Depolymerization liquid generating device

Abstract

A depolymerization liquid generation device (10) is provided with: a depolymerization liquid generation unit (16) for generating a depolymerization liquid by kneading plastic and water in a heated environment; a back pressure valve (19) for adjusting the pressure of the depolymerized liquid output from the depolymerized liquid generation unit (16); a first heat exchange unit (18) provided in a flow path (fpD) between the depolymerization liquid generation unit and the back pressure valve; a second heat exchange unit (14) provided in a supply path (fpW) for supplying water to the depolymerization liquid generation unit; a temperature regulator (22) that regulates the temperature of the heat medium circulating through the first heat exchange unit (18) and the second heat exchange unit (14); and a switching valve (17) that switches between a first flow path (fp1) through which the heat medium from the thermostat circulates to the thermostat (22) via the first heat exchange unit (18), and a second flow path (fp2) through which the heat medium from the thermostat circulates to the thermostat via the first heat exchange unit (18) and the second heat exchange unit (14).

Description

Technical Field

[0001] The invention relates to a depolymerization liquid generating device for depolymerizing plastic to generate depolymerization liquid. Background Art

[0002] As such a technology, there is known an apparatus for mixing waste plastics and water and heating them to cause a degradation reaction of the waste plastics (see, for example, Patent Document 1).

[0003] If the depolymerized liquid after the degradation reaction is excessively cooled, the heat energy during the concentration operation of the depolymerized liquid in the process after the degradation process will increase. In addition, when the device starts to operate, the viscosity of a part of the undepolymerized liquid due to insufficient degradation reaction increases, which may block the flow path of the depolymerized liquid and hinder the stable operation of the device.

[0004] The stable operation and energy saving of the device will contribute to the development of sustainable waste plastic treatment technology.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2001-181651 (JP 2001-181651 A). Summary of the invention

[0008] A depolymerization liquid generating device according to one technical solution of the present invention comprises: a depolymerization liquid generating section, which mixes plastic and water in a heated environment to generate a depolymerization liquid; a back pressure valve, which adjusts the pressure of the depolymerization liquid output from the depolymerization liquid generating section; a first heat exchange section, which is arranged in a flow path between the depolymerization liquid generating section and the back pressure valve; a second heat exchange section, which is arranged in a supply path of water supplied to the depolymerization liquid generating section; a thermostat, which adjusts the temperature of a heat medium circulating in the first heat exchange section and the second heat exchange section; and a switching valve, which switches between a first flow path for circulating the heat medium from the thermostat to the thermostat via the first heat exchange section and a second flow path for circulating the heat medium from the thermostat to the thermostat via the first heat exchange section and the second heat exchange section. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The objects, features and advantages of the present invention will be further clarified through the following description of the embodiments in conjunction with the accompanying drawings.

[0010] Figure 1 A schematic diagram showing an example of the structure of a depolymerization liquid production device according to an embodiment

[0011] Figure 2 This is a flowchart for explaining an example of the processing flow during operation of the depolymerization liquid production apparatus. DETAILED DESCRIPTION

[0012] <Outline>

[0013] The depolymerization liquid production device of the embodiment reduces heat energy used in the depolymerization liquid production device and its periphery in the degradation process of the chemical recovery system of plastics using a depolymerization reaction using water under subcritical conditions as a medium.

[0014] The depolymerization liquid generating device reacts a polyamide resin (e.g., PA6) as a plastic with water under a high temperature and high pressure (e.g., 350°C, 17MPa) environment to generate a depolymerization liquid. The depolymerization liquid contains ε-caprolactam (degradation product). Then, after the heat medium is heated by exchanging heat between the high temperature (the above 350°C) depolymerization liquid and the heat medium oil (hereinafter referred to as the heat medium), the heated heat medium is used to exchange heat with the supply water, thereby reducing the heating energy for the supply water.

[0015] However, if the temperature of the depolymerization liquid is too low due to heat exchange with the high-temperature depolymerization liquid, a large amount of heat energy is required for the concentration operation in the process after the degradation process. Therefore, by appropriately controlling the temperature of the depolymerization liquid by heat exchange, the heat energy used in the process after the degradation process can be suppressed.

[0016] Furthermore, when the depolymerized liquid generating device is cold-started and the startup operation is performed, if the depolymerization reaction is not sufficient, a part of the unreacted resin may remain in the device (referred to as undepolymerized liquid). At this time, if the temperature of the flow channel at the outlet of the device is lower than the undepolymerized liquid, that is, lower than the melting point of PA6 (about 225°C), a part of the undepolymerized liquid will solidify in the flow channel. In addition, compared with the case where the temperature of the flow channel at the outlet is not lower than the melting point, but is sufficiently higher than the melting point near the melting point (for example, 250°C or more), the viscosity of the undepolymerized liquid becomes higher, so it is difficult for the undepolymerized liquid to be discharged through the flow channel. Therefore, during the startup operation, by heating the temperature of the flow channel at the outlet of the device to be sufficiently higher than the melting point of the undepolymerized liquid, it is possible to prevent the undepolymerized liquid from solidifying and stagnating, thereby contributing to the stable operation of the device.

[0017] The structure of such a depolymerization liquid producing device will be described in more detail with reference to the drawings.

[0018] <Device Structure>

[0019] Figure 1 Schematic diagram showing an example of the structure of the depolymerization liquid production device 10 according to the embodiment. Figure 1As shown, the depolymerization liquid generating device 10 comprises: a hopper 11 for feeding a polyamide resin P as a raw material; a tank 12 for storing supply water W; a first pump 13 for conveying the supply water W stored in the tank 12; a second heat exchanger 14 for performing heat exchange between the supply water W and a heat medium; an auxiliary heating unit 15 for heating the supply water W; a kneader 16 for kneading the polyamide resin P and the supply water W; a switching valve 17 for switching a flow path fpH of the heat medium used for heat exchange; a first heat exchanger 18 for performing heat exchange between the depolymerization liquid D flowing out of the kneader 16 and the heat medium; and a back pressure valve 19 provided on the downstream side of the depolymerization liquid D of the first heat exchanger 18 ( Figure 1 on the right side); a third heat exchange unit 20, which performs heat exchange between the depolymerization liquid D that has passed through the back pressure valve 19 and the heat medium; a temperature sensor 21, which measures the temperature of the depolymerization liquid D flowing to the back pressure valve 19; a thermostat 22, which adjusts the temperature of the heat medium; a second pump 23, which transports the heat medium; and a control unit 30.

[0020] The upstream side of the hopper 11 and the kneading machine 16 ( Figure 1 The hopper 11 is connected to the mixing machine 16 (left side) to supply the polyamide resin P to the mixing machine 16. In more detail, the hopper 11 includes a storage portion 11a configured to store the polyamide resin P, and an opening and closing portion 11b capable of switching between a supply state in which the polyamide resin P stored in the storage portion 11a is supplied to the mixing machine 16 and a cut-off state in which the supply to the mixing machine 16 is cut off. The storage portion 11a is formed in a substantially trapezoidal shape in a longitudinal cross-sectional view, and is configured to supply the polyamide resin P to the mixing machine 16 from a supply port 11c provided at the lower end. The opening and closing portion 11b is provided at the supply port 11c, and the amount of the polyamide resin P supplied to the mixing machine 16 is adjusted by controlling the opening and closing portion 11b.

[0021] The tank 12 stores the supply water W. The supply water W stored in the tank 12 is increased in pressure (e.g., 17.5 MPa) by driving the first pump 13, and is supplied to the kneading machine 16 via the second heat exchanger 14 and the auxiliary heating unit 15. The supply water W is supplied to the kneading machine 16 via the droplet nozzle 16e. The droplet nozzle 16e in the kneading machine 16 is located downstream ( 17.5 MPa) from the connection portion of the hopper 11 (the position where the polyamide resin P is supplied). Figure 1 on the right side of the screen).

[0022] The first pump 13 increases the supply pressure of the supply water W to the above-mentioned 17.5 MPa. As an example, the temperature of the supply water W sent out from the first pump 13 is set to 30° C., and the flow rate is set to 30 kg / h.

[0023] The second heat exchange section 14 can be any of a plate type, a double-tube type or a multi-tube type. When the second heat exchange section 14 is in stable operation, the temperature of the supply water W flowing in the supply path fpW is heated from the above-mentioned 30°C to about 320°C by performing heat exchange between a heat medium at a high temperature (for example, about 340°C) and the supply water W. The heat medium input from the heat medium flow channel fp2 to the second heat exchange section 14 is heated to, for example, about 340°C through the first heat exchange section 18 described later. In this embodiment, the state in which the temperature of the mixer 16 reaches a specified temperature (for example, 340°C) and a depolymerization reaction is carried out is called a stable state, and the operation in this state is called a stable operation. In addition, the operation from the start of the depolymerization liquid generating device 10 to the reaching of a stable state is called a startup operation.

[0024] More specifically, since the heat medium flow path fp2 is closed by the switching valve 17 described later, the supply water W passes through the second heat exchanger 14 at 30° C. and flows to the auxiliary heating unit 15 .

[0025] The auxiliary heating unit 15 is composed of a heater or the like that can heat the internal pipe through which the supply water W flows. The auxiliary heating unit 15 heats the supply water W to a temperature of about 350° C. during both the steady operation and the startup operation.

[0026] By preheating the temperature of the supply water W to about 350°C, when the supply water W is injected into the mixer 16 via the droplet nozzle 16e, it is possible to prevent the temperature of the molten polyamide resin P from decreasing at the top end of the droplet nozzle 16e due to the low temperature of the supply water W, thereby preventing the polyamide resin P from solidifying.

[0027] The kneading machine 16 is composed of an extruder in which a screw 16b is stored in a cylindrical cylinder 16a, and the cylinder 16a is configured to be a subcritical condition. More specifically, a heating unit 16c is provided between the connection portion of the hopper 11 and the droplet nozzle 16e in the cylinder 16a. The cylinder 16a is heated by the heating unit 16c, and the temperature in the cylinder 16a is maintained at 350°C, for example. The polyamide resin P introduced from the hopper 11 is melted in the heated cylinder 16a.

[0028] In addition, the downstream end 16d of the cylinder 16a is formed into a top narrowing shape (contracted shape). When the screw 16b is rotated by the motor M to extrude the polyamide resin P and the supply water W toward the downstream side while kneading, the pressure in the cylinder 16a becomes a high pressure of, for example, 17 MPa or more due to the narrowing of the internal flow passage of the back pressure valve 19 described later. In this way, the cylinder 16a becomes a subcritical condition, and the polyamide resin P is depolymerized by kneading the polyamide resin P and the supply water W under the subcritical condition.

[0029] The subcritical condition in the cylinder 16a is maintained by a back pressure valve 19 provided downstream of the depolymerized liquid D in the first heat exchange section 18 connected to the downstream end 16d. The temperature of the downstream end 16d of the cylinder 16a is slightly lower than the temperature (350°C) of the upstream side of the cylinder 16a.

[0030] The kneading machine 16 is constituted by, for example, a twin-screw extruder having two screws 16 b.

[0031] The first heat exchange section 18, the back pressure valve 19 and the third heat exchange section 20 are connected to the downstream side of the kneading machine 16 ( Figure 1 The flow path fpD of the depolymerized liquid D is connected from the downstream end 16d of the kneading machine 16 via the first heat exchanger 18, the back pressure valve 19 and the third heat exchanger 20 to a device (not shown) that is responsible for the process after the degradation process, such as a device for recovering monomers in the depolymerized liquid.

[0032] On the other hand, the heat medium delivered from the second pump 23 passes through the outer periphery of the third heat exchange section 20 , around the back pressure valve 19 , and the outer periphery of the first heat exchange section 18 , and is sent to the switching valve 17 .

[0033] As an example, the first heat exchange section 18 and the third heat exchange section 20 are composed of a coaxial heat exchanger. For example, a back pressure valve 19 is connected between the inner tube of the first heat exchange section 18 and the inner tube of the third heat exchange section 20, and the inner tube of the first heat exchange section 18 → the back pressure valve 19 → the inner tube of the third heat exchange section 20 is used as the flow path fpD of the depolymerization liquid D. Figure 1 In the figure, the flow channel fpD of the depolymerization liquid D is painted white for illustration.

[0034] In addition, the back pressure valve 19 is covered with a jacket (not shown), and the outer periphery of the inner tube in the first heat exchange unit 18, the inside of the jacket around the back pressure valve 19, and the outer periphery of the inner tube in the third heat exchange unit 20 are connected to form a flow path fpH for the heat medium. Figure 1 In the figure, the flow path fpH of the heat medium in the first heat exchange section 18, the back pressure valve 19, and the third heat exchange section 20 is drawn in fine dots.

[0035] The heat medium delivered from the second pump 23 is inputted into the outer periphery of the third heat exchanger 20 from the input portion 20a located at the outer periphery of the third heat exchanger 20. Next, the heat medium is inputted into the hood via the output portion 20b located at the outer periphery of the third heat exchanger 20 and the input portion 19a of the hood covering the periphery of the back pressure valve 19. Furthermore, the heat medium is inputted into the outer periphery of the first heat exchanger 18 via the output portion 19b of the hood covering the periphery of the back pressure valve 19 and the input portion 18a located at the outer periphery of the first heat exchanger 18. In addition, the heat medium is outputted to the switching valve 17 from the output portion 18b located at the outer periphery of the first heat exchanger 18.

[0036] It should be noted that, instead of forming the first heat exchange section 18 and the third heat exchange section 20 with a coaxial heat exchanger, they may be formed with, for example, a double-tube or multi-tube heat exchanger.

[0037] In addition, instead of causing the heat medium to flow in the hood covering the periphery of the back pressure valve 19 , a heating block may be provided so as to surround the back pressure valve 19 , and the heat medium may be caused to flow in the heating block.

[0038] In addition, although the example in which the first heat exchange part 18, the back pressure valve 19, and the third heat exchange part 20 are separately constructed and connected is described, the first heat exchange part 18, the back pressure valve 19, and the third heat exchange part 20 may be constructed as one body.

[0039] According to the above-described configuration, heat exchange is performed between the high-temperature (about 340° C.) depolymerization liquid D flowing out of the kneader 16 and the heat medium adjusted to a predetermined temperature by the temperature regulator 22 described later. The heat exchange during the steady operation will be described in detail below.

[0040] The depolymerization liquid D squeezed out from the downstream end 16d of the cylinder 16a of the mixer 16 flows in the inner tube of the first heat exchange section 18 toward the back pressure valve 19, with the pressure (17 MPa) regulated by the back pressure valve 19, and then flows rightward toward the outlet in the inner tube of the third heat exchange section 20.

[0041] On the other hand, the heat medium (about 40°C during stable operation) delivered from the second pump 23 flows toward the back pressure valve 19 at the periphery of the third heat exchange part 20, and flows toward the output part 18b at the periphery of the first heat exchange part 18 through the shield covering the back pressure valve 19.

[0042] By circulating the depolymerization liquid D at about 340°C and the heat medium at about 40°C in the inner tube and the outer peripheral portion, respectively, the heat of the depolymerization liquid D is transferred to the heat medium, and the depolymerization liquid D is cooled to a predetermined temperature (e.g., about 100°C) in the third heat exchange section 20. By lowering the temperature of the depolymerization liquid D, the life of the consumable components, O-rings, and diaphragms, etc., which constitute the back pressure valve 19, can be extended. However, assuming that the depolymerization liquid D is completely liquid when cooled to 90°C, it becomes too cold in the embodiment. That is, the heat energy when the depolymerization liquid D is concentrated in the process after the degradation process is increased.

[0043] On the other hand, the heat medium is heated by the depolymerization liquid D and is heated to a predetermined temperature (for example, 340° C.) at the output portion 18 b of the first heat exchange unit 18 .

[0044] In addition, the heat exchange during the startup operation will be described in detail as follows.

[0045] The undepolymerized liquid extruded from the downstream end 16d of the cylinder 16a of the kneader 16 flows toward the back pressure valve 19 in the inner tube of the first heat exchange section 18, passes through the back pressure valve 19, and flows rightward toward the outlet in the inner tube of the third heat exchange section 20.

[0046] On the other hand, the heat medium (about 250°C during startup operation) delivered from the second pump 23 flows toward the back pressure valve 19 at the periphery of the third heat exchange section 20, and flows toward the output section 18b at the periphery of the first heat exchange section 18 through the shield covering the back pressure valve 19.

[0047] By allowing the undepolymerized liquid (e.g., about 220° C.) and the heat medium (e.g., about 250° C.) to flow through the inner tube and the outer peripheral portion, respectively, the heat of the heat medium is transferred to the undepolymerized liquid, and the undepolymerized liquid is maintained at a predetermined temperature (e.g., about 250° C.) in the third heat exchange unit 20. 250° C. is higher than the melting point (e.g., about 225° C.) of the undepolymerized liquid in the embodiment, that is, PA6.

[0048] The temperature sensor 21 measures the temperature of the depolymerization liquid D flowing to the back pressure valve 19. The temperature detection signal of the temperature sensor 21 is sent to the control unit 30, for example. Thus, the control unit 30 can monitor the temperature of the depolymerization liquid D and perform a predetermined control. For example, the heat exchange performed by the first heat exchange unit 18, the back pressure valve 19 and the third heat exchange unit 20 is designed to make the temperature of the depolymerization liquid D in the third heat exchange unit 20 about 100 to 120° C. when the flow rate of the heat medium is 60 kg / h, based on the heat transfer area between the inner tube and the outer peripheral part, the total heat transfer coefficient, etc. The control unit 30 can adjust the heat exchange amount by changing the flow rate of the heat medium so that the detection temperature detected by the temperature sensor 21 becomes the above-mentioned 100 to 120° C. It should be noted that the flow rate of the heat medium can be changed, for example, by adjusting the output of the second pump 23.

[0049] The temperature controller 22 adjusts the temperature of the input heat medium to a set temperature by heating or cooling the input heat medium and outputs the heat medium.

[0050] The set temperature of the thermostat 22 during the steady operation is, for example, approximately 40° C., and the set temperature during the startup operation is, for example, approximately 250° C.

[0051] The second pump 23 delivers the heat medium at a pressure of, for example, 0.1 MPa. As an example, the temperature of the heat medium delivered from the second pump 23 follows the set temperature of the thermostat 22, and the flow rate is set to 60 kg / h.

[0052] The switching valve 17 is constituted by, for example, a three-way valve, etc. The switching valve 17 switches the destination of the heat medium input to the switching valve 17 through the heat medium flow path fpH to the flow path fp1 or the flow path fp2 according to a signal from the control unit 30 .

[0053] The switching valve 17 switches to the flow path fp1 during the startup operation, and switches to the flow path fp2 during the steady operation.

[0054] The control unit 30 is composed of a computer having a computing unit (processor) such as a CPU (microprocessor), a storage unit (memory) such as a ROM (read only memory) and a RAM (random access memory), and other peripheral circuits not shown, such as an I / O interface.

[0055] <Explanation of the flow chart>

[0056] Figure 2 This is a flowchart for explaining an example of the processing flow during the operation of the depolymerization liquid production device 10. Steps S10 to S70 correspond to the startup operation, and steps S80 and thereafter correspond to the steady operation.

[0057] When the operator performs an operation start operation, the control unit 30 starts the operation according to a predetermined program. Figure 2 processing.

[0058] exist Figure 2 In step S10, the control unit 30 starts heating the kneading machine 16 and proceeds to step S20.

[0059] In step S20, the control unit 30 switches the flow path fpH of the heat medium to the first flow path through the switching valve 17, and the process proceeds to step S30. The first flow path corresponds to the flow path fp1.

[0060] In step S30, the control unit 30 sets the temperature of the thermostat 22. The control unit 30 sets the set temperature of the thermostat 22 to, for example, approximately 250°C, and the process proceeds to step S40.

[0061] In step S40, the control unit 30 sets the auxiliary heating unit 15. The control unit 30 sets the set temperature of the auxiliary heating unit 15 to, for example, about 350°C, and the process proceeds to step S50.

[0062] In step S50 , the control unit 30 starts supplying the polyamide resin P and the water W as the raw materials, and the process proceeds to step S60 .

[0063] In step S60, the control unit 30 sets the pressure of the back pressure valve 19, and the process proceeds to step S70. The setting pressure of the back pressure valve 19 is set to gradually increase from 0 MPa to 17 MPa, for example.

[0064] In step S70, the control unit 30 determines whether a predetermined time has elapsed since the start of supplying the raw material and the water W. The predetermined time in the embodiment corresponds to the time of the depolymerization reaction in the kneading machine 16 and the time required to heat the first heat exchange unit 18, the back pressure valve 19, and the third heat exchange unit 20 to about 250° C. by the heat medium.

[0065] When the predetermined time, for example, 15 minutes, has elapsed, the control unit 30 makes an affirmative determination in step S70 (S70: Yes) and proceeds to step S80. When the elapsed time is less than 15 minutes, the control unit 30 makes a negative determination in step S70 (S70: No) and repeats the determination process.

[0066] In step S80, the control unit 30 switches the flow path fpH of the heat medium to the second flow path through the switching valve 17, and the process proceeds to step S90. The second flow path corresponds to the flow path fp2.

[0067] In step S90, the control unit 30 sets the temperature of the thermostat 22. The control unit 30 sets the set temperature of the thermostat 22 to, for example, approximately 40°C, and proceeds to step S100.

[0068] In step S100, the control unit 30 sets the auxiliary heating unit 15. The control unit 30 continues to set the setting temperature of the auxiliary heating unit 15 to, for example, about 350°C, and proceeds to step S110.

[0069] In step S110, the control unit 30 adjusts the flow rate of the heat medium and proceeds to step S120. As described above, the flow rate adjustment is to change the flow rate of the heat medium so that the detected temperature detected by the temperature sensor 21 is 120 to 140°C, thereby adjusting the heat exchange amount of the first heat exchange unit 18, the back pressure valve 19, and the third heat exchange unit 20.

[0070] In step S120, the control unit 30 determines whether the operator has performed an end operation. If the end operation has been performed, the control unit 30 determines step S120 as positive (S120: Yes) and proceeds to step S130. If the end operation has not been performed, the control unit 30 determines step S120 as negative (S120: No) and continues the stable operation.

[0071] In step S130, the control unit 30 performs a predetermined stop process and ends Figure 2 processing.

[0072] The above-described embodiment has the following effects.

[0073] (1) The depolymerization liquid generating device 10 includes: a kneading machine 16 as a depolymerization liquid generating unit, which kneads a polyamide resin P as a plastic and supply water W under a heating environment to generate a depolymerization liquid D; a back pressure valve 19 for adjusting the pressure of the depolymerization liquid D output from the kneading machine 16; a first heat exchange unit 18 provided in a flow path fpD between the kneading machine 16 and the back pressure valve 19; a second heat exchange unit 14 provided in a supply path fpW of the supply water W supplied to the kneading machine 16; a thermostat 22 for adjusting the temperature of a heat medium circulating between the first heat exchange unit 18 and the second heat exchange unit 14; and a switching valve 17 for switching between a first flow path fp1 for circulating the heat medium from the thermostat 22 to the thermostat 22 via the first heat exchange unit 18 and a second flow path fp2 for circulating the heat medium from the thermostat 22 to the thermostat 22 via the first heat exchange unit 18 and the second heat exchange unit 14.

[0074] With this configuration, the generated depolymerized liquid D can be appropriately cooled, and the apparatus 10 can be operated stably.

[0075] For example, by switching between the first flow path fp1 and the second flow path fp2 according to the operating state of the device 10 , it is possible to appropriately heat the flow path fpD and the like and cool the depolymerization liquid D and the like.

[0076] (2) In the depolymerization liquid production apparatus 10 of (1) above, the switching valve 17 switches to the first flow path fp1 during the startup operation from the start of operation of the apparatus 10 until the steady state is reached, and switches to the second flow path fp2 during the steady operation after the steady state is reached.

[0077] With such a configuration, during the startup operation of the apparatus 10, the flow path fpD through which the undepolymerized liquid flows can be efficiently heated by heat exchange in the first heat exchange section 18 or the like using the heat of the heat medium heated by the thermostat 22, for example.

[0078] On the other hand, during stable operation of the apparatus 10, for example, the heating of the thermostat 22 can be stopped to reduce the energy consumed by the thermostat 22, and heat exchange in the first heat exchange section 18, etc., for cooling the depolymerization liquid D at about 340° C. output from the kneader 16, and heat exchange in the second heat exchange section 14 for heating the supply water W using the heat obtained by the heat exchange can be appropriately performed.

[0079] (3) In the depolymerized liquid production device 10 of (2) above, the temperature regulator 22 adjusts the temperature of the heat medium during the startup operation to a first temperature (e.g., 250° C.) higher than the melting point (about 225° C.) of the undepolymerized liquid when the depolymerization reaction is insufficient.

[0080] Due to this structure, even if the undepolymerized liquid flows from the downstream end 16d of the mixer 16 to the flow channel fpD connected to the first heat exchange section 18, the back pressure valve 19 and the third heat exchange section 20, it can prevent solidification and retention in the flow channel fpD, which helps to ensure stable operation of the device 10.

[0081] (4) In the depolymerization liquid production apparatus 10 of (3) above, the temperature regulator 22 regulates the temperature of the heat medium during the steady operation so as to reach a second temperature (eg, about 40° C.) lower than the first temperature (about 250° C.).

[0082] With this configuration, compared with a case where the thermostat 22 continues to adjust the temperature to the first temperature even after the device 10 switches from the startup operation to the steady operation, the energy used by the thermostat 22 can be reduced.

[0083] (5) In the depolymerization liquid production device 10 of (1) above, the switching valve 17 is switched to the first flow path fp1 before the elapsed time from the start of operation of the device 10 reaches a predetermined retention time (about 15 minutes), and is switched to the second flow path fp2 after the elapsed time reaches the predetermined retention time. The predetermined retention time in the embodiment refers to a time sufficient for the depolymerization reaction to proceed.

[0084] With this configuration, during the startup operation before the elapsed time from the start of the operation reaches 15 minutes, the flow path fpD through which the undepolymerized liquid flows can be effectively heated by heat exchange in the first heat exchange section 18 using the heat of the heat medium heated by the thermostat 22, for example.

[0085] On the other hand, during stable operation 15 minutes after the start of operation, for example, the heating of the thermostat 22 can be stopped to reduce the energy consumed by the thermostat 22, and heat exchange in the first heat exchange section 18, etc. for cooling the depolymerization liquid D at about 340° C. output from the kneader 16 and heat exchange in the second heat exchange section 14 for heating the supply water W using the heat obtained by the heat exchange can be appropriately performed.

[0086] (6) In the depolymerization liquid generating device 10 of (1) to (5) above, when the switching valve 17 is switched to the first flow channel fp1, the first heat exchange section 18 insulates the flow channel fpD and the back pressure valve 19, and when the switching valve 17 is switched to the second flow channel fp2, the first heat exchange section 18 cools the depolymerization liquid D output from the mixer 16, and the second heat exchange section 14 heats the supply water W supplied to the mixer 16.

[0087] With this configuration, when the heat medium circulates in the first flow path fp1, the flow path fpD and the like through which the undepolymerized liquid flows can be effectively kept warm by heat exchange in the first heat exchange unit 18 and the like using the heat of the heat medium heated by the thermostat 22, for example.

[0088] On the other hand, when the heat medium circulates in the second flow path fp2, for example, the heating of the thermostat 22 can be stopped to reduce the energy consumed by the thermostat 22, and heat exchange in the first heat exchange section 18, etc. for cooling the depolymerization liquid D at about 340° C. output from the mixer 16 and heat exchange in the second heat exchange section 14 for heating the supply water W using the heat obtained by the heat exchange can be appropriately performed.

[0089] The above-described embodiment can be modified in various forms. Modifications will be described below.

[0090] (Variant 1)

[0091] In the above description, the third heat exchanger 20 is provided on the downstream side of the back pressure valve 19, but the third heat exchanger 20 may be omitted. The reason is that the first heat exchanger 18 is provided to heat the heat medium from about 40°C to about 340°C to about 300°C by cooling the temperature of the depolymerized liquid D from about 340°C to about 100°C by about 240°C, and the third heat exchanger 20 is provided to keep the temperature of the depolymerized liquid D at about 100°C. Therefore, in the case where the temperature of the depolymerized liquid D does not need to be kept at about 100°C, the third heat exchanger 20 may be omitted.

[0092] (Variant 2)

[0093] In the above description, the example of directly performing the stop process ( S130 ) is described when the depolymerization liquid production device 10 is stopped after stable operation (step S120 is determined to be positive). Alternatively, the device 10 may be cleaned with a cleaning resin agent (cleaning material) before performing the stop process.

[0094] For example, when the recommended temperature of the cleaning material is 200°C, the set temperature of the thermostat 22 is changed from 40°C during stable operation to 200°C, and the flow path fpD in the first heat exchange section 18, the back pressure valve 19, and the third heat exchange section 20 is heated to prevent the cleaning material from solidifying in the flow path fpD. In addition, during cleaning, in order to stop the supply of the supply water W to the kneading machine 16, the flow path of the heat medium is switched to the first flow path fp1 by the switching valve 17. Stopping the supply of the heat medium, etc., is performed after the cleaning process is completed.

[0095] The above-described embodiment and the modified examples may be arbitrarily combined with one or more of them, and the modified examples may be combined with each other.

[0096] According to the present invention, the generated depolymerization liquid can be appropriately cooled and stable operation can be performed.

[0097] The present invention has been described above in conjunction with the preferred embodiments, but it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the disclosure of the claims set forth below.

Claims

1. A depolymerization liquid generating device (10), characterized in that: have: A depolymerization liquid generating section (16) which mixes plastic and water in a heated environment to generate a depolymerization liquid; a back pressure valve (19) for adjusting the pressure of the depolymerization liquid output from the depolymerization liquid generating unit (16); a first heat exchange section (18) disposed in a flow passage (fpD) between the depolymerization liquid generating section (16) and the back pressure valve (19); a second heat exchange section (14) provided in a supply path (fpW) of the water supplied to the depolymerization liquid generating section (16); a thermostat (22) for adjusting the temperature of the heat medium circulating in the first heat exchange section (18) and the second heat exchange section (14); and A switching valve (17) switches between a first flow path (fp1) for circulating the heat medium from the thermostat (22) via the first heat exchange section (18) to the thermostat (22) and a second flow path (fp2) for circulating the heat medium from the thermostat (22) via the first heat exchange section (18) and the second heat exchange section (14) to the thermostat (22).

2. The depolymerization liquid generating device (10) according to claim 1, characterized in that: The switching valve (17) switches to the first flow path (fp1) during startup operation from when the device (10) starts operating until it reaches a stable state, and switches to the second flow path (fp2) during stable operation after reaching the stable state.

3. The depolymerization liquid generating device (10) according to claim 2, characterized in that: The temperature controller (22) adjusts the temperature of the heat medium during the startup operation so as to reach a first temperature higher than the melting point of the undepolymerized liquid when the depolymerization reaction is insufficient.

4. The depolymerization liquid generating device (10) according to claim 3, characterized in that: The temperature regulator (22) regulates the temperature of the heat medium to a second temperature lower than the first temperature during the stable operation.

5. The depolymerization liquid generating device (10) according to claim 4, characterized in that: The invention further comprises a third heat exchange section (20) for performing heat exchange between the depolymerization liquid having passed through the back pressure valve (19) and the heat medium. The first heat exchange section (18) cools the depolymerization liquid to a predetermined temperature. The third heat exchange unit (20) keeps the depolymerization liquid at the predetermined temperature.

6. The depolymerization liquid generating device (10) according to claim 1, characterized in that: The switching valve (17) switches to the first flow path (fp1) before the elapsed time from the start of operation of the device (10) reaches a predetermined retention time, and switches to the second flow path (fp2) after the elapsed time reaches the predetermined retention time.

7. The depolymerization liquid generating device (10) according to any one of claims 1 to 6, characterized in that: When the switching valve (17) switches to the first flow channel (fp1), the first heat exchange part (18) keeps the flow channel (fpD) and the back pressure valve (19) warm. When the switching valve (17) is switched to the second flow path (fp2), the first heat exchange section (18) cools the depolymerization liquid output from the depolymerization liquid generating section (16), and the second heat exchange section (14) heats the water supplied to the depolymerization liquid generating section (16).

8. The depolymerization liquid generating device (10) according to any one of claims 2 to 5, characterized in that: The stable state is a state in which the depolymerization liquid generating section (16) reaches a predetermined high temperature and a depolymerization reaction proceeds.

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