This section details the proposed processing route for the Kwanika-Stardust Project, based on preliminary engineering and testwork, describing a conventional copper flotation flowsheet designed for an average throughput of 22,000 t/d.
Report context
This information is derived from the NI 43-101 Technical Report and Preliminary Economic Assessment for the Kwanika-Stardust Project, dated February 2023. The report outlines the process design criteria and descriptions for the proposed processing plant, which are based on engineering studies and recent preliminary testwork. This summary focuses exclusively on the recovery methods and associated parameters as presented in the report.
Processing route
Overview
The proposed plant is designed to process an average of 22,000 t/d (8.03 million t/y) of mineralized material. The selected flowsheet involves crushing, grinding, and bulk rougher flotation. The rougher flotation concentrate is reground and upgraded by cleaner flotation to produce a copper concentrate, which is then dewatered. Flotation tailings are sent to a tailings dam.
The plant includes these unit processes: primary crushing, crushed material stockpile and reclaim, gyratory crushing, a SAB (semi-autogenous grinding and ball mill) grinding circuit, copper flotation (comprising rougher flotation, concentrate regrind, and three-stage cleaning with cleaner scavenger flotation), concentrate thickening, filtration, load out and storage, and tailings handling. Reagents storage and distribution facilities are also included.
Primary Crushing
Run-of-mine material is dumped directly into the primary gyratory crusher by haul truck. The crusher reduces the material from a feed P80 of 528 mm to a product with a P80 of 73 mm. The crushed material is transferred via a discharge apron feeder and conveyors to a crushed ore stockpile, which provides a buffer between circuits with different availabilities.
Grinding and Classification
Crushed material is reclaimed from the stockpile by two apron feeders and conveyed to the SAG mill. The SAG mill is 9.75 m in diameter by 4.57 m, with an installed power of 9 MW. Its discharge passes across a trommel screen with a 12 mm opening; oversize is returned to the mill. The undersize is pumped to a cyclone cluster for classification. Cyclone overflow advances to the rougher flotation circuit. Cyclone underflow reports to a ball mill, which is 8.53 m in diameter by 11.73 m with an installed power of 18 MW. The grinding circuit product size is a P80 of 100 µm.
Rougher Flotation
The underflow slurry from the grinding circuit cyclones is conditioned with lime, A208 collector, 3418A promoter, and MIBC frother. The rougher flotation circuit consists of a single bank of five conventional tank cells, each with a volume of 305.4 m³. The nominal feed pulp density is 35% solids. The froth concentrate overflows into concentrate launders, and the tailings from the final cell are pumped to the tailings pond.
Regrind and Cleaner Flotation
The rougher froth concentrate is sent to a regrind circuit. This slurry is combined with cleaner scavenger flotation tailings and pumped to a cyclone pack. Cyclone underflow reports to a 2.2 MW regrind mill, where the material is ground to a P80 of 25 µm, while the cyclone overflow advances directly to the first cleaner flotation. The regrind mill product and cyclone overflow are combined as feed to the first cleaner flotation circuit.
The first cleaner circuit comprises three 110.4 m³ conventional tank cells. Its tailings are fed to a cleaner scavenger circuit of four 58.1 m³ conventional tank cells; the concentrate from this scavenger stage is recirculated to the regrind circuit, and its tailings are sent to the tailings pond. The first cleaner concentrate advances to a second cleaner circuit of three 23.3 m³ conventional tank cells, and its tailings are recirculated to the first cleaner stage. The second cleaner concentrate then reports to a third cleaner circuit, which also consists of three 23.3 m³ conventional tank cells. The tailings from the third cleaner are recirculated to the second cleaner stage. The third cleaner concentrate is the final concentrate and is pumped to the concentrate thickener.
Concentrate Dewatering
The final concentrate is pumped to a 14 m diameter high-rate thickener. The thickener underflow, at 60% solids by weight, is pumped to an agitated storage tank with a nominal capacity of 24 hours of slurry volume. The thickened slurry is pumped to a filter press at a rate of 13 m³/h, producing a final product with a target moisture of 8% by weight. The filter cake is discharged to a stockpile with a working capacity of 12 hours before loadout by front-end loader.
Tailings Handling
Final tailings are a combined product of the rougher flotation tailings and the cleaner scavenger flotation tailings. Most of this combined slurry is pumped to the tailings pond. When underground deposits are being actively mined, 20% of this slurry is planned to be sent back underground as paste. Process water reclaimed from the tailings facility is pumped back to the process water tank.
Reagents and Consumables
- Lime is received as dry powder and mixed with water to create a slurry, distributed to the grinding, rougher, and cleaner circuits. Annual consumption is estimated at 12,286 t.
- A208 collector is received as a liquid and delivered undiluted to the rougher flotation circuit, with an estimated annual consumption of 112 t.
- 3418A promoter is also received as a liquid and delivered undiluted to the rougher and cleaner circuits, with an estimated annual consumption of 132 t.
- MIBC frother is received in liquid form and delivered without dilution to the rougher and cleaner circuits, with an estimated annual consumption of 385 t.
- Flocculant is received as a dry powder, mixed to a concentration of 0.1-0.2 g/L, and pumped to the concentrate thickener. Annual consumption is estimated at 2 t.
Plant Services
- Process Water: The total process plant water demand is 1,852 m³/h. This is sourced from raw water makeup (336 m³/h), concentrate thickener overflow (47 m³/h), concentrate filter filtrate (8 m³/h), and reclaimed water from the tailings storage facility (1,461 m³/h). Raw water is pumped from Kwanika Creek.
- Air Services: Plant air compressors supply air at 750 kPa, with dedicated compressors for the concentrate filter and low-power compressors for the flotation cells.
- Power: The installed power for the process plant is reported as 39,651 kW, with an operating load of 27,756 kW.
Key reported parameters
| Parameter | Units | Value |
|---|---|---|
| Plant design capacity | Mt/y | 8.03 |
| Daily processing rate | t/d | 22,000 |
| Total material milled | Mt | 94 |
| Crushing plant availability | % | 75 |
| Grinding/flotation plant availability | % | 92 |
| Crushing plant nominal rate | t/h | 1,222 |
| Grinding/flotation nominal rate | t/h | 996 |
| Head Cu grade (design) | % | 0.8 |
| Head Au grade (design) | g/t | 0.8 |
| Bond crushing work index (design) | kWh/t | 12.8 |
| Bond Rod Mill Work Index (design) | kWh/t | 19.2 |
| Primary crusher type | – | Gyratory |
| Primary crusher product size (P80) | mm | 73 |
| Grinding circuit description | – | SAB |
| Grinding circuit product size (P80) | µm | 100 |
| SAG mill installed power | MW | 9 |
| Ball mill installed power | MW | 18 |
| Regrind mill power | MW | 2.2 |
| Regrind product size (P80) | µm | 25 |
| Rougher flotation residence time (design) | min | 14 |
| First cleaner residence time (design) | min | 7 |
| First cleaner scavenger residence time (design) | min | 7 |
| Second cleaner residence time (design) | min | 5.5 |
| Concentrate thickener diameter | m | 14 |
| Filter type | – | Filter Press |
| Filter cake moisture | % | 8 |
| Grinding media consumption (SAG + ball) | t/y | 8,841 |
| SAG mill liner consumption | t/y | 1,205 |
| Ball mill liner consumption | t/y | 1,124 |
| Process plant water demand | m³/h | 1,852 |
Project website: https://northwestcopper.ca/projects/kwanika-stardust/overview/
Technical qualifications
The report states that the project flowsheet and unit operations have been selected based on preliminary testwork and financial evaluations. The process description and equipment details are proposed designs and have not been confirmed by detailed engineering or construction. Design parameters, such as head grades, work indices, and reagent consumptions, are based on this preliminary work and may be subject to change upon further testwork and engineering studies. The report does not provide actual operating data from a similar plant, and the equipment listed represents the intended major components of the proposed design.
Source: Kwanika-Stardust Project, NI 43-101 Technical Report and Preliminary Economic Assessment, February 2023, Sections 17 (Recovery Methods) and sub-sections.
