Higher Technological Institute
Mechanical Engineering Department
Research on
Power Plant Stations
Submitted to:
Dr. Hesham Mostafa
Dr. Amr Hassan
Eng. Abdelrahman Essam
Submitted by
Muhammad Hamdy
20170657
Abstract
A power station, also referred to as a power plant and
sometimes generating station or generating plant, is an industrial
facility for the generation of electric power. Power stations are
generally connected to an electrical grid.
Many power stations contain one or more generators, a rotating
machine that converts mechanical power into three-phase
electric power. The relative motion between a magnetic
field and a conductor creates an electric current.
The energy source harnessed to turn the generator varies widely.
Most power stations in the world burn fossil fuels such
as coal, oil, and natural gas to generate electricity.
Clean energy sources include nuclear power, and an increasing
use
of renewables such
as solar, wind, wave, geothermal,
and hydroelectric.
Acknowledgment
At first, Thanks to ALLAH the most merciful the most
gracious, for this moment has come and this work has been
accomplished.
Thanks to the Higher Technological Institute of 10thRamdan for
preparing me to be a successful Engineer and lifting me up to
achieve this online semester an platform that's full of
encouragement and motivation.
Deepest gratitude is to be delivered to Dr. Hesham Mostafa,
Dr. Amr Hassan and Eng. Abdelrahman Essam
they understood the nature of our thoughts and guided us step
by step till this work brought to light.
Contents
Chapter 1 ...................................................................................................6
Classification of Power Plants .................................................................6
1) Renewable Power Plants ....................................................................6
2) Thermal Power Plants.........................................................................6
1.1 Renewable Power Plants...................................................................7
1.2 Thermal Power Plants .......................................................................8
What is nuclear fission? ........................................................................10
Chapter 2 .................................................................................................19
Combined Power stations.......................................................................19
Chapter 3 .................................................................................................24
Pumps and Valves ...................................................................................24
Chapter 4 .................................................................................................27
Turbines ...................................................................................................27
Introduction
A power plant is an industrial facility used to generate electric
power with the help of one or more generators which converts
different energy sources into electric power. – A power plant or
a power generating station, is basically an industrial location
that is utilized for the generation and distribution of electric
power in mass scale, usually in the order of several 1000 Watts.
These are generally located at the sub-urban regions or several
kilometers away from the cities or the load centers, because of
its requisites like huge land and water demand, along with
several operating constraints like the waste disposal etc.
Electricity is produced at an electric power plant. Some fuel
source, such as coal, oil, natural gas, or nuclear energy produces
heat. The heat is used to boil water to create steam. The steam
under high pressure is used to spin a turbine. – For this reason, a
power generating station has to not only take care of efficient
generation but also the fact that the power is transmitted
efficiently over the entire distance and that’s why, the
transformer switch yard to regulate transmission voltage also
becomes an integral part of the power plant.
Chapter 1
Classification of Power Plants
Overview
A power plant (also known as a power station or power generating
station), is an industrial location that is utilized for the generation and
distribution of electric power on a mass scale. Many power stations
contain one or more generators, a rotating machine that converts
mechanical power into three-phase electric power (these are also known
as an alternator). The relative motion between a magnetic field and an
electrical conductor creates an electric current.
A power generating station can be broadly classified into the two
mentioned types
1) Renewable Power Plants
 Hydroelectric
 Solar
 Wind
2) Thermal Power Plants




Diesel
Gas turbine
Steam
Nuclear
1.1 Renewable Power Plants
1.1.1. Hydroelectric Power Plants
In Hydroelectric plants, the energy of the falling water is utilized to
drive the turbine which in turn runs the generator to produce
electricity. This falling water acquires potential energy which leads to
the rotation of the turbine due to the conversion of potential energy
into kinetic energy. This kinetic energy converted into the generator
which rotates its shaft and generate electric power
Figure 1
Advantages
 Requires no fuel as water is used for the generation of electrical
energy
 Clean as no smoke or ash is used
 Simple in construction
 Requires less maintenance
 Doesn’t require a long starting time like steam power station
 Has a longer life
 Beside generating of electricity, they have many purposes as help
in irrigation and controlling floods
Disadvantages
 Requires high capital cost due to construction of dam
 Skilled and experienced hands are required to build the plant
 It requires high cost of transmission line because the plant located
at hilly areas where water is available where they are away areas
from the consumers
Each type of hydroelectric generation method has an associated output
classification based on its capacity
1.2 Thermal Power Plants
1.2.1. Diesel Power Station
Diesel engine is used as the prime mover for the generator shaft. Produce
low capacity of power from range of 2 to 50 MW.
They are used as standby sets for continuity of supply such as hospitals,
radio stations, cinema theatres and industries
Figure 2
Advantages






Occupies less space
Simple in design
Can be located at any place (portable)
Quick start-up
Requires less quantity of water for cooling
Overall cost is cheaper than that of steam power station of the same
capacity
 Higher thermal efficiency than that of steam power station, This is
plant is ≈ 35% efficient.
 Less operating staff
Disadvantages
 High operation cost (expenses which are related to the operation is
too high.)
 Fuel used(diesel) is costly
 The plant doesn’t work satisfactory under overload conditions for a
longer period however in steam power plant can work under 25%
overload continuously.
 High maintenance and lubrication cost
 The noise is a serious problem
 High maintenance cost
 Short lifetime span
1.2.2. Nuclear Power Station
Nuclear power plants are a type of power plant that use the process
of nuclear fission in order to generate electricity. They do this by
using nuclear reactors in combination with the Rankine cycle, where
the heat generated by the reactor converts water into steam, which spins
a turbine and a generator. Nuclear power provides the world with around
11% of its total electricity, with the largest producers being the United
States and France.
What is nuclear fission?
In the fission process, the nuclei of heavy radioactive atoms are broken
into two nearly equal parts. During this breaking of nuclei, a huge
quantity of energy is released. This release of energy is due to a mass
defect. That means the total mass of the initial product would be reduced
during fission. This loss of mass during fission is converted into heat
energy as per the famous equation established by Albert Einstein.
𝐸 = 𝑚𝑐 2
The basic principle of a nuclear power station is the same as a
conventional thermal power station. The only difference is that, instead
of using heat generated due to coal combustion, here in a nuclear power
plant, the heat generated due to nuclear fission is used to produce steam
from water in the boiler.
Note that: One kg of uranium is equivalent to 4500 metric tons of highgrade coal. That means complete fission of 1 kg uranium can produce as
much heat as can be produced by the complete combustion of 4500
metric tons high-grade coal.
Figure 3
Figure 4
Advantages
 Fuel consumption (nuclear fuel required) is low and so the cost of
generating electricity is less than other conventional power
generation methods.
 High output power
 occupies a much smaller space compared to other conventional
power stations of the same capacity.
 low running charges because as a small amount of fuel is used
for producing bulk electrical energy
 long life span
Disadvantages
 fuel is not easily available, and it is very costly
 The initial cost of constructing a nuclear power station is high as
compared to other power plants
 The products of uranium fission are radioactive, and it may cause
high radioactive pollution.
 High maintenance cost
 Need skilled and specialist trained
1.2.3. Gas Power Station
 Working principle
Air is compressed (squeezed) to high pressure by a compressor. fuel and
compressed air are mixed together in the combustion chamber and
ignited. Hot gases are given off which spin the turbine.
 Description
Gas turbines burn fuels as natural gas. Gas turbines use the hot
gases directly to turn the turbine blades.
 Components
i.
ii.
iii.
iv.
Air Inlet System
Air Compressor
Combustion Chamber
Turbine
1.2.3.1. AIR INLET SYSTEM
Air quality can have an enormous impact on gas turbine performance and
reliability and is heavily influenced by the surrounding environment in
which the unit is installed. Furthermore, within any given location, the
quality of air can change dramatically over a years’ time or, in some
situations, within hours. Poor air quality leads to compressor blades
failure.
Figure 5
 Filter Towers
Any tower Consists of number of filters in 5 rows each filter divided into
two parts the first having cylindrical shape and the second having cone
shape, each row having 280 filter with total number 1400 filter per tower.
These filters remove most of the dirt and other solid contaminants from
entering the compressor.
1.2.3.2. Compressor
The axial-flow compressor section consists of 17 stages of the
compressor rotor and the compressor casing. Within the compressor
casing is the variable inlet guide vanes. The various stages of rotor and
stator blading and the exit guide vanes.
The rotor blades supply the force needed to compress the air in each stage
and the stator blades guide the air so that it enters the following rotor
stage at the proper angle. The compressed air exits through the
compressor discharge casing to the combustion chambers.
 Components
1- Inlet guide vanes
Inlet guide vanes used at compressor inlet to ensure the air enters the
first stage rotor as desired angle.
Figure 6
2-Rotor
The Compressor rotor Blades are kept in place by stacking and punching
in discs to protect it from centrifugal force
Figure 7
3-Stator
Stator blades receive the air at high velocity and act as a diffuser which
changing kinetic energy to pressure.
 The Compressor Rotor Stator stages arrangement
4-Exit guide vanes
At the compressor outlet (Stage 17), there are two exit guide vanes their
purpose is to convert flow velocity into pressure and reduce turbulence of
flow to enter the combustion chamber as a laminar flow.
1.2.3.3. COMBUSTION SYSTEM
In the combustion chamber, the compressed air is mixed with the fuel and
then burnt together. The more air is compressed the more pressurized is
the air, the better the mixture effectively burnt.
Figure 8
Note:
 Temperature of the resulted explosion gasses in the Combustion
chamber is between 1100°𝐶 and 1260°𝐶.
 The thermal efficiency of gas turbines of metal components do not
exceed 36%, researches are underway to use ceramic components
at turbine inlet where temperature of gases could reach above
1350°𝐶 with thermal efficiency of 40%.
Advantages
 Simple in design, construction and operation as compared to steam
power plant since no boilers or any auxiliaries are required
 Small in size
 Initial and operation cost are much lower than steam plant
 Low maintenance cost
 Quick start-up
Disadvantages
 The compressor need a start-up mover for the starting of unit. Once
the unit is started the external power is not needed as turbine itself
supplies the necessary power to the compressor.
 The net output is low, since a large portion of the power developed
by the turbine is used in driving the compressor.
 Low thermal efficiency
Chapter 2
Combined Power stations
 2.1.Overview
Combined cycle gas plants are a type of natural gas power plant used
to generate electricity, consisting of a simple cycle gas plant in
combination with a second steam engine that uses the Rankine cycle. The
hot exhaust gases from the initial gas turbine are sent to the steam engine,
and the heat from them is used to generate steam. This steam can then
expand through another turbine, generating even more electricity and
increasing the plant's overall efficiency. The efficiency of these plants can
be as great as 55%.
 2.2.Operation
The first part of the plant operates by use of a gas turbine and the details
can be explored on its page here. Essentially, it works by compressing air,
injecting fuel and igniting the mixture, which expands through the turbine
causing it to spin. This turbine is connected to a generator, which then
causes electricity to flow. This process creates hot exhaust gases, which
are typically released to the atmosphere in a simple cycle plant
(releasing waste heat).
The exhaust gases are made to flow towards the next unit, called the heat
recovery steam generator (HRSG). The HRSG is essentially a heat
exchanger, in which the heat from the hot gases is used to boil preheat water into steam. The steam then expands through a turbine,
generating electricity. Once the steam has passed through,
it condenses and is recycled through.
 2.3.Main components
1.
2.
3.
4.
5.
Gas turbine and a generator
Generator
Heat Recovery Steam Generators (HRSGs)
Steam Turbine and a generator
Condenser
Note that:
 Each HRSG is located behind a gas turbine, using the exhaust
gases of the GT to produce steam. The steam is supplied to the
steam turbine, which drives a generator.
 The Cairo North Power Station combined cycle consists of 4 gas
turbines (with associated generator), 4 HRSGs and 2 steam turbine
(with associated generator).
 One of the most benefits of the combined cycle is that its thermal
efficiency is much greater than that if each of them worked
separately. As in steam power plant thermal efficiency (𝜂) is less
than 40% while in gas plant is not greater than 36%. While in
combined cycle 𝜂 could be up to 60%.
Brayton cycle
Gas turbine is based on Brayton cycle showed at fig.
1-2: Compression process
2-3: combustion process
3-4: Expansion process
4-1: Heat rejection process
Figure 9
Rankine cycle
Steam power plant is based on Rankine cycle showed at fig.
1-2: Compression (occurs at
water pump)
2-3: Preheating (occurs at
preheaters)
3-4: Evaporation (occurs at the
boiler)
4-5: Superheat (at
superheaters)
Figure 10
5-6: Expansion (at turbine)
6-1: Condensation(condenser)
Combination of Rankine and Brayton cycle
Combined power plant is based on combining both cycles. As showed in
fig. note that the expansion process in this cycle is the reason why
combined cycle is much more greater in thermal efficiency.
Figure 11
2.4.Schematic Of Combined Power Plant
Figure 12
2.5.Heat Recovery Steam Generator
To utilize the hot exhaust gases of the Gas Turbine to heat up water and
to convert the water into pressurized superheated steam.
Description
A heat recovery steam generator (HRSG) is one of the major pieces of
equipment in a gas turbine combined cycle power plant that boasts a high
thermal efficiency and produces minimal CO2 emissions. An HRSG is a
kind of heat exchanger that recovers heat from the exhaust gases of a gas
turbine to an extreme degree. The heat is recovered in the form of steam
which is served as the power source of a power-generating steam turbine.
For the heat-transfer tubes of an HRSG, finned tubes with excellent heattransfer performance are employed.
Main parts









Economiser
Pre-heater
Evaporator
Superheater
Steam drum
Piping
Safety (relief) valves
Attemperators
HRSG construction
HRSG Types
i.
Vertical HRSG
Vertical exhaust gas flows through horizontal tubes
Figure 13
ii.
Horizontal HRSG
Horizontal exhaust gas flows through vertical tubes
Figure 14
Chapter 3
Pumps and Valves
Multistage Centrifugal pumps are the type used in Cairo North Power
Stations due to their high flow rate.
Figure 15
Figure 16
3.1Centrifugal Pumps
3.1.1Overview
A centrifugal pump is a mechanical device designed to move a fluid by
means of the transfer of rotational energy from one or more driven rotors,
called impellers. Fluid enters the rapidly rotating impeller along its axis
and is cast out by centrifugal force along its circumference through the
impeller’s vane tips. The action of the impeller increases the fluid’s
velocity and pressure and also directs it towards the pump outlet.
3.1.2.Working principle
The impeller is the key component of a centrifugal pump. It consists of a
series of curved vanes. These are normally sandwiched between two
discs (an enclosed impeller).
This type of pump. Literally throws the Liquid out Liquid enters the eye
of the impeller, at a designed suction pressure the rotation of the impeller
then throw the Liquid radically out of the edge of the impeller where it is
collected in the case of the pump which is called volute
Impeller types
 Open
 Semi-enclosed
 Enclosed
Figure 17
3.2.Valves
 Relief Valves
it’s a Pressure relieving device
which protecting system against the
unwanted increased pressure.
It Discharge of steam/water when
set pressure is exceeded.
Located on:
i.
ii.
iii.
inlet of preheater & IP economiser
Attemperator spray water lines
Steam drums
 Check valve
When pressure changes in the piping cause flow reversal, check
valves protect against damage caused by backflow
 Control Valve
used to control fluid flow by varying the size of the flow passage as
directed by a signal from a controller.
 Butterfly Valve
A butterfly valve regulates flow by starting, slowing, or stopping media.
The disk opens and closes with a low-torque rotation of 90 degrees and
works for any compatible application. Because they cost less and are
lighter weight, the butterfly valve is often preferred over other types of
valves.
Chapter 4
Turbines
4.1.Overview
is a rotary mechanical device that extracts energy from a fluid flow and converts it into
useful work. The work produced by a turbine can be used for generating electrical power when
combined with a generator.[3] A turbine is a turbomachine with at least one moving part called a
rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so
that they move and impart rotational energy to the rotor.
4.2.Energy Conversion in Steam Turbine
Superheated Steam enters the turbine containing the thermal energy
gained in the boiler tubes. It meets with turbine blades which converts
high thermal energy into high kinetic energy which spins the turbine and
the generator.
4.3.Energy Conversion in Gas Turbine
No fluid media is used to transmit the thermal energy gained in boiler to
the turbine where fuel gas products hit the blades and spins them and in
turn spin the generator.
4.4.Turbine types
The difference between impulse and reaction turbine is generally how
potential form of energy is converted to rotate the turbine wheel.
A working fluid holds potential energy as pressure and kinetic energy as
in velocity.
So depending on this classifications there’s two types:
1. Impulse
2. Reaction
4.4.1. Impulse Turbine
Impulse turbines change the direction of fluid flow or gas jet at high
velocities. The resulting impulse rotates the turbine, the kinetic energy of
fluid flow reduces, and then it leaves the turbine. In the turbine moving
blades, there is no pressure change of the fluid (liquid or gas).
In a steam or gas turbine, all the pressure reduction occurs in the
stationary blades (the nozzles). Before reaching the turbine, the change in
pressure head of the fluid to velocity head takes place by accelerating the
fluid with a nozzle.
Figure 18
 No heat drop and no pressure drop occur in the moving blades.
Then the moving blades mechanical work is simply due to the loss
of a proportion of the velocity obtained in the fixed blades(stator)
4.4.2.Reaction Turbine
Reaction turbines generate torque by reacting to the pressure or mass of the
gas or fluid. The gas or fluid pressure changes passing through the turbine
rotor blades.
In a reaction turbine, the nozzles and blades both work as expanding
nozzles. Therefore, the static pressure reduces across both the fixed and
moving blades. The fixed blades perform as nozzles and guide the flow to
the moving blades at a velocity somewhat higher than the moving blade
velocity.
The following figure demonstrates the axial reaction gas turbine
schematically:
Figure 19
 To maximize the work, usually, multistage turbines including impulse
stages in the first few stages followed by reaction turbines are used.
This is because no axial force acted on the blades of the impulse
turbine as due to their symmetrical cross-sectional area the pressure is
constant. But in reaction turbine blade due to the asymmetry of blades
there’s pressure difference
Conclusion
Power plant generation is of great important of humanity daily life.
It reflects how intelligent is the humanity in creating complex engineering
structures