(380al) Solids Mixing Rates of Geldart a and B Powders Predicted By the Two Fluid Model

The influence of particle density and fluidization velocity on mixing behavior of Geldart A and B particles was numerically investigated in bubbling fluidized beds for various operating conditions. An Eulerian-Eulerian approach based on the kinetic theory of granular flow (i.e., the Two Fluid Model, TFM) was applied to perform the simulations. Boundary conditions, grid resolution, as well as the rheological model were carefully chosen to match experimental observations. A variety of systems differing in particle density, particle size, and fluidization speed were investigated to collect data on flow and dispersion rates of particles in the bed. This was done in order to expand the parameter space investigated in previous studies [1,2], as well as to investigate the anisotropy of solids dispersion rates.

To examine the particles’ mixing behavior, characteristic mixing times were computed based on the temporal evolution of a solids-based scalar variance. In addition, scalar dispersion rates were extracted from the simulation data, both in the horizontal and vertical direction. Finally, it was demonstrated that the characteristic mixing time can be correlated with the particle Froude number, the expanded bed height and the solid dispersion coefficient with high accuracy. This new correlation allows practicioners to estimate solids mixing rates for a wide range of fluidization parameters of Geldart A and B powders, without necessitating the knowledge of bubble parameters as is the case in other expressions for the solids mixing time [2].

[1] M. Banaei, N.G. Deen, M. van Sint Annaland, J.A.M. Kuipers, Particle mixing rates using the two-fluid model, Particuology. 36 (2018) 13–26.

[2] A. Bakshi, A.F. Ghoniem, C. Altantzis, Mixing dynamics in bubbling fluidized beds, AIChE J. 63 (2017) 4316–4328.