(70ce) Fluidization Characteristics of Fine Cohesive Powders in a Vibro-Fluidized Bed

Fine cohesive particles, which belong to Geldart C group, are difficult to fluidize due to their strong interaction force between particles. In a case of fluidization with cohesive particle, stable channels and cracks are easily formed in the whole bed and the bed fluidity of such cohesive particle is poor. Adding the vibration to the bed is one of the ways for improving the bed fluidity for cohesive particle bed. Vibration breaks the stable channels and cracks intermittently, which enhances the dispersion of fluidizing gas in the bed entirely. In this study, spherical glass beads whose mean diameters were 6, 10, 20 micron meter were used as a fluidizing particle. Twist vibration was adopted in this study, which was developed by Mori et al.. For 6 micron particle, two operational limits that were the lower and upper limits of gas velocity for intermittent channel breakage were obtained by decreasing or increasing gas velocity method. The lower limit of gas velocity for intermittent channel breakage decreased as the vibration intensity increased. On the other hand, the upper limit had a peak at a certain vibration intensity. For 10 and 20 micron meter particles, the transition phenomena, which were an intermittent channel breakage to bubbling, were observed. These larger particles used in this study were near the boundary between group A and C, hence, the dominant flow patterns for group A (bubbling) and C (channel breakage) simultaneously appeared in the bed.