Selecting fiber materials to improve mist filters

As a filter captures droplets and retains liquid, the efficiency of the filter declines while the pressure drop rises. Making filters that drain more effectively and retain less liquid may minimize efficiency losses and pressure drop increases. Glass, polyester, and polyaramid fibers were observed microscopically as they collected droplets. Liquid spread much more readily on the polyaramid fibers than on the other kinds. Complete filters were then formed from glass and polyaramid fibers and tested for efficiency, pressure drop, and liquid retention as they collected droplets. Although the filters made from polyaramid fibers exhibited less liquid retention and pressure drop increase, the reduction in efficiency between filters made from the two fiber types was not statistically different. These findings suggest that using higher surface energy fibers in mist filters may allow lower levels of liquid retention that result in wet filters with a lower pressure drop.