A suspension flow model for hydrodynamics and concentration polarisation in crossflow microfiltration

A new computer simulation model is proposed for suspension flow in microfiltration systems. In this model, the diffusion of the suspended microparticles is governed by the mechanism of shear-induced migration. Using an Euler-Euler approach, hydrodynamics and convection-diffusion are simultaneously resolved according to the lattice Boltzmann method. The new suspension flow model allows the complete solution of the flow field (including calculation of the actual local shear rate) in systems with complex geometries and the application of a pressure gradient over he feed flow channel as well as over he membrane. The cake layer dimensions and permeability are explicitly taken into account. For a simple cross-flow system, a comparison is made between the new suspension flow model and existing models. The more realistic approach of the suspension flow model is found to be especially significant for the calculation of the cake layer profile at the beginning and the end of the membrane. Also the effect of narrowing of the flow channel by cake formation on the suspension flow pattern (at a constant pressure gradient over the flow channel) is more realistically predicted. Finally, some examples are presented of the concentration polarisation and cake layer formation in microfiltration systems with more complex geometries. The newly developed suspension flow model has generic applicability as a design tool for microfiltration membranes, systems and processes. Extensions of the model o three-dimensional systems (including parallel computations), as well as adaptations of the diffusion model to anisotropic diffusivity can be relatively easily achieved.