Novel quasi-electrostatic air filter: A single-particle study

Abstract

When the enamel-like top layer of the desert soil is compromised, natural and man-made forces result in airborne dust particulate. This is of specific concern in Pu contaminated soil excavation. Conventional water-spraying techniques are effective in preventing large airborne dust particles but are ineffective for dust particles on the order of a few micrometers in diameter and smaller. One means of extracting these fine radio-nuclide particulate from the air is with a quasi-electrostatic air filter which charges, traps, transports, and collects them with the aid of electrostatic and quasi-electrostatic fields. Human intervention is virtually eliminated. The air filter is divided into four sections: the charging region, the electrostatic trapping region, the transport region, and the collection region. This work focuses on the first three regions of the air filter. The charging region employs a photo-ionization mechanism to ionize the sand particle just below the breakdown of air. Large electrostatic fields precipitate the charged micron particles from the air flow in the charging region and direct them into the transport region. The dynamic fields in this region guide the particulate to a collection region. Combining a finite element method with an analytical theory to characterize the fields in the air filter, single-particle dynamics in the charging, electrostatic and the transport regions of the air filter are examined. Design constraints and limitations are studied. Air flow velocities and air viscosity contributions are incorporated into the simulation. Normalized expressions allow for a host of upscale and downscale designs.