On the size distribution of fragments generated by crystal collisions

The present work reports the results of so called "impact experiments" on nine different kinds of crystals, five inorganic salts and four organic acids, performed by letting ten crystals fall through an evacuated tube onto a glass plate. The ratio between the abraded volume of a crystal and the volume of the crystal itself is inversely proportional to the plasticity index of the material. The size distribution of the fragments, in terms of number density function vs. size, is well fitted for all the systems by a power law equation with an order equal to -2.82. For one of the system examined, potassium sulphate, the size distributions of fragments obtained by the impact experiments have been successfully compared with those of the fines produced during batch seeded crystallizations carried out at low supersaturations. It therefore appears that the size distribution of the fragments generated by crystal attrition in a crystallizer may be generally predicted by means of the proposed power law equation.