Spiral Conveyor Selective Dissolution Device and Its Application and Mixed Plastic Separation System

Abstract

The present invention relates to the technical field of separation of mixed plastics, and discloses a spiral conveying selective dissolution device, its application and a mixed plastic separation system. The device comprises a cylinder body and a variable pitch screw arranged inside the cylinder body; a feeding port and a discharging port are respectively arranged at two ends of the cylinder body; the variable pitch screw comprises a middle shaft and spiral blades; the spiral blades successively include a dense spiral blade, a wide spiral blade and a dense spiral blade, and through holes are arranged on the wide spiral blade; the cylinder body is correspondingly divided into a dense spiral blade cylinder body, a wide spiral blade cylinder body and a dense spiral blade cylinder body according to the spiral blades; a solvent inlet is arranged at one end of the wide spiral blade cylinder body close to the discharging port, and a solvent outlet is arranged at one end of the wide spiral blade cylinder body close to the feeding port. The spiral conveying selective dissolution device provided by the present invention can improve the dissolution effect, realize the efficient separation of different types of waste plastics, and is suitable for industrial popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of mixed plastic separation, and particularly relates to a spiral conveying selective dissolution device, its application and a mixed plastic separation system. Background Art

[0002] With the rapid development of the polymer industry, plastics are rapidly applied to all aspects of people's daily production and life, playing an important role in the rapid economic development. However, due to the slow degradation rate of waste plastics, serious "white pollution" is formed in the long term after being discarded.

[0003] Recent research shows that plastic particles formed by the preliminary decomposition of waste plastics have a greater impact on the environment and even appear in the human metabolic system. With the improvement of people's environmental awareness, how to effectively solve the problem of waste plastics has attracted increasing attention.

[0004] The existing waste plastic treatment technologies mainly include landfill, incineration, physical recycling and chemical recycling. Among them, landfill cannot fundamentally solve the problem and is easy to pollute groundwater resources; incineration is easy to cause serious air pollution; chemical recycling can effectively convert waste plastics into pyrolysis oil or pyrolysis gas. However, due to the complex sources and compositions of waste plastics, the processing process system fluctuates greatly, and the quality of the obtained product oil is poor, requiring high post-treatment costs.

[0005] The solubility of different types of plastics in different organic solvents is not the same. By utilizing the solubility differences of various types of plastics in waste plastics in organic solvents, physical recycling of mixed plastics can be achieved. Physical recycling has the advantages of simple operation and low cost. However, the bulk density of waste plastics is low, and conventional dissolution devices have a large floor area and low throughput. Therefore, it is necessary to develop a new type of waste plastic selective dissolution device to improve the processing efficiency of a single device. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of low throughput of existing waste plastic dissolution devices, and provide a spiral conveying selective dissolution device, its application and a mixed plastic separation system.

[0007] To achieve the above object, in a first aspect of the present invention, there is provided a spiral conveying selective dissolution device, the device comprising a cylinder body and a variable pitch screw arranged in the cylinder body; a feeding port and a discharging port are respectively arranged at two ends of the cylinder body; the variable pitch screw comprises an intermediate shaft and spiral blades; characterized in that, along the extending direction from the feeding port to the discharging port, the spiral blades sequentially comprise a dense spiral blade, a wide spiral blade and a dense spiral blade, and through holes are arranged on the wide spiral blade;

[0008] The cylinder body is divided into a dense spiral blade cylinder body, a wide spiral blade cylinder body, and a dense spiral blade cylinder body corresponding to the spiral blades; at one end of the wide spiral blade cylinder body close to the discharge port, a solvent inlet is provided, and at one end of the wide spiral blade cylinder body close to the feeding port, a solvent outlet is provided.

[0009] In a second aspect of the present invention, there is provided an application of the spiral conveying selective dissolution device described in the first aspect of the present invention in the separation of mixed plastics.

[0010] In a third aspect of the present invention, there is provided a mixed plastic separation system, which includes a mixed plastic feeding device, an organic solvent feeding device, the spiral conveying selective dissolution device described in the first aspect of the present invention, a separation device, a drying device, and a condensing device;

[0011] Among them, the mixed plastic feeding device and the organic solvent feeding device are respectively connected to the spiral conveying selective dissolution device, and the spiral conveying selective dissolution device is used to mix the mixed plastics and the organic solvent, perform selective dissolution, and obtain a liquid phase component containing soluble plastics and a solid phase component containing insoluble plastics;

[0012] The separation device is used to process the liquid phase component, recover the organic solvent, and obtain soluble plastics; the drying device is used to process the solid phase component, separate the organic solvent, and obtain insoluble plastics; the condensing device is used to condense the organic solvent separated from the drying device to return to the organic solvent feeding device.

[0013] Through the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0014] 1) A spiral conveying selective dissolution device provided by the present invention can enable the solid phase material entering from the feeding port to contact countercurrently with the liquid phase material entering from the solvent inlet under the action of the screw by opening holes in the wide pitch spiral blade, improving the dissolution effect;

[0015] 2) A spiral conveying selective dissolution device provided by the present invention can promote the contact between the liquid phase material and the solid phase material by the setting method of dense spiral blades at both ends and a wide spiral blade in the middle, further improving the dissolution effect;

[0016] 3) In a mixed plastic separation system provided by the present invention, setting the lower end of the electric stirring paddle in the mixed plastic feeding device in the necking can avoid blockage of the feeding tank and improve the stability of the system operation;

[0017] 4) A mixed plastic selective dissolution and separation system provided by the present invention can achieve efficient separation of different types of waste plastics and is suitable for industrial promotion. Description of the Drawings

[0018] Figure 1 It is a structural sectional view of a screw conveyor selective dissolution device provided by the present invention;

[0019] Figure 2 It is a flow chart of a mixed plastic separation system provided by the present invention.

[0020] Description of the reference numerals

[0021] Detailed implementation manners

[0022] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0023] The first aspect of the present invention provides a screw conveyor selective dissolution device, the device includes a cylinder 1 and a variable pitch screw 2 arranged in the cylinder 1; a feeding port 11 and a discharging port 12 are respectively arranged at both ends of the cylinder 1, and the variable pitch screw 2 includes an intermediate shaft 21 and a spiral blade 22; wherein, along the extension direction from the feeding port 11 to the discharging port 12, the spiral blade 22 successively includes a dense spiral blade 221, a wide spiral blade 222 and a dense spiral blade 221, and through holes 2221 are arranged on the wide spiral blade 222; the cylinder 1 is correspondingly divided into a dense spiral blade cylinder, a wide spiral blade cylinder and a dense spiral blade cylinder; at one end of the wide spiral blade cylinder close to the discharging port 12, a solvent inlet 13 is arranged, and at one end of the wide spiral blade cylinder close to the feeding port 11, a solvent outlet 14 is arranged, as Figure 1 shown.

[0024] Among them, the inventor of the present invention found through research that the setting of the dense spiral blades at both ends can achieve mechanical seal through mechanical extrusion to prevent solvent leakage; opening holes on the wide pitch spiral blade can enable the solid-phase material entering from the feeding port and the liquid-phase material entering from the solvent inlet to contact countercurrently under the action of the screw, promote the contact between the liquid-phase material and the solid-phase material, and improve the dissolution efficiency.

[0025] In an embodiment of the present invention, a heating layer 16 is arranged outside the wide spiral blade cylinder, and a heat preservation layer 17 is arranged outside the dense spiral blade cylinder. Among them, setting the heating layer can adjust the operating temperature of the dissolution device, and setting the heat preservation layer can reduce heat loss and energy consumption.

[0026] In an embodiment of the present invention, the ratio of the inner diameter of the cylinder body 1 to the diameter of the spiral blade 22 is 1:0.95 - 0.99, preferably 1:0.97 - 0.99. Among them, in the present invention, the small difference between the diameter of the spiral blade and the inner diameter of the cylinder body is conducive to preventing backmixing.

[0027] Among them, in the present invention, the ratio of the inner diameter of the cylinder body to the diameter of the spiral blade refers to the diameter ratio between the cylinder body and the spiral blade opposite to the cylinder body, that is, the inner diameter of the close spiral blade cylinder body corresponds to the diameter of the close spiral blade, and the inner diameter of the wide spiral blade cylinder body corresponds to the diameter of the wide spiral blade.

[0028] In an embodiment of the present invention, the thickness of the spiral blade 22 is 0.1 - 3 cm, preferably 0.2 - 2 cm.

[0029] In a preferred embodiment, the ratio of the thickness of the close spiral blade 221 to the thickness of the wide spiral blade 222 is 1:2 - 30, preferably 1:5 - 20.

[0030] In an embodiment of the present invention, the ratio of the diameter of the close spiral blade 221 to the diameter of the wide spiral blade 222 is 1:1 - 5, preferably 1:1 - 3.

[0031] In the present invention, the diameter of the close spiral blade is the same as that of the wide spiral blade, or can be smaller than the diameter of the wide spiral blade. When the ratio of the diameter of the close spiral blade to the diameter of the wide spiral blade is 1:1 - 3, the sealing effect of the screw conveyor selective dissolution device is better.

[0032] In an embodiment of the present invention, the ratio of the length of the close spiral blade 221 to the length of the wide spiral blade 222 is 1:1 - 30, preferably 1:1 - 20.

[0033] Among them, in the present invention, taking the length of the close spiral blade as an example, the length of the close spiral blade refers to the length of the variable pitch screw corresponding to the close spiral blade. The inventors of the present invention have found through research that when the length of the variable pitch screw remains unchanged, if the length of the close spiral blade is too long, the spiral transportation is prone to blockage; if the length of the close spiral blade is too short, the sealing effect is not good. When the ratio of the length of the close spiral blade to the length of the wide spiral blade is within the above-defined range, the transportation effect and dissolution effect are the best.

[0034] In an embodiment of the present invention, both the close spiral blade 221 and the wide spiral blade 222 are equal pitch spiral blades, and the ratio of the pitch of the close spiral blade 221 to the pitch of the wide spiral blade 222 is 1:2 - 10, preferably 1:3 - 7.

[0035] In an embodiment of the present invention, the close-coiled blade 221 is a variable pitch helical blade, and the wide helical blade 222 is a constant pitch helical blade; along the extension direction from the feeding port 11 to the discharging port 12, the pitch between adjacent blades of the close-coiled blade 221 increases by 0.1 - 5 cm in sequence, preferably by 0.5 - 3 cm; the ratio of the maximum pitch of the close-coiled blade 221 to the pitch of the wide helical blade 222 is 1:1 - 8, preferably 1:2 - 5.

[0036] In an embodiment of the present invention, the porosity of the wide helical blade 222 is 1% - 30%, preferably 5% - 20%.

[0037] Among them, in the present invention, in order to prevent the solid-phase material from blocking the through holes on the helical blade, the through holes on the wide helical blade only allow the liquid-phase material to flow through and do not allow the solid-phase material to pass through. The size and shape of the through holes on the helical blade can be adjusted according to the particle size of the solid-phase material therein, and the present invention does not make special limitations. Preferably, the through hole 2221 is a round hole with a diameter between 3 - 100 mm. If the porosity is too large, the mechanical strength of the wide helical blade will be reduced; if the porosity is too small, the countercurrent effect will be poor. When the porosity is within the above-defined range, both the countercurrent and dissolution effects are optimal.

[0038] In an embodiment of the present invention, the present invention does not make special limitations on the positions of the solvent inlet 13 and the solvent outlet 14 on the circumferential direction of the wide helical blade cylinder. Preferably, the solvent inlet 13 is arranged at the bottom of the wide helical blade cylinder, and the solvent outlet 14 is arranged at the top of the wide helical blade cylinder. In order to further improve the mixing effect, an auxiliary solvent inlet 15 can also be provided in the middle of the wide helical blade cylinder. Among them, the auxiliary solvent inlet 15 can be used to recycle a part of the liquid phase flowing out from the solvent outlet back to the screw conveyor selective dissolution device to improve the use efficiency of the liquid-phase material and reduce the energy consumption for the subsequent recovery of the liquid-phase material at the same time.

[0039] In an embodiment of the present invention, in order to improve the tightness of the cylinder 1 during operation, preferably, a feeding pipe is provided on the feeding port 11.

[0040] In an embodiment of the present invention, the variable pitch screw 2 and the cylinder 1 are connected by bearings, and the bearings are arranged at both ends of the screw. In order to improve the tightness of the cylinder, the connection part between the screw and the cylinder is sealed with a sealing member made of polytetrafluoroethylene material.

[0041] In an embodiment of the present invention, the device further includes a variable frequency motor 3, and the variable frequency motor 3 is connected to the variable pitch screw 2 for adjusting the rotation speed of the variable pitch screw 2. Among them, by adjusting the rotation speed of the variable pitch screw, the residence time of the solid-phase material in the cylinder can be changed.

[0042] In the second aspect of the present invention, there is provided an application of the screw conveyor selective dissolution device described in the first aspect of the present invention in the separation of mixed plastics.

[0043] In the third aspect of the present invention, there is provided a mixed plastic separation system, as Figure 2 shown, the system includes a mixed plastic feeding device, an organic solvent feeding device, the screw conveyor selective dissolution device described in the first aspect of the present invention, a separation device, a drying device, and a condensation device;

[0044] Wherein, the mixed plastic feeding device and the organic solvent feeding device are respectively connected to the screw conveyor selective dissolution device, and the screw conveyor selective dissolution device is used to mix the mixed plastics and the organic solvent for selective dissolution to obtain a liquid phase component containing soluble plastics and a solid phase component containing insoluble plastics;

[0045] The separation device is used to process the liquid phase component to recover the organic solvent and obtain soluble plastics; the drying device is used to process the solid phase component to separate the organic solvent and obtain insoluble plastics; the condensation device is used to condense the organic solvent separated from the drying device to return to the organic solvent feeding device.

[0046] In the present invention, the mixed plastic feeding device and the organic solvent feeding device are respectively connected to the screw conveyor selective dissolution device, and the screw conveyor selective dissolution device, the drying device, the condensation device, and the organic solvent feeding device are connected in sequence; the screw conveyor selective dissolution device is further connected to the separation device, and the separation device is further connected to the organic solvent feeding device.

[0047] Wherein, in the present invention, there is no special limitation on the source of the mixed plastics, which can be waste plastics from domestic waste or industrial waste, and is a mixture of various different types of plastics such as PVC, PS, PE, and PP randomly mixed. According to the different solubilities of plastics of different types in different organic solvents, one or some plastics in the mixed plastics can be separated by using an organic solvent. The present invention does not make special limitations on the organic solvent, and can be conventionally selected according to the specific type of plastic to be separated based on the common general knowledge in the art.

[0048] In the present invention, the mixed plastics from the mixed plastics feeding device and the organic solvent from the organic solvent feeding device are transported into the spiral conveying selective dissolution device, where they come into countercurrent contact and undergo selective dissolution to obtain a liquid phase component containing soluble plastics and a solid phase component containing insoluble plastics. The obtained liquid phase component containing soluble plastics is transported to a separation device for separation, separating the soluble plastics from the organic solvent, recovering the organic solvent, and obtaining the soluble plastics. The obtained solid phase component containing insoluble plastics is transported to a drying device for drying, separating out the small amount of organic solvent contained in the drying device, and obtaining the dried insoluble plastics. The organic solvent separated from the drying device is transported to a condensing device, condensed, and then returned to the organic solvent feeding device to achieve the recycling of the organic solvent.

[0049] Among them, the present invention does not make special limitations on the mixed plastics feeding device, the organic solvent feeding device, the separation device, the drying device, and the condensing device, and they can be selected according to the conventional operations in the art.

[0050] In an embodiment of the present invention, the mixed plastics feeding device includes a feeding tank and a stirring paddle connected to a variable frequency motor; wherein, a necking is provided at the lower end of the feeding tank, and the lower end of the stirring paddle is arranged above the necking; preferably, the lower end of the stirring paddle is located 2 - 3 cm above the necking.

[0051] Among them, the inventor of the present invention found through research that setting an electric stirring paddle in the feeding tank helps to press the mixed plastics into the spiral conveying selective dissolution device. When the lower end of the electric stirring paddle passes through the necking, it is easy to cause blockage of the feeding device. To avoid blockage, in the present invention, the lower end of the electric stirring paddle needs to be limited within the necking.

[0052] In an embodiment of the present invention, spiral stirring blades are provided on the stirring paddle, the diameter of the spiral stirring blades changes in the same trend as the inner diameter of the feeding tank, and the distance between the blade edge of the spiral stirring blades and the feeding tank is 0.1 - 10 cm, preferably 3 - 5 cm.

[0053] In an embodiment of the present invention, the lower end of the necking in the mixed plastics feeding device is connected to the feeding pipe on the spiral conveying selective dissolution device through a flange.

[0054] In an embodiment of the present invention, the organic solvent feeding device includes an organic solvent storage tank and a metering pump. In the present invention, the organic solvent is transported into the spiral conveying selective dissolution device through the metering pump.

[0055] In one embodiment of the present invention, the separation device is selected from an extraction device, a spray drying device, and a flash evaporation device.

[0056] In one embodiment of the present invention, the drying device is a wind drying device. The present invention does not make special limitations on the wind drying device. Any wind drying device that can dry solid particles can be used in the present invention. The circulating drying air in the wind drying device can be an inert gas, such as nitrogen.

[0057] In one embodiment of the present invention, the present invention does not make special limitations on the condensation device, and a plate heat exchanger is preferably used.

[0058] In one embodiment of the present invention, the system further includes a circulation pump, and the circulation pump is connected to the spiral conveyor selective dissolution device for returning part of the liquid phase components to the spiral conveyor selective dissolution device.

[0059] In addition, the mixed plastic separation system in the present invention further includes some common auxiliary devices, including but not limited to a water washing device, a pre-drying device, a crushing device, and a solid material transportation device, etc. The present invention will not elaborate one by one. Among them, the auxiliary devices in the present invention can preliminarily process the waste plastics from the landfill to obtain mixed plastics with a diameter of 5 - 200 mm and a water content of ≤ 3 wt%, and transport the mixed plastics.

[0060] The present invention will be described in detail below through examples.

[0061] Among them, the spiral conveyor selective dissolution device in the example includes a variable frequency motor A, a screw, and a cylinder; wherein, a heating layer and a heat insulation layer are sequentially arranged outside the cylinder, a feeding port and a discharging port are respectively arranged at both ends of the cylinder, a feeding pipe is arranged on the feeding port, and an auxiliary solvent inlet is arranged in the middle of the wide spiral blade cylinder; the inner diameter of the dense spiral blade cylinder is 10 cm, and the inner diameter of the wide spiral blade cylinder is 25 cm;

[0062] The variable pitch screw and the cylinder are connected through bearings arranged at both ends of the variable pitch screw, and the connection part between the variable pitch screw and the cylinder is sealed with a sealing member made of polytetrafluoroethylene material;

[0063] The variable pitch screw includes an intermediate shaft and spiral blades. Among them, the dense spiral blade is a variable pitch spiral blade, with a length of 52 cm, a diameter of 9.8 cm, the pitch between adjacent blades increases by 1 cm in sequence, the blade thickness is 2 cm, and the maximum pitch of the dense spiral blade is about 80 mm; the wide spiral blade is an equal pitch spiral blade, with a diameter of 24.5 cm, a length of 500 cm, a pitch of 30 cm, a blade thickness of 2 mm, and circular through holes with a diameter of 5 mm are arranged thereon, and the hole opening rate is 20%.

[0064] The feeding device includes a feeding tank and a stirring paddle connected to the variable-frequency motor B. Among them, the lower end of the feeding tank is provided with a necking, and the lower end of the stirring paddle is located 3 cm above the necking. The lower end of the necking is connected to the feeding pipe on the screw conveyor selective dissolution device through a flange.

[0065] The organic solvent feeding device is a diaphragm metering pump, model GM50 / 1.0. The separation device is a flash evaporation device, a flash evaporation tank, model YLG-01-B. The drying device is a continuous vacuum drying device, model YCV series belt-type continuous vacuum dryer. The condensation device is a plate heat exchanger, model BR005.

[0066] Example 1

[0067] In Figure 2 the shown system, the mixed plastics are separated.

[0068] The mixed plastics (particle size 10 - 20 mm) from the mixed plastic feeding device and the organic solvent from the organic solvent feeding device are transported to the screw conveyor selective dissolution device for countercurrent contact, and selective dissolution occurs, obtaining a liquid phase component containing soluble plastics and a solid phase component containing insoluble plastics.

[0069] Part of the obtained liquid phase component containing soluble plastics is returned to the screw conveyor selective dissolution device through the auxiliary solvent inlet (as Figure 1 shown), and the remaining part is transported to the separation device for separation. The soluble plastics are separated from the organic solvent, and the organic solvent is recovered to obtain the soluble plastics.

[0070] The obtained insoluble plastics are transported to the drying device for drying, and a small amount of the organic solvent contained in the drying device is separated to obtain the dried insoluble plastics. The organic solvent separated from the drying device is transported to the condensation device, condensed, and then returned to the organic solvent feeding device to achieve the recycling of the organic solvent.

[0071] Among them, the mixed plastics, operating conditions, and separation results in Example 1 are shown in Table 1.

[0072] Examples 2 - 5

[0073] Same as Example 1, the difference is that the composition of the mixed plastics and the operating conditions are changed, as specifically shown in Table 1.

[0074] Table 1

[0075]

[0076] Note: The mixed plastic in Example 5 is waste plastic from a landfill: the moisture content is 0.1 wt%, the mechanical impurity content is 7.9 wt%, and the plastic content is 91.7%; among them, the content of PS+PVC in the waste plastic is 5 wt%. The mechanical impurity and moisture content in the waste plastic are determined by the "Industrial Analysis Method of Coal" (GB212-91). The contents of PS and PVC in the waste plastic are measured by flotation using the density difference.

[0077] It can be found from Examples 1-5 that by separating the mixed plastic composed of different waste plastics with different organic solvents in the system provided by the present invention, a good separation effect can be obtained. For multi-component waste plastics, the combination of this system can be selected to achieve the purification and separation of multiple components.

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A spiral conveying selective dissolution device, the device comprising a cylinder body and a variable pitch screw arranged in the cylinder body; a feeding port and a discharging port are respectively arranged at two ends of the cylinder body; the variable pitch screw comprises an intermediate shaft and spiral blades; characterized in that, Along the extension direction from the feeding port to the discharging port, the spiral blades successively include dense spiral blades, wide spiral blades, and dense spiral blades, and through holes are arranged on the wide spiral blades; The cylinder body corresponds to the spiral blades and is divided into a dense spiral blade cylinder body, a wide spiral blade cylinder body, and a dense spiral blade cylinder body; at one end of the wide spiral blade cylinder body close to the discharging port, a solvent inlet is arranged, and at one end of the wide spiral blade cylinder body close to the feeding port, a solvent outlet is arranged.

2. The device according to claim 1, wherein, A heating layer is arranged outside the wide spiral blade cylinder body, and a heat preservation layer is arranged outside the dense spiral blade cylinder body.

3. The apparatus according to claim 2, wherein, The ratio of the inner diameter of the cylinder body to the diameter of the spiral blade is 1:0.95 - 0.

99.

4. The apparatus according to claim 3, wherein, The ratio of the inner diameter of the cylinder body to the diameter of the spiral blade is 1:0.97 - 0.

99.

5. The device according to claim 1, wherein, The thickness of the spiral blade is 0.1 - 3 cm; And / or, the ratio of the thickness of the dense spiral blade to the thickness of the wide spiral blade is 1:2 - 20; And / or, the ratio of the diameter of the dense spiral blade to the diameter of the wide spiral blade is 1:1 - 5; And / or, the ratio of the length of the dense spiral blade to the length of the wide spiral blade is 1:1 - 30.

6. The apparatus according to claim 5, wherein, The thickness of the spiral blade is 0.2 - 2 cm; And / or, the ratio of the thickness of the dense spiral blade to the thickness of the wide spiral blade is 1:5 - 15; And / or, the ratio of the diameter of the dense spiral blade to the diameter of the wide spiral blade is 1:1 - 3; And / or, the ratio of the length of the dense spiral blade to the length of the wide spiral blade is 1:1 - 20.

7. The device according to claim 1, wherein Both the dense spiral blade and the wide spiral blade are equal-pitch spiral blades, and the ratio of the pitch of the dense spiral blade to the pitch of the wide spiral blade is 1:2 - 10.

8. The apparatus according to claim 7, wherein The ratio of the pitch of the dense spiral blade to the pitch of the wide spiral blade is 1:3 - 7.

9. The device according to claim 1, wherein The dense spiral blade is a variable-pitch spiral blade, and the wide spiral blade is an equal-pitch spiral blade; Along the extension direction from the feeding port to the discharging port, the pitch between adjacent blades of the dense spiral blade increases successively by 0.1 - 5 cm; the ratio of the maximum pitch of the dense spiral blade to the pitch of the wide spiral blade is 1:1 - 8.

10. The apparatus according to claim 9, wherein, Along the extension direction from the feeding port to the discharging port, the pitch between adjacent blades of the dense spiral blade increases successively by 0.5 - 3 cm; the ratio of the maximum pitch of the dense spiral blade to the pitch of the wide spiral blade is 1:2 - 5.

11. The apparatus according to claim 1, wherein, The porosity of the holes on the wide spiral blade is 1% - 30%.

12. The apparatus according to claim 11, wherein, The porosity of the holes on the wide spiral blade is 5% - 20%.

13. Application of the device according to any one of claims 1 - 12 in the separation of mixed plastics.

14. A hybrid plastic separation system, characterized in that, The system includes a mixed plastic feeding device, an organic solvent feeding device, the spiral conveying selective dissolution device according to any one of claims 1 - 12, a separation device, a drying device, and a condensation device; Wherein, the mixed plastic feeding device and the organic solvent feeding device are respectively connected to the spiral conveying selective dissolution device, and the spiral conveying selective dissolution device is used to mix the mixed plastics and the organic solvent for selective dissolution to obtain a liquid-phase component containing soluble plastics and a solid-phase component containing insoluble plastics; The separation device is used to process the liquid-phase component, recover the organic solvent, and obtain the soluble plastic; the drying device is used to process the solid-phase component, separate the organic solvent, and obtain the insoluble plastic; the condensation device is used to condense the organic solvent separated from the drying device and return it to the organic solvent feeding device.

15. The system according to claim 14, wherein, The mixed plastic feeding device includes a feeding tank and a stirring paddle connected to a variable-frequency motor; wherein, a necking is provided at the lower end of the feeding tank, and the lower end of the stirring paddle is arranged above the necking.

16. The system according to claim 14, wherein, The organic solvent feeding device includes an organic solvent storage tank and a metering pump; the separation device is selected from one of an extraction device, a spray drying device, and a flash evaporation device; the drying device is an air-drying device, and the condensation device is a plate heat exchanger.

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