Integrated manufacturing method of graphite crucible for rare earth electrolytic cell
Through an integrated manufacturing method, graphite crucibles for rare earth electrolytic cells are prepared by calcined petroleum coke and coal asphalt, which solves the problems of high cost and size limitations of traditional processing methods, achieves more efficient production and larger specifications of crucibles, and improves the production capacity of rare earth electrolytic cells.
Patent Information
- Application Number
- CN202510270246.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-07
- Publication Date
- 2025-06-27
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Traditional graphite electrode processing has high cost and size limitations, which makes it difficult to expand the current capacity and production capacity of rare earth electrolytic cells.
Calcined petroleum coke and coal asphalt are used as raw materials and binders, and graphitization is carried out through integrated press forming, multiple calcination and graphitization treatment, combined with turning processing, graphite crucibles that meet the size requirements are prepared.
The production process has been optimized, material waste and production costs have been reduced, the specifications and size of the crucible have been expanded, and the production capacity of rare earth electrolytic cells has been improved.
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Figure CN120208671A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of rare earth metal electrolysis production, and specifically to an integrated manufacturing method for a graphite crucible used in a rare earth electrolytic cell. Background Art
[0002] The main function of the graphite crucible in the rare earth electrolytic cell is to serve as the anode. Direct current is introduced into the graphite crucible for melting and refining metal liquids as well as solid-liquid heating reactions. Rare earth electrolytic cells usually adopt graphite crucible electrolytic cells, where the graphite crucible not only serves as a container but also plays the role of the anode. During the electrolysis process, direct current is introduced into the graphite crucible through the steel shell, and graphite powder is padded at the inner bottom of the steel shell to maintain close contact with the graphite crucible and ensure good electrical conductivity. This structure enables the graphite crucible to play a key role during the electrolysis process, including but not limited to: the graphite crucible can withstand high temperatures, provide a stable chemical environment, and enable uniform heating and refining of metal liquids; in addition to serving as a melting container, the graphite crucible also supports solid-liquid heating and reactions, which are crucial for the extraction and purification of rare earth metals; the design features of small graphite crucible electrolytic cells, such as the cathode being located at the center of the electrolytic cell and the uniform distribution of power lines, help reduce the dissolution loss and secondary reactions of metals, thereby improving the current efficiency and metal recovery rate. In addition, the use of graphite crucibles in rare earth electrolytic cells also involves specific electrolyte systems, such as the GdF3-LiF-BaF2 ternary system, as well as specific solutes and solute ratios. These factors jointly affect the efficiency of the electrolysis process and the quality of the products. Generally speaking, the graphite crucible plays an indispensable role in the rare earth electrolytic cell and has a direct impact on the production efficiency and product quality of rare earth metals. Graphite is used as the anode in rare earth oxide electrolysis, and possible reactions include primary electrochemical and secondary electrochemical reactions. Primary electrochemical reaction: 0 2- -2e = 1 / 2O2, 1 / 2O + C = CO, 20 2- +C - 4e = CO2, 20 2- -4e = O2. The above reactions may occur simultaneously. When the electrolysis temperature is lower than 857 degrees, the anode gas is mainly carbon dioxide, and when it is higher than 900 degrees, the anode gas is mainly carbon monoxide. For secondary chemical reactions, when the primary gas generated by the electrode escapes, on the surface of the electrolyte with a very high temperature, the carbon dioxide gas reacts with the graphite anode as follows: CO2 + C = 2CO, O2 + C = CO2, O2 + 2C = 2CO. The composition of the anode gas: mainly carbon monoxide and carbon dioxide, and there are also a small amount of fluorides and fluorocarbon compounds, and their generation is mainly due to the interaction between water molecules and fluoride ions in the electrolyte.
[0003] The molten salt electrolysis method is one of the important methods for preparing rare earth metals. Currently, the common method is to electrolyze rare earth fluorides. The electrolytic cell uses a graphite material as a crucible, which is a container for holding the electrolyte and the rare earth metal liquid. The crucible is a bottomed barrel shape and is obtained by machining a finished graphite electrode.
[0004] However, the manufacture of traditional electrolytic cells has the following disadvantages:
[0005] (1) The graphite electrodes on the market are solid cylindrical. During processing, first, a hole is drilled in it, and then the inner and outer wall surfaces and the inner and outer surfaces of the bottom are turned, resulting in a large amount of material loss and high costs.
[0006] (2) Due to the limitations of the graphite electrode production equipment, the diameter of the electrode generally cannot exceed φ750mm, which restricts the outer diameter and inner diameter dimensions of the graphite crucible for rare earth electrolysis, and it is difficult to expand the current capacity and single cell of the rare earth electrolytic cell. Summary of the Invention
[0007] The purpose of the present invention is to provide an integrated manufacturing method for a graphite crucible for a rare earth electrolytic cell to solve the problems in the above-mentioned background technology that the graphite electrodes on the market are solid cylindrical. During processing, first, a hole is drilled in it, and then the inner and outer wall surfaces and the inner and outer surfaces of the bottom are turned, resulting in a large amount of material loss and high costs; due to the limitations of the graphite electrode production equipment, the diameter of the electrode generally cannot exceed φ750mm, which restricts the outer diameter and inner diameter dimensions of the graphite crucible for rare earth electrolysis, and it is difficult to expand the current capacity and single cell of the rare earth electrolytic cell.
[0008] To achieve the above purpose, the present invention provides the following technical solution: An integrated manufacturing method for a graphite crucible for a rare earth electrolytic cell, including the following steps:
[0009] Step 1. Determine raw materials: Select calcined petroleum coke as the raw material and coal tar pitch as the binder.
[0010] Step 2. Product processing: Calcinate, crush, screen, and grind the raw materials respectively to obtain the required particle size.
[0011] Step 3. Prepare paste: Weigh the calcined petroleum coke of various particle sizes proportionally and add a certain proportion of coal tar pitch as the binder, and knead to obtain the paste.
[0012] Step 4. Prepare green body: Inject the paste prepared in Step 3 into a cylindrical outer mold, insert an inner pressure head, and apply pressure to press to obtain a cylindrical crucible green body.
[0013] Step 5. First roasting: Roast the green crucible prepared in Step 4. During roasting, the green crucible is filled with carbonaceous particles and protected by carbonaceous particles on the outside to obtain Product A;
[0014] Step 6. Second roasting: Impregnate Product A with pitch and then conduct the second roasting to obtain Product B;
[0015] Step 7. Graphitization treatment: Subject Product B to graphitization treatment to obtain the finished crucible.
[0016] As a preferred technical solution of the present invention, in Step 1, when calcining petroleum coke, the sulfur content is not more than 1.5%, and in Step 1, the softening point of coal tar pitch is 100 - 115°C.
[0017] As a preferred technical solution of the present invention, in Step 2, the particle sizes specifically refer to crushing and screening the calcined petroleum coke into particle sizes of 4 - 2 mm, 2 - 1 mm, and less than 1 mm, and the particle size of the ground powder is less than 0.15 mm.
[0018] As a preferred technical solution of the present invention, in Step 3, the proportioning of calcined petroleum coke of various particle sizes specifically is 4 - 2 mm : 2 - 1 mm : 1 mm : powder = (26 - 32) : (18 - 24) : (8 - 12) : (36 - 42).
[0019] As a preferred technical solution of the present invention, in Step 3, the usage proportion of the binder coal tar pitch is 18 - 24% of the total amount of the paste.
[0020] As a preferred technical solution of the present invention, in Step 3, the kneading temperature is 150 - 180°C, and the kneading time is 40 - 60 min.
[0021] As a preferred technical solution of the present invention, the specific operation of injecting into the cylindrical outer mold in Step 4 is as follows: Inject the paste into a cylindrical outer mold that meets the dimensional specifications at 150 - 180°C; insert a cylindrical inner punch with a diameter smaller than that of the outer mold, apply a pressure of 18 - 24 MPa, and maintain the pressure for 100 - 150 seconds; the difference between the inner diameter of the outer mold and the outer diameter of the inner punch is 220 - 240 mm, and the height difference is 110 - 120 mm.
[0022] As a preferred technical solution of the present invention, in Step 5, the maximum temperature of the first roasting is 850 - 950°C, and the total curve time of roasting is 320 - 480 h; during roasting, the green crucible is filled with carbonaceous particles and protected by carbonaceous particles on the outside.
[0023] As a preferred technical solution of the present invention, the second roasting in step six is specifically to preheat the primary roasted blank to 210 - 230 °C, push it into the impregnation tank, evacuate the air, add impregnating pitch, apply a pressure of 1.8 - 2.2 MPa, and keep the pressure for 2 - 4 hours; the maximum temperature of the secondary roasting is 950 - 1050 °C, and the total curve time of the roasting is 240 - 320 h.
[0024] As a preferred technical solution of the present invention, the graphitization treatment in step seven is specifically that the graphitization temperature is 2600 - 2800 °C. For the graphitized crucible blank, mechanical processing is carried out on its inner and outer surfaces by turning to obtain a graphite crucible that meets the dimensional requirements.
[0025] Compared with the prior art, the beneficial effects of the present invention are:
[0026] 1. Select calcined petroleum coke as the raw material, crush and screen it into different particle sizes and grind it into powder, use pitch as the binder, proportionally prepare the materials, and adopt integrated pressing and forming to obtain a cylindrical crucible green body. After primary roasting and impregnation, secondary roasting is carried out, and then graphitization treatment is carried out. Finally, turning processing is carried out to obtain a graphite crucible that meets the dimensional requirements. This method can optimize the production process, reduce material waste, lower the production cost, and can expand the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells;
[0027] 2. Through the improvement of the forming method and process, the graphite crucible for rare earth electrolytic cells is integrally manufactured, optimizing the production process, reducing material waste, lowering the production cost, and can expand the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is a flow chart of the present invention;
[0029] Figure 2 is a process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0031] Please refer to Figure 1-2 , the present invention provides an integrated manufacturing method for a graphite crucible for a rare earth electrolytic cell, including the following steps:
[0032] Step 1. Determine the raw materials: Select calcined petroleum coke as the raw material and coal pitch as the binder;
[0033] Step 2. Product processing: Calcining, crushing, screening, and grinding the raw materials respectively to obtain the required particle size.
[0034] Step 3. Preparation of paste: Mixing calcined petroleum coke of various particle sizes proportionally and adding a certain proportion of coal tar pitch as a binder, then kneading to obtain the paste.
[0035] Step 4. Preparation of green body: Injecting the paste prepared in Step 3 into a cylindrical outer mold, inserting an inner pressure head, and applying pressure for pressing to obtain a cylindrical crucible green body.
[0036] Step 5. First baking: Baking the crucible green body prepared in Step 4. During baking, the crucible green body is filled with carbonaceous particles and protected by carbonaceous particles on the outside to obtain Product A.
[0037] Step 6. Second baking: Impregnating Product A with asphalt and then performing the second baking to obtain Product B.
[0038] Step 7. Graphitization treatment: Performing graphitization treatment on Product B to obtain the finished crucible.
[0039] In Step 1, the sulfur content of the calcined petroleum coke is not more than 1.5%, and the softening point of the coal tar pitch in Step 1 is 100 - 115°C.
[0040] In Step 2, the specific particle size is to crush and screen the calcined petroleum coke into particle sizes of 4 - 2 mm, 2 - 1 mm, and below 1 mm, and the particle size of the ground powder is below 0.15 mm.
[0041] In Step 3, the proportional batching of calcined petroleum coke of various particle sizes is specifically: 4 - 2 mm : 2 - 1 mm : 1 mm : powder = (26 - 32) : (18 - 24) : (8 - 12) : (36 - 42).
[0042] In Step 3, the usage ratio of the binder coal tar pitch is 18 - 24% of the total amount of the paste.
[0043] In Step 3, the kneading temperature is 150 - 180°C, and the kneading time is 40 - 60 min.
[0044] In Step 4, injecting into the cylindrical outer mold specifically means: Injecting the paste at 150 - 180°C into a cylindrical outer mold that meets the size specifications; inserting a cylindrical inner pressure head with a diameter smaller than that of the outer mold, applying a pressure of 18 - 24 MPa, and maintaining the pressure for 100 - 150 seconds; the difference between the inner diameter of the outer mold and the outer diameter of the inner pressure head is 220 - 240 mm, and the height difference is 110 - 120 mm.
[0045] In Step 5, the maximum temperature of the first roasting is 850 - 950°C, and the total curve time of roasting is 320 - 480 h; during roasting, the crucible green body is filled with carbonaceous particles and protected by carbonaceous particles on the outside.
[0046] In Step 6, the second roasting is specifically as follows: preheat the first-roasted blank to 210 - 230°C, push it into the impregnation tank, evacuate, add impregnation pitch, apply a pressure of 1.8 - 2.2 MPa, and keep the pressure for 2 - 4 hours; the maximum temperature of the second roasting is 950 - 1050°C, and the total curve time of roasting is 240 - 320 h.
[0047] In Step 7, the graphitization treatment is specifically as follows: the graphitization temperature is 2600 - 2800°C. For the graphitized crucible blank, machine-process its inner and outer surfaces by turning to obtain a graphite crucible that meets the dimensional requirements.
[0048] Example 1:
[0049] In the present invention, calcined petroleum coke with a sulfur content of not more than 1.5% is selected as the raw material, and coal tar pitch with a softening point of 100 - 115°C is selected as the binder; crush, screen, and grind the post-fracture petroleum coke blocks to obtain particle sizes of 4 - 2 mm, 2 - 1 mm, and less than 1 mm, and the particle size of the grinding is less than 0.15 mm; mix the above various particle-size materials in the ratio of 4 - 2 mm : 2 - 1 mm : less than 1 mm : powder = (26 - 32) : (18 - 24) : (8 - 12) : (36 - 42), and add 18 - 24% of the total paste amount of coal tar pitch as the binder, and carry out kneading at a kneading temperature of 150 - 180°C and a kneading time of 40 - 60 min to obtain a paste; keep the above paste at 150 - 180°C and inject it into a cylindrical outer mold that meets the dimensions; insert a cylindrical inner pressure head with a diameter smaller than the outer mold, apply a pressure of 18 - 24 MPa, keep the pressure for 100 - 150 seconds, and cool to obtain a cylindrical crucible green body; the difference between the inner diameter of the outer mold used and the outer diameter of the inner pressure head is 220 - 240 mm, and the height difference is 110 - 120 mm; the maximum temperature of the first roasting of the crucible green body is 850 - 950°C, and the total curve time of roasting is 320 - 480 h. During the first roasting, the crucible green body is filled with carbonaceous particles and protected by carbonaceous particles on the outside; after cooling, take it out of the furnace and remove the carbonaceous particles inside and outside; preheat the first-roasted blank to 210 - 230°C, push it into the impregnation tank, evacuate, add impregnation pitch, apply a pressure of 1.8 - 2.2 MPa, keep the pressure for 2 - 4 hours, relieve the pressure and push it out; then carry out the second roasting, with a maximum temperature of 950 - 1050°C and a total curve time of roasting of 240 - 320 h; carry out graphitization treatment on the above second-roasted block, with a graphitization temperature of 2600 - 2800°C, and cool and take it out of the furnace; for the graphitized crucible blank, machine-process its inner and outer surfaces by turning to obtain a graphite crucible that meets the dimensional requirements.
[0050] Example 2:
[0051] In the present invention, calcined petroleum coke with a sulfur content of 1.4% is selected as the raw material. It is crushed and screened to obtain particle sizes of 4 - 2 mm, 2 - 1 mm, and below 1 mm, and then ground into powders with a particle size below 0.15 mm for standby. The materials of various particle sizes are weighed and proportioned according to the ratio of 4 - 2 mm: 2 - 1 mm: below 1 mm: powders = 26:24:10:40, and coal tar pitch with a softening point of 113°C is added as a binder at 21% of the total amount of the paste for kneading. The kneading temperature is 165°C and the kneading time is 55 min to obtain the paste. The paste at the above temperature is placed in an outer mold with an inner diameter of 7560 mm and a height of 1000 mm, and an inner punch with a diameter of 530 mm and a length of 880 mm is inserted for pressing molding. The pressure is 20 MPa and the pressure holding time is 100 seconds, and then it is cooled to obtain a cylindrical crucible green body with an outer diameter of 760 mm, a wall thickness of 110 mm, and a bottom thickness of 120 mm. After the green body is cooled, carbonaceous particles with a particle size below 6 mm are filled inside, and it is loaded into a roasting furnace. Carbonaceous particles are filled outside the crucible for the first roasting. The maximum temperature is controlled at 900°C and the total roasting curve time is 420 h, and then it is cooled and taken out of the furnace. The above roasted blank is preheated to 215°C, pushed into an impregnation tank, evacuated, impregnated asphalt is added, a pressure of 2.0 MPa is applied, and the pressure is held for 3 hours, and then it is pushed out after the pressure is released. The above impregnated block is subjected to the second roasting. The maximum temperature is controlled at 1000°C and the total roasting curve time is 240 h, and then it is cooled and taken out of the furnace. The above second roasted blank is loaded into a graphitization furnace for graphitization treatment. The graphitization temperature is 2800°C, and then it is cooled and taken out of the furnace. The graphitized blank is subjected to turning processing to obtain a graphite crucible for rare earth electrolysis cells with an outer diameter of 740 mm, an inner diameter of 540 mm, and a bottom thickness of 100 mm. The material loss ratio during turning processing is 9.6%.
[0052] Example 3:
[0053] In the present invention, calcined petroleum coke with a sulfur content of 0.5% is selected as the raw material. It is crushed and screened to obtain particle sizes of 4 - 2 mm, 2 - 1 mm, and below 1 mm, and then ground into powders with a particle size below 0.15 mm for standby. The materials of various particle sizes are weighed and proportioned according to the ratio of 4 - 2 mm : 2 - 1 mm : below 1 mm : powders = 32:18:12:38, and 18% of coal tar pitch with a softening point of 105°C is added as a binder based on the total amount of the paste, followed by kneading at a kneading temperature of 155°C for 45 minutes to obtain the paste. The paste at the above temperature is placed into an outer mold with an inner diameter of 1020 mm and a height of 1000 mm, and an inner punch with a diameter of 780 mm and a length of 880 mm is inserted, and then pressed into shape under a pressure of 22 MPa for a pressure holding time of 150 seconds. After cooling, a cylindrical crucible green body with an outer diameter of 1040 mm, a wall thickness of 120 mm, and a bottom thickness of 120 mm is obtained. After the green body cools, carbonaceous particles with a particle size below 6 mm are filled into the interior, and it is loaded into a roasting furnace. Carbonaceous particles are filled outside the crucible, and the first roasting is carried out, controlling the maximum temperature at 950°C and the total roasting curve time at 480 h, and then taken out of the furnace after cooling. The above roasted blank is preheated to 230°C, pushed into an impregnation tank, evacuated, impregnated asphalt is added, a pressure of 2.2 MPa is applied, and the pressure is held for 4 hours, and then taken out after depressurization. The above impregnated block is subjected to a second roasting, controlling the maximum temperature at 1050°C and the total roasting curve time at 320 h, and then taken out of the furnace after cooling. The above second roasted blank is loaded into a graphitization furnace for graphitization treatment at a graphitization temperature of 2700°C, and then taken out of the furnace after cooling. The graphitized blank is machined by turning to obtain a graphite crucible for rare earth electrolysis cells with an outer diameter of 1000 mm, an inner diameter of 800 mm, and a bottom thickness of 100 mm. The material loss ratio during turning is 16.0%.
[0054] Example 4:
[0055] In the present invention, calcined petroleum coke with a sulfur content of 0.8% is selected as the raw material. It is crushed and screened to obtain particle sizes of 4 - 2 mm, 2 - 1 mm, and below 1 mm, and then ground into powder with a particle size below 0.15 mm for standby. The materials of various particle sizes are weighed and proportioned according to the ratio of 4 - 2 mm: 2 - 1 mm: below 1 mm: powder = 30:20:8:42, and coal tar pitch with a softening point of 110°C is added as a binder at 24% of the total paste amount, and kneading is carried out. The kneading temperature is 175°C and the kneading time is 60 min to obtain a paste. The paste at the above temperature is put into an outer mold with an inner diameter of 960 mm and a height of 1000 mm, and an inner pressure head with a diameter of 720 mm and a length of 890 mm is inserted, and press molding is carried out. The pressure is 19 MPa and the pressure holding time is 120 seconds, and after cooling, a cylindrical crucible green body with an outer diameter of 960 mm, a wall thickness of 120 mm, and a bottom thickness of 110 mm is obtained. After the green body is cooled, carbonaceous particles with a particle size below 6 mm are filled into the interior, and it is loaded into a roasting furnace. Carbonaceous particles are filled outside the crucible, and the first roasting is carried out. The maximum temperature is controlled at 850°C, and the total roasting curve time is 320 h. After cooling, it is taken out of the furnace. The above roasted blank is preheated to 210°C, pushed into an impregnation tank, evacuated, impregnation pitch is added, a pressure of 1.8 MPa is applied, the pressure is held for 2 hours, and then it is pushed out after depressurization. The above impregnated block is subjected to a second roasting. The maximum temperature is controlled at 900°C, and the total roasting curve time is 260 h. After cooling, it is taken out of the furnace. The above second roasted blank is loaded into a graphitization furnace for graphitization treatment. The graphitization temperature is 2600°C, and after cooling, it is taken out of the furnace. The graphitized blank is subjected to turning processing to obtain a graphite crucible for rare earth electrolysis cells with an outer diameter of 940 mm, an inner diameter of 740 mm, and a bottom thickness of 100 mm. The material loss ratio during turning processing is 11.4%.
[0056] Example 5;
[0057] Traditional crucible processing method: When using a graphite electrode to process a graphite crucible for a rare earth electrolytic cell, due to the limitations of production equipment, the maximum diameter of the current graphite electrode is 750 mm. Select a graphite electrode with a diameter of 750 mm and saw it into a solid core section with a length of 1000 mm; first drill holes from the end to meet the requirements of the next turning process; then carry out turning processing. After multiple feed turnings, make the inner diameter meet the dimensional requirements; then process the inner and outer bottom surfaces and the outer diameter surface. Finally, obtain a graphite crucible for a rare earth electrolytic cell with an outer diameter of 740 mm, an inner diameter of 540 mm, and a bottom thickness of 100 mm. This is the graphite crucible with the largest inner diameter that can be processed using a graphite electrode, and the material loss ratio during processing is 49.3%. The technology of the present invention selects calcined petroleum coke as the raw material and coal tar pitch as the binder; crush, screen, and grind the calcined material to obtain the required particle size; proportion the calcined petroleum coke of various particle sizes and add a certain proportion of coal tar pitch as the binder, and carry out kneading to obtain a paste; inject the above paste into a cylindrical outer mold, insert an inner pressure head, and apply pressure for pressing to obtain a cylindrical crucible green body; carry out the first roasting on the crucible green body. During roasting, fill the crucible green body with carbonaceous particles and protect it with carbonaceous particles on the outside; then impregnate it with pitch and then carry out the second roasting; carry out graphitization treatment on the second roasted blank; carry out machining on the graphitized blank to obtain a graphite crucible for a rare earth electrolytic cell with dimensions meeting the requirements.
[0058] Example 6:
[0059] In the present invention, calcined petroleum coke is selected as the raw material and coal tar pitch is used as the binder. The calcined petroleum coke is crushed, screened, and ground to obtain the required particle size. Calcined petroleum coke of various particle sizes is proportioned and a certain proportion of coal tar pitch is added as the binder, followed by kneading to obtain a paste. The above paste is injected into a cylindrical outer mold, an internal pressure head is inserted, and pressure is applied for pressing to obtain a cylindrical crucible green body. The crucible green body is subjected to the first roasting. During roasting, carbonaceous particles are filled inside the crucible green body and are protected by carbonaceous particles on the outside. Then it is impregnated with pitch and then subjected to the second roasting. The above-mentioned second roasted blank is subjected to graphitization treatment. The graphitized blank is machined to obtain a graphite crucible for rare earth electrolytic cells with dimensions meeting the requirements. In this way, a double-crucible structure is prepared. Calcined petroleum coke is selected as the raw material, crushed and screened into different particle sizes and ground, with pitch as the binder, proportioned, and integrally pressed and formed to obtain a cylindrical crucible green body. After the first roasting, it is impregnated, then subjected to the second roasting, then graphitized, and finally machined by turning to obtain a graphite crucible meeting the dimensional requirements. This method can optimize the production process, reduce material waste, lower the production cost, and can enlarge the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells. Through the improvement of the forming method and process, the graphite crucible for rare earth electrolytic cells is integrally manufactured, optimizing the production process, reducing material waste, lowering the production cost, and can enlarge the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells. The double-crucible structure means adding a large graphite crucible on the outside and placing the small graphite crucible inside. The rare earth metals electrolytically produced, overflowed, or spilled on the outer wall of the small graphite crucible are isolated from the large graphite crucible to inhibit the formation of ultra-high carbon products by the electrolytically produced, overflowed, or spilled rare earth metals, making the recycled such metals easy to remelt and refine, achieving the purpose of reducing the reject rate, increasing the recovery rate, and lowering the production cost. Because the large and small crucibles form a compound structure in the graphite electrolytic cell, it isolates the graphite cell body from polluting the rare earth metals, and the large graphite crucible or the small graphite crucible can be used separately according to actual needs, and taking it out can realize two process methods.
[0060] Calcined petroleum coke is selected as the raw material, crushed and screened into different particle sizes and ground, with pitch as the binder, proportioned, and integrally pressed and formed to obtain a cylindrical crucible green body. After the first roasting, it is impregnated, then subjected to the second roasting, then graphitized, and finally machined by turning to obtain a graphite crucible meeting the dimensional requirements. This method can optimize the production process, reduce material waste, lower the production cost, and can enlarge the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells. Through the improvement of the forming method and process, the graphite crucible for rare earth electrolytic cells is integrally manufactured, optimizing the production process, reducing material waste, lowering the production cost, and can enlarge the specification size of the crucible, providing conditions for improving the production capacity of rare earth electrolytic cells.
[0061] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. An integrated manufacturing method for a graphite crucible for a rare earth electrolytic cell, characterized in that: The following steps are involved: Step 1: Determine the raw materials: Use calcined petroleum coke as the raw material and coal tar as the binder; Step 2: Product processing: calcining, crushing, screening and grinding the raw materials to obtain the particle size that meets the requirements; Step 3, preparing a paste: calcined petroleum cokes of various particle sizes are mixed in proportion, and a certain proportion of coal tar pitch is added as a binder, and the mixture is kneaded to obtain a paste; Step 4: preparing a green body: injecting the paste prepared in step 3 into a cylindrical outer mold, inserting an inner pressure head, applying pressure to press, and obtaining a cylindrical crucible green body; Step 5, first calcination: the crucible green body prepared in step 4 is calcined for the first time. During calcination, the crucible green body is filled with carbonaceous particles and the outside is protected by carbonaceous particles to obtain product A; Step 6: Second calcination: impregnating product A with asphalt, and then calcining it for a second time to obtain product B; Step 7: Graphitization treatment: Graphitize product B to obtain a finished crucible.
2. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: In the step 1, the petroleum coke is calcined, and the sulfur content is not more than 1.5%. In the step 1, the softening point of the coal tar pitch is 100-115°C.
3. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: In the step 2, the particle size is specifically that the calcined petroleum coke is crushed and screened into particle sizes of 4-2mm, 2-1mm and below 1mm, and the particle size of the ground powder is below 0.15mm.
4. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: In the step 3, the calcined petroleum cokes of various particle sizes are mixed in the following proportions: 4-2 mm: 2-1 mm: 1 mm: powder = (26-32): (18-24): (8-12): (36-42).
5. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: In the step 3, the proportion of coal tar as the binder is 18-24% of the total amount of the paste.
6. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: In the step 3, the kneading temperature is 150-180° C., and the kneading time is 40-60 min.
7. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: The specific steps of injecting into the cylindrical outer mold in step 4 are as follows: injecting the paste into a cylindrical outer mold that meets the size specifications at 150-180° C.; inserting a cylindrical inner pressure head with a diameter smaller than that of the outer mold, applying a pressure of 18-24 MPa, and holding the pressure for 100-150 seconds; the difference between the inner diameter of the outer mold and the outer diameter of the inner pressure head is 220-240 mm, and the height difference is 110-120 mm.
8. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: The maximum temperature of the first calcination in step 5 is 850-950° C., and the total calcination curve time is 320-480 hours. During calcination, the green body of the crucible is filled with carbonaceous particles, and the outside is protected by carbonaceous particles.
9. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: The second roasting in step six is specifically to preheat the first roasted blank to 210-230°C, push it into the impregnation tank, evacuate it, add impregnation asphalt, apply a pressure of 1.8-2.2MPa, and maintain the pressure for 2-4 hours; the maximum temperature of the second roasting is 950-1050°C, and the total roasting curve time is 240-320h.
10. The integrated manufacturing method of a graphite crucible for a rare earth electrolytic cell according to claim 1, characterized in that: The graphitization treatment in step seven is specifically performed at a graphitization temperature of 2600-2800° C. The graphitized crucible blank is mechanically processed on its inner and outer surfaces by turning to obtain a graphite crucible that meets the size requirements.