Partic. vol. 54 pp. 78-90 (February 2021)
doi: 10.1016/j.partic.2020.03.004

Segregation behavior of a ternary mixture of titanium dioxide particles in a pseudo two-dimensional fluidized bed

Mojtaba Rasteh^a,*, Alireza Bahramian^a, Goodarz Ahmadi^b

mrasteh@hut.ac.ir

Abstract

The segregation behavior of a mixture of silica-coated titanium dioxide (TiO₂) particles of three different sizes in a pseudo two-dimensional fluidized bed was studied experimentally by the freeze–sieving method and numerically by the multi-fluid model (MFM). Three-dimensional computational fluid dynamics (CFD) simulations were carried out to evaluate the effects of the solid wall boundary conditions on particle segregation in terms of specularity and particle–wall restitution coefficients. The quantitative indexes of segregation tendency and segregation degree were used to determine the axial segregation of the mixture in triangular coordinates. The simulation results revealed that the axial segregation increased with the specularity coefficient, whereas the particle–wall restitution coefficient had a minor effect on axial segregation. Comparison of the simulation results with experimental data showed that the appropriate value of the specularity coefficient used in the CFD model depended on superficial gas velocity. The study of the effects of superficial gas velocity on segregation behavior demonstrated that the greatest segregation was obtained at minimum fluidization velocity and the segregation decreased as the gas velocity gradually increased.

Graphical abstract

Keywords

Ternary mixture; Segregation tendency; Segregation degree; Two-fluid model; Computational fluid dynamics(CFD)