Device and test method for directly driving methane dry reforming based on Joule heat

Abstract

The invention provides a device for directly driving methane dry reforming based on Joule heat and a test method, and belongs to the technical field of methane dry reforming reaction. The problems that a traditional methane dry reforming device is high in energy consumption and low in efficiency in the reaction process are solved. A device for directly driving methane dry reforming based on Joule heat comprises a heating device, a reaction container and a resistance wire, and the heating device is arranged outside the reaction container. The method is applied to the field of carbon capture and resource utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of methane dry reforming reaction, and in particular to a device and a test method for directly driving methane dry reforming based on Joule heat. Background Art

[0002] Methane (CH4) and carbon dioxide (CO2) are two major greenhouse gases, whose excessive emissions have profound impacts on global climate change. The global warming potential (GWP) of methane is 28–36 times that of CO2 on a 100-year scale, and its atmospheric concentration has increased by over 150% since the Industrial Revolution, primarily due to agricultural activities, fossil fuel extraction, and waste disposal. As a major contributor to the greenhouse effect, CO2 concentration has exceeded 420 ppm, far exceeding the pre-industrial level of 280 ppm. To mitigate the greenhouse effect, the international community has adopted technologies such as carbon capture and storage (CCS), renewable energy substitution, and methane recovery and utilization. Catalytic conversion (such as dry methane reforming, DRM) is also being promoted to convert CH4 and CO2 into synthesis gas (CO + H2) for resource utilization. However, existing technologies generally suffer from high energy consumption, low efficiency, and secondary pollution, necessitating the development of new, efficient, and low-carbon greenhouse gas conversion strategies.

[0003] Among greenhouse gas recovery technologies, dry reforming of methane (DRM) has attracted considerable attention due to its ability to simultaneously convert CH4 and CO2. Conventional DRM relies on high temperatures (700-1000°C) and nickel-based catalysts. However, these high temperatures lead to significant energy consumption, and the catalysts are easily deactivated by carbon deposition and sintering, requiring frequent regeneration or replacement, significantly increasing costs. Furthermore, side reactions (such as the cracking of methane to produce solid carbon) not only reduce product selectivity but also exacerbate equipment corrosion and environmental pollution. Although other technologies, such as electrocatalysis and photocatalysis, can drive the reaction under mild conditions, their low reaction rates, poor catalyst stability, and reliance on precious metals (such as Pt and Ru) limit their large-scale application. Furthermore, carbon capture technologies (such as amine absorption) consume significant amounts of heat energy during the adsorption-desorption process and may release toxic degradation products. Therefore, developing a fast-response, low-energy, and precious metal-free CH4 / CO2 conversion technology has become a core challenge in current research. Summary of the Invention

[0004] In light of this, the present invention addresses this challenge by innovatively proposing a low-carbon reforming technology system based on in-situ Joule heating catalysis. This system utilizes a coupled electro-thermal-chemical field mechanism, enabling catalyst self-heating through the manipulation of the material's dielectric properties. This direct electrical current heats the catalyst support, enabling rapid temperature rise and control. Combined with in-situ catalytic design, this system is expected to overcome the energy efficiency bottleneck of traditional reactors.

[0005] To achieve the above objectives, according to one aspect of the present invention, there is provided a device for directly driving methane dry reforming based on Joule heat, comprising:

[0006] A methane dry reforming device comprises a heating device, a reaction container and a resistance wire, wherein the heating device is arranged outside the reaction container.

[0007] Furthermore, the upper and lower ends of the reaction container are respectively provided with an upper rubber stopper and a lower rubber stopper to ensure the airtightness of the reaction process. The upper rubber stopper is provided with an upper rubber stopper resistance wire passage, and the lower rubber stopper is provided with a lower rubber stopper resistance wire passage.

[0008] Furthermore, the upper and lower parts of the reaction container are respectively provided with an air inlet channel and an air outlet channel.

[0009] Furthermore, the gas inlet channel is connected to a gas supply assembly for delivering inert gas or methane-carbon dioxide mixed gas into the reaction container.

[0010] Furthermore, the gas outlet channel is connected to a reaction product collecting assembly for collecting the mixed gas after the reaction.

[0011] Furthermore, the reaction container is a quartz glass tube container.

[0012] Furthermore, the resistance wire is a tungsten wire.

[0013] According to another aspect of the present invention, a test method using the device for directly driving methane dry reforming based on Joule heat is provided, comprising the following steps:

[0014] S1. Empty the air in the reaction vessel through the gas supply assembly and install a reaction product collection assembly at the outlet end of the gas outlet channel;

[0015] S2. Start the heating device to heat the resistance wire and stabilize the current of the heating device. When the resistance wire reaches the target temperature and maintains it for a certain period of time, use the gas supply component to deliver a methane-carbon dioxide mixed gas into the intake passage;

[0016] S3, the methane-carbon dioxide mixed gas contacts the resistance wire and reacts with heat to form product gas, which is discharged from the gas outlet channel into the reaction product collection component;

[0017] S4. After the reaction is completed, stop supplying the methane-carbon dioxide mixed gas and turn off the heating device after the gas reaction in the reactor device is complete. Remove the reaction product collection component and the test is completed.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This system is simpler in structure and low in cost, which can increase the cost control advantage;

[0020] 2. The current-carrying conductor of this system also acts as a reaction catalyst, which simplifies the experimental device and facilitates its installation;

[0021] 3. This system reduces the volume of the reactor, can achieve effective heat transfer in the mixed gas, can improve energy utilization efficiency, and increase the reaction product generation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 This is a partial structural diagram of a device for directly driving methane dry reforming based on Joule heat according to the present invention;

[0024] Figure 2 This is a schematic diagram of the overall structure of a device for directly driving methane dry reforming based on Joule heat according to the present invention.

[0025] Methane dry reforming device 1; heating device 1-1; reaction container 1-2; resistance wire 1-3; upper rubber plug 2; upper rubber plug resistance wire passage 2-1; lower rubber plug 3; lower rubber plug resistance wire passage 3-1; air inlet channel 4; air outlet channel 5. DETAILED DESCRIPTION

[0026] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. The features of the embodiments and examples of the present invention can be combined with each other. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0027] It should be noted that the descriptions of the present invention regarding directions such as "left", "right", "left side", "right side", "upper", "lower", "top", and "bottom" are all defined based on the relationship between the orientations or positions shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure described must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0028] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances. Specific implementation method one:

[0030] The present embodiment provides a device for direct Joule heat-driven methane dry reforming, the system comprising:

[0031] Methane dry reforming device 1; heating device 1-1; reaction vessel 1-2; resistance wire 1-3; upper rubber plug 2; upper rubber plug resistance wire passage 2-1; lower rubber plug 3; lower rubber plug resistance wire passage 3-1; gas supply assembly; reaction product collection assembly;

[0032] The gas supply assembly is used to provide an argon gas flow to the methane dry reforming device 1 through the gas pipe, and then provide a methane-carbon dioxide mixed gas flow to the methane dry reforming device 1 through the gas pipe;

[0033] The methane dry reforming device 1 heats the introduced methane-carbon dioxide mixed gas to catalytically dry reform the methane; the catalytic reforming product enters the reaction product collection component through the gas outlet pipe; the methane dry reforming device 2 increases and controls the temperature through the DC power supply of the heating device 1-1.

[0034] Traditional dry reforming of methane (DRM) has problems such as large energy loss, uneven heating, slow response speed, separation of the heating system and catalyst, easy deactivation of traditional catalysts at high temperature and high current density, and poor resistance to carbon deposition, resulting in short catalyst life. These problems lead to low energy transfer efficiency and energy utilization, and unstable product quality.

[0035] The system proposed in this embodiment utilizes Joule heating technology, whereby heat generated by current flowing through a conductive material directly acts on the reactants, achieving rapid and uniform heating. The close integration of the conductive material and catalyst reduces the size and complexity of the equipment while improving heat transfer efficiency and product quality. Specific implementation method 2:

[0037] This embodiment is a further limitation of the device for directly driving methane dry reforming based on Joule heat described in the first embodiment. Before the reaction gas is introduced into the gas supply assembly, sufficient high-purity argon must be introduced into the reaction chamber of the methane dry reforming device 1 through a mass flow meter at a flow rate of 200 ml / min for 5 minutes to ensure that the oxygen content is <10 ppm.

[0038] Argon, an inert gas, is not easily chemically reactive with the methane-CO2 mixture, making it crucial for the methane dry reforming process. Oxygen, a strong oxidant, undergoes a partial oxidation (POX) reaction with methane, competing with CO2 for methane consumption and reducing the selectivity of the primary dry reforming reaction. Residual oxygen also undergoes secondary reactions with the products H2 and CO, severely degrading the syngas quality.

[0039] The surface of tungsten filament will react with oxygen at high temperature to form brittle oxide (such as WO3, melting point 1473℃). The resistivity of this oxide layer is as high as 10^4Ω·cm (12 orders of magnitude higher than that of metal tungsten), resulting in a sharp drop in Joule thermal efficiency (thermal power P=I 2 XPS analysis showed that the oxygen atom coverage of the tungsten filament surface in an oxygen-containing environment reached 32% within 10 minutes, covering the catalytic active sites and reducing the methane conversion rate. Furthermore, WO3 is volatile at high temperatures, causing irreversible catalyst loss.

[0040] Inert gas argon is introduced into the methane dry reforming reaction system to exclude oxygen, maintain the purity of the reaction product gas, maintain thermodynamic equilibrium, avoid the accelerated formation of carbon deposits, inhibit catalyst oxidation deactivation, and avoid the risk of combustion and explosion, ensuring the stability of the methane dry reforming reaction process and improving reaction efficiency. Specific implementation method three:

[0042] This embodiment is a further limitation of the device for direct Joule heat-driven methane dry reforming described in the first embodiment. In the methane dry reforming device 1, the dry reforming reaction (DRM) of methane (CH4) and carbon dioxide (CO2) occurs in a quartz glass tube reaction chamber under high temperature and inert atmosphere. The core reaction is: CH4+CO2→2CO+2H2 (ΔH=+247kJ / mol, endothermic reaction). This process involves multi-physical field coupling such as gas-solid interface catalysis, Joule heat transfer and gas diffusion.

[0043] In this embodiment, a methane dry reforming reaction process is realized. After sufficient inert gas argon passes through, the heating device is started to heat the resistance wire to a stable temperature. The configured methane-carbon dioxide mixed gas is input into the air inlet pipe through the gas supply component to fully contact the resistance wire, thereby realizing the stable progress of the methane dry reforming reaction. The reaction products flow out of the methane dry reforming device 1 through the air outlet pipe and enter the reaction product collection component for collection. Specific implementation method four:

[0045] This embodiment further defines the Joule-heat-based direct-driven methane dry reforming device described in Specific Embodiment 1. The methane dry reforming device 1 comprises a quartz glass reaction chamber, a rubber stopper, an air inlet pipe, an air outlet pipe, and a tungsten metal resistance wire as a heat carrier. The tungsten metal resistance wire is connected to the positive and negative electrodes of a DC power supply for a heating device 1-1 via upper and lower rubber stoppers, respectively. The air inlet pipe is connected to a gas supply assembly.

[0046] In this embodiment, the quartz glass tube reaction chamber serves as a stable container for high-temperature reactions. It is made of high-purity fused quartz material with a suitable thermal expansion coefficient, which can withstand rapid cooling and heating cycles from 1200°C to room temperature. The transmittance is greater than 90% (wavelength 2-5μm), allowing infrared thermometers to monitor the temperature field non-contact. The tube inner diameter of 6mm reduces the frequency of collisions between gas molecules and the tube wall by 50%, reducing the boundary layer thickness and improving mass transfer efficiency.

[0047] In this embodiment, a fluororubber sealing plug is used as a high-temperature airtight barrier. The rubber plug and the quartz tube have an interference fit, using elastic deformation to fill surface microgaps. At high temperatures, the rubber undergoes stress relaxation, and the preload force maintains the seal, minimizing leakage.

[0048] In this embodiment, the preheated mixed gas flows through the ventilation pipe to form a laminar flow (Reynolds number Re < 100), ensuring uniform gas distribution and avoiding uneven mass transfer on the catalyst surface caused by excessive local flow velocity. Specific implementation method five:

[0050] This embodiment is a further limitation of the device for direct-driven methane dry reforming based on Joule heat described in the first embodiment. The tungsten metal resistance wire realizes the dual functions of heat and catalysis. The high-melting-point tungsten wire with excellent performance is selected. It has excellent high-temperature strength (tensile strength > 500MPa at 900°C) and oxidation resistance. According to the formula P=I 2 R(T), resistance R shows positive temperature coefficient (PTC) characteristics as temperature increases (room temperature resistance 5.6×10 -8 Ω·m, increased to 1.2×10 at 900℃ -7 Ω·m), and accurate temperature control is achieved through closed-loop PID control of current.

[0051] A tungsten wire resistor (0.1mm in diameter) is driven by a DC power supply and fed with a current of 15-20W. The Joule effect (P = I 2 R) Rapidly heat up to 800-1000℃ to promote methane dissociation and adsorption:

[0052] CH4→C+4H**(*indicates adsorption state)

[0053] CO2 is adsorbed on the oxygen vacancies on the surface of the tungsten filament at high temperature and activated:

[0054] CO2→CO+O**

[0055] Surface reaction and product desorption

[0056] The adsorbed carbon species (C) combines with surface oxygen (O) to form CO:

[0057] C+O→CO↑**

[0058] Hydrogen atoms (H) combine to form H2:

[0059] 2H→H2↑

[0060] The entire reaction is controlled by a local temperature gradient (>200°C / mm) induced by Joule heat. The high-temperature zone (near the tungsten filament surface) promotes the endothermic main reaction, while the low-temperature zone (near the quartz tube wall) suppresses the reverse water-gas shift (RWGS: CO+H2O→CO2+H2), resulting in a CO selectivity of >90%. Specific implementation method six:

[0062] This embodiment further limits the device for direct Joule heat-driven methane dry reforming described in the first embodiment. The initial flow rate of argon is set to 200 ml / min, and the ventilation time is set to 5 min.

[0063] In this embodiment, the initial argon flow rate is set to 300 mL / min, which helps maintain atmosphere stability during the cracking reaction. The ventilation time is set to 5 minutes, which can effectively remove oxygen from the reaction chamber of the methane dry reforming device 1 and impurities in the air that may affect the experimental results, ensuring experimental safety and improving experimental efficiency. Specific implementation method seven:

[0065] This embodiment further defines the Joule-heat-based direct methane dry reforming device described in Specific Embodiment 1. A methane-CO2 gas stream is introduced into the methane dry reforming device 1 at a volume ratio of 1:1, ensuring that the reactants are supplied strictly according to the stoichiometric ratio and avoiding excess or insufficient amounts of either reactant. Experiments have shown that when the CH4:CO2 ratio deviates from 1:1, the proportion of unreacted gas increases significantly (e.g., at 1.2:1, the residual CO2 content reaches 15%), reducing raw material utilization.

[0066] In this embodiment, when the CO2 ratio is insufficient, the methane cracking reaction (CH4 → C + 2H2) dominates, and the carbon deposition rate increases exponentially. SEM observations show that when the CH4:CO2 ratio is 1.5:1, the carbon thickness on the tungsten filament surface increases, the coverage of the catalyst active sites increases, and the methane conversion rate decreases. Excessive CO2 exacerbates the reverse water-gas shift reaction, which consumes H2 and produces H2O, reducing the quality of the syngas.

[0067] The conclusion drawn from thermodynamic calculations, kinetic experiments, and material characterization is that a 1:1 volume ratio is irreplaceable in inhibiting carbon deposition, maintaining catalyst activity, optimizing product ratios, and reducing overall costs. It is one of the core parameters for achieving efficient, stable, and low-carbon operation of this device. Specific implementation method eight:

[0069] This embodiment further limits the device for direct Joule heat-driven methane dry reforming described in the first embodiment, wherein the methane-carbon dioxide gas flow rate is 5-20 ml / min. In the miniaturized Joule heat-driven methane dry reforming system, controlling the mixed gas flow rate at 5-20 ml / min is a core parameter for balancing reaction kinetics, mass and heat transfer efficiency, catalyst life, and system safety.

[0070] In this embodiment, if the methane-carbon dioxide gas flow rate is too low, the reactants will remain in the reaction zone for too long, potentially leading to overreaction or carbon deposition. If the flow rate is too high, the residence time may be too short, resulting in incomplete reaction and reduced conversion. Furthermore, an appropriate flow rate maintains laminar flow, ensuring uniform gas flow, optimal contact with the tungsten wire conductor, and optimal reaction efficiency, thereby increasing product yield. Specific implementation method nine:

[0072] This embodiment provides a specific example of a device for directly driving methane dry reforming based on Joule heat as described in the first embodiment, and is also used to explain the second to fifth embodiments. Specifically:

[0073] (1) Preliminary preparation

[0074] The quartz glass tube used in this system has an outer diameter of 10mm, an inner diameter of 6mm, a length of 180mm, and a light transmittance greater than 90%. It also uses a closed-loop PID controlled DC power supply system with a maximum power of 150W. The tungsten wire conductor has a diameter of 0.1mm and a melting point of 3410°C. It uses a high-temperature resistant fluororubber rubber stopper, and the reaction product collection component uses an aluminum foil gas collection bag.

[0075] (2) System implementation process

[0076] High-purity argon gas was introduced into the reaction chamber of the methane dry reforming unit 1 through a mass flow meter at a flow rate of 200 ml / min for 5 minutes, ensuring that the oxygen content was <10 ppm. The entire experimental process was maintained in an inert atmosphere. A tungsten metal conductor resistance wire was heated using a DC power supply of 15-20 W using the heating device 1-1. The heating device achieved precise temperature control through a feedback regulation system. Joule heat was transferred to the tungsten wire, thereby increasing its temperature (heating power P = I 2R), the heating device is started for 1 minute to rapidly increase the temperature of the tungsten filament. After heating for 5 minutes, the temperature of the tungsten filament tends to stabilize. The current is adjusted in real time through the temperature sensor feedback system to maintain the resistance filament within the set reaction temperature range, so as to stabilize the temperature field of the catalytic methane dry reforming reaction; a methane-carbon dioxide mixed gas flow is introduced into the reaction chamber of the methane dry reforming device 1 through the gas supply assembly at a flow rate of 5-20 ml / min, with a mixing ratio of methane and carbon dioxide of 1:1 by volume, to optimize the reaction conditions.

[0077] As the mixed gas enters the reaction vessel, it undergoes heat exchange with the resistance wire, forming a reaction environment for methane dry reforming. The reaction products are primarily syngas (H2 and CO). The dry reformed gas product is collected through an outlet pipe into an aluminum foil sampling bag and further analyzed by gas chromatography (GC). The pressure and temperature within the reaction vessel are monitored to ensure they remain within safe ranges and react effectively. The generated gas should be sampled and analyzed regularly for H2, CO, and unreacted CH4 and CO2.

[0078] (3) Data processing

[0079] The experimental gas products, primarily composed of H₂, CO, and unreacted CH₄ and CO₂, were qualitatively and quantitatively analyzed using gas chromatography (GC). The conversion rates of methane (CH₄) and carbon dioxide (CO₂), as well as the yield of syngas (CO + H₂), were calculated through multi-dimensional data calibration and thermodynamic model validation.

[0080] The volume fraction Vi of the gas component i (H2, CH4, CO2, CO) was determined by gas chromatography, and the amount ni of each gas component i (H2, CH4, CO2, CO) was calculated by collecting the total volume of the gas.

[0081] The conversion rate (X) of methane in the methane dry reforming reaction is:

[0082]

[0083] Selectivity (S) is used to evaluate the reaction preference toward syngas:

[0084]

[0085] The methane conversion (X) was used to analyze the efficiency of the in-situ catalytic methane dry reforming reaction, and the selectivity (S) was used to evaluate the quality of the generated gas.

[0086] (IV) Key indicators

[0087] In this embodiment, the system's methane conversion yield and gas yield, gas selectivity for different gas components, and the temperature field in the system were evaluated. The results demonstrate that the Joule-heat-based direct-driven methane dry reforming device constructed in this invention exhibits excellent methane dry reforming gas yield and methane conversion. In-situ Joule-heat-based catalytic methane dry reforming offers a fast-response, low-energy, and precious metal catalyst-free CH4 / CO2 conversion technology for traditional methane dry reforming processes. By tightly integrating conductive materials and catalysts, it improves heat transfer efficiency and product quality.

[0088] The above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions and core principles of the present invention, and do not constitute any limitation on the scope of protection of the present invention. It should be understood by those skilled in the art that any equivalent replacement, component modification, parameter adjustment or process improvement based on the technical concept disclosed in the present invention, without departing from the design purpose of the present invention, should be deemed to fall within the scope of protection defined by the claims of the present invention.

Claims

1. A device for directly driving methane dry reforming based on Joule heat, characterized in that: include: A methane dry reforming device (1) comprises a heating device (1-1), a reaction container (1-2) and a resistance wire (1-3), wherein the heating device (1-1) is arranged outside the reaction container (1-2).

2. The device for direct Joule heat-driven methane dry reforming according to claim 1, characterized in that: The upper and lower ends of the reaction container (1-2) are respectively provided with an upper rubber stopper (2) and a lower rubber stopper (3) for ensuring the airtightness of the reaction process; the upper rubber stopper (2) is provided with an upper rubber stopper resistance wire passage channel (2-1), and the lower rubber stopper (3) is provided with a lower rubber stopper resistance wire passage channel (3-1).

3. The device for direct Joule heat-driven methane dry reforming according to claim 1, characterized in that: An air inlet channel (4) and an air outlet channel (5) are respectively provided at the upper and lower parts of the reaction container (1-2).

4. The device for direct Joule heat-driven methane dry reforming according to claim 3, characterized in that: The gas inlet channel (4) is connected to a gas supply component, and the gas supply component is used to transport inert gas or methane-carbon dioxide mixed gas into the reaction container (1-2).

5. The device for direct Joule heat-driven methane dry reforming according to claim 1, characterized in that: The gas outlet channel (5) is connected to a reaction product collecting component, and the reaction product collecting component is used to collect the mixed gas after the reaction.

6. The device for direct Joule heat-driven methane dry reforming according to claim 1, characterized in that: The reaction container (1-2) is a quartz glass tube container.

7. The device for direct Joule heat-driven methane dry reforming according to claim 1, characterized in that: The resistance wire (1-3) is a tungsten wire.

8. A test method using a device for direct Joule heat driven methane dry reforming according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, evacuating the air in the reaction vessel (1-2) through the gas supply assembly, and installing a reaction product collection assembly at the outlet end of the gas outlet channel (5); S2, starting the heating device (1-1) to heat the resistance wire (1-3), stabilizing the current of the heating device (1-1), and when the resistance wire (1-3) reaches the target temperature and maintains it for a certain period of time, using the gas supply component to deliver a methane-carbon dioxide mixed gas into the intake passage; S3, the methane-carbon dioxide mixed gas contacts the resistance wire (1-3) and reacts with heat to form a product gas, which is discharged from the gas outlet channel (5) into the reaction product collection component; S4. After the reaction is completed, stop supplying the methane-carbon dioxide mixed gas and wait until the gas in the system reacts completely before turning off the heating device (1-1), removing the reaction product collection component, and the test is completed.

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