A wellhead natural gas processing device based on electromagnetic induction heating

Abstract

The present invention provides a wellhead natural gas processing device based on electromagnetic induction heating, including a liquid collecting sand collecting component and a conversion component, the inlet end of the conversion component is connected to the natural gas inlet pipeline, the outlet end of the conversion component is connected to the natural gas outlet pipeline, the conversion component includes a fixed cavity, a rotating permanent magnet group, a rotating shaft and a metal heating body, the rotating shaft is rotatably installed in the fixed cavity, one end of the rotating shaft extending out of the fixed cavity is coaxially fixedly connected to the impeller, the rotating permanent magnet group is fixedly installed on the rotating shaft, the rotating permanent magnet group is located in the fixed cavity, a fixed permanent magnet group is arranged on the outer wall of the fixed cavity, a metal heating body is fixedly installed on the outer peripheral side of the rotating permanent magnet group, and a liquid collecting sand collecting component is arranged below the impeller. The structural design of the present invention is scientific and reasonable, and the kinetic energy of natural gas itself and the electromagnetic induction heating principle are used to generate heat, and no additional heating energy is required. It is green and environmentally friendly and can fully meet the needs of natural gas exploitation, and can be promoted for use.

Description

Technical Field

[0001] The invention relates to a petroleum and natural gas wellhead processing device, in particular to a wellhead natural gas processing device based on electromagnetic induction heating. Background Art

[0002] During the process of natural gas extraction and transportation, a throttling and pressure regulating device needs to be installed at the gas wellhead so that the natural gas pressure coming out of the wellhead meets the pressure requirements of the gathering and transportation pipeline. The throttling and pressure regulation of natural gas will cause its temperature and pressure to drop, produce natural gas hydrates, and block the pipeline. Heating the natural gas at the wellhead is an important measure to prevent the formation of hydrates. While heating, it also has the effect of removing liquid, sand and preventing blockage. The common heating method is to use an electric heater, which consumes a lot of electricity and cannot effectively remove impurities carried by natural gas, which can easily cause pipeline blockage. Based on this, it is necessary to design a wellhead natural gas heating device with high heating efficiency and low energy consumption. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a wellhead natural gas processing device based on electromagnetic induction heating in view of the deficiencies of the above-mentioned prior art. The device has a scientific and reasonable structural design and strong practicality. It utilizes the kinetic energy of natural gas itself and the electromagnetic induction heating principle to generate heat, which can effectively prevent the formation of hydrates. No additional heating energy is required. It is green and environmentally friendly and can fully meet the needs of natural gas extraction. It can also efficiently remove liquid and sand while heating to prevent pipeline blockage, and can be widely used.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a wellhead natural gas processing device based on electromagnetic induction heating, characterized in that it includes a liquid and sand collecting component and a conversion component, the inlet end of the conversion component is connected to the natural gas inlet pipeline through a flange, and the outlet end of the conversion component is connected to the natural gas outlet pipeline through a flange, the conversion component includes a fixed cavity, a rotating permanent magnet group, a rotating shaft and a metal heating body, the rotating shaft is rotatably installed in the fixed cavity, one end of the rotating shaft extending out of the fixed cavity is coaxially fixedly connected to the impeller, the rotating permanent magnet group is fixedly installed on the rotating shaft, the rotating permanent magnet group is located in the fixed cavity, a fixed permanent magnet group is arranged on the outer side wall of the fixed cavity, a metal heating body is fixedly installed on the outer peripheral side of the rotating permanent magnet group, and a liquid and sand collecting component is arranged below the impeller.

[0005] Preferably, the rotating permanent magnet group includes a protective shell, a rotating permanent magnet bracket and a first permanent magnet, the protective shell is cylindrical, one end of the protective shell is coaxially fixedly connected to the rotating shaft, a rotating permanent magnet bracket is arranged at the center position of the protective shell, and a plurality of first permanent magnets are fixedly arranged on the rotating permanent magnet bracket in a circular array, the cross-section of the first permanent magnet is fan-shaped, and the magnetic poles of adjacent first permanent magnets are opposite.

[0006] Preferably, the natural gas inlet pipeline is connected to the inlet side of the fixed cavity through a flow guide cover, the impeller is located in the flow guide cover and the impeller faces the natural gas flow, and a flow limiting ring is arranged between the natural gas inlet pipeline and the flow guide cover. The flow guide cover is used to increase the kinetic energy of the natural gas flow, thereby increasing the rotation speed of the impeller and improving the heating efficiency. The flow and pressure of the natural gas are controlled by the flow limiting ring to ensure the stability of the natural gas impact kinetic energy.

[0007] Preferably, a sand collecting funnel is arranged on the guide cover at a position directly below the impeller, the bottom of the sand collecting funnel is connected to a liquid and sand collecting chamber through a liquid and sand inlet pipe, the bottom of the liquid and sand collecting chamber is connected to a liquid and sand discharge pipe, valves are arranged on the liquid and sand inlet pipe and the liquid and sand discharge pipe, a spray cleaning pipe is installed in the liquid and sand collecting chamber, and a vent pipe is arranged on the liquid and sand collecting chamber.

[0008] Preferably, the fixed cavity includes a side shield and an end head frame, the two end head frames are fixedly connected to the two ends of the cylindrical side shield, the protective shell is rotatably installed between the two end head frames, the fixed permanent magnet group is fixedly sleeved on the outer wall of the side shield, and the inner wall of the side shield is fixedly connected to the metal heating body through the fixed frame.

[0009] Preferably, the end frame is provided with an axial hole for the rotating shaft to pass through, the end frame is provided with a first natural gas flow channel, the end frame is provided with a bearing hole, and a bearing is arranged between the bearing hole and the rotating shaft.

[0010] Preferably, the metal heating body comprises a heating main body ring, an outer gear ring and an inner gear ring, the inner and outer sides of the heating main body ring are respectively fixedly connected to the outer gear ring and the inner gear ring, and a second natural gas flow channel is opened on the fixed frame.

[0011] Preferably, one end of the protective shell is coaxially fixedly connected to the rotating shaft through a transmission hole, a sealing cap is arranged at the other end of the protective shell, a first permanent magnet partition is filled between adjacent first permanent magnets, a rotating permanent magnet insulation layer is arranged between the protective shell and the first permanent magnet, a support shaft hole is opened on the sealing cap, a tail end support shaft is connected in the support shaft hole, and the tail end support shaft is rotatably mounted on the end frame away from the impeller through a bearing.

[0012] Preferably, a first flange is arranged on the deflector, a second flange is arranged on the end frame close to the impeller, a third flange is arranged on the end frame away from the impeller, and a fourth flange is arranged on the natural gas outlet pipeline. The first flange is adaptably connected to the second flange, and the third flange is adaptably connected to the fourth flange.

[0013] Preferably, the fixed permanent magnet group includes a fixed permanent magnet bracket and a second permanent magnet, a plurality of second permanent magnet annular arrays are arranged in the fixed permanent magnet bracket, the cross-section of the second permanent magnet is fan-shaped, the polarities of adjacent second permanent magnets are opposite, and second permanent magnet spacers are filled between adjacent second permanent magnets, the fixed permanent magnet bracket is fixedly sleeved on the outer peripheral side of the side protective tube, and an outer insulation layer is arranged between the fixed permanent magnet bracket and the side protective tube.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The present invention sets a deflector to increase the impact kinetic energy of natural gas, intercepts the liquid phase and solid particles carried by the natural gas through the impeller, realizes preliminary separation, drives the rotating permanent magnet group to rotate through the rotation of the impeller to form a motion of cutting magnetic flux lines, generates electromagnetic induction, generates alternating current in the metal heating body, and thus makes the metal heating body heat up quickly.

[0016] 2. The present invention arranges toothed rings inside and outside the metal heating body to increase the heat exchange area with natural gas, and can also change the flow of natural gas to improve the heat transfer effect, improve energy utilization efficiency, and save energy and protect the environment.

[0017] 3. The present invention is provided with a rotating permanent magnet group and a fixed permanent magnet group, which can generate a magnetic field with a higher frequency of change, increase the frequency of the metal heating body cutting the magnetic flux lines, and improve the heating effect.

[0018] 4. The present invention is energy-saving and efficient. It can directly convert the kinetic energy of natural gas into thermal energy, reduce the energy consumption of heating wellhead natural gas by means of coal-fired boilers or electric heaters, thereby reducing environmental pollution caused by burning fossil energy and improving the energy utilization rate of secondary energy. The magnetic field of the present invention is generated by a permanent magnet group, and no external power supply and wires are required, which is safe and reliable. The induction heating metal heating body is directly fixed to the pipe wall, and the induction heating metal heating body generates eddy currents on the pipe wall and converts them into heat that is directly transferred to the natural gas, with high heat transfer efficiency. The present invention can also effectively avoid the situation where the temperature and pressure of natural gas will drop after throttling and pressure regulation, and the formation of natural gas hydrates will cause the pipeline to block. In addition, the device is safe and reliable and has a long working time.

[0019] 5. The present invention collects the liquid phase and solid particles carried by the natural gas intercepted by the impeller through the liquid and sand collecting components, and gathers them in the liquid and sand collecting chamber, which is convenient for unified treatment and can effectively avoid pipeline blockage.

[0020] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic cross-sectional view of the overall structure of the present invention.

[0022] Figure 2It is a schematic diagram of the main cross-section of the rotating permanent magnet group in the present invention.

[0023] Figure 3 It is a side cross-sectional schematic diagram of the rotating permanent magnet group in the present invention.

[0024] Figure 4 It is a schematic diagram of the main cross-sectional structure of the metal heating body in the present invention.

[0025] Figure 5 It is a schematic diagram of the side cross-sectional structure of the metal heating body in the present invention.

[0026] Figure 6 It is a side cross-sectional schematic diagram of the end head frame in the present invention.

[0027] Figure 7 It is a schematic diagram of the front cross section of the terminal frame in the present invention.

[0028] Figure 8 It is a side cross-sectional schematic diagram of the fixing frame in the present invention.

[0029] Fig. 9 It is a side cross-sectional schematic diagram of the fixed permanent magnet group in the present invention.

[0030] Fig.10 It is a structural schematic diagram of the liquid and sand collecting assembly in the present invention.

[0031] Description of reference numerals:

[0032] 1—Natural gas inlet pipeline; 2—Natural gas outlet pipeline; 3—Flow limiting ring;

[0033] 4— fairing; 5—impeller; 6—first flange; 7—Second flange; 8—Third flange; 9—Fourth flange; 10—fixed permanent magnet group; 10-1—fixed permanent magnet bracket; 10-2—second permanent magnet spacer;

[0035] 10-3—second permanent magnet; 11—rotating shaft; 12—external insulation layer; 13—side shield; 14—metal heating body; 14-1—heating body ring; 14-2—External gear ring; 14-3—Internal gear ring; 15—Fixed frame;

[0036] 15-1—second natural gas flow channel; 16—end frame; 16-1—axial hole;

[0037] 16-2—first natural gas flow channel; 16-3—bearing hole; 17—rotating permanent magnet group; 17-1—protective shell; 17-2—rotating permanent magnet bracket; 17-3—rotating permanent magnet insulation layer;

[0039] 17-4—first permanent magnet; 17-5—first permanent magnet spacer; 17-6—transmission hole; 17-7—support shaft hole; 17-8—sealing cap; 18—bearing;

[0040] 19—sand collecting funnel; 20—valve; 21—liquid and sand collecting chamber; 22—liquid and sand inlet pipe; 23—liquid and sand discharge pipe; 24—spray cleaning pipe; 25—Vent pipe. DETAILED DESCRIPTION

[0041] like Figures 1 to 10 As shown, the present invention includes a liquid collecting and sand collecting component and a conversion component, the inlet end of the conversion component is connected to the natural gas inlet pipeline 1, the outlet end of the conversion component is connected to the natural gas outlet pipeline 2, the conversion component includes a fixed cavity, a rotating permanent magnet group 17, a rotating shaft 11 and a metal heating body 14, the rotating shaft 11 is rotatably installed in the fixed cavity, one end of the rotating shaft 11 extending out of the fixed cavity is coaxially fixedly connected to the impeller 5, the rotating permanent magnet group 17 is fixedly installed on the rotating shaft 11, the rotating permanent magnet group 17 is located in the fixed cavity, a fixed permanent magnet group 10 is arranged on the outer side wall of the fixed cavity, a metal heating body 14 is fixedly installed on the outer peripheral side of the rotating permanent magnet group 17, and a liquid collecting and sand collecting component is arranged below the impeller 5.

[0042] In this embodiment, the rotating permanent magnet group includes a protective shell 17-1, a rotating permanent magnet bracket 17-2 and a first permanent magnet 17-4. The protective shell 17-1 is cylindrical, and one end of the protective shell 17-1 is coaxially fixedly connected to the rotating shaft 11. A rotating permanent magnet bracket 17-2 is arranged at the center position of the protective shell 17-1, and a plurality of first permanent magnets 17-4 are fixedly arranged in a circular array on the rotating permanent magnet bracket 17-2. The cross-section of the first permanent magnet 17-4 is fan-shaped, and the magnetic poles of adjacent first permanent magnets 17-4 are opposite.

[0043] In this embodiment, the natural gas inlet pipe 1 is connected to the inlet side of the fixed cavity through the guide cover 4, the impeller 5 is located in the guide cover 4 and the impeller 5 faces the natural gas flow, and a flow limiting ring 3 is arranged between the natural gas inlet pipe 1 and the guide cover 4. The guide cover 4 is used to increase the gas flow kinetic energy of the natural gas, thereby increasing the rotation speed of the impeller 5 and improving the heating efficiency. The flow and pressure of the natural gas are controlled by the flow limiting ring 3 to ensure the stability of the natural gas impact kinetic energy.

[0044] In this embodiment, a sand collecting funnel 19 is arranged on the guide cover 4 at a position directly below the impeller 5. The bottom of the sand collecting funnel 19 is connected to a liquid and sand collecting chamber 21 through a liquid and sand inlet pipe 22. The bottom of the liquid and sand collecting chamber 21 is connected to a liquid and sand discharge pipe 23. Valves 20 are arranged on both the liquid and sand inlet pipe 22 and the liquid and sand discharge pipe 23. A spray cleaning pipe 24 is installed in the liquid and sand collecting chamber 21. A vent pipe 25 is arranged on the vent pipe 25. A valve is arranged on the vent pipe 25. The spray cleaning pipe 24 is arranged along the upper part of the inner wall of the liquid and sand collecting chamber 21, and a plurality of spray holes are equidistantly provided on the spray cleaning pipe 24.

[0045] In this embodiment, the fixed cavity includes a side protective tube 13 and an end frame 16. The two end frames 16 are fixedly connected at both ends of the cylindrical side protective tube 13. A protective shell 17-1 is rotatably installed between the two end frames 16. The fixed permanent magnet group 10 is fixedly sleeved on the outer wall of the side protective tube 13, and the inner wall of the side protective tube 13 is fixedly connected to the metal heating body 14 through a fixing frame 15.

[0046] In this embodiment, the end frame 16 is provided with an axial hole 16 - 1 for the rotating shaft 11 to pass through, the end frame 16 is provided with a first natural gas flow channel 16 - 2, the end frame 16 is provided with a bearing hole 16 - 3, and a bearing 18 is arranged between the bearing hole 16 - 3 and the rotating shaft 11.

[0047] In this embodiment, the metal heating body 14 includes a heating main ring 14-1, an outer gear ring 14-2 and an inner gear ring 14-3. The inner and outer sides of the heating main ring 14-1 are fixedly connected to the outer gear ring 14-2 and the inner gear ring 14-3 respectively. A second natural gas flow channel 15-1 is opened on the fixed frame 15.

[0048] In this embodiment, one end of the protective shell 17-1 is coaxially fixedly connected to the rotating shaft 11 through a transmission hole 17-6, and a sealing cap 17-8 is provided at the other end of the protective shell 17-1. A first permanent magnet partition 17-5 is filled between adjacent first permanent magnets 17-4, and a rotating permanent magnet insulation layer 17-3 is provided between the protective shell 17-1 and the first permanent magnet 17-4. A support shaft hole 17-7 is provided on the sealing cap 17-8, and a tail end support shaft is connected in the support shaft hole 17-7. The tail end support shaft is rotatably mounted on the end frame 16 away from the impeller 5 through a bearing 18.

[0049] In this embodiment, a first flange 6 is provided on the deflector 4, a second flange 7 is provided on the end frame 16 close to the impeller 5, a third flange 8 is provided on the end frame 16 away from the impeller 5, and a fourth flange 9 is provided on the natural gas outlet pipeline 2. The first flange 6 is adaptably connected to the second flange 7, and the third flange 8 is adaptably connected to the fourth flange 9.

[0050] In this embodiment, the fixed permanent magnet group 10 includes a fixed permanent magnet bracket 10-1 and a second permanent magnet 10-3. A plurality of second permanent magnets 10-3 are arranged in a circular array in the fixed permanent magnet bracket 10-1. The cross-section of the second permanent magnet 10-3 is fan-shaped. The polarities of adjacent second permanent magnets 10-3 are opposite. Second permanent magnet interlayers 10-2 are filled between adjacent second permanent magnets 10-3. The fixed permanent magnet bracket 10-1 is fixedly sleeved on the outer peripheral side of the side protective tube 13. An outer insulation layer 12 is arranged between the fixed permanent magnet bracket 10-1 and the side protective tube 13.

[0051] When in use, natural gas enters the deflector 4 from the natural gas inlet pipeline 1. The kinetic energy of natural gas is increased under the action of the deflector 4. Natural gas impacts the impeller 5, and the impeller 5 rotates. The impeller 5 drives the rotating shaft 11 to rotate, and the rotating shaft drives the rotating permanent magnet group 17 to rotate. The rotating permanent magnet group 17 rotates to generate a changing magnetic field. The metal heating body 14 cuts the magnetic flux lines in the changing magnetic field. Based on the principle of electromagnetic induction, the cutting of the magnetic flux lines generates an alternating current in the metal heating body 14. The alternating current makes the metal heating body 14 heat up, and the heat is transferred to the natural gas to complete the heating of the natural gas to prevent the formation of hydrates to block the pipeline. The heated natural gas is discharged from the natural gas outlet pipeline 2. When the impeller 5 rotates, the natural gas impacting the impeller 5 causes the liquid and small solid particles impurities it carries to be intercepted by the impeller 5 and flow from the impeller 5 into the liquid and sand collecting funnel 19 and finally converge in the liquid and sand collecting chamber 21. The venting pipe 25 and the spray cleaning pipe 24 are opened to clean and empty the liquid and solid impurities, completing the preliminary separation of the natural gas.

[0052] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A wellhead natural gas processing device based on electromagnetic induction heating, characterized in that: The invention comprises a liquid collecting and sand collecting component and a conversion component, wherein the inlet end of the conversion component is connected to a natural gas inlet pipeline (1), and the outlet end of the conversion component is connected to a natural gas outlet pipeline (2). The conversion component comprises a fixed cavity, a rotating permanent magnet group (17), a rotating shaft (11) and a metal heating body (14). The rotating shaft (11) is rotatably mounted in the fixed cavity, and one end of the rotating shaft (11) extending out of the fixed cavity is coaxially fixedly connected to an impeller (5). The rotating permanent magnet group (17) is fixedly mounted on the rotating shaft (11). The rotating permanent magnet group (17) is located in the fixed cavity. A fixed permanent magnet group (10) is arranged on the outer wall of the fixed cavity. The metal heating body (14) is fixedly mounted on the outer peripheral side of the rotating permanent magnet group (17). A liquid collecting and sand collecting component is arranged below the impeller (5).

2. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 1, characterized in that: The rotating permanent magnet group comprises a protective shell (17-1), a rotating permanent magnet bracket (17-2) and a first permanent magnet (17-4); the protective shell (17-1) is cylindrical; one end of the protective shell (17-1) is coaxially fixedly connected to a rotating shaft (11); a rotating permanent magnet bracket (17-2) is arranged at a central position in the protective shell (17-1); a plurality of first permanent magnets (17-4) are fixedly arranged in a ring array on the rotating permanent magnet bracket (17-2); the cross section of the first permanent magnet (17-4) is fan-shaped; and the magnetic poles of adjacent first permanent magnets (17-4) are opposite.

3. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 1, characterized in that: The natural gas inlet pipeline (1) is connected to the inlet side of the fixed cavity via a flow guide cover (4), the impeller (5) is located inside the flow guide cover (4) and the impeller (5) faces the natural gas flow, and a flow limiting ring (3) is provided between the natural gas inlet pipeline (1) and the flow guide cover (4).

4. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 3, characterized in that: A sand collecting funnel (19) is arranged on the guide cover (4) at a position directly below the impeller (5); the bottom of the sand collecting funnel (19) is connected to a liquid collecting and sand collecting chamber (21) via a liquid and sand inlet pipe (22); the bottom of the liquid collecting and sand collecting chamber (21) is connected to a liquid and sand discharge pipe (23); valves (20) are arranged on the liquid and sand inlet pipe (22) and the liquid and sand discharge pipe (23); a spray cleaning pipe (24) is installed in the liquid collecting and sand collecting chamber (21); and a venting pipe (25) is arranged on the liquid collecting and sand collecting chamber (21).

5. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 1, characterized in that: The fixed cavity comprises a side protective tube (13) and an end head frame (16); the two end head frames (16) are fixedly connected to the two ends of the cylindrical side protective tube (13); a protective shell (17-1) is rotatably installed between the two end head frames (16); the fixed permanent magnet group (10) is fixedly sleeved on the outer wall of the side protective tube (13); and the inner wall of the side protective tube (13) is fixedly connected to the metal heating body (14) via a fixing frame (15).

6. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 5, characterized in that: The end frame (16) is provided with an axial hole (16-1) for the rotating shaft (11) to pass through, the end frame (16) is provided with a first natural gas flow channel (16-2), the end frame (16) is provided with a bearing hole (16-3), and a bearing (18) is arranged between the bearing hole (16-3) and the rotating shaft (11).

7. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 5, characterized in that: The metal heating body (14) comprises a heating main body ring (14-1), an outer gear ring (14-2) and an inner gear ring (14-3); the inner and outer sides of the heating main body ring (14-1) are respectively fixedly connected to the outer gear ring (14-2) and the inner gear ring (14-3); and a second natural gas flow channel (15-1) is provided on the fixing frame (15).

8. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 2, characterized in that: One end of the protective shell (17-1) is coaxially fixedly connected to the rotating shaft (11) through a transmission hole (17-6), and a blocking cap (17-8) is arranged at the other end of the protective shell (17-1). A first permanent magnet spacer (17-5) is filled between adjacent first permanent magnets (17-4), and a rotating permanent magnet insulation layer (17-3) is arranged between the protective shell (17-1) and the first permanent magnet (17-4). A support shaft hole (17-7) is provided on the blocking cap (17-8), and a tail end support shaft is connected in the support shaft hole (17-7). The tail end support shaft is rotatably mounted on an end frame (16) away from the impeller (5) through a bearing (18).

9. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 3, characterized in that: A first flange (6) is arranged on the deflector (4), a second flange (7) is arranged on the end frame (16) close to the impeller (5), a third flange (8) is arranged on the end frame (16) away from the impeller (5), a fourth flange (9) is arranged on the natural gas outlet pipeline (2), the first flange (6) is adaptively connected to the second flange (7), and the third flange (8) is adaptively connected to the fourth flange (9).

10. A wellhead natural gas processing device based on electromagnetic induction heating according to claim 5, characterized in that: The fixed permanent magnet group (10) comprises a fixed permanent magnet bracket (10-1) and a second permanent magnet (10-3); a plurality of second permanent magnets (10-3) are arranged in an annular array in the fixed permanent magnet bracket (10-1); the cross section of the second permanent magnet (10-3) is fan-shaped; the polarities of adjacent second permanent magnets (10-3) are opposite; a second permanent magnet spacer (10-2) is filled between adjacent second permanent magnets (10-3); the fixed permanent magnet bracket (10-1) is fixedly sleeved on the outer peripheral side of the side protective tube (13); and an outer thermal insulation layer (12) is arranged between the fixed permanent magnet bracket (10-1) and the side protective tube (13).

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