Radial solids velocity profiles were computed on seven axial levels in the riser of a high-flux circulating fluidized bed (HFCFB) using a two-phase 3-D computational fluid dynamics model. The computed solids velocities were compared with experimental data on a riser with an internal diameter of 76 mm and a height of 10 m, at a high solids flux of 300 kg m(-2) s(-1) and a superficial velocity of 8 m s(-1). Several hundreds of experimental and numerical studies on CFBs have been carried out at low fluxes of less than 200 kg m(-2) s(-1), whereas only a few limited useful studies have dealt with high solids flux. The k-epsilon two-phase turbulence model was used to describe the gas-solids flow in an HFCFB. The model predicts a core-annulus flow in the dilute and developed flow regions similar to that found experimentally, but in the region of highest solids concentration it is somewhat overpredicted at the level close to the inlet. (C) 2007 Elsevier B.V. All rights reserved.