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RoadmapFrom Europe and North America

Workshop on Aluminium Recycling

13th-15th June, 2010 Trondheim, Norway

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ContentsIntroduction 4

1.Collectionofscrap 6Current state- of- the- art 6Bottlenecks 8Goalsforcollection: 8Generalactions 10

2.Sortingofaluminiumscrap 11Current state- of- the- art 11Problems,challengesandopportunities 12Goalsforsortingofscrap 13Generalactions 13

3.Decoatingandmelting 14Current state- of- the- art 14Problems,challengesandopportunities 16Goalsfordecoatingandmelting 16Generalactions 17

4.Refiningofmeltedrecycledaluminium 18Currentstate-of–the-art 18Problems,challengesandopportunities 19Goalsforrefiningofmeltedrecycledaluminium 19Generalactions 20

5.Treatmentdross&saltcake 21Current state of the art 21Problems,challengesandopportunities 22Goalsfortreatmentofdross&saltcake 22Generalactions 22

6.UsingrecycledAlscrap 23Current state- of- the- art 23Problems,challengesandopportunities 24GoalsforusingrecycledAlscrap 24

Conclusion 25

References 26

Abbreviations 26

Participantslist 27

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This Roadmap has givena“birds-eyeview”ofaluminiumrecyclingcoveringimportantdetails.We hope that the Roadmapwillserveasaguideforfuturesolutionsinaluminiumrecycling.

IntroductionThis Aluminium Recycling Roadmap represents the combined efforts of35invitedaluminiumexpertsfromEuropeandNorthAmericawhometinTrondheim,Norway,organisedbySINTEF/NTNUandchairedbyAnneKvithyldofSINTEF,during13th-15thJune,2010. TheResearchCouncilofNorway,NTNUand SINTEF sponsored themeeting. TheRoadmap is intended tofocustheinterestsofallkeystakeholders,especiallyindustrialandacademicresearchers, regarding the current status and technology needs of therecyclingofaluminium.

Withtheemphasisofindustryandmanynationalgovernmentsonincreasingenergyefficiencyanddecreasingemissionofgreenhousegases,thetopicofaluminiumsustainabilityhasreceivedmuchdeservedattentionrecently.Forexample,theInternationalAluminiumInstitute(www.world-aluminium.org)currentlymonitorsaseriesofsustainabilitygoalsonaglobalbasis.Inits Technology Roadmap (publ. Feb. 2003), [The aluminium association,2003]intheUnitedStates,theAluminiumAssociationhassetagoalof100%recycling by 2020. The European Aluminium Association is also active inincreasingtheoverallaluminiumrecyclingratesandawareness. Recyclingrepresentsacriticalcomponentinthesustainabilityofaluminium.Recyclingcanberepeatedwithaverylowlossofmetalquantityandquality.

Recycling of aluminium is vital because it saves ~95% of the energy andassociatedemissionscomparedtoproducingthemetalfromtheore.Alsoitprovidesmetal,savescapitalexpenditures(meltersaremuchlesscostlythanprimarysmelters),andreduceslandfillspacerequirementsandfees.

ThisRoadmapistimelyforatleastthreereasons:

• Withfuelcostsrising,transportation-manufacturingcompaniesareseekingeconomicwaystoimprovethegasmileageoftheirproducts,inresponsetomandatesfromnationalgovernments.Thishasresultedintheincreasinguseoflightmetals,especiallyaluminium.Toincreasetherangeforelectriccarsbetweencharging,aluminiumisessentialsincerangeisinverselyproportionaltovehicleweight.

• Asecondreasonisgovernmentalpoliciesdemandingrecycling.TheEUGovernmenthasmandatedthatallvehiclesmustbe95%recyclablebytheyear2015.[WasteWatch,2011]Asaluminiumrecyclingisawell-establishedprocess,thiswillencouragealuminiumuseandtheadoptionofrecyclingalsoofothermetalsandmaterials.Theuseofaluminiumhasgreatlyincreasedinrecentyears,andnowthealuminiumrecycledfromautomobileswellexceedsthatfrompackaging.

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• Thirdly,ahigherrecyclingrateofaluminiumwillenhancethesustainabilityandpublicimageoftheglobalaluminiumindustry.Theuseofaluminiumisessentialtosupportenvironmentallyfriendlysolutions.Intheproductionofrenewableenergy,aluminiumisusedassupportsystemsforsolarpanels.

Forallthesereasons,thislatestinternationalroadmapistimely.Theroadmapisorganizedtoaddressallmajoraspectsoftherecyclingprocesschain:ScrapCollection,AutomatedSortingTechnology,DecoatingofScrap,MeltingandRefiningTechnology,UseofRecycledAluminium, andDrossHandling andMinimization.

ThisRoadmaphasgivena“birds-eyeview”ofaluminiumrecyclingcoveringimportantdetails.WehopethattheRoadmapwillserveasaguideforfuturesolutionsinaluminiumrecycling.

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1.CollectionofscrapCurrentstate-of-the-artImmensequantitiesofscrapflowthroughtheglobalaluminiumeconomy.UsingthenumbersfromInternationalAluminiumInstitute(IAI)ontheglobalaluminiumflowfrom2007andcategorisingscrapafterithasbeentoanendconsumer:

New scrap: 30.4milliontonnes(MT)ofnewAlscrapwereproducedin2008[InternationalAluminiumInstitute,2009]as:

• Metalinskimmings,whiteandblackdross• Ingots,scalpingchips• Edgeandendtrim• Castingmouldanddietrim• Stampingedgeandskeletontrim• Boringsandturnings

Mostofthiswasmaintainedassegregatedalloys,themajorityofwhich(20MT)wasinternallyremeltedbysemi-producerswithoutreachingthescrapmarket.

Post-consumer scrap: There is no such thing as a dedicated post-consumer Al scrap collectionandprocessingsystem.Discardedend-of-lifeassembliesarecollected inanumberofrecyclablecollectionsystemsthatvarysignificantly.Post-consumerscrap/wastestreamsare:garbage,solidwaste/recyclingdeposits,curbsidecollected recyclables, returns-for-deposit, end-of-life vehicles, scrap yards,buildingdemolitionresidueandwasteelectricalandelectronicequipment.Millionsofhouseholdsinhundredsofthousandsvillagesandmunicipalitiescollect recyclables and feed tens of thousands of junk/scrap yards, de-pollutionandrecyclingdepotsandtransferstations.These,inturn,delivertothousandsofmaterialrecoveryfacilitiesthatgrouptherecyclablesandsellthegroupedproductseitherdirectlytoscrapprocessorsortoshredders.

In2008around9.9MTofpost-consumerscrapwasrecycled.Byfarthelargestsourcesaretransportation(3MT)andpackaging(2MT)(seeFigure1).

However4.1MTwereeitherincineratedwith/withoutenergyrecoveryorwerelandfilledinmunicipalgarbage.Someofthislossisaccountedforbyuncollectedbeveragecansandfoilcontainersmissedbythecurbsideorbydepotcollectionsystems;butalargerfractionarethealuminiumcomponentsofconsumerdurableproductsthatarenotacceptedinthecurrentcurbsidecollectionsystems.

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Also2.7MTaluminiumscrapcouldnotbeaccountedforeitherduetotheuncertaintyinthelifetimesofdurableproducts,orduetometallossesinthelandfilledscrapprocessingresidue.[IAI,2009]

TheIAImodelnumbersalsoimplythatthelossesinthecollectionportionoftherecyclingcycleof4.1(+2.7?)MTaresignificantlyhigher than themetallossesinscrapprocessingremeltingandrefiningwhichtotal1.7MT.Clearlyfocusonimprovedcollectionisimportantfortheoverallefficiencyofthealuminiumrecyclingsystem.

Recycling ratesof thepost consumedscrapvaryconsiderablybyproduct,andlocationasdiscussedbelow:

Packaging• IntheUS,andmanyWesternEuropeancountries,therecyclingrate

foraluminiumcansisaround50%orless.[InternationalAluminiumInstitute,2009]p.23

• Developingcountries(suchasBrazil,IndiaandChina)alongwithScandinaviancountries(suchasNorway),Switzerland,EuropeandJapanhavehigherrecyclingratesofaluminiumcansexceeding90%.ThehigherrecyclingrateinthedevelopingcountriessuchasBrazilisduetotheeconomicincentiveofcollectioning“cashcows”,whereasthehigherrecyclingratesinNorway,Sweden,SwitzerlandandJapanareduetohighsustainabilityconsciousnessandanabundanceofconvenientrecyclinginfrastructure.

Transportation• Thecollectionrateforaluminiumfromautomobilesis>90%[Green,

2008]

• UsedandabandonedairplanesarestockpiledinthedesertsuchasinTucson,Arizona,USA.Therearefewdedicatedrecyclers,andcontaminationisanissueespeciallywithnon-mixablealuminiumalloys.

• Neweraircrafthavemorecompositesandtitaniumcontents.Dismantlingandseparationisdifficultattheendofusefullife.However,reuseofpartsandrecyclingispossibleandcanbeprofitable.

ConstructionandDemolition• Thecollectionratesofaluminiuminthissectorwerefoundtovary

between92%and98%[UdoBoin,2004].ThereisacleardivisionbetweennorthernandsouthernEuropeprobablyduetoclimatedifferences.SouthernEuropehasmoreAlinresidentialareas600g/toninsouthern,35g/toninnorthern.

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Inthebuildingandconstructioncategoryminimalneweffortsarerequired.Separatesheetproducts(mostly5XXX)fromextruded(6XXX)products.Aluminiumseparationshouldtakeplacebeforedismantlingandbeforemixingscrappedbuildingmaterialswithothermaterials,asthealuminiumisasmallpartofthescrapandcaneasilygetlost.

•Giveguidelinesandregulationsfordismantlingbuildingstoeaserecovery.

•Developandimplementafastsortingprocessduringdemolition.EncouragearchitectstoregardAlasgreenandviable.Developconceptsthatencouragerecycling.

Bottlenecks• Convenienceandsocialawarenessisthelargestfactorinfluencing

aluminiumcollectionforrecycling.Thelackofconvenience,especiallyawayfromhomeandlackofdedicatedofficeandpublicplaces,createsasignificantimpediment.

• Itisharderforsmallercommunitiestorecycle,largercitieshaveavailablefunds.

• Depositsareshowntowork,but,historically,therearevestedintereststhathaveresistedtheinstitutionofdeposits.

Goalsforcollectionofscrap:1. Increasedcollectionofaluminiumpackagingincludingusedbev.can

andaluminiumcomponentsofconsumerdurables:in5years>75%+(ultimategoal>90%+)collectedworldwide.

2. Improvedcollectioninfrastructure3. Closinggaponunknownlosses4. Recyclingeducationforconsumers

Figure 1: Global sources of recycled old aluminium scrap

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5. Addressproblemofstockpiledaircrafts6. Learnfromhighrecyclingratecountries(Brazil,Norway,Sweden,

SwitzerlandandJapan)andimplementthesebestpracticesinlowrecyclingareassuchasNorthAmericaandWesternEurope.

7. Makesureregulatorymetricssupportrecycling8. DevelopmethodsforidentificationandseparationofAl-Cu,Al-Zn,and

Al-Lialloysfromend-of-lifeAlaircraftalloyscrap.

CollectioninfrastructureDevelopinfrastructureforcollection.Makeiteasierandconvenient.• Charitableorganizationscollecting• Collectionnearhomes,officesandcommercialbuildings• Assessincentivemethods• Governmentregulations Regulation-depositlaws,mandatoryrecycling. Regulationsshouldbethelaststep,astheycansometimesinhibit, ratherthanhelp.

ClosinggaponunknownlossesThegoalistoexpandtheexistingIAIglobalAlflowmodeltobetteraccountforrecyclingloopsandtheinterrelationwiththerecyclingsystemforthenon-Alcomponentsoftheend-of-lifeassemblies.Thegoalistodevelopanaccurateresearch,technicalandeconomicmaterialflowmodel.Cooperatewithindustryindevelopmentandfinancing.Validatedata,quantifyimpactoflifecycle,anddifferencesbycountry,andincludelossesofunrecoverableAl.

Somedataareconfidential.Agoodwaytoupdatethemodelwouldbetosampleinputtolandfillsandincineratorstofindoutwhatisthrownaway.Includedataforunrecoverablealuminium.• Define,consolidateandagreeononeuniversallyacceptedrecycling

rate.Thereareover5differentwaystocalculatetherecyclingratenow(fromEAOOrganisationofEuropeanAluminiumRefinersandRemelters).

Recyclingeducationforcostumers• Convincethepublicthatrecyclingisameaningfulandsustainable

action.• Conveythateachdiscardedaluminiumcanmeanstheadditionof300

gramsofcarbondioxide,leadingtowardsclimatechangeandglobalwarming.

• Providespecificinformationofrecyclingactionsrequiredoftheconsumer:whatcanberecycled,whereandhow.

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Developmentofrecycle–friendlyaluminiumalloysPrimebasedalloyswithlowalloyingelementcontenthavemoreuseoptionsthanrecycledsecondaryalloys.Primebasedbinaryalloyswithhighcontentofonealloyingelement,canbeusedtoaddthatelementintoavarietyofalloys.Inthissenseprimebasedalloysaremorerecyclablethansecondaryalloyssince,inadditiontoclosed-looprecyclingtheycanbeusedtobatchawidevarietyofsecondaryalloys.Secondaryalloypostconsumerscraphaslimitedalloyoptions.

Alloysshouldnotbedesignedtoacceptmostpost-consumerscrap. Theyshouldbedesignedasmuchaspossiblewithin theexistingalloy families,foroptimumformingandmechanicalandfunctionalproperties.Inthiswaythecomponentweightcanbeminimizedwhichinproperproductlifecycleaccountingisthedominantconsideration.Wewilluselessenergytoproducethecomponent,consumelessenergyusingitandwillhaveintheendlessmetaltorecycle-awin-win-winproposition.

Designforrecycling• Keepthenumberofalloystoaminimum.• Designassembliesforeasyliberationofcompatiblealloypartson

shredding.• Focusonprocessingandproductpropertiesinsteadofalloychemistry;

thisisastrategytoavoidlimitationsbyverytightchemicalcompositionwindowswhichisthesituationtoday.

Inpermanentlybondedstructureswheremono-materialparticleliberationisnotpossible,alloycompatibilityconsiderationsareimportant.Inweldedassembles,oneofthejoinedalloysshouldbeabletoacceptboththeweldalloyandtheotheralloy.Co-castorrollbondedsheetaveragecompositionneedstobecompositioncompatiblewithoneofthebondedsheetalloys.Auni-alloycouldbeusefulforbeveragecanrecyclebusiness.

Generalactions• Consider“urbanmining”ofrichlandfillswithhighconcentrationsof

aluminiumandothermetals.

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2.SortingofaluminiumscrapCurrentstate-of-the-artSortingofscrap isallaboutmaking judiciouslyselectedseparations.TableIliststheseparationtypeskeytorecyclingofaluminiumandthemethodsusedtoaccomplishtheseseparations.

Table I: Key separations and methods for recycling of aluminium

BulkseparationsInbulkseparations,themethoditselfprovidestheforcethatseparatestheparticlesbasedonaphysicalcharacteristicsuchasdensity,shape,magneticsusceptibility,electricalconductivity,etc.• Waterslurriesorairparticlesuspensionsprovidedensemediaforsink-

floatseparations.• Partialfluidizationofawater-filled(oraheavymedia)particlebed

drivesdensityseparationofsmallparticlesinajig.• Airstreamsentrainhigh–aspectratio,low–densityparticlesinairknives

orinelutriators.• Screens,cycloneseparatorsandbag-housesseparateandcollectfines

anddust.• Magnetsseparatetheferromagneticparticles,bothsteelandrust.• Eddycurrentrotorsgeneraterepulsiveforcesinelectricallyconducting

non-magneticparticles.

Average particle stream elemental composition measurement

Particle-by-particle target alloy batching

Alloy grouping & Al by alloy

Bare from painted or dirty Al

Al with attachments from liberated Al

Al - A1

Other metal contaminants from Al

Mg from Al

Light from dense NF metals

Al - other metal

Non-metal or other metal contaminantsfrom A1

Nonmagnetic metal from non-metal

Metal from non-metal fines (<9mm)

Metal - non-metal

Desired separation

Steel from non-metal + non-magnetic metal

Separation method **

Drum magnet, overbelt magnetScreen, air elutriator, eddy current rotor,eddy current coil sensor

Jig, eddy current rotor

hand sorting, colour sensor, XRT sensor

Hand sorting, XRT sensor

Hand sorting, colour sensor

LIBS sensor, XRF sensorLIBS sensor, XRF sensor, PGNAAsensor

Magnetic headpulley, eddy currentrotor, hand sort

Sink-float (wet or dry), eddy currentrotor

LIBS sensor, XRF sensor

**LIBS=Laser–InducedBreakdownSpectroscopy;XRF=X-RayFluorescence;XRT=X-RayTransmission;PGNAA=PromptGammaNeutronActivationAnalysis

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Thesebulkseparationtechnologiesarelowcost,mature,andcanseparatelightmetalsfrommixedshreddedscrap.

ParticlesortingPeople-basedvisualinspectionandhandsortingisusedtogrouprecyclablesduringpost-consumerwastecollection inmostmaterial recovery facilitiesIn Asia, it is used to sort particles of post-consumer Zorba (trade jargonfor shreddednonmagneticmetals) and Twitch (trade jargon for shreddedmix-alloyAl). Particlesareseparatedbyshape,surfacecoatingortexture,attachments, colour and heft. Inspectors can separate old scrap by eachparentmetal,and, inthecaseofAl,cangroupsheet,extrusions,castings,wireandradiators.TheseAlgroupingsmaygivecertainflexibilitytobatchingofsecondaryalloys.However,thetypicalalloymixturesinthesehandsortedcategories still confine theiruse to foundryalloycompositions,hence thevalueaddedbythesortissmall.

Mechanized, sensor-based sorters expand the particle identificationcapability,andenableprofitableparticle-by-particleseparationinthehigherwageeconomiesofNorthAmericaandtheEuropeanUnion.Particlesortersequippedwitheddycurrentcoil,colourorXRTsensorshavetheirapplicationsinfindingresidualmetals,separatingparentmetalsandeliminatingparticleswithattachmentsatshreddersanddownstreamatthenonmagneticscrapmetalprocessors.

To bettermanage the alloying elements among the lightmetal alloys, anelemental concentration sensor combined with a mechanized particlesorterisnecessary.LIBSandXRFsensorsarecompetingfortheelementalconcentrationsensormarket.Forlight-metalalloyapplications,LIBShastheedge since it candetect lightelement signals (includingLi,Mg,AlandSi)fromadistance,whereasXRF isdependentonsignalsfromtransitionandhigher atomic number elements. These elemental concentration sensorshave a capability of sorting simplemixtures of fabrication scrap by alloyand/orparticle-by-particle,batchingtargetalloycompositionfromcomplexmixtureofalloysfoundinpostconsumerscrap.

Problems,challengesandopportunities• ResidualFeandothermetals• Paintremoval• Incompletealuminiumrecovery• MgalloycontaminationandAllossesinoldAlscrap• Mainlyhumansorting• Improperandinsufficientsortingandseparationofscrap,can

significantlyreducemetalrecoveryrateanddowngradetheproductalloy.

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Goalsforsortingofscrap1. Sortoutcomponents,metalsandalloyswhiledismantlingcars2. ImplementgloballymechanicalseparationofAlfromnon-magnetic

steelandothermetals3. Improveremovalofiron,othermetalattachments,andnon-metallic

contaminants4. ProducecleanAlproductcosteffectivelywithhighproductivityand

recoveryrate5. RecoverMgrichstream6. Replacehandsortingofnon-ferrousmetalscrapwithsensorbased

particlesorters7. Separatemixed-alloyAlscraptobatchhighervaluealloys

Generalactions• Alindustryshouldparticipateinthedevelopmentandimplementation

ofthescrapsortingtechnologyandprocesses,byinvestinginscrapsortingplantsthatallowthemtopurchaselowercostscrapearlyintherecyclingloopandtoseparateandup-cyclethislow-gradescraptotheAlalloyspecificationsoftheirownproducts.

• AlindustryshouldspecifylowMg-basedalloycontentforshreddedpostconsumerscrap(Twitch)toencourageremovalofMgalloyparticlesfromthescrapAlshred.ThiswouldpromoterecyclingofMgandwouldreducecostsandlossesintheAlrecyclingsystemassociatedwithchlorinationofMgoutoftheAlmelt.

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3.DecoatingandmeltingCurrentstate-of-the-artScrappre-cleaninganddecoatingisthekeydeterminantofthemetalloss,impurity pickup and the product melt quality. Melting is essential inaluminiumrecycling.RemeltingisthemostenergyintensiveoperationintheAlrecyclingprocess.ThetheoreticalenergyrequirementtoheatandmeltsolidAlfrom20°C-720°Cis316kWh/t.

Refiners and remeltersTwomajorproductionchainsarenotedinthealuminiumrecycling;refinersandremelters.Arefiner isaproducerofcastingalloysandaluminiumfordeoxidation of steel from scrap of various composition. Refiners are abletoaddalloyingelementsand remove someunwantedelementsafter themeltingprocess.Aremelterisaproducerofwroughtalloys,usuallyintheform of extrusion billets and rolling ingots frommainly clean and sortedwroughtalloyscrap.EspeciallyintheUS,butalsoinEurope,bothremeltersandrefiners,transfermoltenmetaltooutsidecustomersratherthancreateafinishedproduct.Thereisalsoalargemarketinrecycledsecondaryingotwhichissoldtotheendusers.

Melting technologiesInrefinerstoprotectthesurfaceofaluminiumagainstattackofthefurnaceatmosphere,thebatchchargedtothefurnaceiscoveredbysalt.Theadditivealsocollectsthenonorganiccontaminationschargedtothefurnace.Thesaltslagdischargedfromthefurnacerequiresfurthertreatment(pleaserefertoSection5)WithintheU.S.recoveryofslagisnotecononomical.

Energyisprovidedtothefurnacesbycombustionofgasoroilorinthecaseofinductionfurnacesbyelectricalenergy.Ifeconomicaloxy-fuelburnersareused,particularlywithreverberatoryormultichamberedfurnaces,theheatofwastegasesnormallyreleasedtotheatmosphereisrecovered

Modernre-meltingplantshavethefollowingfurnaceequipment:• Reverberatoryfurnacesascastingfurnacesandmeltingfurnacesfor

cleanscrapwithsmallspecificsurfacearea.• Rotarydrumsaltfurnacesforsaltapplicationtoprocesscontaminated

scrapwithlargespecificsurfacearea.• Twinchamberfurnaceforscrapcontaminatedwithorganicsonly.

Thestationaryrotarydrumfurnaceisgraduallybeingreplacedbythetiltablerotarydrumfurnaceduetothemorefavorableoperatingparametersofthistypeof furnace. For someapplicationsdryhearth furnacesand inductionfurnacearealsoinoperation.

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SomedataarelistedintheTableIIbelow.

TableII:Furnacetypes:

Collected scrap is contaminated by variousmaterials. The scrap containsoxides,trampmetal,builtinpartsofironorothernonaluminiumalloyssuchasbolts,pistonrings,bushingsetc.,sand,plasticandalsowater.Togetherwithaluminiumtheseadditionsconsumeenergyandmayalsoleadtosomeadditionalmetallossandenvironmentalproblems.Itisanadvantageforthemeltingplant to remove the unwanted components of the scrapprior tomelting.This is referred to in section2.A special case isdross. Evenatacomparatively lowcontentofaluminium,processing ismostlyeconomicalsincedrosscontainsvaluablemetalespeciallyifsuppliedbyprimarysmelters.However,drossresultsinmetalloss,anditsgenerationshouldbekeptaslowaspossible.Pleasereferalsotosection5.

Partof thealuminiumscrap isoftenwet,oily, chemically surface treated,anodized,coated,laminatedoradhesivelybonded.

ReverbFurnaces

ReverbFurnaceswith side bay

Reverb Furnaceswith dry hearths

Multi-chamberfurnace

Rotary furnaces

Salt Process

Stationary Rotary Drum Furnace

Salt Process

Tiltable Rotary Drum Furnace

Organics

Non Al content

Salt factor*

Metal Yield**

Capacity

Energy required****

< 10% <10% <3% <3% <1% <5 %

up to 60% up to 60% <3% <3% <25% <3%

1-2 <0.5

75-95% 80 - 95% 85 – 95%

10-60 t/cycle 10-25 t/cycle 30-135t

600-1400 kWh/t 450-800kWh/t 850-1750

85-98%***

2-5t/h

30-135t

50 - 80%

2-5 t/h

5-100t

80-98

2-5t/h

30-100t

750-1000850-1750

*Thesaltfactorshowninthetablegivestheratiobetweenthenon-aluminiumcontentofthescrapandthequantityofsaltrequired.**Metalyield,istheratioofmetalrecoveredtometalcharged.Therecoveryistheratioofmetalobtainedtoscrapcharged.Oneusuallydoesnotknowthemetalcontentofthescrapprocessed.Themetalyieldnumberswillthereforebeestimates***forsubmergedmeltedscrap,e.g.chips,metalyieldisupto100%****Theenergyconsumptionlistedinthetableistherequiredinputofthetotalfurnaceload.Relatingthisfiguretothealuminiummeltedmaygiveaverydifferentvaluedependingonthequantityofcontaminationofthescrapthatneedstobeheatedtothemeltingtemperatureofaluminiumaswell.

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Delaquering/decoatingToaddressthechallengeoforganiccoatings,somere-meltingplantshaveinvestedindelaquering/decoatingunits.Thetypesofdelaqueringsystemscanbedividedintorotarykilnandbeltconveyors,withvariousflowsystems,directorindirectfired.Someoftheproblemsindustryhasexperiencedwiththeexistingunitsare:variablescrapquality,sensitivitytoscrapfeedingrates,sensitivity to varyingmoisture content,non selective retentiontime,highoxidationlosses,processemissionsproblems,firesinexitgasandcomplexitytooperate.Theadditionalprocessingcosthastobepaidforbythecostandrecoverydifferencebetweencleanandcoatedscrap. Dedicated cleaning for most scrap is favourable as surface contaminantsmayalsocauseoxidationonmelting,producedross,contaminatethemelt,and may prevent accurate sensor identification when sorting. The bestdecoating,pre-cleaningandsubmergencemeltingpracticesgiveadditionalmetalrecoveriesevenforthinwall,heavilypaintedscraplikeUBC.Thermaldecoatingalso improves safety,has loweremissionsand improvesenergyefficiency.Thermaldecoatinginaclosedsystemallowsforsuitablecleaningoftheevolvedgasesandreuseofthepaintcombustionenergy.

Problems,challengesandopportunities• Howmanystagesarerequiredtohandledecoatingandmelting:accept

contaminatedscrap,burnofforganics,usenosalt.Atwostageprocesswillallowcontroloftheexothermicreactionbetweencoatingsandair.

• Themarketisthedriveringlobalscrapflow.Thenumberofalloysisincreasing,soscrapqualityisaproblem.Therecyclersarelimitedintheuseofcontaminatedscrapbytechnologyaswellasbylegalconstraints.Beneficiationofscrapbeforemeltingshouldbeconsidered.(RefertoSection2).

• Predictmetalqualitybasedonscrapqualityusingmassbalanceandkineticmodels.

Goalsfordecoatingandmelting1. Removecontaminationandcleanthealuminiumscrap,forinstance

removeironcontainingcomponentsanddecoatedmaterials.2. Reduceenergylosses(andtherebyCO2emissions).Achievebetterthan

50%energyefficientwhencomparedwiththetheoreticalvaluetomeltaluminium.

3. Preheatthealuminium.Utilizetheenergyintheorganics.4. Replaceburnerswithbetterones,optimisebetweenoxidationand

meltingcapacity.5. Improveoxy-fuelburnersanddesignfurnaceswithdualheating

systems(electricandfuelheating).Monitortemperatureandoff-gases.

6. Improvefurnacedesignwithregardtoheatexchangeandenvironmentalprotection.

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7. Developandapplybettermonitoringandcontrolsystems.Measurethetemperatureetc.in-line,andadjustwhileprocessing.

8. Implementbestpracticesforchargingandtheoperationofthefurnace.

9. Developarobustpre-processingstep10.Processscrapofhigherorganiccontent11.Lowerdrossformation.Monitorandavoid“break-away”oxidation.

Oxidationincreasesovertime,andinparticularforMgalloys.12.Improveandstandardiseskimmingroutines.13.Reclaimaluminiumtrappedinthedrossthatisskimmedoffbycooling

downinclosedunits.(section5)

Generalactions• Developcostmodels.• Developandapplymassandtemperaturemodelstogivehigher

efficiencies.• Analyzedecoupledsystemvs.connectedprocess,alsoregarding

flexibility.• Communicateresearchresultsandindustrialproblemstofindbest

furnacesolutions.Cooperationshouldbeeasiertoattaininproblemsregardingtheenvironment.

• Studypossibilitiesofprocessingmoretypesofscrap

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4.RefiningofmeltedrecycledaluminiumCurrentstate-of-the-artThetreatment(refining)ofmoltenaluminiumiscurrentlyrestrictedtotheremoval of alkali/alkaline earths, hydrogen and non-metallic inclusions.Techniques for removing these are industrially mature and furtherdevelopmentsshouldaddressefficiency,costandenvironmentalimpact.Ontheotherhand,refininginthesenseoftheremovalofotherundesirable/trampelementssuchasiron,copper,siliconorzincfrommoltenaluminiumpresentaconsiderabletechnicalchallengeandisunlikelytobeeconomicallyviable unless the price differential between prime metal and secondaryalloyswidenssignificantly.

Current technologies for alkali/alkaline earth removal involve treatmentwith reactive halides either in gaseous form (e.g. chlorine) or as salts(MgCl2,AlF3,K2SiF6etc.). Inaddition to removing the targetedelements(Li,Na,CaorMg)thesetreatmentsalsogenerallypromotetheremovalofnon-metallic inclusionsby dewetting/flotation. Therearealso anumberof processes for the removal of inclusions including decantation/settling,filtrationandflotation.ProcessesbasedoncentrifugalorMHDforceshavealsobeenproposedbutarenotyetfullydeveloped.Someofthewidelyusedtechnologiesarelistedbelow.

• DeepBedFilters(DBF)areusedforremovalofsolidandliquidinclusions.DBFhaveshowntoremovemorethan95%ofallparticleslargerthan20µm,andpracticallyalllargerthan50–60µm.Thestandardfilterworkssatisfactorilyformetalvolumesexceeding2000metrictonnes.Thedisadvantageisthelargemetalvolumeinthefilterbox,andthelongtimeittakestochangeinthealloy.

• CeramicFoamFilters(CFF)aremuchsmallerfilterunitswhichhavetobereplacedforeverycast.Thefiltrationefficiencycanbeveryhigh,andevenbetterthanfortheDBF,althoughevensmallamountsofinclusionswillblockthefilter.

• PorousTubeFilters(PTF)arealsousedfortheremovalofsolidandliquidinclusionsandgenerallyoffersuperiorperformancetoDBF’salbeitatthecostofsignificantlyreducedthroughput.

• Flotationreactorsareusedforremovalofhydrogen.Incombinationwithsaltorchlorinetheycanalsoremoveinclusions.Theinclusionsaretransportedbythebubblestothetopsurface,walls,orbottom.

• Treatmentinthecastingfurnace(orintroductionoftreatmentgas)usingeitherlanceswithandwithoutrotororporousplugsinthefurnacebottom.

Reliablemeasurementtechniquesareofcourseessentialforbothprocesscontrolanddevelopment.Opticalemissionspectrometryisuniversallyusedasanoff-linetechniquetomeasurethecompositionofthevariouselementspresentinthemelt.

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There are on-going attempts to adapt the technique for on-line analysis.Techniquesforhydrogenanalysisbothon-line(Alscan,ALSPEK-H)andoff-line(LECO,ReducedPressureTest(RPT))exist.Thereareseveraltechniquesto monitor inclusions including LiMCA, PoDFA/Prefil Footprinter /Lais.Theactualvolumeofmoltenmetalexamined ineachofthesetechniquesis relatively small (16 grams in the case of a LiMCA reading, ~2 grams(effective) in thecaseofPoDFA/Prefil/Lais. A technique thatwouldallowthe examinationof a large volumeofmoltenmetalwould be awelcomedevelopment.

Priorityshouldbedirectedtowardsthedevelopmentof technologies thatreduce the environmental impact (e.g. chlorine-free metal treatment orreducedlandfill).Althoughimprovedmethodsofseparationbymetal/alloyfamilypriortomeltingarelikelytobemorecosteffectivethanliquidmetalrefining for the foreseeable future, long term investigations intomethodsof selectively removing contaminants such as Fe, Cu, Si etc. frommoltenaluminiumshouldbeundertaken.Effortstoeitherremoveorneutralizetheeffectsofspecificcontaminantsshouldbedeveloped.Abetterknowledgeof the impact of tracemetals would be of benefit. Elements of currentconcernincludeselenium,phosphorous,bismuth,aswellasthemorewidelyrecognizedtoxicmetals(Hg,As,Cd)Theseelementsposesignificanthealthriskstoemployeesorendproductusers,andareextremelydetrimentalingeneraluse.

Problems,challengesandopportunities• Thepossiblepresenceoflargeinclusions(approximately≥50µm)isa

problem.Toomuchemphasishasbeenplacedonremovinginclusionssmallerthantheintermetallicphasespresentinmostalloys.

• Thereisnotaclearcorrelationbetweenmeasurementtechniques(LiMCA/PoDFA)andproductperformance.

• Theuseofchlorineshouldbediscouraged.Itistoxicintheplantenvironmentandisaproblemintransporttotheplant.

• Entrappedoxidefilmsareaproblem.• Thereislimitedknowledgeoftheeffectsandfateofmanytrace

elementsinAluminium;Pb,Se,Cd,Bi,Sb,REetc.

Goalsforrefiningofmeltedrecycledaluminium1. Implementchlorine-freemelttreatment2. Reduceharmfulimpuritiesinsolidwaste3. Reduceenergyconsumption4. Improvefiltrationfocusedontheremovaloflargeharmfulparticles5. Improve(largersamplevolume)testtomeasureentrappedoxides

inclusions

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6. Developbetterknowledgeoftraceelementseffects7. Removeharmfulelements

GeneralactionsEnvironmental considerationsaregoing todominatedevelopments in theneartermwiththefocusbeingonreducinglandfilldisposalandtheuseofhazardoussubstances.

The group recommends a special focused thinkingon chlorine-freemetaltreatment and a rethinking of filtration in terms of reducing solidwaste.A better understanding of the effects of impurity elements should bedeveloped along with a longer term effort to developmethods for theirselectiveremoval.

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5.Treatmentofdross&saltcakeCurrentstateoftheartDrossisamixtureofaluminiumanditoxidesandNonMetallicComponents(NMC).Dross isgeneratedonthesurfaceofmoltenaluminiumbycontactwith oxygen during melting, holding, refining and transfer. Salt cake isaby-productof aluminium recycling; suchas fromdrossprocessing. Thecompositionisdependentonthesourcematerialsandrecyclingpractice.Itconsistsofaluminiummetal(4-8%),salt(25-45%)andNMC(50-70%).

Submergencemelting dry decoated scrap in the industry gives highmeltrecovery,whilemeltingofscrapbaleswithoutanypreparationoftenleadstolowermeltrecoveries.

Procedures:

Dross processing Priortobeingremeltedinrotaryfurnaceswiththeadditionofsalt,theAlmetalcontentofdrossisoftenup-graded.Thisisachievedbycrushingandscreening the dross and/or by eddy current separation. The product is ametalconcentrateandadust-likeresidue,whichcontainsmetalinclusionsand oxides too small to be separated by affordablemeans. There are noreliablefiguresonthequantityofmetallostindross.ModelcalculationsoftheEuropeanrecyclingaluminiumindustrycarriedoutin2006indicatethatabout8-9%ofthetotalrecyclingmetalproduction isgeneratedasdross.Thisnumberreferstothecombinedproductionofrefinersandremelters,atthattimeabout6.7milliont/y.USgeologicalsurveydatafor2006reportsover600ktofmetal recovered fromdrossandskimmings. It isestimatedthattheUSresidueconsistsofmorethan1,500ktofnon-metallicsperyearcontainingupto30ktofmetalfromslagprocessing.

Aluminiumscrapwithhighcontentsofoxide/NMCisusuallymeltedinrotaryfurnaces(withfixedaxleortiltable)underaliquidlayeroffluxes(NaCl+KCl+fluorides),whichprovideahighlyefficientseparationofmetalandNMC.NMCarecompletelyabsorbedbytheliquidfluxandformsaftertappingandcoolingtheso-calledsaltslagorsaltcake.InEuropeabout1.4MTofsaltslagmightbe generatedevery year and thepredominantpart is processed insaltslagrecyclingplants.Therethesaltcontentandthemetalinclusionsarerecoveredandreturnedtotherefinersforre-use.TheNMC-contentoftheslagisseparatedandsoldasanadditivetothecementorceramicindustry.InEuropesaltslagiscategorizedashazardouswasteandthereforelargelyprocessed. By the combination of scrapmelting with dross and salt slagprocessingthealuminiumcycleisclosed.MeanwhileintheUSsaltcakeisnotconsideredahazardouswaste.Mostsaltcakeisprocessedfortheremovalofentrappedaluminium.Theremainingmaterialisthensenttolandfill.

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Problems,challengesandopportunities• Entrapmentofliquidmetalindrossskimmings(>70%metalcontent)is

aproblem. Hotdrossisoftennotcooledinclosedcontainers,resultinginmetaloxidation(irreversiblemetalloss)IntheUSregulations:saltslagisnotconsideredhazardous,thereforethereiscurrentlynoclosedloopprocessing,justmetalrecoverybydryscreening.IntheEUregulationssaltslagisconsideredhazardous.Itiswetprocessed.

• Recoversalt• DevelopmarketforNMC• Environmentalhazardsofsaltcakeare:

-Itisreactiveinthepresenceofwaterorevenmoisture-NoxiousgasescanbeproducedsuchasPH3,H2SandNH3-AlsotheremaybeinflammablegaseslikeH2andCH4.Chlorideandfluoridemayleachfromlandfill.

Goalsfortreatmentofdross&saltcake1.Minimizethegenerationofdrossthroughadoptionofbestavailable

scrappreparationandmeltingmethods.2. Protectallhotskimanddrossagainstair3. IntheUS:AllsaltslagsaredryprocessedtorecoverAlmetalcontent.

Encourageresponsiblelandfillofresultingresidue.4. IntheEU:DecreasesaltinputtominimizeslagvolumeinEU.5. Designandcommercializerecycle-friendlyleanaluminiumalloysto

minimizedrossformation.Uselessmagnesiuminpackagingalloysandminimizelithium,copperandzincusageinaerospacealloys.

6. CommercializegloballyanadaptableversionofEuropeandrossprocessingtechnologytominimizelandfilldisposalandtheattendantproblems.

GeneralactionsHotdrossmustbeprotectedagainstoxidationofitsvaluablemetalcontent.Efficient protection can be achieved by using sealed dross boxes for hotskimsor throughothertechniques.Oxidicedaluminium is irreversibly lostfromrecycling.

Thespecificinputofsalthastobereduced,asprocessingoftheresultingsaltslagisasizeablecostburdenforrefiners.Sinceliquidsalt/fluxisjustapackagingmaterialforNMC,newfurnacedesigns/techniquesarerequiredtoincreasetheefficiencyofsaltuse.Evenrecyclingofliquidsaltinsiderefinershastobeconsidered.

Itisveryimportantthattheglobalaluminiumindustrydesignandimplementasustainablesolutionto landfillminimizationandprocessingofdrossandsaltcaketolowercostandenhancethepublicimage.

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6.UsingrecycledAlscrapCurrentstate-of-the-art

Post-consumed scrapNew aluminium scrap generated internally at semi-fabrication rolling andextrusionplantsisremeltedandgenerallybatchedintocompatiblerollingorextrusionalloys.PromptAlcastingscrapisalsoclosed-looprecycledinthefoundryorbackatasecondarysmelter.However,newmanufacturingscrapisoftentradedontheinternationalscrapmarketandcomestoaremeltplantor a secondary smelterwitha less reliablepedigree. It isusuallybatchedtogetherwithpost-consumerscrapintosecondaryalloys,asshowninTableIII.

Table III: Markets consuming post-consumer Al scrap

In short supplyCurrentlythemarketconsumesalltheavailablepost-consumerAlscrap.Tosatisfyproductdemand,remeltsandsecondarysmeltershavetosupplementtheoldscrapfeedbypurchasingnewmanufacturingscrapandevenprime-metal-basedingot.AslongasprimaryAlandhardenershavetobepurchasedtosatisfythesemarkets,thevalueoftheseproductsissetbyreferencetotheprimaryAlprice,andthereislittlepricemarginbetweensecondary-andprimary-sourced alloys. In this case, there is no economic justification toadditionallyupgradescrapanddivertittoothermarkets.

Growing marketInthecurrentexpandingmarketforlightmetals,thereisacontinuousneedforprimaryAlproductiontosupplyalargeportionofthedemand.Giventherapid industrializationof thedevelopingworld,which isaddingbillionsofadditionalconsumers,thedemandforlightmetalsandforlight-metalscrapislikelytogrowfortheforeseeablefuture.

Market Secondary alloy

Al packaging

3X04 can body sheet

Building Al 3105 painted sheet

Automotive Al

38X.x casting alloys

319.x casting

Steel deoxidants

95% Al

• Old cans, can manufacturing scrap• Non-can wrought manufacturing scrap• Al- and Mg-based scrap mix from 2-t/m3 float fraction of a dense-media sink-float plant

• Old Al siding• Al siding and extrusion construction scrap• Mixed wrought manufacturing Al scrap with low Cu content• Old wrought scrap

Some 38X alloys can accept a mixture of the most common old scrap varieties without dilution, as long as the Mg concentration is controlled by chlorination

Tighter concentration limits on 319 increase the dilution requirement and limit the types of old scrap that can be added to a 319 alloy batch

This specification can be met by several mixtures of old wrought alloy scrap

as well as limited quantities of old cast scrap.

Compatible scrap sources

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ImpuritiesImpurityelementsarepickedupduring theentiresupplychain invariousconcentrationsdependingonrawmaterialsources,coldmetal/scrapsource,master alloy, processing conditions etc. The effect of these impuritieson product properties depends upon the form they appear in particles,dipersoids,precipitatesandsolidsolutio.Forinstance,asmallconcentrationofagivenelementcanhaveasignificanteffectonthesurfaceappearanceoftheproduct.

Product specificationsHistorically the specification of an aluminium product is on chemicalcomposition.However,processingofAlprocessingparameters(temperatures,timedeformationandchemicaltreatments)isimportanttoattainacertainlevelofproperties.

Problems,challengesandopportunities• Lackofmethodstoremoveundesirable/trampelementslike;Fe,Zn

andCu,thatarepickedupinthesupplychain.• Aclearunderstandingisstillmissinginindustryoftheeffectthat

processinghasonthepropertiesofthefinalproducts.

GoalsforusingrecycledAlscrap1. Aimtorecycle100%ofallnewandoldAlscrap2. Findalternativeapplicationsforcastingalloys3. Developmeltpurificationtechniquesforunwantedalloyingandtrace

elements,suchasFe,butalsoelementslikeZnandCu.Removalofthesefrommoltenaluminiumrepresentsconsiderabletechnicalchallenges(seechapter4)

4. Developanincreasedunderstandingoftheeffectoftraceelementconcentrationsonprocessingandpropertiesoftheexistingsecondaryalloys(3X04,3X05,38X.x,and31X.x)

5. Developanimprovedunderstandingforthestrongeffectthatprocessinghasonthepropertiesofthefinalproducts

6. Continuetotranslatecustomerrequirementsintocompositionandprocessingspecifications

7. Mixwroughtandcastalloysintonewalloys.Developmethodsforcasting,plasticformingandheattreatment

8. Qualifyuseofpost-consumersortedextrusionscrapin6000seriesextrusionalloys

9. Keepthenumberofalloystoaminimum10.Qualifyuseofpost-consumersortedsheetscrapin3000and5000

seriessheetalloys

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11.Articulatecleardistinctionbetweenalloysfor,structuresandsidingsbuilding

12.Developnewapplicationsforaluminiumusingrecycledaluminiumsuchasinrenewableenergydevelopments

13.Designrecyclingindicestakingintoaccountcarbon&energyfootprintsandeaseandcostofrecycling

14.Develop mathematical models linking market, chemistry, processing,physicalmetallurgyandproductattributes

ConclusionTheRoadmapaimstopresentthecurrentstatusandtechnologychallengesinaluminiumrecycling.InthisRoadmapthegoalsarenotbrokendownintosmaller tasksnorhaveprioritiesbetween thevariousgoalsbeenset. Themainobstacleisthatcollectedscrapiscontaminatedandmixedwithvariousmaterialsthatincreasealuminiumlossandlowermetalquality.Itisawishfrom the group thatwe continuewith this Roadmapwork in three yearstime;thatisinJune2013.

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AbbreviationsCFF CeramicFoamFiltersDBF DeepBedFiltersEAO OrganisationofEuropeanAluminiumRefinersandRemeltersEU EuropeanUnionIAI InternationalAluminiumInstituteLIBS Laser-InducedBreakdownSpectroscopyLiMCA LiquidMetalCleanlinessAnalysisMHD MagnetoHydroDynamicsNMP Non-MetallicProductsNTNU NorwegianUniversityofScienceandTechnologyPGNAA PromptGammaNeutronActivationAnalysisPTF PorousTubeFiltersRE Rear EarthUBC UsedBeverageCansXRF X-RayFluorescenceXRT X-RayTransmission

References1. [TheAluminumAssociation,2003“Aluminumindustrytechnology

roadmap”,www1.eere.energy.gov/industry/aluminum/pdfs/al_roadmap.pdf

2. [WasteWatch,2011]http://www.wasteonline.org.uk/resources/informationsheets/legislation.htm Under“8.EndofLifeVehicles(ELV)Directive(2000/53/EC)”

3. [InternationalAluminiumInstitute,2009] “Globalaluminiumrecycling:Acornerstoneofsustainabledevelopments”www.world-aluminium.org/cache/fl0000181.pdf

4. [InternationalAluminiumInstitute,2009]“AluminiumforFutureGenerations/2009update”http://www.world-aluminium.org/cache/fl0000336.pdfp.27

5. [JohnGreen,2008]“DevelopingATechnologyRoadmapForAutomotiveLightweightingMetalsRecycling“ReportdatedDecember2008p.5

6.[UdoBoin,2004].“COLLECTIONOFALUMINIUMFROMBUILDINGSINEUROPE.“AStudybyDelftUniversityofTechnology”http://www.eaa.net/upl/4/default/doc/814.pdfp.4

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ParticipantslistAkhtar,Shahid NTNU NorwayBao,Sarina NTNU(studentmonitor) NorwayBergstrøm,Trond SINTEF NorwayBoinUdo Seniorconsultant GermanyBrommer,Tracey MIT USACiu,Jirang NTNU NorwayDas,Subodh Phinix USADoutre,Don NovelisInc. CanadaEhlen,Boukje Facilitatorboukje.com TheNetherlandsEngh,ThorvaldAbel NTNU NorwayFuru,Jørgen NTNU(studentmonitor) NorwayFuru,Trond NorskHydroASA NorwayGesing,AdamJ. GesingConsultantsInc CanadaGreen,John JASGConsulting USAHryn,John ArgonneNationalLab USAHugdahl,Åse SINTEF NorwayJensrud,Ola SINTEFRaufossManufacturing NorwayKirchain,Randolph MIT USAKirchner,Günter Org.ofEuropeanAluminiumRefinersandRemelters GermanyKvithyld,Anne SINTEF NorwayLi,Yanjun SINTEF NorwayLukat,Berthold AlerisInternational GermanyLuo,Zheng Org.ofEuropeanAluminiumRefinersandRemelters GermanyMassip,Gaultier HydroBuildingSystem FranceModaresi,Roja NTNU NorwayMüller,Daniel NTNU NorwayNordmark,Arne SINTEF NorwayOlivetti,Elsa MIT USAPeterson,Ray AlerisInternational USARay,Denis Seacat USARiddervold,HansOle NorskHydroASA NorwayRombach,Georg NorskHydroASA GermanySchlesinger,Mark MissouriUniversityofScienceandTechnology USASchmitz,Christoph ALCUTECEngineering GermanySkjervold,Svein ECC-ExtrusionEurasia NorwayStevens,Darcy NTNU(studentmonitor) NorwaySyvertsen,Martin SINTEF NorwayUrbach,Ralf Consultant GermanyWærnes,Aud SINTEF Norway

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