Netzsch has released its new PROPHI pre-grinding unit, which grinds coarse feed material that is difficult to handle in a standard mill.
The PROPHI 20 is a disc agitator bead mill modified for coarse grinding with high throughput and a grinding chamber volume of approx. 20 litres. In the peripheral speed range of 8–12 m/s, a product throughput of up to 25 m³/h can be achieved with this machine size. The diameter of the grinding media used typically ranges from 2.0 –4.0 mm.
During development of the pre-grinding unit, a disc agitator was selected because the same net power input yields almost double the grinding chamber volume than when using a pin agitator. This gives significantly more grinding body contacts and a larger cooling surface for grinding.
With a pre-grinding unit, the particle size distribution of a product can be adjusted so that very small grinding media can be used in the subsequent fine-grinding stage. Tests have shown that process control with the Netzsch PROPHI pre-grinding unit can reduce the specific energy requirement by more than 50% as compared with using classic pre-dispersion systems.