The main goal of this paper is to model a multiphase flow of a monodispersed suspensions in various types of crystallizers: Draft Tube Magma (DTM), Double Draft Tube (DDT) and Fluidized bed (FL). To do this, the CFD (Computational Fluid Dynamics) methods were used. The geometry of model apparatus was similar to those applied in industry. The composition of suspensions and their physical properties were the same as in practical cases. The computations showed that axial velocity distribution in the investigated types of crystallizers were far from optimal. In each case backward circulation loops have been observed. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.