Validation of the Eulerian simulated dynamic behaviour of gas-solid fluidised beds

Abstract

In this paper, a Eulerian-Eulerian CFD model for a freely bubbling gas-solid fluidised bed containing Geldart-B particles is developed for studying its dynamic characteristics. This CFD model is based on the kinetic theory of granular flow. Van Wachem et al. (1998a) Comput. Chem. Engng 22 (Suppl.), S299-S307 have shown that this model is capable of providing reasonable predictions of the time-averaged properties. In this paper, the dynamic characteristics of the gas-solids behaviour at different superficial gas velocities, at different column diameters, and at different pressures are evaluated, namely (A) the velocity of pressure and voidage waves through the bed, (B) the power of the low and high frequencies of the pressure and voidage fluctuations, (C) the reorientation of the gas-solids flow just above minimum fluidisation and the effect of elevated pressure upon this reorientation, and (D) the Kolmogorov entropy. The CFD simulation results for items (A)-(D) are compared with published experimental data and with appropriate correlations from the literature. A good agreement is found between the Eulerian-Eulerian CFD simulations of bubbling fluidised-bed dynamics, and the data from experiments in the literature. This is a strong incentive for the further development of this type of simulation models in fluidised-bed reactor design and scale-up.