filter regenerati on and filtrati on efficiency.
Filter regeneration and filter stability depends on both the nature of the dust cake
(thickness, adhesion forces and degree of compressibility), propagation and
distribution of the pressure pulse within the filter element, the defined maximum
allowable pressure drop, and pulsating frequency. It also heavily influences upon the
plant’s efficiency, as typically 60-90% of the emissions is related to this phase
(Klingel 1983 and Schmidt 1995a/b). A schematic presentation is given in Figure
2.10. Additional particle penetration either proceeds via straight through, seepage or
pinhole plugs. Furthermore, a high pulsating frequency (i.e. short filtration periods)
results in enhanced degree of particle penetration into the filter media and typically
leads to both a rapid increase in the residual pressure drop and low filter efficiency.
The higher the dust mass, i.e. the thicker the deposit layer, the higher the cleaning
efficiency (Morris et al. 1987; Sievert and Loeffler 1987; Seville et al. 1989; Berbner
and Löffler 1994)
Tank pressure, valve-opening times and diameter, blow-tube arrangement and
whether the cleaning is operated on/off-line can control the intensity and shape of the
pressure pulse. On-line cleaning generates an ejector (jet-pump) effect. Thus, surplus
air will be entrained into the filter element from the clean air side. This reduces the
demand for pressurised air and has lead to the development of alternative filter inlet
geometry’s (venturies/ejectors).