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Study_3

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Study_3

    Study

ScientiticResearch

    ;StudyonRegenerationofMDEASolutionUsing

    ;MembraneDistillation

    ;CaiPei;WangShuH;ZhaoShuhua

    ;flJiangsuKeyLaboratoryofOilandGasStorageandTransportTechnology, ;Changzhou213016,China,”2DepartmentofScienceandTechnology,Jiangsu

    ;PolytechnicUniversity,Changzhou213016,China)

    ;Abstract:TreatingacidgasescontainedinnaturalgasbyMDEAisusedwidely.Buttheeffici

    encyof

    ;regenerationoftheMDEAsolutionlimitedthedevelopmentofthistechnology.Anoptimaltemperatureis

    ;necessaryforregenerationoftheMDEAsolutionusingmembranedistillation.Theexperimentresults

    ;showedthattheregenerationrateofMDEArosewithanincreasingtemperature.Buttherateincreased

    ;slowlyaftertheregenerationtemperaturearrivedatacertainvalue.Thisstudycanconfirmt

    hatregenera.

    ;tionoftheMDEAsolutionusingmembranedistillationisfeasible.Thistechnologyprovide

    smoreadvan

    ;tagesascomparedtoconventionalregenerationprocess.

    ;Keywords:membranedistillation;regeneration;MDEAsolution ;1Introduction

    ;Atpresent,theinlandnaturalgasproductionisabout17bil- ;lionm/ainourcountry,amongwhichthenaturalgasinthe

    ;Sichuanregion(includingChongqingMunicipality)accounts ;forabouthalfofthetotaloutputwhichcontainsalotof

    ;sulfurcompounds.Thegasmustbetreatedtoremovesul

    ;furcompoundsbeforeitisdeliveredtothemarket.Sichuan ;provincehasbuiltnearly20setsofgaspurificationunits, ;withatotaldesigncapacityofupto24millionm/d.Eight

    ;setsoflargescaleunitswithaprocessingcapacityofmore

    ;thanonemillionm/dofnaturalgasapieceareusedtotreat

    ;abouthalfofthetotalnaturalgasproduction[“.Similarto

    ;thetechnologyusedabroad,naturalgaspurificationunits ;mainlyuseaminesolutionforgasdesulfurization.The

    ;MDEAhasbeenusedwidelythankstoitslowcorrosiveness,

    ;highconcentrationsofsolvent,smallrecyclerate,low

    ;degradability,andlowpowerconsumption.

    ;MDEAsolutionusedinthepurificationprocessisgener.

    ;allystable,butMDEAcanbesubjectedtodeterioration ;becauseofentrainmentofhighsalinityformationwaterin ;gas,andcarryoverofcorrosioninhibitors,methanolandtrace ;oxygeninthesolution.MDEAdeteriorationnotonlycan ;leadtoalOSSofaminewithdecliningeffectiveamine ;concentration,anincreasedcostofsolventconsumption. ;45

    ;butcanalsoresultintheforn1ationofalotofdeterioration ;productstoenhancecorrosionandincreasethefoaming ;tendency,andincreasetheviscosityofthesolutionanden- ;ergyconsumption[.EachyearasizableamountofMDEA ;solutionisabandoned,resultinginseriouspollutiontothe ;environmentandsignificantincreaseinproductioncost. ;RegenerationofMDEAforrecoveringtheprecioussolu

    ;tionanddeepprocessingofsulfidescanraisetheutiliza

    ;tionrateofsolutionandpreventenvironmentalpollution. ;Atpresent,distillationiscommonlyusedathomeandabroad ;fortheregenerationofMDEA,whichusuallyrequiresalarge ;amountofhotairtoblowoffthesulfidefromsolutionin ;theregenerationtower.Onecubicmeterofabsorbenttobe ;regeneratedneeds100to200kilogramsofsteam[.Hence ;theenergyconsumptionisrelativelyhigh.Althoughover ;theyearsalargenumberofindustrialandlaboratorystudies ;onthestructureoftheabsorptiontower,andagreatdealof ;improvementsinfillerspeciesandabsorbentcomposition ;havebeencarriedout,butgreatsuccessstillhasnotbeen ;achieved

    ;Theideaonmembranedistillationwasbroughtf0rthin1967 ;andwasdevelopedinthe1980s.Itisanewtypeofmem

    ;braneseparationtechnology,whichuponapplicationinthe ;distillationprocessdemonstratesalotofadvantages,includ- ;

    ;C.....

    ;h

    ;.......

    ;i

    ;...

    ;n

    ;......

    ;a

    ;.......

    ;P.......

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;tro

    ;——

    ;leum——

    ;ProcessingandPetrochemicalTechnologyNo.4,December2008 ;ingtheuser-friendlyandenergysavingcharacteristics,the

    ;smallplotarearequired,andlowenvironmentalpollution. ;Applicationofthistechnologyindesalination, ;water

    purewaterpreparation,crystallizationand ;treatment,ultra

    ;enrichmentofaqueoussolutionofthenon..volatilesub.. ;stanceshasmadegreatstrides.Especiallyinrecentyears ;theadoptionofthehydrophobicmembranedistillationfilm ;hasbeenfurtherenhancingthesuccessofmembranedistil. ;1ationprocess~,.

    ;Whenthemembranedistillationtechnologyisappliedto ;recovertheMDEAsolution,thehollowfibermembrane ;contactorsboastacontactareaof3000——5000monone

    ;mofvolume,withtherateofregenerationbeing10times ;higherthantheconventionalregenerationtower.Thistech. ;nologyalsohassomeotheradvantages,suchashigh ;efficiency,wideapplication,goodscale-upeffect,readi

    ;nessforcommercialization,lowinvestment,

    ;lowoperating

    ;cost,andreadinessforautomaticcontro1.Andmembrane ;contactorsasanindividualequipmentcanbearrangedinany ;combinationtobeconnectedinparallelorinserieswith ;otherprocessunits[,.

    ;Inthispaper,simulationoftheregenerationprocesswas ;usedtodeterminetheoptimalregenerationtemperature. ;Furthermore,therelationshipbetweentheregenerationrate ;andthetemperaturewasinvestigatedbasedonthetheory. ;Onthebasisoftheoptimaltemperatureforregenerationof ;MDEA,severalexperimentswereconductedtoperformthe ;feasibilityanalysisonthemembranedistillationtechnology. ;Membranedistillationtechnologyfortheregenerationof ;MDEAdoesnothavemanyliteraturereports,therebyalot ;oftheoreticalandexperimentalstudiesneedtobe ;conducted,inordertobringaboutremarkablesocialand ;economicbenefits

    ;2fh?relical”lf

    ;2,lAbso~pli~mre’ic[iollnIcchanism

    ;ThereactionmechanismbetweenCO,

    ;andamineshasbeen

    ;studiedinthepreviousliterature.Theoverallreactioncan

;berepresentedasfollows:

    ;H2s+NR3NH+HS(Instantreaction)(1)

    ;CO2+IH2H20_RNH3++HCO3(2)

    ;Inaddition,Caplowhadputforwardthemechanismofzwit

    ;terionicreactionsin1968.Itwasextendedandusedfores. ;tablishingthealcoholsolutionmodelofCO,

    ;absorptionby

    ;Danckwertsin1979.Ithasalsobeengenerallyadoptedthat ;thereactionofCOwithprimaryandsecondaryaminescan ;bedescribedbythezwitterionicmechanism:

    ;CO,+RNH-RNH2+CO0(3)

    ;RNH~+Co0BRNHCOO+BHf41

    ;InwhichBistheamine,waterandhydrogenioninaqueous ;so1uton

    ;2.2Regenerationreactionmechanisms

    ;Intheregenerationprocess,theabsorbedbyproductsare ;thermallydecomposedtoreleaseCO,

    ;fromthesolutionof

    ;ammoniumcompounds.

    ;RNHCOO-+H,0CO,+RNH,+0|{-(5)

    ;HCOC0,+0}r(6)

    ;CO+H,OCO,+2OH(7)

    ;Itcanbeseenfromthereactionprocess,MDEAcannotbe ;adirectresponsetotheCO2generatedfromcarbonates.In ;responsetoCOandwaterinvolvedinthereaction.remova1 ;ofCOfromMDEAsolutionbywatervaporismorediffi

    ;cultthanremovingHS.

    ;Theabove-mentionedreactionprocessgoestotherightside ;oftheequationatlowtemperature.Atatmosphericpressure, ;whenthetemperatureishigherthan105~Cthereactionpro

    ;ceedstotheleftsideoftheequation.Thereactiongoesto ;therightsideoftheequationathighpressure,andreverses ;totheleftsideatlowpressure.Therefore,theabsorption ;reactionoccursatlowtemperatureandhighpressure.The ;desorptionreactiontakesplaceatlowpressureandhigh ;temperature.

    ;Themainphysicalandchemica1parametersOfMDEAare ;showninTlable1_8J.Thephysicalandchemicalparameters ;ofMDEAindicatethattheboilingpointofMDEAis230.6 ;?.whichishigherthanitstheoreticaldegradation ;temperature.Butwhenthepressureinthedistillationsys

    ;ternisreduced.itsboilingpointisalsolowered.Thismea. ;surenotonlycanreducetheboilingpointofthematerial, ;butcanalsomakethedegradationofMDEAsolutionmore

;ScientificResearch

    ;Fable1PhysicalandchemicalparametersofMDEA ;ItemsIl.?蠢Data|}

    ;Molecularformula|J7,cll

    133. ;Vaporpressure,Pa||l?

    ;FreezizD,nt,oC|j簦一1

    ;Relativemolecular馥峨ss,g/mol|JJ9.J7

    ;Boilipoint,7|||l2

    ;Flashpoint,|||||26.

    ;0:

    ;|I

    ;Density(101.3kPa,20~C),g/cm310418

    ;Solubilityinwater(20??出身脚

    ;Thermaldecompositiontempera-.|

    ;t.ureatatmospherpressure,~C

    ;Viscosity(20mPa-s--..||||J

    ;difficult{91.Whenthedistillationisrealizedundervacuum. ;therelationshipbetweentemperatureandpressurecanbe ;representedby:lgP=A+8,T.InwhichPispressure.Tis ;absolutetemperature,andbothAandBareconstants.IflgP ;isusedastheordinateand1/Tastheabscissatoplota ;curve.astraightlineisobtained.Therefore,thevaluesof ;andBcanbecalculatedfromthetwogroupsofthetern. ;peratureandpressuredata.Andthenthecorrespondingtem

    ;peraturecanbefoundbychoosingthepressurevalue. ;3Experimental

    ;ThetemperatureforregenerationofMDEAsolutionwas ;studiedbyusingsimulatingexperimentsundercertainspeci- ;fledconditionst.Theprocessflowchartforamineregen

    ;erationisshowninFigure1.Ahighperformancecondenser

    ;wasusedtopreventwaterevaporationcausedby ;interference.Theheatingratewascontrolledapproximately ;at910K/min.Theerrorindesorptiontemperaturewas ;controlledwithin4-1.0K.Calciumhydroxidewasputin. ;sidetheabsorptionbottle.WhentheCOdesorptionreac. ;tionoccurred.thesolutioninthebottlebecometurbid.Ca1. ;ciumhydroxidewasconvertedintosolidcalciumcarbonate. ;estatusofCOdesorptionwasinvestigatedatatempera- ;tureof358,368,378,383,393,403K,respectively. ;Figure2showstheeffectofregenerationtemperatureon ;47

    ;F/gurelProcessflowcharttamineregeneration ;1——0ilbath;2.Threeneckedflask;3——Condenser;

    ;4_Absorptionflask

;18O

    ;15O

    ;

    ;12O

    ;

     ;90

    ;60

    ;3O

    ;O

    ;358368378383393403

    ;0O

    ;98

    ;96

    ;94

    ;92

    ;90

    ;88

    ;86

    ;84

    ;82

    ;Temperature,K

    ;Figure2Effect,regenerationtemperature011CO3 ;.formationtimeandregenerationrate

    ;thetimeforCO.formationandtheregenerationrate.The ;efficiencyoftheregenerationincreasedwithanincreasing ;temperature.Withthetemperaturerisingfrom358Kto ;383K.theefficiencyofregenerationincreasedfrom ;86.2%to98-3%.Whenthetemperatureexceeded383K, ;theincreaseinregenerationefficiencysloweddown. ;HowevertheCOformationcyclewasshortenedwithan ;increasingtemperature.Whenthetemperatureincreased ;from358Kto383K,theCOformationcyclewasshort. ;enedfrom166minto44min.Whenthetemperatureex- ;ceeded383K,thecurveleveledoff.FortheDMEAregen. ;erationprocess,energyconsumptionisthemostimportant ;indicator.Whenthetemperaturereached383K.theregen- ;erationefficiencywasveryhighwithashorterCO2forma

    ;I10BJI1

    ;n

    ;O

    ;p

    ;r

    ;0

    ;S

;e

    ;d

    ;n

    ;

    ;p

    ;O

    ;e

    ;f

    ;0

    ;0

    ;a

    ;.eUfteaD

    ;J

    ;3

    ;ChinaPetroleumProcessingandPetrochemicalTechnologyNo.4,December2008

    ;tioncycle.Thereforethemostappropriatetemperaturewas ;383K.

    ;3.2ExperimentalStud)onmembranedistillation ;technology

    ;3.2.1ExperimentalEquipment

    ;TheprocessofmembranedistillationunitisshowninFig

    ;ure3lo_.Beforeandaftermembranedistillationexperiments. ;theMDEAcontentintheabsorbentwasmeasuredbycapil

    ;larygaschromatographycomprisingaGC900

    ;Figure3riowdiagram,.membranedistillation ;experimentalunit

    ;1WasteMDEAsolution;2Magneticpump;3C0nstanttempera

    ;turewaterbath;4——Flowmeter;5----Condenser;6——Buffertank;

    ;7_Membranemodule:8——Vacuumpump;9_1

    ;chromatograph.ThemembranedistillationforMDEAre- ;generationexperimentusinghydrophobicpolypropylene ;hollowfibermembranewasappliedtostudythefactorsin

    ;fluencingtheMDEAregenerationefficiencyatdifferent ;temperatures.WasteMDEAsolutionwasheatedbyacon- ;stanttemperaturewaterbathtothesettemperature.Before ;thesolutionenteredtheregenerationmembranemodule, ;theliquidvelocityandpressureweremeasuredbyaliquid ;flowmeterandapressuregauge.GasseparatedfromMDEA ;wasroutedtotheothersideofthemembranebymeansof ;thesuctionforcecreatedbyavacuumpump.Thevelocity ;andpressureofthegasweremeasuredbyagasflowmeter ;andvacuummeter.Thesampleswerecollectedfromthe ;remainingliquidinthebuffertank,andweremeasuredas ;necessary.Themainparametersoftheequipmentareshown

;jn11ahle2.

    ;3.2.2Membranemodule

    ;Themoduleforthemembranedistillationexperimentalunit ;wascomposedofthehydrophobicpolypropylenehollow ;fibermembrane.ItwasprovidedbyTianjinBlueCrossMem- ;braneTechnologyCo.,Ltd.Thestructuralparametersofthe ;hollowfibermembraneareshowninTable3.

    ;Table2Equipmentlistofexperimentalunit

    .|Remarks ;ItemsBasic~ametersl

    ;Ne,DKB-1906

    ;ConstanttemperatureVoltage220V;Powerconsumption:900W;ShanghaiJingWangExp

    erimental

    ;waterbathFluctuationsi~temperature:~0.1~C.Equipment(_o.’

    ;Temperat~erange:5--99~C.I

    ;Glassr0tameter:LZB-4WB.

    ;LiquidflowmeterChangzhouYuehengInstrumentsCo.LtdM ;eas~ngrange(20”C):4~OOmL/min.||

    ;PressuregaugeRange:0~0.16MPa.||||HangzhouStorkHillFa~ory ;D_.j.

    ;MagneticpumpRatedflow28L/ni:Head:1.4m:KeyuanMagneticPumpWcrks

    . ;Sed:2600ffmin.|?

    ;Glass滢铳璐_3B?jj

    ;GasflowmeterChangzhouYuehengInstrumentsCO.,LtdM ;easuringrange(20~C,101325Pa):0.3~3L/min| ;VacuummeterRange!,——N疆?|||HangzhouStorkHillFactory ;Mode1:SHZ-Dwatercirculationoumps.

    ;Vacuumpump砀口口m删打础l0.1MPa;KongyiCity,HenanYuyingYuHua ;ExtraCtiOnra!lOL~min,Dwer:370WInstrumentFactory

    ;48

    ;ScientificResearch

    ;Table3Characteristicparametersofmembrane ;module

    ;ItemsData0|

    ;Shelldiameter,mm:.?-|

    ;No.offibers.l32o0|

    ;Effectivelength,mm|I300||I

    ;Fiberinsidediameter,mmOi38|

    ;Fiberoutsidediameter,mm||

    ;Membraneporediameter,gm0:010:..

    ;Note:ThedatainthisTableisprovidedbythemanufacturer ;3.2.3Relatedequipment

    ;TheGC--920gaschromatographequippedwithaFIDdetec-- ;torandacapillarycolumnSE54(30mx0.53mmx1.0m)

    ;wasusedtomeasuretheMDEAabsorbent.TheN3000chro

    ;matographyworkstationdatadevisedbytheZhejiangUni- ;versitywereusedtoprocesstheanalyticaldata.Thismethod ;offeredanaccurate,rapidandsimplemeansforthedeter

    ;minationofMDEA.Thisinstrumentwithaminimumerror ;couldfullymeettherequirementsofthisstudy.

    programmedGC--920typegaschromato?- ;Thetemperature--

    ;graphequippedwithaFIDdetectorwasappliedtoanalyze ;theMDEAabsorbent.Thesampleswerecollectedbyaliq- ;uidinjectionsyringe.Theoperatingconditionsofthechro

    ;matographareasfollows[…:

    ;Table4Operatingconditionsofchromatograph ;Itemsl||lD|

    ;ataI

    ;Chromatographiccolumn

    ;Initialtemperature,?

    ;Temperatureatendoftest

    ;VaporizatiOnroomtemperature,?i2I|

    2,800 ;FIDdetectortemperature,?一i

    ;Highpuritynitrogen

    ;,5Flowrateincolumn,mL/minsowatendoftestmL/min

    ;Hydrogenpressure,.MPa.ll0.12I

    ;Pressureofcombustion-supportingair,MPa0.07|| ;4ResultsandDiscussion

    ;Accordingtotheoptimalregenerationtemperatureof383K ;andtherelationbetweentemperatureandpressurefor ;vacuumdistillationwhentheoperatingpressurewasmain

    ;49

    ;tainedat10kPa,theliquidwasheatedtotheregeneration ;temperaturesat35,40,45,55,60,65?,respectively.

    ;Theexperimentaldatawereanalyzed,withtherelationship ;betweentemperatureandrecoveryratepresentedinFigure ;4.

    ;

    ;

    ;

    ;

    ;

    ;354O455O556065

    ;Temperature,?

    ;Figure4EffectojtemperatureoHregenerationrate ;Itcanbeseenfromthetestresultsthattherecoveryrate ;rosegraduallywithanincreasingtemperature.Whenthe ;temperaturereachedacertainvalue,therecoveryraterose ;slowly.Energyconsumptionwasthemostimportantindi

    ;catorfortheeconomicsoftheregenerationtechnology. ;Therewasamuchhigherregenerationrateandloweren- ;ergyconsumptionwhentemperaturereached45?,which

    ;wouldbethemostappropriatetemperatureforregenera

    ;tionofMDEA.Accordingtotherelationshipbetweentern

    ;peratureandpressure,thegasregeneratedfromthemem

    ;branedistillationexperimentsrequiredaslightlyhighertem- ;peraturethanthatvalueobtainedinthesimulation ;experiments.

    ;ThewasteMDEAsolutionwasanalyzedbygas

    ;chromatography,andtheresultsareshowninFigure5.The ;peak[2]onthegraphdenotesMDEA,withtheotherssmall ;peaksrepresentingtheunknownimpurities.

    ;ThechromatogramsforMDEAsolutionregeneratedata ;temperatureof45,55,60,65?,respectively,areshownin

    ;Figure6(a),(b),(c),and(d).Itcanbeseenclearlyfromthe ;chromatogramsthattheeffectofusingmembranedistilla

    ;tiontechnologyforregenerationoftheMDEAsolutionwas ;veryremarkable.

    ;??舳加?如加

    ;ChinaPetroleumProcessingandPetrochemicalTechnologyNo.4,December2008

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    ;Time,min

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