A multi-pass reactor electric heater

Abstract

This application relates to the field of electric heater technology, and in particular to a multi-stroke reactor electric heater, comprising a cavity tube and a sealing plate. The cavity tube is hollow inside and open at one end. The sealing plate is detachably disposed at the open end of the cavity tube. An airtight sealing element is disposed between the cavity tube and the sealing plate. Multiple baffles are disposed inside the cavity tube, dividing the cavity tube into an inlet chamber, a transfer chamber, and an outlet chamber. An inlet pipe communicating with the inlet chamber and an outlet pipe communicating with the outlet chamber are disposed on the cavity tube. Multiple U-shaped gas guide pipes are connected between the inlet chamber and the transfer chamber, and between the transfer chamber and the outlet chamber. Electric heating tubes are inserted into both ends of the U-shaped gas guide pipes. The end of the electric heating tube opposite to the gas guide pipe passes through the sealing plate. A sealing element is disposed between the electric heating tube and the sealing plate. A support element is disposed on the gas guide pipe to support the electric heating tube. This application has the advantages of high heating efficiency, simple maintenance, and low maintenance cost.

Description

Technical Field

[0001] This application relates to the field of electric heater technology, and in particular to an electric heater for a multi-pass reactor. Background Technology

[0002] An electric heater is a device that converts electrical energy into heat energy. Its working principle involves generating Joule heat by an electric current flowing through a heating element, which is then transferred through conduction, convection, or radiation. Based on their structure, electric heaters can be classified into tubular electric heaters, plate electric heaters, infrared electric heaters, and other types.

[0003] In the chemical industry, it is sometimes necessary to heat a gaseous medium (usually air) to 850°C. This heating is typically achieved by using an electric heater to heat the dried gaseous medium. To improve the heating effect, existing technologies often employ spiral-structured tubular electric heaters because their compact heating structure results in high heating efficiency. However, spiral-structured tubular electric heaters are difficult and costly to maintain. While straight-tube electric heaters are simple to maintain and have low maintenance costs, their more dispersed heating structure leads to longer heating times, which is a drawback. Summary of the Invention

[0004] In order to improve the efficiency of gas medium heating and reduce the cost of later maintenance, this application provides a multi-pass reactor electric heater.

[0005] The multi-pass reactor electric heater provided in this application adopts the following technical solution: A multi-pass reactor electric heater includes a cavity tube and a sealing plate. The cavity tube is hollow inside and open at one end. The sealing plate is detachably disposed at the open end of the cavity tube. An airtight sealing element is provided between the cavity tube and the sealing plate. Multiple partitions are disposed inside the cavity tube, dividing the cavity tube into an inlet chamber, a transfer chamber, and an outlet chamber. An inlet pipe communicating with the inlet chamber and an outlet pipe communicating with the outlet chamber are provided on the cavity tube. Multiple U-shaped air guide tubes are connected between the air chamber and the transfer chamber, and between the transfer chamber and the air outlet chamber. Electric heating tubes are inserted into both ends of the U-shaped air guide tubes. The end of the electric heating tube facing away from the air guide tube passes through the sealing plate. A sealing element is provided between the electric heating tube and the sealing plate for sealing. There is a gap between the outer circumferential wall of the electric heating tube and the inner circumferential wall of the air guide tube. A support element for supporting the electric heating tube is provided on the air guide tube.

[0006] By adopting the above technical solution, the gas medium flows into the inlet chamber through the inlet pipe, then flows to the transfer chamber through the guide pipe, and then flows to the outlet chamber through the guide pipe, and finally flows out through the outlet pipe. During this process, the airtight and sealing components seal the gas medium in the cavity, and the support component ensures the stability of the distance between the electric heating tube and the guide pipe. When the gas medium flows between the electric heating tube and the guide pipe, the gas medium is heated, and the transfer chamber and the outlet chamber mix the heated gas medium. The multiple guide pipes increase the channels for gas medium flow, improve the efficiency of gas medium heating, and shorten the overall length. The insertion installation method of the electric heating tube reduces the difficulty and cost of later maintenance.

[0007] Optionally, the airtight component includes an aluminum ring plate disposed between the open end of the cavity tube and the sealing plate, and the sealing plate has a receiving groove for accommodating the aluminum ring plate.

[0008] By adopting the above technical solution, during the heating of the gas medium by the electric heating tube, the gas medium will transfer heat to the cavity tube. At this time, the cavity tube will transfer heat to the aluminum ring plate through heat transfer. When the transferred temperature is insufficient to melt the aluminum ring plate, the thermal expansion of the aluminum ring plate itself will fully fill the receiving groove, thereby achieving a solid seal between the sealing plate and the cavity tube. When the transferred temperature melts the aluminum ring plate, due to the high surface tension of the oxide film on the surface of the aluminum ring plate and the small gap between the sealing plate and the cavity tube, the melted aluminum ring plate will fill the receiving groove and cannot overflow, thereby achieving a dynamic seal between the sealing plate and the cavity tube. Furthermore, as the service time increases, the thickness of the oxide film on the surface of the aluminum ring plate will increase, thereby further improving the sealing effect.

[0009] Optionally, the aluminum ring plate undergoes surface oxidation treatment.

[0010] By adopting the above technical solution, the thickness of the oxide layer on the surface of the aluminum ring plate is increased, thereby improving the dynamic sealing effect of the aluminum ring plate in the molten state.

[0011] Optionally, the sealing element includes a metal airbag disposed on the sealing plate. The interior of the metal airbag is hollow, and the metal airbag has a mounting hole for the electric heating tube to pass through. The mounting hole is not connected to the interior of the metal airbag. The wall thickness of the metal airbag on both sides along the axial direction of the cavity tube is greater than the wall thickness in the circumferential direction. When the metal airbag expands due to heat, the outer circumferential wall of the metal airbag is used to abut against the cavity tube and the partition plate.

[0012] By adopting the above technical solution, when the gas medium transfers heat to the metal airbag, the gas inside the metal airbag will expand. Since the circumferential wall thickness of the metal airbag is smaller than the wall thickness on both sides, the metal airbag will expand circumferentially. The circumferentially expanded metal airbag will abut against the cavity tube and the partition. At the same time, the expanded wall thickness at the mounting hole of the metal airbag will wrap around the electric heating tube, thereby achieving a sealing effect.

[0013] Optionally, the support member includes a strap and a center strip. An expansion strip is connected between the two ends of the center strip. The length of the expansion strip is greater than the length of the center strip. The strap is arranged at both ends of the center strip. Multiple center strips are evenly arranged along the length of the strap. Both ends of the strap are provided with fastening teeth. One end of the strap is provided with a folded strap, and the other end is provided with a buckle. When the folded strap passes through the buckle, the fastening teeth at both ends of the strap can engage with each other.

[0014] By adopting the above technical solution, the installer first loops the strap around the electric heating tube, and then passes the folded strip at one end of the strap through the buckle at the other end and bends it. At this time, the fastening teeth at both ends of the strap engage with each other, and the center strip is attached to the surface of the electric heating tube, thus completing the installation of the strap. During the process of inserting the electric heating tube into the air duct, the expansion strip can deform to allow the electric heating tube to be inserted smoothly. When the electric heating tube is working, the expansion strip can still deform to adapt to its own thermal deformation, thus always providing support for the electric heating tube. Furthermore, when the installer needs to remove the electric heating tube, the expansion strip will not lock the electric heating tube, thereby reducing the difficulty and cost of later maintenance.

[0015] Optionally, the strap strip is provided with anti-slip texture, which is used to abut against the circumferential outer wall of the electric heating tube.

[0016] Optionally, the closed end of the cavity tube is detachably provided with a protective sleeve, the air guide tube is located inside the protective sleeve, and multiple support plates are sleeved on the air guide tube, with the outer circumferential wall of the support plate abutting against the inner circumferential wall of the protective sleeve.

[0017] Optionally, the outer side of the casing is covered with multiple layers of insulation.

[0018] In summary, this application includes at least one of the following beneficial technical effects: The gas medium flows into the inlet chamber through the inlet pipe, then flows to the transfer chamber through the guide pipe, and then to the outlet chamber through the guide pipe, finally flowing out through the outlet pipe. During this process, the airtight and sealing components seal the gas medium in the cavity, and the support components ensure the stability of the distance between the electric heating tube and the guide pipe. When the gas medium flows between the electric heating tube and the guide pipe, the gas medium is heated, and the transfer chamber and the outlet chamber mix the heated gas medium. The multiple guide pipes increase the channels for gas medium flow, improve the efficiency of gas medium heating, and shorten the overall length. The insertion-type installation of the electric heating tube reduces the difficulty and cost of later maintenance. During the heating process of the gas medium by the electric heating tube, the gas medium transfers heat to the cavity tube. At this time, the cavity tube transfers heat to the aluminum ring plate through heat transfer. When the transferred temperature is insufficient to melt the aluminum ring plate, the thermal expansion of the aluminum ring plate itself will fully fill the receiving groove, thereby achieving a solid seal between the sealing plate and the cavity tube. When the transferred temperature melts the aluminum ring plate, due to the high surface tension of the oxide film on the surface of the aluminum ring plate and the small gap between the sealing plate and the cavity tube, the molten aluminum ring plate will fill the receiving groove and cannot overflow, thereby achieving a dynamic seal between the sealing plate and the cavity tube. Furthermore, as the service time increases, the thickness of the oxide film on the surface of the aluminum ring plate will increase, thereby further improving the sealing effect. The installer first loops the strap around the electric heating element, then passes one end of the strap through the loop on the other end and bends it. At this point, the buckle teeth at both ends of the strap engage, and the center strip is against the surface of the electric heating element. This completes the installation of the strap. During the insertion of the electric heating element into the air duct, the expansion strip deforms to allow the heating element to be inserted smoothly. When the electric heating element is working, the expansion strip continues to deform to adapt to its own thermal deformation, thus always providing support for the heating element. Furthermore, when the installer needs to remove the electric heating element, the expansion strip does not lock the heating element, thereby reducing the difficulty and cost of later maintenance. Attached Figure Description

[0019] Figure 1 This is a structural schematic diagram of an embodiment of this application.

[0020] Figure 2 This is a cross-sectional view used in the embodiments of this application to illustrate the positional relationship between the air guide tube, the protective sleeve, and the cavity tube.

[0021] Figure 3 yes Figure 2 Enlarged view of section A.

[0022] Figure 4 This is an exploded view of an embodiment of this application.

[0023] Figure 5This is a cross-sectional view used in the embodiments of this application to illustrate the positional relationship between the air guide pipe, the electric heating pipe and the support.

[0024] Explanation of reference numerals in the attached drawings: 1. Cavity tube; 2. Sealing plate; 3. Airtight component; 31. Aluminum ring plate; 32. Receiving groove; 4. Partition plate; 5. Air inlet chamber; 6. Transfer chamber; 7. Air outlet chamber; 8. Air inlet pipe; 9. Air outlet pipe; 10. Air guide pipe; 11. Electric heating tube; 12. Sealing component; 121. Metal airbag; 122. Mounting hole; 13. Support component; 131. Binding strip; 132. Centering strip; 133. Expansion strip; 134. Fastening teeth; 135. Folding strip; 136. Buckle ring; 14. Anti-slip texture; 15. Protective sleeve; 16. Support plate; 17. Insulation layer. Detailed Implementation

[0025] The following is in conjunction with the appendix Figures 1-5 This application will be described in further detail.

[0026] This application discloses an electric heater for a multi-pass reactor.

[0027] Reference Figure 1 , Figure 2 and Figure 3 A multi-stroke reactor electric heater includes a cavity tube 1 and a sealing plate 2. Both the cavity tube 1 and the sealing plate 2 can be made of stainless steel, which is available in the prior art. The cavity tube 1 is hollow inside and open at one end. The sealing plate 2 is bolted to the open end of the cavity tube 1. The contact ends of the cavity tube 1 and the sealing plate 2 are smooth. An airtight component 3 for sealing is arranged between the cavity tube 1 and the sealing plate 2.

[0028] Reference Figure 3 The airtight component 3 includes an aluminum ring plate 31 arranged between the open end of the cavity tube 1 and the sealing plate 2. The aluminum ring plate 31 is made of aluminum alloy material after surface oxidation treatment. The sealing plate 2 has a receiving groove 32 for accommodating the aluminum ring plate 31. The surface of the aluminum ring plate 31 can be oxidized by electrochemical oxidation.

[0029] Reference Figure 4 Multiple partitions 4 are welded inside the cavity tube 1, which divide the cavity tube 1 into an air inlet chamber 5, a transfer chamber 6 and an air outlet chamber 7. An air inlet pipe 8 connected to the air inlet chamber 5 and an air outlet pipe 9 connected to the air outlet chamber 7 are welded onto the cavity tube 1.

[0030] Reference Figure 2 and Figure 4 Multiple U-shaped air guide tubes 10 are connected between the air inlet chamber 5 and the transfer chamber 6, and between the transfer chamber 6 and the air outlet chamber 7 of the cavity tube 1. Electric heating tubes 11 are inserted into both ends of the U-shape of the air guide tubes 10.

[0031] During the process of the gas medium flowing through the electric heating tube 11, the gas medium will be heated by the electric heating tube 11. As the gas medium flows, the gas medium will transfer heat to the cavity tube 1. At this time, the cavity tube 1 will transfer heat to the aluminum ring plate 31 through heat transfer.

[0032] When the temperature transmitted through the cavity tube 1 is insufficient to melt the aluminum ring plate 31, the thermal expansion of the aluminum ring plate 31 itself will fully fill the entire receiving groove 32, thereby achieving a solid seal between the sealing plate 2 and the cavity tube 1.

[0033] When the transmitted temperature is sufficient to melt the aluminum ring plate 31, due to the constraint of the oxide film on the surface of the aluminum ring plate 31 and the large surface tension of the aluminum ring plate 31 in the molten state, and the small gap between the sealing plate 2 and the cavity tube 1, the molten aluminum ring plate 31 will fill the entire receiving groove 32 and cannot overflow, thereby achieving a dynamic seal between the sealing plate 2 and the cavity tube 1.

[0034] As the electric heating element 11 is used for a longer period of time, the thickness of the oxide film on the surface of the aluminum ring plate 31 will increase, thereby further improving the sealing effect.

[0035] Reference Figure 2 and Figure 4 The closed end of the cavity tube 1 is bolted with a protective sleeve 15 that is hollow inside and open towards one end of the cavity tube 1. The air guide tube 10 is located inside the protective sleeve 15. Multiple support plates 16 are sleeved on the air guide tube 10. The outer circumferential wall of the support plate 16 abuts against the inner circumferential wall of the protective sleeve 15. The outer side of the protective sleeve 15 is covered with multiple layers of heat insulation 17.

[0036] The casing 15 and the insulation layer 17 on the outside of the casing 15 effectively prevent heat loss, thereby reducing energy waste and lowering the cost of heating the gas medium.

[0037] Reference Figure 3 and Figure 4 One end of the electric heating tube 11 passes through the sealing plate 2 behind the air guide tube 10, and a sealing element 12 for sealing is arranged between the electric heating tube 11 and the sealing plate 2.

[0038] Reference Figure 3 and Figure 4 The sealing element 12 includes three metal airbags 121 welded to the sealing plate 2. The metal airbags 121 are assembled by welding multiple parts. The metal airbags 121 are made of metal material with a high coefficient of thermal expansion. The three metal airbags 121 are located in the air inlet chamber 5, the transfer chamber 6 and the air outlet chamber 7 respectively. The interior of the metal airbags 121 is hollow. The metal airbags 121 have mounting holes 122 through which the power supply heating tube 11 passes. The mounting holes 122 are not connected to the interior of the metal airbags 121.

[0039] Reference Figure 3 and Figure 4 The wall thickness of the metal airbag 121 on both sides along the axial direction of the cavity tube 1 is greater than the wall thickness of the metal airbag 121 in the circumferential direction. When the metal airbag 121 is heated and expanded, the outer circumferential wall of the metal airbag 121 is used to abut against the cavity tube 1 and the partition 4.

[0040] When the gas medium transfers heat to the metal airbag 121, the gas inside the metal airbag 121 will expand. Since the circumferential wall thickness of the metal airbag 121 is less than the wall thickness on both sides along the axis of the cavity tube 1, the metal airbag 121 will expand outward in its circumferential direction.

[0041] The circumferentially expanding metal airbag 121 abuts against the circumferential inner wall of the cavity tube 1 and the surface of the partition 4, thereby completely separating and sealing the air inlet chamber 5, the transfer chamber 6 and the air outlet chamber 7. At the same time, the wall thickness at the mounting hole 122 of the metal airbag 121 expands and wraps around the electric heating tube 11, thereby achieving a sealing effect between the electric heating tube 11 and the metal airbag 121.

[0042] Reference Figure 5 There is a gap between the outer circumferential wall of the electric heating tube 11 and the inner circumferential wall of the air guide tube 10, and a support member 13 for supporting the electric heating tube 11 is arranged on the air guide tube 10.

[0043] Reference Figure 5 The support member 13 includes a strap 131 and a center strip 132. An expansion strip 133 is connected between the two ends of the center strip 132. The length of the expansion strip 133 is greater than the length of the center strip 132. The thermal expansion coefficient of the expansion strip 133 is greater than that of the center strip 132. The strap 131 is arranged at both ends of the center strip 132. Anti-slip texture 14 is arranged on the strap 131. The anti-slip texture 14 is used to abut against the circumferential outer wall of the electric heating tube 11.

[0044] Reference Figure 5 Multiple center spacing strips 132 are evenly arranged along the length of the strap strip 131. Both ends of the strap strip 131 are integrally formed with fastening teeth 134. One end of the strap strip 131 is integrally formed with a folded strip 135, and the other end is welded with a buckle 136. When the folded strip 135 passes through the buckle 136, the fastening teeth 134 at both ends of the strap strip 131 can mesh with each other. The strap strip 131, center spacing strip 132 and expansion strip 133 are all made of metal.

[0045] The installer first loops the strap 131 around the electric heating tube 11, and then passes the folded strip 135 at one end of the strap 131 through the buckle 136 at the other end and bends it. At this time, the fastening teeth 134 at both ends of the strap 131 mesh with each other, and the center strip 132 will stick to the surface of the electric heating tube 11, thus completing the installation of the strap 131.

[0046] During the process of inserting the electric heating tube 11 into the air guide tube 10, the expansion strip 133 can deform to allow the electric heating tube 11 to be inserted smoothly. When the electric heating tube 11 is working, the expansion strip 133 can still deform to adapt to its own thermal deformation, thus always supporting the electric heating tube 11.

[0047] When the installer needs to remove the electric heating element 11, the expansion strip 133 will not lock the electric heating element 11, and the installer can smoothly pull the electric heating element 11 out of the air duct 10, thereby reducing the difficulty and cost of later maintenance.

[0048] The implementation principle of a multi-pass reactor electric heater in this application embodiment is as follows: during the process of gas medium flowing through electric heating tube 11, the gas medium will be heated by electric heating tube 11. As the gas medium flows, the gas medium will transfer heat to cavity tube 1. At this time, cavity tube 1 will transfer heat to aluminum ring plate 31 through heat transfer.

[0049] When the temperature transmitted through the cavity tube 1 is insufficient to melt the aluminum ring plate 31, the thermal expansion of the aluminum ring plate 31 itself will fully fill the entire receiving groove 32, thereby achieving a solid seal between the sealing plate 2 and the cavity tube 1.

[0050] When the transmitted temperature is sufficient to melt the aluminum ring plate 31, due to the constraint of the oxide film on the surface of the aluminum ring plate 31 and the large surface tension of the aluminum ring plate 31 in the molten state, and the small gap between the sealing plate 2 and the cavity tube 1, the molten aluminum ring plate 31 will fill the entire receiving groove 32 and cannot overflow, thereby achieving a dynamic seal between the sealing plate 2 and the cavity tube 1.

[0051] As the electric heating element 11 is used for a longer period of time, the thickness of the oxide film on the surface of the aluminum ring plate 31 will increase, thereby further improving the sealing effect.

[0052] When the gas medium transfers heat to the metal airbag 121, the gas inside the metal airbag 121 will expand. Since the circumferential wall thickness of the metal airbag 121 is less than the wall thickness on both sides along the axis of the cavity tube 1, the metal airbag 121 will expand outward in its circumferential direction.

[0053] The circumferentially expanding metal airbag 121 abuts against the circumferential inner wall of the cavity tube 1 and the surface of the partition 4, thereby completely separating and sealing the air inlet chamber 5, the transfer chamber 6 and the air outlet chamber 7. At the same time, the wall thickness at the mounting hole 122 of the metal airbag 121 expands and wraps around the electric heating tube 11, thereby achieving a sealing effect between the electric heating tube 11 and the metal airbag 121.

[0054] The installer first loops the strap 131 around the electric heating tube 11, and then passes the folded strip 135 at one end of the strap 131 through the buckle 136 at the other end and bends it. At this time, the fastening teeth 134 at both ends of the strap 131 mesh with each other, and the center strip 132 will stick to the surface of the electric heating tube 11, thus completing the installation of the strap 131.

[0055] During the process of inserting the electric heating tube 11 into the air guide tube 10, the expansion strip 133 can deform to allow the electric heating tube 11 to be inserted smoothly. When the electric heating tube 11 is working, the expansion strip 133 can still deform to adapt to its own thermal deformation, thus always supporting the electric heating tube 11.

[0056] When the installer needs to remove the electric heating element 11, the expansion strip 133 will not lock the electric heating element 11, and the installer can smoothly pull the electric heating element 11 out of the air duct 10, thereby reducing the difficulty and cost of later maintenance.

[0057] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An electric heater for a multi-pass reactor, characterized in that: The device includes a cavity tube (1) and a sealing plate (2). The cavity tube (1) is hollow inside and open at one end. The sealing plate (2) is detachably installed at the open end of the cavity tube (1). An airtight component (3) for sealing is provided between the cavity tube (1) and the sealing plate (2). Multiple partitions (4) are provided inside the cavity tube (1), which divide the cavity tube (1) into an inlet chamber (5), a transfer chamber (6), and an outlet chamber (7). An inlet pipe (8) communicating with the inlet chamber (5) and an outlet pipe (9) communicating with the outlet chamber (7) are provided on the cavity tube (1). The inlet chamber (5) and the outlet chamber (7) of the cavity tube (1) are connected to each other. Multiple U-shaped air guide pipes (10) are connected between the transfer chambers (6) and between the transfer chambers (6) and the air outlet chamber (7). Electric heating tubes (11) are inserted into both ends of the U-shaped air guide pipes (10). The end of the electric heating tube (11) facing away from the air guide pipe (10) passes through the sealing plate (2). A sealing element (12) for sealing is provided between the electric heating tube (11) and the sealing plate (2). There is a gap between the outer circumferential wall of the electric heating tube (11) and the inner circumferential wall of the air guide pipe (10). A support element (13) for supporting the electric heating tube (11) is provided on the air guide pipe (10).

2. The electric heater for a multi-pass reactor according to claim 1, characterized in that: The airtight component (3) includes an aluminum ring plate (31) disposed between the open end of the cavity tube (1) and the sealing plate (2), and the sealing plate (2) has a receiving groove (32) for accommodating the aluminum ring plate (31).

3. The electric heater for a multi-pass reactor according to claim 2, characterized in that: The aluminum ring plate (31) undergoes surface oxidation treatment.

4. The multi-pass reactor electric heater according to claim 2, characterized in that: The sealing element (12) includes a metal airbag (121) disposed on the sealing plate (2). The interior of the metal airbag (121) is hollow. The metal airbag (121) has an installation hole (122) for the electric heating tube (11) to pass through. The installation hole (122) is not connected to the interior of the metal airbag (121). The wall thickness of the metal airbag (121) on both sides along the axial direction of the cavity tube (1) is greater than the wall thickness of the metal airbag (121) in the circumferential direction. When the metal airbag (121) expands due to heat, the outer circumferential wall of the metal airbag (121) is used to abut against the cavity tube (1) and the partition plate (4).

5. The multi-pass reactor electric heater according to claim 1, characterized in that: The support member (13) includes a strap (131) and a center strip (132). An expansion strip (133) is connected between the two ends of the center strip (132). The length of the expansion strip (133) is greater than the length of the center strip (132). The strap (131) is arranged at both ends of the center strip (132). Multiple center strips (132) are evenly arranged along the length of the strap (131). Both ends of the strap (131) are provided with fastening teeth (134). One end of the strap (131) is provided with a folded strap (135), and the other end is provided with a buckle (136). When the folded strap (135) passes through the buckle (136), the fastening teeth (134) at both ends of the strap (131) can engage with each other.

6. The electric heater for a multi-pass reactor according to claim 5, characterized in that: The strap (131) is provided with anti-slip texture (14), which is used to abut against the circumferential outer wall of the electric heating tube (11).

7. The multi-pass reactor electric heater according to claim 1, characterized in that: The closed end of the cavity tube (1) is detachably provided with a protective sleeve (15). The air guide tube (10) is located inside the protective sleeve (15). Multiple support plates (16) are sleeved on the air guide tube (10). The outer circumferential wall of the support plate (16) abuts against the inner circumferential wall of the protective sleeve (15).

8. The multi-pass reactor electric heater according to claim 7, characterized in that: The outer side of the casing (15) is covered with multiple layers of insulation (17).

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