System for hydrogen production and carbon production through methane cracking synergistically enhanced by plasmas

Abstract

The invention discloses a system for hydrogen production and carbon production through methane cracking synergistically enhanced by plasma. The system comprises a gas source, a cracking reaction bin and a plasma torch, a double-layer stainless steel sleeve catalytic carrier is arranged in the cracking reaction bin, the double-layer stainless steel sleeve catalytic carrier comprises an inner-layer sleeve and an outer-layer sleeve, through holes with the aperture of 5-10 microns are distributed in the inner-layer sleeve, and through holes with the aperture of 20-50 microns are distributed in the outer-layer sleeve; the inner wall of the inner-layer sleeve is coated with a catalytic coating; the gas source provides and conveys methane gas into the cracking reaction bin; and the direct-current plasma torch conveys high-temperature plasma into the double-layer stainless steel sleeve catalytic carrier. A double-layer porous stainless steel sleeve is constructed in a plasma reaction cracking bin to serve as a catalytic carrier to load a catalytic coating, and a deep coupling structure of plasma cracking and catalytic cracking is constructed; and efficient conversion of methane and synchronous preparation of a high-added-value carbon material and high-purity hydrogen energy are realized.

Description

Technical Field

[0001] This invention relates to the field of plasma hydrogen and carbon production technology, and more specifically, to a plasma-enhanced methane cracking hydrogen and carbon production system. Background Technology

[0002] Hydrogen energy, as a clean and carbon-free secondary energy source, is a core medium for promoting deep industrial decarbonization and supporting the large-scale development of renewable energy. Carbon materials (such as carbon black, carbon nanotubes, and graphene) are widely used in rubber, electronics, and new energy batteries due to their reinforcing, conductive, and UV-shielding properties. Methane, as the main component of natural gas (accounting for over 90%), is a key area for achieving low-carbon and high-value utilization of natural gas resources, thanks to technologies that efficiently convert it into hydrogen energy and high-value carbon materials.

[0003] Traditional methane-to-hydrogen processes mainly rely on methane steam reforming and partial oxidation, which suffer from problems such as carbon waste, large-scale carbon dioxide emissions, and high water consumption. Traditional methane-to-carbon processes are mainly furnace-based, failing to effectively collect and utilize hydrogen energy and emitting greenhouse gases and harmful gases. Existing methane-hydrogen-carbon cogeneration technologies (thermal cracking, catalytic cracking, and melt cracking) suffer from drawbacks such as intermittent operation, catalyst deactivation, low conversion rate, low product purity, and high emissions. While existing plasma-based methane cracking technology has certain advantages, it still faces problems such as low coupling between units, insufficient gas-plasma contact, limited carbon product control, insufficient energy recovery, high overall energy consumption, and poor product purity and stability.

[0004] A key technological challenge currently facing the industry is how to overcome the limitations of conventional technologies in methane conversion to achieve the simultaneous and efficient production of hydrogen energy and high-value-added carbon materials, while simultaneously addressing the unconventional technical problems of precise control over carbon product morphology, difficulty in controlling system energy loss, and the inability to simultaneously achieve product purity and stability. Conventional technologies often rely on single pyrolysis methods or simple technology combinations, failing to fundamentally solve these comprehensive challenges and thus unable to meet the urgent needs of high-end sectors for customized carbon materials and high-purity hydrogen energy.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The existing technology faces the challenge of overcoming the limitations of conventional technologies in the methane conversion process to achieve the simultaneous and efficient preparation of hydrogen energy and high-value-added carbon materials. It also addresses the unconventional technical problems of difficulty in precisely controlling the morphology of carbon products, uncontrollable system energy loss, and the inability to simultaneously achieve product purity and stability. To solve these problems, this invention provides a plasma-enhanced methane pyrolysis hydrogen and carbon production system. This system enables the simultaneous and efficient preparation of hydrogen energy and high-value-added carbon materials during the methane conversion process, while precisely controlling the morphology of carbon products, reducing system energy loss, and improving product purity and stability. It overcomes the shortcomings of conventional technologies, such as uncoordinated carbon-hydrogen utilization, singular carbon product control, high energy consumption, and poor product performance.

[0007] This invention is achieved through the following technical solution: This invention provides a plasma-enhanced methane cracking system for hydrogen and carbon production, comprising a gas source, a cracking reaction chamber, and a DC plasma torch; The pyrolysis reaction chamber is equipped with a double-layer stainless steel sleeve catalyst carrier, which includes an inner sleeve and an outer sleeve. The inner sleeve has through holes with a diameter of 5-10 μm, and the outer sleeve has through holes with a diameter of 20-50 μm. The inner wall of the inner sleeve is coated with a catalytic coating; The gas source supplies methane gas into the pyrolysis reaction chamber; the DC plasma torch supplies high-temperature plasma into the double-layer stainless steel sleeve catalyst carrier.

[0008] This invention constructs a double-layer porous stainless steel sleeve as a catalyst carrier to support the catalytic coating within a plasma reaction pyrolysis chamber, thereby creating a deeply coupled structure of plasma pyrolysis and catalytic pyrolysis. Then, by utilizing the synergistic effect of plasma pyrolysis and catalytic pyrolysis, it achieves the simultaneous preparation of high-value-added carbon materials and high-purity hydrogen energy through efficient methane conversion.

[0009] The invention employs a double-layer porous stainless steel sleeve with double-layer through holes. Methane premixed gas enters from the reaction pyrolysis chamber by passing sequentially through the outer sleeve and the inner sleeve, and is injected through the through hole of the inner sleeve. This allows it to form a dual contact mode of "jet-convection" with the plasma. At the same time, the aperture of the through holes decreases from the outside to the inside, forming a gradient pore structure. This ensures both the flowability of the methane premixed gas and prolongs the residence time of the gas in the sleeve, ensuring sufficient reaction with the catalytic coating loaded on the inner wall of the sleeve, thereby achieving a synergistic effect of plasma pyrolysis and catalytic pyrolysis.

[0010] In one specific embodiment, the catalytic coating is a nano-scale Ni-Al2O3-La2O3 composite catalytic coating.

[0011] The composite catalytic coating of the present invention uses Ni as the active center, which can provide catalytic sites for methane cracking; Al2O3 as the support, which can improve the dispersibility and stability of the coating; and La2O3 as an additive, which can regulate the distribution of active sites and inhibit the formation of coke. The present invention strengthens the synergistic effect of "plasma cracking + catalytic cracking" by adapting the three to the high temperature and high activity environment of plasma.

[0012] In one specific embodiment, the thickness of the catalytic coating is 5-10 μm.

[0013] The coating thickness of this invention is controlled at 5-10 μm, which ensures the effective loading of active sites while avoiding excessive thickness that could hinder plasma-gas contact. It also adapts to the pore structure of the double-layer sleeve, ensuring gas flow and sufficient reaction. In a specific embodiment, the catalytic coating is prepared as follows: nickel nitrate, aluminum nitrate, and lanthanum nitrate are used as raw materials, mixed in a mass ratio of Ni:Al₂O₃:La₂O₃ = 80-90:8-15:1-5, with ethylene glycol added as a dispersant and deionized water as a solvent, and stirred to form a uniform sol. The coating is applied inside a double-layer stainless steel sleeve using an immersion-pulling method at a pulling speed of 2-5 mm / s. After drying at room temperature, the coating is calcined in a muffle furnace in stages to form a catalytic coating with stable crystal structure and uniform dispersion.

[0014] In one specific embodiment, the segmented calcination method is as follows: first, preheat to 200℃ for 1-1.5 h, calcinate at 500℃ for 2-3 h, and reduce at 800℃ for 1-1.5 h.

[0015] In one specific embodiment, the DC plasma torch adopts a 30kW bipolar DC arc discharge plasma torch and is equipped with a DC plasma torch power supply, and its specific structure is as follows: (1) Customized electrode materials: The cathode is made of cerium-tungsten alloy (W-2%CeO2), which has the characteristics of high temperature resistance (melting point 3380℃), arc erosion resistance and low work function, effectively extending the service life of the electrode to more than 800 hours; the anode is made of copper-chromium-zirconium alloy (Cu-0.5%Cr-0.1%Zr), which has high conductivity (conductivity ≥80%IACS) and excellent high temperature strength through solid solution strengthening and aging treatment, ensuring stable discharge under high current.

[0016] (2) Power supply adaptation parameters: The power supply adopts full medium frequency inverter technology, with a maximum output power of 30kW, output current of 60-300A, output voltage of 20-100V, and no-load voltage of 500V; in pulse discharge mode, the pulse modulation frequency range is 1-10kHz, the duty cycle is continuously adjustable from 10% to 90%, the arc ignition success rate is 99.9%, and the start-up response time is ≤3 seconds, providing a stable energy supply for the synergistic effect of plasma and catalytic materials.

[0017] In one specific embodiment, a carbon collection steel plate and a carbon product collection tank are provided at the bottom of the pyrolysis reaction chamber. A rotatable nano-carbon collection steel plate is installed below the reaction chamber, with a rotation speed of 0-10 r / min. The nano-carbon generated by methane pyrolysis can be directly enriched on the steel plate, avoiding the accumulation of carbon products and facilitating subsequent collection.

[0018] In one specific embodiment, the carbon collection steel plate is made of multi-layer stainless steel screen (50nm, 100nm, 200nm), the screen material is 316L stainless steel, and it is electrochemically polished to achieve a pore size uniformity of ≤±5%, so as to realize the graded collection of carbon products of different particle sizes.

[0019] In one specific embodiment, a gas mixing device is also included. This device is used to uniformly mix multiple gases supplied by a gas source, which includes nitrogen cylinders, methane cylinders, and helium cylinders. The gas mixing device uses a gas mixer made of polytetrafluoroethylene (PTFE), which is highly corrosion-resistant and does not introduce impurities. Methane and ionized gases (nitrogen / argon) are premixed at a volume ratio of 1:(0.5-2), and auxiliary gases (helium / hydrogen) are added as needed to form a ternary gas mixture system. The flow rate is precisely controlled by a mass flow controller (accuracy ±1%FS).

[0020] In one specific embodiment, the system further includes an integrated filtration-grading-purification system connected to the pyrolysis reaction chamber via a water-cooled pipe, used to filter and purify the generated hydrogen mixture. Specifically, the integrated filtration-grading-purification system uses a palladium-silver alloy membrane (Pd-23%Ag) with a purity of 99.99% and a membrane thickness of 50-100 μm, achieving a hydrogen permeability ≥1.5 × 10⁻⁶ under conditions of 400-450℃ and 0.3-0.5 MPa. -8 mol / (m·s·Pa 0.5 Hydrogen was purified under the condition that the separation factor (H2 / N2) ≥ 1000.

[0021] In one specific embodiment, it also includes an integrated waste heat recovery-water cooling system, which includes a ceramic heat exchanger and a chiller; The chiller is used to supply cooling water to the cooling jacket outside the pyrolysis reaction chamber and the DC plasma torch to achieve cooling. The ceramic heat exchanger is used to recover the heat from the cooling water after heating and to preheat the mixed gas source.

[0022] Specifically, the waste heat recovery-water cooling integrated system consists of a 30kW industrial chiller, a circulating water pump, and a waste heat recovery ceramic heat exchanger. Its core function is to cool high-load components and recover and utilize waste heat. The plasma torch cooling pipes are made of oxygen-free copper (thermal conductivity ≥390W / (m·K)), and the reaction chamber cooling jacket is made of 304 stainless steel, coupled with deionized cooling water (conductivity ≤10μS / cm). The circulating cooling water provides heat dissipation for the plasma torch (to prevent overheating damage, cooling water temperature is controlled at 20-30℃), the pyrolysis reaction chamber (to maintain stable reaction temperature, cooling water temperature is controlled at 40-60℃), and the water-cooled cooling pipes (to rapidly cool the mixed gas), ensuring continuous and stable system operation. The waste heat recovery ceramic heat exchanger is connected in series between the water-cooled cooling pipe and the filtration-grading-purification integrated system. It adopts a shell-and-tube structure and uses the waste heat of the mixed gas after pyrolysis to preheat the premixed gas in the inlet premixing system, raising the temperature of the premixed gas from room temperature to 200-300℃. The recovered heat can reduce the energy consumption of plasma torch preheating.

[0023] In one specific embodiment, an intelligent monitoring and feedback system (16) is also included, which includes a temperature sensor, a gas composition analyzer, and a PID controller. This invention, by equipping a temperature sensor (Pt100, measurement range 0-1200℃, accuracy ±0.5℃) and a gas composition analyzer (detection limit ≤10ppm), and based on a PID algorithm, can dynamically control parameters such as plasma torch discharge power, gas ratio, and cooling water temperature to ensure reaction stability.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention provides a plasma-synergistic enhanced cracking system for methane to produce hydrogen and carbon. By constructing a double-layer porous stainless steel sleeve as a catalyst carrier to support the catalytic coating in the plasma reaction cracking chamber, a deep coupling structure of plasma cracking and catalytic cracking is constructed. Then, by utilizing the synergistic effect of plasma cracking and catalytic cracking, the efficient conversion of methane and the simultaneous preparation of high-value-added carbon materials and high-purity hydrogen energy are achieved. 2. The plasma-enhanced methane-to-hydrogen and carbon production system provided in this embodiment of the invention employs a double-layer porous stainless steel sleeve with double-layer through holes. The methane premixed gas is injected from the reaction cracking chamber through the outer sleeve and the inner sleeve in sequence, and is injected into the inner sleeve through the through hole. It can form a "jet-convection" dual contact mode with the plasma. At the same time, the pore size of the through hole decreases from the outside to the inside, which can form a gradient pore structure. This ensures the flowability of the methane premixed gas and prolongs the residence time of the gas in the sleeve, ensuring sufficient reaction with the catalytic coating loaded on the inner wall of the sleeve, thereby realizing the synergistic effect of plasma cracking and catalytic cracking. 3. The plasma-enhanced methane pyrolysis hydrogen and carbon production system provided in this embodiment of the invention takes "multi-system synergistic enhancement + precise material adaptation" as its core. Through material-equipment coupling optimization and multi-system linkage structure, it realizes the efficient conversion of methane and the simultaneous preparation of high-value-added carbon materials and high-purity hydrogen energy. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the plasma pyrolysis methane hydrogen and carbon production system provided in an embodiment of the present invention; Figure 2 A schematic diagram of the double-layer stainless steel sleeve catalyst support structure provided in an embodiment of the present invention; Figure 3 This invention provides methane conversion rate and hydrogen selectivity under different process parameters in embodiments of the invention. Figure 4 XRD patterns of carbon products under different process parameters provided in embodiments of the present invention; Figure 5 TEM images of carbon products under different process parameters provided in embodiments of the present invention.

[0027] Attached diagrams and component markings: 1-Nitrogen cylinder, 2-Methane cylinder, 3-Helium cylinder, 4-Gas mixing device, 5-Ceramic heat exchanger, 6-Carbon collection steel plate, 7-Pyrolysis reaction chamber, 8-Double-layer stainless steel sleeve catalyst carrier, 9-DC plasma torch power supply, 10-DC plasma torch, 11-Water-cooled cooling pipe, 12-Chiller, 13-Carbon product collection tank, 14-Filtration-classification-purification integrated system, 15-Hydrogen storage tank, 16-Intelligent monitoring system; 81-Catalyst coating, 82-Inner sleeve, 83-Outer sleeve. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0029] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Throughout this specification, references to “an embodiment,” “an example,” or “an example” mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases “an embodiment,” “an example,” “an example,” or “an example” appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0033] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0034] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Existing methane-hydrogen-carbon cogeneration technologies (thermal cracking, catalytic cracking, and melt cracking) suffer from drawbacks such as intermittent operation, catalyst deactivation, low conversion rate, low product purity, and high emissions. While existing plasma cracking methane technology has certain advantages, it still faces problems such as low coupling between units, insufficient gas-plasma contact, limited carbon product control, insufficient energy recovery, high overall energy consumption, and poor product purity and stability.

[0038] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: like Figure 1 and Figure 2 As shown, the present invention provides a plasma-enhanced methane cracking system for hydrogen and carbon production, including a gas source, a cracking reaction chamber 7 and a DC plasma torch 10; The pyrolysis reaction chamber 7 is provided with a double-layer stainless steel sleeve catalyst carrier 8, which includes an inner sleeve 82 and an outer sleeve 83. The inner sleeve 82 has through holes with a diameter of 5-10 μm, and the outer sleeve 83 has through holes with a diameter of 20-50 μm. The inner wall of the inner sleeve 82 is coated with a catalytic coating 81; The gas source supplies methane gas into the cracking reaction chamber 7; the DC plasma torch 10 supplies high-temperature plasma into the double-layer stainless steel sleeve catalyst carrier 8.

[0039] This invention constructs a double-layer porous stainless steel sleeve as a catalyst carrier to support the catalytic coating within a plasma reaction pyrolysis chamber, thereby creating a deeply coupled structure of plasma pyrolysis and catalytic pyrolysis. Then, by utilizing the synergistic effect of plasma pyrolysis and catalytic pyrolysis, it achieves the simultaneous preparation of high-value-added carbon materials and high-purity hydrogen energy through efficient methane conversion.

[0040] The invention employs a double-layer porous stainless steel sleeve with double-layer through holes. Methane premixed gas enters from the reaction pyrolysis chamber by passing sequentially through the outer sleeve and the inner sleeve, and is injected through the through hole of the inner sleeve. This allows it to form a dual contact mode of "jet-convection" with the plasma. At the same time, the aperture of the through holes decreases from the outside to the inside, forming a gradient pore structure. This ensures both the flowability of the methane premixed gas and prolongs the residence time of the gas in the sleeve, ensuring sufficient reaction with the catalytic coating loaded on the inner wall of the sleeve, thereby achieving a synergistic effect of plasma pyrolysis and catalytic pyrolysis.

[0041] In one specific embodiment, the catalytic coating 81 is a nano-scale Ni-Al2O3-La2O3 composite catalytic coating.

[0042] The composite catalytic coating of the present invention uses Ni as the active center, which can provide catalytic sites for methane cracking; Al2O3 as the support, which can improve the dispersibility and stability of the coating; and La2O3 as an additive, which can regulate the distribution of active sites and inhibit the formation of coke. The present invention strengthens the synergistic effect of "plasma cracking + catalytic cracking" by adapting the three to the high temperature and high activity environment of plasma.

[0043] In one specific embodiment, the thickness of the catalytic coating 81 is 5-10 μm.

[0044] The coating thickness of this invention is controlled at 5-10 μm, which ensures the effective loading of active sites while avoiding excessive thickness that would hinder the contact between plasma and gas. At the same time, it is adapted to the pore structure of the double-layer sleeve to ensure gas flow and sufficient reaction.

[0045] In a specific embodiment, the catalytic coating is prepared as follows: nickel nitrate, aluminum nitrate and lanthanum nitrate are used as raw materials, mixed in a mass ratio of Ni:Al2O3:La2O3=80-90:8-15:1-5, ethylene glycol is added as a dispersant, deionized water is used as a solvent, and the mixture is stirred to form a uniform sol. The coating is applied inside a double-layer stainless steel sleeve using an immersion-pulling method at a pulling speed of 2-5 mm / s. After drying at room temperature, the coating is calcined in a muffle furnace in stages to form a catalytic coating with stable crystal structure and uniform dispersion.

[0046] In one specific embodiment, the segmented calcination method is as follows: first, preheat to 200℃ for 1-1.5 h, calcinate at 500℃ for 2-3 h, and reduce at 800℃ for 1-1.5 h.

[0047] In one specific embodiment, the DC plasma torch adopts a 30kW bipolar DC arc discharge plasma torch and is equipped with a DC plasma torch power supply 9, the specific structure of which is as follows: (1) Customized electrode materials: The cathode is made of cerium-tungsten alloy W-2%CeO2, which has the characteristics of high temperature melting point of 3380℃, arc erosion resistance and low work function, effectively extending the service life of the electrode to more than 800 hours; the anode is made of copper-chromium-zirconium alloy Cu-0.5%Cr-0.1%Zr, which has high conductivity (≥80%IACS) and excellent high temperature strength through solid solution strengthening and aging treatment, ensuring stable discharge under high current.

[0048] (2) Power supply adaptation parameters: The power supply adopts full medium frequency inverter technology, with a maximum output power of 30kW, output current of 60-300A, output voltage of 20-100V, and no-load voltage of 500V; in pulse discharge mode, the pulse modulation frequency range is 1-10kHz, the duty cycle is continuously adjustable from 10% to 90%, the arc ignition success rate is 99.9%, and the start-up response time is ≤3 seconds, providing a stable energy supply for the synergistic effect of plasma and catalytic materials.

[0049] In one specific embodiment, a carbon collection steel plate 6 and a carbon product collection tank 13 are provided at the bottom of the pyrolysis reaction chamber 7. A rotatable nano-carbon collection steel plate is provided below the reaction chamber, with a rotation speed of 0-10 r / min. The nano-carbon generated by methane pyrolysis can be directly enriched on the steel plate, avoiding the accumulation of carbon products and facilitating subsequent collection.

[0050] In one specific embodiment, the carbon collection steel plate is made of multi-layer stainless steel screens with diameters of 50nm, 100nm, and 200nm. The screen material is 316L stainless steel and is electrochemically polished to achieve a pore size uniformity of ≤±5%, so as to realize the graded collection of carbon products with different particle sizes.

[0051] In one specific embodiment, a gas mixing device 4 is also included. This device is used to uniformly mix multiple gases supplied by a gas source, which includes a nitrogen cylinder 1, a methane cylinder 2, and a helium cylinder 3. The gas mixing device uses a gas mixer made of polytetrafluoroethylene (PTFE), which is highly corrosion-resistant and does not introduce impurities. Methane is premixed with ionized nitrogen / argon at a volume ratio of 1:(0.5-2), and auxiliary gases helium / hydrogen are added as needed to form a ternary gas mixture system. The flow rate is precisely controlled by a mass flow controller with an accuracy of ±1%FS.

[0052] In one specific embodiment, the system further includes an integrated filtration-grading-purification system 14 and a hydrogen storage tank 15 connected to the pyrolysis reaction chamber 7 via a water-cooled cooling pipe 11, for filtering and purifying the generated hydrogen mixture. Specifically, the integrated filtration-grading-purification system uses a palladium-silver alloy membrane (Pd-23%Ag) with a purity of 99.99% and a membrane thickness of 50-100 μm, achieving a hydrogen permeability ≥1.5 × 10⁻⁶ under conditions of 400-450℃ and 0.3-0.5 MPa. -8 mol / (m·s·Pa 0.5 Hydrogen was purified under the condition that the separation factor H2 / N2≥1000.

[0053] In one specific embodiment, it also includes a waste heat recovery-water cooling integrated system, which includes a ceramic heat exchanger 5 and a chiller 12; The chiller 12 is used to supply cooling water to the cooling jacket outside the pyrolysis reaction chamber 7 and the DC plasma torch 8 to achieve cooling. The ceramic heat exchanger 5 is used to recover the heat from the cooling water after heating and to preheat the mixed gas source.

[0054] Specifically, the waste heat recovery-water cooling integrated system consists of a 30kW industrial chiller, a circulating water pump, and a waste heat recovery ceramic heat exchanger. Its core function is to cool high-load components and recover and utilize waste heat. The plasma torch cooling pipes are made of oxygen-free copper with a thermal conductivity ≥390W / (m·K), and the reaction chamber cooling jacket is made of 304 stainless steel, paired with deionized cooling water with a conductivity ≤10μS / cm. Through circulating cooling water, the system prevents overheating damage to the plasma torch by maintaining a cooling water temperature of 20-30℃, maintains a stable reaction temperature in the pyrolysis reaction chamber by maintaining a cooling water temperature of 40-60℃, and rapidly cools the mixed gas through water-cooled cooling pipes to provide heat dissipation, ensuring continuous and stable system operation. The waste heat recovery ceramic heat exchanger is connected in series between the water-cooled cooling pipe and the filtration-grading-purification integrated system. It adopts a shell-and-tube structure and uses the waste heat of the mixed gas after pyrolysis to preheat the premixed gas in the inlet premixing system, raising the temperature of the premixed gas from room temperature to 200-300℃. The recovered heat can reduce the energy consumption of plasma torch preheating.

[0055] In one specific embodiment, the system further includes an intelligent monitoring and feedback system 16, which comprises a temperature sensor, a gas composition analyzer, and a PID controller. This invention, by equipping the system with a Pt100 temperature sensor (measurement range 0-1200℃, accuracy ±0.5℃) and a gas composition analyzer (detection limit ≤10ppm), and based on a PID algorithm, can dynamically adjust parameters such as plasma torch discharge power, gas ratio, and cooling water temperature to ensure reaction stability.

[0056] Example 1 This invention provides a plasma-enhanced methane pyrolysis system and method for hydrogen and carbon production, used to prepare highly crystalline carbon nanotubes, as detailed below: (1) Material and equipment preparation: Nitrogen (purity 99.99%), methane (purity 99.99%) and helium (purity 99.99%) were used as raw material gases; the inner wall of the inner sleeve of the enhanced contact-type pyrolysis reaction chamber was loaded with a nano-scale nickel-based composite coating (Ni-Al2O3-La2O3) with a La2O3 content of 3% and a coating thickness of 7μm; the discharge gap of the bipolar DC arc discharge plasma torch was adjusted to 1.5mm.

[0057] (2) Preparation process: Nitrogen, methane and helium are introduced into the gas premixer at flow rates of 30 L / min, 40 L / min and 10 L / min respectively and mixed evenly. The mixture is then preheated to 250°C by a waste heat recovery heat exchanger. The mixed gas is introduced into the plasma torch and the power is adjusted to 22 kW in continuous discharge mode. The reaction chamber is preheated to 800°C. Methane is cracked under the synergistic effect of plasma and catalytic coating. The carbon nanotubes generated by the reaction are enriched in the rotatable nano-carbon collection steel plate. After the mixed gas is cooled to 150°C, it is processed by the filtration-grading-purification integrated system.

[0058] (3) Product performance: Highly crystalline carbon nanotubes with a diameter of 15-25 nm and an aspect ratio of ≥500 were obtained, with a carbon product purity of 95.7%; hydrogen purity of 99.995%, methane conversion rate of 96.85%, and hydrogen selectivity of 82.82%.

[0059] Example 2 This invention provides a plasma-enhanced methane pyrolysis system and method for hydrogen and carbon production, used to prepare graphene sheets, as detailed below: (1) Material and equipment preparation: Argon (purity 99.99%), methane (purity 99.99%) and hydrogen (purity 99.99%) are used as raw material gases; the inner wall of the inner sleeve of the enhanced contact-type pyrolysis reaction chamber is loaded with a nano-scale nickel-based composite coating (Ni-Al2O3-La2O3) with a La2O3 content of 1%, and the coating thickness is 5μm; the discharge gap of the bipolar DC arc discharge plasma torch is adjusted to 2mm.

[0060] (2) Preparation process: Argon, methane and hydrogen are introduced into the gas premixer at flow rates of 25 L / min, 35 L / min and 15 L / min respectively and mixed evenly. The mixture is then preheated to 220°C by a waste heat recovery heat exchanger. The mixed gas is introduced into the plasma torch and a pulsed discharge mode (frequency 5 kHz, duty cycle 50%) is adopted. The power is adjusted to 18 kW and the reaction chamber is preheated to 750°C. The methane is cracked under the synergistic effect of plasma and catalytic coating. The graphene sheets generated by the reaction are enriched on the rotatable nano-carbon collection steel plate. After the mixed gas is cooled to 180°C, it is processed by the filtration-grading-purification integrated system.

[0061] (3) Product performance: Graphene sheets with 3-8 layers and lateral dimensions of 1-5 μm were obtained, with carbon product purity of 99.6%; hydrogen purity of 99.992%, methane conversion rate of 94.82%, and hydrogen selectivity of 80.26%.

[0062] Example 3 This invention provides a plasma-enhanced methane pyrolysis system and method for producing hydrogen and carbon, used to prepare fine-particle-size nano-carbon, as detailed below: (1) Material and equipment preparation: Nitrogen (purity 99.99%) and methane (purity 99.99%) were used as raw material gases; the inner wall of the inner sleeve of the enhanced contact-type pyrolysis reaction chamber was loaded with a nano-scale nickel-based composite coating (Ni-Al2O3-La2O3) with a La2O3 content of 5% and the coating thickness was 10μm; the discharge gap of the bipolar DC arc discharge plasma torch was adjusted to 1mm.

[0063] (2) Preparation process: Nitrogen and methane are introduced into the gas premixer at flow rates of 40 L / min and 30 L / min respectively and mixed evenly. The mixture is then preheated to 200°C by a waste heat recovery heat exchanger. The mixed gas is introduced into the plasma torch and the power is adjusted to 15 kW in continuous discharge mode. The reaction chamber is preheated to 780°C and the methane is cracked under the synergistic effect of plasma and catalytic coating. The fine-particle nano-carbon generated by the reaction is enriched in the rotatable nano-carbon collection steel plate. After the mixed gas is cooled to 160°C, it is processed by the filtration-grading-purification integrated system.

[0064] (3) Product performance: Fine-particle nano-carbon with a particle size of 20-50nm and uniform distribution was obtained, with a carbon product purity of 99.5%; hydrogen purity of 99.99%, methane conversion rate of 97.88%, and hydrogen selectivity of 81.53%.

[0065] Comparative Example 1 This comparative example provides a plasma-enhanced methane pyrolysis system and method for hydrogen and carbon production, as detailed below: (1) Material and equipment preparation: Nitrogen (99.99% purity), methane (99.99% purity) and helium (99.99% purity) are used as raw material gases; there is no sleeve in the pyrolysis reaction chamber; the discharge gap of the bipolar DC arc discharge plasma torch is adjusted to 1.5mm.

[0066] (2) Preparation process: Nitrogen, methane and helium are introduced into the gas premixer at flow rates of 30L / min, 40L / min and 10L / min respectively and mixed evenly. The mixture is then preheated to 200℃ by a waste heat recovery heat exchanger. The mixed gas is introduced into the plasma torch and the power is adjusted to 22kW in continuous discharge mode. The reaction chamber is preheated to 750℃ and the methane is cracked under the action of plasma. The carbon material generated by the reaction is enriched in the rotatable nano carbon collection steel plate. After the mixed gas is cooled to 150℃, it is processed by the filtration-grading-purification integrated system.

[0067] (3) Product performance: Irregularly shaped low-crystallinity carbon nanotubes were obtained, with a carbon product purity of 80.5%; hydrogen purity of 95.86%, methane conversion rate of 65.85%, and hydrogen selectivity of 58.28%.

[0068] The difference between this comparative example and Example 1 is that no double-layer sleeve was installed in the pyrolysis reaction chamber.

[0069] Comparative Example 2 This comparative example provides a plasma-enhanced methane pyrolysis system and method for hydrogen and carbon production, as detailed below: (1) Material and equipment preparation: Nitrogen (99.99% purity), methane (99.99% purity) and helium (99.99% purity) are used as raw material gases; the inner wall of the inner sleeve of the pyrolysis reaction chamber is uncoated; the discharge gap of the bipolar DC arc discharge plasma torch is adjusted to 1.5mm.

[0070] (2) Preparation process: Nitrogen, methane and helium are introduced into the gas premixer at flow rates of 30L / min, 40L / min and 10L / min respectively and mixed evenly. The mixture is then preheated to 200℃ by a waste heat recovery heat exchanger. The mixed gas is introduced into the plasma torch and the power is adjusted to 22kW in continuous discharge mode. The reaction chamber is preheated to 750℃ and the methane is cracked under the action of plasma. The carbon material generated by the reaction is enriched in the rotatable nano carbon collection steel plate. After the mixed gas is cooled to 150℃, it is processed by the filtration-grading-purification integrated system.

[0071] (3) Product performance: Irregularly shaped low-crystallinity carbon nanotubes were obtained, with a carbon product purity of 82.4%; hydrogen purity of 96.65%, methane conversion rate of 68.24%, and hydrogen selectivity of 60.46%.

[0072] The difference between this comparative example and Example 1 is that the inner wall of the double-layered sleeve installed in the pyrolysis reaction chamber has no coating.

[0073] Test Results Figure 3 The methane conversion rate and hydrogen selectivity of Examples 1-3 (S3-S5) and Comparative Examples 1-2 (S1-S2) under different process parameters are shown. It can be seen that the methane conversion rate of Examples 1-3 of the present invention is ≥94.8% and the hydrogen selectivity is ≥80.2%, which reflects the efficient conversion effect of the synergistic effect of the materials and processes of the present invention.

[0074] Figure 4 The XRD patterns of carbon products under different process parameters for Examples 1-3 (S3-S5) and Comparative Examples 1-2 (S1-S2) are shown. Curves S1-S5 correspond to the following carbon products: Comparative Example 1 (amorphous carbon, no sleeve, continuous discharge 22kW); Comparative Example 2 (amorphous carbon, with sleeve but no coating inside the sleeve, continuous discharge 22kW); and the following examples (carbon nanotubes, La2O3 content 3%, continuous discharge 22kW), Example 2 (graphene sheets, La2O3 content 1%, pulsed discharge 18kW), and Example 3 (fine-particle-size nanocarbon, La2O3 content 5%, continuous discharge 15kW). The diffraction peaks near 2θ=26° (corresponding to the (002) crystal plane of carbon material) in curves S1 and S2 are relatively weak; the curves S3-S5 show strong diffraction peaks near 2θ=26° (corresponding to the (002) crystal plane of carbon material), with no impurity peaks, indicating high purity of carbon products.

[0075] Figure 5TEM images of carbon products from Examples 1-3 (S3-S5) and Comparative Examples 1-2 (S1-S2) under different process parameters are shown. Figure (a) shows the carbon material prepared in Comparative Example 1, exhibiting an irregular shape; Figure (b) shows the carbon material prepared in Comparative Example 2, also exhibiting an irregular shape; Figure (c) shows the carbon nanotubes prepared in Example 1, showing a tubular structure with a clear lattice in the tube walls and no obvious defects; Figure (d) shows the graphene sheets prepared in Example 2, exhibiting a 3-8 layer stacked sheet structure; Figure (e) shows the fine-particle-size carbon nanotubes prepared in Example 3, with uniformly distributed spherical particles. Figure 5 The TEM images can intuitively verify the effectiveness of the triple synergistic mechanism of "gas ratio + discharge mode + catalytic coating" of the present invention, and confirm that the process can accurately prepare high-value-added carbon materials with different morphologies, which is corroborated by the XRD test results.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A plasma-enhanced methane pyrolysis system for hydrogen and carbon production, characterized in that, Includes a gas source, a pyrolysis reaction chamber (7), and a DC plasma torch (10); The pyrolysis reaction chamber (7) is equipped with a double-layer stainless steel sleeve catalyst carrier (8). The double-layer stainless steel sleeve catalyst carrier (8) includes an inner sleeve (82) and an outer sleeve (83). The inner sleeve (82) has through holes with a diameter of 5-10 μm, and the outer sleeve (83) has through holes with a diameter of 20-50 μm. Both the inner sleeve (82) and the outer sleeve (83) are made of 316L stainless steel and are subjected to high-temperature annealing treatment at 800℃ for 2 hours to improve structural stability and corrosion resistance. The inner wall of the inner sleeve (82) is coated with a catalytic coating (81). The gas source supplies methane gas to the inside of the cracking reaction chamber (7); the DC plasma torch (10) supplies high-temperature plasma to the double-layer stainless steel sleeve catalyst carrier (8).

2. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, The catalytic coating (81) is a nano-scale Ni-Al2O3-La2O3 composite catalytic coating.

3. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 2, characterized in that, The thickness of the catalytic coating (81) is 5-10 μm.

4. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 3, characterized in that, The catalytic coating is prepared as follows: nickel nitrate, aluminum nitrate, and lanthanum nitrate are used as raw materials and mixed in a mass ratio of Ni:Al2O3:La2O3=80-90:8-15:1-5. Ethylene glycol is added as a dispersant and deionized water is used as a solvent. The mixture is stirred to form a uniform sol. The coating is applied inside a double-layer stainless steel sleeve using an immersion-pulling method at a pulling speed of 2-5 mm / s. After drying at room temperature, the coating is calcined in a muffle furnace in stages to form a catalytic coating with stable crystal structure and uniform dispersion.

5. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 4, characterized in that, The specific method for segmented roasting is as follows: first, preheat to 200℃ for 1-1.5 h, roast at 500℃ for 2-3 h, and then reduce at 800℃ for 1-1.5 h.

6. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, The bottom of the pyrolysis reaction chamber (7) is equipped with a carbon collection steel plate (6) and a carbon product collection tank (13).

7. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, It also includes a gas mixing device, which is used to mix multiple gases provided by a gas source evenly. The gas source includes a nitrogen cylinder (1), a methane cylinder (2), and a helium cylinder (3).

8. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, It also includes a waste heat recovery-water cooling integrated system, which includes a ceramic heat exchanger (5) and a chiller (12). The chiller (12) is used to supply cooling water to the cooling jacket outside the pyrolysis reaction chamber (7) and the DC plasma torch (10) to achieve cooling; The ceramic heat exchanger (5) is used to recover the heat of the cooling water after heating and to preheat the mixed gas source.

9. The plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, It also includes a filtration-grading-purification integrated system (14) connected to the pyrolysis reaction chamber (7) via a water-cooled cooling pipe, for filtering and purifying the generated hydrogen mixture.

10. A plasma-enhanced methane pyrolysis system for hydrogen and carbon production according to claim 1, characterized in that, It also includes an intelligent monitoring and feedback system (16), which includes a temperature sensor, a gas composition analyzer and a PID controller.

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