Reforming reaction system based on Joule thermal effect and application thereof

Abstract

The invention provides a reforming reaction system based on a Joule heat effect and application of the reforming reaction system. The reforming reaction system comprises a raw material gas inlet unit, a reaction tube, a Joule heating unit and a power supply device, wherein the reaction tube comprises a gas inlet, a gas outlet and a reaction cavity, and the gas inlet is connected with the raw material gas inlet unit; the Joule heating unit comprises a heating element, the heating element is arranged in the reaction cavity, the heating element comprises a preheating zone and a reaction zone, and the preheating zone is adjacent to the gas inlet; the power supply device provides current to enable the heating element to generate heat. The monolithic catalyst is directly heated in the reaction tube based on the Joule effect, high-temperature accurate control is achieved, generated heat is rapidly and evenly transferred to active sites of the catalyst, the catalyst is applied to a method for preparing synthesis gas through methane and carbon dioxide reforming reaction, catalytic performance is improved, and long-period stable operation of catalytic reaction is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of methane carbon dioxide reforming reaction, and particularly relates to a reforming reaction system based on Joule heat effect and its application. Background Art

[0002] Methane carbon dioxide reforming is an important chemical process for producing valuable chemicals such as syngas. However, this reaction is a strongly endothermic reaction, and traditional reforming processes require very high industrial temperatures, usually requiring external heating. Specifically, the traditional heating method is external heating, that is, burning fossil fuels to provide the heat required for the reaction. This method has many drawbacks. On the one hand, burning fossil fuels consumes a large amount of fuel, increasing production costs; on the other hand, the combustion process produces a large amount of greenhouse gases such as carbon dioxide, having a negative impact on the environment.

[0003] Traditional methane reforming reactors are large in volume and have heat transfer limitations on the inner and outer walls, resulting in a large temperature gradient inside the reactor, and only a very small part of the catalyst can fully play its role, reducing the effective utilization rate of the catalyst. In order to avoid the formation of stress or local hot spots of heat in the reactor tube, it is necessary to precisely balance the energy supplied for heating and the energy consumed by the endothermic reaction. Directly heating the catalyst inside the reaction tube avoids the heat limitation between the tube and the outside, and is expected to become the mainstream heating method in the future.

[0004] With the rise of renewable energy, using readily available renewable energy to provide the heat required for chemical processes through renewable electricity, that is, process electrification, provides an important strategy for replacing traditional fossil fuel combustion. In the past few decades, different electricity-to-heat methods, namely Joule heating, induction heating, microwave heating, and plasma heating, have been widely used in decarbonization and strongly endothermic catalytic processes. Among them, induction heating and microwave heating, as non-contact heating methods, need to convert electrical energy into heat energy through electromagnetic energy, and electromagnetic energy will have energy conversion losses at low temperatures, making it difficult to be compensated in useful process heat. In addition, due to its unique heating principle, the range of materials used as Joule heat heating elements is limited.

[0005] In contrast, Joule heating (also known as resistance heating or ohmic heating) can directly convert electrical energy into high-temperature heat with unit efficiency. This heating method can achieve selective, rapid, and uniform heating inside the reactor, and the equipment structure is simple, which is a process with application potential. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the object of the present invention is to provide a reforming reaction system based on the Joule heat effect and its application, which is used to solve the problems of carbon dioxide emissions and energy consumption generated by relying on external fuel combustion to provide heat for the methane carbon dioxide reforming reaction in the prior art, as well as the problems of low reaction efficiency and low catalyst utilization rate.

[0007] To achieve the above object and other related objects, the present invention provides a reforming reaction system based on the Joule heat effect. The reforming reaction system includes a raw material inlet unit, a reaction tube, a Joule heating unit, and a power supply device;

[0008] Among them, the reaction tube includes a gas inlet, a gas outlet, and a reaction chamber. The gas inlet is connected to the raw material inlet unit. The raw material gas entering the reaction chamber from the raw material inlet unit undergoes a reforming reaction in the reaction chamber, and the gas outlet is used to discharge the reaction products;

[0009] The Joule heating unit includes a heating element. The heating element is arranged in the reaction chamber. The heating element includes a preheating zone and a reaction zone. The preheating zone is adjacent to the gas inlet. The heating element in the reaction zone is coupled with a catalyst to form an integral catalyst. The raw material gas is preheated in the preheating zone and then enters the reaction zone for reforming reaction;

[0010] The power supply device is electrically connected to both ends of the heating element respectively, and the power supply device provides current to make the heating element generate heat.

[0011] Preferably, the heating element includes one or a combination of metals, alloys, ceramics, and carbon materials; among them, the metals include one or a combination of nickel, tungsten, and stainless steel; the alloys include one or a combination of FeCrAl alloy, FeCrNi alloy, and NiCrAl alloy; the ceramics include one or a combination of silicon carbide, silicon nitride, zinc oxide, copper oxide, and tin dioxide; the carbon materials include one or a combination of carbon fiber paper, carbon cloth, carbon nanotubes, and graphene.

[0012] Preferably, the morphology of the heating element is selected from one or a combination of an open pore structure, a wound filamentous shape, a sheet shape, a plate shape, and a honeycomb shape.

[0013] Preferably, the heating element is silicon carbide in a foam-like structure, and the pore density of the silicon carbide is 5 - 40 PPI.

[0014] Preferably, the coupling method when the heating element in the reaction zone is coupled with a catalyst to form an integral catalyst includes one or a combination of a coating method and a filling method;

[0015] Among them, the coating method specifically is to prepare a catalyst into a slurry according to a certain proportion, and then coat the slurry on the reaction zone of the heating element; the filling method specifically is to fill the particulate catalyst into the reaction zone of the heating element according to a certain proportion.

[0016] Preferably, the Joule heating unit further includes a temperature measuring device for detecting the temperatures of the preheating zone and the reaction zone.

[0017] Preferably, the temperature measuring device is a sliding thermocouple, which is arranged in a cylindrical hole at the vertical central axis position of the heating element.

[0018] Preferably, the outer wall of the reaction tube is wrapped with a heat insulation layer to reduce the heat loss in the reaction tube.

[0019] The present invention also provides an application of the above reforming reaction system based on the Joule heat effect.

[0020] Preferably, the reforming reaction system is applied to the reforming reaction of methane, and the reforming reaction of methane includes one of methane steam reforming reaction, methane dry reforming reaction, biogas reforming reaction, and biogas steam reforming reaction.

[0021] Preferably, the methane dry reforming reaction specifically includes the following steps:

[0022] S1. Couple the catalyst with the reaction zone of the heating element to form an integral catalyst, turn on the power device to make the heating element generate heat, and raise the temperature of the reaction zone to the reaction temperature;

[0023] S2. Introduce methane and carbon dioxide as raw material gases into the reaction tube. The raw material gases first enter the preheating zone for preheating and then enter the reaction zone to undergo a reforming reaction.

[0024] Preferably, the active components of the catalyst in step S1 include one or a combination of nickel, cobalt, iron, copper, rhodium, platinum, palladium, ruthenium, and iridium.

[0025] Preferably, in step S2, the molar ratio between methane and carbon dioxide in the raw material gas is 0.2 - 5, and the space velocity of the raw material gas introduced into the reaction tube is 10 - 1500L / g cat / h.

[0026] Preferably, in step S2, the reaction temperature of the reforming reaction is 650 - 1200 °C, and the reaction pressure is 1 - 30 bar (such as 1 - 5 bar, 5 - 10 bar, 10 - 15 bar, 15 - 30 bar, etc.).

[0027] As described above, the reforming reaction system based on the Joule heat effect and its application of the present invention have the following beneficial effects:

[0028] The present invention uses renewable energy "green electricity" as the main energy source to drive the methane carbon dioxide reforming reaction. Based on the Joule heat effect, it drives the strongly endothermic reforming reaction process, enhances the process heat transfer and realizes carbon emission reduction. A heating element is arranged inside the reaction tube for direct Joule heating, and no Joule heating occurs in the area outside the heating element. Only the catalyst bed layer inside the reaction tube is heated, greatly avoiding heat loss and energy consumption. Moreover, Joule heating can selectively, quickly and uniformly heat the inside of the reaction tube, and the temperature of the reaction tube wall is low, reducing the requirements for the selection of reaction tube materials and equipment costs, and solving the heat transfer problem in the strongly endothermic reaction process.

[0029] In the reforming reaction system of the present invention, the overall catalyst is directly heated inside the reaction tube based on the Joule effect, which can effectively avoid the heat transfer loss inside and outside the reaction tube caused by external heating, realize the precise control of the high-temperature reaction, and make the generated heat quickly and evenly transfer to the active sites of the catalyst, avoiding the problem of local "cold spots" leading to catalyst carbon deposition and deactivation. Applying it to the method for preparing syngas by methane carbon dioxide reforming reaction is beneficial to improving the catalytic performance and realizing the long-term stable operation of the catalytic reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It shows a schematic structural diagram of the reforming reaction system based on the Joule heat effect in a specific embodiment of the present invention.

[0031] Figure 2 It shows a physical diagram of silicon carbide in a foam-like structure in a specific embodiment of the present invention.

[0032] DESCRIPTION OF REFERENCE NUMERALS

[0033] 10 Reaction tube

[0034] 101 Gas inlet

[0035] 102 Gas outlet

[0036] 103 Heat insulation layer

[0037] 20 Heating element

[0038] 201 Preheating zone

[0039] 202 Reaction zone

[0040] 30 Power supply device

[0041] 301 Conductive part DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the embodiments of the present invention are for describing specific embodiments, rather than limiting the protection scope of the present invention. The test methods without specific conditions noted in the following examples are generally carried out under conventional conditions or according to the conditions recommended by each manufacturer.

[0044] When the embodiments give a numerical range, it should be understood that unless otherwise specified in the present invention, any value between the two endpoints of each numerical range and the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art of this technology. In addition to the specific methods, devices, and materials used in the embodiments, according to the knowledge of those skilled in the art of this technology and the description of the present invention, any methods, devices, and materials similar or equivalent to the methods, devices, and materials described in the embodiments of the present invention can also be used to implement the present invention.

[0045] Refer to Figure 1 , the present invention provides a reforming reaction system based on the Joule heat effect. The reforming reaction system includes a raw material inlet unit, a reaction tube 10, a Joule heating unit, and a power supply device 30;

[0046] Wherein, the reaction tube 10 includes a gas inlet 101, a gas outlet 102, and a reaction chamber. The gas inlet 101 is connected to the raw material inlet unit, and the raw material gas entering the reaction chamber from the raw material inlet unit undergoes a reforming reaction in the reaction chamber. The gas outlet 102 is used to discharge the reaction products;

[0047] The Joule heating unit includes a heating element 20. The heating element 20 is disposed in the reaction chamber. The heating element 20 includes a preheating zone 201 and a reaction zone 202. The preheating zone 201 is adjacent to the gas inlet 101. The heating element 20 in the reaction zone 202 is coupled with a catalyst to form an integral catalyst. The raw material gas is preheated in the preheating zone 201 and then enters the reaction zone 202 for reforming reaction;

[0048] The power supply device 30 is electrically connected to both ends of the heating element 20, and the power supply device 30 provides current to make the heating element 20 generate heat.

[0049] Specifically, the heating element 20, as a heat source, utilizes electrical energy to generate heat. Refer to Figure 1 , the upper end of the heating element 20 is a preheating zone 201, which is used to preheat the introduced raw material gas. The lower end of the heating element 20 is a reaction zone 202. The reaction zone 202 is coupled with a catalyst to form an integral catalyst. The reaction zone 202 is the main area where the reforming reaction of the raw material gas occurs. The catalyst is directly heated by the heat generated by the externally applied renewable electrical energy passing through the heating element 20.

[0050] Specifically, the heating element 20 directly heats the integral catalyst in the reaction tube 10 through an electric current, so that the generated heat is quickly and evenly transferred to the active sites of the catalyst, avoiding the occurrence of local "cold spots" and resulting in the carbon deposition and deactivation of the catalyst; in a specific embodiment of the present invention, the formed integral catalyst is a structured catalyst with many internal pores. The raw material gas can flow in these pores, and the catalyst is distributed on the inner walls of these pores, so that the surface area of the catalyst is large, the contact between the raw material gas and the catalyst is more sufficient, and the reaction efficiency is higher.

[0051] As an example, refer to Figure 1 , both ends of the heating element 20 are respectively connected with conductive members 301, and the two conductive members 301 are respectively connected to the power supply device 30 through wires to provide current for the heating element 20 to generate heat.

[0052] Preferably, the conductive member 301 is selected from electrode rods.

[0053] As an example, the heating element 20 includes one or a combination of metals, alloys, ceramics, and carbon materials; wherein, the metals include one or a combination of nickel, tungsten, and stainless steel; the alloys include one or a combination of FeCrAl alloy, FeCrNi alloy, and NiCrAl alloy; the ceramics include one or a combination of silicon carbide, silicon nitride, zinc oxide, copper oxide, and tin dioxide; the carbon materials include one or a combination of carbon fiber paper, carbon cloth, carbon nanotubes, and graphene.

[0054] As an example, the morphology of the heating element 20 is selected from one or a combination of an open-cell structure, a wound filamentous shape, a sheet shape, a plate shape, and a honeycomb shape.

[0055] Specifically, the open-cell structure includes a foam structure or a periodic open-cell structure.

[0056] As an example, the heating element 20 is silicon carbide in a foam-like structure, and the pore density of the silicon carbide is 5 - 40 PPI.

[0057] Specifically, refer to Figure 2Photograph of silicon carbide in foam structure (the left figure is the front view and the right figure is the top view). As can be seen from the figure, the silicon carbide has a porous structure and is in foam shape. In a specific embodiment of the present invention, the length L of the silicon carbide in foam structure is usually 25 mm, the outer diameter OD is 15 mm, and a cylindrical hole with a diameter of 3 mm is provided at the position of the silicon carbide for placing a temperature measuring device.

[0058] Specifically, the porous structure in foam shape helps the filling or coating of the catalyst, forming a filling or coating bed where the catalyst is in close contact with the heating element 20, ensuring good heat transfer performance. In a specific embodiment of the present invention, refer to Figure 1 , the heating element 20 is silicon carbide in foam shape and is cylindrical. The shape of the heating element 20 is not specifically limited herein. The pore density of the silicon carbide can include any value within the range such as 5 PPI, 10 PPI, 15 PPI, 20 PPI, 25 PPI, 30 PPI, 35 PPI, 40 PPI, etc. In addition, the silicon carbide foam as the heating element 20 can be heated to a high temperature and is stable under high-temperature heating, has a suitable resistivity, and excellent thermal conductivity to enhance the heat transfer of the whole process.

[0059] Specifically, the upper end of the heating element 20 is the preheating zone 201, and the lower end is the reaction zone 202. The heating element 20 in the reaction zone 202 is coupled with the catalyst to form an integral catalyst. The height of the integral catalyst on the heating element 20 accounts for 25% - 100% of the total height (such as 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.). For example, when the height of the integral catalyst on the heating element 20 accounts for 60% of the total height of the heating element 20, if the length of the heating element 20 is 25 mm, the length of the reaction zone 202 forming the integral catalyst is 15 mm, and the length of the preheating zone 201 is 10 mm. When the height of the integral catalyst on the heating element 20 accounts for 100% of the total height of the heating element 20, it means that the heating element 20 is completely coupled with the catalyst to form an integral catalyst. At this time, there is no preheating zone 201 in the heating element, and all belong to the reaction zone 202.

[0060] As an example, the coupling method when the heating element 20 in the reaction zone 202 is coupled with the catalyst to form an integral catalyst includes one or a combination of coating method and filling method. Among them, the coating method specifically is to prepare a slurry with the catalyst in a certain proportion, and then coat the slurry on the reaction zone 202 of the heating element 20. The filling method specifically is to fill the particulate catalyst into the reaction zone 202 of the heating element 20 in a certain proportion.

[0061] Specifically, the heating element 20 is coupled with the catalyst to form an integral catalyst. Actually, the active component of the catalyst is loaded onto the surface or pores of the heating element 20 to form an integrated coupling structure of the heating element 20 and the catalyst.

[0062] In a specific embodiment of the present invention, the filling method is specifically as follows: the particulate catalyst and an inert material (such as quartz sand particles) are filled into the reaction zone 202 of the heating element 20 according to a certain ratio. Among them, the inert material needs to have certain heat resistance and mechanical strength, and the particle sizes of the inert material and the particulate catalyst are 0.2 - 0.4 mm to ensure uniform loading.

[0063] As an example, the Joule heating unit further includes a temperature measuring device for detecting the temperatures of the preheating zone 201 and the reaction zone 202.

[0064] As an example, the temperature measuring device is a sliding thermocouple, which is arranged in a cylindrical hole at the vertical central axis position of the heating element 20.

[0065] Specifically, the sliding thermocouple is arranged in a cylindrical hole at the vertical central axis position of the heating element 20 and slides in the cylindrical hole to measure the temperatures of different regions. The current magnitude of the power supply device 30 can be adjusted according to the measured value of the sliding thermocouple to meet the reaction temperature required for the reforming reaction.

[0066] As an example, the outer wall of the reaction tube 10 is wrapped with a heat insulation layer 103 for reducing the heat loss in the reaction tube 10.

[0067] Preferably, the heat insulation layer 103 is a quartz wool heat insulation layer 103 to reduce heat dissipation. Of course, heat insulation layers 103 made of other materials can also be used, and no further limitations are made here.

[0068] The present invention also provides an application of the above reforming reaction system based on the Joule heat effect.

[0069] As an example, the above reforming reaction system based on the Joule heat effect is applied to the reforming reaction of methane, and the reforming reaction of methane includes one of methane steam reforming reaction, methane dry reforming reaction, biogas reforming reaction, and biogas steam reforming reaction.

[0070] Of course, the above reforming reaction system based on the Joule heat effect can also be used for other strongly endothermic reactions, including one or a combination of reverse water gas shift reaction, alkane pyrolysis, methane pyrolysis, ammonia decomposition, plastic conversion, and biomass conversion.

[0071] When the reforming reaction system based on the Joule heat effect in the present invention is applied to the methane dry reforming reaction, the specific method includes the following steps:

[0072] S1. Couple the catalyst with the reaction zone 202 of the heating element 20 to form an integral catalyst. Turn on the power supply device 30 to make the heating element 20 generate heat, and raise the temperature of the reaction zone २०२ to the reaction temperature.

[0073] S2. Use methane and carbon dioxide as raw material gases and introduce them into the reaction tube 10. The raw material gases first enter the preheating zone 201 for preheating, and then enter the reaction zone 202 to undergo a reforming reaction. The reaction products are discharged through the gas outlet 102.

[0074] As an example, the active components of the catalyst in step S1 include one or a combination of nickel, cobalt, iron, copper, rhodium, platinum, palladium, ruthenium, and iridium.

[0075] Preferably, the coupling method for coupling the catalyst with the reaction zone 202 of the heating element 20 to form an integral catalyst in step S1 includes the filling method or the coating method.

[0076] As an example, the molar ratio of methane to carbon dioxide in the raw material gas in step S2 is 0.2 - 5, and the space velocity of the raw material gas introduced into the reaction tube is 10 - 1500L / g cat / h.

[0077] Specifically, the molar ratio of methane to carbon dioxide may include any value within the range such as 0.2, 0.5, 1, 2, 3, 4, 5, etc.; the space velocity of the raw material gas entering the reaction tube 10 is 10 - 1500L / gcat / h (such as 10L / gcat / h, 50L / gcat / h, 100L / gcat / h, 500L / gcat / h, 1000L / gcat / h, 1500L / gcat / h, etc.).

[0078] As an example, the reaction temperature of the reforming reaction is 650 - 1200°C, and the reaction pressure is 1 - 30 bar.

[0079] Specifically, an additional heating element 20 is placed inside the reaction tube 10 as a heat source. The lower end of the heating element 20 is coupled with a catalyst to form a reaction zone 202, which is the main area for the methane dry reforming reaction. The externally applied power supply device 30 generates high temperature through the heating element 20 to directly heat the catalyst. Further, by adjusting the power intensity of the power supply device 30, the internal temperature of the reaction zone 202 at the lower end of the heating element 20 is 650 - 1200 °C, that is, the reaction temperature is 650 - 1200 °C, which can include any value within the range such as 650 °C, 700 °C, 750 °C, 800 °C, 900 °C, 1000 °C, 1100 °C, 1200 °C, etc. If the reaction temperature is too low, carbon deposition is likely to occur, and if it is too high, it will exceed the heat resistance limits of the reaction tube 10 and the heating element 20. The reaction pressure is 1 - 30 bar (such as 1 - 5 bar, 5 - 10 bar, 10 - 15 bar, 15 - 30 bar, etc.).

[0080] To better understand the reforming reaction system based on the Joule heat effect in the present invention and its application in the methane dry reforming reaction to produce syngas, the following describes the reforming reaction system based on the Joule heat effect in the present invention and its application in the methane dry reforming reaction to produce syngas with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0081] Example 1

[0082] This example provides a reforming reaction system based on the Joule heat effect. The reforming reaction system includes a raw material inlet unit, a reaction tube 10, a Joule heating unit, and a power supply device 30;

[0083] Among them, the reaction tube 10 includes a gas inlet 101, a gas outlet 102, and a reaction chamber. The gas inlet 101 is connected to the raw material inlet unit. The raw material gas entering the reaction chamber from the raw material inlet unit undergoes a reforming reaction in the reaction chamber, and the gas outlet 102 is used to discharge the reaction products;

[0084] The Joule heating unit includes a heating element 20. The heating element 20 is disposed in the reaction chamber. The heating element 20 includes a preheating zone 201 and a reaction zone 202. The preheating zone 201 is adjacent to the gas inlet 101. The heating element 20 in the reaction zone 202 is coupled with a catalyst to form an overall catalyst. The raw material gas is preheated in the preheating zone 201 and then enters the reaction zone 202 for the reforming reaction. Among them, the heating element 20 is porous foam-shaped silicon carbide, and its average pore diameter (d p) is 2.29 mm, and the total height of the heating element 20 is 25 mm. A sliding thermocouple is placed in the cylindrical hole (3 mm) along the central axis position of the heating element 20 for temperature distribution measurement; the monolithic catalyst is a nickel-based alumina catalyst filled in the pores of the silicon carbide foam. When filling, quartz sand and the nickel-based alumina catalyst are filled in a ratio of 30:1, and the height occupied by the monolithic catalyst is 15 mm;

[0085] The power supply device 30 is connected to two electrode rods through wires, and the two electrode rods are electrically connected to both ends of the heating element 20 respectively. The power supply device 30 provides current to make the heating element 20 generate heat.

[0086] This embodiment also provides an application of the reforming reaction system based on the Joule heat effect. The reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas. The specific method includes the following steps:

[0087] S1. Couple the catalyst with the reaction zone 202 of the heating element 20 to form a monolithic catalyst. Turn on the power supply device 30 to make the heating element 20 generate heat by internal Joule heating. The heating power of the power supply device 30 is 66 W. The average temperature at the center of the catalyst bed (reaction zone 202) is measured to be 811 °C, the lowest temperature is 804 °C, and the average temperature on the outer wall of the reaction tube 10 is 499 °C;

[0088] S2. Methane and carbon dioxide are introduced into the reaction tube 10 as raw material gases at a molar ratio of 1:2, and the space velocity is 60 L / gcat / h. The raw material gases first enter the preheating zone 201 for preheating, and then enter the reaction zone 202 to carry out the reforming reaction under atmospheric pressure. The reaction products are discharged through the gas outlet 102.

[0089] After testing, when the reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 94% and 63% respectively.

[0090] Comparative Example 1

[0091] This comparative example provides a method for reforming methane and carbon dioxide to produce syngas. The difference from Example 1 is that an external heating catalyst method is adopted, the heating power is 141 W, the average temperature at the center of the catalyst bed is 772 °C, the lowest temperature is 769 °C, and the average temperature on the outer wall of the reaction tube 10 is 801 °C to make methane and carbon dioxide undergo the reforming reaction. Other methods are the same as those in Example 1 and will not be elaborated here.

[0092] After testing, the conversion rates of CH4 and CO2 in this comparative example are 79% and 57% respectively.

[0093] Example 2

[0094] This embodiment provides a reforming reaction system based on the Joule heat effect. This reforming reaction system is the same as that in Embodiment 1 and will not be elaborated here.

[0095] This embodiment also provides an application of the reforming reaction system based on the Joule heat effect. The reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas. The specific method is different from that in Embodiment 1 in that the heating power of the power supply device 30 in step S1 is 57 W. The measured average temperature at the center of the catalyst bed (reaction zone 202) is 756 °C, and the lowest temperature is 753 °C. The average temperature on the outer wall of the reaction tube 10 is 462 °C. Other methods and steps are the same as those in Embodiment 1 and will not be elaborated here.

[0096] After testing, when the reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 88% and 58% respectively.

[0097] Comparative Example 2

[0098] This comparative example provides a method for reforming methane and carbon dioxide to produce syngas. The difference from Embodiment 2 is that the method of externally heating the catalyst is adopted, the heating power is 119 W, the average temperature at the center of the catalyst bed is 725 °C, the lowest temperature is 724 °C, and the average temperature on the outer wall of the reaction tube 10 is 751 °C to cause the reforming reaction of methane and carbon dioxide. Other methods are the same as those in Embodiment 2 and will not be elaborated here.

[0099] After testing, the conversion rates of CH4 and CO2 in this comparative example are 67% and 48% respectively.

[0100] Embodiment 3

[0101] This embodiment provides a reforming reaction system based on the Joule heat effect. This reforming reaction system is the same as that in Embodiment 1 and will not be elaborated here.

[0102] This embodiment also provides an application of the reforming reaction system based on the Joule heat effect. The reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas. The specific method is different from that in Embodiment 1 in that the heating power of the power supply device 30 in step S1 is 46 W. The measured average temperature at the center of the catalyst bed (reaction zone 202) is 700 °C, and the lowest temperature is 698 °C. The average temperature on the outer wall of the reaction tube 10 is 412 °C. Other methods and steps are the same as those in Embodiment 1 and will not be elaborated here.

[0103] After testing, when the reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 77% and 52% respectively.

[0104] Comparative Example 3

[0105] This comparative example provides a method for reforming methane and carbon dioxide to produce syngas. The difference from Example 3 is that an external heating method for the catalyst is adopted, with a heating power of 100 W. The average temperature at the center of the catalyst bed is 679 °C, and the lowest temperature is 677 °C. The average temperature on the outer wall of the reaction tube 10 is 701 °C, causing the reforming reaction of methane and carbon dioxide. Other methods are the same as those in Example 3 and will not be elaborated here.

[0106] After testing, the conversion rates of CH4 and CO2 in this comparative example are 54% and 39% respectively.

[0107] Example 4

[0108] This example provides a reforming reaction system based on the Joule heat effect. This reforming reaction system is the same as that in Example 1 and will not be elaborated here.

[0109] This example also provides an application of the reforming reaction system based on the Joule heat effect. Applying the reforming reaction system in this example to the reforming reaction of methane and carbon dioxide to produce syngas, the specific method is different from that in Example 1 in that the heating power of the power supply device 30 in step S1 is 37 W. The average temperature at the center of the catalyst bed (reaction zone 202) is measured to be 642 °C, and the lowest temperature is 637 °C. The average temperature on the outer wall of the reaction tube 10 is 385 °C. Other methods and steps are the same as those in Example 1 and will not be elaborated here.

[0110] After testing, when the reforming reaction system in this example is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 59% and 41% respectively.

[0111] Comparative Example 4

[0112] This comparative example provides a method for reforming methane and carbon dioxide to produce syngas. The difference from Example 3 is that an external heating method for the catalyst is adopted, with a heating power of 85 W. The average temperature at the center of the catalyst bed is 633 °C, and the lowest temperature is 632 °C. The average temperature on the outer wall of the reaction tube 10 is 653 °C, causing the reforming reaction of methane and carbon dioxide. Other methods are the same as those in Example 3 and will not be elaborated here.

[0113] After testing, the conversion rates of CH4 and CO2 in this comparative example are 41% and 30% respectively.

[0114] In summary, by comparing the above embodiments with the comparative examples, it can be seen that the heating power required for direct heating using the Joule heating effect in the embodiments is lower than the external heating power. However, the lowest temperature at the center of the catalyst bed is actually higher than that of external heating. The average temperature on the outer wall of the reaction tube 10 during heating by the Joule heating effect is much lower than that of external heating, indicating that less heat is lost during the heat transfer process of heating by the Joule heating effect compared to external heating, and heat can be utilized more effectively. The heating element 20 directly heats the catalyst, enabling heat to be directly delivered to the catalytic sites, improving the utilization rate of the catalyst and greatly increasing the conversion rates of CH4 and CO2.

[0115] Example 5

[0116] This example provides a reforming reaction system based on the Joule heating effect. The difference between this reforming reaction system and that in Example 1 is that the overall catalyst is a nickel-based alumina catalyst coated on a silicon carbide foam skeleton with a pore density of 25 PPI. The total height of the heating element 20 is 25 mm, and the length of the overall catalyst is 13 mm. The others are the same as those in Example 1 and will not be elaborated here.

[0117] This example also provides an application of the reforming reaction system based on the Joule heating effect. The reforming reaction system in this example is applied to the reforming reaction of methane and carbon dioxide to produce syngas. The specific method is different from that in Example 1 only in that the heating power of the power supply device 30 in step S1 is 123 W, and the average temperature at the center of the catalyst bed (reaction zone 202) is measured to be 801 °C, and the lowest temperature is 800 °C. In step S2, methane and carbon dioxide are introduced into the reaction tube 10 as raw material gases at a molar ratio of 1:2, and the space velocity is 273 L / gcat / h. The other methods and steps are the same as those in Example 1 and will not be elaborated here.

[0118] After testing, when the reforming reaction system in this example is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 97% and 68% respectively.

[0119] Example 6

[0120] This example provides a reforming reaction system based on the Joule heating effect, which is the same as that in Example 5 and will not be elaborated here.

[0121] This embodiment also provides an application of a reforming reaction system based on the Joule heat effect. Applying the reforming reaction system in this embodiment to the reforming reaction of methane and carbon dioxide to produce syngas, the specific method is different from that in Embodiment 5 only in that the heating power of the power supply device 30 in step S1 is 112 W, and the measured average temperature at the center of the catalyst bed (reaction zone 202) is 751 °C, and the lowest temperature is 750 °C. Other methods and steps are the same as those in Embodiment 5 and will not be elaborated here.

[0122] After testing, when the reforming reaction system in this embodiment is applied to the reforming reaction of methane and carbon dioxide to produce syngas, the conversion rates of CH4 and CO2 are maintained at 96% and 65% respectively.

[0123] In summary, the present invention uses renewable energy "green electricity" as the main energy source to drive the reforming reaction of methane and carbon dioxide, drives the strongly endothermic reforming reaction process based on the Joule heat effect, strengthens the heat transfer process and realizes carbon emission reduction; a heating element is arranged inside the reaction tube for direct Joule heating, and no Joule heating is generated in the area outside the heating element, only the catalyst bed inside the reaction tube is heated, greatly avoiding heat loss and energy consumption; and Joule heating can realize selective, rapid and uniform heating inside the reaction tube, the temperature of the reaction tube wall is low, reducing the requirements for the selection of reaction tube materials and equipment costs, and solving the heat transfer problem in the strongly endothermic reaction process; the reforming reaction system in the present invention directly heats the overall catalyst inside the reaction tube based on the Joule effect, which can effectively avoid the heat transfer loss inside and outside the reaction tube caused by external heating, realize the precise control of high-temperature reactions, and make the generated heat quickly and evenly transfer to the active sites of the catalyst, avoiding the problem of local "cold spots" leading to catalyst carbon deposition and deactivation; applying it to the method of reforming methane and carbon dioxide to produce syngas is beneficial to improving the catalytic performance and realizing the long-term stable operation of catalytic reactions. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0124] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A reforming reaction system based on the Joule heating effect, characterized in that: The reforming reaction system includes a raw material inlet unit, a reaction tube, a Joule heating unit, and a power supply device; Wherein, the reaction tube includes a gas inlet, a gas outlet, and a reaction chamber. The gas inlet is connected to the raw material inlet unit. The raw material gas entering the reaction chamber from the raw material inlet unit undergoes a reforming reaction in the reaction chamber, and the gas outlet is used to discharge the reaction products; The Joule heating unit includes a heating element disposed in the reaction chamber. The heating element includes a preheating zone and a reaction zone. The preheating zone is adjacent to the gas inlet. The heating element in the reaction zone is coupled with a catalyst to form a monolithic catalyst. The raw material gas is preheated in the preheating zone and then enters the reaction zone for reforming reaction; The power supply device is electrically connected to both ends of the heating element, and the power supply device provides current to cause the heating element to generate heat.

2. The reforming reaction system based on the Joule heating effect according to claim 1, wherein: The heating element includes one or a combination of metals, alloys, ceramics, and carbon materials; wherein, the metals include one or a combination of nickel, tungsten, and stainless steel; the alloys include one or a combination of FeCrAl alloy, FeCrNi alloy, and NiCrAl alloy; the ceramics include one or a combination of silicon carbide, silicon nitride, zinc oxide, copper oxide, and tin dioxide; the carbon materials include one or a combination of carbon fiber paper, carbon cloth, carbon nanotubes, and graphene.

3. The reforming reaction system based on the Joule heating effect according to claim 2, characterized in that: The morphology of the heating element is selected from one or a combination of an open pore structure, a wound filamentous shape, a sheet shape, a plate shape, and a honeycomb shape.

4. The reforming reaction system based on the Joule heating effect according to claim 3, characterized in that: The heating element is silicon carbide in a foam-like structure, and the pore density of the silicon carbide is 5 - 40 PPI.

5. The reforming reaction system based on the Joule heating effect according to claim 1, characterized in that: The coupling method when the heating element in the reaction zone is coupled with a catalyst to form a monolithic catalyst includes one or a combination of a coating method and a filling method; Wherein, the coating method specifically is to prepare a slurry with the catalyst in a certain proportion, and then coat the slurry on the reaction zone of the heating element; the filling method specifically is to fill the particulate catalyst into the reaction zone of the heating element in a certain proportion.

6. The reforming reaction system based on the Joule heating effect according to claim 1, characterized in that: The Joule heating unit further includes a temperature measuring device for detecting the temperatures of the preheating zone and the reaction zone.

7. The reforming reaction system based on the Joule heating effect according to claim 6, characterized in that: The temperature measuring device is a sliding thermocouple, and the sliding thermocouple is disposed in a cylindrical hole at the vertical central axis position of the heating element.

8. The reforming reaction system based on the Joule heating effect according to claim 1, wherein: The outer wall of the reaction tube is wrapped with a heat insulation layer to reduce the heat loss in the reaction tube.

9. An application of the reforming reaction system based on the Joule heat effect according to any one of claims 1 - 8.

10. The application of the reforming reaction system based on the Joule heating effect according to claim 9, characterized in that: The reforming reaction system is applied to the reforming reaction of methane, and the reforming reaction of methane includes one of methane steam reforming reaction, methane dry reforming reaction, biogas reforming reaction, and biogas steam reforming reaction.

11. The application of the reforming reaction system based on the Joule heating effect according to claim 10, characterized in that: The methane dry reforming reaction specifically includes the following steps: S1. Couple the catalyst with the reaction zone of the heating element to form a monolithic catalyst, turn on the power supply device to cause the heating element to generate heat, and raise the temperature of the reaction zone to the reaction temperature; S2. Methane and carbon dioxide are used as raw material gases and introduced into the reaction tube. The raw material gases first enter the preheating zone for preheating and then enter the reaction zone to undergo a reforming reaction.

12. The application of the reforming reaction system based on the Joule heat effect according to claim 11, wherein: The active components of the catalyst in step S1 include one or a combination of nickel, cobalt, iron, copper, rhodium, platinum, palladium, ruthenium, and iridium.

13. The application of the reforming reaction system based on the Joule heat effect according to claim 11, characterized in that: Step S2 includes one or a combination of the following conditions: The molar ratio of methane to carbon dioxide in the raw material gas is 0.2 to 5, and the space velocity of the raw material gas passing through the reaction tube is 10 to 1500 L / g cat / h; The reaction temperature of the reforming reaction is 650 - 1200 °C, and the reaction pressure is 1 - 30 bar.

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