液液萃取Liquidliquid extraction.docx
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液液萃取Liquidliquid extraction.docx
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液液萃取Liquidliquidextraction
液-液萃取(Liquid-liquidextraction)
Liquid-liquidextraction
Liquidliquidextractionprinciple,calculationandequipment
Summary
Theprincipleoftreatingaliquidhomogeneousmixtureisachievedbyseparatingthesolubilitydifferencesofeachcomponentinaparticularsolvent
*basicprocess:
mixingandclarifying
*basicconcepts:
ThesolublegroupofsoluteA:
inrawliquor.
ThediluentB:
rawmaterialliquidinsolublecomponents.
TheextractionsolventofS:
.
Extractessence
*extractionphaseE:
extractionofaproductcontainingmorethanonephaseofsoluteA
*extractionphaseR:
extractsaphasewithmorediluentBintheproduct
*EandRaremixtures,notpurecomponents,sotheextractionisonlytoconvertthedifficulttoseparatematerialintoeasilyseparatedmaterial
Applicabilityofextractioncomparedwithdistillation
*therelativevolatilityofthetwocomponentsiscloseto1,whichissuitableforextraction;
*thecontentofvolatilecomponentsisveryhigh,andthedistillationprocessrequiresalargeamountofthecomponentstobegasifiedsothattheenergyconsumptionishigh
*systemofheatsensitivecomponents,nothightemperatureoperation.
Thetriangularphasediagramrepresentsthecompositionofthesystem
*compositionofthewholesystemisdeterminedbymassfraction
*vertex:
representspurecomponents
*edge:
representstwobinarysystems.Thecontentofacomponentisatthatpointatconcentration1andtheotherisconcentration0.
*thepointsinthetriangle:
representthethreeelementsystem.Thevalueofacomponentcanbederivedfromthevalueoftheintersectionpointofthepointontheoppositesideofthelineparalleltotheedge
Phaseequilibriumrelationofthreeelementsystem1
*thesolubilitycurve--fromthetwo-phaseregionintoaseriesofmixedmeltingpointandtheformationofthecurveofphase.
*inthetwophaseregionoftheconnectingline,thethreeelementsystemisunstableandeventuallybreaksdownintoabalancedtwophasesegmentconnectingthetwocomponentpointsoftheequilibriumphase
*auxiliarycurve-theintersectionofalltheintersectionsofthetworightanglesparallellinesmadeatbothendsofeachlink
*criticalintersectioncurveandauxiliarymixedmeltingpointsolubilitycurve.Thisconnectionlineisinfinitelyshort,EandR.
Phaseequilibriumrelation2-distributioncurveandpartitioncoefficient
*ateachjunction,thesoluteAcontentatthepointEandRisusedastheordinateyandabscissaXintheCartesiancoordinatesystem,respectively,toobtainapoint,theconnectionofallpoints
*thepartitioncoefficient:
k=y/xreflectsthedifferenceinsolutepartitioningbetweenthetwophases
Leverrule
*animportantbasisforliquidliquidextractioncalculation
*rulecontent:
thetotalmixingpointMandthetwodecompositionphasepoint1,2aresatisfied
ThetotalmixedMattwopoints.Theconnectionbetween1,2decomposition
ThetotalmixedspecificlocationfortheM1andM2linelengthratioandthe1phaseandthe2phaseisinverselyproportionaltothemass.
Theproblemofphaseequilibriumrelation
*whychangethetotalcompositionofC,B,S,totalmixture,A,andthreecomponentlinesalongtheACline?
Whatistheinfluenceofoperatingtemperatureontwo-phasezoneandextractionoperation?
*howtoinferleverrules?
Extractantselectionconsiderations
*beta-AselectivitycoefficientdistributioncoefficientandBcoefficientofdistributionratio.Beta>1,thegreaterthevalue,thebetter.
*themutualsolubilityrelationshipbetweenBandS
*density
*relativevolatilitybetweenAandB
*interfacialtension
Examples
*atacertaintemperature,theequilibriumdataforA,B,S,three,andmattertwoareshownintheschedule.Thedatainthetableismasspercentage.Trytomakethecalculation:
thesolubilitycurveandauxiliarycurve;thecriticalmixedmeltingpoint;whenthedistributioncoefficientkAandselectivitycoefficientinraffinatexA=20%;
HowtoaddsomekgSto100kgintherawliquidcontaining30%Ainthemixturetotherawliquidofstratification;fourth,toobtainextractcontainingA36%phaseEtrialtodeterminethetotalcompositionoftheraffinatephasecompositionandmixture.
Single-stageextraction
*processdescription(seenextpage)
*graphicalkeydifferencemappingmethod:
inthepresenceofsolubilitycurvesandauxiliarycurves,thetotalmixingpointMisusedtocalculatethetotalequilibriumphaseEandRcompositionpoints
*calculationbasis:
leverrule
Singlestageextractionexample1
*extractionofaceticacidfrommixedsolutionofaceticacid(A)andchloroform(B)at25DEGCwithwater(S)asextractant.Itisknownthattheliquidflowrateofrawmaterialis2000kg/h,inwhichthemasspercentageofaceticacidis35%,andtherestis
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- 液液萃取Liquidliquid extraction 萃取 Liquidliquid