Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
  • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
  • C25C3/12—Anodes
  • C25C3/125—Anodes based on carbon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
  • C25C3/16—Electric current supply devices, e.g. bus bars

Definitions

• 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.
• 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 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.
• each anode is generally associated with a structure to form an anode assembly.
• This structure is generally composed of:
• an anode rod made of a material with a high electrical conductivity, 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.
• 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.
• An object of the present invention is to propose a more robust anode assembly than those proposed in documents FR 1 326 481 and WO 2012/100340, this anodic assembly making it possible to improve the distribution of currents in the carbonaceous anode, to reduce the ohmic drop of contact between the carbon and the cast iron as well as limiting the heat losses of the electrolytic cell through the steel conductors penetrating into the carbon anode.
• Another object of the present invention is to provide a method of manufacturing such a robust anode assembly.
• 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.
• 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.
• the training phase can comprise:
• each unsealed area extending between a transverse side face of the longitudinal member and a transverse inner wall of the recess.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• FIG. 1 is a perspective view of an anode assembly
• FIG. 2 is a perspective view of a longitudinal element and an anode rod
• FIG. 3 is a perspective view of an anode including a recess in its upper face
• FIGS. 4 to 6 are top views of various examples of anode assemblies
• FIG. 7 is a block diagram of a method of sealing an anode assembly; more specifically, FIG. 7 illustrates steps of a formation phase of the sealing process, and
• Figure 8 schematically illustrates an anode assembly including a plurality of anodes.
• 'Face / side wall' means a face / wall extending in a plane parallel to the axis A-A 'of the anode rod
• Fiber / longitudinal wall means a face / wall extending parallel to a longitudinal axis of a longitudinal object (for example a recess or a longitudinal element),
• Fiber / transverse wall means a face / wall extending perpendicularly to a longitudinal axis of a longitudinal object.
• FIG. 1 illustrates an example of anode assembly according to the invention.
• the anode assembly comprises an anode rod 1, a longitudinal element 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.
• the longitudinal element is made of steel.
• the dimensions of the longitudinal element 2 may be the following:
• width I and height h between 5 and 50 centimeters.
• 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 BB '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.
• the recess 30 may be of complementary shape to that of the longitudinal element 2.
• the recess 30 has longitudinal lateral internal walls 32, transverse lateral internal walls 31, and a bottom 34.
• 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 .
• 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.
• 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, at the same time. possible exception of peripheral portions of the longitudinal lateral faces located at the longitudinal ends of the longitudinal element 2.
• 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.
• 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.
• sealing material 41 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.
• Unsealed areas may be left empty.
• 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.
• a compressible lining material 42 possibly back-shaped, such as rock wool.
• 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.
• 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®.
• FIGS. 4 to 6 various embodiments of the anode assembly have been illustrated in plan view.
• 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.
• 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.
• 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 material of seal material). formwork). 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.
• the anode assembly may comprise one or more recesses 30 and associated longitudinal elements 2.
• Each gap may comprise sealed areas filled with sealing material 41, unsealed areas composed of packing material 42 and formwork material 43.
• 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 .
• 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 '.
• 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. .
• 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).
• 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.
• a formwork material 43 is put in place to define: at least one "sealing zone" (i.e. area to be sealed) in which it is desired to introduce the sealing material, and
• non-sealing zones i.e. area to be sealed
• 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.
• 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.
• 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.
• the mat can be disposed on the lower face of the longitudinal member 2 (in addition to the longitudinal side faces).
• 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.
• 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.
• the mat can be removed (step 52) to form unsealed areas devoid of formwork material 43.
• 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 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.
• 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 ⁇ - 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.

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• Chemical Kinetics & Catalysis (AREA)
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• Electrolytic Production Of Metals (AREA)

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• 2014
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• 2015
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