Liquid nitrogen mill from Hosokawa

The variation on Hosokawa's Alpine Contraplex 160 C is aimed at processors of heat sensitive products, including pharmaceuticals and foodstuffs, and uses a cryogenic ultrafine grinding system based on liquid nitrogen.

Precrushing energy is reduced as liquid nitrogen causes the feed material to become brittle, allowing the mill to achieve high levels of grinding performance, according to the firm. The cryogenic mode also prevents grinding losses and thermal damage to the feed material that would otherwise be caused by the volatisation or overheating of constituent ingredients.

As an added bonus, the inert gas atmosphere within the mill provides a high degree of safety when grinding flammable and potentially explosive products.

Hosokawa​ nots that the mill design prevents product deposits and ensures trouble free continuous grinding even on sticky products. The speed of the pin disc on the housing side is 16,500 rpm, with a speed of 12,000 rpm on the door side, giving a relative circumferential speed of 240 m per sec.

The mill operates over a temperature range down to -80°C at mill exit and, dependent on the product, a throughput capacity of between 5 and 150 kg per hr is achievable with a fineness range between 20 and 80 microns. It can also be operated without liquid nitrogen.

The range of contra-rotating Contraplex pin mills includes machine sizes from 160C to 1120CW, suitable for a wide variety of different products.