Abstract:
A downflow mixer with a gas injection device and/or a baffle plate is provided to improve performance of mixing and/or aeration in basins, lagoons or tanks, particularly as part of water or wastewater treatment.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present inventions relate to mixers. More particularly, the present inventions relate to mixers that are equipped with gas injection devices and/or baffle plates to improve mixing in a variety of applications, including but not limited to water and wastewater treatment applications. 
         [0002]    There are numerous available mixers for water and wastewater treatment applications. Of particular applicability to the present inventions are floating vertical shaft downflow mixers. Typical devices are shown and described in U.S. Pat. Nos. 4,723,848; 4,442,771 and 2,991,983 (all incorporated herein by reference). In general, such mixers include an annular float to support the mixer on the body of fluid to be mixed. A drive motor is mounted on the top of the float above the surface of the fluid. A propeller or drive shaft is connected to the drive motor and extends downwardly therefrom below the float and into the fluid. A propeller or impeller is attached to the drive shaft. A draft tube is typically mounted to the underside of the float extending downward from the float which encases the propeller. The draft tube is also provided with an intake at its upper end which is near the bottom of the float and a lower end that forms a discharge. When in use, operation of the propeller causes the fluid to be drawn into the intake in a pumping action. The fluid is then forced through the draft tube discharge end to mix the bulk fluid contents. 
         [0003]    Other types of mixers are also known, including those that inject oxygen or other gases into the fluid body. Some such devices are shown and described in U.S. Pat. No. 6,145,815; 6,135,430 and EP0252903. Such known devices that inject gas as part of the mixing process typically include hoods and other mechanical arrangements that are more complicated and expensive than typical downflow mixers. 
         [0004]    There is a need to improve the performance of typical downflow mixers, as well as to incorporate gas injection capabilities into such mixers. The present inventions are directed to such needs. In fact, the present inventions have led to unexpected results in their various combinations. 
       SUMMARY OF THE INVENTION 
       [0005]    The present inventions preserve the advantages of known downflow and other mixers and also provide new features, advantages and results. 
         [0006]    Therefore, it is an object of the present invention to provide a downflow mixer that improves mixing performance using a baffle plate. 
         [0007]    Another object of the present invention is to incorporate a gas injection device on a downflow mixer to improve mixing performance. 
         [0008]    Still another object of the present invention is to provide a downflow mixer with a gas injection device and a baffle to increase mixing performance. 
         [0009]    A further object of the present invention is to provide a gas injection device that may be easily turned on or off as desired. 
         [0010]    An additional object of the present invention is to provide a gas injected downflow mixer wherein the injection of gas does not decrease the pumping efficiency of the mixer and provides increased mixing capabilities. 
         [0011]    Accordingly, the present inventions provide a gas injected downflow mixer having a draft tube with a lower discharge end and a gas source. A gas injection device is also provided which is attached to the lower discharge end of the draft tube. The gas injection device includes an injector body having injection ports, a gas distribution manifold attached to the injector body to distribute the gas to the injection ports, and at least one gas inlet port to provide a gas supply to the gas distribution manifold. A baffle plate may also be attached to a lower end of the injector body to keep gas bubbles from short circuiting the mixer intake. In addition, baffles or preferably v-shaped baffles may be placed on the inside of the injector body above one or more of the injection ports to create low or negative pressure around the injection ports. Flow disruptors may also be located on the interior of the injector body to increase shear. 
         [0012]    The present inventions also provide a downflow mixer having a draft tube with a lower end defining a discharge end and a baffle plate attached to said discharge end which extends horizontally from said discharge end to prevent gas bubbles from interfering with pumping or mixing efficiency and to induce proper mixing flow. 
         [0013]    The present inventions further provide a floating fluid mixer having a draft tube with a lower end submerged in the fluid to be mixed and a gas injection device with a discharge end attached to the lower end of the draft tube. The gas injection device includes an injector body having an interior and an exterior, injection ports in the injector body to distribute the gas and a gas distribution manifold attached to the injector body to distribute the gas to the injection ports. The interior of the injector body is provided with baffles over one or more of the injection ports. And, a baffle plate may be attached to the discharge end of the gas injection device. Flow disruptors may also be provided on the interior of the injector body. 
       INVENTOR&#39;S DEFINITION OF THE TERMS 
       [0014]    The terms used in the claims of this patent are intended to have their broadest meaning consistent with the requirements of law. Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims are intended to be used in the normal, customary usage of grammar and the English language. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The stated and unstated objects, features and advantages of the present inventions (sometimes used in the singular, but not excluding the plural) will become apparent from the following descriptions and drawings, wherein like reference numerals represent like elements in the various views, and in which: 
           [0016]      FIG. 1  is a side view of a typical vertical shaft downflow mixer known in the prior art; 
           [0017]      FIG. 2  is a side view of a typical downflow mixer including a preferred embodiment of a gas injection device of the present invention, with portions of the preferred gas injection device cut away to show detail; 
           [0018]      FIG. 3  is a perspective view of a preferred embodiment of a gas injection device of the present invention; 
           [0019]      FIG. 4  is a detailed cut-away view of the embodiment of  FIG. 2  showing a preferred gas distribution manifold and preferred v-shaped baffles of the present invention; 
           [0020]      FIG. 5  is a perspective view of a preferred gas injection device and a preferred embodiment of a flow baffle or baffle plate of the present inventions, with portions cut away to show detail of a preferred v-shaped baffle; and, 
           [0021]      FIG. 6  is a perspective view of a preferred embodiment of a baffle plate of the present invention shown incorporated on a typical downflow mixer such as shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Set forth below is a description of what is currently believed to be the preferred embodiments or best representative examples of the inventions claimed. Future and present alternatives and modifications to the embodiments and preferred embodiments are contemplated. Any alternatives or modifications which make insubstantial changes in function, purpose, structure or result are intended to be covered by the claims of this patent. 
         [0023]    The present inventions have particular applicability to vertical shaft downflow mixers, including unidirectional and multidirectional mixing devices. It will be understood by those of skill in the art that the present inventions may be used with different types of mixers, including those with and without floats. For discussion purposes, the present inventions are described when used in conjunction with an AquaDDM® direct drive mixer/blender available from Aqua-Aerobic Systems, Inc. of Rockford, Ill. USA, which is preferred. In addition, the preferred gas supply system for the gas injection device is the Vacuum Swing Absorption (“VSA”) unit manufactured and sold by Air Products and Chemicals, Inc. of Allentown, Pa. USA. It will also be understood that other gas supply systems may be used in the present inventions. 
         [0024]    In  FIG. 1 , a typical downflow mixer is shown generally as  10 . Mixer  10  includes an annular float  12  which supports the mixer  10  on the surface of the fluid  11  to be mixed. A drive motor  14  is provided and mounted to float  12  by well known means. A drive shaft (not shown) is connected to the drive motor  14 . Drive shaft (not shown) extends downwardly from drive motor  14  and terminates in a propeller (not shown). A draft tube or volute  20  is provided on the underside of float  12  and may extend through float  12 , as will be understood by those of ordinary skill in the art (see generally U.S. Pat. No. 4,422,771). The upper end  16  of draft tube  20  is provided with an intake  22 . The lower end  24  of draft tube  20  encases a propeller and terminates at a discharge end  26 . A lower attachment flange  28  may also be provided. In operation, because of the action of the propeller, the fluid to be mixed enters intake  22  and is discharged out of discharge end  26  to effectuate mixing in the fluid tank or basin (not shown). In the preferred embodiment, the present inventions are attached to discharge end  26  of draft tube  20  using attachment flange  28 . 
         [0025]    Preferred and exemplary embodiments of the present inventions may best be seen by reference to  FIGS. 2-6 .  FIG. 2  shows a preferred embodiment of a gas injection device  30  without incorporation of a preferred baffle plate  50  of the present invention.  FIG. 5  shows preferred gas injection device  30  used in conjunction with a preferred baffle plate  50 .  FIG. 6  shows a preferred baffle plate  50  without a preferred gas injection device  30 . And,  FIGS. 3 and 4  show details of a preferred embodiment of gas injection device  30 . It will be understood by those of skill in the art that the present inventions may be used with other types of mixers and/or aerators or the like, and may be used in lagoons, basins or tanks. 
         [0026]    A preferred gas injection device  30  is shown in  FIGS. 2-5 . Preferably, gas injection device  30  includes an injector body  31  having an interior  39  and an exterior  41 , as well as a top end  32  and bottom end  33 . It will be understood by those of skill in the art that the shape of injector body  31  of gas injection device  30  does not have to be cylindrical. It is preferred, however, that the shape of the injector body  31  properly mate with and/or compliment draft tube  20  of mixer  10 . Top end  32  of injector body  31  is provided with a flange  34 . Flange  34  is designed to mate with a complimentary lower attachment flange  28  on discharge end  26  of draft tube  20 , and may be attached thereto by welding, bolts or other well known means (attachment means not shown). The length of the injector body  31  of the gas injection device  30  varies depending upon the particular mixer used and the specific application. 
         [0027]    Injector body  31  is provided with a series of injection ports  35  spaced around its circumference. In the preferred embodiment, the injection ports  35  are placed between one-half and two-thirds of the way down from the top  32  of injector body  31 . It has been found that if the injection ports  35  are too close to the propeller or impeller, the gas bubbles injected will rise to the propeller and will interfere with the proper pumping performance and efficiency. At the preferred placement along the length of injector body  31 , the flow of pumped fluid is sufficient to carry away the gas bubbles. In fact, those of skill in the art may find it counter-intuitive to add a gas injector to a pump/mixer because of the potential loss of pumping or mixing power potentially caused by the gas bubbles. Injection ports  35  are designed and sized to permit the passage of oxygen or other gas into the fluid stream. It will be understood by those of ordinary skill in the art that the diameter of injection ports  35  will vary based upon the capability of the oxygen or other gas delivery system such as the preferred VSA unit. In the preferred embodiment, the maximum diameter of injection port  35  was one-eight inch, which helps prevent backflow into the gas injection device  30 . Injector body  31  may be tapered or otherwise modified depending upon the flow characteristics desired. It is preferred, however, that injector body  31  not be tapered. 
         [0028]    Covering and in fluid communication with injection ports  35  is a gas distribution manifold  36  mounted to or on the exterior  41  of the injector body  31 . In the preferred embodiment, manifold  36  is generally a u-shaped channel that is welded or otherwise secured to the exterior  41  of injector body  31  and covers injection ports  35 . In the preferred embodiment, manifold  36  is in two pieces to essentially ring the entire circumference of injection ports  35  around injector body  31 . As a result, end caps  37  are provided to make manifold  36  air tight. It will be understood by those of ordinary skill in the art that manifold  36  may take a variety of shapes sufficient to distribute the gas to be injected through injection ports  35  in a uniform manner. In a preferred embodiment, a gas inlet port  38  is provided for each half of manifold  36 . Gas inlet port  38  is in fluid communication with the interior of manifold  36 . Gas inlet port  38  is then connected to gas line  40  ( FIGS. 2 and 5 ) which is connected to a gas source (not shown), such as the preferred VSA unit. 
         [0029]    Also in a preferred embodiment, a series of v-shaped baffles  42  is provided over each injection port  35  on the interior  39  of injector body  31 . In a preferred embodiment, baffles  42  are fabricated from structural angles and secured by well known means such as welding to the interior  39  of injector body  31  to overhang injection ports  35 . As shown in  FIG. 4 , the preferred angle A of baffle  42  and the interior  39  of injector body  31  is 60°. 
         [0030]    One purpose of baffles  42  is to increase turbulence around injection ports  35  that aids in proper bubble formation. Another purpose is to create low or negative pressure at or around injection ports  35 . It has been found that the highest area low pressure is at the apex or top  45  of baffle  42  (see  FIG. 4 ). Thus, in the preferred embodiment, baffle  42  is located above injection ports  35  so that the top or apex  45  is approximately aligned with injection ports  35 . The creation of these low pressure zones is desirable to prevent clogging of injection ports  35  or backflow of fluid in injection ports  35  because of submergence and/or fluid motion. For example, in some settings, it is desirable to turn gas injection on and off depending upon the treatment or process steps. The presence of baffles  42  prevent clogging or backflow. 
         [0031]    In addition, baffles  42  help induce gas flow so that the delivery system does not have to overcome entry pressure upon start-up and operates more efficiently. Thus, the present inventions obviate the need for complicated and expensive valve systems and the like. Finally, a series of flow disruptors  44  may also be provided at the lower end  33  on the interior  39  of injector body  31 . The optional flow disruptors  44  help increase shear and break-up the gas bubbles for better mixing. 
         [0032]    By reference to  FIGS. 5 and 6 , yet another novel aspect of the preferred inventions may be seen. Specifically,  FIG. 5  shows a preferred baffle plate  50  attached to the lower end  33  of gas injection device  30 . It will be understood that baffle plate  50  may be welded, bolted or otherwise secured to draft tube  20 . An example using a flange  52  is shown in  FIG. 5 .  FIG. 6  shows a preferred embodiment of baffle plate  50  attached to the end of draft tube  20  of a typical downflow mixer  10 . In this embodiment, baffle plate  50  may be bolted or welded to lower attachment flange  28  by bolts, welding or other well known means. Baffle plate  50  is useful when it is desired to limit the gas bubbles from rising back into the influent  22  and affect pumping action. When that “short circuit” occurs, the bubbles flood the propeller and reduce pumping capacity. The use of baffle plate  50  also provided unexpected results. For example, the use of baffle plate  50  resulted in a different and improved mixing pattern in the basin, tank or lagoon which was found to increase gas transfer by approximately 5%. In addition, baffle plate  50  permits the gas/fluid mixture to travel deeper into the tank or basin, and increases the toroidal mixing pattern. It is preferred that baffle plate  50  be large enough to prevent a “short circuit,” but not be too large that it negatively affects the rolling or toroidal motion of the mixing fluid. 
         [0033]    The above description is not intended to limit the meaning of the words used in or the scope of the following claims that define the invention. Rather, it is contemplated that future modifications in structure, function or result will exist that are not substantial changes and that all such insubstantial changes in what is claimed are intended to be covered by the claims. Thus, while preferred embodiments of the present inventions have been illustrated and described, it will be understood that changes and modifications can be made without departing from the claimed invention. In addition, although the term “claimed invention” or “present invention” is sometimes used herein in the singular, it will be understood that there are a plurality of inventions as described and claimed. 
         [0034]    Various features of the present inventions are set forth in the following claims.