Air classification is a process of separation categories of materials by way of differences in their respective aerodynamic characteristics. In the interaction, the drag force and the gravitational force are exerted in different directions upon the particles. The result is that waste particles that have a large drag-to-weight ratio are suspended in the air stream, whereas components that have a small ratio tend to settle out of the air stream. The former fraction conventionally is referred to as the “air-classified light fraction” and the latter fraction is termed “air-classified heavy fraction”. The confined volume in which the separation takes place is called an “air classifier”. The classifier can be divided into three principal groups, which are horizontal, inclined, and vertical.
The velocity of the air stream required to lift a particle in a vertical column must exceed a minimum value, termed the floating velocity. The floating velocity is a function of a lot of parameters.
Air classification is advantageous in that it can enhance the quality of other processes such as magnetic separation by removing unnecessary materials. Also, air classification is able to separate light aluminum from heavier