Having opted to go with a flotation circuit made entirely of Glencore Technology’s Jameson Cells for its New Britannia copper-gold operation in northern Manitoba, the miner is also also making the technology the main sulphide ore separation route for its planned Copper World Complex in Arizona, which includes the recently discovered Copper World deposits along with the Rosemont deposit. The plans are outlined in the just released National Instrument 43-101 technical report for the project.
The Copper World deposits consist of seven deposits, including Bolsa, Broad Top Butte, West, Peach, Elgin, South Limb and North Limb. The mine will consist of four separate open pits; during the first five years (including the year of pre-stripping), 90% of the mineral resources are extracted from the Peach-Elgin, West and Broadtop Butte pits. The East pit (based on Rosemont) becomes a major contributor only in year five.
Hudbay has developed a thorough PFS scope and detailed budget for commencement of the pre–feasibility work for Phase I of the project. Hudbay estimates that in addition to the budget for the infill drilling recommended above, a PFS will cost approximately $17 million to complete and it has the required funding in place to complete the PFS work in 2022.
On to the processing facilities, they include an oxide leach and solvent extraction and electro-winning (SX/EW) facility, a sulphide concentrator, a concentrate leach facility and an acid plant. The oxide leach and SX/EW facility follows a conventional process involving ROM leaching, solvent extraction and electrowinning. The sulphide mill consists of conventional crushing, grinding, flotation, molybdenum separation, concentrate dewatering and tailings dewatering. The sulpide concentrate produced in the sulphide mill is further processed in the concentrate leach facility via atmospheric leach tanks to produce a pregnant leach solution (PLS) which is combined with the PLS from the oxide leaching circuit.
The processing facilities are planned to have annual production capacity of 100,000 t of copper cathode during Phase I and 125,000 t of copper cathode during Phase II, and have been designed to reduce the project’s carbon footprint to produce “Made in America” copper. Phase I of the Copper World Complex includes a 60,000 t per day sulphide concentrator, a 20,000 t per day oxide heap leach, an SX/EW facility and a concentrate leach facility with an initial capital cost estimate of approximately $1.9 billion. The concentrator is intended to expand to 90,000 t per day in Phase II. Phase II expands mining activities onto federal land and extends the mine life to 44 years with average annual copper production of approximately 101,000 t.
Hudbay is evaluating several opportunities to optimise the project, including potential processing and initial capital optimisations, the potential to expand Phase I beyond 16 years with additions to the company’s private land package for tailings and waste rock storage and the potential to accelerate Phase II if federal permits are received earlier than as outlined in the PEA.
Looking at the flotation technology in detail, screened cyclone overflow will serve as feed to the bulk flotation section. During Phase I, the bulk flotation circuit consists of two flotation lines each with three B8500/12 Jameson Cells. Two cells are used for roughing duty and one for scavenging. The scavenger concentrate is pumped to the 1st rougher Jameson cell and the scavenger tailings flow to the tailings dewatering circuit. Concentrate from the two rougher Jameson cells are combined and pumped to a hydrocyclone cluster. The hydrocyclone underflow is pumped to a M10000 regrind IsaMill™. The regrind mill discharge is combined with the cyclone overflow and pumped to the cleaner flotation circuit. The target regrind size is 80% passing 30 um.
For Phase II, the flotation plant is expanded to include a third line of B8500/12 Jameson Cells to handle the additional 30,000 t per day of mill feed. An additional regrind mill is not required as the M10000 IsaMill™ is sufficiently size for the Phase II throughput.
The reground rougher concentrate is pumped to the first of three B5400/18 Jameson cells configured in a scalper– cleaner – scavenger arrangement. The tailings from the scalper is pumped to the cleaner Jameson cell, with the tailings from this cell reporting to the scavenger cell. The scavenger concentrate returns to the cleaner Jameson cell and the scavenger tails reports to the tailings thickener, along with the rougher–scavenger tailings. The concentrate from the first two cleaner Jameson cells is combined as final Cu–Mo concentrate and pumped to the Cu–Mo concentrate thickener. For Phase II, an additional B5400/18 Jameson scavenger cell will be added to the circuit. No other expansion of the bulk cleaner circuit will be required.
Underflow from the Cu–Mo concentrate thickener is pumped to a 4 m3 molybdenum rougher conditioning tank. NaHS, diesel emulsion, and CO2 are added to the conditioning tank to inhibit the flotation of copper minerals and promote the flotation of molybdenite. From the conditioning tank, slurry is pumped to a E2514/3 Jameson rougher cell. The tailings from the rougher cell are pumped to a E2514/3 Jameson scavenger cell. The scavenger tails from the copper concentrate and are pumped to the copper concentrate thickener. The scavenger concentrate is recirculated back to the rougher cell. The molybdenum rougher concentrate reports the first molybdenum cleaner conditioning tank together with the tails from the 2nd cleaner. CO2 and NaHS are added to the cleaner conditioning tank.
The molybdenum cleaner circuit consists of three stages of cleaning. Each stage utilises a single Z1200/1 Jameson cell. From the first stage cleaner the molybdenum concentrate is pumped to the second cleaner flotation cell and the cleaner tails returned to the rougher cell. The concentrate from this cell reports to the third cleaner stage and the tailings are pumped back to the first cleaner cell. The molybdenum third cleaner tails are pumped back to the second cleaner cell and the third cleaner concentrate is the final molybdenum product which report to the molybdenum concentrate thickener.
The Cu–Mo separation plant would be equipped with an online sample analyser (OSA) and operated with nitrogen as the flotation gas. Nitrogen is fed to the plant via a main nitrogen header from the nitrogen storage tank. Conditioning tank pH is automatically controlled using CO2 gas fed from a from a CO2 storage tank and evaporator. All flotation cells, launders and feed sumps are covered and vented to a scrubber operating with dilute NaOH solution. For Phase II of the mine plan, an additional E2514/3 Jameson rougher cell will be added to the molybdenum flotation circuit.
The mine will be a traditional open pit shovel and truck operation with bench heights of 50 and 100 ft, and 255–ton capacity haul trucks (eg Caterpillar 793F or Komatsu 830E) for material and waste movement, loaded by 44 yd3 hydraulic front shovels. The mining sequence follows a two–phase approach, where the first phase of production considers the exploitation of the pits and their associated infrastructure over a footprint requiring only state and local permits for 16 years (plus one year of pre–stripping). During this period, all waste, tailings, and leach pads are disposed within the limits of Hudbay’s private land properties.
After this first phase, it is assumed that all necessary permits have been obtained in order to mine and deposit tailings and waste also on unpatented mining claims for a second production phase. The open pits are mined in a sequence consisting of 17 mining phases for a total lifetime of 44 years, plus one additional year of pre stripping.
The three Copper World pits will measure 5,600 ft on average in diameters with an average depth of 520 ft while the final East pit (formerly referred to as Rosemont) size will measure approximately 8,200 ft in diameter and have a depth of approximately 2,250 ft. Through the life of mine 1.486 Mt of economic material and approximately 2.437 Mt of waste will be extracted, yielding a life of mine stripping ratio of 1.64 (including pre–stripping material).