A simple model for the hydrodynamics in Type I TBC is developed for the prediction of hydrodynamic variables such as the phase holdups, bed expansion and pressure drop based on the model by Chern et al. (1983. Hydrodynamics of constrained inverse fluidization and semifluidization in a gas-liquid-solid system. Chemical Engineering Science 38, 1167). This is done by modelling the TBC as a packed bed with large porosities carrying countercurrent gas-liquid flow. The process parameters considered are gas and liquid velocities, particle size and density. The dependence of hydrodynamic variables on process parameters predicted by simulation agrees well with that reported in literature. © 2005 Elsevier Ltd. All rights reserved.