Fig. 2 The pressure-drop-velocity curve of -0.4+0.3 mm magnetite powder as a function of superficial air velocity.
From point A to point B, the pressure drop of all the three bed heights increase almost linearly as the superficial air velocity
goes up. The transition from fully fixed to fully fluidized states occurs at the incipient fluidization state of point B. From point B
to point C, the pressure drop stabilizes and remains constant. The superficial air velocity after minimum fluidization may be of
help in forming a stable gas-solid fluidized bed system for coal separation. On the other hand, it is clearly seen that as superficial
air velocity goes up, the pressure drop of the low bed height (-30+10 mm) is much larger than that of the high bed heights (-
70+50 mm, -110+90 mm), revealing the similarities to the characteristics of fluid mechanics. This means that, fluidization of
magnetite powder by a gas generally gives rise to a pseudo fluidization systems, characterized by the pressure drop of lower layer
is larger than that of upper layer.