Investigation of oil mist filtration performance of surface modified coalescence filters with asymmetric wettability

Fibrous coalescence filters are widely used to remove oil mists from air and gas streams in industrial applications. The wettability of filter media significantly affects the filtration performance. Although some efforts have been made to improve the filtration performance based on the modification of filter media wettability by surface treatment method, of which the influence on liquid transport mechanism in the filters and the filtration performance is still needed to elucidate. In this paper, oleophilic filter media were treated by fluorocarbon copolymer solution using a spraying method. The effects of the treated area ratio, spraying time and combinations of patterned filter media on the filtration performance were investigated experimentally. The results show that the increase of the treated area ratio contributes to a variation on the wettability from oleophilic to oleophobic, resulting in a decrease in the jump pressure drop and an increase in the filtration efficiency. The treated filter medium under the optimal spraying time has the highest quality factor, which is 2∼3 times the untreated one. For the dual-layer patterned filters with alternative oleophobic and oleophilic strips, when the number of oleophobic strips patterned in the first layer filter medium is the same, the pressure drop and filtration efficiency of the overlapped arrangement are lower than those of the staggered arrangement. In all configurations, the highest quality factor is found in the dual-layer filter with the overlapped arrangement and four oleophobic strips patterned in the first layer, resulting from the lowest steady pressure drop and relatively high filtration efficiency.