Axial mixing and mass transfer in a vibrating perforated plate extraction column

Abstract

Perforated Plate Ont. L8S 4L7The axial mixing and countercurrent mass transfer characteristics of a 5 cm diameter extraction column agitated by vibrating perforated Teflon plates have been investigated. The dispersed phase was an organic liquid (usually kerosene) and the continuous phase was water. Axial mixing was measured in both phases using pulse tracer techniques; in the continuous phase the axial mixing was estimated to have a significant effect on mass transfer, but axial mixing in thc dispersed phase had a negligible effect. Mass transfer was measured for several different solutes; n-butyric acid. benzoic acid and phenol. The overall heights of a transfer unit (cont. phase) were in the order of 10-20 crn for the organic acids but higher for transfer of phenol from very dilute solutions. The characteristics of the vibrating plate column have been compared with those of other types of extractor and suggestions are made for further development..~ ~ ~~ On a CtudiC les caracteristiques du melange axial et du transfert de matiere a contre-courant d'une colonne d'extraction de 5 cm de diamktre agitee par des plateaux de Teflon perforts vibrants. La phase dispersie est un liquide organique (generalement du kerosene) et la phase continue de I'eau. Le mtlange axial a it6 mesure dans les deux phases par des techniques de traqage pulse; dans la phase continue, on a trouve que le melange axial avait un effet significatit sur le transfert de matikre, tandis que dans la phase disperske, I'effet est negligeable. Le transfert de rnatikre ; t eti mesure pour differents solutes: acide n-butyrique, acide benzoi'que et phenol. Les hauteurs globales de I'uniti de transfen (phase continue) sont comprises entre 10 et 20 cm pour les acides organiques mais elles sont plus elevi-es pour le transfert du phenol a partir de solutions trks diluees. Les caracteristiques de la colonne h plateaux vibrants sont coniparees a celles d'autres types d'extracteurs et des suggestions sont apportees pour de nouveaux dkveloppements.Keywords: axial mixing, liquid-liquid extraction, vibrating plate column. ow frequency reciprocating plate and pulsed plate L extraction columns are well known. Less attention has been paid to the use of high frequencies (10-200 Hz) and low amplitudes (< 1 mm) as a means of plate agitation, despite the potential advantage that the electrical service frequency (60 Hz) can be used to power simple and reliable electromagnetic drives.The background in these areas has been reviewed by Baird et al. (1989) who also described preliminary tests of both liquid-liquid and gas-liquid contact in single cells using vibrating perforated plates. Rama Rao et al. (1991) have described the hydrodynamic behaviour of a 5 cm diameter countercurrent extractor agitated by a stack of perforated Teflon plates equipped with segmental downcomers. By the use of small perforations (1 mm or less) it was possible to obtain drops with a Sauter mean diameter considerably less than 1 mm with only moderate levels of agitation (amplitudefrequency product...

Mixing and solid‐liquid mass transfer characteristics in a three phase pulsed plate column with packed bed of solids in interplate spaces—a novel aerobic immobilized cell bioreactor

“…Power dissipation in the system increases due to increase in mechanical agitation caused by increase in vibrational velocity; this in turn increases the dispersion number. These results are consistent with the results of previous investigators who worked on pulsed plate columns in the absence of solid phase, where continuous phase axial mixing was found to increase with increase in ( A × f ) or with the increase in the power input, which is proportional to [( A × f ) 3 ] 29, 30, 34–39. The application of oscillatory motion can also increase gas hold up through its ability to retard the rise velocity of bubbles and increase its residence time in the column 40.…”

Drop behaviour characteristics in different operating regimes in an L‐shaped pulsed sieve‐plate column

“…On the other hand, when there is mass transfer from the continuous phase to the dispersed phase, smaller drops are produced in comparison to the same condition without mass transfer. In fact, because of the consequent interfacial tension gradient, the interface movement of the drop and the inner circulation generated into the drop gain the same direction . Therefore, this mass transfer path leads to increase on the interface deformations, consequent deformation of drops, and higher drop breakage.…”

“…In fact, because of the consequent interfacial tension gradient, the interface movement of the drop and the inner circulation generated into the drop gain the same direction. [44][45][46] Therefore, this mass transfer path leads to increase on the interface deformations, consequent deformation of drops, and higher drop breakage.…”

A Comparison of Mass Transfer Coefficients between Rotating Magnetic Field Mixer and Stirred Tank Reactor

“…Except the result of research carried out for the well-known mechanical agitators, new constructional proposals of the mechanical mixers for performing solid dissolution process in a liquid can be found in the literature. This may have a positive effect on the mass transfer process, for example, using a reciprocating agitator [10,[29][30][31][32]. Among other methods that are commonly used to intensify solid dissolution, a liquid pulsation [33], electrical discharges [34], other physical methods of the interaction [35], and dissolution on the solid or fluidized bed [36] can be found.…”