Reverse flow baghouse

Cake filtration presents complicated problems because the cake can be more or less compressible under the force of the pressure differential across the cake. Some clarification processes do employ cake filtration - such as exhaust gas cleaning in baghouses or the treatment of some dilute liquid slurries in bag filters - where the accumulated cake is usually blown free from the surface of the bag by means of a reverse flow of fluid. 

Dust capture can be effected on the inside of the bag (gas flow from inside out) or its outside (gas flowing from the outside), with the latter by far the most common, especially with the more automated baghouses. Dust cakes on the outside of the bag are more easily removed, either by shaking the bag assembly, or by a reverse flow of compressed air. Internally accumulated dust can be shaken into the bottom of the bag, but eventually the baghouse must be shut down and the bags removed for emptying. 

Bottom-feed units are characterized by the introduction of dnst-laden gas through the baghouse hopper and then to the interior of the filter tube. In top-feed units, dustladen gas enters the top of the filters to the interior or clean-air side. When the gas flow is fiom inside the bag to the outside, by virtue of the pressure differential, the internal area of the filter element will be open and self-supporting irrtsupported filter elements are tubular. When the filtration process is reversed, with the gas flow fiom outside the bag to inside, it is necessary to support the media agairrst the developed pressures so that the degree of collapse is controlled. Supported filter elemerrts are either of the tubirlar or envelope shape. 

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