Electrostatic Charge Measurement and Charge Neutralization of Fine Aerosol Particles during the Generation Process

Abstract

An aerosol charge analyzer has been constructed to measure the charge distribution of NaCl particles generated in the laboratory. A radioactive electrostatic charge neutralizer utilizing Po‐210 was used to neutralize the electrostatic charge of the particles. The atomization technique was used to generate NaCl particles with diameters of 0.2 to 0.8 μm, while the evaporation and condensation method was adopted to generate particles of 0.01 to 0.2 μm in diameter. The experimental data demonstrates that the absolute average particle charge depends on the particle diameter, and is higher than that calculated by the Boltzmann charge equilibrium for particles within the range of 0.2 to 0.8 μm. The charge increases with decreasing NaCl concentration. When these particles are neutralized using the Po‐210 neutralizer, it is found that the electrostatic charge reaches the Boltzmann charge equilibrium. For 0.01 to 0.2 μm NaCl particles generated using the evaporation and condensation method, test results show that the absolute average particle charge is higher than that calculated by the Boltzmann charge equilibrium for particles larger than 0.03 to 0.05 μm in diameter, while it is lower than that predicted by the Fuchs theory [1], for particles smaller than 0.03 to 0.05 μm. However, after charge neutralization, particles with diameter above 0.05 μm reach the Boltzmann charge equilibrium condition, and the charges for particles with diameters of 0.010 to 0.05 μm, agree well with Fuchs' theory.

Constraining Particle Evolution from Wall Losses, Coagulation, and Condensation-Evaporation in Smog-Chamber Experiments: Optimal Estimation Based on Size Distribution Measurements

“…Information about the limonene experiments, including mass-mean aerosol diameters and total suspended mass concentrations at the time of limonene injection and one hour later, for each of the five experiments is given in Table 1. For these limonene experiments the atomized particles were added to the chamber with no neutralization, so their initial charge distribution was likely larger than a Boltzmann distribution (Tsai et al 2005;Forsyth et al 1998). This may cause the wall-loss effects of charge to be quite strong, at least initially.…”

“…Another possible explanation for the decrease in wall-loss rate is that the number of charged particles in the chamber decreases because of the expedited loss of the charged particles to the wall relative to uncharged particles (McMurry and Rader 1985). The initial concentration of charged particles is high due to the atomization of seed particles without subsequent neutralization (Forsyth et al 1998;Tsai et al 2005).…”

“…After 2 h, loss of charged ultrafine particles has shifted the minimum to 75 nm and the maximum to about 150 nm. Various methods of particle generation (e.g., atomization, nucleation, combustion) may result in particles with different initial charge distributions (Tsai et al 2005;Forsyth et al 1998) further complicating the effects of charging on wall loss.…”

Generation and Sizing of Particles for Aerosol-Based Nanotechnology

“…The particles generated by pneumatic atomization are polydisperse ( g of 1.4 or greater) with a moderate charging level that depends on particle diameter and solute concentration (Forsyth et al 1998;Tsai et al 2006). If their size has to be controlled within a narrower range, a classifier (commonly a differential mobility analyzer, cf.…”

Deactivation of SCR Catalysts by Exposure to Aerosol Particles of Potassium and Zinc Salts

“…Acknowledging that the particles have multiple charges an average particle charge for the salts of 5 was calculated based on the TDMA measurements. Average particle charges have been reported by Tsai et al (2005) to be in the order of 2 for atomizing of salt liquids, but charges of 8 was also reported depending on particle diameter and concentration of the salt solution. Theoretically possible collection efficiencies can thus be estimated and are presented in Figure 12.…”