Axial dispersion and enterainment of particles in wakes of bubbles

The entrainment and dispersion of solid particles in bubble columns was investigated experimentally and heoretically. A mechanistic model for the dispersion caused by entrainment in wakes of large solitary bubbles was developed. The dispersion coefficient was found to be dependent on the bubble size, bubble frequency, particle settling velocity and column surface area. Experimental tests were conducted in a rectangular bubble column. The system consisted of air, water and copper powder. Spherical cap bubbles were produced by a single nozzle. Significant entrainment of particles in wakes of rising bubbles observed in the lower region of the column, whereas, turbulence seemed to dominate the dispersion in the upper region of the tank. Calculated particle distributions were found to be in good agreement with experimental data.