Rare earth electrolytic bath insulating material and application thereof

Abstract

The invention discloses a rare earth electrolytic cell insulating material and application thereof, and belongs to the technical field of rare earth molten salt electrolysis. Comprising a surface anti-seepage layer, a reinforced insulating layer and a structure supporting layer which are sequentially arranged from inside to outside, the surface anti-seepage layer is formed by curing plastic, and the plastic is prepared by uniformly mixing a base material, a reinforcing material, an auxiliary filler and a refractory material adhesive; the reinforced insulating layer is composed of a special-shaped brick prepared by mixing rare earth oxyfluoride, aluminum oxide and boron nitride, performing dry pressing, performing cold isostatic pressing and sintering; the structure supporting layer is composed of refractory bricks. In the electrolysis production process, the problems of excessive consumption of the graphite crucible, leakage of the electrolytic cell and the like caused by failure of the insulating layer can be greatly reduced, the overall service life of the praseodymium-neodymium electrolytic cell is remarkably prolonged, and the stability and continuity of electrolysis production are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth molten salt electrolysis, and specifically to an insulating material for a rare earth electrolytic cell and its application, which is applied to the insulation between a water-cooled cover plate and a graphite crucible during the production process of rare earth metal electrolysis. Background Art

[0002] When a rare earth electrolytic cell is built, an insulating layer is usually arranged between the graphite crucible and the water-cooled cover plate, aiming to prevent direct contact between the two, resulting in electrolytic cell leakage and loss of the graphite crucible due to electrochemical corrosion. The inner side of the insulating layer bears the scouring of the electrolyte melt, with an environmental temperature of 1000 - 1100°C, and the outer side environmental temperature of 250 - 400°C; at the same time, the bottom of the insulating layer contacts the graphite crucible, with an environmental temperature of 1000 - 1100°C, and the top contacts the water-cooled cover plate, with an environmental temperature of 150 - 250°C. Currently, production enterprises mainly use traditional refractory materials or asbestos felt covering refractory bricks as the insulating layer. Limited by the high temperature and strong corrosion characteristics of the electrolyte melt, the existing insulating layer has the following deficiencies: poor insulation performance, the resistivity of the insulating layer decreases due to grain boundary corrosion in high-temperature molten salt, easily leading to electrolytic cell leakage; melt penetration: the penetration depth of the electrolyte melt is generally 50 - 90 mm, resulting in damage and failure of the insulating layer; poor process compatibility: after being scoured and corroded by the electrolyte melt, the insulating material enters the electrolysis system, causing the impurity content of rare earth metal products to exceed the standard. Summary of the Invention

[0003] The purpose of the present invention is to provide an insulating material for a rare earth electrolytic cell and its application. The insulating material has a melt infiltration blocking function, which can greatly improve the comprehensive performance of the insulating layer and extend the service life of the rare earth electrolytic cell. Thus, the problems raised in the background art are solved.

[0004] The technical solution adopted by the present invention is as follows:

[0005] An insulating material for a rare earth electrolytic cell includes a surface infiltration blocking layer, a strengthening insulating layer, and a structural support layer arranged in sequence from the inside out. The surface infiltration blocking layer is formed after the plastic mass is solidified. The plastic mass is prepared by uniformly mixing a matrix material, a reinforcing material, an auxiliary filler, and a refractory binder; the strengthening insulating layer is composed of shaped bricks prepared by mixing, dry pressing, cold isostatic pressing, and sintering rare earth fluorides, alumina, and boron nitride; the structural support layer is composed of refractory bricks.

[0006] The plastic mass includes the following raw materials in parts by weight: 50 - 90 parts of matrix material, 0 - 30 parts of reinforcing material, 0 - 10 parts of auxiliary filler, and 0 - 10 parts of refractory binder.

[0007] The matrix material is rare earth fluoroxide; the reinforcing material is selected from one or more of alumina, iron oxide, and silica powder; the auxiliary filler is refractory fiber, selected from one or more of aluminosilicate, high-aluminum, mullite, alumina, and zirconia; the refractory binder is selected from one or more of aluminum dihydrogen phosphate binder, condensed aluminum phosphate binder, aluminum phosphate binder, sodium silicate binder, and potassium silicate binder.

[0008] When preparing the plastic mass, the water content is controlled to be 0-10 parts by weight of water, and the form of the plastic mass is semi-dry and amorphous.

[0009] During the preparation process of the reinforced insulating layer, the dry pressing pressure is 30-50 mPa, the cold isostatic pressing pressure is 150-200 mPa, the sintering temperature is 1400-1600 °C, the heating rate is 5-10 °C / min, the sintering atmosphere is nitrogen or argon, the pressure is 0.5-1.0 mPa, the oxygen partial pressure ≤ 10-5 Pa, and the density of the shaped brick is 2.0-3.0 g / cm3.

[0010] The rare earth fluoroxide is obtained from rare earth carbonate and hydrofluoric acid as raw materials through fluorination, ball milling, drying, and calcination, and its particle size is less than 0.1 mm.

[0011] The reinforced insulating layer comprises the following raw materials in parts by weight: 0-10 parts of rare earth fluoroxide, 0-10 parts of alumina, 80-100 parts of boron nitride, and the relative density of the sintered shaped brick is 2.0-3.0 g / cm3.

[0012] The thickness of the insulating material is 20-70 mm. The reinforced insulating layer and the structural support layer are both segmented and processed into 4-12 fan-shaped ring modules of 30°-90°. The adjacent modules are connected by a simple mortise and tenon structure, and the dimensional tolerance ≤ 1 mm.

[0013] An application of the rare earth electrolytic cell insulating material as described above, the insulating material is installed between the water-cooled cover plate and the graphite crucible of the upper-inserted rare earth electrolytic cell of the anode and cathode. The installation method comprises the following steps:

[0014] S1. Place refractory bricks along the outside of the top of the assembled rare earth electrolytic cell to form a structural support layer;

[0015] S2. Place the fired shaped bricks along the inside of the structural support layer to form a reinforced insulating layer;

[0016] S3. Place a mold closely along the inside of the reinforced insulating layer to the inner edge of the graphite crucible. Place the plastic mass inside the mold, ram it into shape, level the top, remove the mold, and form a surface impermeable layer after curing.

[0017] Further, in step S3, the plastic refractory after masonry is quickly roasted on the surface with a blowtorch, controlling the temperature at 800 - 900 °C for 5 - 10 minutes to complete the preliminary curing and shaping; before starting up the rare earth electrolytic cell, baking is required. By adjusting the current and the addition amount of waste anodes, controlling the furnace mouth temperature at 100 - 200 °C for not less than 36 hours to complete the secondary curing; after starting up the rare earth electrolytic cell, adjust the height of the molten liquid surface to be lower than the surface impermeable layer, controlling the furnace mouth temperature at 800 - 900 °C for not less than 48 hours to complete the final curing.

[0018] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0019] The insulating material of the present invention selects different materials according to the working conditions of different positions, ensuring the insulation performance between the water-cooled cover plate and the graphite crucible. The insulating material as a whole adopts a split-module design, which can effectively reduce thermal stress and enhance the thermal shock resistance. Among them, the plastic refractory is easy to be processed into different shapes and sizes, and can achieve seamless fitting between the water-cooled cover plate and the graphite crucible. At the same time, due to the low phase change volume change of the matrix material rare earth oxyfluoride, the plastic refractory has a small volume shrinkage after curing, and the formed surface impermeable layer can form an enamel layer on the surface when facing the erosion of the melt, resisting the erosion and corrosion of the melt, and effectively preventing the penetration of molten salt. In addition, the reinforced insulation layer and the structural support layer are reused during the masonry process of the rare earth electrolytic cell, effectively reducing the masonry cost. By using the insulating material of the rare earth electrolytic cell of the present invention, during the electrolysis production process, it can greatly reduce the consumption of graphite crucibles and the leakage of electrolytic cells caused by the failure of the insulation layer, effectively extending the overall service life of the praseodymium-neodymium electrolytic cell, and ensuring the stability and continuity of electrolysis production. Description of the Drawings

[0020] Figure 1 It is a cross-sectional structure schematic diagram of the annular insulating material in Embodiment 1 of the present invention;

[0021] Figure 2 It is a diffraction pattern of lanthanum oxyfluoride prepared in Embodiment 1 of the present invention;

[0022] Figure 3 It is a scanning electron microscope image of lanthanum oxyfluoride prepared in Embodiment 1 of the present invention;

[0023] Figure 4 It is an external shape structure schematic diagram (top view, side view and axonometric view) of the insulating special-shaped brick in Embodiment 1 of the present invention;

[0024] Figure 5 It is an assembly schematic diagram of the rare earth electrolytic cell in Application Example 1 of the present invention;

[0025] As shown in the figure: 41. Structural support layer; 42. Reinforced insulation layer; 43. Surface impermeable layer; 44. Graphite crucible; 51. Outer steel shell; 52. Inner steel shell; 53. Graphite crucible; 54. Insulating material; 55. Water-cooled cover plate. Detailed implementation mode

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings of the present invention and the specific data in the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0027] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0028] Embodiment 1

[0029] As Figures 1-4 , this embodiment provides a rare earth electrolytic cell insulating material, where the rare earth element is lanthanum, the total thickness of the insulating material is 25 mm, which is mainly used for insulation between the water-cooled cover plate and the graphite crucible of the metal lanthanum electrolytic cell. As a whole, it consists of a surface impermeable layer (inner ring), a reinforced insulation layer (middle ring), and a structural support layer (outer ring) from the inside out. The segmented processing and assembly process is as follows:

[0030] The thickness of the surface impermeable layer is 28 mm, which is integrally processed and formed from plastic mass. The plastic mass is prepared by uniformly mixing a matrix material (lanthanum oxyfluoride), a reinforcing material (aluminum oxide, iron oxide, silica powder), an auxiliary filler (aluminum silicate refractory fiber), and a refractory material binder (aluminum dihydrogen phosphate). The specific steps are as follows:

[0031] S1. Preparation of lanthanum oxyfluoride: Pulverize lanthanum carbonate, add hydrofluoric acid (HF content 40%) for fluorination, and the molar ratio of lanthanum carbonate to hydrofluoric acid is 1:1; transfer the slurry into a ball mill tank for ball milling, and the ball milling medium is 5 mm zirconia beads; after solid-liquid separation, filter the cake and dry it at 105 °C for 5 hours; calcine the dried material at 1000 °C for 8 hours to prepare lanthanum oxyfluoride powder with a median particle size of 50 μm and a microscopic morphology of monodisperse ellipsoidal particles. Its diffraction pattern and scanning electron microscope image are as shown in Appendix Figure 1 Appendix Figure 2 ;

[0032] S2. Plastic mass preparation: Lanthanum oxyfluoride, alumina, iron oxide, silica powder, and aluminosilicate refractory fiber are mixed evenly according to the weight ratio of 80:5:5:5:5 to obtain a special powder. The powder is stirred evenly with aluminum dihydrogen phosphate binder (colorless viscous liquid, pH value of 2.0, density of 1.47 g / cm3) according to the weight ratio of 90:10 to prepare a plastic mass. The water content is 7.3%, showing a semi-dry and indefinite form, with good adhesion and plasticity;

[0033] The thickness of the strengthened insulation layer is 25 mm and it is assembled by 4 pieces of 90° sector-shaped insulating bricks. The special-shaped bricks have tenon and mortise structures. The specific preparation process is as follows:

[0034] S3. Insulating special-shaped brick preparation: Lanthanum oxyfluoride, alumina, and boron nitride are mixed evenly according to the weight ratio of 5:5:90 and then put into a special mold. It is dry-pressed into shape using a hydraulic press with a pressure of 40 mPa. After the dry-pressed briquette is vacuum-packaged, it is subjected to cold isostatic pressing with a pressure of 160 mPa. The obtained blank material is sintered under a nitrogen atmosphere. The process conditions are a nitrogen pressure of 1.0 mPa, a sintering temperature of 1450 °C, a sintering time of 5 h, and a heating rate of 5 °C / min. The sintered special-shaped brick is polished to remove burrs. Its external structure is as shown in the appendix Figure 3 , and its density is 2.1 g / cm3;

[0035] The thickness of the structure support layer is 25 mm and it is assembled by 4 pieces of 90° sector-shaped refractory bricks. The refractory brick material is silicon nitride-bonded silicon carbide refractory brick (silicon carbide content ≥ 80%).

[0036] The insulating materials are installed from the outside to the inside in sequence. The structure schematic diagram is as shown in the appendix Figure 4 .

[0037] Example 2

[0038] This example provides a rare earth electrolytic cell insulating material. The rare earth element is neodymium. The total thickness of the insulating material is 30 mm, which is mainly used for insulation between the water-cooled cover plate of the neodymium electrolytic cell and the graphite crucible. The whole is composed of a surface anti-seepage layer (inner ring), a strengthened insulation layer (middle ring), and a structure support layer (outer ring). The segmented processing and assembly process is adopted:

[0039] The thickness of the surface anti-seepage layer is 35 mm and it is integrally processed and formed from a plastic mass. The plastic mass is prepared by mixing evenly the matrix material (neodymium oxyfluoride), the reinforcing material (iron oxide and silica powder), the auxiliary filler (high-aluminum refractory fiber), and the refractory material binder (polymeric aluminum phosphate and potassium water glass). The specific steps are as follows:

[0040] S1. Preparation of neodymium oxyfluoride: Pulp neodymium carbonate and add hydrofluoric acid (HF content 40%) for fluorination. The molar ratio of neodymium carbonate to hydrofluoric acid is 1:1. Transfer the slurry to a ball mill tank for ball milling, and the ball milling medium is 5 mm zirconia beads. After solid-liquid separation, the filter cake is dried at 120 °C for 5 hours. The dried material is calcined at 1000 °C for 8 hours to obtain neodymium oxyfluoride powder with a median particle size of 45 μm.

[0041] S2. Preparation of plastic mass: Uniformly mix neodymium oxyfluoride, iron oxide, silica powder, and high-aluminum refractory fiber in a weight ratio of 84:4:4:8 to obtain a special powder. Prepare a binder by mixing polyaluminum phosphate and potassium silicate in a weight ratio of 30:70. After uniformly stirring the two in a weight ratio of 90:10, a plastic mass is obtained, with a water content of 8.1%, in a semi-dry and indefinite form, and having good adhesiveness and plasticity.

[0042] The thickness of the strengthened insulation layer is 30 mm, which is assembled by 6 sector-shaped insulating bricks of 60°. The special-shaped bricks have a mortise and tenon structure, and the specific steps are as follows:

[0043] S3. Preparation of insulating special-shaped bricks: Uniformly mix neodymium oxyfluoride, alumina, and boron nitride in a weight ratio of 5:5:90, put them into a special mold, and dry press them into shape using a hydraulic press with a pressure of 45 mPa. After vacuum packaging the dry-pressed briquettes, cold isostatic pressing is carried out with a pressure of 180 mPa. The obtained blank material is sintered in a nitrogen atmosphere. The process conditions are a nitrogen pressure of 1.0 mPa, a sintering temperature of 1500 °C, a sintering time of 5 h, and a heating rate of 5 °C / min. Polish the sintered special-shaped bricks to remove burrs, and its density is 2.3 g / cm3.

[0044] The thickness of the structural support layer is 30 mm, which is assembled by 6 sector-shaped refractory bricks of 60°. The refractory brick material is corundum refractory brick (aluminum oxide content ≥ 90%).

[0045] Install the prepared insulating materials from the outside to the inside in sequence.

[0046] Example 3

[0047] This example provides a rare earth electrolytic cell insulating material. The rare earth element is gadolinium, and the total thickness of the insulating material is 30 mm. It is mainly used for insulation between the water-cooled cover plate of the gadolinium-iron alloy electrolytic cell and the graphite crucible. The whole is composed of a surface anti-seepage layer (inner ring), a strengthened insulation layer (middle ring), and a structural support layer (outer ring). A segmented processing and assembly process is adopted:

[0048] The thickness of the surface anti-seepage layer is 35 mm, which is integrally processed and formed from the plastic mass:

[0049] S1. Preparation of gadolinium oxyfluoride: Gadolinium carbonate is slurried and fluorinated by adding hydrofluoric acid (HF content 40%); the molar ratio of gadolinium carbonate to hydrofluoric acid is 1:1; the slurry is transferred to a ball mill jar for ball milling, and the ball milling medium is 5 mm zirconia beads; after solid-liquid separation, the filter cake is dried at 120 °C for 5 hours; the dried material is calcined at 1000 °C for 8 hours to prepare gadolinium oxyfluoride powder with a median particle size of 40 μm;

[0050] S2. Preparation of plastic refractory: Gadolinium oxyfluoride, iron oxide, silica powder, and alumina refractory fiber are mixed evenly according to a weight ratio of 80:5:5:10 to obtain a special powder, and then stirred evenly with aluminum dihydrogen phosphate binder (colorless viscous liquid, pH value 2.0, density 1.47 g / cm3) according to a weight ratio of 90:10 to prepare a plastic refractory, with a water content of 7.6%, in a semi-dry and indefinite form, having good adhesion and plasticity;

[0051] The thickness of the strengthened insulation layer is 30 mm, which is assembled by 8 sector-shaped insulating bricks at 45°. The special-shaped bricks have a mortise and tenon structure:

[0052] S3. Preparation of insulating special-shaped bricks: Gadolinium oxyfluoride, alumina, and boron nitride are mixed evenly according to a weight ratio of 5:5:90 and then put into a special mold, and dry-pressed into shape using a hydraulic press with a pressure of 50 mPa. The dry-pressed briquette is vacuum-packaged and then cold isostatically pressed with a pressure of 200 mPa. The obtained blank material is sintered in a nitrogen atmosphere. The process conditions are nitrogen pressure 1.0 mPa, sintering temperature 1600 °C, sintering time 10 h, and heating rate 5 °C / min. The sintered special-shaped bricks are polished to remove burrs, and their density is 2.5 g / cm3;

[0053] The thickness of the structural support layer is 30 mm, which is assembled by 6 sector-shaped refractory bricks at 60°. The refractory bricks are made of high-aluminum refractory bricks (aluminum oxide content ≥ 30%).

[0054] The insulating materials are installed in sequence from the outside to the inside.

[0055] Example 4

[0056] This example provides a rare earth electrolytic cell insulating material, where the rare earth element is lanthanum cerium (lanthanum: cerium = 35:65), and other steps and process parameters are the same as those in Example 1.

[0057] Example 5

[0058] This example provides a rare earth electrolytic cell insulating material, where the rare earth element is praseodymium neodymium (praseodymium: neodymium = 25:75), and other steps and process parameters are the same as those in Example 2.

[0059] Example 6

[0060] This embodiment provides a rare earth electrolytic cell insulation material, where the rare earth elements are praseodymium, neodymium, and gadolinium (praseodymium:neodymium:gadolinium = 65:20:15), and other steps and process parameters are the same as those in Embodiment 3.

[0061] Application Example 1

[0062] As Figure 5 shown, apply the insulation material of Embodiment 1 to the insulation between the water-cooled cover plate and the graphite crucible of an 8kA metal lanthanum electrolytic cell, where the thickness of the surface impermeable layer is 28 mm, the thickness of the enhanced insulation layer is 25 mm, and the thickness of the structural support layer is 25 mm. The installation steps are as follows:

[0063] Assembly of the rare earth electrolytic cell: Complete the assembly of the graphite crucible, inner steel shell, and outer steel shell of the electrolytic cell, making the three concentric and flush at the top. Place silicon nitride-bonded silicon carbide refractory bricks along the outside to form the structural support layer. Place fired shaped bricks along the inside of the structural support layer to form the enhanced insulation layer. Place a mold closely along the inside of the enhanced insulation layer to the inner edge of the graphite crucible. Place the plastic refractory inside the mold, ram it into shape, and level the top to form the surface impermeable layer;

[0064] Curing of the surface insulation layer: Use a blowtorch to quickly roast the surface impermeable layer, control the temperature at 800 - 900 °C for 5 minutes to complete the preliminary curing and shaping. Install the water-cooled cover plate to complete the final assembly of the rare earth electrolytic cell. The overall structure is as shown in the appendix Figure 5 ; During the baking of the metal lanthanum electrolytic cell, adjust the current and the amount of waste anodes added to control the furnace mouth temperature at 100 - 200 °C for 36 hours to complete the secondary curing; after starting the furnace for electrolysis production, adjust the height of the molten metal surface to be 2 - 3 mm below the surface impermeable layer, control the furnace mouth temperature at 800 - 900 °C for 48 hours to complete the final curing.

[0065] Application Example 2

[0066] Apply the insulation material of Embodiment 2 to the insulation between the water-cooled cover plate and the graphite crucible of a 10kA metal neodymium electrolytic cell, where the thickness of the surface impermeable layer is 35 mm, the thickness of the enhanced insulation layer is 30 mm, and the thickness of the structural support layer is 30 mm. The installation steps are as follows:

[0067] Assembly of the rare earth electrolytic cell: Complete the assembly of the graphite crucible, inner steel shell, and outer steel shell of the electrolytic cell, making the three concentric and flush at the top. Place corundum refractory bricks along the outside to form the structural support layer. Place fired shaped bricks along the inside of the structural support layer to form the enhanced insulation layer. Place a mold closely along the inside of the enhanced insulation layer to the inner edge of the graphite crucible. Place the plastic refractory inside the mold, ram it into shape, and level the top to form the surface impermeable layer;

[0068] Curing of the surface insulation layer: Use a blowtorch to quickly roast the surface barrier layer, control the temperature at 800 - 900 °C for 10 minutes to complete the preliminary curing and shaping. Install the water-cooled cover plate to complete the final assembly of the rare earth electrolyzer; when baking the neodymium metal electrolyzer in the furnace, control the furnace mouth temperature at 150 - 200 °C for 48 hours by adjusting the current and the amount of waste anodes added to complete the secondary curing; after starting the electrolysis production, adjust the molten liquid level 5 mm below the surface barrier layer, control the furnace mouth temperature at 800 - 900 °C for 60 hours to complete the final curing.

[0069] Application Example 3

[0070] Apply the insulating material of Example 3 to the insulation between the water-cooled cover plate and the graphite crucible of a 6kA rare earth gadolinium-iron electrolyzer. The thickness of the surface barrier layer is 35 mm, the thickness of the enhanced insulation layer is 30 mm, and the thickness of the structural support layer is 30 mm. The installation steps are as follows:

[0071] Assembly of the rare earth electrolyzer: Complete the assembly of the electrolyzer graphite crucible, inner steel shell, and outer steel shell, making the three concentric and flush at the top. Place corundum refractory bricks along the outside to form the structural support layer. Place fired shaped bricks along the inside of the structural support layer to form the enhanced insulation layer. Place a mold from the inside of the enhanced insulation layer to the inner edge of the graphite crucible, place the plastic refractory inside the mold, ram it into shape, and level the top to form the surface barrier layer;

[0072] Curing of the surface insulation layer: Use a blowtorch to quickly roast the surface barrier layer, control the temperature at 800 - 900 °C for 10 minutes to complete the preliminary curing and shaping. Install the water-cooled cover plate to complete the final assembly of the rare earth electrolyzer; when baking the rare earth gadolinium-iron electrolyzer in the furnace, control the furnace mouth temperature at 150 - 200 °C for 48 hours by adjusting the current and the amount of waste anodes added to complete the secondary curing; after starting the electrolysis production, adjust the molten liquid level 5 mm below the surface barrier layer, control the furnace mouth temperature at 800 - 900 °C for 60 hours to complete the final curing.

[0073] Comparative Example

[0074] Use traditional refractory materials (insulating materials obtained by mixing and stirring CA50 type aluminate refractory cement with water evenly) to build the corresponding insulation layer of the rare earth electrolyzer.

[0075] Test Example

[0076] Statistically record the time from starting the furnace to the furnace shutdown due to leakage and breakage of the rare earth electrolyzer, which is the service life of the electrolyzer; at the same time, statistically record the average penetration depth of the molten salt in the insulating material after the furnace shutdown. The results are shown in the following table:

[0077] Item Average molten salt penetration depth / mm Service life of electrolytic cell / month Example 1 13 14 Comparative Example 1 51 8 Example 2 15 16 Comparative Example 2 55 9 Example 3 9 6 Comparative Example 3 32 3

[0078] The results show that, compared with the rare earth electrolytic cell lined with traditional refractory materials, the average molten salt penetration depth of the rare earth electrolytic cell lined with the insulating material of the present invention is reduced by 70-75%, and at the same time, the service life of the rare earth electrolytic cell is increased by 75-100%. This indicates that in the temperature range of 1000-1100°C for rare earth metal electrolysis, the insulating material of the present invention and the lined insulating layer have good anti-penetration and insulating properties.

Claims

1. A rare earth electrolytic cell insulation material, characterized in that, It includes a surface impermeable layer, a strengthening insulation layer, and a structural support layer which are arranged in sequence from the inside out. The surface impermeable layer is formed after the plastic can is cured. The plastic can is prepared by uniformly mixing a matrix material, a reinforcing material, an auxiliary filler, and a refractory binder; the strengthening insulation layer is composed of shaped bricks prepared by mixing, dry pressing, cold isostatic pressing, and sintering rare earth fluorides, alumina, and boron nitride; the structural support layer is composed of refractory bricks.

2. The insulating material for a rare earth electrolytic cell according to claim 1, wherein: The plastic can includes the following raw materials in parts by weight: 50-90 parts of matrix material, 0-30 parts of reinforcing material, 0-10 parts of auxiliary filler, and 0-10 parts of refractory binder.

3. The rare earth electrolytic cell insulating material according to claim 2, characterized in that: The matrix material is a rare earth fluoride; the reinforcing material is selected from one or more of alumina, iron oxide, and silica powder; the auxiliary filler is a refractory fiber, selected from one or more of aluminosilicate, high-aluminum, mullite, alumina, and zirconia; the refractory binder is selected from one or more of aluminum dihydrogen phosphate binder, condensed aluminum phosphate binder, aluminum phosphate binder, sodium silicate binder, and potassium silicate binder.

4. The rare earth electrolytic cell insulating material according to claim 2, characterized in that: When preparing the plastic can, the water content is controlled so that the mass fraction of water is 0-10 parts by weight, and the form of the plastic can is semi-dry and amorphous.

5. The insulating material for a rare earth electrolytic cell according to claim 1, characterized in that: During the preparation process of the strengthening insulation layer, the dry pressing pressure is 30-50 mPa, the cold isostatic pressing pressure is 150-200 mPa, the sintering temperature is 1400-1600 °C, the heating rate is 5-10 °C / min, the sintering atmosphere is nitrogen or argon, the pressure is 0.5-1.0 mPa, the oxygen partial pressure ≤ 10-5 Pa, and the density of the shaped brick is 2.0-3.0 g / cm3.

6. The rare earth electrolytic cell insulating material according to claim 1, wherein: The rare earth fluoride is obtained by using rare earth carbonate and hydrofluoric acid as raw materials, through fluorination, ball milling, drying, and calcination, and its particle size is less than 0.1 mm.

7. The insulating material for a rare earth electrolytic cell according to claim 1, wherein: The strengthening insulation layer includes the following raw materials in parts by weight: 0-10 parts of rare earth fluoride, 0-10 parts of alumina, 80-100 parts of boron nitride, and the relative density of the sintered shaped brick is 2.0-3.0 g / cm3.

8. The insulating material for a rare earth electrolytic cell according to claim 1, characterized in that: The thickness of the insulating material is 20-70 mm. The strengthening insulation layer and the structural support layer are both segmented and processed into 4-12 fan-shaped ring modules of 30°-90°. The adjacent modules are connected by a simple mortise and tenon structure, and the dimensional tolerance ≤ 1 mm.

9. Use of a rare earth electrolytic cell insulating material according to any one of claims 1-8, characterized in that: The insulating material is installed between the water-cooled cover plate and the graphite crucible of the upper-inserted rare earth electrolytic cell of the anode and cathode. The installation method includes the following steps: S1. Place refractory bricks along the outside of the top of the assembled rare earth electrolytic cell to form a structural support layer; S2. Place the fired shaped bricks along the inside of the structural support layer to form a strengthening insulation layer; S3. Place a mold closely along the inside of the strengthening insulation layer to the inner edge of the graphite crucible. Place the plastic can inside the mold, ram it into shape, level the top, remove the mold, and form a surface impermeable layer after curing.

10. The application of an insulating material for a rare earth electrolytic cell according to claim 9, characterized in that: In step S3, the plastic refractory that has been laid is quickly baked on the surface with a blowtorch, with the temperature controlled at 800 - 900 °C for 5 - 10 minutes to complete the preliminary curing and shaping; before starting up the rare earth electrolytic cell, baking is required. By adjusting the current and the amount of waste anodes added, the temperature at the furnace mouth is controlled at 100 - 200 °C for no less than 36 hours to complete the secondary curing; after starting up the rare earth electrolytic cell, the height of the molten liquid surface is adjusted to be lower than the surface impermeable layer, and the temperature at the furnace mouth is controlled at 800 - 900 °C for no less than 48 hours to complete the final curing.

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