Table Of ContentPower Plant Instrumentation
and Control Handbook
A Guide to Thermal Power Plants
Swapan Basu
Systems & Controls Kolkata, India
Ajay Kumar Debnath
Systems & Controls Kolkata, India
AMSTERDAM lBOSTON lHEIDELBERGlLONDONlNEWYORK lOXFORD lPARIS
SANDIEGO lSANFRANCISCO lSINGAPORE lSYDNEY lTOKYO
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Dedication
This book is dedicated to the promising and growing engineers
working in/around or studying thermal power plant
instrumentation and control systems who can render services
to mankind by providing sparse, pollution-free energy
for human progression.
Foreword
With the advent of technological advancement in all the instrumentationwithalternativearrangements(ifany).The
fields,knowledgeandknow-howarenowavailable,inbits text is well demonstrated with facts and figures that make
andpieces,withjustaclickofthemouse,onthecomputer. this book easy to understand.
However, it can be time-consuming to find the desired in- In general, this book accentuates both subcritical and
formationinaconsolidatedmanner,oritmaybedifficultto supercritical plants, and there are separate appendices
find the exact subject information required. covering supercritical plants as well the emerging demand
Modern power plant engineering is a vast subject with for the higher efficiency and lower pollution aspects of
different fields of application for all branches of technol- subcritical plants.
ogy. In this book, the authors have included their experi- Theauthorsworkedfordecadeswithleadingconsulting
ences from a different angle focusing on instrumentation firms in India and abroad and keep in touch with modern
and control systems. technology. I truly feel that their experiences will greatly
Therearenumberofvaluablebooksavailableonpower benefit both practicing engineers and students of power
plants covering different subjects, but there is a dearth of plant engineering.
a single volumes incorporating the majority of the equip- I wish every success to the authors of this book.
ment in relation to the process. The chapters of this book
cover various subjects on the process and associated S. K. Sen
ix
Preface
Technical books that have theoretical and practical ap- the book to be “all-time companion” for practicing
proachesareavailableworldwideaboutseveralsubsystems engineers.
of thermal power plant instrumentation and controls. This Discussions about both subcritical and super-ultra su-
book endeavors to act as a way to balance two extreme percritical power plants, as well as IGCCs, have been
lines of thinking, giving a comprehensive approach to included in order to take a look at future trends in power
plants’ measurements and controls. plants. Content keeps pace with development work in the
What is here is primarily meant for professionals field of electronics and control and communication engi-
working with thermal power plant instrumentation and neering, with special attention to inclusion of the means
control systems. Budding (fresh) engineers who start their and methods of system integration with fieldbus systems,
careers in thermal power plant instrumentation and control OPC servers, and so on. Application of artificial intelli-
engineering, and those practicing professionals of other gence and fuzzy logic inpower plant instrumentation have
disciplines, will greatly benefit from the comprehensive- been covered in detail.
nessandpracticalapproachesinthisbook.Itwillbeavery In an attempt to incoporate this extensive subject area
good reference for engineering students who are pursuing intotheformofabook,theauthorshavecarriedoutagreat
higher-level studies in various branches of engineering. deal of research over years so as to include the knowledge
Highly developed and advanced mathematical de- gained during their decades-long global experience in
ductions are passed up as much as possible; instead phys- thermalpowerplant instrumentation engineering. We wish
ical explanations have been given so that readers get a to convey our sincere thanks to the companies who
proper feel of the system so that the book could be kept entrustedustoworkinthisspecializedareaofengineering.
withinaverylimiteddimension.Thetextpartincorporates Theauthorsfeelrewardedonlywhentheirresearchworkis
an abridged description on the subject being dealt with able to benefit future engineers who can serve the global
along with relevant figures and tables to visually show a population by providing scarce pollution-free energy for
clearpictureofit.Inallcases,detailedspecificationsofthe human development.
instruments, subsystems, and systems have been included Swapan Basu
inadditiontopracticalcontrolloopsandlogisticstoenable Ajay Kumar Debnath
xi
Acknowledgments
Attheoutset,theauthorswishtoextendtheirgratitudetotheir technicalinformation.Wewouldliketothanktheauthorsof
professors of their engineering institutiondBengal Engi- the works mentioned throughout the book and the Internet
neeringCollege,Sibpore(nowIIEST)dandtheirpowerplant documentsthatstimulatedandhelpeduswritethisbook.The
and instrumentation gurus: the late Samir Kumar Shome authors also like to thank the entire team of Systems &
(formerDCL)andthelateMakhanLalChakraborty(former Controls Kolkata for infrastructural support. The authors
DCL) for their great teaching in this area. The authors are wouldliketothanktheentireteamatElsevier,thepublisher,
extremelyindebtedtoDr.ShankarSen(formerprofessoratB. whotookallthepainstobringitthroughtopublication.
E.College) for his encouragement during development the Last but not the least, we would like to thank our
book. While working on the book we were supported with children Idai(Raj), Piku(Deb), Arijita, and Arijit for their
information and suggestions of former colleagues D. K. continuousinspirationandsupport.Aspecialthankstoour
Sarkar,J.K.Sarkar,D.J.Gupta,S.Chakraborty,A.Thakur, wives, Bani Basu and Syama Debnath, for managing the
and Arijit Ghosh. In addition, we convey sincere thanks to family show with care and for encouraging us so that we
friends: A. Bhattachariya (Kolkata), A. Sarkar (Norway), could dedicate time to the book. The authors sincerely
A. Tendulkar (Mumbai), N. Kirloskar (Pune), and acknowledge that without all these supports it would have
S. Mohanty (Gurgaon) for their support and sharing of been impossible to publish this book.
xiii
Chapter I
Introduction
1. INTRODUCTION 2. FUNDAMENTAL KNOWLEDGE ABOUT
BASIC PROCESS
The authors of this book have been associated with the
Instrumentation and Control System of Modern Power Power plant concepts are based on the Laws of Thermo-
Plants for more than two decades while working with a dynamics, which depict the relationship among heat,
leadingconsultingfirm.Theyarestillintouchwithmodern work, and various properties of the systems. All types
technology by associating with the engineering and con- of energy transformations related to various systems
sultancy activities of ongoing projects. We wanted to (e.g., mechanical, electrical, chemicaletc.) may fallunder
document their extended experience in the form of a the study of thermodynamics and are basically founded
reference book so that professional engineers, working on empirical formulae and system and/or process
engineers in power plants, and students could benefit from behavior.Athermodynamicsystemisaregioninspaceon
the knowledge gathered during their tenure. control volume or mass under study toward energy
There are so many valuable and good books available transformation within a system and transfer of energy
on a variety of subjects related to power plants about across the boundaries of the system.
boilers,turbines,andgeneratorsandtheirsubsystems,butit
is very difficult to get a single book or single volume of a
2.0 Ideas within and Outside the System
book tocater to theequipment, accessories, or items along
with the instrumentation and control systems associated 1. Surrounding: Space and matter outside the thermody-
with them. Inthisbook,there isaverybrief descriptionof namic system.
the system and equipment along with diagrams for a 2. Universe: Thermodynamic system and surroundings
cursory idea about the entire plant. Up-to-date piping and put together.
instrumentation diagrams (P&IDs) are included to better 3. Thermodynamic systems:
understand the tapping locations of measuring and control a. Closed:Onlyenergymaycrosstheboundarieswith
parameters of the plant. the mass remaining within the boundary.
Various types of instruments, along with sensors, b. Open: Transfer of mass takes place across the
transmitters,gauges,switches,signalconditioner/converter, boundary.
etc., have been discussed in depth in dedicated chapters, c. Isolated: The system is isolated from its surround-
whereas special types of instruments are covered in sepa- ing and no transfer of mass or energy takes place
rate chapters. Instrument data sheets or specification across the boundary.
sheetsareincludedsothatbeginnersmayreceiveadequate 4. State:Itistheconditiondetailedinsuchawaythatone
support for preparing the documents required for their state may be differentiated from all other states.
daily work. 5. Property:Anyobservablecharacteristicsmeasurablein
ThecontrolsystemchaptersVIII,IXandXincorporate termsofnumbersandunitsofmeasurement,including
the latest control philosophy that has been adopted in physical qualities such as pressure, temperature, flow,
several power stations. level, location, speed, etc. The property of any system
This book mainly emphasizes subcritical boilers, but a dependsonlyonthestateofthesystemandnotonthe
separate appendix is provided on supercritical boilers process by which the state has been achieved.
becauseoftheireconomicandlow-pollutionaspects,which a. Intensive: Does not depend on the mass of the sys-
create a bigger demand and need than do conventional tem (e.g., pressure, temperature, specific volume,
subcritical boilers. and density).
Itishopedthatthisbookmayhelpstudentsand/orthose b. Extensive: Depends on the mass of thesystem (i.e.,
who perform power plant-oriented jobs. volume).
PowerPlantInstrumentationandControlHandbook 1
Copyright©2015ElsevierLtd.Allrightsreserved.
2 POWERPLANTINSTRUMENTATIONANDCONTROLHANDBOOK
6. Specific weight: The weight density (i.e., weight per 2.0.1.3 Specific Heat
unit volume). Specific heat is defined as the amount of heat required to
7. Specific volume: Volume per unit mass.
raise the temperature of a substance of unit mass by one
8. Pressure: Force exerted by a system per unit area of degree. There are two types of specific heat:
the system.
9. Path: Thermodynamic system passes through a series 1. At constant pressure and denoted as Cp
2. At constant volume and denoted as Cv
of states.
10. Process: Where various changes of state take place. Heat energy is a path function and the amount of heat
11. Cyclic process: The process after various changes of transfer can be given by the following:
state complete their journey at the same initial point
of state. 1Q2 ¼ IntegrationfromT1toT2of mCndT;
ZT2
2.0.1 Zeroeth Law of Thermodynamics i:e:; ðmCndTÞ;
“Iftwosystemsarebothinthermalequilibriumwithathird T1
system, they are in thermal equilibrium with each other.” where 1 and 2 are two points in the path through which
Thermal equilibrium displays no change in the thermody- change takes place in the system, m is the mass, Cn is
namic coordinates of two isolated systems brought into the specific heat and maybe Cp, dT is the differential tem-
contact; thus, they have a common and equal thermody- perature, andT andT arethetwotemperaturesatpoint1
1 2
namic property called temperature. With the help of this and 2 of the path.
law, the measurement of temperature was conceived.
A thermometer uses a material’s basic property, which 2.0.1.4 Perfect Gas
changes with temperature.
A particular gas that obeys all laws strictly under all con-
ditionsiscalledaperfectgas.Inrealitynosuchgasexists;
2.0.1.1 Energy however, but by applying a fair approximation some gases
“The definition in its simplest form is capacity for pro- are considered as perfect (air and nitrogen) and obey the
ducing an effect.” There are a variety of classifications for gas laws within the range of pressure and temperature of a
energy. normal thermodynamic application.
1. Storedenergymaybedescribedastheenergycontained
2.0.2 Boyle’s Law and the Charles Law
within the system’s boundaries. There are various
forms, such as: 2.0.2.1 Boyle’s LawdLaw I
a. Potential Thevolumeofagivenmassofaperfectgasvariesinversely
b. Kinetic as the absolute pressure when temperature is constant.
c. Internal
2. Energy in transition may be described as energy that 2.0.2.2 Charles LawdLaw II
crosses the system’s boundaries. There are various
Thevolumeofagivenmassofaperfectgasvariesdirectly
types, such as:
as the absolute temperature, if the pressure is constant.
a. Heat energy (thermal energy)
b. Electrical energy
2.0.3 General and Combined Equation
c. Work
Fromapracticalpointofview,neitherBoyle’sLawnorthe
Charles Law is applicable to any thermodynamic system
2.0.1.2 Work
because volume, pressure, and temperature, etc., all vary
“Work is transferred from the system during a given
simultaneously as an effect of others. Therefore, it is
operation if the sole effect external to the system can be
necessary to obtain a general and combined equation for a
reduced to the rise of a weight.” This form of energy is
given mass undergoing interacting changes in volume,
transferredfromonesystemtoanothersystemoriginallyat
pressure, and temperature:
different temperatures. It may take place by contact and
without mass flow across the boundaries of the two sys- nNT=p; whenT isconstantðBoyle’sLawÞ
tems. This energy flows from a higher temperature to a
nNT; whenpisconstantðCharlesLawÞ:
lower temperature and is energy in transition only and not
the property. The unit in the metric system is kcal and is Therefore,vNT/pwhenbothpressureandtemperature
denoted by Q. vary
Introduction Chapter | I 3
or 2.0.5.1 Internal Energy
n ¼ k:T=p; There exists a property of a system called energy E, such
that change in its value is the algebraic sum of the heat
wherekisaconstantthatdependsontemperaturescaleand
supplied and the work done during any change in state.
properties of gas, or
dE ¼ vQ(cid:3)vW
pn ¼ mRT; This is also described as corollary 1 of the First Law of
Thermodynamics.
where m is the mass of gas and R is a constant. This Energy E may include many types of energies, such as
dependsontemperaturescaleandpropertiesofgas:p¼ab- kinetic, potential, electric, magnetic, surface tension, etc.,
solute pressure ofgasin kgf/m2, v¼ volume of gasin m3, butthesevalues,negligibleconsideringthethermodynamic
m¼massofgasinkg,andT¼absolutetemperatureofgas system, are ignored and only the energy due to change in
indegreesK.ThereforeR¼pV/mT¼kgf/m2(cid:2)m3/kg(cid:2)K temperature is considered. This type of energy is called
¼ kgf.m/kg/degree K. internal energy and is denoted by U.
R ¼ 30.26 kgf.m/kg/degree K for nitrogen
R ¼ 29.27 kgf.m/kg/per degree K for air 2.0.5.2 Adiabatic Work
R ¼ 26.50 kgf.m/kg/degree K for oxygen Whenever the change of state takes place without any heat
R ¼ 420.6 kgf.m/kg/degree K for hydrogen transfer,itiscalledanadiabaticprocess.Theequationcan
be written as follows:
2.0.3.1 Universal Gas Constant DU ¼ W ;W istheadiabaticworkdone
ad ad
After performing experiments, it was revealed that for It can be established that change in internal energy DU
any ideal gas, the product of its characteristic gas is independent of process path. Thus, it is evident that
constant and molecular weight is a constant number and adiabaticworkW wouldremainthesameforalladiabatic
ad
is equal to 848. Therefore, by virtue of this revelation, paths between the same pair of end states.
848 kgf.m/kg/degree K is called the Universal Gas
Constant.
2.0.6 Law of the Conservation of Energy
For example: MR ¼ molecular weight in kg (cid:2) R
“In an isolated system, the energy of the system remains
MR ¼ 29.00 (cid:2) 29.27 z 848 for air constant.”ThisisknownasthesecondcorollaryoftheFirst
MR ¼ 2.016 (cid:2) 420.6 z 848.5 for hydrogen
Law of Thermodynamics.
MR ¼ 28.016 (cid:2) 30.26 z 847.6 for nitrogen
MR ¼ 32 (cid:2) 26.5 z 848 for oxygen
2.0.6.1 Constant Volume Process
The volume of the system is constant. Work done being
2.0.4 Avogadro’s Law/HypothesisdLaw III
zero, due toheat addition to thesystem, there wouldbe an
This states that the molecular weights of all the perfect increase in internal energy or vice versa.
gases occupy the same volume under the same conditions
of pressure and temperature. 2.0.6.2 Constant Pressure or Isobaric Process
In this process, the system is maintained at constant pres-
2.0.5 First Law of Thermodynamics sure andanytransfer ofheatwouldresultinworkdoneby
the system or on the system.
When a system undergoes a cyclic change, the algebraic
sum of work transfers is proportional to the algebraic sum
2.0.6.3 Enthalpy
ofheattransfersorworkorheatismutuallyconvertibleone
into the other. The sum of internal energy and pressure volume product
Joules’experimentsonthissubjectledtoaninteresting (i.e., U þ pV) is known as enthalpy and is denoted by H.
and important observation showing the net amount of heat As both U, p, and V are known as system properties,
in kcal to be removed from the system was directly pro- enthalpy is also a system property.
portional to the net amount of work done in kcal on the
2.0.6.4 Constant Temperature of the Isothermal
system.
Process
It is the convention that whenever work is done by the
system, the amount of work transfer is considered as þve, The system is maintained at a constant temperature by any
andwhenworkisdoneonthesystem,theamountofwork meansandanincreaseinvolumewouldresultinadecrease
transfer is considered as (cid:3)ve in pressure and vice versa.
4 POWERPLANTINSTRUMENTATIONANDCONTROLHANDBOOK
2.0.7 Second Law of Thermodynamics 2.0.8.1 Kelvin Planck Statement of the Second
Law of Thermodynamics
There is a limitation of the First Law of Thermodynamics,
It is impossible to construct an engine that while operating
asitassumesareversibleprocess.Innaturethereisactually
in a cycle produces no other effect except to extract heat
a directional law, which implies a limitation on the energy
from a single reservoir and do the equivalent amount of
transformationotherthan that imposed bytheFirst Lawof
work. Thus, it is imperative that some heat be transferred
Thermodynamics
from the working substance to another reservoir, or cyclic
Wheneverenergytransfersorchangesfromonesystem
workispossibleonlywithtwotemperaturelevelsinvolved
toanotherareequal,thereisnoviolationoftheFirstLawof
andtheheatistransferredfromahightemperaturetoaheat
Thermodynamics; however, that does not happen in prac-
engine and from a heat engine to a low temperature.
tice.Thus,theremustexistsomedirectionallawgoverning
transfer of energy.
2.0.8.2 Clausius Statement of the Second Law of
Thermodynamics
2.0.8 Heat Engine
“It is impossible for heat energy to flow spontaneously
Aheatengineisacyclicallyoperatingsystemacrosswhose
from a body at lower temperature to a body at higher
boundary is a cyclically operating system across which temperature.”
only heat and work flow. This definition incorporates any
device operating cyclically and its primary purpose is
2.1 Recapitulation: Various Cycles: Carnot,
transformation of heat into work.
Therefore if boiler, turbine, condenser, and pump are Rankine, Regenerative, and Reheat
separately considered in a power plant, they do not stand
2.1.1 Reversible Cycle: Carnot
included in the definition of heat engines because in each
individual device in the system does not complete a cycle Here a reversible cycle was proposed by Sadi Carnot, the
(Figure I/2-1). inventor of this it, in which the working medium receives
When put together, however, the combined system heat at one temperature and rejects heat at another tem-
satisfies the definition of a heat engine. Referring to perature. Thisisachievedbytwoisothermalprocessesand
Figure I/2.1-1, the heat enters the boiler and leaves at the two reversible adiabatic processes, shown in the simplified
condenser. The difference between these equals work at schematic in Figure I/2.1-1.
theturbineandpump.Theworkingmediumiswaterandit Agiven mass of gas (system) isexpanded isothermally
undergoesacycleofprocesses.Passingthroughtheboiler from point 1 at temperature T to point 2 (after receiving
1
and transforming to steam, it goes to the turbine and then heat q from an external source). So, work is done by the
1
tothecondenserwhereitchangesbackintowaterandgoes system. The system is now allowed to expand further to
tothefeedpump,andfinallytotheboileragaintoitsinitial point 3 at temperature T through a reversible adiabatic
2
state.
FIGUREI/2-1 Powerplantasbasicheatengine. FIGUREI/2.1-1 p-vdiagramofaCarnot(reversible)cycle.
