Impact attrition in crystallization processes. Analysis of repeated impacts events of individual crystals

In industrial crystallizers, attrition, which refers to the process by which asperities and fines are removed from the surface of parent crystals, is recognized as a major cause of secondary nucleation. In dilute suspensions, it is mainly a consequence of collisions of particles with parts of the equipment (impeller or walls). This paper compares the attrition of two types of crystals having different mechanical and physico-chemical properties: laboratory made cubic sodium chloride crystals, used as model particles and elongated industrial sodium glutamate crystals. A specific attrition experiment was designed to create impacts of crystals suspended in saturated solution, on a target simulating the impact conditions occurring in crystallizers. The volume of attrition fragments produced by the two products and the influence of impact velocity and number of impacts were studied. An attempt to correlate the data to the impact energy is made by considering the model of Gahn and Mersmann.