Abstract
The size of bubbles leaving a three-phase fluidized bed containing low density particles was investigated photographically with a video camera. The influence of gas and liquid flow rates, size and density of solid particles on the size of bubbles was also studied. The size of the bubbles is almost independent of gas velocity, but decreases with increasing liquid velocity. The bubble coalescence tends to occur in the bed rather than the bubble column. The size of bubbles can be roughly estimated from the bubble size in the bubble column, physical properties of the particles, and operating conditions.