Continuous production system, process and application for efficiently recovering and refining PTA from waste PET

Abstract

The present invention belongs to the technical field of waste PET recycling, and particularly relates to a continuous production system, process and application for efficiently recycling refined PTA from waste PET. The continuous production system and process for efficiently recycling refined PTA from waste PET provided by the present invention achieve continuous production of "obtaining refined PTA from waste PET" through the mutual cooperation of an enzymatic hydrolysis unit, a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit and a recrystallization unit; in addition, by adjusting the flow channel structure of the electrolysis components in the electrolysis unit, the occurrence of electrolysis interruption caused by the easy deposition of TA generated by electrolysis on the surface of the anode plate is avoided, providing guarantee for the continuous progress of the entire degradation and recycling process. This system and process are of great significance for realizing the efficient degradation and recycling of waste PET.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste PET recycling, and particularly relates to a continuous production system, process and application for efficiently recycling refined PTA from waste PET. Background Art

[0002] Polyethylene terephthalate (PET) is widely used in many fields such as plastic bottles, food packaging and textiles due to its excellent transparency, strength and chemical resistance. However, the widespread use of PET materials has exerted great pressure on the ecological environment. Therefore, realizing the green recycling and effective utilization of PET is of crucial significance for promoting green environmental protection and sustainable development.

[0003] In order to promote the recycling of resources, waste PET products are usually recycled into the raw material monomer terephthalic acid (TA) through a degradation process. Currently, most of the processes are batch processes. For example, waste PET is first degraded into terephthalate and ethylene glycol by a chemical method, and then the terephthalate is subjected to steps such as decolorization, acid adjustment and filtration to obtain refined terephthalic acid (PTA) with a higher purity. However, this series of operation steps are complex and the production efficiency is not high. There is also research on obtaining higher purity TA by electrolyzing the terephthalate solution, but the process used is still a batch process, that is, it is necessary to electrolyze using the terephthalate solution as the raw material and cannot directly use waste PET as the initial raw material for the entire process. Moreover, in the actual electrolysis process, the electrolytically deposited TA is very easy to deposit on the electrode surface, affecting the continuous progress of the electrolysis reaction, and may even cause the electrolysis reaction to interrupt, unable to ensure the continuity of the electrolysis process, and the electrolysis efficiency is low.

[0004] Therefore, there is an urgent need for a process that can continuously recover high-purity PTA directly from waste PET, so as to achieve the continuous recovery of "waste PET to refined PTA". Summary of the Invention

[0005] The purpose of the present invention is to provide a process for efficiently recycling refined PTA from waste PET in one time. The process includes an enzymatic hydrolysis unit, a solid-liquid separation unit, an electrolysis unit, a recrystallization unit and an ethylene glycol recovery unit. Through the specific connection and cooperation between each unit and the special design of the electrolytic cell structure in the electrolysis unit, the continuous production from waste PET to refined PTA is realized, and at the same time, ethylene glycol is recovered.

[0006] In view of this, the first aspect of the present invention provides a continuous production system for efficiently recycling refined PTA from waste PET, and the system includes:

[0007] A plurality of enzymatic hydrolysis units configured to sequentially perform an enzymatic hydrolysis reaction on PET to obtain a slurry containing TA basic salt;

[0008] A processing unit, the processing unit includes a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit, and a recrystallization unit connected in sequence; the processing unit is used for solid-liquid separation, dissolution, decolorization, and electrolysis of the slurry of TA basic salt to obtain a crude TA slurry, and then the crude TA slurry is subjected to solid-liquid separation and recrystallization to obtain refined PTA; and

[0009] A switching control unit, configured to: when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction, connect the processing unit to the first enzymatic hydrolysis unit to start the processing operation; during the processing operation of the processing unit on the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis reaction; in response to the processing unit completing the processing operation on the first enzymatic hydrolysis unit, switch the processing unit to be connected to the second enzymatic hydrolysis unit, so that the processing unit cyclically connects each enzymatic hydrolysis unit to achieve continuous processing.

[0010] The continuous production system for efficiently recovering and refining PTA from waste PET provided by the present invention includes a plurality of enzymatic hydrolysis units, these enzymatic hydrolysis units are respectively communicated with the first solid-liquid separation unit, and continuously provide the slurry containing TA basic salt obtained by enzymatic hydrolysis of PET for the first solid-liquid separation unit, ensuring that the system can achieve continuous production; after the enzymatic hydrolysis unit is communicated with the first solid-liquid separation unit, the slurry enters the first solid-liquid separation unit for solid-liquid separation, the separated TA basic salt solid enters the filter cake dissolution and decolorization unit for dissolution, decolorization and impurity removal and filtration, the filtered TA basic salt solution enters the electrolysis unit, the crude TA slurry is recovered in the anode plate tank in the electrolysis unit, and the basic solution is recovered in the cathode plate tank; the obtained crude TA slurry is filtered by the second solid-liquid separation unit to collect the solid crude TA, and the crude TA is refined by the recrystallization unit to obtain refined PTA.

[0011] Combined with the first aspect, the first solid-liquid separation unit is used for separating the TA basic salt in the slurry; the filter cake dissolution and decolorization unit is used for dissolving, decolorizing and filtering the TA basic salt to obtain a TA basic salt solution; the electrolysis unit is composed of a plurality of electrolysis components connected in parallel, each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane, wherein, an anode plate and plate frames arranged on both sides of the anode plate are provided in the anode chamber to form an anode plate tank, a cathode plate and plate frames arranged on both sides of the cathode plate are provided in the cathode chamber to form a cathode plate tank, the TA basic salt solution enters the electrolysis unit from the anode chamber, the crude TA slurry is recovered in the anode plate tank, and the basic solution is recovered in the cathode plate tank; the second solid-liquid separation unit is used for separating the crude TA in the crude TA slurry, and the recrystallization unit is used for refining the crude TA.

[0012] In combination with the first aspect, the continuous production system further includes a rectification unit, which is connected to the solution side of the first solid-liquid separation unit and is used for recycling ethylene glycol in the solution.

[0013] In combination with the first aspect, the anode plate groove or the cathode plate groove is a hollow plate groove, and 2 or more flow channels are arranged along the fluid flow direction. Each flow channel is respectively provided with a pair of fluid inlets and outlets. Among them, the flow channels are separated by arc-shaped corrugated isolation strips.

[0014] The second aspect of the present invention provides a continuous production process for efficiently recovering and refining PTA from waste PET, including:

[0015] An enzymatic hydrolysis step, including multiple enzymatic hydrolysis units. The enzymatic hydrolysis step uses a PET degrading enzyme, the enzymatic hydrolysis temperature is 40-70 °C, and the pH during the enzymatic hydrolysis process is 8-10, to obtain a TA alkaline salt slurry.

[0016] A first solid-liquid separation step for separating the TA alkaline salt in the TA alkaline salt slurry.

[0017] A filter cake dissolution and decolorization step. Add 5-10 times the weight of water to the TA alkaline salt to dissolve the TA alkaline salt, add a decolorizing agent, and filter to obtain a TA alkaline salt solution.

[0018] An electrolysis step, including multiple electrolysis components arranged in parallel. Each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane. The TA alkaline salt solution enters the electrolysis component from the anode, TA slurry is obtained at the anode, an alkaline solution is recovered at the cathode, and oxygen and hydrogen are respectively collected.

[0019] A second solid-liquid separation step for filtering the TA slurry to obtain a crude TA product.

[0020] A refining step, in which the crude TA product is recrystallized to obtain a refined PTA product.

[0021] Among them, when the first solid-liquid separation step is carried out after the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction, the second enzymatic hydrolysis unit carries out the enzymatic hydrolysis step. After completing the processing operation of the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit continues the first solid-liquid separation step to complete the continuity.

[0022] The continuous production process for efficiently recovering and refining PTA from waste PET provided by the present invention realizes the continuous production of refined PTA from waste PET through an enzymatic hydrolysis step, a first solid-liquid separation step, a filter cake dissolution and decolorization step, an electrolysis step, a second solid-liquid separation step, and a refining step. Specifically, the pretreated waste PET is enzymatically hydrolyzed with a PET-degrading enzyme to obtain a slurry containing TA basic salt. Since the solubility of TA basic salt in the crude enzyme solution used for enzymatic hydrolysis is relatively low, the TA basic salt will gradually precipitate as the degree of enzymatic hydrolysis increases. The slurry containing TA basic salt is separated by the first solid-liquid separation step to obtain solid TA basic salt; the TA basic salt filter cake is dissolved with a soluble amount of water and then a decolorizing agent is added for decolorization and impurity removal. After removing the decolorizing agent, the obtained TA basic salt solution is electrolyzed. TA slurry is obtained at the anode of the electrolysis assembly, and an alkaline solution is obtained at the cathode. The TA slurry generated at the anode of each electrolysis assembly is separated by the second solid-liquid separation step, and the solid is collected to obtain crude TA. The crude TA is further recrystallized to obtain refined PTA. Among them, when the first solid-liquid separation step is carried out after the enzymatic hydrolysis reaction of the first enzymatic hydrolysis unit is completed, the second enzymatic hydrolysis unit carries out the enzymatic hydrolysis step. After completing the processing operation of the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit continues the first solid-liquid separation step to complete the continuity.

[0023] Combined with the second aspect, the continuous production process further includes a rectification step of rectifying the solution obtained in the first solid-liquid separation step to recover ethylene glycol.

[0024] Combined with the second aspect, the enzymatic hydrolysis step is specifically as follows: Prepare a sodium phosphate buffer solution with a concentration of 10-1000 mmol / L. Add 100-1000 g of waste PET to each liter of the buffer solution, and add a crude enzyme solution of PET-degrading enzyme accounting for 0.1%-1% of the mass of the buffer solution, and react and enzymatically hydrolyze for 5-25 h; the refining step is specifically as follows: Transport the crude TA to a pulping tank, add a mixed solvent to make the mass concentration of the crude TA 20% - 35 wt%, where the mixed solvent is a mixture of water and at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide; heat up to 265-280 °C and increase the pressure to 6.0-8.0 MPa to dissolve the crude TA; pass the obtained solution through an adsorption column for decolorization and removal of metal impurities, and then carry out step-by-step crystallization through a 1-6 stage cooling and pressure reduction flash crystallizer, wash and dry to obtain refined PTA.

[0025] Exemplarily, at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide is formulated with deionized water into a mixed solvent, wherein the mass proportion of deionized water in the mixed solvent is 80% - 95%.

[0026] Combined with the second aspect, each of the electrolysis components is separated into an anode chamber and a cathode chamber by a cation exchange membrane. An anode plate and a plate frame are provided in the anode chamber, and a cathode plate and a plate frame are provided in the cathode chamber. The plate frames are respectively arranged on both sides of the anode plate and both sides of the cathode plate, correspondingly forming an anode plate groove and a cathode plate groove. TA crude product slurry is recovered in the anode plate groove, and an alkaline solution is recovered in the cathode plate groove. The plate frame is rectangular, and at least 1 arc-shaped corrugated isolation strip is arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow side dimension of the plate groove. The ratio of the long side to the narrow side of the plate groove is 2-5:1, and the depth of the plate groove is 2-20 mm. The distance between the upstream edge of the plate and the upper edge of the plate groove is greater than 1 / 8 of the length of the plate groove, and the distance between the downstream edge of the plate and the lower edge of the plate groove is not less than 1 / 4 of the length of the plate groove.

[0027] In the third aspect of the present invention, a refined PTA is provided, which is prepared by using the above continuous production system for efficiently recovering refined PTA from waste PET or according to the above continuous production process for efficiently recovering refined PTA from waste PET.

[0028] In the fourth aspect of the present invention, an application of the above refined PTA in the preparation of PET products is provided, and the PET products include films, fibers and / or bottle chips made of PET material.

[0029] Exemplarily, the PET material film prepared from refined PTA can be applied in multiple fields and industries. For example, it can be used for food packaging films, heat-sealing films and stretch films in the packaging industry, and can also be used for electronic protection films, light diffusion films and anti-reflection films in the electronic and optical fields, and can also be used for industrial and functional films such as anti-static films, high-temperature resistant films and electrical insulation films. It can also be a biaxially oriented film or a uniaxially oriented film.

[0030] Exemplarily, the PET material fibers prepared from refined PTA can also be applied in multiple fields and industries. For example, they can be polyester filament or polyester staple fiber produced in the textile industry, or can be high-strength fibers, low-elastic fibers or high-modulus fibers commonly used in the industrial field, or can be some functional fibers such as moisture-absorbing and sweat-releasing fibers, anti-static fibers, anti-ultraviolet fibers or flame-retardant fibers, or can be pre-oriented yarns, fully drawn yarns or drawn textured yarns obtained according to different production processes.

[0031] Exemplarily, the PET flakes made from refined PTA can also be applied in multiple fields and industries. For example, they can be used to produce food packaging bottles, beverage packaging bottles, pharmaceutical packaging bottles, cosmetic packaging bottles or industrial chemical bottles. They can also be used to produce PET bottles with different structures, such as single-layer PET bottles, multi-layer PET bottles or composite PET bottles. Additionally, they can be used to produce PET bottles with specific functions, such as anti-ultraviolet PET bottles, high-temperature resistant PET bottles, low-temperature resistant PET bottles or high-barrier PET bottles.

[0032] The above-mentioned system and process provided by the present invention can achieve continuous production of "obtaining refined PTA from waste PET"; moreover, by adjusting the flow channel structure in the electrolysis component, the electrolysis interruption caused by the easy deposition of TA generated by electrolysis on the surface of the anode plate is avoided, providing guarantee for the continuous progress of the entire degradation and recycling process. This system and process are of great significance for the efficient degradation and recycling of waste PET. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic flow chart of the continuous production process for efficiently recovering refined PTA from waste PET provided by the present invention;

[0034] Figure 2 It is a schematic diagram of the electrolysis unit and the second solid-liquid separation unit of the continuous production process for efficiently recovering refined PTA from waste PET provided by the present invention;

[0035] Figure 3 It is a schematic diagram of the structure of the electrolysis component in the electrolysis unit of the continuous production process for efficiently recovering refined PTA from waste PET provided by the present invention;

[0036] Figure 4 It is a schematic cross-sectional view of the electrolysis component of the electrolysis unit, where, Figure 4 (a) is a schematic cross-sectional view of the anode chamber in the electrolysis component, Figure 4 (b) is a schematic cross-sectional view of the cathode chamber in the electrolysis component;

[0037] Figure 5 It is a schematic flow chart of the refining step of the continuous production process for efficiently recovering refined PTA from waste PET provided by the present invention.

[0038] In the figure:

[0039] 021, cathode chamber; 022, anode chamber; 023, cation exchange membrane; 024, cathode plate; 025, anode plate; 026, plate frame; 027, sealing gasket; 028, end plate;

[0040] 301, upstream edge of the plate; 302, downstream edge of the plate;

[0041] 400, arc-shaped corrugated isolation strip; 401, first flow channel; 402, second flow channel;

[0042] 601, anode chamber fluid inlet; 602, anode chamber fluid outlet; 701, fluid pipeline at the upstream edge of the anode plate frame; 702, fluid pipeline at the downstream edge of the anode plate frame; 801, cathode chamber fluid inlet; 802, cathode chamber fluid outlet; 901, fluid pipeline at the upstream edge of the cathode plate frame; 902, fluid pipeline at the downstream edge of the cathode plate frame. Detailed implementation manner

[0043] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Please refer to Figure 1 , and now the continuous production system for efficiently recovering and refining PTA from waste PET provided by the present invention will be described. The system includes: a plurality of enzymatic hydrolysis units configured to sequentially perform enzymatic hydrolysis reactions on PET to obtain a slurry containing TA alkaline salt; a processing unit, the processing unit includes a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit and a recrystallization unit connected in sequence; the processing unit is used to perform solid-liquid separation, dissolution and decolorization, and electrolysis on the slurry of TA alkaline salt to obtain a crude TA slurry, and then obtain high-quality PTA by solid-liquid separation and recrystallization of the crude TA slurry; and a switching control unit configured to: when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction, connect the processing unit to the first enzymatic hydrolysis unit to start the processing operation; during the processing operation of the processing unit on the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis reaction; in response to the processing unit completing the processing operation on the first enzymatic hydrolysis unit, switch the processing unit to be connected to the second enzymatic hydrolysis unit, so that the processing unit cyclically connects each enzymatic hydrolysis unit to achieve continuous processing.

[0045] The continuous production system for efficiently recycling and refining PTA from waste PET provided by the present invention includes multiple enzymatic hydrolysis units, which are respectively connected to the first solid-liquid separation unit to continuously supply the first solid-liquid separation unit with a slurry containing TA alkaline salt obtained by enzymatic hydrolysis of PET, ensuring that the system can achieve continuous production. After the enzymatic hydrolysis unit is connected to the first solid-liquid separation unit, the slurry enters the first solid-liquid separation unit for solid-liquid separation. The separated TA alkaline salt solid enters the filter cake dissolution and decolorization unit for dissolution, decolorization and impurity removal, and filtration. The obtained TA alkaline salt solution enters the electrolysis unit. TA crude product slurry is recovered in the anode plate groove in the electrolysis unit, and alkaline solution is recovered in the cathode plate groove. The obtained TA crude product slurry is filtered by the second solid-liquid separation unit to collect solid TA crude product, and the TA crude product is refined by the recrystallization unit to obtain refined PTA.

[0046] As a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET of the present invention, the continuous production system further includes a control unit, and the control unit is respectively connected to the liquid outlet control ends of multiple enzymatic hydrolysis units; when the enzymatic hydrolysis liquid of one enzymatic hydrolysis unit is processed, the control unit controls the liquid outlet end of another enzymatic hydrolysis unit to be connected to the first solid-liquid separation unit.

[0047] By setting a control unit to control the connection between the enzymatic hydrolysis unit and the first solid-liquid separation unit, it is ensured that the enzymatic hydrolysis liquid generated by the enzymatic hydrolysis unit is sufficient to supply the subsequent unit processes, and the continuous production of the entire system is guaranteed.

[0048] As a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET of the present invention, the continuous production system further includes a rectification unit, and the rectification unit is connected to the solution side of the first solid-liquid separation unit for recycling ethylene glycol in the solution.

[0049] As a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET of the present invention, plate frames are respectively arranged on both sides of the anode plate and both sides of the cathode plate, corresponding to form an anode plate groove and a cathode plate groove; the anode plate groove or the cathode plate groove is a hollow plate groove, and 2 or more flow channels are arranged along the fluid flow direction, and each flow channel is respectively provided with a pair of fluid inlets and outlets. Among them, the flow channels are separated by arc-shaped corrugated isolation strips.

[0050] Please refer to Figure 2 , as a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET of the present invention, the electrolysis unit includes at least 2 groups of electrolysis components, which are composed of alternating anodes and cathodes in the electrolysis components. The TA alkaline salt solution (i.e., the decolorized solution) generated by the filter cake dissolution and decolorization unit enters the electrolysis unit from the anode, and the generated alkaline solution flows out from the cathode.

[0051] Please refer toFigure 3 , as a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET in the present invention, sealing gaskets 027 are provided between the cation exchange membrane 023 and the plate frame 026, between the plate frame 026 and the cathode plate 024 or the anode plate 025, and between the plate frame 026 and the end plate 028 in each electrolysis assembly. Each component is fixed by through screws and nuts at both ends.

[0052] Please refer to Figure 4 , as a specific embodiment of the continuous production system for efficiently recycling and refining PTA from waste PET in the present invention, please refer to Figure 4 (a), in the hollow anode plate groove formed by the anode plate 025 and the plate frame 026, at least two flow channels (the first flow channel 401 and the second flow channel 402) are arranged along the fluid flow direction. The flow channels are separated by arc-shaped corrugated isolation strips 400. Each flow channel is respectively provided with a pair of anode chamber fluid inlets 601 and anode chamber fluid outlets 602, and a pair of anode plate frame upstream edge fluid pipes 701 and anode plate frame downstream edge fluid pipes 702 are respectively arranged at the upstream edge and the downstream edge of the plate frame corresponding to each flow channel. Please refer to Figure 4 (b), in the hollow cathode plate groove formed by the cathode plate 024 and the plate frame 026, at least two flow channels (the first flow channel 401 and the second flow channel 402) are arranged along the fluid flow direction. The flow channels are separated by arc-shaped corrugated isolation strips 400. Each flow channel is respectively provided with a pair of cathode chamber fluid inlets 801 and cathode chamber fluid outlets 802, and a pair of cathode plate frame upstream edge fluid pipes 901 and cathode plate frame downstream edge fluid pipes 902 are respectively arranged at the upstream edge and the downstream edge of the plate frame corresponding to each flow channel.

[0053] The arc-shaped corrugated isolation strip 400 is used to separate each flow channel. When the liquid flows in the plate groove, it collides with the flow channels with a certain curvature separated by the arc-shaped corrugated isolation strip 400, increasing its own flow rate. The fluid with increased flow rate generates a greater impact force on the TA on the surface of the anode plate 025, so that it cannot stably deposit on the surface of the anode plate 025.

[0054] When electrolysis is carried out using an electrolysis cell formed by parallel connection of two electrolysis components, the TA alkaline salt solution (i.e., the decolorized solution) first enters the anode chamber through the anode chamber fluid inlet 601, or first flows through the fluid pipeline 901 at the upstream edge of the cathode plate frame and then enters the anode chamber through the anode chamber fluid inlet 601. The TA alkaline salt combines with the hydrogen ions generated by anode electrolysis in the anode chamber to form crude TA. The slurry containing crude TA flows out from the anode chamber fluid outlet 602 and enters the main pipeline after being mixed with the crude TA slurry flowing out from the anode chamber of another electrolysis component through the fluid pipeline 902 at the downstream edge of the cathode plate frame. Oxygen escapes and is collected. At the same time, the water required for electrolysis enters the cathode chamber through the cathode chamber fluid inlet 801 and the fluid pipeline 702 at the downstream edge of the anode plate frame. The hydroxide ions generated by cathode electrolysis of water react with sodium ions or potassium ions that permeate into the cathode chamber through the cation exchange membrane to generate an alkaline solution, which then flows out from the cathode chamber fluid outlet 802 and enters the main pipeline after being mixed with the alkaline solution flowing out from the cathode chamber of another electrolysis component through the fluid pipeline 701 at the upstream edge of the anode plate frame.

[0055] The second aspect of the present invention provides a continuous production process for efficiently recovering and refining PTA from waste PET, including:

[0056] An enzymatic hydrolysis step, including multiple enzymatic hydrolysis units. The enzymatic hydrolysis step uses a PET-degrading enzyme, the enzymatic hydrolysis temperature is 40 - 70 °C, and the pH during the enzymatic hydrolysis process is 8 - 10, to obtain a TA alkaline salt slurry.

[0057] A first solid-liquid separation step for separating the TA alkaline salt in the TA alkaline salt slurry.

[0058] A filter cake dissolution and decolorization step, adding water 5 - 10 times the weight of the TA alkaline salt to the TA alkaline salt to dissolve it, adding a decolorizing agent, and filtering to obtain a TA alkaline salt solution.

[0059] An electrolysis step, including multiple electrolysis components arranged in parallel. Each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane. The TA alkaline salt solution enters the electrolysis component from the anode, crude TA is obtained at the anode, and an alkaline solution is recovered at the cathode, and oxygen and hydrogen are collected respectively.

[0060] A second solid-liquid separation step for filtering the TA slurry to obtain crude TA.

[0061] A refining step, recrystallizing the crude TA to obtain refined PTA.

[0062] The continuous production process for efficiently recycling and refining PTA from waste PET provided by the present invention realizes the continuous production of refined PTA from waste PET through an enzymatic hydrolysis step, a first solid-liquid separation step, a filter cake dissolution and decolorization step, an electrolysis step, a second solid-liquid separation step, and a refining step. Specifically, the pretreated waste PET is enzymatically hydrolyzed with a PET-degrading enzyme to obtain a slurry containing TA alkaline salt. Since the solubility of TA alkaline salt in the crude enzyme solution used for enzymatic hydrolysis is low, the TA alkaline salt will gradually precipitate as the degree of enzymatic hydrolysis increases. The slurry containing TA alkaline salt is separated by the first solid-liquid separation step to obtain solid TA alkaline salt. The TA alkaline salt filter cake is dissolved in a soluble amount of water, and a decolorizing agent is added for decolorization and impurity removal. After removing the decolorizing agent, the obtained TA alkaline salt solution is electrolyzed. TA slurry is obtained at the anode of the electrolysis assembly, and an alkaline solution is obtained at the cathode. The TA slurry generated at the anode of each electrolysis assembly is separated by the second solid-liquid separation step, and the solid is collected to obtain crude TA. The crude TA is further recrystallized to obtain refined PTA.

[0063] As a specific embodiment of the continuous production process for efficiently recycling and refining PTA from waste PET of the present invention, the continuous production process further includes a TA alkaline salt slurry control step. After the TA alkaline salt slurry in one enzymatic hydrolysis unit is processed, the TA alkaline salt slurry in another enzymatic hydrolysis unit is controlled to undergo the first solid-liquid separation step.

[0064] As a specific embodiment of the continuous production process for efficiently recycling and refining PTA from waste PET of the present invention, the continuous production process further includes a rectification step to rectify the solution obtained in the first solid-liquid separation step to recover ethylene glycol.

[0065] As a specific embodiment of the continuous production process for efficiently recycling and refining PTA from waste PET of the present invention, the enzymatic hydrolysis step is specifically as follows: Prepare a sodium phosphate buffer solution with a concentration of 10 - 1000 mmol / L. Add 100 - 1000 g of waste PET per kilogram of the buffer solution, and add a crude enzyme solution of PET-degrading enzyme accounting for 0.1% - 1% of the mass of the buffer solution, and react and enzymatically hydrolyze for 5 - 25 h.

[0066] After the enzymatic hydrolysis step, in order to precipitate more TA alkaline salt, the slurry can be appropriately cooled according to the actual temperature and then undergo the first solid-liquid separation step.

[0067] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane. An anode plate and a plate frame are provided in the anode chamber, and a cathode plate and a plate frame are provided in the cathode chamber. The plate frames are respectively arranged on both sides of the anode plate and both sides of the cathode plate, correspondingly forming an anode plate groove and a cathode plate groove. Crude TA slurry is recovered in the anode plate groove, and an alkaline solution is recovered in the cathode plate groove. The plate frame is rectangular, and at least 1 arc-shaped corrugated isolation strip is arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow-side dimension of the plate groove. The ratio of the long side to the narrow side of the plate groove is 2-5:1, and the depth of the plate groove is 2-20 mm. The distance between the upstream edge of the plate and the upper edge of the plate groove is greater than 1 / 8 of the length of the plate groove, and the distance between the downstream edge of the plate and the lower edge of the plate groove is not less than 1 / 4 of the length of the plate groove.

[0068] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, the long side length of the plate frame is 30 cm, the narrow side length is 10 cm, the length of the plate groove space is 26 cm, the width is 6 cm, the depth is 5 mm, the curvature diameter of the arc-shaped corrugated isolation strip is 6 cm, the distance between the upstream edge of the plate and the upper edge of the plate groove is 3.5 cm, and the distance between the downstream edge of the plate and the lower edge of the plate groove is 6.5 cm.

[0069] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, the cathode plate or the anode plate is at least one of titanium plated with ruthenium, titanium plated with iridium, or titanium plated with platinum; the voltage between the cathode plate and the anode plate is 1.5-5 V.

[0070] Please refer to Figure 5 , as a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, the refining step of this process is specifically as follows: The crude TA is transported to a pulping tank, and at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide is used to prepare a PTA slurry with a concentration of 20% to 35% with demineralized water, heated to 265 to 280 °C, pressurized to 6.0 to 8.0 MPag to dissolve the crude TA. The obtained solution is subjected to decolorization and removal of metal impurities through an adsorption column, and then subjected to step-by-step crystallization through a 1-6 stage cooling and depressurization flash crystallizer. The crystallized slurry is filtered through a filtration system, and the obtained solid is washed and dried to obtain refined PTA.

[0071] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, the specific parameters of the stepwise crystallization are as follows: the temperature of the first-stage crystallizer is controlled at 250-260 °C, the pressure is controlled at 4.0-4.5 MPag, the temperature of the second-stage crystallizer is controlled at 200-210 °C, the pressure is controlled at 3.0-4.0 MPag, the temperature of the third-stage crystallizer is controlled at 160-185 °C, the pressure is controlled at 0.7-1.1 MPag, and the temperature of the fourth-stage crystallizer is controlled at 130-155 °C, the pressure is controlled at 0.3-0.65 MPag.

[0072] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, the obtained solution can be subjected to decolorization and removal of metal impurities through an adsorption column, specifically by adopting a combination of one or more processes such as continuous adsorption in a fixed bed, precision filtration, and membrane separation to remove colored substances and metal impurities in the crude TA solution. The adsorption material can be selected from at least one of coconut shell activated carbon, zeolite molecular sieve, diatomaceous earth, or chitosan, or other adsorption materials with the functions of decolorization and adsorption of metal impurities can also be selected.

[0073] As a specific embodiment of the continuous production process for efficiently recovering and refining PTA from waste PET according to the present invention, in the refining step, the flash steam generated by the cooling and pressure-reducing flash crystallizer can be introduced into the front-end preheating, dissolution, and pulping processes to achieve energy recovery and utilization.

[0074] The following specifically illustrates the continuous production process and system for efficiently recovering and refining PTA from waste PET provided by the present invention through specific examples:

[0075] Prepare a sodium phosphate buffer solution with a concentration of 1000 mmol / L and a pH of 9.0. Add 1000 g of pre-crushed waste PET per kilogram of the buffer solution, add a crude enzyme solution of PET degrading enzyme at 1 wt% of the buffer solution mass for enzymatic hydrolysis, control the reaction temperature at 40-70 °C, react for 5-25 h, and dropwise add a sodium hydroxide solution with a mass fraction of 5%-50% during the reaction process to maintain the system pH between 8-10 all the time.

[0076] After the enzymatic hydrolysis reaction ended, the enzymatic hydrolysate was naturally cooled to room temperature and then filtered. The filtrate entered the rectification unit to recover ethylene glycol, obtaining 1531 g of TA basic salt cake. 11 kg of water was added to dissolve the TA basic salt, and then 30 g of decolorizing agent was added and stirred for 1 h for decolorization and impurity removal. The decolorizing agent and other insoluble substances were removed by filtration, and the filtrate entered the electrolysis unit. During the electrolysis process, the plate voltage was set at 2 V and the current was 77.0 A, and the current was kept constant during the electrolysis process. After 9 h of electrolysis reaction, the plate voltage increased to 2.2 V, indicating that the deposition amount of the generated TA on the surface of the anode plate 025 was very small and would not affect the electrolysis reaction. The crude TA slurry generated by electrolysis was filtered, and the obtained solid crude TA was recrystallized. Specifically: 1200 g of crude TA was transported to the TA slurrying tank through a spiral pipeline, and 2369 g of mixed solvent was added to obtain a TA slurry (the mixed solvent used was obtained by mixing demineralized water and dimethylformamide in a mass ratio of 85:15). The temperature was raised to 280 °C and the pressure was raised to 6.4 MPa to dissolve the crude TA. Then, it was subjected to decolorization and removal of metal impurities treatment through an adsorption column filled with coconut shell activated carbon. The treated crude TA solution was sent to a 1 - 4 - stage cooling and pressure - reducing flash crystallizer for step - by - step crystallization. The parameters for step - by - step crystallization were set as follows: the temperature of the first - stage crystallizer was controlled at 250 - 260 °C and the pressure was controlled at 4.0 - 4.5 MPa; the temperature of the second - stage crystallizer was controlled at 200 - 210 °C and the pressure was controlled at 3.0 - 4.0 MPa; the temperature of the third - stage crystallizer was controlled at 160 - 185 °C and the pressure was controlled at 0.7 - 1.1 MPa; the temperature of the fourth - stage crystallizer was controlled at 130 - 155 °C and the pressure was controlled at 0.3 - 0.65 MPa. The crystallized slurry was filtered and washed through a filtration system and finally dried to obtain 811 g of refined PTA with a purity of 99.91% and a recovery rate of 93.8%. Among them, the recovery rate (%) = 811 / (1000 / 192*166) = 93.8%.

[0077] However, when the above - mentioned mixed solvent used for recrystallization dissolution in the refining step was replaced with a mixed solution of water:ethanol:isopropanol with a mass ratio of 80:10:10 in sequence, the yield of the obtained refined PTA decreased to 91.5% and the purity decreased to 98.4%, indicating that the above - mentioned recrystallization solvent adopted in the present invention can ensure that the obtained PTA has high purity and higher yield.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A continuous production system for efficiently recycling and refining PTA from waste PET, characterized in that, Comprising: A plurality of enzymatic hydrolysis units configured to sequentially perform enzymatic hydrolysis reactions on PET to obtain a slurry containing TA basic salt; A processing unit, the processing unit including a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit, and a recrystallization unit connected in sequence; the processing unit is used to perform solid-liquid separation, solution decolorization, and electrolysis on the slurry of TA basic salt to obtain a crude TA slurry, and then perform solid-liquid separation and recrystallization on the crude TA slurry to obtain high-quality PTA; And A switching control unit configured to: when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction, connect the processing unit to the first enzymatic hydrolysis unit to initiate a processing operation; during the processing operation of the processing unit on the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs an enzymatic hydrolysis reaction; in response to the processing unit completing the processing operation on the first enzymatic hydrolysis unit, switch the processing unit to be connected to the second enzymatic hydrolysis unit, so that the processing unit cyclically connects to each enzymatic hydrolysis unit to achieve continuous processing; Wherein, the electrolysis unit is composed of a plurality of electrolysis components connected in parallel, and each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane. Among them, an anode plate and plate frames arranged on both sides of the anode plate are provided in the anode chamber to form an anode plate groove, and a cathode plate and plate frames arranged on both sides of the cathode plate are provided in the cathode chamber to form a cathode plate groove. The TA basic salt solution enters the electrolysis unit from the anode chamber, and crude TA slurry is recovered in the anode plate groove, and the basic solution is recovered in the cathode plate groove; the anode plate groove or the cathode plate groove is a hollow plate groove, and 2 or more flow channels are arranged along the fluid flow direction, and each flow channel is respectively provided with a pair of fluid inlets and outlets, and among them, the flow channels are separated by an arc-shaped corrugated isolation strip; the arc-shaped corrugated isolation strip is perpendicular to the corresponding anode plate or cathode plate.

2. The continuous production system for efficiently recovering and refining PTA from waste PET according to claim 1, wherein: The first solid-liquid separation unit is used to separate the TA basic salt in the slurry; The filter cake dissolution and decolorization unit is used to dissolve, decolorize, and filter the TA basic salt to obtain a TA basic salt solution; The second solid-liquid separation unit is used to separate the crude TA in the crude TA slurry, and the recrystallization unit is used to refine the crude TA.

3. The continuous production system for efficiently recycling and refining PTA from waste PET according to claim 1, characterized in that, It further includes a rectification unit, and the rectification unit is connected to the solution side of the first solid-liquid separation unit and is used to recover and utilize ethylene glycol in the solution.

4. A continuous production process for efficiently recovering and refining PTA from waste PET, characterized in that, Comprising: An enzymatic hydrolysis step, including a plurality of enzymatic hydrolysis units, the enzymatic hydrolysis step using a PET degrading enzyme, the enzymatic hydrolysis temperature being 40-70°C, and the pH during the enzymatic hydrolysis process being 8-10, to obtain a TA basic salt slurry; A first solid-liquid separation step for separating the TA basic salt in the TA basic salt slurry; A filter cake dissolution and decolorization step, adding 5-10 times the weight of water to the TA basic salt to dissolve the TA basic salt, adding a decolorizing agent, and filtering to obtain a TA basic salt solution; The electrolysis step includes a plurality of electrolysis components arranged in parallel. Each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane. An anode plate and a plate frame are provided in the anode chamber, and a cathode plate and a plate frame are provided in the cathode chamber. The plate frames are respectively arranged on both sides of the anode plate and both sides of the cathode plate, corresponding to form an anode plate groove and a cathode plate groove. The TA alkaline salt solution enters the electrolysis component from the anode. TA crude slurry is recovered in the anode plate groove, and the alkaline solution is recovered in the cathode plate groove. Oxygen and hydrogen are respectively collected; the plate frame is rectangular, and at least 1 arc-shaped corrugated isolation strip is arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow side dimension of the plate groove; The second solid-liquid separation step is used to filter the TA slurry to obtain crude TA; The refining step is to obtain PTA fine product by recrystallizing the crude TA; Among them, when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction and performs the first solid-liquid separation step, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis step. After completing the treatment operation of the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit continues the first solid-liquid separation step to complete the continuity.

5. The continuous production process for efficiently recovering and refining PTA from waste PET according to claim 4, characterized in that, It also includes a rectification step to rectify the solution obtained in the first solid-liquid separation step to recover ethylene glycol.

6. The continuous production process for efficiently recovering and refining PTA from waste PET according to claim 4, characterized in that, The enzymatic hydrolysis step is specifically: prepare a sodium phosphate buffer solution with a concentration of 10-1000 mmol / L. Add 100-1000 g of waste PET to each liter of the buffer solution, and add 0.1%-1% of the crude enzyme solution of PET degrading enzyme based on the mass of the buffer solution, and react and enzymatically hydrolyze for 5-25 h; The refining step is specifically: Transport the crude TA to a pulping tank, add a mixed solvent to make the mass concentration of the crude TA 20% - 35 wt%, where the mixed solvent is a mixture of water and at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide; Heat up to 265 - 280 °C and increase the pressure to 6.0 - 8.0 MPa to dissolve the crude TA; Pass the obtained solution through an adsorption column for decolorization and removal of metal impurities, and then perform step-by-step crystallization through a 1 - 6 stage cooling and depressurizing flash crystallizer, wash and dry to obtain refined PTA.

7. The continuous production process for efficiently recovering and refining PTA from waste PET as claimed in claim 4, wherein The ratio of the long side to the narrow side of the plate groove is 2 - 5:1, and the depth of the plate groove is 2 - 20 mm; the distance between the upstream edge of the plate and the upper edge of the plate groove is greater than 1 / 8 of the length of the plate groove, and the distance between the downstream edge of the plate and the lower edge of the plate groove is not less than 1 / 4 of the length of the plate groove.

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