PET (Polyethylene Terephthalate) recycling and granulating system and recycling and granulating method thereof

Abstract

The invention discloses a PET (Polyethylene Terephthalate) recycling and granulating system and a recycling and granulating method thereof, the system comprises a PET bottle flake drying and purifying device for drying bottle flakes by using infrared rays and then purifying the bottle flakes by using hot nitrogen; 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 and method, 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 invention relates to the technical field of PET recycling and granulation, in particular to a PET recycling and granulation system and a recycling and granulation method thereof. Background Art

[0002] Recycling PET bottles can not only reduce environmental pollution, but also save resources. Therefore, the research on recycling PET waste has attracted more and more attention. For example, the document with the publication number of CN 115139428A records a waste polyester recycling and granulation method, which includes the following steps S1: selecting, cleaning, crushing, drying, mixing, 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 melting; S3: adding a chain extender to the melt after extrusion to increase the viscosity; S4: filtering the melt after viscosity increase in S3; S5: forming a coarse wire through drawing after filtering; S6: cooling the wire after drawing in S5; S7: pelletizing, dehydrating, and packaging after cooling.

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

[0004] The invention 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 extracts 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. Summary of the invention

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

[0006] Another technical problem to be solved by the present invention is to provide a PET recycling and granulation method, which uses the above-mentioned PET recycling and granulation system to improve the efficiency of granulation and avoid yellowing of PET particles after granulation, thereby meeting the production of PET bottles in the food industry.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a PET recycling and granulation system, comprising

[0008] The PET bottle flake drying and purification device comprises a continuous infrared dryer and a purifier, wherein the continuous infrared dryer comprises a fixed machine base, a drying barrel is rotatably mounted on the fixed machine base, the drying barrel is driven by a drying rotating power device, a spiral stirring blade is arranged in the drying barrel, a feed port is arranged at the upstream end of the drying barrel and is connected to a bottle flake feeding device, a discharge port is arranged at the downstream end of the drying barrel, a drying discharge bin connected to the discharge port is arranged on the fixed machine base, and a The purifier comprises a purifying cylinder, a bottle flake feeding port is arranged at the upper end of the purifying cylinder, the bottle flake feeding port is connected with the dry discharging bin through a first bottle flake conveying device, the lower end of the purifying cylinder is connected with a conical bottle flake discharging hopper for convenient discharging, the lower end of the bottle flake discharging hopper is opened and connected with a bottle flake discharging control device, a dry nitrogen total gas port is arranged on the bottle flake discharging hopper, the dry nitrogen total gas port is connected with a hot nitrogen gas supply system, and a first negative pressure exhaust device is arranged on the top of the purifying cylinder;

[0009] An extruder, wherein the feed port of the extruder is connected to the bottle flake discharge control device through a second bottle flake conveying device;

[0010] A pelletizing device, which is installed downstream of the extruder and is used to pelletize the melt extruded by the extruder;

[0011] A dehydration device, which is arranged below the pelletizing device and is used to dehydrate the PET particles pelletized by the pelletizing device;

[0012] A temporary storage tank, which is arranged downstream of the dehydration device and is used to receive the PET particles dehydrated by the dehydration device;

[0013] A thickening unit, the thickening unit comprises a single-pot infrared dehumidification crystallization drying all-in-one machine and a thickening machine, the feed inlet of the single-pot infrared dehumidification crystallization drying all-in-one machine is connected with the discharge port at the bottom of the temporary storage tank through a first particle conveying device; the thickening machine comprises 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, and 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 gas connected to the hot nitrogen gas supply system, an outer annular chamber is provided between the outer hopper and the intermediate hopper, an inner annular chamber is formed between the intermediate hopper and the inner hopper, the total gas port for thickening nitrogen gas is connected with the outer annular chamber, the upper and lower parts of the outer annular chamber are respectively connected with the inner annular chamber, a connecting hole is provided on the annular connecting plate, 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.

[0014] As a preferred solution, the structure of the bottle flakes discharge hopper is the same as that of the particle discharge hopper.

[0015] As a preferred solution, the outside of the viscosity enhancing cylinder, the outside of the purification cylinder and the outside of the external hopper are all provided with a heat-insulating layer.

[0016] 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 arranged 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 arranged between the second particle conveying device and the particle feeding bin.

[0017] As a preferred solution, the discharge control device includes a particle buffer bin fixed on the lower opening of the particle discharge hopper, a first discharge control valve is arranged between the particle buffer bin and the particle discharge hopper, the lower end of the particle buffer bin is connected to a particle discharge bin, and a second discharge control valve is installed between the particle discharge bin and the particle buffer bin.

[0018] 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 feeders, and the hot nitrogen gas supply system is connected to each vacuum feeder as an isolation gas source.

[0019] As a preferred solution, a vacuum feeding tank is installed at the feeding port of the extruder, 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.

[0020] As a preferred solution, the pelletizing device is a water pelletizing device or an underwater pelletizing device.

[0021] After adopting the above technical scheme, the effects of the present invention 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 to 5×1014C / S, which is a part of electromagnetic waves. Infrared rays penetrate substances and infrared rays reflected by substances do not affect the tissue of the substance. However, the absorbed tissue 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 to 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°C, and the heated bottle flakes are directly sent to the purifier. The heated nitrogen enters the purification cylinder from the bottom to isolate the PET bottle flakes in the purification cylinder from oxygen. At the same time, the hot nitrogen can contact the bottle flakes more evenly, heat evenly, and no stirring is required. At the same time, the first negative pressure exhaust device at 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 performs a thickening treatment on the granulated PET particles. During the thickening, a single-pot infrared dehumidification crystallization drying integrated 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 crystallized particles 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. The negative pressure is drawn from the top of the thickening cylinder to make the particles polymerize in the absence of oxygen. There are terminal hydroxyl groups and terminal carboxyl groups in the particles. The polymerization reaction of the particle molecules causes the molecular chain to continue to grow, thereby increasing the intrinsic viscosity. Since the particles have been subjected to 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, and directly entering the thickening cylinder can reduce the use of hot nitrogen, and the utilization rate of thermal energy is improved; the reaction time of thickening is also reduced.

[0022] Furthermore, since the outside of the thickening cylinder, the outside of the purification cylinder and the outside of the external 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.

[0023] Furthermore, since the material adding device includes a particle feeding bin fixed on the material adding port, a first feeding control valve is arranged 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 arranged between the second particle conveying device and the particle feeding bin. The discharge control device includes a particle buffer bin fixed on the lower opening of the particle discharge hopper, a first discharge control valve is arranged between the particle buffer bin and the particle discharge hopper, a particle discharge bin is connected to the lower end of the particle buffer bin, and a second discharge control valve is installed between the particle discharge bin and the particle buffer bin, so that the particles can be first placed in the particle buffer bin through the above device, 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, so that the new batch of particles added to the thickening cylinder gradually decreases with the batches of particles discharged, and finally discharged from the bottom, for each batch of particles, as long as the frequency of discharge and feeding is controlled, the heating and thickening time of each batch of particles is the same, thereby ensuring the consistent thickening effect of the particles.

[0024] 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 feeders, the hot nitrogen gas supply system is connected to each vacuum feeder as an isolation gas source. Therefore, hot nitrogen can be used to isolate the materials during transportation, thereby reducing contact with oxygen as much as possible and avoiding discoloration of the materials as much as possible.

[0025] Furthermore, 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.

[0026] To solve the above-mentioned another technical problem, the technical solution of the present invention is: a PET recycling and granulation method, which uses the PET recycling and granulation system and comprises the following steps:

[0027] S1. Infrared drying

[0028] 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 perform infrared heating and drying on the PET bottle flakes. During the drying process, the drying barrel continuously rotates and stirs and feeds the dried PET bottle flakes to the purifier.

[0029] S2. Nitrogen heating purification

[0030] 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 evacuated, and the flowing nitrogen is used to heat and purify the PET bottle flakes in the purifier;

[0031] S3, the purified PET bottle flakes are sent to the extruder for extrusion;

[0032] S4, using a pelletizing device to pelletize and cool the PET melt extruded by the extruder;

[0033] S5, using a dehydration device to dehydrate the pelletized PET particles and send them to a temporary storage tank for temporary storage;

[0034] S6. Use the first particle conveying device to deliver 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 vacuum evacuates 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 deliver the crystallized and dried PET particles to the thickening cylinder. Heated nitrogen is introduced into the bottom of the particle discharge hopper. The second vacuum exhaust device on the top of the thickening cylinder exhausts air. The PET particles undergo polyester repolymerization in the thickening cylinder. 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.

[0035] After adopting the above technical scheme, the effect of the present invention is: the PET recycling and granulation method uses the above system, and can perform infrared heating and drying on 3A-level bottle flakes and purify them through heated nitrogen, so as to remove impurities and some small particle powders in the bottle flakes that are volatilized by heat, and then after extrusion granulation and cooling and dehydration, infrared heating crystallization drying is performed in a single-pot infrared dehumidification crystallization drying all-in-one machine, the crystallization drying speed is fast, and the moisture content of the particles after crystallization and drying is low, and then the crystallized PET particles enter the thickening cylinder and are heated and thickened by heated nitrogen, and the crystallized PET particles will not stick together in the thickening cylinder, and the particles in the thickening cylinder are heated while being in a negative pressure environment, so that the polymerization reaction can be well carried out to achieve thickening without contacting with oxygen, thereby avoiding discoloration and yellowing of the particles.

[0036] Preferably, the PET particles are thickened in the thickening cylinder in the following reaction process:

[0037] S61, open the second feeding control valve and close the first feeding control valve, the second particle conveying device feeds the PET particles into the particle feeding bin, and when the particle feeding bin is added to a set amount, close the second feeding control valve and the second particle conveying device stops feeding;

[0038] 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 bin. When the thickened particles in the particle buffer bin 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 bin to enter the lining discharge bin.

[0039] S63, opening the first feeding control valve, adding the particles in the particle feeding bin into the thickening cylinder for heating and thickening;

[0040] S64, repeating 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, and each batch of particles has the same viscosity-increasing reaction time to ensure stable particle quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0042] Figure 1 is a connection diagram of a continuous infrared dryer and a purifier according to an embodiment of the present invention;

[0043] Figure 2 This is the connection diagram of the extruder;

[0044] Figure 3 It is a schematic diagram of the connection between the pelletizing device, the dehydration device and the temporary storage tank;

[0045] Figure 4 It is a connection diagram of a single-pot infrared dehumidification crystallization drying machine and a viscosity increasing machine;

[0046] Figure 5 It is a structural diagram of a continuous infrared dryer;

[0047] Figure 6 This is the connection diagram of the purifier;

[0048] Figure 7 is a cross-sectional view of the viscosity increasing machine;

[0049] Figure 8 is a cross-sectional view of the particle discharge hopper;

[0050] 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 piece conveying device; 41. Feeding suction fan; 42. Suction pipe; 43. Vacuum feeding hopper; 5. First negative pressure suction 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 conveying device; 15. Single pot infrared dehumidification crystallization drying machine; 151 , particle hopper; 152, crystallization barrel; 153, crystallization heating lamp; 154, crystallization discharge bin; 16, thickening machine; 161, thickening 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

[0051] The present invention is further described in detail below through specific examples.

[0052] like Figures 1 to 8 As shown, a PET recycling and granulation system includes

[0053] The PET bottle flake drying and purification device comprises a continuous infrared dryer 1 and a purifier 2. The continuous infrared dryer 1 comprises a fixed machine base 106, on which a drying barrel 102 is rotatably mounted. The drying barrel 102 is driven by a drying rotating power device 104. A spiral stirring blade 107 is arranged in the drying barrel 102. A feed port is arranged at the upstream end of the drying barrel 102 and is connected to a bottle flake feeding device 101.

[0054] The bottle flake feeding device 101 includes a bottle flake feeding hopper, which is connected to a vacuum feeder for feeding PET bottle flakes. The PET bottle flakes are selected from 3A grade bottle flakes, which can meet the production of PET bottles.

[0055] 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 with 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.

[0056] 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 through a first bottle flake conveying device 4, wherein the first bottle flake conveying device 4 also adopts a vacuum feeder, and the hot nitrogen gas supply system 3 is connected to each vacuum feeder as an isolation gas source, and the drying discharge bin 105 is provided with a valve, and hot nitrogen is used as the isolation gas source of the vacuum feeder, which can isolate the air and facilitate the transportation of bottle flakes. The vacuum feeder is a common equipment that uses air pressure differences to convey materials and can be purchased on the market.

[0057] Conventional vacuum loaders on the market insert the suction pipe 42 for loading into the hopper for storing granular or flaky materials, and then start the loading suction fan 41. At this time, the suction pipe 42 will generate negative pressure, thereby sucking the material in the hopper into the vacuum loading hopper 43 to complete the loading of the material. In this embodiment, the dry discharge bin 105 is closed by a valve during loading to form a closed bin, and then the hot nitrogen gas supply system 3 is used for gas supply. In this way, hot nitrogen is added when the suction pipe 42 is sucked, which can isolate oxygen. Therefore, subsequent vacuum loaders use hot nitrogen as the isolation gas source when loading.

[0058] The lower end of the purification cylinder 21 is connected to a conical bottle flake discharge hopper 22 for convenient discharge. The lower part of the bottle flake discharge hopper 22 is open and connected to a bottle flake discharge control device 25. The bottle flake discharge hopper 22 is provided with a dry nitrogen total gas port 24, which is connected to the hot nitrogen gas supply system 3. The top of the purification cylinder 21 is provided with a first negative pressure exhaust device. The structure of the purification cylinder 21 in this embodiment is the same as that of the subsequent viscosity enhancement cylinder 161. The bottle flake discharge control device 25 includes a discharge bin and a discharge valve. When discharge is required, the discharge valve can be opened to discharge the bottle flakes from the bottle flake discharge hopper 22 and then sent to the extruder 6 through the second bottle flake conveying device. The first negative pressure exhaust device includes an exhaust hood 23 arranged inside the purification cylinder 21, and the exhaust hood 23 is connected to a first negative pressure exhaust fan 5.

[0059] The extruder 6 has a feeding port connected to the bottle flake discharging control device 25 through a second bottle flake conveying device; a vacuum feeding tank 7 is installed at the feeding port of the extruder 6, the vacuum feeding tank 7 is connected to the second bottle flake conveying device, and the vacuum feeding tank 7 is connected to a vacuum pumping device 8. The second bottle flake conveying device is also a vacuum feeder, and the vacuum feeding tank 7 is continuously vacuumed to avoid the bottle flakes from contacting with oxygen as much as possible.

[0060] A pelletizing device is installed downstream of the extruder 6 to pelletize the melt extruded by the extruder 6; the pelletizing device can be a conventional water-flushing pelletizing device or an underwater pelletizing device on the market.

[0061] like Figure 3 As shown, Figure 3 The diagram shows a water-flush pelletizing device, which includes a water tank 9, the upstream end of which is connected to the downstream end of the extruder 6, and a pelletizer 10 is provided at the downstream end of the water tank 9, and the pelletizer 10 pelletizes and then sends the pellets to the dehydration device. If an underwater pelletizing device is used, it includes a pelletizing conveying water pipe, which carries away the pelletized particles by water flow, and the cutter of the pelletizer 10 cooperates with the die head of the extruder 6 and the entire pelletizing process is in water. The water-flush pelletizing device or the underwater pelletizing device is also a conventional device at present.

[0062] 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.

[0063] 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.

[0064] like Figure 4 , Figure 7 and Figure 8 As shown, a thickener 16 group includes a single-pot infrared dehumidification crystallization drying integrated machine 15 and a thickener 16 , and 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 .

[0065] 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 arranged at the bottom of the crystallization barrel 152. PET particles enter the particle hopper 151 through the first ion transport device. The particle hopper 151 rotates and is heated by the crystallization heating lamp box 153 to dry, dehumidify and crystallize the particles. During the dehumidification process, air is exhausted to extract 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 increasing machine 16 through the second particle conveying device 17 (vacuum loader) for viscosity increasing 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 is provided with a valve, so that the conveying gas source of the vacuum feeder also uses heated nitrogen, which further protects the PET particles during the conveying process.

[0066] 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 convenient 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 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 to the outside, 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, the outer hopper 1623 is provided with a total gas inlet 1610 for thickening nitrogen gas for communication with the hot nitrogen gas supply system 3, an outer annular chamber 1625 is provided between the outer hopper 1623 and the intermediate hopper 1622, an inner annular chamber 1626 is formed between the intermediate hopper 1622 and the inner hopper 1621, the total gas inlet 1610 for thickening nitrogen gas is communicated with the outer annular chamber 1625, the upper and lower parts of the outer annular chamber 1625 and the inner annular chamber 1626 are respectively communicated, the annular connecting plate 1624 is provided with a connecting hole, the bucket wall of the inner hopper 1621 is also provided with a plurality of air inlet holes 1629, the top of the thickening cylinder 161 is provided with a second negative pressure exhaust device 168, and the thickening cylinder 161 is provided with a negative pressure vacuum gauge and a thermometer.

[0067] 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 connecting chamber 1628 and the lower connecting chamber 1627, wherein the upper connecting chamber 1628 is surrounded by the upper ends of the outer hopper 1623 and the inner hopper 1621, and the lower connecting 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 from the upper connecting chamber 1628 and the lower connecting chamber 1627 to the middle of the inner annular chamber 1626, and finally flow into the inner hopper 1621 from the air inlet.

[0068] Among them, the annular connecting plate 1624 is provided with a connecting hole to facilitate the flow of nitrogen, and the outside of the thickening cylinder 161, the outside of the purification cylinder 21 and the outside of the outer hopper 1623 are all provided with an insulation layer 1613. The insulation layer 1613 can be a heat insulation cotton interlayer, and an auxiliary heating device can be provided in the insulation layer 1613 to perform auxiliary heating on the inside of the thickening cylinder 161. The auxiliary heating device can be a heat transfer oil heating or an electric heating.

[0069] The outer hopper 1623 is provided with a total nitrogen inlet 1610 for viscosity enhancement, which is used to communicate with the hot nitrogen supply system 3. The hot nitrogen supply system 3 heats the nitrogen and then enters through the total nitrogen inlet. The total nitrogen inlet is preferably arranged in the middle of the discharge hopper, so that the nitrogen will flow upward or downward after entering, avoiding the situation where the nitrogen enters from one position and causes uneven heating.

[0070] 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 a suitable process parameter. 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.

[0071] The second negative pressure exhaust device 168 includes an exhaust hood arranged on the top of the viscosity enhancing cylinder 161, and 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.

[0072] The upper and lower parts of the viscosity enhancing cylinder 161 are both provided with sight glasses, which makes it convenient to observe the condition of the internal materials.

[0073] The structure of the bottle flakes discharge hopper 22 is the same as that of the particle discharge hopper 162 .

[0074] The material adding device includes a particle feeding bin 163 fixed on 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 discharging control device includes a particle buffer bin 166 fixed on the lower opening of the particle discharging hopper 162, a first discharge control valve 1611 is provided between the particle buffer bin 166 and the particle discharging hopper 162, a particle discharge bin 167 is connected to the lower end of the particle buffer bin 166, and a second discharge control valve 1612 is installed between the particle discharge bin 167 and the particle buffer bin 166.

[0075] 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.

[0076] The first bottle-piece conveying device 4 , the second bottle-piece 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.

[0077] 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 pieces, and the drying and purification time is shortened; 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 and turn yellow, which meets the manufacturing of food PET bottles; 3. The system performs a viscosity-increasing treatment on the granulated PET particles, first using infrared heating to crystallize the particles, and then the crystallized temperature enters the viscosity-increasing machine 16 for viscosity-increasing, and the hot nitrogen is in uniform contact with all the particles to ensure the viscosity-increasing effect, and at the same time, it also avoids contact with oxygen, and because the ions have been crystallized during the viscosity-increasing process, they will not stick together when entering the viscosity-increasing machine 16, and 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, and because 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.

[0078] This embodiment also discloses a PET recycling and granulation method, which uses the PET recycling and granulation system and includes the following steps:

[0079] S1. Infrared drying

[0080] 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 selected from 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.

[0081] S2. Nitrogen heating purification

[0082] After the PET bottle flakes enter the purification cylinder 21 of the purifier 2, the heated nitrogen is continuously introduced into the lower part of the purifier 2 and the top is evacuated, and the flowing nitrogen is used to heat and purify the PET bottle flakes in the purifier 2;

[0083] S3, the purified PET bottle flakes are sent to the extruder 6 for extrusion;

[0084] S4, pelletizing and cooling the PET melt extruded by the extruder 6 by using a pelletizing device;

[0085] S5, using a dehydration device to dehydrate the pelletized PET particles and send them to a temporary storage tank 13 for temporary storage;

[0086] S6. The PET particles in the temporary storage tank 13 are sent to the single-pot infrared dehumidification crystallization drying all-in-one machine 15 by using the first particle conveying device 14 for infrared heating crystallization drying. The single-pot infrared dehumidification crystallization drying all-in-one machine 15 stirs and exhausts air under negative pressure 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 to the thickening cylinder 161. Heated nitrogen is introduced into the bottom of the particle discharge hopper 162. The second negative pressure 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 negative pressure exhaust device 168 after heating. When the PET particles are thickened, they are discharged from the bottom.

[0087] The viscosity increasing reaction process of the PET particles in the viscosity increasing cylinder 161 is as follows:

[0088] 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 added to the set amount, close the second feeding control valve 164 and the second particle conveying device 17 stops feeding;

[0089] 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 bin 166. When the thickened particles in the particle buffer bin 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 bin 166 to enter the lining discharge bin.

[0090] 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;

[0091] S64, repeating 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, and each batch of particles has the same viscosity-increasing reaction time to ensure stable particle quality.

[0092] After use, the hot nitrogen can be filtered and recovered by a nitrogen recovery system to avoid nitrogen waste.

[0093] The gas circuit system, motor and other actuators mentioned in this embodiment are all conventional technologies at present. The specific structure and principle of the cylinder, motor and other transmission mechanisms and other designs are disclosed in detail in the "Mechanical Design Manual Fifth Edition" printed in Beijing in April 2008, the fifth edition, the twenty-eighth edition, which belongs to the prior art and its structure is clear. The modern practical pneumatic technology, the third edition SMC training textbook published by the Machinery Industry Press on August 1, 2008, discloses the vacuum element, gas circuit and program control in detail, indicating that the gas circuit structure in this embodiment is also the existing technology, which is clear. The book "Motor Drive and Speed ​​Regulation" published by the Chemical Industry Press on July 1, 2015 also introduces the control of the motor and the travel switch in detail, so the circuit and gas circuit connection are clear. The above-mentioned embodiments are only descriptions of the preferred embodiments of the present invention, and are not used as limitations on the scope of the present invention. On the basis of not departing from the design spirit of the present invention, various deformations and modifications made to the technical solution of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A PET recycling and granulation system, characterized in that: include The PET bottle flake drying and purification device comprises a continuous infrared dryer and a purifier, wherein the continuous infrared dryer comprises a fixed machine base, a drying barrel is rotatably mounted on the fixed machine base, the drying barrel is driven by a drying rotating power device, a spiral stirring blade is arranged in the drying barrel, a feed port is arranged at the upstream end of the drying barrel and is connected to a bottle flake feeding device, a discharge port is arranged at the downstream end of the drying barrel, a drying discharge bin connected to the discharge port is arranged on the fixed machine base, and a The purifier comprises a purifying cylinder, a bottle flake feeding port is arranged at the upper end of the purifying cylinder, the bottle flake feeding port is connected with the dry discharging bin through a first bottle flake conveying device, the lower end of the purifying cylinder is connected with a conical bottle flake discharging hopper for convenient discharging, the lower end of the bottle flake discharging hopper is opened and connected with a bottle flake discharging control device, a dry nitrogen total gas port is arranged on the bottle flake discharging hopper, the dry nitrogen total gas port is connected with a hot nitrogen gas supply system, and a first negative pressure exhaust device is arranged on the top of the purifying cylinder; An extruder, wherein the feed port of the extruder is connected to the bottle flake discharge control device through a second bottle flake conveying device; A pelletizing device, which is installed downstream of the extruder and is used to pelletize the melt extruded by the extruder; A dehydration device, which is arranged below the pelletizing device and is used to dehydrate the PET particles pelletized by the pelletizing device; A temporary storage tank, which is arranged downstream of the dehydration device and is used to receive the PET particles dehydrated by the dehydration device; A thickening unit, the thickening unit comprises a single-pot infrared dehumidification crystallization drying all-in-one machine and a thickening machine, the feed inlet of the single-pot infrared dehumidification crystallization drying all-in-one machine is connected with the discharge port at the bottom of the temporary storage tank through a first particle conveying device; the thickening machine comprises 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, and 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 gas connected to the hot nitrogen gas supply system, an outer annular chamber is provided between the outer hopper and the intermediate hopper, an inner annular chamber is formed between the intermediate hopper and the inner hopper, the total gas port for thickening nitrogen gas is connected with the outer annular chamber, the upper and lower parts of the outer annular chamber are respectively connected with the inner annular chamber, a connecting hole is provided on the annular connecting plate, 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 as claimed in 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 external hopper are all provided with a heat preservation 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 arranged 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 arranged 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 buffer bin fixed on the lower opening of the particle discharge hopper, a first discharge control valve is arranged between the particle buffer bin and the particle discharge hopper, a particle discharge bin is connected to the lower end of the particle buffer bin, and a second discharge control valve is installed between the particle discharge bin and the particle buffer bin.

6. A PET recycling and granulation system as claimed in 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 feeders, and the hot nitrogen gas supply system is connected to each vacuum feeder as an isolation gas source.

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

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

9. A PET recovery and granulation method, characterized in that: The recycling and granulation method uses the PET recycling and granulation system according to any one of claims 1 to 8, comprising the following steps: S1. Infrared drying 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 perform infrared heating and drying on the PET bottle flakes. During the drying process, the drying barrel continuously rotates and stirs and feeds the dried PET bottle flakes to the purifier. S2. Nitrogen heating purification 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 evacuated, and the flowing nitrogen is used to heat and purify the PET bottle flakes in the purifier; S3, the purified PET bottle flakes are sent to the extruder for extrusion; S4, using a pelletizing device to pelletize and cool the PET melt extruded by the extruder; S5, using a dehydration device to dehydrate the pelletized PET particles and send them to a temporary storage tank for temporary storage; S6. Use the first particle conveying device to deliver 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 vacuum evacuates 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 deliver the crystallized and dried PET particles to the thickening cylinder. Heated nitrogen is introduced into the bottom of the particle discharge hopper. The second vacuum exhaust device on the top of the thickening cylinder exhausts air. The PET particles undergo polyester repolymerization in the thickening cylinder. 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.

10. A PET recycling and granulation method as claimed in claim 9, characterized in that: The viscosity increasing reaction process of the PET particles in the viscosity increasing cylinder is as follows: S61, open the second feeding control valve and close the first feeding control valve, the second particle conveying device feeds the PET particles into the particle feeding bin, and when the particle feeding bin is added to a set amount, close the second feeding control valve and the second particle conveying device stops feeding; 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 bin. When the thickened particles in the particle buffer bin 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 bin to enter the lining discharge bin. S63, opening the first feeding control valve, adding the particles in the particle feeding bin into the thickening cylinder for heating and thickening; S64, repeat steps S61-S63, adding material once after each discharge.

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