What happens during comminution in a mineral processing plant?

During comminution, ore is physically broken down to liberate valuable minerals from waste rock. This process typically occurs in two primary stages: crushing and grinding.

Crushing

Most ores consist of hard rock masses that require size reduction before processing. Crushing is generally performed in stages under dry conditions:
* Primary Crushing: Large jaw crushers reduce ore to pieces smaller than 150 millimetres.1
* Secondary Crushing: Cone crushers further reduce the material to less than 10 to 15 millimetres, creating a suitable feed for grinding mills.1

Grinding

Grinding reduces the crushed material into a fine powder, with the required fineness determined by how the desired mineral is disseminated within the ore. This stage often utilizes grinding mills, which can operate under wet or dry conditions. Common methods include:2
* Cylinder Mills: These use tumbling grinding bodies, such as steel balls or flint stones, to disintegrate the ore.3
* Autogenous/Semiautogenous Mills: Autogenous mills use the ore itself as the grinding medium, while semiautogenous mills incorporate a small percentage of metal spheres to assist the process.3