The Brunswick Processing Plant processes antimony- and gold-rich sulphide ore through a conventional comminution and flotation concentrator. Operational since 2007 (under Mandalay Resources since 2009), the plant has undergone upgrades to achieve a current throughput of ~13,000 dry metric tonnes/month (dmt/month), with peak capacity of 14,000 dmt/month.
Processing and Recovery Methods
1. Crushing & Screening Circuit
– Equipment: Two diesel-powered Finlay I-130RS mobile impact crushers (duty + standby) in closed circuit with a 12 mm vibrating screen.
– Output: Crushed ore (target size for milling) conveyed to two 120-tonne fine ore bins.
– Upgrades: A third Finlay I-140RS crusher planned for 2022 to transition to two-stage crushing.
2. Milling Circuit
– Configuration: Two ball mills in series (primary and secondary), both closed-circuit.
– Primary Mill: Operates with a Dutch State Mines (DSM) screen; oversize recirculated, undersize fed to a centrifugal gravity concentrator for gold recovery.
– Gravity Recovery:
– Gold recovery: 40–55% (Youle ore feed).
– Concentrate upgraded via shaking table and sold directly to refineries.
– Secondary Mill: Cyclone overflow feeds flotation; underflow recirculated. Target grind: P80 of 60 µm.
3. Flotation Circuit
– Feed: Cyclone overflow conditioned with lead nitrate (activator) and potassium amyl xanthate (PAX, collector).
– Equipment:
– Two 48″ StackCell® roughers + two rougher tank cells (series).
– Original Denver DR100 (rougher/scavenger) and DR15 (cleaner) cells.
– Two Eriez CavTube® columns (added April 2021) for tailings reprocessing.
– Process Flow:
– Rougher/scavenger concentrates cleaned; tailings report to thickener.
– CavTube® columns recover low-grade Sb-Au concentrate.
4. Concentrate Handling
– Dewatering:
– Thickeners (including a 2019-added unit) feed a plate-and-frame pressure filter.
– Filter cake bagged for export; filtrate recycled.
– Upgrades: Second filter press planned for 2022 redundancy.
5. Tailings Management
– Thickened tailings pumped to two TSFs (east and north of plant).
– Water recovery: Thickener overflow and TSF decant recycled.
Key Metrics
– Throughput:
– Historical avg. (2016–2021): 11,900–12,979 dmt/month.
– 2022 forecast: 12,688 dmt/month.
– Recoveries (2021 data):
– Antimony (Sb): 94.6% (plant), 94.1% (2022 forecast).
– Gold (Au): 93% (plant), 92.7% (2022 forecast).
Innovations & Challenges
– Innovations:
– StackCell® and CavTube® flotation technologies improved recovery post-2021.
– Reverse osmosis (RO) plant (2 ML/day) for water management.
– Challenges:
– Crushing capacity constraints during wet seasons (addressed via 2022 crusher upgrade).
– Feed supply limitations (e.g., 2019 throughput dip due to mining delays).
Utilities & Infrastructure
– Water: Positive balance from underground dewatering (1.5–2 ML/day); excess treated via RO and Splitters Creek evaporation.
– Air/Power: Upgraded HP air system (2017) and consolidated electrical supply (2019) support operational stability.
The plant’s robust design and incremental upgrades ensure suitability for Life-of-Mine (LoM) ore processing, with a focus on optimizing recovery and throughput.
