Method for recovering rare earth molten salt electrolytic slag through saturated steam roasting method
Through saturated steam roasting method and hydrochloric acid leaching step, the problems of long process flow, high cost and serious environmental pollution in the recycling of rare earth molten salt electrolytic slag are solved, and efficient recycling of rare earths and lithium and full utilization of resources are achieved.
Patent Information
- Application Number
- CN202510540837.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-27
- Publication Date
- 2025-08-15
AI Technical Summary
The existing rare earth molten salt electrolytic slag recovery methods have problems such as long process flow, high cost and serious environmental pollution, making it difficult to efficiently defluoride and recover rare earth and lithium resources.
The saturated water vapor roasting method is adopted, including carbon removal, ball milling, calcining in saturated water vapor and hydrochloric acid leaching steps. The fluorine element is converted into HF through the coordinated roasting of water vapor and absorbed with deionized water, and then rare earth and lithium elements are leaching in hydrochloric acid.
It realizes efficient defluorination of rare earth molten salt electrolytic slag and efficient recovery of rare earths and lithium, simplifies the process flow, reduces production costs, reduces environmental pollution, and improves resource utilization.
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Figure CN120485523A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of metallurgical waste slag treatment and resource utilization, and in particular to a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting. Background Art
[0002] Due to their unique physical and chemical properties, rare earth elements are widely used in many fields such as electronic information, petrochemicals, metallurgy, aerospace, etc. With the development of the times, the consumption of rare earth resources has increased year by year, from an annual output of 110,000 tons of rare earths in 2012 to an annual output of 300,000 tons of rare earths in 2022. The world's demand for rare earth resources is huge and supply cannot meet demand.
[0003] Currently, high-value rare earth metals such as Nd, Pr, and Dy are primarily produced through rare earth molten salt electrolysis, which is divided into rare earth chloride systems and REF3–LiF–RE2O3 systems. Due to its advantages such as electrolyte stability and high current efficiency, the REF3–LiF–RE2O3 system has become the mainstream molten salt system for rare earth metal production. Molten salt electrolysis produces 2,000–5,000 tons of rare earth molten salt slag annually. This slag contains significant amounts of rare earths and high-value elements such as lithium, as well as significant amounts of harmful fluorine. Therefore, recycling rare earth molten salt slag is not only economically valuable but also environmentally beneficial.
[0004] The key challenges in rare earth molten salt electrolytic slag recovery are achieving efficient recovery of F and rare earth elements from rare earth molten salt electrolytic slag, shortening the process, reducing production costs, and minimizing secondary pollution during the production process. Currently, there are three main methods for recycling rare earth molten salt electrolytic slag: wet recovery, combined fire-wet recovery, and vacuum distillation. These methods all utilize large amounts of chemical reagents, such as acids, bases, and salts, to defluorinate the rare earth molten salt electrolytic slag. This generates significant amounts of wastewater, complicates subsequent processes such as molten salt electrolytic slag leaching, and presents lengthy process flows.
[0005] Therefore, there is an urgent need for a method for recovering rare earth molten salt electrolytic slag that has a short process flow, low processing cost, low environmental pollution, and can efficiently defluorinate and recover rare earths and lithium. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to provide a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting, which has short process flow, low processing cost, small environmental pollution and can efficiently defluorinate and recover rare earth and lithium.
[0007] To solve the above technical problems, the present invention provides a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting, comprising the following steps:
[0008] roasting the rare earth molten salt electrolytic slag to remove carbon and obtain the decarbonized rare earth molten salt electrolytic slag;
[0009] ball milling the decarbonized rare earth molten salt electrolytic slag to obtain decarbonized rare earth molten salt electrolytic slag powder;
[0010] Saturated water vapor is introduced into the rare earth molten salt electrolytic slag powder after carbon removal for roasting to obtain defluorinated rare earth molten salt electrolytic slag, and the generated HF tail gas is absorbed by deionized water;
[0011] The defluorinated rare earth molten salt electrolytic slag is leached in hydrochloric acid, and the rare earth and lithium element enriched leaching solution is obtained by filtration.
[0012] Furthermore, the rare earth molten salt electrolytic slag is a rare earth molten salt electrolytic slag in a fluoride molten salt system.
[0013] Furthermore, the temperature for roasting and decarbonizing the rare earth molten salt electrolytic slag is 500-700° C., and the roasting and decarbonizing time is 4-7 hours.
[0014] Preferably, the temperature for roasting and decarbonizing the rare earth molten salt electrolytic slag is 600° C., and the roasting and decarbonizing time is 5-7 hours.
[0015] Furthermore, the particle size of the rare earth molten salt electrolytic slag powder obtained by ball milling after decarbonization is below 100 meshes.
[0016] Preferably, the particle size of the rare earth molten salt electrolytic slag powder obtained by ball milling after decarbonization is 200-300 meshes.
[0017] Furthermore, the temperature of saturated water vapor introduced into the rare earth molten salt electrolytic slag powder after decarbonization for roasting is 900-1100°C, the roasting time is 1-6 hours, and the gas flow rate of saturated water vapor is 0.6-1.5m 3 / h.
[0018] Preferably, the temperature of saturated steam introduced into the rare earth molten salt electrolytic slag powder after decarbonization for roasting is 1000°C, the roasting time is 2-4 hours, and the gas flow rate of saturated steam is 0.9-1.2 m 3 / h.
[0019] Furthermore, the hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag leached in hydrochloric acid is 1-8 mol / L, the temperature of the defluorinated rare earth molten salt electrolytic slag leaching is 50-90°C, the leaching time is 1-5h, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to hydrochloric acid is 1:5-15:1.
[0020] Preferably, the hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag in hydrochloric acid is 4-6 mol / L, the temperature of the defluorinated rare earth molten salt electrolytic slag during leaching is 70-90°C, the leaching time is 3-4h, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to hydrochloric acid is 10:1.
[0021] The present invention provides a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting. Through steam co-roasting, the fluorine element in the rare earth molten salt electrolytic slag can be defluorinated and converted into HF, and the converted HF gas is absorbed by deionized water, thereby achieving efficient defluorination and efficient recovery of fluorine in the rare earth molten salt electrolytic slag. The defluorinated rare earth molten salt electrolytic slag obtained by steam roasting with hydrochloric acid is then immersed in an acid solution to obtain an enriched leachate, thereby efficiently recovering the rare earth and lithium elements in the rare earth molten salt electrolytic slag. Not only is the process simple and easy to operate, but it can also greatly reduce the use of chemical reagents such as acids and alkalis, reduce the pressure of later wastewater treatment, have low production costs, and cause little environmental pollution. At the same time, it can also achieve efficient defluorination of rare earth molten salt electrolytic slag and full recovery of rare earth and lithium resources in rare earth molten salt electrolytic slag, with high production efficiency and high resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 A flow chart of a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to an embodiment of the present invention;
[0023] Figure 2 An XRD pattern of rare earth molten salt electrolytic slag in a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting provided in an embodiment of the present invention;
[0024] Figure 3 An XRD pattern of defluorinated rare earth molten salt electrolytic slag obtained in a method for recovering rare earth molten salt electrolytic slag by a saturated steam roasting method provided in an embodiment of the present invention;
[0025] Figure 4 The present invention provides an XRD diagram of the leached slag after defluorinated rare earth molten salt electrolytic slag is leached with hydrochloric acid in a method for recovering rare earth molten salt electrolytic slag by a saturated steam roasting method provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0026] See also Figure 1 The embodiment of the present invention provides a method for recovering rare earth molten salt electrolytic slag by saturated steam roasting, comprising the following steps:
[0027] (1) Decarbonization roasting: The rare earth molten salt electrolytic slag is placed in a resistance furnace and fully roasted to obtain the decarbonized rare earth molten salt electrolytic slag.
[0028] Among them, the rare earth molten salt electrolytic slag is the rare earth molten salt electrolytic slag in the fluoride molten salt system. The XRD pattern of the rare earth molten salt electrolytic slag is as follows: Figure 2 As shown, through Figure 2 It can be seen that the main components of the rare earth molten salt electrolytic slag used in the present invention.
[0029] The specific composition and content of the rare earth molten salt electrolytic slag used in the embodiment of the present invention are shown in Table 1.
[0030] Table 1
[0031]
[0032] Since the rare earth molten salt electrolytic slag needs to be subsequently roasted and defluorinated under conditions where saturated water vapor is introduced, the water vapor reacts with the carbon in the molten salt electrolytic slag during the roasting process to produce carbon monoxide and hydrogen. This resulting mixed combustible gas is highly explosive during the roasting process. Furthermore, the reaction between the carbon in the molten salt electrolytic slag and the water vapor reduces the efficiency of the reaction between the water vapor and the rare earth fluoride in the molten salt electrolytic slag, thereby affecting the reaction conversion of fluorine. Therefore, the rare earth molten salt electrolytic slag needs to be roasted and decarbonized before being roasted under saturated water vapor.
[0033] As a specific embodiment of the present invention, in order to effectively decarbonize the rare earth molten salt electrolytic slag by roasting, the temperature for decarbonizing the rare earth molten salt electrolytic slag is controlled at 500-700° C., and the decarbonizing time is controlled at 4-7 hours.
[0034] As a preferred embodiment of the present invention, in order to achieve the best effect of roasting and decarbonizing rare earth molten salt electrolytic slag, the roasting and decarbonizing temperature of rare earth molten salt electrolytic slag is preferably 600°C, and the roasting and decarbonizing time is preferably 5-7h.
[0035] (2) Ball milling: The decarbonized rare earth molten salt electrolytic slag obtained in step (1) is placed in a ball mill and ball milled to obtain decarbonized rare earth molten salt electrolytic slag powder. This can increase the surface area of the decarbonized rare earth molten salt electrolytic slag powder and the contact area between the decarbonized rare earth molten salt electrolytic slag powder and water vapor, which is conducive to the effective defluorination reaction of the rare earth molten salt electrolytic slag by water vapor.
[0036] As a specific embodiment of the present invention, in order to increase the contact area between the rare earth molten salt electrolytic slag powder after decarbonization and water vapor, the particle size of the rare earth molten salt electrolytic slag powder after decarbonization obtained by ball milling is controlled to be below 100 mesh.
[0037] As a best embodiment of the present invention, in order to achieve sufficient contact between the decarbonized rare earth molten salt electrolytic slag powder and water vapor, the particle size of the decarbonized rare earth molten salt electrolytic slag powder obtained by ball milling is preferably 200-300 meshes.
[0038] (3) Steam Calcination: The decarbonized rare earth molten salt electrolytic slag powder obtained in step (2) is placed in a tubular furnace and calcined under conditions of saturated steam to obtain defluorinated rare earth molten salt electrolytic slag. Simultaneously, deionized water absorbs the HF tail gas generated by the calcination of the rare earth molten salt electrolytic slag powder under conditions of saturated steam.
[0039] The present invention removes fluorine from rare earth molten salt electrolytic slag by using saturated water vapor during roasting, significantly reducing the use of chemical reagents such as acids and alkalis, lowering the pressure of subsequent wastewater treatment, reducing production costs, and efficiently recovering fluorine. The chemical reaction equation for this process is as follows:
[0040] 2NdF3+3H2O=Nd2O3+6HF (1)
[0041] 2NdOF+H2O=Nd2O3+2HF (2)
[0042] As a specific embodiment of the present invention, in order to enable saturated water vapor to fully remove the fluorine element in the rare earth molten salt electrolytic slag, the temperature of calcining the rare earth molten salt electrolytic slag powder after carbon removal by introducing saturated water vapor is controlled at 900-1100°C, the calcining time is controlled at 1-6h, and the gas flow rate of saturated water vapor is controlled at 0.6-1.5m 3 / h.
[0043] As a best embodiment of the present invention, in order to make the rare earth molten salt electrolytic slag defluorinated most effectively, the temperature of the rare earth molten salt electrolytic slag powder after carbon removal and the saturated water vapor for roasting is preferably 1000 ° C, the roasting time is preferably 2-4 hours, and the gas flow rate of the saturated water vapor is preferably 0.9-1.2m 3 / h.
[0044] In addition, HF and incompletely reacted water vapor generated during the defluorination process of the rare earth molten salt electrolytic slag powder after decarbonization are discharged from the tubular furnace and enter the cooling device, and then enter the absorption device filled with absorption liquid. The deionized water in the absorption device can absorb the generated HF. At the same time, the unreacted water vapor will also turn into water and enter the deionized water absorption liquid, which also plays a certain role in absorbing HF, so that the HF generated by the defluorination of the rare earth molten salt electrolytic slag powder can be efficiently absorbed.
[0045] At the same time, the deionized water absorption liquid after absorbing the HF tail gas forms a low-concentration hydrofluoric acid, which can be used as a raw material for industrial hydrofluoric acid, thereby achieving efficient defluorination of rare earth molten salt electrolytic slag and efficient recovery of fluorine.
[0046] The XRD pattern of the defluorinated rare earth molten salt electrolytic slag obtained by calcining the defluorinated rare earth molten salt electrolytic slag powder after carbon removal is as follows: Figure 3 As shown, Figure 3 and Figure 2 By comparison, it can be seen that after the rare earth molten salt electrolytic slag powder after carbon removal is defluorinated by steam roasting, the defluorinated rare earth molten salt electrolytic slag obtained has almost no fluorine element, indicating that the steam roasting method used in the present invention has a good effect on the defluorination of rare earth molten salt electrolytic slag.
[0047] (4) Acid leaching: Take the defluorinated rare earth molten salt electrolytic slag obtained in step (3), add it to a hydrochloric acid solution, leach it for a period of time, and then filter it to obtain a rare earth and lithium element enriched leachate.
[0048] During the acid leaching process of defluorinated rare earth molten salt electrolytic slag, the rare earths in the defluorinated rare earth molten salt electrolytic slag mainly exist in the form of rare earth oxides, while lithium exists in the form of lithium oxide. These two types of substances can react with hydrochloric acid to form rare earth chloride and lithium chloride, which then enter the solution. After the acid leaching is complete, the leaching solution is filtered to obtain an enriched leachate rich in rare earths and lithium. The enriched leachate can be subsequently processed to obtain high-value rare earths and lithium, thereby effectively recovering the high-value rare earths and lithium elements in the rare earth molten salt electrolytic slag. The insoluble substances in the rare earth molten salt electrolytic slag are filtered and then recycled in the form of leached slag.
[0049] In order to promote the efficient and sufficient leaching of high-value rare earth and lithium elements in the defluorinated rare earth molten salt electrolytic slag, the defluorinated rare earth molten salt electrolytic slag is added to a hydrochloric acid solution and leached by stirring and heating.
[0050] As a specific embodiment of the present invention, in order to fully and quickly leach the rare earth and lithium elements in the defluorinated rare earth molten salt electrolytic slag, the hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag in hydrochloric acid is controlled to be 1-8 mol / L, the temperature of the defluorinated rare earth molten salt electrolytic slag during leaching is controlled to be 50-90°C, the leaching time is controlled to be 1-5h, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to the hydrochloric acid is controlled to be 1:5-15:1.
[0051] As an optimal embodiment of the present invention, in order to achieve optimal leaching of rare earth and lithium elements in the defluorinated rare earth molten salt electrolytic slag, the hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag in hydrochloric acid is preferably 4-6 mol / L, the temperature during leaching of the defluorinated rare earth molten salt electrolytic slag is preferably 70-90°C, the leaching time is preferably 3-4h, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to hydrochloric acid is preferably 10:1.
[0052] The XRD pattern of the leached residue after defluorinated rare earth molten salt electrolytic slag is as follows: Figure 4 As shown, from Figure 4It can be seen that the diffraction peaks of rare earth elements and lithium elements are basically not detected in the leached slag, indicating that the valuable rare earth and lithium elements in the defluorinated rare earth molten salt electrolytic slag are almost all enriched in the enriched leachate, which can illustrate that the defluorinated rare earth molten salt electrolytic slag of the present invention has a good leaching effect after hydrochloric acid leaching.
[0053] The following examples illustrate in detail the method for recovering rare earth molten salt electrolytic slag by saturated steam roasting provided by the present invention.
[0054] Example 1
[0055] 1. Take 160g of the above rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 6h to obtain 112.37g of decarbonized rare earth molten salt electrolytic slag.
[0056] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0057] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 1000℃ and 1.2m 3 Saturated steam was introduced at a flow rate of 1 / h and calcined for 2h to obtain 12.24g of calcined slag.
[0058] 4. Then, 12 g of the calcined slag was placed in a flask, 4 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 80°C, and a solid-liquid ratio of 10:1. After 5 h, the leachate and filter residue were obtained.
[0059] 5. After the above process, the fluorine removal rate is calculated by the formula: fluorine removal rate = 1-{[calcined slag mass * fluorine content] / [calcined sample mass * (fluorine content * raw material mass / decarbonized slag mass)]}, it can be calculated that the fluorine removal rate in the calcined slag reaches 95.21%.
[0060] According to the rare earth recovery rate calculation formula: rare earth recovery rate = [leachate volume * rare earth content (in terms of oxide)] / [calcined sample mass * (total rare earth amount * raw material mass / carbon removal slag mass)], it can be calculated that the rare earth leaching rate can reach 98.87%.
[0061] According to the lithium leaching rate calculation formula: lithium recovery rate = [leachate volume * lithium content] / [roasting sample mass * (lithium content * raw material mass / carbon removal slag mass)], it can be calculated that the lithium leaching rate can reach 99.99%.
[0062] Example 2
[0063] 1. Take 150 g of the above rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600°C for 5 hours to obtain 105.46 g of decarbonized rare earth molten salt electrolytic slag.
[0064] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0065] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 1000℃ with a temperature of 0.3m 3 Saturated steam was introduced at a flow rate of / h and roasted for 1h to obtain 12.98g of roasted slag.
[0066] 4. Then, 12 g of the calcined slag was placed in a flask, 1 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 60°C, and a solid-liquid ratio of 4:1. After 1 hour, the leachate and filter residue were obtained.
[0067] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 47.46%, the leaching rate of rare earth can reach 10.43%, and the leaching rate of lithium can reach 44.18%.
[0068] Example 3
[0069] 1. Take the above 145g rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 7h to obtain 97.68g of decarbonized rare earth molten salt electrolytic slag.
[0070] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0071] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 900℃ with a temperature of 0.9m 3 Saturated steam was introduced at a flow rate of 1 / h and calcined for 2h to obtain 13.16g of calcined slag.
[0072] 4. Then, 12 g of the calcined slag was placed in a flask, 5 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 90°C, and a solid-liquid ratio of 8:1. After 3 h, the leachate and filter residue were obtained.
[0073] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 74.94%, the leaching rate of rare earth can reach 82.46%, and the leaching rate of lithium can reach 99.99%.
[0074] Example 4
[0075] 1. Take the above 170g rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 6h to obtain 120.17g of decarbonized rare earth molten salt electrolytic slag.
[0076] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0077] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 1000℃ and 0.6m 3 Saturated steam was introduced at a flow rate of / h and calcined for 2h to obtain 12.72g of calcined slag.
[0078] 4. Then, 12 g of the calcined slag was placed in a flask, 2 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 90°C, and a solid-liquid ratio of 10:1. After 4 h, the leachate and filter residue were obtained.
[0079] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 59.17%, the leaching rate of rare earth can reach 35.86%, and the leaching rate of lithium can reach 99.99%.
[0080] Example 5
[0081] 1. Take the above 165g rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 4h to obtain 115.27g of decarbonized rare earth molten salt electrolytic slag.
[0082] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0083] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 700℃ with a temperature of 0.3m 3 Saturated steam was introduced at a flow rate of 1 / h and calcined for 3 h to obtain 13.32 g of calcined slag.
[0084] 4. Then, 12 g of the calcined slag was placed in a flask, 4 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 50°C, and a solid-liquid ratio of 4:1. After 1 h, the leachate and filter residue were obtained.
[0085] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 30.85%, the leaching rate of rare earth can reach 19.88%, and the leaching rate of lithium can reach 69.59%.
[0086] Example 6
[0087] 1. Take the above 130g rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 8h to obtain 85.79g of decarbonized rare earth molten salt electrolytic slag.
[0088] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0089] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 800℃ and 1.2m 3 Saturated steam was introduced at a flow rate of / h and calcined for 1h to obtain 13.69g of calcined slag.
[0090] 4. Then, 12 g of the calcined slag was placed in a flask, 5 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 80°C, and a solid-liquid ratio of 8:1. After 2 h, the leachate and filter residue were obtained.
[0091] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 59.01%, the leaching rate of rare earth can reach 58.34%, and the leaching rate of lithium can reach 99.99%.
[0092] Example 7
[0093] 1. Take 155 g of the above rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600°C for 4 hours to obtain 104.11 g of decarbonized rare earth molten salt electrolytic slag.
[0094] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0095] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 1000℃ and 1.5m 3 Saturated steam was introduced at a flow rate of 1 / h and calcined for 2h to obtain 12.85g of calcined slag.
[0096] 4. Then, 85 g of the calcined slag was placed in a flask, 4 mol / L hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 90°C, and a solid-liquid ratio of 10:1. After 1 hour, the leachate and the filter residue were obtained by filtering.
[0097] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 97.89%, the leaching rate of rare earth can reach 98.19%, and the leaching rate of lithium can reach 99.99%.
[0098] Example 8
[0099] 1. Take the above 140g rare earth molten salt electrolytic slag and place it in a muffle furnace and calcine it at 600℃ for 4h to obtain 95.14g of decarbonized rare earth molten salt electrolytic slag.
[0100] 2. Place the decarbonized molten salt slag in a ball mill and grind it to obtain molten salt slag with a particle size of less than 200 mesh.
[0101] 3. Take 15g of the decarbonized molten salt slag after grinding and place it in a horizontal resistance furnace at 900℃ and 1.5m 3Saturated steam was introduced at a flow rate of / h and calcined for 4h to obtain 12.66g of calcined slag.
[0102] 4. Then, 85 g of the calcined slag was placed in a flask, 8 mol / L of hydrochloric acid was added, and the mixture was stirred and leached at a stirring speed of 100 r / min, a reaction temperature of 80°C, and a solid-liquid ratio of 4:1. After 3 h, the leachate and filter residue were obtained.
[0103] 5. After the above process, the removal rate of fluorine in the roasted slag reaches 96.78%, the leaching rate of rare earth can reach 98.64%, and the leaching rate of lithium can reach 99.99%.
[0104] It can be seen from the removal rates and rare earth and lithium leaching rates of Examples 1-8 that the method for recovering rare earth molten salt electrolytic slag by a saturated steam roasting method provided in the embodiments of the present invention can not only efficiently defluorinate the rare earth molten salt electrolytic slag, but also fully recover the rare earth and lithium resources in the rare earth molten salt electrolytic slag, with high production efficiency and high resource utilization, high economic value and economic benefits, and is worthy of application and promotion.
[0105] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A method for recovering rare earth molten salt electrolytic slag by saturated steam roasting, characterized in that: The steps include: roasting the rare earth molten salt electrolytic slag to remove carbon and obtain the decarbonized rare earth molten salt electrolytic slag; ball milling the decarbonized rare earth molten salt electrolytic slag to obtain decarbonized rare earth molten salt electrolytic slag powder; Saturated water vapor is introduced into the rare earth molten salt electrolytic slag powder after carbon removal for roasting to obtain defluorinated rare earth molten salt electrolytic slag, and the generated HF tail gas is absorbed by deionized water; The defluorinated rare earth molten salt electrolytic slag is leached in hydrochloric acid, and the rare earth and lithium element enriched leaching solution is obtained by filtration.
2. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 1, characterized in that: The rare earth molten salt electrolytic slag is a rare earth molten salt electrolytic slag in a fluoride molten salt system.
3. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 1, characterized in that: The temperature for roasting and decarbonizing the rare earth molten salt electrolytic slag is 500-700° C., and the roasting and decarbonizing time is 4-7 hours.
4. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 3, characterized in that: The temperature for roasting and decarbonizing the rare earth molten salt electrolytic slag is 600° C., and the roasting and decarbonizing time is 5-7 hours.
5. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 1, characterized in that: The particle size of the rare earth molten salt electrolytic slag powder obtained by ball milling after decarbonization is below 100 meshes.
6. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 5, characterized in that: The particle size of the rare earth molten salt electrolytic slag powder obtained by ball milling after decarbonization is 200-300 meshes.
7. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 1, characterized in that: The temperature of calcining the rare earth molten salt electrolytic slag powder after carbon removal by introducing saturated water vapor is 900-1100° C., the calcining time is 1-6 hours, and the gas flow rate of saturated water vapor is 0.6-1.5 m 3 / h.
8. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 7, characterized in that: The temperature of saturated water vapor introduced into the rare earth molten salt electrolytic slag powder after carbon removal is 1000°C, the calcination time is 2-4 hours, and the gas flow rate of saturated water vapor is 0.9-1.2m 3 / h.
9. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 1, characterized in that: The hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag leached in hydrochloric acid is 1-8 mol / L, the temperature of the defluorinated rare earth molten salt electrolytic slag leaching is 50-90° C., the leaching time is 1-5 hours, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to hydrochloric acid is 1:5-15:
1.
10. The method for recovering rare earth molten salt electrolytic slag by saturated steam roasting according to claim 9, characterized in that: The hydrochloric acid concentration of the defluorinated rare earth molten salt electrolytic slag leached in hydrochloric acid is 4-6 mol / L, the temperature of the defluorinated rare earth molten salt electrolytic slag leaching is 70-90° C., the leaching time is 3-4 hours, and the solid-liquid ratio of the defluorinated rare earth molten salt electrolytic slag to hydrochloric acid is 10:1.