A hydrogen production device and method of low-temperature high-pressure ammonia cracking coupled with palladium membrane purification

Abstract

This invention relates to the field of hydrogen production technology and discloses a hydrogen production device and method using low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification. The device includes a container-type enclosure containing a liquid ammonia storage tank, a liquid ammonia vaporizer, a high-pressure cracking reactor, thermally coupled connecting pipelines, and a palladium alloy membrane separator, all connected in sequence. The high-pressure cracking reactor is equipped with fireproof bricks, with a furnace liner embedded inside each fireproof brick. Heating strips are attached to the outside of the fireproof bricks. The rated operating pressure of the device is 0.8–1.5 MPa, and the reaction temperature is 450–560 °C. It is used to catalytically crack ammonia into a mixed gas containing H2 and N2. This low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification hydrogen production device and method achieves direct thermal coupling between the cracking unit and the membrane separation unit through specific parameter matching, eliminating the need for intermediate cooling and pressurization equipment. This significantly reduces energy consumption and system volume while obtaining high-purity hydrogen with a purity of not less than 7N (99.99999%).

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, specifically to an integrated hydrogen production device and method that uses liquid ammonia as raw material and couples low-temperature high-pressure catalytic cracking with selective permeation purification through a palladium alloy membrane. Background Technology

[0002] Ammonia (NH3) has advantages such as high hydrogen content (17.6 wt%), ease of liquefaction and storage, and well-developed infrastructure, making it considered one of the most promising hydrogen energy carriers. The overall reaction formula for hydrogen production from ammonia decomposition is: 2NH3→N2+3H2 (ΔH=+92kJ / mol), which is an endothermic reaction and requires external heating.

[0003] Existing ammonia-to-hydrogen technologies mainly suffer from the following problems: First, traditional catalytic cracking temperatures are typically above 550℃, even reaching above 800℃ (industrial furnace tube cracking), resulting in high energy consumption and stringent requirements for equipment and materials; Second, the equilibrium conversion rate of ammonia decomposition is limited under 1MPa conditions, and traditional catalysts have insufficient low-temperature activity; Third, the cracking products contain undecomposed residual ammonia (up to several thousand ppm), which can poison the platinum catalyst in proton exchange membrane fuel cells (PEMFCs); Fourth, traditional purification processes (pressure swing adsorption PSA or cryogenic liquefaction) require the use of compressors, chillers, and other equipment, resulting in complex processes, large equipment sizes, and difficulty in achieving miniaturization and distributed applications; Fifth, the overall system integration is low, making it difficult to use as mobile or on-site hydrogen production equipment.

[0004] In addition, the applicant has filed separate patent applications for the ammonia cracking catalyst and palladium alloy membrane used in this device. The innovation of this invention lies in the parameter adaptation and system integration scheme between the two authorized / pending components and the high-pressure cracking reactor (3), rather than the repeated protection of the components themselves. Relevant comparative literature can also be found in: CN102049178A (Dalian Institute of Chemical Physics, ammonia decomposition hydrogen production reactor); CN103318848B (Dalian Institute of Chemical Physics, Pd membrane ammonia cracking integrated reactor); US10173897B2 (H2SITE, Pd membrane catalytic membrane reactor for hydrogen production).

[0005] Existing similar technologies include: CN202420549571.X (Kapso, ammonia cracking hydrogen production reactor coupled with palladium membrane), CN222034694U (Kapso, ammonia cracking high-purity hydrogen production device including membrane separation), and MIT's research on high-temperature palladium membranes published in Advanced Functional Materials, 2025. Among these, the Kapso patent uses an integrated reactor structure, making equipment maintenance difficult, and it does not disclose specific technical means for achieving temperature matching between the cracking unit and the membrane separation unit using natural heat dissipation through pipelines. MIT's research focuses on improving the upper temperature resistance limit of the palladium membrane and does not address the system design for the thermo-pressure coupling optimization of cracking and membrane separation under high-pressure conditions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydrogen production device and method for low-temperature high-pressure ammonia cracking coupled with palladium membrane purification. By matching specific parameters, the cracking unit and the membrane separation unit are directly thermally coupled, eliminating the need for intermediate cooling and pressurization equipment. This significantly reduces energy consumption and system volume while obtaining high-purity hydrogen with a purity of not less than 7N (99.99999%).

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A hydrogen production device for low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification includes a container-type body. Inside the container-type body are sequentially connected a liquid ammonia storage tank, a liquid ammonia vaporizer, a high-pressure cracking reactor, thermally coupled connecting pipelines, a palladium alloy membrane separator, and a tail gas catalytic oxidation reactor. The high-pressure cracking reactor is equipped with fireproof bricks, with a furnace liner embedded inside the fireproof bricks. Heating strips are attached to the outside of the fireproof bricks. The rated operating pressure of the device is 0.8–1.5 MPa, and the reaction temperature is 450–560 °C. It is used to catalytically crack ammonia into a mixed gas containing H2 and N2. The thermally coupled connection pipeline is an insulated pipeline with a length of 1.0m to 2.0m. The thermal conductivity of the insulation layer is ≤0.05W / (m·K). It is configured so that when the pyrolysis mixed gas at 440℃ to 550℃ flows through the pipeline at a pressure of 0.8 to 1.5MPa, the temperature drops to 340℃ to 360℃ through natural heat dissipation, and the pressure drop does not exceed 0.02MPa. The two ends of the thermally coupled connection pipeline are respectively connected to the outlet of the high-pressure pyrolysis reactor and the inlet of the palladium alloy membrane separator. There are no cooling devices or pressurizing devices, and the pressure is maintained at 0.8 to 1.5MPa throughout the process. The palladium alloy membrane separator has a built-in palladium alloy membrane module. The reaction temperature is 340℃ to 360℃, and the inlet pressure is 0.8 to 1.5MPa. The palladium alloy membrane module has a product hydrogen outlet on the permeate side and a tail gas outlet on the non-permeate side. The high-pressure pyrolysis reactor, thermally coupled connecting pipeline, and palladium alloy membrane separator constitute a continuous high-pressure system without compressors or chillers throughout the process. The device also includes an explosion-proof control cabinet, which is electrically connected to temperature sensors, pressure sensors, and flow regulating valves on the liquid ammonia vaporizer, high-pressure pyrolysis reactor, palladium alloy membrane separator, and tail gas catalytic oxidation reactor, respectively, for monitoring and controlling each unit.

[0008] Furthermore, the furnace chamber has a U-shaped tube bundle structure and is made of 10S stainless steel. There are three sets of furnace chambers connected in parallel, and electric heating tubes are installed inside the furnace chamber.

[0009] Furthermore, the furnace liner is filled with an ammonia cracking catalyst, the catalyst particles are cylindrical in shape, and the filling amount is 8-9 kg; the catalyst has an ammonia single-pass conversion rate of not less than 99.3% under the conditions of rated working pressure of 0.8-1.5 MPa and reaction temperature of 550℃.

[0010] Furthermore, the palladium alloy membrane used in the palladium alloy membrane assembly has an effective membrane area of ​​9m². 2 The palladium alloy membrane exhibits high selective permeation capability for H2 under reaction temperature of 340℃~360℃ and inlet side pressure of 0.8~1.5MPa, with a product hydrogen purity of not less than 99.99999% (7N) and a hydrogen recovery rate of not less than 91%.

[0011] Furthermore, the thermal coupling connection pipeline has a length of 1.0m to 2.0m, an insulation layer thickness of 30mm to 50mm, and the insulation material is aluminum silicate fiber or aerogel composite material; the outlet gas temperature of the pyrolysis reactor is 440℃ to 550℃, and after natural heat dissipation through the thermal coupling connection pipeline, the temperature drops to 340℃ to 360℃ before entering the palladium alloy membrane separator, with a temperature drop of about 100℃ to 200℃, and no active cooling device is required throughout the process; the pressure drop of the gas in the pipeline does not exceed 0.02MPa.

[0012] Furthermore, the method employed is catalytic oxidation: (Pd / Al2O3 catalyst, 250℃, NH3 catalytic oxidation to N2 and H2O, the treated exhaust gas meets emission standards); the product hydrogen outlet and exhaust gas outlet are located on the same side of the container-type body, and this side is also equipped with a liquid ammonia inlet.

[0013] The present invention also provides a method for producing hydrogen using a hydrogen production apparatus employing low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification, comprising the following steps: Step 1, Ammonia Cracking: Liquid ammonia is vaporized in a liquid ammonia vaporizer and then enters a high-pressure cracking reactor. Under a preset rated working pressure of 0.8–1.5 MPa and a reaction temperature of 450–560°C, it undergoes catalytic cracking through a catalyst bed. The outlet gas temperature is 440°C–550°C, and the single-pass conversion rate of ammonia is not less than 99.3%. Step 2, direct thermo-pressure coupling introduction: The pyrolysis mixed gas is introduced directly into the palladium alloy membrane separator through the thermocoupled pipeline without cooling or pressurization, relying on the natural heat dissipation of the pipeline to reduce the temperature from 440℃~550℃ to 340℃~360℃, with the temperature drop rate controlled at 50℃ / m~150℃ / m, under a pressure of 0.8~1.5MPa. Step 3, Palladium membrane selective separation: Driven by a hydrogen partial pressure difference of 0.8–1.5 MPa between the inlet and permeate sides, hydrogen selectively permeates through the palladium alloy membrane module. High-purity hydrogen with a purity of not less than 99.99999% (7N) is obtained through the product hydrogen outlet on the permeate side, with a hydrogen recovery rate of not less than 91%. Step 4, exhaust gas treatment: The nitrogen-rich exhaust gas from the non-permeable side enters the exhaust gas catalytic oxidation reactor through the exhaust gas outlet. After catalytic oxidation treatment (NH3→N2+H2O, meeting emission standards), it is either discharged or recycled.

[0014] Furthermore, in step one, the preset rated working pressure of the high-pressure pyrolysis reactor is 0.8–1.5 MPa, and the preset reaction temperature is 450–560 °C; in step two, the heat dissipation area of ​​the thermally coupled connection pipeline is matched with the gas flow rate, so that the residence time of the pyrolysis outlet gas in the pipeline is 1–5 s.

[0015] Furthermore, the ammonia cracking catalyst used in step one has a gas hourly space velocity of 1000 h⁻¹. -1 Under the conditions of rated working pressure of 0.8~1.5MPa and reaction temperature of 450~560℃, the ammonia conversion rate is not less than 99.3%, and after 1000 hours of continuous operation, the ammonia conversion rate retention rate is not less than 98%.

[0016] Furthermore, in step three, the purity of the hydrogen produced is not less than 99.99999% (7N), and the hydrogen recovery rate is not less than 91%.

[0017] The beneficial effects of this invention are: 1. Under high pressure of 1.0 MPa, the pyrolysis temperature of this invention is 450-560℃. Actual test data shows that the ammonia conversion rate reaches 99.3% at 550℃ / 1MPa. Compared with the traditional process above 800℃, the energy consumption is significantly reduced, saving about 30% of heating energy consumption.

[0018] 2. This invention eliminates the need for a compressor and chiller, reducing the system volume by approximately 47% compared to traditional processes. The overall dimensions are only 3000mm × 1600mm × 2000mm, and the weight is approximately 2.8t.

[0019] 3. The hydrogen produced by this invention has a purity of not less than 99.99999% (7N grade) and a residual ammonia content of less than 0.1 ppb, meeting the stringent requirements of PEMFC for hydrogen quality.

[0020] 4. The hydrogen recovery rate of this invention is not less than 91%, and the utilization rate of raw materials is significantly improved.

[0021] 5. The device of this invention has a high degree of integration and can be applied to scenarios such as on-site hydrogen production at hydrogen refueling stations and distributed hydrogen supply in industrial parks.

[0022] The calculation basis and comparison conditions for the above-mentioned beneficial effects are as follows: Heating energy consumption saving calculation: Based on the traditional atmospheric pressure pyrolysis process (pyrolysis temperature 800℃, yield 30Nm³), 3 Based on the standard of high-purity hydrogen ( / h), the traditional process of cracking heating consumes about 115kW, and the energy consumption of the supporting compressor and chiller is about 35kW, with a total energy consumption of about 150kW. Under the typical operating conditions of this invention, the cracking heating energy consumption is about 70kW, with no compressor or chiller energy consumption, and a total energy consumption of about 105kW. The overall energy saving ratio of heating is (150-105) / 150×100%=30%.

[0023] System volume reduction calculation: The total volume of a conventional atmospheric pressure pyrolysis + PSA process unit is approximately 18m³. 3 The device of this invention has external dimensions of 3000mm × 1600mm × 2000mm and a volume of 9.6m³. 3 The volume reduction ratio is (18-9.6) / 18×100%≈47%. Attached Figure Description

[0024] Figure 1 This is a front view of the structure of the present invention; Figure 2 This is a top view of the structure of the present invention; Figure 3 This is a rear view of the structure of the present invention; Figure 4 This is a schematic diagram of the internal structure of the high-pressure pyrolysis reactor of the present invention; Figure 5 This is a process flow diagram of the present invention; Figure 6 This is a schematic block diagram of the device of the present invention; Figure 7 This is a timing diagram of the process flow of the present invention.

[0025] In the picture: 1—Liquid ammonia storage tank; 2—Liquid ammonia vaporizer; 3—High-pressure pyrolysis reactor; 4—Furnace chamber (U-shaped tube bundle); 5—Heating belt; 6—Fireproof brick; 7—Thermal coupling connection piping; 8—Palladium alloy membrane separator; 9—Palladium alloy membrane module; 10—Tail gas catalytic oxidation reactor; 11—Explosion-proof control cabinet; 12—Containerized enclosure; 13—Product hydrogen export; 14—Tail gas export; 15—Liquid ammonia import. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] (I) Overall Device Structure (Refer to) Figure 1-3 ) like Figure 1-3 As shown, the low-temperature, high-pressure ammonia cracking coupled palladium membrane purification hydrogen production device provided in this embodiment is integrated into a container-type body 12, with external dimensions of 3000mm × 1600mm × 2000mm and a total weight of approximately 2.8t. On the same side of the body 12, there are one product hydrogen outlet 13, one exhaust gas outlet 14, one liquid ammonia inlet 15, one drain outlet, one purging nitrogen outlet, and a power interface, facilitating centralized on-site piping.

[0028] The internal components of the device are arranged sequentially according to the process flow: liquid ammonia storage tank 1, liquid ammonia vaporizer 2, high-pressure pyrolysis reactor 3, thermally coupled connection pipeline 7, palladium alloy membrane separator 8, and tail gas catalytic oxidation reactor 10. An explosion-proof control cabinet 11 is independently arranged at one end of the enclosure 12. The explosion-proof control cabinet 11 is electrically connected to the temperature sensors, pressure sensors, and flow regulating valves installed on the liquid ammonia vaporizer 2, high-pressure pyrolysis reactor 3, palladium alloy membrane separator 8, and tail gas catalytic oxidation reactor 10, respectively, for monitoring and controlling each unit.

[0029] (ii) Liquid ammonia vaporizer 2 Liquid ammonia vaporizer 2 is connected to the outlet pipe of liquid ammonia storage tank 1. The inlet liquid ammonia pressure is approximately 1.0 MPa. It uses electric heating to vaporize the liquid ammonia within the pipe, with a heating power of 4.5 kW, a reaction temperature of 40℃~50℃, and a rated operating pressure of approximately 1.0 MPa. The vaporized gaseous ammonia is then piped into the inlet of high-pressure pyrolysis reactor 3, with a feed flow rate of approximately 15 Nm³. 3 / h (standard conditions). The exhaust gas discharged from the tail gas catalytic oxidation reactor 10 contains approximately 2.5 Nm³. 3 Hydrogen gas of 1 / h is introduced to the liquid ammonia inlet through heat exchange pipeline to preheat the liquid ammonia, which can save about 3.5kW of electric heating energy consumption in the vaporizer and improve the overall energy utilization efficiency of the machine.

[0030] (III) Internal structure of high-pressure pyrolysis reactor 3 (refer to) Figure 4 ) like Figure 4 As shown, the high-pressure pyrolysis reactor 3 is a sealed pressure vessel structure with a rated working pressure of 0.8 to 1.5 MPa, a reaction temperature of 450 to 560°C, and a designed maximum heating power of 35 kW.

[0031] The internal structure of reactor 3, from the outside to the inside, consists of: fireproof bricks 6 – furnace chamber 4 – catalyst packing layer. The specific structure is as follows: Fireproof brick 6: Refractory and heat-insulating brick layer, laid tightly against the inner wall of reactor 3, plays the role of heat insulation and heat uniformity, prevents heat loss to the outer shell of reactor, and provides a uniform thermal radiation environment for furnace 4. Heating band 5: Resistance heating band, attached to the outer surface of fireproof brick 6 (i.e., between the fireproof brick and the inner wall of the reactor), generates heat after being energized, and is evenly conducted to the furnace chamber 4 and catalyst bed through the fireproof brick 6, with a maximum heating power of 35kW; Furnace chamber 4: U-shaped tube bundle structure, made of 310S stainless steel (high temperature resistant, ammonia corrosion resistant), tube specifications are outer diameter × wall thickness = 76 × 6 mm, effective length 1500 mm, a total of 3 sets connected in parallel, embedded inside the fireproof brick 6. The total volume of the catalyst bed is approximately 16L (i.e., effective reaction space); After entering through the inlet of reactor 3, ammonia gas is evenly distributed to the tubes of the three sets of furnace chambers 4. Under the action of the catalyst, a cracking reaction occurs. The cracked mixed gas is collected at the reactor outlet and transported to the palladium alloy membrane separator 8 through the thermally coupled connection pipeline 7.

[0032] (iv) Catalyst loading (catalyst bed) Furnace chamber 4 is filled with ammonia cracking catalyst, model ZQADC-450. The catalyst particles are cylindrical (5mm in diameter, 6-10mm in length), with a loading of 8kg, a bulk density of approximately 0.50kg / L, corresponding to a total catalyst bed volume of approximately 16L and a gas hourly space velocity (GHSV) of approximately 1000h. -1 .

[0033] The key performance parameters of this catalyst are as follows: the active component is a Ni-Co bimetallic compound with a loading of 15%–25%; the support is γ-Al₂O₃ with a specific surface area of ​​150–200 m². 2 / g; the preparation conditions are calcination at 500-600℃ for 4-6 hours. Under the conditions of rated working pressure of 1.0MPa and reaction temperature of 550℃, the single-pass conversion rate of ammonia is not less than 99.3%, and the catalyst service life is not less than 3 years. The composition and preparation method of this catalyst are detailed in the applied independent patent (CN202511536504.X).

[0034] (v) Thermal coupling connection piping 7 (refer to) Figure 1-4 ) The thermal coupling connection pipe 7 is a short-distance connection pipe with an insulation layer, with a length of approximately 1.5m (preferred embodiment parameters), and is covered with high-temperature resistant insulation material. The two ends of the pipe are respectively connected to the outlet flange of the high-pressure pyrolysis reactor 3 and the inlet flange of the palladium alloy membrane separator 8. No cooling device (no chiller) or pressurization device (no compressor) is installed throughout the entire process.

[0035] The temperature and pressure adaptation principle of the thermally coupled connection pipeline 7 is as follows: The outlet gas temperature of the high-pressure pyrolysis reactor 3 is 440℃~550℃, and the pressure is about 0.8~1.5MPa; when the mixed gas flows through the approximately 1.5m long insulated pipeline, the temperature naturally decreases from 440℃~550℃ to 340℃~360℃ due to natural heat dissipation from the pipeline surface, a temperature drop of about 100℃~200℃ compared to the tail gas catalytic oxidation reactor; this temperature range is exactly within the optimal reaction temperature window of the palladium alloy membrane module 9, 340℃~360℃. The total gas pressure drop does not exceed 0.02MPa, and the pressure when entering the palladium alloy membrane separator 8 is about 0.8~1.5MPa. This pressure difference can be directly used as the driving force for hydrogen permeation through the palladium alloy membrane without the need for external pressurization.

[0036] The natural matching of temperature and pressure described above is the core technical basis for eliminating the need for a compressor and chiller in this invention, and realizes direct thermo-pressure coupling between the pyrolysis and purification units.

[0037] (vi) Palladium alloy membrane separator 8 and palladium alloy membrane module 9 The palladium alloy membrane separator 8 has a built-in palladium alloy membrane module 9. The pressure on the inlet side (high pressure side) is 0.8 to 1.5 MPa, the reaction temperature is 340℃ to 360℃, and the pressure on the permeation side (low pressure side) is about 0.1 MPa (atmospheric pressure).

[0038] The key parameters of the palladium alloy membrane used in palladium alloy membrane module 9 are as follows: effective membrane area is approximately 9m². 2The membrane thickness is 5μm to 20μm, and the alloy composition is Pd-Ag or Pd-Cu, with an Ag / Cu content of 20% to 30wt%. The support material is porous stainless steel or ceramic with a pore size of 0.5μm to 5μm. Under the above operating conditions, hydrogen can selectively permeate through the palladium alloy membrane, while N2, NH3, and other gases are retained on the non-permeable side. Details regarding the material, specifications, and preparation method of this palladium alloy membrane can be found in the filed independent patent (CN202021466536.X).

[0039] The permeate side outputs high-purity hydrogen through product hydrogen outlet 13, with a product hydrogen purity of not less than 99.99999% (7N), a hydrogen recovery rate of not less than 91%, and a residual ammonia content of less than 0.1 ppb, meeting the stringent hydrogen quality requirements of proton exchange membrane fuel cells (PEMFC). The above performance data are subject to the test report submitted by the applicant.

[0040] (vii) Tail gas catalytic oxidation reactor 10 The tail gas from the non-permeable side of the palladium alloy membrane separator 8 (main components: N2 about 91 vol%, uncracked NH3 about 6 vol%, H2 about 3 vol%) enters the tail gas catalytic oxidation reactor 10 through the tail gas outlet 14.

[0041] The tail gas catalytic oxidation reactor 10 adopts a catalytic oxidation method: using Pd / Al2O3 as a catalyst, at a reaction temperature of about 250℃, the residual NH3 in the tail gas is catalytically oxidized into N2 and H2O (reaction equation: 4NH3+3O2→2N2+6H2O). After treatment, the NH3 concentration in the tail gas is lower than the emission standard, and it is discharged in compliance with the standard through the tail gas outlet 14.

[0042] Approximately 2.5 Nm in exhaust gas 3 Hydrogen gas (approximately 3 vol%) per hour can be introduced to the inlet of liquid ammonia vaporizer 2 via a bypass pipe before catalytic oxidation to preheat liquid ammonia, saving approximately 3.5 kW of electric heating energy and improving the system's energy utilization rate.

[0043] (viii) Explosion-proof control cabinet 11 The explosion-proof control cabinet 11 uses a Siemens S7-1200 series PLC as the core control unit, and is equipped with closed-loop control modules for temperature, pressure, and flow, as well as a remote monitoring and communication module. Its main control functions include: ① Pyrolysis temperature control: By adjusting the power of heating belt 5, the reaction temperature of high-pressure pyrolysis reactor 3 is maintained at the set value (adjustable within the range of 450~560℃), with a control accuracy of ±5℃; ② Rated working pressure monitoring: Real-time acquisition of the inlet pressure of reactor 3, thermal coupling connection pipeline 7 and palladium alloy membrane separator 8; automatic triggering of safety valve interlock action when overpressure occurs; ③ Liquid ammonia feed control: The feed rate of liquid ammonia vaporizer 2 is controlled by a flow regulating valve to maintain a hydrogen production rate of approximately 20 Nm³. 3 / h; ④ System interlock protection: Multiple safety interlock logics, including ammonia leak detection, high temperature and over-temperature protection, and over-pressure protection, ensure the safe and stable operation of the system; ⑤ Remote monitoring: Supports industrial Ethernet communication, enabling remote real-time monitoring of system status.

[0044] (ix) Implementation steps of hydrogen production method (refer to) Figure 5 , Figure 6 , Figure 7 ) like Figure 5 (Process flow diagram) Figure 6 (Principle block diagram) and Figure 7 As shown in the timing control diagram, the hydrogen production method in this embodiment operates continuously according to the following steps: Step 1: Liquid ammonia vaporization and ammonia cracking (refer to...) Figure 5 ) Liquid ammonia enters the liquid ammonia vaporizer 2 through liquid ammonia inlet 15, and is vaporized into gaseous ammonia under electric heating (reaction temperature 40℃~50℃, pressure about 1.0MPa), at a velocity of about 15Nm. 3 A flow rate of / h enters the high-pressure pyrolysis reactor 3.

[0045] In high-pressure cracking reactor 3, gaseous ammonia is subjected to a rated operating pressure of 0.8–1.5 MPa (typically 1.0 MPa) and a reaction temperature of 450–560 °C (typically 550 °C) before passing through a catalyst bed (ZQADC-450 catalyst, GHSV for approximately 1000 h). -1 Catalytic cracking occurs, resulting in the following reaction: 2NH3→N2+3H2 (ΔH=+92kJ / mol) Under conditions of 1.0 MPa and 550℃, the single-pass conversion rate of ammonia is not less than 99.3%. The outlet gas temperature of the cracking reactor 3 is 440℃~550℃, and the composition of the outlet gas is approximately: H2 about 74.5 vol%, N2 about 25.0 vol%, and uncracked NH3 about 0.5 vol%.

[0046] Step 2: Direct thermo-pressure coupling introduction (refer to...) Figure 5 , Figure 6 ) The high-temperature, high-pressure mixed gas after pyrolysis (temperature 440℃~550℃, pressure 0.8~1.5MPa) is directly transported to the inlet of the palladium alloy membrane separator 8 via thermally coupled pipeline 7. The entire process involves no cooling (no chiller) and no pressurization (no compressor), relying solely on natural heat dissipation through an approximately 1.5m long insulated pipeline. The temperature drops from 440℃~550℃ to 340℃~360℃, a temperature drop of approximately 100℃~200℃, and the pressure drop does not exceed 0.02MPa.

[0047] At this time, the temperature of the mixed gas entering the palladium alloy membrane separator 8 is 340℃~360℃, which is precisely matched with the optimal reaction temperature window of the palladium alloy membrane module 9. The inlet side pressure of 0.8~1.5MPa can directly provide sufficient hydrogen partial pressure driving force for hydrogen permeation through the membrane without the need for additional heat exchange equipment or pressurization equipment.

[0048] Step 3: Palladium membrane selective separation and purification (refer to...) Figure 6 ) In the palladium alloy membrane separator 8, in the mixed gas on the inlet side (high pressure side, 0.8~1.5MPa), H2 molecules selectively permeate through the palladium alloy membrane module 9 through the dissolution-diffusion mechanism described by Sievert's law, driven by the high hydrogen partial pressure difference (H2 partial pressure on the inlet side is about 0.6~1.1MPa, and on the permeation side is about 0.1MPa). Meanwhile, gas molecules such as N2 and NH3 are retained on the non-permeation side (nitrogen-rich side) because they cannot dissolve into the palladium lattice.

[0049] The product hydrogen gas output from the permeate side (atmospheric pressure side, approximately 0.1 MPa) is collected at product hydrogen outlet 13. The reaction temperature is 340℃~360℃, and the effective membrane area is approximately 9m². 2 Under the specified conditions, the product's hydrogen purity shall not be less than 99.99999% (7N), the hydrogen recovery rate shall not be less than 91%, the residual NH3 content shall be less than 0.1 ppb, and the residual N2 content shall be less than 0.1 ppm. The above performance indicators shall be subject to the test report.

[0050] Step 4: Catalytic oxidation treatment of exhaust gas (refer to...) Figure 5 ) The nitrogen-rich tail gas (main components: N2, small amounts of NH3 and H2) from the non-permeable side of the palladium alloy membrane separator 8 is discharged through tail gas outlet 14 and enters the tail gas catalytic oxidation reactor 10 (Pd / Al2O3 catalyst, reaction temperature approximately 250℃). Under the action of the catalyst, NH3 reacts with O2 in the air and is oxidized into N2 and H2O. 4NH3 + 3O2 → 2N2 + 6H2O The NH3 concentration in the treated exhaust gas meets national emission standards and is discharged compliantly through exhaust outlet 14. The H2 concentration in the exhaust gas is approximately 2.5 Nm³. 3 The liquid ammonia can be preheated via a bypass before catalytic oxidation, saving approximately 3.5 kW of electricity.

[0051] Step 5: System Timing Control (Refer to...) Figure 7 ) like Figure 7 As shown, the startup, normal operation, and shutdown of the entire system proceed in the following sequence: ① Start-up phase (approximately 60–90 min): The explosion-proof control cabinet 11 controls the heating belt 5 to raise the temperature of the high-pressure cracking reactor 3 from room temperature to the catalyst activation temperature (approximately 400°C). At the same time, the palladium alloy membrane separator 8 is purged with nitrogen (to prevent damage to the palladium membrane due to hydrogen embrittlement during the heating process). When the membrane temperature stabilizes within the range of 340°C–360°C, the feed is switched to ammonia, and the system enters normal operation mode. ② Normal operation phase: All process parameters remain stable under PLC closed-loop control, hydrogen is continuously output, and exhaust gas is continuously treated and discharged; ③ Shutdown phase: First, stop the liquid ammonia feed, purge and replace the residual ammonia and hydrogen in the system with N2, and stop heating after the membrane temperature drops below 150℃ to complete the safe shutdown.

[0052] Example 2: Comparison of the effects of rated operating pressure on hydrogen recovery rate Other conditions remain unchanged (catalyst ZQADC-450, loading 8kg, target yield approximately 20Nm³). 3 / h pure hydrogen, palladium alloy membrane with an effective area of ​​approximately 9m² 2 Under the condition of changing the rated operating pressure of the high-pressure pyrolysis reactor 3, the hydrogen recovery rate of the palladium alloy membrane separator 8 was investigated, and the results are shown in the table below:

[0053] As shown in the table above, within the pressure range of 0.8–1.5 MPa, the hydrogen recovery rate increases with increasing rated operating pressure, but the equipment cost also increases accordingly. Considering the hydrogen recovery rate, equipment cost, palladium membrane pressure life, and system safety margin, this invention recommends a rated operating pressure range of 0.8–1.5 MPa, with a typical recommended operating condition of 1.0 MPa. At this pressure, the hydrogen recovery rate is approximately 91%, and the overall system performance is optimal.

[0054] Example 3 (Comparative Example): Comparison of the present invention with the traditional atmospheric pressure pyrolysis + PSA process With the same production target (30Nm) 3 Based on the standard of (high-purity hydrogen per hour), this invention is comprehensively compared with the traditional atmospheric pressure catalytic cracking + pressure swing adsorption (PSA) process. The results are shown in the table below:

[0055] As shown in the table above, compared with the traditional atmospheric pressure cracking + PSA process, this invention has the following significant advantages: First, it eliminates the need for a compressor and chiller, reducing the device volume by approximately 47% and the overall weight from approximately 6 tons to approximately 2.8 tons, effectively achieving miniaturization and integration; Second, the hydrogen purity is increased from 5N to 7N, an improvement of two orders of magnitude, meeting the stringent requirements of high-end application scenarios such as PEMFC; Third, the hydrogen recovery rate is increased from approximately 85% to ≥91%, effectively improving the utilization rate of raw materials; Fourth, the overall cost per ton of hydrogen is reduced by approximately 39%; Fifth, the system is fully integrated into the enclosure, making installation and commissioning simple and applicable to various scenarios such as on-site hydrogen production at hydrogen refueling stations, distributed hydrogen supply in industrial parks, and mobile hydrogen supply.

[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hydrogen production device for low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification, comprising a container-type enclosure (12), characterized in that, The container-type body (12) is equipped with a liquid ammonia storage tank (1), a liquid ammonia vaporizer (2), a high-pressure pyrolysis reactor (3), a thermally coupled connection pipeline (7), a palladium alloy membrane separator (8), and a tail gas catalytic oxidation reactor (tail gas catalytic oxidation reactor 10) connected in sequence; the high-pressure pyrolysis reactor (3) is equipped with fireproof bricks (6), the fireproof bricks (6) are embedded with a furnace liner (4), and the fireproof bricks (6) are attached to the outside with heating belts (5); The thermal coupling connection pipeline (7) is a connection pipeline with a heat insulation layer. The two ends of the thermal coupling connection pipeline (7) are respectively connected to the outlet of the high pressure pyrolysis reactor (3) and the inlet of the palladium alloy membrane separator (8). The palladium alloy membrane separator (8) has a built-in palladium alloy membrane module (9). The permeation side of the palladium alloy membrane module (9) is provided with a product hydrogen outlet (13), and the non-permeation side is provided with a tail gas outlet (14). The device also includes an explosion-proof control cabinet (11). Temperature sensors, pressure sensors and flow regulating valves are installed on the liquid ammonia vaporizer (2), high-pressure pyrolysis reactor (3), palladium alloy membrane separator (8) and tail gas catalytic oxidation reactor. The explosion-proof control cabinet (11) is electrically connected to the temperature sensor, pressure sensor and flow regulating valve respectively.

2. The hydrogen production apparatus for low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification according to claim 1, characterized in that: The furnace chamber (4) has a U-shaped tube bundle structure and is made of 10S stainless steel. There are three sets of furnace chambers (4) connected in parallel. Electric heating tubes are installed inside the furnace chamber (4).

3. A hydrogen production apparatus for low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification according to claim 1 or 2, characterized in that: The furnace chamber (4) is filled with ammonia cracking catalyst. The catalyst particles are cylindrical in shape and the filling amount is 8-9 kg.

4. The hydrogen production apparatus for low-temperature, high-pressure ammonia cracking coupled with palladium membrane purification according to claim 1, characterized in that: The palladium alloy membrane used in the palladium alloy membrane assembly (9) has an effective membrane area of ​​9m². 2 .

5. The hydrogen production apparatus for low-temperature high-pressure ammonia cracking coupled with palladium membrane purification according to claim 1, characterized in that: The thermal coupling connection pipeline (7) has a length of 1.0m to 2.0m, a thermal insulation layer thickness of 30mm to 50mm, and the thermal insulation material is aluminum silicate fiber or aerogel composite material.

6. The hydrogen production apparatus for low-temperature high-pressure ammonia cracking coupled with palladium membrane purification according to claim 1, characterized in that: The product hydrogen outlet (13) and tail gas outlet (14) are located on the same side of the container body (12), and a liquid ammonia inlet (15) is also provided on this side.

7. A method for producing hydrogen using the low-temperature, high-pressure ammonia cracking coupled palladium membrane purification apparatus according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1, ammonia cracking: Liquid ammonia is vaporized by liquid ammonia vaporizer (2) and then enters high-pressure cracking reactor (3). Under the preset rated working pressure of 0.8 to 1.5 MPa and reaction temperature of 450 to 560°C, it is catalytically cracked by catalyst bed. The outlet gas temperature is 440°C to 550°C, and the single-pass conversion rate of ammonia is not less than 99.3%. Step 2, direct thermal-pressure coupling introduction: The pyrolysis mixed gas is introduced directly into the palladium alloy membrane separator (8) through the thermal coupling connection pipeline (7) without cooling or pressurization, relying on the natural heat dissipation of the pipeline to reduce the temperature from 440℃~550℃ to 340℃~360℃, with the temperature drop rate controlled at 50℃ / m~150℃ / m, under a pressure of 0.8~1.5MPa. Step 3, selective separation by palladium membrane: Driven by a hydrogen partial pressure difference of 0.8 to 1.5 MPa between the inlet side and the permeate side, hydrogen selectively permeates through the palladium alloy membrane module (9), and high-purity hydrogen with a purity of not less than 99.99999% (7N) is obtained through the product hydrogen outlet (13) on the permeate side, with a hydrogen recovery rate of not less than 91%; Step 4, exhaust gas treatment: The nitrogen-rich exhaust gas from the non-permeable side enters the exhaust gas catalytic oxidation reactor (10) through the exhaust gas outlet (14), and is discharged or recycled after catalytic oxidation treatment.

8. The method for hydrogen production by low-temperature high-pressure ammonia cracking coupled with palladium membrane purification according to claim 7, characterized in that: In step one, the preset rated working pressure of the high-pressure pyrolysis reactor (3) is 0.8 to 1.5 MPa, and the preset reaction temperature is 450 to 560 °C. In step two, the heat dissipation area of ​​the thermal coupling connection pipeline (7) is matched with the gas flow rate so that the residence time of the pyrolysis outlet gas in the pipeline is 1 to 5 seconds.

9. A method for producing hydrogen by low-temperature high-pressure ammonia cracking coupled with palladium membrane purification according to claim 7 or 8, characterized in that: The ammonia cracking catalyst used in step one has a gas hourly space velocity (GHSV) of 1000 h⁻¹ for the tail gas catalytic oxidation reactor. -1 Under the conditions of rated working pressure of 0.8~1.5MPa and reaction temperature of 450~560℃, the ammonia conversion rate is not less than 99.3%, and after running the tail gas catalytic oxidation reactor continuously for 1000 hours, the ammonia conversion rate retention rate is not less than 98%.

10. The method for hydrogen production by low-temperature high-pressure ammonia cracking coupled with palladium membrane purification according to claim 7, characterized in that: In step three, the purity of the hydrogen produced is not less than 99.99999% (7N), and the hydrogen recovery rate is not less than 91%.

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