Real and Potential Metallurgical Real and Potential Metallurgical Benefits of High Pressure Benefits of High Pressure

Grinding RollsGrinding Rolls

byby

Hans von MichaelisHans von MichaelisRANDOLRANDOL PERTH 2005PERTH 2005

Thank youThank you

AcknowledgementsAcknowledgements

Wolfgang Baum, Phelps Dodge Mining CompanyPeter Rowe, AngloGold Ashanti Robert C. Dunne, Newmont Australia Polysius Corporation

WarningWarning

This presentation includes speculation about possible benefits and potential future applications of HPGR. Some of these have yet to be even lab tested ……

WarningWarning

HPGR benefits are ore-specific….Careful testing is essential….How one goes about this testing is all-important……

Breaking NewsBreaking News

This meeting today will reveal that the mining industry is now proving some previously speculative HPGR benefits some beyond even our wildest dreams

Cyprus Cyprus SierritaSierrita Pilot Test 1995Pilot Test 1995

1,250 tonnes per hour Copper Ore

HPGR's in Minerals Processing

0

5

10

15

20

25

30

35

1985 1990 1995 2000 2005 2010Year of installation

No.

inst

alle

d

DiamondsIron OresCopperGold

High Pressure Grinding Rolls

Overview Overview Overview

HPGR's in Minerals Processing

0

5

10

15

20

25

30

35

1985 1990 1995 2000 2005 2010Year of installation

No.

inst

alle

d

DiamondsIron OresCopperGold

High Pressure Grinding Rolls

Overview Overview Overview

POLYCOM

Roll diameter : 2,8 m

Roll width : 0,6 m

Motor Power : 2 x 600 kW

High Pressure Grinding Rolls Largest Diameter HPGRLargest Diameter HPGR

LABWAL Test POLYCOM

Roll diameter 250 mm

Roll width 100 mm

High Pressure Grinding Smallest UnitSmallest Unit

HPGR Benefits in CrushingHPGR Benefits in Crushing

High Pressure Grinding Rolls

Selective Breaking of softer rock to liberate hard diamonds

High Pressure Grinding Rolls

Selective Breaking of softer rock around hard diamonds

Applicable also, for example, for liberation of softer magnetite from hard chert for magnetic

preconcentration ahead of milling….

Compare Crusher and HPGR Compare Crusher and HPGR ProductsProductsPassing [%]

100

50

20

105

2

0.01 0.03 0.1 0.3 1 3 5 10 mmmesh41648150

Material from HighPressure Grinding

Material from HighPressure Grinding

More Fine Product Due to Increased Pressure

More Fine Product Due to Increased Pressure

CrushedMaterialCrushedMaterial

FeedMaterial

FeedMaterial

Closed Systems Crusher

Closed Systems Crusher

HPGR Benefits in GrindingHPGR Benefits in Grinding

Overview - Feed Materials -Overview Overview -- Feed Materials Feed Materials --

High Pressure Grinding Rolls

0.0

10.0

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100.0

0.01 0.1 1 10 100

Particle size [µm]

Fine

ness

% p

assi

ng [%

]HPGR products

Cone crusherproducts

Feed material

0.0

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Particle size [µm]

Fine

ness

% p

assi

ng [%

]HPGR products

Cone crusherproducts

Feed material

Conventional Crushed Particle

HPGR Crushed Particle

Idea: Liberation of Industrial Idea: Liberation of Industrial MineralsMinerals

Hard rock rutile, zircon and/or garnet?Liberation of tantalite?Recovery of phosphate rock

Feed Materials -Feed MaterialsFeed Materials --

High Pressure Grinding Rolls

Fine and Ultra-fine GrindingFine and UltraFine and Ultra--fine Grindingfine Grinding

High Pressure Grinding Rolls

Fine-grinding of iron-ore ahead of pelletizingHPGR saves energy

Fine and Ultra-fine GrindingFine and UltraFine and Ultra--fine Grindingfine Grinding

High Pressure Grinding Rolls

Idea:How about fine-grinding

sulfide concentrates ahead of Activox or Albion leach

processes?

Fine GrindingFine GrindingFine Grinding

High Pressure Grinding Rolls

Idea to test:HPGR benefits

in the re-treatment of tailings

Wear and AbrasionWear and Abrasion

High Pressure Grinding Rolls

Copper & Gold Ores

0102030405060708090

100

0 100 200 300 400Unconfined compressive strength, MPa

ATW

AL

wea

r rat

e, g

/t

Diamond

Iron ore

Copper

Gold ores

Low abrasivecopper ores

Platinum OrePebbles

Platinum OreUG2

Test Results - Abrasion Index of Various OresTest Results - Abrasion Index of Various Ores

ATWAL Test POLYCOM

Roll diameter 100 mm

Roll width 30 mm

Material req.: 100 kg

High Pressure Grinding of Platinum OresAbrasion TestAbrasion Test

Primary Mill

To Flotation and Secondary Milling

Primary Mill

To Flotation and Secondary Milling

High Pressure Grinding RollsFlow Sheet - HPGR for Pebble CrushingFlow Sheet - HPGR for Pebble Crushing

HPGR Benefits in GrindingHPGR Benefits in GrindingBreaks on grain boundaries = Improved liberation of particlesMay reduce the “effective Bond index”= Energy savingsCleaner liberation of valuable mineral grainsAdjustable pressure….better control of breakageBenefits extremely hard ores that are not ideal for SAGReduced steel consumptionFaster delivery than SAG mills

HPGR Benefits in FlotationHPGR Benefits in Flotation& Gravity Concentration& Gravity Concentration

Conventional Crushed Particle

HPGR Crushed Particle

Flotation : Less Flotation : Less ““UltraUltra--FinesFines””

Crusher - BM Product

HPGR - BM Product

Improved Flotation recoveryLess “slimes” =

Rod Mill vs. HPGR Rod Mill vs. HPGR -- Tin OreTin Ore70

60

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30

10

0Tin

Dis

trib

utio

n (%

)T

in D

istr

ibut

ion

(%)

40

20

Rod Mill Rod MillHPGR HPGR

Gravity Concentrate

Gravity Tails

Slimes

+325M Material+325M Material -325M Slimes-325M Slimes(Modified After Clarke & Wills, 1989)

(Modified After Morsky et al 1995)

Size (Mesh)Size (Mesh)

706050

30

100

40

20

325 200 100 35

Liberated ChromiteLiberated Chromite

Cumul.RecoveredLiberated Chromite

(%)

Cumul.RecoveredLiberated Chromite

(%)

Cumulative RecoveryCumulative Recovery

Soft GangueSoft GangueHPGRHPGR

Rod MillRod Mill

Ball MillBall Mill

HPGR Benefits in Flotation & HPGR Benefits in Flotation & GravityGravity

Better liberation of particlesDry comminution; less surface oxidationReduced ultra-fines (“slimes”) generationHope to make flash flotation feed without millingDry comminution = Positive control of pulp density----------------------------------------------------------Improved recovery retreating tailings?

Primary Mill

Primary Flotation

Secondary Mill

Secondary Flotation

High Pressure Grinding of Platinum OresFlow Sheet - MF2 CircuitFlow Sheet - MF2 Circuit

Primary Flotation

Secondary Flotation

Secondary Mill

H2O

High Pressure Grinding of Platinum OresFlow Sheet - HPGR / BM CircuitFlow Sheet - HPGR / BM Circuit

HPGR / BM Circuit - IntegralHPGR / BM Circuit - Integral

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P a rtic le s ize [m m ]

O rigina l F eed D ischa rge S creen O /S S c reen U /S

Scale Up of PSD for an Industrial UnitUG2 Ore

Flash Flotation

HPGR Benefits in Heap LeachingHPGR Benefits in Heap Leaching

Conventionally & HPGR Conventionally & HPGR Crushed ParticlesCrushed Particles

MicroMicro--Fractures Fractures -- HPGRHPGR--Treated OreTreated Ore

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Gol

d E

xtra

ctio

n %

Gol

d E

xtra

ctio

n %

Leach Time (days)Leach Time (days)

Column Leach Results of Column Leach Results of Highly Siliceous Gold OreHighly Siliceous Gold Ore

Conventional Crusher

Conventional Crusher

POLYCOM HPGRPOLYCOM HPGR

Size Fraction Size Fraction (Mesh)(Mesh)

HPGR Particle Fracturing HPGR Particle Fracturing vsvsConventional CrushingConventional Crushing

100

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40

20

0

Frac

ture

d Fr

actu

red

Par

ticl

es (

Vol

. %)

Par

ticl

es (

Vol

. %)

100

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60

40

20

0

+10 -10+20

-20+48

-48+100

-100+200

-200

Low Pressure POLYCOM HPGRLow Pressure Low Pressure

POLYCOM HPGRPOLYCOM HPGR

High Pressure POLYCOM HPGRHigh Pressure High Pressure

POLYCOM HPGRPOLYCOM HPGR

ConventionalCrushing

ConventionalConventionalCrushingCrushing

SemiSemi--Refractory Gold Ore (Nevada)Refractory Gold Ore (Nevada)

Benefits in BioBenefits in Bio--Oxidation?Oxidation?

HPGR

Benefits in BioBenefits in Bio--Oxidation?Oxidation?

HPGRAsking to be tested…..e.g. Bio-heap oxidation

HPGR MicroHPGR Micro--Fracture Effect Fracture Effect on Sulfideson Sulfides

Hard Rock HPGR Benefits in:Hard Rock HPGR Benefits in:

Inter-particle Breaking: Energy SavingsAutogenous Liners: Reduced steel wearBreaks along grain boundaries: better liberation – less slimes - better flotation recoveriesAbrasion characteristics: lower steel wearHeap Leaching: Micro-fractures & Fines:better leach recovery, faster leach recovery Gravity Gold: less lock-up; not flattened

HPGR HPGR –– Potential Potential Improvement of MetallurgyImprovement of MetallurgyIn

crea

se (

%)

Incr

ease

(%

)3535

2020

1515

1010

55

00

3030

2525Gold

Copper

Leaching

SulfideLiberation

GravitySeparation

CycloneEfficiency

Flotation

HPGR HPGR –– Potential Improvement Potential Improvement of Operating Parametersof Operating Parameters

Increase or

Reduction(%)

Increase or

Reduction(%)

8080

6060

4040

2020

00

100100

Capacity

Power SteelWear

Bond WI

+

- -

-

PolycomPolycom HPGR at Anglo HPGR at Anglo Platinum PPLPlatinum PPL

Treating Platreef Ore

P90 - 6 mm

Big QuestionsBig Questions

Are we witnessing a step-change improvement in comminution? Is this a milestone in mineral processing history?

Big QuestionsBig Questions

Are we witnessing a step-change improvement? Is this a milestone in mineral processing history?Ore-specific - Is HPGR applicable for your ore? …for your location?

Big QuestionsBig Questions

Are we witnessing a step-change improvement? Is this a milestone in mineral processing history?Ore-specific - Is HPGR applicable for your ore? ….for your location?Operational availability & wear rates, and hence operating cost?

Big CautionBig Caution

The monkeys are now out of the cage, and there’s no getting them back in…Avoid rushing in too fast with inadequate testing and ending up with a misapplication.

Enjoy the RideEnjoy the Ride…………..