NOVEL QUASI-ELECTROSTATIC AIR FILTER - A SINGLE-PARTICLE STUDY

When the enamel-like top layer of the desert soil is compromised, natu ral and man-made forces result in airborne dust particulate. This is o f specific concern in Pu contaminated soil excavation. Conventional wa ter-spraying techniques are effective in preventing large airborne dus t particles but are ineffective for dust particles on the order of a f ew micrometers in diameter and smaller. One means of extracting these fine radio-nuclide particulate from the air is with. a quasi-electrost atic air filter which charges, traps, transports, and collects them wi th the aid of electrostatic and quasi-electrostatic fields. Human inte rvention 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 p hoto-ionization mechanism to ionize the sand particle just below the b reakdown of air. Large electrostatic fields precipitate the charged mi cron particles from the air flow in the charging region and direct the m into the transport region. The dynamic fields in this region guide t he particulate to a collection region. Combining a finite element meth od with an analytical theory to characterize the fields in the air fil ter, single-particle dynamics in the charging, electrostatic and the t ransport regions of the air filter are examined. Design constraints an d limitations are studied. Air flow velocities and air viscosity contr ibutions are incorporated into the simulation. Normalized expressions allow for a host of upscale and downscale designs. (C) 1997 Elsevier S cience B.V.