POWER PLANT ENGINEERING

POWER PLANT ENGINEERING

Dr. S. SuyambazhahanM.E., Ph.D. (IITM)

Principal, S.A. Engineering College

Avadi-Poonamallee High Road,

Veeraraghavapuram, Thiruverkadu Post

Chennai, Tamilnadu

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POWER PLANT ENGINEERING

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Several books on “Power Plant Engineering” are available in the market today. But thebuyers must be smart enough to know which book to purchase. The first edition of the bookcomprising five units namely Thermal Power Plants, Hydroelectric Power Plants, NuclearPower Plants, Gas and Diesel Power Plants, and NOn-Conventional Power Generation. It isassured that this book will satisfy the need for why it is bought and also serves as a goodtextbook for both students and faculties. All kinds of suggestions and constructive criticisms areearnestly solicited for enhancements. I dedicate this book to the Almighty for this opportunity.

This book is designed by profoundly comprehending the needs of emerging Electricaland Electronics Engineers and as per the syllabus of fourth semester course “EE2252 PowerPlant Engineering” prescribed by Anna University, Chennai. This book is prepared in avery systematic and self-explanatory approach and the contents are presented in an elegant,comprehensive and lucid fashion with neat diagrams wherever required. The contents of thebook are made available in such a way that even the beginners of the subject can understandthe concepts of Power Plant Engineering and various power plants from the scrap. The contentof the book is sectioned into five units namely Thermal Power Plant, Hydroelectric PowerPlants, Nuclear Power Plants, Gas and Diesel Power Plants, and Non-Conventional PowerGeneration. Particularly topics such as boilers, turbines, condensers, pumps, HydroelectricPower Plants nuclear Power Plants, gas and Diesel Power Plants, various non-conventionalpower generation techniques are elaborately dealt. All the units are provided with ample ofreview questions and solved problems. This book will surely satisfy the students in preparingfor the University examinations and achieving prolific results and also it will quench thethirst of success in preparing other competitive examinations.

—Dr. S. Suyambazhahan

Preface

( v )

Preface (v)

1. Thermal Power Plants 1–841.1 Introduction—Power Plant Engineering ............................................................................... 11.2 Classification of Power Plants ................................................................................................ 11.3 Sources of Energy .................................................................................................................... 1

1.3.1 Conventional Sources of Energy ............................................................................. 11.3.2 Non-Conventional Sources of Energy .................................................................... 21.3.3 Comparison of Sources of Energy ........................................................................... 4

1.4 History of Thermodynamics ................................................................................................... 41.4.1 Temperature and Heat ............................................................................................ 51.4.2 Laws of Thermodynamics ....................................................................................... 71.4.3 Thermodynamic Processes ...................................................................................... 91.4.4 Thermodynamic Cycles ......................................................................................... 10

1.5 Steam or Thermal Power Plant ............................................................................................ 161.6 Major Components of Thermal (Steam) Power Plant ........................................................ 18

1.6.1 Boiler ...................................................................................................................... 181.6.2 Turbines ................................................................................................................. 281.6.3 Condensers ............................................................................................................. 331.6.4 Pumps ..................................................................................................................... 40

1.7 Pulverised Coal Burners ....................................................................................................... 451.8 Principle of Fluidised Bed Combustion (FBC) System ...................................................... 491.9 Coal Handling Systems ......................................................................................................... 561.10 Ash Handling System ........................................................................................................... 621.11 Forced Draught...................................................................................................................... 671.12 Superheaters .......................................................................................................................... 691.13 Regenerator ........................................................................................................................... 751.14 Dearearators (Air Preheaters) ............................................................................................. 751.15 Economizer ............................................................................................................................. 771.16 Cooling Towers ...................................................................................................................... 781.17 Selection of Steam Power Station ........................................................................................ 80Review Questions .............................................................................................................................. 81

Contents

( vii )

( viii )

2. Hydroelectric Power Plant 85–942.1 Introduction ........................................................................................................................... 852.2 Classifications ........................................................................................................................ 852.3 Layout of Hydroelectric Power Plant ................................................................................... 862.4 Dams....................................................................................................................................... 882.5 Selection of Water Turbines ................................................................................................. 882.6 Factors to be Considered While Selecting the Site for Hydroelectric Power Plant ......... 902.7 Pumped-Storage Plants ........................................................................................................ 902.8 Mini Hydro Plants ................................................................................................................. 912.9 Micro Hydro Plant ................................................................................................................. 922.10 Pumped Storage Hydroelectric Power Plants in India ...................................................... 93Review Questions .............................................................................................................................. 93

3. Nuclear Power Plant 95–1263.1 Principles of Nuclear Energy ............................................................................................... 953.2 Elements and Atoms ............................................................................................................. 953.3 Radioactivity .......................................................................................................................... 963.4 Biological Effects of Radiation ............................................................................................. 973.5 Radioactive Decay ................................................................................................................. 973.6 Nuclear Life Cycle ............................................................................................................... 1013.7 Nuclear Energy—Fission and Fusion ................................................................................ 1033.8 Uranium-235 Chain Reaction ............................................................................................ 1063.9 Use of Water for Cooling ..................................................................................................... 1083.10 Nuclear Power Plant Reactors ........................................................................................... 1093.11 Types of Nuclear Reactions ................................................................................................ 1173.12 Outside a Nuclear Power Plant .......................................................................................... 1183.13 The Significant Problems with Nuclear Power Plants ..................................................... 1183.14 Nuclear Power Plants - Safety ........................................................................................... 1183.15 Working Principle of Nuclear Power Plant ....................................................................... 1193.16 General Components of Nuclear Reactor .......................................................................... 1213.17 Merits and Demerits of Nuclear Power Plant ................................................................... 1243.18 Nuclear Power Plants in India ........................................................................................... 124Review Questions ............................................................................................................................ 125

4. Gas Power Plant 127–1454.1 Gas Power Plant .................................................................................................................. 127

4.1.1 Introduction.......................................................................................................... 1274.1.2 Classification of Gas Turbines ............................................................................ 1274.1.3 Closed Cycle Gas Turbine Power Plant ............................................................. 1274.1.4 Open Cycle Gas Turbine Power Plant ............................................................... 1294.1.5 Gas Turbine Plant with Intercooling ................................................................. 1304.1.6. Gas Turbine Plant with Reheating .................................................................... 1304.1.7 Gas Turbine Plant with Regeneration ............................................................... 1324.1.8 Merits and Demerits of Gas Power Plant .......................................................... 1344.1.9 Solved Problems ................................................................................................... 134

4.2 Diesel Engine Power Plant ................................................................................................. 1374.3 Fuel Supply System in Diesel Engine ............................................................................... 138

( ix )

4.4 Types of Diesel Power plants ............................................................................................. 1404.5 Working Principle of Diesel Power Plant .......................................................................... 1414.6 Merits and Demerits of Diesel Power Plant ...................................................................... 1424.7 Application of Diesel Power Plant ..................................................................................... 1424.8 Comparison of Power Plants .............................................................................................. 143Review Questions ............................................................................................................................ 144

5. Non-Conventional Power Generating Systems 146–1905.1 Solar Power Plant ............................................................................................................... 1465.2 Wind Power Generation ...................................................................................................... 1505.3 Tidal Power Generation ...................................................................................................... 1555.4 Geothermal Power Plant .................................................................................................... 1565.5 Ocean Thermal Energy Conversion (OTEC) ..................................................................... 1595.6 Biogas Generation ............................................................................................................... 1635.7 Fuel Cells ............................................................................................................................. 1685.8 MHD Power Generation ..................................................................................................... 1705.9 Typical Configuration of Thermoelectric Power Generation System .......................... 1735.10 Thermionic Power Generation ........................................................................................... 1815.11 Solar Inverter ...................................................................................................................... 183

5.11.1 How an Inverter Works ....................................................................................... 1835.12 Lighting Arrester ................................................................................................................ 186Review Questions ............................................................................................................................ 188

University Question Papers 191–197

Index 198–200

1

1.1 INTRODUCTION—POWER PLANT ENGINEERINGIn the modern scenario, the need for electricity is increasing very rapidly. Electric power isconsidered as the heart of any industry. Electricity is used in our day-to-day life for lighting,heating, lifting, and cooking and so on. Therefore, it is necessary to produce electricity in largescale and also economically. The large scale power production could be achieved only by meansof suitable power producing units like power plants. The most commonly used power plantsare steam/thermal, Gas, Diesel, Hydroelectric and nuclear power plants. The main aspectsconsider while constructing or designing a power plant is the selection of proper location andappropriate equipments for the plant such that maximum output is achieved. The generatedpower must also be cost effective, reliable and fairly uninterrupted.

1.2 CLASSIFICATION OF POWER PLANTSBulk electric power is generated by special plants known as generating stations or powerplants. A generating station consists of a prime mover coupled to an alternator to produceelectric power.

The prime mover converts different energy forms like kinetic energy, potential energy,chemical energy, into mechanical energy. The alternator converts the mechanical energy toelectrical energy.

Depending upon the energies or input converted by prime mover into mechanical energy,the power plants are classified as follows:

1. Steam power plants2. Hydroelectric power plants3. Diesel power plants4. Nuclear power plants.

1.3 SOURCES OF ENERGYThe energy sources can be classified as:

• Conventional energy sources or Non-renewable energy sources• Non-conventional energy sources or Renewable energy sources

1.3.1 Conventional Sources of EnergyThe conventional resources are finite and exhaustible. Once consumed, these sources cannotbe replaced by others. Examples are coal, timber, petroleum, lignite, natural gas, fossil fuels,nuclear fuels etc.

Thermal Power Plants1

2 POWER PLANT ENGINEERING

The examples for conventional sources of energy are:(i) Fossil fuel energy

(ii) Nuclear energy(iii) Hydro energy

Fossil Fuel EnergyFossil fuel is an invaluable source of energy produced due to chemical changes taking place inthe absence of oxygen in plants and animals that have been buried deep in the earth’s crust formany million years. Fossil fuels like coal, petroleum and natural gas are formed in this manner.These are conventional sources of energy. For example, energy from, Petroleum, natural gas,coal, nuclear energy, etc.

Nuclear EnergyNuclear energy is obtained by fission of nuclear material. Uranium is a fairly common elementin earth’s crust. Naturally found uranium contains 0.72% of uranium 235 (U-235) by massrest being Uranium 238 (U-238) and small amount of isotopes. Isotopes are atoms of sameelement having different atomic weights. Plutonium and thorium are another alternate fuelfor creating nuclear energy.

Hydro EnergyIt is the energy possessed by the water. The potential energy of water stored in a reservoir athigh level is converted into high kinetic energy water by passing to the turbine through thenozzles to produce mechanical energy. Then the mechanical energy is converted into electricalenergy by coupling turbine with generator. Thus the hydro energy is obtained for producingelectricity. The conventional power plants are producing electricity using conventional energy

1.3.2 Non-Conventional Sources of EnergyThe non-conventional sources are being continuously produced in nature and are notexhaustible. Examples are wood, geothermal energy, wind energy, tidal energy, nuclear fusion,gobar gas, biomass, solar energy etc.

The examples for non-conventional sources of energy are:(i) Solar energy

(ii) Wind energy(iii) Geothermal energy(iv) Ocean energy such as tidal energy, wave energy(v) Biomass energy such as gobar gas.It is evident that all energy resources based on fossil fuels has limitations in availability

and will soon exhaust. Hence the long-term option for energy supply lies only with non-conventional energy sources. The non-conventional power plants are producing electricity usingnon-conventional energy.

Renewable EnergyRenewable energy is energy which is generated from natural sources i.e., sun, wind, rain,tides and can be generated again and again as and when required. They are available inplenty and by far most the cleanest sources of energy available on this planet. For example,Energy that we receive from the sun can be used to generate electricity. Similarly, energyfrom wind, geothermal, biomass from plants, tides can be used this form of energy to anotherform.

THERMAL POWER PLANTS 3

Advantages• The sun, wind, geothermal, ocean energy are available in the abundant quantity and free

to use.• The non-renewable sources of energy that we are using are limited and are bound to

expire one day.• Renewable sources have low carbon emissions, therefore they are considered as green

and environment friendly.• Renewable helps in stimulating the economy and creating job opportunities. The money

that is used to build these plants can provide jobs to thousands to lakhs of people.• You don’t have to rely on any third country for the supply of renewable sources as in case

of non-renewable sources.• Renewable sources can cost less than consuming the local electrical supply. In the long-run,

the prices of electricity are expected to soar since they are based on the prices of crude oil,so renewable sources can cut your electricity bills.

• Various tax incentives in the form of tax waivers, credit deductions are available forindividuals and businesses who want to go green.

Disadvantages• It is not easy to set up a plant as the initial costs are quite steep.• Solar energy can be used during the daytime and not during night or rainy season.• Geothermal energy which can be used to generate electricity has side effects too. It can

bring toxic chemicals beneath the earth surface onto the top and can create environmentalchanges.

• Hydroelectric provide pure form of energy but building dams across the river which isquite expensive can affect natural flow and affect wildlife.

• To use wind energy, you have to rely on strong winds therefore you have to choose suitablesite to operate them. Also, they can affect bird population as they are quite high.

Non-Renewable EnergyRenewable energy is energy which is taken from the sources that are available on the earth inlimited quantity and will vanish fifty–sixty years from now. Non-renewable sources are notenvironmental friendly and can have serious affect on our health. They are called non-renewablebecause they can be re-generated within a short span of time. Non-renewable sources exist inthe form of fossil fuels, natural gas, oil and coal.

Advantages• Non-renewable sources are cheap and easy to use. It can easily fill up in car tank and

power the motor vehicle.• It can use small amount of nuclear energy to produce large amount of power.• Non-renewable have little or no competition at all. For example, in a battery driven car,

battery gets discharged then it won’t be able to charge in the middle of the road rather itis easy to find a gas pumping station.

• It is very cheap when converting from one type of energy to another.

Disadvantages• Non-renewable sources will expire some day and we have to us our endangered resources

to create more non-renewable sources of energy.

4 POWER PLANT ENGINEERING

• The speed at which such resources are being utilized can have serious environmentalchanges.

• Non-renewable sources release toxic gases in the air when burnt which are the majorcause for global warming.

• Since these sources are going to expire soon, prices of these sources are soaring dayby day.

1.3.3 Comparison of Sources of Energy

Sl. No. Renewable energy sources Non-renewable energy sources

1. They don’t cause pollution to atmosphere. They cause pollution to atmosphere.

2. Their efficiency is comparatively less. Their efficiency is comparatively high.

3. They are available at low intensities. They are available at high intensities.

4. Their initial cost is comparatively less. Their initial cost is comparatively high.

5. Their running cost is less. Their running cost is more.

1.4 HISTORY OF THERMODYNAMICSThermodynamics is a branch of physics and of chemistry that studies the effects of changesin temperature, pressure, and volume on physical systems at the macroscopic scale by analyzingthe collective motion of their particles using statistics. Roughly, heat means “energy in transit”and dynamics relates to “movement”; thus, in essence thermodynamics studies the movementof energy and how energy instills movement. Historically, thermodynamics developed out ofneed to increase the efficiency of early steam engines.

A brief history of thermodynamics begins with Otto von Guericke who in 1650 built anddesigned the world’s first vacuum pump and created the world’s first ever vacuum (known asthe Magdeburg hemispheres). He was driven to make a vacuum in order to disprove Aristotle’slong-held supposition that ‘nature abhors a vacuum’. Shortly thereafter, Irish physicist andchemist Robert Boyle had learned of Guericke’s designs and in 1656, in coordination withEnglish scientist Robert Hooke, built an air pump. Using this pump, Boyle and Hooke noticeda correlation between pressure, temperature, and volume. In time, Boyle’s Law wasformulated, which states that pressure and volume are inversely proportional. Then, in 1679,based on these concepts, an associate of Boyle’s named Denis Papin built a bone digester,which was a closed vessel with a tightly fitting lid that confined steam until a high pressurewas generated.

Later designs implemented a steam release valve that kept the machine from exploding. Bywatching the valve rhythmically move up and down, Papin conceived of the idea of a pistonand a cylinder engine. He did not, however, follow through with his design. Nevertheless, in1697, based on Papin’s designs, engineer Thomas Savery built the first engine. Althoughthese early engines were crude and inefficient, they attracted the attention of the leadingscientists of the time. One such scientist was Sadi Carnot, the “father of thermodynamics”,who in 1824 published Reflections on the Motive Power of Fire, a discourse on heat, power,and engine efficiency. The paper outlined the basic energetic relations between the Carnotengine, the Carnot cycle, and Motive power. This marks the start of thermodynamics as amodern science.

THERMAL POWER PLANTS 5

1.4.1 Temperature and HeatAlthough they are closely related, heat (denoted ΔQ) and temperature (denoted T) are NOTthe same. Temperature is a measure of the kinetic energy of vibration of the molecules thatmake up a substance. Because the molecules are connected to one another in vastly differentways from one substance to the next, the simplest and most useful way to think of temperatureis based upon a comparison system. The idea is the following. If two substances are at thesame temperature, then nothing will happen when they are placed in thermal contact withone another. That is, neither will heat up of cool down. If they are at different temperatures,then the hotter one will cool down and the cooler one will heat up ... until they reach the sametemperature! We say the two objects are in thermodynamic equilibrium. (Doesn’t that soundmore impressive than the same temperature?) This simple idea is encoded in the Zeroth Lawof Thermodynamics:

If object A is in thermodynamic equilibrium with object B, and object B is in thermodynamicequilibrium with object C, then object A is in thermodynamic equilibrium with object C.

You can think of object B as a thermometer. The two most commonlyused temperature scales are the Fahrenheit scale and the Celsius scale.On the Fahrenheit scale, water freezes at 32 oF and boils at 212 °F. Onthe Celsius scale (also referred to as the centigrade scale) water freezesat 0°C and boils at 100°C. To convert from one scale to the other, use

T°C = 5/9 (T°F – 32)For a quick estimate of the Celsius temperature, subtract 30 from the Fahrenheit

temperature and divide by two. For the reverse conversion estimate, multiply the Celsiustemperature by 2 and add 30. There is a third scale used in science that is important. It is theKelvin or Absolute scale. The Kelvin temeprature is found from the Celsius temperature bysimply adding 273.

T°K = T°C + 273On the Kelvin scale, water freezes at the scorching temperature of 273K. The coldest

temperature possible is 0°K, often referred to as absolute zero. (Absolute zero is the temperatureat which all atomic and molecular motion ceases, in the “classical theory”. The more accurate“quantum theory” paints a more complicated picture).

HeatHeat is one of the many forms of energy. We do not usually refer to the absolute amount ofheat energy in an object. That can be complicated and is generally not a useful quantity.Instead, we refer to the amount of heat that “flows into” or “flows out of” an object. Let’sconsider an experiment where we place a hot block of aluminum (Al) in contact with a coldblock of iron (Fe). For now, assume the blocks have exactly the same mass. (So why are theydifferent sizes in the picture?) Heat flows out of the hot aluminum (and it’s temperaturedecreases) and flows into the cold iron (and it’s temperature increases). Of course, heat couldalso flow into and out of the surrounding environment. But we eliminate this by carefullyinsulating the system. This process continues until the block reach the same temperature.Since the masses are the same, is the final temperature exactly halfway between the originaltemperatures? NO! How much the temperature increases or decreases depends upon the amount(specifically the mass) of the substance AND upon the substance itself. It takes more energy toheat up or cool off the block of Al than it does for Fe. We say the Al has a greater heat capacity.For a substance of mass m, the amount of heat energy ΔQ required to raise it’s temperature byan amount ΔT, is given by:

ΔQ = m c ΔT

Power Plant Engineering

Publisher : Laxmi Publications ISBN : 9789383828524 Author : S Suyambazhahan

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