JP5126699B2 - Electrostatic sorting device - Google Patents

Description

  The present invention relates to an electrostatic sorting device, and more particularly to an electrostatic sorting device that sorts charged plastic by dropping it.

  When a mixture of plastics (particles) exhibiting charging behavior (mixed plastics) is triboelectrically charged, individual particles are positively charged depending on the ease of charging of the constituent materials in the mixture and the plastic material type (resin type). Or is negatively charged. An electrostatic sorting device is known in which particles of the charged mixture are freely dropped in an electric field and sorted for each constituent material.

  As an electrostatic sorting device for sorting two or more kinds of plastics, for example, an electrostatic sorting device described in Japanese Patent Laid-Open No. 2003-311183 (Patent Document 1) has been proposed. The electrostatic sorting device is provided with a charged chute material and a dropping chute that drops the sorting material and a downward direction of the dropping chute and applies an electrostatic field to the sorting material to deflect the sorting material in parallel. It has an electrode and a C-shaped electrode.

  Further, for example, in Japanese Patent Application Laid-Open No. 2002-177820 (Patent Document 2), a reverse-polarity voltage is applied to an electrode of an electrostatic separation unit that introduces a charged plastic pulverized product into an electrostatic field and separates it by type. There has been proposed an electrostatic sorting device for plastic crushed material that removes the plastic crushed material adhering to the electrode surface.

JP 2003-311183 A JP 2002-177820 A

  In the electrostatic sorting device disclosed in Japanese Patent Laid-Open No. 2003-311183, the constituent materials to be sorted are sorted by being separated by the electric field formed by the parallel electrode and the C-shaped electrode, and the first and second Collected in a container. In this method, usually, plastic crushed mixed particles obtained by decomposing and crushing used recovered products are often used. For example, the crushed mixed particles are mainly plate-like and granular particles having a representative length of about several mm to 20 mm. However, powders, extremely thin plates and films are also produced during crushing. Therefore, the crushed mixed particles are in a mixed state.

  In actual electrostatic sorting, all the mixed plastics are charged to different polarities depending on the resin type as 100% theoretically, and are not electrostatically sorted for each resin type depending on the charging polarity and the charge amount. Sorting is insufficient for some reason, and some plastic particles fall in the middle of the two collection containers, or plastic particles are collected as impurities in the opposite container that should not be collected. Both rate and recovery purity do not reach 100%. If there is no sufficient contrivance, the recovery rate is generally about 70%, for example, and the recovery purity is generally about 90%, for example.

  One of the causes of such poor sorting is a problem that plastic particles charged during electrostatic sorting adhere to the electrode surfaces of different polarities, weakening the electric field strength of the electric field and lowering the performance. Specifically, powder, thin plate, or film-like plastic particles have a large charge with respect to weight, and are extremely attracted to the electrode while dropping the electric field, so some of these particles adhere to the electrode surface. To do. Since the plastic particles adhering to the electrode are charged with a polarity opposite to that of the electrode, the electric field strength between the counter electrodes is lowered and the sorting performance is lowered. For this reason, it is necessary to remove the plastic particles adhering to the electrode surface.

  In the electrostatic sorting apparatus for pulverized plastics disclosed in Japanese Patent Application Laid-Open No. 2002-177820, the plastic particles are separated from the electrode surface by an electrostatic force in the opposite direction when a voltage having a reverse polarity is applied to the electrodes. Thereafter, when the voltage application is stopped, the plastic particles are dropped by their own weight and removed from the electrode surface. In addition, the supply of the pulverized plastic is stopped before the reverse polarity voltage is applied. It is described that a decrease in the recovery rate and purity of plastic particles (polypropylene) is suppressed by applying a reverse voltage every 5 minutes and setting the voltage application stop time to 3 seconds.

  Temporarily stopping the sorting and removing the attached plastic, and then restarting the sorting and repeating the above steps are problematic especially in terms of the productivity of the sorting work and the equipment cost. Specifically, in conjunction with the removal of adhered plastic, operations such as stopping the supply of mixed plastic, stopping the recovery of plastic to the collection container, taking out the removed plastic out of the system, applying a high voltage, and changing the polarity are necessary. Therefore, additional equipment and human work are required. In addition, there is a problem such as a risk that the purity of the product is lowered due to dropping of the attached plastic during removal or removal or mixing into the product side. In terms of work time, it is necessary to perform a series of operations including line stop, removal and recovery of attached plastic, and line resumption including safety confirmation. Even for a second and a short time, an additional time of at least about 5 minutes is required. As a result, the productivity of the electrostatic sorting device is reduced by about half.

  This invention is made | formed in view of the said subject, The objective is to provide the electrostatic sorting apparatus which can classify | mix the constituent material of a mixed plastic with high purity and efficiently.

  The electrostatic sorting apparatus of the present invention is an electrostatic sorting apparatus that sorts by dropping charged plastic, and has a first electrode portion having a first surface facing a drop region for dropping charged plastic. And a second electrode portion having a second surface facing the drop region and capable of applying a voltage different from that of the first electrode portion, and a plastic adhered to each of the first and second surfaces. Therefore, a scraper portion that is movable along each of the first and second surfaces and is movable between the falling area and the outside of the falling area, and made of an electrically insulating material, and the first and second And a drive control unit that performs control so that the movement of the scraper unit in the falling region and the stop of the scraping unit outside the dropping region are repeated while a voltage is applied to the electrode unit.

  According to the electrostatic sorting apparatus of the present invention, the scraper portion made of an electrically insulating material moves within the drop region and stops outside the drop region with a voltage applied to the first and second electrode portions. Therefore, the plastic adhering to each of the first and second surfaces is removed without stopping electrostatic sorting. Therefore, the sorting efficiency can be improved. Further, since the scraper unit stops outside the falling area, the charged plastic does not collide with the scraper unit when stopped. Therefore, the selection purity can be improved. Thereby, the constituent material of the mixed plastic can be efficiently selected with high purity.

It is a schematic block diagram of the electrostatic selection apparatus in Embodiment 1 of this invention. 1 is a schematic plan view of an electrostatic sorting device according to Embodiment 1 of the present invention. It is a schematic perspective view which shows a mode that the scraper part of the electrostatic selection apparatus in Embodiment 1 of this invention moves along each surface of the 1st and 2nd electrode part. It is a schematic block diagram of the electrostatic selection apparatus in Embodiment 2 of this invention. It is a schematic plan view of the electrostatic screening apparatus in Embodiment 2 of the present invention. It is a schematic perspective view which shows a mode that the scraper part of the electrostatic selection apparatus in Embodiment 2 of this invention moves along each surface of the 1st and 2nd electrode part.

Hereinafter, an electrostatic sorting device according to an embodiment of the present invention will be described with reference to the drawings.
(Embodiment 1)
First, the configuration of the electrostatic sorting device according to the first embodiment of the present invention will be described.

  With reference to FIG. 1 and FIG. 2, the electrostatic sorting apparatus 1 of this Embodiment sorts by dropping the charged plastic 3. FIG. The electrostatic sorting device 1 includes a first electrode portion 2a, a second electrode portion 2b, an electrode cleaning mechanism 4, a supply portion 5, first and second recovery containers 6a and 6b, a rail 8, It has mainly. The electrode cleaning mechanism 4 includes a scraper unit 4a, a scraper drive unit 4b, a drive control unit 4c, and a support unit 4d.

  The supply part 5 for supplying the charged plastic 3 is disposed above the first and second electrode parts 2a and 2b. The supply unit 5 is, for example, a vibration feeder. The plastic 3 may be charged in advance by a charging unit for charging the plastic 3 (not shown), and the supply unit 5 may include the charging unit. The plastic 3 may include various shapes such as particles (crushed pieces).

  A drop region A <b> 1 for dropping the charged plastic 3 is formed below the supply unit 5. This fall area A1 is an area indicated by a one-dot chain line in FIGS. 1 to 3, and passes between the first and second electrode parts 2a, 2b from the supply part 5 and the first and second recovery containers 6a, It is an area until it falls to 6b. That is, it is a region including a space sandwiched between the first and second electrode portions 2a and 2b and a space directly above and below the space. The first and second electrode portions 2a and 2b are arranged with the drop region A1 interposed therebetween. The first electrode portion 2a has a first surface 2as facing the drop area A1. The second electrode portion 2b has a second surface 2bs facing the drop area A1. The first and second electrode portions 2a and 2b are arranged such that the charged plastic 3 falls between the first surface 2as and the second surface 2bs.

  The second electrode part 2b can be applied with a voltage different from that of the first electrode part 2a by, for example, a DC power source. By applying different voltages to the first and second electrode portions 2a and 2b, an electric field 9 is formed between the first electrode portion 2a and the second electrode portion 2b. The first and second electrode portions 2a and 2b may have a flat plate shape. In this case, the 1st and 2nd electrode parts 2a and 2b may be arrange | positioned so that the space | interval of the 1st electrode part 2a and the 2nd electrode part 2b may expand toward the fall direction of the plastic 3. FIG. That is, the 1st and 2nd electrode parts 2a and 2b are each inclined and arrange | positioned diagonally, and may be arrange | positioned in C shape. The first and second electrode portions 2a and 2b are supported by, for example, an insulating support mechanism 7 made of an insulating member at both longitudinal ends.

  The scraper portion 4a is configured to be movable along the first and second surfaces 2as and 2bs in order to remove the plastic 3 attached to the first and second surfaces 2as and 2bs. The scraper portion 4a is configured to be movable between the falling area A1 and the outside of the falling area A1. The scraper unit 4a is supported by the scraper driving unit 4b by a support unit 4d. When the scraper driving unit 4b moves on the rail, the scraper unit 4a is configured to be movable along the rail.

  The scraper driving unit 4b has, for example, an electric motor unit 4e, and is configured to move the scraper unit 4a at a predetermined speed by the driving force of the electric motor unit 4e. The rail 8 is disposed along the moving direction of the scraper portion 4a. The moving direction of the scraper portion 4a coincides with the longitudinal direction of the first and second electrode portions 2a and 2b.

Further, the scraper unit 4a includes a main body 4a _1, may include a sweep down portion 4a _2. The sweep-off portion 4a ₂ is for sweeping off the plastic 3 adhering to each of the first and second surfaces 2as, 2bs. The sweep-off portion 4a ₂ is attached to a surface along each of the first and second surfaces 2as and 2bs of the main body 4a ₁ . The sweep-off part 4a ₂ has higher flexibility than the main body 4a ₁ . The sweep-off part 4a ₂ is made of, for example, a brush.

  The drive control unit 4c repeats the movement of the scraper unit 4a within the fall region A1 and the stop outside the fall region A1 in a state where a voltage is applied to the first and second electrode units 2a and 2b. Control.

  The drive control unit 4c is connected to, for example, a DC power source, and is configured to control the DC power source so that a voltage can be applied to the first and second electrode units 2a and 2b. The drive control unit 4c is connected to the scraper drive unit 4b, and is configured to control the scraper drive unit 4b to be intermittently movable with the rail 8 as a guide.

  The first and second collection containers 6a and 6b are disposed below the drop region A1 and below the first and second electrode portions 2a and 2b. The first recovery container 6a and the second recovery container 6b are disposed so as to be able to recover the plastics 3 charged in different polarities selected by the first and second electrode portions 2a and 2b.

Next, the operation of the electrostatic sorting device according to the present embodiment will be described.
The plastic (particle) 3 is charged by frictional charging between particles of different resin types in a charging unit (not shown). Thereafter, the charged plastic 3 is sent to the supply unit 5 which is, for example, a vibration feeder.

  With reference to FIG. 1 and FIG. 3, the charged plastic 3 is supplied from the supply part 5 to fall area A1. As shown in FIG. 2, when a high voltage is applied to the first and second electrode portions 2a and 2b by, for example, a DC power source, the first and second electrode portions 2a and 2b are interposed between the first electrode portion 2a and the second electrode portion 2b. An electric field 9 is formed. The dropping trajectory of the plastic 3 charged by the action of the Coulomb force received from the electric field 9 is different for each resin type. As shown in FIG. 1, by electrifying and collecting the mixed plastic 3 for each resin type, the charged plastic 3 is selected for each resin type.

  The mixed and crushed plastic 3 includes fine particles, thin plate-like particles, and film-like particles, but these particles have a relatively large surface area compared to the mass. Therefore, the specific charge amount (charge amount / mass ratio) increases. Accordingly, since the Coulomb force received per mass is large, it is strongly attracted to the first and second electrode portions 2a and 2b having a polarity different from that of the charge. Therefore, a part of the charged plastic 3 adheres to the surfaces 2as and 2bs of the first and second electrode portions 2a and 2b.

  As shown in FIGS. 2 and 3, the scraper unit 4 a is moved in the direction of the arrow D <b> 1 in the drawing when the scraper driving unit 4 b moves on the rail 8. Therefore, the scraper part 4a moves along the first and second surfaces 2as and 2bs. Thereby, the plastic 3 adhering to the first and second surfaces 2as and 2bs is removed by the scraper portion 4a.

  As shown in FIG. 3, the scraper unit 4a moves in the fall area A1 when moving while the voltage is applied to the first and second electrode units 2a, 2b. Therefore, the scraper unit 4a collides with the charged plastic 3 during movement. The scraper unit 4a stops outside the fall area A1 when stopped. Therefore, the scraper unit 4a does not collide with the charged plastic 3 when stopped.

  As shown in FIG. 1, the plastic 3 that has been swept away from the first and second surfaces 2as and 2bs by the scraper portion 4a falls freely in a charged state. Therefore, since the first and second electrode portions 2a and 2b having polarities different from those of the charged charges are not greatly separated from each other, the first and second recovery containers 6a and 6b are appropriately selected.

Next, the scraper part of the electrostatic sorting apparatus of this embodiment will be described in detail.
The scraper portion 4a of the electrostatic sorting device 1 according to the present embodiment is made of a dielectric material (electrical insulating material). Since the scraper portion 4a has electrical insulation, the insulation between the first and second electrode portions 2a and 2b is maintained, and the first and second electrode portions 2a and 2b are adhered while maintaining electrostatic sorting. The plastic 3 can be removed. Since the scraper unit 4a is operated near normal temperature in terms of temperature, a general polymer insulating material or ceramic insulating material can be used as a material.

In general, when the plastic (particles) 3 adhering by electrostatic force is swept away with a brush-like object, the sweep-off portion 4a ₂ has conductivity in order to prevent electrostatic adhesion between the brush and the plastic 3 A flexible member (for example, a static elimination brush) may be used. However, in the scraper unit 4a of the electrostatic sorting apparatus according to the present embodiment, the use of the static eliminating brush is not always appropriate. The reason will be described below.

  If a static elimination brush is used in a state where a high voltage (for example, about 30 to 100 kV) is applied between the first and second electrode portions 2a and 2b, the first and second electrode portions 2a and 2b and the static elimination brush are removed. In some cases, a partial discharge occurs in a portion where a gap is formed between the brush and the brush. In that case, there is a risk of material deterioration at the location where the partial discharge occurs, which causes a problem during long-term operation.

Therefore, an electrical insulating material is used in the scraper unit 4a of the electrostatic sorting device 1 of the present embodiment. When the sweep-off part 4a ₂ is used, for example, a flexible insulating brush (for example, a brush made of a polymer insulating material) is used for the sweep-off part 4a ₂ . In addition, when the sweepability of the sweep-off portion 4a ₂ made of an insulating brush is insufficient due to electrostatic adhesion of the plastic (particle) 3, the scraper portion 4a sweeps the first and second surfaces 2as and 2bs a plurality of times. Sweeping performance can be secured by dropping.

  In addition, the scraper unit 4a of the electrostatic sorting device 1 of the present embodiment is designed such that the scraper unit 4a does not substantially affect the falling motion of the plastic (particle) 3 in the electric field 9. Specifically, first, the projected area from above the scraper portion 4a and the support portion 4d is designed to be sufficiently smaller than the falling area of the electric field 9 where the plastic (particle) 3 falls. . Secondly, the plastic (particle) 3 that has passed through the upper surface of the scraper part 4a has a sufficient frequency of colliding with the side surfaces of the moving scraper part 4a and the support part 4d in the direction of movement D1 while falling. Designed to be smaller. As a result, the risk of occurrence of a sorting error caused by the collision between the plastic (particle) 3 and the scraper unit 4a is sufficiently reduced with respect to the sorting error allowed by the electrostatic sorting device 1.

  When the scraper portion 4a is configured to be able to contact the first and second surfaces 2as, 2bs and extend continuously between the first electrode portion 2a and the second electrode portion 2b, It is preferable that the length ST of the scraper portion 4a in the moving direction D1 of the scraper portion 4a is designed to satisfy the formula (1).

ST ≦ EL × CP + SI × SV × CP / SF−FT × SV (1)
Here, EL (cm) is the length of the first and second electrode portions 2a and 2b in the direction D1 in which the scraper portion 4a moves. CP is a collision frequency allowable value of the plastic 3 to the scraper portion 4a. SI (s) is the stop time of the scraper unit 4a. SV (cm / s) is the moving speed of the scraper unit 4a. SF is the number of movements of the scraper unit 4a. FT (s) is a drop time between the first electrode portion 2a and the second electrode portion 2b of the plastic 3.

  As a result, the collision frequency of the plastic (particles) 3 falling on the scraper part 4a that falls in the electric field 9 becomes less than an allowable value, so that the collision between the plastics (particles) 3 and the scraper part 4a does not affect the sorting performance. .

  Subsequently, an example of the length ST of the scraper unit 4a in the moving direction of the scraper unit 4a is calculated. For example, the EL is 200 cm (2 m), the SV is 10 cm / s (seconds), the movement of the scraper unit 4a is 20 minutes (1200 seconds) (SI is approximately 1200 seconds), and the scraper unit 4a is the first and The second electrode portions 2a and 2b are reciprocated once (SF is twice), and the FT is 0.25 seconds (the height of the first and second electrode portions 2a and 2b is 30 cm). The fall time in the FT is modeled as a free fall phenomenon in a gravitational field, for example, and is calculated by a general theoretical formula. The collision frequency tolerance CP is set based on the sorting purity allowed for the electrostatic sorting device 1. For example, when the sorting error allowed by the electrostatic sorting device is 1%, the collision frequency tolerance CP of the scraper unit 4a is assumed to be, for example, 0.1% smaller by one digit. In that case, ST becomes 3.7 cm or less as follows.

ST ≦ 200 (cm) × 0.001 + 1200 (s) × 10 (cm / s) × 0.001 / 2−0.25 (s) × 10 (cm / s)
ST ≦ 3.7cm
The stop time SI (approximately the interval time), which is a parameter for determining ST, may be determined as a time when the influence of the attached plastic 3 becomes significant, and is, for example, 10 minutes or more and 30 minutes or less.

  If the moving speed SV of the scraper unit 4a is excessively large, the adverse effect of the rebound of the plastic 3 becomes large, and the load of the electrode cleaning mechanism 4 becomes large, which causes a problem. If the moving speed SV of the scraper unit 4a exceeds 20 cm / second, for example, the plastic 3 will be rebounded and the load on the electrode cleaning mechanism 4 will be increased, which causes problems in terms of sorting accuracy and device fabrication.

  Further, when the moving speed SV is reduced, the difference between the stop time SI and the interval time cannot be ignored. For example, when the moving speed SV is 3 cm / sec, the time required to make one round trip of the 2 m-long first and second electrode portions 2a and 2b is about 2 minutes. SI is about 18 minutes. Along with the increase in the stay time of the scraper part 4a in the electric field 9 due to the decrease in the moving speed SV, the ST becomes as small as about 1 cm. Therefore, when the moving speed SV is 3 cm / second, ST approaches the design limit of the scraper unit 4a. Therefore, under this condition, the preferred moving speed SV is between about 3 cm / second and about 20 cm / second.

If the scraper part 4a makes one or more reciprocations per movement, there is little leftover of the attached plastic 3, and the expected effect can be obtained. However, excessive reciprocation increases the staying time of the scraper unit 4a, and thus causes a reduction in the selection purity. Therefore, the necessary number of movements SF is determined in consideration of the removal performance of the sweep-off unit 4a ₂ and the selection purity.

  The scraper unit 4a is preferably held away from the first and second electrode units 2a and 2b when stopped. For example, when the first and second electrode portions 2a and 2b are supported by the insulating support mechanism 7 made of an insulating member at both ends as shown in the P1 portion of FIG. The scraper portion 4a and the support portion 4d are moved to the region of the insulating support mechanism 7 away from the second electrode portions 2a and 2b. Thereby, the dielectric breakdown risk resulting from installation of the electrode cleaning mechanism 4 can be reduced. There is always a small risk of dielectric breakdown due to the aging of dust and materials adhering to the surfaces of the scraper 4a and the support 4d.

Next, the function and effect of the electrostatic sorting device of the present embodiment will be described.
In a general electrostatic sorting apparatus, the amount of the charged plastic 3 attached to the first and second electrode portions 2a and 2b increases with the sorting time. Thereby, the electric field between the 1st and 2nd electrode parts 2a and 2b is weakened. Therefore, when the charged plastic 3 adheres to the first and second electrode portions 2a and 2b by a certain amount or more, the recovered amount and recovery purity (sorting performance) of the plastic 3 are lowered.

  The rate of increase in the amount of the charged plastic 3 adhering to the first and second electrode portions 2a, 2b depends on the amount and method of supplying the mixed plastic 3 to the electric field 9, and the first and second electrode portions 2a. , 2b, the shape and distribution of the plastic (particle) 3, the charge amount of the plastic 3, the specifications and operating conditions of the electrostatic sorting device 1, the performance of the upstream equipment, and the like.

  For example, used household electrical appliances are fragmented using a crusher, and mixed plastic (particles) 3 obtained by removing fragments such as metal using an eddy current sorter or specific gravity sorter is electrostatically sorted. In this case, the charged plastic (particle) 3 adheres to the first and second electrode portions 2a and 2b. When the attached plastic 3 is not removed, for example, when the sorting time for carrying out electrostatic sorting is 10 minutes or more, the plastic 3 adheres to the surfaces 2as and 2bs of the first and second electrode portions 2a and 2b. Become. When the selection is continued for more than 30 minutes, the plastic (particle) 3 adheres to almost the entire surface 2as, 2bs of the first and second electrode portions 2a, 2b. Thereafter, as the two layers of the attached plastic 3 progress, the falling of a part of the attached plastic 3 starts, and the charged plastic 3 becomes the first and second electrode portions 2a while the multilayering and the drop are almost balanced. , 2b is maintained.

  On the other hand, the electrostatic sorting device 1 according to the present embodiment prevents a drop in sorting performance due to the adhesion of the plastic 3 as described above, so that a high voltage is applied to the first and second electrode portions 2a and 2b. The first and second electrode portions 2a are applied by the scraper portion 4a while maintaining the operation of electrostatic sorting such as application, supply of the mixed plastic 3 and recovery of the plastic 3 to the first and second recovery containers 6a and 6b. , 2b, the plastic (particles) 3 adhering to the surfaces 2as, 2bs is removed.

  According to the electrostatic sorting device 1 of the present embodiment, the scraper portion 4a made of an electrically insulating material is applied in the fall region A1 with a voltage applied to the first and second electrode portions 2a and 2b. Since the movement and the stop outside the drop region A1 are repeated, the plastic 3 attached to the first and second electrode portions 2a and 2b is removed without stopping the electrostatic sorting operation. Therefore, the production amount can be improved. Therefore, the sorting efficiency can be improved.

  Moreover, the scraper part 4a stops outside the fall area A1. For this reason, the charged plastic 3 does not collide with the scraper part 4a at the time of a stop. Therefore, the selection purity can be improved.

  Further, the plastic 3 attached to the first and second electrode portions 2a and 2b is removed from the first and second surfaces 2as and 2bs in a state where a voltage necessary for selection is applied. Therefore, since the removed plastic 3 is in a charged state, the plastic 3 is not greatly separated from the first and second electrode portions 2a and 2b having a polarity different from that of the charged charges. Therefore, the removed plastic 3 is appropriately sorted into the first and second collection containers 6a and 6b. Therefore, the sorting purity can be improved.

  When the plastic 3 adhered to the electrode by applying a voltage having a polarity opposite to that at the time of sorting is removed from the electrode surface as in the past, the removed plastic 3 is opposite to that at the time of sorting due to the electrostatic force in the opposite direction. There is a risk of moving to the electrode. In the present embodiment, a voltage having a polarity opposite to that at the time of selection is not applied, so that the plastic 3 is attracted to the first and second electrode portions 2a and 2b electrodes having the same polarity as the charged charges by an electrostatic force in the opposite direction. Absent. Therefore, the selection purity can be improved.

  Further, there is no risk of purity reduction on the product side due to the removed attached plastic 3, and the removed plastic 3 can also be used as a product. In addition, operations and facilities such as the supply stop of the mixed plastic 3, the stop of the recovery of the plastic 3 to the recovery container, and the removal of the removed plastic 3 out of the system are unnecessary. Therefore, it is possible to improve the production volume and product purity and simplify the facilities and work.

  According to the electrostatic sorting device 1 of the present embodiment, the scraper portion 4a can contact the respective surfaces 2as and 2bs of the first and second electrode portions 2a and 2b, and the first electrode portion 2a. And the second electrode portion 2b may be configured to extend continuously. The length of the first and second electrode parts 2a, 2b in the direction in which the scraper part 4a moves is EL, the allowable frequency of collision of the plastic 3 with the scraper part 4a is CP, and the stop time of the scraper part 4a is SI. The moving speed of the scraper unit 4a is SV, the number of movements of the scraper unit 4a is SF, and the falling time of the plastic 3 between the first electrode unit 2a and the second electrode unit 2b is FT. In this case, the length ST of the scraper unit 4a in the moving direction of the scraper unit 4a may be configured to satisfy the formula ST ≦ EL × CP + SI × SV × CP / SF−FT × SV.

  Thereby, since the collision frequency of the plastic 3 with respect to the scraper part 4a becomes an allowable value or less, it is possible to sort with higher purity.

  According to the electrostatic sorting device 1 of the present embodiment, the scraper unit 4a may be held away from the first and second electrode units 2a and 2b when stopped. Thereby, the dielectric breakdown risk resulting from installation of the scraper part 4a can be reduced. Therefore, the insulation safety of the first and second electrode portions 2a and 2b can be increased.

According to the electrostatic sorting device 1 of the present embodiment, the scraper unit 4a includes the sweep-off unit 4a ₂ for sweeping off the plastic 3 adhering to the first and second surfaces 2as and 2bs. The part 4a ₂ has higher flexibility than the main body 4a ₁ . Thereby, since the plastic 3 adhering to the 1st and 2nd surface 2as and 2bs can be swept away more, a production amount can be improved.

  According to the electrostatic sorting device 1 of the present embodiment, the first and second electrode portions 2a and 2b have a flat plate shape and the first electrode portion 2a toward the falling direction of the plastic 3. And the second electrode portion 2b are arranged so as to be widened. For this reason, the electrostatic sorting apparatus 1 can be reduced in size compared with the case where an electrode is a cylindrical type, for example.

(Embodiment 2)
The second embodiment of the present invention is mainly different from the first embodiment in the configuration of the scraper unit 4a.

  Referring to FIGS. 4 and 5, scraper portion 4a includes a first scraper portion 4af and a second scraper portion 4as that are separated from each other. The first and second scraper portions 4af and 4as are independently supported by the first electrode portions 2a and 2b, respectively. Each of the first and second scraper portions 4af and 4as and each scraper driving portion 4b are disposed with the first and second electrode portions 2a and 2b interposed therebetween. Each of the first and second scraper portions 4af and 4as is held by the scraper driving portion 4b by each support portion 4d formed so as to cover the outer circumferences of the first and second electrode portions 2a and 2b. Yes.

  The first scraper portion 4af is configured to move along the first surface 2as by using the first electrode portion 2a as a guide by the scraper driving portion 4b. The second scraper unit 4as is configured to move along the second surface 2bs by using the second electrode unit 2b as a guide by the scraper driving unit 4b.

  The length ST of each of the first and second scraper portions 4af and 4as of the present embodiment is such that the first and second scraper portions 4af and 4as bridge between the first and second electrode portions 2a and 2b. Therefore, it is designed in consideration of the area ratio.

  When the first and second scraper portions 4af and 4as can contact the first and second surfaces 2as and 2bs, respectively, the first and second scraper portions 4af and 4as are moved in the first direction D1. The length ST of each of the second scraper portions 4af and 4as is preferably designed to satisfy the formula (2).

ST ≦ EL × CP / SR + SI × SV × CP / SF / SR−FT × SV (2)
Here, EL (cm) is the length of the first and second electrode portions 2a and 2b in the direction D1 in which the first and second scraper portions 4af and 4as move. CP is a collision frequency allowable value of the plastic 3 to the first and second scraper portions 4af and 4as. SR is the first and second scraper with respect to the distance between the first electrode part 2a and the second electrode part 2b in the direction intersecting the direction D1 in which the first and second scraper parts 4af and 4as move. This is the ratio of the total length of the parts 4af and 4as. SI (s) is a stop time of the first and second scraper units 4af and 4as. SV (cm / s) is a moving speed of the first and second scraper portions 4af and 4as. SF is the number of movements of the first and second scraper units 4af and 4as. FT (s) is a drop time between the first electrode portion 2a and the second electrode portion 2b of the plastic 3.

  As a result, since the collision frequency of the plastic 3 to the first and second scraper portions 4af and 4as is less than an allowable value, the collision between the plastic 3 and the first and second scraper portions 4af and 4as has a sorting performance. Does not affect.

  Subsequently, an example of the length ST of each of the first and second scraper portions 4af and 4as in the moving direction D1 of the first and second scraper portions 4af and 4as will be calculated. For example, the EL is 200 cm, the moving speed SV is 10 cm / second, the movement of the first and second scraper parts 4af and 4as is 20 minutes apart (approximately SI is 1200 seconds), and the first and second scraper parts 4af, 4as reciprocates the first and second electrode portions 2a, 2b once (SF is twice), the total length ratio SR is 4 cm × 2/20 cm = 0.4, and the collision frequency allowable value CP is 0. When 1% and FT is 0.25 seconds, ST is 13 cm or less.

  As described above, in the present embodiment, the first and second scraper portions 4af and 4as are separated from each other, and therefore the first and second electrode portions 2a, A central region between 2b becomes a gap. Therefore, the risk of generating errors due to the collision between the mixed plastic 3 and the first and second scraper portions 4af and 4as is greatly reduced. This risk of error occurrence can be halved or less compared to the case where the central region is not a void. Accordingly, the frequency of movement of the first and second scraper portions 4af and 4as can be increased without difficulty. For example, it can be moved every 5 to 10 minutes. For this reason, it is possible to improve the recovery rate under sorting conditions in which the amount of the plastic (particle) 3 attached is particularly large.

  In addition, since the structure other than this of this Embodiment is the same as the structure of Embodiment 1 mentioned above, about the same element, the same code | symbol is attached | subjected and the description is not repeated.

Next, the operation of the electrostatic sorting device according to the present embodiment will be described.
Referring to FIG. 6, charged plastic 3 is supplied to drop area A1. At this time, a part of the charged plastic 3 adheres to the first and second surfaces 2as and 2bs. The first and second scraper portions 4af and 4as are moved in the direction of the arrow D1 in the figure as the scraper driving portion 4b moves along each of the first and second surfaces 2as and 2bs. Therefore, the plastic 3 adhering to the surfaces 2as and 2bs of the first and second electrode portions 2a and 2b is removed by the first and second scraper portions 4af and 4as, respectively.

  Each of the first and second scraper portions 4af and 4as moves in the fall region A1 when moving while the voltage is applied to the first and second electrode portions 2a and 2b. Therefore, each of the first and second scraper portions 4af and 4as collides with the charged plastic 3 during movement. Since the first scraper portion 4af and the second scraper portion 4as are separated from each other, the area where the first scraper portion 4af and the second scraper portion 4as collide with the charged plastic 3 is reduced. Therefore, the collision frequency between the first scraper portion 4af and the second scraper portion 4as and the charged plastic 3 is reduced.

  Each of the first and second scraper portions 4af, 4as is preferably held away from the first and second electrode portions 2a, 2b when stopped. For example, when the first and second electrode portions 2a and 2b are supported by the insulating support mechanism 7 made of an insulating member at both ends as shown in the P2 portion of FIG. The first and second scraper portions 4af and 4as are moved away from the second electrode portions 2a and 2b to the region of the insulating support mechanism 7 respectively.

Next, the function and effect of the electrostatic sorting device of the present embodiment will be described.
According to the electrostatic sorting device 1 of the present embodiment, the scraper unit 4a includes the first scraper unit 4af and the second scraper unit 4as that are separated from each other, and the first scraper unit 4af includes the first scraper unit 4af. The second scraper portion 4af moves along the second surface 2as, and is moved along the second surface 2bs.

  Thus, since the 1st and 2nd electrode parts 2a and 2b are isolate | separated, the risk of an electrode short circuit can be reduced. Thereby, the insulation safety | security of the 1st and 2nd electrode parts 2a and 2b can be made high.

  Further, since the first and second scraper portions 4af and 4as are in contact with the respective surfaces 2as and 2bs using the first and second electrode portions 2a and 2b as guides, the dimensional accuracy of the contact is increased. be able to. Therefore, the plastic 3 attached to the first and second electrode portions 2a and 2b can be evenly swept off.

  In addition, since the first and second electrode portions 2a and 2b are separated, the first and second electrode portions 2a and 2b are processed with high accuracy and the distance between the first and second electrode portions 2a and 2b. In particular, the long first and second electrode portions 2a and 2b can be manufactured at low cost.

  According to the electrostatic sorting device 1 of the present embodiment, the first and second scraper portions 4af and 4as can come into contact with the respective surfaces 2as and 2bs of the first and second electrode portions 2a and 2b, respectively. It may be configured. The lengths of the first and second electrode portions 2a and 2b in the direction D1 in which the first and second scraper portions 4af and 4as move are set to EL, and the first and second scraper portions 4af and 4as of the plastic 3 are moved to EL. The collision frequency allowable value of the first and second scraper portions 4af and 4as is CP, and the distance between the first electrode portion 2a and the second electrode portion 2b in the direction intersecting the direction D1 in which the first and second scraper portions 4af and 4as move is The sum of the lengths of the first and second scraper parts 4af, 4as is SR, the stop time of the first and second scraper parts 4af, 4as is SI, and the first and second scraper parts 4af, 4as Is set to SV, the number of movements of the first and second scraper units 4af and 4as is set to SF, and the drop time of the plastic 3 between the first electrode unit 2a and the second electrode unit 2b is set to FT. To. In this case, the length ST of each of the first and second scraper units 4af and 4as in the moving direction of the first and second scraper units 4af and 4as is ST ≦ EL × CP / SR + SI × SV × CP / You may be comprised so that the formula of SF / SR-FTxSV may be satisfy | filled.

  Thereby, since the collision frequency of the plastic 3 with respect to the first and second scraper portions 4af and 4as is less than an allowable value, it is possible to sort with higher purity.

  Further, since the central region between the first and second electrode portions 2a and 2b where a relatively large amount of unselected mixed plastic 3 falls is a gap, the mixed plastic 3 and the first and second scraper portions 4af, The risk of error occurrence due to collision with 4as can be greatly reduced. Accordingly, the frequency of movement of the first and second scraper portions 4af and 4as can be increased without difficulty. For this reason, it is possible to improve the recovery rate under sorting conditions in which the amount of the plastic (particle) 3 attached is particularly large.

Hereinafter, examples of the present invention will be described in comparison with comparative examples.
An electrostatic sorting test was conducted on a mixed plastic of ABS (acrylonitrile / butadiene / styrene) resin and PS (polystyrene) resin. The test results are shown in Table 1.

  The electrode cleaning in Table 1 is to remove the plastic adhered to the first and second electrode parts by the scraper part. The voltage application cleaning is to perform electrode cleaning in a state where a voltage is applied to the first and second electrode portions. The no-voltage cleaning is to perform electrode cleaning in a state where no voltage is applied to the first and second electrode portions. In addition, the test was performed under different test conditions with different ABS / PS ratios, electrode cleaning intervals, and collection positions. The ratio of ABS / PS was about 27/73 wt% and 35/65 wt%. The electrode cleaning interval was 20 minutes and 60 minutes.

  The recovery purity of the ABS resin of Example 1 subjected to electrostatic sorting of the present invention is 99% (Example 1), which is higher than 96% (Comparative Example 1) of Comparative Example 1 without electrode cleaning. It was. Moreover, the recovery rate of the ABS resin of Example 1 was 76% (Example 1), which was higher than 70% of Comparative Example 1 (Comparative Example 1) without electrode cleaning.

  In order to use the recycled plastic which has been sorted and collected with mechanical properties equivalent to the new material (for example, tensile strength, tensile breaking elongation, bending strength, etc.), a recovery purity of at least 98% or more, preferably 99% is required. In Example 1, the performance target related to purity was achieved by periodically removing plastic particles adhering to the electrode. In addition, in Examples 1 to 3, the above-described cleaning of the electrode surface is performed while maintaining electrostatic sorting, so that there is no risk of lowering the purity due to mixing of the removed plastic compared to Comparative Example 4 in which sorting is stopped for each cleaning. In addition, the productivity of electrostatic sorting (electrostatic sorting production amount per unit occupation time) was increased.

  Note that in order to ensure 99% recovery purity without electrode cleaning, it is necessary to change the installation position of the recovery container of the electrostatic sorting device to a purity priority position. Specifically, the electrostatic sorting apparatus was operated with the collection container moved away from the intermediate position between both electrodes (purity priority operation). However, in this case, the recovery rate is greatly reduced, although the recovery purity is improved as compared with the case where the electrostatic sorting apparatus is operated by arranging the recovery container at an intermediate position between both electrodes (recovery rate priority operation). For example, in Comparative Example 2, compared with Comparative Examples 1 and 3, it decreased by 20% or more.

  In addition, as shown in Table 1, the performance of electrostatic sorting depends on the composition of the mixed plastic as the sorting raw material and the sorting conditions such as the cleaning interval time when performing electrode cleaning. As shown in Table 1, Examples 1 to 3 of the present invention are effective in achieving both purity and productivity.

  In the above description, the case where the plastic 3 adhered to the first and second surfaces 2as and 2bs facing each other across the drop area A1 has been described, but the opposite sides of the first and second surfaces 2as and 2bs, respectively. The plastic 3 adhered to the surface may also be removed by the scraper portion 4a.

  In the above description, the case where the removed plastic 3 is freely dropped has been described. However, a mechanism for automatically collecting the removed plastic 3 may be provided by providing a suction port or the like in the scraper portion 4a.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Electrostatic sorting apparatus, 2a 1st electrode part, 2b 2nd electrode part, 3 plastic, 4 electrode cleaning mechanism, 4a scraper part, 4a ₁ main body, 4a ₂ sweeping-out part, 4af 1st scraper part, 4as 2nd scraper part, 4b scraper drive part, 4c drive control part, 4d support part, 4e electric motor part, 5 supply part, 6a first recovery container, 6b second recovery container, 7 insulating support mechanism, 8 Rail, 9 electric field, A1 fall area.

Claims (7)

An electrostatic sorting device for sorting by dropping charged plastic,
A first electrode portion having a first surface facing a drop region for dropping the charged plastic;
A second electrode portion having a second surface facing the drop region and capable of applying a voltage different from the first electrode portion;
Moveable along each of the first and second surfaces to remove the plastic adhered to each of the first and second surfaces, and between the fall region and outside the drop region And a scraper part made of an electrically insulating material,
A drive control unit that controls to repeatedly move the scraper unit within the fall region and stop outside the fall region in a state where a voltage is applied to the first and second electrode units; , Electrostatic sorting device. The scraper portion is configured to be able to contact the first and second surfaces, and to extend continuously between the first electrode portion and the second electrode portion,
The length of the first and second electrode parts in the direction in which the scraper part moves is EL,
CP is the allowable collision frequency of the plastic to the scraper part,
The stop time of the scraper unit is SI,
The moving speed of the scraper unit is SV,
The number of movements of the scraper unit is SF,
When the fall time between the first electrode portion and the second electrode portion of the plastic is FT,
The length ST of the scraper part in the moving direction of the scraper part is:
ST ≦ EL × CP + SI × SV × CP / SF−FT × SV
The electrostatic sorting device according to claim 1, satisfying the formula: The scraper unit includes a first scraper unit and a second scraper unit separated from each other,
The electrostatic scrap according to claim 1, wherein the first scraper portion is configured to move along the first surface, and the second scraper portion is configured to move along the second surface. Sorting device. The first and second scraper portions can contact the first and second surfaces, respectively.
The length of the first and second electrode parts in the direction in which the first and second scraper parts move is EL,
The collision frequency allowable value of the plastic to the first and second scraper parts is CP,
The lengths of the first and second scraper portions with respect to the distance between the first electrode portion and the second electrode portion in a direction intersecting with the moving direction of the first and second scraper portions. Let SR be the total proportion,
SI is the stop time of the first and second scraper parts,
The moving speed of the first and second scraper parts is SV,
The number of movements of the first and second scraper parts is SF,
When the fall time between the first electrode portion and the second electrode portion of the plastic is FT,
Each length ST of the first and second scraper parts in the direction in which the first and second scraper parts move is:
ST ≦ EL × CP / SR + SI × SV × CP / SF / SR−FT × SV
The electrostatic sorting device according to claim 3, satisfying the formula:   5. The electrostatic sorting device according to claim 1, wherein the scraper unit is held away from the first and second electrode units at the time of the stop. The scraper part is
The body,
A sweeping portion attached to the main body for sweeping off the plastic adhered to each of the first and second surfaces;
The electrostatic screening apparatus according to claim 1, wherein the sweep-off unit has higher flexibility than the main body.   The first and second electrode portions have a flat plate shape and are arranged so that a distance between the first electrode portion and the second electrode portion is increased in a direction in which the plastic drops. The electrostatic sorting device according to claim 1.

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