airclassification

Air classification is a size-separation technology that uses an air stream to separate particles in a powder based on their aerodynamic properties. In a typical air-classified system, milled or ground material is carried by a high-velocity air flow. The classifier chamber applies a balance of drag forces and centrifugal forces to determine a cut-off particle size; particles finer than the cut point are carried away with the air, while coarser particles are redirected for further grinding. The resulting product can exhibit a narrow particle size distribution.

Key components include a blower or fan to generate the air flow, a classifier (which may be a rotating wheel or a set of stationary vanes) to establish the cut point, and a separation stage such as a cyclone or bag filter to collect the fines and the coarse fraction separately. The feed rate, air flow rate, and classifier speed are the primary parameters that control the final particle size distribution.

There are two main classifier approaches: dynamic (rotating) classifiers, which use a rotor or impeller to create a centrifugal field, and static (vaned) classifiers, which rely on flow patterns within a fixed chamber. Air classifiers are often integrated with milling equipment such as hammer mills, pin mills, or impact mills, enabling in-line production of powders with specified size ranges. Additional controls may include temperature, humidity management, and dust collection systems to maintain product quality and workplace safety.

Applications are widespread in cement, minerals, pigments, chemicals, pharmaceuticals, and food processing. Benefits include the ability to achieve tight particle size distributions, reduce overgrinding, and improve process efficiency. Limitations can involve material moisture sensitivity, wear of classifier components, and the need for proper dust control and system maintenance.