WO2020151478A1 - 一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法 - Google Patents

一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法 Download PDF

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WO2020151478A1
WO2020151478A1 PCT/CN2020/070215 CN2020070215W WO2020151478A1 WO 2020151478 A1 WO2020151478 A1 WO 2020151478A1 CN 2020070215 W CN2020070215 W CN 2020070215W WO 2020151478 A1 WO2020151478 A1 WO 2020151478A1
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rare earth
ndfeb
waste
rich
bismuth
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English (en)
French (fr)
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何杰
陈斌
马浩博
赵九洲
江鸿翔
张丽丽
郝红日
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中国科学院金属研究所
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B15/00—Other processes for the manufacture of iron from iron compounds
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B59/00—Obtaining rare earth metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention belongs to the field of metal resource recovery and reuse, and in particular relates to a method for extracting and recovering rare earth elements in NdFeB waste with liquid metal bismuth.
  • Rare earth elements have unique physical and chemical properties and are widely used in the development and innovation of science and technology, and the global demand for rare earth metal resources is increasing year by year. Especially in recent years, new technologies dedicated to reducing energy consumption and developing renewable energy have significantly increased their dependence on rare earth resources. Rare earth elements are widely used in new materials such as permanent magnet materials, luminescent materials, hydrogen storage alloys, nickel-hydrogen battery electrode materials, polishing and catalysts. However, most rare earth elements are used in the preparation of rare earth permanent magnet materials.
  • rare earth permanent magnet samarium cobalt developed in 1967 to the third generation of rare earth permanent magnet NdFeB developed in 1983
  • the rare earth elements used are samarium, praseodymium, neodymium, terbium, dysprosium, lanthanum, cerium, and gadolinium , Holmium, erbium, yttrium, etc.
  • the third-generation neodymium iron boron rare earth permanent magnet material has the advantages of light weight, small size, strong magnetism, extremely high magnetic energy, easy availability of raw materials, and low price. It has developed extremely rapidly. It is by far the most cost-effective permanent magnet material.
  • the field of magnetism is known as the "magnet king".
  • NdFeB permanent magnet materials are still used in elevators, magnetic separation and magnetic refrigeration equipment.
  • rare earth permanent magnet materials mainly include sintered NdFeB (accounting for 91.4%), bonded NdFeB (accounting for 6.7%), hot pressing/hot deformation NdFeB (accounting for 0.6%) and sintered samarium cobalt (accounting for 1.3%) Four categories.
  • the waste NdFeB mainly comes from: 1The waste produced during the preparation of the NdFeB material and 2The waste produced when the NdFeB material finally fails due to the failure of the used device.
  • the production and preparation process of rare earth neodymium iron boron permanent magnet materials mainly include: batching, alloy melting, hydrogen crushing, jet milling, magnetic field orientation forming, isostatic pressing, oil stripping, sintering, machining and other links and processes.
  • Various processes in the production process of NdFeB permanent magnet materials will produce a certain amount of waste or waste, mainly including: the loss of raw materials in the pretreatment process of raw materials, and the neodymium produced by severe oxidation during the induction melting process.
  • NdFeB rare earth permanent magnets Iron boron waste, ultra-fine powder produced in the powdering process, powder oxidized in the powdering process, neodymium iron boron block material oxidized in the sintering process, a large amount of scrap and surface produced in the process of processing Substandard products produced during the processing, etc.
  • the utilization rate of raw materials is only about 70%, and about 30% of waste is generated.
  • NdFeB rare earth permanent magnet materials are widely used in new technologies and products such as hard disk drives, wind turbines, electric power steering, hybrid and electric vehicles, electric bicycles, consumer electronics and household appliances. These products have a useful life and expire when they expire.
  • the service life of voice coil motors is 8 years
  • the service life of hybrid/electric vehicles is 15 years
  • the service life of consumer motors is 15 years
  • the service life of wind power motors is 20 years.
  • China's installed wind power capacity exceeded 188GW.
  • approximately 1 ton of neodymium iron boron permanent magnets are needed.
  • my country's installed wind power capacity has increased year by year, especially in the past 10 years.
  • the total amount of scrapped rare earth NdFeB permanent magnets in the world was 50,000 to 60,000 tons, and China accounted for more than 60%, and the scrap volume increased year by year.
  • NdFeB rare earth permanent magnet materials the content of rare earth elements such as praseodymium, neodymium, and dysprosium is as high as 25-30%, and the rest are mainly metallic iron, cobalt, nickel, and element boron. If a large number of waste NdFeB rare earth permanent magnets cannot be recycled efficiently and greenly, not only will it produce a large number of pollution sources and secondary pollution, but also a waste of resources, which goes against the development of circular economy. Therefore, the recovery of metal elements from waste NdFeB rare earth permanent magnet materials not only contributes to ecological environment protection, but also alleviates the crisis of rare earth resources and promotes resource recycling, which is of great significance to environmental protection and economic development.
  • the recovery of NdFeB permanent magnet waste mainly includes two treatment methods: wet method and fire method.
  • the wet method mainly includes 4 steps: 1 dissolving the waste with chemical reagents, so that the metal ions are distributed in the solution, that is, leaching; 2 separating the leaching solution from the residue; 3 using ion exchange, solvent extraction or other chemical precipitation methods to make the leaching Liquid purification and separation; 4Extract compounds from the purified solution.
  • the sulfate double salt precipitation method, the sulfide precipitation method, the hydrochloric acid solution method, the hydrochloric acid solution method, and the oxalic acid precipitation method have been developed at home and abroad.
  • the literature (Lin Hecheng, Research on the Preparation of Neodymium Oxide, Rare Metals and Cemented Carbide, 03:4-7, 1997) reported the use of sulfuric acid-double salt method to recover rare earths from neodymium iron boron waste and prepare neodymium oxide products.
  • the literature (Chen Yunjin, Recovery of Rare Earth and Cobalt in NdFeB Waste Residue by Full Extraction Method, 06:10-12, 2004) reported that the NdFeB waste was dissolved in hydrochloric acid by the total solution method of hydrochloric acid, and the pH value was adjusted to make the iron and cobalt Separation of rare earth elements.
  • the invention patent (a method for recovering and extracting rare earth oxides from neodymium iron boron waste, publication number CN107012330A) discloses a method for recovering and extracting rare earth oxides from neodymium iron boron waste, which uses crushing-incineration-cleaning- Rare earth oxides are obtained after acid dissolution-extraction-roasting process.
  • the invention patent (a method for recovering rare earths from NdFeB waste, publication number CN106319249A) discloses a method for recovering rare earths from NdFeB waste, which uses hydrogen peroxide and oxidizing and weak acid to make NdFeB waste Dissolve, and then use N503 to extract the iron element in the solution first, then use P507 to extract the rare earth elements, and finally use oxalic acid and potassium carbonate to precipitate the corresponding rare earth ions.
  • the invention patent discloses a method for recovering rare earth from NdFeB waste, which includes the steps of roasting-acid dissolution-separation-burning, and the filtrate adopts modified bumps Rare earth oxides are obtained after the treatment of corroded soil and hydrogen peroxide, centrifugal slag removal, extraction separation, precipitation separation and other processes.
  • the invention patent discloses a method for recovering rare earth elements from NdFeB waste materials.
  • the steps are: mixing NdFeB waste materials with water and then grinding and oxidation After grinding the neodymium iron boron, the secondary grinding oxidation product, acid leaching, solid-liquid separation, extraction and removal of iron, rare earth chloride, extraction and separation of rare earths, extraction and removal of aluminum, precipitation and burning, etc.
  • Fire treatment is mainly divided into glass slag method, alloy method, chlorination method, selective oxidation method, slag finance method, etc.
  • Saito et al. used the glass slag method to oxidize the rare earth elements in the NdFeB waste into neodymium oxide using boron oxide as the oxidant, and the boron oxide was reduced to boron as a simple substance and entered into the iron to form an iron-boron alloy.
  • Uda used FeCl 2 as the chlorinating agent.
  • the rare earth elements in the NdFeB waste were chlorinated at 800°C, and then the rare earth chlorides were recovered by vacuum distillation.
  • the purpose of the present invention is to provide a method for extracting and recovering rare earth elements from NdFeB waste with liquid metal bismuth, which has a short process flow, high efficiency, no need for harsh chemical reagents, zero emissions, and is environmentally friendly. Combining the metallurgical characteristics of liquid-liquid phase separation and the selective distribution of multi-metal components in the liquid phase separation system, it solves the problems of comprehensive and efficient recovery and recycling of NdFeB waste including rare earth, iron and boron elements.
  • a method for extracting and recovering rare earth elements from NdFeB waste with liquid metal bismuth is carried out according to the following steps:
  • Step 1 Clean the dirt on the surface of the waste NdFeB and dry it
  • Step 2 Construct a Fe-Bi liquid-liquid separation system from waste NdFeB and bismuth-rich extractant: liquid rich Fe+liquid Bi rich;
  • Step 3 Put the mixture of waste NdFeB and bismuth-rich extractant in an alumina crucible to heat and melt, stir the melt in the crucible, so that the liquid bismuth-rich extractant fully contacts the liquid NdFeB melt, waste NdFeB All the rare earth elements in the bismuth are extracted into the bismuth rich extractant melt in one step
  • Step 4 After the melt in the alumina crucible is kept warm, the Fe-rich melt in the upper layer is separated from the Bi-rich melt in the lower layer.
  • the chemical composition of the waste NdFeB recovered in step 1 mainly contains transition metal elements, light rare earth elements and heavy rare earth elements.
  • the transition metal elements are Fe, Co, Ni, Cu
  • the light rare earth elements are Nd and Pr
  • the heavy rare earth elements are Dy or Tb.
  • the bismuth-rich extractant used in step 2 is: metallic Bi with a purity of more than 99wt%; or, a Bi-rich Bi alloy, wherein the content of Bi is not low ⁇ 50wt%.
  • the weight percentage of metal Bi is 15%-60% in the mixture of waste neodymium iron boron and bismuth-rich extractant.
  • step 3 the temperature of heating and melting the mixture of waste neodymium iron boron and the bismuth-rich extractant is 1200°C to 1450°C.
  • step 3 is one-step extraction and separation of rare earth elements in waste NdFeB with liquid bismuth-rich extractant, including light rare earth elements Nd, Pr and heavy rare earth elements Dy or Tb.
  • the temperature of the melt in the alumina crucible is between 1350°C and 1450°C, and the time of holding is between 5 and 10 minutes.
  • the upper Fe-rich melt separated in step 4 is mainly composed of transition metals Fe, Co, Ni, Cu with a weight percentage of more than 98%, and
  • the alloy melt composed of boron B element with a weight percentage of about 1 to 2% is refined and recycled as an intermediate alloy to produce neodymium iron boron permanent magnet materials.
  • the lower Bi-rich melt separated in step 4 is mainly composed of metal Bi with a weight percentage of 40-70% and a weight percentage of 25-
  • a Bi-RE bismuth rare earth alloy melt composed of 50% light rare earth elements Nd and Pr and 5-10% heavy rare earth elements Dy or Tb by weight.
  • the metal Bi in the Bi-RE alloy is combined with the metal Bi in the Bi-RE alloy by vacuum distillation technology.
  • the design idea of the present invention is:
  • the positive heat of mixing means that the atoms of two elements repel each other
  • the negative heat of mixing means that the atoms of the element attract each other.
  • Rare earth has the reputation of "industrial vitamin" and is widely used in the preparation of rare earth permanent magnets, polishing, hydrogen storage, catalysis and other materials.
  • NdFeB rare earth permanent magnets are used in hard disk drives, motors, wind power generation, new energy vehicles, etc. Key material.
  • these rare earth materials such as neodymium iron boron permanent magnet materials
  • waste materials such as sludge and scraps are generated.
  • these products containing key rare-earth materials (such as computers, motors, automobiles, etc.) have a useful life and expire when they expire, resulting in a large amount of waste rare-earth permanent magnets.
  • the present invention helps reduce the pressure of waste on the ecological environment.
  • Rare earth permanent magnet materials are widely used in electronic appliances, industrial motors, wind power generation, electric vehicles, automobiles and other products. With the continuous progress of science and technology and the upgrading of products, these products have gradually become solid waste. If the rare earth permanent magnet waste is improperly handled during the recycling process, the secondary pollution caused will bring great harm to the ecological environment, and pose a great threat to animals, plants and humans. For example, the acidity and alkalinity of groundwater and soil are seriously exceeding the standard; a large amount of smoke and dust are generated, causing serious pollution to the atmosphere. It can be seen that exploring new technologies and new processes for NdFeB waste recycling, and carrying out comprehensive and efficient separation and recycling of NdFeB waste have significant environmental benefits.
  • the present invention uses liquid metal bismuth to extract and separate rare earth metals in waste NdFeB, and enables various metal resources in waste NdFeB to obtain efficient and green recycling and reuse methods to realize the recovery and reuse of waste NdFeB permanent magnets use. Therefore, under environmentally friendly conditions, rare earth elements such as neodymium in waste neodymium iron boron can be extracted in one step, and iron and boron elements can be recycled and reused.
  • Figures 1(a)-(c) are schematic diagrams of using the selective distribution law of rare earth element RE in a liquid phase separation system (L 1 +L 2 ) to efficiently separate and recover rare earth elements in NdFeB waste.
  • 2(a)-(d) are schematic diagrams of the specific implementation process of extracting and recovering rare earth metals from neodymium iron boron waste using liquid metal bismuth according to the present invention.
  • 1 plug rod
  • 2 alumina crucible
  • 3 induction coil
  • 4 Fe-rich melt
  • 6 melt diversion port
  • 7 metal container.
  • Fig. 3 is a microstructure diagram of the lower Bi-RE alloy melt from which rare earth elements are extracted after cooling and solidification.
  • Figure 4 is a schematic diagram of the vacuum distillation separation of Bi-RE alloy, that is, the saturated vapor pressure logP(Pa)-temperature T(°C) relationship diagram of metal Bi and rare earth elements Nd, Pr, Dy.
  • Figure 5 shows the solidification structure of the upper Fe-B-rich alloy melt after the NdFeB waste melt is extracted and separated by the liquid metal Bi to separate the rare earth elements.
  • the present invention provides a method for efficiently separating and recovering rare earth elements in neodymium iron boron waste, using the selective distribution law of rare earth elements in a liquid phase separation system to achieve extraction and separation of rare earth metal elements from neodymium iron boron waste .
  • the rare earth element RE (Nd, Pr, Dy, etc.) in the NdFeB scrap is separated from the transition metal TM (Fe, Co, Ni, Cu, etc.) efficiently, and almost all the rare earth elements are enriched in the liquid state.
  • TM transition metal
  • a Bi-RE alloy melt is formed.
  • the existing industrial mature technology such as vacuum distillation
  • Liquid metal Bi is used to extract rare earth elements from NdFeB scrap, and then the rare earth elements are separated and recovered from the Bi-RE alloy melt.
  • the present invention is a method for extracting and recovering rare earth metals from waste permanent magnetic materials with liquid metal bismuth. The process flow is short, no chemical reagents are needed, operation time period, low energy consumption, zero emission, no secondary pollution, and metal resource recovery is at a utilization rate. Higher merit.
  • the method for extracting and recovering rare earth elements in NdFeB waste with liquid metal bismuth provided by the present invention, the key is to make the waste NdFeB and bismuth-rich extractant construct an Fe-Bi liquid-liquid separation system, that is, the bismuth-rich extractant and the waste NdFeB contacts to form a liquid-liquid contact surface (rather than a liquid-solid contact surface).
  • the two liquid phases can be stirred to produce a huge contact area.
  • a liquid-solid separation system is formed between the liquid metal bismuth and the NdFeB waste (that is, the NdFeB waste is solid). Specifically, under the condition of 800° C., a liquid/solid reaction interface is formed between the liquid metal bismuth Bi and the solid NdFeB, and the interface is maintained at a temperature of 800° C. for 2 hours to cause a diffusion reaction between the two. Then, the diffusion couple was observed and analyzed. The results showed that a diffusion reaction occurred at the liquid/solid interface. The rare earth elements in the solid NdFeB diffused into the liquid metal bismuth.
  • the thickness of the rare earth element diffusion layer in the solid NdFeB was about 2.3 mm. If other conditions remain unchanged, the holding time is increased from 2 hours to 5 hours. At this time, it is observed that the thickness of the rare earth element diffusion layer in the solid NdFeB is about 4.1mm, and in the thickness region of the solid NdFeB diffusion layer, the rare earth neodymium The content is still about 6-8% by mass.
  • the method first melts the metal bismuth in an induction heating furnace; then adds the waste NdFeB to the liquid metal bismuth, and heats it to a certain temperature to melt the NdFeB waste, and liquid-liquid phase separation occurs to form bismuth-rich and iron-rich Two immiscible solution phases; then, hold for a certain period of time to enrich the rare earth elements in the NdFeB scrap into the liquid metal bismuth to form a bismuth rare earth alloy melt, and the iron-rich liquid phase is an iron-boron alloy melt; finally, The two alloy melts (the upper layer is the iron-rich boron alloy melt and the lower layer is the bismuth rare earth alloy melt) that are completely layered up and down are separated.
  • the refined Fe-B iron-boron alloy can be recycled to produce neodymium-iron-boron permanent magnet materials; the metals Bi and Nd in the bismuth rare-earth alloy are separated by vacuum evaporation.
  • Step 1 Clean the oil stains and other dirt on the surface of the NdFeB waste material and dry it;
  • Step 2 Configure the NdFeB scrap and metallic bismuth according to a certain ratio to construct an Fe-Bi liquid-liquid phase separation system: liquid rich Fe + liquid rich Bi;
  • Step 3 Put the NdFeB waste and the metal bismuth mixture in an alumina crucible to heat and melt, stir the melt in the crucible, and make the liquid metal bismuth fully contact the NdFeB melt and all the rare earth elements in the NdFeB waste One-step extraction and separation into metallic bismuth melt;
  • Step 4 After the melt in the alumina crucible is kept for a period of time, the liquid Fe-rich + liquid Bi-rich melt is layered up and down, and the upper Fe-B rich alloy melt is separated from the lower Bi-RE rich melt.
  • Chemical composition analysis shows that the mass percentage of Bi in the Bi-rich metal melt is 40-65%, and the total mass percentage of rare earth elements Nd, Pr, Dy, etc. is between 30-50%.
  • the schematic diagram of the vacuum distillation separation of Bi-RE alloy that is, the saturated vapor pressure-temperature relationship diagram of metallic Bi and rare earth elements Nd, Pr, and Dy.
  • vacuum distillation is used to separate various metals to obtain high-purity metal elements; or based on metals at the same temperature Bi has the highest vapor pressure.
  • the Bi element in the Bi-RE alloy is separated by vacuum evaporation technology, and then the remaining mixed rare earth (containing Nd, Dy, Pr, etc.) is recycled as an intermediate alloy to produce NdFeB permanent magnet materials.
  • the solidification structure morphology of the upper Fe-B-rich alloy melt after the NdFeB waste melt is extracted with the rare earth elements by the liquid metal Bi.
  • Chemical composition analysis shows that the total mass percentage of transition metals Fe, Co, Ni, etc. in the Fe-rich metal melt is above 98%, and the total mass percentage of rare earth elements Nd, Pr, and Dy is between 0.1 and 1%. This shows that it is feasible to extract and recover rare earth elements in NdFeB waste using liquid metal Bi.
  • the invention can comprehensively recover light rare earth elements Nd, Pr, etc., heavy rare earth elements Dy, etc., transition metals Fe, Co, Ni, Cu, etc.
  • the melt in the crucible was kept standing at 1450°C for 10 minutes.
  • Liquid-liquid separation forms two liquid phases that are rich in Fe and rich in Bi. Because the density of the Fe-rich liquid phase is lower than that of the Bi-rich liquid phase, the Fe-rich liquid phase floats up under the action of gravity, while the Bi-rich liquid phase sinks, forming a layered structure of Fe-rich and Bi-rich liquid phases. Start the stopper rod and move the stopper rod upwards by 6-8mm. At this time, the lower Bi-rich liquid melt flows out through the diversion port, and the iron crucible is used to contain the Bi-rich alloy melt.
  • the weight percentage of rare earth elements is 34.4%
  • the weight percentage of extracted metal Bi is 63.8%
  • the weight percentage of metal Fe is 1.65%
  • the weight percentage of metal Al is 63.8%.
  • the weight percentage content is 0.09%
  • the element Si weight percentage content is 0.06%.
  • the weight percentage of rare earth elements is 0.78%
  • the weight percentage of extracted metal Bi is 1.01%
  • the weight percentage of metal Fe is 93.14%
  • the weight percentage of metal Al The content is 0.46%
  • the elemental Si weight percentage is 0.34%
  • the metal Mn weight percentage is 0.12%
  • the metal Ni weight percentage is 2.19%
  • the metal Co weight percentage is 1.83%
  • the metal Cu weight percentage is The content is 0.13%.
  • the melt in the crucible was kept standing at 1400°C for 10 minutes.
  • Liquid-liquid separation forms two liquid phases that are rich in Fe and rich in Bi. Because the density of the Fe-rich liquid phase is lower than that of the Bi-rich liquid phase, the Fe-rich liquid phase floats up under the action of gravity, while the Bi-rich liquid phase sinks, forming a layered structure of Fe-rich and Bi-rich liquid phases. Start the stopper rod and move the stopper rod upwards by 6-8mm. At this time, the lower Bi-rich liquid melt flows out through the diversion port, and the iron crucible is used to contain the Bi-rich alloy melt.
  • the weight percentage of rare earth elements is 0.45%
  • the weight percentage of extracted metal Bi is 0.51%
  • the weight percentage of metal Fe is 95.54%
  • the weight percentage of metal Al The content is 0.32%
  • the elemental Si weight percentage is 0.22%
  • the metal Mn weight percentage is 0.12%
  • the metal Ni weight percentage is 1.52%
  • the metal Co weight percentage is 1.2%
  • the metal Cu weight percentage is The content is 0.12%.
  • Example 2 is mainly in contrast with Example 1 when the weight of the extracted metal is added, reflecting the influence of the added amount of the extracted metal Bi.
  • the melt in the crucible was kept at 1400°C for 5 minutes.
  • Liquid-liquid separation forms two liquid phases that are rich in Fe and rich in Bi. Because the density of the Fe-rich liquid phase is lower than that of the Bi-rich liquid phase, the Fe-rich liquid phase floats up under the action of gravity, while the Bi-rich liquid phase sinks, forming a layered structure of Fe-rich and Bi-rich liquid phases. Start the stopper rod and move the stopper rod upwards by 6-8mm. At this time, the lower Bi-rich liquid melt flows out through the diversion port, and the iron crucible is used to contain the Bi-rich alloy melt.
  • the weight percentage of rare earth elements is 29.37%
  • the weight percentage of extracted metal Bi is 68.97%
  • the weight percentage of metal Fe is 1.58%
  • the weight percentage of metal Al is 68.97%.
  • the weight percentage is 0.04%
  • the element Si is 0.04% by weight.
  • the weight percentage of rare earth elements (Nd, Pr, Dy) totals 0.46%
  • the weight percentage of extracted metal Bi is 0.6%
  • the weight percentage of metal Fe is 95.44%
  • the weight percentage of metal Al The content is 0.31%
  • the elemental Si weight percentage is 0.23%
  • the metal Mn weight percentage is 0.12%
  • the metal Ni weight percentage is 1.53%
  • the metal Co weight percentage is 1.19%
  • the metal Cu weight percentage is The content is 0.12%.
  • the ratio and total weight of the neodymium iron boron and the extracted metal Bi of this example are exactly the same, except that the holding time is 5 minutes. Judging from the results of testing and analysis, appropriately reducing the heat preservation and standing time has little effect on the extraction of rare earth elements from NdFeB waste with metallic Bi. This shows that the rare earth elements can be extracted by the liquid metal Bi quickly, and the Bi-rich liquid phase and the Fe-rich liquid phase can achieve complete separation in a relatively short time. At this time, the recovery rate of the rare earth elements is about 97.1% .
  • This embodiment 3 is mainly in contrast with the embodiment 2 in terms of heat preservation and standing time, which is of significance for lower energy consumption.

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Abstract

一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法。首先在感应加热炉中熔化金属铋；再将废旧钕铁硼加入到液态金属铋中，并加热使钕铁硼废料熔化，发生液-液相分离，形成富铋和富铁两不混溶液相；然后，保温使钕铁硼废料中的稀土元素富集到液态金属铋中，形成铋稀土合金熔体，而富铁液相为铁硼合金熔体；最后，上下完全分层的两合金熔体(上层为富铁硼合金熔体，下层为铋稀土合金熔体)分离。Fe-B铁硼合金精炼后可循环用作于生产钕铁硼永磁材料；铋稀土合金中的金属Bi、Nd等通过真空蒸发分离。在环境友好条件下，一步式分离钕铁硼中钕等稀土元素，并实现铁、硼元素循环再利用。

Description

一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法
本申请要求于2019年01月21日提交中国专利局、申请号为201910052446.1、发明名称为“一种液态金属铋萃取回收汝铁硼废料中稀土元素的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明属于金属资源回收再利用领域，具体涉及一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法。
背景技术
稀土元素具有独特的物理化学性质，在科学技术发展与创新中被广泛应用，进而全球对稀土金属资源的需求逐年提高。尤其近些年来，致力于减少能耗和发展可再生能源的新科技对稀土资源的依赖性显著增强。稀土元素广泛应用于永磁材料、发光材料、储氢合金、镍氢电池电极材料、抛光和催化剂等新材料中。然而，大多数稀土元素应用于稀土永磁材料制备。从1967年研制的第一代稀土永磁钐钴到1983年研制的第三代稀土永磁钕铁硼，这其中使用的稀土元素有钐、镨、钕、铽、镝、镧、铈、钆、钬、铒、钇等。第三代钕铁硼稀土永磁材料因其具有质量轻、体积小、磁性强、磁能极高、原料易得、价格便宜等优点，发展极为迅速，是迄今为止性价比最高的永磁体材料，在磁学界被誉为“磁王”。它被广泛应用于硬盘驱动器、风力发电、电动助力转向、混合动力和电动汽车、电动自行车、电子消费品和家用电器等方面。另外，钕铁硼永磁材料还在升降机、磁选以及磁制冷设备上。当前广泛应用的稀土永磁材料主要有烧结钕铁硼(占91.4％)、粘结钕铁硼(占6.7％)、热压/热变形钕铁硼(占0.6％)和烧结钐钴(占1.3％)四大类。在2017年，全球钕铁硼永磁体产量近20万吨，其中中国约占85％。
废旧钕铁硼主要来源于：①钕铁硼材料制备过程产生的废料和②钕铁硼材料最终随使用器件失效而产生的废料。稀土钕铁硼永磁材料在生产制备过程中主要包括：配料、合金熔炼、氢破碎、气流磨磨粉、磁场取向成型、等静压、剥油、烧结、机加工等环节和工艺。在钕铁硼永磁材料的生产过程中的各道工艺都会产生一定量的废料或 废品，主要包括：在原料的预处理工序中产生的原材料损耗、在感应熔炼过程中因严重氧化产生的钕铁硼废料、在制粉过程中产生的超细粉、在制粉过程中被氧化的粉末、在烧结过程中被氧化的钕铁硼块状料、在加工成形过程中产生的大量边角料和表面处理过程中产生的不合格产品等。据统计，在钕铁硼稀土永磁体生产过程中，原料的利用率只有70％左右，产生约30％的废料。另外，钕铁硼稀土永磁材料广泛应用于硬盘驱动器、风力发电机、电动助力转向、混合动力和电动汽车、电动自行车、电子消费品和家用电器等新技术和产品上。这些产品有使用年限，到期失效。例如，音圈电机使用年限为8年、混合动力/电动汽车使用年限为15年、消费电机使用年限为15年、风电电机使用年限为20年等。2017年中国风电装机容量超过188GW，每装机1.5MW容量，约需要1吨钕铁硼永磁体。自2000年以来，我国风电装机容量逐年增加，尤其近10年来增长迅猛。2016年全球报废稀土钕铁硼永磁体总量在5～6万吨，中国占比60％以上，且报废量逐年增加。在钕铁硼稀土永磁材料中镨、钕、镝等稀土元素含量高达25～30％，其余主要是金属铁、钴、镍，以及元素硼等。大量的废旧钕铁硼稀土永磁体如果得不到高效绿色回收，不但将产生大量的污染源和二次污染，而且是资源浪费，有悖循环经济的发展。因此，从废旧钕铁硼稀土永磁材料中回收金属元素不仅有助于生态环境保护，而且可以缓解稀土资源危机和促进资源循环生产，这对环保保护和经济发展都具有重要意义。
目前，钕铁硼永磁废料的回收主要有湿法和火法两种处理方法。湿法主要包括4个步骤：①化学试剂溶解废料，使金属离子分布在溶液中，即浸取；②浸取溶液与残渣分离；③用离子交换，溶剂萃取或者其他化学沉淀方法，使浸取液净化和分离；④从净化溶液中提取化合物。基于湿法回收稀土，国内外发展硫酸复盐沉淀法、硫化物沉淀法、盐酸优溶法、盐酸全溶法、草酸沉淀法等。文献(林河成，制取氧化钕的研究，稀有金属与硬质合金，03:4-7,1997)报道采用硫酸-复盐法从钕铁硼废料中回收稀土并制备氧化钕产品。文献(陈云锦，全萃取法回收钕铁硼废渣中的稀土与钴，06:10-12，2004)报道采用盐酸全溶法将钕铁硼废料溶解于盐酸中，通过调节PH值使铁与稀土元素分离。文献(尹小文等，草酸盐沉淀法回收钕铁硼废料中稀土元素的研究，稀有金属，06:1093-1098,2014)报道采用草酸沉淀法将钕铁硼废料溶解于浓盐酸中，将浸取液中加入草酸得到草酸稀土沉淀，使稀土与铁元素分离。此外，发明专利(一种从钕铁硼废料中回收提取稀土氧化物的方法，公开号CN107012330A)公布一种从钕铁硼废料中回收提取稀土氧化物的方法，它采用粉碎—焚烧—清洗—酸溶—萃取—焙烧处理工艺后获得稀土氧化物。发明专利(一种从钕铁硼废料中回收稀土的方 法，公开号CN106319249A)公布一种从钕铁硼废料中回收稀土的方法，它是利用双氧水和氧化性和弱酸性，使钕铁硼废料溶解，然后采用N503先提取溶液中的铁元素，再用P507萃取稀土元素，最后采用草酸和碳酸钾分别沉淀相应的稀土离子。发明专利(从钕铁硼废料中回收稀土的方法，公开号CN103146925A)公布从钕铁硼废料中回收稀土的方法，它包括焙烧—酸溶—分离—灼烧等步骤，对滤液采用改性凹凸棒土与双氧水处理，离心去渣、萃取分离、沉淀分离等工艺后获得稀土氧化物。发明专利(从钕铁硼废料中回收稀土元素的方法，公开号CN102011020A)公布一种从钕铁硼废料中回收稀土元素的方法，其步骤为：将钕铁硼废料与水混合后研磨，氧化研磨后的钕铁硼，二次研磨氧化产物，加酸浸出，固液分离，萃取除铁，氯化稀土，萃取分离稀土，萃取除铝，沉淀和灼烧等。
火法处理主要分为玻璃渣法、合金法、氯化法、选择性氧化法、渣金融分法等。2003年Saito等人采用玻璃渣法，以氧化硼作氧化剂，把钕铁硼废料中的稀土元素氧化为氧化钕，而氧化硼被还原为硼单质进入到铁中形成铁硼合金。2002年Uda以FeCl 2为氯化剂，在800℃条件下钕铁硼废料中的稀土元素被氯化，然后采用真空蒸馏的方式回收其中的稀土氯化物。2014年Hua等人提出利用复合熔盐MgCl 2-KCl选择性氯化稀土元素的特性，从钕铁硼废料中回收稀土。2003和2004年Takeda等人提出用金属镁或银作提取剂，将钕铁硼固态废料中的稀土元素提取。对获得的镁钕合金，采用蒸馏将镁钕合金中的镁与钕元素分离；对获得银钕合金，采用选择性氧化将稀土钕元素氧化成为固态氧化钕，然后液/固分离得到到氧化钕和熔融的金属银。但是，采用金属银显然很难实现工业化生产。2018年Okabe等人提出将固态钕铁硼废料浸在1000℃的熔融MgCl 2中3～12小时，以选择性氯化稀土元素，从而提取钕铁硼固态废料中的稀土元素。该方法处理时间较长，能耗较大。
由此可见，上述回收钕铁硼废料中稀土的方法，需要对钕铁硼废料作预处理，存在工艺流程长、化学试剂消耗量大、能耗高，存在二次污染和铁元素回收难等问题。
发明内容
为了克服现有技术的不足，本发明的目的在于提供一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其工艺流程短、效率高、无需苛性化学试剂、零排放、环境友好，结合液-液相分离的冶金学特点和多金属组分在液相分离系统中的选择性分配规律，解决钕铁硼废料包括稀土和铁以及硼元素的综合高效回收和循环再利用等问题。
本发明的技术方案是：
一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法，按以下步骤进行：
步骤1，将废旧钕铁硼表面的污垢清洗干净，并进行干燥处理；
步骤2，将废旧钕铁硼与富铋萃取剂构建Fe-Bi液-液相分离系统：液态富Fe+液态富Bi；
步骤3，将废旧钕铁硼与富铋萃取剂混合料置于氧化铝坩埚中加热熔化，搅拌坩埚中的熔体，使液态富铋萃取剂充分接触液态钕铁硼熔体，废旧钕铁硼中所有的稀土元素一步式全部萃取到富铋萃取剂熔体中；
步骤4，氧化铝坩埚中的熔体保温后，将上层的富Fe熔体与下层的富Bi熔体分离。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤1所回收处理的废旧钕铁硼的化学组成主要包含过渡金属元素，以及轻稀土元素和重稀土元素。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，过渡金属元素为Fe、Co、Ni、Cu，轻稀土元素为Nd、Pr，重稀土元素为Dy或Tb。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤2所采用的富铋萃取剂为：纯度99wt％以上的金属Bi；或者，富Bi的Bi合金，其中Bi含量不低于50wt％。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤3废旧钕铁硼与富铋萃取剂混合配料中，金属Bi的重量百分含量15％～60％。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤3加热熔化废旧钕铁硼与富铋萃取剂混合配料的温度在1200℃～1450℃。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤3液态富铋萃取剂一步式萃取分离废旧钕铁硼中的稀土元素包括轻稀土元素Nd、Pr和重稀土元素Dy或Tb。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤4氧化铝坩埚中熔体保温温度在1350℃～1450℃之间，保温时间在5～10分钟。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤4分离的上层富Fe熔体中，主要由重量百分含量98％以上的过渡金属Fe、Co、Ni、Cu，以及重量百分含量约为1～2％的硼B元素组成的合金熔体，经精炼后以中间合金循环用于生产钕铁硼永磁材料。
所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，步骤4分离的下层富Bi熔体中，主要由重量百分含量40～70％的金属Bi，以及重量百分含量25～50％的轻稀土元素Nd、Pr和重量百分含量5～10％的重稀土元素Dy或Tb组成的Bi-RE铋稀土 合金熔体，通过真空蒸馏技术将Bi-RE合金中的金属Bi和各种稀土金属Dy或Tb、Nd、Pr逐次分离；或者基于相同温度下金属Bi蒸气压高于稀土金属Dy或Tb、Nd、Pr，采用真空蒸馏技术先将Bi-RE合金中的金属Bi提取分离，然后剩余的混合稀土含有Nd、Pr以及Dy或Tb以中间合金循环用于生产钕铁硼永磁材料。
本发明的设计思想是：
基于金属原子间的相互作用原理，两组元间的混合热绝对值越大，相互作用越强。通常正混合热表示两元素原子之间相互排斥，负混合热值则意味着元素原子之间相互吸引。从钕铁硼合金中各元素来看，元素Fe、Nd、B中任意两者的混合热为ΔH Fe-Nd＝+1kJ/mol、ΔH Fe-B＝-11kJ/mol、ΔH Nd-B＝-34kJ/mol，这表明元素Fe、Nd、B之间主要表现为相互吸引，具有较好的亲和性，也意味着钕铁硼合金熔融态下这三种元素很难实现分离。当引入萃取剂金属Bi后，它们与Bi之间的混合热为ΔH Fe-Bi＝+26kJ/mol、ΔH Nd-Bi＝-55kJ/mol、ΔH B-Bi＝+46kJ/mol。可见，Bi原子与Fe/B原子相互强烈排斥，但是Bi原子与Nd原子相互强烈吸引。因此，稀土Nd等元素将扩散到萃取剂Bi中，实现稀土元素与铁硼之间的高效绿色分离。
本发明的优点及有益效果是：
1、稀土有“工业维生素”美誉，大量用于稀土永磁、抛光、储氢、催化等材料的制备，而钕铁硼稀土永磁体又是硬盘驱动器、电机、风力发电、新能源汽车等的关键材料。然而，在这些稀土材料如钕铁硼永磁材料的制备过程中，约产生30％的废料如油泥、边角料等。此外，这些含有稀土关键材料的产品(如：电脑、电机、汽车等)有使用年限，到期失效，以致产生大量废旧的稀土永磁体。据悉，我国钕铁硼稀土永磁体年报废量在3～5万吨，且逐年增加。在钕铁硼永磁体中稀土元素重量占比达到25～35％左右，铁元素重量占比达到65～75％左右。可见，开展钕铁硼废料的综合高效分离与回收具有显著的经济效益。
2、本发明有助于减小废弃物给生态环境带来的压力，稀土永磁材料广泛应用于电子电器、工业电机、风力发电、电动车、汽车等产品中。随着科学技术不断进步与产品的更新换代，这些产品逐渐成为固体废弃物。如果稀土永磁废料回收过程中处理不当，造成的二次污染会给生态环境带来巨大危害，对动植物和人类造成极大威胁。例如，地下水和土壤中酸碱性严重超标；产生大量烟尘，使大气受到严重污染等。由此可见，探索钕铁硼废料资源化新技术和新工艺，开展钕铁硼废料的综合高效分离与回收具有显著的环境效益。
3、本发明利用液态金属铋萃取分离废旧钕铁硼中的稀土金属，并使废旧钕铁硼中 各种金属资源得到高效绿色循环和再利用的方法，实现废旧钕铁硼永磁体回收与再利用。从而，在环境友好条件下，一步式提取废旧钕铁硼中钕等稀土元素，对铁、硼元素实现回收再利用。
附图说明
图1(a)-(c)为本发明利用稀土元素RE在液相分离系统(L 1+L 2)选择性分配规律，高效分离和回收钕铁硼废料中稀土元素的原理图。
图2(a)-(d)为本发明利用液态金属铋萃取回收钕铁硼废料中稀土金属的具体实施过程示意图。图中，1—塞杆，2—氧化铝坩埚，3—感应线圈，4—富Fe熔体，5—富Bi熔体，6—熔体导流口，7—金属容器。
图3为萃取稀土元素的下层Bi-RE合金熔体冷却凝固后的显微组织结构图。
图4为Bi-RE合金真空蒸馏分离的原理图，即金属Bi及稀土元素Nd、Pr、Dy的饱和蒸气压logP(Pa)-温度T(℃)关系图。
图5为钕铁硼废料熔体被液态金属Bi萃取分离稀土元素后的上层富Fe-B合金熔体的凝固组织形貌图。
具体实施方式
在具体实施过程中，本发明提供高效分离与回收钕铁硼废料中稀土元素的方法，利用稀土元素在液相分离系统中的选择性分配规律，实现稀土金属元素从钕铁硼废料中萃取分离。如图1(a)-(c)所示，一般来说，稀土元素RE在液相分离系统中有三种选择性分配情况：①稀土元素RE溶解在液相分离系统中的L 1中，见图1(a)；②稀土元素RE溶解在液相分离系统中的L 2中，见图1(b)；③稀土元素RE既不溶解在液相分离系统中的L 1中，也不溶解在L 2中，而是分布在两分离液相L 1和L 2的界面处附近，见图1(c)。
根据这一原理，使钕铁硼废料中的稀土元素RE(Nd、Pr、Dy等)与过渡金属TM(Fe、Co、Ni、Cu等)高效分离，而几乎所有的稀土元素富集到液态金属Bi中，形成Bi-RE合金熔体。然后，采用现有工业成熟技术(如真空蒸馏法)，将Bi-RE合金熔体中金属Bi以及稀土元素RE(Nd、Pr、Dy等)分离。采用液态金属Bi萃取钕铁硼废料中稀土元素，然后从Bi-RE合金熔体中实现稀土元素的分离与回收；此外，钕铁硼废料中的稀土元素被液态金属Bi萃取后，剩余的金属绝大部分为过渡金属TM(Fe、Co、Ni、Cu等)以及少量B元素。Fe-B合金经精炼后以中间合金循环用于生产钕铁硼永磁材料。本发明一种液态金属铋萃取回收废旧永磁材料中稀土金属的方法，工艺流程短、无需使用化学试剂、操作时间段、能耗少、零排放、无二次污染、金属 资源回收在利用率高等优点。
本发明提出的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，关键在于：使废旧钕铁硼与富铋萃取剂构建Fe-Bi液-液相分离系统，即富铋萃取剂与废旧钕铁硼相接触，形成液-液接触面(而不是液-固接触面)，同时，在不低于钕铁硼熔点温度的条件下，可以通过机械搅拌使两液相产生巨大的接触面积，稀土元素向液态金属铋扩散距离减小，稀土元素快速并充分富集到液态金属铋中，使不低于95％稀土元素在5-30分钟内富集到液态金属铋中；然后采用机械振动技术，促进存在密度差的液态铁硼合金与液态铋稀土合金两相快速分离，形成上下两层。
若在液态金属铋萃取回收钕铁硼废料中稀土元素时，液态金属铋与钕铁硼废料之间形成的是液-固分离系统(即，钕铁硼废料为固态)。具体地，在800℃条件下，液态金属铋Bi与固态钕铁硼之间形成液/固反应界面，并在温度800℃的温度下保持2小时，使两者之间发生扩散反应。然后，对扩散偶进行观察和分析，结果表明液/固界面处发生了扩散反应，固态钕铁硼中的稀土元素向液态金属铋中扩散，固态钕铁硼中稀土元素扩散层厚度约为2.3mm。如果其他条件不变，保温的时间由2小时增加到5小时，此时观察到固态钕铁硼中稀土元素扩散层厚度约为4.1mm，且在固态钕铁硼扩散层厚度区域内，稀土钕的含量仍约6-8％质量含量。由此可见，采用液-固界面接触提取稀土元素时，会存在如下技术问题：1)操作时间长，提取效率低；2)能耗(时间×温度)高，成本高；3)对钕铁硼废料的尺寸大小受限，对于尺寸较大(如大于5mm)的块体废料存在较大难度；4)稀土的提取率偏低、回收率不高；5)液态金属铋与固态钕铁硼颗粒彻底分离难，工业化连续性生产不便实现；6)操作时间长，易导致金属铋的挥发。而本发明构建Fe-Bi液-液相分离系统可以解决液-固分离系统存在的上述技术问题。
该方法首先在感应加热炉中熔化金属铋；再将废旧钕铁硼加入到液态金属铋中，并加热到一定温度使钕铁硼废料熔化，发生液-液相分离，形成富铋和富铁两不混溶液相；然后，保温一定时间，使钕铁硼废料中的稀土元素富集到液态金属铋中，形成铋稀土合金熔体，而富铁液相为铁硼合金熔体；最后，上下完全分层的两合金熔体(上层为富铁硼合金熔体，下层为铋稀土合金熔体)分离。Fe-B铁硼合金精炼后可循环用作于生产钕铁硼永磁材料；铋稀土合金中的金属Bi、Nd等通过真空蒸发分离。按以下步骤进行：
步骤1，将钕铁硼废料表面的油渍等污垢清洗干净并进行干燥处理；
步骤2，将钕铁硼废料与金属铋按照一定比例配置，构建Fe-Bi液-液相分离系统： 液态富Fe+液态富Bi；
步骤3，将钕铁硼废料与金属铋混合料置于氧化铝坩埚中加热熔化，搅拌坩埚中的熔体，使液态金属铋充分接触钕铁硼熔体，钕铁硼废料中所有的稀土元素一步式全部萃取分离到金属铋熔体中；
步骤4，氧化铝坩埚中的熔体保温一段时间后，液态富Fe+液态富Bi熔体上下分层，将上层的富Fe-B合金熔体与下层的富Bi-RE熔体分离。
如图2(a)-(d)所示，本发明利用液态金属铋萃取回收废旧钕铁硼中稀土金属的具体实施过程如下：
图2(a)按一定比例配置好后的钕铁硼废料与金属铋混合料置于氧化铝坩埚2内，用塞杆1将熔体导流口6密合堵塞住，然后采用真空中频感应炉的感应线圈3进行加热，直到钕铁硼废料熔化，液-液分离形成上层密度较小的富Fe熔体4和下层密度较大的富Bi熔体5。由于稀土RE原子与金属Bi原子之间具有更大的亲和力，稀土元素几乎完全被萃取到富Bi金属熔体5中。图2(b)经过在一定时间保温后，将塞杆1往上稍提起，下层的富Bi金属熔体5经熔体导流口6流入到盛装熔体的金属容器7中。图2(c)当下层的富Bi金属熔体5从坩埚中导出后，将塞杆1复位使熔体导流口6塞住，同时将盛装有富Bi金属熔体5的金属容器7移送后续处理。图2(d)将塞杆1往上再次稍提起，上层的富Fe金属熔体4经熔体导流口6流入到另一金属容器中。
将钕铁硼废料和金属Bi按重量1:1配比获得混合料，用塞杆1将熔体导流口6密合堵塞住，然后将混合料置于真空中频感应炉的氧化铝坩埚2中，在氩气保护环境下对混合料感应加热，加热到钕铁硼稀土永磁废料(即：钕铁硼废料)完全熔化，用氧化铝杆搅拌时感觉坩埚中没有明显未熔化的固体即可。在一定的温度下保温一段时间并静置后，上层富Fe熔体4和下层富Bi熔体5两液相通过导流口流出，冷却后分别获得富Fe-B合金锭和富Bi-RE合金锭。
如图3所示，萃取稀土元素的下层富Bi金属熔体冷却凝固后的显微组织结构图。化学成分分析表明，富Bi金属熔体中金属Bi的质量百分含量40～65％，稀土元素Nd、Pr、Dy等总质量百分含量在30～50％之间。
如图4所示，Bi-RE合金真空蒸馏分离的原理图，即金属Bi及稀土元素Nd、Pr、Dy的饱和蒸气压-温度关系图。基于Bi-RE合金熔体中相同温度下Bi、Nd、Pr、Dy等各金属元素的蒸气压不同，采用真空蒸馏法分离各种金属，进而获得高纯度的金属单质；或者基于相同温度下金属Bi蒸气压最高，采用真空蒸发技术先将Bi-RE合金中Bi元素分离，然后剩余的混合稀土(含有Nd、Dy和Pr等)以中间合金循环用于生 产钕铁硼永磁材料。
如图5所示，钕铁硼废料熔体被液态金属Bi萃取稀土元素后的上层富Fe-B合金熔体的凝固组织形貌图。化学成分分析表明，富Fe金属熔体中过渡金属Fe、Co、Ni等总质量百分含量在98％以上，稀土元素Nd、Pr、Dy总质量百分含量在0.1～1％之间。这表明，采用液态金属Bi萃取回收钕铁硼废料中的稀土元素是可行的。本发明可一步式综合回收钕铁硼废料中的轻稀土元素Nd、Pr等和重稀土元素Dy等，以及过渡金属Fe、Co、Ni、Cu等和硼B元素，使金属资源化分离与提取工艺更简化，具有高效、节能、零排放、环境友好等特点，具有经济和环境效益。
下面，通过实施例对发明进一步详细描述。
实施例1
将市面收购的稀土强磁体钕铁硼废料进行退磁，然后将其表面污渍清洗干净，烘干后备用。按重量比2:1配置钕铁硼废料和金属Bi，称取钕铁硼废料1.33千克和金属Bi重量为0.67千克，共计混合料2千克。用氧化铝塞杆将氧化铝坩埚的熔体导流口密合堵塞住，然后将2千克的混合料装入中频感应熔炼炉的氧化铝坩埚中，在氩气保护环境下对混合料感应加热，加热到钕铁硼稀土永磁废料熔化，直到用氧化铝杆搅拌时感觉坩埚中没有明显未熔化的固体即可。然后，坩埚中熔体在1450℃下保温静置10分钟。液-液分离形成富Fe和富Bi液相两液相。由于富Fe液相密度较富Bi液相小，在重力作用下富Fe液相上浮，而富Bi液相下沉，形成富Fe和富Bi两液相分层的结构。启动塞杆，使塞杆往上移动6～8mm，这时下层富Bi液熔体通过导流口流出，用铁坩埚盛装富Bi合金熔体。当氧化铝坩埚中的下层富Bi液相从导流口流出完事后，启动塞杆复位，将导流口塞住，更换好另一个铁坩埚容器后，再次启动塞杆，使氧化铝坩埚中剩余的富Fe熔体从导流口导入铁坩埚中。待氧化铝坩埚中的富Fe金属熔体流净后，启动塞杆复位，塞住导流口，加入下一炉钕铁硼废料和金属Bi的混合料，开始下一批次循环作业。两只铁坩埚中富Fe和富Bi合金熔体冷却凝固后，分别取样做分析检测。
结果表明，富Bi合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占34.4％、萃取金属Bi重量百分含量为63.8％、金属Fe重量百分含量为1.65％、金属Al重量百分含量为0.09％、元素Si重量百分含量为0.06％。富Fe合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占0.78％、萃取金属Bi重量百分含量为1.01％、金属Fe重量百分含量为93.14％、金属Al重量百分含量为0.46％、元素Si重量百分含量为0.34％、金属Mn重量百分含量为0.12％、金属Ni重量百分含量为2.19％、金属Co重量百分含 量为1.83％、金属Cu重量百分含量为0.13％。
由此可见，当钕铁硼废料和金属Bi按照重量比2:1配置时，钕铁硼废料中的重稀土和轻稀土在较短时间被液态金属Bi萃取，稀土元素的回收率达到95.6％。本实施例1证实本发明的原理的正确性。
实施例2
将市面收购的稀土强磁体钕铁硼废料进行退磁，然后将其表面污渍清洗干净，烘干后备用。按重量比3:2配置钕铁硼废料和金属Bi，称取钕铁硼废料1.33千克和金属Bi重量为0.87千克，共计混合料2.2千克。用氧化铝塞杆将氧化铝坩埚的熔体导流口密合堵塞住，然后将2.2千克的混合料装入中频感应熔炼炉的氧化铝坩埚中，在氩气保护环境下对混合料感应加热，加热到钕铁硼稀土永磁废料熔化，直到用氧化铝杆搅拌时感觉坩埚中没有明显未熔化的固体即可。然后，坩埚中熔体在1400℃下保温静置10分钟。液-液分离形成富Fe和富Bi液相两液相。由于富Fe液相密度较富Bi液相小，在重力作用下富Fe液相上浮，而富Bi液相下沉，形成富Fe和富Bi两液相分层的结构。启动塞杆，使塞杆往上移动6～8mm，这时下层富Bi液熔体通过导流口流出，用铁坩埚盛装富Bi合金熔体。当氧化铝坩埚中的下层富Bi液相从导流口流出完事后，启动塞杆复位，将导流口塞住，更换好另一个铁坩埚容器后，再次启动塞杆，使氧化铝坩埚中剩余的富Fe熔体从导流口导入铁坩埚中。待氧化铝坩埚中的富Fe金属熔体流净后，启动塞杆复位，塞住导流口，加入下一炉钕铁硼废料和金属Bi的混合料，开始下一批次循环作业。两只铁坩埚中富Fe和富Bi合金熔体冷却凝固后，分别取样做分析检测。
结果表明，富Bi合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占29.41％、萃取金属Bi重量百分含量为69.08％、金属Fe重量百分含量为1.44％、金属Al重量百分含量为0.03％、元素Si重量百分含量为0.04％。富Fe合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占0.45％、萃取金属Bi重量百分含量为0.51％、金属Fe重量百分含量为95.54％、金属Al重量百分含量为0.32％、元素Si重量百分含量为0.22％、金属Mn重量百分含量为0.12％、金属Ni重量百分含量为1.52％、金属Co重量百分含量为1.2％、金属Cu重量百分含量为0.12％。
由此可见，与实施例1相比较，当相同重量的钕铁硼废料与不同重量的萃取金属Bi配比时，增大萃取金属Bi重量，萃取金属Bi中的稀土元素含量减少，但钕铁硼废料中的稀土被萃取得更完全，最终富Fe合金锭中的萃取金属Bi含量较少，金属Fe含量增高，此时稀土元素的回收率达到97.4％。本实施例2主要是与实施例1在添加 萃取金属重量形成对比，反映萃取金属Bi加入量的影响。
实施例3
将市面收购的稀土强磁体钕铁硼废料进行退磁，然后将其表面污渍清洗干净，烘干后备用。按重量比3:2配置钕铁硼废料和金属Bi，称取钕铁硼废料1.33千克和金属Bi重量为0.87千克，共计混合料2.2千克。用氧化铝塞杆将氧化铝坩埚的熔体导流口密合堵塞住，然后将2.2千克的混合料装入中频感应熔炼炉的氧化铝坩埚中，在氩气保护环境下对混合料感应加热，加热到钕铁硼稀土永磁废料熔化，直到用氧化铝杆搅拌时感觉坩埚中没有明显未熔化的固体即可。然后，坩埚中熔体在1400℃下保温静置5分钟。液-液分离形成富Fe和富Bi液相两液相。由于富Fe液相密度较富Bi液相小，在重力作用下富Fe液相上浮，而富Bi液相下沉，形成富Fe和富Bi两液相分层的结构。启动塞杆，使塞杆往上移动6～8mm，这时下层富Bi液熔体通过导流口流出，用铁坩埚盛装富Bi合金熔体。当氧化铝坩埚中的下层富Bi液相从导流口流出完事后，启动塞杆复位，将导流口塞住，更换好另一个铁坩埚容器后，再次启动塞杆，使氧化铝坩埚中剩余的富Fe熔体从导流口导入铁坩埚中。待氧化铝坩埚中的富Fe金属熔体流净后，启动塞杆复位，塞住导流口，加入下一炉钕铁硼废料和金属Bi的混合料，开始下一批次循环作业。两只铁坩埚中富Fe和富Bi合金熔体冷却凝固后，分别取样做分析检测。
结果表明，富Bi合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占29.37％、萃取金属Bi重量百分含量为68.97％、金属Fe重量百分含量为1.58％、金属Al重量百分含量为0.04％、元素Si重量百分含量为0.04％。富Fe合金锭中，稀土元素(Nd、Pr、Dy)重量百分含量共占0.46％、萃取金属Bi重量百分含量为0.6％、金属Fe重量百分含量为95.44％、金属Al重量百分含量为0.31％、元素Si重量百分含量为0.23％、金属Mn重量百分含量为0.12％、金属Ni重量百分含量为1.53％、金属Co重量百分含量为1.19％、金属Cu重量百分含量为0.12％。
由此可见，与实施例2相比较，本实施例钕铁硼与萃取金属Bi的配比和总重量完全相同，不同的是保温静置时间为5分钟。从检测分析结果来看，适当减小保温静置时间，对金属Bi萃取钕铁硼废料中的稀土元素的效果影响不大。这表明，稀土元素能较快被液态金属Bi萃取，而且富Bi液相和富Fe液相在较短的时间内能达到较完全彻底的分层，此时稀土元素的回收率约达到97.1％。本实施例3主要是与实施例2在保温静置时间上形成对比，这对较小能耗具有意义。

Claims (10)

  1. 一种液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，按以下步骤进行：
    步骤1，将废旧钕铁硼表面的污垢清洗干净，并进行干燥处理；
    步骤2，将废旧钕铁硼与富铋萃取剂构建Fe-Bi液-液相分离系统：液态富Fe+液态富Bi；
    具体地，将废旧钕铁硼与富铋萃取剂混合料置于坩埚中加热熔化，搅拌坩埚中的熔体，使液态富铋萃取剂充分接触液态钕铁硼熔体，废旧钕铁硼中稀土元素一步式萃取到富铋萃取剂熔体中；
    步骤3，坩埚中的熔体保温后，将上层的富Fe熔体与下层的富Bi熔体分离；
    优选的，所述坩埚选用氧化铝坩埚。
  2. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤1所回收处理的废旧钕铁硼的化学组成主要包含过渡金属元素，以及轻稀土元素和重稀土元素。
  3. 按照权利要求2所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，过渡金属元素为Fe、Co、Ni、Cu，轻稀土元素为Nd、Pr，重稀土元素为Dy或Tb。
  4. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤2所采用的富铋萃取剂为：纯度99wt％以上的金属Bi；或者，富Bi的Bi合金，其中Bi含量不低于50wt％。
  5. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤2废旧钕铁硼与富铋萃取剂混合料中，金属Bi的重量百分含量15％～60％。
  6. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤2加热熔化废旧钕铁硼与富铋萃取剂混合料的温度在1200℃～1450℃。
  7. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤2液态富铋萃取剂一步式萃取分离废旧钕铁硼中的稀土元素包括轻稀土元素Nd、Pr和重稀土元素Dy或Tb。
  8. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其 特征在于，步骤3坩埚中熔体保温温度在1350℃～1450℃之间，保温时间在5～10分钟。
  9. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤3分离的上层富Fe熔体中，主要由重量百分含量98％以上的过渡金属Fe、Co、Ni、Cu，以及重量百分含量约为1～2％的硼B元素组成的合金熔体，经精炼后以中间合金循环用于生产钕铁硼永磁材料。
  10. 按照权利要求1所述的液态金属铋萃取回收钕铁硼废料中稀土元素的方法，其特征在于，步骤3分离的下层富Bi熔体中，主要由重量百分含量40～70％的金属Bi，以及重量百分含量25～50％的轻稀土元素Nd、Pr和重量百分含量5～10％的重稀土元素Dy或Tb组成的Bi-RE铋稀土合金熔体，通过真空蒸馏技术将Bi-RE合金中的金属Bi和各种稀土金属Dy或Tb、Nd、Pr逐次分离；或者基于相同温度下金属Bi蒸气压高于稀土金属Dy或Tb、Nd、Pr，采用真空蒸馏技术先将Bi-RE合金中的金属Bi提取分离，然后剩余的混合稀土含有Nd、Pr以及Dy或Tb以中间合金循环用于生产钕铁硼永磁材料。
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