Single liquid drop breakage probabilities and characteristic velocities in Kühni columns

Abstract

Studies have been made on the extent and mechanism of breakage of single liquid drops of organic liquids immiscible in water rising through short sections of Kuhni liquid-liquid extraction columns. Information on drop breakage probabilities is required for calculation of drop size distributions developed under counter-current column operating conditions. The breakage probability data from two small diameter Kuhni columns containing one, three or five stages have been correlated as a function of a modified Weber number based on the shearing forces on drops. The critical condition for breakage, giving a maximum stable drop size, is based on an impeller Weber number. Characteristic velocities of drops were measured relative to terminal velocity and the ratio was tentatively correlated with a function of an impeller Reynolds number together with the fractional free area of the perforated plates used to separate compartments. The drops were found to break predominantly at the holes in the plates, not at the turbine, in the region of transitional Reynolds number used in this work. The results apply only to non-turbulent conditions so further work on larger diameter equipment is called for.

Measurement of Drop Rise Velocities within a Kühni Extraction Column

“…The magnitude of this slowing coefficient was consistent with the correlation of Fang et al (1995) (see eq 2) at low rotor speeds. This indicates that, under conditions of low rotor speed and holdup, such single drop studies provide an accurate representation of drop behavior.…”

“…Thus, Haunold et al (1990), Seikova et al (1992), and Fang et al (1995) all measured the velocity of single drops through a Kü hni column, while Fan et al (1987) measured similar velocities in an RDC. Gourdon et al(1991) used both a Kü hni and a pulsed sieve plate column.…”

The interaction of solute transfer, contaminants and drop break‐up in rotating disc contactors: Part I. Correlation of drop breakage probabilities

“…In contrast, few studies have been made in the field of drop break-up in extraction columns, probably because the geometry and the means of agitation are relatively complex; turbulence theory has little chance of being successfully applied because turbulence is not usually fblly developed. Empirical studies have recently been undertaken (Eid et al, 1986;Cabassud et al, 1990;Fang et al, 1995) with the objective of deriving the parameters that are required for quantifying breakage rates in pulsed sieve plate and Kuhni columns. Bahmanyar and Slater (1991) and Bahmanyar et al (1991) did some first experiments in a rotating disc contactor (RDC), but these only covered a limited range of physical properties.…”

Description of Disperse Multiphase Processes: Quo Vadis?

“…Thereby, numerous effects need to be investigated. In fluid/liquid systems, coalescence and breakage phenomena are often quantified with single drops and bubbles to derive kernels for the description of the swarm behavior for example using population balance equations. The effects of turbulence, internals, dispersion units and general fluid dynamics (shear, viscous forces, deformation, etc.)…”