Two-fluid modeling of Geldart A particles in gas-fluidized beds--颗粒学报PARTICUOLOGY

Ye, M., Wang, J., van der Hoef, M. A., & Kuipers, J. A. M. (2008). Two-fluid modeling of Geldart A particles in gas-fluidized beds. Particuology, 6(6), 540–548. https://doi.org/10.1016/j.partic.2008.07.005

Two-fluid modeling of Geldart A particles in gas-fluidized beds

Mao Ye, Junwu Wang, M.A. van der Hoef^*, J.A.M. Kuipers

Faculty of Science & Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

10.1016/j.partic.2008.07.005

Volume 6, Issue 6, December 2008, Pages 540-548

Received 3 April 2008, Accepted 15 July 2008, Available online 11 November 2008.

E-mail: M.A.vanderHoef@tnw.utwente.nl

Highlights

Abstract

We have investigated the effect of cohesion and drag models on the bed hydrodynamics of Geldart A particles based on the two-fluid (TF) model. For a high gas velocity U₀ = 0.03 m/s, we found a transition from the homogeneous fluidization to bubbling fluidization with an increase of the coefficient C₁, which is used to account for the contribution of cohesion to the excess compressibility. Thus cohesion can play a role in the bed expansion of Geldart A particles. Apart from cohesion, we have also investigated the influence of the drag models. When using the Wen and Yu drag correlation with an exponent n = 4.65, we find an under-prediction of the bed expansion at low gas velocities (U₀ = 0.009 m/s). When using a larger exponent (n = 9.6), as reported in experimental studies of gas-fluidization, a much better agreement with the experimental bed expansion is obtained. These findings suggest that at low gas velocity, a scale-down of the commonly used drag model is required. On the other hand, a scale-up of the commonly used drag model is necessary at high gas velocity (U₀ = 0.2 and 0.06 m/s). We therefore conclude that scaling the drag force represent only an ad hoc way of repairing the deficiencies of the TF model, and that a far more detailed study is required into the origin of the failure of the TF model for simulating fluidized beds of fine powders.

Graphical abstract

Keywords

Gas-fluidized bed; Geldart A particles; Two-fluid model; Cohesive force; Drag correlation

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