Ethanol Dehydration Plant

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DesignofanEthanolDehydrationSystemJamieHiltz ZackTaylor MarkBaierDepartmentofChemicalEngineeringUniversityofSaskatchewan20072008iAbstractHaloConsultinghasbeenworkingonthedesigntopurifyethanolwithMarchConsultingAssociatesInc.Thesystemwasneededtodehydratealiquidfeedof95%v/vethanol5%v/vwatertoaminimumof99.5%v/vproduct.AfterHaloConsultingexaminedavarietyofdifferentmasstransferapplicationstocarryoutthistask,itwasdecidedthattheuseofpressureswingadsorptionwouldbebest.Thefinaldesignconsistsoftwoparallelcolumnsoneofwhichisadsorbingwhiletheotheriseitherdesorbingorinstandby.TheliquidfeedisheatedandvaporizedbeforeitissenttotheadsorbingcolumnwhereitisdehydratedbyapackedbedofType3Amolecularsieve.Theregenerationtimeandadsorptiontimeswerefoundtobe6.33and23.9minutesrespectively.Forthefirst6.33minutesofadsorption,40%ofthedryethanolproductissenttohelpregeneratethedesorbingcolumnwhiletheother60%iscondensedtothefinalproduct.Fortheremaining17.61minutesintheadsorptioncycle,theregeneratingpurgestreamisnolongerneededand100%oftheproductstreamiscondensedtothefinalproduct.Thephysicalpropertiesofthecolumnsandtheadditionalequipmentweredeterminedusingmassbalances.iiThecostsoftheequipmentandtheannualoperatingcostsforthisdesignwerefound.Aneconomicanalysiswascompleted,comparingthecostofenergytobreaktheazeotropewiththisdesigntothatofazeotropicdistillationanditwasdeterminedthatthisdesignismoreeconomicallyfeasible.AsafetyanalysiswasperformedthatconsistedofaHAZOPanalysisandaDOWFireandExplosionIndexanalysisononeofthecolumns.Themosthazardouspossibledeviationsweredeterminedtobehightemperatureandleaks.Recommendedpreventativeactionshavebeenincludedinthisreport. iiiAcknowledgmentsThemembersofHaloConsultingwouldliketoacknowledgethefollowingpeoplefortheirdirectionandguidancethroughoutthedurationofthisdesignproject: Dr.GordonA.Hill,ChemicalEngineering422Advisor,DepartmentofChemicalEngineering,UniversityofSaskatchewan Dr.HuiWang,ChemicalEngineering422Advisor,DepartmentofChemicalEngineering,UniversityofSaskatchewan Dr.RichardEvitts,FacultyAdvisor,DepartmentofChemicalEngineering,UniversityofSaskatchewan DongmeiFangSeniorProcessEngineer,MarchConsultingAssociatesInc. TaraZrymiakSeniorProcessEngineer,MarchConsultingAssociatesInc.ivTableofContents1.0 INTRODUCTION 11.1 Background 11.2 PurposeandProposedDesign 12.0 LITERATURESURVEY 22.1 Introduction 22.2 Distillation 32.2.1 AzeotropicDistillation 32.2.2 PressureSwingDistillation 42.3 ThermalSwingAdsorption 53.0 DETAILEDQUALITATIVEPROCESSDESCRIPTION 63.1 Introduction 63.2 FeedPreparation 73.3 Dehydration 83.3.1 Pressurization 103.3.2 Adsorption 103.3.3 Blowdown 133.3.4 Regeneration 143.4 CoolingandCondensing 174.0 SIMULATIONANDBALANCES 184.1 Introduction 184.2 FeedPreparation 194.3 Dehydration 214.4 VacuumPump 244.5 Condensation 254.6 Overall 26v5.0 EQUIPMENTDESCRIPTIONANDSIZES 295.1 Introduction 295.2 HeatExchangers 305.2.1 HeatExchanger#1 305.2.2 HeatExchanger#2 315.2.3 HeatExchanger#3 315.3 VacuumPump 325.4 AdsorptionTowers 335.5 MolecularSieve 395.6 ValvesandPiping 416.0 ECONOMICS 436.1 Introduction 436.2 EquipmentCosts 446.3 MolecularSieveCosts 466.4 AlternativeEconomicComparison 467.0 SAFETYANALYSIS 487.1 Introduction 487.2 ChemicalProperties 497.2.1 Ethanol 497.2.2 AluminoSillicate 507.3 HazardandOperabilityanalysis 507.3.1 HAZOPStrategy 507.3.2 HAZOPConclusions 517.4 DOWFireandExplosionIndexAnalysis 547.5 ProcessSafetyManagement 548.0 Conclusions 567.0 Recommendations 58References 62AppendixA:ProcessFlowDiagrams 59viAppendixB:MassBalances 66AppendixC:AdsorptionData 70AppendixD:SizingCalculations 75 ColumnSizing 76 BreakthroughCurveCalculations 77 EquipmentSizing 81 SummaryTables 87AppendixE:EconomicsCalculations 90AppendixF:PipingandInstrumentationDiagram 94AppendixG:MaterialSafetyDataSheets 96AppendixH:HAZOP 111viiListofTablesTable4.1:Molebalancedataforadsorptioncolumnwithuseofpurgestream 22Table4.2:Molebalancedataforadsorptioncolumnwithoutuseofpurgestream23Table4.3:Molebalancedataforregenerationstep 23Table4.4:Molebalancedataforoverallsystem 27Table5.1:Physicaladsorptionpropertiesofadsorptioncolumn 36Table5.2:TypicalpropertiesofZEOCHEM.Z303 38Table5.3:Ethanoldehydrationequipment 42Table6.1:Summaryofequipmenteconomics 45Table6.2:Summaryofalternativecomparison 47TableB.1:Massbalanceforadsorbingcolumn(Bed1) 67TableB.2:Massbalancefordesorbingcolumn(Bed2) 68TableB.3:Massleavingsystem 69TableB.4:Overallsystemmassbalance 69TableC.1:Tableofgivenandcalculateddatafordeterminingthebreakthroughcurve74TableD.1:UTubeheatexchangercalculateddataforpreheatingfeed 87TablesD.2:Bayonetheatexchangercalculateddataforfeedvaporization 87 TableD.2a:Calculateddataforsensibleheating 87 TableD.2b:Calculateddataforphasechange 87 TableD.2c:Calculateddataforsuperheating 88viiiTablesD.3:Bayonetheatexchangercalculateddataforproductcondensation 88 TableD.3a:CalculatedDataforphasechange 88 TableD.3b:CalculatedDataforsensiblecooling 88 TableD.4:CalculatedDataforliquidringvacuumpump 89ixListofFiguresFigure3.1:Processflowdiagramofentiresystem 9Figure3.2:Switchingsequenceforadsorptioncolumns 9Figure3.3:Pressureswingadsorptioncyclepressurizationandadsorptionofbed11Figure3.4:Breakthroughcurve 13Figure3.5a:Valvesequenceforblowdownstep 14Figure3.5b:Valvesequenceforregenerationstep 14Figure3.6:Cyclestepsforpressureswingadsorption 16Figure4.1a:SummaryofdataforUTubeheatexchangertopreheatfeed 20Figure4.1b:SummaryofdataforBayonetheatexchangertovaporizefeed 20Figure4.2:Summaryofdataforadsorptioncolumn 21Figure4.3:HYSYSscreenshotofvacuumpump 25Figure4.4:SummaryofdataforBayonetheatexchangertocondenseproduct 26Figure4.5:HYSYSscreenshotofoverallmassbalance 27Figure5.1a:Theoreticalcurve 35Figure5.1b:Actualcurve 35Figure5.2:Breathroughcurveswithvariedbedheights 37Figure5.3:Visualofoneadsorptioncolumn 40Figure5.4:Visualofaluminosilicate 38FigureA.1:ProcessflowdiagrammimickingthedehydrationsysteminHYSYSwhenBed2(BAL2)isinregeneration 63FigureA.2:ProcessflowdiagrammimickingthedehydrationsysteminHYSYS whenBed2(BAL2)isdoneregenerating 64xFigureA.3:Processflowdiagramoftheethanoldehydrationsystem 65FigureC.1:Isothermaldataforwateradsorptiononatype3Amolecularsieve 71FigureC.2:Watervapourisothermat120forType3Amolecularsieve 72FigureC.3:Graphforthedeterminationofequilibriumconstant usingLanguirsform 73FigureF.1:Processandinstrumentationdiagram 95FigureH.1:SummaryofHAZOPanalysis 112xiRomanNomenclatureSymbol Name UnitsAPhusc Phasechangearea m2AscnsbIc Sensibleheatarea m2ASupchcutng Superheatingarea m2A1otuI Totalarearequiredforheatexchanger m2A Crosssectionalareaofthecolumn m2Ac Annualcost $o Utilitycostcoefficient nounitsb Utilitycostcoefficient nounitsCpA Heatcapacityofethanol k]kgKCpB Heatcapacityofwater k]kgKCpmix Heatcapacityofmixedstream k]kgKCs] Costoffuelusedtogenerateutility $u]c] Concentrationentering kg H20m3 adsorptioncolumn xiico Concentrationleaving kg H20m3 adsorptioncolumn Columndiameter mAB Diffusivityofethanolinto cm2s water c]] EffectiveDiffusivity cm2s K Knudsendiffusivity cm2s p Particlediameter mS Surfacediffusivity cm2s Pd Porediameter cmF Pumpdownfactor nounitsF1 Correctionfactor nounitsG Gassuperficialmassvelocity kgm2sEuds HeatofAdsorption kcuIkgH20K Adsorptionequilibriumconstant nounitsK Constant nounitskc Masstransfercoefficient cms xiiiI Columnlength mIb Bedlength mIES Lengthofequilibriumzone mIuB Lengthofunusedbed mHA Molecularweightofethanol molgHB Molecularweightofwater molgHAB MolecularWeightoftheethanol molg andwatermixture H AverageMolecularWeight molgHwmx MolecularweightofthemixedstreamkgkgmoIm constant nounitsm Massflowrate kgh m] Massflowrateentering kgh adsorptioncolumn mo Massflowrateleaving kgh adsorptioncolumn xivms] Auxiliaryplantcapacity kgs msw Massflowrateentering kgs vacuumpump NRc Reynoldsnumber nounitsNSc Schmidtnumber nounitsNSh Sherwoodnumber nounitsP] Pressureentering otm adsorptioncolumn Pn Pressureenteringvacuumpump kPoPo Pressureleaving otm adsorptioncolumn Pout Pressureleavingvacuumpump kPoPP Pressureofthepurgestream otmPCI Plantcostindex nounits Heatduty k]h ] Volumetricflowrateentering m3h adsorptioncolumn xvo Volumetricflowrateleaving m3h adsorptioncolumn q Adsorptioncapacity kgH20kg R Gasconstant gmoIKorcuImoIKS Pumpcapacity m3h Sg Surfaceareaofmolecularsieve m2g I Timerequiredtoreachaspecific min vacuumlevel I] Temperatureentering K adsorptioncolumn Io Temperatureleaving K adsorptioncolumn IP Temperatureofthepurgestream Ktu Adsorptiontime mintb Breakthroughtime btc Thicknessofthecolumn mmtp Regenerationtime bt- Idealadsorptiontimefor b Verticalbreakthrough xviu Overallheattransfercoefficient ]m2sKuP UtilityPrice $kg o] stcumuo Superficialvelocity ms uomux Maximumsuperficialvelocity ms I Volumeofcolumntobeevacuated t3Iubs Volumeofadsorbent m3IcoIumn Volumeofthecolumn m3Iod Volumeifvoidinthecolumn m3w] Molarflowrateentering kmoIh adsorptioncolumn wo Molarflowrateleaving kmoIh adsorptioncolumn ws Shaftwork Kw xviiGreekNomenclaturee Intrinsicefficiency nouni