Comparison of nonwoven glass and stainless steel microfiber media in aerosol coalescence filtration

Abstract

Abstract Coalescing filters are used to remove fine drops from aerosols and emulsions. Fibrous nonwoven filter media are commonly used to coalesce small drops into larger drops for easier removal. The coalescing performance of a medium is dependent upon several parameters including permeability, porosity, and wettability. In many coalescing filters, glass fibers are used. In this work, we measure the properties of steel fiber media to see how these properties compare to glass fibers in coalescence performance. Steel fiber media have several differences in material properties from glass fiber media that may prove advantageous in performance and filter design. Steel fiber media are more ductile than glass fibers making them more suitable for vibrating environments and easier to machine with reduction of fiber shedding. The steel fiber media are elastic and can be compressed to change media properties such as permeability and porosity. The steel fibers have different wetting properties than glass and may give better coalescing performance for some liquids and they can be applied at higher operating temperatures than glass fibers. Nonwoven stainless steel and glass fiber media with fiber diameters of 2 and 6 μm were used. Permeabilities were measured using a Frazier Permeability Tester, porosities were measured using a custom made pycnometer, and wetting properties were measured with a modified Washburn test. The media performances were evaluated in a coalescence test apparatus. The overall performances of the steel fiber and glass fiber media are compared using a filtration index. 2 μm glass and 6 μm stainless steel fiber media had separation efficiencies of about 85%. Due to the higher permeability of 6 μm stainless steel media, its filtration index was significantly higher.