The contribution of small leaks in a baghouse filter to dust emission in the PM2.5 range

Kurtz, O., Meyer, J., & Kasper, G. (2017). The contribution of small leaks in a baghouse filter to dust emission in the PM2.5 range—A system approach. Particuology, 30, 40-52. https://doi.org/10.1016/j.partic.2016.08.001

The contribution of small leaks in a baghouse filter to dust emission in the PM_2.5 range—A system approach

Oliver Kurtz ^1 *, Jörg Meyer, Gerhard Kasper

Institut für Mechanische Verfahrenstechnik und Mechanik, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

10.1016/j.partic.2016.08.001

Volume 30, February 2017, Pages 40-52

Received 24 April 2016, Revised 17 July 2016, Accepted 2 August 2016, Available online 24 November 2016, Version of Record 27 January 2017.

E-mail: oliver.kurtz@kit.edu oliver.kurtz@freudenberg-filter.com

Highlights

• Emissions from a small leak were separated from transient media emissions.

• Dust leakage through small holes depended mainly on the upstream PM_2.5 fraction.

• The equivalent leak surface area was ≤1 ppm of installed filter surface area.

• Equivalent leak surface area was independent of dust inlet concentration.

• Seamlines contributed up to 50% of emissions from conventional PS needle felt.

Abstract

The contribution of leakage in a baghouse filter (defined as a short circuit between the upstream and downstream sides of the filter) to the emission of fine particles is quantified in comparison to other dust emission sources, and the influence of key operating variables on overall system response is analyzed. The study was conducted on a well-maintained pilot-scale filter unit (9 bags of 500 g/m² calendered polyester needle felt; total surface area 4.2 m²) operated in Δp-controlled mode over a range of pulsing intensities, with two types of test dust (one free-flowing and the other cohesive) at inlet concentrations of 10 and 30 g/m³. Leaks included single holes between 0.5 and 4 mm diameter, intentionally placed in either the plenum plate or one of the filter bags, as well as seamlines from bag confectioning. Emissions were separated by source into a transient contribution due to dust penetration through the filter bags after each cleaning pulse, and a continuous contribution from leaks. This separation was based on a novel method of data processing that relies on time-resolved concentration measurements with a specially calibrated optical particle counter. Tiny leaks on the order of 1 mm generated the same emission level as all the bags combined, and dominated continuous emissions. The equivalent leak cross section (leakage = media emission) was about 1 ppm of the total installed filter surface, independent of upstream dust concentration. Leakage through open seamlines amounted to 75% of media emissions in case of free-flowing test dust. Leakage was restricted to aerodynamic diameters less than ∼5 μm (roughly the PM_2.5 mass fraction). For comparison, time-averaged mass penetration through conventional needle-felt media ranged from about 10⁻⁵ to 10⁻⁶, depending on cohesiveness of the particle material and pulse cleaning intensity, giving emission levels between about 0.02 and 0.2 mg/m³ at the reference concentration of 10 g/m².

Graphical abstract

Keywords

Air filtration; Baghouse; Pulse-cleaned filters; Leaks; PM_2.5; Dust emission

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