Fluidized bed membrane reactor for producing hydrogen through methane cracking and method for producing hydrogen through methane cracking

Abstract

The invention provides a methane cracking hydrogen production fluidized bed membrane reactor and a methane cracking hydrogen production method.The methane cracking hydrogen production fluidized bed membrane reactor comprises a reactor shell, a hollow fiber membrane bundle, a carbon carrying medium and a carbon collecting mechanism, the lower shell is filled with the carbon carrying medium, and the reactor shell comprises an upper shell and a lower shell which are separated from each other; a reaction tail gas outlet and a methane feeding hole are formed in the side wall of the lower shell, and a material discharging hole is formed in the bottom of the lower shell; the hollow fiber membrane bundle is arranged in the reactor shell and comprises a reaction layer and a separation layer which are sequentially stacked from outside to inside, the outer side of the reaction layer and an inner cavity of the lower shell jointly form a reaction cavity, and the separation layer and an inner cavity of the upper shell jointly form a separation cavity; the carbon collecting mechanism comprises a carbon collecting bin, and the carbon collecting bin communicates with the material discharging opening. Compared with the prior art, the technical problem that hydrogen separation and purification and carbon product separation cannot be carried out simultaneously in the existing methane cracking hydrogen production process is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hydrogen production, and more particularly relates to a fluidized bed membrane reactor for hydrogen production by methane cracking, and further relates to a method for hydrogen production by methane cracking. BACKGROUND

[0002] Hydrogen energy is considered as a core component of future energy system due to its clean, renewable, and high energy density characteristics. Currently, large-scale hydrogen production in industry mainly relies on steam reforming or partial oxidation of fossil fuels. These methods not only produce hydrogen with low purity, which needs to be purified through complex steps to meet the needs of high-end applications such as fuel cells, but also produce a large amount of carbon dioxide in the production process, resulting in serious carbon emission problems.

[0003] Hydrogen production by methane cracking is a promising alternative technology. This reaction theoretically produces only hydrogen and solid carbon, without producing carbon dioxide, thus avoiding carbon emissions directly from the source. At the same time, the by-product solid carbon (such as carbon nanotubes, carbon black, etc.) has high economic value, which can effectively reduce the overall cost of hydrogen production.

[0004] However, methane cracking technology faces two major challenges: first, non-catalytic cracking requires extremely high reaction temperatures (usually higher than 1200℃), resulting in huge energy consumption. Second, although the introduction of catalysts can reduce the reaction temperature, the carbon produced in the reaction will quickly cover the active sites of the catalyst and the inner wall of the reactor, leading to rapid deactivation of the catalyst, and the accumulated carbon is difficult to continuously and effectively remove from the reaction system, making the reaction unable to be carried out stably and continuously. In addition, the reaction products are a mixture of hydrogen, unreacted methane and carbon powder, which requires additional separation and purification devices to obtain high-purity hydrogen, increasing the complexity and cost of the system.

[0005] Therefore, how to solve the problems of rapid deactivation of the catalyst layer caused by carbon accumulation and the need for additional separation and purification of hydrogen in the existing process of hydrogen production by methane cracking has become a key technical problem to be solved in the field. SUMMARY

[0006] The purpose of the present application is to provide a fluidized bed membrane reactor for hydrogen production by methane cracking to solve the technical problem that the separation and purification of hydrogen and the separation of carbon products in the existing process of hydrogen production by methane cracking cannot be carried out simultaneously, so as to realize stable and efficient continuous production and reduce the cost of hydrogen production.

[0007] To achieve the above purpose, the technical solution adopted by the present application is to provide a fluidized bed membrane reactor for hydrogen production by methane cracking, comprising: A reactor shell comprising an upper shell and a lower shell which are separated from each other, the upper shell being provided with a hydrogen outlet at the top end, the lower shell being provided with a reaction tail gas outlet and a methane feed inlet on the side wall, and the bottom of the lower shell being provided with a material discharge outlet; A hollow fiber membrane bundle is arranged in the reactor shell, and comprises a reaction layer and a separation layer arranged in sequence from outside to inside, the outer side of the reaction layer and the inner wall of the lower shell jointly form a reaction cavity, and the inner side of the separation layer and the inner wall of the upper shell jointly form a separation cavity; The lower shell is filled with carbon carrier medium; A carbon collection mechanism comprises a carbon collection bin in communication with the material discharge outlet.

[0008] In a possible implementation, the carbon collection mechanism further comprises a screen mesh arranged between the material discharge outlet and the carbon collection bin; The pore size of the screen mesh is smaller than the diameter of the carbon carrier medium, and with vibration of the screen mesh, the carbon product adsorbed on the surface of the carbon carrier medium falls off and passes through the screen mesh to fall into the carbon collection bin.

[0009] In a possible implementation, the carbon collection mechanism further comprises a screen mesh arranged between the material discharge outlet and the carbon collection bin; The pore size of the screen mesh is greater than the diameter of the carbon carrier medium, and with vibration of the screen mesh, the carbon carrier medium with the carbon product adsorbed on the surface passes through the screen mesh to fall into the carbon collection bin.

[0010] In a possible implementation, the methane cracking hydrogen production fluidized bed membrane reactor further comprises a medium feeding part arranged at the top of the lower shell, the medium feeding part comprises a carrier bin and a feeding pipe, and the carrier bin is in communication with the lower shell through the feeding pipe.

[0011] In a possible implementation, the methane cracking hydrogen production fluidized bed membrane reactor further comprises a vibration motor arranged outside the middle wall of the lower shell to vibrate the side wall of the lower shell.

[0012] In a possible implementation, the methane cracking hydrogen production fluidized bed membrane reactor further comprises a combustion channel arranged in the cavity of the lower shell, used for combustion of reaction tail gas and heat supply for methane cracking, and the top of the combustion channel is in communication with the reaction tail gas outlet of the lower shell, and the bottom of the combustion channel is provided with an exhaust port.

[0013] Compared with the prior art, the methane cracking hydrogen production fluidized bed membrane reactor provided by the present application has the following beneficial effects: Methane enters the lower shell from the methane inlet, and a cracking reaction is carried out on the surface of the hollow fiber membrane bundle to generate hydrogen and carbon. The hydrogen penetrates the separation layer of the hollow fiber membrane bundle to the upper shell and is discharged from the hydrogen outlet. In the process of hydrogen production by methane cracking, the methane that is not completely cracked is generated in the lower shell in the form of reaction tail gas at the same time, and is discharged from the reaction tail gas outlet. At the same time, the carbon product deposited on the surface of the hollow fiber membrane bundle is deposited and attached to the surface of the carbon-loaded medium, and is discharged through the material discharge outlet. In this way, hydrogen production by methane cracking and in-situ separation of hydrogen are realized, and the continuous removal of carbon products is achieved, which reduces the accumulation of carbon products on the reaction side, promotes the reaction equilibrium, and improves the reaction rate and hydrogen production rate and purity. The above effects solve the technical problems of low hydrogen separation efficiency and easy clogging of the reactor by carbon products in the traditional methane cracking reaction.

[0014] In addition to the above scheme, the present application also provides a method for producing hydrogen by cracking methane, which is realized based on the fluidized bed membrane reactor for producing hydrogen by cracking methane as described above, and comprises the following steps: S1. Introducing methane into the lower shell filled with carbon-loaded medium and having sufficient reaction temperature to carry out a cracking reaction; S2. Applying vacuum to the inner cavity of the upper shell by the vacuum pumping device to separate and permeate the hydrogen generated by the reaction; S3. Introducing the heat generated by the combustion of the reaction tail gas into the lower shell to supply heat to the lower shell; S4. Intermittently removing the carbon product and supplementing the carbon-loaded medium.

[0015] In a possible implementation, step S1 further comprises the following step: S101. Adjusting the flow rate of the methane feed and / or the vibration frequency of the reactor shell to control the movement speed of the carbon-loaded medium in the reactor.

[0016] In a possible implementation, in step S1, the reaction temperature is 700-1000 DEG C, and the volume space velocity of the methane feed is 1000 / h-50000 / h.

[0017] In a possible implementation, in step S2, the vacuum degree of the inner cavity of the upper shell is 0.001-0.01 MPa.

[0018] Compared with the prior art, the methane cracking hydrogen production method in the application has all the advantages of the methane cracking hydrogen production fluidized bed membrane reactor described above, which will not be repeated here. Meanwhile, under the cooperation of the above steps, hydrogen is generated by cracking of methane under optimized conditions, hydrogen is quickly separated by membrane separation driven by vacuum, tail gas combustion provides self-heating, and carbon products are removed regularly. The combination of these functions realizes the whole process integration and automatic control of methane cracking hydrogen production, and achieves the technical effects of efficient production of high-purity hydrogen, reduction of external energy consumption and carbon resource recovery. In this way, the application can solve the technical problems of low hydrogen yield, high energy consumption and difficult carbon treatment in the traditional methane cracking method through the above effects. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort. In the drawings: Figure 1 The overall structure schematic diagram of the methane cracking hydrogen production fluidized bed membrane reactor provided by the application; Figure 2 The connection relationship schematic diagram of the hollow fiber membrane and the fixing part in the methane cracking hydrogen production fluidized bed membrane reactor provided by the application; Figure 3 The position relationship schematic diagram of the combustion channel and the eccentric turbine in the methane cracking hydrogen production fluidized bed membrane reactor of the application; Figure 4 The step diagram of the methane cracking hydrogen production method in the application; Figure 5 The scanning electron microscope diagram of the cross section of the hollow fiber bundle with carbon deposited on the surface; Figure 6 The scanning electron microscope diagram of the carbon-loaded medium with carbon attached to the surface.

[0020] In the drawings: 1, reactor shell; 11, upper shell; 12, lower shell; 2, hollow fiber membrane bundle; 21, reaction layer; 22, separation layer; 3, carbon-loaded medium; 4, combustion channel; 41, eccentric turbine; 42, vibration motor; 5, carbon collection mechanism; 51, carbon collection bin; 52, screen; 6, fixing part; 61, fixing disc; 62, nickel alloy solder layer; 63, sealing sleeve. DETAILED DESCRIPTION

[0021] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0022] In the description of the present application, it should be noted that if the terms indicating the orientation or position relationship such as "upper", "lower", "inner", "back" and the like appear, they are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation on the present application that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0023] In addition, in the description of the present application, unless otherwise explicitly limited, the terms "mounting", "connecting", "connection", "connector" should be understood broadly. For example, the connection can be a fixed connection, or a detachable connection, or an integral connection; can be a mechanical connection, or an electrical connection; can be a direct connection, or an indirect connection through an intermediate medium, or a communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood in combination with the specific circumstances.

[0024] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0025] Please refer to Figures 1 to 3 , now the methane cracking hydrogen production fluidized bed membrane reactor provided by the present application will be described. The methane cracking hydrogen production fluidized bed membrane reactor comprises a reactor shell 1, a hollow fiber membrane bundle 2, a carbon carrier medium 3 filled in a lower shell 12 and a carbon collection mechanism 5, wherein the reactor shell 1 comprises a upper shell 11 and a lower shell 12 which are separated from each other, the upper shell 11 is provided with a hydrogen outlet at the top end, the lower shell 12 is provided with a reaction tail gas outlet and a methane inlet on the side wall, and the bottom of the lower shell 12 is provided with a material discharge outlet; the hollow fiber membrane bundle 2 is arranged in the reactor shell 1 and comprises a reaction layer 21 and a separation layer 22 which are arranged in layers from outside to inside, the outer side of the reaction layer 21 and the inner chamber of the lower shell 12 jointly form a reaction chamber, and the separation layer 22 and the inner chamber of the upper shell 11 jointly form a separation chamber; the carbon collection mechanism 5 comprises a carbon collection bin 51 which is communicated with the material discharge outlet.

[0026] In the specific implementation process of the above embodiment, after the methane enters the lower shell 12 from the methane inlet, the methane is cracked on the surface of the hollow fiber membrane bundle 2 to generate hydrogen and carbon, the hydrogen permeates through the separation layer 22 of the hollow fiber membrane bundle 2 to the upper shell 11 and is discharged from the hydrogen outlet.

[0027] The carbon product deposited on the surface of the hollow fiber membrane bundle 2 in the above reaction process adheres to the surface of the carbon-loaded medium 3 and is discharged through the material discharge outlet. In this way, the methane cracking reaction for hydrogen production and in-situ separation of hydrogen and continuous removal of carbon product are achieved, the accumulation of carbon product on the reaction side is reduced, the reaction balance is promoted, and the reaction rate and hydrogen production rate and purity are improved. In this way, the technical problems of low hydrogen separation efficiency and easy clogging of the reactor by carbon product in the traditional methane cracking reaction can be solved.

[0028] In addition to the above feasible embodiments, for the carbon collection mechanism 5, a screen 52 is arranged between the material discharge outlet and the carbon collection bin 51. When the pore size of the screen 52 is smaller than the diameter of the carbon-loaded medium 3, the carbon product falls off the surface of the carbon-loaded medium 3 and falls into the carbon collection bin 51 through the screen 52 by vibration of the screen 52. In this way, the present embodiment can block the carbon-loaded medium 3 and only allow the carbon product to be discharged. The screen 52 can be removed when the carbon-loaded medium 3 needs to be replaced. In specific implementation, the pore size of the screen 52 and the diameter of the carbon-loaded medium 3 (as shown in the figure) are 0.5 mm and the diameter of the carbon-loaded medium 3 is less than 0.5 mm. Figure 6

[0029] Based on the above embodiments, in another embodiment, the pore size of the screen 52 is greater than the diameter of the carbon-loaded medium 3. In specific application, when no vibration is applied to the reactor shell 1 and the screen 52, the screen 52 can hinder the carbon-loaded medium 3 from flowing out due to the aggregation of the carbon-loaded medium 3. When the reactor shell 1 or the screen 52 is vibrated, the carbon-loaded medium 3 with carbon product adhered thereto can more smoothly pass through the screen 52. That is, the screen 52 in the present embodiment simultaneously plays a role in hindering the carbon-loaded medium 3 from flowing out and controlling the flow rate of the carbon-loaded medium 3.

[0030] Further, in order to supplement the carbon-loaded medium 3, the methane cracking hydrogen production fluidized bed membrane reactor further comprises a medium feeding part arranged at the top of the lower shell 12, the medium feeding part comprising a medium feeding bin and a feeding pipe, and the medium feeding bin being in communication with the lower shell 12 through the feeding pipe. In this way, the medium feeding part in the present embodiment can cooperate with the screen 52 to continuously or intermittently supplement the carbon-loaded medium 3 from the medium feeding bin to the inside of the lower shell 12 through the feeding pipe and mix with the reaction material, so as to maintain the sufficient amount of carbon-loaded medium 3 in the reactor. In this way, the medium feeding part realizes convenient supplement of the carbon-loaded medium 3 and continuous reaction. The arrangement of the carbon-loaded medium feeding part reduces the downtime, improves the continuity of the reactor operation, and ensures the stability of the reaction efficiency.

[0031] ​Preferably, in order to prevent the problem of reactor gas leakage during the replenishment of the carbon carrier medium 3, the carbon carrier medium 3 is fed by an automatic feeder, which is connected to the reactor shell 1 below by a pipeline. During the entire feeding process, the flow path of the carbon carrier medium 3 is always sealed from the outside world to prevent gas leakage.

[0032] In addition, compared with the existing fiber bundle, the hollow fiber membrane bundle 2 in the present application has a reaction layer 21 outside with a thickness much greater than that of the separation layer 22, and both layers are made of metal alloy. In the present embodiment, the reaction layer 21 can provide stable support for the structure of the entire fiber bundle, ensuring that the fiber bundle has sufficient structural strength. Under the premise of ensuring structural strength, the hollow fiber membrane bundle 2 in the present embodiment can prevent the fiber bundle from being structurally damaged during the movement of the carbon carrier medium 3. At the same time, the flow direction of the carbon carrier medium 3 in the present embodiment is parallel to the extension direction of the fiber bundle, reducing the transverse shear force to further prevent damage to the structure of the hollow fiber membrane bundle 2 during the flow of the carbon carrier medium 3.

[0033] In addition to the above feasible embodiments, the methane cracking hydrogen fluidized bed membrane reactor in the present embodiment also includes a combustion channel 4 arranged in the cavity of the lower shell 12 for burning the reaction tail gas and providing heat for methane cracking, and the top of the combustion channel 4 is in communication with the reaction tail gas outlet of the lower shell 12, and the bottom of the combustion channel 4 is provided with an exhaust port.

[0034] Through the above arrangement, during the process of methane cracking for hydrogen production, uncracked methane is generated in the form of reaction tail gas in the lower shell 12, and under the action of the conveying pressure, the reaction tail gas enters the combustion channel 4 from the reaction tail gas outlet of the lower shell 12 for combustion, providing continuous heat energy to the lower shell 12 to maintain the reaction temperature. As arranged above, the combustion channel 4 in the present embodiment raises the internal temperature of the reactor, which is conducive to the continuous progress of the reaction in the reactor. The combustion channel 4 also reduces the heat energy loss of the reactor, making the reactor more energy-saving and environmentally friendly.

[0035] In specific implementation, the reaction tail gas can also contain unreacted methane and unseparated hydrogen. The above gas is mixed with air and burned in the combustion channel 4. The entire combustion path is from top to bottom, with the top temperature being lower than the bottom temperature, while the heat distribution in the lower shell 12 is that the heat is concentrated at the top and the bottom temperature is relatively lower. In this way, the present embodiment can use the heat at the top to provide temperature for the combustion of the reaction tail gas and air. The combustion channel 4 transports heat to the bottom of the lower shell 12 through the flow path of gas combustion, and forms a counterflow with the blowing of methane to the carbon carrier medium 3, which provides heat to the reaction chamber in the lower shell 12 and makes the temperature distribution in the lower shell 12 more reasonable.

[0036] In addition, for the problem that carbon elements may block the reaction layer 21 of the hollow fiber membrane bundle 2, it should be noted that although the fiber bundle (i.e. the hollow fiber membrane bundle 2) surface may be attached with carbon elements (growing carbon nanotubes) (as shown in Figure 5 the figure), under the action of the flowing carbon-carrying medium 3, the carbon elements attached to the surface thereof can be cleaned in time by the carbon-carrying medium 3. The thickness of the deposited carbon elements cannot cause visible influence on the catalysis and separation of hydrogen, and cannot cause negative effects on the normal operation of the hollow fiber membrane bundle 2.

[0037] At the same time, the carbon elements accumulated on the surface of the fiber bundle are in a loose and porous structure, and the growing carbon nanotubes even have a certain accumulation, but since the diameter of hydrogen element is far smaller than the gap spacing between the accumulated carbon layers, the cracked hydrogen element can easily pass through the carbon layers, so the carbon layers grown and accumulated on the surface of the fiber bundle cannot cause visible influence on the separation of hydrogen.

[0038] In order to solve the problem that the long fiber bundle made of metal nickel material is easily damaged by the flowing carbon-carrying medium 3 in a high-temperature environment, the hollow fiber membrane bundle 2 in the present application can be arranged in a small-diameter high-temperature-resistant tubular device, which can play a certain fixing and supporting role on the fiber bundle to prevent it from being deformed excessively. Of course, other ways to fix the hollow fiber membrane bundle 2 to a certain extent are also a feasible implementation manner, which will not be described here.

[0039] When the length of the hollow fiber membrane bundle 2 itself is short, the structural rigidity of the hollow fiber membrane bundle 2 itself can meet the use requirements under this condition, and only the two ends thereof need to be fixed. Since the diameter of the carbon-carrying particles is about 0.5 mm, the carbon-carrying particles of this size are extremely difficult to cause substantial damage to the fiber bundle under normal use temperature (generally within 900 degrees). Moreover, the carbon-carrying particles flow in the upward and downward directions, and the fiber bundle receives very small radial load, so the fiber bundle can be normally used in a high-temperature environment.

[0040] Based on the above embodiment, a feasible implementation manner is proposed, the methane cracking hydrogen production fluidized bed membrane reactor further comprises a fixing piece 6, the fixing piece 6 comprises a fixing disc 61, a nickel alloy solder layer 62 and a sealing sleeve 63, the fixing disc 61 is provided with a mounting hole, the sealing sleeve 63 is sleeved on the outer periphery of the hollow fiber membrane bundle 2 and located between the hollow fiber membrane bundle 2 and the mounting hole, and the nickel alloy solder layer 62 is located between the sealing sleeve 63 and the hollow fiber membrane bundle 2.

[0041] In the present embodiment, when the hollow fiber membrane bundle 2 is inserted into the reactor shell 1 through the mounting hole by the cooperation of the fixing disc 61, the nickel alloy solder layer 62 and the fixing part 6 of the sealing sleeve 63, the sealing sleeve 63 is sleeved on the outer periphery of the membrane and provides sealing, and the nickel alloy solder layer 62 is melted at high temperature to form a firm sealing and fixing. The above arrangement can ensure the air tightness and mechanical stability between the hollow fiber membrane bundle 2 and the reactor shell 1. The above functions realize the reliable installation and leakage prevention of the hollow fiber membrane bundle 2, improve the sealing and durability of the reactor, reduce the hydrogen leakage, prevent the materials between the upper shell 11 and the lower shell 12 from flowing into each other, and ensure the technical effect of separation efficiency. The above technical effect can solve the technical problems that the hollow fiber membrane bundle 2 is easy to loosen, leak or damage in high temperature environment.

[0042] In addition to the above feasible embodiments, in order to prevent the carbon-loaded medium 3 from being stuck in the lower shell 12 after the carbon is attached, it is necessary to vibrate the lower shell 12 to enhance the flowability of the carbon-loaded medium 3. Based on the above idea, an eccentric turbine 41 driven by the flow of combustion gas is arranged in the combustion channel 4. The eccentric turbine 41 is driven to rotate by the combustion gas, and its own center of gravity changes constantly with its rotation, causing the combustion channel 4 to vibrate, and further causing the lower shell 12 to vibrate. In combination with the impact of methane, the flow efficiency of the carbon-loaded medium 3 in the lower shell 12 is improved.

[0043] In addition to the above feasible embodiments, a feasible embodiment is proposed, and the methane cracking hydrogen production fluidized bed membrane reactor further comprises a vibration motor 42 arranged on the outer side wall of the middle part of the lower shell 12. In the present embodiment, the vibration motor 42 generates mechanical vibration when it operates, which is transmitted to the inside of the lower shell 12, so that the particles of the carbon-loaded medium 3 continuously flow and mix, preventing them from agglomerating or depositing. In combination with the screen 52 in the above, the carbon-loaded medium 3 can be discharged through the vibrating screen 52, and the vibrating side wall also promotes the sufficient contact of the carbon-loaded medium 3 and the shedding of the carbon product. The vibrating side wall is also conducive to the long-term maintenance of the dynamic fluidization state of the carbon-loaded medium 3, thereby improving the reaction efficiency, enhancing the carbon product removal capacity, and reducing the risk of blockage. The above effects solve the technical problems that the carbon-loaded medium 3 in the fluidized bed reactor is easy to agglomerate and flow poorly, resulting in interruption of the reaction.

[0044] Based on the above embodiments, a feasible embodiment is proposed, and the carbon-loaded medium 3 is inert spherical particles or hollow cylindrical Raschig rings. The material of the carbon-loaded medium 3 is ceramic, quartz or graphite, and the ratio of the diameter of the lower shell 12 to the particle size of the carbon-loaded medium 3 is greater than 100. In this way, the carbon-loaded medium 3 acts as a carrier of carbon element in the reactor, and its shape and material ensure high specific surface area, good thermal stability and mechanical strength.

[0045] The further setting of the particle size ratio optimizes the hydrodynamic characteristics of the fluidized bed, making the medium uniformly fluidized.

[0046] The above setting mode realizes the optimized selection of the carbon-loaded medium 3 and the stable operation of the fluidized bed. The carbon loading area is increased, the heat transfer efficiency is enhanced, and the medium wear is reduced, thereby solving the technical problems of low reaction efficiency, fast wear, or unstable fluidization caused by improper selection of the carbon-loaded medium 3.

[0047] In a specific implementation, the process of the present application for hydrogen production by methane cracking is as follows: The methane is introduced into the lower shell 12 at a mass space velocity of 10000 / h for hydrogen production by cracking. The nickel-based alloy hollow fiber membrane bundle 2 separates hydrogen from the mixed product by using the vacuum pump connected to the upper shell 11, and maintains the vacuum degree at 0.01 MPa. The permeate gas is extracted as hydrogen. The lumen of the lower shell 12 is filled with solid alumina balls with a diameter of 0.1 mm, and the packing ratio is 1. The combustion channel 4 is filled with Pt-Fe / diaiamium trioxide catalyst, and the packing volume ratio is 0.85. The mesh size of the screen 52 is 2000 meshes. The one-end-sealed metal nickel hollow fiber membrane bundle 2 includes 30 hollow fiber membranes (i.e., the hollow fiber membrane bundle 2). The unreacted methane and the unpermeated hydrogen are introduced into the combustion channel 4 for mixing and combustion with air by opening the control valve. The movable sealing plate of the carbon collection bin 51 is opened, and the carbon product is sieved from the carbon-loaded medium 3 under the action of the screen 52 and falls into the carbon collection bin 51 from the top. Then, the movable sealing plate is closed, and the carbon product can be taken out by opening the carbon collection bin 51. As the temperature increases from 600℃ to 1000℃, the methane conversion rate increases from 43% to 86%, the carbon product output rate increases from 0.8 mg / min to 18 mg / min, the volume fraction of carbon nanotubes in the obtained product is about 5%, the hydrogen flow increases from 4.15 mL / min to 86.1 mL / min, and the hydrogen concentration is always higher than 99.9%.

[0048] When the methane is introduced into the reactor at a mass space velocity of 20000 / h for hydrogen production by cracking, the vacuum degree of the upper shell 11 is maintained at 0.005 MPa, the one-end-sealed metal nickel hollow fiber membrane bundle 2 includes 40 hollow fiber membranes, the vibration motor is opened, the vibration amplitude of the carbon-loaded particles is controlled to be 1.5 mm, and the reaction temperature is 1000℃. In this case, the methane conversion rate is 79%, the carbon product output rate is 34.6 mg / min, the hydrogen flow is 129.15 mL / min, and the hydrogen concentration is always higher than 99.9%.

[0049] When the methane is introduced into the reactor at a mass space velocity of 50000 / h for hydrogen production by cracking, the vacuum degree of the upper shell 11 needs to be maintained at 0.002 MPa. At 1000℃, the methane conversion rate is 73%, the carbon product output rate is 137.4 mg / min, the hydrogen flow is 513.2 mL / min, and the hydrogen concentration is always higher than 99.9%.

[0050] Optionally, in addition to the nickel-based hollow fiber membrane, the hollow fiber membrane is also an optional embodiment of the iron-based hollow fiber membrane, which is not repeated here.

[0051] Based on the same inventive concept, in addition to the above scheme, the present application also proposes a method for producing hydrogen by cracking methane, which is realized based on the fluidized bed membrane reactor for producing hydrogen by cracking methane as described above, and the method for producing hydrogen by cracking methane comprises the following steps: S1, introducing methane into the lower shell 12 filled with the carbon-loaded medium 3 and having sufficient reaction temperature to perform the cracking reaction; S2, applying vacuum to the inner cavity of the upper shell 11 by the vacuum pumping device to separate and permeate the hydrogen generated by the reaction; S3, introducing the heat generated by the combustion of the tail gas into the lower shell 12 to heat the lower shell 12; S4, intermittently removing the carbon product and supplementing the carbon-loaded medium 3.

[0052] In the specific implementation process, the above steps crack methane to generate hydrogen under optimized conditions, drive hydrogen to quickly pass through the membrane for separation under vacuum, provide self-heating by burning tail gas, and periodically remove carbon products. These functions realize the full-process integration and automatic control of hydrogen production by cracking methane, efficiently produce high-purity hydrogen, reduce external energy consumption, and achieve the technical effect of carbon resource recovery, which is beneficial to solve the technical problems of low hydrogen yield, high energy consumption, and difficult carbon treatment in traditional methane cracking methods.

[0053] Based on the above embodiment, a feasible implementation is proposed, and step S1 further comprises the following steps: S101, adjusting the flow rate of the methane feed and / or the vibration frequency of the reactor shell 1 to control the moving speed of the carbon-loaded medium 3 in the reactor.

[0054] In this way, by changing the feed flow rate to adjust the reactant concentration and residence time, and adjusting the vibration frequency to optimize the fluidization degree and mixing efficiency of the carbon-loaded medium 3, dynamic and accurate control of the reaction conditions is realized. Furthermore, this embodiment can achieve the technical effects of improving methane conversion rate, optimizing hydrogen yield, and preventing medium deposition. The above effects solve the technical problems of low reaction efficiency or excessive accumulation of carbon products caused by inflexible reaction parameters.

[0055] Based on the above embodiment, a feasible implementation is proposed, in step S1, the reaction temperature is 700-1000 DEG C; the feed volume space velocity of methane is 1000 / h-50000 / h. The above steps, the reaction rate of methane cracking at high temperature is accelerated, and the space velocity is adjusted to ensure that the reactants have enough residence time to achieve high conversion rate, while avoiding excessive reaction or byproduct generation. The above functions realize the optimization balance of the reaction conditions, improve the hydrogen yield and selectivity, and reduce the technical effect of reducing the carbon deposition side reaction.

[0056] Based on the above embodiment, a feasible implementation is proposed, in step S2, the vacuum degree of the inner cavity of the upper shell 11 is 0.001-0.01 MPa. The vacuum device reduces the hydrogen partial pressure, forms a pressure difference to drive the hydrogen to rapidly penetrate from the hollow fiber membrane bundle 2 separation layer 22 to the upper layer. The above setting mode enhances the mass transfer efficiency of hydrogen, realizes the efficient separation and purification of hydrogen. In this way, the embodiment can achieve the technical effects of improving the hydrogen recovery rate and product purity, and reducing the residual gas.

[0057] In summary, the present application realizes the efficient cooperation and optimization of the whole process from reaction, separation to carbon removal through the cooperation of the integrated structure and the matching method of the methane cracking hydrogen production fluidized bed membrane reactor, and finally achieves the significant technical effects of improving the hydrogen yield and purity and the process continuity. Systematically solves the multiple technical problems existing in the traditional methane cracking technology.

[0058] Specifically, the upper and lower separation design of the reactor shell 1, combined with the hollow fiber membrane bundle 2 with reaction and separation functions, makes the methane in the lower shell 12 efficiently crack on the surface of the carbon-containing medium 3 in operation, and the generated hydrogen is selectively extracted from the reaction layer 21 to the separation layer 22 and collected in the upper shell 11 for discharge. This combination not only enhances the mass transfer and separation efficiency, but also effectively promotes the shift of the cracking reaction equilibrium to the right, thereby solving the problems of low hydrogen separation efficiency and limited reaction conversion rate.

[0059] The combustion channel 4 skillfully guides the unreacted tail gas and other components into combustion, and the released heat directly provides a continuous and stable heat source for the strong endothermic cracking reaction of the lower shell 12, forming an efficient internal circulation heat management, solving the technical difficulties of high external heating energy consumption and difficulty in maintaining uniform and stable reaction temperature. The carbon collection mechanism 5 is linked with the vibration motor 42 and the medium feeding part, which maintains the fluidization state of the carbon-containing medium 3 by mechanical vibration to prevent caking, and allows the medium with attached carbon products to be removed intermittently and fresh medium to be supplemented or only the carbon products to be discharged. Combined with the optimized medium form and particle size control, the reactor can be continuously and stably operated for a long time, fundamentally solving the problems of reactor blockage and frequent shutdown caused by carbon deposition.

[0060] In addition, the fixing member 6 forms a reliable seal at high temperature through a nickel alloy solder layer 62 or the like, ensuring the long service life and safety of the membrane assembly under severe working conditions. Based on the hydrogen production method of the reactor structure, through the synergistic control of key parameters such as reaction temperature, feed air speed, vacuum degree and medium fluidization state, the entire system can operate under optimal working conditions. Not only maximizes hydrogen yield and purity, but also minimizes process energy consumption and orderly manages carbon byproducts, ultimately comprehensively solves a series of core technical bottlenecks such as low efficiency, high energy consumption, discontinuous operation and carbon treatment difficulty in traditional technology. Provides an efficient, economical and reliable solution for green low-carbon hydrogen production.

[0061] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fluidized bed membrane reactor for methane cracking to produce hydrogen, characterized in that, include: The reactor shell (1) includes an upper shell (11) and a lower shell (12) that are separated from each other. The upper shell (11) is provided with a hydrogen outlet at the top, and the lower shell (12) is provided with a reaction tail gas outlet and a methane inlet on the side wall. The lower shell (12) is provided with a material outlet at the bottom. Hollow fiber membrane bundle (2) is disposed inside the reactor shell (1) and includes a reaction layer (21) and a separation layer (22) arranged sequentially from the outside to the inside. The outer side of the reaction layer (21) and the inner wall of the lower shell (12) together form a reaction cavity, and the inner side of the separation layer (22) and the inner wall of the upper shell (11) together form a separation cavity. The lower shell (12) is filled with a carbon-carrying medium (3). The carbon collection mechanism (5) includes a carbon collection bin (51) connected to the material discharge outlet.

2. The fluidized bed membrane reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The carbon collection mechanism (5) also includes a screen (52), which is located between the material discharge port and the carbon collection bin (51); The aperture of the screen (52) is smaller than the diameter of the carbon-carrying medium (3). As the screen (52) vibrates, the carbon products adsorbed on the surface of the carbon-carrying medium (3) fall off and pass through the screen (52) into the carbon collection bin (51).

3. The fluidized bed membrane reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The carbon collection mechanism (5) also includes a screen (52), which is located between the material discharge port and the carbon collection bin (51); The aperture of the screen (52) is larger than the diameter of the carbon-carrying medium (3). As the screen (52) vibrates, the carbon-carrying medium (3) with carbon products adsorbed on its surface passes through the screen (52) and falls into the carbon collection bin (51).

4. The fluidized bed membrane reactor for methane cracking to hydrogen production as described in claim 3, characterized in that, The methane cracking hydrogen production fluidized bed membrane reactor also includes a medium feed section located at the top of the lower shell (12). The medium feed section includes a feed bin and a feed pipe. The feed bin is connected to the lower shell (12) through the feed pipe.

5. The fluidized bed membrane reactor for methane cracking to hydrogen production as described in claim 2 or 3, characterized in that, The methane cracking hydrogen production fluidized bed membrane reactor also includes a vibration motor (42), which is located on the outer side wall of the middle part of the lower shell (12) to make the side wall of the lower shell (12) vibrate.

6. The fluidized bed membrane reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The methane cracking hydrogen production fluidized bed membrane reactor also includes a combustion channel (4), which is located in the chamber of the lower shell (12) for burning the reaction tail gas and providing heat for methane cracking. The top of the combustion channel (4) is connected to the reaction tail gas outlet of the lower shell (12), and the bottom of the combustion channel (4) is provided with an exhaust port.

7. A method for producing hydrogen from methane through cracking, based on a fluidized bed membrane reactor for producing hydrogen from methane through cracking as described in any one of claims 1-6, characterized in that, The methane cracking method for hydrogen production includes the following steps: S1. Methane is introduced into the lower shell (12) filled with carbon-carrying medium (3) and with sufficient reaction temperature to carry out the cracking reaction; S2. Apply a vacuum to the inner cavity of the upper shell (11) using a vacuum pumping device to allow the hydrogen gas generated in the reaction to permeate and separate. S3. The heat from the combustion of the reaction tail gas is introduced into the lower shell (12) to heat the lower shell (12); S4. Intermittently remove carbon products and replenish carbon-carrying media (3).

8. The method for producing hydrogen from methane through cracking as described in claim 7, characterized in that, Step S1 also includes the following steps: S101. Adjust the methane feed flow rate and / or the vibration frequency of the reactor shell (1) to control the movement speed of the carbon-carrying medium (3) in the reactor.

9. The method for producing hydrogen from methane through cracking as described in claim 7, characterized in that, In step S1, the reaction temperature is 700℃-1000℃; the feed volume hourly space velocity of methane is 1000 / h-50000 / h.

10. The method for producing hydrogen from methane through cracking as described in claim 7, characterized in that, In step S2, the vacuum degree of the inner cavity of the upper shell (11) is 0.001 MPa-0.01 MPa.

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