Skin layer in cyclic loading-cleaning of a nanofiber filter in filtering nano-aerosols

W. W.-F. Leung*, C. W. Y. Hau, The Hong Kong Polytechnic University, Hong Kong

Nano-aerosols from viruses to virgin pollutant particulates from combustion, 100nm or smaller, are harmful to our health as they penetrate readily into our body causing various diseases. Nanofiber filter can capture effectively these nano-aerosols. However, over time the pressure drop increases dramatically and cleaning of the filter by backpulse/backblow is essential for filter reuse. The cyclic loading-and-cleaning of a nanofiber filter is unknown and the reuse of a loaded and cleaned nanofiber filter is uncertain. This aspect has been investigated for the first time experimentally and theoretically.

The experimental study involves a test rig for accelerated loading of a home-made nanofiber filter using sodium chloride nanoparticles 50-400nm. During loading, the pressure drop across the filter is periodically monitored. After a critical pressure drop has been reached, the loading is stopped and back-pulse followed by backblow is used to clean the filter. The filter is repeated loaded and cleaned for another 5 more cycles. All along the pressure drop is monitored. Analytical models are used to analyze the behavior of the measured pressure drop excursion.

The “skin” layer, a thin region upstream of the nanofiber filter, plays a pivoting role in controlling the pressure drop excursion of the filter. We model the skin layer to be made up of numerous fine capillaries and examine how continuous aerosols deposited in the capillaries affect rapid rise in pressure drop followed by bridging of aerosols across the capillary openings leading to more bridging and ultimately formation of cake on top of the bridges and filter surface. We have been able to describe the deposition of aerosols in the capillary pores for depth filtration, the deposition of aerosols in the cake (surface filtration), and the intermediate bridging regime between these two. We can depict...

Session: G6 - Nanofibre Filter Media
Day: 14 March 2018
Time: 10:45 - 12:00 h

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