SPATIO-TEMPORAL MODELLING OF FILTER CAKE FORMATION IN FILTRATION PROCESSES

摘要

The operation of membrane filtration units, used in many industrial, medical and environmental applications, is mainly hampered by the operational cost due to membrane fouling. Mathematical modelling can provide knowledge build-up, better process control and decision support tools to improve the operation of these processes. However, the knowledge concerning the underlying mechanisms of filter cake formation is still quite limited. As a result, the majority of fouling models is still very empirical and does not provide an adequate framework for a generic membrane fouling model. In order to further elucidate the underlying mechanisms of membrane fouling, a mechanistic Euler-Lagrangian model was developed with a detailed description of all the relevant subprocesses (Figure 1).The Eulerian model layer is based on computational fluid dynamics and computes the Navier-Stokes equations to obtain a velocity/pressure profile in the simulated domain. The movement of the dispersed particles is modelled through the Lagrangian model layer where each particle and its modelled quantities (velocity, forces, etc. ) are individually tracked by a moving frame of reference. The velocity of these particles is determined by a force balance. The formation of filter cake is modelled by means of a collision detection algorithm that tracks the collision of free moving particles with the wall and the existing filter cake. If a collision occurs, particles can attach to the wall and the cake layer, contributing to the growth of this layer.