DEVICE FOR EXTRACTING A METAL ELECTROLYTICALLY DEPOSITED ON A CATHODE

Abstract

A device for producing a pure metal or an alloy of the pure metal via electrolytic reduction of an ore of the pure metal or of a substance containing an oxidized form of the pure metal includes: a cell equipped with an anode, a cathode, an electrolytic area comprising an electrolyte, and a removable cell closing system, the cathode having a coating non-adherent for an electrolytically deposited metal; and an electrically conductive metal sheet for extraction of a plate of the electrolytically deposited metal on the cathode, the metal sheet being arranged in the cell in a continuation of the cathode or partially overlapping the cathode, with mechanical and electrical contact at one end with the cathode and extending at least partly beyond the electrolytic area of the cell so as to allow simultaneous depositing of the pure metal on the cathode and on a portion of the metal sheet.

Claims

1. A device for producing a pure metal or an alloy of the pure metal via electrolytic reduction of an ore of the pure metal or of a substance containing an oxidized form of the pure metal, the device comprising: a cell equipped with an anode, a cathode, an electrolytic area comprising an electrolyte, and a removable cell closing system, the cathode having a coating non-adherent for an electrolytically deposited metal; and an electrically conductive metal sheet for extraction of a plate of the electrolytically deposited metal on the cathode, the metal sheet being arranged in the cell in a continuation of the cathode or partially overlapping the cathode, with mechanical and electrical contact at one end with the cathode and extending at least partly beyond the electrolytic area of the cell so as to allow simultaneous depositing of the pure metal on the cathode and on a portion of the metal sheet in contact with the electrolytic area, wherein an adherence between the cathode and the electrolytically deposited metal being less than an adherence between the metal sheet and the electrolytically deposited metal such that the electrolytically deposited metal is separated from the cathode and is drawn out by the metal sheet during a subsequent extraction of the metal sheet via a mechanical means applied on a portion of the metal sheet, which extends beyond the electrolytic area by a translational movement.

2. The device of claim 1, wherein a length of the metal sheet is less than 50% of a length of the cathode.

3. The device of claim 1, wherein the cathode comprises at least one of carbon, graphite having low surface roughness, graphite impregnated or coated with pore fillers, or pure metals or coated alloys thereof.

4. The device of claim 1, wherein one portion of the metal sheet, in continuation of the cathode and projecting beyond the electrolytic area, is received in the removable closing system, which is closed in operation to hold the electrolyte within the cell.

5. The device of claim 1, further comprising: grasping means cooperating with the metal sheet or elements thereof to allow extraction of an assembly of the metal sheet and the electrolytically deposited metal.

6. The device of claim 5, wherein the grasping means comprise clamping means, or added geometric elements cooperating together to ensure a pulling action.

7. The device of claim 5, further comprising: locking means configured to hold the metal sheet and the electrolytically deposited metal in position when opening the cell and for subsequent extraction of an assembly of the plate and metal sheet by the grasping means, the locking means coinciding with the grasping means.

8. The device of claim 1, wherein the cell is tilted at an angle of 20 to 60 from horizontal, wherein the device further comprises electrodes that are planar and that have an inter-electrode distance of between 1 mm and 50 mm, wherein the cathode is permanently fixed in the device, and wherein the device further comprises mechanical extraction means configured to carry out extraction of an assembly of the metal sheet and electrolytically deposited metal along a translational movement parallel to the electrodes.

9. The device of claim 1, wherein the device provides that, after extraction, the metal sheet is either separated from the electrolytically deposited pure metal or alloy of the electrolytically deposited metal to prevent pollution, or subsequently melted with the electrolytically deposited metal.

10. The device of claim 1, wherein the device provides electrolytic deposition of iron in a basic medium, and wherein the metal sheet comprises a low-carbon steel sheet.

11. The device of claim 1, wherein the device provides electrorefining of zinc, nickel, or copper, in an acid medium, and wherein the metal sheet comprises a zinc, nickel, or copper plate, respectively.

12. The device of claim 2, wherein the length of the metal sheet is less than 10% of the length of the cathode.

13. The device of claim 6, wherein the grasping means comprise the clamping means, and wherein the clamping means comprise grippers, cylinders, bolts, or traction hooks cooperating with holes in the metal sheet.

14. The device of claim 8, wherein the inter-electrode distance is between 6 and 20 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

[0021] FIG. 1 schematically illustrates a closed iron-electrowinning cell according to one embodiment of the present invention, during the production phase of the metal deposit.

[0022] FIG. 2 schematically illustrates an open iron-electrowinning cell according to one embodiment of the present invention, during the extraction phase of the deposited iron plate.

[0023] FIG. 3 illustrates a practical example of embodiment of the present invention comprising an electrolytic cell with a removable closing system and a system for recovery of the iron plate deposited at the cathode.

[0024] FIG. 4 shows an example of the movement imparted to the removable cell closing system.

[0025] FIG. 5 shows a detailed view of an example of the system allowing extraction of the deposited iron plate.

DETAILED DESCRIPTION

[0026] In an embodiment, the present invention provides a practical, easy means for separating the plates of metal deposited on the cathodes in electrolytic production processes, this extraction necessarily being in situ since it must take into consideration the physical constraints imposed by the electrolytic cell such as those relating to a closed cell, non-dismantling of the cell, a short anode-cathode distance to maintain good energy efficiency, etc.

[0027] A first aspect of the present invention relates to a device for the production of a pure metal or an alloy of this metal via electrolytic reduction of an ore of this metal or of a substance containing an oxidized form of this metal, said device comprising a cell equipped with an anode, a cathode, an electrolytic area comprising an electrolyte and a removable cell closing system, the cathode being provided with a non-adherent coating for the electrolytically deposited metal, wherein the device additionally comprises a metal sheet having advantageously a consumable function, which is electrically conductive and intended to facilitate the extraction of a plate of said metal electrolytically deposited on the cathode, said metal sheet being arranged in the cell in the continuation of the cathode or partially overlapping the latter, with mechanical and hence electrical contact at one end with the cathode, and extending partly beyond the electrolytic area of the cell so as to allow, when in operation, the simultaneous depositing of said metal on the cathode and on a portion of the metal sheet in contact with the electrolytic area, the adherence between the cathode and the deposit being less than the adherence between the metal sheet and the deposit, so that the metal deposit is separated from the cathode and drawn out by the metal sheet during a subsequent extraction of the metal sheet via a mechanical means applied on the portion of the latter extending beyond the electrolytic area by a translational movement.

[0028] According to preferred embodiments, the device is also limited by one of the following features or by any suitable combination thereof: [0029] the length of the metal sheet is less than 50%, preferably less than 10% the length of the cathode; [0030] the cathode is in carbon, graphite with low surface roughness, graphite impregnated or coated with pore fillers, or in pure metals and/or some of the optionally coated alloys thereof; [0031] a portion of the metal sheet in the continuation of the cathode and projecting beyond the electrolytic area is received in the removable closing system which is closed in operation to hold the electrolyte within the cell; [0032] the device comprises grasping means cooperating with the metal sheet or elements thereof, to allow extraction of the metal sheet/deposited metal assembly; [0033] the grasping means are clamping means such as grippers or cylinders, bolts or traction hooks cooperating with holes made in the metal sheet, or added geometric elements cooperating together to ensure a pulling action; [0034] the device comprises locking means to hold the metal sheet and the deposited plate in position when opening the cell and for subsequent extraction of the plate and metal sheet assembly by the grasping means, the locking means coinciding with the grasping means; [0035] the electrolytic cell is tilted at an angle of 20 to 60 from the horizontal, the electrodes are planar with an inter-electrode distance of between 1 and 50 mm, and preferably between 6 and 20 mm, the cathode is permanently fixed in the device and the mechanical extraction means is configured to carry out extraction of the metal sheet/metal assembly along a translational movement parallel to the electrodes.

[0036] Another aspect of the invention relates to the use of the above-described device wherein, after extraction, the metal sheet is either separated from said deposited pure metal or metal alloy to prevent any pollution, or it is subsequently melted with the deposited metal.

[0037] Advantageously, the use relates to the electrolytic deposition of iron in a basic medium, wherein the metal sheet is a low-carbon steel sheet.

[0038] Also advantageously, the use relates to the electrorefining of zinc, nickel or copper in an acid medium, the metal sheet being a zinc, nickel, or copper plate respectively.

[0039] The present invention not only consists in obtaining an electrolytic metal deposit on a cathode, but also in co-depositing the metal adherently onto at least one portion of an electrically conductive consumable, more precisely a metal sheet, prepared for example in the form of a steel plate which can be compatible with subsequent melting steps of the metal. The consumable element is placed in the electrolytic cell before starting the depositing operation, and is positioned so that electrical contact with the cathode is ensured. This allows extraction of the deposit, deposition being performed simultaneously on the cathode and on the consumable, through the use of a grasping system such as grippers or similar elements preferably positioned on a portion of the consumable which has not received any deposit or only a scarce deposit. The cell is preferably positioned so that it is tilted, allowing the consumable to be positioned in a lower part and the cathode to be positioned in an upper part of the cell, with at least one portion of the consumable not covered by the deposit to permit mechanical gripping of the consumable when opening the cell in the lower part thereof, after draining and rinsing the cell.

[0040] In the description that follows, the terms consumable and metal sheet/plate are considered as equivalent terms.

[0041] Extraction of the deposited metal is therefore achieved by withdrawing the consumable concomitantly with the entire deposit which does not adhere to the cathode, preferably by means of a special coating of the cathode having for example a carbon or graphite base with low surface roughness. Metal extraction is performed by a guided translational movement.

[0042] The deposited metal plate/consumable is then transferred onto a supporting table to prevent material breakage during the extraction process.

[0043] According to the invention, the cell can be tilted at an angle between the horizontal and vertical, but preferably at an angle of between 20 and 60 from the horizontal to take advantage of the effect of gravity and also for compactness. The height of the cell is preferably between 50 mm and 700 mm, and further preferably between 100 mm and 300 mm. It has a length of 1 m to 4 m and preferably between 1 m and 3.5 m. The width of the cell is from 1 m to 2 m and preferably from 1 m to 1.5 m.

[0044] According to invention, the length of the consumable portion is less than 50% of the length of the cathode, and preferably less than 20% of the length of the cathode, and more preferably 10% less. The width of the consumable portion must be at least approximately equal to the width of the cathode with which it is in contact.

[0045] The expected thickness of the deposit is between 2 mm and 50 mm, preferably between 3 mm and 5 mm, depending on the surface area of the cathode, to obtain a plate that has sufficient mechanical strength to allow extraction thereof, whilst maintaining a minimum anode-cathode distance throughout the entire depositing phase.

[0046] FIG. 1 schematically illustrates a configuration of an electrolytic cell 1 adapted for the electrowinning of iron, during the production phase by means of a device according to the invention.

[0047] In this cell 1, one end of the anode 2 is positioned facing part of the cathode 3 and also facing part of the consumable 5 which adjoins or overlaps the lower edge of the cathode 3, with which it is in physical contact, thereby ensuring perfect electrical continuity between the cathode 3 and the consumable 5. These two factors allow the obtention of a metal deposit 4 covering not only the cathode 3 but also a section 5 of the consumable 5. The consumable 5 is therefore sized to project downwardly beyond the area of the cell containing the electrolyte 8. One portion of the consumable 5 will therefore not be covered by the electrolytically deposited metal and the protruding portion 5 of the consumable 5 will allow easier grasping thereof.

[0048] According to the invention, the electrolytic cell 1 is constantly closed when in operation, and a removable closing system 6 is used to close the cell 1. The connection between the cell 1 and the closing system 6 is sealed to prevent any leakage of electrolyte 8.

[0049] The system according to the invention is advantageously designed to automate extraction of the deposited iron plate. In one embodiment, a table on runners 7 is able to be brought close to the cell 1 and to rotatably tilt at an angle to lie parallel with the cell (FIG. 2). For example, three pneumatic grippers 10 equipping the table 7 (FIG. 5) grasp the consumable 5 and withdraw it out of the cell. Once the iron plate/consumable is recovered, the table 7 can rotatably return to horizontal position and the plate can be transferred onto a carriage to be used at the next step of the treatment process. In another embodiment, the table could be already inclined and come to position itself before drawing away. The deposited plate will then remain in the tilted position until it is removed.

[0050] FIG. 2 schematically illustrates one embodiment to extract the iron plate 4 at the end of the production process. The cell 1 has been previously drained of its electrolyte 8 to prevent outflow thereof when extracting the plate. The removable closing and recovery system 6 is moved by horizontal translation, for example to provide access to the consumable 5 and recovery thereof (see FIG. 4).

[0051] According to the invention, there must be significant differential adherence between the cathode and the iron deposit, and between the consumable and the iron deposit, the first being weaker than the second. Therefore, the cathode is to be formed of a material that scarcely adheres to iron, such as a material in carbon, graphite with low surface roughness, graphite impregnated or coated with pore fillers, or pure metals such as silver or copper and some of the optionally coated alloys thereof.

[0052] Given the required short inter-electrode distance, at the time of extraction the deposited sheet 4 cannot be lifted to be directly detached from the cathode 3 as in prior art stripping methods. When the cell 1 is open, one portion of the consumable 5 must be able to protrude therefrom as indicated above, to allow recovery of the plate via a mobile grasping and recovery system 7 such as a table. The removable system 6 is then used to place a new consumable 5 in contact with the cathode 3. The plate 4 together with the consumable 5 is grasped by grippers, clamps, or similar elements 10 and is withdrawn along a guided translational movement parallel to the cell. The metal deposit glued to the consumable 5 but not to the cathode 3, which is non-adhering, detaches itself from the cathode 3 and is drawn out of the cell by the translational movement of the consumable 5 (see FIG. 5). The iron plate 4 is then transferred onto a table during extraction thereof as described above.

[0053] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.

[0054] The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article a or the in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of or should be interpreted as being inclusive, such that the recitation of A or B is not exclusive of A and B, unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of at least one of A, B and C should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of A, B and/or C or at least one of A, B or C should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

LIST OF REFERENCE SYMBOLS

[0055] 1: electrowinning cell [0056] 2: anode [0057] 3: cathode in carbon or graphite with low surface roughness [0058] 4: iron deposit/plate [0059] 5: consumable (metal sheet) [0060] 5: iron deposit area on the consumable [0061] 5: protruding part of the consumable not covered with metal deposit [0062] 6: removable cell closing system [0063] 7: iron plate extraction system [0064] 8: electrolyte (electrolytic area) [0065] 9: extraction movement [0066] 10: grasping means