WO2008062097A1

WO2008062097A1 - Rotor for a flotation machine, method for forming same, and method for maintenance of same

Info

Publication number: WO2008062097A1
Application number: PCT/FI2007/050605
Authority: WO
Inventors: Antti Rinne
Original assignee: Outotec Oyj
Priority date: 2006-11-22
Filing date: 2007-11-09
Publication date: 2008-05-29
Also published as: CL2007003322A1; FI20061027A; FI20061027A0; PE20081205A1; EA014815B1; FI119047B; EA200900661A1; BRPI0719296B1; BRPI0719296A2

Abstract

The invention relates to a rotor (1) for a flotation machine for dispersing air into slurry around the ro- tor, the rotor comprising a body (2) equipped with a set of blades (3). The body (2) is assembled from ra- dial sector modules (9). The rotor comprises fastening means (10) for joining the sector modules (9) to each other. In the method for forming a rotor, radial sec- tor modules (9) are produced, and the rotor body (2) is assembled from a number of sector modules (9). Fi- nally, in the method for maintenance of a rotor, a damaged sector module (9) is detached from the body (2) and replaced by a defect-free sector module.

Description

ROTOR FOR A FLOTATION MACHINE, METHOD FOR FORMING SAME, AND METHOD FOR MAINTENANCE OF SAME

FIELD OF THE INVENTION The invention relates to a rotor for a flotation machine as defined in the preamble of claim 1. The invention also relates to a method as defined in the preamble of claim 21. Furthermore, the invention relates to a method as defined in the preamble of claim 22.

BACKGROUND OF THE INVENTION

The invention relates generally to a flotation machine used for separating valuable ingredients for example from slurry containing minerals in a so- called flotation process. The object of the invention, namely the rotor of the flotation machine, is rotated in a cell that contains slurry, or a so-called flotation cell, such that the rotor sets the slurry in mo- tion and disperses air, which is needed to produce froth, into the slurry in order to form air bubbles. The air is let into the rotor through an air communication that is provided in the rotation shaft of the rotor. Air bubbles that are dispersed into the slurry rise to the surface of the slurry, and the ingredients to be separated adhere to the air bubbles in the froth. The ingredients that are to be separated can then be removed with the froth. The rotor is used together with a fixed stator encircling the rotor, which stator will not be described in any detail in this disclosure .

Different rotors for flotation machines are known in prior art for example from publications WO 2006/037843 Al, WO 02/081093 Al, US 2004/0112835 Al, US 6,805,243 Bl and US 6,772,885. These rotors nor- mally comprise a body equipped with a set of blades which extend substantially radially outwards relative to the center of the rotor and taper toward their lower end. The rotor body further comprises an upper wall extending in cross direction relative to the blades at the upper end of the blades such that mutually adjacent blades and the portion of the upper wall between them define ducts between each other. The upper wall defines an air space below in the upper part of the rotor, into which air space air can be conducted. In a set of air channels, each one opens at one end into the air space and at the other end into a duct to conduct air from the air space through a duct into the slurry. When in rotation, the rotor causes slurry to flow through the ducts in an upward direction and radially further out of the rotor.

Rotors such as these may have a diameter ranging from half a meter up to nearly two meters, which means they are rather large and heavy. The prior-art rotor is made of a single welded steel plate body having a wear resistant coating that is achieved by molding and may be made for example from natural rubber or polyurethane . In larger rotors this has meant producing large but dimensionally high-precision welded steel plate bodies and purchasing and maintaining expensive and large molds. Due to the production method, the price of large rotors is quite high. More deviations from the usual quality have been found at the larger end of the present rotor diameter sizes (having a diameter of more than one meter) than with smaller sizes, which has lead to even more stricter dimensional precision limits. Large article sizes together with strict dimensional precision requirements is a very unfavorable combination. Rotor is a part that wears and has to be reconditioned from time to time by coating it and by fixing other potential damages. A problem with the prior-art rotor is that for fixing a damage or for maintenance the entire rotor has to be removed from the flotation cell, even if only a part of it required fixing, and it must be transported to a maintenance site. Handling, transportation and storage of large and heavy parts is difficult and costly.

OBJECTIVE OF THE INVENTION The objective of the invention is to eliminate the drawbacks referred to above.

One specific objective of the invention is to disclose a rotor which can be considerably larger than the prior-art sizes. A further objective of the invention is to disclose a rotor, the structure of which allows the production of parts that are smaller than heretofore, in a manner easier and more affordable than heretofore . Another objective of the invention is to disclose a rotor that can be maintained more affordably than heretofore.

SUMMARY OF THE INVENTION The rotor in accordance with the invention is characterized by what has been presented in claim 1. Furthermore, the production method in accordance with the invention is characterized by what has been presented in claim 21. Finally, the maintenance method in accordance with the invention is characterized by what has been presented in claim 22.

In accordance with the invention, the rotor body is assembled from radial sector modules. The rotor comprises fastening means for joining the sector modules together. Thanks to the modular rotor structure, the invention provides the advantage of considerable reduction of size of the parts that require dimensional precision, while at the same time the molding tools required for coating the modules, and the mold expenses, become smaller as well. Rotors that are larger than before can thus be produced in an affordable manner. Moreover, the manufacture, handling, transportation and storage of sector modules and other rotor parts that are smaller and lighter than a whole rotor is easier and more affordable than with a whole rotor. Thanks to the modular structure, the production quality will be improved as well. Reconditioning the rotor only requires changing those sector modules that need reconditioning or replacing with a new one. The rotor can preferably be maintained inside the flotation cell without the need to remove the entire rotor from the cell.

In one embodiment of the rotor, the blades ex- tend substantially radially outwards relative to the center of the rotor.

In one embodiment of the rotor, the rotor comprises an upper wall which extends in cross direction relative to the blades at the upper end of the blades in such manner that mutually adjacent blades and the portion of the upper wall between them define radial ducts between each other. The upper wall defines an air space below, which is positioned in the upper part of the rotor and into which air space air can be conducted. In one embodiment of the rotor, the ducts comprise air ducts and slurry ducts.

In one embodiment of the rotor, the rotor comprises a set of air channels, each of which opens at one end into the air space and at the other end into an air duct in order to conduct air from the air space through an air duct into the slurry. In one embodiment of the rotor, the air ducts and the slurry ducts are arranged in the rotor in a mutually alternate manner.

In one embodiment of the rotor, the body is di- vided into sector modules in a number of n, wherein the sector division angle α is 360°/n, and the number n is equal to or greater than 2.

In one embodiment of the rotor, the number n of the sector modules is preferably 2 - 12. Preferably, the sector modules are mutually identical. However, they do not have to be identical, but may instead be different .

In one embodiment of the rotor, each sector module comprises at least part of an air duct and at least part of a slurry duct.

In one embodiment of the rotor, each sector module comprises two blades and part of the upper wall, defining an air duct and half of a slurry duct on both sides of the air duct. In one embodiment of the rotor, the fastening means comprises a cover flange, which is fitted on top of the upper wall portions of the sector modules. The sector modules are fastened to the cover flange to form the rotor. The rotation shaft of the rotor is preferably fastened to the cover flange. The cover flange preferably has a central aperture, through which the air conducted via the rotation shaft is conducted further into the air space of the rotor.

In one embodiment of the rotor, the sector mod- ules are fastened to the cover flange by means of bolts.

In one embodiment of the rotor, the fastening means comprises an adhesive joint, by which the sector modules are fastened to the cover flange and/or to each other. In one embodiment of the rotor, the rotor comprises a central slurry space surrounded by the air ducts in a circular manner, the slurry space being defined at the top by the upper wall and opening downwards to receive the slurry flow from below into the inside of the slurry space, and opening radially further in lat- eral direction into the slurry ducts for removing the slurry flow from the slurry space through the slurry ducts .

In one embodiment of the rotor, the rotor comprises a bottom collar which is concentric with the ro- tor, placed at the lower end of the blades and arranged to encircle part of the slurry space to guide the slurry flow into the slurry space.

In one embodiment of the rotor, the bottom collar has a cylindrical shape. In one embodiment of the rotor, the bottom collar is shaped as a truncated cone which enlarges towards its lower end. The inner surface of the bottom collar is preferably convexly curved. A convexly curved inner surface promotes the formation of the preferred flow pattern. Correspondingly , the outer surface of the bottom collar may be concavely curved to form the preferred flow pattern. Alternatively, the outer and/or inner surface of the bottom collar may be straight.

In one embodiment of the rotor, the bottom col- lar is a single uniform part that is fastened to the sector modules.

In one embodiment of the rotor, the bottom collar is divided into collar sector parts using angular division corresponding to that of the sector modules. In this case, a collar sector part together with a sector module forms a uniform construction, and the bottom collar is formed as the rotor body is being assembled from the sector modules.

In one embodiment of the rotor, the rotor com- prises a set of internal blades which enlarge towards their upper end and extend in the slurry space from the intersection of the blades defining an air duct substantially to the opposite side relative to the protruding direction of the blades, towards the center of the rotor. Each sector module comprises at least one inter- nal blade.

In the method for forming a rotor for a flotation machine which comprises a body equipped with blades, radial sector modules are produced, the rotor body is assembled by joining together a number of sec- tor modules.

In the method for maintenance of a rotor for a flotation machine which comprises a body equipped with blades, a damaged sector module is detached from the body and replaced by a defect-free sector module.

LIST OF FIGURES

In the following section, the invention will be described in detail with the aid of examples of its embodiments, referring to the accompanying drawing, in which

Fig. 1 axonometrically represents a first embodiment of the rotor in accordance with the invention as seen obliquely from above and having six sector modules, Fig. 2 represents an exploded view of the rotor of Fig. 1, with the cover flange, the bottom collar and one sector module separated,

Fig. 3 represents the rotor of Fig. 1 as seen from the side, Fig. 4 represents the rotor of Fig. 1 as seen from above,

Fig. 5 represents a sector module of a second embodiment of the rotor in accordance with the invention, Fig. 6 axonometrically represents an exploded view of a rotor in accordance with a third embodiment of the invention as seen obliquely from above and comprising five sector modules with the cover flange, the bottom collar and one sector module separated.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 - 4 show a rotor 1 of a flotation machine used for dispersing air into slurry that is mixed by the rotor in a flotation cell (not shown) . The rotor is fastened to a rotation shaft (not shown) . The rotor comprises a cover flange 11 to which the rotation shaft can be fastened, a modular body 2 and a bottom collar 14.

The rotor body 2 comprises blades 3, there being 12 of them in the exemplary embodiment of Fig. 1 - 4. The blades 3 extend radially outwards relative to the center of the rotor and taper in a curved manner towards their lower end. The rotor body 2 further comprises an upper wall 4, extending in cross direction (horizontally) relative to the blades 3 at the upper end of the blades 3 so that mutually adjacent blades and the portion of the upper wall 4 between them define alternating radial air ducts 5 and slurry ducts 6 between each other. Furthermore, the inclined part of the upper wall 4 which extends towards the center de- fines an airspace 7 below in the upper part of the rotor. Air can be conducted into the air space 7 through air communication (not shown) arranged in a manner known per se in conjunction with the rotation shaft. The body 2 further comprises a set of air channels 8, each of which opens at one end into the air space 7 and at the other end into an air duct 5. Through an air channel 8, air is able to flow from the air space 7 through an air duct 5 into the slurry. When the rotor is rotating it causes the slurry to flow upwards through the air ducts and the slurry ducts and radially out of the rotor. In the exemplary embodiment of Fig. 1 - 4, the body 2 is radially divided into six sector modules

9 that are connected to each other by fastening means

10 to form said body 2. The sector modules 9 are all mutually identical. In this case, the sector division angle α of the sector modules 9 is 60°. In the example of Fig. 6, the body 2 of the rotor 1 is divided into five identical sector modules 9. In some other embodiments there may be fewer or more sector modules 9, the body 1 comprising preferably 2 - 12 sector modules .

Still referring to Fig. 1 - 4, each sector module 9 comprises at least part of an air duct 5 and at least part of a slurry duct 6. As shown in Fig. 2, a sector module 9 of the exemplary embodiment comprises two blades 3 and part of the upper wall 4, defining an air duct 5 and half of a slurry duct 6 on both sides of the air duct 5. A rotor assembled from six sector modules 9 has therefore six air ducts 5 and, correspondingly, six slurry ducts 6. The sector modules 9 are connected to each other by means of a circular cover flange 11. The cover flange 11 is fitted on top of the portions of the upper wall 4 of the sector modules 9 and against them, as they form to- gether a planar surface, and the sector modules are fastened to the cover flange 11 by means of bolts 12. Alternatively or additionally, the sector modules 9 can be fastened to each other and/or to the cover flange by gluing. The structural and operational principle of the rotor shown in the examples of the figures corresponds to that disclosed in international published patent application WO 2006/037843 Al by the same applicant. It is obvious that the modular principle of the rotor structure can be applied to any known rotor for a flotation machine, regardless of the shape and the operational principle of the rotor.

Thus the rotor 1 also comprises a central slurry space 13, surrounded by the air ducts 5 in a circular manner, defined on the top by the upper wall 4, and opening at the bottom to receive the slurry flow from below into the inside of the slurry space 13. The slurry space 13 opens radially further in lateral direction into the slurry ducts 6 to remove the slurry flow from the slurry space 13 through the slurry ducts 6. The rotor 1 further comprises a bottom collar 14 that is concentric with the rotor and shaped as a truncated cone which enlarges towards its lower end, placed at the lower end of the blades 3 and ar- ranged to encircle part of the slurry space 13 to guide the slurry flow into the slurry space. As shown in Fig. 2, the inner surface 15 of the bottom collar 14 is preferably convexly curved to form as preferable a flow pattern as possible. In the examples of Fig. 1- 4 and 6 the bottom collar 14 is a single uniform part that is fastened to the sector modules 9.

Fig. 5 illustrates one sector module 9, a number of which can be assembled together to form a rotor in which the bottom collar 14 is divided into collar sector parts 16 using angular division corresponding to that of the sector modules 9, and a collar sector part 16 together with a sector module 9 forms a uniform construction.

The rotor 1 further comprises a set of inter- nal blades 17 which enlarge towards their upper end and extend in the slurry space 13 from the intersection 18 of the blades 3 defining an air duct 6 substantially to the opposite side relative to the protruding direction of the blades, towards the center of the rotor. Each sector module 9 comprises one such internal blade 17. The invention is not limited merely to the examples of its embodiments referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.

Claims

1. A rotor (1) for a flotation machine for dispersing air into slurry around the rotor, the rotor comprising a body (2) equipped with a set of blades (3) , cha r a c t e r i z e d in that the body (2) is assembled from radial sector modules (9), and that the rotor comprises fastening means (10) for joining the sector modules to each other.

2. The rotor in accordance with claim 1, cha r a c t e r i z e d in that the blades (3) extend substantially radially outwards relative to the center of the rotor.

3. The rotor in accordance with claim 2, cha r a c t e r i z e d in that it comprises an upper wall (4) extending in cross direction relative to the blades at the upper end of the blades so that mutually adjacent blades and the part of the upper wall between them define radial ducts (5, 6) between each other, the upper wall also defining an air space (7) below in the upper part of the rotor, into which air space air can be conducted.

4. The rotor in accordance with claim 3, cha r a c t e r i z e d in that the ducts (5, 6) comprise air ducts (5) and slurry ducts (6) .

5. The rotor in accordance with claim 4, cha r a c t e r i z e d in that it comprises a set of air channels (8), each of which opens at one end into the air space (7) and at the other end into an air duct (5) to conduct air from the air space through an air duct into the slurry.

6. The rotor in accordance with claim 4 or 5, cha r a c t e r i z e d in that the air ducts (5) and the slurry ducts (5) are arranged in the rotor in a mutually alternate manner.

7. The rotor in accordance with any one of claims 1 - 6, cha r a c t e r i z e d in that the body (2) is divided into sector modules (9) in a number of n, wherein the sector division angle α is 360°/n, and n is equal to or greater than 2.

8. The rotor in accordance with claim 7, cha r a c t e r i z e d in that the number n of the sector modules (9) is preferably 2 - 12.

9. The rotor in accordance with any one of claims 1 - 8, cha r a c t e r i z e d in that the sector modules (9) are mutually identical.

10. The rotor in accordance with any one of claims 1 - 9, cha r a c t e r i z e d in that each sector module (9) comprises at least part of an air duct (5) and at least part of a slurry duct (6) .

11. The rotor in accordance with claim 10, cha r a c t e r i z e d in that each sector module (9) comprises two blades (3) and part of the upper wall (4), defining an air duct (5) and half of a slurry duct (6) on both sides of the air duct.

12. The rotor in accordance with any one of claims 1 - 11, cha r a c t e r i z e d in that the fastening means (10) comprises a cover flange (11), fitted on top of the upper walls (4) of the sector modules (9), and the sector modules are fastened to the cover flange (11) to form the rotor.

13. The rotor in accordance with claim 12, cha r a c t e r i z e d in that the sector modules (9) are fastened to the cover flange (11) and/or to each other by screws/bolts (12), by welding, and/or by gluing.

14. The rotor in accordance with any one of claims 4 - 13, cha r a c t e r i z e d in that the rotor (1) comprises a central slurry space (13), surrounded by the air ducts (5) in a circular manner, the slurry space (13) being defined at the upper end by the upper wall (4), opening at the bottom to receive the slurry flow from below into the inside of the slurry space, and opening radially further in lateral direction into the slurry ducts (6) to remove the slurry flow from the slurry space through the slurry ducts .

15. The rotor in accordance with claim 14, cha r a c t e r i z e d in that the rotor (1) comprises a bottom collar (14) which is concentric with the rotor, placed at the lower end of the blades (3) and arranged to encircle part of the slurry space (13) to guide the slurry flow into the slurry space.

16. The rotor in accordance with claim 15, cha r a c t e r i z e d in that the bottom collar (14) is shaped as a cylinder or a truncated cone which enlarges towards its lower end.

17. The rotor in accordance with claim 16, cha r a c t e r i z e d in that the inner surface (15) of the bottom collar (14) is convexly curved.

18. The rotor in accordance with any one of claims 15 - 17, cha r a c t e r i z e d in that the bottom collar (14) is a single uniform part fastened to the sector modules (9) .

19. The rotor in accordance with any one of claims 11 - 18, cha r a c t e r i z e d in that the bottom collar (14) is divided into collar sector parts (16) using angular division corresponding to that of the sector modules (9); and that a collar sector part (16) together with a sector module (9) forms a uniform construction .

20. The rotor in accordance with any one of claims 14 - 19, cha r a c t e r i z e d in that the rotor (1) comprises a set of internal blades (17) which enlarge towards their upper end and extend in the slurry space (13) from the intersection (18) of the blades (3) defining an air duct (6) substantially to the opposite side relative to the protruding direction of the blades, towards the center of the rotor; and that each sector module (9) comprises at least one internal blade (17) .

21. A method for forming a rotor (1) for a flotation machine comprising a body (2) equipped with blades (3) , cha r a c t e r i z e d in that radial sector modules (9) are produced, and the rotor body (2) is assembled by joining together a number of sector modules .

22. A method for maintenance of a rotor (1) of a flotation machine comprising a body (2) equipped with blades (3) , cha r a c t e r i z e d in that a damaged sector module (9) is detached from the body (2) and replaced by a defect-free sector module.