10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Control of Number Concentration of Aerosol Nanoparticles Generated by Nanospray Drying

MASAKI SAKAMOTO, Fumitaka Ichihara, Takafumi Seto, Yoshio Otani, Kanazawa University

     Abstract Number: 197
     Working Group: Instrumentation

Abstract
Generation of test aerosol particles with a narrow size distribution and a precise number concentration is important for various aerosol experiments such as filtration test and the calibration of particle counters. In terms of uniformity of particle size, polystylene latex (PSL) microspheres have been widely used as standard particles with size range from nanometer to micron. Spray drying method is generally used to obtain the monodispersed PSL test particles in the aerosol phase. However, in the spray drying process, it is difficult to precisely control the number concentration of aerosol. Small amount of impurity contained in the PSL suspension may produce residual nanoparticles of undesirable size and it sometimes increases the number concentration of test aerosol. Reduction of atomized droplet size is known to be effective in decreasing the effect of these contaminants.

In this study, a new atomizer is designed to generate droplets with a peak diameter smaller than 200nm. In order to reduce the contamination, an ultrapure water system was connected to the atomizer. The PSL solution with a known liquid-based concentration was introduced to the atomizer by a syringe pump. The gas phase concentration was measured by a laser particle counter (LPC, >0.1micron, Met ONE model A0100B) and a condensation particle counter (CPC, >4nm, TSI model 3775). The background aerosol concentration with the introduction of ultrapure water was 0.5/cc-gas by the LPC and 1670/cc-gas by the CPC. The relationship between liquid-based PSL concentration and the aerosol concentration was analyzed by changing the diameter of standard particles (100, 200, or 500 nm) and the concentration of the PSL suspension (10^4 to 10^7 /cc-liquid). The minimum controllable aerosol concentration was as small as 0.1 particle/cc-air for the LPC and 1000 particle/cc-air for the CPC.