Depolymerization apparatus, chemical recycling apparatus, and depolymerization method

Abstract

This invention relates to depolymerization apparatus, chemical recovery apparatus, and depolymerization method, and provides a depolymerization apparatus capable of effectively carrying out depolymerization reactions in a depolymerization reaction tank. The depolymerization apparatus (5) includes: a depolymerization reaction tank (300) for initiating a depolymerization reaction in which PET is decomposed into BHET by EG; and a heater (320) for increasing the temperature inside the depolymerization reaction tank (300) based on the increase in BHET concentration caused by the depolymerization reaction in the depolymerization reaction tank (300). The depolymerization apparatus (5) includes: a return channel (53) for returning at least a portion of the BHET-containing product discharged from the depolymerization reaction tank (300) to the interior of the depolymerization reaction tank (300). The depolymerization apparatus (5) includes a return amount adjustment unit (6) for adjusting the amount of product returned through the return channel (53).

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2024-229213, filed on December 25, 2024. The entire contents of that Japanese application are incorporated herein by reference.

[0002] This invention relates to a depolymerization device, etc. Background Technology

[0003] Patent Document 1 discloses a method for manufacturing PET sheets, which are raw materials for new PET bottles, by crushing PET bottles for recycling. Specifically, mechanical recycling methods are known, such as heating and melting crushed PET bottles and obtaining PET sheets through solid-state polymerization, or chemical recycling methods, such as depolymerizing crushed PET bottles into intermediates or depolymers like bis(2-hydroxyethyl) terephthalate (BHET) through a depolymerization reaction and then obtaining PET sheets through a repolymerization reaction.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-153176

[0005] Patent Document 2: Japanese Patent Application Publication No. 2022-27158

[0006] To effectively recycle PET chemically, it is preferable to shorten the depolymerization reaction time by increasing the temperature inside the depolymerization tank that initiates the depolymerization reaction of PET into BHET using ethylene glycol (EG) as a depolymerizing agent. However, when the temperature inside the depolymerization tank exceeds the boiling point of EG at atmospheric pressure (approximately 197°C), EG will boil and fail to induce the desired depolymerization reaction. Summary of the Invention

[0007] The present invention was made in view of this situation, and its object is to provide a depolymerization apparatus, etc., capable of effectively carrying out the depolymerization reaction in a depolymerization reaction tank.

[0008] To address the aforementioned issues, one aspect of the depolymerization apparatus of the present invention comprises: a depolymerization reaction tank for initiating a depolymerization reaction in which polyester is decomposed into depolymerized products by a depolymerizing agent; and a heater for increasing the temperature inside the depolymerization reaction tank in a non-boiling manner based on the increase in the concentration of the depolymerized products caused by the proceeding of the depolymerization reaction in the depolymerization reaction tank.

[0009] According to this embodiment, focusing on the increase in boiling point caused by the increase in concentration of depolymerized products due to the depolymerization reaction in the depolymerization reaction tank, boiling can be avoided while increasing the temperature inside the depolymerization reaction tank.

[0010] Another aspect of the present invention is a chemical recycling apparatus. This apparatus comprises: a depolymerization reaction tank for initiating a depolymerization reaction that breaks down polyester into depolymers using a depolymerizing agent; a heater for increasing the temperature inside the depolymerization reaction tank in a non-boiling manner based on the increase in the concentration of the depolymers caused by the proceeding of the depolymerization reaction in the depolymerization reaction tank; and a polymerization reaction tank for synthesizing the depolymers into polymers through a polymerization reaction.

[0011] Another aspect of the present invention is a depolymerization method. This method involves performing the following steps inside a depolymerization reaction tank: initiating a depolymerization reaction that decomposes polyester into depolymerized products using a depolymerizing agent; and increasing the temperature inside the depolymerization reaction tank in a non-boiling manner based on the increase in the concentration of the depolymerized products caused by the proceeding of the depolymerization reaction in the tank.

[0012] Furthermore, any combination of the above-mentioned constituent elements, and the manner in which these are manifested in methods, apparatus, systems, storage media, computer programs, etc., are also included in this invention.

[0013] Invention Effects

[0014] According to the present invention, the depolymerization reaction in the depolymerization reaction tank can be carried out effectively. Attached Figure Description

[0015] Figure 1 The structure of a chemical recycling molding system is shown schematically.

[0016] Figure 2 The diagram illustrates the polymerization and depolymerization reactions of PET.

[0017] Figure 3 This represents a modified example of a byproduct removal device.

[0018] Figure 4 The depolymerization device is shown schematically.

[0019] Figure 5 This schematically illustrates the relationship between the reaction temperature inside the depolymerization reactor and the relative time required for the depolymerization reaction.

[0020] Figure 6 This schematically illustrates the relationship between the proportion of BHET in a mixture of BHET and EG and the boiling point of the mixture.

[0021] Figure 7 This describes the first embodiment of the depolymerization reaction monitoring device.

[0022] Figure 8A as well as Figure 8B This example illustrates how the progress of the depolymerization reaction is monitored through a depolymerization reaction progress monitoring unit.

[0023] Figure 9 This represents the second embodiment of the depolymerization reaction monitoring device.

[0024] Figure 10 This illustrates an example of diluting the depolymerizing agent through a depolymerizing agent dilution section.

[0025] Figure 11 This is a flowchart illustrating a specific measurement sequence example in the second embodiment.

[0026] Figure 12 This represents the third embodiment of the depolymerization reaction monitoring device.

[0027] Figure 13 This is a flowchart illustrating a specific measurement sequence example in the third embodiment.

[0028] Symbol Explanation

[0029] 1-Injection molding machine, 5-Depolymerization device, 6-Return flow adjustment unit, 7-Discharge flow adjustment unit, 30-Depolymerization reaction monitoring device, 51-Supply port, 52-Discharge port, 53-Return flow channel, 61-Flow regulating valve, 62-Flow regulating valve, 71-Flow regulating valve, 100-Chemical recovery device, 300-Depolymerization reaction tank, 320-Heater, 400-Polymerization reaction tank. Detailed Implementation

[0030] Hereinafter, embodiments of the present invention (hereinafter also referred to as embodiments) will be described in detail with reference to the accompanying drawings. In the following description and / or drawings, identical or equivalent components, parts, and processes are labeled with the same symbols, and repeated descriptions are omitted. For ease of description, scales and shapes of the illustrated parts are appropriately provided, and unless otherwise specifically stated, they are not intended to be limiting. Embodiments are provided as examples and do not limit the scope of the present invention in any way. All features and combinations thereof shown in the embodiments are not necessarily essential to the present invention. For convenience, embodiments are shown in detail as components that implement each function and / or each group of functions of the embodiment. However, one component in an embodiment may be implemented by a combination of multiple components that are actually separate entities, and multiple components in an embodiment may be implemented by a single component that is actually integrated. Furthermore, multiple embodiments and modifications may be disclosed side by side, but any components of each embodiment and / or modification may be combined in any manner as long as they do not impede each other's functions.

[0031] Figure 1The diagram schematically illustrates the structure of a chemical recovery molding system to which the depolymerization apparatus and / or chemical recovery apparatus according to embodiments of the present invention can be applied. The chemical recovery molding system includes a chemical recovery apparatus 100 and an injection molding machine 1. The chemical recovery apparatus 100 includes a polymer conditioning device 200, a depolymerization reaction tank 300 (depolymerization apparatus 5), a polymerization reaction tank 400, a byproduct removal device 500, and a polymer supply unit 600. The injection molding machine 1 ( Figure 1 The number of injection molding machines 1 (illustrated as 2 units), polymer conditioning unit 200, depolymerization reaction tank 300, polymerization reaction tank 400, by-product removal unit 500, and polymer supply unit 600 is arbitrary. In particular, typically, the processing performance is improved by having a larger number of polymerization reaction tanks 400 (which have slower processing or reaction speeds than other processing units) than other processing units, so that these processing units do not become serious bottlenecks.

[0032] The polymer conditioning device 200 conditions the polymer, such as PET, that constitutes the first molded product, such as a PET bottle, for use in the subsequent depolymerization reaction tank 300. Specifically, the polymer conditioning device 200 processes the first molded product, such as the PET bottle, by crushing, heating and melting, mixing, etc., to condition the polymer, such as PET, to a state (phase, shape, size, etc.) suitable for the depolymerization reaction in the depolymerization reaction tank 300. Furthermore, the first molded product can be any molded product other than a bottle, such as a sheet, film, or fiber. Moreover, the polymer constituting the first molded product can be any polymer or aggregate other than PET, such as polyester (including PET), polyamide, or polyurethane.

[0033] The depolymerization reaction tank 300 decomposes polymers such as PET, which have been adjusted by the polymer conditioning device 200, into depolymerized products through a depolymerization reaction. When the polymer supplied from the polymer conditioning device 200 is PET, BHET, as an intermediate, can be obtained as a depolymerized product through the depolymerization reaction in the depolymerization reaction tank 300. Furthermore, the depolymerized products obtained in the depolymerization reaction tank 300 may include monomers or polymers of the polymer. For example, monomers when the polymer is PET include ethylene glycol, terephthalic acid, dimethyl terephthalate, and ethylene glycol terephthalate. Details will be described later, but the depolymerization apparatus according to embodiments of the present invention may be configured to include the depolymerization reaction tank 300.

[0034] like Figure 2 Schematic representation: In the depolymerization reaction (300) of PET as a polymer, by means of a depolymerizing agent supply section 310 ( Figure 1Ethylene glycol (EG), supplied as a depolymerizing agent, is added to the depolymerization reaction tank 300 to decompose PET and obtain BHET as a depolymerized product. Alternatively, EG can be supplied in the polymer conditioning device 200 instead of the depolymerizing agent supply unit 310, or EG can be supplied in the polymer conditioning device 200 in addition to the depolymerizing agent supply unit 310. To promote this depolymerization reaction, a heater 320 is provided parallel to the depolymerization reaction tank 300. Figure 1 (or use a heatsink to adjust the temperature inside the depolymerization reaction tank 300 to a suitable temperature for the depolymerization reaction.) Figure 2 The suitable temperature for the depolymerization reaction of PET to BHET is between 180°C and 250°C, preferably between 230°C and 245°C, and more preferably between 235°C and 240°C. Furthermore, typically, Figure 2 The pressure suitable for the depolymerization reaction of PET to BHET is 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. Furthermore, the pressure unit MPa, G refers to gauge pressure. The pressure within the depolymerization reaction tank 300 can be adjusted by a pump (not shown) or similar device arranged parallel to the depolymerization reaction tank 300.

[0035] However, in this embodiment, as described later, the interior of the depolymerization reaction tank 300 is at atmospheric pressure or normal pressure. In other words, there is no need to install pumps or the like to pressurize the interior of the depolymerization reaction tank 300 to above atmospheric pressure. This allows for cost reduction of the depolymerization apparatus. Furthermore, even when it is necessary to remove the contents from the depolymerization reaction tank 300, since there is almost no pressure difference between the inside and outside of the depolymerization reaction tank 300, there is no risk of sudden boiling. When the interior of the depolymerization reaction tank 300 is pressurized to above atmospheric pressure as in the past, sudden boiling may occur due to the pressure difference between the inside and outside of the depolymerization reaction tank 300, thus requiring depressurization before removing the contents. Moreover, to restart the depolymerization reaction, the interior of the depolymerization reaction tank 300 needs to be pressurized again using pumps or the like, resulting in low efficiency.

[0036] The fluid viscosity in the depolymerization reaction tank 300, which produces BHET with a molecular weight smaller than PET as a polymer, is lower than the fluid viscosity in the polymerization reaction tank 400, which produces PET with a larger molecular weight. Therefore, a low-viscosity stirring blade is used as the stirring blade 330 for stirring the fluid in the depolymerization reaction tank 300 to promote the depolymerization reaction. Examples of low-viscosity stirring blades 330 include propeller blades, disc turbine blades, and paddle blades. Furthermore, in Figure 1 In this embodiment, the depolymerization apparatus, including the depolymerization reaction tank 300, is simplified, and its detailed structure will be described later with reference to other figures.

[0037] Impurity removal devices 340, 350, and 360 are installed downstream of the depolymerization reactor 300 to remove impurities from the fluid, which is mainly composed of BHET as a depolymerized product. The heteropolymer removal device 340 removes resins different from the target resin such as PET and / or their depolymerized products using the principles of flotation separation and sedimentation removal. The colorant removal device 350 removes colorants using activated carbon or similar methods. The metal ion removal device 360 ​​removes metal ions using principles such as ion exchange. A buffer tank 370 is installed downstream of the impurity removal devices 340, 350, and 360 to temporarily store the fluid, which is mainly composed of BHET after impurity removal, before it is supplied to the polymerization reactor 400.

[0038] A buffer tank 370 can be installed before the polymerization reactor 400 to a first preheater 371 to heat or maintain the temperature of the depolymerized material (a fluid mainly composed of BHET, etc.). The first preheater 371 can maintain the depolymerized material at the same temperature (between 180°C and 250°C) as the heater 320 arranged in parallel with the depolymerization reactor 300, or at the same temperature suitable for the polymerization reaction (between 250°C and 300°C) as the heater 410 arranged in parallel with the polymerization reactor 400. Thus, by installing a buffer tank 370 equipped with a preheating mechanism (first preheater 371) in front of the polymerization reactor 400 as needed, it is typically possible to store the depolymerized material waiting to be fed into the polymerization reactor 400, whose processing speed or reaction speed is slower than that of the depolymerization reactor 300, the by-product removal device 500, etc., while maintaining it at a suitable temperature. As a result, the overall capacity of the chemical recovery unit 100 is increased, enabling stable and continuous operation of the chemical recovery unit 100 while timely supplying appropriate amounts of reactants to each processing unit, such as the depolymerization reaction tank 300, polymerization reaction tank 400, by-product removal device 500, and polymer supply unit 600 (without the so-called "resin supply interruption"). Furthermore, the preheating mechanism, such as the first preheater 371, is not limited to the buffer tank 370 and can be installed in any manner at any location between the depolymerization reaction tank 300 and the polymerization reaction tank 400 (e.g., impurity removal devices 340, 350, 360).

[0039] The polymerization reactor 400 synthesizes BHET and other depolymerized products, which were generated in the depolymerization reactor 300 and whose impurities have been removed by the impurity removal devices 340, 350, and 360, into a polymer through a polymerization reaction. When the depolymerized product generated in the depolymerization reactor 300 is BHET, PET, as a polymer, can be obtained again through a polymerization reaction in the polymerization reactor 400.

[0040] like Figure 2Schematic illustration shows that in the polymerization reaction (400) of BHET, which is a depolymerizer, EG is generated as a byproduct along with PET, which is the polymer and the main product. This EG can be recycled to the depolymerizer supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reaction tank 300. Since the EG generated in the polymerization reaction tank 400 is not wasted and can be reused on-site (in the depolymerization reaction tank 300), the operating efficiency of the chemical recovery unit 100 can be improved. In particular, since the amount of EG used for the depolymerization reaction of PET in the depolymerization reaction tank 300 can be significantly reduced, the operating cost of the chemical recovery unit 100 is reduced.

[0041] To promote the polymerization reaction described above, a heater 410, which serves as a second heater, is arranged in parallel with the polymerization reactor 400. Figure 1 (or a heatsink) to maintain the polymerization reaction tank 400 at a temperature suitable for the polymerization reaction. Figure 2 The suitable temperature for the polymerization reaction of BHET to PET 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 based on the heater 410 arranged in parallel in the polymerization reactor 400 is higher than the depolymerization heating temperature based on the heater 320 arranged in parallel in the depolymerization reactor 300. PET with a larger molecular weight and higher melting point is generated in the polymerization reactor 400, but by maintaining a temperature higher than that of the depolymerization reactor 300, which generates BHET with a smaller molecular weight and lower melting point, the main product of the polymerization reactor 400, i.e., PET, is kept in a molten state. Furthermore, Figure 2 The polymerization reaction of BHET to PET is preferably carried out under vacuum. Therefore, vacuum pumps (not shown) can be installed side by side in the polymerization reactor 400.

[0042] Since the fluid viscosity in the polymerization reactor 400, which produces PET with a larger molecular weight, is higher than the fluid viscosity in the depolymerization reactor 300, which produces BHET with a smaller molecular weight than PET as a polymer, a high-viscosity stirring blade is used as the stirring blade 420 for stirring the fluid in the polymerization reactor 400 to promote the polymerization reaction. Examples of high-viscosity stirring blades 420 include anchor blades and helical ribbon blades.

[0043] As a numerical value associated with the degree of polymerization of polymers such as PET, the intrinsic viscosity (IV) value is known. The IV value (dL / g) is also used as an indicator of the polymer's application. In PET, an IV value of approximately 0.72 or higher is suitable for bottles, an IV value of approximately 0.65 or higher is suitable for sheets, films, etc., and an IV value of approximately 0.58 or higher is suitable for fibers. In this embodiment, the aim is to ultimately obtain PET with an IV value suitable for bottles and sheets. As will be described later, since the IV value is also increased in the by-product removal device 500 at the downstream end of the polymerization reactor 400, the IV value of the PET synthesized in the polymerization reactor 400 can 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.

[0044] A buffer tank 430 can be installed at the downstream end of the polymerization reactor 400 to temporarily store the polymer synthesized in the polymerization reactor 400 before it is supplied to the downstream by-product removal device 500 and / or polymer supply unit 600. A second preheater 431 can be installed on the buffer tank 430 to heat or keep the polymer warm before it is supplied to the downstream by-product removal device 500 and / or polymer supply unit 600. The second preheater 431 can maintain the polymer at the same temperature (between 250°C and 300°C) as the heater 410 arranged in parallel with the polymerization reactor 400, or at the same temperature suitable for polymerization (between 250°C and 290°C) as the heater 520 arranged in parallel with the by-product removal device 500 (described later), or at the same temperature (between 250°C and 290°C) as the heater 620 arranged in parallel with the polymer supply unit 600 (described later).

[0045] Thus, by placing a buffer tank 430 equipped with a preheating mechanism (second preheater 431) upstream of the by-product removal device 500 and / or the polymer supply unit 600 as needed, polymer awaiting delivery to the by-product removal device 500 and / or the polymer supply unit 600 can be stored while maintaining a suitable temperature. As a result, the overall capacity of the chemical recovery device 100 is increased, enabling stable and continuous operation of the chemical recovery device 100 while timely supplying appropriate amounts of reactants to each processing unit, such as the depolymerization reaction tank 300, polymerization reaction tank 400, by-product removal device 500, and polymer supply unit 600 (without the so-called "resin supply interruption"). Furthermore, the preheating mechanism, such as the second preheater 431, is not limited to the buffer tank 430 and can be installed in any manner at any location between the polymerization reaction tank 400 and the by-product removal device 500 and / or at any location between the by-product removal device 500 and the polymer supply unit 600.

[0046] A byproduct removal device 500 is provided at the rear section of the polymerization reactor 400 (and at the front section of the polymer supply section 600, described later) to allow PET (main product) and EG (byproduct) generated by the polymerization reaction in the polymerization reactor 400 to pass through and remove EG as a byproduct. The byproduct removal device 500 illustrated in the figure has a plurality of linear members 510 extending from top to bottom. Due to the increased surface area caused by the plurality 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.

[0047] The EG can be circulated to the depolymerizing agent supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reactor 300. Since the EG removed in the by-product removal device 500 is not wasted and can be reused on-site (in the depolymerization reactor 300), the operating efficiency of the chemical recovery unit 100 can be improved. In particular, since the amount of EG purchased for the depolymerization reaction of PET in the depolymerization reactor 300 can be significantly reduced, the operating cost of the chemical recovery unit 100 is reduced.

[0048] Furthermore, since PET with a relatively low degree of polymerization (i.e., IV value) and BHET that did not react in the polymerization reactor 400 are also attached to the surface of each linear component 510, the same polymerization reaction as in the polymerization reactor 400 can be carried out effectively due to the large surface area. Therefore, since it passes through the by-product removal device 500, the IV value of PET, as the main product, is increased. Specifically, the IV value of PET after passing through the by-product removal device 500 is 0.7 or more, preferably 0.8 or more, and more preferably 0.85 or more.

[0049] To facilitate this polymerization reaction, a heater 520, which serves as a second heater, is arranged in parallel with the by-product removal device 500. Figure 1 The byproduct removal device 500 is maintained at a temperature suitable for the polymerization reaction by means of a heater or insulator. Specifically, the heating temperature of the heater 520 is between 250°C and 290°C, preferably between 260°C and 280°C. Here, the heating temperature of the heater 520, which is arranged in parallel with the polymerization reactor 400, is preferably higher than the polymerization heating temperature of the heater 410, which is arranged in parallel with the polymerization reactor 400. In the byproduct removal device 500, the polymerization reaction progresses further compared to the polymerization reactor 400. As a result, the molecular weight of PET, as a polymer, increases and its melting point increases. Therefore, by maintaining the temperature in the byproduct removal device 500 at a higher level than that in the polymerization reactor 400, the PET, as a product of the byproduct removal device 500, can be kept in a molten state. Furthermore, around the piping between the polymerization reactor 400 and the by-product removal device 500, at least a heater or heatsink, serving as a second heater, can be installed to heat or maintain the temperature to the polymerization heating temperature based on the heater 410 arranged parallel to the polymerization reactor 400. Also, similar to the polymerization reaction in the polymerization reactor 400, the polymerization reaction in the by-product removal device 500 is preferably carried out under a vacuum. Therefore, a vacuum pump (not shown) can be installed parallel to the by-product removal device 500. By keeping the by-product removal device 500 under a vacuum (reduced pressure), EG as a by-product can be effectively removed.

[0050] Furthermore, the structure of the by-product removal device 500 is not limited to... Figure 1 The "vertical" form is shown. For example, as shown... Figure 3 The "horizontal twin-shaft" stirring device shown can also be used as a by-product removal device 500. This stirring device has a direction perpendicular to... Figure 3 The system consists of two rotating shafts extending in the direction of the paper surface and two stirring blades rotating around each shaft to agitate PET and EG, the objects of the agitation. By utilizing the two stirring blades to agitate and promote the volatilization of EG, EG can be effectively separated and removed from high-viscosity PET. Furthermore, Figure 3 The details of the stirring device are disclosed in Japanese Patent No. 2925599, which is incorporated herein by reference.

[0051] 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 for molding second-generation products such as PET bottles. The polymer supply unit 600 is equipped with a transfer pump 610, such as a gear pump or a screw pump, which is suitable for supplying high-purity and high-viscosity (i.e., high degree of polymerization or high IV value) PET to the injection molding machine 1 while keeping it in a molten state after EG, which is removed as a by-product in the by-product removal device 500, is removed.

[0052] A heater 620 or a heatsink, serving as a first heater, is provided in the polymer supply section 600 to heat or keep the polymer, such as PET, supplied to the injection molding machine 1 via a transfer pump 610 in a molten state. Specifically, the heating temperature of the heater 620 is between 250°C and 290°C, preferably between 260°C and 280°C. Here, the heating temperature of the heater 620 (first heater) in the polymer supply section 600 (first heating temperature) is preferably higher than the second heating temperature of a second heater, such as the heater 410 arranged in parallel with the polymerization reactor 400, the heater 520 arranged in parallel with the by-product removal device 500, or a heater (not shown) arranged between the polymerization reactor 400 and the by-product removal device 500. The polymerization reaction, which begins in the polymerization reactor 400, proceeds gradually and is completed in the by-product removal device 500. As a result, compared to the polymerization reactor 400 and the by-product removal device 500, the molecular weight of polymers such as PET in the polymer supply section 600 increases and the melting point becomes higher. Therefore, by setting the first heating temperature in the polymer supply section 600 to a higher than the previous second heating temperature, polymers such as PET with high viscosity (i.e., high degree of polymerization or high IV value) and high melting point can be maintained in a molten state.

[0053] A temperature gradient can also be set in a manner where the heating temperature gradually increases from the polymerization reactor 400 to the polymer supply unit 600. For example, by increasing the heating temperature of a heater (not shown) located between the polymerization reactor 400 and the by-product removal device 500 compared to the heating temperature of the heater 410 located in parallel with the polymerization reactor 400, increasing the heating temperature of the heater 520 located in parallel with the by-product removal device 500 compared to the heating temperature of the heater (not shown), and increasing the heating temperature of the heater 620 located in the polymer supply unit 600 compared to the heating temperature of the heater 410, the polymer with a higher melting point, such as PET, can be reliably maintained in a molten state from the polymerization reactor 400 to the polymer supply unit 600. Alternatively, a heater can be provided between the polymer supply unit 600 and the injection molding machine 1 to heat or maintain the polymer, such as PET, in a molten state.

[0054] The injection molding machine 1 molds molten polymers such as PET generated in the chemical recycling unit 100 into a second molded product. The second molded product can be the same type as or different from the first molded product, which undergoes pulverization or other processing in the polymer conditioning unit 200. For example, both the first and second molded products can be PET bottles. Furthermore, one of the first and second molded products can be a PET bottle, while the other can be a molded product other than a bottle, such as a sheet, film, or fiber. Typically, in mechanical recycling, the IV value of the recycled second molded product is lower than the IV value of the original first molded product. However, according to the chemical recycling unit 100 of this embodiment, which is equipped with devices for improving IV values ​​such as impurity removal devices 340, 350, 360, and by-product removal devices 500, the IV value of the recycled second molded product can be higher than the IV value of the original first molded product. For example, according to this embodiment, it is also possible to recycle low-IV-value PET fibers, which are the first molded product, into high-IV-value PET bottles, which are the second molded product.

[0055] Injection molding machine 1 molds molten resin such as PET into a second molded article. An injection molding machine using molten resin as raw material is disclosed, for example, in Patent Document 2. This application incorporates the entire contents of that document (Japanese Patent Application 2020-130985), filed July 31, 2020, by reference. Figure 1 This schematically illustrates that multiple injection molding machines 1 can be connected in parallel. Furthermore, the molding machine that supplies molten resin, etc., from the chemical recovery unit 100 is not limited to an injection molding machine, but can be any molding machine (e.g., a compression molding machine).

[0056] In this embodiment as described above, the polymer synthesized in the polymerization reactor 400 is not made into sheets or granules, but is supplied to the injection molding machine 1 as is via the polymer supply unit 600. Since the cooling and heating processes associated with sheets and granules are not required as in the past, molded products such as PET bottles can be recycled with less energy than before.

[0057] In this chemical recovery apparatus 100 of this embodiment, since the polymer resynthesized in the polymerization reaction tank 400 is supplied to the injection molding machine 1 in its original form, it is necessary to achieve the required IV value of the polymer for the molded article (second molded article) at high speed. In this embodiment, in addition to the polymerization reaction tank 400, a by-product removal device 500 with the function of promoting the polymerization reaction and increasing the IV value of the polymer is also provided, so this requirement can be adequately met.

[0058] exist Figure 1In the example, only one of each of the polymer conditioning device 200, depolymerization reaction tank 300, polymerization reaction tank 400, by-product removal device 500, and polymer supply unit 600 is provided, but multiple units can also be provided. These multiple processing units can be connected in parallel to perform the same processing, thus improving the processing performance of the processing unit group. Furthermore, the difference in processing speed or reaction rate between the processing units can be reduced by increasing the number of slower processing units.

[0059] Furthermore, one or more processing units may be used to receive materials from the front-end processing unit, or, in addition to receiving materials from the front-end processing unit, to receive materials from the front-end processing unit. Figure 1 The chemical recycling molding system shown can accommodate external materials supplied to different locations or facilities. For example, when multiple polymerization reactors 400 are provided, depolymerized material from the depolymerization reactor 300 can be supplied to one part, while externally supplied depolymerized material can be supplied to another part. Similarly, when multiple by-product removal devices 500 and / or polymer supply units 600 are provided, polymer from the polymerization reactors 400 can be supplied to one part, while externally supplied polymer can be supplied to another part. In this way, by allowing the reception of external materials at each stage of processing in the chemical recycling molding system, the flexibility and efficient operation of the chemical recycling molding system can be ensured.

[0060] Figure 4 The depolymerization apparatus 5 according to this embodiment is schematically shown. The depolymerization apparatus 5 is configured to include the depolymerization reaction tank 300 described above. The depolymerization reaction tank 300 initiates a depolymerization reaction that decomposes the polyester into depolymerized products using a depolymerizing agent. In this embodiment, with... Figure 2 Similarly, the polyester is polyethylene terephthalate (PET), the depolymerizing agent is ethylene glycol (EG) as an alcohol, and the depolymerized product is bis(2-hydroxyethyl) terephthalate (BHET).

[0061] However, the present invention is also applicable to combinations with these different polyesters, depolymerizing agents, and depolymerized products. For example, the polyester can be polybutylene acrylate (PPT), the depolymerizing agent can be propylene glycol (PG), 1,3-propanediol, or other alcohols, and the depolymerized product can be bis(2-hydroxypropyl) terephthalate (BHPT). Furthermore, the polyester can be polybutylene terephthalate (PBT), the depolymerizing agent can be butanediol (BG), 1,4-butanediol, or other alcohols, and the depolymerized product can be bis(2-hydroxybutyl) terephthalate (BHBT). Such combinations of polyesters, depolymerizing agents, and depolymerized products share the following common characteristics: the product of the depolymerization reaction, i.e., the depolymerized product (BHET, BHPT, BHBT, etc.), is soluble in the reactants or reaction solvent of one side of the depolymerization reaction, i.e., the depolymerizing agent (EG, PG, BG, etc.); on the other hand, the reactants of the other side of the depolymerization reaction, i.e., the polyester (PET, PPT, PBT, etc.), are insoluble in the depolymerizing agent (EG, PG, BG, etc.).

[0062] The depolymerization device 5 described in this embodiment is not limited to those installed in the above-described manner. Figure 1 The depolymerization reaction tank 300 in the chemical recycling molding system shown can also be applied to depolymerization reaction tanks 300 set in any system or independent depolymerization reaction tanks 300.

[0063] The depolymerization reaction tank 300 includes a tank body 31 for initiating a depolymerization reaction of polyester or polymer. The above-mentioned... Figure 1 The heater 320 is provided inside the tank body 31 with the above-mentioned features. Figure 1 The stirring blades 330 and heater 320 control or adjust the temperature inside the tank body 31. Furthermore, Figure 1 The stirring blades in example 330 are shown as a pair of inclined blades, one above the other.

[0064] As mentioned above Figure 1 The polymer, such as PET, or polyester is supplied to the depolymerization reaction tank 300 from the polymer adjustment device 200, etc., and the depolymerizing agent, such as EG, or alcohol is supplied to the depolymerization reaction tank 300 from the depolymerizing agent supply unit 310, etc. In Figure 4 In this example, PET from the polymer conditioning device 200 and EG from the depolymerizing agent supply unit 310 are supplied to the interior of the tank body 31 through a common supply port 51, but they can also be supplied to the interior of the tank body 31 through different supply ports (not shown).

[0065] A discharge port 52 is provided at the bottom of the tank body 31 to discharge the liquid or fluid product containing the depolymerization product (BHET) and unreacted EG to the outside of the tank body 31. While the chemical term "product" usually refers only to BHET, in this embodiment, for convenience, the substance containing unreacted EG discharged from the discharge port 52 of the tank body 31 is collectively referred to as "product". The discharge port 52 is located near the bottom of the tank body 31. Figure 4 The upper part of the outlet 52 is provided with a filter 521, for example a screen-like filter, to prevent unreacted solid components or insoluble substances such as PET from being discharged from the outlet 52.

[0066] Such as about Figure 1 As explained, the product containing BHET and EG (hereinafter referred to as BHET / EG) discharged from the depolymerization reactor 300 passes through impurity removal devices 340, 350, 360, and buffer tank 370 before heading towards the polymerization reactor 400. In addition to this main production line, in... Figure 4 In the example, a return pipe or return channel 53 is also provided to return at least a portion of the product (BHET / EG) containing depolymerizers such as BHET discharged from the depolymerization reaction tank 300 to the interior of the depolymerization reaction tank 300 (tank body 31). However, as will be described later, even without the return channel 53, the minimum effects involved in the present invention can be achieved.

[0067] The depolymerization apparatus 5 according to this embodiment may include a return amount adjustment unit 6 for adjusting the amount of BHET / EG returned to the depolymerization reaction tank 300 via the return channel 53. The return amount adjustment unit 6 may be composed of a flow regulating valve 61 provided in the return channel 53. By controlling the opening degree of the flow regulating valve 61, the amount or flow rate of BHET / EG returning to the depolymerization reaction tank 300 via the flow regulating valve 61 can be directly adjusted. In addition to the flow regulating valve 61, a pump that can perform the function of the return amount adjustment unit 6 may also be provided in the return channel 53, or a pump that can perform the function of the return amount adjustment unit 6 may be provided instead of the flow regulating valve 61.

[0068] The return flow adjustment unit 6 can be composed of a flow control valve 62 located on the main production line facing the polymerization reactor 400, further downstream of the branch point of the return flow channel 53. By controlling the opening degree of this flow control valve 62, the amount or flow rate of BHET / EG towards the polymerization reactor 400 can be adjusted, thus indirectly adjusting the amount or flow rate of BHET / EG returning to the depolymerization reactor 300 through the return flow channel 53 and / or the flow control valve 61. Furthermore, in addition to the flow control valve 62, a pump that functions as the return flow adjustment unit 6 can be installed on the main production line, or a pump that functions as the return flow adjustment unit 6 can be installed instead of the flow control valve 62.

[0069] The depolymerization apparatus 5 according to this embodiment may include a discharge volume adjustment unit 7 for adjusting the discharge volume of the product (BHET / EG) containing depolymerized substances such as BHET discharged from the depolymerization reaction tank 300. The discharge volume adjustment unit 7 may be composed of a flow regulating valve 71 located at the rear section of the discharge port 52 of the tank body 31 (and at the section before the branch point of the backfeed channel 53 on the main production line toward the polymerization reaction tank 400). By controlling the opening degree of this flow regulating valve 71, the amount or flow rate of BHET / EG discharged from the depolymerization reaction tank 300 through this flow regulating valve 71 can be directly adjusted. In addition to the flow regulating valve 71, a pump 72 that can function as the discharge volume adjustment unit 7 may be provided at the rear section of the discharge port 52 of the tank body 31 (and at the section before the branch point of the backfeed channel 53 on the main production line toward the polymerization reaction tank 400), or a pump 72 that can function as the discharge volume adjustment unit 7 may be provided instead of the flow regulating valve 71.

[0070] As mentioned above, in Figure 4 In the embodiments described below, the effects of the invention described later can be maximized by providing three flow control valves 61, 62, 71 (and / or up to three pumps), but these are not necessary to achieve the minimum effects of the invention. For example, any one of the three flow control valves 61, 62, 71 may be provided, or none of the flow control valves 61, 62, 71 may be provided.

[0071] The depolymerization device 5 of this embodiment raises the temperature inside the depolymerization reaction tank 300 in such a way that the contents of the depolymerization reaction tank 300 do not boil under normal pressure or atmospheric pressure by means of heaters 320 arranged in parallel in the depolymerization reaction tank 300, based on the increase in the concentration of depolymerized products such as BHET caused by the depolymerization reaction in the depolymerization reaction tank 300.

[0072] like Figure 5Schematic illustration: The higher the reaction temperature inside the depolymerization reaction tank 300, the shorter the relative required time for the depolymerization reaction. Therefore, it is preferable to increase the temperature inside the depolymerization reaction tank 300 as much as possible. However, when the temperature inside the depolymerization reaction tank 300 is higher than the boiling point of EG (approximately 197°C), EG will boil at atmospheric pressure, preventing the desired depolymerization reaction from occurring. Therefore, conventional depolymerization reaction tanks 300 employ a method of increasing the internal pressure to above atmospheric pressure using pumps or the like to suppress EG boiling while simultaneously raising the temperature.

[0073] Compared to existing technologies, the depolymerization apparatus 5 of this embodiment allows the interior of the depolymerization reaction tank 300 to be at atmospheric pressure or atmospheric pressure. In other words, it is not necessary to install a pump or the like to pressurize the interior of the depolymerization reaction tank 300 to above atmospheric pressure. Instead, the depolymerization apparatus 5 of this embodiment addresses the situation where the boiling point of the contents rises due to the increase in BHET concentration within the depolymerization reaction tank 300 caused by the proceeding of the depolymerization reaction. Specifically, by using a heater 320 to appropriately raise the temperature inside the depolymerization reaction tank 300 in a manner that substantially does not exceed the gradually rising boiling point of the contents due to the increase in BHET as the depolymerization reaction proceeds at atmospheric pressure, a temperature rise and reaction promotion are achieved while preventing the contents from boiling.

[0074] Figure 6 This schematically illustrates the relationship between the proportion of BHET (i.e., the concentration of BHET) in the liquid phase (or BHET / EG as a product of the depolymerization reaction tank 300) and the inside temp. Figure 6 As shown, the boiling point of the BHET / EG mixture increases as the BHET concentration rises due to the depolymerization reaction. In other words, as the BHET concentration increases, there is room for the temperature to rise without causing the BHET / EG mixture to boil. For example, at a BHET concentration of 0% (EG concentration of 100%), the boiling point of EG (approximately 197°C) is the upper limit temperature, but at a BHET concentration of 20% (EG concentration of 80%), the upper limit temperature rises to approximately 205°C.

[0075] Utilizing the principles or phenomena described above, the depolymerization apparatus 5 of this embodiment effectively increases the concentration of BHET in the depolymerization reaction tank 300 through flow regulating valves 61, 62, and 71, while simultaneously increasing the temperature through heater 320, thereby promoting the depolymerization reaction (towards...). Figure 5 (Right-side transition in the middle).

[0076] The depolymerization apparatus 5 according to this embodiment can operate in two main phases: a heating phase and a holding phase. In the heating phase, to increase the temperature within the depolymerization reaction tank 300, the concentration of BHET within the tank 300 is preferentially increased. In the holding phase, after the depolymerization reaction tank 300 has been sufficiently heated through the heating phase, this temperature and the concentration of BHET are preferentially maintained. Typically, the heating phase corresponds to the start-up of the depolymerization reaction tank 300, and therefore can also be referred to as the start-up phase. The holding phase can be referred to as the steady-state operation phase following the start-up phase.

[0077] During the heating phase, the flow regulating valves 61 and / or 62 constituting the return amount adjustment unit 6 can cause the return amount of BHET / EG passing through the return channel 53 to be greater than the specified return amount (e.g., gradually increasing the opening of the flow regulating valve 61 and / or gradually decreasing the opening of the flow regulating valve 62), thereby causing the concentration of BHET inside the depolymerization reaction tank 300 to be higher than the specified concentration (e.g., Figure 6 (60% of the total). The specified return amount can be interpreted as the return amount that causes the concentration of BHET inside the depolymerization reactor 300 to be higher than the specified concentration of BHET / EG. Based on the increase in the concentration of BHET inside the depolymerization reactor 300, the heater 320 raises the temperature to above the specified temperature within a range where the BHET / EG contained in the reactor does not boil (e.g., according to...). Figure 6 At a specified concentration of 60%, the temperature is approximately 220°C, at which the contents do not boil. This specified temperature is higher than the boiling point of EG (approximately 197°C) at normal pressure, which acts as a depolymerizing agent. Furthermore, the specified temperature can be any temperature above 200°C, any temperature above 210°C, any temperature above 220°C, any temperature above 230°C, any temperature above 240°C, or any temperature above 250°C.

[0078] During the heat preservation phase following the heating phase, while maintaining a state where the concentration of BHET inside the depolymerization reaction tank 300 is higher than a specified concentration (e.g., 60%) and the temperature inside the depolymerization reaction tank 300 is higher than a specified temperature (e.g., 220°C) (and, if necessary, maintained by the heater 320), the flow control valves 61 and / or 62 constituting the return amount adjustment unit 6 reduce the return amount of BHET / EG that has passed through the return channel 53 to a specified return amount (e.g., decreasing the opening of the flow control valve 61 and / or increasing the opening of the flow control valve 62). This increases the amount or flow rate of BHET / EG flowing through the main production line toward the polymerization reaction tank 400, allowing the entire chemical recycling molding system to transition to a steady-state operating state.

[0079] During the heating phase, in addition to or in place of the return flow adjustment unit 6, the flow regulating valve 71 (and / or pump 72) constituting the discharge flow adjustment unit 7 can be used to reduce the discharge rate of BHET / EG from the discharge port 52 to a predetermined discharge rate (e.g., by gradually reducing the opening of the flow regulating valve 71), thereby increasing the concentration of BHET inside the depolymerization reaction tank 300 to a predetermined concentration (e.g., Figure 6 (60% of the total). The specified discharge rate can be interpreted as the discharge rate that causes the concentration of BHET inside the depolymerization reaction tank 300 to be higher than the specified concentration of BHET / EG. Based on the increase in the concentration of BHET inside the depolymerization reaction tank 300, the heater 320 raises the temperature above the specified temperature within a range where the BHET / EG contained in the tank does not boil (e.g., according to...). Figure 6 At a specified concentration of 60%, the temperature is approximately 220°C, at which the contents do not boil. This specified temperature is higher than the boiling point of EG (approximately 197°C) at normal pressure, which acts as a depolymerizing agent. Furthermore, the specified temperature can be any temperature above 200°C, any temperature above 210°C, any temperature above 220°C, any temperature above 230°C, any temperature above 240°C, or any temperature above 250°C.

[0080] During the heat preservation phase following the heating phase, while maintaining a BHET concentration inside the depolymerization reaction tank 300 above a specified concentration (e.g., 60%) and a temperature inside the depolymerization reaction tank 300 above a specified temperature (e.g., 220°C) (if necessary, heat preservation is performed via heater 320), in addition to or replacing the return flow adjustment unit 6, the flow control valve 71 (and / or pump 72) constituting the discharge flow adjustment unit 7 causes the discharge rate of BHET / EG from the discharge port 52 to exceed a specified discharge rate (e.g., by increasing the opening of the flow control valve 71). This increases the amount or flow rate of BHET / EG flowing through the main production line toward the polymerization reaction tank 400, allowing the entire chemical recycling molding system to transition to a steady-state operating state.

[0081] In addition, from obtaining based on Figure 5 Temperature-induced reaction promotes the effect, while based on Figure 6 Considering the view that the BHET / EG reflux rate should be minimized (as the reflux rate increases, not only does the amount of BHET delivered to the main production line decrease, but the power consumption for reflux cannot be ignored), the concentration of BHET at the end of the heating stage and / or the heat preservation stage is, for example, 10-85 mol%, preferably 15-60 mol%, and more preferably 20-40 mol%.

[0082] As described above, the return flow adjustment unit 6 and the discharge flow adjustment unit 7 can work together during the heating and / or heat preservation stages to achieve the aforementioned priority objectives of each stage. Alternatively, a stage can be set where only one of the return flow adjustment unit 6 and the discharge flow adjustment unit 7 operates. For example, immediately after the depolymerization reactor 300 starts operating, in order to maximize the concentration by retaining virtually all of the generated BHET within the depolymerization reactor 300, the flow control valve 71 in the discharge flow adjustment unit 7 can be completely closed. At this time, the return channel 53 and the return flow adjustment unit 6 are essentially inactive, and only the discharge flow adjustment unit 7 is functional. In this immediate post-operation stage, the concentration of BHET suddenly increases, and when the flow control valve 71 is opened after heating by the heater 320, BHET / EG flows into the main production line and the return channel 53, and the return flow adjustment unit 6 begins to function. Alternatively, the discharge flow adjustment unit 7 can be effectively rendered ineffective by switching the flow control valve 71 to the fully open state at this moment.

[0083] As described above, in this embodiment, to optimize the BHET concentration and temperature inside the depolymerization reaction tank 300, the flow control valves 61, 62, and 71 and the heater 320 work together. To support this coordinated operation, a depolymerization concentration detection unit can be provided to detect the concentration of depolymerized products such as BHET inside the depolymerization reaction tank 300.

[0084] By detecting the concentration of BHET, according to Figure 6 Since the boiling point of the contents of the polymerization reaction tank 300 can be determined, the heater 320 can heat the depolymerization reaction tank 300 within a range where the contents do not boil. That is, the heater 320 can appropriately increase the temperature inside the depolymerization reaction tank 300 based on the concentration of BHET detected by the depolymerization concentration detection unit.

[0085] Furthermore, by detecting the concentration of BHET, deviations from the target concentration can be identified. Therefore, the flow control valves 61, 62, and 71 can adjust their respective openings to reduce these deviations. That is, the return flow adjustment unit 6 and / or the discharge flow adjustment unit 7 can appropriately adjust the return flow of BHET / EG through the return channel 53 and / or the discharge flow of BHET / EG from the depolymerization reaction tank 300 based on the BHET concentration detected by the depolymerization concentration detection unit.

[0086] The depolymerization concentration detection unit can be composed of a measuring device or sensor based on any principle that directly or indirectly measures the BHET concentration within the depolymerization reaction tank 300. For example, the depolymerization concentration detection unit can be composed of a spectrophotometer based on a spectral method such as Raman spectroscopy, which indirectly measures the BHET concentration by irradiating the contents of the depolymerization reaction tank 300 with measuring light and analyzing the scattered light. Furthermore, the depolymerization concentration detection unit can be composed of a depolymerization reaction monitoring device 30 that indirectly detects or calculates the BHET concentration by monitoring the progress of the depolymerization reaction.

[0087] Figure 7 This describes a first embodiment of the depolymerization reaction monitoring device 30 according to the present invention. The depolymerization reaction monitoring device 30 is configured to include the depolymerization reaction tank 300 described above.

[0088] The depolymerization reaction tank 300 includes a tank body 31 for initiating a depolymerization reaction of polyester or polymer, and a depolymerizing agent flow section 32 through which a depolymerizing agent such as EG flows. The depolymerizing agent flow section 32 forms a flow path for the depolymerizing agent such as EG outside the tank body 31. As shown in the figure, one end 321 and the other end 322 of the tubular depolymerizing agent flow section 32 are connected to different parts of the tank body 31. As will be described later, the depolymerizing agent such as EG can flow from one end 321 to the other end 322 of the depolymerizing agent flow section 32, or it can flow from the other end 322 to one end 321.

[0089] The depolymerization agent flow section 32 is provided with a depolymerization reaction characteristic measuring section 33, an intrusion prevention section 34, a direction switching section 35, and a cooling section 36.

[0090] The depolymerization reaction characteristic measuring unit 33 measures the characteristics of depolymerizing agents such as EG after BHET and other depolymers have dissolved in the depolymerization reaction tank 300. Specifically, the depolymerization reaction characteristic measuring unit 33 measures the characteristics of depolymerizing agents such as EG in the depolymerizing agent flow section 32.

[0091] Figure 7In this example, the depolymerization reaction characteristic measuring unit 33 measures the optical properties of depolymerizers such as EG in the depolymerizer flow section 32. This depolymerization reaction characteristic measuring unit 33 includes 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 forms suitable for measuring the optical properties of depolymerizers such as EG after dissolution of BHET. The light from the light source 331 enters the interior of the depolymerizer flow section 32 through a translucent window 333, which forms part of the tube wall of the tubular depolymerizer flow section 32, and irradiates the depolymerizers such as EG. The light is subjected to optical effects such as reflection, refraction, absorption, scattering, diffraction, polarization, interference, and dispersion according to the optical properties of the depolymerizers such as EG after dissolution of BHET. The light receiving unit 332 receives the light subjected to these optical effects through the window 333. The light received by the light receiving unit 332 indicates the optical properties of the depolymerizers such as EG after dissolution of BHET. Thus, refractive index and spectrum are examples of optical properties that can be measured by the depolymerization reaction characteristic measuring unit 33. In this embodiment, an example of measuring the refractive index of depolymerizing agents such as EG after the depolymerization reaction characteristic measuring unit 33 has dissolved depolymerized products such as BHET will be described.

[0092] The refractive index measured by the depolymerization reaction characteristic measuring unit 33 is provided to the depolymerization reaction progress monitoring unit 37, which is composed of a computer and a processor. The depolymerization reaction progress monitoring unit 37 monitors the progress of the depolymerization reaction in the depolymerization reaction tank 300 (especially the tank body 31) based on the optical properties such as the refractive index of the depolymerizing agent such as EG measured by the depolymerization reaction characteristic measuring unit 33.

[0093] Figure 8A as well as Figure 8B This illustrates an example of monitoring the progress of the depolymerization reaction via the depolymerization reaction progress monitoring unit 37. For example... Figure 8A As shown, there is a proportional relationship, or other correlation, between the refractive index measured by the depolymerization reaction characteristic measuring unit 33 and the concentration of depolymers such as BHET in the depolymerizing agent such as EG, which is the object of measurement. Figure 8A (The point (○) in the diagram is an example of a measured value). As described above, in the depolymerization reaction tank 300 (especially the tank body 31), PET is decomposed by EG as a depolymerizing agent, thereby obtaining BHET as a depolymerized product. Therefore, the concentration of BHET indicates the progress of the PET depolymerization reaction. That is, the depolymerization reaction progress monitoring unit 37 can determine the progress of the depolymerization reaction based on the refractive index measured by the depolymerization reaction characteristic measuring unit 33. Figure 8A By understanding the concentration of depolymers such as BHET based on the correlation shown, the progress of the depolymerization reaction of polymers such as PET can be identified. For example, as Figure 8B As shown, the depolymerization reaction progress monitoring unit 37 monitors the progress of the depolymerization reaction based on the data obtained from... Figure 8AThe total amount of BHET generated in the depolymerization reactor 300 is determined by the concentration of BHET identified in the reaction, and expressed as a change over time relative to the reaction time. Figure 8B The point (○) in the diagram is an example of a measured value. (To conduct...) Figure 1 The chemical recycling molding system and the control of the chemical recycling device 100 are described. Figure 8A or Figure 8B The monitoring results of the depolymerization reaction progress monitoring unit 37 shown can be provided to their controllers, as well as to their managers and operators through a management screen and operation screen.

[0094] Furthermore, the depolymerization reaction characteristic measuring unit 33 can also measure the non-optical properties of depolymerizing agents such as EG after the depolymerization of BHET and other depolymers has dissolved. For example, the depolymerization reaction characteristic measuring unit 33 can measure the electrical properties of depolymerizing agents such as EG after the depolymerization of BHET and other depolymers has dissolved in the depolymerization reaction tank 300. In this case, instead of... Figure 7 The optical depolymerization reaction characteristic measuring unit 33 is provided with electrodes that electrically interact (e.g., contact) with depolymerizers such as EG in the depolymerizer flow section 32. Furthermore, the method of the depolymerization reaction characteristic measuring unit 33 is not limited as long as its characteristics can be measured without collecting depolymerizers such as EG from the depolymerizer flow section 32 (depolymerization reaction tank 300).

[0095] Furthermore, if the polymers such as PET remaining in the tank body 31 that have not dissolved in the depolymerizing agent such as EG do not hinder the measurement, the depolymerization reaction characteristic measuring unit 33 can be arranged side-by-side in the tank body 31 instead of the depolymerizing agent flow section 32. However, for Figure 7 Since the depolymerization reaction characteristic measuring unit 33 of the optical method shown has undesirable effects such as diffuse reflection of the measuring light by residual polymers such as PET, the depolymerization reaction characteristic measuring unit 33 is preferably provided in the depolymerizing agent flow section 32 outside the tank body 31, and more preferably in the intrusion prevention section 34 described below.

[0096] The intrusion prevention section 34 includes a first filter 341 disposed at one end 321 of the tubular depolymerizing agent flow section 32 and a second filter 342 disposed at the other end 322 of the tubular depolymerizing agent flow section 32. The first filter 341 and the second filter 342 prevent insoluble substances that are not dissolved in depolymerizing agents such as EG from entering the depolymerizing agent flow section 32 from the tank body 31. As described above, examples of insoluble substances that are not dissolved in depolymerizing agents such as EG include polyesters such as PET, polymers, and oligomers formed by partial depolymerization of these as reactants in the depolymerization reaction. In this way, insoluble substances that may interfere with the optical measurement of the depolymerization reaction characteristic measuring section 33 in the depolymerizing agent flow section 32 can be effectively removed by the first filter 341 and / or the second filter 342.

[0097] The direction switching unit 35 is configured with a backwash pump or the like, capable of switching the flow direction of depolymerizing agents such as EG in the tubular depolymerizing agent 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, to prevent clogging of the first filter 341 and / or the second filter 342. By causing the depolymerizing agent such as EG to flow along the first direction, the direction switching unit 35 returns insoluble matter captured by the second filter 342 at the other end 322 to the tank body 31, thus eliminating clogging in the second filter 342. Similarly, by causing the depolymerizing agent such as EG to flow along the second direction, the direction switching unit 35 returns insoluble matter captured by the first filter 341 at one end 321 to the tank body 31, thus eliminating clogging in the first filter 341. To avoid clogging of both the first filter 341 and the second filter 342, the direction switching unit 35 preferably switches the flow direction of the depolymerizing agent such as EG in the depolymerizing agent flow section 32 repeatedly or periodically between the first direction and the second direction.

[0098] Furthermore, the backwash pump and other components constituting the direction switching unit 35 only need to operate before or during the measurement by the depolymerization reaction characteristic measuring unit 33, and can be stopped at other times. When the backwash pump and other components constituting the direction switching unit 35 are operating, the depolymerizing agent such as EG, which is the test target measured by the depolymerization reaction characteristic measuring unit 33, is input from one end 321 and the other end 322 of the depolymerizing agent flow section 32 from the tank body 31. At this time, the "old" depolymerizing agent that was originally present in the depolymerizing agent flow section 32 is discharged from the other end 321 and the other end 322 of the depolymerizing agent flow section 32 into the tank body 31, thus eliminating the blockage of the other end of the first filter 341 and the second filter 342 provided here. Moreover, the depolymerization reaction characteristic measuring unit 33 can measure the "new" depolymerizing agent newly input from the tank body 31.

[0099] The cooling section 36 cools the depolymerizing agent, such as EG, in the tubular depolymerizing agent flow section 32. Optical properties such as refractive index and other properties that can be measured by the depolymerization reaction characteristic measuring section 33 depend on the temperature of the depolymerizing agent, such as EG, being measured. Therefore, by cooling the depolymerizing agent, such as EG, to a predetermined temperature before measurement by the depolymerization reaction characteristic measuring section 33, the cooling section 36 stabilizes the measurement accuracy of the depolymerization reaction characteristic measuring section 33. As described above, the depolymerizing agent, such as EG, in the depolymerizing agent flow section 32 can flow in either the first direction or the second direction via the direction switching section 35. Therefore, the cooling section 36 preferably includes a first cooling section 361 located at one end 321 of the depolymerization reaction characteristic measuring section 33 and a second cooling section 362 located at the other end 322 of the depolymerization reaction characteristic measuring section 33.

[0100] Alternatively, a heating section can be provided instead of a cooling section 36 to heat the depolymerizing agent such as EG to a predetermined temperature. However, typically, most components such as sensors constituting the depolymerization reaction characteristic measuring section 33 operate at low temperatures (e.g., below 150°C), so it may be impossible to directly measure the temperature of the depolymerizing agent such as EG within the tank body 31, for example, between 180°C and 250°C. Therefore, it is preferable to reduce the temperature of the depolymerizing agent such as EG to the measurable temperature (operating temperature) of the depolymerization reaction characteristic measuring section 33 via the cooling section 36. Figure 7 As shown, the cooling section 36, located before (or above) the depolymerization reaction characteristic measuring section 33, can also cool the depolymerization reaction characteristic measuring section 33 itself. Furthermore, by providing a temperature sensor (not shown) facing the depolymerization reaction characteristic measuring section 33 and measuring the temperature of depolymerizing agents such as EG, the cooling section 36 and / or the heating section are controlled so that the temperature measured by the temperature sensor is close to the predetermined measurable temperature of the depolymerization reaction characteristic measuring section 33.

[0101] According to the depolymerization reaction monitoring device 30 or depolymerization reaction progress monitoring unit 37 of the first embodiment described above, by measuring the characteristics of depolymerizing agents such as EG in the depolymerization reaction tank 300 (depolymerizing agent flow section 32) by the depolymerization reaction characteristic measuring unit 33, the progress of the depolymerization reaction of polyesters or polymers obtained by dissolving depolymerized products such as BHET as reactants or depolymerizing agents such as EG as reaction solvents can be effectively monitored. Since it is not necessary to collect depolymerizing agents such as EG, which are the objects of measurement, from the depolymerization reaction tank 300 (depolymerizing agent flow section 32), the progress of the depolymerization reaction can be monitored in real time.

[0102] In addition, Figure 1 During the period before the depolymerization reaction progress in the depolymerization reaction tank 300, as monitored by the depolymerization reaction progress monitoring unit 37, reaches the desired value, the supply of depolymerized material from the depolymerization reaction tank 300 to the downstream impurity removal devices 340, 350, 360, and polymerization reaction tank 400 can be temporarily stopped. Thus, the temporarily retained liquid containing depolymerized material can be retained in the piping or buffer tank 370 located between the depolymerization reaction tank 300 and the polymerization reaction tank 400, or it can be returned to the depolymerization reaction tank 300 for further depolymerization. Furthermore, a depolymerization supply regulating valve (not shown) can be installed between the depolymerization reaction tank 300 and the polymerization reaction tank 400. This depolymerization supply regulating valve is configured to open when the progress of the depolymerization reaction in the depolymerization reaction tank 300, as monitored by the depolymerization reaction progress monitoring unit 37, reaches the desired value, so as to supply depolymerization material to the polymerization reaction tank 400. When the progress of the depolymerization reaction in the depolymerization reaction tank 300, as monitored by the depolymerization reaction progress monitoring unit 37, is lower than the desired value, it is configured to close to stop supplying depolymerization material to the polymerization reaction tank 400.

[0103] Figure 9This describes a second embodiment of the depolymerization reaction monitoring device 30 according to the present invention. Regarding... Figure 7 The same structures as those in the first embodiment are labeled with the same symbols, and repeated descriptions are omitted.

[0104] The depolymerizing agent flow section 32 is provided with a depolymerizing agent dilution section 38, which further adds EG or other depolymerizing agents to the depolymerizing agent flow section 32 for dilution. The depolymerizing agent dilution section 38 includes a depolymerizing agent supply section 381 for supplying EG or other depolymerizing agents for dilution, a dilution pipe 382 connecting the depolymerizing agent supply section 381 and the depolymerizing agent flow section 32, a dilution valve 383 provided in the dilution pipe 382, ​​a connection section in the depolymerizing agent flow section 32 connected to the dilution pipe 382 and a first valve 384 located on one end 321 of the depolymerization reaction characteristic measuring section 33 and on the other end 322 of the first cooling section 361, and a second valve 385 located in the depolymerizing agent flow section 32 connected to the dilution pipe 382 and on the other end 322 of the depolymerization reaction characteristic measuring section 33 and on one end 321 of the second cooling section 362.

[0105] Figure 10 This illustrates an example of diluting the depolymerizer based on the depolymerizer dilution section 38. For example... Figure 8A As shown, there is a proportional relationship between the refractive index of depolymerizing agents such as EG after the dissolution of depolymerizing agents such as BHET and the concentration of depolymerizing agents such as BHET in the depolymerizing agents such as EG. However, as Figure 10 As shown (before dilution), this correlation does not hold when the concentration of BHET, etc., exceeds the specified value A. Therefore, the depolymerization reaction progress monitoring unit 37 may not be able to accurately determine the concentration of BHET, etc., based on the refractive index measured by the depolymerization reaction characteristic measuring unit 33.

[0106] Therefore, for high-concentration solutions such as BHET that would disrupt the linearity measured in the depolymerization reaction characteristic measuring unit 33, the depolymerizing agent dilution unit 38 additionally supplies depolymerizing agents such as EG from the depolymerizing agent supply unit 381. As a result, the concentration of depolymerized products such as BHET in the depolymerizing agent flow section 32 (between the first valve 384 and the second valve 385) decreases, such as... Figure 10 As shown (after dilution), the correlation or linearity is apparent to be maintained even in the high concentration region. That is, by reducing the concentration of depolymerizers such as BHET in the depolymerizing agent flow section 32, the refractive index measured by the depolymerization reaction characteristic measurement section 33 converges to... Figure 10 Within the linear range. Furthermore, based on the refractive index normally measured by the depolymerization reaction characteristic measuring unit 33 within the linear range and the amount of EG, etc., used for dilution by the dilution depolymerizer supply unit 381 (adjusted via the dilution valve 383 as described later), the depolymerization reaction progress monitoring unit 37 can accurately grasp the concentration of BHET, etc., in the original (undiluted) tank body 31. Figure 10 The concentration on the straight line after dilution.

[0107] To improve the measurement accuracy of the depolymerization reaction characteristic measuring unit 33 when using the depolymerizing agent dilution section 38 as described above, various valves such as dilution valve 383, first valve 384, and second valve 385 are provided. Hereinafter, according to... Figure 11 The flowchart shown illustrates a specific measurement sequence and explains the opening and closing actions of each valve. In the flowchart description, "S" indicates a step or process.

[0108] In S1, at the start of the measurement, valves 384 and 385 are open, while 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 object of measurement, is introduced from the tank body 31 into the depolymerizing agent flow section 32. At this time, as described above, the first cooling section 361 and / or the second cooling section 362 cool the introduced depolymerizing agent, such as EG, to a predetermined measurable temperature of the depolymerization reaction characteristic measuring section 33. As a result, the depolymerizing agent, such as EG, cooled by the first cooling section 361 and / or the second cooling section 362, enters the space between valves 384 and 385, which were open in S1. In S3, valves 384 and 385 are switched to the closed state. As a result, a closed space is temporarily formed between valves 384 and 385, and the total amount of BHET and the like in this closed space can be determined.

[0109] In S4, the depolymerization reaction characteristic measurement unit 33 performs a first measurement of the refractive index of the depolymerizing agent such as EG in the enclosed space formed in S3. In S5, it is determined whether the refractive index measured in S4 exceeds... Figure 10 The saturation threshold B is shown. If the result is "No" in S5, the refractive index measured in S4 converges to a linear range below the saturation threshold B. Therefore, in S6, the measurement result from the depolymerization reaction characteristic measurement unit 33 is directly adopted. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of depolymerized substances such as BHET based on the refractive index measurement result obtained in S6.

[0110] If the condition is "yes" in S5, the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measuring unit 33. Therefore, even if we proceed directly to S6 and S7, we cannot obtain an accurate concentration of depolymerized substances such as BHET. Therefore, in S8, the dilution valve 383 is switched to the open state. In the subsequent S8(2), the second valve 385 is switched to the open state in order to introduce EG and the like for dilution into the depolymerization reaction characteristic measuring unit 33. Moreover, in S9, the backwash pump and the like constituting the direction switching unit 35 operate, and the EG and the like for dilution are supplied from the dilution depolymerizing agent supply unit 381 through the open dilution valve 383 to the space between the first valve 384 and the second valve 385. In S9, the amount of EG and the like used for dilution is measured by a flow sensor or the like (not shown) installed in the dilution valve 383. In S10, dilution valve 383 is switched to the closed state, and in S10(2), second valve 385 is switched to the closed state, thereby forming a closed space again between first valve 384 and second valve 385.

[0111] In S11, the depolymerization reaction characteristic measurement unit 33 performs a secondary measurement of the refractive index of depolymerizing agents such as EG in the enclosed space formed in S3 and S10 (2), and returns to S5. If the result in S5 is "no", the refractive index of diluted EG measured in S11 converges to a linear range below the saturation threshold B, so the measurement result of the depolymerization reaction characteristic measurement unit 33 is directly adopted in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of BHET and other substances in the original (undiluted) tank body 31 based on the secondary measurement result of the refractive index within the linear range obtained in S11 and the amount of EG and other substances used for dilution in S9. Figure 10 (The concentration on the straight line after dilution). That is, as described above, by means of dilution valve 383, first valve 384 and second valve 385, the amount of depolymerizing agent such as EG entering the closed space (divided by the three valves) formed in S3 from the tank body 31 and the dilution depolymerizing agent supply unit 381 respectively can be controlled. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET and the like in the tank body 31 while grasping the quantitative effect of dilution by the depolymerizing agent dilution unit 38.

[0112] If the result in S5 is "yes", proceed to S8-S11 again, and repeat the dilution in S9 and the secondary measurement in S11 until the result in S5 is "no", that is, until the result of the secondary measurement of refractive index in S11 converges to the linear range below the saturation threshold B. In S7 at the end of the measurement, valve 384, valve 385 and dilution valve 383 are closed.

[0113] Not only can the amount of EG for dilution supplied by the dilution depolymerizing agent supply unit 381 be controlled by the dilution valve 383, but its temperature can also be controlled. For example, by supplying the EG for dilution, whose temperature is controlled in S9, to the closed space formed in S3, the EG in the closed space can be cooled to the measurable temperature specified by the depolymerization reaction characteristic measuring unit 33. In this way, at least a portion of the functions of the cooling unit 36 ​​can be achieved by the EG for dilution supplied by the dilution depolymerizing agent supply unit 381. At this time, it is not necessary to install... Figure 9 At least a portion of the first cooling section 361 and the second cooling section 362.

[0114] Figure 12 This represents a third embodiment of the depolymerization reaction monitoring device 30 according to the present invention. Regarding... Figure 7 The first embodiment and / or Figure 9 The same structures as those in the second embodiment are labeled with the same symbols, and repeated descriptions are omitted.

[0115] An extraction section 39 is provided in the depolymerizing agent flow section 32, capable of extracting a specified amount of depolymerizing agent such as EG flowing within it. The extraction section 39 includes, for example, an injection pump 391 and an extraction valve 392. The injection pump 391 extracts, inputs, or discharges the depolymerizing agent such as EG according to the position of a movable piston housed within it. The extraction valve 392 is located between the tubular depolymerizing agent flow section 32 and the injection pump 391.

[0116] A depolymerization reaction characteristic measuring unit 33 is provided in the syringe pump 391. Specifically, as schematically illustrated, the aforementioned optical measurement is performed through the window 333 provided in the syringe pump 391 (illustrations of the light source 331 and the light receiving unit 332 are omitted). This depolymerization reaction characteristic measuring unit 33 measures the characteristics of depolymerizing agents such as EG extracted by the extraction unit 39 (syringe pump 391).

[0117] and Figure 9 Similar to the second embodiment, the depolymerizing agent flow section 32 is provided with a depolymerizing agent dilution section 38, which further adds depolymerizing agents such as EG to the depolymerizing agent extracted by the extraction section 39 (injection pump 391) for dilution. The depolymerization reaction characteristic measurement section 33 measures the characteristics of the depolymerizing agent such as EG after dilution by the depolymerizing agent dilution section 38.

[0118] Figure 13 This is a flowchart illustrating a specific measurement sequence example. (Regarding the second embodiment...) Figure 11 The same steps or processes are marked with the same symbols, and repeated descriptions are omitted.

[0119] In S1, at the start of the measurement, extraction valve 392 is open and 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 object of measurement, is introduced from the tank body 31 into the depolymerizing agent flow section 32. In S12, extraction unit 39 extracts (one extraction) a specified amount (first specified amount) of the depolymerizing agent, such as EG, introduced into the depolymerizing agent flow section 32 in S2. In S3, extraction valve 392 is switched to the closed state. As a result, the first specified amount of depolymerizing agent, such as EG, is secured within extraction unit 39 (injection pump 391).

[0120] In S4, the depolymerization reaction characteristic measuring unit 33 measures the refractive index of the first specified amount of depolymerizing agent such as EG, which was ensured in the extraction unit 39 (injection pump 391) in S3. In S5, it is determined whether the refractive index measured in S4 exceeds... Figure 10 The saturation threshold B is shown. If the result is "No" in S5, the refractive index measured in S4 converges to a linear range below the saturation threshold B. Therefore, in S6, the measurement result from the depolymerization reaction characteristic measurement unit 33 is directly adopted. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of depolymerized substances such as BHET based on the refractive index measurement result obtained in S6.

[0121] If the condition is "yes" in S5, the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measuring unit 33. Therefore, even if we proceed directly to S6 and S7, we cannot obtain an accurate concentration of depolymerized substances such as BHET. Therefore, in S8, the dilution valve 383 is switched to the open state. In S13, the extraction unit 39 extracts (secondarily extracts) a specified amount (second specified amount) of EG for dilution from the dilution depolymerizing agent supply unit 381 through the open dilution valve 383. Furthermore, in S9, the EG in the extraction unit 39 (injection pump 391) is diluted using the EG for dilution 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 depolymerizing agents such as BHET) extracted once in S12, the extraction unit 39 (injection pump 391) also ensures a second specified amount of depolymerizing agent such as EG (containing undissolved depolymerizing agents such as BHET) extracted a second time in S13.

[0122] In S11, the depolymerization reaction characteristic measurement unit 33 performs a second measurement on the refractive index of the first and second specified amounts of depolymerizing agent such as EG, which were ensured in the extraction unit 39 (injection pump 391) in S3 and S10, and returns to S5. If the result in S5 is "no", the refractive index of the diluted EG measured in S11 converges to a linear range below the saturation threshold B, so the measurement result of the depolymerization reaction characteristic measurement unit 33 is directly adopted in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of BHET and the like in the original (undiluted) tank body 31 based on the second measurement result of the refractive index within the linear range obtained in S11, the first specified amount extracted once in S12 (obtained from injection pump 391 and extraction valve 392), and the second specified amount extracted twice in S13 (obtained from injection pump 391 and dilution valve 383). Figure 10 (The concentration on the straight line after dilution). That is, as described above, by means of the injection pump 391, the extraction valve 392 and the dilution valve 383, the amount of depolymerizing agent such as EG entering the extraction unit 39 (injection pump 391) from the tank body 31 (or depolymerizing agent flow section 32) and the dilution depolymerizing agent supply section 381 respectively can be controlled. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET and the like in the tank body 31 while grasping the quantitative effect of dilution by the depolymerizing agent dilution section 38.

[0123] If the result in S5 is "yes", proceed to S8-S11 again, and repeat the secondary extraction in S13, the dilution in S9, and the secondary measurement in S11 until the result in S5 is "no", that is, until the result of the secondary refractive index measurement in S11 converges to the linear range below the saturation threshold B. At the end of the measurement in S7, the extraction valve 392 and the dilution valve 383 are in the closed state.

[0124] The present invention has been described above based on embodiments. Various modifications can be implemented in the combinations of constituent elements or processes in the illustrated embodiments, and such modifications are included within the scope of the present invention, as will be apparent to those skilled in the art.

[0125] exist Figure 4In this embodiment, a return channel 53, flow regulating valves 61, 62, and 71, and a pump 72 are provided as components for adjusting the BHET concentration within the depolymerization reaction tank 300, but not all of them are required. That is, it can be a simple structure where BHET / EG discharged from the depolymerization reaction tank 300, where heaters 320 are arranged in parallel, does not flow back to the depolymerization reaction tank 300 but towards the polymerization reaction tank 400. In this case, as the depolymerization reaction proceeds in the depolymerization reaction tank 300 and the BHET concentration increases, there is room for heating via the heaters 320 as the boiling point rises.

[0126] Furthermore, the configuration, function, and purpose of each apparatus and method described in the embodiments can be implemented using hardware resources, software resources, or a combination of both. Hardware resources include, for example, processors, ROMs, RAMs, and various integrated circuits. Software resources include, for example, operating systems, application programs, and other programs.

Claims

1. A depolymerization apparatus comprising: A depolymerization reaction tank initiates a depolymerization reaction that breaks down polyester into depolymerized products using a depolymerizing agent; and The heater raises the temperature inside the depolymerization reaction tank in a non-boiling manner, based on the increase in the concentration of the depolymerized product caused by the depolymerization reaction in the depolymerization reaction tank.

2. The depolymerization apparatus according to claim 1, comprising: The return channel returns at least a portion of the product containing the depolymerized material discharged from the depolymerization reactor to the interior of the depolymerization reactor.

3. The depolymerization apparatus according to claim 2, comprising: The return amount adjustment unit adjusts the return amount of the product that has passed through the return channel.

4. The depolymerization apparatus according to claim 3, wherein, The return volume adjustment unit operates in the following stages: During the heating phase, the amount of product returned through the return channel is greater than a predetermined amount, causing the concentration of the depolymerized material inside the depolymerization reaction tank to exceed a predetermined concentration. Furthermore, the temperature inside the depolymerization reaction tank is raised above a predetermined temperature by the heater. During the heat preservation stage, after the heating stage is completed, while maintaining the concentration of the depolymerized material inside the depolymerization reaction tank higher than the specified concentration and the temperature inside the depolymerization reaction tank higher than the specified temperature, the amount of the product returned through the return channel is lower than the specified return amount.

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

6. The depolymerization apparatus according to any one of claims 3 to 5, comprising: The depolymerization concentration detection unit detects the concentration of the depolymerization product inside the depolymerization reaction tank. The return amount adjustment unit adjusts the return amount of the product that has passed through the return channel based on the detected concentration of the depolymerized product.

7. The depolymerization apparatus according to claim 6, wherein, The heater increases the temperature inside the depolymerization reaction tank based on the detected concentration of the depolymerized material.

8. The depolymerization apparatus according to any one of claims 3 to 5, wherein, The return flow adjustment unit is a flow regulating valve installed in the return channel.

9. The depolymerization apparatus according to any one of claims 1 to 5, comprising: The depolymerization concentration detection unit detects the concentration of the depolymerization product inside the depolymerization reaction tank. The heater increases the temperature inside the depolymerization reaction tank based on the detected concentration of the depolymerized material.

10. The depolymerization apparatus according to any one of claims 1 to 5, comprising: The discharge adjustment unit adjusts the discharge rate of the product containing the depolymerized material from the depolymerization reaction tank.

11. The depolymerization apparatus according to claim 10, wherein, The discharge adjustment unit operates in the following stages: During the heating phase, the discharge rate of the product from the depolymerization reaction tank is lower than a predetermined discharge rate, thereby increasing the concentration of the depolymerized material inside the depolymerization reaction tank to a predetermined concentration. Furthermore, the temperature inside the depolymerization reaction tank is increased to a predetermined temperature by the heater. During the heat preservation stage, after the heating stage is completed, while maintaining the concentration of the depolymerized product inside the depolymerization reaction tank higher than the specified concentration and the temperature inside the depolymerization reaction tank higher than the specified temperature, the discharge amount of the product from the depolymerization reaction tank is made greater than the specified discharge amount.

12. The depolymerization apparatus according to claim 10, comprising: The depolymerization concentration detection unit detects the concentration of the depolymerization product inside the depolymerization reaction tank. The discharge adjustment unit adjusts the discharge rate of the product from the depolymerization reactor based on the detected concentration of the depolymerized product.

13. The depolymerization apparatus according to any one of claims 1 to 5, wherein, The depolymerization reaction tank is kept at normal or atmospheric pressure.

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

15. A chemical recovery device, comprising: The depolymerization reaction tank initiates a depolymerization reaction that breaks down polyester into depolymers using a depolymerizing agent. A heater that increases the temperature inside the depolymerization reaction tank based on the increase in the concentration of the depolymerized product caused by the depolymerization reaction in the tank; and The polymerization reactor is used to synthesize the depolymerized material into a polymer through a polymerization reaction.

16. A depolymerization method comprising the following steps: Inside the depolymerization reactor, a depolymerization reaction is initiated, initiating the breakdown of polyester into depolymerized products using a depolymerizing agent; and The temperature inside the depolymerization reaction tank is increased based on the increase in the concentration of the depolymerized product caused by the depolymerization reaction in the depolymerization reaction tank.

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