Method for treating object to be treated

Abstract

Provided is a treatment method for efficiently separating stainless steel from an object to be treated which contains copper and austenitic stainless steel. This method for treating an object to be treated which contains copper and austenitic stainless steel includes: a first step for applying a physical pressure to the object to be treated so as to cause strain-induced martensitic transformation in the stainless steel; and a second step for separating the copper and the stainless steel from each other by eddy current separation.

Description

Method for treating a treatment object

[0001] The present invention relates to a method for treating a treatment object. In particular, the present invention relates to a method for treating a treatment object containing copper and austenitic stainless steel.

[0002] In recent years, from the perspective of resource protection, it has become increasingly popular to recover valuable metals from industrial waste (for example, waste household appliances, electronic and electrical equipment parts scraps such as PCs and mobile phones), and efficient recovery methods have been studied and proposed.

[0003] For example, Japanese Patent Application Laid-Open No. 9-78151 (Patent Document 1) discloses a method for recycling valuable metals from scraps containing valuable metals by charging the scraps into a self-smelting furnace for copper ore smelting from the shaft ceiling part and recovering the valuable metals into the matte staying in the furnace. According to the configuration of Patent Document 1, since the scrap treatment is combined with the copper smelting in the copper smelting self-smelting furnace, valuable metals can be recovered at low cost even from scraps with a low valuable metal content.

[0004] It has also been proposed to crush the electronic and electrical equipment parts scraps before treating them in a copper smelting self-smelting furnace to reduce the volume. For example, Japanese Patent Application Laid-Open No. 2015-123418 (Patent Document 2) describes that after incinerating the electronic and electrical equipment parts scraps containing copper, they are crushed to a predetermined size or less, and the crushed electronic and electrical equipment parts scraps are treated in a copper smelting furnace.

[0005] And as a facility for melting industrial waste mixed with metals such as aluminum, iron, copper, zinc, lead and vinyl chloride serving as a chlorine source, such as automobile shredder dust (Automobile Shredder Residue, hereinafter also referred to as "ASR") and household appliance shredder dust, a melting treatment facility for industrial waste equipped with a fluidized bed type gasification furnace is known. For example, there is a melting treatment facility as disclosed in Japanese Patent Application Laid-Open No. 11-302748 (Patent Document 3).

[0006] Japanese Patent Application Laid-Open No. 9-78151, Japanese Patent Application Laid-Open No. 2015-123418, Japanese Patent Application Laid-Open No. 11-302748

[0007] Prior to recovering valuable metals such as copper in copper smelting furnaces such as self-smelting furnaces and converters, it is desirable to perform a sorting process on these copper-containing materials to remove a certain amount of material that is not necessary for copper smelting.

[0008] The materials to be processed may contain stainless steel (SUS) in addition to copper. Since stainless steel contains high levels of Cr and Ni, which are substances that adversely affect copper smelting operations (hereinafter referred to as copper smelting inhibitors), it is desirable to remove it before introducing it into the copper smelting process.

[0009] One possible method for removing stainless steel is manual sorting by human hands, but this incurs production costs such as labor expenses, and there are limitations in the accuracy and speed of sorting.

[0010] The present invention was completed in view of the above problems, and in one embodiment, aims to provide a processing method for efficiently separating stainless steel from a material to be processed that includes copper and austenitic stainless steel.

[0011] As a result of diligent research by the inventors, it has been found that applying physical pressure to the material to be processed, followed by eddy current separation, is effective. Stainless steel other than austenitic stainless steel is magnetic and can be separated from the material to be processed by magnetic separation. On the other hand, austenitic stainless steel is not magnetic and cannot be separated by magnetic separation. However, when physical pressure is applied to the material to be processed, austenitic stainless steel undergoes a work-induced martensitic transformation and becomes magnetic. Subsequently, when eddy current separation is performed, non-magnetic metals such as copper repel each other due to the induction of eddy currents, but stainless steel containing the work-induced martensitic phase can be separated from the material by the magnetic force of a magnet. The present invention was completed based on the above findings and is illustrated below.

[0012] [Aspect 1] A method for processing an object to be processed, comprising: a first step of applying physical pressure to the object to be processed to induce a processing-induced martensitic transformation in the stainless steel; and a second step of separating the copper and the stainless steel by eddy current separation. [Aspect 2] The method according to aspect 1, wherein in the first step, the degree of applying physical pressure is set such that, when eddy current separation is performed on the object to be processed before the processing under the same conditions as the eddy current separation in the second step, 50% by weight or more of the stainless steel alone that is distributed to the repulsive material is distributed to the non-repulsive material in the second step after the processing. [Aspect 3] The method according to aspect 1, wherein in the first step, the degree of processing to which physical pressure is applied is set such that, when the weight of individual stainless steel pieces that are magnetically attached to a magnet with the same magnetic force as the surface magnetic flux density in the eddy current separation of the second step is confirmed for the object to be processed before the processing, 50% by weight or more of the individual stainless steel pieces that are not magnetically attached are magnetically attached to the magnet after the processing. [Aspect 4] The method according to any one of aspects 1 to 3, further comprising performing preliminary eddy current separation to separate magnetic stainless steel from the object to be processed by eddy current separation before the first step. [Aspect 5] The method according to any one of aspects 1 to 4, further comprising performing crushing as the processing to which physical pressure is applied in the first step. [Aspect 6] The method according to aspect 5, further comprising performing the crushing using a vertical crusher in the first step. [Aspect 7] The method according to aspect 5, further comprising performing the crushing using a hammer crusher in the first step.

[0013] According to one embodiment of the present invention, a processing method is provided for efficiently separating stainless steel from a material to be processed, which includes copper and austenitic stainless steel.

[0014] This is a flowchart illustrating the procedure of one embodiment of the method of the present invention. This is a schematic diagram illustrating an example of the operating principle of an eddy current separator.

[0015] Next, embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes, improvements, etc., can be made based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention.

[0016] Figure 1 is a flowchart illustrating the procedure of one embodiment of the method of the present invention. One embodiment of the present invention includes a first step of applying physical pressure to a workpiece to induce a work-induced martensitic transformation in stainless steel, and a second step of separating the copper and the stainless steel by eddy current separation. Details of the first and second steps will be described later. Eddy current separation can be optionally performed before the first step.

[0017] (1. Materials to be processed) Various industrial wastes, including copper and austenitic stainless steel, can be used as materials to be processed. In this embodiment, we will describe materials to be processed using ASR, shredded home appliance dust, or scrap electronic and electrical equipment parts as raw materials. ASR, shredded home appliance dust, and scrap electronic and electrical equipment parts can be crushed and sorted as appropriate, then processed in a gasification melting furnace or the like to remove combustible components such as resin, and then magnetic materials such as iron scrap can be removed by magnetic separation or the like. Alternatively, mixed metals (non-ferrous metals, plastics) obtained after removing iron from ASR and shredded home appliance dust by magnetic separation, and then metal scraps (mainly mixtures of stainless steel, copper, etc.) recovered after separating aluminum by eddy current separation or heavy liquid separation can be used as materials to be processed. Since automobiles and home appliances usually contain electronic and electrical equipment, ASR and shredded home appliance dust may also contain scrap electronic and electrical equipment parts. Furthermore, the material to be processed may also be the material after processing ASR and home appliance shredder dust in a fluidized bed gasification furnace to gasify the contained waste plastics and then magnetically separating it (gasification furnace non-ferrous metal).

[0018] The processed material from which magnetic material has been removed may contain stainless steel, particularly austenitic stainless steel, which cannot be completely removed by magnetic separation and may contain either Cr or Ni, which are copper refining inhibitors. As described later, in some embodiments of the present invention, by applying physical pressure to the processed material, austenitic stainless steel undergoes a work-induced martensitic transformation and becomes magnetic. Subsequently, when the processed material is fed into an eddy current separator and eddy current separation is performed, the magnetic stainless steel and non-magnetic copper can be separated. The processed material containing stainless steel may include both pure stainless steel and stainless steel composites. Pure stainless steel is made up of stainless steel only, or substantially made up of stainless steel only (such as stainless steel containing impurities, or stainless steel with other substances attached to its surface due to crushing during the recycling process). Examples of pure stainless steel are bolts and nuts. Stainless steel composites are made up of a combination of stainless steel and non-stainless steel parts.

[0019] The shape and size of the copper contained in the material to be processed are not limited. For example, it can contain copper in any proportion, such as in chunks, wires, or plates. Furthermore, copper can include not only pure copper but also copper alloys. The material containing copper can include both pure copper and copper composites. Pure copper refers to materials composed solely of copper, or materials substantially composed solely of copper (such as materials containing impurities in copper, or materials composed solely of copper with other substances attached to the surface due to crushing during the recycling process). Copper composites are materials in which a copper portion and a non-copper portion are combined. Copper composites include scrap electronic and electrical equipment parts containing copper as wiring material.

[0020] (2. Processing by applying physical pressure to the object to be processed (first step)) Although there is no intention to restrict the present invention by theory, when austenitic stainless steel is processed, the processed area changes to martensite and becomes magnetic. This changed martensite is called processing-induced martensite, and it is the cause of stainless steel becoming magnetic. One possible method to induce processing-induced martensitic transformation is to perform processing by applying physical pressure to the object to be processed.

[0021] The specific method of applying physical pressure during processing is not particularly limited, as long as it can induce processing-induced martensitic transformation. Any processing method involving physical pressure, such as impact, shear, compression, friction, or bending, is applicable. In the following embodiment, crushing using a crusher will be described as a processing method that applies physical pressure.

[0022] The type of crusher is not particularly limited as long as it can induce processing-induced martensitic transformation. For example, shear crushers and impact crushers (e.g., hammer crushers and vertical crushers of shredders) can be suitably used, and impact crushers are particularly preferred because they easily induce processing-induced martensitic transformation in stainless steel by applying impact. Multiple crushing can also be performed by using multiple crushers in combination. In one embodiment of the present invention, a vertical crusher that repeatedly applies a composite physical pressure by impact, shear, compression, and friction can be used.

[0023] Conditions such as the number of crushing cycles and duration can be appropriately set according to the properties of the material to be processed, the performance of the eddy current separator used thereafter, and the required degree of separation. For example, conditions such as the number of crushing cycles and duration may be set so that, when the eddy current separation described below is performed under the same conditions before and after crushing the same material, 50% or more by weight (more preferably 60% or more by weight) of the stainless steel material distributed to the repulsive material in the eddy current separation before crushing (or before the first crushing if crushing is performed multiple times) is distributed to the non-repulsive material in the eddy current separation after crushing (or after the last crushing if crushing is performed multiple times). Furthermore, the conditions such as the number of crushing cycles and the duration may be set so that, when the weight of individual stainless steel pieces that are magnetized to a magnet with the same magnetic force as the surface magnetic flux density of the subsequent eddy current separation is confirmed before and after crushing the same object to be processed, 50% or more by weight (more preferably 60% or more by weight) of the individual stainless steel pieces that were not magnetized before crushing (or before the first crushing if crushing is performed multiple times) become magnetized after crushing (or after the last crushing if crushing is performed multiple times).

[0024] Alternatively, the number of crushing cycles may be determined by checking the weight of the material that magnetically attaches to a magnet with a magnetic force equivalent to the surface magnetic flux density of eddy currents in eddy current sorting after each crushing cycle. If the weight of the magnetically attached material increases between before and after crushing, the crushing cycle may be repeated until the rate of increase falls below a certain value. Furthermore, by repeating the crushing and checking the weight magnetically attached to the magnet in this manner, the total crushing time until the rate of increase in weight falls below a certain value can be determined, and the number of crushing cycles and the time of each crushing cycle may be set based on this. For example, if the number of crushing cycles is set to one, the time of that crushing cycle will be the total crushing time as described above.

[0025] By setting conditions such as the number of crushing cycles and duration, sufficient work-induced martensitic transformation can be achieved, allowing for effective separation of stainless steel in the subsequent eddy current separation. Furthermore, the crushing conditions do not need to be readjusted each time the material is processed. Once the crushing conditions are set to a level sufficient to induce work-induced martensitic transformation, the material can be repeatedly processed without readjusting the crushing conditions.

[0026] (3. Eddy Current Separation (Second Process)) When a conductive metal is placed in a magnetic field where the magnetic poles (N pole and S pole) alternate (alternating magnetic field), eddy currents are generated on its surface, and a magnetic field is created on the conductor that repels the alternating magnetic field. Since the magnetic field generated by these eddy currents is always the same pole as the alternating magnetic field, the conductor is momentarily repelled from the alternating magnetic field and flies away. Due to the difference in the strength of this repulsion, non-magnetic copper and stainless steel that has become magnetic can be effectively separated.

[0027] Figure 2 is a schematic diagram illustrating an example of the operating principle of an eddy current separator. As shown in Figure 2, the material to be processed is transported by a belt conveyor and, upon passing near a rotating magnetic rotor, is affected by the magnetic field generated by the rotor. When a partition plate is placed in front of the belt conveyor, the material to be processed is separated into those that fly over the partition plate and those that fall before reaching the partition plate. The former are called repulsive materials, and the latter are called non-repulsive materials. By adjusting the angle θ of the partition plate with respect to the horizontal, the amount of non-repulsive and repulsive materials distributed, as well as the materials being distributed, can be adjusted.

[0028] During eddy current sorting, the degree of repulsion between various materials is determined by both their magnetism and electrical conductivity. Higher electrical conductivity leads to a larger induced current and a stronger repulsive force. On the other hand, strong magnetism creates an attractive force towards the magnetic rotor, counteracting the repulsive force.

[0029] Table 1 shows an example of how non-repulsive and repulsive materials are separated based on a combination of electrical conductivity and magnetism. In this example, using an eddy current separator equipped with a partition plate, materials classified as "strong" magnetism and materials classified as "weak" magnetism with "low" electrical conductivity were separated as non-repulsive materials, while other materials (gray highlighted areas) were separated as repulsive materials. The specific configuration of the eddy current separator is not limited as long as it can separate the material to be processed into repulsive and non-repulsive materials according to the principle described above. Furthermore, it is also possible to use an eddy current separator with a partition plate that further separates magnetic and non-magnetic materials from the non-repulsive materials, thereby separating only SUS as magnetic material. This can increase the resource value of SUS.

[0030] The repulsive material includes wire-like copper and lumpy copper and brass. Therefore, valuable metals such as copper can be recovered by introducing the repulsive material into the copper smelting process. The copper smelting process is not particularly limited, but may include pretreatment (such as thermal decomposition of organic materials like plastics) as needed, and introducing the pretreated repulsive material into a copper smelting furnace such as a self-smelting furnace or converter.

[0031] Non-repulsive materials include stainless steel. Austenitic stainless steel without a work-induced martensite phase is non-magnetic. Therefore, austenitic stainless steel without a work-induced martensite phase is allocated to the repulsive materials. However, in this embodiment, physical pressure is applied to the material to be processed before eddy current sorting to process the austenitic stainless steel and generate a work-induced martensite phase. Austenitic stainless steel with a work-induced martensite phase has weak magnetism, and coupled with its low electrical conductivity, it is allocated to the non-repulsive materials.

[0032] Thus, in this embodiment, austenitic stainless steel can be distributed to non-repulsive materials in the same way as non-austenitic stainless steel. Therefore, stainless steel including austenitic stainless steel can be separated from the repulsive materials introduced into the copper smelting process, and the introduction of copper smelting inhibitory components (Cr, Ni) contained in the stainless steel into the copper smelting process can be suppressed.

[0033] As shown in Table 1, the nickel-plated copper and brass blocks were distributed among the repulsive materials. Although nickel plating has weak magnetism, similar to austenitic stainless steel, the nickel-plated copper and brass blocks have high electrical conductivity, resulting in repulsive forces due to eddy currents. Austenitic stainless steel contains components that inhibit copper smelting, while nickel-plated copper and brass blocks contain copper. Therefore, this distribution is favorable for the subsequent copper smelting process. For example, this distribution cannot be achieved with magnetic separation, which sorts based solely on magnetism. This is another advantage of employing eddy current separation in this embodiment.

[0034]

[0035] The type of eddy current separator is not particularly limited, and any known type can be used.

[0036] The conditions for eddy current separation, such as the number of passes and duration, can be appropriately set according to the properties of the material being processed and the required degree of separation. However, since complete separation of each component is impossible with eddy current separation, the separation of each component in this specification does not necessarily mean complete separation.

[0037] Furthermore, if the object to be processed, including stainless steel, is rod-shaped, even if the stainless steel is magnetized by applying physical pressure, there is a risk that the object will be distributed to the repulsive material, resulting in stainless steel being mixed into the repulsive material. This is because, if the longitudinal direction of the rod-shaped object to be processed is aligned with the conveying direction of the belt conveyor and it is sent to the eddy current separator, even if it is attracted to the magnetic rotor by magnetic force, the rod-shaped tip may get caught on the partition plate and pass over the partition plate.

[0038] From this perspective, it is desirable to place rod-shaped objects to be processed on the belt conveyor so that their longitudinal direction forms an angle of at least 45° with respect to the conveying direction of the belt conveyor (preferably, so that the longitudinal direction of the objects to be processed is perpendicular to the conveying direction of the belt conveyor) and send them to the eddy current separator.

[0039] As a means of positioning the rod-shaped object to be processed on the belt conveyor, the first belt conveyor and the second belt conveyor may be positioned so that their respective conveying directions are at an angle of 45° or more, the object to be processed is conveyed from the first belt conveyor to the second belt conveyor, and then sent from the second belt conveyor to the eddy current separator. Generally, when the surface of the belt conveyor is observed in a cross-section perpendicular to the conveying direction of the belt conveyor, both ends are higher and the central part is recessed and lower. Therefore, when a rod-shaped object to be processed is dropped onto the surface of the first belt conveyor, the object to be processed naturally moves to the recessed central part and is positioned so that its longitudinal direction is aligned with the conveying direction of the first belt conveyor. In this state, when the object to be processed is transported from the first belt conveyor to the second belt conveyor, the transport direction of the second belt conveyor is at an angle of 45° or more with respect to the transport direction of the first belt conveyor. Therefore, on the mounting surface of the second belt conveyor, the object to be processed is positioned such that its longitudinal direction is at an angle of 45° or more with respect to the transport direction of the second belt conveyor.

[0040] Alternatively, when dropping the material to be processed onto a belt conveyor that leads to an eddy current separator using a chute, the discharge port of the chute may be rectangular, and the longer side of the discharge port may be at an angle of at least 45° with respect to the conveying direction of the belt conveyor. By making the longer side of the discharge port longer and the shorter side shorter than the length of the rod-shaped material to be processed, the material can be dropped onto the belt conveyor so that the length of the rod-shaped material is aligned with the longer side of the discharge port. The longer side of the discharge port may be, for example, twice or more the length of the shorter side of the discharge port.

[0041] And in one embodiment of the present invention, before the aforementioned first step, eddy current separation can be optionally performed (hereinafter referred to as "preliminary eddy current separation"). By performing preliminary eddy current separation, magnetized (i.e., magnetic) stainless steel and non-magnetized stainless steel can be separated, and the magnetized stainless steel can be removed from the object to be processed. Generally, shredders that crush waste automobiles, waste household appliances, etc. have a large motor output and a very high power cost. Therefore, in order to magnetize some stainless steel, it is more efficient and economical to separate the magnetized stainless steel by eddy current separation once rather than extending the shredding time (retention time) of the shredder or returning the total amount of crushed materials to the shredder and crushing them again with the shredder, and only subject the non-magnetized stainless steel to crushing treatment.

[0042] Hereinafter, the present invention will be specifically described by way of examples. However, the description here is for the purpose of mere illustration and is not intended to be limited thereto.

[0043] Processing was carried out without applying physical pressure to the object to be processed, and it was directly fed into an eddy current separator. Also, before feeding it into the eddy current separator, stainless steel and copper were manually separated in advance. The separated stainless steel was a single stainless steel material. These stainless steel and copper were each separately fed into the eddy current separator.

[0044] As a result of the eddy current separation, the repelled objects that passed over the partition plate and the objects that fell in front of the partition plate were regarded as non-repelled objects. Next, crushing was performed on the stainless steel (hereinafter referred to as stainless steel in the repelled objects) and copper (hereinafter referred to as copper in the repelled objects) distributed to the repelled objects, respectively, in order to apply physical pressure separately.

[0045] A vertical crusher was used. The stainless steel in the repulsive material was fed into the crusher and crushed once. Then, a magnetic rod having a surface magnetic flux density equivalent to that on the magnetic rotor of the eddy current separator was applied to the stainless steel in the repulsive material discharged from the crusher. The number and weight of the stainless steel in the repulsive material that adhered to the magnetic rod were recorded, and the material was fed back into the crusher. This crushing and recording of the number and weight of the stainless steel that adhered to the magnetic rod was repeated until the number of stainless steel in the repulsive material that adhered to the magnetic rod no longer changed. Next, the copper in the repulsive material was fed into the crusher the same number of times as the stainless steel in the repulsive material was crushed. The stainless steel and copper in the repulsive material after crushing were subjected to eddy current separation separately using the same equipment and conditions as described above.

[0046] The results of this second eddy current separation are shown in Table 2. As shown in Table 2, even stainless steel that was separated as repulsive material in the eddy current separation before the crushing process became non-repulsive material at a rate of 69% by weight after the crushing process, indicating that it was effectively separated from copper. Furthermore, more than 99% by weight of copper became repulsive material, indicating that the amount of copper lost due to being included in the non-repulsive material was extremely small.

[0047]

Claims

1. A method for processing an object to be processed, which includes copper and austenitic stainless steel, comprising: a first step of applying physical pressure to the object to be processed to induce a processing-induced martensitic transformation in the stainless steel; and a second step of separating the copper and the stainless steel by eddy current separation.

2. The method according to claim 1, wherein in the first step, the degree of processing to which physical pressure is applied is set such that 50% by weight or more of the stainless steel individual material distributed to the repulsive material when eddy current sorting is performed on the object to be processed before the processing under the same conditions as the eddy current sorting in the second step is distributed to the non-repulsive material in the second step after the processing.

3. The method according to claim 1, wherein, in the first step, the degree of processing to which physical pressure is applied is set such that, when the weight of individual stainless steel pieces that are magnetically attached to a magnet having the same magnetic force as the surface magnetic flux density in the eddy current sorting of the second step is confirmed for the object to be processed before the processing, 50% by weight or more of the individual stainless steel pieces that are not magnetically attached are magnetically attached to the magnet after the processing.

4. The method according to claim 1, further comprising performing preliminary eddy current separation to separate magnetic stainless steel from the material to be processed by eddy current separation before the first step.

5. The method according to claim 1, wherein the first step includes crushing as the process of applying the physical pressure.

6. The method according to claim 5, wherein the first step includes performing the crushing process using a vertical crusher.

7. The method according to claim 5, wherein the first step includes performing the crushing process using a hammer-type crusher.

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