Electrolysis cell and method of operating an electrolysis cell

Abstract

The invention relates to an electrolysis cell comprising: - a pusher (40) pushing a first refractory block against a second refractory block; and / or - a blower (60) arranged to blow a jet of gas into a joint extending between said first and second blocks. Abbreviated figure: Figure 5

Description

Title of the invention: Electrolysis cell and method for operating an electrolysis cell technical field

[0001] The invention relates to an electrolysis cell and a method of operating such an electrolysis cell. State of the art

[0002] The production of metals by electrolysis, in particular aluminum, has been known since the beginning of the 20th century. Production processes and tools have notably been described in WO0065130A, WO2009082642, WO2017165838A1 or EP3875635A1, WO2018009862A1, US8764962B2, WO2019 / 027978Al or US20200263313A1.

[0003] Figure 1 illustrates, for example, an industrial aluminum metal production cell 8 by electrolysis of alumina in solution in a bath 10 based on molten cryolite. The electrolyte bath 10 is conventionally contained in an electrolysis cell 12. The cell 12 has a side wall 14 and a bottom 16. The bottom 16 is composed of an assembly of refractory bottom blocks 17, or "bottom lining," and cathode blocks 24 and, in its lower part, insulating blocks. The side wall 14 is formed of an assembly of refractory side blocks 18, or "side lining" 19.

[0004] The “tank lining” consists of the side lining and the bottom lining.

[0005] The tank 12 also includes a metallic casing 20, or "casing", enveloping, at least partially, the tank lining.

[0006] The dimensions of a lateral refractory block 18 are variable. They are classically greater than 75 x 300 x 300 mm3 and can reach 120 x 600 x 1500 mm3.

[0007] The space between the first and second adjacent refractory blocks is called a "joint." Joints can be filled with refractory cement 21. Alternatively, the blocks can be dry-mounted, that is, without the interposition of refractory cement. The adjacent blocks are then preferably in contact, although a free space may still exist between the blocks, depending on the dimensional accuracy of said blocks and the quality of the assembly.

[0008] A distinction is made between a "lateral joint" and a "bottom joint" depending on whether the first and second refractory blocks are lateral blocks or bottom blocks, respectively.

[0009] The cell 8 comprises, in addition to the tank 12, at least one anode 22 and at least one cathode 24. The anodes 22 and cathodes 24 are arranged so as to be in contact with the molten metal bath, the cathode 24 being conventionally arranged near the bottom 16.

[0010] Fig. 2 illustrates other examples of more recent generation electrolysis cells.

[0011] Under the effect of the electrical energizing of electrodes 22 and 24, an electrolysis reaction occurs in the bath 10. This results in the formation of an aluminum bath in the tank which is deposited on the cathode.

[0012] The passage of a high-intensity electric current through the bath 10 also produces heat through the Joule effect. The dissipation of this heat through the wall 14 of the tank 12 results in the deposition of a layer 26 of solidified cryolite on the inner surface 27 of the lateral blocks 18. This layer is called "self-bonding".

[0013] The side blocks 18 must provide protection for the metal casing 20. They are often exposed to corrosive environments (high-temperature liquid metal, molten cryolite in the lower part, corrosive gases in the upper part) and subjected to high temperatures and significant thermal and mechanical stresses.

[0014] Furthermore, the side blocks 18 are conventionally designed to allow sufficient heat dissipation to ensure temperature stabilization of the molten bath 10. In particular, it is necessary to avoid reaching temperatures beyond which the self-sealing layer 26 of solidified cryolite would become liquid again and contribute to very rapid corrosion of the tank sides.

[0015] The tank, and in particular the side wall 14, must be sealed to prevent leaks of molten metal or electrolyte bath, especially when there is no self-sealing layer at the base of the side wall and / or when the side blocks are dry-mounted. This sealing is more difficult to achieve when: - the thickness of the side wall is small, - the viscosity of the molten metal is low, and - the temperature of the electrolyte bath is high.

[0016] In particular, deformation of the tank in service increases the risk of leakage by widening of the seals.

[0017] Deformation can, in particular, result from the expansion or contraction of the side blocks due to Joule heating, especially after assembly of the tank lining and temperature increase, or from metal oxide loading operations (due to a temperature of this oxide being lower than that of the cell itself or due to an increase in the electrical resistivity of the added charge). A variation Temperature fluctuations can also occur during the removal of molten metal from the cell. A change in the anode or cathode can also lead to a substantial temperature variation.

[0018] Any modification of the thermal equilibrium of the cell can induce a dimensional variation of the blocks and / or a relative movement of the blocks, and therefore an at least partial opening of the joints between said blocks.

[0019] Deformation of the cell can also result from corrosion and infiltration of the tank contents into the tank lining.

[0020] To make the bottom of the tank watertight, it is known to place an unshaped refractory product under the bottom blocks. However, this solution is not practical for making the side lining watertight. It would prevent any access to the inside of the tank through the side wall without a cumbersome dismantling process. Furthermore, the mechanical strength of the resulting monolithic product is lower than that of an assembly of bottom blocks.

[0021] In traditional electrolysis cells, the seal is also reinforced by the application of a carbon-based 25% solder paste, or "soldering paste," to the base of the side panel. However, the seal can degrade as the electrolysis cell ages.

[0022] There is therefore a permanent need for an electrolysis cell: - allowing to reduce the risk of leakage of molten metal and / or electrolyte; - simple and quick to implement; - resistant to oxidation and corrosion by the electrolyte bath and possibly its vapors; - substantially no impact on the thermal stability of the tank, or even having a positive impact on thermal stability; - limiting the risk of contamination of the metal bath; - allowing easy access to the inside of the tank through the side wall, particularly for repairs and / or to replace all or part of the tank lining.

[0023] One object of the invention is to satisfy, at least partially, this need. Summary of the invention

[0024] According to the invention, this goal is achieved by means of an electrolysis cell intended for the synthesis of a metal by reduction of an oxide of said molten metal, said electrolysis cell comprising - an assembly of refractory blocks, or "tank lining", defining a side wall and a bottom, and - an external metallic casing at least partially enclosing said tank lining, said tank lining comprising a first refractory block and a second refractory block adjacent to the first block, the space between the first and second blocks being called the "joint".

[0025] According to the invention, the electrolysis cell is remarkable in that it further comprises: - a pusher exerting a force from the first block against the second block; and / or - a blower positioned to blow a jet of gas onto the joint.

[0026] As will be seen in more detail later in the description, these simple-to-implement means make it possible to meet the need effectively and at a reduced cost: the pusher prevents any widening of the joint between the first and second blocks; the blower maintains a surface temperature on this joint, particularly on the cold side of the lining, lower than the temperature of the molten material contained in the tank and in contact with said joint. Depending on the location of the joint, the molten material may be, in particular, molten metal or the electrolyte bath.

[0027] In one embodiment, the first and second blocks are background blocks.

[0028] In a preferred embodiment, the first and second blocks are side blocks.

[0029] Preferably, an electrolysis cell according to the invention further comprises one and preferably several of the following optional features: - the electrolysis cell comprises an adjustment mechanism: - the intensity of said thrust; and / or - the flow rate and / or temperature of the gas jet; - the pusher is interposed between an anchor and the first block and has a usable length, measured between the anchor and the first block, - adjustable so as to be fixed at a setpoint value, or - variably elastically; - the pusher includes an elastic element allowing a reversible variation, preferably elastically, of said useful length, the stiffness of the elastic element being preferably adjustable; - hot faces of the first and second blocks extend in a common plane, at least locally around the joint, at least a part of the joint not extending perpendicularly to said plane, and being preferably inclined at an angle between 100° and 170° with respect to said plane, said angle being preferably between 120° and 150°; - the joint has a variation in slope, i.e. is not flat, and preferably has at least one break in slope, preferably extends along a plurality of flat sides; - the joint shows a variation in slope when following the direction of the thickness of the first and second blocks; - the anchoring extends between the metal casing and the tank lining; - the direction of the thrust is horizontal; - the direction of the thrust is inclined with respect to a plane in which at least part of the joint between the first and second blocks extends, that is to say, it is not perpendicular to this plane; - at least one of the first and second blocks has, in a cross-section, preferably in any cross-section, a trapezoidal contour or one with a step, the contour preferably being the same regardless of the cross-section considered; -the break produces a slope break of more than 60°; - the tank lining consists of first and second layers; - the joint extends between the said first and second layers; - the first and second layers extend vertically, and therefore belong to the lateral coating; - the blocks of the first and second layers are arranged in a staggered pattern, and preferably extend horizontally, thus belonging to the base coating; - one or more, preferably all the joints of the layer which extends on the inside side of the tank, i.e. of the "hot" layer, is / are, on the cold side, covered(s) by a porous material or uncovered in order to facilitate the blowing of said gas; - the open porosity of said porous material is preferably greater than 60%, more preferably greater than 70%, or even greater than 80%; - preferably, the porous material is a foam, preferably a ceramic foam; - the pressure resulting from the thrust is preferably between 0.5 and 20 MPa, preferably at ambient temperature; - the electrolysis cell contains an aluminium oxide or an iron oxide; - the electrolysis cell includes at least one inert anode and / or at least one aluminum wettable cathode.

[0030] The invention also relates to a method of operating an electrolysis cell according to the invention, in which: A setpoint value is determined based on the operating conditions of the electrolysis cell, preferably based on temperature and / or deformation of the electrolysis cell, then We adjust, according to the setpoint value, - the intensity of said thrust and / or - the flow rate and / or temperature of the gas jet.

[0031] It is thus advantageously possible to adapt said thrust and / or said gas jet to said operating conditions in order to limit the width of the seal and / or to solidify a liquid infiltrated into the seal, respectively.

[0032] In particular, if a seal is infiltrated by the electrolyte bath and / or molten metal, the infiltrated material solidifies within the seal, which can lead to shrinkage or swelling during solidification. The tightening torque can be adjusted accordingly. Brief description of the figures

[0033] Other features and advantages of the invention will become apparent upon examination of the following description and with regard to the accompanying drawing in which: - Fig. 1 [Fig. 1] schematically represents a cross-section, in a vertical transverse plane, of an electrolysis cell with carbon anode and cathode, typically for the production of aluminium; - Fig. 2 schematically represents a partial cross-section, in a vertical longitudinal plane, of examples (A) and (B) of an electrolysis cell with inert or "non-consumable" anodes and aluminum-wettable cathodes, differing in the design of the tank lining; - Fig. 3 represents, seen from above and partially, different side coverings; - Fig. 4 schematically illustrates the implementation of a push button, with the side panel being viewed from the side; - [Fig.5] [Fig.5] schematically illustrates the implementation of another push button, with the side covering being observed from the side; - Fig. 6 schematically represents a partial longitudinal section of examples (A) and (B) of electrolysis cell according to the invention; - Fig. 7 [Fig. 7] schematically illustrates, seen from above and partially, examples (A) and (B) of electrolysis cell according to the invention; - Fig. 8 schematically illustrates, viewed from above and partially, a side panel of an electrolysis cell according to the invention equipped with a blower; - Fig. 9 schematically illustrates, viewed from above and partially, a side panel of an electrolysis cell according to the invention equipped with a blower intended to ventilate the joints of this side panel. In the different figures, identical references are used to designate identical or similar organs. Definitions

[0034] A refractory material is a material having a melting point above 1500°C. This definition is commonly used by those skilled in the art and cited in "Refractory Materials and Technical Ceramics (Elements of Ceramics and Technology)", G. Aliprandi, Septima Paris, 1979. This work also gives, on pages 297 to 301, examples of refractory materials, including oxides, carbides and nitrides.

[0035] The total porosity is conventionally equal to 100 x (absolute density - apparent density) / absolute density. Apparent density measurements are carried out according to ISO 5017 on a bar of material taken from the core of the part. Absolute density is conventionally measured on ground powder using a helium pycnometer.

[0036] Open porosity is measured according to ISO5017.

[0037] The term "Ceramic Matrix Composite," or "CMC," classically refers to a product composed of fibers bonded together by a ceramic matrix. The fibers will be chosen according to the environment in which the ceramic matrix composite is to be placed, particularly with regard to temperature, corrosion, thermal cycling, expansion, and the nature of the refractory material to be lined.

[0038] For the sake of clarity, chemical formulas, for example, of oxides, are used to designate the contents of these oxides in a composition. For example, "ZrO2", "SiO2", or "Al2O3" designate the contents of these oxides, and "zirconia", "silica", and "alumina" are used to designate phases of these oxides composed of ZrO2, SiO2, and Al2O3, respectively. The same applies to non-oxides such as "SiC", for example.

[0039] The adjectives "superior", "inferior", "horizontal" and "vertical" and the adverbs "above" and "below" refer to a service position in which the electrolysis cell rests on a horizontal floor.

[0040] “Contain” or “include” or “present” must be interpreted as in a non-exhaustive manner. Detailed description

[0041] As described in the preamble, an electrolysis cell according to the invention comprises a base 16 and a side wall 14. Bottom

[0042] In one embodiment, the base comprises a monolithic product arranged in one or more layers. This improves watertightness. Preferably, the monolithic product is refractory concrete or rammed earth, preferably non-carbonated.

[0043] In one embodiment, the tank bottom comprises an assembly of refractory bottom blocks, or "bottom lining", in particular an assembly of slabs, preferably in a refractory material, preferably chosen from an electrofused material, a carbon material, a TiB2 material, a SiC material and / or Silicon nitride material.

[0044] The base blocks are adjacent to each other and separated by joints. The joints, called "base joints", between the refractory base blocks are filled or not with refractory cement. Side wall

[0045] The side wall comprises a side covering 19 and a metal casing 20, which encircles the side covering.

[0046] The metal casing can be any prior art metal casing.

[0047] The side cladding defines: - a "hot face" 19c which, in the operating position, is in contact with the environment inside the tank, - a "cold face" 19f, opposite the hot face, which, in the service position, is opposite the metal casing.

[0048] The thickness e^ of the side coating, measured between the hot face 19c and cold face 19f, is greater than 50 mm, preferably greater than 100 mm, preferably greater than 150 mm and / or is less than 400 mm, preferably less than 300 mm, preferably less than 200 mm.

[0049] The height of the side cladding, measured from the bottom to the free end of the side cladding, is preferably greater than 0.5 m, preferably greater than 1.0 m, and / or is less than 2.0 m.

[0050] The side lining 19 comprises an assembly of refractory side blocks 18, in the form of one or more layers (referenced Cl and C2 on [Fig.3](D)).

[0051] The joints, called "lateral joints", between the refractory lateral blocks are filled or not with refractory cement.

[0052] As illustrated in [Fig.4] for block 182, the surface of a lateral block 18 comprises: - the upper face 18s and lower face 18i, oriented towards the top and bottom of the tank, respectively, which extend substantially horizontally; and - a set of "lateral" faces, which connect the upper face 18s and lower face 18i and extend substantially vertically.

[0053] We distinguish between the lateral faces which delimit a joint, or "joint face" 18j, and the other lateral faces, called "exposed faces".

[0054] Depending on whether a side face is oriented towards the inside or outside of the tank, it can be described as a "hot face" or a "cold face", respectively.

[0055] In [Fig. 4], face 18c is a hot face of the side block 182. It is an exposed face. Face 18f is a cold face of the block 182. It is a joint face 18j.

[0056] A block may not have a hot face, such as block 182 in [Fig.7](A). This block 182 has two joint faces which respectively delimit the joints 30i2 and 3023, and two exposed faces, which are cold faces.

[0057] Block 182 of [Fig.7](B) has two joint faces which respectively delimit the joints 30i2 and 3023, and four exposed faces, three of the exposed faces being cold faces, one of the exposed faces being a hot face.

[0058] A hot face 18c may be in contact with the environment inside the tank, like the hot face of block 182 of [Fig.4] (it then partially defines the hot face 19c of the side cladding), or not, like the hot face of block 181 of [Fig.4], which is a sealing face.

[0059] A cold face can face the metal casing 20 (it is then an exposed face) or an adjacent block so as to delimit a joint (it is then a joint face).

[0060] The hot face and / or the cold face can be joint faces. For example, in [Fig.4], the cold face of block 182 is a joint face.

[0061] In one embodiment, the side cladding comprises an assembly of side blocks, in particular an assembly of slabs, preferably made of a refractory material, preferably selected from an electrofused material, a carbon material, a TiB2 material, a SiC material and / or Silicon nitride material.

[0062] Fig. 3 illustrates different assemblies of lateral blocks 18.

[0063] In embodiment (A), the side cladding comprises a single layer of side blocks. The side blocks 18 are profiled, meaning that the contour of their cross-section, i.e., in a horizontal plane, is the same regardless of the height at which the block is sectioned. The contour of the two blocks on the left of the figure is trapezoidal.

[0064] The joint faces of the lateral blocks 181 and 182 are shaped so that the joint 30 between these blocks is substantially flat and inclined at an angle α greater than 100°, preferably greater than 120°, preferably greater than 130°, with respect to the plane P along which the hot face of the blocks 181 and 182 extend. This inclination advantageously reduces the risk of infiltration and also improves the efficiency of the pusher.

[0065] In embodiment (B), the side cladding has joints 30, which, along the direction of the thickness of the side cladding, have a step 32. Preferably, a single joint may have a plurality of steps. The direction of the block thickness is considered to be that of the lateral facing. It is preferably between 5 and 300 mm.

[0066] Generally speaking, a joint that does not extend solely along the thickness of the lateral coating is more difficult for a liquid infiltrating the joint to traverse. Any variation in the slope of a joint thus limits the risk of leakage. Preferably, at least one joint, or even each joint, exhibits a variation in slope along the thickness of the lateral coating, i.e., is not planar, and preferably has at least one break in slope, i.e., an edge. It may, for example, extend along a plurality of planar surfaces.

[0067] In one embodiment, the adjacent blocks have joint faces in the form of a groove and a bead.

[0068] Block 18i has, on its left side, two adjacent blocks 182 and 183, and therefore two seals 3012 and 30b, which are successive. Block 182 allows, by the action of a push button, the access of the electrolyte bath or molten metal that would begin to seep into the seal 30n-

[0069] In embodiment (C), the side cladding has "bayonet" joints which have a step 32.

[0070] In general, a break in slope preferably leads to a break in slope of more than 45°, preferably more than 60°, preferably more than 80°, preferably approximately 90°.

[0071] In embodiment (D), the side lining comprises several layers, and in particular a "hot" layer C1, on the inside side of the tank, preferably in contact with the electrolyte bath and / or the molten metal, and a "cold" layer C2, preferably thermally insulating, covering at least partially the first layer. The blocks of the thermally insulating layer preferably have sufficient mechanical strength so as not to be crushed under the effect of a pusher.

[0072] In embodiment (E), at least some of the joints between the hot layer blocks open to the outside of the tank or to the metal casing; in particular, they do not open to the cold layer. In other words, all or part of the joints between said hot layer blocks are exposed on the cold side, that is, are visible from outside the tank or from the metal casing. Advantageously, this exposure of the hot layer joints facilitates cooling ventilation by means of the blower.

[0073] Preferably, the blocks of the first and second layers are arranged in a staggered pattern. Advantageously, no joint can thus cross the lateral cladding along its thickness in a straight line. Side block

[0074] Generally, a lateral block can have various shapes. It is preferably parallelepiped-shaped. It is preferably a profile, preferably a profile at least in the vertical direction.

[0075] In a horizontal cross-sectional plane, the contour of the lateral block may be trapezoidal. The lateral block may also have a joint face and / or a hot face and / or a cold face that is flat, concave or convex, in particular conical, cylindrical or angle-shaped.

[0076] According to one embodiment, the lateral block has a non-horizontal upper face and a slope to facilitate the progressive supply of metal oxide to the lateral part of the tank in order to locally saturate the electrolytic bath with metal oxide and reduce, where appropriate, the corrosive action of the electrolyte bath.

[0077] In one embodiment, the side block is a corner block. The side block may have a cold face and / or a hot face defining an edge with a wide chamfer, as illustrated in [Fig. 7](B). This configuration advantageously allows pressure to be applied to two differently oriented seals with a single pusher.

[0078] The cumulative surface area of ​​the cold face(s) and / or the hot face(s) is preferably between 500 and 20,000 cm2.

[0079] Preferably, a lateral block, preferably a block in contact with the interior of the tank, i.e., belonging to a hot layer, preferably each lateral block is made of a refractory material comprising, preferably, one or more oxides. The oxide(s) is / are preferably chosen from Al₂O₃, MgO, CaO, ZrO₂ and SiO₂.

[0080] A block of a cold layer may also comprise a thermally insulating material and / or a thermally conductive material. The conductive material is preferably selected from a carbide and / or a nitride and / or a boride, preferably from SiC, Si3N4, B4C, TiB2, ZrB2, and TiC. Preferably, the thermally insulating material is selected from porous alumina materials, preferably in the form of a foam whose open porosity allows the gas intended to cool the joint to circulate with reduced thermal shock to the blocks of the hot layer. According to another possible embodiment, the thermally insulating material is a ceramic matrix composite with an open porosity greater than 5% by volume, preferably a composite with mineral fibers.

[0081] The total porosity of a lateral block, in particular of a block of a hot layer, is preferably less than 40%, more preferably less than 20%, or even less than 10%, or even less than 5% and even less than 1%.

[0082] The total porosity of a side block of a cold layer is preferably greater than 60%, more preferably greater than 70%, or even greater than 80%. Preferably, the side block is made of a ceramic material, preferably a porous ceramic foam.

[0083] The total porosity of a lateral block of a hot layer is preferably less than 40%, more preferably less than 20%, or even less than 10%, or even less than 5% and even less than 1%.

[0084] The preceding description relates to a lateral block 18, but may relate to several lateral blocks, or even all the lateral blocks. Seal

[0085] A joint is the space between two blocks placed side by side, in such a way adjacent. It therefore extends between two joint faces of the two blocks. The two blocks may belong to the same layer or to two different layers.

[0086] The width of a joint, between these two joint faces, preferably of any joint, may be variable or constant. It is preferably substantially constant. The maximum width of a joint, preferably of any joint, is typically less than 5 mm, less than 3 mm, less than 1 mm, or less than 0.5 mm.

[0087] In one embodiment, a joint, preferably any joint, is filled with a refractory cement, preferably a cement that is not wettable by the molten metal and / or the electrolyte bath.

[0088] When not filled with cement, the smallest width of the joint may be zero, the blocks then being in contact, possibly leaving gaps, or non-zero.

[0089] In one embodiment, the side cladding comprises a first layer of refractory side blocks in contact with the electrolyte bath, and all or part of the joints between said blocks are covered, on the cold side of the side cladding, with a thermally conductive plate. In one embodiment, a blower 60 blows a jet of gas onto said plate. The plate is optionally fixed to the blocks of the first layer by means of a cement. The plate covering the joint is preferably made of a matrix composite material (MCM), for example, a composite comprising a conductive material is preferably selected from a carbide and / or a nitride and / or a boride, preferably from SiC, Si3N4, B4C, TiB2, ZrB2 and TiC. Push button

[0090] Pushers 40 can be implemented to limit the risk of leakage through the seals.

[0091] A pusher is a device arranged to push two blocks against each other. The two blocks may be in contact with each other and / or separated by a joint made of cement.

[0092] Preferably, the pusher bears against a cold face 18f of a refractory block and on an anchorage 42, for example on a pillar, as illustrated for example by figures 4 and 5. In the service position, it is compressed between the cold face 18f and the anchorage 42. The seal is thus closed under pressure.

[0093] The pressure resulting from the thrust, equal to the total force exerted by the pusher(s) on the cold face of the refractory block divided by the contact area of ​​the pusher with said cold face, is preferably between 0.5 and 20 MPa, preferably between 1 and 10 MPa, preferably measured at an ambient temperature of 20°C.

[0094] The contact surface by which a pusher bears on the cold face, optionally by means of a plate 47, is preferably between 25 and 2500 cm2 and / or preferably represents between 5 and 30% of the surface of said cold face of said block including said contact surface.

[0095] Preferably, the electrolysis cell includes a mechanism for adjusting the intensity of the thrust exerted by the pusher. Preferably, the intensity of the thrust is adjusted according to the temperature of the cell or certain known and predeterminable events, such as a change or anode effect, pumping of the molten metal, or evacuation of the metal from the cell by gravity.

[0096] In one embodiment, a sensor measures thermal variations, or an effect of these variations, for example the deformation of the metal casing 20 and / or the bottom of the tank, and the intensity of the thrust is adjusted according to said measurement, preferably so as to maintain a substantially constant thrust over time and / or so as to keep the seals closed.

[0097] The thrust can be exerted on the block in any direction. However, the direction of the thrust is preferably horizontal, i.e. parallel to the bottom of the electrolysis tank.

[0098] The direction of the thrust is preferably perpendicular to the cold face 18f of the block on which the pusher pushes.

[0099] In a preferred embodiment, the anchor forms a fixed support point relative to the structure or the ground S on which the cell rests. Preferably, the anchor is rigidly fixed to the ground S extending around the cell. Preferably, the anchor is made of concrete or a substantially rigid part of the cell, for example, the edge of a cathode.

[0100] In one embodiment, illustrated in [Fig. 6](A), the anchor 42 is disposed between said cold face 18f and the metal casing. Preferably, the metal casing includes a hatch 43 allowing access to the pusher.

[0101] In another embodiment, illustrated in [Fig.6](B), the anchorage 42 is located outside the metal casing 20, which is locally interrupted to allow passage of the pusher.

[0102] To exert the thrust, the pusher is configurable in short and long configurations in which a useful length L of the pusher is less than and greater than the distance between the cold face and the anchor, respectively. It can thus be interposed between the cold face and the anchor in the short configuration, and then extended towards the long configuration. It then comes to rest against both the cold face and the stationary anchor, and the continuation of the extension operation results in said thrust.

[0103] The length L is said to be "useful" because it is this length which will determine the intensity of the thrust, symbolized by the white arrow in the figures, in particular in figures 4 and 5.

[0104] Preferably, the pusher 40 comprises a rod 44 with axis X which extends between the cold face and the anchorage, preferably substantially perpendicular to the cold face, and whose position, along the axis X, is modifiable in order to exert said thrust and preferably to regulate its intensity.

[0105] The rod can be supported on the anchor or the plate by means of a pivot or a ball joint 46, which improves the support on the anchor or the cold face, respectively.

[0106] Preferably, the pusher includes a locking member 45 adapted to lock the rod 44 in position.

[0107] Preferably, the pusher 40 further comprises a plate 47 bearing against the cold face so as to distribute the thrust onto the cold face. The plate 47 may, for example, be in the shape of a plate or a disc.

[0108] In one embodiment, the pusher 40 maintains the usable length to which it has been set. The pusher then acts as a conventional strut. All mechanisms used for struts are conceivable.

[0109] In this embodiment, the pusher, referred to as "static," thus fixes the distance separating the anchor and the block on which it rests and, in particular, prevents the joint from widening. It is advantageously simple to implement.

[0110] Figure 4 illustrates an embodiment of a static pusher in which the pusher comprises a threaded rod 44 screwed onto a thread formed in the anchor 42 or in a nut of the anchor, the degree of tightening determining the effective length L of the pusher. The threaded rod and the thread together constitute a mechanism for adjusting the effective length of the pusher, and therefore the intensity of the thrust.

[0111] The pusher further includes a handle, preferably in the form of a handwheel 49, which an operator can turn to screw the threaded rod 44.

[0112] The locking member 45 may include a locking collar, or a lock nut, to lock the threaded rod 44 in order to prevent undesired unscrewing.

[0113] In an unillustrated variant, the pusher includes a cylinder, preferably pneumatic, pushing the rod 44 towards the cold face and a lock to immobilize the rod of the cylinder.

[0114] In one embodiment, the pusher includes an elastic element 48, for example a spring or a pneumatic or hydraulic cylinder, tending to increase the length of the pusher towards the long configuration. After interposition of the pusher between the cold face and the anchor, in the short configuration, the elastic element thus contributes to the abutment and then to the application of the thrust.

[0115] Preferably, the stiffness of the elastic element is adjustable. All known means of adjusting the stiffness are usable. In particular, it is common to modify the stiffness of a spring by changing its rest length. The thrust can thus be adjusted to adapt to the cell configuration.

[0116] In this embodiment, the pusher thus elastically resists any expansion of the seal. Furthermore, the elasticity allows the pusher to remain active if the seal contracts.

[0117] Such an "elastic" pusher therefore makes it possible in particular to accompany a dimensional variation of the lateral blocks and to avoid the opening as well as the closing of the joint between the blocks.

[0118] Fig. 5 illustrates an example of an elastic pusher.

[0119] In one embodiment, the elastic element is a Belleville washer on which a rod 44 bears. Preferably, the stiffness can be adjusted, for example by changing the effective length of the rod 44. The rod 44 can be, for example, a threaded rod, as described previously, the Belleville washer being interposed between the end of the rod and the cold face, for example in place of the plate 47 or between said end and the plate 47.

[0120] Preferably, the pusher also includes a first plate 47 bearing on the cold face and / or a second plate 47' bearing on the anchor.

[0121] Regardless of the embodiment, the pusher is made of a material resistant to the temperature of its operating environment, and in particular to the temperature of the cold face on which it rests. This temperature depends in particular on the refractory material of the block that defines the cold face and on the temperature of the cell.

[0122] More particularly, the material of a pusher, preferably of each pusher, is preferably chosen from metallic alloys.

[0123] A push button, preferably each push button, preferably comprises, at its end in contact with the cold face of the block, an interface material. Preferably, the interface material is thermally insulating, that is to say, having, at 600°C, a thermal conductivity of less than 5 W / mK

[0124] A pusher can bear against one or more blocks, for example by means of a cross member 50, as illustrated in [Fig.3](D).

[0125] Several pushers can bear on the same block. The directions of the pushes can be identical, as illustrated in [Fig.3] (C), or different, as illustrated in [Fig.7](A).

[0126] Preferably, the direction of the thrust is perpendicular to at least one joint 30, as in the embodiments of Figures 4, 5 and 7(A), or to at least a part of at least one joint, as in the embodiment of Figures 3(B) or 3(C).

[0127] The direction of the thrust can alternatively be oblique with respect to at least one joint 30 which the thrust tends to close, as in the embodiments of [Fig.7](B), in which the thrust compresses both the joint 30[2 and the joint 3023, or of [Fig.3](A).

[0128] In one embodiment, no joint is parallel to the direction of at least one thrust exerted by a pusher. In other words, all joints are subjected to the effect of at least one thrust.

[0129] An inclination of the joints, as illustrated for example in [Fig.3](A), is particularly advantageous for taking into account the space constraints for positioning the pushers. Blower

[0130] In one embodiment, illustrated in [Fig.8], the cell includes a blower 60 arranged to blow a jet of gas G towards a seal 30.

[0131] The gas is preferably air, preferably dry.

[0132] It is at a temperature lower than the solidification temperature of the metal and that of the electrolyte bath. The blowing thus makes it possible to cool and solidify any flow of liquid, in particular of molten metal or electrolyte, that has seeped between the refractory blocks.

[0133] Preferably, the temperature of the blown gas is at least 20%, and preferably at least 30%, higher than the temperature below which the refractory block material may exhibit thermal shock cracking. For this purpose, the gas can be heated, for example in a heat exchanger.

[0134] The electrolysis cell preferably includes a mechanism for adjusting the flow rate of the cooling gas and / or its temperature in order to adapt the gas jet to the desired cooling.

[0135] All known flow or temperature control mechanisms can be considered. The control mechanism may, for example, include a valve with an adjustable degree of opening and / or a heat exchanger.

[0136] The flow rate is further determined so as not to disturb the aspiration of gases emitted by the electrolysis bath (fluorinated gases in particular) or by the electrolysis process itself (release of oxidizing gas at the anode).

[0137] Preferably, the blower generates a gas flow specifically directed towards the joint 30. In other words, the blowing is not a blowing over the entire cold face 19f of the side cladding, but a blowing limited to one or more joints 30.

[0138] To improve efficiency, the blower can be equipped with a gas jet guide 62, for example in the form of a deflector or a bell. The guide preferably has a shape that allows it to follow one or more seals 30. For example, if the seals 30 extend over the cold face 19f of the side cladding as illustrated in [Fig. 9], the guide can have the shape of a gas distribution network, for example a network of channels or tubing or a perforated ramp, the network being adapted to distribute the air to the different seals, preferably according to the cooling requirements, as illustrated in [Fig. 9].

[0139] Blown gas leaks are thus limited and the local effect of blowing is optimized.

[0140] The blower is preferably integrated into the cell. In particular, the network of distribution is preferably rigidly fixed to other parts of the cell, for example to the tank casing 20.

[0141] In one embodiment, the blower is removable. It can thus be advantageously used for different electrolysis cells.

[0142] As is now clear, the invention makes it possible to improve the sealing of the tank, and in particular of the side wall, even when the viscosity of the liquid in contact with the seals is low and the temperature of the electrolyte bath is high and varies.

[0143] Of course, the present invention is not limited to the embodiments described, which are provided by way of illustrative and non-limiting examples.

[0144] In particular, unless there is a technical incompatibility, the detailed description of the invention, relating to first and second side blocks, is applicable to first and second bottom blocks. The two blocks can therefore be blocks belonging to the side cladding or the bottom cladding.

Claims

Demands

1. Electrolysis cell for the synthesis of a metal by reduction of an oxide of said molten metal, said cell comprising a tank (12) having - a tank lining defining a side wall (14) and a bottom (16), and - an external metal casing (20) at least partially enveloping said tank lining, said tank lining having a first refractory block (181) and a second refractory block (182) adjacent to the first block (181), the space between the first and second blocks being called a "seal" (30); the electrolysis cell being characterized in that it further comprises - a pusher (40) exerting a push of the first block against the second block; and / or - a blower (60) arranged to blow a jet of gas (G) onto the seal (30).

2. Electrolysis cell according to the preceding claim, wherein the first and second blocks are lateral blocks.

3. Electrolysis cell according to any one of the preceding claims, comprising an adjustment mechanism (44) - of the intensity of said thrust; and / or - of the flow rate and / or temperature of the gas jet.

4. Electrolysis cell according to any one of the preceding claims, wherein the pusher is interposed between an anchor (42) and the first block and has a useful length (L), measured between the anchor and the first block, - adjustable so as to be fixed at a setpoint value, or - elastically variable.

5. Electrolysis cell according to the immediately preceding claim, wherein the anchorage (42) extends between the metal casing (20) and the tank lining.

6. Electrolysis cell according to any one of the preceding claims, in which - hot faces (18c) of the first and second blocks extend in a common plane (P), at least locally around the joint (30), at least part of the joint being inclined at an angle between 100° and 170° with respect to said plane; and / or - the joint exhibits a variation in slope (32) when following the direction of the thickness of the first and second blocks.

7. Electrolysis cell according to any one of the preceding claims, wherein the thrust direction is horizontal.

8. Electrolysis cell according to any one of the preceding claims, wherein the thrust direction is inclined with respect to a plane in which extends at least a part of the joint (30) between the first and second blocks.

9. Electrolysis cell according to any one of the preceding claims, wherein at least one of the first and second blocks has, in a cross-section, a trapezoidal contour or a step (32), the break in slope resulting from the step being preferably more than 60°.

10. Electrolysis cell according to any one of the preceding claims, wherein the tank lining comprises first and second layers, - the joint being between said first and second layers; and / or - the first and second layers extending vertically; and / or - the blocks of the first and second layers being arranged in a staggered pattern; and / or - one or more, preferably all of the joints of the layer on the side of the inside of the tank is / are, on the cold side, covered(s) by a porous material or uncovered in order to facilitate the blowing of said gas.

11. Electrolysis cell according to any one of the preceding claims, wherein the thrust exerts a pressure between 0.5 and 20 MPa.

12. Electrolysis cell according to any one of the preceding claims, containing an aluminum oxide or an iron oxide.

13. Electrolysis cell according to the immediately preceding claim, comprising at least one inert anode and / or at least one aluminum wettable cathode.

14. A method for operating an electrolysis cell according to any one of the preceding claims, wherein: A setpoint value is determined based on the operating conditions of the electrolysis cell, then We adjust, according to the setpoint value, - the intensity of said thrust; and / or - the flow rate and / or temperature of said gas jet (G).

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