What you didn’t know about breakage of anisotropic rod-shaped particles

Authors: V Penkavova1*, L Kulaviak1, MC Ruzicka1, M Puncochar2, P Zamostny3

1 Department of Multiphase Reactors, Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Prague, Czech Republic,

2 Environmental Process Engineering Laboratory, Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Prague, Czech Republic,

3 Department of Organic Technology, University of Chemistry and Technology, Prague, Czech Republic


Summary

Many products and intermediaries in industry are manufactured in the form of anisometric particles, depending on the molecular composition and finalization process (e.g. active pharmaceutical ingredients or pigments in dye industry). Some technological steps (filtration, filter washing, drying, transportation) can lead to uncontrolled changes in the Particle Size Distribution (PSD) due to particles attrition and breakage. When a randomly packed layer of anisometric particles is compressed (its weight, external force), it is of interest, both academic and practical, to find the relationship between the applied stress, compressibility and breakage.

In this experimental study, behaviour of dry granular layers of monodisperse cylindrical particles (8×1 mm) under uniaxial compression was studied. The layer compressibility and PSD were evaluated. The effect of several parameters was investigated: piston speed, layer size (diameter and height), applied pressure. Two modes of compression were tested: non-recurring and recurring. In the former mode, after the compression, the particles were taken out of the measuring cell for granulometry. In the latter mode, after granulometry, the particles returned to the cell for the next run with the same pressure.

It was found that neither the piston speed nor the layer size were relevant, within our experimental range. The resulting compressibility and PSD were affected mainly by the normal pressure and the way it was applied. In the non-recurring mode, with increasing pressure, PSD moves toward smaller sizes of broken particles always leaving some initial particles intact. In the recurring mode, the pressure had more destructive effect, resulting in larger particle fragmentation. The reason is seen in the particle re-arrangement between the successive tests.

 

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