Comparative performance of philic and phobic oil‐mist filters

Abstract

The evolution of pressure drop, drainage rate, saturation, and efficiency of combined philic, and phobic oil mist filters in real‐time are examined. The experiments used four different filter configurations, with a combination of oleophobic and oleophilic fibrous filter media, and one oleophilic only reference. The effect of separating filter materials of differing wettability, with a mesh, was also explored. It was found that inclusion of a mesh between layers promoted increased drainage rates and resulted in a significantly lower pressure drop across the filter. The overall mass‐based filtration efficiency was also slightly higher for the configurations containing the mesh. Conversely, re‐entrainment of droplets from the rear face of the filter was only observed in filter configurations without the central mesh. Filters with oleophobic initial layers did not display a classical “depth filtration” pressure drop curve. The oleophobic media was found to possess lower steady‐state saturation than oleophilic media. Additionally, the steady‐state saturation of the oleophilic filter media, when placed at the rear of the filter, was lower when the central mesh was present. The saturation values were compared with recently published theory. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2976–2984, 2014

Measurement of oil entrainment rates and drop size spectra from coalescence filter media

“…Aside from micron-sized entrainment droplets, one may also expect the formation of much larger drops due to blow-off or fragmentation of bursting bubbles, as suggested recently by Mullins et al (2014). However, such very large drops tend to settle or impact rapidly rather than follow the gas stream, and are therefore not readily detected by measurements downstream of the filter (Schmidt et al, 2010).…”

“…However, such quantitative information is scarce in the scientific literature, especially for oil Mullins et al, 2014), and not helpful in identifying the underlying mechanisms.…”

“…This has been done by electrostatic precipitation of the aerosol followed by gravimetric determination of the deposited mass (Conder and Liew, 1989;Raynor and Leith, 2000), or more recently by capturing the aerosol on a highefficiency filter placed further downstream (Contal et al, 2004;Mead-Hunter et al, 2013;Mullins et al, 2014). Others have used more indirect techniques such as condensation and weighing in the case of water mist (Carpenter and Othmer 1955;El-Dessouky et al, 2000), or even chemical precipitation and titration in the case of sulfuric acid (Bürkholz, 1970).…”

“…Non-contact techniques such as electrical mobility spectrometry (Frising et al, 2005;Charvet et al, 2008;Mead-Hunter et al, 2013) or optical particle counters (Leith et al, 1996;Boundy et al, 2000;Peters et al, 2001;Mullins et al, 2014) are readily available today, and have been used extensively to obtain droplet size spectra and concentrations below 20 μm. However, with the exception of Mead-Hunter et al (2013) these techniques were never employed to study entrainment, but primarily to measure aerosol penetration through filters in the micron and submicron range, with large drops mostly outside the field of view.…”

Aerosol-mist coalescing filters – A review

“…For information about the angles of the drainage channels in the aforementioned works or the angles of inclination used in Agranovski et al [7] and Agranovski et al [6], please refer to the original work. Jankowski [56], MeadHunter et al [71], and Mullins et al [85] have considered filters made up of multiple layers, in these cases the properties listed are for the single filter layers used.…”