A production system for chemical vapor deposition reactions
By employing a chemical vapor deposition reaction system with an optimized design using a vertical reactor, agitator, and preheater, the problems of high processing difficulty and low production capacity of traditional reactors have been solved, achieving high-efficiency mass and heat transfer performance and high yield of carbon nanotubes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YINGNAMATERIALS TECHNOLOGY (ZHENJIANG) CO LTD
- Filing Date
- 2023-03-02
- Publication Date
- 2026-05-15
AI Technical Summary
Existing chemical vapor deposition reactors suffer from high processing difficulty, low production capacity, high equipment cost, and difficulty in scaling up production due to their slender structure, and their mass and heat transfer performance is insufficient.
A vertical reactor with an external heating device and an internal stirrer is adopted, with a height-to-diameter ratio of no more than 5. The feed gas is preheated by a preheater, the reaction zone design and stirrer length are optimized, and fins are used to enhance the heat exchange area. Dust removal equipment is used to filter particulate matter in the exhaust gas.
This reduces the difficulty of reactor processing and maintenance, improves production capacity and mass and heat transfer performance, and enhances the yield of carbon nanotubes and equipment efficiency.
Smart Images
Figure CN116173869B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of chemical vapor deposition reaction equipment, specifically relating to a production system for chemical vapor deposition reactions. Background Technology
[0002] Chemical vapor deposition (CVD) involves mass and heat transfer between the gas and solid phases, and reactors for CVD have always been a challenge in the chemical engineering field. For example, industrially produced carbon nanotube reactors, due to the high-temperature requirements of the reaction, generally employ fluidized bed reactors with a large aspect ratio to achieve good mass and heat transfer performance. These reactors are elongated and slender, utilizing the upward airflow of the feed gas to fluidize the catalyst and facilitate the reaction. However, these elongated reactors are not only difficult to manufacture, have a narrow range of adaptability to materials and feedstocks, and have low production capacity, making scale-up difficult, but also require tall plant structures and related equipment, increasing the difficulty of installation and maintenance. Summary of the Invention
[0003] To address the aforementioned problems, this invention provides a production system for chemical vapor deposition (CVD) reactions, comprising a preheater, a reactor, and a dust removal device connected in sequence. The outlet of the preheater is connected to several raw material gas inlets of the reactor for inputting preheated raw material gas into the reactor. The tail gas outlet of the reactor is connected to the inlet of the dust removal device for filtering particulate matter in the tail gas of the reactor.
[0004] The reactor is a vertical reactor with an external heating device and an internal stirrer. The upper part of the reactor has a tail gas outlet, and the lower part has a raw material gas inlet.
[0005] Optionally, the reactor includes a reaction zone for chemical vapor deposition reaction, the vertical height difference between the highest and lowest points of the reaction zone is h1, and the equivalent circle diameter of the maximum horizontal cross-section of the reaction zone is h2. The relationship between the two satisfies the following formula: h1 / h2≤5.
[0006] For vertical reactors, the top and part of the bottom areas, which do not reach the required reaction temperature, basically do not react or have very low reaction efficiency. The reaction zone mentioned in this invention refers to the area inside the reactor that can reach the reaction temperature, that is, the area where an effective reaction can occur, which is generally located in the middle and lower part of the reactor.
[0007] In a specific embodiment, the reactor is cylindrical, and the ratio of the height to the diameter of the reaction zone inside the reactor is h1 / h2.
[0008] Optionally, the temperature difference between the temperature of the mixture of several raw material gases entering the reactor and the reaction temperature inside the reactor is not greater than 100°C, and preferably, the difference is not greater than 50°C.
[0009] The reactor described in this invention abandons the traditional elongated fluidized bed reactor and instead adopts a reactor with a height-to-diameter ratio of no more than 5. This not only reduces the difficulty of reactor processing, installation, and maintenance, resulting in lower equipment costs, but also significantly increases the production capacity of the reactor compared to elongated fluidized bed reactors while maintaining the same reactor height. This solves the problem of chemical vapor deposition reactors being difficult to scale up production capacity. Mass and heat transfer problems caused by the large diameter are mitigated by an agitator, and a preheater is used to preheat the feed gas, allowing the feed gas entering the reactor to quickly reach the reaction temperature. This enables the reactor to maintain a high yield even with a relatively small height-to-diameter ratio.
[0010] Optionally, the preheater is selected from shell and tube heat exchangers, plate heat exchangers, or coil heat exchangers.
[0011] Optionally, the reactor is provided with a feed inlet at the top and a discharge outlet at the bottom, for inputting catalyst and discharging carbon nanotube products, respectively; a number of raw material gas inlets are evenly arranged around the axis of the reactor at the bottom of the reactor for uniformly inputting raw material gas into the reactor.
[0012] A gas distribution plate is installed at the bottom of the reactor, located between the discharge port and the raw material gas inlet.
[0013] Optionally, fins are uniformly arranged on the outer surface of the reactor, that is, fins are provided between the reactor and the heating device to increase the heat exchange area of the reactor.
[0014] Through practical engineering research, this invention has identified several key factors significantly affecting mass and heat transfer in reactors: the total heat exchange area of the preheater, the total heat exchange area of the reactor, the height of the reaction zone, the diameter of the reaction zone, and the vertical length of the stirrer extending into the reaction zone. These factors exhibit a certain degree of coordination. By satisfying these coordination relationships, good mass and heat transfer performance can be ensured in the reaction zone while maintaining a relatively low height-to-diameter ratio. Further optionally, the relationship between the total heat exchange area of the reactor, the total heat exchange area of the preheater, and the reactor's h1 and h2 values satisfies the following formula:
[0015]
[0016] Where h1 and h2 are in meters; S1 is the total heat exchange area of the preheater, in meters. 2 S2 is the total heat exchange area of the reactor, in meters. 2 h is the vertical length of the stirrer extending into the reaction zone, in meters.
[0017] The total heat exchange area of the preheater is the total heat exchange area indicated on the nameplate of the preheater equipment. The total heat exchange area of the reactor is the sum of the outer surface area of the reactor surrounded by the heating device and the surface area of the fins.
[0018] As the length h of the stirrer extending into the reaction zone increases, the stirring and mass transfer within the reaction zone are enhanced, further increasing the conversion rate of the raw materials and resulting in an increase in the production weight of carbon nanotubes.
[0019] Optionally, the dust removal equipment has an exhaust port at the top and an internal cavity containing a porous filter material. The porous filter material filters particulate matter in the exhaust gas, and the filtered exhaust gas is discharged through the exhaust port. Conventional dust removal porous filter materials can be used.
[0020] Optionally, the dust removal equipment is provided with an exhaust port at the top, a collector at the bottom, and an air inlet on the side in the middle. The exhaust gas discharged from the reactor is input into the dust removal equipment. After filtration, the solid material falls into the collector under gravity, and the filtered exhaust gas is discharged from the exhaust port.
[0021] Optionally, the dust removal equipment is selected from gravity dust collectors, bag filters, ceramic filter tubes, metal sintered filter tubes, or cyclone dust collectors.
[0022] Optionally, a cooling device can also be installed between the reactor and the dust removal equipment. The inlet of the cooling device is connected to the tail gas outlet of the reactor, and the outlet of the cooling device is connected to the air inlet of the dust removal equipment. This device is used to cool the tail gas discharged from the reactor and reduce the operating temperature of the dust removal equipment. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of a production system used for chemical vapor deposition reactions;
[0024] Figure 2 This is a schematic diagram of the reactor structure.
[0025] In the attached diagram, 1-preheater, 2-reactor, 3-dust removal equipment, 4-raw material gas inlet, 5-tail gas outlet, 6-air inlet, 7-heating device, 8-stirrer, 9-feed inlet, 10-discharge outlet, 11-gas distribution plate, 12-exhaust outlet, 13-collector. Detailed Implementation
[0026] Example 1
[0027] This embodiment provides a production system for chemical vapor deposition reactions, such as... Figure 1- As shown in the figure, it includes a preheater 1, a reactor 2 and a dust removal device 3 connected in sequence. The outlet of the preheater 1 is connected to the four raw material gas inlets 4 of the reactor 2 for inputting the preheated raw material gas into the reactor 2. The tail gas outlet 5 of the reactor 2 is connected to the air inlet 6 of the dust removal device 3 for filtering particulate matter (e.g., catalyst) in the tail gas of the reactor 2.
[0028] The reactor 2 is a vertical reactor, with an external heating device 7 and an internal stirrer 8. Several stirring paddles are provided in the reaction zone of the reactor 2. The upper part of the reactor 2 is provided with a tail gas outlet 5 and the lower part is provided with a raw material gas inlet 4.
[0029] The reactor includes a reaction zone for chemical vapor deposition (CVD) reactions. The reaction zone is located in the middle of the reactor. The vertical height difference between the highest and lowest points of the reaction zone is h1 = 1 m. The equivalent circular diameter of the maximum horizontal cross-section of the reaction zone is h2 = 0.8 m, therefore h1 / h2 = 1.25. The reaction zone is cylindrical.
[0030] The vertical length of the stirrer extending into the reaction zone is h = 0.5 meters, and the volume of the reaction zone is 0.5024 m³. 3 The temperature difference between the raw gas entering reactor 2 and the reaction temperature inside reactor 2 is 100℃.
[0031] The preheater 1 is a shell-and-tube heat exchanger.
[0032] The reactor 2 is provided with a feed inlet 9 at the top and a discharge outlet 10 at the bottom, which are used to input the catalyst and discharge the carbon nanotube product, respectively; four raw material gas inlets 4 are evenly arranged around the axis of the reactor 2 at the bottom of the reactor 2, which are used to evenly input raw material gas into the reactor 2.
[0033] A gas distribution plate 11 is provided at the bottom of reactor 2. The gas distribution plate 11 is located between the discharge port 10 and the raw material gas inlet 4, so that the incoming raw material gas is evenly distributed at the bottom of reactor 2 without obstructing the discharge of product. The gas distribution plate 11 can be a conventional form in the art with its surface densely covered with through holes.
[0034] The outer surface of the reactor is uniformly provided with fins, that is, fins are provided between the reactor and the heating device to increase the heat exchange area of the reactor.
[0035] The dust removal device 3 has an exhaust port 12 at the top, a collector 13 at the bottom, and an air inlet 6 on the side in the middle. The exhaust gas discharged from the reactor 2 is input into the dust removal device 3. After filtration, the solid material falls into the collector 13 under gravity, waiting to be reused for the catalyst and carbon nanotubes. The filtered exhaust gas is discharged from the exhaust port 12. It can be discharged into the outside air or collected for subsequent professional purification treatment.
[0036] The dust removal device 3 is a combination of a gravity dust removal device and a porous ceramic filter rod.
[0037] A cooling device is also provided between the reactor 2 and the dust removal equipment 3. The inlet of the cooling device is connected to the tail gas outlet 5 of the reactor 2, and the outlet of the cooling device is connected to the air inlet 6 of the dust removal equipment 3. The cooling device is used to cool the tail gas discharged from the reactor 2 to reduce the operating temperature of the dust removal equipment.
[0038] In this embodiment, the feed gas is ethylene, and the catalyst introduced through inlet 9 is a powdered supported Fe-Ni bimetallic catalyst. The ethylene flow rate is 28.125 m³ / h. 3 The reaction rate was 100 rpm, the catalyst dosage was 3.287 kg, the preheated feed gas temperature was 550 °C, the reaction temperature inside the reactor was 650 °C, and the stirring rate was 5 r / min. At the end of the reaction, the packing density of carbon nanotubes was 60 kg / m³. 3 The filling rate is 50% (the percentage of the total volume of carbon nanotube material accumulated in the static state after the reaction is completed) and the reaction cycle for each batch is 1 hour. The reactor produces 15.072 kg of carbon nanotubes per hour.
[0039] The total heat exchange area of the preheater is S1 = 15.0 m². 2 The total heat exchange area of the reactor is S2 = 5.024 m². 2 .
[0040] Comparative Example 1
[0041] The production system for chemical vapor deposition provided in this comparative example is the same as that in Example 1, and the catalyst is also the same powdered supported Fe-Ni bimetallic catalyst. The difference is that the reactor is a conventional fluidized bed reactor without an internal stirrer. The catalyst is fluidized in the reactor by the upward flow of the reactant gas. The height of the reaction zone in the reactor is 1 m, the inner diameter is 0.1 m, the height-to-diameter ratio is 10, and the volume of the reaction zone is 0.00785 m³. 3 It is 1.56% of the volume of the reaction zone in Example 1.
[0042] The reaction conditions were the same as in Example 1. After the reaction was complete, the packing density of the carbon nanotubes was also 60 kg / m³. 3 The filling rate was 30% (in a fluidized reactor, the gas velocity inside the reactor is relatively fast, and the material bed expands significantly, so the filling rate is also low after it stops). The reactor produced 0.141 kg of carbon nanotubes per hour, which is significantly less than that of Example 1.
[0043] Example 2
[0044] The production system for chemical vapor deposition reaction provided in this embodiment is the same as that in Embodiment 1, except that the vertical length of the stirrer extending into the reaction zone is increased, h = 0.8m, which improves the mass and heat transfer performance of the reaction zone.
[0045] Example 3
[0046] The production system for chemical vapor deposition (CVD) provided in this embodiment is the same as that in Embodiment 1, except that the reactor has h1 = 5m, h2 = 1.2m, h1 / h2 = 4, h = 4m, and the volume of the reaction zone is 5.652m³. 3 The bulk density of the carbon nanotube product is 30 kg / m³. 3 The fill rate is 50%. The total heat exchange area of the preheater is S1 = 75.0 m². 2 The total heat exchange area of the reactor is S2 = 43.5 m². 2 .
[0047] Example 4
[0048] The production system for chemical vapor deposition (CVD) provided in this embodiment is the same as that in Embodiment 3, except that the reactor has h1 = 5m, h2 = 0.98m, h1 / h2 = 5.1, h = 4m, and the volume of the reaction zone is 3.77m³. 3 The bulk density of the carbon nanotube product is also 30 kg / m³. 3 The fill rate is 35%. The total heat exchange area of the preheater is S1 = 50.5 m². 2 The total heat exchange area of the reactor is S2 = 35.2 m². 2 .
[0049] Examples 1-3 all conform to the following formula, but Example 4 does not conform to the following formula:
[0050]
[0051] Table 1. Comparison of production capacity in Examples 1-4
[0052] Production capacity (kg / h) Example 1 15.07 Example 2 18.08 Example 3 84.78 Example 4 39.58 Comparative Example 1 0.14
[0053] As can be seen from the table above, the production system for chemical vapor deposition reaction proposed in this invention has a large reaction zone volume, which greatly improves the production capacity. Moreover, by controlling the size of the preheater and reactor, the size of the preheater and reactor can meet a certain relationship, thus achieving a high production capacity.
Claims
1. A production system for chemical vapor deposition reactions, characterized in that, It includes a preheater, a reactor, and a dust removal device connected in sequence. The outlet of the preheater is connected to several raw material gas inlets of the reactor for inputting the preheated raw material gas into the reactor. The tail gas outlet of the reactor is connected to the air inlet of the dust removal device for filtering particulate matter in the tail gas of the reactor. The reactor is a vertical reactor with an external heating device and an internal stirrer. The upper part of the reactor has a tail gas outlet, and the lower part has a raw material gas inlet. The reactor includes a reaction zone for chemical vapor deposition (CVD) reactions. The vertical height difference between the highest and lowest points of the reaction zone is h1, and the equivalent circle diameter of the maximum horizontal cross-section of the reaction zone is h2. The relationship between the total heat exchange area of the preheater, the total heat exchange area of the reactor, and the reactor's h1 and h2 satisfies the following formula: ； Where h1 and h2 are in meters; S1 is the total heat exchange area of the preheater, in meters. 2 S2 is the total heat exchange area of the reactor, in meters. 2 h is the vertical length of the stirrer extending into the reaction zone, in meters. The relationship between h1 and h2 satisfies the following formula: h1 / h2≤5.
2. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, The reactor has an inlet at the top and an outlet at the bottom for feeding the catalyst and discharging the carbon nanotube product, respectively; several raw material gas inlets are located at the bottom of the reactor for uniformly feeding the raw material gas into the reactor.
3. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, A gas distribution plate is installed at the bottom of the reactor, located between the discharge port and the raw material gas inlet.
4. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, The outer surface of the reactor is provided with fins to increase the heat exchange area of the reactor.
5. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, The dust removal equipment has an exhaust port at the top and an internal cavity with a porous filter material inside. The porous filter material filters particulate matter in the exhaust gas, and the filtered exhaust gas is discharged from the exhaust port.
6. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, The dust removal equipment has an exhaust port at the top, a collector at the bottom, and an air inlet on the side in the middle. The exhaust gas discharged from the reactor is input into the dust removal equipment. After filtration, the solid material enters the collector, and the filtered exhaust gas is discharged from the exhaust port.
7. The production system for chemical vapor deposition reaction according to claim 1, characterized in that, A cooling device is also installed between the reactor and the dust removal equipment. The inlet of the cooling device is connected to the tail gas outlet of the reactor, and the outlet of the cooling device is connected to the air inlet of the dust removal equipment. It is used to cool the tail gas discharged from the reactor to reduce the operating temperature of the dust removal equipment.