Multilayer adhering model for holdup and separation behavior of fine particles in a powder-particle fluidized bed

• Behavior of aerosol fine particles in a powder-particle fluidized bed was modeled.
• The holdup of fines at high gas velocities changed little with aerosol concentration.
• Modified multilayer adhering model explained well with the experimental results.
• Aerosol fines of 1 μm or smaller form separable multilayers on a coarse particle.
• Aerosol fines of 3 μm can no longer form a complete monolayer on a coarse particle.

Time variation of the holdup of fine particles in a powder-particle fluidized bed was formulated on the basis of a multilayer adhering model. Unsteady-state experiments using a fluidized bed of 550 μm-silica sand, limestone, and glass beads were conducted under different operating conditions, changing the inlet concentration of aerosol fines (aluminum hydroxide), superficial gas velocity, and particle size of the fines (0.5 to 3 μm). The multilayer adhering model provided nearly the same value as that experimentally obtained. The model was modified so as to interpret numerous separable layers, which were subjected to being removed as fine-particle agglomerates. A change in the mechanism of the elutriation of fine particles with the size of fine particles was explained.

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