Improving performance and drainage of coalescing filters.

摘要

Pure air or gas is very critical to many industrial applications. Gas streams contain impurities in the form of solid and liquid aerosols of micron and submicron sizes. It is very important to remove these aerosols for improving the economy and reliability of industrial processes and equipment as well as protecting our health and environment. Among different filters being used, coalescing filters are effectively used to remove liquid aerosols from gas streams and hence has numerous industrial applications. The performance of the filter affects the economy of the process.A coalescing filter captures the oil droplets and the captured liquid typically drains from the filter by action of gravity. The saturation or hold-up of liquid in the filter constricts the gas flow, increases pressure drop, and increases the operating costs of the filter. The filter loaded with liquid droplet indicates limited filter life and needs to be replaced which increases the cost of process. Filter performance and filter life can be improved if the liquid saturation is reduced without reduction in capture efficiency. In this research work filter media are modified with drainage structures to reduce saturation and to reduce drag resistance. The media are tested in horizontal and vertical orientations to determine whether their orientation with gravity influences the performance. The experimental results show that with no drainage channels the media oriented with flow vertically downward operates the best whereas with drainage channels the horizontally oriented media had the best performance. The results also show filter geometries developed by embedding low surface energy woven drainage channels at 45 degree downward angles have the overall best performance. Adding nanofibers to improve the performance of the filter media is an effective way of improving filter media's capture efficiency with moderate increase in pressure drop. Nanofiber augmented filter media indicated higher pressure drop but when the drainage channels are incorporated in the filter, the increase in the pressure drop is significantly low. The pressure drop increase will be significant for a nanofiber augmented filter media without the drainage channels. Filter geometries developed by incorporating drainage channels at downward angles indicate significantly low pressure drop, the drainage channels create a path of lower resistance and hence maximum flow goes through the drainage channel improving the filter performance and drainage.This research work allows to develop cost effective filter geometries which will significantly increase filter performance as compared to the glass fiber filter media which are commonly used in the industry.