Plastic drying device

Abstract

This plastic drying device is provided with: a container (11) in which a plastic piece (P) is accommodated; a microwave generation unit (12) that irradiates the interior of the container (11) with microwaves; and a vacuum pump (13) that communicates with the interior of the container (11) and evacuates the interior of the container (11).

Description

Plastic Drying Equipment

[0001] The present disclosure relates to a plastic drying apparatus.

[0002] In recent years, recycling of used plastics has been actively considered. In order to recycle used plastics, mixed plastic fragments containing multiple types of plastic fragments obtained by collecting and crushing the used plastics must be sorted by material type. One method for sorting plastics is to charge electrically charged plastics by friction or other means, and then sort them by type in an electrostatic field, taking advantage of the different charging characteristics of various plastics. Such a plastic sorting technique is disclosed, for example, in Patent Document 1.

[0003] Japanese Patent Application Publication No. 10-323580

[0004] In the plastic sorting technology disclosed in Patent Document 1, when plastic pieces are wet with water or the like, the plastic pieces are less likely to become electrically charged. Therefore, it is difficult for the plastic sorting technology disclosed in Patent Document 1 to properly sort the plastic pieces.

[0005] In an attempt to solve the above problem, it has been considered to dry the plastic pieces before charging them and sorting them, but when drying the plastic pieces, if the plastic pieces are directly heated, there is a risk that the plastic pieces will melt.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a plastic drying device that can selectively heat water attached to plastic pieces without directly heating the plastic pieces.

[0007] The plastic drying device according to the present disclosure comprises a container in which plastic pieces are stored, a microwave generating unit that irradiates microwaves into the interior of the container, and a vacuum unit that is connected to the interior of the container and draws a vacuum inside the container.

[0008] According to the present disclosure, it is possible to selectively heat water adhering to plastic pieces without directly heating the plastic pieces, thereby preventing the plastic pieces from dissolving when drying.

[0009] Fig. 1 is a schematic configuration diagram of a plastic drying device according to embodiment 1. Fig. 2 is a schematic configuration diagram of another plastic drying device according to embodiment 1. Fig. 3 is a schematic configuration diagram of a plastic drying device according to embodiment 2. Fig. 4 is a schematic configuration diagram of a plastic drying device according to embodiment 3. Fig. 5 is a schematic configuration diagram of a plastic drying device according to embodiment 4. Fig. 6 is a schematic configuration diagram of a plastic drying device according to embodiment 5. Fig. 7 is a schematic configuration diagram of a plastic drying device according to embodiment 6.

[0010] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0011] Embodiment 1. Embodiment 1 will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram of a plastic drying device according to embodiment 1. Figure 2 is a schematic diagram of another plastic drying device according to embodiment 1.

[0012] The plastic drying device according to the first embodiment shown in Fig. 1 dries wet plastic pieces P (including plastic pieces containing moisture). The plastic pieces P are obtained, for example, by crushing used plastics. The plastic pieces P may be made of the same type of material or different types of materials.

[0013] As shown in FIG. 1, the plastic drying device according to the first embodiment includes a container 11, a microwave generating unit 12, and a vacuum pump 13.

[0014] The container 11 has a hollow structure. The interior of the container 11 is a closed space. The container 11 is, for example, cylindrical. Wet plastic pieces (a group of plastic pieces) P are contained inside the container 11. Note that a lid (not shown) that allows the plastic pieces P to be put in and taken out is provided on either of the left and right side surfaces and the outer periphery of the container 11.

[0015] The microwave generating unit 12 emits microwaves toward the inside of the container 11. The microwave generating unit 12 is provided, for example, on either the left or right side surface of the container 11. The microwaves emitted from the microwave generating unit 12 are irradiated evenly into the inside of the container 11.

[0016] At this time, the microwaves emitted from the microwave generator 12 selectively heat the water adhering to the plastic pieces P, but do not directly heat the plastic pieces P. In other words, the plastic pieces P receive heat only through the water heated by the microwave irradiation. Therefore, the temperature of the plastic pieces P does not exceed the temperature of the heated water, and therefore dissolution of the plastic pieces P is suppressed.

[0017] It is known that microwave heating results in different amounts of microwave power absorbed by different materials. For example, the microwave power absorbed by water is greater than that absorbed by plastic. Therefore, when microwaves are irradiated into the interior of the container 11, the microwaves can selectively heat and evaporate the water adhering to the plastic pieces P, ignoring the plastic pieces P. As a result, the plastic drying device according to the first embodiment can heat only the desired object.

[0018] In addition, when microwaves are applied to water, frictional heat is generated as molecules collide with each other, causing the entire water to heat up and rise in temperature. In this way, when microwave heating is used, the entire object to be heated in the microwave electric field is heated simultaneously. Therefore, microwave heating can heat the entire object to be heated uniformly, allowing for efficient heating without wasting energy.

[0019] In the plastic drying device according to embodiment 1 shown in Figure 1, the microwave generating unit 12 is attached directly to the container 11, but the microwave generating unit 12 may be provided at a position away from the container 11, as in the other plastic drying device according to embodiment 1 shown in Figure 2.

[0020] The vacuum pump 13 has a vacuum exhaust pipe 13a. The tip of this vacuum exhaust pipe 13a is connected to either the left or right side of the container 11 and is connected to the inside of the container 11. Therefore, when the vacuum pump 13 is driven, the vacuum pump 13 evacuates the container 11 via the vacuum exhaust pipe 13a. As a result, the air pressure inside the container 11 drops to a pressure below atmospheric pressure. Therefore, the boiling point of water inside the container 11 drops. In other words, water attached to the plastic pieces P becomes more likely to evaporate. The vacuum pump 13 constitutes a vacuum section.

[0021] Therefore, when drying water-soaked plastic pieces P, first, the water-soaked plastic pieces P are supplied into the container 11. Next, the plastic drying device drives the microwave generator 12. As a result, microwaves emitted from the microwave generator 12 are irradiated toward the inside of the container 11. Then, the plastic drying device drives the vacuum pump 13. As a result, the inside of the container 11 is evacuated, thereby reducing the pressure.

[0022] As a result, the microwaves emitted from the microwave generator 12 heat and evaporate the water adhering to the plastic pieces P supplied inside the container 11. Furthermore, because the inside of the container 11 is depressurized by evacuating, the boiling point of water inside the container 11 is lowered. This makes it easier for the water adhering to the plastic pieces P to evaporate. As a result, the time it takes for the water to completely evaporate, in other words, the time it takes for the plastic pieces P to dry, is shorter than when the inside of the container 11 is not evacuated.

[0023] As described above, the plastic drying apparatus according to the first embodiment includes a container 11 in which plastic pieces P are stored, a microwave generator 12 that irradiates microwaves into the interior of the container 11, and a vacuum pump 13 that communicates with the interior of the container 11 and draws a vacuum inside the container 11. Therefore, the plastic drying apparatus according to the first embodiment can selectively heat water adhering to the plastic pieces P without directly heating the plastic pieces P. As a result, the plastic drying apparatus according to the first embodiment can prevent the plastic pieces P from dissolving when drying the plastic pieces P.

[0024] Embodiment 2 A plastic drying device according to embodiment 2 will be described with reference to Fig. 3. Fig. 3 is a schematic diagram of the plastic drying device according to embodiment 2. Note that components having the same functions as those described in embodiment 1 above are given the same reference numerals, and descriptions thereof will be omitted.

[0025] As shown in FIG. 3, the plastic drying device according to the second embodiment has a structure in which a rotating section 14 is added to the structure of the plastic drying device according to the first embodiment.

[0026] The rotating unit 14 rotates the cylindrical container 11 around its central axis. The rotating unit 14 is, for example, a motor. When the rotating unit 14 rotates the container 11 in this manner, the plastic pieces P contained inside the container 11 are agitated by the rotation of the container 11. This makes it easier for the plastic pieces P to separate from each other and from each other and from the water. As a result, the plastic drying device according to the second embodiment can prevent uneven drying of the plastic pieces P.

[0027] Furthermore, the plastic pieces P contained inside the container 11 rub against each other as they are stirred by the rotation of the container 11. Therefore, the plastic drying device according to the second embodiment can charge the electrically charged plastic pieces P by friction, taking advantage of the fact that the charging characteristics of the various plastic pieces P are different. As a result, the plastic drying device according to the second embodiment can also function as a charging device.

[0028] As described above, the plastic drying device according to the second embodiment includes the rotating unit 14 that rotates the container 11 around the central axis. Therefore, the plastic drying device according to the second embodiment can prevent uneven drying of the plastic pieces P. Furthermore, the plastic drying device according to the second embodiment can also function as a charging device.

[0029] Embodiment 3 A plastic drying device according to embodiment 3 will be described with reference to Fig. 4. Fig. 4 is a schematic diagram of the plastic drying device according to embodiment 3. Note that components having the same functions as those described in the above-mentioned embodiments 1 and 2 are given the same reference numerals, and their description will be omitted.

[0030] As shown in Fig. 4, the plastic drying device according to the third embodiment has a structure in which one or more protrusions 15 are added to the structure of the plastic drying device according to the second embodiment. Fig. 4 shows an example in which one protrusion 15 is provided.

[0031] The protrusion 15 is provided on the inner peripheral surface of the cylindrical container 11. The protrusion 15 protrudes from the inner peripheral surface of the container 11 toward the inside in the radial direction of the container 11. The protrusion 15 is arranged over the entire axial area of ​​the inner peripheral surface of the container 11. The protrusion 15 may be integral with the inner peripheral surface of the container 11 or may be separate.

[0032] In this way, the plastic drying apparatus according to the third embodiment is provided with the protrusion 15, and by rotating the container 11 with the rotating part 14, the plastic pieces P contained inside the container 11 can be thoroughly mixed. Therefore, the plastic drying apparatus according to the third embodiment can prevent uneven drying of the plastic pieces P. Furthermore, the plastic drying apparatus according to the third embodiment can shorten the time required to charge the plastic pieces P.

[0033] As described above, the plastic drying device according to the second embodiment is provided with the protrusion 15 that protrudes inward from the inner surface of the container 11. Therefore, the plastic drying device according to the second embodiment can further suppress uneven drying of the plastic pieces P.

[0034] Embodiment 4 A plastic drying device according to embodiment 4 will be described with reference to Fig. 5. Fig. 5 is a schematic diagram of a plastic drying device according to embodiment 3. Note that components having the same functions as those described in the above-mentioned embodiments 1 and 2 are given the same reference numerals, and their description will be omitted.

[0035] As shown in FIG. 5, the plastic drying device according to the fourth embodiment has a structure in which a hole 11a of a container 11 and an outer container 16 are added to the structure of the plastic drying device according to the third embodiment.

[0036] The container 11 has a plurality of holes 11a. The plurality of holes 11a are provided in the outer wall of the container 11. The plurality of holes 11a are formed, for example, in each of the side surface and the outer peripheral surface of the container 11. The size of the holes 11a is smaller than the size of the plastic pieces P.

[0037] The outer container 16 houses the container 11. The outer container 16 has an inclined surface 16a below the housed container 11. The inclined surface 16a gradually slopes downward as it approaches the outside of the outer container 16. The container 11 is rotatably supported inside the outer container 16. The outer container 16 is formed of, for example, a metal material.

[0038] The tip of the vacuum exhaust pipe 13a of the vacuum pump 13 is connected to the side surface of the external container 16 and communicates with the interior of the external container 16. Therefore, when the vacuum pump 13 is driven, the vacuum pump 13 evacuates the external container 16 via the vacuum exhaust pipe 13a. At this time, since a plurality of holes 11a are formed in the container 11, the container 11 is evacuated together with the external container 16 via these holes 11a.

[0039] Furthermore, when the container 11 is rotated by the rotating part 14, the plastic pieces P contained inside the container 11 are agitated by the rotation of the container 11. At this time, some of the water adhering to the plastic pieces P evaporates from the plastic pieces, and some of the water scatters from the plastic pieces and drips into the interior of the external container 16 through the holes 11a. Of these, the water that drips into the interior of the external container 16 flows along the slope of the inclined surface 16a, is collected, and then is discharged from the external container 16. Therefore, the plastic drying device according to the fourth embodiment can shorten the drying time for plastics.

[0040] Here, the size of the hole 11a is smaller than the size of the plastic piece P, so the plastic piece will not fly out from the hole 11a into the inside of the outer container 16 when the vacuum pump 13 is evacuated and the container 11 is rotating. Furthermore, since the outer container 16 is made of a metal material, leakage of the microwaves emitted from the microwave generating unit 12 can be prevented.

[0041] As described above, the plastic drying apparatus according to the fourth embodiment includes a plurality of holes 11a provided on the outer wall of the container 11 and communicating with the interior of the container 11, and an outer container 16 that rotatably houses the container 11, and the vacuum pump 13 draws a vacuum inside the container 11 via the inside of the outer container 16. Therefore, the plastic drying apparatus according to the fourth embodiment can drain water from the plastic pieces P.

[0042] The plastic drying apparatus according to the fourth embodiment is provided with an inclined surface 16a that is provided on the external container 16 and slopes downward from the container 11 toward the outside of the external container 16. Therefore, the plastic drying apparatus according to the fourth embodiment can easily collect water that has dripped from the container 11 into the external container 16 and discharge it from the external container 16.

[0043] Furthermore, in the plastic drying apparatus according to the fourth embodiment, the outer container 16 is made of a metal material, so that the plastic drying apparatus according to the fourth embodiment can prevent microwaves from leaking from the outer container 16.

[0044] Embodiment 5 A plastic drying device according to embodiment 5 will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of the plastic drying device according to embodiment 5. Note that components having the same functions as those described in the above-mentioned embodiments 1, 2, and 4 are given the same reference numerals, and their description will be omitted.

[0045] Fig. 6 specifically shows the configuration of the microwave generating unit 12. As shown in Fig. 6, the microwave generating unit 12 has a microwave source 12a, an antenna 12b, a rotary joint 12c, and a microwave transmission line 12d.

[0046] The microwave source 12a is a part that generates microwaves and is provided on the inner surface of the outer container 16. Note that the microwave source 12a does not necessarily have to be provided in the outer container 16, but may be provided outside the container 11 at a position separated from the container 11.

[0047] The antenna 12b is a part that emits microwaves. The antenna 12b has a circular shape. The antenna 12b is fixed to the container 11. Specifically, the antenna 12b is arranged coaxially with the central axis that serves as the rotation axis of the container 11 and perpendicular to the central axis of the container 11.

[0048] The rotary joint 12c is provided at the center of the antenna 12b and is electrically connected to the antenna 12b while allowing the antenna 12b to rotate.

[0049] The microwave transmission line 12d is capable of transmitting microwaves. The microwave transmission line 12d electrically connects the microwave source 12a and the rotary joint 12c. That is, the microwave source 12a is electrically connected to the antenna 12b via the microwave transmission line 12d and the rotary joint 12c. The microwave transmission line 12d may be any line capable of transmitting microwaves, such as a coaxial cable or a waveguide.

[0050] Therefore, the microwave source 12a, which is installed stationary in the external container 16, can maintain an electrical connection with the antenna 12b even if the antenna 12b rotates together with the container 11. The microwaves emitted from the microwave source 12a are transmitted to the antenna 12b via the microwave transmission line 12d and the rotary joint 12c.

[0051] In this way, the microwave generating unit 12 can arrange the antenna 12b on the central axis of the container 11 so as to be perpendicular to the central axis of the container 11. As a result, the microwave generating unit 12 can uniformly irradiate the microwaves emitted from the antenna 12b onto the plastic pieces P contained inside the container 11.

[0052] As described above, in the plastic drying apparatus according to the fifth embodiment, the microwave generating unit 12 is provided in the external container 16 and includes a microwave source 12a that generates microwaves, an antenna 12b that is coaxial with the central axis of the container 11 and is arranged perpendicular to the central axis of the container 11 and that irradiates microwaves toward the interior of the container 11, and a rotary joint 12c that is electrically connected to the microwave source 12a via a microwave transmission line 12d and that electrically connects to the antenna 12b while allowing the antenna 12b to rotate. Therefore, the plastic drying apparatus according to the fifth embodiment can uniformly irradiate the microwaves emitted from the antenna 12b to the plastic pieces P stored inside the container 11.

[0053] Sixth Embodiment A plastic drying device according to a sixth embodiment will be described with reference to Fig. 7. Fig. 7 is a schematic diagram of the plastic drying device according to the sixth embodiment. Note that components having the same functions as those described in the first, second, fourth, and fifth embodiments are given the same reference numerals, and the description thereof will be omitted.

[0054] As shown in FIG. 7, the plastic drying device according to the sixth embodiment has a structure in which a barometer 17 and a blower 18 are added to the structure of the plastic drying device according to the fourth embodiment.

[0055] The barometer 17 is connected to the vacuum exhaust pipe 13a of the vacuum pump 13. Therefore, the barometer 17 can measure the air pressure inside the container 11. The blower 18 is connected to the inside of the external container 16. Therefore, the blower 18 can send air into the container 11 via the inside of the external container 16.

[0056] The plastic drying apparatus according to the sixth embodiment controls the airflow rate of the air blower 18 based on the air pressure measured by the barometer 17. Therefore, the plastic drying apparatus according to the sixth embodiment can maintain the air pressure inside the container 11 within a predetermined range, thereby suppressing the generation of plasma inside the container 11. The generation of plasma may adversely affect the efficiency of microwave irradiation.

[0057] As described above, the plastic drying apparatus according to the sixth embodiment includes the barometer 17 connected to the vacuum pump 13 and measuring the air pressure inside the container 11, and the air blower 18 that blows air into the container 11 based on the air pressure measured by the barometer 17. Therefore, the plastic drying apparatus according to the sixth embodiment can suppress plasma generation inside the container 11.

[0058] It should be noted that within the scope of the present disclosure, the embodiments may be freely combined, or any component in each embodiment may be modified, or any component in each embodiment may be omitted.

[0059] The plastic drying device of the present disclosure is equipped with a microwave generating unit and a vacuum unit for the container that holds the plastic pieces, thereby selectively heating the water adhering to the plastic pieces without directly heating the plastic pieces, making it suitable for use in plastic drying devices, etc.

[0060] 11 container, 11a hole, 12 microwave generating part, 12a microwave source, 12b antenna, 12c rotary joint, 12d microwave transmission line, 13 vacuum pump, 13a vacuum exhaust pipe, 14 rotating part, 15 protrusion, 16 outer container, 16a inclined surface, 17 barometer, 18 blower part, P plastic piece.

Claims

1. A plastic drying device comprising: a container in which plastic pieces are stored; a microwave generating unit that irradiates microwaves into the inside of the container; and a vacuum unit that communicates with the inside of the container and draws a vacuum inside the container.

2. The plastic drying device according to claim 1, further comprising a rotating part for rotating the container around a central axis.

3. The plastic drying device according to claim 2, further comprising a protrusion protruding inward from the inner surface of the container.

4. A plastic drying device as described in claim 2 or 3, characterized in that it comprises a plurality of holes provided in the outer wall of the container and communicating with the inside of the container, and an external container that rotatably houses the container, and the vacuum section draws a vacuum inside the container through the inside of the external container.

5. The plastic drying device according to claim 4, characterized in that the external container is provided with an inclined surface that is inclined downwardly toward the outside of the external container.

6. The plastic drying device according to claim 4 or 5, characterized in that the outer container is made of a metal material.

7. A plastic drying device as claimed in any one of claims 4 to 6, characterized in that the microwave generating unit comprises: a microwave source provided in the external container for generating microwaves; an antenna arranged coaxially with and perpendicular to the central axis of the container for irradiating microwaves toward the inside of the container; and a rotary joint electrically connected to the microwave source via a microwave transmission path and electrically connected to the antenna while allowing the antenna to rotate.

8. A plastic drying device as claimed in any one of claims 1 to 7, characterized in that it comprises: a barometer connected to the vacuum section for measuring the air pressure inside the container; and an air blowing section for blowing air into the container based on the air pressure measured by the barometer.

9. The plastic drying device according to claim 1, characterized in that the microwave generating unit is provided in the container.

10. The plastic drying device according to claim 1, characterized in that the microwave generating unit is provided at a position away from the container.

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