Three-dimensional numerical study of flow characteristics and membrane fouling evolution in an enzymatic membrane reactor

In order to enhance the understanding of the membrane fouling mechanism, the hydrodynamics of the granular flow in a stirred enzymatic membrane reactor is numerically investigated in the present paper. A three-dimensional Euler-Euler model, coupled with the k-ε mixture turbulence model and the drag function proposed by Syamlal and O’Brien (1989) for the interphase momentum exchange, is built to simulate the two-phase (fluid-solid) turbulent flow. Numerical simulations of single- or two-phase turbulent flows at various stirring speeds are carried out. The numerical results agree very well with the published experimental data. Results include the distributions of the velocity, the shear stress and the turbulent kinetic energy. It is shown that the increase of the stirring speed not only enlarges the circulation loops in the reactor, but also increases the shear stress on the membrane surface and accelerates the mixing process for the granular materials. The time evolution of the volumetric function of the granular materials on the membrane surface can qualitatively explain the evolution of the membrane fouling.