A gas heating device, a fluidized bed reactor and a method for preparing carbon nanotubes

Abstract

This invention relates to the field of carbon nanotube preparation equipment technology, and particularly to a gas heating device, a fluidized bed reactor, and a method for preparing carbon nanotubes. The gas heating device includes a heating tube through which a carrier gas flows, and a heating component for heating the carrier gas is fitted over the heating tube. This invention provides a fluidized bed reactor with a reasonable overall structure, convenient installation, and good practicality and potential for large-scale promotion. Specifically, this invention uses electromagnetic induction to uniformly heat the entire heating tube, thereby rapidly and stably heating the carrier gas to a set temperature, ensuring a uniform temperature field distribution within the reaction chamber, and effectively improving the consistency of carbon nanotube growth and product quality. Furthermore, by eliminating traditional resistance wire heating, problems such as high-temperature aging and burnout of the resistance wire are avoided. The equipment has no easily damaged parts, resulting in a low failure rate, reduced maintenance costs, and a significantly extended service life.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube preparation equipment technology, and in particular to a gas heating device, a fluidized bed reactor, and a method for preparing carbon nanotubes. Background Technology

[0002] Carbon nanotubes, also known as buckytubes, are one-dimensional quantum materials with a unique structure. Their radial dimensions are on the nanometer scale, and their axial dimensions are on the micrometer scale, with both ends essentially sealed. Since their initial discovery in 1991, carbon nanotubes have attracted significant attention from scientists in materials science, physics, electronics, and chemistry due to their unique structure and excellent mechanical, electrical, and chemical properties, becoming a research frontier and hot topic in the international field of new materials. Currently, significant progress has been made in the research of carbon nanotube properties and preparation methods, with the focus shifting towards their large-scale production and application.

[0003] Fluidized bed reactors are commonly used in the large-scale production of carbon nanotubes. Existing carbon nanotube fluidized bed reactors mostly employ internal or external heating methods with resistance wires, but these methods have the following drawbacks in practical applications:

[0004] 1. Uneven temperature transfer: Resistance wire heating is an external conduction heating method. Heat is transferred to the furnace body through air radiation or contact, which can easily cause uneven temperature field distribution inside the furnace. This results in inconsistent growth rates of carbon nanotubes, large differences in morphology and performance, and affects the stability of product quality.

[0005] 2. Severe equipment wear and tear: The resistance wire is prone to aging and burnout due to long-term operation in a high-temperature environment, resulting in a high failure rate and frequent replacement, which increases equipment maintenance costs and affects production continuity.

[0006] 3. Poor heat preservation and high energy consumption: Traditional reactors lose heat quickly, and a large amount of electricity needs to be continuously consumed to maintain the reaction temperature, resulting in high energy costs.

[0007] 4. Low heating efficiency: Resistance wire heating has a slow heating rate and insufficient temperature control accuracy, making it difficult to quickly respond to the temperature adjustment requirements of the production process and unsuitable for efficient continuous production.

[0008] Therefore, those skilled in the art are dedicated to developing a gas heating device, fluidized bed reactor, and carbon nanotube preparation method with low maintenance costs and long service life. Summary of the Invention

[0009] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a gas heating device, a fluidized bed reactor and a method for preparing carbon nanotubes.

[0010] To achieve the above objectives, the present invention provides a gas heating device, including a heating tube through which a carrier gas flows, and a heating component for heating the carrier gas is provided on the outer sleeve of the heating tube.

[0011] Preferably, the carrier gas is an inert gas.

[0012] Preferably, the heating component has an internal heat-insulating shielding layer.

[0013] Preferably, the heating assembly includes an electromagnetic heating controller, which is electrically connected to an electromagnetic induction coil, the electromagnetic induction coil being spirally wound around the outside of the heating tube.

[0014] Preferably, the winding pitch of the electromagnetic induction coil is 8mm to 15mm, and the winding height is 2500mm to 3000mm.

[0015] Preferably, the electromagnetic induction coil has 250 to 300 turns and a total length of 85 to 150 meters.

[0016] The present invention also provides a fluidized bed reactor, including any of the gas heating devices described above.

[0017] Preferably, it also includes a furnace body with an internal reaction chamber, the furnace body including an inner wall and an outer wall, and a vacuum interlayer is provided between the inner wall and the outer wall.

[0018] Preferably, the outlet of the heating tube is connected to the air inlet of the reaction chamber;

[0019] Preferably, the furnace body is also provided with a catalyst feeding bin, a discharge port, a carbon source gas inlet, and a tail gas outlet.

[0020] The present invention also provides a method for preparing carbon nanotubes using any of the fluidized bed reactors described above, comprising the following steps:

[0021] S1. Carrier gas is introduced into the heating tube;

[0022] S2. Activate the heating assembly to heat the carrier gas to 600℃-800℃;

[0023] S3. Introduce the heated carrier gas into the reaction chamber of the furnace.

[0024] S4. Add a catalyst to the reaction chamber and introduce carbon source gas, so that the carbon source gas reacts under the thermal atmosphere provided by the carrier gas and the action of the catalyst to generate carbon nanotubes.

[0025] The beneficial effects of this invention are as follows: This invention provides a fluidized bed reactor with a reasonable overall structure, convenient installation, and good practicality and potential for large-scale promotion. Specifically, this invention uses electromagnetic induction to make the heating tubes heat up uniformly, thereby rapidly and stably heating the carrier gas to the set temperature, ensuring a uniform temperature field distribution within the reaction chamber, and effectively improving the consistency of carbon nanotube growth and product quality. Secondly, by eliminating traditional resistance wire heating, problems such as resistance wire aging and burnout due to high temperatures are avoided. The equipment has no vulnerable parts, resulting in a low failure rate, reduced maintenance costs, and a significantly extended service life. In addition, this application uses a double-layer vacuum jacket insulation design to significantly reduce heat loss, achieving energy saving while perfectly adapting to the needs of continuous production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the heating component in a specific embodiment of the present invention.

[0027] Figure 2 This is a top view of the heating component in a specific embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of a fluidized bed reactor in a specific embodiment of the present invention.

[0029] Figure 4 This is a flowchart illustrating the preparation process of carbon nanotubes in a specific embodiment of the present invention.

[0030] Figure 5 This is a SEM image of carbon nanotubes produced using a specific embodiment of the present invention.

[0031] 11. Heating tube; 12. Heating assembly; 121. Electromagnetic heating controller; 122. Electromagnetic induction coil; 13. Thermal insulation shielding layer; 21. Furnace body; 22. Reaction chamber; 23. Inner wall; 24. Outer wall; 25. Vacuum jacket; 26. Catalyst feeding bin; 27. Discharge port; 28. Carbon source gas inlet; 29. ​​Tail gas outlet; 31. Gas transmission pipe; 32. Thermal insulation layer. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific manner. Therefore, they should not be construed as limitations on the present invention. Terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] like Figure 1-2 As shown, the present invention provides a gas heating device. The device mainly includes a vertically arranged heating tube 11, which is made of 310S stainless steel with an outer diameter of 100mm-150mm. This material has excellent high-temperature oxidation resistance and corrosion resistance, and is suitable for long-term operation in high-temperature environments.

[0034] The heating tube 11 is a hollow cylindrical shape, with its inner cavity used for the flow of carrier gas, which serves as the heat transfer medium. The carrier gas enters the heating tube 11 through an inlet (not shown in the figure). In this embodiment, an inert gas is selected as the carrier gas, which will not undergo side reactions with the catalyst or reactants at high temperatures, thus helping to maintain the purity and stability of the reaction environment. In specific implementations, nitrogen can be used, and other embodiments may also select argon, helium, etc., according to actual needs.

[0035] A heating assembly 12 is fitted around the heating tube 11. The heating assembly 12 is used to heat the carrier gas flowing through the heating tube 11. In this embodiment, electromagnetic induction is used for heating. Specifically, the heating assembly 12 includes an electromagnetic heating controller 121, which is electrically connected to an electromagnetic induction coil 122. The electromagnetic induction coil 122 is made of high-temperature resistant, high-conductivity copper wire and is tightly wound in a spiral around the outside of the heating tube 11. The winding pitch is 8mm to 15mm, the winding height is 2500mm to 3000mm, the corresponding number of turns is 250 to 300, and the total length is 85m to 150m. In use, the electromagnetic heating controller 121 is activated, and a high-frequency current is supplied to the electromagnetic induction coil 122. The coil generates a rapidly changing magnetic field. The changing magnetic field passes through the heating tube 11, causing eddy currents to be generated inside the heating tube 11. The eddy currents generate heat inside the heating tube 11, thereby rapidly and uniformly heating the carrier gas inside the tube to a preset temperature.

[0036] Furthermore, the heating component 12 is provided with a heat insulation shielding layer 13, which is made of high-temperature resistant heat insulation materials such as ceramic fiber and aerogel. The heat insulation shielding layer 13 has both heat preservation and shielding functions, which can reduce heat loss during the heating process and improve heating efficiency, and also shield electromagnetic radiation to avoid interference with surrounding equipment.

[0037] like Figure 3 As shown, the present invention also provides a fluidized bed reactor, which includes the gas heating device and furnace body 21 as described above. A reaction chamber 22 is provided inside the furnace body 21, and the gas inlet of the reaction chamber 22 is connected to the outlet of the aforementioned heating pipe 11, so that the heated carrier gas can flow into the reaction chamber 22 from the heating pipe 11. In a specific implementation, the reaction chamber 22 and the heating pipe 11 can be connected by a gas supply pipe 31. To prevent heat dissipation from the gas supply pipe 31, an insulation layer 32 can also be wrapped around its exterior.

[0038] The furnace body 21 adopts a vertical double-layer cylindrical structure, and its vertical design is compatible with the aforementioned gas heating device. The double-layer design of the furnace body 21 includes an inner wall 23 and an outer wall 24. The inner wall 23 is the reaction chamber wall, and the outer wall 24 is a protective shell, with a vacuum interlayer 25 between them. This vacuum interlayer 25 can effectively block heat conduction and achieve efficient heat preservation, thereby minimizing heat loss in the reaction chamber 22 and reducing system energy consumption.

[0039] In addition, the furnace body 21 is equipped with multiple functional interfaces, including but not limited to a catalyst feeding chamber 26 for adding catalyst, a carrier gas inlet for introducing carrier gas, a carbon source gas inlet 28 for adding reaction raw materials, a discharge port 27 for discharging products, and a tail gas port 29 located at the top for discharging tail gas. All interfaces are sealed to ensure the airtightness of the reaction chamber 22 during operation.

[0040] The fluidized bed reactor provided by this invention has a reasonable overall structure, is easy to install, and possesses good practicality and potential for large-scale promotion. Specifically, this invention uses electromagnetic induction heating to ensure uniform heating of the heating tube 11, thereby rapidly and stably heating the carrier gas to the set temperature, ensuring a uniform temperature field distribution within the reaction chamber 22, and effectively improving the consistency of carbon nanotube growth and product quality. Secondly, by eliminating traditional resistance wire heating, problems such as high-temperature aging and burnout of the resistance wire are avoided. The equipment has no easily damaged parts, resulting in a low failure rate, reduced maintenance costs, and a significantly extended service life. Furthermore, this application utilizes a double-layer vacuum jacket insulation design to significantly reduce heat loss, achieving energy saving while perfectly adapting to the needs of continuous production.

[0041] like Figure 4-5 As shown, the present invention also provides a method for preparing carbon nanotubes using the aforementioned fluidized bed reactor, specifically including the following steps:

[0042] S1. Carrier gas is introduced into heating tube 11 at a flow rate of 400L / min-600L / min.

[0043] S2. Start the heating component 12 to heat the carrier gas to 600℃-800℃.

[0044] S3. The heated carrier gas flows into the reaction chamber 22 of the furnace body 21 through the gas supply pipe 31 to provide a stable ambient temperature for subsequent reactions.

[0045] S4. Add 150g-250g of catalyst to reaction chamber 22 and introduce carbon source gas at a flow rate of 150L / min-250L / min. The carbon source gas reacts under the thermal atmosphere created by the carrier gas and the action of the catalyst to generate carbon nanotubes. After the reaction is completed, the grown carbon nanotubes are discharged through the outlet, and the tail gas is collected and treated through the top tail gas port 29 before being discharged.

[0046] To illustrate the technical solution of the present invention more specifically and verify its effect, the following examples 1-3 are used as examples for further explanation. Examples 1-3 are all prepared using the aforementioned fluidized bed reactor and the preparation method described therein. The main difference lies in the partial structural design of the fluidized bed reactor, the material ratio parameters and the specific process conditions.

[0047] In Examples 1-3, nitrogen was selected as the carrier gas and propylene was selected as the carbon source gas.

[0048] Example 1:

[0049] S1. First, assemble the double-layer furnace body 21, and evacuate and seal the vacuum interlayer 25 between its inner wall 23 and outer wall 24. Then, vertically install the 310S heating tube 11 with an outer diameter of Φ100mm. Using high-temperature resistant copper wire, tightly spirally wind it along the outside of the heating tube 11 at a pitch of 8mm, with 250 turns and a winding height of 2500mm. The total length of the electromagnetic induction coil 122 is approximately 85 meters. After winding, cover the inside of the electromagnetic induction coil 122 with a heat-insulating shielding layer 13. Finally, turn on the nitrogen supply device (not shown in the figure) and adjust the nitrogen flow rate to 400L / min.

[0050] S2. A high-frequency current is passed through the electromagnetic induction coil 122 to heat up the heating tube 11 and uniformly heat the nitrogen gas flowing through it to 600°C.

[0051] S3. The heated nitrogen gas flows into the reaction chamber 22 of the furnace body 21 through the heating pipe 11.

[0052] S4. Add 200g of catalyst to reaction chamber 22 and introduce propylene at a flow rate of 150L / min. Under the thermal atmosphere provided by high-temperature nitrogen and the action of the catalyst, the reaction continues for 1 hour. After the reaction is completed, the mass of carbon nanotube product collected through discharge port 27 is 14.8kg.

[0053] Example 2:

[0054] Compared with Example 1, the main difference is that the outer diameter of the heating tube 11 is Φ108mm. The electromagnetic induction coil 122 has a winding pitch of 10mm, 280 turns, a winding height of 2800mm, and a total length of 115m.

[0055] The nitrogen flow rate was 500 L / min, and the heating temperature was 700 °C. The propylene flow rate was 200 L / min, and the reaction time remained at 1 h. The final mass of carbon nanotube product collected in this example was 15.6 kg.

[0056] Example 3:

[0057] Compared with Example 1, the main difference is that the outer diameter of the heating tube 11 is Φ150mm. The winding pitch of the electromagnetic induction coil 122 is 15mm, the number of winding turns is 300, the winding height is 3000mm, and the total length is 150m.

[0058] The nitrogen flow rate was 600 L / min, and the heating temperature was 800 °C. The propylene flow rate was 250 L / min, and the reaction time was 1 h. The final mass of carbon nanotube product collected in this example was 13.5 kg.

[0059] The experimental results of Examples 1-3 above show that the method and apparatus described in this invention for preparing carbon nanotubes have the dual advantages of high yield and high convenience. Under strictly controlled reaction conditions, the growth efficiency of carbon nanotubes is significant. In the examples, 13.5 kg to 15.6 kg of product can be obtained per 200 g catalyst within 1 hour, demonstrating good yield and process stability.

[0060] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A gas heating device, characterized by: It includes a heating tube (11) through which a carrier gas flows, and a heating component (12) for heating the carrier gas is provided on the outer sleeve of the heating tube (11).

2. The gas heating device of claim 1, wherein: The carrier gas is an inert gas.

3. The gas heating device of claim 1, wherein: The heating component (12) has a heat insulation shielding layer (13) inside.

4. The gas heating device according to any one of claims 1-3, characterized in that: The heating assembly (12) includes an electromagnetic heating controller (121), on which an electromagnetic induction coil (122) is electrically connected, and the electromagnetic induction coil (122) is spirally wound around the outside of the heating tube (11).

5. The gas heating device as described in claim 4, characterized in that: The winding pitch of the electromagnetic induction coil (121) is 8mm to 15mm, and the winding height is 2500mm to 3000mm.

6. The gas heating device as described in claim 4, characterized in that: The electromagnetic induction coil (121) has 250 to 300 turns and a total length of 85 to 150 meters.

7. A fluidized bed reactor, characterized in that: Includes the gas heating device as described in any one of claims 1-6.

8. The fluidized bed reactor as described in claim 7, characterized in that: It also includes a furnace body (21) with an internal reaction chamber (22), the furnace body (21) including an inner wall (23) and an outer wall (24), and a vacuum interlayer (25) is provided between the inner wall (23) and the outer wall (24).

9. The fluidized bed reactor as described in claim 8, characterized in that: The outlet of the heating tube (11) is connected to the air inlet of the reaction chamber (22); The furnace body (21) is also equipped with a catalyst feeding bin (26), a discharge port (27), a carbon source gas inlet (28), and a tail gas outlet (29).

10. A method for preparing carbon nanotubes using a fluidized bed reactor as described in any one of claims 7-9, characterized in that, Includes the following steps: S1. Carrier gas is introduced into the heating tube (11); S2. Start the heating component (12) to heat the carrier gas to 600℃-800℃; S3. The heated carrier gas is introduced into the reaction chamber (22) of the furnace body (21); S4. Add a catalyst to the reaction chamber (22) and introduce carbon source gas, so that the carbon source gas reacts under the thermal atmosphere provided by the carrier gas and the action of the catalyst to generate carbon nanotubes.

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