Device and method for recycling polyester glycol alcoholysis solution

Abstract

The invention relates to the technical field of cyclic utilization of polyester glycol alcoholysis solution, and discloses a device and a method for cyclic utilization of polyester glycol alcoholysis solution, the device comprises a buffer tank V1, a rectifying tower T1, a rectifying tower condenser E2 and a rectifying tower return tank V2 which are connected in sequence; and the vacuum tower T2 is connected with the rectifying tower T1. According to the method, ethylene glycol and water can be effectively recycled, recycling of the solvent is achieved, the PET recovery rate is increased, the use amount of ethylene glycol is greatly reduced, and wastewater discharge is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of recycling polyester glycol alcoholysis solution, specifically to an apparatus and method for recycling polyester glycol alcoholysis solution. Background Technology

[0002] PET (Polyester Petroleum) is the world's most widely used polyester material. Its excellent physical and chemical properties lead to its widespread use in single-purpose or multi-purpose products such as food and beverage containers, resulting in significant environmental pressure and a large amount of waste PET urgently needing recycling. Among the chemical degradation methods for PET, alcoholysis is a more mature process compared to other chemical recycling methods. Through years of continuous theoretical analysis and practice, the alcoholysis process has been gradually improved, and several companies now have industrial-scale facilities. Industrially, alcoholysis is mainly divided into methanol alcoholysis and ethylene glycol alcoholysis. Methanol alcoholysis refers to the breaking of ester bonds in PET in a methanol reaction atmosphere, producing dimethyl terephthalate (DMT). DMT can be used as a monomer for the repolymerization of PET and PBT.

[0003] The ethylene glycol alcoholysis process has a simple reaction route, is not demanding in terms of temperature and pressure, and is relatively easy to design and implement. It also offers a higher safety factor, making it suitable for industrial-scale production and maximizing economic benefits. Furthermore, the ethylene glycol alcoholysis route does not contain corrosive substances, reducing pollution emissions and lowering equipment maintenance costs. From a practical perspective, the monomer ethylene glycol terephthalate (BHET) produced by this route can be directly fed into the polymerization process and integrated into conventional PET production facilities without pretreatment or the generation of other byproducts.

[0004] To address the issues of low depolymerization efficiency and incomplete depolymerization in existing chemical recycling processes for waste PET, research has been conducted on novel green and efficient depolymerization technologies. However, the recrystallization process consumes a large amount of ethylene glycol and water, making it urgent to develop technologies for the recycling of ethylene glycol hydrolysate to achieve circular utilization. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low depolymerization efficiency and incomplete depolymerization in existing chemical recycling processes for waste PET, as well as the large amount of ethylene glycol and water used in the recrystallization process of depolymerization technology. This invention provides an apparatus and method for recycling polyester ethylene glycol alcoholysis solution. This method can effectively recover and recycle ethylene glycol and water, realize the recycling of solvents, improve PET recovery rate, and reduce the consumption of ethylene glycol and water, thereby reducing wastewater discharge.

[0006] To achieve the above objectives, the first aspect of the present invention provides an apparatus for recycling polyester glycol alcoholysis liquid, wherein the apparatus comprises: a buffer tank V1, a distillation column T1, a distillation column condenser E2, and a distillation column reflux tank V2 connected in sequence; and a pressure reducing column T2 connected to the distillation column T1.

[0007] A second aspect of the present invention provides a method for recycling polyester glycol alcoholysis solution using the aforementioned apparatus, wherein the method comprises:

[0008] (1) The alcoholysis liquid S1 of polyester ethylene glycol is distilled through buffer tank V1 and then through distillation column feed pump P1 to distill the alcoholysis liquid S2, and the alcoholysis liquid S3 after passing through distillation column feed pump P1 is fed into distillation column T1.

[0009] (2) The top gas S4 from the top outlet of distillation column T1 is cooled by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0010] (3) The bottom liquid S6 of the distillation column T1 enters the lower part of the vacuum column T2 for vacuum distillation. The top gas S8 of the vacuum column T2 is condensed by the vacuum column condenser E4 and then enters the vacuum column reflux tank V3. All the liquid phase condensed in the vacuum column reflux tank V3 is refluxed.

[0011] (4) The recovered ethylene glycol S10 obtained from the bottom of the vacuum distillation tower T2 is pumped to the depolymerization unit for recycling via the vacuum distillation tower bottom pump P4.

[0012] Through the above technical solution, the method of the present invention can effectively recycle ethylene glycol and water. The treated ethylene glycol and water meet the reuse requirements while realizing the recycling of raw materials and significantly reducing wastewater discharge. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the recycling of polyester glycol alcoholysis solution according to the present invention.

[0014] Explanation of reference numerals in the attached figures

[0015] V1 Buffer Tank, T1 Distillation Column, V2 Distillation Column Reflux Tank, E1 Distillation Column Reboiler, E2 Distillation Column Condenser, P1 Distillation Column Feed Pump, P2 Vacuum Distillation Column Feed Pump, P3 Distillation Column Top Discharge Pump, T2 Vacuum Distillation Column, V3 Vacuum Distillation Column Reflux Tank, E3 Vacuum Distillation Column Reboiler, E4 Vacuum Distillation Column Condenser, E5 Vacuum Condenser, C1 Vacuum System, P4 Vacuum Distillation Column Bottom Discharge Pump, P5 Mixture Pump;

[0016] S1, S2, and S3 polyester glycol alcoholysis solutions;

[0017] S4 distillation column overhead gas;

[0018] S5 recycled water;

[0019] S6 and S7 distillation column bottom liquid

[0020] S8 pressure reducing tower top gas

[0021] S9 Mixture

[0022] S10 and S11 recover ethylene glycol. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] As mentioned above, in order to achieve the above objectives, the first aspect of the present invention provides an apparatus for recycling polyester glycol alcoholysis liquid, wherein the apparatus comprises: a buffer tank V1, a distillation column T1, a distillation column condenser E2, and a distillation column reflux tank V2 connected in sequence; and a pressure reducing column T2 connected to the distillation column T1.

[0025] The inventors of this invention discovered that by using a dual-tower process (distillation tower T1 and vacuum tower T2) in combination, the treated ethylene glycol and water meet the requirements for reuse while achieving solvent recycling, improving PET recovery rate, significantly reducing ethylene glycol consumption, and reducing wastewater discharge.

[0026] According to the present invention, in a preferred embodiment, the apparatus further includes: a buffer tank V1, a distillation column feed pump P1, a distillation column T1, a distillation column condenser E2, a distillation column reflux tank V2, and a distillation column top outlet pump P3, which are connected in sequence; and a vacuum distillation column feed pump P2 and a vacuum distillation column T2, which are connected in sequence to the distillation column T1.

[0027] According to the present invention, in a preferred embodiment, a distillation column condenser E2 and a distillation column reflux tank V2 are provided at the top of the distillation column T1.

[0028] According to the present invention, in a preferred embodiment, the bottom of the distillation column reflux tank V2 is connected to the distillation column top pump P3.

[0029] According to the present invention, in a preferred embodiment, the bottom outlet of the distillation column T1 is connected to the vacuum column T2 via a vacuum column feed pump P2.

[0030] According to the present invention, in a preferred embodiment, a distillation column reboiler E1 is also provided on the bottom reboiler outlet pipeline of the distillation column T1.

[0031] According to the present invention, the top of the pressure reducing tower T2 is provided with a pressure reducing tower condenser E4, a pressure reducing tower reflux tank V3, a vacuum condenser E5 and a vacuum system C1 connected in sequence; preferably, the pressure reducing tower condenser E4 is connected to the top of the pressure reducing tower reflux tank V3; the vacuum condenser E5 is connected to the top of the pressure reducing tower reflux tank V3.

[0032] According to the present invention, the bottom of the pressure reducing tower reflux tank V3 is connected to the mixing pump P5.

[0033] According to the present invention, the bottom outlet pipeline of the pressure reducing tower T2 is connected to the bottom pump P4 of the pressure reducing tower.

[0034] According to the present invention, a reboiler E3 is also provided on the bottom outlet pipeline of the pressure reducing tower T2.

[0035] A second aspect of the present invention provides a method for recycling polyester glycol alcoholysis solution using the aforementioned apparatus, wherein the method comprises:

[0036] (1) The alcoholysis liquid S1 of polyester ethylene glycol is passed through buffer tank V1 and then the alcoholysis liquid S2 is distilled through distillation column feed pump P1, and the alcoholysis liquid S3 after passing through distillation column feed pump P1 is fed into distillation column T1.

[0037] (2) The top gas S4 from the top outlet of distillation column T1 is cooled by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0038] (3) The bottom liquid S6 of the distillation column T1 enters the lower part of the vacuum column T2 for vacuum distillation. The top gas S8 of the vacuum column T2 is condensed by the vacuum column condenser E4 and then enters the vacuum column reflux tank V3. All the liquid phase condensed in the vacuum column reflux tank V3 is refluxed.

[0039] (4) The recovered ethylene glycol S10 obtained from the bottom of the vacuum distillation tower T2 is pumped to the depolymerization unit for recycling via the vacuum distillation tower bottom pump P4.

[0040] In this invention, it should be noted that the terms "lower middle section" and "lower section" are not specifically defined and are generally known to those skilled in the art. Preferably, in this invention, for example, the lower middle section of the pressure reducing tower T2 is 1 / 2 to 7 / 8 of the length of the pressure reducing tower T2. Similarly, for example, the lower section of the buffer tank V1 is 5 / 8 to 7 / 8 of the length of the buffer tank V1.

[0041] According to the present invention, the polyester glycol alcoholysis solution S1 contains ethylene glycol and water; preferably, based on the total weight of the polyester glycol alcoholysis solution S1, the content of ethylene glycol is 20-45% by weight, more preferably 25-35% by weight; and the content of water is 55-80% by weight.

[0042] In this invention, preferably, a polyester glycol alcoholysis solution with a mass ratio of 0.01-2% (mol) of ethylene glycol and water is selected.

[0043] According to the present invention, the polyester glycol alcoholysis solution S1 further contains less than 0.01% by weight of a polymerization inhibitor.

[0044] According to the present invention, the polyester glycol alcoholysis solution S1 further contains one or more of diethylene glycol, polyethylene terephthalate (BHET), and dimers.

[0045] According to the present invention, in step (1), the conditions of the distillation process include: pressure of 0.01-1.00 MPa, top temperature of 98-120°C, and bottom temperature of 100-120°C.

[0046] According to the present invention, the number of theoretical plates in the distillation column T1 is 1-30.

[0047] According to the present invention, in step (3), the conditions for vacuum distillation include: pressure of -0.10 MPa to 0.00 MPa, top temperature of 50-100°C, and bottom temperature of 150-197°C.

[0048] According to the present invention, the theoretical number of plates in the pressure reducing tower T2 is 1-30.

[0049] According to the present invention, the distillation column T1 is a packed column or a plate column.

[0050] According to the present invention, the pressure reducing tower T2 is a packed tower or a plate tower.

[0051] According to the present invention, preferably, the packing material in the packed tower is structured packing or random packing, specifically, the packing material is 250Y packing or IMTP packing.

[0052] According to the present invention, preferably, the plate tower is a floating valve tower or a bubble cap tower.

[0053] According to the present invention, the purity of the recovered ethylene glycol S10 is greater than 99%, preferably greater than 99.5%.

[0054] According to the present invention, no additional components such as catalysts are introduced into the method.

[0055] According to a particularly preferred embodiment of the present invention, a method for recycling polyester glycol alcoholysis solution using the aforementioned apparatus includes:

[0056] (1) The polyester ethylene glycol alcoholysis solution S1 after passing through the buffer tank V1, the alcoholysis solution S2 is distilled from the bottom of the buffer tank V1 through the distillation column feed pump P1, and the alcoholysis solution S3 after passing through the distillation column feed pump P1 enters the distillation column T1 from the middle.

[0057] The polyester glycol alcoholysis solution with a mass ratio of 0.01-2% (mol) of ethylene glycol and water is distilled in a packed column or a plate column.

[0058] (2) The top gas S4 from the top outlet of distillation column T1 is cooled by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0059] Among them, the theoretical number of plates of distillation column T1 is 1-30, the operating pressure of distillation column is 0.01-1.00 MPa(G), the top temperature of column is 98-120℃, and the bottom temperature of column is 100-120℃;

[0060] (3) The bottom liquid S6 of the distillation column T1 enters the lower part of the vacuum distillation column T2 from the middle of the vacuum distillation column T2 through the vacuum distillation column feed pump P2 for vacuum distillation operation. The top gas S8 of the vacuum distillation column T2 is condensed by the vacuum distillation column condenser E4 and then enters the vacuum distillation column reflux tank V3. All the liquid phase condensed in the vacuum distillation column reflux tank V3 is refluxed.

[0061] The pressure reducing tower T2 has a theoretical number of 1-30 plates, an operating pressure of -0.10 MPa(G) to 0.00 MPa(G), a top temperature of 50-100℃, and a bottom temperature of 150-197℃.

[0062] (4) The recovered ethylene glycol S10 obtained from the bottom of the vacuum distillation tower T2 is pumped to the depolymerization unit for recycling via the vacuum distillation tower bottom pump P4.

[0063] The present invention will be described in detail below through embodiments.

[0064] Example 1

[0065] like Figure 1 As shown, according to Figure 1 The polyester glycol alcoholysis recycling device shown recycles the polyester glycol alcoholysis solution.

[0066] The system includes: V1 buffer tank, T1 distillation column, V2 distillation column reflux tank, E1 distillation column reboiler, E2 distillation column condenser, P1 distillation column feed pump, P2 vacuum column feed pump, P3 distillation column top product pump, T2 vacuum column, V3 vacuum column reflux tank, E3 vacuum column reboiler, E4 vacuum column condenser, E5 vacuum condenser, C1 vacuum system, P4 vacuum column bottom product pump, and P5 mixed liquid pump;

[0067] The feed line connects to buffer tank V1. The lower part of buffer tank V1 is connected to distillation column feed pump P1. Distillation column feed pump P1 is connected to the middle inlet of distillation column T1. The top outlet of distillation column T1 connects to distillation column condenser E2 and distillation column reflux tank V2. The recovered water collected from distillation column reflux tank V2 is returned to the depolymerization unit for recycling. The bottom outlet of distillation column T1 is connected to vacuum distillation column feed pump P2.

[0068] The outlet pipeline of the T2 vacuum distillation tower is connected to the bottom pump P4, and the top outlet of the T2 vacuum distillation tower is connected to the condenser E4 and the reflux tank V3. The recovered ethylene glycol collected from the reflux tank V3 is returned to the depolymerization unit for recycling.

[0069] The distillation column is a plate column (vacuum-flying column);

[0070] The pressure of the distillation column is 0.00 MPa (g);

[0071] The top temperature of the distillation column is 100℃;

[0072] The packed tower is a plate tower (specifically, a 250Y random packing).

[0073] The pressure in the pressure reducing tower is -0.086 (g);

[0074] The temperature at the top of the pressure reducing tower is 5℃.

[0075] Methods for recycling polyester glycol alcoholysis solution include:

[0076] (1) Ethylene glycol depolymerization solution S1 from the depolymerization unit (ethylene glycol content 0.04758 mol%, water content 0.95179 mol%), pressure 0.01 MPa (g), temperature 70℃, mass flow rate 14000 kg / hr enters buffer tank V1. After passing through buffer tank V1, alcoholysis solution S2 enters distillation column T1 from the bottom of buffer tank V1 through distillation column feed pump P1, and alcoholysis solution S3 enters distillation column T1 from the middle.

[0077] (2) The top gas S4 from the top outlet of distillation column T1 is cooled to 100°C by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0078] (3) The bottom liquid S6 of the distillation column TI is fed into the middle of the vacuum distillation column T2 by the feed pump P2 and the bottom liquid S7 of the vacuum distillation column T2 for vacuum distillation operation.

[0079] (4) The top gas S8 of the pressure reducing tower T2 is cooled to 54°C by the pressure reducing tower condenser E4 and enters the pressure reducing tower reflux tank V3. The mixed liquid in the pressure reducing tower reflux tank V3 is collected by the mixed liquid pump P5 to obtain mixed liquid S9. The top of the pressure reducing tower reflux tank V3 is equipped with a vacuum condenser E5 and a vacuum system C1.

[0080] (5) The recovered ethylene glycol S10 obtained from the bottom liquid at the bottom outlet of the vacuum tower T2 is pumped out of the vacuum tower bottom pump P4 to obtain recovered ethylene glycol S11, which is then returned to the depolymerization unit for recycling.

[0081] The quality composition of each major logistics item is shown in Table 1.

[0082] Table 1

[0083]

[0084] Example 2

[0085] like Figure 1 As shown, according to Figure 1 The polyester glycol alcoholysis recycling device shown recycles the polyester glycol alcoholysis solution.

[0086] The system includes: V1 buffer tank, T1 distillation column, V2 distillation column reflux tank, E1 distillation column reboiler, E2 distillation column condenser, P1 distillation column feed pump, P2 vacuum column feed pump, P3 distillation column top product pump, T2 vacuum column, V3 vacuum column reflux tank, E3 vacuum column reboiler, E4 vacuum column condenser, E5 vacuum condenser, C1 vacuum system, P4 vacuum column bottom product pump, and P5 mixed liquid pump;

[0087] The feed line connects to buffer tank V1. The lower part of buffer tank V1 is connected to distillation column feed pump P1. Distillation column feed pump P1 is connected to the middle inlet of distillation column T1. The top outlet of distillation column T1 connects to distillation column condenser E2 and distillation column reflux tank V2. The recovered water collected from distillation column reflux tank V2 is returned to the depolymerization unit for recycling. The bottom outlet of distillation column T1 is connected to vacuum distillation column feed pump P2.

[0088] The outlet pipeline of the T2 vacuum distillation tower is connected to the bottom pump P4, and the top outlet of the T2 vacuum distillation tower is connected to the condenser E4 and the reflux tank V3. The recovered ethylene glycol collected from the reflux tank V3 is returned to the depolymerization unit for recycling.

[0089] The distillation column is a packed column (specifically, a 250Y type structured packing);

[0090] The pressure of the distillation column is 0.05 MPa (g);

[0091] The distillation column temperature is 105℃;

[0092] The pressure reducing tower is a packed tower (specifically, a 250Y type structured packing);

[0093] The pressure of the pressure reducing tower is -0.075 MPa (g);

[0094] The pressure reducing tower temperature is 58℃;

[0095] Methods for recycling polyester glycol alcoholysis solution include:

[0096] (1) Ethylene glycol depolymerization solution S1 (ethylene glycol content 0.048 mol%, water content 0.942 mol%) from the depolymerization unit, pressure 0.01 MPa (g), temperature 50℃, mass flow rate 8000 kg / hr enters buffer tank V1. After passing through buffer tank V1, alcoholysis solution S2 enters distillation column T1 from the bottom of buffer tank V1 through distillation column feed pump P1, and alcoholysis solution S3 enters distillation column T1 from the middle.

[0097] (2) The top gas S4 from the top outlet of distillation column T1 is cooled to 105°C by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0098] (3) The bottom liquid S6 of the distillation column T1 is fed into the middle of the vacuum distillation column T2 by the feed pump P2 and the bottom liquid S7 of the vacuum distillation column T2 for vacuum distillation operation.

[0099] (4) The top gas S8 of the pressure reducing tower T2 is cooled to 58°C by the pressure reducing tower condenser E4 and enters the pressure reducing tower reflux tank V3. The mixed liquid in the pressure reducing tower reflux tank V3 is collected by the mixed liquid pump P5 to obtain mixed liquid S9. The top of the pressure reducing tower reflux tank V3 is equipped with a vacuum condenser E5 and a vacuum system C1.

[0100] (5) The recovered ethylene glycol S10 obtained from the bottom liquid at the bottom outlet of the vacuum tower T2 is pumped out of the vacuum tower bottom pump P4 to obtain recovered ethylene glycol S11, which is then returned to the depolymerization unit for recycling.

[0101] The quality composition of each major logistics item is shown in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] Example 3

[0106] like Figure 1 As shown, according to Figure 1 The polyester glycol alcoholysis recycling device shown recycles the polyester glycol alcoholysis solution.

[0107] The system includes: V1 buffer tank, T1 distillation column, V2 distillation column reflux tank, E1 distillation column reboiler, E2 distillation column condenser, P1 distillation column feed pump, P2 vacuum column feed pump, P3 distillation column top product pump, T2 vacuum column, V3 vacuum column reflux tank, E3 vacuum column reboiler, E4 vacuum column condenser, E5 vacuum condenser, C1 vacuum system, P4 vacuum column bottom product pump, and P5 mixed liquid pump;

[0108] The feed line connects to buffer tank V1. The lower part of buffer tank V1 is connected to distillation column feed pump P1. Distillation column feed pump P1 is connected to the middle inlet of distillation column T1. The top outlet of distillation column T1 connects to distillation column condenser E2 and distillation column reflux tank V2. The recovered water collected from distillation column reflux tank V2 is returned to the depolymerization unit for recycling. The bottom outlet of distillation column T1 is connected to vacuum distillation column feed pump P2.

[0109] The outlet pipeline of the T2 vacuum distillation tower is connected to the bottom pump P4, and the top outlet of the T2 vacuum distillation tower is connected to the condenser E4 and the reflux tank V3. The recovered ethylene glycol collected from the reflux tank V3 is returned to the depolymerization unit for recycling.

[0110] The distillation column is a packed column (specifically, 250Y structured packing);

[0111] The pressure of the distillation column is 0.05 MPa (g);

[0112] The distillation column temperature is 105℃;

[0113] The pressure reducing tower is a packed tower (specifically, 250Y structured packing);

[0114] The pressure of the pressure reducing tower is -0.075 MPa (g);

[0115] The pressure reducing tower temperature is 58℃;

[0116] Methods for recycling polyester glycol alcoholysis solution include:

[0117] (1) Ethylene glycol depolymerization solution S1 from the depolymerization unit (ethylene glycol content is 0.09 mol%, water content is 0.91 mol%), pressure 0.01 MPa (g), temperature 70℃, mass flow rate 12833 kg / hr enters buffer tank V1. After passing through buffer tank V1, alcoholysis solution S2 enters distillation column T1 from the bottom of buffer tank V1 through distillation column feed pump P1, and alcoholysis solution S3 enters distillation column T1 from the middle.

[0118] (2) The top gas S4 from the top outlet of distillation column T1 is cooled to 100°C by distillation column condenser E2 and enters distillation column reflux tank V2. The recovered water in the reflux tank is treated by distillation column top pump P3 and then returned to the depolymerization unit for recycling.

[0119] (3) The bottom liquid S6 of the distillation column T1 is fed into the middle of the vacuum distillation column T2 by the feed pump P2 and then enters the middle of the vacuum distillation column T2 for vacuum distillation.

[0120] (4) The top gas S8 of the pressure reducing tower T2 is cooled to 56°C by the pressure reducing tower condenser E4 and enters the pressure reducing tower reflux tank V3. The mixed liquid in the pressure reducing tower reflux tank V3 is collected by the mixed liquid pump P5 to obtain mixed liquid S9. The top of the pressure reducing tower reflux tank V3 is equipped with a vacuum condenser E5 and a vacuum system C1.

[0121] (5) The recovered ethylene glycol S10 obtained from the bottom liquid at the bottom outlet of the vacuum tower T2 is pumped out of the vacuum tower bottom pump P4 to obtain recovered ethylene glycol S11, which is then returned to the depolymerization unit for recycling.

[0122] The quality composition of each major logistics item is shown in Table 3.

[0123] Table 3

[0124]

[0125]

[0126] The results above show that the method of the present invention enables the recycling of solvents, improves PET recovery rate, significantly reduces ethylene glycol usage, and reduces wastewater discharge.

[0127] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A device for recycling polyester glycol alcoholysis solution, characterized in that, The apparatus includes: a buffer tank (V1), a distillation column (T1), a distillation column condenser (E2), and a distillation column reflux tank (V2) connected in sequence; and a pressure reducing column (T2) connected to the distillation column (T1).

2. The apparatus according to claim 1, wherein, The device further includes: a buffer tank (V1), a distillation column feed pump (P1), a distillation column (T1), a distillation column condenser (E2), a distillation column reflux tank (V2), and a distillation column top outlet pump (P3) connected in sequence; and a vacuum distillation column feed pump (P2) and a vacuum distillation column (T2) connected in sequence to the distillation column (T1).

3. The apparatus according to claim 1 or 2, wherein, The top of the distillation column (T1) is equipped with a distillation column condenser (E2) and a distillation column reflux tank (V2); And / or, the bottom of the distillation column reflux tank (V2) is connected to the distillation column top outlet pump (P3); And / or, the bottom outlet of the distillation column (T1) is connected to the vacuum column (T2) via a vacuum column feed pump (P2); And / or, a distillation column reboiler (E1) is also installed on the bottom reboiler outlet line of the distillation column (T1).

4. The apparatus according to any one of claims 1-3, wherein, The top of the pressure reducing tower (T2) is equipped with a pressure reducing tower condenser (E4), a pressure reducing tower reflux tank (V3), a vacuum condenser (E5), and a vacuum system (C1) connected in sequence. Preferably, the vacuum condenser (E4) is connected to the top of the vacuum reflux tank (V3); the vacuum condenser (E5) is connected to the top of the vacuum reflux tank (V3). Preferably, the bottom of the pressure reducing tower reflux tank (V3) is connected to the mixing pump (P5).

5. The apparatus according to any one of claims 1-4, wherein, The bottom outlet pipeline of the pressure reducing tower (T2) is connected to the pressure reducing tower bottom pump (P4); And / or, a reboiler (E3) is also installed on the bottom outlet line of the vacuum distillation tower (T2).

6. A method for recycling polyester glycol alcoholysis solution using the apparatus according to any one of claims 1-5, characterized in that, The method includes: (1) The polyester ethylene glycol alcoholysis solution S1 is passed through a buffer tank (V1) and the alcoholysis solution S2 is distilled through a distillation column feed pump (P1), and the alcoholysis solution S3 after passing through the distillation column feed pump (P1) is fed into the distillation column (T1). (2) The top gas S4 from the top outlet of the distillation column (T1) is cooled by the distillation column condenser (E2) and enters the distillation column reflux tank (V2). The recovered water in the reflux tank is treated by the distillation column top pump (P3) and then returned to the depolymerization unit for recycling. (3) The bottom liquid S6 of the distillation column (T1) enters the lower part of the vacuum column (T2) for vacuum distillation. The top gas S8 of the vacuum column (T2) is condensed by the vacuum column condenser (E4) and enters the vacuum column reflux tank (V3). All the liquid phase condensed in the vacuum column reflux tank (V3) is refluxed. (4) The recovered ethylene glycol S10 obtained from the bottom of the vacuum distillation tower (T2) is pumped to the depolymerization unit for recycling via the vacuum distillation tower bottom pump (P4).

7. The method according to claim 6, wherein, The polyester glycol alcoholysis solution S1 contains ethylene glycol and water; Preferably, based on the total weight of the polyester glycol alcoholysis solution S1, the ethylene glycol content is 20-45% by weight, preferably 25-35% by weight; and the water content is 55-80% by weight. Preferably, the polyester glycol alcoholysis solution S1 further contains less than 0.01% by weight of a polymerization inhibitor.

8. The method according to claim 6, wherein, In step (1), the conditions for the distillation process include: a pressure of 0.01-1.00 MPa, a top temperature of 98-120°C, and a bottom temperature of 100-120°C. And / or, the theoretical number of plates in the distillation column (T1) is 1-30.

9. The method according to claim 6, wherein, In step (3), the conditions for vacuum distillation include: pressure of -0.10 MPa to 0.00 MPa, top temperature of 50-100°C, and bottom temperature of 150-197°C. And / or, the theoretical number of plates in the pressure reducing tower (T2) is 1-30.

10. The method according to any one of claims 6-9, wherein, The distillation column (T1) is a packed column or a plate column; And / or, the pressure reducing tower (T2) is a packed tower or a plate tower.

11. The method according to any one of claims 6-10, wherein, The purity of the recovered ethylene glycol S10 is greater than 99%, preferably greater than 99.5%.

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