The Alpine AFG Fluidized Bed Jet Mill is suitable for fine and ultrafine size reduction of any material up to a Moh's hardness of 10 that can be fluidized by the expanded compressed gas in the grinding chamber. The addition of an internal forced vortex classifier is capable of controlling particle top sizes (D97) as low as 3 microns.
The key to maintaining a consistent particle size distribution is the integral air classifier. Air classification is defined as the separation of bulk material according to the settling velocity in a gas. In this type of jet mill two opposing forces act on the particle, the mass force and the drag force. The particle size at which the mass force and the drag force act equally on the particle is defined as the cut point. If the mass force (or weight of the particle) exerts a greater influence on the particles coarser than the cut point, they are returned to the grinding zone of the jet mill and reduced further. If the drag force (or airflow through the classifier) acts upon particles finer than the cut size, they are carried through the classifier wheel and recovered as product.
By changing the parameter of classifier wheel speed, airflow, and grind pressure, a wide variety of particle size cut points can be achieved. Achievable particle size ranges include D97 as low as 3 microns to as high as 60 microns.