Residence Time of Particles in Fluidized Bed

To obtain information concerning residence time of particles in fluidized bed, the effects of gas velocity on hold-up and concentration of smaller-sized particles in fluidized bed were observed and the following results were obtained.1) Particle hold-up in bed decreases as gas velocity increases. (See Fig. (a)-(c)). Specific contact area is correlated to modified Reynolds number, as shown in Fig. 4 (a) and (b).2) Fluidized bed consisting of particles of two sizes tends to give a higher percentage of coarse particles than that given by the feed. This tendency becomes remarkable with the increase of gas velocity and decrease of feed rate, as shown in Fig. 5 (a). But it diminishes in case the fluidized bed is placed higher than L, the height of overflow pipe, as seen in Fig. 5 (b).