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transcript
Extraction
Components, systems and installationsfrom GEA Westfalia Separator
engineering for a better world GEA Mechanical Equipment
2
Contents
4 1. Introduction
4 1.1 Fundamentalaspectsofextraction
6 2. MethodofOperationofExtraction
8 2.1 Designprinciplesforcounter-current
extraction
11 2.2 Antibiotics
Directextraction–totalyieldupto98%
12 2.3 Statins
Directextractionforhi-techdrugs
13 2.4 Steroids/hormones
Obtainingestrogenandsimilarsubstances
14 2.5 Plantextracts
Gentleextractionforsensitiveactive
ingredients
15 2.6 Polycarbonate
Polymerextraction/washingprocesses
16 2.7 Pectin
Fromcitrusfruitstosettingagent
18 3. CentrifugalExtraction
18 3.1 Mixers
19 3.1.1 Centrifugalmixer
19 3.1.2 Integratedmixerinthebowlhead
20 3.2 Centrifuges
21 3.3 Liquid-liquidextraction
21 3.3.1 Separatorwithsolid-wall
disc-typebowl
22 3.3.2 Separatorwithself-cleaning
disc-typebowl
23 3.3.3 Driveconceptsforseparators
24 3.4 Solid-liquid-liquidextraction
24 3.4.1 Extractiondecanters
25 3.5 Solid-liquidextraction
25 3.5.1 Clarifyingdecanters
25 3.5.2 Clarifyingseparators
26 3.5.2 GEAWestfaliaSeparatorvaripond®–
reliablemasteringphaseseparation
26 3.5.3 Innovativedriveconcepts
fordecanters
28 3.6 Alternativeprocesses:
Filtrateextractionordirectextraction
28 3.6.1 Filtrateextraction:
Antibiotics
29 3.6.2 Directextraction
30 4. Explosion-ProtectedCentrifuges
32 5. CeramicMembraneFiltration–
Ultra-andMicro-FineClarification
33 6. AutomationSystems–PlugandPlay
34 7. SpecialMaterials
35 8. CentralProcessEngineering–
theReliableBasisforDecision-Making
3
1. Introduction
Theterm“extraction”isderivedfromtheLatinword
“extrahere”;“ex”specifiesthedirection, i.e.outof,
and“trahere”describestheaction,namelydrawing
orremoving.Extractionisaccordinglydefinedasthe
processofremovingasubstanceorseveralsubstances
from another substance. The process is extremely
importantinawiderangeoftechnicalapplications,
forinstancebiotechnology,thepharmaceuticaland
foodindustriesaswellasenvironmentalprotection.
Extraction is a separating process which has the
advantageoflowenergyconsumption.
Overall,particularlygentleprocessesarecharacteris-
ticofthese“lifesciences”methods.Inbiotechnology
productioninstallations,theprocessofseparatingthe
valuablesubstancesfromthebiosuspensionandthe
subsequentpurificationofsuchsubstanceswiththe
aidofextractionarekeyaspects.Sensitivesubstances
arefrequentlyprocessedinbioprocesses.Theirstruc-
tureandbiologicalactivityrequireverynarrowtol-
erancesinthemediumconditionsparticularlywith
regardtotheprocessingstageofextraction.Thishas
tobeadjustedtobebroughtintolinewiththeambi-
entconditions.Thevitalprocessparametersinthis
respectarethepHvalue,thesaltconcentrationand
thetemperatureaswellasthestructureofthevalu-
ablesubstance.
Innumerousareasofapplication,extractionisthe
more efficient, more selective and less expensive
alternative compared with competing separating
methodssuchasdistillation,evaporationandmem-
branetechnology.Extractionhasbecomeestablished
particularlyinconjunctionwiththefollowingprocess
conditions:
• Minorboilingpointdifferencesofthe
componentstobeseparatedoraceotropic
separatione.g.separationofisomers,
aromaticsubstancesoraliphates
• Heat-sensitiveorunstablesubstancese.g.
antibiotics
• Non-volatilesubstances,recoveryand
purificationofcatalystsorheavymetals
• Mixtureswithinorganiccomponentswhich
wouldresultinencrustationofevaporator
surfacesinconjunctionwiththethermal
separatingprocess
• Separationoflowmasscontentsofa
componentwhichisnotreadilyvolatile
Thetasksofextractioncoverawiderangeofappli-
cations. In thefieldofhydrometallurgy,extraction
methodsareusedforprocessingore,recoveringmet-
alsfromwastesludgesandforpurification.
Environmental protection with its wide range of
requirementsisalsoanareaofapplicationforextrac-
tionwhichisbecomingmoreandmoreimportant.
1.1Fundamentalaspectsofextraction
Theextractionagentorsolventisextremelyimpor-
tant for carrying out an extraction process, as the
valuablesubstance (theextractE), is releasedwith
theaidofextractionagent.Thenatureofthephases
whichareinvolvedcharacterizetheextractionprocess
assolid-liquidextractionorliquid-liquidextraction.
Liquid-liquidextractionisusedforseparatingvitamin
mixtures;anewmethod isalsousedforpurifying
phosphoricacid.Theprincipleofliquid-liquidextrac-
tionisillustratedinthefollowingdiagram.
Afundamentalcriterionforliquid-liquidextractionis
thattheextractionagentandtheliquidinwhichthe
extractisdissolved(thecarriermedium(T))arenot
perfectlymiscible.Inexcessofacertainconcentra-
tion,twophasesformwithaclearlydefinedbound-
ary.Afamiliarexampleinthisrespectisthemixing
behaviourofwaterandbutylacetate.
Thetwophasesareknownastheextract(E)phase
andtheraffinatephase(R).Theextractphaseisthe
phaseintowhichtheextractistransferredfromthe
carriermedium.Ideally,itconsistsexclusivelyofthe
extractionagentandtheextract,whereastheraffi-
natephaseconsistsonlyofthecarriermedium.Apart
frombeinglessthanperfectlymisciblewiththecar-
riermedium,theextractionagenthastomeetfurther
requirements.
4
Thesecriteriaincludethefollowing:
• Capacitytoabsorbalargeamountofextract
(highcapacity)
• Highdegreeofselectivity
• Minimumcostforprocessingtheextract
• Highavailabilityandlowprice
• Lowlevelofcorrosion
• Lowor,ifpossible,notoxicity
Oftheabove-mentionedrequirements,capacityand
selectivity are of primary interest. However, the
points corrosion properties as well as toxicity are
alsobecomingmoreandmoresignificant,particularly
whenextractionmethodsareusedinthefoodand
drugfield(lifescience)withrespecttoGMPguide-
lines.Capacityisameasureofquantity,i.e.itspecifies
theamountofextractwhichcanbeabsorbedbythe
extractionagent.
Ontheotherhand,selectivityisameasureofqual-
ity.Itexpressestheefficiencywithwhichthesolvent
distributesthevaluablesubstancesoverthevarious
phaseswithinaseparatingstage.
Thehigherthecapacity,thegreateristheefficiency
with which the volume streams can be adjusted.
Assumingthatvolumestreamsremainunchanged,
asolventwithhighcapacityisabletoabsorbmore
extractthanasolventwithlowercapacity.
Thehighertheselectivity,thelowerthenumberof
separating stages, this means that the installation
or the separating device becomes smaller. When
thechoiceofsolvent isbeingconsidered, ithas to
beborneinmindthatthereisfrequentlyaninverse
relationshipbetweencapacityandselectivity.Inother
words,highcapacityisfrequentlyaccompaniedby
lowselectivity,andviceversa.Accordingly,thechoice
ofsolvent isfrequentlyanoptimizationprocess in
whichacompromisehastobefoundbetweenselec-
tivityandcapacity.
Fig. 1 Example of liquid-liquid extraction
Before extraction
Solvent (LM)
Liquid mixture(X + Y)
Carrier liquid Y(raffinate phase)
Extraction solution LM + X(extract phase)
Mixing
After extraction andseparation
Fig. 2 Various extraction agent / carrier substance mixtures
5
2. Method of Operation of Extraction
With the same number of separating stages, the
variousmethodsofoperationofphasedextraction
providedifferentseparatingresults,orrequirediffer-
entquantitiesofsolventsinordertoattainthesame
separatingresults.Inthevariousstages,themixeris
responsibleforensuringthatthevaluablesubstance
istransferredfromthecarriermediumtotheextrac-
tionagent.
Theselectedmethodofoperationoftheprocessisone
ofthecriteriaapplicablefordefiningthenumberof
separatingstagesnecessaryforattainingthedesired
separatingresult.Thefollowingextractionmethods
canbeconsidered:
• Directcurrent
• Counter-current
• Cross-current
Fig. 3 2-stage extraction, cross-current process
Fig. 4 2-stage extraction, counter-current method
Vm cm,r1 r1
Vt ct,r1 r1
Vt ct,r2 r2
Vt ct,e1 e1
Vt ct,e2 e2
Vm cm,r2 r2
Vm cm,e1 e1
Vm cm,e2 e2
Vm cm,r1 r1
Vt ct,r1 r1
Vt ct,r2 r2Vt ct,e1 e1
Vt ct,e2 e2
Vm cm,r2 r2
Vm cm,e1 e1
Vm cm,e2 e2
6
cess.Cross-streamextraction,inwhichfreshsolventis
addedineverystage,alsoprovidesahighextraction
yield.However,comparedwiththecounter-current
principle,thismethodrequireshigherquantitiesof
freshsolvent.Thisinvolveshighercostsforprovid-
ingthesolventandalsoforseparatingextractand
solvent.
Theraffinatephaseandtheextractphasearethensep-
aratedinacentrifuge.Thecounter-currentarrange-
mentisthemosteffectivemethod.Unlikethesitu-
ationwiththedirectcurrentarrangement,amuch
largerproportionofextractistransferredfromthe
carrier medium to the solvent. The concentration
gradientasthedrivingforceforthemasstransferis
utilizedmosteffectivelyinthecounter-currentpro-
Fig. 5 2-stage extraction, direct current process
Thevolumeequationsforthecounter-currentprocessareasfollows:
Theoverallequationisaccordingly:
Thetotalmassequationisasfollows:
Indices: V : Volume stream, c: Concentration, r: Raffinate, e: Extract, m: Mixer, t: Separator
Thetotalmassequationisasfollows:
1ststage:
1ststage:
2ndstage:
2ndstage:
Transfer1 2
Transfer1 2
Transfer2 1
Transfer2 1
Equation2-1
Equation2-6
Equation2-10
Equation2-5
Equation2-2
Equation2-7
Equation2-3
Equation2-8
Equation2-4
Equation2-9
Vmr1
cm
cm
cm
ct
ct
ct
e1
e2
e2
e1
e1
e2
Vmr1
Vmr1
Vmr2
Vmr2
Vme1
Vtr1
Vtr2
Vtr1
Vte2
Vtr2
cm
cm
cm
cm
cm
ct
ct
ct
ct
ct
r1
r1
r2
r2
e1
r1
r2
r1
e2
r2
Vmr1
Vmr2
Vmr2
Vme1
Vtr1
Vtr2
Vtr2
Vtr1
Vte2
Vte1
Vte1
Vte2
Vme1
Vme1
Vme2
Vme2
Vte1
Vte1
Vte2
Vme2
Vme2
+
⋅
⋅
⋅
⋅
⋅
⋅
+
+
+
+
+
+
⋅
⋅
⋅
⋅
⋅
⋅
⋅
⋅
⋅
⋅
+
+
+
+
+
=
=
=
=
=
=
=
=
=
=
Vm cm,r1 r1
Vt ct,r1 r1
Vt ct,r2 r2Vt ct,e1 e1 Vt ct,e2 e2
Vm cm,r2 r2
Vm cm,e1 e1 Vm cm,e2 e2
7
Thevolumestreamsofthecarriercomponentsremain
constantthroughoutallextractionstages.
InaccordancewiththeNernst’sdistributionlaw,the
followingequationisapplicableforthesubstanceto
beextractedusinganexampleof three theoretical
extractionstages:
concentrationintheraffinateandextractarespeci-
fied,theextractionyieldtobeexpectedcanbecalcu-
latedasfollows:
2.1Designprinciplesfor
counter-currentextraction
The calculations involved in continuous counter-
currentextractionarerelativelysimple,onthebasis
oftheassumptionthattheraffinatephaseandextract
phaseareinsolubleineachotherirrespectiveofthe
concentrationofthesubstancetobeextracted.
Theseconditionscanbeusedforestablishingasys-
temconsistingofthreelinearequationswiththree
unknownfactors,namelycE2,cE3,cE4.Whentheinitial
cR1
1st stage 2nd stage 3rd stage
cR2 cR3 cR4
cE4 cE3 cE2 cE1
Fig. 6 Diagram of 3-stage counter-current extraction
cR = Concentration of the substance to be extracted in the raffinate phase [g / l]
cE = Concentration of the substance to be extracted in the extract phase [g / l]
VR= Throughput capacity of the raffinate [l / h]
VE = Throughput capacity of the extract [l / h]
Thetotalmassequationisasfollows:
1ststage:
Whereby:
CriteriaofequilibriumaccordingtoNernst:
And:
(Phaseratioextract/raffinate)
2ndstage:
3rdstage:
cR1
cR2
cR3
⋅
⋅
⋅
⋅
⋅
⋅
+
+
+
+
+
+
⋅
=
= = =
⋅
⋅
⋅
⋅
⋅
=
=
=
VR
VE
VR
VR
V
k
k⋅V=E
VE
VE
VE
cE3
cE2
cE1
VR
VR
VR
cR2
cR3
cR4
VE
VE
VE
cE4
cE3
cE2
cE4
cR2
cE3
cR3
cE2
cR4
VR
8
=
=
cRn
n
cR1
1−
E−1
logE−η
En+1−1
logE
V ⋅cE1
0
−cR1
cR3−(1+E)cR4
cR2−(1+E)cR3+E cR4
−(1+E)cR2+E cR3
−(1+E)
1
0
E
−(1+E)
1
−cR1
0
−VcE1
cR4
1−cR1
0
E
−(1+E)
=
=
=
Thecoefficientdeterminantisasfollows:
Thecorrespondingsolutionvectoris:
Inthematrixcalculation,andgivencR1,cE1,Vandktheresidualconcentrationof
thetransitionalsubstanceaftertheindividualstagescanbecalculated,whereby
cRN = Raffinate concentration after the nth stage. = Extraction yield
Iftheextractionyieldisgiven,thefollowingformulacanbeusedfordetermining
thetheoreticallynecessarynumberofstages:
isthepercentageextractionyieldafterthe3rdstage.
Thecoefficientmatrixandthesolutionvectorhavetobeextendedaccordingly
andcalculatedinaccordancewiththecorrespondingnumberofstages.
Thecalculationisverymuchsimplifiedwiththeassumptionofanegligibleextraction
concentrationoftransitionalsubstanceupstreamoftheinitialstage(cE1=0)
andthefollowingequationisapplicableforanynumberofstages:
η =
−1
9
Fig. 7 Diagram for establishing the extraction yield
Thisdiagramcanaccordinglybeusedforascertain-
ingthetheoreticalnumberofstagesnecessaryfora
certainextractionyieldinarelativelysimplemanner
ifthephaseratioisgivenandiftheequilibriumdata
areknown.
Thefollowingexampleillustratesthewayinwhich
thediagramcanbeused:
• Given:Nernst’sdistributionlaw=20
(e.g.fromlaboratorymeasurement);
phaseratioextract/raffinateV=0.5
• Accordingly:ExtractionfactorE=10;
attainableyieldfor1,2,3theoreticalstages
Result:
Theoretical number Yield (%)of stages
1 91.0
2 99.1
3 99.9
100
10
1
Num
ber
of id
eal s
tage
s
Yield in %99.9 99 90 0
Extraction factor k · V
1.2 1.1 0.9 0.8 0.7 0.6 0.51.0 0.4 0.3 0.2 0.1
1.3
1.41.5
1.6
1.8
2.0
2.5
3
4
56810142030
10
Thisdecanterallowssuspensionswithahighsolids
contenttobeprocessed,andthispropertymakesit
suitablefordirectextractionofantibioticsfromthe
culturesolution,whichhasahighmyceliumcontent.
Filtration,whichusedtobeessential,istherebyren-
deredobsolete, and the continuousprocess avoids
lossesofvaluablematerial,aproblemassociatedwith
filtration.
This increases totalyieldtoupto98%.Compared
to conventional counter-current extraction, direct
extractionworkssignificantlymorecheaply,ifonly
because filteraidsareno longerrequired.Thefer-
mentationbrothisnotdilutedbyfilterwashwater,
likewise reducing the requirement for solventand
theriskofinfection.Asafinalconsequence,thenew
methodalsoreduceswastewaterpollutionandthe
volumeofwastewaterproduced.
2.2Antibiotics
Directextraction–totalyieldupto98%
Antibioticsformthemostimportantgroupofdrugs
inthefightagainstinfectiousdiseases.Representing
around13%of totalpharmaceutical consumption,
theyhavethehighestmarketshareofanypharmaceu-
ticalproduct.Thepharmaceuticalindustryextracts
antibioticsfromfermentationbroths.
GEAWestfaliaSeparatorGroup supports thispro-
cesswithspecialdecanterswhichresultinefficient
directextractionwhichissimultaneouslykindtothe
environment.Extractionalwaysconsistsofmixing
andseparating,processeswhichcanbeviewedasa
complex.ThisiswhyGEAWestfaliaSeparatorGroup
developedapatentedextractiondecanterforextract-
ingactiveingredientswhichcombinesthetwopro-
cesssteps,mixingandseparating,inasinglemachine.
Fig. 8 Extraction of antibiotics
Filtration
Counter-currentliquid-liquid extraction
Continuous directextraction using decanter
Precipitation
CentrifugationWashingCentrifugation
Drying
Raw salt
Liquid-liquidextractors
FermentationMold fungus
Mycelium and contamination
Nutrient solution
Counter-currentextraction decanter
or
11
Under the effect of statins such asLovastatin, the
humanbodyproduceslesscholesterol.
The relative lack of cholesterol means that higher
numbersofLDLreceptorsare formed in thecells;
theseabsorbLDL(low-densitylipoprotein)fromthe
blood,renderingitharmless.LDLisconsideredthe
mostimportantfactorindamageduetoanexcessively
highcholesterollevel.
Lovastatin was licensed as a cholesterol-lowering
agentas longagoas1987andsincethenhasbeen
oneof themost importantdrugsof thiskind.The
flowchartshowsthecomplexprocessinvolvedinthe
directextractionofLovastatinfromthefermentation
broth.Extractiondecantersoperatedonthecounter-
currentprincipleareusedinfourconsecutivestages.
Apolishingseparatorobtainstheenrichedextract.
Themachinesaredesignedtobegas-tightinaccord-
ancewith current explosionprotectionguidelines,
withtheresultthattheysatisfyallsafetyspecifica-
tions.Thisversatileprocesscanbeusedinasimilar
waytoobtainPravastatinandNystatin.
2.3Statins
Directextractionforhi-techdrugs
DirectextractionwithdecantersfromGEAWestfalia
SeparatorGroupplaysanimportantroleinspheres
otherthanobtainingantibiotics.Hi-techdrugssuch
as the so-called statins are also obtained by this
method.Inpharmacology,astatinisadrugbelonging
totheclassofsubstancesknownasHMG-CoAreduc-
tase inhibitors.AsHMG-CoAisan intermediateof
humancholesterolsynthesis,statinssuchasLovas-
tatinareusedprimarilyascholesterol-loweringagents
(CSEinhibitors).Inadditiontofatmetabolismdis-
orders, statins are also successfully used to treat
diseasesofourmodernsocietysuchasdiabetes(Pra-
vastatin)orfungalinfections(Nystatin).GEAWestfalia
Separator Group has developed extraction decan-
tersandpolishingseparatorswhichcanbeusedto
obtain these statins particularly economically by
directextraction.
Fig. 9 Lovastatin extraction
1st stageextraction decanter
Fermentation brothButyl acetateWetting agent
First-stage extract
Alkali water
Extracted broth
Sulfuric acidButyl acetateWetting agent
Butyl acetateWetting agent
Butyl acetateWetting agent
2nd stageextraction decanter
Polishing separator Enriched extract
4th stageextraction decanter
3rd stageextraction decanter
12
In the target cells, they dock with highly-specific
receptorsandperformakeyfunctionintheforma-
tionofproteins.Inordertoproducesteroidhormones
forpharmaceuticalapplicationsoutsidethebody,we
usedirectextractionfromspecialnutrientsolutions.
IncontinuousdirectextractionfromGEAWestfalia
SeparatorGroup,thefermentednutrientsolutionis
treatedby liquid-liquid extractionor in a counter-
current process. Following precipitation, concen-
tration,crystallizationanddryingoftheextract,the
steroidhormonesareavailableintheformofaraw
salt and can be correspondingly processed by the
pharmaceuticalindustry.
2.4Steroids/hormones
Obtainingestrogenandsimilarsubstances
Steroidsareendogenoushormonessuchasthesex
hormonesestrogenandtestosteroneorthehormones
oftheadrenalcortex,cortisolandaldosterone.Their
significance for the metabolism means that ste-
roidhormonesarealsoveryimportantinmedicine,
wheretheyareusedforhormonetherapyaswellas
inantirheumatic,antiarthriticandmuscle-building
preparations.Supportinobtainingthemefficientlyis
providedbyextractiondecantersfromGEAWestfalia
SeparatorGroup.
Virtuallyallsteroidsarebasedoncholesterol.Inthe
humanbody,steroidhormonesaresynthesizedinthe
endocrineglandsandtransportedtotargettissueby
theblood.
Fig. 10 Obtaining steroids
Filtration or
Counter-currentliquid-liquid extraction
Continuous directextraction using decanter
Precipitation
Crystallizedproduct
Concentration /precipitation
Drying
Raw salt
Liquid-liquidextraction
FermentationMold fungus
Mycelium and foreign substances
Nutrient solution
Counter-currentextraction decanter
13
preparationsofliquid,solidorviscousconsistency.
Asaruletheyareobtainedbymaceration(extraction
toequilibriumwithwateroralcohol)orpercolation
(extractiontoexhaustionwithwateroralcohol).A
keyfactorinproductionisselectionoftheextraction
agent.Water-soluble(hydrophilic)constituentscan
beextractedwithwater,whilstfat-soluble(lipophilic)
constituentsareextractedfromaparticularpartofthe
plantwithalcoholorothersolvents.
Comparedtocompetingseparationprocessessuchas
distillation,concentrationandmembranetechnology,
extractionhasprovedmoreefficientintermsofpro-
cesstechnology,moreselectiveandcheaperinnumer-
ousapplications.Itisnotonlyextremelygentle,butis
alsocharacterizedbyalowenergyrequirement.The
extraction decanter and polishing separators from
GEAWestfaliaSeparatorGroupusedinthepharma-
ceutical industrycoverallprocessesandmodesof
operation:liquid-liquidextractioncanberealized,as
can liquid-liquid-solid and liquid-solid extractions,
whether in one or more stages on the cocurrent,
counter-currentandcross-currentprinciples.Theflow
chartshowsatypicalplantextractionprocess.
2.5Plantextracts
Gentleextractionforsensitiveactiveingredients
There are some 500,000 species of higher plants
aroundtheworld,ofwhicharound70,000serveas
abasisforplant-baseddrugs.Muchasapplications
forvegetableactiveingredientsvary,theyallshare
one common feature: theyare extremely sensitive
substanceswhichhavetobetreatedcorrespondingly
gently by the biotechnical process used to obtain
them.Extractiondecantersandpolishingseparators
fromGEAWestfaliaSeparatorGroupareperfectly
designedforthispurpose.
Thestructureandbiologicalactivityofthesubstances
meanthatveryspecificmediumconditionshaveto
beused.Theextractionprocessisparticularlysuit-
ableforthis,buthastobepreciselyadaptedtosuit
process parameters such as pH, temperature, con-
centrationandthedelicatestructureofthevaluable
substances.
Theefficacyofaphytopharmaceuticalproductalso
dependsonadequateandconsistentdosageof the
plantextract,soindustrialstandardizationisofhuge
significance.Plantextractsaredefinedasconcentrated
Fig. 11 Plant extraction
Phase mixing
Extract
Solid
Extract
Solid for recovering solvent
Solvent
Medium fromfermentation Solvent
1st separatingdecanter
2nd separatingdecanter
Phase mixing
Polishing separator
14
Thewashingprocessiscarriedoutinamulti-stage
processwithacidandcompletelydesalinatedwater.
Separatorswithasolid-wallbowlareusedforsepara-
tingthepolymersolutionandwashingliquidinthe
individualwashingstages.
Stand-alonemachinesandcompletelines
Theaimistoachievenotonlyextremepuritybutalso
minimumresidualwatercontentintheorganicphase
tomeetthemarket’sincreasinglystringentproduct
quality requirements.Theseproduct requirements
aremetpreciselybyusingseparator technologyat
highspeeds.Solid-wall,disc-typeseparatorsoftype
XTAandXTCareusedattheacidstage;thesehaveall
product-contactcomponentsmadeofhighcorrosion
resistantmaterials.Inadditiontothesestandalone
machines,GEAWestfaliaSeparatorGroupalsosup-
pliescompleteprocesslinesforwashing.
2.6Polycarbonate
Polymerextraction/washingprocesses
Much was changed around 25 years ago with the
adventofthecompactdisc.Itchangedstereosystems,
recordshopsandturnedpolycarbonateintoaworld
star.Today,polycarbonatesaresomeofthemostpopu-
larplasticsasaresultoftheirexcellenttransparency
andimpactresistantproperties.Theycanbefound
innumerousapplicationssuchaselectro-technology,
equipmentconstruction,thecarmakingindustryor
formakinglensesforspectacles.
Separatorsareusedinthephaseboundarymethodin
theproductionofpolycarbonateinwhichthepolycar-
bonate,afterthereaction,isdissolvedinanorganic
solvent. A second water phase contains dissolved
salts and unwanted additives. Pure polycarbonate
isobtainedbydistillingoffthesolventafterbeing
washedelectrolyte-free.
Fig. 12 Production of polycarbonate
Reactor
Caustic sodasolution
Catalyst acid
Outgoing air
Wastewater
Polycarbonatesolution
Demineral-ized water
HCl
NaOH
Bisphonel A, methylene chloride,phosgene and additives
Separator I
Separator III
Separator II
Separator IV
Separator V
15
Thepectinsareextractedbyavarietyofacidswith
apH-valueof1to3,atatemperaturebetween65°C
and 85 °C and for an extraction period of 0.5 to
6 hours. Extraction delivers a raw extract with
0.3 to 1% pectin. Separating this viscous solution
from theheavily swollenand in somecasesdisin-
tegratedpomacecake is thekeytechnicalproblem
in the pectin industry. In the pectin process from
GEAWestfaliaSeparatorGroupshownintheflow
chart,thistaskismanagedbycombininganumber
ofdecantersandafilterpress.Theextractthenruns
throughtheseparatorandprecoatfiltrationbeforethe
pectinisprecipitatedusingisopropanol.Theexcess
precipitantisthenseparatedbyagas-tightdecanter
untilonlydrypurecitruspectinwithgoodstorage
propertiesremains.
2.7Pectin
Fromcitrusfruitstosettingagent
Pectin(fromtheGreek“pektos”=gel)occursinall
higherterrestrialplants.Citrusfruitsoccupyaspecial
position,astheyhaveanunusuallyhighconcentra-
tionofpectinsubstancesintheflavedoandalbedo
(about25%moistmassofthewholecitrusfruit).The
pectinobtainedfromthecitruspeelisusedmainlyas
asettingagentinthefoodindustry,butalsoforphar-
maceuticalandcosmeticproducts.Globalproduction
ofpurepectinisestimatedatapprox.35,000tonsof
which70%comesfromcitruspeel.Thepectinpro-
cessfromGEAWestfaliaSeparatorGroupprovides
today’sproducerswithanextractionprocesswhich
isasgentleontheproductasitisefficient.
Followingaspecialinitialtreatmentofthefreshpeel
and storage in mechanized silos, the dried peel is
milledandfedintotheextractionprocess.
16
Fig. 13 Obtaining pectin
Reaction tankpH = 1.5 – 3
Separator
TankpH = 2.2 T~ 65 ºC
Adsorber toremove colour
Decanter,gas-tight
Screens
Filter press
Precoat filtration
Isopropanolprecipitation
Isopropanol
Isopropanol(recovery)
Precipitated pectin gel
Pectin fibers
Dryer
Decanter IIDecanter I Decanter III
Dried pectinRaw materialH2OHNO3
17
3. Centrifugal Extraction
principles,whereasthedesignofthecentrifugeand
theseparatingprocessarebasedonmechanicalprin-
ciples.
Centrifugalextractionisthelinkbetweenthermaland
mechanicalprocessengineering.Thechoiceofsolvent
isbasedonthermodynamicandchemical/physical
3.1Mixers
Anextractionstagealwaysconsistsofamixingunit
andacentrifugeunit.Inthecaseofthemixingunit,
therearetwoequipmentalternatives;firstthecen-
trifugalmixerandsecondtheintegratedmixerinthe
bowlheadofseparators.
Advantages of centrifugal extraction of … so that you …
GEA Westfalia Separator Group …
Low phase hold-up have a low solvent requirement and can
accordingly reduce operating costs
Short contact time to a large extent avoid valuable substance decay
and achieve a higher overall yield
High stage efficiency minimize the number of stages and reduce the
investment costs
High load range and optimum throughput minimize investment costscapacity with minimum space requirement
Close contact time distribution achieve a significant improvement in substance
interchange between the phases by avoiding backmixing and achieve a higher overall yield
Separation of systems with low density can considerably extend the range of solvents which
differences and high viscosities can be used and achieve higher product backmixing
and achieve a higher overall yield qualities
Efficient phase separation achieve a higher overall yield
Optimum substance transfer due to achieve a higher overall yieldfine drop distribution
Operations not affected by achieve higher process security and availabilitysolid contaminations
18
3.1.1Centrifugalmixer
Inthecaseofthecentrifugalmixer,thetwophasesto
bemixedarepumpedjointlyintoarotatingmixing
druml(2),wheretheyareacceleratedtothecircum-
ferentialvelocityofthebowl.Thecentripetalpump
(3)discharges the liquidmixture from themixing
drum.Thetwophasesaremixedintensivelyinthe
channelsofthecentripetalpump.Themixedliquid
isthendischargedfromthemixeratoutlet(4).The
pressure in thedischarge line isadjustedwith the
aidofathrottlingvalve;thisaffectsthesuspension
in suchaway that the channels of the centripetal
pumpareimmersedunderthesurfaceofthesuspen-
sionandpreventanyairintake.Thehermeticversion
isthestandardversionforgas-tightapplications.A
slideringpackingensuresahermeticsealbetweenthe
drumandthehood.Theslideringpackingconsistsof
astainlesssteelhousingslideringandacounter-ring
madeofhardcarbon.
Theoutputof the3-phaseACmotor is transferred
directlyfromthehorizontalmotorshafttothemixer
drum. The variable speed mixer with a frequency
converterdriveisafurtherdevelopmentoftheorigi-
nalZAmixer.Inthissolution,afrequencyconverter
canbeusedforinfiniteelectricadjustmentofphase
mixing.Themixingcharacteristicscanaccordingly
beadjustedindividually,andthisaspectisofgreat
importanceparticularlyinthecaseof“multipurpose”
applications.Thedropsizeandtherequiredturbu-
lencevaryasafunctionofthespeed.Thefrequency
converterenablestheperformanceofthemixertobe
adjustedatanytime.
Fig. 14 Drum of a centrifugal mixer in hermetic design, type ZA 40-67-905
1
1
4 3 23.1.2Integratedmixerinthebowlhead
Besidesthemixersinstalledupstreamofthecentri-
fuges,itisalsopossibleforafacilityformixingthe
extractphaseandraffinatephasetobeinstalledinside
theactualseparators.Amixturetobeseparatedisfed
inthroughfeed(1).Theextractphaseofthenextstage
orfreshextractionagent(4)ismixedwiththeheavy
phaseseparatedintheseparator(theraffinate)inthe
centripetalpump(5).Themixedphaseisdischarged
fromtheseparatoratoutlet(3).Theclarifiedextract
phase leaves theseparator throughthe lightphase
discharge(2).Apartfromthefacilityformixingin
thecentripetalpumpchamber,itisalsopossiblefor
theextractionagent(4)tobeaddedtotheraffinate
directlybeforeitenterstheseparator.Theactualpro-
cesswherebythetwophasesaremixedtakesplace
inthedistributorchamberofthebowl(6)underthe
actionofcentrifugalforce.
1
2
4
5
6
3
Fig. 15 Section through the bowl of a solid-wallseparator with mixing device in the bowl head
19
3.2Centrifuges
Therearevariousoptionsavailablefortheextraction
process,wherebytheappropriatevariantandassuch
thechoiceofthecentrifugetobeusedisdetermined
bythenatureofthephases.
Extraction
Liquid-liquid-solid
Extraction decanter
Multi-stage
Counter-current
Single-stage
Direct current
Liquid-solid
Clarifying decantercentrifugal clarifier
Liquid-liquid
Disc separator
Fig. 16 Overview of centrifugal extraction processes and equipment from GEA Westfalia Separator Group
Fig. 17 Overview: Solid content as a selection criterion for centrifugal extractors Suitable for light solvents Suitable for heavy solvents
Extraction process
Liquid-liquid Liquid-liquid-solid Liquid-solid
< 0.1 ÷ 7 ÷ 15 ÷ 60 ÷ 7 ÷ 60
Separator with solid-wall bowl
Self-cleaning separator
Self-cleaning clarifier
Nozzle-type separator
Clarifying decanter
Extraction decanter
Phases Solids content in % (by vol.) Centrifugal extractors
20
Fig. 18 Section through a bowl of a separatorwith solid-wall bowl
In the gas-tight version, which is always essential
whenused forhandling solvents, this separator is
equippedwithexplosion-protectedcomponents,and
thebrakechamberisofflame-proofenclosure.The
framechamber,sealingchamberandgearchamber
areequippedwithconnectionsforinertgasblanket-
ing.Anexternalcontrolunitregulatesandmonitors
the pressure and the flows to the corresponding
chambersforalloperatingstatusesoftheseparator.
Thesolid-walldisc-typeseparatorisusedprimarily
forseparatingliquidmixtureswithnoorwithonly
minimalsolidcontents(lessthan<0.1%byvol.),as
otherwiseitwouldbenecessaryforoperationtobe
interruptedfrequentlyinordertoremovethesepa-
ratedsolids fromtheseparatoreithermanuallyor
usingflushingprograms.
3.3Liquid-liquidextraction
Disc-typeseparatorsintheversionswithsolid-wall
bowlsandself-cleaningdisc-typebowlsareusedfor
liquid-liquidextractionprocesses.
3.3.1Separatorwithsolid-walldisc-typebowl
Theseparatorisequippedwithasolid-wallbowl.The
productflowsthroughthehydrohermeticfeed,which
minimizestheshearingforcesforsensitiveproducts,
andisbrokendownintoalightphaseandaheavy
phaseinthediscstack.Theseparatedcomponents
aredischargedunderpressurebymeansofthecorre-
spondingcentripetalpumpsthroughoutlets.Theuse
ofadiscstackincreasestheequivalentclarification
area∑oftheseparatormanytimesovercompared
withacentrifugewiththesamevolumewhichcon-
sistsofasinglechamber.Dependingontheparticu-
larproductcharacteristics,thebowlcanbeequipped
withdischargeboreholessothatthesuspensioncan
bedrainedformaintenancepurposesfromthebowl
whenthemachinehascometoastandstill;theadvan-
tageofthisarrangementisthatmaintenanceperson-
neldonothavetocomeintoexcessivecontactwith
theprocessmedia.Atthesametime,CIP(cleaning-in-
place)isalsopossiblewithoutthebowlbeingopened.
Theselectedpairofcentripetalpumpsalsoenables
the separatingzone tobeadjusted inanoptimum
mannerevenwhenthere isamajordensitydiffer-
encebetweentheproducts;theseparatingzonecan
beadjusteddependingonthevolumeoftheproducts
involved.Theseparatingzoneisadjustedbyadapt-
ingtheregulatingrings.Theseregulatingringsalso
guaranteeextremelyefficientseparationevenwhen
therearemajor fluctuations in thecompositionof
thephases.
Feed
Heavy phase discharge
Light phase discharge
21
3.3.2Separatorwithself-cleaningdisc-typebowl
Unlikethesituationwiththesolid-walldisc-typesepa-
rator,self-cleaningseparatorsareabletodischarge
theseparatedsolidsatfullbowlspeed,whichmeans
thattheyarealsoabletooperatewithproductswith
asolidcontentsofupto7%(byvol.).However,ithas
tobeborneinmindthatseparatorsareliquid-oriented
machinesandarenotusedprimarilyforremoving
solids.
Fig. 19 Section through the bowl of a separator with a self-cleaning disc-type bowl
Fig. 20 Installation with type XSC 35 separators
Feed
Heavy phase discharge
Light phase discharge
22
3.3.3Driveconceptsforseparators
Different drive concepts are also available for the
separators.Twodriveconceptsareintheprogramme:
flat-beltanddirectdrive.
Flat-beltdrive
Inthissolution,themotorpoweristransferredtothe
spindlebymeansofanantistaticflat-belt.Oilcircu-
lationlubricationensuresthatbearingsarecontin-
uouslylubricated.Comparedtothegeardrive,which
isstillusedinoldermodels,themotorpoweristrans-
ferredwithupto10%lowerpowerlosses.Thebelt
itselfcanbereplacedquicklyandinaservicefriendly
mannerwithoutthebowlormotorhavingtobedis-
mantledbeforehand.
Directdrivesystem
Thedirectdriveisanexampleofintelligentsimplifi-
cationinseparatingtechnology.Wherevertheupper
limitforgearloadshasbeenreachedorbeltdrives
areundesirable,ourseparatorswithdirectdriveper-
mitvirtuallyloss-freepowertransmission.Thisboost
inperformancesimultaneouslyreducesthecostsof
energy,wear,maintenanceandspace.Therequired
poweristransmitteddirectlytothebowlspindleby
a3-phaseACmotorwithfrequencyconvertercontrol
viaatorsionallyelasticclutch.Thespindleassembly
islikewisesupportedbyrubber-metalcushions.This
makespossiblelow-vibrationrunningathighbowl
speeds.
Ataglance:
• Extremelyspace-savingdesign
• Avoidanceofhousingdeformation
• Highperformanceinput
• Lowmaintenancerequirement
• Lessparts
• Reducednoice
23
3.4Solid-liquid-liquidextraction
3.4.1Extractiondecanters
Decantersareaveryefficientmeansofcarryingout
liquid-liquidextractionwithahighsolidscontent.
GEA Westfalia Separator Group has developed a
continuouscounter-currentdecanterspecificallyfor
such applications. The counter-current extraction
decanterisahorizontalscroll-typecentrifugewitha
cylindricalconicalsolid-wallbowl.Ascrolladaptedto
thebowlwallrotateswithadifferentialspeedinside
thebowl.
These decanters are able to extract valuable sub-
stancesdirectlyoutofthesuspensions.Atypicalarea
ofapplicationforthesemachinesistheextractionof
antibioticsfromfermentationsolutions.Thesuspen-
siontobeextracted,e.g.fermentationbroth,flows
throughtheexternalcentrallyarrangedinlettubeand
is fed into themachineviadistributorslots in the
scrollof thebowl.Thesuspension thenenters the
counter-currentextractionzoneofthebowl,whereit
flowstotheconicalendofthebowlviatheseparat-
ingdiscagainsttheflowdirectionoftheextraction
agent(counter-currenteffect).Theextractedsuspen-
sion(raffinate)isdischargedundergravityfromthe
dischargeofthemachine.Thesedimentedsolidsare
conveyedby thescrollwhichrotatesatadifferen-
tialspeedinrelationtothebowl,andaredischarged
undergravitytogetherwiththeraffinate.Theextrac-
tionagent (solvent) flows through the internalcen-
trallyarrangedinlettubeintothedistributor,where
itentersthecounter-currentextractionzonethrough
apertures.Theextractionagentflowstothecylindri-
calendofthebowlagainsttheflowdirectionofthe
suspensiontobeextracted,and is thendischarged
underpressureviathecentripetalpump.Bothphases,
namelytheextractandtheraffinate,arefirstmixed
andthenflowthroughtheclarifyingzonestoenable
the phases to be separated efficiently. In order to
permitsafeoperationinexplosivesurroundings,the
decanterhasbeenprovidedwithagas-tightdesign
andcanalsobeblanketedwithinertgas.
Fig. 21 Section through an extraction decanter
ExtractExtractionagent
Suspension
Raffinate
24
3.5Solid-liquidextraction
3.5.1Clarifyingdecanters
Theprinciplesofsolid-liquidextractionhavebeen
explainedinchapter1.Speciallydevelopeddecanters
areusedforrealizingtheprocesstechnology.
Before entering the decanter, the extraction prod-
uct,whichhaspreviouslybeencomminuted,broken
down or ground down, is mixed intensively with
theextractionagent ina separatemixer.The inlet
throughwhichthesuspensionflowsintothedecanter
isarrangedaxiallyinrelationtotherotatingbowl.The
solid-wallbowlhasacylindricalsectionforefficient
clarificationof the liquidandaconicalsectionfor
dewateringthesolids.Thescroll,whichrotateswitha
slightdifferentialspeedrelativetothebowl,conveys
thesolids(extractionresidue)tothesolidsdischarge
attheconicalendofthebowl.
Theextractisconveyedtothecylindricalendofthe
bowlwhereitisdischargedviaacentripetalpump.
3.5.2Clarifyingseparators
Inthecaseofsolid-liquidextractionprocesseswith
lowsolidcontents(uptoapprox.7%byvol.),clari-
fierswithaself-cleaningdisc-typebowlcanalsobe
usedasanalternativesolution.Becauseoftheirhigher
speedsandclarifyingarea,thesemachinesprovidea
higherclarifyingperformancethanisthecasewith
decanters.
Fig. 22 Section through a clarifying decanter
Suspension
Solids discharge
Light phase discharge
25
Fig. 23 GEA Westfalia Separator varipond®
Fig. 24 2-gear drive
3.5.2GEAWestfaliaSeparatorvaripond®–
reliablemasteringphaseseparation
The pond depth in the decanter is an important
parameterwithwhichtheseparatingzonebetween
the light and heavy phase can be influenced. The
varipond® system gives the user the opportu-
nity to alter the pond depth to adapt to specific
conditions during ongoing operation. A so-called
varipond® disc dips into the clarified light phase
directly in front of the regulating ring. This disc
forms a hermetic chamber (“varipond®” chamber)
together with the centripetal pump, to which
pressurecanbeappliedthroughaholeinthefeed
tube. Since the liquid level between the
varipond® disc and the regulating ring is defined
by the overflow diameter, overpressure in the
varipond®chamberhas theeffectofenlargingthe
ponddepthinthedecanterbowlinaccordancewith
theprincipleofthecommunicatingtubes.Asaresult,
theseparatingzonebetweenlightandheavyphase
isdisplacedoutwards.Theprocessoperatorconse-
quentlyhasatoolthatpermitspreciseadjustmentof
thepurityofheavyandlightphase.Thisisindispen-
sableforefficientandcost-savingdecanteroperation,
particularlyinthecaseofchangingfeedconditions.
Particularly in the case of gastight decanters, the
varipond®systemhastheadvantagethatitrequires
no mechanically adjustable parts such as rotary
leadthroughs. It thereforeprovides ahigh level of
protectionagainstdischargingharmfulgases.
3.5.3Innovativedriveconceptsfordecanters
Flexible process management with simultaneous
maximum availability are essential requirements
for modern drive concepts.The variety of process
engineering applications in which decanters from
GEA Westfalia Separator Group are used requires
differentdriveconcepts.Thisistheonlywaytomeet
thecorrespondingproductrequirementsinanopti-
mummanner.Theproduct line therefore includes
drive systems with and without the possibility of
simple regulation of the differential speed. The
requirementsforthemachineandprocessbutalso
customerwishesdeterminewhattypeofdriveisused.
Inthecaseofdecanterswhichareusedinthefield
ofchemicalindustry,flexibleandpreciseregulation
of thedifferential speed isparticularly important.
Thisistheonlywaytoachieveextremelyhighsolid
concentrationsandthushighseparatingefficiency.
The2-geardriveandthedifferentialgeardrivehave
thereforebecomeestablishedinpractise.
2-geardrive
The advantage of the 2-gear-drive drive which has
been developed and patented by GEA Westfalia
SeparatorGroupisthefacilityforregulatingthescroll
drive.Thedifferentialspeedisadaptedautomatically
andextremelypreciselyasa functionof thescroll
torque–andthusasafunctionofthesolidscontent
in thebowl.Accordingly, thesolidsaredischarged
fromthebowlwithaconstantconcentrationandin
anextremelydrystate.2-gear-drivedrivesareused
wheneverthevolumeofsolidsisnotconstant,when
thesolidsaredifficulttoconveyandwhenveryhigh
requirementsareapplicablewithregardtotheresid-
ualwatercontentofthesolids.
26
Fig. 25 Differential gear drive
Differentialgeardrive
Thedifferentialgeardrive is recommendedwhen-
everitisnecessarytoautomaticallyregulatethescroll
speedinadditiontoregulatingthebowlspeed.This
canbeachievedbymeansoftwogears.Thesecondary
motordrivesthecentralinputshaftandgeneratesthe
differentialspeedproportionallytoitsownspeed.A
secondinputshaftwithoutanyspeedisconnectedto
thehousing.Thismeansthatthedifferentialspeedis
notdependentonthebowlspeed.Differentialgear
drivesareusedprimarilyinthelowerrangeofthe
differentialspeeds.
27
ratorswithanupstreamfiltrationsystem.Thedirect
extractionprocess,alsoknownas“wholebrothextrac-
tion”,makesuseofdirectextractiondecanters(see
fig.21Continuouscounter-currentdecanter).
endproduct–penicillinrawsalt–isobtainedinthe
purityrequiredbythemanufacturer.Themaximum
efficiencyofthetwoseparatorsismaximallyequiva-
lenttothatoftwotheoreticalstages,andis94–96%
measuredagainstthefeedtothefirstseparator.How-
ever,thefiltrationstageupstreamoftheextraction
stagemeansthatthismethodsuffersseveraldisadvan-
tagescomparedwiththedirectextractionprocess:
• Increasedriskofcontaminationduetouseof
washwater
• Increaseduseofsolvent–higherenergycosts
forrecoveringvaluablesubstancefromthe
extractionsolution(morewashwater more
raffinate moresolvent highercosts)
• Lossofvaluablesubstance(>5%)
• Onlyfilterablemyceliumstructuresfrom
fermentationcanbeprocessed.
3.6Alternativeprocesses:
Filtrateextractionordirectextraction
Bothprocessesaresuitableforextractingantibiotics
(e.g. scraps) fromafermentationsolution.Thefil-
trateextractionprocessmakesuseofdisc-typesepa-
3.6.1Filtrateextraction:Antibiotics
Inthefirststep,theaqueousbiomasswhichcontains
thefungalmyceliumischannelledviaavacuumbowl
filterandseparated.Thefiltercakewhichformson
thebowliswashedwithwaterinordertoachievea
maximumyieldofpenicillin.Subsequently,sulphuric
acidisaddedinordertochangethepHvalueinsuch
awaythattheconditionsformasstransferareopti-
mized.Theadditionofwettingagentensureshigher
separatingefficiencyduringtheextractionprocess.
Theaqueousfermentationsolutionfromwhichmost
ofthesolidshavebeenremovedisthenconveyedto
thefirstdisc-typeseparator in the2-stagecounter-
currentextractionstage,whereitismixedwiththe
solvent from the second separator which already
containspenicillin.Thesolventwhichisdischarged
fromthefirstseparatorissubsequentlyprecipitated
and processed in centrifuges until the provisional
Fig. 26 2-stage extraction, direct current process
Nutrient solution
Aeration
Spore emulsion
Starterfermenter
1. Discseparator
Buffer tank
Basket centrifuge
Penicillin raw salt
Effluent
Fresh solvent
Biomass
Wash water
Vacuum drum filter
2. Discseparator
Acid or caustic
Demulsifier
28
Theyieldoftwoextractiondecantersoperatedina
counter-currentarrangement is95–96%.Labora-
torytrialshavedemonstratedthat,dependingonthe
particularsubstancesystem,atheoreticalstagecoeffi-
cientofupto1.7perextractiondecanterispossible.In
ordertoseparateveryfinesolidparticles,thesolvent
(extract)whichisdischargedfromthefirstextraction
decantercanbepolishedinadownstreamdisc-type
separator;thisenablesextremelypureextracttobe
obtained.Thefollowingprocessstages–precipita-
tiontankandbasket-typecentrifuge–areidentical
tothefinalstagesofcounter-currentextractionwith
disc-typeseparators.
1 Fermentationbroth
2 Enrichedsolvent
1stDecanter
3 Extract
2ndDecanter
4 Raffinate
1stDecanter
5 Raffinate
2ndDecanter
3.6.2Directextraction
Theuseofextractiondecantersoffersmajoradvan-
tages.Thedecanterisabletoextractsuspensionswith
asolidscontentofupto60%(byvol.),whichmeans
thatonlyasinglestageisnecessaryforseparatingthe
solids(thefungalmycelium)fromthefermentation
solutionandforextractingthevaluablesubstance(the
antibiotic).Thismeansthattheprefiltrationstagecan
bedispensedwithandthattheextractionstagecan
beinstalleddirectlydownstreamofthefermentation
stage.Sulphuricacidandwettingagentareaddedto
thefermentationsolution,whichisthenprocessedin
the2-stagecounter-currentprocess.
Fig. 28 2-stage direct extraction with extraction decanters
Nutrient solution
Aeration
Spore emulsion
Fresh solvent
Acid or caustic
1. Extractiondecanter
2. Extractiondecanter
Demulsifier
Enrichedsolvent
Disc separatorExtract polishing
Buffer tank Basket centrifuge
Effluent
Biomass
Penicillin raw salt
3 5 2 4 1
Fig. 27 Spinning samples of a 2-stage direct extraction
29
4. Explosion-Protected Centrifuges
Centrifugesareusedinthechemicalindustryforclarify-
ingandseparatingreadilypharmaceuticalflammable
liquids.Theoretically,suchapplicationscanresultin
criticalconcentrationsofsolventvapoursandoxygen
insidethecentrifugethatcancauseexplosionsorfires.
However, thevapoursmust alsobeprevented from
escapingsoasnottoposearisktothehealthofthe
operators.Boththeseriskscanbepreventedreliably
by using gas-tight centrifuges from GEA Westfalia
SeparatorGroup.
Nosparks,nostaticcharges,nohotbearings–the
test criteriaof the strictEuropeanATEXstandard
are of course implemented in all GEA Westfalia
SeparatorGroupexplosion-protectedcentrifuges.In
addition,beforethestartofoperation,thecentrifuge
isfloodedwithinertgasandblanketedwithaslight
excesspressuresothatnofurtheroxygenisableto
penetrate.This isbecausefire isnotpossiblewith-
outoxygen.Whenprocessingsensitiveliquids,the
necessary inert gas atmosphere in the separator
is automatically monitored throughout the entire
operation.
Nothingisabletopenetratethisbarrier
Anessentialdesign featureof thegas-tight separa-
torsfromGEAWestfaliaSeparatorGroupistheneck
bearingbridgethatseparatesthedrivewiththemotor
andgearboxfromtheproductchamber.Thisbridgeis
blanketedwithinertgas,andtheconnectingspindle
isprotectedwithdynamicspecialseals.
Theneckbearingbridgereliablypreventsthesolvent
frompassingfromtheproductchambertothedrive
chamberorintothesurroundings.Thisisbeneficial
notonlyfromthepointofviewoffireandhealthpro-
tection,itisalsonotpossibleforsolventtodilutethe
oil,whichwoulddiminishitslubricatingefficiency
andthusposearisktothedriveunit.
Thesameisalsotrueinreverse:nooilisabletopene-
tratetheproductchamberandthushaveanegative
impactonthequalityofthevaluableproduct.
ATEX95(directive94/9EC)
Adirectiveformachinesoperatinginhazardoussur-
roundingshasbeeninforceinEuropesince1July
2003. This affects numerous applications in the
chemicalandpharmaceuticalindustries,particularly
wheregas-tightmachinesareused.Accordingtothe
directive,thefirststepistocarryoutariskassessment
oftherelevantmachinestoidentifyanypresentor
potentialrisks.
The measures are documented and the documen-
tationissubmittedtoanEntitledBody.Inspecific
terms,thismeansthatGEAWestfaliaSeparatorGroup
decantersarenowequippedwithfailsafevibration
monitoringequipment,atemperaturemeasurement
facilityaswellasaninertgasfacility.
All electrical equipment must have been awarded
anATEXcertificateoramanufacturerdeclaration.
Thisdirectiveisonlyapplicabletonewmachines.A
separatedirectiveATEX137(directive1999/92EC)is
applicableforoperatorsofinstallationsinhazardous
areas.Inthisway,operatorshavealsobeenobligedto
carryoutriskassessmentsforexistinginstallations.
30
Machinesandinstallationsmusthavebeenassessed
by no later than 1 January 2006. GEA Westfalia
Separator Group offers its customers support for
assessing and where reasonable converting these
centrifuges.
GEAWestfaliaSeparatorGroupimproves
inertgasconcept
Requirementswithregardtosafetyandreliabilityare
becomingmorestringentforseparatorsanddecant-
ersusedinzoneswithariskofexplosion.Theexist-
inginertgasconceptisconstantlyimprovedtomeet
theserequirements.ThelatestEuropeanstandards,
aswellasGEAWestfaliaSeparatorGroup’spractical
operatingexperience,areincorporatedintheconcept.
Ashasbeenthecasewithmostexistingconcepts,the
atmosphereintheseparatorisdisplacedwithinert
gasbeforeeverystart-upandtheexcesspressureis
maintainedduringoperationtomeettherequirement
forminimuminertgasconsumption.
Thefittingsandmeasuringdevicesusedhavebeen
subjecttoanextensivetestandhavealsobeenopti-
mizedasfarasinvestmentcostsareconcerned.The
newinertgassupplyfacilitycompliesnotonlywith
thefamiliardirective94/9EC(ATEX)butalsowith
theTA Luft, i.e. product leakages from the equip-
mentarereducedtoaminimumusingstate-of-the-art
technology.
GEAWestfaliaSeparatorGroupplacesgreatemphasis
oncompleteandeasy-to-understandoperatordocu-
mentationaswellasacarefullyperformedconformity
assessmentprocedure(CEsymbol).Thecompanyalso
providesinformationconcerningthecorrectinstal-
lationofseparatorsanddecantersinzonesthatare
exposedtotheriskofexplosion.
31
5. Ceramic Membrane Filtration – Ultra- and Micro-Fine Clarification
GEAWestfaliaSeparatorGrouphasachievedanew
dimensionofultra-fineclarificationwithsolutions
comprising a centrifugal separation system and
filtrationtechnology.
In addition to centrifugal separation systems,
GEAWestfaliaSeparatorGroupalsohasanexpertcom-
mandofmembranefiltrationwithceramicelements
forultra-fineclarificationofparticleswithasizeofup
toonenanometer.Thecompanyisaccordinglyableto
significantlyexpandproductclarificationwithina
process chain.The intelligent combination of cen-
trifugationandmembranefiltrationinaninnovative
solutionfurtherimprovestheefficiencyoftheoverall
installation.
Individualspecifications
The ceramic membrane installations continuously
supplyaclear filtratewith thespecifieddegreeof
clarification and the desired performance. The
ceramicmembraneformsamechanicalbarrierwith
adefinedporesize.
GEAWestfaliaSeparatorGroupprovidesawiderange
ofceramicmembranemodulesintheporesizerange
ofultraandmicrofiltration.
Themodulesaremainlystandardized,withvariable
channeldiameters,element lengthsandporesizes.
Thismembraneinstallationdownstreamofthesepa-
ratorpermitsextremelyfineclarificationofparticles
withadiameterof<1micrometer.
Ataglance:
• GEAWestfaliaSeparatorGroupsolutions
comprisingcentrifugationandmembrane
filtration
• Everythingfromasinglesource
• Intelligentharmonizingofallcomponents
enhancesprocessefficiency
• Widerangeofceramicmembranemodules
• Individualconfigurationaccordingtospecific
requirements
32
6. Automation Systems – Plug and Play
GEAWestfaliaSeparatorGrouphasextensiveexperi-
enceinthedriveandcontroltechnologyofseparation
systems.Customer-specificautomationofcentrifuges
andmembranefiltrationmeansthattheiroperation
is particularly simple, reliable and safe. Solutions
fromGEAWestfaliaSeparatorGroupcombinetried-
and-testedprocessandmachinetechnologywiththe
latestdrive and control technology.Theautomation
conceptsarecustomizedinallregardstomeettheindi-
vidualrequirements–fromadviceprovidedbyexperi-
encedengineeringspecialists,compactcontrolunitsfor
individualmachinesandpowerfulPC-basedinstallation
controlsrightthroughtocomprehensiveoriginalmanu-
facturerservice.
Highcompatibility
In addition to the company‘s own compact control
units,theS7controlunitsfromSiemensconstitutethe
coreitemofinstallationautomation.However,compo-
nentsfromAllenBradley,GroupSchneider,Mitsubishi,
Modicon or Telemechanique can also be used and
combinedwitheachotherasrequired.Thevisualiza-
tionoptionsalwaysensureoptimumuser-friendliness.
WinCCorIntouchcanbeusedforuptofivevisualiza-
tionfacilitiesintheprocessline,andcanalsobecom-
binedwitheachother.Whetherasimplenotification
signaloracomplexprocessdataexchangearrangement
isrequired:theconnectiontoexistinginstallationsor
processesviasoftwareisnowadaysalmostobligatory.
ThespecialistsfromGEAWestfaliaSeparatorGroup
usethebest-knownsystemssuchasProfibusDP/PA
orIndustrialEthernetaswellasadditionalconnections
suchasDeviceNet,ControlNetorModbusforthispur-
pose.Fullyautomaticoperationoftheinstallationcan
alsobesupportedbyremotedatatransferbymeans
of Internet, modem or GPRS. With GEA Westfalia
Separatorwewatch®,anindependentandcomprehen-
siveserviceconceptisavailableforremotediagnosis.
Withtheseadvantages…
• Strongcompetenceindriveandcontroltechnology
• Individualautomationconcepts
• Adviceprovidedbyengineeringspecialists
• Compactcontrolunitfromawiderangeof
manufacturers
• Uptofivevisualizationsintheprocessline
• Comprehensivecontrolpossibilitiesfroma
simplereportingsignalrightthroughtocomplex
processdatainterchange
• ConnectionviasoftwarewithProfibusDP/PA,
IndustrialEthernetorothersystems
• Supportforremotetransmissionanddiagnosis
(wewatch®)
…customers benefit from user-friendliness and
security.
Everything from a single source.
33
7. Special Materials
Thepropertoolforthejob;thisistheprincipleused
by GEA Westfalia Separator Group for selecting
materials.Thisisapplicableparticularlyforcompo-
nentsthatcomeintocontactwithproduct,suchasthe
bowl,scrollordiscstack.Strength,corrosionresistance
andhygienicspecificationsareimportantcriteriain
thisrespect.Ingeneral,thequalityofthematerialmust
increaseastherequirementsbecomemorestringent.
Thestandardmaterialisthetried-and-testedstainless
duplexsteel,whichhashighstrengthandexcellent
corrosionresistance.Ontheotherhand,superduplex
steel is the preferred material for more complex
applications. For particularly “hard” applications,
GEAWestfaliaSeparatorGroupusesspecialalloys
suchasIncoloy“Titanium”825orHastelloyC4.The
load-bearingparts(bowlbottomandbowltop)can
alsobeofcomplete1.4501superduplexmaterial.
Morewouldbewaste
AgenuineGEAWestfaliaSeparatorGroupspeciality
istheliningofsolid-wallbowlswithHastelloyC4or
eventitaniumpalladium.Thisknowhowisuniqueto
GEAWestfaliaSeparatorGroupthroughouttheworld.
In this process, sheets of the appropriate special
materialareincorporatedinthebowltopandbowl
bottomtoensurelongcorrosionprotection.Theload-
bearing bowl parts however continue to be made
withstandardmaterialstopermithighbowlspeeds.
Thisprocedurehasspecificadvantages:ifitisreally
necessary,theliningcanbereplaced;theuseofthe
expensivespecialmaterialisreducedtoanabsolute
minimum.
1. Inserting the lining in the bowl bottom
2. Dye penetration test after welding the lining
3. Bowl bottom with lining in place
34
8. Central Process Engineering –the Reliable Basis for Decision-Making
Ataglance:
• Testserieswiththeoriginalproductsof
thecustomer–practicalandrepresentative
• InthelaboratoryofGEAWestfalia
SeparatorGrouporinpilotinstallationsonsite
• Detailedtestdocumentation
• Specificmachinerecommendation
• Detailedmassbalance
• Totalcostanalyses
Customer-specifictestseriesinCentralProcessEngi-
neeringprovideareliablebasisfordecision-making
forallinvestmentsinmechanicalseparationtechnolo-
gy.Noproducttobeseparatedisidenticalwithanoth-
er.Inmanycases,itisthereforenecessarytoperform
testseriesbeforethecorrectdecisioncanbetakenfor
aspecificinstallation.GEAWestfaliaSeparatorGroup
hassetuptheCentralProcessEngineeringdepartment
(CPE)forthispurpose.Dependingonthespecifictask
involved,testseriescanberunwiththeoriginalprod-
uctofthecustomerinamobilepilotinstallationonsite
orinthelaboratoryatGEAWestfaliaSeparatorGroup.
Thespecificationofthecustomerwithoperatingtem-
perature,throughputcapacity,clarifyingorseparat-
ingefficiencyandotherfactorsconstituteadditional
importantinformationnecessarytoenablearepre-
sentativeandreliableanalysis.Aftereverytestseries,
thecustomerreceivesinformativedocumentationin
whichthetechnicalandeconomicdataaredetailed.
Focusoninvestmentprotection
The results ofCentralProcessEngineering canbe
used to precisely identify what machine type and
whatmodelfromGEAWestfaliaSeparatorGroupare
most suitable for the specific task.Thisprocedure
avoidspoorinvestmentsrightfromtheverybegin-
ning.Thecustomerachievesareliablebasisonwhich
hecantakethecorrectinvestmentdecision.
Scale-upforextractionapplications
Thescale-upofextractionapplicationsisoftenbased
onpracticaltrialscarriedoutwithtestcentrifuges.If
extractionischemicallydeterminedandifthesolvent,
thetemperaturesettingandthepHvaluearedefined,
apilotscaleoperationcanbetested.Themixingchar-
acteristicstogetherwiththemixingtimeanddrop
sizeaswellassubsequentcentrifugalseparationhave
tobeadjustedindividuallyforthespecificsubstance
system.Thephaseratiobetweentheraffinateandthe
extractisoptimizedinordertotakefulladvantageof
thegivencapacityofthesolvent.
35
GEA Mechanical Equipment
GEA Westfalia Separator Group GmbH
Werner-Habig-Straße 1, 59302 Oelde, GermanyPhone: +49 2522 77-0, Fax: +49 2522 77-2828www.gea.com Th
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GEA Group is a global engineering company with multi-billion euro sales and operations in more than
50 countries. Founded in 1881, the company is one of the largest providers of innovative equipment and
process technology. GEA Group is listed in the STOXX® Europe 600 Index.
We live our values.Excellence • Passion • Integrity • Responsibility • GEA-versity