Overview
The Casa Berardi Mine operates a gold processing facility using a Carbon-in-Leach (CIL) circuit to address preg-robbing effects from graphitic carbon in the ore. The plant, operational since 2015, has undergone multiple upgrades to optimize throughput and recovery. The circuit integrates crushing, grinding, gravity concentration, and cyanide leaching with a design capacity of 1.4 million tonnes annually.
Key Process Stages
- Crushing: Ore passes through a static grizzly (500×500 mm), scalping screen (89 mm), and jaw crusher (762×1400 mm) before storage in a 3,000-tonne bin.
- Grinding: SAG mill (5.5m x 2.7m, 1,130 kW) operates in closed circuit with a vibrating screen (5×16 mm). Ball mill (4.0m x 5.3m, 1,325 kW) works with primary (660 mm) and secondary cyclones (250 mm) to achieve P80 of 91.5 µm.
- Gravity Circuit: Two Knelson concentrators (762 mm) recover 36.5% of gold, with concentrate processed in an intensive leach reactor (Gekko ILR).
- CIL Circuit: Seven 700 m³ tanks with 20-hour residence time, 24 g/L carbon concentration, and 450 ppm NaCN. Pulp density maintained at 50% solids.
- Carbon Management: Loaded carbon undergoes acid washing, elution (ZADRA process at 135°C), and regeneration in a kiln (0.76m x 7.3m, 350 kW).
- Gold Recovery: Electrowinning cells (4.53 m³) process pregnant solution, with gold sludge smelted in a 750-lb induction furnace.
Critical Data
| Parameter | Value | Unit |
|---|---|---|
| Throughput (2019) | 1.4 | Mt/a |
| Feed Grade | 2.8 | g/t Au |
| Overall Recovery | 86.7% | – |
| Grinding P80 | 91.5 | µm |
| CIL Cyanide Concentration | 450 | ppm |
| Reagent Consumption (NaCN) | 0.55 | kg/t |
| Tailings Cyanide (WAD) | <10 | ppm |
Major Equipment
- SAG Mill: 5.5m diameter x 2.7m EGL, 1,130 kW motor
- Ball Mill: 4.0m diameter x 5.3m length, 1,325 kW motor
- Production Thickener: 34m diameter high-rate type
- Elution Vessel: 1.68m diameter, 5.5t carbon capacity
Recent Upgrades (2017-2018)
- Increased SAG mill discharge grate area (3.1% → 4.0%)
- Ball mill pinion replacement for higher power draw
- New NKM screens in CIL tanks (2017)
- Enhanced cyanide destruction system (2019)
