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CN-122006282-A - Device and method for recycling polyester glycol alcoholysis liquid

CN122006282ACN 122006282 ACN122006282 ACN 122006282ACN-122006282-A

Abstract

The invention relates to the technical field of recycling of polyester ethylene glycol alcoholysis liquid, and discloses a device and a method for recycling the polyester ethylene glycol alcoholysis liquid, wherein the device comprises a buffer tank V1, a rectifying tower T1, a rectifying tower condenser E2 and a rectifying tower reflux tank V2 which are sequentially connected; and a vacuum tower T2 connected with the rectifying tower T1. The method can effectively recycle ethylene glycol and water, realize the recycling of the solvent, improve the recovery rate of PET, greatly reduce the consumption of ethylene glycol and reduce the discharge of wastewater.

Inventors

  • SUN RULIU
  • GUO LIANG
  • LI CHUNFANG
  • LI YULONG
  • WANG JING
  • CHEN GUANYU
  • QIU XINYAN

Assignees

  • 中国石油化工股份有限公司
  • 中石化(北京)化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20241112

Claims (11)

  1. 1. The device for recycling the polyester glycol alcoholysis liquid is characterized by comprising a buffer tank (V1), a rectifying tower (T1), a rectifying tower condenser (E2) and a rectifying tower reflux tank (V2) which are sequentially connected, and a decompression tower (T2) connected with the rectifying tower (T1).
  2. 2. The device according to claim 1, wherein the device further comprises a buffer tank (V1), a rectifying tower feed pump (P1), a rectifying tower (T1), a rectifying tower condenser (E2), a rectifying tower reflux tank (V2) and a rectifying tower top extraction pump (P3) which are sequentially connected, and a reducing tower feed pump (P2) and a reducing tower (T2) which are sequentially connected with the rectifying tower (T1).
  3. 3. The apparatus according to claim 1 or 2, wherein a rectifying column condenser (E2) and a rectifying column reflux drum (V2) are provided at the top of the rectifying column (T1); And/or the bottom of the rectifying tower reflux tank (V2) is connected with a rectifying tower top extraction pump (P3); And/or a tower kettle outlet at the bottom of the rectifying tower (T1) is connected with the vacuum tower (T2) through a vacuum tower feeding pump (P2); And/or a rectifying tower reboiler (E1) is also arranged on a tower kettle outlet pipeline at the bottom of the rectifying tower (T1).
  4. 4. A device according to any one of claims 1-3, wherein the top of the vacuum tower (T2) is provided with a vacuum tower condenser (E4), a vacuum tower reflux drum (V3), a vacuum condenser (E5) and a vacuum evacuation system (C1) which are connected in sequence; preferably, the vacuum condenser (E4) is connected with the top of the vacuum tower reflux tank (V3), and the vacuum condenser (E5) is connected with the top of the vacuum tower reflux tank (V3); Preferably, the bottom of the reflux drum (V3) of the vacuum tower is connected with the mixed liquid pump (P5).
  5. 5. The device according to any one of claims 1-4, wherein a bottom tank outlet line of the vacuum tower (T2) is connected to a vacuum tower tank extraction pump (P4); And/or a tower kettle outlet pipeline at the bottom of the vacuum tower (T2) is also provided with a vacuum tower reboiler (E3).
  6. 6. A method for recycling a polyester ethylene glycol alcoholysis liquid by using the device of any one of claims 1-5, comprising the steps of: (1) Rectifying the alcoholysis solution S2 of the polyester glycol alcoholysis solution S1 after passing through a buffer tank (V1) by a rectifying tower feeding pump (P1), and feeding the alcoholysis solution S3 after passing through the rectifying tower feeding pump (P1) into a rectifying tower (T1); (2) The top gas S4 of the rectifying tower at the top outlet of the rectifying tower (T1) is cooled by a rectifying tower condenser (E2), enters a rectifying tower reflux tank (V2), and the recovered water S5 of the reflux tank after being treated by a rectifying tower top extraction pump (P3) returns to the depolymerization unit for recycling; (3) The rectifying tower bottom solution S6 at the outlet of the bottom of the rectifying tower (T1) enters the middle lower part of the vacuum tower (T2) for vacuum rectification, and the vacuum tower top gas S8 at the top of the vacuum tower (T2) enters a vacuum tower reflux tank (V3) after being condensed by a vacuum tower condenser (E4); (4) The recovered glycol S10 obtained at the bottom of the tower kettle of the vacuum tower (T2) is pumped to the depolymerization unit for recycling through a vacuum tower kettle extraction pump (P4).
  7. 7. The method according to claim 6, wherein the polyester ethylene glycol alcoholysis liquid S1 contains ethylene glycol and water; preferably, the content of ethylene glycol is 20-45 wt%, preferably 25-35 wt%, and the content of water is 55-80 wt%, based on the total weight of the polyester ethylene glycol alcoholysis solution S1; preferably, the polyester ethylene glycol alcoholysis solution S1 further contains less than 0.01 wt% of a polymerization inhibitor.
  8. 8. The process according to claim 6, wherein in the step (1), the conditions of the rectification treatment include a pressure of 0.01 to 1.00MPa, a column top temperature of 98 to 120 ℃ and a column bottom temperature of 100 to 120 ℃; and/or the theoretical plate number of the rectifying tower (T1) is 1-30.
  9. 9. The process according to claim 6, wherein in the step (3), the conditions of the reduced pressure distillation include a pressure of-0.10 Mpa to 0.00Mpa, a column top temperature of 50 to 100 ℃ and a column bottom temperature of 150 to 197 ℃; And/or the theoretical plate number of the vacuum tower (T2) is 1-30.
  10. 10. The process according to any one of claims 6 to 9, wherein the rectification column (T1) is a packed column or a tray column; and/or the vacuum tower (T2) is a packed tower or a plate tower.
  11. 11. A process according to any one of claims 6-10, wherein the recovered ethylene glycol S10 has a purity of more than 99%, preferably more than 99.5%.

Description

Device and method for recycling polyester glycol alcoholysis liquid Technical Field The invention relates to the technical field of recycling of polyester ethylene glycol alcoholysis liquid, in particular to a device and a method for recycling the polyester ethylene glycol alcoholysis liquid. Background Polyester PET is the polyester material with the largest world consumption, and the excellent physical and chemical properties of PET lead to the wide application of the PET in single-purpose or multi-purpose products such as food and beverage containers, and brings great environmental protection pressure, and a large amount of waste PET needs to be recycled. In the chemical degradation method of PET, the degradation and recovery of PET by an alcoholysis method is more mature than other chemical recovery processes, and the alcoholysis process is gradually improved through continuous geographic analysis and practice for many years, so that a plurality of companies have industrialized devices. The industrial alcoholysis method is mainly divided into methanolysis and glycolysis. The methanolysis means that ester bonds in PET are broken in a reaction atmosphere of methanol to generate dimethyl terephthalate (DMT), and the DMT can be used as a polymerization monomer of PET and PBT to be polymerized again. The glycol alcoholysis method has the advantages of simple reaction route, no harsh requirements on temperature and pressure, simple experimental design and implementation, higher safety coefficient of reaction, suitability for industrial mass production, and maximized improvement of economic benefit, and besides, the glycol alcoholysis route does not contain corrosive substances, so that the pollution emission is reduced, and meanwhile, the maintenance cost of equipment is also reduced. From a practical standpoint, the monomer ethylene terephthalate (BHET) produced by this route can be directly fed to the polymerization route and incorporated into conventional PET production facilities without pretreatment and without the production of other by-products. Aiming at the problems of low depolymerization efficiency and incomplete depolymerization in the existing waste PET chemical method recovery process, a novel green efficient depolymerization technology is developed, but the consumption of glycol and water in the recrystallization process is large, and the development of a recycling technology of glycol alcoholysis liquid is urgently needed to realize recycling. Disclosure of Invention The invention aims to overcome the problems of low depolymerization efficiency and incomplete depolymerization in the existing chemical method recovery process of waste PET and the defect of large consumption of glycol and water in the recrystallization process in the depolymerization technology, and provides a device and a method for recycling polyester glycol alcoholysis liquid. In order to achieve the aim, the first aspect of the invention provides a device for recycling polyester glycol alcoholysis liquid, which comprises a buffer tank V1, a rectifying tower T1, a rectifying tower condenser E2 and a rectifying tower reflux tank V2 which are sequentially connected, and a vacuum tower T2 connected with the rectifying tower T1. The second aspect of the invention provides a method for recycling a polyester glycol alcoholysis liquid by adopting the device, wherein the method comprises the following steps: (1) Rectifying the alcoholysis solution S2 of the polyester glycol alcoholysis solution S1 after passing through a buffer tank V1 by a rectifying tower feeding pump P1, and feeding the alcoholysis solution S3 after passing through the rectifying tower feeding pump P1 into a rectifying tower T1; (2) The top gas S4 of the rectifying tower at the top outlet of the rectifying tower T1 is cooled by a rectifying tower condenser E2 and enters a rectifying tower reflux tank V2, and the reclaimed water S5 of the reflux tank, which is treated by a rectifying tower top extraction pump P3, returns to the depolymerization unit for recycling; (3) The tower bottom solution S6 of the rectifying tower at the outlet of the bottom of the rectifying tower T1 enters the middle lower part of the vacuum tower T2 for vacuum rectification, and the tower top gas S8 of the vacuum tower at the top of the vacuum tower T2 enters a vacuum tower reflux tank V3 after being condensed by a vacuum tower condenser E4; (4) The recovered glycol S10 obtained at the bottom of the tower kettle of the vacuum tower T2 is pumped to the depolymerization unit for recycling through a vacuum tower kettle extraction pump P4. Through the technical scheme, the method can effectively recycle glycol and water, and the treated glycol and water meet the recycling requirement, so that the recycling of raw materials is realized, and the wastewater discharge is greatly reduced. Drawings FIG. 1 is a schematic diagram of recycling of the polyester ethylene glycol alcoholysis liquid of the p