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LONMIN AND UG2 Presentation to the MMMA President’s Technical Seminar JJ Steyn 20 May 2011.

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Presentation on theme: "LONMIN AND UG2 Presentation to the MMMA President’s Technical Seminar JJ Steyn 20 May 2011."— Presentation transcript:

1 LONMIN AND UG2 Presentation to the MMMA President’s Technical Seminar JJ Steyn 20 May 2011

2 PRESENTATION CONTENT Background UG2 Challenges Processing of UG2 Types of UG2 Lonmin Results on UG2 Conclusions

3 BACKGROUND Lonmin’s typical production profile: Merensky OreUG2 Ore Lonmin Production (%)2080 PGM Grade (g/t)3.505.00 Cr 2 O 3 Grade (%)125 Cu/Ni Grade (%)0.250.1 SG3.13.8

4 BACKGROUND Advantages of UG2 vs. Merensky More PGM’s per ton (head grade) More tons per meter advanced (SG) Disadvantages of UG2 ore vs. Merensky UG2 reef deeper than Merensky Less Cu/Ni per ton More Cr 2 O 3 per ton

5 UG2 CHALLENGES Smelter Constraints: Total Cr2O3 in concentrate < 2.2% Total Cu/Ni in concentrate > 3.8% UG2 Mineralogy – PGM’s associated with: Base metal sulphides (±30  m BMS grains) Locked in siliceous minerals (±5  m PGM grains) On gangue and BMS grain boundaries Classification: Density difference between chromite and silica host Reverse classification

6 UG2 ORE PROCESSING Material report to flotation conc. via two mechanisms True flotation (dependant on particle surface properties) Entrainment (dependent on particle size and density) True Flotation: PGM BMS Floatable gangue Entrainment: Chromite Non-floatable siliceous gangue

7 THE UG2 DILEMMA… Needs fine grinding to liberate PGM’s 5  m PGM’s are locked in gangue Chromite entrains at fine grinds Fine particles don’t float well Reduced chance of particle-bubble collision Reduced chance of particle-bubble attachment Increased chance of particle detachment Gangue surface coatings more detrimental for fines The result – complicated circuits and innovative designs

8 ACHIEVING A FINE GRIND Installed Power Merensky Plant - ± 14 kWh/ton Karee B & K4 - ± 28 kWh/ton Dedicated coarse and fine mills Cleaner circuit milling

9 MINIMISE CHROMITE ENTRAINMENT Don’t over-grind chromite! Two-stage flotation - float as coarse as possible in primary rougher Reverse classification in hydrocyclone Cyclone classifies on mass Chromite is a lot denser than siliceous minerals Results in fine chromite in cyclone underflow Results in coarse siliceous minerals in cyclone overflow Solution – mills in open circuit

10 UG2 MILLING CIRCUITS Primary MillSecondary Mill Flotation ROM Flotation Prim Tails Flotation

11 FINES FLOTATION Increase particle-bubble collisions Frother – finer bubbles High energy cells – finer bubbles Increase chance of particle-bubble attachment High energy cells – particle momentum Decrease chance of particle detachment Shallow froths Clean surfaces Dispersant Separate cleaning circuits for fast and slow floating material MINTEK PROCESS

12 MINTEK PROCESS – CLEANING CIRCUIT First recover fast floating particles – High Grade Then focus on slow floating particles – Low Grade High depressant dosages High frother dosage Shallow levels These conditions also favour water recovery Thus higher entrainment and chrome recoveries Running on the edge!

13 EPC FLOW SHEET To Secondary Mill Secondary Mill Primary Mill Primary Roughers Secondary Roughers Primary Cleaners (3 Stage) Secondary Cleaners (2 stage) ISA Mill Final Tails To Secondary Cleaners

14 DIFFERENCE TYPES OF LONMIN UG2 Western UG2 (Karee, Western Platinum) Eastern UG2 (Eastern Platinum) Split Reef (WPL) IRUP (WPL) Mechanised Ore (mostly EPL)

15 BASIC MINERALOGY OF LONMIN UG2 WPLEPLSplitIRUPMech BMS347231610 BMS-Gan3619402722 Lock-Gan1963264658 PGM Sul94733 Lock-Cr27487 100 Met343245

16 PERFORMANCE OF LONMIN UG2 WPLEPLSplitIRUPMech Head Grade (g/t) Mass Pull (%) 1.1 Recovery (%)9086 8380 Conc Grade (g/t)470520270310330 Cleaner Tails (g/t)

17 CONCLUSIONS UG2 needs fine grind for valuable recovery Lots of power Two stage milling Cr 2 O 3 is recovered at fine grinds Open circuit milling Fines recovery Mintek process

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