Scavenging Flotation Tailings using a Continuous Centrifugal Gravity Concentrator Hassan Ghaffari, Bern Klein UBC Mining Ish Grewal, Knelson Gravity Solutions

Continuous Centrifugal Gravity Concentrators Kelsey Jig Falcon Model C Knelson CVD

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 CVD42-1 70 – 100

CVD Applications Industrial Applications Density separator 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

Flotation Recovery versus Particle 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 Cyclone O/F Conc. Feed 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 P80 (µm) Au Ag +100 mesh Fraction +150 mesh Fraction (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 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

Au Grade versus Particle Size in CVD Concentrate and Tailing

S Grade versus Particle Size in CVD Concentrate and Tailing

Au Grade/Recovery versus Mass Yield

Size Partition to CVD Conc.

Eskay Creek Plant Trials Thickened flotation tailings 26 Trials

Eskay Creek Plant Trials

Eskay Creek Plant Trials

Eskay Creek – Plant Trial Flotation of CVD Concentrate

Proposed Hybrid Flotation / Gravity Flowsheet Feed Cyclone O/F Tailings Ball Mill Hydrocyclone Flotation Conc. Batch Knelsone Knelson CVD Conc. Gemini Table Tailing Conc. Smelter

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

Barrick Eskay Creek Mine Knelson Gravity Solutions NSERC IPS Thank You Acknowledgements Barrick Eskay Creek Mine Knelson Gravity Solutions NSERC IPS