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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
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
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
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
Overview - Feed Materials -Overview Overview -- Feed Materials Feed Materials --
High Pressure Grinding Rolls
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
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
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.01 0.1 1 10 100
Particle size [µm]
Fine
ness
% p
assi
ng [%
]HPGR products
Cone crusherproducts
Feed material
Idea: Liberation of Industrial Idea: Liberation of Industrial MineralsMinerals
Hard rock rutile, zircon and/or garnet?Liberation of tantalite?Recovery of phosphate rock
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
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
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
50
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
0
10
20
30
40
50
60
70
80
90
100
0 ,010 0 ,100 1 ,000 10 ,000 100 ,000
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
100
80
60
40
20
00 10 20 30 40 50 60 70
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
80
60
40
20
0
Frac
ture
d Fr
actu
red
Par
ticl
es (
Vol
. %)
Par
ticl
es (
Vol
. %)
100
80
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?
HPGRAsking to be tested…..e.g. Bio-heap oxidation
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
+
- -
-
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.