Calcium Carbonate

In our first trial, we wanted to test the grindability of sample by impact and shearing force.

Because the start size uses to be that smaller as 1 mm, we used the smallest available sieve ring directly, without a pre grinding step.

The desired sample amount has been fed within 90 seconds. Only a bit of sample dust use to stick on the surface of the rotor ribs and sieve ring. There is no significant blocking of openings on the sieve ring. For this, even higher amounts of sample can be ground this way.

To determine the achieved fineness, we used the Laser Particle Sizer ANALYSETTE 22 Compact and found a d50 < 5,5 µm which use to be fulfilling.

Rapid cleaning can be performed by vacuuming with a soft brush. For an intensive cleaning, all grinding parts can be dissembled and washed with water.

Also a Mortar Grinder PULVERISETTE 2 might be capable to achieve the desired fineness.

With a standard setting of downforce and side pressure (1 ring ≙ ~16 daN), sample starts to stick after a grinding time of 20 minutes.

This uses to happen after the majority of particles reached a fineness of < 20 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and become compressed by the pestle. These clusters of particles also contain bigger particles which will not be ground any further.

A longer dry grinding time is not possible anymore. Only grinding in suspension might be possible to improve the grinding result.

A fineness of d50 < 2,6 µm has been determined (with Laser Particle Sizer ANALYSETTE 22 Compact) .