The Investigation of Separability of Particles Smaller Than 5 mm by Eddy Current Separation Technology. Part I: Rotating Type Eddy Current Separators

Magnetic and Electrical Separation, Vol.9,pp. 233-251 Reprints available directly from the publisher Photocopyingpermitted bylicenseonly

(C)1999OPA (OverseasPublishersAssociation) N.V. Publishedbylicenseunder theGordon andBreachScience Publishersimprint. Printed in Malaysia,

THE

INVESTIGATION OF SEPARABILITY

OF

PARTICLES SMALLER

THAN

5 mm

BY

EDDY

CURRENT

SEPARATION

TECHNOLOGY.

PART I:

ROTATING

TYPE

EDDY

CURRENT SEPARATORS

SHUNLI

ZHANG

a,

PETER

C.

REM

b,. _and

ERICFORSSBERGa

aDivision

_of

MineralProcessing, Luled University

_of

Technology, S-97187 Luled, Sweden," bDepartment

_of

RawMaterials Technology,

Delft

University

_of

Technology, 2628RX Delft, The Netherlands

(Received3November1998;Accepted17December1998)

Owingto thegrowingemergence of theend-of-life electrical and electronicproductswith

complexmaterialstructures andan ever-diminishing particlesizeofthevaluable metals involved, development of eddycurrent separators (ECS) has been targeting selective

separation of small non-ferrousmetalparticles smaller than 5mm.Separability ofvarious materialssmaller than 5 ram, includingfinecopper wires,hasbeen investigated usingECS with variousdesignconcepts. Thepresent research workisdividedinto twoparts,with Part focusingontherotatingtype ECSwhich aretodaycommon inpractice, andwith PartIIdedicated totheECSwithnovel concepts suchas wetECStechnology.In PartI, three rotating belted-drum ECS wereemployed,which are manufactured by Bakker

Magnetics, the Netherlands, Huron Valley Steel Co., US, andEriez Magnetics, UK

respectively. Itisfound thatthebelted-drumECSareeffectivefor separatingmaterials

below 5 mmifthe magnetic drumrotatesinoppositedirection totheconveyor belt. The separation principle, particularlythe"backward phenomenon"of therotating typeECS

for small particles has been unravelledin thepresent study.Moreover,separation ofAI

fromthe 0-10 mm fraction of electronicscrap hasbeenconducted. The resultsobtained

demonstrate that the belted-drum ECSwithappropriate design maybeapplicable for separation ofsmall aluminumparticles fromelectronicscrap.

Keywordv." Rotating eddycurrentseparator; Separability; Eddycurrentforce; Backward phenomenon;Electronicscrap

Correspondingauthor. E-mail:_{P.C.Rem@ta.tudelft.nl.}

1. INTRODUCTION

The design and performance of the rotating belted-drum type eddy

current separators have been improved substantially in the last ten

years, due primarilytothe advanceof the magnet materials and magnet

configurations, andto abetter understandingofthe separation

mech-anisms

[1-3]. Yet,

problemsassociated with separation of small

parti-cles, remain in particular, those smaller than 5mm. Therefore, the

currentdevelopmentofeddycurrentseparators

(ECS)

hasbeendirected

toselectiveseparationof smallnon-ferrous metal particles.

In

the presentstudy, separability of various materials of 3mm size,

including finecopperwires, has been investigated using different

ECS

with various design concepts. Onthe basis ofthepresent investigation

and of the critical comparison of different

ECS,

each with a unique

design, it can be anticipated that a novel ECS capable of separating

metal particles smaller than 5 mm with bothahigh selectivity andalarge

capacity will bedeveloped.

Thisresearch workis dividedinto twoparts,withPart

I

focusingon

the rotating typeECSwhicharepresentlycommon inpractice andwith

Part

II

dedicatedtoECSwithnovelconcepts such

as

weteddycurrent

separation technology.

In

Part

I,

three rotating belted-drum ECS

were employed, which are manufactured by Bakker Magnetics, the

Netherlands,

Huron

Valley Steel

Co., US,

and EriezMagnetics,

UK

respectively. The separation results obtained from those three devices

areanalyzed, in terms ofvariousseparation forces and theseparation

mechanisms for small particles are discussed in the present study.

Further, the aluminum recovery from the 0-10mm fraction of

elec-tronicscrap has been conducted usingtwo of the threedevices.

Addi-tionally, the present resultsareevaluatedto demonstrate that modern

ECS

may well beprogressedtoseparatefinemetal particles like copper

wires effectively and efficiently.

2.

EXPERIMENTAL

2.1. Materials

Aluminum

(A1),

copper

(Cu)

and polyvinyl chloride

(PVC)

particles

ROTATINGTYPEEDDYCURRENTSEPARATORS 235

Printed

Circuit"boards

(pre-dismantled)

Slow-running

shredder

Fast-running

shredder

Hammermill

Air

jig

I-9.6%

by

weight

by weight

53.0%

by weight

Dust

Light"

fraction

Heavy

fraction

FIGURE The process producing the light fraction which is used in the present study.

semi-automatic cutting machine.

A

3kg electronic scrap sample was obtained in the way shown in Fig. 1. The light fraction of theairjig

separation, consisting essentially ofaluminumandvariousplastics,was

used in the present study. Its particle size distributionis presented in

Fig. 2.

2.2. Equipment to beUsed

The rotating belted-drum eddy current separators

(RBECS)

used

are illustrated in Fig. 3.

In

this study, three types of

RBECS,

manu-facturedby Bakker Magnetics, the Netherlands (Bakker

ECS,

Model

BM

29.701/18),

Huron

Valley Steel

Co.,

US (Huron ECS, Model

8O

7O

6O

50

40

30

2O

10

-0.5

+0.5-1.0

+

1.0-2.0

+2.0-10.0

particle size,mm

FIGURE2 The particlesize distributionof the lightfractionfrom theairjig separation of shredded printedcircuitboards.

respectively, were employed. Several major characteristics of the

equipment, that are relevant to their performance, are compared in

TableI.

2.3. The Separability Investigation

The separability of thematerials was characterizedbytheirdistribution

in anarray of thecollection bins which wereplacedin front ofthe

con-veyor beltpulley,asshown in Fig. 3. Twelvecollectionbins, eachwith

dimensions of 400 x 40 x 90 (length xwidth x height)mm, were used. The material distribution was analyzed by its percent weight in each

collection binsuch that:

W/

_100%

₍₁₎

P W _i

’4

2,

where

(P W)ij

isthe percent weight of the ith materialin the.jth

ROTATINGTYPE EDDY CURRENT SEPARATORS 237

conveyorbelt

Small metal

[llllllillllJ

400mm

_

Bin1_

_.Bn

12

@

Magneticdrum rotates inaForwardmode

()

MagneticdrumrotatesinaBackwardmode

@

12 collectionbins

FIGURE3 Schematicpresentation ofbelted-drumeddycurrentseparator,s

illustrat-ingtheseparation principle.

TABLE MajorcharacteristicsofECSused in thestudy

Name Magneticstrength Numberof Rotational Maximumspeed onthe_surfaceof pairsof directions_ofthe _ofthe magnetic

theshell(Tesla) magnets magneticdrum drum(rpm/rps)

BakkerECS 0.38 9 Forwardand Backward 3000/50

Huron ECS 0.26 12 Forward 3000/50

EriezECS 0.35 11 Forward andBackward 6500/108

The separability of small particles with Eriez ECS was carried outby

adjustingits splitters,insteadof usingthe collection bins.

3. EXPERIMENTAL RESULTS

3.1. Separability of 3 mm Particles

Binary mixtures of

A1/Cu

andPVC with 3 mmparticle sizewere

rotational direction of the magnetic drum. Figures 4 and 5 show the

separability of mixtures of A1-PVC and

Cu-PVC,

respectively, by

employing Bakker ECS with a forward or clockwise rotation of the

drum. Itcan beseenthat small conducting particleslikeA1andCuare

either mixed up with the non-conducting ones or distributed in the

collectionbins thatareclosertothe magnetic drum.

Analysis of the material distribution indicates that it is difficult to

separate small metal particles from non-metalonesselectively, when the

magnetic drum rotates in the "Forward" mode. It has been found,

though, thatif themagnetic drumrotatesin the "Backward" or coun-terclockwise manner, separation of small conducting particles from

non-conductingonesisimproved drastically.ItisshowninFigs. 6 and 7

that more than 80% ofA1 and Cu of 3 mm size isdistributed in the

collection bins which are farther away from the magnetic drum.

In

addition, as was anticipated, non-conducting PVC particles have

approximatelyconsistentdistribution in Figs. 4-7,sincethe oscillating

directionof the magneticfieldhasnoeffectonnon-conductors.

Similar results were obtained by using Eriez ECS which permits both "Forward" and "Backward" rotation of the magnetic drum.

100 90 80 70 60 50 40 30 20 10 0 DAI []PVC 1 2 3 4 5 6

7

8 9 10 11 12

collection binNo.

FIGURE4 Material distribution in the collection bins forAI and PVC by Bakker ECS (particle size=31nm, belt speed=1.6m/s, drum speed=3000rpm, forward rotation).

ROTATINGTYPEEDDY CURRENT SEPARATORS 239 100 9

t

80 70 60 50 40 30 20 10 0 1 2 3

4

5 6

7

8

9 10 11 12

collectionbinNo.

FIGURE5 Material distribution in the collection bins forCuand PVC byBakker

ECS (particle size=3mm, belt speed=1.6m/s, drum speed=3000rpm, forward rotation). I00 9

t

80 70 60 50 40 30 20 10 0 DAI IPVC 1 2 3 4 5 6 7 8 9 10 11 12

collection binNo.

FIGURE6 Material distribution in the collection bins for AI and PVC by Bakker

ECS (particle size=3mm, belt speed=1.6m/s, drum speed 3000 rpm, backward rotation).

100 90 80 70 60 | ₅₀

,,

₄₀ 3O 2O 10 1 2 3 4 5 6

7

8 9 10

11

12

collection binNo.

FIGURE 7 Material distribution in the collection binsfor Cu andPVC by Bakker

ECS (particle size--3mm, belt speed=1.6m/s, drum speed=3000rpm, backward

rotation).

Figure 8 shows thatapproxiately85% Alcanbeseparatedfromamixture

of A1 andPVCof 3mm size withalmost 100% purity, asthe magnetic

drum spinsin"Backward"direction.

However,

withthe magneticdrum

spinninginthe"Forward"mode,lessthan50% ofA1canberecovered.

Unfortunately Huron ECScan be operated only inthe "Forward"

mode. The material distributionof the mixtures of A1-PVCand

Cu-PVCispresentedinFigs. 9 and 10. Itappears thatwhencompared to

BakkerECSin the"Forward"mode,less conducting particlesare mixed

up withnon-conductingones.

Yet,

selective separation of smallmetal

particles fromnon-metal ones is still difficult.

Basedonacomparative investigationonthree belted-drumECS,it is

foundthat a selectiveseparation of metal particles below5 mmmay be

established by spinning the magnetic drum in the "Backward" mode. Thisisreferredtoasthe "backwardphenomenon"in thepresent study.

Therefore,therotating belted-drumECS tentatively designed for

pro-cessing small particles below 5ram shall incorporate a "Backward"

mode likethe Bakker and Eriez

ECS,

enabling the magneticdrum to

100 0 70 60 50 40 :30 20 recovery, % grade,% Case I: mixture ofAIandPVCof 3 mm,

beltspeed 2m/s,drumspeed 3000rpm

backward rotation

Case II: mixture ofCuandPVCof 3 mm,

belt speed 2m/s,drumspeed 3000rpm

backward rotation

CaseIII:mixtureofAl andPVCof 3 mm, beltspeed=2m/s,drumspeed 3000rprn

forward rotation

case

I

case

II

case

III

operationcondition

FIGURE8 Separation results of binarymixturesby usingEriezECS.

100 80 70 60 50 40 30 20 10 2 3 4 5 6

7

8 9 10

11

12

collectionbinNo.

FIGURE 9 Material distribution in the collection bins for AI and PVC by Huron

ECS (particle size=3mm, belt speed=2m/s, drum speed=3000rpm, forward rotation).

100 90 8O 70 60 5O 40 30 20 10

0

1 2 3 4

5

6

7

8

9

10

11

12

collection binNo.

FIGURE 10 Materialdistribution inthecollection binsforCuandPVC byHuron

ECS (particle size=3mm, belt speed=2m/s, drum speed 3000rpm, forward

rotation).

3.2. The SeparationResults of Electronic Scrap

byBelted-Drum ECS

The traditional "burning and smelting" recycling technique for handling

electronicscrap is,to agreatextent,appliedin practice, whichis aimed

at recovering precious metals and copper. It is known that efficient

removal of

AI

by using modernECSisableto facilitatethe metallurgical

process. Furthermore, an extrarevenue, due to the high value of the

recovered A1, can be obtained. It is for those reasons that the eddy

current separation technology is ofa great interest for the electronic

scrap recycling industry.

A

point ofconcernisthat theliberation sizeof

AI

particles presentis ingeneral small. Ourstudy

[4]

shows that,after

atwo-stageliberationabout 50% of A1 in the printedcircuitboardsis

distributed in the -7mmfraction.With a view towardsimplementing

an effective ECSforthisspecificmaterial stream, twomodern

belted-drumECSwereattempted,withtheresults giveninTableII.

Clearly, the results of

Huron

ECS show thatit is able to recover

ROTATINGTYPE EDDY CURRENT SEPARATORS 243 TABLE II Separationresultsof theelectronicscrap

Weight, % A1grade, % AIrecovery,%

Huron ECS

Concentrate 7.4 52.5 97.6

Waste 92.6 0.1 2.4

Total 100.0 4.0 100.0

BakkerECS(Forward mode)

Concentrate 1.8 84.1 36.0

Waste 98.2 2.7 64.0

Total 100.0 4.2 100.0

BakkerECS(Backward mode)

Concentrate 2.0 94.8 47.6

Waste 98.0 2.1 52.4

Total 100.0 4.0 100.0

A1concentrate. Itwasindeedobserved thatasubstantialproportion of

plastics particles with Culaminates reportto the A1 fraction. On the

contrary,it canbeseenthat BakkerECSiscapableof producingahigh

qualityA1product

(about

95% purity) inasinglepass, but the recovery

isapproximately 50% in the "Backward" operation mode.Also,Table

II

indicatesthat both the recovery and selectivityinthe "Backward" mode

is muchbetter than in the "Forward" mode. Itisnoteworthy that the

splitter of BakkerECS can be adjustedso as to recover almost all A1

particlesin asingle passasdoesthe

Huron ECS,

buttheproductquality

willthendeterioratesignificantly.

As

aresult,thesetwoECSwillhavea

similarperformanceintermsof both recovery andgradeof theproduct.

Theperformanceof BakkerECSshall beenhanced,if the feedmaterial

is screenedinto +5mmand -5mmfractions, as aconsequence of the

"backwardphenomenon". Itisalsoexpectedthateffectiverecovery of

small A1 particles will be realized by means of a multi-pass circuit

configuration.

4. DISCUSSION

4.1. The Separating Forceson Small Particles and

the"Backward Phenomenon"

Separation mechanisms of small particles in eddy current separation

eddy current forces

(F,.

and

Ft)

as well as the force derived from the

electromagnetic torque

(Fa-)

are givenbythe authors in

[3].

Therefore,

radialand tangentialaccelerations

(ar

and

at)

aswell astheacceleration

component from

F-r

(a-r)

canbeexpressedas:

27rss’2B

a2

_{(#okCOdrumO-R2)}

2 lzoPw

+

s’2(#okcOdrumrR2)

2 27rssIBag-

_#okCOdrumcr

R2 at

(3)

I-toPw

₊

_{s’Z(#okCOdrumcrR2)}

2

sst

Ba2

#okCOdrumcrR

2

(4)

#opR

₊

_{s’2(okwdrumo’R2)}

2

wheresistheshapefactor relatedtothe magnetization ofaparticle,

s’

is theshapefactor relatedtothecharacteristicdecaytimeof eddy currents,

Ba

isthe amplitude of the magnetic field, kisthe numberof pairs of the

magnetsin adrum,COdrumistheangular velocity ofthemagnetic drum,

R is the characteristic particle size, w is the width of one pair of the

magnets, cr is the electrical conductivity, p is the mass density and

#0 47r x 10-7

Tm/A.

Forsimplicity, the following analysisisdone foraspherical particle,

due mainly to the fact that the spherical particle is

orientation-inde-pendent.

In

the case of Bakker ECS

(k

9 and C0drum

1007rrad/s),

accelerations of aluminum particles, which are computed by using

Eqs. (2)-(4),

aregiveninFig. 11,as afunctionof

_#0kcoarumcrR

-

(inwhich

Ris variable from 1.0 to

25.0mm).

It isclear from Fig. 11 that, fora

small particle, the dominant acceleration is the one from the

electro-magnetic torque and theradial acceleration isnegligible, whereas fora

large particle the predominant acceleration is in the radial direction.

Thus, itfollows,in terms of Fig. 1, that:

aT ))at

> ar

0

(R

<

5

mln)

(5)

a,.

>>

at

<

aT

(R >

20

ram).

(6)

Evaluation of

Eq. (2)

shows that the radial force acting on a small particleis sofeeble thatit isunabletoliftuptheparticle,whichinstead rotates withthe fielddueto astrong electromagnetic torque. Figure 12

illustratestherotationofasmall conducting particlewith thefield and

ROTATINGTYPE EDDY CURRENT SEPARATORS 245 250 2O0 a 150 --B-- a 100 50 0 0 5 10 15 20 25 30 35 40 45 50 55 l.tokcoa,.,,,,,crR

FIGURE 11 Accelerations of A1 particles resulting from eddy current forces as a

functionof/z0kCOdrumffR2.

clockwiseorin the "Forward"mode,the dynamic frictional force

(F

fric)

as aresult ofthe electromagnetic torquewillbe anti-parallel

(backward)

tothe tangential force

(Ft, forward)

asindicatedby thesolid lineshown

in Fig. 12. On the other hand, ifthe magnetic drumrotates

counter-clockwise or in the "Backward" mode,the tangential force is directed

backwards andthe frictionalforceisdirectedforwards. Consequently,

selective separation ofsmallparticleswill be determinedby a

compe-titionbetween the tangential eddycurrentforce and the dynamic fric-tionalforce. In effect,thisconceptcanbe quantified as:

Ft

>

Ffric

=:

the magnetic drum shall rotate clockwise orforwards

(7)

Ft

<

Ffric

=

the magnetic drum shall rotatecounterclockwise

Notethatthe dashedline isrelevanttothe "Backward"rotation

FIGURE 12 Eddycurrentforces, electromagnetic torques and competing forces on smallparticles.

Since

_Fr

isnegligible, wehave Ffric

=famg

where

fa

is the dynamic

frictional coefficient, rn is the massof the particle and g isthe

accel-erationdue togravity. Equations

(7)

and

(8)

arealsoexpressedas:

at

>

fag

=

the magnetic drum shallrotate clockwise or forwards

(9)

at

<

fdg

=

the magnetic drum shall rotate counterclockwise

orbackwards.

(10)

Forthe rubber belt of BakkerECSthatisusedinthe present study,

fd

is about 1.1 on average, so that

fag

is about 10

_m/s

2.

It mustalso be

pointed out thatthe beltisused for suchalong time that it iscovered

withdirt, thereby rendering the belt surfaceevenrougher.

The average tangentialaccelerationof small particlesas afunctionof

thedrum speedandparticlesize areshowninFig. 13.Itis clearthat,at

50 rps drum speed which is the operatingconditionfor Figs. 4-7, the

average tangential acceleration of 3mm

AI

particles is much smaller

than

10m/s

2 whilst the average tangential acceleration of 5mm Al

particlesislarger than 10

m/s

2.

Therefore,it ispredictedthatinorderto

ROTATINGTYPE EDDYCURRENTSEPARATORS 247

3O

25

0 20 40 60 80 100

drum speed,rps

FIGURE13 Tangentialacceleration as afunction ofdrum speedandparticlesize.

"Forward" mode. This is in line withthe experimentalwork,asshown

inFigs. 14 and 5.

Alternatively, the above argument canbe verified further by

calcu-lating the averagehorizontaldisplacements of3 mmA1 particles for the

presentexperiments. Itfollows that:

S+/-

1/2

gAt

2

₍₁₁₎

where

S_L

is the vertical displacement ofaparticle, and

At

isthe time

neededfor thatverticaldisplacement.

SinceS_=0.6 m, we haveAt--0.35s. Ifthemagnetic drumrotates

backwards, the particle rolls forwards on the belt. The time for the particle from startingtorollto leaving the belt

(Atroll)

isestimated as:

Sroll

troll

(12)

90

80 70

60

50 40 30 20 10 0

1

2 3 4 5 6

7

8 9 10 11 12

collection binNo.

FIGURE 14 Material distribution in the collection binsfor A1and Pbby Bakker ECS (particlesize 5mm,beltspeed 1.6m/s,drumspeed 3000rpm, forwardrotation).

00 90

8O

70 60 5O 40 30 20 10 1 2 3 4 5 6

7

8 9 10

11

12

collectionbinNo.

FIGURE 15 Material distribution in the collection bins forAIandPbbyBakkerECS

ROTATINGTYPE EDDYCURRENTSEPARATORS 249

Itwasmeasured that thedistancefortheparticle from startingtorollto

leavingthebelt

(Srol)

isabout 0.11mand the beltspeed

(Vbelt)

is 1.6

m/s,

suchthat

_Atroll

=0.069s. Therefore, we are nowable to estimate the

averagehorizontaldisplacement

(SII)

of 3mmA1particlesas:

SI]--

(Vbelt

+

all

/ktroll /kt.

₍₁₃₎

Since _all

=fag_

_at-10.78 3.2 7.58

m/s

2,

we obtain

_SII

=0.735m

73.5 cm, asis in line with theresults showninFig. 6. Itisworth

men-tioning thatthedynamicfrictional

_coefficientf

dvariesremarkably

[5].

This isthereasonwhyin Fig. 6 thedistributionof3 mmA1 particlesis

widespread.

We

conclude thateffectiveseparation of3 mmA1particles from

non-metallicparticlescanbe realizedonly by rotating the magnetic drumin

the "Backward"mode.Accordingto

Eqs. (9)

and

(10),

the critical particle

size, atwhichtherotational directionofthemagnetic drum should be

changedfrom forwardtobackwardor viceversa,isabout 4.8mm.

4.2. The Enhancement ofSeparationSelectivity for SmallParticles

Aspreviously discussed,problemsassociated with selective separation

of small particlesare:

(1)

negligibleradialeddycurrentforce,implying

that a small particle cannot be lifted off the belt;

(2)

competition

between the tangential eddycurrent force and the dynamic frictional

forceas a result of the electromagnetic torque.

In

anefforttoaddress thoseproblems,the followingattemptsmay be

madeto improvetheseparation selectivity of small particles:

(1)

Enhancement of the tangential eddycurrent forcewith respectto

theeffects oftheelectromagnetic torque by optimizing the magnetic

drum system.

(2)

Elimination of the competing forces like the dynamic frictional

forcecreatedbytheelectromagnetic torque.

(3)

Introduction of the assistant separating forces, for instance, by

convertingtheeffects of the electromagnetic torqueto aseparating

effect.

(4)

Effective combinationsthereof.

As

isclearlyindicatedby

Eqs. (3)

and(4),thetangential eddycurrent force will be enhancedbyanincreaseofthe magneticfieldstrengthand

adecrease of the magnetpolewidth.

However,

achangeof the magnet

polewidthhas no effecton the electromagnetictorque. Reflectingthis

concept, a recent design is a prototype TNO

ECS,

which has been

conceived by the Netherlands Organization for Applied Scientific

Research

(TNO),

Apeldoorn, the Netherlands. This newECS will be

discussedin

Part

II

of this paperseries.Otherdevicesincorporating our

conceptsmentionedabovewillbedescribed in detail inPart II.

5.

CONCLUSIONS

The present study yields the following major findings:

(1)

Metal particles smaller than 5mm can be separatedeffectively by

the Bakker and Eriez

ECS,

only if the magnetic drum rotates

backwards.

(2)

The"backwardphenomenon"results from the competition between

the tangentialeddycurrentforce and the dynamicfrictionalforce

created by the electromagnetic torque.

(3)

The critical particle size for which the magnetic drum rotates

backwardsisabout 4.8mm.

Acknowledgements

The authors wish to express their gratitude to the Minerals and

Metals Recycling Research Center

(MIMER),

LuleA University of

Technology, Sweden, forfinancialsupport. Appreciation also goes to

the

Department

of

Waste

andMaterialsTechnology,TheNetherlands

Organization for Applied Scientific Research (TNO), Apeldoorn, the

Netherlands, for assistance and providing an Eriez Model 1222

laboratory eddycurrentseparator.

References

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[2] P. Rem, E.BeunderandA. vanderAkker,Simulationof eddy-current separators.

ROTATINGTYPE EDDYCURRENTSEPARATORS 251 [3] S. Zhang,P. Remand E. Forssberg (1998),Particletrajectorysimulationof

two-drumeddycurrentseparators. ManuscriptsubmittedtoResources, Conservation&

Recycling.

[4] S.Zhang andE.Forssberg,Electronicscrapcharacterizationformaterialsrecycling.

Journal_ofWasteManagement &ResourceRecovery,3(1997)157-167.

[5] D. Stoianovici andY.Hurmuzlu,Acriticalstudy of the applicability of rigid-body