the low pressure feed heater and highpressure feed heater thus the temperature of feed water get increased.
The heated feed water is fed into the boiler.
Advantages of thermal power plant
Capital cost is more.
Takes less time for the construction of the power plant
Power developed is constant.
Can be located near to the load centers.
Disadvantages of thermal power plant
Discharge large quantities of SO2 .
Ash disposal is a serious problem.
Large quantities of cooling water required for condensing of steam.
Transportation of coal is very high.
Cost of production of electricity is very high.
Maintenance and operating cost are high.
Thermal Power Plant
H d El i P Pl
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Hydro-Electric Power Plants
H d El i P Pl
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Layout of Hydro-Electric Power Plant
Catchment area
Reservoir
Dam
Trash racks
Gate valve
Surge tank
Penstock
Inlet valve(Nozzle)Water turbine
Draft tube
Tail race
Power house
Hydro-Electric Power Plants
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Working principle
The source of energy is water
Water at higher altitude possess potential energy.
When water falls from higher level to lower level its potential energy is
converted into kinetic energy.
Then the kinetic energy is converted into mechanical energy.
The mechanical energy is drawn by allowing the water to flow through the
hydraulic turbine.
The mechanical energy is utilised to run the electric generator to produce the
electricity.
Hydro-Electric Power Plants
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Advantage of Hydro-electric power plant
No consumption of energy of raw material
It is cheapest in source of energy
Useful life of plant is 100 years
Free from environment pollutionMaintenance cost is very less
Disadvantage of Hydro-electric power plant
Capital cost is high compare to TPP
Takes longer time for construction of plant
Largely depends on the nature
Requires longer transmission line to transmit power to load centre
Hydro-Electric Power Plants
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Diesel Power Plants
Diesel power are more suitable for medium output power plantand have capacities upto 5MW.
Main components of diesel power plant
Diesel engine
Engine air intake system
Fuel system
Exhaust system Cooling system
Lubrication system
Engine starting system
Di l P Pl t
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Diesel Power Plants
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Diesel Power Plants
Working Principle
In diesel engine, air first compressed to a high pressure and
temperature.
A metered quantity of fuel in the form of fine sprays is injected
into the hot compressed air by the fuel injector.
The temperature at the end of compression is sufficient to self-
ignite the fuel and the combustion process begins.
The combustion products expand doing work.
Exhaust of the products then takes place at the end of which
fresh air is taken into the cylinder and the cycle repeats itself.
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Gas Turbine Power Plants
Gas power plant are used for smaller capacities.
It has found application in ship, aircraft engines and locomotives.
Main components of gas turbine power plant
Low pressure compressor(LPC)
Compression is carried out in two stages
Low pressure stage
High pressure stage
An intercooler is provided in between the two stages
The atmospheric air enters the low pressure its pressure is
increased
Air at the exit of LPC is hot due to its pressure rise
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Gas Turbine Power Plants
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Gas Turbine Power Plants
Intercooler
An intercooler is provided in between the two stages of compression
in order to minimize the power required for compression at the
higher stages.
The hot compressed air from LPC enter the intercooler where theheat of the compressed air is removed.
The cooling medium used in the intercooler is water.
High Pressure Compressor
The cooled air coming out of the intercooler is further compressed
in the HPC.
The pressure and temperature of air further increases in HPC.
Nearly 66% of the power developed by high pressure turbine is used
to run the compressor
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Gas Turbine Power Plants
Regenerator
The air from HPC enters the regenerator before it enters into
the combustion chamber.
In this, air is preheated by the exhaust gases coming out of the
turbine.
It is used to make use of this heat.
Combustion chamber
The hot air from regenerator mixes with fuel and the fuel is
burnt in the combustion chamber.
The fuel used in the gas turbine is coal gas.
The products of combustion enters into the HP turbine.
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Gas Turbine Power Plants
High pressure turbine
The hot combination gases expand in the HP turbine.
Almost 65-70% of the total power is developed in this stage.
The power is used to drive the HP compressor and LP
compressor.
The compressors mounted on the same shaft as that of the turbine
shaft.
Low pressure turbine and reheater
The expanded gases coming out of the HP turbine is again burntin the reheater by adding some amount of fuel and the products
of combustion is allowed to expand in the LP turbine.
The remaining 35% of the power developed in this stage used to
generate electrical power.
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Gas Turbine Power Plants
Working Principle
The atmospheric air enter the compressor where it is
compressed to a high pressure and temperature.
The hot air then enters into the combustion chamber and mixes
with the fuel and the fuel is burnt.
The product of combustion expand in the turbine and thus
mechanical energy is produced.
Part of this mechanical energy is used in driving the
compressor mounted on the same shaft.
The remaining part of this mechanical energy is utilized for
producing electric power.
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N l P Pl
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Nuclear Power Plants
Nuclear power plant consist of two main circuits
Primary circuitSecondary circuit
Important elements in primary circuit
Nuclear reactor
Nuclear reactor is an apparatus in which heat is produced due to nuclear
fission chain.
To control and sustain chain reaction , the nuclear fuel should be placed in
a nuclear reactor.
The main function of the nuclear reactor is to control the emission and
absorption of neutrons.
Nuclear reactor may be different types
Pressurized water reactor
Boiling water reactor
Fast breedor reactor
N l P Pl
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Nuclear Power Plants
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Nuclear Power Plants
Reactor core It consists of fuel rods and assemblies
All reactors have a central core in which nuclear fission occurs.
In reactor fuel is used in the form of rods and the moderator surrounds the
fuel elements
Moderator
Fast neutrons are emitted after the fission of uranium atoms.
The fast neutrons are less effective in causing the fission of uranium 235
and try to escape from the reactor.
Moderator are used to reduce the speed of fast neutrons.
The commonly used moderator materials are graphite and heavy water.
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Nuclear Power Plants
Reflector The main purpose of reflector is to turn back neutrons that escape from
the reactor core.
It surrounds the reactor core within the thermal shielding.
In actual practice, the same material can be used for both moderatorand reflector.
Control rods
The control rods are inserted into the reactor core from the top of the
reactor.
The function of the control rod is to absorb the excess neutrons and thechain reaction.
Control rod is used to start and stop nuclear chain reaction.
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Nuclear Power Plants
Thermal shield The reactor is a source of instance radiations like gamma rays and fast
neutrons and these neutrons are very harmful to human life.
To prevent this, a thermal shield which surrounds the entire reactor core
is essential.
Concrete Shield
It absorbs the radiations emitted during emission fission.
The radiation are harmful for living organism
Coolant
The main purpose of coolant is to carry away the heat produced in the
reactor.
The same heat carried by the coolant is used in the heat exchanger for
further utilization in power generation.
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Nuclear Power Plants
Important Element in Secondary CircuitBoiler
The primary coolant in the primary circuit gets heated by absorbing
the fission energy in the reactor core and the some energy is utilized
in the heat exchanger to generate steam.Turbine
The generated steam then passes through a steam turbine where the
thermal energy of steam is further used for generating electric
power.
Condenser and feed pump
The steam coming out of the turbine is condensed in the condenser
and the condensate is supplied back to the boiler with the help of
feed pump.
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Nuclear Power Plants
Advantages Floor space requirement are very less as compared to other power plant of
the same capacity
As very small amount of fuel is needed for nuclear power plant, fuel
transportation and storage cost are minimised.
Nuclear power plant can be located at any place, so they can be established
near rural areas to develop that area.
Power transmission losses are minimised by locating the power plant near
load centres.
Disadvantage
Initial Cost is very high
Disposal of radioactive waste is a serious problem
Cooling water requirements are more
Well trained and highly specialised people are not available in NPP.
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Nuclear Power Plants
Working Principle
Matter consists of minute particles known as atom.
The atom consists of enormous amount of binding energy
Controlled fission of heavier unstable atom such as U235, Th23
This heat energy is utilised to produce steam in heat exchangers and
the steam is passed through the turbine generator set up to produce
electricity.
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Pump Pump are hydraulic machine which convert mechanical energy into
hydraulic energy.
A pump is define as a device, when driven from some extended sources,
lifts water from a lower level to a higher level.
Pump are classified into two types
Reciprocating Pump
Centrifugal Pump The pump which lift water or a liquid from a lower level to a higher level
by the action of sucking the liquid into the cylinder and pushing out the
liquid from the cylinder by the reciprocating motion of piston is known as
reciprocating pump.
The pump which lift water from lower level to a higher level by the actionof centrifugal force which is created by the rotation of impeller in the liquid
is known as centrifugal pump.
Reciprocating pump are called as positive displacement pump.
Centrifugal pump are called as rotodynamic pump.
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R i i P
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Reciprocating Pump
R i i P
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Working Priniciple of Reciprocating Pump
Let the crank be initially at its extreme left position. Now the crank is driven at
an uniform speed by an electric motor.
When the crank start rotating from =0 to 180, the piston moves outwards and
creates a partial vacuum in the cylinder.
The atmospheric pressure acting on the water surface in the sump, forces water to
enter into suction pipe.
The water rises in the suction pipe and forces the suction valve to open and enters
the cylinder. It is called as suction stroke.
When the piston is at the extreme right position =180 the cylinder is full of
water, the suction valve is closed and the delivery valve is just at the point of
opening.
When the crank start rotating from =180 to 360 , the piston moves inwardsand creates a partial vacuum in the cylinder.
The movement of piston right to left increases the pressure of water in the
cylinder to raise above atmospheric, due to which the suction valve closes and
the delivery valve opens. The water then rises in the delivery pipe and supplied
to the upper tank. This is knows as delivery stroke
Reciprocating Pump
R i i P
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Types of Reciprocating Pump
According to Action of Water Single & double acting pump
According to number of cylinder
Single, Double, Triple cylinder pump
According to Existence of air vessels
Without air vessels & without air vessels
Advantages.
It does not need priming.
It has more efficiency.
Disadvantages It operates at lower speed.
It is not able to discharge large quantities of liquid.
It is complicated in construction because of more number of parts.
Reciprocating Pump
R i i P
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Reciprocating Pump
C if l P
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Centrifugal PumpImpeller
The impeller is a wheel which has a series of backward curved vanes.
It is mounted on a shaft which is coupled to an electrical motor, it is enclosing
in the casing.
The fluid enters in the central portion known as the eye of the impeller and
flow out radially outward and it is then discharge around the entire
circumference into the casing.
Casing
It is an air tight chamber that surrounded the impeller
Volute casing
Diffuser casing
Strainer and foot valve
The lower end of the suction pipe is fitted with a strainer and foot valve.
The liquid first enters the strainer and it prevents the debris and impurities to
enter into the impeller.
The foot valve is of non return type and its permits the liquid to flow in theupward direction.
C if l P
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Suction PipeOne end of the suction pipe is connected to the strainer and foot valve
The other end is connected to the eye of the impeller.
A poorly designed suction pipe causes insufficient net positive head,
vibration, noise etc.,Delivery Pipe
A delivery pipe is connected to the flange of the casing and it delivers
the liquid to the upper pump.
The diameter of the suction and delivery pipe are usaully the same.Delivery valve
Nearer to the outlet of the pump on the delivery valve is fitted.
The function of delivery valve is to regulate the discharge from the
pump.
Centrifugal Pump
C t if l P
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Centrifugal Pump
C if l P
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Working Principle
The first step in the operation of centrifugal pump is priming
Priming is the process of filling up the suction pipe, casing and portion of
the delivery valve with the liquid which is to be pumped.
This is required to remove the air from the portion of pump.
If an impeller is made to rotate in the presence of air, only negligible
pressure will be developed. As a result no liquid is lifted up by the pump.
After priming the motor is started and the delivery valve is still kept closed
in order to reduce the starting torque of the motor.
The rotation of the impeller in the casing full of liquid produces a forced
vortex which imparts a centrifugal forces to the liquid and this result in anincreased pressure throughout the liquid mass.
Due to increase in pressure the liquid rushes out of the casing into the
delivery pipe and is discharged into the upper sump.
When the delivery valve is opened, the liquid is discharged through the
delivery pipe.
Centrifugal Pump
C if l P
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AdvantagesInitial Cost is low
It runs at much higher speed.
It is easy to install and maintain.
Efficiency is high.Discharge is high.
Disadvantages
It need to be primed
Centrifugal Pump
T bi
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In steam. Gas or hydroelectric power plant. The device that drivesthe generator is the turbine.
As the fluid passes through the turbine blades which are attached to
the shaft, the shaft rotates and the turbine produces the work.
Turbine is a prime mover in which rotary motion is obtained by the
gradual changes of momentum of fluid.
Turbines are classified into:
Steam turbine
Hydraulic turbine
Gas turbine.
Turbine
Hydraulic Turbine (Water Turbine)
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Machine Which converts hydraulic energy into mechanical energy.
Turbines are installed at place where a continuous supply of water under high
head is available.
Water is carried from the dam to the turbine through large pipes know as
penstock.
Hydraulic turbines are classified into following types:
According to the energy available at inlet
Impulse turbine
Reaction turbine
According to the direction of flow
Tangential flow turbine
Radial flow turbine Axial flow turbine
According to the head at inlet
Low head turbine
Medium head turbine
High head turbine
Hydraulic Turbine (Water Turbine)
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Impulse turbineAll the hydraulic energy of water is converted into kinetic energy when
it enter the impulse turbine.
The jet of water from the nozzle strike against a number of buckets
fixed on the periphery of a wheel, called runner and do work over it.
Pelton Wheel
Water is conveyed from the reservoir to the turbine through penstock.
A powerful jet which comes out of the nozzle, impinges on the vane
provide on the periphery of the wheel.
The water after importing its energy to the turbine is discharged into
the tailrace.
Hydraulic Turbine (Water Turbine)
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Reaction turbine
Water entering the turbine has got pressure as well as kinetic energy.
Only a part of available hydraulic energy is transformed into kinetic
energy before it enters the turbine under pressure.
A air tight casing is necessary for a reaction turbine.
Different types of reaction turbine
Francis Turbine
Kaplan Turbine
The water flows parallel to the axis of rotation.
The shaft of the turbine is vertical and lower end of the shaft is made
larger to form the boss or hub. A number of vanes are fixed to the boss.
The turbine is enclosed in a scrolling casing which receives water from
the main.
From the scrolling casing water is directed to the runner blades through
Hydraulic Turbine (Water Turbine)