Structural Properties and Filter Loading Characteristics of Soot Agglomerates

Abstract

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.

Deposition of silica agglomerates in a cast of human lung airways: Enhancement relative to spheres of equal mobility and aerodynamic diameter

“…(1) to the data for particles covering a range of mobility sizes gives e m . For very open agglomerate structures, e m falls in the range of 1.7-1.9 (Kim et al, 2009b;Scheckman et al, 2009); for perfect spheres, e m ¼3 (Kim et al, 2009a;McMurry et al, 2002;Pagels et al, 2009); various studies have reported intermediate values (Kim et al, 2009a;Ku et al, 2006;McMurry et al, 2002;Park et al, 2003Park et al, , 2004. The mass-mobility exponent is qualitatively similar to the fractal dimension in the sense that it approaches a value of 3.0 for spheres and a value below 2 for diffusion-limited aggregates.…”

“…Several researchers have measured deposition of agglomerates in various types of filters and found that agglomerates deposit consistently more than spheres of equal mobility size (Fu et al, 1990;Kim et al, 2009aKim et al, , 2009bLange et al, 1999Lange et al, , 2000. In general, the additional deposition was attributed to interception-agglomerates typically have maximum dimensions significantly larger than their mobility size (Park et al, 2004;Rogak et al, 1993), so they are affected more by interception than their mobility-equivalent spheres.…”

Fine Particle Filtration Technology Using Fiber as Dust Collection Medium

“…(25) and (26) assuming λ = 5 m 3 /kg. Clogging of nano-size particles in HEPA filter was carried out concerning effect of gas slip Hung C.-H. 2008, 2009), particle distribution (Brourrous S. et al, 2014), structure and loading capacity (Contal P. et al, 2004;Kim S.C. et al, 2009), liquid and humidity, hygroscopicity (Payet S. et al,1992;Contal P. et al, 2004;Gupta A. et al, 1993;Joubert A. et al, 2010;Agranovski I.E. and Shapiro M., 2001) and etc.…”

Effects of relative humidity and particle type on the performance and service life of automobile cabin air filters

“…Meanwhile the particle size distribution of the filtration cake cannot be treated as the same as that of the upstream of the low efficiency filters, which is the normally utilized method for high efficiency ones, due to the significantly different filtration efficiencies for different particle sizes by the low efficiency filters. Even though there is no exact analytical equation to express the pressure drop for low efficiency pleated filters, Equations (S1) to (S5) in the SI can be used to describe the relationships among the related parameters qualitatively (Cheng and Tsai 1998;Kim et al 2009;Liu et al 2013). In practice, loading capacity is an important indicator for the performance of a filter, which can be used to estimate its proper service life time.…”