ABSTRACT
The industrial applications of hollow fiber extraction technology require a comprehensive understanding of the key parameters that are used in design, scale-up and optimization. Mathematical or computational modeling can help in providing an in-depth understanding of the working of a hollow fiber membrane contactor and interplay of different variables that affect its separation performance. This effort is to understand the approaches followed for the modeling of separation processes using hollow fiber liquid membranes. Broadly, models of hollow fiber liquid membranes can be classified as diffusive mass transfer models, flow and mass transfer models and computational fluid dynamic (CFD) based models. As it is difficult to measure the interfacial concentrations, mass transfer models are represented with respect to bulk concentrations with different system specific assumptions, such as evaluation of overall mass transfer coefficients from individual mass transfer coefficients by ignoring some resistances such as the one on strip side in certain cases. One-dimensional flow models assume axial variation of concentration but the assumption of plug flow is often invoked to simplify the models. Two-dimensional models consider both axial and radial variations of the flow, as well as concentrations. However, only a few works are reported on two-dimensional modeling because of the complexities involved with it. With the availability of better computational hardware, it is possible to easily implement two-dimensional and even three-dimensional models using CFD, which allows for a better understanding of flow and mass transport phenomena, variation of concentration with space and time, and the identification of key parameters for design and optimization. CFD models also help in the quantification of interfacial concentrations, mass transfer fluxes and their spatial and temporal variations. The effect of geometry of the hollow fiber contactor on its separation performance can also be analyzed using CFD models.
