Filtering method and apparatus therefor

A filter apparatus for removing fine particulates from a gas stream comprising:

• a housing containing a substantially gas-permeable microporous filter element having restricted flow paths therethrough for the collection, adjacent an upstream face thereof, of fine particulates from a gas stream with an efficiency greater than 80 percent;
• a substantially vertical granular material retention member having upstream and downstream faces and provided with openings for the substantially unimpeded flow of a fine particulate-containing gas stream therethrough, said retention member being located in said housing and having its downstream face spaced apart from the upstream face of said microporous filter element to provide a passageway therebetween;
• a body of granular material disposed in said passageway and permeable to the flow of the fine particulate-containing gas stream therethrough;
• gas inlet means for the delivery of the fine particulate-containing gas stream to the upstream face of said retention member for passage through said retention member and body of granular material to the upstream face of said microporous filter element for collection of particulates from the gas stream;
• means for scouring the upstream face of said microporous filter element with the granular material by at least intermittent movement of said body of granular material adjacent said upstream face of said microporous filter element to remove collected fine particulates therefrom;
• and
• gas outlet means for the removal of a substantially particulate-free gas stream from a downstream face of said microporous filter element, said retention member, body of granular material, and microporous filter element providing the sole means for gas communication between said gas inlet and gas outlet means.