The paper is dealing with new model describing the crystal attrition in the crystallizer with inner circulation forced by means of propeller. The model has been testified on the basis of experimental data. The experiments were carried out, using potash alum crystals, in laboratory scale mixer of volume 1.5(.)10(-3) m(3). Proposed solution enables to determine the kinetics of particle attrition in the hydraulic conditions close to that which are generated in the typical DTM apparatus.