WO2003078013A2

WO2003078013A2 - Flotation arrangement and method

Info

Publication number: WO2003078013A2
Application number: PCT/FI2003/000171
Authority: WO
Inventors: Heikki Oravainen
Original assignee: Outokumpu Oyj
Priority date: 2002-03-18
Filing date: 2003-03-06
Publication date: 2003-09-25
Also published as: FI115447B; AR039006A1; AU2003208381A8; FI20020500A7; WO2003078013A3; AU2003208381A1; FI20020500A0; PE20030878A1

Abstract

The invention relates to a flotation arrangement (1, 15) for flotating minerals or the like from slurries containing these particles, said flotation arrangement comprising a flotation cell (3) including edges (2) and a bottm (10), and a mixing mechanism arranged in the flotation cell, elements for feeding air inot the cell and elements for feeding material to be flotated into the cell and for removing the flotated material out of the cell, so that in connection with the top edge (4) of the flotation cell (3) there is arranged at least one support element (6, 14) for facilitating the discharge of the foam layer (5) and for supporting the foam layer (5). In addition, the invention relates to a method for flotating minerals or the like from slurries containing these particles by means of a flotation arrangement (1, 15), said flotation arrangement comprising a flotation cell (3) including edges (2) and a bottom (10), and a mixing mechanism arranged in the flotation cell, elements for feeding air into the cell and elements for feeding material to be flotated into the cell and for removing the flotated material out of the cell, so that the foam layer (5) is supported and its removal is facilitated by at least one support element (6, 14) arranged in connection with the top edge (4) of the flotation cell (3).

Description

FLOTATION ARRANGEMENT AND METHOD

The invention relates to a flotation arrangement and method, defined in the preambles of the independent claims, for flotating minerals or the like from slurries containing these particles.

Generally a flotation machine used for recovering valuable ingredients, such as metal concentrates, comprises a flotation cell provided with an inlet aperture for feeding slurry into the cell and an outlet aperture for removing the non-flotated material from the flotation cell. Flotation cells can be single mixing vessels, or they can be coupled in series or in parallel. In shape, they can be rectangular or cylindrical, with a horizontal or vertical position. The air needed for producing the foam is fed in through a hollow rotatable axis, which axis is connected to an agitating member that mixes the slurry in order to maintain the slurry in suspension. When the agitator rotates, air is fed into the slurry, and air bubbles are dispersed in the slurry. The cell can also be pneumatic, in which case air is fed to the cell through specific elements, and mechanical mixing is not applied. Into the flotation cell, there are also fed reagents attached onto the surface of the valuable particles that are contained in the slurry and should be recovered. These reagents make the valuable particles hydrophobic, and thus help them to be attached to the air bubbles. When the valuable particles are attached to the air bubbles, they start rising upwards, towards the free top surface of the flotation cell, where they form a stabile foam bed. From the foam layer, the valuable particles rise further out of the cell to discharge chutes. In a so-called reversed flotation, the useless ingredients are made hydrophobic, in which case the valuable material remains non-flotated in the flotation process.

Nowadays the trend is towards using vertical cells that are still cylindrical and normally level-based. One of the recurring problems is that the mineral particles that are already attached to the gas bubbles cannot be discharged from the flotation cell, because the circulations created in the cell and particularly on the surface and top part thereof are too weak or oriented in a wrong direction, i.e. they are not capable of transferring the flotated gas bubbles out of the cell. It is often necessary to provide several flotation cells in succession in order to achieve the desired end result. From the practical point of view, an advantageous result in obtaining the foam in the discharge chutes requires that there is created a sufficiently thick foam layer, depending on the mineral to be flotated and the stage in the flotation process. Usually a good result in obtaining the foam in the discharge chutes requires a relatively thick foam layer.

If the slurry viscosity is high, large amounts of air cannot be dispersed therein, because the air bubbles grow too big and thus hinder the foam from being obtained over the cell edge. In that case, when the slurry surface is low, the foam layer in the cell is supported against the cell edges and is well formed, but it is more difficult to get it out of the cell due to the limited amount of air. The amount of air is not sufficient for lifting the foam layer out of the cell. Particularly with low-content ores, such as precious metals, the problem often is the fact that the foam bed in the top part of the cell collapses, because the length of the slurry edge is too long with respect to the required concentrate production. On the other hand, such foam beds that are highly loaded can grow to be so heavy that they are nearly impossible to discharge through the discharge chutes, in which case the foam bed may collapse completely. As the foam collapses, at least some of the mineral particles return to the slurry. Now a new air bubble is needed in order to lift each mineral particle back to the foam layer. This slows down the flotation process, the efficiency in the use of air is low and the excess air mechanically lifts into the foam more and more valueless minerals and other material.

From the FI patent 78628, there is known a flotation machine where inside the created foam bed, there is installed a downwardly narrowing, wedge-like or conical element for adjusting the volume and/or surface area of the foam bed. By means of said adjusting element, the foam bed becomes thick, and simultaneously the foam is directed, when proceeding upwardly, towards the flotation machine walls and discharge chutes connected to the walls. From the FI patent 88268 there is known a flotation machine, and in the slurry tank of said flotation machine, essentially underneath the foam bed created in the machine, there is installed at least one control element, so that the free surface of the flotation machine, essentially at least in the slurry tank underneath the foam bed, can be reduced when proceeding upwardly. Now the creation speed of the air bubbles containing mineral particles can be increased, because the volume flow of the air bubbles containing mineral particles per area unit increases, as the free space decreases. In addition to accelerating the foam creation speed, the invention also aims at increasing the removal of the foam contained in the foam bed from the flotation cell. However, arrangements according to the above described solutions take up space in the total volume space of the cell, but they do not seem to provide a sufficiently advantageous solution for supporting the foam bed and for facilitating the foam discharge.

The object of the present invention is to realize a novel solution whereby the drawbacks of the prior art can be avoided. In particular, the object of the invention is to facilitate a continuously operated foam discharge from the flotation cell, so that at the top edge of the flotation cell, there is arranged at least one support element that supports the foam layer and helps to discharge the foam layer out of the flotation cell.

The invention is characterized by what is set forth in the characterizing parts of the independent claims. Preferred embodiments of the invention are characterized by what is set forth in the other claims.

Remarkable advantages are achieved by using an apparatus and method according to the invention. The flotation arrangement according to the invention for flotating minerals and the like from slurries containing these particles comprises a flotation cell, provided with edges and a bottom, and a mixing mechanism arranged in the flotation cell. In addition, the flotation arrangement comprises means for feeding air into the cell and elements for feeding the material to be flotated into the cell and for discharging it out of the cell. In order to support the foam layer and in order to facilitate its removal from the cell, in connection with the top edge of the cell, there is arranged at least one support element. There is provided a sufficient number of support elements, depending on the concentrate to be treated and on the cell size. The support element can be formed of one single part, or it may be composed of several different parts. The support element can be formed of the cell edge, or it can be a separate element to be attached to the edge. Advantageously the shape of the support element is serrated, undulated or the like. The use of the support element enhances a continuous removal of the mineral foam from the cell to the discharge chutes. In particular, it enhances the flotation of low-content ores in processes where the length of the slurry edge is too long in comparison with the required concentrate production, and thus the flotation becomes difficult because the foam collapses. In addition, it particularly enhances the flotation of such ores where the viscosity of the slurry is so high, that large amounts of air cannot be dispersed into the slurry. Now, because of the small amount of air, the foam does not rise over the edges, although the foam layer is well created and supported by the cell edges. In order to successfully remove the foam from the cell, the length of the foam edge is limited to a certain length per a given concentrate production. Now the support element according to the invention helps the already created foam layer to stay together, and to be discharged from the cell. In order to succeed in obtaining a given concentrate production in flotation, there also is required a suitable length of slurry edge in the cell. When the edge is too long, as it is with low-content ores, the result may be the collapsing of the foam layer. By using a support element having a serrated, undulated or other similar shape in connection with the top edge of the flotation cell, it is possible to see a suitable length for the foam edge in order to successfully remove the foam from the cell. By means of the support element, the length of the foam edge is adjusted to the desired concentrate production. Thus the length of the foam edge changes steplessly from zero to a hundred per cent of the length of the slurry edge, when raising the slurry surface located underneath the foam. By means of the support element, there can be found a suitable height for the slurry surface, corresponding to the length of an optimal slurry edge. When the length for an optimal slurry edge is obtained, the flotation process proceeds without interruptions that are often due to the collapsing of the foam. The solution according to the invention is easy to realize and economical in costs. When possible future interruptions in the process are eliminated even at one cell, a flotation process maintained by a series of cells is remarkably enhanced.

The invention is described in more detail below with reference the appended drawings.

Figure 1 An arrangement according to the invention.

Figure 2 An arrangement according to another preferred embodiment of the invention.

Figures 1 and 2 illustrate flotation arrangements 1 and 15 according to different embodiments of the invention. In the flotation arrangement 1 illustrated in figure 1 , the shape of the support element 6 is serrated. Figure 2 illustrates another embodiment of the invention, according to which the support element 14 is undulated in shape. In the flotation cell 3 comprising edges 2 and a bottom 10, there is processed slurry 13, which is fed into the cell 3 from below. The mixing mechanism arranged inside the flotation cell is not illustrated, and neither are the elements for feeding air into the cell, because they are likewise located inside the cell. When air is fed in, along with the flotation process there is created a foam layer 5 on the slurry surface 13, and the creation of said foam layer 5 as it rises further up in the cell 3, is supported by the support element 6 and 14 according to the invention. In shape, the support element is either undulated or serrated, and it is made of a separate element and attached at the top edge 4 of the cell by using fastening elements, for instance bolts. By means of the support element 6 and 14, the change in the length 7 of the foam edge is observed as the slurry surface 11 rises, and it is adjusted to the desired concentrate production. The length of the foam edge is changed steplessly from zero to a hundred per cent of the length 8 of the slurry edge, as the slurry surface 11 is raised. When the suitable length 7 of the foam edge is determined by the serrated or undulated support element, there can be found a suitable height 9 for the slurry surface, corresponding to the length of an optimal slurry edge. When the length of an optimal slurry edge is known, the continuous discharge of the foam from the cell 3 to the discharge chutes 12 located in connection with the top edge 4 is enhanced.

For a man skilled in the art, it is obvious that the various embodiments of the invention are not restricted to the above described embodiments only, but may vary within the appended claims.

Claims

1. A flotation arrangement (1 , 15) for flotating minerals or the like from slurries containing these particles, said flotation arrangement comprising a flotation cell (3) including edges (2) and a bottom (10), and a mixing mechanism arranged in the flotation cell, elements for feeding air into the cell and elements for feeding material to be flotated into the cell and for removing the flotated material out of the cell, characterized in that in connection with the top edge (4) of the flotation cell (3) there is arranged at least one support element (6, 14) for facilitating the discharge of the foam layer (5) and for supporting the foam layer (5).

2. A flotation arrangement according to claim 1 , characterized in that the support element (6, 14) is made of one single part.

3. A flotation arrangement according to claim 1 , characterized in that the support element (6, 14) is formed of several parts.

4. A flotation arrangement according to claim 1 - 3, characterized in that the support element (6, 14) is part of the edge (2) of the cell (3).

5. A flotation arrangement according to claim 1 - 3, characterized in that the support element (6, 14) is a separate part to be attached to the edge (2) of the cell (3).

6. A flotation arrangement according to any of the preceding claims, characterized in that the support element (6) is essentially serrated in shape.

7. A flotation arrangement according to claim 1 - 5, characterized in that the support element (6) is essentially undulated in shape.

8. A flotation arrangement according to any of the preceding claims, characterized in that the stepless change of the length (7) of the foam bed edge from zero to a hundred per cent of the length (8) of the slurry edge can be observed when raising the slurry surface (11).

9. A flotation arrangement according to any of the preceding claims, characterized in that by means of the support element (6,14), there can be found a suitable height (9) for the slurry surface, corresponding to the length of an optimal slurry edge.

10. A method for flotating minerals or the like from slurries containing these particles by means of a flotation arrangement (1 , 15), said flotation arrangement comprising a flotation cell (3) including edges (2) and a bottom (10), and a mixing mechanism arranged in the flotation cell, elements for feeding air into the cell and elements for feeding material to be flotated into the cell and for removing the flotated material out of the cell, characterized in that the foam layer (5) is supported and its removal is facilitated by at least one support element (6, 14) arranged in connection with the top edge (4) of the flotation cell (3).

11. A method according to claim 10, characterized in that the length (7) of the foam bed changes steplessly from zero to a hundred per cent of the length (8) of the slurry edge as the slurry surface (11) is raised.

12. A method according to claim 10 - 11 , characterized in that by means of the support elements (6, 14) there is found a suitable height (9) for the slurry surface, corresponding to the length of an optimal slurry edge.