iron ore

Because of the limited amount of sample, 250 ml grinding bowl has been used. For a grinding of higher amounts, up to 4 grinding bowls of 500 ml volume can be used for a simultaneous grinding of sample.

After 5 minutes of dry grinding, sample starts sticking. 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.

The achieved fineness has been determined by sieving with our Vibratory Sieve Shaker ANALYSETTE 3 Pro and a test sieve of 140 µm mesh. Already 83% of sample use to be < 140 µm as desired.

To improve the grinding result, it is possible to separate desired fine fraction by sieving or sifting (classifying) and proceed dry grinding the coarse fraction.

It is also possible to grind in suspension to avoid sticking of sample and achieve 100 % < 140 µm.