Recent International Concentrator Start-ups Do’s and Don’ts for Effective Grinding Mill Design

1. Recent International Concentrator Start-ups Do’s and Don’ts for Effective Grinding Mill Design Minerals Engineering International Comminution 2012 Conference Cape Town, SA April 17, 2012 John Starkey1, Paul Scinto1 and David Meadows2 1 Starkey & Associates Inc. 2 FLSmidth Salt Lake City Inc. Oakville, ON, Canada Midvale, Utah, USA

2. INTRODUCTION 2 • Accurate mill design is goal (t/h, grind) • 40 ft dia mills - all eggs in one basket • Meeting financial goals = design • What works and what does not for design • Base design on client’s ore • Use proven technology • Step back to use 1st principles that you understand • Don’t rely only on proprietary methods • At least 2 SAG mill design methods is the norm today • A quick look at some recent start-ups from SAG 2011 • For IMPC 2012 in New Delhi – TOMS presentation

3. Summary - International Start-ups Consider five selected plants – not all chosen Not easy to find evidence relating method to performance 3

4. PROJECTS – Grind size and results 4 Papers written to describe operation – design info limited Proprietary designs cannot be fully documented Every property used a different method Consensus – 2 methods focusing on ore to be treated We need education – more publication of design experience

5. PROJECTS - Mill sizes and design capacity 5 First three plants achieved tonnage and grind Phu Kam well conceived – will add a BM when 2 kt/h needed Gibraltar made good use of operating data to design SAG Single stage SAG mill achieved t/h but not grind Hard ore not allowed for at Damang = < 50% of t/h Should never take 7 months to achieve design production Look at what happens when SAG is undersized

6. DISCUSSION – Testing and Design 6 Understand deposit – team Spacial separation vs depth Spend required $ Do many small scale tests – (historical) SMC, JKDWT no composites. SAGDesign yes Don’t design SAG mill on Bond Wi Measure Bond Wi at liberation size Power split SAG vs BM – Is it defendable? Define grind vs metal recovery early Availability in NA 92% < 94%

7. DISCUSSION – Engineering, Operation and Start-up 7 • Accurate result in 3 months = good value • Don’t let commercial override technical • Consider logistics in selecting technology • BMk size vs power. High SG, steel & RPM = +kW • Check motor size – speed, charge, ore SG, liners • BMk review to compare with similar plants • Understand F:F and EGL • Consider all ancillary equipment • Keep layout simple and workable • Start manual control – add expert system

8. CONCLUSIONS 8 Not all plants from SAG 2011 included 3 plants OK, 1 not easy to expand, 1 made t/h not grind Reasons unclear. Lack of data, understanding of SAG, agreement between methods, robust design did not happen Lack of power to treat harder ores = problem Single stage SAG easy to expand by adding a ball mill SAG limited ores require large SAG for expansion Always study lessons learned after a similar plant is running Proprietary methods are not taught in universities - education New methods are emerging that are better No reason to change procedure from SAG 2011

9. Future start-ups – make yours a good one! Thank you! 9