Waste substrate pretreatment method, and waste substrate pretreatment facility

Abstract

To provide a method of pretreating a waste substrate, capable of easily handling a heat-treated waste substrate.SOLUTION: The method of pretreating a waste substrate includes a roasting step S3 of roasting a crushed waste substrate, a primary cooling step S6 of subjecting the roasted substrate obtained by the roasting, being conveyed by a conveyer to primary cooling to cool the same to a predetermined temperature by spraying cooling water, and a cooling / dehydration step S7 of housing the roasted substrate subjected to the primary cooling, in a container, applying secondary cooling to the roasted substrate housed therein by spraying cooling water, and subsequently sucking the container to dehydrate the roasted substrate in a wet state resulting from the secondary cooling. Preferably, the amount of cooling water to be sprayed to the roasted substrate being conveyed by the conveyer, is adjusted according to the measurement result of the temperature of the roasted substrate subjected to the primary cooling.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pretreatment method and a pretreatment facility for waste substrates. [Background technology]

[0002] Printed circuit boards containing trace amounts of valuable metals such as gold, silver, copper, palladium, and platinum are used in various electronic devices such as home appliances, personal computers, smartphones, and network devices. When these electronic devices are discarded after use, used printed circuit boards are discarded in large quantities as waste boards (also called waste electronic boards), and the amount of waste tends to increase year by year. As can be seen from the fact that these waste boards are called "urban mines," they often contain higher grades of precious metals and rare metals (hereinafter, these will be collectively referred to as precious metals, etc., unless otherwise specified) than ores mined from mines. Therefore, precious metals, etc. are recovered from the waste boards by dry or wet processing depending on the type and amount of waste boards.

[0003] For example, in dry processing, the precious metals contained in the waste substrates can be distributed to the blister copper side by processing the waste substrates together with the raw copper concentrate in a smelting furnace of a dry copper smelting process, or by processing the waste substrates together with matte in a converter downstream of the smelting furnace. By electrolytically refining the copper electrolytic anode obtained by casting the blister copper, the copper can be commercialized as high-purity electrolytic copper, and the precious metals, which have a lower ionization tendency than copper, can be recovered as anode mud (also called anode slime).

[0004] However, most general waste circuit boards are made of printed circuit boards, which are made of insulators such as glass epoxy boards, to which electronic components such as IC chips and memory are soldered, and so in addition to metal components, they contain hydrocarbons, such as epoxy resins, derived from glass epoxy boards, and halogens, such as organic bromine compounds derived from flame retardants. These hydrocarbons and halogens are so-called repellent components that are difficult to process in dry copper smelting, so they must be removed by pretreatment.

[0005] Therefore, a technology has been proposed in which the waste substrates are heat-treated at high temperatures before being processed by dry copper smelting to remove the above-mentioned repellent components.For example, Patent Document 1 discloses a technology in which, before performing magnetic separation and gravity separation on the crushed waste substrates to separate them into magnetic, heavy non-magnetic, and light non-magnetic materials, the crushed waste substrates are cut into pieces of about 1 to 10 cm square as a pretreatment, and then finely crushed using a ball impact crusher, and the resulting crushed material is press-molded to obtain a molded body of a predetermined shape, which is then roasted at 300 to 1000°C to gasify and remove the organic matter and bromine compounds contained in the waste substrates.

[0006] Patent Document 2 discloses a valuable metal recovery and processing device that includes a first processing furnace that thermally decomposes and gasifies precious metal scrap containing valuable metals, a second processing furnace that further combusts the gasified reduced volume material that is the residue after gasification in the first processing furnace, and a third processing furnace that completely combusts the combustible pyrolysis gas and combustion exhaust gas discharged from the first and second processing furnaces, respectively. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2001-259603 A [Patent Document 2] JP 2015-147985 A Summary of the Invention [Problem to be solved by the invention]

[0008] As disclosed in the above Patent Documents 1 and 2, waste substrates are charged into a general heat treatment furnace such as a kiln and heat-treated at an appropriate temperature, thereby making it possible to remove repellent components such as hydrocarbons and halogens. However, the facility for performing pretreatment such as roasting on the waste substrates as described above may be installed in a location separate from the smelting plant performing dry copper smelting. In addition, since the waste substrates are continuously treated in the roasting furnace for roasting as the pretreatment, when the roasted substrates discharged from the roasting furnace are charged into a converter for batch processing, it is necessary to temporarily store the roasted substrates.

[0009] Therefore, the waste substrates that have been subjected to heat treatment such as roasting must be temporarily stored in a flexible container or shipped in a flexible container. The heat-resistant temperature of this flexible container is generally 70 to 80°C, so it is necessary to cool the roasted substrates discharged from the roasting furnace at a high temperature of several hundred°C. Methods for cooling the roasted substrates include air cooling and water cooling, but the water cooling method, which can efficiently cool the roasted substrates in a short time, is preferred, and the water cooling method, which cools the roasted substrates by spraying cooling water from above them, is more preferred.

[0010] However, when the water cooling method is used, the roasted substrate after water cooling becomes wet with a moisture content of about 30%, which may cause handling problems such as clogging when loading into a smelting furnace or converter or when transporting in a later process. Therefore, when cooling heat-treated waste substrates using the water cooling method, appropriate moisture management is required after cooling. The present invention has been made in view of the above circumstances, and aims to provide a pretreatment method for waste substrates that allows easy handling of heat-treated waste substrates, such as roasted substrates. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the pretreatment method for waste substrates according to the present invention is characterized by including a step of roasting pulverized waste substrates, a primary cooling step of primarily cooling the roasted substrate material obtained by the roasting to a predetermined temperature by spraying cooling water while transporting the roasted substrate material by a conveyor, and a cooling / dehydration step of placing the primarily cooled roasted substrate material in a container and secondary cooling by spraying cooling water, and then aspirating the container to dehydrate the roasted substrate material that has been moistened by the secondary cooling.

[0012] In addition, the waste substrate pretreatment equipment of the present invention is characterized by including a roasting furnace that roasts pulverized waste substrates, a conveyor that transports the roasted substrates and stores them in a container, a cooling device that primarily cools the roasted substrates to a predetermined temperature by spraying cooling water on the roasted substrates being transported, and a cooling / dehydration device that secondarily cools the roasted substrates by spraying cooling water from above the container in which the primarily cooled roasted substrates are stored, and dehydrates the roasted substrates that have been moistened by the secondary cooling by suctioning the container. Effect of the Invention

[0013] According to the present invention, waste substrates that have been subjected to heat treatment can be easily handled. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block flow diagram showing an embodiment of a pretreatment method for waste substrates according to the present invention. [Diagram 2] FIG. 1 is a process flow diagram of an embodiment of pretreatment equipment for waste substrates according to the present invention. [Diagram 3] 3 is a perspective view of a specific example of a cooling device included in the pretreatment facility shown in FIG. 2. [Figure 4] 3 is a perspective view of a specific example of a cooling / dehydration device included in the pretreatment facility shown in FIG. 2. [Diagram 5] 1 is a graph showing the moisture content of roasted substrates obtained when waste substrates are pretreated using the pretreatment methods of the examples and comparative examples of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the pretreatment method for waste substrates according to the present invention will be described with reference to the drawings. A pretreatment method shown in the block flow diagram of FIG. 1 can be mentioned as a general method for separating and removing repellent components such as hydrocarbons and halogens contained in waste substrates that are difficult to treat in dry copper smelting. The pretreatment method shown in FIG. 1 includes a crushing step S1 in which the waste substrates are crushed to a predetermined particle size so that the waste substrates can be easily handled and treated thereafter, a blending step S2 in which the waste substrates crushed in the crushing step S1 are mixed with crushed waste substrates from other lots or other recycled materials (hereinafter, these will be collectively referred to as other raw materials), a roasting step S3 in which the waste substrates mixed with the other raw materials are roasted to separate and remove the repellent components mentioned above, a secondary combustion step S4 in which exhaust gas discharged during the roasting step S3 is burned, and a secondary combustion step S5 in which the secondary combustion step S6 is mixed with the waste substrates crushed in the crushing step S1 and mixed with the other raw materials (hereinafter, these will be collectively referred to as other raw materials). The process includes a cooling / detoxification process S5 for cooling the treated exhaust gas that has been combusted in S4 and removing harmful components contained in the treated exhaust gas, a primary cooling process S6 for primarily cooling the roasted material obtained by separating and removing repulsive components in the roasting process S3 to a predetermined temperature by spraying cooling water, and a cooling / dehydration process S7 for placing the roasted material cooled by the primary cooling in a container and secondary cooling by spraying cooling water thereon, and then dehydrating the substrate roasted material that has been moistened by the secondary cooling by aspirating the container.

[0016] Each of the above steps will be described with reference to the process flow diagram shown in FIG. 2. First, in the crushing step S1, the waste substrates, which are raw materials received in a raw material hopper 11, are cut from the bottom, and the waste substrates are fed into a crusher 13 via a first conveying means 12 such as a bucket conveyor, and crushed to a predetermined particle size. There is no particular limitation on the type of the crusher 13, but a ball mill that crushes the material to be crushed with a crushing medium such as steel balls pre-loaded in a horizontally oriented cylindrical container by rotating the container around its central axis, or a high-speed rotary crusher that crushes the material to be crushed by impact or shearing by rotating a hammer, blade, or pin at high speed in a casing, can be suitably used. Note that, before crushing with the crusher 13, the waste substrates may be crushed using a crusher such as a jaw crusher or shredder (not shown). In addition, a classification means such as a screen (not shown) may be provided downstream of the crusher 13. The waste substrates which have been pulverized as described above and, if necessary, crushed or classified before or after the pulverization are transferred by a second transport means 14 such as a bucket conveyor to a facility where the next mixing step S2 is carried out.

[0017] In the blending step S2, the crushed waste substrates and other raw materials such as crushed waste substrates of other lots fed by the second conveying means 14 are fed from the bottoms of two or more blending bins 21 in which the crushed waste substrates and other raw materials are separately received, and these crushed waste substrates and other raw materials are fed to a predetermined blending ratio by a feeder or other means. An inlet of a third conveying means 22 such as a bucket conveyor is opened below the two or more blending bins 21, and the crushed waste substrates and other raw materials fed to the predetermined blending ratio are fed to an intermediate raw material hopper 23 after being conveyed by the third conveying means 22. As a result, an intermediate raw material composed of the crushed waste substrates and other raw materials mixed to the predetermined blending ratio is prepared in the intermediate raw material hopper 23.

[0018] In the roasting step S3, the intermediate raw material cut out from the bottom of the intermediate raw material hopper 23 is measured by a load cell 31, and then charged into a roasting furnace 32 and roasted at a temperature of about 750 to 850°C. This removes repellent components such as halogens such as bromine and hydrocarbons. There is no particular limitation on the type of this roasting furnace 32, but a rotary kiln-type roasting furnace having a cylindrical furnace body rotatably supported with its central axis slightly tilted from the horizontal direction is preferred.

[0019] In the secondary combustion step S4, the exhaust gas discharged from the roasting furnace 32 is received in the secondary combustion furnace 42 via the duct 41, where the exhaust gas is heated to about 850°C by the heat of combustion of heavy oil, thereby decomposing harmful substances such as dioxins contained in the exhaust gas. In the cooling / detoxification step S5 following the secondary combustion step S4, the exhaust gas treated in the secondary combustion furnace 42 is introduced into the temperature reducing tower 51, where the exhaust gas is cooled to about 200°C by spraying cooling water from the top. This makes it possible to lower the exhaust gas temperature below the maximum operating temperature of the first bag filter 52 and the second bag filter 53 in the subsequent stage, and also makes it possible to prevent dioxins from being resynthesized in the exhaust gas. Fly ash consisting of fine powder derived from waste substrates can be collected from the bottom of the temperature reducing tower 51.

[0020] It is preferable to add diatomaceous earth such as Radiolite to the exhaust gas leaving the temperature reducing tower 51 before it is introduced into the first bag filter 52, thereby forming a precoat layer on the filter fabric surface of the first bag filter 52. Fly ash consisting of fine powder derived from waste substrates can be collected by this first bag filter 52. The fly ash collected from the bottom of the temperature reducing tower 51 and the first bag filter 52 contains precious metals derived from the waste substrates, so it may be repeatedly recycled to the roasting furnace 32 as a raw material, or may be sold as a valuable resource.

[0021] It is preferable to add slaked lime or activated carbon (AC) to the exhaust gas that has left the first bag filter 52 before it is introduced into the second bag filter 53. Slaked lime can neutralize alkaline components such as bromine contained in the exhaust gas. On the other hand, activated carbon can adsorb and remove harmful substances such as dioxins contained in the exhaust gas. The exhaust gas to which slaked lime or activated carbon has been added as described above is introduced into the second bag filter 53, where fine solid matter that could not be completely removed by the first bag filter 52 is removed. The exhaust gas that has left the second bag filter 53 is released into the atmosphere through a chimney 54. The fly ash recovered from the bottom of the second bag filter 53 can be used for landfill fly ash or other purposes by adding a chelating agent to stabilize it as necessary.

[0022] On the other hand, the roasted substrates discharged from the roasting furnace 32 are subjected to primary cooling and secondary cooling / dehydration in a primary cooling step S6 and a cooling / dehydration step S7, respectively, after being subjected to magnetic separation, gravity separation, or other separation as necessary. In the former primary cooling step S6, the high-temperature roasted substrates discharged from the roasting furnace 32 and having a maximum temperature of about 400°C are transported using a fourth transport means 61 consisting of a continuous track conveyor such as a belt conveyor, while cooling water is sprayed from above onto the high-temperature roasted substrates during transport using a water spray pipe 62. This allows the high-temperature roasted substrates to be primarily cooled to about 200°C or less.

[0023] In the primary cooling of the high-temperature roasted substrate on the fourth conveying means 61, it is preferable to adjust the amount of cooling water to be sprayed for the primary cooling based on the temperature measurement result of the primary-cooled roasted substrate. This can be realized by using, for example, the cooling device shown in Fig. 3. That is, the cooling device shown in Fig. 3 has at least one sprinkler pipe 62 arranged directly above the endless track of the fourth conveying means 61 so as to extend perpendicularly to the traveling direction. The sprinkler pipe 62 has a plurality of spray nozzles at equal intervals in the axial direction on the lower side thereof, and an electromagnetic valve 62a for controlling the supply amount of cooling water to be supplied to the plurality of spray nozzles.

[0024] Furthermore, a non-contact thermometer, for example, an infrared radiation thermometer 63, is preferably provided downstream of the water spray pipe 62 with respect to the fourth conveying means 61 to measure the temperature of the roasted substrates primarily cooled by spraying cooling water. The measured value of this thermometer 63 is input to a control means 64 such as a central processing unit (CPU), and a control algorithm for the control means 64 is constructed so that, for example, if this measured value is lower than a predetermined set value, a closing signal or a signal to reduce the opening degree is output to the solenoid valve 62a. This makes it possible to efficiently and stably primarily cool the roasted substrates to a predetermined temperature without wasting cooling water.

[0025] The roasted substrates primarily cooled as described above are dropped from the end of the fourth transport means and received in a number of metallic containers 70 each having an open top and a rectangular tubular shape with a height of about 800 to 1200 mm and a side length of about 800 to 1500 mm. At this point, the roasted substrates have a maximum temperature of about 200°C, which is higher than the heat-resistant temperature of the flexible containers in the final packaging form, which is 70 to 80°C. Then, the containers 70 containing the roasted substrates are transported to a cooling / dehydration device where the next cooling / dehydration step S7 is performed using a fifth transport means such as a forklift or roller conveyor.

[0026] In the cooling / dehydration step S7, secondary cooling and dehydration are performed using a cooling / dehydration device consisting of, for example, two or more pipes 71, a flexible pipe 72, a decompression tank 73, an exhaust pipe 74, and an exhaust pump 75 as shown in FIG. 4. Specifically, cooling water is sprayed from above the open-topped container 70, which is transported to a predetermined position by the fifth transport means, by two or more pipes 71 arranged parallel and horizontal to each other. Each pipe 71 is provided with a plurality of discharge holes or a plurality of spray nozzles in its axial direction, and when the container 70 is transported to a predetermined position, cooling water is supplied to each pipe 71 and sprayed in a spray form from the discharge hole group or spray nozzle group. At that time, the roasted substrate in the container 70 may be entirely submerged under the surface of the cooling water.

[0027] In order to cool the substrate roasted product in the above manner, a metal plate 70a made of, for example, punching metal having a plurality of through holes with a hole diameter that allows only water to pass through is provided in the container 70 at a distance from the bottom surface, and a valve-equipped nozzle 70b is preferably provided at the bottom of the container 70 so that the cooling water that passes through the separated metal plate 70a and remains in the space between the metal plate 70a and the bottom surface of the container 70 can be drained. The metal plate 70a may be provided so as to cover the entire bottom surface of the container 70, but from the viewpoint of manufacturing costs, it is preferable to provide the rectangular metal plate 70a at an angle to the bottom surface so that the space is formed only on one of the four sides of the container 70 when viewed from directly above, as shown in FIG.

[0028] One end of a flexible pipe 72, preferably made of an at least partially transparent material, is detachably connected to the valved nozzle 70b provided at the bottom of the container 70, and the other end of the flexible pipe 72 is connected to the top of a rectangular cylindrical reduced pressure tank 73. One end of an exhaust pipe 74 is further connected to the top of the reduced pressure tank 73, and the other end of the exhaust pipe 74 is connected to an exhaust pump 75. The bottom of the reduced pressure tank 73 is inclined toward the center, and a square-shaped water reservoir 73a is formed in the center. The valved nozzle 73b is provided on the side wall of the water reservoir 73a.

[0029] During the spraying of cooling water from the pipe 71 to the substrate roasted product in the container 70, it is preferable to open the valve of the valved nozzle 70b and not connect one end of the flexible pipe 72 to the nozzle 70b. Then, by appropriately adjusting the supply amount and the drainage amount so that the spray flow rate of the cooling water from the pipe 71 is greater than the drainage flow rate from the nozzle 70b, the substrate roasted product in the container 70 can be submerged below the surface of the cooling water, preferably entirely. After this cooling, the supply of cooling water to the pipe 71 is stopped, and one end of the flexible pipe 72 is connected to the valved nozzle 70b when the cooling water in the container 70 is drained to a certain extent. Then, the nozzle of the valved nozzle 73b of the decompression tank 73 is closed, the exhaust pump 75 is started, and the container 70 is sucked through the decompression tank 73. As a result, it is possible to efficiently dehydrate the substrate roasted product in the wet state in the container 70, which has a moisture content of about 30%, by submerging it in the cooling water. During this dehydration, the container 70 may be sealed by covering the open portion at the top of the container 70.

[0030] As described above, by forming at least a portion of flexible piping 72 from transparent piping, it is possible to visually confirm that the spin-drying is almost complete, and at this timing, the operation of exhaust pump 75 can be stopped. After exhaust pump 75 is stopped, the valve of valved nozzle 73b of reduced pressure tank 73 can be opened to drain the cooling water accumulated in water reservoir 73a.

[0031] By carrying out the cooling / dehydration step S7 in the above manner, the temperature of the roasted substrate can be lowered to 70°C or less, which is the heat-resistant temperature of the flexible container, and the moisture content of the roasted substrate, which has a moisture content of about 20 to 30% and was handled in the conventional pretreatment method for waste substrates, can be reduced by more than half. This makes it possible to avoid problems that occurred when handling roasted substrates with a high moisture content in the conventional pretreatment method for waste substrates. Specifically, it is possible to make it difficult to cause handling problems such as so-called sticking and clogging, in which the roasted substrate adheres to and remains in a hopper or chute, which are likely to occur when roasted substrates with a high moisture content of about 20 to 30% are charged into a smelting furnace or converter in a copper smelting plant. EXAMPLES

[0032] [Example 1] By using the pretreatment equipment as shown in FIG. 2 and FIG. 4, the pretreatment of the waste substrate was performed according to the block flow shown in FIG. 1. In the cooling / dehydration step S7, the roasted substrate was cooled by spraying cooling water from the pipe 71 at a flow rate of 100 L / min for 10 minutes onto the roasted substrate housed in the container 70. At that time, the valve of the valved nozzle 70b was opened, and one end of the flexible pipe 72 was not connected to the nozzle 70b, so that the cooling water was sprayed while being drained from the nozzle 70b. In addition, the spray flow rate of the cooling water from the pipe 71 was made greater than the drainage flow rate from the nozzle 70b, so that the roasted substrate in the container 70 could be entirely submerged in water for only a few minutes. Thereafter, the supply of cooling water to the pipe 71 was stopped, one end of the flexible pipe 72 was connected to the nozzle 70b, and the exhaust pump 75 was started to suction the container 70 through the reduced pressure tank 73 for 20 minutes. As a result, the moist roasted substrate in the container 70 was dehydrated.

[0033] [Example 2] During the primary cooling in the primary cooling step S6, a cooling device as shown in Fig. 3 was used, and the amount of cooling water sprayed from the spray pipe 62 was adjusted by controlling the opening and closing of the solenoid valve 62a so that the temperature of the roasted substrate measured by the contact thermometer 63 was 200°C or less. Except for this, the pretreatment of the waste substrate was performed in the same manner as in Example 1.

[0034] [Comparative Example 1] For comparison, waste substrates were pretreated in the same manner as in Example 1, except that the container 70 was not suctioned by the exhaust pump 75 via the reduced pressure tank 73 .

[0035] [evaluation] When the moisture content of the substrate roasted material obtained by pretreatment in Comparative Example 1 is taken as a reference value of 1.00, the ratio of the moisture content of the substrate roasted material obtained by pretreatment in Example 1 and Example 2 to the moisture content of Comparative Example 1 is shown in Fig. 5. From the results in Fig. 5, it can be seen that by adopting the pretreatment method of Example 1 or Example 2 that satisfies the requirements of the present invention, the moisture content of the substrate roasted material in a wet state after water cooling can be reduced to a level that does not cause handling problems in the subsequent process, and particularly in Example 2 in which temperature control was performed during primary cooling, the moisture content of the substrate roasted material can be reduced by about 56% compared to Comparative Example 1. [Explanation of symbols]

[0036] 11 Raw material hopper 12 First conveying means 13 Crusher 14 Second conveying means 21 Mixing Bottle 22 Third conveying means 23 Intermediate raw material hopper 31 Load Cell 32 Roasting furnace 41 Duct 42 Secondary Combustion Furnace 51 Cooling tower 52 First Bag Filter 53 No. 2 Bag Filter 54 Chimney 61 Fourth conveying means 62 Sprinkler pipe 62a Solenoid valve 63 Thermometer 64 Control Means 70 containers 70a metal plate 70b Nozzle with valve 71 Piping 72 Flexible piping 73 Pressure Reducing Tank 73a Water reservoir 73b Nozzle with valve 74 Exhaust piping 75 Exhaust Pump

Claims

1. A pretreatment method for waste substrates, comprising: a step of roasting pulverized waste substrates; a primary cooling step of primarily cooling the roasted substrates obtained by the roasting to a predetermined temperature by spraying cooling water while transporting the roasted substrates on a conveyor; and a cooling / dehydration step of placing the primarily cooled roasted substrates in a container and secondary cooling by spraying cooling water thereon, and then aspirating the container to dehydrate the roasted substrates that have been moistened by the secondary cooling.

2. 2. The waste substrate pretreatment method according to claim 1, further comprising the step of adjusting an amount of cooling water sprayed while the conveyor is transporting the roasted substrate based on a measurement result of the temperature of the primarily cooled roasted substrate.

3. A pretreatment facility for waste substrates, the pretreatment facility including a roasting furnace for roasting pulverized waste substrates, a conveyor for transporting the roasted substrates that have been roasted and storing them in a container, a cooling device for primarily cooling the roasted substrates to a predetermined temperature by spraying cooling water onto the roasted substrates being transported, and a cooling / dehydration device for secondarily cooling the roasted substrates by spraying cooling water from above the container that stores the primarily cooled roasted substrates and dehydrating the roasted substrates that have been moistened by the secondary cooling by suctioning the container.

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