A resistive salt bath heater, a manufacturing method and a use method

Abstract

The present invention discloses a resistive salt bath heater, a manufacturing method and a use method, comprising a double-layer cylinder assembly, wherein the inner cavity of the double-layer cylinder assembly is provided with a coil assembly, and the inner cavity of the double-layer cylinder assembly is filled with molten salt; an explosion-proof heating core assembly is arranged on the double-layer cylinder assembly; a first metal tubular electric heating element is distributed in a ring shape on the outer side of the double-layer cylinder assembly. In the present invention, molten salt is used as a heat transfer carrier, the temperature difference between the cold source / heat source heat exchange surface is small, and the temperature field is uniform, which solves the problems of medium decomposition caused by uneven temperature field of heater equipment and local overheating, high product impurity rate, low production efficiency and high production cost, and can be widely used in many explosive gas / dust environments, has no safety hazards, and meets the needs of safe production.

Description

Technical Field

[0001] The present invention belongs to the technical field of heating equipment, and in particular relates to a resistive salt bath heater, a manufacturing method and a use method. Background Art

[0002] Currently in the fields of polysilicon photovoltaics and silane specialty gases, liquid silane needs to be heated, vaporized and superheated during the production process to generate silane gas that meets the process temperature requirements. In the field of specialty amine preparation, specialty amines need to be heated during the production process to reach the conditional temperature required by the process.

[0003] All of the above working conditions have the following common requirements: 1. The equipment uses clean energy electric heating; 2. The working temperature is high and the pressure is high; 3. The cleanliness of the heating medium is required to be high; 4. The heating medium is temperature sensitive and will decompose if it is slightly overheated, so the temperature control accuracy of the heat exchange surface it contacts is required to be high; 5. The temperature field is required to be evenly distributed; 6. The equipment requires low flow resistance; 7. The equipment needs to be used in explosive gas environments; 8. It needs to be easy to repair. Even if the heater fails, it can be repaired online without shutting down the production line and returning to the factory for repair;

[0004] At present, the mainstream heaters on the market cannot meet the above 8 requirements at the same time, especially the uneven temperature field and the large temperature difference between the heat exchange surface and the medium, which leads to partial decomposition of materials in the production process, high product impurity rate, and the need for secondary purification. The production efficiency is low and the production cost increases. For this reason, we propose a resistive salt bath heater, a manufacturing method and a use method. Summary of the invention

[0005] The object of the present invention is to provide a resistive salt bath heater, a manufacturing method and a use method to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a resistive salt bath heater, comprising:

[0007] A double-layer cylinder assembly, wherein the inner cavity of the double-layer cylinder assembly is provided with a coil assembly, and the inner cavity of the double-layer cylinder assembly is filled with molten salt;

[0008] An explosion-proof heating core assembly, wherein the explosion-proof heating core assembly is arranged on the double-layer cylinder assembly;

[0009] A first metal tubular electric heating element is distributed in an annular shape on the outside of the double-layer cylinder assembly.

[0010] Preferably, the double-layer cylinder assembly comprises an outer cylinder and an inner cylinder;

[0011] An internal cavity is formed between the outer cylinder and the inner cylinder. Sealing plates are provided at the upper ends of the outer cylinder and the inner cylinder. A molten salt filling port and an exhaust port are provided on the sealing plates.

[0012] Preferably, a molten salt viewing window is provided on the outer side of the upper portion of the outer cylinder.

[0013] Preferably, the outer cylinder is provided with a coil temperature measuring sleeve extending into the internal cavity, and the coil temperature measuring sleeve is provided with a coil temperature measuring thermocouple.

[0014] Preferably, a cylinder base is provided at the bottom of the outer cylinder and the inner cylinder, symmetrically distributed hanging ears are provided on the outside of the outer cylinder, and a nameplate bracket is also provided on the outside of the outer cylinder.

[0015] Preferably, the coil assembly is arranged in an internal cavity between the outer cylinder and the inner cylinder;

[0016] The coil assembly comprises a coil body, a medium inlet port to be heated and a heating medium outlet port;

[0017] The coil body is arranged in the inner cavity between the outer cylinder and the inner cylinder through a coil support, the heated medium inlet port is arranged at the lower part of the outer cylinder and communicates with the coil body, and the heating medium outlet port is arranged at the upper part of the outer cylinder and communicates with the coil body;

[0018] The heating medium discharge port is provided with a heating medium temperature measuring thermocouple.

[0019] Preferably, the explosion-proof heating core assembly comprises an explosion-proof junction box, a heating core barrel and a second metal tubular electric heating element;

[0020] The explosion-proof junction box is connected to the heating core cylinder, the heating core cylinder is arranged inside the inner cylinder, and the explosion-proof junction box is arranged at the upper ends of the outer cylinder and the inner cylinder;

[0021] The second metal tubular electric heating elements are distributed in an annular shape on the outer periphery of the heating core barrel body through fixing tie bands, and limiting round steels arranged on the outer periphery of the heating core barrel body are arranged between the second metal tubular electric heating elements distributed in an annular shape.

[0022] Preferably, thermal insulation cotton is arranged on the outer cylinder, the heating core cylinder and the cylinder base.

[0023] A method for manufacturing a resistive salt bath heater comprises the following steps:

[0024] A1. Making explosion-proof heating core components:

[0025] The explosion-proof junction box, the heating core barrel, the second metal tubular electric heating element and the limiting round steel are manufactured in sequence;

[0026] Fill the heating core cylinder with heat-insulating cotton, weld and fix the explosion-proof junction box and the heating core cylinder, weld the limiting round steel in a ring shape with equal intervals on the outer periphery of the heating core cylinder, then install the second metal tubular electric heating element in a ring shape between the limiting round steels on the outer periphery of the heating core cylinder, and fix it with a cable tie, and fix the electrical terminal of the second metal tubular electric heating element in the explosion-proof junction box;

[0027] A2. Make double-layer cylinder assembly and coil assembly:

[0028] The outer cylinder, the inner cylinder, the sealing plate, the molten salt filling port, the exhaust port, the molten salt viewing window, the coil temperature measuring sleeve, the cylinder base, the lifting lug, the nameplate bracket, the coil body, the inlet port for the medium to be heated, the outlet port for the heating medium and the supporting parts are manufactured in sequence;

[0029] Install the coil body on the outer periphery of the inner cylinder through the support, and connect the inlet port of the medium to be heated and the outlet port of the heating medium to the two ports of the coil body respectively, then install the outer cylinder on the outside of the coil body, and install the sealing plate, molten salt filling port, exhaust port, molten salt viewing window, coil temperature measuring sleeve, cylinder base, lifting lug and nameplate bracket on the outer cylinder, then fill the molten salt into the internal cavity between the outer cylinder and the inner cylinder through the molten salt filling port, and vibrate the filling to make it uniform and dense, and observe the molten salt filling height at the molten salt viewing window until the coil body is completely buried;

[0030] A3. Overall assembly:

[0031] Place the explosion-proof heating core assembly in the double-layer cylinder assembly and fix it. Then install the first metal tubular electric heating element in a ring shape on the outside of the double-layer cylinder assembly. Fix the electrical terminal of the first metal tubular electric heating element in the explosion-proof junction box. Install insulation cotton on the outer cylinder, heating core cylinder and cylinder base. Then install the coil temperature measuring thermocouple and heating medium temperature measuring thermocouple, and install the equipment nameplate on the nameplate bracket. The production is completed.

[0032] A method for using a resistive salt bath heater comprises the following steps:

[0033] B1: The heater equipment is transported to the site and hoisted onto the civil engineering foundation using the lifting lugs. After the equipment is installed, observe the amount of molten salt filled through the molten salt viewing window. If the molten salt does not cover the molten salt viewing window, fill the molten salt at the molten salt filling port until the molten salt covers the molten salt viewing window. Test the electrical performance of the heater equipment, set the operating parameters of the heater equipment, turn on the power of the equipment, and the equipment starts working.

[0034] B2: The first metal tubular electric heating element and the second metal tubular electric heating element generate heat as heat sources, and the heat is transferred to the outer cylinder and the inner cylinder in the form of heat conduction and heat radiation. The inner cavity between the outer cylinder and the inner cylinder is filled with molten salt, and the molten salt buries the coil assembly and completely covers the outer surface of the coil assembly; the heat on the outer cylinder and the inner cylinder is transferred to the molten salt by heat conduction, and the molten salt absorbs heat and melts into liquid as a heat transfer carrier. The temperature field inside the molten salt is uniform through heat convection, and the molten salt transfers heat to the coil assembly;

[0035] B3: The medium to be heated enters the coil body at the medium inlet port, circulates inside the coil body pipe, and finally leaves the coil body at the heating medium outlet port. During this process, the cold source / heat source contacts the inner / outer surface of the coil body, and heat exchange is carried out through the coil body. The heat transfer medium molten salt transfers heat to the coil body, and the coil body then transfers heat to the medium to be heated inside it; at the same time, the power input of the first metal tubular electric heating element and the second metal tubular electric heating element at the heating end is controlled by the signal fed back by the heating medium temperature measuring thermocouple, so that the temperature rise of the medium to be heated meets the process requirements, and the fault chain overheating protection of the entire heater equipment is performed by the signal fed back by the coil temperature measuring thermocouple.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention adopts molten salt as the heat transfer carrier, the temperature difference between the cold source and the heat source heat exchange surface is small, and the temperature field is uniform, which solves the problems of medium decomposition, high product impurity rate, low production efficiency and high production cost caused by uneven temperature field and local overheating of the heater equipment. It can be widely used in many explosive gas / dust environments without potential safety hazards, and meets the needs of safe production;

[0038] 2. The heater device of the present invention has small flow resistance, high design temperature, high design pressure, strong corrosion resistance, and can cope with various high-standard and high-requirement working conditions;

[0039] 3. The flow surface of the heater device of the present invention has high cleanliness, which effectively avoids the pollution of the process medium by the production equipment body from the root;

[0040] 4. The heater equipment of the present invention is easy to maintain, and damaged components can be quickly repaired / replaced online, avoiding on-site shutdowns due to equipment failures, and ensuring stable on-site production operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the main cross-sectional structure of the present invention;

[0042] Figure 2 It is a schematic diagram of a top view and cross-section structure of the present invention;

[0043] Figure 3 It is a schematic diagram of the front cross-sectional structure of the explosion-proof heating core assembly of the present invention;

[0044] Figure 4 It is a schematic diagram of a top view and cross-section structure of an explosion-proof heating core assembly of the present invention;

[0045] Figure 5 It is a schematic diagram of the front and cross-sectional structure of the double-layer cylinder assembly and the coil assembly of the present invention;

[0046] Figure 6 It is a schematic diagram of the top view and cross-section structure of the double-layer cylinder assembly and the coil assembly of the present invention.

[0047] In the figure: 1. Double-layer cylinder assembly; 101. Outer cylinder; 102. Inner cylinder; 103. Sealing plate; 104. Molten salt filling port; 105. Exhaust port; 106. Molten salt viewing window; 107. Coil temperature measuring sleeve; 108. Coil temperature measuring thermocouple; 109. Cylinder base; 110. Lifting ear; 111. Nameplate bracket; 2. Coil assembly; 201. Coil body; 202. Inlet port for medium to be heated; 203. Heating medium outlet port; 204. Coil support; 205. Heating medium temperature measuring thermocouple; 3. Molten salt; 4. Explosion-proof heating core assembly; 401. Explosion-proof junction box; 402. Heating core cylinder; 403. Second metal tubular electric heating element; 404. Fixing tie; 405. Limiting round steel; 5. First metal tubular electric heating element; 6. Insulation cotton. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] See also Figure 1-Figure 6 The resistive salt bath heater provided by the present invention comprises:

[0050] A double-layer cylinder assembly 1, the double-layer cylinder assembly 1 comprises an outer cylinder 101 and an inner cylinder 102; an internal cavity is formed between the outer cylinder 101 and the inner cylinder 102, a sealing plate 103 is provided at the upper ends of the outer cylinder 101 and the inner cylinder 102, a molten salt filling port 104 and an exhaust port 105 are provided on the sealing plate 103, a molten salt viewing window 106 is provided on the outer side of the upper part of the outer cylinder 101, a coil temperature measuring sleeve 107 extending into the internal cavity is provided on the outer cylinder 101, a coil temperature measuring sleeve 107 is provided with a coil temperature measuring thermocouple 108, a cylinder base 109 is provided at the bottom of the outer cylinder 101 and the inner cylinder 102, symmetrically distributed lifting ears 110 are provided on the outer side of the outer cylinder 101, and a nameplate bracket 111 is also provided on the outer side of the outer cylinder 101;

[0051] The inner cavity of the double-layer cylinder assembly 1 is provided with a coil assembly 2, and the coil assembly 2 is arranged in the inner cavity between the outer cylinder 101 and the inner cylinder 102; the coil assembly 2 includes a coil body 201, a heated medium inlet port 202 and a heating medium outlet port 203; the coil body 201 is arranged in the inner cavity between the outer cylinder 101 and the inner cylinder 102 through a coil support 204, the heated medium inlet port 202 is arranged at the lower part of the outer cylinder 101 and communicated with the coil body 201, and the heating medium outlet port 203 is arranged at the upper part of the outer cylinder 101 and communicated with the coil body 201; a heating medium temperature measuring thermocouple 205 is arranged on the heating medium outlet port 203, and the inner cavity of the double-layer cylinder assembly 1 is filled with molten salt 3;

[0052] An explosion-proof heating core assembly 4, the explosion-proof heating core assembly 4 is arranged on the double-layer cylinder assembly 1, and the explosion-proof heating core assembly 4 includes an explosion-proof junction box 401, a heating core cylinder 402 and a second metal tubular electric heating element 403; the explosion-proof junction box 401 is connected to the heating core cylinder 402, the heating core cylinder 402 is arranged on the inner side of the inner cylinder 102, and the explosion-proof junction box 401 is arranged on the upper ends of the outer cylinder 101 and the inner cylinder 102; the second metal tubular electric heating element 403 is distributed in an annular shape on the outer periphery of the heating core cylinder 402 through a fixing tie 404, and a limiting round steel 405 arranged on the outer periphery of the heating core cylinder 402 is arranged between the annularly distributed second metal tubular electric heating elements 403;

[0053] A first metal tubular electric heating element 5, which is distributed in an annular shape on the outside of the double-layer cylinder assembly 1;

[0054] The outer cylinder 101 , the heating core cylinder 402 and the cylinder base 109 are all provided with heat-insulating cotton 6 .

[0055] In the present invention, molten salt 3 is used as a heat transfer carrier, the temperature difference between the cold source / heat source heat exchange surface is small, and the temperature field is uniform, which solves the problems of medium decomposition, high product impurity rate, low production efficiency and high production cost caused by uneven temperature field of heater equipment and local overheating. It can be widely used in many explosive gas / dust environments without potential safety hazards, and meets the needs of safe production.

[0056] The heater device of the present invention adopts the coil assembly 2, which has small flow resistance, high design temperature, high design pressure, strong corrosion resistance, and can cope with various high-standard and high-requirement working conditions;

[0057] The heater device of the present invention has a high degree of cleanliness on the circulation surface, which effectively avoids the pollution of the process medium by the production equipment body from the root;

[0058] The heater device of the present invention is easy to maintain and can quickly repair / replace damaged components online, thus avoiding on-site shutdowns due to equipment failures and ensuring stable on-site production operations.

[0059] The manufacturing method of the resistive salt bath heater provided by the present invention comprises the following steps:

[0060] A1. Making explosion-proof heating core components:

[0061] An explosion-proof junction box 401, a heating core barrel 402, a second metal tubular electric heating element 403 and a limiting round steel 405 are manufactured in sequence;

[0062] Fill the heating core barrel 402 with heat-insulating cotton 6, weld and fix the explosion-proof junction box 401 and the heating core barrel 402, and then weld the limiting round steel 405 to the outer periphery of the heating core barrel 402 in an annular shape with equal intervals, then install the second metal tubular electric heating element 403 in an annular shape between the limiting round steel 405 on the outer periphery of the heating core barrel 402, and fix it with a cable tie, and fix the electrical terminal of the second metal tubular electric heating element 403 in the explosion-proof junction box 401;

[0063] A2. Make double-layer cylinder assembly and coil assembly:

[0064] The outer cylinder 101, the inner cylinder 102, the sealing plate 103, the molten salt filling port 104, the exhaust port 105, the molten salt viewing window 106, the coil temperature measuring sleeve 107, the cylinder base 109, the lifting ear 110, the nameplate bracket 111, the coil body 201, the inlet port 202 for the medium to be heated, the outlet port 203 for the heating medium and the support 204 are manufactured in sequence;

[0065] The coil body 201 is installed on the outer periphery of the inner cylinder 102 through the support 204, and the inlet port 202 for the medium to be heated and the outlet port 203 for the heating medium are connected to the two ports of the coil body 201 respectively, and then the outer cylinder 101 is installed on the outer side of the coil body 201, and the sealing plate 103, the molten salt filling port 104, the exhaust port 105, the molten salt viewing window 106, the coil temperature measuring sleeve 107, the cylinder base 109, the lifting lug 110 and the nameplate bracket 111 are installed on the outer cylinder 101, and then the molten salt 3 is filled into the internal cavity between the outer cylinder 101 and the inner cylinder 102 through the molten salt filling port 104, and the filling is vibrated to be uniform and dense, and the molten salt filling height is observed at the molten salt viewing window 106 until the coil body 201 is completely buried;

[0066] A3. Overall assembly:

[0067] Place the explosion-proof heating core assembly in the double-layer cylinder assembly and fix it. Then install the first metal tubular electric heating element 5 in a ring shape on the outside of the double-layer cylinder assembly 1. Fix the electrical terminal of the first metal tubular electric heating element 5 in the explosion-proof junction box 401. Install the thermal insulation cotton 6 on the outer cylinder 101, the heating core cylinder 402 and the cylinder base 109. Then install the coil temperature measuring thermocouple 108 and the heating medium temperature measuring thermocouple 205, and install the equipment nameplate on the nameplate bracket 111. The production is completed.

[0068] The method for using the resistive salt bath heater provided by the present invention comprises the following steps:

[0069] B1: The heater equipment is transported to the site, and the lifting lug 110 is used to hoist the heater equipment onto the civil engineering foundation. After the equipment is installed, the molten salt filling amount is observed through the molten salt viewing window 106. If the molten salt 3 does not bury the molten salt viewing window 106, the molten salt 3 needs to be filled in the molten salt filling port 104 until the molten salt 3 buries the molten salt viewing window 106. The electrical performance of the heater equipment is tested, the operating parameters of the heater equipment are set, the equipment power is turned on, and the equipment starts working;

[0070] B2: The first metal tubular electric heating element 5 and the second metal tubular electric heating element 403 generate heat as heat sources, and the heat is transferred to the outer cylinder 101 and the inner cylinder 102 in the form of heat conduction and heat radiation. The inner cavity between the outer cylinder 101 and the inner cylinder 102 is filled with molten salt 3, and the molten salt 3 buries the coil assembly 2 and completely covers the outer surface of the coil assembly 3; the heat on the outer cylinder 101 and the inner cylinder 102 is transferred to the molten salt 3 by heat conduction, and the molten salt 3 absorbs heat and melts into liquid as a heat transfer carrier. The temperature field inside the molten salt 3 is uniform through heat convection, and the molten salt 3 transfers heat to the coil assembly 2;

[0071] B3: The medium to be heated enters the coil body 201 at the medium to be heated inlet port 202, circulates inside the pipe of the coil body 201, and finally leaves the coil body 201 at the heating medium outlet port 203. During this process, the cold source / heat source contacts the inner / outer surface of the coil body 201, and heat exchange is performed through the coil body 201. The heat transfer carrier molten salt 3 transfers heat to the coil body 201, and the coil body 201 then transfers heat to the medium to be heated inside it; at the same time, the power input of the first metal tubular electric heating element 5 and the second metal tubular electric heating element 403 at the heating end is controlled by the signal fed back by the heating medium temperature measuring thermocouple 205, so that the temperature rise of the medium to be heated meets the process requirements, and the whole set of heater equipment is protected against fault chain overheating by the signal fed back by the coil temperature measuring thermocouple 108.

[0072] Instructions for online maintenance / replacement of the heater of the present invention:

[0073] 1. Disconnect the power supply of the equipment and cool it down;

[0074] 2. Remove the thermal insulation cotton 6;

[0075] 3. Remove the first metal tubular electric heating element 5, lift out the explosion-proof heating core assembly 4, replace the faulty / damaged second metal tubular electric heating element 403, fasten it with a fixing tie 404, and reinstall the explosion-proof heating core assembly 4;

[0076] 4. Replace the faulty / damaged first metal tubular electric heating element 5;

[0077] 5. Reinstall the insulation cotton 6;

[0078] 6. Check the electrical performance of the equipment. If it is qualified, turn on the power of the equipment and heat it up.

[0079] Features: The process heating medium pipeline valve does not need to be closed, the production line operates normally without stopping production, the equipment (heater) does not need to be returned to the factory, and the first metal tubular electric heating element 5 and the second metal tubular electric heating element 403 can be replaced online.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A resistive salt bath heater, characterized in that: include: A double-layer cylinder assembly (1), wherein the inner cavity of the double-layer cylinder assembly (1) is provided with a coil assembly (2), and the inner cavity of the double-layer cylinder assembly (1) is filled with molten salt (3); An explosion-proof heating core assembly (4), wherein the explosion-proof heating core assembly (4) is arranged on the double-layer cylinder assembly (1); A first metal tubular electric heating element (5), the first metal tubular electric heating element (5) being distributed in an annular shape on the outside of the double-layer cylinder assembly (1); The double-layer cylinder assembly (1) comprises an outer cylinder (101) and an inner cylinder (102); An internal cavity is formed between the outer cylinder (101) and the inner cylinder (102); a sealing plate (103) is provided at the upper ends of the outer cylinder (101) and the inner cylinder (102); and a molten salt filling port (104) and an exhaust port (105) are provided on the sealing plate (103); A molten salt viewing window (106) is provided on the outer side of the upper portion of the outer cylinder (101); The outer cylinder (101) is provided with a coil temperature measuring sleeve (107) extending into the internal cavity, and the coil temperature measuring sleeve (107) is provided with a coil temperature measuring thermocouple (108); The bottoms of the outer cylinder (101) and the inner cylinder (102) are provided with cylinder bases (109); the outer side of the outer cylinder (101) is provided with symmetrically distributed hanging ears (110); and the outer side of the outer cylinder (101) is also provided with a nameplate bracket (111); The coil assembly (2) is arranged in an internal cavity between the outer cylinder (101) and the inner cylinder (102); The coil assembly (2) comprises a coil body (201), an inlet port (202) for a medium to be heated, and a discharge port (203) for a heating medium; The coil body (201) is arranged in an internal cavity between the outer cylinder (101) and the inner cylinder (102) via a coil support (204); the heated medium inlet port (202) is arranged at the lower part of the outer cylinder (101) and is in communication with the coil body (201); and the heating medium outlet port (203) is arranged at the upper part of the outer cylinder (101) and is in communication with the coil body (201); The heating medium discharge port (203) is provided with a heating medium temperature measuring thermocouple (205); The explosion-proof heating core assembly (4) comprises an explosion-proof junction box (401), a heating core barrel (402) and a second metal tubular electric heating element (403); The explosion-proof junction box (401) is connected to the heating core barrel (402), the heating core barrel (402) is arranged inside the inner barrel (102), and the explosion-proof junction box (401) is arranged at the upper ends of the outer barrel (101) and the inner barrel (102); The second metal tubular electric heating elements (403) are distributed in an annular shape on the outer periphery of the heating core barrel (402) via fixing straps (404), and a limiting round steel (405) arranged on the outer periphery of the heating core barrel (402) is arranged between the second metal tubular electric heating elements (403) distributed in an annular shape; The outer cylinder (101), the heating core cylinder (402) and the cylinder base (109) are all provided with thermal insulation cotton (6).

2. The method for manufacturing a resistive salt bath heater according to claim 1, characterized in that: The steps include: A1. Making explosion-proof heating core components: An explosion-proof junction box (401), a heating core barrel (402), a second metal tubular electric heating element (403) and a limiting round steel (405) are manufactured in sequence; Fill the heating core barrel (402) with heat-insulating cotton (6), weld and fix the explosion-proof junction box (401) and the heating core barrel (402), weld the limiting round steel (405) to the outer periphery of the heating core barrel (402) in a circular shape and at equal intervals, then install the second metal tubular electric heating element (403) in a circular shape between the limiting round steels (405) on the outer periphery of the heating core barrel (402), and fix it with a cable tie, and fix the electrical terminal of the second metal tubular electric heating element (403) in the explosion-proof junction box (401); A2. Make double-layer cylinder assembly and coil assembly: The outer cylinder (101), the inner cylinder (102), the sealing plate (103), the molten salt filling port (104), the exhaust port (105), the molten salt viewing window (106), the coil temperature measuring sleeve (107), the cylinder base (109), the lifting lug (110), the nameplate bracket (111), the coil body (201), the inlet port for the medium to be heated (202), the outlet port for the heating medium (203), and the support member (204) are manufactured in sequence; The coil body (201) is installed on the outer periphery of the inner cylinder (102) through the support member (204), and the inlet port (202) for the medium to be heated and the outlet port (203) for the heating medium are connected to the two ports of the coil body (201) respectively. Then, the outer cylinder (101) is installed on the outer side of the coil body (201), and the sealing plate (103), the molten salt filling port (104), the exhaust port (105), the molten salt viewing window (106), the coil temperature measuring sleeve (107), the cylinder base (109), the lifting lug (110) and the nameplate bracket (111) are installed on the outer cylinder (101). Then, the molten salt (3) is filled into the internal cavity between the outer cylinder (101) and the inner cylinder (102) through the molten salt filling port (104), and the filling is vibrated to make it uniform and dense, and the molten salt filling height is observed through the molten salt viewing window (106) until the coil body (201) is completely buried. A3. Overall assembly: The explosion-proof heating core assembly is placed and fixed in the double-layer cylinder assembly, and then the first metal tubular electric heating element (5) is installed in a ring shape on the outside of the double-layer cylinder assembly (1), and the electrical terminal of the first metal tubular electric heating element (5) is fixed in the explosion-proof junction box (401). Insulation cotton (6) is installed on the outer cylinder (101), the heating core cylinder (402) and the cylinder base (109), and then the coil temperature measuring thermocouple (108) and the heating medium temperature measuring thermocouple (205) are installed, and the equipment nameplate is installed on the nameplate bracket (111). The production is completed.

3. The method for using a resistive salt bath heater according to claim 1, characterized in that: The steps include: B1: The heater equipment is transported to the site and is hoisted onto the civil engineering foundation using the lifting lug (110). After the equipment is installed, the amount of molten salt filled is observed through the molten salt viewing window (106). If the molten salt (3) does not cover the molten salt viewing window (106), the molten salt (3) needs to be filled into the molten salt filling port (104) until the molten salt (3) covers the molten salt viewing window (106). The electrical performance of the heater equipment is tested, the operating parameters of the heater equipment are set, the equipment power is turned on, and the equipment starts to work; B2: The first metal tubular electric heating element (5) and the second metal tubular electric heating element (403) act as heat sources to generate heat, which is transferred to the outer cylinder (101) and the inner cylinder (102) in the form of heat conduction and heat radiation. The inner cavity between the outer cylinder (101) and the inner cylinder (102) is filled with molten salt (3), and the molten salt (3) buries the coil assembly (2) and completely covers the outer surface of the coil assembly (3). The heat on the outer cylinder (101) and the inner cylinder (102) is transferred to the molten salt (3) in the form of heat conduction. The molten salt (3) absorbs heat and melts into liquid as a heat transfer carrier. The temperature field inside the molten salt (3) is made uniform through heat convection, and the molten salt (3) transfers heat to the coil assembly (2). B3: The medium to be heated enters the coil body (201) through the medium to be heated inlet port (202), circulates inside the pipe of the coil body (201), and finally leaves the coil body (201) through the heating medium outlet port (203). During this process, the cold source / heat source contacts the inner / outer surface of the coil body (201), and heat exchange is performed through the coil body (201). The heat transfer medium molten salt (3) transfers heat to the coil body (201), and the coil body (201) then transfers heat to the medium to be heated inside it. At the same time, the power input of the first metal tubular electric heating element (5) and the second metal tubular electric heating element (403) at the heating end is controlled by the signal fed back by the heating medium temperature measuring thermocouple (205), so that the temperature rise of the medium to be heated meets the process requirements, and the whole set of heater equipment is protected against fault chain overheating by the signal fed back by the coil temperature measuring thermocouple (108).

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