The 2023 Technical Report describes a two-phase, staged-expansion process plant designed to produce nickel flotation and magnetite concentrates from an ultramafic komatiite-hosted Ni-Cu-Co-(PGE) deposit with an iron formation cap.
Report context
The Crawford Nickel Sulphide Project NI 43-101 Technical Report and Feasibility Study, dated November 24, 2023, presents a process plant design that incorporates staged expansion to deploy capital efficiently, with Phase 1 designed for 60 kt/d (21.9 Mt/a) and Phase 2 duplicating the Phase 1 design for a total capacity of 120 kt/d (43.8 Mt/a) by Year 5 of operation. The overall circuit design is based on interpretation of testwork conducted by SGS-Lakefield, COREM and XPS in 2022 and 2023, as well as optimizations based on Ausenco's experience and industry best practices.
Processing route
Comminution and desliming
Run-of-mine or stockpiled ore is dumped into a 580-tonne live capacity hopper above a primary gyratory crusher operating at a closed-side setting of 120 mm, reducing ore from an F80 of 500 mm to a P80 of 128 mm. The crusher product is conveyed to a 667-tonne surge bin feeding two identical open-circuit secondary screening/crushing streams. Double-deck secondary screens with 90 mm top deck and 38 mm bottom deck apertures feed cone crushers operating at a closed-side setting of 38 mm. Combined material from secondary screening and crushing has a product size of P80 40 mm.
Crushed ore is conveyed to a covered stockpile with 32,860-tonne live capacity (12 hours of mill feed) and total capacity of approximately 155,770 tonnes. Ore is reclaimed via three variable-speed apron feeders into the primary grinding circuit consisting of an 18 MW SAG mill (11.6 m diameter x 6.71 m EGL) followed by an 18 MW ball mill (8.1 m diameter x 13.4 m EGL) in closed circuit with an 838 mm cyclone cluster, designed for a recirculating load of 350%. The circuit reduces particle size from F80 40 mm to P80 230 µm.
The ball mill cyclone overflow is deslimed using small diameter (102 mm) cyclone clusters to remove fine fibrous particles that can interfere with flotation kinetics. The deslime cyclone overflow has a target P80 of approximately 8 µm and reports to the tailings thickener. The deslimed underflow reports to the coarse nickel flotation circuit.
Coarse and fine nickel flotation
The deslimed underflow is fed to two banks of two agitated coarse rougher conditioning tanks where flotation reagents (collector, frother, and depressant) are added. Conditioned slurry gravitates to two banks of conventional forced-air flotation cells (five 311 m³ cells per bank) for rougher flotation. The coarse rougher concentrate is pumped to a single bank of conventional cell first cleaning stage (five 36.5 m³ cells) operating in open-circuit configuration. First cleaner concentrate is reground in a 355 kW regrind ball mill (2.7 m diameter x 4.0 m EGL) in closed circuit with hydrocyclones to produce a product size of P80 55 µm. The regrind cyclone overflow is sent to second cleaner flotation (two 36.5 m³ cells) and then third cleaner flotation (two 36.5 m³ cells). Tailings from the coarse rougher and first cleaning stages are combined and sent to secondary milling.
The secondary grinding circuit consists of an 18 MW ball mill (8.1 m diameter x 13.4 m EGL) in closed circuit with an 838 mm cyclone cluster (350% recirculating load), reducing coarse flotation tailings to a product size of P80 100 µm. This is followed by desliming using four cyclone clusters with 101 mm cyclones (366 operating, 34 standby), with overflow (P80 approximately 8 µm) sent to the final tailings thickener and underflow to fines flotation.
Fines flotation comprises two banks of eight 311 m³ rougher forced-air flotation cells, followed by first cleaner (six 58.1 m³ cells), second cleaner (two 58.1 m³ cells), and third cleaner (one 58.1 m³ cell). First cleaner concentrate is reground in a 315 kW regrind ball mill (2.5 m diameter x 3.2 m EGL) to P80 55 µm. Both coarse and fines flotation concentrates report to a common nickel concentrate thickener and filter press before stockpiling.
Magnetic separation and sulphide flotation
Fines rougher flotation tailings are processed through three stages of low-intensity magnetic separation (LIMS) with dedicated regrind stages between each stage. The rougher stage comprises two trains of seven double-drum magnetic separators (3.05 m long x 1.2 m diameter) at 2,000 gauss. Rougher magnetic concentrate is reground in a 4.5 MW vertical stirred mill to P80 60 µm, then fed to secondary magnetic separation using six triple-drum separators (3.05 m long x 1.2 m diameter) at 1,500 gauss. Secondary concentrate is reground in a 4.5 MW vertical stirred mill to P80 25 µm, then fed to tertiary magnetic separation using four triple-drum separators (3.05 m long x 1.2 m diameter) at 1,500 gauss.
Tertiary magnetic concentrate is processed through a sulphide flotation stage using four 58.1 m³ forced-air flotation cells. The sulphide flotation concentrate is dewatered using 4,000 gauss magnetic separators to 65% w/w solids, then filtered to 93% w/w solids before stockpiling. Magnetic separation tailings from all stages, including sulphide flotation, are combined and sent to the final tailings thickener.
Tailings processing and carbon sequestration
Deslime cyclone overflows and magnetic separation tailings are combined and thickened in a 63 m diameter high-rate thickener to an underflow density of 40% w/w solids. The thickened slurry is pumped into three carbon-capture streams, each split into three agitated, enclosed tanks (nine total, 15.5 m diameter) where carbon dioxide at 97% purity is passed through the slurry for capture and sequestration, converting brucite into nesquehonite. The tailings are then pumped either to the surface tailings management facility (TMF) or to the pits for in-pit deposition. The TMF, located south of the mine with an approximate footprint of 2,300 ha, will be operated as a "thickened tailings cone" with deposition near the centre, and containment provided by a staged perimeter dam with a low permeability core.
Staged expansion
Phase 2 expansion assumes duplication of the Phase 1 design to achieve total design capacity of 120 kt/d by Year 5, with services and utilities shared between phases. Phase 2 will include primary and secondary crushing, crushed ore stockpile and reclaim, SAG mill grinding, primary ball mill grinding and desliming, coarse rougher and cleaner flotation with regrind, secondary ball mill grinding and desliming, fines rougher and cleaner flotation with regrind, magnetic separation with regrind, sulphide flotation, concentrate thickening and filtration, tailings thickening, and carbon sequestration.
Reagents and consumables
Estimated reagent consumption per tonne of mill feed for Phase 1 includes: potassium amyl xanthate (PAX) 184 g/t, methyl isobutyl carbinol (MIBC) 36 g/t, Cytec 65 4 g/t, Calgon (sodium hexametaphosphate) 300 g/t, carboxy methyl cellulose (CMC) 21 g/t, sulphuric acid 1,000 g/t, and flocculant 19 g/t. Annual consumable usage includes ball mill media 4,027 t/a, SAG mill media 1,539 t/a, and various regrind media.
Key reported parameters
| Parameter | Units | Design Value | Basis |
|---|---|---|---|
| Plant Design Capacity – Phase 1 | kt/d | 60 | Design |
| Plant Design Capacity – Phase 1 & 2 (Total) | kt/d | 120 | Design |
| Operating Availability – Crushing | % | 75.0 | Design |
| Operating Availability – Grinding, Flotation, Magnetic Recovery | % | 91.3 | Design |
| Operating Availability – Concentrate Filtration | % | 84.0 | Design |
| Plant Feed Grade – Nickel (Design) | % | 0.28 | Design |
| Plant Feed Grade – Iron (Design) | % | 7.42 | Design |
| Plant Feed Grade – Sulphur (Design) | % | 0.27 | Design |
| Plant Feed Grade – Chromium (Design) | % | 0.69 | Design |
| Nickel Recovery – Flotation Concentrate (Design) | % | 47.4 | Design |
| Iron Recovery – Magnetic Concentrate (Design) | % | 51.1 | Design |
| Nickel Concentrate Grade (Design) | % | 24.3 | Design |
| Nickel Concentrate Grade (Life-of-Mine Average) | % | 34.2 | Life-of-Mine Average |
| Iron Concentrate Grade (Design) | % | 51.6 | Design |
| Iron Concentrate Grade (Life-of-Mine Average) | % | 55.0 | Life-of-Mine Average |
| Consumed Power Specific Energy – Phase 1 | kWh/t | 36.5 | Design |
| Consumed Power Specific Energy – Phase 2 | kWh/t | 35.7 | Design |
Project website: https://canadanickel.com/projects/
Technical qualifications
The report explicitly states that the overall circuit design is based on the interpretation of testwork conducted by SGS-Lakefield, COREM and XPS in 2022 and 2023, as well as optimizations based on Ausenco's experience and industry best practices. No historical operating data from a similar commercial plant is presented; the design and performance criteria are derived from testwork and engineering design assumptions. The process plant design criteria were established based on the metallurgical data and requirements to deliver a robust design for optimum recovery, as stated in the report. The report notes that Phase 2 consumable usage is assumed to be double Phase 1's usage and "may change based on operational knowledge and optimizations during Phase 1." The key design and performance summary describes the reported recoveries and grades as "Design" values, with the exception of the nickel and iron concentrate grades for which a "Life-of-Mine Average" is separately reported.
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Source: Crawford Nickel Sulphide Project NI 43-101 Technical Report and Feasibility Study, November 24, 2023, Sections 1.16, 1.17, 17.1–17.7.
