Characterization of hydrodynamic parameters in a multistage column contactor

Abstract

Accurate knowledge of hydrodynamic parameters is of major importance for the performance study of liquid-liquid column extractors. The effects of operating parameters on dispersed phase holdup profiles. drop size distributions, and axial mixing in both phases were investigated in a 127 mm diameter multistage contactor of pilot plant scale for the toluene-water physically equilibrated system. Correlations for the mean holdup, the mean drop size, and the continuous phase backmixing were obtained. A stronger dependence of holdup and drop size on the operating conditions and especially on the agitation speed was observed as compared to previous investigations for the same type of contactor. The axial mixing for the single phase flow was found to follow adequately an existing correlation, while the continuousphase axial mixing in two-phase flows showed some deviations from other existing correlations. Also, flooding criteria. important for the control of the extraction process, were determined based on the shape of the holdup profiles. ~~. ~. ~~ II est trbs important de connaitre exactement les parametres hydrodynamiques pour I'etude de performance des extracteurs B colonne liquide-liquide. Les effets des parametres d'operation sur les profils de rktention de la phase dispersee, les distributions de taille des particules et le melange axial dans les deux phases, ont Cte etudies dans un contacteur pilote multietage de 127 mm de diametre pour le systkme equilibre physiquement toluene-eau. On a obtenu des correlations pour la retention moyenne, la taille moyenne des gouttes et le retromelange en phase continue. On a observe une forte dependance de la retention et de la taille des gouttes par rapport aux conditions d'operation et en particulier par rapport la vitesse d'agitation comparativement i des recherches anterieures pour le mCme type de contacteur. On a trouve que le melange axial pour I'Ccoulement de la phase simple suivait bien une correlation existante, tandis que le melange axial en phase continue dans les Ccoulements diphasiques montrent quelques @carts avec les autres correlations existantes. En outre, on a determine des critt-res d'engorgement, importants pour le contrble du processus d'extraction, en se basant sur la forme des profils de retention.

Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

“…The Sauter mean diameter decreases everywhere in the column with agitation, while drop size distribution becomes narrower. On the other hand, an augmentation of flow rates results in larger drops, an effect that was found to be stronger in the case of the dispersed phase flow rate in comparison with the continuous phase (Tsouris et al, 1990).…”

“…On the other hand, no significant correlation between l and r was found in the case of the log-normal function, which was hence chosen to represent the drop size distributions in the RDC column. It should be emphasized that the log-normal function has already been found adequate for representing drop size distributions in extraction columns (Giles et al, 1971;Tsouris et al, 1990), as well as bubble size distributions in bubble columns operating in the homogeneous regime (Akita and Yoshida, 1974;Parthasarathy and Ahmed, 1996).…”

“…Experimental investigations with agitated columns reveal that drop size distributions of rising organic phase drops dispersed in a continuous aqueous phase are broad in the first stages, becoming narrower and shifting toward smaller drop sizes in the later stages of the column, until a final, steady-state distribution has been achieved. Such behavior indicates that drop breakage dominates in the base of the column, whereas coalescence and breakage rates reach equilibrium in the upper stages (Tsouris et al, 1990), thus evidencing a strong variation in drop size and local holdup parameters. According to Kirou et al (1988), the holdup profile along the column changes from a concave shape to a sigmoidal form, with a maximum near the bottom of the column depending on the operating conditions.…”

Three‐Dimensional Simulation of Hydrodynamics in a Rotating Disc Contactor using Computational Fluid Dynamics

“…Experimental investigations with agitated columns reveal that the drop size distributions of rising organic phase drops dispersed in a continuous aqueous phase are broad in the first stages, becoming narrower and shifting toward smaller drop sizes in the later stages of the column, until a final, steady-state distribution has been achieved; thus, providing evidence that drop breakage dominates in the base of the column, whereas coalescence and breakage rates reach equilibrium in the upper stages [10].…”

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

“…According to the literature, all of the correlations which are available to predict the mean drop size in the pulsed extraction columns are proposed for dispersion regime. [8][9][10][11][12][13][14][15] Among them, the correlations of Kumar and Hartland [16] and Sreenivasulu et al [17] were considered as the most accurate among the other literature correlations. [18] The working regimes in the pulsed extraction columns have been the aim of various experimental investigations.…”