Investigation on local and average static hold‐ups in liquid–liquid systems in a rotary disc contactor

Abstract

A rotating disc contactor with inner diameter of 91 mm and 21 compartments was used to investigate local and average static hold-ups in the column. Three chemical systems, including distilled water as stagnant continuous phase and toluene, kerosene, and butyl acetate as dispersed phase, in case of no mass transfer, were applied. Different parameters consisting of drop size and static hold-up were measured experimentally under various operating conditions, and two dimensionless correlations for estimation of local static hold-up as a function of average mother drop size, physical properties, rotor speed, and stage number were proposed in two cases: (1) immovable and (2) rotating rotor discs. Furthermore, two dimensionless correlations were presented to estimate average static hold-up as a function of average mother drop size, physical properties, rotor speed, and number of stages in the column in the two aforementioned conditions. Un contacteur de disque rotatif avec un diamètre interne de 91 mm et 21 compartiments aété utilisé pourétudier les retenues statiques locales et moyennes dans la colonne. Trois systèmes chimiques, y compris de l'eau distillée comme phase continue stagnante et du toluène, du kérosène et de l'acétate de butyle comme phase dispersée, en cas d'aucun transfert de masse, ontété utilisés. Différents paramètres composés de la dimension des gouttes et la retenue statique ontété mesurés de façon expérimentale selon diverses conditions de fonctionnement et deux corrélations adimensionnelles pour l'estimation de la retenue statique locale comme fonction de la dimension de la goutte mère moyenne, des propriétés physiques, du régime rotor et du nombre d'étapes ontété proposées dans deux cas: (1) disques du rotor fixes et (2) rotatifs. De plus, deux corrélations adimensionnelles ontété présentées pour estimer la retenue statique moyenne comme fonction de la dimension de la goutte mère moyenne, des propriétés physiques, du régime rotor et du nombre d'étapes dans la colonne dans les deux conditions mentionnées précédemment.

Investigation of Copper Extraction from Aqueous Sulfate Solution in a Rotating Disc Contactor

“…In fact, drops may have coalescence with static hold-up which may result in drops with bigger sizes. 33 Moreover, the static hold-up could have important roles on drop coalescence, residence time, interfacial area and efficiency of the column where it adds on to the dynamic hold-up. 30 The detailed procedure of measuring static hold-up was as following: to reach local static hold-up in the space between the (n + 1) th and n th valve (namely position n), the whole liquid volume was drained from the n th valve.…”

“…Characteristic velocity varies rapidly with rotor speed after the first critical rotor speed up to the rotor speed that called second critical rotor speed then, the mentioned variation becomes moderate. 35 After determining the first critical rotor speed, the operating parameters such as rotor speed, dispersed phase and continuous phase flow rate varied to investigate the effect of the parameters on the static hold-up, drop sizes and extraction efficiency.…”

“…Moreover, the second critical rotor speed (for a drop with a particular size) is a rotor speed at which the probability of breaking that drop is equal to 1. 35 The breakage probabilities versus rotor speed for mentioned chemical systems using glassy nozzles with different inner diameters (1.2 and 2.5 mm) to form various drop sizes by adjusting the Q c /Q d ratios and continuous phase heights are presented in Figures 5 and 6. Regarding to these graphs, the drop breakage increases by increasing the volumetric phase ratio that leads to decrease of the first critical rotor speed.…”

Local Static Hold-up in a Rotary Sieved Disc Contactor for a Butyl Acetate-water System

“…In order to measure the static holdup, collect samples from five valves according to the draining procedure described by Molavi et al (2011).…”

“…However, in spite of this fact that static holdup has an important role on drop coalescence, residence time and interfacial area, a few works have been carried out in this area (Westerterp et al, 1984;Yin et al, 2002;Molavi et al, 2011).…”