Polyester recycling system and method

Abstract

The present invention relates to the field of organic synthesis, and in particular to a polyester recycling system and method. The system comprises, sequentially in a feeding direction, a polyester alcoholysis system, a solid filtration system, a solvent recovery system, a diethyl terephthalate refining system, a bishydroxyethyl terephthalate preparation system, and a polyester recycling system. In the present invention, by means of the optimization of a polyester recycling process route, a polyester is degraded into an intermediate product diethyl terephthalate, then bishydroxyethyl terephthalate is prepared from the diethyl terephthalate, and finally the bishydroxyethyl terephthalate is subjected to polycondensation to obtain a recycling polyester, so that the yield of the recycling polyester can be improved, and thus the method is more suitable for industrial application.

Description

A polyester recycling system and method TECHNICAL FIELD

[0001] The present application relates to the field of organic synthesis, in particular to a polyester recycling system and method. BACKGROUND

[0002] Polyester is one of the most commonly used polymers at present, which is mainly used for preparing fibers, films and bottles, etc. According to statistics, since 2003, the global polyester production capacity has expanded at an average annual rate of about 9%, and China's polyester production capacity reached 29 million tons in 2010, becoming the world's largest producer and consumer of polyester. Due to the increasing social demand, the global polyester production is growing rapidly, and most of the polyester products are disposable consumer goods, which leads to the generation of a large amount of polyester waste. Waste polyester materials are not easily degraded by air or microorganisms in a short period of time due to their strong chemical inertness, which causes great pressure on the protection of the ecological environment. Therefore, there are many related researches on the degradation of waste polyester materials at home and abroad, but the intermediate product diethyl terephthalate obtained by alcoholysis of waste polyester materials has no direct application in the market, which leads to the fact that the existing various recycling methods cannot meet the industrial application.

[0003] CN118063755A discloses a polyester waste recycling method, which comprises the following steps: (1) filtering: using monoethylene glycol as an alcoholysis agent, the polyester waste is alcoholized into a coarse terephthalic acid glycol ester solution, and then the coarse terephthalic acid glycol ester solution is filtered by a centrifugal membrane to obtain an impurity mixture and a fine terephthalic acid glycol ester solution; (2) purifying: the fine terephthalic acid glycol ester solution is cooled and crystallized to obtain coarse terephthalic acid glycol ester crystals; the coarse terephthalic acid glycol ester crystals are heated, dissolved and then placed in ice water to stand and crystallize to obtain fine terephthalic acid glycol ester crystals; the fine terephthalic acid glycol ester crystals are subjected to dealcoholization treatment to obtain terephthalic acid glycol ester powder; (3) recycling: the terephthalic acid glycol ester powder is subjected to polyester reaction, and the recycled chips are obtained after cooling and granulation. However, the polyester yield obtained by the method is low, and therefore the method is not suitable for large-scale industrial application. TECHNICAL PROBLEM

[0004] Therefore, how to improve the yield of regenerated polyester is a technical problem to be solved. TECHNICAL SOLUTION

[0005] To solve the above technical problems, the present application provides a polyester recycling system and method, which can solve the problem of low yield of regenerated polyester by optimizing the process route of polyester recycling.

[0006] The application provides a polyester recycling system, which comprises, in sequence in the feeding direction, a polyester alcoholysis system, a solid filtering system, a solvent recovery system, a diethyl terephthalate refining system, a bis-hydroxyethyl terephthalate preparation system and a polyester regeneration system, wherein,

[0007] The polyester alcoholysis system comprises a depolymerization reactor.

[0008] The solid filtering system comprises, in sequence in the feeding direction, a centrifuge and a filter.

[0009] The solvent recovery system comprises an ethanol recovery tower.

[0010] The diethyl terephthalate refining system comprises, in sequence in the feeding direction, a diethyl terephthalate distillation tower and a diethyl terephthalate crystallizer.

[0011] The bis-hydroxyethyl terephthalate preparation system comprises, in sequence in the feeding direction, an ester exchange reactor, a bis-hydroxyethyl terephthalate crystallizer and an ethylene glycol recovery tower.

[0012] The polyester regeneration system comprises, in sequence in the feeding direction, a polycondensation reactor, a pelletizer and a dryer.

[0013] Further, the depolymerization reactor is used for subjecting the polyester to a depolymerization reaction to obtain a depolymerization solution, which is continuously fed into the centrifuge.

[0014] Further, the depolymerization reactor is provided with an electric agitator, which is used for stirring the material.

[0015] Further, the centrifuge is used for centrifuging the depolymerization solution to obtain a depolymerization centrifuged solution, which is continuously fed into the filter.

[0016] Further, the filter is used for filtering the depolymerization centrifuged solution to obtain a depolymerization filtered solution, which is continuously fed into the ethanol recovery tower.

[0017] Further, the ethanol recovery tower is used for recovering ethanol in the depolymerization filtered solution to obtain crude diethyl terephthalate, which is continuously fed into the diethyl terephthalate distillation tower.

[0018] Further, the diethyl terephthalate distillation tower is used for distilling the crude diethyl terephthalate to obtain distilled diethyl terephthalate, which is continuously fed into the diethyl terephthalate crystallizer.

[0019] Further, the diethyl terephthalate crystallizer is used for crystallizing the refined diethyl terephthalate to obtain diethyl terephthalate crystals, and the diethyl terephthalate crystals continue to enter the transesterification reactor.

[0020] Further, the transesterification reactor is used for performing transesterification reaction on the diethyl terephthalate crystals to obtain crude bis-hydroxyethyl terephthalate, and the crude bis-hydroxyethyl terephthalate continues to enter the bis-hydroxyethyl terephthalate crystallizer.

[0021] Further, the bis-hydroxyethyl terephthalate crystallizer is used for crystallizing the crude bis-hydroxyethyl terephthalate to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after the crystallization treatment continues to enter the ethylene glycol recovery tower.

[0022] Further, the ethylene glycol recovery tower is used for recovering ethylene glycol in the filtrate.

[0023] Further, the polycondensation reactor is used for performing pre-polycondensation and polycondensation reaction on the bis-hydroxyethyl terephthalate crystals to obtain regenerated polyester, and the regenerated polyester continues to enter the pelletizer.

[0024] Further, the pelletizer is used for performing pelletizing treatment on the regenerated polyester to obtain regenerated polyester particles, and the regenerated polyester particles continue to enter the dryer.

[0025] Further, the dryer is used for performing drying treatment on the regenerated polyester particles to obtain dried regenerated polyester.

[0026] The present application provides a polyester recycling method, which comprises a polyester alcoholysis method, a solid filtration method, a solvent recovery method, a diethyl terephthalate refining method, a bis-hydroxyethyl terephthalate preparation method, and a polyester regeneration method.

[0027] Further, in the polyester alcoholysis method, the following steps are included:

[0028] Step 1.1: the polyester, anhydrous ethanol, and a depolymerization catalyst are subjected to the depolymerization reaction in the depolymerization reactor to obtain the depolymerization solution.

[0029] Further, in the solid filtration method, the following steps are included in sequence:

[0030] Step 2.1: the depolymerization solution is subjected to centrifugal treatment in the centrifuge to obtain the depolymerization centrifugal liquid;

[0031] Step 2.2: the depolymerization centrifugal liquid is subjected to filtration treatment in the filter to obtain the depolymerization filtrate.

[0032] Further, in the solvent recovery method, comprising the following steps:

[0033] Step 3.1: the depolymerization filtrate is subjected to recovery ethanol treatment in the ethanol recovery column to obtain the crude terephthalic acid diethyl ester, and the recovered ethanol is returned to the depolymerization reactor through a pipeline.

[0034] Further, in the terephthalic acid diethyl ester refining method, comprising the following steps in sequence:

[0035] Step 4.1: the crude terephthalic acid diethyl ester is subjected to rectification treatment in the terephthalic acid diethyl ester rectification column to obtain the rectified terephthalic acid diethyl ester;

[0036] Step 4.2: the rectified terephthalic acid diethyl ester is subjected to crystallization treatment in the terephthalic acid diethyl ester crystallizer to obtain the terephthalic acid diethyl ester crystal.

[0037] Further, in the preparation method of the polyethylene terephthalate, comprising the following steps in sequence:

[0038] Step 5.1: the terephthalic acid diethyl ester crystal, ethylene glycol and ester exchange catalyst are subjected to the ester exchange reaction in the ester exchange reactor to obtain the crude polyethylene terephthalate;

[0039] Step 5.2: the crude polyethylene terephthalate is subjected to crystallization treatment in the polyethylene terephthalate crystallizer to obtain the polyethylene terephthalate crystal;

[0040] Step 5.3: the filtrate after the crystallization treatment is subjected to recovery ethylene glycol treatment in the ethylene glycol recovery column, and the recovered ethylene glycol is returned to the ester exchange reactor through a pipeline.

[0041] Further, in the polyester regeneration method, comprising the following steps in sequence:

[0042] Step 6.1: the polyethylene terephthalate crystal is subjected to the pre-polycondensation and polycondensation reactions in the polycondensation reactor to obtain the regenerated polyester;

[0043] Step 6.2: the regenerated polyester is subjected to pelletization treatment in the pelletizer to obtain the regenerated polyester pellet;

[0044] Step 6.3: the regenerated polyester pellet is subjected to drying treatment in the dryer to obtain the dried regenerated polyester.

[0045] Further, in the step 1.1, the polyester is one or a mixture of both of polyethylene terephthalate and polyethylene terephthalate-1,4-cyclohexane dimethanol.

[0046] Further, in the step 1.1, the mass ratio of the polyester to the anhydrous ethanol is 1: (5-10).

[0047] Further, in the step 1.1, the depolymerization catalyst is one of zinc acetate, manganese acetate, sodium hydroxide or sulfuric acid, and the amount of the depolymerization catalyst is 4-8% of the total mass of the polyester.

[0048] Further, in the step 1.1, the temperature of the depolymerization reactor is 170-220°C, and the time of the depolymerization reaction is 1-3h.

[0049] Further, in the step 1.1, the pressure of the depolymerization reactor is 1.5-1.8MPa.

[0050] Further, in the step 1.1, the depolymerization rate of the polyester is 96-99%.

[0051] Further, in the step 3.1, the temperature of the ethanol recovery tower is 85-100°C.

[0052] Further, in the step 4.1, the temperature of the diethyl terephthalate rectification tower is 150-200°C.

[0053] Further, in the step 4.1, the pressure of the diethyl terephthalate rectification tower is 1-5MPa.

[0054] Further, in the step 4.2, the rectified diethyl terephthalate is crystallized using anhydrous ethanol, and the mass ratio of the rectified diethyl terephthalate to the anhydrous ethanol is 1: (0.5-1).

[0055] Further, in the step 4.2, the temperature of the crystallization is 0-10°C.

[0056] Further, in the step 4.2, the purity of the diethyl terephthalate crystal is 99.9%.

[0057] Further, in the step 5.1, the mass ratio of the diethyl terephthalate crystal to the ethylene glycol is 1: (1-5).

[0058] Further, in the step 5.1, the transesterification catalyst is one of calcium oxide, titanium dioxide, aluminum oxide or vanadium oxide, and the amount of the transesterification catalyst is 2-5% of the mass of the diethyl terephthalate crystal.

[0059] Further, in the step 5.1, the initial temperature of the transesterification reactor is 180-220℃, and the initial reaction time is 1-3h, and then the transesterification reactor is heated to 230-280℃, and the reaction is continued for 1-3h.

[0060] Further, in the step 5.1, the pressure of the transesterification reactor is (-0.002)-0.006MPa.

[0061] Further, in the step 5.2, the crude bis-hydroxyethyl terephthalate is crystallized using ethylene glycol, and the mass ratio of the crude bis-hydroxyethyl terephthalate to the ethylene glycol is 1:(1-5).

[0062] Further, in the step 5.2, the temperature of the bis-hydroxyethyl terephthalate crystallizer is 10-20℃.

[0063] Further, in the step 5.2, the purity of the bis-hydroxyethyl terephthalate crystal is 99.5%.

[0064] Further, in the step 5.3, the temperature of the ethylene glycol recovery tower is 90-110℃.

[0065] Further, in the step 6.1, the pre-polycondensation and polycondensation catalyst is a mixture of ethylene glycol antimony and zinc acetate, and the amount of the ethylene glycol antimony in the catalyst is 0.1-0.5% of the total mass of the bis-hydroxyethyl terephthalate crystal, and the amount of the zinc acetate is 0.05-0.2% of the total mass of the bis-hydroxyethyl terephthalate crystal.

[0066] Further, in the step 6.1, the temperature of the pre-polycondensation reaction is 240-260℃, and the time of the pre-polycondensation reaction is 2-3h, and the temperature of the polycondensation reaction is 260-290℃, and the time of the polycondensation reaction is 2-3h.

[0067] Further, in the step 6.1, the pressure of the polycondensation reactor is 2-8MPa.

[0068] Further, in the step 6.2, the granulator is a gantry type granulator, and the length of the regenerated polyester particles is 3-5mm.

[0069] Further, in the step 6.3, the drying temperature of the dryer is 60-80℃. Advantages

[0070] 1. While existing technologies can recycle and regenerate polyester, the yield of the recycled polyester is low, making it unsuitable for large-scale industrial applications. This invention, however, employs an unexpected preparation system and method to first degrade polyester into the intermediate product diethyl terephthalate, then prepare diethyl terephthalate from diethyl terephthalate, and finally polycondense diethyl terephthalate into recycled polyester. This invention optimizes the process route for polyester recycling and regeneration, improving the yield of recycled polyester and making it more suitable for industrial applications.

[0071] 2. This invention recycles and regenerates waste polyester, which is beneficial to the recycling of resources and the sustainable development of society.

[0072] 3. This invention reduces pollution from waste polyester by degrading it, which is beneficial to the protection of the ecological environment. Attached Figure Description

[0073] Figure 1 is a system flow diagram of polyester recycling and regeneration according to the present invention.

[0074] 1-Polyester alcoholysis system; 2-Solids filtration system; 3-Solvent recovery system; 4-Diethyl terephthalate refining system; 5-Diethyl terephthalate preparation system; 6-Polyester regeneration system; 1-1-Depolymerization reactor; 2-1-Centrifuge; 2-2-Filter; 3-1-Ethanol recovery tower; 4-1-Diethyl terephthalate distillation tower; 4-2-Diethyl terephthalate crystallizer; 5-1-Transesterification reactor; 5-2-Diethyl terephthalate crystallizer; 5-3-Ethylene glycol recovery tower; 6-1-Polycondensation reactor; 6-2-Pelletizer; 6-3-Dryer. The best embodiment of the present invention

[0075] A polyester recycling system comprises, in order of feed direction, a polyester alcoholysis system 1, a solids filtration system 2, a solvent recovery system 3, a diethyl terephthalate refining system 4, a diethyl terephthalate preparation system 5, and a polyester regeneration system 6. As shown in Figure 1, the polyester alcoholysis system 1 includes a depolymerization reactor 1-1; the solids filtration system 2 includes, in order of feed direction, a centrifuge 2-1 and a filter 2-2; the solvent recovery system 3 includes an ethanol recovery tower 3-1; the diethyl terephthalate refining system 4 includes, in order of feed direction, a diethyl terephthalate distillation tower 4-1 and a diethyl terephthalate crystallizer 4-2; the diethyl terephthalate preparation system 5 includes, in order of feed direction, an transesterification reactor 5-1, a diethyl terephthalate crystallizer 5-2, and an ethylene glycol recovery tower 5-3; and the polyester regeneration system 6 includes, in order of feed direction, a polycondensation reactor 6-1, a pelletizer 6-2, and a dryer 6-3.

[0076] The polyester enters the depolymerization reactor 1-1, and at the same time, the depolymerization reactor 1-1 is also provided with an electric agitator, to obtain a depolymerization solution. The depolymerization solution continues to enter the centrifuge 2-1, to obtain a depolymerization centrifugal solution, which continues to enter the filter 2-2, to obtain a depolymerization filtered solution, which continues to enter the ethanol recovery tower 3-1, to obtain crude diethyl terephthalate. The crude diethyl terephthalate continues to enter the diethyl terephthalate rectification tower 4-1, to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer 4-2, to obtain diethyl terephthalate crystals.

[0077] The diethyl terephthalate crystals continue to enter the ester exchange reactor 5-1, to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer 5-2, to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after the crystallization treatment continues to enter the glycol recovery tower 5-3.

[0078] The bis-hydroxyethyl terephthalate crystals continue to enter the polycondensation reactor 6-1, to obtain regenerated polyester, which continues to enter the pelletizer 6-2, to obtain regenerated polyester particles, which continue to enter the dryer 6-3, to obtain dried regenerated polyester. Embodiment of the present application

[0079] Example 1

[0080] A polyester recycling system, which comprises, in sequence in the feeding direction: a polyester alcoholysis system 1, a solid filter system 2, a solvent recovery system 3, a diethyl terephthalate refining system 4, a bis-hydroxyethyl terephthalate preparation system 5, and a polyester regeneration system 6. As shown in FIG. 1, the polyester alcoholysis system 1 comprises a depolymerization reactor 1-1; the solid filter system 2 comprises, in sequence in the feeding direction: a centrifuge 2-1, a filter 2-2; the solvent recovery system 3 comprises an ethanol recovery tower 3-1; the diethyl terephthalate refining system 4 comprises, in sequence in the feeding direction: a diethyl terephthalate rectification tower 4-1, a diethyl terephthalate crystallizer 4-2; the bis-hydroxyethyl terephthalate preparation system 5 comprises, in sequence in the feeding direction: an ester exchange reactor 5-1, a bis-hydroxyethyl terephthalate crystallizer 5-2, a glycol recovery tower 5-3; and the polyester regeneration system 6 comprises, in sequence in the feeding direction: a polycondensation reactor 6-1, a pelletizer 6-2, and a dryer 6-3.

[0081] The polyester enters the depolymerization reactor 1-1, and at the same time, an electric agitator is arranged in the depolymerization reactor 1-1, to obtain a depolymerization solution. The depolymerization solution continues to enter the centrifuge 2-1, to obtain a depolymerization centrifugal solution, which continues to enter the filter 2-2, to obtain a depolymerization filtrate, which continues to enter the ethanol recovery tower 3-1, to obtain crude diethyl terephthalate. The crude diethyl terephthalate continues to enter the diethyl terephthalate rectification tower 4-1, to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer 4-2, to obtain diethyl terephthalate crystals.

[0082] The diethyl terephthalate crystals continue to enter the ester exchange reactor 5-1, to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer 5-2, to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after the crystallization treatment continues to enter the glycol recovery tower 5-3.

[0083] The bis-hydroxyethyl terephthalate crystals continue to enter the polycondensation reactor 6-1, to obtain regenerated polyester, which continues to enter the pelletizer 6-2, to obtain regenerated polyester particles, which continue to enter the dryer 6-3, to obtain dried regenerated polyester. Embodiment

[0084] A method for recycling polyester, comprising the following steps:

[0085] Step 1: polyester alcoholysis: take 10 kg of polyester, 50 kg of anhydrous ethanol, and 0.4 kg of depolymerization catalyst zinc acetate in the depolymerization reactor 1-1 to carry out a depolymerization reaction, to obtain a depolymerization solution, the temperature of the depolymerization reactor 1-1 is 200°C, the pressure is 1.5 MPa, the time of the depolymerization reaction is 1 h, and the depolymerization rate of the polyester is 96%.

[0086] Step 2: solid filtration: take the depolymerization solution obtained in step 1 to carry out centrifugal treatment in the centrifuge 2-1, to obtain a depolymerization centrifugal solution, which is filtered in the filter 2-2, to obtain a depolymerization filtrate.

[0087] Step 3: solvent recovery: take the depolymerization filtrate obtained in step 2 to carry out anhydrous ethanol recovery treatment in the ethanol recovery tower 3-1, to obtain crude diethyl terephthalate, the temperature of the ethanol recovery tower 3-1 is 95°C, and the recovered anhydrous ethanol returns to the depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0088] Step 4: Purification of diethyl terephthalate: The crude diethyl terephthalate obtained in Step 3 is first subjected to purification in a diethyl terephthalate distillation column 4-1 at a temperature of 150°C and a pressure of 1 MPa to obtain purified diethyl terephthalate. Then, 5 kg of the purified diethyl terephthalate and 2.5 kg of anhydrous ethanol are subjected to crystallization in a diethyl terephthalate crystallizer 4-2 at a temperature of 5°C to obtain diethyl terephthalate crystals having a purity of 99.9%.

[0089] Step 5: Preparation of bis-hydroxyethyl terephthalate: 1 kg of the diethyl terephthalate crystals obtained in Step 4, 3 kg of ethylene glycol, and 20 g of an ester exchange catalyst, calcium oxide, are subjected to ester exchange reaction in an ester exchange reactor 5-1 at an initial temperature of 180°C for 1 h, and then the temperature of the ester exchange reactor 5-1 is raised to 230°C for an additional 3 h at a pressure of -0.002 MPa to obtain crude bis-hydroxyethyl terephthalate.

[0090] Then, 0.8 kg of the crude bis-hydroxyethyl terephthalate and 0.8 kg of ethylene glycol are subjected to crystallization in a bis-hydroxyethyl terephthalate crystallizer 5-2 at a temperature of 10°C to obtain bis-hydroxyethyl terephthalate crystals having a purity of 99.5%. The filtrate after the crystallization is subjected to ethylene glycol recovery in an ethylene glycol recovery column 5-3 at a temperature of 110°C, and the recovered ethylene glycol is returned to the ester exchange reactor 5-1 as a solvent for the ester exchange reaction.

[0091] Step 6: Regeneration of polyester: 0.5 kg of the bis-hydroxyethyl terephthalate crystals obtained in Step 5 and a mixed catalyst are subjected to pre-polycondensation and polycondensation in a polycondensation reactor 6-1. The mixed catalyst contains 0.5 g of antimony glycolate and 0.25 g of zinc acetate. The pre-polycondensation is performed at a temperature of 240°C for 2 h, and the polycondensation is performed at a temperature of 275°C for 2 h at a pressure of 8 MPa to obtain regenerated polyester having a yield of 90%. The regenerated polyester is then subjected to pelletization in a gantry pelletizer 6-2 to obtain regenerated polyester pellets having a length of 3 mm. Finally, the regenerated polyester pellets are subjected to drying in a dryer 6-3 at a temperature of 70°C to obtain dried regenerated polyester. Example

[0092] A method for recycling and regenerating polyester, comprising the following steps:

[0093] Step 1: Polyolysis of polyester: Take polyester 10 kg, anhydrous ethanol 75 kg and depolymerization catalyst zinc acetate 0.8 kg in depolymerization reactor 1-1 to carry out depolymerization reaction to obtain depolymerization solution, the temperature of the depolymerization reactor 1-1 is 170 ℃, the pressure is 1.8 MPa, the time of the depolymerization reaction is 2 h, and the depolymerization rate of the polyester is 98%.

[0094] Step 2: Solid filtration: Take the depolymerization solution obtained in step 1 to carry out centrifugal treatment in centrifuge 2-1 to obtain depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is filtered in filter 2-2 to obtain depolymerization filtrate.

[0095] Step 3: Solvent recovery: Take the depolymerization filtrate obtained in step 2 to carry out anhydrous ethanol recovery treatment in ethanol recovery tower 3-1 to obtain crude diethyl terephthalate, the temperature of the ethanol recovery tower 3-1 is 100 ℃, and the recovered anhydrous ethanol is returned to the depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0096] Step 4: Diethyl terephthalate refining: Take the crude diethyl terephthalate obtained in step 3 to carry out distillation treatment in diethyl terephthalate distillation tower 4-1 to obtain distilled diethyl terephthalate, the temperature of the diethyl terephthalate distillation tower 4-1 is 200 ℃, and the pressure is 3 MPa, and then take 5 kg of the distilled diethyl terephthalate and 4 kg of anhydrous ethanol to carry out crystallization treatment in diethyl terephthalate crystallizer 4-2, the temperature of the crystallization treatment is 10 ℃, to obtain diethyl terephthalate crystals with a purity of 99.9%.

[0097] Step 5: Preparation of bis-hydroxyethyl terephthalate: Take 1 kg of the diethyl terephthalate crystals obtained in step 4, 5 kg of ethylene glycol and 30 g of ester exchange catalyst calcium oxide in ester exchange reactor 5-1 to carry out ester exchange reaction to obtain crude bis-hydroxyethyl terephthalate, the initial temperature of the ester exchange reactor 5-1 is 220 ℃, the initial reaction time is 3 h, then the ester exchange reactor 5-1 is heated to 260 ℃, and the reaction is continued for 1 h, and the pressure of the ester exchange reactor 5-1 is 0.006 MPa.

[0098] Then take 0.8 kg of the crude bis-hydroxyethyl terephthalate and 2 kg of ethylene glycol to carry out crystallization treatment in bis-hydroxyethyl terephthalate crystallizer 5-2, the temperature of the crystallization treatment is 15 ℃, to obtain bis-hydroxyethyl terephthalate crystals with a purity of 99.5%, and the filtrate after the crystallization treatment is subjected to ethylene glycol recovery treatment in ethylene glycol recovery tower 5-3, the temperature of the ethylene glycol recovery tower 5-3 is 100 ℃, and the recovered ethylene glycol is returned to the ester exchange reactor 5-1 through a pipeline to continue to participate in the ester exchange reaction as a solvent.

[0099] Step 6: Polyester regeneration: Take the terephthalic acid bis-hydroxyethyl ester crystal 0.5 kg obtained in step 5 and the mixed catalyst in the polycondensation reactor 6-1 to carry out pre-polycondensation and polycondensation reaction, the amount of antimony glycol in the mixed catalyst is 1.5 g, the amount of zinc acetate is 0.5 g, the yield of regenerated polyester is 91%, the pre-polycondensation reaction temperature is 260°C, the pre-polycondensation reaction time is 2h, the polycondensation reaction temperature is 260°C, the polycondensation reaction time is 3h, and the pressure of the polycondensation reactor 6-1 is 5 MPa. Then take the regenerated polyester in the gantry pelletizer 6-2 for pelletizing treatment to obtain regenerated polyester particles with a length of 4 mm, and finally take the regenerated polyester particles in the dryer 6-3 for drying treatment to obtain dried regenerated polyester, and the drying temperature is 60°C. Embodiment

[0100] A method for polyester recycling and regeneration, comprising the following steps:

[0101] Step 1: Polyester alcoholysis: Take polyester 10 kg, anhydrous ethanol 100 kg and depolymerization catalyst zinc acetate 0.6 kg in depolymerization reactor 1-1 to carry out depolymerization reaction to obtain depolymerization solution, the temperature of the depolymerization reactor 1-1 is 220°C, the pressure is 1.8 MPa, the depolymerization reaction time is 3h, and the depolymerization rate of the polyester is 99%.

[0102] Step 2: Solid filtration: Take the depolymerization solution obtained in step 1 in the centrifuge 2-1 for centrifugal treatment to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is filtered in the filter 2-2 to obtain a depolymerization filtrate.

[0103] Step 3: Solvent recovery: Take the depolymerization filtrate obtained in step 2 in the ethanol recovery tower 3-1 to recover ethanol to obtain crude terephthalic acid diethyl ester, the temperature of the ethanol recovery tower 3-1 is 85°C, and the recovered anhydrous ethanol returns to the depolymerization reactor 1-1 through the pipeline to continue to participate in the depolymerization reaction as a solvent.

[0104] Step 4: Terephthalic acid diethyl ester refining: Take the crude terephthalic acid diethyl ester obtained in step 3 to carry out distillation treatment in the terephthalic acid diethyl ester distillation tower 4-1 to obtain distilled terephthalic acid diethyl ester, the temperature of the terephthalic acid diethyl ester distillation tower 4-1 is 180°C, and the pressure is 5 MPa, then take 5 kg of the distilled terephthalic acid diethyl ester and 5 kg of anhydrous ethanol in the terephthalic acid diethyl ester crystallizer 4-2 to carry out crystallization treatment, the crystallization treatment temperature is 0°C, and the purity of the terephthalic acid diethyl ester crystal obtained is 99.9%.

[0105] Step 5: Preparation of bis-hydroxyethyl terephthalate: The bis-hydroxyethyl terephthalate crystals obtained in step 4, 1 kg, ethylene glycol, 1 kg, and an ester exchange catalyst, calcium oxide, 50 g, were subjected to an ester exchange reaction in an ester exchange reactor 5-1 to obtain crude bis-hydroxyethyl terephthalate, the initial temperature of the ester exchange reactor 5-1 was 200°C, the initial reaction time was 1 h, and then the ester exchange reactor 5-1 was heated to 280°C, and the reaction was continued for 2 h, the pressure of the ester exchange reactor 5-1 was 0.004 MPa.

[0106] Then, the crude bis-hydroxyethyl terephthalate, 0.8 kg, and ethylene glycol, 4 kg, were subjected to a crystallization treatment in a bis-hydroxyethyl terephthalate crystallizer 5-2, the temperature of the crystallization treatment was 20°C, to obtain bis-hydroxyethyl terephthalate crystals with a purity of 99.5%, and the filtrate after the crystallization treatment was subjected to an ethylene glycol recovery treatment in an ethylene glycol recovery tower 5-3, the temperature of the ethylene glycol recovery tower 5-3 was 90°C, and the recovered ethylene glycol was returned to the ester exchange reactor 5-1 through a pipeline to continue to participate in the ester exchange reaction as a solvent.

[0107] Step 6: Regeneration of polyester: The bis-hydroxyethyl terephthalate crystals obtained in step 5, 0.5 kg, and a mixed catalyst were subjected to a pre-polycondensation and polycondensation reaction in a polycondensation reactor 6-1, the amount of ethylene glycol antimony in the mixed catalyst was 2.5 g, and the amount of zinc acetate was 1 g, to obtain regenerated polyester with a yield of 90%, the temperature of the pre-polycondensation reaction was 250°C, the time of the pre-polycondensation reaction was 3 h, the temperature of the polycondensation reaction was 290°C, the time of the polycondensation reaction was 2 h, and the pressure of the polycondensation reactor 6-1 was 2 MPa. Then, the regenerated polyester was subjected to a pelletizing treatment in a gantry pelletizer 6-2 to obtain regenerated polyester particles with a length of 5 mm, and finally, the regenerated polyester particles were subjected to a drying treatment in a dryer 6-3 to obtain dried regenerated polyester, the temperature of the drying was 80°C. Industrial applicability

[0108] The present application optimizes the process route of polyester recycling and regeneration, can improve the yield of regenerated polyester, and makes it more suitable for industrial application.

Claims

1. A system for polyester recycling, characterized by, The system sequentially comprises, in the feeding direction: a polyester alcoholysis system (1), a solid filtering system (2), a solvent recovery system (3), a diethyl terephthalate refining system (4), a bis-hydroxyethyl terephthalate preparation system (5) and a polyester regeneration system (6), wherein, The polyester alcoholysis system (1) comprises: a depolymerization reactor (1-1); The solid filtering system (2) sequentially comprises, in the feeding direction: a centrifuge (2-1), a filter (2-2); The solvent recovery system (3) comprises: an ethanol recovery tower (3-1); The diethyl terephthalate refining system (4) sequentially comprises, in the feeding direction: a diethyl terephthalate rectifying tower (4-1), a diethyl terephthalate crystallizer (4-2); The bis-hydroxyethyl terephthalate preparation system (5) sequentially comprises, in the feeding direction: an ester exchange reactor (5-1), a bis-hydroxyethyl terephthalate crystallizer (5-2), an ethylene glycol recovery tower (5-3); The polyester regeneration system (6) sequentially comprises, in the feeding direction: a polycondensation reactor (6-1), a pelletizer (6-2), a dryer (6-3).

2. The system of claim 1, wherein, The depolymerization reactor (1-1) is used for making the polyester to carry out a depolymerization reaction to obtain a depolymerization solution, which continues to enter the centrifuge (2-1).

3. The system of claim 2, wherein, The centrifuge (2-1) is used for centrifuging the depolymerization solution to obtain a depolymerization centrifugal liquid, which continues to enter the filter (2-2); The filter (2-2) is used for filtering the depolymerization centrifugal liquid to obtain a depolymerization filtered liquid, which continues to enter the ethanol recovery tower (3-1).

4. The system of claim 3, wherein, The ethanol recovery tower (3-1) is used for recovering ethanol in the depolymerization filtered liquid to obtain crude diethyl terephthalate, which continues to enter the diethyl terephthalate rectifying tower (4-1).

5. The system of claim 4, wherein, The diethyl terephthalate rectifying tower (4-1) is used for rectifying the crude diethyl terephthalate to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer (4-2).

6. The system of claim 5, wherein, The diethyl terephthalate crystallizer (4-2) is used for crystallizing the rectified diethyl terephthalate to obtain diethyl terephthalate crystals, which continue to enter the ester exchange reactor (5-1).

7. The system of claim 6, wherein, The ester exchange reactor (5-1) is used for making the diethyl terephthalate crystals to carry out an ester exchange reaction to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer (5-2).

8. The system of claim 7, wherein, The bis-hydroxyethyl terephthalate crystallizer (5-2) is used for crystallizing the crude bis-hydroxyethyl terephthalate to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after the crystallization process continues to enter the ethylene glycol recovery tower (5-3).

9. The system of claim 8, wherein, The polycondensation reactor (6-1) is used for making the bis-hydroxyethyl terephthalate crystals to carry out a pre-polycondensation and polycondensation reaction to obtain regenerated polyester, which continues to enter the pelletizer (6-2).

10. A method for polyester recycling using the system according to any one of claims 1 to 9, characterized in that, The method includes a polyester glycolysis method, a solid filtration method, a solvent recovery method, a diethyl terephthalate purification method, a bis-hydroxyethyl terephthalate production method, and a polyester regeneration method.

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