In the present work, CFD simulations have been carried out to study solid suspension in gas-liquid-solid mechanically agitated contactor using Eulerian-Eulerian multifluid approach along with standard k -epsilon turbulence model. A multiple frame of reference (MFR) has been used to model the impeller and tank region. The CFD model predictions are compared qualitatively with the literature experimental data and quantitatively with our experimental data. The present study also involves the effects of impeller design, particle size and gas flow rate on the critical impeller speed for solid suspension in gas-liquid-solid mechanically agitated contactor. The values predicted by CFD simulation for critical impeller speed agrees well with experimental data for various operating conditions. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.