LaboMill - complete with LaboFeeder (left)     JetMill series (right)

Most of the spiral jet mills currently on the market still have the original flat rectangular shape dating back to the 40’s that creates turbulences (therefore caking problems) and do not allow laminar jet streams.

Some mills still have the original lateral tangential product entry, with blowback problems, asymmetrical spiral, need to work with higher pressure at Venturi, penalising grinding nozzles pressure, poor particles classification and broad Particle Size Distributions (broad Gauss curve with top size problems).

FPS has brought spiral jet mill technology to a real step further by re-designing in 2003 the internal geometries of the milling chamber, geometries that have remained untouched on all jet mills on the market for the last decades !

All angles and all discontinuous geometries typical in rectangular and octagonal jet mills were eliminated and all forms have been brought to a continuous shape as far as technically possible.

Further upgrades were brought to the development of special grinding nozzles that help maintaining jet streams as laminar as possible.

Other upgrades were brought to the geometry of the static classifier optimising the ideal classification of the particles and keeping the PSD with a narrow Gauss curve and eliminating the top-size effect typical in rectangular and octagonal jet mills.

We are pleased to list hereafter the main advantages FPS can offer today to its customers when comparing its newly developed spiral jet mills with the other currently found on the market.

Enhanced productivity

By the elimination of the angles and dead spots and thus elimination of turbulences we have optimised the laminar development of the jet streams formed by the expansion of the process gas through the micronisation nozzles.
This translates in a proper acceleration of the particle in a laminar stream in the shortest space and time and hence in an ideal micronisation effect.
The short transit time in the milling chamber means higher productivities.

Elimination of the “caking” of sticky powders

Turbulences deviate the particles from their laminar acceleration and in many cases send them to collide against the walls of the milling chamber. These collisions leave residuals attached to the walls, especially with sticky powders, that helps the formation of crusts (caking effect) with successive collisions by other particle deviated by turbulences.
Eliminating turbulences and optimising laminar jet streams our mills avoid the caking effect.

Better classification giving very narrow Gauss curves (Particle Size Distribution)

The deviation of the particles given by the turbulences also send them in other directions and of course also towards the centre of the mill where the particles are classified. Eliminating turbulences also avoid coarse particles from being prematurely classified and eliminates the top-size typical of the rectangular and octagonal mills.

Lowest consumptions on the market

Our jet mills are by far the lowest consuming mills on the international market. Consumptions of process gas, especially when utilising Nitrogen can be an important influencing factor in determining production costs.

Low consumptions may also translate in further saving in capital investment, when the purchase of a smaller compressor can be sufficient to operate with our mills.

Elimination of the “blowback” phenomenon

FPS has designed a non-tangential Venturi-entry, entering diagonally from the top directly into the spiral with a special geometry that allows our mills to operate with the same pressure at the Venturi-entry and at the micronisation nozzles, without having the blowback phenomenon. We have eliminated the blowback and, additionally, we can fully exploit 100 % of the available energy at the micronisation nozzles.

Optimised gas-solid separation and unique collecting point with yields close to 100%

Development studies have been carried out by FPS to ameliorate the gas-solid separation in the cyclone-filter. Our new design offers a better separation limiting the fines going to the cartridges or alternatively to the filtering sleeves (both solutions are available). This means less reverse blowing, or less shaking of the filtering media and therefore a much more stable micronisation process. The micronised powder is collected in a single point under the cyclone and typical yields of production are close to 100% (>99.7-99.8%).

Balance and control of pressures within the whole micronisation system

We can control the pressures within the whole system from the milling chamber to the lower and upper part of the cyclone-filter in order to keep the process always perfectly balanced and hence allow the ideal classification of the micronised particles. This is another very important factor influencing the control of very tight particle size distributions (narrow Gauss curve)

Reduction of contact surfaces – rapid cleaning and lower product loss

With the utilisation of the filtering sleeves we drastically reduce the contact surface of the cyclone-filter and keep it to the minimal terms. In fact the filtering sleeves (octopus) are connected to the lower conical part of the cyclone filter and have an inside-out filtering effect. Hence the only part in contact with the powder is the lower conical part. This translates in very rapid cleaning operation, as well as in a drastic reduction of product losses.

Easy cleaning validation operations and short turnaround time

We have eliminated all screws, all angles and we have reduced the weight of each single component for easy handling and cleaning. We use AISI 316L with a mirror polished roughness of Ra < 0.25 my for the contact surfaces. This to allow easy and rapid cleaning and cleaning validation operations and to shorten turnover times between micronisation campaigns.