Rare earth metal electrolytic cell and preparation method of high-purity rare earth iron intermediate alloy

Abstract

This invention belongs to the field of rare earth metal electrolysis technology, and provides a rare earth metal electrolytic cell and a method for preparing high-purity rare earth iron master alloys. The rare earth metal electrolytic cell includes a cell body, an anode conductive plate, an anode assembly, and an anode isolation device. The anode assembly includes an anode plate. The anode isolation device forms a relatively closed cavity around the portion of the anode plate above the electrolyte surface, and by introducing a protective gas into the cavity, it creates and / or maintains an oxygen-free or low-oxygen atmosphere, thereby inhibiting the oxidation and consumption of the portion of the anode plate above the electrolyte surface by oxygen. The cavity has a gas escape channel that allows the internal gas to escape outwards. By setting up the anode isolation device, this invention creates an oxygen-free or low-oxygen protective atmosphere around the portion of the anode plate above the electrolyte surface, fundamentally inhibiting the oxidation and consumption of the upper part of the anode, thereby obtaining a rare earth iron master alloy with lower carbon content and higher purity.

Description

Technical Field

[0001] This invention relates to the field of rare earth metal electrolysis technology, specifically to a rare earth metal electrolytic cell and a method for preparing a high-purity rare earth iron master alloy. Background Technology

[0002] Rare earth iron master alloys (such as gadolinium iron alloy, dysprosium iron alloy, holmium iron alloy, yttrium iron alloy, etc.) are key raw materials for preparing high-performance rare earth permanent magnet materials, and their purity directly affects the performance of the final magnet. Currently, the production of rare earth iron master alloys generally adopts the oxide-fluoride system molten salt electrolysis process, using graphite as the anode, an iron rod as the consumable cathode, and REF-LiF as the molten salt electrolyte. Under the action of a DC electric field, rare earth oxides are electrolytically reduced to rare earth metals, which are then alloyed with iron to obtain rare earth iron alloys.

[0003] In the aforementioned electrolysis process, the graphite anode is not completely immersed in the molten salt electrolyte; a portion is exposed to the air above the electrolyte surface. The electrolysis temperature is typically maintained at around 1050℃. At such a high temperature, the portion of the anode exposed to air undergoes a violent oxidation reaction with oxygen, resulting in a significantly higher rate of wear compared to the lower portion of the anode, which is immersed in the electrolyte and only undergoes electrochemical consumption. After long-term operation, the anode exhibits an uneven wear pattern, being thinner at the top and thicker at the bottom. This not only shortens the overall lifespan of the anode, increases replacement frequency and production costs, but also leads to uneven anode current density distribution and increased cell voltage fluctuations during electrolysis, ultimately affecting the quality stability of rare earth ferroalloy products.

[0004] To address this issue, a common approach in existing technologies is to design the anode plate with an asymmetrical structure, thicker at the top and thinner at the bottom, in order to balance the difference in wear rates between the upper and lower parts by allowing for more wear margin. However, while this passive adaptive design delays the overall failure time of the anode to some extent, it does not fundamentally suppress the oxidation reaction at the top of the anode. The anode plate still suffers from localized excessively rapid wear and requires frequent replacement. During the replacement of the anode assembly, workers need to be close to the high-temperature radiation source and perform strenuous physical labor, which not only poses occupational health risks such as lumbar strain and burns, but also requires interrupting electrolysis during the replacement process, and the heating operation upon restarting results in additional energy consumption.

[0005] Furthermore, during the high-temperature oxidation process, the gases generated by the oxidation reaction can easily blow off the incompletely oxidized fine graphite particles from the upper part of the anode plate and carry them into the electrolytic cell. These graphite particles, along with the tumbling of the electrolyte, eventually flow into the crucible for collecting rare earth metals, resulting in a high carbon content in the rare earth iron master alloy product, severely affecting the product's purity. The existing "thick at the top, thin at the bottom" structural design can only slow down the rate of oxidation consumption, but it cannot suppress the shedding of graphite particles during oxidation, thus failing to effectively solve the problem of high carbon content in the product.

[0006] Therefore, how to fundamentally suppress the oxidation consumption of the upper part of the anode during the electrolysis process, while avoiding the shedding of graphite particles due to oxidation, thereby extending the service life of the anode, reducing the replacement frequency, and obtaining rare earth iron master alloys with lower carbon content and higher purity, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a rare earth metal electrolytic cell and a method for preparing high-purity rare earth iron master alloys. By setting up an anode isolation device, an oxygen-free or low-oxygen protective atmosphere is formed around the portion of the anode plate located above the electrolyte surface, fundamentally suppressing oxidation consumption at the top of the anode, thereby obtaining a rare earth iron master alloy with lower carbon content and higher purity.

[0008] To achieve the above objectives, the present invention provides a rare earth metal electrolytic cell, comprising a cell body, an anode conductive plate, and an anode assembly, wherein the anode assembly includes an anode plate and a clamp for fixing the anode plate to the anode conductive plate; and further comprising:

[0009] An anode isolation device is disposed outside the anode plate to form a relatively closed cavity around the portion of the anode plate above the electrolyte surface. By introducing a protective gas into the cavity, an oxygen-free or low-oxygen atmosphere is formed and / or maintained within the cavity, thereby inhibiting the oxidation and consumption of the portion of the anode plate above the electrolyte surface by oxygen.

[0010] The cavity has a gas escape channel that allows internal gas to escape outward, and the gas escape channel is configured to allow gas inside the cavity to escape outward while preventing external air from entering.

[0011] Furthermore, the anode isolation device includes:

[0012] An isolation cover, in the form of a cylindrical structure, is fitted over the outside of the anode plate, with its lower end extending below the electrolyte surface to form a cavity around the portion of the anode plate above the electrolyte surface;

[0013] A cover is provided on the clamp and covers the top of the isolation cover;

[0014] A connector is provided on each of the two sides of the upper end of the isolation cover, connecting the upper part of the isolation cover and the anode conductive plate, for fixing the isolation cover to the anode conductive plate;

[0015] A vent pipe, one end of which extends into the isolation hood and has at least one air outlet, and the other end of which extends out of the cavity through the fit between the isolation hood and the cover, for connection to an external protective gas source;

[0016] The gas escape channel includes the fitting gap between the isolation cover and the cover, and / or the vent hole opened on the cover.

[0017] Furthermore, the isolation cover is made of a ceramic matrix composite material that is electrically insulating, resistant to high temperatures above 1100°C, and resistant to corrosion by fluoride molten salts.

[0018] Furthermore, the isolation shield has a layered structure at least in the central region near the electrolyte surface, the layered structure comprising:

[0019] The inner layer is composed of the ceramic matrix composite material having a first resistivity;

[0020] The outer layer is composed of the ceramic matrix composite material having a second resistivity, which is lower than the first resistivity;

[0021] A conductive collection layer, embedded between the inner layer and the outer layer, is used to collect the charge accumulated on the surface of the shield;

[0022] The anode isolation device further includes:

[0023] A conductive circuit, one end of which is electrically connected to the conductive collection layer;

[0024] An electrostatic discharge ring is disposed on the outer side of the upper part of the isolation cover and electrically connected to the other end of the conductive line, for releasing the charge collected by the conductive collection layer into the air in the form of corona discharge;

[0025] The conductive circuit has high resistivity to limit the electrostatic discharge current and achieve slow discharge.

[0026] Furthermore, the ventilation tube includes:

[0027] An inflation tube, in the form of a ring, is disposed in the cavity and located above the electrolyte liquid level. The inflation tube has at least one air outlet for introducing the protective gas into the cavity.

[0028] The air supply pipe has one end connected to the air inflation pipe and the other end extending to the outside of the cavity through the fit between the isolation cover and the cover, for connecting to an external protective gas source.

[0029] The anode isolation device further includes two suspension members, which are respectively disposed at both ends of the isolation cover along its circumference. Each suspension member has a first hook at its lower end for holding the air inlet pipe; and a second hook at its upper end, which is hooked onto the top of the isolation cover to prevent the suspension member from falling into the electrolytic cell.

[0030] The lower surface of the cover has a first groove at a position corresponding to each of the second hooks, so that when the cover is placed on top of the isolation cover, the second hooks are received in the first groove; the lower surface of the cover also has a second groove to avoid the gas supply pipe, so that the gas supply pipe can extend from the mating point between the isolation cover and the cover to the outside of the cavity; the first groove and / or the second groove constitute part of the gas escape channel.

[0031] Furthermore, the opening direction of the air outlet on the inflation tube is inclined downward relative to the horizontal plane.

[0032] Furthermore, it also includes an anode plate anti-detachment mechanism, which comprises:

[0033] Two mounting holes are provided opposite to each other on the cover;

[0034] Two booms are respectively inserted into the two mounting holes, and each boom can move in the mounting hole in a direction close to or away from the anode plate; the upper end of each boom extends above the cover; the lower end of each boom has a support portion extending in a direction close to the anode plate.

[0035] Two third grooves are respectively formed on two opposite sidewalls of the anode plate, and the position of each third groove corresponds to the corresponding support portion;

[0036] Under normal operating conditions, the support portion is housed within the corresponding third groove but does not bear any load; when the fixed connection of the anode plate fails and causes the anode plate to fall downwards, the support portion supports the anode plate and prevents the anode plate from falling further.

[0037] Furthermore, the connector includes:

[0038] The first connecting arm is arranged vertically, and its lower end is used to be fixedly connected to the outer wall of the isolation cover. The first connecting arm has at least one U-shaped structure that is bent in a vertical plane.

[0039] The second connecting arm is arranged laterally, with one end fixedly connected to the upper end of the first connecting arm and the other end detachably fixed to the anode conductive plate.

[0040] The U-shaped structure is configured to absorb the displacement of the isolation shield relative to the anode conductive plate through its own elastic deformation when the isolation shield expands or contracts due to heat.

[0041] Furthermore, the inner and outer contours of the cross-section of the isolation cover are both fan-shaped, and the isolation cover has an outer arc side facing the inner wall of the tank.

[0042] The isolation cover has an axially extending stress relief groove on its outer surface at least on the outer arc side. The stress relief groove is configured to cut off the tensile stress transmission path of the isolation cover in the circumferential direction in order to release stress concentration caused by uneven thermal expansion.

[0043] Furthermore, this invention also provides a method for preparing a high-purity rare-earth iron master alloy, which is prepared using the aforementioned rare-earth metal electrolytic cell and includes the following steps:

[0044] The anode plate is fixed to the anode conductive plate by the clamp, the isolation cover is sleeved on the outside of the anode plate so that the lower end of the isolation cover extends below the electrolyte liquid surface, and the cover is placed on the top of the isolation cover to form a relatively closed cavity around the part of the anode plate above the electrolyte liquid surface.

[0045] Protective gas is introduced into the cavity through the vent pipe to form and / or maintain an oxygen-free or low-oxygen atmosphere in the cavity, thereby inhibiting the oxidation consumption of the upper part of the anode plate.

[0046] An electrolytic reaction is carried out to reduce rare earth oxides to rare earth metals at the cathode and alloy them with iron to obtain a high-purity rare earth iron master alloy.

[0047] By using the above method, the upper part of the anode plate is always in an oxygen-free or low-oxygen protective atmosphere during the electrolysis process, which effectively suppresses high-temperature oxidation consumption, makes the consumption of the anode plate more uniform, and helps to extend the service life of the anode, reduce the replacement frequency, and stabilize the electrolysis process parameters, thereby obtaining rare earth iron master alloy products with lower carbon content and higher purity.

[0048] The beneficial effects of this invention are:

[0049] 1. By using an isolation cover fitted over the anode plate and a cover placed on top of the isolation cover to form a relatively closed cavity around the portion of the anode plate above the electrolyte surface, and by introducing protective gas into the cavity through a vent pipe to create and / or maintain an oxygen-free or low-oxygen atmosphere, the portion of the anode plate above the electrolyte surface is effectively isolated from oxygen in the air throughout the entire electrolysis cycle. This fundamentally solves the problem of excessively rapid oxidation and consumption in this part, extends the service life of the anode plate, reduces the frequency of replacement, and lowers the safety risks and energy losses associated with replacement operations.

[0050] 2. Because the isolation cover creates an oxygen-free or low-oxygen protective atmosphere around the part of the anode plate above the electrolyte surface, the high-temperature oxidation reaction at the top of the anode plate is effectively suppressed, and the CO2 gas produced by oxidation is greatly reduced. This prevents the loose graphite inside the anode plate from falling into the electrolytic cell as unoxidized fine graphite particles under the scouring of CO2 gas. This reduces the pathway for graphite particles to enter the rare earth iron master alloy from the source, thereby effectively controlling the carbon content of the product and obtaining a rare earth iron master alloy with higher purity.

[0051] 3. Due to the layered structure adopted in the middle region of the isolation shield, the inner layer is composed of high resistivity ceramic matrix composite material, the outer layer is composed of medium resistivity ceramic matrix composite material, and the conductive collection layer is embedded between the inner and outer layers. Together with the conductive circuit and the electrostatic discharge ring, a complete electrostatic discharge path is formed. This allows the charge accumulated on the surface of the isolation shield to be controlled and introduced into the conductive collection layer through the outer layer, and then slowly discharged through the conductive circuit to the electrostatic discharge ring and safely released in the form of corona discharge. This avoids the thermal stress cracking of the isolation shield caused by surface flashover due to charge accumulation, and also eliminates the spark discharge and electrolytic electric field interference that may be generated by low resistance discharge, ensuring the long-term operational reliability of the isolation shield in high temperature and strong electric field environments.

[0052] 4. Because the lower first hook of the suspension component holds the inflation tube and the upper second hook is hooked to the top of the isolation cover, and the lower surface of the cover has a first groove and a second groove to accommodate the second hook and avoid the air supply tube respectively, the installation and fixing of the inflation tube and the air supply tube do not require any holes or slots to be made on the isolation cover, thus maintaining the structural integrity and airtightness of the isolation cover. At the same time, the first groove and the second groove also serve as part of the gas escape channel, realizing the integration of structural avoidance and gas escape functions.

[0053] 5. Because the first connecting arm of the connector has a U-shaped structure that bends in the vertical plane, when the isolation cover expands due to heat or contracts due to cooling, the U-shaped structure can absorb the displacement of the isolation cover relative to the anode conductive plate through its own elastic deformation, thereby effectively avoiding excessive thermal stress at the connection part of the ceramic isolation cover due to thermal expansion differences, and preventing the isolation cover from cracking due to thermal stress concentration.

[0054] 6. Due to the anode plate anti-detachment mechanism, the boom is movably inserted into the mounting hole on the cover, and its lower support is housed in the third groove on the side wall of the anode plate. Under normal operating conditions, it is in a standby state without bearing any load. When the pin between the clamp and the anode plate fails due to overheating, causing the anode plate to fall downwards, the support can immediately support the anode plate and prevent it from falling further. This provides redundant mechanical protection for the anode plate, independent of the main fixed connection, and significantly improves the operational safety of the electrolytic cell. Attached Figure Description

[0055] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0056] Figure 1 A perspective view of a rare earth metal electrolytic cell provided in an embodiment of the present invention;

[0057] Figure 2 A perspective view of an anode assembly provided in an embodiment of the present invention;

[0058] Figure 3 A perspective view of an anode isolation device provided in an embodiment of the present invention;

[0059] Figure 4 A perspective view of a cover provided according to an embodiment of the present invention;

[0060] Figure 5 A perspective view of a vent pipe and a suspension component provided in an embodiment of the present invention;

[0061] Figure 6 A perspective view of an inflation tube provided in an embodiment of the present invention, viewed from a low angle.

[0062] Figure 7 A perspective view of a portion of the structure of an anode plate anti-detachment mechanism provided in an embodiment of the present invention;

[0063] Figure 8 This is a side view of an isolation shield provided according to an embodiment of the present invention;

[0064] Figure 9 for Figure 8 Sectional view of plane AA in the middle;

[0065] Figure 10 A perspective view of the anode assembly, anode isolation device, and anode plate anti-detachment mechanism assembled together;

[0066] Figure 11 for Figure 1 A top view of a rare earth metal electrolytic cell from one perspective;

[0067] Figure 12 for Figure 11 BB section view in the middle;

[0068] Figure 13 for Figure 12 A schematic diagram of the structure of a rare earth metal electrolytic cell with the addition of a cathode and electrolyte.

[0069] Figure label:

[0070] 10. Tank body; 20. Anode conductive plate; 30. Anode assembly; 31. Anode plate; 32. Clamp; 321. Mounting plate; 322. Fixing arm; 33. Pin; 40. Clamping assembly; 41. Clamping seat; 42. Pressure plate; 43. Wedge block; 50. Anode isolation device; 51. Isolation cover; 511. Inner layer; 512. Outer layer; 513. Conductive collection layer; 514. Stress relief groove; 52. Cover; 521. First groove; 522. Second groove; 53. Connecting Components; 531, First connecting arm; 532, Second connecting arm; 54, Vent pipe; 541, Inflation pipe; 5411, Air outlet; 542, Air supply pipe; 55, Conductive circuit; 56, Static discharge ring; 57, Suspension component; 571, First hook; 572, Second hook; 60, Anode plate anti-detachment mechanism; 61, Mounting hole; 62, Lifting arm; 621, Support; 63, Third groove; 64, Load-bearing seat; 65, Locking bolt; 100, Cavity; 200, Cathode. Detailed Implementation

[0071] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0072] It should be noted that before describing the specific embodiments of the present invention, the electrolysis process principle and current conduction path of the rare earth iron master alloy involved in this application will be briefly explained in order to facilitate understanding of the technical background and improvement basis of the present invention.

[0073] The production of rare earth iron master alloys such as gadolinium iron alloy, dysprosium iron alloy, holmium iron alloy, and yttrium iron alloy involved in this application adopts an oxide-fluoride system molten salt electrolysis process. This process uses graphite as the anode, an iron rod as the consumable cathode, a crucible as the rare earth iron alloy receiver, REF3-LiF as the molten salt electrolyte system, and rare earth oxides (RE2O3) as the electrolytic raw material. The electrolysis temperature is controlled at approximately 1050℃.

[0074] Under the influence of a direct current electric field, rare earth ions (REs) dissolve in the electrolyte. 3+ On the surface of the iron cathode, oxygen ions are reduced to rare earth metals (RE), and simultaneously alloy with iron to form a rare earth iron alloy (RE-Fe), which then falls into the receiver along the cathode. 2- The oxygen is oxidized to oxygen (O2) on the anode surface, and then reacts with the graphite anode to produce CO2 and CO gas. The specific reaction is as follows:

[0075] Cathode: RE 3+ +3e→RE, RE+Fe→RE-Fe.

[0076] Anode: 2O 2 -2e→O 2 O 2 +C→CO 2 O 2 +2C→2CO.

[0077] In the electrolysis process described above, the current conduction path is as follows: positive terminal of the power supply → anode conductive plate → clamp → anode plate → electrolyte (molten salt) → cathode. Among these, the contact between the anode plate and the electrolyte (molten salt) is the key link in realizing the electrochemical reaction and current conduction.

[0078] like Figure 1-13 As shown, this application proposes an improved rare earth metal electrolytic cell based on the above-mentioned electrolysis process principle, addressing the problem of harmful oxidation and consumption of the portion of the anode plate located above the electrolyte surface.

[0079] In this embodiment, the rare earth metal electrolytic cell includes a cell body 10, an anode conductive plate 20, a cathode 200, an anode assembly 30, a clamping assembly 40, and an anode isolation device 50.

[0080] The tank 10 is circular, and a cathode 200 is disposed in the middle of the tank 10. The lower end of the cathode 200 is inserted below the electrolyte liquid surface inside the tank 10. The anode conductive plate 20 is installed on the top of the tank 10, and is usually square. It has cooling channels inside to allow coolant to enter and exit and cool the anode conductive plate 20.

[0081] like Figure 2As shown, the anode assembly 30 includes an anode plate 31, a clamp 32, and pins 33. Each rare earth metal electrolytic cell is provided with four anode assemblies 30, which are evenly distributed along the circumference of the cell body 10, with a certain distance maintained between adjacent anode assemblies 30. The anode plate 31 has a fan-shaped cross-section, and multiple pin holes are formed on its top surface. The clamp 32 includes a mounting plate 321 and a fixing arm 322. The mounting plate 321 is horizontally positioned on the top surface of the anode plate 31, and multiple through holes corresponding to the pin holes are formed on the mounting plate 321. The fixing arm 322 is L-shaped, including a vertical section connected to the mounting plate 321 and a horizontal section extending outward from the upper end of the vertical section. The horizontal section is used to rest on the anode conductive plate 20. The pins 33 are set one-to-one with the pin holes. After the pins 33 pass through the corresponding through holes on the mounting plate 321, they are inserted into the corresponding pin holes and achieve an interference fit with the pin holes, thereby connecting the mounting plate 321 and the anode plate 31 together.

[0082] like Figure 1 As shown, the clamping assembly 40 includes a clamping seat 41, a pressure plate 42, and a wedge block 43. The clamping seat 41 is fixed to the anode conductive plate 20. Each clamping assembly 40 includes two opposing clamping seats 41, which are L-shaped. The pressure plate 42 is placed below the two clamping seats 41 and above the horizontal section of the fixing arm 322. The fixing arm 322 is clamped onto the anode conductive plate 20 by inserting the wedge block 43 between the pressure plate 42 and the horizontal section of the fixing arm 322, thus fixing the anode assembly 30 onto the anode conductive plate 20.

[0083] The specific structures of the aforementioned tank 10, anode conductive plate 20, anode assembly 30, and clamping assembly 40 are all existing technologies and will not be described in detail here.

[0084] like Figure 3 As shown, the anode isolation device 50 is disposed outside the anode plate 31, and its function is to form a relatively closed cavity 100 around the portion of the anode plate 31 located above the electrolyte surface. The anode isolation device 50 introduces a protective gas into the cavity 100 to form and / or maintain an oxygen-free or low-oxygen atmosphere within the cavity 100, thereby effectively inhibiting the oxidation reaction of the portion of the anode plate 31 located above the electrolyte surface with oxygen and thus preventing its consumption.

[0085] The protective gas can be an inert gas, such as N2, or CO2, with CO2 being preferred. CO2 is denser than air, and upon introduction, it naturally sinks and fills the lower part of cavity 100, effectively displacing air. In the initial stage after replacing the anode plate 31, the protective gas is introduced into cavity 100 to expel the existing air and oxygen, quickly establishing an oxygen-free or low-oxygen atmosphere. Since cavity 100 is not completely sealed, the protective gas will slowly escape, but the slight positive pressure within cavity 100 prevents external air from entering. During electrolysis, the CO2 and / or CO gas produced by the anode reaction continuously replenishes cavity 100. Therefore, after the initial introduction of the protective gas, subsequent continuous introduction is not necessary, or it can be introduced intermittently as needed to maintain an oxygen-free or low-oxygen atmosphere within cavity 100.

[0086] The cavity 100 has a gas escape channel. The gas escape channel allows the protective gas and electrolysis-generated gas accumulated inside the cavity 100 to escape to the outside, while the slight positive pressure of the gas inside the cavity 100 prevents the entry of external air. This one-way ventilation mechanism enables the cavity 100 to continuously maintain a stable atmosphere of no oxygen or low oxygen.

[0087] By adopting the technical solution of this embodiment, the portion of the anode plate 31 located above the electrolyte liquid surface is under the protection of the atmosphere throughout the entire electrolysis working cycle, effectively isolating it from oxygen in the air. This fundamentally solves the problem of excessively rapid oxidation and consumption of this portion, thereby helping to extend the service life of the anode plate 31, reduce the frequency of replacement, stabilize the electrolysis process parameters, and reduce the safety risks and energy losses caused by replacement operations.

[0088] Meanwhile, the installation of the isolation cover 51 also produces another beneficial technical effect: effectively suppressing the phenomenon of excessively high carbon content in rare earth iron master alloy products. The mechanism is as follows: during actual electrolysis, the current is mainly conducted to the anode plate 31 through the clamp 32. Theoretically, the mounting plate 321, as the ideal conductive component in the design, undertakes the function of current conduction. However, because the contact between the mounting plate 321 and the top surface of the anode plate 31 is not ideal, the contact resistance is relatively high. The pin 33 and the pin hole have an interference fit, resulting in a tighter contact and providing a lower resistance conduction path for the current. This causes a large amount of current to concentrate through the pin 33, generating significant Joule heating at the pin 33, leading to a relatively higher local temperature in the upper part of the anode plate 31 (usually referring to the area approximately 100mm downwards from the top). At this higher local temperature, the oxidation reaction in this area is more intense. The anode plate 31 is usually formed by powder pressing during production, resulting in a denser exterior and a relatively porous interior. When the dense graphite layer on the outer side of the upper part of the anode plate 31 is completely consumed by oxidation, the loose graphite inside is more easily detached as unoxidized fine graphite particles and fall into the electrolytic cell under the scouring action of the CO2 gas generated by oxidation. As the electrolyte tumbles up and down, these fine graphite particles eventually flow into the crucible for collecting rare earth metals, resulting in a high carbon content in the rare earth iron master alloy product and reducing product quality. By setting up an isolation cover 51 to provide a gas protection environment, the oxidation reaction on the upper part of the anode plate 31 is suppressed, and the detachment of graphite particles caused by severe oxidation and CO2 gas scouring is also avoided. This reduces the pathway for graphite particles to enter the rare earth iron master alloy from the source, effectively controls the carbon content of the product, and obtains a rare earth iron master alloy with higher purity.

[0089] In one embodiment, such as Figure 3-6 as well as Figure 12 As shown, the anode isolation device 50 includes an isolation cover 51, a cover 52, a connector 53, and a vent pipe 54.

[0090] The isolation cover 51 has a cylindrical structure and is fitted over the outside of the anode plate 31. The lower end of the isolation cover 51 extends appropriately below the electrolyte surface to form a cavity 100 around the portion of the anode plate 31 above the electrolyte surface, while avoiding excessive insertion to reduce unnecessary material consumption and molten salt disturbance. The cavity 100 is formed by the inner wall of the isolation cover 51, the outer surface of the anode plate 31, the lower surface of the cover 52, and the electrolyte surface. The upper end of the isolation cover 51 is close to the anode conductive plate 20.

[0091] like Figure 4As shown, the cover 52 is mounted on the clamp 32, preferably fixed to the mounting plate 321 of the clamp 32 via a detachable connection, such as by bolts. The cover 52 covers the top of the isolation cover 51. The cover 52 can be removed or placed together with the clamp 32 and the anode plate 31 without obstructing the replacement of the anode plate 31. After the cover 52 is closed, there is not a tight seal between the cover 52 and the top of the isolation cover 51, but a fitting gap exists, which constitutes part of the gas escape channel. In addition, vent holes can also be provided on the cover 52 as needed to further enrich the composition of the gas escape channel.

[0092] like Figure 3 and Figure 10 As shown, there are two connectors 53 on each side of the upper end of the isolation cover 51, which are used to fix the isolation cover 51 to the anode conductive plate 20. The connectors 53 bear the weight of the isolation cover 51 itself and ensure that the isolation cover 51 maintains a stable spatial position in the electrolytic cell.

[0093] like Figure 5 As shown, one end of the vent pipe 54 extends into the isolation cover 51, and the extended end has at least one vent 5411 for introducing protective gas into the cavity 100. The other end of the vent pipe 54 extends to the outside of the cavity 100 through the mating joint between the isolation cover 51 and the cover 52, for connecting to an external protective gas source (such as a CO2 cylinder). The extension of the vent pipe 54 makes full use of the existing mating gap between the isolation cover 51 and the cover 52, eliminating the need for additional extension holes on the isolation cover 51 and maintaining the structural integrity of the isolation cover 51.

[0094] The isolation enclosure 51 needs to withstand high temperatures of 1050℃ to 1100℃ under normal operating conditions, be exposed to molten fluoride salts composed of REF3-LiF and their vapor environment for extended periods, and be situated in a strong electric field with a field strength of 200-500V / m between the anode and cathode 200. Therefore, the isolation enclosure 51 should be made of a material with comprehensive properties such as high temperature resistance, electrolyte corrosion resistance, electrical insulation, and thermal shock resistance. Candidate materials that meet the above requirements include Si3N4-SiC composite materials, SiC-based composite materials, and other nitride ceramics and other ceramic matrix composite materials.

[0095] In one embodiment, the isolation cover 51 is made of a ceramic matrix composite material that is electrically insulating, resistant to temperatures above 1100°C, and resistant to corrosion by fluoride molten salts. This ceramic matrix composite material is preferably a Si3N4-SiC composite material. The Si3N4-SiC composite material maintains good chemical stability and electrical insulation properties at electrolysis temperatures ranging from 1050°C to 1100°C, and has sufficient thermal shock resistance to withstand repeated temperature cycling.

[0096] Using Si3N4-SiC ceramic matrix composite material as the material of the isolation cover 51 ensures that the isolation cover 51 will not form a conductive channel that interferes with electrolysis in the strong electric field of the electrolytic cell, and will not undergo significant chemical corrosion or performance degradation under high temperature and strong corrosive atmosphere, thus ensuring the long-term operational reliability of the anode isolation device 50.

[0097] In one embodiment, Si3N4-SiC ceramic exhibits semiconductor properties due to intrinsic excitation at temperatures above 1050°C, resulting in a decrease in bulk resistance. Simultaneously, fluoride molten salt vapor condenses on the ceramic surface, forming an ionicly conductive liquid film. Under the strong electric field of the electrolytic cell, a large amount of induced charge easily accumulates on the surface of the isolation cover 51. If these charges cannot be effectively discharged, they may accumulate to a certain level and trigger surface flashover. The localized high temperature generated by the flashover can lead to thermal stress cracking of the ceramic, causing catastrophic failure of the isolation cover 51.

[0098] To address the aforementioned issues, in this embodiment, the isolation shield 51 has a layered structure at least in the central region near the electrolyte surface, which is the area with the highest risk of charge accumulation and flashover. Both the upper and lower parts of the isolation shield 51 are made of a high-resistivity Si3N4-SiC ceramic matrix composite material, eliminating the need for layering. Figure 8 and Figure 9 As shown, the middle layered structure includes an inner layer 511, an outer layer 512, and a conductive collection layer 513.

[0099] The inner layer 511 is composed of a Si3N4-SiC ceramic matrix composite material with a first resistivity, which is typically greater than 10 at room temperature. 14 The resistivity is Ω·cm, which falls within the high resistivity range. The inner layer 511 faces the anode plate 31, and its core function is to maintain the main insulation. It is important to note that the inner layer 511 must have high resistivity rather than medium or low resistivity because: the inner layer 511 and the electrolyte are connected in parallel in the strong electric field between the anode and cathode 200, sharing the electrolysis voltage. If the inner layer 511 has medium resistivity, its bulk resistance will be significantly reduced, resulting in a considerable parallel leakage current. This would cause unnecessary energy loss during electrolysis, and the uneven conduction of the leakage current within the ceramic body could lead to localized current concentrations at grain boundaries, micro-defects, etc., accelerating the deterioration of the ceramic material. The high resistivity of the inner layer 511 limits this parallel leakage current to the negligible picoampere to nanoampere level, ensuring that the vast majority of the electrolysis current is used for effective electrolysis. The resistivity of the upper and lower parts of the isolation cover 51 is the same as or similar to that of the inner layer 511.

[0100] The outer layer 512 is composed of a Si3N4-SiC ceramic matrix composite material with a second resistivity lower than the first resistivity, typically 10 Ω·cm at room temperature. 8 -10 10The resistivity of the outer layer 512 (Ω·cm) falls under the category of electrostatic dissipative materials. The resistivity of the outer layer 512 can be achieved by adding a conductive phase to the Si3N4-SiC matrix, such as TiC or TiN. The resistivity of the outer layer 512 can be precisely controlled to fall within the target range by adjusting the volume fraction of the conductive phase. The function of the outer layer 512 is to provide a controlled bulk conductivity migration path for the charge accumulated on the surface of the shield 51, guiding the charge to the conductive collection layer 513 and preventing excessive charge accumulation on the surface.

[0101] A conductive collection layer 513 is embedded between the inner layer 511 and the outer layer 512, for example, using a molybdenum wire mesh woven from molybdenum wires with a diameter of about 0.3 mm and a mesh count of 10-20. The conductive collection layer 513 is in close contact with the inner layer 511 and the outer layer 512 to efficiently collect charges from the outer layer 512.

[0102] like Figure 3 and Figure 10 As shown, the anode isolation device 50 also includes a conductive line 55 and an electrostatic discharge ring 56. One end of the conductive line 55 is electrically connected to the conductive collection layer 513, and the other end is electrically connected to the electrostatic discharge ring 56. The conductive line 55 has a high resistivity, with a resistance value typically in the range of 10 ohms. 12 The current is on the order of Ω to limit the electrostatic discharge current, so that the charge is discharged slowly when passing through the conductive line 55.

[0103] The conductive lines 55 can be directly formed on the outer wall of the isolation cover 51 using thick film printing technology. Specifically, after the isolation cover 51 is sintered, high-temperature metal paste is printed onto the outer surface of the isolation cover 51 along a preset path using screen printing or micro-pen direct writing technology. After high-temperature sintering, a conductive track is formed that is firmly bonded to the ceramic substrate. The conductive lines 55 extend downwards along the outer wall of the isolation cover 51 to the central region, and then achieve electrical connection with the internal conductive collection layer 513 through conductive through holes formed during the co-firing process of the isolation cover 51, without the need to drill additional holes in the finished isolation cover 51.

[0104] An electrostatic discharge ring 56 is disposed on the outer side of the upper part of the isolation cover 51. The electrostatic discharge ring 56 can be made of an oxide dispersion-strengthened high-temperature alloy, such as MA956 or PM2000. A nickel-based high-temperature alloy, such as GH3044, can also be used. The electrostatic discharge ring 56 is fixed to the outer surface of the isolation cover 51 by active metal brazing. The electrostatic discharge ring 56 collects the charge collected by the conductive collection layer 513 and conducted through the conductive line 55, and releases it safely and spark-free into the surrounding air in the form of corona discharge.

[0105] In this embodiment, the layered structure, conductive line 55, and electrostatic discharge ring 56 together constitute a complete electrostatic protection system: the outer layer 512 acquires surface charge and guides it into the body in a controlled manner, the conductive collection layer 513 efficiently collects charge, the conductive line 55 limits the discharge rate, and the electrostatic discharge ring 56 achieves the final safe discharge.

[0106] In one embodiment, such as Figure 5 As shown, the vent pipe 54 includes an inflation pipe 541 and a gas supply pipe 542. The inflation pipe 541 is annular, disposed within the cavity 100 and above the electrolyte level, surrounding the anode plate 31. The inflation pipe 541 has at least one outlet 5411 from which protective gas is ejected, supplying gas into the cavity 100. One end of the gas supply pipe 542 is connected to the inflation pipe 541, and the other end extends to the outside of the cavity 100 via the mating joint between the isolation cover 51 and the cover 52, for connection to an external protective gas source. The gas supply pipe 542 is preferably arranged against the inner wall of the isolation cover 51 to reduce its occupation of space within the cavity 100 and to avoid interference with the anode plate 31.

[0107] like Figure 5 As shown, the anode isolation device 50 also includes two suspension members 57. The two suspension members 57 are respectively disposed at both ends of the isolation cover 51 along its circumference. Each suspension member 57 has a first hook 571 at its lower end for holding the inflation tube 541; each suspension member 57 has a second hook 572 at its upper end, which hooks onto the top of the isolation cover 51. The suspension members 57 achieve reliable suspension and fixation of the inflation tube 541 within the cavity 100 through the hook structure at both ends. This entire fixing method completely eliminates the need for any holes or slots to be opened on the inner wall of the isolation cover 51, maintaining the structural integrity of the isolation cover 51.

[0108] The lower surface of the cover 52 has a first groove 521 at a position corresponding to each second hook 572. When the cover 52 is placed on top of the isolation cover 51, the second hook 572 is received in the first groove 521, ensuring that the cover 52 can close smoothly without interfering with the second hook 572. The cross-sectional dimension of the first groove 521 may be slightly larger than the cross-sectional dimension of the second hook 572, so that the cover 52 can still close smoothly even if there is a certain installation error.

[0109] The lower surface of the cover 52 is also provided with a second groove 522 to avoid the gas supply pipe 542, so that the gas supply pipe 542 can smoothly extend from the mating area between the isolation cover 51 and the cover 52 to the outside of the cavity 100, and the gas supply pipe 542 will not be flattened or bent by the cover 52. The cross-sectional dimension of the second groove 522 is slightly larger than the cross-sectional dimension of the gas supply pipe 542, providing appropriate tolerance space for the gas supply pipe 542. The first groove 521 and the second groove 522 not only serve to avoid the gas supply pipe, but also serve as part of the gas escape channel, forming a complete path for the gas to escape outward together with the mating gap between the isolation cover 51 and the cover 52.

[0110] The inflation tube 541 and the air supply tube 542 can be made of high-temperature and corrosion-resistant metal materials, such as heat-resistant stainless steel 310S.

[0111] In one embodiment, such as Figure 6 As shown, the opening direction of the air outlet 5411 on the inflation tube 541 is inclined downward relative to the horizontal plane. Preferably, the inclination angle ranges from 30° to 60°. After the protective gas is ejected downward, it diffuses downward along the outer surface of the anode plate 31, forming an upward air curtain around the anode plate 31, which helps to fully displace the residual air in the cavity 100. At the same time, the downward-sloping opening can effectively reduce the risk of molten salt splashes or electrolyte vapors entering the air outlet 5411 and causing blockage. In addition, carbon dioxide gas is denser than air, and it naturally sinks after being ejected downward, further enhancing the maintenance effect of the oxygen-free or low-oxygen environment in the cavity 100.

[0112] In one embodiment, due to the concentrated current passing through pin 33, significant Joule heating is generated at pin 33, leading to localized overheating. This heat is conducted to the upper part of the anode plate 31, and combined with the heat insulation effect of the isolation cover 51, the temperature of the upper part of the anode plate 31 rises significantly. Under these conditions, the interference fit between pin 33 and anode plate 31 may loosen or even fail due to thermal creep, posing a safety hazard of the anode plate 31 falling downwards into the electrolytic cell. Therefore, the rare earth metal electrolytic cell of this embodiment also includes an anode plate anti-detachment mechanism 60. Figure 2 , Figure 4 and Figure 7 As shown, the anode plate anti-detachment mechanism 60 includes two mounting holes 61, two lifting arms 62, and two third grooves 63.

[0113] Two mounting holes 61 are formed opposite to each other on the cover 52. Two lifting arms 62 are respectively inserted into the two mounting holes 61. Each lifting arm 62 can move within the mounting hole 61 in a direction close to or away from the anode plate 31. The upper end of each lifting arm 62 extends above the cover 52, facilitating manipulation by the operator outside the cover 52. The lower end of each lifting arm 62 has a support portion 621 extending towards the anode plate 31. Because the lifting arms 62 can move within the mounting holes 61, the cross-sectional dimension of the mounting holes 61 is larger than the cross-sectional dimension of the portion of the lifting arms 62 within the mounting holes 61. Thus, the mounting holes 61 also serve as part of the gas escape channel, forming a complete path for gas to escape outward together with the fitting clearance between the isolation cover 51 and the cover 52.

[0114] Two third grooves 63 are respectively formed on two opposite side walls of the anode plate 31, and the position of each third groove 63 corresponds to the corresponding support part 621.

[0115] Under normal electrolysis conditions, the support portion 621 is housed within the corresponding third groove 63, but is in a "standby" state and does not bear the load from the anode plate 31. An appropriate gap may be left between the support portion 621 and the groove wall of the third groove 63 to accommodate the thermal expansion of the anode plate 31 at high temperatures and to prevent compression between the anode plate 31 and the support portion 621 during expansion.

[0116] When the pin 33 between the clamp 32 and the anode plate 31 fails to secure the connection due to overheating or other factors, the anode plate 31 begins to detach downwards under gravity. At this time, the support part 621 immediately contacts the groove wall of the third groove 63, supporting the anode plate 31 and preventing it from falling further. The anode plate anti-detachment mechanism 60 constitutes redundant mechanical protection independent of the main fixed connection, effectively improving the operational safety of the electrolytic cell.

[0117] When replacing the anode plate 31, the operator can move the upper end of the boom 62 above the cover 52 to move the support part 621 away from the anode plate 31, thus removing it from the third groove 63 and releasing the constraint on the anode plate 31, making it easier to remove the anode plate 31 smoothly.

[0118] In a further preferred embodiment, the anode plate anti-detachment mechanism 60 further includes a support base 64 and a locking bolt 65. The support base 64 is fixedly connected to the upper end of each boom 62. The cross-sectional dimension of the support base 64 is larger than the cross-sectional dimension of the mounting hole 61 to limit the boom 62 to above the cover 52 and prevent the boom 62 from slipping out of the mounting hole 61. The locking bolt 65 passes through the support base 64. When the support portion 621 is received in the corresponding third groove 63, the operator can tighten the locking bolt 65 to lock the boom 62 in the current position, preventing the boom 62 from moving due to equipment vibration or other unexpected factors, and ensuring that the support portion 621 is always in a reliable standby position.

[0119] In one embodiment, the connector 53 is used to fix the isolation cover 51 to the anode conductive plate 20. Since the isolation cover 51 is made of Si3N4-SiC ceramic matrix composite material, while the anode conductive plate 20 is typically made of metal, there is a significant difference in their coefficients of thermal expansion at high temperatures. If the connector 53 is a rigid structure, the thermal stress generated during the heating and cooling process may concentrate at the connection point of the isolation cover 51, leading to ceramic cracking.

[0120] To solve the above problems, such as Figure 3 and Figure 10 As shown, the connector 53 in this embodiment includes a first connecting arm 531 and a second connecting arm 532. The first connecting arm 531 is arranged vertically, and its lower end is used for fixed connection with the outer wall of the isolation cover 51, for example, by active metal brazing to achieve a reliable connection. The first connecting arm 531 has at least one U-shaped structure bent in a vertical plane. The second connecting arm 532 is arranged laterally, with one end fixedly connected to the upper end of the first connecting arm 531, and the other end detachably fixed to the anode conductive plate 20.

[0121] The U-shaped structure endows the first connecting arm 531 with elastic deformation capability. During the heating process of the electrolytic cell, when the isolation cover 51 and the anode conductive plate 20 experience relative displacement due to differences in thermal expansion, the U-shaped structure absorbs this displacement through its own elastic bending deformation, avoiding excessive thermal stress at the connection point of the isolation cover 51. During the cooling and shrinking process, the U-shaped structure also adapts to dimensional changes through elastic recovery. This flexible connection design effectively protects the ceramic isolation cover 51 from the risk of thermal stress cracking.

[0122] The detachable connection between the second connecting arm 532 and the anode conductive plate 20 facilitates the on-site installation and regular maintenance of the isolation cover 51. The connector 53 can be made of materials with high temperature resistance, corrosion resistance and good elasticity, such as ODS high temperature alloy, for example, MA956 or PM2000.

[0123] In one embodiment, the cross-section of the anode plate 31 is a fan-shaped annulus. To ensure uniform wall thickness at all points when the isolation cover 51 is fitted over the anode plate 31, thereby guaranteeing uniform thermal expansion and overall structural strength, the inner and outer contours of the cross-section of the isolation cover 51 are also designed as fan-shaped annulus lines that match the anode plate 31. Therefore, both the inner and outer contours of the cross-section of the isolation cover 51 are fan-shaped annulus lines.

[0124] The geometric characteristics of the fan-shaped ring determine that the arc length of the outer arc side is greater than that of the inner arc side. When the isolation shield 51 is heated from room temperature to an operating temperature above 1000℃, the expansion of the material on the outer arc side is greater than that on the inner arc side, resulting in circumferential tensile stress on the outer arc side and circumferential compressive stress on the inner arc side. The tensile strength of ceramic materials is much lower than their compressive strength; therefore, the tensile stress on the outer arc side is the main risk factor for thermal stress cracking of the isolation shield 51.

[0125] To relieve the aforementioned tensile stress concentration, such as Figure 3 As shown, in this embodiment, the isolation cover 51 has an outer arc side facing the inner wall of the groove 10. At least on the outer surface of this outer arc side, the isolation cover 51 has an axially extending stress relief groove 514. The stress relief groove 514 extends axially along the isolation cover 51, and its direction is perpendicular to the direction of the circumferential tensile stress, thereby effectively cutting off the transmission path of the circumferential tensile stress and forming a stress relief zone at the tip of the groove, avoiding large-area stress concentration. The depth of the stress relief groove 514 preferably does not exceed one-third of the total wall thickness of the isolation cover 51, and the groove cross-section can be V-shaped to release stress without excessively weakening the structural strength of the isolation cover 51. When necessary, a stress relief groove 514 can also be formed on the outer surface of the inner arc side of the isolation cover 51. The stress relief groove 514 can be formed after the isolation cover 51 has been sintered and molded by laser processing or ultrasonic vibration processing, etc.

[0126] In one embodiment, a method for preparing a high-purity rare earth iron master alloy is provided, which is carried out using the rare earth metal electrolytic cell described in any of the above embodiments, and specifically includes the following steps.

[0127] First, the anode plate 31 is fixed to the anode conductive plate 20 using the clamp 32. The isolation cover 51 is then fitted over the anode plate 31, with its lower end extending below the electrolyte level. The cover 52 is then placed over the top of the isolation cover 51. After the above installation is completed, a relatively enclosed cavity 100 is formed around the portion of the anode plate 31 located above the electrolyte level.

[0128] Then, a protective gas, such as carbon dioxide, is introduced into the cavity 100 through the vent pipe 54. Upon entering the cavity 100, the protective gas displaces the existing air and oxygen, creating an oxygen-free or low-oxygen atmosphere within the cavity 100. As the electrolysis reaction proceeds, the carbon dioxide and carbon monoxide produced by the anode reaction are continuously added to the cavity 100, working together with the initially introduced protective gas to maintain the oxygen-free or low-oxygen state within the cavity 100. The gas within the cavity 100 continuously escapes through the gas escape channel, maintaining a slight positive pressure, preventing external air from entering.

[0129] The electrolytic reaction was carried out under the aforementioned protective atmosphere. Rare earth oxides dissolved in the electrolyte, RE 3+ On the surface of the iron cathode 200, the rare earth metals are reduced to rare earth metals and alloyed with iron to form a rare earth iron alloy, which falls into an iron crucible. The molten rare earth iron alloy is periodically removed from the furnace and cast into a high-purity rare earth iron master alloy ingot after cooling.

[0130] Using the preparation method of this embodiment, the upper part of the anode plate 31 is always in a protective atmosphere throughout the electrolysis process, effectively suppressing high-temperature oxidation consumption and making the consumption of the anode plate 31 more uniform. This is beneficial for extending the anode's service life, reducing the replacement frequency, and stabilizing the electrolysis process parameters. At the same time, because the oxidation reaction is suppressed, the CO2 gas generated by oxidation is greatly reduced, avoiding the shedding of loose graphite particles inside, thereby obtaining a rare earth iron master alloy product with lower carbon content and higher purity.

[0131] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A rare earth metal electrolytic cell comprising a cell body (10), an anode current collector plate (20) and an anode assembly (30), the anode assembly (30) comprising an anode plate (31) and a clamp (32) for securing the anode plate (31) to the anode current collector plate (20), characterised in that, Also includes: An anode isolation device (50) is disposed outside the anode plate (31) to form a relatively closed cavity (100) around the portion of the anode plate (31) above the electrolyte liquid surface, and to form and / or maintain an oxygen-free or low-oxygen atmosphere in the cavity (100) by introducing a protective gas into the cavity (100), thereby inhibiting the oxidation and consumption of the portion of the anode plate (31) above the electrolyte liquid surface by oxygen. The cavity (100) has a gas escape passage that allows internal gas to escape outward, the gas escape passage being configured to allow gas inside the cavity (100) to escape outward while preventing external air from entering.

2. The rare earth metal electrolytic cell according to claim 1, characterized in that, The anode isolation device (50) includes: An isolation cover (51) has a cylindrical structure and is fitted over the outside of the anode plate (31). Its lower end extends below the electrolyte liquid surface to form the cavity (100) around the portion of the anode plate (31) above the electrolyte liquid surface. A cover (52) is disposed on the clamp (32) and covers the top of the isolation cover (51); Connectors (53) are provided on both sides of the upper end of the isolation cover (51), connecting the upper part of the isolation cover (51) and the anode conductive plate (20), for fixing the isolation cover (51) to the anode conductive plate (20); and A vent pipe (54) has one end inserted into the isolation cover (51) and has at least one vent (5411), and the other end extends out of the cavity (100) through the mating part between the isolation cover (51) and the cover (52) for connection to an external protective gas source. The gas escape channel includes the fitting gap between the isolation cover (51) and the cover (52), and / or the vent hole opened on the cover (52).

3. The rare earth metal electrolytic cell according to claim 2, characterized in that, The isolation cover (51) is made of a ceramic matrix composite material that is electrically insulating, resistant to high temperatures above 1100°C, and resistant to corrosion by fluoride molten salts.

4. The rare earth metal electrolytic cell according to claim 3, characterized in that, The isolation shield (51) has a layered structure at least in the central region near the electrolyte surface, the layered structure comprising: The inner layer (511) is composed of the ceramic matrix composite material having a first resistivity; The outer layer (512) is composed of the ceramic matrix composite material having a second resistivity lower than the first resistivity; and A conductive collection layer (513) is embedded between the inner layer (511) and the outer layer (512) for collecting the charge accumulated on the surface of the shield (51); The anode isolation device (50) further includes: Conductive line (55), one end of which is electrically connected to the conductive collection layer (513); and An electrostatic discharge ring (56) is disposed on the outer side of the upper part of the isolation cover (51) and electrically connected to the other end of the conductive line (55) for releasing the charge collected by the conductive collection layer (513) into the air in the form of corona discharge; The conductive line (55) has a high resistivity to limit the electrostatic discharge current and achieve slow discharge.

5. The rare earth metal electrolytic cell according to claim 2, characterized in that, The ventilation tube (54) includes: An inflation tube (541), in a ring shape, is disposed within the cavity (100) and above the electrolyte level. The inflation tube (541) has at least one outlet (5411) for introducing the protective gas into the cavity (100); and The gas supply pipe (542) has one end connected to the inflation pipe (541) and the other end extends to the outside of the cavity (100) through the mating part between the isolation cover (51) and the cover (52) for connecting to an external protective gas source. The anode isolation device (50) further includes two suspension members (57), which are respectively disposed at both ends of the isolation cover (51) along its circumference. Each suspension member (57) has a first hook (571) at its lower end for holding the air inlet pipe (541); each suspension member (57) has a second hook (572) at its upper end, which is hooked to the top of the isolation cover (51) to prevent the suspension member (57) from falling into the electrolytic cell. The lower surface of the cover (52) has a first groove (521) at a position corresponding to each of the second hooks (572), so that when the cover (52) is placed on the top of the isolation cover (51), the second hooks (572) are received in the first groove (521); the lower surface of the cover (52) also has a second groove (522) to avoid the gas supply pipe (542), so that the gas supply pipe (542) can extend from the mating point between the isolation cover (51) and the cover (52) to the outside of the cavity (100); the first groove (521) and / or the second groove (522) constitute part of the gas escape channel.

6. The rare earth metal electrolytic cell according to claim 5, characterized in that, The opening direction of the air outlet (5411) on the air inflator (541) is inclined downward relative to the horizontal plane.

7. The rare earth metal electrolytic cell according to claim 2, characterized in that, It also includes an anode plate anti-detachment mechanism (60), which includes: Two mounting holes (61) are provided opposite to each other on the cover (52); Two booms (62) are respectively inserted into the two mounting holes (61), each boom (62) being movable within the mounting hole (61) in a direction approaching or away from the anode plate (31); the upper end of each boom (62) extends above the cover (52); the lower end of each boom (62) has a support portion (621) extending in a direction approaching the anode plate (31); and Two third grooves (63) are respectively opened on two opposite side walls of the anode plate (31), and the position of each third groove (63) corresponds to the corresponding support part (621); Under normal operating conditions, the support part (621) is housed in the corresponding third groove (63) but does not bear any load; when the fixed connection of the anode plate (31) fails and the anode plate (31) falls downward, the support part (621) supports the anode plate (31) and prevents the anode plate (31) from falling further.

8. The rare earth metal electrolytic cell according to claim 2, characterized in that, The connector (53) includes: A first connecting arm (531), arranged vertically, has its lower end for fixed connection to the outer wall of the isolation cover (51). The first connecting arm (531) has at least one U-shaped structure bent in a vertical plane. The second connecting arm (532) is arranged laterally, with one end fixedly connected to the upper end of the first connecting arm (531) and the other end detachably fixed to the anode conductive plate (20). The U-shaped structure is configured to absorb the displacement of the isolation shield (51) relative to the anode conductive plate (20) through its own elastic deformation when the isolation shield (51) expands or contracts due to heat.

9. The rare earth metal electrolytic cell according to claim 3, characterized in that, The inner and outer contours of the cross-section of the isolation cover (51) are both fan-shaped, and the isolation cover (51) has an outer arc side facing the inner wall of the groove (10). The isolation cover (51) has an axially extending stress relief groove (514) on its outer surface at least on the outer arc side. The stress relief groove (514) is configured to cut off the tensile stress transmission path of the isolation cover (51) in the circumferential direction to release stress concentration caused by uneven thermal expansion.

10. A method for producing a high-purity rare earth iron master alloy, using the rare earth metal electrolytic cell according to any one of claims 2 to 9, characterized in that, Includes the following steps: The anode plate (31) is fixed to the anode conductive plate (20) by the clamp (32), and the isolation cover (51) is sleeved on the outside of the anode plate (31) so that the lower end of the isolation cover (51) extends below the electrolyte liquid surface. The cover (52) is placed on the top of the isolation cover (51) to form a relatively closed cavity (100) around the part of the anode plate (31) above the electrolyte liquid surface. Protective gas is introduced into the cavity (100) through the vent pipe (54) to form and / or maintain an oxygen-free or low-oxygen atmosphere in the cavity (100) and suppress oxidation consumption of the upper part of the anode plate (31); An electrolytic reaction is carried out to reduce rare earth oxides to rare earth metals at the cathode (200) and alloy them with iron to obtain a high-purity rare earth iron master alloy.

Images