High efficiency a wetted surface cyclonic air sampler

Measuring and testing – Sampler – sample handling – etc. – With constituent separation

Reexamination Certificate

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Reexamination Certificate

active

06484594

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to air samplers. More particularly, it relates to air samplers that strip a target material from the ambient air (the air mass being sampled), and concentrate it in a stripping liquid. The stripping liquid may then be delivered to any suitable detection apparatus for the target material.
SUMMARY OF THE INVENTION
One aspect of the present invention may be to provide a high efficiency wetted wall cyclonic air sampler that is so small, so light weight and so low in energy consumption that it may be battery powered and human-portable; and that is so efficient that it may be used to strip target material that is present in the ambient air in concentrations of only a few parts per trillion, or less.
The target material may comprise one or more solids, liquids and/or gasses. If the target material is a solid, it may comprise particulate matter such as dust, bacteria, or viruses, for example. If the target material is a liquid, the particulate matter may comprise liquid droplet, such as a mist or fog, for example. If the target material is a gas, it may comprise any gas-phase molecular species.
Another aspect of the present invention may be that the air flow through the air sampler's main body and air inlet section may be provided by a fan, such as when the air sampler is stationary or is moving at a relatively low velocity with respect to the ambient air. Air flow through the air sampler may also be provided by movement of the air sampler through the ambient air.
A first embodiment of the air sampler may comprise an air inlet section, a main body and a fan. If a fan is used, it may urge air through the air inlet section and the main body during use of the air sampler.
The air sampler's main body may comprise a cyclonic cup, a stripping column and a demister. Ambient air flows tangentially into the cyclonic cup's perimeter from the air inlet section, creating a rapidly rotating air flow within the cyclonic cup and an upwardly rising air vortex that extends from the cyclonic cup, through the stripping column and into the demister.
The low pressure area created by the air vortex in the center of the cyclonic cup may be used to permit, or assist, the stripping liquid to be gravity fed into the cyclonic cup through an input port in the center of cyclonic cup's base, with little or no external pump pressure for the stripping liquid being needed.
The shear forces generated by the upwardly rising air vortex within the cyclonic cup may urge the incoming stripping liquid to form around the cup's input port a thin film that flows radially outwardly across the cyclonic cup's base, that then flows in a spiral path up the inner surface of the cyclonic cup's sidewalls, and that then flows onto the inner surface of the stripping column.
Similarly, the shear forces generated by the upwardly rising air vortex within the stripping column may urge the stripping liquid from the cyclonic cup to form a thin film that flows in a spiral path up the inner surface of the stripping column, and that then flows across the top edge of the stripping column; to fall into the demister's reservoir under the force of gravity.
From the reservoir, the stripping liquid may be recycled one or more times by gravity feed back to the input port in the cyclonic cup, so that it may pass through the cyclonic cup, the stripping column and the demister again; to strip still more target material from the air passing through the air sampler. A liquid level control may be provided for the reservoir.
Thus, the cyclonic cup, the stripping column and the demister may be “self-pumping”, in the sense that no external liquid pump may be needed to force the stripping liquid through them, since that job may be done by the action of the air/liquid shear forces generated by the upwardly rising air vortex within them; and since no external liquid pump may be needed to recirculate the stripping liquid from the demister's reservoir back into the cyclonic cup, since that job may be done by gravity feed.
All along its journey from the cyclonic cup's input port to the demister's reservoir, the thin film of stripping liquid may strip the target material from the upwardly rising air vortex at high efficiencies. Such high efficiencies may be due to such factors as the high velocity of the circulating air and the upwardly rising air vortex; the very large surface area of the thin film; the very long path followed by the thin film as it flows across the cyclonic cup's base and spirals up the inside of the inner surfaces of the sidewalls of the cyclonic cup and the stripping column; the very low volume of stripping liquid that resides in the air sampler's main body and air inlet section at any one time; the very low flow rate of the stripping liquid through the air sampler's main body and air inlet section; the very high volume of air flowing through the air sampler; and/or the evaporation of substantial amounts of the stripping liquid by the air flowing through the air sampler.
The internal diameter of the stripping column may be less than that of the cyclonic cup, to cause the air vortex within the stripping column to rotate at a higher speed as compared to the air vortex in the cyclonic cup. The higher speed of rotation may help the stripping column to more effectively strip liquid and solid particulate target material from the air due to higher centrifugal forces; and may create a relatively lower pressure within the stripping column that may permit the relatively higher pressure within the cyclonic cup to urge the stripping liquid from the inner surface of the cyclonic cup to the inner surface of the stripping column.
The inner surface of the stripping column may be provided with spiral grooves for increasing its surface area; for providing a long spiral path for the thin film of stripping liquid to follow on its inner surface; and/or for helping to prevent air-entrainment of the stripping liquid on its inner surface by encouraging the air flow to follow a spiral path, by shielding the stripping liquid from the air flow's axially-directed shear forces, by preventing the stripping liquid from forming large surface waves that may be captured and subsequently broken into droplets by the air flow, and by providing a partially-protected path by which the stripping liquid can spill into the demister.
A portion of the stripping column may extend into the demister, and the diameter of the demister may be greater than the diameter of the stripping column, to provide a space between the larger sidewall of the demister and the smaller sidewall of the stripping column that may serve as the demister reservoir, and to reduce the speed of rotation and upward velocity of the air vortex within the demister to the point that at least some of any air-entrained stripping liquid may be dropped by the air vortex in the demister.
The air sampler's cyclonic cup may further comprise a passive (i.e., non-powered or non-moving) means for producing a fog of stripping liquid droplets that utilizes the low pressure area created in the center of the cyclonic cup by the cyclonic cup's air vortex, and that utilizes the extremely high tangential air velocities that may be created by the cyclonic cup's air vortex near the cyclonic cup's longitudinal axis.
A first embodiment of the passive fog generating means may comprise a radially oriented slot centered in the cyclonic cup's base that is fed by the cyclonic cup's stripping liquid input port. A second embodiment of the passive fog generating means may comprise a spiral fog generating nozzle having an input port located over the cyclonic cup's stripping liquid input port. With both embodiments of the passive fog generating means, the fog particles they produce may, during their passage through the cyclonic cup, the stripping column and the demister, strip the target material from the air and be deposited on the inner surfaces of the cyclonic cup, the stripping column a

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