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ENERGY EFFICIENCIES FROM CONCENTRATEREGRIND in an ISAMILL™
Anglo Base Metals
Procemin Mineral Processing Conference
October 2008
Cecilia Arrué and Leonardo Soto
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Las Tórtolas Cu and Mo Concentrator
• Part of the Los Bronces Division and wholly owned by AngloAmerican Chile
• During 2007, the entire Los Bronces Division produced231,216 tons of Cu, 182,894 ton as concentrates, 46,420 tonas cathodes and 1 903 ton as sul hates lus 2 582 ton fine
Anglo Base Metals
Mo.
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Flowsheet
Rougher and ScavengerConcentrate Regrind
Anglo Base Metals
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Test Objectives
• Evaluate the energy savings and enhanced flotationcharacteristics from regrinding in an IsaMill.
• Of particular interest was regrinding the concentrate whenthe plant was treating a higher amount of a harder orecalled Donoso Este. – Chalcopyrite finely dissimilated. Increased liberation is needed.
Anglo Base Metals
– This ore is expected to constitute a greater portion of the plant’sfeed in the near future. Extra grinding capacity is required.
• Earlier studies: Donoso Este ore, theconcentrate would need to be ground
to a P80 of 30 µm at a minimumenergy requirement of 42.9 kWh/t.
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IsaMill™
Impeller pumps liquid back into
chamber to retain media
Shaft rotating at highspeeds generating disc tip
speeds ~ 20 m/s
DisplacementBody
Multiple stages of grinding
GrindingDisks
GRINDING MECHANISM & MEDIA RETENTION
Impeller pumps liquid back into
chamber to retain media
Shaft rotating at highspeeds generating disc tip
speeds ~ 20 m/s
DisplacementBody
Multiple stages of grinding
GrindingDisks
GRINDING MECHANISM & MEDIA RETENTION
Anglo Base Metals
Recirculating grinding patterns of mediaoccur between disks due to variation invelocity profile across disks
Media centrifuged to outside of grindingchamber by high centrifugal forcegenerated inside mill
Rotor
Productexit
GrindingChamberShaft
PATENTEDPRODUCT
SEPARATOR
CLASSIFICATION ZONE
Recirculating grinding patterns of mediaoccur between disks due to variation invelocity profile across disks
Media centrifuged to outside of grindingchamber by high centrifugal forcegenerated inside mill
Rotor
Productexit
GrindingChamberShaft
PATENTEDPRODUCT
SEPARATOR
CLASSIFICATION ZONE
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Methodology
• The tests were conducted using a M20 IsaMill pilot unit in accordancewith Xstrata Technology’s standard signature plot procedures.
• These proven procedures allow for direct scale up data for large scaleinstallations.
• Signature plot tests areessentially a batch type testwhere slurr is assed throu h
Anglo Base Metals
the mill in 4 to 5 successivestages.
• Used 3.5 mm MT1 ceramicmedia. Fine media key toIsaMill™’s energy efficiency.
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Results
Gross Specific Energy vs Product Size
100
g y ( k W h / t )
Upper Range Limit
Lower Range Limit
29 kWh/t
Ball Mill (Minimum) = 42.9 kWh/t
Anglo Base Metals
1
10
10 100
Product Size (µm)
G r o s s S p e c i f i c E n
e r
Test 5
Test 8
Test 12
Test 9
Test 10
Ball Mill - minimum
30
17 kWh/t
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Effect on Flotation
20,0
25,0
30,0
35,0
40,0
r a d e ,
%
Anglo Base Metals
0,0
5,0
10,0
15,0
0% 10% 20% 30% 40% 50% 60% 70% 80%
Cu Rec, %
C u
Standard
Isamill - T8
Isamill - T9
• Samples were floated several weeks after grinding and therefore the particlesurface may have been oxidized
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Operating Cost Estimates
Anglo Base Metals
Operating Expenses for Forecasted Energy Prices
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Conclusions
• Testwork results demonstrate that the IsaMill can processthe rougher-scavenger concentrate achieving the desiredP80.
• The IsaMill was found to offer advantages in energyefficiency even when:
Anglo Base Metals
– Assuming the higher energy requirements found in the measuredrange. – Preliminary estimates for the alternatives is significantly
underestimated.
• When using the IsaMill to regrind down to a P80 of 25 µm,an increase in final concentrate grade was observed (from18% to 31% Cu) in the preliminary flotation tests, with nomajor impact on Cu or Mo recovery.
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Conclusions
• An IsaMill at Las Tórtolas would be operated in opencircuit thus eliminating the recirculating load and simplifythe flowsheet. Pre-cyclones or thickeners would beconsidered only to increase the IsaMill feed density.
• Despite the higher purchase price for ceramic media than
Anglo Base Metals
that of steel, IsaMills offer reduced total operating costsbecause of more efficient milling and lower mediaconsumption.
• Not the complete picture – more work should be carriedout to further demonstrate the benefits of regrinding in anIsaMill.
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Advancements in the field of ConcentrateRegrind in an IsaMill™
• Continuous operation.- Confirm grinding media consumption and/or optimal type and size.
- Test different ore types (to have a complete idea of energy savings)
• Analysis of energy requirements for different plant feed.
Anglo Base Metals
• Further analysis of a narrow size distribution and inertgrinding media on cleaner flotation.
• A more detailed comparison of the IsaMill™ performance toother technology types. – High confidence head-to-head tests?
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ISAMILL™
Anglo Base Metals