Novel drying machine and drying method for recycling and regenerating PET (Polyethylene Terephthalate)

Abstract

The invention relates to the technical field of drying machines, in particular to a novel drying machine for recycling and regenerating PET. A novel drying machine for recycling and regenerating PET comprises a preheating hopper, the upper portion of the preheating hopper is communicated with a material collector, the material collector is connected with a feeding machine, one side of the preheating hopper is communicated with a preheating box, the lower portion of the preheating hopper is communicated with a heating hopper, the lower portion of the heating hopper is connected with a material suction box, and the material suction box is connected with a first material collector through a connecting pipe. A vacuum hopper is communicated below the first material collector, a main heat preservation hopper is communicated below the vacuum hopper, a vacuum isolation hopper is arranged among the vacuum hopper, the first material collector and the main heat preservation hopper for isolation, and a metering, proportioning and mixing unit is connected below the main heat preservation hopper. Compared with the prior art, the steps of molecular sieve, oil removal condensation, cooling water and the like are not needed, the energy consumption is greatly reduced, and different formulas can be rapidly switched.

Description

Technical Field

[0001] The invention relates to the technical field of dryers, in particular to a novel dryer and a drying method for recycling recycled PET. Background Art

[0002] PET bottles are the most widely used beverage packaging today, and are widely used in many fields such as food, chemical, and pharmaceutical packaging. China produces tens of billions of PET bottles each year, and more than 500,000 tons of PET are used in the manufacture of PET bottles each year. The recycling of PET bottles can not only solve environmental problems, but also serve as a new raw material resource to alleviate the contradiction of insufficient PET raw materials in China. At present, the drying time of PET bottle materials is too long, usually more than 6 hours, plus other recycling and regeneration steps, at least 6 to 8 hours or more. The time consumption is too long to meet such a large supply. The production of PET requires more efficient drying. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a new type of dryer and drying method for recycling recycled PET. The gas containing water finally comes out from the top of the preheating hopper and is filtered before being discharged to the outside, which can achieve a drying effect, remove any dust and particles, and also remove benzene and acetaldehyde.

[0004] In order to achieve the above purpose, a new type of dryer for recycling recycled PET is designed, including a preheating hopper, a receiver is connected to the top of the preheating hopper, the receiver is connected to the feeder, one side of the preheating hopper leads to a preheating box, the preheating hopper is connected to the heating hopper, the heating hopper is connected to a suction box, the suction box is connected to the receiver through a connecting pipe, the receiver is connected to a vacuum hopper, the vacuum hopper is connected to a main insulation hopper, a vacuum isolation hopper is provided between the vacuum hopper and the receiver and the main insulation hopper for isolation, and a metering and proportioning mixing unit is connected to the main insulation hopper; One side of the preheating hopper is connected to a preheating box, which is connected to a preheating fan. The preheating fan draws air through a filter and sends it into the preheating box. A filter is also provided on the other side of the preheating hopper. One side of the heating hopper is connected to a heating box, which is connected to a heating fan. The heating fan draws air from the heating hopper through a filter and sends it into the heating box. The vacuum hopper and the vacuum isolation hopper below are connected to a vacuum pump, the main insulation hopper is connected to a main hopper heating box, the main hopper heating box is connected to a main hopper fan, and the main hopper fan is externally connected to a compressed air dryer.

[0005] The receiver is opened and closed by installing an interruption valve. Ball valves are provided between the receiver and the vacuum isolation hopper, between the vacuum isolation hopper and the vacuum hopper, and between the vacuum isolation hopper and the main insulation hopper. One end of the connecting pipe is connected to the cleaning valve.

[0006] The outlets of the preheating hopper, heating hopper, vacuum hopper and main insulation hopper are provided with pneumatic knife gates, the preheating hopper and heating hopper are provided with continuous material levels, and the vacuum hopper and main insulation hopper are provided with capacitive material levels.

[0007] The motor drive modules of the preheating fan, heating fan, main hopper fan and vacuum pump are respectively connected to the digital signal output end of the control unit, the contactor of the preheating box is respectively connected to the digital output end, digital input end and analog input end of the control unit, the frequency converter of the heating box is respectively connected to the digital output end, digital input end and analog output end of the control unit, the control heating group of the main hopper heating box is respectively connected to the digital output end, digital input end and analog input end of the control unit, the signal contactor of the compressed air dryer is connected to the digital output end, digital input end and analog input end of the control unit, and the control unit model is S7-1200.

[0008] The connecting pipe, preheating hopper, heating hopper, vacuum hopper and main insulation hopper are all made of AISI304 stainless steel.

[0009] A drying method of a novel dryer for recycling recycled PET comprises the following steps: S1: The receiver collects the recycled PET from the mixer and conveys it to the preheating hopper; S2: In an open loop, the gas in the preheating box is heated to 100°C, and 100°C hot air is passed into the recycled PET, and the recycled PET is preheated in the preheating hopper for 2 hours; S3: The recycled PET is unloaded into the heating hopper through the pneumatic gate; S4: In a closed loop, the air circulating in the heating box is repeatedly filtered and heated to 170°C, and the recycled PET is dried for 2 hours; S5: The receiver extracts the recycled PET from the bottom of the heating hopper into The vacuum isolation hopper then enters the vacuum hopper, and the moisture and air in the vacuum hopper are extracted by a vacuum pump. After drying for 1.5 hours, the recycled PET is further dried in the vacuum hopper and benzene and acetaldehyde are removed; S6: It flows into the main insulation hopper through the vacuum isolation hopper below; S7: Under a closed loop, the main insulation hopper sucks air from the compressed air dryer, and the main hopper heating box heats the air to 170°C, and the hot air is passed into the main insulation hopper, and the recycled PET in the main insulation hopper is heated again for 2 hours; S8: After drying, the recycled PET is directly transported to the injection molding machine or extruder.

[0010] The water content of the recycled PET entering the heating box in S4 is lower than 1250ppm, the benzene content is lower than 65ppb, and the acetaldehyde content is less than 1.2ppm.

[0011] The water content of the recycled PET entering the vacuum hopper in S5 is less than 1250ppm, the benzene content is less than 65ppb, and the acetaldehyde content is less than 1.2ppm.

[0012] After the drying in S8 is completed, the water content of the recycled PET obtained is less than 40 ppm, the benzene content is less than 10 ppb, and the acetaldehyde content is less than 1 ppm.

[0013] Compared with the prior art, the present invention does not require steps such as molecular sieve, oil removal condensation, cooling water, etc., and the energy consumption is greatly reduced, and different formulations can be quickly switched. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the present invention.

[0015] Figure 2 It is a material collecting and loading structure.

[0016] Figure 3 Partial schematic diagram of the preheating hopper and heating hopper.

[0017] Figure 4 Partial schematic diagram of the vacuum hopper and main insulation hopper.

[0018] See also Figures 1 to 4 , 1 is a preheating hopper, 2 is a heating hopper, 3 is a heating box, 4 is a preheating box, 5 is a preheating fan, 6 is a pneumatic knife, 7 is a heating fan, 8 is a connecting pipe, 9 is a feeder, 10 is a metering and proportioning mixing unit, 11 is a vacuum isolation hopper, 12 is a vacuum hopper, 13 is a suction box, 14 is a cleaning valve, 15 is a main insulation hopper, 16 is a main hopper fan, 17 is a vacuum pump, 18 is a ball valve, 19 is a compressed air dryer, 20 is an interruption valve, 21 is a main hopper heating box, 22 is a capacitive material level, 23 is a control unit, 24 is a filter, 24.1 is a filter one, 25 is a continuous material level, 26 is a receiver, and 26.1 is a receiver one. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] like Figure 1 As shown, the preheating hopper 1 is connected to a receiver 26 above. Figure 2 As shown, the receiver 26 is connected to the feeder 9, as shown in FIG. Figure 3 , 4As shown, one side of the preheating hopper 1 leads to the preheating box 4, and the preheating hopper 1 is connected to the heating hopper 2 below, and the heating hopper 2 is connected to a suction box 13 below, and the suction box 13 is connected to the receiver 26.1 through a connecting pipe 8, and the receiver 26.1 has a heat preservation function, and the receiver 26.1 is connected to the vacuum hopper 12 below, and the vacuum hopper 12 is connected to the main insulation hopper 15 below, and a vacuum isolation hopper 11 is provided between the vacuum hopper 12 and the receiver 26.1 and the main insulation hopper 15 for isolation, and the vacuum isolation hopper 11 ensures the vacuum environment in the vacuum hopper 12, and the main insulation hopper 15 is connected to a metering and proportioning mixing unit 10 below.

[0021] One side of the preheating hopper 1 is connected to a preheating box 4, which is connected to a preheating fan 5. The preheating fan 5 draws air through a filter 24 and sends it into the preheating box 4. The other side of the preheating hopper 1 is also provided with a filter 24.1. The filter 24 is used to ensure that the air introduced is free of impurities. The filter 24.1 separates the dust and particles generated inside. One side of the heating hopper 2 is connected to a heating box 3, which is connected to a heating fan 7. The heating fan 7 draws air from the heating hopper 2 through the filter 24 and sends it into the heating box 3.

[0022] The vacuum hopper 12 and the vacuum isolation hopper 11 below are connected to a vacuum pump 17. The vacuum pump 17 can separate the moisture, benzene and acetaldehyde in the recycled PET in the vacuum hopper 12 by extracting air. The main insulation hopper 15 is connected to a main hopper heating box 21, and the main hopper heating box 21 is connected to the main hopper fan 16. The main hopper fan 16 is externally connected to a compressed air dryer 19.

[0023] The receiver 26 is switched on and off by installing an interruption valve 20. A ball valve 18 is provided between the receiver 26.1 and the vacuum isolation hopper 11, between the vacuum isolation hopper 11 and the vacuum hopper 12, and between the vacuum isolation hopper 11 and the main insulation hopper 15. One end of the connecting pipe 8 is connected to the cleaning valve 14.

[0024] Pneumatic gates 6 are provided at the outlets of the preheating hopper 1 , the heating hopper 2 , the vacuum hopper 12 , and the main insulation hopper 15 . The pneumatic gates 6 are used to unload the recycled PET. A continuous material level 25 is provided in the preheating hopper 1 and the heating hopper 2 . A capacitive material level 22 is provided in the vacuum hopper 12 and the main insulation hopper 15 .

[0025] The motor drive modules of the preheating fan 5, the heating fan 7, the main hopper fan 16, and the vacuum pump 17 are respectively connected to the digital signal output end of the control unit 23, the contactor of the preheating box 4 is respectively connected to the digital output end, the digital input end, and the analog input end of the control unit 23, the frequency converter of the heating box 3 is respectively connected to the digital output end, the digital input end, and the analog output end of the control unit 23, the control heating group of the main hopper heating box 21 is respectively connected to the digital output end, the digital input end, and the analog input end of the control unit 23, and the signal contactor of the compressed air dryer 19 is connected to the digital output end, the digital input end, and the analog input end of the control unit 23. The model of the control unit 23 is S7-1200.

[0026] The connecting pipe 8, the preheating hopper 1, the heating hopper 2, the vacuum hopper 12, and the main insulation hopper 15 are made of AISI304 stainless steel.

[0027] The water content of the recycled PET entering the heating box 3 in S4 is lower than 1250 ppm, the benzene content is lower than 65 ppb, and the acetaldehyde content is less than 1.2 ppm.

[0028] The water content of the recycled PET entering the vacuum hopper 12 in S5 is less than 1250 ppm, the benzene content is less than 65 ppb, and the acetaldehyde content is less than 1.2 ppm.

[0029] After the drying in S8 is completed, the water content of the recovered PET obtained is less than 40 ppm, the benzene content is less than 10 ppb, and the acetaldehyde content is less than 1 ppm.

[0030] The specific implementation process of the present invention is as follows: the receiver 26 collects the recycled PET from the mixer and conveys it to the preheating hopper 1, operating under open-loop conditions, the indoor air extracted by the preheating fan 5 and filtered by the filter 24 reaches the preheating box 4, the air is heated to the set process temperature of 100°C, the heated air is sent to the preheating hopper 1, and is conveyed to the preheating hopper 1 from the bottom through the heat dissipation cone at the bottom so that it can reach all the recycled PET contained in the preheating hopper 1, the hot air passes through the recycled PET and finally comes out from the top of the preheating hopper 1, and finally passes through the filter 24.1 before being discharged into the room, where dust and particles are separated and discharged, and there is a filter at the bottom of the preheating hopper 1. A pneumatic gate 6 is used to unload the recycled PET. The recycled PET is unloaded into the heating hopper 2. The circulating air extracted by the heating fan 7 reaches the heating box 3, where the air is heated to the process temperature of 170°C. The recycled PET is dried in the heating hopper 2. The required moisture content of the recycled PET at this time is less than 1250ppm, the benzene content is less than 65ppb, and the acetaldehyde content is 1.2ppm. The air returning to the heating hopper 2 passes through the filter 24 before reaching the heating fan 7, and is transported from the bottom to the heating hopper 2 through the heat dissipation cone at the bottom so that it can reach all the recycled PET contained in the heating hopper 2. After 2 hours of high-temperature heating and drying, the receiver 26.1 extracts the recycled PET from the bottom of the heating hopper 2, passes through the vacuum isolation hopper 11 and the ball valve 18, and enters the vacuum hopper 12. The vacuum pump 17 evacuates the vacuum hopper 12, and the recycled PET is dried and the benzene and acetaldehyde therein are removed. After 1.5 hours, the dried recycled PET passes through the vacuum isolation hopper 11. And the ball valve 18 flows into the main insulation hopper 15. In this process, the water content of the recycled and regenerated PET must be lower than 1250ppm, the benzene content is less than 65ppb, and the acetaldehyde content is 1.2ppm. The main hopper fan 16 draws dry air from the compressed air dryer 19 and is heated to the set process temperature of 170°C in the main hopper heating box 21. Due to heat loss after vacuuming, the recycled and regenerated PET is heated again in the main insulation hopper 15. The hot air contacts the recycled and regenerated PET and finally circulates from the top of the main insulation hopper 15 through the filter 24 to the main hopper fan 16. The drying is completed after 2 hours. At this time, the entire drying system is completed, and the recycled and regenerated PET is directly transported to the injection molding machine or the extruder. After completing the entire process, the water content of the recycled and regenerated PET after drying is lower than 40ppm, the benzene content is less than 10ppb, and the acetaldehyde content is less than 1ppm.

Claims

1. A novel dryer for recycling recycled PET, comprising a preheating hopper, characterized in that: The preheating hopper (1) is connected to a material receiver (26) at the top, the material receiver (26) is connected to a feeder (9), one side of the preheating hopper (1) is connected to a preheating box (4), the preheating hopper (1) is connected to a heating hopper (2) at the bottom, a suction box (13) is connected to the heating hopper (2) at the bottom, the suction box (13) is connected to the material receiver (26.1) at the bottom through a connecting pipe (8), the material receiver (26.1) is connected to a vacuum hopper (12) at the bottom, the vacuum hopper (12) is connected to a main insulation hopper (15) at the bottom, a vacuum isolation hopper (11) is provided between the vacuum hopper (12) and the material receiver (26.1) and the main insulation hopper (15) for isolation, and the main insulation hopper (15) is connected to a metering and proportioning mixing unit (10) at the bottom; One side of the preheating hopper (1) is connected to a preheating box (4), the preheating box (4) is connected to a preheating fan (5), the preheating fan (5) draws air through a filter (24) and sends the air into the preheating box (4), the other side of the preheating hopper (1) is also provided with a filter 1 (24.1), one side of the heating hopper (2) is connected to a heating box (3), the heating box (3) is connected to a heating fan (7), the heating fan (7) draws air from the heating hopper (2) through the filter (24) and sends the air into the heating box (3); The vacuum hopper (12) and the vacuum isolation hopper (11) below are connected to a vacuum pump (17), the main insulation hopper (15) is connected to a main hopper heating box (21), the main hopper heating box (21) is connected to a main hopper fan (16), and the main hopper fan (16) is externally connected to a compressed air dryer (19).

2. A novel dryer for recycling regenerated PET according to claim 1, characterized in that: The receiver (26) is opened and closed by installing an interruption valve (20). A ball valve (18) is provided between the receiver 1 (26.1) and the vacuum isolation hopper (11), between the vacuum isolation hopper (11) and the vacuum hopper (12), and between the vacuum isolation hopper (11) and the main insulation hopper (15). One end of the connecting pipe (8) is connected to the cleaning valve (14).

3. A novel dryer for recycling regenerated PET according to claim 1, characterized in that: The outlets of the preheating hopper (1), the heating hopper (2), the vacuum hopper (12), and the main insulation hopper (15) are provided with pneumatic gates (6); the preheating hopper (1) and the heating hopper (2) are provided with continuous material levels (25); and the vacuum hopper (12) and the main insulation hopper (15) are provided with capacitive material levels (22).

4. A novel dryer for recycling regenerated PET according to claim 1, characterized in that: The motor drive modules of the preheating fan (5), the heating fan (7), the main hopper fan (16), and the vacuum pump (17) are respectively connected to the digital signal output end of the control unit (23); the contactor of the preheating box (4) is respectively connected to the digital output end, the digital input end, and the analog input end of the control unit (23); the frequency converter of the heating box (3) is respectively connected to the digital output end, the digital input end, and the analog output end of the control unit (23); the control heating group of the main hopper heating box (21) is respectively connected to the digital output end, the digital input end, and the analog input end of the control unit (23); the signal contactor of the compressed air dryer (19) is connected to the digital output end, the digital input end, and the analog input end of the control unit (23); and the control unit (23) is of model S7-1200.

5. A novel dryer for recycling regenerated PET according to claim 1, characterized in that: The connecting pipe (8), the preheating hopper (1), the heating hopper (2), the vacuum hopper (12), and the main insulation hopper (15) are all made of AISI304 stainless steel.

6. A drying method of the novel dryer for recycling regenerated PET as claimed in any one of claims 1 to 5, Its characteristics are as follows, including the following steps: S1: The receiver (26) collects the recycled PET from the mixer and conveys it to the preheating hopper (1); S2: In an open loop, the gas in the preheating box (4) is heated to 100°C, and hot gas at 100°C is introduced into the recycled PET. The recycled PET is preheated in the preheating hopper (1) for 2 hours; S3: The recycled PET is unloaded into the heating hopper (2) through the pneumatic gate (6); S4: In a closed loop, the air circulating in the heating box (3) is repeatedly filtered and heated to 170°C. At this time, the recycled PET is dried for 2 hours; S5: The receiver 1 (26.1) removes the recycled PET from the heating hopper (2 ) is extracted from the bottom and enters the vacuum isolation hopper (11) and then enters the vacuum hopper (12). The water and air in the vacuum hopper (12) are extracted by the vacuum pump (17). After drying for 1.5 hours, the recovered recycled PET is further dried in the vacuum hopper (12) and the benzene and acetaldehyde are removed; S6: It flows into the main insulation hopper (15) through the vacuum isolation hopper (11) below; S7: In a closed loop, the main insulation hopper (15) sucks in the air in the compressed air dryer (19), and the main hopper heating box (21) heats the air to 170°C. The hot air is passed into the main insulation hopper (15), and the recovered recycled PET in the main insulation hopper (15) is heated again for 2 hours; S8: After drying, the recycled PET is directly conveyed to the injection molding machine or extruder.

7. The drying method of the novel dryer for recycling regenerated PET according to claim 6, characterized in that: The water content of the recycled PET entering the heating box (3) in S4 is less than 1250 ppm, the benzene content is less than 65 ppb, and the acetaldehyde content is less than 1.2 ppm.

8. The drying method of the novel dryer for recycling regenerated PET according to claim 6, characterized in that: The water content of the recycled PET entering the vacuum hopper (12) in S5 is less than 1250 ppm, the benzene content is less than 65 ppb, and the acetaldehyde content is less than 1.2 ppm.

9. The drying method of the novel dryer for recycling regenerated PET according to claim 6, characterized in that: After the drying in S8 is completed, the water content of the recycled PET obtained is less than 40 ppm, the benzene content is less than 10 ppb, and the acetaldehyde content is less than 1 ppm.

Images