Depolymerization apparatus, chemical recycling apparatus, depolymerization method

Abstract

The present invention provides a depolymerization apparatus that can efficiently carry out the depolymerization reaction in a depolymerization reactor. [Solution] The depolymerization apparatus 5 includes a depolymerization reactor 300 that carries out a depolymerization reaction in which PET is decomposed into BHET by EG, and a heater 320 that raises the temperature inside the depolymerization reactor 300 in accordance with the increase in the concentration of BHET due to the progress of the depolymerization reaction in the depolymerization reactor 300. It also includes a return passage 53 that returns at least a portion of the product containing BHET discharged from the depolymerization reactor 300 back into the depolymerization reactor 300. It also includes a return amount adjustment unit 6 that adjusts the amount of product returned through the return passage 53.

Description

Technical Field

[0001] The present disclosure relates to a depolymerization apparatus and the like.

Background Art

[0002] Patent Document 1 discloses a method for producing PET flakes that become raw materials for new PET bottles by pulverizing the PET bottles, etc. for recycling PET (polyethylene terephthalate) bottles. Specifically, after heating and melting the pulverized PET bottles, mechanical recycling to obtain PET flakes by solid-phase polymerization or the like, and chemical recycling to obtain PET flakes by depolymerizing the pulverized PET bottles into intermediates or depolymerized products such as bis(2-hydroxyethyl) terephthalate (BHET) by a depolymerization reaction and then subjecting them to a repolymerization reaction are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to efficiently perform the chemical recycling of PET, it is preferable to increase the temperature inside the depolymerization reaction tank that causes a depolymerization reaction to decompose PET into BHET by ethylene glycol (EG) as a depolymerizing agent and shorten the time of the depolymerization reaction. However, when the temperature inside the depolymerization reaction tank becomes higher than the boiling point of EG (about 197°C) at normal pressure or atmospheric pressure, EG boils and the desired depolymerization reaction does not occur.

[0005] This disclosure is made in view of these circumstances and aims to provide a depolymerization apparatus, etc., that can efficiently carry out the depolymerization reaction in a depolymerization reactor. [Means for solving the problem]

[0006] To solve the above problems, a depolymerization apparatus according to one embodiment of the present disclosure comprises a depolymerization reactor that causes a depolymerization reaction in which polyester is decomposed into a depolymer by a depolymerizing agent, and a heater that raises the temperature inside the depolymerization reactor to prevent boiling in accordance with the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor.

[0007] According to this embodiment, by focusing on the fact that the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor leads to an increase in the boiling point, the temperature inside the depolymerization reactor can be increased while avoiding boiling.

[0008] Another aspect of the present disclosure is a chemical recycling apparatus. This apparatus comprises a depolymerization reactor that causes a depolymerization reaction in which polyester is broken down into a depolymer by a depolymerizing agent; a heater that raises the temperature inside the depolymerization reactor to prevent boiling in accordance with the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor; and a polymerization reactor that synthesizes the depolymer into a polymer by a polymerization reaction.

[0009] A further aspect of this disclosure is a depolymerization method. This method involves carrying out a depolymerization reaction inside a depolymerization reactor in which a depolymerizing agent is used to decompose a polyester into a depolymer, and increasing the temperature inside the depolymerization reactor to prevent boiling in response to the increase in the concentration of the depolymer due to the progress of the depolymerization reaction inside the reactor.

[0010] Furthermore, any combination of the above components, as well as any representations thereof converted into methods, apparatus, systems, recording media, computer programs, etc., are also included in this disclosure. [Effects of the Invention]

[0011] According to this disclosure, the depolymerization reaction in the depolymerization reactor can be carried out efficiently. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram of the chemical recycling molding system is shown. [Figure 2] The polymerization and depolymerization reactions of PET are schematically shown. [Figure 3] A modified example of the by-product removal apparatus is shown. [Figure 4] A schematic diagram of the depolymerization apparatus is shown. [Figure 5] The relationship between the reaction temperature inside the depolymerization reactor and the relative time required for the depolymerization reaction is schematically shown. [Figure 6] The relationship between the proportion of BHET in a mixture of BHET and EG and the boiling point of the mixture is schematically shown. [Figure 7] A first embodiment of a depolymerization reaction monitoring device is shown. [Figure 8] An example of monitoring the progress of a depolymerization reaction by a depolymerization reaction progress monitoring unit is shown. [Figure 9] A second embodiment of the depolymerization reaction monitoring device is shown. [Figure 10] An example of dilution of the depolymerizer using a dilution portion of the depolymerizer is shown. [Figure 11] This is a flowchart of a specific measurement procedure example in the second embodiment. [Figure 12] A third embodiment of the depolymerization reaction monitoring device is shown. [Figure 13] This is a flowchart showing a specific measurement procedure example in the third embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments for implementing the present disclosure (hereinafter also referred to as embodiments) will be described in detail while referring to the drawings. In the description and / or the drawings, the same or equivalent components, members, processes, etc. are denoted by the same reference numerals, and redundant descriptions are omitted. The scales and shapes of each part shown are set for convenience for simplification of the description, and are not to be construed restrictively unless otherwise specified. The embodiments are examples and do not limit the scope of the present disclosure in any way. All features presented in the embodiments and combinations thereof are not necessarily essential to the essence of the present disclosure. The embodiments are presented by being decomposed into components for each function and / or function group for realizing it for convenience. However, one component in the embodiments may actually be realized by a combination of a plurality of components as separate entities, or a plurality of components in the embodiments may actually be realized by one component as an integral entity. Also, a plurality of embodiments and modification examples may be disclosed in parallel, but any components of each embodiment and / or each modification example may be combined in any manner as long as they do not inhibit each other's functions.

[0014] FIG. 1 schematically shows the configuration of a chemical recycling molding system to which a depolymerization device and / or a chemical recycling device according to an embodiment of the present disclosure can be applied. The chemical recycling molding system includes a chemical recycling device 100 and an injection molding machine 1. The chemical recycling device 100 includes a polymer adjustment device 200, a depolymerization reaction tank 300 (depolymerization device 5), a polymerization reaction tank 400, a by-product removal device 500, and a polymer supply unit 600. The number of installations of each of the injection molding machine 1 (two are schematically shown in FIG. 1), the polymer adjustment device 200, the depolymerization reaction tank 300, the polymerization reaction tank 400, the by-product removal device 500, and the polymer supply unit 600 is arbitrary. In particular, typically, by increasing the number of injection molding machines 1 and polymerization reaction tanks 400, which are slower in processing speed or reaction speed than other processing parts, the processing performance can be enhanced so that these processing parts do not become serious bottlenecks.

[0015] The polymer adjustment device 200 adjusts a polymer such as PET that constitutes a first molded product such as a PET bottle for the subsequent depolymerization reaction tank 300. Specifically, the polymer adjustment device 200 subjects the first molded product such as a PET bottle to processes such as pulverization, heat melting, and mixing, and adjusts the polymer such as PET to a state (phase, shape, size, etc.) suitable for the depolymerization reaction in the depolymerization reaction tank 300. Note that the first molded product may be any molded product other than a bottle, such as a sheet, film, fiber, etc. Further, the polymer that constitutes the first molded product may be any polymer or polymer other than PET, such as polyester (including PET), polyamide, polyurethane, etc.

[0016] The depolymerization reaction tank 300 decomposes a polymer such as PET adjusted by the polymer adjustment device 200 into a depolymerized product by a depolymerization reaction. When the polymer supplied from the polymer adjustment device 200 is PET, through the depolymerization reaction in the depolymerization reaction tank 300, BHET, which is an intermediate, is obtained as the depolymerized product. Note that the depolymerized product obtained in the depolymerization reaction tank 300 may contain monomers or monomers of the polymer. The monomers in the case where the polymer is PET are, for example, ethylene glycol, terephthalic acid, dimethyl terephthalate, and ethylene terephthalate. Although details will be described later, the depolymerization device according to an embodiment of the present disclosure may be configured to include the depolymerization reaction tank 300.

[0017] As schematically shown in Figure 2, in the depolymerization reaction (300) of PET as a polymer, PET is decomposed by ethylene glycol (EG) supplied as a depolymerizer from the depolymerizer supply unit 310 (Figure 1) to the depolymerization reactor 300, yielding BHET as a depolymer. Alternatively, EG may be supplied by the polymer adjustment device 200 instead of, or in addition to, the depolymerizer supply unit 310. To promote this depolymerization reaction, the temperature inside the depolymerization reactor 300 is adjusted to a temperature suitable for the depolymerization reaction by a heater 320 (Figure 1) or a warmer attached to the depolymerization reactor 300. The suitable temperature for the depolymerization reaction of PET to BHET in Figure 2 is between 180°C and 250°C, preferably between 230°C and 245°C, and more preferably between 235°C and 240°C. Furthermore, the suitable pressure for the depolymerization reaction of PET to BHET in Figure 2 is typically between atmospheric pressure (0 MPa, G) and 0.8 MPa, G, preferably between 0.4 MPa, G and 0.6 MPa, G, and more preferably between 0.45 MPa, G and 0.55 MPa, G. Note that MPa, G is gauge pressure. The pressure inside the depolymerization reactor 300 may be adjusted by a pump (not shown) or the like, which is installed alongside the depolymerization reactor 300.

[0018] However, in this embodiment, as will be described later, the inside of the depolymerization reactor 300 is kept at atmospheric pressure or normal pressure. In other words, there is no need to provide a pump or the like to pressurize the inside of the depolymerization reactor 300 to above atmospheric pressure. Therefore, the cost of the depolymerization apparatus can be reduced. Also, even when it is necessary to remove the contents from the depolymerization reactor 300, there is no risk of bumping because there is almost no pressure difference between the inside and outside of the depolymerization reactor 300. Conventionally, if the inside of the depolymerization reactor 300 is pressurized to above atmospheric pressure, bumping can occur due to the pressure difference between the inside and outside of the depolymerization reactor 300, so depressurization treatment or the like was necessary before removing the contents. Furthermore, in order to restart the depolymerization reaction, it was necessary to pressurize the inside of the depolymerization reactor 300 again with a pump or the like, which was inefficient.

[0019] Since the viscosity of the fluid in the depolymerization reactor 300, which produces BHET (a polymer with a smaller molecular weight than PET), is lower than the viscosity of the fluid in the polymerization reactor 400 (described later), which produces PET (a polymer with a larger molecular weight), a low-viscosity stirring blade 330 is used to stir the fluid in the depolymerization reactor 300 and promote the depolymerization reaction. Examples of low-viscosity stirring blades 330 include propeller blades, disk turbine blades, and paddle blades. Note that in Figure 1, the depolymerization apparatus according to this embodiment, including the depolymerization reactor 300, is simplified, and its detailed configuration will be described later with reference to another figure.

[0020] Downstream of the depolymerization reactor 300, foreign matter removal devices 340, 350, and 360 are provided to remove foreign matter from the fluid mainly composed of BHET as the depolymer. The foreign resin removal device 340 removes resins other than the target resin, such as PET, and / or their depolymers, by the principles of flotation separation and sedimentation removal. The coloring removal device 350 removes coloring using activated carbon or the like. The metal ion removal device 360 ​​removes metal ions by the principles of ion exchange or the like. Downstream of the foreign matter removal devices 340, 350, and 360, a buffer tank 370 is provided to temporarily store the fluid mainly composed of BHET, etc., after the foreign matter has been removed, before supplying it to the polymerization reactor 400.

[0021] The buffer tank 370 may be equipped with a first preheater 371 for heating or maintaining the temperature of the depolymer (a fluid mainly composed of BHET, etc.) before it is supplied to the subsequent polymerization reactor 400. The first preheater 371 may maintain the depolymer at a temperature similar to that of the heater 320 attached to the depolymerization reactor 300 (between 180°C and 250°C), or at a temperature suitable for the polymerization reaction similar to that of the heater 410 attached to the polymerization reactor 400 described later (between 250°C and 300°C). In this way, by providing a buffer tank 370 equipped with a preheating mechanism (first preheater 371) as needed, upstream of the polymerization reactor 400, the depolymer awaiting input to the polymerization reactor 400, which typically has a slower processing or reaction rate than the depolymerization reactor 300 or other processing units such as the by-product removal device 500 described later, can be stored while maintaining an appropriate temperature. As a result, the overall capacity of the chemical recycling apparatus 100 can be increased, and the chemical recycling apparatus 100 can be operated stably and continuously while supplying appropriate amounts of reactants to each processing unit such as the depolymerization reactor 300, polymerization reactor 400, by-product removal device 500, and polymer supply unit 600 in a timely manner (without causing so-called "resin depletion"). Furthermore, preheating mechanisms such as the first preheater 371 are not limited to the buffer tank 370, but can be provided in any manner at any point between the depolymerization reactor 300 and the polymerization reactor 400 (for example, in the foreign matter removal devices 340, 350, 360).

[0022] The polymerization reactor 400 synthesizes a polymer from the depolymerized polymer, such as BHET, which is produced in the depolymerization reactor 300 and from which foreign matter has been removed by the foreign matter removal devices 340, 350, and 360, through a polymerization reaction. If the depolymer produced in the depolymerization reactor 300 is BHET, the polymer PET is obtained again through the polymerization reaction in the polymerization reactor 400.

[0023] As schematically shown in Figure 2, in the polymerization reaction (400) of BHET as a depolymer, EG is produced as a by-product along with PET as the main polymer product. This EG may be recirculated to the depolymerizer supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reactor 300. Since the EG produced in the polymerization reactor 400 can be reused on-site (in the depolymerization reactor 300) without being wasted, the operating efficiency of the chemical recycling device 100 can be increased. In particular, the amount of EG purchased for the depolymerization reaction of PET in the depolymerization reactor 300 can be significantly reduced, leading to a reduction in the operating costs of the chemical recycling device 100.

[0024] To promote the polymerization reaction described above, the polymerization reactor 400 is kept at a temperature suitable for the polymerization reaction by a heater 410 (Figure 1) or a warmer, which is installed as a second heater attached to the polymerization reactor 400. The temperature suitable for the polymerization reaction of BHET to PET in Figure 2 is between 250°C and 300°C, preferably between 260°C and 290°C, and more preferably between 270°C and 280°C. Here, the polymerization heating temperature by the heater 410 attached to the polymerization reactor 400 is higher than the depolymerization heating temperature by the heater 320 attached to the depolymerization reactor 300. In the polymerization reactor 400, PET with a large molecular weight and a high melting point is produced, but by maintaining a higher temperature than the depolymerization reactor 300, where BHET with a small molecular weight and a low melting point is produced, the PET, which is the main product of the polymerization reactor 400, is kept in a molten state. It should be noted that the polymerization reaction of BHET to PET in Figure 2 is preferably carried out under vacuum conditions. Therefore, a vacuum pump or the like (not shown) may be installed in the polymerization reactor 400.

[0025] The viscosity of the fluid in the polymerization reactor 400, where PET with a large molecular weight is produced, is higher than the viscosity of the fluid in the depolymerization reactor 300, where BHET, which has a smaller molecular weight than the polymer PET, is produced. Therefore, a high-viscosity type of stirring blade 420 is used to stir the fluid in the polymerization reactor 400 and promote the polymerization reaction. Examples of high-viscosity stirring blades 420 include anchor blades and helical ribbon blades.

[0026] The intrinsic viscosity (IV) value is known as a numerical value correlated with the degree of polymerization of polymers such as PET. The IV value (dL / g) is also used as an indicator of the polymer's application. For PET, an IV value of approximately 0.72 or higher allows it to be used for bottles, an IV value of approximately 0.65 or higher allows it to be used for sheets and films, and an IV value of approximately 0.58 or higher allows it to be used for fibers. In this embodiment, the objective is to ultimately obtain PET with an IV value suitable for use in bottles and sheets. As will be described later, the IV value is also increased in the by-product removal device 500 downstream of the polymerization reactor 400, so the IV value of the PET synthesized in the polymerization reactor 400 may be relatively low. Specifically, the IV value of the PET synthesized in the polymerization reactor 400 is between 0.2 and 0.7, preferably between 0.3 and 0.7, and more preferably between 0.3 and 0.55.

[0027] A buffer tank 430 may be provided downstream of the polymerization reactor 400 to temporarily store the polymer synthesized in the polymerization reactor 400 before supplying it to the downstream by-product removal device 500 and / or polymer supply unit 600. The buffer tank 430 may be provided with a second preheater 431 to heat or maintain the temperature of the polymer before supplying it to the downstream by-product removal device 500 and / or polymer supply unit 600. The second preheater 431 may maintain the polymer at a temperature similar to that of the heater 410 attached to the polymerization reactor 400 (between 250°C and 300°C), or at a temperature suitable for polymerization reactions similar to that of the heater 520 attached to the by-product removal device 500 described later (between 250°C and 290°C), or at a temperature similar to that of the heater 620 attached to the polymer supply unit 600 described later (between 250°C and 290°C).

[0028] In this way, by providing a buffer tank 430 equipped with a preheating mechanism (second preheater 431) as needed, upstream of the by-product removal device 500 and / or polymer supply unit 600, polymers awaiting input to the by-product removal device 500 and / or polymer supply unit 600 can be stored while maintaining an appropriate temperature. As a result, the overall capacity of the chemical recycling device 100 can be increased, and the chemical recycling device 100 can be operated stably and continuously while supplying appropriate amounts of reactants to each processing unit such as the depolymerization reactor 300, polymerization reactor 400, by-product removal device 500, and polymer supply unit 600 in a timely manner (without causing so-called "resin depletion"). Note that a preheating mechanism such as the second preheater 431 is not limited to the buffer tank 430, but can be provided in any manner at any point between the polymerization reactor 400 and the by-product removal device 500 and / or at any point between the by-product removal device 500 and the polymer supply unit 600.

[0029] Downstream from the polymerization reactor 400 (and upstream from the polymer supply unit 600 described later), a by-product removal device 500 is provided through which PET (main product) and EG (by-product) generated by the polymerization reaction in the polymerization reactor 400 are passed to remove EG as a by-product. The by-product removal device 500 in the illustrated example comprises a number of linear members 510 extending from top to bottom. Due to the increased surface area caused by the number of linear members 510, the volatilization of EG adhering to the surface of each linear member 510 is promoted, and EG is effectively separated and removed from the high-viscosity PET.

[0030] This EG may be recirculated to the depolymerization agent supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reactor 300. Since the EG separated and removed by the byproduct removal device 500 can be reused on-site (in the depolymerization reactor 300) without waste, the operating efficiency of the chemical recycling device 100 can be increased. In particular, the amount of EG purchased for the PET depolymerization reaction in the depolymerization reactor 300 can be significantly reduced, leading to a reduction in the operating costs of the chemical recycling device 100.

[0031] Furthermore, PET with a relatively low degree of polymerization (i.e., IV value) and BHET that remained unreacted in the polymerization reactor 400 adhere to the surface of each linear member 510, allowing the polymerization reaction to proceed effectively due to its large surface area, similar to that in the polymerization reactor 400. As a result, the IV value of PET as the main product is increased by passing through the by-product removal device 500. Specifically, the IV value of PET after passing through the by-product removal device 500 is 0.7 or higher, preferably 0.8 or higher, and more preferably 0.85 or higher.

[0032] To promote this polymerization reaction, the inside of the by-product removal device 500 is maintained at a temperature suitable for the polymerization reaction by a second heater 520 (Figure 1) or a warmer attached to the by-product removal device 500. Specifically, the heating temperature by the heater 520 is between 250°C and 290°C, preferably between 260°C and 280°C. Here, it is preferable that the heating temperature by the heater 520 attached to the by-product removal device 500 is higher than the polymerization heating temperature by the heater 410 attached to the polymerization reaction tank 400. As the polymerization reaction progresses more rapidly in the by-product removal device 500 than in the polymerization reaction tank 400, the molecular weight of the PET polymer increases and its melting point rises. Therefore, by maintaining the inside of the by-product removal device 500 at a higher temperature than in the polymerization reaction tank 400, the PET as a product of the by-product removal device 500 can be kept in a molten state. Furthermore, a second heater or warmer may be provided around the piping between the polymerization reactor 400 and the by-product removal device 500 to heat or maintain the polymerization heating temperature at least to that of the heater 410 attached to the polymerization reactor 400. In addition, it is preferable that the polymerization reaction in the by-product removal device 500 be carried out under vacuum conditions, similar to the polymerization reaction in the polymerization reactor 400. For this reason, a vacuum pump or the like (not shown) may be attached to the by-product removal device 500. By creating a vacuum (reduced pressure) inside the by-product removal device 500, EG as a by-product can be efficiently removed.

[0033] The configuration of the by-product removal device 500 is not limited to the "vertical" type shown in Figure 1. For example, a "horizontal two-axis" stirring device, as shown in Figure 3, may be used as the by-product removal device 500. This stirring device has two rotating shafts extending perpendicular to the plane of the paper in Figure 3, and two stirring blades that rotate around each shaft to stir the PET and EG, which are the objects to be stirred. The stirring by the two stirring blades promotes the volatilization of EG, so that EG is effectively separated and removed from high-viscosity PET. Details of the stirring device in Figure 3 are disclosed in Japanese Patent No. 2925599, which is incorporated herein by reference.

[0034] The polymer supply unit 600 supplies polymers such as PET synthesized in the polymerization reactor 400 (or the polymerization reactor 400 and the by-product removal device 500) to the injection molding machine 1 which molds second molded products such as PET bottles. The polymer supply unit 600 is equipped with a transfer pump 610, such as a gear pump or screw pump, which is suitable for supplying high-purity and high-viscosity (i.e., high degree of polymerization or high IV value) PET, from which EG as a by-product has been removed by the by-product removal device 500, to the injection molding machine 1 in a molten state.

[0035] The polymer supply unit 600 is provided with a heater 620 or warmer, which serves as a first heater, for heating or maintaining the temperature of the polymer such as PET that is transferred to the injection molding machine 1 by the transfer pump 610 to keep it in a molten state. Specifically, the heating temperature by the heater 620 is between 250°C and 290°C, and preferably between 260°C and 280°C. Here, it is preferable that the heating temperature (first heating temperature) by the heater 620 (first heater) provided in the polymer supply unit 600 is higher than the second heating temperature by a second heater, such as a heater 410 attached to the polymerization reaction tank 400, a heater 520 attached to the by-product removal device 500, or a heater (not shown) provided between the polymerization reaction tank 400 and the by-product removal device 500. As the polymerization reaction, which begins in the polymerization reactor 400, gradually progresses and is completed in the by-product removal device 500, the molecular weight of the polymer, such as PET, becomes larger and the melting point higher in the polymer supply unit 600 than in the polymerization reactor 400 and the by-product removal device 500. Therefore, by setting the first heating temperature in the polymer supply unit 600 higher than the preceding second heating temperature, it is possible to maintain high viscosity (i.e., high degree of polymerization or high IV value) and high melting point polymers such as PET in a molten state.

[0036] A temperature gradient may be provided such that the heating temperature increases in stages from the polymerization reactor 400 to the polymer supply unit 600. For example, by setting the heating temperature of a heater (not shown) located between the polymerization reactor 400 and the by-product removal device 500 to be higher than the heating temperature of the heater 410 located next to the polymerization reactor 400, setting the heating temperature of a heater 520 located next to the by-product removal device 500 to be higher than the heating temperature of the heater (not shown), and setting the heating temperature of a heater 620 located in the polymer supply unit 600 to be higher than the heating temperature of the heater 520, it is possible to reliably maintain a molten state of polymers such as PET, whose melting point increases from the polymerization reactor 400 to the polymer supply unit 600. In addition, a heater for heating or keeping the polymer such as PET warm to maintain a molten state may be provided between the polymer supply unit 600 and the injection molding machine 1.

[0037] The injection molding machine 1 molds a molten polymer such as PET, generated in the chemical recycling device 100, into a second molded product. The second molded product may be the same type as the first molded product, which is subjected to processing such as crushing in the polymer adjustment device 200, or it may be a different type. For example, both the first and second molded products may be PET bottles. Alternatively, one of the first and second molded products may be a PET bottle, and the other may be a molded product other than a bottle, such as a sheet, film, or fiber. Generally, in mechanical recycling, the IV value of the recycled second molded product is lower than the IV value of the first molded product before recycling. However, according to the chemical recycling device 100 of this embodiment, which is equipped with mechanisms to increase the IV value, such as foreign matter removal devices 340, 350, 360 and by-product removal device 500, the IV value of the recycled second molded product can be made higher than the IV value of the first molded product before recycling. For example, according to this embodiment, PET fibers with a low IV value as the first molded product can be recycled into PET bottles with a high IV value as the second molded product.

[0038] The injection molding machine 1 molds molten resin such as PET into a second molded product. An injection molding machine that uses molten resin as a raw material is disclosed, for example, in Patent Document 2. This application is based on the entire contents of the said document (Japanese Patent Application No. 2020-130985) filed on July 31, 2020. As schematically shown in Figure 1, multiple injection molding machines 1 may be provided in parallel. Note that the molding machine to which molten resin etc. is supplied from the chemical recycling device 100 is not limited to an injection molding machine and may be any molding machine (for example, a compression molding machine).

[0039] In this embodiment, the polymer resynthesized in the polymerization reactor 400 is supplied directly to the injection molding machine 1 by the polymer supply unit 600 without being converted into flakes or pellets. Since the cooling and heating processes required for flakes and pellets in the conventional method are eliminated, molded products such as PET bottles can be recycled with less energy than before.

[0040] In the chemical recycling apparatus 100 according to this embodiment, the polymer resynthesized in the polymerization reactor 400 is supplied directly to the injection molding machine 1, so it is necessary to quickly achieve the required IV value of the polymer for the molded product (second molded product). In this embodiment, a by-product removal device 500, which has the function of promoting the polymerization reaction and increasing the IV value of the polymer, is provided in addition to the polymerization reactor 400, so this requirement can be fully met.

[0041] In the example shown in Figure 1, only one polymer preparation device 200, a depolymerization reactor 300, a polymerization reactor 400, a by-product removal device 500, and a polymer supply unit 600 were provided, but multiple units of each may be provided. Such multiple processing units can perform equivalent processing in parallel, thereby improving the processing performance of the group of processing units. Furthermore, the difference in processing speed or reaction speed between each processing unit can be reduced by increasing the number of slower processing units.

[0042] Furthermore, one or more processing units may accept external materials procured from a different location or facility than the chemical recycling molding system shown in Figure 1, in place of or in addition to the materials from the preceding processing units. For example, if multiple polymerization reactors 400 are provided, some may be supplied with depolymerized material from the depolymerization reactor 300, while others may be supplied with depolymerized material procured from an external source. Similarly, if multiple by-product removal devices 500 and / or polymer supply units 600 are provided, some may be supplied with polymerized material from the polymerization reactor 400, while others may be supplied with polymerized material procured from an external source. In this way, allowing the acceptance of external materials at each stage of processing in the chemical recycling molding system ensures the flexibility and efficient operation of the chemical recycling molding system.

[0043] Figure 4 schematically shows the depolymerization apparatus 5 according to this embodiment. The depolymerization apparatus 5 is composed of the aforementioned depolymerization reactor 300. The depolymerization reactor 300 carries out a depolymerization reaction in which the polyester is broken down into a depolymer by a depolymerizing agent. In this embodiment, as in Figure 2, the polyester is polyethylene terephthalate (PET), the depolymerizing agent is ethylene glycol (EG) as an alcohol, and the depolymer is bis(2-hydroxyethyl) terephthalate (BHET).

[0044] However, this disclosure is also applicable to combinations of polyesters, depolymerizers, and depolymers other than those described above. For example, the polyester may be polypropylene terephthalate (PPT), the depolymerizer may be propylene glycol (PG) or an alcohol such as 1,3-propanediol, and the depolymer may be bis(2-hydroxypropyl) terephthalate (BHPT). Alternatively, the polyester may be polybutylene terephthalate (PBT), the depolymerizer may be butylene glycol (BG) or an alcohol such as 1,4-butanediol, and the depolymer may be bis(2-hydroxybutyl) terephthalate (BHBT). Such combinations of polyester, depolymerizer, and depolymer share the common characteristic that the depolymer (BHET, BHPT, BHBT, etc.), which is the product of the depolymerization reaction, dissolves in the depolymerizer (EG, PG, BG, etc.), which is one of the reactants or reaction solvents in the depolymerization reaction, while the polyester (PET, PPT, PBT, etc.), which is the other reactant in the depolymerization reaction, does not dissolve in the depolymerizer (EG, PG, BG, etc.).

[0045] The depolymerization apparatus 5 according to this embodiment, as described above, is not limited to the depolymerization reactor 300 provided in the chemical recycling molding system shown in Figure 1, but is applicable to any depolymerization reactor 300 provided in any system, or to any standalone depolymerization reactor 300.

[0046] The depolymerization reactor 300 comprises a tank body 31 for carrying out a depolymerization reaction of polyester or polymer. A heater 320, as previously described in Figure 1, is provided outside the tank body 31, and a stirring blade 330, as previously described in Figure 1, is provided inside the tank body 31. The heater 320 controls or adjusts the temperature inside the tank body 31. In this figure, the stirring blade 330 is exemplified as a pair of upper and lower inclined paddle blades.

[0047] As previously described with respect to Figure 1, polymers such as PET or polyester are supplied to the depolymerization reactor 300 from the polymer preparation device 200, etc., and depolymerizing agents such as EG or alcohol are supplied from the depolymerizing agent supply unit 310, etc. In the example of Figure 4, PET from the polymer preparation device 200 and EG from the depolymerizing agent supply unit 310 are supplied into the inside of the reactor body 31 through a common supply port 51, but they may also be supplied into the inside of the reactor body 31 through separate supply ports (not shown).

[0048] An outlet 52 is provided at the bottom of the tank body 31 to discharge liquid or fluid products, including BHET and unreacted EG, which are products of the depolymerization reaction, to the outside of the tank body 31. In chemical terminology, "product" generally refers only to BHET, but in this embodiment, for convenience, the products discharged from the outlet 52 of the tank body 31, including unreacted EG, are collectively referred to as "products." In front of the outlet 52 at the bottom of the tank body 31 (upwards in Figure 4), a filter 521, such as a mesh filter, is provided to prevent solid components or insoluble matter, such as unreacted PET, from being discharged from the outlet 52.

[0049] As explained with respect to Figure 1, the product containing BHET and EG (hereinafter abbreviated as BHET / EG) discharged from the depolymerization reactor 300 proceeds to the polymerization reactor 400 via the foreign matter removal devices 340, 350, 360 and the buffer tank 370. In addition to this main production line, in the example of Figure 4, a return line or return passage 53 is provided to return at least a portion of the product containing the depolymerization of BHET, etc. (BHET / EG) discharged from the depolymerization reactor 300 back into the depolymerization reactor 300 (tank body 31). However, as will be described later, even if the return passage 53 is not provided, the minimum effects of this disclosure can be achieved.

[0050] The depolymerization apparatus 5 according to this embodiment may include a return volume adjustment unit 6 that adjusts the amount of BHET / EG returned to the depolymerization reactor 300 through the return passage 53. The return volume adjustment unit 6 may be composed of a flow rate adjustment valve 61 provided in the return passage 53. By controlling the opening degree of this flow rate adjustment valve 61, the amount or flow rate of BHET / EG returning to the depolymerization reactor 300 through the flow rate adjustment valve 61 can be directly adjusted. In addition to or instead of the flow rate adjustment valve 61, a pump capable of functioning as the return volume adjustment unit 6 may be provided in the return passage 53.

[0051] The return volume adjustment unit 6 may be composed of a flow rate adjustment valve 62 installed downstream of the branching point to the return passage 53 in the main production line leading to the polymerization reactor 400. By controlling the opening degree of this flow rate adjustment valve 62, the amount or flow rate of BHET / EG heading to the polymerization reactor 400 can be adjusted, thereby indirectly adjusting the amount or flow rate of BHET / EG returning to the depolymerization reactor 300 through the return passage 53 and / or the flow rate adjustment valve 61. In addition to or instead of the flow rate adjustment valve 62, a pump capable of functioning as the return volume adjustment unit 6 may be provided in the main production line.

[0052] The depolymerization apparatus 5 according to this embodiment may include an discharge adjustment unit 7 for adjusting the discharge amount of the product containing the depolymer (BHET / EG), such as BHET, from the depolymerization reactor 300. The discharge adjustment unit 7 may be composed of a flow rate adjustment valve 71 located downstream of the discharge port 52 of the tank body 31 (and before the branching point to the return line 53 in the main production line leading to the polymerization reactor 400). By controlling the opening degree of this flow rate adjustment valve 71, the amount or flow rate of BHET / EG discharged from the depolymerization reactor 300 through the flow rate adjustment valve 71 can be directly adjusted. In addition to or instead of the flow rate adjustment valve 71, a pump 72 that can function as the discharge adjustment unit 7 may be provided downstream of the discharge port 52 of the tank body 31 (and before the branching point to the return line 53 in the main production line leading to the polymerization reactor 400).

[0053] As described above, in the embodiment of Figure 4, the effects of the present disclosure described later can be maximized by providing three flow control valves 61, 62, and 71 (and / or up to three pumps), but these are not essential for achieving the minimum effects of the present disclosure. For example, at least one of the three flow control valves 61, 62, and 71 may be provided, or none of the flow control valves 61, 62, and 71 may be provided at all.

[0054] In this embodiment, the depolymerization apparatus 5 uses a heater 320 attached to the depolymerization reactor 300 to raise the internal temperature of the depolymerization reactor 300 so that the contents of the depolymerization reactor 300 do not boil at normal pressure or atmospheric pressure, in response to the increase in the concentration of the depolymer such as BHET due to the progress of the depolymerization reaction in the depolymerization reactor 300.

[0055] As schematically shown in Figure 5, the higher the reaction temperature inside the depolymerization reactor 300, the shorter the relative time required for the depolymerization reaction. Therefore, it is preferable to raise the temperature inside the depolymerization reactor 300 as much as possible. However, if the temperature inside the depolymerization reactor 300 exceeds the boiling point of EG (approximately 197°C), EG will boil under normal pressure, and the desired depolymerization reaction will not occur. For this reason, conventional depolymerization reactors 300 employ a method of raising the temperature while suppressing the boiling of EG by pressurizing the inside above normal pressure using a pump or the like.

[0056] In contrast to such conventional technologies, the depolymerization apparatus 5 according to this embodiment may maintain the internal pressure of the depolymerization reactor 300 at atmospheric pressure or normal pressure. In other words, it is not necessary to provide a pump or the like to pressurize the internal pressure of the depolymerization reactor 300 above normal pressure. Instead, the depolymerization apparatus 5 according to this embodiment focuses on the fact that the increase in the concentration of BHET inside the depolymerization reactor 300 due to the progress of the depolymerization reaction leads to an increase in the boiling point of the contents. Specifically, the internal temperature of the depolymerization reactor 300 is adaptively increased by the heater 320 so as not to exceed the boiling point of the contents, which gradually rises due to the BHET that increases as the depolymerization reaction progresses substantially under normal pressure, thereby achieving a temperature increase and reaction acceleration while avoiding boiling of the contents.

[0057] Figure 6 schematically shows the relationship between the proportion of BHET (i.e., the concentration of BHET) in the mixture of BHET and EG coexisting in the liquid phase (or BHET / EG as a product of the depolymerization reactor 300) and the boiling point (inside temp.) of the mixture (under atmospheric pressure). As shown in this figure, as the concentration of BHET increases due to the progress of the depolymerization reaction, the boiling point of the BHET / EG mixture rises. In other words, as the concentration of BHET increases, there is room to raise the temperature of the BHET / EG mixture without boiling. For example, when the concentration of BHET is 0% (the concentration of EG is 100%), the boiling point of EG (approximately 197°C) is the upper limit of the temperature, but when the concentration of BHET is 20% (the concentration of EG is 80%), the upper limit of the temperature rises to approximately 205°C.

[0058] Utilizing the principles or phenomena described above, the depolymerization apparatus 5 according to this embodiment promotes the depolymerization reaction by efficiently increasing the concentration of BHET in the depolymerization reaction vessel 300 using flow control valves 61, 62, and 71, while simultaneously increasing the temperature with the heater 320 (transitioning to the right in Figure 5).

[0059] The depolymerization apparatus 5 according to this embodiment may operate mainly in two phases: a heating phase and a temperature-maintaining phase. In the heating phase, priority is given to increasing the concentration of BHET in the depolymerization reactor 300 in order to raise the temperature inside the depolymerization reactor 300. In the temperature-maintaining phase, priority is given to maintaining the temperature and the concentration of BHET inside the depolymerization reactor 300 after it has been sufficiently heated through the heating phase. The heating phase typically corresponds to the start of operation of the depolymerization reactor 300 and may be referred to as the startup phase. The temperature-maintaining phase may be referred to as the steady-state operation phase after the startup phase.

[0060] In the heating phase, the flow rate control valves 61 and / or 62 constituting the return amount adjustment unit 6 may increase the amount of BHET / EG returned through the return passage 53 to more than a predetermined return amount (for example, by gradually increasing the opening of the flow rate control valve 61 and / or gradually decreasing the opening of the flow rate control valve 62), thereby raising the concentration of BHET inside the depolymerization reactor 300 above a predetermined concentration (for example, 60% in Figure 6). The predetermined return amount can be rephrased as the amount of BHET / EG returned that raises the concentration of BHET inside the depolymerization reactor 300 above a predetermined concentration. In response to the increase in the concentration of BHET inside the depolymerization reactor 300, the heater 320 raises the temperature above a predetermined temperature (for example, if the predetermined concentration is 60%, then approximately 220°C, based on Figure 6, where the contents do not boil) within a range where the BHET / EG contents do not boil. This predetermined temperature is higher than the boiling point of EG as a depolymerizing agent under normal pressure (approximately 197°C). Furthermore, the predetermined temperature may be any temperature higher than 200°C, any temperature higher than 210°C, any temperature higher than 220°C, any temperature higher than 230°C, any temperature higher than 240°C, or any temperature higher than 250°C.

[0061] During the heat retention phase after the heating phase, while maintaining a state in which the concentration of BHET inside the depolymerization reactor 300 is higher than a predetermined concentration (e.g., 60%) and the temperature inside the depolymerization reactor 300 is higher than a predetermined temperature (e.g., 220°C) (maintained by the heater 320 if necessary), the flow control valves 61 and / or 62 constituting the return amount adjustment unit 6 may reduce the amount of BHET / EG returned through the return passage 53 to less than a predetermined amount (e.g., by lowering the opening of flow control valve 61 and / or increasing the opening of flow control valve 62). This results in an increase in the amount or flow rate of BHET / EG heading to the polymerization reactor 400 through the main production line, bringing the entire chemical recycling molding system into a steady-state operation state.

[0062] In the heating phase, in addition to or instead of the return volume adjustment unit 6, the flow rate adjustment valve 71 (and / or pump 72) constituting the discharge volume adjustment unit 7 may reduce the discharge amount of BHET / EG from the outlet 52 to less than a predetermined discharge amount (for example, by gradually lowering the opening of the flow rate adjustment valve 71), thereby increasing the concentration of BHET inside the depolymerization reactor 300 above a predetermined concentration (for example, 60% in Figure 6). The predetermined discharge amount can be rephrased as the discharge amount of BHET / EG that raises the concentration of BHET inside the depolymerization reactor 300 above a predetermined concentration. The heater 320 raises the temperature above a predetermined temperature (for example, if the predetermined concentration is 60%, then approximately 220°C, based on Figure 6, where the contents do not boil) in response to the increase in the concentration of BHET inside the depolymerization reactor 300, within a range where the BHET / EG contents do not boil. This predetermined temperature is higher than the boiling point of EG as a depolymerizing agent under normal pressure (approximately 197°C). Furthermore, the specified temperature may be any temperature higher than 200°C, any temperature higher than 210°C, any temperature higher than 220°C, any temperature higher than 230°C, any temperature higher than 240°C, or any temperature higher than 250°C.

[0063] During the heat retention phase after the heating phase, while maintaining a state in which the concentration of BHET inside the depolymerization reactor 300 is higher than a predetermined concentration (e.g., 60%) and the temperature inside the depolymerization reactor 300 is higher than a predetermined temperature (e.g., 220°C) (maintained by the heater 320 if necessary), the flow control valve 71 (and / or pump 72) constituting the discharge adjustment unit 7 may, in addition to or instead of the return amount adjustment unit 6, discharge a larger amount of BHET / EG from the outlet 52 than the predetermined discharge amount (e.g., by increasing the opening of the flow control valve 71). This results in an increase in the amount or flow rate of BHET / EG heading to the polymerization reactor 400 through the main production line, bringing the entire chemical recycling molding system into a steady-state operation state.

[0064] Furthermore, the concentration of BHET at the completion of the heating phase and / or during the heat retention phase is preferably, for example, 10-85 mol%, 15-60 mol%, and more preferably 20-40 mol%, from the viewpoint of obtaining the reaction-promoting effect of temperature as shown in Figure 5 while minimizing the BHET / EG reflux rate as shown in Figure 6 (if the reflux rate is high, not only will less BHET be sent to the main production line, but the power consumption for reflux will also become negligible).

[0065] As described above, the return volume adjustment unit 6 and the discharge volume adjustment unit 7 may work in coordination during the heating phase and / or heat retention phase to achieve the aforementioned priority objectives for each phase. Alternatively, there may be phases in which only one of the return volume adjustment unit 6 or the discharge volume adjustment unit 7 operates independently. For example, immediately after the start of operation of the depolymerization reactor 300, the flow rate adjustment valve 71 in the discharge volume adjustment unit 7 may be completely closed in order to keep substantially all of the generated BHET inside the depolymerization reactor 300 and maximize its concentration. In this case, the return passage 53 and the return volume adjustment unit 6 are substantially inactive, and only the discharge volume adjustment unit 7 is substantially active. In this initial phase immediately after the start of operation, the concentration of BHET increases rapidly, and after it is heated by the heater 320, the flow rate adjustment valve 71 is opened, BHET / EG flows into the main production line and the return passage 53, and the return volume adjustment unit 6 begins to function. At this timing, the flow rate adjustment valve 71 may be switched to the fully open state, thereby substantially disabling the discharge volume adjustment unit 7.

[0066] As described above, in this embodiment, the flow control valves 61, 62, 71 and the heater 320 work in coordination to optimize the BHET concentration and temperature inside the depolymerization reactor 300. To support such coordinated operation, a depolymerization concentration detection unit may be provided to detect the concentration of the depolymer, such as BHET, inside the depolymerization reactor 300.

[0067] By detecting the concentration of BHET, the boiling point of the contents of the depolymerization reactor 300 can be determined according to Figure 6, and the heater 320 can heat the depolymerization reactor 300 within a range where the contents do not boil. In other words, the heater 320 can adaptively increase the temperature inside the depolymerization reactor 300 according to the concentration of BHET detected by the depolymerization concentration detection unit.

[0068] Furthermore, by detecting the concentration of BHET, the deviation from the target concentration can be determined, allowing the flow control valves 61, 62, and 71 to adjust their openings to reduce the deviation. In other words, the return volume adjustment unit 6 and / or discharge volume adjustment unit 7 can adaptively adjust the amount of BHET / EG returned through the return passage 53 and / or the amount of BHET / EG discharged from the depolymerization reactor 300 according to the concentration of BHET detected by the depolymerization concentration detection unit.

[0069] The depolymer concentration detection unit may be composed of a measuring device or sensor based on any principle that directly or indirectly measures the BHET concentration in the depolymerization reactor 300. For example, the depolymerization concentration detection unit may be composed of a spectroscopic measuring device based on a spectroscopic method such as Raman spectroscopy, which indirectly measures the BHET concentration by irradiating the contents of the depolymerization reactor 300 with measuring light and analyzing the scattered light. Alternatively, the depolymerization concentration detection unit may be composed of a depolymerization reaction monitoring device 30 that indirectly detects or estimates the BHET concentration by monitoring the progress of the depolymerization reaction.

[0070] Figure 7 shows a first embodiment of the depolymerization reaction monitoring device 30 according to the present disclosure. The depolymerization reaction monitoring device 30 is configured to include the aforementioned depolymerization reactor 300.

[0071] The depolymerization reaction tank 300 comprises a tank body 31 for causing a depolymerization reaction of polyester or polymer, and a depolymerizer flow section 32 through which a depolymerizer such as EG flows between the tank body 31 and the tank body 31. The depolymerizer flow section 32 constitutes a flow path for the depolymerizer such as EG outside the tank body 31. As shown in the figure, one end 321 and the other end 322 of the tubular depolymerizer flow section 32 are connected to different locations on the tank body 31. As will be described later, the depolymerizer such as EG may flow from one end 321 to the other end 322 of the depolymerizer flow section 32, or it may flow from the other end 322 to one end 321 of the depolymerizer flow section 32.

[0072] The depolymerizing agent distribution section 32 is equipped with a depolymerizing reaction characteristic measurement section 33, an intrusion prevention section 34, a direction switching section 35, and a cooling section 36.

[0073] The depolymerization reaction characteristic measurement unit 33 measures the properties of the depolymerizing agent, such as EG, into which the depolymerized polymer, such as BHET, has dissolved in the depolymerization reactor 300. Specifically, the depolymerization reaction characteristic measurement unit 33 measures the properties of the depolymerizing agent, such as EG, in the depolymerizing agent flow unit 32.

[0074] In the example shown in Figure 7, the depolymerization reaction characteristic measurement unit 33 measures the optical properties of the depolymerizer, such as EG, in the depolymerizer flow unit 32. This depolymerization reaction characteristic measurement unit 33 comprises a light source 331, a light receiving unit 332, and a window 333. The light source 331 emits light of any intensity, pattern, wavenumber, wavelength, frequency, and other characteristics suitable for measuring the optical properties of the depolymerizer, such as EG in which the depolymer, such as BHET, is dissolved. The light from the light source 331 passes through the translucent window 333, which forms part of the wall of the tubular depolymerizer flow unit 32, and enters the interior of the depolymerizer flow unit 32, irradiating the depolymerizer, such as EG. Depending on the optical properties of the depolymerizer, such as EG in which the depolymer, such as BHET, is dissolved, this light undergoes optical effects such as reflection, refraction, absorption, scattering, diffraction, polarization, interference, and dispersion. The light receiving unit 332 receives the light that has undergone such optical effects through the window 333. The light received by the light receiving unit 332 represents the optical properties of the depolymerizing agent, such as EG, into which the depolymerized polymer, such as BHET, has dissolved. Examples of optical properties that the depolymerization reaction characteristic measuring unit 33 can measure include refractive index and spectrum. In this embodiment, an example will be described in which the depolymerization reaction characteristic measuring unit 33 measures the refractive index of the depolymerizing agent, such as EG, into which the depolymerized polymer, such as BHET, has dissolved.

[0075] The refractive index measured by the depolymerization reaction characteristic measurement unit 33 is provided to the depolymerization reaction progress monitoring unit 37, which is composed of a computer or processor. The depolymerization reaction progress monitoring unit 37 monitors the progress of the depolymerization reaction in the depolymerization reactor 300 (particularly the reactor body 31) based on the optical properties and other characteristics of the depolymerizing agent such as EG, measured by the depolymerization reaction characteristic measurement unit 33.

[0076] Figure 8 shows an example of monitoring the progress of the depolymerization reaction by the depolymerization reaction progress monitoring unit 37. As shown in Figure 8A, there is a correlation, such as a proportional relationship, between the refractive index measured by the depolymerization reaction characteristic measurement unit 33 and the concentration of the depolymer, such as BHET, in the depolymerizing agent, such as EG, which is the target of measurement (the dots (○) in Figure 8A are examples of measured values). As mentioned above, in the depolymerization reaction tank 300 (especially the tank body 31), PET is decomposed by EG as the depolymerizing agent, and BHET is obtained as the depolymer. Therefore, the concentration of BHET represents the progress of the PET depolymerization reaction. In other words, the depolymerization reaction progress monitoring unit 37 can recognize the progress of the depolymerization reaction of polymers such as PET based on the concentration of the depolymer, such as BHET, which is determined based on the correlation as shown in Figure 8A, from the refractive index measured by the depolymerization reaction characteristic measurement unit 33. For example, as shown in Figure 8B, the depolymerization reaction progress monitoring unit 37 can determine the total amount of BHET generated in the depolymerization reactor 300 based on the BHET concentration recognizable from Figure 8A, and express it as a change over time with respect to the reaction time (the dots (○) in Figure 8B are examples of measured values). The monitoring results from the depolymerization reaction progress monitoring unit 37, as shown in Figures 8A and 8B, may be provided to the controllers of the chemical recycling molding system and chemical recycling apparatus 100 in Figure 1, or they may be displayed on management screens or operation screens that can be viewed by their administrators or operators.

[0077] The depolymerization reaction characteristic measurement unit 33 may also measure the non-optical properties of the depolymerizer, such as EG, into which the depolymer, such as BHET, has dissolved. For example, the depolymerization reaction characteristic measurement unit 33 may measure the electrical properties of the depolymerizer, such as EG, into which the depolymer, such as BHET, has dissolved in the depolymerization reactor 300. In this case, instead of the optical depolymerization reaction characteristic measurement unit 33 shown in Figure 7, a depolymerization reaction characteristic measurement unit equipped with electrodes that electrically interact (e.g., make contact) with the depolymerizer, such as EG, in the depolymerizer flow unit 32 is provided. Furthermore, the method of the depolymerization reaction characteristic measurement unit 33 is not limited as long as it can measure the properties of the depolymerizer, such as EG, without taking a sample of it from the depolymerizer flow unit 32 (depolymerization reactor 300).

[0078] Furthermore, if polymers such as PET that remain undissolved in the depolymerizing agent such as EG in the tank body 31 do not interfere with the measurement, the depolymerization reaction characteristic measurement unit 33 may be installed in the tank body 31 instead of the depolymerizing agent flow unit 32. However, for an optical depolymerization reaction characteristic measurement unit 33 as shown in Figure 7, since the remaining polymers such as PET exert undesirable effects such as diffuse reflection on the measurement light, it is preferable that the depolymerization reaction characteristic measurement unit 33 be installed in the depolymerizing agent flow unit 32 outside the tank body 31, and it is also preferable that an intrusion prevention unit 34, which will be described below, be installed.

[0079] The intrusion prevention section 34 comprises a first filter 341 provided on one end 321 of the tubular depolymerizer flow section 32 and a second filter 342 provided on the other end 322 of the tubular depolymerizer flow section 32. The first filter 341 and the second filter 342 prevent insoluble substances that do not dissolve in the depolymerizer, such as EG, from entering the depolymerizer flow section 32 from the tank body 31. As mentioned above, examples of insoluble substances that do not dissolve in the depolymerizer, such as EG, include polyesters and polymers such as PET, which are reactants of the depolymerization reaction, and oligomers produced by the partial depolymerization of these. In this way, insoluble substances that may interfere with optical measurements by the depolymerization reaction characteristic measurement section 33 in the depolymerizer flow section 32 can be effectively removed by the first filter 341 and / or the second filter 342.

[0080] The direction switching section 35 is configured with a backwash pump or the like that can switch the direction of flow of the depolymerizer such as EG in the tubular depolymerizer flow section 32 between a first direction from one end 321 to the other end 322 and a second direction from the other end 322 to one end 321, in order to prevent clogging of the first filter 341 and / or the second filter 342. When the direction switching section 35 flows the depolymerizer such as EG in the first direction, insoluble matter collected by the second filter 342 at the other end 322 is returned to the tank body 31, and clogging of the second filter 342 is resolved. Also, when the direction switching section 35 flows the depolymerizer such as EG in the second direction, insoluble matter collected by the first filter 341 at one end 321 is returned to the tank body 31, and clogging of the first filter 341 is resolved. To avoid clogging in both the first filter 341 and the second filter 342, it is preferable that the direction switching unit 35 repeatedly or periodically switches the direction of the flow of the depolymerizer, such as EG, in the depolymerizer flow unit 32 between the first direction and the second direction.

[0081] The backwash pump and other components constituting the direction switching section 35 only need to operate before or during measurement by the depolymerization reaction characteristic measurement section 33, and may be stopped at other times. When the backwash pump and other components constituting the direction switching section 35 operate, the depolymerizing agent such as EG, which is the target of measurement by the depolymerization reaction characteristic measurement section 33, is taken in from the tank body 31 at one of the two ends 321 and 322 of the depolymerizing agent flow section 32. At this time, the "old" depolymerizing agent that was originally in the depolymerizing agent flow section 32 is discharged into the tank body 31 from the other end 322 of the depolymerizing agent flow section 32, thus clearing the clogging of the other end of the first filter 341 and the second filter 342 provided therein. The depolymerization reaction characteristic measurement section 33 can then perform measurements on the "new" depolymerizing agent newly taken in from the tank body 31.

[0082] The cooling section 36 cools the depolymerizer, such as EG, in the tubular depolymerizer flow section 32. Optical properties such as refractive index and other properties that can be measured by the depolymerization reaction characteristic measurement section 33 depend on the temperature of the depolymerizer, such as EG, that is being measured. Therefore, the cooling section 36 stabilizes the measurement accuracy of the depolymerization reaction characteristic measurement section 33 by cooling the depolymerizer, such as EG, to a predetermined temperature before measurement by the depolymerization reaction characteristic measurement section 33. As described above, since the depolymerizer, such as EG, in the depolymerizer flow section 32 can flow in either the first direction or the second direction by the direction switching section 35, it is preferable that the cooling section 36 comprises a first cooling section 361 on one end 321 side of the depolymerization reaction characteristic measurement section 33 and a second cooling section 362 on the other end 322 side of the depolymerization reaction characteristic measurement section 33.

[0083] Alternatively, instead of the cooling unit 36, a heating unit may be provided to heat the depolymerizing agent such as EG to a predetermined temperature. However, generally, many components such as sensors that constitute the depolymerization reaction characteristic measurement unit 33 have low operating temperatures (for example, 150°C or less), so it may not be possible to measure the depolymerizing agent such as EG in the tank body 31 at temperatures between 180°C and 250°C as is. For this reason, it is preferable to use the cooling unit 36 ​​to lower the depolymerizing agent such as EG to the measurable temperature (operating temperature) of the depolymerization reaction characteristic measurement unit 33. As shown in Figure 7, the cooling units 36 provided before and after (or above and below) the depolymerization reaction characteristic measurement unit 33 may cool the depolymerization reaction characteristic measurement unit 33 itself. Furthermore, by providing a temperature sensor (not shown) that measures the temperature of the depolymerizing agent such as EG facing the depolymerization reaction characteristic measurement unit 33, the cooling unit 36 ​​and / or heating unit may be controlled so that the temperature measured by the temperature sensor approaches the predetermined measurable temperature of the depolymerization reaction characteristic measurement unit 33.

[0084] According to the depolymerization reaction monitoring device 30 or depolymerization reaction progress monitoring unit 37 of the first embodiment described above, the progress of the depolymerization reaction of a polyester or polymer in which the depolymer product, such as BHET, dissolves in the reactant or reaction solvent, such as EG, can be efficiently grasped through the measurement of the properties of the depolymerizer, such as EG, by the depolymerization reaction characteristic measurement unit 33 in the depolymerization reaction tank 300 (depolymerizer flow unit 32). Since there is no need to collect the depolymerizer, such as EG, which is the target of measurement, from the depolymerization reaction tank 300 (depolymerizer flow unit 32), the progress of the depolymerization reaction can be grasped in real time.

[0085] In Figure 1, until the progress of the depolymerization reaction in the depolymerization reactor 300, monitored by the depolymerization reaction progress monitoring unit 37, reaches a predetermined value, the supply of the depolymerized polymer to the downstream foreign matter removal devices 340, 350, 360 and the polymerization reactor 400 may be temporarily stopped. The liquid containing the temporarily retained depolymerized polymer may be retained in piping or a buffer tank 370 provided between the depolymerization reactor 300 and the polymerization reactor 400, or it may be refluxed into the depolymerization reactor 300 to further advance the depolymerization reaction. Furthermore, a depolymer supply control valve (not shown) may be provided between the depolymerization reactor 300 and the polymerization reactor 400. This valve opens to allow the supply of depolymer to the polymerization reactor 400 when the progress of the depolymerization reaction in the depolymerization reactor 300, as monitored by the depolymerization reaction progress monitoring unit 37, reaches a predetermined value, and closes to stop the supply of depolymer to the polymerization reactor 400 when the progress of the depolymerization reaction in the depolymerization reactor 300, as monitored by the depolymerization reaction progress monitoring unit 37, falls below a predetermined value.

[0086] Figure 9 shows a second embodiment of the depolymerization reaction monitoring apparatus 30 according to the present disclosure. Components similar to those in the first embodiment in Figure 7 are denoted by the same reference numerals, and redundant explanations are omitted.

[0087] The depolymerizer distribution section 32 is provided with a depolymerizer dilution section 38 for further diluting the depolymerizer such as EG in the depolymerizer distribution section 32 by adding another depolymerizer such as EG. The depolymerizer dilution section 38 includes a dilution depolymerizer supply section 381 for supplying a dilution depolymerizer such as EG, a dilution pipe 382 connecting the dilution depolymerizer supply section 381 and the depolymerizer distribution section 32, a dilution valve 383 provided on the dilution pipe 382, ​​a first valve 384 provided in the depolymerizer distribution section 32 at the connection point with the dilution pipe 382 and on one end 321 side of the depolymerization reaction characteristic measurement section 33 and on the other end 322 side of the first cooling section 361, and a second valve 385 provided in the depolymerizer distribution section 32 at the connection point with the dilution pipe 382 and on the other end 322 side of the depolymerization reaction characteristic measurement section 33 and on one end 321 side of the second cooling section 362.

[0088] Figure 10 shows an example of dilution of the depolymer by the depolymerizer dilution unit 38. As shown in Figure 8A, there is a correlation, such as a proportional relationship, between the refractive index of the depolymerizer such as EG in which the depolymer such as BHET is dissolved, and the concentration of the depolymer such as BHET in the depolymerizer such as EG. However, as shown in Figure 10 (before dilution), this correlation breaks down when the concentration of BHET etc. exceeds a predetermined value A. Therefore, the depolymerization reaction progress monitoring unit 37 may not be able to correctly determine the concentration of BHET etc. from the refractive index measured by the depolymerization reaction characteristic measurement unit 33.

[0089] Therefore, the depolymerizer dilution unit 38 supplies additional depolymerizers such as EG from the dilution depolymerizer supply unit 381 to high-concentration solutions such as BHET that thus break the linearity of the measurement in the depolymerization reaction characteristic measurement unit 33. As a result, the concentration of depolymers such as BHET in the depolymerizer flow unit 32 (between the first valve 384 and the second valve 385) decreases, and as shown in Figure 10 (after dilution), the correlation or linearity is maintained even in the high-concentration region. In other words, by lowering the concentration of depolymers such as BHET in the depolymerizer flow unit 32, the refractive index measured by the depolymerization reaction characteristic measurement unit 33 falls within the linear range shown in Figure 10. The depolymerization reaction progress monitoring unit 37 can accurately determine the original (undiluted) concentration of BHET, etc. in the tank body 31 (the concentration on the straight line "after dilution" in Figure 10) based on the refractive index normally measured in a linear range by the depolymerization reaction characteristic measurement unit 33 and the amount of EG, etc. used for dilution by the dilution depolymerizer supply unit 381 (adjusted by the dilution valve 383 as described later).

[0090] To improve the measurement accuracy of the depolymerization reaction characteristic measurement unit 33 when using the depolymerization agent dilution unit 38 as described above, various valves such as the dilution valve 383, the first valve 384, and the second valve 385 are provided. Below, the opening and closing operations of each valve will be explained in accordance with the flowchart of a specific measurement procedure example shown in Figure 11. In the flowchart explanation, "S" means a step or process.

[0091] At the start of measurement in S1, the first valve 384 and the second valve 385 are open, and the dilution valve 383 is closed. In S2, the backwash pump and other components constituting the direction switching unit 35 operate, and the depolymerizing agent, such as EG, which is the target of measurement, is taken in from the tank body 31 to the depolymerizing agent flow unit 32. At this time, as described above, the first cooling unit 361 and / or the second cooling unit 362 cool the taken-in depolymerizing agent, such as EG, to a predetermined measurable temperature of the depolymerization reaction characteristic measurement unit 33. As a result, the depolymerizing agent, such as EG, cooled by the first cooling unit 361 and / or the second cooling unit 362 enters the space between the first valve 384 and the second valve 385, which were open in S1. In S3, the first valve 384 and the second valve 385 are switched to the closed state. As a result, a closed space is temporarily formed between the first valve 384 and the second valve 385, and the total amount of BHET, etc. in the closed space is determined.

[0092] In S4, the depolymerization reaction characteristic measurement unit 33 performs a primary measurement of the refractive index of the depolymerizing agent such as EG in the closed space formed in S3. In S5, it is determined whether the refractive index measured in S4 exceeds the saturation threshold B shown in Figure 10. If the result in S5 is "No", it means that the refractive index measured in S4 is within the linear range below the saturation threshold B, and is therefore adopted as the measurement result by the depolymerization reaction characteristic measurement unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of the depolymer such as BHET based on the refractive index measurement result obtained in S6.

[0093] If "Yes" is determined in S5, the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measurement unit 33, and therefore, proceeding to S6 and S7 will not yield the correct concentration of the depolymer such as BHET. Therefore, in S8, the dilution valve 383 is switched to the open state. In the following S8(2), the second valve 385 is switched to the open state in order to guide the dilution EG, etc. to the depolymerization reaction characteristic measurement unit 33. Then, in S9, the backwash pump, etc., which constitute the direction switching unit 35, operates, and the dilution EG, etc., is supplied from the dilution depolymerizer supply unit 381 to the space between the first valve 384 and the second valve 385 through the open dilution valve 383. The amount of EG, etc., used for dilution in S9 is measured by a flow sensor, etc. (not shown) provided on the dilution valve 383, etc. In S10, the dilution valve 383 is switched to the closed state, and in S10(2), the second valve 385 is switched to the closed state, thereby creating a closed space again between the first valve 384 and the second valve 385.

[0094] In S11, the depolymerization reaction characteristic measurement unit 33 performs a secondary measurement of the refractive index of the depolymerizing agent such as EG in the closed space formed in S3 and S10(2), and returns to S5. If "No" is determined in S5, the refractive index of the diluted EG measured in S11 falls within a linear range below the saturation threshold B, and is therefore adopted as the measurement result by the depolymerization reaction characteristic measurement unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of BHET etc. in the original (undiluted) tank body 31 (the concentration on the "after dilution" line in Figure 10) based on the secondary measurement result of the refractive index within the linear range obtained in S11 and the amount of EG etc. used for dilution in S9. In other words, as described above, the dilution valve 383, the first valve 384, and the second valve 385 allow control of the amount of depolymerizing agent such as EG entering the closed space (the space demarcated by the three valves) formed in S3 from the tank body 31 and the dilution depolymerizing agent supply unit 381, respectively. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET and other substances in the tank body 31 while grasping the quantitative effect of dilution by the depolymerizing agent dilution unit 38.

[0095] If "Yes" is determined in S5, the process proceeds again to S8-S11, and the dilution in S9 and the secondary measurement in S11 are repeated until "No" is determined in S5, that is, until the secondary measurement result of the refractive index in S11 falls within the linear range below the saturation threshold B. At the end of the measurement in S7, the first valve 384, the second valve 385, and the dilution valve 383 are closed.

[0096] In addition to controlling the amount of dilution EG, etc., supplied by the dilution depolymerizer supply unit 381 using a dilution valve 383, etc., the temperature of the dilution EG, etc., may also be controlled. For example, by supplying the temperature-controlled dilution EG, etc., in S9 to the closed space formed in S3, the EG, etc., in the closed space can be cooled to a predetermined measurable temperature of the depolymerization reaction characteristic measuring unit 33. In this way, at least some of the functions of the cooling unit 36 ​​may be realized by the dilution EG, etc., supplied by the dilution depolymerizer supply unit 381. In this case, at least a part of the first cooling unit 361 and the second cooling unit 362 in Figure 9 may not be provided.

[0097] Figure 12 shows a third embodiment of the depolymerization reaction monitoring apparatus 30 according to the present disclosure. Components similar to those in the first embodiment in Figure 7 and / or the second embodiment in Figure 9 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0098] The depolymerizer distribution section 32 is provided with an extraction section 39 capable of extracting a specified amount from the depolymerizer, such as EG, circulating inside it. The extraction section 39 comprises, for example, a syringe pump 391 and an extraction valve 392. The syringe pump 391 extracts, takes in, or discharges the depolymerizer, such as EG, depending on the position of a movable piston housed inside it. The extraction valve 392 is provided between the main body of the tubular depolymerizer distribution section 32 and the syringe pump 391.

[0099] The depolymerization reaction characteristic measurement unit 33 is provided on the syringe pump 391. Specifically, as schematically shown, the optical measurement described above is performed through a window 333 provided on the syringe pump 391 (the light source 331 and light receiving unit 332 are not shown). This depolymerization reaction characteristic measurement unit 33 measures the properties of the depolymerizing agent such as EG extracted by the extraction unit 39 (syringe pump 391).

[0100] Similar to the second embodiment shown in Figure 9, the depolymerizer distribution unit 32 is provided with a depolymerizer dilution unit 38 that further dilutes the depolymerizer, such as EG, extracted by the extraction unit 39 (syringe pump 391) by adding more depolymerizer, such as EG. The depolymerization reaction characteristic measurement unit 33 measures the characteristics of the depolymerizer, such as EG, diluted by the depolymerizer dilution unit 38.

[0101] Figure 13 is a flowchart of a specific measurement procedure example. Steps or processes similar to those in Figure 11 in the second embodiment are denoted by the same reference numerals, and redundant explanations are omitted.

[0102] At the start of measurement in S1, the extraction valve 392 is open and the dilution valve 383 is closed. In S2, the backwash pump and other components constituting the direction switching unit 35 operate, and the depolymerizer, such as EG, which is the target of measurement, is drawn from the tank body 31 into the depolymerizer flow unit 32. In S12, the extraction unit 39 extracts (primary extraction) a specified amount (first specified amount) of the depolymerizer, such as EG, that was drawn into the depolymerizer flow unit 32 in S2. In S3, the extraction valve 392 is switched to the closed state. As a result, the first specified amount of depolymerizer, such as EG, is secured in the extraction unit 39 (syringe pump 391).

[0103] In S4, the depolymerization reaction characteristic measurement unit 33 performs a primary measurement of the refractive index of the first specified amount of depolymerizing agent such as EG, which was secured in the extraction unit 39 (syringe pump 391) in S3. In S5, it is determined whether the refractive index measured in S4 exceeds the saturation threshold B shown in Figure 10. If "No" is determined in S5, the refractive index measured in S4 falls within the linear range below the saturation threshold B, and is therefore adopted as the measurement result by the depolymerization reaction characteristic measurement unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of the depolymer such as BHET based on the refractive index measurement result obtained in S6.

[0104] If "Yes" is determined in S5, the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measurement unit 33, so the correct concentration of the depolymer such as BHET cannot be obtained by proceeding to S6 and S7. Therefore, in S8, the dilution valve 383 is switched to the open state. In S13, the extraction unit 39 extracts a specified amount (second specified amount) of dilution EG etc. from the dilution depolymerizer supply unit 381 through the open dilution valve 383 (secondary extraction). Then, in S9, the EG etc. in the extraction unit 39 (syringe pump 391) is diluted with the dilution EG etc. extracted in S13. In S10, the dilution valve 383 is switched to the closed state. As a result, in addition to the first specified amount of depolymerizing agent such as EG (containing dissolved depolymer such as BHET) that was primarily extracted in S12, the extraction unit 39 (syringe pump 391) also contains a second specified amount of depolymerizing agent such as EG (without dissolved depolymer such as BHET) that was primarily extracted in S13.

[0105] In S11, the depolymerization reaction characteristic measurement unit 33 performs a secondary measurement of the refractive index of the first and second specified amounts of depolymerizing agent such as EG, which were secured in the extraction unit 39 (syringe pump 391) in S3 and S10, and returns to S5. If "No" is determined in S5, the refractive index of EG after dilution measured in S11 is within a linear range below the saturation threshold B, and is therefore adopted as the measurement result by the depolymerization reaction characteristic measurement unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of BHET, etc., in the original (undiluted) tank body 31 (concentration on the "after dilution" line in Figure 10) based on the secondary measurement result of the refractive index within the linear range obtained in S11, the first specified amount (obtained from the syringe pump 391 or extraction valve 392) that was primarily extracted in S12, and the second specified amount (obtained from the syringe pump 391 or dilution valve 383) that was secondarily extracted in S13. In other words, as described above, the syringe pump 391, extraction valve 392, and dilution valve 383 allow control of the amount of depolymerizing agent such as EG entering the extraction unit 39 (syringe pump 391) from the tank body 31 (or depolymerizing agent flow unit 32) and the dilution depolymerizing agent supply unit 381, respectively. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET, etc., in the tank body 31 while grasping the quantitative effect of dilution by the depolymerizing agent dilution unit 38.

[0106] If "Yes" is determined in S5, the process proceeds again to S8-S11, and the secondary extraction in S13, dilution in S9, and secondary measurement in S11 are repeated until "No" is determined in S5, that is, until the secondary measurement result of the refractive index in S11 falls within the linear range below the saturation threshold B. At the end of the measurement in S7, the extraction valve 392 and dilution valve 383 are closed.

[0107] The present disclosure has been described above based on embodiments. Various modifications are possible for each component and each combination of processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included in the scope of the present disclosure.

[0108] In the embodiment shown in Figure 4, components such as a return passage 53, flow control valves 61, 62, 71, and a pump 72 are provided as elements that can be used to adjust the BHET concentration in the depolymerization reactor 300, but it is not necessary to provide all of these. In other words, a simple configuration is also possible in which the BHET / EG discharged from the depolymerization reactor 300, which is equipped with a heater 320, goes to the polymerization reactor 400 without being refluxed back into the depolymerization reactor 300. Even in this case, the BHET concentration increases as the depolymerization reaction progresses in the depolymerization reactor 300, so there is room for heating by the heater 320 due to the rise in boiling point.

[0109] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources or software resources, or by the cooperation of hardware resources and software resources. Hardware resources include, for example, processors, ROMs, RAMs, and various integrated circuits. Software resources include, for example, operating systems and application programs. [Explanation of Symbols]

[0110] 1 Injection molding machine, 5 Depolymerization device, 6 Return volume adjustment unit, 7 Discharge volume adjustment unit, 30 Depolymerization reaction monitoring device, 51 Supply port, 52 Discharge port, 53 Return path, 61 Flow rate adjustment valve, 62 Flow rate adjustment valve, 71 Flow rate adjustment valve, 100 Chemical recycling device, 300 Depolymerization reaction tank, 320 Heater, 400 Polymerization reaction tank.

Claims

1. A depolymerization reactor that carries out a depolymerization reaction in which polyester is broken down into a depolymer by a depolymerizing agent, A heater is provided to raise the internal temperature of the depolymerization reactor to prevent boiling in response to the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor, A depolymerization apparatus equipped with the following features.

2. The depolymerization apparatus according to claim 1, further comprising a return path for returning at least a portion of the product containing the depolymer discharged from the depolymerization reactor back into the depolymerization reactor.

3. The depolymerization apparatus according to claim 2, further comprising a return amount adjustment unit for adjusting the amount of the product returned through the return path.

4. The aforementioned return amount adjustment unit is A heating phase is performed in which the amount of the product returned through the return path is increased to a predetermined amount, thereby increasing the concentration of the depolymer inside the depolymerization reactor above a predetermined concentration, and the temperature inside the depolymerization reactor is raised above a predetermined temperature by the heater. After the completion of the heating phase, a heat retention phase is performed in which the concentration of the depolymer inside the depolymerization reactor is higher than the predetermined concentration and the temperature inside the depolymerization reactor is higher than the predetermined temperature, while the amount of the product returned through the return path is reduced to less than the predetermined amount. A depolymerization apparatus according to claim 3, which operates in the following manner.

5. The depolymerization apparatus according to claim 4, wherein the predetermined temperature is higher than the boiling point of the depolymerizer at normal pressure or atmospheric pressure.

6. The depolymer concentration detection unit is provided for detecting the concentration of the depolymer inside the depolymer reaction vessel. The return volume adjustment unit adjusts the amount of the product returned through the return path according to the detected concentration of the depolymer. A depolymerization apparatus according to any one of claims 3 to 5.

7. The depolymerization apparatus according to claim 6, wherein the heater increases the temperature inside the depolymerization reactor according to the detected concentration of the depolymer.

8. The depolymerization apparatus according to any one of claims 3 to 5, wherein the return volume adjustment unit is a flow rate adjustment valve provided in the return path.

9. The depolymer concentration detection unit is provided for detecting the concentration of the depolymer inside the depolymer reaction vessel. The heater increases the temperature inside the depolymerization reactor according to the detected concentration of the depolymer. A depolymerization apparatus according to any one of claims 1 to 5.

10. The depolymerization apparatus according to any one of claims 1 to 5, further comprising a discharge adjustment unit for adjusting the discharge amount of the product containing the depolymerized polymer from the depolymerization reactor.

11. The aforementioned emission adjustment unit is A heating phase is performed in which the amount of the product discharged from the depolymerization reactor is reduced to less than a predetermined amount, thereby increasing the concentration of the depolymer inside the depolymerization reactor above a predetermined concentration, and the temperature inside the depolymerization reactor is raised above a predetermined temperature by the heater. After the completion of the heating phase, a heat retention phase is performed in which the concentration of the depolymer inside the depolymerization reactor is higher than the predetermined concentration and the temperature inside the depolymerization reactor is higher than the predetermined temperature, while the amount of product discharged from the depolymerization reactor is greater than the predetermined discharge amount. A depolymerization apparatus according to claim 10, which operates in the following manner.

12. The depolymer concentration detection unit is provided for detecting the concentration of the depolymer inside the depolymer reaction vessel. The discharge adjustment unit adjusts the discharge amount of the product from the depolymerization reactor according to the detected concentration of the depolymer. The depolymerization apparatus according to claim 10.

13. The depolymerization apparatus according to any one of claims 1 to 5, wherein the inside of the depolymerization reactor is at normal pressure or atmospheric pressure.

14. The aforementioned polyester is polyethylene terephthalate, The aforementioned depolymer is bis(2-hydroxyethyl) terephthalate, The depolymerizing agent is ethylene glycol. A depolymerization apparatus according to any one of claims 1 to 5.

15. A depolymerization reactor that carries out a depolymerization reaction in which polyester is broken down into a depolymer by a depolymerizing agent, A heater that raises the temperature inside the depolymerization reactor in accordance with the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor, A polymerization reactor for synthesizing the aforementioned depolymer into a polymer by polymerization reaction, A chemical recycling device equipped with [a specific feature / feature].

16. Inside the depolymerization reactor, a depolymerization reaction occurs in which the polyester is broken down into a depolymer by a depolymerizing agent, In response to the increase in the concentration of the depolymer due to the progress of the depolymerization reaction in the depolymerization reactor, the temperature inside the depolymerization reactor is increased. A depolymerization method that performs this operation.

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