Design and characterization of a fluidized bed aerosol generator: A sourcefor dry, submicrometer aerosol

A fluidized bed aerosol generator has been designed and built for the purpo se of generating a constant output of dry, submicrometer particles with a l arge number density. The output of the fluidized bed for generating aerosol particles from dry soot powder has been characterized using a differential mobility analyzer and a condensation particle counter. The particle size d istribution is bimodal, with a mode in the submicrometer diameter size rang e and a mode in the supermicrometer diameter size range. The larger diamete r mode is fully separated from the smaller mode and can thus be easily remo ved from the aerosol pow using impaction techniques. The distribution in th e submicrometer size range is nearly log-normal, with a count median diamet er falling between 0.1 and 0.3 micrometers. A number density of >10(5) part icles cm(-3) of soot particles in the submicrometer range can be produced, constant to within 25% (1 standard deviation) over a 4 h time period. The n umber density of particles produced in the submicrometer range was found to vary with the ratio of soot to bronze beads in the bed mixture, whether or not a feed system was used, and nitrogen flow rate through the fluidized b ed and feed system.