JP2010119911A - Electrostatic sorting method and electrostatic sorting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic sorting method and an electrostatic sorting apparatus, for highly accurately sorting and recovering granular plastic used for recycling, for every material. <P>SOLUTION: The electrostatic sorting apparatus comprises: granular plastics 2a, 2b made of different materials; a charging device 3 for charging the granular plastics 2a, 2b; a sending device 4 which disperses the granular plastics 2a, 2b charged by the charging device 3 and gives such a kinetic energy that the granular plastics reach the upper side; a pair of electrodes 5a, 5b; electric fields 7, 7h formed by the electrodes 5a, 5b; and recovery containers 8a, 8b for respectively recovering the granular plastics 2a, 2b which are sent from the sending part 4f to the high electric field 7h by the sending device 4 and sorted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to, for example, an electrostatic sorting method and an electrostatic sorting apparatus for sorting and collecting granular plastics used for recycling by material.

  In order to collect plastic materials from products and recycle them, it is required to sort and collect the crushed granular plastics by material. For this reason, electrostatic sorting methods are widely used in which granular plastics are charged and sorted by an external electric field depending on the charged state depending on the material. Furthermore, it is required to improve the quality of plastic products using recycled materials by improving the material selection accuracy.

Therefore, in the electrostatic sorting apparatus according to Patent Document 1, a plurality of types of granular materials such as charged plastics are charged by being dropped between two electrodes that are arranged opposite to each other and to which an electric field is applied. In an electrostatic sorting device that separates granular materials with electrostatic force according to the amount of positive and negative charges, a transport path made of an insulating material that transports a plurality of types of granular materials while leveling in the direction of the falling portion with a drop portion formed at the tip. And a conveying device having a drive source for applying vibration to the conveying path, a first electrode extending in the dropping direction from immediately below the dropping portion of the conveying device, and a first portion from a front portion of the dropping portion of the conveying device. By providing a counter electrode, which is a second electrode that is disposed opposite to the first electrode and is charged positively or negatively with respect to the first electrode, even if the frictional charge amount of a granular material such as plastic is small, an error occurs. Eliminate sorting It can be screened well reliably every time. The mixed granular plastic is transported without discharging the charge applied at the charging part. Alternatively, by optimizing the material of the insulating material, the charge amount can be further increased by the friction between the mixed granular plastic and the transport surface on the transport path. As a result, even when the frictional electrification amount of the crushed plastic granule is small, it is possible to eliminate the erroneous sorting due to insufficient charging and to accurately and reliably sort.
JP 2005-138030 A

  However, in the conventional electrostatic sorting apparatus, when a mixture of a plurality of granular plastics made of different materials is sent to the electric field, the initial speed is suppressed and the sorting accuracy is improved by a certain amount. There is a limit to the improvement due to the restriction of the positional relationship with the electrodes provided in. Specifically, a minimum clearance (for example, about 4 cm) is required between the vibrating transfer device and the electrode located below to avoid collision of members, and as a result, the initial speed is reduced. There is a problem that the improvement of the sorting performance (recovery rate) cannot be obtained sufficiently (for example, the design cannot make the initial velocity in the downward direction zero). In addition, in the conventional electrostatic sorting apparatus, there is a limit to the improvement of the sorting accuracy due to the configuration of the sorting unit, and instability occurs in the conveyance of the mixture of granular plastics, and it is difficult to further improve the sorting accuracy. There was a problem.

  The present invention has been made in order to solve the above-described problems, and is capable of stably supplying a mixture of granular plastics to the sorting unit and further improving the sorting accuracy. It is an object of the present invention to provide an electrostatic sorting method and an electrostatic sorting apparatus.

  In order to solve the above-described problems, an electrostatic sorting method according to the present invention charges a mixture of a plurality of types of granular plastics made of different materials, and in the electric field, the charged granular plastics are placed above the delivery unit. The granular plastic is sorted according to the material according to the amount of charge charged to the granular plastic.

  The electrostatic sorting apparatus according to the present invention includes a charging device that charges a mixture of a plurality of types of granular plastics made of different materials, a pair of electrodes that form an electric field, and the charged granular plastics in the electric field. A delivery device having a delivery portion made of a conductive material to be delivered, and for delivering the granular plastic above the delivery portion of the delivery device, and disposed opposite to the delivery device forming an electric field. The upper end of one electrode is set to be higher than the arrival height of the delivered granular plastic, and the other electrode arranged below the delivery unit of the delivery device is held at the same potential as the delivery unit and charged to the granular plastic. The granular plastic is sorted according to the material according to the amount of electric charge.

  According to the present invention, by giving upward kinetic energy to a plurality of types of granular plastics made of different materials and sending them into an electric field, even if the amount of charged electric charge is small or the electric field region is short. It has a remarkable effect that the granular plastic can be efficiently sorted by material with high accuracy.

Hereinafter, an electrostatic sorting method and an electrostatic sorting apparatus according to embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing an electrostatic sorting apparatus according to Embodiment 1 of the present invention.
As shown in FIG. 1, the electrostatic sorting device 1 includes a granular plastic 2a and 2b made of different mixed materials to be sorted, a charging device 3 for charging the granular plastic 2a and 2b, and the charging device. Dispersing the granular plastics 2a and 2b charged by the device 3 to give the upper kinetic energy, a pair of electrodes 5a and 5b, a power source 6 for applying a voltage to the electrodes 5a and 5b, and the electrodes The electric field fields 7 and 7h formed by 5a and 5b, and collection containers 8a and 8b for collecting the sorted granular plastics 2a and 2b, respectively, sent from the sending unit 4f to the high electric field 7h by the sending device 4 Has been.

Next, the operation principle of the electrostatic sorting device will be described with reference to FIG.
Granular plastics of different materials are a variety of resin molded products that are produced in the recycling process for recovering valuable metals and glass from used home appliances, office machines such as copiers, or automobiles. A crushed mixture (outer diameter of several mm to several tens of mm). In order to reuse plastics, it is necessary to select and collect the plastic with as high purity as possible (for example, with a purity of about 99%) from the viewpoint of maintaining the quality of the recycled plastic. The electrostatic sorter of the present invention is one of such sorters, and as one use form, a plastic mixture (for example, ABS (acrylonitrile butadiene styrene) that is difficult to sort by the specific gravity sorting method because of the close specific gravity. Application of separation of resin and PS (polystyrene) resin) is expected.

  As a granular plastic 2a of different materials crushed for recycling, for example, a mixture of plastics made of PS resin, for example, ABS resin, granular plastic 2b, is charged into a hopper-shaped charging device 3 and charged by friction by stirring. Is done. At this time, the granular plastic (ABS resin) 2a is charged positively (+) and the granular plastic 2b (PS resin) is negatively charged (−) in accordance with the plastic triboelectric charge train. Next, the charged granular plastics 2 a and 2 b are sent to the delivery device 4, and the excitation of the delivery device 4 is performed in an electric field 7 formed between the electrodes 5 a and 5 b to which a voltage is applied by the power source 6. The machine 4a receives upward kinetic energy from the sending part 4f and sends it upward into the electric field 7. The delivered granular plastics 2a and 2b start to fall spontaneously after reaching a predetermined height due to kinetic energy, but the positively charged 2a is attracted to the electrode 5b, and the negatively charged granular plastic 2b is Are attracted to the electrodes 5a. Since the distance between the granular plastics 2a and 2b increases according to the total distance (the vertical movement distance of the granular plastics) where the granular plastics are placed in the electric field 7, the positive / negative of the charging, and the amount of charge, The collection containers 8a and 8b are installed at the respective dropping positions of the granular plastics 2a and 2b, and are collected by sorting.

  The delivery device 4 in the first embodiment is based on an oscillating mechanism, and is similar in that the conventional conveying device also has an oscillating mechanism. However, in the conventional conveying device, the granular plastic is caused by vibrations from the oscillating device. In the delivery device 4 of the first embodiment, the charged granular plastics 2a and 2b supplied from the charging device 3 by the vibration exciter 4a are horizontally moved by vibrating and transporting in the horizontal direction. In addition to vibrating and transporting in the direction, an upper kinetic energy is given to obtain a sufficient sorting performance, and the granular plastics 2a and 2b are forced to jump up to a predetermined height from the delivery part 4f to the electric field 7 It is characterized in that it is sent out. By setting the reaching height of the splashed granular plastic, the recovery rate (in the case where the purity of the recovered granular plastic is set to a predetermined value) can be greatly improved.

  Next, the material of the granular plastic 2a is ABS resin, the material of the granular plastic 2b is PS resin, the particle size is 4-12mm, the electric field strength of the upper high electric field 7h is 280kV / m (electrode spacing 20cm), the bottom When the electric field strength of the electric field 7 is 140 kV / m (electrode spacing 40 cm), the height of the jumped granular plastics 2a and 2b (the height of the center of gravity of the granular plastic with respect to the transport path 4d surface) and An experiment was conducted with respect to the relationship with the recovery rate (when purity was 98 to 99%). The recovery rate when the arrival height of the granular plastic was 1.0 to 3.3 cm was 71% or more, whereas the recovery rate when it was less than 1.0 cm was 54% or less. From the results of this experiment, it was found that the required height after jumping up to 1 cm or more is necessary to obtain the required effect (70% or more of the recovery rate). In principle, the sorting performance should be improved as the arrival height increases, but in reality, the variation in the arrival height due to jumping increases. Therefore, there is an appropriate range for the height reached by the flip-up. Under these conditions, it is desirable that the reach height range is 2 to 3.3 cm. In addition, since the reaching height and the spread of each granular plastic after jumping vary depending on the specific gravity, size, shape and distribution state of the granular plastic, it depends on the properties of the target mixed granular plastic. , Set the appropriate range for reaching up. In general, for the purpose of transporting granular plastic as in the conventional example, in order to avoid breakage of the granular plastic, the transport is performed with a minimum amount of splashing.

  In the example of the present invention, as the vibration exciter 4a that gives the necessary vibration force to the granular plastic and jumps the granular plastic to a predetermined height, for example, an excitation method using a vibration motor or a voltage / voltage adjusted to an electromagnet An existing vibration mechanism such as an electromagnetic feeder method that vibrates by applying an alternating voltage of a frequency, a vibration air cylinder method, or the like can be used.

  Compared to the case where the granular plastic is naturally dropped in the electric field of the conventional example, since the charged granular plastic is sent upward, it is longer by the reciprocating distance until it falls (returns) to the height of the sending section. By staying in the electric field, the time for receiving the Coulomb force becomes longer, the separation interval can be further increased, and the sorting accuracy can be improved. Further, since the electric field 7 is formed between the electrode 5 b and the electrode 5 a opposed to each other by the sending part 9, the front surface of the sending part 9 is the electric field 7. In addition, on the front surface of the delivery part 9, the distance from the opposing electrode 5a is small, that is, a high electric field 7h having a high electric field strength. The downward movement speed of the granular plastics 2a and 2b increases due to the gravitational acceleration as the granular plastics 2a and 2b fall, and therefore the downward movement speed before and after the movement locus sent from the delivery unit 9 reaches the apex. Is the region where the stay time per moving length is long. The granular plastics 2a and 2b are quickly subjected to a large Coulomb force for a long time after the delivery by matching the area from the front surface of the delivery part 9 where the moving speed is low to the slightly upper side with the high electric field 7h. Thus, the sorting performance can be improved.

  Actually, in the result when the purity of the granular plastic to be selected is 98 to 99%, in the case where the granular plastic is naturally dropped into the electric field in the conventional example, the residence time in the electric field is 0.28. While the recovery rate is 50 to 60% in seconds (the delivery part is made of resin), in the first embodiment, the residence time in the electric field when the granular plastic is flipped up 2 cm is 0.44 seconds It extends about 1.6 times, and the recovery rate is improved to 76-81% (the delivery part is made of metal). Here, the length of the lower electric field (18 cm) from the delivery part is the same, the distance from the lower ends of the electrodes 5a, 5b to the collection containers 8a, 8b is 60 cm, and the particle size of the granular plastic is 4-8 mm It is. In this evaluation, the purity of the recovered granular plastic was 98 to 99%, and the sorting performance was expressed by the ratio (recovery rate) of the recovered plastic obtained at that time. However, in any case, it goes without saying that the recovery rate can be further increased if the purity of the recovered plastic is allowed to decrease. Further, the purity required for the recovered plastic is determined according to the use application of the recovered plastic and the like.

  These series of operations are performed in a low humidity environment in order to maintain the charged state of the granular plastic. When the length of the transport path 4d of the delivery device 4 was set to 1.5 m, the relationship between the charged charge amount and the ambient humidity was examined. As a result, when the granular plastic was supplied in an environment with a humidity of 69%, the charged charge amount decreased to 37% of the initial value, resulting in poor sorting. On the other hand, the charge amount of 88% of the initial value was maintained at a humidity of 52% and the initial charge amount of 100% was maintained at a humidity of 35%, and good sorting results were obtained. In a separately conducted test, when the collision between the charged granular plastic and the metal surface was continued for 10 minutes, the charged charge was sent even in a low humidity environment, and the charge amount was reduced to about 1/4 of the initial value. In the first embodiment, since the length of the conveyance path 4d is set to 1.5 m, the staying time of the granular plastic is as short as about 25 seconds and is in a low humidity environment (for example, humidity of 52%). The discharge of the charged charge is suppressed.

  In addition, in the conventional electrostatic sorting apparatus, in order to avoid discharge of charged granular plastic to the conveyance surface of the conveyance path, a conveyance path made of an insulating material is used. As a result of the frictional charging, the conveying speed and the conveying form of the granular plastic become unstable, and the sorting purity and the recovery rate are lowered. Specifically, for example, the charge on the transfer surface is weakened due to the degree of drying of the transfer surface and the difference in dirt on the transfer path surface, and the transport of mixed plastics is slow at places where the charge is strong, and retention occurs in extreme cases. In addition, the transport speed varies with time in the width direction of the transport path and with time, including changes in the charging state over time. As a result, when the supply is excessive, the frequency of collisions between the granular plastics increases on the conveying path and in the electric field, causing agglomeration due to Coulomb force, resulting in a decrease in sorting purity and recovery rate.

  On the other hand, in the first embodiment, unlike the conventional example, the surface where the conveying path 4d and the sending part 4f of the sending device 4 are in contact with the granular plastics 2a and 2b is made of a conductive material, and its potential is an electrode. It is kept at the same potential as 5b (grounded in FIG. 1). There is no accumulation of charge on the surface of the delivery unit 9, the electrostatic force between the delivery unit 9 and the charged granular plastics 2a and 2b is minimized, and the charged charge amount of the granular plastic is stably maintained. . As a result, the delivery speed becomes uniform in the width direction of the delivery section 9 (depth direction in FIG. 1), and the agglomeration phenomenon between the granular plastics is also suppressed (the granular plastic due to the mirror image force of the induced charges caused by the charged charges of the granular plastics) Although the interaction with the delivery part remains, it is relatively small and the generation of induced charges is uniform regardless of the surface state of the delivery part), and the selection accuracy does not decrease.

  As described above, according to the first embodiment of the present invention, the kinetic energy is given to the plurality of kinds of granular plastics made of different materials by the delivery device having the excitation mechanism, and is sent into the electric field, thereby charging Even if the amount of electric charge is small or the electric field region is short, it is possible to achieve a remarkable effect that the granular plastic can be efficiently sorted by material with high accuracy.

Embodiment 2. FIG.
FIG. 2 is a schematic diagram showing an electrostatic sorting device according to Embodiment 2 of the present invention.
As shown in FIG. 2, in the electrostatic sorting apparatus according to the second embodiment, the electrostatic sorting apparatus 1 includes granular plastics 2a and 2b made of different mixed materials to be sorted, and these granular plastics 2a. , 2b, a conveying device 9 for dispersing and conveying the granular plastics 2a, 2b charged by the charging device 3, and the granular plastics 2a, 2b conveyed by the conveying device 9 in dry air A blower pipe 12 that gives upward kinetic energy by a blower 11 using 10, a pair of electrodes 5a and 5b with a narrower interval between them, a power supply 6 that supplies power to the electrodes 5a and 5b, and this electrode 5a , 5b, and the granular plastics 2a, 2b which are sent from the sending part 12f to the high electric field 7h by the blower tube 12 and selected. Collection container 8a to be recovered, is constituted by the 8b.

Hereafter, the operation | movement by the electrostatic selection apparatus of Embodiment 2 is demonstrated using FIG.
As a granular plastic 2a of different materials crushed for recycling, for example, a mixture of plastics made of PS resin, for example, ABS resin, granular plastic 2b, is charged into a hopper-shaped charging device 3 and charged by friction by stirring. Is done. At this time, the granular plastic (ABS resin) 2a is charged positively (+) and the granular plastic 2b (PS resin) is negatively charged (−) in accordance with the plastic triboelectric charge train. Next, the charged granular plastics 2a and 2b are dropped on the carrier 9, dispersed by the vibration exciter 9a, and the dry air 10 is further sent by the blower 11 to the blower pipe 12 serving as a sending device, and the power supply 6 In the electric field 7 formed between the electrodes 5a and 5b to which a voltage is applied, the upper kinetic energy is applied from the sending part 12f by the blower 11 and is sent upward into the electric field 7. The delivered granular plastics 2a and 2b start to fall spontaneously after reaching a predetermined height due to kinetic energy, but the positively charged 2a is attracted to the electrode 5b, and the negatively charged granular plastic 2b is Are attracted to the electrodes 5a. Since the distance between the granular plastics 2a and 2b increases according to the total distance (the vertical movement distance of the granular plastics) where the granular plastics are placed in the electric field 7, the positive / negative of the charging, and the amount of charge, The collection containers 8a and 8b are installed at the respective dropping positions of the granular plastics 2a and 2b, and are collected by sorting. Further, the gap between the electrodes 2a and 2b is narrow at the top and widened at the bottom, and the sprung granular plastics 2a and 2b are put into the high electric field 7h and easily separated. Yes.

  The delivery device is a blower, and by adjusting the air volume, it is possible to change the reach height for jumping up the granular plastic over a wide range, and it is possible to easily adjust even a large particle size. Furthermore, since the blower is used without using the vibrator, there is no problem of noise caused by vibration and the structural life problem associated therewith, and there is an effect that the manufacturing and life design are facilitated.

  As described above, according to the second embodiment of the present invention, the upper kinetic energy can be easily given to a plurality of types of granular plastics made of different materials by the blower pipe using the blower, and the kinetic energy is sent into the electric field. As a result, it is possible to select efficiently, and further, it is possible to easily change the amount of jumping up by adjusting the air flow rate, and to achieve a remarkable effect that adjustment according to the granular plastic material and shape is possible.

Embodiment 3 FIG.
FIG. 3 is a schematic diagram showing an electrostatic sorting apparatus according to Embodiment 3 of the present invention.
As shown in FIG. 3, in the electrostatic sorting device 1 according to the third embodiment, other components are shown in FIG. 1 except that a conveying device 9 is installed between the charging device 3 and the delivery device 4. Since it is the same as that of the electrostatic sorting apparatus 1 of Embodiment 1, description is abbreviate | omitted.

  Next, the operation of the electrostatic sorting apparatus according to the third embodiment will be described with reference to FIG. Compared to the first embodiment, the function of dispersing and conveying is separated into the conveying device 9 and the function of sending out into the electric field into the sending device 4, so that the operation of separating and conveying the granular plastic and the operation of jumping up are independent. Each can be adjusted independently. That is, independent operation is possible under the optimum conditions for conveyance and optimum conditions for delivery, and there is an effect that the application range can be expanded, such as changing the particle size, purity, and recovery rate of the granular plastic.

  As described above, according to the third embodiment of the present invention, the separating and transporting operation and the jumping operation are performed by separating the function of dispersing and transporting into the transporting device and the function of sending out the electric field into the sending device. Can be adjusted and optimized independently, and there is a remarkable effect that adjustment according to the granular plastic material and shape is possible.

  In the first and third embodiments, the distal end portion (sending port) of the sending portion 4f is configured to slightly enter the high electric field 7h slightly beyond the electrode 5b. The reason is to prevent the negatively charged granular plastic 2b from being attracted to the electrode 5b by the Coulomb force and colliding with the electrode 5b. The strongly impacted granular plastic is reflected by the electrode 5b and is erroneously collected in the collection box 8b. On the other hand, when the initial velocity in the forward direction of the granular plastic 2b delivered from the delivery part 4f is sufficient and the possibility of collision with the electrode 5b is low, the position of the tip part of the delivery part 4f is the upper part of the electrode 5b. It may be the same. In this case, the electric field intensity at the upper part of the electrode 5b is substantially the same as the electric field intensity at the front surface of the sending part 4f. As the maximum value of the electric field strength to be set, the maximum value in a range where no corona discharge is generated in the air is usually adopted. If the length of the electrode is increased, the accuracy of selecting the granular plastics 2a and 2b is improved. However, since the space between the lower portions of the electrodes is widened, the electric field strength is also weakened. I can't expect it. The space between the collection containers 8a and 8b (in the above example, about 15 cm) is opened, but granular plastics that cannot be sufficiently selected due to factors such as the charged state and are insufficiently sorted are collected between the collection containers 8a and 8b. A sorting container (not shown) that cannot be discriminated is provided to improve the sorting accuracy.

  In the first and third embodiments, the delivery unit 4f is vibrated, and the mixed granular plastic is delivered forward and upward. At this time, the state of vibration is monitored and stable operation is performed. It is important for practical use. Therefore, for example, an acceleration sensor or a displacement sensor may be attached to the sending unit 4f and the vibration state may be monitored, and the vibration exciter 4a may be controlled using the state data.

  In the drawings, the same reference numerals indicate the same or corresponding parts.

1 is a configuration diagram illustrating an outline of an electrostatic sorting device according to Embodiment 1. FIG. It is a block diagram which shows the outline of the electrostatic selection apparatus in Embodiment 2. FIG. 6 is a configuration diagram showing an outline of an electrostatic sorting device in a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrostatic sorter 2a, 2b Granular plastic 3 Charging device 4 Sending device 4a, 9a Exciter 4f, 12f Sending part 5a, 5b Electrode 6 Power supply 7 Electric field 7h High electric field 8a, 8b Collection container 9 Conveying device 12 Air blower tube

Claims (8)

  A mixture of a plurality of types of granular plastics made of different materials is charged, and in the electric field, the charged granular plastics are sent upward from the delivery part, and the granular plastics are made of materials according to the amount of charge charged in the granular plastics. An electrostatic sorting method characterized by sorting separately.   2. The electrostatic sorting method according to claim 1, wherein the reaching height of the granular plastic is in the range of 1 cm to 3.3 cm above the delivery part. A charging device for charging a mixture of a plurality of kinds of granular plastics made of different materials;
A pair of electrodes forming an electric field;
A delivery device having a delivery part made of a conductive material that delivers the charged granular plastic into the electric field, and
The granular plastic for delivering the granular plastic above the delivery unit of the delivery device, and having the upper end of the one electrode disposed facing the delivery device forming the electric field being delivered. The other electrode disposed below the delivery unit of the delivery device is held at the same potential as the delivery unit, and the granular plastic is charged by the amount of charge charged in the particulate plastic. Electrostatic sorting device characterized by sorting by material.   The electrostatic sorting device according to claim 3, wherein the delivery device is a vibrator.   The electrostatic sorting device according to claim 3, wherein the delivery device is a blower tube.   The static electric field according to any one of claims 3 to 5, wherein the electric field strength of the electric field above the sending portion of the granular plastic is made higher than the electric field strength of the electric field below the sending portion. Electric sorting device.   The electrostatic sorting device according to any one of claims 3 to 6, wherein an arrival height of the granular plastic is in a range of 1 cm to 3.3 cm above the delivery portion.   The electrostatic sorting device according to any one of claims 3 to 7, wherein the electrostatic sorting device is operated in an environment having a relative humidity of 52% or less.

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