AU2016200642A1 - A bulk liquid storage mixer - Google Patents

Abstract

Abstract A bulk storage mixer comprises a conduit having an inlet and an outlet with a fixed vortex inducing member mounted to the conduit between the inlet and the outlet and a mounting assembly fast with the conduit for mounting within a vessel for containment of bulk liquid. The vortex inducing member comprises a nozzle fixed to the pipe, the nozzle including screw flight blades arranged to create vortex flow as liquid is discharged from the pipe at high velocity.

Description

IMPROVEMENTS TO BULK LIQUID STORAGE MIXERS

TECHNICAL FIELD

The present invention is directed to an apparatus for mixing bulk liquids, such as slurries, potable water, raw water and wastewater to prevent undesirable settling and to maintain a homogenous consistency.

BACKGROUND ART

Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

Many bulk liquid storages need to be actively mixed to avoid undesirable phenomenon such as thermal stratification, liquid composite de-construction, organic growth or settlement occurring.

Various apparatus are known in the prior art for mixing bulk liquids in storage.

One approach involves the use of an electrically driven propeller that is submersed in the liquid and supported on a lightweight frame supported on the floor of the storage unit. The propeller operates to propel liquid, either vertically or at an incline, to facilitate the circulation of the liquid and in addition the creation of a vortex effect in the bulk liquid which causes the liquid to be mixed.

Another approach makes use of a submersed, electrically driven pump on the floor of the storage unit. In similar fashion to the previously mentioned propeller-based mixer, the pump propels liquid, either vertically or at an incline, to facilitate the circulation of the liquid in the bulk liquid storage unit which causes the liquid to be mixed.

Another approach makes use of a floating device, with an electrically driven impellor near the surface of the bulk liquid. Liquid is propelled downwards to facilitate the circulation of the liquid in the bulk liquid storage unit which causes the liquid to be mixed. A further mixing system involves a floating, electrically driven, shallow submersed pump that has an intake coupled to a suction hose with an inlet near the base of the storage unit. Liquid is sucked via the suction hose from the lower region of the storage unit and pumped to the surface, thereby creating a vertical circulation of the liquid and so causing mixing.

An alternative to the above systems has been to inject measured amounts of high pressure gas (e.g. air). A sudden release of a large volume of gas pushes the liquid in the storage unit upward and so induces a vertical circulation of the liquid that results in mixing.

The Inventor, who has had first-hand experience with the problem of mixing liquids in storage units, including tanks and reservoirs, has observed a number of problems with various of the above described prior art approaches to mixing bulk liquids. A problem that arises where submersed pumps are used is that of supplying them with electricity. Electricity is a safety hazard underwater when cabling or equipment ages or is subject to damage.

Another problem is that of maintaining a driven submersed motor or pump. Servicing or replacement of a submersed installations either requires draining the storage unit, which may not be viable, or employing divers, which is expensive and a high risk activity. A problem that arises where an electric motor drives an underwater impeller is that the motor life is shortened where humidity is above normal conditions such as a roofed reservoir. Electricity is a safety hazard near water especially when cabling or equipment ages or is subject to damage.

Another issue with submerged motors and pumps is that the ongoing wear and tear results in the need for maintenance and replacement at regular intervals. Again this either requires draining the storage unit, which may not be viable, or employing divers, which is expensive and a high risk activity.

In relation to the high pressure gas mixing system, it will be realized that this system makes use of pneumatic hoses that contain unreleased energy which poses a safety hazard. In addition, the circulation by air is purely vertical and fails to achieve rotary circulation in a horizontal plane.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a bulk liquid storage mixer comprising: a conduit having an inlet and an outlet; a fixed, vortex inducing member mounted to the conduit between the inlet and the outlet; and a mounting assembly fast with the conduit for mounting within a vessel for containment of bulk liquid.

Preferably the conduit comprises a rigid pipe.

The vortex inducing member may comprise a propeller with a hollow hub that mounts around the rigid pipe.

It is preferred that the propeller be mounted adjacent the outlet of the conduit.

Alternatively, in a preferred embodiment of the invention the vortex inducing member comprises a nozzle fixed to the pipe, the nozzle having internal and external screw flight blades arranged to create vortex flow as liquid is discharged from the pipe at high velocity. The inventor has found that as the discharged liquid passes through the nozzle it moves in a vortex which then drags the surrounding liquid to also induce vortex flow therein.

In one embodiment of the invention the mounting assembly comprises a tripod for supporting the conduit upon a base of the vessel.

Alternatively, and more preferably, the mounting assembly may comprise a support leg for supporting the conduit upon the base of the vessel.

The conduit may include a right-angled bend wherein an inlet portion of the conduit extends parallel to the base of the vessel and wherein an outlet portion of the conduit extends upwardly. Alternatively, the conduit may include a bend of another angle so that the conduit is directed at a non-orthogonal angle relative to the base.

According to a further embodiment of the present invention there is provided a method for causing mixing of a bulk liquid within a vessel comprising the steps of: inducing vertical circulation within the vessel placing at least one vortex inducing members in a path of the vertical circulation to thereby induce a vortex flow within the vessel and thereby mix the bulk liquid.

It is preferred that the at least one vortex inducing member comprises a vortex inducing nozzle located centrally within the vertical circulation.

Alternatively, in a second embodiment the at least one vortex inducing member may comprise a fixed propeller located centrally within the vertical circulation within the vessel.

In some situations multiple mixers may be required for bulk storage facilities that have a low depth to surface area ratio. Where the liquid body is extensive horizontally compared to depth a single mixer may be insufficient to create horizontal circulation over the entire mass. Accordingly, in one aspect of the present invention multiple mixers of the previously described type are placed at a suitable distance, for example, approximately 1/3 radius from the centre of the storage facility with the nozzle discharges aimed at an acute angle, e.g. approximately 30 degrees from vertical, and in a tangential horizontal direction to create both vertical flow and either clockwise or anti-clockwise flow horizontally.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

Figure 1, illustrates a bulk liquid mixer according to a first embodiment of the present invention, installed on a base of a storage vessel. Figure 2 is a sagittal cross section through the bulk liquid mixer of Figure 1.

Figure 3, is a cross section through a storage vessel in which the bulk liquid mixer of Figure 1 is installed illustrating a vertical circulation induced during operation of the mixer.

Figure 4, is a top plan view of the storage vessel indicating an induced vortex flow imparted to the liquid by a fixed propeller of the mixer.

Figure 5, presents three views of a fixed vortex inducing nozzle of a bulk liquid mixer according to a second and preferred embodiment of the invention.

Figure 5A, is a cross section near the base of the nozzle in Figure 5 with 4 straight blades.

Figure 5B, is a cross section of a three bladed version of the mixing nozzle near the base of the nozzle.

Figure 6 is a cross section through a storage vessel in which the bulk liquid mixer of Figure 5 is installed, illustrating a vertical circulation introduced by the mixer.

Figure 7 is a top plan view of the storage vessel indicating a vortex flow caused by the forcing of liquid through the fixed nozzle.

Figure 8 is a plan view of an arrangement of multiple mixers according to a further aspect of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to figures 1 and 2 there is depicted a side view and sagittal cross-sectional view, of a mixer 100 according to a first embodiment of the present invention. The mixer 100 is mounted to a base 12 of a bulk liquid storage vessel.

Mixer 100 is comprised of a conduit in the form of a rigid metal pipe 9 that is supported by a mounting assembly in the form of a tripod 10. The pipe 9 is formed with a right-angled bend 102. An inlet portion 103 of the pipe 9 extends parallel to the base 12 of the vessel whilst an outlet portion 105 extends upwardly.

The outlet portion 105 terminates in an outlet nozzle 7. As will be explained the nozzle 7 serves to increase the velocity of the liquid leaving the conduit in use and so assists in producing a vertical circulation within the storage vessel. A vortex inducing member in the form of a propeller 8 is mounted fast about the outside of the pipe 9. Preferably the propeller 8 has a hollow hub 106 which fits snugly over the outside of the pipe 9 and which is welded or otherwise fastened thereto. It will be understood that the propeller 8 does not rotate or otherwise move relative to the pipe 9. In one embodiment the propeller has a radius of 300mm though it will be realized that other embodiments will have different dimensions depending on factors such as the volume of bulk liquid to be mixed and the size of the vessel.

It is preferred that the propeller 8 is mounted adjacent the nozzle 7 as shown in Figures 1 and 2. Flowever it could be mounted lower in other embodiments of the invention provided that it is placed in a portion of the induced circulation that will be discussed shortly.

The mixer 100 includes a mounting assembly in the form of a tripod 10 that stands upon base 12 and which is fastened to the pipe 9 by means of a support collar 11 (shown in Figure 2), thereby supporting the pipe 9 upon the base 12 of the vessel.

Referring now to Figure 3, in a typical installation the mixer 100 is mounted to the base 12 of a storage vessel 5, such as a reservoir, dam or tank. A pump 4 is located external to the storage vessel 5 and draws liquid from the vessel and forces it through the pipe 9 of the mixer 100 so that a high velocity liquid discharge 6 (Fig. 1) issues upwardly from the nozzle 7. If desired, the bulk liquid storage mixing flow from the pump can be controlled by fitting a variable speed drive control module to the electric pump in order to minimize energy consumption.

In some situations a supply of high pressure liquid, e.g. mains pressure water or an elevated storage vessel, may be available in which case a pump will not be required. Alternatively, an external liquid source (which can be independent from the storage tank) may be provided to supply the energy to create current/agitation/vortex and subsequent mixing. This is possible because the volume of liquid required to drive the mixing action in the storage tank is small compared to the volume of liquid in the storage tank.

The force between the high velocity liquid 6, that is discharged from the nozzle 7 and the bulk liquid 109 in the vessel 5 causes an induced circulatory flow 2 that proceeds upwardly, then outwardly, then downwardly parallel to the walls of the storage vessel, inwardly along the base of the vessel and back up adjacent the mixer. As the circulatory flow passes back up adjacent the mixer the blades of the propeller 8 cause a localized eddy to form on the downstream side of the propeller. The localized eddy causes an induced vortex flow 1 which in turn causes the bulk liquid 109 to rotate as indicated in the plan view of Figure 4.

The direction of the induced vortex (clockwise or anti-clockwise) is determined by the lay of the mixer blades.

In some situations, multiple mixers are required to mix the bulk liquid 109. In that case the mixers are arranged to work in harmony to minimize the energy input required to produce the most efficient mix. A typical arrangement requires the mixers to be angled in the direction of the intended clockwise or anticlockwise flow in which the bulk liquid 109 is desired to rotate. This is achieved by lowering the angle of the pipe 9 and outlet portion 105 to an angle less than vertical with bend 102 subsequently modified to a more obtuse angle. The mounting assembly is modified to support pipe 9 and outlet portion 105 at the same angle, which is less than vertical.

Referring now to Figure 5, there are depicted three side views of a mixer 400 according to a second, and preferred, embodiment of the present invention. The mixer 400 is supported on a base 412 of a bulk storage vessel.

Mixer 400 is comprised of a conduit in the form of a rigid pipe 409 that is supported by a mounting assembly 410. An inlet portion 403 of the pipe 409 extends parallel to the base 412 of the vessel whilst an outlet portion 405 extends upwardly.

The outlet portion 405 is coupled to an inlet 415 of a mixer nozzle 408. The mixer nozzle 408 includes a central hollow pipe 417 which defines a passageway 419, best seen in Figure 5A. The mixer nozzle is formed with screw flight blades 407 which have portions 407a and 407b (shown in Figure 5A) that are respectively located within the passageway 419 and outside the hollow pipe 417. The mixer nozzle inlet 415 that is mounted to the pipe 409 is preferably of the same inner diameter as the pipe 409. Flowever, because the screw flight blades 407 have portions 407a that penetrate into the nozzle passageway 419 the liquid velocity through the passageway 419 is forced to increase due to the constriction of the passageway by the internal portions 407a of the screw flight blades 407. The rapid passage of liquid through the nozzle and out the outlet 421 of the pipe 417 causes an interaction of the liquid with the screw flight blades 407 that assists in producing a vertical circulation within the storage vessel.

The mixer 400 includes a mounting assembly in the form of a removable support leg 410 that stands upon base 412 and which is fastened to the pipe 409 by means of a support cleat 411, thereby supporting the pipe 409 upon the base 412 of the vessel.

Figure 5B is a cross section through an alternative version of the mixer nozzle which has three, rather than four, screw flight blades.

Referring now to Figure 6, in a typical installation the mixer 400 is supported on the base 412 of a storage vessel 405, such as a reservoir, dam or tank. A pump 404 is located external to the storage vessel 405 and draws liquid from either the vessel 405 or an external source such as a water main 413 or a reservoir. The liquid is forced through the pipe 409 to the mixer 400 so that a high velocity liquid discharge 406 (Figure 5) is forced through the mixer 400. If desired, the flow from the pump 404 can be controlled by fitting a variable speed drive to the electric pump in order to minimize energy consumption.

In some situations a supply of high pressure liquid, e.g. mains pressure water or an elevated storage vessel is available for supplying the mixer 400, in which case a pump may not be required to create sufficient flow to maintain desirable mixing in the bulk liquid storage vessel 405.

The interaction of the high velocity liquid 406 with the screw flight blades 407 produces a circulatory flow 402 that proceeds upwardly, then outwardly, then downwards parallel to the walls of the storage vessel, inwardly along the base of the vessel and back up adjacent the mixer. As the circulatory flow passes back up through the mixer the blades of the mixer nozzle 408, there is a localized eddy formed on the discharge side of the mixer. The localized eddy causes an induced vortex flow 401 which in turn causes the bulk liquid 109 to rotate as indicated in the plan view of Figure 7.

It will be realized that the direction of the induced vortex (clockwise or anticlockwise) is determined by the lay of the mixer blades.

It will therefore be realized that a method according to one aspect of the present invention for causing mixing of a bulk liquid within a vessel comprises, with reference to Figure 1 inducing a circulation 2 within the vessel 5 and placing at least one vortex inducing member, e.g. in the form of propeller 8 in a path of the circulation 2. Placing the propeller in the path of the circulation 2 induces a vortex flow 1 within the vessel 5 and thereby further promotes the mixing by imparting a rotation to the bulk liquid 109 in the horizontal plane.

In some situations multiple mixers may be required for bulk storage facilities that have a low depth to surface area ratio. Where the liquid body is extensive horizontally compared to depth a single mixer may be insufficient to create horizontal circulation over the entire mass. Referring now to Figure 8, multiple mixers 400a,..,400d of the type illustrated in Figure 5 are placed at a suitable distance, for example on a circle approximately 1/3 radius from the centre of the storage facility 405. The mixers are coupled via respective pipes 9a,..,9d to a manifold 450 which is in turn coupled to pipe 9 and thence to pump 404. Alternative arrangements for supplying the nozzles are of course possible. For example each nozzle could be independently coupled to a separate pump. The mixers 400a,..,400d are orientated so that nozzle discharges of each of the mixers are aimed at an acute angle, e.g. approximately 30 degrees from vertical, and in a tangential horizontal direction to create both vertical flow and either clockwise or anti-clockwise flow horizontally in the liquid stored in the storage facility.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term “comprises” and its variations, such as “comprising” and “comprised of” is used throughout in an inclusive sense and not to the exclusion of any additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Throughout the specification and claims (if present), unless the context requires otherwise, the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms.

Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims (18)

1. The claims defining the invention are as follows:

   1. A bulk storage mixer comprising: a conduit having an inlet and an outlet; a fixed vortex inducing member mounted to the conduit between the inlet and the outlet; and a mounting assembly fast with the conduit for mounting within a vessel for containment of bulk liquid.
2. 2. A mixer according to claim 1 wherein the conduit comprises a rigid pipe.
3. 3. A mixer according to claim 1 or claim 2, wherein the vortex inducing member comprises a propeller with a hollow hub that mounts around the rigid pipe.
4. 4. A mixer according to claim 3, wherein the propeller is mounted adjacent the outlet of the conduit.
5. 5. A mixer according to claim 2, wherein the vortex inducing member comprises a nozzle fixed to the pipe, the nozzle including screw flight blades arranged to create vortex flow as liquid is discharged from the pipe at high velocity.
6. 6. A mixer according to claim 4, wherein the outlet terminates in a nozzle for increasing fluid flow there through.
7. 7. A mixer according to any one of the preceding claims, wherein the mounting assembly comprises a tripod for supporting the conduit upon a base of the vessel.
8. 8. A mixer according to claim 5, wherein the mounting assembly comprises a support leg for supporting the conduit upon the base of the vessel.
9. 9. A mixer according to any one of the preceding claims, wherein the conduit includes an angled bend wherein an inlet portion of the conduit extends parallel to the base of the vessel and wherein an outlet portion of the conduit extends upwardly.
10. 10. A mixer according to anyone of the preceding claims wherein the conduit is coupled to an external source of liquid for supplying energy to the mixer to thereby create the vortex in use.
11. 11. A mixer according to any one of claims 1 to 9, wherein the conduit is coupled to the external source of liquid by means of a pump.
12. 12. A method for causing mixing of a bulk liquid within a vessel comprising the steps of: inducing vertical circulation within the vessel placing a vortex inducing member in a path of the vertical circulation to thereby induce a vortex flow within the vessel and thereby mix the bulk liquid.
13. 13. A method according to claim 12, wherein the at least one vortex inducing member comprises a vortex inducing nozzle located centrally within the vertical circulation.
14. 14. A method according to claim 12, wherein the least one vortex inducing member comprises a fixed propeller located centrally within the vertical circulation within the vessel.
15. 15. A method of powering a mixer according to any one of claims 1 to 9 to mix the bulk liquid within the vessel including utilising an external pump and piping system to draw liquid from the bulk liquid storage.
16. 16. A method of powering a mixer according to any one of claims 1 to 9 to mix the bulk liquid within the vessel including utilising an external pump and piping system to draw liquid from an external source.
17. 17. A method of powering a mixer according to any one of claims 1 to 9 utilising an external pressurised liquid source and piping it to the mixer.
18. 18. A multiplicity of mixers each according to any one of claims 1 to 9, each placed at a distance from the center of a bulk liquid storage facility and each having the nozzle arranged to discharge at an acute angle from vertical and in a tangential horizontal direction to create both vertical flow and either clockwise or anti-clockwise flow horizontally. * * *