Integrated design and simulation of chemical processes

855 Pages·2014·27.66 MB·English

by  Bildea

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Preface
WelcometothesecondeditionofIntegratedDesignandSimulationofChemicalProcesses.Thebody
of work has been greatly expanded, improved and updated. Five new chapters have been added on
ProcessIntensification,BatchProcesses,ChemicalProductDesign,Health,SafetyandEnvironment
and Sustainability Analysis. The chapters on Dynamic Simulation and Plantwide Control were fully
rewritten.Thenewmaterialrepresents35%ofthebook,about50%ofthecontentissignificantlyim-
provedversustheoriginalversionandtherestwasupdatedasdeemednecessary.Thetheoryisamply
illustrated with 432 figures, 167 tables, 3 case studies and numerous examples spread across the
chapters.
The book is a comprehensive body of work that covers the fundamentals of modern Conceptual
ProcessDesign.Theemphasisisondevelopingcreativitytodesigninnovativeandsustainablechem-
icalprocessesbyusingthesystemsapproach,systematicmethods,advancedthermodynamictoolsand
computer simulation. The book comprises five sections: Process Simulation, Thermodynamic
Methods,ProcessSynthesis, ProcessIntegration andDesignProject.
ThisneweditionissuitableasgeneralteachingmaterialforChemicalProcessandProductDesign
courses for students aiming at an MSc degree in Chemical Engineering. The book is intended to
respond to the European education needs using the ECTS system but is compatible with academic
requirements worldwide. Advanced features such as process intensification and plantwide control
aresuitableforpostgraduatestudieslikePhDorDrandPDEng(ProfessionalDoctorateinEngineer-
ing). Professional engineers will find here an update on the latest developments in modern process
designas well asthe efficient useof computersimulationtools.
Whatsetsthisbookapartistheintensiveuseofprocesssimulationforanalysis,designandeval-
uation.Threechaptersaredevotedtovariousgenericaspectsincludingdynamicsimulationwithpro-
cess control implementation. Another unique characteristic is the emphasis on thermodynamic
modelling and on the computation of physical properties, including those with an impact on health,
safetyandtheenvironment.Moderntrendsinequipmentdesignareillustratedbyprocessintensifica-
tion.Finally,thisbookdevelopsanoriginalapproachforintegratingprocessdesignandplantwidecon-
trol that is particularly useful for complex plants with recycles. These features involved original
research bythe authors, their teams and their collaborators.
Despiteallofoureffortsintherevision,weareawarethatsomeerrorsmightstillbepresent.Weare
open toany remarksand therefore grateful inadvancefor feedback from our readers.
AlexandreC.Dimian
Costin S. Bildea
Anton A.Kiss
xix
Acknowledgements
Completingthesecondeditionofthisbookhasbeenaconsiderablechallengefortheauthorsconsid-
eringtheamountofnewmaterialandthevarietyoftopicsadded.Wehadthechancetoknoweachother
forabout15yearsandtocooperatecloselyinbotheducationalandresearchactivities,whichmadethis
ambitious endeavourpossible andenjoyable.
Firstly,wewouldliketoexpressourcommitmenttotheEuropeanculturalvaluesthatshapedour
educationandskills.WesharethesevalueswithcolleaguesfromdifferentEuropeancountries,namely
by actively participating in different research and academic exchange programmes supported by the
EuropeanUnion.TheannualmeetingsESCAPEorganisedbytheEuropeanComputer-AidedProcess
Engineering (CAPE) community with worldwide participation play in particular a major role in
disseminating the latest developments inour field.
Thematerialofthisbookhasbeentaughtforabout20yearsatdifferentgraduateandpostgraduate
courses in The Netherlands and Romania. We thank so many students and colleagues from
TheNetherlandsandallovertheworld,whohelpedustodevelopandrefineoureducationalapproach.
WearegratefulnamelytotheUniversityofAmsterdam,UniversityofTwente,TechnicalUniversityof
Eindhoven,DelftUniversityofTechnologyandUniversity‘Politehnica’ofBucharestfortheirsupport.
WearethankfultoElsevierfortheprofessionalsupportandkindlyassistance,andtoourcollab-
orators inthe research programmesthat we are carrying out.
Finally,weareindebtedtoourfamiliesfortheirlong-standingencouragementandunderstanding,
namely for the late-evening call conferences andlong working weekends.
AlexandreC.Dimian,
Costin S. Bildea
Anton A.Kiss
xxi
CHAPTER
1
INTEGRATED PROCESS AND
PRODUCT DESIGN
1.1 INTRODUCTION
1.1.1 MOTIVATION
TheproductsmanufacturedbytheChemicalProcessIndustries(CPIs)arevitalforfulfillingtheneeds
ofthemodernsociety.Theprocessdesigneristhepersoninchargeoftransformingavaluableideaor
experimentintoanindustrialprocess.Thecreativeeffortshouldberewardedbysubstantialtechnical
and economic advantages. Thus, novelty and efficiency are key motivations for process designers.
Today,sustainabledevelopmentsetsnewchallengesfordesigners,namelythetransitiontorenewable
resources, aswell as the protection ofthe natural environment.
Thejobofaprocessdesigneristofulfilnotonlyoriginality,efficiencyandsustainabilitycriteria,but
toconsideralargenumberofconstraints,oftencontradictory.Forexample,usingbiomassasrenewable
feedstockimpliestypicallyacomplexchemistry,withmanyby-productsandimpurities.Betterselec-
tivitymaybeachievedworkingatlowerconversion,butwithsupplementarycostsinequipmentand
energyforhandlingtherecycles.Theenvironmentalregulationssetseveretargetsforwasteandemis-
sions,addingsupplementarycosts.Modernplantsshoulduselessland.Intheend,thedesignerhasto
find an optimum ensuring high valorisation of materials, low energy requirements and no pollution,
byemployingcompactandefficientequipment.Thecombinationofsomanyaspectsgiveshighlyin-
tegrated processes. Their optimal design makes useof systematic conceptualmethods and powerful
computersimulationtoolsformingthecoreoftheProcessSystemsEngineering(PSE)discipline.
Etymologically,thewordengineercomesfromtheLatiningeniummeaningtheskillstounderstand,
createandinvent.Today,theCPIsareconfrontedwithmultiplecrisesandchallenges,butinnovationis
ultimatelythekeyissue.Inthiscontext,enhancingthecreativityofdesignersplaysacentralrole.We
believe thatthecreativityshouldbeaccessibletoeveryone havingadequateprofessional knowledge
andmotivationfordiscovery.Creativitycanbelearnedandteachingthecreativityofprocessdesigners
isthe goal ofthis book.
Theintellectualsupportforenhancingcreativityistheemploymentofasystemsapproachandsys-
tematicmethods.Thishasatleasttwomerits:(1)Itprovidesguidanceinidentifyingthefeasibilityof
theprojectbeforethedesignofunits.(2)Notjustasinglesolutionbutseveralalternativesaregenerated
andevaluated,correspondingtodesigndecisionsandconstraints.Afterrankingbysomeperformance
criteria,themostconvenientalternativesarerefinedandoptimised.Notethatbyapplyingsystematic
methods, quasi-optimal targets for unitscan beset well ahead oftheir detailed sizing.
Theassemblyofthesystematicmethodsemployedfordevelopingprocessflowsheetsandensuring
the optimal use of materials andenergy forms the paradigm of Integrated ProcessDesign (IPD). Its
application relies on the intensive use of Process Simulation. This approach allows the engineer to
1
ComputerAidedChemicalEngineering.Volume35.ISSN1570-7946.http://dx.doi.org/10.1016/B978-0-444-62700-1.00001-2
©2014ElsevierB.V.Allrightsreserved.
2 CHAPTER 1 INTEGRATED PROCESS AND PRODUCT DESIGN
understandthebehaviourofcomplexprocesssystems,explorealternativesandproposeeffective in-
novative solutions.
Traditionally, process design was oriented to commodity chemicals. Recent years have seen an
increasinginterestinamoresystematicapproachtoProductDesign,whichdealswithmanufacturing
ofhighervalue-addedchemicals.Thus,theintegratedparadigmconcernstodaybothprocessandprod-
uct design.
1.1.2 THE ROAD MAP OF THE BOOK
Thebookcontainsfivesections:ProcessSimulation,Thermodynamics,ProcessSynthesis,ProcessIn-
tegrationandDesignProject.Eachsectionhasseveralchapters,21intotalplusappendices.Theroad
map depicted inFigure 1.1 shows anoverview ofthe chapters.
The main avenue links the introductory chapter on IPD with the section devoted to the Design
Project, the final goal, and at the same time allows the circulation of information between different
sectionsandchapters.Doublesenseroadsindicatethattheinformationgoesinandoutbetweensec-
tions andsomechapters.
Inthisbook,weadoptedthestrategyofteachingtheprinciplesbytheassignmentofadesignpro-
ject.Forthisreason,therearenoproblemsattheendofchapters.Instead,studentswillbetrainedby
applying the theoretical concepts totheir own project.
Guiding examples can be found in the book published by Dimian and Bildea (2008) containing
11 detailed computer-aided case studies.
Viewedfromthetop,therightsideoftheavenuedealswithissuesregardingthetools,andtheleft
side handles the principles ofIPD.A rapidtour presents the key topics of each chapter.
ThejourneybeginswithanintroductorychapteronIntegratedProcessandProductDesign.This
canbedescribedasthemarriageoftwotypesofactivities:ProcessSynthesis,asarchitecturaldesign,
andProcessIntegration,asdevelopmentandoptimisationofsub-systems.Keytopicsaresystemsap-
proach, sustainable development andproduction-integrated environmentalprotection.
ThefirstsectionteacheshowtouseefficientlythepowerfulcapabilitiesofProcessSimulation.The
treatmentisgeneric, notdedicated to specific commercial software.
Chapter2servesasanIntroductioninProcessSimulation.Particularattentionispaidtosystems
analysisbysimulation,commonlycalledflowsheeting.Thischapterprovidesanoverviewofcomputer
simulationinprocessengineering,includingthekeystepsinasimulationapproach,thearchitectureof
flowsheeting software and the integration of simulation tools.
Chapter3presentsthefundamentalsofSteady-StateFlowsheetingsuchasdegreesoffreedomanal-
ysis, efficient use of sequential-modular approach, equation-solving approach, thermodynamic tools
and the treatment of convergence and optimisation. Mastering the flowsheeting techniques allows
the user to get valuableinsightsinto more subtle aspects, such asplantwide control.
Chapter4isdevotedtoDynamicFlowsheeting,nowadaysamajorinvestigationtoolinprocessop-
erationandcontrol.Keytopicsarehowsettingupadynamicsimulationmodel,dynamicsimulation
tools, numerical problems, dynamic simulation ofkey unitsand process control tools.
ThesecondsectiondealswithThermodynamicMethodsusedincomputer-aidedprocessdesign.It
islargelyrecognisedthatinappropriatethermodynamicmodellingisthemostfrequentcauseoffailure
whenusingcomputersimulationforpredictingthebehaviourofrealsystems.Therefore,thissectionis
highly recommended asself-study for upgradingthe knowledgein thermodynamics.
1.1 INTRODUCTION 3
1-INTEGRATED
PRODUCT & PROCESS DESIGN
III – PROCESS SYNTHESIS
I - PROCESS
8 – Reaction 9 – Separation
SIMULATION System System
2 - Introduction
7 - Process 10 - Process
Synthesis Intensification
3 - Flowsheeting
11 - Batch 12 - Product
4 – Dynamic Processes Design
Simulation
IV-PROCESS INTEGRATION
13 - Pinch Point 14 – Applied
II-THERMODYNAMICS Analysis Energy Integration
5 - Computational
15 - Plantwide
Methods
Control
16 – Health, Safety,
6 - Phase Environment
Equilibria 17 - Sustainability
Analysis
19 – Economic
18 - Design Project
Analysis
20 - Equipment
21 - Case Studies
sizing
V- DESIGN PROJECT
FIGURE1.1
Theroadmapofthebook.
Chapter5describestheGeneralisedComputationalMethods,namelythePVT(pressure/volume/
temperature)behaviouroffluids,thermodynamicproperties,generalisedcomputationalmethodsusing
PVT relationshipand the estimationofphysical properties.
Chapter6developsthecomputationofPhaseEquilibriabyvariousthermodynamicmodels,suchas
equationsofstateandliquidactivity.Particularattentionispaidtotheregressionofparametersfrom
experimental data.
Thethirdpart,ProcessSynthesis,entersthecoreoftheconceptualdesignandteacheshowtoinvent
processflowsheets bya generic approach based on systemsanalysisand systematic methods.
4 CHAPTER 1 INTEGRATED PROCESS AND PRODUCT DESIGN
Chapter7presentsthedevelopmentofflowsheetsbyapplyingtheHierarchicalApproach.Thein-
put/outputanalysisisextendedtocapturetheessentialofecologicalanalysis.Emphasisisonthema-
terialbalanceenvelopeformedbythesub-systemsofreactionsandseparationsconnectedbyrecycles.
Here, the structure called Reactor-Separation-Recycle dominates the conceptual frame of the whole
flowsheet.Thisisthebasisforsettinguptheplantwidecontrolofthematerialbalance,whichinturn
dominates the operation costs. Separate chapters present a deeper analysis of the synthesis of sub-
systems.
Sinceflowsheetsynthesisstartsfromthereactor,Chapter8dealingwiththeSynthesisofReaction
Systemsisparticularlyimportant.Akeyissueisthechemistry,includingtheformationofby-products
andimpurities.Anothercentralsubjectisreactorselectionanditsintegrationwiththeutilitysystem.
Chapter9presentstheSynthesisofSeparationSystems.Thischapterdevelopsagenericknowledge-
basedframework.Theapproachreliesongeneratingalternativetaskstakingintoaccounttherelation
betweencharacteristicpropertiesofthecomponentsandthetargetassignedforseparation,aswellas
the evaluationof the appropriate separation methods.
Chapter10,ProcessIntensification,presentsmoderntechniquesforincreasingtheeco-efficiency
ofthechemicalequipmentwiththebenefitoflowercapitalcosts,substantialenergysaving,reduced
footprintandsafetybydesign.Centraltopicsarereactiveseparationdevices(e.g.reactivedistillation,
reactive absorption), and more advanced distillation technologies such as the dividing-wall column
(Kiss, 2013).
Chapter 11, Chemical Product Design, presents an approach that integrates both product and
processdesign.Wesharetheviewthatallprocessdesignsaredevotedtoproducts.Inthecaseofcom-
modities,focusissetonflowsheetdesignthatensuresthelowestcapitalandoperationcosts,whilefor
industrial and consumer-configured goods the emphasis is on specifications satisfying the customer
needsforwhichaprocessdesignshouldbefound,inmanycasesemployingmultipurposeequipment.
Chapter12,BatchProcesses,coversthedesignofprocessestypicallyemployedformanufacturing
specialitychemicals.Keytopicsarebatchdistillationandbatchreactors.Here,processoperationissues
rather than flowsheet synthesis are important, such as productivity improvement, energy saving and
safety preservation.
Thefourthsectionofthebook,devotedtoProcessIntegration(PI),addressesthecombinationof
individualunitsinanoptimalsystemfromtheperspectiveoflowenergyconsumption,goodcontrol-
labilityproperties and superior environmental performance.
Chapter13,devotedtoPinchAnalysis,addressestheprinciplesofachievingoptimalenergyutili-
sation.Theprincipleisthattheanalysisoftheprocessasasystemleadstomuchmoreefficientsolu-
tions for saving energy than by just optimising the stand-alone units. Namely, this method can set
optimumenergytargetswellaheadthedetaileddesignofheatexchangers.Theappropriateplacement
ofunitoperationswithrespecttoPinchgivesvaluableinsightsforimprovingtheenergeticandenvi-
ronmental efficiency ofthe whole process.
Chapter 14 deals with Applied Energy Integration in process industries, more specifically with
combinedheatandpowerproduction,newrefrigerants,wasteheatrecovery,energysavingindistil-
lation, integration ofchemical reactors and site utilitysystem.
Chapter15isdevotedtoPlantwideControlasaholisticapproachtointegratingprocessdesignwith
processcontrolatthelevelofthewholeplant.Morespecifically,thechapterdealswiththestabilityand
flexibilityinoperationrelatedtothedesignofreactorsandseparators.Akeytopicisthebifurcation
analysisof the Reactor/Separator/Recycle system characterisingthe process.
1.2 INTEGRATED PROCESS AND PRODUCT DESIGN 5
Chapter 16 handles the basics of Health, Safety and Environment (HSE) activities in conceptual
process design. The first section describes impact factors on health, as well as estimation methods
assistedbycomputersimulation.SafetyisatbestachievedbyInherentlySaferDesign.Theprotection
oftheequipmentbysafetyvalvesisbrieflycovered.Thechapterendswithmethodsfortheassessment
and preventionof technological risks.
Chapter17dealswithSustainabilityAnalysis,animportantsubjecttodayforbothsocietyandin-
dustry. Central issues are the concept of life cycle assessment (LCA), eco-cost value ratio, eco-
efficiency analysisand sustainability metrics.
Thelastpartofthebookisdevotedtotopicshelpingtheplanningandtheexecutionofaconceptual
designproject.
Chapter18onProcessDesignProjectdiscusseseducationalaspects.Guidelinesareprovidedfor
developingcoursesandprojectsatMScleveladaptedtotheEuropeanCreditTransferSystem,aswell
as topostgraduate and continuouseducation activities.
Chapter 19 handles the Economic Evaluation of a conceptual design project. Central topics are
time-value of money, estimationof capital and operationcostsand profitability analysis.
Chapter20 presents guidelines for EquipmentSelectionand Sizing, namely shortcut methods for
quickassessmentofreactionvessels,separationcolumns,heatexchangersanddevicesforthetransport
of fluids, which associated with the sizing capabilities of a simulation package can be used for esti-
mating the total investmentcost.
Chapter21presentsCaseStudiesillustratinginmoredetailsomeexamples,includingfulldynamic
simulationwithcontrol implementation.
HelpfulengineeringdatafordesignprojectsaregiveninAppendices,suchasestimationofcostsfor
equipmentandutilities,materialsofconstruction,steamtables,vapourpressureofsomekeyfluidsand
conversion factors.
ThematerialofthisbookissuitableforsettingupcoursesinChemicalProcessandProductDesignfora
MScdegreeinchemicalengineering.Thematerialshouldbeadaptedtospecificteachingenvironments,
namelythebackgroundknowledgeinchemicalengineering,aswellthetimeallocationinthecurriculum.
AdvancedfeaturesareofinterestforPhDandpostgraduatestudentsinvolvedindesignorresearchprojects.
Finally,thebookwillbehelpfultoprofessionalengineersasanupdateonthelatestconceptualdevelop-
mentsindesigningsustainableprocesses,aswellasontheefficientuseofcomputersimulationtools.
Thebestmannertoconsolidatethecreativeskillsacquiredduringaconceptualdesignprojectisby
workingoutacomprehensiveplantdesignproject,whichissuitedfordevelopingprofessionaldesigner
expertiseasrequiredinengineeringcompanies.Ascomplementarymaterial,werecommendtherecent
book of Towler and Sinnott (2013).
1.2 INTEGRATED PROCESS AND PRODUCT DESIGN
1.2.1 CREATIVE ASPECTS IN PROCESS DESIGN
Thefollowing definition of Douglas (1988) highlights the roleof creativity:
ProcessDesignisthecreativeactivitywherebywegenerateideasandthentranslatethemintoequip-
ment and process for producing new materials or for significantly upgrading the value of existing
materials.
6 CHAPTER 1 INTEGRATED PROCESS AND PRODUCT DESIGN
ConceptualDesignreferstothatpartofadesignprojectthatdealswiththefundamentalelementsofa
process:layoutoftheunitsorflowsheet,materialandenergybalances,specifications,performanceand
sizingoftheequipment,energyrequirements,safety,hazardandenvironmentalissuesandeconomic
efficiency.Attheconceptualdesignphase,theemphasisisonthebehaviouroftheprocessasasystem
of connections of functional units rather than on the detailed sizing of the equipment and the plant
design.
It is important to note that conceptual design isresponsible for the largest part ofthe investment
costs in a process plant, even if its fraction of the total project’s fees is very limited. An erroneous
decisionattheconceptuallevelwillpropagatethroughoutthewholechainoftheequipmentprocure-
mentandplantdesign.Eventuallymuchhighercostswillariselaterinoperationwhencorrectingde-
sign misconceptions.
Figure1.2illustratestheeconomicincentivesofaplantproject,fromtheconceptualphasedownto
constructionandcommissioning(Pingen,2001).Theconceptualphasetakesonly2%ofthetotalpro-
jectcost,althoughitcouldcontributemorethan30%incost-reductionopportunities.Atthedetailed
designphase,thecostofengineeringrisessharplyto12%,whilesavingopportunitiesfalltoonly15%.
In contrast, the cost of procurement and construction increases to more than 80%, while the saving
opportunities drop to10%. At the commissioning stage, the total cost isfrozen.
Thelongroutefromanideatoarealprocesscanbebestmanagedbymeansofasystemsapproach
forevaluatingtheprocessasawholeandbysystematicmethodsfordesigningthesub-systems,suchas
reaction, separations and utilities.
Asystematicmethodconsistsinacombinationoftwosteps,analysisandsynthesis.Inthiscontext,
theAnalysisstepdealswiththeknowledgeoftheelementsdefiningthesystem,suchasthephysical
propertiesofthechemicalcomponentsandmixtures,theperformancecharacteristicsofreactorsand
unitoperations,theecologicalaspectsandtheprofitabilityissues.Ontheotherhand,theSynthesisstep
30%
2%
25%
40%
20% Cost Total
reduction project
opportunity cost
15%
44%
10%
12%
5%
2%
Concept Design Procure Construct Commission
FIGURE1.2
Economicincentivesinaproject.
1.2 INTEGRATED PROCESS AND PRODUCT DESIGN 7
handlesthearchitectureofthesystem,theselectionandthepre-designofthesuitablefunctionalunits,
as well asthe effect ofinteractions of materials, energy andinformation.
Inthepast,thedevelopmentofanewprocesshasbeendescribedoftenasakindof‘art’.Thestrat-
egy,calledsometimestheengineeringmethod,consistedofdrawinganinspiredsketchandthenim-
provingitbysuccessivelayersofrefinementandevaluation,uptothefinaloptimisation.Theskillsof
the designer, the expertise of the company and the availability of plant operation knowledge were
crucial.
Nowadays,theconceptualprocessdesignisbecomingincreasinglyanappliedchemicalengineer-
ingscience.Engineerswithasolidscientificbackgroundandmasteringcomputerdesigntoolsareca-
pable of finding valuable innovative ideas. Inspiration and expertise, as well as the availability of
corporate knowledge, still play an important role, but these can be greatly enhanced by employing
a systematic approach. Actually, it is the combination of science and engineering art that makes the
conceptual process design such a fascinating challenge!
A design problem is always under-defined, either by the lack of data or by insufficient time and
resources.Moreover,adesignproblemisalwaysopen-ended.Thereisneverasinglesolution,butal-
ternativesdependingonthedesigndecisionsthattheengineerhastotakeatdifferentstagesofthepro-
jectinorder tofulfilthe constraints oftechnical, economical and environmental nature.
Thesystematicgenerationofalternativesisthemostimportantfeatureofthemodernconceptual
design.Then,thebestdesignisidentifiedastheoptimalsolutioninthecontextofconstraintsbyusing
consistent evaluationand ranking ofalternatives.
1.2.2 PROCESS SYNTHESIS AND PROCESS INTEGRATION
ProcessIntegrationemergedinthe1980sasanewdisciplineinchemicalengineeringwithemphasison
theefficientuseofenergy.PIrevealedthatsignificantenergysavingcanbeachievedbyanalysingthe
probleminthecontextofthewholeprocess(system),contrarytotheviewpointofthestand-aloneunits.
The traditional process design comprises a hierarchy of activities, which can be depicted by the
successivelayersofanOnionDiagram,asillustratedinFigure1.3(Linnhoffetal.,1994).Thedevel-
opmentbeginswiththechemicalReactor(R),afterwhichitcontinueswiththesystemofSeparations
(S).Then,thedesignaddressestheHeatExchange(H)andUtility(U)layers.Ideally,thesolutionofthe
designproblemshouldbeglobal,sinceacompleteseparationoftheaboveactivitiesisnotpossible.For
example, the separation system is intimately linked with the reactor design. Similarly, the heat
R
R – Reactor system
S S – Separation system
H – Heat Recovery system
H
U – Utility system
U
FIGURE1.3
HierarchicaldescriptionofprocessdesignbytheOnionDiagram.