For
intermediate values, each particle becomes individually suspended in the fluid flow, the upper surface of the bed becomes plane
and horizontal, the particles inside the layer can move slowly and rearrange, this bed is said to be fluidized state [37]. According
to Archimedes law, clean coal and gangue separate from each other by the pseudo fluid density with heavy particles sinking and
light particles floating. The experimental magnetite material is divided into group B in Geldart’s classification (1973) [38], which
only requires the particle diameter and density. The minimum fluidization velocity represents the transition between the fixed and
fluidized states, and it is sensitive to the particle shape, size, and density. For a given size of medium, the minimum fluidization
velocity for fluidization can be calculated using