An experimental investigation of particle motion in liquid fluidized beds

A laboratory study was made on particle motion in liquid fluidized beds. In Part 1, experiments made in a bed of 4-inch inside diameter with a large length-to-diameter ratio of 24 to 1 are described. Particle motion in the bed was found to be essentially a diffusion process. Diffusion coefficients for motion in the vertical direction were measured for glass beads of .236-inch diameter at a range of average bead concentrations. Vertical diffusion was independent of radial position in the bed. The experimental findings on particle diffusion in the bed were compared to principles of diffusion of a turbulent fluid. A significant correlation between two successive vertical step lengths of short duration suggested that a bead is within an eddy of beads and fluid for a short time. The diffusion coefficients of the beads were much larger than the diffusion coefficients of the turbulent fluid in the absence of the beads, indicating that particles in a liquid fluidized bed augment instabilities. Steady and quasi-steady patterns of particle circulation were observed in both a cylindrical bed with a length-to-diameter ratio of 5 to 1 and in beds of conical shape, and are described in Part 2. Weak waves also formed in this cylindrical bed; the observed propagating speed compared roughly to that estimated using the theory of kinematical waves. Photographic materials on pages 17, 18, 65, and 94 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered