Anode for molten salt electrolysis and preparation method and application thereof

Abstract

The invention relates to an anode for molten salt electrolysis and a preparation method and application thereof, belongs to the technical field of molten salt electrolysis, and solves the problems that in the prior art, during molten salt electrolysis, the effective working area of the anode is reduced due to oxygen bubbles generated on the surface of the anode, so that the anode current density is increased; and irregular escape of the bubbles is unfavorable for stable operation of the electrolytic cell. Two or more through holes are formed in the direction perpendicular to the cross section of the anode, and the diameter of each through hole ranges from 5 mm to 12 mm; and in the direction parallel to the cross section of the anode, the total area of the cross sections of the through holes accounts for 0.3-4% of the total area of the cross sections of the anode. Smooth discharge of bubbles can be ensured, so that the current density is reduced, the cell voltage stability is improved, and the current efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt electrolysis, and in particular to an anode for molten salt electrolysis, a preparation method thereof, and an application thereof. Background Art

[0002] In molten salt electrolysis, when metals are produced by electrolyzing oxides, CO, or O2 are generated near the electrodes. These gas molecules aggregate on the anode surface and form bubbles, which grow and aggregate, eventually forming clusters of bubbles of varying sizes on the anode surface. The released O2 bubbles are typically 1-3 mm in diameter and are typically formed into a foam from tiny bubbles before being released.

[0003] The generation of bubbles will greatly reduce the effective working area of the anode, resulting in an increase in the anode current density and thus an increase in the anode overpotential; in addition, due to their poor conductivity, bubbles will increase the resistance between the cathode and anode electrodes, leading to a voltage increase. The irregular escape of bubbles is detrimental to the stable operation of the electrolytic cell.

[0004] In the existing technology, a carbon ridge is set on the top of the anode carbon block, and a number of carbon holes are evenly distributed on the surface of the carbon ridge. All the edges and corners of the carbon block and the carbon ridge are rounded, and there are arc-shaped grooves between adjacent exploration holes. An air guide groove is provided at the bottom of the carbon block, which can improve the conductivity and stability. However, its air guide effect is not good.

[0005] CN115799532A discloses a method for bubble aggregation and detachment on porous surfaces based on tree-like superaerophilic tracks. This method leverages the aerosol affinity and diffusivity of the superaerophilic tracks' multi-stage, bifurcated structure to rapidly aggregate and grow microbubbles, which are difficult to detach from the porous surface, to a point where they can easily detach, thereby improving the performance of methanol fuel cells. However, this device targets the track structure on the surface of the anode gas diffusion layer substrate, and the track's complex fabrication can pose challenges to the voltage stability of the electrolyzer during the microbubble aggregation and growth process. Summary of the Invention

[0006] In view of the above analysis, the embodiments of the present invention aim to provide an anode for molten salt electrolysis and its preparation method and application, so as to solve at least one of the problems such as the generation of oxygen bubbles on the anode surface, which reduces the effective working area of the anode, leads to an increase in the anode current density, and the irregular escape of bubbles is detrimental to the stable operation of the electrolytic cell.

[0007] The first aspect of the present invention provides an anode material for molten salt electrolysis, which is provided with no less than 2 through holes with a diameter of 4-12 mm in a direction perpendicular to the cross section of the anode;

[0008] Wherein, in a direction parallel to the cross section of the anode, the total cross-sectional area of the through holes accounts for 1-4% of the total cross-sectional area of the anode.

[0009] Furthermore, the cross-sectional area of each through hole accounts for 0.05-0.6% of the total cross-sectional area of the anode.

[0010] Furthermore, on the cross section of the anode, every 100 cm 2 The number of through holes in the cross-sectional area is ≤4.

[0011] Furthermore, the anode is selected from at least one of metal, ceramic and metal-ceramic composite material.

[0012] Furthermore, the shape of the anode is selected from one of a cuboid, a cube, a cylinder or an inverted T-shape.

[0013] Furthermore, the shape of the anode is a cuboid, and the distance between the centers of adjacent through holes parallel to the long side of the cuboid is 60-90 mm.

[0014] Furthermore, in a direction parallel to the wide side of the cuboid, the distance between the centers of adjacent through holes is 60-90 mm.

[0015] Furthermore, a straight-line distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge is 15-60 mm.

[0016] Furthermore, the shape of the anode is a cube, and the distance between the centers of adjacent through holes is 40-70 mm.

[0017] Furthermore, the shape of the anode is a cube, and the straight-line distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge is 15-60 mm.

[0018] Furthermore, the shape of the anode is cylindrical, and in the clockwise or counterclockwise direction along the cross section of the anode, the angle formed by the line connecting the centers of adjacent through holes and the center of the cross section of the anode is 60-90°.

[0019] Furthermore, the shape of the anode is cylindrical, and in the direction of the cross section of the anode, in the direction of the line connecting the center of the through hole and the center of the anode cross section, the distance L1 between the tangent of the anode cross section perpendicular to the connecting line and the center of the through hole is 15-60 mm.

[0020] Furthermore, along the radial direction of the cross section, the distance between the centers of adjacent through holes is L2, wherein L1 is smaller than L2.

[0021] A second aspect of the present invention provides a method for preparing the anode according to the first aspect of the present invention, the method comprising:

[0022] S1. Pre-setting at least two cores in the inner cavity of the mold, wherein the cores are used to form through-holes in the electrode block, and the design and size of the cores match the design and size of the through-holes in the anode according to the first aspect of the present invention;

[0023] S2. pouring a melt or slurry for forming an electrode block into the inner cavity of the mold, filling the inner cavity and wrapping the core;

[0024] S3, solidifying the cast melt or slurry to form an electrode block, taking out the electrode block from the mold and removing the core to form the through hole;

[0025] Alternatively, the electrode block is placed on a drilling machine, and the anode is directly punched to obtain the anode for molten salt electrolysis, wherein the position and size of the punched hole match the position and size of the through hole in the anode described in the first aspect of the present invention.

[0026] In the present invention, taking a rectangular anode as an example, the design and size of the core match the design and size of the through-hole, meaning that the diameter of the core is the same as the diameter of the through-hole formed, the "distance between the centers of adjacent cores parallel to the long side of the mold" is consistent with the "distance between the centers of adjacent through-holes parallel to the long side of the anode"; the "distance between the centers of adjacent cores parallel to the wide side of the mold" is consistent with the "distance between the centers of adjacent through-holes parallel to the wide side of the anode"; the "distance between the center of the core adjacent to the long side of the mold" is consistent with the "distance between the center of the through-hole adjacent to the long side of the anode"; the "distance between the center of the core adjacent to the long side of the mold" is consistent with the "distance between the center of the through-hole adjacent to the long side of the anode"; and the "distance between the center of the core adjacent to the wide side of the mold" is consistent with the "distance between the center of the through-hole adjacent to the wide side of the anode". The same applies when the anode is a cube, cylinder, or inverted T-shaped.

[0027] A third aspect of the present invention provides a use of the anode described in the first aspect of the present invention in the electrolysis of molten salt oxides.

[0028] The present invention can achieve at least one of the following beneficial effects:

[0029] 1. The present invention provides a plurality of through holes in a direction perpendicular to the cross section of the anode, thereby preventing bubbles on the anode surface from gathering at the bottom and gradually growing, resulting in poor bubble discharge, thereby improving the stability of the electrolytic cell pressure and further improving the current efficiency.

[0030] 2. The present invention optimizes the number and diameter of the through holes in the anode, and the ratio of the total cross-sectional area of the through holes to the total cross-sectional area of the anode, thereby further improving the stability of the electrolytic cell voltage while ensuring the excellent corrosion resistance of the anode.

[0031] 3. In the present invention, the anode is controlled to 2 The number of through holes in the cross-sectional area and the distribution of the through holes in the electrode material, such as the distance between the centers of adjacent through holes, the distance between the through holes and the outer edge of the anode, and the angles of adjacent through holes in the cylindrical electrode material, meet the requirements of the present invention, can ensure the uniformity of the distribution of the through holes, and at the same time improve the discharge efficiency of bubbles, reduce the current density of the anode, thereby improving the current efficiency, and enhance the cell voltage stability.

[0032] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. Throughout the drawings, the same reference symbols denote the same components.

[0034] Figure 1 Schematic diagram of the structure of anode A1 prepared in Preparation Example 1;

[0035] Figure 2 Schematic diagram of a cross section of anode A1 prepared in Preparation Example 1;

[0036] Figure 3 This is a graph showing the change in electrolytic cell voltage after 24 hours of electrolysis of anode A1 prepared in Preparation Example 1;

[0037] Figure 4 This is a graph showing the change in electrolytic cell voltage after 5 days of electrolysis of anode A1 prepared in Preparation Example 1;

[0038] Figure 5 This is a graph showing changes in electrolytic cell voltage in Example 10;

[0039] Figure 6 This is a graph showing the electrolytic cell voltage variation of Comparative Example 1;

[0040] Figure 7 This is the electrolytic cell voltage change diagram of Comparative Example 2. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0042] A first aspect of the present invention provides an anode for molten salt electrolysis, wherein the anode has no less than 2 through holes with a diameter of 5-12 mm in a direction perpendicular to the cross section of the anode;

[0043] In a direction parallel to the cross section of the anode, the total cross-sectional area of the through holes accounts for 0.3-4% of the total cross-sectional area of the anode.

[0044] In the present invention, in order to prevent the bubbles on the anode surface, especially the bottom, from gathering at the bottom and growing gradually, Figure 1 As shown, taking the rectangular anode as an example, there are 6 through holes in the anode. During the electrolysis process, according to Figure 1 The through holes arranged in the manner shown can effectively allow oxygen bubbles generated on the anode surface, especially the bottom surface, to be discharged in a timely manner along the through holes, thereby improving the stability of the electrolytic cell voltage (cell voltage).

[0045] In the present invention, the number of the through holes is set to be not less than 2 in consideration of electrolysis stability. This is to avoid as much as possible the situation where the oxygen bubbles cannot be discharged or are discharged poorly due to uneven distribution of the through holes or the area of the through holes accounts for too small a proportion of the total anode cross-sectional area. The oxygen bubbles gather and grow at the bottom of the electrode, reducing the effective area of the electrode, increasing the current density of the anode and reducing the current efficiency.

[0046] In the present invention, the diameter of the through-hole is set to 5-12 mm, taking into account electrolysis stability, electrode strength, and electrode corrosion resistance. If it is less than 5 mm, bubbles cannot escape smoothly, affecting the stability of the cell voltage and resulting in low current efficiency. If it exceeds 12 mm, the strength of the electrode will be affected, and the contact area between the molten salt and the anode will increase, making the anode more susceptible to corrosion.

[0047] In the present invention, specifically, the diameter of the through hole is 5mm, 5.5mm, 6mm, 6.3mm, 7mm, 7.5mm, 8mm, 8.2mm, 9mm, 9.6mm, 10mm, 10.1mm, 10.2mm, 10.5mm, 11mm, 11.5mm, 11.8mm, 12mm and a range consisting of any two of the above values, preferably 6-10mm.

[0048] In the present invention, considering electrolytic stability, electrode strength, and electrode corrosion resistance, the total cross-sectional area of the through-holes, parallel to the anode cross-section, accounts for 0.3-4% of the total cross-sectional area of the anode. If it is less than 0.3%, oxygen discharge efficiency will be poor, causing cell voltage fluctuations. If it is greater than 4%, the strength and corrosion resistance of the anode will be affected.

[0049] In the present invention, specifically, the total cross-sectional area of the through holes accounts for 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.1%, 2.3%, 2.5%, 2.8%, 3%, 3.2%, 3.6%, 3.8%, 3.9%, 4% of the total cross-sectional area of the anode, and the range consisting of any two of the above values, preferably 0.5-3.5%.

[0050] In the present invention, the plurality of through holes in the anode are arranged as regularly as possible. For example, in a cubic anode, the distances between adjacent through holes are equal, or in a cylindrical anode, the angles formed by the lines connecting the centers of adjacent through holes and the center of the cross section of the anode in the direction of the cross section of the cylindrical anode are equal. This enables the bubbles on the surface of the anode to be discharged more evenly, avoiding the bubbles from gathering around one or some through holes, resulting in unstable cell pressure and poor oxygen discharge effect.

[0051] According to a particularly preferred embodiment of the present invention, the diameter of the through-holes is 6-8 mm, and the total area of the through-holes accounts for 1-3.2% of the total cross-sectional area of the anode.

[0052] When the diameter of the through hole and the percentage of the total cross-sectional area of the through hole to the total cross-sectional area of the anode both meet the above ranges, the exhaust efficiency of oxygen bubbles can be further improved, thereby improving the cell voltage stability and the current efficiency.

[0053] In the present invention, after extensive research, the inventors found that only when the cross-sectional area of each through hole accounts for 0.05-0.6% of the total cross-sectional area of the anode, and at the same time, the cross-sectional area of the anode is 100cm 2 The number of through holes on the cross-sectional area of 4 is ≤4, which can balance the exhaust efficiency of bubbles and ensure the stability of cell pressure. This is because meeting the above limit can reduce the fluctuation of the current density of the anode, ensure the stability of the cell pressure, and thus improve the current efficiency. Preferably, on the cross-sectional area of the anode, every 100cm 2 The number of through holes in the cross-sectional area is 2-3.

[0054] In the present invention, the cross-sectional area of each of the through holes accounts for 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.12%, 0.15%, 0.2%, 0.22%, 0.25%, 0.3%, 0.4%, 0.45%, 0.48%, 0.5%, 0.52%, 0.55%, 0.6% of the total cross-sectional area of the anode, and the range consisting of any two of the above values, preferably 0.1-3%.

[0055] According to the present invention, considering that the gas generated on the anode surface is oxygen, the anode is selected from at least one of metal, ceramic and metal-ceramic composite materials.

[0056] Furthermore, considering that the anode has good electrical conductivity during operation, the metal is preferably Cu, Ni, Cu-Al alloy, Ni-Fe alloy, Ni-Fe-Cr alloy, or Cu-Ni-Fe alloy.

[0057] Furthermore, considering the corrosion resistance, the ceramic is preferably a SnO-based oxide ceramic, a Ni2FeO4-based oxide ceramic or a Nb2O5-based oxide ceramic.

[0058] Furthermore, considering the electrical conductivity and corrosion resistance, the metal-ceramic composite material is preferably a composite material comprising the above alloy and the above ceramic.

[0059] According to the present invention, the shape of the anode is selected from one of a cuboid, a cube, a cylinder or an inverted T-shape. Preferably, the shape of the anode is a cuboid or a cylinder.

[0060] According to one embodiment of the present invention, the anode is in the shape of a cuboid, and the distance between the centers of adjacent through holes parallel to the long side of the cuboid is 60-90 mm.

[0061] In the present invention, after extensive research, the inventors found that oxygen exhaust efficiency is only guaranteed when the distance between the centers of adjacent through-holes, parallel to the long side of the cuboid, falls within the aforementioned range (60-90 mm). If the distance is less than 60 mm, some areas may have denser holes, increasing current density and affecting current efficiency. If the distance is greater than 90 mm, oxygen bubbles may concentrate in unperforated areas, grow, and then be exhausted through the exhaust holes, slowing oxygen exhaust and affecting the cell pressure.

[0062] In the present invention, the shape of the anode is a rectangular parallelepiped, and the distance between the centers of adjacent through holes parallel to the long side of the rectangular parallelepiped is 60mm, 62mm, 63mm, 65mm, 66mm, 68mm, 70mm, 71mm, 72mm, 73mm, 75mm, 76mm, 78mm, 80mm, 81mm, 82mm, 85mm, 88mm, 90mm and a range consisting of any two of the above values, preferably 70-90mm.

[0063] In the present invention, the inventor unexpectedly discovered through research that when the distance between the centers of adjacent through holes in the direction parallel to the long side of the rectangular parallelepiped is further between 75-85 mm, further effects can be achieved in simplifying the process, improving oxygen exhaust efficiency, cell voltage stability, current efficiency, and reducing current density.

[0064] According to the present invention, considering the oxygen exhaust effect, the distance between the centers of adjacent through holes in the direction parallel to the wide side of the rectangular parallelepiped is 60-90 mm.

[0065] In the present invention, parallel to the wide side of the rectangular parallelepiped, only when the distance between the centers of adjacent through holes meets the above range can the oxygen discharge effect be guaranteed. If it is less than 60 mm, the holes in some areas will be denser, and it will be difficult to achieve uniform distribution of the holes, resulting in poor oxygen discharge effect. If it exceeds 90 mm, oxygen bubbles will be concentrated in the unopened area and grow before being discharged through the exhaust holes. The oxygen discharge is slow, which affects the pressure of the electrolytic cell.

[0066] In the present invention, the shape of the anode is a rectangular parallelepiped, and the distance between the centers of adjacent through holes parallel to the wide side of the rectangular parallelepiped is 60mm, 62mm, 63mm, 65mm, 66mm, 68mm, 70mm, 71mm, 72mm, 73mm, 75mm, 76mm, 78mm, 80mm, 81mm, 82mm, 85mm, 88mm, 90mm and a range consisting of any two of the above values, preferably 70-90mm.

[0067] In the present invention, the inventor unexpectedly discovered through research that when the distance between the centers of adjacent through holes in the direction parallel to the wide side of the rectangular parallelepiped is further 65-75 mm, further effects can be achieved in simplifying the process, improving oxygen exhaust efficiency, cell voltage stability, current efficiency and other performance.

[0068] According to a particularly preferred embodiment of the present invention, when the through holes in the anode simultaneously meet the following ranges, the optimal effect can be achieved in terms of simplifying the process, improving oxygen discharge efficiency, cell voltage stability, current efficiency and other performance: 1. The distance between the centers of adjacent through holes in the direction parallel to the long side of the cuboid is 75-80 mm; 2. The distance between the centers of adjacent through holes in the direction parallel to the wide side of the cuboid is 65-75 mm.

[0069] According to one embodiment of the present invention, the anode is in the shape of a cube, and the distances between the centers of adjacent through holes are equal.

[0070] In the present invention, the shape of the anode is a cube. When the distances between the centers of adjacent through holes are equal, the bubbles can be discharged more evenly and efficiently, which is more conducive to the stability of the cell pressure.

[0071] According to one embodiment of the present invention, the distance between the centers of adjacent through-holes is 40-70 mm to optimize oxygen discharge efficiency. A distance less than 40 mm results in densely packed holes in some areas, making it difficult to achieve uniform hole distribution, resulting in poor oxygen discharge efficiency. A distance exceeding 70 mm causes oxygen bubbles to concentrate in unperforated areas, grow, and then be discharged through the vents, slowing oxygen discharge and impacting the cell pressure.

[0072] In the present invention, the shape of the anode is a cube, and the distance between the centers of adjacent through holes is 45mm, 46mm, 48mm, 50mm, 51mm, 52mm, 53mm, 55mm, 58mm, 60mm, 62mm, 63mm, 65mm, 66mm, 68mm, 70mm and a range consisting of any two of the above values, preferably 45-60mm.

[0073] In order to obtain a further better effect, the inventor unexpectedly discovered that when the distance between the centers of adjacent through holes is 45-55 mm, the electrolytic cell voltage can be further stabilized and the current efficiency can be improved.

[0074] According to a preferred embodiment of the present invention, when the anode is selected from a rectangular parallelepiped or a cube, the linear distance between the outer edge of the anode and the center of the through-hole adjacent to the outer edge is less than the distance between the centers of adjacent through-holes and greater than the diameter of the through-hole. Specifically, the linear distance between the outer edge of the anode and the center of the through-hole adjacent to the outer edge is 15-60 mm.

[0075] In the present invention, the inventor unexpectedly discovered during research that the anode as a whole can have a better oxygen discharge effect only when the straight-line distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge satisfies the above-mentioned relationship. If it is smaller than the diameter of the through hole, the oxygen bubbles generated near the middle area of the electrode will easily gather and grow, making them difficult to discharge. If the distance exceeds the distance between adjacent through holes, the arrangement pattern of the exhaust holes will be affected, which is not conducive to the discharge of oxygen.

[0076] In the present invention, the straight-line distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge can be either the straight-line distance between the outer edge of the long side of the anode and the center of the through hole adjacent to the outer edge of the long side, or the straight-line distance between the outer edge of the wide side of the anode and the center of the through hole adjacent to the outer edge of the wide side.

[0077] According to one embodiment of the present invention, the anode is cylindrical in shape, and along the cross section of the anode in the clockwise or counterclockwise direction, the angle formed by the line connecting the centers of adjacent through holes and the center of the cross section of the anode is 60-90°.

[0078] In the present invention, the shape of the anode is cylindrical, and the angle formed by the line connecting the centers of adjacent through holes and the center of the cross section of the anode in the clockwise or counterclockwise direction along the cross section of the anode is 60°, 72° or 90°. Preferably, the angle formed by the line connecting the centers of adjacent through holes and the center of the cross section of the anode in the clockwise or counterclockwise direction along the cross section of the anode is 60-72°.

[0079] In the present invention, the angle formed by the line connecting the centers of adjacent through holes and the centers of the cross sections of the anode in the clockwise or counterclockwise direction along the cross section of the anode satisfies the above range, which can make the bubbles more uniform and efficient when discharged, reduce the current density of the anode and thus improve the current efficiency, which is more conducive to the stability of the cell voltage.

[0080] According to one embodiment of the present invention, in the direction of the anode cross section, in the direction of the line connecting the center of the through hole and the center of the anode cross section, the distance between the tangent of the anode cross section perpendicular to the connecting direction and the center of the through hole is L1, and along the radius direction of the cross section, the distance between the centers of adjacent through holes is L2, wherein L1 is smaller than L2.

[0081] In the present invention, specifically, L1 is 15-60 mm, and L2 is 60-90 mm. Meeting the above ranges can improve current efficiency and be more conducive to the stability of the slot voltage.

[0082] In the present invention, it should be noted that the shape of the anode is an inverted T-shape, which is a "thumbnail" style. Its cross-section is circular, just like the cross-section of the cylindrical anode. Therefore, the process and parameters for setting the through hole on the inverted T-shaped anode are the same as those for the cylindrical anode, and will not be repeated here.

[0083] According to a particularly preferred embodiment of the present invention, when the number of the through holes is 6-8, the diameter is 8-10 mm, and the total area of the through holes accounts for 1-3.2% of the total cross-sectional area of the anode, and the cross-sectional area of each of the through holes is 0.1-0.6% of the total cross-sectional area of the anode, the various parameters can synergize to enhance the effect, so that the prepared anode has a significantly better effect. Specifically, the average change rate of the cell voltage over 24 hours is not higher than 3%, and the current efficiency is not lower than 90%.

[0084] A second aspect of the present invention provides a method for preparing the anode for molten salt electrolysis according to the first aspect, the method comprising:

[0085] S1. Pre-setting at least two cores in the inner cavity of the mold, wherein the cores are used to form through holes in the electrode block, and the design of the cores matches the design of the through holes in the anode described in the first aspect of the present invention;

[0086] S2. pouring a melt or slurry for forming an electrode block into the inner cavity of the mold, filling the inner cavity and wrapping the core;

[0087] S3, solidifying the cast melt or slurry to form an electrode block, taking out the electrode block from the mold and removing the core to form the through hole;

[0088] Alternatively, the electrode block is placed on a drilling machine and the anode is directly punched to obtain the anode for molten salt electrolysis, wherein the position and size of the punched holes match the position and size of the through holes in the anode described in the first aspect of the present invention.

[0089] In the present invention, taking the rectangular anode as an example, the design and size of the core match the design and size of the through hole described in claim 1, which means that the diameter of the core is the same as the diameter of the through hole formed, "the distance between the centers of adjacent cores parallel to the long side of the mold" is consistent with "the distance between the centers of adjacent through holes parallel to the long side of the anode"; "the distance between the centers of adjacent cores parallel to the wide side of the mold" is consistent with "the distance between the centers of adjacent through holes parallel to the wide side of the anode"; "the distance between the outer edge of the long side of the mold and the center of the core adjacent to the outer edge of the long side" is consistent with "the distance between the outer edge of the long side of the anode and the center of the through hole adjacent to the outer edge of the long side"; "the distance between the outer edge of the wide side of the mold and the center of the core adjacent to the outer edge of the wide side" is consistent with "the distance between the outer edge of the wide side of the anode and the center of the through hole adjacent to the outer edge of the wide side". The same applies when the anode is in the shape of a cube, a cylinder or an inverted T.

[0090] A third aspect of the present invention provides a use of the anode described in the first aspect in the electrolysis of molten salt oxides.

[0091] According to the present invention, when the anode is used for molten salt electrolysis, the molten salt electrolyte is at least one of KF, NaF, and AlF3, preferably a mixture of KF, NaF, and AlF3, and the molecular ratio CR is between 1.1 and 1.5, wherein the molecular ratio CR = (n KF +n NaF ) / n AlF3 , n represents the amount of substance.

[0092] The raw materials for electrolysis can be aluminum, magnesium, vanadium, titanium and rare earth element oxides, such as Al2O3, MgO, V2O3, TiO2 and rare earth element oxides, and the concentration is not more than 4wt%.

[0093] According to the present invention, the electrolysis conditions include: electrolysis temperature: 750℃-950℃, current density: 0.3A / cm 2 -1A / cm 2 , pole distance: 2-6cm, electrolyte level: 10-16cm.

[0094] The present invention will be described in detail below through preparation examples. In the following preparation examples,

[0095] The cell pressure of the electrolytic cell is measured and recorded in real time by a data recorder using the voltage difference between the anode and cathode every 5 seconds.

[0096] The average change rate of the electrolytic cell pressure over 24 hours is calculated by calculating the average cell pressure within 24 hours, then calculating the change rate of the cell pressure at each point, and then calculating the average change rate of the cell pressure;

[0097] During the electrolysis process, the current efficiency is measured by the mass of the product obtained by electrolysis and calculated according to the formula: current efficiency = (actual mass of the product obtained / theoretical mass of the product obtained) × 100%.

[0098] Preparation Example 1

[0099] A 52Cu-30Ni-18Fe alloy anode was prepared by the casting method to obtain a Ni-Fe-Cu alloy anode A1 (200*100*100mm). The specific steps are as follows:

[0100] S1. In the inner cavity of the mold (internal dimensions 200*100*100mm) Figure 2 The design is as follows: 6 cores are preset, and the cores are used to form the through holes in the electrode block. The diameter of the cores is 10 mm. The distance between the centers of adjacent cores parallel to the long side of the mold is 80 mm, and the distance between the centers of adjacent cores parallel to the wide side of the mold is 70 mm. The distance between the outer edge of the long side of the mold and the center of the core adjacent to the outer edge of the long side is 15 mm, and the distance between the outer edge of the wide side of the mold and the center of the core adjacent to the outer edge of the wide side is 20 mm.

[0101] S2. pouring a melt (52Cu-30Ni-18Fe mixture melt) for forming an electrode block into the inner cavity of the mold, filling the inner cavity and wrapping the core;

[0102] S3, after the melt to be poured solidifies, the solidified electrode block is taken out from the mold and the core is removed, thereby forming Figure 1 The through-hole shown;

[0103] like Figure 1 and Figure 2 As shown, the anode A1 obtained is a rectangular parallelepiped with 6 identical through holes perpendicular to the cross section of the anode A1, each with a diameter of 10 mm. In the direction parallel to the long side of the anode A1, the distance between the centers of adjacent through holes is 80 mm, and in the direction parallel to the wide side of the anode A1, the distance between the centers of adjacent through holes is 70 mm. The distance between the outer edge of the long side of the anode A1 and the center of the through hole adjacent to the outer edge of the long side is 15 mm, and the distance between the outer edge of the wide side of the anode A1 and the center of the through hole adjacent to the outer edge of the wide side is 20 mm. On the cross section of the anode A1, every 100 cm 2 The number of through holes within the cross-sectional area is 3.

[0104] The cross-sectional area of each through hole accounts for 0.4% of the total cross-sectional area of the anode, and the total area of the six through holes accounts for 2.4% of the total cross-sectional area of the anode.

[0105] Preparation Example 2

[0106] Anode A2 (200*100*100mm) was prepared according to the method of Preparation Example 1, except that the diameter of the through hole was 5mm, wherein the distance between the centers of adjacent through holes parallel to the long side of anode A2 was 80mm, and the distance between the centers of adjacent through holes parallel to the wide side of anode A2 was 70mm, the distance between the outer edge of the long side of anode A2 and the center of the through hole adjacent to the outer edge of the long side was 15mm, and the distance between the outer edge of the wide side of anode A2 and the center of the through hole adjacent to the outer edge of the wide side was 20mm. On the cross section of anode A2, every 100cm 2 The number of cross-sectional area through-holes is 3.

[0107] The cross-sectional area of each through hole accounts for 0.1% of the total cross-sectional area of the anode, and the total area of the six through holes accounts for 0.6% of the total cross-sectional area of the anode.

[0108] Preparation Example 3

[0109] A Ni-Fe-Cu alloy anode A3 (200*100*100mm) was prepared according to the method of Preparation Example 1, except that the diameter of the through hole was 12mm, wherein the distance between the centers of adjacent through holes parallel to the long side of the anode A3 was 80mm, and the distance between the centers of adjacent through holes parallel to the wide side of the anode A3 was 70mm, the distance between the outer edge of the long side of the anode A3 and the center of the through hole adjacent to the long side was 15mm, and the distance between the outer edge of the wide side of the anode A3 and the center of the through hole adjacent to the wide side was 20mm. On the cross section of the anode A3, every 100cm 2 The number of cross-sectional area through-holes is 3.

[0110] The cross-sectional area of each through hole accounts for 0.6% of the total cross-sectional area of the anode, and the total area of the six through holes accounts for 3.4% of the total cross-sectional area of the anode.

[0111] Preparation Example 4

[0112] A Ni-Fe-Cu alloy anode A4 (200*100*100mm) was prepared according to the method of Preparation Example 1, except that the number of the through holes was set to 4. In the direction parallel to the long side of the anode A4, the distance between the centers of the adjacent through holes was 80mm, and in the direction parallel to the wide side of the anode A4, the distance between the centers of the adjacent through holes was 70mm. The distance between the outer edge of the long side of the anode A4 and the center of the through hole adjacent to the outer edge of the long side was 15mm, and the distance between the outer edge of the wide side of the anode A4 and the center of the through hole adjacent to the outer edge of the wide side was 60mm. On the cross section of the anode A4, every 100cm2 The number of cross-sectional area through-holes is 2.

[0113] The cross-sectional area of each through hole accounts for 0.4% of the total cross-sectional area of the anode, and the total cross-sectional area of the four through holes accounts for 1.6% of the total cross-sectional area of the anode.

[0114] Preparation Example 5

[0115] A Ni-Fe-Cu alloy anode A5 was prepared according to the method of Preparation Example 1, except that the anode was a cube (side length 200 mm, height 100 mm). The distance between the centers of adjacent through holes was 50 mm, and the distance between the outer edge of the anode A5 and the center of the through hole adjacent to the outer edge was 25 mm. On the cross section of the anode A5, every 100 cm 2 The number of cross-sectional area through-holes is 2.

[0116] The cross-sectional area of each through hole accounts for 0.4% of the total cross-sectional area of the anode, and the total area of the eight through holes accounts for 3.2% of the total area of the anode.

[0117] Preparation Example 6

[0118] A Ni-Fe-Cu alloy anode A6 was prepared according to the method of Preparation Example 1, except that the anode was cylindrical (200 mm in diameter and 100 mm in height). In the clockwise or counterclockwise direction along the cross section of the cylindrical anode, the angle formed by the line connecting the centers of the adjacent through holes and the center of the cross section of the anode is 72° (corresponding to 10 through holes), and along the radial direction of the cross section, the distance between the centers of the adjacent through holes is 60 mm, and in the direction of the line connecting the centers of the through holes and the centers of the anode cross section, the distance between the tangent of the anode cross section perpendicular to the direction of the line and the center of the through hole is 15 mm, and the diameter of the through hole is 10 mm. On the cross section of the anode A6, every 100 cm 2 The number of through holes within the cross-sectional area is 3.

[0119] The cross-sectional area of each through hole accounts for 0.25% of the total cross-sectional area of the anode, and the total cross-sectional area of the ten through holes accounts for 2.5% of the total cross-sectional area of the anode.

[0120] Preparation Example 7

[0121] Anode A7 (200 mm in diameter and 100 mm in height) was prepared according to the method of Preparation Example 6, except that the distance between the center of the through hole and the center of the anode cross section, perpendicular to the direction of the line connecting the center of the through hole and the center of the anode cross section, and the center of the through hole was 20 mm, and the diameter of the through hole was 8 mm. The distance between the center of the through hole and the center of the adjacent through hole in the direction of the line connecting the center of the anode cross section was 60 mm. Every 100 cm 2 There are three holes inside.

[0122] The cross-sectional area of each through hole accounts for 0.16% of the total cross-sectional area of the anode, and the total cross-sectional area of the ten through holes accounts for 1.6% of the total cross-sectional area of the anode.

[0123] Preparation Example 8

[0124] Anode A8 (200 mm in diameter and 100 mm in height) was prepared according to the method of Preparation Example 1, except that, along the cross section of the cylindrical anode, the angle formed by the line connecting the center of the circle of the adjacent through-holes and the center of the cross section of the anode in the clockwise or counterclockwise direction was 90° (corresponding to 8 through-holes). Along the radial direction of the cross section, the distance between the centers of adjacent through-holes was 60 mm. On the cross section of anode A8, every 100 cm 2 The number of through holes within the cross-sectional area is 3.

[0125] The cross-sectional area of each through hole accounts for 0.25% of the total cross-sectional area of the anode, and the total cross-sectional area of the eight through holes accounts for 2% of the total cross-sectional area of the anode.

[0126] Preparation Example 9

[0127] By drilling on 52Cu-30Ni-18Fe alloy anode (200*100*100mm) Figure 2 Anode A9 was produced by drilling directly into the anode as shown in the drawing.

[0128] Preparation Example 10

[0129] The method of Preparation Example 6 was followed, except that the distance between the centers of adjacent through-holes along the radial direction of the cross section was 40 mm, and the distance between the tangent line of the anode cross section perpendicular to the connecting line and the center of the anode cross section and the center of the through-hole was 30 mm. 2 The number of through holes within the cross-sectional area is 3.

[0130] The cross-sectional area of each through hole accounts for 0.25% of the total cross-sectional area of the anode, and the total cross-sectional area of the ten through holes accounts for 2.5% of the total cross-sectional area of the anode.

[0131] Preparation Example 11

[0132] The method of Preparation Example 1 was followed, except that the melt 52Cu-30Ni-18Fe used to form the electrode block of the 52Cu-30Ni-18Fe alloy anode was replaced with SnO2 ceramic slurry. Other steps were the same as those of Preparation Example 1. Anode A11 was obtained.

[0133] Preparation Example 12

[0134] Anode A12 was prepared in the same manner as in Example 1, except that the linear distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge was 10 mm.

[0135] Preparation Example 13

[0136] The method of Preparation Example 6 was followed, except that the angle formed by the line connecting the centers of the adjacent through holes and the center of the cross section of the anode in the clockwise or counterclockwise direction along the cross section of the anode was 30°, and only 12 through holes were provided. Other aspects were the same as those of Preparation Example 1 to obtain anode A13. On the cross section of anode A13, every 100 cm 2 The number of through holes in the cross-sectional area is 4.

[0137] The cross-sectional area of each through hole accounts for 0.25% of the total cross-sectional area of the anode, and the total cross-sectional area of the ten through holes accounts for 3% of the total cross-sectional area of the anode.

[0138] Comparative Preparation Example 1

[0139] A 52Cu-30Ni-18Fe alloy was used as the anode (200mm*100mm*100mm), and two air guide grooves were opened at the bottom with an interval of 30mm. The air guide grooves were parallel to the long side, 30mm deep and 5mm wide. In the direction parallel to the long side, the outer edge of the air guide groove was 30mm away from the outer edge of the anode, and anode D1 was prepared.

[0140] Comparative Preparation Example 2

[0141] A 52Cu-30Ni-18Fe alloy anode (200 mm * 100 mm * 100 mm) was used. Based on Preparation Example 1, two air guide grooves, 5 mm wide and 30 mm deep, were cut at the bottom, parallel to the long sides. The two air guide grooves were 30 mm apart and parallel to the long sides, with the outer edges of the air guide grooves 30 mm away from the outer edge of the anode. Anode D2 was prepared.

[0142] Comparative Preparation Example 3

[0143] Anode D3 was prepared according to the method of Preparation Example 1, except that only through-hole 1 (with a diameter of 10 mm) was retained.

[0144] The cross-sectional area of each through hole accounts for 0.4% of the total cross-sectional area of the anode, and the total cross-sectional area of one through hole accounts for 0.4% of the total cross-sectional area of the anode.

[0145] Comparative Preparation Example 4

[0146] Anode D4 was prepared according to the method of Preparation Example 1, except that only through-hole 1 (with a diameter of 20 mm) was retained.

[0147] The cross-sectional area of each through hole accounts for 1.57% of the total cross-sectional area of the anode, and the total cross-sectional area of one through hole accounts for 1.57% of the total cross-sectional area of the anode.

[0148] Comparative Example Preparation 5

[0149] The method of Preparation Example 5 was followed, except that the diameter of the through hole was 4 mm.

[0150] The cross-sectional area of each through hole accounts for 0.04% of the total cross-sectional area of the anode, and the total cross-sectional area of the ten through holes accounts for 0.4% of the total cross-sectional area of the anode.

[0151] Examples 1-14, Comparative Examples 1-5

[0152] In order to verify the effects of the anodes prepared in the preparation examples and the comparative preparation examples, they were applied to the electrolysis of aluminum oxide. Unless otherwise specified, the electrolysis conditions during the electrolysis process were as follows: graphite material was used as the cathode, anodes A1-A13 prepared in preparation examples 1-13 and anodes D1-D5 prepared in the comparative preparation examples were used as anodes, the electrolysis temperature was 780°C, and the current density was 0.5 A / cm 2 The electrode distance was 4 cm, the electrolysis time was 24 h, the electrolyte level was 14 cm, and the molten salt electrolyte was 22.7 wt% KF-20.5 wt% NaF-52.8 wt% AlF3-4 wt% Al2O3. The results are shown in Table 1.

[0153] In order to further illustrate that the prepared anode has long-term electrolytic stability, the anode A1 prepared in Preparation Example 1 was electrolyzed for 5 days and then tested. The results are as follows: Figure 4 .

[0154] Figure 3 This is the electrolytic cell voltage change diagram when anode A1 is electrolyzed for 24 hours. Figure 4 The voltage change diagram of the electrolytic cell after 5 days of electrolysis of anode A1 is shown in Figure 2. Figure 3It can be seen that the electrolytic cell pressure has excellent cell pressure stability within 24 hours, and the cell pressure change during the electrolysis operation does not exceed 1.1%. Figure 4 It can be seen that anode A1 maintains a stable cell pressure after 5 days of continuous operation, indicating that during long-term electrolysis operation of the anode, the cell pressure fluctuation caused by the growth of oxygen bubbles is very small, which can be judged as an excellent oxygen discharge effect.

[0155] In order to further illustrate that the anode prepared by the present invention can be well applied to different electrolytes, the preparation example 6 was applied to the electrolysis temperature of 850 ° C, the electrolysis current density of 0.5 A / cm 2 The electrolysis was carried out under the condition of 3 wt % V2O3 concentration. The results are shown in Example 14 in Table 1.

[0156] Figure 5 The electrolytic cell voltage variation diagram of Example 14 is shown in FIG. Figure 5 It can be seen that the electrolytic cell voltage remains stable, and the electrolytic cell voltage fluctuates little in the subsequent 24 hours, indicating that during the electrolysis operation, the cell voltage fluctuation caused by the growth of oxygen bubbles is very small, and the oxygen discharge effect is good.

[0157] Table 1

[0158]

[0159] As can be seen from the above, the embodiments that meet the solution of the present invention achieve better results, wherein the current density is not higher than 0.522A / cm 2 , the current efficiency is not less than 90%, and at the same time, the average change rate of the slot voltage within 24 hours is not greater than 5.

[0160] Examples 1, 4-6 that further meet the preferred range of the present invention all achieved significantly better results, wherein the current density was not higher than 0.492 A / cm 2 , the current efficiency is not less than 95%, and the average change rate of the slot voltage within 24 hours is not greater than 1.5.

[0161] Figure 6-7 This is a graph showing the voltage variation of the electrolytic cell of Comparative Example 1-2. Figure 6 It can be seen from the figure that the cell pressure fluctuates significantly, indicating that the oxygen discharge effect of the alloy anode with grooves at the bottom is not good, and the bubbles grow and discharge periodically at the bottom, causing the cell pressure to rise and fall periodically. Figure 7 It can be seen that the cell pressure fluctuates significantly, indicating that adding two gas guide grooves on the basis of Preparation Example 1 cannot better discharge oxygen bubbles. At the same time, due to more processing, the anode strength and current density are significantly affected, resulting in abnormal cell pressure fluctuations.

[0162] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. An anode for molten salt electrolysis, characterized in that: In a direction perpendicular to the cross section of the anode, there are provided at least 2 through holes with a diameter of 5-12 mm; In a direction parallel to the cross section of the anode, the total cross-sectional area of the through holes accounts for 0.3-4% of the total cross-sectional area of the anode.

2. The anode for molten salt electrolysis according to claim 1, characterized in that: The cross-sectional area of each through hole accounts for 0.05-0.6% of the total cross-sectional area of the anode.

3. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: On the anode cross section, every 100cm 2 The number of through holes in the cross-sectional area is ≤4.

4. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: The anode is selected from at least one of metal, ceramic and metal-ceramic composite materials.

5. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: The shape of the anode is selected from one of a cuboid, a cube, a cylinder or an inverted T-shape.

6. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: The shape of the anode is a cuboid, and the distance between the centers of adjacent through holes parallel to the long side of the cuboid is 60-90 mm; and / or, in a direction parallel to the wide side of the cuboid, the distance between the centers of adjacent through holes is 60-90 mm; and / or, the linear distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge is 15-60 mm; Alternatively, the anode is in the shape of a cube, and the distance between the centers of adjacent through holes is 40-70 mm; And / or, the anode is in the shape of a cube, and the straight-line distance between the outer edge of the anode and the center of the through hole adjacent to the outer edge is 15-60 mm.

7. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: The shape of the anode is cylindrical. In the clockwise or counterclockwise direction along the cross section of the anode, the angle formed by the line connecting the centers of the adjacent through holes and the center of the cross section of the anode is 60-90°.

8. The anode for molten salt electrolysis according to claim 1 or 2, characterized in that: The shape of the anode is cylindrical, and in the direction of the cross section of the anode, in the direction of the line connecting the center of the through hole and the center of the cross section of the anode, the distance L1 between the tangent line of the cross section of the anode and the center of the through hole perpendicular to the connecting line is 15-60 mm; And / or, along the radial direction of the cross section, the distance between the centers of adjacent through holes is L2, wherein L1 is smaller than L2.

9. A method for preparing an anode for molten salt electrolysis according to any one of claims 1 to 8, characterized in that: The method comprises: S1. Pre-setting at least two cores in the inner cavity of the mold, wherein the cores are used to form through holes in the electrode block, and the design of the cores matches the design of the through holes in the anode according to claim 1; S2. pouring a melt or slurry for forming an electrode block into the inner cavity of the mold, filling the inner cavity and wrapping the core; S3, solidifying the cast melt or slurry to form an electrode block, taking out the electrode block from the mold and removing the core to form the through hole; Alternatively, the electrode block is placed on a drilling machine, and the anode is directly punched to obtain the anode for molten salt electrolysis, wherein the position and size of the punched holes match the position and size of the through holes in the anode according to claim 1.

10. Use of the anode for molten salt electrolysis according to any one of claims 1 to 8 in the electrolysis of molten salt oxides.

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