Conversion air velocity at which reverse density segregation converts to normal density segregation in a vibrated fluidized bed of binary particulate mixtures

Jun Oshitani, Masaki Hino, Shinichiro Oshiro, Yoshihide Mawatari, Takuya Tsuji, Zhaohua Jiang, George V. Franks

It is well known, when binary mixtures of different-density particles of the same size are vertically
vibrated or fluidized by airflow through the bottom, the particles segregate by density. Reverse density
segregation occurs in the vibrated bed; heavier particles move upward and lighter ones move downward,
and normal density segregation occurs in the fluidized bed; lighter particles move upward and the heavier
ones move downward. In this study, we investigated the particles’ behavior in a vertically vibrated
fluidized bed at various air velocity using two types of particulate mixtures of glass beads (GB) and stainless
steel powder (SP) or iron powder (IP) of same size. We found that reverse segregation converts to
normal segregation at a certain air velocity; here we call it ‘‘conversion air velocity”. Then, we investigated
the likely origin of the conversion air velocity considering the minimum fluidization air velocity
umf determined for the three monocomponent particles (GB, SP and IP) with and without vibration.
We found that the conversion air velocity is close to the umf of the lower density particles (GB) with vibration,
indicating that the conversion from reverse segregation to normal segregation occurs around umf of
lighter particles with vibration.

Advanced Powder Technology

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103583