Stripping in a bubbling pool under vacuum-contribution of the interfacial tension to the pressure inside the bubbles

In a stripping process conducted under vacuum where the gas is dispersed in the liquid mixture as very small bubbles (microbubbles), the contribution of the interfacial tension to the pressure inside a bubble is significant. As a result, the bubble does not expand significantly approaching the liquid free surface, even if the pressure drop in the gas is considerable comparatively to the pressure outside the bubble. This behaviour certainly determines the mass transfer rate mainly in the upper portion of the bubbling pool. In the present study a simplified model of the mass transfer process is proposed for this situation. One important conclusion is obtained from the predictions for the system pentane / n-paraffins in operations conducted under a pressure of 300 N m−2: the amount of solute removed from the liquid is lower when microbubbles are injected in the liquid although the interfacial area per unit volume of gas is very high.