The liquid–solid countercurrent fluidization process in an extraction columnwas numerically simulated based on
the particle trajectorymodel of Eulerian–Lagrangianmethod. The simulation approach was validated by previous
experiments. A power function correlationwas proposed for dimensionless slip velocity Uslip/Ut and hold-up fraction
ϕ, and the operational zone in the countercurrent fluidizationwas determined. Simultaneous countercurrent
fluidization of particles with different diameters was also simulated. The comparison shows that the simulation
results are consistentwith the calculation values fromthemulti-particle free sedimentation model based on noninterference
assumption, verifying the reliability of the approach in present work.