A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste

Abstract

This invention discloses a method for efficiently extracting iron and enriching rare earth elements from NdFeB waste. The main equipment and materials include a rotary kiln, NdFeB waste, sulfate, a jaw crusher, carbon monoxide, and a synthesis reactor. The preparation method is as follows: NdFeB waste is oxidatively roasted in a rotary kiln at 600-800℃ to obtain the corresponding mixed oxides, which are then ground. The roasted ore is treated with a saturated solution of sulfate, calcium sulfate, magnesium sulfate, and nickel sulfate to achieve a sulfate content of 2%. The ore is then reduced at a reduction temperature of 800-950℃ for four hours with a carbon ratio of 30% to obtain reduced lumps. This step has two objectives: selective reduction and iron reduction rate exceeding 95%. This invention has the advantages of simultaneous and efficient extraction and high-value recycling of iron metal from NdFeB waste while enriching rare earth metals, a short process flow, environmental friendliness, and high product value.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, specifically to a method for efficiently extracting and enriching rare earth elements from NdFeB waste. Background Technology

[0002] my country is a major producer of NdFeB magnetic materials, and its annual production is still growing at a rate of approximately 20%. However, the production process generates about 30 wt% NdFeB waste, including machined blocks and oil-immersed waste. Reports indicate that this NdFeB waste contains approximately 30% rare earth elements (of which neodymium accounts for about 90%, with the remainder being other rare earth elements) and about 60%-70% iron.

[0003] Currently, the main methods for recovering and extracting high-value elements from NdFeB waste include vacuum melting, sulfuric acid method, electroreduction method, hydrochloric acid method, and hydrometallurgical method. Among these, the hydrometallurgical process utilizes large amounts of acid and alkali solutions to separate impurities from rare earth elements through solvent extraction and precipitation, thereby achieving the goal of rare earth recovery. It is widely applicable to processing NdFeB waste of different compositions and forms, and is currently the most widely used method. However, the process for treating NdFeB waste based on this method requires the leaching and recycling of rare earth elements in stages. Although this method can obtain rare earth oxides with high purity, the entire recycling process has the drawbacks of long process and low rare earth recovery rate. Moreover, most current processing technologies still only focus on the recovery of rare earth elements from the waste, while ignoring the recycling of the abundant iron elements in NdFeB waste (iron accounts for about 60%-70% of NdFeB waste). Usually, the iron slag after leaching is only used as raw material for ironmaking, which makes it difficult to achieve high-value utilization of iron resources. Therefore, there is a greater need for a method to efficiently extract iron and enrich rare earth elements from NdFeB waste. Summary of the Invention

[0004] The purpose of this invention is to provide a method for efficiently extracting iron and enriching rare earth elements from NdFeB waste. This method has the advantages of simultaneous and efficient extraction, high-value recycling of iron metal from NdFeB waste and enrichment of rare earth metals, short process flow, environmental friendliness, and high product value, thus solving the problems in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for efficiently extracting iron and enriching rare earth elements from NdFeB waste, the main equipment and materials being a rotary kiln, NdFeB waste, sulfate, a jaw crusher, carbon monoxide, and a synthesis reactor, etc.; the preparation method is as follows;

[0006] Its manufacturing steps are as follows:

[0007] Step (1) The NdFeB waste is oxidized and roasted in a rotary kiln to obtain the corresponding mixed oxide, which is then ground into 200 roasted sand. The reaction formulas during the roasting process are: Nd+O2→Nd2O3 and Fe+O2→Fe2O3.

[0008] Step (2) The calcined sand is treated with a saturated sulfate solution (calcium sulfate, magnesium sulfate, nickel sulfate, etc.) to make the sulfate content in the calcined sand reach 2%;

[0009] Step (3) Under the conditions of a reduction temperature of 800-950℃, a reduction time of four hours, and a carbon ratio of 30%, the calcined sand is reduced to obtain reduced lumps; the reduction reaction formulas are: Fe2O3+C→Fe+CO2 and CaSO4→CaO+SO3;

[0010] Step (4) Use a jaw crusher to crush the reduced lumps to obtain reduced lumps of the desired particle size;

[0011] Step (5) The reduced material and carbon monoxide are synthesized in a synthesis reactor to produce iron pentacarbonyl and synthesis residue. The iron pentacarbonyl is used to produce high-value-added micron-sized carbonyl iron powder. The rare earth elements in the synthesis residue are enriched, and the grade is increased from 30% to 70%.

[0012] Preferably, in step (1), the NdFeB waste is oxidized and roasted in a rotary kiln at a temperature of 600-800℃.

[0013] Preferably, step (3) includes ① selective reduction: the reduction rate of iron reaches more than 95%, and rare earth elements are basically not reduced; ② the sulfate ions in the sulfate decompose to generate sulfur trioxide, which is absorbed by the reduced iron. The iron contains 0.2 to 0.6% sulfur, which can greatly increase the rate of carbonyl synthesis reaction.

[0014] Preferably, the particle size of the reduced block material in step (4) is <30mm.

[0015] Preferably, the synthesis reaction in step (5) is carried out in the synthesis reactor under conditions of 11.0-30.0 MPa.

[0016] Compared with the prior art, the beneficial effects of this invention are as follows: This invention provides a method for efficiently extracting iron and enriching rare earth elements from NdFeB waste. The NdFeB waste is oxidatively roasted in a rotary kiln to obtain corresponding mixed oxides, which are then ground. The roasted ore is treated with a saturated solution of sulfate, calcium sulfate, magnesium sulfate, nickel sulfate, etc., to reduce the ore and obtain reduced lumps. The iron reduction rate reaches over 95%, and the rare earth elements are essentially not reduced. The sulfate ions in the sulfate decompose to generate sulfur trioxide, which is absorbed by the reduced iron. The iron contains 0.2-0.6% sulfur, which can significantly increase the carbonyl group content. The synthesis reaction rate involves crushing the reduced lumps using a jaw crusher, followed by a synthesis reaction between the reduced lumps and carbon monoxide in a synthesis reactor to produce iron pentacarbonyl and synthesis residue. The iron pentacarbonyl is used to produce high-value-added micron-sized iron carbonyl powder, while rare earth elements in the synthesis residue are enriched. In summary, the iron extraction rate in these steps reaches over 90%, and the rare earth element grade in the synthesis residue is enriched to nearly 70%, which is then exported as a high-grade NdFeB raw material. This process has the advantages of simultaneous and efficient extraction, high-value recycling of iron metals from NdFeB waste, enrichment of rare earth metals, short process flow, environmental friendliness, and high product value. Detailed Implementation

[0017] The following will describe the technical solutions in the embodiments of the present invention in a clear and complete manner, taking into account the features of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Example 1:

[0019] A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste, the main equipment and materials of which are a rotary kiln, NdFeB waste, sulfate, jaw crusher, carbon monoxide and synthesis kettle, etc.; the preparation method is as follows;

[0020] Its manufacturing steps are as follows:

[0021] Step (1) The NdFeB waste is oxidized and roasted in a rotary kiln to obtain the corresponding mixed oxide, which is then ground into 200 roasted sand. The reaction formulas during the roasting process are: Nd+O2→Nd2O3 and Fe+O2→Fe2O3.

[0022] Step (2) The calcined sand is treated with a saturated sulfate solution (calcium sulfate, magnesium sulfate, nickel sulfate, etc.) to make the sulfate content in the calcined sand reach 2%;

[0023] Step (3) Under the conditions of a reduction temperature of 800-950℃, a reduction time of four hours, and a carbon ratio of 30%, the calcined sand is reduced to obtain reduced lumps; the reduction reaction formulas are: Fe2O3+C→Fe+CO2 and CaSO4→CaO+SO3;

[0024] Step (4) Use a jaw crusher to crush the reduced lumps to obtain reduced lumps of the desired particle size;

[0025] Step (5) The reduced material and carbon monoxide are synthesized in a synthesis reactor to produce iron pentacarbonyl and synthesis residue. The iron pentacarbonyl is used to produce high-value-added micron-sized carbonyl iron powder. The rare earth elements in the synthesis residue are enriched, and the grade is increased from 30% to 70%.

[0026] Specifically, in step (1), the NdFeB waste is oxidized and roasted in a rotary kiln at a temperature of 600-800℃. Step (3) includes ① selective reduction: the reduction rate of iron reaches more than 95%, and rare earth elements are basically not reduced; ② the sulfate ions in the sulfate are decomposed to generate sulfur trioxide, which is absorbed by the reduced iron. The iron contains 0.2-0.6% sulfur, which can greatly increase the rate of carbonyl synthesis reaction. Step (4) the particle size of the reduced block is <30mm. Step (5) the synthesis reaction is carried out in the synthesis kettle under the conditions of 11.0-30.0MPa. In summary, the iron extraction rate in the above steps reaches more than 90%, and the rare earth element grade in the synthesis residue is enriched to nearly 70%, which is used as a high-grade NdFeB raw material for export.

[0027] The typical composition of NdFeB waste before and after treatment using this method is as follows:

[0028] Nd Fe B Al Typical components of NdFeB waste 33.8% 64.7% 1% 0.5% Typical components of NdFeB waste processed by this method 67.94% 12.36% 2.01% 1.01%

[0029] This invention involves oxidizing and roasting NdFeB waste in a rotary kiln at 600-800℃ to obtain the corresponding mixed oxides, which are then ground to 200 mesh. The roasting process is as follows: Nd + O2 → Nd2O3 and Fe + O2 → Fe2O3. The roasted ore is then treated with a saturated solution of sulfate, calcium sulfate, magnesium sulfate, and nickel sulfate to achieve a sulfate content of 2%. The ore is further reduced at a reduction temperature of 800-950℃ for four hours with a carbon ratio of 30% to obtain reduced lumps. The reduction process is as follows: Fe2O3 + C → Fe + CO2 and CaSO4 → CaO + SO3. This step serves two purposes: selective reduction, achieving an iron reduction rate of over 95%, while minimizing the reduction of rare earth elements. In the original process, the sulfate ions in sulfate decompose to generate sulfur trioxide, which is absorbed by the reduced iron. The iron contains 0.2-0.6% sulfur, which can significantly increase the rate of carbonyl synthesis reaction. The reduced material is crushed by a jaw crusher to obtain reduced material with a particle size of <30mm. The reduced material and carbon monoxide are synthesized in a synthesis reactor under 11.0-30.0MPa conditions to generate pentacarbonyl iron and synthesis residue. Pentacarbonyl iron is used to produce high-value-added micron-sized carbonyl iron powder. The rare earth elements in the synthesis residue are enriched, and the grade is increased from 30% to 70%. In summary, the iron extraction rate in the above steps reaches more than 90%, and the rare earth element grade in the synthesis residue is enriched to nearly 70%, which is then sold as a high-grade neodymium iron boron raw material.

[0030] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0031] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste, characterized in that: The main equipment and materials are rotary kiln, NdFeB waste, sulfate, jaw crusher, carbon monoxide and synthesis reactor; The method is as follows: Step (1) The NdFeB waste is oxidized and roasted in a rotary kiln to obtain the corresponding mixed oxides. The roasted sand is ground to 200 mesh. At the same time, the reaction formulas of the roasting process are: Nd+O2→Nd2O3 and Fe+O2→Fe2O3. Step (2) The calcined sand is treated with a saturated sulfate solution to make the sulfate content in the calcined sand reach 2%; wherein the sulfate is calcium sulfate, magnesium sulfate or nickel sulfate; Step (3) Under the conditions of a reduction temperature of 800-950℃, a reduction time of four hours, and a carbon ratio of 30%, the calcined sand is reduced to obtain reduced lumps; the reduction reaction formulas are: Fe2O3+C→Fe+CO2 and CaSO4→CaO+SO3; The step (3) includes ① selective reduction: the reduction rate of iron reaches more than 95%, and rare earth elements are basically not reduced; ② the sulfate ions in the sulfate decompose to generate sulfur trioxide, which is absorbed by the reduced iron, and the iron contains 0.2 to 0.6% sulfur. Step (4) Use a jaw crusher to crush the reduced lumps to obtain reduced lumps of the desired particle size; Step (5) The reduced material and carbon monoxide are synthesized in a synthesis reactor to produce iron pentacarbonyl and synthesis residue. The iron pentacarbonyl is used to produce high-value-added micron-sized carbonyl iron powder. The rare earth elements in the synthesis residue are enriched, and the grade is increased from 30% to 70%.

2. A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste as described in claim 1, characterized in that: In step (1), the NdFeB waste is oxidized and roasted in a rotary kiln at a temperature of 600-800℃.

3. A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste as described in claim 1, characterized in that: In step (4), the particle size of the reduced block material is <30mm.

4. A method for efficiently extracting iron and enriching rare earth elements from NdFeB waste as described in claim 1, characterized in that: The synthesis reaction in step (5) is carried out in the synthesis reactor under conditions of 11.0-30.0 MPa.