Gas separation: apparatus – With gas and liquid contact apparatus – Means forming flowing contact liquid film on apparatus...
Reexamination Certificate
1999-12-23
2001-05-08
Smith, Duane (Department: 1724)
Gas separation: apparatus
With gas and liquid contact apparatus
Means forming flowing contact liquid film on apparatus...
C096S328000, C096S384000, C055SDIG007
Reexamination Certificate
active
06228154
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improvements in right angled venturi gas scrubber systems for removing contaminants in the air of a work area, such as a vehicle paint spray booth. The gas scrubber system of this invention reduces the noise level generated by the gas scrubber system in the work area.
BACKGROUND OF THE INVENTION
Gas scrubbers mounted in the floor of a work area are now commonly used to remove air borne contaminants in a work area, such as a vehicle or appliance paint application booth. U.S. Pat. No. 5,100,442 assigned to the assignee of the present application discloses an improved venturi gas scrubber system which is now commonly used to remove paint particles and other contaminants from a paint spray booth. The improved gas scrubber system disclosed in this patent includes an inlet section, which receives water and the contaminated air having planar converging walls which promote uniform flow of the liquid, an intermediate section, which receives the liquid and gas from the inlet section having diverging planar walls, and a lower section including a bottom wall which is generally perpendicular to the diverging walls and an end wall having an orifice opening. The lower section promotes turbulent flow of the liquid which results in transfer of the contaminants to the liquid and the liquid is projected through the orifice preferably at a right angle to the longitudinal axis to the inlet and intermediate sections. This improved gas scrubber system not only efficiently removes the air borne contaminants in the spray booth, but also results in a reduced noise level in the spray booth because sound generated by the nozzle is reflected off of the internal surfaces compared to a“straight-through” scrubber system wherein the liquid and gas are projected downwardly through an orifice opening in the scrubber. The reduced diameter portion between the diverging walls of the inlet section and the converging walls of the intermediate section thus act as a noise barrier reducing the noise in the paint booth as described in the above-referenced patent.
Nevertheless, there is a need to further reduce the sound generated in a work area, such as a paint spray booth, by a venturi gas scrubber system of the type disclosed in the above-referenced patent. Although the automotive industry, for example, is converting to robotic paint application systems, workers still enter the robotic paint spray booth. Further, there are many other applications where the paint is applied by an operator and further applications requiring gas scrubber systems in other industries. A primary object of the gas scrubber system of this invention is to reduce the noise generated in a work area having a gas scrubber system.
The prior art includes numerous examples of gas scrubber systems, many of which are very complex. The prior art also includes gas scrubber systems which comprise a plurality of spaced discrete straight-through venturi-type scrubbers generally having a common inlet. However, the purpose of using spaced discrete scrubbers in the prior art is to reduce manufacturing costs. It is another object of this invention to reduce manufacturing costs and permit easy cleaning of the scrubber pods; however, the primary object of this invention is to reduce the noise projected to the work area.
SUMMARY OF THE INVENTION
The gas scrubber system of this invention comprises a plurality of spaced, generally aligned discrete venturi scrubber pods each having the general configuration of the gas scrubber system described in the above-referenced patent. That is, each scrubber pod includes an inlet section having opposed generally planar converging walls and opposed side walls. The converging walls are angled to promote laminar flow of the liquid through the inlet section, preferably about fifteen degrees relative to vertical, within a range of about two degrees. The gas scrubber pods each further include an intermediate section which communicates with the inlet section having outwardly diverging walls which again promote laminar flow of the water or liquid through the center section and forming a venturi or restricted opening. The included angle between the walls of the inlet section and the outlet section are about one hundred fifty five to one hundred sixty degrees. Finally, the gas scrubber pods each include a lower section having opposed top and bottom walls, wherein the bottom wall is generally perpendicular to the longitudinal axis of the scrubber pod through the inlet and intermediate sections, such that turbulent flow is promoted only in the lower section, wherein the liquid, generally water, mixes thoroughly with the gas and the contaminants are transferred from the gas to the liquid. The intermediate and lower sections also include side walls and the lower section includes an end wall having an outlet port or orifice which projects the liquid and gas outwardly, generally parallel to the bottom wall as shown in the above-referenced patent.
As stated above, a primary object of the gas scrubber system of this invention is to further reduce the noise generated from the scrubbers to the work area. Although the right angled or elbow configuration of the scrubber system disclosed in the above-referenced patent does reduce noise, there is still a need to further reduce the noise reflected to the work area through the scrubbers. This object is accomplished by the use of separate or discrete scrubber pods each having the configuration described above, wherein the combined lengths of the discrete scrubber pods are between fifty and ninety percent of the total length of the scrubber system, which comprises the combined lengths of the scrubber pods plus the length of the spaces between the scrubber pods. More preferably, the combined lengths of the scrubber pods are between sixty and eighty-five percent of the total length of the scrubber system or most preferably about seventy percent plus or minus five percent. The lengths of each scrubber pod measured between the side walls is between two and eight feet, wherein the space between the scrubber pods is preferably between six inches and three feet. More preferably, the length of the scrubber pods is between three and six feet, most preferably about three feet plus or minus six inches. As set forth below, this configuration of aligned discrete scrubber pods results in a significant decrease in the noise reflected upwardly to the work area.
The use of discrete scrubber pods, particularly in combination with a variable outlet orifice, has been experimentally found to significantly reduce the noise transmitted to the work area. It has been found by experimentation that the noise emitted from the scrubber inlet into the work area is generated by the scrubber orifice. With the right angled venturi gas scrubber described in the above-referenced patent, sound waves are required to make several deflections prior to escaping through the inlet section of the scrubber into the work area. That is, there is not a direct path for the sound waves generated at the orifice to escape through the scrubber inlet. It has been found that by increasing the size of the scrubber orifice, the probability is that more of the reflected sound waves will escape through the scrubber orifice rather than the scrubber inlet. That is, a larger outlet orifice results in lower sound levels in the work area.
The effect of reducing the sound reflected to the work area through the scrubber by increasing the size of the orifice is not obvious from the configuration of scrubber. That is, for a fixed scrubber pressure drop, as the scrubber orifice size increases, the air velocity (exhaust volume) through the scrubber increases. Thus, it would be logical to assume that the higher velocity would create higher sound levels in the work area. Further, it would be assumed that the sound would be further increased by reducing the overall length of the scrubber system by dividing the scrubber into separate scrubber pods. Nevertheless, it has been found that the noise generated in the work area
Cole David J.
Pakkala James L.
Yu Guang
Durr Industries, Inc.
Hopkins Robert A.
Howard & Howard
Smith Duane
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