Aerosol electrostatic classifier

Specific advancements ia the chemical synthesis of coUoidal materials are noteworthy. Many types of genera ting devices have been used to produce coUoidal Hquid aerosols (qv) and emulsions (qv) (39—43) among them are atomizers and nebulizers of various designs (30,44—50). A unique feature of produciag Hquid or soHd coUoids via aerosol processes (Table 3) is that material with a relatively narrow size distribution can be routinely prepared. These monosized coUoids are often produced by relying on an electrostatic classifier to select desired particle sizes ia the final stage of aerosol production. 

Constant-ouput atomizer, tri-jet aerosol generator, electrostatic classifier, vibrating-orifice aerosol generator, fluidized-bed aerosol... 

The electrostatic classifier (Fig. 6.7) is used to measure particle size distributions in Hk size range from about 0.01 /im to 0.5 pm (Pui and Liu, 1988), The classifier is operated at atmospheric pressure to select narrow size ranges from a polydisperse aerosol. The concentration in each size range is measured usually with a conden.saiion particle counter, and in this way the particle size distribution can be determined. 

Fissan, H.J., Helsper, C., Thielen, H.J., 1983. Determination of particle size distributions by means of an electrostatic classifier. J. Aerosol Sci. 14, 354-357. 

A differential mobility analyser (DMA) works on the same principle as the EAA, with some operational differences. In a DMA, an electrostatic classifier is used instead of a mobility analyser and aerosol particles can be sorted by size from 0.01 to 0.9 pm while suspended in air [124]. 

On-line measurements of the sulfur content of atmospheric aerosols have been made by removing gaseous sulfur species from the aerosol and then analyzing the particles for sulfur with a flame photometric detector (24) or by using an electrostatic precipitator to chop the aerosol particles from the gas so that the sulfur content could be measured by the difference in flame photometric detector response with and without particles present. These and similar methods could be extended to the analysis of size-classified samples to provide on-line size-resolved aerosol composition data, although the analytical methods would have to be extremely sensitive to achieve the size resolution possible in size distribution analysis. 

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