Abstract
A mathematical model was developed to predict the particle size distribution (PSD) in a steady-state fluidized-bed granulator with selective withdrawal of large particles, and was confirmed through a series of experiments using sodium chloride and sodium sulfate as bed materials. The model was extended from Kunii’s PSD model, which was derived only for the backmix-flow fluidized-bed reactor where discharged particles have the same PSD as the materials in the bed.
From batch experiments, operating windows that permit the growth mode to be coating were identified and used in steady-state fluidized-bed granulation experiments.
The segregation factor of materials was obtained from a cold-bed segregation experimental apparatus where large particles were withdrawn selectively through a segregation boot. Using this segregation factor, the steady-state PSD was calculated by computer simulation. It was found from the simulation that as the input flow rate of seed particles increases, average particle size of bed material and output flow rate of grown material decrease.
It was also demonstrated that the simulation results was in good agreement with experimental results obtained from a 10 cm-diameter steady-state fluidized-bed granulation system.
