Pre-melting tank and spiral tube type reactor coupled waste plastic cracking system

Abstract

The invention relates to the technical field of waste plastic recycling, in particular to a pre-melting tank and spiral tube type reactor coupled waste plastic cracking system. The device comprises a material feeding and conveying part, a guiding part and a recycling part. Through raw material pretreatment and homogenization, the reactor efficiency bottleneck caused by poor thermal conductivity of solid plastic is fundamentally solved, the pre-melting tank is innovatively arranged, and waste plastic is firstly molten into a homogeneous liquid state by utilizing system waste heat, so that the subsequent small-caliber spiral tube type reactor can realize efficient and uniform heating and cracking, and the energy consumption is reduced. Therefore, on the premise that pretreatment energy consumption is not remarkably increased, high treatment capacity and high reaction efficiency are achieved at the same time, fluidization sealed conveying of the whole process is achieved at the same time, the common sealing problem of solid feeding is thoroughly avoided, the gas leakage risk is reduced, stable pressure and atmosphere in the system are kept, and the system is suitable for large-scale industrial production. And better conditions are created for continuous, stable and safe cracking reaction.

Description

Technical Field

[0001] This invention relates to the field of waste plastic recycling technology, and more particularly to a waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor. Background Technology

[0002] Plastics, with their low cost, ease of molding, and diverse properties, have long been widely used in packaging, transportation, electronics, construction, and other fields. However, the large number of disposable or short-life plastic products has led to a surge in waste, making their resource utilization an urgent need for developing a circular economy and protecting the environment. Pyrolysis (cracking) technology, which converts waste plastics into liquid hydrocarbons, carbon slag, and combustible gases at high temperatures under anaerobic or low-oxygen conditions, is considered one of the effective ways to achieve high-value-added conversion.

[0003] Nevertheless, the physical properties of plastics (such as low density, poor thermal conductivity, high viscosity after melting, and easy expansion and adhesion to the reactor walls) pose significant challenges to continuous and large-scale pyrolysis engineering. These challenges include difficulties in continuous and stable feeding, easy adhesion and coking of molten material to the reactor walls, slow heating, uneven temperature distribution within the reactor, and low product separation efficiency. These problems severely restrict the industrial scale-up and economical operation of pyrolysis technology.

[0004] While some exploration has been conducted with existing technologies, significant limitations still exist:

[0005] Although the rotary pyrolysis system proposed in CN114989846A can achieve continuous processing, it is difficult to overcome the heat and mass transfer resistance caused by the high viscosity of molten plastic, resulting in limited improvement in product selectivity and yield.

[0006] CN102260515A relates to a batch-type or fire-tube pyrolysis device that is prone to problems such as molten plastic sticking to the wall, low heat transfer efficiency, local overheating and coking. Moreover, it requires frequent shutdowns for cleaning during industrial operation, which affects the continuity and economy of the system.

[0007] CN117660040A uses a combination of fixed bed and screw feed, but high-viscosity materials are prone to sticking to the wall and bridging during conveying; the fixed bed has slow heat transfer, and after scale-up, it is easy to have insufficient central reaction and overheating at the edge.

[0008] In summary, existing waste plastic pyrolysis technologies still have significant shortcomings in terms of continuous and stable feeding, efficient and uniform heat transfer, system sealing, and long-term operational stability. In particular, there is a lack of systematic solutions that can simultaneously improve the pyrolysis reaction rate and system sealing. To address this, we propose a waste plastic pyrolysis system that couples a pre-melting tank with a spiral tube reactor. Summary of the Invention

[0009] The purpose of this invention is to provide a waste plastic pyrolysis system that couples a pre-melting tank with a spiral tube reactor to solve the problems mentioned in the background art.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor includes a feeding and conveying section, a guiding section, and a recycling section. The feeding and conveying section is connected to the recycling section through the guiding section. The feeding and conveying section includes a feeding hopper, a screw feeder, and a pre-melting tank. The screw feeder is fixed to the bottom of the feeding hopper, and the pre-melting tank is fixed to the output end of the screw feeder.

[0012] Preferably, the guiding section includes a primary orifice plate, a vent cap, a gas supply pipe, a secondary orifice plate, a screw pump, and a spiral reactor. The primary orifice plate is provided on the upper part of the inner side of the pre-melting tank, and vent caps are provided on both sides of the primary orifice plate. A gas supply pipe is provided below the primary orifice plate. The secondary orifice plate is provided on the inner side of the pre-melting tank and below the gas supply pipe. Multiple screw pumps are connected to the bottom of the pre-melting tank, and the output ends of the screw pumps are all connected to the spiral reactor.

[0013] Preferably, a bracket is fixed to the top of the gas pipeline, an inclined partition is fixed to the top of the bracket, and exhaust holes are provided on both sides of the bottom of the gas pipeline.

[0014] Preferably, the reuse section includes a cyclone separator, a carbon slag tank, a condenser, an oil storage tank, a first induced draft fan, and a combustion chamber. The output ends of the plurality of spiral tube reactors are connected to a cyclone separator. The solid discharge end of the cyclone separator is connected to the carbon slag tank. The gas discharge end of the cyclone separator is connected to the condenser. The condensate outlet of the condenser is connected to the oil storage tank. The gas outlet of the condenser is connected to the combustion chamber through the first induced draft fan. The flue gas outlet of the combustion chamber is connected to the input end of the spiral tube reactor.

[0015] Preferably, the reuse section further includes a second induced draft fan, an air preheater, an exhaust gas treatment device, a first blower, and a fourth induced draft fan. Part of the flue gas inside the spiral tube reactor is transported to the pre-melting tank by the second induced draft fan, and another part of the flue gas inside the spiral tube reactor is transported to the air preheater by the third induced draft fan to preheat the air in the air preheater transported by the first blower. The exhaust port of the pre-melting tank is returned to the combustion chamber by the fourth induced draft fan.

[0016] Preferably, an auxiliary mechanism is provided on one side of the feed hopper. The auxiliary mechanism includes an equipment frame, a crusher, and a temporary storage bin. The equipment frame is mounted on one side of the feed hopper, the crusher is fixed on the top of the equipment frame, and the temporary storage bin is fixed at the output end of the crusher.

[0017] Preferably, a quantitative feeding mechanism is installed between the temporary storage bin and the feeding bin. The quantitative feeding mechanism includes a rectangular frame, a drive motor, a half-circular gear, a drive gear, a positioning shaft, a Y-shaped frame, a fixing plate, a sleeve, a first disc, and a mating assembly. A rectangular frame is fixed to one end of the bottom of the equipment frame. A drive motor is fixed to the bottom of the inner side of the rectangular frame. A half-circular gear is fixed to the output end of the drive motor. The outer side of the half-circular gear is composed of a half-arc surface and a half-gear surface. A drive gear is meshed with one side of the gear surface. A positioning shaft is fixed to the inner side of the drive gear. The positioning shaft is rotatably connected to the rectangular frame. A Y-shaped frame is fixed to one side of the equipment frame. A fixing plate is installed on the top of the Y-shaped frame. A sleeve is slidably connected to the outer side of the positioning shaft. A first disc is fixed to the outer side of the first disc. A mating assembly is installed between the first disc and the Y-shaped frame.

[0018] Preferably, the mating assembly includes a second disc, a first feeding cylinder, a second feeding cylinder, a sealing cap, a magnet, an extension handle, a cylindrical protrusion, a T-shaped bracket, a cam ring, and a semi-circular arc sleeve. The top of the positioning shaft is fixed with the second disc, and the bottom of the temporary storage bin slides in contact with the second disc. The inner sides of both ends of the second disc are fixed with the first feeding cylinder. The bottom inner diameter of the temporary storage bin is the same as the inner diameter of the first feeding cylinder. The inner sides of both ends of the first disc are fixed with the second feeding cylinder corresponding to the position of the first feeding cylinder. The inner sides of the first and second feeding cylinders are slidably connected. The second feeding cylinders correspond to the positions of the feeding bins. A... Each side is rotatably connected to a sealing cap. A magnet is fixed to one end of each sealing cap, and an extension handle is fixed to the other end of each sealing cap. A cylindrical protrusion is fixed to the top of each extension handle. A T-shaped bracket is fixed to the top of one end of the fixing plate. A cam ring is fixed to the outer side of the top of the T-shaped bracket. The cam ring and the sleeve are in clearance fit, and the center of the cam ring coincides with the center of the sleeve. The bottom of the cam ring is composed of a smooth surface and an arc-shaped concave surface. The cylindrical protrusions slide in contact with the smooth surface and the arc-shaped concave surface. A collar is fixed to the bottom of the outer side of the first disc. A semi-circular arc sleeve is fixed to one end of the fixing plate. The semi-circular arc sleeve is rotatably connected to the inner side of the collar.

[0019] Preferably, the mating assembly further includes a rack, a self-locking motor, and a force-applying gear. The self-locking motor is fixed to the inner side of the Y-shaped frame, and the force-applying gear is fixed to the output end of the self-locking motor. The rack is meshed with one side of the force-applying gear, and the rack is slidably connected to the Y-shaped frame. The top of the rack is fixed to the fixing plate.

[0020] It is clear without a doubt that the technical solution described above in this application can solve the technical problem that this application aims to address.

[0021] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects:

[0022] 1. This invention fundamentally solves the reactor efficiency bottleneck caused by the poor thermal conductivity of solid plastics through raw material pretreatment and homogenization. Traditional spiral tube and rotary kiln reactors use external indirect heating. When directly processing solid plastics, if a larger throughput is desired, the reactor diameter needs to be increased. However, the poor thermal conductivity of plastics easily leads to insufficient heating of the material in the central area, incomplete reaction, or extremely slow reaction rate. If a small-diameter reactor is used to ensure heat transfer, the raw material needs to be crushed to a very fine size, resulting in a sharp increase in pretreatment energy consumption. This invention innovatively sets up a pre-melting tank, using the system's waste heat to melt the waste plastic into a homogeneous liquid state. Molten plastic has good fluidity and high heat transfer efficiency, enabling the subsequent small-diameter spiral tube reactor to achieve efficient and uniform heating and pyrolysis. Thus, without significantly increasing pretreatment energy consumption, both high throughput and high reaction efficiency are achieved.

[0023] 2. This invention achieves fully fluidized, sealed transport throughout the entire process, significantly improving system sealing and operational stability. Traditional spiral tube and rotary kiln reactors face sealing challenges when processing waste plastic feed, easily leading to air infiltration or pyrolysis gas leakage, affecting safety and product quality. This solution uses a pre-melting tank to convert the material into a molten state and then quantitatively and controllably transports it to subsequent reactors via a screw pump. This fully enclosed fluidized transport method not only completely avoids the common sealing problems of solid feed and reduces the risk of gas leakage, but also helps maintain stable pressure and atmosphere within the system, creating better conditions for continuous, stable, and safe pyrolysis reactions.

[0024] 3. Through the structural design of the auxiliary mechanism and the quantitative feeding mechanism, the present invention can pre-treat waste plastics before feeding, prevent the screw feeder from getting stuck and blocked, and at the same time enable quantitative feeding, which helps to improve processing efficiency. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the system architecture of the present invention;

[0027] Figure 2 This is a left view of the gas delivery pipe of the present invention;

[0028] Figure 3 This is a schematic diagram of the connection structure between the rectangular frame and the drive motor of the present invention;

[0029] Figure 4 This is a schematic diagram of the connection structure between the Y-shaped frame and the rack of the present invention;

[0030] Figure 5 This is a schematic diagram of the connection structure between the semi-circular gear and the drive motor of the present invention;

[0031] Figure 6 This is a schematic diagram of the connection structure between the second disk and the first feeding cylinder of the present invention;

[0032] Figure 7 This is a schematic diagram of the connection structure between the cylindrical protrusion and the cam ring of the present invention.

[0033] The attached diagram lists the components represented by each number as follows:

[0034] In the diagram: 1. Feed hopper; 2. Screw feeder; 3. Pre-melting tank; 4. Primary orifice plate; 5. Vent cap; 6. Gas delivery pipe; 61. Inclined baffle; 62. Support; 63. Exhaust port; 7. Secondary orifice plate; 8. Screw pump; 9. Spiral tube reactor; 10. Cyclone separator; 11. Carbon slag tank; 12. Condenser; 13. Oil storage tank; 14. First induced draft fan; 15. Combustion chamber; 16. Second induced draft fan; 17. Third induced draft fan; 18. Air preheater; 19. Exhaust gas treatment device; 20. First blower; 21. Fourth induced draft fan; 22. 23. Equipment frame; 24. Crusher; 25. Temporary storage bin; 26. Rectangular frame; 27. Drive motor; 28. Half-circumferential gear; 29. ​​Drive gear; 30. Positioning shaft; 31. Y-shaped frame; 32. Fixing plate; 33. Sleeve; 34. First disc; 35. Second disc; 36. First feeding cylinder; 37. Second feeding cylinder; 38. Sealing cover; 39. Magnet; 40. Extension handle; 41. Cylindrical protrusion; 42. T-shaped bracket; 43. Cam ring; 44. Collar; 45. Half-circumferential arc sleeve; 46. Rack; 47. Self-locking motor; 48. Force-applying gear. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] Example 1

[0037] Reference Figure 1-2A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor includes a feeding and conveying section, a guiding section and a recycling section. The feeding and conveying section is connected to the recycling section through the guiding section. The feeding and conveying section includes a feeding hopper 1, a screw feeder 2 and a pre-melting tank 3. The screw feeder 2 is fixed at the bottom of the feeding hopper 1 and the pre-melting tank 3 is fixed at the output end of the screw feeder 2.

[0038] The guiding section includes a primary orifice plate 4, a vent 5, a gas supply pipe 6, a secondary orifice plate 7, a screw pump 8, and a spiral reactor 9. The primary orifice plate 4 is installed on the upper part of the inner side of the pre-melting tank 3. Vents 5 are installed on both sides of the primary orifice plate 4. The gas supply pipe 6 is installed below the primary orifice plate 4. The secondary orifice plate 7 is installed on the inner side of the pre-melting tank 3 and below the gas supply pipe 6. Multiple screw pumps 8 are connected to the bottom of the pre-melting tank 3. The output ends of the screw pumps 8 are all connected to the spiral reactor 9. Several holes are evenly distributed on the primary orifice plate 4 to achieve preliminary mechanical barrier, dispersion and discharge of incoming waste plastic, and flue gas circulation.

[0039] A bracket 62 is fixed to the top of the gas pipe 6, and an inclined baffle 61 is fixed to the top of the bracket 62. Exhaust holes 63 are provided on both sides of the bottom of the gas pipe 6. The inclined baffle 61 can effectively guide the molten plastic to flow in a set direction, avoid local accumulation, reduce the risk of overheating and coking, and ensure that the material falls smoothly into the secondary orifice plate 7.

[0040] The reuse section includes a cyclone separator 10, a carbon slag tank 11, a condenser 12, an oil storage tank 13, a first induced draft fan 14, and a combustion chamber 15. The output ends of multiple spiral tube reactors 9 are connected to a cyclone separator 10. The solid discharge end of the cyclone separator 10 is connected to the carbon slag tank 11. The gas discharge end of the cyclone separator 10 is connected to the condenser 12. The condensate outlet of the condenser 12 is connected to the oil storage tank 13. The gas outlet of the condenser 12 is connected to the combustion chamber 15 through the first induced draft fan 14. The flue gas outlet of the combustion chamber 15 is connected to the input end of the spiral tube reactor 9. The reuse section also includes a second induced draft fan 16, an air preheater 18, an exhaust gas treatment device 19, a first blower 20, and a fourth induced draft fan 21. Part of the flue gas inside the spiral tube reactor 9 is transported to the pre-melting tank 3 by the second induced draft fan 16, and another part of the flue gas inside the spiral tube reactor 9 is transported to the air preheater 18 by the third induced draft fan 17 to preheat the air transported to the air preheater 18 by the first blower 20. The exhaust port of the pre-melting tank 3 is connected to the exhaust port of the fourth induced draft fan 21. 1. The gas is conveyed back to the combustion chamber 15. During the pyrolysis process, the molten plastic undergoes efficient thermal pyrolysis, generating pyrolysis gas, a mixture of liquid hydrocarbons and carbon slag. These products are first separated into solid and gas by a cyclone separator 10. The solid carbon slag is collected in the carbon slag tank 11, and the remaining gas-liquid mixture enters the carbon slag tank 11. After being cooled in stages, the condensable components are collected through the oil storage tank 13, while the non-condensable gases are conveyed to the combustion chamber 15 by the first induced draft fan 14 for use as fuel, thus completing the recycling process.

[0041] Example 2

[0042] Further optimizations to Example 1, specifically, such as... Figure 3-7 As shown, an auxiliary mechanism is provided on one side of the feed hopper 1. The auxiliary mechanism includes an equipment frame 22, a crusher 23, and a temporary storage bin 24. The equipment frame 22 is mounted on one side of the feed hopper 1. The crusher 23 is fixed on the top of the equipment frame 22. The temporary storage bin 24 is fixed at the output end of the crusher 23. By setting up the crusher 23, the recycled waste plastic can be coarsely crushed. This process can avoid the subsequent screw feeder 2 from getting stuck and blocked.

[0043] A quantitative feeding mechanism is installed between the temporary storage bin 24 and the feeding bin 1. The quantitative feeding mechanism includes a rectangular frame 25, a drive motor 26, a half-circular gear 27, a drive gear 28, a positioning shaft 29, a Y-shaped frame 30, a fixing plate 31, a sleeve 32, a first disc 33, and mating components. A rectangular frame 25 is fixed to one end of the bottom of the equipment frame 22. A drive motor 26 is fixed to the bottom inside the rectangular frame 25. A half-circular gear 27 is fixed to the output end of the drive motor 26. The outer side of the half-circular gear 27 is composed of a semi-arc surface and a semi-gear surface. One side of the gear surface meshes with the drive gear 28, while the arc surface does not contact the drive gear 28. A positioning shaft 29 is fixed to the inner side of wheel 28. The positioning shaft 29 is rotatably connected to rectangular frame 25. A Y-shaped frame 30 is fixed to one side of equipment frame 22. A fixing plate 31 is mounted on the top of Y-shaped frame 30. A sleeve 32 is slidably connected to the outer side of positioning shaft 29. A first disc 33 is fixed to the outer side of first disc 33. A mating component is assembled between first disc 33 and Y-shaped frame 30. The maximum outer diameter of the periphery of half-circular gear 27 is the same as the outer diameter of drive gear 28. Since the outer side of half-circular gear 27 is composed of half arc surface and half gear surface, when half-circular gear 27 rotates one revolution, the gear surface can mesh with drive gear 28 to rotate half revolution.

[0044] The assembly includes a second disc 34, a first feeding cylinder 35, a second feeding cylinder 36, a sealing cap 37, a magnet 38, an extension handle 39, a cylindrical protrusion 40, a T-shaped bracket 41, a cam ring 42, and a semi-circular arc sleeve 44. The top of the positioning shaft 29 is fixed to the second disc 34, and the bottom of the temporary storage bin 24 slides in contact with the second disc 34. The inner sides of both ends of the second disc 34 are fixed to the first feeding cylinder 35. The inner diameter of the bottom of the temporary storage bin 24 is the same as the inner diameter of the first feeding cylinder 35. When the crushed plastic falls from the temporary storage bin 24 into the first feeding cylinder 35, the second disc 34 rotates and engages with the bottom of the temporary storage bin 24 to generate a shearing force on the crushed plastic, facilitating the separation of the crushed plastic between the temporary storage bin 24 and the first feeding cylinder 35. In other embodiments... The bottom of the temporary storage bin 24 can be equipped with an electric baffle to measure the amount of material falling into the first feeding cylinder 35. The inner sides of both ends of the first disc 33 are fixed with second feeding cylinders 36 corresponding to the positions of the first feeding cylinder 35. The inner sides of the first feeding cylinder 35 and the second feeding cylinder 36 are slidably connected. The second feeding cylinders 36 are all corresponding to the positions of the feeding bin 1. A sealing cover 37 is rotatably connected to one side of the bottom of the second feeding cylinder 36. A magnet 38 is fixed to one end of the sealing cover 37. It can be understood that the first feeding cylinder 35 and the second feeding cylinder 36 are both made of iron alloy. One end of the sealing cover 37 can be magnetically connected to the second feeding cylinder 36 through the magnet 38, which can play an auxiliary role in sealing the second feeding cylinder 36.

[0045] The other end of the sealing cover 37 is fixed with an extension handle 39, and the top of the extension handle 39 is fixed with a cylindrical protrusion 40. A T-shaped bracket 41 is fixed to the top of one end of the fixing plate 31. A cam ring 42 is fixed to the outer side of the top of the T-shaped bracket 41. The cam ring 42 is in clearance fit with the sleeve 32, and the center of the cam ring 42 coincides with the center of the sleeve 32. The bottom of the cam ring 42 consists of a smooth surface and an arc-shaped concave surface. The cylindrical protrusions 40 slide in contact with both the smooth surface and the arc-shaped concave surface. The first disc... A collar 43 is fixed to the bottom of the outer side of the 33, and a semi-circular arc sleeve 44 is fixed to one end of the fixing plate 31. The semi-circular arc sleeve 44 is rotatably connected to the inner side of the collar 43. When material needs to be unloaded, in the initial state, one of the first feeding cylinders 35 corresponds to the bottom position of the temporary storage bin 24. At this time, the crushed plastic in the temporary storage bin 24 falls into the first feeding cylinder 35 and also into the second feeding cylinder 36, completing the temporary storage of materials. Then, the drive motor 26 is started, and the output of the drive motor 26 is controlled. After the end rotates one revolution, it stops. The gear surface meshes with the drive gear 28 to rotate, which in turn drives the positioning shaft 29 and the second disc 34 to rotate. This causes the first feeding cylinder 35 to drive the second feeding cylinder 36 to rotate synchronously. The second feeding cylinder 36 rotates to the top of the feeding hopper 1 and then stops. During this process, the cylindrical protrusion 40 is initially limited by the smooth surface. Then, when the second feeding cylinder 36 rotates to the top of the feeding hopper 1, the cylindrical protrusion 40 gradually contacts the arc-shaped concave surface. Under the action of gravity, the broken plastic in the second feeding cylinder 36 and the first feeding cylinder 35 presses down on the sealing cover 37, causing the magnet 38 to separate from the second feeding cylinder 36. At the same time, the sealing cover 37 rotates downward, so that the bottom of the second feeding cylinder 36 is no longer blocked. The plastic falls along the upper surface of the sealing cover 37 into the feeding hopper 1 below, completing the quantitative feeding process. This process can achieve quantitative feeding and quantitative control of the broken plastic entering the feeding hopper 1.

[0046] The cooperating components also include a rack 45, a self-locking motor 46, and a force-applying gear 47. The self-locking motor 46 is fixed to the inner side of the Y-shaped frame 30, and the force-applying gear 47 is fixed to the output end of the self-locking motor 46. The rack 45 is meshed with one side of the force-applying gear 47. The rack 45 is slidably connected to the Y-shaped frame 30, and the top of the rack 45 is fixed to the fixed plate 31. By starting the self-locking motor 46, the output end of the self-locking motor 46 drives the force-applying gear 47 to mesh with the rack 45 and move it up or down. This can drive the fixed plate 31 to move vertically, so that the fixed plate 31 can drive the collar 43 and the sleeve 32 to adjust their vertical positions through the semi-circular arc sleeve 44. This allows the relative distance between the second feeding cylinder 36 and the first feeding cylinder 35 to be adjusted, thereby adjusting the total capacity of the first feeding cylinder 35 and the second feeding cylinder 36. In other embodiments, capacity scales are provided on the outer sides of the second feeding cylinder 36 and the first feeding cylinder 35 to facilitate precise control of the quantitative feeding value.

[0047] In summary:

[0048] This invention addresses the technical problem that existing waste plastic pyrolysis technologies still have significant shortcomings in terms of continuous and stable feeding, efficient and uniform heat transfer, system sealing, and long-term operational stability, especially lacking a systematic solution that can simultaneously improve the pyrolysis reaction rate and system sealing. The invention employs the technical solutions described in the above embodiments. Furthermore, the implementation process of the above technical solutions is as follows:

[0049] Waste plastic is first fed into the feed hopper 1 and continuously and stably conveyed to the pre-melting tank 3 by the screw feeder 2. When the high-temperature flue gas comes into direct contact with the plastic on the primary perforated plate 4, the plastic undergoes a melting change and enters the lower area through the primary perforated plate 4. To prevent the molten plastic from locally accumulating at the holes of the primary perforated plate 4, which would obstruct the upward flow of high-temperature flue gas and increase pressure in the lower part of the primary perforated plate 4, wind caps 5 are installed on both sides of the primary perforated plate 4. When the pressure is too high, the high-temperature flue gas can enter from the lower part of the wind caps 5 and escape from the small holes in the middle and upper parts, thereby maintaining the pressure stability inside the pre-melting tank 3.

[0050] Below the primary orifice plate 4, a gas delivery pipe 6 is installed. High-temperature flue gas from the second induced draft fan 16 enters the pre-melting tank 3 through this pipe, directly exchanging heat with the waste plastic and rapidly transforming it from a solid to a molten state. The gas delivery pipe 6 has an exhaust port 63 on its lower side and an inclined baffle 61 on its upper side, the two being welded together by a bracket 62. The inclined baffle 61 effectively guides the molten plastic to flow in a set direction, avoiding local accumulation, reducing the risk of overheating and coking, while ensuring the material smoothly falls onto the secondary orifice plate 7.

[0051] Molten waste plastic falls under gravity to the secondary orifice plate 7, and is then quantitatively transported to the helical tube reactor 9 by the screw pump 8. This helical tube reactor 9 employs external heating, with high-temperature flue gas flowing externally and molten plastic flowing internally in opposite directions. The helical tube reactor 9 is preferably characterized by a small diameter and long length. The molten plastic forms a thin-layer plug flow inside the tube, allowing the external heat source to rapidly and uniformly penetrate the tube wall to heat the material, achieving "small reaction channels, but complete reactions everywhere," completely eliminating the "cold core" phenomenon in the center of large-diameter reactors. Increased throughput is achieved by adding parallel reaction tubes or extending the pipeline, rather than increasing the diameter, thus overcoming heat transfer limitations.

[0052] Under the continuous high-temperature flue gas, the molten plastic undergoes efficient thermal cracking, generating cracked gas, a mixture of liquid hydrocarbons, and carbon slag. The products are first separated into gas and solid phases by a cyclone separator 10. The solid carbon slag is collected in a carbon slag tank 11, while the remaining gas-liquid mixture enters a condenser 12. After staged cooling, the condensable components are collected in an oil storage tank 13, while the non-condensable gases are transported to the combustion chamber 15 by the first induced draft fan 14 for use as fuel.

[0053] The high-temperature flue gas generated in combustion chamber 15 is directly fed into spiral tube reactor 9 to provide a heat source for the pyrolysis reaction. Part of the heat-exchanged flue gas is sent back to pre-melting tank 3 by the second induced draft fan 16 for pre-melting utilization; the other part is sent to air preheater 18 by the third induced draft fan 17 to preheat the air supplied by the first blower 20 before entering combustion chamber 15 to improve combustion efficiency. The flue gas after heat exchange in air preheater 18 is purified by exhaust gas treatment device 19 and discharged in compliance with standards. Furthermore, the low-temperature flue gas after heat exchange in the upper part of pre-melting tank 3 is returned to combustion chamber 15 by the fourth induced draft fan 21, reducing nitrogen oxide emissions through flue gas recirculation.

[0054] With the above-mentioned settings, this application will certainly solve the above-mentioned technical problems, and at the same time achieve the following technical effects:

[0055] 1. This invention fundamentally solves the reactor efficiency bottleneck caused by the poor thermal conductivity of solid plastics through raw material pretreatment and homogenization. Traditional spiral tube and rotary kiln reactors use external indirect heating. When directly processing solid plastics, if a larger throughput is desired, the reactor diameter needs to be increased. However, the poor thermal conductivity of plastics easily leads to insufficient heating of the material in the central area, incomplete reaction, or extremely slow reaction rate. If a small-diameter reactor is used to ensure heat transfer, the raw material needs to be crushed to a very fine size, resulting in a sharp increase in pretreatment energy consumption. This invention innovatively sets up a pre-melting tank 3, which uses the system's waste heat to melt the waste plastic into a homogeneous liquid state. The molten plastic has good fluidity and high heat transfer efficiency, enabling the subsequent small-diameter spiral tube reactor 9 to achieve efficient and uniform heating and pyrolysis. Thus, without significantly increasing pretreatment energy consumption, both high throughput and high reaction efficiency are achieved.

[0056] 2. This invention achieves fully fluidized, sealed transport throughout the entire process, significantly improving system sealing and operational stability. Traditional spiral tube and rotary kiln reactors face sealing challenges when processing waste plastic feed, easily leading to air infiltration or pyrolysis gas leakage, affecting safety and product quality. This solution uses a pre-melting tank to convert the material into a molten state and then quantitatively and controllably transports it to subsequent reactors via a screw pump. This fully enclosed fluidized transport method not only completely avoids the common sealing problems of solid feed and reduces the risk of gas leakage, but also helps maintain stable pressure and atmosphere within the system, creating better conditions for continuous, stable, and safe pyrolysis reactions.

[0057] 3. Through the structural design of the auxiliary mechanism and the quantitative feeding mechanism, the present invention can pre-treat waste plastics before feeding, prevent the screw feeder 2 from getting stuck and blocked, and at the same time enable quantitative feeding, which helps to improve processing efficiency.

[0058] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor, characterized in that, It includes a feeding and conveying section, a guiding section and a recycling section. The feeding and conveying section is connected to the recycling section through the guiding section. The feeding and conveying section includes a feeding bin (1), a screw feeder (2) and a pre-melting tank (3). The bottom of the feeding bin (1) is fixed with the screw feeder (2), and the output end of the screw feeder (2) is fixed with the pre-melting tank (3).

2. The waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 1, characterized in that, The guiding section includes a primary orifice plate (4), a wind cap (5), a gas supply pipe (6), a secondary orifice plate (7), a screw pump (8), and a spiral reactor (9). The upper part of the inner side of the pre-melting tank (3) is provided with a primary orifice plate (4). Wind caps (5) are provided on both sides of the primary orifice plate (4). A gas supply pipe (6) is provided below the primary orifice plate (4). A secondary orifice plate (7) is provided inside the pre-melting tank (3) and below the gas supply pipe (6). Multiple screw pumps (8) are connected to the bottom of the pre-melting tank (3). The output ends of the screw pumps (8) are all connected to the spiral reactor (9).

3. The waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 2, characterized in that, The top of the gas pipe (6) is fixed with a bracket (62), the top of the bracket (62) is fixed with an inclined partition (61), and exhaust holes (63) are provided on both sides of the bottom of the gas pipe (6).

4. The waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 2, characterized in that, The reuse section includes a cyclone separator (10), a carbon slag tank (11), a condenser (12), an oil storage tank (13), a first induced draft fan (14), and a combustion chamber (15). The output ends of the plurality of spiral tube reactors (9) are connected to a cyclone separator (10). The solid discharge end of the cyclone separator (10) is connected to the carbon slag tank (11). The gas discharge end of the cyclone separator (10) is connected to the condenser (12). The condensate outlet of the condenser (12) is connected to the oil storage tank (13). The gas outlet of the condenser (12) is connected to the combustion chamber (15) through the first induced draft fan (14). The flue gas outlet of the combustion chamber (15) is connected to the input end of the spiral tube reactor (9).

5. The waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 4, characterized in that, The reuse section also includes a second induced draft fan (16), an air preheater (18), a tail gas treatment device (19), a first blower (20), and a fourth induced draft fan (21). Part of the flue gas inside the spiral tube reactor (9) is transported to the pre-melting tank (3) by the second induced draft fan (16), and another part of the flue gas inside the spiral tube reactor (9) is transported to the air preheater (18) by the third induced draft fan (17) to preheat the air in the air preheater (18) transported by the first blower (20). The exhaust port of the pre-melting tank (3) is transported back to the combustion chamber (15) by the fourth induced draft fan (21).

6. The waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 1, characterized in that, An auxiliary mechanism is provided on one side of the feed hopper (1). The auxiliary mechanism includes an equipment frame (22), a crusher (23), and a temporary storage bin (24). The equipment frame (22) is mounted on one side of the feed hopper (1). The crusher (23) is fixed on the top of the equipment frame (22). The temporary storage bin (24) is fixed at the output end of the crusher (23).

7. A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 6, characterized in that, A quantitative feeding mechanism is assembled between the temporary storage bin (24) and the feeding bin (1). The quantitative feeding mechanism includes a rectangular frame (25), a drive motor (26), a half-circular gear (27), a drive gear (28), a positioning shaft (29), a Y-shaped frame (30), a fixing plate (31), a sleeve (32), a first disc (33), and a mating assembly. A rectangular frame (25) is fixed to one end of the bottom of the equipment frame (22). A drive motor (26) is fixed to the bottom inside the rectangular frame (25). A half-circular gear (27) is fixed to the output end of the drive motor (26). The outer side of the half-circular gear (27) is... The side is composed of a half-arc surface and a half-gear surface. A drive gear (28) is meshed with one side of the gear surface. A positioning shaft (29) is fixed on the inner side of the drive gear (28). The positioning shaft (29) is rotatably connected to the rectangular frame (25). A Y-shaped frame (30) is fixed on one side of the equipment frame (22). A fixing plate (31) is mounted on the top of the Y-shaped frame (30). A sleeve (32) is slidably connected to the outer side of the positioning shaft (29). A first disc (33) is fixed on the outer side of the first disc (33). A mating component is assembled between the first disc (33) and the Y-shaped frame (30).

8. A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 7, characterized in that, The mating components include a second disc (34), a first feeding cylinder (35), a second feeding cylinder (36), a sealing cap (37), a magnet (38), an extension handle (39), a cylindrical protrusion (40), a T-shaped bracket (41), a cam ring (42), and a semi-circular arc sleeve (44). The top of the positioning shaft (29) is fixed with the second disc (34), and the bottom of the temporary storage chamber (24) is in sliding contact with the second disc (34). A first feeding cylinder (35) is fixed to the inner side of both ends. The bottom inner diameter of the temporary storage bin (24) is the same as the inner diameter of the first feeding cylinder (35). A second feeding cylinder (36) corresponding to the position of the first feeding cylinder (35) is fixed to the inner side of both ends of the first disc (33). The first feeding cylinder (35) and the second feeding cylinder (36) are slidably connected inside each other. The second feeding cylinder (36) is corresponding to the position of the feeding bin (1). The bottom of the second feeding cylinder (36) A sealing cap (37) is rotatably connected to one side of the part. A magnet (38) is fixed to one end of each sealing cap (37). An extension handle (39) is fixed to the other end of each sealing cap (37). A cylindrical protrusion (40) is fixed to the top of each extension handle (39). A T-shaped bracket (41) is fixed to the top of one end of the fixing plate (31). A cam ring (42) is fixed to the outer side of the top of the T-shaped bracket (41). The cam ring (42) and the sleeve ( 32) The cam ring (42) is in clearance fit and the center of the cam ring (42) coincides with the center of the sleeve (32). The bottom of the cam ring (42) is composed of a smooth surface and an arc-shaped concave surface. The cylindrical protrusions (40) are in sliding contact with the smooth surface and the arc-shaped concave surface. A collar (43) is fixed at the bottom of the outer side of the first disc (33). A semi-circular arc sleeve (44) is fixed at one end of the fixing plate (31). The semi-circular arc sleeve (44) is rotatably connected to the inner side of the collar (43).

9. A waste plastic pyrolysis system coupled with a pre-melting tank and a spiral tube reactor according to claim 8, characterized in that, The mating assembly also includes a rack (45), a self-locking motor (46), and a force-applying gear (47). The self-locking motor (46) is fixed to the inner side of the Y-shaped frame (30), and the force-applying gear (47) is fixed to the output end of the self-locking motor (46). The rack (45) is meshed with one side of the force-applying gear (47). The rack (45) is slidably connected to the Y-shaped frame (30), and the top of the rack (45) is fixed to the fixing plate (31).

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