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In the present study, computational fluid dynamics (CFD) simulations have been carried out to characterize a solid suspension in a gas−liquid−solid mechanically agitated contactor using the Eulerian multifluid approach with a standard k−ε turbulence model. A steady state method of 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 (Guha et al. Chem. Eng. Sci. 2007, 62, 6143; Spidla et al. Chem. Eng. J. 2005, 113, 73; Aubin et al. Exp. Therm. Fluid Sci. 2004, 28, 447) and quantitatively with our experimental data. Also the effect of different types of impellers (disk turbine and pitched blade turbine with downward pumping), impeller speed, particle size (125−230 μm), and gas flow rate (0−1 vvm) on the critical impeller speed for solid suspension in a gas−liquid−solid mechanically agitated contactor is investigated. The values predicted by CFD simulation agree well with experimental data for various operating conditions.

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Axial bed depth profiles were experimentally measured in a rotary kiln containing ilmenite particles under steady state and transient conditions. The variables include feed rate of solids, inclination and rotational speed of the kiln. and dam height. The variation of the axial velocity with kiln axis was estimated. The semi-experimental model proposed by Perron and Bui (1990) was modified to include the effect of the variables of the present study. The mean residence time of solids was estimated from the fractional hold-up and expressed in terms of the process variables. The transients induced by a step change in any of the operating conditions were measured as variation of discharge rate of solids with time.