MINERAL RECOVERY APPARATUS

Abstract: A cell assembly (10) is described for extracting mineral from a flowing electrolyte, including a housing having an inlet (23) and an outlet (22) for passing electrolyte through the housing. The housing confines the flow of electrolyte through a removable sleeve-like cathode (13) and is also provided with an anode (21) extending into the housing, and electrical connecting means for connecting an electrical circuit to the cathode (13) and the anode (21). The housing is preferably a fixed cylindrical housing and includes a removable top cap supporting an anode assembly for removal therewith. The anode (21) is supported concentrically and is part of an anode assembly which extends fully through the housing to be located concentrically in the housing with a bottom support (31) in the housing by locating means provided on the distal end of the anode (21). It is also proferred that the anode (21) includes an exposed conductive portion (29) within end extremities of the sleeve-like cathode.

Description: "MINERAL RECOVERY APPARATUS" This invention relates to mineral recovery apparatus. This invention has particular but not exclusive application to electrowinning and/or electrofining of copper, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications such as electrowinning or electrofining of other metals. This invention also has particular application to electrowinning copper from ore leachates without the need for refining or concentrating the leachate liquor as is a common practice. In one embodiment of a prior system, as disclosed in International Patent Application No. PCT/AU93/00361, electrodeposited metal is removed as a rigid inner tube from the internal surface of a tubular electrode of dissimilar metal, such as for example, stainless steel. In removing the inner tube of electrodeposited metal from the electrode, there are occasions where considerable force or effort is required, and this increases the risk of damaging the tubular electrode. Additionally, the electrode is used as a part of the housing, requiring the dual properties of being conductive and of sufficient dimensions to maintain structural integrity of the apparatus, which may result in the apparatus being more costly than if a more economical material were able to be used. Additionally, it is not possible to provide a simple unitary construction where a conductive material is utilised as the tubular part of the housing and the remainder is not of metallic construction. Since the electrochemical cell, to operate in a cost effective manner, is required to withstand operating pressures which permit relatively large flow rates, the non-metallic fittings on each end of the tubular cathode are required to be fastened to one another independently from the tubular housing, resulting in an expensive mechanical arrangement for each electrochemical cell. The present invention aims to alleviate one or more of the above disadvantages and to provide mineral extraction apparatus which will be reliable and efficient in use. With the foregoing in view, this invention in one aspect resides broadly in a cell assembly for extracting mineral from a flowing electrolyte, including:- a housing having inlet and outlet means for passing electrolyte therethrough; the housing confining flow of electrolyte through a removable sleeve-like cathode; an anode extending into said housing, and electrical connecting means for connecting an electrical circuit to said cathode and said anode. Preferably the housing is a fixed cylindrical housing and includes a removable top cap which locates the anode concentrically within the cathode. The top cap preferably supports the anode assembly for removal therewith and suitably the anode is part of an anode assembly which extends through the housing to expose a conductive portion within end extremities of the sleeve-like cathode. It is also preferred that the distal end of the anode assembly be provided with locating means which locates concentrically in the housing by engagement with a bottom support in the housing. The electrical connecting means for the cathode is preferably associated with said housing and connected to a direct current supply. Preferably, the housing is formed from plastics material, such as rigid polyvinyl chloride, which may be glass or mineral reinforced. The housing suitably includes a tubular portion extending between end portions, the sleeve¬ like cathode being adapted to fit within the internal surface of the tubular portion. The housing may include a conductive surface disposed about the internal periphery of the tubular portion and electrically isolated from the anode but in electrical contact with said sleeve-like cathode and the electrical connecting means may include electrical terminations on the conductive surface. Preferably, however, conductor means is provided extending at least partly along an inner surface of the tubular portion for electrical contact with, but being mechanically separable from, the sleeve-like cathode. For example, the conductor means may include a conductor bar extending through the tubular portion against the internal surface of the tubular portion. The conductor bar may be of relatively flat or thin cross-section, and may be inlaid into a groove or slot in the tubular portion, but with at least some of the bar sitting proud of the surface for electrical contact with the sleeve-like cathode. Suitably, the profile of the conductor bar is adapted for electrical contact with the sleeve-like cathode but permitting the sleeve-like cathode to be separated from the conductor bar. Preferably, the sleeve-like cathode includes a sleeve member co-operable with the housing for insertion of the sleeve member into the housing and removal of the sleeve member from the housing. It is also preferred that the sleeve member includes release means for releasing the sleeve member from the electrodeposited material. The release means may be include an expansion member or folding or hinging arrangement for the sleeve member. However, in a preferred embodiment the sleeve member includes a slit, split or break in its circumference, and is resiliently biassed to expand when not constrained to the internal dimensions of the tubular portion of the housing. For example, where the tubular portion is substantially cylindrical and circular in cross-section, the sleeve-like cathode is suitably a cylindrical sleeve member circular in cross-section but having a slit extending from one end of the sleeve member to the other. When not constrained, the sleeve member is formed to have a larger diameter than the internal dimensions of the tubular portion of the housing, but is resiliently deformable to fit within the tubular portion of the housing and make electrical contact with the conductor means. It is preferred for example that the sleeve member is constructed from 316 stainless steel or titanium having a thickness in the range of 0.4 mm to 0.7 mm, rolled from flat sheet to retain the resilient nature of the metals. The inlet and outlet means are preferably provided in the end portions, such that an inlet is provided in one end portion and an outlet is provided in the other end portion. The inlet and outlet are preferably arranged substantially tangentially for inducing a tangential component to liquid entering and leaving the electrochemical cell through the inlet and outlet respectively. The anode is preferably located substantially centrally in the housing to form a substantially annular cavity between the anode and the sleeve-like cathode. Preferably, the housing is of substantially unitary construction, but permitting the sleeve-like cathode to be removed for recovery of electrodeposited material from the cell. For example, the anode, sleeve and related components of the electrochemical cell may be arranged in one part and be adapted to be removed through one of the end portions. Preferably, the anode is removable in a first removable portion and the sleeve is removable from a second removable portion, the remainder of the housing forming a fixed portion. The end portion through which the removable portion may pass is preferably solvent or fusion welded to the tubular portion, as is the other end portion. Thus, in order to maintain the liquid tight integrity of the electrochemical cell, sealing means is provided in operative association with the removable portion or portions and the fixed portion. The arrangement of the removable portion may also be adapted to seal the inlet against liquid flow whilst the removable portion is removed from the fixed portion, and the outlet may be provided with backflow prevention means, so that successive electrochemical cells may have the electrodeposited material removed by the means described above without requiring shut-down of the electrochemical cell battery. For example, the anode assembly may include a spider arrangement for associating the anode assembly with the sleeve-like cathode such that the anode assembly and cathode are provided in a unitary removable portion. Preferably, however, the anode assembly is removable separately from the removable sleeve-like cathode. In another aspect, this invention resides broadly in an electrolytic cell having a cathode formed by a flexible sheet of metal constrained in the form of a tube disposed concentrically of and surrounding an anode defining an annular space between the anode and the cathode; a housing formed with an inlet and an outlet such that electrolyte may be passed through the housing; said anode being associated with an end cap which is removable from said housing, and said cathode being removable from said housing when said anode has been removed therefrom. In another aspect, this invention resides broadly in a method of electrodepositing a metal from an electrolyte solution containing the metal, the method including:- providing an electrolytic cell assembly as hereinbefore defined; operating the electrolytic cell for a time sufficient to deposit a desired thickness of metal on the internal surface of the sleeve-like cathode; removing the top cap and the anode assembly supported thereby from the housing; removing the sleeve-like cathode from the housing; removing the sleeve-like cathode from the metal; replacing the sleeve-like cathode and the top cap and the anode assembly to the housing. Preferably, the process is repeated and fresh electrolyte may be added to replenish the depleted metal cations for electrowinning. In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical embodiment of the invention, wherein:- Figure 1 is a sectional view of an electrolytic cell according to the invention, and Figure 2 is a pictorial view an inner sleeve for the electrolytic cell shown in Figure 1. The electrolytic cell 10 shown in Figures 1 and 2 includes a housing assembly 11 which comprises a tubular portion 12 to the external periphery of which an upper end cap assembly 18 and a lower end cap assembly 14 are bonded. The upper end cap assembly 18 includes an upper removable portion 15, and the lower end cap assembly 14 includes a lower removable portion 16, each removable portion 15 and 16 being preferably provided with a quarter turn, bayonet type, or quick release type fitting or arrangement to facilitate rapid removal and replacement of the removable portions 15 and 16. The upper removable portion 15 permits access to the electrolytic cell 10 for removal of the electrodeposited material, and the lower removable portion 16 permits access to the electrolytic cell 10 for maintenance purposes. An inner sleeve 13 is located within the tubular portion 12 and includes a slit 19 extending co-axially from one end to the other. A sealing gland 20 is formed centrally in the upper end cap assembly 18, and an anode assembly 21 passes through a central aperture 30 in the upper removable portion 15 to form an annular cavity 24 in the housing assembly 11. The anode assembly 21 is terminated at its other end within a tubular recess 31 projecting inward from the lower removable portion 16 and the lower end of the anode assembly 21 is tapered or shaped to permit easy insertion of the anode assembly 21 into the recess 31. A liquid outlet 22 is formed in the upper end cap assembly 18, and a liquid inlet 23 is formed in the lower end cap assembly 14. The outlet 22 and the inlet 23 are aligned as shown with their axes perpendicular to the axis of the housing assembly 11 and tangential to the annular cavity 24 formed between the housing assembly 11 and the anode assembly 21. The housing assembly 11 is formed in the from plastics material such as PVC such that the housing assembly comprising the tubular portion 12, the upper end cap assembly 18 and the lower end cap assembly 14 are formed integrally by a welding or plastics moulding process. If desired, a gas vent (not shown) may be provided with a float valve or the like which opens when gas has collected within the upper end cap assembly 18, and closes after the gas has been vented. The tubular portion includes a contactor bar 25 for electrically contacting the inner sleeve 13. Two electrical terminations 26 are provided in electrical contact with the contactor bar 25. The electrical terminations 26 pass through the tubular portion 12 as shown and are connected in use to an electrical supply. The contactor bar 25 also includes a lip portion 27 to prevent the inner sleeve 13 from dropping below its operative position in the electrolytic cell 10. The anode assembly 21 also includes non-conductive portions 28 and a conductive portion 29 such that an applied current passes between the anode assembly 21 and the inner sleeve 13 substantially radially, or in particular, with substantially no axial component. Additionally, the removable portions 15 and 16 permit an alternative dimensioned anode assembly 21 and sleeve 13 to be inserted if the electrolytic cell 10 is to be used for processing an alternative electrolyte. The inner sleeve is formed from an inert material such as stainless steel from which the deposited material may be readily removed. The anode assembly 21, upper removable portion 15 and inner sleeve 13 may be removed in a unitary piece, but preferably, the anode assembly 21 and the upper removable portion 15 are first removed, and an outwardly extending claw assembly or the like inserted to grab the inner sleeve 13 (and the electrodeposited material on the internal surface of the inner sleeve 13). Upon operation of the claw assembly or the like, the inner sleeve 13 with its electrodeposited material is removed from the housing assembly 11 and the inner sleeve 13 removed from the electrodeposited material by expanding the inner sleeve 13 away from the electrodeposited material along the slit 19. The inner sleeve 13, the upper removable portion 15 and the anode assembly 21 are returned to the housing assembly 11 for resumption of electrolytic operation of the electrolytic cell 10. In use, an electrolytic cell assembly of the present invention may be constructed as herein described, and more particularly, a battery of cells may be assembled with the anode assembly 21 and upper removable portion 15 in a manifolded assembly, and the respective inner sleeves 13 in another manifolded assembly. For example, the electrolytic cell 10 may be supported by its inlet 23 and outlet 22 rigidly mounted on a frame assembly, with hose connections connecting the inlet 23 and outlet 22 to respective inlet and outlet manifolds. Union connections in the may be provided on the inlet 23 and outlet 22 to permit the electrolytic cell to be removed from its battery. Electrolyte is introduced into the respective cells, from the bottom or, particularly if fed from the top, at a sufficiently high flow rate that the air in the cells may be chased out, and electric potential applied once flow conditions are established. Once a suitable layer of electrodeposited material is deposited on the inner surface of the inner sleeves 13, the battery may be disassembled in order to retrieve the sleeves from their respective tubular portions 12, or single cells may in turn may be opened for removal of the electrodeposited material. It will be appreciated that the cells may be disposed horizontally or obliquely, and further, that irrespective of the orientation of the cells, flow may be from either end. Moreover, a battery of cells may installed in any combination of series and parallel flow suitable for the flow regime desired according to the fluid mechanics and electrodynamics of the cell battery. In one embodiment, the tubular portions are vertical and fixed to an upper manifold, and the lower manifold is removable from the tubular portions so that a sleeve removing assembly may be inserted into the respective cells to remove the sleeves from the tubes. An alternative set of sleeves may be used in rotation with the first set, or the sleeves may be removed from the electrodeposited shell, and replaced into the tubular portions for further electrolytic processing of electrowinnable material. It will be appreciated that controlled mechanisms may be utilised to automate the process of removing the sleeves to permit separation of the electrodeposited material from the sleeves. Preferably, the controlled mechanisms remove one sleeve at a time and release the sleeve from the electrodeposited material before returning the sleeve to the electrolytic cell. However, it will be appreciated that two or more cells may be treated in this way simultaneously or by independently operating controlled mechanisms. Each side of the slit in the sleeve member is preferably engaged to prise the sleeve member from the electrodeposited material. For example, an electrodeposited layer of copper in the range of 1 mm to 10 mm may be recovered from the sleeve member by removing the sleeve member as described above. The hollow cylinders of copper are preferably flattened for transport and subsequent smelting. It will be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as claimed in the following claims.

Claims: — CLAIMS — 1. A cell assembly for extracting mineral from a flowing electrolyte, including:- a housing having inlet and outlet means for passing electrolyte therethrough; the housing confining flow of electrolyte through a removable sleeve-like cathode; an anode extending into said housing, and electrical connecting means for connecting an electrical circuit to said cathode and said anode. 2. A cell assembly as claimed in claim 1, wherein said housing is a fixed cylindrical housing and includes a removable top cap supporting an anode assembly concentrically within said housing. 3. A cell assembly as claimed in claim 1 or claim 2, wherein said anode is supported by an anode assembly which includes a distal end located with a bottom support in the housing. 4. A cell assembly as claimed in any one of the preceding claims, wherein said anode includes an exposed conductive portion extending substantially the full length of the sleeve-like cathode. 5. A cell assembly as claimed in any one of the preceding claims, wherein said housing includes a tubular portion having an internal surface extending between end portions, and said sleeve-like cathode is adapted to fit against said internal surface. 6. A mineral extraction cell assembly as claimed in any one of the preceding claims and including conductor means extending at least partly into said housing for electrical contact with said sleeve-like cathode. 7. A mineral extraction cell assembly as claimed in claim 6, wherein said conductor means includes a conductor bar extending through said tubular portion against said internal surface. 8. A mineral extraction cell assembly as claimed in claim 7, wherein said sleeve-like cathode includes release means for releasing electrodeposited material. 9. A mineral extraction cell assembly as claimed in claim 8, wherein said sleeve-like cathode is a stainless steel sleeve member which is slit longitudinally whereby it may be opened for disengagement from the electrodeposited material. 10. A mineral extraction cell assembly as claimed in claim 9, wherein said sleeve member is resiliently biassed to expand when not constrained by said internal surface. 11. A mineral extraction cell assembly as claimed in any one of the preceding claims, wherein said end portions include an inlet in one end portion and an outlet in the other end portion, and said inlet and said outlet are arranged substantially tangentially for inducing a tangential component to a liquid entering and leaving said mineral extraction cell assembly through said inlet and said outlet respectively. 12. A mineral extraction cell assembly as claimed in any one of the preceding claims, wherein said housing is an open topped housing which permits said sleeve-like cathode to be inserted and removed through said open top. 13. A method of electrodepositing a metal from an electrolyte solution containing the metal, the method including:- providing an electrolytic cell assembly as claimed in claim 12; operating the electrolytic cell for a time sufficient to deposit a desired thickness of metal on the internal surface of the sleeve-like cathode; removing the top cap and the anode assembly from the housing; removing the sleeve-like cathode from the housing; removing the sleeve-like cathode from the metal, and replacing the sleeve-like cathode, the top cap and the anode assembly to the housing.

Inventors: TREASURE PATRICK ANTHONY, TREASURE, PATRICK, ANTHONY
Applicants: ELECTROMETALS MINING LIMITED, TREASURE PATRICK ANTHONY, TREASURE, PATRICK, ANTHONY
Application year: 1996
Main classification: C25C1
IPC codes: C25C1, C25C7