A series of ideally mixed fluidized beds is used to obtain a narrow product size distribution in industrial scale applications. Thereby, the fluidized bed compartments or stages are divided from each other by weirs with defined openings (slots) for particle exchange. The knowledge of particle exchange streams and residence times in different compartments, respectively, is crucial for the process design and optimization of such processes. This particle exchange behavior between different compartments in 3D-fluidized bed systems cannot be easily evaluated by experiments. Hence, a CFD multiphase model is used here and applied to a horizontal two-compartment batch fluidized bed apparatus to obtain particle exchange streams as a function of process parameters, e.g. slot height and bed mass. Good comparison of numerical and experimental results shows that this model can reasonably predict the particle exchange in two-compartment fluidized bed processes. On the basis of this work, the validated and predictive multiphase model can be applied to continuous horizontal multi-compartment fluidized beds as a future perspective to identify best-case process parameters, e.g. optimal slot height. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.