Characterization of hydrodynamic parameters in a multistage column contactor

Tsouris, Costas; Ferreira, R. T. S.; Tavlarides, Lawrence L.

doi:10.1002/cjce.5450680604

Cited by 33 publications

(20 citation statements)

References 24 publications

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“…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).…”

Section: Introductionmentioning

confidence: 82%

“…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).…”

Section: Drop Size Distributionsmentioning

confidence: 98%

“…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.…”

Section: Introductionmentioning

confidence: 98%

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Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

Moreira

Pimenta

Carneiro

et al. 2005

Chemical Engineering Communications

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The hydrodynamics of a rotating disc contactor (76.2 mm diameter, 19 stages, and operating height of 815 mm) has been investigated at limiting operational conditions of low holdup (/ 3%) and low agitation (Re R 22,000) for the water=n-heptane system in the absence of mass transfer. Water was chosen as the continuous phase, and it was kept stagnant inside the column. Local drop size distribution, local mean drop diameter, and total holdup have been measured at different flow rates of the dispersed phase (70 to 640 mL=min) and rotor speeds (0 to 700 rpm). Drop size distributions along the column were suitably described using the log-normal probability density function, and empirical expressions were derived to predict the parameters of the distribution curve as a function of operating conditions. An empirical expression was also proposed to predict the Sauter mean drop diameter along the column with a mean deviation of 3.4%. Statistical analysis has revealed no significant effect of the rotor speed on the total holdup, which changed solely with the dispersed phase flow rate for the operating conditions investigated.

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Section: Introductionmentioning

confidence: 82%

Section: Drop Size Distributionsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

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Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

Moreira

Pimenta

Carneiro

et al. 2005

Chemical Engineering Communications

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“…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].…”

Section: Introductionmentioning

confidence: 98%

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

et al. 2008

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The 3D simulation of the hydrodynamic behavior of a rotating disc contactor (RDC) by means of computational fluid dynamics (CFD) was investigated for the n-butanol-succinic acid-water (BSW) system. For the two-phase liquid-liquid flow, the velocity distribution of the continuous phase and drop size distributions were determined using the k-x turbulence model in conjunction with the Eulerian-Eulerian approach and MUSIG model. In this system in which the holdup of the dispersed phase is low, the continuous phase velocity was computed by simultaneously solving the Navier-Stokes equations beside the different models of turbulence. The motions of the dispersed phase was calculated while considering buoyancy, drag and inertia forces, and equations related to the continuous and dispersed phases were coupled to each other by considering the momentum transfer on the interface and the effect of drop motions in turbulence. In this simulation, by considering drops' breakage, their path, the velocity profile, and also the velocity contour plot of the dispersed phase were obtained. A comparison of the holdup experimental values with the results predicted by CFD showed that the k-x model is the best descriptive model for the computation of holdup in a RDC. IntroductionLiquid-liquid extraction is an important separation process that is widely used in the chemical, biochemical, petrochemical, pharmaceutical, and food industries [1][2][3][4]. The rotating disc contactor (RDC) is one of the most important extraction columns, which was initially introduced by the Royal Dutch/ Shell Group [5]. RDC columns have extensively been used in the industry, particularly for liquid-liquid systems with low interfacial tension. The low interfacial tension means small drop sizes, thereby causing the efficiency of the RDC extractor to ameliorate.These columns consist of a set of distinct discs with equal horizontal intervals between the stators. The agitation provided by the discs mounted on the rotor shaft improves the performance of the RDC by breaking the dispersed phase droplets, hence increasing the interfacial area for mass transfer [4,6]. Drop sizes are controlled by the ratio of buoyancy to interfacial tension forces under the conditions of no agitation or low levels of turbulence (Re R N R D 2 R m c < 10000) 1) [7].Too high an agitation speed will exacerbate the axial mixing, thereby reducing the column performance. Axial mixing ends in concentration jumps all over the column so that this phenomenon causes operating lines to be closer to each other, the result of which is the decrease of concentration driving force and the need for more discs inside the column [2,8,9].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 dro...

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“…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.…”

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confidence: 99%

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

Amani¹,

Esmaieli²

2017

Can J Chem Eng

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In this study, the influence of different operating regimes on drop behaviour in an L-shaped pulsed sieve-plate column has been investigated and the effects of pulsation intensity and phase superficial velocities on drop diameters are evaluated. The toluene-water system with 0.03 L/L (3 vol%) acetone as a mass transfer agent is used. Experimental observations reveal that with increasing pulsation intensity, drop sizes slightly decrease and by reaching to the end of mixer-settler regime, they significantly decrease followed by a mild decrease in the dispersion regime. Moreover, it is observed that mean drop size firstly varies inversely as both phase superficial velocities change, while it slightly increases with further increase in superficial velocities. Finally, some of the most recommended correlations are compared to the experimental data. It is revealed that these correlations show the highest deviation in the lower end of the mixer-settler regime (> 40 %), while in the dispersion regime it becomes < 15 %, indicating that they are only applicable in the region of practical regimes. Accordingly, two of these correlations are modified in order to cover different operating regimes by means of two correlations proposed to predict the transition regime in each section of the column. The AARE values of the modified correlations are found to be < 14.7 %.

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Characterization of hydrodynamic parameters in a multistage column contactor

Cited by 33 publications

References 24 publications

Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

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

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

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