Geometallurgy vs

Project Development

Derek Barratt, P. Eng.Mineral Process Consultant

DJB Consultants, Inc.(Assisted by Ms. Mariela Zuñiga-S., EIT)

Vancouver, B.C.Canada

• Formula HistoryFormula History• Millpower 2000 – Concept & UseMillpower 2000 – Concept & Use• Geometallurgy & Testwork Geometallurgy & Testwork • ExamplesExamples• Where to Select Grindability SamplesWhere to Select Grindability Samples• HPGR & Phantom CycloneHPGR & Phantom Cyclone• Mine-to-MillMine-to-Mill• Aspects for DesignAspects for Design• ConclusionConclusion

Overview

Where to Select Grindability Samples

• Where in an orebody:– Data gathering

• Where in a drill hole:– Preliminary Interpretation,– Field Examination

• Properly selected sample gives meaning interpretation• Collaboration with the geologists

– Direct communication & participation• Representative of the variability• Open mind = Open mines

Where to Select Grindability Samples

Where in an Orebody

Data Analysis:• Goal – produce a set of representative data• Identify important lithology and alteration• Drill length should intercept pit envelope or above

cut-off grade• Place drill doles to cover zones of lithology and

alteration• Space drill holes w.r.t. size of resource

Where in an Orebody

Where in an Orebody

Where in an Orebody

• Zone– Sapolite, supergene, transitional, primary, hypogene...

• Lithology• Alteration

– Types and intensity• Mineralization

– Massive, disseminated sulphides and oxides...• Geotechnical Data

– Core recovery, RQD, PLI, fracture frequemcy, R-value hardness...

• Weathering

Where in a Drill Hole

Preliminary Interpretation - Selection of sample intervals:• Determine interval length

– Based on grinding tests, SG, drill diameter...• Consistency in rock characteristics within an

interval– Avoid producing biased, skewed, masked results

• Can mix (leave out) short intervals with different characteristics because of insufficient mass.

Where in a Drill Hole

Field Examination:• Confirm geological &

geotechnical logs• Use a geological hammer• Observe lithology,

alteration (type & intensity), grain size, particle size, texture, fault, dykes, filling, colour, RQD, and other distinct physical features

Where in a Drill Hole• Tap the core• Scratch the surface• Test with a magnet• Record the observations• Confirm sample intervals• Collect sample

Sample Quantity

Conceptual Pre-Feasibility Feasibility BFS Basic Engineering

Mine Years for Payback 5 5 5 5

No. of Mine Weeks - - 250 -

No. of Mine Months 60 - - -

No. of Samples 60 100 250 375 - 500

Comminution StudiesRequired Number of Geometallurgical Samples

DJB Projects – Program Size

Remarks on Selecting Grindability Samples

• Know the orebody and the samples that you will be collecting

• Achieve representative samples that capture variability & grinding behaviours

• Minimize risk, increase confidence level, & reduce contingency consistent with levels of design

Overview

• Formula HistoryFormula History• Millpower 2000 – Concept & UseMillpower 2000 – Concept & Use• Geometallurgy & Testwork Geometallurgy & Testwork • ExamplesExamples• Where to Select Grindability SamplesWhere to Select Grindability Samples• HPGR & Phantom CycloneHPGR & Phantom Cyclone• Mine-to-MillMine-to-Mill• Aspects for DesignAspects for Design• ConclusionConclusion

“Mine-to-Mill”

“Mine-to-Mill”

“Mine-to-Mill”

• Regularly scheduled meetings:– Geologists– Mine Planning– Metallurgists– Concentrator operation management

• Focus: to maximize (optimize) mill throughput• Daily to weekly

“Mine-to-Mill”

• Criteria to be reviewed:– Blasting practice:

• Bench location• Bench width and height• Drill holes spacing• Powder factor• Timing (delays)• Stemming types

“Mine-to-Mill”

• Criteria to be reviewed:– Rock strength:

• Point load index (PLI)• Hardness value (R-

value)• Unconfined compressive

strength (UCS)• Fracture frequency and

competency

– Influenced by:• Lithology• Type of alteration• Degree of alteration• Grain size• Variation of ambient

temperature

“Mine-to-Mill”

• Size analysis of mill feed:– Secondary blasting– Effect of blast on mid-sized material (30 mm to 100 mm)– Proportion of fines (-30 mm)– Primary crushing practice:

• Dump through at coarse Open Slide Set (OSS)• Choke feed at nominal OSS

– Segregation in coarse ore stockpile– Mill operator control practice– Automatic measurement (WIPFRAG, Split)

“Mine-to-Mill”

“Mine-to-Mill”

• Prediction of mill feed rate:– Specific power consumption for whole comminution

circuit– Discern AG/SAG mill limiting– Discern ball mill limiting– Discern necessary for pebble crushing– Power efficient mills

“Mine-to-Mill”

• Criteria for power efficiency:– Ultimate power

capability– Maximum ball charge

volume– Total mill charge

volume– Mill speed range– Grate open area– Grate aperture

– Pebble crushing– Circulating load– Classification system– Hydraulic gradient– Minimizing slurry

pooling– Operating power level

“Mine-to-Mill”

Bench Marking Power

0 50 100 150 200 250 3000

5

10

15

20

25

30

Large Mill Power34' 36' 38' 40' 42+

MW

20% balls

Upgraded Freeport mill

Upgraded Pelambres mill

First 42' mill

D2.5×EGL1000

First two 40' mills were underpowered

Mill Selection – Case Study:Liners

• Worn (75 mm) • New (150 mm)

Based on change in mill volume, does not consider charge motion

Conclusions

• Process risk can be minimized by a thorough understanding of:– Project geology and geotechnical parameters throughout

mineable resource– A “mine-to-mill” approach in operation– Comminution testwork by bench-scale, pilot-scale or

combination of both– Ore variability, range of specific power consumption and

power-sharing between primary and secondary grinding for the foreseeable life-of-mine and potential planned expansion

Conclusions (cont'd)

– Application of known engineering and manufacturing procedures and practices with respect to ensuring structural integrity and operability of both the mill and the motor at the most economical cost

– Third party review of engineering by mill supplier, motor supplier, and engineer-of-record

• SAG circuits with(out) secondary grinding can be designed confidently without pilot plant testwork using power-based models supported by breakage rate models and bench-scale testwork:

• KW (net) = PN * ρ * D2.5 * L

Empirical Formula (Barratt)

Overall Power Requirement, ASAG Circuit (1979)

Empirical Formula (Barratt)

Modified power requirement based on El Teniente Surveys (1986)

With a Bond Work index-based Phantom Cyclone Approach (1989)*ESSBM for secondary/tertiary crushing and single-stage ball milling (Rowland, 1982)

• An evaluation of project geology• Definition of ore zones, ore types and rock types• Definition of variations in ore types and rock types with

depth• Definition of zones of alteration and type(s) of alteration • Definition of zones of weathering• Definition of zones of oxidation, e.g., copper oxides;

supergenes, secondary sulphides; hypogenes, primary sulphides

• Definition of a preliminary mining plan

Factors Influencing Selection of Samples

Factors Influencing Process Design Criteria

Some Useful Definitions

• Impact Grinding: Crushing of ore particles by direct hits with other ore particles, steel balls, or mill lining

• Abrasion Grinding: Frictional contact between ore particles, steel media, or mill lining

• Attrition Grinding: Nipping of ore particles between larger ore particles, steel media, or mill lining

• Critical Size: Accumulation of a size range, usually 12mm-50mm which cannot be crushed by large ore particles or steel media

Diamond Core Drilling

• Selective coverage• Obtained by large dia. Core, trenching, pitting, ripping,

blasting an exposed face (pit or U/G), primary crushed ore from a stockpile

• Used for pilot testing comminution and metallurgical process, confirmatory test

• Avoid effects of over-blasting or crushing too fine on testwork results

• Limitation: time schedule for U/G access and development vs. alternative and better coverage with PQ core

• Relative cost: moderate to high for feasibility and basic engineering

Bulk Samples

Additional Considerations

• Individual samples vs. compositing• Compositing for large-scale testing• Consider tests on selected intervals of core, both for

individual drill holes and compositing to reflect vertical distance by time in mine production plan

• Compositing for pay-back and planned plant expansions

• Repeat tests vs. storage and protection against oxidation refrigeration; cleanliness: contaminants

• Water source and quality at site, effect on test results• Climate, hot desert vs. permafrost

Comminution Tests

• Bond work indices:– WiC, WiRM, WiBM into a

power model– Empirical based on plant

surveys– Good for mill sizing and

power determination,kW (net) = PN * ρ * D2.5 & EGL

– Limitations in assessing effects of pre-crushing and circulating loads

– Shows importance of WiRM on AG/SAG mill power

– Permits shift of power onto secondary grinding from primary milling when pebble crushing

– Can be used in geometallurgical assessment of ore blocks in mine models (HQ/PQ core)

– Uses identified contiguous core intervals as sample source

Ore Characterization – Batch Scale Tests and Mill Sizing

Ore Characterization – Batch Scale Tests

Ore Characterization – Batch Scale Tests

Benchmarking – DJB & SPI Models

DJB Executed Projects

Ore Characterization – Bulk Sample Tests

End of Presentation