Electrostatic mechanisms of aerosol collection by granular filters: A review

The paper reviews the state of the art of aerosol filtration by granular filters in the presence of electrostatic forces. Firstly, six types of electrostatic interactions are described, together with the respective means of electrostatic enhancement, namely electric charging of aerosol particles, charging of filter granules and application of an external electrostatic field to the filter bed. Solution methods for calculating the efficiency of diffusionally, inertially and electrostatically governed aerosol deposition processes are presented. Existing flow field and electrostatic force models within the filter bed and their merits in accounting for bed void fraction, when calculating aerosol collection rates, are described. Known theoretical results are generalized and conveniently presented in the form of tables for each specific electrostatic interaction. Experimental data on the role of electrostatic forces in aerosol filtration are given. Several industrial applications of electrostatically enhanced granular filters are described. The advantages and the limitations of the existing aerosol filtration models are emphasized by means of a comparison between theoretical and experimental results.