ESP generated nanoparticles

CHIH-WEI LIN, Sheng-Hsiu Huang, Chih-Chieh Chen

College of Public Health, National Taiwan University

     Abstract Number: 430
     Last modified: May 12, 2010

Abstract
The objective of this work is to illustrate the ESP transformation from a dust collector to an aerosol generator and to characterize the factors affecting ESP particle generation. A lab-scale wire-plate ESP was assembled to conduct both aerosol collection and generation tests. The discharge wire was made of 0.1 mm stainless steel and the collecting plates were aluminum. Aerosol number concentration and size distribution were monitored by using a scanning mobility particle sizer. The challenge particles were generated by a constant output atomizer. Air temperatures before and after ESP were measured by k-type thermal couples. Particle number concentration and size distribution obtained in the power-on and power-off modes were used to evaluate the collection efficiency and ESP particle generation rate. Scanning electron microscopy and energy disperse X-ray were use to analyze nanoparticle geometry. The ESP particle generation was measured under different air flow rate, air velocity, field strength, and applied voltage.

The aerosol size distribution generated by the ESP ranged from several nanometers to submicron. After the generation test, the stainless steel wire became brown and the erosion on the discharge wire could be observed from SEM pictures, the evidences showing that nanoparticles were generated from the discharge wire. The results also showed that particle generation rate decreased with increasing air velocity and the distance between two collection plates. This is because higher air velocity shortened the retention time of ions and reduced frequency of the ions collision with discharge wire. The ESP had the highest particle generation rate when current was around 80 micro-A. Too low current could not provide enough energy for charged particle to knock out nanoparticles from the electrode and higher current could result in higher collection efficiency. The ESP particle generation rate decreased with increasing challenge particle concentration, a phenomenon to be further studied.