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stone

Protocol number:	M002224
Industry:	Geology / mineralogy
Feed Size:	~ 8 mm
Desired Fineness:	d90 < 30 µm
Quantity:	100 g
Recommendation:	This kind of stone use to show excellent a grinding behavior. The desired fineness can be achieved shortly with Vibrating Cup Mill PULVERISETTE 9. Even a dry grinding of sample is possible.

Result 1

	Vibrating Cup Mill PULVERISETTE 9 speed: 1300 rpm
Equipment:	100 ml grinding set made of tempered steel
Feed quantity:	100 g
Feed Size:	~ 8 mm
Grinding time:	2 min
Final fineness:	d50 <4,1 µm d90 <24,9 µm
Comments:	After the first minute of grinding, the d90 use to be < 38,3 µm; after the second minute of grinding, a d90 < 25 µm has been achieved. A d90 < 4,1 µm as present after 2 minutes of grinding use to be an excellent dry grinding result. The sample starts to stick to the grinding set. 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. Because of this, a further size reduction is not possible by dry grinding. The sample needs to be ground in suspension to get finer.