JP2012041588A - Separation method and separation system for rare earth element by chloride volatilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively separating and recovering rare earth elements from a raw material containing the rare earth elements and a metal element other than the rare earth elements.SOLUTION: A separation method includes: an oxidation treatment step of obtaining an oxidized raw material by applying oxide treatment; a carbon source mixing step of mixing a carbon source; and a heat treatment step of heat-treating in a chlorine atmosphere after the oxidation treatment step and the carbon source mixing step, with respect to the raw materials containing the rare earth elements and the metal element other than the rare earth elements.

Description

  The present invention relates to a method and system for separating and recovering rare earth elements from a raw material containing rare earth elements and other metal elements.

  High-power motors are installed in hybrid vehicles and electric vehicles whose demand has been increasing in recent years, and magnets provided in the high-power motors have excellent magnetic properties and high strength. Rare earth magnets containing elements are used. In addition, motors using rare earth magnets are widely used in home appliances and the like that are required to be lightweight because they are small and can provide high output. Furthermore, rare earth elements are also used in various products other than magnets due to their characteristics, and further increase in demand is expected in the future. On the other hand, rare earth elements are produced in small quantities, and there is concern about a shortage of supply due to future increases in demand. Therefore, it is important to efficiently collect and reuse rare earth elements during product recycling, or to use rare earth elements without waste during product manufacture. For example, in the rare earth magnet manufacturing process, about 20 to 30% by mass becomes polishing scraps due to cutting, polishing or breakage. If the rare earth elements can be efficiently separated and recovered from the polishing scraps and reused, the rare earth elements can be used without waste. It is also important to efficiently separate and recover rare earth elements from scrap of used rare earth magnets.

  On the other hand, one of the techniques for separating and recovering a predetermined element from a raw material is a dry separation and recovery method using a chemical volatilization method. The dry method has various advantages such as a small amount of waste liquid processing, a facility scale can be reduced, and a processing time can be shortened. In particular, the chlorination volatilization method enables volatilization at a low temperature even when a high-boiling-point compound is used, and it is considered that metal elements can be separated and recovered with energy saving (Patent Documents 1 to 3). 3 and non-patent literature 1). If such a chlorination volatilization method can be applied to the separation and recovery of rare earth elements, it is possible to efficiently separate and recover rare earth elements from scraps and the like produced in conventional products and manufacturing processes, and supply of rare earth elements expected in the future It seems possible to cope with the shortage.

JP 2009-132960 A JP 2008-222499 A JP 2000-144275 A

Toshise Nonaka, “Reaction Engineering Research on Chlorination of Metal Resources and Carbon Reduction”, Akita University Doctoral Dissertation 2004

  Here, separation and purification methods using the chlorination volatilization method described in Patent Document 1 and Patent Document 2 are In, Ti, Fe, Cr, Si, Al, and C, or Ta, Nb, Cr, Co, and Ni. , Ti and W can be separated and purified. However, separation of rare earth elements from other metal elements has not been studied. On the other hand, Patent Document 3 discloses that by applying a chloride volatilization method, only iron can be separated from a raw material containing rare earth elements and iron, and the rare earth elements can be concentrated in a solid residue. The method was considered suitable for the separation and recovery of rare earth elements and other elements. However, as a result of experiments by the present inventors, when the raw material contains non-metallic elements such as non-ferrous metals and boron in addition to the rare-earth elements and iron, the conventional chloride volatilization method is used for the rare-earth elements. Even when the separation and recovery are attempted, it has been found that non-ferrous metals and non-metals remain together with the rare earth elements in the residue, and it is difficult to concentrate and separate only the rare earth elements in the residue.

  The present invention has been made in view of the above problems, and it is an object to provide a method and system capable of appropriately separating and recovering a rare earth element from a raw material containing a rare earth element and a metal element other than the rare earth element. And

In order to solve the above problems, the present invention adopts the following configuration. That is,
According to a first aspect of the present invention, a carbon source is mixed with an oxidation treatment step of obtaining a raw material oxidized by subjecting a raw material containing a rare earth element and a metal element other than the rare earth element to an oxidation treatment. And a rare earth element separation method in which a carbon source mixing step and a heat treatment step of heat treatment in a chlorine atmosphere after the oxidation treatment step and the carbon source mixing step are performed.

  In the present invention, “a raw material containing a rare earth element and a metal element other than the rare earth element” is not limited to a raw material consisting of only a rare earth element and other metal elements, but a rare earth element and other metals. In addition to the elements, it means that nonmetallic elements such as boron and carbon may be further contained. Further, a plurality of metal elements may be included as the metal element other than the rare earth element. The “carbon source” may be a compound containing carbon in addition to carbon itself. For example, carbon derived from a resin having a carbon chain or inorganic carbide may be used. “Mixing the carbon source” means that the carbon source is intentionally mixed in the raw material before the heat treatment, or if the carbon source is previously contained in the raw material itself, By using it as it is, it can be regarded as "mixed carbon source".

  In the first aspect of the present invention, a pulverization step of pulverizing the raw material may be provided, and the oxidation treatment step may be performed after the pulverization step. By crushing the raw material, carbon reduction and chlorination can be performed to the inside of the raw material, and separation efficiency between the rare earth element and other elements can be improved during the heat treatment.

  In the first aspect of the present invention, the oxidation treatment step may be a step of obtaining polishing waste as an oxidized raw material by polishing the raw material. Since the polishing scraps are naturally oxidized by cutting and polishing the raw materials, the polishing scraps can be directly subjected to chlorination. That is, for example, it is possible to separate and collect rare earth elements from the polishing scraps by using the polishing scraps generated in the raw material manufacturing process as “oxidized raw materials” as they are.

  1st aspect of this invention WHEREIN: It is preferable that a heat processing process is equipped with the temperature holding process which hold | maintains the said temperature in any temperature between 300 degreeC-1000 degreeC. Between 300 ° C. and 1000 ° C., the metal element other than the rare earth element can be selectively chlorinated and volatilized while leaving the rare earth element in the solid residue of the raw material. Therefore, by holding the temperature at any temperature between 300 ° C. and 1000 ° C., it becomes possible to concentrate only the rare earth element more easily in the solid residue.

  In the first aspect of the present invention, an Nd—Fe—B magnet may be used as a raw material. The Nd—Fe—B magnet includes a plurality of other metal elements and nonmetal elements such as Fe, B, and Co in addition to rare earth elements such as Nd and Pr. In the present invention, even when such a raw material containing a plurality of elements is used, only rare earth elements can be appropriately separated and recovered.

  According to a second aspect of the present invention, there is provided an oxidation treatment means, a carbon source mixing means, a carbon source mixing means, and a heating process for performing an oxidation treatment on a raw material containing a rare earth element and a metal element other than the rare earth element. A rare earth element separation system comprising a heat treatment means for treating, and further comprising a chlorine supply means for supplying chlorine to the heat treatment means.

  In the second aspect of the present invention, a crushing means for crushing the raw material may be further provided, and the oxidation treatment may be performed after the crushing of the raw material. By crushing the raw material by the crushing means, carbon reduction and chlorination can be performed to the inside of the raw material, and the separation efficiency of the rare earth element can be improved.

  In the second aspect of the present invention, the oxidation treatment means may be a polishing means for polishing the raw material. Polishing waste is generated by polishing the raw material by the polishing means. Here, since the polishing scraps obtained by polishing are naturally oxidized, the polishing scraps can be directly subjected to chlorination.

  In the second aspect of the present invention, the heating means may hold the temperature at any temperature between 300 ° C and 1000 ° C. Between 300 ° C. and 1000 ° C., the metal element other than the rare earth element can be selectively chlorinated and volatilized while leaving the rare earth element in the solid residue of the raw material. Therefore, by holding the temperature at any temperature between 300 ° C. and 1000 ° C., it becomes possible to concentrate only the rare earth element more easily in the solid residue.

  In the second aspect of the present invention, an Nd—Fe—B magnet can be used as a raw material.

  According to the present invention, the raw material can be appropriately subjected to chlorination by oxidizing the raw material in a pretreatment, and then performing a heat treatment in a chlorine atmosphere using carbon reduction. A rare earth element can be separated and recovered from a raw material containing a metal element other than the rare earth element.

It is a flowchart for demonstrating the separation method of rare earth elements. It is a figure for demonstrating one form of the separation system of rare earth elements. It is a figure which shows roughly the structure of the experimental apparatus used in the Example. It is a figure which shows a thermodynamic equilibrium calculation result about the Nd-Fe-B magnet (sample A) in a chlorine atmosphere, and the thing which oxidized the said magnet (sample B). It is a figure which shows the change of the weight change in a chlorine atmosphere, and the volatilization rate of a magnet constituent element about the sample A. It is a figure which shows the form change of the magnet constituent element about the sample A in a chlorine atmosphere. It is a figure which shows the change of the weight change in a chlorine atmosphere, and the volatility rate of a magnet constituent element about the sample B. FIG. It is a figure which shows the form change of the magnet constituent element about the sample B in chlorine atmosphere. It is a figure which shows the change of the weight change in a chlorine atmosphere, and the volatility rate of a magnet constituent element about the case where a carbon source is added to the sample B. It is a figure which shows the form change of the magnet structural element in a chlorine atmosphere about the case where a carbon source is added to the sample B. It is a figure which shows the form change of the magnet structural element in a chlorine atmosphere about the case where a carbon source is added to the sample B.

  The method and system for separating rare earth elements according to the present invention can be applied to a process for separating and recovering rare earth elements from a raw material containing rare earth elements and metal elements other than the rare earth elements. The raw material is not particularly limited as long as it is a raw material containing a rare earth element and a metal element other than the rare earth element, but from the viewpoint that the effect of the present invention is sufficiently exerted, other than the rare earth element and the rare earth element. It is preferable to use a raw material containing a plurality of metal elements. In the present invention, a raw material further containing a nonmetallic element in addition to these elements may be used. As a specific raw material, for example, a neodymium magnet (Nd—Fe—B magnet) containing Nd and Pr as rare earth elements, Fe and Co as other metal elements, and B as a nonmetal element is used. it can. The raw material can be assumed to have various forms such as a block shape and a plate shape, but from the viewpoint of sufficiently proceeding the reaction, it is preferable to pulverize the raw material before use in chlorination and use it as a powder. Furthermore, in the present invention, the raw material is oxidized from the viewpoint of improving the handleability of the raw material. Oxidation treatment of the raw material makes it possible to appropriately control the volatilization behavior of the metal element by forming an intermediate during volatilization of chloride. In the present invention, a carbon source is included in the raw material from the viewpoint of allowing the reaction (reduction reaction) to proceed at a lower temperature and appropriately allowing only the rare earth element to remain in the solid residue. When a carbon source is included in the raw material, for example, a metal element (compound) present as an oxide in the raw material is carbothermally reduced during the chlorination volatilization reaction, and reacts with chlorine to volatilize as a chloride. .

  In the present invention, rare earth elements are separated and recovered by the chloride volatilization method using such raw materials and conditions. The rare earth element separation method and separation system according to the present invention will be described below.

1. Separation Method of Rare Earth Elements FIG. 1 shows each step of the separation method S10 of rare earth elements according to the present invention. As shown in FIG. 1, the rare earth element separation method S10 according to the present embodiment includes a pulverization step (step S1) for pulverizing the raw material, and an oxidation treatment step (step S2) for obtaining an oxidized raw material by oxidizing the raw material. ), A carbon source mixing step (step S3) for mixing the carbon source with the raw material, and a heat treatment step (step S4) for heat-treating the raw material in a chlorine atmosphere after the oxidation treatment and the carbon source mixing. . Moreover, it is preferable that the chloride volatilized in process S4 is collect | recovered as a solid after cooling by the collection process (process S5).

1.1. Grinding process (process S1)
Step S1 is a step of pulverizing a raw material containing a rare earth element and a metal element other than the rare earth element. For example, when an Nd—Fe—B magnet is used as a raw material, each element is dense and stabilized by high temperature melting. Therefore, even if lump or plate-like raw materials are subjected to chlorination volatilization as they are, a certain amount of chlorination volatilization processing is possible, but it is not easy to supply chlorine to the inside of the raw materials, and therefore, the inside of the raw materials It is considered that it is not easy to separate the existing rare earth element and the metal element other than the rare earth element. For the pulverization of the raw material, a known pulverization method (pulverization using a mill or the like) may be applied. The size of the raw material after pulverization is not particularly limited, and is preferably as fine as possible.

1.2. Oxidation process (process S2)
Step S2 is a step of oxidizing the pulverized raw material to obtain an oxidized raw material. For the oxidation treatment of the raw material, a known method such as heat treatment in an oxygen atmosphere may be used. In the case where heat treatment is performed in an oxygen atmosphere, the oxygen atmosphere may be an oxygen atmosphere that can oxidize the raw material. For example, an air atmosphere may be used, and a substantially pure oxygen atmosphere of 99 vol% or more is preferable. The heating temperature and the heating time may be a temperature at which the raw material can be sufficiently oxidized. For example, about 500 ° C. and about 10 minutes are sufficient. In the present invention, step S2 may be performed before step S1. In this case, the structure of the raw material is destroyed by oxidizing the raw material. As a result, even if the raw material is dense and stabilized by high-temperature melting, pulverization can be easily performed. However, in this case, it is preferable to re-oxidize the raw material surface newly appearing by pulverization.

  Or in this invention, you may consider that the oxidation process was performed by cutting and grinding | polishing a raw material. That is, when polishing scraps are generated by cutting and polishing the raw material, the polishing scraps are naturally oxidized. Here, the polishing scrap can be regarded as already finely pulverized, and therefore the polishing scrap can be used as it is as an oxidized raw material.

  In particular, when an Nd—Fe—B magnet is used as a raw material, the raw material is stabilized by oxidizing the raw material, and there is no risk of ignition or the like, so that storage properties and handling properties are improved. In addition, due to the oxidation treatment of the raw material, when the chlorination volatilizes, the raw material is not rapidly chlorinated and is chlorinated via an intermediate, so that the chlorination volatilization behavior can be appropriately controlled. Become. Furthermore, there are metal elements other than rare earth elements that can be easily chlorinated by oxidation, which makes it possible to more efficiently separate rare earth elements from other metal elements.

1.3. Carbon source mixing step (step S3)
Step S3 is a step of mixing a carbon source with the raw material. The timing of mixing the carbon source may be before or after the step S2, but is preferably performed after the step S2 from the viewpoint of suitably leaving the carbon source in the raw material. As the carbon source, in addition to carbon itself, carbon derived from a resin having a carbon chain, or carbon derived from an inorganic carbide such as silicon carbide may be used. For example, when a scrap of Nd—Fe—B magnet is used as a raw material, a resin such as a binder remains in the scrap. In this invention, you may consider that the carbon source mixing process S3 was performed by using the resin as it is, without removing the resin. Alternatively, when polishing scraps of Nd—Fe—B magnets are used as oxidized raw materials, silicon carbide is contained in the polishing scraps. In this invention, you may consider that the carbon source mixing process S3 was performed by using the silicon carbide as it is, without removing the silicon carbide. The form of the carbon source is not particularly limited, and an appropriately pulverized one may be used. The raw material and the carbon source may be mixed uniformly using a mixing means or the like. About the mixing ratio of a raw material and a carbon source, it is preferable to set it as 0.5-1.5 as a carbon / raw material by mass ratio.

1.4. Heat treatment process (process S4)
Step S4 is a step of subjecting the obtained raw material to a heat treatment after steps S1 to S3. In step S4, heat treatment is performed in a chlorine atmosphere, and metal elements other than rare earth elements are volatilized as chlorides from the raw material. Step S4 is performed in an atmosphere in which at least chlorine is circulated, and heat treatment is preferably performed in a chlorine atmosphere of 99 vol% or more, more preferably 99.4 vol% or more of chlorine. The higher the chlorine concentration, the greater the chlorination reaction rate. In the step S4, it is preferable that chlorine gas is circulated in the system and continuously discharged out of the system. In this case, the flow rate of chlorine is not particularly limited as long as it can appropriately perform the chlorination and volatilization treatment, but the space velocity is 100 h on the basis of the volume of the heat treatment part of the reactor in which the raw material is installed. It is preferable that the flow rate be ⁻¹ or higher. If the circulation rate of chlorine is too low, chlorine backflow may occur in the system. In setting the chlorine atmosphere, the inside of the system may be once cleaned with an inert gas, and then chlorine may be circulated to form a chlorine atmosphere.

  In step S4, the metal element other than the rare earth element contained in the raw material is heated to a temperature at which it is volatilized as a chloride. The heating temperature is preferably 300 ° C. or higher and 1000 ° C. or lower, and more preferably 650 ° C. or higher and 1000 ° C. or lower. Thereby, rare earth elements and metal elements other than rare earth elements are efficiently separated. In particular, when an Nd—Fe—B magnet containing Nd, Pr, Fe, B, Co or the like as a raw material is used, the heating temperature in step S4 is set to 300 ° C. or more and 1000 ° C. or less, so that Nd and Pr are contained in the solid residue. In this state, Fe, B and Co can be separated by volatilization with chloride.

  In step S4, the temperature may be raised to the above heating temperature and then immediately cooled. However, it is preferable to perform heating and holding at any temperature of not less than 300 ° C and not more than 1000 ° C. The heat holding time is not particularly limited as long as the metal element other than the rare earth element contained in the raw material is sufficiently volatilized as a chloride. This makes it possible to more appropriately separate the rare earth element and the metal element other than the rare earth element.

1.5. Recovery process (process S5)
Step S5 is a step of cooling the metal chloride volatilized from the raw material in step S4 and recovering it as a solid. The step S4 is not particularly limited as long as it is a step in which the metal element (chloride) chlorinated and volatilized is cooled and solidified, and can be recovered as a solid. The metal elements chlorinated and volatilized in step S4 have different solidification temperatures. For example, the cooling temperature field in the system is controlled so that the temperature decreases as it goes to the outlet side in the system chlorine flow direction. Thus, each metal element (chloride) can be deposited with a certain distribution with respect to the flow direction in the system. That is, a predetermined metal element (chloride) can be separated and deposited at a predetermined location in the system. The step S5 may be a form in which the deposited chloride is recovered as it is as a solid, or is dissolved in a solvent or the like and recovered as a liquid.

  After the metal elements other than the rare earth elements contained in the raw material are separated and recovered by the steps S1 to S4, the residual solid remaining in the system is taken out of the system. The residual solid contains, for example, Nd, Pr and the like in a concentrated manner.

  Thus, according to the rare earth element separation method of the present invention, by applying all of the oxidation treatment, the carbon mixing treatment, and the chlorination volatilization treatment (heat treatment), the rare earth element contained in the raw material and the other metal elements. Can be appropriately selected and separated. Further, since the rare earth element can be separated and recovered only by controlling the temperature in the system, the number of steps can be reduced, and the rare earth element can be separated and recovered easily and efficiently. Further, by adopting a combination of carbon reduction and chloride volatilization, it becomes possible to lower the heat treatment temperature required for separation and recovery, and it is possible to perform separation and recovery of rare earth elements with energy saving.

2. Rare Earth Element Separation System FIG. 2 shows a rare earth element separation system 100 according to the present invention. As shown in FIG. 2, the rare earth element separation system 100 according to the present invention includes a pulverizing means 10 for pulverizing a raw material 1 containing a rare earth element and a metal element other than the rare earth element into a powdery raw material 2; The obtained raw material 2 is subjected to an oxidation treatment to obtain an oxidized raw material 3, and an oxidation treatment means 20, and a mixing means 30 to obtain a treated raw material 5 by mixing the oxidized raw material 3 with a carbon source 4. And a heating means 40 for heating the processing raw material 5 inside, and a chlorine supply means 50 for supplying chlorine to the processing raw material 5 in the heating means 40. Moreover, you may provide the collection | recovery means 60 provided so that it might connect with the heating means 40 as needed. In addition, an introduction means (not shown) for introducing the processing raw material 5 into the heating means 40, a discharge means (not shown) for discharging / recovering the finally remaining solid after the chlorination volatilization process, etc. are provided. It may be done.

2.1. Crushing means 10
The crushing means 10 is means for executing the crushing step S1 on the raw material 1. As the pulverizing means 10, a known pulverizing means such as a mill can be appropriately selected and applied. The pulverization using the pulverizing means 10 may be performed manually in a batch manner, or the raw material 1 is mechanically continuously supplied from the inlet of the pulverizing means 10, and inside the pulverizing means 10. Then, after the raw material 1 is pulverized, the powdery raw material 2 may be mechanically continuously discharged from the outlet of the pulverizing means 10 and continuously supplied to the oxidation treatment means 20 described later.

2.2. Oxidation treatment means 20
The oxidation treatment means 20 is a means for performing the oxidation treatment step S2 on the obtained raw material 2 to obtain an oxidized raw material 3. As the oxidation treatment means 20, a known means capable of performing oxidation treatment, such as a means for heat-treating the raw material 2 in an oxygen atmosphere, can be appropriately selected and applied. Alternatively, in the present invention, polishing scraps may be obtained as the oxidized raw material 3 by cutting and polishing the raw material. That is, a polishing means may be used as the pulverizing means 10 and the oxidation treatment means 20. For example, when using Nd—Fe—B magnet polishing scraps as the oxidized raw material 3, the polishing means used in the manufacturing process of the Nd—Fe—B magnet is regarded as the pulverizing means 10 and the oxidation treatment means 20 in the present invention. be able to. The oxidation treatment in the oxidation treatment means 20 may be performed manually by a batch method, or the raw material 2 continuously supplied from the pulverization means 10 is mechanically continuously from the inlet of the oxidation treatment means 20. After the oxidation treatment of the raw material 2 is performed inside the oxidation treatment means 20, the oxidized raw material 3 is continuously discharged mechanically from the outlet of the oxidation treatment means 20, and the mixing means 30 described later It is good also as what supplies continuously.

2.3. Mixing means 30
The mixing unit 30 is a unit that performs the carbon source mixing step S3 on the oxidized raw material 3. As the mixing means 30, known means such as a mixer may be used. The mixing process in the mixing unit 30 may be performed batchwise by hand, or the oxidized raw material 3 continuously supplied from the oxidation unit 20 is mechanically continuously supplied from the inlet of the mixing unit 30. The carbon source 4 continuously supplied from the means (not shown) for supplying the carbon source 4 is mechanically continuously introduced from the inlet of the mixing means 30 and mixed inside the mixing means 30. After the processing, the processing raw material 5 may be mechanically continuously discharged from the outlet of the mixing unit 30 and continuously supplied into the heat processing unit 40 described later.

2.4. Heat treatment means 40
The heat treatment means 40 is means for performing the heat treatment according to the above step S4 on the treatment raw material 5. As the heat treatment means 40, a known means such as a heating furnace may be used. The heat treatment in the heat treatment means 40 may be performed manually in a batch manner, or the processing raw material 5 continuously supplied from the mixing means 30 is mechanically continuously from the inlet of the heat treatment means 40. After introducing and heat-treating the treatment raw material 5 inside the heat treatment means 40, the solid residue is mechanically continuously discharged from the outlet of the heat treatment means 40, and the solid residue enriched with rare earth elements is removed. It is good also as what is obtained continuously.

2.5. Chlorine supply means 50
The chlorine supply means 50 is a means for supplying a chlorine source into the heat treatment means 40. The form of the chlorine supply means 50 is not particularly limited as long as it can appropriately supply chlorine into the heat treatment means 40 and volatilize the elements contained in the processing raw material 5. . For example, a high pressure chlorine gas can be ejected from a chlorine source and the chlorine gas can be sent into the heat treatment means 40. Further, chlorine gas may be supplied using a pump or the like. The chlorine supply means 50 makes the inside of the reaction system a chlorine atmosphere. It is preferable that the chlorine gas in the system is circulated in the system at a predetermined speed and continuously discharged to the recovery means 60. The system may be cleaned using nitrogen supply means or the like before the chlorine supply means 50 is made to function.

2.6. Collection means 60
The recovery means 60 is a means for cooling and recovering a metal element (chloride) other than the rare earth element chlorinated by the heat treatment means 40 as a solid. The inside of the recovery means 60 is controlled to a temperature lower than the heating temperature in the heat treatment means 40, and the metal element (chloride) chlorinated and vaporized as a gas is solidified inside the recovery means 60. Deposit as a solid. That is, at least when the metal element (chloride) chlorinated and volatilized is recovered, the gas flow direction is the direction from the chlorine source toward the recovery means 60 (the arrow direction in FIG. 2). In this case, in particular, by controlling so that the cooling temperature field in the recovery means 60 has a predetermined distribution (for example, the temperature is lowered toward the outlet side in the flow direction in the system), chlorination and volatilization are performed. Further, each metal element (chloride) can be deposited at different locations depending on the type of element. The collecting means 60 may have a form in which the deposited chloride is recovered as it is as a solid, or may be dissolved in a solvent or the like and recovered as a liquid.

2.7. Other Configurations In addition to the above configuration, the rare earth element separation system 100 may include a supply unit, a discharge unit, and the like that connect the units. For example, the discharge means provided in the heat treatment means 40 is a means for taking out the remaining solid component without being volatilized by chloride after the heat treatment by the heat treatment means 40. The form of the discharge means is not particularly limited, and can be, for example, a discharge port provided on the side portion of the heat treatment means 40. The removal of the residual solid may be performed manually by the operator or may be mechanically continuously discharged.

  As described above, the rare earth element separation system 100 of the present invention can appropriately execute the rare earth element separation method S10 of the present invention. That is, according to the present invention, a rare earth element can be concentrated and separated into a solid residue for a raw material containing a rare earth element and a metal element other than the rare earth element. Further, since the rare earth element and other metal elements can be separated only by controlling the temperature in the system, the number of steps can be reduced, and the rare earth element can be separated and recovered simply and efficiently.

  Hereinafter, the method for separating rare earth elements according to the present invention will be described in more detail with reference to examples.

(Sample preparation)
In the examples, the Nd—Fe—B magnet was pulverized to 200 mesh or less by a pulverizing means (sample A), and this sample was oxidized in an air atmosphere at 500 ° C. for 10 minutes, and then again 200 mesh or less. (Sample B) was used. The average particle sizes of Samples A and B were 50.4 μm and 47.5 μm, respectively. The average particle diameter in the present application is a value measured with a laser diffraction / scattering particle size analyzer (Microtrack, manufactured by Nikkiso Co., Ltd.). Table 1 shows the composition of each sample.

Nd-Fe-B magnets are
Nd ₂ Fe ₁₄ B + O ₂ → Fe + Nd ₂ O ₃ + Fe ₂ B (<230 ° C.)
Fe + O ₂ → Fe ₂ O ₃ (<500 ° C.)
Fe ₂ O ₃ + Nd ₂ O ₃ → FeNdO ₃ (> 500 ° C.)
It is reported that B exists in the Nd ₂ O ₃ crevice. Therefore, when the sample is subjected to XRD analysis, Fe ₂ O ₃ appears as a main peak, but it is considered that Nd ₂ O ₃ is also present.

  In the examples, carbon particles derived from phenolphthalein (C: 88.3 wt%, H: 3.6 wt%, O: 8.0 wt%, average particle size: 60.9 μm) as a carbon source to be mixed with the sample. And silicon carbide (manufactured by Katayama Chemical Co., Ltd., carborundum, 400 mesh, average particle size: 38.5 μm) were used. Here, the carbon particles are phenolphthalein (Nacalai Tesque GR) in a fixed bed reactor in a nitrogen stream under conditions of a heating rate of 30 ° C./min, a maximum temperature of 500 ° C., and a holding time of 10 minutes. It is adjusted by heat treatment, pulverization and sieving with 200 mesh. The carbon particles and the sample were mixed at a mass ratio of 1: 1. On the other hand, when using silicon carbide, it mixed so that carbon content might become mass ratio 1: 1 with respect to a sample.

(Experimental equipment and experimental method)
In the chloride volatilization experiment, an experimental apparatus as shown in FIG. 3 was used. That is, for the heating of the sample, a horizontal tubular furnace 104 (EKR-16K, manufactured by Isuzu Seisakusho, length 69 cm) and a transparent quartz tube 103 (inner diameter 36 mm, outer diameter 40 mm, tube length 123.5 mm) as a reactor are used. It was. The reactor temperature was measured and controlled by inserting a thermocouple 105 vertically from the outside of the furnace and contacting the outside of the reaction tube 103. In the experiment, 1 g of a sample was first weighed on an alumina board 106 and inserted into the central portion of the reaction tube 103. Then, the system was cleaned with a nitrogen gas cylinder 101 in a nitrogen atmosphere and switched to a chlorine gas cylinder 102. After making the inside of the system sufficiently chlorine atmosphere, the sample was heated under the conditions of a temperature rising rate of 30 ° C./min and a maximum temperature of 100-1000 ° C. The chlorine gas flow rate at this time was 200 ml / min. When the chlorine gas flow rate was about 100 ml / min, a back flow of chlorine occurred in the system.
The sample was cooled without holding after reaching the maximum temperature. Chlorine gas and volatile products were discharged out of the system through traps 107 and 108 containing distilled water or sodium hydroxide aqueous solution installed at the outlet of the reaction tube 103. After cooling the furnace to room temperature, a sample was taken out and subjected to various analyses.

(Analysis method)
The sample before and after heating was dissolved in a container made of Teflon (Teflon is a registered trademark of DuPont). A mixed acid composed of 10 ml of nitric acid and 20 ml of hydrochloric acid was placed in a Teflon (registered trademark) container together with the sample and sealed, followed by heat treatment at 140 ° C. for 3 hours. Thereafter, the decomposition vessel was cooled to room temperature, and then the solution was recovered by filtration. In the dissolution of the sample to which the carbon source was added, the residue generated after the dissolution was dissolved based on the total iron determination method in JIS M 8812 iron ore. The concentration of each element in the solution was measured by ICP (manufactured by Seiko Instruments Inc., SPS-3000). The samples before and after heating were subjected to substance identification by a powder X-ray diffractometer (manufactured by Rigaku Corporation, Ultimate IV). Furthermore, in order to clarify the morphological change of each element during chlorination, 200 ml of distilled water is placed in a Teflon (registered trademark) container with respect to about 0.2 g of the sample before and after heating and stirred at room temperature for 4 hours. Then, the chloride dissolution operation was performed. Thereafter, the residue was recovered by filtration, and dissolution and quantitative analysis were performed in the same procedure as described above.

<Experimental result>
(Thermodynamic equilibrium calculation)
In conducting the chloride volatilization experiment, thermodynamic equilibrium calculation based on the composition of each sample was performed using thermodynamic equilibrium calculation software HSC (Outkump research oy., HSC chemistry for windows ver. 5.0). FIG. 4A shows a calculation result of the sample A under a chlorine atmosphere. As can be seen from the figure, Fe and B form chlorides from a low temperature and volatilize in the form of Fe ₂ Cl ₆ , FeCl ₃ , FeCl ₂ , BCl ₃ . Co, Pr and Nd also form chlorides at low temperatures, but the volatilization start temperature was 600 ° C. or higher. The calculation result in the system in which carbon or SiC was added to sample B was the same as that of sample A. FIG. 4B shows a calculation result of the sample B under a chlorine atmosphere. Fe forms chloride and oxychloride from a low temperature and volatilizes in the form of Fe ₂ Cl ₆ , FeCl ₃ and FeCl ₂ . The other elements were found to have the same volatilization behavior as in FIG.

(Dynamic behavior of constituent elements of Nd-Fe-B magnet in chloride volatilization)
FIG. 5 shows the change in weight during chlorination and the volatilization behavior of the five elements constituting the magnet for the Nd—Fe—B magnet itself (sample A). As can be seen, the weight of the sample increases at 400 ° C. This is thought to originate from the formation of chloride in the solid phase. Thereafter, the weight of the sample decreased with increasing temperature and decreased to 50% at 1000 ° C. The sample after the heat treatment at each temperature was subjected to water treatment and classified into two types, a water-soluble component and a water-insoluble component. Since the composition of the magnet is an Nd—Fe—B alloy, chloride is considered as the water-soluble component. As a result of XRD measurement of the residue after chlorination, peaks attributable to hydrates of FeCl ₃ and NdCl ₃ were confirmed. The presence of these water-soluble components was not confirmed in the sample before heating. Regarding the volatilization behavior of the magnet constituent elements, Co, B and Fe were volatilized from about 200 ° C. where a significant change in weight occurred, and 70%, 90% and 95% were volatilized at 1000 ° C., respectively. On the other hand, Nd and Pr were volatilized at 800 ° C. or higher, and the volatilization rates were 25% and 23% at 1000 ° C., respectively. It has been reported that the volatilization behavior of rare earth elements depends on the size of rare earth ions (Murase et al. 1993). The above results show that the size of the ions of Nd and Pr are close, The melting point of chlorides Pr and Nd are volatile behavior of NdCl ₃ is 823 ° C., since PrCl ₃ is 784 ° C., Nd and Pr Are considered to be similar.

  FIG. 6 shows the morphological changes of the constituent elements in the chlorination of the Nd—Fe—B magnet. It can be seen that, in all the constituent elements, chloride, which is a water-soluble component, is rapidly generated in the solid from a low temperature range of 200 ° C. or lower. As for Fe, Co, and B, the formation of chlorides peaked around 600 ° C., and only volatilization into the gas phase occurred thereafter. For Pr and Nd, the chloride formation reaction has been completed by 400 ° C., but the chloride volatilization reaction in the gas phase does not occur unless the temperature rises to around 900 ° C. From these results, it is possible to volatilize Fe and B only by heating the Nd—Fe—B magnet in chlorine gas, but Co remains in the solid residue together with Nd and Pr, and the rare earth It became clear that elements and other metal elements could not be separated.

(Volatilization behavior of oxidized Nd-Fe-B magnet)
FIG. 7 shows the change in weight and the volatilization behavior of each element in the chlorination of the oxidized Nd—Fe—B magnet pulverized sample (sample B). The weight increased in the temperature range of 200-300 ° C. and thereafter decreased with increasing temperature. Similarly, the water-soluble content also decreased after reaching a maximum at 300 ° C. and became 2% at 1000 ° C. Fe and Co began to evaporate from 100 ° C or higher, and all evaporated at 1000 ° C. On the other hand, the volatilization of B was not confirmed by 1000 ° C. About Pr and Nd, 15% volatilized in 900-1000 degreeC. The volatilization behavior of Co, B, Pr and Nd in this oxidized sample was significantly different from that of the unoxidized sample (Sample A). Regarding Fe, when compared with Sample A, a decrease in volatilization rate in a low temperature range of 500 ° C. or lower was confirmed. From the thermodynamic equilibrium calculation result, this is considered to originate from the formation of oxychloride.

  FIG. 8 shows the morphological changes of the constituent elements of the oxidized Nd—Fe—B magnet during chlorination. For all elements, non-oxidized magnets formed water-soluble chlorides from a low temperature range of 100 ° C. or lower, whereas oxidized magnets had a proportion soluble in water at 100 ° C. or lower. Fe and Co are small, and Pr, Nd and B do not exist in a form soluble in water up to 500 ° C. When the unoxidized sample was heat-treated in a chlorine atmosphere, melting was observed from around 400 ° C., but the oxidized sample was melted at 1000 ° C. This is because the structure itself of the Nd—Fe—B magnet collapses by subjecting the magnet to an oxidation treatment, and Nd, Pr, and B are in a form that is hardly chlorinated by forming an oxide, Fe and Co are considered to be easily chlorinated. From these results, it is possible to selectively volatilize Fe and Co by 1000 ° C. only by chlorinating the oxidized Nd—Fe—B magnet, but B together with Nd and Pr. It will be concentrated in the solid residue, and although it was possible to separate the rare earth element and other metal elements, it became clear that the rare earth element and the non-metallic element B could not be separated. .

(Effect of carbon source addition on chlorination volatilization of oxidized Nd-Fe-B magnet)
FIG. 9 shows the change in weight and the volatilization behavior of each element when carbon particles or SiC is mixed in Sample B and chlorination is performed. The weight change here shows the change with respect to the total weight of the sample to which carbon particles and SiC are added. As shown in FIG. 9A, when carbon was added as a reducing agent, the weight increased from 100 ° C. to 300 ° C., and thereafter decreased with increasing temperature. The ratio of water-soluble components in the solid phase also showed the same behavior. Looking at the volatilization behavior of each element, B, Fe, and Co began to evaporate from around 300 ° C., and reached 100% volatilization at 500 ° C., 800 ° C., and 900 ° C., respectively. Pr and Nd volatilized from around 800 ° C. as in the chlorination of the oxidized and non-oxidized samples, and remained at about 20% volatilization at 1000 ° C. On the other hand, as shown in FIG. 9 (B), when SiC was added as a reducing agent, the change in weight was greatly different from that in the case of carbon addition, and an increase was confirmed at 300 ° C., but thereafter, it was almost constant up to 900 ° C. A sudden decrease was confirmed at 900-1000 ° C. When SiC is heat-treated in chlorine gas, thermodynamic calculation reports that a reaction of 1/2 SiC + Cl ₂ = 1/2 SiCl ₄ + 1 / 2C occurs at 650 ° C. (Takeuchi et al. 2004). . In addition, it has been reported that the reaction of SiC + 4Cl ₂ → 2Cl ₂ + SiCl ₄ + C starts from 800 ° C. or higher and covers the sample surface where C coexists at 900 ° C. or higher (Okutani et al. 1985, etc.). Therefore, the significant reduction in weight in the temperature range of 900 to 1000 ° C. is due to the simultaneous occurrence of Si volatilization due to chlorination of SiC, reduction by carbon generated from SiC, and volatilization reaction by chlorine gas. It is thought that. Fe and Co began to volatilize from a low temperature range of 200 ° C. or higher, and all volatilized at 700 ° C. and 1000 ° C., respectively. Volatilization of B progressed rapidly from 700 ° C to 1000 ° C. The volatilization start temperature of B was 400 ° C. higher than that in the case of carbon addition. Nd and Pr had the same volatilization behavior as the carbon-added sample. As described above, the difference in volatilization behavior of B between the addition of carbon and the addition of SiC is that the temperature at which SiC undergoes chlorination to form carbon is 650 ° C. or higher. This is thought to be because the volatilization rate was greater when carbon was added than when SiC was added. It should be noted that Nd and Pr chlorides have a volatilization start temperature of 800 ° C. or higher and are sufficiently higher than the carbon formation temperature from SiC, so it is considered that there was no difference in volatilization behavior from when carbon was added. .

  FIG. 10 shows the morphological changes of the constituent elements in Sample B when chlorinating by adding carbon. In Fe, Co, and B, water-soluble forms (chlorides and oxychlorides) are starting to form rapidly from around 100 ° C. As for Nd and Pr, it became clear that water-soluble components were generated from around 100 ° C. Further, most of Nd and Pr remaining in the solid phase at 900-1000 ° C. are soluble in water. It can be said that only Nd and Pr can be selectively recovered by subjecting the solid residue to water treatment after the elements are volatilized selectively.

  In FIG. 11, the result at the time of using SiC as a carbon source is shown. The morphological change of each element was greatly different from that when carbon was added. It can be seen that the amount of water-soluble components produced for Fe, Co, and B is less at each temperature than when carbon is added. In addition, the generation start temperature of the water-soluble component is a low temperature region of 100 ° C. or more in the carbon-added sample, whereas the generation of the water-soluble component occurs almost simultaneously with the volatilization start temperature in the SiC-added sample. As for Nd and Pr, since water-soluble components are generated abruptly from 600 ° C. or higher, carbon is more reactive than SiC and contributes to reduction of oxides from a lower temperature range. Became clear. On the other hand, even when SiC was used, it was found that Pr and Nd can be concentrated and recovered by performing water treatment on a solid residue that has been subjected to chlorination and volatilization treatment up to 1000 ° C.

  In addition, even if a carbon source is added to the sample A that has not been oxidized, it is considered that the volatilization behavior is not greatly different from that in the case where it is not added. That is, in this example, since the carbon source acts as a reducing agent for the oxidized sample, it is considered that the carbon source is not particularly effective for the non-oxidized sample A.

From the above results, when separating Nd and Pr (rare earth elements), Fe and Co (metal elements other than rare earth elements), and B (nonmetal elements) from the Nd-Fe-B magnet,
(1) Oxidation treatment of Nd—Fe—B magnet (2) Mixing of carbon source with Nd—Fe—B magnet (3) When all conditions for heating treatment in a chlorine atmosphere are met It turned out to be appropriate.

  ADVANTAGE OF THE INVENTION According to this invention, the method and system which can isolate | separate and collect a rare earth element efficiently from the raw material containing metal elements other than the rare earth element and the said rare earth element are provided. In other words, rare earth elements can be efficiently separated and recovered even for raw materials for which the separation and recovery system has not been properly constructed for the contained elements, such as rare earth magnet scraps and polishing scraps, and have high rare value. It leads to recycling and securing of raw materials.

DESCRIPTION OF SYMBOLS 1 Raw material 2 Powdered raw material 3 Oxidized raw material 4 Carbon source 5 Process raw material 10 Grinding means 20 Oxidation means 30 Mixing means 40 Heat treatment means 50 Chlorine supply means 60 Recovery means 100 Rare earth element separation system

Claims (10)

For raw materials containing rare earth elements and metal elements other than the rare earth elements,
An oxidation treatment step of obtaining an oxidized raw material by performing an oxidation treatment;
A carbon source mixing step of mixing a carbon source;
A heat treatment step of performing a heat treatment in a chlorine atmosphere after the oxidation treatment step and the carbon source mixing step;
A method for separating rare earth elements.   The method for separating a rare earth element according to claim 1, further comprising a pulverization step of pulverizing the raw material, wherein the oxidation treatment step is performed after the pulverization step.   The rare earth element separation method according to claim 1, wherein the oxidation treatment step is a step of polishing the raw material to obtain polishing waste as the oxidized raw material.   The method for separating rare earth elements according to any one of claims 1 to 3, wherein the heat treatment step includes a holding step of holding the temperature at any temperature between 300 ° C and 1000 ° C.   The method for separating a rare earth element according to claim 1, wherein the raw material is an Nd—Fe—B magnet. For raw materials containing rare earth elements and metal elements other than the rare earth elements,
Oxidation treatment means for performing oxidation treatment;
A carbon source mixing means for mixing the carbon source;
A heat treatment means for heat treatment;
With
Chlorine supply means for supplying chlorine to the heat treatment means,
A rare earth element separation system.   The rare earth element separation system according to claim 6, further comprising a pulverizing unit for pulverizing the raw material, wherein the oxidation treatment is performed after the raw material is pulverized.   The rare earth element separation system according to claim 6, wherein the oxidation treatment means is a polishing means for polishing the raw material.   The rare earth element separation system according to any one of claims 6 to 8, wherein the heating means is configured to maintain the temperature at any temperature between 300C and 1000C.   The rare earth element separation system according to any one of claims 6 to 9, wherein the raw material is an Nd-Fe-B magnet.