Impact of water droplet and humidity interaction with soluble particles on the operational performance of surface filters in gas cleaning applications

The behavior of salt particles on a surface filter exposed to a high humidity gas flow and water droplets was studied to gain a better understanding of the influence of water content in its different states on the operational performance of such filters. Two sets of experiments were carried out: in both, polydisperse sodium chloride particles were filtered from a dry air stream onto hydrophobic filter media, which were subsequently exposed to either relative humidity above the deliquescence relative humidity or to water droplets. Results show that the rearrangement of salt particles on the filter face side takes place in both sets of experiments. However, rearrangements resulting from the influence of high humidity can be clearly distinguished from the ones resulting from contact with water droplets. Recordings of the pressure drop across the test filters, as well as scanning electron microscope images of the sodium chloride particles on the face side of the medium, show this difference clearly. No penetration of salt particles through the filter medium occurred under the conditions presented in this study.