Nanonization – Jet Milling with Steam

The successful start of the new s-Jet®® process developed by NETZSCH-CONDUX Mahltechnik has now produced a further addition to the existing program of this new technology.

A compact laboratory-steam jet mill plant was developed for laboratory use and/or for small charges. This mill will be introduced at this year's POWTECH-exhibition in Nuremberg.

The compactly assembled s-Jet®® 25 plant includes all necessary components such as feeding, mill, product separation, control system, armatures and steam generator all on one skid. The space required is only 3 m2 with a maximum required height of only 2450 mm.

During the development of the plant, particular emphasis was placed on obtaining a system for the production of small amounts and product samples as well as for application tests. Further requirements were ergonomic design and easy cleaning as well as condensation of the steam vapor produced during the process. This in turn enables a flexible mounting arrangement of the system.

Easy and quick cleaning and the lowest product loss possible at high efficiency are further points which were emphasized during the development of this plant.

The plant is completely mounted and is dispatched after an internal test run. Central connection points for compressed air and electricity, water and waste water guarantee short installation and commissioning times.

What is behind the s-Jet®®?

Previously, when talking about the ultra-fine milling of solid matters, the term micronization was used, which meant the specific mechanical size-reduction down to a range of approx. 2 µm to 200 µm (d97). Up until now, in the field of dry-grinding this 2 µm was the feasibility limit.

The fact that even finer products, in the submicron- and/or nano-range were required, led to the development of a new technology, which now makes real grinding down to these ranges possible. The „Nanonization“ of solid matters by dry-grinding is now possible with the newly developed s-Jet®®-system and therefore represents the finest form of jet milling.

The name s-Jet®® stands for steam & superfine. Contrary to the conventional dry grinding method using jet mills, the s-Jet®® system uses superheated steam as the grinding gas.

As steam has a considerably higher sound velocity than air, the possible peripheral speed of the flow inside the classifier wheel increases and as a consequence the acceleration energy influencing the product being classified. Therefore, an important step is made to enable the classification of particles down to the sub-micron range by means of dry-grinding.

In addition to this, the s-Jet®® system also has interesting, economic aspects: Jet speeds of up to 1.200m/s can be achieved with steam and the kinetic impact energy of the product particles within the fluidized bed increases more than fourfold! This leads to a considerable increase of the mill throughput compared to that obtained in air operation at similar finenesses.

Since the first s-Jet®® plant in production scale was installed many different products have been tested. The results obtained are convincing and speak for themselves. They show that now, with the newly developed s-Jet®® system, it is possible to achieve particles sizes in the nano-range, which were only achievable with wet-grinding up until now.

Visit us at POWTECH 2011 (Nuremberg, October 11 to 13) in Hall 7, Stand 168