Dust Dislodgement from Woven Fabrics Versus Filter Performance

Dennis, Richard; Cass, Reed W.; Hall, R.R.

doi:10.1080/00022470.1978.10470563

Cited by 22 publications

(10 citation statements)

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“…3 ' 4 The above modeling process, Figure 2, depends on the fact that the cleaned area fraction, a c , is always associated with a characteristic fabric drag, S c .…”

Section: Specific Resistance Coefficient (K2)mentioning

confidence: 99%

“…Except for heavily napped surfaces, however, the apparent variability in K 2 is usually attributable to the partial cleaning effect or to massive pinhole leakage that may divert as much as 20% of the approaching gas flow through as little as <0.1% of the filter face area. 4 The path of these curves is governed by several parallel flow paths in which the approaching gas stream is apportioned according to the local drag values at any specified time for cleaned and uncleaned surfaces:…”

Section: Basic Filtration Relationshipsmentioning

confidence: 99%

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A Model for Coal Fly Ash Filtration

Dennis¹,

Klemm²

1979

Journal of the Air Pollution Control Association

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A new mathematical model for predicting the performance of woven glass filters with coal fly ash is described. The data base for this development includes an extensive bench and pilot scale study, field data from prior studies of fly ash filtration with glass fabrics, past studies of fabric filter cleaning mechanisms and a literature survey. Trial model applications with utility boilers operating at Sunbury, PA and Nucla, CO indicate excellent agreement between theory and practice for penetration and resistance characteristics. The introduction and experimental confirmation of two physical relationships were instrumental in model design. The first describes how dust dislodges from a fabric and its subsequent impact upon resistance and penetration in a multichambered system. The second concept relates to the large fraction of ash that passes through temporarily or permanently unblocked pores such that particle penetrations are essentially size independent. Additionally, the quantitation of the cleaning action and energy with dust removal method is included in the model. The calculation of dust specific resistance coefficient, based on size distribution parameters provides improved estimates of K 2 in lieu of its preferred direct measurement.In this paper, a filtration model is described which, based upon limited field validation, provides good estimates of performance for woven glass bags with coal fly ash in real filter systems. -2 The success of the model is attributed to the introduction of three new concepts or approaches to the modeling process. The first relates to the fact that dust remaining on a fabric surface after cleaning is characterized by a distinctive, nonuniform distribution in which the unique resistance and collection properties of cleaned and uncleaned areas are definable and thus amenable to mathematical analysis.The second concept allows us to specify the relationship between the amount of dust removed from a filter and (a) the method of cleaning and (b) the filter dust loading prior to cleaning. -5The third concept evolves from the unique penetration properties observed for fly ash with glass fabric in which failure to obtain rapid and/or complete pore bridging allows significant dust leakage through the filter.3 Such penetration occurs because of nonuniformity in both pore sizes and in the dispersion of the loose fiber substrate that obstructs the pore openings.3 ' 4The relatively low resistance to gas flow of the larger pores results in the passage of a disproportionately large fraction of the uncleaned gas along with most dust particles <15 ^m diameter. Because the quantity of fly ash penetrating the fabrics via the pores or pinholes greatly exceeds that which penetrates the unbroken dust cake, ~100 times, the particle size properties of the effluent are essentially the same as those for the entering aerosol.The above phenomenon explains why the fractional efficiencies for glass fabrics often appear to be independent of particle size. It is also pointed out that rear face slough-off of a...

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“…3 ' 4 The above modeling process, Figure 2, depends on the fact that the cleaned area fraction, a c , is always associated with a characteristic fabric drag, S c .…”

Section: Specific Resistance Coefficient (K2)mentioning

confidence: 99%

Section: Basic Filtration Relationshipsmentioning

confidence: 99%

A Model for Coal Fly Ash Filtration

Dennis¹,

Klemm²

1979

Journal of the Air Pollution Control Association

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show abstract

“…4a) confirms the duration of this transition period. The concavity is logical because it reflects an analogy with a patchy cleaning (such behavior has been observed by other authors [39,[49][50][51][52][53]). The parallel with a patchy cleaning can be explained as follow: areas, which are still clogged after a patchy cleaning, correspond to the first cleaned bags (because both have the higher airflow resistances); and areas, in which dust cake has been detached in a patchy cleaning, are similar to the last cleaned bags (because both have the smallest airflow resistances).…”

Section: Distribution Of Airflows Amongst Bags During Pulse-jet Cleanmentioning

confidence: 78%

Consequences of high transitory airflows generated by segmented pulse-jet cleaning of dust collector filter bags

Simon¹,

Bémer²,

Chazelet³

et al. 2010

Powder Technology

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“…This illustrates a fundamental difference between pulse-jet cleaned, nonwoven systems and shaker or reverse air cleaned, woven systems. The latter have almost all the dust deposit removed during cleaning; Dennis, et al 3 report on the basis of bench scale tests that woven fabrics with loadings before cleaning of about 1000 g/m 2 have residual dust loadings which range from 10-100 g/m 2 after cleaning.…”

Section: Discussionmentioning

confidence: 99%