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