Process for recovering permanent magnets and valuable metals from hard drives

Abstract

A process for recovering NdFeB permanent magnets from waste electrical and electronic equipment, comprising the following successive steps: - subjecting demagnetized permanent magnets to a first magnetic separation using a 400 G drum, - recovering a first magnetic phase (1FM), - subjecting the first magnetic phase (1FM) to a first magnetic separation using an overband separator, so that a second non-magnetic phase (2FNM) resulting from the first overband magnetic separation is enriched in demagnetized magnets, - recovering the second non-magnetic phase (2FNM). Figure 1 for the abstract

Description

Title of the invention: Method for recovering permanent magnets and valuable metals from hard drives

[0001] 1 - Technical field of the invention

[0002] The invention relates to a method for recovering NdFeB permanent magnets from waste electrical and electronic equipment (WEEE), and in particular from WEEE hard drives. The invention also relates to a method for extracting metals such as rare earth elements, aluminum, copper, gold, silver, platinum, and palladium from WEEE.

[0003] 2 - State of the art

[0004] The increasing use of rare earth elements (REEs) in many recent technological innovations has led to a sharp rise in their demand. Green technologies, which help reduce environmental impacts due to their lower energy consumption and are particularly reliant on these elements, contribute significantly to this sustained demand. In this context, Europe has placed recycling, in its "Raw Materials" strategy, as one of the main pillars for securing a portion of its strategic metal supplies, including rare earth elements. Industrial-scale rare earth recycling operations remain relatively few, although they offer numerous advantages compared to the exploitation of primary resources:

[0005] - Europe constitutes one of the most important regions of land consumption rare through its high value-added industries. It has also accumulated consumer goods for decades which, at the end of their life, constitute secondary resources from which rare earths can be extracted.

[0006] - European and French dependence on resources from countries foreign exchange could be reduced through the recycling of post-consumer waste.

[0007] - The processing of secondary resources for the production of rare earths would not entail health and environmental risks, whereas the exploitation of primary deposits presents such risks, linked to the presence of radionuclides in primary deposits.

[0008] - The production of metallic resources by exploitation of secondary resources is most often done with energy consumption much lower than that observed for the exploitation of primary resources.

[0009] Furthermore, the production volume of Neodymium has increased dramatically since the development of powerful (Nd-Fe-B) magnets in 1980. This development has made it possible to considerably improve the performance of Smaller motors help reduce the size and weight of portable electronic devices. For example, most mobile phones use miniaturized motors built on small Nd-based magnets for their vibration functions. These magnets are also widely used in computer hard drives, where they form the motor that positions the read / write heads. They significantly improve the performance of this storage device and contribute to reducing the size of computers. The technological revolution in developed countries has led to supply shortages and tensions that have resulted in soaring prices since January 2010.

[0010] However, the recycling of permanent magnets contained in WEEE categories faces many obstacles such as those mentioned below.

[0011] - The WEEE deposit is heterogeneous and it is difficult to obtain samples representative.

[0012] - Rare earths are dispersed in the WEEE deposit.

[0013] - The rare earth content of the small mixed device (SMD) stream and of Central processing units are poorly understood.

[0014] - The magnetic property of permanent magnets constitutes a technical obstacle when recycling operations; indeed, these magnets "stick" to the crushing and sorting equipment.

[0015] - The WEEE entering the process is run-of-the-mill, at the base of the process, and their nature is therefore variable.

[0016] - The efficiency of unit operations of grinding and sorting from dies complex is questioned. As an example, a hard drive is made up of 80% aluminum, 7% electronic board, 8% scrap metal, 1% plastics, 3% magnets and 1% other metals.

[0017] - The separation of rare earth elements from the metals constituting the coatings of magnets obtaining the fraction below 80 pm after grinding is difficult.

[0018] However, in Japan, rare earth elements from permanent magnets are already being recycled. Recycling is carried out primarily through extractive metallurgy.

[0019] In France, current discussions focus on the recycling of magnets contained in wind turbines and hybrid or all-electric vehicles.

[0020] Document WO2017 / 079183 also proposes a process for recycling rare-earth magnets from manufactured articles. This process involves aligning the manufactured articles in a predetermined orientation, then separating the magnets from the articles, and subsequently heating them to demagnetize them. Finally, the demagnetized magnets are separated from the residual parts of the manufactured articles. This process therefore requires an installation particularly, especially for aligning items. It is a long and economically burdensome process with low efficiency.

[0021] The Fraunhofer Institute has developed a process for recycling magnets from electric motors and generators by melting the magnets in an induction furnace at 1000°C. A drawback of this type of melting process is the high energy consumption, resulting in a significant cost. Furthermore, the efficiency of this process needs improvement, as does the quality of the resulting product.

[0022] Finally, it has also been proposed to recover hard drive magnets using mechanical sorting. Magnets demagnetized by heat treatment are recovered using fragmentation, classification, and magnetic separation. In this process, a fraction rich in magnets is recovered from the magnetic fraction. Thus, in this process, the magnets are recovered along with other magnetic objects, such as scrap metal. To purify the magnets, they must then be separated from these other magnetic objects. The yield of this process is therefore not optimal.

[0023] Description of the invention

[0024] The invention aims in particular to propose an alternative method for recovering permanent magnets, which does not present all or part of these disadvantages.

[0025] To this end, the invention relates to a process for recovering NdFeB-type permanent magnets from waste electrical and electronic equipment. The process comprises the following successive steps: - subjecting demagnetized permanent magnets to a first magnetic separation using a 400 G drum, - to recover a first magnetic phase, - subject the first magnetic phase to a first magnetic separation on an Overband separator, so that a second non-magnetic phase resulting from the first Overband magnetic separation is enriched in demagnetized magnets, - recover the second non-magnetic phase.

[0026] Due in particular to their iron alloy content, demagnetized permanent magnets, when subjected to magnetic separation, are drawn into the magnetic fraction. Surprisingly, the inventors have developed a process that, through magnetic separation, allows the demagnetized magnets to be separated from the rest of the magnetic fraction, which includes, for example, scrap metal. Therefore, no additional step is required to separate the magnets from the scrap metal. The process according to the invention offers improved efficiency. Furthermore, when the recovered magnets are used to obtain rare earth elements, it is particularly advantageous to limit the presence of iron, as it will then have to be separated from the rare earth elements.

[0027] Overband magnetic separators are commonly used in waste treatment devices. For example, in document FR2962924, An overband separator ensures the extraction of ferrous residues separated from other materials during previous crushing. The overband consists of a fixed magnetic system around which a discharge belt rotates. It is positioned above or below a conveyor and allows magnetic particles to be carried off the conveyor while non-magnetic particles pass through. Typically, the magnetic field strength of the overband is between 380 and 400 G.

[0028] To obtain the demagnetized magnets, the WEEE is first heated, preferably between 325°C and 450°C, i.e., above its Curie temperature. For example, one ton of hard drives is treated for a minimum of 2 hours in a furnace. The WEEE is then shredded, preferably in an autogenous shredder.

[0029] Depending on other optional features of the magnet recovery process, taken alone or in combination:

[0030] - The Overband separator comprises a fixed magnetic system placed above or below a conveyor for transporting demagnetized magnets, and the magnetic system is located at a distance of 7 to 15 cm, preferably 8 to 10 cm, and preferably about 9 cm. At this distance, the demagnetized magnets are carried into the non-magnetic fraction. To move the magnets into the non-magnetic fraction, one could, for example, vary the intensity of the magnetic field. Adjusting the distance allows for a simple and effective way to move the demagnetized magnets into the non-magnetic fraction.

[0031] - Demagnetized magnets are obtained by grinding and then selecting the fraction of particles up to 16 mm in size. By selecting these particle sizes, the magnets are concentrated because it is visually identifiable that the majority of the magnets are located in this fraction.

[0032] - Particles larger than 5 mm are selected. Indeed, the The fraction of particles smaller than 5 mm is poorly suited to magnetic separation, and passing these particles through magnetic separators risks contaminating the phases obtained after separation, as these small particles do not necessarily exhibit the expected behavior. Furthermore, the fraction smaller than 5 mm does not contain many magnets.

[0033] - Permanent magnets are recovered from waste hard drives of electrical and electronic equipment. Among this waste, hard drives systematically contain permanent magnets. The permanent magnets are thus concentrated, and the recovery process will then be carried out on them.

[0034] - The process further comprises at least one of the following successive steps: . recovery of a first non-magnetic phase following the first magnetic separation using a 400 G drum, . second magnetic separation using a 400 G drum of the first non-magnetic phase, to obtain a third magnetic phase, . second magnetic separation Overband of the third magnetic phase, and . recovery of a fourth non-magnetic phase. Advantageously, these additional steps are combined together and allow the recovery of magnets that had not passed into the magnetic phase after the first 400 G drum magnetic separation.

[0035] - The process further comprises a preliminary demagnetization step by heating between 325°C and 450°C of waste electrical and electronic equipment. For example, one tonne of hard drives is heated between 325°C and 450°C for 2 hours in an induction furnace.

[0036] The process also includes a preliminary step of releasing the demagnetized magnets by grinding. For example, 50 kg of hard drives are subjected for 45 minutes to grinding in an autogenous grinder, at a rotational speed of 25 revolutions per minute.

[0037] The invention also relates to the products obtained directly from the magnet recovery process according to the invention and their subsequent use, particularly in the field of electronics.

[0038] The invention also relates to a process for extracting metals such as rare earths, aluminium, copper, gold, silver, platinum and palladium, from NdFeB type permanent magnets from waste electrical and electronic equipment, incorporating a magnet recovery process as described above.

[0039] The invention also relates to the products obtained directly from the rare earth extraction process according to the invention and their subsequent use, particularly in the field of electronics.

[0040] The invention also relates to a method for manufacturing permanent magnets from NdFeB type permanent magnets from waste electrical and electronic equipment, incorporating a magnet recovery process as described above.

[0041] The invention also relates to the products obtained directly from the process of manufacturing magnets according to the invention and their subsequent use, particularly in the field of electronics. Brief description of the figures

[0042] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0043] [Fig.l] schematically illustrates a metal recovery process, including the steps of the permanent magnet recovery process according to the invention;

[0044] [Fig.2] is a photograph of the fraction greater than 40 mm obtained after the classification step of a magnet recovery process according to the invention;

[0045] [Fig.3] is a photograph of the 20 to 40 mm fraction obtained after the classification step of a magnet recovery process according to the invention;

[0046] [Fig.4] is a photograph of the fraction less than 5 mm obtained after the classification step of a magnet recovery process according to the invention;

[0047] [Fig.5] is a photograph of the 5 to 16 mm fraction obtained after the classification step of a magnet recovery process according to the invention;

[0048] [Fig.6] is a photograph of the fraction obtained in step 9 of a magnet recovery process according to the invention. Detailed description

[0049] Figure 1 schematically illustrates a metal recovery process, including rare earth extraction. This process includes the steps of the permanent magnet recovery process according to the invention (steps 1 to 10 of the schematic process). In the process according to the invention, the magnets are recovered from WEEE waste. In the example described below, the permanent magnets are more specifically recovered from WEEE hard drives.

[0050] Example 1

[0051] In the first steps 1 and 2, the magnets are recovered from the hard drives and demagnetized. They are then freed by grinding in step 3. The rare earth elements contained in the magnets are then selectively recovered by hydrometallurgy in steps 9 and 10. The other metals separated from the magnets are shredded and recovered by extractive metallurgy in steps 11 to 15.

[0052] In step 1, a batch of used hard drives collected from an industrial site was gathered. Industrial companies recover used hard drives using two techniques, namely manual dismantling and mechanical dismantling of small mixed devices (SMD) using a rotating drum with lifters to release the computer components.

[0053] In step 2, a ton of hard drives was then heated to between 325°C and 450°C (Curie temperature) in order to demagnetize the magnets, in a manner also known per se. More specifically, the magnets were heated to 350°C for 2 hours in an induction furnace.

[0054] In step 3, approximately 415 kg of hard drives from step 2 were introduced into an autogenous shredder to release the magnets from the hard drives. The hard drives were grouped into batches of 50 kg. Each batch was placed in the autogenous shredder for 45 minutes at a rotational speed of 25 rpm.

[0055] In step 4, the ground material from step 3 was classified by sieving into different particle size classes: larger than 40 mm, 20 to 40 mm, 16 to 20 mm, 5 to 16 mm, and smaller than 5 mm. The fraction with a particle size smaller than 40 mm was sieved at 5, 16, and 20 mm. The fractions with a particle size smaller than 5 mm, 5 to 16 mm, 16 to 20 mm, and larger than 20 mm represented 14.2%, 19.9%, 8.2%, and 57.7% by weight, respectively.

[0056] Figures 2, 3, 4 and 5 show respectively photographs of the fraction with a size greater than 40 mm, the fraction from 20 to 40 mm, the fraction with a size less than 5 mm and the fraction from 5 to 16 mm.

[0057] It is visually identified that magnets are more prevalent in the two fractions of size 5-16 mm and smaller than 5 mm. Thus, the classification makes it possible to concentrate the permanent magnets to be recovered.

[0058] Permanent magnets from hard drives recovered after the classification step were subjected to qualitative chemical analysis by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). Under scanning electron microscopy, the magnets have a granular structure. They consist of Nd2Fe4B phase crystals sintered in the presence of an intergranular phase. The analysis was performed on the crystals.

[0059] The following table shows the distribution of the chemical elements detected.

[0060] [Tables 1] Element % by mass Nd2Fe4B theoretical Nd 28.1 27.0 Fe 69.6 72.0 Dy 2.3 1.0

[0061] Thus, in sintered Nd2Fei4B phase crystals, Fe is the predominant element and Nd is well represented. In the intergranular phase, the emission lines of Nd and Pr are particularly identifiable. Therefore, the magnets contain an Nd / Fe / B alloy as a matrix, and other rare earth elements such as Dy and Pr, in the form of oxides, are present in the interfaces.

[0062] Steps 5 to 8 of the process in [Fig.1] were carried out using the 5-16 mm fraction from step 4 of classification.

[0063] In step 5, approximately 80 kg of the 5 to 16 mm fraction were subjected to low-intensity permanent magnet dry drum (400G) separation to separate the magnetic and non-magnetic products. Visual analysis showed that the resulting 1FM magnetic fraction was rich in magnets.

[0064] In step 6, the magnetic fraction 1FM from step 5 was processed by an overband magnetic separator. In this step 6, the overband magnetic separator was positioned 8 to 10 cm away from the conveyor belt. Under these conditions, the non-magnetic fraction 2FNM from the overband separation step 6 was rich in magnets.

[0065] Thus, the exemplified recovery process comprises the following successive steps: - subject the demagnetized permanent magnets to a 400 G drum magnetic separation, - recover a 1FM magnetic phase, - subject the magnetic phase 1FM to magnetic separation on an Overband separator, so that a non-magnetic phase 2FNM resulting from the Overband magnetic separation is enriched in demagnetized magnets.

[0066] The non-magnetic fraction 2FNM from step 6, enriched in magnets, was then subjected to steps 9 and 10, which will be described later. Alternatively, the non-magnetic fraction 2FNM is used to manufacture permanent magnets. Indeed, the non-magnetic fraction can undergo a "long loop," that is, hydrometallurgical processing to extract rare earths, and then possibly manufacture permanent magnets from these rare earths. It can also undergo a "short loop," that is, the non-magnetic phase is used to form magnets again, without going through rare earth recovery steps by a hydrometallurgical process. In the short loop, the magnetic phase is, for example, reduced to powder, and magnets are again manufactured from this powder. The short loop generally involves the addition of materials.

[0067] The magnetic fraction 2FM from step 6 was then subjected to step 15 which will be described later.

[0068] During step 7, the non-magnetic fraction 1FNM from step 5 was subjected to a second magnetic separation under the same conditions as in step 5.

[0069] Following step 7, in step 8, the magnetic fraction 3FM was subjected to magnetic separation under the same conditions as in step 6. The non-magnetic fraction 3FNM from step 7 was then subjected to step 15.

[0070] At the end of step 8, the magnetic fractions 4FM and non-magnetic fractions 4NFM were treated respectively as the fractions 2FM and 2FNM at the output of step 6.

[0071] Thus the process further comprises the following successive steps: . recovery of a first non-magnetic phase 1FNM following the first magnetic separation using a 400 G drum, . second magnetic drum separation 400 G of the first non-magnetic phase 1FNM, to obtain a third magnetic phase 3FM, . second magnetic separation Overband of the third magnetic phase 3FM, and . recovery of a fourth non-magnetic phase 4FNM. These additional steps allow the recovery of magnets that had not passed into the 1FM magnetic phase after the first 400 G drum magnetic separation.

[0072] In total, approximately 32 kg of the magnet-rich fraction (phases 2FNM and 4FNM) representing 7.7% by weight of the hard drives subjected to the process, were obtained.

[0073] During steps 9 and 10, the magnet-rich fractions, respectively 2FNM from step 6, and 4FNM from step 8, are ground (step 9), as is the fraction smaller than 5mm ([Fig.4]), and are leached to selectively recover rare earths during step 10, according to the process described in the applicant's document WO 2017207947.

[0074]

[0075] Thus, rare earths were extracted from NdFeB type permanent magnets from waste electrical and electronic equipment, by implementing the magnet recovery process described above.

[0076] Alternatively, permanent magnets are manufactured from NdFeB type permanent magnets from waste electrical and electronic equipment, by implementing the magnet recovery process described above.

[0077] Steps 11 to 15 list the steps implemented, following step 4 (classification), on the fractions larger than 40 mm, 20 to 40 mm, 16 to 20 mm, and on the magnetic fractions 2FM and 4FM, to recover other metals contained in the hard drives.

[0078] Fractions larger than 40 mm, 20 to 40 mm, and 16 to 20 mm are sorted using unit operations employed in mineral processing: physical sorting techniques (overband magnetic separation to recover scrap metal, eddy current separation to recover aluminum and electronic boards in step 11). Metallic iron is recovered by magnetic separation and recycled in electric arc furnaces. CE-marked electronic boards are recovered by optical sorting or by the eddy current separator and shredded (step 12). The recovered electronic boards are injected into copper metallurgy furnaces to recover copper and precious metals (step 15). Aluminum and copper wires are recovered by the eddy current separator or by the gravimetric separator. The various metals contained are selectively recovered by extractive metallurgy (step 15).The recovered metals are sent to smelters.

[0079] The mixed fraction from step 11 is shredded (step 13) to release the various metals and magnets contained.

[0080] The residual magnets are shredded and ground to 80 µm. SEM analysis shows that the pulverized product is concentrated in rare earth elements (27% Nd, 5% Dy, and 3% Pr). These rare earth elements are selectively recovered using conventional hydrometallurgical techniques. As shown in [Fig. 1], the residual magnets can be processed by steps 9 and 10 of the process.

[0081] The mixture (plastics, metals and ceramics) is shredded to release the different compounds, and treated by pyrolysis to eliminate the resins and concentrate the metals (base and precious) which will be selectively recovered by hydrometallurgical means.

[0082] The aluminum and scrap metal recovered from step 11 are sent respectively to the non-ferrous metallurgy and steel industry.

[0083] The invention is not limited to the embodiments shown, and other embodiments will be obvious to a person skilled in the art

Claims

Demands

1. A process for recovering NdFeB type permanent magnets from hard drives from waste electrical and electronic equipment, comprising the following successive steps: - obtaining demagnetized permanent magnets by demagnetizing the hard drives, by heating the waste electrical and electronic equipment between 325°C and 450°C, and grinding and then selecting the fraction of particles whose size is up to 16 mm and is greater than 5 mm, - subjecting the demagnetized permanent magnets to a first magnetic separation on a 400 G drum, - recovering a first magnetic phase (1FM), - subjecting the first magnetic phase (1FM) to a first magnetic separation on an Overband separator, so that a second non-magnetic phase (2FNM) from the first Overband magnetic separation is enriched in demagnetized magnets, - recovering the second non-magnetic phase (2FNM).

2. A method for recovering permanent magnets according to the preceding claim, wherein the Overband separator comprises a fixed magnetic system placed above or below a conveyor for conveying the demagnetized magnets, and the magnetic system is located at a distance of 7 to 15 cm, preferably 8 to 10 cm, preferably about 9 cm.

3. A method for recovering permanent magnets according to any one of the preceding claims, further comprising the following successive steps: - recovery of a first non-magnetic phase (1FNM) after the first 400 G drum magnetic separation, - second 400 G drum magnetic separation of the first non-magnetic phase (1FNM), to obtain a third magnetic phase (3FM), - second Overband magnetic separation of the third magnetic phase (3FM), and - recovery of a fourth non-magnetic phase (4FNM). 12

4. A method for recovering permanent magnets according to any one of the preceding claims, wherein the grinding is carried out in an autogenous grinder.

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