Ageing of electret filter media due to deposition of submicron particles – Experimental and numerical investigations

Abstract

Electret filter media are electrostatically charged nonwovens which are commonly used for separation of fine particles from gases. The separation behavior of the unloaded filter media has been extensively investigated in the past for a variety of filter media and particles using experiments and simulations. Moreover, the phenomenom of filter ageing of filter ageing by particle deposition and possible causes for that are well known, but to what extent these individual effects contribute to the ageing is still unclear. Thus, the aim of this work is to investigate the dominant effects causing filter ageing by means of experiments and simulations.The experiments revealed a decreasing filtration efficiency with increasing exposure to sodium chloride particles. A detailed consideration of the particle size and charge distribution indicated that charge neutralization is the dominant effect for filter ageing in this case. The implementation of this interaction between particle and fiber charge in a numerical simulation tool showed a good agreement in the decrease of the filtration efficiency with the experimental findings.