Luchtjetmilling

Luchtjetmilling, or air jet milling, is a dry comminution technique in which fine powders are produced by the impact and attrition of particles accelerated through high-velocity jets of compressed gas, usually air or nitrogen, inside a sealed grinding chamber. Unlike conventional ball milling, it uses no moving grinding media, and the predominant size-reduction mechanism is particle-particle and particle-wall collision driven by gas jets.

In a typical installation, feed material enters the grinding chamber and is subjected to jets issuing from nozzles. The gas accelerates particles, causing repeated collisions that fracture the material. A classifier integrated into the mill or mounted downstream separates product in the desired size range; oversized material recirculates for continued milling.

The technique is widely used for heat-sensitive or moisture-sensitive materials such as pharmaceuticals, pigments, ceramics, and some polymers because there is no liquid grinding medium and minimal contamination from grinding media. Particle sizes can be driven to very fine ranges, often from tens of micrometers down to sub-micron levels with appropriate equipment and control. Choice of gas (air or inert) and cooling can mitigate temperature rise during processing.

Practical considerations include energy intensity, throughput limitations for very hard materials, and the need for specialized handling due to fine dust. Safety concerns include dust explosions and requires proper ventilation, dust control, and containment; inert gas may be used for flammable powders. Costs are higher than some alternative mills, but product purity and the absence of grinding media can justify its use in suitable applications.