The installation of inclined plates into fluidised beds yields significant increases in segregation rates, and hence new opportunities for achieving process intensification. The expansion behaviour of suspensions in such a system was investigated both experimentally and theoretically. The present paper builds upon the work of Galvin and Nguyentranlam (2002), incorporating improvements into the general theoretical framework, and extending the description of the system to cover binary suspensions. The paper provides a definitive assessment of the model, using an idealised experimental system that matches the arrangement used to define the model. The validation of the model is far more thorough than in the previous study, covering both the suspension concentrations, and the suspension lengths within the inclined channel. The theoretical description is likely to prove useful when applying the new system to adsorption, crystallization, and particle separations. In general, there is good agreement between the theoretical model and the experimental data, thus indicating the essential elements of this new fluidised bed system have been captured. (C) 2004 Elsevier Ltd. All rights reserved.