Generating and Characterizing Smoke Aerosol for HEPA Filter Media Loading

DRAKE LARSON, Spencer Phillips, Jaime Gibson, Mississippi State University

     Abstract Number: 546
     Working Group: Combustion

Abstract
The Institute for Clean Energy Technology (ICET) at Mississippi State University (MSU) performs applied research regarding HEPA filter performance for the Department of Energy nuclear complex. One area of interest is HEPA capability during fire scenarios. Currently there is little data available. More thorough data is needed to support facilities in safely planning for fire scenarios.

The Flat Media Loading System (FMLS1) was designed to fill the void in the context of fire and soot behavior by reducing the time and resources it takes to fully characterize assembled AG-1 filters. This system’s focus is collecting performance characterization data of flat media samples of AG-1 HEPA filter media.

A miniature Combustion Aerosol Standard soot generator (miniCAST) was chosen for this research. The miniCAST allows fine control of the particle geometric mean diameter with good stability. However, a few difficulties have presented themselves in this application.

This work has shown that the particle size of the output soot changes drastically when diluted. This is likely due to chemical reactions in newly formed soot particles. This issue was discovered due to a need for dilution of samples to prevent exceeding the concentration limit of the particle sizing instrument (Scanning Mobility Particle Sizer). It was found that changing the dilution ratio changes the particle size greatly. This led to the need for a soot growth chamber, to allow an appropriate residence time for the soot to agglomerate and form into matured particles. Changing the dilution ratio now has a minimal effect on resulting particle size distributions. As dilution is still needed for sizing, the aerosol challenge presented to the filter media samples is also diluted, resulting in slow loading results. This paper presents work performed to increase filter loading times by understanding the relationship between soot aerosol before and after dilution.