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

Definitions

• the present invention relates to an anode assembly for tanks for the production of aluminum by electrolysis, as well as to a method of manufacturing such an anode assembly.
• Aluminum is mainly produced by electrolysis of alumina dissolved in a cryolitic bath.
• the electrolysis tank which allows this operation is made up of a steel box and lined internally with refractory insulating products.
• a cathode formed of carbon blocks is placed in the box. It is surmounted by an anode or a plurality of carbon anodes, or carbon anode blocks, plunging into the cryolitic bath. This (or these) carbon anode (s) is (are) oxidized (s) progressively by the oxygen coming from the decomposition of the alumina.
• the current flows from the anode to the cathode through the cryolitic bath, maintained in the liquid state by the Joule effect.
• the aluminum produced is liquid and is deposited by gravity on the cathode. Regularly, the aluminum produced, or a part of the aluminum produced, is sucked up by a ladle and transferred to foundry furnaces. Once the anodes have worn out, 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:
• anode rod made of a material with high electrical conductivity, such as aluminum or copper, and
• the attachment means generally comprise a multipod formed of a cross member secured to the base of the rod associated with a plurality of advantageously cylindrical logs whose axis is parallel to the rod.
• the logs are partly introduced inside recesses made on the upper face of the anode, and the gaps existing between the logs and the recesses are filled by pouring a molten metal, typically cast iron.
• the metal sockets thus produced ensure good mechanical attachment and a good electrical connection between the rod and the anode.
• anode assemblies of the prior art preferably included cylindrical logs, this is in particular to limit the risks of deterioration of the anode due to the expansion undergone by the attachment means during the introduction of the anode in the cryolitic bath whose temperature is between 930 and 980 ° C.
• This solution consists in providing at least one space having no sealing material at one of the longitudinal ends of the connection bar, said space advantageously being able to be lined with a compressible lining material, such as refractory fiber.
• a compressible lining material such as refractory fiber.
• An object of the present invention is to provide a less expensive and less complex manufacturing process than that proposed in document WO 2015/1 10906, this manufacturing process making it possible to form an anode assembly presenting a lower risk of cracking of the anode. under the effect of thermal expansion of the connection bar.
• Another object of the present invention is to provide an anode assembly which can be obtained by said manufacturing process.
• the invention provides a method of manufacturing an anode assembly intended for cells for the production of aluminum by electrolysis, the anode assembly being of the type comprising an anode rod, a metal block integral with the one of the ends of the anode rod, said metal block being able to expand in a longitudinal direction under the effect of heat, and a carbon anode including a recess in which the metal block is housed for sealing the metal block to the carbon anode, a sealed area filled with sealing material extending between the metal block and the carbon anode, characterized in that the method comprises a step of forming at least a first cavity inside the anode carbonaceous, said at least first cavity forming with said recess a first zone of less thickness inside the carbon anode, said first zone of lesser thickness being able to deform or to fracture under the effect of the expansion of the metal block in the longitudinal direction.
• the manufacturing process according to the invention makes it possible to form an anode assembly presenting less risk of cracking of the carbon anode under the effect of the expansion of the metal block.
• the method of the invention may further comprise a step of forming at least a second cavity inside the carbon anode, said at least second cavity forming with said recess a second zone of least thickness inside the carbon anode, said second zone of lesser thickness being capable of deforming or fracturing under the effect of the expansion of the metal block in the longitudinal direction.
• the metal block has substantially the shape of a parallelepiped defined in particular by four longitudinal faces connected by two transverse faces, said at least first zone of least thickness, respectively said at least second zone of least thickness, being arranged parallel to one of said transverse faces and being separated from the latter by the sealed area.
• each zone of reduced thickness will advantageously extend at a respective longitudinal end of the metal block.
• the thinner zones will then be distributed on either side of the anode rod, which will allow 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 assembly.
• the step of forming said at least first cavity, respectively of said at least second cavity may comprise a step of placing an insert in a mold intended to form the carbon anode so defining at least one projecting part inside the mold, said projecting part being intended to form said at least first cavity, respectively said at least second cavity.
• the step of forming said at least first cavity, respectively of said at least second cavity can comprise a step of machining the carbon anode.
• the invention also relates to an anode assembly intended for tanks for the production of aluminum by electrolysis, the anode assembly comprising an anode rod, a metal block integral with one of the ends of the anode rod, said block metal which can expand in a longitudinal direction under the effect of heat, and a carbon anode including a recess in which is housed the metal block for sealing the metal block with the carbon anode, a sealed area filled with sealing material s extending between the metal block and the carbon anode, characterized in that the carbon anode comprises at least a first cavity, said at least first cavity forming with said recess a first zone of reduced thickness inside the anode carbonaceous, said first area of reduced thickness being able to deform or fracture under the effect of the expansion of the metal block in the longitudinal direction
• Preferred but non-limiting aspects of the anode assembly are the following:
• the carbon anode comprises at least a second cavity, said at least second cavity forming with said recess a second zone of reduced thickness inside the carbon anode, said second zone of reduced thickness being capable of deforming or fracture under the effect of the expansion of the metal block in the longitudinal direction;
• the metal block has substantially a shape of parallelepiped defined in particular by four longitudinal faces connected by two transverse faces, said at least first zone of least thickness, respectively said at least second zone of least thickness, being arranged parallel to one of said faces transverse and being separated therefrom by the sealed area;
• the second, thinner area has a substantially flat profile and is oriented perpendicular to said direction
• the first, respectively the second, thinner zone has a three-part profile, namely a central part surrounded by two end parts, said central part being substantially flat and being oriented perpendicular to said longitudinal direction and said end parts being oriented obliquely to said central part;
• the first, respectively the second, thinner zone has a profile in two parts, namely a first part and a second part linked together at a connection zone, each of said first and second parts having a biconvex profile , and wherein the first, respectively the second, thinner area has a thinner thickness at said connecting area;
• the first, respectively the second, thinner zone has a profile in two parts, namely a first part and a second part linked together at a connection zone, each of said first and second parts having a profile substantially flat, and wherein the first, respectively the second, thinner area has a thinner thickness at said connecting area;
• the first, respectively the second, thinner zone has a profile in two parts, namely a first part and a second part connected together at a connection zone, each of said first and second parts having a piano-convex profile, and in which the first, respectively the second, thinner area has a thinner thickness at the level of said connecting area.
• Figure 1 is a perspective view of an anode assembly according to a first alternative embodiment of the invention
• FIG 2 is a perspective view of the metal block fixed to the anode rod before its integration into the anode assembly shown in Figure 1,
• FIG 3 is a perspective view of the carbon anode used for the manufacture of the anode assembly shown in Figure 1,
• Figure 4 is a top view of an anode assembly according to a second embodiment of the invention.
• Figure 5 is a sectional view along CC ’of the anode assembly shown in Figure 4,
• Figures 6a-6e are partial views, from above, of several alternative embodiments of the invention.
• FIG 7 is a block diagram of a process for manufacturing an anode assembly according to the invention.
• lateral face “lower face”, “upper face”, “side walls” and “bottom” will be used in the following text with reference to an anode rod extending along an axis A -AT'.
• transverse face / wall a face / wall extending perpendicular to a longitudinal axis of a longitudinal object
• longitudinal direction or “longitudinally”, a direction parallel to a longitudinal axis of a longitudinal object (for example a recess or a metal block),
• FIG. 1 An example of an anode assembly according to the invention is illustrated in FIG. 1.
• the anode assembly 10 includes an anode rod 1, a metal block 2, and a carbon 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 metal block 2 forms attachment means.
• the metal block 2 is made of an electrically conductive material capable of withstanding the high temperatures of use of the anode assembly.
• the metal block is made of steel.
• the dimensions of the metal block 2 can be as follows:
• the length L is at least twice the width I of the metal block 2.
• the metal block 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 metal block 2 comprises an upper face 23 in contact with the anode rod 1, a lower face 24 opposite the upper face 23, two longitudinal side faces 22 and two transverse side faces 21.
• the metal block 2 is for example a bar, possibly having the shape of a rectangular parallelepiped, and may include teeth, in particular with rounded profile, on its lateral faces 21, 22 and / or its lower face 24.
• Anode 3 is an anode block of precooked carbonaceous material, the composition and general shape of which 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 metal block 2 is housed.
• the recess 30 may be of shape complementary to that of the metal block 2.
• the recess 30 has longitudinal lateral internal walls 32, transverse lateral internal walls 31, and a bottom 34.
• the width G of the recess or of the groove is provided greater than the width I of the metal block 2 to allow the insertion of the metal block 2.
• the anode assembly further includes sealed areas filled with sealing material 41.
• the sealed areas extend between the longitudinal internal walls 32 of the recess 30, and the longitudinal side faces 22 of the metal block 2.
• the term “sealing material” is intended to mean a material allowing the formation of a rigid and conductive bond between an anode and a metal block, this bond being typically provided by a metal cast between the block. metal and the anode such as cast iron, or by a conductive paste.
• the sealing material 41 covers all the lateral faces 21, 22 of the metal block 2.
• the forces applied longitudinally by the metal block 2 during its expansion will therefore be transmitted in full, via the sealed zones 41 adjoining the transverse lateral faces 21 of the metal block 2, at the anode 3.
• the anode 3 is advantageously provided with a pair of cavities 42 arranged on either side of the recess 30 along the axis. longitudinal B-B ', each of the cavities 42 being located near a sealed zone 41 adjoining one of the transverse lateral faces 21 of the metal block 2.
• each of the cavities 42 forms with the recess 30 a zone of lesser thickness 43 in the anode 3, said zone of lesser thickness 43 being between said sealed zone 41 and said cavity 42.
• This zone of lesser thickness 43 will in particular be configured to be deformable or fracturable under the effect of the forces applied longitudinally by the metal block 2.
• the thickness of the thinner zone 43 is advantageously less than 5 cm and preferably between 0.5 and 3 cm in order to be able to deform or fracture without propagation of cracks in the rest of the anode.
• the cavity 42 will advantageously have a thickness greater than 0.5 cm and preferably greater than 1 cm in order to be able to absorb the deformation of the thickness of the thinner zone 43 caused by the expansion of the metal block 2.
• the forces applied longitudinally by the metal block 2 will advantageously be transmitted in the first place to the zones of lesser thickness 43, which will result either in deformation or in fracturing of said zones of lesser thickness 43
• the rest of the anode 3 in particular the parts of the anode 3 included between one of the lateral edges 33 of the anode 3 and the outer wall of the cavity 42 closest to the latter, n 'is not directly subject to all of the forces applied longitudinally by the metal block, the risk of deterioration is considerably reduced.
• FIGS. 4 and 5 another embodiment of the anode assembly has been illustrated, respectively in top view and in cross-sectional view along C-C ’.
• the anode 3 comprises only a single cavity 42 defining with the recess 30 a single zone of reduced thickness 43. This zone of reduced thickness 43 will however be sufficient to limit the risk of deterioration of the anode assembly 3.
• the anode 3 comprises at least one cavity 42 spaced from the recess 30 so that a zone of lesser thickness 43 of the anode 3 is formed between said at least one cavity 42 and said recess 30.
• the anode 3 therefore comprises at least one zone of least thickness 43.
• the zone of least thickness 43 is a structure of the anode 3 able to deform or fracture under the effect of the expansion of the metal block, for example in the longitudinal direction.
• the cavity 42 extends transversely and vertically beyond a longitudinal projection of the transverse lateral internal wall 31.
• Such a configuration allows any cracks in the cavity 42 to fade.
• ' extending from the transverse lateral internal wall in a mainly longitudinal direction away slightly from the axis C-C'.
• the protrusion is advantageously less than 5 cm and preferably less than 3 cm so as not to weaken the anode 3 and not to disturb the distribution of the current to the entire underside of the anode 3.
• the shape of the thinner zone 43, of the cavity 42 and of the recess 30 may vary as a function of various parameters, such as, in particular, the constituent material, the dimensions and / or the shape of the anode 3 and / or of the metal block 2.
• the shape of the thinner area 43 may include at least one fracturing interface of the anode 3 configured so that the thinner area 43 is suitable for fracturing at said at least one fracturing interface, for example under the effect of a given stress resulting from the expansion of the metal block.
• a fracturing interface could adjoin a concave surface of the recess 30 or of the cavity 42.
• This concave surface could be curved, that is to say defining a curve (as for example at the ends of the cavity 42 of the Figure 6a).
• the curve of such a concave surface could be configured in a more or less accentuated manner so that a stress concentration effect in the thinner zone 43 can be more or less significant.
• the concave surface could also be angled, that is to say defining an angle between two parts of said concave surface (as for example at the ends of the cavity 42 of FIG. 6b). The angle of such a concave surface could be configured in a more or less accentuated manner so that the stress concentration effect in the thinner zone 43 can be more or less significant.
• FIGS. 6a to 6e several advantageous examples of anode 3 are shown which can be used within the anode assembly of the present invention.
• the thinner area 43 has a substantially flat profile and is oriented perpendicular to the axis B-B 'of the metal block 2.
• the transverse lateral internal wall 31 of the recess 30 adjoining the thinner area 43 and the inner and outer walls of the corresponding cavity 42 are, in this case, with a straight profile and perpendicular to the axis B-B '.
• the thinner zone 43 has a profile in two parts, namely a first part 434 and a second part 435 linked together at a connection zone 430.
• Each of the parts 434, 435 has a biconvex profile, and the thinner area 43 has a thinner thickness at the connection area 430.
• the transverse lateral internal wall 31 of the recess 30 adjoining the thinner area 43 is, in this case, with a curved profile, complementary to that of the zone of least thickness 43, and the internal wall of the corresponding cavity 42 also has a curved profile, complementary to that of the zone of least thickness 43.
• the thinner zone 43 has a profile in two parts, namely a first part 436 and a second part 437 linked together at a connection zone 430.
• Each of the parts 436, 437 has a substantially flat profile, and the thinner area 43 has a thinner thickness at the connection area 430.
• the transverse lateral internal wall 31 of the recess 30 adjoining the thinner area 43 and the internal wall of the corresponding cavity 42 are, in this case, with a substantially straight profile and perpendicular to the axis B-B ', with the exception of their respective zones which are aligned with the connection zone 430, for which the profile is substantially triangular.
• the thinner zone 43 has a three-part profile, namely a central part 431 surrounded by two end parts 432 and 433.
• the central part 431 is substantially flat and is oriented perpendicular to the axis B-B ', and the end parts 432 and 433 are oriented obliquely to the central part 431.
• the transverse lateral internal wall 31 of the recess 30 adjoining the zone of least thickness 43 is, in this case, with a straight profile and perpendicular to the axis B-B ', and the internal and external walls of the corresponding cavity 42 have a profile substantially complementary to that of the zone of least thickness 43.
• the thinner zone 43 has a profile in two parts, namely a first part 438 and a second part 439 connected together at a connection zone 430.
• Each of the parts 438, 439 has a piano-convex profile, and the thinner area 43 has a thinner thickness at the connection area 430.
• the transverse lateral internal wall 31 of the recess 30 adjoining the thinner area 43 is , in this case, with a curved profile, complementary to that of the zone of least thickness 43, and the internal wall of the corresponding cavity 42 also has a profile complementary to that of the zone of least thickness 43.
• the cavity 42 therefore has, in this case, a gull wing profile.
• This manufacturing process 100 can be applied to form an anode assembly 10, the anode 3 of which has a single thinner zone 43 adjoining one of the transverse lateral internal walls 31 of the recess 30.
• this manufacturing method 100 can also be applied to form an anode assembly 10, the anode 3 of which has two zones of lesser thickness 43 arranged on either side of a recess 30, each of the zones of lesser thickness 43 adjoining one of the transverse lateral internal walls 31 of the recess 30.
• a metal block 2 secured to an anode rod 1 is provided.
• a carbon anode 3 provided with a recess 30 and at least one cavity 42 is formed.
• the second step 102 may, in a first variant of the method, comprise, prior to a step of molding the carbon anode 3, a step of placing an insert in a mold intended to form the carbon anode 3 so as to define at least one projecting part inside the mold, said projecting part being intended to form said at least one cavity 42.
• the second step 102 may include a step of molding the carbon anode 3 followed by a step of machining the carbon anode 3 to form said at least one cavity 42.
• the metal block 2 is introduced inside the recess 30 and the gap separating the metal block 2 from the anode 3 is filled with a sealing material so as to form the zone sealed 41.
• an anode assembly 10 according to the present invention.
• this anode assembly 10 makes it possible to limit the risks of cracks and / or bursting of the anode 3 during its introduction into a cryolitic bath.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)

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• 2018
  • 2018-12-20 FR FR1873580A patent/FR3090699B1/fr active Active
• 2019
  • 2019-12-12 CN CN201980083098.2A patent/CN113195792A/zh active Pending
  • 2019-12-12 CA CA3122504A patent/CA3122504A1/fr active Pending
  • 2019-12-12 WO PCT/CA2019/051794 patent/WO2020124209A1/fr unknown
  • 2019-12-12 EP EP19901100.8A patent/EP3899105A1/de active Pending
  • 2019-12-12 AU AU2019407845A patent/AU2019407845A1/en active Pending
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