Interior lining system for an electrolytic cell

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

INTERIOR LINING SYSTEM FOR ELECTROLYSIS TANK TECHNICAL FIELD

[0001] The present technology relates to coating systems for electrolysis tanks, electrolysis tanks equipped with such systems, and aluminum plants comprising electrolysis tanks equipped with such systems. PRESENTATION OF PREVIOUS ART

[0002] Aluminum production on an industrial scale is commonly carried out in aluminum smelters, using the Hall-Héroult process for electrolysis of alumina. This process requires an electrolysis cell consisting of a typically steel-framed enclosure lined with a refractory material. The bottom of the cell contains a cathode assembly with a cathode formed from at least one typically carbonaceous block. Electrical conductors from the cathode assembly carry the electrolysis current to cathode outlets. The top of the cathode assembly and the lining define a crucible for holding a molten cryolite bath, also called the electrolytic bath. In this bath, alumina is dissolved to form a layer of aluminum at the bottom of the crucible, which accumulates on the cathode assembly.The electrolysis cell also includes at least one anodic block suspended from an anodic support, such as a rod and crossbar, with the anodic block partially immersed in the electrolytic bath above the cathode blocks. An upstream electrical conductor carries the electrolysis current to the anodic assembly, either from a source or from a cathodic output of an upstream electrolysis cell, as required for the electrolysis reaction to occur in the bath, provided the anodic block is properly positioned and the temperature is adequate, among other conditions. During the reaction, the electrolytic current flows to the cathode assembly from the anodic block, through the electrolytic bath and the metal sheet. The cell is often constructed and designed to cause the formation of a solidified bath embankment on the cell's side walls.The slope is generally formed by a cooling mechanism. As discussed below, a uniform slope formation along the tank walls is desirable.

[0003] French patent application no. 14 / 01518 teaches the use of internal facing blocks superimposed on an external layer of the cladding. However, even in the presence of For these facing blocks, managing the temperature of the electrolytic bath and the formation of the slope opposite the metal remains a challenge.

[0004] French patent application no. 98 / 05040 describes the use of means for evacuating and dissipating the heat produced by the electrolysis cell, located outside the casing. These means are presented as blowing devices that can be directed onto the casing, generally towards the interface between the metal sheet and the electrolyte bath. However, temperature control from inside the crucible is also crucial, particularly with regard to the formation of an adequately distributed berm around the crucible. Specifically, excessive heat dissipation can lead to an overly large berm that may interfere with the descent of the anodic blocks. Conversely, insufficient heat dissipation can result in inadequate berm formation, exposing the lateral lining of the cell to the aluminum sheet and leading to 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 lifespan of certain components of the tank, and consequently to the efficiency of the tank. TECHNOLOGY SUMMARY

[0005] One of the goals of the present technology is to overcome the aforementioned drawbacks. To this end, the present technology proposes an electrolysis cell comprising an internal lining system configured to allow the management of heat transfer from the inside of a crucible within the cell to the outside of a cell casing, promoting a homogeneous creation of slopes inside the crucible adjacent to an internal layer of said internal lining system.

[0006] A second objective of at least one realization of the proposed technology is to distribute heat losses evenly on the side walls all around the electrolysis cell in order to stabilize the cell's heat balance, as well as the formation of a stable and uniform slope which ensures a long cell life.

[0007] According to one aspect, the present technology relates to an electrolysis cell comprising a casing having side walls including a pair of longitudinal walls and a pair of transverse walls, a cathode inside the casing, and a side coating including an inner layer at the periphery of the cathode and an outer layer adjoining the side walls of the casing at 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 lateral wall of the lateral 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 casing.

[0008] 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 to an end of the upstream longitudinal wall, and the conducting segment extends from near the end of the upstream longitudinal wall to the longitudinal center.

[0009] According to one embodiment, the conducting 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.

[0010] According to one embodiment, the conducting segment is a first conducting segment, a downstream longitudinal wall of the pair of longitudinal walls is located downstream of the cathode, and the segments include a second conducting segment extending from the longitudinal center of the cathode to one end of the downstream longitudinal wall, the second conducting segment having a thermal conductivity greater than the nominal thermal conductivity.

[0011] 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.

[0012] According to one embodiment, the first conducting segment has a first thermal conductivity and the second conducting segment has a second thermal conductivity lower than the first thermal conductivity.

[0013] 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 nominal thermal conductivity.

[0014] According to one embodiment, the first conducting segment and the second conducting segment are axially offset relative to a transverse axis of the cathode.

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

[0016] According to one embodiment, the nominal segment is a first nominal segment, and the segments include a second nominal segment disposed between the second conducting segment and the insulating segment, the second nominal segment having the nominal thermal conductivity.

[0017] According to one embodiment, the segments include a transverse conducting 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 an end of the transverse wall downstream of the transverse center, the nominal transverse segment having the nominal thermal conductivity and the transverse conducting segment having a thermal conductivity greater than the nominal thermal conductivity.

[0018] According to one embodiment, the nominal transverse segment has the nominal conductivity and the transverse conducting segment has the second thermal conductivity.

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

[0020] According to another aspect, the present technology is intended for an aluminum plant characterized in that it includes an electrolysis cell having the aforementioned characteristics.

[0021] According to one embodiment, the aluminum plant includes a cooling means disposed outside the side walls of the casing, characterized in that the cooling means is arranged in the inner layer of the side cladding so that the cooling means has a greater density with respect to a portion of the casing along the conductive segment than with respect to a portion of the casing along the nominal segment. BRIEF DESCRIPTION OF THE FIGURES

[0022] Other advantages and features of this technology will become apparent from the following description of several implementation variants given by way of non-limiting examples, some of which are shown with reference to the attached drawings in which:

[0023] Figure 1 is a partial schematic view of an electrolysis tank according to one embodiment of the invention;

[0024] Figure 2 is a horizontal sectional view of the inside of an electrolysis tank according to one embodiment of the invention;

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

[0026] Figure 4 is a partial cross-sectional view of the interior of an electrolysis tank according to one embodiment of the invention. DETAILED DESCRIPTION

[0027] 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 using the Hall-Héroult electrolysis process. For this purpose, an electrolysis cell 10 is provided according to one embodiment of the technology. The cell 10 has an upstream side 10A, a downstream side 10B opposite the upstream side 10A extending along the longitudinal axis of the cell 10, and a pair of head sides 10C opposite each other and extending along the transverse axis of the cell 10. The upstream-downstream direction is aligned with the direction of the current in the electrolysis series. The cell 10 includes a casing 20, typically made of steel and having a rectangular perimeter.The tank 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 internal surfaces are provided with a coating system 30. As illustrated in Figures 2 and 3, a cathode assembly 40 of the tank 10 comprises a cathode typically made up of a multitude of cathode blocks 42 of carbon material, supported above the bottom 26 of the tank 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 top, of the cathode assembly, generally parallel to the XY plane. As illustrated in Figures 1 and 4, this upper surface 44 represents the bottom of a crucible C intended to contain alumina and other substances required for carrying out the electrolysis process. Below the upper surface 44, each cathode block is connected to an electrical output conductor 12 of the tank 10, designed to receive an electrolysis current I from the cathode assembly 40 and conduct it out of the tank 10 along the Y-axis, i.e., 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 casing 20, designated as the downstream wall 22B. One of the longitudinal walls 22A, 22B arranged opposite the downstream wall 22B is therefore designated upstream wall 22A.Other electrical conductor configurations and tank 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 an electrical rise conductor 14 of the tank 10. The rise conductor 14 is electrically connected to a series of anode assemblies 50 of the tank 10 located above the cathode assembly 40. Each anode assembly 50 comprises at least one anode block 52 having an underside 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 cross member. It should be noted that the rise conductor is positioned at a distance from the box 20, overhanging the upstream wall 22A, so that the current I can descend along the Z axis into the tank 10 through the anode assemblies 50. To achieve this, the tank 10 also includes a superstructure 60 extending over the box 20.This superstructure 60 notably consists of at least one beam positioned along a longitudinal direction X of the tank 10 and held in position relative to the casing 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, closable by a cover system 70 of the tank 10, extends longitudinally above the casing 20 on each side of the superstructure 60. The cover system 70 is arranged to the casing 20 and the superstructure 60 to reversibly close each opening O, thus forming with the casing 20 a containment enclosure for the tank 10. The superstructure 60 is arranged to support other components of the tank 10, notably the anode assemblies 50 by means of an anode frame 62 attached to the superstructure 60. Each rod 56 is connected. Electrically, the electrolysis current I is supplied to the electrical riser conductor 14 of the tank 10 via the frame 62, thus enabling the electrolysis current I to be carried to the corresponding anodic block 52. A movable part of the frame 62 allows the anodic assembly 50 to be moved relative to the superstructure 60 in a vertical direction Z of the tank 10, through the opening O, thereby allowing the anodic block 52 to be immersed in the crucible C while controlling the position of the anodic block 52 relative to the cathode and / or a surface of a metal sheet forming at the bottom of the crucible C.

[0029] As illustrated in Figures 3 and 4, a lower portion 32 of the coating system 30 encircles a base of the cathode that houses the electrical conductors 12. In the illustrated example, the lower portion 32 extends vertically to within a portion 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 portion 32 to beyond the upper surface 44. The upper portion 34 of the coating system 30 forms a perimeter around the crucible C, extending vertically from the bottom of the crucible C.

[0030] The coating system 30 serves both to form the contours of the crucible C and to protect the side walls of the chamber 20 from 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 inner layer 80 located at the periphery of the cathode and an outer layer 90 adjoining the side walls of the chamber 20 at the periphery of the inner layer 80. A space at the periphery of the cathode and surrounded by the inner layer 80 is sealed with brazing paste 28. The contours of the crucible C are therefore formed by the upper surface 44 of the cathode, the brazing paste 28, the inner layer 80 of the coating system, and the top of the outer layer 90.

[0031] The outer layer 90 is typically made of elements composed of refractory material based on silicon carbide (SiC) or another thermally refractory composition. In this example, the outer layer 90 includes a first and a second layer vertically superimposed on the first layer, each comprising a series of elements 92 and 94 respectively, placed end-to-end against the casing 20. In this example, elements 92 are refractory bricks and elements 94 are SiC slabs. It should be noted that in some embodiments, elements 94 may be omitted. Also, other insulating materials containing mica may be added as needed. As illustrated in Figure 3, the inner layer 80 comprises a series of internal facing blocks 82 placed horizontally end-to-end against the outer layer 90. Each of the internal facing blocks 82 serves a dual purpose. On the one hand, each of the blocks 82 helps to protect both the wall portion 22A, 22B, 24G, 24D of the casing 20 and the outer layer portion 90 located opposite it from wear by the molten aluminum and / or electrolyte in the crucible C. Each of the internal facing blocks 82 is made of a carbonaceous material. The blocks 82 include so-called "nominal" blocks, that is, blocks having a nominal thermal conductivity allowing a certain reference (or nominal) heat transfer that proves appropriate for several locations around the perimeter of the crucible C.

[0032] The inventors of this technology discovered that a vessel whose inner layer 80 of the lining system 30 was made exclusively of nominal blocks 82 does not perfectly meet the heat transfer requirements specific to certain areas around the perimeter of the crucible C. Indeed, electromagnetic characteristics inherent to the vessel 10 induce localized thermal effects within the crucible C which, in the presence of a typical inner layer 80, can adversely affect the formation of slope T within the crucible C. The slope T, a formation including solidified electrolyte, is deposited around the perimeter of the crucible C as soon as the contents of the crucible C, at around 970 °C at its center, are cooled outwards. Depending on its location around the perimeter of the crucible C, a nominal block 82 can, due to its intrinsic characteristics, induce adequate, excessive, or insufficient heat transfer.Excessive heat transfer can lead to excessive formation of slope T, which may eventually cover the cathode and even interfere with the descent of an anodic block 52 into the crucible C. Insufficient heat transfer can lead to insufficient formation of slope T, and even to a lack of slope T. When exposed to the contents of the crucible C in the absence of slope T, the inner layer 80 of the coating system 30 is subject to premature degradation by a phenomenon resembling erosion.

[0033] Thus, on the other hand, the series of blocks 82 in the inner layer 80 of the present technology also serves to locally regulate heat transfer from the crucible C to the outer layer 90 and out of the casing 20. To this end, 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 heat transfer requirement. The blocks 82 thus include so-called "specific" blocks, with thermal conductivities enabling heat transfer other than the reference heat transfer, strategically placed along certain lengths of the inner layer 80 of the lining system 30, alternating with other lengths covered by nominal blocks 82. As will be described below, the specific blocks 82 may include, Depending on the implementation, conductive blocks 82, with a higher thermal conductivity than the nominal blocks 82, and / or insulating blocks 82 with a lower thermal conductivity than the nominal blocks 82. The blocks 82 can be constructed from one of the following types of materials, listed in order of increasing thermal conductivity: anthracite [~7W / m*K], semi-graphitic [~11 W / m*K], graphitic [~20 W / m*K], graphitized [~110 W / m*K], super-graphitized [~125 W / m*K]. In some low-power implementations of the tank 10, the insulating blocks 82 are made of anthracite material, the nominal blocks 82 are made of semi-graphitic material, and the conductive blocks 82 are made of graphitic and / or graphitized, or even super-graphitized, material.In some high-power implementations of tank 10, the insulating 82 blocks are made of semi-graphitic material, the nominal 82 blocks are made of graphitic material, and the conductive 82 blocks are made of graphitized and / or over-graphitized material.

[0034] 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 (along the Z axis) from the anodic blocks 52 to the cathodic blocks 42 and then horizontally (along the Y axis) from the cathodic blocks 42 to the output conductors 12, induces a magneto-hydrodynamic field in the contents of the crucible C. This field manifests itself by vortices (or velocity fields) V1, V2, V3, V4 (Figure 2) observable directly on the metal sheet, among other places at the level of the interface between the molten electrolyte with the metal sheet (also called the bath-metal interface).The cell 10 is generally symmetrical about the longitudinal center CL of the cathode, and similarly, the vortices V1, V3, and V2, V4 are respectively pairs of corresponding vortices formed generally symmetrically about the longitudinal center CL when the current inputs and outputs in the cell are well balanced, as well as the magnetic environment surrounding the cell. In practice, there may be a difference between the vortices, and they are not always symmetrically arranged, particularly on end-of-series cells. Generally, the vortices V1, V2 are formed in the right half of the cell 10 extending along the X-axis from the longitudinal center CL, while the vortices V3, V4 are formed in the left half of the cell 10.Although the following description will focus primarily on the right half of tank 10 and the vortices V1 and V2 formed there, it is understood that the characteristics described for the right half apply, mutatis mutandis, to the left half of tank 10. Nevertheless, it is emphasized that a difference of approximately 50% may exist between the dimensions of an element located in the right half and those of a corresponding symmetrical element located in the left half. Although tank 10 is also... Although generally symmetrical with respect to the transverse center CT of the cathode, the vortices V1 and V2 are not distributed symmetrically with respect to the transverse center CT. Consequently, the vortices V1 and V2 can circulate near the coating 30 with varying 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 vortex V1 circulates clockwise in the right half of the tank 10. From near one end 22A' of the upstream wall 22A, the vortex V1 exerts pressure on the upstream wall 22A and travels along the upstream wall 22A for a certain distance, heading towards the longitudinal center CL, creating a first zone Z1 of increased thermal stress on the tank 10. Again, according to the example in Figure 2, the vortex V1 then detaches from the upstream wall 22A at a distance from the longitudinal center CL and branches off towards the downstream wall 22B. From near the longitudinal center CL, the vortex V1 exerts pressure on the downstream wall 22B and travels along the downstream wall 22B for a certain distance, heading towards one end 22B' of the downstream wall 22B, creating a second zone Z2 of increased thermal stress.At a distance from end 22B', vortex V1 detaches from the downstream wall 22B before moving to the transverse wall 24D at a distance from opposite ends 24D' of the transverse wall 24D, creating a zone ZR of reduced thermal stress at the junction between the downstream wall 22B and the transverse wall 24D. Vortex V2 circulates in the zone ZR of reduced thermal stress in a counterclockwise direction and at a lower speed than vortex V1, following the downstream wall 22B near end 22B', inducing a low pressure on the downstream wall 22B. Then, vortex V1 exerts pressure on the transverse wall 24D on either side of the transverse center CT and follows the transverse wall 24D at a distance from the upstream wall 22A and downstream wall 22B, creating a third zone Z3 of increased thermal stress.

[0035] Continuing with the example in Figure 2, zones Z1 and Z2 exhibit normal flow to the side walls and therefore a higher heat flux than in the nominal flow pattern, where the flow is lateral. Zone Z3 may show counter-vortices that facilitate the formation of slopes and limit heat fluxes. The difference in heat flux, and more specifically the variations in heat exchange between the bath / metal and the slope, in the various zones Z1, Z2, Z3, and ZR, can be observed by measuring the slope distribution around the tank. Balancing the heat fluxes in the various zones is therefore desirable in order to re-homogenize the slope thickness around the tank.

[0036] With reference to Figure 2, in order to counteract the adverse effects of the electromagnetism of the tank 10 on the formation of slopes T along the periphery of the crucible C, the inner layer 80 of the lining system 30 is made up of segments, i.e., series of blocks 82 that are either nominal (or nominal segments 84), conductive (or conductive segments 86), or insulating (or insulating segments 88). Each of the segments 84, 86, 88 inherits the properties of the blocks 82 from which it is made, and can therefore be constructed, depending on the embodiment, from one or another of the following types of materials, listed in order of increasing thermal conductivity: anthracite, semi-graphitic, graphitic, graphitized, or over-graphitized.Thus, depending on the embodiment, each nominal segment 84 is constructed of a semi-graphitic, graphitic, or graphitized material; each conductive segment 86 is constructed of a graphitic, graphitized, or over-graphitized material; and each insulating segment 88 is constructed of an anthracite, semi-graphitic, or graphitic material, so that the conductive segments 86 have a higher thermal conductivity than the nominal segments 84, while the insulating segments 88 have a lower thermal conductivity than the nominal segments 84. The segments 84, 86, and 88 are placed alternately along the side walls of the box 20. Depending on the embodiment, the segments 84, 86, and 88 may include more than one nominal segment 84, more than one conductive segment 86, and / or more than one insulating segment 88 along the same side wall.In the example shown, along the upstream wall 22A, a first nominal segment 84A extends from the longitudinal center CL to an end 22A' of the upstream wall 22A. A first conducting segment 86A extends from near the end 22A' towards the longitudinal center CL. The first conducting segment 86A is adjacent to zone Z1. It should be noted that the first nominal segment 84A is longer than the first conducting segment 86A. The first conducting segment 86A has a length equivalent to 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 conducting segment 86A can 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'.

[0037] Along the downstream wall 22B, a second conducting segment 86B extends from the longitudinal center CL to an end 22B' of the downstream wall 22B. The second conducting segment 86B is adjacent to zone Z2. Note that the first nominal segment 84A is larger than the second conducting segment 86B. The second conducting segment 86B has a length equivalent to between 0 and 70% of the distance between the longitudinal center CL and the end 22B'. Between the second conducting segment 86B and the end 22B', the internal layer 80 has a thermal conductivity equal to or less than the nominal thermal conductivity. In this case, an insulating segment 88 extends from near end 22B' towards the longitudinal center CL. The insulating segment 88 is adjacent to zone ZR. The insulating segment 88 has a length equivalent to between 0 and 40% of the distance between the longitudinal center CL and 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 end 22B'.

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

[0039] In this example, the nominal segments 84A, 84B, and 84C are made of graphitic 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 graphitic material. The insulating segment 88 is made of semi-graphitic material. In other embodiments of the tank 10, the nominal segments 84A, 84B, and 84C are made of semi-graphitic material. The first conductive segment 86A is made of graphitic 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, the segments of the inner layer 80 of the coating system 30, by virtue of their nature and positioning relative to the vortices V1 and V2, share the characteristic of enabling adequate local heat transfer for the formation of the slope T, so that the slope T will be of an adequate and homogeneous overall size. Homogeneous size is defined as a slope thickness T that is substantially the same horizontally (in the XY plane) along the entire length of the inner layer 80.

[0041] In some designs, the tank may be equipped with exhaust means that include cooling means for the aluminum smelter 1 located outside the tank 10 and distributed around the casing 20. The cooling means may include fins. The fins may advantageously be designed to have a higher density along the segments conductors 86A, 86B, 86C than along the nominal segments 84A, 84B, 84C. In other words, a fin area per unit segment length ratio of conductors 86A, 86B, 86C is greater than a fin area per unit segment length ratio of nominal segments 84A, 84B, 84C.

[0042] The cooling means may include blowing means adapted to direct a localized jet of air. The blowing means may advantageously be designed so that a greater blowing density is present along the conductive segments 86A, 86B, 86C than along the nominal segments 84A, 84B, 84C. In other words, the ratio of incident airflow of the blowing means per unit length of conductive segments 86A, 86B, 86C is greater than the ratio of incident airflow of the blowing means per unit length of nominal segments 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 with moderate expertise in the art for the purpose of this document, which would also be included within the scope of this technology.

Claims

DEMANDS 1. Electrolysis cell (10) comprising a casing (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 lining (30) including an inner layer (80) at 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 inner layer (80), the side lining (30) extending vertically beyond the cathode (40), characterized in that: the inner 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 box (20);the nominal segment (84) having a nominal thermal conductivity and the conducting segment (86) having a thermal conductivity greater than the nominal thermal conductivity, the conducting 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 an upstream longitudinal wall (22A) of the pair of longitudinal walls (22A, 22B) located upstream of the cathode (40), the nominal segment (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 upstream longitudinal wall (22A) to the longitudinal center (CL).

3. Electrolysis tank (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-hydrodynamic field in the content of the tank.

4. Electrolysis cell (10) according to any one of claims 1 to 3, wherein the conducting segment (86) is a first conducting 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 conducting segment (86B) extending from the longitudinal center (CL) of the cathode (40) to one end of the downstream longitudinal wall (22B), the second conducting segment (86B) having a thermal conductivity greater than the nominal thermal conductivity.

5. Electrolysis tank (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 insulating segment (88) having a thermal conductivity lower than the nominal thermal conductivity.

6. Electrolysis tank (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. Electrolysis 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 lower than the nominal thermal conductivity.

8. Electrolysis cell (10) according to claim 6, in which 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. Electrolysis tank (10) according to claim 7, in which the insulating segment (88) is constructed of an anthracitic, semi-graphitic or graphitic type material.

10. Electrolysis tank (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 conducting segment (86B) and the insulating segment (88), the second nominal segment (84) having the nominal thermal conductivity.

11. Electrolysis 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 one end of the transverse wall downstream of the transverse center (CT), the nominal transverse segment (84C) having the nominal thermal conductivity and the transverse conductive segment (86C) having a thermal conductivity greater than the nominal thermal conductivity.

12. Electrolysis tank (10) according to claim 11 in that it depends on claim 6, wherein the nominal transverse segment (84C) has the nominal conductivity and the transverse conducting segment (86C) has the second thermal conductivity.

13. Electrolysis tank (10) according to any one of claims 2 to 12, wherein the nominal segment (84) is constructed of a semi-graphitic, graphitic or graphitized type material, and the conducting segment (86) is constructed of a graphitic, graphitized or over-graphitized type material.

14. Aluminum plant, characterized in that it comprises at least one electrolysis cell (10) according to any one of claims 1 to 13.

15. Aluminum plant according to claim 14, comprising a cooling means disposed outside the side walls of the casing, characterized in that the cooling means is arranged in the inner layer of the side cladding so that the cooling means has a greater density with respect to a portion of the casing along the conductive segment than with respect to a portion of the casing along the nominal segment. 16

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