A preliminary economic assessment for the Kwyjibo rare earth project envisions a process flowsheet spread across two sites in Quebec, using a combination of magnetic separation and a multi-stage hydrometallurgical plant. The design is based on test work from COREM and Hazen Research.
The Kwyjibo project is a rare earth element project located on the Côte-Nord of Quebec, about 125 km northeast of Sept-Îles. It is owned by Nordique Critical Metals Inc. under an earn-in agreement with SOQUEM. The project is at a preliminary economic assessment stage. A future construction timeline is not stated. The proposed development includes an underground mine at the Kwyjibo site and a separate hydrometallurgical complex at Rivière-au-Tonnerre (Sheldrake), roughly 144 km to the south.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Mine type | Underground | Not applicable | Not stated |
| Annual mineralized material feed to concentrator | 387,000 | t/a | Design value |
| Concentrator weight recovery | 45 | % | Test result |
| Concentrator rare earth recovery | 95.5 | % | Test result |
| Annual concentrator non-magnetic concentrate production | 174,000 | t/a | Design value |
| Annual hydrometallurgical plant REO production | 10,053 | t/a | Design value |
| Hydrometallurgical plant cumulative TREO + Y recovery | 77.97 | % | Test result |
| Hydrometallurgical plant cumulative HREE recovery | 80.4 | % | Test result |
| Crushing system availability | 65 | % | Design value |
| Concentrator availability | 92 | % | Design value |
| Year 2-9 mine operating cost | 78.34 | $/t treated | Estimate |
| Year 2-9 concentrator operating cost | 56.73 | $/t treated | Estimate |
| Year 2-9 hydrometallurgical plant operating cost | 265.31 | $/t treated | Estimate |
Overview
The process design for the Kwyjibo project treats material from a magnetite-rich iron oxide-copper-gold (IOCG) deposit. The flowsheet uses a comparatively simple concentrator to produce a non-magnetic rare earth concentrate, which is then processed in a more complex hydrometallurgical plant to produce separated rare earth oxides. The concentrator uses crushing, grinding, and low-intensity magnetic separation. The hydrometallurgical plant was designed using results from metallurgical test work. The process involves several leaching, neutralization, and solvent extraction steps.
Key Process Stages
The flowsheet starts at the hydrometallurgical complex. Trucks deliver run-of-mine material from the underground mine to an outdoor tipping bin. A vibrating feeder feeds a jaw crusher that reduces the material from 600 mm to 150 mm. The crushed material goes to a 1,750-tonne silo, then is fed to the concentrator. The concentrator availability is a design value of 92%.
In the concentrator, a primary semi-autogenous grinding mill in closed circuit with a single-deck vibrating screen handles the initial grinding. Material minus 4 mm goes to the secondary grinding circuit, and plus 4 mm is returned to the mill. A vertical ball mill in closed circuit with four ultrafine vibrating screens handles the secondary grind. The target grind size is 80% passing 45 μm. Material plus 53 μm is returned to the vertical mill.
The ground slurry goes to two stages of low-intensity magnetic separation. The non-magnetic fraction becomes the rare earth concentrate. The magnetic fraction reports to tailings. The non-magnetic concentrate is thickened to about 60% solids and then filtered to produce a filter cake with about 91% solids. The concentrate is then conveyed to the adjacent hydrometallurgical plant.
The hydrometallurgical plant has a design value of 78.0% overall rare earth recovery. The plant processes 476 t/d of the non-magnetic concentrate. The main process steps include an initial hydrochloric acid leach at 90°C to dissolve the rare earths and other elements. This is followed by a ferric iron reduction step. The pregnant leach solution is then treated in a solvent extraction circuit using tri-butyl phosphate to remove iron. Another solvent extraction circuit using D2EHPA is used to remove thorium, and a chelating resin column is used to remove uranium. The thorium and uranium are directed back to the underground mine as backfill.
After the iron and radionuclide removal, the solution is neutralized in stages to precipitate the rare earths as phosphates. The precipitate undergoes a second leaching and neutralization step to reduce calcium content. The resulting solids then go through a metathesis step at 160°C, converting the rare earth phosphates to hydroxides using sodium hydroxide. The hydroxide solids are then given a final leach with hydrochloric acid to produce a purified rare earth chloride solution. This solution goes to a conventional solvent extraction circuit using PC88A in an aromatic diluent. The solvent extraction circuit separates the rare earths into Nd-Pr, Dy, Tb, Y, and a mixed rare earth product. The separated rare earth chlorides are precipitated with oxalic acid and then calcined to final oxides. The barren chloride solutions are sent to a hydrochloric acid regeneration plant. That plant uses sulfuric acid to convert the chlorides to sulfates. The sulfates are calcined to produce sulfur dioxide gas for a new sulfuric acid plant, which supplies acid back to the HCl regeneration step. The oxide residue from the calcination, which is free of thorium, uranium, sulfur, and phosphorus, is sent to a dry storage facility near the hydrometallurgical complex.
The magnetic tailings from the concentrator, the primary leach residue from the hydrometallurgical plant, and the phosphorus precipitation residue are all combined. This combined residue contains trace thorium, uranium, phosphorus, and sulfur. The combined residue is thickened, filtered to about 88% solids, and trucked back to the underground mine. It is mixed with cement and water to produce a cemented paste backfill for the mined-out stopes.
Additional Interesting Data and Summary
The PEA notes that the concentrator and hydrometallurgical plant are sized based on available test data. The PEA recommends additional test work on grinding, sedimentation, and filtration to confirm the sizing of equipment. The hydrometallurgical process risks identified include the need to confirm recovery values at a larger scale.
Key Processes
- Crushing to minus 100 mm using a jaw crusher.
- Primary and secondary grinding in a SAG mill and vertical ball mill to a target P80 of 45 μm.
- Low-intensity magnetic separation (two stages) to produce a non-magnetic rare earth concentrate.
- Thickening and filtration of the non-magnetic concentrate.
- Hydrochloric acid leaching of the concentrate at 90°C.
- Solvent extraction of iron using TBP.
- Solvent extraction of thorium using D2EHPA.
- Uranium removal using a chelating resin.
- Multi-stage neutralization and precipitation of rare earth phosphates.
- Metathesis of rare earth phosphates to hydroxides at 160°C using NaOH.
- Final hydrochloric acid leach of rare earth hydroxides.
- Solvent extraction (PC88A) and separation of rare earths.
- Oxalic acid precipitation and calcination of final rare earth oxides.
Source: Rapport technique Évaluation économique préliminaire – Mise à jour Projet Kwyjibo Québec, Canada, 14 août 2026. Project website: Kwyjibo
