Waste disposal methods

Abstract

To provide an efficient treatment method for waste containing metal wires, capable of preventing troubles caused by the metal wires.SOLUTION: A treatment method for waste includes: a heating step of heating waste containing metal wires; a crushing step of crushing the waste after the heating; a first sieving and sorting step of separating the crushed waste into an upper sieve group and a lower sieve group through a comb type inclined sieve with a sieve mesh of less than 20 mm; a second sieving and sorting step of sieving and sorting, through a punching metal or a comb type sieve, the lower sieve group after the first sieving and sorting into two grain groups or three or more grain groups; and a physical sorting step of separating each grain group after the second sieving and sorting into metals and non-metals by performing one or more physical sorts, selected from specific gravity sorting, eddy current sorting, shape sorting, color sorting and electromagnetic induction sorting, for each grain group after the second sieving and sorting.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for treating waste. [Background technology]

[0002] Metal wires, coated copper wires, and other wire-like objects are used as components of electronic and electrical equipment such as the electrical components of automobiles, home appliances, communication devices, and computers. A large amount of wire-like objects is generated when various electronic devices are discarded, and the wire-like objects are collected and recycled. For example, since copper wires are highly valuable, a method of recovering copper wires from coated copper wires is adopted in which the coated copper wires are cut and then separated into copper nuggets and coatings. However, although nugget separation is particularly effective for recovering thick metal wires with a diameter of 1 mm or more, thin metal wires are not recovered because it is difficult to separate them from the coatings.

[0003] In this regard, as a method for separating and recovering minute copper wires and plastics from discarded home appliances with high accuracy, a method has been proposed in which the discarded home appliances are crushed to a predetermined size, foamed resin is extracted from the crushed material by wind sorting, ferrous metals are extracted from the crushed material from which the foamed resin has been removed by magnetic sorting, non-ferrous metals are extracted from the crushed material from which the ferrous metals have been removed by eddy current sorting, coated copper wires are separated from the crushed material from which the non-ferrous metals have been removed, small lump-shaped metals are extracted from the crushed material from which the coated copper wires have been separated by wind sorting, minute copper wires are extracted from the crushed material from which the small lump-shaped metals have been removed by a vibrating sieve, and finally plastics are recovered (Patent Document 1). Also, a method has been proposed in which crushed electronic and electrical device parts are wind sorted to recover light weight materials including at least linear and plate-shaped materials, and the light weight materials are placed on a filter of a vibrating sieve machine equipped with a filter having a plurality of rods extending at intervals from each other, and the filter is vibrated to separate the linear materials by sieving (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-320311 A [Patent Document 2] International Publication No. 2019 / 151350 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the shape of the metal wires is not uniform (curved, U-shaped, spiral, etc.), when waste containing metal wires is crushed, the metal wires become entangled with each other and coarse, and when the waste is screened, the metal wires become entangled in the sieve mesh, causing problems such as clogging the equipment and forcing the shutdown of the equipment. As such, it is difficult to efficiently and stably treat waste containing metal wires. An object of the present invention is to provide a method for efficiently disposing of waste containing metal wires, while suppressing problems caused by metal wires. [Means for solving the problem]

[0006] The inventors of the present invention found that by heating waste containing metal wires to embrittle them, crushing the embrittled waste, sieving the crushed waste through a specific sieve having a specific sieve mesh, further sieving the waste that falls under the sieve through a specific sieve, and then physically separating the waste, the entanglement of the metal wires with each other, the associated coarsening, and the entanglement of the metal wires with the sieve mesh can be suppressed, thereby eliminating problems caused by the metal wires, and waste containing metal wires can be efficiently and stably treated.Furthermore, by intentionally entangling the metal wires contained in the waste before crushing the embrittled waste, problems caused by the metal wires in the subsequent treatment can be further suppressed, and waste containing metal wires can be efficiently and stably treated.

[0007] That is, the present invention provides the following [1] to [5]. [1] A heating process for heating waste containing metal wires; a crushing step of crushing the heated waste; a first sieve sorting step of separating the crushed waste into over-sieve and under-sieve using a comb-tooth inclined sieve with mesh sizes of less than 20 mm; A second sieving step of sieving the undersize particles obtained by the first sieving into two or more particle groups using a punching metal or a comb-tooth sieve; A physical sorting process in which each particle group obtained by the second sieve sorting is subjected to one or more physical sorting methods selected from specific gravity sorting, eddy current sorting, shape sorting, color sorting, and electromagnetic induction sorting to separate the particles into metals and non-metals. A method for treating waste, comprising: [2] The method for treating waste according to [1] above, further comprising a wrapping step of wrapping metal wires in the heated waste together after the heating step and before the crushing step. [3] The method for treating waste according to [1] or [2] above, wherein in the heating step, the waste containing the metal wire is heated to 250 to 500°C. [4] The waste treatment method according to any one of the above [1] to [3], wherein the mesh size of the inclined comb-tooth sieve used in the first sieve sorting step is 8 mm or more and 15 mm or less. [5] The method for treating waste according to any one of the above [1] to [4], wherein the mesh size of the punched metal or comb-tooth sieve used in the second sieve sorting step is 10 mm or less. Effect of the Invention

[0008] According to the present invention, problems caused by metal wires can be suppressed, and waste containing metal wires can be efficiently and stably treated. [Brief description of the drawings]

[0009] [Figure 1] 1 is a flowchart showing one embodiment of a manufacturing method of the present invention. [Diagram 2] 4 is a flowchart showing another embodiment of the manufacturing method of the present invention. [Diagram 3] 4 is a flowchart showing another embodiment of the manufacturing method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The waste treatment method of the present invention will now be described.

[0011] (First embodiment) A flowchart of the waste treatment method according to this embodiment is shown in FIG. In the treatment method according to the present embodiment, first, a heating step is performed to heat the waste containing the metal wires, as shown in Fig. 1. The purpose of this step is to embrittle the waste without incinerating it.

[0012] The waste used in this process is not particularly limited as long as it contains metal wires, but examples thereof include automobile shredder dust, and shredder dust from household and commercial electrical appliances and furniture. These wastes include electronic parts such as cables, cable terminals, plugs, speakers, motors, printed circuit boards, relays, and button contacts, and may contain materials other than metal wires, such as resin, soil, glass, paper, and wood chips. These electronic parts include, for example, metal wires such as copper, brass, and aluminum, metal foils, springs, fixing and connecting jigs (screws, bands, stables, etc.), handles, ornaments, and flexible tubes and support wires made of stainless steel or carbon steel.

[0013] Heat treatment of waste is usually carried out in a heating furnace. The heating furnace is not particularly limited as long as it can accommodate waste and can be set to a desired temperature, but examples of the furnace include a fixed furnace, a stoker furnace, a rotary kiln furnace, a fluidized bed furnace, a vertical furnace, and a multi-tier furnace. The shape of the heating furnace is not particularly limited, and it can have any appropriate shape, such as a cylindrical shape or a rectangular cross section. A conveyor for transporting waste from the waste supply port to the waste discharge port may be installed inside the heating furnace.

[0014] Among them, from the viewpoint of fixing a large amount of the heat value of the organic components contained in the waste in the solid fuel and increasing its value, it is preferable to use an externally heated rotary kiln as the heating furnace and heat the waste in a low-oxygen atmosphere. Methods for making the atmosphere inside the furnace low-oxygen include, for example, filling the furnace with nitrogen or water vapor, or filling the furnace with gases (H2O, CO2, combustible gases, etc.) generated by heating the raw materials themselves to make the atmosphere low-oxygen.

[0015] The heating temperature is preferably from 250 to 500°C, more preferably from 275 to 475°C, and even more preferably from 300 to 450°C, from the viewpoint of promoting embrittlement of the waste. The heating time can be appropriately selected depending on the type and volume of resin contained in the waste, but is usually 30 to 120 minutes, and preferably 60 to 90 minutes.

[0016] Next, as shown in Figure 1, a crushing process is carried out to crush the heated waste. This breaks down the resin lumps contained in the waste into fine particles, and makes it possible to peel off the resin attached to the metal. Note that in this process, the metal wire lumps contained in the waste are hardly broken down into fine particles. In the crushing step, a crusher can be used. The crusher is not particularly limited as long as it can crush the waste, and for example, a jaw crusher, an impact crusher, a hammer crusher, a roll crusher, or a rotary crusher can be appropriately selected. A screen with a desired mesh size can be attached to the crusher for the purpose of adjusting the particle size, and when a screen is not attached, the fixed teeth, rotating teeth, inner wall, etc. may be adjusted to a desired clearance.

[0017] The size of the crushed waste is usually 3 mm or more, preferably 5 mm or more, in terms of particle diameter D90. In this specification, "particle diameter D90" refers to the cumulative 90% particle diameter in the volume-based particle size distribution measured in accordance with JIS R 1629 "Method for measuring particle size distribution by laser diffraction / scattering method for fine ceramic raw materials." For example, a laser diffraction / scattering type particle size distribution measuring device can be used for measuring the particle size distribution.

[0018] Next, the crushed waste is subjected to a first sieve sorting process as shown in Fig. 1. This not only selectively removes coarse metal wires that tend to get entangled in the sieve mesh, but also separates coarse metal pieces and resins that remain on the sieve. In the first sieving step, the crushed waste is sieved using a comb-tooth type inclined sieve with mesh sizes of less than 20 mm. The comb-type tilting sieve machine may be of either a vibrating type or a fixed type. From the viewpoint of improving the screening accuracy, the sieve openings are preferably 8 mm or more and 17 mm or less, and more preferably 8 mm or more and 15 mm or less. The cross section of the comb teeth may be any of a square, an inverted triangle, and a round shape, and the shape of the tip may be any of a flat, conical, and truncated shape. In order to encourage the metal wire to slide down, the inclination angle is preferably 10 to 60°, more preferably 20 to 55°, and even more preferably 30 to 50°. If the inclination angle exceeds 60°, particles smaller than the sieve openings that are repelled by the comb teeth may be collected as particles on the sieve. In addition, the comb teeth may be installed in multiple stages to improve sorting accuracy, but in order to prevent the metal wire from remaining on the comb teeth, it is desirable to arrange them so that they do not come into contact with the upper or lower comb teeth or the shaft supporting them. In addition, a commercially available device may be used as the inclined comb-tooth type sieve machine, and examples of such devices include a Grisly Feeder and a Finger Screen.

[0019] Next, as shown in FIG. 1, the undersize particles obtained in the first sieving step are subjected to a second sieving step, where they are sieved into two or three or more particle groups. For the second sieving, a punching metal or comb-tooth sieving machine is used. By using a punching metal or comb-tooth sieving machine, it is possible to prevent the fine metal wires from getting tangled or remaining in the sieve mesh. If a sieve with a fine wire diameter such as a woven mesh (plain weave, twill weave, etc.) is used, the metal wires after the crushing process will have a curved, U-shaped, spiral, or clump-like shape, and will get caught or tangled in the wire mesh, making sieving difficult. The punched metal may be, for example, a steel plate having a plurality of holes formed therein. The shape of the holes may be, for example, either a rectangular hole (square, rectangular, etc.) or a round hole (circular, elliptical, etc.). The comb-tooth sieving machine may be, for example, any of a fixed mesh surface type, a horizontal motion type (in-plane motion type), a vertical motion type, a vertical in-plane rotation type, a three-dimensional vibration sieve type, and the like. The mesh size of the sieve is preferably 10 mm or less. If the number of stages is small, the efficiency of the physical separation step described below decreases, so that a sieve with two stages or more is preferable. When two or more stages are provided, two or more sieves may be provided in one device, or two or more devices each having one sieve may be provided in series. In this case, the sieve mesh size of the first stage is preferably 4 to 10 mm, and the sieve mesh size of the second stage and thereafter is preferably 1 / 2 or less of the sieve mesh size of the previous stage. Examples of hole arrangements include, but are not limited to, 60° staggered, 45° staggered, and parallel. The hole pitch is preferably such that the ratio of pitch to hole diameter is 1.5 to 2.5. If the pitch is less than 1.5, the metal wire is likely to become entangled between the holes due to the short pitch, whereas if it exceeds 2.5, the opening rate is small and the processing capacity is likely to decrease.

[0020] Next, as shown in FIG. 1, each particle group obtained in the second sieving step is subjected to physical sorting to separate it into metals and non-metals. Metals include metal wires (often copper) as well as plate or granular metals. Most of the plate or granular metals are, for example, stainless steel, aluminum, brass, and copper, and some contain precious metals such as gold, silver, platinum, and palladium. Non-metals include resins and rubbers, which can be reused, for example, as solid fuel.

[0021] The physical sorting may be one or more selected from specific gravity sorting, eddy current sorting, shape sorting, color sorting, and electromagnetic induction sorting. The gravity separation can be performed using a known gravity separator, which may be either a dry type or a wet type. A dry type table type gravity separator is preferred, and an air table is more preferred. In gravity separation, for example, when an air table is used, the waste plastic embrittlement supplied to the top surface of the vibrating table is floated from the top surface of the vibrating table by the air flow passing through the vibrating table, and the vibration applied in the inclination direction of the vibrating table causes the heavy objects with a high specific gravity to move to the lower layer and the light objects with a low specific gravity to move to the upper layer, and the heavy objects in the lower layer move diagonally upward due to friction and vibration forces from the top surface of the vibrating table, while the light objects in the upper layer are swept diagonally downward without being subjected to friction and vibration forces from the top surface of the vibrating table. Then, the heavy objects and the light objects are discharged separately from the vibrating table, and metals are recovered as heavy products, and non-metals such as resins are recovered as light products. In addition, the metal wires are crushed and are finely divided, with almost no tangling, and the particle size is adjusted by crushing and sieving in advance, so they can be efficiently recovered as metals.

[0022] For eddy current sorting, a known eddy current sorter can be used, and although there is no particular limitation, examples of the sorting machine include a rotating magnet type, a cross-belt conveyor type, and a rotating cylinder type. In eddy current sorting, for example, the waste transported to the tip of the conveyor belt is subjected to a thrust in the direction of rotation of the rotating magnet through the interaction between the induced current generated inside due to the electromagnetic induction effect of the moving magnetic field of the rotating magnet body installed at the tip of the conveyor belt and the moving magnetic field, and the waste can be sorted into plate-shaped and granular metal pieces that are easy to jump, metal wires (mainly copper wires) that are difficult to jump, and non-metals such as resin and glass that do not jump. Note that metal wires are thin and therefore less likely to jump than plate-shaped and granular metal pieces, but by adjusting the collection plate, it is possible to separate them from non-metals such as resin and glass. In addition, if the above-mentioned collected materials are subjected to eddy current sorting again and a branch plate is installed at a position where only plate-shaped and granular metal pieces are collected, only the metal wires can be collected. The rotation speed of the rotating magnet body is preferably 1500 rpm or more, more preferably 3000 rpm or more, and even more preferably 4500 rpm or more.

[0023] Shape sorting can be achieved by removing only plate-like and granular materials with air, leaving only the copper-based metal wire. Color sorting can be done by removing only the silver, black, and gray colors with air, leaving only metals such as copper and brass. Electromagnetic induction sorting has the advantage that it can recover coarse metal particles larger than a few millimeters by blowing them away with air. In addition, resin and glass may be mixed into the recovered metals. In that case, the quality of the metal can be improved by crushing the material in a crusher (roller mill, ball mill, tube mill, etc.) and then removing the fine particles by sieving or air sorting.

[0024] Second embodiment A flowchart of the waste treatment method according to this embodiment is shown in FIG. As shown in Fig. 2, the treatment method according to this embodiment first performs a heating step of heating the waste material containing the metal wires, as in the first embodiment. The specific configuration of the heating step is as described in the first embodiment.

[0025] Next, as shown in Fig. 2, the heated waste is subjected to a wrapping process in which the metal wires in the waste are wrapped around each other. By intentionally causing the metal wires contained in the waste to wrap around each other, it is possible to further suppress problems caused by the metal wires in the subsequent processing steps. In the wrapping process, the waste is stirred up during the cooling of the high-temperature waste discharged from the heating furnace and the transport to the next process, causing the metal wires to intertwine with each other. For example, an indirect rotary cooler having a shell with a stirring blade or a cooling screw conveyor that rotates the inside of a shaft with blades while cooling with water can be used during cooling. Also, a screw conveyor that can rotate a shaft with blades or a screw conveyor that can rotate a shaftless spiral can be used during transport. In this way, by stirring up the waste after heating during cooling and / or transport, the resin-based particles and metal pieces are pushed into the lower side of the packed bed, while the metal wires are stirred up to the surface side of the packed bed, so that the neighboring metal wires intertwine with each other and gradually become coarse.

[0026] Next, as shown in Fig. 2, a crushing process is performed to crush the wrapped waste, and the crushed waste is subjected to a first sieving process. The specific configurations of the crushing process and the first sieving process are as described in the first embodiment.

[0027] Next, as shown in Figure 2, the undersize waste from the first sieving process is air-sorted to separate it into heavy and light materials, allowing metals, glass, undecomposed resins, and large particles contained in the undersize waste to be collected as heavy materials, while cotton-like foreign matter, fine powder, and fine grains can be removed as light materials. In the air sorting step, a known air sorter can be used, and although there is no particular limitation, examples thereof include a zigzag type and an internal circulation type. In wind sorting, for example, when an internal circulation type is used, when an air flow is created from the bottom to the top by a fan, the heavy objects below the sieve move downward against the air flow, while the light objects move upward with the air flow. In this way, the objects are separated into heavy objects and light objects, and the heavy objects are sent to the next process. In the case of wind sorting, it is preferable to set the wind speed for wind sorting so that metals, glass, undecomposed resins, and large particles are mainly on the heavy waste side. Specifically, the wind speed is preferably 5 m / s or more, more preferably 7 m / s or more, and even more preferably 8 m / s or more. The upper limit of the wind force can be set appropriately depending on the type of waste, and is usually 30 m / s or less. However, if the wind speed is too fast, the amount of coarse metals, glass, and resin mixed into the light waste increases, so it is preferably 15 m / s or less. The recovered light waste can be used as an alternative fuel to pulverized coal in cement kilns, etc. In addition, the light waste has a sufficiently fine particle size of about 0.5 to 3 mm in average particle size (D50), but if necessary, it can be pulverized with a roller mill or the like to improve combustibility and make it easier to use. The average particle size (D50) refers to the cumulative 50% particle size in the volume-based particle size distribution explained above.

[0028] Next, as shown in Figure 2, the heavy materials separated by wind separation are separated into magnetized and non-magnetized materials by magnetic separation. This allows metals to be efficiently recovered as magnetized materials and prevents fibers and other materials from being mixed into the magnetized materials. Furthermore, by removing the magnetized materials, not only can the amount of non-magnetized materials to be processed in the next process be reduced, but metal wires, mainly copper wires, can also be recovered. For the magnetic separation, a known magnetic separator can be used, and for example, any of a drum type, a pulley type, and a hanging type may be used, without any particular limitation. In magnetic separation, for example, magnetic materials are separated from non-magnetic materials using a magnetic separation device having a magnetic drum with a strong magnetic field, a belt conveyor (moving belt) wound around the magnetic drum, and a feeder that supplies samples onto the belt surface of the belt conveyor. The surface magnetic flux density of the magnetic separation device is preferably 40 to 300 mT, because if the magnetic force is too strong, the molten resin that has taken in iron or magnet particles and powder will also be collected.

[0029] Next, the non-magnetic materials separated by the magnetic separation are subjected to the second sieving step and the physical step as shown in Fig. 2. The specific configurations of the crushing step and the first sieving step are as described in the first embodiment.

[0030] Third embodiment A flowchart of the waste treatment method according to this embodiment is shown in FIG. The treatment method according to this embodiment is for treating the surplus matter obtained in the first sieve screening step, as shown in Fig. 3. The surplus matter obtained in the first sieve screening step may be either the surplus matter according to the first embodiment or the surplus matter according to the second embodiment described above. The sieve residue from the first sieve separation process contains not only resin and metal pieces, but also metal wires. Therefore, metals and non-metals are also recovered from the sieve residue. Since the metal wire is thin and has a small repulsive force, it is not possible to recover the metal wire on the conductive product side by eddy current sorting alone. Therefore, in this embodiment, eddy current sorting and specific gravity sorting are combined. This allows the resin and the metal wire to be separated efficiently. Gravity separation can use a liquid or solid medium, for example, heavy liquid separation or fluidized bed separation. In gravity separation, metal wire rods having a specific gravity of 3 or more are preferably recovered as the sinking matter. The specific configuration of the eddy current sorting is as explained in the first embodiment. As shown in (a) and (b) of Figure 3, it does not matter which order the eddy current sorting and the specific gravity sorting are performed first. In either order, the three types of materials, resin, metal pieces, and metal wires, can be collected. The steps shown in (a) and (b) of Figure 3 are as follows. (a) The sieved material obtained in the first sieving process is separated into conductive and non-conductive products by eddy current sorting, and then the non-conductive products are separated into floating and sinking materials by specific gravity sorting, and metal wires are recovered as the sinking materials. (b) The sieved material obtained in the first sieving process is subjected to gravity separation to separate it into floating matter and sinking matter, and then the sinking matter is subjected to eddy current separation to separate it into conductive products and non-conductive products, and then metal wires are recovered as the non-conductive products.

[0031] Although the present invention has been described in detail based on the preferred embodiment, the present invention is not limited to the above embodiment. Various modifications of the present invention are possible without departing from the gist of the present invention. For example, in the first embodiment, after the heating step and before the crushing step, the heated waste may be subjected to a wrapping step in which the metal wires in the waste are wrapped around each other. By intentionally inducing the entanglement of the metal wires contained in the waste by the wrapping step, it is possible to further suppress problems caused by the metal wires in the subsequent processing steps. In the second embodiment, the magnetic separation step is performed after the air separation step, but it is also possible to perform the magnetic separation step before the air separation step. In this case, the collected magnetic materials are subjected to an air separation process to remove fibers and metals. Furthermore, the air separation step and the magnetic separation step can be carried out in any order after the heating step or before the physical separation step. For example, the following methods can be mentioned. (c) A method in which the waste after the heating step is subjected to magnetic separation to separate magnetic and non-magnetic materials, the non-magnetic materials are separated by air separation to separate heavy and light materials, and the heavy materials are then subjected to a first sieving step. (d) A method in which the undersize waste from the first sieving step is separated by air force to separate it into heavy and light materials, the heavy materials are separated by magnetic force to separate it into magnetic and non-magnetic materials, and the non-magnetic materials are then subjected to a second sieving step. EXAMPLES

[0032] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0033] The apparatus used in this example is as follows: (1) Heating furnace An externally heated rotary kiln was used. (2) Cooling and conveying machine An indirect rotary cooler and a water-cooled shaft screw conveyor (both manufactured by Hokuko Kakoki) were connected in that order. (3) Crusher A hammer crusher (MHM-50R, manufactured by Oike Iron Works) was used with a screen of φ20 mm attached.

[0034] (4) Sieving machine used in the first screening process A comb-tooth type tilted sieving machine was used with the following specifications: Round bar with outer diameter of φ8 mm, mesh size (= spacing between each round bar) 8~20 mm, inclination angle 40°, fixed type (5) Wind sorter A zigzag-type wind sorting machine (manufactured by Oike Iron Works) was used. (6) Magnetic separator A drum-type magnetic separator (RENS-φ318×350L, manufactured by Nippon Magnetics) was used.

[0035] (7) Sieving machine used in the second screening process First stage screening We used one of the following, with the specifications also shown. (a) Comb-tooth sieving machine Round bar with outer diameter of φ8 mm, sieve mesh (= spacing between each round bar) of 10 mm, inclination angle of 40°, fixed type (not vibrating type) (b) Cylindrical vibration sieving machine (KF-1000-3D, manufactured by Kowa Industries, Ltd.) Punched metal (round holes 60° staggered), hole diameter 4 mm (pitch 6 mm) or 10 mm (pitch 15 mm) (c) Cylindrical vibration sieving machine (KF-1000-3D, manufactured by Kowa Industries, Ltd.) Woven net (twill weave), 10mm

[0036] Second stage screening We used one of the following, with the specifications also shown. (d) Cylindrical vibration sieving machine (KF-1000-3D, manufactured by Kowa Industries, Ltd.) Punched metal (round holes 60° staggered), hole diameter 2mm (pitch 3mm) or 4mm (pitch 6mm) (e) Cylindrical vibration sieving machine (KF-1000-3D, manufactured by Kowa Industries, Ltd.) Woven mesh (twill weave), 4mm

[0037] Examples 1 to 4 and Comparative Examples 1 to 4 As waste containing metal wires, shredder dust containing household and commercial electrical appliances, furniture, etc. was used and processed according to the flow chart shown in Figure 2. Specifically, the process is as follows. (Heating process) The waste was embrittled by feeding it into a heating furnace at 350°C at a rate of 1000 kg / h. (Wrapping process) The waste after the heating process was discharged from the heating furnace and cooled while being conveyed in the order of an indirect rotary cooler and a water-cooled shaft screw conveyor. During the conveyance, the waste was rolled up to promote entanglement of the metal wires. (Crushing process) The waste after the wrapping process was crushed by a hammer crusher. The hammer crusher was equipped with a screen with an opening diameter of 20 mm to collect the undersize waste. (First screening process) The undersize fraction obtained in the crushing step was screened using the sieves shown in Table 1 to separate the oversize fraction and the undersize fraction. (Wind sorting process) The undersize waste from the first sieving step was subjected to wind force sorting at a wind speed of 9.0 m / s to separate it into heavy and light materials. (Magnetic sorting process) The heavy materials obtained in the air sorting process were subjected to magnetic sorting using a magnetic force of 3000 gauss to separate them into magnetic and non-magnetic materials. (Second screening process) The non-magnetic materials obtained in the magnetic separation step were screened using the sieves shown in Table 1 to separate the oversieve and undersieve materials (first stage). The undersieve was further screened using the sieves shown in Table 1 to separate the oversieve and undersieve (second stage). (Physical sorting) The three particle groups obtained in the second sieving step were separated into metal and non-metal using an air table.

[0038] Table 1 shows the type of sieving machine used in the first and second sieving steps in each Example and Comparative Example. Table 2 shows the balance of the recovered materials in each step. In Tables 1 and 2, "-" means that the step was not performed, and in Table 2, if a sorting failure occurs during a step, the balance results for the subsequent steps are not shown.

[0039] [Table 1]

[0040] [Table 2]

[0041] From Table 2, it can be seen that by heating waste containing metal wires to embrittle them, crushing the embrittled waste, sieving the crushed waste using a comb-tooth inclined sieve with mesh sizes of less than 20 mm, and then further sieving the waste that falls below the sieve using a specific sieve and then physically separating it, problems caused by metal wires can be suppressed, and therefore waste containing metal wires can be efficiently and stably processed.

Claims

1. A heating step of heating the waste material including the metal wire; a crushing step of crushing the heated waste; a first sieve sorting step of separating the crushed waste into over-sieve and under-sieve using a comb-tooth inclined sieve with mesh sizes of less than 20 mm; a second sieving step of sieving the undersize fraction obtained in the first sieving into two or three or more particle groups using a punching metal or a comb-tooth sieve; A physical sorting process in which each particle group obtained by the second sieve sorting is subjected to one or more physical sorting methods selected from specific gravity sorting, eddy current sorting, shape sorting, color sorting, and electromagnetic induction sorting to separate the particles into metals and non-metals. Including, This waste treatment method includes a wrapping step of wrapping metal wires in the heated waste together after the heating step and before the crushing step.

2. 2. The method for treating waste according to claim 1, wherein the waste containing metal wires is heated to 250 to 500° C. in the heating step.

3. 3. The method for treating waste according to claim 1 or 2, wherein the mesh size of the inclined comb-tooth sieve used in the first sieve sorting step is 8 mm or more and 15 mm or less.

4. 4. The method for treating waste according to claim 1, wherein the mesh size of the punching metal or comb-tooth sieve used in the second sieve sorting step is 10 mm or less.

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