Structure of bubble holdups in a viscous slurry bubble column with low surface tension media

The structure of bubble holdups was investigated in a viscous slurry bubble column (0.105 m ID x 1.5 m in height) with low surface tension media. It was found that the bubble holdup was composed of three kinds of holdups of bubbles such as large, small and fine bubbles. The individual holdups of three kinds of bubbles were measured by using the static pressure drop (SPD) and dynamic gas disengagement (DGD) methods simultaneously. Effects of gas velocity (U-G), solid content in the slurry phase (C-s and viscosity (mu(L)) and surface tension (sigma(L)) of liquid media on the holdups of three kinds of bubbles were determined. The bubble size demarcating the fine and small bubbles was found to be in the range of 2.5-3.0 x 10(-3) in within these experimental conditions. The total bubble holdup measured by means of DRP method was lower than that obtained by using the SPD method but higher than that using the DGD method. The holdup of fine bubbles increased with increasing U-G, but decreased with increasing C-s, sigma(L) of mu(L). The holdups of large, small and fine bubbles were well correlated in terms of operating conditions, respectively. (C) 2012 Elsevier B.V. All rights reserved.