Method and system for recovering key metals from rare earth permanent magnet waste

Abstract

The application discloses a method and system for recycling key metals in rare earth permanent magnet waste, and belongs to the technical field of secondary resource recycling.The method comprises the following steps: demagnetization crushing, fluidized oxidation roasting, hydrogen-based fluidized reduction, grinding and magnetic separation operation and leaching, and key metals are recycled from the rare earth permanent magnet waste.Iron is separated before leaching, the influence of iron on subsequent leaching is avoided, hydrogen-based fluidized mineral phase conversion-magnetic separation process is adopted to increase iron content, the addition of reagents can be avoided or greatly reduced, the discharge of three wastes in the leaching process is reduced, the method is environment-friendly, solid waste resource utilization can be realized, the material can be pretreated through the fluidized oxidation reactor, air is introduced into the fluidized oxidation reaction system, rare earth in the powder can be converted into corresponding rare earth oxides, and the reduction efficiency of the subsequent fluidized reduction system is improved.

Description

Technical Field

[0001] This invention belongs to the field of secondary resource recycling technology, and relates to a method and system for recycling key metals from rare earth permanent magnet waste. Background Technology

[0002] Rare earth elements, due to their unique optical, electrical, and magnetic properties, play a crucial role in the development of advanced materials such as phosphors, permanent magnets, catalytic converters, lasers, and batteries. With the increasing demand for rare earth resources, the global imbalance between supply and demand is gradually intensifying. Simultaneously, against the backdrop of the international community's development of a circular economy, countries worldwide are actively conducting various rare earth recycling studies to address the challenges of rare earth recycling. Rare earth permanent magnet materials, due to their excellent comprehensive performance, are widely used in numerous fields. The clean energy transition, primarily driven by electric vehicles and wind power, will be a key driver of the increasing demand for neodymium iron boron (NdFeB) magnets. Since their introduction, their production and usage have increased rapidly, resulting in a staggering social stock. NdFeB waste mainly originates from the disposal of electronic products and waste generated during manufacturing processes; its recycling has become an important part of rare earth technology. Compared to ore, recovering rare earth elements from NdFeB waste is more energy-efficient and cost-effective, with production costs less than one-third of those from ore, and material consumption, energy consumption, and pollutant emissions less than one-fifth of those from ore. Therefore, recycling rare earth elements from rare earth permanent magnet waste not only facilitates the efficient utilization of rare earth resources and reduces the mining of rare earth ore, but also reduces industrial waste, protects the environment, and generates significant economic and environmental benefits. Currently, the main methods for recovering rare earths from rare earth permanent magnet waste are hydrometallurgical processes and pyrometallurgical processes. Compared with pyrometallurgical processes, hydrometallurgical processes have the advantages of lower cost, lower energy consumption, less waste generation, and lower emissions of toxic gases.

[0003] Patent CN117887987A relates to a method for selectively recovering rare earth elements from rare earth permanent magnet waste. The method involves oxidizing and roasting the rare earth permanent magnet waste, mixing it with a eutectic solvent, and then leaching it to obtain a leachate and filter residue. After adjusting the pH of the leachate, oxalic acid is added, reacting to obtain rare earth oxalate, which is then calcined to obtain rare earth oxides. However, this method has an excessively long leaching time, resulting in some Fe being leached out, affecting subsequent extraction processes. Patent CN114075626A proposes a method for integrated hydrothermal extraction and leaching to recover rare earth metals from rare earth permanent magnet waste. This method utilizes a series of structurally similar leaching agents, such as ammonium salts and ionic liquids, to extract and recover rare earth elements from the waste under high temperature and pressure. The advantage of this process is that it eliminates the need for further iron removal extraction; the disadvantage is that some rare earth (Ce) is lost to the leaching residue. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method and system for recovering key metals from rare earth permanent magnet waste. The method involves demagnetization and crushing, fluidized bed oxidation roasting, hydrogen-based fluidized bed reduction, grinding and magnetic separation, and leaching to recover key metals from rare earth permanent magnet waste. This invention separates iron oxides using hydrogen-based fluidized bed reduction-magnetic separation and reduces tetravalent cerium to trivalent cerium, improving the leaching rate of rare earth elements. It also avoids the iron precipitation process and the addition of reagents during reduction, reducing the resulting pollution.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for recycling key metals from rare earth permanent magnet waste includes the following steps:

[0007] 1. Crushing, grinding, drying, and demagnetizing: The rare earth permanent magnet waste is mechanically crushed and ground to a particle size of less than 0.18mm, then dried, dispersed, and subsequently demagnetized to obtain demagnetized powder.

[0008] 2. Fluidized oxidative roasting: The demagnetized powder is fed into the fluidized oxidative reactor after being separated by a primary cyclone separator. Air is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is well fluidized. The reactor temperature is stabilized at 400℃~1000℃ and the reaction time is 30min~300min.

[0009] 3. Hydrogen-based fluidized bed reduction: The oxidized powder is fed into a fluidized bed reduction reactor after being separated by a two-stage cyclone separator. A mixture of reducing gas and inert gas is introduced from the bottom of the reactor for reduction. After reduction, the material is cooled to below 200°C in an oxygen-free atmosphere.

[0010] 4. Grinding and magnetic separation: The obtained fluidized bed reduction product is ball-milled, and the particle size of the ball-milled product is controlled to be more than 50% of the particle size of -0.074mm. Then, the obtained ball-milled product is separated by wet weak magnetic separation to obtain magnetic concentrate product and non-magnetic tailings product. The magnetic product is ferrite, which is used as a raw material for iron and steel smelting, and the non-magnetic product is rare earth oxide, which is used for subsequent rare earth extraction.

[0011] 5. Leaching: The non-magnetic product is fed into a constant temperature leaching mixer to leach rare earth elements, and a leachate containing rare earth ions is obtained. The leaching temperature is 40℃~100℃, the leaching time is 5min~180min, and hydrochloric acid is used for leaching. The mass concentration of hydrochloric acid used is 5%~30%.

[0012] The above separation method, wherein:

[0013] In step 1, the rare earth permanent magnet waste is neodymium iron boron or cerium iron boron.

[0014] In step 2, the introduced air can be a mixture of oxygen and an inert gas, wherein the inert gas is nitrogen, argon, or helium, either alone or in a mixture. At this stage, the rare earth elements in the powder are mainly converted into their rare earth oxides, and iron and other elements are converted into ferric oxide (Fe₂O₃) and its corresponding oxides. Sufficient oxidation during calcination simplifies downstream processing. The reactions that occur are as follows:

[0015] 4Nd2Fe 14 B + 51O2 → 28Fe2O3 + 4Nd2O3 + 2B2O3

[0016] 4Ce2Fe 14 B + 53O2 → 28Fe2O3 + 8CeO2 + 2B2O3

[0017] In step 3, the proportion of reducing gas in the mixture of reducing gas and inert gas is 5% to 50%, preferably 15% to 25%; wherein the reducing gas is H2, CO, NH3 or a mixture thereof, and the inert gas is N2, Ar or a mixture thereof.

[0018] The reduction temperature is 400℃~800℃, preferably 450℃~600℃; the reduction time is 10min~90min, preferably 20min~60min. This stage mainly involves reducing oxidized Fe2O3 to the more magnetic Fe3O4, and reducing tetravalent rare earth Ce(IV) to the more easily leached trivalent rare earth Ce(III), facilitating subsequent magnetic separation and leaching operations. The reactions that occur are as follows:

[0019] 3Fe₂O₃ + H₂ = 2Fe₃O₄ + H₂O

[0020] 2CeO2 + H2 = Ce2O3 + H2O

[0021] In step 4, the purpose of grinding is to dissociate the reduced strongly magnetic Fe3O4 from the weakly magnetic rare earth oxide monomers as much as possible, thereby improving the magnetic separation efficiency.

[0022] In step 5, the preferred leaching temperature is 75℃~95℃, the preferred leaching time is 10min~60min, the preferred hydrochloric acid concentration is 15%~25%, the acid dosage during leaching is 100%~300% of the theoretical acid dosage, and the preferred leaching acid dosage is 100%~150% of the theoretical acid dosage. The theoretical dosage of leaching hydrochloric acid is calculated based on the total consumption of oxides such as REO in the fully oxidized material of the permanent magnet waste. The reaction equation is as follows:

[0023] RE₂O₃ + 6HCl = 2RECl₃ + 3H₂O

[0024] A system for recovering key metals from rare earth permanent magnet waste, used to implement the above method, consists of a demagnetizing feeding system, a fluidized oxidation system, a fluidized reduction roasting system, a cooling system, a grinding and magnetic separation system, a leaching system, and a dust removal system;

[0025] The dust removal system includes a dust collector and a chimney, with the outlet of the dust collector connected to the chimney;

[0026] The demagnetizing feeding system includes a silo, a loss-in-weight scale, a crusher, a No. 1 ball mill, a material dryer, a material disperser, and a demagnetizer; the silo, loss-in-weight scale, crusher, No. 1 ball mill, material dryer, material disperser, and demagnetizer are connected in sequence; the discharge port of the demagnetizer is connected to the fluidized bed oxidation system;

[0027] The fluidized bed oxidation system includes a primary cyclone separator, a primary sealing valve, a fluidized bed oxidation reactor, a secondary cyclone separator, a burner, and a blower. The feed inlet of the primary cyclone separator is connected to the discharge outlet of the demagnetizer, and the air outlet of the primary cyclone separator is connected to the dust collector via a pipeline. The discharge outlet of the primary cyclone separator is sequentially connected to the primary sealing valve and the feed inlet at the top of the fluidized bed oxidation reactor. The burner and the blower are connected to the air inlet at the bottom of the fluidized bed oxidation reactor via pipelines. The discharge outlet at the top of the fluidized bed oxidation reactor is connected to the feed inlet of the secondary cyclone separator, the air outlet of the secondary cyclone separator is connected to the dust collector, and the discharge outlet of the secondary cyclone separator is connected to the fluidized bed reduction roasting system.

[0028] The fluidized bed reduction roasting system includes a two-stage sealing valve, a fluidized bed reduction reactor, and a three-stage cyclone separator. The inlet of the two-stage sealing valve is connected to the outlet of the two-stage cyclone separator, and the outlet of the two-stage sealing valve is connected to the inlet at the top of the fluidized bed reduction reactor. The outlet at the top of the fluidized bed reduction reactor is connected to the inlet of the three-stage cyclone separator, and the bottom of the fluidized bed reduction reactor has inlets for reducing gas and nitrogen. The outlet of the three-stage cyclone separator is connected to a dust collector, and the outlet of the three-stage cyclone separator is connected to the recovery inlet at the top of the fluidized bed reduction reactor. The outlet at the top of the fluidized bed reduction reactor is connected to a cooling system.

[0029] The cooling system includes a four-stage cyclone separator and a cooling sealing valve. The four-stage cyclone separator has two feed inlets located at opposite positions on its upper part, which are connected to the discharge outlet at the top of the fluidized bed reduction reactor and the air outlet at the top of the cooling sealing valve, respectively. The air outlet of the four-stage cyclone separator is connected to a dust collector, and the discharge outlet of the four-stage cyclone separator is connected to the feed inlet at the top of the cooling sealing valve. The discharge outlet at the top of the cooling sealing valve is connected to the grinding and magnetic separation system.

[0030] The grinding and magnetic separation system includes a No. 2 ball mill, a weak magnetic separator, a concentrate pool, and a tailings pool; the outlet of the cooling and sealing valve is connected to the inlet of the No. 2 ball mill and the weak magnetic separator in sequence through pipelines; the magnetic product outlet of the weak magnetic separator is connected to the concentrate pool, and the tailings outlet is connected to the tailings pool.

[0031] The leaching system includes a constant temperature leaching mixer and a leachate collection tank. The feed port of the constant temperature leaching mixer is connected to the tailings pond, and the discharge port is connected to the leachate collection tank.

[0032] The main gas flow direction in this invention is:

[0033] 1. Fluidized bed reduction reactor → three-stage cyclone separator → dust collector → chimney;

[0034] 2. Cooling sealing valve → four-stage cyclone separator → dust collector → chimney;

[0035] 3. Fan → Fluidized bed oxidation reactor → Secondary cyclone separator → Primary cyclone separator → Dust collector → Chimney.

[0036] The material flow path is as follows: silo → loss-in-weight weigher → crusher → ball mill No. 1 → material dryer → material disperser → demagnetizer → primary cyclone separator → primary sealing valve → fluidized bed oxidation reactor → secondary cyclone separator → secondary sealing valve → fluidized bed reduction reactor → quaternary cyclone separator → cooling sealing valve → ball mill No. 2 → weak magnetic separator → concentrate pool, tailings pool → constant temperature leaching mixer → leachate collection pool.

[0037] This invention first crushes, grinds, dries, and disperses the raw ore into powder using a demagnetizing feeding system. The powder is then demagnetized and enters a fluidized bed oxidation system. In the fluidized bed oxidation system, the powder undergoes heating, dehydration, and oxidation before entering a fluidized bed reduction roasting system for reduction roasting in a reducing atmosphere. The reduced material then enters a cooling system, first cooled with nitrogen, and then enters a grinding and magnetic separation system to separate magnetic and non-magnetic products. The non-magnetic product then enters a leaching system. A dust removal system handles the dust-laden gases generated by the fluidized bed oxidation system, fluidized bed reduction roasting system, and cooling system, and discharges them after treatment.

[0038] Key points of the technical solution of this invention:

[0039] 1. This invention replaces the traditional static roasting with a fluidized mineral phase transformation process that has better mass and heat transfer, thereby reducing roasting time and avoiding multiple oxidation processes.

[0040] 2. This invention employs a hydrogen-based fluidized bed reduction-magnetic separation process to separate the ferrites, thus avoiding the influence of the presence of iron during the leaching process on subsequent leaching.

[0041] 3. When using cerium iron boron as raw material, this invention can simultaneously reduce tetravalent Ce to trivalent Ce, which is easier to leach, during the process of reducing weakly magnetic Fe2O3 to Fe3O4, thereby improving the leaching rate of rare earth elements and avoiding the addition of reducing agents and the generation of chlorine gas in subsequent leaching processes.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. Short roasting time: Existing processes often involve oxidative roasting as the first step, oxidizing waste into Fe2O3, NdBO3, GdFeO3, and CeO2 or NdBO3, NdFeO3, and Fe2O3. However, this process is mostly static roasting, which suffers from high roasting temperature, long roasting time, and the need for multiple oxidation processes. This invention uses a fluidized bed oxidation reactor for fluidized bed heating, replacing static roasting. This allows for more complete gas-solid reaction, higher system calorific value utilization efficiency, significantly reduced roasting time, and only requires one oxidation step, resulting in significant cost savings.

[0044] 2. This invention separates iron before leaching, avoiding its impact on subsequent leaching: During leaching, the presence of Fe2O3 leads to a large amount of Fe ions entering the leachate, increasing the amount of leaching acid required. Furthermore, to avoid affecting subsequent rare earth extraction processes, reagents such as NaOH are needed to precipitate and remove iron ions. This invention employs a hydrogen-based fluidized bed mineralization-magnetic separation process for iron extraction, which avoids or significantly reduces the need for reagents and lowers the emission of waste gas, wastewater, and solid waste during the leaching process.

[0045] 3. Compact Process and High Processing Capacity: The process of this invention is conducted in a closed system, resulting in a compact flow. In the oxidative roasting, the fluidized bed oxidation reactor has six chambers, significantly extending the oxidation time and ensuring thorough oxidation of the material. In the reduction roasting, the fluidized bed reduction reactor has four chambers, enabling simultaneous processing of a larger quantity of material and greatly improving reaction efficiency. This invention can obtain iron oxides with a TFe content of over 68 wt% and a rare earth leaching rate as high as 97%.

[0046] 4. This invention can be applied not only to NdFeB but also to CeFeB. For CeFeB permanent magnet waste, the oxidation process oxidizes Ce to Ce(IV), which is more difficult to leach, leading to a decrease in leaching rate, increased leaching difficulty, and the use of reducing agents such as thiourea in the leaching process. The hydrogen-based fluidized bed mineral phase conversion-magnetic separation process for iron extraction simultaneously reduces Ce(IV) to the more easily leached Ce(III) during iron reduction, avoiding the need for reducing agents in rare earth leaching. 5. This invention, through demagnetization and hydrogen-based fluidized bed mineral phase conversion technology, can more efficiently and precisely control the iron phase in rare earth permanent magnet waste, transforming it from an antiferromagnetic Fe2O3 phase to a strongly magnetic Fe3O4 phase. The non-magnetic product is then used for subsequent leaching, thereby efficiently recovering iron resources and rare earth elements such as NdFeB and Ce from rare earth permanent magnet waste.

[0047] 6. Environmentally friendly, enabling the utilization of solid waste resources. This system is equipped with a dust removal device, making exhaust emissions more environmentally friendly. Furthermore, this invention can use green energy sources such as hydrogen or ammonia as reducing agents, achieving zero carbon emissions throughout the entire process. This invention can treat permanent magnet waste through demagnetization, realizing the utilization of difficult-to-treat solid waste resources. At the same time, compared with existing processes, this invention has a simpler process, uses less leaching acid and reagents, reducing environmental pollution during production.

[0048] 7. The present invention can pretreat materials through a fluidized bed oxidation reactor. By introducing air into the fluidized bed oxidation reaction system, rare earth elements in the powder can be converted into corresponding rare earth oxides, and iron and other elements can be converted into ferric oxide (Fe2O3) and its corresponding oxides, thereby improving the reduction efficiency of the subsequent fluidized bed reduction system. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the process for recovering key metals from rare earth permanent magnet waste according to the present invention.

[0050] Figure 2 This is a schematic diagram of the system for recovering key metals from rare earth permanent magnet waste according to the present invention;

[0051] The components are as follows: 1. silo; 2. loss-in-weight scale; 3. crusher; 4. No. 1 ball mill; 5. material dryer; 6. material disperser; 7. demagnetizer; 8. primary cyclone separator; 9. primary sealing valve; 10. fluidized bed oxidation reactor; 11. secondary cyclone separator; 12. secondary sealing valve; 13. fluidized bed reduction reactor; 14. tertiary cyclone separator; 15. quaternary cyclone separator; 16. cooling sealing valve; 17. No. 2 ball mill; 18. weak magnetic separator; 19. constant temperature leaching mixer; 20. fan; 21. burner; 22. dust collector; 23. chimney; 24. concentrate pool; 25. tailings pool; 26. leachate collection pool. Detailed Implementation

[0052] The following will combine Figure 1 and Figure 2 This invention provides a clear and complete description of the technical solutions implemented in this patent. It should be noted that the examples described in this invention are for further explanation and illustration only, and are not intended to limit its scope of application. All other embodiments obtained by those skilled in the art based on this invention without inventive effort are within the protection scope of this patent.

[0053] This invention provides a method for recycling key metals from rare earth permanent magnet waste, the process flow is as follows: Figure 1 As shown, it includes the following steps:

[0054] 1. Crushing, grinding, drying, and demagnetizing: The rare earth permanent magnet waste neodymium iron boron or cerium iron boron is mechanically crushed and ground to a particle size of less than 0.18mm, then dried, dispersed, and subsequently demagnetized to obtain demagnetized powder.

[0055] 2. Fluidized bed oxidation roasting: The demagnetized powder is fed into a fluidized bed oxidation reactor after primary cyclone separation for oxidation roasting. Air is introduced from the bottom of the reactor to ensure good fluidization of the material in the reaction chamber. The reactor temperature is stabilized at 400℃~1000℃, and the reaction time is 30min~300min. The air can be a mixture of oxygen and inert gas, wherein the inert gas is nitrogen, argon, or helium, either alone or in a mixture.

[0056] 3. Hydrogen-based fluidized bed reduction: The oxidized powder is fed into a fluidized bed reduction reactor after being separated by a two-stage cyclone separator. A mixture of reducing gas and inert gas is introduced from the bottom of the reactor for reduction. After reduction, the material is cooled to below 200°C in a non-oxygen atmosphere. In the mixture of reducing gas and inert gas, the proportion of reducing gas is 5% to 50%, preferably 15% to 25%. The reducing gas is H2, CO, NH3 or a mixture thereof, and the inert gas is N2, Ar or a mixture thereof. The reduction temperature is 400°C to 800°C, preferably 450°C to 600°C. The reduction time is 10 min to 90 min, preferably 20 min to 60 min.

[0057] 4. Grinding and magnetic separation: The obtained fluidized bed reduction product is ball-milled, and the particle size of the ball-milled product is controlled to be more than 50% of the particle size of -0.074mm. Then, the obtained ball-milled product is separated by wet weak magnetic separation to obtain magnetic concentrate product and non-magnetic tailings product. The magnetic product is ferrite, which is used as a raw material for iron and steel smelting, and the non-magnetic product is rare earth oxide, which is used for subsequent rare earth extraction.

[0058] 5. Leaching: The non-magnetic product is fed into a constant temperature leaching mixer for leaching rare earth elements to obtain a leachate containing rare earth ions; the leaching temperature is 40℃~100℃, preferably 75℃~95℃; the leaching time is 5min~180min, preferably 10min~60min; the leaching process uses hydrochloric acid, and the mass concentration of the hydrochloric acid used is 5%~30%, preferably 15%~25%; the amount of acid used in the leaching process is 100%~300% of the theoretical acid amount, preferably 100%~150% of the theoretical acid amount.

[0059] This invention also provides a system for recovering key metals from rare earth permanent magnet waste, such as... Figure 2 As shown, this is used to implement the above method.

[0060] The present invention will now be further described with reference to specific embodiments.

[0061] Example 1:

[0062] This embodiment provides a fluidized oxidation-reduction-magnetic separation-leaching system, which consists of a demagnetizing feeding system, a fluidized oxidation system, a fluidized reduction roasting system, a cooling system, a grinding and magnetic separation system, a leaching system, and a dust removal system;

[0063] The dust removal system includes a dust collector 22 and a chimney 23, with the outlet of the dust collector 22 connected to the chimney 23.

[0064] The demagnetizing feeding system includes a silo 1, a loss-in-weight scale 2, a crusher 3, a No. 1 ball mill 4, a material dryer 5, a material disperser 6, and a demagnetizer 7; the silo 1, loss-in-weight scale 2, crusher 3, No. 1 ball mill 4, material dryer 5, material disperser 6, and demagnetizer 7 are connected in sequence; the discharge port of the demagnetizer 7 is connected to the fluidized bed oxidation system.

[0065] The fluidized bed oxidation system includes a primary cyclone separator 8, a primary sealing valve 9, a fluidized bed oxidation reactor 10, a secondary cyclone separator 11, a burner 21, and a blower 20. The feed inlet of the primary cyclone separator 8 is connected to the discharge outlet of the demagnetizer 7, and the air outlet of the primary cyclone separator 8 is connected to the dust collector 22 via a pipeline. The discharge outlet of the primary cyclone separator 8, the primary sealing valve 9, and the feed inlet at the top of the fluidized bed oxidation reactor 10 are sequentially connected. The burner 21 and the blower 20 are connected to the air inlet at the bottom of the fluidized bed oxidation reactor 10 via a pipeline. The discharge outlet at the top of the fluidized bed oxidation reactor 10 is connected to the feed inlet of the secondary cyclone separator 11, the air outlet of the secondary cyclone separator 11 is connected to the dust collector 22, and the discharge outlet of the secondary cyclone separator 11 is connected to the fluidized bed reduction roasting system.

[0066] The fluidized bed reduction roasting system includes a secondary sealing valve 12, a fluidized bed reduction reactor 13, and a tertiary cyclone separator 14. The inlet of the secondary sealing valve 12 is connected to the outlet of the secondary cyclone separator 11, and the outlet of the secondary sealing valve 12 is connected to the inlet at the top of the fluidized bed reduction reactor 13. The outlet at the top of the fluidized bed reduction reactor 13 is connected to the inlet of the tertiary cyclone separator 14, and the bottom of the fluidized bed reduction reactor 13 is provided with reducing gas and nitrogen inlets. The outlet of the tertiary cyclone separator 14 is connected to a dust collector 22, and the outlet of the tertiary cyclone separator 14 is connected to the recovery inlet at the top of the fluidized bed reduction reactor 13. The outlet at the top of the fluidized bed reduction reactor 13 is connected to a cooling system.

[0067] The cooling system includes a four-stage cyclone separator 15 and a cooling sealing valve 16. The four-stage cyclone separator 15 has two feed inlets located at opposite positions on its upper part, which are connected to the discharge outlet at the upper part of the fluidized bed reduction reactor 13 and the air outlet at the top of the cooling sealing valve 16, respectively. The air outlet of the four-stage cyclone separator 15 is connected to the dust collector 22, and the discharge outlet of the four-stage cyclone separator 15 is connected to the feed inlet at the top of the cooling sealing valve 16. The discharge outlet at the upper part of the cooling sealing valve 16 is connected to the grinding and magnetic separation system.

[0068] The grinding and magnetic separation system includes a No. 2 ball mill 17, a weak magnetic separator 18, a concentrate pool 24, and a tailings pool 25; the discharge port of the cooling sealing valve 16 is connected to the inlet of the No. 2 ball mill 17 and the weak magnetic separator 18 in sequence through pipelines; the magnetic product outlet of the weak magnetic separator 18 is connected to the concentrate pool 24, and the tailings outlet is connected to the tailings pool 25.

[0069] The leaching system includes a constant temperature leaching mixer 19 and a leachate collection tank 26. The feed port of the constant temperature leaching mixer 19 is connected to the tailings pond 25, and the discharge port is connected to the leachate collection tank 26.

[0070] This embodiment uses the above system to conduct fluidized bed oxidation roasting-fluidized bed reduction roasting-magnetic separation-leaching tests on NdFeB waste. The NdFeB permanent magnet waste contains 29.37% rare earth oxides (REO), of which 21.3% is Pr, 74.97% is Nd, 2.29% is Dy, and the Fe content is 66.79%. The specific method is carried out according to the following steps:

[0071] 1. Crushing and demagnetizing operation: The rare earth permanent magnet waste is fed into the hopper 1 and crushed to below 0.18mm by the crusher 3 and the mill 4, then dried by the dryer 5 and broken up by the disperser 6. Finally, it is demagnetized by the demagnetizer 7 to obtain powder.

[0072] 2. Fluidized bed oxidation roasting operation: After the demagnetized powder is separated by the first-stage cyclone separator 8, it is fed into the fluidized bed oxidation reactor 10 for oxidation roasting. Air is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is in good fluidization, the temperature in the reactor is stabilized at 800℃, and the material residence time is 120min.

[0073] 3. Hydrogen-based fluidized bed reduction operation: The oxidized rare earth permanent magnet waste is separated by a two-stage cyclone separator 11 and fed into the fluidized bed reduction reactor 13. H2 and N2 are introduced from the bottom of the reactor, with the proportion of H2 being 20%. The temperature inside the reactor is stabilized at 425℃, the material residence time is 30 minutes, and the material is kept in a fluidized state. After reduction, the material is separated by a four-stage cyclone separator 15 and fed into a cooling and sealing valve 16 to be cooled to below 200℃.

[0074] 4. Grinding and magnetic separation operation: The hydrogen-based fluidized bed reduction product obtained in step 3 is fed into ball mill 17 (No. 2). The ball mill product particle size of -0.074mm accounts for more than 50%. Then, the ball mill product is fed into a weak magnetic separator 18 for wet weak magnetic separation to obtain magnetic concentrate product and non-magnetic tailings product. The magnetic product is ferrite with a TFe grade of 68.72% and a TFe recovery rate of 95.98%. The non-magnetic product is rare earth oxide.

[0075] 5. Leaching operation: The non-magnetic product is fed into the constant temperature leaching mixer 19 for leaching of rare earth elements to obtain a leachate containing rare earth ions. The leaching temperature is 90℃, the leaching time is 60min, the concentration of hydrochloric acid used is 20%, and the amount of hydrochloric acid used is 130% of the theoretical amount of hydrochloric acid used. The leaching rate of rare earth in the obtained high-value rare earth ion leachate is 95.42%.

[0076] Example 2:

[0077] This embodiment involves fluidized bed oxidation roasting-fluidized bed reduction roasting-magnetic separation-leaching tests on cerium-iron-boron waste, using the same system as in Example 1. The cerium-iron-boron waste contains 33.97% rare earth oxides (REO), of which 40.23% is Ce, 19.80% is Nd, 34.84% is Gd, and 4.82% is Pr; the Fe content is 63.79%. The specific method is as follows:

[0078] 1. Crushing and demagnetizing operation: The rare earth permanent magnet waste is fed into the hopper 1 and crushed to below 0.18mm by the crusher 3 and the mill 4, then dried by the dryer 5 and broken up by the disperser 6. Finally, it is demagnetized by the demagnetizer 7 to obtain powder.

[0079] 2. Fluidized bed oxidation roasting operation: After the demagnetized powder is separated by the first-stage cyclone separator 8, it is fed into the fluidized bed oxidation reactor 10 for oxidation roasting. Air is introduced from the bottom of the reactor to ensure that the material in the reaction chamber is in good fluidization, the temperature in the reactor is stabilized at 800℃, and the material residence time is 120min.

[0080] 3. Hydrogen-based fluidized bed reduction operation: The oxidized rare earth permanent magnet waste is separated by a two-stage cyclone separator 11 and fed into the fluidized bed reduction reactor 13. H2 and N2 are introduced from the bottom of the reactor, with the proportion of H2 being 20%. The temperature inside the reactor is stabilized at 425℃, the material residence time is 30 minutes, and the material is kept in a fluidized state. After reduction, the material is separated by a four-stage cyclone separator 15 and fed into a cooling and sealing valve 16 to be cooled to below 200℃.

[0081] 4. Grinding and magnetic separation operation: The hydrogen-based fluidized bed reduction product obtained in step 3 is fed into ball mill 17 (No. 2). The ball mill product particle size of -0.074mm accounts for more than 50%. Then, the ball mill product is fed into a weak magnetic separator 18 for wet weak magnetic separation to obtain magnetic concentrate product and non-magnetic tailings product. The magnetic product is ferrite with a TFe grade of 68.07% and a TFe recovery rate of 96.14%. The non-magnetic product is rare earth oxide.

[0082] 5. Leaching operation: The non-magnetic product is fed into the constant temperature leaching mixer 19 for leaching of rare earth elements to obtain a leachate containing rare earth ions. The leaching temperature is 90℃, the leaching time is 60min, the concentration of hydrochloric acid used is 20%, and the amount of hydrochloric acid used is 130% of the theoretical amount of hydrochloric acid used. The leaching rate of rare earth in the obtained high-value rare earth ion leachate is 96.33%.

[0083] Example 3:

[0084] This comparative example is the same as Example 1, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 850°C and the material residence time was changed to 90 min; the temperature of the fluidized bed reduction reactor 13 was adjusted to 450°C and the material residence time was adjusted to 25 min, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 67.19% and a TFe recovery rate of 93.77% was obtained, as well as a rare earth leachate with a rare earth leaching rate of 95.56%.

[0085] Example 4:

[0086] This comparative example is the same as Example 1, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 700°C and the material residence time was changed to 150 min; the temperature of the fluidized bed reduction reactor 13 was adjusted to 500°C and the material residence time was adjusted to 15 min, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 68.71% and a TFe recovery rate of 90.24% was obtained, as well as a rare earth leachate with a rare earth leaching rate of 93.71%.

[0087] Example 5:

[0088] This comparative example is the same as Example 1, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 400°C, the material residence time was changed to 300 min, and other conditions remained unchanged. Finally, ferrite with a TFe grade of 65.48% and a TFe recovery rate of 91.95% was obtained, as well as a rare earth leachate with a rare earth leaching rate of 92.97%.

[0089] Example 6:

[0090] This comparative example is the same as Example 1, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 1000°C, the material residence time was changed to 30 min, and other conditions remained unchanged. Finally, ferrite with a TFe grade of 66.81% and a TFe recovery rate of 94.46% was obtained, along with a rare earth leachate with a rare earth leaching rate of 95.72%.

[0091] Comparative Example 1:

[0092] This comparative example is the same as Example 1, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 300°C, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 50.61% and a TFe recovery rate of only 12.49% was obtained, as well as rare earth leachate with a rare earth leaching rate of 29.65%.

[0093] Comparative Example 2:

[0094] This comparative example is the same as Example 1, except that the fluidized bed oxidation reactor 10 was replaced with a rotary kiln, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 53.69% and a TFe recovery rate of only 22.49% was obtained, as well as rare earth leachate with a rare earth leaching rate of 57.88%.

[0095] Example 7:

[0096] This comparative example is the same as Example 2, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 825°C and the material residence time was changed to 100 min; the temperature of the fluidized bed reduction reactor 13 was adjusted to 475°C and the material residence time was adjusted to 25 min, while other conditions remained unchanged. Finally, ferrite with a TFe content of 68.37% and a TFe recovery rate of 92.65% was obtained, as well as a rare earth leachate with a rare earth leaching rate of 94.11%.

[0097] Example 8:

[0098] This comparative example is the same as Example 2, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 750°C and the material residence time was changed to 140 min; the temperature of the fluidized bed reduction reactor 13 was adjusted to 470°C and the material residence time was adjusted to 25 min, while other conditions remained unchanged. Finally, ferrite with a TFe content of 66.75% and a TFe recovery rate of 93.07% was obtained, as well as a rare earth leachate with a rare earth leaching rate of 92.79%.

[0099] Comparative Example 3:

[0100] This comparative example is the same as Example 2, except that the temperature of the fluidized bed oxidation reactor 10 was adjusted to 300°C, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 48.46% and a TFe recovery rate of only 11.93% was obtained, as well as rare earth leachate with a rare earth leaching rate of 31.82%.

[0101] Comparative Example 4:

[0102] This comparative example is the same as Example 2, except that the fluidized bed oxidation reactor 10 was replaced with a rotary kiln, while other conditions remained unchanged. Finally, ferrite with a TFe grade of 51.84% and a TFe recovery rate of only 20.73% was obtained, as well as rare earth leachate with a rare earth leaching rate of 53.19%.

Claims

1. A method for recycling key metals from rare earth permanent magnet waste, characterized in that, Includes the following steps: Step 1. Crushing, grinding, drying, and demagnetizing: The rare earth permanent magnet waste is mechanically crushed and ground to a particle size of less than 0.18mm, then dried, dispersed, and subsequently demagnetized to obtain demagnetized powder. Step 2. Fluidized bed oxidation roasting: After the demagnetized powder is separated by a primary cyclone separator, it is fed into a fluidized bed oxidation reactor for oxidation roasting. Air is introduced from the bottom of the fluidized bed oxidation reactor to stabilize the reactor temperature at 400℃~1000℃ and the reaction time is 30min~300min. Step 3. Hydrogen-based fluidized bed reduction: The oxidized powder is fed into the fluidized bed reduction reactor after being separated by a two-stage cyclone separator. A mixture of reducing gas and inert gas is introduced from the bottom of the fluidized bed reduction reactor for reduction. After reduction, the material is cooled to below 200°C in an oxygen-free atmosphere; Step 4. Grinding and magnetic separation: The obtained fluidized reduction product is ball-milled, and the particle size of the ball-milled product is controlled to be more than 50% of the particle size of -0.074mm. Then, the obtained ball-milled product is separated by wet weak magnetic separation to obtain magnetic concentrate product and non-magnetic tailings product. Step 5. Leaching: The non-magnetic product is fed into a constant temperature leaching mixer to leach rare earth elements, obtaining a leachate containing rare earth ions. The leaching temperature is 40℃~100℃, the leaching time is 5min~180min, and hydrochloric acid is used for leaching. The mass concentration of hydrochloric acid used is 5%~30%, and the amount of hydrochloric acid used is 100%~300% of the theoretical acid amount.

2. The method for recycling key metals from rare earth permanent magnet waste according to claim 1, characterized in that, In step 1, the rare earth permanent magnet waste is neodymium iron boron or cerium iron boron.

3. The method for recycling key metals from rare earth permanent magnet waste according to claim 1, characterized in that, In step 2, the air introduced can also be a mixture of oxygen and an inert gas, wherein the inert gas is nitrogen, argon, helium, or a single or mixed inert gas.

4. The method for recycling key metals from rare earth permanent magnet waste according to claim 1, characterized in that, In step 3, the proportion of reducing gas in the mixture of reducing gas and inert gas is 5% to 50%. The reducing gas is H2, CO, NH3 or a mixture thereof, and the inert gas is N2, Ar or a mixture thereof. The reduction temperature is 400℃~800℃, and the reduction time is 10min~90min.

5. The method for recycling key metals from rare earth permanent magnet waste according to claim 4, characterized in that, The proportion of reducing gas is 15% to 25%, the reduction temperature is 450℃ to 600℃, and the reduction time is 20 min to 60 min.

6. The method for recycling key metals from rare earth permanent magnet waste according to claim 1, characterized in that, In step 5, the leaching temperature is 75℃~95℃, the leaching time is 10min~60min, the hydrochloric acid concentration is 15%~25%, and the amount of hydrochloric acid used is 100%~150% of the theoretical acid amount.

7. A system for recycling key metals from rare earth permanent magnet waste, used to implement the method described in any one of claims 1 to 6, characterized in that, It consists of a demagnetizing feeding system, a fluidized oxidation system, a fluidized reduction roasting system, a cooling system, a grinding and magnetic separation system, a leaching system, and a dust removal system; The demagnetizing feeding system includes a silo, loss-in-weight weigher, crusher, No. 1 ball mill, material dryer, material disperser, and demagnetizer; the fluidized bed oxidation system includes a primary cyclone separator, a primary sealing valve, a fluidized bed oxidation reactor, a secondary cyclone separator, burner, and blower; the fluidized bed reduction roasting system includes a secondary sealing valve, a fluidized bed reduction reactor, and a tertiary cyclone separator; the cooling system includes a quaternary cyclone separator and a cooling sealing valve; the grinding and magnetic separation system includes a No. 2 ball mill, a weak magnetic separator, a concentrate pool, and a tailings pool; the leaching system includes a constant temperature leaching mixer and a leachate collection pool; and the dust removal system includes a dust collector and a chimney, with the dust collector outlet connected to the chimney.

8. A system for recycling key metals from rare earth permanent magnet waste according to claim 7, characterized in that, The silo, loss scale, crusher, No. 1 ball mill, material dryer, material disperser and demagnetizer are connected in sequence; The feed inlet of the primary cyclone separator is connected to the discharge outlet of the demagnetizer, and the air outlet of the primary cyclone separator is connected to the dust collector via a pipeline. The discharge outlet of the primary cyclone separator is sequentially connected to the primary sealing valve and the feed inlet at the top of the fluidized bed oxidation reactor. The burner and the blower are connected to the air inlet at the bottom of the fluidized bed oxidation reactor via pipelines. The discharge outlet at the top of the fluidized bed oxidation reactor is connected to the feed inlet of the secondary cyclone separator, the air outlet of the secondary cyclone separator is connected to the dust collector, and the discharge outlet of the secondary cyclone separator is connected to the inlet of the secondary sealing valve.

9. A system for recycling key metals from rare earth permanent magnet waste according to claim 7, characterized in that, The outlet of the secondary sealing valve is connected to the feed inlet at the top of the fluidized bed reduction reactor; the outlet at the top of the fluidized bed reduction reactor is connected to the feed inlet of the tertiary cyclone separator; the bottom of the fluidized bed reduction reactor is provided with reducing gas and nitrogen gas inlets; the outlet of the tertiary cyclone separator is connected to the dust collector; and the outlet of the tertiary cyclone separator is connected to the recovery feed inlet at the top of the fluidized bed reduction reactor.

10. A system for recycling key metals from rare earth permanent magnet waste according to claim 7, characterized in that, The four-stage cyclone separator has two feed inlets located at opposite positions on its upper part, which are connected to the discharge outlet at the top of the fluidized bed reduction reactor and the air outlet at the top of the cooling sealing valve, respectively. The air outlet of the four-stage cyclone separator is connected to the dust collector, and the discharge outlet of the four-stage cyclone separator is connected to the feed inlet at the top of the cooling sealing valve. The discharge outlet at the top of the cooling sealing valve is connected to the inlet of the No. 2 ball mill and the weak magnetic separator in sequence through pipelines. The magnetic product outlet of the weak magnetic separator is connected to the concentrate pool, and the tailings outlet is connected to the tailings pool, the constant temperature leaching mixer, and the leachate collection pool in sequence.

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