Method for separating bastnaesite from monazite in mixed rare earth concentrate

Abstract

The application discloses a method for separating bastnaesite from monazite in mixed rare earth concentrate, and belongs to the technical field of rare earth chemical beneficiation, and specifically comprises the following steps: 1. feeding the mixed rare earth concentrate into a fluidized ore phase conversion reactor to perform non-oxygen selective ore phase conversion; 2. cooling the ore phase conversion product in a non-oxygen environment; 3. performing leaching on the cooled ore phase conversion product in hydrochloric acid; 4. filtering the mixed slurry after leaching to obtain leaching liquor and leaching residue, and sequentially washing the leaching residue with hydrochloric acid and pure water to obtain leaching liquor containing rare earth ions and leaching residue rich in monazite. The separation method provided by the application has the advantages of simple process, low production cost, reduced environmental pollution and realized selective separation of bastnaesite and monazite in rare earth ore.

Description

Technical Field

[0001] This invention belongs to the field of rare earth chemical beneficiation technology, and relates to a chemical beneficiation method for non-oxygen selective mineral phase transformation-leaching of bastnaesite in mixed rare earth concentrate and separation of bastnaesite from monazite. Background Technology

[0002] The Bayan Obo mining area in Baotou, Inner Mongolia, is the world's largest rare earth mineral deposit. The mixed rare earth concentrate it contains is a unique composite rare earth mineral in my country. This rare earth mineral is mainly composed of bastnaesite and monazite, and the mass ratio of bastnaesite to monazite fluctuates between 9:1 and 6:4 depending on the mining site, and is unrelated to the rare earth grade.

[0003] The Bayan Obo mixed rare earth concentrate contains both bastnaesite and monazite. Unlike processes that treat bastnaesite or monazite alone, this process requires consideration of both minerals, necessitating the use of enhanced techniques. Currently, commonly used industrial processes for processing rare earth concentrates include high-temperature roasting with concentrated sulfuric acid and decomposition with NaOH. The former suffers from severe pollution and waste of associated thorium resources, while the latter requires high rare earth grades, involves long roasting times, low rare earth yields, and unsafe operation. In contrast, the metallurgical extraction processes for bastnaesite (oxidative roasting) and monazite (caustic soda decomposition) are relatively simple, energy-efficient, and environmentally friendly. Therefore, developing a separation process for bastnaesite and monazite in mixed rare earth concentrates is of great significance. Patent CN201210388991.6 describes a flotation method consisting of one rougher, three cleaners, and four scavengers to separate bastnaesite and monazite. The modifier used in this method is alum or aluminum sulfate, the collector is phthalic acid or N-hydroxyphthalimide, and the frother is 2... # Oil can produce single bastnaesite and monazite concentrates, but the process is complex, consumes a large amount of flotation reagents, and is environmentally unfriendly. Patent CN201210388995.4 uses a roasting-flotation process to separate bastnaesite and monazite. This method uses the same reagents as patent CN201210388991.6, but adds a roasting process before flotation. The roasting temperature is 480-650℃, and the roasting time is 0.5-2 hours, reducing one cleaning and one scavenging step. The overall process is not significantly different, but the disadvantages are the same as above. In addition, when the roasting temperature is below 600℃, a roasting time of 1 hour or more is generally required, resulting in low decomposition efficiency. Patent CN201010600833.3 uses a complexation method to cause fluoride ions in cerium carbonate ore to form complexes that enter the solution, thereby destroying the cerium carbonate ore and causing it to dissolve and enter the solution, thus achieving the purpose of separation from monazite ore. However, this method has been verified to have not achieved a good separation effect, and the leaching time is relatively long.

[0004] In summary, existing methods for separating bastnaesite and monazite from mixed rare earth concentrates suffer from drawbacks such as cumbersome processes, low decomposition efficiency, and environmental pollution. Therefore, conducting research on cutting-edge technologies for enhanced separation of mixed rare earth concentrates is of great strategic significance for promoting the development of rare earth resources and fostering the environmentally friendly development of downstream industries. Summary of the Invention

[0005] To address the above-mentioned issues, this invention provides a method for separating bastnaesite and monazite from mixed rare earth concentrates. The aim is to achieve non-oxygen selective mineral phase transformation-leaching of bastnaesite and separation of bastnaesite and monazite from mixed rare earth concentrates. The method mainly comprises four stages: non-oxygen selective mineral phase transformation, non-oxygen cooling, leaching, and washing, to achieve the directional transformation, leaching, and separation of bastnaesite and monazite from mixed rare earth concentrates. This invention uses the non-oxygen selective mineral phase transformation process to directionally transform bastnaesite into rare earth fluorides with better leaching performance. Furthermore, during the leaching of rare earth fluorides, aluminum chloride hexahydrate is added as a leaching aid to avoid the formation of hydrate REF3·nH2O. The formation of REF3·nH2O reduces the leaching rate of rare earths and is detrimental to solid-liquid separation.

[0006] The method for separating bastnaesite and monazite in a mixed rare earth concentrate according to the present invention comprises the following steps:

[0007] Step 1: Non-oxygen selective mineral phase conversion: The mixed rare earth concentrate is fed into a fluidized bed mineral phase conversion reactor for selective mineral phase conversion. Non-oxygen gas is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized and not oxidized. The inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature at 400-700℃ for 10-120 minutes. The converted mixed rare earth concentrate is called mineral phase conversion product.

[0008] Step 2: Oxygen-free cooling: Cool the mineral phase conversion product to 25-100°C in the reactor. During the cooling process, oxygen-free gas should be introduced to protect the generated rare earth fluorides from oxidation.

[0009] Step 3: Leaching: Add the cooled mineral phase transformation product and leaching aid to 5% to 25% hydrochloric acid for slurry preparation, and then stir at 10 to 100°C for 5 to 120 minutes;

[0010] Step 4: Washing: After leaching, the mixed slurry is filtered to obtain leachate and leach residue. The leach residue is first washed with dilute hydrochloric acid with a concentration of 0.1% to 10%, and then with pure water to obtain leachate containing rare earth ions and leach residue rich in monazite.

[0011] The above separation method, wherein:

[0012] In step 1, this stage primarily involves the directional conversion of bastnaesite (REFCO3) in the mixed rare earth concentrate into more easily leached rare earth fluoride (REOF), while monazite and other minerals remain unchanged. The main chemical reactions that occur are:

[0013] REFCO3→REOF+CO2↑

[0014] In step 1, the preferred temperature of the material in the reaction chamber is 500-600℃, and the preferred heating time is 20-60 min.

[0015] In steps 1 and 2, the non-oxygen gas is a single or mixed inert gas of nitrogen, argon, or helium, or a mixture of an inert gas and a reducing gas of carbon monoxide or hydrogen.

[0016] In step 3, the preferred leaching temperature is 60–95℃, and the preferred leaching time is 20–60 min; the mass ratio of the mineral phase transformation product to the hydrochloric acid solution is 1:0.5–10; the mass of the added leaching aid is 5%–200% of the mass of the mineral phase transformation product, and the added leaching aid is AlCl3·6H2O, Al 3+ Able to be with F - A complexation reaction occurs, thereby promoting the dissolution of the rare earth fluoride precipitate (REF3) formed during the leaching process. This not only increases the leaching rate of rare earth elements but also prevents the formation of REF3·nH2O, thus improving the efficiency and speed of solid-liquid separation. Simultaneously, the addition of the leaching aid also promotes the leaching of fluorite. The main chemical reactions occurring during the leaching process are as follows:

[0017] 3REOF+6HCl→2RECl3+REF3↓+3H2O

[0018] REF3 + nH2O → REF3·nH2O

[0019] 2REF3+Al 3+ →2RE 3+ +AlF6 3-

[0020] 3CaF2+Al 3+ →3Ca 2+ +AlF6 3-

[0021] In step 4, the monazite content in the leaching residue is above 90%.

[0022] Key points of the technical solution of this invention:

[0023] 1. A selective fluidization mineral phase conversion process has been added, which enables bastnaesite to be directionally converted into rare earth fluoride oxides with better leaching performance, while monazite remains unchanged; and fluidization can increase heat transfer efficiency, promoting faster and more complete decomposition of bastnaesite.

[0024] 2. The gas introduced during the fluidized bed mineralization phase transformation and cooling process is a non-oxygen gas, which avoids the oxidation of rare earth oxides in the transformation product of fluorocarbon cerium ore, which would lead to the transformation of Ce(Ⅲ) with better leaching performance into Ce(IV) with poorer leaching performance. At the same time, it avoids the generation of harmful gas Cl2 during the leaching process of Ce(IV).

[0025] 3. A leaching aid, AlCl3·6H2O, was added during the leaching process. During the hydrochloric acid leaching of the mineral phase transformation products, precipitate REF3 and hydrate REF3·nH2O hydrate are generated, which not only hinders the leaching of rare earth elements but also increases the difficulty of solid-liquid separation. The leaching aid AlCl3·6H2O... 3+ Able to be with F - Generates complex AlF6 3- This promotes the dissolution of REF3, which not only increases the leaching rate of rare earth elements but also prevents the formation of REF3·nH2O, thus improving the efficiency of solid-liquid separation. In addition, the addition of the leaching aid also promotes the leaching of fluorite, while the complex AlF6... 3- It can also be used as a raw material for preparing cryolite.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. Through precise transformation of rare earth concentrate phases under an oxygen-free atmosphere, the difficult-to-leach bastnaesite in rare earth ores is directionally transformed into easily leached rare earth fluoride oxides, increasing the leaching rate of F-REO from 35% to over 90%, thus promoting the leaching of bastnaesite; at the same time, monazite is stable and not easily leached, achieving selective separation of bastnaesite and monazite in rare earth ores.

[0028] 2. This invention can obtain monazite concentrate with a monazite content of over 96%.

[0029] 3. This invention can serve as a method for extracting rare earth elements from a single fluorocarbon cerium ore.

[0030] 4. This invention uses gas to fluidize the mineral phase of mixed rare earth concentrate. Compared with traditional roasting, it has higher heat and mass transfer efficiency, requires a shorter reaction time, and the reaction is more thorough, and the bastnaesite in it can be completely decomposed.

[0031] 5. This invention can control the orientation of fluorine in bastnaesite and fluorite, allowing F to interact with Al. 3+ Generate AlF6 3- This reduces the generation of wastewater containing sulfur (F).

[0032] 6. Compared with traditional flotation separation processes, the present invention has a simpler process, lower production costs, and reduces environmental pollution caused by flotation methods.

[0033] 7. This invention completes the decomposition and smelting of bastnaesite during the separation of bastnaesite and monazite, saving the subsequent metallurgical process of bastnaesite.

[0034] 8. The leachate obtained after leaching separation by the method of the present invention can be directly used to extract rare earth elements, reducing the smelting process. The leaching residue can be used as monazite for subsequent smelting, providing new ideas and directions for the reform of mixed rare earth concentrate beneficiation process. Attached Figure Description

[0035] Figure 1 A schematic diagram of the process for separating bastnaesite and monazite in a mixed rare earth concentrate according to the present invention. Detailed Implementation

[0036] In the examples of this invention, the rare earth oxide (REO) grade of the mixed rare earth concentrate selected is 50% to 67%, wherein the acid-soluble rare earth oxide (F-REO) mainly exists in the form of bastnaesite, and the acid-insoluble rare earth oxide (P-REO) mainly exists in the form of monazite; the F grade is 2% to 12%, mainly existing in the form of bastnaesite and fluorite.

[0037] Unless otherwise specified, the methods, reagents, and materials described in the following examples are all commercially available; the experimental methods described are conventional methods.

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, as follows:

[0039] Example 1

[0040] A method for separating bastnaesite and monazite from a mixed rare earth concentrate, the process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0041] 1. Non-oxygen selective mineral phase conversion: First, a mixed rare earth concentrate with an F-REO content of 37.63%, a P-REO content of 22.84%, and an F content of 5.73% is fed into a fluidized bed mineral phase conversion reactor for non-oxygen selective mineral phase conversion. Nitrogen gas is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized and not oxidized. The inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature at 550℃ for 20 minutes.

[0042] 2. Oxygen-free cooling: The mineral phase conversion products in the reactor are cooled to 25°C under a nitrogen atmosphere.

[0043] 3. Leaching: The cooled mineral phase transformation product and leaching aid are added to 20% hydrochloric acid for slurry preparation, and then stirred at 90℃ for 30 min. The solid-liquid ratio of mineral phase transformation product to hydrochloric acid solution is 1:2. The added leaching aid is AlCl3·6H2O, and the mass of the added leaching aid is 40% of the mass of mineral phase transformation product.

[0044] 4. Washing: After leaching, the mixed slurry is filtered, and the leaching residue is washed first with 1% dilute hydrochloric acid and then with pure water to obtain a leachate containing rare earth ions and a leaching residue rich in monazite.

[0045] The leaching rate of F-REO in the obtained filtrate was 93.68%, the leaching rate of P-REO was 3.14%, the leaching rate of F was 76.74%, and the monazite content in the leaching residue was 91.21% and the fluorite content was 4.72%.

[0046] Example 2

[0047] A method for separating bastnaesite and monazite from a mixed rare earth concentrate, the process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0048] 1. Non-oxygen selective mineral phase conversion: First, a mixed rare earth concentrate with an F-REO content of 37.63%, a P-REO content of 22.84%, and an F content of 5.73% is fed into a fluidized bed mineral phase conversion reactor for selective mineral phase conversion. Nitrogen gas is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized and not oxidized. The inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature at 550℃ for 30 minutes.

[0049] 2. Oxygen-free cooling: The mineral phase conversion products in the reactor are cooled to 25°C under a nitrogen atmosphere.

[0050] 3. Leaching: The cooled mineral phase transformation product and leaching aid are added to 20% hydrochloric acid for slurry preparation, and then stirred at 90℃ for 30 min. The solid-liquid ratio of mineral phase transformation product to hydrochloric acid solution is 1:2. The added leaching aid is AlCl3·6H2O, and the mass of the added leaching aid is 60% of the mass of mineral phase transformation product.

[0051] 4. Washing: After leaching, the mixed slurry is filtered, and the leaching residue is washed first with 1% dilute hydrochloric acid and then with pure water to obtain a leachate containing rare earth ions and a leaching residue rich in monazite.

[0052] The leaching rate of F-REO in the obtained filtrate was 93.97%, the leaching rate of P-REO was 3.23%, the leaching rate of F was 98.06%, the monazite content in the leaching residue was 96.13%, and the fluorite content was 0.71%.

[0053] Example 3

[0054] A method for separating bastnaesite and monazite from a mixed rare earth concentrate, the process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0055] 1. Non-oxygen selective mineral phase conversion: First, a mixed rare earth concentrate with an F-REO content of 40.73%, a P-REO content of 20.12%, and an F content of 6.20% is fed into a fluidized bed mineral phase conversion reactor for selective mineral phase conversion. Nitrogen gas is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized and not oxidized. The inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature at 550℃ for 20 minutes.

[0056] 2. Oxygen-free cooling: The mineral phase conversion products in the reactor are cooled to 25°C under a nitrogen atmosphere.

[0057] 3. Leaching: The cooled mineral phase transformation product and leaching aid are added to 20% hydrochloric acid for slurry preparation, and then stirred at 90℃ for 30 min. The solid-liquid ratio of mineral phase transformation product to hydrochloric acid solution is 1:2. The added leaching aid is AlCl3·6H2O, and the mass of the added leaching aid is 40% of the mass of mineral phase transformation product.

[0058] 4. Washing: After leaching, the mixed slurry is filtered, and the leaching residue is washed first with 1% dilute hydrochloric acid and then with pure water to obtain a leachate containing rare earth ions and a leaching residue rich in monazite.

[0059] The leaching rates of F-REO in the obtained filtrate were 94.68%, P-REO 2.97%, and F 77.59%. The monazite content in the leaching residue was 90.18%, and the fluorite content was 5.12%.

[0060] Example 4

[0061] A method for separating bastnaesite and monazite from a mixed rare earth concentrate, the process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0062] 1. Non-oxygen selective mineral phase conversion: First, a mixed rare earth concentrate with F-REO content of 35.53%, P-REO content of 19.71%, and F content of 5.96% is fed into a fluidized bed mineral phase conversion reactor for selective mineral phase conversion. Nitrogen gas is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized and not oxidized. The inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature at 550℃ for 20 minutes.

[0063] 2. Oxygen-free cooling: The mineral phase conversion products in the reactor are cooled to 25°C under a nitrogen atmosphere.

[0064] 3. Leaching: The cooled mineral phase transformation product and leaching aid are added to 20% hydrochloric acid for slurry preparation, and then stirred at 90℃ for 30 min. The solid-liquid ratio of mineral phase transformation product to hydrochloric acid solution is 1:2. The added leaching aid is AlCl3·6H2O, and the mass of the added leaching aid is 40% of the mass of mineral phase transformation product.

[0065] 4. Washing: After leaching, the mixed slurry is filtered, and the leaching residue is washed first with 1% dilute hydrochloric acid and then with pure water to obtain a leachate containing rare earth ions and a leaching residue rich in monazite.

[0066] The leaching rate of F-REO in the obtained filtrate was 92.76%, the leaching rate of P-REO was 2.88%, the leaching rate of F was 74.96%, the monazite content in the leaching residue was 92.66%, and the fluorite content was 4.34%.

[0067] Comparative Example 1

[0068] Similar to Example 1, the difference is that the mixed rare earth concentrate was leached directly without undergoing non-oxygen selective mineralization and non-oxygen cooling processes, and the leaching time was increased to 120 min, while other conditions remained unchanged. Ultimately, the leaching rate of F-REO was 35.61%, the leaching rate of P-REO was 1.12%, and the leaching rate of F was 54.93%. The monazite content in the leaching residue was 49.11%, and the fluorite content was 3.91%.

[0069] Comparative Example 2

[0070] Similar to Example 1, the difference is that no leaching aid was added, while other conditions remained unchanged. Ultimately, the leaching rate of F-REO was 59.59%, the leaching rate of P-REO was 2.47%, the leaching rate of F was 35.65%, the monazite content in the leaching residue was 57.14%, and the fluorite content was 3.49%.

[0071] Comparative Example 3

[0072] Similar to Example 1, the difference is that the gas introduced during the mineral phase transformation process was changed to air, and the residence time during the mineral phase transformation process was increased to 30 minutes, while other conditions remained unchanged. Ultimately, the leaching rate of F-REO was 86.90%, the leaching rate of P-REO was 3.11%, and the leaching rate of F was 73.53%. The monazite content in the leaching residue was 87.48%, and the fluorite content was 3.59%.

[0073] Comparative Example 4

[0074] Similar to Example 1, the difference is that cooling was carried out in an air atmosphere, while other conditions remained unchanged. Ultimately, the leaching rate of F-REO was 90.81%, the leaching rate of P-REO was 3.04%, the leaching rate of F was 74.95%, the monazite content in the leaching residue was 89.66%, and the fluorite content was 3.89%.

[0075] Comparative Example 5

[0076] Similar to Example 3, the difference is that the amount of leaching aid added is increased to 60% of the mineral phase transformation product quality, while other conditions remain unchanged. Ultimately, the leaching rate of F-REO was 96.89%, the leaching rate of P-REO was 3.07%, the leaching rate of F was 97.66%, the monazite content in the leaching residue was 95.81%, and the fluorite content was 0.83%.

[0077] As can be seen from the above examples and comparative results, the present invention can effectively separate bastnaesite from monazite, and the bastnaesite can enter the leaching solution, reducing the metallurgical process of bastnaesite. The resulting leaching residue can also be used as monazite for subsequent smelting work, providing a new direction for the development of mixed rare earth concentrate beneficiation and smelting processes.

Claims

1. A method for separating bastnaesite and monazite in a mixed rare earth concentrate, characterized in that, The specific steps are as follows: Step 1: Non-oxygen selective mineral phase conversion: The mixed rare earth concentrate is fed into a fluidized mineral phase conversion reactor for selective mineral phase conversion. Non-oxygen gas is introduced to ensure that the material in the reaction chamber is well fluidized and not oxidized. The internal material temperature is heated and maintained. The mixed rare earth concentrate after conversion is called mineral phase conversion product. Step 2: Oxygen-free cooling: The mineral phase conversion product is cooled in the reactor. During the cooling process, oxygen-free gas is introduced to protect the generated cerium fluoride from oxidation. Step 3: Leaching: Add the cooled mineral phase transformation product and leaching aid to hydrochloric acid for slurry preparation and stirring to obtain a mixed slurry; Step 4: Washing: After leaching, the mixed slurry is filtered to obtain leachate and leach residue. The leach residue is washed first with dilute hydrochloric acid and then with pure water to obtain leachate containing rare earth ions and leach residue rich in monazite. In step 1, the temperature of the material in the reaction chamber is 500~600℃, and the heating time is 20~30min; In step 2, the mineral phase transformation product is cooled to 25~100℃ without oxygen. In step 3, the leaching aid is AlCl3·6H2O, and the mass of the added leaching aid is 40-60% of the mass of the mineral phase transformation product; the stirring time is 30 min; the leaching temperature is 10-100℃; and the mass ratio of the mineral phase transformation product to the hydrochloric acid solution is 1:0.5-10. In step 4, the concentration of the dilute hydrochloric acid used is 0.1%~10%; After separation by the aforementioned method, the leaching rate of soluble rare earth oxides is 92.76-96.89%, the leaching rate of F is 74.96-98.06%, and the monazite content in the leaching residue is 90.18-96.13%. In steps 1 and 2, the non-oxygen gas is a single or mixed inert gas of nitrogen, argon, or helium, or a mixture of inert gas and reducing gas of carbon monoxide or hydrogen.

2. The method for separating bastnaesite and monazite in a mixed rare earth concentrate according to claim 1, characterized in that, During the selective mineral phase conversion described in step 1, non-oxygen gas is introduced from the bottom of the reactor; the inner wall of the reactor is equipped with heating wires to heat and maintain the internal material temperature.

3. The method for separating bastnaesite and monazite in a mixed rare earth concentrate according to claim 1, characterized in that, In step 3, the concentration of hydrochloric acid is 5% to 25%.

4. The method for separating bastnaesite and monazite in a mixed rare earth concentrate according to claim 1, characterized in that, The leaching temperature is 60~95℃.

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