AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Effects of Particle and Spray Droplet Charge on Respirable Dust Capture by Surfactant Sprays
MEI WANG, Peter Raynor, University of Minnesota
Abstract Number: 28 Working Group: Control Technology
Abstract Objective
To measure the effects of particle and surfactant-containing spray droplets on the capture of respirable particles.
Methods
Monodisperse polystyrene latex aerosols (with diameters of 0.6, 1.0, or 2.1 micro-meters) and polydisperse coal dust aerosols were generated in a nebulizer and fluidized bed aerosol generator respectively. The aerosols then either remained unneutralized or were given a neutralized, net positive, or net negative charge using a neutralizer and a diffusion charger before entering a wind tunnel.
Some of the particles were removed as they passed through sprays with 0 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, then counted and sized in an aerodynamic particle sizer. Measurements with the spray on and off allowed the calculation of spray collection efficiency. Overall collection efficiencies and efficiencies against particles with specific charge levels were measured. Spray droplets of plain water or different surfactant solutions were also sampled and charge-separated at different voltage levels using an electrostatic mobility analyzer, and then counted and sized in an image-based droplet sizer.
Results
Dust collection significantly increased with increasing particle diameter (p<0.001) for both PSL and coal dust aerosols. Both droplet and particle charge significantly affect spray efficiency. Negatively and positively charged particles were captured most efficiently when highly charged particles interacted with highly charged droplets with opposite charge. Strongly-charged particles tend to be collected more efficiently than weakly-charged particles. Charged particle capture was associated more strongly with surfactant-containing spray droplet charge level rather than with surfactant type.
Conclusions
The charge level of both particles and spray droplets critically influences the capture of both PSL and coal dust particles, especially for higher charge levels and smaller particle sizes.