SYSTEM HAVING FOAM BUSTING NOZZLE AND SUB-SURFACE MIXING NOZZLE

Abstract

A surface foam diffuser and digester tank system prevents and/or suppresses the formation of foam during digestion. The system includes a first nozzle disposed above a top surface of the at least partially liquid contents, a splash plate positioned adjacent to the first nozzle outlet, and a second nozzle disposed below the top surface of the at least partially liquid contents for suppressing foaming in the large processing tanks. The system nozzles each have an inlet for receiving pressurized liquid and an outlet for ejecting a liquid stream into the tank, the depth of the second nozzle and the direction of the liquid stream there from being such that rotation of the top surface is facilitated. The spray of the first nozzle, as dispersed by the splash plate, reduces foam on at least a portion of the top surface, with the rotation of the top surface bringing each portion of the top surface to eventually fall within the reducing spray.

Claims

1. A tiered nozzle system for suppressing foam on a top surface of fluid material substantially filling a large digester tank, the system comprising: a first nozzle positioned to remain above the top surface of the fluid material when the digester tank is substantially filled, the nozzle having an inlet for receiving pressurized liquid and an outlet for discharging a liquid stream into the digester tank; a splash plate positioned below the outlet of the first nozzle such that the splash plate contacts a discharging liquid stream at an angle of inclination relative to the stream direction to thereby deflect at least a portion of the stream upward and disperse the liquid stream over a greater portion of the top surface than the liquid stream would otherwise cover without a splash plate; and a second nozzle disposed below the top surface of the at least partially liquid contents, the second nozzle having an inlet for receiving pressurized liquid and an outlet for discharging a liquid stream directly into the fluid material, the position of the second nozzle and the direction of the discharged liquid stream being such that rotation of the top surface is facilitated.

2. The system of claim 1, wherein the first and second nozzle are connected at their respective inlets.

3. The system of claim 1, wherein the first nozzle and the second nozzle are secured to and positioned proximate an inner periphery of the digester tank.

4. The system of claim 3, wherein the outlet of the first nozzle is directed toward the center of the digester tank.

5. The system of claim 1, wherein the splash plate disperses the liquid stream over at least 20% of the top surface.

6. The system of claim 1, wherein the second nozzle is disposed at a depth of no more than 30% of the digester tank contents below the top surface.

7. The system of claim 6, wherein the second nozzle is disposed at a depth of no more than 20% of the digester tank contents below the top surface.

8. The system of claim 6, wherein the second nozzle is disposed at a depth of no more than 10% of the digester tank contents below the top surface.

9. The system of claim 2, wherein the first and second nozzles are positioned such that the direction of the liquid stream from the first nozzle is offset from the direction of the liquid stream from the second nozzle.

10. A digester tank system comprising: a digester tank containing material having at least a partially liquid composition prone to foaming as a result of gas byproducts from biological digestion; a discharge line connected to the bottom of the digester tank; a pump having an inlet connected to the discharge line; a feed line connected to a outlet of the pump; a first nozzle disposed above a top surface of the at least partially liquid material, the nozzle having an inlet for receiving pressurized liquid from the feed line and an outlet for ejecting a liquid stream in a direction toward one of either a center or a side of the digester tank; a splash plate positioned adjacent to the first nozzle outlet contacting the liquid stream at an angle of inclination relative to the stream direction to thereby disperse the liquid stream over a greater portion of the top surface; and a second nozzle disposed below the top surface of the at least partially liquid contents, the nozzle having an inlet for receiving pressurized liquid from the feed line and an outlet for ejecting a liquid stream into the digester tank, the depth of the nozzle and the direction of the liquid stream being such that rotation of the top surface is facilitated.

11. The system of claim 10, wherein the digester tank is a waste-water treatment tank comprising one of either an aerobic digester or an anaerobic digester.

12. The system of claim 10, wherein the inlet of the first nozzle and inlet of the second nozzle are aligned and connected.

13. The system of claim 10, wherein the first nozzle and the second nozzle are positioned proximate an inner periphery of the digester tank.

14. The system of claim 10, wherein the outlet of the first nozzle is directed toward the center of the digester tank.

15. The system of claim 10, wherein the second nozzle is disposed no more than one foot below the top surface.

16. The system of claim 10, further comprising a plurality of mixing nozzles positioned proximate a bottom surface of the tank.

17. The system of claim 16, wherein outlets of the mixing nozzles are aimed such that a discharging stream creates a liquid flow pattern in the digester tank contents.

18. The system of claim 10, wherein the first and second nozzles are positioned such that the direction of the liquid stream from the outlet of the first nozzle is offset from the direction of the liquid stream from the outlet of the second nozzle.

19. The system of claim 10, wherein the second nozzle is disposed at a depth of no more than 30% of the tank contents below the top surface.

20. The system of claim 19, wherein the second nozzle is disposed at a depth of no more than 20% of the tank contents below the top surface.

21. The system of claim 19, wherein the second nozzle is disposed at a depth of no more than 10% of the tank contents below the top surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.

[0015] FIG. 1 is a plan view of one embodiment of the present system;

[0016] FIG. 2 is a side view of the system illustrated in FIG. 1;

[0017] FIG. 3 is a close up view of an embodiment of a sub-surface nozzle and surface defoaming spray nozzle combination;

[0018] FIGS. 4-6 are various views of one embodiment of a mixing nozzle used in embodiments of the present system;

[0019] FIGS. 7-9 are various views of one embodiment of another mixing nozzle used in embodiments of the present system; and

[0020] FIGS. 10 and 11 are views of one embodiment of an anti-foaming nozzle used in embodiments of the present system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0021] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated.

[0022] Referring to FIGS. 1-11, there is illustrated an anti-foaming tank and nozzle system, generally designated by the numeral 10. The described system 10 is discussed with respect to mixing tank contents, which is typically a combination of liquids and solids. More specifically, however, the system 10 is described for use on very large tanks, where mixing at the surface is somewhat diminished, and for use in digesters and the like, wherein a viscous top surface, due to the formation of scum and foam, reduces surface mixing. These particular foaming and scum problems may be found anywhere large processing tanks are used, such as, but not limited to, bio-waste plants, chemical plants, water treatment plants, waste-water treatment plants and where the tank contents include a 1-6% total solids concentration.

[0023] Accordingly, the system 10 is described herein with reference to three distinct zones: tank bottom (A), content upper surface (B), and above the content surface (C). The drawings illustrate a specific embodiment of the system as used in a specific tank construction, but principles of the invention can be used for virtually any storage tank in which surface foam (including scum) may cause a problem.

[0024] In the embodiment illustrated in FIGS. 1 and 2, a tank 11 is shown to include a lid 12, a sidewall 13 and a conical base 14. The representative embodiment is used for a cylindrical digester tank having a radius of 108 feet (about 32.9 meters), a bottom cone of 4.25 feet (129.5 cm) depth, an overall depth from the bottom sidewall of 30 to 50 feet, and a mixing system including a chopper pump 16 and nozzle assemblies 18 such as those available from Vaughan Co., Inc., of Montesano, Wash., and sold under the trademark ROTAMIX.

[0025] The present system 10 can be installed to achieve its defoaming effect wherever it is needed. Appropriate valves are provided at the pump 16 for directing liquid from the tank 11 to the pipe 22 and then to supply pipes 28 for the mixing system nozzle assemblies 18, and pipes 30 for the diffuser 24 and sub-surface mixing nozzle 26. By sub-surface it is meant that the nozzles are positioned within the tank contents below the surface within the top 30% of the content depth (e.g., not more than 3 feet deep in 10 feet of tank contents), preferably within the top 20% of the content depth, and most preferably within the top 10% of the content depth. Liquid from the tank 11 is supplied to the pump 16 by inlet piping, which can withdraw liquid from the lower center portion of the tank 11 (via a sump), and extends to the pump 16.

[0026] As illustrated in FIG. 1, the mixing nozzle assemblies 18 can include an inner ring of nozzles and an outer ring of nozzles positioned at the tank bottom (A), with each nozzle oriented in the same general rotational direction to induce rotation of the contents of the tank about a vertical axis 20. The outer ring preferably comprises four dual nozzle assemblies 40, while the inner ring comprises at least two single nozzle assemblies 50. The pump outlet is connected to a supply pipe 22 feeding pipes 28 to the mixing nozzle assemblies 18. The purpose of the lower mixing nozzle assemblies 18 is to create a rotational, stirring flow pattern in the tank contents. A suitable system is described in U.S. Pat. No. 7,025,492 to Dorsch et al., and assigned to Vaughan Co., Inc. or Montesano, Wash. The '492 patent is hereby incorporated by reference

[0027] FIGS. 4-6 illustrate the preferred single nozzle 52 as a glass-lined ductile iron nozzle having an 8-inch inlet reduced to 6-inch at the bend before reaching a tapered outlet. Although the nozzle outlet 44 is of substantially lesser diameter than the pipes 22 and 28, nevertheless, the diameter at the outlet 44 still is much larger than conventional spray nozzles or apertures so that the nozzle will not become clogged with rags, hair, fiber, or other thick, tough, stringy, or solid material from the tank.

[0028] The dual nozzle assemblies 40 are created using the same single nozzle of FIG. 5 coupled to the intermediate nozzle 27 of FIG. 9. Similarly, the sub-surface nozzle 26 also utilizes the configuration illustrated in the drawings of FIGS. 7-9. The configuration of the intermediate nozzle 27 (as nozzle 26 or nozzle 52) is well-known in the field, allowing a second nozzle (e.g., diffuser nozzle 24) to be connected adjacent using the same feed pipe. The nozzles 27 and 52 should be 360 fully adjustable to allow directional positioning to create the desired stirring flow pattern within the tank 11, be it for lower tank mixing or sub-surface mixing.

[0029] As shown and described in U.S. Pat. No. 7,628,183, a diffuser can be conveniently mounted in a manhole of the type commonly used in tanks of this type. However, for the presently illustrated embodiment, the supply pipe 22 which feeds pipe 30 to the surface foam diffuser 24 and sub-surface mixing nozzle 26 is preferably located within the tank 11, running from the bottom center of the tank 11 toward the sidewall 13. The location of the diffuser 24 along the sidewall 13, of course, varies depending on the tank.

[0030] Referring to FIG. 2, supply pipe 22 (8-inch diameter in a representative embodiment) connects to the upright diffuser inlet pipe 30. Pipe 30 extends upward to an 8-inch to 6-inch reducer 32 to allow attachment of the 6-inch flange 34 and piping 36 of mixing nozzle 26 (FIG. 3). A diffuser nozzle 24 is then attached approximately one foot or more above the mixing nozzle 26. The mixing nozzle 26 and the diffuser nozzle 24 are identical to the nozzles described above, with the added features described below.

[0031] The outlet of the diffuser nozzle 24 is sized for a desired concentration of the liquid ejected from the nozzle, and can be 1 inches (3.8 cm) to 2 inches (7.0 cm) in diameter for a representative installation. The horizontally directed stream of liquid impinges on a splash plate or deflector 38 to break the liquid stream into a reasonably uniform dispersion of droplets over a substantial area of the surface of the liquid in the tank 11 without a great upward arc which would contact the lid 12 of the tank or require that liquid be maintained at a lower level, thereby wasting room in the tank 11. For most installations, an additional four feet (1.2 meters) of head room is required above the diffuser nozzle 24 to allow the stream to be dispersed without contacting the tank lid 12.

[0032] As shown in FIGS. 10 and 11, the diffuser nozzle 24 includes a standard coupling 41 to attach to the pipe 36 leading from mixing nozzle 26 (FIG. 3). The splash plate or deflector 38, described in detail below is carried by a support arm 46 pivoted to the underside of the nozzle coupling 48 by a pivot pin or bolt 51. Upright clamps 52 are attached to the support arm 46 and secure the deflector 38 to the nozzle at the desired angle.

[0033] The deflector 38 is a key component of the surface foam diffuser system 10. As noted above, it is desired that the nozzle outlet be of substantial diameter to prevent clogging. It also is desired that the exit velocity of the stream be quite high in order to reach a sizeable area. The purpose of the deflector is to break up the stream from the nozzle into droplets and disburse the droplets over a long and wide area, while minimizing the height of the spray to minimize the headroom required inside the tank 11. Many different shapes and contours have been tested, with the illustrated device constituting the current preferred embodiment.

[0034] The deflector plate 38 is angled upward from below the nozzle outlet at a small acute angle so that the horizontally directed stream of liquid from the nozzle is deflected upward without excessive loss of energy or a resulting high arc. A 10 to 20 angle of inclination, preferably about 15, has been found to achieve the desired deflection.

[0035] The outer peripheral edge of the deflector 38 is a circular arc centered at about the nozzle outlet, and of at least 90 angular extent, preferably at least about 120. If the shape is too narrow, the spray and droplets fall off the sides of the plate in an uncontrolled manner. In this embodiment, the radius of the arc is about 14 inches (35.6 cm), resulting in the maximum width of the fan being just over 21 inches (over 53.3 cm).

[0036] The outer arcuate edge is preferably formed with saw tooth fingers 62 bent up relative to the inner portion of the plate, preferably at an angle of about 45. The fingers or teeth are of a sharp V shape having a tip radius no greater than 0.06 inch (1.5 mm), and a base radius between teeth no greater than 0.06 inch (1.5 mm). The teeth are small and closely spaced which has been found to break up the stream and spread apart the spray of droplets. A simple deflector with no teeth tends to concentrate the spray pattern at a constant radius, whereas large teeth at mixed angles and sizes break up the spray pattern, but not much water falls within a 10-foot radius of the nozzle and the pattern is not evenly distributed. The small, sharp teeth achieve a more uniform pattern. In this embodiment, the teeth are about 0.625 inch (1.59 cm) long with a pitch (tip-to-tip) of about 0.575 inch (1.46 cm), resulting in an included angle between adjustment tooth edges of about 50.

[0037] The plate portion of the deflector 38 is not planar, but rather is curved about its center line at a radius of approximately 36 inches so that the outer corners droop downward about 2 inches (5.1 cm) with respect to the center of the deflector 38. The convex upper surface has been found to assist in disbursing the spray more evenly from side to side.

[0038] The resulting spray from the diffuser 24 may cover as much as about 50% of the top surface area of the tank contents. The sub-surface mixing nozzle 26 facilitates rotation of the top surface along with the lower mixing nozzles 18 to allow for the eventual coverage of the entire top surface by the de-foaming spray.

[0039] The following TABLE illustrates the effectiveness of the present system compared to the use of chemical defoamants.

TABLE-US-00001 TABLE Spray vs. Chemical Increasing High Level Diffuser Nozzle Concentration of Concentration of with Sub-Surface Foam Height Chemical Defoamant Chemical Defoamant Mixing Nozzle Maximum 17 to 19+ feet 11 to 12 feet 4+ feet Foam above liquid level Minimum 5.5 to 6.5 feet 8 to 9 feet 2 feet Foam above liquid level Approx. Avg. 12 to 13 feet 10 feet 3 feet Foam above liquid level

[0040] The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants' contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.