Segregation patterns in binary fluidization

Segregation mechanism of an initially mixed, size-dispersed binary mixture of particles in a gassolid fluidized bed has been studied. The non-monotonic mixing/segregation behavior of binary particles with equal mass fraction is explained through variation of mixing indices with time and superficial gas velocities. The study implies that the segregation of particles initiates as the gas flow is introduced. However, beyond a specific gas velocity, the system exhibits remixing of particles in the bed. The pressure drop obtained from the simulations of the packed state of the bed was found to be in agreement with the values predicted by the Kozeny- Carman equation. Two initial states of the bed were used to investigate the segregation during fluidization. First, the fluid was introduced to an initially packed bed. In the second approach, fluid was introduced to the steady state condition of the bed achieved at a lower velocity. Mixing indices were determined using two methods: the entropy-based mixing index and the Lacey mixing index, to assess the macroscopic mixing or segregation within the bed.