Comparison of Three Real-Time Measurement Methods for Airborne Ultrafine Particles in the Silicon Alloy Industry

Abstract

The aim of this study was to compare the applicability and the correlation between three commercially available instruments capable of detection, quantification, and characterization of ultrafine airborne particulate matter in the industrial setting of a tapping area in a silicon alloy production plant. The number concentration of ultrafine particles was evaluated using an Electric Low Pressure Impactor (ELPI(TM)), a Fast Mobility Particle Sizer (FMPS(TM)), and a Condensation Particle Counter (CPC). The results are discussed in terms of particle size distribution and temporal variations linked to process operations. The instruments show excellent temporal covariation and the correlation between the FMPS and ELPI is good. The advantage of the FMPS is the excellent time- and size resolution of the results. The main advantage of the ELPI is the possibility to collect size-fractionated samples of the dust for subsequent analysis by, for example, electron microscopy. The CPC does not provide information about the particle size distribution and its correlation to the other two instruments is somewhat poor. Nonetheless, the CPC gives basic, real-time information about the ultrafine particle concentration and can therefore be used for source identification.

Keywords: aerodynamic diameter; airborne particulate matter; condensation particle counter; electric arc furnace tapping; electric low pressure impactor; fast mobility particle sizer; mobility diameter; silica fume.

Figure 1

Schematic illustration of the placement of the instruments in the furnace tapping area between two electric arc furnaces. Both furnaces were continuously tapped.

Figure 2

PM concentration as a function of collection time from the two different days of measurement. CPC, FMPS, and ELPI are compared and PM-increasing events are market by arrows. Results from day 1 are shown to the left, day 2 to the right.

Figure 3

Scatterplots of the particle concentrations of the different instruments together with regression analyses.

Figure 3

Scatterplots of the particle concentrations of the different instruments together with regression analyses.

Figure 4

Particle size distributions measured by the ELPI and the FMPS during two different days of measurement. Results from day 1 are shown on the left, day 2 on the right.

Figure 5

Transmission electron micrographs of ultrafine PM collected by the ELPI.

Figure 6

Ultrafine PM concentration as a function of collection time, as recorded by the ELPI and the FMPS during two different days of measurement. Results from day 1 are shown on the left, day 2 on the right.