Reactor and monomer production system

Abstract

The present invention suppresses reduction in the yield of a monomer. A reactor according to the present invention depolymerizes a polyester upon introduction of the polyester and a reaction solvent that reacts with the polyester. The reactor has a reaction unit comprising: a circulation section having a plurality of first flow paths that extend from an introduction port through which is introduced a reaction solvent from which a first depolymerized polyester, which is a polyester that has been depolymerized, has been extracted, to a lead-out port from which is led out a reaction solvent from which a second depolymerized polyester, which is obtained by further depolymerizing the first depolymerized polyester, has been extracted; and a resistor that is provided at a position so as to cover the lead-out port of the circulation section and forms a second flow path through which the reaction solvent that flows through the first flow paths circulates. The resistor has a pressure loss higher than that of the circulation section.

Description

Reactor and monomer production system

[0001] The present disclosure relates to a reactor and a monomer production system.

[0002] In polyester recycling, a technique for monomerizing polyester by depolymerization (a reverse reaction of polymerization) is known. Patent Document 1 describes a reaction vessel having a first reaction section in which a polyester raw material is reacted with a reaction solvent, and a second reaction section in which the low-molecular-weight polyester obtained in the first reaction section is further reacted with the reaction solvent from which the monomer has been extracted to monomerize the polyester. Patent Document 1 also describes that providing a rectifying means for rectifying the reaction solvent in the second reaction section can prevent uneven flow of the reaction solvent.

[0003] Japanese Patent Application Laid-Open No. 2005-289826

[0004] However, in the second reaction section, uneven temperature distribution of the reaction solvent may cause convection, shortening the residence time of the reaction solvent and potentially reducing the yield of the monomer.

[0005] An object of the present disclosure is to provide a reactor and a monomer production system that can suppress a decrease in monomer yield.

[0006] The reactor according to the present disclosure is a reactor into which a polyester and a reaction solvent that reacts with the polyester are introduced and which depolymerizes the polyester, the reactor comprising a circulating section having a plurality of first flow paths extending from an inlet into which the reaction solvent is introduced, from which a first depolymerized polyester, which is the depolymerized polyester, has been extracted, to an outlet from which the reaction solvent is extracted, from which a second depolymerized polyester, which is the first depolymerized polyester, has been further depolymerized, is extracted, and a resistor that is disposed at a position to block the outlet of the circulating section and forms a second flow path through which the reaction solvent that flows through the first flow paths circulates, and the resistor has a higher pressure loss than the circulating section.

[0007] The monomer production system according to the present disclosure includes the reactor and a separation unit connected to the reactor and configured to separate the reaction solvent in which the second depolymerized polyester is dissolved into the reaction solvent, a monomer derived from a carboxylic acid contained in the second depolymerized polyester, and a monomer of an alcohol component contained in the second depolymerized polyester.

[0008] According to the present disclosure, a decrease in the yield of the monomer can be suppressed.

[0009] 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 diagram of a second reaction section. Fig. 4 is a schematic top view of a circulation section.

[0010] 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.

[0011] (Recycling Process) FIG. 1 is a schematic diagram of the polyester recycling process in this embodiment. In this embodiment, the polyester raw material Pm is depolymerized to form monomers, and the monomers are then repolymerized to recycle (regenerate) the polyester raw material Pm. Specifically, as shown in FIG. 1 , the polyester raw material Pm is flaked (step S100), the flaked polyester raw material Pm is dissolved in a carboxylic acid-derived monomer D to produce a polyester solution (step S101), foreign matter is removed from the polyester solution (step S102), the polyester solution from which the foreign matter has been removed is mixed with a reaction solvent M for depolymerization (step S103), the depolymerized polyester monomer is purified (separated) to produce a carboxylic acid-derived monomer D and an alcohol component monomer E (step S104), the monomer D is hydrolyzed to separate the reaction solvent M (step S106), and the monomer F produced by hydrolysis of the monomer D is polymerized with the monomer E (step S108), thereby regenerating the 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.

[0012] (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.

[0013] (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.

[0014] (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).

[0015] (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).

[0016] 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.

[0017] (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 dissolving section 12, a solvent storage section 14, a reactor 16, a separation section 18, and a control section 19.

[0018] (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.

[0019] (Dissolving Section) The dissolving section 12 is a tank in 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 discharged into the reactor 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.

[0020] 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.

[0021] 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.

[0022] (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 reactor 16 via an inlet pipe 14a. The reaction solvent M in the solvent reservoir 14 is supplied to the reactor 16 through the inlet pipe 14a. More specifically, the inlet pipe 14a is provided with a heating and pressurizing section 14b that pressurizes and heats the reaction solvent M. The heating and pressurizing 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 solvent M in a supercritical state or a subcritical state (pressurized gas or pressurized liquid) is supplied to the reactor 16.

[0023] (Reactor) The reactor 16 is a mechanism into which polyester and a reaction solvent M that reacts with the polyester are introduced to depolymerize the polyester. Specifically, the reactor 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 reactor 16 includes a first reaction section 16A as a pre-reaction section and a second reaction section 16B as a reaction section. Hereinafter, within the reactor 16, the direction from the first reaction section 16A toward the second reaction section 16B is referred to as direction Y1, and the direction opposite to direction Y1 (the direction from the second reaction section 16B toward the first reaction section 16A) is referred to as direction Y2. In this embodiment, direction Y2 is the direction of gravity (vertically downward).

[0024] (First Reaction Section) The first reaction section 16A is formed in the reactor 16. In this embodiment, the first reaction section 16A can be said to be a portion of the reactor 16 that is filled with a packing material. A known packing material used in gas-liquid or liquid-liquid contactors can be used as the packing material in the first reaction section 16A, such as a packing material similar to that used in a contactor that brings heavy oil and water into contact to extract an active ingredient. Specific examples of packing materials include pipes made of stainless steel or the like, Raschig rings, Berl saddles, and Terralets.

[0025] 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 reactor 16 on the direction Y1 side of the surface 16A1 of the first reaction section 16A.

[0026] An inlet pipe 14a is connected to the reactor 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 reactor 16. The inlet 16D is connected closer to the Y2 direction than the surface 16A2 on the Y2 side of the first reaction unit 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 unit 16A. However, this is not limited thereto. For example, the inlet 16D may be directly connected to the first reaction unit 16A or may be connected to the surface 16A2 of the first reaction unit 16A.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] (Second Reaction Section) The second reaction section 16B is provided in the reactor 16 at a location where the first solvent M1 is discharged from the first reaction section 16A. In this embodiment, the second reaction section 16B is provided on the first direction D1 side of the first reaction section 16A.

[0031] 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.

[0032] 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.

[0033] The detailed structure of the second reactor 16B will be described later.

[0034] A discharge pipe 16b is connected to the bottom (the bottom surface on the direction Y2 side) of the reactor 16. More specifically, a discharge port 16F, which is an opening of the discharge pipe 16b through which the non-extractable material in the reactor 16 is discharged, is connected to the bottom of the reactor 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 reactor 16 is discharged from the discharge port 16F through the discharge pipe 16b to the outside of the reactor 16. The non-extractable material discharged from the discharge pipe 16b can be said to be components of the polyester solution P that were not led to the separation section 18 as the second solvent M2 (reaction solvent M containing the second depolymerized polyester P2) and remained in the first reaction section 16A and the second reaction section 16B.

[0035] The reactor 16 may be provided with a heating unit that heats the inside of the reactor 16 and a pressurizing unit that maintains the pressure inside the reactor 16 at a predetermined value or higher. The temperature inside the reactor 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 reactor 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 unit and the heating unit may be controlled by the control unit 19.

[0036] (Separation Section) The separation section 18 is introduced with a second solvent M2 containing a second depolymerized polyester P2, and separates the second solvent M2 into a 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 an oligomer.

[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 reaction solvent M and 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. 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] (Control Unit) The control unit 19 is a control device that controls the monomer production system 1. The control unit 19 controls the adjusting unit 10b to control the amount of polyester raw material Pm supplied from the raw material storage unit 10 to the dissolving unit 12. The control unit 19 controls the supply unit 12b to control the amount of polyester solution P supplied from the dissolving unit 12 to the first reaction unit 16A. The control unit 19 controls the heating unit 12c to control the heating degree of the polyester solution P. The control unit 19 controls the heating and pressurizing unit 14b to bring the reaction solvent M to a supercritical state or subcritical state (pressurized gas or pressurized liquid) and controls the amount of reaction solvent M in the supercritical state or subcritical state (pressurized gas or pressurized liquid) supplied to the reactor 16. The control unit 19 controls the adjusting unit 18Ce to control the amount of monomer D supplied to the dissolving unit 12. The control unit 19 controls the adjusting unit 18Cg to control the amount of residual material R supplied to the dissolving unit 12.

[0047] In this embodiment, the control unit 19 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 contents of calculations performed by the processor and programs. The control unit 19 executes control of the monomer production system 1 by reading out the programs from the storage unit.

[0048] However, the monomer production system 1 is not limited to being automatically controlled by the control unit 19, and for example, at least a part of the processing may be controlled by the operation of an operator.

[0049] (Operation of Monomer Production System) Next, the operation of the monomer production system 1 will be described. The control unit 19 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 19 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.

[0050] (Configuration of Second Reaction Section) Next, the configuration of the second reaction section 16B will be described. Fig. 3 is a schematic diagram of the second reaction section. As shown in Fig. 3, the second reaction section 16B has a circulating section 20 and a resistor 30.

[0051] (Circulation Section) The circulation section 20 is a member having a plurality of first flow paths 22 extending from an inlet 22a to an outlet 22b. The inlet 22a is an opening on the Y2-direction side of the first flow paths 22, and the outlet 22b is an opening on the Y1-direction side of the first flow paths 22. The first flow paths 22 are flow paths that connect the inlet 22a and the outlet 22b, and in this embodiment, extend along the Y1 direction from the inlet 22a to the outlet 22b. That is, the circulation section 20 extends along the Y1 direction. The first flow paths 22 are arranged side by side in a direction perpendicular to the Y1 direction (Y2 direction). That is, the inlet 20a, which is an opening on the Y1-direction side of the circulation section 20, is constituted by the inlets 22a of the respective first flow paths 22, and the outlet 20b, which is an opening on the Y2-direction side of the circulation section 20, is constituted by the outlet 22b of the respective first flow paths 22. The number and size of the first flow paths 22 may be arbitrary.

[0052] FIG. 4 is a schematic top view of the flow section. As shown in FIG. 4 , in this embodiment, the flow section 20 has an outer pipe 24 and multiple inner pipes 26. The outer pipe 24 is a tubular member extending in the Y1 direction. In this embodiment, the side wall of the reactor 16 constitutes the outer pipe 24, but the outer pipe 24 may be provided inside the side wall of the reactor 16. The inner pipe 26 is a tubular member provided inside the outer pipe 24 and extending in the Y1 direction. The inner pipes 26 are arranged side by side in a direction perpendicular to the Y1 direction (Y2 direction). In this embodiment, the space inside each inner pipe 26 and the space surrounded by the inner wall of the outer pipe 24 and the outer wall of the inner pipe 26 form the first flow path 22. The number and arrangement of the inner pipes 26 are not limited to the example in FIG. 4 and may be arbitrary.

[0053] The first solvent M1 containing the first depolymerized polyester P1 discharged from the first reaction section 16A is introduced into each of the first flow paths 22 from the inlet 20a of the circulation section 20 (the inlet 22a of each of the first flow paths 22). The first solvent M1 introduced into the first flow paths 22 flows toward the outlet 20b of the circulation section 20 (the outlet 22b of each of the first flow paths 22), and the first depolymerized polyester P1 contained in the first solvent M1 is further depolymerized by the reaction solvent M, and the second solvent M2 containing the second depolymerized polyester P2 is discharged from the outlet 20b (the outlet 22b of each of the first flow paths 22).

[0054] (Resistor) The resistor 30 is a component through which the second solvent M2 flows in the circulating portion 20 (first flow path 22) and has a higher pressure loss than the circulating portion 20. A high pressure loss means that the pressure loss of the fluid is higher than that of a comparison target when the same flow rate of fluid is flowed. In other words, when a fluid is introduced into the end face 30a of the resistor 30 and discharged from the end face 30b, the pressure loss of the fluid is higher than the pressure loss when the same amount of fluid is introduced into the inlet 20a of the circulating portion 20 and discharged from the outlet 20b. Note that the resistor 30 preferably has a higher pressure loss than the first reaction portion 16A.

[0055] The resistor 30 is provided at a position where it blocks the outlet 20b of the circulating portion 20. The position where it blocks the outlet 20b refers to a position between the inlet 20a and the outlet 20b in the circulating portion 20, or a position where it covers the outlet 20b that opens in the direction Y1. The resistor 30 may be provided at any position where it blocks the outlet 20b of the circulating portion 20, but in the present embodiment, it is provided at a position facing the outlet 20b of the circulating portion 20 (a position where it covers the outlet 20b). That is, the resistor 30 is placed on the Y1-direction end face of the circulating portion 20 (the Y1-direction ends of the inner tube 26 and the outer tube 24 in this example) and is in contact with the Y1-direction end face of the circulating portion 20. However, the present invention is not limited thereto, and the resistor 30 may be provided inside the first flow path 22 of the circulating portion 20.

[0056] Moreover, the resistor 30 preferably blocks the outlets 22b of all the first flow paths 22 of the circulating portion 20. That is, the resistor 30 is preferably provided so as to block the entire area of ​​the outlets 20b of the circulating portion 20 (the entire area of ​​the outlets 22b of all the first flow paths 22).

[0057] The resistor 30 is formed with a second flow path 32 through which the second solvent M2 flowing through the first flow path 22 flows. That is, by forming the second flow path 32, the resistor 30 increases the pressure loss of the second solvent M2 while allowing the second solvent M2 to flow. The second flow path 32 is a flow path that connects an end face 30a of the resistor 30 on the Y2 direction side with an end face 30b of the resistor 30 on the Y1 direction side. A plurality of second flow paths 32 are provided within the resistor 30.

[0058] The second flow path 32 may have any shape that connects the end face 30a and the end face 30b while increasing the pressure loss of the second solvent M2 compared to the flow section 20. For example, the second flow path 32 preferably extends from the opening on the end face 30b side to the opening on the end face 30a side so as not to extend along the Y1 direction. For example, if the length in the Y1 direction from the end face 30b to the end face 30a is length L, the flow path length from the opening on the end face 30b side of the second flow path 32 to the opening on the end face 30a side is preferably longer than the length of the first flow path 22 in the section of length L in the Y1 direction. This allows the pressure loss of the resistor 30 to be appropriately increased.

[0059] The resistor 30 may be any structure in which the second flow path 32 is formed, such as a porous body or a mesh structure, and a sintered filter is preferably used.

[0060] The pressure loss of the resistor 30 is preferably 50 Pa or more, more preferably 75 Pa or more and 125 Pa or less. The ratio of the pressure loss of the resistor 30 to the pressure loss of the flow section 20 is preferably 110% or more, more preferably 200% or more. When the pressure loss of the resistor 30 is within this range, acceleration of the flow of the first solvent M1 and the second solvent M2 can be appropriately suppressed, thereby appropriately suppressing a decrease in the monomer yield. The pressure loss of the resistor 30 can be measured by measuring the difference between the fluid pressure at the end face 30 a (the inlet of the second flow path 32) and the fluid pressure at the end face 30 b (the outlet of the second flow path 32) when air in a standard state as a fluid is introduced into the resistor 30 from the end face 30 a at a linear velocity of 2.3 mm / sec.

[0061] The ratio of the length of the resistor 30 in the Y1 direction (the length in the Y1 direction from the end face 30a to the end face 30b) to the length of the flow section 20 in the Y1 direction (the length in the Y1 direction from the inlet 20a to the outlet 20b) is preferably 0.0005% or more, and more preferably 0.005% or more. Furthermore, the ratio of the length in the Y1 direction of the second reaction section 16B to the length in the Y1 direction of the first reaction section 16A is preferably 50% to 200%, and more preferably 100% to 150%. By setting the lengths (heights) in the Y1 direction of the resistor 30 and the second reaction section 16B within this range, depolymerization can be performed appropriately, and a decrease in the monomer yield can be appropriately suppressed.

[0062] (Effects) The reactor 16 according to the first aspect of the present disclosure is adapted to receive a polyester and a reaction solvent M that reacts with the polyester and depolymerize the polyester. The reactor 16 has a reaction section (second reaction section 16B) including a circulating section 20 and a resistor 30. The circulating section 20 has a plurality of first flow paths 22 extending from an inlet 20a through which a reaction solvent (first solvent M1) is introduced, from which a first depolymerized polyester P1, which is a depolymerized polyester, has been extracted, to an outlet 20b through which a reaction solvent (second solvent M2) is extracted, which is a second depolymerized polyester P2, which is a further depolymerized first depolymerized polyester P1, has been extracted. The resistor 30 is positioned to block the outlet 20b of the circulating section 20, and a second flow path 32 is formed through which the reaction solvent (second solvent M2) flowing through the first flow path 22 flows. The resistor 30 has a higher pressure loss than the circulating section 20.

[0063] In the reactor 16 of the present disclosure, the second reaction section 16B has a structure including a flow section 20 having multiple first flow paths 22. This allows the first solvent M1 flowing through the second reaction section 16B to be rectified, thereby enabling appropriate depolymerization of the polyester and suppressing a decrease in the monomer yield. Furthermore, the inventors discovered through extensive research that convection of the first solvent M1 in the flow section 20 locally accelerates the flow of the first solvent M1, shortening the residence time of some of the first solvent M1. A shortened residence time of the first solvent M1 results in insufficient time for depolymerization, resulting in a decrease in the monomer yield. In contrast, in the present disclosure, a resistor 30 is provided at a position blocking the outlet 20b of the flow section 20, thereby suppressing the acceleration of the first solvent M1 and suppressing a shortened residence time. Therefore, the present disclosure allows appropriate suppression of a decrease in the monomer yield.

[0064] A reactor 16 according to a second aspect of the present disclosure is the reactor 16 according to the first aspect, and preferably, the resistor 30 blocks the outlets 22 b of all of the first flow paths 22 in the circulation section 20. Here, the position where convection of the first solvent M1 occurs and accelerates in the circulation section 20 may vary depending on the external environment, etc. In contrast, by providing the resistor 30 at a position where the resistor 30 blocks the outlets 22 b of all of the first flow paths 22, even if the position where the first solvent M1 is accelerated varies, acceleration can be appropriately suppressed, and a decrease in the monomer yield can be appropriately suppressed.

[0065] The reactor 16 according to a third aspect of the present disclosure is the reactor 16 according to the first or second aspect, and the resistor 30 is preferably provided at a position facing the outlet 20b of the flow section 20. By providing the resistor 30 at such a position, it is not necessary to insert the resistor 30 inside the first flow path 22, which simplifies the structure and assembly work of the resistor 30. Furthermore, by not inserting the resistor 30 inside the first flow path 22, the flow can be properly rectified, and a decrease in the yield of the monomer can be suppressed.

[0066] A reactor 16 according to a fourth aspect of the present disclosure is the reactor 16 according to any one of the first to third aspects, and preferably further includes a pre-reaction section (first reaction section 16A). A polyester solution P having a polyester dissolved therein and a reaction solvent M are introduced into the first reaction section 16A, and the polyester solution P is brought into contact with the reaction solvent M to depolymerize the polyester in the polyester solution P, and a first depolymerized polyester P1 containing the depolymerized polyester is extracted into the reaction solvent M. This allows the polyester to be appropriately depolymerized, thereby suppressing a decrease in the monomer yield.

[0067] The reactor 16 according to a fifth aspect of the present disclosure is the reactor 16 according to the fourth aspect, and preferably the resistor 30 has a higher pressure loss than the first reaction section 16A, thereby making it possible to appropriately suppress a decrease in the yield of the monomer.

[0068] A reactor 16 according to a sixth aspect of the present disclosure is the reactor 16 according to any one of the first to fifth aspects, in which the polyester is preferably polyethylene terephthalate and the reaction solvent M is preferably methanol. According to the present disclosure, PET can be appropriately monomerized.

[0069] A monomer production system 1 according to a seventh aspect of the present disclosure includes a reactor 16 according to any one of the first to sixth aspects, and a separation unit 18 connected to the reactor 16 and configured to separate a reaction solvent (second solvent M2) in which a second depolymerized polyester P2 is dissolved into the reaction solvent M, a monomer D derived from a carboxylic acid contained in the second depolymerized polyester, and a monomer C of an alcohol component contained in the second depolymerized polyester. According to the present disclosure, a decrease in the yield of the monomers can be appropriately suppressed.

[0070] 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.

[0071] REFERENCE SIGNS LIST 10 Reservoir 12 Dissolution section 14 Solvent reservoir 16 Reactor 16A First reaction section (pre-reaction section) 16B Second reaction section (reaction section) 18 Separation 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 reactor into which a polyester and a reaction solvent that reacts with the polyester are introduced to depolymerize the polyester, the reactor comprising: a circulation section having a plurality of first flow paths extending from an inlet into which the reaction solvent from which a first depolymerized polyester, which is the depolymerized polyester, is introduced to an outlet from which the reaction solvent from which a second depolymerized polyester, which is the first depolymerized polyester, is extracted, is discharged; and a resistor that is provided at a position to block the outlet of the circulation section, and that forms a second flow path through which the reaction solvent flowing through the first flow paths is circulated, the resistor having a higher pressure loss than the circulation section.

2. The reactor according to claim 1, wherein the resistor blocks the outlets of all of the first flow paths in the circulation section.

3. The reactor according to claim 1 or 2, wherein the resistor is provided at a position facing the outlet of the flow section.

4. The reactor according to claim 1 or 2, further comprising a pre-reaction section into which a polyester solution having the polyester dissolved therein and the reaction solvent are introduced, the polyester solution is brought into contact with the reaction solvent, the polyester in the polyester solution is depolymerized, and the first depolymerized polyester containing the depolymerized polyester is extracted into the reaction solvent.

5. The reactor according to claim 4, wherein the resistor has a higher pressure loss than the pre-reaction section.

6. The reactor according to claim 1 or 2, wherein the polyester is polyethylene terephthalate and the reaction solvent is methanol.

7. A monomer production system comprising: the reactor according to claim 1 or 2; and a separation section connected to the reactor for separating the reaction solvent in which the second depolymerized polyester is dissolved into the reaction solvent, a monomer derived from a carboxylic acid contained in the second depolymerized polyester, and a monomer of an alcohol component contained in the second depolymerized polyester.

Images