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The glass packing QVF DURAPACK® was developed to use the advantages of structured mass transfer packings, especially when handling corrosive media. To match up with the latest developments for sheet metal packings, further optimization for liquid-liquid separation processes was performed for the QVF DURAPACK®. The complex geometry of structured packings and the wall thickness of glass sheets complicate the numerical investigations. The modeling strategy is presented, and the limitations of CFD tools are given. The experimental and numerical results show similar trends as known for perforated metal structures. The extraction efficiency of the packing prototype could also be reproduced with the column design tool LLECMOD. [ABSTRACT FROM AUTHOR]

This paper is about the numerical solutions for a computational fluid dynamics-population balance model (CFD-PBM) coupled model of two-phase flow in a liquid-liquid extraction column. The model accounts for a complete description between both the dispersed and continuous phases, and constitutes a hyperbolic system of equations having a linearly degenerate nature. A numerical algorithm based on operator splitting approach for the numerical solution of the model is used. The homogeneous part is solved using the TVD MUSCL-Hancock scheme. Numerical results are presented, demonstrating the accuracy of the proposed methods and in particular, the accurate numerical description of the flow in the vicinity of the contact discontinuities. [ABSTRACT FROM AUTHOR]

A process for recovery of zinc from acid solution with di(2-ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso-dodecane was carried out at 20°C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1-l.0g/L), pH 0.1-2.1, and D2EHPA concentrations (2-8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38-0.80 L/min) and organic flow rate (0.22-0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2 × 10-6 m/s to 25.3 × 10-6 m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer. [ABSTRACT FROM AUTHOR]

The mass transfer into droplets in metal extraction is investigated in the system ZnSO4–H2SO4/di(2ethylhexyl)phosphoric acid in isododecane. Results of equilibrium measurements and stirred cell experiments are described in a mathematical model based on gradients of chemical potential. Concentration profiles measured with Laser Induced Fluorescence technology were calculated with the Maxwell–Stefan equations. Diffusion coefficients were estimated using the Wilke and Chang equation. Additional eddy diffusion coefficients measured in single droplet experiments in a venturi tube are described with different models known from literature. Whereas equilibria and mass transfer into droplets in stagnant conditions can be calculated with good agreement with the experimental results, none of the known models describes eddy diffusion in reactive extraction occurring in free moving droplets sufficiently well over a broad concentration range. [Copyright &y& Elsevier]

The influence of high-frequency AC fields on mass transfer from aqueous pendant and moving droplets into a continuous organic phase is investigated. Results are compared with those of applied DC voltage and those with no electric field present. Experiments are carried out in a low viscosity water–toluene system with acetone as the solute and in a high viscosity water–isotridecanol system with 1-propanol as the solute. AC and DC effects on Marangoni phenomena at pendant droplets are studied. High-frequency AC voltage is found to depress Marangoni phenomena whereas DC voltage enhances or initially induces Marangoni phenomena. Mass transfer from moving droplets could not be enhanced by the use of electric fields (AC or DC) at constant droplet size. The experimentally achieved concentration–time profiles are compared with those calculated from different mass transfer models for single droplets. [Copyright &y& Elsevier]

The initial mass transfer rate of acetic acid from the aqueous to the organic phase with tri-n-octylamine and toluene or isododecane as solvents has been studied in a constant interfacial cell area as a function of the stirring speed, concentrations of the transfer species, and the influence of chemical adsorption layers. For a detailed understanding of the mass transfer process, the electrophoretic mobility of oil-in-water droplets for these systems has been measured with a ZETA-sizer. The electrophoretic mobilities of the different reactive extraction systems were investigated for their dependence on the pH value and with different interfacial charges. It was proved that a change of the interfacial charge influences the zeta potential of the dispersed oil drops in the same way as the reaction kinetics, and thus the mass transfer of acetic acid. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the influence of reactive mass transfer on droplet-droplet interactions and droplet size distribution under steady state and transient conditions in a miniplant Kühni extraction column (DN 32).

• Membrane-based microreactor is used for determination of chemical kinetics. • Kinetic models for cobalt and manganese are established considering back reaction. • Back reaction has even at low metal concentrations in the organic phase a strong influence on mass transfer. • Overall mass transfer from the aqueous to the organic phase could be modeled within a deviation of 5%. The separation of manganese from cobalt sulfate solutions is crucial in the field of spent lithium-ion battery recycling. A membrane-based microreactor is used to reveal required mass transfer characteristics as is diffusion and chemical reaction. The dependence of di-(2-ethylhexyl)phosphoric acid (D2EHPA) concentration, pH, and metal ion concentration on the extraction efficiency are investigated. A back-reaction term is introduced giving a significant influence on the effective extraction rate even at small metal complex concentrations as initial extraction rates proved to be inaccurate to describe the system. It is shown that the extraction of manganese at a pH of 3.0 is mainly diffusive while the cobalt extraction is strongly kinetically controlled. At a separating pH of 3.9 a good agreement between the model and experimental data is only given if the equilibrium back-extraction rate is considered (deviation less than 5%). [ABSTRACT FROM AUTHOR]

The glass packing QVF DURAPACK® was developed to use the advantages of structured mass transfer packings, especially when handling corrosive media. To match up with the latest developments for sheet metal packings, further optimization for liquid-liquid separation processes was performed for the QVF DURAPACK®. The complex geometry of structured packings and the wall thickness of glass sheets complicate the numerical investigations. The modeling strategy is presented, and the limitations of CFD tools are given. The experimental and numerical results show similar trends as known for perforated metal structures. The extraction efficiency of the packing prototype could also be reproduced with the column design tool LLECMOD. [ABSTRACT FROM AUTHOR]

Bubble columns are widespread in chemical process engineering. The overall performance of these reactors relies on the interaction between the hydrodynamics, interfacial mass transfer and chemical reactions. The layout of these columns is commonly based on simplified integral models that are not able to track the complex interactions between the local hydrodynamics and the reactions. Hence, a detailed knowledge about the ongoing interactions is required. The local and temporal evolution of the carbon dioxide ( CO 2 ) chemisorption in aqueous NaOH solution in a cylindrical bubble column is investigated. Therefore, local measurements of hydrodynamics, bubble size and velocity, liquid velocity and concentration (pH-value) are done using a high speed PIV/LIF system combined with shadowgraphy. The results are compared to Euler-Euler based computational fluid dynamics simulations that take into account the ongoing reaction. [ABSTRACT FROM AUTHOR]