CN117401706B - Preparation method and application of large-particle rare earth oxide - Google Patents
Preparation method and application of large-particle rare earth oxide Download PDFInfo
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- 229910001404 rare earth metal oxide Inorganic materials 0.000 title claims abstract description 107
- 239000002245 particle Substances 0.000 title claims abstract description 67
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims abstract description 99
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 60
- 150000003839 salts Chemical class 0.000 claims abstract description 42
- 239000000203 mixture Substances 0.000 claims abstract description 23
- 238000010438 heat treatment Methods 0.000 claims abstract description 5
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 claims description 58
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 42
- 150000002910 rare earth metals Chemical class 0.000 claims description 35
- MMKQUGHLEMYQSG-UHFFFAOYSA-N oxygen(2-);praseodymium(3+) Chemical compound [O-2].[O-2].[O-2].[Pr+3].[Pr+3] MMKQUGHLEMYQSG-UHFFFAOYSA-N 0.000 claims description 22
- 229910003447 praseodymium oxide Inorganic materials 0.000 claims description 22
- 239000000463 material Substances 0.000 claims description 13
- 239000000956 alloy Substances 0.000 claims description 9
- 229910045601 alloy Inorganic materials 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 abstract description 53
- 239000003792 electrolyte Substances 0.000 abstract description 41
- 238000010304 firing Methods 0.000 abstract description 15
- 238000004519 manufacturing process Methods 0.000 abstract description 11
- 238000004090 dissolution Methods 0.000 abstract description 7
- 239000011230 binding agent Substances 0.000 abstract description 4
- 230000008021 deposition Effects 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 4
- 239000013589 supplement Substances 0.000 abstract 1
- 239000002994 raw material Substances 0.000 description 14
- 239000000047 product Substances 0.000 description 10
- -1 rare earth chloride Chemical class 0.000 description 9
- 239000013049 sediment Substances 0.000 description 7
- 238000003756 stirring Methods 0.000 description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/224—Oxides or hydroxides of lanthanides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/34—Electrolytic production, recovery or refining of metals by electrolysis of melts of metals not provided for in groups C25C3/02 - C25C3/32
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/36—Alloys obtained by cathodic reduction of all their ions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
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- Chemical & Material Sciences (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Analytical Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
The invention belongs to the technical field of rare earth oxides, and particularly relates to a preparation method and application of a large-particle rare earth oxide. The invention mixes rare earth oxide and lithium fluoride to obtain a mixture; heating the mixture to burn to obtain the large-particle rare earth oxide D 50 And more than or equal to 35 mu m. The invention realizes dynamic balance by utilizing dynamic reduction of electrolyte lithium fluoride and proper supplement in rare earth oxide in the molten salt electrolysis process. In addition, in the high-temperature firing process, lithium fluoride is liquefied to become a binder of rare earth oxide, and the particle size of the prepared rare earth oxide is 2-3 times larger than that of the rare earth oxide prepared by the traditional production method. The method has the advantages that the dissolution speed of the oxide is high, a cavity effect is formed by dissolution of lithium fluoride in the rare earth oxide in the electrolytic process, the phenomenon of the bottom of a rare earth oxide deposition tank is reduced, and the electrolytic process is optimized.
Description
Technical Field
The invention belongs to the technical field of rare earth oxides, and particularly relates to a preparation method and application of a large-particle rare earth oxide.
Background
The rare earth metal is mainly used for producing high-performance rare earth permanent magnetic materials, and is an important basic raw material in the fields of electronic information, new energy automobiles, new materials and the like. The production process of rare earth metal mainly adopts molten salt electrolysis method. Molten salt electrolysis is largely divided into two types depending on the electrolyte system, one being a rare earth chloride electrolysis system, i.e. a binary electrolyte system, such as RECl 3 -KCl (RE is rare earth); the other being a fluoride-oxide electrolyte system, i.e. ternary systems, e.g. RE 2 O 3 -REF 3 -LiF; for a rare earth chloride electrolysis system, the volatility of the chloride molten salt is high, the solubility of rare earth metal in the chloride molten salt is high, so that the electricity consumption is high, the current efficiency is low and the yield is low; the fluoride-oxide electrolyte system has high current efficiency and stable raw materials, and is a main electrolyte system of the prior fused salt electrolysis method.
For a fluoride-oxide electrolyte system, in the process of electrolysis, raw material rare earth oxide is dissolved in electrolyte and dissociated into complex rare earth cations and complex oxygen anions, and under the action of a direct current electric field, the complex rare earth cations move to a cathode, and electrons are obtained at the cathode and reduced into rare earth metals; the complex oxygen anions migrate to the anode where electrons are lost to produce oxygen.
Because the rare earth electrolyte has limited dissolving capacity to rare earth oxide, the rare earth oxide can not be dissolved in time when being added into the electrolyte in the electrolytic process, and the rare earth oxide is deposited at the bottom of the electrolytic tank. And because of insufficient complexing rare earth cations in the electrolyte, the concentration polarization phenomenon of the cathode is serious, the cell voltage is increased, and the power consumption is increased. Especially rare earth oxide with too small particle size (the particle size range of the rare earth oxide produced by the traditional preparation method is D at present) 50 =2 to 10 μm), a "crust" phenomenon is formed in the entering electrolyte, and the oxide is wrapped by the electrolyte and sinks into the bottom of the electrolyte, further deteriorating the electrolysis process. Thus, many researchers have studied the technique of preparing large-particle rare earth oxide in order to expect that the large-particle rare earth oxide is not agglomerated and wrapped to form a precipitate after entering the electrolyte, but slowly settles and is continuously dissolved in the electrolyte.
Lithium fluoride is used as a constituent of the electrolyte and has the functions of lowering the melting point of the electrolyte, reducing the viscosity of the electrolyte and improving the conductivity of the electrolyte. However, since lithium fluoride has a higher saturated vapor pressure than rare earth fluoride, lithium fluoride has a relatively large volatilization loss under electrolysis conditions. Therefore, lithium fluoride needs to be added periodically during the electrolysis process to facilitate the normal progress of the electrolysis.
Chinese patent CN1899967a discloses a large-particle rare earth oxide, a method for preparing the same, and chinese patent CN114604886a discloses a method for preparing a large-particle rare earth oxide, which basically focuses on the precipitation stage, and changes the precipitation conditions so that the precipitated rare earth compound particles are relatively large. However, the rare earth oxide produced by the preparation process disclosed in the patent has higher chloride ion content and has adverse effects on the subsequent processes and products. Meanwhile, the precipitation process is changed in the precipitation process, so that the production cost is increased and the yield of equipment is reduced.
Disclosure of Invention
The invention aims to provide a preparation method and application of a large-particle rare earth oxide, wherein the particle size of the rare earth oxide prepared by the preparation method is 2-3 times larger than that of the rare earth oxide prepared by the traditional production method; the rare earth oxide prepared by the method has high dissolution rate in preparing rare earth metal or rare earth alloy by a molten salt electrolysis method, can reduce the phenomenon of the bottom of a rare earth oxide deposition tank, and optimizes the process for preparing rare earth metal or rare earth alloy by molten salt electrolysis.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of large-particle rare earth oxide, which comprises the following steps:
mixing rare earth oxide and lithium fluoride to obtain a mixture;
heating the mixture to burn to obtain the large-particle rare earth oxide D 50 ≥35μm。
Preferably, the purity of the rare earth oxide is more than or equal to 99 percent.
Preferably, the rare earth oxide comprises neodymium oxide and/or praseodymium oxide.
Preferably, when the rare earth oxide includes neodymium oxide and praseodymium oxide, the mass ratio of the neodymium oxide to the praseodymium oxide is (20-25): (75-80).
Preferably, the purity of the lithium fluoride is more than or equal to 99%.
Preferably, the mass percentage of the lithium fluoride in the mixture is 0.5-1%.
Preferably, the firing temperature is 880-920 ℃.
Preferably, the firing heat preservation time is 1-3 hours.
Preferably, after the firing is finished, the method further comprises the step of air-cooling the material obtained by firing to room temperature in air to obtain the large-particle rare earth oxide.
The invention provides application of large-particle rare earth oxide in preparing rare earth metal or rare earth alloy by a molten salt electrolysis method, wherein the large-particle rare earth oxide is obtained by the preparation method in the technical scheme.
The invention provides a large-particle rare earth oxideThe preparation method of (2) comprises the following steps: mixing rare earth oxide and lithium fluoride to obtain a mixture; heating the mixture to burn to obtain the large-particle rare earth oxide D 50 And more than or equal to 35 mu m. According to the invention, lithium fluoride is added as a raw material in the preparation of rare earth oxide, so that when the electrolyte lithium fluoride is dynamically reduced in the molten salt electrolysis process, the electrolyte in the molten salt electrolysis process is dynamically and properly supplemented by utilizing the lithium fluoride in the large-particle rare earth oxide prepared by the invention, thereby realizing the dynamic balance of the electrolyte in the molten salt electrolysis process, and ensuring the smooth proceeding of the molten salt electrolysis without adding the electrolyte in the molten salt electrolysis process. In addition, in the high-temperature firing process, lithium fluoride is liquefied to become a binder of rare earth oxide, so that the rare earth oxide prepared by the method has the particle size D 50 The granularity range of the rare earth oxide produced by the traditional preparation method is D 50 The particle size of the large-particle rare earth oxide prepared by the method is 2-10 mu m, which is 2-3 times larger than that of the rare earth oxide prepared by the traditional production method. The rare earth oxide prepared by the method has high dissolution rate in the preparation of rare earth metal or rare earth alloy by a molten salt electrolysis method, and a cavity effect is formed by dissolution of lithium fluoride in the large-particle rare earth oxide in the electrolysis process, so that the phenomenon of the bottom of a rare earth oxide deposition tank is reduced, and the molten salt electrolysis process for preparing the rare earth metal is optimized.
Detailed Description
The invention provides a preparation method of large-particle rare earth oxide, which comprises the following steps:
mixing rare earth oxide and lithium fluoride to obtain a mixture;
heating the mixture to burn to obtain the large-particle rare earth oxide D 50 ≥35μm。
In the present invention, all preparation materials/components are commercially available products well known to those skilled in the art unless specified otherwise.
The invention mixes rare earth oxide and lithium fluoride to obtain a mixture. In the present invention, the purity of the rare earth oxide is preferably 99% or more, with 99.7% or 99.8% being preferred. The rare earth oxide preferably comprises neodymium oxide and/or praseodymium oxide, more preferably neodymium oxide or a mixture of neodymium oxide and praseodymium oxide. In a specific embodiment of the present invention, when the rare earth oxide includes neodymium oxide and praseodymium oxide, the mass ratio of the neodymium oxide to the praseodymium oxide is preferably (20 to 25): (75-80), more preferably 1:4 or 1:3. The purity of the lithium fluoride is preferably greater than or equal to 99%. The mixing is preferably carried out in a blendor. The invention has no special requirements on the specific implementation process of the mixing, and ensures that the two raw materials are uniformly mixed. The mass percentage of the lithium fluoride in the mixture is preferably 0.5-1%, more preferably 0.9%, 0.8% or 0.5%. In the invention, the mass percent of lithium fluoride in the mixture cannot be too much or too little, and after the addition of the lithium fluoride is more than 1%, the lithium fluoride is continuously enriched in the electrolyte in the molten salt electrolysis process, so that the content of the lithium fluoride in the electrolyte is too high, the volatilization loss of the lithium fluoride is increased, and the quality of rare earth metal is influenced. After the addition of lithium fluoride is less than 0.5%, the rare earth oxide cannot be polymerized into large particles, and the particle size is not obviously increased.
After the mixture is obtained, the invention heats the mixture to burn to obtain the large-particle rare earth oxide D 50 And more than or equal to 35 mu m. In the invention, the firing temperature is preferably 880-920 ℃, more preferably 890-900 ℃. The heat preservation time of the firing is preferably 1-3 hours, more preferably 1.5-2 hours.
In the invention, the temperature of the firing temperature cannot be too high or too low, the firing temperature is too high, the rare earth oxide can generate crystal phase change at the temperature exceeding 1000 ℃ to generate the rare earth oxide with a more stable crystal structure, and the crystal form of the rare earth oxide obtained at high temperature is not easy to dissolve in electrolyte, which is unfavorable for the electrolytic process. The firing temperature is too low, below 845 ℃, and the melting temperature of the lithium fluoride cannot be reached, and the lithium fluoride cannot be used as a binder to bond small particles into large-particle rare earth oxides.
In the invention, the burning heat preservation time cannot be too long or too short. The heat preservation time is too short and is less than 1h, the amount of the lithium fluoride bonded rare earth oxide is reduced, the particles of the bonded rare earth oxide are reduced, and the D of the particles of the obtained rare earth oxide product is reduced 50 The thickness of the film is 15-25 μm, which is not satisfactory. The heat preservation time is too long and is longer than 3 hours, and the method has no adverse effect on the formation of large-particle rare earth oxide, but wastes heat in production, consumes unnecessary energy and causes the rise of production cost.
The invention preferably charges the mixture into a crucible for firing in a muffle furnace. The crucible is preferably an alumina crucible. After the firing is finished, the invention preferably further comprises the step of air-cooling the material obtained by firing to room temperature in air to obtain the large-particle rare earth oxide. In the present invention, D of the large-particle rare earth oxide 50 Preferably 35 to 40. Mu.m.
The invention provides application of large-particle rare earth oxide in preparing rare earth metal or rare earth alloy by a molten salt electrolysis method, wherein the large-particle rare earth oxide is obtained by the preparation method in the technical scheme.
In the present invention, the application preferably includes the steps of: and carrying out molten salt electrolysis by taking the large-particle rare earth oxide as a raw material to obtain rare earth metal or rare earth alloy. The electrolysis temperature of molten salt electrolysis is preferably 1050-1100 ℃; the current intensity is preferably 6000A; the average cell voltage is preferably 9.0 to 9.2V, particularly preferably 9.0V, 9.1V or 9.2V; the material ratio is preferably 1.192-1.194, and particularly preferably 1.192, 1.193 or 1.194. The material ratio is the mass ratio of the large-particle rare earth oxide raw material used for molten salt electrolysis to the rare earth metal or rare earth alloy product. The time of molten salt electrolysis is preferably 1-2 hours, the sediment at the bottom of the molten salt electrolysis process is less, and the frequency of stirring the electrolytic tank by an operator is preferably 2-3 times.
The application of the large-particle rare earth oxide obtained by the preparation method in the preparation of rare earth metal or rare earth alloy by a molten salt electrolysis method can be used for dynamically supplementing the electrolyte in the molten salt electrolysis process by utilizing the lithium fluoride in the large-particle rare earth oxide prepared by the preparation method when the electrolyte lithium fluoride in the molten salt electrolysis process is dynamically reduced, so that the dynamic balance of the electrolyte in the molten salt electrolysis process is realized, and the smooth proceeding of the molten salt electrolysis can be ensured without adding the electrolyte in the molten salt electrolysis process.
The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
Example 1
6000g of neodymium oxide is taken and the granularity D is detected by a laser particle sizer 50 The purity was 99.8% and 60g of lithium fluoride was taken at a purity of 99% with a particle size of 8. Mu.m. Mixing thoroughly and uniformly with a mixer, loading into an alumina crucible, burning in a muffle furnace at 890 deg.C, maintaining the temperature for 2 hr, cooling, and detecting the granularity of rare earth oxide (neodymium oxide) with a laser granularity meter, wherein D is 50 40 μm.
The rare earth oxide prepared in example 1 was used for molten salt electrolysis at 1100 ℃, with a current intensity of 6000A, an average cell voltage of 9.0V, and a material ratio of 1.192 (mass ratio of large-particle neodymium oxide raw material to rare earth neodymium metal product). In the 1h electrolysis process, the sediment at the bottom of the tank is reduced, and the times of stirring the electrolytic tank by an operator are 2 times.
Example 2
12000g of a mixture of praseodymium oxide and neodymium oxide was taken and the particle size D was measured by a laser particle sizer 50 5 μm, wherein the content of praseodymium oxide is 25%, the content of neodymium oxide is 75%, the purities of praseodymium oxide and neodymium oxide are 99.7%, 96g of lithium fluoride is taken, and the purity is 99%. Mixing thoroughly and uniformly with a mixer, loading into an alumina crucible, burning in a muffle furnace at 920 ℃, preserving heat for 3h, cooling, and detecting the granularity of rare earth oxide with a laser particle sizer, wherein D is 50 35 μm.
The rare earth oxide prepared in example 2 was used for molten salt electrolysis at 1050 deg.c, a current intensity of 6000A, an average cell voltage of 9.1V, and a material ratio of 1.193 (mass ratio of rare earth oxide raw material to rare earth metal product). In the 2h electrolysis process, the sediment at the bottom of the tank is reduced, and the times of stirring the electrolytic tank by an operator are 3 times.
Example 3
6000g of the mixture of praseodymium oxide and neodymium oxide is taken, and the granularity D is detected by a laser particle sizer 50 10 μm, wherein the content of praseodymium oxide is 20%, the content of neodymium oxide is 80%, the purities of praseodymium oxide and neodymium oxide are 99.8%, 30g of lithium fluoride is taken, and the purity is 99%. Mixing thoroughly and uniformly with a mixer, loading into an alumina crucible, burning in a muffle furnace at 900 ℃, preserving heat for 1h, cooling, and detecting the granularity of rare earth oxide with a laser particle analyzer, wherein D is 50 40 μm.
The rare earth oxide prepared in example 3 was used for molten salt electrolysis at 1050 deg.c, with a current intensity of 6000A, an average cell voltage of 9.2V, and a material ratio of 1.194 (mass ratio of rare earth oxide raw material to rare earth metal product). In the 1h electrolysis process, the sediment at the bottom of the tank is reduced, and the times of stirring the electrolytic tank by an operator are 2 times.
Comparative example 1
6000g of neodymium oxide prepared by the traditional method is taken, and the granularity D is detected by a laser particle sizer 50 The neodymium oxide is used for molten salt electrolysis at the temperature of 1100 ℃, the current intensity of 6000A, the average cell voltage of 9.5V and the material ratio of 1.210 (the mass ratio of the neodymium oxide raw material to the rare earth neodymium metal product prepared by the traditional method). In the 1h electrolysis process, electrolyte volatilizes and loses partial lithium fluoride, the increase of electrolyte viscosity is unfavorable for electrolysis, 80g of lithium fluoride is needed to be added manually, and the number of times of stirring the electrolytic tank by an operator is 4 times due to sediment at the bottom of the tank.
Comparative example 2
12000g of a mixture of praseodymium oxide and neodymium oxide was taken and the particle size D was measured by a laser particle sizer 50 5 μm, wherein the praseodymium oxide content is 25%, the neodymium oxide content is 75%, and the purities of the praseodymium oxide and the neodymium oxide are 99.7%. The rare earth oxide is used for molten salt electrolysis, the electrolysis temperature is 1050 ℃, the current intensity is 6000A, the average cell voltage is 9.4V, and the material ratio is 1.198 (the mass ratio of the rare earth oxide raw material to the rare earth metal product). In the 2h electrolysis process, partial lithium fluoride is lost by volatilization of electrolyte, and the viscosity of the electrolyteThe increase is unfavorable for the electrolysis, 110g of lithium fluoride needs to be added manually, and the number of times of stirring the electrolytic tank by an operator is 5 because of sediment at the tank bottom.
Comparative example 3
6000g of the mixture of praseodymium oxide and neodymium oxide is taken, and the granularity D is detected by a laser particle sizer 50 10 μm, wherein the praseodymium oxide content is 20%, the neodymium oxide content is 80%, the purities of the praseodymium oxide and the neodymium oxide are 99.8%, the rare earth oxide is used for molten salt electrolysis, the electrolysis temperature is 1050 ℃, the current intensity is 6000A, the average cell voltage is 9.5V, and the material ratio is 1.221 (the mass ratio of the rare earth oxide raw material to the rare earth metal product). In the 1h electrolysis process, electrolyte volatilizes and loses partial lithium fluoride, the increase of electrolyte viscosity is unfavorable for electrolysis, 80g of lithium fluoride is needed to be added manually, and the number of times of stirring the electrolytic tank by an operator is 4 times due to sediment at the bottom of the tank.
According to the method provided by the embodiment of the invention, lithium fluoride is added as a raw material when the rare earth oxide is prepared, so that when the electrolyte lithium fluoride is dynamically reduced in the molten salt electrolysis process, the electrolyte in the molten salt electrolysis process is dynamically and properly supplemented by utilizing the lithium fluoride in the large-particle rare earth oxide prepared by the method, thereby realizing the dynamic balance of the electrolyte in the molten salt electrolysis process, and ensuring the smooth proceeding of the molten salt electrolysis without adding the electrolyte in the molten salt electrolysis process. In addition, in the high-temperature firing process, lithium fluoride is liquefied to become a binder of rare earth oxide, so that the rare earth oxide prepared by the method has the particle size D 50 The granularity range of the rare earth oxide produced by the traditional preparation method is D 50 The particle size of the large-particle rare earth oxide prepared by the method is 2-10 mu m, which is 2-3 times larger than that of the rare earth oxide prepared by the traditional production method. The rare earth oxide prepared by the method provided by the invention has high dissolution speed, a cavity effect is formed in electrolyte due to dissolution of lithium fluoride, the phenomenon of the bottom of a rare earth oxide deposition tank is reduced, and the molten salt electrolysis process for preparing rare earth metal is optimized.
Although the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments may be obtained according to the present embodiments without departing from the scope of the invention.
Claims (6)
1. The application of the large-particle rare earth oxide in preparing rare earth metal or rare earth alloy by a molten salt electrolysis method is characterized in that the preparation method of the large-particle rare earth oxide comprises the following steps:
mixing rare earth oxide and lithium fluoride to obtain a mixture; the mass percentage of the lithium fluoride in the mixture is 0.5-1%; the particle diameter of the rare earth oxide is D 50 8 μm, 5 μm or 10 μm;
heating the mixture to burn to obtain the large-particle rare earth oxide, wherein the burning temperature is 880-920 ℃; the burning heat preservation time is 1-3 h; d of the large-particle rare earth oxide 50 ≥35μm。
2. The use according to claim 1, characterized in that the rare earth oxide has a purity of 99% or more.
3. Use according to claim 1 or 2, characterized in that the rare earth oxide comprises neodymium oxide and/or praseodymium oxide.
4. The use according to claim 3, wherein when the rare earth oxide comprises neodymium oxide and praseodymium oxide, the mass ratio of neodymium oxide to praseodymium oxide is (20 to 25): (75-80).
5. The use according to claim 1, wherein the purity of the lithium fluoride is not less than 99%.
6. The use according to claim 1, further comprising air-cooling the burned material in air to room temperature after the end of the burning, to obtain the large-particle rare earth oxide.
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CN108275710A (en) * | 2018-01-15 | 2018-07-13 | 赣州湛海工贸有限公司 | A method of preparing large particle rare-earth oxide |
CN113881973A (en) * | 2021-11-09 | 2022-01-04 | 中国恩菲工程技术有限公司 | Method for preparing aluminum-scandium alloy by electrolysis with scandium-containing fluoride molten salt as supplementary electrolyte |
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