AU713279B2 - Mineral recovery apparatus - Google Patents

Description

1 MINERAL RECOVERY APPARATUS This invention relates to mineral recovery apparatus. More specifically, this invention relates to apparatus for electrowinning metal from electrolytic solution.

This invention relates particularly to apparatus for electrowinning metals such as copper, tin, gold and nickel from an electrolytic solution containing these metal ions and it will be convenient to hereinafter describe the invention with reference to this example application. However, it is to be clearly understood that the invention is capable of broader application.

A prior art electrowinning cell for recovering metal ions from solution is 0:08 disclosed in international patent application no. PCT/AU92/00052 in the name of Materials Research Pty Ltd. The entire contents of the specification are hereby explicitly incorporated into this document by cross-reference. This specification discloses an electrowinning cell comprising a substantially cylindrical housing forming a cylindrical cathode having a rod-like anode extending through the middle of the housing. Thus, the cathode effectively forms the cylindrical side wall of the housing. While the electrowinning cell described in this specification is highly effective in electrowinning metals from solution, and in particular low-grade solutions, the harvesting process is not a streamlined process. This is particularly so when the process is to be applied commercially to a bank of at least 50 cells. The housing has to be substantially 00:025 disassembled each time metal is harvested and then the plated metal, e.g.

copper tube, has to be hammered out of the cylindrical housing. When this has 0 been accomplished, the housing then has to be reassembled before the flow of electrolytic solution can be returned to the cell. Considerable force is sometimes 0 0 a 0 required to remove the plated metal tube from the cathode. Naturally, this also risks damage to the cathode.

7< 7/j- Another disadvantage of this construction is that the side wall of the housing is limited to being constructed of a conductive or metallic material. It is not able to be manufactured of a engineering plastics material which may be cheaper and/or stronger. It is therefore difficult to optimise engineering design with these constraints.

Accordingly, it would be advantageous if a cell assembly could be devised which was capable of a more streamlined harvesting procedure and which lent itself more readily to commercial usage in an industrial scale plant.

According to an aspect of this invention, there is provided a cell assembly for extracting a metal from an electrolyte, the cell assembly including: a housing having a substantially cylindrical side wall and two opposed 15 end caps, at least one said end cap being removable, the housing defining an inlet and an outlet axially spaced from the inlet, the inlet and the side wall being °00 configured so as to induce the electrolyte to flow through the housing with a flow pattern in the form of a helical spiral; •0 so a removable cathode in the form of a sleeve which is split longitudinally, the cathode being snugly received within the side wall of the housing such that it is positioned adjacent the side wall of the housing and being removable from the housing for the harvesting of metal deposited on the sleeve; 25 an elongate anode projecting substantially axially through one of the end caps into the housing, said anode being substantially centrally positioned within S the housing spaced radially inwardly from the cathode and defining an annular flow passage between the anode and the cathode; and 00 releasable electrical connecting means for electrically connecting said cathode to an electrical circuit.

<I I ,1 S C/ Preferably, the inlet is configured to direct electrolyte substantially tangentially into the annular flow passage between the anode and the cathode.

More preferably, both the inlet and the outlet extend substantially perpendicular to the longitudinal axis of the housing and tangentially relative to the side wall of the housing.

Thus, by having a cathode which is separate and distinct from the cylindrical wall of the housing, the cathode can be removed from the housing without physically disassembling the housing. Further, the side wall of the housing can be manufactured of material which is nonconductive and is not required to have the electrically conducting properties of the cathode.

The split sleeve may have longitudinal edges which are adjacent each 0 other when the sleeve is in a closed position and spaced from each other in an 15 open position, and the sleeve may be spring biased to the open position. The sleeve may acquire the bias to the open position by being rolled from a flat sheet into a cylindrical form.

o S-By having a split sleeve cathode which is capable of being opened, a convenient means is provided for detaching the plated metal tube from the circumferentially surrounding cathode. This is even more useful if the sleeve is biased towards a sprung or open position.

S.i S SoAdvantageously, the anode is mounted to and passes through the same end cap which is removed to permit the sleeve to be removed from the housing for harvesting. With this arrangement, the anode is removed with the end cap S each time the cathode is harvested.

In a preferred form, both end caps are removable. One of the end caps, e.g. the upper end cap, is removable to permit the split sleeve cathode to be removed from the housing for the harvesting of metal deposited thereon.

Advantageously, the other end cap is removable so as to permit access to the interior of the housing for maintenance purposes.

Advantageously, the inlet is defined in the housing towards one end of the housing, and the outlet is defined in the side wall towards the other end of the housing.

Typically, the anode has a rod-like configuration and is supported by the end cap through which it projects into the housing. Further advantageously, the distal end of the anode is supported by the opposed end cap.

The anode may comprise a central conductive portion with nonconductive portions on each side of the conductive portion, and the conductive portion may typically be substantially aligned with the cathode.

Advantageously, the releasable electrical connecting means connects S. said cathode to the electrical circuit without positive physical attachment Sg thereto, e.g. by means of abutting contact.

•20 In one embodiment, the electrical connecting means includes a bar, positioned on the side wall of the housing, e.g. extending substantially vertically, so as to make contact with the cathode when the cathode is received within the 00 housing. Typically, the bar has a flattened configuration.

2S. 5 In a particularly preferred form, the side wall of the housing defines a groove or slot, and the bar is at least partially received within the groove, with at least part of the bar projecting outwardly proud of the surface of the side wall for making electrical contact with the cathode.

Preferably, the side wall of the housing is made of a plastics material, e.g. an engineering plastics material, such as polyvinylchloride which may be glass or mineral reinforced.

Optionally, the cathode may be made of stainless steel, e.g. 316L stainless steel or titanium. Advantageously, the cathode is made of an inert material.

In one particularly preferred form, the cell is disposed substantially vertically with the anode passing through the end cap at the upper end of the cell. It is this end cap and associated anode which is removed each time the cathode is harvested. Further, in this embodiment, the inlet is positioned towards the upper end of the cell and solution passes down through the cell the outlet positioned towards the lower end of the cell.

In a particularly preferred application of the cell, the cell is used to treat a low grade copper containing solution, e.g. acid mine drainage or a leachate 15 from a heap leaching process.

i:: Yet further, in a typical commercial application of the cell assembly, there is provided a bank of cell assemblies, each said cell assembly being substantially as described above. Typically, each of the cell assemblies in the bank of cells is supported by mechanical support. Optionally, a worker platform may be provided to provide worker access to the end cap and anode at the upper end of the cell assembly.

O An electrolytic cell assembly for extracting a metal from an electrolytic solution may manifest itself in a variety of forms. It will be convenient to hereinafter describe in detail one preferred embodiment of the invention with reference to the accompanying drawings. The purpose of providing this description is to instruct a person having an interest in the subject matter of the invention how to carry the invention into practical effect. It is to be clearly understood however that the specific detailed nature of this specific description does not supercede the generality of the preceding broad description. In the drawings: 6 Fig. 1 is a schematic cross-sectional view of a cell assembly for extracting a metal from electrolyte in accordance with the invention; and Fig. 2 is a schematic three-dimensional view of a split sleeve cathode for the cell assembly of Fig. 1.

In Fig. 1, reference numeral 10 refers generally to a cell assembly (cell) in accordance with the invention.

The cell 10 comprises broadly a housing 11, a cathode 12 in the form of a split sleeve, and a rod-like anode 14 projecting through an end of the housing 11 into the interior thereof. The cell 10 also includes releasable electrical ~connection means 16 for electrically connecting the anode 14 and the cathode 15 12 to an electrical energising means, e.g. an electrical power supply.

i: Turning now specifically to the housing 11, it comprises a substantially cylindrical side wall 20 having two end caps 22 and 24 mounted over the ends of the side wall 20. Further, the side wall 20 defines an inlet 26 towards an end 28 of the housing 11 and an outlet 30 towards the other end 32 of the housing 11. The inlet and outlet 26 and 30 are arranged tangentially relative to the housing and perpendicular to the axis of the housing 11. This induces liquid, 0 e.g. electrolytic solution, to flow through the housing from the inlet 26 to the outlet 30 with a flow pattern in the form of a helical spiral.

Typically, each of the end caps 22, 24 is removable from the housing.

The removal of end cap 22 forms part of the operating cycle of the cell 10 as will be described in more detail hereunder. Further, the cell is mounted in a vertically extending position with the inlet at the bottom and the outlet at the top.

The cell may be supported in its vertically extending position by a mechanical support, e.g. a framework (not shown). Further, the support may include a platform for including work access to the end cap at the top of the cell.

In the illustrated embodiment, the end caps 22, 24 are mounted on the side wall 20 by means of quick release connections, e.g. bayonet-type fittings.

While quick release attachments are convenient for this purpose, it will be readily appreciated that many other types of attachments may also be used.

In the illustrated embodiment, the side wall 20 comprises a tubular central portion 31 and end portions 33 on either side of the central portion 31.

Typically the side portions 33 are bonded to the central portion 31, e.g. by bonding agents such as adhesive cement. In a particularly preferred embodiment, the side wall and end caps are formed of plastic material such as PVC. The plastic material may be reinforced e.g. by glass.

Turning now to the cathode 12, the sleeve thereof is split longitudinally to define opposed longitudinal edges 36 and 37. The sleeve 12 is typically made from an inert material such as stainless steel, e.g. 316L stainless steel or titanium. The use of an inert material helps ease the detachment of the plated metal from the sleeve 12.

The sleeve is interchangeable between a closed position in which the longitudinal edges 36 and 37 are adjacent each other and an open position in which the longitudinal edges are spaced from each other. Typically, the sleeve is spring biased to the open position, This has to be dominated e.g. by manual force to move the sleeve to the closed position e.g. to fit it into the housing 11.

::25 Typically, the sleeve acquires this bias towards the open position by its process of manufacture, e.g. by rolling a flat sheet into a cylindrical form.

The anode 14 is rod-like and passes through the upper end cap 22 and into the housing 11. The anode 14 is supported and mounted to the upper end cap 24. Thus, when the upper end cap 22 is removed from the housing, the anode 14 is removed with it. The anode 14 is substantially centrally positioned within the housing 11 and in the illustrated embodiment, it extends fully down to the opposite end cap 24. The free end of the anode 14 is received within a locating formation 40 defined in the end cap 22 which helps position the anode centrally within the housing.

In the illustrated embodiment, the anode 14 comprises a central conducting portion 42 with non-conducting portions 44 and 46 disposed on either side of the conducting portion 42. The conducting portion 42 is somewhat shorter than the longitudinal extent of the sleeve 12 and is substantially longitudinally aligned therewith. By virtue of its central position within the housing 11, the anode 14 is substantially equidistant from the cathode around the full circumference of the cathode, i.e. the so-called electrode gap is substantially the same around the circumference of the housing.

The purpose of having the conducting portion shorter than the cathode is to inhibit the growth of plated metal dendrites from the upper and lower ends of the sleeve which are regions of high current density. The growth of dendrites has the potential to short out the cell. It can also interfere with harvesting of the plated metal.

0@ .00: The releasable electrical connecting means includes an electrical circuit (not shown) coupled to an electrical power supply. The connecting means includes a conductor bar for electrically connecting the sleeve 12 leads for the .CC C electrical circuit. The bar which may be a flat bar extends substantially axially C along the length of the housing 11.

In particular, the bar may be partially received within a groove or recess defined in the housing with an outer portion thereof projecting out of the groove for contacting the sleeve. Two electrical terminations are shown in the drawings for connecting the bar to the electrical circuit.

The illustrated conductor bar also includes a shoulder for engaging the lower end of the sleeve and checking its position in the housing. Naturally however, this is an optional feature and there are other ways of positioning the sleeve in the housing.

The electrolytic process which takes place in the cell leads to the evolution of gases, particularly H 2 and 02 which have to be vented from the system. The housing may also include a gas vent (not shown) which opens when gaseous accumulation takes place in an upper region of the housing and the pressure of this gaseous accumulation exceeds a predetermined level.

In use, an electrolytic solution containing metal ions to be recovered is passed upwardly through the housing from the inlet 26 to the outlet Simultaneously, electrical energy is applied across the anode 14 and cathode 12 causing current to flow through the electrolyte. This causes the deposition of metal, e.g. metal plate, on the cathode. The metal progressively builds up until it reaches a thickness of approximately 6mm to 10mm at which point the metal needs to be harvested.

To harvest the metal, the electrical energy applied to the cell is o interrupted and the flow of electrolytic solution to this cell is cut off. The end cap and anode is removed from the side wall by rotation of the end cap to release the bayonet-type connection. This provides access to the interior of the cell particularly the split sleeve cathode 12 and the attached tube of deposited metal.

The sleeve 12 and associated plated tube of metal can then be lifted out of the cell 10. This is usually accomplished by means of a harvesting tool which includes a claw assembly which grips the plated tube. The tool is inserted down into the plated tube and the claw is then displaced radially outwardly into •S frictional gripping contact with the tube.

Once the sleeve 12 and associated tube have been lifted out of the housing 11, it is detached from the plated tube by pulling it outwardly away from the tube or if necessary, prising, e.g. with the assistance of a tool, the sleeve 12 away from the plated tube of metal. Once this has done, the sleeve 12 can then be returned to a closed position and then reinserted into the cell.

The flow of electrolytic solution can then be recommenced and the cycle of plating and harvesting copper can be repeated. The tubes of copper are typically flattened to make them easier to transport and then further processed.

It would be clearly apparent to a person skilled in the art that while the harvesting procedure described above may be adequate, there would also be potential to automate it at some point in the future.

Typically, the cell 10 shown in Fig. 1 forms part of a bank of many cells through which an electrolytic solution is passed in series. Typically, the cells are *w e harvested sequentially although this is not essential. Valves may be provided to saw: permit the cell to be disconnected from the remaining cells in the batch, e.g. for harvesting or maintenance purposes.

An advantage of the cell described above with reference to the drawings S is that it facilitates the orderly and predictable harvesting of copper from the cell.

Specifically, it enables the copper to be harvested without the need to disassemble the cell. The removal of the end cap and associated anode is a relatively simple operation. Further, the use of the split sleeve enables the cathode to be readily detached from the plated tube of metal, e.g. by expansion of the sleeve at its longitudinal ends.

The cell described above with reference to the drawings is suitable for application in a commercial plant comprising one or more banks of cell assemblies. An electrolytic solution containing metal to be recovered can be passed through the cells making up a bank of cells in series thereby plating metal in each of the cells. The metal can then be harvested from the cells sequentially by one or two operators.

11 It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambient of the invention as herein set forth.

S a* 9 e• o 9 9

Claims (14)

1. A cell assembly for extracting a metal from an electrolyte, the cell assembly including: a housing having a substantially cylindrical side wall and two opposed end caps, at least one said end cap being removable, the housing defining an inlet and an outlet axially spaced from the inlet, the inlet and the side wall being configured so as to induce the electrolyte to flow through the housing with a flow pattern in the form of a helical spiral; a removable cathode in the form of a sleeve which is split longitudinally, the cathode being snugly received within the side wall of the housing such that it is positioned adjacent the side wall of the housing and being removable from the housing for the harvesting of metal deposited on the sleeve; an elongate anode projecting substantially axially through one of the end caps into the housing, said anode being substantially centrally positioned within •o the housing spaced radially inwardly from the cathode and defining an annular flow passage between the anode and the cathode; and releasable electrical connecting means for electrically connecting said cathode to an electrical circuit.

2. A cell assembly according to claim 1, wherein the inlet is configured to direct electrolyte substantially tangentially into the annular flow passage between the anode and the cathode. a*00 000 00 0 o

3. A cell assembly according to claim 1 or claim 2, wherein both the inlet and the outlet extend substantially perpendicularly to the longitudinal axis of the housing and tangentially relative to the side wall of the housing. 13

4. A cell assembly according to any one of claims 1 to 3, wherein the anode is mounted on and passes through the same end cap which is removed to permit the sleeve to be lifted out of the housing for harvesting.

5. A cell assembly according to any one of claims 1 to 4, wherein the split sleeve has longitudinal edges which are adjacent each other when the sleeve is in a closed position, and spaced from each other in an open position, and wherein the sleeve is spring biased to the open position.

6. A cell assembly according to claim 5, wherein said sleeve acquires said bias to the open position by being rolled from a flat sheet into a cylindrical form.

7. A cell assembly according to any one of claims 1 to 6, wherein both end caps are removable, and wherein the inlet is defined in the side wall towards ,15 one end of the housing, and the outlet is defined in the side wall towards the t. l other end of the housing. 000

8. A cell assembly according to any one of claims 1 to 7, wherein the anode has a rod-like configuration and is supported by the end cap through which it 0 20 projects into the housing, and wherein the distal end of the anode is supported by the opposed end cap. 000:0 00i

9. A cell assembly according to claim 8, wherein the anode comprises a central conductive portion and non-conductive portions on each side of the conductive portion, and wherein the conductive portion is substantially aligned with the cathode.

10. A cell assembly according to any one of claims 1 to 9, wherein the releasable electrical connecting means connects said cathode to the electrical circuit without positive physical attachment of the cathode to the circuit. 14

11. A cell assembly according to claim 10, wherein the electrical connecting means includes a bar positioned on the side wall of the housing so as to make contact with the cathode when the cathode is received within the housing.

12. A cell assembly according to claim 11, wherein the bar extends broadly in a longitudinal direction relative to the housing.

13. A cell assembly according to claim 11 or claim 12, wherein the side wall of the housing defines a groove or slot, and wherein the bar is at least partially received within the groove, with at least part of the bar projecting outwardly proud of the surface of the side wall for making electrical contact with the cathode.

14. A cell assembly for extracting metal from an electrolyte substantially as o 15 herein described with reference to the drawings. Si DATED this twenty-seventh day of September 1999 ELECTROMETALS MINING LIMITED By 20 PIZZEYS PATENT TRADE MARK ATTORNEYS. C S