Modeling Concepts for Pulse Jet Filtration

Predicting Pressure Loss for Pulse Jet Filters

“…5 - 8 The very brief duration of a typical cleaning pulse, ~0.1 s, does not permit significant gravitational fallout in contrast to that obtained with mechanically shaken baghouses in which the gas flow is interrupted for as much as 2 to 5 minutes.…”

“…5 * 8 Dennis and Klemm have postulated, however, that the surface dust loading prior to cleaning, W c + AW, is uniquely defined by the adhesive force between the dust layer and fabric, FA , and the separation force, Fs, produced by the average acceleration imparted to the dust layer by the jet pulse. 8 Furthermore, they have asserted, based upon prior studies, 2 that the magnitude of W c depends mainly upon the FA-FS relationship for the specific dust-fabric combination with large variations in inlet concentration and filtration velocity exerting little effect on W c values. It was also reported that the specific resistance coefficient, (#2)0 for the cycling dust loading, W c , should be considerably lower than that for the freshly deposited dust, AW, because of the highly agglomerated state of the cycling layer.…”

“…Although these studies help to explain how pulse jet filters work, none provide a clear insight as to the actual physical processes taking place during filtration or fabric cleaning. Recently, Dennis and Klemm 8 have proposed that the filter drag, S, for a single bag pulse jet unit can be described by the relationship:…”

“…It was also reported that the specific resistance coefficient, (#2)0 for the cycling dust loading, W c , should be considerably lower than that for the freshly deposited dust, AW, because of the highly agglomerated state of the cycling layer. 8 Additionally, whereas W c was described as varying from 400 to 1000 g/m 2 , AW levels usually ranged from only 3 to 60 g/m 2 . 5 ' 8 Although Eq.…”

“…= S E +(K 2 ) C W C (1) cycling fraction of the total dust loading that is alternately dislodged and redeposited on the fabric; W c , the cycling portion of the dislodgeable dust holding; 8 and K 2 , the specific resistance coefficient for the freshly deposited dust fraction, AW, that accumulates over the filtration interval, At, at inlet concentration, C, and face velocity, V. Despite the large amounts of dust residing upon or within felt fabrics, ~400 to 1000 g/m 2 , various investigators have determined that less than 1 to 10% of the dust dislodged by the cleaning action actually descends to the dust hopper. 5 - 8 The very brief duration of a typical cleaning pulse, ~0.1 s, does not permit significant gravitational fallout in contrast to that obtained with mechanically shaken baghouses in which the gas flow is interrupted for as much as 2 to 5 minutes.…”