Scavenging Flotation Tailings using a Continuous Centrifugal Gravity

Concentrator

Hassan Ghaffari, Bern KleinUBC MiningIsh Grewal, Knelson Gravity Solutions

Kelsey Jig Falcon Model C Knelson CVD

Continuous Centrifugal Gravity Concentrators

CVD Concentrator

•Operating Variable•Bowl speed•Fluidization water•Pinch valve open time•Pinch valve closed time•Variable interactions

Model Feed Rate (t/h)

CVD6-1 0.5 – 2

CVD32-1 40 – 70

CVD32-2 40 – 70

CVD42-1 70 – 100

CVD Applications

• Industrial Applications– Separation of iron oxides from talc– Cassiterite– Chromite – Gold and gold bearing sulfides

• Tested Application– Scavenging rougher flotation tailings– Scavenging cleaner flotation tailings– Separation of ash and sulfur from

coal

•Density separator

•Size classifier

•Mass yields (1 to 40%)

•De-slime

FlotationRecovery versus Particle Size

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Particle Size (um)

Rec

over

y (%

)

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trib

utio

n (%

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Recovery

Particle Size

Preferred Size

Scavenging Flotation Tailings• CVD - Size enhanced density separator

• Recover coarse middling particles from tailings in small mass yield (<5%)– Recycle CVD concentrate to grinding circuit– Reduce losses at coarse end of particle size distribution– Improve overall metal recovery

• Potential opportunity– Increase grind size– Reduce losses at fine end of particle size distribution– Increase grinding circuit throughput– Reduce energy requirements

• Effectively produce narrower size distribution of liberated sulfide minerals in particle size range where flotation is most efficient

Eskay Creek Mine

• Au/Ag Mine

• Flotation of bulk sulfide concentrate grading 100 g/t Aueq

Eskay Creek Mine Flotation Circuit

Ball Mill Hydrocyclone Flotation

Knelson

Gemini Table

Smelter

CycloneO/F

Conc.

Feed

Conc.

Conc.

Tailing

• Au/Ag Flotation recoveries average 90%

• Variations in ore mineralogy affect recoveries

Pilot Scale Testing-Lab testing-Plant testing

UBC Center for Mineral Processing

Sample Characterization

SampleP80

(µm)

Au Ag+100 mesh

Fraction+150 mesh Fraction

(ppm) (ppm) Weight % Au Distrib. %S Distrib.

%

LGT 130 1.9 48.3 9.3 27.9 20.6

HGT 100 3.2 39.0 5.3 10.6 10.7

Batch Knelson Tests

Sample Mass Yield % Au (ppm) Au Recovery %

LGT 5.0 5.1 20.0

HGT 4.0 3.9 8.8

Lab Pilot Scale Tests Results - LGT

Test Au (ppm) Au Recov % Upgrade Ratio Mass Yield %

1 6.31 5.5 5.95 0.93

2 4.46 6.5 3.88 1.67

3 12.51 28.4 8.67 3.27

4 3.66 14.7 3.33 4.43

5 5.60 35 4.52 7.74

6 4.36 15.3 1.64 9.32

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Size Class (mesh)

Au

Gra

de

(pp

m) Concentrate Tailing

Au Grade versus Particle Size in CVD Concentrate and Tailing

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Size Class (mesh)

S G

rad

e %

ConcentrateTailing

S Grade versus Particle Size in CVD Concentrate and Tailing

Au Grade/Recovery versus Mass Yield

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Mass Yield %

Au

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012345678910

Au

Upg

rade

Rat

io

Au Recovery % Au Upgrade Ratio

Size Partition to CVD Conc.

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Size (µm)

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rtit

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mb

er

%

Test 3 Test 6

Eskay Creek Plant Trials• Thickened flotation tailings• 26 Trials

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CVD Masspull (%)

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ld E

q R

eco

very

(%

)

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CVD Masspull (%)

Co

nc.

Au

Eq

(g

/t)

Eskay Creek Plant Trials

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425300212150106755338-38

Particle Size (um)

Au

(g

/t)

CVD Conc

CVD Tails

Eskay Creek Plant Trials

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425300212150106755338-38

Particle Size (um)

Ag

(g

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CVD Conc

CVD Tails

Eskay Creek – Plant Trial• Flotation of CVD Concentrate

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Flot. Conc. Mass Yield (%)

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g/t

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Gold Grade.

Gold Rec.

TailingsBall Mill Hydrocyclone Flotation

Batch Knelsone

Gemini Table

Smelter

CycloneO/F

Conc.

Feed

Conc.

Conc.

Proposed Hybrid Flotation / Gravity Flowsheet

KnelsonCVD

Tailing

CONCLUSIONS & RECOMMENDATIONS

• Pilot scale testing indicated that the CVD was effective at recovering metals from flotation tailings.

• The results indicated that the metal recovered was primarily in the coarse size fractions, which would likely contain middling particles (sulfide + silicates) ie size enhanced density separation.

• Flotation of the reground gravity concentrate yielded good grades and recoveries.

CONCLUSIONS & RECOMMENDATIONS

• Continuous Centrifugal Gravity Concentrators may have a role in hybrid flotation gravity circuits that exploit the strengths of each technology

•

• The next step is to assess the potential for increasing grind size to reduce losses in ultrafine fraction, reduce energy requirements and increase throughput

• Thank You

• Acknowledgements– Barrick Eskay Creek Mine– Knelson Gravity Solutions

– NSERC IPS