Surfactant effects on oscillations on sieve trays

Abstract

The objective of this work was to study the effects of surface active agents on the lateral oscillations on sieve trays and the cognate hydrodynamic phenomena. It dealt with the air/water system with the presence of soluble and insoluble surfactants in a 50cm diam. column. Three trays were built with different hole sizes and fractional free areas. The surfactant effects on oscillations were either to stabilize or destabilize depending on the hole diameter of the tray. For trays with small and medium size holes, surfactants raised the initiation points of oscillations to higher air velocities than those without surfactants. The reverse effect was found for a large hole diameter tray. The degree of these effects was greater for the surfactant of larger surface activity. The presence of surfactants shifted the full-wave peaks on weepage curve to higher or lower air velocities in the exactly same manner as for the oscillation initiation points. Combining these results suggested further that the oscillations on sieve trays were caused by hydrodynamic effects in a biphase rather than an accoustic resonance in a whole system. Meanwhile, backmixing on tray increased by the occurrance of oscillations and further by addition of surfactants.