Membrane transport and process modelling in OSN: a multiscale approach
Patrizia Marchetti 1 , Binchu Shi 1,2, Dimitar Peshev 3, Andrew G. Livingston 1,2 *
1 Department of Chemical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
2 Evonik Membrane Extraction Technology Limited, Unit 6 Greenford Park, Ockham Drive, Greenford, London, UB6 0AZ, United Kingdom
3 Department of Chemical Engineering, University of Chemical Technology and Metallurgy, 8, Kl. Ohridsky Blvd, Sofia 1756, Bulgaria
In Organic Solvent Nanofiltration (OSN), a fundamental understanding of the basic separation mechanism is useful to advance the field and wisely tune new materials and processes. The development of membrane processes usually involves several stages, starting from feasibility tests at membrane scale, passing through fluid dynamics and mass transfer in membrane modules and finishing with large industrial scale process design (Figure 1) [1,2].
Figure 1. Modelling levels for the development of a membrane process .
Substantial research has focused on the description of the transport mechanism through membranes (Figure 1(a)) aiming at: parameter estimation, when experimental data for standard solute/solvent systems are available, and it is desired to estimate relevant parameters for as yet uncharacterized systems; and prediction, when the model parameters for the solvent-solute are available, and modelling can be applied to describe performance of a different solute/solvent system [1,3]. Most of these studies have used flat sheet membranes. On the other hand, there is lack of studies on the fluid dynamics and mass transfer characteristics in OSN spiral-wound modules (Figure 1(b)), and attempts to implement fundamental transport models on a process level (Figure 1(c)) are few, and are based on simple, non-predictive membrane transport models.
This paper reports a systematic comparison of different transport models using selected experimental data for various solutes, solvents and membranes . Solution-diffusion, pore-flow and transient models were used to perform regression of experimental data, and prediction, based on the regressed model parameters. It was observed that solution-diffusion models described permeation through glassy membranes better than pore-flow models, against both positive and negative rejection data. Afterwards, the classical solution-diffusion model combined with the film theory was applied to model the performance of different rubber-coated spiral-wound modules (1.8”x12”, 2.5”x40” and 4.0”x40”) under various pressures and retentate flowrates. Correlations for the fluid dynamics and mass transfer in the modules were derived by regression of experimental data. Finally, OSN unit operations at membrane and module levels were made available in the Aspen Plus process modelling environment, to streamline process design using the so-called “OSN Designer” . Matlab routines for the relevant models were interfaced to Aspen Plus by means of CAPE OPEN and custom OSN unit operations for common batch and steady-state membrane processes were developed. The suitability of this technique was demonstrated by comparing the model simulation to the experimental data for both ideal and non-ideal solutions.
 P. Marchetti, M.F. Jimenez Solomon, G. Szekely, A. Livingston, Chem. Rev. 114 (2014) 10735
 D. Peshev, A. Livingston, Chem. Eng. Sci. 104 (2013) 975
 P. Marchetti, A. Livingston, J. Membr. Sci. 476 (2015) 530