The Whabouchi concentrator, located 675 m northeast of the open pit, applies crushing, ore sorting, dense media separation, grinding, and flotation to produce a 5.5% Li₂O spodumene concentrate, with the processing design updated in phases since 2014.
Report context
The Whabouchi Mine Project technical report dated 2023, NI 43-101 Technical Report – Nemaska Whabouchi Mine Project – Nemaska, Quebec, describes the processing facilities for the spodumene operation. The process design is split between the concentrator near the open pit and a planned conversion plant in Bécancour. This article covers the concentrator flowsheet, equipment selection, and the reported process design basis, drawing on Section 17 of the report.
Processing route
Crushing and ore sorting
Run-of-mine (ROM) material is dumped into a ROM stockpile, rehandled by front-end loader, and transferred to a ROM feed hopper equipped with a static grizzly and rock breaker. An apron feeder withdraws material to a primary jaw crusher (1,000 mm × 1,300 mm, 160 kW) with a P80 of 95 mm. A triple-deck vibrating screen classifies the crushed ore. The top deck oversize (+80 mm) is sent to a secondary jaw crusher (800 mm × 1,150 mm, 132 kW). Screen middle deck oversize (80+35 mm) reports to a coarse ore sorter, while bottom deck oversize (35+10 mm) reports to a fine ore sorter. The screen undersize (-10 mm) bypasses sorting to fine crushing.
Ore sorting uses X-Ray Transmission (XRT) sensors. The coarse ore sorter feed is -80+35 mm; the fine ore sorter feed is -35+10 mm. Sorting rejects an estimated 10-15% of feed, with design capacity for instantaneous rejection rates near 30%. A future scavenger ore sorter is planned to be operational in year 5. The fine crushing circuit comprises a double-deck vibrating screen (top deck 20 mm, bottom deck 9 mm), two secondary cone crushers (P80 21 mm), and one tertiary short head cone crusher (P80 12.7 mm), all in closed circuit to produce a final crushed product with P80 5.8 mm.
Dense media separation
The DMS circuit is a two-stage system: a rougher stage with one DMS cyclone and a cleaner stage with one DMS cyclone. Feed is prepared by screening on the fine ore screen (top deck 2.7 mm, bottom deck 0.85 mm). Screen oversize reports to a coarse muscovite removal hydraulic separator, with screen undersize sent to fine muscovite removal. Ferrosilicon is used as the dense medium, with circulating and dilute media circuits; low intensity magnetic separators and densifying cyclones recover ferrosilicon for reuse.
The rougher floats become DMS tailings. The rougher sinks are cleaned, with cleaner floats (middlings) sent to the ball mill and cleaner sinks as DMS concentrate. The DMS concentrate is dried in a rotary dryer to below 1% moisture for dry magnetic separation. Magnetic separation includes a low intensity stage followed by a rare earth high intensity stage. Final DMS concentrate grade is approximately 6.0% Li₂O.
Grinding and classification
DMS middlings are ground in a ball mill in closed circuit with a screen with 850 μm apertures. The screen undersize, at P80 640 μm, combines with fine ore screen undersize for fine muscovite removal. A cyclone cluster densifies the slurry; overflow is screened at 212 μm, with screen oversize (mostly muscovite) sent to tailings.
Fine muscovite removal and desliming
The fine ore screen undersize and ball mill product are pumped to a cyclone. Cyclone underflow is introduced into the fine muscovite removal hydraulic separator. Overflow containing muscovite and particles finer than 200 μm is screened at 212 μm, with screen oversize sent to tailings. The underflow is mixed with screen undersize and pumped to a cyclone cluster for de-sliming; overflow is rejected to tailings.
Wet magnetic separation and attrition scrubbing
Magnetic separation is performed in two stages: first, a Low Intensity Magnetic Separator (LIMS) removes residual dense media and steel from the ball mill; second, a Wet High Intensity Magnetic Separator (WHIMS) removes paramagnetic material from flotation feed. Non-magnetic products feed a densifying cyclone cluster that removes additional slimes and densifies the attrition scrubber feed.
Attrition scrubbing is performed at high pulp density with high shear mixing. A dispersant is added to loosen tenacious fine particles, and caustic soda raises pH to 12. The attrition scrubber discharges to a hydraulic separator with a cut size of 200 μm. Underflow feeds the coarse particle flotation circuit; overflow goes to a third desliming stage.
Spodumene flotation
The hydraulic separator underflow is sent to the hydroflotation split-feed vibrating screen. Screen oversize (+500 μm) goes to ultracoarse conditioning tanks, while undersize is densified in a cyclone before coarse conditioning. Both circuits use four stages of high-density conditioning with spodumene collector and sulfuric acid to achieve pH 8.
Hydroflotation uses Eriez HydroFloat separators. The ultracoarse and coarse hydroflotation concentrates are combined and screened at 210 μm. Screen undersize is recycled to column flotation; screen oversize, grading approximately 4.1% Li₂O, reports to the concentrate holding tank. Coarse hydroflotation underflow goes to tailings; ultracoarse underflow is screened at 600 μm, with oversize recycled to the ball mill and undersize sent to tailings.
The column flotation circuit has three flotation columns: rougher, scavenger, and cleaner. Rougher concentrate is pumped to the cleaner column; rougher tailings go to the scavenger column. Scavenger concentrate is recirculated to the 3rd desliming cyclone cluster; scavenger tailings go to tailings. Cleaner concentrate is final concentrate at approximately 5.1% Li₂O, with cleaner tail recycled to the 3rd desliming cyclone pump box.
Concentrate dewatering and handling
Hydroflotation concentrate screen oversize is sent directly to the concentrate holding tank. Column flotation concentrate is thickened to 62% solids in a high-capacity thickener. Combined flotation concentrate is filtered to approximately 8% moisture on a vacuum belt filter. The filtered concentrate is combined with dried DMS concentrate and conveyed to a covered concentrate stockpile with approximately 41 hours capacity. The combined concentrate is expected to have 4% moisture, is rehandled by front-end loader into containers on trucks for shipment to Matagami, then by rail to the conversion plant.
Tailings dewatering and storage
Coarse tailings are screened and discharged onto the final tailings conveyor. Fine tailings are thickened in an inclined plate settler to 61% solids, then filtered to 15% moisture using a vacuum belt filter. Combined tailings at 12% moisture are conveyed to a loadout bin with emergency stockpile, then transported by mine trucks to the on-site filtered tailings storage facility (CSF).
Expansion allowances
A Phase 1 expansion to increase production by 11.5% has not been defined in detail. A debottlenecking evaluation will be performed during operation, expected to require additional capacity in DMS, grinding, and dewatering. An allowance is included in sustaining capital for Phase 1 and a potential Phase 2 expansion in year 24 as the mine transitions from open-pit to underground.
Key reported parameters
The table below summarizes the process design basis, distinguishing the 2019 design (6.25% Li₂O) from the updated design (5.5% Li₂O) for three production periods.
| Parameter | Units | 2019 Design | Average Years 1-6 | Average Years 7-24 | Average Years 25-34 |
|---|---|---|---|---|---|
| Annual ore processing rate | dry t/y | 1,030,831 | 963,230 | 1,152,518 | 1,243,024 |
| Average ore processing rate | dry t/d | 2,824 | 2,639 | 3,158 | 3,406 |
| Spodumene ore grade (Li₂O) | % | 1.53 | 1.31 | 1.33 | 1.29 |
| Overall lithium recovery (sorting + concentrator) | % | 85.2 | 83.0 | 84.3 | 81.9 |
| Spodumene concentrate grade | % Li₂O | 6.25 | 5.50 | 5.50 | 5.50 |
| Annual spodumene concentrate production | dry t/y | 205,000 | 190,252 | 234,473 | 238,841 |
| Daily spodumene concentrate production | dry t/d | 562 | 521 | 642 | 654 |
| DMS circuit operating time | % | 80.0 | 80.0 | 80.0 | 80.0 |
| Concentrator effective availability | % | 92.0 | 85 | 85 | 85 |
Project website: https://nemaskalithium.com/en/the-whabouchi-mine/
The design daily ore throughput is 2,639 tonnes requiring 221 m³/d of makeup water. Most water is lost in tailings at about 12% moisture for dry stacking in a CSF with waste rock. The average ore processing rate for years 1-7 is 963,230 dry tonnes per year at a feed grade of 1.32% Li₂O, producing 190,252 dry tonnes per year of 5.5% Li₂O concentrate.
For years 1-7, DMS recovers 8-11% by weight while flotation recovers 12-14% by weight, for a total of 21-24% weight recovery depending on year. Annual production figures are based on an effective concentrator availability of 85%. The mass balance table in the report shows 2,638.1 dry t/d of spodumene ore entering the concentrator with total mass 2,917.1 t/d, and 549.9 t/d of final concentrate exiting (including 22.2 m³/d water).
The current design targets a 5.5% Li₂O spodumene concentrate from ore averaging 1.32% Li₂O, equivalent to 68.5% spodumene (LiAlSi₂O₆). The concentrator design factors are 30% for crushing equipment, 15% for most concentrator equipment, and 5% for slurry pumps.
Technical qualifications
The report identifies several limitations on the process design. The target availability of 91.5% is considered optimistic by the qualified person, with an upper limit potentially as low as 75-85%, or recovery may decrease to maintain concentrate production. An effective availability of 85% was used for design production profiles. The 2019 design assumed 91.5% effective availability, producing at lower throughput for the same annual production.
The report notes the flowsheet is complex and constrained by existing procured equipment, the erected building, and half-constructed plant. Following 2021 modifications, design factors across the process plant are no longer systematic, with an increased risk of bottlenecking on equipment with low design factors. Ramping up to target production values may take longer than anticipated and may require additional sustaining capital projects.
Concentrate production and recovery estimates are based on individual stage recoveries from bench and pilot scale work compiled into a metallurgical model; this estimate has not been confirmed through full pilot plant testing, which is not required at a Pre-Feasibility Study level. The Phase 1 expansion has not been defined, and the Phase 2 expansion is an allowance only.
Source: NI 43-101 Technical Report – Nemaska Whabouchi Mine Project – Nemaska, Quebec, Sections 13, 17 and Table 17-1 through 17-3.
