WO2015063557A1

WO2015063557A1 - Sealing device for a cover of an electrolysis cell

Info

Publication number: WO2015063557A1
Application number: PCT/IB2014/002138
Authority: WO
Inventors: Jean-Marc BERTOLO
Original assignee: Rio Tinto Alcan International Limited
Priority date: 2013-10-30
Filing date: 2014-10-13
Publication date: 2015-05-07
Also published as: CN105683420A; FR3012473A1; EP3063313A1; EP3063313A4; CA2924551A1

Abstract

The invention concerns a sealing device for a cover of an electrolysis cell (100) intended for the production of aluminium, the sealing device comprising a fastening portion intended to be secured to a side portion of a first cover (1) and a sealing portion intended to laterally protrude from the first cover and cover a junction area between the first cover (1) and a second cover juxtaposed with the first cover, cutouts extending into the sealing portion in such a way as to increase the flexibility of the sealing portion. The invention also concerns a covering device comprising a cover (1) onto a side portion of which at least one sealing device as described above is secured. The invention further concerns an electrolysis cell (100) for the production of aluminium comprising at least one covering device as described above.

Description

Sealing device for an electrolysis cell cover

The present invention relates to a sealing device for an electrolysis cell cover intended for the production of aluminum. The present invention also relates to a covering device for an electrolysis cell and an electrolysis cell comprising such a sealing device.

Aluminum is conventionally produced in aluminum smelters, by electrolysis, according to the Hall-Héroult process. For this purpose, there is provided an electrolysis cell comprising a box and an inner lining of refractory material. The electrolysis cell also comprises cathode blocks arranged at the bottom of the box, traversed by conductive bars intended to collect the electrolysis current to lead it to a next electrolytic cell, and at least one anode block suspended from a transom and partially immersed in an electrolytic bath, above the cathode blocks. A liquid aluminum sheet, covering the cathode blocks, is formed as and when the reaction.

The flow of current is from the anode block to the cathode via the electrolytic bath at a temperature of about 970 ° C wherein the alumina is dissolved. This electrolysis current has an intensity of up to several hundred thousand ampere.

This electrolysis process is at the origin of the formation of gas whose diffusion out of the electrolysis cell must be avoided.

For this purpose, it is known to use hoods, curved or flat, resting on the edges of the electrolytic cell and against a superstructure so as to limit the diffusion of gases and heat losses. These covers are generally juxtaposed next to each other along the axis of longitudinal extension of the tank, so as to form a closed enclosure. But gas leaks as well as heat losses can take place in the junction zone between the covers. To remedy this, seals were then fixed on the edges of the covers so as to cover these junction areas.

However, operations require access to the interior of the electrolysis cell, including changes of anodes, so that it is necessary to regularly lift at least one of the covers overhanging the tank. The superposition of a seal at the junction area between two adjacent covers hinders handling. Typically, when the seal covers the junction area partially covering the outer face of the second cover, the first cover on which the seal has been attached is shifted from its initial position when the second cover underlying the seal is raised. Alternatively, when the seal covers the junction zone partially covering the inner face of the second cover, the second cover underlying the seal is shifted from its initial position when the first cover on which the seal has been attached is raised. This shift of the first (alternatively the second) hood can, by a domino effect, also affect a third adjacent hood. Thus, once the maintenance operation performed, the operator must put the various covers in place. This results in additional manipulations, gaseous releases and potentially significant heat losses in the meantime.

The present invention aims to facilitate the movement of a hood among a set of juxtaposed covers, while maintaining good thermal insulation properties and fluidic sealing of the electrolysis cell. For this purpose, the present invention proposes a sealing device for an electrolysis cell cover intended for the production of aluminum, the sealing device comprising a fixing portion intended to be fixed on a lateral portion of a first bonnet and a sealing portion for overflowing laterally of the first cover and cover a junction zone between the first cover and a second cover juxtaposed to the first cover, characterized in that notches extend in the sealing portion. Said cuts increase the flexibility of the sealing portion and allow dissociation of the different sections separated by the notches which can deform independently and possibly differently.

In this configuration, for example when the sealing portion partly covers the outer face of the second cover, when the second cover is raised for an operation on the tank, the notches of the sealing portion of the sealing device fixed on the first cap allow significant deformation of the sealing portion located between the notches. Also, the covers are generally lifted by pivoting around their lower part (or base) so that the splitting of the sealing portion into a plurality of sections by means of the notches allows the sealing portion to deform progressively with the movement imposed on the second hood. In other words, when the operator grasps the second cover and begins to rotate it around its lower part, the spacing between the first and second covers is greater at the upper part of the covers than the part bottom of the covers so that the sections arranged in the upper part of the sealing portion are rapidly greatly deformed while the sections arranged in the lower part of the sealing portion are not yet or slightly deformed. The stresses exerted by the sections arranged in the upper part are released when these sections are no longer in contact with the second cover and the deformation of the sections moves. gradually from top to bottom. Thus, the stress exerted on the first hood is limited. The latter is not or little stressed remains substantially in place so that the diffusion of gas and thermal losses are limited. Furthermore, it is not necessary for the operator to reposition the first cover once the manipulation is completed. The movement of the second hood generated by the operator is also facilitated because the opposing resistance is lower than in the absence of nicks.

The notches are more particularly simple cuts of linear type made in the material of the sealing portion. The cuts do not remove material to the material of the sealing portion and the edges on either side of the cut remain contiguous. These notches thus do not induce significant seal discontinuity in the sealing portion due in particular to the thickness of the sealing portion of the material and the fineness of the cut line forming the notch.

Preferably, the sealing portion comprises a first edge secured to the attachment portion and a second edge opposite the first edge, the notches extending from the second edge. This configuration makes it possible to optimize the flexibility of the sealing portion.

Advantageously, the extension axis of the notches extends at an angle between 45 ° and 135 ° relative to the axis defined by the second edge. Preferably, the axis of extension of the notches extends transversely to the axis defined by the second edge. The extension axis of the notches may, however, extend obliquely with respect to the axis defined by the second edge, for example to accompany and facilitate the movement of the cover according to the movement applied to it. For example, when the hood is designed to be moved in a downward movement, the oblique cuts may be advantageously provided at an inclination from the bottom upwards from the second side edge of the sealing portion.

According to a particular embodiment of the invention, the notches are regularly spaced.

According to a variant of the invention, the distance between two adjacent cuts decreases in a predetermined direction. It is advantageous to provide a small distance between two notches in the upper part of the second edge of the sealing portion and a greater distance in its lower part when the displacement of the covers is exerted in a pivoting movement around its lower part. . The constraint exerted on the sealing device by this displacement is indeed the most important at the initiation of the movement, the sections located between the notches lifting and disengaging progressively from top to bottom. It is therefore advantageous to confer greater flexibility at the upper part of the sealing portion by a smaller distance between two notches than in the lower part.

Preferably, the distance between two adjacent cuts is between 10 and 300 millimeters, preferably between 30 and 200 mm, and more preferably between 50 and 150 mm. This dimension makes it possible to confer the desired flexibility on the sealing portion while limiting the risk of gaseous diffusion and thermal losses. The optimum distance can be determined simply, empirically, according to the stiffness, the thickness, the nature of the material, the length of the sealing portion and / or the configuration of the junction area (distance between two adjacent covers and possible deformations of the edges of these covers).

According to another particular provision of the present invention, the notches extend to the first edge of the sealing portion. This arrangement makes it possible to improve the flexibility of the sealing portion.

Preferably, the sealing portion comprises a silicone-coated fiberglass material. This material intrinsically has good flexibility, is resistant to high temperatures and has thermal insulation properties.

According to a particular arrangement of the present invention, the fixing portion comprises means for fixing the fixing portion on the lateral portion of the first cover. More particularly, these means for fixing comprises perforations for the passage of fastening means, the latter may for example be rivets or bolts.

According to a second aspect, the invention also relates to a covering device for an electrolysis cell intended for the production of aluminum, comprising at least one sealing device as previously described and a cover on a lateral portion of which is attached to said less a sealing device.

The covering device comprises in particular fastening means for fixing the sealing device to the cover, via the fixing portion.

Advantageously, the sealing device is fixed on an outer face of the cover. The sealing device and the fastening means of the sealing device are then less exposed to the high temperatures and the gases present inside the cell. The fastening means may in particular be rivets or bolts. The fixing portion of the sealing device may in particular comprise perforations for the passage of these fastening means. According to one possibility, two sealing devices are fixed on two opposite lateral portions of a cover. This gives a better seal.

According to a third aspect, the invention also relates to an electrolysis cell for the production of aluminum comprising at least one covering device as previously described and at least one second cover juxtaposed to the cover of the covering device, in which the portion sealing means covers a junction zone between the cover of the covering device and the second cover.

Advantageously, the sealing portion (8) covers at least partially the second cover (2).

It is understood in this document that when the electrolysis cell comprises several cover devices, each cover is juxtaposed with the neighboring cover so that each sealing portion covers the junction area between two adjacent covers. The sealing portions advantageously advantageously cover at least part of the adjacent cap.

Preferably, the notches extend along the axis of longitudinal extension of the electrolysis cell. This configuration makes it possible to obtain a better flexibility of the sealing device.

By outer face of the covers (respectively inner) is meant the face of the covers which is turned towards the outside (respectively the interior) of the electrolysis cell. Other aspects, objects and advantages of the present invention will appear better on reading the following description of several embodiments thereof, given by way of non-limiting examples and with reference to the appended drawings. The figures do not necessarily respect the scale of all the elements represented so as to improve their readability. In the remainder of the description, for the sake of simplification, identical, similar or equivalent elements of the various embodiments bear the same numerical references.

Figure 1 illustrates a sectional view of an electrolysis cell according to one embodiment of the invention.

Figure 2 illustrates a sectional top view of the junction area between two cover devices according to one embodiment of the invention.

Figure 3 illustrates a sectional top view of the junction area between two cover devices according to one embodiment of the invention.

FIG. 4 illustrates a schematic view of a sealing device according to a first embodiment of the invention. FIG. 5 illustrates a schematic view of a sealing device according to a second embodiment of the invention.

Figure 6 illustrates a schematic view of a sealing device according to a third embodiment of the invention.

Figure 7 illustrates a sectional top view of a covering device according to a second embodiment of the invention.

FIG. 8 illustrates a top view in section of a covering device according to a third embodiment of the invention.

Figure 9 illustrates a sectional top view of two cover devices according to a third embodiment of the invention.

As illustrated in FIG. 1, an electrolysis cell 100 intended for the production of aluminum comprises several hoods 1, 2 juxtaposed with respect to each other, along a caisson 3 (along the axis of longitudinal extension). L of the electrolysis cell 100), so as to form a closed chamber. As can be seen in FIG. 2, a sealing device 4 (visible in FIGS. 2 to 9) is fixed on a cover 1 and covers the junction zone 10 between the covers, 2 juxtaposed, so as to limit the diffusion of gas from electrolysis and heat losses. Advantageously, a sealing device 4 is fixed on each of the covers 1, 2 of the electrolysis cell. This sealing device 4 illustrated in FIGS. 2 and 3 comprises in particular a fastening portion 5 fastened to a lateral portion 6 of a first cover 1 (forming a covering device 15), and a sealing portion 8 which protrudes laterally from the first cover 1 so as to cover the junction zone 10 formed with a second cover 2 adjacent to the first cover 1. As illustrated in FIGS. 2 and 3, the sealing portion 8 also partially covers the second cover 2 of to optimize the confinement of the cell 100.

In Figure 2, the sealing device 4 covers the junction area 10 extending on similar faces of the hoods 1, 2 juxtaposed. Preferably, the sealing device 4 is fixed on the outside face of the cover 1 so as to limit the degradation of the sealing device and the fixing means by exposure to the temperature and the gases confined in the electrolysis cell. For the same reason, the sealing device 4 preferably covers partially the second cover on its outer face. Such a configuration also has the advantage of improving the seal because the cell is slightly depressed due to the suction of the gases, so that the sealing device tends to be pressed against the outer face of the second hood . Alternatively, as can be seen in FIG. 3, the sealing device 4 covers the junction zone 10 by crossing this junction zone 10, that is to say by extending from opposite sides of the juxtaposed caps 1, 2 .

As illustrated in Figure 4, the sealing portion 8 comprises a first edge 9 secured to the fixing portion 5 of the sealing device 4 and a second edge 1 1 opposite. Notches 12 formed in the sealing portion 8 extend with regular spacing from the second edge 11 to the first edge. These cuts 12 divide the sealing portion 8 into a plurality of sections of small sizes and provide a great flexibility of the sealing portion 8, which limits the shift of the first cover 1 to which it is connected when moving the second cover 2 adjacent.

According to a variant illustrated in FIG. 5, the distance between the cuts 12 varies along the second edges 11. In the upper part 14 of the sealing portion 8, the distance is indeed lower than in the lower part 13. This arrangement is particularly effective when the second cover 2 is designed to be moved in a pivoting movement around the lower part of the cover. The strongest stress is indeed exerted at the beginning of the movement and is compensated by a greater flexibility of the upper part 14 of the sealing portion 8.

As illustrated in Figure 6, the extension axis of the notches 12 may extend at an angle relative to the axis defined by the second edge. This angle is preferably between 45 ° and 135 °. The notches 12 are oriented towards the upper part 14 of the sealing portion 8, starting from the second edge 11, so as to promote the movement of the second cap 2 in a direction from bottom to top (from the proximal portion to the portion distal hood relative to the box 3 and the edge of the tank on which it rests).

As can be seen in FIGS. 4 to 6, the fixing portion 5 of the sealing device 4 can comprise perforations 20 for the passage of fixing means on the cover, for example rivets or bolts.

FIG. 7 illustrates an alternative embodiment of the covering device 15 in which a sealing device 4 is fixed on each of the two opposite lateral portions 6 of a first cover 1. Thus, each of the sealing portions 4 is adapted to partially cover two covers 2 adjacent the first cover 1 in opposite manner.

FIG. 8 illustrates another alternative embodiment of the covering device 15 in which a sealing device 4 is fixed on each of the two opposite lateral portions 6 of a first cover 1, on opposite faces of the covers. A sealing device 4 is fixed on the outer face of the cover, while the other sealing device 4 is fixed on the inside facade of the cover. Figure 9 illustrates two covers 1.2 14 002138

8

adjacent flats of the type shown in FIG. 8. Such a configuration further improves fluidic sealing in the junction zone 10 between two covers 1, 2.

The sealing devices advantageously extend over the entire length of the lateral portion of the covers, ie typically over a length of between 1 and 2 meters. The width of the sealing devices is typically between 3 and 20 cm, and preferably between 5 and 10 cm, with a sealing portion extending over more than 20%, preferably more than 40% of the width of the sealing devices, and the notches extending over more than 30%, preferably more than 50% of the sealing portion. The distance between two adjacent notches is advantageously between 10 and 300 millimeters, preferably between 30 and 200 mm, and more preferably between 50 and 150 mm.

Thus, the present invention proposes a sealing device 4 for effectively reducing the heat loss and the diffusion of gas between two adjacent covers 1, 2 for an electrolysis cell 100, while promoting the displacement of the second cover 2 without shifting the first cover 1. The juxtaposition of covering devices 15 comprising a sealing device 4 fixed on a cover 1 resting on the edges of the tank ensures the production of an electrolysis cell 100 minimizing handling and having diffusion reduced gas and thermal losses. It goes without saying that the invention is not limited to the embodiments described above as examples but that it includes all the technical equivalents and variants of the means described as well as their combinations. In particular, the rectilinear shape of the notches shown in the figures is not limiting, these notches may for example have other shapes zig-zag or rounded.

Claims

1. Sealing device (4) for an electrolysis cell cover (1, 2) for the production of aluminum, the sealing device (4) comprising a fixing portion (5) for to be fixed on a lateral portion (6) of a first cover (1) and a sealing portion (8) intended to protrude laterally from the first cover (1) and cover a junction area (10) between the first cover ( 1) and a second cover (2) juxtaposed to the first cover (1), characterized in that notches (12) extend in the sealing portion (8).

2. Sealing device (4) according to claim 1 wherein the sealing portion (8) comprises a first edge (9) integral with the fixing portion (5) and a second edge (1 1) opposite the first edge (9), the notches (12) extending from the second edge (1 1).

3. Sealing device (4) according to claim 2, wherein the axis of extension of the notches (12) extends at an angle between 45 ° and 135 ° relative to the axis defined by the second edge (1 1).

4. Sealing device (4) according to one of claims 2 and 3, wherein the axis of extension of the notches (12) extends transversely to the axis defined by the second edge (1 1).

5. Sealing device (4) according to one of claims 1 to 4, wherein the notches (12) are regularly spaced.

6. Sealing device (4) according to one of claims 1 to 4, wherein the distance between two adjacent notches (12) decreases in a predetermined direction.

7. Sealing device (4) according to one of claims 1 to 6, wherein the distance between two adjacent cuts (12) is between 10 and 300 millimeters, preferably between 30 and 200 mm, and more preferably between 50 and 150 mm.

8. Sealing device (4) according to one of claims 1 to 7, wherein the notches (12) extend to the first edge (9) of the sealing portion (8).

9. Sealing device (4) according to one of claims 1 to 7, wherein the sealing portion (8) comprises a silicone-coated fiberglass material.

10. Sealing device (4) according to one of claims 1 to 9, wherein the fixing portion (5) comprises means for fixing the fastening portion (5) on the lateral portion (6) of the first hood.

11. Sealing device (4) according to claim 10, wherein said means for fixing comprises perforations (20) for the passage of fixing means.

12. Covering device (15) for an electrolysis cell (100) intended for the production of aluminum, comprising at least one sealing device (4) according to one of claims 1 to 1 1 and a cover (1, 2) on a lateral portion (6) of which is fixed said at least one sealing device (4).

13. Covering device (15) according to claim 12, wherein the sealing device is fixed on an outer face of the cover (1, 2).

14. Covering device (15) according to claim 12, wherein two sealing devices (4) are attached to two opposite side portions (6) of a cover (1).

15. The covering device (15) according to claim 13, wherein a first sealing device (4) is fixed on an outer face of the cover (1, 2) and a second sealing device (4) is fixed on an inner face of the cover (1, 2).

16. Covering device (15) according to one of claims 12 to 15, comprising fastening means for fixing the sealing device to the cover (1, 2).

17. Electrolysis cell (100) for the production of aluminum comprising at least one covering device (15) according to one of claims 10 to 14 and at least one second cover (2) juxtaposed to the cover (1) of the covering device (15), in which the sealing portion (8) of the sealing device (4) covers a junction zone (10) between the cover (1) of the covering device (15) and the second cover (2).

18. Electrolysis cell according to claim 17, wherein the sealing portion (8) covers at least partly the second cover (2).