Monomer production system, control method, and program

Abstract

The present invention appropriately produces a monomer. This monomer production system comprises: a dissolution unit into which a polyester starting material that contains a polyester is introduced and in which a polyester solution that has the polyester dissolved therein is retained; a reaction unit into which the polyester solution and a reaction solvent that reacts with the polyester are introduced so as to depolymerize the polyester in the polyester solution, thereby generating a reaction solvent in which the depolymerized polyester is dissolved; a separation unit that separates the reaction solvent, in which the depolymerized polyester has been dissolved, into a monomer and the reaction solvent; a detection unit that detects a parameter relating to the concentration of the monomer that is contained in the reaction solvent in which the depolymerized polyester is dissolved; and a control unit that controls the amount of the polyester starting material to be introduced into the dissolution unit on the basis of the parameter.

Description

Monomer production system, control method and program

[0001] The present disclosure relates to a monomer production system, a control method, and a program.

[0002] In polyester recycling, a technique for converting polyester into monomers by depolymerization (a reverse reaction of polymerization) is known. Patent Document 1 describes a monomer production system having a dissolving section in which a polyester solution is stored, a first reaction section and a second reaction section in which the polyester solution and a reaction solvent are introduced and the polyester in the polyester solution is depolymerized, a separation section in which the reaction solvent in which the depolymerized polyester is dissolved is separated into the reaction solvent and residual substances containing monomers and oligomers, and a pipe in which the monomers and oligomers are returned to the dissolving section.

[0003] Japanese Patent Application Laid-Open No. 2022-184116

[0004] In such a monomer production system, it is required to produce the monomer appropriately.

[0005] An object of the present disclosure is to provide a monomer production system, a control method, and a program that are capable of appropriately producing a monomer.

[0006] The monomer production system according to the present disclosure comprises: a dissolution section into which a polyester raw material containing a polyester is introduced and which stores a polyester solution in which the polyester is dissolved; a reaction section into which the polyester solution and a reaction solvent that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved; a separation section that separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent; a detection section that detects a parameter related to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved; and a control section that controls the amount of the polyester raw material introduced into the dissolution section based on the parameter.

[0007] The control method according to the present disclosure is a control method for a monomer production system having a dissolution section into which a polyester raw material containing a polyester is introduced and which stores a polyester solution in which the polyester is dissolved, a reaction section into which the polyester solution and a reaction solvent that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved, and a separation section which separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent, and includes the steps of: detecting a parameter related to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved; and controlling the amount of the polyester raw material introduced into the dissolution section based on the parameter.

[0008] The program according to the present disclosure is a program that causes a computer to execute a control method for a monomer production system having: a dissolution section into which a polyester raw material containing a polyester is introduced and which stores a polyester solution in which the polyester is dissolved; a reaction section into which the polyester solution and a reaction solvent that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved; and a separation section that separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent. The program causes the computer to execute the steps of detecting a parameter related to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved, and controlling the amount of the polyester raw material introduced into the dissolution section based on the parameter.

[0009] According to the present disclosure, the monomer can be appropriately produced.

[0010] Fig. 1 is a schematic diagram of a polyester recycling process according to this embodiment. Fig. 2 is a schematic diagram of a monomer production system according to this embodiment. Fig. 3 is a schematic block diagram of a control unit. Fig. 4 is a flowchart illustrating the control flow of the control unit.

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations in which the respective embodiments are combined.

[0012] (Recycling Process) FIG. 1 is a schematic diagram of a polyester recycling process according to this embodiment. In this embodiment, polyester raw material Pm is depolymerized to form monomers, and the monomers are then repolymerized to recycle (regenerate) polyester raw material Pm. Specifically, as shown in FIG. 1 , polyester raw material Pm is flaked (step S100), the flaked polyester raw material Pm is dissolved in carboxylic acid-derived monomer D to produce a polyester solution, foreign matter is removed from the polyester solution, and the polyester solution from which the foreign matter has been removed is mixed with reaction solvent M for depolymerization (step S102), the monomers of the depolymerized polyester are purified (separated) to produce carboxylic acid-derived monomer D and alcohol component monomer E (step S104), monomer D is hydrolyzed to separate reaction solvent M (step S106), and monomer F produced by hydrolysis of monomer D is polymerized with monomer E (step S108), thereby regenerating polyester raw material Pm. In addition, in the recycling process employing the monomer production system 1 of this embodiment, the flaking in step S100 may be omitted, or only the process of recovering monomers D and E shown in step S102 and step S104, and monomer F shown in step S106 may be performed 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, but examples include 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, and may also contain components (impurities) other than polyester components. 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 include clothing in which polyester and other components are knitted into fibers.

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

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

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

[0017] In the following, an example will be described in which the polyester is PET, the reaction solvent M is methanol, the monomer D is DMT, and the monomer E is EG.

[0018] (Monomer Production System) Fig. 2 is a schematic diagram of a monomer production system according to this embodiment. The monomer production system 1 according to this embodiment is a system that monomerizes polyester contained in a polyester raw material Pm to produce monomers D and E. As shown in Fig. 2, the monomer production system 1 has a raw material storage section 10, a dissolution section 12, a solvent storage section 14, a reaction section 16, a separation section 18, and a control section 20.

[0019] (Raw Material Storage Section) The raw material storage section 10 is a tank into which the polyester raw material Pm is introduced and stored. In this embodiment, the raw material storage section 10 stores flaked polyester raw material Pm, but the shape and size of the polyester raw material Pm may be arbitrary. The raw material storage section 10 is connected to the dissolving section 12 via an inlet pipe 10a. The polyester raw material Pm in the raw material storage section 10 is supplied to the dissolving section 12 through the inlet pipe 10a. The inlet pipe 10a is provided with an adjustment section 10b that adjusts the amount of polyester raw material Pm supplied from the raw material storage section 10 to the dissolving section 12. The adjustment section 10b is, for example, an on-off valve. When in an open state, the adjustment section 10b allows the polyester raw material Pm in the raw material storage section 10 to be supplied to the dissolving section 12, and when in a closed state, it stops the supply of the polyester raw material Pm in the raw material storage section 10 to the dissolving section 12. However, the adjusting section 10b is not limited to being an on-off valve, and may be any mechanism capable of adjusting the supply of the polyester raw material Pm to the dissolving section 12. Furthermore, the polyester raw material Pm may be supplied directly to the dissolving section 12 without passing through the raw material storage section 10, the introduction pipe 10a, and the adjusting section 10b.

[0020] (Dissolving Section) The dissolving section 12 is a tank into which the polyester raw material Pm is introduced and into which the polyester solution P is stored. The polyester solution P is a solution in which the polyester contained in the polyester raw material Pm is dissolved in monomer D. It is a solution produced by mixing the polyester raw material Pm and monomer D. Monomer D and polyester raw material Pm are supplied to the dissolving section 12, and the polyester contained in the polyester raw material Pm is dissolved in monomer D in the dissolving section 12 to produce the polyester solution P. By dissolving the polyester in monomer D in this manner, the viscosity can be reduced and the fluidity can be improved, allowing the polyester to be easily introduced into the reaction section 16. Furthermore, the residual substance R described below is also supplied to the dissolving section 12, and the polyester contained in the polyester raw material Pm is dissolved in monomer D and the oligomer contained in the residual substance R in the dissolving section 12 to produce the polyester solution P. In other words, the polyester solution P can be said to be a solution in which the polyester is dissolved in monomer D and residual substance R. However, the polyester solution P is not limited to a solution in which the entire amount of polyester is dissolved in monomer D and residual substance R; at least a portion of the polyester may be in a state in which it is not dissolved in monomer D and residual substance R. Furthermore, the polyester raw material Pm may contain impurities, which are substances other than polyester. In this case, it can be said that the polyester solution P contains the monomer D, the dissolved polyester, and the impurities.

[0021] The polyester solution P is not limited to a solution in which polyester is dissolved in monomer D, but may be a solution in which polyester is dissolved in monomer E. In this case, monomer E and polyester raw material Pm are supplied to the dissolving section 12, and the polyester contained in the polyester raw material Pm is dissolved in monomer E in the dissolving section 12 to produce the polyester solution P.

[0022] The dissolving section 12 is connected to a first reaction section 16A (described later) via an inlet pipe 12a. The polyester solution P in the dissolving section 12 is supplied to the first reaction section 16A through the inlet pipe 12a. The inlet pipe 12a is also provided with a supply section 12b and a heating section 12c. The supply section 12b is a mechanism for supplying the polyester solution P in the dissolving section 12 to the first reaction section 16A, and is a pump in this embodiment. The heating section 12c is a mechanism for heating the polyester solution P.

[0023] (Solvent Reservoir) The solvent reservoir 14 is a tank into which the reaction solvent M is introduced and where the reaction solvent M is stored. The solvent reservoir 14 is connected to the reaction section 16 via an inlet pipe 14a. The reaction solvent M in the solvent reservoir 14 is supplied to the reaction section 16 through the inlet pipe 14a. More specifically, the inlet pipe 14a is provided with a heating and pressure increasing section 14b and an adjusting section 14c. The adjusting section 14c is a mechanism for supplying the reaction solvent M in the solvent reservoir 14 to the first reaction section 16A, and is a pump in this embodiment. The heating and pressure increasing section 14b is a mechanism for pressurizing and heating the reaction solvent M. The heating and pressure increasing section 14b pressurizes and heats the reaction solvent M, thereby bringing the reaction solvent M into a supercritical state or a subcritical state (pressurized gas or pressurized liquid). The reaction section 16 is supplied with the reaction solvent M in a supercritical state or a subcritical state (pressurized gas or pressurized liquid).

[0024] (Reaction Section) The reaction section 16 is a mechanism into which polyester and a reaction solvent M that reacts with the polyester are introduced, depolymerizing the polyester and producing a reaction solvent in which the depolymerized polyester is dissolved. Specifically, the reaction section 16 is a container into which a polyester solution P and the reaction solvent M are supplied, and the supplied reaction solvent M depolymerizes the polyester in the polyester solution P. The reaction section 16 includes a first reaction section 16A and a second reaction section 16B. Hereinafter, within the reaction section 16, the direction from the first reaction section 16A to the second reaction section 16B will be referred to as direction Y1, and the direction opposite to direction Y1 (the direction from the second reaction section 16B to the first reaction section 16A) will be referred to as direction Y2.

[0025] (First Reaction Section) The first reaction section 16A is formed within the reaction section 16. In this embodiment, the first reaction section 16A can be said to be a portion of the reaction section 16 that is filled with a filler. A known filler used in gas-liquid or liquid-liquid contactors can be used for the first reaction section 16A, such as a filler similar to that used in contactors that bring heavy oil and water into contact to extract active ingredients. Specific examples of fillers include pipes made of stainless steel or the like, Raschig rings, Berl saddles, and Terralets.

[0026] An inlet pipe 12a is connected to the first reaction section 16A. More specifically, an inlet 16C, which is an opening of the inlet pipe 12a through which the polyester solution P from the dissolution section 12 is introduced, is connected to the first reaction section 16A. The inlet 16C is connected to a surface 16A1 on the direction Y1 side of the first reaction section 16A. The inlet pipe 12a is connected to the surface 16A1 so that the inlet 16C opens toward the direction Y2. In this embodiment, the inlet 16C opening toward the direction Y2 is connected to the surface 16A1 of the first reaction section 16A, but this is not limited thereto. For example, the inlet 16C does not have to be directly connected to the first reaction section 16A, and the inlet 16C opening toward the direction Y2 may be connected to the surface 16A1 of the first reaction section 16A in the reaction section 16 on the direction Y1 side.

[0027] An inlet pipe 14a is connected to the reaction section 16. More specifically, an inlet 16D, which is an opening of the inlet pipe 14a through which the reaction solvent M is introduced from the solvent reservoir 14, is connected to the reaction section 16. The inlet 16D is connected closer to the Y2 direction than the surface 16A2 on the Y2 side of the first reaction section 16A. The inlet pipe 14a is connected closer to the Y2 direction than the surface 16A2 so that the inlet 16D opens toward the Y1 direction or from the side toward the center. In this embodiment, the inlet 16D, which opens toward the Y1 direction or from the side toward the center, is connected closer to the Y2 direction than the surface 16A2 of the first reaction section 16A. However, this 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.

[0028] In this embodiment, the inlet 16C through which the polyester solution P is introduced opens in the direction Y2, and the inlet 16D through which the reaction solvent M is introduced opens in the direction Y1 or from the side toward the center. Therefore, the polyester solution P and the reaction solvent M are introduced into the first reaction section 16A in directions facing each other.

[0029] The polyester solution P introduced into the first reaction section 16A through the inlet 16C moves in the direction Y2 on the surface of the filler in the first reaction section 16A. Meanwhile, the reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid) introduced through the inlet 16D moves in the direction Y1 within the first reaction section 16A. In the first reaction section 16A, the reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid) comes into contact with the polyester solution P. The polyester in the polyester solution P is depolymerized (reduced in molecular weight) by the reaction solvent M, and the depolymerized polyester is extracted into the reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid). Hereinafter, the polyester depolymerized in the first reaction zone 16A will be referred to as a 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) will be referred to as a first solvent M1. The first solvent M1 containing the first depolymerized polyester P1 proceeds in the direction Y1 through the first reaction zone 16A and is discharged to the direction Y1 side of the first reaction zone 16A.

[0030] The first depolymerized polyester P1 includes monomers D and E produced by depolymerizing the polyester in the polyester solution P, monomer D that was originally mixed in the polyester solution P, and oligomers produced by depolymerizing the polyester. The oligomers referred to here refer to carboxylic acid or alcohol oligomers that are not monomerized but are depolymerized from the polyester (carboxylic acid or alcohol oligomers with smaller molecular weights than the polyester). Furthermore, oligomers contained in the residual substance R in the polyester solution P are also depolymerized by the reaction solvent M. Therefore, the first depolymerized polyester P1 also includes the depolymerized residual substance R. The depolymerized residual substance R includes oligomers contained in the residual substance R that have been depolymerized, as well as monomers D and E produced by depolymerizing the oligomers contained in the residual substance R.

[0031] (Second Reaction Unit) The second reaction unit 16B is provided in the reaction unit 16 at a location where the first solvent M1 is discharged from the first reaction unit 16A. In this embodiment, the second reaction unit 16B is provided on the first direction D1 side of the first reaction unit 16A.

[0032] In the second reaction zone 16B, the first depolymerized polyester P1 contained in the first solvent M1 is further depolymerized (reduced in molecular weight) by the reaction solvent M contained in the first solvent M1. Hereinafter, the first depolymerized polyester P1 further depolymerized in the second reaction zone 16B will be referred to as the second depolymerized polyester P2, and the mixture of the second depolymerized polyester P2 and the reaction solvent M (the reaction solvent M containing the second depolymerized polyester PE) will be referred to as the second solvent M2. An outlet pipe 16a is connected to the second reaction zone 16B. More specifically, an outlet 16E, which is an opening of the outlet pipe 16a through which the second solvent M2 from the second reaction zone 16B is discharged, is connected to the second reaction zone 16B. The second solvent M2 containing the second depolymerized polyester P2 in the second reaction zone 16B is discharged from the outlet 16E through the outlet pipe 16a to the outside of the second reaction zone 16B.

[0033] The second depolymerized polyester P2 contains monomers D and E produced by depolymerizing the oligomers in the first depolymerized polyester P1, and oligomers produced by depolymerizing the first depolymerized polyester P1.

[0034] A discharge pipe 16b is connected to the bottom of the reaction zone 16 (the bottom surface on the direction Y2 side). More specifically, a discharge port 16F, which is an opening of the discharge pipe 16b through which the non-extractable material in the reaction zone 16 is discharged, is connected to the bottom of the reaction zone 16. The non-extractable material includes impurities such as metal compounds that were not extracted into the reaction solvent M and residues of undecomposed polyester that were not extracted into the reaction solvent M. That is, the non-extractable material at the bottom of the reaction zone 16 is discharged from the discharge port 16F through the discharge pipe 16b to the outside of the reaction zone 16. The non-extractable material discharged from the discharge pipe 16b can be considered to be components of the polyester solution P that were not introduced into the separation zone 18 as the second solvent M2 (reaction solvent M containing the second depolymerized polyester P2) and remained in the first reaction zone 16A and the second reaction zone 16B.

[0035] The reaction section 16 may also be provided with a heating section that heats the interior of the reaction section 16 and a pressurizing section that maintains the pressure inside the reaction section 16 at a predetermined value or higher. The temperature inside the reaction section 16 is preferably 250°C or higher and 400°C or lower, and more preferably 250°C or higher and 350°C or lower. The pressure inside the reaction section 16 is preferably 1 MPa or higher and 30 MPa or lower, and more preferably 6 MPa or higher and 25 MPa or lower. The pressurizing section and the heating section may be controlled by the control section 20.

[0036] (Separation Section) The separation section 18 is introduced with a second solvent M2 (a reaction solvent in which the depolymerized polyester is dissolved) containing the second depolymerized polyester P2, and separates the second solvent M2 into the reaction solvent M and the monomer. More specifically, the separation section 18 separates the second solvent M2 into the reaction solvent M, a monomer D derived from a carboxylic acid contained in the second depolymerized polyester P2, a monomer E of an alcohol component contained in the second depolymerized polyester P2, and a residual substance R. The residual substance R is a component of the second solvent M2 other than the reaction solvent M, the monomer D, and the monomer E, and includes oligomers.

[0037] In this embodiment, the separation section 18 has a first separation section 18A, a second separation section 18B, and a third separation section 18C.

[0038] The first separation section 18A is a separation column connected to the outlet pipe 16a. A second solvent M2 containing the second depolymerized polyester P2 is introduced into the first separation section 18A via the outlet pipe 16a. The first separation section 18A separates the second solvent M2 into a low-boiling component and a high-boiling component having a higher boiling point than the low-boiling component. For example, in the first separation section 18A, the second solvent M2 may be heated to a predetermined temperature, with the gaseous component being the low-boiling component and the liquid component being the high-boiling component. The first separation section 18A is connected to outlet pipes 18Aa and 18Ab. The low-boiling component is discharged from the outlet pipe 18Aa, and the high-boiling component is discharged from the outlet pipe 18Ab.

[0039] The second separation section 18B is a separation column connected to the first separation section 18A via an outlet pipe 18Aa. Low-boiling point components are introduced into the second separation section 18B via the outlet pipe 18Aa. The second separation section 18B separates the low-boiling point components into a reaction solvent M and a monomer E. Outlet pipes 18Ba and 18Bb are connected to the second separation section 18B. The reaction solvent M is discharged from the outlet pipe 18Ba, and the monomer E is discharged from the outlet pipe 18Bb.

[0040] The outlet pipe 18Ba is connected to the second separation section 18B and the solvent reservoir 14. Therefore, the reaction solvent M discharged from the second separation section 18B is returned to the solvent reservoir 14 and reused for polyester monomerization. In addition, the outlet pipe 18Ba is provided with an adjustment section 18Bb. The adjustment section 18Bb is a mechanism for supplying the reaction solvent M discharged from the second separation section 18B to the solvent reservoir 14, and is a pump in this embodiment.

[0041] The third separation section 18C is a separation column connected to the first separation section 18A via the outlet pipe 18Ab. High-boiling components are introduced into the third separation section 18C via the outlet pipe 18Ab. The third separation section 18C further separates the high-boiling components into high-boiling residual material R, low-boiling components containing reaction solvent M and monomer E, and monomer D. The third separation section 18C is connected to outlet pipes 18Ca, 18Cb, and 18Cc. The outlet pipe 18Ca is connected to the second separation section 18B. The low-boiling components separated in the third separation section 18C are discharged to the second separation section 18B via the outlet pipe 18Ca. The monomer D separated in the third separation section 18C is discharged from the outlet pipe 18Cb, and the residual material R separated in the third separation section 18C is discharged from the outlet pipe 18Cc.

[0042] An inlet pipe 18Cd is connected to the third separation section 18C. The inlet pipe 18Cd is also connected to the dissolving section 12 and introduces the monomer D discharged from the third separation section 18C into the dissolving section 12. In the example shown in FIG. 2 , the inlet pipe 18Cd branches off from the outlet pipe 18Cb. The inlet pipe 18Cd is provided with an adjustment section 18Ce that adjusts the amount of monomer D supplied from the third separation section 18C to the dissolving section 12. The adjustment section 18Ce is, for example, an on-off valve that, when open, allows the monomer D to be supplied to the dissolving section 12 and, when closed, stops the supply of the monomer D to the dissolving section 12. However, the adjustment section 18Ce is not limited to an on-off valve and may be any mechanism capable of adjusting the supply of monomer D to the dissolving section 12. In this embodiment, the adjustment section 18Ce is provided at the point where the inlet pipe 18Cd branches off from the outlet pipe 18Cb, but the adjustment section 18Ce may be provided at any position. Furthermore, the inlet pipe 18Cd does not have to be connected to the outlet pipe 18Cb, and may be directly connected to the third separation section 18 C. Alternatively, for example, the outlet pipe 18Cb may be provided with a reservoir (tank) for storing the monomer D, and the inlet pipe 18Cd may be connected to the reservoir.

[0043] An inlet pipe 18Cf is connected to the third separation section 18C. The inlet pipe 18Cf is also connected to the dissolving section 12 and introduces the residual material R discharged from the third separation section 18C into the dissolving section 12. In the example shown in FIG. 2, the inlet pipe 18Cf branches off from the outlet pipe 18Cc. The inlet pipe 18Cf is provided with an adjustment section 18Cg that adjusts the amount of residual material R supplied from the third separation section 18C to the dissolving section 12. The adjustment section 18Cg is, for example, an on-off valve. When open, the adjustment section 18Cg allows the residual material R to be supplied to the dissolving section 12, and when closed, the adjustment section 18Cg stops the supply of the residual material R to the dissolving section 12. However, the adjustment section 18Cg is not limited to an on-off valve and may be any mechanism capable of adjusting the supply of the residual material R to the dissolving section 12. In this embodiment, the adjustment section 18Cg is provided at the point where the inlet pipe 18Cf branches off from the outlet pipe 18Cc, but the adjustment section 18Cg may be provided at any location. Furthermore, the inlet pipe 18Cf does not have to be connected to the outlet pipe 18Cc, and may be directly connected to the third separation section 18C.

[0044] For example, the discharge pipe 18Cc may be provided with a reservoir (tank) for storing the residual substance R, and the introduction pipe 18Cf may be connected to the reservoir. The introduction pipe 18Cf may also be provided with a filter that allows oligomers in the residual substance R to pass through while collecting foreign matter in the residual substance R.

[0045] 2, the inlet pipe 10a, the inlet pipe 18Cd, and the inlet pipe 18Cf connected to the dissolving section 12 are not connected to each other but are directly connected to the dissolving section 12. However, at least two of the inlet pipe 10a, the inlet pipe 18Cd, and the inlet pipe 18Cf may be connected (merged) and the connected pipe may be connected to the dissolving section 12.

[0046] In this embodiment, since the polyester solution P is a solution in which polyester is dissolved in monomer D, the monomer D is introduced into the dissolving section 12 via the inlet pipe 18Cd. However, if the polyester solution P is a solution in which polyester is dissolved in monomer E, the inlet pipe 18Cd may be connected to the second separation section 18B and the dissolving section 12. That is, in this case, the monomer E separated in the second separation section 18B is introduced into the dissolving section 12 via the inlet pipe 18Cd. A reservoir (tank) for storing the monomer E may be provided, and the inlet pipe 18Cd may be connected to the reservoir.

[0047] (Detection Unit) The detection unit 19 is a sensor that detects a parameter related to the concentration of a monomer contained in the second solvent M2 (a reaction solvent in which the depolymerized polyester is dissolved) containing the second depolymerized polyester P2. The parameter here refers to a parameter related to the concentration of the monomer contained in the second solvent M2. The detection unit 19 is provided at a position where this parameter can be detected. Note that the monomer contained in the second solvent M2 here is monomer D in this example, but may also refer to monomer E when the polyester solution P is produced with monomer E.

[0048] In this embodiment, the parameter detected by the detection unit 19 is the temperature of the separation unit 18. As the concentration of the monomer contained in the second solvent M2 increases, the temperature of the separation unit 18 increases. Therefore, the temperature of the separation unit 18 can be considered a parameter related to the concentration of the monomer contained in the second solvent M2. In this case, the detection unit 19 is a temperature sensor and is provided at a position where it can detect the temperature of the separation unit 18. Here, the temperature of the separation unit 18 may be the temperature of the outer wall of the separation unit 18 or the temperature inside the separation unit 18. The parameter detected by the detection unit 19 is preferably the temperature of the first separation unit 18A. By detecting the temperature of the first separation unit 18A, into which the second solvent M2 is introduced from the reaction unit 16, changes in the concentration of the monomer contained in the second solvent M2 can be quickly detected. Furthermore, the temperature of the lower part of the first separation unit 18A (a position below the center of the first separation unit 18A) is more preferably detected. By detecting the temperature of the lower part of the first separation unit 18A, the concentration of the monomer contained in the second solvent M2 can be more effectively detected.

[0049] The parameter detected by the detection unit 19 may be the concentration of the monomer contained in the second solvent M2 discharged from the reaction unit 16. In this case, the detection unit 19 is a concentration detection sensor and is provided in the discharge pipe 16a.

[0050] (Operation of Monomer Production System) Next, the operation of the monomer production system 1 will be described. The control unit 20 introduces the polyester raw material Pm, the monomer D, and the residual substance R into the dissolution unit 12 to produce a polyester solution P. The control unit 20 then introduces the polyester solution P and the reaction solvent M into the first reaction unit 16A to depolymerize them, extracting the first depolymerized polyester P1 into the reaction solvent M. The first solvent M1 from which the first depolymerized polyester P1 has been extracted is then introduced into the second reaction unit 16B, where the first depolymerized polyester P1 is further depolymerized to produce the second depolymerized polyester P2. The separation unit 18 then separates the second solvent M2 in which the second depolymerized polyester P2 has been dissolved into the reaction solvent M, the monomer D, the monomer E, and the residual substance R.

[0051] (Controller) Fig. 3 is a schematic block diagram of the controller. The controller 20 is a control device that controls the monomer production system 1, and is a computer in this embodiment. As shown in Fig. 3, the controller 20 includes an input unit 30, an output unit 32, a communication unit 34, a storage unit 36, and a processing unit 38.

[0052] The input unit 30 is a device that accepts user operations and may be, for example, a mouse, keyboard, or touch panel. The output unit 32 is a device that outputs information and may be, for example, a display that displays images. The input unit 30 and the output unit 32 are not essential components. The communication unit 34 is a module that communicates with external devices and may include, for example, an antenna. In this embodiment, the communication method used by the communication unit 34 is wireless communication, but the communication method may be any. The control unit 20 may be configured as a standalone device, may be configured integrally with other devices, or may be configured as a system combining various devices such as a computing device and a data server, and is not particularly limited.

[0053] The storage unit 36 ​​is a memory that stores various information such as the calculation contents and programs of the processing unit 38, and includes at least one of a main storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and an external storage device such as an HDD (Hard Disk Drive). The programs for the processing unit 38 saved in the storage unit 36 ​​may be stored in a recording medium that can be read by the control unit 20.

[0054] The processing unit 38 is an arithmetic device and includes an arithmetic circuit such as a CPU (Central Processing Unit). The processing unit 38 includes a detection control unit 40, an information acquisition unit 42, and a system control unit 44. The processing unit 38 reads and executes a program (software) from the storage unit 36, thereby realizing the detection control unit 40, the information acquisition unit 42, and the system control unit 44 and performing their processing. The processing unit 38 may perform these processes using a single CPU, or may be provided with multiple CPUs and perform the processes using the multiple CPUs. Furthermore, at least a portion of the detection control unit 40, the information acquisition unit 42, and the system control unit 44 may be realized by hardware.

[0055] The detection control unit 40 controls the detection unit 19 to detect parameters and acquires the detection results. The information acquisition unit 42 acquires information on the amount of polyester in the polyester raw material Pm introduced into the dissolution unit 12 (or the raw material storage unit 10). The system control unit 44 controls each mechanism of the monomer production system 1. For example, the system control unit 44 controls the adjustment unit 10b to control the amount of polyester raw material Pm supplied from the raw material storage unit 10 to the dissolution unit 12. The system control unit 44 controls the supply unit 12b to control the amount of polyester solution P supplied from the dissolution unit 12 to the first reaction unit 16A. The system control unit 44 controls the heating unit 12c to control the heating degree of the polyester solution P. The system control unit 44 controls the adjustment unit 14c to control the amount of reaction solvent M supplied from the solvent storage unit 14 to the first reaction unit 16A. The system control unit 44 controls the heating and pressurization unit 14b to bring the reaction solvent M into a supercritical state or a subcritical state (pressurized gas or pressurized liquid). The system control unit 44 controls the adjusting unit 18Ce to control the amount of monomer D supplied to the dissolving unit 12. The system control unit 44 controls the adjusting unit 18Cg to control the amount of remaining substance R supplied to the dissolving unit 12. The system control unit 44 controls the adjusting unit 18Bb to control the amount of reaction solvent M supplied to the solvent reservoir 14.

[0056] (Processing of the control unit) In this embodiment, the control unit 20 controls the monomer production system 1 based on at least one of the parameters detected by the detection control unit 40 and the amount of polyester in the polyester raw material Pm acquired by the information acquisition unit 42. It is preferable that the control unit 20 controls the monomer production system 1 based on both the parameters and the amount of polyester.

[0057] The specific processing contents of the control unit 20 will be described below. Note that the control unit 20 may perform at least one of the controls described below. However, it is preferable that the control unit 20 perform a combination of two or more of the controls described below, and more preferably perform all of the controls described below. In other words, it can be said that the control unit 20 preferably performs a combination of any two, any three, any four, any five, any six, any seven, or all eight of the first to eighth controls described below.

[0058] (Control of the Amount of Polyester Raw Material Pm Introduced) (First Control) The detection control unit 40 causes the detection unit 19 to detect a parameter (a parameter related to the concentration of the monomer contained in the second solvent M2). The system control unit 44 controls the amount of polyester raw material Pm introduced into the dissolving unit 12 based on the parameter detected by the detection unit 19. That is, the system control unit 44 determines the amount of polyester raw material Pm introduced into the dissolving unit 12 based on the parameter detected by the detection unit 19, and controls the adjustment unit 10b to supply polyester raw material Pm to the dissolving unit 12 so as to achieve the determined amount introduced. The system control unit 44 may determine the amount of polyester raw material Pm introduced using any method based on the parameter. For example, if the parameter indicates that the concentration of the monomer contained in the second solvent M2 is higher than a predetermined threshold, the system control unit 44 may determine that more monomer is being produced than expected and reduce the amount of polyester raw material Pm introduced. The parameter indicating that the monomer concentration is higher than the predetermined threshold means, for example, that the detected temperature of the separation unit 18 is higher than the predetermined threshold or that the detected monomer concentration itself is higher than the predetermined threshold. On the other hand, when the parameter indicates that the monomer concentration contained in the second solvent M2 is lower than the predetermined threshold, the system control unit 44 may increase the amount of polyester raw material Pm introduced, assuming that the amount of monomer produced is lower than expected.

[0059] In this way, by controlling the amount of polyester raw material Pm introduced into the dissolution section 12 based on a parameter related to the concentration of the monomer contained in the second solvent M2, it is possible to prevent the amount of monomer produced from deviating from the expected amount, and to appropriately produce the monomer. For example, the amount of monomer produced by the reaction in the reaction section 16 (the amount of monomer in the second solvent M2) may vary depending on the polyester purity in the polyester raw material Pm, the reaction state in the reaction section 16, etc. In contrast, by controlling the amount of polyester raw material Pm introduced based on the amount of monomer contained in the second solvent M2, it is possible to adjust the amount of polyester raw material Pm introduced depending on the state of monomer production, and therefore it is possible to appropriately produce the monomer.

[0060] (Second Control) The information acquisition unit 42 acquires information on the amount of polyester in the polyester raw material Pm. The amount of polyester in the polyester raw material Pm refers to the amount of polyester contained in the polyester raw material Pm (the amount of polyester contained relative to the weight of the polyester raw material Pm), but may also refer to the amount of impurities contained in the polyester raw material Pm (the amount of impurities contained relative to the weight of the polyester raw material Pm). The information acquisition unit 42 may acquire the amount of polyester using any method. For example, the amount of polyester in the polyester raw material Pm may be estimated based on the type of polyester raw material Pm supplied, and the information acquisition unit 42 may acquire the estimated amount of polyester in the polyester raw material Pm. Alternatively, the information acquisition unit 42 may calculate the amount of polyester in the polyester raw material Pm based on the type of polyester raw material Pm supplied. In this case, for example, a correspondence relationship between the type of polyester raw material Pm and the amount of polyester may be preset, and the information acquisition unit 42 may calculate the amount of polyester in the polyester raw material Pm based on this correspondence relationship and the type of polyester raw material Pm supplied. The system control unit 44 may control the amount of polyester raw material Pm introduced into the dissolving unit 12 based on the amount of polyester in the polyester raw material Pm. That is, the system control unit 44 determines the amount of polyester raw material Pm introduced into the dissolving unit 12 based on the amount of polyester in the polyester raw material Pm, and controls the adjustment unit 10b to supply the polyester raw material Pm to the dissolving unit 12 so that the determined amount is introduced. The system control unit 44 may determine the amount of polyester raw material Pm introduced using any method based on the amount of polyester in the polyester raw material Pm. For example, if the amount of polyester is higher than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is higher than expected and decrease the amount of polyester raw material Pm introduced. On the other hand, if the amount of polyester is lower than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is lower than expected and increase the amount of polyester raw material Pm introduced.

[0061] In this way, by controlling the amount of polyester raw material Pm introduced into the dissolving section 12 based on the amount of polyester in the polyester raw material Pm, it is possible to prevent deviations in the amount of monomer produced from expectations, and monomer can be produced appropriately. The amount of polyester in the polyester raw material Pm, i.e., the purity of the polyester, may vary depending on the type of polyester raw material Pm, and the amount of monomer produced may vary depending on the purity of the polyester, which may result in the failure to produce the expected amount of monomer. In contrast, by controlling the amount of polyester raw material Pm introduced based on the purity of the polyester, the amount of polyester raw material Pm introduced can be adjusted depending on the purity of the polyester, and monomer can be produced appropriately.

[0062] (Control of the Amount of Residual Substance Introduction) (Third Control) The system control unit 44 controls the amount of residual substance R supplied to the dissolution unit 12 based on the parameters detected by the detection unit 19. That is, the system control unit 44 determines the amount of residual substance R supplied to the dissolution unit 12 based on the parameters detected by the detection unit 19, and controls the adjustment unit 18Cg to supply the residual substance R to the dissolution unit 12 at the determined amount. The system control unit 44 may determine the amount of residual substance R introduced using any method based on the parameters. For example, if the parameter indicates that the concentration of the monomer contained in the second solvent M2 is higher than a predetermined threshold, the system control unit 44 may determine that more monomer is being produced than expected and decrease the amount of residual substance R supplied. On the other hand, if the parameter indicates that the concentration of the monomer contained in the second solvent M2 is lower than a predetermined threshold, the system control unit 44 may determine that less monomer is being produced than expected and increase the amount of residual substance R supplied. Because the residual substance R serves as a source of monomer, such control allows for appropriate control of the amount of monomer produced.

[0063] In this way, by controlling the amount of residual material R supplied to the dissolution section 12 based on a parameter related to the concentration of the monomer contained in the second solvent M2, deviations from the expected amount of monomer production can be suppressed, allowing for appropriate production of the monomer. In particular, in a system in which the residual material R is returned to the dissolution section 12, which is the upper stage, there is a risk that deviations from the expected amount of monomer production will be amplified, resulting in a large deviation from the expected amount of monomer production. In contrast, by controlling the amount of residual material R returned based on the amount of monomer contained in the second solvent M2, it is possible to suppress the amplification of deviations from the expected amount of monomer production, allowing for appropriate production of the monomer.

[0064] (Fourth Control) The system control unit 44 may control the amount of residual material R supplied to the dissolving unit 12 based on the amount of polyester in the polyester raw material Pm. That is, the system control unit 44 determines the amount of residual material R supplied to the dissolving unit 12 based on the amount of polyester in the polyester raw material Pm, and controls the adjustment unit 18Cg to supply the residual material R to the dissolving unit 12 to the determined amount. The system control unit 44 may determine the amount of residual material R supplied using any method based on the amount of polyester in the polyester raw material Pm. For example, if the amount of polyester is higher than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is higher than expected and decrease the amount of residual material R supplied. On the other hand, if the amount of polyester is lower than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is lower than expected and increase the amount of residual material R supplied.

[0065] In this way, by controlling the amount of residual substance R returned based on the amount of polyester in the polyester raw material Pm, the amount of residual substance R returned can be adjusted according to the purity of the polyester, thereby suppressing the amplification of control deviations and enabling appropriate production of monomers.

[0066] (Control of Reaction Solvent Supply Amount) (Fifth Control) The system control unit 44 controls the supply amount of reaction solvent M to the reaction unit 16 (first reaction unit 16A) based on the parameters detected by the detection unit 19. That is, the system control unit 44 determines the supply amount of reaction solvent M to the reaction unit 16 based on the parameters detected by the detection unit 19, and controls the adjustment unit 14c to supply the reaction solvent M to the reaction unit 16 so as to achieve the determined supply amount. The system control unit 44 may determine the supply amount of reaction solvent M using any method based on the parameters. For example, when the parameters indicate that the concentration of the monomer contained in the second solvent M2 is less than a predetermined threshold, the system control unit 44 may increase the supply amount of reaction solvent M, assuming that the amount of monomer produced is lower than expected.

[0067] In this way, by controlling the supply amount of reaction solvent M based on parameters related to the concentration of the monomer contained in the second solvent M2, it is possible to prevent the amount of monomer produced from deviating from the expected amount, and to produce the monomer appropriately.

[0068] (Sixth Control) The system control unit 44 may control the amount of reaction solvent M supplied to the reaction unit 16 (first reaction unit 16A) based on the amount of polyester in the polyester raw material Pm. That is, the system control unit 44 determines the amount of reaction solvent M supplied to the reaction unit 16 based on the amount of polyester in the polyester raw material Pm, and controls the adjustment unit 14c to supply the reaction solvent M to the reaction unit 16 to the determined amount. The system control unit 44 may determine the amount of reaction solvent M supplied using any method based on the amount of polyester in the polyester raw material Pm. For example, if the amount of polyester is higher than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is higher than expected and increase the amount of reaction solvent M supplied. On the other hand, if the amount of polyester is lower than a predetermined threshold, the system control unit 44 may determine that the purity of the polyester is lower than expected and decrease the amount of reaction solvent M supplied.

[0069] In this way, by controlling the supply amount of the reaction solvent M based on the amount of polyester in the polyester raw material Pm, it is possible to prevent the amount of monomer produced from deviating from the expected amount, and to appropriately produce the monomer.

[0070] (Control of the Amount of Reaction Solvent Introduction) (Seventh Control) The system control unit 44 controls the amount of reaction solvent M introduced from the separation unit 18 (second separation unit 18B) to the solvent reservoir 14 based on the parameters detected by the detection unit 19. That is, the system control unit 44 determines the amount of reaction solvent M introduced to the solvent reservoir 14 based on the parameters detected by the detection unit 19, and controls the adjustment unit 18Bb to supply the reaction solvent M to the solvent reservoir 14 so as to achieve the determined amount introduced. The system control unit 44 may determine the amount of reaction solvent M introduced using any method based on the parameters. For example, if the parameters indicate that the concentration of the monomer contained in the second solvent M2 is less than a predetermined threshold, the system control unit 44 may increase the amount of reaction solvent M introduced, assuming that the amount of monomer produced is lower than expected.

[0071] In this way, by controlling the amount of reaction solvent M returned based on a parameter related to the concentration of the monomer contained in the second solvent M2, it is possible to suppress the amplification of control deviations and appropriately produce the monomer.

[0072] (Eighth Control) The system control unit 44 may control the amount of reaction solvent M introduced from the separation unit 18 (second separation unit 18B) to the solvent reservoir 14 based on the amount of polyester in the polyester raw material Pm. That is, the system control unit 44 determines the amount of reaction solvent M to be introduced into the solvent reservoir 14 based on the amount of polyester in the polyester raw material Pm, and controls the adjustment unit 14c to supply the reaction solvent M to the solvent reservoir 14 to the determined supply amount. The system control unit 44 may determine the supply amount of reaction solvent M using any method based on the amount of polyester in the polyester raw material Pm. For example, if the amount of polyester is higher than a predetermined threshold, the system control unit 44 may increase the amount of reaction solvent M introduced, assuming that the purity of the polyester is higher than expected. On the other hand, if the amount of polyester is lower than a predetermined threshold, the system control unit 44 may decrease the amount of reaction solvent M introduced, assuming that the purity of the polyester is lower than expected.

[0073] In this way, by controlling the amount of reaction solvent M returned based on the amount of polyester in the polyester raw material Pm, it is possible to suppress the amplification of deviations in control and to appropriately produce the monomer.

[0074] As described above, the control unit 20 may perform at least one of the first to eighth controls described above. For example, among the second, fourth, sixth, and eighth controls based on the amount of polyester in the polyester raw material Pm, the control unit 20 preferably performs at least the fourth control (supply of residual substance R), and more preferably performs at least one of the sixth and eighth controls (supply of reaction solvent M) in addition to the fourth control. Furthermore, for example, among the first, third, fifth, and sixth controls based on the parameters detected by the detection unit 19, the control unit 20 preferably performs at least the first control (supply of polyester raw material Pm), more preferably performs the third control (supply of residual substance R) in addition to the fourth control, and even more preferably performs at least one of the sixth and eighth controls (supply of reaction solvent M) in addition to the fourth and third controls.

[0075] (Temperature and Pressure of Reaction Section) It is preferable that the system control section 44 does not perform control to change the temperature and pressure inside the reaction section 16 even when the parameters detected by the detection section 19 or the amount of polyester in the polyester raw material Pm fluctuate, but rather keeps the temperature and pressure inside the reaction section 16 within a constant range. This allows the reaction in the reaction section 16 to be carried out stably.

[0076] (Control by Machine Learning) Note that each of the controls described above may be performed using a model learned by machine learning. That is, the system control unit 44 may input an input value into a model that has learned the correspondence between input and output by machine learning, thereby obtaining an output value, and perform control based on the output value. This allows for highly accurate control and appropriate production of monomers. Note that the model used here may be any machine learning model, such as a CNN (Convolutional Neural Network) model.

[0077] For example, in the case of the first control described above, the system control unit 44 determines the supply amount of polyester raw material Pm by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between the parameters (input) and the amount of polyester raw material Pm introduced as output (output). In this case, it is preferable that the system control unit 44 uses the parameter fluctuation pattern (the parameter fluctuation pattern in a time series) as an input value. In this case, the system control unit 44 determines the supply amount of polyester raw material Pm by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between the parameter fluctuation pattern and the amount of polyester raw material Pm introduced. Using the parameter fluctuation pattern as an input may also be adopted in other control methods.

[0078] For example, in the case of the above-mentioned second control, the system control unit 44 determines the supply amount of polyester raw material Pm by inputting the amount of polyester acquired by the information acquisition unit 42 into a model that has learned the correspondence between the amount of polyester in the polyester raw material Pm (input) and the amount of polyester raw material Pm introduced (output).

[0079] For example, in the case of the above-mentioned third control, the system control unit 44 determines the supply amount of remaining material R by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between parameters (input) and the supply amount (output) of remaining material R.

[0080] For example, in the case of the above-mentioned fourth control, the system control unit 44 determines the supply amount of remaining material R by inputting the amount of polyester acquired by the information acquisition unit 42 into a model that has learned the correspondence between the amount of polyester (input) in the polyester raw material Pm and the supply amount of remaining material R (output).

[0081] For example, in the case of the above-mentioned fifth control, the system control unit 44 determines the supply amount of reaction solvent M by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between parameters (input) and the supply amount (output) of reaction solvent M.

[0082] For example, in the case of the sixth control described above, the system control unit 44 determines the supply amount of reaction solvent M by inputting the amount of polyester acquired by the information acquisition unit 42 into a model that has learned the correspondence between the amount of polyester (input) in the polyester raw material Pm and the supply amount of reaction solvent M (output).

[0083] For example, in the case of the above-mentioned seventh control, the system control unit 44 determines the amount of reaction solvent M introduced by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between the parameters (input) and the amount of reaction solvent M introduced (output).

[0084] For example, in the case of the above-mentioned eighth control, the system control unit 44 determines the amount of reaction solvent M introduced by inputting the amount of polyester acquired by the information acquisition unit 42 into a model that has learned the correspondence between the amount of polyester (input) in the polyester raw material Pm and the amount of reaction solvent M introduced (output).

[0085] (Control Flow) The control flow of the control unit 20 described above will now be described. Fig. 4 is a flowchart illustrating the control flow of the control unit. As shown in Fig. 4, the control unit 20 causes the detection control unit 40 to cause the detection unit 19 to detect parameters (step S10), the information acquisition unit 42 to acquire information on the amount of polyester in the polyester raw material Pm (step S12), and the system control unit 44 to control the monomer production system 1 based on at least one of the parameters and the amount of polyester (step S14). The control details of the system control unit 44 have been described above, so description thereof will be omitted.

[0086] (Effects) As described above, the monomer production system 1 according to the first aspect of the present disclosure includes a dissolving section 12 into which a polyester raw material Pm containing a polyester is introduced and which stores a polyester solution P in which the polyester is dissolved, a reaction section 16 into which the polyester solution P and a reaction solvent M that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution P to produce a reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved, a separation section 18 that separates the reaction solvent (second solvent M2) in which the depolymerized polyester is dissolved into a monomer and the reaction solvent M, a detection section 19 that detects a parameter related to the concentration of the monomer contained in the reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved, and a control section 20 that controls the amount of polyester raw material Pm introduced into the dissolving section 12 based on the parameter. According to the present disclosure, by controlling the amount of polyester raw material Pm introduced based on the amount of monomer contained in the second solvent M2, the amount of polyester raw material Pm introduced can be adjusted depending on the state of monomer production, thereby enabling appropriate monomer production.

[0087] A monomer production system 1 according to a second aspect of the present disclosure is the monomer production system 1 according to the first aspect, in which the detection unit 19 detects, as a parameter, the concentration of the monomer contained in the reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved. According to the present disclosure, the amount of polyester raw material Pm introduced can be adjusted depending on the state of monomer production, thereby enabling appropriate monomer production.

[0088] A monomer production system 1 according to a third aspect of the present disclosure is the monomer production system 1 according to the first aspect, in which the detection unit 19 detects, as a parameter, the temperature of the separation unit 18. According to the present disclosure, by adjusting the amount of polyester raw material Pm introduced according to the temperature of the separation unit 18, it is possible to appropriately produce monomers.

[0089] A monomer production system 1 according to a fourth aspect of the present disclosure is the monomer production system 1 according to any of the first to third aspects, wherein the separation unit 18 separates the second solvent M2 into monomer, reaction solvent M, and residual substance R, which is an oligomer different from the monomer and reaction solvent M, and further includes an adjustment unit 18Cg that supplies the residual substance R separated in the separation unit 18 to the dissolution unit 12, and the control unit 20 controls the amount of residual substance R supplied to the dissolution unit 12 by the adjustment unit 18Cg based on parameters. By controlling the amount of residual substance R returned based on the amount of monomer contained in the second solvent M2, it is possible to suppress the amplification of control deviation and appropriately produce monomer.

[0090] A monomer production system 1 according to a fifth aspect of the present disclosure is the monomer production system 1 according to any one of the first to fourth aspects, further including an adjustment unit 14c that supplies reaction solvent M to the reaction unit 16, and a control unit 20 that controls the amount of reaction solvent M supplied to the reaction unit 16 by the adjustment unit 14c based on a parameter. According to the present disclosure, by controlling the amount of reaction solvent M supplied based on a parameter related to the concentration of the monomer contained in the second solvent M2, it is possible to prevent the amount of monomer produced from deviating from the expected amount, and to appropriately produce the monomer.

[0091] A monomer production system 1 according to a sixth aspect of the present disclosure is the monomer production system 1 according to any one of the first to fifth aspects, and the control unit 20 preferably performs control also based on the amount of polyester contained in the polyester raw material. By performing control based on a parameter related to the concentration of the monomer contained in the second solvent M2 and the amount of polyester contained in the polyester raw material, the monomer can be appropriately produced.

[0092] A monomer production system 1 according to a seventh aspect of the present disclosure is the monomer production system 1 according to any one of the first to sixth aspects, in which the control unit 20 determines the amount of polyester raw material Pm to be introduced into the dissolving unit 12 by inputting the parameters detected by the detection unit 19 into a model that has learned the correspondence between the parameters and the amount of polyester raw material Pm introduced. By using the machine-learned model, control can be performed with high precision, and monomer can be produced appropriately.

[0093] A control method according to an eighth aspect of the present disclosure controls a monomer production system 1 having: a dissolving section 12 into which a polyester raw material Pm containing a polyester is introduced and which stores a polyester solution P in which the polyester is dissolved; a reaction section 16 into which the polyester solution P and a reaction solvent M that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution P to produce a reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved; and a separation section 18 that separates the reaction solvent (second solvent M2) in which the depolymerized polyester is dissolved into a monomer and the reaction solvent M. The control method includes the steps of detecting a parameter related to the concentration of the monomer contained in the reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved; and controlling the amount of polyester raw material Pm introduced into the dissolving section 12 based on the parameter. According to the present disclosure, by controlling the amount of polyester raw material Pm introduced based on the amount of monomer contained in the second solvent M2, the amount of polyester raw material Pm introduced can be adjusted depending on the state of monomer production, thereby enabling appropriate monomer production.

[0094] A program according to a ninth aspect of the present disclosure causes a computer to control a monomer production system 1 having: a dissolving section 12 into which a polyester raw material Pm containing a polyester is introduced and which stores a polyester solution P in which the polyester is dissolved; a reaction section 16 into which the polyester solution P and a reaction solvent M that reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution P to produce a reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved; and a separation section 18 that separates the reaction solvent (second solvent M2) in which the depolymerized polyester is dissolved into a monomer and the reaction solvent M. The program causes a computer to execute the following steps: detecting a parameter related to the concentration of the monomer contained in the reaction solvent M (second solvent M2) in which the depolymerized polyester is dissolved; and controlling the amount of polyester raw material Pm introduced into the dissolving section 12 based on the parameter. According to the present disclosure, by controlling the amount of polyester raw material Pm introduced based on the amount of monomer contained in the second solvent M2, the amount of polyester raw material Pm introduced can be adjusted depending on the state of monomer production, thereby enabling appropriate monomer production.

[0095] Although the embodiments of the present disclosure have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0096] REFERENCE SIGNS LIST 10 Reservoir 12 Dissolution section 14 Solvent reservoir 16 Reaction section 16A First reaction section 16B Second reaction section 18 Separation section 20 Control section D, E Monomer M Reaction solvent M1 First solvent M2 Second solvent P Polyester solution Pm Polyester raw material P1 First depolymerized polyester P2 Second depolymerized polyester

Claims

1. A monomer production system comprising: a dissolution section into which a polyester raw material containing a polyester is introduced and which stores a polyester solution in which the polyester is dissolved; a reaction section into which the polyester solution and a reaction solvent which reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved; a separation section which separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent; a detection section which detects a parameter relating to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved; and a control section which controls the amount of the polyester raw material introduced into the dissolution section based on the parameter.

2. The monomer production system according to claim 1, wherein the detection unit detects, as the parameter, a concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved.

3. The monomer production system according to claim 1, wherein the detection unit detects a temperature of the separation unit as the parameter.

4. A monomer production system as described in any one of claims 1 to 3, wherein the separation section separates the reaction solvent in which the depolymerized polyester is dissolved into monomers, the reaction solvent, and a residual substance which is an oligomer different from the monomer and the reaction solvent, and further has an adjustment section which supplies the residual substance separated in the separation section to the dissolution section, and the control section controls the amount of the residual substance supplied to the dissolution section by the adjustment section based on the parameters.

5. A monomer production system as described in any one of claims 1 to 3, further comprising an adjustment unit that supplies the reaction solvent to the reaction section, and the control unit controls the amount of the reaction solvent supplied to the reaction section by the adjustment unit based on the parameters.

6. The monomer production system according to any one of claims 1 to 3, wherein the control unit also performs control based on the amount of the polyester contained in the polyester raw material.

7. A monomer production system as described in any one of claims 1 to 3, wherein the control unit determines the amount of polyester raw material to be introduced into the dissolution unit by inputting the parameters detected by the detection unit into a model that has learned the correspondence between the parameters and the amount of polyester raw material introduced.

8. A control method for a monomer production system having a dissolution section into which a polyester raw material containing a polyester is introduced and a polyester solution in which the polyester is dissolved is stored, a reaction section into which the polyester solution and a reaction solvent which reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved, and a separation section which separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent, the control method comprising: a step of detecting a parameter related to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved; and a step of controlling an amount of the polyester raw material introduced into the dissolution section based on the parameter.

9. A program causing a computer to execute a control method for a monomer production system having: a dissolution section into which a polyester raw material containing a polyester is introduced and a polyester solution in which the polyester is dissolved is stored; a reaction section into which the polyester solution and a reaction solvent which reacts with the polyester are introduced and which depolymerizes the polyester in the polyester solution to produce a reaction solvent in which the depolymerized polyester is dissolved; and a separation section which separates the reaction solvent in which the depolymerized polyester is dissolved into a monomer and the reaction solvent, the program causing a computer to execute the steps of: detecting a parameter related to the concentration of the monomer contained in the reaction solvent in which the depolymerized polyester is dissolved; and controlling the amount of the polyester raw material introduced into the dissolution section based on the parameter.

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