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Power 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 AcademicPressisanImprintofElsevier AcademicPressisanimprint ofElsevier 32JamestownRoad,LondonNW17BY,UK 525BStreet,Suite1800,SanDiego, CA92101-4495,USA 225WymanStreet,Waltham,MA02451,USA TheBoulevard, LangfordLane,Kidlington,OxfordOX51GB,UK Copyright ©2015Elsevier Ltd.Allrightsreserved. Nopartofthispublication maybereproducedor transmitted inanyformor byanymeans,electronicormechanical, including photocopying,recording,or anyinformationstorage andretrieval system,without permissioninwritingfrom thepublisher. Details onhowtoseekpermission, further informationaboutthePublisher’spermissionspoliciesandour arrangements with organizationssuchas theCopyright ClearanceCenterandtheCopyrightLicensingAgency,canbefoundatourwebsite: www.elsevier.com/permissions. Thisbookandthe individualcontributionscontainedinitareprotected undercopyright bythePublisher (otherthanas maybe notedherein). Notices Knowledgeandbest practiceinthisfieldareconstantly changing.Asnewresearchandexperiencebroadenour understanding, changesinresearchmethods,professionalpractices,or medicaltreatmentmay becomenecessary. Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgeinevaluatingandusinganyinformation, methods,compounds,orexperiments describedherein.In usingsuchinformationor methodstheyshould bemindfuloftheir ownsafetyandthesafety ofothers,includingpartiesfor whomthey haveaprofessionalresponsibility. Tothefullestextentof thelaw,neither thePublishernor theauthors,contributors, oreditors, assumeanyliabilityforanyinjury and/ordamagetopersons orproperty asamatterof productsliability, negligenceorotherwise, orfromanyuseor operationof anymethods,products,instructions, orideascontained inthematerialherein. British LibraryCataloguing-in-Publication Data Acataloguerecordfor thisbookisavailablefrom theBritishLibrary LibraryofCongress Cataloging-in-Publication Data Acatalogerecordfor thisbookisavailablefrom theLibraryofCongress ISBN:978-0-12-800940-6 ForinformationonallAcademic Presspublications visit ourwebsiteathttp://store.elsevier.com/ 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.

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