Extruder for thermal decomposition, method for producing decomposition gas, and method for discharging the same

Abstract

To provide an extruder for thermal decomposition which is capable of suppressing a decomposition gas generated by thermal decomposition of a polymer to be discharged from a hopper hole, and a manufacturing method of a decomposition gas.SOLUTION: In an extruder for thermal decomposition 10, a hopper 14 is cylindrical. A bottom edge of the hopper 14 is attached to a transportation part 11. By these, an internal space of the hopper 14 is connected to an internal space of the transportation part 11 (cylinder 10) via a hopper hole 11a. A side wall of the hopper 14 is provided with a discharge hole 14b. The discharge hole 14b is penetrated through the side wall of the hopper 14. Thus, the discharge hole 14b is connected to the internal space of the hopper 14, and a decomposition gas generated on thermal decomposition of a polymer is discharge to outside of the hopper 14.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to an extruder for pyrolysis, a pyrolysis system, a method for producing and discharging a decomposition gas.

Background Art

[0002] Japanese Patent Application Laid-Open No. 11-106427 (Patent Document 1) describes an extruder. In the extruder described in Patent Document 1, an acrylic resin introduced into the cylinder from a hopper is plasticized and pyrolyzed in the cylinder by the shearing force from a twin-screw and the heat from a heater.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The decomposition gas generated by pyrolyzing an acrylic resin may flow backward and be released into the atmosphere from the hopper.

[0005] The present disclosure provides an extruder for pyrolysis capable of suppressing the decomposition gas generated by pyrolyzing a polymer from being released from the hopper.

Means for Solving the Problems

[0006] In the extruder for pyrolysis according to one aspect of the present disclosure, the upper end of the hopper is closed, and a discharge hole for discharging the decomposition gas generated when the polymer is pyrolyzed is provided in the side wall of the hopper to the outside of the hopper.

Effects of the Invention

[0007] According to the extruder for pyrolysis according to one aspect of the present disclosure, it is possible to suppress the decomposition gas generated by the pyrolysis of the polymer from being released from the hopper.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations are not repeated.

[0010] (Pyrolysis System According to the First Embodiment) The configuration of the pyrolysis system according to the first embodiment will be described.

[0011] <Schematic Configuration of the Pyrolysis System According to the First Embodiment> FIG. 1 is a schematic diagram of a pyrolysis system according to the first embodiment. As shown in FIG. 1, the pyrolysis system according to the first embodiment includes an extruder 100, a residue tank 110, a cooler 120, a receiver tank 130, and a suction device 140.

[0012] The pyrolysis system according to the first embodiment further includes a cooler 150 and a receiver tank 160. The pyrolysis system according to the first embodiment further includes pipelines 181, 182, 183, 184, and 185. Note that the solid arrows in FIG. 1 indicate the flow of the polymer, and the dotted arrows in FIG. 1 indicate the flow of the decomposition gas or the liquid monomer.

[0013] The residue tank 110 is connected to the extruder 100. The cooler 120 is connected to the residue tank 110 by the pipeline 181. The receiver tank 130 is connected to the cooler 120 by the pipeline 182 and is connected to the suction device 140 by the pipeline 183.

[0014] The cooler 150 is connected to the hopper 14 of the extruder 100 by a pipeline 184. The receiver tank 160 is connected to the cooler 150 by a pipeline 185.

[0015] <Detailed structure of the extruder 100> FIG. 2 is a schematic cross-sectional view of an extruder 100 used in the pyrolysis system according to the first embodiment. As shown in FIG. 2, the extruder 100 has a cylinder 10, a heater 20, a screw 30, a motor 40, and a gear box 50. The extruder 100 may further have a shaft seal mechanism 60. The extruder 100 is an extruder for pyrolysis of polymers.

[0016] The cylinder 10 has an upstream end 10a and a downstream end 10b. The downstream end 10b is the end on the opposite side of the upstream end 10a. The downstream end 10b is connected to the residue tank 110.

[0017] The heater 20 is disposed on the outer peripheral surface of the cylinder 10. The heater 20 is, for example, an embedded heater, a cartridge heater, etc. The heater 20 heats the polymer in the cylinder 10. However, the heater 20 is not limited to an electric heater such as an embedded heater or a cartridge heater. The polymer in the cylinder 10 may be heated by steam or oil. In this case, the steam or oil passes through a jacket provided in the cylinder 10 to heat the polymer in the cylinder 10.

[0018] The screw 30 is disposed in the cylinder 10. The screw 30 is, for example, a twin-screw. The screw 30 conveys the polymer in the cylinder 10 from the upstream end 10a side to the downstream end 10b side while applying a shearing force to the polymer in the cylinder 10.

[0019] The cylinder 10 has a conveying section 11, a plasticizing section 12, and a pyrolysis section 13. The plasticizing section 12 is on the downstream end 10b side of the conveying section 11. The pyrolysis section 13 is on the downstream end 10b side of the plasticizing section 12.

[0020] A hopper 14 is attached to the conveying unit 11. Inside the conveying unit 11, the polymer is introduced through the hopper 14. The polymer introduced into the conveying unit 11 is conveyed to the plasticizing unit 12 as the screw 30 rotates. The polymer is, for example, polymethyl methacrylate resin, polylactic acid resin, polyethylene terephthalate resin, polystyrene resin, polyamide resin, and polypropylene resin. However, the polymer is not limited to these. Any polymer that can be thermally decomposed into decomposition gas may be used.

[0021] The polymer in the plasticizing unit 12 is plasticized by the heat from the heater 20 and the shearing force from the screw 30. Also, the polymer in the plasticizing unit 12 is conveyed to the thermal decomposition unit 13 as the screw 30 rotates. The polymer in the thermal decomposition unit 13 is thermally decomposed by the heat from the heater 20 and the shearing force from the screw 30. The thermally decomposed polymer becomes decomposition gas.

[0022] The motor 40 has a motor body 41 and a shaft 42. The motor body 41 rotates the shaft 42 around its axis. The gearbox 50 is connected to the screw 30 and the shaft 42. The gearbox 50 transmits the rotation of the shaft 42 to the screw 30. Thereby, the motor 40 drives the screw 30.

[0023] The shaft seal mechanism 60 hermetically seals the upstream end 10a in a state where the screw 30 is operable. The shaft seal mechanism 60 is, for example, a mechanical seal.

[0024] Figure 3 shows a first configuration example of the screw 30. As shown in Figure 3, the screw 30 has a shaft 31 and a shaft 32, a plurality of kneading disks 33a, and a plurality of kneading disks 34a.

[0025] The shafts 31 and 32 extend in the same direction as the cylinder 10. The shafts 31 and 32 are rotated about their axes by the gear box 50. The plurality of kneading disks 33a are attached to the shaft 31. The plurality of kneading disks 34a are attached to the shaft 32.

[0026] The phase of the kneading disk 33a on the most upstream end 10a side is shifted by 180° from the phase of the kneading disk 33a on the most downstream end 10b side. The phase of the kneading disk 33a changes as it goes from the upstream end 10a side to the downstream end 10b side. The amount of phase change between two adjacent kneading disks 33a in the extending direction of the shaft 31 is equal to the value obtained by dividing 180° by the number of kneading disks 33a minus 1. In the example of FIG. 3, since the number of kneading disks 33a is 5, two adjacent kneading disks 33a have a phase difference of 45°.

[0027] Adjacent kneading disks 33a and kneading disks 34a have a phase difference of 90° from each other. The direction of phase change of the kneading disk 33a and the direction of phase change of the kneading disk 34a when going from the upstream end 10a side to the downstream end 10b side are the same. In the configuration example shown in FIG. 3, the screw 30 sends out the polymer in the direction from the upstream end 10a to the downstream end 10b while applying a shearing force to the polymer.

[0028] FIG. 4 shows a second configuration example of the screw 30. As shown in FIG. 4, the direction of phase change of two adjacent kneading disks 33a in the extending direction of the shaft 31 and the direction of phase change of two adjacent kneading disks 34a in the extending direction of the shaft 32 are respectively opposite to the direction of phase change shown in FIG. 3. In other respects, the configuration example shown in FIG. 4 is common to the configuration example shown in FIG. 3. In the configuration example shown in FIG. 4, the screw 30 returns the polymer in the direction from the downstream end 10b to the upstream end 10a while applying a shearing force to the polymer.

[0029] FIG. 5 shows a third configuration example of the screw 30. As shown in FIG. 5, the screw 30 may have a full-flight screw 33b and a full-flight screw 34b instead of the plurality of kneading disks 33a and the plurality of kneading disks 34a.

[0030] The structures of the full-flight screw 34b and the full-flight screw 33b are common. However, the phase of the full-flight screw 33b is different by 90° from the phase of the full-flight screw 34b. In the configuration example shown in FIG. 5, the screw 30 mainly serves to send the polymer in the direction from the upstream end 10a to the downstream end 10b.

[0031] The screw 30 in the plasticizing section 12 is used, for example, in combination with the configuration example shown in FIG. 3 and the configuration example shown in FIG. 4. Thereby, the polymer is likely to be filled in the plasticizing section 12, and the shearing force from the screw 30 is likely to act on the polymer in the plasticizing section 12. As a result, the plasticization of the polymer in the plasticizing section 12 is likely to proceed.

[0032] The screw 30 in the thermal decomposition section 13 is used, for example, in combination with the configuration example shown in FIG. 3, the configuration example shown in FIG. 4, and the configuration example shown in FIG. 5. Thereby, the polymer is likely to be filled in the thermal decomposition section 13, and the shearing force from the screw 30 is likely to act on the polymer in the thermal decomposition section 13. As a result, the thermal decomposition of the polymer in the thermal decomposition section 13 is likely to proceed.

[0033] On the other hand, the screw 30 in the conveying section 11 uses the configuration example shown in FIG. 5. Thereby, the polymer is smoothly conveyed to the plasticizing section 12.

[0034] In short, it is preferable that the screws 30 in the plasticizing section 12 and the decomposition section 13 have a structure that facilitates filling of the polymer in the plasticizing section 11 and the thermal decomposition section 13 and facilitates the application of shear force to the polymer. On the other hand, it is preferable that the screw 30 in the conveying section 11 has a structure that can smoothly convey the polymer to the plasticizing section 12.

[0035] FIG. 6 is a cross-sectional view of the hopper 14 used in the extruder 100 of the thermal decomposition system according to the first embodiment. As shown in FIG. 6, the hopper 14 is cylindrical. The lower end of the hopper 14 is attached to the conveying section 11. Thereby, the internal space of the hopper 14 and the internal space of the conveying section 11 (cylinder 10) are connected by the hopper hole 11a. The upper end of the hopper 14 is closed by a lid member 14a.

[0036] A discharge hole 14b is provided in the side wall of the hopper 14. The discharge hole 14b penetrates the side wall of the hopper 14. That is, the discharge hole 14b is connected to the internal space of the hopper 14. A pipe line 184 is connected to the discharge hole 14b.

[0037] A chute 14c is provided in the side wall of the hopper 14. The polymer is introduced into the hopper 14 through the chute 14c. The polymer introduced from the chute 14c is introduced into the conveying section 11 through the hopper hole 11a provided in the conveying section 11.

[0038] An introduction hole 14d is provided in the chute 14c. An inert gas is introduced into the hopper 14 from the introduction hole 14d. The inert gas is introduced into the hopper 14 along the inner wall surface of the side wall of the hopper 14. Thereby, the inert gas introduced into the hopper 14 forms a swirling flow in the hopper 14. The inert gas is, for example, nitrogen gas.

[0039] <Operation of the thermal decomposition system according to the first embodiment> FIG. 7 is a process diagram showing a method for producing a decomposition gas using the pyrolysis system according to the first embodiment. As shown in FIG. 7, the method for producing a decomposition gas using the pyrolysis system according to the first embodiment includes a polymer charging step S1, a polymer plasticization step S2, a polymer pyrolysis step S3, and a monomer recovery step S4. Further, the method for producing a decomposition gas using the pyrolysis system according to the first embodiment further includes a decomposition gas discharge step S5 and a monomer recovery step S6.

[0040] In the polymer charging step S1, the polymer is charged into the extruder 100. More specifically, the polymer is charged into the conveying section 11 through the hopper 14 and the hopper hole 11a. The polymer charged into the conveying section 11 is conveyed to the plasticizing section 12 as the screw 30 rotates. The polymer charged into the conveying section 11 is heated by the heater 20 while being conveyed to the plasticizing section 12 by the screw 30.

[0041] In the polymer plasticization step S2, the extruder 100 plasticizes the polymer. The plasticization of the polymer is performed in the plasticizing section 12. More specifically, the polymer is plasticized by the shearing force from the screw 30 and the heat from the heater 20 in the plasticizing section 12.

[0042] In the polymer pyrolysis step S3, the extruder 100 pyrolyzes at least a part of the polymer plasticized in the polymer plasticization step S2. The pyrolysis of the polymer is performed in the decomposition section 13. More specifically, the polymer is pyrolyzed by the shearing force from the screw 30 and the heat from the heater 20 in the decomposition section 13. The pyrolyzed polymer becomes a decomposition gas. In the polymer pyrolysis step S3, not all of the polymer needs to be pyrolyzed.

[0043] In the monomer recovery step S4, liquid monomers are recovered. In the monomer recovery step S4, first, the decomposition gas generated in the polymer pyrolysis step S3 is recovered. More specifically, by driving the suction device 140 (for example, a vacuum pump), the inside of the residue tank 110, the cooler 120, and the receiver tank 130 becomes negative pressure with respect to the inside of the cylinder 10. As a result, the decomposition gas is sent from the downstream end 10b through the residue tank 110 to the cooler 120. In addition, due to the volume change when the decomposition gas is condensed in the cooler 120, the inside of the cooler 120 becomes negative pressure, so the decomposition gas can be sent to the cooler 120 without using the suction device 140.

[0044] Next, the decomposition gas sent to the cooler 120 is cooled inside the cooler 120. This cooling is performed, for example, by water cooling. More specifically, the decomposition gas sent to the cooler 120 passes through the cooling pipes arranged inside the cooler 120. Since water is flowing around the cooling pipes, the decomposition gas sent to the cooler 120 is condensed by this cooling and becomes a liquid (liquid monomer). The liquid monomer condensed inside the cooler 120 is recovered by being stored in the receiver tank 130.

[0045] The liquid monomer is taken out from the receiver tank 130 through the outlet 131 (see FIG. 2) provided on the outer wall of the receiver tank 130. The recovered liquid monomer can be reused as a polymer by performing the polymerization step.

[0046] When the extruder 100 is operating, a part of the polymer in the plasticizing section 12 may be thermally decomposed, generating decomposition gas. Also, when the extruder 100 is stopped, a part of the polymer in the conveying section 11, the plasticizing section 12, and the thermal decomposition section 13 may be thermally decomposed, generating decomposition gas. Some of these decomposition gases may flow backward in the cylinder 10 in the direction from the downstream end 10b to the upstream end 10a. The decomposition gas that has flowed backward may be referred to as the backward-flowing decomposition gas.

[0047] In the decomposition gas discharge step S5, the reverse decomposition gas is discharged from the discharge hole 14b. More specifically, the reverse decomposition gas flowing backward to the transport unit 11 is sucked into the hopper 14 and discharged from the discharge hole 14b due to the cyclone phenomenon accompanying the swirling of the inert gas introduced from the introduction hole 14d in the hopper 14.

[0048] In the monomer recovery step S6, first, the reverse decomposition gas discharged from the discharge hole 14b is sent to the cooler 150 through the pipeline 184. Second, the reverse decomposition gas sent to the cooler 150 is cooled in the cooler 150. This cooling is performed, for example, by water cooling. More specifically, the reverse decomposition gas sent to the cooler 150 passes through the cooling pipes arranged in the cooler 150. Since water is flowing around the cooling pipes, the reverse decomposition gas sent to the cooler 150 is condensed into a liquid (liquid monomer) when passing through the cooling pipes. The liquid monomer condensed in the cooler 150 is stored in the receiver tank 160 through the pipeline 185.

[0049] Third, the liquid monomer stored in the receiver tank 160 is recovered. The liquid monomer is taken out from the outlet 161 (see FIG. 2) provided on the outer wall of the receiver tank 160.

[0050] The polymer that was not thermally decomposed in the polymer thermal decomposition step S3 and the impurities (residues) contained in the polymer are discharged from the downstream end 10b and stored in the residue tank 110. A heater 111 (see FIG. 2) may be attached to the outer wall of the residue tank 110. By operating the heater 111, it is possible to suppress the decomposition gas from being cooled to the outside air temperature and condensed in the residue tank 110. The residue stored in the residue tank 110 is taken out from the outlet 112 (see FIG. 2) provided on the outer wall of the residue tank 110.

[0051] (Effect of the thermal decomposition system according to the embodiment) The effect of the thermal decomposition system according to the embodiment will be described in comparison with the comparative example.

[0052] In the pyrolysis system according to the comparative example, an extruder 200 is used instead of the extruder 100. FIG. 8 is a schematic cross-sectional view of the extruder 200. As shown in FIG. 8, the pyrolysis system according to the comparative example does not have a cooler 150 and a receiver tank 160. Further, the pyrolysis system according to the comparative example does not have a pipeline 184 and a pipeline 185.

[0053] FIG. 9 is a cross-sectional view of the hopper 14 used in the extruder 200. As shown in FIG. 9, in the extruder 200, the upper end of the hopper 14 is not blocked by a lid member 14a. Further, in the extruder 200, a discharge hole 14b, a chute 14c, and an introduction hole 14d are not provided on the side wall of the hopper 14. Except for these points, the pyrolysis system according to the comparative example is the same as the pyrolysis system according to the first embodiment.

[0054] As described above, a part of the decomposition gas generated in the cylinder 10 may become a reverse flow decomposition gas. In the pyrolysis system according to the comparative example, since the upper end of the hopper 14 is not blocked, the reverse flow decomposition gas may be discharged out of the system from the upper end of the hopper 14.

[0055] On the other hand, in the pyrolysis system according to the first embodiment, a discharge hole 14b is provided in the hopper 14 and the upper end of the hopper 14 is blocked. In the pyrolysis system according to the first embodiment, since an inert gas is supplied from the introduction hole 14d, the reverse flow decomposition gas does not flow into the chute 14c. Therefore, the reverse flow decomposition gas is discharged from the discharge hole 14b. The reverse flow decomposition gas discharged from the discharge hole 14b is condensed in the cooler 150 and stored in the receiver tank 160, so that the discharge to the outside of the system is suppressed.

[0056] Depending on the operating conditions of the extruder 100, the reverse decomposition gas may reach a high temperature (for example, a temperature equal to or higher than the ignition point or spontaneous ignition point of the reverse decomposition gas). For example, when the polymer is a polymethyl methacrylate resin, depending on the operating conditions of the extruder 100, the reverse decomposition gas may reach 400°C or higher. In the pyrolysis system according to the embodiment, since the reverse decomposition gas is cooled and then stored, the safety of treating the reverse decomposition gas can be enhanced.

[0057] (Pyrolysis System According to the Second Embodiment) The pyrolysis system according to the second embodiment will be described. Here, the points different from the pyrolysis system according to the first embodiment will be mainly described, and overlapping descriptions will not be repeated.

[0058] FIG. 10 is a schematic diagram of the pyrolysis system according to the second embodiment. As shown in FIG. 10, the pyrolysis system according to the second embodiment includes an extruder 100, a residue tank 110, a cooler 120, a receiver tank 130, and a suction device 140.

[0059] The pyrolysis system according to the second embodiment further includes a cooler 150, a receiver tank 160, and a suction device 170. The pyrolysis system according to the second embodiment further includes pipelines 181, 182, 183, 184, 185, and 186. The suction device 170 is connected to the receiver tank 160 by the pipeline 186. The suction device 170 is, for example, a vacuum pump. However, the suction device 170 is not limited thereto. The solid arrows in FIG. 10 indicate the flow of the polymer, and the dotted arrows in FIG. 10 indicate the flow of the decomposition gas or liquid monomer.

[0060] FIG. 11 is a cross-sectional view of the hopper 14 used in the extruder 100 of the pyrolysis system according to the second embodiment. As shown in FIG. 11, in the pyrolysis system according to the second embodiment, the introduction hole 14d is not provided in the chute 14c. However, in order to purge the inside of the hopper 14 with an inert gas, in the pyrolysis system according to the second embodiment, the introduction hole 14d may be provided in the side wall of the hopper 14.

[0061] In the pyrolysis system according to the second embodiment, by driving the suction device 170, the inside of the cooler 150 and the receiver tank 160 are under negative pressure with respect to the inside of the hopper 14. As a result, the cracked gas is sent to the cooler 120 through the discharge hole 14b and the pipeline 184. Therefore, also in the pyrolysis system according to the second embodiment, the release of the reverse-flow cracked gas to the outside of the system is suppressed.

[0062] (Pyrolysis System According to the Third Embodiment) The pyrolysis system according to the third embodiment will be described. Here, mainly the differences from the pyrolysis system according to the first embodiment will be described, and overlapping descriptions will not be repeated.

[0063] FIG. 12 is a schematic view of the pyrolysis system according to the third embodiment. As shown in FIG. 12, the pyrolysis system according to the third embodiment includes an extruder 100, a residue tank 110, a cooler 120, a receiver tank 130, and a suction device 140.

[0064] The pyrolysis system according to the third embodiment further includes a cooler 150, a receiver tank 160, and a receiver tank 162. The pyrolysis system according to the third embodiment further includes pipelines 181, 182, 183, 184, 185, and 187. The pipeline 187 connects the hopper 14 of the extruder 100 and the receiver tank 162. Note that the solid arrows in FIG. 12 indicate the flow of the polymer, and the dotted arrows in FIG. 12 indicate the flow of the cracked gas or the liquid monomer.

[0065] FIG. 13 is a cross-sectional view of the hopper 14 used in the extruder 100 of the pyrolysis system according to the third embodiment. As shown in FIG. 13, in the pyrolysis system according to the third embodiment, a flow path 14e is provided in the side wall of the hopper 14. A refrigerant flows through the flow path 14e. Thereby, the side wall of the hopper 14 is cooled. The reverse flow pyrolysis gas in the hopper 14 condenses on the side wall of the hopper 14 and becomes a liquid monomer.

[0066] Further, in the pyrolysis system according to the third embodiment, a discharge hole 14f is provided in the side wall of the hopper 14. The discharge hole 14f penetrates the side wall of the hopper 14. That is, the discharge hole 14f is connected to the internal space of the hopper 14. A pipe 187 is connected to the discharge hole 14f. The liquid monomer condensed on the side wall of the hopper 14 is stored in the receiver tank 162 through the discharge hole 14f and the pipe 187. Therefore, also in the pyrolysis system according to the third embodiment, the release of the reverse flow pyrolysis gas to the outside of the system is suppressed. In addition, in order to facilitate the discharge of the liquid monomer condensed from the discharge hole 14f, a receiving portion 14g for receiving the liquid polymer condensed on the side wall of the hopper 14 is provided on the side wall of the hopper 14.

[0067] (Pyrolysis System According to the Fourth Embodiment) The pyrolysis system according to the fourth embodiment will be described. Here, the points different from the pyrolysis system according to the first embodiment will be mainly described, and overlapping descriptions will not be repeated.

[0068] FIG. 14 is a schematic view of the pyrolysis system according to the fourth embodiment. As shown in FIG. 14, the pyrolysis system according to the fourth embodiment includes an extruder 100, a residue tank 110, a cooler 120, a receiver tank 130, and a suction device 140. The pyrolysis system according to the fourth embodiment further includes a pipe 181, a pipe 182, and a pipe 183.

[0069] However, the pyrolysis system according to the fourth embodiment does not have the cooler 150 and the receiver tank 160. Further, the pyrolysis system according to the fourth embodiment does not have the pipeline 184 and the pipeline 185. In addition, the solid arrows in FIG. 14 indicate the flow of the polymer, and the dotted arrows in FIG. 14 indicate the flow of the decomposition gas or the liquid monomer. However, the pyrolysis system according to the fourth embodiment may have the cooler 150, the receiver tank 160, the pipeline 184, and the pipeline 185.

[0070] FIG. 15 is a cross-sectional view of the hopper 14 used in the extruder 100 of the pyrolysis system according to the fourth embodiment. As shown in FIG. 15, in the pyrolysis system according to the fourth embodiment, the upper end of the hopper 14 is not blocked by the lid member 14a. In addition, in the pyrolysis system according to the fourth embodiment, the upper end of the hopper 14 may be partially blocked. In the pyrolysis system according to the fourth embodiment, the discharge hole 14b, the chute 14c, and the introduction hole 14d are not provided on the side wall of the hopper 14. In addition, in the pyrolysis system according to the fourth embodiment, the discharge hole 14b, the chute 14c, and the introduction hole 14d may be provided on the side wall of the hopper 14.

[0071] In the pyrolysis system according to the fourth embodiment, the extruder 100 has the opening and closing device 70. The opening and closing device 70 is, for example, a gate valve. The opening and closing device 70 has a main body portion 71 and a partition plate 72. A through hole 71a is provided in the main body portion 71.

[0072] The opening and closing device 70 can switch between a state where the through hole 71a is blocked by the partition plate 72 and a state where the through hole 71a is not blocked by the partition plate 72 by sliding the partition plate 72.

[0073] When the partition plate 72 does not block the through hole 71a, the internal space of the hopper 14 is connected to the external space of the hopper 14 through the through hole 71a. In this state, the polymer can be introduced into the hopper 14 from a feeder (not shown) through the through hole 71a. When the partition plate 72 blocks the through hole 71a, the internal space of the hopper 14 is blocked from the external space of the hopper 14.

[0074] When the extruder 100 is operating, the partition plate 72 does not block the through hole 71a. On the other hand, when the extruder 100 is in an emergency stop or normal stop state (when the screw 30 is stopped), the partition plate 72 blocks the through hole.

[0075] When the extruder 100 is operating, the plasticizing section 12 is filled with the polymer, so it is difficult for the reverse-flow decomposition gas to return to the conveying section 11. However, even when the extruder 100 is stopped, the decomposition of the polymer proceeds. Therefore, the spatial separation between the conveying section 11 and the thermal decomposition section 13 due to the polymer filled in the plasticizing section 12 disappears, and the reverse-flow decomposition gas easily returns to the conveying section 11. The reverse-flow decomposition gas that has returned to the conveying section 11 may be discharged out of the system from the hopper 14.

[0076] In the thermal decomposition system according to the fourth embodiment, when the extruder 100 is stopped, the opening / closing device 70 blocks the internal space of the hopper 14 from the external space of the hopper 14, so the discharge of the reverse-flow decomposition gas out of the system is suppressed. In the thermal decomposition system according to the fourth embodiment, when the extruder 100 is operating, since the internal space of the hopper 14 is connected to the external space of the hopper 14, there is no hindrance to introducing the polymer into the conveying section 11 through the hopper 14.

[0077] (Thermal decomposition system according to the fifth embodiment) The thermal decomposition system according to the fifth embodiment will be described. Here, the points different from the thermal decomposition system according to the first embodiment will be mainly described, and repeated descriptions will not be repeated.

[0078] FIG. 16 is a schematic diagram of a pyrolysis system according to the fifth embodiment. As shown in FIG. 16, the pyrolysis system according to the fifth embodiment includes an extruder 100, a residue tank 110, a cooler 120, a receiver tank 130, and a suction device 140. The pyrolysis system according to the fifth embodiment further includes a pipeline 181, a pipeline 182, and a pipeline 183.

[0079] However, the pyrolysis system according to the fifth embodiment does not include a cooler 150 and a receiver tank 160. Also, the pyrolysis system according to the fifth embodiment does not include a pipeline 184 and a pipeline 185. The pyrolysis system according to the fifth embodiment includes a receiver tank 163 and a pipeline 188. The pipeline 188 connects the extruder 100 and the receiver tank 163. Note that the solid arrows in FIG. 16 indicate the flow of the polymer, and the dotted arrows in FIG. 16 indicate the flow of the decomposition gas or the liquid monomer. However, the pyrolysis system according to the fifth embodiment may include a cooler 150, a receiver tank 160, a pipeline 184, and a pipeline 185.

[0080] FIG. 17 is a cross-sectional view of a cylinder 10 used in the extruder 100 of the pyrolysis system according to the fifth embodiment. As shown in FIG. 17, in the pyrolysis system according to the fifth embodiment, the cylinder 10 is composed of a plurality of divided cylinders 15 arranged along the direction from the upstream end 10a to the downstream end 10b. Each of the divided cylinders 15 is provided with a flow path 16. A refrigerant flows through the flow path 16. Preferably, the refrigerant can flow independently through the flow path 16 of each of the divided cylinders 15. It is preferable that the divided cylinders 15 constituting the pyrolysis section 13 are provided with the flow path 16, but the divided cylinders 15 constituting the pyrolysis section 13 may not be provided with the flow path 16.

[0081] In the flow path 16 of the split cylinder 15 that constitutes the conveying unit 11, refrigerant does not flow when the extruder 100 is operating (i.e., when the screw 30 is operating), while refrigerant flows when the extruder 100 is stopped (i.e., when the screw 30 is stopped). However, refrigerant may always flow in the flow path 16 provided in the split cylinder 15 where the hopper hole 11a is provided.

[0082] In the flow path 16 of the split cylinder 15 that constitutes the plasticizing unit 12, refrigerant does not flow when the extruder 100 is operating, while refrigerant flows when the extruder 100 is stopped. In the flow path 16 of the split cylinder 15 that constitutes the thermal decomposition unit 13, refrigerant does not flow when the extruder 100 is operating, while refrigerant flows when the extruder 100 is stopped. However, in the flow path 16 of the split cylinder 15 that constitutes the thermal decomposition unit 13, refrigerant does not necessarily flow when the extruder 100 is stopped.

[0083] In the thermal decomposition system according to the fifth embodiment, a slit 11b is provided in the split cylinder 15 where the hopper hole 11a is provided. The slit 11b penetrates the split cylinder 15 and connects the internal space of the split cylinder 15 and the external space of the split cylinder 15. The slit 11b is connected to the pipeline 188. The slit 11b is provided at the lower part of the split cylinder 15 where the hopper hole 11a is provided. Instead of the slit 11b, a mesh may be provided in the split cylinder 15 where the hopper hole 11a is provided. Note that a slit 11b (mesh) may be provided in the split cylinder 15 that constitutes the conveying unit 11 other than the split cylinder 15 where the hopper hole 11a is provided. Also, the slit 11b (mesh) may be provided at a position other than the lower part of the split cylinder 15.

[0084] Note that when the screw 30 is stopped, the heater 20 stops operating (heating of the polymer is stopped).

[0085] FIG. 18 is a cross-sectional view of the hopper 14 used in the extruder 100 of the pyrolysis system according to the fifth embodiment. As shown in FIG. 18, in the pyrolysis system according to the fifth embodiment, the upper end of the hopper 14 is not blocked by the lid member 14a. That is, in the pyrolysis system according to the fifth embodiment, the polymer is introduced into the hopper 14 from the upper end side of the hopper 14. In the pyrolysis system according to the fifth embodiment, the discharge hole 14b, the chute 14c, and the introduction hole 14d are not provided on the side wall of the hopper 14. However, in the pyrolysis system according to the fifth embodiment, the discharge hole 14b, the chute 14c, and the introduction hole 14d may be provided on the side wall of the hopper 14, and the upper end of the hopper 14 may be blocked by the lid member 14a.

[0086] When the extruder 100 is operating, since the plasticizing section 12 is filled with the polymer, it is difficult for the reverse-flow decomposition gas to return to the conveying section 11. However, since the decomposition of the polymer proceeds even when the extruder 100 is stopped, the spatial separation between the conveying section 11 and the pyrolysis section 13 due to the polymer filled in the plasticizing section 12 disappears, and the reverse-flow decomposition gas easily returns to the conveying section 11. The reverse-flow decomposition gas that has returned to the conveying section 11 may be released outside the system from the hopper 14.

[0087] In the pyrolysis system according to the fifth embodiment, when the extruder 100 is stopped, the plasticizing section 12 is cooled, so that the polymer filled in the plasticizing section 12 is solidified. Therefore, even when the extruder 100 is stopped, the spatial separation between the conveying section 11 and the pyrolysis section 13 due to the polymer filled in the plasticizing section 12 can be maintained, and the release of the reverse-flow decomposition gas outside the system is suppressed.

[0088] Even when the extruder 100 is stopped, thermal decomposition of the polymer in the conveying section 11 and the plasticizing section 12 may progress, generating reverse decomposition gas. In the thermal decomposition system according to the fifth embodiment, since the conveying section 11 and the plasticizing section 12 are cooled when the extruder 100 is stopped, the reverse decomposition gas generated by thermal decomposition of the polymer in the conveying section 11 and the plasticizing section 12 condenses in the conveying section 11 and the plasticizing section 12 to become a liquid polymer. This liquid polymer is stored in the receiver tank 163 through the slit 11b and the pipe 188. Therefore, in the thermal decomposition system according to the fifth embodiment, the release of the reverse decomposition gas generated in the conveying section 11 and the plasticizing section 12 to the outside of the system is suppressed.

[0089] Although the embodiments of the present disclosure have been described as above, it is also possible to variously modify the above-described embodiments. Further, the scope of the present invention is not limited to the above-described embodiments. The scope of the present invention is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Description of Reference Numerals

[0090] 100, 200 extruder, 10 cylinder, 10a upstream end, 10b downstream end, 11 conveying section, 11a hopper hole, 11b slit, 12 plasticizing section, 13 thermal decomposition section, 14 hopper, 14a lid member, 14b discharge hole, 14c chute, 14d introduction hole, 14e flow path, 14f discharge hole, 14g receiving section, 15 split cylinder, 16 flow path, 20 heater, 30 screw, 31 shaft, 32 shaft, 33a kneading disk, 33b full flight screw, 34a kneading disk, 34b full flight screw, 40 motor, 41 motor body, 42 shaft, 50 gear box, 60 shaft seal mechanism, 70 opening and closing device, 71 main body section, 71a through hole, 72 partition plate, 110 residue tank, 111 heater, 112 outlet, 120 cooler, 130 receiver tank, 131 outlet, 140 suction device, 150 cooler, 160 receiver tank, 161 outlet, 162, 163 receiver tank, 170 suction device, 181, 182, 183, 184, 185, 186, 187, 188 pipeline, S1 polymer feeding process, S2 polymer plasticizing process, S3 polymer thermal decomposition process, S4 monomer recovery process, S5 decomposition gas discharge process, S6 monomer recovery process.

Claims

1. An extruder for thermal decomposition of polymers, comprising: A screw for conveying, plasticizing and thermally decomposing the polymer; A cylinder in which the screw is housed; A hopper for introducing the polymer into the cylinder; and A shaft seal mechanism attached to the upstream end of the cylinder, wherein the upper end of the hopper is closed, the side wall of the hopper is provided with discharge holes for discharging decomposition gas generated when the polymer is thermally decomposed to the outside of the hopper, the shaft seal mechanism blocks the outflow of the decomposition gas from the upstream end of the cylinder, the cylinder has a conveying section for conveying the polymer, a plasticizing section for plasticizing the polymer, and a thermal decomposition section for thermally decomposing the polymer to generate decomposition gas, when the screw is stopped, the conveying section and the plasticizing section are cooled.

2. The extruder for thermal decomposition according to claim 1, wherein the side wall of the hopper is provided with an introduction hole for introducing an inert gas into the hopper along the inner wall surface of the side wall of the hopper.

3. The extruder for thermal decomposition according to claim 1 or claim 2, wherein a flow path for flowing a refrigerant is provided in the side wall of the hopper.

4. An extruder for thermal decomposition of polymers, comprising: A screw for conveying, plasticizing and thermally decomposing the polymer; A cylinder in which the screw is housed; and A shaft seal mechanism attached to the upstream end of the cylinder, which blocks the outflow of decomposition gas generated when the polymer is thermally decomposed from the upstream end of the cylinder, wherein the cylinder has a conveying section for conveying the polymer, a plasticizing section for plasticizing the polymer, and a thermal decomposition section for thermally decomposing the polymer to generate decomposition gas, when the screw is stopped, the conveying section and the plasticizing section are cooled.

5. An extruder for thermal decomposition of polymers, comprising: A screw for conveying, plasticizing and thermally decomposing the polymer; and A cylinder in which the screw is housed, wherein the cylinder has a conveying section for conveying the polymer, a plasticizing section for plasticizing the polymer, and a thermal decomposition section for thermally decomposing the polymer to generate decomposition gas, when the screw is stopped, the conveying section and the plasticizing section are cooled.

6. The pyrolysis extruder according to claim 5, wherein when the screw is stopped, the conveying section, the plasticizing section, and the pyrolysis section are cooled.

7. The pyrolysis extruder according to claim 5 or 6, wherein the conveying section is provided with a slit or a mesh for discharging the liquefied decomposition gas to the outside of the cylinder.

8. A method for producing a decomposition gas, comprising the following steps: (a) A step of introducing a polymer into a cylinder of a pyrolysis extruder via a hopper; (b) A step of plasticizing the polymer by a screw in the cylinder; (c) After step (b), a step of pyrolyzing the polymer; (d) A step of discharging the decomposition gas generated in step (c) to the outside of the hopper through a discharge hole provided in a side wall of the hopper; and (e) After step (d), a step of recovering the discharged decomposition gas. Here, the cylinder has a conveying section for conveying the polymer, a plasticizing section for plasticizing the polymer, and a pyrolysis section for pyrolyzing the polymer to generate a decomposition gas, when the screw is stopped, the conveying section and the plasticizing section are cooled.

9. The method for producing a decomposition gas according to claim 8, wherein step (d) is performed by utilizing the flow of an inert gas introduced into the hopper.

10. A method for discharging a decomposition gas, comprising the following steps: (a) A step of introducing a polymer into a cylinder of a pyrolysis extruder via a hopper; (b) A step of plasticizing the polymer by a screw in the cylinder; (c) After step (b), a step of pyrolyzing the polymer; and (d) A step of discharging the decomposition gas generated in step (c) to the outside of the hopper through a discharge hole provided in a side wall of the hopper. Here, the cylinder has a conveying section for conveying the polymer, a plasticizing section for plasticizing the polymer, and a pyrolysis section for pyrolyzing the polymer to generate a decomposition gas, when the screw is stopped, the conveying section and the plasticizing section are cooled.

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