Measurement of Drop Rise Velocities within a Kühni Extraction Column

Abstract

A new method is presented for the determination of droplet rise velocities within liquid-liquid extraction columns. This method utilizes the difference between the static drop size distribution as measured by a photographic technique and the dynamic drop size distribution as measured by a capillary probe technique. The ratio of the two volume densities multiplied by the average flow velocity is then a direct measure of the individual drop velocity. Droplet velocities measured using this technique are consistent with single drop velocities measured by other workers at low holdups. However, at higher holdups the droplet velocities converge toward a single value rather than retaining a range of drop size dependent values.

Optical probe technique for two‐phase flow measurements in an extraction column

“…The signal curves of fibers I and II are very similar except for the time delay. The time delay values, ( t AII − t AI ) d , of droplets with different sizes were similar in duration at constant pulse energy input, consistent with the conclusions made by Kentish et al15 Figure 4 shows the influence of the energy input on drop velocity under the same flow rates.…”

Mass Transfer Performance in Karr Reciprocating Plate Extraction Columns

“…Measurement of the drop size is typically carried out photographically, with a transparent sided square “box” around the outside of the column wall to avoid distortion. An alternate method is to draw out droplets using capillaries, of which a photograph is taken of the drops passing in the capillary …”

“…An alternate method is to draw out droplets using capillaries, of which a photograph is taken of the drops passing in the capillary. 21 The Sauter-mean diameter is a key variable in extractor column design due to its influence on both throughput and specific mass transfer rate. As seen from eq 2, the drop size distribution is related to the specific interfacial area available for mass transfer and it also influences the mass transfer coefficient, the dispersed phase holdup, and flooding conditions for the direction of c f d mass transfer γ ) 34.3 mN/m d 32 ) 0.41(Af) -0.59 µd ) 0.58 mPa s for the direction of d f c mass transfer d 32 ) 0.757(Af) -0.400 Vc -0.232 Vd 0.414 a Kumar and Hartland (1996) 2 water, methyl isobutyl ketone, kerosene (c)-toluene, kerosene, water (d) of the column.…”

Estimation of axial dispersion in pulsed-plate extraction columns

“…The characteristic velocity v y is assumed to be the mean rise velocity of the droplets based on the continuous phase. Kentish et al (1997) and Tang et al (2005) reported that the rise velocities of the droplets turned to be a uniform value ud under the high holdup of the dispersed phase. The average velocity of the dispersed phase can be written as Eq.…”