Two-stage waste plastic pyrolysis device

Abstract

The utility model discloses a two -segment type waste plastics thermal cracking device, including one -level pre -cracking unit, two -level depth cracking unit and afterheat treatment unit, one -level pre -cracking unit's export end is linked with two -level depth cracking unit's import end, and the inlet of afterheat treatment unit is connected with the top of two -level depth cracking unit, and the export of afterheat treatment unit is connected external condensing system, and one -level pre -cracking unit includes pre -cracking cylinder, installs electromagnetic heating cover on the outer wall of pre -cracking cylinder, and the seal cover and feed hopper of detachable installation in pre -cracking cylinder one end, install servo motor and one end fixed connection on servo motor output end on the seal cover on spiral feeding rod, and the outer wall of spiral feeding rod is fixedly connected with spiral blade, and the other end of pre -cracking cylinder is linked with two -level depth cracking unit, and is equipped with the smoke pipe on the outer wall of pre -cracking cylinder another end.

Description

Technical Field

[0001] This utility model relates to the field of waste plastic treatment technology, specifically a two-stage waste plastic pyrolysis device. Background Technology

[0002] Single-stage waste plastic pyrolysis is a waste plastic resource utilization technology. By heating waste plastics to high temperatures under anaerobic or oxygen-deficient conditions, its macromolecular chains are broken down into smaller molecule compounds. This process can convert mixed waste plastics into valuable products such as fuel oil, combustible gas, and carbon black, achieving the reduction, harmlessness, and resource utilization of waste plastics.

[0003] In existing technologies, traditional single-stage pyrolysis furnaces have defects. The temperature uniformity inside the furnace is poor, and large pieces of plastic are prone to an abnormal situation of "external charring and internal carbonization" during the pyrolysis process. That is, the outer layer is over-pyrolyzed and carbonized, while the inner layer is not fully pyrolyzed. This not only leads to a significant reduction in the recovery rate of pyrolysis oil, but also results in a large amount of unpyrolyzed plastic remaining in the carbon black, which seriously affects the product quality. At the same time, the high-temperature oil and gas (500-600℃) enters the condensation system directly without any heat recovery treatment, resulting in a large amount of sensible heat being wasted, leading to extremely poor economic efficiency of the entire pyrolysis process. Utility Model Content

[0004] The purpose of this invention is to provide a two-stage waste plastic pyrolysis device to solve the problems mentioned in the background art, such as low pyrolysis oil recovery rate and carbon black containing unpyrolyzed plastic affecting quality.

[0005] To achieve the above objectives, this utility model provides the following technical solution: It includes a primary pre-pyrolysis unit, a secondary deep pyrolysis unit, and a waste heat treatment unit. The outlet end of the primary pre-pyrolysis unit is connected to the inlet end of the secondary deep pyrolysis unit. The inlet end of the waste heat treatment unit is connected to the top of the secondary deep pyrolysis unit. The outlet end of the waste heat treatment unit is connected to an external condensation system. The primary pre-pyrolysis unit includes a pre-pyrolysis cylinder, an electromagnetic heating jacket installed on the outer wall of the pre-pyrolysis cylinder, a detachable sealing cover and a feed hopper installed at one end of the pre-pyrolysis cylinder, a servo motor installed on the sealing cover, and a spiral conveyor rod with one end fixedly connected to the output end of the servo motor. The outer wall of the screw conveyor is fixed with screw blades. The other end of the pre-pyrolysis cylinder is connected to the secondary deep pyrolysis unit. The outer wall of the other end of the pre-pyrolysis cylinder is provided with a flue pipe. The secondary deep pyrolysis unit includes a heating box fixed to the pre-pyrolysis cylinder, a deep pyrolysis cylinder fixed to the inner wall of the heating box, a heat-insulating bearing base fixed to the lower end of the heating box, and an inspection door movably installed on the outer wall of the heating box. The outer wall of the heating box is also provided with a door for adding fuel. The outer wall of the deep pyrolysis cylinder is fixed with an oil and gas pipe. The oil and gas pipe is connected to the waste heat treatment unit through a rigid branch pipe. The oil and gas from the thermal pyrolysis of waste plastics flow from the deep pyrolysis cylinder into the waste heat treatment unit through the oil and gas pipe.

[0006] According to the preferred embodiment of this technical solution, the waste heat treatment unit includes a box body set on the top of the heating box, an inlet and an outlet water outlet opened on the upper part of the box body, and a serpentine heat exchange tube fixed in the box body. The inlet water outlet is connected to an inlet water pipe connected to an external cold water device, and the outlet water outlet is connected to an outlet water pipe connected to an external water storage tank. One end of the heat exchange tube is connected to the pipe opening of a rigid branch pipe, and the other end of the heat exchange tube is connected to an external condensation system. Cold water is heated in the box body through the inlet water pipe and then flows to the outlet water pipe.

[0007] In a preferred embodiment of this technical solution, a rotary motor is installed on the outer wall of the heating box, and a rotating shaft extending into the heating box is fixedly connected to the output end of the rotary motor. An agitator is fixedly connected to the outer wall of the rotating shaft, and a scraper is detachably connected to the end of the agitator.

[0008] Based on the preferred embodiment of this technical solution, the stirring paddle is provided with an insertion hole, and the surface of the scraper plate is fixed with an insertion rod that matches the insertion hole, and the insertion rod can be inserted and installed in the insertion hole.

[0009] In the preferred embodiment of this technical solution, a limiting groove is formed on the inner wall of the insertion hole, and a convex rail is fixedly connected to the insertion rod, with the convex rail slidably connected to the limiting groove.

[0010] In the preferred embodiment of this technical solution, a permanent magnet is embedded in the contact surface between the insertion rod and the insertion hole, and the insertion rod and the insertion hole are magnetically connected.

[0011] In the preferred embodiment of this technical solution, a baffle plate is nested in the serpentine path of the heat exchange tube, and an array of vent holes is formed on the surface of the baffle plate.

[0012] Based on the preferred embodiment of this technical solution, the edge of the scraper plate is provided with a detachable wear-resistant plate, which is connected to the surface of the scraper plate through a threaded structure.

[0013] Compared with the prior art, the beneficial effects of this utility model are: 1. By adopting a two-stage pyrolysis design (pre-pyrolysis + deep pyrolysis), the efficiency of waste plastic pyrolysis is improved. The electromagnetic heating jacket realizes uniform heating of the pre-pyrolysis cylinder and avoids local overheating. The combination of the stirring paddle and the detachable scraper ensures that the material in the deep pyrolysis cylinder is heated evenly, preventing plastic from sticking to the wall and carbonizing, and reducing the generation of residue. 2. The waste heat treatment unit exchanges heat with high-temperature oil and gas through a serpentine heat exchange tube, which can raise the water temperature to medium and high temperature for external use, maximize the recovery of waste heat from high-temperature oil and gas, and reduce energy consumption. 3. The serpentine heat exchange tubes are nested with baffles, which create turbulence through the vent holes, prolonging the residence time of oil and gas and improving heat exchange efficiency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the first structure of one embodiment of the two-stage waste plastic pyrolysis device of this utility model; Figure 2 This is a second structural schematic diagram of one embodiment of the two-stage waste plastic pyrolysis device of this utility model; Figure 3 This is a front sectional view of the present invention; Figure 4 This is a schematic diagram of the structure of the stirring paddle of this utility model; Figure 5 This is a schematic diagram of the structure of the heat exchange tube of this utility model; Figure 6 This is a schematic diagram of the structure of the insertion hole and insertion rod of this utility model; Figure 7 This is a schematic diagram of the flow-blocking plate of this utility model.

[0015] In the diagram: 1. Pre-pyrolysis cylinder; 2. Electromagnetic heating jacket; 3. Sealing cover; 4. Servo motor; 5. Spiral conveyor rod; 6. Spiral blade; 7. Feed hopper; 8. Exhaust pipe; 9. Heating box; 10. Deep pyrolysis cylinder; 11. Support base; 12. Inspection door; 13. Bin door; 14. Oil and gas pipe; 15. Rigid branch pipe; 16. Box body; 17. Water inlet; 18. Water outlet; 19. Heat exchange pipe; 20. Water inlet pipe; 21. Water outlet pipe; 22. Rotary motor; 23. Rotating shaft; 24. Agitator; 25. Scraper; 26. Insertion hole; 27. Insertion rod; 28. Limiting groove; 29. ​​Convex rail; 30. Baffle plate; 31. Ventilation hole array. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] Please see Figures 1-7This utility model provides an embodiment comprising a primary pre-pyrolysis unit, a secondary deep pyrolysis unit, and a waste heat treatment unit. The outlet end of the primary pre-pyrolysis unit is connected to the inlet end of the secondary deep pyrolysis unit, the inlet end of the waste heat treatment unit is connected to the top of the secondary deep pyrolysis unit, and the outlet end of the waste heat treatment unit is connected to an external condensation system. The primary pre-pyrolysis unit includes a pre-pyrolysis cylinder 1, an electromagnetic heating jacket 2 mounted on the outer wall of the pre-pyrolysis cylinder 1, a detachable sealing cover 3 and a feed hopper 7 mounted on one end of the pre-pyrolysis cylinder 1, a servo motor 4 mounted on the sealing cover 3, and a spiral conveying rod 5 fixedly connected at one end to the output end of the servo motor 4. Spiral blades 6 are fixedly attached to the outer wall of the spiral conveying rod 5. The other end of the pre-pyrolysis cylinder 1 is connected to the secondary deep pyrolysis unit. A flue pipe 8 is provided on the outer wall of the other end of the pre-pyrolysis cylinder 1. The secondary deep pyrolysis unit includes a heating box 9 fixedly connected to the pre-pyrolysis cylinder 1, a deep pyrolysis cylinder 10 fixedly connected to the inner wall of the heating box 9, a heat-insulating bearing base 11 fixedly connected to the lower end of the heating box 9, and an inspection door 12 movably installed on the outer wall of the heating box 9. The outer wall of the heating box 9 is also provided with a fuel filling door 13. An oil and gas pipe 14 is fixedly connected to the outer wall of the deep pyrolysis cylinder 10. The oil and gas pipe 14 is connected to the waste heat treatment unit through a rigid branch pipe 15. The oil and gas from the thermal pyrolysis of waste plastics flow from the deep pyrolysis cylinder 10 into the waste heat treatment unit through the oil and gas pipe 14. The pre-pyrolysis cylinder 1 is a horizontally placed cylindrical reaction chamber, serving as a container for the pre-pyrolysis of waste plastics. An electromagnetic heating jacket 2 is fitted on the outer wall of the pre-pyrolysis cylinder 1, and is powered by an electric current. Magnetic induction generates eddy current heat, achieving rapid and uniform heating. A sealing cap 3 is fixed to the inlet of the pre-pyrolysis cylinder 1 to ensure a sealed pyrolysis process and prevent gas leakage. A servo motor 4 drives the spiral conveyor rod 5 to rotate. Spiral blades 6 are fixed to the outer wall of the spiral conveyor rod 5 to convey materials. The feed hopper 7 is used for continuous feeding of waste plastics, and the exhaust pipe 8 is used to discharge the flue gas generated during pre-pyrolysis. The electromagnetic heating jacket 2 generates eddy currents on the wall of the pre-pyrolysis cylinder 1 through a high-frequency alternating magnetic field, directly heating the cylinder with a rapid heating rate. The servo motor 4 drives the spiral conveyor rod 5 to rotate, and the spiral blades 6 propel the material forward. The molten plastic undergoes initial pyrolysis, and the flue gas is discharged from the top exhaust pipe 8. Simultaneously, the spiral conveyor rod 5 continuously pushes residual carbon to the secondary deep pyrolysis unit, completing material transfer. The heating box 9 is used for... The deep pyrolysis cylinder 10 is heated, serving as a secondary pyrolysis reaction chamber. A door 13 is located on the outer wall of the heating chamber 9 for adding fuel (such as coal). The heating chamber 9 raises the temperature of the deep pyrolysis cylinder 10 to 500-700℃ through fuel combustion, further decomposing the pre-pyrolysis residue into small-molecule oil and gas (C1-C4 hydrocarbons) and fixed carbon. The heat-insulating support base 11 is made of ceramic fiber or aluminosilicate fiber to reduce heat transfer to the outside. The pre-pyrolysis products enter the secondary deep pyrolysis cylinder 10. The heating chamber 9 is activated, and the temperature of the deep pyrolysis cylinder 10 rises to the set value, generating high-quality oil and gas. The oil and gas are transported to the waste heat treatment unit via the oil and gas pipe 14 and rigid branch pipe 15. Fixed carbon remains inside the cylinder and is periodically cleaned. When the temperature of the heating chamber 9 is insufficient...Fuel is replenished through hopper 13 to maintain a stable pyrolysis temperature.

[0018] Please see Figure 5 A further embodiment of this solution is as follows: The waste heat treatment unit includes a box 16 located at the top of the heating box 9, an inlet 17 and an outlet 18 located on the upper part of the box 16, and a serpentine heat exchange pipe 19 fixed inside the box 16. An inlet pipe 20 connected to an external cold water device is connected inside the inlet 17, and an outlet pipe 21 connected to an external water storage tank is connected inside the outlet 18. One end of the heat exchange pipe 19 is connected to the opening of a rigid branch pipe 15, and the other end is connected to an external condensation system. Cold water is heated inside the box 16 through the inlet pipe 20 and flows to the outlet pipe 21. The box 16 serves as a container for waste heat recovery, with the inlet 17 and outlet 18 respectively located within the box 16. 6. The upper part connects to the external chilled water equipment and the water storage tank. One end of the serpentine heat exchange tube 19 is connected to the rigid branch pipe 15 (to receive high-temperature oil and gas), and the other end is connected to the external condensation system. The inlet pipe 20 and the outlet pipe 21 are connected to the inlet 17 and the outlet 18 respectively, forming a water circulation path. At the same time, valves are installed. When the high-temperature oil and gas (500-600℃) passes through the heat exchange tube 19, it exchanges heat with the circulating water in the tank 16. The temperature of the oil and gas decreases and the temperature of the water increases. The serpentine tube design increases the heat exchange area, prolongs the contact time between the oil and gas and the water, and improves the heat exchange efficiency. The external chilled water equipment supplies water to the tank 16 through the inlet pipe 20. The heated water enters the water storage tank through the outlet pipe 21 to complete the waste heat recovery.

[0019] Please see Figure 4 A further solution based on this embodiment is as follows: A rotary motor 22 is installed on the outer wall of the heating box 9. The output end of the rotary motor 22 is fixedly connected to a rotating shaft 23 extending into the heating box 9. A stirring paddle 24 is fixedly connected to the outer wall of the rotating shaft 23. A scraper 25 is detachably connected to the end of the stirring paddle 24. The rotary motor 22 drives the rotating shaft 23 to rotate. The stirring paddle 24 stirs the material in the heating box 9 so that it is heated evenly. The scraper 25 is close to the inner wall of the heating box 9 and scrapes off the plastic stuck to the inner wall to avoid local charring and carbonization. The plastic is completely decomposed into "heavy oil gas" (the main component that can be turned into fuel oil) and "black carbon black slag" (like fine coal powder, a by-product). The oil gas is discharged from the top oil gas pipe 14, and the carbon black slag is treated periodically. Please see Figure 6 A further solution based on this embodiment is as follows: the stirring paddle 24 is provided with a socket 26, and the surface of the scraper plate 25 is fixed with a rod 27 that is compatible with the socket 26. The rod 27 can be inserted into the socket (26). After the rod 27 is inserted into the socket 26, the scraper plate 25 is installed on the upper stirring paddle 24. This installation method can be quickly disassembled and assembled without tools, and adapts to the scraping needs under different material working conditions.

[0020] Please see Figure 6A further solution based on this embodiment is as follows: a limiting groove 28 is formed on the inner wall of the insertion hole 26, and a convex rail 29 is integrally fixed to the outer wall of the insertion rod 27. The convex rail 29 is slidably connected to the limiting groove 28. The limiting groove 28 and the convex rail 29 are slidably connected to restrict the rotational freedom of the insertion rod 27 and prevent the insertion rod 27 from rotating. At the same time, the geometric fit between the limiting groove 28 and the convex rail 29 avoids installation deviation and improves the fit between the scraper plate 25 and the inner wall of the heating box 9.

[0021] Please see Figure 6 A further solution based on this embodiment is as follows: a permanent magnet is embedded in the contact surface between the insertion rod 27 and the insertion hole 26. The insertion rod 27 and the insertion hole 26 are magnetically connected. When the insertion rod 27 is aligned with the insertion hole 26 and inserted, the convex rail 29 slides into the limiting groove 28, and the permanent magnet is automatically attracted and fixed. When disassembling, the attraction force of the permanent magnet is overcome, and the insertion rod 27 is directly pulled out to complete the replacement of the scraper plate 25, which saves time and effort. In addition, a graphite heat insulation pad is added to the insertion rod 27 to reduce the direct impact of heat conduction on the permanent magnet. Please see Figure 7 A further solution based on this embodiment is as follows: a baffle plate 30 is nested in the serpentine path of the heat exchange tube 19. The surface of the baffle plate 30 is provided with an array of vent holes 31. The baffle plate 30 forces the oil and gas to spend more time in the heat exchange tube 19, thereby enhancing the heat exchange efficiency. The vent holes allow the oil and gas to pass through while extending their residence time in the heat exchange tube 19, ensuring sufficient heat exchange. When the high-temperature oil and gas flow into the serpentine tube, the flow velocity decreases after encountering the baffle plate 30. When the oil and gas pass through the vent holes, local turbulence is formed, which enhances the thermal convection with the tube wall. The heat exchange coefficient between the oil and gas and the circulating water in the turbulent state is increased, and the heat exchange per unit length is increased.

[0022] Please see Figure 6 A further solution based on this embodiment is as follows: the edge of the scraper plate 25 is provided with a detachable wear-resistant plate. The wear-resistant plate is connected to the surface of the scraper plate 25 through a threaded structure. The wear-resistant plate is made of a high-hardness material (such as tungsten carbide) and directly bears the friction of the inner wall of the heating box 9, extending the overall life of the scraper plate 25. The threaded connection design allows for individual replacement of the wear-resistant plate, reducing maintenance costs. The thickness of the wear-resistant plate is checked regularly, and it is replaced when it wears to a critical value. The old wear-resistant plate is unscrewed, and a new wear-resistant plate is installed to restore the performance of the scraper plate 25.

[0023] Working principle: The operator first feeds the waste plastic into the pre-pyrolysis cylinder 1 of the first-stage pre-pyrolysis unit through the feed hopper 7, and starts the electromagnetic heating jacket 2 to achieve rapid and uniform heating. At the same time, the servo motor 4 drives the screw conveyor 5 to rotate, and the screw blades 6 push the material forward. The molten plastic is initially pyrolyzed during the movement, and the generated flue gas is discharged from the top exhaust pipe 8. The screw conveyor 5 continuously pushes the residual carbon into the deep pyrolysis cylinder 10 of the second-stage deep pyrolysis unit. In the secondary deep pyrolysis unit, fuel (such as coal) is added through the door 13 on the outer wall of the heating box 9. The combustion of fuel raises the temperature inside the heating box 9 to 500-700℃. The deep pyrolysis cylinder 10 serves as a secondary pyrolysis reaction chamber, where the pre-pyrolysis residue is further decomposed into small molecule oil and gas (C1-C4 hydrocarbons) and fixed carbon. At this time, the rotary motor 22 is started to drive the rotating shaft 23 to rotate, and the stirring paddle 24 stirs the material inside the heating box 9 to ensure that it is heated evenly. The scraper plate 25 is closely attached to the inner wall of the heating box 9 through the magnetic connection between the insertion rod 27 and the insertion hole 26, scraping off the plastic stuck to the inner wall to prevent local charring and carbonization and ensure that the plastic is completely decomposed. When the insertion rod 27 is inserted into the insertion hole 26, the convex rail 29 slides into the limiting groove 28 to restrict the degree of rotation freedom. At the same time, the permanent magnet is attracted and fixed to achieve quick disassembly and assembly. The detachable wear-resistant plate on the edge of the scraper plate 25 is made of high-hardness material and directly bears the friction. The thickness is checked regularly, and when it is worn to the critical value, it is replaced by a threaded structure. The high-quality oil and gas produced by deep pyrolysis is transported through oil and gas pipe 14 and rigid branch pipe 15 to the serpentine heat exchange pipe 19 of the waste heat treatment unit. When the high-temperature oil and gas (500-600℃) flows into the heat exchange pipe 19, it encounters the nested baffle plate 30, which reduces the flow rate. It forms local turbulence through the vent array 31, prolongs the contact time with the circulating water, and enhances the heat exchange efficiency. The external cold water equipment supplies water to the tank 16 through the water inlet pipe 20. The heated water enters the water storage tank through the water outlet pipe 21 to complete the waste heat recovery. The cooled oil and gas is transported from the other end of the heat exchange pipe 19 to the external condensation system. The fixed carbon remains in the deep pyrolysis cylinder 10 and is cleaned regularly. When the temperature of the heating box 9 is insufficient, fuel is added through the door 13 to maintain the stability of the pyrolysis temperature.

[0024] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A two-stage waste plastic pyrolysis device, characterized in that: It includes a primary pre-pyrolysis unit, a secondary deep pyrolysis unit, and a waste heat treatment unit. The outlet end of the primary pre-pyrolysis unit is connected to the inlet end of the secondary deep pyrolysis unit, the inlet end of the waste heat treatment unit is connected to the top of the secondary deep pyrolysis unit, and the outlet end of the waste heat treatment unit is connected to an external condensation system. The primary pre-pyrolysis unit includes a pre-pyrolysis cylinder (1), an electromagnetic heating jacket (2) installed on the outer wall of the pre-pyrolysis cylinder (1), a detachable sealing cover (3) and a feed hopper (7) installed on one end of the pre-pyrolysis cylinder (1), a servo motor (4) installed on the sealing cover (3), and a spiral conveying rod (5) fixedly connected to the output end of the servo motor (4) at one end. The outer wall of the spiral conveying rod (5) is fixed with spiral blades (6). The other end of the pre-pyrolysis cylinder (1) One end is connected to the secondary deep pyrolysis unit, and the other end of the pre-pyrolysis cylinder (1) is provided with a flue pipe (8). The secondary deep pyrolysis unit includes a heating box (9) fixed to the pre-pyrolysis cylinder (1), a deep pyrolysis cylinder (10) fixed to the inner wall of the heating box (9), a heat-insulating bearing base (11) fixed to the lower end of the heating box (9), and an inspection door (12) movably installed on the outer wall of the heating box (9). The outer wall of the heating box (9) is also provided with a door (13) for adding fuel. The outer wall of the deep pyrolysis cylinder (10) is fixed with an oil and gas pipe (14). The oil and gas pipe (14) is connected to the waste heat treatment unit through a rigid branch pipe (15). The oil and gas from the thermal pyrolysis of waste plastics flows into the waste heat treatment unit from the deep pyrolysis cylinder (10) through the oil and gas pipe (14).

2. The two-stage waste plastic pyrolysis device according to claim 1, characterized in that: The waste heat treatment unit includes a box (16) set on top of the heating box (9), an inlet (17) and an outlet (18) opened on the upper part of the box (16), and a serpentine heat exchange tube (19) fixed in the box (16). The inlet (17) is connected to an inlet pipe (20) connected to an external cold water device, and the outlet (18) is connected to an outlet pipe (21) connected to an external water storage tank. One end of the heat exchange tube (19) is connected to the opening of a rigid branch pipe (15), and the other end of the heat exchange tube (19) is connected to an external condensation system. Cold water is heated in the box (16) through the inlet pipe (20) and flows to the outlet pipe (21).

3. The two-stage waste plastic pyrolysis device according to claim 1, characterized in that: A rotary motor (22) is installed on the outer wall of the heating box (9). The output end of the rotary motor (22) is fixedly connected to a rotating shaft (23) extending into the heating box (9). A stirring paddle (24) is fixedly connected to the outer wall of the rotating shaft (23). A scraper (25) is detachably connected to the end of the stirring paddle (24).

4. The two-stage waste plastic pyrolysis device according to claim 1, characterized in that: The stirring paddle (24) has an insertion hole (26), and the scraper plate (25) has a plug rod (27) that is compatible with the insertion hole (26) fixed to its surface. The plug rod (27) can be inserted into the insertion hole (26).

5. A two-stage waste plastic pyrolysis apparatus as claimed in claim 4, wherein: A limiting groove (28) is provided on the inner wall of the insertion hole (26), and a convex rail (29) is fixedly connected to the insertion rod (27). The convex rail (29) is slidably connected to the limiting groove (28).

6. The two-stage waste plastic pyrolysis device according to claim 4, characterized in that: A permanent magnet is embedded in the contact surface between the insertion rod (27) and the insertion hole (26), and the insertion rod (27) and the insertion hole (26) are magnetically connected.

7. The two-stage waste plastic pyrolysis device according to claim 1, characterized in that: A baffle plate (30) is nested in the serpentine path of the heat exchange tube (19), and an array of vent holes (31) is opened on the surface of the baffle plate (30).

8. A two-stage waste plastic pyrolysis apparatus as claimed in claim 3, wherein: The edge of the scraper (25) is provided with a removable wear-resistant plate, which is connected to the surface of the scraper (25) by a threaded structure.

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