To model liquid–liquid extraction columns (LLE-columns) accurately, correlations for occurring phenomena inside the columns (e.g., drop sedimentation) are necessary. Currently, existing correlations for the sedimentation velocity of drops in LLE-columns equipped with structured packings do not consider the interaction of the drops with different packing material surfaces or the complex geometry of those. Therefore, utilizing these correlations for designing these LLE-columns still exhibits high uncertainties, which commonly necessitate cost- and time-expensive experiments. To accelerate the efficiency of the design of these LLE-columns, we present a measuring cell in which single drop-wall interactions can be investigated. To quantify the drop-wall interaction, drop velocity, contact angle, and contact line can be measured optically while varying the counter-current flow, drop size, tilting angle, and surface material. The experimentally determined velocities are in accordance with sedimentation velocities in structured packings. Common correlations for sedimentation velocities in structured packings turned out not to be universally applicable.
Mielke et al. (Wed,) studied this question.