JP2011245451A - Apparatus and method for electrostatic sorting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a plastic that is a sorting object with high purity and at high recovery rate even when impurities are mixed to a mixed plastic.SOLUTION: A recovery box 141 includes a strong triboelectric series product recovery chamber 141D, which is disposed at an end close to a negative electrode 131 for recovering, of a plurality of plastic pieces recovered in a negative electrode-side recovery box 141A, plastic pieces positively-charged more stronger than the other plastic pieces. A mixed plastic 101 containing ABS, SP, heavy PP and trace of PA is charged by a charging cylinder 121 and electrostatically separated by the electrostatic field between the electrodes. The ABS which is easily positively-charged is recovered in the negative electrode-side recovery box 141A, and the PS and heavy PP which are easily negatively-charged are recovered in a positive electrode-side recovery box 141B. Since the PA which is more easily positively-charged than ABS is captured in the strong triboelectric series product recovery chamber 141D, the ABS can be recovered in the negative electrode-side recovery box 141A with high purity and at high recovery rate.

Description

  The present invention relates to an electrostatic sorting apparatus and an electrostatic sorting method for electrostatically sorting mixed plastics, for example.

  2. Description of the Related Art Generally, a plastic electrostatic sorter that frictionally charges a material to be sorted including a plurality of types of plastic pieces and sorts each charged plastic piece with an electrostatic field is generally known.

The plastic piece is charged in accordance with a frictional charging sequence (hereinafter referred to as “charging column”).
A charged column is a sequence in which substances that are easily charged positively when friction is made between different materials are arranged on the upper side and substances that are easily charged negatively are arranged on the lower side.
For example, if the charging order of plastics is expressed in the order from positively charged to easily negatively charged, the order is “PA → ABS → PS → PE → PP → PET → PVC”.

  “PA” is polyamide (nylon), “ABS” is a polymer of acrylonitrile, butadiene and styrene, “PS” is polystyrene, “PE” is polyethylene, “PP” is polypropylene, “PET” is polyethylene terephthalate, “ “PVC” is polyvinyl chloride.

  By using the charging sequence, waste plastic can be sorted and reused.

Patent Document 1 discloses an electrostatic sorting device that sorts two or more types of plastic pieces (sorted materials).
This electrostatic sorting apparatus is generally composed of a loading stocker, a drying furnace, a loading hopper, a charging feeder, a charging cylinder, a loading feeder, an electrode unit, and a collection box.

The material to be sorted is transferred to the charging hopper and supplied to the charging cylinder by a charging feeder provided under the charging hopper. The feeding feeder adjusts the feeding speed of the material to be sorted into the charging cylinder by vibrating and feeding the material to be sorted into the charging cylinder. A certain amount of material to be sorted is put into the charging cylinder per unit time.
In the rotating charging cylinder, a plurality of types of plastic pieces constituting the material to be sorted are rubbed with each other, and each plastic piece is charged with a polarity (plus or minus) and a charge amount corresponding to the charge train. The charged material to be sorted causes pairing in which a positively charged plastic piece and a negatively charged plastic piece stick together by electrostatic force (Coulomb force).
The material to be sorted out from the charging cylinder is transferred to the carry-in feeder. The carry-in feeder eliminates the pairing of the materials to be sorted by the vertical pushing vibration that pushes forward the materials to be sorted while moving the materials up and down.
The material to be sorted whose pairing has been eliminated is dropped into an electrostatic field generated between electrodes to which a direct high voltage is applied. Then, each plastic piece contained in the material to be sorted is drawn toward one of the electrodes by an electrostatic force corresponding to the polarity and the charge amount while naturally dropping. Therefore, each plastic piece falls while drawing a parabolic trajectory.
The plastic pieces that fall along the parabolic trajectory are collected in a collection box provided under the electrodes.

Therefore, if the inside of the collection box is appropriately partitioned, plastic pieces can be collected for each type in each part of the collection box.
For example, if ABS, PS, and PP are included in the material to be sorted, if the collection box is divided into three parts, the negative electrode side, the positive electrode side, and the middle, the ABS is recovered on the negative electrode side, and the positive electrode side PS and PP can be recovered. In the middle, ABS, PS and PP are mixed and recovered.

JP 2005-138030 A JP 2000-342998 A

The electrostatic sorter for plastics is a mixture of crushed plastic collected by crushing and sorting household electrical appliances, etc., and tribo-charging the mixed plastic collected by wet specific gravity sorting. Sort into plastic groups.
Such an electrostatic sorting device for plastic also collects unsorted plastic that is more easily charged positively than the plastic to be sorted in the collection box on the negative electrode side. As a result, the purity of the plastic to be sorted collected in the collection box on the negative electrode side is lowered.

  An object of the present invention is to make it possible to recover a plastic to be sorted with high purity and a high recovery rate even when impurities are mixed in the mixed plastic, for example.

The electrostatic sorting device of the present invention is
A charging unit for charging a plurality of pieces to be sorted having different charging characteristics;
A plurality of pieces to be sorted having a plus electrode to which a plus voltage is applied and a minus electrode to which a minus voltage is applied, and being charged by the charging unit and falling between the plus electrode and the minus electrode An electrostatic separation portion that draws the positive electrode and the negative electrode to one of the electrodes,
A collection box that is disposed below the positive electrode and the negative electrode and collects a plurality of pieces to be sorted, and that is disposed on the positive electrode side and collects a plurality of pieces to be negatively charged. A collection box having an electrode-side collection unit and a minus electrode-side collection unit that collects a plurality of pieces to be sorted that are arranged on the minus electrode side and are positively charged;
The collection box is arranged at an end of the collection box on the negative electrode side, and the pieces to be sorted that are more positively charged than other pieces to be sorted among the plurality of pieces to be collected collected by the minus electrode side collection unit. A strong positive charge recovery part that collects the positive electrode and a positive electrode side of the recovery box that is disposed at the end on the positive electrode side, and is more strongly negative than the other pieces to be selected among a plurality of pieces to be collected on the positive electrode side recovery part It has at least any one of the strong minus charge collection | recovery part which collect | recovers the to-be-sorted charged piece.

  According to the present invention, for example, even when impurities (sorted pieces to be positively charged) are mixed in mixed plastic, the plastic to be sorted (selected pieces to be positively charged) is highly purified and highly recovered. It can be recovered at a rate.

FIG. 3 is a schematic diagram showing a plastic sorting method in the first embodiment. 1 is a perspective view showing a structure of a plastic electrostatic sorting device 100 according to Embodiment 1. FIG. The block diagram of the collection box 141 of the plastic electrostatic sorting apparatus 100 in Embodiment 1. FIG. FIG. 3 is a configuration diagram of a negative electrode side recovery box 141A of the plastic electrostatic sorting device 100 according to the first embodiment. The perspective view which shows the structure of the plastic electrostatic sorting apparatus 100 in Embodiment 2. FIG. The block diagram of the stock | stock part 150 in Embodiment 2. FIG. FIG. 6 shows a switching valve 154 according to Embodiment 2.

Embodiment 1 FIG.
Electrostatic sorting to improve the collection purity of the plastic to be sorted by providing a strongly charged column collection room to capture a small amount of plastic that is more likely to be positively charged than the sorting target at the upper end of the collection box on the negative electrode side The apparatus will be described.

FIG. 1 is a schematic diagram showing a plastic sorting method in the first embodiment.
An outline of the plastic sorting method in the first embodiment will be described with reference to FIG.

In home appliance recycling, large-sized plastic members that are easy to remove and disassemble by hand dismantling home appliances are collected, and the collected plastic members are reused as materials for new products. However, the amount of plastic that can be recovered by manual disassembly is small.
The remaining plastic that could not be recovered by manual dismantling is crushed and sorted as crushed mixed plastic as shown in FIG.

  The crushing and mixing plastic is a mixture of PP, ABS, PS, PE, PET, PVC, PA, and the like.

First, the crushed mixed plastic is sorted by a wet specific gravity sorting process.
In the wet specific gravity sorting process, the water is sorted into PP having a specific gravity of less than 1.0, heavy specific plastic having a specific gravity of 1.1 or more, and mixed plastic having a specific gravity of 1.0 or more and less than 1.1 (wet process). Specific gravity selection).

Next, foreign materials such as rubber and magnetic material are removed from the mixed plastic having a specific gravity of 1.0 or more and less than 1.1, and the mixed plastic from which the foreign materials have been removed is sorted by electrostatic sorting.
ABS, PS, heavy PP, and a small amount of PA are mixed in the mixed plastic subjected to electrostatic sorting. Heavy PP is PP containing glass used for parts such as washing machines. PA is used for a cellular phone case, a band for binding a power cord, and the like, and is used in a small amount.
The charged series of the mixed plastic is “PA → ABS → PS → heavy PP” in order from the one that tends to be positively charged.

  In the first stage electrostatic sorting, the mixed plastic is triboelectrically charged, and the positively charged ABS and the negatively charged PS and heavy PP are sorted. At the same time, a small amount of PA that is positively charged more strongly than ABS is selected. Thereby, ABS can be recovered with high purity and high recovery rate.

In the second stage electrostatic sorting, a mixed plastic of PS and heavy PP charged negatively in the first stage electrostatic sorting is sorted. In this mixed plastic, in addition to PS and heavy PP, a small amount of ABS that could not be correctly sorted by the first stage electrostatic sorting is mixed.
In the second stage electrostatic sorting, the mixed plastic is triboelectrically charged again and sorted into a positively charged PS and a negatively charged heavy PP. At the same time, a small amount of ABS that is more positively charged than PS is selected. Thereby, PS can be recovered with high purity and high recovery rate.

  As mentioned above, by sorting the impurities contained in a small amount in the mixed plastic (PA in the first stage electrostatic sorting) at the same time as the target to be originally sorted (ABS, PS, PP in the first stage electrostatic sorting), The electrostatic sorting process can be simplified.

  The first stage electrostatic sorting will be described in the first embodiment, and the second stage electrostatic sorting will be described in the second embodiment.

FIG. 2 is a perspective view showing the structure of the plastic electrostatic sorting device 100 according to the first embodiment.
The configuration and operation of the plastic electrostatic sorting apparatus 100 according to Embodiment 1 will be described with reference to FIG. In FIG. 2, the arrows indicate the paths of the mixed plastic 101.

  First, the configuration of the plastic electrostatic sorting apparatus 100 will be described.

  The plastic electrostatic sorting device 100 (an example of an electrostatic sorting device) includes a frictional charging pre-processing unit 110, a frictional charging unit 120, an electrostatic separation unit 130, and a recovery unit 140.

The frictional charging pre-processing unit 110 is a part for feeding the mixed plastic 101 (an example of a material to be sorted) into the frictional charging unit 120.
The frictional charging pre-processing unit 110 includes a charging stocker 111, a dryer 112, a charging hopper 113, and a charging feeder 114.

The friction charging unit 120 rubs and charges a plurality of plastic pieces (an example of a piece to be sorted) mixed in the mixed plastic 101 input from the friction charging pre-processing unit 110, and electrostatically charges the plurality of plastic pieces charged. This is the part that is carried into the separation unit 130.
The friction charging unit 120 includes a charging cylinder 121 (an example of a charging unit), a carry-in feeder 122, and a feeder driving device 123.

The electrostatic separation unit 130 is a part that electrostatically separates a plurality of plastic pieces carried from the frictional charging unit 120.
The electrostatic separation unit 130 includes a negative electrode 131 to which a negative voltage is applied, a positive electrode 132 to which a positive voltage is applied, and a voltage control device 133 that applies a predetermined voltage to each electrode.

The collection unit 140 is a part that collects a plurality of plastic pieces electrostatically separated by the electrostatic separation unit 130.
The collection unit 140 includes a collection box 141 disposed below the negative electrode 131 and the positive electrode 132.

The collection box 141 includes a minus electrode side collection box 141A (minus electrode side collection unit), a plus electrode side collection box 141B (plus electrode side collection unit), and a middle collection box 141C (middle collection unit).
The minus electrode side collection box 141A collects plastic pieces that are arranged on the minus electrode 131 side and are positively charged.
The plus electrode side collection box 141B collects plastic pieces that are arranged on the plus electrode 132 side and are negatively charged.
The middle collection box 141C is disposed between the minus electrode side collection box 141A and the plus electrode side collection box 141B, and collects plastic pieces that are not collected in either the minus electrode side collection box 141A or the plus electrode side collection box 141B. .

The negative electrode side collection box 141A is a strongly charged column product collection room 141D (strong plus charge) that collects plastic pieces that are more positively charged than other plastic pieces among a plurality of plastic pieces collected in the negative electrode side collection box 141A. (Collecting part).
The strongly charged column product collection chamber 141D is located at the end of the collection box 141 on the negative electrode 131 side.

  Next, the operation of the plastic electrostatic sorting apparatus 100 will be described with reference to FIG.

  The mixed plastic 101 is replenished to the input stocker 111 at any time or periodically.

  The mixed plastic 101 is supplied from the input stocker 111 to the dryer 112 and dried by the dryer 112.

The mixed plastic 101 dried by the dryer 112 is transferred to the charging hopper 113 and supplied to the charging cylinder 121 by the charging feeder 114 provided under the charging hopper 113.
The feeding feeder 114 adjusts the feeding speed of the mixed plastic 101 into the charging cylinder 121 by vibrating. The charging cylinder 121 is charged with a certain amount of the mixed plastic 101 per unit time.

The charging cylinder 121 rotates to stir the mixed plastic 101.
In the charging cylinder 121, a plurality of plastic pieces constituting the mixed plastic 101 are rubbed with each other, and each plastic piece is charged with a polarity (plus or minus) and a charge amount corresponding to the charging column.
The charging cylinder 121 is made of a material having specific charging characteristics (for example, ABS), and the charging cylinder 121 itself is charged according to the charging train.

The mixed plastic 101 coming out of the charging cylinder 121 is transferred to the carry-in feeder 122 through the shooter. At this time, the mixed plastic 101 causes pairing in which a positively charged plastic piece and a negatively charged plastic piece stick together by electrostatic force.
The carry-in feeder 122 eliminates the pairing of the mixed plastic 101 by the vertical pushing vibration that pushes the mixed plastic 101 forward while moving the mixed plastic 101 up and down.
The feeder driving device 123 pushes the carry-in feeder 122 up and down to vibrate.

The voltage control device 133 applies a high DC voltage to the negative electrode 131 and the positive electrode 132 to create an electrostatic field between the electrodes.
The mixed plastic 101 whose pairing is eliminated by the carry-in feeder 122 is dropped between the electrodes (electrostatic field). Then, each plastic piece constituting the mixed plastic 101 naturally falls while being drawn toward one of the electrodes by an electrostatic force corresponding to the polarity and the charge amount.
That is, each plastic piece draws a parabolic trajectory corresponding to the polarity and the charge amount and falls to a different position.

Below the minus electrode 131 and the plus electrode 132, a collection box 141 divided into a minus electrode side collection box 141A, a plus electrode side collection box 141B, and a middle collection box 141C is installed.
The negative electrode side recovery box 141A has a strongly charged column product recovery chamber 141D.

  Each plastic piece is collected in the negatively charged column product collection chamber 141D provided in the minus electrode side collection box 141A, the plus electrode side collection box 141B, the middle collection box 141C, or the minus electrode side collection box 141A according to the dropping position. .

As described with reference to FIG. 1, the mixed plastic 101 contains a small amount of PA as an impurity in addition to ABS, PS, and heavy PP as a plastic piece. The weight ratios of ABS, PS, heavy PP and PA are approximately 50%, 40%, 8% and 2% on average.
The charged rows of these plastic pieces are “PA → ABS → PS → heavy PP” in order from those that are easily charged positively.

Since PA and ABS are easily charged positively, they are recovered in the negative electrode side recovery box 141A, and PS and heavy PP are easily charged negatively, so they are recovered in the positive electrode side recovery box 141B and are not sufficiently charged. , PS and heavy PP are collected in the middle collection box 141C.
However, since PA is more easily charged positively than ABS, it is attracted to the negative electrode 131 larger than ABS, and is selectively collected in the strongly charged column product recovery chamber 141D provided in the negative electrode side recovery box 141A.

  Thereby, ABS can be recovered with high purity and a high recovery rate.

The purity is the ratio of the target plastic piece to the plastic piece collected in the collection box.
For example, when 50 kg of ABS and 2 kg of PA are collected in the negative electrode side collection box 141A (including the strongly charged column product collection room 141D), the purity of the ABS is 96% (= 50 kg / (50 kg + 2 kg)). .
Here, if 1.5 kg of PA is collected in the strongly charged column product recovery chamber 141D, the negative electrode side recovery box 141A (excluding the strongly charged column product recovery chamber 141D) has 50 kg of ABS and 0.5 kg. (= 2.0 kg-1.5 kg) of PA was recovered.
That is, by providing the strongly charged column product recovery chamber 141D, it is possible to recover ABS with a higher purity of 99% (= 50 kg / (50 kg + 0.5 kg)).

The recovery rate is the ratio of the amount of the target plastic piece collected in the collection box to the amount of the target plastic piece contained in the mixed plastic.
For example, when 50 kg of ABS is included in the mixed plastic 101 and 40 kg of ABS is recovered in the negative electrode side recovery box 141A, the ABS recovery rate is 80% (= 40 kg / 50 kg).

  The PA recovered in the strongly charged column product recovery chamber 141D is discarded, and the ABS recovered in the negative electrode side recovery box 141A is reused as a resource.

  The mixed plastic of PA, ABS, PS, and heavy PP collected in the middle collection box 141C is processed again by the plastic electrostatic sorter 100. At this time, if each plastic piece constituting the mixed plastic is sufficiently charged by the charging cylinder 121, each plastic piece is electrostatically separated between the electrodes and is collected in the collection box 141.

The mixed plastic of PS and heavy PP recovered in the positive electrode side recovery box 141B may contain a small amount of ABS that could not be correctly sorted. Therefore, the mixed plastic of PS, heavy PP, and a small amount of ABS collected in the plus electrode side collection box 141B is processed again by the plastic electrostatic sorter 100.
The reprocessing of the mixed plastic will be described in Embodiment 2.

FIG. 3 is a configuration diagram of the collection box 141 of the plastic electrostatic sorting device 100 according to the first embodiment.
The configuration of the collection box 141 of the plastic electrostatic sorting apparatus 100 in the first embodiment will be described below with reference to FIG.

For simplification of explanation, it is assumed that the minus electrode 131 and the plus electrode 132 form a substantially vertical plane having the same size and face each other in parallel. In the electric field Ef (electrostatic field) between the electrodes, a Coulomb force E (electric force) is generated in a substantially horizontal direction.
Further, the electric field generated in the space other than between the electrodes is not considered because the Coulomb force is very small as compared with the electric field Ef between the electrodes.
In addition, the plastic piece 102 forms a granular material, and the air resistance applied to the plastic piece 102 is small, and the air resistance is not considered.

  The plastic piece 102 that naturally falls moves in the horizontal direction while accelerating in response to the Coulomb force E in the electric field Ef, and moves in the horizontal direction at a constant speed until it is recovered in the recovery box 141 after passing through the electric field Ef.

The horizontal acceleration a _y applied to the plastic piece 102 in the electric field Ef is expressed as follows using the Coulomb force E of the electric field Ef and the charge amount q / m (m: mass, q: charge amount) per mass of the plastic piece 102. (1a).
The Coulomb force E of the electric field Ef can be expressed by the following formula (1b) using the voltage V applied to the electrodes and the distance d between the electrodes.

The horizontal distance y (t ₁ ) in which the plastic piece 102 moves within the electric field Ef can be expressed by the following equation (2a) by integrating the acceleration a _y twice.
Further, the horizontal velocity v _y (t ₁ ) of the plastic piece 102 when passing through the electric field Ef can be expressed by the following equation (2b) by integrating the acceleration a _y once.
The horizontal distance y (t ₂ −t ₁ ) in which the plastic piece 102 moves from the electric field Ef to the collection box 141 reaches the collection box 141 after the plastic piece 102 passes through the electric field Ef. it can be expressed time to reach the _"t 2 -t _1" by multiplying the velocity _{v y} of the following formula (2c).

However, the time when the plastic piece 102 is positioned at the upper end of the electric field Ef (falling start time) is “0”, and the time when the plastic piece 102 reaches the lower end of the electric field Ef is “t ₁ ”. The time when the plastic piece 102 reaches the upper end of the collection box 141 is “t ₂ ”.

That is, the horizontal movement distance y (t ₂ ) of the plastic piece 102 is expressed by the movement distance y (t ₁ ) within the electric field Ef and the movement distance y (t ₂ −t ₁ ) after passing through the electric field Ef. The sum can be expressed by the following formula (3).

In the above formula (3), the time t ₁ when the plastic piece 102 reaches the lower end of the electric field Ef and the time t ₂ when the plastic piece 102 reaches the upper end of the collection box 141 are obtained as follows. .

The plastic piece 102 receives gravity in the vertical direction and falls while accelerating.
The falling distance x (vertical moving distance) of the plastic piece 102 can be expressed by the following equation (4a) by integrating the gravitational acceleration g twice.
The time t when the plastic piece 102 falls by the distance x can be expressed by the following formula (4b) based on the formula (4a).
However, the drop start time of the plastic piece 102 is set to “0”, and the drop speed (vertical speed) of the plastic piece 102 at the drop start time is set to “0”.

Here, the fall distance x of the plastic piece 102 at time t ₁ is equal to the height h ₁ of the electric field Ef.
Further, the falling distance x of the plastic piece 102 at time t ₂ is “h ₁ + h ₂ ”, which is the sum of the height h ₁ of the electric field Ef and the height h ₂ from the lower end of the electric field Ef to the upper end of the collection box 141. is there.
When these fall distance x into equation (4b) of the time t ₁ can be represented by the following formula (5a), the time t ₂ can be expressed by the following equation (5b).

The horizontal movement distance y (t ₂ ) of the plastic piece 102 is calculated by substituting the above equations (5a) and (5b) into the time t ₁ and the time t ₂ in the above equation (3). (6).

The size of the strongly charged column product collection room 141D can be determined as follows based on the horizontal movement distance y (t ₂ ) of the plastic piece 102 obtained by the above equation (6).

FIG. 4 is a configuration diagram of the negative electrode side collection box 141A of the plastic electrostatic sorting apparatus 100 according to the first embodiment.
4, strongly charged column article collecting room 141D provided on an end portion of the negative electrode side collection box 141A has a size including a position shifted by shift amount Δy from the center line L _A of the negative electrode side collection box 141A. In particular, good position shifted by shift amount Δy from the center line L _A is in strong triboelectric series article collecting room center of 141D (or near the center).
The center line L is a vertical line including the position where the plastic piece 102 falls most. However, the drop position of the plastic piece 102 is assumed to be normally distributed.
The shift amount [Delta] y, plastic pieces 102 to recover to the center line _{L A} and strongly charged column article collecting room 141D of plastic pieces 102 to recover the negative electrode side collection box 141A (ABS) between the center line _{L D} of (PA) Distance.
The shift amount Δy is obtained as follows using the above equation (6).

For example, it is assumed that the difference q / m in the charge amount per mass between PA and ABS is 10 [nc / g]. Further, E = 300 [kV / m], g = 9.8 [m / s ² ], h ₁ = 20 [cm], and h ₂ = 100 [cm].
A value y (t ₂ ) = 24 [cm] obtained by substituting these values into the above equation (6) is Δy.
That is, it is possible to be provided a strong triboelectric series article collecting room 141D to include a position deviated 24cm from the center line L _A of the negative electrode side collection box 141A, efficiently collecting a small amount of PA.

In addition, only y (t ₂ ) obtained by substituting the charge amount q / m per mass of PA into the above equation (6), not the difference in charge amount q / m per mass between PA and ABS, a strong triboelectric series article collecting room 141D may be provided to include a location away from the fall line L _F of the PA.
The fall line L _F of PA, a vertical line containing the drop starting position of PA (for example, a vertical line including the tip of the loading feeder 122).

In the first embodiment, for example, the following plastic electrostatic sorting apparatus 100 has been described.
The plastic electrostatic sorting apparatus 100 has a strongly charged column product collection room 141D at the uppermost portion of the minus electrode side collection box 141A farthest from the minus electrode 131.
Since PA is located on the plus side of ABS in the electrification column, PA is pulled to the minus electrode 131 side of ABS and falls to a position away from minus electrode 131 in collection box 141. Therefore, PA is selectively collected in the strongly charged column product collection room 141D.
On the other hand, the ABS drops before the strongly charged column product recovery chamber 141D and is recovered in the negative electrode side recovery box 141A.
As a result, PA is not mixed in the negative electrode side recovery box 141A, and ABS can be recovered with high purity.

In the first embodiment, the combination of plastic pieces mixed in the mixed plastic 101 is not limited to a combination of ABS, PS, heavy PP, and a small amount of PA.
That is, other plastic pieces (PE, PET, PVC, etc.) may be selected. Furthermore, it is also possible to select items other than plastic pieces.

  Further, a positively charged column product recovery chamber is provided in the positive electrode side recovery box 141B to collect plastic pieces that are charged more negatively than the plastic pieces (eg, PS, PP) to be recovered in the positive electrode side recovery box 141B. It doesn't matter.

In addition, the pair of electrodes (the negative electrode 131 and the positive electrode 132) of the electrostatic separation unit 130 may have any configuration.
For example, it may be arranged in parallel, in a C-shape (mountain shape), or one may be a drum electrode as disclosed in Patent Document 2.

  Further, the method of frictionally charging the mixed plastic 101 is not limited to the method using the charging cylinder 121.

Embodiment 2. FIG.
The second stage electrostatic sorting (see FIG. 1) will be described.
Hereinafter, items different from the first embodiment will be mainly described. Matters whose description is omitted are the same as those in the first embodiment.

FIG. 5 is a perspective view showing the structure of the plastic electrostatic sorting device 100 according to the second embodiment.
The configuration and operation of the plastic electrostatic sorting apparatus 100 according to the second embodiment will be described with reference to FIG.

  The plastic electrostatic sorting apparatus 100 includes a stock unit 150 (circulation unit) in addition to the configuration described in the first embodiment (see FIG. 2). Further, the dryer 112 described in Embodiment 1 is not necessary.

The stock unit 150 bags the ABS collected in the negative electrode side collection box 141A at the end of the first stage electrostatic sorting (see FIG. 1) and the mixed plastic collected in the middle collection box 141C. .
Then, the stock unit 150 circulates the mixed plastic 103 of PS and heavy PP collected in the plus electrode side collection box 141 </ b> B to the input stocker 111.
However, the mixed plastic 103 includes a small amount of ABS that cannot be correctly sorted by the first stage electrostatic sorting in addition to PS and heavy PP.
In addition, when the mixed plastic 103 is circulated through the input stocker 111, the input stocker 111 is assumed to be empty. That is, only the mixed plastic 103 is electrostatically sorted again.
In addition, it is assumed that a small amount of PA collected in the strongly charged column product collection room 141D by the first stage electrostatic sorting has been removed.

The mixed plastic 103 circulated to the input stocker 111 is charged by the charging cylinder 121 as in the first embodiment (see FIG. 2), electrostatically separated by the electrostatic field between the electrodes, and sorted by the collection box 141.
The mixed plastic 103 contains PS, heavy PP, and a small amount of ABS. The weight ratio of PS, heavy PP and PA is approximately 60%, 38% and 2% on average. Further, the charging column of each plastic piece is “ABS → PS → heavy PP” in order of positive charging.
Therefore, a small amount of ABS is collected in the strongly charged column product collection chamber 141D, PS is collected in the minus electrode side collection box 141A, and heavy PP is collected in the plus electrode side collection box 141B. Further, PS, heavy PP, and a small amount of ABS are mixed and collected in the middle collection box 141C.
Thereby, PS can be recovered in the negative electrode side recovery box 141A with high purity and high recovery rate.

  The ABS collected in the strongly charged column product collection room 141D and the heavy PP collected in the plus electrode side collection box 141B are discarded, and the PS collected in the minus electrode side collection box 141A is reused as a resource.

  The mixed plastic of ABS, PS, and heavy PP collected in the middle collection box 141C is processed again by the plastic electrostatic sorter 100. At this time, if each plastic piece constituting the mixed plastic is sufficiently charged by the charging cylinder 121, each plastic piece is electrostatically separated between the electrodes and is collected in the collection box 141.

  The strongly charged column product collection room 141D may be replaced at the start of the second stage electrostatic sorting and installed at a position corresponding to the mass q / m per unit of ABS.

For example, it is assumed that the difference q / m in the charge amount per mass of ABS and PS is 20 [nc / g]. In FIG. 3, it is assumed that E = 300 [kV / m], g = 9.8 [m / s ² ], h ₁ = 20 [cm], and h ₂ = 100 [cm].
Substituting these values into the equation (6) described in the first embodiment yields y (t ₂ ) = Δy = 48 [cm].
That is, it is possible to be provided a strong triboelectric series article collecting room 141D to include a position deviated 48cm from the center line L _A of the negative electrode side collection box 141A, efficiently collecting ABS traces.

FIG. 6 is a configuration diagram of the stock unit 150 according to the second embodiment.
The configuration of the stock unit 150 in the second embodiment will be described below with reference to FIG.

The stock unit 150 includes a transport device 151 (for example, a belt conveyor), a hopper 152, a flexible container 153 (flexible container bag), a switching valve 154, and a circulation transport device 155 (for example, a belt conveyor).
The conveyor 151, the hopper 152, and the flexible container 153 are provided in the lines of the negative electrode side recovery box 141A, the middle recovery box 141C, and the positive electrode side recovery box 141B, respectively.
The switching valve 154 and the circulating transfer device 155 are provided only in the line for the positive electrode side collection box 141B.

The switching valve 154 is provided between the hopper 152B and the flexible container 153B on the line of the positive electrode side collection box 141B.
The circulation transporter 155 is provided between the switching valve 154 and the input stocker 111.

At the end of the first stage electrostatic sorting (see FIG. 1), the transporter 151A transports the ABS collected in the negative electrode side collection box 141A and puts it in the hopper 152A, and the hopper 152A releases the put ABS. And bag the flexible container 153A.
The conveyor 151C conveys the mixed plastic collected in the middle collection box 141C and puts it in the hopper 152C. The hopper 152C discharges the mixed plastic that has been put in and packs it in the flexible container 153C.
Further, the transport device 151B transports the mixed plastic 103 collected in the positive electrode side collection box 141B and puts it into the hopper 152B.

  At the start of the second stage electrostatic sorting (see FIG. 1), the switching valve 154 is closed (see FIG. 7 (a)), the hopper 152B releases the mixed plastic 103, and the circulating transfer machine 155 feeds the mixed plastic into the stocker 111. Transport to.

At the end of the second stage electrostatic sorting, the transport device 151A transports the PS collected in the negative electrode side collection box 141A and puts it in the hopper 152A, and the hopper 152A releases the put PS and bags it in the flexible container 153A. Stuff.
At the end of the second stage electrostatic sorting, the switching valve 154 is opened (FIG. 7B). The transporter 151B transports the heavy PP collected in the positive electrode side collection box 141B and puts it into the hopper 152B, and the hopper 152B discharges the loaded heavy PP and packs it in the flexible container 153B.
The conveyor 151C conveys the mixed plastic collected in the middle collection box 141C and puts it in the hopper 152C. The hopper 152C discharges the mixed plastic that has been put in and packs it in the flexible container 153C.

FIG. 7 is a diagram illustrating the switching valve 154 according to the second embodiment.
The switching valve 154 according to the second embodiment will be described below with reference to FIG.

  The switching valve 154 is a rotating body having an L-shaped cross section. The position of the switching valve 154 is below the hopper 152B and above the flexible container 153B.

  The switching valve 154 closes the lower part at the start of (a) the second stage electrostatic sorting, and (b) opens the lower part at the end of the second stage electrostatic sorting.

  The switching valve 154 can be switched between (a) a closed state and (b) a released state by, for example, a switch.

In the second embodiment, for example, the following plastic electrostatic sorting apparatus 100 has been described.
The plastic electrostatic sorting apparatus 100 has a strongly charged column product collection room 141D at the uppermost portion of the minus electrode side collection box 141A farthest from the minus electrode 131.
Since ABS is positioned on the positive side of PS in the charged column, ABS is pulled to the negative electrode 131 side of PS and falls in a position away from the negative electrode 131 in the collection box 141. Accordingly, ABS is selectively collected in the strongly charged column product collection room 141D.
On the other hand, PS falls before the strongly charged column product recovery chamber 141D and is recovered in the negative electrode side recovery box 141A.
As a result, ABS is not mixed in the negative electrode side recovery box 141A, and PS can be recovered with high purity.

In the second embodiment, the switching valve 154 and the circulation transfer device 155 may be provided in the line of the middle collection box 141C.
Then, the mixed plastic (ABS, PS, heavy PP, PA) collected in the middle recovery box 141C by the first stage electrostatic sorting or the mixed plastic (PS that is collected in the middle collection box 141C by the second stage electrostatic sorting. , Heavy PP, ABS) to the stocker. If the circulated mixed plastic is sufficiently charged by the charging cylinder 121, it is electrostatically separated by the electrostatic field between the electrodes and sorted into the collection box 141. Thereby, a recovery rate can be improved.

  DESCRIPTION OF SYMBOLS 100 Plastic electrostatic sorter, 101 Mixed plastic, 102 Plastic piece, 103 Mixed plastic, 110 Friction pre-treatment part, 111 Input stocker, 112 Dryer, 113 Input hopper, 114 Input feeder, 120 Friction charging part, 121 Charge cylinder , 122 carry-in feeder, 123 feeder drive device, 130 electrostatic separation unit, 131 negative electrode, 132 positive electrode, 133 voltage control device, 140 recovery unit, 141 recovery box, 141A negative electrode side recovery box, 141B positive electrode side recovery box , 141C Middle collection box, 141D Strongly charged column product collection room, 150 Stock section, 151, 151A, 151B, 151C Transporter, 152, 152A, 152B, 152C Hopper, 153, 153A, 153B, 153C flexible container, 154 changeover valve, 155 circulation conveyor.

Claims (4)

A charging unit for charging a plurality of pieces to be sorted having different charging characteristics;
A plurality of pieces to be sorted having a plus electrode to which a plus voltage is applied and a minus electrode to which a minus voltage is applied, and being charged by the charging unit and falling between the plus electrode and the minus electrode An electrostatic separation portion that draws the positive electrode and the negative electrode to one of the electrodes,
A collection box that is disposed below the positive electrode and the negative electrode and collects a plurality of pieces to be sorted, and that is disposed on the positive electrode side and collects a plurality of pieces to be negatively charged. A collection box having an electrode-side collection unit and a minus electrode-side collection unit that collects a plurality of pieces to be sorted that are arranged on the minus electrode side and are positively charged;
The collection box is arranged at an end of the collection box on the negative electrode side, and the pieces to be sorted that are more positively charged than other pieces to be sorted among the plurality of pieces to be collected collected by the minus electrode side collection unit. A strong positive charge recovery part that collects the positive electrode and a positive electrode side of the recovery box that is disposed at the end on the positive electrode side, and is more strongly negative than the other pieces to be selected among a plurality of pieces to be collected on the positive electrode side recovery part An electrostatic sorting apparatus comprising at least one of a strong minus charge collection unit for collecting charged pieces to be sorted. The collection box is disposed between the plus electrode side collection unit and the minus electrode side collection unit and includes a plurality of pieces to be sorted that are not collected by either the plus electrode side collection unit or the minus electrode side collection unit. The electrostatic sorting apparatus according to claim 1, further comprising a middle collection unit for collecting. The collection box has the strong plus charging unit in the minus electrode side collection unit,
The electrostatic sorting device further includes:
3. The electrostatic sorting apparatus according to claim 1, further comprising a circulation unit that circulates a plurality of pieces to be sorted collected in the plus electrode side collection unit of the collection box to the charging unit. The charging unit charges a plurality of pieces to be sorted with different charging characteristics,
The electrostatic separation unit has a positive electrode to which a positive voltage is applied and a negative electrode to which a negative voltage is applied. The electrostatic separation unit is charged by the charging unit and falls between the positive electrode and the negative electrode. To draw a plurality of pieces to be sorted to one of the positive electrode and the negative electrode,
A collection box is disposed below the plus electrode and the minus electrode, and includes a plus electrode side collection unit disposed on the plus electrode side and a minus electrode side collection unit disposed on the minus electrode side. A plurality of negatively charged pieces to be collected in the positive electrode side collecting section, and a plurality of positively charged pieces to be collected are collected in the negative electrode side collecting section,
The recovery box has a strong positive charge recovery portion at an end of the recovery box on the negative electrode side, and the negative electrode is used when a plurality of positively charged pieces are recovered in the negative electrode side recovery portion. An electrostatic sorting method characterized in that a piece to be sorted, which is more positively charged than other pieces to be sorted among a plurality of pieces to be sorted collected by the side collection unit, is collected by the strong plus charge collection unit.

Images