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 (0.105m ID×1.5m 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 (UG), solid content in the slurry phase (CS) and viscosity (μL) and surface tension (σL) 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 2.5–3.0×10−3m 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 UG, but decreased with increasing CS, σL of μL. The holdups of large, small and fine bubbles were well correlated in terms of operating conditions, respectively. [Display omitted] ▶ We find the fine bubbles in a viscous slurry bubble column. ▶ The demarcating size of fine bubbles is 2.5–3.0×10–3m. ▶ The fine bubble holdup increases with increasing gas velocity but decreases with increasing solid content. ▶ The fine bubble holdup decreases with increasing viscosity and surface tension of liquid media. ▶ The holdups of three kinds of bubbles are correlated in terms of dimensionless groups.