Patent Application
20110088556
None.
1. Field of the Invention
The invention is in the field of removing particulates from the air, particularly as applied to sampling contaminants.
2. Background
Removing particulate contaminants from the atmosphere may be achieved with several known technologies. One known device is an electrostatic particulate collector. Known electrostatic particulate collectors have traditionally been designed for continuous, high volume use, as for example, as antipollution devices. Prior art devices are disadvantageous in contaminant sampling situations for multiple reasons.
Electrostatic particulate collectors are typically designed with a metallic chamber through which a gas, typically air, is directed for removal of particulate matter such as contaminants. Disposed within the chamber is a current carrying element supplied with sufficient electrical voltage that the potential between itself and the metallic walls of the chamber creates a coronal discharge. The coronal discharge electrostatically charges particulates in the gas within the chamber, and these ionized particles are thereby electrostatically driven to adhere to the walls of the chamber.
Once collected on the chamber walls, the contaminants may be removed. Manual removal of collected contaminants requires frequent shutdown for a replacement and/or cleaning of the chamber walls. To avoid this, it is known to rinse the chamber walls with a liquid in order to collect the removed contaminants and also retard contaminant buildup on the chamber walls. Purified water is often used as a rinse liquid.
Some prior art designs fail to wet all of the chamber wall, allowing disadvantageous contaminant buildup on dry portions of the chamber wall. Prior art devices do not wet the chamber walls quickly, and require significant volumes of liquid in order to achieve adequate wetting of the chamber walls. Prior art designs typically use large cumbersome components, use larger volumes of rinse liquid and demand a high power draw for both rinse liquid distributors and blowers used to propel the atmosphere being treated through the treating chambers.
The present invention is an electrostatic particulate collector having a novel structure. One aspect of the present invention is to achieve 100% wetting of the inner surface of the chamber wall with a minimum volume of liquid. It is another aspect of the invention to achieve 100% wetting of the inner surface of the chamber wall quickly. In so doing, the structure of the present invention promotes greater efficiency, greater throughput of air to be sampled, greater portability and/or greater automation. Smaller volumes of the required purified water need to be transported or installed with the test unit. Power requirements may be reduced. Speed, water volume and volume of air throughput may be improved because impedance of air flow by the wetting structures is reduced.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
Referring now to the drawings in which like reference numbers indicate like elements,
Within the housing 12 are the major components of the electrostatic particulate collector including a battery 16, electronic control module 18, high voltage power supply 20, an air handling system having a blower 22, fluid connector 24, pump 26 and the test chamber 30. A fluid reservoir 28 which may be separate, is provided to supply any rinse liquid for wetting the test chamber internally.
In the depicted embodiments the test chamber is a tube.
The chamber is a cylindrical tube 32 in the depicted embodiment which may be made of metal. The metal may be steel, titanium, aluminum or otherwise. In the depicted embodiment the tube 32 is comprised of a cylindrical wall 44 having an inner surface 46. The inner surface may be comprised of titanium. Providing a titanium inner surface may be achieved by constructing the entire tube wall 44 of titanium. Alternatively, the tube wall 44 may be aluminum, stainless steel, or other material, with a coating of titanium on its inner surface 46.
As is known in the prior art, disposed within the collection chamber is a voltage potential inducer 50 (see
In operation, air flow is created through the chamber by a blower (22 in
The grooves 60 and the rinse channels they form are oriented in a spiral configuration. Each rinse channel is at an angle therefore to the longitudinal axis of the cylinder 32. As will be appreciated by those of skill in the art, this spiral orientation advantageously avoids the streaking and consequent dry portions of the inner surface 46 of the chamber that was typical of prior art devices. That is, injection of the rinse liquid in a spiral fashion, at an angle to the axis of the tube, promotes 100% wetting. 100% wetting, in the shortest amount of time and/or with the smallest volume of rinse liquid, is further promoted by the titanium surface 46 of the cylindrical chamber 32.
As best seen in
Upon assembly, the liquid exit ports 170 are disposed so that an outer side of the exit port 170 is substantially flush with the first diameter that is the inner wall of the collection chamber. The aperture of the exit ports 170 are on the step 184 that is the inner end of the liquid distribution extension 142.
In one embodiment, the particulate collector may be a cylinder having an internal diameter of between about 0.25 inches and about 6.0 inches. The particulate collector may have a length of between about 1.0 inches and about 36 inches. In embodiments with Titanium coatings, the coatings may be from about 0.25 microns to about 6 microns thick. In the depicted embodiments, the cylinder has a diameter of about 2 inches. The rinse liquid ports in the depicted embodiment are spaced about ¾ of an inch apart and the ports have a complex cross section ranging from about 1/64 of an inch to about ¼ of an inch.
Test data confirm an unexpected, synergistic effect when combining both a swirl liquid distributor with a titanium collection chamber wall in the configuration disclosed herein, as compared to the effect of either component by itself. The time and liquid volume needed to attain substantially 100% wetting is only marginally increased by combining a swirl liquid distributor as depicted herein with a traditional steel or aluminum inner chamber surface, in a compact contaminant sampling device. At a flow rate of 528 mil/min, 100% wetting was obtained in a range of from 9 to 34 seconds, with an average of about 19 seconds. Little or no improvement is achieved by combining a titanium inner chamber surface with a prior art weir liquid distributor, as compared to a traditional aluminum inner chamber surface combined with a weir liquid distributor, in a compact contaminant sampling device. In fact, 100% wetting was not achieved in experimental apparatuses combining a Titanium coated cylinder with a weir distributor.
Surprisingly, combining the swirl liquid distributors depicted herein with a titanium inner chamber surface in a compact contaminant sampling device improves results more than the sum of the individual degrees of improvement attained by each component individually. In a compact sample collector having both a swirl injector and titanium inner surface, substantially 100% wetting was attained faster and with less liquid than the expected sum of the two features tested individually. Hence, test data confirms an unexpected synergy when combining both features.
The particulate collector of this invention may attain substantially 100% wetting of said inner surface of said chamber with a rinse liquid flow rate of no more than about 520 milliliters/minute. The particulate collector may attain substantially 100% wetting of said inner surface of said chamber within no more than about 26 seconds. The particulate collector having a collection chamber of titanium coated aluminum may attain substantially 100% wetting of said inner surface of said chamber within no more than about 11 seconds at a rinse liquid flow rate of about 290 milliliters/minute.
In each of the examples, De-ionized (DI) water was used as the rinse liquid. DI water was pumped from a reservoir into the Fluid Distributor. Depending on the flow rate required, one or two diaphragm pumps were used to deliver the DI water to the Fluid Distributor. The DI water was collected in a beaker placed under the test item.
Using the test set-up described above, the flow rate required to produce a fully wetted collection surface within approximately 30 seconds was determined for each device configuration. The actual flow rate was calculated by measuring the amount of fluid collected in the beaker per unit time.
Using these fluid pump settings, a repetitive series of tests was performed to determine the required time to fully wet the collection surface. The collection surface was air dried between every test using a small fan.
In
As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
