Spiral jet mills are frequently used in the pharmaceutical industry and for the production of fine chemicals. The operation of the spiral jet mill of Ebbecke Verfahrenstechnik AG from Bruchköbel is relatively simple: The grinding air is injected tangentially at the nozzle ring via Laval nozzles. This creates the spiral flow in the grinding chamber from which the mill gets its name. Due to the spiral flow, a high pressure is built up within the mill. The attached injector, operated by compressed air, ensures that the material to be ground is fed into the machine despite the overpressure. The material to be ground is circulating near the nozzle ring and is repeatedly picked up by the air jets.

Size reduction is achieved by particle collisions due to different particle velocities in the nozzle jet. Along with the air, the comminuted material is drawn to the outlet orifice. The particles are subjected to a classifying effect due to the spiral movement: only fine particles are discharged, coarse particles remain in the mill.

The characteristics of a spiral jet mill at a glance:

• Vertical mill housing for easy handling
• Special grinding chamber geometry for products free of particles
• Grinding chamber without rotating inserts
• Material feed via injector
• Interchangeable nozzle ring

Spiral jet mills are mainly used for high-quality pharmaceutical substances, e.g. antibiotics or fine chemicals, where high demands are placed on the purity and fineness of the products.