Effective pore diameter and monodisperse particle clogging of fibrous filters

Nanoparticle agglomerates are pervasive in atmospheric sciences, air pollution, and manufacturing of powdered materials, yet studies for filtration of nanoparticle agglomerates are still scarce compared to those for spherical particles. We investigated loading of soot nanoparticle agglomerates on fibrous air filter media. The soot agglomerates were generated from a diffusion burner with propane gas as fuel and compressed air as oxidant/sheath. The mode of the number distribution was determined to be 120 nm. A Differential Mobility Analyzer (DMA)-Aerosol Particle Mass Analyzer (APM) system was used to measure the mass of agglomerates as a function of the mobility size, which gave a mass-mobility exponent of 1.9 ± 0.1. Using transmission electron microscopy (TEM), we found that the primary particles in the agglomerates had a mean diameter of 28 nm with a geometric standard deviation of 1.26. Loading experiments were carried out with the face velocity of 10 cm/s on a fiberglass filter media. The pressure drop increased approximately linearly with the loading mass. The porosity of the cakes was calculated using cake mass and cake thickness, and the average cake porosity was 0.95. We found that the model of Endo et al. (1998) for cake loading was applicable to soot agglomerate loading. The cake could be regarded as formed by primary particles in soot agglomerates, and agglomerates are indistinguishable once deposited in the cake. When the size distribution of the primary particles was used in the model of Endo et al. good agreement between the experimental and computed results was obtained.

Section: Introductionmentioning

confidence: 99%

Structural Properties and Filter Loading Characteristics of Soot Agglomerates

Kim

Wang

Shin

et al. 2009

“…The pressure drop of the filter on which propolis was deposited for 120 s increased by approximately 20% more than did the control filter, whereas the pressure drop of the filter on which GSE was deposited for 120 s increased by only »5% compared with the control filter. This is probably because the fiber morphologies were similar in the control filter and filters on which GSE was deposited (Figures 3a and b AIR FILTERS USING ANTIMICROBIAL NATURAL PRODUCTS pressure drop across the fibrous filters typically occur with at least several hundred mg/cm 2 of deposited particles (Japuntich et al 1997;Thomas et al 2001), which is one order of magnitude greater than that used in this work. The filters investigated as part of this study were therefore probably in the initial clogging stage by depth filtration (Rebai et al 2010).…”

Section: Resultsmentioning

confidence: 77%

Treatment of Air Filters Using the Antimicrobial Natural Products Propolis and Grapefruit Seed Extract for Deactivation of Bioaerosols

Woo

Kang

Kim

et al. 2015

Two natural products; i.e., grapefruit seed extract (GSE) and propolis, were investigated for use in antimicrobial air filters. Staphylococcus aureus was investigated as a test bioaerosol, and was deposited on the antimicrobial filters, which were treated by spraying with various areal densities of GSE and propolis. The pressure drop and particle penetration were investigated to assess the filtration performance of the bioaerosol, and the bacterialinactivation performance of the filters was evaluated by quantifying S. aureus. There was little change in the pressure drop as a function of the areal density of GSE up to 185.9 mg/ cm 2 ; however, a significant change in the pressure drop was found for the air filter coated with propolis at an areal density of 98.4 mg/cm 2 . The penetration levels of bioaerosols in both filters were uniform and in the range 1.4-2.0% (based on particle number), regardless of the areal density of the deposited GSE or propolis. The inactivation rates of the filters with identical deposition masses of GSE and propolis were similar in the ranges of 92. 1-100%, 75.2-89.1%, and 54.4-75.5% at the control filters with colony numbers of 10 3 , 10 4 , and 10 5 CFU/mL, respectively. The bacterial inactivation rate could be described by an exponential function of the areal density of GSE/propolis per number of colonies.

“…Thomas et al (1999 and) modified Bergman's model by considering a filter as a series of slices, with each one acting as an independent filter and becoming challenged only by the particles that penetrated the upper layers. Japuntich et al (1997) experimentally studied the pressure drop of a stack of several identical filter layers. The increase in pressure drop during loading was due to the first layer alone.…”

Section: Previous Studiesmentioning

confidence: 99%

Filter Clogging by Bimodal Aerosol

Valmari

Lehtimäki

Taipale

2006

Pressure drop evolution during filtration of bimodal aerosol was studied experimentally. A low-pressure drop pre-filter upstream of the actual collection filter was demonstrated to significantly reduce the pressure drop growth rate, when the aerosol is dominated by coarse particles. The pressure drop evolution during depthfiltration, that took place mainly in a pre-filter, could be predicted by adding up the separately measured contributions from the unimodal fine and coarse aerosols. However, the cake filtration (prefilter was not used) of coarse particles alone resulted in a faster clogging rate as compared to the same amount of coarse particles accompanied with fine particles (mass ratio coarse:fine 3:1). Apparently, fine particles deposited on coarse particles affect their surface properties and thus the porosity of the cake formed.