6. Bag filters

These are dust collectors in which the dust-laden fumes pass through a filter layer on which the particles are deposited. Unlike cyclone separators or scrubbers, where particles are removed continuously, in this case they accumulate and must be periodically separated by a cleaning process. The filter layer can consist of :

• of woven media;

• loose fibers or felts;

• porous membranes, usually attached to a support ;

• filter papers.

Filters can be either high-efficiency, used in nuclear and cleanroom applications, or standard-efficiency. In the former case, accumulated dust is often eliminated with the filter media itself, as entire cassettes have to be changed, whereas in the latter case, filter media last for...