How to design copper sulfide flotation process?

Copper exists mainly in oxide and sulfide ores in nature. Oxide ores are processed by hydrometallurgical routes because they dissolve easily in acids. In contrast, sulfide ores are practically insoluble in acids and must go through the pyrometallurgical route.

The first stage in copper processing is comminution, which frees copper-bearing minerals from the gangue by reducing the ore particle size. Explode in the mine first to break rocks, producing various ore fragments. These large pieces are then crushed in crushers, which is also usually done in mines. Finally, water is added to the crushed ore, and this mixture is sent to a mill where the ore particle size is further reduced and copper minerals are released. The comminution process is energy intensive and energy consumption depends heavily on the composition and texture of the ore, such as mineral particle size distribution and mineral assemblage.

After the crushing step, the minerals go to the concentration step through flotation, filtration and drying. Flotation is aimed at the selective separation and recovery of copper-bearing minerals. It thus produces a process stream concentrated in copper, which is then sent to the smelting and conversion stages, and another flotation tailings stream. The flotation technique concentrates copper sulfide minerals by taking advantage of differences in their surface properties by adding chemical reagents that make them hydrophobic. Then, air is injected at the bottom of the flotation tank to promote the migration of hydrophobic copper sulfide minerals to the surface. Finally, the copper-rich material is dehydrated to a concentration of 20%–45% copper.

The efficiency of a flotation operation depends on the nature and texture of the particles (e.g. mineralogy, morphology, size, mineral assemblage) as well as the type and design of the flotation cells and operating variables (e.g. pH, air flow, pulp density, reagent type and dosage) . In particular, since fine and coarse particles follow different trends in flotation, the effect of particle size on flotation and thus process efficiency is often assessed. Generally, the maximum recovery of copper from sulfide ores is achieved in the median particle size range of 50-70 μm.

Another factor that must be evaluated to ensure flotation efficiency is mineral composition. In copper flotation, valueless iron sulfides (mainly pyrite) are often associated with valuable sulfide minerals such as chalcocite and chalcopyrite. Therefore, the separation of pyrite and copper minerals is more important in the flotation stage.