A method and system for processing rare earth concentrate using strong base decomposition

Abstract

The application discloses a method and system for treating rare earth concentrate by using strong alkali decomposition, wherein the method is to immediately send the rare earth concentrate into a high-pressure reaction kettle for leaching after twice strong alkali continuous grinding and leaching, so as to treat the rare earth concentrate. The application significantly improves the leaching rate and recovery rate of rare earth elements, and significantly reduces the overall energy consumption in the working process, realizes the effects of energy saving and consumption reduction and production cost reduction.

Description

Technical Field

[0001] This invention relates to a method and system for the decomposition and processing of rare earth concentrates, and more particularly to a method and system for the decomposition and processing of rare earth concentrates using strong alkali, belonging to the field of rare earth metallurgical technology. Background Technology

[0002] Rare earth elements, due to their unique optical, electrical, and magnetic physicochemical properties, are widely used in permanent magnet materials, luminescent materials, polishing materials, catalysts, and new energy fields, playing an irreplaceable fundamental role in high-end manufacturing and strategic emerging industries. With the rapid development of industries such as new energy vehicles, wind power generation, and energy-saving lighting, the demand for rare earth resources continues to grow, leading countries to place higher demands on the security and efficient utilization of rare earth resources.

[0003] Rare earth concentrates, such as monazite concentrate, Baotou mixed rare earth concentrate, or mixtures thereof, are used in mining. Currently, traditional metallurgical processes for rare earth concentrates mainly include sulfuric acid roasting-water leaching and caustic soda decomposition-water leaching processes. In the caustic soda decomposition process, the rare earth concentrate reacts with sodium hydroxide at a high temperature, converting the rare earth minerals into rare earth hydroxides or corresponding leached components, which are then recovered through acid leaching or water leaching.

[0004] For complex rare earth concentrates containing fluorine and phosphorus, since rare earth elements often exist in the form of stable phosphates or fluorocarbonates, traditional sulfuric acid roasting or conventional caustic soda decomposition often fails to achieve complete decomposition, resulting in incomplete leaching and low recovery rates. Literature and existing patents indicate that when processing fluorine-containing rare earth concentrates, the formation of stable fluorides or insoluble mesophases by rare earth elements frequently occurs, affecting not only the leaching rate but also increasing the difficulty of subsequent separation and purification, and reagent consumption. Furthermore, some processes are lengthy, energy-intensive, and heavily reliant on operational condition control, making it difficult to simultaneously achieve multiple objectives such as high recovery rates, low costs, and environmental friendliness.

[0005] The following relevant patent documents were retrieved: 1. Chinese invention patent application CN101824554A, published on September 8, 2010, discloses a mixed rare earth concentrate liquid alkaline roasting decomposition extraction process, which includes the following steps: 1) Mixing the mixed rare earth concentrate and sodium hydroxide solution at a weight ratio of 1:0.5 to 1.5; 2) Roasting the mixture from step (1) for 0.5 to 4 hours at a roasting temperature of 150°C. ~550℃; 3) The roasted ore obtained from roasting is slurryed with hot water, and an oxidant is added for oxidation. The ratio of oxidant to roasted ore by weight is 0.5~4:1. Then, it is washed with hot water until neutral to form an alkali cake and washing liquid; 4) The alkali cake after water washing is preferentially dissolved with 1~10M hydrochloric acid to dissolve the trivalent rare earth elements, and the pH is controlled at 4~5 to obtain a low-cerium rare earth chloride solution; 5) The residue after preferential dissolution with hydrochloric acid is dissolved with 1~10M hydrochloric acid and a reducing agent is added at the same time to dissolve it, and the pH is controlled at 4~5 to obtain a cerium-rich chloride solution.

[0006] 2. Chinese invention patent application CN119979877A, published on May 13, 2025, discloses a method for alkaline treatment of rare earth concentrate. The method includes the following steps: Step 1, the rare earth concentrate is pre-melted with caustic soda, and then leached with an alkaline solution to dissolve beryllium and silicon in the alkaline solution, and filtered to obtain a leachate and an insoluble residue; Step 2, calcium hydroxide is added to the leachate obtained in Step 1, and carbon dioxide gas is introduced to precipitate silicon and calcium, and filtered to obtain a silicon-calcium slag and a filtrate; Step 3, the filtrate obtained in Step 2 is boiled to precipitate beryllium, and filtered to obtain basic beryllium carbonate and a filtrate; Step 4, the filtrate obtained in Step 3 is causticized with calcium hydroxide, filtered to obtain calcium carbonate precipitate and a filtrate, and the filtrate is returned to the leaching step in Step 1, wherein the filtrate is alkaline.

[0007] The processing methods described in the aforementioned patent documents still suffer from problems such as low rare earth element recovery rate and high energy consumption when implemented.

[0008] In summary, designing a method and system for treating rare earth concentrates using thermal alkaline decomposition to significantly improve the leaching rate and recovery rate of rare earth elements while significantly reducing the overall energy consumption during the process is an urgent technical problem that needs to be solved. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the deficiencies in the existing technology by providing a method and system for decomposing rare earth concentrates using strong alkali, which significantly improves the leaching rate and recovery rate of rare earth elements and significantly reduces the overall energy consumption in the working process, thereby achieving the effects of energy saving, consumption reduction and production cost reduction.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for treating rare earth concentrate by decomposing it with strong alkali, wherein the rare earth concentrate is subjected to two consecutive strong alkali grinding and leaching processes, and then immediately sent into a high-pressure reactor for leaching to treat the rare earth concentrate.

[0011] Preferably, the specific steps are as follows: S1: Preparation and Supply of Alkali Solution Prepare an alkali solution in an alkali tank, and then transfer the prepared alkali solution to a slurry tank. S2: Concentrate Storage and Pulping Rare earth concentrate is first stored in a silo, and then the rare earth concentrate is also sent to the pulping tank through the silo. In the pulping tank, it is made into slurry through stirring and compressed air. S3: Buffer tank adjustment The pulped slurry is then transported to a buffer tank; S4: First grinding and soaking operation The slurry is fed from the buffer tank into the first grinding and leaching mill, where the first grinding and leaching operation is carried out in a strongly alkaline environment. The slurry after grinding and leaching flows into the first intermediate tank. S5: Second grinding and soaking operation The slurry in intermediate tank one is fed into mill leaching two for a second grinding and leaching operation in a strongly alkaline environment. The slurry after grinding and leaching flows into intermediate tank two. S6: Pressure Leaching The slurry in intermediate tank 2 is transported to a high-pressure reactor for leaching. S7: Water washing operation The slurry leached from the high-pressure reactor is sent to a washing tank for washing. The washed slurry is then sent to the next process for solid-liquid separation.

[0012] Preferably, the "immediately sent to the high-pressure reactor for leaching" means that after two strong alkali grinding leaching processes, the material is sent to the high-pressure reactor for leaching within ≤5 hours.

[0013] Preferably, in step S6, pressurized leaching refers to continuous leaching in a high-pressure, strongly alkaline environment in a high-pressure reactor without cooling or depressurization.

[0014] Preferably, after the second grinding and leaching operation in step S5, the particle size distribution of the slurry is D80 = 10 μm to 20 μm, and the solid-liquid ratio is 40:60; in step S6, when the leaching is carried out in the high-pressure reactor, the temperature of the high-pressure reactor is 150 degrees to 280 degrees, the pressure is 1.5 MPa to 2.5 MPa, and the reaction time is 5 hours to 9 hours.

[0015] Preferably, the high-pressure reactor has a double-layer structure, with the inner layer providing corrosion protection and primary pressure bearing, and the outer layer serving as an independent pressure-bearing and sealing shell.

[0016] Preferably, a monitorable jacketed pressure chamber is formed by utilizing the inner and outer double-layer structure of the high-pressure reactor. A pressure sensor for detecting the jacketed pressure chamber is installed on the outer layer of the high-pressure reactor, and the pressure sensor is electrically connected to the control system. When the pressure in the interlayer pressure chamber detected by the pressure sensor exceeds the threshold, the control system immediately stops and issues an alarm.

[0017] This invention also discloses a system for decomposing rare earth concentrates using a strong alkali, comprising: The pulping unit includes an alkali tank and a pulping tank; Two continuous grinding and impregnation units, comprising a buffer tank, a first grinding and impregnation machine, a first intermediate tank, a second grinding and impregnation machine, and a second intermediate tank connected in sequence; The pressurized leaching unit includes a high-pressure reactor connected to the intermediate tank 2; A water washing unit, which includes a water washing tank, and the high-pressure reactor is connected to the water washing tank.

[0018] Preferably, the alkali tank is connected to the pulping tank via a high-pressure pump; the rare earth concentrate is stored in a silo, which is connected to the pulping tank. The slurry tank is connected to the buffer tank via a high-pressure pump.

[0019] Preferably, the pressurized leaching unit further includes an electric high-pressure diaphragm pump, through which the slurry in the intermediate tank is transported to the high-pressure reactor for leaching.

[0020] The beneficial effects of this invention are as follows: By employing two consecutive strong alkali grinding and leaching processes, focusing on lattice disruption and re-leaching dissociation at different stages, and combined with a highly active strong alkali medium, the structure of difficult-to-leach minerals is gradually opened up. This process not only shortens the diffusion path but also maintains sufficient ion exchange driving force through continuous replenishment of strong alkali, inhibiting the reverse exchange and re-adsorption of leached rare earth ions to the solid phase surface. This promotes the full entry of rare earth ions into the liquid phase from both kinetic and mass transfer perspectives. By strictly limiting the time from the end of grinding and leaching to entering the high-pressure reactor to no more than 5 hours, secondary particle agglomeration, flocculation, and re-adsorption and surface complexation of rare earth ions by clay gangue caused by prolonged residence are effectively avoided. High-pressure alkali leaching is performed immediately when the mineral is in a state of abundant microcracks and relaxed stress, forming an "activated lattice," completely eliminating the recovery bottleneck caused by excessive residence time, thereby increasing the recovery rate to approximately 90% or higher. Furthermore, this invention achieves optimal control of reaction kinetics and energy conservation through continuous, non-repressurized high-pressure leaching. The high-pressure reactor of this invention performs continuous leaching in a high-pressure, strongly alkaline environment without cooling or depressurization, avoiding the lattice recovery, reaction interruption, and significant heat loss caused by repeated "heating-cooling-pressurization-depressurization" in batch reactors. Under constant high-temperature and high-pressure intensification conditions, the reaction proceeds more thoroughly from the particle surface to the interior. The entire leaching process gradually shifts from strong diffusion control to chemical reaction control or mixing control, achieving near-complete mineral decomposition within 5 to 9 hours, significantly reducing overall energy consumption and achieving energy conservation, energy saving, and reduced production costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process flow equipment according to an embodiment of the present invention; In the diagram: 1. Alkali tank; 2. High-pressure pump one; 3. Slurry tank; 4. Silo; 5. High-pressure pump two; 6. Buffer tank; 7. High-pressure pump three; 8. Grinding and immersion machine one; 9. Intermediate tank one; 10. High-pressure pump four; 11. Grinding and immersion machine two; 12. Intermediate tank two; 13. High-pressure reactor; 14. Washing tank. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example: A method for treating rare earth concentrate using strong alkali decomposition involves subjecting the rare earth concentrate to two consecutive strong alkali grinding and leaching processes, followed immediately by leaching in a high-pressure reactor. This treatment significantly improves the leaching rate and recovery rate of rare earth elements while significantly reducing overall energy consumption, achieving energy conservation, cost reduction, and reduced production costs. In this example, strong alkali refers to an alkaline solution with a pH value ≥13 and a mass fraction ≥50%, such as LiOH, NaOH, or KOH. "Immediately after two strong alkali grinding and leaching processes, immediately followed by leaching in a high-pressure reactor" means that the concentrate is leached within ≤5 hours after the two strong alkali grinding and leaching processes.

[0024] like Figure 1 As shown, the specific steps are as follows: S1: Preparation and Supply of Alkali Solution In the alkali tank 1, caustic soda is dissolved in fresh water and returned alkali solution to prepare alkali solution. The prepared alkali solution is then transported to the pulping tank 3 by the high-pressure pump 2. S2: Concentrate Storage and Pulping Rare earth concentrate is first stored in silo 4, and then sent to pulping tank 3 through silo 4. In pulping tank 3, slurry that meets the requirements of solid-liquid ratio and alkalinity is made by stirring and compressed air. S3: Buffer tank adjustment The pulped slurry is transported to the buffer tank 6 by the high-pressure pump 25. The buffer tank 6 is used to balance the feed fluctuations and stabilize the flow rate and concentration entering the grinding and leaching section. S4: First grinding and soaking operation The slurry is sent from the buffer tank 6 to the grinding and leaching mill 8 by the high-pressure pump 3 7. The first grinding and leaching operation is carried out in a strongly alkaline environment. The slurry after grinding and leaching flows into the intermediate tank 9. S5: Second grinding and soaking operation The slurry in intermediate tank 9 is sent to grinding and leaching mill 211 by high-pressure pump 410. The second grinding and leaching operation is carried out in a strongly alkaline environment. The slurry after grinding and leaching flows into intermediate tank 22. The function of the intermediate tank is to regulate the slurry flow and properties between the grinding and leaching section and the pressurized leaching section to ensure continuous and stable operation of pressurized leaching. S6: Pressure Leaching An electric high-pressure diaphragm pump was used to pump the slurry in intermediate tank 2-12 at a rate of approximately 3.5 m³ / min. 3 The flow rate is conveyed to the high-pressure reactor 13 at a rate of / h for leaching; S7: Water washing operation The leached slurry from high-pressure reactor 13 is fed into a 20m... 3 The washing process is carried out in the washing tank 14, and the washed decomposed slurry is sent to the next process for solid-liquid separation.

[0025] The high-pressure pumps one through three in the above steps can also be electric high-pressure diaphragm pumps.

[0026] One of the innovations of this embodiment lies in the use of a two-stage strong alkali continuous grinding and leaching process. During the first strong alkali grinding and leaching, the mill operates at a high concentration of strong alkali. Utilizing the impact and shearing of the grinding media, combined with the corrosive effect of the strong alkali on silicate and carbonate gangue, the inclusions surrounding the rare earth minerals are partially destroyed, forming more microcracks and fresh reaction interfaces. Under the condition of "grinding and leaching simultaneously," the strong alkali simultaneously penetrates the freshly exposed mineral surface, causing preliminary alkali decomposition and preferentially dissolving the rare earths in easily leached areas, significantly shortening the time and energy required for subsequent leaching. After the first stage of grinding and leaching, some rare earths have entered the solution, but some remain in the incompletely dissociated fine particles or secondary inclusion structures, and there is a risk of re-adsorption in the solution. At this point, the second grinding and leaching process further refines the particle size while continuously supplementing with strong alkali, allowing the slurry to operate in a new high-alkalinity, high-turbulence environment. This further refines undissociated particles, monomerizing unexposed rare earth minerals and shortening diffusion paths. Simultaneously, by increasing the concentration of strong alkali cations in the solution, sufficient ion exchange driving force is maintained, inhibiting the reverse exchange and re-adsorption of leached rare earth ions to the solid surface. The overall mechanism of the two-stage continuous grinding and leaching process is as follows: Rare earth elements in rare earth concentrates often exist in the form of solid solution within the lattice of minerals such as monazite or are finely encapsulated by gangue. A single grinding and leaching process often fails to achieve sufficient dissociation and leaching, resulting in high residue and limited recovery. This scheme, through two stages of continuous grinding and leaching with strong alkali, focuses on lattice disruption and supplementary dissociation at different stages, combined with a highly active strong alkali medium, gradually opening the structure of difficult-to-leach minerals and continuously providing sufficient driving force. This promotes the full entry of rare earth ions into the liquid phase from both kinetic and mass transfer perspectives, thereby increasing the recovery rate to approximately 90% or higher.

[0027] Another innovation of this embodiment lies in the leaching process: the slurry is fed into the high-pressure reactor within a time frame of ≤5 hours. This utilizes the brief window of high activation and easy leaching of the slurry after grinding and leaching. By strictly limiting the time between the end of grinding and leaching and entry into the high-pressure reactor (no more than 5 hours, the shorter the better), re-adsorption and slurry aging are suppressed, thereby achieving more complete reaction and mass transfer during the high-pressure leaching stage, increasing the final rare earth recovery rate to approximately 96%–98%. This is because during the strong alkali grinding and leaching process, the rare earth concentrate undergoes partial destruction of its mineral crystal structure under the combined effects of mechanical impact and strong alkali chemical action, generating numerous microcracks, fresh surfaces, and "activated lattices" in a state of stress relaxation. At this time, the diffusion path within the rare earth minerals is shortened, and the reaction potential energy is increased, placing it in a state most favorable for subsequent leaching. If the slurry is introduced into the high-pressure reactor as soon as possible under this highly activated state, the effects of this lattice relaxation and crack network can be further amplified under the high temperature, high pressure, and strong alkali environment, making the deep decomposition of the minerals by high-pressure alkali leaching more thorough and significantly improving the migration degree of rare earths into the liquid phase, laying the foundation for achieving a 96%–98% recovery rate. If the slurry remains in the solution for an extended period after grinding and leaching, various adverse changes will occur, such as secondary agglomeration and flocculation between particles, reducing the effective specific surface area and clogging pores; and re-adsorption and surface complexation of rare earth ions on the clay and gangue surfaces, causing some rare earths to be re-fixed from the liquid phase to the solid phase. This embodiment limits the time interval between the end of grinding and leaching and the start of high-pressure leaching to "the shorter the better, and not exceeding 5 hours." Essentially, this embodiment sets the high-pressure leaching within a time window before significant re-adsorption and agglomeration occur, greatly mitigating the aforementioned adverse processes and mechanistically avoiding the occurrence of a recovery rate ceiling due to excessively long residence time.

[0028] To verify the synergistic effect of the "two-stage strong alkali continuous grinding and leaching" and the "residence time window of ≤5 hours" of this invention on the final rare earth element leaching rate and recovery rate, the applicant conducted the following comparative experiments: 1) Basic experimental conditions All comparative groups and this embodiment used the same batch of Baotou mixed rare earth concentrate. The conditions for entering the high-pressure reactor were kept consistent: the temperature was set at 220°C, the pressure was set at 2.0 MPa, the continuous leaching reaction time in the high-pressure reactor was uniformly 7 hours, and the alkali solution was a 50% NaOH solution.

[0029] 2) Comparative experimental grouping In this embodiment, two consecutive strong alkali grinding and leaching processes were used (D80=15um). After grinding and leaching, the sample was sent to a high-pressure reactor for leaching within 2 hours.

[0030] Comparative Example 1: Traditional single-stage strong alkali grinding and leaching (D80=15um) was used. After grinding and leaching, the sample was sent to a high-pressure reactor for leaching within 3 hours.

[0031] Comparative Example 2: Two strong alkali continuous grinding and leaching processes were adopted (D80=15um). After grinding and leaching, the slurry was kept in a room temperature stirred storage tank for 5 hours before being sent to a high-pressure reactor for leaching.

[0032] Comparative Example 3: Two strong alkali continuous grinding and leaching processes were adopted (D80=15um). After grinding and leaching, the slurry was kept in a normal temperature storage tank for 6 hours before being sent to a high-pressure reactor for leaching.

[0033] 3) Experimental results and data comparison

[0034] The above experiments demonstrate that this embodiment, through the design of a combination of "two strong alkali continuous grinding and leaching" and "a residence time window of ≤5 hours", can increase the rare earth element recovery rate to about 90% or more.

[0035] In step S6, pressurized leaching refers to continuous leaching in a high-pressure, strong-alkali environment in a high-pressure reactor without cooling or depressurization. During operation, the high-pressure reactor maintains stable high temperature, high pressure, and a high concentration of strong alkali. By continuously replenishing the strong alkali and slurry, the material continues to react under constant intensification conditions, avoiding the lattice recovery and reaction interruption caused by repeated "heating-cooling-pressurization-depressurization" in batch reactors. Under such constant temperature and pressure conditions, the strong alkali can continuously penetrate into the particle interior along the microcracks, grain boundaries, and defects formed during the grinding and leaching stage. The high pressure and high temperature significantly increase the alkali decomposition reaction rate and diffusion coefficient, making the reaction more thorough from the particle surface to the interior, thereby achieving a higher final leaching rate. Furthermore, in the continuous operation mode without cooling or depressurization, the flow pattern and energy supply within the high-pressure reactor are stable, and the slurry remains in a high-shear, high-turbulence state, which is beneficial for reducing the liquid film thickness, increasing the external diffusion rate, maintaining particle dispersion, reducing agglomeration and sedimentation, and ensuring effective contact time and area between the particle surface and the strong alkali. This allows the entire leaching process to gradually shift from diffusion control to chemical reaction control or mixing control, further amplifying the advantages of mass transfer and reaction kinetics based on grinding and leaching pre-activation. This, in turn, increases the rare earth recovery rate under reasonable time and reagent consumption conditions. In this embodiment, the minerals are consistently subjected to a comprehensive enhanced environment of high activation, high alkalinity, high temperature, and high pressure, thereby breaking through the recovery rate ceiling of traditional processes and increasing the rare earth recovery rate to approximately 90% or higher.

[0036] After the second grinding and leaching operation in step S5, the particle size distribution of the slurry is D80 = 10 μm to 20 μm, and the solid-liquid ratio is 40:60. In step S6, when the leaching is carried out in the high-pressure reactor, the temperature of the high-pressure reactor is 150 degrees to 280 degrees, the pressure is 1.5 MPa to 2.5 MPa, and the reaction time is 5 hours to 9 hours.

[0037] In this embodiment, the slurry particle size is controlled to D80 = 10µm to 20µm after secondary grinding and leaching. Essentially, this compresses the characteristic size of most particles to a range that is "fully liberated without excessive ultrafine processing." Within this range, rare earth minerals achieve essentially complete or high-level liberation, significantly shortening the diffusion path of rare earths from the particle interior to the solution. It also avoids the formation of large amounts of colloidal ultrafine mud, reducing adverse effects such as agglomeration, increased viscosity, and filtration difficulties, thus maintaining good fluidity and mass transfer conditions. The solid-liquid ratio is controlled at 40:60, ensuring the slurry has a sufficiently high solids concentration to improve the processing capacity per unit volume, while retaining sufficient liquid volume to guarantee contact and diffusion between the alkali and rare earth minerals, thereby achieving a balance between leaching efficiency and equipment scale. By controlling the temperature of the high-pressure reactor between 150°C and 280°C, and the pressure between 1.5 MPa and 2.5 MPa, the high temperature significantly increases the leaching reaction rate constant, accelerating the chemical reaction process between the rare earth mineral lattice and the leaching agent. The high pressure ensures the solution remains in a liquid phase at high temperatures and increases the solubility of certain gases in the solution, further promoting oxidative decomposition or synergistic reactions. With a particle size of D80 = 10 μm to 20 μm, the outer diffusion film thins, the inner diffusion path shortens, and the high temperature and pressure increase the diffusion coefficient. The overall leaching process gradually shifts from strong diffusion control to "chemical reaction control or mixing control," achieving near-complete mineral decomposition and rare earth leaching within a reaction time of 5 to 9 hours. Furthermore, controlling the reaction time to 5 to 9 hours avoids the problem of incomplete decomposition of some difficult-to-leach rare earth minerals in reactions shorter than 5 hours, and the limited recovery rate improvement but significantly increased energy consumption and equipment occupancy in reactions longer than 9 hours. Therefore, 5 to 9 hours represents a compromise between overall economic efficiency and high recovery rate. Therefore, this embodiment uses a two-stage grinding and leaching process to precisely control the particle size and concentration of the slurry. Combined with the high-pressure leaching conditions of the high-pressure reactor, the leaching process is made to be close to the optimal in terms of reaction kinetics, mass transfer conditions, and liquid-solid contact state. This improves the recovery rate without relying on excessive reagent consumption.

[0038] The high-pressure reactor has a double-layer structure. The inner layer directly contacts high-temperature, high-pressure, and highly corrosive acids, alkalis, or chlorine- and fluorine-containing media, and is made of corrosion-resistant materials (such as stainless steel, nickel-based alloys, PTFE-lined composite structures, etc.). Its primary functions are corrosion protection and pressure bearing. The outer layer is designed and calculated as a completely independent pressure-bearing shell according to pressure vessel standards. Its materials and thickness are capable of withstanding the design pressure and temperature inside the reactor independently under the most unfavorable operating conditions of inner layer failure, without plastic instability or leakage. During long-term operation, uniform corrosion, pitting corrosion, or crevice corrosion will inevitably occur in the inner layer. When local corrosion penetrates the inner layer, the medium will leak into the interlayer space between the inner and outer layers, rather than directly reaching the external environment. This embodiment upgrades the high-pressure reactor from a traditional single-layer pressure-bearing shell to a double-shell safety barrier with inner and outer layers. The inner layer mainly undertakes the functions of corrosion protection and primary pressure bearing. Even if the inner layer is perforated under long-term corrosive conditions, the outer layer still serves as an independent pressure-bearing and sealing shell. Combined with interlayer leakage detection, it prevents the medium from leaking directly into the environment, thereby fundamentally reducing the risk of safety accidents such as sudden explosion of the high-pressure reactor and spraying of toxic media.

[0039] A pressure sensor is installed on the outer layer of the high-pressure reactor to detect the pressure between the inner and outer layers. Under normal operating conditions, the interlayer space is isolated from the reactor's internal medium, communicating only with the outside environment or a dedicated gas source, and its pressure is controlled at a stable baseline value. When the inner layer corrodes and perforates or cracks, the high-temperature, high-pressure medium inside the reactor enters the interlayer space through the defect, causing the interlayer pressure to rapidly or gradually deviate from the baseline value. This pressure surge is much larger than normal minute fluctuations and can be reliably detected by the pressure sensor. The pressure sensor continuously collects the interlayer pressure signal and inputs it to the control system. When the interlayer pressure exceeds a threshold, the control system automatically determines that the inner layer may have perforated or experienced a serious leak, immediately shuts down the reactor, and issues an alarm. This cuts off the danger chain in the early stages of an accident, preventing media leakage and explosions.

[0040] like Figure 1 As shown, this embodiment also discloses a system for decomposing rare earth concentrate using a strong alkali, which includes: The pulping unit, used to prepare rare earth concentrate into slurry, includes an alkali tank 1 for preparing alkali solution and a pulping tank 3 for preparing slurry; Two continuous grinding and leaching units are used to perform continuous grinding and leaching operations on the slurry in a strongly alkaline environment. Each unit includes a buffer tank 6, a first grinding and leaching mill 8, an intermediate tank 9, a second grinding and leaching mill 11, and an second intermediate tank 12, which are connected by pipelines in sequence. A pressure leaching unit is used for continuous leaching of the slurry after two grinding and leaching processes, and includes a high-pressure reactor 13 connected to the intermediate tank 12; The washing unit is used to wash the decomposed slurry after high-pressure leaching. It includes a washing tank 14, and the discharge port of the high-pressure reactor 13 is connected to the washing tank 14 through a pipeline.

[0041] In summary, this invention employs two consecutive strong alkali leaching processes, focusing on lattice disruption and re-leaching dissociation at different stages, combined with a highly active strong alkali medium, to gradually open up the structure of difficult-to-leach minerals. This process not only shortens the diffusion path but also maintains sufficient ion exchange driving force through continuous replenishment of strong alkali, inhibiting the reverse exchange and re-adsorption of leached rare earth ions to the solid phase surface. This promotes the full entry of rare earth ions into the liquid phase from both kinetic and mass transfer perspectives. By strictly limiting the time from the end of leaching to entry into the high-pressure reactor to no more than 5 hours, secondary particle agglomeration, flocculation, and re-adsorption and surface complexation of rare earth ions by clay gangue caused by prolonged residence are effectively avoided. High-pressure alkali leaching is performed immediately when the mineral is in a state of abundant microcracks and relaxed stress, creating an "activated lattice," completely eliminating the recovery bottleneck caused by excessive residence time, thereby increasing the recovery rate to approximately 90% or higher. Furthermore, this invention achieves optimal control of reaction kinetics and energy conservation through continuous, non-repressurized high-pressure leaching. The high-pressure reactor of this invention performs continuous leaching in a high-pressure, strongly alkaline environment without cooling or depressurization, avoiding the lattice recovery, reaction interruption, and significant heat loss caused by repeated "heating-cooling-pressurization-depressurization" in batch reactors. Under constant high-temperature and high-pressure intensification conditions, the reaction proceeds more thoroughly from the particle surface to the interior. The entire leaching process gradually shifts from strong diffusion control to chemical reaction control or mixing control, achieving near-complete mineral decomposition within 5 to 9 hours, significantly reducing overall energy consumption and achieving energy conservation, energy saving, and reduced production costs.

[0042] In the embodiments, "multiple" refers to "two or more". The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the protection scope of the invention, which is defined by the claims.

Claims

1. A method for treating rare earth concentrates by decomposing them with a strong alkali, characterized in that: The process involves leaching rare earth concentrate twice with strong alkali, followed by immediate feeding into a high-pressure reactor for further leaching.

2. The method according to claim 1, characterized in that: The specific steps are as follows: S1: Preparation and Supply of Alkali Solution Prepare an alkali solution in an alkali tank, and then transfer the prepared alkali solution to a slurry tank. S2: Concentrate Storage and Pulping Rare earth concentrate is first stored in a silo, and then the rare earth concentrate is also sent to the pulping tank through the silo. In the pulping tank, it is made into slurry through stirring and compressed air. S3: Buffer tank adjustment The pulped slurry is then transported to a buffer tank; S4: First grinding and soaking operation The slurry is fed from the buffer tank into the first grinding and leaching mill, where the first grinding and leaching operation is carried out in a strongly alkaline environment. The slurry after grinding and leaching flows into the first intermediate tank. S5: Second grinding and soaking operation The slurry in intermediate tank one is fed into mill leaching two for a second grinding and leaching operation in a strongly alkaline environment. The slurry after grinding and leaching flows into intermediate tank two. S6: Pressure Leaching The slurry in intermediate tank 2 is transported to a high-pressure reactor for leaching. S7: Water washing operation The slurry leached from the high-pressure reactor is sent to a washing tank for washing. The washed slurry is then sent to the next process for solid-liquid separation.

3. The method according to claim 2, characterized in that: The phrase "immediately sent to the high-pressure reactor for leaching" refers to leaching the material after two strong alkali grinding leaches within ≤5 hours in a high-pressure reactor.

4. The method according to claim 2, characterized in that: In step S6, pressurized leaching refers to continuous leaching in a high-pressure, strongly alkaline environment in a high-pressure reactor without cooling or depressurization.

5. The method according to claim 4, characterized in that: After the second grinding and leaching operation in step S5, the particle size distribution of the slurry is D80 = 10 μm to 20 μm, and the solid-liquid ratio is 40:

60. In step S6, when the leaching is carried out in the high-pressure reactor, the temperature of the high-pressure reactor is 150 degrees to 280 degrees, the pressure is 1.5 MPa to 2.5 MPa, and the reaction time is 5 hours to 9 hours.

6. The method according to any one of claims 2 to 5, characterized in that: The high-pressure reactor has a double-layer structure, with the inner layer providing corrosion protection and primary pressure bearing, and the outer layer serving as an independent pressure-bearing and sealed shell.

7. The method according to claim 6, characterized in that: A monitorable jacketed pressure chamber is formed by utilizing the inner and outer double-layer structure of the high-pressure reactor. A pressure sensor for detecting the jacketed pressure chamber is installed on the outer layer of the high-pressure reactor, and the pressure sensor is electrically connected to the control system. When the pressure in the interlayer pressure chamber detected by the pressure sensor exceeds the threshold, the control system immediately stops and issues an alarm.

8. A system for treating rare earth concentrates by decomposing them with a strong alkali, comprising: The pulping unit includes an alkali tank and a pulping tank; Two continuous grinding and impregnation units, comprising a buffer tank, a first grinding and impregnation machine, a first intermediate tank, a second grinding and impregnation machine, and a second intermediate tank connected in sequence; The pressurized leaching unit includes a high-pressure reactor connected to the intermediate tank 2; A water washing unit, which includes a water washing tank, and the high-pressure reactor is connected to the water washing tank.

9. The system according to claim 8, characterized in that: The alkali solution tank is connected to the slurry tank via a high-pressure pump; the rare earth concentrate is stored in a silo, which is connected to the slurry tank. The slurry tank is connected to the buffer tank via a high-pressure pump.

10. The system according to claim 8, characterized in that: The pressurized leaching unit also includes an electric high-pressure diaphragm pump, through which the slurry in the intermediate tank is transported to the high-pressure reactor for leaching.

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