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Significance
Membrane separation procedures, which are based on hollow low fiber membrane contactors, come with a number of benefits including high interfacial area as well as a dispersion-free operation. For these units, the porous membrane operates as a barrier and fortifies the aqueous-organic interface. The hollow fiber contactors have the advantage of being versatile and easy to operate. They also have a straightforward extrapolation from the laboratory to industrial conditions and flow rates. This is possible by raising the number of modules applied due to the fact that the same fibers as well as fluid velocities can be implemented in both environments.
The concept of hollow fiber based non-dispersive solvent extraction method has gained a lot of popularity. This concept has been investigated for a number of applications including organic acid separation from fermentation broths, metal and rare earth elements recovery, and recovery of aroma compounds from natural resources.
Yaidelin Manrique, Ana Ribeiro, and José Loureiro at University of Porto in Portugal in collaboration with Ahmet Özdural at Hacettepe University in Turkey and Dominique Trébouet CNRS in France developed an explicit equation for determining the overall mass transfer coefficient in the hollow fiber membrane modules while considering the unsteady state conditions within the membrane contactor and measuring the transient profiles of the inlet concentration in the aqueous phase. Their research work is published in journal, Chemical Engineering Science.
The authors computed the mass transfer coefficient measuring only the transient profiles of the inlet aqueous concentration. This was possible without the need of an optimization procedure. They obtained the explicit equation by the solution of the model equations of a membrane contactor when the concentration of the solute in the organic extractant phase could be assumed as zero in the system operation.
The authors then applied the characteristics method to solve the partial differential equation representing the mass balance to the aqueous phase in the fibers. They introduced a linear combination between the solutions in the two physical directions in a bid to combine the evolution of the solute concentration in the reservoir.
The researchers then used the numerical solution of the membrane contactor model in a bid to validate the approximation and define its validity region. The proposed explicit equation gave reasonable estimations of the mass transfer coefficient even when it was applied when the concentration in the organic phase could not be assumed to be zero. For example, when there was a recirculation of the organic phase from its reservoir, through the casing of the contactor and back to its reservoir.
The authors then proposed a method that allowed them to apply the explicit equation in the approximation of the overall mass transfer coefficient in the unit with recirculation of the organic phase and in the single pass units. This method was then applied to approximate the overall mass transfer coefficient from experimental data published in literature and the experimental outcomes were simulated. This indicated that the developed equation was capable of estimating the number of mass transfer units with appreciable precision even when the units were operated far a bit from the conditions for which the equation was derived.
Reference
Yaidelin A. Manrique, Ahmet R. Özdural, Dominique Trébouet, Ana M. Ribeiro, José M. Loureiro. Explicit equation for the determination of the overall mass transfer coefficient in a hollow fiber membrane contactor. Chemical Engineering Science, volume 166 (2017), pages 210–219.
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