The Increased Recovery Project at the Phu Kham Copper-Gold Operation, Laos PDR. Authors: A Hoyle, D Bennett, and P Walker

Transcription

1 The Increased Recovery Project at the Phu Kham Copper-Gold Operation, Laos PDR Authors: A Hoyle, D Bennett, and P Walker

2 IRP Presentation Summary 1. Phu Kham mineralogy and implications for process design 2. Process development to Grade-recovery improvement studies leading to the IRP 4. IRP design and engineering 5. IRP implementation and results

3 Phu Kham Operation - Laos Nam Ve Phu Nam Wan Pha Lek

4 Geology with Process Design Implications Extreme variability in rock type, alteration, weathering, and mineralogy across short distances Wide range of copper minerals native, oxides, secondary/arsenic sulphides in transition/supergene zones and bornite/chalcopyrite in primary zones Areas of high sphalerite, galena, pyrophyllite and kaolinite Wide chalcopyrite particle size range, insensitive to grind size Up to 25 times more pyrite than copper sulphide mineral in feed, and secondary copper mineral intergrowth with pyrite

5 Original Process Design Implications Bulk sulphide rougher flotation high recoveries in laboratory but concentrate specifications not achieved even for transition and supergene ore types Selective rougher flotation for pyrite depression resulted in poor recovery of slow-floating copper minerals and composites Original concentrator was a capital efficient, low-risk compromise

6 Original 12Mtpa Process Design 2008 GYRATORY CRUSHER SAG MILL MILL CYCLONES COARSE ORE STOCKPILE BALL MILL ROUGHER FLOTATION CELLS ROUGHER CYCLONES 1st CLEANER FLOTATION CELLS TAILINGS DAM ISAMILL 2nd CLEANER FLOTATION CELLS THICKENER 3rd CLEANER FLOTATION CELLS TANK FILTER STOCKPILE

7 Process Development - Incremental 2009 Conversion of conditioning tanks to flotation cells in roughers and 1 st cleaners FloatForce mechanisms installation in roughers, completed Tenth 200m³ rougher cell installed Jameson Cell installed in cleaner scalping duty

8 Process Development 2012 Upgrade MILL CYCLONES GYRATORY SAG MILL No.1 BALL MILL COARSE ORE STOCKPILE NEW MILL CYCLONES NEW No.2 BALL MILL NEW CYCLONE OVERFLOW TANK NEW ROUGHER FLOTATION CELLS ROUGHER FLOTATION CELLS ROUGHER CYCLONES 1st CLEANER FLOTATION CELLS TAILINGS DAM PROCESS WATER ISAMILL 2nd CLEANER FLOTATION CELLS JAMESON CELL Designed to maintain copper production with decreasing ore grade expected from 2013 NEW 3rd CLEANER FLOTATION CELLS Upgrade design to nominal 16Mtpa throughput, maximum 18Mtpa Major bottlenecks eliminated in ball milling, rougher flotation and 2 nd cleaner capacities THICKENER TANK FILTER STOCKPILE

9 Copper and Gold Recovery - Stalled Increased metal production capacity is not the same as increased recovery 100.0% 90.0% 80.0% 70.0% Recovery % 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% Copper Gold

10 Grade-Recovery Improvement Projects Commenced study in 2010 with process development work on Phu Kham tailings streams to increase copper recovery Monthly plant composites mineralogy data collected since 2008 provided critical information on copper deportment in tailings Reviewed geology and petrology information for clues on gold occurrence ADIS, diagnostic leaching, and laser ablation work conducted on plant samples for gold deportment in tailings

11 Copper Deportment in Tailings 45.0% % Copper Sulphide Loss by Size and Class 40.0% 35.0% 30.0% 25.0% 20.0% 15.0% 10.0% 5.0% 0.0% >106µm <106>53µm <53>33µm <33>16µm <16>12µm <12µm Liberated Copper Sulphide Binary with Pyrite Binary with Non-Sulphide Gangue Multiphase

12 Gold Deportment in Tailings Gold Loss to Tailings by Association Class Liberated Au Au-Copper Sulphide Au-Pyrite 30% 0% 90% Gn Ma He Py Py Cp Gn Au Area:192µm 2 Py Area:76µm 2 Au Py Gn Cp Area:5787µm 2 Au Py Unliberated: Locked in pyrite Composite with coarse pyrite Liberated: Too fat to float Fine gold due to high lime environment for pyrite depression Gn Area:38µm 2 Au

13 The Pilot Plant Tailings retreatment process developed by 2011 could increase copper recovery by 15% and gold recovery by 25% with Albion process 1.5tph M20 IsaMill and flotation pilot plant to make Albion leach feed Capital cost update received during pilot for tailings flotation and hydrometallurgical plants a lot higher than previous estimates Change of pilot plant focus to test a less selective rougher flotation concept encouraging results

14 Mineral Processing Alternatives Mainstream Inert Grinding Classification of rougher tailings stream -53µm fraction discharge to final tailings Regrind +53µm fraction to P80 53µm Scavenger flotation, tailings to final tailings, concentrate return to combine with rougher concentrate Particle size based mass balance, very predictable Approximately 7% additional copper and gold recovery achieved in bench tests Very high grinding energy requirement and capital cost Less Selective Flotation Become less selective in rougher flotation, increase rougher mass recovery Finer regrind due to lower quality composites in rougher concentrate Increase first cleaner capacity Mineralogy and liberation based mass balance, difficult to predict Risk of flooding cleaning with pyrite Approximately 7% additional copper and gold recovery achieved in bench and pilot tests Low capital and operating costs

15 Less Selective Flotation Work at bench and pilot scale indicated that lean Cs-NSG composites could be recovered into rougher concentrate, with finer regrind to achieve 80%Cs liberation Unlike other options, less selective flotation option was not a tailings retreatment process no risk of destroying project value with future plant improvements Full-scale plant trial conducted to test concept: Run plant at 50% of normal rate Increase rougher mass recovery from 10% to 20% of feed mass Maximise regrind power to get as fine a product as possible

16 Full Plant Trial Results Trial 1-15 January 2012 Trial 2-27 January 2012 Preliminary Trails Baseline LSF Difference Baseline LSF Difference Rougher Recovery (%) Overall Copper Recovery (%) Overall Gold Recovery (%) Trial results confirmed that the less selective flotation concept worked at full scale in 200m³ rougher cells Trail mineralogy samples showed a decrease in +53µm Cs-NSG composite quality in rougher tailings compared to baseline samples

17 The Decision Results supported a $65M investment case approved February 2012 economics compelling even at +4% copper and gold recovery Less selective flotation re-branded as the Increased Recovery Project Long lead M10000 IsaMill (ex works 10 months) ordered immediately Critical design criteria confirmed: Regrind product size at 20µm to achieve 80% copper sulphide liberation Concentrate filtration rate with fine regrind too slow, another filter required Rougher mass recovery

18 Rougher Mass Recovery How Much? Flotation data indicated rougher copper recovery reached maximum at 20-25% mass recovery for most ore types 100 Rougher Copper Recovery (%) O r i g i n a l D e s i g n I R P D e s i g n tph 500 tph Rougher Mass Recovery (% of Rougher Feed) Overall Ore Types Chalcocite Transition Very High Pyrite High Pyrite Chalcocite Desseminated Chalcocite - Chalcopyrite Chalcopyrite Disseminated Chalcopyrite Primary

19 IRP Design and Engineering Compression of schedule to start construction in Q before Phu Kham Upgrade project (completed September 2012) resources demobilised Key issues in design for IRP: Cleaner circuit mass balance with lower grade rougher concentrate Integration with existing plant, already very crowded Modular design required with minimal impact on operating plant during construction Fix all niggling issues with existing plant, mainly slurry pumping

20 IRP Progress GR Engineering Services selected for FEED and EP FEED commenced March 2012 FEED completed May 2012, capital cost reduced to $45M EP complete September 2012 Phu Kham Upgrade construction completed August 2012 IRP construction commenced August 2012 All major equipment on site by February 2013 Construction complete and commissioning complete April 2013 Ramp-up underway May 2013, completed in July 2013 Final cost of project $35M

21 IRP Flowsheet GYRATORY CRUSHER SAG MILL No.1 BALL MILL No.1 MILL CYCLONES COARSE ORE STOCKPILE No.2 MILL CYCLONES No.2 BALL MILL CYCLONE OVERFLOW TANK ROUGHER FLOTATION CELLS ROUGHER FLOTATION CELLS NEW ROUGHER CYCLONES 1st CLEANER FLOTATION CELLS TAILINGS DAM PROCESS WATER ISAMILL No.1 NEW 1st CLEANER FLOTATION CELLS THICKENER NEW ISAMILL No.2 JAMESON CELL 2nd CLEANER FLOTATION CELLS 3rd CLEANER FLOTATION CELLS NEW FILTER SURGE TANKS FILTER STOCKPILES

22 What Went Wrong Regrind cyclone underflow splitter box bias, new IsaMill low flow and high temperatures not picked up - burned out the shell liner Faulty density gauge settings on new IsaMill feed high density nearly burned out the spare liner Existing pumps upgraded or swapped to new duties no-one had thought to check VFD settings or even check wet ends

23 What Went Wrong Assumption that process was simple just pull the roughers harder! Fill up the cleaning circuit! 12.0 IRP Immediate positive impact on rougher copper and gold recovery, but cleaner copper recovery worse no net copper recovery increase 10.0 CUSUM Copper Final Recovery % No Net Recovery Increase Shift Number

24 What Went Right The design objective was met.

25 What Went Right Copper recovery up by 6%, gold by over 10% during lower head grades and declining ore quality period, less than 1 year payback 100.0% 90.0% IRP Reconciled Recovery % 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% Copper Gold

26 IRP Summary 1. Understand the geology and process development history 2. Collection of monthly mineralogy, mineral association, and mineral liberation data since 2008 was critical 3. Focused test programs determined the greatest opportunities 4. Process concept proven at bench, pilot, and full-scale 5. Lowest risk and highest value option, easy to get support for development 6. Project outcomes certain

27 Thank You