Filtration efficiency is an important characteristic of filters used to remove aerosol and dust particles from air. It is a function of several variables, such as porosity and thickness of the filter media, size of the filter elements, gas flow rate and the degree of filter loading. Changing some of the parameters of the filter in order to increase filtration efficiency is usually accompanied by an increase in pressure drop across the filter. Application of external fields, such as electrical or acoustical might enhance the filtration efficiency without change in pressure drop across the filter. The influence of acoustic fields on the filtration efficiency is well known. Several investigations have shown that an acoustic field can increase filtration efficiency.
Another important parameter is the operating lifetime of a filter. Every filter undergoes clogging with time. The captured dust builds up in a layer on the filter forming a filter cake. The layer grows with time, and so does the overall pressure drop across the filter. When the pressure drop reaches some critical value, the filter is defined as clogged, and it should either be cleaned or replaced.
The common methods of filter cleaning are, shaking the cake of the filter cloth and cleaning by air jets or by reverse flow. All these methods have their advantages and disadvantages. The shaking operation destroys the filter material requiring its frequent replacement. Jet and reverse flow cleaning add to the complexity of the device, and also consume a considerable amount of energy.
No prior art is known to us for the application of acoustic fields to increase the lifetime of gas filters.
It is an objective of the invention described herein to apply the influence of acoustic waves on the kinetics of filters to reduce clogging and increase the lifetime of a gas filter, by slowing down the increase in pressure drop across the filter caused by clogging.