Tackifier and tackifying unit for recycling PET (Polyethylene Terephthalate)

Abstract

The tackifier comprises a tackifying cylinder, the lower end of the tackifying cylinder is connected with a discharging hopper, the discharging hopper comprises an inner hopper, a middle hopper and an outer hopper from inside to outside, the inner hopper, the middle hopper and the outer hopper are fixedly connected through annular connecting plates, the outer hopper is provided with a nitrogen total gas port, and the nitrogen total gas port is communicated with the nitrogen total gas port. An outer annular cavity is formed between the outer hopper and the middle hopper, an inner annular cavity is formed between the middle hopper and the inner hopper, the nitrogen total gas port is communicated with the outer annular cavity, the upper portion and the lower portion of the outer annular cavity are communicated with the upper portion and the lower portion of the inner annular cavity respectively, a plurality of air inlet holes are further formed in the hopper wall of the inner hopper, and an air extractor is arranged at the top of the tackifying barrel. And a negative pressure vacuum meter and a thermometer are arranged on the tackifying cylinder. According to the tackifier, heated nitrogen is used for heating a PET material, negative-pressure air exhaust is carried out while heating is carried out, the material is prevented from making contact with oxygen in the reaction process, and therefore the color of the tackified PET material is whiter and closer to that of a new material.

Description

Technical Field

[0001] The invention relates to the technical field of PET recycling, and in particular to a PET recycling viscosity increasing machine and a viscosity increasing machine unit. Background Art

[0002] In the field of PET recycling technology, a viscosity increasing machine is generally used for viscosity increasing. Since the source of recycled polyester is complex and the composition is difficult to ensure consistency, the viscosity of the melt fluctuates greatly during the production process. In order to stabilize the viscosity and make it meet the requirements of secondary use, the current viscosity increasing machine mainly heats the PET material inside the reactor by heating the reactor and heat transfer oil. For example, the viscosity increasing device disclosed in the public text of a solid phase viscosity increasing device with less volatility of heat transfer oil with the authorization announcement number CN220328623U uses heat transfer oil to heat the reactor to heat the PET material inside, and the inside needs to be stirred by a stirring device to make the inside heated as evenly as possible.

[0003] However, the viscosity increasing device of this structure still has the following disadvantages: 1. The space utilization of this reactor is relatively small. A stirring device needs to be set inside the reactor, which will occupy a certain space, resulting in a reduction in the space for storing materials inside, which leads to a relatively large size of the entire equipment. In addition, since the heat transfer oil is hotter to the side wall of the reactor, the temperature of the side wall will always be higher than the temperature of the middle part. Therefore, even if the material is stirred, the uniformity of heating cannot be guaranteed. 2. The efficiency of this viscosity increasing device is relatively low. In order to ensure that the reaction time of the PET material in the reactor is consistent, it is necessary to first fill the reactor with PET material, then conduct a certain period of repolymerization reaction, and then discharge the material in the reactor. The whole process requires one-time filling and one-time discharge, resulting in a long interval time; 3. The reactor does not isolate oxygen in the air during the reaction, resulting in the color of the viscosity increasing PET material being yellowish compared with the new PET material. Therefore, the PET material cannot be used in the production of transparent PET. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a PET recycling thickener, which uses heated nitrogen to heat the PET material and vacuums it under negative pressure during heating to avoid contact between the material and oxygen during the reaction, so that the color of the PET material after thickening is whiter and closer to new material.

[0005] Another technical problem to be solved by the present invention is to provide a thickening unit for PET recycling, which connects an infrared dehumidification crystallization drying integrated machine with the thickening machine. The recovered granulated PET material enters the infrared dehumidification crystallization drying integrated machine for infrared heating and crystallization drying, and then is directly sent to the thickening machine for thickening, thereby saving the time for thickening treatment.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a PET recycling thickening machine, comprising a vertical thickening cylinder, the upper end of the thickening cylinder is provided with a material adding port for convenient entry of PET material, a material adding device is installed on the material adding port, the lower end of the thickening cylinder is connected to a conical discharge hopper for convenient discharge, the lower opening of the discharge hopper is connected to a discharge control device, the discharge hopper includes an inner hopper, an intermediate hopper and an outer hopper from the inside to the outside, 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 nitrogen main gas port for connecting with a hot nitrogen supply system, an outer annular chamber is provided between the outer hopper and the middle hopper, an inner annular chamber is formed between the middle hopper and the inner hopper, the nitrogen main gas port is communicated with the outer annular chamber, 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, a plurality of air inlet holes are also provided on the hopper wall of the inner hopper, an 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.

[0007] As a preferred solution, the outside of the viscosity enhancing cylinder and the outside of the external hopper are both provided with a heat-insulating layer.

[0008] As a preferred solution, a material level meter is provided on the upper portion of the viscosity enhancing cylinder.

[0009] As a preferred solution, the material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, and a second feeding control valve is arranged between the vacuum loader and the feeding bin.

[0010] As a preferred solution, the discharge control device includes a cache bin fixed on the lower opening of the discharge hopper, a first discharge control valve is arranged between the cache bin and the discharge hopper, a discharge bin is connected to the lower end of the cache bin, and a second discharge control valve is installed between the discharge bin and the cache bin.

[0011] As a preferred solution, an auxiliary heating device for auxiliary heating the viscosity-enhancing cylinder is also provided in the thermal insulation layer.

[0012] As a preferred solution, the upper and lower parts of the viscosity enhancing cylinder are both provided with sight glasses.

[0013] As a preferred solution, the nitrogen main gas inlet is arranged in the middle of the discharge hopper.

[0014] After adopting the above technical scheme, the effect of the present invention is as follows: a PET recycling 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 material, a material adding device is installed on the material adding port, the lower end of the thickening cylinder is connected to a conical discharge hopper for convenient discharge, the lower end of the discharge hopper is opened and connected to a discharge control device, the discharge hopper includes an inner hopper, an intermediate hopper and an outer hopper from the inside to the outside, 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 nitrogen total gas port for communicating with a 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 nitrogen total gas port is communicated with the outer annular chamber, the outer annular chamber is communicated with the upper and lower parts of the inner annular chamber respectively, 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, an air extraction device is provided on the top of the viscosity increasing cylinder, and a negative pressure vacuum gauge and a thermometer are provided on the viscosity increasing cylinder, so The viscosity enhancer uses heated nitrogen to enter from the nitrogen main gas port. The nitrogen line passes through the outer annular chamber and flows upward and downward, then passes through the upper connecting chamber and the lower connecting chamber into the inner annular chamber, and evenly enters the inner hopper through the air inlet holes on the inner hopper, and gradually flows upward and is exhausted by the exhaust device at the upper end of the viscosity enhancer cylinder. In this way, the whole process is protected by nitrogen to prevent the PET material from coming into contact with oxygen during the reaction and causing discoloration. At the same time, nitrogen enters the inner hopper from the bottom and top, and the nitrogen will pass through the gaps between the materials to the materials. The material is heated evenly, avoiding heating dead corners, and the heating effect is more uniform, so the stirring device is omitted, and the space utilization rate is higher. In addition, since the material is fed at the upper end and discharged at the lower end of the thickening cylinder, the material residence time in the thickening cylinder can be controlled by controlling the feeding frequency and the discharging frequency, so that the reaction time can be controlled more accurately and the thickening effect is better. Vacuuming is performed during the heating process, and the low molecular substances in the material are vaporized and extracted at high temperature, thereby improving the purity of the material. Therefore, the PET material treated by the thickening machine can be used for the production of PET bottles.

[0015] Furthermore, since the outside of the viscosity increasing cylinder and the outside of the external hopper are both provided with a heat-insulating layer, the heat-insulating layer can keep the viscosity increasing cylinder warm and avoid heat loss.

[0016] Furthermore, since a material level meter is provided on the upper part of the viscosity enhancing cylinder, the material level meter can detect the height of the material in the viscosity enhancing cylinder to ensure that the amount of material added is appropriate.

[0017] Furthermore, since the material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, and a second feeding control valve is arranged between the vacuum loader and the feeding bin, therefore, when adding materials, the vacuum loader can deliver the PET material to the feeding bin. When the material in the feeding bin is full, the vacuum loader can stop feeding, and at the same time, the first feeding control valve at the bottom of the feeding bin is opened to add the material in the entire feeding bin into the thickening cylinder, so that the volume of the material added each time is the same.

[0018] Furthermore, since the discharge control device includes a cache bin fixed on the lower opening of the discharge hopper, a first discharge control valve is arranged between the cache bin and the discharge hopper, a discharge bin is connected to the lower end of the cache bin, and a second discharge control valve is installed between the discharge bin and the cache bin. Similarly, when the material needs to be turned over, the material is first placed in the cache bin for cache. At this time, the size of the cache bin is set to be consistent with the size of the feeding bin, so that the feeding amount and the discharge amount can be kept consistent, thereby accurately controlling the heating reaction time of the material.

[0019] Furthermore, since an auxiliary heating device for auxiliary heating of the viscosity enhancing cylinder is also provided in the thermal insulation layer, when the temperature in the viscosity enhancing cylinder does not meet the standard, auxiliary heating can be performed by the auxiliary heating device to meet the heating requirements in some low temperature environments.

[0020] In order to solve the above-mentioned second technical problem, the solution of the present invention is: to provide a PET recycling thickening unit, which includes an infrared dehumidification crystallization drying all-in-one machine and the PET recycling thickening machine, the discharge port of the infrared dehumidification crystallization drying all-in-one machine is connected with the feeding port of the material adding device through a material conveying pipeline, and the hot nitrogen supply system is connected with the nitrogen total gas port through a pipeline.

[0021] Further preferably, the material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, a second feeding control valve is arranged between the vacuum loader and the feeding bin, and the hot nitrogen gas supply system is also connected to the vacuum loader.

[0022] After adopting the above technical scheme, the effect of the present invention is: the infrared dehumidification crystallization drying integrated machine can heat, dry and crystallize the PET particles, so that the moisture content of the PET particles is controlled to be very low, and then the crystallized PET particles are sent to the thickening cylinder of the thickening machine, so that the heat of the PET particles themselves is not lost, which can further shorten the thickening time. At the same time, the thickening cylinder is heated by heated nitrogen, which makes the heating more uniform and can also prevent the PET particles from coming into contact with oxygen and causing discoloration.

[0023] Furthermore, since the material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, a second feeding control valve is arranged between the vacuum loader and the feeding bin, and the hot nitrogen gas supply system is also connected to the vacuum loader, therefore, the hot nitrogen gas supply system supplies the heated nitrogen to the vacuum loader, therefore, the vacuum loader also uses hot nitrogen as the gas source for feeding, thereby ensuring nitrogen protection during the transportation process to avoid contact with oxygen. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Figure 1 is a structural cross-sectional view of an embodiment of the present invention;

[0026] Figure 2 yes Figure 2 A partial enlarged schematic diagram of

[0027] Figure 3 Schematic diagram of the structure of the viscosity increasing unit in the embodiment of the present invention;

[0028] In the attached figure: 1, viscosity increasing cylinder; 2, vacuum feeder; 3, feeding bin; 4, second feeding control valve; 5, first feeding control valve; 6, exhaust device; 7, discharge hopper; 8, sight glass; 9, frame; 10, insulation layer; 11, material level meter; 12, negative pressure vacuum gauge; 13, thermometer; 14, buffer bin; 15, discharge bin; 16, first discharge control valve; 17, second discharge control valve; 18, extraction pipe; 71, inner hopper; 72, intermediate material Bucket; 73, outer hopper; 74, annular connecting plate; 75, outer annular chamber; 76, upper connecting chamber; 77, inner annular chamber; 78, lower connecting chamber; 79, nitrogen total gas inlet; 710, air inlet; 100, viscosity enhancer; 200, infrared dehumidification crystallization drying integrated machine; 2001, feeding device; 2002, barrel; 2003, light box; 2004, discharge bin; 300, material conveying pipeline; 400, hot nitrogen supply system. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below through specific examples.

[0030] like Figure 1 and Figure 2As shown, a PET recycling thickening machine includes a vertical thickening cylinder 1, which is fixed on a frame 9 and arranged in an upright manner. The upper end of the thickening cylinder 1 is provided with a material addition port for facilitating the entry of PET materials, and a material addition device is installed on the material addition port. The material addition device includes a feeding bin 3 fixed on the material addition port, a first feeding control valve 5 is provided at the bottom of the feeding bin 3, a vacuum feeder 2 is fixedly installed on the upper end of the feeding bin 3, and a second feeding control valve 4 is provided between the vacuum feeder 2 and the feeding bin 3. The first feeding control valve 5 and the second feeding control valve 4 can select pneumatic butterfly valves. The vacuum feeder 2 is a conventional feeding device at present, which is a conventional technology in this field.

[0031] The lower end of the viscosity enhancing cylinder 1 is connected to a conical discharge hopper 7 for convenient discharge of materials. The lower side of the discharge hopper 7 is open and connected to a discharge control device.

[0032] In this embodiment, the discharge control device includes a buffer bin 14 fixed on the lower opening of the discharge hopper 7, a first discharge control valve 16 is provided between the buffer bin 14 and the discharge hopper 7, a discharge bin 15 is connected to the lower end of the buffer bin 14, and a second discharge control valve 17 is installed between the discharge bin 15 and the buffer bin 14. Similarly, the first discharge control valve 16 and the first discharge control valve 16 also use pneumatic butterfly valves, and the bottom of the discharge bin 15 is connected with a pumping pipe 18 to facilitate the delivery of materials.

[0033] like Figure 2 As shown, the discharge hopper 7 includes an inner hopper 71, an intermediate hopper 72 and an outer hopper 73 from the inside to the outside. The inner hopper 71, the intermediate hopper 72 and the outer hopper 73 are fixedly connected by an annular connecting plate 74. The annular connecting plate 74 is provided with connecting holes. The number of the connecting holes is multiple and evenly distributed around the circumference, so that nitrogen can pass through evenly. Of course, the annular connecting plate 74 can also be replaced by discrete connecting blocks. The spacing formed between the connecting blocks can facilitate the passage of nitrogen.

[0034] The outer hopper 73 is provided with a nitrogen main gas port 79 for communicating with a hot nitrogen gas supply system, and the hot nitrogen gas supply system heats the nitrogen and then enters through the nitrogen main gas port 79. The nitrogen main gas port 79 is preferably arranged in the middle of the discharge hopper 7, 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.

[0035] An outer annular chamber 75 is provided between the outer hopper 73 and the middle hopper 72, an inner annular chamber 77 is formed between the middle hopper 72 and the inner hopper 71, the total nitrogen gas port 79 is connected with the outer annular chamber 75, an upper connecting chamber 76 is formed between the upper part of the outer hopper 73 and the upper part of the inner hopper 71, and a lower connecting chamber 78 is formed between the lower part of the outer hopper 73 and the lower part of the inner hopper 71. The upper connecting chamber 76 and the lower connecting chamber 78 connect the upper and lower parts of the outer annular chamber 75 and the inner annular chamber 77 respectively, and a plurality of air inlet holes 710 are further provided on the hopper wall of the inner hopper 71. An exhaust device 6 is provided on the top of the thickening cylinder 1, and a negative pressure vacuum gauge 12 and a thermometer 13 are provided on the thickening cylinder 1. The negative pressure vacuum gauge 12 and the thermometer 13 monitor the pressure and temperature inside the thickening cylinder 1 in real time to ensure that the reaction of the PET material is carried out under a suitable process parameter. A material level meter 11 is provided on the upper portion of the viscosity enhancing cylinder 1 to control the upper limit position of the material.

[0036] The vacuum device 6 includes a vacuum hood arranged on the top of the thickening cylinder 1, and the vacuum port of the vacuum hood extends out of the thickening cylinder 1 and is connected to the vacuum pump, so that the internal gas is continuously extracted.

[0037] The outside of the viscosity enhancing cylinder 1 and the outside of the outer hopper 73 are both provided with a heat-insulating layer 10, and the heat-insulating layer 10 can be made of heat-insulating cotton or other heat-insulating materials.

[0038] The insulation layer 10 is also provided with an auxiliary heating device for auxiliary heating of the viscosity increasing cylinder 1. The auxiliary heating device can be assisted by electric heating or thermal oil heating. Under normal circumstances, pneumatic operation is not required, and only the nitrogen temperature needs to be controlled. In special circumstances, such as when the nitrogen heating device fails and the nitrogen temperature is insufficient, the auxiliary heating device can be started to replenish energy.

[0039] The upper and lower parts of the viscosity enhancing cylinder 1 are both provided with sight glasses 8, which facilitates observation of the internal material.

[0040] The working principle of the present invention is: first, the PET material is delivered to the feeding bin 3 by the vacuum feeder 2, and then the material is delivered to the thickening cylinder 1 through the first feeding control valve 5. When the material in the thickening cylinder 1 reaches the upper limit, it will be detected by the level meter 11. At this time, the feeding is stopped, and the heated nitrogen is evenly introduced into the thickening cylinder 1. The upper end exhaust device 6 performs continuous exhaust to ensure that the vacuum degree in the thickening cylinder 1 reaches the set value. After heating, the PET material undergoes polyester repolymerization reaction in a vacuum environment, and the low molecular substances in the raw materials are vaporized and extracted at high temperature, thereby improving the purity of the melt. At the same time, the molecules of the PET material undergo polymerization reaction, resulting in the continuous growth of the molecular chain, thereby increasing the characteristic viscosity, and isolating oxygen, so that the color of the thickened PET material is not yellow, so it can meet the production of transparent PET bottles.

[0041] like Figure 3 As shown, Figure 3 The diagram shows a PET recycling thickening unit, which includes an infrared dehumidification crystallization drying all-in-one machine 200 and the PET recycling thickening machine 100. The discharge port of the infrared dehumidification crystallization drying all-in-one machine 200 is connected to the feeding port of the material adding device 2 through a material conveying pipeline 300, and the hot nitrogen supply system 400 is connected to the nitrogen total gas port 79 through a pipeline.

[0042] The basic structure of the infrared dehumidification crystallization drying machine has been applied for a domestic patent by the applicant before, and the specific publication number is CN 214521287 U. The basic structure of the infrared dehumidification crystallization drying machine includes a rotating barrel 2002, an infrared heating light box 2003, a fan for exhausting air inside, a feeding device 2001 for feeding, and a discharge port arranged on the side wall of the barrel 2002. A discharge bin 2004 is arranged at the bottom of the barrel 2002. PET particles enter the barrel 2002 through the feeding device 2001. The barrel 2002 rotates and is heated inside by the infrared light box 2003 to dry, dehumidify and crystallize the particles. During the dehumidification process, air is exhausted to remove the heated and evaporated moisture and impurities. When the crystallization and drying are completed, the water content of the PET particles is very low, and then the material is discharged, and the PET particles enter the discharge bin 2004 and are then transported to the viscosity increasing machine 100 through the vacuum feeder 2 for viscosity increasing treatment, and the material adding device includes a feeding bin 3 fixed on the material adding port, a first feeding control valve 5 is arranged at the bottom of the feeding bin, a vacuum feeder 2 is fixedly installed at the upper end of the feeding bin 3, a second feeding control valve 4 is arranged between the vacuum feeder 2 and the feeding bin 3, and the hot nitrogen gas supply system 400 is also connected to the vacuum feeder 2. The discharge bin 2004 is set to a closed structure, so that the conveying gas source of the vacuum feeder 2 also uses heated nitrogen, so that the PET particles are further protected during the conveying process.

[0043] The hot nitrogen supply system 400 in this embodiment may be composed of a nitrogen recovery system and a nitrogen heating supply system to achieve nitrogen recovery and reuse.

[0044] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A PET recycling thickener, characterized in that: The invention comprises a vertical viscosity increasing cylinder, wherein the upper end of the viscosity increasing cylinder is provided with a material adding port for facilitating the entry of PET material, a material adding device is installed on the material adding port, the lower end of the viscosity increasing cylinder is connected with a conical discharging hopper for facilitating discharging, the lower end of the discharging hopper is opened and connected with a discharging control device, the discharging hopper comprises an inner hopper, an intermediate hopper and an outer hopper from the inside to the outside, the inner hopper, the intermediate hopper and the outer hopper are fixedly connected by an annular connecting plate, and the outer hopper is provided with a material for connecting with hot nitrogen. A nitrogen main gas port connected to the air supply system, an outer annular chamber is provided between the outer hopper and the middle hopper, an inner annular chamber is formed between the middle hopper and the inner hopper, the nitrogen main gas port is connected to the outer annular chamber, the upper and lower parts of the outer annular chamber and the inner annular chamber are respectively connected, 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, an 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 viscosity increasing machine as claimed in claim 1, characterized in that: The outside of the viscosity enhancing cylinder and the outside of the outer hopper are both provided with a heat-insulating layer.

3. A PET recycling viscosity increasing machine as claimed in claim 2, characterized in that: A material level meter is arranged on the upper part of the viscosity enhancing cylinder.

4. A PET recycling viscosity increasing machine as claimed in claim 1, characterized in that: The material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, and a second feeding control valve is arranged between the vacuum loader and the feeding bin.

5. A PET recycling viscosity increasing machine as claimed in claim 1, characterized in that: The discharge control device includes a buffer bin fixed on the lower opening of the discharge hopper, a first discharge control valve is arranged between the buffer bin and the discharge hopper, a discharge bin is connected to the lower end of the buffer bin, and a second discharge control valve is installed between the discharge bin and the buffer bin.

6. A PET recycling viscosity increasing machine as claimed in claim 2, characterized in that: The thermal insulation layer is also provided with an auxiliary heating device for auxiliary heating of the viscosity enhancing cylinder.

7. A PET recycling viscosity increasing machine as claimed in claim 1, characterized in that: The upper and lower parts of the viscosity enhancing cylinder are both provided with sight glasses.

8. A PET recycling viscosity increasing machine as claimed in claim 1, characterized in that: The nitrogen main gas inlet is arranged in the middle of the discharge hopper.

9. A PET recovery viscosity increasing unit, characterized in that: The thickening unit comprises an infrared dehumidification crystallization drying all-in-one machine and a PET recycling thickening machine as described in any one of claims 1 to 8, wherein the discharge port of the infrared dehumidification crystallization drying all-in-one machine is connected to the feeding port of the material adding device through a material conveying pipeline, and the hot nitrogen gas supply system is connected to the nitrogen total gas port through a pipeline.

10. A PET recovery and thickening unit as claimed in claim 9, characterized in that: The material adding device includes a feeding bin fixed on the material adding port, a first feeding control valve is arranged at the bottom of the feeding bin, a vacuum loader is fixedly installed at the upper end of the feeding bin, a second feeding control valve is arranged between the vacuum loader and the feeding bin, and the hot nitrogen gas supply system is also connected to the vacuum loader.

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