PET (Polyethylene Terephthalate) recycling and granulating system

Abstract

The utility model discloses a PET (Polyethylene Terephthalate) recycling and granulating system, which comprises a PET bottle flake drying and purifying device, a PET bottle flake drying and purifying device, a PET bottle flake drying and purifying device and a PET bottle flake drying and purifying device, then the bottle chips purified by the purifying machine are conveyed into an extruding machine through a second bottle chip conveying device to be extruded, the bottle chips are pelletized, dehydrated and then tackified in a tackifying unit, the tackifying unit adopts a single-pot type infrared dehumidifying, crystallizing and drying all-in-one machine, and the bottle chips directly enter a tackifying machine for tackifying by hot nitrogen after being heated and crystallized by infrared rays; according to the recycling and granulating system, infrared heating, drying and purifying are carried out through the continuous infrared drying machine and the purifying machine before extrusion and granulation, moisture and low-molecular-weight substances in bottle chips are removed, the overall efficiency is higher, the purifying effect is better, then tackifying treatment is carried out through heated nitrogen, contact with oxygen is avoided, and the service life of the bottle chips is prolonged. The color of the final PET particles is not yellow.

Description

Technical Field

[0001] The utility model relates to the technical field of PET recycling and granulation, in particular to a PET recycling and granulation system. Background Art

[0002] Currently, the environmental pollution caused by discarded PET bottles is becoming increasingly serious. Recycling PET bottles can not only reduce environmental pollution but also save resources. Therefore, research on the recycling of PET waste is gaining increasing attention. For example, document CN115139428A describes a waste polyester recycling and granulation method, which includes the following steps: S1: selecting, cleaning, crushing, drying, and mixing the waste PET, and then drying to remove moisture to reduce the moisture content of the waste polyester; S2: melting the dried waste polyester and extruding the melt after the melt; S3: adding a chain extender to the extruded melt to increase viscosity; S4: filtering the melt after viscosity increase in S3; S5: drawing the filtered filaments into coarse filaments; S6: cooling the filaments after drawing in S5; S7: pelletizing, dehydrating, and packaging after cooling.

[0003] However, this recycling and granulation method has the following problems: 1. This recycling and granulation method adds a chain extender to the melt after extrusion to increase viscosity, which makes the recycled and granulated PET particles unusable in the food industry; 2. In this recycling and granulation method, since the PET material is exposed to oxygen, the recycled and granulated PET particles turn yellow, and the color of the PET bottles produced is also yellow.

[0004] The utility model disclosure document with publication number CN112549355A records a production device and process for high-quality bottle flake recycling, granulation and reuse. The production device uses 3A standard bottle flakes as raw materials, and removes impurities and precipitates them through the process steps of eddy current separator, material separator, fluidized bed and drying reaction tower. However, the production device does not have a viscosity increase step, and the impurity removal and purification steps are very complicated, inefficient, require a lot of equipment, and are costly. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a PET recycling and granulation system. Before extrusion and granulation, the recycling and granulation system uses a continuous infrared dryer and a purifier to perform infrared heating, drying and purification to remove moisture and low-molecular substances in the bottle flakes, with higher overall efficiency and better purification effect. Then, heated nitrogen is used for viscosity-increasing treatment to avoid contact with oxygen, so that the color of the final PET particles is not yellow.

[0006] In order to solve the above technical problems, the technical solution of the utility model is: a PET recycling and granulation system, including

[0007] The PET bottle flake drying and purification device includes a continuous infrared dryer and a purifier. The continuous infrared dryer includes a fixed base, on which a drying barrel is rotatably mounted. The drying barrel is driven by a drying rotary power device. A spiral stirring blade is provided in the drying barrel. The upstream end of the drying barrel is provided with a feed port and is connected to a bottle flake feeding device. The downstream end of the drying barrel is provided with a discharge port. The fixed base is provided with a drying discharge bin connected to the discharge port. The fixed base is also provided with a An internally heated infrared light box and an exhaust device are provided. The purifier includes a purification cylinder, a bottle flake feeding port is provided at the upper end of the purification cylinder, and the bottle flake feeding port is connected to the drying discharge bin via a first bottle flake conveying device. The lower end of the purification cylinder is connected to a conical bottle flake discharge hopper for convenient discharge. The lower end of the bottle flake discharge hopper is open and connected to a bottle flake discharge control device. A dry nitrogen main gas port is provided on the bottle flake discharge hopper, and the dry nitrogen main gas port is connected to a hot nitrogen supply system. A first negative pressure exhaust device is provided on the top of the purification cylinder;

[0008] An extruder, wherein the feeding port of the extruder is connected to the bottle flake discharge control device through a second bottle flake conveying device;

[0009] a pelletizing device installed downstream of the extruder for pelletizing the melt extruded by the extruder;

[0010] A dehydration device, the dehydration device is arranged below the pelletizing device and is used to dehydrate the PET particles pelletized by the pelletizing device;

[0011] A temporary storage tank is provided downstream of the dehydration device and is used to receive the PET particles dehydrated by the dehydration device;

[0012] A thickening unit, the thickening unit includes a single-pot infrared dehumidification crystallization drying all-in-one machine and a thickening machine, the feed port of the single-pot infrared dehumidification crystallization drying all-in-one machine is connected to the discharge port at the bottom of the temporary storage tank through a first particle conveying device; the thickening machine includes a vertical thickening cylinder, the upper end of the thickening cylinder is provided with a material adding port for convenient entry of PET particles, a material adding device is installed on the material adding port, the material adding device is connected to the discharge port of the single-pot infrared dehumidification crystallization drying all-in-one machine through a second particle conveying device, the lower end of the thickening cylinder is connected to a conical particle discharge hopper for convenient discharge, the lower end of the particle discharge hopper is opened and connected to a particle discharge control device, the particle discharge hopper From the inside to the outside, it includes an inner hopper, an intermediate hopper and an outer hopper. The inner hopper, the intermediate hopper and the outer hopper are fixedly connected by an annular connecting plate. The outer hopper is provided with a total gas port for thickening nitrogen for communicating with the hot nitrogen supply system. An outer annular chamber is provided between the outer hopper and the intermediate hopper, and an inner annular chamber is formed between the intermediate hopper and the inner hopper. The total gas port for thickening nitrogen is communicated with the outer annular chamber, and the upper and lower parts of the outer annular chamber and the inner annular chamber are respectively communicated. A connecting hole is provided on the annular connecting plate, and a plurality of air inlet holes are also provided on the hopper wall of the inner hopper. A second negative pressure exhaust device is provided on the top of the thickening cylinder, and a negative pressure vacuum gauge and a thermometer are provided on the thickening cylinder.

[0013] As a preferred solution, the structure of the bottle flakes discharge hopper is the same as that of the particle discharge hopper.

[0014] As a preferred solution, the outside of the viscosity-increasing cylinder, the outside of the purification cylinder and the outside of the outer hopper are all provided with a heat-insulating layer.

[0015] As a preferred solution, the material adding device includes a particle feeding bin fixed on the material adding port, a first feeding control valve is provided at the bottom of the particle feeding bin, the upper end of the particle feeding bin is connected to the second particle conveying device, and a second feeding control valve is provided between the second particle conveying device and the particle feeding bin.

[0016] As a preferred solution, the discharge control device includes a particle cache bin fixed on the lower opening of the particle discharge hopper, a first discharge control valve is arranged between the particle cache bin and the particle discharge hopper, the lower end of the particle cache bin is connected to the particle discharge bin, and a second discharge control valve is installed between the particle discharge bin and the particle cache bin.

[0017] As a preferred solution, the first bottle flake conveying device, the second bottle flake conveying device, the first particle conveying device and the second particle conveying device are all vacuum loaders, and the hot nitrogen gas supply system is connected to each vacuum loaders as an isolation gas source.

[0018] As a preferred solution, a vacuum feeding tank is installed at the feeding port of the extruder, and the vacuum feeding tank is connected to the second bottle piece conveying device, and the vacuum feeding tank is connected to the vacuum pumping device.

[0019] As a preferred solution, the pelletizing device is a water pelletizing device or an underwater pelletizing device.

[0020] After adopting the above technical scheme, the effects of the utility model are as follows: 1. The PET recycling and granulation system uses a continuous infrared dryer to perform infrared heating and drying on PET bottle flakes. The frequency of infrared rays is about 1012C / S~5×1014C / S, which is a part of electromagnetic waves. Infrared rays penetrate substances and the infrared rays reflected by substances do not affect the tissue of the substances. However, the absorbed tissues will be converted into heat energy due to molecular agitation, causing the temperature of the substance to rise. Taking PET as an example, the drying temperature can be reached in a very short time, which can save energy, maintain the physical properties of lipid particles and improve the IV value; the drying temperature of the bottle flakes can be controlled at 170-180℃, and the heated bottle flakes are directly sent to the purifier, and the heated nitrogen enters the purification cylinder from the bottom, so that the PET bottle flakes in the purification cylinder are isolated from oxygen, and the hot nitrogen can contact the bottle flakes more evenly, heating evenly without stirring, and then the first negative pressure exhaust device on the top is used to exhaust air, so as to discharge the volatilized water and other low-molecular impurities, and the purification effect is better. The drying efficiency is higher; 2. The system carries out a thickening treatment on the PET particles after granulation. During the thickening, a single-pot infrared dehumidification crystallization drying machine is first used for infrared crystallization drying. Infrared rays are used to heat a whole pot of particles, so that the PET particles are quickly heated and crystallized and dried in a very short time. The moisture content of the particles is less than 50ppm. The particles after crystallization are sent to the thickening cylinder, and the heated nitrogen enters evenly from the particle discharge hopper at the bottom of the thickening cylinder to heat the particles. Negative pressure is drawn from the top of the thickening cylinder to cause the particles to undergo polymerization reaction in the absence of oxygen. There are terminal hydroxyl groups and terminal carboxyl groups in the particles. The particle molecules undergo polymerization reaction, resulting in continuous growth of the molecular chain, thereby increasing the characteristic viscosity. Due to the infrared crystallization drying, the particles in the thickening cylinder will not stick together, so there is no need to stir in the thickening cylinder, and the space utilization rate is higher. In addition, the temperature of the particles after crystallization and drying is relatively high. Directly entering the thickening cylinder can reduce the utilization of hot nitrogen and improve the utilization rate of thermal energy; the reaction time of thickening is also reduced.

[0021] Furthermore, since the outside of the thickening cylinder, the outside of the purification cylinder and the outside of the outer hopper are all provided with a heat-insulating layer, the heat-insulating layer can insulate the inside of the thickening cylinder and reduce energy loss.

[0022] Furthermore, since the material adding device includes a particle feeding bin fixed to the material adding port, a first feeding control valve is provided at the bottom of the particle feeding bin, the upper end of the particle feeding bin is connected to the second particle conveying device, and a second feeding control valve is provided between the second particle conveying device and the particle feeding bin. The discharge control device includes a particle buffer bin fixed to the lower opening of the particle discharge hopper, a first discharge control valve is provided between the particle buffer bin and the particle discharge hopper, the lower end of the particle buffer bin is connected to the particle discharge bin, and a second discharge control valve is installed between the particle discharge bin and the particle buffer bin. Therefore, through the above device, particles can be first placed into the particle buffer bin, and a feeding space will appear at the upper end of the thickening cylinder after the discharge, and then the particles in the particle feeding bin are added to the thickening cylinder. In this way, the newly added batch of particles to the thickening cylinder gradually descends with the batches of particles discharged, and is eventually discharged from the bottom. For each batch of particles, as long as the frequency of feeding and discharging is controlled, the heating and thickening time of each batch of particles is the same, thereby ensuring the consistent thickening effect of the particles.

[0023] Furthermore, since the first bottle flake conveying device, the second bottle flake conveying device, the first particle conveying device, and the second particle conveying device are all vacuum loaders, the hot nitrogen gas supply system is connected to each vacuum loaders as an isolation gas source. Therefore, the hot nitrogen can be used to isolate the materials during transportation, thereby minimizing contact with oxygen and avoiding discoloration of the materials as much as possible.

[0024] Since a vacuum feeding tank is installed at the feeding port of the extruder, the vacuum feeding tank is connected to the second bottle flake conveying device, and the vacuum feeding tank is connected to the vacuum pumping device, vacuum pumping is also performed during the feeding process of the extruder, thereby reducing the contact between the PET bottle flakes and oxygen and avoiding discoloration of the bottle flakes.

[0025] In addition, the technical solution of the utility model further discloses a PET recycling and granulation method, which uses the PET recycling and granulation system and includes the following steps:

[0026] S1. Infrared drying

[0027] The crushed and cleaned PET bottle flakes are fed into the continuous infrared dryer through the bottle flake feeding device. The continuous infrared dryer starts to dry the PET bottle flakes with infrared heating. During the drying process, the drying barrel continuously rotates and stirs, and the dried PET bottle flakes are sent to the purifier.

[0028] S2, Nitrogen heating purification

[0029] After the PET bottle flakes enter the purification cylinder of the purifier, heated nitrogen is continuously introduced into the lower part of the purifier and the top is vacuumed. The flowing nitrogen is used to heat and purify the PET bottle flakes in the purifier.

[0030] S3, the purified PET bottle flakes are sent to the extruder for extrusion;

[0031] S4, utilizing a pelletizing device to pelletize and cool the PET melt extruded from the extruder;

[0032] S5, using a dehydration device to dehydrate the pelletized PET particles and send them to a temporary storage tank for temporary storage;

[0033] S6. Use the first particle conveying device to send the PET particles in the temporary storage tank to the single-pot infrared dehumidification crystallization drying machine for infrared heating crystallization drying. The single-pot infrared dehumidification crystallization drying machine stirs and vacuums during the crystallization drying process. After the set crystallization drying time is reached, the discharge port of the single-pot infrared dehumidification crystallization drying machine is opened to send the crystallized and dried PET particles into the thickening cylinder. Heated nitrogen is introduced into the bottom of the particle discharge hopper, and the second vacuum exhaust device on the top of the thickening cylinder exhausts air. The PET particles undergo polyester repolymerization in the thickening cylinder, and the low molecular weight substances in the PET particles are extracted by the second vacuum exhaust device after heating; when the PET particles are thickened, they are discharged from the bottom.

[0034] After adopting the above technical scheme, the effect of the utility model is: the PET recycling and granulation method uses the above system, which can perform infrared heating and drying on 3A-grade bottle flakes and purify them through heated nitrogen, remove impurities volatilized by heat and some small particle powders in the bottle flakes, and then use a single-pot infrared dehumidification crystallization drying machine to perform infrared heating crystallization drying after extrusion granulation and cooling dehydration. The crystallization drying speed is fast, and the moisture content of the particles after crystallization and drying is low. The crystallized PET particles then enter the thickening cylinder and are heated and thickened by heated nitrogen. The crystallized PET particles will not stick together in the thickening cylinder. At the same time, the particles in the thickening cylinder are heated while being in a negative pressure environment. Therefore, the polymerization reaction can be carried out well to achieve thickening without contacting oxygen, thereby avoiding discoloration and yellowing of the particles.

[0035] Preferably, the PET particles are thickened in the thickening cylinder in the following manner:

[0036] S61, open the second feeding control valve and close the first feeding control valve, and the second particle conveying device feeds the PET particles into the particle feeding bin. When the particle feeding bin is filled to a set amount, close the second feeding control valve and the second particle conveying device stops feeding.

[0037] S62: After the particles in the thickening cylinder have thickened for a set time, the first discharge control valve is opened and the second discharge control valve is closed to discharge the particles into the particle buffer. When the thickened particles in the particle buffer reach a set amount, the first discharge control valve is closed and the second discharge control valve is opened to allow the particles in the particle buffer to enter the lining discharge bin.

[0038] S63, opening the first feeding control valve, adding the particles in the particle feeding bin into the thickening cylinder for heating and thickening;

[0039] S64. Repeat steps S61-S63, adding material once after each discharge. Through the above-mentioned viscosity-increasing reaction process, quantitative discharge and quantitative addition can be achieved. Each batch of particles has the same viscosity-increasing reaction time to ensure stable particle quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] Figure 1 This is a connection diagram of a continuous infrared dryer and a purifier according to an embodiment of the present utility model;

[0042] Figure 2 This is a connection diagram of the extruder;

[0043] Figure 3 It is a schematic diagram of the connection between the pelletizing device, dehydration device and temporary storage tank;

[0044] Figure 4 This is a schematic diagram of the connection between a single-pot infrared dehumidification crystallization drying machine and a viscosity increasing machine;

[0045] Figure 5 It is a structural diagram of a continuous infrared dryer;

[0046] Figure 6 This is the connection diagram of the purifier;

[0047] Figure 7 It is a cross-sectional view of the viscosity increasing machine;

[0048] Figure 8 It is a cross-sectional view of the particle discharge hopper;

[0049] In the attached figure: 1. Continuous infrared dryer; 101. Bottle flake feeding device; 102. Drying barrel; 103. Infrared light box; 104. Drying rotary power device; 105. Drying discharge bin; 106. Fixed machine base; 107. Spiral stirring blade; 2. Purifier; 21. Purification barrel; 22. Bottle flake discharge hopper; 23. Exhaust hood; 24. Dry nitrogen main gas port; 25. Bottle flake discharge control device; 3. Hot nitrogen Air supply system; 4. First bottle flake conveyor; 41. Feeding suction fan; 42. Suction pipe; 43. Vacuum hopper; 5. First negative pressure exhaust fan; 6. Extruder; 7. Vacuum feeding tank; 8. Vacuum device; 9. Water tank; 10. Pelletizer; 11. Dehydrator; 12. Vibrating screen; 13. Temporary storage tank; 14. First particle conveyor; 15. Single-pot infrared dehumidification and crystallization drying machine; 151 , particle hopper; 152, crystallization barrel; 153, crystallization heating lamp; 154, crystallization discharge bin; 16, viscosity enhancer; 161, viscosity enhancer barrel; 162, particle discharge hopper; 1621, inner hopper; 1622, middle hopper; 1623, outer hopper; 1624, annular connecting plate; 1625, outer annular chamber; 1626, inner annular chamber; 1627, lower connecting chamber; 1628, upper connecting chamber; 1629, air inlet; 163, particle feeding bin; 164, second feeding control valve; 165, first feeding control valve; 166, particle buffer bin; 167, particle discharge bin; 168, second negative pressure exhaust device; 169, material level meter; 1610, total gas port for thickening nitrogen; 1611, first discharge control valve; 1612, second discharge control valve; 1613, insulation layer; 17, second particle conveying device. DETAILED DESCRIPTION

[0050] The present invention will be described in further detail below through specific embodiments.

[0051] like Figures 1 to 8 As shown, a PET recycling and granulation system includes

[0052] The PET bottle flake drying and purification device includes a continuous infrared dryer 1 and a purifier 2. The continuous infrared dryer 1 includes a fixed machine base 106, on which a drying barrel 102 is rotatably mounted. The drying barrel 102 is driven by a drying rotary power device 104. A spiral stirring blade 107 is provided in the drying barrel 102. A feed port is provided at the upstream end of the drying barrel 102 and is connected to a bottle flake feeding device 101.

[0053] The bottle flake feeding device 101 includes a bottle flake feeding hopper connected to a vacuum feeder for feeding PET bottle flakes. The PET bottle flakes are 3A grade, which can meet the production requirements of PET bottles.

[0054] The downstream end of the drying barrel 102 is provided with a discharge port, and the fixed machine base 106 is provided with a drying discharge bin 105 connected to the discharge port. The fixed machine base 106 is also equipped with an infrared lamp box 103 for heating the interior of the drying barrel 102 and an exhaust device.

[0055] The purifier 2 includes a purification cylinder 21, and a bottle flake feeding port is provided at the upper end of the purification cylinder 21. The bottle flake feeding port is connected to the drying discharge bin 105 via a first bottle flake conveying device 4, wherein the first bottle flake conveying device 4 also adopts a vacuum loader, and the hot nitrogen gas supply system 3 is connected to each vacuum loader as an isolation gas source, and the drying discharge bin 105 is provided with a valve. Using hot nitrogen as the isolation gas source of the vacuum loader can isolate the air while facilitating the transportation of bottle flakes. The vacuum loader is a common device for conveying materials using air pressure differences and can be purchased on the market.

[0056] Conventional vacuum loaders on the market insert a feeding suction pipe 42 into a hopper storing granular or flaky materials, then activate the feeding suction fan 41. This creates negative pressure in the suction pipe 42, drawing the material from the hopper into the vacuum loading hopper 43, completing the loading process. In this embodiment, however, the dryer discharge bin 105 is closed with a valve during loading, forming a closed hopper. A hot nitrogen supply system 3 is then used to supply air. This ensures that hot nitrogen is introduced into the suction pipe 42, effectively isolating the material from oxygen. Therefore, subsequent vacuum loaders will use hot nitrogen as the isolation gas source during loading.

[0057] The lower end of the purification cylinder 21 is connected to a conical flake discharge hopper 22 for convenient discharging. The lower opening of the flake discharge hopper 22 is connected to a flake discharge control device 25. A dry nitrogen main gas port 24 is provided on the flake discharge hopper 22, which is connected to the hot nitrogen supply system 3. A first negative pressure exhaust device is installed at the top of the purification cylinder 21. The structure of the purification cylinder 21 in this embodiment is identical to that of the subsequent viscosity-enhancing cylinder 161. The flake discharge control device 25 includes a discharge bin and a discharge valve. When discharge is required, the discharge valve is opened to discharge the flakes from the flake discharge hopper 22, which are then transported to the extruder 6 via a second flake conveyor. The first negative pressure exhaust device includes an exhaust hood 23 located within the purification cylinder 21 and connected to a first negative pressure exhaust fan 5.

[0058] Extruder 6, the feed port of which is connected to the bottle flake discharge control device 25 via a second bottle flake conveying device; a vacuum feeding tank 7 is mounted at the feed port of extruder 6, which is in communication with the second bottle flake conveying device, and in communication with a vacuum pumping device 8. The second bottle flake conveying device is also a vacuum feeder, and the vacuum feeding tank 7 continuously draws a vacuum to minimize contact between the bottle flakes and oxygen.

[0059] The pelletizing device is installed downstream of the extruder 6 and is used to pelletize the melt extruded by the extruder 6; the pelletizing device can adopt a conventional water-flushing pelletizing device or an underwater pelletizing device on the market.

[0060] like Figure 3 As shown, Figure 3 The diagram shows a water-flush pelletizing device, which includes a water trough 9, the upstream end of which is connected to the downstream end of the extruder 6. A pelletizer 10 is located at the downstream end of the trough 9. Pellets 10 then cut into pellets and then transported to a dehydration device. An underwater pelletizing device, on the other hand, includes a pelletizing water pipe, which carries the pelletized particles away through the water flow. The cutter of the pelletizer 10 cooperates with the die head of the extruder 6, and the entire pelletizing process occurs underwater. Both water-flush and underwater pelletizing devices are currently conventional equipment.

[0061] The dehydration device is arranged below the pelletizing device and is used to dehydrate the PET particles pelletized by the pelletizing device. The dehydration device uses a dehydrator 11 for dehydration, and the dehydrated particles are screened by a vibrating screen 12.

[0062] The temporary storage tank 13 is arranged downstream of the dehydration device and is used to receive the PET particles dehydrated by the dehydration device.

[0063] like Figure 4 、 Figure 7 and Figure 8 As shown, the thickener 16 group includes a single-pot infrared dehumidification crystallization drying integrated machine 15 and a thickener 16. The feed port of the single-pot infrared dehumidification crystallization drying integrated machine 15 is connected to the discharge port at the bottom of the temporary storage tank 13 through the first particle conveying device 14.

[0064] The applicant has previously applied for a domestic patent for the basic structure of the single-pot infrared dehumidification crystallization drying machine 15, with the specific publication number being CN 214521287. U, the basic structure of the infrared dehumidification crystallization drying machine includes a rotating crystallization barrel 152, an infrared heating crystallization heating lamp box 153, a fan for exhausting the interior, a particle feeding device for feeding, and a discharge port arranged on the side wall of the crystallization barrel 152. A crystallization discharge bin 154 is provided at the bottom of the crystallization barrel 152. The PET particles enter the particle hopper 151 through the first ion transport device. The particle hopper 151 rotates and is heated inside by the crystallization heating lamp box 153 to dry, dehumidify and crystallize the particles. During the dehumidification process, air is exhausted to remove the moisture and impurities evaporated by heating. When the crystallization and drying is completed, the water content of the PET particles is very low, and then the material is discharged. The PET particles enter the crystallization discharge bin 154 and are then transported to the viscosity enhancer 16 through the second particle conveying device 17 (vacuum loader) for viscosity enhancement treatment. Similarly, the hot nitrogen gas supply system 3 is also connected to the second particle conveying device 17 (vacuum loader). The crystallization discharge bin 154 is configured as a closed structure and provided with a valve, so that the conveying gas source of the vacuum loader also uses heated nitrogen, which further protects the PET particles during the conveying process.

[0065] like Figure 7 and Figure 8As shown, the thickening machine 16 includes a vertical thickening cylinder 161, the upper end of the thickening cylinder 161 is provided with a material adding port for facilitating the entry of PET particles, a material adding device is installed on the material adding port, the material adding device is connected to the crystallization discharge bin 154 of the discharge port of the single-pot infrared dehumidification crystallization drying machine 15 through a second particle conveying device 17, the lower end of the thickening cylinder 161 is connected to a conical particle discharge hopper 162 for convenient discharge, the lower end of the particle discharge hopper 162 is opened and is connected to a particle discharge control device, the particle discharge hopper 162 includes an inner hopper 1621, an intermediate hopper 1622 and an outer hopper 1623 from the inside out, and the inner hopper 1621, the intermediate hopper 1622 and the outer hopper 1623 are connected by an annular connecting plate 16 24 is fixedly connected, and the outer hopper 1623 is provided with a total gas port 1610 for thickening nitrogen gas for communication with the hot nitrogen supply system 3, an outer annular chamber 1625 is provided between the outer hopper 1623 and the intermediate hopper 1622, and an inner annular chamber 1626 is formed between the intermediate hopper 1622 and the inner hopper 1621, the total gas port 1610 for thickening nitrogen gas is communicated with the outer annular chamber 1625, and the upper and lower parts of the outer annular chamber 1625 and the inner annular chamber 1626 are respectively communicated, a connecting hole is provided on the annular connecting plate 1624, and a plurality of air inlet holes 1629 are further provided on the hopper wall of the inner hopper 1621, a second negative pressure exhaust device 168 is provided on the top of the thickening cylinder 161, and a negative pressure vacuum gauge and a thermometer are provided on the thickening cylinder 161.

[0066] Among them, the upper and lower parts of the outer annular chamber 1625 and the inner annular chamber 1626 are connected respectively through the upper communicating chamber 1628 and the lower communicating chamber 1627, wherein the upper communicating chamber 1628 is surrounded by the upper ends of the outer hopper 1623 and the inner hopper 1621, and the lower communicating chamber 1627 is surrounded by the lower ends of the outer hopper 1623 and the inner hopper 1621. After entering from the outer annular chamber 1625, the hot nitrogen will flow upward and downward, and then flow in the opposite direction to the middle from the upper communicating chamber 1628 and the lower communicating chamber 1627 to the inner annular chamber 1626, and finally flow into the inner hopper 1621 from the air inlet.

[0067] The annular connecting plate 1624 is provided with a connecting hole to facilitate the flow of nitrogen. The exterior of the thickening cylinder 161, the exterior of the purification cylinder 21, and the exterior of the outer hopper 1623 are all provided with an insulation layer 1613. The insulation layer 1613 can be a layer of insulating cotton, and an auxiliary heating device can be provided within the insulation layer 1613 to provide auxiliary heating for the interior of the thickening cylinder 161. This auxiliary heating device can be a thermal oil heater or an electric heater.

[0068] The outer hopper 1623 is provided with a total nitrogen inlet 1610 for thickening, which is connected to the hot nitrogen supply system 3. The hot nitrogen supply system 3 heats the nitrogen before it enters through the total nitrogen inlet. The total nitrogen inlet is preferably located in the middle of the discharge hopper so that the nitrogen flows upward or downward after entering, avoiding the situation where the nitrogen enters from a single location and causes uneven heating.

[0069] The viscosity increasing cylinder 161 is provided with a negative pressure vacuum gauge and a thermometer, which monitor the pressure and temperature inside the viscosity increasing cylinder 161 in real time to ensure that the reaction of the PET material is carried out under appropriate process parameters. The upper part of the viscosity increasing cylinder 161 is provided with a material level meter 169 to control the upper limit position of the material.

[0070] Among them, the second negative pressure exhaust device 168 includes an exhaust hood arranged on the top of the viscosity-enhancing cylinder 161. The exhaust port of the exhaust hood extends out of the viscosity-enhancing cylinder 161 and is connected to the exhaust pump, so as to continuously extract the internal gas.

[0071] The upper and lower parts of the viscosity increasing cylinder 161 are both provided with sight glasses, which makes it easy to observe the condition of the internal materials.

[0072] The structure of the bottle flakes discharge hopper 22 is the same as that of the particle discharge hopper 162 .

[0073] The material adding device includes a particle feeding bin 163 fixed to the material adding port, a first feeding control valve 165 is provided at the bottom of the particle feeding bin 163, the upper end of the particle feeding bin 163 is connected to the second particle conveying device 17, and a second feeding control valve 164 is provided between the second particle conveying device 17 and the particle feeding bin 163. The discharge control device includes a particle buffer bin 166 fixed to the lower opening of the particle discharge hopper 162, a first discharge control valve 1611 is provided between the particle buffer bin 166 and the particle discharge hopper 162, the lower end of the particle buffer bin 166 is connected to the particle discharge bin 167, and a second discharge control valve 1612 is installed between the particle discharge bin 167 and the particle buffer bin 166.

[0074] The first feeding control valve 165 , the second feeding control valve 164 , the first discharging control valve 1611 and the second discharging control valve 1612 are preferably pneumatic butterfly valves.

[0075] The first bottle flake conveying device 4 , the second bottle flake conveying device, the first particle conveying device 14 and the second particle conveying device 17 are all vacuum feeders, and the hot nitrogen gas supply system 3 is connected to each vacuum feeder as an isolation gas source.

[0076] Compared with conventional recycling and granulation, the entire PET recycling and granulation system has at least the following advantages: 1. The recycling and granulation system uses infrared continuous heating and drying and hot nitrogen to quickly heat, dry and purify the bottle flakes, shortening the drying and purification time; 2. Hot nitrogen is used for protection throughout the entire recycling and granulation process to isolate the sample gas, so that the final PET particles are not easy to change color or turn yellow, meeting the requirements of the manufacture of food PET bottles; 3. The system performs a viscosity-increasing treatment on the diced PET particles. First, the particles are crystallized by infrared heating, and then the temperature after crystallization enters the viscosity-increasing machine 16 for viscosity-increasing. The hot nitrogen is in uniform contact with all the particles, ensuring the viscosity-increasing effect. At the same time, it also avoids contact with oxygen. Moreover, since the particles have already crystallized during the ion viscosity-increasing process, they will not stick together into a mass when entering the viscosity-increasing machine 16. At the same time, the particles entering the viscosity-increasing machine 16 also have some temperature, so that the heat is fully utilized; 4. The increase and decrease process is fast and efficient. Moreover, since a batch is added during the viscosity-increasing process, the height of the entire viscosity-increasing cylinder 161 does not need to be too high, thereby saving workshop space.

[0077] This embodiment also discloses a PET recycling and granulation method, which uses the PET recycling and granulation system and includes the following steps:

[0078] S1. Infrared drying

[0079] The crushed and cleaned PET bottle flakes are fed into the continuous infrared dryer 1 through the bottle flake feeding device 101. The PET bottle flakes are 3A food grade bottle flakes to facilitate the production and use of PET bottles. The continuous infrared dryer 1 is started to perform infrared heating and drying on the PET bottle flakes. During the drying process, the drying barrel 102 continuously rotates and stirs and feeds the dried PET bottle flakes to the purifier 2.

[0080] S2, Nitrogen heating purification

[0081] After the PET bottle flakes enter the purification cylinder 21 of the purifier 2, heated nitrogen is continuously introduced into the lower part of the purifier 2 and the top is vacuumed, and the flowing nitrogen is used to heat and purify the PET bottle flakes in the purifier 2;

[0082] S3, the purified PET bottle flakes are sent to the extruder 6 for extrusion;

[0083] S4, using a pelletizing device to pelletize and cool the PET melt extruded by the extruder 6;

[0084] S5, using a dehydration device to dehydrate the pelletized PET particles and send them to a temporary storage tank 13 for temporary storage;

[0085] S6. Use the first particle conveying device 14 to send the PET particles in the temporary storage tank 13 to the single-pot infrared dehumidification crystallization drying all-in-one machine 15 for infrared heating crystallization drying. The single-pot infrared dehumidification crystallization drying all-in-one machine 15 stirs and vacuums during the crystallization drying process. After the set crystallization drying time is reached, the discharge port of the single-pot infrared dehumidification crystallization drying all-in-one machine 15 is opened to send the crystallized and dried PET particles into the thickening cylinder 161. Heated nitrogen is introduced into the bottom of the particle discharge hopper 162. The second vacuum exhaust device 168 at the top of the thickening cylinder 161 exhausts air. The PET particles undergo polyester repolymerization in the thickening cylinder 161. The low molecular weight substances in the PET particles are extracted by the second vacuum exhaust device 168 after heating; when the PET particles are thickened, the material is discharged from the bottom.

[0086] The PET particles are thickened in the thickening cylinder 161 as follows:

[0087] S61, open the second feeding control valve 164 and close the first feeding control valve 165, the second particle conveying device 17 feeds the PET particles into the particle feeding bin 163, and when the particle feeding bin 163 is filled to a set amount, close the second feeding control valve 164 and the second particle conveying device 17 stops feeding;

[0088] S62: After the particles in the thickening cylinder 161 have thickened for a set time, the first discharge control valve 1611 is opened and the second discharge control valve 1612 is closed to discharge the particles into the particle buffer 166. When the thickened particles in the particle buffer 166 reach a set amount, the first discharge control valve 1611 is closed and the second discharge control valve 1612 is opened to allow the particles in the particle buffer 166 to enter the lining discharge bin.

[0089] S63, opening the first feeding control valve 165, adding the particles in the particle feeding bin 163 into the thickening cylinder 161 for heating and thickening;

[0090] S64. Repeat steps S61-S63, adding material once after each discharge. Through the above-mentioned viscosity-increasing reaction process, quantitative discharge and quantitative addition can be achieved. Each batch of particles has the same viscosity-increasing reaction time to ensure stable particle quality.

[0091] After use, the hot nitrogen can be filtered and recovered through a nitrogen recovery system to avoid nitrogen waste.

[0092] The air circuit system, motor, and other actuators mentioned in this embodiment are all conventional technologies. The specific structures and principles of the cylinder, motor, and other transmission mechanisms, as well as other designs, are detailed in the "Mechanical Design Manual, Fifth Edition," the 28th edition, published in Beijing in April 2008. These are prior art, and their structures are clear and concise. The SMC training material "Modern Practical Pneumatic Technology, 3rd Edition," published by the Machinery Industry Press on August 1, 2008, details vacuum components, gas circuits, and program control, demonstrating that the air circuit structure in this embodiment is also prior art and clear and concise. The book "Motor Drive and Speed ​​Regulation," published by the Chemical Industry Press on July 1, 2015, also provides detailed descriptions of motor control and travel switches, so the circuits and air circuit connections are clear. The above-described embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications and alterations to the technical solution of the present invention, without departing from the spirit of the present invention, should fall within the scope of protection defined by the claims.

Claims

1. A PET recycling and granulation system, characterized by: include The PET bottle flake drying and purification device includes a continuous infrared dryer and a purifier. The continuous infrared dryer includes a fixed base, on which a drying barrel is rotatably mounted. The drying barrel is driven by a drying rotary power device. A spiral stirring blade is provided in the drying barrel. The upstream end of the drying barrel is provided with a feed port and is connected to a bottle flake feeding device. The downstream end of the drying barrel is provided with a discharge port. The fixed base is provided with a drying discharge bin connected to the discharge port. The fixed base is also provided with a An internally heated infrared light box and an exhaust device are provided. The purifier includes a purification cylinder, a bottle flake feeding port is provided at the upper end of the purification cylinder, and the bottle flake feeding port is connected to the drying discharge bin via a first bottle flake conveying device. The lower end of the purification cylinder is connected to a conical bottle flake discharge hopper for convenient discharge. The lower end of the bottle flake discharge hopper is open and connected to a bottle flake discharge control device. A dry nitrogen main gas port is provided on the bottle flake discharge hopper, and the dry nitrogen main gas port is connected to a hot nitrogen supply system. A first negative pressure exhaust device is provided on the top of the purification cylinder; An extruder, wherein the feeding port of the extruder is connected to the bottle flake discharge control device through a second bottle flake conveying device; a pelletizing device installed downstream of the extruder for pelletizing the melt extruded by the extruder; A dehydration device, the dehydration device is arranged below the pelletizing device and is used to dehydrate the PET particles pelletized by the pelletizing device; A temporary storage tank is provided downstream of the dehydration device and is used to receive the PET particles dehydrated by the dehydration device; A thickening unit, the thickening unit includes a single-pot infrared dehumidification crystallization drying all-in-one machine and a thickening machine, the feed port of the single-pot infrared dehumidification crystallization drying all-in-one machine is connected to the discharge port at the bottom of the temporary storage tank through a first particle conveying device; the thickening machine includes a vertical thickening cylinder, the upper end of the thickening cylinder is provided with a material adding port for convenient entry of PET particles, a material adding device is installed on the material adding port, the material adding device is connected to the discharge port of the single-pot infrared dehumidification crystallization drying all-in-one machine through a second particle conveying device, the lower end of the thickening cylinder is connected to a conical particle discharge hopper for convenient discharge, the lower end of the particle discharge hopper is opened and connected to a particle discharge control device, the particle discharge hopper From the inside to the outside, it includes an inner hopper, an intermediate hopper and an outer hopper. The inner hopper, the intermediate hopper and the outer hopper are fixedly connected by an annular connecting plate. The outer hopper is provided with a total gas port for thickening nitrogen for communicating with the hot nitrogen supply system. An outer annular chamber is provided between the outer hopper and the intermediate hopper, and an inner annular chamber is formed between the intermediate hopper and the inner hopper. The total gas port for thickening nitrogen is communicated with the outer annular chamber, and the upper and lower parts of the outer annular chamber and the inner annular chamber are respectively communicated. A connecting hole is provided on the annular connecting plate, and a plurality of air inlet holes are also provided on the hopper wall of the inner hopper. A second negative pressure exhaust device is provided on the top of the thickening cylinder, and a negative pressure vacuum gauge and a thermometer are provided on the thickening cylinder.

2. A PET recycling and granulation system according to claim 1, characterized in that: The structure of the bottle flakes discharge hopper is the same as that of the particle discharge hopper.

3. A PET recycling and granulation system as claimed in claim 2, characterized in that: The outside of the viscosity increasing cylinder, the outside of the purification cylinder and the outside of the outer hopper are all provided with a heat insulation layer.

4. A PET recycling and granulation system as claimed in claim 3, characterized in that: The material adding device includes a particle feeding bin fixed on the material adding port, a first feeding control valve is provided at the bottom of the particle feeding bin, the upper end of the particle feeding bin is connected to the second particle conveying device, and a second feeding control valve is provided between the second particle conveying device and the particle feeding bin.

5. A PET recycling and granulation system as claimed in claim 4, characterized in that: The discharge control device includes a particle cache bin fixed on the lower opening of the particle discharge hopper, a first discharge control valve is arranged between the particle cache bin and the particle discharge hopper, the lower end of the particle cache bin is connected to the particle discharge bin, and a second discharge control valve is installed between the particle discharge bin and the particle cache bin.

6. A PET recycling and granulation system according to claim 5, characterized in that: The first bottle piece conveying device, the second bottle piece conveying device, the first particle conveying device and the second particle conveying device are all vacuum loaders, and the hot nitrogen gas supply system is connected to each vacuum loader as an isolation gas source.

7. A PET recycling and granulation system according to claim 6, characterized in that: A vacuum feeding tank is installed at the feeding port of the extruder, and the vacuum feeding tank is connected to the second bottle piece conveying device, and the vacuum feeding tank is connected to the vacuum pumping device.

8. A PET recycling and granulation system according to claim 7, characterized in that: The pelletizing device is a water-flushing pelletizing device or an underwater pelletizing device.

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