Overview
The Björkdal gold processing plant, originally commissioned in 1989, has undergone numerous upgrades to increase throughput while maintaining gold recovery. The circuit combines crushing, grinding, gravity concentration, and flotation to produce multiple gold concentrates.
Key Process Stages
- Crushing Circuit: Three-stage crushing (primary jaw + secondary/tertiary cone crushers) to achieve P80 of 8mm
- Grinding Circuit: Parallel primary ball/rod mills (No.1 & No.2) with classifying screen, secondary ball mill (No.3) for regrinding
- Gravity Concentration: Rougher/cleaner spirals → shaking tables → Knelson concentrators → final cleaner tables producing 60% Au concentrate
- Flotation Circuit: SkimAir flash flotation → rougher/scavenger flotation → two-stage cleaning producing final concentrate
- Recent Upgrades: G-max cyclone battery (2021), ball mill conversion to grate discharge (2023), toe position measurement system (2024)
Critical Data
| Parameter | Value |
|---|---|
| Primary Grinding P80 | 560 µm |
| Primary Cyclone Underflow P80 | 800 µm |
| Secondary Ball Mill Discharge P80 | 475 µm |
| Primary Cyclone Overflow P80 | 230 µm |
| Flotation Cyclone Overflow P80 | 125 µm |
| Gravity Concentrate Grade | 60% Au |
| Middlings Grade | 1,500 g/t Au |
Historical Modifications
| Year | Modification |
|---|---|
| 1990 | 750 kW regrind mill installed |
| 1992 | Sala 6.6 m³ flotation cell added |
| 2005 | Knelson CD12 + 7.5 kWh regrind mill installed |
| 2009 | Knelson XD30 installed pre-flotation |
| 2013 | Reichert cones replaced by rougher spirals, SkimAir-240 installed |
| 2017 | Flotation expansion for increased capacity/recovery |
| 2018 | Mintek Expert Process Control System installed |
Planned Improvements
The recent conversion of Ball Mill 2 from overflow to grate discharge has shown significant grinding efficiency improvements, with further throughput gains expected. The new toe position measurement system (2024) will optimize mill performance.
