Liquid Liquid Separation Technology

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<ul><li><p>Liquid-Liquid Separation Technology</p><p>Sulzer Chemtech</p><p> Sulzer_Brosch_Liquid_Liquid.indd 1 20.09.12 09:19</p></li><li><p>Introduction</p><p>2</p><p>Content Page</p><p>Introduction 2</p><p>ProductSummary 4</p><p>Mellaplate 6</p><p>FeedInletsandCalmingBaffles 9</p><p>DCCoalescer 10</p><p>DusecCoalescer 11</p><p>WashTankDistributor 14</p><p>TestingandNewDevelopments 15</p><p>In industrial process equipments liquid-liquidmixturesareproducedbyessentiallytwodifferentmechanisms.</p><p>a) Mixingofthephasesineitherpurpose-built equipment, mechanical mixers,staticmixerswherepressureenergyisappliedtoincreasethesurfacefreeen-ergyof thefluids toproducedroplets,or inshearflowof thefluidmixture inpipes.</p><p>b)Thecoolingofasaturatedliquidbelowthe solution point so that the solutephase condenses out of solution re-sultingintheformationofasecondliq-uidphase.Thistakesplacefrequentlyin storage tanks and in processesdownstreamofcondensersorcoolers</p><p>Whentwophasesareformed,thismixtureismostoften in the formofadispersion(droplets of one phase distributed in thesecondorcontinuousphase).Themixtureis thermodynamically unstable, meaningthatgiventime,thedropletswillseparateout to form twobulk liquid phases. Thistakes place by droplets coalescing bothwith near neighbor droplets (drop-drop</p><p>The Brownian force additionally acts onsmallerdropletsinafluid.Aneverydayex-ampleisseeninabeamofsunlightwheredustparticlesintheairareseentoshim-mer,therandommotionbeingduetothebombardmentof thesmalldustparticlesby air molecules. The dust particles af-fectedinthiswayareinthesizerangeof0.1~2mm.Largerparticlesarenotaffect-edinthisway.Inasimilarmannersmallerliquid droplets in a liquid continuum areso affected and since the settling veloc-ityduetogravityofsuchdroplets isverylow, therandommotion impartedonthedropletsbyBrownianmotionturnsouttobeoftheorderofthesettlingvelocity.Thenetresult is thatdroplets in thisrangeofsizeswillnotsettleoutandthereforearenotamenabletogravitysettlingmethods.Such dispersions are called secondarydispersions.Technically theyarestill ther-modynamicallyunstablebutthekineticsofseparation by gravity only is so low thatformostpurposestheyappearstable.Se-condarydispersionscannotbeseparatedeffectively in gravity or primary separati-on equipment and require different tech-niquesforseparation.</p><p>coalescence)andwiththebulkphaseasthis forms and settles from the mixture(drop-interface coalescence). The kinet-ics,orrateatwhichtheseprocessestakeplace,determinetheselectionanddesignof equipment. The driving force promot-ingcoalescence isgravityand inagivensystemisproportionaltor g,rbeingthedensitydifferencebetweenthetwoliq-uidphases.Thediameterofthedropletsisacriticalparameter. Indeterminingthesettling velocity in a liquid-liquid disper-sionthedropletsizecombinedwithr gwilldefinethesettlingforceonadroplet.This separation principle is governed bytheStokesLawwhichisdefinedas:</p><p>Where:</p><p>vd Settlingvelocityofadispersed droplet</p><p>Dr Densitydifferencebetweenthe twoliquidphases</p><p>d Dropsizediameter</p><p>mc Dynamicviscosityofcontinuous phase</p><p>g Gravitationalacceleration</p><p>g |Dr| d2</p><p> 18 mcvd =</p><p> Sulzer_Brosch_Liquid_Liquid.indd 2 20.09.12 09:19</p></li><li><p>Introduction</p><p>3</p><p>The simplest forms of equipment usedto separate dispersions are horizontal orvertical gravity settling tanks. The capac-ityofsuchvesselsdecreasesastherateofcoalescenceandseparationdecreases.Therefore, there will be circumstanceswhere the dimensions of such vesselsare uneconomical for some applicationsand methods to improve the separationkineticsneed tobeapplied.Thiscanbeachievedbyincreasingthedrivingforcetoacceleratethestepsinthemechanismofcoalescence.</p><p>Sulzer offers a range of equipment de-signed to accelerate the separation ofeither primary or secondary immiscibleliquiddispersions.Coalescers -and theirinherent benefits - are today often con-sidered preferable to conventional grav-ity separators. Figure 1 gives a simpleoverview of how primary and secondarydispersionsareusuallyformedandwhichSulzercoalescersaresuitabletoseparatethesedispersions.</p><p>Immiscible Dispersions</p><p>Typically Formed</p><p>Deliberately By:</p><p>LowShearProcessessuchas:</p><p>SolventExtractionMixerSettlersSteamStrippingWashingProcessesCounter-currentTowers</p><p>Creating Primary Dispersions:</p><p>CoarsedropletdistributionPredominantly&gt;30mSeparatereadilyundergravity</p><p>Waxyfeeds?SolidsContent?LowPressureDrop?</p><p>Accidentally By:</p><p>HighShear&amp;ThermalProcess-essuchas:</p><p>CentrifugalPumpsChokeValvesCondensationofImmiscibleLiquidsEntrainedDispersionfromPrimarySeparationsSub-coolingofLiquidsinStorage</p><p>Creating Secondary Dispersions:</p><p>FinelydisperseddropletsTypically1-30mSlowtoseparateundergravityAppearanceoftenhazy</p><p>SeparatedUsing</p><p>MellaplateCoalescers</p><p>SeparatedUsing</p><p>DCCoalescers</p><p>DusecCoalescers</p><p>Dusec PlusCoalescers</p><p>Separated Using</p><p>Fig. 1: Overview about Formation of Dispersion and suitable Sulzer Coalescer Types</p><p>Yes No</p><p> Sulzer_Brosch_Liquid_Liquid.indd 3 20.09.12 09:19</p></li><li><p>4Type of Separator</p><p>MellaplateTM</p><p>DCCoalescerTM</p><p>DusecTM</p><p>DusecPlusTM</p><p>ShellSchoepentoeterTMandSchoepentoeterPlusTMInletDevice</p><p>GIRZCycloneInletDevice</p><p>Materials </p><p>StainlesssteelsAlloy625,825</p><p>Theseareproducedbytwodissimilarfilamentsknittedtogethertoformthemesh.OnefilamentisametallicwiremadeofstainlesssteeloralloyC22,C276,400,625or800andtheotherismadeofPP,FEP,ETFE,PTFE,orglassfibers</p><p>Incartridgeformwiththeliquidflowingfromthecenterradiallyoutwards,theDusecandDusecPlusCoalescerconsistofase-lectionoffibermaterials.</p><p>Stainlesssteels,Alloy625,825</p><p>Stainlesssteels,Alloy625,825</p><p>Applications</p><p>Improvedseparationefficiency.Twophasesdisengagecontinuouslyalongtheplateorsheets.Improvedflowstability.Reducedriskofdropletre-entrainment.Verysuitableinsystemssusceptibletofoulingwithincreasedplateangleandplatespacing.Efficiencymaintainedevenwithphaseinversionofdispersedliquid.Suitableforoperationwithagasphase.</p><p>Improvedseparationefficiency.Highercapacitiesallowde-bottleneckingofconventionalseparators.Largecostsavingsinpressurevessels.Efficiencymaintainedevenwithphaseinversionofdispersedliquid.Highfreevolumemeanssmallerpressuredrop.</p><p>Fibertopologyandsurfacepropertiescombinedwithoptimizedlayercompositionsmeanhigherefficiency.Separationefficiencydownto10ppmentrainmentoffreedroplets.Higherloadingsandabsenceofjettingfromouterlayersmeanhigherpackingdensities.Smallervesselsizemeanscapitalcostreduction.Pressuredropminimized.Quickperformancerecoveryfollowingfeedconditionchanges.</p><p>TheSchoepentoeteristhemostcommon-lyusedvaneinletdeviceforintroducinggas/liquidmixturesintocolumns.TheSchoepentoeterPlusisanadvancedfeedinletvanedevicewithconsiderablyincreasedde-entrainmentefficiency.Bothdevicessuppressandminimizetheturbulenceintheinletcompartmentoftheseparator.Entryofgasintotheliquidphaseislow.</p><p>TheGIRZisusedasadefoamingcyclonicinletdevicetosuppressandbreakmanytypesofprocessfoams.Sometypicalapplicationsincludefreewaterknockoutdrums,flashdrums,testseparators,2and3-phaseproductionseparators.</p><p>Product Summary</p><p>0604 2507-4</p><p> Sulzer_Brosch_Liquid_Liquid.indd 4 20.09.12 09:19</p></li><li><p>5Typical Operational Range</p><p>Applicableforprimarydispersions.Dependingonthetypeused,Mellaplatecoalescerscanoperateatseparationfluxesofupto100m3/m2h.Comparedtoemptysettlersimprovedcut-offdiam-etersareachievedduetoshortersettlingdistancebetweenplates.</p><p>Applicableforprimarydispersions.Lowcut-offdiameters,thereforeextendedrangeofoperation.Thelowerlimitisatornearthetransitionregionfromprimarytosecondarydispersioni.e.,cut-offdropletsize~30-40m.DependingontheDCCoalescertypeandapplication,highseparationfluxesofupto120m3/m2hcanbeachieved.</p><p>Applicableforsecondarydispersionswherethedropletsaresosmalltheydonotreadilywetasurfaceorsettleundergravitytypicaldropsizesareintherangeof1to30microns.Designedtoachievehighperformancewithminimumpressuredrop,theDusecPlusmodelprovidesahighcapacityalter-nativetoconventionalDuseccartridges.Thesmallerdiameterandincreasedpack-ingdensitymakeitsuitableformaximizingtheeffectiveareaofthecoalescermediainagivensizeofvessel.</p><p>Generallydesignedatdynamicpressures70vol%.Suitableforinstallationinhorizontalorverticalseparators.Suitableforliquidslugs.</p><p>TheGIRZcyclonicinletdeviceutilizesthemomentumofthefeedstreaminletinor-dertogeneratehighg-forces.Defoamingisachievedasgasbubblesareseparatedfromtheliquidphasebythecentripetalforcesinthecyclonetubes.Gasisre-leasedfromthetopofthedeviceandthebottomopeningofthecyclonesissub-mergedbelowtheliquidintheseparatorinordertoavoidagasblowout.</p><p>Characteristics</p><p>MellaplateWismadeupofasetofparallelplatesthatisfittedintoavesselintheseparationsectionsuchthattheplaneoftheplatesisarrangedintheaxialdirectionofthevessel.Theplatesarenormallyinclinedtotheaxisatanangleof45or60.Theplatespacingisoftheorderof15to100mm.MellaplateM,MGandNaremadeupofstructuredcor-rugatedmetalorplasticsheets.Highpackingdensitymeansmoresheetsinagivenvesselvolume.</p><p>Manufacturedasaknittedwiremeshpacking.Canbeeasilycustomizedtosuitmostvesselshapesandsizes.DCCoalescersaresensitivetothepresenceofsolidsinthefeed.Typically,particlesizesbelow~50mdonotcauseexcessiveblockage.</p><p>DusecandDusecPluscoalescersaresuppliedascar-tridges.Scopeofsupplyusuallyincludessupportsandmountingplatesuitablefordirectinstallationinavesselofeitherhorizontalorverticalorientation.Cartridgesareavailableforhighlyaggressivechemicalenvironmentsandhightemperatureapplications.</p><p>Constructedfrombanksofsweptvanes.Designsavail-ableforoperationinmostgas/liquidflowregimes.TheSchoepentoeterPlusisequippedwithsophisticatedcatchingrimstominimizeentrainment.</p><p>TheGIRZconsistsofanarrangementoftwoormorecyclonessymmetricallyarrangedoffacommon,central-lylocatedheader.Thedevicecanbeinstalledinverticalorhorizontalvessels.Ifrequired,mixingelementsatthecyclonegasoutletwillimprovethedistributiontothedownstreamdevice.</p><p>Product Summary</p><p> Sulzer_Brosch_Liquid_Liquid.indd 5 20.09.12 09:19</p></li><li><p>Mellaplate</p><p>6</p><p>Sulzer MellaplateTM Type W </p><p>Thistypeofcoalescerconsistsofacombi-nationofinclinedparallelplates,withfixedspacing,so thatdropletsettlingdistanceisreducedsignificantlyandthisenhancesthe coalescence process. The inclinedarrangement of plates allows the liquidphases to disengage diagonally towardsthe liquid interface. The flow is normallykeptinthelaminarregionforbettersepa-ration performance. The inclination andthe spacing between the plates is deter-</p><p>SulzeroffersMellaplateTMcoalescers,whichenhancetheseparationprocessbyallowingthereducingthedropletsettlingdistance,thusaidingthecoalescenceofthedroplets.</p><p>SulzerMellaplatecoalescersareavail-ableinfourdifferenttypes:</p><p>Construction Form</p><p>Relative Capacity 1)</p><p>Typical droplet cut-off size</p><p>Pressure drop</p><p>Solids Handling</p><p>Remarks</p><p>Mellaplate W</p><p>Flatparallelplates</p><p>1</p><p> 50m</p><p>Negligible</p><p>Highfoulingresistance</p><p>Mellaplate MG</p><p>Structuredcorrugatedflatplates</p><p>1.5</p><p> 100m</p><p>0.54mbar</p><p>Goodtohighfoulingresistance</p><p>Mellaplate M</p><p>Structuredcorrugatedmetalsheets</p><p>1.5</p><p> 50m</p><p>110mbar</p><p>Moderatetogoodfoulingresistance</p><p>Alsousedaswaveandfoambreakerelements</p><p>Mellaplate N</p><p>Structuredcorrugatedplasticsheets</p><p>1.5</p><p> 50m</p><p>1.515mbar</p><p>Moderatetogoodfoulingresistance</p><p>Moresuitedforde-oilingduetotheplasticsurface</p><p>Table A 1)ValuesarerelativetoMellaplateWtype</p><p>mined by the application, the nature ofcontaminantspresent in themixtureandthedegreeofseparationneeded.Typically,the angle is either 45 or 60 with platespacing from15 to100mm.Due to thehigh fouling resistance, theMellaplateW(Fig.2) is, forexample,used incrudeoilproduction separators. It is also ideal forretrofittinganexistinggravitysettlertoop-erateatahigherthroughputandimprovetheseparationperformance.</p><p>From the construction aspect, the Mel-laplateWcanbemadeinmodularframearrangementorboxes(Fig.3).Alternative-ly,itcanalsobeconstructedinonepiece(Fig. 4) for vessels with access throughthe body flange. Experienced engineersatSulzercanassistyouindesigningthisseparator to ensure trouble-free installa-tionandoperation.</p><p> Sulzer_Brosch_Liquid_Liquid.indd 6 20.09.12 09:19</p></li><li><p>7Mellaplate</p><p>Fig. 2a: Sulzer Mellaplate W</p><p>Fig. 2b: Sulzer Mellaplate W</p><p>Fig. 3: Frame and Box Arrangement</p><p>Fig. 4: One Piece Sulzer Mellaplate W</p><p>Framearrangement Boxarrangement</p><p>0611 2505-4</p><p> Sulzer_Brosch_Liquid_Liquid.indd 7 20.09.12 09:20</p></li><li><p>8Mellaplate</p><p>TheSulzerMellaplateCoalescer typesW,M,MGandN canbe used flexibly in ei-therhorizontalorverticalvessels.Atypicalsketch of a 3-phase separator is shown</p><p>SulzerMellachevronmisteliminator</p><p>SulzerMellaplateMwaveandfoambreaker</p><p>ShellSchoepentoeterinletdevice</p><p>Calmingbaffleplate</p><p>SulzerMellaplateWcoalescer</p><p>Weir</p><p>Sulzer MellaplateTM Type M, MG and N</p><p>This type of coalescer is made of struc-tured corrugatedmetal or plastic sheets(Fig. 5). Various universities and oil com-panieshavetestedMellaplateM,MGandNtypesinoil/waterseparatorsalsoundermoving conditions. Sulzer supplied thefirstMellaplatein1988fortheHuttonTen-sionLegPlatform(TLP)inUK.Sincethenhundreds of oil/water separators havebeenequippedwithvariousMellaplateM,MGandNstyles.Somehavebeenusedaswavebreakersordampersinoil/waterseparatorsonTLPsandFPSOs(FloatingProductionStorageandOffloading).</p><p>Fig. 5: Sulzer Mellaplate - M</p><p>Vessel Arrangement with Sulzer MellaplateTM Coalescer</p><p>Fig. 6: Horizontal 3-phase separator</p><p>below(Fig.6)whichshowstheSulzerMel-laplateWascoalescerandtheMellaplateMaswavebreakingdevice.</p><p> Sulzer_Brosch_Liquid_Liquid.indd 8 20.09.12 09:20</p></li><li><p>9Inlet Devices</p><p>Feed Inlets </p><p>For two phase liquid/liquid separators orthreephaseseparators,itisimportantthattheflowinthevesselisequalized.</p><p>Any turbulence or disturbances such asflowvariations,surgesorexternalmotionmaysignificantlycompromisethesepara-tionefficiency.Separatorsinanupstreamoil and gas environment are particularlyexposed to such problems. Sulzer inletdevices help to significantly improve theflowdistributionacrossthevesselwithoutcausingdropletstoshatter.</p><p>Fig. 8b: Calming baffle boxes in front of a Mellaplate W</p><p>Fig. 8a: Calming baffle plate</p><p>Fig. 7: CFD prediction of axial velocity distribu-tion after the second baffle of a two calming baffle arrangement</p><p>Calming Baffles</p><p>Sulzer recommends using the calmingbaffle in all liquid/liquid andgas/liquid/liq-uidseparators,eitheroperatedassimplegravity settler or equipped with SulzerMellaplateorDCCoalescer.Thesebafflesareprovidedwithuniformholeswhichareoptimized to achieve good flow distribu-tion and minimize any turbulence in theliquid phases towards the coalescer in-ternals. Depending on the type of appli-cations,twocalmingbafflesmaybeused.</p><p>Fora3-phaseseparator,dependingon thecharacteristicand inletmomentumof thefeedmixture,differenttypesofinletsaresuitable:</p><p>Elbowpipe</p><p>Halfopenpipe</p><p>ShellSchoe-pentoeterTM</p><p>vanetypeinlet</p><p>SulzerGIRZcyclonicinlet</p><p>Suitabilityforlargegasvol.</p><p>fraction</p><p>+</p><p>+++</p><p>+++</p><p>InletMomentum</p><p>+</p><p>++</p><p>+++</p><p>Defoaming</p><p>+</p><p>+++</p><p>Degassing</p><p>++</p><p>+++</p><p>RelativeCostofDevice</p><p>$</p><p>$$</p><p>$$$</p><p>$$$$</p><p>Table B</p><p>0.115 m/s</p><p>0.102</p><p>0.090</p><p>0.077</p><p>0.064</p><p>0.051</p><p>0.038</p><p>0.026</p><p>0.013</p><p>0-000</p><p>CDE = 15</p><p> Sulzer_Brosch_Liquid_Liquid.indd 9 20.09.12 09:20</p></li><li><p>10</p><p>DC Coalescer</p><p>Sulzer DC CoalescerTM</p><p>TheSulzerDCCoalescerTechnologyprovidessignificantlylowersettling times forprimarydispersionswithdroplets as small as30microns.</p><p>Whilethedropletspassthroughthecoalescer,theygrowinsizethrough a continuous process of coalescing and draining. Thefastersettlingvelocityofcoalesceddroplets leadstominimizedvesseldimensionsasopposedtogravityseparationalone....</p></li></ul>

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