Penetration of soluble material through surface filters due to exposure to water mist - Impact of the filter material wettability
FILTECH 2022, The Filtration Event
A.D. Schwarz, J. Meyer, A. Dittler
The presence of water droplets in gas cleaning filtration systems due to fog, spray rain or condensation has an impact on the filters’ operating performance. The differential pressure between the raw and the clean gas side of the filter is a key parameter considering the energy efficiency of the filter.
The exposure of an established filter cake with soluble components on the filter surface to water mist leads to structural changes of the deposited particle collective. Dendrite structures collapse and particles rearrange on the filter surface. Soluble particles dissolve. The solution may penetrate through the filter medium to the clean gas side depending on the composition of the cake (e.g. ratio of soluble salt particles and insoluble dust), the operation parameters (mainly duration of liquid exposure) and filter medium properties such wettability.
The presented work focuses on the penetration of soluble material through surface filters due to contact with water mist and the resulting change in the differential pressure, depending on the wettability of the filter (hydrophilic or hydrophobic filter medium). During the experimental procedure, surface filters are loaded with soluble particles (K2SO4) at low relative humidity < 10 %. Following cake build up, the filter is exposed to water mist. After this exposure to water mist, the filter is dried in a final step. Scanning electron microscope images are used to illustrate the connection between deposit structures on the filter and the pressure drop evolution.