POWER PLANT 2019.pdfHGUBYBHUBUOBUBGYUYUBGB

Department of Mechanical Engineering
DEDAN KIMATHI UNIVERSITYOFTECHNOLOGY

CourseContents
Course Purpose
Expected Learning Outcome
Course Description
Prerequisite
Text Books
References

1.0Course Purpose
The purpose of this course is to
enable the student to:
1. Learn principles of power
production in a variety of power
generation setups,
2. Design and construct simple
power plants,
3. Analyze the processes,
technology and challenges of
power generation.
▪ At the end of this unit,
the student should be
able to:
1. Classify the various types of
power plants according to the
process/energy source applied,
2. Identify the fundamental
components of a power -
generation plant,
3. Calculate the requirements of a
particular power plant from a
given power demand.
2.0LearningOutcome

3.0Course Description
❑ Steam power plant, cycles and efficiencies:
Boilers, steam turbines, condensers, heat exchangers, Anti pollution
systems and safety.
❑ Internal combustion engines:
Construction and efficiencies; gas turbine, diesel engine, co-
generation, gas and steam combined power plant.
❑ Natural energy power plant:
Construction and operation; geothermal, solar, windmill, water
turbine.
❑ Nuclear power plant:
Pressurized Water Reactor (PWR); BoilingWater Reactor (BWR),
reactor vessel, steam generator. Recycling of used nuclear fuel.

5.0PrescribedTextbooks
1) Veatch B. (1995) Power Plant
Engineering, Springer.
2) Rogers G.F.C. & Mayhew Y.R.,
(1992) Engineering
Thermodynamics, Longman
Singapore Publishers, 4th Ed.
1) Eastop T.D. and
McConkey A., (1993)
Applied
Thermodynamics for
Engineering
Technologists,
Prentice and Hall, 4th
Ed.
2) Burghardt M.D.
▪ EMG 2308
Engineering
Thermodynami
cs III
6.0References
4.0Prerequisites

7.0TeachingMethodology
1) 2 hours of lectures per
week, and;
2) 1 hour tutorials per week
3) Three hours laboratory
work per week
1) Computer laboratory
2) Overhead projector
3) Mechanical Engineering
laboratories and
workshop
8.0InstructionMaterials

9.0Boilers
A boiler is a steam generator
and is basically a closed
vessel made of high
quality steel in which
steam is generated from
water by the application
of heat.

9.0Boilers
A closed vessel in which
water or other fluid is
heated. The fluid does
not necessarily boil. (In
North America the term
"furnace" is normally
used if the purpose is not
actually to boil the fluid.)

9.0Boilers:Applications
The steam from the boiler
can be used for power
generation by expansion
of the same through a
steam turbine, for
process heating, central
/space heating and
sanitation.

9.0Boilers:Materials
Boilers are made from high quality
steel/steel alloys. Copper or
brass is used for live steam
boilers due to good formability
and good thermal
conductivity. In the 19th
century boilers were made
from wrought Iron. Wrought
iron is of high quality and was
used to make boilers for high
pressure applications.

9.0Boilers:Fuels
The source of heat for boilers is combustion such fuels like
biomass (wood, charcoal, briquettes), coal, oil, biogas, or
natural gas. Electric steam boilers use resistance- or
immersion-type heating elements. Nuclear fission is also
used as a heat source for generating steam, either
directly (BWR) or, in most cases, in specialized heat
exchangers called "steam generators" (PWR). Heat
recovery steam generators (HRSGs) use the heat rejected
from other processes such as gas turbines.

9.0Boilers:Classification
➢ Pot or Haycock boiler
➢ Fire tube
➢ Water tube
➢ Flash boilers
➢ Fire tube with water tube firebox (thermic siphon)
➢ Superheated steam boilers
➢ Supercritical boilers

9.0Boilers:Firetube
In fire tube boiler the hot products of combustion pass
through the tubes, which are surrounded, by water. Fire
tube boilers have low initial cost, and they come as
packaged systems. The disadvantage is that they are
prone to explosion, they have a higher water volume with
poor circulation and thus they cannot quickly meet rapid
changes in steam demand. They also have a larger outer
shell for the same steam output as water-tube boiler.

9.0Boilers:Watertube
In water tube boiler, boiler feed water
flows through the tubes and enters
the boiler drum. The circulated water
is heated by the combustion gases
and converted into steam at the
vapour space in the drum. These
boilers are selected when the steam
demand as well as steam pressure
requirements are high as in the case
of process cum power boiler / power
boilers.
Most modern water boiler tube
designs are within the capacity range
4,500 – 120,000 kg/hour of steam, at
very high pressures.

▪ What is the turbine?
▪ What is the principle of steam turbine?
▪ Types of steam turbine.
▪ Component of steam turbine.
▪ Problems in steam turbine.

Whatexactlyistheturbine?
Turbine is an engine that
converts energy of fluid
into mechanical energy
The steam turbine is
steam driven rotary
engine.

Principle of steam turbine:
▪ The steam energy is converted mechanical work by
expansion through the turbine.
▪ Expansion takes place through a series of fixed
blades(nozzles) and moving blades.
▪ In each row fixed blade and moving blade are called
stage.

22
Steam turbine:
• Widely used in CHP(combined heat and power)
applications.
• Oldest prime mover technology
• Capacities: 50 kW to hundreds of MWs
• Thermodynamic cycle is the “Rankin cycle” that uses a
boiler
• Most common types
• Back pressure steam turbine
• Extraction condensing steam turbine
Steam Turbine System:

23
• Steam exits the turbine at a higher pressure that the
atmospheric
Back Pressure Steam Turbine
Figure: Back pressure steam turbine
Advantages:
-Simple configuration
-Low capital cost
-Low need of cooling water
-High total efficiency
Disadvantages:
-Larger steam turbine
Boiler Turbine
Process
HP Steam
Condensate LP
Steam
Steam turbine:

24
• Steam obtained by
extraction from an
intermediate stage
• Remaining steam is
exhausted
• Relatively high
capital cost, lower
total efficiency
Extraction Condensing Steam
Turbine
Boiler Turbine
Process
HP Steam
LP Steam
Condensate
Condenser
Fuel
Figure: Extraction condensing steam turbine
Steam turbine:

Types of steam turbine:
▪ There are two main types
1. Impulse steam turbine
2. Reaction steam turbine

Impulse steam turbine:
▪ The basic idea of an impulse turbine is that a
jet of steam from a fixed nozzle pushes
against the rotor blades and impels them
forward.
▪ The velocity of steam is twice as fast as the
velocity of blade.
▪ Pressure drops take place in the fixed blade
(nozzle).

Thesinglestageimpulseturbine:
▪ The turbine consists of a single rotor to which
impulse blades are attached.
▪ The steam is fed through one or several
convergent nozzles.
▪ If high velocity of steam is allowed to flow
through one row of moving blades.
▪ It produces a rotor speed of about 30000 rpm
which is too high for practical use.

Componentofimpulsesteamturbine:
▪ Main components are
1. Casing
2. Rotor
3. Blades
4. Stop and control valve
5. Oil befell, steam befell
6. governor
7. Bearing(general and thrust bearing)
8. Gear box(epicyclic gear box)
9. Oil pumps

Constructionofsteamturbines
1 – steam pipeline
2 – inlet control valve
3 – nozzle chamber
4 – nozzle-box
5 – outlet
6 – stator
7 – blade carrier
8 – casing
9 – rotor disc
10 – rotor
11 – journal bearing
13 – thrust bearing
14 – generator rotor
15 – coupling
16 – labyrinth packing
19 – steam bleeding (extraction)
21 – bearing pedestal
22 – safety governor
23 – main oil pump
24 – centrifugal governor
25 – turning gear
29 – control stage impulse blading

Reactionsteamturbine:
▪ A reaction turbine utilizes a jet of steam that
flows from a nozzle on the rotor.
▪ Actually, the steam is directed into the
moving blades by fixed blades designed to
expand the steam.
▪ The result is a small increase in velocity over
that of the moving blades.

Problemsinsteamturbine:
▪ Stress corrosion carking
▪ Corrosion fatigue
▪ Pitting
▪ Oil lubrication
▪ Imbalance of the rotor can lead to vibration
▪ Misalignment
▪ Thermal fatigue

BLADEFAILURES:
▪ Unknown 26%
▪ Stress-Corrosion Cracking 22%
▪ High-Cycle Fatigue 20%
▪ Corrosion-Fatigue Cracking 7%
▪ Temperature Creep Rupture 6%
▪ Low-Cycle Fatigue 5%
▪ Corrosion 4%
▪ Other causes 10%

Corrosion:
▪ Resultant damage:
▪ Extensive pitting of airfoils, shrouds, covers,
blade root surfaces.
▪ Causes of failure:
▪ Chemical attack from corrosive elements in
the steam provided to the turbine.

Creep:
▪ Airfoils, shrouds, covers permanently
deformed.
▪ Deformed parts subjected to steam
temperatures in excess of design limits.

Fatigue:
▪ Cracks in airfoils, shrouds, covers, blade
roots.
▪ Loosing of parts (cover, tie wire, etc.)
▪ Exceeded part fatigue life design limit

StressCorrosionCracking:
▪ Cracks in highly stressed areas of the blading.
▪ caused by the combined presence of
corrosive elements and high stresses in highly
loaded locations.

A closed vessel in which steam is condensed by abstracting the heat and where
the pressure is maintained below atmospheric pressure is known as a condenser.

Condensers:
▪ Thermal efficiency of a closed cycle power using steam
as working fluid and working on Carnot cycle is given by
an expression (T1–T2)/T1
▪ The maximum temperature T1 of the steam supplied to
a steam prime mover is limited by material
considerations.
▪ The temperature T2 can be reduced to the atmospheric
temperature if the exhaust of the steam takes place
below atmospheric pressure.
▪ Low exhaust pressure is necessary to obtain low
exhaust temperature. Steam is exhausted into a vessel
known as condenser.

Condensers:
▪ Surface condenser
In surface condensers there is no direct contact between
the steam and cooling water and the condensate can be
re-used in the boiler:
▪ Jet condenser
In jet condensers the exhaust steam and cooling water
come in direct contact with each other. The temperature
of cooling water and the condensate is same when leaving
the condensers.

Condensers:surface
Down-flow type

Condensers:surface
Central FlowType

Condensers:surface
Evaporative Type

Condensers:Jet
Low level jet condensers (Parallel flow type)

Condensers:Jet
High level or Barometric condenser

Condensers:Jet
Ejector Condenser

PollutionControl
❖Coal furnaces combustion contain particles of solid matter-smoke or
dust.
❖smoke indicates that combustion conditions are faulty and amount of
smoke produced can be reduced by improving the furnace design.
❖In spreader stokers and pulverised coal fired furnaces the coal is burnt in
suspension and due to this dust in the form of fly ash is produced.
❖Dust particles are mainly ash particles called fly ash intermixed with
some quantity of carbon ash material called cinders.

PollutionControl
Effects of smoke disposal to the
atmosphere:
1. A smoky atmosphere is harmful to
living beings;
2. In a smoky atmosphere lower
standards of cleanliness are prevalent.
Buildings, clothing, furniture becomes
dirty due to smoke. Smoke corrodes
the metals and darkens the paints.
3. Smoke production is a sign of
incomplete combustion which lead to
economic loss;

PollutionControl
❖To avoid smoke pollution, coal should be completely burnt in the furnace.
The presence of dense smoke indicates poor furnace conditions and a loss in
efficiency and capacity of a boiler plant. A small amount of smoke leaving
chimney shows good furnace conditions whereas smokeless chimney does
not necessarily mean a better efficiency in the boiler room.
❖To avoid the atmospheric pollution the fly ash must be removed from the
gaseous products of
combustion before they leaves the chimney.
❖The removal of dust and cinders from the flue gas is usually effected using
commercial dust collectors which are installed between the boiler outlet
and chimney.

PollutionControl
The various types of dust collectors are as follows :
1. Mechanical dust collectors: Wet (water scrubber) or Dry (cyclone, louvered,
baffle) .
2. Electrical dust collectors: two sets of electrodes, insulated from each other that
maintain an electrostatic field between them at high voltage (30,000 to 60,000 volts).
The flue gases pass between them. The electric field ionises the dust particle
attracting them to the electrode of opposite charge. The dust particles are removed
from the collecting electrode by rapping the electrode periodically.
3. Fly Ash Scrubber: It is similar to a mechanical ash collector but has a flowing water
film on its inner walls. Due to this film, the collected ash is removed more rapidly

Description
❖Internal Combustion Engines poweplants running on Diesel,
furnace oil or gas.
❖Applications of AggrekoTemporary Power Plants
➢Supplementing the grid
➢Seasonal peak shaving
➢Overcoming transmission and distribution limitations
➢Power during planned maintenance or unplanned outages
➢Power for construction or commissioning

Description
❖Aggreko is supplies KenGen with
150 MW of temporary power from
sites at Embakasi and Eldoret.
Additional sites planned for
Naivasha. Additional capacity will
see Aggreko despatch 290 MW to
the national grid.

ICEDescription
❖Oil engines and Gas engines are called Internal Combustion Engines.
❖IC engines fuels burn inside the engine and the products of combustion
form the working fluid that generates mechanical power.
❖Gas Turbines the combustion occurs in another chamber and hot working
fluid containing thermal energy is admitted in turbine.

ICEEngineParts
1) Cylinder-fuel and air are admitted and combustion occurs.
2) Piston-which receives high pressure of expanding hot products of
combustion and the piston, is forced to linear motion.
3) Connecting rod-crankshaft linkage to convert reciprocating motion into
rotary motion of shaft.
4) Connected Load-mechanical drive or electrical generator.
5) Valves (ports) for control of flow of fuel, air, exhaust gases, fuel injection,
and ignition systems.
6) Lubricating & cooling system

OperatingPrinciple
Gas engines and Oil engines operate in the same general way. The
working fluid under-goes repeated cycles. A thermodynamic cycle is
composed of a series of sequential events in a closed loop on P-V or T-S
diagram.
Typical cycle operations:
1) Cylinder is charged
2) Cylinder contents are compressed
3) Combustion (Burning) of charge, creation of high pressure pushing
the piston and expansion of products of combustion.
4) Exhaust of spent products of combustion to atmosphere.
The route taken for these steps is illustrated conveniently on P-V
diagram andT-S diagram for the cycle.

OperatingPrinciple:Cycles
❖There are various types of Gas Engines and Oil Engines
❖classified on the basis of their operating cycles.
1) Carnot Cycle;
2) DieselCycle;
3) Otto Cycle;
4) Sterling Cycle;
5) Bryton Cycle;
6) DualCycle, etc.
❖Two principal categories of IC Engines are:
1) Four Stroke Engines
2) Two Stroke Engines

OperatingPrinciple:4Stroke
❖In a Four Stroke Engine Cycle, the piston strokes are used to obtain the
four steps (intake, compression, expansion, exhaust) and one power
stroke in two full revolutions of crankshaft.

OperatingPrinciple:2-Stroke
❖In a Two Stroke Engine Cycle, one power stroke is obtained during
each full revolution of the crankshaft.

DieselPowerplants
The disadvantages of diesel power plants:
❖High Maintenance and operating costs;
❖High fuel cost;
❖The plant cost per kW is comparatively more.
❖The life of diesel power plant is short;
❖High noise pollution;
❖Very expensive for large scale power provision.

DieselPowerplants
Diesel power plants find wide application in the following fields.
❖They are suitable for mobile power generation and are widely used in
transportation systems consisting of railroads, ships, automobiles and
aeroplanes.
❖They can be used for electrical power generation in capacities from
100 to 5000 H.P.
❖They can be used as standby power plants.

GASTURBINEPOWERPLANTS
❖The gas turbine obtains its power by utilizing the energy of burnt
gases and air, which is at high temperature and pressure by expanding
through the several rings of fixed and moving blades.
❖It resembles a steam turbine and requires large amounts of working
fluid(combustion gases).
❖To get a high pressure (4 to 10 bar) of working fluid, which is essential
for expansion,Centrifugal/Axial compressor, is required.

GasTurbinePowerplants
❖Compressor and the turbine assembled on the same shaft
❖Power output of the turbine is the power input into the compressor
❖Resulting in zero work done
❖Increase in volume of the working fluid under constant pressure or
increase in pressure under constant volume results in net work done
❖Increase in pressure/volume is achieved through a rise in temperature
❖A combustion section is used to raise the temperature of the working
fluid
❖Can work with oil, natural gas, coal gas, producer gas, blast furnace
and pulverized coal.

(a) OPEN CYCLE GASTURBINE
Ambient air enters into the compressor and gases coming out of turbine are
exhausted into the atmosphere, the working medium must be replaced
continuously.

(a) CLOSED CYCLE GASTURBINE
Ambient air enters into the compressor and gases coming out of turbine are
exhausted into the atmosphere, the working medium must be replaced
continuously.

❖Generally, the thermal efficiency of the simple open cycle is only about
16 to 23% as lot of heat energy goes waste in the exhaust gases.
❖ Cycle efficiency directly depends upon the temperature of the inlet
gases to the turbine but metallurgical limitations do not permit the use of
temperatures higher than about 1000°C
❖Regeneration to improve thermal efficiency by preheating the
compressed air before it enters the combustion chamber
❖Reheat-combustion gases expanded through a HPT and the exhaust
gases from HPT reheated through a heat exchanger before the same is
expanded through a LPT.

The latest gas turbine designs use turbine inlet temperatures of 1,500C
(2,730F) and compression ratios as high as 30:1 giving thermal efficiencies
of 35 percent or more for a simple-cycle gas turbine.

COGENERATIONSYSTEMS
❖Decentralized combined heat and power production-cogeneration is a very
flexible and efficient way of utilizing fuels. Cogeneration based on biomass is
environmentally friendly, and all kinds of biomass resources can be used.
❖Cogeneration plants can be used in all situations where there is simultaneous
demand for electrical and thermal power such as district heating, institutions,
industries, etc.
❖Their primary interest fuel use optimization typical efficiencies 85-95% compared
to the relatively low energy efficiency of centralized thermal power plants, 55%
❖Decentralized cogeneration offers possibilities to utilize renewable bio fuels straw,
wood, manure, etc. There are furthermore a few circumstances which are not that
much noticed in the political debate.

COMBINEDCYCLEPOWERPLANTS
❖Considerable amount of heat energy goes to waste with the exhaust of gas
turbine.The energy in the exhaust can still be utilized.
❖The complete use of the energy available to a system is called the total energy
approach. The objective of this approach is to use all of the heat energy in a power
system.
❖The best approach is the use of combined cycles. There are configurations/
combinations of the combined cycles depending upon site and country
requirements. Even nuclear power plant may be used in the combined cycles.

CombinedCyclePowerPlants
❖In the previous slide, combination of an open cycle gas turbine and
steam turbine. The exhaust of gas turbine which has high oxygen content
is used as the inlet gas to the steam generator where the combustion of
additional fuel takes place. This combination allows nearer equality
between the power outputs of the two units than is obtained with the
simple recuperative heat exchanger.
❖The explained system results in higher fuel use efficiency, lower invest
cost to power ratio for the gas turbine.
❖Good cogeneration systems and runs on low quality fuels

9.0SolarEnergy
❖Radiant light and heat from the sun, has been harnessed by
humans since ancient times using a range of ever-evolving
technologies.
❖Solar energy technologies include solar heating, solar
photovoltaic, solar thermal electricity, solar architecture and
artificial photosynthesis
❖Solar technologies are broadly characterized as either
passive solar or active solar depending on the way they
capture, convert and distribute solar energy.

9.0SolarEnergy
❖Active solar techniques include the use of photovoltaic
panels and solar thermal collectors to harness the energy.
❖Passive solar techniques include orienting a building to the
Sun, selecting materials with favourable thermal mass or light
dispersing properties, and designing spaces that naturally
circulate air.

9.0SolarEnergy
❖In 2011, the International Energy Agency said that "the
development of affordable, inexhaustible and clean solar
energy technologies will have huge longer-term benefits. It
will increase countries’ energy security through reliance on an
indigenous, inexhaustible and mostly import-independent
resource, enhance sustainability, reduce pollution, lower the
costs of mitigating climate change, and keep fossil fuel prices
lower than otherwise.These advantages are global.

9.0SolarEnergy
▪ The Earth receives 174 petawatts (PW) of incoming solar
radiation (insolation) at the upper atmosphere.
Approximately 30% is reflected back to space while the rest is
absorbed by clouds, oceans and land masses. The spectrum
of solar light at the Earth's surface is mostly spread across the
visible and near-infrared ranges with a small part in the near-
ultraviolet.

9.0Hydropower
❖Power from falling water
❖Hydropower plants are actually based on a rather simple concept
-- water flowing through a dam turns a turbine, which turns a
generator.
❖As the water falls through a height (H), its potential energy (PE) is
converted into kinetic energy (KE) and this kinetic energy is
converted to the mechanical energy (ME) by water flowing through
hydraulic turbine runner. This mechanical energy is utilized to run an
electric generator which is coupled to the turbine shaft.

9.0Hydropower
▪Dam - Most hydropower plants rely on a dam that holds
back water, creating a large reservoir such as Masinga dam.
▪Intake - Gates on the dam open and gravity pulls the water
through the penstock, a pipeline that leads to the turbine.
Water builds up pressure as it flows through this pipe.
▪Turbine - The water strikes and turns the turbine which is
attached to a generator above it by way of a shaft. The most
common type of turbine for hydropower plants is the
Francis Turbine.

9.0Hydropower
▪Generators - As the turbine blades turn, so do a series of
magnets inside the generator. Giant magnets rotate past
copper coils, producing alternating current (AC).
•Transformer - The transformer inside the powerhouse takes
the AC and converts it to higher-voltage current.
▪Power lines - Out of every power plant come four wires: the
three phases of power being produced simultaneously plus a
neutral or ground common to all three.
▪Outflow - Used water is carried through pipelines, called
tailraces, and re-enters the river downstream.

9.0Hydropower:PumpedStorage
A pumped-storage plant has two reservoirs:
Upper reservoir - Like a conventional hydropower plant, a
dam creates a reservoir. The water in this reservoir flows
through the hydropower plant to create electricity.
Lower reservoir - Water exiting the hydropower plant flows
into a lower reservoir rather than re-entering the river and
flowing downstream.
Using a reversible turbine, the plant can pump water back to
the upper reservoir.

9.0Hydropower:Data
The largest hydroelectric power plant in the world is the
Itaipu power plant, jointly owned by Brazil and Paraguay.
Itaipu can produce 12,600 megawatts.
The second largest hydroelectric power plant is the Guri
power plant, located on Caroni River in Venezuela. It can
produce 10,300 megawatts.
The biggest hydropower plant in Kenya is Kindaruma, it can
generate 115 MW.

9.0Hydropower:Classification
Pico Hydropower <5kW Isolated use, Direct
drives of machines,
isolated electricity
supply to households

9.0Hydropower:Conventional
Hoover Dam
Hydropower
Station, 7000 MW

9.0Hydropower:Conventional
Turkwel Dam
Hydropower
Station, 106 MW

9.0Hydropower:Components (large)

9.0TurbineTypes
REACTIONTURBINES:
▪Francis
▪Kaplan, Propeller
▪Tyson
▪Gorlov
IMPULSETURBINE:
▪Waterwheel
▪Pelton
▪Turgo
▪Crossflow
▪Jonval turbine
▪Reverse overshot water-wheel
Reaction turbines are acted on by water,
which changes pressure as it moves through
the turbine and gives up its energy. They must
be encased to contain the water pressure (or
suction), or they must be fully submerged in
the water flow. For low to medium heads (<30
m to <300m) applications
Impulse turbines change the velocity of a
water jet. The jet pushes on the turbine's
curved blades which changes the direction of
the flow. The resulting change in momentum
(impulse) causes a force on the turbine blades.
Since the turbine is spinning, the force acts
through a distance (work) and the diverted
water flow is left with diminished energy. For
high heads application(>300m)

9.0TurbineTypes:Originalpeltonwheel

9.0TurbineTypes: Francisturbinerunner

9.0Hydropower:PowerCalculation

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