NO347913B1

NO347913B1 - Connector for the mechanical and electrical connection of an anode to the anode frame of an aluminum production cell

Info

Publication number: NO347913B1
Application number: NO20170677A
Authority: NO
Inventors: Roger Boinet; Frank-Peter Schaum
Original assignee: Reel Gmbh
Priority date: 2016-04-26
Filing date: 2017-04-24
Publication date: 2024-05-13
Also published as: RU2017114520A3; FR3050462A1; RU2017114520A; RU2724774C2; NO20170677A1; FR3050462B1

Description

CONNECTOR FOR THE MECHANICAL AND ELECTRICAL CONNECTION OF AN ANODE TO THE ANODE FRAME OF AN ALUMINUM PRODUCTION CELL

DOMAIN OF THE INVENTION

The present invention pertains to the field of aluminum production implementing the well-known fused-salt electrolysis technology.

According to this technology, the production of aluminum is carried out within series-assembled production cells, each comprising a molten pool, especially of cryolite and alumina, conducting an electric current of high amperage. Anodes, typically made of a carbon material, are partially immersed in cells and are consumed along the progress of the electrolysis reaction, so that the periodic replacement thereof should be provided.

For this purpose, the anodes are mounted at the end of a metal rod intended to enable their electrical and mechanical connection to a metal frame, called anode frame, which is mobile relative to a fixed gantry arranged above the electrolytic cells. Such an anode frame moves down to compensate for the clearance of the anodes due to their consumption, and thus substantially keep the anode-cathode distance between the anode and the cell used as a cathode substantially constant. To ensure the fastening of the anodes to the anode frame, connectors used both as a mechanical connection of the anode rods to the anode frame and for the electric conduction enabling to provide the electrolysis reaction.

The main issues of the implementation of such a connector are, first, the achieving of a very efficient fastening to prevent the anodes from falling into the electrolytic cell, which might damage it, and on the other hand, the optimizing of the electric connection to limit voltage drops at the contact level, due to the very high amperages conducted by each of the anodes.

PRIOR STATE OF THE ART

Most of the connectors currently used are mobile. In other words, they do not permanently remain on the anode frame.

Among such mobile connectors, that described in document FR 2039 543 is known. This document describes a connector formed of two levers hinged on a common pin, the respective ends of said pin being received in clips fastened to the anode frame. The levers are capable of moving towards or away from each other under the action of a doubled threaded clamping screw.

The effective clamping of the anode rod against the anode frame results from the relative displacement of the edge of the levers with respect to the clip. Thereby, the pressing surface of the levers, close to the common hinge pin, is such that when the opposite ends of said levers are brought towards each other by means of the clamping screw, this induces a clamping force adapted to the envisaged application. As a corollary, when said ends are moved away from each other, the pressing surface of the levers is moved away from the reference frame defined by the clips, thus releasing the considered anode rod.

This type of connector has also been described in document FR 2854 906. This document more particularly discloses an upper lever provided with a gripping edge intended to cooperate with catching means formed within a device for handling said connectors.

Document EP 0584 024 also describes a mobile connector where the area intended to cooperate with the anode rod, to ensure the connection thereof to the anode frame, is formed by the edge of cross-pieces forming part of the connector levers. Document US2015/114833 discloses a preheating connector intended to be implemented during the preheating phase of the electrolysis tank. Said connector comprises jaws connected to cross pieces, adapted to interact with a pin that acts as a hinge as well as interacting with clips on the anode frame. The connector is actuated by a clamping screw. The connector is provided with pressing surfaces in the form of rollers arranged on cross pieces in a form of an axle, enabling a rotating motion of the pressing surface relative to the cross piece.

These different documents describe a hyperstatic connector between the axis defined by the common hinge pin of the levers, and the plane defined by the parallelism of the anode clamping surfaces. Indeed, since the connector-anode contact is of cylinder-on-plane type and, further, the pressure stress is not uniform due to the hyperstaticity of the device, the anode rods are deformed by the jaws or levers of the connector, thus decreasing the clamping effect and thereby affecting the function of mechanical fastening of the anode to the anode frame, and on the other hand, affect the voltage drop between the anode rod and the anode frame.

To overcome these disadvantages, document FR 2902 443 provides a connector of the considered type having its pressing body, due to its structure on the one hand, and to the mode in which it is fastened to the levers on the other hand, giving it an isostatic character capable of increasing the surface area, and accordingly the efficiency of the anode rod on the anode frame, and further, the optimization of the electric conduction between the anode frame and the anode rod.

To achieve this, the pressing body is distinct from the levers or cross-pieces rigidly attaching the levers to each other, the isostatic character being obtained by the use of two planar surfaces assembled on swivel joints of the connector, to give said planar surfaces a degree of clearance in a horizontal plane and in a vertical plane during operations of tightening / loosening of the clamping screw, said planar surfaces extending substantially vertically from the median area of the connector.

If, undoubtedly, such an isostatic connector is fully satisfactory in terms of mechanical fastening as well as in terms of electric connection, however, experience has shown that due to the conditions to which such connectors are submitted, which are inherent, in particular, to certain short-circuit phases, in addition to the temperature conditions, some fatigue resulting from the thermal effect inherent to the short-circuit phase appears, which results in recurring breakage phenomena, requiring a total replacement of the connector.

The object targeted by the present invention aims at doing away with such breakage problems.

SUMMARY OF THE INVENTION

The invention thus aims at a connector for the mechanical and electrical connection of an anode to the anode frame of a cell of aluminum production by fused-salt electrolysis, said anode frame being provided with fixing clips intended to cooperate with the connector, which is made up of two clamps or jaws used as levers, said clamps or jaws being each formed of two lateral flanges connected together by means of back and front cross-pieces, said clamps or jaws being hinged on a common pin having its respective extensions received within said clips, said levers being actuated in an antagonistic manner at their free ends by means of a clamping screw with two right and left threaded areas, cooperating at the level of back cross-pieces connecting said free ends of the clamps, the pressing surface of the connector, that is, the area intended to cooperate with the anode rod to enable to connect the latter to the anode frame, being formed by two pressing bodies distinct from the clamps or jaws and from the front and back cross-pieces rigidly attaching together said clamps or jaws, and arranged on either side of the pin along which the levers or jaws are hinged together, the pressing surface or each of the two pressing bodies cooperating with a swivel joint assembled at the end of the front cross-pieces connecting the two clamps or jaws based on which the connector is formed, wherein the pressing bodies are each formed of two generally U-shaped branches, the free ends of the branches being rigidly attached together by a plate and the base of the U being rigidly attached to the corresponding pressing surface.

Thereby, the pressing bodies are made isostatic, and in parallel, by separating the pressing surfaces and the bodies associated therewith from one another, phenomena of fatigue and, as a corollary, of breakage likely to result from the fatigue phenomena inherent to the conditions to which said connectors are submitted are avoided.

Further, each of the pressing bodies is assembled to float around the front cross-pieces, each defining a swivel joint cooperating with the corresponding pressing surface, thus giving it the desired isostaticity. Thereby, and to avoid giving the pressing body too much lateral clearance, the cross-pieces used as a swivel joint have a specific profile, bulged towards the anode frame, so that the two U-shaped branches based on which each of the pressing bodies are formed are located on either side of the apex of the bulged shape. Further, said front cross-pieces are each provided with two protrusions extending on either side of the corresponding pressing surface, to limit the clearance thereof in the lateral plane.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and advantages of the present invention will now be discussed in the following non-limiting description of a specific embodiment, in relation with the accompanying drawings.

Figure 1 is a simplified representation illustrating a cell of aluminum production by fused-salt electrolysis, showing different anodes affixed to the associated anode frame.

Figures 2 and 3 are two simplified perspective representations seen under two different angles of the connector according to the invention.

Figures 4, 5, and 6 are two simplified vertical cross-section representations of the connector of the invention, respectively in transport mode, in nominal mode, and in maximum mode, in terms of pressure exerted on the anode rod against the anode frame.

Figures 7, 8, and 9 are simplified representations in top view of the connector of the invention, according to the same respective positions as those of Figures 4, 5, and 6.

Figure 10 is a simplified cross-section representation illustrating the cooperation of a device for handling the connector of the invention with such a connector.

DETAILED DESCRIPTION OF THE DRAWINGS

An electrolytic cell (1) intended to enable the production of aluminum by socalled fused-salt technology has been shown in relation with Figure 1. A series of prebaked anodes (2), typically made of carbon and each fastened to an anode frame (3) via a substantially vertical electrically-conductive metal rod (4), are plunged into this cell.

The anode frame (3) is also metallic and thus electrically-conductive, and is mobile with respect to a fixed gantry (5), arranged above the electrolytic cell (1). Thus, the anode frame (3) is capable of vertically shifting with respect to the gantry (5).

The rods (4) of the anodes (2), enable to fasten the latter to the anode frame (3) by means of connectors (10) described in further detail hereafter, each provided with a hinge pin, received within clips (6) fastened to said anode frame (3).

The connector according to the invention is more particularly described in relation with Figures 2 to 9.

The connector comprises in known fashion two levers or jaws (11) and (12), each formed of two lateral flanges connected together by means of back and front cross-pieces, (13) and (14) and (15) and (16).

The two levers or jaws (11) and (12) are hinged together on a pin (17), in the case in point formed of a cylindrical metal rod. The rod protrudes on either side of the connector, to be received by the clips (6) fastened to the anode frame, so as to thus enable the connectors to be received on said frame and, as a corollary, to ensure the function of clamping of the anode rods (4) against the anode frame.

The back cross-pieces (13) and (14) are each provided with a boring provided with an inner thread intended to receive a clamping screw (18) comprising two collinear portions (19) and (20), having an opposite thread. The screw (18) is provided with a head (21) here having a square-shaped cross-section, intended to cooperate with a clamping body, not shown. The cross-pieces (13) and (14) are rotatably mounted on the lateral flanges forming the levers (11) and (12), to substantially linearly hold the rod of the clamping screw during connector tightening or loosening operations.

According to the invention, the connector further comprises two pressing bodies (22) and (23), independent from each other, isostatically fastened to said connector. Each of the pressing bodies (22) and (23) is provided with a pressing surface (24) and (25). The pressing surfaces are intended to come into contact with the anode rod, to ensure the mechanical fastening thereof to the anode frame, in addition to the electric conduction between said anode frame and the corresponding anode rod.

More specifically, each of the pressing bodies is formed of two U-shaped structures, having the free ends of their branches interconnected by means of a planar plate (26), and having their base rigidly attached to pressing surfaces (24) and (25). Thereby, each of the pressing bodies (22) and (23) surround the front cross-pieces, respectively (15) and (16), without for all this being rigidly attached thereto.

Front cross-pieces (15) and (16) cause, as levers (11) and (12) move away from each other, a movement of pressing surfaces (24) and (25) towards the anode rod by cooperation of the front end (26) of said cross-pieces used as a swivel point, received in a complementary semi-spherical shape of said pressing surfaces (24) and (25), which can even be observed in Figures 4, 5, and 6.

Further, the lateral clearance of pressing bodies (22) and (23) is limited by the specific shape of said cross-pieces (15) and (16), as can be observed in Figures 7, 8, and 9. More specifically, on the one hand, the cross-pieces are slightly bulged towards the anode rod, so that the apex of said bulged areas is located between the U-shaped structures forming the pressing bodies and, on the other hand, said cross-pieces are provided with protrusions or outgrowths (27) extending on either side of the U-shaped structures, which can here again be observed in Figures 7, 8, and 9.

However, the pressing bodies (22, 23) are freer to move, particularly vertically, to give said pressing bodies the desired isostaticity.

Thus, the protrusions or lugs (27) laterally hold the pressing bodies in the connector clamping direction.

Further, the plates (26) hold the pressing bodies around the cross-pieces during the handling of the connector. Further, the plate (26) of the lower pressing body is used to grasp the connector during the handling thereof, as can be seen in Figure 10.

In this drawing, reference numeral (30) designates the device enabling to handle, and accordingly to actuate, the connector according to the invention. The device, fastened to a specific machine associated with a dedicated gantry, capable of displacing above the electrolysis cell (not shown), basically comprises a fork (31) having its lower end forming a hook (32) intended to receive the lower end of the plate (26) of the lower pressing body. The device also comprises a key wrench (33), intended to receive the screw head (21) to tighten or loosen the connector.

Due to the independence of the two pressing bodies (22) and (23) relative to each other, an additional degree of liberty is given, in a way, during the actuation of the connector, more particularly during operations of tightening and thus of mechanical fastening of the anode rods against the anode frame.

Further, and above all, this independence of the two pressing bodies enables to do away with fatigue phenomena observed with prior art connectors.

Another advantage of this solution is to make the connector repairable at a low cost. Indeed, the two pressing bodies are those undergoing the most damage due to the electric arcs of very high intensity capable of occurring during the fastening of the anode rod to the anode frame. Such electric arcs prematurely destroy the pressing bodies but no longer the other components of the connector tightening system, which are not affected by the electric arcs due to their central position. Thereby, it is then sufficient to only change the damaged pressing body or bodies, and no longer the entire connector.

Claims

1. A connector (10) for the mechanical and electrical connection of an anode to the anode frame (3) of a cell (1) of aluminum production by fused-salt electrolysis, said anode frame (3) being provided with fixing clips (6) intended to cooperate with the connector (10), which is made up of two clamps or jaws (11, 12) used as levers, said clamps or jaws (11, 12) being each formed of two lateral flanges connected together by means of back (13, 14) and front (15, 16) cross-pieces, said clamps or jaws (11, 12) being hinged on a common pin (17) having its respective extensions received within said clips, said levers being actuated in an antagonistic manner at their free ends by means of a clamping screw (18) with two right and left threaded areas (19, 20), cooperating at the level of back cross-pieces (13, 14) connecting said free ends of the clamps, the pressing surface of the connector, that is, the area intended to cooperate with the anode rod (4) to enable to connect the latter to the anode frame (3), being formed by two pressing bodies (22, 23) distinct from the clamps or jaws (11, 12) and from the front (15, 16) and back (13, 14) cross-pieces rigidly attaching together said clamps or jaws, and arranged on either side of the pin (17) along which the levers or jaws are hinged together, the pressing surface (24, 25) or each of the two pressing bodies cooperating with a swivel joint assembled at the end of the front cross-pieces (15, 16) connecting the two clamps or jaws based on which the connector is formed, characterized in that the pressing bodies (22, 23) are each formed of two generally U-shaped branches, the free ends of the branches being rigidly attached together by a plate (26) and the base of the U being rigidly attached to the corresponding pressing surface (24, 25).

2. The connector (10) for the mechanical and electrical connection of an anode to the anode frame (3) of a cell (1) of aluminum production by fusedsalt electrolysis of claim 1, characterized in that each of the pressing bodies (22, 23) is assembled to float around the front cross-pieces (15, 16) each defining a swivel joint cooperating with the corresponding pressing surface.

3. The connector (10) for the mechanical and electrical connection of an anode to the anode frame (3) of a cell (1) of aluminum production by fusedsalt electrolysis of any of claims 1 and 2, characterized:

• in that the front cross-pieces (15, 16) used as a swivel joint have a specific profile, bulged towards the anode frame, so that the two U-shaped branches based on which each of the pressing bodies are formed are located on either side of the apex of the bulged shape;

• and in that said front cross-pieces are each provided with two protrusions extending on either side of the corresponding pressing surface, to limit the clearance thereof in the lateral plane.