Electrostatic sorting device

Abstract

Provided is an electrostatic sorting device including a feeding unit, an electrifying unit, an electrostatic separating unit, a collection container, a circulating unit, and a control unit. In this invention, the feeding unit feeds a material to be sorted, which includes multiple types of objects with different electrification characteristics. The electrifying unit electrifies the multiple types of objects. The electrostatic separating unit has a plurality of electrodes with a predetermined voltage applied thereto, and the multiple types of objects falling between the plurality of electrodes are attracted toward one of the electrodes according to the electrification state. The collection container is disposed below the plurality of electrodes and is divided into a plurality of areas by partitions. The circulating unit circulates a portion of the sorted objects from the collection container to the electrifying unit. The control unit determines a sorting condition on the basis of first and second evaluation results, the first evaluation result being the result of evaluating the composition ratio and amount fed of objects fed into the electrifying unit from the feeding unit, the second evaluation result being the result of evaluating the composition ratio and amount fed of objects fed into the electrifying unit from the circulating unit.

Description

Electrostatic Separation Device

[0001] The present disclosure relates to an electrostatic separation device.

[0002] Conventionally, there has been known a technique for separating a mixture containing multiple types of objects (e.g., plastic pieces) into individual object types. This separation technique, for example, includes an electrostatic separation device that electrically charges the multiple types of objects contained in the mixture and separates specific objects as objects to be recycled by electrostatic separation. For example, the electrostatic separation device described in Patent Document 1 is known as a technique for improving the accuracy of electrostatic separation.

[0003] The electrostatic separation device includes a raw material composition evaluation unit that measures the composition of the mixed plastics, and a circulation unit that sends either the separated first plastic or the separated second plastic to the charging unit. The circulation unit switches between sending the separated first plastic to the charging unit or the separated second plastic to the charging unit based on the measurement results of the raw material composition evaluation unit.

[0004] Patent No. 5194320

[0005] However, when the circulation unit sends the objects to the charging unit, the composition ratio and amount of the objects fed into the charging unit change, which can cause the sorting conditions (e.g., the position of the partitions and the strength of the electrostatic field) to deviate from the appropriate range, resulting in a decrease in the purity of the objects and a decrease in the recovery rate.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an electrostatic sorting device that can maintain appropriate sorting conditions even when objects are circulated.

[0007] In order to solve the above problem, the electrostatic separation device of the present disclosure comprises an input section for inputting a material to be sorted that includes multiple types of objects with different charging characteristics; a charging section for charging the multiple types of objects contained in the material to be sorted; an electrostatic separation section having a pair of electrodes to which a predetermined voltage is applied and attracting the multiple types of objects falling between the multiple electrodes to one of the electrodes depending on their charging states; a collection container arranged below the multiple electrodes and divided into multiple areas by partitions; a circulation section for circulating some of the sorted objects from the collection container to the charging section; and a control section for determining sorting conditions, wherein the control section determines the sorting conditions based on a first evaluation result which is the result of evaluating the composition ratio and input amount of the objects input from the input section to the charging section, and a second evaluation result which is the result of evaluating the composition ratio and input amount of the objects input from the circulation section to the charging section.

[0008] According to the present disclosure, it is possible to provide an electrostatic separation device that can maintain appropriate separation conditions even when objects are circulated.

[0009] 1 is a diagram illustrating an electrostatic separation device according to an embodiment.

[0010] Hereinafter, an electrostatic separation device according to an embodiment will be described with reference to the drawings.

[0011] As shown in FIG. 1, the electrostatic separation device 1 according to this embodiment includes an input section 10, a charging section 20, a conveying section 30, an electrostatic separation section 40, a collection container 50, a circulation section 60, and a control section 70.

[0012] The electrostatic separation device 1 is a device for separating multiple types of objects with different charge characteristics. "Different charge characteristics" refers to differences in whether the objects are positively or negatively charged, or differences in how easily they are charged. For example, in the case of polyvinyl chloride (PVC) resin, polypropylene (PP) resin, polystyrene (PS) resin, ABS resin, and polyamide (PA) resin, PVC resin is most likely to be negatively charged, and PA resin is most likely to be positively charged. More specifically, PVC resin is most likely to be negatively charged, followed by PP resin, PS resin, ABS resin, and PA resin, and then PA resin, followed by ABS resin, PS resin, PP resin, and PVC resin. Objects separated by the electrostatic separation device 1 include, for example, plastic fragments, food fragments, and metal fragments. However, the objects separated by the electrostatic separation device 1 are not limited to these, and can be changed as long as they can be separated using differences in charge characteristics.

[0013] The charging unit 20 according to this embodiment is a cylindrically shaped charging drum (charging tube). The charging unit 20 may be formed in a cylindrical shape, a polygonal prism shape, or the like. The charging unit 20 has a central axis O. A charging space I is formed inside the charging unit 20, through which the material to be sorted passes. As long as the charging space I is formed inside the charging unit 20, the inner and outer diameters of the charging unit 20 may or may not be constant in the axial direction parallel to the central axis O.

[0014] The charging unit 20 is configured to be rotatable about a central axis O. By rotating about the central axis O, the charging unit 20 charges multiple types of objects passing through the charging unit 20 (charging space I). The charging space I may be provided with blade members that protrude from the inner circumferential surface of the charging unit 20 toward the central axis O, or partition plates that divide the charging space I in the axial direction. Note that the type of the charging unit 20 is not limited to a charging drum and can be changed as appropriate, as long as it is capable of charging objects.

[0015] The conveying section 30 conveys the materials to be sorted. The conveying section 30 according to this embodiment includes a first conveying device 31 and a second conveying device 32. The first conveying device 31 conveys the materials to be sorted supplied from the input section 10 to the charging section 20. The second conveying device 32 conveys the materials to be sorted discharged from the charging section 20 to the electrostatic separation section 40.

[0016] The input unit 10 is a device for inputting materials to be sorted, which include multiple types of objects, into the charging unit 20. The input unit 10 according to this embodiment inputs the materials to be sorted into the charging unit 20 via a first conveyor 31. Note that the input unit 10 may input the materials to be sorted directly into the charging unit 20 without using the first conveyor 31. In this case, the electrostatic separation device 1 does not need to have the first conveyor 31.

[0017] The electrostatic separation unit 40 separates the various types of objects charged by the charging unit 20 according to the charging characteristics of each object. The electrostatic separation unit 40 according to this embodiment has a plurality of electrodes 41, 42 (a pair in the illustrated example) to which a predetermined voltage is applied. Hereinafter, the pair of electrodes 41, 42 will be referred to as the first electrode 41 and the second electrode 42, respectively. Note that the electrostatic separation unit 40 may have a plurality of first electrodes 41 or a plurality of second electrodes 42. Furthermore, the number of first electrodes 41 and the number of second electrodes 42 do not have to be equal.

[0018] The multiple types of objects charged by the charging unit 20 are transported by the first conveyor 31 and then fall between the first electrode 41 and the second electrode 42. Note that the objects charged by the charging unit 20 may fall directly between the electrodes 41 and 42 without passing through the first conveyor 31. In this case, the electrostatic separation device 1 does not need to have the second conveyor 32.

[0019] Different voltages are applied to the first electrode 41 and the second electrode 42, for example, by a DC power supply. For example, a positive voltage is applied to the first electrode 41, and a negative voltage is applied to the second electrode 42. Various types of objects falling between the electrodes 41 and 42 are attracted to either the first electrode 41 or the second electrode 42 depending on their charged state.

[0020] The voltage applied to the electrodes 41, 42 may be configured to be changeable. In this case, by changing the voltage applied to the electrodes 41, 42, it becomes easier to perform appropriate sorting according to the mixture ratio of the objects to be sorted, etc.

[0021] The collection container 50 is disposed below the multiple electrodes 41, 42. The collection container 50 according to this embodiment has a first partition 51 and a second partition 52. The first partition 51 and the second partition 52 divide the internal space S of the collection container 50 into multiple regions, including a first collection region S1, a second collection region S2, and an intermediate region S3 located between the collection regions S1, S2. The first collection region S1 is a region that collects objects attracted to the first electrode 41. The second collection region S2 is a region that collects objects attracted to the second electrode 42. The intermediate region S3 is a region that collects objects that are not collected in either the collection region S1 or S2.

[0022] The positions of the partitions 51 and 52 may be configured to be changeable. In this case, changing the positions of the partitions 51 and 52 makes it easier to perform appropriate sorting according to the mixture ratio of the objects to be sorted. The number of partitions and the number of regions can be changed as appropriate.

[0023] The circulation unit 60 circulates some of the sorted objects from the collection container 50 to the charging unit 20. In the illustrated example, the circulation unit 60 circulates the objects collected in the intermediate region S3 to the charging unit 20 via the first conveyor 31. However, the circulation unit 60 may also circulate the objects collected in the collection regions S1 and S2 to the charging unit 20. Alternatively, the circulation unit 60 may circulate the objects directly to the charging unit 20 without going through the first conveyor 31.

[0024] The control unit 70 according to this embodiment includes an input material evaluation unit 71, a circulation evaluation unit 72, and an estimation unit 73. The functions of the control unit 70 (the input material evaluation unit 71, the circulation evaluation unit 72, and the estimation unit 73) may be implemented by a central processing unit (CPU) executing a program. Alternatively, the functions of the control unit 70 may be implemented using hardware (including circuitry) such as a large-scale integration (LSI), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a graphics processing unit (GPU). Alternatively, the functions of the control unit 70 may be implemented by a combination of software and hardware. Furthermore, each function of the control unit 70 (input raw material evaluation unit 71, circulation evaluation unit 72, and estimation unit 73) may be realized by the same hardware, or may be realized by separate hardware.

[0025] The input raw material evaluation unit 71 evaluates the composition ratio and input amount of the object input from the input unit 10 to the charging unit 20. Hereinafter, this evaluation result will be referred to as the "first evaluation result." The input raw material evaluation unit 71 outputs the first evaluation result to the estimation unit 73. An example of a method for evaluating the composition ratio is to extract a portion of the input raw material, identify the type of object using infrared light, and estimate the composition ratio. An example of a method for evaluating the input amount is to install a particle sensor at a location where the input raw material passes and estimate the input amount. Another example is a method in which the composition ratio and input amount are not evaluated each time, but rather past evaluation results are used.

[0026] The circulation evaluation unit 72 evaluates the composition ratio and input amount of the object input from the circulation unit 60 to the charging unit 20. Hereinafter, this evaluation result will be referred to as the “second evaluation result.” The circulation evaluation unit 72 outputs the second evaluation result to the estimation unit 73.

[0027] The estimation unit 73 acquires the first evaluation result output from the input raw material evaluation unit 71. The estimation unit 73 also acquires the second evaluation result output from the circulation evaluation unit 72. The estimation unit 73 estimates the total composition ratio and total input amount of the objects input into the input unit 10 from both the input unit 10 and the circulation unit 60 based on the first evaluation result and the second evaluation result. Specifically, the "total composition ratio" refers to the composition ratio of the objects when the objects input into the charging unit 20 from the input unit 10 and the objects input into the charging unit 20 from the circulation unit 60 are combined. The "total input amount" refers to the total amount (input amount) of the objects input into the charging unit 20 from the input unit 10 and the objects input into the charging unit 20 from the circulation unit 60.

[0028] An example of estimation by the estimation unit 73 is shown below. The following example is an example in which ABS resin pieces and polystyrene (PS) resin pieces contained in the material to be sorted are sorted by the electrostatic sorting device 1. <First evaluation result by the input raw material evaluation unit 71> Composition ratio ABS:PS = 50:50 Input amount 500 kg / h <Second evaluation result by the circulation evaluation unit 72> Composition ratio ABS:PS = 90:10 Input amount 100 kg / h <Estimation by the estimation unit 73> Total composition ratio ABS:PS = 57:43 Total input amount 600 kg / h

[0029] The control unit 70 determines the sorting conditions based on the estimation results by the estimation unit 73. The "sorting conditions" refer to conditions (parameters) that affect the sorting of objects by the electrostatic sorting device 1. Examples of the sorting conditions include the positions of the partitions 51 and 52, the voltages applied to the electrodes 41 and 42, etc.

[0030] The control unit 70 controls the electrostatic separation device 1 based on the determined separation conditions. That is, the control unit 70 applies the determined separation conditions to the electrostatic separation device 1. For example, the control unit 70 controls at least one of the positions of the partitions 51 and 52 and the voltages applied to the electrodes 41 and 42 based on the determined separation conditions.

[0031] The control unit 70 may determine the sorting conditions directly based on the first evaluation result and the second evaluation result without the estimation by the estimation unit 73. That is, the control unit 70 does not need to estimate the total composition ratio and the total input amount. In this case, the control unit 70 does not need to include the estimation unit 73.

[0032] The electrostatic sorting method according to the embodiment will be described below with reference to FIG.

[0033] As shown in FIG. 2, the electrostatic sorting method according to this embodiment includes an input raw material evaluation process ST1, a sorting process ST2, a circulating raw material evaluation process ST3, an estimation process ST4, and a sorting condition adjustment process ST5.

[0034] In the input raw material evaluation step ST1, the input raw material evaluation unit 71 evaluates the composition ratio and input amount of the object input from the input unit 10 to the charging unit 20. The input raw material evaluation unit 71 outputs the resulting first evaluation result to the estimation unit 73.

[0035] In the sorting step ST2, the electrostatic sorting device 1 performs a sorting process on the objects input from the input unit 10 to the charging unit 20. That is, multiple types of objects are sorted into one of multiple regions S1 to S3 of the collection container 50 depending on their charge states. After the sorting step ST2 is performed, some of the sorted objects are circulated to the charging unit 20 by the circulation unit 60. For example, the objects collected in the intermediate region S3 are circulated to the charging unit 20 by the circulation unit 60.

[0036] In the circulating raw material evaluation step ST3, the circulation evaluation unit 72 evaluates the composition ratio and input amount of the object input from the circulation unit 60 to the charging unit 20. The circulation evaluation unit 72 outputs the second evaluation result, which is the result of the evaluation, to the estimation unit 73.

[0037] In the estimation step ST4, the estimation unit 73 estimates the total composition ratio and the total input amount based on the first evaluation result and the second evaluation result.

[0038] In the sorting condition adjustment step ST5, the control unit 70 determines sorting conditions based on the estimated total composition ratio and total input amount. Then, the control unit 70 controls the electrostatic separation device 1 based on the determined sorting conditions. Based on the sorting conditions controlled in this way, the sorting step ST2 is performed again. Thereafter, steps ST2 to ST5 are repeatedly performed. Note that not only steps ST2 to ST5 but also the input raw material evaluation step ST1 may be repeatedly performed. In other words, steps ST1 to ST5 may be repeatedly performed.

[0039] As described above, the electrostatic separation device of this embodiment includes an input section 10 into which the material to be sorted, which includes multiple types of objects with different charging characteristics, a charging section 20 that charges the multiple types of objects contained in the material to be sorted, an electrostatic separation section 40 having multiple electrodes 41, 42 to which a predetermined voltage is applied and that attracts the multiple types of objects falling between the multiple electrodes 41, 42 toward one of the electrodes 41, 42 depending on their charge states, a collection container 50 that is arranged below the multiple electrodes 41, 42 and is divided into multiple regions S1 to S3 by partitions 51, 52, a circulation section 60 that circulates some of the sorted objects from the collection container 50 to the charging section 20, and a control section 70 that determines the sorting conditions. The control section 70 determines the sorting conditions based on a first evaluation result that is a result of evaluating the composition ratio and input amount of the objects input from the input section 10 to the charging section 20, and a second evaluation result that is a result of evaluating the composition ratio and input amount of the objects input from the circulation section 60 to the charging section 20.

[0040] With this configuration, the sorting conditions are determined using not only the first evaluation result but also the second evaluation result, which is the result of evaluating the composition ratio and input amount of the objects input from the circulation unit 60 to the charging unit 20. Therefore, it is possible to set appropriate sorting conditions even when the objects are circulated. By setting appropriate sorting conditions, it is possible to improve the purity and recovery rate of the objects.

[0041] Furthermore, the control unit 70 may estimate the total composition ratio and the total input amount of the objects input into the charging unit 20 from both the input unit 10 and the circulation unit 60 based on the first evaluation result and the second evaluation result. According to this configuration, the sorting conditions can be appropriately adjusted using the total composition ratio and the total input amount.

[0042] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments and can be freely modified within the scope of the present disclosure.

[0043] Each component of the electrostatic separation device 1 described above has an internal computer system. A program for implementing the functions of each component of the electrostatic separation device 1 described above may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform processing in each component of the electrostatic separation device 1 described above. Here, "reading a program recorded on a recording medium into a computer system and executing it" includes installing the program into a computer system. The term "computer system" here includes hardware such as an OS and peripheral devices.

[0044] Furthermore, a "computer system" may include multiple computer devices connected via a network including the Internet or communication lines such as a WAN, LAN, or dedicated line. Furthermore, a "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Thus, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0045] The recording medium also includes internal or external recording media accessible from a distribution server for distributing the program. The program may be divided into multiple parts, downloaded at different times, and then combined by each component of the electrostatic separation device 1. Each divided program may be distributed by a different distribution server. Furthermore, the term "computer-readable recording medium" also includes a medium that stores a program for a certain period of time, such as volatile memory (RAM) within a computer system that serves as a server or client when a program is transmitted over a network. The program may also be a program that realizes part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-described functions in combination with a program already stored in the computer system.

[0046] REFERENCE SIGNS LIST 1... electrostatic separation device 10... input section 20... charging section 40... electrostatic separation section 41... first electrode 42... second electrode 50... collection container 51... first partition 52... second partition 60... circulation section 70... control section

Claims

1. An input unit that inputs materials to be sorted that include a plurality of types of objects with different electrostatic characteristics; a charging unit that charges a plurality of types of objects contained in the material to be sorted; an electrostatic separation unit having a plurality of electrodes to which a predetermined voltage is applied, and attracting a plurality of types of objects falling between the plurality of electrodes to one of the electrodes depending on a charged state of the objects; a collection container disposed below the plurality of electrodes and divided into a plurality of regions by partitions; a circulation unit that circulates a portion of the sorted objects from the collection container to the charging unit; A control unit that determines a selection condition, The control unit is A first evaluation result obtained by evaluating a composition ratio and an input amount of the object input from the input unit to the charging unit; determining the sorting conditions based on a second evaluation result which is a result of evaluating a composition ratio and an input amount of the objects input from the circulation unit to the charging unit; Electrostatic separation device.

2. The control unit estimates a total composition ratio and a total input amount of the objects input to the charging unit from both the input unit and the circulation unit based on the first evaluation result and the second evaluation result.

2. The electrostatic separation device according to claim 1.

3. An input section for inputting a material to be sorted that includes a plurality of types of objects with different electrostatic characteristics; a charging unit that charges a plurality of types of objects contained in the material to be sorted; an electrostatic separation unit having a plurality of electrodes and attracting a plurality of types of objects falling between the plurality of electrodes to one of the electrodes depending on a charged state of the objects; a circulation unit that circulates a portion of the object separated by the electrostatic separation unit; A control unit that determines a selection condition, The control unit is A composition ratio and an input amount of the object input from the input unit to the charging unit; determining the sorting conditions based on a composition ratio and an input amount of the objects input from the circulation unit to the charging unit; Electrostatic separation device.