clinker

The used 20 mm Ø grinding balls use to be capable for grinding the clinker start size.

Sample starts sticking to bowl and ball after the first minute of dry grinding.This uses to happen after the majority of particles reached a fineness of < 20-30 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 used grinding balls. These clusters of particles also contain bigger particles which will not be ground any further.

To improve grinding result, anti-sticking agents can be added to delay the sticking effect. It is also possible removing fine ground particles by sieving or sifting and proceed dry grinding with coarse fraction until sticking of sample use to be displayed again.

Also a pre drying of sample can improve the grinding result (moisture will lead to a faster sticking of sample).

By grinding in suspension, interacting forces will be eliminated and sample can be ground completely to < 180 µm (and much finer) too.

Methanol can be used as anti-sticking agent (just as aerosil, talcum, glycol,…). Before grinding, we added 6 droplets of methanol to the sample. After 1 minute of grinding, we checked the present fineness with our Laser Particle Sizer ANALYSETTE 22 and found 99,6 % of sample < 180 µm.

We recommend varying the amount of anti-sticking agent for achieving 100 % < 180 µm.

After grinding, the used methanol use to evaporate quickly after grinding (boiling point ~ 65 °C).