DOC

Study_3

By Greg Griffin,2014-07-24 03:04
17 views 0
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.......

    ;e

    ;....

;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