AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Effects of Spray Surfactant and Particle Charge on Respirable Dust Control
MEI WANG, Peter Raynor, University of Minnesota
Abstract Number: 749 Working Group: Control Technology
Abstract Objective
This research measured the effects of spray surfactant and particle charge on the capture of respirable particles by water spray droplets.
Methods
Polystyrene latex particles with diameters of 0.6, 1.0, or 2.1 micro-meter were generated in a variable speed wind tunnel. Particles were given either a neutralized, unneutralized, net positive, or net negative charge condition using a neutralizer and a diffusion charger. Some of the particles were removed as they passed through sprays with 0, 1×10$^(-6) or 1×10$^(-4) M concentrations of anionic, cationic, or nonionic surfactant. The remaining particles were sampled and charge-separated at different voltage levels using an electrostatic classifier. Size and concentration were then measured using an aerodynamic particle sizer. Measurements with the spray on and off allowed calculation of efficiency. Overall collection efficiencies, as well as efficiencies of particles with specific charge levels, were measured.
Results
The overall collection efficiency significantly increased with increasing particle diameter (p<0.001): collection efficiencies of 19.0±8.7%, 57.6±16.1%, and 95.9±60.9% (Mean±SD) were observed for particles 0.6, 1.0, and 2.1 micro-meter in diameter, respectively. Particle charge condition, surfactant type, and surfactant concentration do not significantly affect the overall collection efficiency. Strongly-charged particles tend to be collected more efficiently than weakly-charged particles. Negative particles are collected most efficiently by cationic surfactant sprays and least efficiently by anionic surfactant sprays, whereas positive particles are collected most efficiently by low concentration anionic surfactant sprays and least efficiently by cationic surfactant sprays. Collection efficiency is associated more strongly with surfactant spray droplet charge level rather than with surfactant classification.
Conclusions
Particle diameter is the most important determinant of the collection efficiency. The charge level of the surfactant spray droplets may also critically impact the particle collection efficiency, especially for charged particles.