Blast optimisation of hard ores in the Phu Kham open-pit · • The Operation comprises an open-pit...

Blast optimisation of hard ores in the Phu Kham open-pit

Presenter: Wayne RogersCo-authors: Arthur Pacunana and Kell Monro

Presentation overview

Company and Operations overview

Hard ore baseline measurements

Blast trials

Results

Conclusion

A successful mid-tier copper and gold producer

Brisbane-headquartered

Phu Kham Copper-GoldOperation

Ban HouayxaiGold-SilverOperation

Chinese-owned

Frieda River Copper-Gold Project

Exploration Licences

PanAust owns a 90 per cent interest in the Lao-registered company, Phu Bia Mining Limited; the Government of Laos owns the remaining 10 per cent

PanAust Limited

Operations in Laos

Phu Kham Copper-Gold Operation:• The Operation comprises an open-pit mine feeding

ore to a process plant with recovery of copper and precious metals into a saleable concentrate using conventional flotation technology

• The concentrate contains between 23 and 25 per cent copper, up to 9 gram per tonne (g/t) of gold and up to 60g/t silver

• The concentrate is hauled in covered containers to the ports of Vung Ang or Hon La in Vietnam (80 per cent) and Sriracha Harbour in Thailand (20 per cent) for export to smelters mainly in Asia

Ban Houayxai Mine:• Comprises an open-pit mine feeding ore to a

conventional four million tonne per annum (Mtpa) carbon in leach and gravity process plant

• Produces gold doré bars along containing a silver by-product credit

Phu Kham Copper-Gold Operation

Phu Kham Copper-Gold Operation

• Production commenced in 2008

• 97 per cent Lao-national workforce

• Single large pit of 450 metres in depth – largest open-pit mine in Laos

• Owner operator fleet moving 55Mtpa using:

– 55 CAT 777D 100t trucks loaded by five primary loading units (four PC3000 and two PC200 excavators

– Fleet of ancillary gear PC 1250, PC300s, CAT D10Ts, 16Msm ADT 740s, drill DM45s/L7

• Real-time fleet dispatch system (Jigsaw) from central mine and process control room

• Owner maintenance model

• Advancing geotechnical and hydrological services on site including real-time radar

Phu Kham Hard Ores

• As pit gets deeper in ore hardness increases (primary skarns and diorite)

• Availability of softer blending ores reduce

• SAG mill primary bottleneck

– Higher resistance to impact breakage & higher mill residence times

– overload the mill weight and increase the total energy load required to break harder ores

• Reduced SAG mill throughput rates (2,300 – 1,600 tph)

• Hard Ores Management Program initiated, second half 2016

• Involved conducting innovative and process control driven blasting trials

Baseline measurements

• Baseline measurements were conducted in order to establish a benchmark to quantify and compare against any improvements in blast outcomes and mill performance gained from future hard ore blasting trials

• Begun measuring CV01 belt cuts of hard ore inOctober 2016

– PSD, lithology, density, hardness (PLT)

• Blast QA/QC, HSV, VOD, movement

• Fragmentation, heave, shovel productivity, truck payloads

• Milling performance

Baseline D&B DesignHole Diameter 200 mm 7.87”Burden 3.5 m (11.5 ft)Spacing 4.5 m (14.8 ft)Bench Height 10 m (32.8 ft)

Stemming Height 4.0 m (13.1 ft)Explosive type 70:30 EM:ANFO

Explosive density 1.15 sgVOD 5300 m/s 17,388 ft/sPowder Factor 1.56 kg/m3 2.70 lbs/yd3D&B unit cost 0.75 $/t

Baseline measurements

• SAG mill tph will increase if the ROM PSD is optimised by:

– Increasing the percentage of fines (<25mm & <10mm, <1.0 inch & <0.40 inch),

– Minimising critical size percentage (25 – 75mm, 1.0 – 3.0 inch)

– Reducing the SAG media percentage (+100mm, +4.0 inch)

Blasting trials

• Aim - to identify the most effective way to improve mill throughput of harder ores

• Success criteria based on ‘value for money’ approach the additional cost to implement vs. measured improvement in mill throughput

• Blasting trials:

– High powder factor (PF) blasts– Electronic detonators (ED) and fast initiation timing– High velocity of detonation (VOD) / high density explosives – Double-priming (DP) and deck blasting

High powder factor blasts

• Aim - increase the percentage of fines in ROM PSD, by increasing blast energy• Method - 4 x blasts with a 70:30 EM:ANFO blend and various powder factors:

– 1 x 1.6kg/m3 (2.70 lbs/yd3) PF baseline– 1 x 2.0kg/m3 (3.37 lbs/yd3) PF– 2 x 2.4kg/m3 (4.05 lbs/yd3) PF -> 50% more than baseline– Hard ore zone, 400RL bench, Stage 5 central pit– Single-sourced through mill for 4 – 6 hours and the mill performance measured

High powder factor blasts

Results:

• The high 2.4 PF blasts required 30% more drill hour/tonne, than 1.6 PF baseline blast

• The cost was approximately 1.12 $/t, compared to 0.94 $/t for 2.0 PF, and 0.75 $/t for 1.6 PF baseline blasts (~ 50% increase)

• Significant cratering and flyrock observed along the initiation control row in all blasts (baseline and high PF)

– The amount of cratering and flyrock did not appear to increase much with the higher energy 2.4PF blasts.

– The maximum heave increased from 6.3m (20.6 ft) in the 1.6 PF blast, to 9.7m (31.8 ft) in the 2.0 PF blast, to 10.3m (33.8 ft) in the 2.4 PF blast. Dozing off the heave was required for the 2.4 PF blasts prior to digging

Electronic detonator blast trials

• Generate a finer and more uniform ROM PSD, by improving blast timing control, explosive energy distribution, and shock/stress wave interaction.

• First time trialled at PBM, focus also on ability to reduce workload, simplify logistics, improve wall control & grade control, and reduce costs and energy of downstream processing.

• Method - 5 blasts in the hard ore zone on the 380RL bench, stage 5 central pit:

– 1 x ED blast using baseline conditions (PF 1.6 kg/m3, 70:30 emulsion blend explosive, and single priming)

– 1 x ED and double priming– 1 x ED and faster timing– 1 x ED and higher VOD / high density explosives– 1 x final optimised ED blast & full 4-6 hour mill trial

conducted

Electronic detonator blastsBlast 380-19a 380-19b 380-16a 380-16b 380-16c

Burden 3.5m (11.5 ft) 3.5m (11.5 ft) 3.5m (11.5 ft) 3.9m (12.8 ft) 3.8m (12.5 ft)Spacing 4.5m (14.8 ft) 4.5m (14.8 ft) 4.5m (14.8 ft) 4.5m (14.8 ft) 4.5m (14.8 ft)

ExplosiveEm:ANFO % 70:30 70:30 70:30 100:0 90:10

Density (g/cc) 1.15 1.15 1.15 1.28 1.25VOD (m/sec) 5200 – 5500 5200 – 5500 5200 – 5500 5600 – 6000 5600 – 6000

Initiation (ED)No. of primers Single (SP) Double (DP) Single (SP) Single (SP) Single (SP)

IH& IR (ms) 9 ms & 30 ms 9 ms & 30 ms 4 ms & 15 ms 4 ms & 15 ms 9 ms & 30 msCosts

D&B unit cost 0.79 $/t 0.80 $/t 0.79 $/t 0.78 $/t 0.78 $/tDrill yield (t/m) 42.2 (11.7 t/ft) 42.2 (11.7 t/ft) 42.2 (11.7 t/ft) 47.0 (13.0 t/ft) 45.8 (12.7 t/ft)

CV01 belt cuts 380-19a 380-19b 380-16a 380-16bDetails 70:30 Em, Elec, 1.6

PF, SP70:30 Em, Elec, 1.6

PF, DP70:30 Em, Elec, 1.6 PF, SP, fast timing

100:0 Em, Elec, 1.6 PF, SP, high VOD

No. of samples 2 2 3 2Fines % (-10 mm)

mean 28.1% 25.7% 25.3% 28.8%

Fines % (-25 mm) mean 43.0% 41.6% 42.4% 47.6%

Critical size % (25 –75mm) 23.6% 25.4% 26.9% 29.5%

Media % (+100 mm) 28.9% 27.8% 26.7% 17.4%

Final optimised ED blast: 380-16c

High VOD / density explosive

• Higher VOD explosives produce greater shock energy (as opposed to heave/gas energy of ANFO) -> increase potential for ‘fines’ generation.

• Micro-fracturing? Reduction in inherent strength of the blasted rock fragments.

Fragmentation results: ROM

• Image analysis software used to measure ROM blast fragmentation

• Results show the high PF blasts produced the lowest blast P80 (mm)

• Electronic detonator and high VOD blast produced the largest top size (mm)

• Image analysis unable to quantify amount of fines % (<30mm) in blast

Blast Trial Baseline High Energy 2.4PF Electronic & high VODDetails 70:30Em, NONEL,1.6PF 70:30Em, NONEL,2.4PF 90:10 Em, Elec, 1.6 PFTop size, mean 630 mm (24.8”) 670 mm (26.4”) 915 mm (36.0”)P80, mean 157 mm (6.18”) 144 mm (5.67”) 246 mm (9.68”)Blast count (#) 32 2 1Image count (#) 200+ 26 12

Truck fill times (PC3000’s, ave) and truck payloads didn’t vary between high PF, ED blasts and are comparable to baseline.

CV01 belt cut results

• CV01 belt cuts taken to quantify the amount of fines generated in the blast

• Assumed the primary crusher contributes very little to the fines end (< 25 mm, <1.0 inch particles) of the ROM PSD - hence most fines originate from the blast

• High PF blasts produced the most amount of fines percentage (<10mm, & <25mm, 0.4” & 1”), and the greatest amount of SAG media percentage (+100mm, 3.9”)

• ED and high VOD blast produced more fines % than the baseline, and also the least amount of SAG media percentage

Blast Trial Baseline High Energy 2.4PF Electronic & high VODDetails 70:30Em,NONEL, 1.6PF 70:30Em,NONEL, 2.4PF 90:10 Em, Elec, 1.6 PF

No. of samples 15 4 2Fines % (-10 mm, 0.4”), mean 26.1 % 32.9 % 26.9 %Fines % (-25 mm, 1”), mean 44.7 % 50.4 % 45.4 %

Critical size% (25 –75mm, 0.1-3”) 31.7 % 23.3 % 31.9 %Media % (+100 mm, 3.9”) 18.7 % 21.7 % 17.6 %

Ore hardness and lithology

• AIM - to ensure the same lithology and ore hardness characteristics were maintained across all trials.

• All trials were conducted in the hard ore (diorite and skarn) areas of the stage 5 central pit. 400 RL -> 380 RL. Baseline 430 RL -> 420 RL.

• Belt cut samples underwent comminution test work: SMC (DWi, JK rock breakage parameters A and b), UCS, JK Bond Ball (JKBB), and Point Load Index (PLI) testing.

• A similar range of rock strengths were tested across all trials

Trial success – ‘value for money’

• AIM - identify most cost effective way to improve mill throughput of harder ores

• ‘Value for money’ criteria is a cost/benefit analysis that weighed-up the additional operating cost to implement the trial against the improvement in SAG mill tph

• Each trial single-sourced through mill for 4 – 6 hour and mill performance measured

Trial success – ‘value for money’

• Value for money – ED and High VOD produced the best ‘value for money’ measure (0.04 $/t), achieving an increase in mill throughput of 757 tph (increase of 54 per cent), for an additional cost of only 0.03 $/t.

• The high 2.4 PF blast produced a poorer ‘value for money’ measure of 1.65 $/t, achieving an increase in mill throughput of 201 tph, for a much greater additional cost of 0.37 $/t.

Blast Trial Baseline High Energy 2.4PF Electronic & high VOD

Mill trial duration (hrs:mm) 8:00 9:45 5:15Lith% diorite (idi), skarn (xkn) 69% (idi), 31%(xkn) 84% (idi), 10%(xkn) 85% (idi), 15%(xkn)Blast PF (kg/m3) 1.6 (2.70 lbs/yd3) 2.4 (4.05 lbs/yd3) 1.6 (2.70 lbs/yd3)Explosive type (Em. Blend) 70:30 Em:ANFO 70:30 Em:ANFO 90:10 Em:ANFOInitiation: IH & IR (ms) NONEL,25ms&42ms NONEL,25ms&42ms ED, 9ms & 30msSAG mill tph, mean 1,412 1,613 2,169SAG mill tph, standard dev. 112 126 113Increase in SAG mill tph % - 14% 54%Cost: additional operating ($/t) - 0.37 0.03Benefit: Increase in mill tph - 201 757Value for money ($/t) - 1.65 0.04

Validation of results

• As of second half 2017, ED and high VOD 90:10 EM blasting fully implemented in all PKM hard ore.

• Additional belt cuts sourced to validate results of blast trials

• Blasts were in the hard ore zone

• Results show ED and high VOD blasts successfully produced more fines per cent and less critical size per cent than baseline

• Ongoing monitoring of SAG mill performance will validate the trial results over the longer term

CV01 belt cuts Baseline Validation blastsDetails 70:30 Em, NONEL, 1.6 PF 90:10 Em, ED, 1.6 PF

No. of samples 15 7Fines % (-10 mm, 0.4”), mean 26.1 % 31.3 %Fines % (-25 mm, 0.1”), mean 44.7 % 47.4 %

Critical size% (25 –75mm, 0.1-3”) 31.7 % 29.1 %Media % (+100 mm, 3.9”) 18.7 % 22.3%

Continuous improvement

Continued measurement and tracking of blast implementation, design and performance outcomes, is important to ensure blasts are managed and continuously improved

Conclusions

• NPV Analysis

– The use of electronic detonators will incur an additional 0.9M USD blasting Life of Mine cost, but the resulting increase in mill throughput consequently brings forward 5.8kt copper production in 2017-2019 and earlier closure. The increase in copper production and fixed cost savings due to early closure provides additional 5.7M USD Phu Kham Operations net present value (NPV).

• This marginal increase in blasting costs in the pit will result in less work downstream at the primary crusher and ultimately the Concentrator communition circuit.

Acknowledgements

• Mining, Geology and Processing Departments, Phu Kham Operation

• PanAust General Manager Operations, David Reid

• PanAust Technical Services Group, Brisbane, Australia

• Tenaga Kimia Sdn Bhd (TKPV), Phu Kham Operation, Laos

• JKTech Pty Ltd, Brisbane, Australia.