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Grinding is the main part of the mineral beneficiation process. Its purpose is to fully dissociate the gangue minerals from the target minerals, and to provide materials with suitable particle size for subsequent flotation operations. The flotation effect of minerals is mainly determined by the mineral surface properties and pulp properties, and these two decisive factors are affected by the grinding method, grinding medium and grinding fineness in the grinding process.
Let's learn about them one by one!
Take sulphide ore as an example, compared with the product after dry grinding and wet grinding under the same conditions, the flotation froth of the particles after dry grinding is more stable and the flotation speed is faster, the surface of the minerals after wet grinding is smoother, while the surface of the minerals after dry grinding is rougher, which increases the area of the trapping agent SIBX (sodium isobutyl xanthate) and the action of sulphide ore. Therefore, the flotation of sulfide ore after dry grinding is better than wet grinding，but the flotation of sulfide ore is a complex system, and the influence of oxidation degree on the grinding-flotation system should also be considered.
The research on the effect of grinding media on flotation mainly focuses on iron media, ceramic media, agate media and zircon balls. During the grinding process, the grinding medium and the ore particles collide continuously, and the composition of the medium will have an important influence on the surface properties of the mineral.
Taking galena as an example, different grinding media can cause significant differences in pH, pulp potential, dissolved oxygen content, Pb and Fe concentration, which affect the flotation effect of galena. The flotation effect of galena was better than that of iron media grinding with ceramic media; meanwhile, the flotation speed of galena was faster with ceramic media grinding compared with iron media grinding, indicating that ceramic grinding is more favorable to the rapid flotation of galena.
The main role of grinding operation is to provide qualified size products for subsequent flotation operations, the impact of grinding fineness on flotation is crucial.
If the material is too coarse, the dissociation of the useful minerals is not high, and the particles are too large to be easily floated by the froth, resulting in a low recovery of the target minerals; too fine particles will lead to a reduction in the selectivity of the flotation chemicals, which will not only result in a low concentrate grade, but also greatly increase the amount of flotation chemicals.
For most of the ores, the content of grinding fineness -74 μm directly affects the flotation recovery index, and the suitable grinding fineness not only determines the flotation recovery, but also reduces the energy consumption and steel consumption of the mill.
Taking molybdenum ore as an example, a better overall recovery and concentrate grade can be obtained at a grinding fineness of -74 μm accounting for 65%. Industrial tests showed that after optimizing the on-site grinding fineness -74 μm to 65.22% from 60.13%, the molybdenum recovery increased by 0.83 percentage points, the molybdenum concentrate grade increased by 0.78 percentage points, and the electricity and steel consumption of the ball mill were reduced.
Grinding is a complex physical and chemical process, Different grinding methods, grinding media and grinding fineness will have an important influence on the flotation effect of minerals. Grinding and flotation operations should be considered as a whole, and the impact between the two should be considered comprehensively. It is recommended that all mine owners consult a qualified concentrator manufacturer to design the grinding and flotation process and purchase equipment such as grinding and flotation machines.
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