A filtration and spinning pack assembly residual pet recycling apparatus and method

Abstract

This invention discloses a PET recycling system for filtration and spinneret components, comprising a reactor with a basket inside; a heating system for controlling the reaction temperature within the reactor; a circulation system including an overflow sub-tank and a circulation pump, the overflow sub-tank being connected to the reactor; a condensation separation system including a first condenser, a second condenser, and a third condenser, the first condenser being connected to the first exhaust port of the reactor, the second condenser being connected to the second exhaust port of the reactor, and the third condenser being connected to the third exhaust port of the reactor; and a product collection system including a first product outlet, a second product outlet, and valves mounted thereon for collecting DOTP and EG respectively. This invention integrates alcoholysis reaction, material circulation, and staged condensation separation into one unit, completing the entire process from PET feeding to product separation within a single reactor, thus simplifying the recycling process.

Description

Technical Field

[0001] This invention relates to the field of PET recycling technology, specifically to equipment and method for recycling residual PET from filtration and spinneret components. Background Technology

[0002] Polyethylene terephthalate (PET), a high-performance thermoplastic, is widely used in fibers, films, and bottle flakes. During PET production, melt spinning, and processing, such as in extruders, filters, and spinnerets, a large amount of waste material is inevitably generated. In particular, the PET remaining in filter and spinneret components, due to its irregular shape, complex composition (potentially containing degradation products, gels, inorganic fillers, and other impurities), and tight bonding with metal parts, is difficult to effectively handle using traditional physical recycling methods (such as direct crushing and granulation). This not only wastes resources but also places environmental pressure on enterprises.

[0003] Chemical recycling is an effective way to treat this type of waste PET. Through methods such as alcoholysis, PET is depolymerized into monomers or oligomers, which can then be used to produce high-value-added products. In existing technologies, ethylene glycol (EG) alcoholysis has been extensively studied. However, current technologies mostly focus on the overall recycling of PET bottle flakes or fiber waste, lacking specially designed, integrated recycling equipment and methods for treating specific forms of waste such as residual PET in filtration and spinning components. Existing processes often suffer from problems such as complex procedures, high energy consumption, and difficulties in product separation. For example, in the process of preparing dioctyl terephthalate (DOTP) plasticizer using 2-ethylhexanol (2-EG) alcoholysis, the separation of byproducts such as water, excess alcohol, and the final product requires multiple steps, resulting in complex equipment and requiring improved efficiency. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an equipment and method for recycling residual PET in filtration and spinneret components. The aim is to achieve efficient and integrated chemical recycling of residual PET in filtration and spinneret components, simplify the process flow, and improve product separation efficiency and purity.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A device for recycling residual PET from a filter and spinneret assembly, comprising:

[0007] The reactor is equipped with a basket inside to hold the PET material to be recycled;

[0008] A heating system is used to control the reaction temperature inside the reactor.

[0009] The circulation system includes an overflow sub-tank and a circulation pump. The inlet of the overflow sub-tank is connected to the overflow port of the reactor, and the outlet of the overflow sub-tank is connected to the return port of the reactor through the circulation pump.

[0010] A condensation separation system includes a first condenser, a second condenser, and a third condenser. The first condenser is connected to the first exhaust port of the reactor, the second condenser is connected to the second exhaust port of the reactor, and the third condenser is connected to the third exhaust port of the reactor.

[0011] The product collection system includes a first product outlet, a second product outlet, and valves disposed thereon for collecting dioctyl terephthalate (DOTP) and ethylene glycol (EG), respectively.

[0012] Furthermore, the reactor is equipped with multiple temperature sensors for real-time monitoring of the internal temperature.

[0013] Furthermore, the basket has multiple filter holes distributed on it.

[0014] Furthermore, the heating system is a heat transfer oil circulating heating jacket system, which includes a heat transfer oil furnace, a circulating pump, and a jacket covering the outer wall of the reactor.

[0015] Furthermore, the heating system includes an electric heating tube disposed inside the reactor, which is located inside the reactor and is evenly arranged along the circumference of the reactor, or spirally surrounding the inner wall of the reactor.

[0016] A method for recovering residual PET from filter and spinneret components, using the recovery equipment described above, includes the following steps:

[0017] Step S1: Place the PET material to be recycled in the basket of the reactor and add 2-ethylhexanol (2-EG).

[0018] Step S2: Heat the reactor to the first temperature range to dehydrate 2-EG, and start the first condenser for condensation, heat exchange, and exhaust.

[0019] Step S3: Heat the reactor to the second temperature range to preheat the material, and start the second condenser for condensation, heat exchange, and exhaust.

[0020] Step S4: Heat the reactor to the third temperature range to allow the reactants to enter the alcoholysis reaction stage. The 2-EG vapor generated by the reaction overflows to the overflow sub-tank and is sent back to the reactor by the circulation pump to form a cycle. At the same time, the second condenser continues to work.

[0021] Step S5: Heat the reactor to the fourth temperature range to allow the materials to undergo the final reaction;

[0022] Step S6: After the reaction is complete, the basket is lifted out and the third condenser is started for heat exchange. According to the difference in boiling point or condensation temperature of the target product, the valves are controlled to collect DOTP and EG respectively.

[0023] Furthermore, in step S2, the first temperature range is 110-130℃, preferably 120℃; in step S3, the second temperature range is 150-170℃, preferably 160℃; in step S4, the third temperature range is 170-190℃, preferably 180℃; and in step S5, the fourth temperature range is 190-210℃, preferably 200℃.

[0024] Furthermore, in step S4, the circulation volume and reaction uniformity of the material in the reactor are adjusted by controlling the start and stop of the circulating pump and its flow rate.

[0025] Furthermore, in step S6, the collection of DOTP and EG is achieved by utilizing the difference in volatility between DOTP and EG at a specific temperature, and by controlling the temperature of the reactor or subsequent separation tank, EG is preferentially vaporized and condensed and collected by the third condenser, with the remaining liquid product being DOTP.

[0026] Furthermore, the PET material to be recycled is waste material remaining in the filtration and spinneret assembly, including but not limited to clumps or adhering material on the filter screen, spinneret, and inner wall of the pipe.

[0027] Furthermore, in step S1, the mass ratio of the added 2-EG to the PET material is (1.5-3):1.

[0028] Furthermore, during the reaction process, the reaction vessel is maintained at atmospheric pressure or a slightly positive pressure.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) This invention integrates functions such as alcoholysis reaction, material circulation, and staged condensation separation into one unit. The entire process from PET feeding to product separation can be completed in one reactor, avoiding energy consumption and material loss caused by material transfer between different equipment and simplifying the recycling process.

[0031] (2) By setting specific operations (such as dehydration, preheating, overflow circulation, and final reaction) at key temperature points such as 120℃, 160℃, 180℃, and 200℃, and using different condensers for graded treatment, the reaction process was precisely controlled, effectively separating water, unreacted alcohol and final product, and improving the purity of the target product DOTP and the by-product EG.

[0032] (3) During the critical stage of the reaction at 180℃, the 2-EG vapor generated by the reaction is condensed or directly returned to the reactor through the overflow sub-tank and the circulation pump, forming an internal circulation of materials, which not only promotes heat transfer and reaction uniformity, but also improves the efficiency of alcoholysis reaction.

[0033] (4) A detachable basket is installed inside the reactor, which is specifically used to place irregularly shaped waste materials of the filter and spinneret assembly that are combined with metal parts. After the reaction is completed, solid impurities (such as inorganic packing and unreacted materials) and metal parts can be lifted out together with the basket, realizing rapid solid-liquid separation and facilitating subsequent cleaning and maintenance.

[0034] (5) By taking advantage of the boiling point difference between DOTP and EG, the products can be separated and collected online by controlling the temperature and using a third condenser, without the need for additional distillation equipment, thus reducing equipment investment and operating costs. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the present invention;

[0036] Figure 2 This is a process flow diagram of the present invention;

[0037] In the diagram: 1-Reaction vessel, 2-Suspended basket, 3-Heating system, 4-Overflow auxiliary tank, 5-Circulation pump, 6-First condenser, 7-Second condenser, 8-Third condenser, 9-First product outlet, 10-Second product outlet. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a device for recycling residual PET from a filtration and spinneret assembly, the specific structure of which is as follows:

[0041] The reactor is a vertical jacketed structure with an internal liftable and detachable basket made of stainless steel mesh with a pore size of 2-5mm, used to hold residual PET waste removed from the spinneret and filter. The top of the reactor is equipped with a feed port, an exhaust port (including first, second, and third exhaust ports), and a reflux port.

[0042] The reactor is equipped with an automatic temperature control system, consisting of 2-4 temperature sensors distributed at the top, middle, bottom, and inside the basket, a local thermometer, a pressure gauge, a controller, and an actuator. The thermometers are bimetallic or digital, allowing for direct reading by on-site operators. The pressure gauge monitors the pressure inside the reactor, ensuring the reaction proceeds safely under atmospheric or slightly positive pressure conditions and preventing the risk of overpressure.

[0043] When the heating system adopts a heat transfer oil circulation heating jacket system, it includes a heat transfer oil furnace, a circulation pump, and a jacket covering the outer wall of the reactor. Specifically: the outer wall of the reactor is covered by a jacket, which has a heat transfer oil inlet and a heat transfer oil outlet. The heat transfer oil furnace is an electrically heated or gas-fired heated type. Its oil outlet is connected to the heat transfer oil inlet of the jacket through a first oil supply pipe. The heat transfer oil outlet of the jacket is connected to the oil inlet of the circulation pump through a second oil supply pipe. The oil outlet of the circulation pump is connected to the oil return port of the heat transfer oil furnace through a third oil supply pipe, thereby forming a closed heat transfer oil circulation loop. An expansion tank is set at the high position of the circulation loop (preferably between the oil inlet of the circulation pump and the outlet of the jacket). The expansion tank is connected to the loop through a connecting pipe and stores a portion of the heat transfer oil inside to absorb the volume change of the heat transfer oil due to thermal expansion during heating. It also has the functions of oil replenishment and venting. In addition, valves are installed at the oil outlet of the thermal oil furnace, the inlet and outlet of the jacket, and the inlet and outlet of the circulating pump to control the flow rate of the thermal oil or to cut off the circuit during maintenance.

[0044] The controller automatically adjusts the heating power of the thermal oil furnace or the flow rate of the circulating pump based on the preset segmented temperature control curves (120℃, 160℃, 180℃, 200℃) and sensor feedback signals, thereby achieving precise closed-loop control of the reaction temperature and ensuring that the temperature of each reaction stage is stable and controllable.

[0045] When the heating system uses electric heating tubes, the heating system includes several electric heating tubes and a power regulator. The electric heating tubes are located inside the reactor and are evenly arranged circumferentially along the reactor, or spirally encircled around the inner wall of the reactor. The parts of the heating tubes that contact the material are made of corrosion-resistant, high-temperature-resistant stainless steel or Incoloy alloy and have explosion-proof properties. The temperature sensor monitors the temperature inside the reactor in real time, and the power regulator adjusts the heating power of the heating tubes according to the temperature feedback signal to achieve segmented, stepped temperature control.

[0046] In summary, both the heat transfer oil circulation heating jacket system and the electric heating tube are existing technologies, and those skilled in the art can install them on the reactor according to the actual situation. This invention will not describe them in detail.

[0047] Furthermore, the heating system can employ various heating methods known in the art, including but not limited to heat transfer oil circulation heating jacket, built-in electric heating tube, electromagnetic induction heating, etc. As a preferred embodiment, for considerations of heating uniformity and safety, the present invention employs a heat transfer oil circulation heating jacket system.

[0048] The circulation system includes an overflow sub-tank and a high-temperature resistant circulation pump. An overflow port is located in the upper part of the reactor and is connected to the top of the overflow sub-tank via a pipe. The bottom of the overflow sub-tank is connected to the inlet of the circulation pump via a pipe, and the outlet of the circulation pump is connected to the reflux port at the bottom of the reactor.

[0049] The condensation separation system includes three independent shell-and-tube condensers. The first condenser is connected to the first exhaust port and is used to process the 2-EG vapor containing a small amount of moisture discharged at 120°C; the second condenser is connected to the second exhaust port and is used to process the 2-EG vapor discharged during the 160°C-180°C stage; the third condenser is connected to the third exhaust port and is used to process the vapor generated during the final EG separation after the reaction.

[0050] The product collection system includes two outlets and valves. The first product outlet is used to collect DOTP, and the second product outlet is used to collect EG.

[0051] Example 2

[0052] This embodiment uses the equipment described in Embodiment 1 to recover approximately 5 kg of PET agglomerated material (containing a small amount of filter screen metal wire) cleaned from a filter assembly in a chemical fiber plant. The specific steps are as follows:

[0053] Loading: Place the PET material to be recycled (most of the metal frame has been removed, but a small amount of metal still adheres) into the basket, and lower the basket into the reactor. Add 2-ethylhexanol (2-EG) to the reactor, with a 2:1 mass ratio of 2-EG to PET.

[0054] Low-temperature dehydration (120℃): Start the heating system to raise the reactor temperature to 120℃ and maintain this temperature for 30 minutes. During this stage, any moisture that may be present in 2-EG and trace amounts of adsorbed water in PET are evaporated and enter the first condenser through the first exhaust port. The condensate (mainly water and a small amount of 2-EG) is discharged or collected. This process effectively prevents moisture from negatively impacting the subsequent alcoholysis reaction.

[0055] Preheating (160℃): Continue heating to 160℃ and hold for 20 minutes. At this temperature, the material is fully preheated, PET begins to swell, some low molecular weight substances escape, and the generated vapor enters the second condenser through the second exhaust port, is condensed, and then flows back into the reactor or is discharged to the auxiliary tank.

[0056] Circulating alcoholysis (180℃): The temperature is raised to 180℃ and the circulating pump is started. The 2-EG and PET in the reactor begin the alcoholysis reaction. The 2-EG vapor produced by the reaction rises and enters the overflow sub-tank through the overflow port. After being pressurized by the circulating pump, it is pumped back in through the reflux port at the bottom of the reactor, forming a strong material circulation. This process lasts for approximately 1.5 hours, ensuring the uniformity and efficiency of the reaction. The second condenser continues to operate during this stage, recovering the volatilized 2-EG and refluxing it.

[0057] Final reaction (200℃): The reactor temperature is raised to 200℃ for the final reaction, which lasts for 1 hour. At this temperature, the alcoholysis reaction tends to be complete, and PET is depolymerized into dioctyl terephthalate (DOTP) and ethylene glycol (EG).

[0058] Product Separation and Collection: After the reaction is complete, the heating is turned off, and the basket is lifted out of the reactor. A small amount of unreacted solid impurities and metal residue remain in the basket, achieving solid-liquid separation. Subsequently, the third condenser is turned on, and the reactor temperature is lowered to below the boiling point of EG (approximately 197°C) and above the boiling point of DOTP (e.g., controlled at 150-180°C). At this point, the EG in the reaction liquid vaporizes due to its lower boiling point and enters the third condenser through the third exhaust port for condensation. Valve 4 is opened, yielding pure byproduct EG. The remaining liquid in the reactor is the target product DOTP, which is collected by opening valve 3. Testing shows that the purity of DOTP can reach over 98.5%, and the purity of EG can reach over 95%.

[0059] Example 3

[0060] This embodiment is basically the same as Embodiment 2, except that in steps S2, S3, S4, and S5, the first temperature range is 110°C, the second temperature range is 150°C, the third temperature range is 170°C, and the fourth temperature range is 190°C. The mass ratio of 2-EG to PET is 1.5:1. After the reaction is complete, the DOTP yield reaches 92% and the purity is 97%.

[0061] Example 4

[0062] This embodiment is basically the same as Embodiment 2, except that in steps S2, S3, S4, and S5, the first temperature range is 130°C, the second temperature range is 170°C, the third temperature range is 190°C, and the fourth temperature range is 210°C. The mass ratio of 2-EG to PET is 3:1. After the reaction is complete, the DOTP yield reaches 94% and the purity is 98%.

[0063] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for recycling residual PET from a filter and spinneret assembly, characterized in that, include: The reactor (1) is equipped with a basket (2) for holding the PET material to be recycled. Heating system (3) is used to control the reaction temperature inside the reactor; The circulation system includes an overflow sub-tank (4) and a circulation pump (5). The inlet of the overflow sub-tank (4) is connected to the overflow port of the reactor (1), and the outlet of the overflow sub-tank (4) is connected to the return port of the reactor (1) through the circulation pump (5). The condensation separation system includes a first condenser (6), a second condenser (7) and a third condenser (8). The first condenser (6) is connected to the first exhaust port of the reactor (1), the second condenser (7) is connected to the second exhaust port of the reactor (1), and the third condenser (8) is connected to the third exhaust port of the reactor (1). The product collection system includes a first product outlet (9), a second product outlet (10), and valves disposed thereon for collecting dioctyl terephthalate (DOTP) and ethylene glycol (EG), respectively.

2. The equipment for recycling residual PET from the filtration and spinneret assembly according to claim 1, characterized in that, The reactor (1) is equipped with multiple temperature sensors, which are respectively arranged in the upper, middle, lower and inside the basket of the reactor, for real-time monitoring of the temperature in different areas of the reactor.

3. The equipment for recycling residual PET from the filtration and spinneret assembly according to claim 1, characterized in that, The basket (2) has several filter holes.

4. The equipment for recycling residual PET from the filtration and spinneret assembly according to claim 1, characterized in that, The heating system (3) is a heat transfer oil circulating heating jacket system, which includes a heat transfer oil furnace, a circulating pump and a jacket covering the outer wall of the reactor.

5. The equipment for recycling residual PET from the filter and spinneret assembly according to claim 1, characterized in that, The heating system (3) includes an electric heating tube disposed inside the reactor. It is located inside the reactor and is evenly arranged along the circumference of the reactor or spirally surrounding the inner wall of the reactor.

6. A method for recovering residual PET from a filter and spinneret assembly, characterized in that, The recycling equipment described in any one of claims 1-5 includes the following steps: Step S1: Place the PET material to be recycled into the basket of the reactor and add 2-EG; Step S2: Heat the reactor to the first temperature range to dehydrate 2-EG, and start the first condenser for condensation, heat exchange, and exhaust. Step S3: Heat the reactor to the second temperature range to preheat the material, and start the second condenser for condensation, heat exchange, and exhaust. Step S4: Heat the reactor to the third temperature range to allow the reactants to enter the alcoholysis reaction stage. The 2-EG vapor generated by the reaction overflows to the overflow sub-tank and is sent back to the reactor by the circulation pump to form a cycle. At the same time, the second condenser continues to work. Step S5: Heat the reactor to the fourth temperature range to allow the materials to undergo the final reaction; Step S6: After the reaction is complete, the basket is lifted out and the third condenser is started for heat exchange. According to the difference in boiling point or condensation temperature of the target product, the valves are controlled to collect DOTP and EG respectively.

7. The method for recovering residual PET from the filter and spinneret assembly according to claim 6, characterized in that, In step S2, the first temperature range is 110-130℃, preferably 120℃; in step S3, the second temperature range is 150-170℃, preferably 160℃; in step S4, the third temperature range is 170-190℃, preferably 180℃; and in step S5, the fourth temperature range is 190-210℃, preferably 200℃.

8. The method for recovering residual PET from the filter and spinneret assembly according to claim 6, characterized in that, In step S4, the circulation volume and reaction uniformity of the material in the reactor are adjusted by controlling the start and stop of the circulating pump and the flow rate.

9. The method for recovering residual PET from the filter and spinneret assembly according to claim 6, characterized in that, In step S6, the collection of DOTP and EG is achieved by utilizing the difference in volatility between DOTP and EG at a specific temperature, and by controlling the temperature of the reactor or subsequent separation tank, EG is preferentially vaporized and collected by the third condenser, with the remaining liquid product being DOTP.

10. The method for recovering residual PET from the filter and spinneret assembly according to claim 6, characterized in that, In step S1, the mass ratio of the added 2-EG to the PET material is (1.5-3):1.

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