Concentration measurement system, separation system, and concentration measurement method

Abstract

To enable appropriate measurement of impurity concentration of polyester.SOLUTION: A concentration measurement device is provided, comprising: an impurity adding unit for adding a given amount of impurity to a solution containing a polyester solution obtained by dissolving polyester in a carboxylic acid-derived monomer and impurities defined as components other than the polyester; and a concentration detection unit for detecting impurity concentration of post-addition solution being solution after the addition of the impurity.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a concentration measuring device, a separation system, and a concentration measuring method.

Background Art

[0002] For example, in order to recycle polyester, it is necessary to separate impurities from the polyester. Patent Document 1 discloses a method for preparing a solution that can be used for the quantitative analysis of aldehydes and ketones contained in polyester, and a method for quantifying the absolute amounts of aldehydes and ketones contained in polyester.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When removing impurities contained in the polyester to be processed, the concentration of the impurities may be measured in order to confirm whether the impurities are appropriately removed. However, the polyester may contain impurities of components similar to the polyester, and it may be difficult to measure the concentration of the impurities. Therefore, it is required to appropriately measure the concentration of the impurities contained in the polyester.

[0005] The present disclosure solves the above-described problems, and an object thereof is to provide a concentration measuring device, a separation system, and a concentration measuring method capable of appropriately measuring the concentration of impurities contained in polyester.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a concentration measuring apparatus according to the present disclosure includes an impurity adding unit that adds a predetermined amount of impurities to a solution containing a polyester solution in which a polyester is dissolved in a monomer derived from a carboxylic acid and impurities that are components other than the polyester, and a concentration detecting unit that detects the concentration of the impurities in the added solution that is the solution after the impurities are added.

[0007] In order to solve the above-described problems and achieve the object, a separation system according to the present disclosure includes the above-described concentration measuring apparatus and a storage unit that stores the solution and separates the impurities from the solution by gravity, and the impurity adding unit adds the impurities to the solution discharged from the storage unit.

[0008] In order to solve the above-described problems and achieve the object, a concentration measuring method according to the present disclosure includes a step of adding a predetermined amount of impurities to a solution containing a polyester solution in which a polyester is dissolved in a monomer derived from a carboxylic acid and impurities that are components other than the polyester, and a step of detecting the concentration of the impurities in the added solution that is the solution after the impurities are added.

Advantages of the Invention

[0009] According to the present disclosure, the concentration of impurities contained in the polyester can be appropriately measured.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] With reference to the accompanying drawings below, preferred embodiments of the present invention will be described in detail. Note that the present invention is not limited by this embodiment, and when there are multiple embodiments, those configured by combining each embodiment are also included.

[0012] (First Embodiment) (Recycling Process) FIG. 1 is a schematic diagram of the polyester recycling process in this embodiment. In this embodiment, a process of recycling (reproducing) the polyester raw material Pm is performed by depolymerizing the polyester raw material Pm to monomerize it and then repolymerizing the monomers. Specifically, as shown in FIG. 1, the polyester raw material Pm is flaked (step S100), the flaked polyester raw material Pm is dissolved in the monomer D derived from carboxylic acid to generate a solution (step S101), foreign substances are removed from the solution (step S102), the solution from which foreign substances have been removed is mixed with the reaction solvent M and depolymerized (step S103), the monomers of the depolymerized polyester are purified (separated) to generate the monomer D derived from carboxylic acid and the monomer E of the alcohol component (step S104), the monomer D is hydrolyzed to separate the reaction solvent M (step S106), the monomer F generated by the hydrolysis of the monomer D and the monomer E are polymerized (step S108), and the polyester raw material Pm is reproduced. Note that the recycling process employing the separation system 1 of this embodiment may omit the flaking in step S100, or may perform only the process of recovering the monomers D, E shown in steps S102 and S104 and the monomer F shown in step S106 without performing the repolymerization process as in step S108.

[0013] (Polyester Raw Material) In this embodiment, the polyester raw material Pm to be depolymerized is a substance containing polyester. The polyester raw material Pm is not particularly limited. For example, it may be waste products such as polyethylene terephthalate (PET), polyethylene butylene terephthalate (PEBT), polybutylene terephthalate (PBT), polycyclohexane dimethyl terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polycarbonate (PC). The polyester raw material Pm is not limited to those containing only polyester components, but also includes components other than the polyester component. Examples of components other than polyester contained in the polyester raw material Pm include plastics other than polyester such as polyethylene, polystyrene, polypropylene, and polyvinyl chloride, metals, dyes, pigments, and polymerization catalysts. Examples of the polyester raw material Pm also include clothes in which polyester and other components are woven in a fibrous form. Hereinafter, components other than polyester contained in the polyester raw material Pm are referred to as impurities R.

[0014] (Reaction solvent) The reaction solvent M is a solvent that reacts with polyester to depolymerize the polyester. The reaction solvent M may be, for example, at least one of methanol, ethanol, water, and ethylene glycol.

[0015] (Monomer derived from carboxylic acid) The monomer D derived from carboxylic acid is a monomer having a carboxyl group generated by the depolymerization reaction of polyester. The monomer D may be, for example, dimethyl carboxylate or diethyl carboxylate. Furthermore, the monomer D is preferably a monomer of terephthalic acid and may be, for example, dimethyl terephthalate (DMT).

[0016] (Monomer of alcohol component) Monomer E of the alcohol component is a monomer of the alcohol component produced by the depolymerization reaction of the polyester. Monomer E may be, for example, a dihydroxy compound (dihydric alcohol), and more specifically, may be ethylene glycol (EG).

[0017] Hereinafter, the case where the polyester is PET, the reaction solvent M is methanol, monomer D is DMT, and monomer E is EG will be described as an example.

[0018] (Separation system) FIG. 2 is a schematic diagram of the separation system according to the first embodiment. The separation system 1 according to the first embodiment is a system that monomerizes the polyester contained in the polyester raw material Pm to generate monomers D and E. As shown in FIG. 2, the separation system 1 includes a raw material storage unit 10, a dissolution unit 12, a solid-liquid separation unit 13, a storage unit 20, a removal unit 26, a reaction solvent storage unit 14, a reaction unit 16, a separation unit 18, a control unit 30, and a concentration measurement device 61.

[0019] (Mechanism for obtaining a dissolved solution) Hereinafter, the mechanism for obtaining the dissolved solution Pd described later, that is, the raw material storage unit 10, the dissolution unit 12, the solid-liquid separation unit 13, the storage unit 20, the removal unit 26, and the concentration measurement device 61 will be described.

[0020] (Raw material storage unit) The raw material storage section 10 is a tank into which the polyester raw material Pm is introduced and stored. In this embodiment, the flaked polyester raw material Pm is stored in the raw material storage section 10, but the shape and size of the polyester raw material Pm may be arbitrary. The raw material storage section 10 is connected to the dissolution section 12 via the introduction pipe 10a. The polyester raw material Pm in the raw material storage section 10 is supplied to the dissolution section 12 through the introduction pipe 10a. The introduction pipe 10a is provided with an adjustment section 10b for adjusting the amount of the polyester raw material Pm supplied from the raw material storage section 10 to the dissolution section 12. The adjustment section 10b is, for example, an on-off valve. In the open state, the polyester raw material Pm in the raw material storage section 10 is supplied to the dissolution section 12, and in the closed state, the supply of the polyester raw material Pm in the raw material storage section 10 to the dissolution section 12 is stopped. However, the adjustment section 10b is not limited to an on-off valve and may be any mechanism capable of adjusting the supply of the polyester raw material Pm to the dissolution section 12. Also, the polyester raw material Pm may be supplied directly to the dissolution section 12 without passing through the raw material storage section 10, the introduction pipe 10a, and the adjustment section 10b.

[0021] (Dissolution section) The dissolution section 12 is a tank in which the dissolved liquid Pd is stored. The dissolved liquid Pd is a solution formed by mixing the polyester raw material Pm and the monomer D. Here, the polyester component contained in the polyester raw material Pm dissolves in the monomer D, but the impurities R, which are components other than polyester contained in the polyester raw material Pm, remain without dissolving in the monomer D. Therefore, it can be said that the dissolved liquid Pd contains the polyester solution P in which the polyester contained in the polyester raw material Pm is dissolved in the monomer D and the impurities contained in the polyester raw material Pm.

[0022] The monomer D and the polyester raw material Pm are supplied to the dissolution unit 12. In the dissolution unit 12, the polyester contained in the polyester raw material Pm dissolves in the monomer D, while the impurities R remain without dissolving in the monomer D, and a dissolution liquid Pd containing the polyester solution P and the impurities R is generated. By dissolving the polyester in the monomer D in this way, the viscosity can be reduced and the fluidity can be improved, and the polyester can be easily led out to the reaction unit 16. Note that the polyester solution P is not limited to the case where all of the polyester is dissolved in the monomer D, and at least a part of the polyester may be in a state of not dissolving in the monomer D. Further, among the components other than the polyester contained in the polyester raw material Pm, if there is a component that can be dissolved in the monomer D, the polyester solution P may also contain that component dissolved in the monomer D.

[0023] Note that the polyester solution P is not limited to a solution in which the polyester is dissolved in the monomer D, and may be a solution in which the polyester is dissolved in the monomer E. In this case, the monomer E and the polyester raw material Pm are supplied to the dissolution unit 12, and the polyester contained in the polyester raw material Pm dissolves in the monomer E in the dissolution unit 12, and the polyester solution P is generated.

[0024] In this embodiment, a heating unit 12A is provided in the melting unit 12. By heating the inside of the melting unit 12, the heating unit 12A heats the monomer D and the polyester raw material Pm supplied to the melting unit 12 to a predetermined temperature. The predetermined temperature is a temperature at which the polyester can be dissolved in the monomer D. By heating at such a predetermined temperature, the polyester contained in the polyester raw material Pm can be appropriately dissolved in the monomer D. The predetermined temperature is preferably 140°C or higher and 300°C or lower, more preferably 160°C or higher and 280°C or lower, and even more preferably 190°C or higher and 250°C or lower. Note that the impurity R also includes a component that melts when heated to a predetermined temperature (a temperature at which the polyester can be dissolved in the monomer D). Therefore, when the impurity R contains a component that melts when heated to the predetermined temperature, a part of it will be contained in the dissolved solution Pd in a molten state. In this embodiment, the heating unit 12A is provided in the melting unit 12, but the position where the heating unit 12A is provided is not limited thereto and is arbitrary.

[0025] (Solid-liquid separation unit) The solid-liquid separation unit 13 is disposed in the melting unit 12. The solid-liquid separation unit 13 collects the solid impurities R contained in the dissolved solution Pd stored in the melting unit 12 and separates the solid impurities R from the dissolved solution Pd. The solid-liquid separation unit 13 is a mesh-shaped filter through which the liquid passes and the solid is collected. The solid-liquid separation unit 13 of this embodiment has a container shape with an open top surface and is disposed at a predetermined interval with respect to the side surface and the bottom surface of the melting unit 12. The solid-liquid separation unit 13 is disposed on the downstream side of the introduction pipe 10a and the supply pipe to which the monomer D is supplied, and on the upstream side of the introduction pipe 12a that supplies the dissolved solution Pd from the melting unit 12 to the downstream storage unit 20. The dissolved solution Pd flowing from the melting unit 12 into the introduction pipe 12a passes through the solid-liquid separation unit 13. Thereby, the solid-liquid separation unit 13 collects solids larger than the opening diameter of the mesh. The solid-liquid separation unit 13 preferably has an opening diameter of the mesh of 1 mm or more and 50 mm or less.

[0026] The solid-liquid separation unit 13 of this embodiment uses a method of filtering with a mesh-shaped filter, but is not limited thereto. The solid-liquid separation unit 13 may separate the impurity R from the dissolved solution Pd by centrifugally stirring the inside of the dissolution unit 12 around a predetermined axis and moving the impurities to the outside in the radial direction of the rotating shaft. The solid-liquid separation unit 13 only needs to be able to separate solid impurities larger than a predetermined size from the dissolved solution Pd, and is not limited to filtration and centrifugation.

[0027] The foreign matter recovery unit 50 recovers the solid impurities collected by the solid-liquid separation unit 13. For example, the foreign matter recovery unit 50 moves the filter of the solid-liquid separation unit 13 to recover the attached impurities. Further, the solid-liquid separation unit 13 may be provided with a pressing device that presses the impurities attached to the mesh-shaped filter against the filter to squeeze out the dissolved solution Pd contained in the impurities. Before the foreign matter recovery unit 50 recovers the impurities, by squeezing the dissolved solution with the pressing device, more dissolved solution Pd can be left in the separation system 1. When the solid-liquid separation unit 13 separates by centrifugation, the foreign matter recovery unit 50 recovers the impurities from the region where the impurities are stored by centrifugation. Note that the solid-liquid separation unit 13 and the foreign matter recovery unit 50 may not be provided.

[0028] (Storage unit) The storage unit 20 is a tank in which the dissolved solution Pd is stored. The storage unit 20 is connected to the dissolution unit 12 via the introduction pipe 12a. The dissolved solution Pd in the dissolution unit 12 is supplied to the storage unit 20 through the introduction pipe 12a. The introduction pipe 12a is provided with an adjustment unit 12a1 for adjusting the amount of the dissolved solution Pd supplied from the dissolution unit 12 to the storage unit 20. The adjustment unit 12a1 is, for example, an on-off valve. In the open state, the dissolved solution Pd in the dissolution unit 12 is supplied to the storage unit 20, and in the closed state, the supply of the dissolved solution Pd in the dissolution unit 12 to the storage unit 20 is stopped. However, the adjustment unit 12a1 is not limited to being an on-off valve, and may be any mechanism capable of adjusting the supply of the dissolved solution Pd to the storage unit 20. In this embodiment, the storage unit 20 is connected to the dissolution unit 12 via the introduction pipe 12a, but an intermediate storage unit for temporarily storing the dissolved solution Pd may be provided between the dissolution unit 12 and the storage unit 20.

[0029] In the storage unit 20, impurities R are separated from the dissolution solution Pd by gravity. Here, the impurities R separated in the storage unit 20 are the impurities that were not recovered by the solid-liquid separation unit 13 and moved to the storage unit 20 together with the dissolution solution Pd. In the present embodiment, by allowing the dissolution solution Pd stored in the storage unit 20 to stand still, the impurities R are separated by gravity.

[0030] In the present embodiment, the dissolution solution Pd stored in the storage unit 20 is separated by gravity into a layer of first impurities R1, a layer of dissolution solution Pd, and a layer of second impurities R2. The layer of first impurities R1 is formed vertically below the layer of dissolution solution Pd. That is, the first impurities R1 are those among the impurities R that do not dissolve in the monomer D and have a specific gravity greater than that of the dissolution solution Pd. The first impurities R1 settle in the dissolution solution Pd within the storage unit 20 to form a layer of first impurities R1. On the other hand, the layer of second impurities R2 is formed vertically above the layer of dissolution solution Pd. That is, the second impurities R2 are those among the impurities R that do not dissolve in the monomer D and have a specific gravity smaller than that of the dissolution solution Pd. The second impurities R2 float in the dissolution solution Pd within the storage unit 20 to form a layer of second impurities R2.

[0031] Note that the dissolution solution Pd in the storage unit 20 is maintained at a predetermined temperature (a temperature at which the polyester can dissolve in the monomer D) or higher. Since the first impurities R1 and the second impurities R2 are components that melt in a state heated to the predetermined temperature among the impurities R, they also exist in a molten state within the storage unit 20. The first impurities R1 and the second impurities R2 are, for example, plastics other than polyester (such as polyethylene, polystyrene, polypropylene, polyvinyl chloride, etc. other than polyester).

[0032] In this embodiment, the layer of the dissolution liquid Pd contains a third impurity R3. The third impurity R3 is a component among the impurities R that does not dissolve in the monomer D and does not melt even at a predetermined temperature (a temperature at which the polyester can dissolve in the monomer D). That is, the third impurity R3 is not separated from the dissolution liquid Pd by gravity separation and exists in the dissolution liquid Pd in a solid state that does not melt. In this embodiment, the third impurity R3 is dispersed in the dissolution liquid Pd. The third impurity R3 is, for example, at least one of a pigment and a dye. More specifically, the third impurity R3 is, for example, an organic compound, and examples thereof include disperse dyes such as benzene azo-based (monoazo and disazo), heterocyclic azo-based (thiazole azo, benzothiazole azo, pyridone azo, pyrazolone azo, thiophene azo, etc.), anthraquinone-based, and condensed-based (quinophthalone, styryl, coumarin, etc.), cationic dyes having a basic functional group in the molecular structure, carbon black, etc., and additives used for coloring such as dyeing and matting of polyester. The third impurity R3 contains at least one of these. In this embodiment, the pigment adheres to the fiber surface to color the fiber, and the dye penetrates into the fiber to color the fiber.

[0033] A discharge pipe 20a is connected to the storage section 20. The discharge pipe 20a is a pipe for discharging the first impurity R1 separated in the lower layer from the dissolution liquid Pd from the storage section 20. The discharge pipe 20a is connected to the position where the layer of the first impurity R1 in the storage section 20 is formed, and in the example of this embodiment, it is connected to the bottom of the storage section 20. A first discharge section 22a is provided in the discharge pipe 20a. The first discharge section 22a is a mechanism for discharging the first impurity R1 in the storage section 20 from the storage section 20, and in this embodiment, it is a pump.

[0034] A discharge pipe 20b is connected to the storage section 20. The discharge pipe 20b is a pipe for discharging the second impurity R2 separated above the dissolution liquid Pd from the storage section 20. The discharge pipe 20b is connected to the position where the layer of the second impurity R2 in the storage section 20 is formed, and is connected vertically above the discharge pipe 20a. In the storage section 20, second discharge portions 22b1 and 22b2 for discharging the second impurity R2 in the storage section 20 from the storage section 20 are attached. The second discharge portion 22b1 is a skimmer provided at the position of the liquid surface of the dissolution liquid Pd, and recovers (scrapes) the second impurity R2 floating on the liquid surface of the dissolution liquid Pd. The second discharge portion 22b2 is provided in the discharge pipe 20b and is a mechanism for discharging the second impurity R2 recovered by the second discharge portion 22b1 through the discharge pipe 20b, and is a pump in this embodiment. Thus, in the example of this embodiment, the second discharge portions 22b1 and 22b2 are provided as a mechanism for discharging the second impurity R2, but the configuration of the second discharge portion for discharging the second impurity R2 is not limited to this and may be arbitrary.

[0035] The first impurity R1 and the second impurity R2 separated from the dissolution liquid Pd in the storage section 20 are discharged to the outside of the storage section 20 by the first discharge portion 22a and the second discharge portions 22b1 and 22b2. Thereby, the first impurity R1 and the second impurity R2 are removed from the dissolution liquid Pd. Hereinafter, when the first discharge portion 22a and the second discharge portions 22b1 and 22b2 are not distinguished, they are described as the discharge portion 22. In the above description, the impurity R includes the first impurity R1 having a specific gravity greater than that of the dissolution liquid Pd and the second impurity R2 having a specific gravity smaller than that of the dissolution liquid Pd, but it is not limited thereto, and the impurity R may include only one of the first impurity R1 and the second impurity R2.

[0036] The storage section 20 is connected to an introduction pipe 20c. The introduction pipe 20c is a pipe for leading out the solution Pd separated from the impurities R from the storage section 20. The introduction pipe 20c is connected to a position where a layer of the solution Pd is formed in the storage section 20, and in the example of this embodiment, is connected to a position between the discharge pipe 20a and the discharge pipe 20b in the vertical direction. The introduction pipe 20c is provided with an outlet section 24. The outlet section 24 is a mechanism for leading out the solution Pd in ​​the storage section 20 from the storage section 20, and is a pump in this embodiment. In this embodiment, the introduction pipe 20c includes an introduction pipe 20c1 connecting the storage section 20 and a filter 26a described later, an introduction pipe 20c2 connecting the filter 26a and an adsorption tower 26b described later, and an introduction pipe 20c3 connecting the adsorption tower 26b and the reaction section 16.

[0037] (Removal part) The removal unit 26 is a mechanism for removing the third impurity R3 contained in the solution Pd from the solution Pd. The removal unit 26 is connected to the storage unit 20, and removes the third impurity R3 present in the solution Pd discharged from the storage unit 20 from the solution Pd. In this embodiment, a filter 26a and an adsorption tower 26b are provided as the removal unit 26.

[0038] The filter 26a is connected to the storage unit 20 via an inlet pipe 20c1. The dissolution liquid Pd discharged from the storage unit 20 is introduced into the filter 26a through the inlet pipe 20c1. The filter 26a collects solid components contained in the third impurity R3 of the dissolution liquid Pd.

[0039] The adsorption tower 26b is connected to the filter 26a via the introduction pipe 20c2. The dissolved solution Pd (the dissolved solution Pd after the solid components are collected by the filter 26a) discharged from the filter 26a is introduced into the adsorption tower 26b through the introduction pipe 20c2. The adsorption tower 26b has a collection section for collecting the third impurity R3 contained in the dissolved solution Pd. The collection section of the adsorption tower 26b may be an adsorbent that adsorbs the third impurity R3 contained in the dissolved solution Pd, or may be a filtration section that collects the third impurity R3 by filtration. That is, the adsorption tower 26b may collect the third impurity R3 by at least one of adsorption or filtration. The adsorbent stored in the adsorption tower 26b preferably has the ability to adsorb the molecular skeleton (for example, quinone group, azo group, heterocyclic ring, benzene ring) of the third impurity R3. By the adsorbent being able to adsorb the molecular skeleton of the third impurity R3, various pigments and dyes can be adsorbed. The adsorbent is preferably activated carbon, for example.

[0040] The adsorption tower 26b is connected to the reaction section 16 described below via the introduction pipe 20c3. That is, the dissolved solution Pd after the third impurity R3 is removed in the adsorption tower 26b is introduced into the reaction section 16 through the introduction pipe 20c3.

[0041] Thus, the dissolved solution Pd led out from the storage section 20 to the introduction pipe 20c1 is introduced into the filter 26a, and at least a part of the third impurity R3 contained in the dissolved solution Pd is collected by the filter 26a. The third impurity R3 collected by the filter 26a is discharged to the outside through the discharge pipe 26a1 connected to the filter 26a. In the example of FIG. 2, the discharge pipe 26a1 merges with the discharge pipe 20a, but it does not have to merge with the discharge pipe 20a. The dissolved solution Pd from which at least a part of the third impurity R3 has been removed by the filter 26a is led out from the filter 26a and introduced into the adsorption tower 26b through the introduction pipe 20c2. In the adsorption tower 26b, the third impurity R3 remaining in the dissolved solution Pd is adsorbed or filtered by the adsorption tower 26b and removed from the dissolved solution Pd. The dissolved solution Pd from which the third impurity R3 has been removed by the adsorption tower 26b is led out from the adsorption tower 26b and introduced into the reaction section 16 through the introduction pipe 20c3.

[0042] Thus, in this embodiment, as a mechanism for removing the third impurity R3 from the dissolution solution Pd, the filter 26a and the adsorption tower 26b are provided. However, the configuration of the removal unit 26 that discharges the third impurity R3 is not limited to this and may be arbitrary. Also, a configuration that does not have the filter 26a but has the adsorption tower 26b may be used.

[0043] (Circulation pipe) Further, a circulation pipe 60a is connected to the adsorption tower 26b. One end 60b of the circulation pipe 60a is connected to a downstream side of the collection part of the adsorption tower 26b (a part where the dissolution solution Pd after the third impurity R3 is collected is stored). Also, the other end 60c of the circulation pipe 60a is connected to an upstream side of the collection part of the adsorption tower 26b. In the example of this embodiment, the end 60b of the circulation pipe 60a is connected to the introduction pipe 20c2, and the end 60c is connected to the introduction pipe 20c3. However, it is not limited thereto. The end 60b of the circulation pipe 60a may be directly connected to a part on the downstream side of the collection part of the adsorption tower 26b, or the end 60c of the circulation pipe 60a may be directly connected to a part on the upstream side of the collection part of the adsorption tower 26b.

[0044] In the circulation pipe 60a, the dissolved solution Pd (the dissolved solution Pd after the third impurity R3 has been removed) discharged from the adsorption tower 26b is supplied from the end portion 60b. The dissolved solution Pd supplied to the circulation pipe 60a is introduced into (returned to) the adsorption tower 26b from the end portion 60c. The circulation pipe 60a is provided with an adjustment unit 60 that adjusts the amount of the dissolved solution Pd flowing through the circulation pipe 60a. The adjustment unit 60 is a mechanism that adjusts the amount of the dissolved solution Pd flowing through the circulation pipe 60a. In the present embodiment, the adjustment unit 60 is a pump and adjusts so that a certain amount of the dissolved solution Pd flows through the circulation pipe 60a. However, the adjustment unit 60 is not limited to being a pump and may be any mechanism capable of adjusting the amount of the dissolved solution Pd flowing through the circulation pipe 60a. For example, the adjustment unit 60 may be a mechanism that adjusts so that a certain amount of the dissolved solution Pd flows through the circulation pipe 60a with a pump and a flow meter. By doing so, the flow rate of the dissolved solution Pd flowing through the circulation pipe 60a can be controlled, and the dissolved solution Pd can be returned to the upstream side of the adsorption tower 26b.

[0045] (Concentration measuring device) Here, it is preferable that the amount of the impurity R contained in the dissolved solution Pd discharged from the adsorption tower 26b and introduced into the reaction unit 16 is small. Therefore, it is required to measure the concentration of the impurity R (particularly the third impurity R3) contained in the dissolved solution Pd introduced into the reaction unit 16. In the present embodiment, the concentration measuring device 61 measures the concentration of the impurity (the third impurity R3) contained in the dissolved solution Pd discharged from the adsorption tower 26b. As shown in FIG. 2, the concentration measuring device 61 includes an impurity adding unit 62 and a concentration detecting unit 66.

[0046] (Impurity adding unit) The impurity addition unit 62 is a device for adding a third impurity R3 to the dissolved solution Pd. In the present embodiment, the impurity addition unit 62 is connected to the circulation pipe 60a, and adds the third impurity R3 to the dissolved solution Pd discharged from the adsorption tower 26b and flowing through the circulation pipe 60a. In the example of FIG. 2, the impurity addition unit 62 is connected to the circulation pipe 60a via the addition pipe 62a. By adding the third impurity R3 to the dissolved solution Pd, the impurity addition unit 62 increases the concentration of the third impurity R3 in the dissolved solution Pd. The impurity addition unit 62 may add only the third impurity R3 to the dissolved solution Pd, or may add the third impurity R3 to the dissolved solution Pd in a state where the third impurity R3 is dissolved in a solvent (preferably monomer D). However, the solvent for dissolving the third impurity R3 is not limited to monomer D. The solvent for dissolving the third impurity R3 is preferably the same as the solvent supplied to the dissolution unit 12. For example, the solvent for dissolving the third impurity R3 may be monomer E.

[0047] The third impurity R3 added by the impurity addition unit 62 may be the same component as the third impurity R3 dissolved in the dissolved solution Pd, or may be a third impurity R3 having a different component from the third impurity R3 dissolved in the dissolved solution Pd. The third impurity R3 added by the impurity addition unit 62 preferably has the same molecular skeleton as the third impurity R3 dissolved in the dissolved solution Pd (for example, both have a benzene ring).

[0048] The impurity addition unit 62 adds a predetermined amount of the third impurity R3. In other words, the impurity addition unit 62 preferably keeps the ratio of the addition amount of the third impurity R3 to the amount of the dissolved solution Pd (the dissolved solution Pd to which impurities are to be added) flowing through the circulation pipe 60a constant. Thereby, the concentration of impurities in the dissolved solution Pd before the addition of the third impurity R3 can be appropriately measured using the dissolved solution Pd after the addition of the third impurity R3. The impurity addition unit 62 preferably adds a predetermined amount of the third impurity R3 so that the concentration of the third impurity R3 in the dissolved solution Pd becomes several hundred times, for example, about 100 times higher. In the present embodiment, the predetermined amount is a fixed amount and is preset according to pigments and dyes contained in the polyester raw material to be recovered.

[0049] The addition amount of the third impurity R3 from the impurity addition section 62 may be controlled by any method. In the present embodiment, however, the addition amount of the third impurity R3 may be controlled by the adjustment section 64 provided in the addition pipe 62a. In the present embodiment, the adjustment section 64 is a pump, and is adjusted so that a predetermined amount of the third impurity R3 is supplied to the molten solution Pd flowing through the circulation pipe 60a. However, the adjustment section 64 is not limited to being a pump, and may be any mechanism capable of adjusting the addition amount of the third impurity R3 from the impurity addition section 62. For example, the adjustment section 64 may be a mechanism having a pump and a flow meter. Also, for example, the adjustment section 64 may be an on-off valve.

[0050] Hereinafter, the molten solution Pd after the third impurity R3 is added by the impurity addition section 62 is appropriately described as the added molten solution Pd2.

[0051] (Concentration detection section) The concentration detection section 66 is a device (sensor) that detects the concentration of the third impurity R3 in the added molten solution Pd2. In the present embodiment, the concentration detection section 66 is connected to the circulation pipe 60a. More specifically, in the direction in which the molten solution Pd flows, it is connected to the downstream side of the location where the impurity addition section 62 (addition pipe 62a) of the circulation pipe 60a is connected.

[0052] The concentration detection section 66 may detect the concentration of the third impurity R3 in the added molten solution Pd2 by any method. In the present embodiment, however, the concentration of the third impurity R3 may be detected by detecting the color of the added molten solution Pd2.

[0053] When detecting the color of the added dissolution solution Pd2, the concentration detector 66 is, for example, a color difference meter. The concentration detector 66 calculates the concentration of the third impurity R3 based on the detected color of the added dissolution solution Pd2. That is, for example, the correspondence relationship between color and concentration is stored as a table, and the concentration detector 66 may detect the concentration of the added dissolution solution Pd2 based on the table and the detected color. For example, as the concentration of the third impurity R3 increases, the color of the added dissolution solution Pd2 tends to become darker, so the concentration of the third impurity R3 can be calculated based on the color of the added dissolution solution Pd2. Note that the concentration detector 66 may detect one (preferably the b value or the a value) of the three parameters of chromaticity, namely the L value, the b value, and the a value, as the color of the added dissolution solution Pd2, or may detect two or more (preferably the b value and the a value). By detecting two or more, even when the colors of the third impurity R3 contained in the dissolution solution Pd and the third impurity R3 to be added are different, the concentration of the third impurity R3 can be appropriately detected.

[0054] In addition, the concentration detector 66 may detect the concentration of the third impurity R3 based on the degree of light transmission of the light irradiated on the added dissolution solution Pd2. In this case, for example, the concentration detector 66 includes an irradiation unit that irradiates the added dissolution solution Pd2 with light and a light receiving unit that receives the light transmitted through the added dissolution solution Pd2, and detects the concentration of the third impurity R3 based on the intensity of the light transmitted through the added dissolution solution Pd2. That is, since the intensity of the light transmitted through the added dissolution solution Pd2 depends on the concentration of the third impurity R3, the concentration of the third impurity R3 can be detected based on the degree of light transmission of the light irradiated on the added dissolution solution Pd2. Note that the degree of light transmission of the light irradiated on the added dissolution solution Pd2 can be said to be the ratio of the intensity of the light transmitted through the added dissolution solution Pd2 to the intensity of the light irradiated on the added dissolution solution Pd2.

[0055] The wavelength of the light irradiated by the light source unit of the concentration detector 66 may be arbitrary, but in this embodiment, it is preferably light in the ultraviolet wavelength band (for example, 10 nm to 400 nm). By irradiating light in the ultraviolet wavelength band, the detection accuracy can be improved. Also, the wavelength to be detected for the light transmittance may be arbitrary, but it is preferably a wavelength such that the absorbance of the light by the components contained in the polyester solution P is below a predetermined value and the absorbance of the light by the third impurity R3 is above a predetermined value. Thereby, the detection accuracy of the concentration of the third impurity R3 can be improved.

[0056] The concentration detector 66 thus detects the concentration of the third impurity R3 in the added and dissolved solution Pd2 after the third impurity R3 is added by the impurity addition unit 62. Here, since the amount of the third impurity R3 added from the impurity addition unit 62 is known, the concentration detector 66 can detect the concentration of the third impurity R3 in the dissolved solution Pd before the third impurity R3 is added by detecting the concentration of the third impurity R3.

[0057] The added and dissolved solution Pd2 used for the concentration detection in the concentration detector 66 is returned from the end 60c of the circulation pipe 60a to the adsorption tower 26b. Thereby, the third impurity R3 is removed from the added and dissolved solution Pd2 in the adsorption tower 26b and supplied to the reaction unit 16 as the dissolved solution Pd.

[0058] In the example described above, there was one adsorption tower 26b, but a plurality of units of the adsorption tower 26b, the circulation pipe 60a, and the concentration measuring device 61 may be provided. In this case, each unit is connected in parallel to the introduction pipe 20c2 and may be capable of switching the connection and disconnection with the introduction pipe 20c2. Thereby, when replacing the collection part of one adsorption tower 26b, the adsorption tower 26b can be disconnected from the introduction pipe 20c2 and another adsorption tower 26b can be connected to the introduction pipe 20c2, and the collection part of the adsorption tower 26b can be replaced without stopping the equipment.

[0059] As described above, the concentration measuring device 61 is connected to the circulation pipe 60a and detects the concentration of the third impurity R3 in the dissolved solution Pd discharged from the adsorption tower 26b, but is not limited thereto. That is, the concentration measuring device 61 may detect the concentration of the third impurity R3 in the dissolved solution Pd at an arbitrary position in the separation system 1. For example, the concentration measuring device 61 may detect the concentration of the dissolved solution Pd in the process before the adsorption process by the adsorption tower 26b. In this case, for example, the concentration measuring device 61 may be connected to the dissolution unit 12 or may be connected to the storage unit 20.

[0060] (Mechanism for obtaining monomers) Hereinafter, the mechanism for obtaining monomers from the obtained dissolved solution Pd, that is, the reaction solvent storage unit 14, the reaction unit 16, and the separation unit 18 will be described.

[0061] (Solvent storage unit) The reaction solvent storage unit 14 is a tank into which the reaction solvent M is introduced and the reaction solvent M is stored. The reaction solvent storage unit 14 is connected to the reaction unit 16 via the introduction pipe 14a. The reaction solvent M in the reaction solvent storage unit 14 is supplied to the reaction unit 16 through the introduction pipe 14a. More specifically, the introduction pipe 14a is provided with a heating and pressurizing unit 14b for pressurizing and heating the reaction solvent M. The heating and pressurizing unit 14b pressurizes and heats the reaction solvent M to bring the reaction solvent M into a supercritical state or a subcritical state (pressurized gas or pressurized liquid). The reaction unit 16 is supplied with the reaction solvent M in a supercritical state or a subcritical state (pressurized gas or pressurized liquid).

[0062] (Reaction unit) The reaction unit 16 is a container into which the dissolved solution Pd separated from the impurity R in the storage unit 20 and the reaction solvent M are introduced, and the polyester in the dissolved solution Pd is depolymerized. The reaction unit 16 includes a first reaction unit 16A and a second reaction unit 16B.

[0063] (First reaction unit) The first reaction part 16A is formed within the reaction part 16. In the present embodiment, the first reaction part 16A can be said to be the location within the reaction part 16 where the filler is filled. For the first reaction part 16A, a known filler used in a gas-liquid or liquid-liquid contact device can be used as the filler. For example, a filler similar to that used in a contact device for contacting heavy oil and water to extract the active ingredient can be used. Specific examples of the filler include pipes made of SUS or the like, Raschig rings, Berl saddles, and teralettes.

[0064] An introduction pipe 20c3 is connected to the first reaction part 16A. More specifically, an inlet 16C, which is an opening through which the dissolved liquid Pd from the storage part 20 is introduced into the introduction pipe 20c3, is connected to the first reaction part 16A. The inlet 16C is connected to the surface 16A1 on the first direction D1 side of the first reaction part 16A. The introduction pipe 20c is connected to the surface 16A1 such that the inlet 16C opens facing the second direction D2, which is opposite to the first direction D1. Thus, in the present embodiment, the inlet 16C that opens facing the second direction D2 is connected to the surface 16A1 of the first reaction part 16A, but it is not limited thereto. For example, the inlet 16C may not be directly connected to the first reaction part 16A, and the inlet 16C that opens facing the second direction D2 may be connected to a position on the first direction D1 side of the surface 16A1 of the first reaction part 16A within the reaction part 16.

[0065] The introduction pipe 14a is connected to the reaction section 16. More specifically, an inlet 16D, which is an opening through which the reaction solvent M from the reaction solvent storage section 14 is introduced into the introduction pipe 14a, is connected to the reaction section 16. The inlet 16D is connected to the second direction D2 side of the surface 16A2 of the first reaction section 16A. The introduction pipe 14a is connected to the second direction D2 side of the surface 16A2 such that the inlet 16D faces the first direction D1 side or opens from the side surface toward the center side. Thus, in the present embodiment, the inlet 16D that faces the first direction D1 side or opens from the side surface toward the center side is connected to the second direction D2 side of the surface 16A2 of the first reaction section 16A, but is not limited thereto. For example, the inlet 16D may be directly connected to the first reaction section 16A or may be connected to the surface 16A2 of the first reaction section 16A.

[0066] Thus, in the present embodiment, the inlet 16C through which the dissolved solution Pd is introduced opens facing the second direction D2, and the inlet 16D through which the reaction solvent M is introduced faces the first direction D1 or opens from the side surface toward the center side. Therefore, the dissolved solution Pd and the reaction solvent M are introduced into the first reaction section 16A in directions facing each other.

[0067] The dissolved solution Pd introduced from the inlet 16C into the first reaction section 16A moves on the surface of the packing material in the first reaction section 16A in the second direction D2. On the other hand, the reaction solvent M in the supercritical state or subcritical state (pressurized gas or pressurized liquid) introduced from the inlet 16D moves in the first reaction section 16A in the first direction D1. In the first reaction section 16A, the reaction solvent M in the supercritical state or subcritical state (pressurized gas or pressurized liquid) comes into contact with the dissolved solution Pd. The polyester in the dissolved solution Pd is depolymerized (molecular weight reduced) by the reaction solvent M, and the depolymerized polyester is extracted by the reaction solvent M in the supercritical state or subcritical state (pressurized gas or pressurized liquid). Hereinafter, the polyester depolymerized in the first reaction section 16A is referred to as the first depolymerized polyester P1, and the mixture of the first depolymerized polyester P1 and the reaction solvent M (the reaction solvent M from which the first depolymerized polyester P1 has been extracted) is referred to as the first solvent M1. The first solvent M1 containing the first depolymerized polyester P1 advances in the first reaction section 16A toward the first direction D1 side and is led out to the first direction D1 side of the first reaction section 16A.

[0068] Note that the first depolymerized polyester P1 includes monomers D and E generated by depolymerizing the polyester in the dissolved solution Pd, monomer D originally mixed in the dissolved solution Pd, and oligomers generated by depolymerizing the polyester. The oligomers here refer to oligomers derived from carboxylic acids or alcohol components that have not been monomerized but have been depolymerized from the polyester (oligomers derived from carboxylic acids or alcohol components with a molecular weight smaller than that of the polyester).

[0069] (Second reaction section) The second reaction section 16B is formed in the reaction section 16, and the second reaction section 16B is formed at the location where the first solvent M1 is led out from the first reaction section 16A. In this embodiment, since the first solvent M1 is led out to the first direction D1 side, the second reaction section 16B can be said to be a space formed on the first direction D1 side of the first reaction section 16A.

[0070] In the second reaction section 16B, the first depolymerized polyester P1 contained in the first solvent M1 is further depolymerized (molecular weight reduced) by the reaction solvent M contained in the first solvent M1. Hereinafter, the first depolymerized polyester P1 further depolymerized in the second reaction section 16B is referred to as the second depolymerized polyester P2, and a mixture of the second depolymerized polyester P2 and the reaction solvent M (reaction solvent M in which the second depolymerized polyester P2 is dissolved) is referred to as the second solvent M2. A lead-out pipe 16a is connected to the second reaction section 16B. More specifically, a lead-out port 16E, which is an opening from which the second solvent M2 from the second reaction section 16B is led out of the lead-out pipe 16a, is connected to the second reaction section 16B. The second solvent M2 containing the second depolymerized polyester P2 in the second reaction section 16B is led out to the outside of the second reaction section 16B through the lead-out pipe 16a from the lead-out port 16E.

[0071] Note that the second depolymerized polyester P2 contains monomers D and E in the first depolymerized polyester P1, monomers D and E generated by depolymerization of oligomers in the first depolymerized polyester P1, and oligomers generated by depolymerization of the first depolymerized polyester P1.

[0072] A discharge pipe 16b is connected to the bottom of the reaction section 16. More specifically, a discharge port 16F, which is an opening from which non-extracts (described later) in the reaction section 16 are discharged, of the discharge pipe 16b is connected to the bottom of the reaction section 16. From the discharge port 16F, non-extracts containing impurities such as metal compounds not extracted by the reaction solvent M and residues of undegraded polyester not extracted by the reaction solvent M are discharged. That is, the non-extracts at the bottom of the reaction section 16 are discharged to the outside of the reaction section 16 through the discharge pipe 16b from the discharge port 16F. The non-extracts discharged from the discharge port 16F can be said to be components remaining in the first reaction section 16A and the second reaction section 16B without being led out to the separation section 18 as the second solvent M2 (reaction solvent M in which the second depolymerized polyester P2 is dissolved) in the polyester solution P.

[0073] Further, the reaction section 16 may be provided with a heating section for heating the inside of the reaction section 16 and a pressurizing section for maintaining the pressure inside the reaction section 16 at a predetermined value or more. The temperature inside the reaction section 16 is preferably set to 250°C or more and 400°C or less, and more preferably 250°C or more and 350°C or less. Also, the pressure inside the reaction section 16 is preferably 1 MPa or more and 30 MPa or less, and more preferably 6 MPa or more and 25 MPa or less. The pressurizing section and the heating section may be controlled by the control section 30.

[0074] (Separation section) The separation section 18 has the second solvent M2 containing the second depolymerized polyester P2 introduced therein, and separates the second solvent M2 into the reaction solvent M, the monomer D derived from the carboxylic acid contained in the second depolymerized polyester P2, the monomer E of the alcohol component contained in the second depolymerized polyester P2, and the residual substance. The residual substance is a component other than the reaction solvent M, the monomer D, and the monomer E in the second solvent M2, and contains oligomers.

[0075] In the present embodiment, the separation section 18 includes a first separation section 18A, a second separation section 18B, and a third separation section 18C.

[0076] The first separation section 18A is a separation column connected to the lead-out pipe 16a. The second solvent M2 containing the second depolymerized polyester P2 is introduced into the first separation section 18A via the lead-out pipe 16a. The first separation section 18A separates the second solvent M2 into a low-boiling component and a high-boiling component having a boiling point higher than that of the low-boiling component. For example, in the first separation section 18A, the second solvent M2 may be set to a predetermined temperature, and the component that has become a gas may be defined as the low-boiling component, and the liquid component may be defined as the high-boiling component. The lead-out pipes 18Aa and 18Ab are connected to the first separation section 18A. The low-boiling component is led out from the lead-out pipe 18Aa, and the high-boiling component is led out from the lead-out pipe 18Ab.

[0077] The second separation unit 18B is a separation column connected to the first separation unit 18A via the lead-out pipe 18Aa. The low-boiling components are introduced into the second separation unit 18B via the lead-out pipe 18Aa. The second separation unit 18B separates the low-boiling components into the reaction solvent M and the monomer E. The lead-out pipes 18Ba and 18Bb are connected to the second separation unit 18B. The reaction solvent M is led out from the lead-out pipe 18Ba, and the monomer E is led out from the lead-out pipe 18Bb. Note that the lead-out pipe 18Ba is connected to the second separation unit 18B and the reaction solvent storage unit 14. Therefore, the reaction solvent M led out from the second separation unit 18B is returned to the reaction solvent storage unit 14 and reused for the depolymerization of the polyester.

[0078] The third separation unit 18C is a separation column connected to the first separation unit 18A via the lead-out pipe 18Ab. The high-boiling components are introduced into the third separation unit 18C via the lead-out pipe 18Ab. The third separation unit 18C separates the high-boiling components into a residue with an even higher boiling point, a low-boiling component containing the reaction solvent M and the monomer E, and the monomer D. The lead-out pipes 18Ca, 18Cb, and 18Cc are connected to the third separation unit 18C. The lead-out pipe 18Ca is connected to the second separation unit 18B. The low-boiling component separated within the third separation unit 18C is led out to the second separation unit 18B via the lead-out pipe 18Ca. Also, the monomer D separated within the third separation unit 18C is led out from the lead-out pipe 18Cb, and the residue separated within the third separation unit 18C is led out from the lead-out pipe 18Cc.

[0079] A introducing pipe 18Cd is connected to the third separation unit 18C. The introducing pipe 18Cd is also connected to the dissolving unit 12, and introduces the monomer D derived from the third separation unit 18C into the dissolving unit 12. In the example of FIG. 2, the introducing pipe 18Cd branches from the leading pipe 18Cb. The introducing pipe 18Cd is provided with an adjusting unit 18Ce for adjusting the amount of the monomer D supplied from the third separation unit 18C to the dissolving unit 12. The adjusting unit 18Ce is, for example, an on-off valve. In the open state, the monomer D is supplied to the dissolving unit 12, and in the closed state, the supply of the monomer D to the dissolving unit 12 is stopped. However, the adjusting unit 18Ce is not limited to an on-off valve, and may be any mechanism capable of adjusting the supply of the monomer D to the dissolving unit 12. In the present embodiment, the adjusting unit 18Ce is provided at the branching position of the introducing pipe 18Cd from the leading pipe 18Cb, but the position where it is provided is not limited thereto and may be arbitrary. Further, the introducing pipe 18Cd may not be connected to the leading pipe 18Cb, and may be directly connected to the third separation unit 18C. Further, for example, a storage unit (tank) for storing the monomer D may be provided in the leading pipe 18Cb, and the introducing pipe 18Cd may be connected to the storage unit.

[0080] Note that by connecting the leading pipe 18Cc to the dissolving unit 12, at least a part of the residual substance may be introduced into the dissolving unit 12. By introducing the residual substance into the dissolving unit 12, it becomes possible to depolymerize the oligomer contained in the residual substance again in the reaction unit 16, and the yield of the monomer can be improved.

[0081] In the present embodiment, since the polyester solution P is a solution in which the polyester is dissolved in the monomer D, the monomer D is introduced into the dissolving unit 12 through the introducing pipe 18Cd. However, when the polyester solution P is a solution in which the polyester is dissolved in the monomer E, the introducing pipe 18Cd may be connected to the second separation unit 18B and the dissolving unit 12. That is, in this case, the monomer E separated in the second separation unit 18B is introduced into the dissolving unit 12 through the introducing pipe 18Cd. Further, a storage unit (tank) for storing the monomer E may be provided, and the introducing pipe 18Cd may be connected to the storage unit.

[0082] (Control Unit) The control unit 30 is a control device that controls the separation system 1. The control unit 30 controls the adjustment unit 10b to control the amount of the polyester raw material Pm supplied from the raw material storage unit 10 to the dissolution unit 12. The control unit 30 controls the foreign matter recovery unit 50 to recover the impurities collected by the solid-liquid separation unit 13. Also, when the solid-liquid separation unit 13 is provided with a drive unit, the control unit 30 controls the operation of the solid-liquid separation unit 13. The control unit 30 controls the adjustment unit 12a1 to control the amount of the dissolved solution Pd supplied from the dissolution unit 12 to the storage unit 20. The control unit 30 controls the discharge unit 22 to discharge the impurities R separated from the polyester solution P in the storage unit 20 from the storage unit 20. The control unit 30 controls the derivation unit 24 to control the amount of the polyester solution P separated from the impurities R in the storage unit 20 and derived from the storage unit 20 and introduced into the reaction unit 16. The control unit 30 controls the adjustment unit 60 to control the amount of the dissolved solution Pd discharged from the adsorption tower 26b to a predetermined amount. The control unit 30 controls the adjustment unit 64 to control the amount of the third impurity R3 added by the impurity addition unit 62 to a predetermined amount. The control unit 30 controls the concentration detection unit 66 to detect the concentration of the third impurity R3 by the concentration detection unit 66. The control unit 30 controls the heating and pressurizing unit 14b to make the reaction solvent M in a supercritical state or a subcritical state (pressurized gas or pressurized liquid), and controls the supply amount of the reaction solvent M in the supercritical state or the subcritical state (pressurized gas or pressurized liquid) to the reaction unit 16. The control unit 30 controls the adjustment unit 18Ce to control the supply amount of the monomer D to the dissolution unit 12.

[0083] In this embodiment, the control unit 30 is a computer and includes a processor including an arithmetic circuit such as a CPU (Central Processing Unit) and a storage unit that stores various information such as the arithmetic content and programs by the processor. The control unit 30 executes the control of the separation system 1 by reading a program from the storage unit.

[0084] However, the separation system 1 is not limited to being automatically controlled by the control unit 30. For example, at least some of the processes may be controlled by an operator's operation. For example, when the control unit 30 determines that the adsorption tower 26b needs to be replaced, the operation of replacing the adsorbent in the adsorption tower 26b and the operation of switching the adsorption tower 26b may be performed either by automatic control or by an operator.

[0085] (Operation of the separation system) Next, the operation of the separation system 1 will be described. The control unit 30 controls the adjustment units 10b and 18Ce to introduce the polyester raw material Pm and the monomer D into the dissolution unit 12, and mixes the polyester raw material Pm and the monomer D in the dissolution unit 12 to generate a dissolution liquid Pd. The control unit 30 controls the adjustment unit 12a1 to introduce the dissolution liquid Pd generated in the dissolution unit 12 into the storage unit 20. The separation system 1 removes the impurities R from the dissolution liquid Pd supplied from the dissolution unit 12 to the storage unit 20 in the solid-liquid separation unit 13. The dissolution liquid Pd introduced into the storage unit 20 is separated by gravity into a layer of the first impurity R1, a layer of the dissolution liquid Pd, and a layer of the second impurity R2 by being allowed to stand for a predetermined time. Note that the method of allowing the dissolution liquid Pd to stand may be arbitrary.

[0086] The control unit 30 controls the discharge unit 22 to discharge the first impurity R1 and the second impurity R2 in the storage unit 20, and controls the derivation unit 24 to derive the dissolved solution Pd in the storage unit 20 from the storage unit 20. The dissolved solution Pd derived from the storage unit 20 has the third impurity R3 removed by the removal unit 26 and is introduced into the first reaction unit 16A. At this time, the control unit 30 subtracts the added amount of the third impurity R3 added by the impurity addition unit 62 from the detected concentration value detected by the concentration detection unit 66, and calculates the concentration of the third impurity R3 contained in the dissolved solution Pd discharged from the adsorption tower 26b. The control unit 30 determines whether to replace the adsorbent stored in the adsorption tower 26b based on the calculation result of the concentration. The control unit 30 controls the heating and pressurizing unit 14b to supply the reaction solvent M in a supercritical state or a subcritical state (pressurized gas or pressurized liquid) to the reaction unit 16. The control unit 30 preferably sets the reaction solvent M to be 250°C or higher and 400°C or lower, and more preferably 250°C or higher and 350°C or lower. The control unit 30 preferably sets the reaction solvent M to be 1 MPa or higher and 30 MPa or lower, and more preferably 6 MPa or higher and 25 MPa or lower.

[0087] In this way, by supplying the dissolved solution Pd and the reaction solvent M to the reaction unit 16, in the first reaction unit 16A, the polyester contained in the dissolved solution Pd is depolymerized to generate the first depolymerized polyester P1. Then, in the second reaction unit 16B, the first depolymerized polyester P1 is further depolymerized to generate the second solvent M2, which is a mixture of the second depolymerized polyester P2 and the reaction solvent M. The second solvent M2 is separated into the reaction solvent M, the monomer D, the monomer E, and the residual substance in the first separation unit 18A, the second separation unit 18B, and the third separation unit 18C. Thereby, the monomers D and E are recovered from the polyester raw material Pm, and the polyester can be regenerated by polymerizing them.

[0088] Regarding the addition of impurities to the separation system 1 described above, it will be described based on the flowchart. FIG. 3 is a flowchart for explaining the addition of impurities to the separation system. As shown in FIG. 3, the impurity addition unit 62 adds impurities to the dissolution solution (step S10). The concentration detection unit 66 detects the concentration of impurities in the added dissolution solution Pd2 (step S12). The control unit 30 determines whether to replace the adsorption tower (step S14).

[0089] (Effect) The polyester raw material Pm may contain impurities R other than polyester. In order to depolymerize and recycle the polyester, it is necessary to remove the impurities R. In order to confirm whether the impurities R have been removed, it is required to measure the concentration of the impurities R (especially the third impurity R3). However, it may be difficult to measure the concentration of the third impurity R3 in the state contained in the dissolution solution Pd. In particular, when the third impurity R3 is at a low concentration, the sensitivity becomes low, making it difficult to measure the concentration. On the other hand, in the present embodiment, since the third impurity R3 is added by the impurity addition unit 62 and then the concentration of the third impurity R3 is measured, it is possible to measure in a high-concentration state, so the sensitivity can be improved and the concentration of the third impurity R3 contained in the dissolution solution Pd can be appropriately measured. Further, in the separation system 1, the impurity addition unit 62 and the concentration detection unit 66 are connected to the downstream side of the adsorption tower 26b. Therefore, it is possible to know the adsorption amount of impurities in the adsorption tower 26b continuously or periodically, and it is possible to replace the adsorbent stored in the adsorption tower 26b at an appropriate time. Also, when there are two or more adsorption towers 26b, it is possible to switch to another adsorption tower.

[0090] In addition, the separation system 1 is provided with a solid-liquid separation unit 13, and by removing solid matter of a predetermined size from the dissolved liquid in the dissolution unit 12, foreign matter can be appropriately separated from the object to be treated. In particular, when treating clothes or the like containing solid impurities as the object to be treated, foreign matter can be preferably separated. Further, by arranging the solid-liquid separation unit 13 in the dissolution unit 12 that generates the dissolved liquid Pd as in the present embodiment, impurities contained in the liquid supplied from the dissolution unit 12 to the storage unit 20 can be reduced.

[0091] In addition, the separation system 1 stores the dissolved liquid Pd treated by the solid-liquid separation unit 13 in the storage unit 20, and by removing impurities by gravity separation, foreign matter can be more preferably separated. Since the impurity R may exist as a high-viscosity melt, there is a risk that the opening of the filter of the filter may be blocked when the opening is small, and the impurity R cannot be appropriately recovered and separated. On the other hand, in the present embodiment, the impurity R is separated from the dissolved liquid Pd by gravity separation. Then, the gravity-separated impurity R is discharged, and depolymerization is performed using the gravity-separated dissolved liquid Pd. As a result, the opening of the filter of the filter is not blocked, and the impurity R can be appropriately recovered, and the polyester and the foreign matter can be appropriately separated.

[0092] In addition, in the present embodiment, after removing the impurity R, the dissolved liquid Pd is depolymerized. Therefore, depolymerization can be performed in a state where the purity of the polyester at the time of depolymerization is increased, and the yields of the monomers D and E can be improved. In addition, the impurity R may contain a polymerization catalyst. Since the polymerization catalyst is a catalyst that promotes polymerization, there is a risk of inhibiting depolymerization. On the other hand, in the present embodiment, since depolymerization is performed after removing the polymerization catalyst, depolymerization can be appropriately performed, and the yields of the monomers D and E can be improved. Furthermore, when depolymerization is performed by adding a depolymerization catalyst, the amount of the depolymerization catalyst added can be reduced by the amount of the polymerization catalyst removed.

[0093] (Second Embodiment) Next, the second embodiment will be described. In the separation system 1A of the second embodiment, each part for recovering foreign matters is arranged downstream of the reaction part 106 that performs depolymerization. For the same configurations as those in the first embodiment, the same reference numerals are given and detailed descriptions thereof are omitted.

[0094] FIG. 4 is a partial schematic view of the separation system according to the second embodiment. As shown in FIG. 4, the separation system 1A according to the second embodiment includes a dissolution part 12, a reaction part 16, a first storage part 112, a solid-liquid separation part 13, a second storage part 20, a removal part 26, a concentration measuring device 61 (an impurity addition part 62 and a concentration detection part 66), and a control part 30. The first storage part 112, the solid-liquid separation part 13, the second storage part 20, and the removal part 26 are foreign matter removal parts that remove impurities from the solution containing the depolymerized monomer. The liquid that has passed through the removal part 26 is supplied to the separation part 18. The control part 30 controls the operations of each part in the same manner as in the first embodiment.

[0095] The dissolution part 12 generates a dissolution liquid in which the polyester raw material Pm to be processed is dissolved. The dissolution part 12 preferably supplies the monomer D to generate the dissolution liquid, but the polyester raw material Pm may be dissolved with components other than the monomer D.

[0096] The reaction part 16 has the dissolution liquid (polyester solution) generated in the dissolution part 102 and the reaction solvent M introduced therein, and depolymerizes the polyester in the polyester solution P.

[0097] The first storage part 112 stores the liquid generated in the reaction part 106, that is, the liquid containing the polyester (the second depolymerized polyester P2 in this embodiment) generated by depolymerizing the polyester. The first storage part 112 discharges the liquid from the discharge pipe 112a. An adjustment part 112a1 is arranged in the discharge pipe 112a to control the discharge of the liquid.

[0098] The solid-liquid separation part 13 removes impurities having a size equal to or larger than a predetermined size contained in the liquid passing through the first storage part 112.

[0099] The second storage section 20 has the same configuration as that of the first embodiment, and the liquid from which the impurities have been removed in the solid-liquid separation section 113 is supplied from the first storage section 112 and stored therein. The second storage section 20 is left stationary for a predetermined time, and is separated by gravity into a layer of the first impurity R1, a layer containing the second depolymerized polyester P2, and a layer of the second impurity R2. The discharge pipe 20a is a pipe for discharging the first impurity R1 separated into a lower layer below the liquid from the second storage section 20. The discharge pipe 20a is provided with a first discharge section 22a. The first discharge section 22a is a mechanism for discharging the first impurity R1 in the second storage section 20 from the second storage section 120, and is a pump in this embodiment. The discharge pipe 20b is connected to the second storage section 20. The discharge pipe 20b is a pipe for discharging the second impurity R2 separated into an upper layer above the liquid from the second storage section 20. An inlet pipe 20c1 is connected to the second storage section 20. The inlet pipe 20c1 is a pipe for leading out the liquid containing the second depolymerized polyester P2 separated from the impurities R from the second storage section 20. The inlet pipe 20c1 is provided with an outlet section 24. The outlet section 24 is a mechanism for leading out the liquid in the second storage section 20 from the second storage section 20, and is a pump in this embodiment.

[0100] The removal section 26 is a mechanism for removing the third impurity R3 from the liquid containing the second depolymerized polyester P2. The removal section 26 is connected to the inlet pipe 20c1. The removal section 26 includes a filter 26a and an adsorption tower 26b. The filter 26a collects solid components. The adsorption tower 26b adsorbs solid components that have not been collected by the filter 26a. The configuration of each part of the removal section 26 is the same as that of the first embodiment.

[0101] A concentration measuring device 61 is connected to the downstream side of the adsorption tower 26b. That is, an impurity adding unit 62 and a concentration detecting unit 66 are connected. The impurity adding unit 62 is connected to the circulation pipe 60a and adds a third impurity R3 to the solution Pd discharged from the adsorption tower 26b. The concentration detecting unit 66 is connected to the circulation pipe 60a and detects the concentration of the third impurity R3 in the added solution Pd2 after the impurity adding unit 62 adds the third impurity R3. The configurations of the impurity adding unit 62 and the concentration detecting unit 66 are the same as those of the first embodiment.

[0102] The separation system 1A performs solid-liquid separation to remove foreign substances of a predetermined size in the depolymerized liquid by the solid-liquid separation unit 13, and then performs separation using gravity in the second storage unit 20, thereby preferably removing foreign substances contained in the liquid. In this way, even when removing foreign substances contained in the depolymerized liquid, after solid-liquid separation by the solid-liquid separation unit 13, separation using gravity is performed in the second storage unit 20, so that foreign substances can be preferably removed. Further, in the removal unit 26, foreign substances can be preferably removed from the depolymerized liquid by removing foreign substances. Note that in the separation system 1A of the present embodiment, either the solid-liquid separation unit 13 or the second storage unit 20 may be omitted for the depolymerized liquid.

[0103] (Effect of the present disclosure) The concentration measuring device according to the first aspect of the present disclosure includes an impurity adding unit 62 that adds a predetermined amount of impurities to a dissolution liquid Pd containing a polyester solution P in which a monomer D derived from a carboxylic acid is dissolved in a polyester and impurities that are components other than the polyester, and a concentration detecting unit 66 that detects the concentration of the impurities in the added dissolution liquid Pd2 which is the dissolution liquid after the impurities are added.

[0104] Therefore, the concentration of the impurities contained in the polyester can be appropriately measured.

[0105] The separation system according to the second aspect of the present disclosure includes the concentration measuring device 61 according to the first aspect, and a storage unit 20 in which the dissolution liquid Pd is stored and impurities are separated from the dissolution liquid Pd by gravity. The impurity adding unit 62 adds impurities to the dissolution liquid Pd discharged from the storage unit 20. Therefore, the concentration of the impurities contained in the polyester can be appropriately measured, the impurities can be appropriately removed from the dissolution liquid Pd, and the recovery efficiency of the monomer can be improved.

[0106] The separation system according to the third aspect of the present disclosure is the separation system according to the second aspect, further comprising a dissolution unit 12 into which a polyester raw material Pm containing polyester and a monomer D derived from a carboxylic acid are introduced to generate a dissolution solution Pd. The storage unit 20 is connected to the dissolution unit 12, and the dissolution solution Pd is introduced from the dissolution unit 12. Thereby, the concentration of impurities contained in the polyester can be appropriately measured, impurities can be appropriately removed from the dissolution solution Pd, and the recovery efficiency of the monomer can be improved.

[0107] The separation system according to the fourth aspect of the present disclosure is the separation system according to the second aspect or the third aspect, further comprising an adsorption tower 26b that is connected to the storage unit 20 and removes impurities present in the dissolution solution Pd discharged from the storage unit 20 from the dissolution solution Pd, and a circulation pipe 60a that is connected to the downstream side of the adsorption tower 26b and through which the dissolution solution Pd discharged from the adsorption tower 26b flows. The impurity addition unit 62 is connected to the circulation pipe 60a and adds impurities to the dissolution solution Pd flowing through the circulation pipe 60a. The concentration detection unit 66 is connected to the circulation pipe 60a and detects the concentration of impurities in the added dissolution solution Pd2 flowing through the circulation pipe 60a.

[0108] Therefore, the concentration of impurities in the dissolution solution Pd flowing through the adsorption tower 26b can be detected sensitively continuously or periodically. Therefore, it is possible to know how much impurities the adsorption tower 26b has adsorbed from the dissolution solution Pd. Therefore, the adsorption tower 26b can be replaced at an appropriate time.

[0109] The separation system according to the fifth aspect of the present disclosure is the separation system according to any one of the second aspect to the fourth aspect, wherein the circulation pipe 60a is connected upstream of the adsorption tower 26b and returns the added dissolution solution Pd2 upstream of the adsorption tower 26b. Thereby, impurities can be removed from the added dissolution solution Pd2 to which impurities have been added for concentration measurement, and the recovery efficiency of the monomer can be improved.

[0110] The separation system according to the sixth aspect of the present disclosure is the separation system according to any one of the second to fifth aspects, wherein the concentration detection unit 66 detects the concentration of impurities in the added solution Pd2 based on the color of the solution Pd or the transmittance of the light irradiated on the solution Pd. Thereby, the concentration of impurities contained in the polyester can be appropriately measured.

[0111] The separation system according to the seventh aspect of the present disclosure is the separation system according to any one of the second to sixth aspects, wherein the impurities are at least one of a pigment and a dye. Since pigments and dyes are components similar to polyester, it is particularly difficult to detect their concentration. According to the present disclosure, since the concentration is measured in a state where impurities are added to make a high concentration, the concentration of such difficult-to-detect impurities can be appropriately detected.

[0112] The concentration measurement method according to the eighth aspect of the present disclosure includes a step of adding a predetermined amount of impurities to a solution Pd containing a polyester solution P in which a polyester is dissolved in a monomer D derived from a carboxylic acid and impurities that are components other than the polyester, and a step of detecting the concentration of impurities in the added solution Pd2 which is the solution after the impurities are added.

[0113] Therefore, the concentration of impurities contained in the polyester can be appropriately measured.

[0114] As described above, the embodiments of the present invention have been described, but the embodiments are not limited by the contents of these embodiments. Further, the above-described components include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or changes of the components can be made without departing from the gist of the above-described embodiments.

Explanation of Reference Numerals

[0115] 1 Separation system 12 Dissolution unit 13 Solid-liquid separation unit 14 Reaction solvent storage unit 16 Reaction unit 18 Separation section 20 Storage section, second storage section 22 Discharge section 30 Control section 61 Concentration measuring device 62 Impurity addition section 66 Concentration detection section D, E monomers M Reaction solvent P Polyester solution Pd Dissolved solution Pd2 Added dissolved solution Pm Polyester raw material R Impurities R1 First impurity R2 Second impurity R3 Third impurity

Claims

1. An impurity addition unit that adds a predetermined amount of impurities to a polyester solution in which a polyester is dissolved in a monomer derived from a carboxylic acid and a solution containing impurities that are components other than the polyester; A concentration detection unit that detects the concentration of the impurities in the added solution, which is the solution after the impurities are added; Comprising: A concentration measuring device.

2. The concentration measuring device according to claim 1, and A storage unit in which the solution is stored and the impurities are separated from the solution by gravity, having, The impurity addition unit adds the impurities to the solution discharged from the storage unit, A separation system.

3. Further comprising a dissolution unit into which a polyester raw material containing a polyester and a monomer derived from a carboxylic acid are introduced to generate the solution, The storage unit is connected to the dissolution unit, and the solution is introduced from the dissolution unit, the separation system according to claim 2.

4. An adsorption tower connected to the storage unit and removing the impurities present in the solution discharged from the storage unit from the solution, Further comprising a circulation pipe connected to the downstream side of the adsorption tower through which the solution discharged from the adsorption tower flows, The impurity addition unit is connected to the circulation pipe and adds the impurities to the solution flowing through the circulation pipe, The concentration detection unit is connected to the circulation pipe and detects the concentration of the impurities in the added solution flowing through the circulation pipe, the separation system according to claim 2 or claim 3.

5. The circulation pipe is connected upstream of the adsorption tower and returns the added solution upstream of the adsorption tower, the separation system according to claim 4.

6. The concentration detection unit detects the concentration of the impurities in the added solution based on the color of the added solution or the degree of light transmittance of the light irradiated on the added solution, the separation system according to claim 2 or claim 3.

7. The impurities are at least one of a pigment and a dye, the separation system according to claim 2 or claim 3.

8. A step of adding a predetermined amount of impurities to a polyester solution in which a polyester is dissolved in a monomer derived from a carboxylic acid and a solution containing impurities that are components other than the polyester; A step of detecting the concentration of the impurities in the added solution, which is the solution after the impurities are added; Including: A concentration measuring method.

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