Modelling of filtration processes of fibrous filter media

This work presents a stochastic approach, based on Monte Carlo method, to simulate liquid filtration processes through non-woven fibrous materials. The real filter material is represented as a multilayer medium with a network of multiply connected pores. To describe the deposition and resuspension of particles on and from the filter medium, the following four mechanisms were considered: particle capture by sieving, patricle capture by fibers; particle capture by blocked pores; and particle re-entrainment. The particle capture by fibers and blocked pores, and particle re-entrainment depend on the balance between the adhesion and removal forces. The adhesion forces for particles of diameter smaller than 20 mu m were determined through the concept of London-Van Der Waals forces. For particles of diameter greater than 20 mu m, gravitational forces were considered. Three-dimensional random flow was assumed to stimulate the particles motion through the multilayer medium. The pressure drop across the filter medium was calculated as the sum of the pressure drop across the clean filter plus the pressure drop due to the deposited particles. A FORTRAN Program was developed to implement the filtration process model. For a wide range of typical filtration conditions, the calculated filter efficiencies predicted the experimental results with a percent difference between 0.5 and 19.3 depending on the particle size. The filter material capacities were predicted with an average discrepancy of 23.0%.