Quick lime sample (gray and beige)

As desired, also a Disk Mill PULVERISETTE 13 has been tested with both of your samples. With this machine, particles need to be ground to < 0,1 mm in one dimension to pass the gap. For this, still longer and wider particles can be found in the collecting vessel.

It took 20 seconds until the complete sample amount got ground. The grinding disks use to be lightly polluted, electrostatic charged sample (usually about 8 ± 2 g) remains loose inside the grinding chamber.

A grinding of higher amounts of sample is still possible. Cleaning of the machine can be performed rapidly by vacuuming with a soft brush.

To determine the final particle size, we used a Vibratory Sieve Shaker ANALYSETTE 3 with a test sieve of 100 µm mesh. 10-20 g of ground sample has been sieved for 5 minutes at amplitude 2,5 mm. Afterwards, we determined a fraction < 100 µm of 79,3 %.

Second sample with gray surface has been ground equally. Without changing the settings of gap, it took 30 seconds until the complete sample amount has been ground.

After grinding, electrostatic charged sample use to stick lightly to the grinding chamber by electrostatic charge. Cleaning can be performed rapidly by vacuuming with a soft brush. The grinding disks are not polluted in the outer area where the gap uses to be smallest, for this, a grinding of higher amounts of sample is still possible.

As mentioned in result 1, particles only need to be ground to < 0,1 mm to pass the gap of the grinding disks. Therefore, by sieving still higher amounts of sample > 0,1 mm can be found.

We determined by sieving a fraction of 56 % of ground particles which uses to be the < 100 µm.

Also a planetary mill comes into question for a rapid grinding of samples. After one minute of grinding, the sample is lightly sticking to the grinding bowls,

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.

Much longer dry grinding times are recommended.

We aborted the grinding process after a total of 2 minutes. By sieving, present fineness has been determined. Already 91,4 % of sample use to be < 100 µm.

Just for demonstration, we took a further sample and ground for a total of 4 minutes. Afterwards, reagglomerated particles only partly got sieved and therefore, 88,3 % of particles have been found < 100 µm.

Gray surfaced quick lime sample has been ground analogue result 3. After 3 minutes of grinding, the sample started sticking stronger to the grinding balls.

A longer dry grinding is not recommended for this sample.

By sieving, a fineness of 93 % < 100 µm has been determined.

To achieve a better fineness, we recommend grinding in suspension (e.g. with solvents for fast evaporation); or a grinding in batches with steps of separation of fine particles (by sieving or sifting).

With the smaller 100 ml grinding set made of tempered steel, maximum 160 g of sample do fit in. With a 250 ml grinding set, a grinding of 250 grams of sample should be possible.

After 1 minutes of grinding, sample already starts sticking to the radius of the grinding set. A longer dry grinding is not recommended.

We determined a fineness of > 98 % < 100 µm.

The rests of gray surfaced sample have been ground in the bigger 250 ml grinding set made of hardmetal tungsten carbide. A 250 ml grinding set will be suitable for comminution as well. Probably grinding time will be lightly increased with a set made of steel.

After only 1 minute of grinding, sample use to stick stronger in the radius of the grinding set.

A present fineness of 90 % < 100 µm has been determined by sieving.