In this work, experimental and computational fluid dynamic studies have been carried out for hollow self-inducing three-phase stirred tank systems. The effect of different impeller designs (hollow self-inducing pitched blade down flow turbines of different blade angles (PBTD30, PBTD45, PBTD60), and self-inducing modified double disc (MDD) impeller) and operating conditions such as solid loading (0-7 wt. %) and solid particle size (125-700 mu m) have been investigated on critical impeller speed for solid suspension (N-CS), gas induction rate (Q(G)) and overall gas hold-up (is an element of(G)). Computational fluid dynamics model based on the Eulerian multi-fluid approach has been employed along with the standard k-epsilon. turbulence model. A multiple reference frame (MRF) approach was used to model the impeller rotation. In this study, the multiphase flow has been simulated using a commercial CFD code, Fluent v6.2.16. A good agreement was found between the CFD predictions and the experimental values of N-CS. (C) 2008 Elsevier B.V. All rights reserved.