A system for preparing silicon-carbon composite materials

Abstract

The utility model discloses a system of preparation silicon carbon composite material belongs to the field of silicon carbon composite material preparation. The system includes the heat exchanger, gasification mixer, chemical vapor deposition fluidized bed reactor, centrifugal fan, deacidification hydrogen production fixed bed reactor, dryer that connects gradually, chemical vapor deposition fluidized bed reactor is the main reactor of the system, and low concentration hydrogen and trichlorosilane occur gas phase photochemistry under the lower temperature and make the active carbon surface and pore of elemental silicon in fluidized state high -efficient even and form into silicon carbon composite material. The system effectively solved the equipment dispersion, the operation complex, the high cost etc. of traditional technology problem, provided reliable technical support for the large -scale preparation of high -performance composite material.

Description

Technical Field

[0001] This utility model relates to the field of materials chemical production, specifically to the field of silicon-carbon composite material preparation, and particularly to a system for preparing silicon-carbon composite materials. Background Technology

[0002] With the surge in demand for high-energy-density batteries from new energy vehicles and high-end consumer electronics, upgrading lithium-ion battery anode materials has become a key breakthrough. Traditional graphite anodes have a low theoretical specific capacity, severely limiting breakthroughs in battery performance. Silicon-based anodes, due to their high theoretical specific capacity, are widely recognized as the core direction for next-generation anodes. However, silicon materials undergo severe volume expansion / contraction during charging and discharging, leading to particle pulverization, active material shedding, and repeated volume changes causing continuous rupture and regeneration of the solid electrolyte interface film, consuming electrolyte and increasing internal resistance.

[0003] Combining silicon-based materials with carbon materials is an effective way to improve their cycle stability and conductivity. In existing technologies, mixing silicon-based materials with a carbon source, performing solid-state pyrolysis, and then chemically vapor-depositing carbon coating on the surface of the silicon-based material are common methods for preparing silicon-carbon composites. However, current mainstream preparation processes typically require separating the key steps of mixing, solid-state pyrolysis, and chemical vapor deposition, involving multiple independent sets of equipment and complex process connections, resulting in cumbersome processes and high equipment investment and operating costs.

[0004] Chinese Patent 2016207460161, "A Special Equipment for Producing Silicon-Carbon Composite Materials," provides a special equipment that attempts to achieve silicon-based material mixing, solid-phase pyrolysis, and chemical vapor deposition within a single device. Chinese Patent 2018109842535, "A Method and Apparatus for Preparing High-Performance Silicon-Carbon-Based Anode Materials," discloses a method for constructing carbon coatings using a vibration fluidized bed vapor deposition system.

[0005] However, existing technologies still have shortcomings in terms of equipment integration, process synergy, and cost-effectiveness. In particular, the precise temperature control and uniformity of the solid-phase pyrolysis process, as well as low-cost chemical vapor deposition coating technology, still require further optimization. Therefore, there is an urgent need to develop a new, highly integrated reactor and system to solve the key problems of existing technologies, such as equipment dispersion, complex operation, high cost, and the resulting agglomeration of particulate materials and uneven coating quality. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a system for preparing silicon-carbon composite materials. This system features a highly integrated design, compact equipment structure, significantly simplified process flow, and substantial reduction in production costs. The prepared composite material exhibits good dispersibility, uniform coating, and stable and controllable quality. The system performs chemical vapor deposition (CVD) reactions in a fluidized state, ensuring thermal field uniformity while achieving low-cost, high-efficiency CVD coating. This system effectively solves the problems of equipment dispersion, complex operation, and high costs in traditional technologies, providing reliable technical support for the large-scale preparation of high-performance composite materials.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A system for preparing silicon-carbon composite materials, comprising a heat exchanger, a gasification mixer, a chemical vapor deposition fluidized bed reactor, a centrifugal fan, a deacidification and hydrogen production fixed bed reactor, and a dryer connected in sequence, wherein... Nitrogen and hydrogen are introduced into the inner tube of the heat exchanger and connected to a combined heating and cooling unit, which heats and cools the gases. Trichlorosilane is added to the gasification mixer and mixed with nitrogen and hydrogen. The chemical vapor deposition fluidized bed reactor is the main reactor of the system. Activated carbon particles are fluidized in the reactor, and hydrogen and trichlorosilane undergo a gas-phase photochemical reaction to generate elemental silicon that is uniformly deposited on the surface and pores of the activated carbon, forming a silicon-carbon composite material. When the system is working, the gas circulates within each of the above units under the drive of a centrifugal fan; The system also includes a diaphragm vacuum pump, which is connected to the chemical vapor deposition fluidized bed reactor, the centrifugal fan, the deacidification and hydrogen production fixed bed reactor, and the waste gas treatment outlet.

[0008] Furthermore, the shell side of the heat exchanger is filled with low-viscosity methyl silicone oil as the heat exchange medium.

[0009] Furthermore, nitrogen and hydrogen in the heat exchanger are heated to 120°C to 180°C before entering the gasification mixer.

[0010] Furthermore, the volume ratio of nitrogen to hydrogen is 5-8:1 when the system is in operation.

[0011] Furthermore, in addition to a gas inlet and a gas outlet, the chemical vapor deposition fluidized bed reactor also has a feed inlet and a discharge outlet. Inside, there is a gas distribution plate encapsulated in a quartz tube. Low-pressure mercury lamps are installed above and below the gas distribution plate. The feed inlet is located above the low-pressure mercury lamps, and the discharge outlet is located above the gas distribution plate. A cyclone separator is connected to the gas outlet and is located at the top of the chemical vapor deposition fluidized bed reactor.

[0012] Furthermore, the gas distribution plate is a conical cap with side seams.

[0013] Furthermore, the main peak of the low-pressure mercury lamp is 254nm. The low-pressure mercury lamps below the gas distribution plate are arranged in a vertical equilateral triangle with an irradiance of 20,000 to 30,000 milliwatts per square meter. The low-pressure mercury lamps above the gas distribution plate are arranged in a horizontal equilateral triangle with an irradiance of 30,000 to 50,000 milliwatts per square meter.

[0014] Furthermore, the interior of the deacidification hydrogen production fixed-bed reactor is filled with zinc wire mesh.

[0015] Furthermore, the dryer is a molecular sieve dryer, filled with 3A molecular sieve desiccant or 4A molecular sieve desiccant.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows: Compared with existing technologies, the system of this invention enables hydrogen and trichlorosilane to undergo a gas-phase photochemical reaction in a chemical vapor deposition fluidized bed reactor under the excitation of ultraviolet light emitted by a low-pressure mercury lamp. This not only allows for the efficient and uniform deposition of elemental silicon on the surface and in the pores of fluidized activated carbon, but also significantly reduces the reaction temperature and pressure, while greatly reducing the concentration of hydrogen and trichlorosilane in the system, making it difficult for the system to form explosive conditions. The hydrogen chloride byproduct of the reaction reacts with zinc wire mesh in a deacidification hydrogen production fixed bed reactor to generate hydrogen, further reducing the amount of hydrogen used, improving production efficiency and system safety, and lowering production costs, thus possessing great market competitiveness. Attached Figure Description

[0017] Figure 1 This is a system structure diagram of the present invention; Figure 2 This is a structural diagram of a chemical vapor deposition fluidized bed reactor; In the diagram, 1-heat exchanger, 2-gasification mixer, 3-chemical vapor deposition fluidized bed reactor, 31-feed inlet, 32-discharge outlet, 33-gas distribution plate, 34-low-pressure mercury lamp, 35-cyclone separator, 4-centrifugal fan, 5-acid removal and hydrogen production fixed bed reactor, 6-dryer, 7-diaphragm vacuum pump, 8-integrated cooling and heating unit, 9-exhaust gas treatment outlet. Detailed Implementation

[0018] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. It should be noted that these descriptions of the embodiments are for the purpose of helping to understand this utility model, but do not constitute a limitation on this utility model.

[0019] In the description of this utility model, it should be noted that the terms "above", "below", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and 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 orientation. Therefore, they should not be construed as limitations on this utility model.

[0020] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0021] The pipes or valves used in this utility model (the “valve” used in the following embodiments) are all commonly used pipes or valves in the chemical industry, and there are no special limitations on them. As long as they can enable the operation of the system, they can be used in this utility model.

[0022] The dryer employs a molecular sieve dryer, a gas treatment device that uses molecular sieves as adsorbents. It achieves continuous operation by alternating adsorption and regeneration processes in two containers. Its core structure includes components such as an inlet duct, a regeneration branch duct, and an outlet duct, enabling selective adsorption of water molecules and specific components from the gas. Its specific structure is existing technology and will not be described in detail in this invention.

[0023] Other equipment not specifically described, such as centrifugal fans, diaphragm vacuum pumps, cyclone separators, and integrated cooling and heating units, are common commercially available equipment and will not be described in detail in this utility model. Example 1

[0024] like Figure 1 As shown, this embodiment provides a system for preparing silicon-carbon composite materials. The system includes a heat exchanger 1, a gasification mixer 2, a chemical vapor deposition fluidized bed reactor 3, a centrifugal fan 4, a deacidification and hydrogen production fixed bed reactor 5, and a dryer 6, which are connected sequentially by pipes. The heat exchanger 1 is a shell-and-tube heat exchanger with a gas inlet and a gas outlet. Nitrogen is introduced into the tube side of the heat exchanger through valve V1, and hydrogen is introduced into the tube side through valve V2. The gas flows through the tube side of the heat exchanger 1. Low-viscosity methyl silicone oil is used as the heat exchange medium and flows through the shell side of the heat exchanger 1. The heat exchanger 1 is connected to the integrated heating and cooling unit 8 through valves V14 and V15. The integrated heating and cooling unit 8 realizes the heating and cooling of the gas. The gasification mixer 2 adds trichlorosilane through valve V3 and mixes it with nitrogen and hydrogen. The chemical vapor deposition fluidized bed reactor 3 is the main reactor of the system of this utility model. Inside it, activated carbon particles are fluidized, and hydrogen and trichlorosilane undergo a gas-phase photochemical reaction to generate elemental silicon that is uniformly deposited on the surface and pores of the activated carbon, forming a silicon-carbon composite material. The material is fed through valve V4 and discharged through valve V5. When the system is working, the gas circulates within the aforementioned units under the drive of the centrifugal fan 4; The system also includes a diaphragm vacuum pump 7, which is connected to the chemical vapor deposition fluidized bed reactor 3, the centrifugal fan 4, the deacidification and hydrogen production fixed bed reactor 5, and the waste gas treatment output port 9. Specifically, the inlet of the diaphragm vacuum pump 7 is connected to the chemical vapor deposition fluidized bed reactor 3 through valve V8, to the centrifugal fan 4 through valves V8 and V6, to the deacidification and hydrogen production fixed bed reactor 5 through valves V9 and V11, and to the waste gas treatment output port 9 through valves V9, V12, and V13; the outlet of the diaphragm vacuum pump 7 is connected to the waste gas treatment output port 9 through valves V10 and V13.

[0025] The gasification mixer 2, chemical vapor deposition fluidized bed reactor 3, centrifugal fan 4, deacidification hydrogen production fixed bed reactor 5, dryer 6, and connecting pipelines of the system are lined with polytetrafluoroethylene.

[0026] like Figure 2 As shown, the chemical vapor deposition fluidized bed reactor 3, in addition to having a gas inlet and a gas outlet, also has a feed inlet 31 and a discharge outlet 32. Inside, there is a gas distribution plate 33 encapsulated in a quartz tube. Low-pressure mercury lamps 34 are installed above and below the gas distribution plate 33. The feed inlet 31 is located above the low-pressure mercury lamps 34, and the discharge outlet 32 ​​is located above the gas distribution plate 33. A cyclone separator 35 is connected to the gas outlet and is installed at the top of the chemical vapor deposition fluidized bed reactor 2.

[0027] The gas distribution plate 33 is a conical cap side-slit type.

[0028] The main peak of the low-pressure mercury lamp 34 used in this invention is 254nm. The low-pressure mercury lamps 34 below the gas distribution plate 33 are arranged in a vertically placed equilateral triangle, with an irradiance of 20,000 to 30,000 milliwatts per square meter. In this embodiment, the irradiance is 20,000 milliwatts per square meter. The low-pressure mercury lamps 34 above the gas distribution plate 33 are arranged in a horizontally placed equilateral triangle, with an irradiance of 30,000 to 50,000 milliwatts per square meter. In this embodiment, the irradiance is 30,000 milliwatts per square meter.

[0029] The feed inlet 31 is the feed inlet for activated carbon particles. The activated carbon particles used in this invention have a particle size of 50-100 mesh.

[0030] In this embodiment, the low-viscosity methyl silicone oil used in the shell side of the heat exchanger can be a 0.65~10 cSt type methyl silicone oil, preferably a 5 cSt type methyl silicone oil. The heat exchanger used in this utility model is a shell-and-tube heat exchanger, which is prior art, and its specific structure will not be described in detail in this utility model.

[0031] Nitrogen and hydrogen are heated to 120°C to 180°C in the heat exchanger 1 and then enter the vaporization mixer 2. The low-boiling-point trichlorosilane comes into contact with the gas containing nitrogen and hydrogen at a temperature of 120°C to 180°C and directly vaporizes to form a mixed gas containing trichlorosilane, nitrogen and hydrogen.

[0032] In this embodiment, the fixed-bed reactor 5 for deacidification and hydrogen production is filled with zinc wire mesh. The zinc wire mesh provides a zinc source for the reaction with hydrogen chloride. Therefore, the specific structure of the zinc wire mesh is not particularly limited, as long as it can provide a zinc source. After the reaction is completed, the zinc wire mesh is removed, washed with water to remove the zinc chloride produced in the reaction, dried, and then replenished with new zinc wire mesh according to the weight loss before being loaded back into the fixed-bed reactor.

[0033] In this embodiment, the dryer 6 is filled with 3A molecular sieve desiccant.

[0034] When using this system, after loading activated carbon granules into the chemical vapor deposition fluidized bed reactor, close valves V1, V2, V3, V4, V5, V6, V7, and V12, and open valves V8, V9, V10, V11, and V13. Start the diaphragm vacuum pump to reduce the system gauge pressure to -90 kPa. Then close valves V8, V9, V10, and V13 and the diaphragm vacuum pump, and open valve V1 to replenish nitrogen into the system to restore it to atmospheric pressure. Next, close valves V1, V2, V3, V4, V5, V6, V7, and V12, open valves V8, V9, V10, V11, and V13, and start the diaphragm vacuum pump to reduce the system gauge pressure to -90 kPa. After the pressure drops to -90 kPa, close valves V8, V9, V10, V13 and the diaphragm vacuum pump, then open valve V1 again to replenish nitrogen into the system and restore the system to normal pressure. Repeat this operation 4 times to replace the system with air and nitrogen. Then close valves V1, V2, V3, V4, V5, V6, V7, and V12, open valves V8, V9, V10, V11, and V13, start the diaphragm vacuum pump, and reduce the system gauge pressure to -90 kPa. Then close valves V8, V9, V10, V13 and the diaphragm vacuum pump, open valves V1 and V2 to adjust the gas flow rate so that the volume ratio of nitrogen to hydrogen is 8:1, and replenish nitrogen and hydrogen into the system to restore the system to normal pressure.

[0035] Open valves V6, V7, and V11 to start the centrifugal fan and circulate the gas within the system. Open valves V14 and V15 to heat the gas to 180°C using a heating medium. Open valve V3 to send trichlorosilane into the gasification mixer, where it comes into contact with a 180°C gas containing nitrogen and hydrogen. This gas directly vaporizes, forming a mixture of trichlorosilane, nitrogen, and hydrogen. This mixture enters the chemical vapor deposition fluidized bed reactor through the gas inlet, agitating the activated carbon particles packed on the gas distribution plate. Under the excitation of ultraviolet light emitted by a low-pressure mercury lamp, hydrogen and trichlorosilane undergo a gas-phase photochemical reaction, generating elemental silicon that is uniformly deposited on the surface and in the pores of the activated carbon, forming a silicon-carbon composite material.

[0036] Hydrogen chloride, a byproduct of the reaction between hydrogen and trichlorosilane, is sent along with the system gas to a deacidification and hydrogen production fixed-bed reactor via a centrifugal fan. There, it reacts with zinc wire mesh to generate hydrogen. After being dried by 3A molecular sieves in a dryer, the hydrogen is heated by a heat exchanger and then enters a gasification mixer where continuously replenished trichlorosilane is gasified and mixed with it. The mixture then continues in a chemical vapor deposition fluidized bed reactor to generate elemental silicon, which is uniformly deposited on the surface and in the pores of activated carbon, forming a silicon-carbon composite material. Simultaneously, hydrogen chloride gas is produced as a byproduct of the reaction.

[0037] After the reaction is complete, the gas in the system is replaced with nitrogen three times using the air and nitrogen replacement method described above. The waste gas is then sent to the waste gas treatment device through the waste gas treatment outlet. The discharge valve V5 is opened to discharge the obtained silicon-carbon composite material.

[0038] During the reaction, a mixed gas containing trichlorosilane, nitrogen, and hydrogen is introduced from the bottom, suspending the activated carbon solid particles and fluidizing them. The activated carbon particles tumble, collide, and circulate violently under the influence of the gas flow, creating strong radial and axial mixing, which helps eliminate local temperature differences and ensures the uniformity of the thermal field. Excitation by ultraviolet light emitted from a low-pressure mercury lamp causes the silicon-chlorine bonds in trichlorosilane to break, forming dichlorosilane radicals and chlorine radicals. This triggers a linear reaction: dichlorosilane radicals react with hydrogen to form dichlorosilane and hydrogen radicals; chlorine radicals react with hydrogen to form hydrogen chloride and chlorine radicals; and hydrogen radicals react with trichlorosilane to form dichlorosilane and chlorine radicals. The resulting dichlorosilane decomposes at a relatively low temperature to form elemental silicon and hydrogen chloride. The hydrogen chloride produced is then carried by the system gas through a centrifugal fan into a deacidification and hydrogen production fixed-bed reactor, where it reacts with the zinc wire mesh to generate hydrogen.

[0039] Therefore, the prepared composite material has good dispersibility, uniform coating, and stable and controllable quality. The system undergoes chemical vapor deposition reaction in a fluidized state, ensuring thermal field uniformity and achieving low-cost and high-efficiency chemical vapor deposition coating.

[0040] This invention's system device induces a gas-phase photochemical reaction between hydrogen and trichlorosilane in a chemical vapor deposition fluidized bed reactor under the excitation of ultraviolet light emitted by a low-pressure mercury lamp. This not only enables efficient and uniform deposition of elemental silicon on the surface and in the pores of fluidized activated carbon, but also significantly reduces the reaction temperature and pressure, while greatly reducing the concentration of hydrogen and trichlorosilane in the system, making it difficult for the system to form explosive conditions. Furthermore, the hydrogen chloride byproduct of the reaction reacts with zinc wire mesh in a deacidification hydrogen production fixed-bed reactor to generate hydrogen, further reducing hydrogen consumption, improving production efficiency and system safety, and lowering production costs, thus possessing significant market competitiveness. Example 2

[0041] The system described in this embodiment is basically the same as that in Embodiment 1, except that the dryer in this embodiment is filled with 4A molecular sieve desiccant. The irradiance of the low-pressure mercury lamp below the gas distribution plate of the chemical vapor deposition fluidized bed reactor is 30,000 mW / m², and the irradiance of the low-pressure mercury lamp above the gas distribution plate is 50,000 mW / m².

[0042] During operation, after loading the activated carbon granules into the chemical vapor deposition fluidized bed reactor, close valves V1, V2, V3, V4, V5, V6, V7, and V12, and open valves V8, V9, V10, V11, and V13. Start the diaphragm vacuum pump to reduce the system gauge pressure to -95 kPa. Then, close valves V8, V9, V10, and V13 and the diaphragm vacuum pump, and open valve V1 to replenish nitrogen into the system to restore it to atmospheric pressure. Next, close valves V1, V2, V3, V4, V5, V6, V7, and V12, open valves V8, V9, V10, V11, and V13, and start the diaphragm vacuum pump to reduce the system gauge pressure to -95 kPa. Close valves V8, V9, V10, V13 and the diaphragm vacuum pump, then open valve V1 again to replenish nitrogen into the system and restore the system to normal pressure. Repeat this operation 3 times to complete the replacement of air and nitrogen in the system. Then close valves V1, V2, V3, V4, V5, V6, V7, and V12 again, open valves V8, V9, V10, V11, and V13, start the diaphragm vacuum pump, and reduce the system gauge pressure to -95 kPa. Then close valves V8, V9, V10, V13 and the diaphragm vacuum pump, open valves V1 and V2 to adjust the gas flow rate so that the volume ratio of nitrogen to hydrogen is 5:1 to replenish nitrogen and hydrogen into the system and restore the system to normal pressure.

[0043] Open valves V6, V7, and V11 to start the centrifugal fan and circulate the gas within the system. Open valves V14 and V15 to heat the gas to 120°C using a heating medium. Open valve V3 to send trichlorosilane into the gasification mixer, where it comes into contact with a 180°C gas containing nitrogen and hydrogen. This gas directly vaporizes, forming a mixture of trichlorosilane, nitrogen, and hydrogen. This mixture enters the reactor through the gas inlet of the chemical vapor deposition fluidized bed reactor, agitating the activated carbon particles packed on the gas distribution plate of the reactor. Under the excitation of ultraviolet light emitted by a low-pressure mercury lamp, hydrogen and trichlorosilane undergo a gas-phase photochemical reaction, generating elemental silicon that is uniformly deposited on the surface and in the pores of the activated carbon, forming a silicon-carbon composite material.

[0044] Hydrogen chloride, a byproduct of the reaction between hydrogen and trichlorosilane, is sent to the deacidification and hydrogen production fixed-bed reactor via a centrifugal fan along with the system gas. It reacts with the zinc wire mesh in the reactor to generate hydrogen. After being dried by 4A molecular sieve in a dryer, it is heated by a heat exchanger and enters a gasification mixer to vaporize and mix with the continuously replenished trichlorosilane. The mixture then continues to react in a chemical vapor deposition fluidized bed reactor to generate elemental silicon, which is uniformly deposited on the surface and in the pores of activated carbon to form a silicon-carbon composite material. The hydrogen chloride gas is produced as a byproduct of the reaction.

[0045] After the reaction is complete, the gas in the system is replaced with nitrogen three times using the air and nitrogen replacement method described above. The waste gas is then sent to the waste gas treatment device through the waste gas treatment outlet. The discharge valve V5 is opened to discharge the obtained silicon-carbon composite material.

[0046] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for preparing silicon-carbon composite materials, characterized in that, The system comprises, in sequence, a heat exchanger, a gasification mixer, a chemical vapor deposition fluidized bed reactor, a centrifugal fan, a deacidification and hydrogen production fixed bed reactor, and a dryer. Nitrogen and hydrogen are introduced into the inner tube of the heat exchanger and connected to a combined heating and cooling unit, which heats and cools the gases. The vaporization mixer is used to mix trichlorosilane, nitrogen, and hydrogen. The chemical vapor deposition fluidized bed reactor is the main reactor of the system, used to fluidize activated carbon particles, and to cause hydrogen and trichlorosilane to undergo a gas-phase photochemical reaction to generate elemental silicon that is uniformly deposited on the surface and pores of the activated carbon, forming a silicon-carbon composite material. When the system is working, the gas circulates within each unit driven by a centrifugal fan; The system also includes a diaphragm vacuum pump, which is connected to the chemical vapor deposition fluidized bed reactor, the centrifugal fan, the deacidification and hydrogen production fixed bed reactor, and the waste gas treatment outlet.

2. The system according to claim 1, characterized in that, The heat exchanger shell side is filled with low-viscosity methyl silicone oil as the heat exchange medium.

3. The system according to claim 1, characterized in that, Nitrogen and hydrogen are heated to 120°C to 180°C in the heat exchanger before entering the gasification mixer.

4. The system according to claim 1, characterized in that, The volume ratio of nitrogen to hydrogen is 5-8:1 when the system is in operation.

5. The system according to claim 1, characterized in that, In addition to a gas inlet and a gas outlet, the chemical vapor deposition fluidized bed reactor also has a feed inlet and a discharge outlet. Inside, there is a gas distribution plate encapsulated in a quartz tube. Low-pressure mercury lamps are installed above and below the gas distribution plate. The feed inlet is located above the low-pressure mercury lamps, and the discharge outlet is located above the gas distribution plate. A cyclone separator is connected to the gas outlet and is located at the top of the chemical vapor deposition fluidized bed reactor.

6. The system according to claim 5, characterized in that, The gas distribution plate is a cone-shaped plate with side seams.

7. The system according to claim 5, characterized in that, The main peak of the low-pressure mercury lamp is 254 nm. The low-pressure mercury lamps below the gas distribution plate are arranged in a vertical equilateral triangle with an irradiance of 20,000 to 30,000 milliwatts per square meter. The low-pressure mercury lamps above the gas distribution plate are arranged in a horizontal equilateral triangle with an irradiance of 30,000 to 50,000 milliwatts per square meter.

8. The system according to claim 1, characterized in that, The deacidification hydrogen production fixed-bed reactor is filled with zinc wire mesh.

9. The system according to claim 1, characterized in that, The dryer is a molecular sieve dryer, filled with 3A or 4A molecular sieve desiccant.

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