Gas separation: apparatus – With gas and liquid contact apparatus – Nonliquid gas separating means downstream of liquid contact...
Reexamination Certificate
2002-01-07
2003-09-23
Spitzer, Robert H. (Department: 1724)
Gas separation: apparatus
With gas and liquid contact apparatus
Nonliquid gas separating means downstream of liquid contact...
C096S358000, C096S360000, C055S443000, C055S465000, C055SDIG007
Reexamination Certificate
active
06623551
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved baffle system for separating entrained liquids from a gas stream. The baffle system of this invention is particularly, but not exclusively suitable for removing contaminants from the air of a work area, such as a paint spray booth having a scrubber system.
BACKGROUND OF THE INVENTION
Baffle systems for separating liquid entrained in a gas stream have been used for many years. For example, baffle systems are conventionally used for separating water from an air stream in a paint application system. Paint overspray is removed from the paint application booth by downdraft air. The floor of the booth is flooded with water or water emulsion. The water and paint overspray are then received through scrubbers generally located in the floor below the paint application booth. The gas scrubber removes paint particles from the air in the paint booth, entraining the paint particles in the liquid. The air stream is then passed through baffles, removing the entrained liquid from the air stream.
A common form of baffle used by the automotive industry in paint application systems, for example, comprise at least two columns of U-shaped rectangular vertical baffles. The baffles each include a web portion and perpendicular flange portions, such that the web portions of the first column of baffles faces the direction of the air flow and the second column of baffles overlaps the baffles in the first column with the flanges extending toward the direction of air flow. The baffle system thus requires the gas stream to flow around the web portions of the first column of baffles into the rectangular U-shaped baffles of the second column of baffles and around the flange portions of the second column of baffles, depositing the liquid on the baffles which flows downwardly and out of the system. The particle size of the liquid droplets or particles is generally greater than about twenty microns (20&mgr;). In a conventional baffle system of this type, the width of the web portion is eight inches, the length of the flange portions are four inches and the flange portions overlap 0.25 inches. The average face velocity measured parallel to the duct in a baffle system for a paint application system of this type is generally between one hundred fifty to three hundred fifty feet per minute (fpm). The problems with this baffle system include re-entrainment and difficulty cleaning.
Various attempts have been made to improve the efficiency of baffle systems for removing entrained liquid from a gas stream. For example, the velocity of the gas stream through the baffle system may be increased by overlapping the ends of the flange portions, thereby improving the efficiency of the baffle system. However, a liquid having entrained paint particles will collect between the overlapping flanges requiring more frequent maintenance. It is also more difficult to clean between the overlapping flanges. More importantly, overlapping flanges provide no improvement in the re-entrainment performance of the baffles. Other proposed attempts to improve the efficiency of baffle systems for removing entrained liquid from a gas stream include complex baffle systems including, for example, spiral baffles, baffles having hook-shapes which further increase the velocity of the gas stream through the baffles to improve efficiency, etc. However, such complex baffle systems are relatively expensive to manufacture and require frequent maintenance particularly where a tacky substance, such as paint, is entrained in the liquid droplets or particles. Such complex baffle systems have not been found suitable for removing liquid entrained in a gas stream in a paint application system.
Thus, there remains a long-felt need for an improved baffle system which is relatively simple in construction, low in cost and having improved efficiency. Further, there is a need to reduce the maintenance costs of conventional baffle systems which reduces the collection of liquid and entrained tacky particles and which is easily cleaned, if necessary. As described below, the improved baffle system of this invention is relatively simple in construction, having reduced costs, particularly when compared to the complex baffle systems described above, and the baffle system of this invention has reduced maintenance costs when compared to baffle systems having overlapping elements.
This application discloses further improvements made to the baffle system of this invention which improves efficiency by reducing re-entrainment of liquid into the gas stream and improves cleaning of accumulation of contaminants on the baffle system during periodic cleaning of the baffle system of this invention.
SUMMARY OF THE INVENTION
As set forth above, the baffle system of this invention may be utilized in a paint spray booth wherein the water, air and paint overspray is received through a scrubber or scrubbers located in the floor beneath the paint spray booth. The scrubber removes the paint particles from the air in the paint spray booth and entrains the paint particles in the liquid. The liquid received from the scrubbers is then received in a tank or trough located below the scrubber as disclosed, for example, in U.S. Pat. Nos. 5,100,442 and 6,228,154 assigned to the assignee of the present application. The air is then received through a plurality of baffles where the entrained liquid and paint particles are removed. As will be understood, the efficiency of the baffle system in removing the liquid and entrained particles is critical to the efficiency of the overall system. The baffle system of this invention may also be utilized to separate entrained liquid from a gas stream in other applications.
The baffle system of this invention includes a first column of spaced aligned generally U-shaped baffle members each having a web portion and flange portions extending away from the direction of gas flow and a second column of spaced aligned generally U-shaped baffle members each having a web portion overlapping a web portion of the first column of baffle members and flange portions extending toward the web portions of the first column, such that the baffle members of each column overlap the adjacent column. The gas flowing through the columns of baffles is thus required to take a tortuous path between the baffles and deposits the liquid on the baffles. In the preferred embodiment, the baffles are suspended vertically and the liquid then flows down the baffles into a tank or trough for further processing. In the preferred embodiment of the baffle system, the flange portions extend generally perpendicular to the web portions from the opposed ends of the web portions and the web portions have a width at least three times the length of the flanges as disclosed in the above-referenced parent application.
The improvements to the baffle system disclosed in this application include (1) extending a portion of at least the first column of baffles into the tank or trough which receives the liquid, (2) providing flashing plates at the upper extent of the baffles in contact with the web portions of the coplanar baffle members, wherein the flashing plate on the first column at the upstream side of the baffle assembly has a greater vertical length than the flashing plate on the second column of baffles at the downstream side, (3) utilizing a vertical inlet baffle plate spaced upstream of the baffle members extending into the tank, wherein the upper end has a height of at least 30% of the effective height of the baffle members, and (4) spacing the flange portions of the baffle members of the first and second columns of baffle members a distance of 0.3 to 0.6 inches. As will be understood, these improvements may be utilized individually in the baffle system of this invention. However, it has been found that the greatest improvement in collection efficiency results from using these improvements in combination.
One problem addressed by the improved baffle system of this invention is “re-entrainment” of water droplets on the baffles. As set forth above, the pu
Klobucar Joseph M.
Pakkala James L.
Still Gregory M.
Yu Guang
Durr Industries, Inc.
Howard & Howard
Spitzer Robert H.
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