Patent Publication Number: US-2021187537-A1

Title: Plastic scrubber for paint spray booth

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 62/950,262, filed Dec. 19, 2019, the contents of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to a wet scrubber for separating and removing oversprayed particles in a paint spray booth. More specifically, the present invention relates to a wet scrubber for such applications that is molded from a plastic material. 
     2. Description of Related Art 
     Many industrial processes require the application of a coating or protective layer to an article. For instance, applying a surface coating (e.g., paint) to an object requires application of the coating material (such as a liquid or powder slurry) which is sprayed or otherwise delivered to the article. Typically, this material application will occur in a contained environment that enables control of the material. For example, paint is often applied in a paint spray booth that allows control of the atmospheric conditions and containment of the paint. Inherent in the paint spraying process is overspray, that is, paint that does not adhere to the object being painted which floats in the air as a mist. In order to provide a safe working environment and a high quality finished product, paint spray booths require a substantially continuous supply of clean, fresh air, which also assists with discharge of the overspray from the booth. 
     Various configurations of spray booths have been developed for different material application processes and handling of the overspray. These booths are often classified by the direction of the airflow in the spraying area. For instance, cross-draft booths have an airflow which moves parallel to the floor from behind the operator (or robotic device) toward a dry filter or a water curtain. Downdraft booths have an airflow which moves from the ceiling vertically downward to an exhaust system below the floor. Semi-downdraft booths include an airflow which moves in a diagonal direction in the booth towards an exhaust. 
     Since the overspray contains paint particles, it is important to filter or otherwise clean this air before discharging it back into the environment. Several methods have been developed for separating the paint mist from the air exhaust stream. For instance, a dry method results in air entrained with paint being forced through a dry filter or screen which absorbs or otherwise captures the paint particles. A wet method requires the air entrained with paint to contact and be mixed with liquid, such as water, so that the paint particles are captured by the liquid. 
     Due to the large amount of paint used by some industrial paint facilities, such as those in automotive plants, the wet method in a downdraft booth is the preferred configuration. These booths generally have a wet scrubber that captures the coating overspray and assists with separating the oversprayed particles from the air. 
     Over time, various configurations of wet scrubbers have been developed in attempts to increase the efficiency of the particle separation and minimize operating costs for the paint facility. For instance, a Venturi type of scrubber utilizes a restriction or Venturi to accelerate the paint laden air, generate turbulence, and break-up the supply water (or the capturing fluid) running along its walls into small drops that capture or trap the paint particles in the exhaust air. Another type consists of an elongated tube with a nozzle positioned at the tube exit, whereby water flows downward along the walls of the tube and into a pool of liquid contained within a capturing chamber, in which turbulence is generated and the paint particles in the air are captured or trapped within the water. Although these designs capture the overspray and separate some of the paint particles, they use a large amount of energy and/or allow a sub-optimal amount of paint particles to penetrate the system and be exhausted to the outside air. More modern scrubber designs utilize vortex chambers to capture and separate paint particles and volutes to decelerate the air flow and recover pressure. Although these designs capture a greater amount of paint particles than the Venturi or tube type wet scrubbers, the volutes permit back flow of the exhaust, creating recirculation that perturbs the vortex flow, thereby decreasing capturing efficiency, taking away energy, reducing the recoverable pressure energy, and reducing the effective flow area, precluding airflow deceleration and precipitation of the water droplets. 
     In U.S. Pat. No. 8,241,405 (B2) the present applicant describes a wet scrubber that includes (referencing element numbers used in the patent) a conduit  12  having an inlet  14 , a mixing chamber  16 , a pair of vortex chambers  18 , and a pair of exhaust extensions  45 . Fluid flow enters the mixing chamber and directs the fluid flow toward an impingement pool so as to trap particles from the airflow into the impingement pool. The airflow is directed into vortex chambers by a divider so that, as described, centrifugal force provides contact between the particles in the air and the water and, therefore, enhancing capturing. Adjustable plates  23   a ,  23   b  are provided in the outlet of the conduit  12  to optimize the speed of air entrained with paint that exits the outlet of conduit  12 . 
     The present invention provides a wet scrubber that is formed by a plastic molding process and nozzle inserts for the wet scrubber that allow for quick adjustment of airflow for changes in operating conditions of the overall systems in which the wet scrubber is incorporated in. Moreover, the nozzle inserts provide additional benefits related to installation, maintenance and operation of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a paint spray booth having a wet scrubber assembly incorporating the principles of the present invention; 
         FIGS. 2 and 3  are schematic front and side views of a scrubber according to one embodiment of the present invention; 
         FIG. 4  is a schematic exploded view that depicts how a nozzle insert is received in an inlet and a scrubber according to the present invention; 
         FIGS. 5A and 5B  are schematic side and front views of a nozzle insert according to one embodiment of the present invention; 
         FIGS. 6A and 6B  are schematic front and side views of an exhaust extension according to one embodiment of the present invention, and  FIG. 6C  is a pictorial view of an exhaust extension, and 
         FIG. 7  is a schematic view that depicts the mounting arrangement of a scrubber according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION 
     The plastic molded scrubber of the present invention generally functions in the same manner as the wet scrubber disclosed in U.S. Pat. No. 8,241,405 (B2) issued to the same inventor, the entire disclosure of which patent is hereby expressly incorporated by reference. 
     Taking the internal shape of the scrubber of the present invention into consideration, it was determined that a rotational molding process could be used to fabricate a structure with a small number of separate components including a main body, a front exhaust extension, and a back exhaust extension. In this process, commonly used for kayak fabrication, the mold is shaped to match the desired exterior shape of the scrubber. The amount of material is calculated to generate a certain wall thickness. The molding material is placed inside the mold and the mold is warmed and rotated until the material is melted and covers as uniformly as possible the interior of the mold. The mold is subsequently cooled. The solidified part is then extracted. The part is typically a fully enclosed shape. The openings, discussed below, for the inlet and outlet in the scrubber are cut after the molding process is completed. Other molding processes may be used to form the scrubber of the present invention. 
     While the scrubbers of the present invention can be made out of any various plastic materials that are mechanically suitable, preferred materials for a particular use should be able to withstand chemical or solvents that are present in the fluids to be processed. Polyolefin resins are typically used for rotational molding, with thermoplastic polymers of ethylene being most often used. For general purposes it was determined that High Density Polyethylene (HDP) and Low Density Polyethylene (LHP) are particularly suitable for forming the scrubber of the present invention. 
     Due to the limitations involved in molding a plastic scrubber, nozzle inserts were developed during the course of the present invention to provide for adjustment of airflow that correspond or reflect changes in operating conditions of the overall system in which the scrubbers of the present invention are incorporated in. Details about such nozzle inserts as well as its components and advantages are discussed below. 
     Use of the scrubber will be described below in reference to a downdraft paint spray booth as disclosed in U.S. Pat. No. 8,241,405 (B2) and U.S. Pat. No. 9,981,281 (B2), the complete disclosures of which are hereby expressly incorporated by reference, it being noted that the scrubber could be used in other types of paint booths, including semi-downdraft paint booths. 
     Typical automotive spray booths are manufactured in modular sections that are repeated lengthwise to create the complete booth. As seen in  FIG. 1 , a modular paint spray booth  1  includes an upper or spraying section  2  and an under or capturing section  3 . The upper section  2  is in fluid communication with an air supply  4 , such as conditioned air blown in from outside the booth. Some of this air from the air supply  4  may be directed through filters  5  to a spraying area  6  that contains a plurality of paint spray guns  7 . As a workpiece, which for illustration purposes, is an automobile body  8 , enters the spraying area  6 , the paint spray guns  7  are activated to deliver paint to the body  8 . 
     During this spraying process, paint that does not stick to the body  8  floats in the air as paint mist or overspray. With the assistance of an exhaust fan connected to the booth by exhaust duct  9 , the flowing air and paint mist are directed from the spraying area  6 , through a floor grating  10  and towards an inlet  11  of a wet scrubber  12 , the details of which, according to the present invention, are further discussed below. Depending on the amount of air flow handled by the paint spray booth  1 , the module of the paint spray booth  1  may include one or more wet scrubbers  12  with a common central inlet or individual inlets. 
     The under section  3  further includes an exhaust enclosure  13 . Within the exhaust enclosure  13 , the water and scrubbed air exit the wet scrubber  12  by way of a flow director or exhaust extension  14  that empties the water onto a floor  15  of the exhaust enclosure  13 , which may be the floor of the under section  3 . Ideally, the water containing the paint particles captured in the wet scrubber  12  flows out of an outlet  16  of the exhaust extension  14 , along the floor  15  of the exhaust enclosure  13  and into a sluice  17 . Preferably, the floor  15  of the exhaust enclosure  13  is sloped toward the sluice  17 . From the sluice  17 , the paint laden water  18  may be collected for treatment and recycling or disposal, as desired. The exhaust extension configuration described previously is substantially similar in operation and overall configuration to that of the scrubber described in U.S. Pat. No. 8,241,405 (B2), which is hereby expressly incorporated by reference. 
     Air exiting the outlet  16  of the exhaust extension  14  is routed toward an exhaust plenum  19  of the exhaust assembly  9 , but may have a minimal amount of paint particles and water droplets suspended therein. To capture the residual water droplets and paint particles, en route to the exhaust plenum  19 , the air proceeds through a plurality of baffles or mist eliminators  20  where the residual paint particles and water droplets are further collected. Finally, the air passes through the exhaust assembly  9  where it may be directed through a final exhaust filter or filter system (not shown) before it is discharged into the surrounding environment. 
     In one configuration of a wet scrubber  12 , the inlet  11  of the wet scrubber  12  is mounted in a sealed manner to what is known as a flooded floor  21 , which is a floor having a film or flow of water that is also directed to the inlet  11 . In the described embodiment the inlet  11  is provided as a separate component and may be formed of sheet-metal which facilitates attachment to flooded floor  21  in a sealed manner. Moreover, forming the inlet  11  of metal provides enhanced protection against damage due to drop parts etc. within spraying area  6 . Since the inlet  11  provides the only exit path for the paint laden air from the spraying area  6 , a mixture of water from the flooded floor  21  and air entrained with paint particles enters the inlet  11  of the wet scrubber  12  together. As described below, in accordance with the present invention, the inlet  11  and a nozzle insert  24  are mounted in a sealed manner to the flooded floor  21  of a paint booth  1  and to the inlet of the scrubber so that the paint laden air from the spraying area  6  mixed with water from the flooded floor  21  enter the inlet  11  of the scrubber flowing through the nozzle insert  24  and exits from the bottom of the nozzle insert  24  into the wet scrubber  12 . 
     With reference to  FIGS. 2 and 3 , wet scrubber  12  forming one aspect of the present invention is formed of a body including an inlet  11 , a mixing chamber  22 , and a pair of vortex chambers  23 , with the body connected with an exhaust extension  14 . A nozzle insert  24  is a separate component placed into the inlet  11 . The inlet  11  as depicted in  FIGS. 2 and 3  has a substantially rectangular or square cross-section, it being understood that other cross-sectional configurations could be used. 
     The body of wet scrubber  12  is molded from a plastic material such as HDP or LDP as discussed above. A nozzle insert  24  is configured to be received in the inlet  11  of the wet scrubber  12 . As discussed below the nozzle insert  24  is used to optimize the speed and mass flow rate of the air entrained with paint that enters the mixing chamber  22  of the wet scrubber  12 . 
     Preferably, the nozzle insert  24  is positioned in substantially the center of the wet scrubber  12  to provide optimal delivery of air entrained with paint and water to the mixing chamber  22  and the vortex chamber  23 . Proceeding from the inlet  11  to the outlet  26  of the nozzle insert  24 , the nozzle insert  24  has a decreasing cross-sectional area. This change in dimension results in the speed of the air flow increasing as it proceeds through the nozzle insert  24 . As discussed below, the sides of the nozzle insert  24  are angled inward from top to bottom at an angle or configuration that can optimize the speed of the air entrained with paint that exits the nozzle insert  24 . The scrubber inlet  11  can be conveniently welded to structure of the flooded for floor  21 . As mentioned above the nozzle inlet  11  and insert  24  are preferably formed of metal which is more conveniently attached by welding to other metal components and further is more damage resistant in the environment of the spray booth interior. When the nozzle insert  24  is inserted into the mixing chamber  22  it can be sealed against the interior surface of the inlet  11  by use of caulking, gaskets etc. One approach for attaching the inlet  11  to the main body of scrubber  12  is provided via attachment flanges  60  and  62  connected together via mechanical fasteners  64 . 
     The mixing chamber  22  includes an impingement pool  27  positioned adjacent to the outlet  26  of the nozzle insert  24 . Water flowing down the nozzle insert  22  is collected in the impingement pool  27 . The air proceeding down the nozzle insert  24  strikes the water in the impingement pool  27 , thereby mixing with the water. Because of the turbulence created by this mixing, some of the paint particles in the air become transferred to the water and stay suspended therein. Hence, the water serves to “trap” these particles. 
     To increase this turbulence and assist with substantially evenly diverting the air into the vortex chambers  23 , the mixing chamber  22  includes a flow divider  28 , which also provides stability to the flow inside the wet scrubber  12 . As shown in  FIG. 2 , the flow divider  28  forms joined curved surfaces  29   a ,  29   b  of the impingement pool  27 , such that the apex of the divider  28  substantially forms a line having a width W 1  (see  FIG. 3 ), which may be substantially equal to the width at the outlet  26 . Accordingly, at least a portion of the air and water that exits the outlet  26  engages the divider  28  and/or the curved surfaces  29   a ,  29   b . Ideally, the divider  28  substantially evenly divides the air, thus providing a similar amount of air to each vortex chamber  23 . This helps to create a stable system which further increases efficiency and saves energy. Besides dividing the supply of air and water, the divider  28  causes further mixing of the air and water in the impingement pool  27 , thereby increasing the mixing of these fluids and trapping more paint particles in the water. 
     The principle by which the flow divider  28  placed at the center of the impingement pool  27  may assist particulate capturing while pre-conditioning the mixture that enters the vortex chambers  23  is explained next. In a similar manner as described in U.S. Pat. No. 8,241,405 (B2), when entering the nozzle insert  24  through the inlet  11 , water coming from a flooded floor  21  of a paint booth  1  runs as a film over the internal surfaces of walls  30  of the nozzle insert  24 , while the paint laden air flows mainly through the center region of the nozzle insert  24 . Due to acceleration of the air in the nozzle insert  24 , the water film is broken into droplets that penetrate into the center region of the nozzle insert  24  where the air is flowing. However, it is possible that, at outlet  26 , segregated regions containing air entrained with overspray and a partially broken water film would still exist at the central and peripheral regions of the flow, respectively. The divider  28  further enhances capturing by bisecting these segregated regions and reversing their relative locations. For example, after being acted upon by the divider  28 , the region containing paint laden air enters the vortex chamber  23  at the peripheral region while the water film enters the vortex chamber  23  at the center region. Therefore, the paint laden air is “sandwiched” between the water film and the water contained at the bottom of the impingement pool  27  of the mixing chamber  22 . Since water is roughly three orders of magnitude heavier than air, as soon as the sandwiched region enters the vortex chambers  23 , the centrifugal force exerted squeezes the air and forces it through the water, hence, providing contact between the particles in the air and the water and, therefore, enhancing capturing. 
     The wet scrubber  12  includes two vortex chambers  23  symmetrically positioned about the line Y-Y. As shown, the vortex chambers  23  are substantially cylindrical, each having an inner wall surface  31 . Upon entering the vortex chambers  23 , the air and some of the water from the impingement pool  27  and/or the outlet  26 , begin to circulate. Given the geometry of the vortex chambers  23 , the air/water mixture rotates around the chamber, thereby forming vortices. These vortices cause heavier particles, such as paint particles and water droplets, to move toward the outer periphery of the vortex chambers  23  and displace smaller droplets toward the center of the vortex where they stay colliding with other small droplets until they are big enough to precipitate to the outer periphery of the vortex chambers  23 . As these heavier particles contact one another, they join or coagulate to form bigger particles. Specifically, the centrifugal force on the air/water mixture propels large water droplets and paint particles toward the inner wall surface  31  of the vortex chambers  23 , which is covered with a water film. As the paint particles collide with the water on this surface, they become trapped in the water. 
     With reference to  FIG. 3 , the vortex chambers  23  may include a projection or protrusion, such as a rib  32 , projecting from the inner wall surface  31  of each vortex chamber  23 . As shown, the rib  32  extends less than halfway around the periphery of each vortex chamber  23 ; however, the rib  32  may have a longer extension. Preferably, the rib  32  is attached approximately midway along the length of the vortex chamber  23  between end caps  33  of the vortex chambers  23 . This results in the rib  32  dividing the vortex chamber  23  into substantially equal sized sub-chambers  23   a ,  23   b . The rib  32  functions in a way similar to that of flow divider  28  by dividing the volume of air entering sub-chambers  23   a ,  23   b  equally, thereby further stabilizing the vortex and enhancing capturing. Due to the high speed circulation flow in the vortex chambers  23 , the region at its center (the central vortex) has the lowest pressure. To reduce the pressure drop through the scrubber (that is, the difference between the pressure values at the inlet and outlet of the scrubber), this lowest pressure has to be returned to a higher pressure value at the exit, hence, recovering pressure energy. By conservation of energy, this pressure recovery process is achieved by smoothly decelerating the flow that exits the scrubber. This deceleration has to be done in such a way that no substantial recirculation appear at the outlet of the scrubber. 
     After the air/water mixture goes through the vortex chambers  23  it enters the diffuser  68 . As shown in  FIGS. 2 and 3 , a plurality of diffusers  68  are positioned on the wet scrubber  12 . Preferably, one diffuser  68  would be positioned at each end of each vortex chamber  23 . The diffusers  68  include a plurality of curved surfaces  34  extending away from the vortex chamber  23 . In other words, the surfaces  34  forming the diffuser  68  are curved in a opposite direction than the curvature of the vortex chambers  23 . This difference in curvature helps to prevent the exhausted air from recirculating back into the vortex chambers  23 , thereby resulting in a more efficient wet scrubber. Since the higher speed flow runs close to the peripheral regions of the vortex chamber  23 , the opposite curvature helps decelerate the flow in that region to better equalize the speed of the flow exiting the scrubber  12 . 
       FIGS. 2 and 3  illustrate a nozzle insert  24  according to one embodiment of the present invention. The design of the nozzle inserts  24  of the present invention was developed as a way to provide structures that function similar to the adjustable plates  23   a  and  23   b  in U.S. Pat. No. 8,241,405 (B2). In the preferred manner of fabricating the body of the scrubber of the present invention out of plastic by a rotational molding process it was determined that structures similar to the adjustable plates  23   a  and  23   b  in U.S. Pat. No. 8,241,405 (B2) could not be readily produced by the rotational molding process. Further in the case of using HDP or LHP as the material or choice structural elements cannot be glued or welded to the internal walls of the plastic scrubber or otherwise attached in any acceptable manner. 
     In order to provide for adjustment of airflow in the plastic scrubbers of the present invention it was determined that nozzle inserts  24  could be configured and used which replace the adjustable plates  23   a  and  23   b  in U.S. Pat. No. 8,241,405 (B2). Nozzle inserts  24  may be formed of metal or another material. 
       FIG. 4  depicts the manner in which the nozzle insert  24  is received in the inlet  11  of the wet scrubber  12  and  FIG. 2  depicts the nozzle insert  24  positioned in the wet scrubber  12 . Proper alignment of the nozzle insert  24  in the wet scrubber  12  is achieved when the flow divider  28  ( FIG. 2 ) is received in alignment notch  35  that is formed in the bottom of the front and rear walls of the nozzle insert  24 . 
     With reference to  FIGS. 5A and 5B  the nozzle insert  24  includes front and rear walls  36  and  37  that have alignment notches  35  formed centrally in the bottoms of the front and rear walls  36  and  37 . As discussed above when the nozzle insert  24  is inserted into the inlet  11  of the wet scrubber  12  and lowered downward the flow divider  28  of the wet scrubber  12  is received in alignment notches  35  to assist in properly aligning the nozzle insert  24  in the wet scrubber  12 . As depicted in  FIGS. 5A and 5B  the side walls  38  and  39  of the nozzle insert  24  taper or slant inward from the top to the bottom of the nozzle insert  24 . As can be understood by those skilled in the art, the degree to which the side walls  38  and  39  taper or slant inwardly affects the speed of the air entrained with paint that exits the nozzle insert  24 . According to the present invention, the adjustment of airflow for changes in operating conditions can be accomplished merely by providing nozzle inserts  24  that are configured to produce different airflow characteristics and changing the nozzle inserts  24  to accommodate or optimize operating conditions for a given system process. As can be understood, nozzle inserts  24  can be exchanged by removing and installing each from the top of the scrubber  12 . This operation can be easily performed from the upper section  2  without having to access under section  3  as in other scrubber designs. In the case of scrubber inlet  11  and the nozzle insert  24  being formed of metal, the inlet  11  can be directly welded or otherwise affixed to the flooded floor  21  which facilitates installation. In addition, by forming the scrubber inlet  11  and the nozzle insert  24  of metal enhanced durability is provided in the case that hard heavy objects are dropped or otherwise inserted into the inlet of the scrubber. 
     The inlet  25  at the top of the nozzle insert  24  has a funnel shape with an angle slightly larger than the local angle of the wall of the scrubber inlet  11 . This configuration allows the inlet  25  of the nozzle scrubber  24  to sit flush and to seal against the internal surface of the scrubber inlet  11 . As a result, the scrubbing liquid flowing down from the flooded floor  21  of a paint booth  1  enters the scrubber inlet  11  and continues toward the nozzle inserts  24 , avoiding flow from the inlet to bypass the nozzle insert  24 . In one embodiment, the nozzle insert  24  is maintained in position by its own weight and by the pressure drop generated in the same nozzle insert  24 . To further avoid leaking between the nozzle insert  24  and the scrubber inlet  11 , the exterior edge of the nozzle insert  24  is provided with some caulking material. Of course, other means of maintaining the insert  24  in place and of avoiding leaks between the inlet  11  and the insert  24  are also possible. For example, the insert  24  could be held in place by using screws, pins, clips, etc. Also, leaks could be avoided by using gaskets, neoprene tape, or other sealing materials. 
       FIGS. 6A and 6B  depict frontal and side views of an exhaust extension  14  according to one embodiment of the present invention. The illustrated exhaust extension is molded from a similar plastic material as that from which the wet scrubber  12  is molded. Here it is noted that during the course of the present invention it was determined that the use of plastic materials such as HDP or LDP prevent materials from sticking on the surfaces of the molded scrubber and exhaust extension, thus providing a self-cleaning function that reduces or eliminates periodic manual cleaning. 
     The general shape and function of the exhaust extension  14  is similar to that taught in U.S. Pat. No. 10,857,494 (B2) by the present inventor, the complete disclosure of which is hereby expressly incorporated by reference. 
     Exhaust extension  14  is provided in the form of a generally rectangular or square cross-section closed duct with side walls  40 , a top wall  41  and a bottom wall  42 . Attached to end of the exhaust extension  14  and located laterally adjacent to the sides of the outlet  16  is a pair of wings  43  which extend from the side walls  40 . For simplicity and ease of fabrication, the wings  43  presented herein are flat and generally triangular in shape. The surface of the wings  43 , however, need not necessarily be flat or triangular. Rather, in the direction proceeding from the outlet of the wet scrubber  12  toward a distal end or tip  44  of the wings  43 , a curved shape may be employed. Specifically, partially circular, parabolic or other curved shapes could be used to efficiently provide a smooth and gradual deceleration of the flow of air out of the outlet  16 . The depicted triangular shape of the wings  43  could also be varied. For example, the tips  44  of the wings  43  may be rounded or otherwise truncated to avoid sharp points or edges that could be encountered during handling, installation or maintenance of the wet scrubber  12 . Additionally, the triangular shape of the wings  43  can be substituted with a rectangular shape, a rounded shape, a parabolic, etc. In each case, the wings  43  could be flat or curved (as previously discussed), all with the purpose of enhancing deceleration of the exhaust airflow and the further separation of any entrained water droplets. The outlet  16  of the exhaust extension  14  can be reinforced to prevent deformation created by the effect of airflow passing through the exhaust extension  14 , bending by the action of weight when the exhaust extension  14  is stored sideways before installation, deformation when the plastic material of the flow extension  14  dries and/or softens in a harsh environment, etc. According to one embodiment, such reinforcement can be accomplished by providing or molding ribs  70  that surround the opening of the outlet  16  and/or ribs that extend across the opening of the outlet  16 . Such reinforcement ribs can be molded or simply formed when cutting the outlet  16  into the plastic molded exhaust extension  14 . 
     A flange  45  is formed so as to extend outwardly around inlet of the exhaust extension  14  as shown. A similar flange  46  is attached so as to extend outwardly around the outlet of the wet scrubber  12  as shown in  FIG. 7 . The inlet of the exhaust extension  14  is attached to the outlet of the main body of the scrubber  12  by placing a gasket (not shown) between the flanges  45  and  46  and securing the flanges  45  and  46  together by suitable mechanical fasteners  50  such as, clips, pins, threated elements such as bolts and nuts, etc. 
     As shown in  FIG. 7  on the ends of the vortex chambers  23  can be provided with embedded fastener elements  47  that can be used to secure the wet scrubber  12  beneath a flooded floor or other structure of a processing system. Non-limiting examples of embedded fasteners include threaded screws, rods, bolts, nuts, pins, etc. In the embodiment shown in  FIG. 7  the embedded elements  47  are internally threaded nuts and, as show in  FIG. 7 , the wet scrubber  12  is mounted to the illustrated overhead structure by means of brackets  48  that are secured to the embedded nuts  47  by threaded fasteners  49 . The location of the embedded fasteners are according to convenience or to minimize any interference with the flow inside the wet scrubber  12 . 
     The plastic molded scrubbers of the present invention are very light in weight. As compared to a wet vortex scrubber having a similar design, shape and size and fabricated from metal, a plastic molded scrubber according to the present invention may provide a weight reduction on the order of 85%. This difference in weight becomes very significant when workers have to install wet scrubbers in the limited space inside the under section  3  (see  FIG. 1 ) of a paint booth which may be as small as only 4 feet high. Reduction of weight also reduces labor cost of installation and replacement. The plastic material of the scrubber acts as a thermal insulator reducing heat transfer and enhancing the performance of the dehumidification effect provided by operation of the scrubber. 
     While the design of the nozzle inserts  24  described herein was driven by the inability to mold internal air adjustment plates in the plastic scrubbers of the present invention, the nozzle inserts  24  can be used in metal wet scrubbers in place of typical or customary adjustment plates. An advantage associated with the use of the nozzle inserts of the present invention is that they can be easily removed, replaced and exchanged from the top of a wet scrubber. In the case of fixed adjustment plates, they can be inadvertently contacted during cleaning or maintenance and go out of adjustment in which case they can only be accessed and manually readjusted from below. 
     The configuration of the nozzle insert presented here is for illustration purposes. Other configurations and designs are possible to achieve the same objective of controlling the optimum speed inside the wet scrubber  12  (see  FIG. 2 ) while providing the advantage of being accessed and replaced from the upper section  2  of spray booth  1  (see  FIG. 1 ). 
     The embodiments described above were chosen to provide the best application to thereby enable one of ordinary skill in the art to utilize the disclosed inventions in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.