Full definition
A hydrocyclone is a critical classification device widely used in the mining and mineral processing industries. It operates on the principle of centrifugal force, which is generated by the tangential feed of a slurry into a cylindrical-conical vessel. This design allows the hydrocyclone to separate particles based on size and density with no moving parts, leading to its robustness and low maintenance requirements. The slurry enters the cyclone at high velocity, creating a vortex that facilitates the separation process. The centrifugal force can range from 300 to 2,000 times that of gravity, depending on the diameter of the cyclone, which significantly enhances the efficiency of particle separation.
The separation occurs as heavier and coarser particles experience greater centrifugal force, pushing them outward and downward through the underflow (apex/spigot). In contrast, lighter and finer particles are carried inward and upward through the overflow via the vortex finder. The cut size, or d50, is a critical measurement that indicates the particle size at which 50% of particles report to each product stream, typically ranging from 5 to 150 μm. This cut size can be manipulated through various parameters, including the cyclone's diameter, feed pressure, and the sizes of the apex and vortex finder, as well as the properties of the slurry itself.
Cyclone diameters vary significantly, from 25 mm used in laboratory settings for fine classification to 1,500 mm for primary grinding circuits. The wear components of the hydrocyclone are also crucial for its longevity and efficiency. Common materials used include rubber linings (with a Shore A hardness of 40-55 for impact zones), polyurethane for fine abrasion zones, and ceramic inserts for extreme wear conditions. Leading brands in the hydrocyclone market include Metso Outotec with its CAVEX involute feed design, Weir Minerals (Krebs), FLSmidth, and Eral. Applications of hydrocyclones extend beyond classification in grinding circuits to include thickener feed, desliming, and dewatering, making them versatile tools in mineral processing.