1. By John Wates and Michael Knight Fraser Alexander An evaluation of cyclone performance to improve the quality of cyclone underflow material for tailings disposal

2. Use of cyclones for tailings? Self raising configuration Downstream Centreline Upstream Location of cyclones Off wall cyclones trucked into place Off wall cyclones pumped into place On wall cyclones UnderflowOverflow SUITABLE FOR COARSE TAILINGS

7. The problem Split not achieved Geometry Non compliance Tried! Split increase Specs not achieved Stacking not achieved Non compliance

9. Cyclone theory Inputs PSD Solids concentration Rheology Parameters influencing underflow properties (PSD & W/C) Diameter Vortex finder Spigot size Pressure/vacuum Operation

10. Why are underflow properties important? Shear strength 15% passing 75 micron/200 mesh Liquefaction potential (Drainage, PSD and Compaction) Permeability contrast (k uf > 100 x k of ) Geometry Stacking Split to underflow UnderflowOverflow

11. Permeability contrast (k uf > 100 x k of ) Permeability related to (D 10 ) 2 Efficiency of cut at 75 micron determines split Percent passing 75 micron can be increased to increase split Up to 30% passing 75 micron tested in this case

12. Stacking and split Stacking is function of yield stress and flow rate 15% passing 75 micron target 30% passing 75 micron also tested Alternative flow distribution methods tested Split Pressure Feed solids concentration Feed grading

13. What we investigated Spigot/vortex finder combinations Pressure Barrel extension Pressurization Split

14. Test configurations

26. Conclusions There is an optimum vortex finder and spigot size 135/65 Feed pressure of 180 kPa is the optimum Barrel extensions and pressurization improve split Splitting u/f discharge improves stacking (1:6 to 1:5) Stacking angle improves with increasing u/f RD and as % passing 75 micron increases (1:5 for 10% passing 1:50 for >25% passing) Split decreases as u/f RD increases and % passing 75 micron decreases

28. Opportunities Improved efficiency and control in split Refinement of underflow criteria Handling finer tailings Higher rates of rise for finer tailings Reducing water consumption

29. Acknowledgements Co-author Michael Knight DRD Anglo Gold Ashanti The Fraser Alexander team