Cathode assembly for electrolytic cell

Abstract

The invention relates to a cathode assembly for an electrolytic cell comprising, firstly, a cathode block (10) having a second surface (11) and a first surface (12). The cathode block (10) also comprises at least one sealing groove (13) opening onto the first surface (12) thereof and a plurality of electric contact pins (50) mounted in electrical contact with the first surface (12) of the cathode block (10). The cathode assembly then comprises at least one first current-carrying plate (20) in electrical contact with at least one electric contact pin (50), and which is connected to at least one unit for connecting to a source of electric current. The cathode assembly finally comprises at least one current-carrying bar (30) having an expansion coefficient substantially identical to the expansion coefficient of the current-carrying plate (20), which is sealed in the at least one sealing groove (13) while being attached to at least one current-carrying plate (20). Figure

Description

[0001] Cathode assembly for electrolysis cell

[0002] Scope of the invention

[0003] The present invention relates to a cathode assembly for an electrolysis cell.

[0004] Prior art: As is known, US patent 6113756 describes an electrolytic reduction cell for the production of a metal, such as aluminum. US patent 6113756 relates specifically to a cathode construction used in such cells.

[0005] Said cathode comprises a carbon block, a plurality of electrical contact plugs mounted in electrical contact with a lower part of the cathode and at least one collector plate in electrical contact with the electrical contact plugs.

[0006] The plurality of electrical contact plugs is positioned or distributed on the lower surface of the cathode in such a way as to obtain an isopotential surface. In particular, the required number of electrical contact plugs can be positioned in space to reduce unwanted current flow and produce minimal electric field resistance between the plugs. With this approach, the overall resistance can be minimized and the current distribution within the assembly controlled.

[0007] However, these solutions do not provide complete satisfaction.

[0008] Indeed, the use of electrical contact plugs positioned or distributed on the lower surface of the cathode to obtain an isopotential surface has the effect of stiffening the cathode assembly including the cathode and the collector plate.

[0009] Since the collector plate has a coefficient of expansion greater than the coefficient of expansion of the cathode, once the cathode assembly reaches operating temperature, the collector plate may create cracks in the cathode.

[0010] A cracked cathode has a significantly shorter lifespan than an uncracked one. This lifespan can be reduced to just a few days in the case of large cracks. The present invention aims to overcome all or some of the aforementioned drawbacks.

[0011] Description of the invention

[0012] To this end, the present invention relates to a cathode assembly for an electrolysis cell comprising: a. a cathode block having a second surface and a first surface, at least one sealing groove opening onto the first surface, a plurality of electrical contact plugs being mounted in electrical contact with the first surface of the cathode block; and b. at least one current supply plate in electrical contact with at least one electrical contact plug, and which is intended to be connected to at least one connection unit to an electrical current source; c. at least one current supply bar having a coefficient of expansion substantially identical to the coefficient of expansion of the current supply plate is sealed in at least one sealing groove and fixed to at least one current supply plate.

[0013] For the purposes of the present invention, "a substantially identical coefficient of expansion" means "an identical coefficient of expansion" or "a coefficient of expansion that is identical to within 10%".

[0014] For the purposes of the present invention, "a substantially identical coefficient of expansion" means "an identical coefficient of expansion" or "an identical coefficient of expansion within 5%".

[0015] As an example, a measurement of the coefficient of expansion of a current supply bar is carried out by measuring the evolution of the size of said current supply bar as a function of temperature.

[0016] According to one advantage, a current supply bar fixed to a current supply plate and sealed to the cathode block reduces the electrical resistance of the cathode assembly and thus limits the number of electrical contact plugs because the mechanical hold between the current supply plate and the cathode block is ensured partially by the connection between the current supply bar, the current supply plate and the cathode block.

[0017] Sealing the current supply bar in the sealing groove allows one degree of freedom of the current supply bar relative to the cathode block.

[0018] Furthermore, limiting the number of contact points also allows for greater mechanical flexibility in the cathode assembly. Thus, the resulting cathode assembly presents a limited risk of cracking.

[0019] According to one embodiment, the current supply bar is fixed by welding to the current supply plate.

[0020] One advantage is that a current feed plate welded to a current feed bar having the same coefficient of expansion allows for a longer weld life.

[0021] According to one advantage, a current supply plate welded to a 30 supply bar having the same coefficient of expansion helps to limit the risk of cracking of the cathode block.

[0022] According to one embodiment, the electrical contact plugs are mounted in electrical contact with the first surface of the block by inserting said electrical contact plugs into different bores present on the first surface of said cathode block.

[0023] In one embodiment, the cooperation space between at least one current supply bar and the cathode ray tube defines a first zone. The cooperation space between the electrical contact pins and the cathode ray tube defines a second zone, which is excluded from the first zone.

[0024] According to one advantage, a plurality of electrical contact plugs mounted in electrical contact with the first surface of the cathode block improves the distribution of current lines in said cathode block.

[0025] According to one advantage, improving the distribution of current lines in said cathode block improves the performance of the cathode assembly for electrolysis cell.

[0026] According to one advantage, improving the distribution of current lines in said cathode block helps to limit wear of the cathode block and thus helps to extend the life of the cathode assembly for electrolysis cell.

[0027] One advantage is that using multiple current-carrying plates reduces the differential expansion between each current-carrying plate and the cathode ray tube. Reducing this differential expansion helps limit the risk of cathode ray tube cracking.

[0028] One advantage is that limiting the risk of cracking of the cathode block helps to extend the lifespan of the cathode assembly for electrolysis cells.

[0029] One advantage is that using multiple current supply bars makes handling the cathode assembly easier.

[0030] One advantage is that using multiple current supply bars helps limit the risk of cathode block cracking.

[0031] According to one embodiment, the sealing of the current supply bar in the sealing groove of the cathode block is a cast seal.

[0032] According to one embodiment, the cast iron sealing is carried out with white phosphorus cast iron.

[0033] According to one embodiment, the cast iron sealing is carried out with a grey phosphorus cast iron.

[0034] According to one advantage, a cast iron seal allows a degree of freedom of the current supply bar relative to the cathode block sufficient to limit the risks of cracking of said cathode block.

[0035] According to one embodiment, the sealing of the current supply bar in the sealing groove of the cathode block is a sealing with sealing paste.

[0036] According to one embodiment, sealing with sealing paste is carried out with a paste comprising carbon powder and a binder.

[0037] One advantage of the sealant 40 is that it shrinks as the electrolysis cell heats up. This shrinkage of the sealant during the heating of the electrolysis cell helps to limit the risk of cracking of the cathode block 10 caused by the expansion of the current supply bar 30.

[0038] According to one advantage, the 40 sealant paste is a paste free of tar and pitch as well as polycyclic aromatic hydrocarbons.

[0039] One advantage of sealant paste 40 is that it is a paste free of phenolic resin.

[0040] In one embodiment, the paste sealant is applied cold. One advantage of cold paste sealing is its cost-effectiveness.

[0041] In one embodiment, the electrical contact plugs are cylindrical in shape and include a deformation groove. According to one advantage, this deformation groove allows for local deformation of the electrical contact plug, resulting in low elastic resistance. Low elastic resistance in electrical contact plugs helps to limit the risk of cathode ray tube cracking.

[0042] According to one embodiment, the deformation groove extends over 5% to 50% of the length of an electrical contact plug.

[0043] According to one embodiment, the deformation groove preferentially extends over 15% to 35% of the length of the electrical contact plug.

[0044] For the purposes of the present invention, length is a dimension that is substantially longer than the other dimensions.

[0045] According to one advantage, a deformation groove 51 allows local deformation of an electrical contact plug 50 and enables said electrical contact plug 50 to undergo elastic and plastic deformation. An electrical contact plug 50 capable of undergoing elastic and plastic deformation helps to limit the risk of cracking of the cathode block 10.

[0046] According to one embodiment, the deformation throat has a circular cross-section.

[0047] In one embodiment, the deformation groove has a rectangular cross-section. A rectangular cross-section allows for guided deformation of the deformation groove.

[0048] According to one embodiment, the deformation groove is adapted to delimit at least partially a connecting head and a connecting member on either side of an electrical contact plug.

[0049] According to one advantage, the connecting element of an electrical contact plug is adapted to be linked to the cathode block while the connecting head of an electrical contact plug is adapted to be linked to a current supply plate.

[0050] According to one embodiment, the electrical contact plugs are electrical contact plugs with twisted wire bundles.

[0051] One advantage is that electrical contact plugs with twisted wire bundles allow for low elastic resistance and thus limit the risk of cracking of the cathode block.

[0052] Cathode assembly for an electrolysis cell according to any one of claims 1 to 4, wherein the electrical contact plugs are anisotropic. According to one advantage, anisotropic electrical contact plugs allow for lower elastic resistance of said electrical contact plug and thus limit the risk of cracking of the cathode block.

[0053] According to one embodiment, the electrical contact plugs have different elastic resistances compared to each other.

[0054] One advantage of electrical contact plugs having different elastic resistances from each other is to allow for a good fixing of at least one current supply plate to the cathode block while limiting the risks of cracking of said cathode block.

[0055] According to one embodiment, the cathode block consists of a mixture of anthracite and graphite.

[0056] According to one advantage, a cathode block made of a mixture of anthracite and graphite improves the distribution of current lines in said cathode block.

[0057] According to one advantage, a cathode block made of a mixture of anthracite and graphite improves current distribution and limits wear on said cathode block, thus extending the life of the cathode assembly for electrolysis cells.

[0058] According to one embodiment, the cathode block 10 is made of graphite.

[0059] One advantage is that a cathode block 10 made of graphite helps to limit energy consumption during the operation of the electrolysis cell.

[0060] According to one embodiment, the number of electrical contact plugs per square meter is between 10 and 80.

[0061] According to one embodiment, the number of electrical contact plugs per square meter is preferably between 20 and 65.

[0062] According to one embodiment, the number of electrical contact plugs per square meter is ideally between 30 and 50.

[0063] According to one advantage, a number of electrical contact plugs per square meter between 10 and 80 allows a good connection between at least one current supply plate and the cathode block.

[0064] Another advantage is that a number of electrical contact points per square meter between 10 and 80 helps limit the risk of cathode ray tube cracking. Furthermore, a number of electrical contact points per square meter between 10 and 80 improves the distribution of current lines within the cathode ray tube.

[0065] The invention also relates to an electrolysis cell for the production of a metal, comprising: d. an outer steel casing; e. a layer of insulating material adjacent to the outer steel casing; f. a carbon layer covering the insulating material and protecting the insulating material from an electrolytic bath intended to be contained in the cell; and g. a cathode assembly for an electrolysis cell according to any one of claims 1 to 9.

[0066] The various aspects defined above, which are not incompatible, can be combined.

[0067] Brief description of the figures

[0068] The invention will be even better understood with the aid of the detailed description set forth below, in conjunction with the accompanying drawings, in which:

[0069] • Figure 1 represents a cross-sectional view of a cathode ray assembly according to the present invention;

[0070] • Figure 2 represents a cross-sectional view of a cathode ray assembly according to the present invention;

[0071] • Figure 3 represents a cross-sectional view of a cathode ray assembly according to the present invention;

[0072] • Figure 4 represents a current supply plate according to the present invention;

[0073] • Figure 5 represents a current supply bar according to the present invention;

[0074] • Figure 6 represents an electrical contact plug according to the present invention; and • Figure 7 represents a cathode block according to the present invention.

[0075] Description with reference to the figures

[0076] Figures 1 to 3 represent a cathode assembly for an electrolysis cell comprising a cathode block 10, a current supply plate 20 and two current supply bars 30.

[0077] Figure 4 illustrates a current supply plate 20 comprising several insertion holes 21.

[0078] Figure 5 illustrates a current supply bar 30.

[0079] Figure 7 represents a cathode block 10 having a second surface 11 and a first surface 12, two sealing grooves 13 opening onto the first surface 12 and a plurality of electrical contact plugs 50.

[0080] According to one embodiment, the cathode block 10 is made of graphite.

[0081] One advantage is that a cathode block 10 made of graphite helps to limit energy consumption during the operation of the electrolysis cell.

[0082] According to one embodiment, the cathode block 10 is made up of a mixture of anthracite and graphite.

[0083] According to one advantage, a cathode block 10 made of a mixture of anthracite and graphite improves the distribution of current and makes it possible to limit the wear of said cathode block 10 and thus makes it possible to extend the life of the cathode assembly for electrolysis cell.

[0084] Figure 6 illustrates an electrical contact plug 50 in the shape of a cylinder comprising a deformation groove 51.

[0085] According to one advantage, a deformation groove 51 permits local deformation of an electrical contact plug 50 and allows said electrical contact plug 50 to have low elastic resistance.

[0086] According to one embodiment, the deformation groove 51 extends over 5% to 50% of the length of the electrical contact plug 50.

[0087] According to one embodiment, the deformation groove 51 extends preferentially over 15% to 35% of the length of the electrical contact plug 50.

[0088] For the purposes of the present invention, length is a dimension that is substantially longer than the other dimensions. According to one advantage, a deformation groove 51 extending over 5% to 50% of the length of an electrical contact plug 50 allows for elastic and plastic deformation of said electrical contact plug 50.

[0089] According to one embodiment, the deformation groove 51 has a circular section.

[0090] In one embodiment, the deformation groove 51 has a rectangular cross-section. A rectangular cross-section allows for guided deformation of the deformation groove 51.

[0091] According to one embodiment, the deformation groove 51 is adapted to delimit at least partially a connecting head 52 and a connecting member 53 on either side of the electrical contact plug 50.

[0092] As illustrated in Figure 1, the electrical contact plugs 50 are mounted in electrical contact with the first surface 12 of the cathode block 10.

[0093] According to one embodiment, the electrical contact plugs 50 are mounted in electrical contact with the first surface of the block by inserting said electrical contact plugs 50 into different bores present on the first surface of said cathode block 50.

[0094] According to one embodiment, the current supply bar 30 is sealed in at least one sealing groove 13.

[0095] The sealing of the current supply bar 30 in the sealing groove 13 allows one degree of freedom of the current supply bar 30 with respect to the cathode block 10.

[0096] According to one embodiment, the sealing of the current supply bar 30 in the sealing groove 13 of the cathode block 10 is a cast sealing.

[0097] According to one embodiment, the cast iron sealing is carried out with white phosphorus cast iron.

[0098] According to one embodiment, the cast iron sealing is carried out with a grey phosphorus cast iron.

[0099] According to one advantage, a cast iron seal allows a degree of freedom of the current supply bar 30 relative to the cathode block 10 sufficient to limit the risks of cracking of said cathode block 10.

[0100] According to one advantage, limiting the risk of cracking of the cathode block 10 extends the service life of the cathode assembly for the electrolysis cell. In one embodiment, the sealing of the current supply bar 30 in the sealing groove 13 of the cathode block 10 is achieved using a sealing paste 40.

[0101] According to one embodiment, sealing with sealing paste 40 is carried out with a paste comprising a carbon powder and a binder.

[0102] One advantage of the sealant 40 is that it shrinks as the electrolysis cell heats up. This shrinkage of the sealant during the heating of the electrolysis cell helps to limit the risk of cracking of the cathode block 10 caused by the expansion of the current supply bar 30.

[0103] As an example, a measurement of a coefficient of expansion of a current supply bar 30 is carried out by measuring the evolution of the size of said current supply bar 30 as a function of temperature.

[0104] According to one advantage, the 40 sealant paste is a paste free of tar and pitch as well as polycyclic aromatic hydrocarbons.

[0105] One advantage of sealant paste 40 is that it is a paste free of phenolic resin.

[0106] In one embodiment, the paste sealant is applied cold. One advantage of cold paste sealing is its cost-effectiveness.

[0107] According to one embodiment, the cooperation space between at least one current supply bar 30 and the cathode ray tube 10 defines a first zone. The cooperation space between the electrical contact pins 50 and the cathode ray tube 10 defines a second zone, which is excluded from the first zone.

[0108] According to one embodiment, the current supply bar 30 is fixed to at least one current supply plate 20.

[0109] According to one embodiment, the current supply bar 30 is fixed by welding to the current supply plate 20.

[0110] According to one embodiment, the current supply bar 30 has a coefficient of expansion substantially identical to the coefficient of expansion of the current supply plate 20.

[0111] For the purposes of the present invention, "a substantially identical coefficient of expansion" means "an identical coefficient of expansion" or "a coefficient of expansion that is identical to within 10%".

[0112] For the purposes of this invention, "a substantially identical coefficient of expansion" means "an identical coefficient of expansion" or "a coefficient of expansion that is identical within 5%". According to one advantage, a current-carrying plate 20 welded to a current-carrying bar 30 having the same coefficient of expansion allows for an extended weld life.

[0113] According to one advantage, a current supply plate 20 welded to a supply bar 30 having the same coefficient of expansion makes it possible to limit the risk of cracking of the cathode block 10. According to one embodiment, the current supply plate 20 is in electrical contact with at least one electrical contact plug 50, and includes at least one unit for connection to an electrical current source.

[0114] According to one embodiment, the electrical contact plugs 50 are inserted into insertion holes 21 of the current supply plate 20.

[0115] According to one advantage, a current supply bar 30 fixed to a current supply plate 20 and sealed to the cathode block 10 makes it possible to reduce the electrical resistance of the cathode assembly and thus to limit the number of electrical contact plugs 50 because the mechanical retention between the current supply plate 30 and the cathode block 20 is ensured partially by the connection between the current supply bar 30, the current supply plate 20 and the cathode block 10.

[0116] Furthermore, limiting the number of contact pins (50) also allows for greater mechanical flexibility in the cathode assembly. Thus, the resulting cathode assembly presents a limited risk of cracking in the cathode block.

[0117] According to one advantage, a plurality of electrical contact plugs 50 mounted in electrical contact with the first surface 12 of the cathode block 10 allows for a better distribution of current lines in the cathode block 10.

[0118] According to one advantage, a cathode block 10 made of a mixture of anthracite and graphite improves the distribution of current lines in said cathode block 10.

[0119] According to one advantage, a better distribution of current lines in the cathode block 10 improves the performance of the cathode assembly for electrolysis cell.

[0120] According to one advantage, improved current distribution in the cathode ray tube 10 reduces wear on the cathode ray tube 10 and thus extends the service life of the cathode assembly for the electrolysis cell. In one embodiment, the electrical contact pins 50 are cylindrical in shape and include a deformation groove 51.

[0121] According to one advantage, a deformation groove 51 allows local deformation of an electrical contact plug 50 and enables said electrical contact plug 50 to undergo elastic and plastic deformation. An electrical contact plug 50 capable of undergoing elastic and plastic deformation helps to limit the risk of cracking of the cathode block 10.

[0122] According to one advantage, the connecting member 53 of an electrical contact plug 50 is adapted to be connected to the cathode block 10 while the connecting head 52 of an electrical contact plug 50 is adapted to be connected to a current supply plate 20.

[0123] According to one embodiment, electrical contact plugs 50 are electrical contact plugs 50 with twisted wire bundles.

[0124] According to one advantage, electrical contact plugs 50 with twisted wire bundles allow low elastic resistance and thus limit the risks of cracking of the cathode block 10.

[0125] According to one embodiment, the electrical contact plugs 50 are anisotropic electrical contact plugs 50.

[0126] According to one advantage, an anisotropic electrical contact plug 50 allows a lower elastic resistance of said electrical contact plug 50 and thus limits the risks of cracking of the cathode block 10.

[0127] According to one embodiment, the electrical contact plugs 50 have different elastic resistances from each other.

[0128] According to one advantage, electrical contact plugs 50 having different elastic resistances from each other makes it possible to combine a good fixing of at least one current supply plate 20 to the cathode block 10 while limiting the risks of cracking of said cathode block 10.

[0129] According to one embodiment, the number of electrical contact plugs per square meter is between 10 and 80.

[0130] According to one embodiment, the number of electrical contact plugs per square meter is preferably between 20 and 65.

[0131] According to one embodiment, the number of electrical contact plugs per square meter is ideally between 30 and 50.

[0132] According to one advantage, a number of electrical contact points between 10 and 80 per square meter allows for a good connection between at least one current supply plate 20 and the cathode block 10. According to another advantage, a number of electrical contact points between 10 and 80 per square meter helps to limit the risk of cracking of the cathode block 10.

[0133] According to one advantage, a number of electrical contact plugs 50 per square meter between 10 and 80 improves the distribution of current lines in said cathode block 10.

[0134] According to one embodiment, the cathode assembly comprises two current supply bars 30 per sealing groove 13.

[0135] One advantage is that the use of two 30 current supply bars makes it easier to handle the cathode assembly.

[0136] According to one advantage, the use of two current supply bars 30 helps to limit the risk of cracking of the cathode block 10.

[0137] According to an embodiment not shown, several current supply plates 20 are fixed to the current supply bar 30.

[0138] According to one advantage, the use of several current supply plates 20 reduces the differential expansion between each current supply plate 20 and the cathode block 10. The reduction of the differential expansion between each current supply plate 20 and the cathode block 10 helps to limit the risks of cracking of said cathode block 10.

[0139] The invention also relates to an electrolysis cell for the production of a metal, comprising:

[0140] an outer steel casing;

[0141] a layer of insulating material adjacent to the outer steel shell; a carbon layer covering the insulating material and protecting the insulating material from an electrolytic bath intended to be contained within the cell; and a cathode assembly for the electrolysis cell.

[0142] Of course, the invention is not limited to the embodiments represented and described above, but on the contrary covers all variants thereof.

Claims

DEMANDS 1. Cathode assembly for electrolysis cell comprising: a. a cathode block (10) having a second surface (11) and a first surface (12), at least one sealing groove (13) opening onto the first surface (12), a plurality of electrical contact plugs (50) being mounted in electrical contact with the first surface (12) of the cathode block (10); and b. at least one current supply plate (20) in electrical contact with at least one electrical contact plug (50), and which is intended to be connected to at least one connection unit to an electrical current source; c. at least one current supply bar (30) having a coefficient of expansion substantially identical to the coefficient of expansion of the current supply plate (20) is sealed in at least one sealing groove (13) and fixed to at least one current supply plate (20).

2. Cathode assembly for electrolysis cell according to claim 1 in which the sealing of the current supply bar (30) in the sealing groove (13) of the cathode block (10) is a cast iron seal.

3. Cathode assembly for electrolysis cell according to claim 1 in which the sealing of the current supply bar (30) in the sealing groove (13) of the cathode block (10) is a sealing with the sealing paste (40).

4. Cathodic assembly for electrolysis cell according to any one of claims 1 to 3 wherein the electrical contact plugs (50) are in the form of a cylinder comprising a deformation groove (51).

5. Cathode assembly for electrolysis cell according to any one of claims 1 to 4 wherein the electrical contact plugs (50) are electrical contact plugs (50) with twisted wire bundles.

6. Cathode assembly for electrolysis cell according to any one of claims 1 to 4 wherein the electrical contact plugs (50) are anisotropic electrical contact plugs (50).

7. Cathode assembly for an electrolysis cell according to any one of claims 1 to 6, wherein the electrical contact pins (50) have different elastic resistances.

8. Cathode assembly for an electrolysis cell according to any one of claims 1 to 7, wherein the cathode block (10) is made of a mixture of anthracite and graphite.

9. Cathode assembly for electrolysis cell according to any one of claims 1 to 8 wherein the number of electrical contact plugs (50) per square meter is between 10 and 80.

10. Electrolysis cell for the production of a metal, comprising: a. an outer steel casing; b. a layer of insulating material adjacent to the outer steel casing; c. a carbon layer covering the insulating material and protecting the insulating material from an electrolytic bath intended to be contained in the cell; and d. a cathode assembly for an electrolysis cell according to any one of claims 1 to 9.

Images