Isothermal fixed bed reactor

Abstract

The present invention relates to the field of petrochemical equipment, and discloses an isothermal fixed bed reactor, which comprises: a reaction tube (5) for accommodating a filler and a thermocouple, the side surface of the top end of the reaction tube (5) is provided with a reaction feed pipe (6), and the side surface of the bottom end of the reaction tube (5) is provided with a reaction discharge pipe (16); the heating cylinder (13) is arranged on the peripheral side of the reaction tube (5) in a sleeving manner, an annular hollow heating cavity (14) is formed by the heating cylinder (13) and the reaction tube (5), and the heating cavity (14) is used for filling molten salt; at least one heating rod (12) is arranged in the heating cavity (14) and is used for heating the molten salt; and at least one stirring inert gas pipe (10) is arranged in the heating cavity (14), and a plurality of gas outlet holes (15) are formed in the pipe wall of each stirring inert gas pipe (10) and used for outputting inert gas to promote molten salt to flow so as to accelerate heat exchange.

Description

Technical Field

[0001] This invention relates to the field of petrochemical equipment technology, and more specifically to an isothermal fixed-bed reactor. Background Technology

[0002] Catalysts are crucial in the chemical industry, significantly impacting production capacity. Catalyst performance is primarily evaluated using assessment devices that measure a comprehensive range of indicators, including activity, selectivity, and lifetime. Therefore, improving the reliability of catalyst screening experiments is beneficial for increasing catalyst development efficiency and shortening the development cycle.

[0003] Fixed-bed reactors are key equipment in petrochemical research and experiments, with a wide range of applications, including catalyst evaluation and screening, and application in various types of reactions. Their operating pressures include atmospheric, medium, and high pressure reactions, but all reactions have very strict temperature requirements; typically, the temperature difference within the reaction section must not exceed 1 degree Celsius. Electric heaters, as the main heat source of the reactor, provide heating or insulation to the reaction tubes to achieve the required reaction temperature. Currently, most reactors place heaters on the outer perimeter of the reactor wall, before the reactor, or inside the reaction tubes. During the experiment, the reactor temperature is directly or indirectly raised to the reactants via heaters (heating belts, heating wires, or heat transfer oil) according to the required temperature. This heating method easily leads to localized excessively high or low temperatures and uneven heating, directly affecting the equilibrium of the material reaction and indirectly affecting the accuracy and validity of experimental data. Furthermore, when the reaction stops and the material is discharged for cooling, uneven heating in the reactor can easily cause localized catalyst overheating, carbon buildup, and other damage.

[0004] Chinese invention patent application CN105457559A discloses a high-pressure resistant reaction tube for fixed beds. The reaction tube is made of stainless steel or other metal. A reducing adapter is connected to the upper end of the reaction tube to facilitate the connection of a metal tube of suitable diameter. This metal tube is then connected to the lower end of a three-way adapter. The right end of the three-way adapter is connected to the reaction gas inlet. A straight tube with an external thread structure at its upper end is fixed to the tube, used to fix a thermocouple sheath. The thermocouple sheath passes through the port at the upper end of the three-way adapter, then through the three-way adapter and the reducing adapter at the upper end of the reaction tube, and is inserted into the sample inside the reaction tube. A metal liner of a certain length is installed inside the reaction tube, on which a layer of quartz wool of a certain thickness is placed, and then the catalyst sample is placed on top of the quartz wool. This reaction tube has a simple structure, is easy to disassemble and replace, and is resistant to high pressure and high temperature, making it widely applicable in fixed-bed reactors.

[0005] Chinese utility model patent CN207694759U discloses a reaction tube for a fixed-bed reactor. It includes a transparent reaction tube body and a transparent heat-conducting sleeve fitted over the transparent reaction tube body. The transparent heat-conducting sleeve has a cavity for containing heat-conducting oil. An oil inlet pipe is connected to the lower end of the transparent heat-conducting sleeve, and an oil outlet pipe is connected to the upper end. A detachable heating rod is mounted on the transparent heat-conducting sleeve and extends into the cavity. The upper part of the transparent reaction tube body has a feed inlet, the lower part has a discharge outlet, and the middle part of the transparent reaction tube body has a constriction. An air inlet pipe is connected to the upper end of the transparent reaction tube body. This invention, through the transparent reaction tube body and the transparent heat-conducting sleeve, allows for real-time monitoring of the reaction state of the substances within the transparent reaction tube body. Simultaneously, the transparent heat-conducting sleeve, which allows for continuous injection of heat-conducting oil, provides uniform heat to the transparent reaction tube body, ensuring rapid heat supply or rapid heat dissipation during the reaction process.

[0006] Chinese utility model patent CN208474690U discloses a high-pressure reaction tube. The device includes a titanium alloy reaction tube, an inner liner, and a sealed air inlet unit. The titanium alloy reaction tube is a hollow structure open at both ends. The inner liner, also open at both ends, passes through the titanium alloy reaction tube. The sealed air inlet unit is fixedly installed at one end of the titanium alloy reaction tube and has an air inlet chamber. The chamber wall of the air inlet chamber has an air inlet through-hole and a connecting through-hole. One end of the inner liner passes through the connecting through-hole and extends into the air inlet chamber, with the outer wall of the inner liner sealingly fitting against the wall of the connecting through-hole. This high-pressure reaction tube's titanium alloy reaction tube is less likely to react with reactants, exhibits high pressure resistance, and good stability. The gap between the inner liner and the titanium alloy reaction tube does not require sealing, there is no pressure difference between the inside and outside of the inner liner, and no pressure balancing component is needed. The structure is simple, assembly is convenient, and production costs are low.

[0007] Chinese invention patent application CN110260989A discloses a temperature-regulating device, system, and method for a fixed-bed reactor. The device includes a robotic arm and a lifting device. The robotic arm is horizontally arranged to grip or release thermocouples, and the lifting device is connected to the robotic arm and drives it to move upward or downward. This temperature-regulating device is compact in structure and flexible and convenient to use. The temperature-regulating system can move the thermocouples up and down in the fixed-bed reactor to measure the temperature, thereby controlling the reaction temperature of the fixed-bed reactor. The entire process is safe, accurate, and convenient.

[0008] The aforementioned existing patented technologies mainly focus on technical modifications to the reaction tubes in microreactor evaluation devices, emphasizing improvements in corrosion resistance, high-pressure airtightness, and ease of control. The technical solutions mentioned above rarely address reactor temperature uniformity control and cannot effectively solve the problem of material temperature uniformity in the reactor.

[0009] Therefore, optimizing the reactor heater structure to ensure uniform heating of materials, balanced material reaction within the reactor, improve the validity of experimental data, and ensure catalyst activity is of great significance. Summary of the Invention

[0010] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide an isothermal fixed-bed reactor. This device heats molten salt through heating rods. The uniformly heated molten salt transfers heat to the reaction tube, so that all points in the reaction tube are heated evenly and the reaction is balanced, effectively preventing local temperatures from being too high or too low due to uneven heating of the reaction tube.

[0011] To achieve the above objectives, the present invention provides an isothermal fixed-bed reactor, comprising: A reaction tube is used to contain the filling material and thermocouples. A reaction feed pipe is provided on the top side of the reaction tube and a reaction discharge pipe is provided on the bottom side of the reaction tube. A heating cylinder is sleeved on the outer periphery of the reaction tube and forms an annular hollow heating cavity therebetween, the heating cavity being used to fill molten salt; A heating rod, at least one of the heating rods is disposed in the heating chamber for heating molten salt; A stirring inert gas tube is provided inside the heating chamber. At least one stirring inert gas tube is provided inside the heating chamber. The stirring inert gas tube has several gas outlet holes on its tube wall for outputting inert gas to promote the flow of molten salt and accelerate heat exchange.

[0012] Preferably, it further includes an upper support frame inserted downward from the top of the reaction tube, the top of the upper support frame being fastened to the top of the reaction tube by an upper clamping nut, and an upper support plate being fixed to the bottom of the upper support frame.

[0013] Preferably, it further includes a lower support frame inserted upward from the bottom end of the reaction tube, the bottom end of the lower support frame being fastened to the bottom end of the reaction tube by a lower clamping nut, and a lower support plate being fixed to the top end of the lower support frame.

[0014] Preferably, the upper support plate has a plurality of through holes arranged in a circular array, and / or the lower support plate has a plurality of through holes arranged in a circular array.

[0015] Preferably, the outer wall of the upper clamping nut is provided with heat dissipation fins, and / or the outer wall of the lower clamping nut is provided with heat dissipation fins.

[0016] Preferably, the upper support frame has a flange at its top and a first sealing ring is provided at the connection between the upper support frame and the top of the reaction tube, and / or, the lower support frame has a flange at its bottom and a second sealing ring is provided at the connection between the lower support frame and the bottom of the reaction tube.

[0017] Preferably, the heating chamber further includes an inert gas inlet pipe and an inert gas outlet pipe inserted from the top of the heating chamber to its bottom, wherein the bottom end of the inert gas inlet pipe is connected to the bottom end of the inert gas outlet pipe.

[0018] Preferably, the inert gas inlet pipe and the inert gas outlet pipe are in multiple sets, and the multiple sets of inert gas inlet pipes and the inert gas outlet pipes are distributed in a ring-shaped array at equal intervals around the axis of the heating chamber.

[0019] Preferably, the reaction tube is coaxially arranged with the heating cylinder.

[0020] Preferably, the heating rod extends along the length of the heating cavity, and there are multiple heating rods, which are distributed in a ring-shaped array at equal intervals around the axis of the heating cavity.

[0021] Preferably, there are multiple stirring inert gas tubes, which are arranged in a ring-shaped array at equal intervals around the axis of the heating chamber.

[0022] Preferably, the top of the heating cylinder is provided with a detachable jacketed flat cover.

[0023] Preferably, the jacket cover is provided with a pressure relief hole for discharging inert gas during stirring.

[0024] Preferably, a molten salt discharge port is provided on the bottom side of the heating cylinder, and a switch valve is installed at the molten salt discharge port.

[0025] Preferably, the molten salt is one or a mixture of two or more of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate, potassium sulfate, alkaline earth metal halides, nitrates, and sulfates; and the inert gas is one or a mixture of two or more of nitrogen, helium, and argon.

[0026] The above technical solution heats the molten salt with a heating rod, and the uniformly heated molten salt transfers heat to the reaction tube, ensuring that all points in the reaction tube are heated evenly and the reaction is balanced. This effectively prevents local temperatures from being too high or too low due to uneven heating of the reaction tube. By setting the input of stirring inert gas, the molten salt is stirred evenly, which accelerates the heat transfer efficiency. Attached Figure Description

[0027] Figure 1 This is a cross-sectional structural diagram of an isothermal fixed-bed reactor according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the upper or lower support plate of an isothermal fixed-bed reactor according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures 1-Upper clamping nut; 2-First sealing ring; 3-Upper support frame; 4-Upper support plate; 5-Reaction tube; 6-Reaction feed pipe; 7-Pressure relief hole; 8-Jacket flat cover; 9-Inert gas inlet pipe; 10-Stirring inert gas pipe; 11-Inert gas outlet pipe; 12-Heating rod; 13-Heating cylinder; 14-Heating chamber; 15-Gas outlet; 16-Reaction discharge pipe; 17-Lower support plate; 18-Lower support frame; 19-Lower clamping nut; 20-Second sealing ring; 21-Heat dissipation fins; 22-Molten salt discharge port. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0030] See Figure 1 As shown, an isothermal fixed-bed reactor according to the present invention includes a reaction tube 5, a heating cylinder 13, a heating rod 12, and a stirring inert gas tube 10. The middle part of the reaction tube 5 is a cylindrical hollow structure, and both the upper and lower ends of the reaction tube 5 are conical sections. The top end of the upper conical section of the reaction tube 5 is provided with a pipe section with a diameter smaller than that of the middle part, and a reaction feed pipe 6 is provided laterally extending from the side wall of this pipe section. The bottom end of the lower conical section of the reaction tube 5 is provided with a pipe section with the same diameter smaller than that of the middle part, and a reaction discharge pipe 16 is provided laterally extending from the side wall of this pipe section. The reaction tube 5 is filled with packing material and thermocouples. The packing material is inert packing material, catalyst, and adsorbent, etc. The reaction feed pipe 6 is used for inputting the packing material, and the reaction discharge pipe 16 is used for outputting the packing material. Both the reaction feed pipe 6 and the reaction discharge pipe 16 are connected to process pipelines. A heating cylinder 13 is sealed around the outer periphery of the reaction tube 5, forming an annular hollow heating chamber 14 between them. The heating chamber 14 is used to fill molten salt. At least one heating rod 12 is installed inside the heating chamber 14 to heat the molten salt. The heating rod 12 is connected to an external power source, and the number of heating rods 12 is determined based on the volume of the reaction tube 5 and the heating requirements. At least one stirring inert gas pipe 10 is installed inside the heating chamber 14. Several vent holes 15 are formed on the wall of the stirring inert gas pipe 10, which are used to output inert gas into the molten salt to promote its flow and accelerate heat exchange. The molten salt is heated by heating rod 12, and the uniformly heated molten salt transfers heat to the reaction tube 5, ensuring that all points in the reaction tube 5 are heated evenly and the reaction is balanced. This effectively prevents local overheating or underheating caused by uneven heating of the reaction tube 5. By setting the input of stirring inert gas, the molten salt is stirred evenly, which accelerates the heat transfer efficiency. If overheating or excessive temperature occurs during the reaction, it can be rectified by reducing the power of heating rod 12 or increasing the heat transfer of inert gas.

[0031] In the above embodiments, the molten salt is preferably one or a mixture of two or more alkali metal and alkaline earth metal halides, nitrates, and sulfates, such as sodium chloride, potassium chloride, potassium nitrate, sodium nitrate, and potassium sulfate. When the molten salt is a mixture of two or more substances, the proportions of each substance are determined according to actual needs and are not limited here. The preferred operating temperature of the molten salt is 100℃-800℃, which can be widely used in fixed-bed reactors and has high practical value and application prospects. The heating rods 12 extend along the length of the heating chamber 14. When there are multiple heating rods 12, they are arranged in a ring-shaped array with equal intervals around the axis of the heating chamber 14. Through the above-mentioned arrangement of the heating rods 12, the uniformity of heating the molten salt around the reaction tube 5 is significantly improved. The stirring inert gas tube 10 extends into the heating chamber 14 from the side wall below the top conical section of the reaction tube 5. The main body of the stirring inert gas tube 10 extends along the length of the heating chamber 14. When there are multiple stirring inert gas tubes 10, they are arranged in a ring-shaped array with equal intervals around the axis of the heating chamber 14. The number of stirring inert gas tubes 10 and heating rods 12 are equal and they are set one-to-one. Through this multi-point layout, it is ensured that the inert gas used for stirring is evenly agitated by the stirring inert gas tubes 10 to fully disturb the heated molten salt around the heating rods 12, which significantly improves the fluidity of the heated molten salt and accelerates the efficiency of heat exchange.

[0032] See Figure 1 As shown, in a preferred embodiment of the present invention, an upper support frame 3 is inserted downward from the top of the reaction tube 5, and a lower support frame 18 is inserted upward from the bottom of the reaction tube 5. The top of the upper support frame 3 is fastened to the top of the reaction tube 5 by a threaded connection of an upper clamping nut 1. An upper support plate 4 is fixed to the bottom of the upper support frame 3, and the bottom of the lower support frame 18 is fastened to the bottom of the reaction tube 5 by a threaded connection of a lower clamping nut 19. A lower support plate 17 is fixed to the top of the lower support frame 18. Preferably, the upper support frame 3 and the lower support frame 18 are arranged opposite each other, and the axes of the upper support frame 3 and the lower support frame 18 are both coaxial with the axis of the reaction tube 5. This arrangement significantly improves the stability of the upper support frame 3 and the lower support frame 18 in fixing the internal filling material and thermocouple of the reaction tube 5, and ensures the uniformity of the force on the upper support frame 3 and the lower support frame 18.

[0033] See Figure 2As shown, in the above embodiment, the upper support plate 4 has a plurality of through holes arranged in a ring array, and / or the lower support plate 17 has a plurality of through holes arranged in a ring array. The through holes in both the upper and lower support plates 4 and 17 are circular holes, and their number is determined according to the volume of the reaction tube 5. By setting the through holes, the reactants in the reaction tube 5 are supported while facilitating their smooth passage. Preferably, the through holes on the upper support plate 4 and the lower support plate 17 are equally spaced, thereby improving the uniformity of the reactant flow.

[0034] See Figure 1 As shown, in a preferred embodiment of the present invention, the outer wall of the upper clamping nut 1 is provided with heat dissipation fins 21, and / or the outer wall of the lower clamping nut 19 is provided with heat dissipation fins 21. The heat dissipation fins 21 are radially extending sheet-like structures, which can be configured as a whole annular sheet-like structure or as multiple segmented sheet-like structures. By providing heat dissipation fins 21, the upper clamping nut 1 and the lower clamping nut 19 are effectively cooled, preventing damage to the equipment due to excessive temperature. To ensure the mechanical strength of the upper clamping nut 1 and the lower clamping nut 19, the heat dissipation fins 21 on their outer walls are integrally formed structures.

[0035] In the above embodiment, the upper support frame 3 has a flange at its top and a first sealing ring 2 is provided at the connection with the top of the reaction tube 5, and / or, the lower support frame 18 has a flange at its bottom and a second sealing ring 20 is provided at the connection with the bottom of the reaction tube 5. Both the first sealing ring 2 and the second sealing ring 20 are preferably O-rings. By providing the first sealing ring 2 and the second sealing ring 20, the sealing performance at the connection between the upper clamping nut 1 and the reaction tube 5 is significantly improved, and the sealing performance at the connection between the lower clamping nut 19 and the reaction tube 5 is significantly improved, effectively preventing the leakage of reactant materials.

[0036] See Figure 1As shown, in a preferred embodiment of the present invention, an inert gas inlet pipe 9 and an inert gas outlet pipe 11 are inserted from the top to the bottom of the heating chamber 14. The bottom ends of the inert gas inlet pipe 9 and the inert gas outlet pipe 11 are connected. Multiple sets of inert gas inlet pipes 9 and 11 are arranged in a ring-shaped, equally spaced array around the axis of the heating chamber 14. Preferably, the inert gas inlet pipes 9 are fitted against the inner wall of the heating chamber 14, and the inert gas outlet pipes 11 are fitted against the outer wall of the heating chamber 14. The number of inert gas inlet pipes 9 and 11 is equal to the number of heating rods 12 and they are arranged in a one-to-one correspondence. The heating rods 12 and the stirring inert gas tube 10 are both located within the space between the inert gas inlet pipes 9 and 11. By setting an inert gas inlet pipe 9 and an inert gas outlet pipe 11, when the reaction in the isothermal fixed bed reactor stops or ends, the heating rod 12 stops working, inert gas is introduced into the inert gas inlet pipe 9 and discharged through the inert gas outlet pipe 11, and inert gas is introduced into the stirring inert gas pipe 10, which can achieve rapid and uniform cooling of the reactor. This can prevent local overheating of the catalyst in the reaction tube due to shutdown and material interruption, which can cause damage such as overheating, carbon buildup, and sintering.

[0037] In the preferred embodiment described above, the inert gas introduced into the inert gas inlet pipe 9, the inert gas outlet pipe 11, and the stirring inert gas pipe 10 is one or a mixture of two or more of nitrogen, helium, and argon. Specifically, when the inert gas is a mixture of two or more, the proportion of each gas is determined according to actual needs.

[0038] See Figure 1 As shown, in a preferred embodiment of the present invention, to facilitate the addition and replenishment of molten salt, a detachable jacketed flat cover 8 is provided at the top of the heating cylinder 13. The jacketed flat cover 8 can be connected to the top of the heating cylinder 13 by means of threaded connection or plug-in connection. In addition, the jacketed flat cover 8 facilitates the maintenance and replacement of components such as the heating rod 12 in the heating chamber 14 when the heating rod 12 in the heating chamber 14 fails. In order to maintain the pressure stability inside the heating chamber 14, a pressure relief hole 7 for discharging stirring inert gas is provided on the jacketed flat cover 8. The pressure relief hole 7 can be connected to a right-angle elbow, and the stirring inert gas is discharged from the pressure relief hole 7. The pressure relief hole 7 can be connected to a process venting pipeline. To facilitate the removal and replacement of molten salt, a molten salt discharge port 22 is provided on the bottom side of the heating cylinder 13. A switch valve is installed on the molten salt discharge port 22. The switch valve is used to open and close the molten salt discharge port 22. The switch valve can be set as a manual ball valve, thereby significantly reducing the processing cost of the device.

[0039] In the preferred embodiment described above, to ensure the stability of the temperature within the heating chamber 14 in real time, a temperature sensor can be installed in the heating chamber 14. The temperature sensor monitors and provides real-time feedback on the temperature within the heating chamber 14. When the temperature is too low, the controller controls the heating rod 12 to increase the temperature; when the temperature is too high, the heating rod 12 is stopped, and the inert gas inlet pipe 9, inert gas outlet pipe 11, and stirring inert gas pipe 10 are controlled to exhaust gas and cool the chamber. To ensure uniform heating of the reaction tube 5, the reaction tube 5 is coaxially arranged with the heating cylinder 13.

[0040] In the preferred embodiment described above, to maintain the stability of the inert gas input to the inert gas inlet pipe 9 and the stirring inert gas pipe 10, a gas pump and a gas source are provided at the input ends of both. To control the flow rate and volume of the inert gas input, solenoid valves can also be installed on the inert gas inlet pipe 9 and the stirring inert gas pipe 10. To improve the corrosion resistance of the reaction tube 5 and the heating cylinder 13, the reaction tube 5 is preferably made of stainless steel or other metal materials, and the heating cylinder 13 is preferably made of stainless steel or other metal materials. The heating cylinder 13 can be fixed to the outer wall of the reaction tube 5 by welding.

[0041] In the preferred embodiment described above, in order to ensure the uniformity of the exhaust gas from the outlet 15 of the stirring inert gas tube 10 into the molten salt, the multiple outlets 15 can all be set as round holes, and the multiple outlets 15 are spirally wound around the axis of the main body of the stirring inert gas tube 10 on its side wall. The spiral winding layout can be a single spiral or a double spiral structure, thereby increasing the distribution density of the outlets 15.

[0042] In the description of this invention, the terms "front," "rear," "upper," and "lower" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An isothermal fixed-bed reactor, characterized in that, include: The reaction tube (5) is used to contain the filling material and thermocouple. The top side of the reaction tube (5) is provided with a reaction feed pipe (6) and the bottom side is provided with a reaction discharge pipe (16). Heating cylinder (13), which is sleeved on the outer periphery of the reaction tube (5) and forms an annular hollow heating cavity (14) therewith, the heating cavity (14) is used to fill molten salt; A heating rod (12) is provided in the heating chamber (14) for heating molten salt; Stirring inert gas tube (10), at least one stirring inert gas tube (10) is provided in the heating chamber (14), and several gas outlet holes (15) are opened on the tube wall of the stirring inert gas tube (10) to output inert gas to promote the flow of molten salt to accelerate heat exchange.

2. The isothermal fixed-bed reactor according to claim 1, characterized in that, It also includes an upper support frame (3) inserted downward from the top of the reaction tube (5), the top of the upper support frame (3) being fastened to the top of the reaction tube (5) by an upper clamping nut (1), and an upper support plate (4) being fixed to the bottom of the upper support frame (3).

3. The isothermal fixed-bed reactor according to claim 2, characterized in that, It also includes a lower support frame (18) inserted upward from the bottom end of the reaction tube (5). The bottom end of the lower support frame (18) is fastened to the bottom end of the reaction tube (5) by a lower clamping nut (19). The top end of the lower support frame (18) is fixed with a lower support plate (17).

4. The isothermal fixed-bed reactor according to claim 3, characterized in that, The upper support plate (4) has a plurality of through holes arranged in a ring array, and / or the lower support plate (17) has a plurality of through holes arranged in a ring array.

5. The isothermal fixed-bed reactor according to claim 3, characterized in that, The outer wall of the upper clamping nut (1) is provided with heat dissipation fins (21), and / or the outer wall of the lower clamping nut (19) is provided with heat dissipation fins (21).

6. The isothermal fixed-bed reactor according to claim 3, characterized in that, The upper support frame (3) has a flange at its top and a first sealing ring (2) is provided at the connection between the upper support frame (3) and the top of the reaction tube (5), and / or, the lower support frame (18) has a flange at its bottom and a second sealing ring (20) is provided at the connection between the lower support frame (18) and the bottom of the reaction tube (5).

7. The isothermal fixed-bed reactor according to claim 1, characterized in that, It also includes an inert gas inlet pipe (9) and an inert gas outlet pipe (11) inserted from the top of the heating chamber (14) to its bottom, with the bottom end of the inert gas inlet pipe (9) connected to the bottom end of the inert gas outlet pipe (11).

8. The isothermal fixed-bed reactor according to claim 7, characterized in that, The inert gas inlet pipe (9) and the inert gas outlet pipe (11) are in multiple sets, and the multiple sets of the inert gas inlet pipe (9) and the inert gas outlet pipe (11) are distributed in a ring-shaped array at equal intervals around the axis of the heating chamber (14).

9. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, The reaction tube (5) is coaxially arranged with the heating cylinder (13).

10. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, The heating rod (12) extends along the length of the heating cavity (14). There are multiple heating rods (12), and the multiple heating rods (12) are distributed in a ring-shaped array with equal intervals around the axis of the heating cavity (14).

11. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, There are multiple stirring inert gas tubes (10), and the multiple stirring inert gas tubes (10) are distributed in a ring-shaped array at equal intervals around the axis of the heating chamber (14).

12. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, The top of the heating cylinder (13) is provided with a detachable jacket cover (8).

13. The isothermal fixed-bed reactor according to claim 12, characterized in that, The jacket flat cover (8) is provided with a pressure relief hole (7) for stirring and discharging inert gas.

14. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, The bottom side of the heating cylinder (13) is provided with a molten salt discharge port (22), and the molten salt discharge port (22) is equipped with a switch valve.

15. The isothermal fixed-bed reactor according to any one of claims 1 to 8, characterized in that, The molten salt is one or a mixture of two or more of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate, potassium sulfate, alkaline earth metal halides, nitrates, and sulfates; the inert gas is one or a mixture of two or more of nitrogen, helium, and argon.

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