CN107953482B

CN107953482B - Electrostatic sorting device and electrostatic sorting method

Info

Publication number: CN107953482B
Application number: CN201710793222.7A
Authority: CN
Inventors: 西川祐介; 梅村园子; 衣川胜; 鹤田明三
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2016-10-17
Filing date: 2017-09-06
Publication date: 2020-03-10
Anticipated expiration: 2037-09-06
Also published as: CN107953482A

Abstract

The present invention relates to an electrostatic sorting apparatus and an electrostatic sorting method. An electrostatic sorting device (1) is provided with: a charging device (3) for frictionally charging the plurality of resin sheets (2a, 2 b); a pair of electrodes (7a, 7b) between which an electrostatic field is generated; a conveying device (5) for guiding the resin sheets (2a, 2b) to an electrostatic field from the vertical upper side; a collection container (10) which is provided vertically below the electrostatic field and collects the resin sheets (2a, 2b) falling by the electrostatic field; and a measuring sensor (6) that measures the amount of the resin sheets (2a, 2b) falling in the measuring space between the electrostatic field and the recovery container (10).

Description

Electrostatic sorting device and electrostatic sorting method

Technical Field

The present invention relates to an electrostatic resin sorting apparatus and an electrostatic resin sorting method.

Background

In recycling resins such as plastics used for casings of household electrical appliances and the like, a plurality of types of resin pieces after crushing treatment are separated and recovered by material in order to be formed into resin materials again. As a means for sorting and collecting the resin sheets, an electrostatic sorting method is widely used which sorts plural kinds of resin sheets as sorted materials by an electrostatic field using a difference in triboelectric characteristics depending on the material.

The mixed crushed resin sheet obtained by crushing a used household appliance mainly includes a polypropylene (hereinafter, referred to as "PP") resin, an acrylonitrile, a butadiene, a styrene (hereinafter, referred to as "ABS") resin, or a polystyrene (hereinafter, referred to as "PS") resin. As a method for sorting and collecting the mixed crushed resin pieces, for example, the following methods are mentioned: the PP resin having a smaller specific gravity than the resin is initially sorted and recovered by a specific gravity sorting method, and then the ABS resin and the PS resin are sorted and recovered from the resin mixed raw material containing the remaining ABS resin and PS resin (including the residue of the PP resin) by an electrostatic sorting method.

As an electrostatic separation method for separating and recovering ABS and PS, which are main two components, from the 3-component series of the mixed crushed resin sheet of ABS, PS, and PP, there is a method in which electrostatic separation processes are combined into two stages. Specifically, ABS resin was sorted and recovered in the 1 st stage, and PS resin was sorted and recovered from a mixture of PS resin and PP resin in the 2 nd stage. In this way, the electrostatic sorting method is particularly suitable for sorting of mixed crushed resin pieces in which the specific gravity values of the resins are close and separation is difficult in the specific gravity sorting method.

In an electrostatic sorting apparatus using the above electrostatic sorting method, it is known that the optimization conditions of the sorting conditions change depending on the mixing ratio of resin pieces included in the sorted material for each resin type (hereinafter referred to as "mixing ratio"). For example, when the average mixing ratio remaining after the specific gravity sorting of the mixed crushed resin pieces recovered and reused from home appliances such as air conditioners, refrigerators, or washing machines is ABS: PS: PP 33: 60: in case 7, the separation conditions are optimized so that predetermined recovery purity and recovery amount can be secured by adjusting the separator position of the recovery vessel according to the mixing ratio.

However, the types and the number of discarded home appliances to be recycled vary in different seasons or dates. Therefore, the mixing ratio of the resin of the mixed crushed resin pieces as the sorted material obtained by crushing the household electrical appliance changes in different seasons, months, or dates. In the recycling machine, the timing of charging the sorted raw material is determined according to the processing status and the stock status. Therefore, the mixing ratio of the sorted materials in the sorting process also varies during the day and night and at different hours.

Therefore, when the separator position of the collection container is set according to a certain average mixing ratio for a varying mixing ratio of the sorted materials, it is not always possible to collect each resin sheet with a high recovery rate and a high recovery rate of a predetermined value or more under the same collection conditions.

The improvement of the electrostatic separation technique for obtaining a high recovery purity and a high recovery rate is an extremely important subject for the purpose of material recovery and reuse and for business purposes. In order to solve the above-described problems, for example, as described below, a technique for recovering a mixture of plastics with high recovery purity and high recovery rate even if the mixing ratio of the resins of the sorted materials varies is disclosed.

An electrostatic sorting apparatus using a conventional electrostatic sorting method includes: a recovery container provided below the electrodes, the recovery container having a structure in which separators can be moved to the high-voltage electrode side and the ground electrode side; a sampling unit that samples a part of the sorted material as an analysis target; a mixing analysis unit that determines the proportion of resin contained in the sampled resin sheet; and a recovery control unit that moves the separator position of the recovery container to one of the one electrode side and the other electrode side in accordance with the determined ratio.

The electrostatic sorting apparatus determines a mixing ratio of the resins of the sorted materials to be fed to the sorting apparatus, and moves the separator position according to the mixing ratio of the resins based on the database information constructed in advance. Therefore, the recovery purity and the recovery amount are optimized (see, for example, Japanese patent application laid-open No. 2011-115753).

Further, conventionally, there has been known a plastic sorting apparatus including two separators movable in a horizontal direction for dividing a collection container disposed below a sorting section having a metal drum electrode into 3 collection chambers, a meter for measuring the weight of plastic pieces collected in a lower portion of the collection container, and a control device for moving the separators based on an output result from the meter.

The plastic sorting apparatus adjusts the separator to a known optimum position according to the mixing ratio of the resins at the start of feeding. Then, when the weight ratio of the resin pieces recovered to the recovery container changes during the sorting, the plastic sorting apparatus determines the change as a change in the feed mixing ratio. Then, the plastic sorting apparatus moves the separator position to the optimum position again based on the database information experimentally constructed in advance, thereby achieving high efficiency of sorting and recovery (see, for example, japanese patent application laid-open No. 2001-129435).

Disclosure of Invention

In an environment in which the fluctuation and disturbance in electrostatic separation are merely changes in the mixing ratio of the resin of the fed material to be separated and no other fluctuation and disturbance are present at all, the objective of sufficiently achieving high recovery purity and high recovery rate can be achieved by the method of feed-forward control shown in japanese patent application laid-open No. 2011-115753 and the method of adjusting the separation conditions with reference to the database information shown in japanese patent application laid-open No. 2001-129435.

However, in the actual electrostatic sorting, there are combinations of various disturbances such as (1) variations in the shape of the resin sheet due to (a) variations in the size, thickness, and surface area of the sorted material, (b) variations in the average value and variance of the weight of the resin sheet, and (c) variations in the amount of charge due to surface contamination and variations in the dry state of the resin sheet, and (2) variations in the amount of charge of the resin sheet due to variations in the temperature and humidity of the sorting environment, in addition to variations in the mixing ratio of the sorted material. Therefore, the falling position and the distribution of the falling amount of the resin sheet falling into the collection container by the electrostatic field between the electrodes are greatly varied at all times by the influence of these fluctuations and disturbances. In the electrostatic sorting apparatus and the electrostatic sorting method shown in japanese patent laid-open nos. 2011-115753 and 2001-129435, when a change other than the mixing ratio of the resins of the sorted material occurs, the optimum position of the separator existing in the preset database does not match the actual optimum position. As a result, there is a problem that the recovery purity and the optimization of the recovery rate are insufficient.

Further, in the technique disclosed in japanese patent application laid-open No. 2001-129435, it is necessary to reconstruct a database for coping with new fluctuations and disturbances each time they are applied, and there is a problem that a huge test operation is required.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an electrostatic sorting apparatus and an electrostatic sorting method for measuring the influence of fluctuation and disturbance on a resin sheet during dropping before sorting and collection.

The electrostatic sorting device of the present invention includes:

a charging device for frictionally charging the plurality of resin sheets;

a pair of electrodes between which an electrostatic field is generated;

a conveying device for guiding the resin sheet to an electrostatic field from vertically above;

a recovery container that is provided vertically below the electrostatic field and opens vertically upward to recover the resin sheet falling by the electrostatic field; and

and a measuring sensor for measuring the falling amount of the resin sheet in the measuring space between the electrostatic field and the recovery container.

The electrostatic sorting method of the present invention includes:

a measuring step of measuring, by a measuring sensor, a drop amount in a measurement space between an electrostatic field of a plurality of types of resin sheets dropped and collected into a collection container by the electrostatic field generated between a pair of electrodes, the collection container being provided vertically below the electrostatic field and opening vertically above the electrostatic field; and

an analysis step of analyzing, by a computer, the amount of the resin pieces falling down corresponding to the plurality of collection sections formed in the collection container based on a predetermined fitting curve and the amount of the resin pieces falling down in the measurement space measured in the measurement step,

the plurality of recovery sections are partitioned by the plurality of separators, are opened vertically upward, and recover the resin sheet falling by the electrostatic field from the opening.

In the electrostatic sorting apparatus and the electrostatic sorting method configured as described above, it is possible to measure the influence of the fluctuation and the disturbance on the resin sheet during the falling process before being sorted and collected in the collection container.

The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description, which is to be read in connection with the accompanying drawings.

Drawings

Fig. 1 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 1 of the present invention.

Fig. 2 is a diagram illustrating an example of an output signal when a resin sheet falls onto a measurement sensor of an electrostatic sorting device in embodiment 1 of the present invention.

Fig. 3 is a diagram showing an example of measurement and an example of analysis of the drop distribution of the electrostatic sorting apparatus according to embodiment 1 of the present invention.

Fig. 4 is a graph illustrating the recovery rate and the recovery purity in embodiment 1 of the present invention.

Fig. 5 is a flowchart illustrating an electrostatic sorting method in embodiment 1 of the present invention.

Fig. 6 is a diagram illustrating an example in which a beam sensor is used as the measurement sensor in embodiment 1 of the present invention.

Fig. 7 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 2 of the present invention.

Fig. 8 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 3 of the present invention.

Fig. 9 is a flowchart illustrating an electrostatic sorting method in embodiment 3 of the present invention.

Fig. 10 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 4 of the present invention.

Fig. 11 is a flowchart illustrating an electrostatic sorting method in embodiment 4 of the present invention.

Fig. 12 is a graph showing the results of analyzing the recovery purity and recovery rate of the recovered ABS resin and PS resin for each separator position based on the measurement data of the drop distribution of the sorted resin sheets in embodiment 4 of the present invention.

Detailed Description

Hereinafter, details of an electrostatic sorting apparatus and an electrostatic sorting method according to an embodiment of the present invention will be described with reference to the drawings.

Embodiment 1.

Embodiment 1 of the present invention will be described. In the description of the drawings below, the same or similar parts are denoted by the same or similar reference numerals, and the description thereof is omitted. The drawings used in the following description are schematic drawings used for easy understanding, and the ratio of the dimensions may be different from the actual ratio. It is needless to say that the drawings include portions having different dimensional relationships and ratios. The present invention is not limited to the following embodiments, and can be implemented by appropriately changing the embodiments without departing from the scope of the present invention.

Fig. 1 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 1 for carrying out the present invention. The cross-sectional view is a plane including the direction of the electrostatic field applied between the pair of

electrodes

7a and 7b of the electrostatic sorting apparatus 1 and the falling direction of the

resin sheets

2a and 2 b.

As shown in fig. 1, the electrostatic sorting apparatus 1 includes, in order from the upper side in the cross section: a charging device 3 for frictionally charging the plurality of types of

resin sheets

2a and 2b to be sorted; a supply device 4 for supplying the

resin sheets

2a and 2b as resin materials to the charging device 3; the vibration feeder 5 conveys the

resin sheets

2a and 2b charged by the charging device 3.

The electrostatic sorting apparatus 1 includes a pair of

electrodes

7a and 7b below the end in the conveying direction (the x direction is a positive direction in the drawing) of the vibrating feeder 5. The electrode 7a is a ground electrode. The electrode 7b is a high voltage electrode having a higher potential than the electrode 7 b. In order to generate an electrostatic field between the

electrodes

7a and 7b, the counter electrode 7a is connected to a power supply 8.

The vibrating feeder 5 is an electrostatic field conveying device that guides the

resin sheets

2a and 2b from vertically above to the pair of

electrodes

7a and 7 b.

Below the pair of

electrodes

7a and 7b, a recovery section 10a for recovering the resin sheet 2a sorted by the electrostatic field, a recovery section 10b for recovering the resin sheet 2b, and a recovery section 10c for recovering the

resin sheets

2a and 2b not sorted are arranged. A separator 11a that partitions the

recovery section

10a and 10c, and a separator 11b that partitions the

recovery section

10b and 10c are connected to the

actuators

12a, 12b, respectively. The

actuators

12a and 12b are driving units that move the

separators

11a and 11b in the x direction in fig. 1.

That is, the electrostatic sorting apparatus 1 includes a collection container 10, and the collection container 10 is provided vertically below the electrostatic field and opens vertically upward, thereby collecting the

resin sheets

2a and 2b dropped by the electrostatic field. The collection container 10 is partitioned by a plurality of

separators

11a, 11b, thereby forming a plurality of

collection partitions

10a, 10b, 10 c.

A measurement sensor 6 is disposed in a measurement space between the

electrodes

7a and 7b and the collection container 10, and the measurement sensor 6 measures the amount of the resin sheet falling into the collection container 10. The plurality of measurement sensors 6 are arranged linearly in the x direction in fig. 1 on the horizontal plane of the upper surface of the collection container 10. In fig. 1, for ease of explanation of the present embodiment, detailed descriptions of the support member and the like of the measurement sensor 6 are omitted. Further, the measurement sensor 6 is sufficiently small in the y direction in fig. 1 with respect to the electrostatic sorting apparatus 1 so as not to prevent the

resin sheets

2a and 2b from falling into the collection container 10.

That is, the electrostatic sorting apparatus 1 includes a plurality of measuring sensors 6, and the plurality of measuring sensors 6 measure the amount of the

resin sheets

2a and 2b falling in the measuring space between the electrostatic field and the collection container 10. The plurality of measurement sensors 6 are disposed vertically above the

recovery sections

10a, 10b, and 10 c.

Further, the plurality of measurement sensors 6 are not limited to the x direction, as long as they are arranged in the direction along the electrostatic field of the

electrodes

7a, 7 b. The measurement sensor 6 is not limited to the level of the upper surface of the recovery container 10, and may be located between the

electrodes

7a and 7b and the recovery container 10.

The plurality of measurement sensors 6 are electrically connected to the computer 9, respectively, so that measurement signals can be output to the computer 9. Further, the computer 9 is electrically connected to the

actuators

12a and 12b, and can output control signals for operating the

actuators

12a and 12 b. Since the drawing is complicated, in fig. 1, only the connection to the right-hand 1 measurement sensor 6 is shown for the connection between the measurement sensor 6 and the computer 9, and the other description is omitted. The measurement sensor 6 and the computer 9, and the computer 9 and the

actuators

12a and 12b may be connected by wireless.

According to the configuration described above, in the electrostatic sorting apparatus 1, the plurality of measurement sensors 6 arranged linearly in the x direction in fig. 1 on the horizontal plane of the upper surface of the collection container 10 output signals corresponding to the number of resin sheets or the weight of the resin sheets at respective positions, which indicate the amount of resin sheets falling by the electrostatic field between the

electrodes

7a and 7 b. The output of the measurement sensor 6 at each position is subjected to data processing by the computer 9 as the amount of falling of the resin sheet by the measurement sensor 6 at each position. Thus, the amount of the resin sheets separated by the electrostatic field that fall per unit time at each position on the collection container 10, that is, the falling distribution of the resin sheets reflecting the result of sorting by the electrostatic field can be measured.

Further, the peaks of the measured drop distribution are separated by the computer 9 using a known fitted curve. Then, the falling amounts of the

resin sheets

2a and 2b are analyzed by a computer. The computer 9 determines the positions of the

separators

11a and 11b based on the analysis result of the falling amount of each resin sheet so that an arbitrary recovery purity and recovery rate can be obtained. The computer 9 outputs the control amounts of the

actuators

12a, 12b corresponding to the determined positions of the

separators

11a, 11 b. The detailed definition of the recovery purity and recovery rate will be described later.

By providing the measurement sensor 6 at the level of the upper surface of the collection container 10 disposed below the

electrodes

7a and 7b and measuring the resin sheet falling on the upper surface of the collection container 10 in this manner, the distribution of the resin sheet falling on the collection container 10 can be monitored. Therefore, the optimum positions of the

separators

11a and 11b for obtaining high recovery purity and high recovery rate can be determined according to the falling distribution of the resin sheets. Therefore, it is possible to quickly determine the sorting conditions with high purity and high recovery rate for the change of the drop distribution under various factors, such as the change of the average value and the fluctuation in the particle size and the weight of the resin sheet, the change of the charge amount of the resin due to the change of the external factors such as the dry state of the resin and the humidity of the environment, and the like, not only when the mixing ratio of the resin in the sorted material is changed. In addition, even when the drop distribution changes during the sorting process, the difference between the set value and the analysis value can be fed back to the

separators

11a and 11b (

actuators

12a and 12b) as a control deviation in the recovery purity and the recovery rate, and therefore, the sorting with high recovery purity and high recovery rate can be stably performed.

Hereinafter, the operation principle of the electrostatic sorting method and the electrostatic sorting apparatus according to the present embodiment will be described with reference to fig. 1.

Here, a case where sorting and collection are performed will be described by taking a case where the resin sheet 2a shown in a white background is an ABS resin and the resin sheet 2b shown in a black background is a PS resin as an example. According to the triboelectric series of the resin, the ABS resin is charged positively (+) and the PS resin is charged negatively (-).

The

resin sheets

2a and 2b fed from the feeding port of the charging device 3 to the charging device 3 by the feeding device 4 are stirred and rotated in the inclined charging device 3. With the rotation stirring, the resin sheets 2a are charged positively (+) and the resin sheets 2b are charged negatively (-) by the friction between the

resin sheets

2a and 2 b. The charged

resin sheets

2a and 2b are discharged from the charging device 3. Then, the charged

resin sheets

2a and 2b are fed to the electrostatic field of the sorting section formed by the high voltage electrode 7a and the ground electrode 7b while being uniformly spread on the vibrating feeder 5 as a conveying device.

As shown in fig. 1, when passing through the electrostatic field formed between the high-voltage electrode 7a and the ground electrode 7b, the positively (+) charged resin sheet 2a falls so as to be pulled toward the ground electrode 7b side while receiving a force in the same direction as the direction of the electric field from the electrostatic field, and is collected in the collection partition 10 a. The negative (-) charged resin sheet 2b is pulled toward the high voltage electrode 7a by a force in a direction opposite to the direction of the electric field from the electrostatic field, falls, and is collected in the collection partition 10 b. The insufficiently charged

resin sheets

2a and 2b are not subjected to an electrostatic force required for sorting from an electrostatic field when falling, and fall directly and are collected in the collection section 10c disposed between the

collection sections

10a and 10 b.

In the sorting of resins by the electrostatic sorting method, the mixing ratio of the resins in the fed sorted materials is correlated with the charge amount of the resin sheet, and when the mixing ratio varies, the drop distribution at the time of sorting is affected. Further, the variation of the drop distribution in the sorting of the resin does not depend only on the variation of the mixing ratio of the sorted materials. For example, various fluctuations and disturbances in the process such as changes in the average value or fluctuation of the shape, particle size, and weight of the resin sheet, changes in the charge amount due to surface contamination and fluctuation of the dry state of the resin sheet, and changes in the charge amount of the resin sheet due to the temperature and humidity conditions of the sorting environment are combined. The falling positions and the distribution of the falling amounts of the

resin sheets

2a and 2b sorted and collected in the collection container 10 by the electrostatic field between the

electrodes

7a and 7b fluctuate under the influence of these fluctuations and disturbances. Therefore, in order to stably perform sorting with high recovery purity and high recovery rate, for example, it is not sufficient to fix the

separators

11a and 11b of the recovery vessel 10.

Therefore, the number and weight of the resin sheets sorted and dropped by the electrostatic field between the

electrodes

7a and 7b are measured by the plurality of measuring sensors 6, and the drop distribution of the

resin sheets

2a and 2b on the collection container 10 is measured.

Fig. 2 is a diagram illustrating an example of an output signal when a resin sheet falls onto the measurement sensor 6 of the electrostatic sorting apparatus in the present embodiment. In fig. 2, the horizontal axis represents the measured time, and the vertical axis represents F (force) converted from the output signal of the measurement sensor 6. The time range on the horizontal axis is a range obtained by extracting a predetermined time during the measurement. Fig. 2 shows a case where a load cell is used as the measurement sensor 6, and the force on the vertical axis represents a force converted from the voltage of the output signal of the load cell. When the

resin sheets

2a, 2b are dropped onto the measurement sensor 6 as a load cell, the measurement sensor 6 outputs a signal of an intensity corresponding to a force (input signal) at the time of the drop. If the measurement sensor 6 outputs the signal to the computer 9, the number of the

resin sheets

2a and 2b dropped per unit time can be calculated and the weight of the dropped

resin sheets

2a and 2b can be calculated using the integrated value of the input signal.

Therefore, the measurement sensor 6 in the electrostatic sorting apparatus 1 can measure the influence of various fluctuations and disturbances on the

resin sheets

2a and 2b falling down before sorting and collection in the collection container 10, such as changes in the average value or fluctuation of the shape, particle size, and weight of the resin sheet, changes in the amount of charge due to surface contamination and fluctuation of the resin sheet in a dry state, and changes in the amount of charge of the resin sheet due to temperature and humidity conditions in the sorting environment.

Fig. 3 is a diagram showing an example of measurement and an example of analysis of the falling distribution of the electrostatic sorting apparatus in the present embodiment. In fig. 3, the horizontal axis represents the recovery positions of the

resin sheets

2a and 2b in the x direction of fig. 1, and the vertical axis represents the weight ratio of the recovered

resin sheets

2a and 2b to the total weight. Based on the signals output from the respective measurement sensors 6, the computer 9 calculates a drop distribution indicating the number of drops of the vertically

upper resin sheets

2a and 2b or the weight of the stacked

resin sheets

2a and 2b in the collection container 10. Further, the drop distribution of the

resin sheets

2a and 2b obtained by calculation is analyzed as the drop distribution of the resin sheet 2a and the drop distribution of the resin sheet 2b by separating peaks on the positive charging side and the negative charging side using two known fitting curves.

That is, the electrostatic sorting apparatus 1 further includes a computer 9, and the computer 9 analyzes a drop distribution, which is a drop amount of the

resin sheets

2a and 2b corresponding to the

recovery sections

10a, 10b, and 10c, based on a predetermined fitting curve and the drop amounts of the

resin sheets

2a and 2b in the measurement space measured by the measurement sensor 6.

Fig. 4 is a diagram illustrating the recovery rate and the recovery purity in the present embodiment. In fig. 4, as in fig. 3, the horizontal axis represents the recovery positions of the

resin sheets

2a and 2b to the total weight. The recovery purity and recovery rate are represented by the following formulae (1) to (3).

The recovery purity [% ] of the resin sheet 2a is a1/(a1+ b1) × 100 … (1)

Recovery purity [% ] of the resin sheet 2b is b3/(a3+ b3) × 100 … (2)

Recovery [% ]) [% ]/((a 1+ a2+ a3) + (b1+ b2+ b3)) × 100 … (3) ] [% ], ((a1+ b1) + (b3+ a3))/((a1+ a2+ a3) + (b1+ b2+ b3) ]100 36

Here, a1 represents the total amount of the number or the total amount of the weight of the resin pieces 2a collected in the collection compartment 10a, a2 represents the total amount of the number or the total amount of the weight of the resin pieces 2a collected in the collection compartment 10c, a3 represents the total amount of the number or the total amount of the weight of the resin pieces 2a collected in the collection compartment 10b, b1 represents the total amount of the number or the total amount of the weight of the resin pieces 2b collected in the collection compartment 10a, b2 represents the total amount of the number or the total amount of the weight of the resin pieces 2b collected in the collection compartment 10c, and b3 represents the total amount of the number or the total amount of the weight of the resin pieces 2b collected in the collection compartment 10 b.

The computer 9 determines the positions of the

separators

11a and 11b at which an arbitrary recovery purity and recovery rate can be obtained. The computer 9 outputs a control amount corresponding to the determined position of the

separators

11a, 11b to the

actuators

12a, 12b, thereby adjusting the positions of the

separators

11a, 11 b. Since the measurement sensor 6 always measures the drop distribution in real time, the computer 9 performs feedback control using the difference between an arbitrary set value and an analysis value as a control deviation with respect to the recovery purity and the recovery rate even when the drop distribution fluctuates. Thus, in the electrostatic sorting apparatus 1, sorting can be stably performed with high recovery purity and high recovery rate.

That is, the electrostatic sorting apparatus 1 includes

actuators

12a and 12b that move the

separators

11a and 11b in the x direction in which the collection capacity of the

collection sections

10a, 10b, and 10c is changed. The computer 9 controls the

actuators

12a and 12b to move the

separators

11a and 11b to positions corresponding to the analysis result of the falling amount of the

resin sheets

2a and 2 b.

Fig. 5 is a flowchart illustrating an electrostatic sorting method in the present embodiment. In the measurement step S11 of fig. 5, the amount of the plurality of types of

resin sheets

2a, 2b dropped and recovered into the recovery container 10 disposed vertically below the electrostatic field by the electrostatic field generated between the pair of

electrodes

7a, 7b in the measurement space between the electrostatic field and the recovery container 10 is measured by the measurement sensor 6.

Next, in an analysis step S12, the computer 9 analyzes the falling amounts of the

resin sheets

2a and 2b corresponding to the plurality of

recovery sections

10a, 10b, and 10c formed in the recovery container 10, based on the predetermined fitting curve and the falling amounts of the

resin sheets

2a and 2b in the measurement space measured in the measurement step S11. The plurality of

recovery sections

10a, 10b, and 10c are partitioned by the plurality of

separators

11a and 11b, and have openings that open vertically upward, and the

resin sheets

2a and 2b that have fallen by the electrostatic field are recovered from the openings.

Next, in the movement control step S13, the computer 9 controls the

actuators

12a, 12b to move the

separators

11a, 11b in a direction to change the collection capacity of the collection compartments 10a, 10b, 10 c. That is, the computer 9 moves the

separators

11a, 11b to positions corresponding to the analysis results of the drop amounts of the

resin sheets

2a, 2b analyzed in the analysis step S12.

After the movement control step S13 is completed, if the supply of the

resin sheets

2a and 2b to the electrostatic sorting apparatus 1 is not completed in step S19, the measurement step S11 is returned to and the above steps S11 to S13 are repeated, so that the

separators

11a and 11b can be moved to the optimum positions in accordance with the change in the amount of the

resin sheets

2a and 2b dropped after the elapse of the predetermined time.

For example, a resin sheet supplied to an electrostatic sorting device generally used in the industry of recycling plastics, among plastic mixtures obtained by crushing and recycling used home appliances, is a mixed resin sheet that is crushed to a diameter of 8mm or less and that is applied with a 2mm mesh. When mixed resin sheets having an ABS resin content of about 45% and a PS resin content of about 55% are sorted and collected, the ABS resin is charged positively (+) and the PS resin is charged negatively (-) due to frictional charging between the resin sheets caused by rotational stirring for 10 minutes or longer by the charging device 3. The charged resin sheet is conveyed by a vibration feeder 5 as a vibration type conveying device to a position between

electrodes

7a and 7b generating an electrostatic field of 200kV/m or more, and passes through the position. The ABS resin is recovered to the recovery section 10a located on the ground electrode 7b side according to the charge amount of the resin sheet. In addition, the PS resin is collected into the collection partition 10b located on the high voltage electrode 7a side according to the charge amount of the resin sheet. In order to use the resin recovered from the above-mentioned scrapped home appliances in accordance with the use equivalent to a new material which is a new resin material, the recovery purity of the resin recovered by sorting is required to be 99% or more.

At this time, when the recovery purity of the ABS resin sorted into the recovery section 10a is set to 99% or more and the recovery purity of the PS resin sorted into the recovery section 10b is set to 99% or more as the conditions of the recovery purity, the positions of the

separators

11a and 11b having the maximum recovery rate are uniquely determined from the analysis result of the drop distribution.

Thus, by using the electrostatic sorting method and electrostatic sorting apparatus according to the present embodiment, the optimum positions of the

separators

11a and 11b can be determined from the falling distribution of the resin sheet. Therefore, the positions of the

separators

11a and 11b that can maximize the recovery rate or the positions of the

separators

11a and 11b that can obtain an arbitrary recovery rate can be uniquely determined for any condition such as that the recovery purity is 99% or more. In addition, by measuring the drop distribution all the time, it is possible to quickly provide feedback on the recovery purity and recovery rate when the drop distribution has changed. Therefore, the following remarkable effects are achieved: it goes without saying that the change in the mixing ratio of the

resin sheets

2a and 2b, which affects the drop distribution of the

resin sheets

2a and 2b, can stably perform sorting and collection with high collection purity and high recovery rate even when the drop distribution changes due to various environmental changes.

In the present embodiment, the load cell is used as the measurement sensor 6, but an optical sensor using optics, such as a beam sensor or a laser sensor, may be used as the measurement sensor 6.

Fig. 6 is a diagram illustrating an example in which a beam sensor is used as the measurement sensor 6. Fig. 6 corresponds to a view of the recovery vessel 10 in fig. 1 viewed from above in the z direction of the recovery vessel 10 in a plane parallel to the x-y plane. In fig. 6, as the measurement sensor 6, a beam sensor including a light emitter 6a and a light receiver 6b is used. The computer 9 counts the number of the

resin sheets

2a and 2b passing between the light emitter 6a and the light receiver 6b, and can obtain a drop distribution based on the number of drops. The light emitter 6a and the light receiver 6b are not limited to the horizontal surfaces located on the upper surface of the collection container 10, and may be located between the

electrodes

7a and 7b and the collection container 10.

The light emitter 6a and the light receiver 6b can detect the resin sheet by the

resin sheets

2a and 2b dropped between the

electrodes

7a and 7b and the collection container 10 by a light beam emitted from the light emitter 6a to the light receiver 6 b. Therefore, the measurement sensor 6 is less likely to inhibit the

resin sheets

2a and 2b from falling, compared to the case of the load cell.

For example, a mirror or the like, not shown, may be disposed on the path of the light beam between the light emitter 6a and the light receiver 6 b. In this case, the light emitter 6a and the light receiver 6b do not need to be located between the

electrodes

7a and 7b and the collection container 10.

Embodiment 2.

Fig. 7 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 2 for carrying out the present invention. In fig. 7, for the sake of simplicity of explanation, details of the movable mechanism, the support member, and the like of the measurement sensor 6 are omitted.

In fig. 7, an electrostatic sorting apparatus 101 of the present embodiment is different from the electrostatic sorting apparatus 1 of embodiment 1 in the points described below.

The electrostatic sorting apparatus 101 according to the present embodiment includes 1 measurement sensor 6c on the horizontal surface of the upper surface of the collection container 10, instead of the measurement sensor 6 described in embodiment 1, and the measurement sensor 6c includes a mechanism movable in the x direction in fig. 7. The measurement sensor 6c is sufficiently small in the y direction of fig. 7 with respect to the electrostatic sorting apparatus 101 so as not to prevent the

resin sheets

2a and 2b from falling into the collection container 10.

As in embodiment 1, the measurement sensor 6c is electrically connected to the computer 9 so that its measurement signal can be output to the computer 9. Further, the computer 9 is electrically connected to output control signals for operating the

actuators

12a and 12 b.

According to this configuration, the measurement sensor 6c measures the falling distribution of the

resin sheets

2a and 2b while scanning in the x direction positive and negative directions in the measurement space on the collection container 10 by the computer 9. That is, the measurement sensor 6c measures the amount of the

resin sheets

2a and 2b falling while scanning in the horizontal direction in the measurement space. Therefore, the measurement sensor 6c in the present embodiment can expect an effect of obtaining data of a smoother (high-resolution) drop distribution in the x direction of the measurement space, as compared to the case of using a plurality of measurement sensors 6 described in embodiment 1. Although the effect of improving the resolution in the x direction can be obtained by increasing the number of the measurement sensors 6c in embodiment 1, it is generally advantageous in terms of maintenance and cost to perform scanning with 1 measurement sensor 6 c.

Further, the measurement sensor 6c in the electrostatic sorting apparatus 101 can measure, as in embodiment 1, (a) changes in the average value or fluctuation of the shape, particle size, and weight of the resin sheet, (b) changes in the charge amount due to surface contamination and fluctuation of the dry state of the resin sheet, (c) changes in the charge amount of the resin sheet due to the temperature and humidity conditions of the sorting environment, and the like, which are affected by various fluctuations and disturbances to which the

resin sheets

2a, 2b fall before being sorted and collected in the collection container 10.

In the present embodiment, the 1 measurement sensor 6c is not limited to the load cell, and may be a measurement sensor for optical applications such as a beam sensor or a laser sensor.

Embodiment 3.

Fig. 8 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 3.

In fig. 8, an electrostatic sorting apparatus 102 of the present embodiment is different from the electrostatic sorting apparatus 1 of embodiment 1 in the points described below.

In the electrostatic sorting apparatus 102 of the present embodiment, the control amount from the computer 9 is not output to the

actuators

12a, 12b that move the

separators

11a, 11 b. The computer 9 is electrically connected to the power supply 8 and the temperature and humidity adjustment device 13, or is connected by wireless communication. The temperature and humidity adjusting device 13 controls the temperature or humidity vertically above the recovery container 10.

With this configuration, the computer 9 can adjust the voltage of the power supply 8 based on the falling distribution of the resin sheet measured by the measuring sensor 6, and adjust the intensity of the electrostatic field between the

electrodes

7a and 7 b. The computer 9 controls the temperature and humidity adjustment device 13 to adjust the temperature or humidity vertically above the collection container 10, thereby adjusting the drop distribution of the

resin sheets

2a and 2 b.

That is, the computer 9 outputs a temperature command value or a humidity command value to the temperature/humidity adjustment device 13 based on the analysis result of the amount of the

resin sheets

2a and 2b dropped, and controls the temperature or the humidity vertically above the collection container 10.

Fig. 9 is a flowchart illustrating an electrostatic sorting method in the present embodiment. In fig. 9, the measurement step S11, the analysis step S12, and the movement control step S13 are the same as the measurement step S11, the analysis step S12, and the movement control step S13 included in the flowchart of fig. 5. After the measurement step S11 to the movement control step S13 are performed, in a temperature and humidity control step S14 in fig. 9, the computer 9 outputs a temperature command value or a humidity command value to the temperature and humidity adjustment device 13 based on the analysis result of the falling amount of the

resin sheets

2a and 2b analyzed in the analysis step, and controls the temperature or the humidity vertically above the collection container 10 to be a temperature corresponding to the temperature command value or a humidity corresponding to the humidity command value.

In addition, regarding the falling amounts of the

resin sheets

2a and 2b obtained by analyzing the falling distribution of the

resin sheets

2a and 2b, when the average value (peak position) of the fitting curves used for peak separation is shifted and the interval between the two peaks is decreased, it can be determined that there is a possibility that the amount of charge required for separating the

resin sheets

2a and 2b is insufficient for some reason. In this case, the computer 9 outputs a voltage command value as a control amount to the power supply 8, and adjusts the output voltage of the power supply 8 so that the force received by the charged

resin sheets

2a and 2b from the electrostatic field becomes larger than that in the steady state, and the recovery rate can be improved even when the charging of the

resin sheets

2a and 2b is insufficient.

That is, the electrostatic sorting apparatus 102 further includes a power supply 8, and the power supply 8 applies a voltage to the pair of

electrodes

7a and 7b to generate an electrostatic field in the pair of

electrodes

7a and 7 b. The computer 9 outputs a voltage command value to the power supply 8 based on the analysis result of the falling amount of the resin sheet, and controls the voltage.

In the voltage control step S15 of fig. 9, the computer 9 outputs a voltage command value based on the analysis result of the drop amount of the

resin pieces

2a and 2b analyzed in the analysis step S13, and controls the voltage of the power supply 8. The voltage of the power supply 8 is supplied to the pair of

electrodes

7a, 7b, and the pair of

electrodes

7a, 7b generates an electrostatic field.

After the completion of the temperature/humidity/voltage control step S16 of performing at least one of the temperature/humidity control step S14 and the voltage control step S15, the process returns to the measurement step S11, and the steps S11 to S13 are repeated, so that the

separators

11a and 11b can be moved to the optimum positions in accordance with the change in the amount of dropping of the

resin sheets

2a and 2b after the elapse of a predetermined time.

In addition, the drop distribution of the

resin sheets

2a and 2b can be adjusted in accordance with a change in the drop amount of the

resin sheets

2a and 2b after a predetermined time has elapsed. In addition, the recovery rate can be improved even when the charging of the

resin sheets

2a and 2b is insufficient in accordance with the change in the amount of the

resin sheets

2a and 2b dropped after the elapse of a predetermined time.

By providing the control target based on the falling profile with the function of adjusting the voltage of the power supply 8 or the function of adjusting the temperature or humidity of the temperature/humidity control device 13 in this way, even when the peak of the falling profile is shifted, the sorting condition can be improved while referring to the falling profile data in order to obtain an arbitrary recovery purity and recovery rate.

In the present embodiment, the measurement sensor 6 is not limited to the load cell. For example, a method of obtaining the drop distribution by counting the number of resin sheets dropped using an optical sensor such as a beam sensor or a laser sensor may be used.

Embodiment 4.

Fig. 10 is a sectional view showing a schematic configuration of an electrostatic sorting apparatus according to embodiment 4 for carrying out the present invention. As shown in fig. 10, the electrostatic sorting apparatus 103 of the present embodiment is different from the electrostatic sorting apparatus 1 of embodiment 1 in the points described below.

The electrostatic sorting device 103 further includes a computer 9a, and the computer 9a includes a processor 14 and a storage device 15. The storage device 15 includes a volatile storage device such as a random access memory, and a non-volatile auxiliary storage device such as a flash memory, although not shown. Although not shown, the storage device 15 may include an auxiliary storage device such as a hard disk instead of the nonvolatile auxiliary storage device.

The processor 14 executes a program input from the storage device 15. The storage device 15 includes an auxiliary storage device and a volatile storage device, and therefore, a program is input from the auxiliary storage device to the processor 14 via the volatile storage device. The processor 14 may output data such as the operation result to a volatile storage device of the storage device 15, or may store the data in an auxiliary storage device via the volatile storage device.

Fig. 11 is a flowchart illustrating an electrostatic sorting method according to embodiment 4. In fig. 11, the process of returning to the measurement step S11 after the measurement step S11, the analysis step S12, and the movement control step S13 to adjust the drop distribution of the resin sheet is the same as the process of the flowchart of embodiment 1 shown in fig. 5.

The flowchart of fig. 11 differs from the flowchart of fig. 5 in that: a process continuation determination step S17 of determining continuation or interruption of the processing cycle of the measurement step S11 to the movement control step S13 when the sorting process is completed or a process interruption time is generated due to no sorted material or the like; and a separator initial position control step S18 for determining and moving the positions of the

separators

11a, 11b at the start of the next process based on the data on the recovery purity and the recovery rate.

In the present embodiment, according to the above-described flowchart, the initial positions of the

separators

11a and 11b are determined based on the data of the recovery purity and the recovery rate of the sorting process before the sorting process is started, and the delay in response of the

separators

11a and 11b at the start of the process, that is, the loss of the recovery purity and the recovery rate at the initial stage of the sorting process can be improved.

Fig. 12 is a graph showing the results of analyzing the recovery purity and recovery rate of the recovered ABS resin and PS resin with respect to the positions of the

separators

11a and 11b based on the measurement data of the drop distribution of the sorted resin sheets. In fig. 12, the horizontal axis represents the recovery position of the resin sheet in the x direction of fig. 10, and the vertical axis represents the recovery purity and recovery rate of the recovered resin sheet. The vertical thick lines in fig. 12 indicate the positions of the

separators

11a, 11b in the recovery vessel 10. From the left in fig. 12, the respective thick lines correspond to the

separators

11a, 11 b. That is, in fig. 12, the left side of the separator 11a (the negative direction at the coordinates indicating the recovery position) corresponds to the recovery section 10a, the right side of the separator 11b (the positive direction at the coordinates indicating the recovery position) corresponds to the recovery section 10c, and the section sandwiched by the

separators

11a and 11b corresponds to the recovery section 10 b. When the sorted raw materials are ABS resin and PS resin, the ABS resin is positively charged and the PS resin is negatively charged, and the resins are collected into the respective sections of the collection container 10.

For example, when the recovered resin requires a recovery purity of the resin pieces of 99% or more, the positions of the

separators

11a and 11b, in which the recovery purity of the recovered resin pieces is 99% or more and the recovery rate is the maximum, are as follows for each resin. As shown in fig. 12, when the left end of the recovery tank for positively charged resin of the recovery vessel 10 is taken as the zero point, the position coordinate of the separator 11a on the ABS recovery side is 350, and the position coordinate of the separator 11b on the PS recovery side is 640, which are uniquely determined.

As described above, in the electrostatic sorting apparatus according to the present embodiment, the sorting process is performed by repeating the process continuation determination in the measurement step S11 to the movement control step S13 and the process continuation determination step S17, and data of the recovery purity and the recovery rate of each resin is continuously acquired. However, when the sorting process is completed or interrupted, a response delay of the

separators

11a, 11b occurs before new fall profile data is acquired at the start of the next process.

Therefore, in the present embodiment, in the process continuation determination step S17, the computer 9 stores the acquired data of the recovery purity and the recovery rate in the storage device 15 of the computer. Then, after the sorting process is completed or the process is interrupted due to an emergency stop or the like in the process continuation determination step S17, the initial position control step S18 refers to the stored immediately preceding process data (recovery purity and recovery rate) from the storage device 15, and determines and moves the initial positions of the

separators

11a and 11b so as to reduce the delay in response at the start of the next process. Then, returning to the measurement step S11, the continuation determination of the measurement step S11 to the movement control step S13 and the process continuation determination step S17 is repeated. This improves the delay in response of the

separators

11a and 11b at the start of the next process.

The processing of the measurement step S11, the analysis step S12, the movement control step S13, the processing continuation determination step S17, and the initial position control step S18 in fig. 11 is realized by the processor 14 executing the program stored in the storage device 15 or a processing circuit such as a system LSI, not shown. Further, the plurality of processors 14 and the plurality of storage devices 15 may cooperatively perform the above-described functions. Further, a plurality of processing circuits may cooperate to execute the above-described functions. Further, the functions described above may be executed by a combination of a plurality of processors 14 and a plurality of storage devices 15 in cooperation with a plurality of processing circuits.

For example, in sorting of plastics for the purpose of recycling materials, it is preferable that the sorted resin pieces have a recovery purity of 99% or more. Accordingly, the initial positions of the

separators

11a and 11b are preferably in the range of 100% or less to 99% or more of the recovery purity of each resin. Further, from the viewpoint of ensuring high response speed and robustness at the start of the treatment, it is preferable that the recovery purity of each resin is in the range of 100% or less and 99% or more. In the case of the example shown in fig. 12, the separator 11a is in the range of 200 to 350, preferably in the position 275 midway therethrough, and the separator 11b is in the range of 650 to 950, preferably in the position 800.

As described above, although there is a case where a response delay of the positions of the

separators

11a and 11b occurs immediately after the start of the sorting process in which the data of the falling distribution is not sufficiently obtained, by setting the initial position at the start of the next process based on the recovery purity and the recovery rate of the data of the sorting process immediately before, it is possible to quickly move the

separators

11a and 11b to the optimum position while obtaining the robustness of the sorting process in addition to obtaining an arbitrary recovery purity and recovery rate.

When the peak position of the falling distribution or the width of the distribution of the sorted materials is known from the resin mixing ratio or the charge amount of the sorted raw materials to be processed, the initial positions of the

separators

11a and 11b may be corrected with reference to the peak position or the width of the falling distribution.

In embodiments 1 to 4, the case where the ABS resin and the PS resin are selected as the resins has been described, but a combination of other resins may be used.

While the embodiments of the present invention have been described, the embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. An electrostatic sorting device is provided with:

a charging device for frictionally charging the plurality of resin sheets;

a pair of electrodes between which an electrostatic field is generated;

a conveying device for guiding the resin sheet to the electrostatic field from vertically above;

a recovery container that is provided vertically below the electrostatic field and opens vertically above the electrostatic field, thereby recovering the resin sheet that has fallen down by the electrostatic field; and

a measuring sensor that measures a falling amount of the resin sheet in a measuring space between the electrostatic field and the recovery container,

said recovery vessels being separated by a plurality of separators, thereby forming a plurality of recovery partitions,

the electrostatic sorting apparatus further includes a computer configured to analyze the amount of the resin pieces falling in the collection section based on a predetermined fitting curve and the amount of the resin pieces falling in the measurement space measured by the measurement sensor.

2. The electrostatic sorting apparatus according to claim 1,

the measuring sensor is arranged above the plurality of recovery subareas in the vertical direction.

3. The electrostatic sorting apparatus according to claim 1,

the electrostatic sorting apparatus is provided with a plurality of the measurement sensors,

the plurality of measurement sensors are arranged above the plurality of recovery subareas in the vertical direction.

4. The electrostatic sorting apparatus according to claim 2,

the measuring sensor scans in the measuring space in a horizontal direction.

5. The electrostatic sorting apparatus according to any one of claims 1 to 4,

the measuring sensor is a load cell, and measures the weight of the resin sheet.

6. The electrostatic sorting apparatus according to any one of claims 1 to 4,

the measuring sensor is an optical sensor and measures the number of the resin sheets.

7. The electrostatic sorting apparatus according to claim 1,

the electrostatic separator further includes a driving unit for moving the separator in a horizontal direction,

the computer controls the driving unit to move the separator to a position corresponding to an analysis result of the amount of the resin pieces falling, thereby changing the collection capacity of the collection section.

8. The electrostatic sorting apparatus according to claim 1 or 7,

the electrostatic sorting apparatus further includes a power supply for applying a voltage to the pair of electrodes to generate the electrostatic field in the pair of electrodes,

the computer controls the output voltage of the power supply based on the analysis result of the falling amount of the resin sheet.

9. The electrostatic sorting apparatus according to claim 1 or 7,

the electrostatic separation device further comprises a temperature and humidity adjusting means disposed vertically above the recovery container for adjusting the temperature or humidity,

the computer controls the temperature and humidity adjusting device according to the analysis result of the falling amount of the resin sheet.

10. The electrostatic sorting apparatus according to claim 7,

the computer determines the initial position of the separator using the recovery purity of the resin sheet and the recovery rate of the resin sheet calculated from the analysis result of the amount of the resin sheet falling.

11. The electrostatic sorting apparatus according to claim 10,

the computer has a storage device for storing an analysis result of the amount of the resin pieces dropped, and determines the initial position of the separator using the recovery purity of the resin pieces and the recovery rate of the resin pieces calculated from the stored analysis result of the amount of the resin pieces dropped.

12. The electrostatic sorting apparatus according to claim 10 or 11,

the computer determines an initial position of the separator as a position where a recovery purity of the resin sheet is in a range of not less than a predetermined value and not more than 100%.

13. An electrostatic sorting method includes:

a step of measuring, with a measurement sensor, the amount of dropping of a plurality of types of resin sheets in a measurement space between an electrostatic field and a recovery container, the plurality of types of resin sheets being recovered by dropping the plurality of types of resin sheets into the recovery container by the electrostatic field generated between a pair of electrodes, the recovery container being provided vertically below the electrostatic field and opening vertically above; and

a step in which a computer analyzes the amount of the resin pieces dropped collected into the plurality of collection sections formed in the collection container based on a predetermined fitting curve and the amount of the resin pieces dropped into the measurement space measured in the measuring step,

the recovery vessel is separated by a plurality of separators, thereby forming the plurality of recovery partitions.

14. The electrostatic sorting method according to claim 13,

the electrostatic sorting method further includes a step in which the computer controls a driving unit that moves the separator to move the separator to a position corresponding to an analysis result of the amount of the resin pieces falling analyzed in the analyzing step.

15. The electrostatic sorting method according to claim 13 or 14,

the electrostatic sorting method further includes a step in which the computer controls a voltage of a power supply to be applied to the pair of electrodes so that the pair of electrodes generate the electrostatic field, based on an analysis result of the falling amount of the resin sheet analyzed in the analyzing step.

16. The electrostatic sorting method according to claim 13 or 14,

the electrostatic sorting method further includes a step in which the computer controls the temperature or humidity of a temperature and humidity adjustment device disposed vertically above the collection container based on the analysis result of the amount of the resin pieces dropped analyzed in the analyzing step.

17. The electrostatic sorting method according to claim 14,

the electrostatic sorting method further includes a step in which the computer determines an initial position of the separator using a recovery purity of the resin pieces and a recovery rate of the resin pieces, which are calculated from an analysis result of the amount of the resin pieces that have fallen.