In mining, the term “grinding process” describes the mechanical reduction of ore or rock particles’ size in order to make the extraction of important minerals easier. It is an essential part of the comminution circuit, which is in charge of getting the ore ready for flotation, leaching, and smelting, among other phases of mineral processing.
Grinding significantly affects downstream recovery in flotation by influencing mineral liberation, particle size distribution, surface chemistry, and flotation circuit design.
Effect on mineral liberation and recovery
Proper grinding liberates valuable minerals from the gangue, which is critical for flotation recovery. If grinding is insufficient, minerals remain locked in composites, reducing flotation efficiency. Conversely, overly coarse particles float poorly due to incomplete liberation. Ultrafine grinding to sizes below 15 µm, when done in appropriate equipment such as an IsaMill, can increase liberation and thus flotation recovery, as observed in Mount Isa Mines where ultrafine grinding improved lead recovery by 5% and zinc recovery by 10%.
Particle size distribution and flotation efficiency
Grinding affects the size distribution of particles entering flotation. A narrow size distribution optimized for flotation favours better recovery because flotation conditions can be tailored effectively. Flotation works best when particles have similar sizes since fine and coarse particles have different hydrodynamics and reagent requirements. Mixing wide size ranges can limit recovery, especially for fines, which tend to float poorly when floated together with coarser particles.
Surface chemistry and grinding environment
The grinding environment impacts surface chemistry. For example, grinding in steel mills can introduce contaminations that depress flotation performance, while inert grinding environments (like IsaMill) enhance mineral surface properties, improving flotation behavior. Ultrafine grinding can remove surface deposits that slow fine particle flotation, improving recovery even for ultra-fines below 15 µm.
Flotation circuit design implications
Effective grinding supports staged flotation circuits where concentrates are reground to finer sizes to improve liberation and recoveries. This approach minimizes circulating loads, reduces reagent consumption, and stabilizes flotation circuits, leading to better overall plant performance. The Mount Isa plant’s staged grinding and flotation circuit is a classic example where grinding and flotation are closely integrated for maximum recovery.
Summary
- Grinding improves mineral liberation, which is crucial for flotation recovery.
- Optimal particle size distribution from grinding allows tailored flotation conditions, improving fine and coarse particle recovery.
- Grinding environment affects surface chemistry and flotation efficiency.
- Staged grinding and flotation circuits reduce circulating loads and reagent use while enhancing recovery.
Thus, grinding affects downstream flotation recovery by enabling mineral liberation, optimizing particle size, improving surface characteristics, and allowing more effective flotation circuit design.
