Overview
The North Island Project features a sophisticated mineral processing plant designed to handle varying ore characteristics across its three deposits (Northwest Expo, Red Dog, and Hushamu) through a staged expansion approach. The facility processes copper, gold, and molybdenum through integrated flotation and leaching circuits, with Phase 1 operating at 40 kt/d and Phase 2 expanding to 80 kt/d capacity.
Key Process Stages
- Phase 1 (Years 1-5): Single-stage crushing, SAG/ball mill grinding, bulk flotation, and separate rougher/cleaner tailings leaching circuits producing copper concentrate and gold doré
- Phase 2 (Years 6+): Duplicated crushing/grinding lines, pebble crushing, and new molybdenum flotation circuit to process Hushamu deposit material
- Crushing: Primary gyratory crusher reduces ROM from F80 475mm to P80 63mm (Phase 1) and 79mm (Phase 2)
- Grinding: SAG mills (35′ x 20′, 14MW) with ball mills (24′ x 33.5′, 11MW) achieve P80 of 150μm
- Flotation: Bulk rougher (300m³ cells) with regrind (7MW mill), followed by 3-stage cleaning to final concentrate
- Leaching: Dual CIL circuits (4800m³ tanks) for rougher/cleaner tailings with 24h residence time
- Molybdenum Separation (Phase 2): Dedicated circuit with NaHS depression, 5-stage cleaning including Jameson cell
Critical Data
| Parameter | Phase 1 | Phase 2 |
|---|---|---|
| Plant Capacity | 40,000 t/d | 80,000 t/d |
| Copper Head Grade | 0.24% | 0.22% |
| Gold Head Grade | 0.67 g/t | 0.30 g/t |
| Molybdenum Grade | – | 0.008% |
| Grinding P80 | 150 μm | 150 μm |
| Bond Ball Work Index | 10.4 kWh/t | 14.2 kWh/t |
| Bulk Flotation Mass Pull | 13.0% | 19.0% |
| Installed Power | 63.2 MW | 119.1 MW |
| Water Consumption | 3.2 Mm³/a | 11.8 Mm³/a |
Circuit Highlights
Phase 1 Configuration
- Single 450kW gyratory crusher feeding 14MW SAG mill
- Bulk flotation with PAX/MIBC collectors at 13% mass pull
- Dual leaching circuits for rougher/cleaner tailings
- Copper concentrate thickening (14m⌀) and filtration
Phase 2 Upgrades
- Duplicated crushing/grinding lines with pebble crushers
- Molybdenum circuit with NaHS depression (292 t/a consumption)
- Reconfigured leaching for cleaner tailings only
- Molybdenum concentrate drying system
Reagent System
The plant utilizes comprehensive reagent systems including:
- Lime (40,393 t/a Phase 1) for pH control
- Sodium cyanide (11,871 t/a Phase 1) for leaching
- PAX/3418A/MIBC for flotation
- SMBS (11,247 t/a Phase 1) for cyanide detox
- Specialty flocculants (326 t/a Phase 1) for thickening
