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Research_2 (2)

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Research_2 (2)

    Research

2005PetroleumScienceV.01.2No.3

    ;ResearchontheDesignofaDeoilingCompoundHydrocyclone

    ;andItsSeparationCharacteristics

    ;wangZunce,YuHaiboandLiuXiaomin

    ;(DaqingPetroleumInstitute,Daqing,Heilong/iang16331&Chin

    ;ReceivedMay2005

    ;Abstract:AcompoundhydrocycloneisanewstrategYforoil.waterseparation.Itisbasedonthestudyofstaticand

    ;dynamichydrocyclones.InthisPaDerareintroduceditsgeometrictraitsandseparationmechanism.Experimentsare

    ;carriedoutabouttherelationshipbetweengeometricparameters&operatingparametersandtheseparationefficiencyof

    ;thecompoundhydrocyclone.Underexperimentalconditions,theappropriatestructuralparametersoptimizedareas

    ;follows:Therotatinggridisofthestraightboardtype,3straightvaneswithalengthofabove95mm;thediameterofthe

    ;overflowventranges3.12mm;theseparationefficiencyisbetterwhenthelargeconicalangleofthestaticvo~exbodyis

    ;about20.andthesmallconicalangleintherangeof1..4..Theseparationeffectisbeaerunderthefollowing ;conditions:Therotaryspeedisl,7002,400r/min;thedisposalcapacityis5.5m/h;thelossofworkingpressureisO.05

    ;O.25MPa:andthesplitratioranges5%.15%.Theexperimentalstudyprovidesacertainbasisforthedesignand

    ;applicationofthecompoundhydrocyclone.

    ;Keywords:Compoundhydrocyclone,geometricparameters,operatingparameters

    ;1.Introduction

    ;Recently,theapplicationofavortexseparation

    ;techniqueisextendinginoilfields.Afteroilfieldsstep

    ;intothemiddleandhighwater-cutstages,the

    ;hydrocycloneplaysairreplaceableroleinthepre

    ;separationofproducedfluidandthetreatfnentofoily

    ;sewageascomparedwithotherseparators.Itsvirtues

    ;arematuretechniques.asmallvolumeandarea

    ;occupied,afastdisposalspeed,resistanttojamming,

    ;steadyandcontinuousrunningandalowcost.

    ;Combiningthematuretheoriesabouttheseparation

    ;techniqueofstatichydrocyclone,thecompound

    ;hydrocyclonehasabrightapplicationinthefuture

    ;(Triponey,ela1.,l992).Itsshortcomingsareahigh

    ;pressureofthefeedingliquid,agreatlossofpressure ;andaslightchangeintherateddisposalcapacity.Over ;manyyearsofstudy,thestructureofthestatic ;hydrocyclonehasbeendeveloped(PatentNo.ZL ;96210084.6),andanew.appliedpatentachievedforthe ;dynamichydrocyclone(PatentNo.ZL98244285.81, ;providingatechnicalguaranteetoasuccessfu1 ;developmentofanewcompoundhydrocyclonethatis ;characterizedbythemeritsofboththestaticand ;dynamichydrocyclones.Thehydrocyclonehas ;increasinglyturnedintoanewpopularliquiddisposal ;devicebecauseitsrunningcycleiscloseandthereisno ;pollutionintheseparationprocess.

    ;2.Structureandworkingprinciple

    ;Thetypeofdriveiscoaxialandtheelectricmotor ;drivesitsseparationforthecompoundhydrocyclone.It ;consistsofanelectricmotor,ahollowdrivingspindic,a ;rotatinggrid,anoverflowvent,aninletcavity,an ;overflowcavity,astaticvortexbody,abracketanda ;pedestal(asshowninFig.1).

    ;/,,.I广u——二一,

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    ;Fig.1Sketchofthestructureandworkingprincipleofthe ;compoundhydrocyclone

    ;1-Overflowcavity;2-Inletcarity;3-Hollowspindle;4-Overflowvent;5-Static

    ;vortexbody;6-Underflowvent;7-Pedestal;8-Rotatingd;9-Sealassemble;

    ;l0Electricmotor

    ;Thehydrocycloneisusedtocentrifugallyseparate ;twoimmiscibleliquids,whichhavedifferentdensities. ;insidethevortexcavity.Theseparationprocessofthe ;mixedfluidisthattheelectricmotordrivestherotating ;gridtoturnatahighspeedthroughthecoupling.After ;beingaccelerated,thepressurizedliquidwaitingfor ;

    ;Vo1.2No.3ResearchontheDesignofaDe?oilingCompoundHydrocycloneandItsSe

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    ;separationentersthestaticvortexbOdythroughtheflow ;passageoftherotatinggrid,andthentheliquidbegins ;torotateatahightangentialspeed,whoseliquid ;rotationalstrengthisenhancedinboththelargeand ;smallconicalsections.Oilmovestothevortexcentre ;underacentrifugalforceandfornlsanucleus.During ;thisprocess,thedrivingaxleattheendoftheelectric ;motorisclosed.andtheoilinthecentremovestothe ;overflowventthroughthecentralboreandthenenters ;theoverflowcavitybytheradialinclined.straightbore ;(ortrough)atthehollowspindle;thewatermovestothe ;innerwallofthestaticvortexbodyandthenisventedat ;theunderflowvent.

    ;3.Structuraldesignofthefeedingpowerto

    ;therotationalliquid

    ;Theprimaryaimofdesigningthehydrocycloneisto ;increasethevortexstrengthandthefieldstability.and ;lowerthepressureofthefeedingliquid.thus ;strengtheningtheseparationperformance.Itisobvious ;thatoptimizingthestructureofthefeedingliquidand ;separationmaynotonlyimprovethestructureofthe ;staticanddynamichydrocyclones(forexample,the

    ;pressurelOSSofthestatichydrocycloneisheavyandthe ;vortexstrengthneedstobeenhanced;thedynamic ;hydrocyclonehasastrongervibration,andeasily ;producesresonance),butalsoeffectivelyachievesteady ;oilwaterseparation.

    ;Threekindsofschemesareselectedbasedontwo. ;separationsegments(asshowninFig.21.Inthese ;schemestherotarybodyisinsidethestaticshel1.witha ;slitvibration,sotheoperatingrangesoftheinlet ;pressureandtheflowrateareconsiderablyflexible.For ;Scheme1.separationcanbefinishedpreferablyunder ;onlyalowbackpressure.andtheseparatedliquidis ;ventedfromtheendoftheoverflowpipeafterbeing ;acceleratedtorotate.Thishassettledtheissuethata ;smallamountofoverflowisventedalongwiththe ;undertowafterbeingseparated,thusreducingthe ;dicultyinoperationandadjustingeasilytheoperating ;parameters.However,theflowtowards.overflowis ;blockedtoacertainextentbecauseoftheangular ;momentumcompensatedfromboththelargeandthe ;smallconicalsections.Fortheothertwoschemes.the ;undertowisventedintheoppositedirectionofthe ;overflowandtheoverflowpipeisrevolving,which ;furtherreducesthepressurethathasbeenverylow.So. ;theseparationperformanceisaffected,eventhoughthe ;overtowventscompletely.ForScheme2,onethruster ;isaddedattheendoftheundertowpipeforforcingthe ;overtowtowardtheotherendtoventeasily,andfor ;stabilizingtheliquidfieldattheundertowvent. ;However.thestabilityoftheunderflowfieldisworse. ;ForScheme3,withthetailpipelengthened,itis ;possiblethattheoverflowproducedaftercompensating ;theangularmomentumlOSScanmovetotheotherend. ;Alongtailpipecanstabilizetheundertowfieldbetter ;althoughitservestheseparationless.Thepreferable ;backpressureisneededtoensuretheseparation ;effectivelyandsteadily.Manyexperimentsarecarried ;outbyusingScheme3.

    ;ProjectI

    ;2

    ;Fig.2Schematicdiagramsofthreeversionsofthecompound ;hydrocyclone

    ;1Pipeofoverflow;2-Sealassembly;3-Pipeofundertow;4-Pipeofrotational

    ;flow;5-Corebodyoftherotatinggnd;6-Vaneoftherotatinggnd:7-Flow

;enteringpipe;8-Flow?-enteringinlet;9-Oiloutlet;10Wateroutlet

    ;4.Analysisoftheinfluencingfactors

    ;Thegeometricparametersinfluencingtheseparation ;performanceincludemostlygeometricformsand ;parametersoftherotatinggrid,theoverflowventand ;thestaticvortexbodV.Operatingfactorsaffectingthe ;separationperformancemainlyincludetherotaryspeed. ;theflowrate,theworkingpressureandthesplitratio. ;4.1Geometricformsandparametersoftherotating ;grid

    ;Therotatinggrid,fixedattheendoftheinletto ;acceleratetheliquidflow,isoneoftheforemost ;componentsofthevortex-separator.Tworotatinggrids, ;whichareofastraightboardtypeoraspiraltypewith ;airtightstructure,aredesignedasitsleadingrotating ;structure.Experimentsindicatethatthespiralrotating ;gridisbetterbecauseitsstructurecancommendably ;avoidthehydraulicimpactandmakethesteamlineof ;liquidagreewiththevortexlineperfectly, ;andatthe

    ;sametimeensureinvarianceofthestreamlineandthe ;vortexlineoftheliquid.Twoorthreespiralvanes, ;with

    ;alengthofabove98iilli1,cansatisfythedesign ;

    ;30PetroleumScience2005

    ;requirements.Theflowrateiswel1.distributedwhen ;thisstructureisused.butitisdifficulttoprocessthose ;varies.Moreover,thespiralrisingangleofthespiral ;rotatinggridiscommonly3O..6O.becausetoobigor ;smallallangleisunfavorabletoseparation.Whenthe ;straightboardrotatinggridwitll3vanesisused.the ;separationefHciencyisthebestandthepressurelOSSiS ;theleast.Itstailisaleadingstreamtaperlikean ;ellipticalbal1.whichmakestheliquidflowfillthe ;separationcavityandavoidsproducingastrong ;turbulentflow.Threevanes.withalengthofabove95 ;111111,aredistributedevenlyonthecircle,whichcan ;meetthedesignrequirements.Acoatshieldlengthened ;attl1etwoendsofrotatinggriddecreasesthehydraulic ;impactandpressure1osstoalargeextent.Andwhatis ;importantisagreatloweringoftheprobabilityofa ;sheardamagetoliquiddroplets,thusincreasingthe ;stabilityoftheflowfield.

    ;4.2Geometricformsandparametersoftheoverflow ;vent

    ;Theoverflowventisfixedonarotaryhollow

    ;spindlemostlyforreceivingoilandforstabilizingthe ;localflowfield.Itsexteriorcontourisconicalorlikean ;ellipticalballanditsinteriorsurfaceattheventisa ;designedconicalsurfacelikeafunne1.whichgreatly ;relaxesthesymmetricalshrinkage(Zhang,1993)atthe ;oil.receivingvent.Theefficientinnerdiameterofthe ;innerborecorrelatescloselywiththeadiustmentof ;operatingparameters(Wang,eta1.,2001).Somewater ;istakenawayfromtheoilreceivingventiftheeffective ;innerdiameteristoobig;andnooilisreceivedifthe ;effectiveinnerdiameteristoosmal1.Controllingan ;appropriatesplitratioandkeepinganappropriateback ;pressureoftheundertowwillbenefitseparation(Wang, ;efa1..2001).Anefficientinnerdiameteroftheoverflow ;ventusuallyranges3.12ITlnlaccordingtodifferent ;concentrationsandpropertiesoftheseparatingmedia. ;4.3Geometricformsandparametersofthestatic ;vortexbody

    ;Thelargeconicalangleofthestaticvortexbodyis ;usuallychosenatabout20..thesmallconicalangle ;usuallyintherangeOf1..4..Therotaryspeedofthe ;hollowspindleisusuallychosenintherangeof1.500. ;3,000r/min.Asampledevice,withadisposalcapacity ;of8m/h,wasmachinedaccordingtothestructureof ;mostcomponentsdesignedabove.Experimentsare ;carriedoutinawiderangeoftherateddisposalcapacity ;(3-10m/l1),andtheresultsaresatisfactory.Asshown ;inFig.3,weconductedtestsontheflowrate.Atthe ;sametime,wealsoconfirmthatthestructureofmost ;componentsintheoptimizingsampledeviceis ;reasonableandfeasible

    ;Disposalcapacity,mVh

    ;Fig.3Plotsofseparationefficiencyversusflowrate ;4.4Rotaryspeed

    ;Anacademicanalysisindicatesthatthefasterthe ;rotaryspeedis,thehighertheseparationefficiencywill ;be.Itisbecausethatthefastertherotaryspeedofliquid ;flowis.thegreatertheradialpressureprovidedbyoil ;andwaterwillbe.andthenthebettertheseparation ;eciency.However.itcanbeseeninFig.4

    ;(experimentalcurves),afasterrotaryspeeddoesnot

    ;meansahigherseparationefHciency.Theseparation ;efHciencyisrelatedtomanyinfluencingfactors.The ;fastertherotaryspeedis.themorechancestherewillbe ;fortheshearemulsificationoftheoildrops.andthe ;strongerthevibrationofequipmentwillbe.On ;examination,theappropriaterotaryspeedranges1,700- ;2,400r/min,whichcansatisfythedemandofthevortex ;intensityandavoidstrongervibrations.

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    ;Rotaryspeed,r/min

    ;Fig.4Plotsofseparationefficiencyversusrotaryspeed ;4.5Disposalcapacity

    ;Theseparationefficiencyofthecompound

    ;hydrocycloneisbetteratalowerflowrate.whichis ;consistentwiththedynamichydrocyclone.However, ;theseparationefficiencyofthestatichydrocycloneis ;loweratalowerflowrate.Whentherotaryspeedis ;fixed.theliquidofalowflowratecanstayinthecavity ;foralongtimeandtheseparationissufficient.When ;theflowrateincreases.thepressureoftheliquid ;increasesandtheliquiddropscanstayinthecavityfor ;ashorttime,whichisdisadvantageoust;

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    ;rangesoftheflowrates(310m/l1),butthereareslight

    ;changes.AsshowninFig.3.theseparationefficiencyis ;thebestastherotaryspeedofthegridis1.734r/min. ;Theseparationefficiencyisthebestwhenthedisposal ;capacityis5.5m3/h,asshowninFig.4.Onthewhole, ;theseparationemciencyisthebestat30Hzofthed ;frequencyand5.5m3/hofthedisposalcapacity.These ;resultsdemonstratethatthedisposalcapacityofthe ;compoundhydrocyclonehasgreatoperatingflexibility, ;butwecanfindsomerulesandwaystoObtainahigher ;eciency.whichisthebasisforutilizingand ;developingthebestcompoundhydrocyclone. ;4.6Workingpressure

    ;Thecompoundhydrocycloneneedsafeedingliquid ;ofalowerpressureenthedisposalcapacityand

    ;otherparametersarefixed,theseparationefficiency ;increaseswithadvancingproperlytherotaryspeedand ;theworkingpressure.?enotherparametersarefixed.

    ;theworkingpressureincreasesinsuccessionby ;properlyadjustingtheunderflowvalveandproperly ;increasingthebackpressureoftheundertow.Inso ;doing.theseparationeciencyisbetter.Itcanbeseen

    ;fromFigs.5and6thatthedisposalcapacityisbasically ;proportionaltotheworkingpressure.Itisalsotruefor ;therotaryspeedandtheworkingpressure.By ;measuringpressuresontheinletandtheundertow ;outletofthestaticvortexbody,weknowthatabouttwo ;thirdsofthepressurelOSSiSattwotangentialinletsfor ;thestatichydrocyclone.whichindicatesthatthereis ;onlyonethirdofthelOSSatboththe1argeandsmall ;conicalsectionsdesignedrationally.Theworking ;pressureofthehydrocyclonehasagreatoperating ;flexibility(above0.1MPa1andthepressurelossranges ;0.050.25MPa.whichis1essthanthatofthestatic ;hydrocyclone.

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    ;Disposalcapacity,m/h

    ;ratioissmal1thebackpressureprovidedbythe ;undertowisverylow.whichisunfavorablefortheoil ;nucleustobeventedforitslowcentralpressure. ;becausefactorsinfluencingtheflowfieldattheoil

    ;receivingventwillplayamajorrole.Aaceamountof

    ;oilisventedalongwiththeunderflow.andthe ;separationefciencyisimprovedevidently.ifwe

    ;properlyincreasethesplitratiornamelyincreasethe ;flowrateoftheoverflow)andproperlyraisetheback ;pressureoftheundertow.Butitwill1cadtoagreat ;decreaseintheflowrateoftheunderflowandsome ;liquidseparatedincompletelywillalsoprematurely

    ;entertheoverflowunderthehigherbackpressureofthe ;undertowifweincreaseblindlythesplitratio.which ;fallsshortofproductionpractice.InFig.7.curvesof ;theseparationeciencyversusthedisposalcapacity ;indicatethattoobigorsmallasplitratioisnotgood ;whenthedisposalcapacityisfixed(theseparation ;eciencyisbetterwhenthesplitratiois10%or12%1. ;Weshouldlogicallyapplythesplitratioforbetter ;separationeffectsinlightofdifferentdisposal ;capacities.Thesplitratiousuallyranges5%15%.

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    ;Rotaryspeed,r/min

    ;Fig.6Plotsofpressureversusrotaryspeed ;ow

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    ;Fig.7Curvesofsplitratioversusseparationefficiency ;Fig_5?.fpressureversusdisposalapa.i~5

    ;.ConclusiOns

    ;4.7Splitratio

    ;Fig.7illustratesthattheseparationefficiency ;obviouslyincreaseswithproperlyadvancingthesplit ;ratiowhenotherparametersarefixed.Whenthesplit ;Thecompoundhydrocycloneischaracterizedby ;doublemeritsofboththedynamicandstatic ;hydrocyclones,suchasahighseparationefficiency,a ;steadyflowfield,abig,flexibledisposalcapacityofan

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    ;32PetroleumScience2005

    ;individualmachine,andarelativelylowlossofpressure. ;Primarygeometricfactorsinfluencingtheseparation ;efficiencyincludetherotatinggrid,theoverflowvent ;andthevortexbOdV.Therotatinggridisofthestraight ;boardtype,3vane

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