Scavenging Flotation Tailings using a Continuous Centrifugal Gravity Concentrator

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

2. Knelson CVD Kelsey Jig Falcon Model C Continuous Centrifugal Gravity Concentrators

3. CVD Concentrator • Operating Variable • Bowl speed • Fluidization water • Pinch valve open time • Pinch valve closed time • Variable interactions

4. 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

5. FlotationRecovery versus Particle Size

6. 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

7. Eskay Creek Mine • Au/Ag Mine • Flotation of bulk sulfide concentrate grading 100 g/t Aueq

8. Feed Cyclone O/F Ball Mill Hydrocyclone Flotation Tailing Conc. Knelson Conc. Gemini Table Conc. Smelter Eskay Creek Mine Flotation Circuit • Au/Ag Flotation recoveries average 90% • Variations in ore mineralogy affect recoveries

9. Pilot Scale Testing • Lab testing • Plant testing UBC Center for Mineral Processing

10. Sample Characterization

11. Batch Knelson Tests

12. Lab Pilot Scale Tests Results - LGT

13. Au Grade versus Particle Size in CVD Concentrate and Tailing

14. S Grade versus Particle Size in CVD Concentrate and Tailing

15. Au Grade/Recovery versus Mass Yield

16. Size Partition to CVD Conc.

17. Eskay Creek Plant Trials • Thickened flotation tailings • 26 Trials

18. Eskay Creek Plant Trials

19. Eskay Creek Plant Trials

20. Eskay Creek – Plant Trial • Flotation of CVD Concentrate

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

22. 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.

23. 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

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