AU2018241189A1 - Centrifugal Pump - Google Patents

Abstract

Abstract A centrifugal pump comprising a pumping chamber, an inlet for entry of fluid into the pumping chamber, an impeller, and an element upstream of the impeller, the impeller and the element mounted for rotation within the pumping chamber about an axis of rotation, the element being configured to shear the fluid entering through the inlet, and the assembly comprising the an impeller, and an element upstream of the impeller, the impeller and the element mounted for rotation within the pumping chamber about an axis of rotation, the element being configured to shear the fluid entering through the inlet. There is also provide a method for method of pumping fluid comprising use of the centrifugal pump and 37 and a method of handling a thick slurry (such as 'Bingham Plastics' slurry), the method comprising use of the centrifugal pump. Fig 2 02-Rc [V 4 .41 Nev I(Q7 ~i -47

Description

2018241189 05 Oct 2018

Centrifugal Pump

TECHNICAL FIELD [0001] This invention relates to a centrifugal pump.

[0002] The invention has been devised particularly for pumping slurry material.

[0003] The invention also relates to pumping slurry material and also handling slurry material.

BACKGROUND ART [0004] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0005] Water is becoming more precious alongside the drive for mining companies to be more environmentally friendly. Historically gangue slurried with significant amounts of water were pumped out to tailings dams whereupon much of the water evaporated. The particle sizes of the gangue solids were often larger than 100 pm in size. Conventional centrifugal slurry pumps could be used without operating problems.

[0006] The vast majority of mineral processing plants around the world are now ‘reclaiming’ the water via advanced ‘thickener’ technology. Dirty reclaimed water is returned to the process via ‘thickener overflow’ and gangue slurry is sent to tails via the ‘thickener underflow’.

[0007] Additionally, to extract the maximum amount of mineral from the ore it is ground to much finer sizes.

[0008] The gangue slurry, also known as tailings slurry, is frequently becoming so concentrated that conventional centrifugal slurry pumps become problematic and in many instances can no longer be used.

2018241189 05 Oct 2018 [0009] Fewer modern plants are being designed with ‘conventional’ thickeners as these are considered to waste water. Many plants are now using high density thickeners or paste thickeners to ensure water is reclaimed and reused.

[0010] With the specialist flocculants used in modern thickener designs, combined with a finer solids grind, the underflow is frequently becoming paste-like. More water is being recovered so tailings are becoming more concentrated.

[0011] When the solids size is less than about 75 pm d50 particle size, as their concentration by weight continues to increases above 50% they become progressively more difficult to pump. Put simply, the better the water recovery, the worse the pump performance.

[0012] The difficulty in pumping occurs as very small particles, when concentrated sufficiently, interact with each other and create a resistance to flow. They frequently form what is known as a ‘Bingham Plastic Slurry’. These slurries are non-Newtonian by nature, forming an ‘apparent viscosity’ with a high yield stress that needs to be overcome before the slurry will begin to flow. When the yield stress increases above 50Pa, the slurries become progressively more difficult for a conventional centrifugal pump to handle.

[0013] High density thickeners and paste thickeners are producing slurries so thick they have a yield stress great than 50Pa. As the slurry becomes thicker, via the water being extracted, they head into the ‘paste’ realm, whereupon standard centrifugal pumps reach their limit and can no longer be used. Very expensive positive displacement pumps are available but are used with great reluctance due to their initial capital cost, long lead times, specialist overhaul requirements, and high ongoing maintenance costs.

[0014],It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed.

[0015] While the present invention was developed against this background, it need not necessarily overcome any or all of the problems and difficulties referred to above. Rather, the invention may merely offer an alternative arrangement for pumping a fluid.

2018241189 05 Oct 2018

SUMMARY OF INVENTION [0016] Broadly, according to a first aspect of the present invention there is provided a centrifugal pump for pumping a slurry and operable to shear the slurry to enable, or at least assist in enabling, the slurry to flow.

[0017] The centrifugal pump may have an impeller and an element upstream of the impeller for shearing the slurry to enable, or at least assist in enabling, the slurry to flow towards the impeller.

[0018] In one arrangement, the element may be configured to merely agitate the slurry.

[0019] In another arrangement, the element may be configured to agitate the slurry and to also induce the agitated slurry to flow towards the impeller.

[0020] The impeller and the element may be operable to rotate in unison.

[0021] The impeller may have an axis of rotation, and the element may be operable to rotate in unison with the impeller about the axis of rotation.

[0022] The element may be coupled to the impeller.

[0023] More particular, the element may be mounted on an extension projecting from the impeller.

[0024] The extension and the element may be constructed as separate parts adapted to be coupled together to provide an assembly. However, an assembly of integral construction is also contemplated.

[0025] The extension may comprise a shaft extending from the impeller.

[0026] The shaft may have an end section adapted for mounting on the impeller.

[0027] More particularly, the shaft may have an end section adapted for mounting on a hub of the impeller. The mounting may be provided by way of a releasable connection; for example a threaded connection.

2018241189 05 Oct 2018 [0028] The impeller may be an open impeller or a closed impeller.

[0029] In the case of a ‘Bingham Plastics’ slurry, the shearing action breaks down the yield structure of the slurry, making it flowable. Turbulence created by the shearing effectively destroys the yield structure in ‘Bingham Plastics’ slurry, resulting in the slurry behaving as a Newtonian liquid with a viscosity about that of the coefficient of rigidity.

[0030] The centrifugal pump may also be provided with an inlet so sized that incoming flow is of sufficient velocity to destroy the yield structure of the slurry before it enters the pump. At higher velocities, typical of those found in tailings lines, when the yield stress is overcome the slurry is able to flow (effectively behaving like water) [0031] Broadly, according to a second aspect of the present invention there is provided a method of pumping slurry, the method comprising shearing the slurry to enable it to flow, and subjecting the slurry to a centrifugal pumping action.

[0032] According to a third aspect of the present invention there is provided a centrifugal pump comprising a pumping chamber, an inlet for entry of fluid into the pumping chamber, an impeller, and an element upstream of the impeller, the impeller and the element mounted for rotation within the pumping chamber about an axis of rotation, the element being configured to shear the fluid entering through the inlet.

[0033] Preferably, the impeller and element are coupled together.

[0034] Preferably, the impeller and element rotate in unison during operation of the pump.

[0035] Preferably, the impeller and element rotate in unison during operation of the pump.

[0036] Preferably, the impeller has an axis of rotation rotating around the axis of rotation, and the element rotating around the rotational axis of the impeller.

[0037] Preferably, the pump further comprises an extension provided on an inlet side of the pumping impeller extending from the impeller, the element being mounted on the extension.

2018241189 05 Oct 2018 [0038] Preferably, the extension and the element are constructed as separate parts adapted to be coupled together.

[0039] Preferably, the extension comprises a shaft extending from the impeller.

[0040] Preferably, the shaft comprises an end section adapted for mounting on a hub of the impeller.

[0041] Preferably, the end section is releasably attached to the hub.

[0042] Preferably, the inlet is configured to inhibit vortex flow of fluid entering the centrifugal pump.

[0043] Preferably, the inlet is configured by provision of a formation about the inlet.

[0044] Preferably, the formation comprises a plurality of anti-vortex ribs spaced circumferentially about the inlet.

[0045] Preferably, the inlet is so sized that incoming flow is of sufficient velocity to destroy the yield structure of the slurry before it enters the pump.

[0046] Preferably, the relevant practical size range of the inlet is about 25 to 500 mm and in particular 75 to 200 mm.

[0047] Preferably, the inlet comprises a smaller cross-sectional flow area smaller than conventional froth pumps.

[0088] Preferably, the ratio of reduction in diameter of the inlet with respect to conventional froth pumps is from 1.5 to 2 and in particular 1.8.

[0089] Preferably, the element is configured to agitate the fluid.

[0090] Preferably, the element is configured to assist the flow of the fluid towards the impeller.

[0091] Preferably, the impeller comprises an open impeller.

2018241189 05 Oct 2018 [0092] Preferably, the element is configured as a rotor having a hub and rotor blades extending radially from the hub.

[0093] Preferably, the element comprises a plurality of rotor blades arranged in a diametrally opposite relationship with respect to each other.

[0094] Preferably, the inlet comprises a first section adjacent an entry end of the inlet, and a second section adjacent the pumping chamber, the second section tapering inwardly from the first section and opens onto the pumping chamber.

[0095] According to a fourth aspect of the invention there is provided an assembly comprising a pumping impeller and an element operable to shear fluid prior to pumping thereof by the impeller.

[0096] Preferably, the impeller and element are coupled together.

[0097] Preferably, the impeller and element rotate in unison during operation of the assembly.

[0098] Preferably, the impeller and element rotate in unison during operation of the assembly.

[0099] Preferably, the impeller has an axis of rotation, and the element rotating around the axis of rotational of the impeller.

[00100] Preferably, the assembly further comprises an extension provided on an inlet side of the impeller extending from the impeller, the element being mounted on the extension.

[00101] Preferably, the extension and the element are constructed as separate parts adapted to be coupled together.

[00102] Preferably, the extension comprises a shaft extending from the impeller.

[00103] Preferably, the shaft comprises an end section adapted for mounting on a hub of the impeller.

2018241189 05 Oct 2018 [00104] Preferably, the end section is releasably attached to the hub.

[00105] Preferably, the element is configured to agitate the fluid.

[00106] Preferably, the element is configured to assist the flow of the fluid towards the impeller.

[00107] Preferably, the impeller comprises an open impeller.

[00108] Preferably, the element is configured as a rotor having a hub and rotor blades extending radially from the hub.

[00109] Preferably, the element comprises a plurality of rotor blades arranged in a diametrally opposite relationship with respect to each other.

[00110] Preferably, the inlet comprises a first section adjacent an entry end of the inlet, and a second section adjacent the pumping chamber, the second section tapering inwardly from the first section and opens onto the pumping chamber.

[00111] According to a fifth aspect of the invention there is provided a method of pumping a fluid, the method comprising use of a centrifugal pump according to the first or third aspect of the invention.

[00112] According to a sixth aspect of the invention there is provided a method of handling a thick slurry (such as ‘Bingham Plastics’ slurry), the method comprising use of a centrifugal pump according to the first or third aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [00113] Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

2018241189 05 Oct 2018

Figure 1 is a schematic perspective view of a first embodiment of a centrifugal pump according to the invention;

Figure 2 is a sectional side view of first embodiment of the centrifugal pump;

Figure 3 is an exploded view of a portion of the centrifugal pump;

Figure 4 is a fragmentary perspective view, on an enlarged scale, illustrating in particular an inlet end of the pump and an element for shearing fluid entering the inlet;

Figure 5 is a fragmentary sectional view, on an enlarged scale, illustrating in particular the pumping chamber and associated componentry;

Figure 6 is a perspective view of an assembly comprising a pumping impeller, a shaft and the element for shearing fluid undergoing pumping;

Figure 7 is a view of the assembly shown in Figure 6 but in an exploded condition;

Figure 8 a schematic perspective view of a second embodiment of a centrifugal pump according to the invention;

Figure 9 is a sectional side view of the second embodiment of the centrifugal pump;

Figure 10 is an exploded view of the second embodiment of the centrifugal pump;

Figure 11 is a fragmentary sectional view, on an enlarged scale, illustrating in particular the pumping chamber and associated componentry;

Figure 12 is a perspective view of an assembly comprising a pumping impeller, a shaft and the element for shearing fluid undergoing pumping; and

Figure 13 is a view of the assembly shown in Figure 12 but in an exploded condition.

[00114] The drawings shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the present invention.

2018241189 05 Oct 2018 [00115] The figures depict embodiments of the invention. The embodiments illustrates certain configurations; however, it is to be appreciated that the invention can take the form of many configurations, as would be obvious to a person skilled in the art, whilst still embodying the present invention. These configurations are to be considered within the scope of this invention.

DESCRIPTION OF EMBODIMENTS [00116] Referring to Figures 1 to 7, there is shown a first embodiment of a centrifugal pump for handling thick slurry, such as ‘Bingham Plastics’ slurry.

[00117] In the arrangement shown, the centrifugal pump 10 comprises a pump body 11 comprising a pump casing 13 and a pedestal 15 on which the pump casing is supported. The pump casing 13 accommodates a pumping chamber 17 having an inlet 21 and an outlet 22. The pumping chamber 17 is of involute configuration, as would be understood by a person skilled in the art.

[00118] A pump impeller 25 is mounted within the pumping chamber 17 for rotation about a rotational axis. The rotational axis is depicted schematically in the drawings by a broken line identified by reference numeral 27. The pump impeller 25 is mounted on a pump shaft 29 which is rotatably supported by the pedestal 15 and which is adapted to be coupled to a drive motor (not shown).

[00119] The pump impeller 25 has a front side 31 and a rear side 33. The front side 31 provides an inlet side of the pump impeller 25 and faces the inlet 21. More particularly, the inlet 21 is aligned with and centred upon the axis of rotation 27 of the impeller 25.

[00120] The impeller 25 comprises a central hub 35 and a plurality of pumping vanes 36 mounted on the hub. In the arrangement shown, the impeller 25 comprises a closed impeller featuring a front shroud 37 and an inlet opening which provides the impeller eye 39.

[00121] An element 41 is provided upstream of the impeller 25 for shearing slurry entering through inlet 21 to enable, or at least assist in enabling, the slurry to flow towards the impeller.

2018241189 05 Oct 2018 [00122] In this embodiment, the element 41 is configured to agitate the slurry and to also induce the agitated slurry to flow towards the impeller 25. For this purpose, the element 41 is configured as a supplementary impeller 43 having a hub 45 and vanes

47. In other embodiments, the element 41 may be configured to merely agitate the slurry, with suction only being relied upon to induce flow towards the impeller 25.

[00123] The element 41 is coupled to the impeller 25 to rotate in unison with the impeller about the axis of rotation 27.

[00124] More particular, the element 41 is mounted on an extension 51 projecting from the impeller 25. The extension 51 is provided on the front side 31 of the impeller 25 about the axis of rotation 27. The extension 51 protrudes from the impeller 25 towards and into the inlet 21, as best seen in Figures 2 and 5.

[00125] The impeller 25 and the element 41 together provide an assembly 52, which in the arrangement shown also includes the extension 51.

[00126] In the arrangement shown, the extension 51 comprises a shaft 53 having an inner end section 55 and an outer end section 57. The shaft 53 is tapered, with the outer end section 57 being of smaller diameter than the inner end section 55. In other words, the shaft 53 tapered outwardly from the outer end section 57 to the inner end section 55. It should, however, be understood that the shaft 53 need not necessarily be tapered, and in fact may be cylindrical or any other appropriate configuration.

[00127] The inner end section 55 of the shaft 53 is adapted to be mounted on the hub 35 of the impeller 25, with the shaft 53 extending outwardly from the impeller through the impeller eye 39. The shaft 53 and the impeller eye 39 are sized to provide sufficient clearance about the shaft for fluid entry into the impeller 25 via the impeller eye 39.

[00128] The inner end section 55 of the shaft 53 is configured for threaded engagement with the hub 35. In the arrangement shown in the inner end section 55 of the shaft 53 is provided with a male formation the 58 for threaded engagement with a counterpart female threaded formation 59 provided on the hub 35 adjacent the front side 31 thereof.

2018241189 05 Oct 2018 [00129] The outer end section 57 of the shaft 53 is adapted to support the element

41. For this purpose, the outer end section 57 has a stub portion 60 upon which the hub 45 of element 41 is mounted.

[00130] The inlet 21 is so sized that incoming slurry flows at a sufficient velocity to destroy the yield structure of the slurry before it enters the centrifugal pump 10. In a particular arrangement, the relevant practical size range of the inlet is about 75 to 200 mm; however, alternative arrangements could have size range of the inlet of about 25 to 500 mm. This may require that the inlet 21 be smaller cross-sectional flow area than is the case with conventional froth pumps; in particular, the ratio of reduction in diameter of the inlet with respect to conventional froth pumps is about 1.8; however, it could range from 1.5 to 2.

[00131] A relatively large inlet can result in the suction line flow not having a sufficient velocity to destroy the yield structure of the slurry before it enters the pump. In such cases thick paste will be travelling down the suction line as a ‘sliding bed’, with very high friction, which could result in pump cavitation.

[00132] In this embodiment, the inlet 21 is configured to provide a first section 21a adjacent the entry end 21c of the inlet and a second section 21b adjacent the pumping chamber 17. The first section 21a is generally cylindrical and defines the zone within which the element 41 is accommodated. The second section 21b tapers inwardly from the first section 21a and opens onto the pumping chamber 17. The tapering configuration of the second section 21b serves to increase the velocity profile of the fluid flow, thereby increasing the shear.

[00133] In operation, slurry flow along the suction line of the centrifugal pump 10 enters the inlet 21 whereupon it is exposed to the element 41 rotating in unison with the impeller 25. The rotating element 41 agitates and shears the slurry, enabling it to flow towards the impeller 25. In this embodiment, the element 41 also induces flow of the slurry towards the impeller 25, thereby supplementing the effect of suction in inducing flow.

[00134] Referring now to Figures 8 to 13, there is shown a second embodiment of a centrifugal pump 10 for handling thick slurry, such as ‘Bingham Plastics’ slurry. The

2018241189 05 Oct 2018 second embodiment is similar in many respects to the first embodiment and so similar reference numerals are used to denote similar parts.

[00135] In this second embodiment, the impeller 25 is an open impeller (rather than a closed impeller as used in the first embodiment).

[00136] Further in this second embodiment, the element is 41 configured to merely agitate and shear the slurry, and not induce it to flow towards the impeller 25. With this arrangement, flow is induced only by suction provided by the pump 10.

[00137] More particularly, the element 41 is configured as a rotor 81 having a hub 83 and rotor blades 85 extending radially from the hub. In the arrangement shown, there are two rotor blades 85 in diametrally opposed relation.

[00138] Still further in this second embodiment, the inlet 21 is simply of a cylindrical configuration, comprising a cylindrical side wall 21 d extending from the entry end 21c to the pumping chamber 17. The inlet 21 is sized and configured to match the impeller eye 39.

[00139] The foregoing disclosure is intended to explain how to fashion and use the particular embodiment described, rather than to limit the true, intended, and fair scope and spirit of the invention. The foregoing description is not intended to be exhaustive, nor to be limited to the precise forms disclosed.

[00140] Further, it should be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

[00141] Reference to any positional descriptions, such as inner, outer, top”, “bottom and “side”, are to be taken in context of the embodiments described (and depicted in the drawings in the case of the first embodiment), and are not to be taken as limiting the invention to the literal interpretation of the term but rather as would be understood by the skilled addressee.

[00142] Additionally, where the terms “system”, “device”, and “apparatus are used in the context of the invention, they are to be understood as including reference to any group of functionally related or interacting, interrelated, interdependent or associated

2018241189 05 Oct 2018 components or elements that may be located in proximity to, separate from, integrated with, or discrete from, each other.

[00143] Throughout this specification, unless the context requires otherwise, the word comprise or variations such as comprises or comprising, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (41)

1. A centrifugal pump comprising a pumping chamber, an inlet for entry of fluid into the pumping chamber, an impeller, and an element upstream of the impeller, the impeller and the element mounted for rotation within the pumping chamber about an axis of rotation, the element being configured to shear the fluid entering through the inlet.

2. A pump according to claim 1 wherein the impeller and element are coupled together.

3. A pump according to claims 1 or 2 wherein the impeller and element rotate in unison during operation of the pump.

4. A pump according to any one of claims 1 to 3 wherein the impeller and element rotate in unison during operation of the pump.

5. A pump according to claim 4 wherein the impeller has an axis of rotation rotating around the axis of rotation, and the element rotating around the rotational axis of the impeller.

6. A pump according to any one of claims 1 to 5 further comprising an extension provided on an inlet side of the pumping impeller extending from the impeller, the element being mounted on the extension.

7. A pump according to claim 6 wherein the extension and the element are constructed as separate parts adapted to be coupled together.

8. A pump according to claims 6 or 7 wherein the extension comprises a shaft extending from the impeller.

9. A pump according to claim 8 wherein the shaft comprises an end section adapted for mounting on a hub of the impeller.

10. A pump according to claim 9 wherein the end section is releasably attached to the hub.

11. A pump according to any one of the preceding claims wherein the inlet is configured to inhibit vortex flow of fluid entering the centrifugal pump.

2018241189 05 Oct 2018

12. A pump according to claim 11 wherein the inlet is configured by provision of a formation about the inlet.

13. A pump according to claim 12 wherein the formation comprises a plurality of antivortex ribs spaced circumferentially about the inlet.

14. A pump according to any one of the preceding claims wherein the inlet is so sized that incoming flow is of sufficient velocity to destroy the yield structure of the slurry before it enters the pump.

15. A pump according claim 14 wherein the relevant practical size range of the inlet is about 25 to 500 mm and in particular 75 to 200 mm.

16. A pump according to claim 15 wherein the inlet comprises a smaller crosssectional flow area smaller than conventional froth pumps.

17. A pump according to claim 16 wherein the ratio of reduction in diameter of the inlet with respect to conventional froth pumps is from 1.5 to 2 and in particular 1.8.

18. A pump according to any one of claims 1 to 17 wherein the element is configured to agitate the fluid.

19. A pump according to any one of the preceding claims wherein the element is configured to assist the flow of the fluid towards the impeller.

20. A pump according to any one of claims 1 to 18 wherein the impeller comprises an open impeller.

21. A pump according to claim 20 wherein the element is configured as a rotor having a hub and rotor blades extending radially from the hub.

22. A pump according to claim 21 wherein the element comprises a plurality of rotor blades arranged in a diametrally opposite relationship with respect to each other.

23. A pump according to any one of the preceding claims wherein the inlet comprises a first section adjacent an entry end of the inlet, and a second section adjacent the pumping chamber, the second section tapering inwardly from the first section and opens onto the pumping chamber.

2018241189 05 Oct 2018

24. An assembly comprising a pumping impeller and an element operable to shear fluid prior to pumping thereof by the impeller.

25. An assembly according to claim 24 wherein the impeller and element are coupled together.

26. An assembly according to claims 24 or 25 wherein the impeller and element rotate in unison during operation of the assembly.

27. An assembly according to any one of claims 24 to 26 wherein the impeller and element rotate in unison during operation of the assembly.

28. An assembly according to claim 27 wherein the impeller has an axis of rotation, and the element rotating around the axis of rotational of the impeller.

29. An assembly according to any one of claims 24 to 28 further comprising an extension provided on an inlet side of the impeller extending from the impeller, the element being mounted on the extension.

30. An assembly according to claim 29 wherein the extension and the element are constructed as separate parts adapted to be coupled together.

31. An assembly according to claims 29 or 30 wherein the extension comprises a shaft extending from the impeller.

32. An assembly according to claim 31 wherein the shaft comprises an end section adapted for mounting on a hub of the impeller.

33. An assembly according to claim 32 wherein the end section is releasably attached to the hub.

34. An assembly according to any one of claims 24 to 33 wherein the element is configured to agitate the fluid.

35. An assembly according to any one of claims 24 to 33 wherein the element is configured to assist the flow of the fluid towards the impeller.

36. An assembly according to any one of to any one of claims 24 to 35 wherein the impeller comprises an open impeller.

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37. An assembly according to claim 36 wherein the element is configured as a rotor having a hub and rotor blades extending radially from the hub.

38. An assembly according to claim 37 wherein the element comprises a plurality of rotor blades arranged in a diametrally opposite relationship with respect to each other.

39. An assembly according to any one claims 24 to 38 wherein the inlet comprises a first section adjacent an entry end of the inlet, and a second section adjacent the pumping chamber, the second section tapering inwardly from the first section and opens onto the pumping chamber.

40. A method of pumping a fluid, the method of pumping fluid comprising use of a centrifugal pump as defined in any one of claims 1 to 23.

41. A method of handling a thick slurry (such as ‘Bingham Plastics’ slurry), the method comprising use of a centrifugal pump as defined in any one of claims 1 to 23.