WO2023087107A1 - Interior lining system for an electrolytic cell - Google Patents

Abstract

The invention relates to an electrolytic cell comprising a chamber having sidewalls including a pair of longitudinal walls and a pair of transverse walls, a cathode inside the chamber, and a side lining including an inner layer on the periphery of the cathode and an outer layer adjoining the side walls of the chamber on the periphery of the inner layer, the side lining extending vertically beyond the cathode, characterised in that the inner layer comprises segments including a nominal segment and a conductive segment arranged one after the other along a side wall of the side walls of the chamber; the nominal segment having a nominal thermal conductivity and the conductive segment having a thermal conductivity greater than the nominal thermal conductivity, the conductive segment adjoining an area of the chamber subjected to increased thermal stress. The invention also relates to a foundry comprising an electrolytic cell having the above-mentioned characteristics.

Description

INTERNAL LINER SYSTEM FOR ELECTROLYSIS TANK

TECHNICAL AREA

The present technology relates to coating systems for electrolytic cells, electrolytic cells equipped with such systems as well as aluminum smelters comprising electrolytic cells provided with such systems.

PRESENTATION OF PRIOR ART

Commonly, the production of aluminum on an industrial scale is carried out in an aluminum smelter, and this by electrolysis from alumina according to the Hall-Héroult process. The implementation of this process requires an electrolytic cell comprising a casing typically constructed of steel and lined with an interior lining typically constructed of refractory materials. A bottom of the vessel comprises a cathode assembly having a cathode formed of at least one cathode block typically constructed of carbonaceous material, which is traversed by electrical conductors of the cathode assembly intended to collect therein an electrolysis current to conduct it to cathode outputs. The top of the cathode assembly and the coating define a crucible intended to contain a bath of molten cryolite, also called an electrolytic bath, in which the alumina can be dissolved to form an aluminum sheet at the bottom of the crucible, s accumulating on the cathode assembly. The electrolytic cell also comprises at least one anode block suspended from an anode support, such as a rod and a crosspiece, the anode block being partially immersed in the electrolytic bath, above the cathode blocks. An upstream electrical conductor carries electrolysis current to the anode assembly, either from a source or from a cathode outlet of an upstream electrolysis cell, as required for the electrolysis reaction can take place in the bath in the presence of a suitably positioned anode block and a suitable temperature, among other conditions. During the reaction, the passage of the electrolytic current to the cathode assembly takes place from the anode block, via the electrolytic bath and the sheet of metal. The vessel is often constructed and operated in such a way as to cause the formation of a solidified pool slope on the side walls of the vessel. The slope is usually formed by a cooling mechanism. As discussed below, a homogeneous berm formation along the vessel walls is desirable.

French patent application No. 14/01518 teaches the use of internal facing blocks superimposed on an outer layer of the coating. However, even in the presence of these facing blocks, the management of the temperature of the electrolytic bath and the formation of the embankment vis-à-vis the metal remains an issue.

[0004] French patent application no. 98/05040 teaches the use of means for evacuating and dissipating the heat produced by the electrolytic cell placed outside the box, presented in the form of means of blowing can be directed on the casing generally towards the interface between the sheet of metal and the bath of electrolyte. Nevertheless, temperature management from inside the crucible is also decisive, particularly with regard to the formation of an appropriately distributed slope all around the crucible. In particular, excessive heat dissipation can induce excessive embankment formation that can possibly interfere with the descent of the anode blocks. On the other hand, insufficient heat dissipation can induce insufficient slope formation, exposing the side lining of the vessel to the aluminum ply, leaving room for premature wear of the lining blocks. A deficient distribution of the slope is therefore detrimental to the proper functioning of the electrolysis process, to the life of certain components of the tank, and thereby to the performance of the tank.

TECHNOLOGY SUMMARY

[0005] One of the aims of the present technology aims to overcome the aforementioned drawbacks. To do this, the present technology proposes an electrolytic cell comprising an interior coating system configured to allow management of heat transfers from the inside of a crucible of the cell to the outside of a the tank, favoring a homogeneous creation of embankments inside the crucible adjoining an internal layer of said internal lining system.

A second objective of at least one embodiment of the proposed technology is to evenly distribute the heat losses on the side walls all around the electrolysis cell in order to stabilize the heat balance of the cell, as well as the formation of a stable and uniform embankment which ensures a long service life of the cell.

According to one aspect, the present technology relates to an electrolytic cell comprising a casing comprising side walls including a pair of longitudinal walls and a pair of transverse walls, a cathode inside the casing, and a coating side including an inner layer on the periphery of the cathode and an outer layer adjoining the side walls of the casing on the periphery of the inner layer, the side coating extending vertically beyond the cathode, characterized in that the inner layer comprises segments including a nominal segment and a conductive segment arranged one after the other along a side wall of the side walls of the casing; the nominal segment having a nominal thermal conductivity and the conductive segment having a thermal conductivity greater than the nominal thermal conductivity, the conductive segment adjoining an area of increased thermal stress of the tank.

According to one embodiment, the side wall is an upstream longitudinal wall of the pair of longitudinal walls located upstream of the cathode, the nominal segment extends from a longitudinal center of the cathode towards an end of the longitudinal wall upstream, and the conductive segment extends from near the end of the upstream longitudinal wall toward the longitudinal center.

[0009]According to one embodiment, the conductive segment is located in an area having a flow normal to said side wall, said flow induced by a magneto-hydrodynamic field in the contents of the tank.

According to one embodiment, the conductive segment is a first conductive segment, a downstream longitudinal wall of the pair of longitudinal walls is located downstream of the cathode, and the segments include a second conductive segment extending from the center longitudinal from the cathode towards one end of the downstream longitudinal wall, the second conductive segment having a thermal conductivity greater than the nominal thermal conductivity.

According to one embodiment, the segments include an insulating segment extending along said side wall, the insulating segment having a thermal conductivity lower than the nominal thermal conductivity.

According to one embodiment, the first conductive segment has a first thermal conductivity and the second conductive segment has a second thermal conductivity lower than the first thermal conductivity.

According to one embodiment, the segments include an insulating segment extending from near the end of the downstream longitudinal wall towards the longitudinal center of the cathode, the insulating segment having a thermal conductivity lower than the thermal conductivity nominal. According to one embodiment, the first conductive segment and the second conductive segment are axially offset relative to a transverse axis of the cathode.

[0015] According to one embodiment, the insulating segment is constructed from a material of the anthracite, semi-graphitic or graphitic type.

According to one embodiment, the nominal segment is a first nominal segment, and the segments include a second nominal segment disposed between the second conductive segment and the insulating segment, the second nominal segment having the nominal thermal conductivity.

According to one embodiment, the segments include a transverse conductive segment extending from a transverse center of the cathode along a transverse wall of the pair of transverse walls and a nominal transverse segment located near a end of the transverse wall downstream of the transverse center, the transverse nominal segment having the nominal thermal conductivity and the transverse conductive segment having a thermal conductivity greater than the nominal thermal conductivity.

According to one embodiment, the transverse nominal segment has the nominal conductivity and the transverse conductive segment has the second thermal conductivity.

[0019]According to one embodiment, the nominal segment is constructed in a material of the semi-graphitic, graphitic or graphitized type, and the conductive segment is constructed in a material of the graphitic, graphitized or over-graphitized type.

According to another aspect, the present technology relates to an aluminum smelter characterized in that it comprises an electrolytic cell having the aforementioned characteristics.

[0021]According to one embodiment, the aluminum smelter comprises a cooling means disposed outside the side walls of the box, characterized in that the cooling means is arranged at the internal layer of the side coating so that the means cooling has a greater density vis-à-vis a portion of the casing along the conductive segment than vis-à-vis a portion of the casing along the nominal segment. BRIEF DESCRIPTION OF FIGURES

Other advantages and characteristics of this technology will emerge from the description below of several variant embodiments given by way of non-limiting examples, some of which with reference to the appended drawings in which:

Figure 1 is a partial schematic view of an electrolytic cell according to one embodiment of the invention;

Figure 2 is a horizontal sectional view of the interior of an electrolytic cell according to one embodiment of the invention;

[0025] Figure 3 is a partial schematic view of a crucible of an electrolytic cell according to one embodiment of the invention, and

Figure 4 is a partial cross-sectional view of the interior of an electrolytic cell according to one embodiment of the invention.

DETAILED DESCRIPTION

With reference to Figures 1 and 2, the present technology relates to equipment intended for use in an aluminum smelter as part of an industrial metallurgical transformation process for the production of aluminum from alumina according to the electrolysis process. of Hall-Heroult. For this purpose, an electrolytic cell 10 is provided according to one embodiment of the technology. The tank 10 has an upstream side 10A, a downstream side 10B opposite the upstream side 10A extending along a longitudinal orientation of the tank 10, and a pair of head sides 10C opposite to each other and extending according to a transverse orientation of the tank 10. The upstream-downstream direction is oriented in the direction of the current in the electrolysis series. The tank 10 comprises a box 20, conventionally made of steel and falling within a rectangular perimeter. The box 20 has side walls, including a pair of longitudinal walls 22A, 22B and a pair of transverse walls 24G, 24D, as well as a bottom 26 whose interior surfaces are provided with a coating system 30. Such illustrated in Figures 2 and 3, a cathode assembly 40 of the vessel 10 comprises a cathode typically consisting of a multitude of cathode blocks 42 of carbonaceous material, is supported above the bottom 26 of the box 20. The cathode blocks 42 extend symmetrically from a longitudinal center CL of the cathode assembly and along the X axis of the tank 10, and on either side of a transverse center CT of the cathode assembly and along the Y axis of the tank 10. The cathode blocks 42 together define an upper surface 44, or above, of the cathode assembly generally parallel to the XY plane. As illustrated in Figures 1 and 4, this upper surface 44 represents a bottom of a crucible C intended to contain the alumina and other substances required for the implementation of the electrolysis process. Below the upper surface 44, each cathode block is connected to an electrical output conductor 12 of the tank 10 intended to receive an electrolysis current I from the cathode assembly 40 to lead it out of the tank 10 according to the axis Y, therefore downstream of the tank 10 In other words, the electrolysis current I is routed from the transverse center of the cathode to the downstream side 10B of the tank 10 through one of the longitudinal walls 22A, 22B of the box 20 being designated downstream wall 22B. One of the longitudinal walls 22A, 22B arranged opposite the downstream wall 22B is therefore designated the upstream wall 22A. Other electrical conductor configurations and vessel orientations are also possible. .

[0028] As illustrated in Figure 1, on the upstream side 10A of the tank 10, a source or an output conductor from another tank (not shown) carries the electrolysis current I to a conductor of electrical riser 14 of the tank 10. The riser conductor 14 is electrically connected to a series of anode assemblies 50 of the vessel 10 located above the cathode assembly 40. Each anode assembly 50 comprises at least one anode block 52 having a bottom defining a portion of a lower surface 54 of the anode assemblies 50. Each anode block 52 is suspended from an anode support, such as a conductive rod 56 and a crosspiece. It should be noted that the rising conductor is arranged at a distance from the casing 20, overhanging the upstream wall 22A, so that the current I can descend along the Z axis in the tank 10 via the anode assemblies 50. For To do this, the tank 10 also comprises a superstructure 60 extending above the box 20. This superstructure 60 consists in particular of at least one beam positioned in a longitudinal direction X of the tank 10 and held in position relative to the box 20, for example by means of feet (not shown) arranged on either side of the tank 10 at its transverse edges, also called heads. An opening O that can be closed by a cowling system 70 of the tank 10 extends longitudinally above the casing 20 on each side of the superstructure 60. The cowling system 70 is arranged on the casing 20 and on the superstructure 60 to close off each opening O reversibly, thus forming with box 20 a containment enclosure for vessel 10. Superstructure 60 is arranged to support other components of vessel 10, in particular anode assemblies 50 via an anode frame 62 attached to the superstructure 60. Each rod 56 is connected electrically to the electric rise conductor 14 of the tank 10 via the frame 62, which makes it possible to convey the electrolysis current I to the corresponding anode block 52. A movable part of the frame 62 makes it possible to move the anode assembly 50 relative to the superstructure 60 in a vertical direction Z of the vessel 10, through the opening O, thus making it possible to immerse the anode block 52 in the crucible C while by controlling the position of the anode block 52 relative to the cathode and/or a surface of a sheet of metal forming at the bottom of the crucible C..

According to the example illustrated in Figures 3 and 4, a lower part 32 of the coating system 30 surrounds a base of the cathode receiving the electrical conductors 12 . According to the example illustrated, the lower part 32 extends vertically to below the upper surface 44 of the cathode. An upper portion 34 of the coating system 30 surrounds the upper surface 44 of the cathode and extends vertically from the lower part 32 to beyond the upper surface 44. The upper part 34 of the coating system 30 forms a circumference of the crucible C extending vertically from the bottom of the crucible C.

The coating system 30 serves both to form the contours of the crucible C and to protect the side walls of the box 20 with respect to the contents of the crucible C. In particular, with reference to Figures 3 and 4, the upper part 34 of the coating system 30 comprises an internal layer 80 located on the periphery of the cathode and an external layer 90 adjoining the side walls of the casing 20 on the periphery of the internal layer 80. A space on the periphery of the cathode and surrounded by the internal layer 80 is clogged with potlining paste 28. The contours of the crucible C are therefore formed by the upper surface 44 of the cathode, the potlining paste 28, the internal layer 80 of the coating system and the top of the external layer 90.

The outer layer 90 typically consists of elements composed of refractory material based on silicon carbide (SiC) or other thermally refractory composition. In the present example, the outer layer 90 includes a first stage and a second stage vertically superimposed on the first stage comprising respectively a series of elements 92, 94 affixed one after the other against the box 20. In the For example, the elements 92 are refractory bricks and the elements 94 are SiC slabs. It should be noted that according to certain embodiments, the elements 94 can be omitted. Also, other insulating materials with mica can be added as needed. As illustrated in Figure 3, the inner layer 80 comprises a series of blocks 82 of internal facing affixed horizontally one after the other against the outer layer 90. Each of the blocks 82 of internal facing has a double vocation. On the one hand, each of the blocks 82 contributes to protecting both the wall portion 22A, 22B, 24G, 24D of the box 20 and the outer layer portion 90 located opposite it from wear by the aluminum and/or the molten electrolyte in the crucible C. Each of the blocks 82 of internal facing is constructed from a carbonaceous material. The blocks 82 include blocks 82 called "nominal", that is to say having a nominal thermal conductivity allowing a certain reference (or nominal) heat transfer which proves to be appropriate for several places around the periphery of the crucible C.

[0032] The inventors of the present technology have discovered that a tank whose inner layer 80 of the coating system 30 was exclusively made of nominal blocks 82 does not perfectly meet the specific heat transfer requirements at certain places around the perimeter. of the crucible C. Indeed, electromagnetic characteristics specific to the vessel 10 induce localized thermal effects in the crucible C which can, in the presence of typical internal layer 80, have an adverse influence on the formation of slope T in the crucible C. The embankment T, a formation including solidified electrolyte, is deposited on the periphery of crucible C as soon as the contents of crucible C, around 970°C at its center, undergoes cooling outwards. Depending on the place on the periphery of the crucible C, a nominal block 82 can, by its intrinsic characteristics, induce an adequate, excessive, or insufficient heat transfer. Excessive heat transfer can lead to excessive slope formation T, which can eventually coat the cathode and even interfere with the descent of an anode block 52 into crucible C. Insufficient heat transfer can lead to slope formation insufficient T, and even an absence of a slope T. When exposed to the contents of the crucible C in the absence of a slope T, the internal layer 80 of the coating system 30 is subject to premature degradation by a phenomenon similar to 'erosion.

Thus, on the other hand, the series of blocks 82 of the inner layer 80 of the present technology is also intended to locally regulate the transfer of heat from the crucible C to the outer layer 90 and out of the box 20 To do this, the horizontal series of blocks 82 comprises several types of blocks 82 differentiated among other things on the basis of their thermal conductivity, and arranged horizontally along the wall of the vessel so that their thermal conductivity meets a local need in heat transfer. The blocks 82 thus include so-called "specific" blocks, of thermal conductivity allowing a heat transfer other than the reference heat transfer, strategically placed over certain lengths of the internal layer 80 of the coating system 30 in alternation with other lengths traveled by nominal 82 blocks. As will be described below, specific 82 blocks may include, depending on the embodiment, conductive blocks 82, with higher thermal conductivity than that of the nominal blocks 82, and/or insulating blocks 82 with lower thermal conductivity than that of the nominal blocks 82. Blocks 82 may be constructed of any of the following types of materials, listed in order of increasing thermal conductivity: anthracitic [~7W/m*K], semi-graphitic [~11 W/m*K] , graphitic [~20/m*K], graphitized [~110W/m*K], over-graphitized [~125W/m*K], In certain low power implementations of the vessel 10, the insulating blocks 82 are made of material anthracite, the nominal blocks 82 are made of semi-graphitic material, and the conductive blocks 82 are made of graphitic and/or graphitized, or even over-graphitized material. In some high power implementations of vessel 10, insulating blocks 82 are of semi-graphitic material, nominal blocks 82 are of graphitic material, and conductive blocks 82 are of graphitized and/or over-graphitized material.

The electromagnetic characteristics of the tank 10 influencing the formation of slope T will now be summarized with reference to the example of Figures 1 and 2. The routing of the current I through the tank 10, first vertically (according to the axis Z) from the anode blocks 52 to the cathode blocks 42 and then horizontally (along the Y axis) from the cathode blocks 42 to the output conductors 12, induces a magneto-hydrodynamic field in the contents of the crucible C This field is manifested by vortices (or velocity fields) V1, V2, V3, V4 (Figure 2) observable on the sheet of metal, among others at the height of the interface between the electrolyte in fusion with the sheet of metal (also called bath-metal interface). The tank 10 is generally symmetrical with respect to the longitudinal center CL of the cathode and, similarly, the vortices V1, V3, and V2, V4 are respectively pairs of corresponding vortices formed in a generally symmetrical manner with respect to the longitudinal center CL when the inlets and current outputs in the tank are well balanced as well as the magnetic environment surrounding the tank. In practice, there may be a difference between the whirlpools and the latter are not always symmetrically arranged, in particular on the tanks at the end of the series. Generally, the vortices V1, V2 are formed in the right half of the tank 10 extending along X from the longitudinal center CL, while the vortices V3, V4 are formed in the left half of the tank 10. Although the description which follows will relate mainly to the right half of tank 10 and to the vortices V1, V2 being formed there, it is understood that the characteristics of the recited right half apply, mutatis mutandis, to the left half of tank 10. Nevertheless, it is emphasized that a difference of the order of approximately 50% may exist between a dimension of an element situated in the right half and that of a corresponding symmetrical element situated in the left half. Although tank 10 is also generally symmetrical with respect to the transverse center CT of the cathode, the vortices V1, V2 are not distributed symmetrically with respect to the transverse center CT. It follows that the vortices V1, V2 can circulate around the coating 30 with more or less intensity on either side of the transverse center CT (at two positions along the Y axis) for the same position along the X axis.

In the example illustrated in Figure 2, the tourbillon V1 circulates in the right half of the vessel 10 in a clockwise direction. From close to an end 22A' of the upstream wall 22A, the vortex V1 puts pressure on the upstream wall 22A and runs along the upstream wall 22A over a certain distance while heading towards the longitudinal center CL, creating a first zone Z1 of increased thermal stress on the vessel 10. Still according to the example of FIG. 2, the vortex V1 then takes off from the upstream wall 22A at a distance from the longitudinal center CL and branches off towards the downstream wall 22B. From close to the longitudinal center CL, the vortex V1 puts pressure on the downstream wall 22B and runs along the downstream wall 22B over a certain distance while heading towards an end 22B' of the downstream wall 22B, creating a second zone Z2 of thermal stress. increased. At a distance from the end 22B′, the vortex V1 unhooks from the downstream wall 22B before going to rejoin the transverse wall 24D at a distance from opposite ends 24D′ of the transverse wall 24D, creating a zone ZR of thermal stress reduced to the junction between the downstream 22B and transverse 24D walls. The vortex V2 circulates in the zone ZR of reduced thermal stress counterclockwise and at a lower speed than the vortex V1, along the downstream wall 22B near the end 22B', inducing a low pressure on the downstream wall 22B. Then, the vortex V1 puts pressure on the transverse wall 24D on either side of the transverse center CT and runs along the transverse wall 24D at a distance from the upstream 22A and downstream 22B walls, creating a third zone Z3 of increased thermal stress.

[0035] Still according to the example of Figure 2, the zones Z1, Z2 see a normal flow to the side walls and therefore a greater heat flux than nominal where the flow is lateral. The Z3 zone can show counter-vortices which facilitate the formation of slopes and limit heat fluxes. The difference in heat flux, and more particularly the variations in heat exchange between the bath/metal and the embankment, in the various zones Z1, Z2, Z3 and ZR, can be observed by measuring the distribution of the embankment around the tank. A balancing of the heat fluxes in the various zones is therefore desirable in order to re-homogenize the thickness of the embankment around the tank 10. [0036] With reference to Figure 2, in order to overcome the adverse effects of the electromagnetism of the tank 10 on the formation of slope T along the periphery of the crucible C, the internal layer 80 of the coating system 30 consists of segments, that is to say series of blocks 82 either nominal (or nominal segments 84), or conductive (or conductive segments 86), or either insulating (or insulating segments 88). Each of the segments 84, 86, 88 inherits the properties of the blocks 82 of which it is made, and can therefore be constructed, depending on the embodiment, of one or other of the following types of materials, listed in order of increasing thermal conductivity : anthracitic, semi-graphitic, graphitic, graphitized, or over-graphitized. Thus, depending on the embodiment, each nominal segment 84 is constructed in a material of the semi-graphitic, graphitic or graphitized type, each conductive segment 86 is constructed in a material of the graphitic, graphitized or over-graphitized type, and each insulating segment 88 is constructed of an anthracitic, semi-graphitic, or graphitic material such that conductive segments 86 have higher thermal conductivity than nominal segments 84, while insulating segments 88 have less thermal conductivity than nominal segments 84. The segments 84, 86, and 88 are alternately affixed along the side walls of box 20. Depending on the embodiment, segments 84, 86, and 88 may include more than one nominal segment 84, more than one conductive segment 86, and/or or more than one insulating segment 88 along a single side wall. In the example shown, along the upstream wall 22A, a first nominal segment 84A extends from the longitudinal center CL towards an end 22A' of the upstream wall 22A. A first conductive segment 86A extends from near end 22A' toward longitudinal center CL. The first conductive segment 86A adjoins zone Z1. Note that first nominal segment 84A is longer than first conductive segment 86A. The first conductive segment 86A has an equivalent length between 0 and 66% of the distance between the longitudinal center CL and the end 22k'. In the example provided, the length of the first conductive segment 86A may correspond to a distance covered by 2 to 8 cathode blocks 42 along the X axis, considering that the tank has 12 blocks between the longitudinal center CL and the end 22k' .

Along the downstream wall 22B, a second conductive segment 86B extends from the longitudinal center CL towards an end 22B' of the downstream wall 22B. The second conductive segment 86B adjoins zone Z2. Note that first nominal segment 84A is larger than second conductive segment 86B. The second conductive segment 86B has an equivalent length between 0 and 70% of the distance between the longitudinal center CL and the end 22B'. Between the second conductive segment 86B and the end 22B', the inner layer 80 has a thermal conductivity equal to or less than nominal thermal conductivity. In the present case, an insulating segment 88 extends from near the end 22B' towards the longitudinal center CL. Insulating segment 88 adjoins zone ZR. The insulating segment 88 has an equivalent length between 0 and 40% of the distance between the longitudinal center CL and the end 22B'. A second nominal segment 84B is disposed between the second conductive segment 86B and the insulating segment 88. In other embodiments, the insulating segment 88 is omitted, so that the second nominal segment 84B extends to near the end 22B'.

[0038] Along the transverse wall 24D, a third conductive segment 86C, or transverse conductive segment, extends from the transverse center CT to a distance from opposite ends 24D′ of the transverse wall 24D. The third conductive segment 86C has an equivalent length between 0 and 75% of the length of the transverse wall 24D. A pair of third nominal segments 84C, or transverse nominal segments, extend from either side of the third conducting segment 86C to the ends 24D'.

In this example, the nominal segments 84A, 84B, 84C are made of graphite material. The first conductive segment 86A is made of over-graphitized material. The second conductive segment 86B and the third conductive segment 86C are made of graphitized material. The insulating segment 88 is made of semi-graphitic material. In other embodiments of the tank 10, the nominal segments 84A, 84B, 84C are made of semi-graphitic material. The first conductive segment 86A is made of graphitized material. The second conductive segment 86B and the third conductive segment 86C are made of graphitic material. The insulating segment 88 is made of anthracite material.

[0040] Referring to Figure 4, by their nature and their positioning with respect to the vortices V1, V2, the segments of the inner layer 80 of the coating system 30 have in common to make possible a local heat transfer adequate for the formation of the embankment T, so that the embankment T will prove globally of an adequate and homogeneous dimension. By homogeneous dimension is meant a slope thickness T being substantially the same horizontally (in the XY plane) throughout the inner layer 80.

[0041] In some embodiments, the vessel may be provided with evacuation means include means for cooling the aluminum smelter 1 arranged outside the vessel 10 and distributed around the box 20. The cooling means may include fins. The fins can advantageously be provided to have a greater density along the segments conductors 86A, 86B, 86C than along nominal segments 84A, 84B, 84C. In other words, a fin area ratio per unit length of conductive segments 86A, 86B, 86C is greater than a fin area ratio per unit length of nominal segments 84A, 84B, 84C.

[0042] The cooling means may include blowing means suitable for directing a localized jet of air. The blowing means can advantageously be provided so that a blowing density is greater along the conductive segments 86A, 86B, 86C than along the nominal segments 84A, 84B, 84C. In other words, a ratio of incident air flow from the blowing means per unit length of conductive segments 86A, 86B, 86C is greater than a ratio of incident air flow from the blowing means per unit length of segments nominal 84A, 84B, 84C. The blowing means can be located opposite the conductive segments 86A, 86B, 86C or oriented towards the conductive segments 86A, 86B, 86C and/or away from the nominal segments 84A, 84B, 84C.

[0043] Other changes could be implemented by a person of ordinary skill in the art for the purposes of this document, which would also be within the scope of this technology.

Claims

1 . Electrolysis cell (10) comprising a box (20) having side walls (22A, 22B, 24G, 24D) including a pair of longitudinal walls (22A, 22B) and a pair of transverse walls (24G, 24D), a cathode (40) inside the casing (20), and a side coating (30) including an inner layer (80) around the periphery of the cathode (40) and an outer layer (90) adjoining the side walls (22A, 22B, 24G, 24D) of the casing (20) at the periphery of the internal layer (80), the lateral coating (30) extending vertically beyond the cathode (40), characterized in that: the internal layer ( 80) comprises segments (84, 86, 88) including a nominal segment (84) and a conductive segment (86) arranged one after the other along a side wall of the side walls (22A, 22B, 24G, 24D) of the casing (20); the nominal segment (84) having a nominal thermal conductivity and the conductive segment (86) having a thermal conductivity greater than the nominal thermal conductivity, the conductive segment (86) adjoining an area of increased thermal stress (Z1, Z2) of the tank (10). 2. Electrolysis cell (10) according to claim 1, wherein the side wall is a longitudinal wall (22A) upstream of the pair of longitudinal walls (22A, 22B) located upstream of the cathode (40), the segment nominal (84) extends from a longitudinal center (CL) of the cathode (40) to an end of the upstream longitudinal wall (22A), and the conductive segment (86) extends from near the end of the longitudinal wall (22A) upstream towards the longitudinal center (CL). 3. Electrolytic cell (10) according to claim 1 or 2, in which the zone of increased thermal stress (Z1, Z2) has a flow normal to said side wall (22A, 22B), said flow induced by a magneto field - hydrodynamics in the contents of the tank. 4. Electrolysis cell (10) according to any one of claims 1 to 3, wherein the conductive segment (86) is a first conductive segment (86A), a downstream longitudinal wall (22B) of the pair of longitudinal walls (22A, 22B) is located downstream of the cathode (40), and the segments (84, 86, 88) include a second conductive segment (86B) extending from the longitudinal center (CL) of the cathode (40) towards one end of the downstream longitudinal wall (22B), the second conductive segment (86B) having a thermal conductivity greater than the nominal thermal conductivity. 5. An electrolytic cell (10) according to any one of claims 1 to 4, wherein the segments (84, 86 and 88) include an insulating segment (88) extending along said side wall, the segment insulation (88) having a thermal conductivity less than the nominal thermal conductivity. 6. An electrolytic cell (10) according to claim 4 or 5, wherein the first conductive segment (86A) has a first thermal conductivity and the second conductive segment (86B) has a second thermal conductivity lower than the first thermal conductivity. 7. An electrolytic cell (10) according to claim 4, wherein the segments (84, 86, 88) include an insulating segment (88) extending from near the end of the downstream longitudinal wall (22B). towards the longitudinal center (CL) of the cathode (40), the insulating segment (88) having a thermal conductivity less than the nominal thermal conductivity. 8. Electrolytic cell (10) according to claim 6, wherein the first conductive segment (86A) and the second conductive segment (86B) are axially offset relative to a transverse axis (CT) of the cathode (40). 9. Electrolytic cell (10) according to claim 7, in which the insulating segment (88) is constructed of an anthracitic, semi-graphitic or graphitic type material. 10. An electrolytic cell (10) according to any one of claims 7 to 9, wherein the nominal segment (84) is a first nominal segment (84A), and the segments (84, 86, 88) include a second nominal segment (84B) disposed between the second conductive segment (86B) and the insulating segment (88), the second nominal segment (84) having the nominal thermal conductivity. 11 . An electrolytic cell (10) according to any one of claims 1 to 10, wherein the segments (84, 86, 88) include a transverse conductive segment (86C) extending from a transverse center (CT) of the cathode (40) along a transverse wall of the pair of transverse walls (24G, 24D) and a nominal transverse segment (84C) located near an end of the transverse wall downstream of the transverse center (CT), the transverse nominal segment (84C) having the nominal thermal conductivity and the transverse conductive segment (86C) having a thermal conductivity greater than the nominal thermal conductivity. 12. An electrolytic cell (10) according to claim 11 as dependent on claim 6, wherein the transverse nominal segment (84C) has the nominal conductivity and the transverse conductive segment (86C) has the second thermal conductivity . 13. Electrolytic cell (10) according to any one of claims 2 to 12, in which the nominal segment (84) is constructed from a material of the semi-graphitic, graphitic or graphitized type, and the conductive segment (86) is constructed from a graphitic, graphitized or over-graphitized type material. 14. Smelter, characterized in that it comprises at least one electrolytic cell (10) according to any one of claims 1 to 13. 15. Smelter according to claim 14, comprising a cooling means arranged outside the side walls of the box, characterized in that the cooling means is arranged at the internal layer of the side coating so that the cooling means has a greater density vis-à-vis a portion of the casing along the conductive segment than vis-à-vis a portion of the casing along the nominal segment. 16