Fluid Dynamics Studies on Bottom Liquid Detachment from a Rising Bubble Crossing a Liquid–Liquid Interface

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.