chegp project.docx
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chegp project.docx
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chegpproject
CHEG231project
XiaokeLiu
Abstract
Themainreasontohavethisprojectistotestwhetherourownprojectcompound,1-butanol,isagoodrefrigerant.Forapproachingtofigureouttheanswer,firstofall,weneedtoknowwhatourprojectcompoundis,whatitisusedfor.Afterobtainingsomethermodynamicsinformation,wecanstarttocalculateandtoplotusefulthermodynamicsdatabyourselves.Oncewehaveconstructedacknowledgeoftheprojectcompound,itwillbethetimeforustomakeajudgmentwhethertheprojectcompoundisagoodrefrigerant.
Introduction
a.Basicchemistry
ChemicalName:
1-butanol
ChemicalStructure:
ChemicalFormula:
CH3CH2CH2CH2OH
MolecularWeight[M]:
74.1
CriticalTemperature[Tc]:
283.2°C
CriticalPressure[Pc]:
4.65MPa
Triplepoint:
184.51K
b.Compoundusage:
1-butanolisanintermediateintheproductionofbutylacrylate,butylacetateandotherbutylesters,butyletherssuchasethyleneglycolmonobutylether.1-butanolcanalsobeusedtoproduceextractingagentandsurfaceactiveagent.Otherindustrialusesincludethemanufactureofpharmaceuticals,polymers,pyroxylinplastics,herbicideestersandbutylxanthate.Itisalsousedasadiluent/reactantinthemanufactureofurea–formaldehydeandmelamine–formaldehyderesins.Also,BPandDuponthaveannounceaplanforusing1-butanolasbiofueltoreplaceethanol,whichmeans1-butanolhaspotentialtobeusedasbiofuel.Becausebutanolislesscorrosivethanethanolmeaningitcanbedistributedviaexistingpipelines.
c.safetyissues
1-butanoliscommonwithmostorganicsolvents,itisextremelyirritatingtotheeyes;repeatedcontactwiththeskincancauseirritation.Withaflashpointof29 °C(84 °F),1-butanolpresentsamoderatefirehazard,anditcanbeconsideredaflammableliquidbutlessflammablethanmanyothercommonorganicsolvents.Thedepressanteffectonthecentralnervoussystemisapotentialhazardwhenworkingwith1-butanolinenclosedspaces.1-butanolhastheeffectofanesthesia.Themainsymptomsareeye,noseandthroatofirritation.Itmayresulttoheadache,dizzinessanddrowsiness,handcontactdermatitismayoccur.
d.environmentissues
Bysearchingonline,itisstillnotcleartosaywhether1-butanolissortofenvironmentissues.1-Butanolisconsideredavolatileorganiccompound(VOC)andisemittedbynaturalsourcessuchasplants(rape,ryeandgrass),trees(beech,birchandhornbeam),animalwaste,microbesandinsects.1-Butanolenterstheenvironmentfromeithernaturalsourcesor,toasmallextent,duringitsproduction,transport,storageanduseasachemicalintermediateandasolvent.Theprimaryrouteforenteringtheenvironmentisthereleasetotheatmospherewhenusedasasolvent.1-Butanolisreadilydegradableinwaterandreadilydecomposedintheairbyphotodegradation.Itdoesadsorbonsoil,andfavorspartitioningtowaterversusair(80%to15-20%).Becausethedegradationanddecompositionisrapid,bioaccumulationorbioconcentrationisunlikely.1-Butanolispracticallynon-toxictoaquaticorganismsandbirdsonanacutebasis.Therefore,1-butanolishardtobeconsideredasamenacetotheenvironment.
e.Manufacturingprocess
Onesimplewaytoproduce1-butanolisfermentation.Firstofall,weneedaAlgaefarmtanktocollectcarbondioxideandsunlight,andthenconnectthisAlgaefarmtanktoafermentationtankinthepresenceofbutanolproducingbacteria.Afterthat,aforceoccurreddrivingcontentsinthefermentationtanktothenextoperator,cooler.Afterwaitingforseveraldays,thebutanolwillbecooledto0Celsius,andthenseparatedfromwater.
Methodology
a.Peng-RobinsonEOSandVDWEOSdescriptions
EquationofState:
Arelationshipbetweenthestatevariablesofthesystem.Simplesystemsinequilibriumarefullyspecifiedbytwopropertiessuchastemperatureandvolume;alltheotherfunctionsofstatearefunctionsofthese.Foranidealgas,theequationofstateis
.
VDWEOS:
Anequationthatrepresentsthebehaviorofagas,similarlybutmoreaccuratelythandoestheidealgaslaw.VanderWaals'equationofstateis:
(P+a/(V^2))*(V-b)=RT
Theterma/V^2isacorrectionforthemutualattractionofthemolecules,andbisacorrectionfortheactualvolumeofthemoleculesthemselves.(Thevaluesoftheconstantsaandbdependontheparticulargas,differentgashasdifferentaandb).20.90and0.1323ismycompoundaandbvaluerespectively.TheattractiveforcesbetweenmoleculesareknownasvanderWaal'sforces.
Peng-RobinsonEOS:
Anequationthatrepresentsthebehaviorofagas,similarlybutmoreaccuratelyandcomplicatedthandoesVanderWaals.ThePeng-RobinsonEOSwassuggestedin1976tosatisfythefollowingobjectives:
1.ParametersofthisEOSshouldbedefinedintermsofthecriticalpropertiesandtheacentricfactor.
2.Reasonableaccuracynearthecriticalpoint,particularlyforcalculationsofthecompressibilityfactorandliquiddensity.
3.Asinglebinaryinteractionparameter,whichshouldbeindependentoftemperaturepressureandcomposition,isneededforthemixingrules.
4.PREOSshouldbeapplicableinnaturalgasprocesses.
Peng-RobinsonEOSasshownbelow:
Thevalueof
isdependentonspecificgas.Differentgashasdifferent
mycompound(1-butanol)
is0.194.
b.Criticalproperties
Inthermodynamics,acriticalpointspecifiestheconditions(temperature,pressureandsometimescomposition)atwhichaphaseboundaryceasestoexist.Therearemultipletypesofcriticalpointssuchasvapor-liquidcriticalpointsandliquid-liquidcriticalpoints.
Mycompoundcriticalpropertieswillbeusedinprogrammingasshownbelow:
Tc=556.2K
Pc=4.56*10^6Pa
Ttriple=184.51K
Ptriple=3.5Pa(ThisdataiscalculatedbymatlabinsteadofNISTwebbook)
c.Outlineofproceduresusedtogeneratethethermodynamiccharts
1.ForP-Tphasediagram:
ThemethodtosolveP-TdiagramproblemisshowninPage306,Figure7.5-1.Themainidealforthismethodistofindphaseequilibrium,whichiswhenfugacityvaporisequaltofugacityliquid.
Firstofall,fordrawingthelinebetweenliquidandvapor,weneedtoguessapressure,andalsoweneedtoensurethispressureisbelowPcsothatVLandVvexist.Andthen,bycomputingaandbusingEqs.6.7-1,6.7-2,6.7-3,computingAandBusing6.7-5,wecanfinallygetZLandZV.SincewehaveZLandZV,wecanuse7.4-14tocalculatefLandfV.IffLandfVareequaltoeachother,itmeansthepressurethatweguessisthecorrectpressureforthespecifictemperature.However,iffLandfVarenotequaltoeachother,weneedanewpressureguess(P=P*fL/fV)anddothecalculationagainuntilfLandfVareequaltoeachother.Therefore,onespecifictemperatureshouldhaveonespecificpressurethatfLandfVareequaltoeachother,andwegetarangeoftemperaturefromTtripletoTc,wecaneasilygetalinebetweenliquidandvapor.
Fortheothertwophaseboundaries,themainidealisthesame,butjustchangethecriteriafromfL=fVtofL=fSandfV=fSrespectively,andwecanalsoeasilygettwolines.Andweputthesethreelinestogether,wecangetaphasediagramintheP-Tplane,justlikeFigure7.3-6showninthetextbook.
2.ForP-Vphasediagram
Todrawaliquid-vaporenvelope,weneedtoknowVVandVLatconditionoffL=fVwhenTr=0.75,0.85..BecausewealreadyknowPatthephaseequilibriumwhenTr=0.75,0.85,itisveryeasytogetVVandVLbyjustsubstitutingTandPintoPeng-RobinsonEOS,andsolveEOSforV.Twotemperaturesshouldleadto4valuesofV,andwecanplotthesefourVinagraph,connectthemtoacurvewhichcontainsapeakat(Vc,Pc).Thisgraphistheliquid-vaporenvelope.
Todrawspinodalofthegraph,themethodisverysimilartothepreviousonethatistodrawtheliquid-vaporenvelope.InsteadofgettingfourvaluesofVwhenfL=fV,thistimeweneedfourvaluesofVderivingfromthefirstderivativeofPeng-RobinsonEOSequalstozerowhenTr=0.75and0.85.Andthen,similartotheliquid-vaporenvelope,plotthesefourVinagraph,connectthemtoacurvewhichalsocontainsthepeakat(Vc,Pc).Thisgraphisthespinodal.
3.Cp
WeknowaformulathatisCp=Cp*-T*∫(dV2)/(dT2)PdP.Also,bytripleproductrule,wecanget(dV/dT)Pisequalto-(dP/dT)V/(dP/dV)T.Thismeansifwecancalculate(dP/dT)Vand(dP/dV)Trespectively,andderivatethequotientofVholdingconstantPtogetsecondderivative.SincethereisnoPintheequation,whenintegratethesecondderivative,simplyjusttimesP.Finally,substitutealltheparameters;wecangettherealCp.
4.JT(T)
Forthisgraph,themethodissimilartothepreviousmethod.Bycheckingimportanttable,Page196,wecangetJoule-Thomsoncoefficientexpression:
μ=-[V-T(dV/dT)P]/Cp
Since(dV/dT)P,Cp,T,andVareallknownalreadyfromchart3,therefore,simplyplugin,wecangettheJT(T)chart.
(d)OutlineofproceduresusedtoconstructtheRankinecycle.
Tomakeajudgmentwhethermycompound1-butanolisagoodrefrigerant,theworkIconsideristocalculatetheefficiencyoftheRankincycleprocessbyusingthecompoundspecificthermodynamicsinformationtosolveit.Firstofall,weneedtosetupatemperature,whichisTboiling,anduseP-Tdiagramtogetthecorrespondingpressure.Andthen,wecanuseequation4.4-3,Page125tocalculateanotherpressurebygivinganotherappropriatetemperature.Also,sincewealreadygettherealCpbycalculatingPeng-Robisonequation,wecansimplyuseCp*Ttocalculateenthalpy.OnethingshouldbenoticedthatthereistwoCp,CpvandCpl,whenusetheCp,weshouldchoosewisely.Oncewehavedonethesewo
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