EP3099845B1 - Anode assembly and associated production method - Google Patents

Description

Technical area

The present invention relates to an anode assembly for tanks for the production of aluminum by electrolysis, as well as a method of manufacturing such an anode assembly.

It is particularly suitable for electrolytic cells with pre-baked anodes.

Presentation of the prior art

Aluminum is essentially produced by electrolysis of alumina dissolved in a cryolite bath. The electrolytic cell that allows this operation is constituted by a steel box and lined internally with refractory insulating products.

A cathode formed of carbonaceous blocks is placed in the box. It is surmounted by an anode or a plurality of carbon anodes, or carbonaceous anode blocks, plunging into the cryolite bath. This (or these) anode (s) carbon is (are) oxidized (s) gradually by the oxygen from the decomposition of alumina.

The passage of the current is effected from the anode to the cathode through the cryolite bath, maintained in the liquid state by the Joule effect.

The usual operating temperatures of a tank being between 930 and 980 ° C, the product aluminum is liquid and is deposited by gravity on the cathode. Regularly the produced aluminum, or a part of the produced aluminum, is sucked by a ladle, and transferred into foundry furnaces. Once the anodes are worn, they are replaced by new anodes.

• d'une tige d'anode en matériau à haute conductivité électrique, tels que de l'aluminium ou du cuivre, et
• de moyens d'accrochage en matériaux résistants aux températures élevées d'utilisation de l'anode, tels que de l'acier.

To allow its manipulation and power supply, each anode is generally associated with a structure to form an anode assembly. This structure is generally composed of:

• an anode rod of high electrical conductivity material, such as aluminum or copper, and
• fastening means made of materials resistant to high temperatures of use of the anode, such as steel.

The attachment means generally comprise a multipode formed of a cross member integral with the base of the rod associated with a plurality of advantageously cylindrical logs whose axis is parallel to the rod.

The logs are introduced partly inside recesses made on the upper face of the anode, and the interstices existing between the logs and the recesses are filled by casting a molten metal, typically cast iron. The metal sleeves thus produced make it possible to ensure good mechanical fastening and a good electrical connection between the rod and the anode.

However, it has been found in the prior art that the presence of logs induced an ohmic drop in the connection of the anode, as well as thermal losses through the anode assembly.

This is why the document WO 2012/100340 proposes an anode assembly in which the assembly composed of the crossbar and the logs is replaced by a longitudinal connection bar. When sealing, this connecting bar is introduced into a longitudinal groove made on the upper face of the anode. Molten cast iron is then deposited at the periphery of the connection bar to fill the space between the connection bar and the groove.

This solution makes it possible to improve the distribution of the currents in the anode, to reduce the ohmic drop of contact between the carbon and the cast iron and to limit heat losses, as had already been taught in the document FR 1 326 481 which proposed an identical solution to WO 2012/100340 .

However, if the anode assemblies of the prior art preferably included cylindrical logs, it is in particular to limit the risk of deterioration of the anode due to the expansion experienced by the attachment means during the introduction of the anode in the cryolite bath whose temperature is between 930 and 980 ° C.

Indeed, unlike cylindrical logs whose expansion induces the application of a radial thermal expansion force on the anode, the thermal expansion of a metal bar induces the application of transverse and longitudinal forces on the anode tending to crack it.

No solution to this problem of cracking is proposed in FR 1 326 481 or in WO 2012/100340 .

An object of the present invention is to provide a more robust anode assembly than those proposed in the documents FR 1 326 481 and WO 2012/100340 , this anode assembly for improving the distribution of currents in the carbon anode, to reduce the ohmic contact drop between the carbon and the cast iron and to limit the heat losses of the electrolytic cell through the conductors of penetrating steel in the carbonaceous anode.

Another object of the present invention is to provide a method of manufacturing such a robust anode assembly.

Summary of the invention

For this purpose, the invention proposes a method of manufacturing an anode assembly for the tanks for the production of aluminum by electrolysis, the anode assembly being of the type comprising an anode rod, a longitudinal member integral with the one of the ends of the anode rod and a carbonaceous anode including a recess in which is housed the longitudinal member for sealing the longitudinal member to the carbonaceous anode, characterized in that the method comprises a formation phase of at least one sealed area filled with sealing material and at least one unsealed area devoid of sealing material, said at least one unsealed area extending at one of the longitudinal ends of the longitudinal member.

The longitudinal member is therefore sealed to the carbon anode to establish mechanical attachment and electrical connection, and the fact that one of the longitudinal ends of the longitudinal member is devoid of sealing material makes it possible to limit the risk of cracking. the carbon anode.

Indeed, the presence of a volume having no sealing material at one of the longitudinal ends of the longitudinal element makes it possible to limit the intensity of the forces applied to the anode by the longitudinal element during its expansion. , more particularly the expansion along the longitudinal direction of the longitudinal element.

• la formation d'une zone scellée remplie de matériau de scellement, ladite zone scellée s'étendant entre des faces latérales longitudinales de l'élément longitudinal et des parois internes longitudinales de l'évidement, et
• la formation de deux zones non scellées aux deux extrémités longitudinales de l'élément longitudinal, chaque zone non scellée s'étendant entre une face latérale transversale de l'élément longitudinal et une paroi interne transversale de l'évidement.

Advantageously, the training phase can comprise:

• forming a sealed area filled with sealing material, said sealed area extending between longitudinal side faces of the longitudinal member and longitudinal inner walls of the recess, and
• forming two unsealed areas at both longitudinal ends of the longitudinal member, each unsealed area extending between a transverse side face of the longitudinal member and a transverse inner wall of the recess.

In this case, the anode assembly comprises two unsealed areas, each unsealed area extending at a respective longitudinal end of the longitudinal member. The unsealed areas are then distributed on either side of the anode rod, which allows on the one hand a better distribution of the intensity of the expansion forces, and on the other hand a better balance of the masses of the anode set.

The formation phase may comprise a step of placing a formwork material in a gap between the longitudinal element and internal walls of the recess - such as longitudinal internal walls and possibly a bottom of the recess - so as to define at least one sealing zone and at least one zone non-sealing. To do this, the formwork material can be placed at at least one end of the longitudinal member so that the formwork material extends on the longitudinal side faces of the longitudinal member. Once the formwork material is placed, the longitudinal member can be inserted with the formwork material into the recess so that the form material defines, with the inner walls of the recess and the faces of the longitudinal member, sealing and non-sealing areas. Having the formwork material on the longitudinal member prior to insertion into the recess facilitates the introduction of the formwork material. This also ensures better control of the position of the formwork material.

In an alternative embodiment, the formwork material is a mat. This can be fixed on the longitudinal element by gluing or knotting around the longitudinal side faces and a lower face of the longitudinal member. The fact that the formwork material extends on the underside of the longitudinal member defines a space under the longitudinal member into which sealing material can be introduced. The introduction of sealing material between the underside of the longitudinal member and a bottom of the recess improves the current distribution in the anode.

Preferably, the forming phase comprises a step of filling the sealing zone by casting the sealing material in the liquid or viscous state. Sealing the sealing material in the liquid or viscous state ensures a good distribution of the sealing material throughout the sealing area.

The forming phase may also include a step of removing the formwork material after the filling step, and optionally a step of packing the unsealed area with packing material. This makes it possible to limit the risks of clogging of the unsealed zone (s) with a material used in the manufacture of aluminum, such clogging being able in certain cases to induce an increase in the risks of cracking of the surface. 'anode.

The invention also relates to an anode assembly for tanks for the production of aluminum by electrolysis, the anode assembly comprising an anode rod, a longitudinal member integral with one of the ends of the anode rod and an anode carbon fiber including a recess in which the longitudinal member is housed, characterized in that the anode assembly further comprises a gap between the recess and the longitudinal member, the gap including at least one sealed area containing a sealing material and at least one unsealed area devoid of sealing material, said and at least one unsealed area extending at one of the longitudinal ends of the longitudinal member.

• l'ensemble anodique comprend au moins deux zones non scellées aux deux extrémités longitudinales de l'élément longitudinal, et au moins une zone scellée s'étendant entre des faces latérales longitudinales de l'élément longitudinal et des parois internes longitudinales de l'évidement,
• la zone scellée s'étend en outre entre une face inférieure de l'élément longitudinal et un fond de l'évidement,
• la zone non scellée comporte du matériau de garnissage, ledit matériau de garnissage étant comprimé à une valeur nominale suffisamment inférieure à son taux de compression maximal pour autoriser la dilatation de l'élément longitudinal,
• le matériau de garnissage est de la laine de roche.

Preferred but non-limiting aspects of the anode assembly are as follows:

• the anode assembly comprises at least two unsealed areas at both longitudinal ends of the longitudinal member, and at least one sealed area extending between longitudinal side faces of the longitudinal member and longitudinal inner walls of the recess,
• the sealed zone further extends between a lower face of the longitudinal element and a bottom of the recess,
• the unsealed area comprises packing material, said packing material being compressed to a nominal value sufficiently lower than its maximum compression ratio to allow expansion of the longitudinal member,
• the packing material is rock wool.

According to an advantageous embodiment, the anode assembly comprises a support to which is fixed a plurality of anode rods, longitudinal elements and carbon anodes. The support extends more particularly horizontally perpendicular to the longitudinal elements.

Brief description of the figures

• la figure 1 est une vue en perspective d'un ensemble anodique,
• la figure 2 est une vue en perspective d'un élément longitudinal et d'une tige d'anode,
• la figure 3 est une vue en perspective d'une anode incluant un évidement dans sa face supérieure,
• les figures 4 à 6 sont des vues de dessus de différents exemples d'ensembles anodiques,
• la figure 7 est un schéma de principe d'un procédé de scellement d'un ensemble anodique ; plus précisément la figure 7 illustre des étapes d'une phase de formation du procédé de scellement, et
• la figure 8 illustre schématiquement un ensemble anodique incluant une pluralité d'anodes.

Other advantages and characteristics of the anode assembly and its associated manufacturing method will emerge from the following description of several alternative embodiments, given by way of non-limiting examples, from the appended drawings in which:

• the figure 1 is a perspective view of an anode assembly,
• the figure 2 is a perspective view of a longitudinal member and anode rod,
• the figure 3 is a perspective view of an anode including a recess in its upper face,
• the Figures 4 to 6 are top views of different examples of anode assemblies,
• the figure 7 is a schematic diagram of a method of sealing an anode assembly; more precisely the figure 7 illustrates steps of a formation phase of the sealing process, and
• the figure 8 schematically illustrates an anode assembly including a plurality of anodes.

detailed description

An example of a process for manufacturing an anode assembly as well as examples of anode assemblies obtained from the process will now be described. In these different figures, the equivalent elements bear the same numerical references.

In the rest of the text, the terms "side face", "bottom face", "upper face", "side walls" and "bottom" will be used with reference to an anode rod extending along an axis A -AT'.

• « face inférieure » ou « face supérieure », une face s'étendant dans un plan perpendiculaire à l'axe A-A', la face supérieure d'une pièce donnée étant plus proche de la tige d'anode que la face inférieure,
• « face/paroi latérale », une face/paroi s'étendant dans un plan parallèle à l'axe A-A' de la tige d'anode,
• « face/paroi longitudinale », une face/paroi s'étendant parallèlement à un axe longitudinal d'un objet longitudinal (par exemple un évidement ou un élément longitudinal),
• « face/paroi transversale », une face/paroi s'étendant perpendiculairement à un axe longitudinal d'un objet longitudinal.

The reader will appreciate that in the context of the present invention, the following is meant:

• "Lower face" or "upper face", a face extending in a plane perpendicular to the axis A-A ', the upper face of a given piece being closer to the anode rod than the lower face,
• 'Face / side wall' means a face / wall extending in a plane parallel to the axis AA 'of the anode rod,
• "Face / longitudinal wall" means a face / wall extending parallel to a longitudinal axis of a longitudinal object (for example a recess or a longitudinal element),
• "Face / transverse wall" means a face / wall extending perpendicularly to a longitudinal axis of a longitudinal object.

We illustrated at the figure 1 an example of anode assembly according to the invention. With reference to Figures 1 to 3 the anode assembly comprises an anode rod 1, a longitudinal member 2, and a carbonaceous anode 3.

The anode rod 1 is made of an electrically conductive material. It extends along the axis A-A '. The anode rod is of a type conventionally known to those skilled in the art and will not be described in more detail below.

The longitudinal element 2 forms hooking means. The longitudinal element 2 is in an electrically conductive material capable of withstanding the high temperatures of use of the anode assembly. For example, the longitudinal element is made of steel.

• longueur L comprise entre 80 et 200 centimètres,
• largeur I et hauteur h comprises entre 5 et 50 centimètres.

The dimensions of the longitudinal element 2 may be the following:

• length L between 80 and 200 centimeters,
• width I and height h between 5 and 50 centimeters.

In any case, the length L is at least two times greater than the width I of the longitudinal element 2.

The longitudinal element 2 is integral with the anode rod 1 at one of its ends 11, and extends along a longitudinal axis B-B 'perpendicular to the axis A-A'. The longitudinal element 2 comprises an upper face 23 in contact with the anode rod 1, a lower face 24 opposite to the upper face 23, two longitudinal lateral faces 22 and two transverse lateral faces 21. The longitudinal element 2 is example a bar, possibly rectangular, and may include teeth, including a rounded profile on its side faces 21, 22 and / or its lower face 24.

The anode 3 is an anode block of precured carbon material whose composition and general shape are known to those skilled in the art and will not be described in more detail below. The upper face of the anode 3 has a recess 30 in which the longitudinal element 2 is housed.

Advantageously, the recess 30 may be of complementary shape to that of the longitudinal element 2. In this case, the recess 30 has longitudinal lateral internal walls 32, transverse lateral internal walls 31, and a bottom 34.

Alternatively the recess 30 may consist of a groove extending between two side edges 33 of the anode 3. This facilitates the process of forming the recess 30.

The width I of the recess or groove is greater than the width I of the longitudinal element 2 to allow insertion of the longitudinal element 2.

The anode assembly further comprises sealed areas filled with a sealing material 41. The sealed areas extend between the longitudinal inner walls 32 of the recess 30, and the longitudinal side faces 22 of the longitudinal member 2 .

In the context of the present invention, the term "sealing material" is intended to mean a material that makes it possible to form a rigid and conductive connection between an anode and a longitudinal element, this bond being typically provided by a metal cast between the longitudinal element and the anode such as cast iron, or by a conductive paste.

As illustrated in figures 1 and 4 to 6 , the sealing material 41 does not cover all the lateral faces 21, 22 of the longitudinal element 2. On the contrary, the sealing material 41 covers only the longitudinal lateral faces 22, with the possible exception of peripheral portions of the lateral faces longitudinally located at the longitudinal ends of the longitudinal member 2.

In other words, the anode structure has unsealed areas at the longitudinal ends of the longitudinal member 2, each end being composed of a transverse lateral face 21 and possibly of an end portion of the longitudinal lateral faces 22.

Possibly the lower face 24 may also be covered with sealing material 41, except possibly peripheral portions of the lower face 24 located at the longitudinal ends of the longitudinal member 2. The fact that the lower face 24 is at less partially covered with sealing material 41 improves the conduction of the current between the longitudinal element 2 and the anode 3.

Unsealed areas are therefore devoid of sealing material 41. This makes it possible to define a sufficient free space to ensure that the forces applied longitudinally by the longitudinal element 2 during its expansion are less than a limit value of cracking of the anode. 3.

Indeed, it is recalled as a guide that a longitudinal steel element of length equal to 1 meter can undergo longitudinal expansion up to 2 centimeters at 1000 ° C. It is then understood that this longitudinal expansion can induce a very significant deterioration of the anode 3 (cracks, bursting, etc.) when the longitudinal element 2 is covered with sealing material 41 on all its lateral faces 21, 22.

Unsealed areas may be left empty.

Alternatively, the unsealed areas may be lined, in whole or in part, with a compressible lining material 42, possibly back-shaped, such as rock wool. This makes it possible to avoid the risk of clogging of the unsealed zones by clusters of non-compressible material from, for example, powders of roofing material, which could transmit the expansion stresses of the longitudinal element to the anode 3.

Preferably, the packing material 42 is compressed to a nominal value sufficiently lower than its maximum compression ratio to allow expansion of the longitudinal element while limiting the forces applied to the anode 3.

In addition to the packing material 42, the unsealed areas may comprise a formwork material 43 between the sealing material 41 and the packing material 42. This formwork material 43 is used to define a containment volume corresponding to a sealing area (ie sealing area) in which the sealing material 41 is introduced during the manufacturing process of the anode assembly which will be described in more detail below.

The formwork material 43 is preferably a compressible material resistant to high temperatures without degrading or burning, such as vitreous, refractory, ceramic or advantageously biosoluble fibers such as for example Insulfrax® Fiberfrax®.

With reference to Figures 4 to 6 various embodiments of the anode assembly have been illustrated in plan view.

As illustrated in figure 4 the gap between the recess 30 and the longitudinal member 2 may comprise only sealed areas filled with sealing material 41 and unsealed areas devoid of material. To do this, the formwork material 43 is removed from the anode assembly after filling the sealing zones, and no packing material is introduced at the longitudinal ends of the longitudinal element 2.

As illustrated in figure 5 the gap between the recess 30 and the longitudinal member 2 may comprise sealed areas filled with sealing material 41 and unsealed areas containing only packing material 42 (ie, no formwork material). To do this, the formwork material 43 is removed after forming the sealed areas and a packing material 42 is introduced at the longitudinal ends of the longitudinal member 2.

Finally and as illustrated in figure 6 , the anode assembly may comprise one or more recesses 30 and longitudinal elements 2 associated. Each gap may comprise sealed areas filled with sealing material 41, unsealed areas composed of packing material 42 and formwork material 43.

Whatever the embodiment, the anode assembly comprises at least one unsealed zone situated at one of the longitudinal ends of the longitudinal element 2, this unsealed zone being devoid (ie not comprising) of sealing material .

Preferably, and as illustrated in the various figures, the anode assembly comprises two unsealed areas, each unsealed area extending at a respective end of the longitudinal member. This allows a better distribution of the currents in the anode, the intensity of the expansion forces, and a better balance of the masses of the anode assembly by improving its symmetry with respect to the axis A-A '.

An example of a method of sealing a longitudinal element 2 to a carbon anode 3 to obtain an anode assembly will now be described. More specifically, will be described later with reference to the figure 7 a sealed and unsealed zone forming phase of the sealing process.

This formation phase can be applied to form a single unsealed zone and a single sealed area, the unsealed area extending at one of the longitudinal ends of the longitudinal member 2 and the sealed area extending over the remainder of the volume defined between the recess 30 and the longitudinal member. .

Alternatively, this forming step 5 may be applied to form two unsealed areas at the longitudinal ends of the longitudinal member 2, and one (or more) sealed area (s).

In the following, it is assumed the manufacture of an anode assembly including two unsealed areas each associated with a respective longitudinal end of the longitudinal member 2. It is also assumed that the recess 30 of the anode 3 has been previously made, by molding or by any other technique known to those skilled in the art.

• au moins une « zone de scellement » (i.e. zone à sceller) dans laquelle on souhaite introduire le matériau de scellement, et
• deux « zones de non-scellement » (i.e. zone à ne pas sceller) dans lesquelles on souhaite éviter la présence de matériau de scellement.

In a step 50 of the method, a formwork material 43 is put in place to define:

• at least one "sealing zone" (ie zone to be sealed) in which it is desired to introduce the sealing material, and
• two "non-sealing zones" (ie zone not to be sealed) in which it is desired to avoid the presence of sealing material.

The formwork material 43 may be placed either on the longitudinal element 2 or directly in the recess 30.

This formwork material 43 may be a mat of vitreous fibers whose diameter is greater than or equal to the distance between the longitudinal side faces 22 and the longitudinal inner walls 32 opposite. The use of a mat makes it easier to set up the formwork material 43.

This mat can for example be placed 501 - possibly by gluing or knotting - on the longitudinal element 2, prior to its insertion into the recess 30.

Once the mat is placed, the longitudinal member 2 is introduced 502 into the recess 30. The mat is compressed between the longitudinal side faces and the longitudinal inner walls.

Advantageously, the mat may have a non-zero radial elasticity. This ensures that the mat is in contact on the one hand with the longitudinal element 2 and on the other hand with the inner walls of the recess 30, even when one (or more) groove (s) hanging are formed in the longitudinal inner walls 32 of the recess 30 to improve the attachment between the sealing material and the anode.

Advantageously, the mat can be disposed on the lower face of the longitudinal member 2 (in addition to the longitudinal side faces). Once the longitudinal element 2 introduced into the recess 30, this creates a gap between the lower face 24 and the bottom 34. Due to the formation of this space, it is possible to deposit sealing material 41 between the bottom 34 and the bottom wall 24 This improves the electrical performance of the anode assembly thus obtained.

The longitudinal side faces 22, the longitudinal inner walls 32 and the formwork material 43 - and possibly the bottom face 24 and the bottom 34 - define a confinement volume corresponding to the sealing zone. The transverse lateral faces 21, the transverse inner walls 31 and the mat 43 define two zones of non-sealing at the longitudinal ends of the longitudinal element 2.

In another step 51, a sealing material 41 in the liquid or viscous state is introduced into the sealing zone, possibly by casting. The sealing material 41 is deposited between the longitudinal lateral faces 22 and the longitudinal inner walls 32.

Once the sealing material 41 has solidified, the mat can be removed (step 52) to form unsealed areas devoid of formwork material 43.

Alternatively, the mat can be left in unsealed areas.

The non-sealing zones can then be filled (step 53) with a packing material 42.

An anode assembly is thus obtained comprising at least one unsealed zone located at one of the longitudinal ends of the longitudinal element. This makes it possible to limit the risks of cracks and / or bursting of the anode 3 when it is introduced into a cryolite bath.

As illustrated in figure 8 the method described above can be used to make a wide anode assembly. Such an anode assembly is then composed of a longitudinal support 6 extending horizontally including an electric contactor 61 at at least one of its ends for the electrical supply of anode subsets suspended from the support 6, each anode subset being attached to the support 6 via its associated anode rod 1, the longitudinal members 2 extending transversely to the support 6 so that a longitudinal axis II 'of the support is perpendicular to the longitudinal side faces 22 of the elements 2. The support advantageously extends from one side to the other of the electrolytic cell and is supported and electrically connected at its ends.

Claims (15)

1. A method of manufacturing an anode assembly intended for cells for the production of aluminum by electrolysis, the anode assembly being of the type having an anode rod (1), a longitudinal member (2) interdependent with one (11) end of the anode rod (1) and a carbon anode (3) including a cavity (30) in which is housed the longitudinal member (2) for sealing the longitudinal member (2) to the carbon anode (3), characterized in that the method comprises a formation (5) phase of at least one sealed area filled with sealing material (41) and at least one unsealed area devoid of sealing material, said at least one unsealed area extending to one of the longitudinal ends of the longitudinal member (2).
2. Manufacturing method according to claim 1, wherein the formation phase (5) comprises:

   - formation of a sealed area filled with sealing material (41), said sealed area extending between the longitudinal side faces (22) of the longitudinal member (2) and the longitudinal internal walls (32) of the cavity (30), and

   - formation of two unsealed areas at both longitudinal ends of the longitudinal member (2), each unsealed area extending between a transverse side face (21) of the longitudinal member (2) and a transverse internal wall of the cavity (30).
3. Method according to any of claims 1 or 2, wherein the formation phase (5) includes a step involving fitting (50) a shuttering material (43) into a gap between the longitudinal member (2) and the internal walls of the cavity (30) so as to define at least one sealing area and at least one non-sealing area.
4. Method according to claim 3, wherein the fitting step (50) comprises:

   - a sub-step involving placement (501) of the shuttering material (43) at at least one end of the longitudinal member (2) so that the shuttering material (43) extends on the longitudinal side faces (22) of the longitudinal member (2), and

   - a sub-step involving inserting (502) the longitudinal member (2) with the shuttering material (43) into cavity (30) so that the shuttering material (43) defines, with the internal walls (31, 32, 34) of the cavity (30) and the faces (21, 22, 24) of the longitudinal member (2) sealing and non-sealing areas.
5. Manufacturing method according to claim 4, wherein the sub-step involving fixing (501) of the shuttering material (43) comprises gluing or tying of at least one mat around the longitudinal side faces (22) and a lower side (24) of the longitudinal member (2).
6. Manufacturing method according to any one of claims 3 to 5, wherein the formation phase (5) further comprises a step involving filling (51) of the sealing area by casting of the sealing material (41) in liquid or viscous state.
7. Manufacturing method according to any one of claims 3 to 6, wherein the formation step (5) further comprises a step involving removing (52) the shuttering material (43) after the filling step (51).
8. Manufacturing method according to any one of claims 3 to 7, wherein the formation phase (5) further comprises a step involving packing (53) the unsealed area with packing material (42).
9. Anode assembly intended for cells for the production of aluminum by electrolysis, the anode assembly having an anode rod (1), a longitudinal member (2) interdependent with one (11) of the ends of the anode rod (1) and a carbon anode (3) including a cavity (30) in which is housed the longitudinal member (2) for sealing the longitudinal member (2) to the carbon anode (3), characterized in that the anode assembly further comprises a gap between the cavity (30) and the longitudinal member (2), the gap including at least one sealed area containing a sealing material (41) and at least one unsealed area devoid of sealing material, said and at least one unsealed area extending to one of the longitudinal ends of the longitudinal member (2).
10. Anode assembly according to claim 9, which comprises at least two unsealed areas at both longitudinal ends of the longitudinal member (2), and at least one sealed area between the longitudinal side faces (22) of the longitudinal member (2) and the longitudinal internal walls (32) of the cavity (30).
11. Anode assembly according to claim 10, wherein the sealed area further extends between a lower face (24) of the longitudinal member (2) and a base (34) of the cavity (30).
12. Anode assembly according to any one of claims 9 to 11, wherein the unsealed area comprises packing material (42), said packing material being compressed to a nominal value sufficiently lower than its maximum compression ratio to allow expansion of the longitudinal member.
13. Anode assembly according to claim 12, wherein the packing material is rock wool.
14. Anode assembly according to any of claims 9 to 13, comprising a support (6) to which is attached a plurality of anode rods (1), longitudinal members (2) and carbon anodes (3).
15. Anode assembly according to claim 14, wherein the support (6) extends horizontally perpendicular to the longitudinal members (2).

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