Hydrogen production equipment and hydrogen production method based on sodium-catalyzed ammonia cracking

Abstract

The invention discloses hydrogen production equipment and a hydrogen production method based on sodium-catalyzed ammonia cracking, and the hydrogen production equipment comprises a reactor which is a pressure-bearing shell and tube type heat exchange reactor and is internally provided with a plurality of heat exchange tubes filled with a sodium-based catalyst, two ends of the reactor are sealed through a first sealing cover and a second sealing cover, and the first sealing cover is connected with an ammonia storage tank; the second sealing cover is connected with a gas purification separator; the ammonia storage tank is used for storing liquid ammonia and supplying ammonia to the reactor through the booster pump; the gas purification separator is used for separating unreacted ammonia, nitrogen and hydrogen from emissions of the reactor; the temperature control system controls the reaction temperature by adjusting the flow of the heat source gas entering the reactor. A sodium-based catalyst is adopted, and in-situ regeneration of the catalyst is realized through a dynamic circular reaction mechanism; sodium serves as an intermediate medium and is continuously consumed and regenerated in the ammonia cracking process, external supplementation is not needed, the reaction path specificity is high, the byproduct generation rate is low, and the heat transfer efficiency is improved through the design of the countercurrent shell and tube type heat exchange reactor.

Description

Technical Field

[0001] The present invention relates to the field of clean energy technology, and in particular to a hydrogen production device and a hydrogen production method based on sodium-catalyzed ammonia cracking. Background Art

[0002] Ammonia (NH3) is a hydrogen energy carrier, and due to its high hydrogen storage density (17.6 wt%) and easy storage and transportation in liquid form, it has become an important medium for hydrogen energy utilization. Existing ammonia cracking hydrogen production technology mainly relies on transition metal catalysts such as iron and ruthenium, but has the following drawbacks: 1. Insufficient catalyst activity and stability: Traditional catalysts are prone to sintering and deactivation at high temperatures (>500°C), have low selectivity for ammonia cracking, and produce high rates of by-products (such as N2O); 2. Low heat and mass transfer efficiency of the reactor: Uneven gas distribution in fixed-bed or fluidized-bed reactors leads to local overheating or cold zones, reducing ammonia conversion; 3. Low ammonia recovery rate: Unreacted ammonia is mixed with the product hydrogen and nitrogen and then directly discharged or burned, resulting in waste of ammonia resources and environmental pollution. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a hydrogen production device and method based on sodium-catalyzed ammonia cracking to address the problems of insufficient activity and stability of hydrogen production catalysts, poor heat transfer, and low hydrogen production efficiency in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, an embodiment of the present application provides a hydrogen production device based on sodium-catalyzed ammonia cracking, comprising: The reactor is a pressurized shell and tube heat exchange reactor, which is provided with multiple heat exchange tubes filled with sodium-based catalysts. Both ends are closed by a first sealing cover and a second sealing cover. The first sealing cover is connected to the ammonia storage tank, and the second sealing cover is connected to the gas purification separator. An ammonia storage tank, used to store liquid ammonia and supply ammonia to the reactor through a booster pump; a gas purification separator for separating unreacted ammonia, nitrogen and hydrogen from the discharge of the reactor; The temperature control system controls the reaction temperature by adjusting the flow rate of heat source gas entering the reactor.

[0005] In some embodiments, the heat exchange tube is filled with a sodium amide catalyst wrapped in a nickel wire mesh bag.

[0006] In some embodiments, the pressure-bearing shell of the reactor is provided with a heat source gas inlet and a heat source gas outlet, wherein the heat source gas inlet is located above the shell, and the heat source gas outlet is located below the shell, forming a countercurrent heat exchange structure.

[0007] In some embodiments, the gas purification separator comprises a refrigeration unit, a heat exchanger, a molecular sieve and a hydrogen storage tank. The refrigeration unit cools the discharge of the reactor to below -40°C through the heat exchanger, and the generated condensed liquid ammonia is re-injected into the ammonia storage tank via a transfer pump. The molecular sieve is used to separate hydrogen and nitrogen in the exhaust, discharge the nitrogen into the atmosphere, and introduce the hydrogen into the hydrogen storage tank.

[0008] In some embodiments, the temperature control system dynamically adjusts the fuel flow of the burner through a temperature controller to maintain the temperature in the reactor at no less than 500°C.

[0009] In some embodiments, pressure sensors are respectively provided on the first sealing cover and the second sealing cover of the reactor to trigger the start and stop of the gas booster pump.

[0010] In some embodiments, the sodium-based catalyst is a mixture of metallic sodium and sodium amide, and the catalyst packing density is 80% to 95% of the volume of the heat exchange tube.

[0011] In a second aspect, an embodiment of the present application provides a method for producing hydrogen based on sodium-catalyzed ammonia cracking, using the above-mentioned hydrogen production equipment, comprising the following steps: S1. Heat the reactor to no less than 500°C and inject liquid ammonia into the heat exchange tubes through a booster pump; S2, liquid ammonia undergoes a cracking reaction under the action of a sodium-based catalyst to produce nitrogen, hydrogen and unreacted ammonia; S3, the mixed gas is condensed through a gas purification separator to recover liquid ammonia, and the remaining gas is separated into hydrogen through a molecular sieve; S4. Dynamically adjust the reaction temperature and gas flow rate through the temperature control system and pressure sensor.

[0012] In some embodiments, the cleavage reaction in step S2 comprises: First reaction: 2NaNH2 decomposes into 2Na, nitrogen and hydrogen, the reaction formula is 2NaNH2→2Na+N2↑+H2↑; Second reaction: 2Na reacts with 2NH3 to generate 2NaNH2 and hydrogen. The reaction formula is 2Na+2NH3→2NaNH2+H2↑; Sodium circulates as an intermediate medium and participates in the reaction.

[0013] In some embodiments, the pressure in the reactor is monitored in real time. When the pressure exceeds a first preset pressure threshold, a gas booster pump is started to extract the mixed gas from the reactor outlet and transport it to the gas purification separator; when the pressure is lower than a second preset pressure threshold, the gas booster pump is stopped. Monitor the temperature inside the reactor in real time. When the temperature reaches the preset upper limit, reduce the fuel flow rate of the burner fuel nozzle to suppress the temperature rise. When the temperature drops to the preset lower limit and the system is in operation, increase the fuel nozzle flow rate or re-ignite to raise the temperature and maintain the reaction temperature within the preset range. Monitor the liquid ammonia level in the ammonia storage tank in real time. When the level is lower than the preset minimum level, shut down the booster pump, reactor inlet and outlet valves, and the system master switch, and trigger an alarm signal.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: This application uses a sodium-based catalyst to achieve in-situ regeneration of the catalyst through a dynamic cyclic reaction mechanism (2NaNH2→2Na+N2↑+H2↑ and 2Na+2NH3→2NaNH2+H2↑). Sodium, as an intermediate medium, is continuously consumed and regenerated during the ammonia cracking process, without the need for external supplementation. The reaction pathway is highly specific and the by-product generation rate is low. The countercurrent shell-and-tube heat exchange reactor design maximizes the temperature differential driving force by countercurrently flowing the heat source and reactant gases. Combined with the uniform filling of the catalyst with nickel-based alloy wire mesh (packing density 80-95%), this solves the localized overheating and cold spots often seen in traditional fixed-bed reactors. The high thermal conductivity of the nickel wire mesh allows for rapid heat transfer to the catalyst bed, keeping the reactor's axial temperature gradient within ±5°C and improving ammonia cracking conversion.

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative effort.

[0017] Figure 1 The present invention is a structural schematic diagram of a hydrogen production device based on sodium-catalyzed ammonia cracking provided in an embodiment.

[0018] Figure 2 It is a structural schematic diagram of a hydrogen production device based on sodium-catalyzed ammonia cracking provided under another embodiment. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0022] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0023] Reference Figure 1 In a first aspect, an embodiment of the present application provides a hydrogen production device based on sodium-catalyzed ammonia cracking, comprising: Reactor 1 is a pressurized shell and tube heat exchange reactor 1, which adopts a 316 stainless steel shell and is provided with a plurality of heat exchange tubes filled with a sodium-based catalyst. Both ends are closed by a first sealing cover 11 and a second sealing cover 12. The first sealing cover 11 is connected to the ammonia storage tank 2, and the second sealing cover 12 is connected to the gas purification separator; An ammonia storage tank 2 is used to store liquid ammonia and supply ammonia to the reactor 1 through a booster pump 21. The ammonia storage tank 2 is a corrosion-resistant, heat-insulating, and pressure-bearing container for anhydrous liquid ammonia. Ammonia gas is supplied to the reactor 1 and the burner 3 through a switch on the pipeline and the booster pump 21. A gas purification separator for separating unreacted ammonia, nitrogen and hydrogen from the discharge of reactor 1; The temperature control system includes a burner 3, which controls the operating state of the burner 3 to adjust the flow rate of the heat source gas entering the reactor 1, thereby controlling the reaction temperature.

[0024] It should be noted that the reactor 1 is a corrosion-resistant heat exchange reactor 1, a pressure shell and tube heat exchange reactor 1 made of 316 stainless steel, the outer shell is pressure-bearing, with flat end plates at both ends, the end plates have multiple openings, and multiple heat exchange tubes are welded to the end plates at the openings of the end plates to form a leak-proof tube bundle, the heat exchange tubes are filled with catalyst, and the end plates are respectively provided with a first sealing cover 11 and a second sealing cover 12 in the shape of a pot cover. The sealing covers are connected to the flanges on the pressure shell by bolts. The first sealing cover 11 has an opening, which is connected to the ammonia storage tank 2 pipeline; the second sealing cover 12 has an opening, which is connected to the gas purification separator pipeline; the pressure shell of the reactor 1 is provided with a heat source gas inlet 13 and a heat source gas outlet 14. The heat source gas inlet 13 is located above the shell, and the heat source gas enters the pressure shell and tube heat exchange reactor 1 from here, and the heat source gas outlet 14 is located below the shell, and the heat source gas after heat exchange is discharged from here, thereby forming a countercurrent heat exchange structure. Each pipeline connected to the four openings at the front, back, top and bottom of the reactor 1 is equipped with an electric valve, which is controlled to open or close by an electric control system.

[0025] like Figure 2 As shown, as an embodiment, a liquid ammonia evaporative mixed gas precooler 5 is installed on the pipeline between the first sealing cover 11 and the second sealing cover 12, that is, the ammonia storage tank 2 injects liquid ammonia into the liquid ammonia evaporative mixed gas precooler 5 through the booster pump 21, and evaporates to form gaseous ammonia after heat exchange with the mixed gas discharged from the second sealing cover 12 of the reactor 1, and enters the reactor 1. The step of vaporizing the liquid ammonia to form gaseous ammonia occurs before the reactor 1, which can further improve the reaction efficiency and thermal energy utilization rate in the reactor 1.

[0026] Optionally, after liquid ammonia is vaporized to form gaseous ammonia, a branch is taken out to enter the burner 3, and by providing combustible gas in an adjustable manner, the heat source gas flow of the burner 3 is changed and the reaction temperature is controlled, and the amount of gaseous ammonia supplied to the reactor 1 is adapted.

[0027] As an embodiment, the heat exchange tube is filled with a sodium amide catalyst wrapped in a nickel wire mesh bag; it should be noted that this embodiment only illustrates that the sodium-based catalyst includes a sodium amide catalyst wrapped in a nickel wire mesh bag, and does not limit the sodium-based catalyst to only this type of sodium amide catalyst, wherein the nickel wire mesh bag is in the form of a nickel-based alloy wire mesh.

[0028] Furthermore, the sodium-based catalyst is a mixture of metallic sodium and sodium amide, and the catalyst filling density is 80% to 95% of the volume of the heat exchange tube.

[0029] Specifically, sodium-based catalysts (such as mixtures of sodium metal and sodium amide) are susceptible to sintering, volatilization, or chemical decomposition at high temperatures (above 500°C) and in an ammonia atmosphere. This can lead to catalyst particle agglomeration, reduced surface area, and loss of active sites, thus reducing ammonia cracking efficiency. For example, sodium metal can melt at high temperatures and clog heat exchange tubes, while sodium amide (NaNH2) can decompose into Na and NH3 at sustained high temperatures, disrupting the catalytic cycle.

[0030] Therefore, in this embodiment, the catalyst carrier is optimized, using a high-temperature-resistant, high-mechanical-strength inert carrier (nickel-based alloy mesh) to encapsulate the sodium-based catalyst, limiting its mobility and volatility. The core goal of the nickel-based alloy mesh-encapsulated sodium amide catalyst design is to achieve efficient encapsulation of the catalyst's active ingredients, sufficient mass transfer of the reactant gases, and long-term stable operation of the equipment through refined control of structural parameters and adaptation of material properties. First, the mesh's pore size must be precisely matched to the catalyst particle size, typically within the range of 50-200 microns. This design prevents melted or pulverized catalyst particles from escaping through the mesh at high temperatures while ensuring sufficient contact between ammonia molecules and the catalyst surface as they flow through the mesh. For example, if the average catalyst particle size is 150 microns, a mesh with a pore size of 100 microns is selected. This physically confines the catalyst to a limited space, while the high porosity reduces gas flow resistance and avoids uneven gas distribution or localized pressure drops caused by the mesh's inherent structure.

[0031] Secondly, the material selection and wire diameter design of nickel-based alloy wire mesh must balance high-temperature strength and corrosion resistance. Nickel-based high-temperature alloys with high chromium and molybdenum content maintain excellent mechanical stability at operating temperatures of 500-800°C. The dense chromium oxide (Cr2O3) film formed on its surface effectively resists the synergistic corrosion of sodium and ammonia. Wire diameter is typically controlled between 0.1-0.3 mm. This finer wire diameter not only reduces the wire mesh's own thermal inertia, enabling it to quickly respond to temperature changes in the heat exchange tube wall, but also enhances heat transfer efficiency between the catalyst bed and the tube wall by increasing the wire mesh surface area per unit volume. Furthermore, the wire mesh weave pattern must be flexibly selected based on the catalyst packing density. Plain weave, with its denser nodes and stronger structural rigidity, is suitable for high-filling tube sections (90-95%), preventing catalyst displacement due to airflow impact. The flexibility of twill weave is suitable for installation scenarios requiring a close fit to the heat exchange tube wall, reducing stress concentration caused by differential thermal expansion.

[0032] Furthermore, the surface treatment of the wire mesh is crucial to its long-term stability. Pre-oxidation or ceramic coating (such as a 5-10 micron thick alumina coating) can form an inert barrier layer on the wire mesh surface, blocking direct contact between the sodium-based catalyst and the nickel alloy substrate, thereby preventing the formation of low-melting-point sodium-nickel eutectic compounds (such as NaNi3) that could cause localized melting of the wire mesh. For example, the alumina coating not only offers excellent sodium corrosion resistance, but its porous structure also facilitates the diffusion and penetration of ammonia at high temperatures, while inhibiting wear and tear of catalyst particles caused by vibration or thermal cycling. This surface modification technology, combined with the high-temperature performance of the wire mesh material, enables the wire mesh to maintain a service life of over 10,000 hours in the harsh ammonia cracking environment, significantly reducing the risk of equipment downtime due to catalyst carrier failure.

[0033] As an embodiment, the gas purification separator includes a refrigeration unit, a heat exchanger 41, a molecular sieve 42 and a hydrogen storage tank 43. The front end of the heat exchanger 41 is connected to a gas booster pump 3121 to extract the mixed gas of ammonia + nitrogen + hydrogen generated by the reactor 1 and transport it to the heat exchanger 41. The refrigeration unit cools the discharge of the reactor 1 to below minus 40°C through the heat exchanger 41, and the gaseous ammonia therein is condensed into liquid. The condensed liquid ammonia produced by the separation is injected back into the ammonia storage tank 2 by the delivery pump 44, and the remaining hydrogen and nitrogen mixture enters the molecular sieve 42; the molecular sieve 42 is used to separate the hydrogen and nitrogen in the discharge, discharge the nitrogen into the atmosphere, and introduce the hydrogen into the hydrogen storage tank 43.

[0034] Preferably, the temperature control system dynamically adjusts the fuel flow of the burner 3 through a temperature controller to maintain the temperature in the reactor 1 to no less than 500°C.

[0035] Preferably, pressure sensors are respectively provided on the first sealing cover 11 and the second sealing cover 12 of the reactor 1 to trigger the start and stop of the gas booster pump 3121 .

[0036] In a second aspect, an embodiment of the present application provides a method for producing hydrogen based on sodium-catalyzed ammonia cracking, using the above-mentioned hydrogen production equipment, comprising the following steps: S1, heating the reactor 1 to not less than 500°C, and injecting liquid ammonia into the heat exchange tubes through the booster pump 21; S2, liquid ammonia undergoes a cracking reaction under the action of a sodium-based catalyst to produce nitrogen, hydrogen and unreacted ammonia; S3, the mixed gas is condensed through a gas purification separator to recover liquid ammonia, and the remaining gas is separated into hydrogen through a molecular sieve 42; S4. Dynamically adjust the reaction temperature and gas flow rate through the temperature control system and pressure sensor.

[0037] It should be noted that liquid ammonia is pressurized and poured into the liquid ammonia tank through the filling port, and the burner 3 is controlled to start the blower and the liquid ammonia booster pump 21 and inject ammonia gas for ignition and combustion. The high-temperature gas enters the heat source gas inlet 13 of the shell of the pressure-bearing shell and tube heat exchange reactor 1 to heat the catalyst in the heat exchange tube bundle of the reactor 1 to a preset temperature, which is not less than 500° C. in this embodiment. Then, the valve of the liquid ammonia pipeline is controlled to open, and liquid ammonia is injected into the heat exchange tubes through the booster pump 21. Liquid ammonia is heated and vaporized in reactor 1, and the pressure increases. Under the action of pressure, the gaseous ammonia flows through the high-temperature catalyst filled in the heat exchange tube, and a chemical reaction occurs. Specifically, the cracking reaction produced includes: First reaction: 2NaNH2 decomposes into 2Na, nitrogen and hydrogen, the reaction formula is 2NaNH2→2Na+N2↑+H2↑; Second reaction: 2Na reacts with 2NH3 to generate 2NaNH2 and hydrogen. The reaction formula is 2Na+2NH3→2NaNH2+H2↑; Sodium circulates as an intermediate medium and participates in the reaction.

[0038] These two reactions are carried out simultaneously. Sodium is consumed as an intermediate medium in the reaction and then regenerated. In theory, there is no need for continuous replenishment. Sodium continues to exist in the reaction heat exchange tube in the form of metallic sodium and sodium amide. Combining the two-step reaction, the overall effect is the decomposition of ammonia: 2NH3→N2+3H2 The mixed gas composed of nitrogen, hydrogen and some unreacted ammonia, driven by the pressure of the gasified liquid ammonia in the cavity of the first sealing cover 11, passes through the reaction heat exchange tube and the catalyst and enters the cavity formed by the second sealing cover 12.

[0039] As an embodiment, a liquid ammonia evaporative mixed gas precooler 5 is installed on the pipeline between the first sealing cover 11 and the second sealing cover 12. That is, liquid ammonia is injected into the evaporation side of the liquid ammonia evaporative mixed gas precooler 5 through the booster pump 21, and is heated by the high-temperature mixed gas discharged from the second sealing cover 12 of the reactor 1 on the condensation side of the heat exchanger 41 to evaporate into gaseous ammonia. The step of vaporizing liquid ammonia to form gaseous ammonia occurs before the reactor 1, which can further improve the reaction efficiency and thermal energy utilization rate in the reactor 1.

[0040] As an embodiment, the pressure in the reactor 1 is monitored in real time. When the pressure exceeds a first preset pressure threshold, the gas booster pump 3121 is started to extract the mixed gas from the outlet of the reactor 1 and transport it to the gas purification separator; when the pressure is lower than a second preset pressure threshold, the gas booster pump 3121 is stopped. The temperature in the reactor 1 is monitored in real time. When the temperature reaches a preset upper temperature limit, the fuel flow rate of the fuel nozzle of the burner 3 is reduced to suppress the temperature rise. When the temperature drops to the preset lower temperature limit and the system is in operation, the fuel nozzle flow rate is increased or the ignition is restarted to raise the temperature and maintain the reaction temperature within the preset range. The liquid ammonia level in the ammonia storage tank 2 is monitored in real time. When the liquid level is lower than the preset minimum level, the booster pump 21, the inlet and outlet valves of the reactor 1 and the main switch of the system are closed, and an alarm signal is triggered.

[0041] It should be noted that when the pressure sensor in the reactor 1 detects that the pressure has risen to a preset value, the gas booster pump 3121 is started to extract the mixed gas from the outlet of the second sealing cover 12 of the reactor 1 and pressurize it to the gas purification separator. The gas purification separator freezes the mixed gas output from the reactor 1 to below -40 degrees Celsius, condensing the gaseous ammonia into liquid. A delivery pump 44 injects the separated liquid ammonia back into the ammonia storage tank 2. The remaining hydrogen and nitrogen mixed gas enters the molecular sieve 42 for gas separation. The nitrogen is discharged into the atmosphere, and the hydrogen is introduced into the hydrogen storage tank 43 for standby use. When the pressure in the reactor 1 drops to the preset value, the gas booster pump stops.

[0042] When the thermostat detects that the temperature inside reactor 1 has reached a preset maximum value, it reduces the flow rate of the fuel nozzle of burner 3, slowing the temperature rise until combustion stops. When the thermostat detects that the temperature inside reactor 1 has dropped to a preset minimum value while the entire hydrogen production equipment is still running, it increases the flow rate of the fuel nozzle of burner 3 or ignites it again to begin heating, thereby controlling the temperature of reactor 1 within a preset range.

[0043] When the liquid level controller of the ammonia storage tank 2 detects that the liquid ammonia level drops to a preset minimum value, it turns off the boost pump 21, closes the valves on the first sealing cover 11 and the second sealing cover 12 pipelines, turns off the control system switch of the hydrogen production equipment, and triggers the alarm indicator light.

[0044] As an implementation method, in the process of cooling the discharge of the reactor 1 to below -40°C through the heat exchanger 41 and then condensing the gaseous ammonia into liquid ammonia, how to accurately balance the condensation temperature directly affects the liquefaction efficiency of ammonia in the mixed gas, because the ideal condensation temperature needs to be controlled below -40°C. If the temperature fluctuates beyond the range of ±2°C, for example, it rises to -38°C for a short time, some gaseous ammonia will not be condensed and enter the subsequent molecular sieve 42 unit along with the hydrogen and nitrogen, causing the molecular sieve 42 adsorbent to quickly deactivate due to the occupation of active sites by ammonia molecules, and the purity of hydrogen will drop sharply. The traditional single-stage condensation process relies on a high-power refrigeration unit to achieve a low temperature of -40°C, and the energy consumption accounts for as much as 35% of the total energy consumption of the system. In addition, continuous low-temperature operation is prone to form a frost layer on the surface of the fins of the heat exchanger 41, increasing the heat transfer resistance and blocking the flow channel, forcing the system to frequently start and stop defrosting, further exacerbating energy consumption and operational instability.

[0045] Therefore, in this embodiment, a staged condensation and adaptive temperature control strategy is adopted. In the first-stage pre-cooling section, liquid ammonia is used to flow into the evaporation side of the liquid ammonia evaporative mixed gas pre-cooler 5. The high-temperature mixed gas discharged from the second sealing cover 12 is rapidly cooled to below the dew point on the condensation side of the liquid ammonia evaporative mixed gas pre-cooler 5. After the liquid ammonia absorbs heat and evaporates, it enters the reactor 1 in gaseous form, so that more than 90% of the gaseous ammonia in the mixed gas is initially liquefied and separated. The remaining gas enters the second-stage cryogenic section. The compressor frequency and expansion valve opening of the cascade refrigeration system (such as the combination of R23 and R508B) are dynamically adjusted by the PID algorithm to strictly control the temperature in the range of -40~-42°C to ensure the complete liquefaction of the residual ammonia. At the same time, the load of the cryogenic section is reduced by the diversion of the pre-cooling section, so as to reduce the overall energy consumption.

[0046] Furthermore, in the coordinated control of liquid ammonia reinjection and gas separation, system pressure fluctuations and flow rate matching directly impact process continuity and safety. When liquid ammonia is pressurized and reinjected into the storage tank via transfer pump 44, if the pump flow rate and tank pressure regulation are mismatched—for example, if high flow rate is continued when the tank pressure approaches the upper limit of 1.5 MPa—the gas phase space within the tank will be compressed. The liquid ammonia partially vaporizes due to the increased saturated vapor pressure, forming a gas-liquid two-phase flow that rushes back into the delivery pipeline, causing water hammer and pump cavitation damage.

[0047] To this end, this solution has designed a pressure-flow coordinated control system. A buffer tank with a volume of 0.5 m³ is added to the outlet of the delivery pump 44. A porous energy dissipation plate is installed in the tank to attenuate the fluid kinetic energy. The tank pressure is monitored in real time by a high-precision pressure sensor. The speed of the variable frequency pump is dynamically adjusted using a fuzzy logic algorithm to ensure that the reinjection flow rate and the tank pressure have a negative linear correlation. Preferably, in this embodiment, the flow rate is reduced by 10% for every 0.1 MPa increase in pressure, ensuring that the liquid ammonia is always injected smoothly in a single-phase liquid state.

[0048] Compared to the prior art, the above embodiment provides a hydrogen production device and method based on sodium-catalyzed ammonia cracking, which solves the problems of insufficient ammonia conversion and high by-product generation rate caused by the high-temperature sintering and deactivation of traditional transition metal catalysts (such as iron and ruthenium) and low reaction selectivity in the existing ammonia cracking hydrogen production technology, as well as the local overheating or cold zone effect caused by uneven heat transfer in the fixed bed / fluidized bed reactor 1. At the same time, it overcomes the resource waste and environmental pollution caused by the direct discharge of unreacted ammonia. Through the sodium-based catalyst recycling regeneration system (2NaNH2→2Na+N2↑+H2↑ and 2Na+2NH3→2NaNH2+H2↑ coupled reactions), the structural optimization of the countercurrent shell and tube heat exchange reactor 1 (316 stainless steel shell + nickel-based alloy wire mesh encapsulated catalyst), and the low-temperature condensation-molecular sieve 42 separation system, efficient ammonia cracking, high-purity hydrogen separation, and closed-loop recycling of unreacted ammonia are achieved. The temperature-pressure linkage control strategy is used to improve the stability of equipment operation and energy utilization efficiency.

[0049] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A hydrogen production device based on sodium-catalyzed ammonia cracking, characterized in that: include: The reactor is a pressurized shell and tube heat exchange reactor, which is provided with multiple heat exchange tubes filled with sodium-based catalysts. Both ends are closed by a first sealing cover and a second sealing cover. The first sealing cover is connected to the ammonia storage tank, and the second sealing cover is connected to the gas purification separator. An ammonia storage tank, used to store liquid ammonia and supply ammonia to the reactor through a booster pump; a gas purification separator for separating unreacted ammonia, nitrogen and hydrogen from the discharge of the reactor; The temperature control system controls the reaction temperature by adjusting the flow rate of heat source gas entering the reactor.

2. A hydrogen production device based on sodium-catalyzed ammonia cracking according to claim 1, characterized in that: The heat exchange tube is filled with a sodium amide catalyst wrapped in a nickel wire mesh bag.

3. A hydrogen production device based on sodium-catalyzed ammonia cracking according to claim 2, characterized in that: The pressure-bearing shell of the reactor is provided with a heat source gas inlet and a heat source gas outlet. The heat source gas inlet is located above the shell, and the heat source gas outlet is located below the shell, forming a countercurrent heat exchange structure.

4. A hydrogen production device based on sodium-catalyzed ammonia cracking according to claim 3, characterized in that: The gas purification separator comprises a refrigeration unit, a heat exchanger, a molecular sieve and a hydrogen storage tank. The refrigeration unit cools the discharge of the reactor to below -40°C through the heat exchanger, and the generated condensed liquid ammonia is re-injected into the ammonia storage tank through a delivery pump; The molecular sieve is used to separate hydrogen and nitrogen in the exhaust, discharge the nitrogen into the atmosphere, and introduce the hydrogen into the hydrogen storage tank.

5. A hydrogen production device based on sodium-catalyzed ammonia cracking according to claim 4, characterized in that: The temperature control system dynamically adjusts the fuel flow of the burner through the temperature controller to maintain the temperature in the reactor at no less than 500°C.

6. A hydrogen production device based on sodium-catalyzed ammonia cracking according to claim 5, characterized in that: The first sealing cover and the second sealing cover of the reactor are respectively provided with pressure sensors for triggering the start and stop of the gas booster pump.

7. The hydrogen production equipment based on sodium-catalyzed ammonia cracking according to claim 1, characterized in that: The sodium-based catalyst is a mixture of metallic sodium and sodium amide, and the catalyst filling density is 80% to 95% of the volume of the heat exchange tube.

8. A method for producing hydrogen based on sodium-catalyzed ammonia cracking, using the hydrogen production equipment according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Heat the reactor to no less than 500°C and inject liquid ammonia into the heat exchange tubes through a booster pump; S2, liquid ammonia undergoes a cracking reaction under the action of a sodium-based catalyst to produce nitrogen, hydrogen and unreacted ammonia; S3, the mixed gas is condensed through a gas purification separator to recover liquid ammonia, and the remaining gas is separated into hydrogen through a molecular sieve; S4. Dynamically adjust the reaction temperature and gas flow rate through the temperature control system and pressure sensor.

9. A method for producing hydrogen based on sodium-catalyzed ammonia cracking according to claim 8, characterized in that: The cleavage reaction in step S2 includes: First reaction: 2NaNH2 decomposes into 2Na, nitrogen and hydrogen, the reaction formula is 2NaNH2→2Na+N2↑+H2↑; Second reaction: 2Na reacts with 2NH3 to generate 2NaNH2 and hydrogen. The reaction formula is 2Na+2NH3→2NaNH2+H2↑; Sodium circulates as an intermediate medium and participates in the reaction.

10. The method for producing hydrogen based on sodium-catalyzed ammonia cracking according to claim 9, characterized in that: monitoring the pressure in the reactor in real time, and when the pressure exceeds a first preset pressure threshold, starting a gas booster pump to extract the mixed gas from the reactor outlet and transport it to the gas purification separator; and stopping the gas booster pump when the pressure is lower than a second preset pressure threshold; Monitor the temperature inside the reactor in real time. When the temperature reaches the preset upper limit, reduce the fuel flow rate of the burner fuel nozzle to suppress the temperature rise. When the temperature drops to the preset lower limit and the system is in operation, increase the fuel nozzle flow rate or re-ignite to raise the temperature and maintain the reaction temperature within the preset range. Monitor the liquid ammonia level in the ammonia storage tank in real time. When the level is lower than the preset minimum level, shut down the booster pump, reactor inlet and outlet valves, and the system master switch, and trigger an alarm signal.

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