Flow Characteristics of Three-Phase Fluidized Bed with Draft Tube—Effect of Outer Column Diameter and Determination of Gas–Liquid Interfacial Area—

The flow characteristics of a three-phase fluidized bed with draft tube were studied, using air, aqueous sodium sulfite solution, and nylon particles (2.5 mm in diameter) as gas, liquid, and solid, respectively.Gas holdup decreased with increasing concentration of solid. When the diameter ratio of draft tube to outer column was about 0.6, the maximum of liquid circulation flow rate was obtained. Further, when this ratio was fixed, gas holdup decreased with increasing concentration of solid and with decreasing diameter of outer column. Circulation flow rates of solid and gas depended strongly on that of liquid. The specific gas–liquid interfacial area was larger in the annular section than in the inner section. from the relation between gas holdup and gas–liquid interfacial area, it was found that, in the inner section, large bubbles were broken into small ones by the existence of solid particles.