EP2014800B1 - Cathode stripping device - Google Patents

Abstract

A cathode peeling device, comprising bracket for cathode to be peeled, the cathode comprise two opposite faces on which has metallic sediment; a pair of separating tools; device for driving the separating tool; and mechanism for producing relative movement between the cathode and the separating tool. A cathode peeling device, comprising bracket for cathode to be peeled, the cathode comprise two opposite faces on which has metallic sediment; a pair of separating tools suitable for each faces respectively acted on the cathode, to at least partially separate metallic sediment; device for driving the separating tool, the riving device is designed so that the separating tool is moved between releasing position and working position, where the separating tool is placed on all sides of the cathode, the faces has pre-determined distance there between; and mechanism for producing relative movement between the cathode and the separating tool, to at least partially separate the metallic sediment, the separating tool is placed in the working position; a pair of stopping components, each stopping component is related to the separating tools corresponding with the stopping component pair, and combined with it in the movement, the stopping component is located and manufactured so that they are contacted to each other in the working position of the separating tool, and limit the pre-determined interval between the pair of separating tools.

Description

Technical area

The present invention generally relates to the hydrometallurgical production of metals such as zinc, and more particularly to a cathode stripping device for harvesting metal foils deposited on these cathodes.

State of the art

• grillage du sulfure de zinc (ZnS) pour obtenir un oxyde de zinc (ZnO) et supprimer certaines impuretés ;
• lixiviation pour solubiliser le zinc sous forme de sulfate de zinc (ZnSO4);
• cémentation pour éliminer les impuretés (cobalt, nickel, cadmium et cuivre) de la solution de sulfate de zinc ;
• électrolyse pour transformer le sulfate de zinc en zinc métal.

As is known, the main stages of zinc production by hydrometallurgical means are:

• roasting of zinc sulphide (ZnS) to obtain a zinc oxide (ZnO) and remove some impurities;
• leaching to solubilize zinc in the form of zinc sulphate (ZnSO4);
• carburizing to remove impurities (cobalt, nickel, cadmium and copper) from the zinc sulphate solution;
• electrolysis to transform zinc sulfate into zinc metal.

This last stage of electrowinning of zinc (in English "electrowinning", abbreviated "EW") thus consists in carrying out the electrolysis of the purified solution of zinc in electrolysis cells by passage of a direct current between anodes and cathodes. This process makes it possible to electrolytically deposit high quality metallic zinc (purity of the order of 99.99%) on the cathodes.

In practice, a cathode typically consists of an aluminum plate disposed vertically in the electrolysis cell. This plate is provided on its upper edge with a bar of a width greater than the width of the plate, which serves as a support, electrical terminal and allows its handling. The vertical edges of the cathode are generally covered with an electrical insulator to prevent the deposition of zinc. Thus, during the electrolysis, the metal is deposited on the exposed surfaces of the cathode, on the height immersed in the electrolysis bath.

The zinc metal deposit, which strongly adheres to the cathode, must then be removed. This operation is conventionally performed by means of a stripping device (also stripping or tearing in English "cathode stripping machine"). The defoliated cathodes are returned, after cleaning, in the electrolysis cells to be recharged again with zinc.

In the machine, the stripping operation typically comprises two successive phases. In the first, one acts on each of the faces of the cathode by means of a pair of chisels to tear / take off an upper corner of each sheet. Then, in the second phase, the zinc foil is completely torn off and separated from the cathode by means of scissors which extend over the entire width of the cathode.

For the initial tearing of the upper corner of the sheet using the chisels, the latter are precisely adjusted so as to be as close as possible to the surface of the cathode to be able to fit under the metal deposit, however, as much as possible, without touching the cathode to avoid damaging it.

In practice, the chisels are placed in the working position, and a vertical displacement is exerted on the cathode support, so that the chisels attack the upper corner.

It will be understood that in this operation the chisels may scratch the surface of the cathode if they are poorly positioned. Similarly, the chisels may move (deflect) if they are not sufficiently maintained, including getting closer, tightening around the cathode and scraping its surface. These damage to the cathode are harmful and lead to premature degradation of the cathode, further compromising the quality of subsequent metal deposits.

Object of the invention

The object of the present invention is to provide a cathode stripping device which minimizes the problems of cathode damage mentioned above.

According to the invention, this object is achieved by a cathode stripping device according to claim 1.

General description of the invention

• un support de cathode à effeuiller, la cathode comprenant deux faces opposées revêtues d'un dépôt métallique;
• au moins une paire d'outils d'arrachage aptes à agir chacun sur une face respective de la cathode pour y arracher au moins partiellement le dépôt métallique;
• un moyen d'actionnement de la paire d'outils d'arrachage conçu pour déplacer les outils d'arrachage entre une position dégagée et une position de travail, dans laquelle ils sont disposés de part et d'autre de la cathode, avec un espacement prédéterminé entre eux;
• un mécanisme pour effectuer un mouvement relatif entre la cathode et la paire d'outils d'arrachage pour décoller au moins partiellement le dépôt métallique, les outils d'arrachage étant en position de travail.

According to the present invention, a cathode stripping device comprises:

• a cathode support to be stripped, the cathode comprising two opposite faces coated with a metal deposit;
• at least one pair of tearing tools each capable of acting on a respective face of the cathode to tear at least partially the metal deposit;
• means for actuating the pair of tear tools adapted to move the pulling tools between a disengaged position and a working position, in which they are arranged on either side of the cathode, with a spacing predetermined between them;
• a mechanism for effecting a relative movement between the cathode and the pair of tear-off tools to at least partially unstick the metal deposit, the pulling tools being in the working position.

According to an important aspect of the invention, the present device comprises a pair of abutments associated with said pair of tear-off tools, each of the abutments being associated with a respective tear-off tool of displacement thereof, the abutments being positioned and dimensioned so as to be in contact with each other in the working position of the pulling tools, thus preventing a bringing together of the pulling tools.

Each stop being secured to the tear-off tool with which it is associated, the control of the pulling tool by means of its actuating mechanism necessarily leads to a displacement of the stop. For pulling the metal deposit, the tearing tools are close to the cathode, each of its respective face. The pulling tools are thus close together, enclosing the cathode for at least partial tearing of the metal deposit when relative movement between the tools and the cathode is performed. By bringing the pulling tools closer together, the abutments also get closer and come into contact, thus leaving a certain spacing between the pulling tools: the pulling tools are in their working position. The stops being in contact, it is not possible to bring the pulling tools closer because they are integral with them. The stops therefore guarantee a minimum separation of the pulling tools.

The tearing tools may be chisels for punctually attacking the upper edge of the metal deposit on each of the faces of the cathode, or scissors extending over the entire width of the cathode to completely tear off the sheets previously partially peeled off by the chisels . Indeed, it is possible to associate a pair of abutments according to the invention with chisels, scissors, or even both. Indeed, chisels and scissors are typically movable around the cathode and they are put in working position just before stripping.

In practice, the positioning of chisels is the most critical because they are placed a few tenths of millimeters from the surface of the cathode. We will therefore usually associate at least one pair of stops with the chisels.

According to one embodiment, the pulling tools are pivotally mounted on both sides of the cathode. The setting in working position of the chisels therefore typically consists in rotating them to grip the cathode, which causes a reconciliation of chisel heads. The stops can then be fixed to the same rotary shaft as the chisels, and designed to come into contact after a rotation corresponding to the setting work position chisels. The actuating means of the pair of tearing tools may comprise a linear actuator mounted to rotate the pair of tools pulling between the unobstructed and working positions.

Note however that the stops can also be used in the case where they are displaced axially, for example. The general principle is that the abutments are linked in displacement to the pulling tools, and they meet, next to the cathode, when pulling tools are brought together to act on the cathode. The point at which the stops meet must correspond to the operating position of the pulling tools with which they are associated.

Preferably, each chisel comprises a tool holder fixed on the pivoting support, and a sharp tool mounted on this tool holder. Note that in this case we can vary the spacing between the chisel heads by changing the tool holder / tool assembly, mounted on the pivoting support. Indeed, the stop point in rotation of the chisels being defined by the stops, the gap between the chisels is fixed for a given set of chisels. A removable chisel structure allows to interchange them to work with different gaps. An alternative would be to inter-change the stops.

Preferably, the tearing of the metal deposits is done by moving the cathode relative to the pulling tools, the latter being in their fixed working positions. To do this, the device advantageously comprises a linear traction system of the sheet in the vertical direction and upwards.

Description of the drawings

• FIG.1: une vue de face d'un mode de réalisation préféré d'un dispositif d'effeuillage de cathodes selon l'invention ;
• FIG.2: une vue de détail des différents éléments pour l'arrachage de feuilles dans le dispositif de la Fig.1 ;
• FIG.3: une vue de détail des burins, et butées associées, en position de travail.

Other features and features of the invention will become apparent from the detailed description of an advantageous embodiment presented below, by way of illustration, with reference to the accompanying drawings. These show:

• FIG.1 : a front view of a preferred embodiment of a cathode stripping device according to the invention;
• FIG.2 : a detailed view of the various elements for tearing leaves in the device of the Fig.1 ;
• FIG.3 : a detail view of chisels, and associated stops, in working position.

Detailed description of some preferred embodiments

The Fig.1 illustrates an overview of a preferred embodiment of the present cathode stripping device. The device 10 comprises a structure 12 forming a rectangular frame which comprises cathode support means to be stripped as well as tearing tools to remove the metal deposits of the two faces of the cathode and thus remove the latter.

Although not illustrated, the device 10 is typically traversed by a conveyor, for example of the chain type. On this conveyor, as seen with respect to the stripping device 10, there is thus distinguished an upstream storage zone which contains the cathodes to be stripped and a downstream storage zone which contains the treated cathodes (stripped). On the conveyor, the cathodes are generally stored with a given inter-cathode spacing, which corresponds to the inter-cathode space in the electrolysis cell. Such a storage greatly simplifies the handling of the cathodes because they can be collected en bloc in the electrolysis cells and repositioned in block with the appropriate spacing. Between the two storage areas, at the level of the stripping device 10, the cathode support means are advantageously designed to allow the removal, on the conveyor, of a cathode to be stripped, and its removal on the conveyor after treatment.

As we see best on the Fig.2 the cathode support means, generally indicated 14, here comprise a frame consisting of a transverse bar 18 and two vertical uprights 20 (only one shown) equipped at their respective lower end with a housing 22 adapted to receive, suspension, the ends of the head bar 24 of the cathode 26. It is recalled that in the hydrometallurgical production of metals such as zinc, conventionally used cathodes 26 consist of an aluminum plate 28, which is provided on its upper edge of a head bar 24 with a width greater than the width of the plate 28, this head bar 24 serving as a support, an electrical terminal and for its manipulation. The vertical edges of the cathode plate 28 are generally covered with an insulator electric (not shown) to prevent zinc deposition.

• un coin supérieur du dépôt métallique 29 sur chaque face de la cathode 26 est tout d'abord décollé au moyens de deux burins 30, lesquels constituent une première paire d'outils d'arrachage ;
• puis les dépôts métalliques 29 sont complètement arrachés des faces respectives de la cathode 26 au moyens de deux couteaux 32, lesquels constituent une deuxième paire d'outils d'arrachage.

In the present variant, the stripping device 10 is designed for a stripping in two steps:

• an upper corner of the metal deposit 29 on each face of the cathode 26 is first peeled off by means of two chisels 30, which constitute a first pair of tear tools;
• then the metal deposits 29 are completely torn from the respective faces of the cathode 26 by means of two knives 32, which constitute a second pair of tearing tools.

As regards more specifically the 30 chisels, as we see well on the Figs. 2 and 3 these are arranged on either side of the cathode 26 so as to attack each an upper edge of the metal deposit. In the Figs. 2 and 3 the chisels are in the so-called working position: they are positioned on either side of the cathode 26 just above the upper edge of the metal deposit 29. In addition, they are preferably arranged very close to the cathode 26, to a few tenths of a millimeter from its surface, so as not to touch the cathode but to attack the deposit as close as possible to the interface plate 28 - metal deposit 29. In the working position, there is therefore a predefined spacing between each chisel 30 and the cathode 26 (generally the same on both sides), which therefore corresponds to a predefined spacing between the two chisels 30.

An actuating means is provided for moving the chisels between the working position as illustrated in FIGS. Figs. 2 and 3 , and a disengaged position (not shown) in which the chisels 30 are out of range of the cathode 26 and can not attack the metal deposits 29 or the cathode plate 28.

In the present embodiment, each chisel 30 is pivotally mounted around a respective rotary shaft 34, horizontal and parallel to the plane of the cathode 26. The actuating means comprises a linear actuator 36, e.g. of the mechanical jack type, electrical or hydraulic, associated with each chisel 30. More specifically, the rod 38 of each actuator 36 is coupled to the shaft 34 of the respective chisel 30 by means of a crank 40, so that the elongation where the narrowing of the actuator rod 38 causes rotation of the respective shaft 30 in one direction or the other and thus associated chisel. Note that to allow such a mode of operation, the actuator rod 38 has an articulated end portion which follows the curved path of the crank, completed by an articulated mounting of the actuator body.

It will be understood, so that the chisels 30 actually attack the metal deposit 29 in the configuration of the Figs.2 and 3 there must be a relative movement between the chisels 30 and the cathode 26. This relative movement is preferably obtained by moving the cathode 26 upwards, the tearing tools remaining fixed. To do this, the transverse bar 18 of the cathode support 14 is securely fixed to a vertical traction mechanism 42 comprising a jack 44 and a system of pulleys 46 and counterweight 48. The controlled displacement of the cathode 26 upwards makes it possible to take off / tear off, on one or more centimeters, the metal deposit 29 of the plate 28.

As is known, in this operation, if the chisels are misplaced (too close to the cathode plate or directly against it), there is a significant risk of damaging the surface of the cathode 26. The spacing chisel / cathode, and therefore between the chisels 30 themselves, must therefore be respected and adjusted accurately. It is also necessary to avoid that the chisels 30 deviate from their working position by coming closer, either during their positioning or during tearing.

It will be appreciated that to avoid bringing the chisels 30 closer together, and thus to respect the inter-chisel spacing, the device 10 comprises a pair of stops 50, each of the stops 50 being associated with each respective chisel 30. The abutments 50 are integral in displacement, here in rotation, their respective abutment 30, and are dimensioned so as to be in contact with one another in the working position of the chisels 30, as is the case on the Figs. 2 and 3 . In the present variant, the stops 50 are firmly fixed to the rotary shaft 34 of the chisels 30 and extend perpendicular to them. In the direction of rotation of each shaft 34 corresponding to the approach of the chisels 30, to bring them into the working position, the rotation is automatically blocked once the stops 50 in contact. The ends of the abutments that meet have a suitable shape.

For better efficiency, especially in order to minimize bending / torsion forces, the abutments 50 are advantageously placed to meet in the vicinity of the cathode, near the action zone of the chisels (see FIG. Fig.2 ). In addition, the contact zone of each stop 50 is at a distance between the rotary shaft and the contact point substantially corresponding to the distance between the rotary shaft and the sharp tool 56 of the corresponding chisel 30.

The stops 50 are therefore useful for controlling the positioning of the chisels 30 in the working configuration, and ensure a minimum separation between the chisels 30, respectively between the chisel holders.

It will be noted that in the present variant, the chisels 30 are mounted on supports 52 integral with the respective rotary shaft 34, thus forming pivoting supports. The chisels 30 themselves consist of a tool holder 54 and a sharp tool 56 firmly attached to the tool holder 54. In the present variant, each tool holder 54 is fixed on its support 52 by two screws 58 .

There will also be an interesting aspect of this structure. The stops 50 limit the approach of the chisels 30 by contacting them, which thus defines given radial positions for the chisel supports 52, and also defining the spacing between the sharp tools 56 of the two chisels 30 in the working position. For a given set of chisels, the spacing between chisels in working position is constant, because determined by the contact between the two stops.

If it is desired to work with a different inter-burin spacing, for example due to a different cathode thickness, it is necessary to replace the chisels 30, ie the tool holder assembly 54 and tool 56. A second set of chisels will be used, with a different configuration of the tool-tool / sharp tool assembly, corresponding to a different spacing between the chisels 30, and respectively between the sharp tools 56, once mounted on the supports. 52.

The subsequent stripping, that is to say the complete tearing of the metal deposits of the cathode 26, is done conventionally using the knives 32, under the action of a vertical pull exerted by the mechanism 42 on the bar 18 of the cathode support 14. The knives 32 extend over the entire width of the cathode plate and are slightly inclined so that they engage, when the cathode 26 is pulled upwards under the metal deposit 29 at its upper corner taken off by the chisels 30.

The knives 32 are attached to rotating shafts 60 so that they can be moved closer to or away from the cathode 26 via a linear actuator 62 coupled to a crank 64. The knife-cathode distance is greater than for the chisels so that their positioning is less critical and less likely to damage the cathode plate 28. For this reason, in the present variant, a system of integral stops, as for chisels, is not considered necessary. However, for precise control of the spacing between knives, it is possible to associate with each one an integral abutment in displacement in the same manner as for the chisels.

In the present variant, for reasons of compactness, the rotary shafts 34, respectively 60, chisels 30 and knives 32 are mounted coaxially. Furthermore, the spacing between the rotary shafts 34, 60 is such that it allows the passage of the cathode when pulled up by the traction system. The skilled person can of course consider different configurations.

Claims (10)

1. Cathode stripping device comprising:

   - a support for a cathode to be stripped, the cathode comprising two opposite faces with a metal deposit thereon;

   - a pair of detaching tools suitable for acting each on one respective face of the cathode to at least partially detach the metal deposit;

   - means for actuating the pair of detaching tools designed to move the detaching tools between a release position and a working position, in which they are placed on either side of the cathode, with a predetermined spacing between them; and

   - a mechanism for producing a relative movement between the cathode and the pair of detaching tools to at least partially detach the metal deposit, the detaching tools being in the working position,

   characterized by
   a pair of stops, each of the stops being associated with a respective detaching tool of the said pair, and joined thereto in motion, the stops being positioned and dimensioned so as to be in contact with one another in the working position of the detaching tools, thereby defining said predetermined spacing between the pair of detaching tools.
2. Device according to Claim 1, characterized in that the detaching tools are chisels designed to locally attack the top edge of the metal deposit on each face of the cathode.
3. Device according to Claim 1, characterized in that the detaching tools are knives extending along the whole width of the cathode
4. Device according to Claim 1, characterized in that the detaching tools are chisels and the said stops are associated with the said chisels; and in that it further comprises a pair of knives
5. Device according to any one of the preceding claims, characterized in that the detaching tools are pivotingly mounted.
6. Device according to Claim 5, characterized in that the stop associated with each detaching tool is fixed to the same pivoting shaft as the latter
7. Device according to any one of the preceding claims, characterized in that the detaching tools are each mounted on a respective pivoting support.
8. Device according to Claim 7, characterized in that each chisel comprises a tool-holder fixed to the said pivoting support, and a sharp tool mounted on the said tool-holder
9. Device according to any one of the preceding claims, characterized in that the means for actuating the pair of detaching tools comprises a linear actuator mounted to pivot the pair of detaching tools between the release and working positions
10. Device according to any one of the preceding claims, characterized in that the said mechanism for producing a relative movement between the cathode and the pair of detaching tools comprises a system for linear traction of the sheet in the vertical and upward direction

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