TABLE OF CONTENTS Dust collection systems are a big user of nonwoven filter media. The filter housings often referred to as bag houses are very large and usually consist of a large number of filter elements. The filter elements are usually fabric bags or fabric envelopes. Cartridge filter elements are also used in these systems. For very high temperature (up to 1000 C) applications, candle filters composed of ceramic fiber may be used.
The fabrics for the bag or envelope filter elements are either woven fabrics or non-woven felts. It is estimated that the market split between these two filter media types is 50:50. Dickenson, argues that the filters operate by sieving the particles from dust-laden air and building a filter cake on the media. The filter cake actually does most of the filtering. The fabric serves as a support structure. Figures 8.1 and 8.2 are diagrams of two types of modular baghouses: MBT and MBW. The MBT module is one where the bags are replaced from the top. The MBW module provides a walk-in space for replacing the bags.
Economics requires that the filter elements be able to be reconditioned or cleaned. The most common methods for doing this are mechanical shaking, low-pressure reverse air, and high pressure-reverse jet (pulse jet). Figure 8.3 depicts a pulse-jet filter. Figure 8.4 diagrams the normal filtering mode and the reverse jet cleaning operation of a reverse...
