Classification is a process that separates coarse particles from fine particles. This allows the control of product particle size to achieve characteristics such as better flowability. Hosokawa’s classifiers are of the dynamic type where a flow of gas carrying powder flows through a rotating rotor. The rotor imparts a centrifugal aerodynamic force onto the particles which pushes heavier particles out of the rotating rotor while the lighter particles flow with the air through the rotor and out of the classifier. Depending upon the product requirements, either the fine powder or the coarse powder may become the product. In some cases, both the coarse and fine powder can become different grades of product. The optimum classifier model is selected depending upon requirements such as particle size, agglomeration properties and wear properties of the processed material. As a guideline, a model selection chart is shown in Fig.1.
Various different types of classifier rotors have been developed to meet different requirements such as achieving the smallest possible classification point or to give the maximum throughput rate at the lowest power consumption. Typical classifier rotors are shown below.