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Five Years of Innovative VeRo Liberator® Comminution – From Invention to Industrial‐scale Pilot Phase Testing

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The efficiency improvement in the comminution of ores has been on the international agenda of the mining industry for some time but substantial advances are still relatively scarce. It is generally agreed upon that major goals include a substantially reduced energy consumption, systems that operate dry, markedly enhanced particle size reduction, and improved particle liberation. The VeRo Liberator® has been invented some five years ago and applies a completely new, mechanical comminution principle, which applies high‐velocity and high‐frequency impact comminution. The industrial scale 100 t/h VeRo Liberator® prototype features a vertical four‐fold axle‐in‐axle system, equipped with a large number of hammer tools, which rotate on three levels clockwise and anticlockwise against each other. The resulting high‐frequency, high‐velocity impacts cause a highly turbulent particle flow and trigger fracture nucleation and fracture propagation preferentially at and along phase boundaries. Breakage occurs from the high‐velocity stimulation of particles, where the elasticity and compressibility modules control differential particle behaviour. This differential behaviour results in the build‐up of stress along particle boundaries and eventual failure and breakage nucleation on mineral phase boundaries. Fracture nucleation and fracture propagation on particle boundaries rather than cross‐ boundary breakage explains the high degree of liberation and low energy consumption, compared to traditional comminution systems that feature breakage development parallel to 1 between point‐loads. Current research and high‐velocity impact experiments support our postulated breakage principle and further our understanding of this new and unconventional comminution process. The improved breakage behaviour results in a drastically reduced energy consumption of between 3 and 13 kWh/t, very high degrees of particle liberation, and particle size reduction ratios of up to 6.250 in single pass comminution. The VeRo Liberator® can either replace several conventional comminution steps or can reduce the application of less (energy) efficient technique to a minimum. The invention and production of the first industrial‐scale prototype (2011‐2012) was followed by extensive test comminution of bulk samples of a wide range of typical ores from various mines around the world (2012‐1014). This test work was accompanied by independent geometallurgical and mineralogical documentation and research (2013‐2015). In‐house presentations to mining houses and at international comminution conferences drew strong industrial interest and resulted in even more extensive test comminution of various types of industry‐supplied ores and smelter‐slags (2015‐2016). Presently, the first industrial‐scale pilot test phase is being launched jointly by PMS and Anglo American to test the VeRo Liberator® at one of their operations beginning in 2017.
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Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
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FiveYearsofInnovativeVeRoLiberator®Comminution–FromInventiontoIndustrial‐scale
PilotPhaseTesting
GregorBorg1,2,FelixScharfe1,andChristofLempp3
1PMSGmbH,Abteistrasse1,D‐20149Hamburg,Germany
2EconomicGeologyandPetrology,MartinLutherUniversityHalle‐WittenbergGermany
(correspondingauthor):gregor.borg@geo.uni‐halle.de
3RockMechanics/EngineeringGeology,MartinLutherUniversityHalle‐Wittenberg,Germany
Abstract
The efficiency improvement in the comminution of ores has been on the int ernational agenda of the
miningindustryforsometimebutsubstantialadvancesarestillrelativelyscarce. It is generallyagreed
upon that major goals include a substantially reduced energy consumption, systems that operate dry,
markedlyenhancedparticlesizereduction,andimprovedparticleliberation.
TheVeRo Liberator®hasbeeninventedsome five yearsagoandappliesacompletelynew, mechanical
comminution principle, which applies high‐velocity and high‐frequency impact comminution. The
industrial scale 100 t/h VeRo Liberator® prototype features a vertical four‐fold axle‐in‐axle system,
equippedwithalargenumberofhammertools,whichrotateonthreelevelsclockwiseandanticlockwise
againsteachother.Theresultinghigh‐frequency,high‐velocityimpactscauseahighlyturbulentparticle
flowandtriggerfracturenucleationandfracturepropagationpreferentially at and along phase
boundaries. Breakage occurs from the high‐velocity stimulation of particles, where the elasticity and
compressibilitymodules controldifferentialparticlebehaviour.This differentialbehaviourresults inthe
build‐upofstressalongparticleboundariesandeventualfailureandbreakagenucleationonmineralphase
boundaries. Fracture nucleation and fracture propagation on particle boundaries rather than cross‐
boundary breakage explains the high degree of liberation and low energy consumption, compared to
traditionalcomminutionsystemsthatfeaturebreakagedevelopmentparalleltoߪ1betweenpoint‐loads.
Current research and high‐velocity impact experiments support our postulated breakagep rinciple and
furtherourunderstandingofthisnewandunconventionalcomminutionprocess.
Theimprovedbreakagebehaviourresultsinadrasticallyreducedenergyconsumptionofbetween3and
13kWh/t,veryhighdegreesofparticleliberation,andparticlesizereductionratiosofupto6.250insingle
passcomminution.TheVeRoLiberator®caneitherreplaceseveralconventionalcomminutionstepsorcan
reducetheapplicationofless(energy)efficienttechniquetoaminimum.
Theinventionandproductionofthefirstindustrial‐scaleprototype(2011‐2012)wasfollowedbyextensive
testcomminution of bulksamplesofa widerangeoftypicalores from variousminesaroundthe world
(2012‐1014). This test work was accompanied by independent geometallurgical and mineralogical
documentationandresearch(2013‐2015).In‐housepresentationstomininghousesandatinternational
comminution conferences drew strong industrial interest and resultedinevenmoreextensivetest
comminutionofvarioustypesofindustry‐suppliedoresandsmelter‐slags(2015‐2016).Presently,thefirst
industrial‐scale pilot test phaseis being launchedjointlyby PMS and AngloAmericanto test the VeRo
Liberator®atoneoftheiroperationsbeginningin2017.

Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
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Introduction
Theunfavourablyhighlevelofenergyconsumptioninconventionalcomminution,i.e.crushingandmilling,
of mining and mineral processing operations as well as in recycling of metallurgical slags and waste
incinerator slags is well known (Fig. 1, http://www.visualcapitalist.com and Napier‐Munn 2014). Cost
reduction by improved efficiency is therefore a ubiquitous taskfortheextractiveindustry.Asa
consequence,allstagesofmining,mineralprocessing,andmetallurgyneedto be reviewedcarefullyto
identifysubstantialandsuitabletechnicalinnovations(CutifaniandBryant2015).
Fig. 1: Distribution of energy consumption at typical mine sites (modified from
http://www.visualcapitalist.com). Note that processes such as electro‐winning, refining, or smelting
processesarenotconsideredhere.
Fig.2: Schematic pie chartshowingtheutilisationofenergy,consumedby conventionalmillsduring
operation(Manouchehrietal.2015).Pleasenotethatonlyone(!)percentoftheenergyisusedforthe
actualbreakageandthussizereductionofthematerial.
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
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InventionandDevelopmentHistory
TheVeRoLiberator®hasbeeninventedin2011and,initially,amuchsmallertestunithasbeenbuilt(Fig.
3)andtriedonmaterialssuchassteel‐armouredconcreteandincineratorslags.PromisingresultsledPMS
GmbH to look for independent, standardised scientific investigation and documentation of the
comminution success by mineralogical characterisation of feed and product materials. An 18 month
cooperationprojectwiththeEconomicGeologyandPetrologyResearchUnitofMartinLutherUniversity
Halle‐Wittenberg,GermanyandPMSGmbHhasbeenestablishedandbulksamplesofadiverserangeof
oreshasbeenobtainedfortest‐comminution(Fig.4).Thesebulksampleshavebeenselected,basedon
themining‐networkofthefirstauthorbutalsowith theattempttoincludea varietyofdifferenttypical
oretypes, such as massive sulphide ores (Rio Tinto and AguasTenidas, Spain and Pyhäsalmi, Finland),
tungstenore(WolframCampMine,Queensland,Australia),fluoriteandbariteore(ClaraMine,Germany),
large‐flakedgraphiteore (Kropfmühl Mine,Germany),andanodecoppersmelterslag(AurubisSmelter
Lünen,Germany).Thesebulksamplesallowed for detailed and in‐depth testcomminution and for the
initialadaptationandoptimisationoftheVeRoLiberator®,whichunderwentsignificantdevelopmentand
modificationsduringtheseearlystagesbetween2011and2014(Figs.3and4).
Fig.3:DifferentdevelopmentstagesoftheVeRoLiberator®,fromthefirstlab‐scaletrialmachine
(topleft)throughafirstprototypetothecurrentandforthcomingfullindustrial‐scalemodels.
Based on the impressive and encouraging empirical results,first in‐house presentations were offed to
selectedminingandsmeltingcompanies,whichresultedinstimulating–althoughinitiallypartlysceptical
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
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– discussions, but which also provided the PMS team with highly constructive technical questions.
Presentations at selected international comminution conferences, publi cation of papers in conf erence
proceeding volumes and technical international journals, as well a website presentation and
advertisementbrochureallhelpedtopublicisethenewVeRoLiberator®technique(Fig.3).
Fig. 4: Graphically summarised invention and development history of the VeRo Liberator® with
accompanying research, in‐house industry presentations, public presentations at conferences, and
printedpublications.
Thepositiveresultsandreactionstothesepublicpresentationscame inth efor mofabun d ant bulk sam ples
ofores,nowsentattherequestofinterestedminingandsmelting companies from all continents.
Accompanying scientific research on the characterisation of feeds and products continued but was
extendedtoresearch,tryingtounderstandthefunctionalprincipleoftheVeRoLiberatothatdelivers
suchinnovativeand drastically more efficient unintendedcomminutionresults.Theuniversityresearch
team was enlarged by including the rockmechanics group, to test the initially proposed comminution
mechanism(Borgetal.2015a)andtorefineit to ourcurrentunderstanding(Borg et al.2015b,2015c,
2016andthispaper).Marketentryhasbeenachievedinlate2016,whenAngloAmerican,afteraseries
ofcomminutiontestsondifferentores,orderedabespokeVeRoLiberator®,speciallydesignedtobeused
inalarge‐scalepilottestatoneoftheiroperations.
TechnicalParameters
ThemaximumsizeofthefeedforthecurrentVeRoLiberatomodelispreferably120mmindiameter.
Depending on the input material from mining, this could be material from a primary crusher or could
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
5
replacetheprimarycrusheritselfplussubsequentcrushingandmillingstages.Reductionratiosinclassical
drycrushingaregenerallysmallandtypicallyrangebetweenthreeandsixinasinglecrushingstage(Wills
andNapier‐Munn2007).Moreinnovativesingle‐levelimpactcrushersandhammermillsreachreduction
ratios,rar ely ashighas40to60(pers. com m.HolgerLieberwirth,InstituteofMineralProcessingMachines,
TUBAFreiberg,Germany).However,thereductionratiooftheVeRoLiberator®isfundamentallylarger
andrangesfromaminimumratioof100(at120mmfeeddiameter)toareductionratioof1.000forRio
Tintomassivesulphidesandcanbeashighas6.250.Thelatter,extremereductionratiohasbeenachieved
ona bulksampleofanaturalindustrialmineral compositeofminutesilicaskeletonsin acalcitematrix,
withanF80of120mmandaP80of16µm,thusrepresentinganimpressivereductionratioof6.250(Saeid
Moradi,inprep.).
TheVeRoLiberator®workswithoutprocesswaterandisthusmostsuitableforoperationinaridregions
where costs and availability of water are an even bigger issue than in wetter regions. However, the
machineworksnotonlyinadryprocessbutisadditionallycapableofactivelywarming/heatingandthus
dryingthecomminutedmaterialbyconvertingtheimpactenergyintothermalenergy.Anothereffectof
thehighvelocityoftheimpactsistheembrittlementofviscous(“ductile”) particles, such as spherical
metalliccopper dropletsinsmelterslagsthat remain sphericalandarenotflattenedasinconventional
comminutionsystems(Fig.13inBorgetal.2015c).Technically,theequipmentiseasytomaintainsince
thehousingcanbe liftedhydraulicallyforsingle‐toolreplacementortheentiredriveshaftandtoolunit
canbepulledfromthemainframe.Thisallowsforthemaintenanceofastand‐bydriveshaftandtoolunit
andaquickexchangeafterpossiblerepair.
ComminutionResults
Todate,tensofbulksamplesofvariousoresandslagsfromseveralminesandsmeltersaroundtheworld
have beenorarecurrently beingt est co mminutedb ytheVeroLiberator®.Thesematerialsincludeprimary
oresofmetalcommoditiessuchascopper,lead,zinc,tungsten,molybdenum,gold,andplatinumaswell
asindustrialmineralssuchasgraphite,fluorite,barite,limestone,diatomite,nephelinesyeniteandothers.
The following examples of test‐comminuted materials are thus not intended as presentation of full
investigationresults,someofwhichhavebeenpublishedelsewherealready (Borg etal.2015a,2015b,
2015cand2016).Additionalcomprehensivefactsheets,coveringthetest‐comminution results ofmost
bulksamplestestedsofar,arealsoavailable‐unlessconfidential‐upone‐mailrequestfromPMS.
However,thepresentpapernotonlyhigh‐lightstheparticularapplicabilityoftheVeRoLiberator®forthe
processingofclassicalporphyrycopperore,tungstenore,andindustrialmineralssuchasgarnetandrutile
ineclogite,butalsoallowstoelaborateinmoredetailontheworkingprinciplethatcausessuchdrastic
liberationatextremelylowenergyconsumptionlevels.
Tungstenore,WolframCampMine,Queensland,Australia
Tungsten is one of the critical strategic metals and occurs as the commodity minerals scheelite and
wolframite, typically associated with the tin mineral cassiterite and locally molybdenite and some
sulphides. Mined and explored tungsten deposits in China, Spain, Portugal, Australia, Germany and
elsewhere are all characterised by low to verylow grades of 0,6 ‐ 0,2 % WO3.Particularly wolframite‐
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
6
dominatedtungstendeposits face an additionalchallengeduetothefriablenatureofthemineralthat
stems from an excellent mineral cleavage. This cleavage causes the wolframite to break or split
unintentionallytofartoosmallparticlesizesduringconventional(ball)milling,particleswhicharetypically
lostinsubsequentfrothflotation,reducingthemeagreoregradesevenmoreandeasilytosub‐economic
levels.
Abulk sample of tungsten‐tin‐molybdenumorefrom Wolfram Camp Mine,Queensland,Australia,has
beentestcomminutedalreadyin2014andinthemeantime,themine and plant , owned by Almonty
Industries,have beenputoncareandmaintenance,notleast duetotheaboveproblemoflossofore
mineral fines after passing the ball mill. The back scatter scanning electron microscope imagesof the
comminuted ore shows complete particle liberation (Figs. 5 and 6) of the ore minerals scheelite,
wolframite,and molybdenitefrom the silicatemineralsquartz,muscoviteandfeldspar,which make up
thegraniticgneisshostrock.Theimagesshowthatbreakagehasoccurredalongparticleboundariesand
thatparticlesdisplayhighlyangularshapes,withoutanyabrasiveroundingfromtumblingandgrindingor
milling.
Fig. 5: Backscatter electron microscope image of
tungstenorefromWolframCampMine,
Queensland, Australia, showing ore minerals
(white) liberated from gangue minerals (grey).
Notethesharpangularshapes,particularlyofthe
silicategangueminerals,whichdocumentthatthe
minerals have been liberated but not abraded
from tumbling or milling, which reduced the
generationoffines.
Fig. 6: Close‐up backscatter electron microscope
imageshowingsilicategangueminerals(medium
todarkgrey)andoreminerals(white).Tungsten
ore minerals include scheelite (Sch) and
wolframite (Wof), together with molybdenite
(Mol).Notethatparticleliberationisc omplete and
particles are highly angular from
separation/liberation along particle boundaries
withoutabrasionfromtumblingandmilling.
Thesetexturesofthecomminutedproductdocumentthattheparticleshaveseparatedfromeachother
inaprocessofdisintegrationthatisobviouslyverydifferent from conventional milling and breakage
processes.Evensheet‐likemicaparticles(shownaslathsinFigs.5and6)havemaintainedtheiroriginal
crystalandparticleshapesandmoreductilelaminatedmolybdeniteshowsonlyslightbendingatthetail
ends(Fig.6).
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
7
Thelack–orbetteromission–ofabrasionfromtumblingandmillingof the ore particlesduringVeRo
Liberator® comminution prevents the production of unwanted fines and thus can prevent the loss of
valuablecommodityminerals.Especiallyintungsten(‐tin)deposits,theapplicationoftheVeRoLiberator®
techniquecanmakeamajordifferenceinimprovingtherecoveryratesubstantially.
PorphyryCopperOre,LosBroncesMine,Chile
Porphyry copper ores are the biggest source of primary copperproduced. A bulk sample of porphyry
copperorefromAngloAmericansLosBroncesMineinChilehasbeen test‐comminuted by the VeRo
Liberator®.
Fig. 7: Hand specimen of porphyry copper ore
fromLosBroncesMine,Chile,showingtypical
crackle‐brecciated and massive breccia‐hosted
ore.Theoremineralispredominantly
chalcopyrite. Note that the ore has passed
throughaprimaryandsecondarycrushingcircuit
already.
Fig. 8: Backscatter electron microscope image
showingsilicategangueminerals (medium to dark
grey) and sulphide minerals (white). Sulphide
mineralsinclude pyrite(py)andchalcopyrite (ccp),
whichhavebeenliberatedfromthesilicategangue
toaveryhighdegree.Shownhereisthe250‐125µm
sievefraction.
Fig.9:LosBroncesore,12563µ msievefraction,
with higher degree of particle liberation
Fig.10:Close‐upofLosBroncesore,<63µmsieve
fraction, with complete particle liberation
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
8
comparedtothecoarserfractionshowninFig.8. comparedtothecoarserfractionsshown inFigs.8
and9.
Thejig‐sawbreccia‐andmoremassivebreccia‐hostedore(Fig.7)containschalcopyriteasoremineraland
pyriteasadditional,non‐commoditysulphidemineral,hostedonfractures,veinletsandinbrecciamatrices
withinsilicategangueminerals(K‐feldspar,somealbite,quartz,aswellasthetypicalalterationminerals).
Mostoftheoremineralshavebeenliberatedfromthegangueminerals although very fine‐grained
sulphides still occur within the gangue mineral aggregates in thecoarserfractionofthecomminuted
product(Fig.8).However,liberationincreasesclearlyinthefinerparticlefractions(Figs.9‐10).
Rutile‐GarnetEclogiteOre,NordicMining,Norway
A bulk sample of eclogite for the recovery of rutile and garnethasbeentest‐comminutedforNordic
Mining,Norway.Therutile(TiO2)isthe mostessentialindustrialmineral fortheproductionof titanium
oxideasawhitepigmentforwallpaint,whereasgarnetisusedasanabrasiveandinsomecasesforthe
recoveryofrareearthelements.TheeclogitefromNordicMining’soperation isaveryhard,tough and
densemetamorphicrock.
Fig. 11:Binocularmicrophotographof
comminutionproductofeclogitefromNordic
Mining, Norway, showing perfectly liberated
garnet (light red), omphacitic pyroxene (green)
andrutile(brownish‐black).Widthoffieldofview
is4mm.PicturecourtesyofNordicMining.
Fig.12:Backscatterelectronmicroscopeimageof
comminutedeclogite,showingperfectlyliberated
silicate and oxide minerals. Garnet (Grt),
omphacitic pyroxene (Omp). Note the surface
roughness and angularity of the liberated
minerals.
Thecomminutionproductshowscompleteparticleliberationofallthreemineralsthatconstitutethisrock,
which are pink garnet, green omphacitic pyroxene, and brownish‐black rutile (Fig. 11). Backscatter
electronmicroscopyimagesshowalsoaveryhighdegreeofparticleliberationwithfewintergrownmixed
mineralcompositeparticles only.Industrialmineraloresarethusequallyamenabletocomminutionby
VeRo Liberator® compared to ores of metal commodities and smelter slags. Other examples of test‐
comminuted industrial minerals have included graphite ore, fluorite ore, barite ore, diatomite, and
nephelinesyeniteforglassproduction.
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
9
TheWorkingPrincipleoftheVeRoLiberator®andExperimentalResults
Theworking principle oftheVeRoLiberator®is apparently onlysubordinatelycharacterizedbyfracture
propagation between load points, but is probably the consequence of several rock mechanical
phenomena, all of which are based on the differential deformation behaviour of the various mineral
components.ThemoststrikingphenomenonoftheVeRoLiberator®isthatfragmentationresultsfrom
fracturenucleationandfracturepropagationpredominantlyonandalongparticleormineralboundaries.
Thisstarkl ydi ffe ren two rkingprinciple oft heVeRoLib era tor app earsto accoun tforthedrasticall yre duc ed
energyconsumption.Fractureformationonandfracturepropagationalongparticleboundariesisfarmore
energyefficientsincethefractureshavetoovercomesignificantlylesstensilestrengthcomparedtocross‐
boundaryfracturing.Inotherwords,interfacialstrengthistypicallymuchlessthanthestrengthwithina
homogenous particle or mineral (Cleveland and Tello 2004) and the nucleation and propagation of
fracturesbetweenparticlescanberegardedasa“debonding”process(ClevelandandTello2004)withthe
highdegreeofparticleliberationthatwe observeinVeRoLiberator®comminution.Thisobservationis
relatively well known in other disciplines and has been researched and documented for fracture
development (or rather fracture prevention) in technical, laminated composite materials of different
viscosity and/or brittleness (Bloyter et al. 1999). The theoretical explanation for such a separation of
mineralsduetodifferentmoduliofdeformation(deformationmodulusorYoung´smodulus)hasalready
beendescribedandillustratedinapreviouspublication(Borgetal.2015a)andisapparentlyoneofthe
causesbutprobablynottheonlyone.
An additional significant aspect is apparently the velocity‐dependence and thus time‐dependence of
comminution processes inside the VeRo Liberator®. The induced stress difference between two
componentsmustbehighenoughforfractureformationandseparationtotakeplaceattheboundaryof
twomineralswithasubstantiallydifferentdeformationstate.Itmustthereforebeassumedthatakindof
stressaccumulationin theoscillatingandvibratingcomponentsplays asignificantrolein inter‐granular
fractureformationandthusinparticleliberation.Innormalimpactevents,areleaseofstresstakesplace
betweenthevariouscomponentsduetoatime‐dependentstressrelaxationprocessandcommonlydoes
notleadtobreakage.However,incaseoftheVeRoLiberatothe extremely high frequency of h igh‐
velocityimpactsisapparentlyfarhigherandfasterthanstressrelaxationcanoccurwithintheindividual
components.Asaconsequence,veryhighstressdifferencesbuildupbetweenadjacentmineralsandcause
fractureformationat the particle boundaries. These processesarepossiblycomparabletowell‐known,
supersonicfrequency‐dependent processes such astheonesappliedinultrasoniccleaningandmedical
kidney stone disintegration devices (Cleveland and Tello 2004). This model explanation has first been
published by Borg et al. (2015a) and has been subsequently refined(Borgetal.2015b,2015c,2016)
althoughstillbasedonthesamefundamentalmechanisms,whichhasnotbeenfundamentallyquestioned
inanyofthemanydiscussionswithcolleagues.
Initialrockmechanicalexperimentsfeaturedstaticanddynamicuni‐axialloadtestsofdrilled‐outcylinders
ofcoppersmelterslag,carriedoutattheRockMechanicsLaboratoriesofMartinLutherUniversityHalle‐
Wittenberg.As first experimental testsforour model, we haveconductedboth static and dynamically
steereduniaxialcompressiontests,thelatter resultinginsignificantlyreducedrockmechanicalstrength
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
10
underrepeatedhigh‐frequencypulsatingloadevents.Adrilled‐outcylindricalcopperslagsample(30mm
diameter,80mmheight)hasbeenadditionallystressedbyincreasedloadingstepsinthreesubsequent
periodsofdynamicloadingandunloading.Thisdynamicloadingservedasafirstapproximationofthehigh
velocityimpactforces(waves)thatareinflictedonandwhich pass through the material in VeRo
Liberator® comminution. During the third dynamic loading and unloadingphase,thefailureoccurred
already at approximately 50% of the uniaxial strength, compared to a static loading test on a similar
cylindricalsampleofthesamecopperslag.Thishighlysignificantreductionoftheuniaxialstrengthduring
the dynamic load test is a clear indication of significant changes in rock mechanical behavior due to
dynamic, high‐frequency loading. Generally, this strength reduction is contrary to standard static load
experimentalresults,inwhichincreasedvelocitiesnormallyresultinahigherstrengthoftherockstested.
Ourhigh‐frequencypulsatingloadtests,whichleadtomechanicalfatiguefailureoftherocksamplethus
appeartocomeclosesttothehighlyefficientcomminutioneffectsachievedbythehigh‐frequency,high‐
velocityimpactsinflictedonheterogeneoussolidmaterialbytheVeRoLiberator®.
Recentexperimentalstudiesonrockimpactandbreakagebehaviourandtoolwearincludedhigh‐speed
videodocumentationofmaficmagmaticrocksamplesbeingballisticallyimpactedontoasteeltool.The
threeselectedimagesshowninFigure13(left)showtherocksamplewithamassof12,46gimmediately
aftertheimpactandoneandtwosecondslater,respectively.
Our initial and highly preliminary results from these ballistic high‐velocity impact experiments show
severalsurprisingphenomenaoffractureformation,rockdisintegration,androck‐toolinteraction.What
happensatsuch high impact velocitiesistotallydifferent from static ordynamic point loadsituations,
whicharetypicalforthecompressivestresssituationscreatedintraditionalcomminution,e.g.inclassical
ballmills.Insuchtraditionalmills,therockiswedgedbetweentwosteelballs,asteelballandthemachine
casing,orbetweenrocksandtheabovementioneditems.Instarkcontrast,thehighvelocityimpactleads
onlytoinitialandvisiblecompressionofthefrontal20%oftherocksample.Theremaining,muchlarger
portionoftherocksampledoesnotonlyremainuncompressedbutdisintegratesandexpandsbyliterally
“exploding”and“expanding”inallthreedirectionsof space,awayfromthesteeltool.Itisimportantto
note that this disintegration, explosion, and expansion is happening without contact to the tool and
withoutoutsidecompressivestressappliedtothismajorportionoftherock.
Sinceonlyanestimated20%oftherockvolumeiscomminutedbycompressionandtheremainingpart
bytriggered“auto‐disintegration”,itnowappearshardlysurprisingthattheenergyconsumptionforthis
process is drastically lower, compared to conventional comminution pro cesses.L argerparticles  of the
disintegratedrocksamplewillbehitbytheothertools,bytheliner,orbyotherrockfragmentsand–due
to the high and even doubled impact velocity from counter‐rotating tools – will again be largely
comminutedanddisintegratedfurtherwithaslittleenergyconsumed.

Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
11
Fig.13leftside:Threeselectedphotographsfromballistichigh‐velocityimpacttestsofarocksample
(12,46 g) impacting onto a steel tool at relevant velocities, each taken 1 second apart. At this h igh
velocity,onlythefrontalportionoftherockbecomescompressed,whereasthelargerportion ofthe
rockdisintegrates,without being under outside compressivestress andwithoutmakingcontactwith
thesteeltool.Thelargerpartoftherockfracturesandexpandsfrom internal stress,inflictedbythe
high‐velocityimpactanddifferentialparticlereaction.Thesephenomenamostprobablyaccountforthe
highparticleliberation,lowenergyconsumption,andcomparativelylowwearontoolsandliners.Right
side:SchematicworkingprincipleoftheVeRoLiberator®asproposedandillustratedinitiallybyBorget
al.(2015a).
Borg,Scharfe,Lempp‐VeRoLiberator–ConferenceProceedings‐PhysicalSeparation2017,Falmouth,Cornwall
12
CONCLUSIONS
ThenewVeRo Liberator® offers anumberof innovative and highlyefficient features that improve the
comminution of ores and metallurgical slags. Improved energy consumption, size reduction ratio and
particle liberation are due to the VeRo Liberator®’s innovative technical layout and unusual working
principle.Theenergyconsumptionisverylow,mainlyduetothefactsthati)the comminutionmaterial
fallsgravitationallythroughtheVeRoLiberator®,ii)thekineticenergyoftheimpactsismultiplieddueto
theanticyclicalrotationandimpactsofthethreetoollevels,iii)thestresslevelrequiredforrockbreakage
isapparentlyloweredduetohigh‐velocityandhigh‐frequencyimpacts,andiv)fracturenucleationatand
fracturepropagationalongparticleboundaries.Thecombinationofsuchalargenumberofhammertools,
thespecialinner liners, and the highrotationalspeedsofthecounter‐rotatingaxlesandtools all make
surethatnomaterialcanpasstheVeRoLiberator®withoutbeing impacted repeatedly.Asunderstood
from recent ballistic high velocity impact experiments, these high velocity impacts only compress a
relativelysmallportionoftherock,whereasthemajorportionoftherock materialisdisintegratedand
“explodes”duetointernallybuilt‐upstressonparticleboundaries.
ThemostinnovativeachievementsoftheVeRoLiberator®aretheextremereductionratiosformassive
sulphides and industrialminerals (1.000 and up to > 6.000as of now) and the high degree of particle
liberation,bothachievedwithsignificantlylessenergycomparedtoconventionalsystems.Theunusually
highreductionratioenablestheVeRoLiberator®topushcomminution from energy intensive milling
towards more energy efficient crushing of materials. Embrittlement of viscous materials by ultra‐high
velocityimpactsisanothersurprisingeffectoftheVeRoLiberator®wherebothcausesand applications
needtobeinvestigatedfurther.
Insummary one can statethattheVeRoLiberator® achieves,toasubstantialextent,the mechanically‐
induced, partly contactless disintegration, particle liberation, particle size reduction, and thus highly
efficientcomminution.
PMSGmbH,Hamburg,hasmovedfrominvention,tooptimisation,tomarketentryinthecomparatively
shortperiodoffourtofiveyearsonly.Webelievethatthisisduetothecombinationofahighlyinnovative
ideaandconcept,ahealthyentrepreneurialstart‐upapproach,combinedwithsuitablyselectedscientific
research in a very small and interdisciplinary team. However, success will eventually depend on the
successfulintroductionoftheVeRoLiberator®techniqueintofullindustrial‐scaleoperationsandforthis
theupcomingpilotscaletestphaseisthenextstep.
Acknowledgements
Anglo American plc is gratefully acknowledged for granting permission to present results from test‐
comminutionofLosBroncesoresandveryrecentexperimentalresultsfromballistichigh‐velocityimpact
tests.AndreasKamradt,NicolasMeyer,TimRödelandSabineWaltherareallacknowledgedforproviding
theirserviceswithsamplepreparationandScanningElectronMicroscopywork.
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... The VeRo Liberator® was invented in 2012 and market entry was achieved in late 2016 (Borg et al. 2017). As the first global player in the mining world, Anglo American plc, ordered three bespoke VeRo Liberator® units so far, all specially designed to be used in industrial-scale pilot tests at their operations. ...
... The general comminution principle of the VeRo Liberator® has been proposed based on empirical results and has been confirmed by experimental studies and further developed to the current understanding (Borg et al. b, 2015(Borg et al. c, 2016(Borg et al. , 2017. ...
Conference Paper
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Efficiency improvement in the comminution of ores has been on the international agenda of the mining industry for some time but substantial advances are still relatively scarce. It is generally agreed upon that major goals include a substantially reduced energy consumption, improved particle liberation, and the move from ultra-fine grinding to coarse particle liberation and flotation. The innovative VeRo Liberator® applies a mechanical high-velocity comminution principle, where numerous hammer tools rotate clockwise and anticlockwise on three levels around a vertical shaft-in-shaft (hollow shaft) system. The resulting high-frequency, high-velocity impacts cause a highly turbulent particle flow and trigger fracture nucleation and fracture propagation preferentially at and along mineral boundaries. Breakage of coarser particles occurs from the high-velocity stimulation of bulk ore particles, where the elasticity and compressibility modules control differential particle behaviour. The improved breakage behaviour results in a drastically reduced energy consumption of only 3 to 13 kWh/t and very high degrees of particle liberation in the relatively coarse fraction of the product. On an industrial scale, Anglo American applies already two VeRo Liberators® in their South African operations and Penoles and Fresnillo, Mexico, have carried out advanced test-comminution of ores from several of their gold-silver-zinc-lead mines in Mexico. The current paper describes results from test-comminution by VeRo Liberator® of ores from Cienega Mine, Durango Province, Mexico, in comparison to Cienega's conventional comminution by SAG milling and ball milling. The results show that the VeRo Liberator® achieves a similarly high degree of particle liberation compared to the SAG mill, but at a drastically coarser particle size. This is achieved at significantly lower energy consumption and thus energy costs and allows for more efficient dewatering of comminuted waste material and, consequently, for potentially more stable slimes dams. The mechanical high-velocity impact comminution by VeRo Liberator® hence overcomes the notorious problems of inefficient breakage in conventional ball and SAG mills.
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The comminution of commodity particles such as ore minerals in mining and metals from recycling of slags, armoured concrete, and incinerator slags by crushing, grinding, and milling makes up the biggest single cost factor in mineral processing. In spite of a marked lack in the development of new and significantly more efficient comminution equipment, an engineering start-up, PMS Hamburg, has invented and produced an innovative high-velocity impact crusher, the VeRo Liberator®, featuring highly improved particle size reduction ratios and very high degrees of particle liberation together with low levels of energy consumption and operational noise and operates dry, i.e. without using any water. The VeRo Liberator® is currently designed for a throughput of approximately 100 t per hour and has been tested on a number of different typical bulk ore and slag samples from mines and smelters around the world. Massive sulphide ore from the classic Rio Tinto Mine of the Iberian Pyrite Belt in Spain has been test-comminuted by the VeRo Liberator®. The ore and rare gangue minerals have been reduced in size by an amazing reduction ratio of 480 and have been liberated to a very high degree. According to our current understanding, these results are due to the unique working principle of the VeRo Liberator®, which is based on high-frequency, high-velocity and therefore high-kinetic-energy impacts inflicted on the material by hammer tools. The hammer tools are mounted on three separate levels of a vertical axle-in-axle system and rotate at variably high speeds clockwise and counterclockwise against each other. The material and particle stream within the machine is thus highly turbulent and each particle is certainly hammered with high impact forces several times at a high frequency. These high-frequency and high-velocity impacts occur apparently so fast, that stress builds up along the particle boundaries due to differential mechanical behaviour of the inhomogeneous materials. The high frequency of the impacts prevents the various minerals from relaxing sufficiently so that the stress between the different particles is not released quickly enough. Eventually this results in fracture formation along particle boundaries. This new comminution concept offered by the VeRo Liberator® allows the significantly more efficient comminution of ores and recycling materials at far lower energy costs and with far higher 13-15 August, 2015 San Luis Potosí, México 278 degrees of particle liberation. Due to its enormous reduction ratio the VeRo Liberator® can also replace two to three traditional crushing and milling stages, saving substantially both in CAPEX and OPEX.
Article
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The new VeRo Liberator® has been recently developed by PMS, Hamburg, Germany, and represents a highly efficient impact crushing system for dry comminution of ore, slag, armoured concrete, and aggregate in the 100 t per hour throughput class. The VeRo Liberator® operates with a vertical axle-in-axle system, which is equipped with a total of up to 144 hammer tools, each approximately 90 cm long. The hammer tools rotate on three levels clockwise and anticlockwise against each other at high rotation speeds. The gravitational flow of the material through the machine results in a very low energy consumption. The multiple high-velocity impacts of the tools inflicted on the material achieve unparalleled reduction ratios of up to more than 400 without clogging the system. The VeRo Liberator® achieves also an unusually high degree of particle liberation. Intergranular breakage is the predominant form of particle separation and is caused by the high velocity impacts, inflicted by the hammer tools, casing, and particles on each other. Apparently, the shock waves travelling through the impacted material stimulate the particles to react individually according to their elasticity “E” and compressibility “K” moduli. The specific “reaction” of the various shock-stimulated particles leads apparently to the pronounced intergranular breakage, separation, and thus particle liberation.
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The comminution of commodity particles such as ore minerals in mining and metals from recycling of slags, armored concrete, and incinerator slags by crushing, grinding, and milling makes up the biggest single cost factor in mineral processing. The comminution of graphite in various innovative applications is a particular challenge to the mineral processing industry. Ideally, the host rock containing the graphite without reducing the sixe of the graphite flakes and without leaving remnants of gangue minerals attached to the graphite flakes. Natural graphite is a high-tech commodity with a globally increasing demand for a growing number of highly innovative technical applications and products.
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A time-domain finite-difference solution to the acoustic wave equation was used to model the propagation of lithotripsy shock waves in kidney stones. Varying the sound-speed of the stone had minimal effect on the pressure within the stone. Reducing stone diameter dramatically reduced negative, but not positive, pressures. For composite stones the pressures am-plitude changed little, but specific configurations resulted in the peak negative pressure occurring at an internal interface—a likely weak point in the stone. These results indicate that the pressure field in a kidney stone is very sensitive to the size and internal composition of the stone.
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A time domain finite difference solution to the acoustic wave equation was used to model the propagation of lithotripsy shock waves in kidney stones. The stones were modeled as cylindrical objects and the impact of stone sound speed, stone diameter, and the internal structure on the pressure field inside the stones was calculated. The sound speed was varied from 2500 to 3500 m/s and had a minimal effect on the peak pressures within the stone. However, reducing the stone diameter from 15 mm to 3 mm reduced the peak negative pressure by 67%. For cases where the sound speed of the stone was inhomogeneous (inner core different from outer ring), the amplitudes of the peak pressures varied slightly, however the spatial distribution of the peak negative pressure varied significantly. In particular configurations with a lower outer sound speed lead to the peak negative pressure occurring at the boundary between the layers. The results indicate that the pressure field in a kidney stone is very sensitive to the size and internal composition of a kidney stone. This effect could be partly responsible for the large variance in fragility observed in human stones. [Work supported by the Whitaker Foundation and NIH‐DDK.]
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Comminution is known to be an inefficient user of energy. This makes it the largest energy consumer in many mine sites and therefore a large component of cost. One would therefore have thought that improving comminution energy efficiency would be receiving the undivided attention of the mining industry, but this is not the case. This paper considers why this is so and what the future might hold, by posing and attempting to answer three questions: • Is this really an important issue for the mining industry? • If so, can comminution energy be substantially reduced in a reasonable time frame? • What are the drivers that will motivate change, and what should now be done? The conclusions of the paper are pessimistic in the sense that forces may be gathering that will demand that the issue be addressed across the industry in the relatively near future, but optimistic in the sense that there is a clear development path. There is much that can be done with what is already known, and considerable promise exists in new developments which can be realised through sustained and focused R&D, building on new knowledge acquired in the last 20 years. These are outlined in the paper. It is concluded that there is a case for a global initiative to significantly reduce comminution consumption over say the next 10 years through a partnership between all parts of industry and the research community, covering short, medium and long-term innovation.
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A study has been made of the fatigue-crack propagation properties of a series of laminated Nb-reinforced Nb3Al intermetallic-matrix composites with varying microstructural scale but nominally identical reinforcement volume fraction (20 pct Nb). It was found that resistance to fatigue-crack growth improved with increasing metallic layer thickness (in the range 50 to 250 µm) both in the crack-divider and crack-arrester orientations. For a given layer thickness, however, the properties in the crack-arrester orientation were superior to the crack-divider orientation. Indeed, the fatigue resistance of the crack arrester laminates was better than the fatigue properties of unreinforced Nb3Al and pure Nb; both laminate orientations had significantly better fatigue properties than Nb-particulate reinforced Nb3Al composites. Such enhanced fatigue performance was found to result from extrisic toughening in the form of bridging metal ligaments in the crack wake, which shielded the crack tip from the applied (far-field) driving force. Unlike particulate-reinforced composites, such bridging was quite resilient under cyclic loading conditions. The superior crack-growth resistance of the crack-arrester laminates was found to result from additional intrinsic toughening, specifically involving trapping of the entire crack front by the Nb layer, which necessitated crack renucleation across the layer.
Reinventing mining: Creating sustainable value. Kellogg Innovation Network
  • M Cutifani
  • P Bryant
Cutifani M and Bryant P (2015) Reinventing mining: Creating sustainable value. Kellogg Innovation Network. Available at: http://www.kinglobal.org/catalyst.php Accessed 25 July 2015