Ban Phuc Nickel Project — 2013 Technical Report

The 2013 technical report documents a process plant designed for 450,000 tpa nominal throughput using a bulk nickel/copper flotation flowsheet, with design basis derived from metallurgical testwork and equipment selected for the project's remote Vietnamese location.

Report context

This technical report, dated 2013, presents the processing plant design for the Ban Phuc Nickel Project, owned by Asian Mineral Resources Limited. The design evolved through multiple iterations since the 2005 Feasibility Study, with the current configuration based on the 450,000 tpa design criteria document provided by Ban Phuc Nickel Mines. The report draws upon design documentation prepared by Metplant Engineering Services in 2008, prior to project suspension, and shows the Owner-Builder approach adopted after the Force Majeure declaration in October 2008.

Processing route

Design evolution and basis

The processing plant design progressed from a 200,000 tpa capacity in the November 2005 Feasibility Study to 250,000–300,000 tpa under Metplant Engineering Services' engagement in 2007, and subsequently to 450,000 tpa under a change order issued 12 May 2008. The process flowsheet and metallurgical concepts remained consistent through these iterations, with changes focused on equipment sizing and physical design. The report states that the Metplant process description for the 450,000 tpa design was not available, so the information was developed from the design criteria document provided by Ban Phuc Nickel Mines, assuming the flowsheet remained unchanged.

The design throughput of 450,000 tpa significantly exceeds the scheduled mine ore production of approximately 360,000 tpa, providing substantial excess plant capacity.

Crushing and ore storage

Ore will be reclaimed from a ROM stockpile kept to a minimum storage capacity (preferably less than 5,000 t) due to the ore's potential to oxidize relatively rapidly. A front end loader will feed a 45 t live capacity ROM bin through a 500 mm square aperture static grizzly. The primary crushing circuit is designed for 79 tph with 65% design availability.

Primary crusher discharge will be classified on a double deck screen with 25 mm and 12 mm apertures. Screen oversize reports to a secondary cone crusher, with mid-size to a tertiary cone crusher. The final product discharges at P80 of 9 mm to a fine ore bin with 450 t live capacity. A belt weightometer on the mill feed conveyor provides feed rate indication and tonnage totalization.

Grinding

Fine ore will be fed to a second-hand ball mill, 3.6 m diameter by 6.2 m flange to flange, with an option to shorten the mill if required. The ball mill, rubber lined, will operate in closed circuit with a cyclone cluster (three cyclones, two operating plus one standby) at a design cut-size of 90 µm. A flash flotation cell installed beneath the cyclone cluster will receive cyclone underflow feed, with flash flotation concentrate reporting to final concentrate.

Automatic control loops in the grinding circuit include ball mill feed rate control via variable speed fine ore feeder, feed water ratio control, cyclone feed pump speed control based on sump level, and mill discharge water addition to maintain cyclone overflow pulp density.

Flotation

The flotation circuit comprises rougher, scavenger, cleaner, and cleaner scavenger banks. Rougher flotation uses five 16 m³ forced air tank cells in a 3+2 configuration. Cleaner flotation cells are installed in a bank of five 8 m³ cells in a 3+2 configuration. Cleaner scavenger concentrate can be directed to final concentrate if grade is suitable, or recirculated to the cleaner cells. Rougher tailings combine with cleaner scavenger tailings to flotation tailings.

Control provisions include:

• Flotation stage air flow control with dedicated low pressure air headers and automatic flow control valves
• Froth level control via pneumatically actuated discharge pinch valves
• On-stream analysis (OSA) for nickel, copper, iron and slurry density, with SCADA integration for metal recovery calculation
• Reagent addition with sodium carbonate (soda ash) for pH control, sodium ethyl xanthate (SEX) as collector, InterFroth IF50 as frother, sodium metabisulphite (SMBS) as sulphide gangue depressant, CMC as non-sulphide gangue depressant, and flocculant for thickening

Concentrate and tailings dewatering

Rougher and scavenger concentrates will be pumped to a 9 m diameter high-rate thickener. Thickener underflow will be pumped to the ball mill feed via a flash flotation cell. The concentrate stock tank provides approximately 17 hours surge capacity. Concentrate slurry will be filtered using a filter press, with filter cake discharged to a conveyor feeding the concentrate shed.

The concentrate shed provides approximately seven days storage at maximum production rate, with space allocated for stockpiling concentrates of different grades. Concentrate will be reclaimed and loaded into bulka-bags via a hopper with weighing system.

Flotation tailings will be pumped to a 9 m diameter high-rate thickener. Thickener underflow pumps to the tailings storage facility (TSF) with flocculant addition for settling. Supernatant from the TSF returns to the process water tank using skid mounted pumps with floating suctions.

Water and utilities

Process water will be sourced primarily from tailings thickener and concentrate thickener overflows and concentrate filtrate. Due to positive catchment water balance, surplus water from the TSF is expected for most of the year, with raw water make-up provided for dry spells and plant start-ups. Raw water from bores will be stored in a combined raw and fire water tank, with outlets positioned to maintain minimum fire water reserve.

Potable water will be commercialized bottled water, with local bore water suitable for showers and other non-drinking purposes.

Process control and instrumentation

The plant will use a PLC-based SCADA system with PC-based operator stations, providing graphic displays, alarms, trends, and control loop functionality. Control philosophy accounts for limited availability of instrument technicians, remote location, and limited project scale, favoring a moderate level of instrumentation and automation.

Key control features include:

• Conveyor drives with pull-wire switches, belt drift limit switches, and speed sensors
• Chute level switches for blockage detection
• Sump pumps with automatic operation via float switches and SCADA alarms
• Mass flow measurement using belt weightometers for conveyors, and magnetic flow meters with nuclear density meters for slurry streams
• Ball mill control with power draw monitoring and kilowatt-hour metering
• Thickener controls with bed pressure sensors, nuclear density gauges, and interface detectors to prevent sliming conditions

Flotation cells have dedicated control provisions including current transducers on agitator starters, with drives controlled through the plant SCADA system.

Concentrate quality

The project concentrate production is scheduled at 30,309 t contained nickel over the reported mine life, with 15,453 t contained copper and 592 t contained cobalt. Nominal concentrate grade is approximately 9.5% Ni with a high copper tenor (approximately 2:1 nickel:copper) and approximately 0.2% cobalt. No significant precious metal or platinum group metal values are reported.

Typical concentrate analysis indicates low levels of deleterious elements, particularly low MgO, with no smelter penalties expected.

Key reported parameters

Technical qualifications

The design information presented in the report was generated from working design documents by Metplant Engineers, understood to be produced in 2008 prior to cessation of EPCM activity. The Metplant process description for the upgraded plant throughput of 450,000 tpa was not available; therefore, the information was developed from the 450,000 tpa design criteria document and the assumption that the flowsheet remained unchanged from the prior design. The previous 2007 Technical Report provides a more detailed process description based on throughputs of 250,000 tpa and 300,000 tpa.

The report notes that the size and number of rougher and cleaner flotation cells remained unchanged despite the throughput increase from 300,000 to 450,000 tpa, with the key mitigating factor being the installation of the flash flotation cell. The ball mill was procured second-hand and may need to be shortened and refurbished to match the overall plant capacity.

Flotation circuit control systems include provisions for automatic air flow control, froth level control, pump control, pH control via soda ash addition, and SCADA-based monitoring. The control system design accounts for limited availability of experienced instrument technicians and the remote Vietnamese location, favoring a moderate level of automation.

Source: *Ban Phuc Nickel Project , 2013 Technical Report*, Report No: R124.2013, Asian Mineral Resources Limited, Sections 17.1, 17.2, 17.3, 17.4, 17.7, 17.8, and Table 64.