Limestone

To get the desired fineness of <1µm, the start size is too big for grinding in one Step. Therefore, a first pre grinding is done in dry form by using 20mm balls.

*1: After 3 minutes of pre grinding, all sample is < 100µm. The sample shows a very light sticking; a longer dry grinding is not recommended. This is a good start size for grinding with 5mm balls to the desired fineness.

See step 1b.

*2: See our particle size analysis after 3min of grinding with ANALYSETTE 22 NanoTec,on Meas.No 9616.

This test has been done twice. Once to proceed in trial 1b and a second time to show the fineness of a dry grinding (see sample 1a).

After trial 1a, we changed the balls to 5mm, we added 175ml of water and grinded the sample to the full hour.

*1: After 1 hour of grinding, the bowl is filled to the maximum. The sample becomes a gray paste. To achieve an optimum grinding result, it is recommended to grind in more oily slurries.

For a further grinding, we recommend to use less of sample (see trial 1c / separately packed of sample/water mixture after 1h of grinding. ) or start with a bowl of 500ml for grinding.

To avoid overpressure by grinding with water, it is necessary to keep the temperature of the bowl < 90°C. Therefore, we grinded in steps of 5 minutes followed of a programmed pause of 10 minutes. By observing the temperature, the cooling time might be readjusted. This also applies to all following trials. While grinding this sample, the outside of the bowl staid <90°C, therefore, the pausing time can be down regulated.

*1: For a further grinding of trial 1b, the bowl was filled too much. We packed 85g of the water/sample mixture after 1 hour and replaced it with 80ml of water. It is also possible to use the 500ml bowl with about 2000x 5mm balls (~800g) for grinding the desired amount of 100g of sample.

*2: During the grinding, the sample gets finer each time we measured its particle size distribution.

After 2 hours of grinding, a d50 < 1µm was found. See our particle size analysis after 120min of grinding with ANALYSETTE 22 NanoTec,on Meas.No 9624.

After 4 hours of grinding, the bowl is almost filled to the maximum again.

*3: See our particle size analysis after 4 hours of grinding with ANALYSETTE 22 NanoTec,on Meas.No 9639.

To obtain a better result, a longer grinding is still possible.

We recommend using the 500ml bowl with 800g of 5mm balls for grinding your sample. To obtain a better result, a longer grinding is still possible.