Polyester micro-plastic recycling and impurity removing method and equipment

Abstract

The invention relates to the technical field of regeneration of waste polyester, in particular to a polyester micro-plastic recycling and impurity removing method and equipment. According to the method, the irradiation technology is adopted for treating the polyester micro-plastic, the polyvinyl chloride is removed by combining electron beam irradiation with the specific gravity method, the radiation dosage and time are accurately controlled, the polyvinyl chloride in the polyester micro-plastic can be effectively removed, the color of the polyester micro-plastic is not affected, and the treated polyester micro-plastic can meet the spinning requirement. The equipment is used for realizing the impurity removal method and comprises irradiation treatment equipment, a separation tank, a cleaning tank, a dehydrator and a drying tower. The equipment is simple in structure and convenient to operate, the radiation dosage and time can be accurately controlled in the impurity removal process, the surface temperature of the polyester micro-plastic is effectively controlled, and production and popularization are easy.

Description

Technical Field

[0001] The present invention relates to the technical field of waste polyester recycling, and specifically, to a method and equipment for removing impurities from recycled polyester microplastics. Background Art

[0002] Waste plastics enter the environment through various channels and are decomposed into plastic fragments under physical, chemical or biological actions. Among them, plastic microparticles with a particle size less than 5 mm are defined as microplastics. Microplastics currently cause serious pollution in rivers, oceans and soil, and have an impact on biodiversity and the physical and chemical properties of soil. At present, the research on microplastics mainly focuses on the distribution, degradation and impact on biodiversity of microplastics in water and soil environments, and there are few reports on the recycling of microplastics.

[0003] Currently, recycled polyester mainly uses polyester bottle chips as raw materials. Due to the wide source of polyester bottle chips and the action of the external environment, waste polyester contains many impurities, so it must be cleaned before recycling. A large amount of polyester microplastics will be generated during the cleaning and treatment of polyester bottle chips. The main components of these microplastics are polyester, and they also contain a relatively large amount of polyvinyl chloride. The generation of this polyvinyl chloride is mainly due to the residue of the wrapping paper on the polyester bottle chips during the polyester recycling process. The presence of polyvinyl chloride will not only affect the color of polyester fibers, but also affect the melt viscosity. Therefore, the content of polyvinyl chloride is an important parameter index for the quality of bottle chips. However, due to the small size and color of polyvinyl chloride in microplastics being close to that of polyester bottle chips, it is very difficult to separate them, which severely limits the large-scale use of polyester microplastics and seriously wastes this potentially recyclable resource of polyester microplastics.

[0004] The Chinese invention patent (publication number: CN115230018A, publication date: October 25, 2022) applied by the applicant discloses a method and system for recycling polyester microplastic particles. The method performs cleaning, impurity removal, boiling, rinsing, removal of other microplastic particles and color selection processes on waste polyester microplastic sludge through a friction cleaning machine, a microplastic particle impurity removal elutriation device, a heating tank, a cleaning and rinsing tank, a micro-particle material separator and a micro-particle color sorter, and obtains high-quality polyester microplastic particles. However, this invention does not involve the problem of removing polyvinyl chloride in polyester microplastics. Therefore, the applicant further deeply studies the impurity removal process of polyester microplastics to improve the recycling rate and recycling quality of polyester microplastics.

[0005] The Chinese invention patent applied by the applicant (Publication No.: CN102873792A, Publication Date: January 16, 2013) discloses a method for separating recycled polyester bottle chips by specific gravity method. This method includes the following steps: preparing a saturated sodium chloride solution; adding an aqueous solution of industrial white oil emulsified industrially to the saturated sodium chloride solution; putting the recycled polyester bottle chips into a stirring tank. During the stirring process, metal or non-metal impurities with a specific gravity greater than 1.50 g / cm 3 gradually sink to the bottom of the separation device, and the recycled polyester bottle chips float on the surface of the mixed solution. Using a special mechanical device to fish out the floating recycled polyester bottle chips can achieve the separation of recycled polyester bottle chips. However, for the specific gravity of polyvinyl chloride in polyester microplastics is approximate, and both float on the surface of the saturated sodium chloride solution, and cannot be separated by this method. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method and equipment for recycling and removing impurities from polyester microplastics. This impurity removal method can effectively remove polyvinyl chloride in polyester microplastics without affecting the color of polyester microplastics, and the treated polyester microplastics can meet the spinning requirements.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A method for recycling and removing impurities from polyester microplastics, including the following steps: 1) Pretreatment: irradiating the polyester microplastics by using electron beam irradiation technology; the operation parameters of the electron beam irradiation include: the electron beam energy is 3 - 5 MeV, the electron beam current intensity is 40 - 80 mA, and the irradiation time is 1 - 5 min; 2) Impurity removal: removing polyvinyl chloride impurities in the irradiated polyester microplastics by using the specific gravity method; 3) Post-treatment: cleaning, dehydrating, and drying the polyester microplastics after impurity removal.

[0008] Preferably, during the irradiation treatment in step 1), the surface temperature of the polyester is controlled at 180°C - 220°C; and / or, in step 2), the laying thickness of the polyester microplastics is 1 - 3 cm.

[0009] Preferably, the polyester microplastics are derived from polyester microplastics generated after polyester bottle chip cleaning or color sorting.

[0010] Preferably, in step 2), a liquid medium is used for impurity removal, and the density of the liquid medium is 1.35 g / cm 3 ~1.45 g / cm 3 ; Preferably, in step 2), the liquid medium is used for impurity removal twice. The density of the liquid medium used for the first impurity removal is 1.40 g / cm3 ~1.45 g / cm 3 For the second impurity removal, the density of the liquid medium used is 1.35 g / cm 3 ~1.42 g / cm 3 .

[0011] Preferably, the liquid medium is one of calcium chloride solution, compound calcium chloride and sodium chloride solution, ethanol - aqueous solution, glycerol - aqueous solution, calcium nitrate solution.

[0012] Preferably, in step 3), the polyester microplastics are cleaned with clear water; and / or, the polyester microplastics are dehydrated with a dehydrator; and / or, the polyester microplastics are dried with hot air. Preferably, the parameters of hot - air drying include: the hot - air flow rate is 8000 m³ / h to 12000 m³ / h, and the hot - air temperature is 100 - 120 °C.

[0013] Furthermore, the present invention also provides a polyester microplastic impurity - removal device, which is used to implement the above - mentioned polyester microplastic recycling and impurity - removal method, and includes an irradiation treatment device, a separation tank, a cleaning tank, a dehydrator, and a drying tower.

[0014] Preferably, the device further includes a raw material bin, an air conveyor, and a discharging screw. The raw material bin is connected to the irradiation treatment device through a first conveying screw, the irradiation treatment device is connected to the separation tank through a second conveying screw, the dehydrator is connected to the air conveyor through a conveyor belt, and the drying tower is arranged between the air conveyor and the discharging screw.

[0015] Preferably, the separation tank includes a primary separation tank and a secondary separation tank connected to each other. Multi - stage separation can improve the separation effect; and / or, an infrared thermometer is arranged on the irradiation treatment device to monitor the surface temperature of the polyester microplastics in real time; and / or, a hot - air device is arranged in the drying tower.

[0016] Preferably, a stirring device is arranged in the raw material bin to prevent the polyester microplastics from caking.

[0017] The beneficial effects of the present invention are as follows: 1) The present invention uses irradiation technology to treat polyester microplastics. Electron irradiation initiates cross - linking reactions between polyvinyl chloride molecular chains to form a three - dimensional network structure, reducing the free volume of molecular chains, thereby increasing the specific gravity of polyvinyl chloride. Then, the specific - gravity method is used to remove polyvinyl chloride, breaking through the technical bottleneck of efficient impurity removal and directional separation of polyester microplastics; 2) The present invention uses irradiation technology to treat polyester microplastics, precisely controlling the radiation dose and time, effectively controlling the surface temperature of polyester microplastics, with a short treatment time, and the color change of polyester microplastics does not affect their recycling, laying a foundation for the high-value utilization of polyester microplastics; 3) The present invention can control the removal rate of polyvinyl chloride in polyester microplastics above 90%. The treated polyester microplastics can meet the spinning requirements, effectively improving the performance of recycled polyester fibers and promoting low-carbon circular technology innovation and industrial transformation; 4) The equipment adopted by the present invention has a simple structure and convenient operation, and can precisely control the radiation dose and time and effectively control the surface temperature of polyester microplastics during the impurity removal process, being easy to produce and promote. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the impurity removal equipment for polyester microplastics.

[0019] Reference Signs: 01 - raw material bin, 02 - conveying screw, 03 - irradiation treatment equipment, 04 - infrared thermometer, 05 - conveying screw, 06 - primary separation tank, 07 - secondary separation tank, 08 - cleaning tank, 09 - dehydrator, 10 - conveyor belt, 11 - pneumatic conveyor, 12 - drying tower, 13 - discharging screw. Detailed Embodiments

[0020] Combined with the embodiments of the present invention below, the technical solutions in the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0021] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application.

[0022] In the first aspect, the present invention discloses a method for recycling and removing impurities from polyester microplastics, using irradiation technology combined with the specific gravity method to remove polyvinyl chloride in polyester microplastics.

[0023] In the second aspect, the present invention also discloses an impurity removal device for polyester microplastics, which is used to implement the method for recycling and removing impurities from polyester microplastics of the present invention.

[0024] Example 1 Raw materials: Polyester microplastics generated during the cleaning and recycling process of polyester bottle chips, with a polyvinyl chloride content of 2350 ppm.

[0025] The specific steps for impurity removal are as follows: 1) Pretreatment: Feed the recycled polyester microplastics into the irradiation treatment equipment 03. The operating parameters of the electron beam irradiation are set as follows: the electron beam energy is 4 MeV, the electron beam current intensity is 80 mA, the irradiation time is 2 min, the flat thickness of the polyester microplastics is 1 - 3 cm, and the surface temperature of the polyester microplastics is controlled at 180 - 220 °C.

[0026] 2) Impurity removal: Feed the irradiated polyester microplastics into the primary separation tank 06 and the secondary separation tank 07 in sequence, and use a compound solution of calcium chloride and sodium chloride as the medium solution. The density of the medium solution in the primary separation tank is 1.44 g / cm 3 , and the density of the medium solution in the secondary separation tank is 1.38 g / cm 3 .

[0027] 3) Post-treatment: Wash the separated polyester microplastics with clean water in the washing tank 08, and then rotate and dehydrate the washed polyester microplastics using a dehydrator 09; Feed the dehydrated polyester microplastics into a drying tower 12 for hot air drying, with a hot air flow rate of 10000 m³ / h and a hot air temperature of 110 °C.

[0028] Example 2 The difference from Example 1 is that in step 1), the electron beam current intensity is set to 40 mA and the irradiation time is set to 5 min.

[0029] Example 3 The difference from Example 1 is that in step 1), the electron beam current intensity is set to 60 mA and the irradiation time is set to 3 min.

[0030] Example 4 The difference from Example 1 is that the raw materials are polyester microplastics screened by a vibrating sieve during the color sorting process of polyester bottle chips, with a PVC content of 1560 ppm.

[0031] Comparative Example 1 The difference from Example 1 is that the electron beam current intensity is set to 100 mA.

[0032] Comparative Example 2 The difference from Example 1 is that the electron beam energy is 6 MeV.

[0033] Comparative Example 3 The difference from Example 2 is that the electron beam current intensity is set to 30 mA.

[0034] Comparative Example 4 The difference from Example 2 is that the irradiation time is 7 min.

[0035] The above-mentioned examples and comparative examples use the polyester microplastic impurity removal equipment of the present invention for impurity removal. As Figure 1 shown, the equipment includes a raw material bin 01, an irradiation treatment device 03, a primary separation tank 06, a secondary separation tank 07, a cleaning tank 08, a dehydrator 09 and a drying tower 12 that are connected to each other. The raw material bin 01 is connected to the irradiation treatment device 03 through a first conveying screw 02, and the irradiation treatment device 03 is connected to the primary separation tank 06 through a second conveying screw 05. The primary separation tank 06, the secondary separation tank 07, the cleaning tank 08, and the dehydrator 09 are connected in sequence. The dehydrator 09 is connected to a pneumatic conveyor 11 through a conveyor belt 10, and the drying tower 12 is arranged between the pneumatic conveyor 11 and a discharge screw 13.

[0036] Furthermore, an infrared thermometer 04 is provided on the irradiation treatment device 03, a hot air device is provided in the drying tower 12, a stirring device is provided in the raw material bin 01, and the cleaning tank 08 includes two tanks connected in sequence.

[0037] The specific operation process of the equipment is as follows: Put the polyester microplastics into the raw material bin 01. The stirrer in the raw material bin 01 prevents the polyester microplastics from caking. The polyester microplastics are sent into the irradiation treatment device 03 through the conveying screw 02. An infrared thermometer 04 is installed on the irradiation treatment device 03 to monitor the surface temperature of the polyester microplastics in real time. After being irradiated, the polyester microplastics enter the primary separation tank 06 and the secondary separation tank 07 in sequence through the conveying screw 05 for impurity removal. The polyester microplastics after impurity removal are washed in the cleaning tank 08, dehydrated by the dehydrator 09, and then sent into the drying tower 12 through the conveyor belt 10 and the pneumatic conveyor 11 for drying treatment. After drying is completed, it is discharged through the discharge screw 13 for packaging.

[0038] Samples of the polyester microplastics in the above-mentioned examples and comparative examples were taken before and after impurity removal, and the changes in the polyvinyl chloride content and L, a, b values in the polyester microplastics were measured. The test results are shown in Table 1.

[0039] Table 1 Results of index changes of polyester microplastics before and after impurity removal As can be seen from Table 1, the impurity removal method of the present invention can effectively remove polyvinyl chloride in polyester microplastics, control the polyvinyl chloride content in polyester microplastics within 150 ppm, and control the surface color difference change of polyester microplastics within an acceptable range. From Example 1 and Comparative Examples 1 and 2, it can be seen that too high an electron beam current intensity or too high an electron beam energy will cause the surface color of polyester microplastics to be severely yellowish, which is not conducive to the subsequent recycling of polyester microplastics. From Example 2 and Comparative Examples 3 and 4, it can be seen that a lower electron beam current intensity has a smaller impact on the surface color of polyester microplastics, but the impurity removal effect will also weaken; the extension of the irradiation time will cause the surface color of polyester microplastics to be more yellowish, which is likely to be unfavorable for the subsequent recycling of polyester microplastics. Therefore, it is very important to set a suitable parameter range, which should not only achieve a certain impurity removal effect, but also control the surface color difference change within an acceptable range.

[0040] The above is the description of the embodiments of the present invention. Through the above description of the disclosed embodiments, those skilled in the art can implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel points disclosed herein.

Claims

1. A method for recycling and removing impurities from polyester microplastics, characterized in that, It includes the following steps: 1) Pretreatment: Irradiate the polyester microplastics using electron beam irradiation technology; the operating parameters of the electron beam irradiation include: the electron beam energy is 3 - 5 MeV, the electron beam current intensity is 40 - 80 mA, and the irradiation time is 1 - 5 min; 2) Impurity removal: Remove the polyvinyl chloride impurities in the irradiated polyester microplastics by the specific gravity method; 3) Post-treatment: Wash, dehydrate, and dry the polyester microplastics after impurity removal.

2. The method for recycling and removing impurities from polyester microplastics according to claim 1, characterized in that, During the irradiation treatment process of step 1), the surface temperature of the polyester is controlled at 180°C - 220°C; And / or, in step 2), the laying thickness of the polyester microplastics is 1 - 3 cm.

3. A method for recycling and removing impurities from polyester microplastics according to claim 1, characterized in that, The polyester microplastics are sourced from the polyester microplastics generated after polyester bottle chips are washed or color - sorted.

4. A method for recycling and removing impurities from polyester microplastics according to claim 1, characterized in that, In step 2), liquid medium is used for impurity removal, and the density of the liquid medium is 1.35 g / cm 3 ~1.45 g / cm 3 ; In the said step 2), impurity removal is carried out twice using a liquid medium. The density of the liquid medium used for the first impurity removal is 1.40 g / cm 3 ~1.45 g / cm 3 , and the density of the liquid medium used for the second impurity removal is 1.35 g / cm 3 ~1.42 g / cm 3 .

5. A method for recycling and removing impurities from polyester microplastics according to claim 4, characterized in that, The liquid medium is one of calcium chloride solution, compound calcium chloride and sodium chloride solution, ethanol - aqueous solution, glycerol - aqueous solution, calcium nitrate solution.

6. The method for recycling and removing impurities from polyester microplastics according to claim 1, characterized in that, In step 3), wash the polyester microplastics with clean water; And / or, dehydrate the polyester microplastics using a dehydrator; And / or, dry the polyester microplastics by hot air drying, and the parameters of the hot air drying include: the hot air flow rate is 8000 m³ / h - 12000 m³ / h, and the hot air temperature is 100 - 120°C.

7. A polyester microplastic impurity removal device, characterized in that, This equipment is used to implement a method for recycling and impurity removal of polyester microplastics described in any one of claims 1 - 7, and includes an irradiation treatment device (03), a separation tank, a washing tank (08), a dehydrator (09), and a drying tower (12).

8. The polyester microplastic impurity removal device according to claim 8, characterized in that, This equipment also includes a raw material bin (01), an air conveyor (11), and a discharge screw (13). The raw material bin (01) is connected to the irradiation treatment device (03) through a first conveying screw (02), the irradiation treatment device (03) is connected to the separation tank through a second conveying screw (05), the dehydrator (09) is connected to the air conveyor (11) through a conveyor belt (10), and the drying tower (12) is arranged between the air conveyor (11) and the discharge screw (13).

9. The polyester microplastic impurity removal device according to claim 7 or 8, characterized in that, The separation tank includes a primary separation tank (06) and a secondary separation tank (07) connected to each other; And / or, an infrared thermometer (04) is provided on the irradiation treatment device (03); And / or, a hot air device is provided inside the drying tower (12).

10. The polyester microplastic impurity removal device according to claim 8, characterized in that, A stirring device is provided inside the raw material bin (01).

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