Ammonia cracking hydrogen production device and method with plasma-assisted PSA tail gas combustion heating

Abstract

The present application relates to the technical field of ammonia utilization, hydrogen production and fuel cell power generation, and particularly relates to an ammonia cracking hydrogen production device and method with plasma-assisted PSA tail gas combustion heating. The technical scheme comprises a liquid ammonia supply unit, a combustion heating unit, a heat exchange cracking unit, a separation and purification unit and a control system. The liquid ammonia supply unit converts liquid ammonia into gaseous ammonia, and divides the gaseous ammonia into first gaseous ammonia and second gaseous ammonia. The combustion heating unit comprises a hot blast furnace and a plasma generating device, and the hot blast furnace is in communication with the liquid ammonia supply unit and the separation and purification unit. The present application constructs a multi-energy complementary zero-carbon closed-loop energy system among electric energy, thermal energy and hydrogen energy, realizes efficient and stable conversion of ammonia fuel and full-process energy self-sufficiency, and significantly improves the comprehensive energy utilization rate and economy of the system.

Description

Technical Field

[0001] This invention relates to the fields of ammonia energy utilization, hydrogen energy production and fuel cell power generation technology, and in particular to an ammonia cracking hydrogen production device and method for plasma-assisted PSA tail gas combustion heating. Background Technology

[0002] Hydrogen energy has attracted widespread attention due to its advantages such as zero carbon emissions and high energy conversion efficiency. However, currently, hydrogen is mainly produced from fossil fuel hydrogen production processes such as natural gas reforming and coal gasification, which have problems such as high carbon dioxide emissions, high transportation costs, and insufficient storage and transportation safety, thus limiting the large-scale promotion and application of hydrogen energy.

[0003] Ammonia possesses high mass and volumetric hydrogen storage density, mild liquefaction conditions, and well-developed transportation and storage infrastructure, making it a promising zero-carbon hydrogen storage carrier. Ammonia cracking can produce hydrogen and nitrogen, providing high-purity hydrogen fuel for fuel cells; therefore, ammonia cracking for hydrogen production has become an important development direction for hydrogen energy utilization.

[0004] Existing ammonia cracking hydrogen production systems generally use electric furnaces or gas burners as the cracking heat source, resulting in high external energy consumption and low system energy utilization. Simultaneously, the large amount of high-temperature waste heat generated during cracking is often not fully utilized, leading to energy waste. Furthermore, pure ammonia combustion has a low flame propagation speed, is difficult to ignite, and has poor combustion stability, usually requiring the co-firing of auxiliary fuels such as natural gas and hydrogen to maintain stable combustion. This not only increases operating costs but also reduces the system's low-carbon advantages. On the other hand, most existing ammonia cracking hydrogen production systems focus only on the hydrogen production process; the hydrogen produced by cracking usually needs to be transported externally to fuel cells or other terminal equipment. The system integration is low, and a coordinated operation mechanism between cracking hydrogen production, fuel cell power generation, and system equipment power supply is not established, making it difficult to achieve efficient energy recycling. When pressure swing adsorption (PSA) is used for hydrogen purification in existing systems, the exhaust gas is often not fully recovered and utilized, further reducing the overall energy utilization efficiency of the system.

[0005] Therefore, developing an energy supply system that integrates PSA tail gas combustion heating, plasma stabilization, multi-stage waste heat recovery, ammonia cracking hydrogen production, hydrogen purification, fuel cell power generation, and equipment self-powering is of great significance for improving ammonia fuel utilization, reducing system energy consumption, and enhancing overall energy efficiency. This application proposes an ammonia cracking hydrogen production device and method with plasma-assisted PSA tail gas combustion heating. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the background art by proposing an ammonia cracking hydrogen production device and method for plasma-assisted PSA tail gas combustion heating.

[0007] In the first aspect, this application provides an ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating, including a liquid ammonia supply unit, a combustion heating unit, a heat exchange cracking unit, a separation and purification unit, and a control system. The liquid ammonia supply unit converts liquid ammonia into gaseous ammonia and then divides the gaseous ammonia into a first gaseous ammonia output and a second gaseous ammonia output. The combustion heating unit includes a hot air furnace and a plasma generator. The hot air furnace is connected to the liquid ammonia supply unit and the separation and purification unit respectively, and receives the first gaseous ammonia and the ammonia-containing tail gas returned by the separation and purification unit as fuel. The plasma generator is used to assist the combustion of the hot air furnace, and the hot air furnace generates high-temperature flue gas. The heat exchange pyrolysis unit includes a catalytic pyrolysis reactor and a heat exchange component. The heat exchange component is disposed between the liquid ammonia supply unit and the catalytic pyrolysis reactor, and between the catalytic pyrolysis reactor and the separation and purification unit. The second gaseous ammonia is preheated by the heat exchange component and then enters the catalytic pyrolysis reactor for pyrolysis reaction to generate hydrogen-containing pyrolysis gas. The hydrogen-containing pyrolysis gas is cooled by the heat exchange component and then enters the separation and purification unit. The separation and purification unit is used to separate hydrogen products from the hydrogen-containing cracked gas and to further separate the purified tail gas, returning the separated ammonia-containing gas to the hot blast furnace. The control system is communicatively connected to the liquid ammonia supply unit, combustion heating unit, heat exchange pyrolysis unit, and separation and purification unit, respectively.

[0008] Optionally, the liquid ammonia supply unit includes a liquid ammonia storage tank, a liquid ammonia booster, an evaporator, and an electric heater. The liquid ammonia in the liquid ammonia storage tank is pressurized by the liquid ammonia booster and then enters the evaporator, where it evaporates into gaseous ammonia with the assistance of the electric heater. The first stream of gaseous ammonia enters the hot air furnace through an ammonia pressure reducing valve, and the second stream of gaseous ammonia enters the heat exchange assembly.

[0009] Optionally, the heat exchange assembly includes a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, and a quaternary heat exchanger; the second gaseous ammonia flows sequentially through the primary, secondary, and tertiary heat exchangers for preheating before entering the catalytic cracking reactor; the high-temperature flue gas flows sequentially from the hot blast furnace through the tertiary, primary, and quaternary heat exchangers before being discharged; the hydrogen-containing cracked gas flows sequentially from the catalytic cracking reactor through the secondary and quaternary heat exchangers for cooling before entering the separation and purification unit.

[0010] Optionally, the primary heat exchanger is used for heat exchange between the second gaseous ammonia and the flue gas from the tertiary heat exchanger; the secondary heat exchanger is used for heat exchange between the gaseous ammonia preheated by the primary heat exchanger and the hydrogen-containing cracked gas from the catalytic cracking reactor; the tertiary heat exchanger is used for heat exchange between the gaseous ammonia heated by the secondary heat exchanger and the high-temperature flue gas from the hot blast furnace; and the quaternary heat exchanger is used for comprehensive heat exchange between the flue gas from the primary heat exchanger, the hydrogen-containing cracked gas from the secondary heat exchanger, and the gaseous ammonia output from the liquid ammonia supply unit. The hydrogen-containing cracked gas cooled by the quaternary heat exchanger enters the separation and purification unit, and the gaseous ammonia heated by the heat exchange enters the hot blast furnace.

[0011] Optionally, the hot air furnace includes a plasma stabilizer and a burner. The plasma stabilizer is equipped with a ground electrode, a high-voltage electrode, an ammonia-hydrogen mixture inlet, a high-voltage line, and a first swirling gas ring. The burner is equipped with an air inlet, a second swirling gas ring, and an arc-shaped nozzle. The plasma generating device is a plasma power supply, which is electrically connected to the high-voltage electrode via the high-voltage line. The first gaseous ammonia and the ammonia-containing tail gas returned from the separation and purification unit enter the plasma stabilizer through the ammonia-hydrogen mixture inlet. Under the high-voltage discharge between the high-voltage electrode and the ground electrode, a plasma jet is formed. Air forms a swirling flow through the air inlet and the second swirling gas ring and then mixes and burns with the plasma jet.

[0012] Optionally, the combustion heating unit further includes a fan, an air storage tank, and an air pressure reducing valve. The fan compresses air into the air storage tank, and the air in the air storage tank enters the hot air furnace after being pressure-regulated by the air pressure reducing valve.

[0013] Optionally, the separation and purification unit includes a molecular sieve purifier and a separation purifier. The molecular sieve purifier is used to adsorb and separate high-purity hydrogen from the hydrogen-containing cracked gas. The separation purifier is used to further separate uncracked ammonia and hydrogen from the tail gas purified by the molecular sieve purifier, and return the separated ammonia-containing gas to the hot blast furnace. The heat exchange cracking unit also includes a buffer tank disposed between the heat exchange component and the separation and purification unit to stabilize the flow rate and pressure of the hydrogen-containing cracked gas entering the separation and purification unit.

[0014] Optionally, it also includes a power generation unit and an energy storage unit. The power generation unit includes a hydrogen booster and a fuel cell. The hydrogen booster pressurizes the hydrogen product separated by the separation and purification unit and sends it to the fuel cell. The fuel cell is electrically connected to an external electrical load. The energy storage unit is a battery. The fuel cell is also electrically connected to the battery. The battery is electrically connected to at least one of the plasma generator, the electric heater, the fan, and the molecular sieve purifier.

[0015] Secondly, this application provides a method for hydrogen production by ammonia cracking using plasma-assisted PSA tail gas combustion heating, employing the ammonia cracking hydrogen production apparatus for ammonia cracking using plasma-assisted PSA tail gas combustion heating as described in the first aspect, including the following steps: Liquid ammonia is converted into gaseous ammonia, and the gaseous ammonia is divided into a first gaseous ammonia stream and a second gaseous ammonia stream. The first gaseous ammonia is mixed with the separated and recovered ammonia-containing tail gas and then fed into a hot blast furnace for combustion under plasma assistance to produce high-temperature flue gas. The second gaseous ammonia is preheated by a heat exchanger and then fed into a catalytic cracking reactor to undergo a cracking reaction, generating hydrogen-containing cracked gas. The hydrogen-containing cracked gas is cooled by the heat exchange component and then purified and separated to obtain hydrogen products. The purified exhaust gas is further separated, and the ammonia-containing gas is recovered and returned to the hot blast stove for recycling and combustion.

[0016] Optionally, the preheating process of the second gaseous ammonia via the heat exchange components is as follows: the second gaseous ammonia flows sequentially through a primary heat exchanger, a secondary heat exchanger, and a tertiary heat exchanger for step-by-step heat exchange and temperature increase, so that the ammonia temperature before entering the catalytic cracking reactor reaches the cracking reaction temperature; the cooling process of the hydrogen-containing cracked gas via the heat exchange components is as follows: the hydrogen-containing cracked gas flows sequentially through a secondary heat exchanger and a quaternary heat exchanger for step-by-step heat exchange and temperature decrease; the waste heat recovery path of the high-temperature flue gas is as follows: the high-temperature flue gas flows sequentially through a tertiary heat exchanger, a primary heat exchanger, and a quaternary heat exchanger for staged waste heat recovery before being discharged; The plasma-assisted combustion generates a plasma jet by applying a high-voltage discharge into the hot blast stove. The high-energy electrons and active particles in the plasma jet enhance the combustion reaction of ammonia fuel and broaden the combustion stability limit. It also includes a power generation step: the purified and separated hydrogen product is pressurized and sent to the fuel cell to generate electricity. Part of the generated electricity is supplied to external electrical loads, and the other part is supplied to the electrical equipment in the device for self-powered operation.

[0017] Compared with the prior art, this application includes at least one of the following beneficial technical effects: By adopting a plasma stabilizer coupled with the burner, the high-energy electrons and active particles generated by plasma discharge are used to enhance the combustion reaction of ammonia fuel, effectively solving the problems of low flame propagation speed and difficult ignition of pure ammonia combustion. Stable combustion can be achieved without the need to co-fire auxiliary fuels such as natural gas and hydrogen, reducing operating costs and maintaining the system's low-carbon advantage.

[0018] A multi-stage heat exchange network is established to coordinate the utilization of combustion heat and pyrolysis waste heat. A four-stage heat exchanger is used to realize the cascade waste heat recovery between flue gas, pyrolysis gas and ammonia. The combustion heat of the hot blast stove and the pyrolysis waste heat are used together to provide a heat source for liquid ammonia evaporation and ammonia preheating, thereby improving the overall thermal efficiency of the system.

[0019] The high-purity hydrogen produced by cracking is directly fed into the fuel cell power generation system, realizing the integration of ammonia cracking hydrogen production and fuel cell power generation, which improves system integration and energy utilization efficiency.

[0020] In addition to supplying external electrical loads, the fuel cell output also powers the battery, which in turn powers electrical equipment such as electric heaters, plasma power supplies, fans, and molecular sieve purifiers, forming a self-powered closed loop that reduces the need for external power supply.

[0021] A recycling path for uncracked ammonia-hydrogen mixture is set up. The uncracked ammonia and hydrogen in the PSA purification tail gas are returned to the hot blast stove for re-combustion through a separator and purifier, thereby improving ammonia fuel utilization, reducing ammonia emissions, and reducing system operating costs.

[0022] In summary, this invention constructs a zero-carbon closed-loop energy system that complements multiple energy sources, including electricity, heat, and hydrogen, through the synergistic coupling of plasma-assisted combustion, multi-stage waste heat utilization, PSA tail gas recirculation combustion, and fuel cell self-powering. This achieves efficient and stable conversion of ammonia fuel and full-process energy self-sufficiency, significantly improving the overall energy utilization rate and economy of the system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the ammonia cracking hydrogen production device based on plasma-assisted PSA tail gas combustion heating according to the present invention.

[0024] Figure 2 This is a schematic diagram of the system flow of the ammonia cracking hydrogen production device based on plasma-assisted PSA tail gas combustion heating according to the present invention.

[0025] Figure 3 This is a schematic diagram of the plasma stabilizer and burner structure of the present invention.

[0026] Attached reference numerals: 1. Liquid ammonia pressurization and evaporation system; 2. PSA tail gas combustion and heating system; 3. Heat exchange and pyrolysis system; 4. Separation, purification, and power generation system; 5. Control system; 6. Liquid ammonia storage tank; 7. Liquid ammonia pressurizer; 8. Electric heater; 9. Evaporator; 10. Ammonia pressure reducing valve; 11. Hot air furnace; 12. Plasma power supply; 13. Air pressure reducing valve; 14. Fan; 15. Air storage tank; 16. Battery; 17. Primary heat exchanger; 18. Secondary heat exchanger; 19. Tertiary heat exchanger; 20. Four-stage heat exchanger; 21. Catalytic cracker; 22. Buffer tank; 23. Molecular sieve purifier; 24. Separator and purifier; 25. Hydrogen booster; 26. Fuel cell; 27. Electrical load; 28. Plasma flame stabilizer; 29. ​​Combustor; 30. Ground electrode; 31. High-voltage electrode; 32. Ammonia-hydrogen mixture inlet; 33. High-voltage line; 34. Swirl ring one; 35. Air inlet; 36. Swirl ring two; 37. Arc nozzle; 38. Ammonia flame. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0028] Example: Figure 1 , Figure 2 As shown, this invention provides an ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating, comprising a liquid ammonia pressurization and evaporation system 1, a PSA tail gas combustion heating system 2, a heat exchange and cracking system 3, a separation, purification and power generation system 4, and a control system 5. The details of each system part are described below.

[0029] In this embodiment, the liquid ammonia pressurization and evaporation system 1 includes a liquid ammonia storage tank 6, a liquid ammonia booster 7, an electric heater 8, and an evaporator 9. The outlet of the liquid ammonia storage tank 6 is connected to the inlet of the liquid ammonia booster 7 via a liquid ammonia pipeline, and the outlet of the liquid ammonia booster 7 is connected to the shell-side inlet of the evaporator 9 via a high-pressure liquid ammonia pipeline. The electric heater 8 is located on the outer wall or inside the evaporator 9 and is fixedly connected to the evaporator 9, providing heat to the evaporator 9 during the start-up phase. The gaseous ammonia outlet of the evaporator 9 is connected to a three-way pipeline, dividing the gaseous ammonia into a first path and a second path: the first path is connected to the fuel inlet of the hot air furnace 11 via an ammonia gas pipeline and an ammonia gas pressure reducing valve 10, and the second path is connected to the cold-side inlet of the primary heat exchanger 17 of the heat exchange and cracking system 3 via an ammonia gas pipeline. The liquid ammonia booster 7 and the electric heater 8 are electrically connected to the control system 5, which controls their start-up, shutdown, and operating power.

[0030] It should be noted that the liquid ammonia storage tank 6 is used to store liquid ammonia. After being pressurized by the liquid ammonia booster 7, the liquid ammonia enters the evaporator 9. An electric heater 8 is installed on the outside of the evaporator 9 to provide initial heat to the evaporator during the system startup phase, so that the liquid ammonia evaporates rapidly to form gaseous ammonia. The evaporated gaseous ammonia is divided into two streams. A small portion of the ammonia gas, i.e., the first stream of gaseous ammonia, enters the hot air furnace 11 as fuel through the ammonia gas pressure reducing valve 10. The majority of the ammonia gas, i.e., the second stream of gaseous ammonia, enters the heat exchange and cracking system 3 as cracking feedstock. The ammonia gas pressure reducing valve 10 is installed on the pipeline between the evaporator 9 and the hot air furnace 11 to regulate the pressure and flow rate of the ammonia gas entering the hot air furnace 11, ensuring stable combustion of pure ammonia.

[0031] like Figure 1 - Figure 2In this embodiment, the PSA exhaust gas combustion heating system 2 includes an air storage tank 15, a fan 14, an air pressure reducing valve 13, a plasma power supply 12, a plasma flame stabilizer 28, and a burner 29, as well as a battery 16 for power supply. The inlet of the fan 14 is connected to the atmosphere, and the outlet of the fan 14 is connected to the inlet of the air storage tank 15 through an air pipeline. The outlet of the air storage tank 15 is connected to the air inlet 35 of the burner 29 through an air pipeline via the air pressure reducing valve 13. The air pressure reducing valve 13 is installed on the pipeline between the air storage tank 15 and the burner 29 to regulate the air pressure and flow rate entering the burner 29. The plasma flame stabilizer 28 is installed upstream or at the front end of the burner 29, and the two together form a hot air furnace 11, with the injection direction of the plasma flame stabilizer 28 facing the combustion zone of the burner 29. The ammonia-hydrogen mixture inlet 32 ​​of the plasma flame stabilizer 28 is connected via pipelines to the outlet of the ammonia pressure reducing valve 10 and the gas outlet of the separator / purifier 24, respectively, to receive the first stream of gaseous ammonia and the ammonia-containing tail gas returned from the separator / purifier 24. The plasma power supply 12 is electrically connected to the high-voltage electrode 31 of the plasma flame stabilizer 28 via a high-voltage line 33, and its control terminal is electrically connected to the control system 5. The output terminal of the storage battery 16 is electrically connected to the power supply terminals of the fan 14 and the plasma power supply 12, respectively, to supply power to both. The storage battery 16 is also electrically connected to the output terminal of the fuel cell 26 to receive and store the electrical energy output by the fuel cell 26. The fan 14, air pressure reducing valve 13, and plasma power supply 12 are all electrically connected to the control system 5, whose operating status is controlled by the control system 5.

[0032] A small portion of the ammonia gas, namely the first-stage gaseous ammonia and the ammonia-hydrogen mixture from the separator 24, enters the plasma stabilizer 28. The plasma power supply 12 applies high-voltage alternating current to the plasma stabilizer 28, forming a plasma discharge between the high-voltage electrode 31 and the ground electrode 30, generating a large number of high-energy electrons, free radicals, and active particles. The battery 16 provides power to the fan 14, which compresses air into the air storage tank 15. The air in the air storage tank 15 is then sent to the air pressure reducing valve 13, and after pressure regulation, it enters the burner 29. Under the action of the swirling air ring 36, a stable swirling flow is formed. After mixing with the plasma-activated gas flow, stable combustion is achieved with plasma assistance, producing high-temperature flue gas.

[0033] In addition, the high-temperature flue gas generated by the hot blast furnace 11 serves as a heat source for the catalytic cracker 21 and also as a heat source for waste heat recovery in the system. Compared with the traditional electric heating cracking method, this invention utilizes PSA tail gas combustion for heating, which not only reduces external power consumption but also enhances combustion through plasma, effectively improving flame stability and combustion efficiency.

[0034] In this embodiment, the heat exchange and pyrolysis system 3 includes a primary heat exchanger 17, a secondary heat exchanger 18, a tertiary heat exchanger 19, a quaternary heat exchanger 20, a catalytic cracker 21, and a buffer tank 22. The primary heat exchanger 17 is located between the evaporator 9 and the secondary heat exchanger 18. The cold-side inlet of the primary heat exchanger 17 is connected to the gaseous ammonia outlet of the evaporator 9 (the second path) via a pipeline. The cold-side outlet of the primary heat exchanger 17 is connected to the cold-side inlet of the secondary heat exchanger 18 via an ammonia pipeline. The secondary heat exchanger 18 is located between the primary heat exchanger 17 and the tertiary heat exchanger 19. The cold-side outlet of the secondary heat exchanger 18 is connected to the cold-side inlet of the tertiary heat exchanger 19 via an ammonia pipeline. The tertiary heat exchanger 19 is located between the secondary heat exchanger 18 and the catalytic cracker 21. The cold-side outlet of the tertiary heat exchanger 19 is connected to the inlet of the catalytic cracker 21 via a high-temperature ammonia pipeline. The catalytic cracker 21 is located downstream of the tertiary heat exchanger 19, and its outlet is connected to the hot side inlet of the secondary heat exchanger 18 through the cracked gas pipeline.

[0035] It should be noted that the hot-side inlet of the secondary heat exchanger 18 is connected to the outlet of the catalytic cracker 21 via a pipeline, and the hot-side outlet of the secondary heat exchanger 18 is connected to the first hot-side inlet of the fourth-stage heat exchanger 20 via a cracked gas pipeline. The fourth-stage heat exchanger 20 is located downstream of the secondary heat exchanger 18 and upstream of the buffer tank 22, and its first hot-side outlet is connected to the inlet of the buffer tank 22 via a cracked gas pipeline. The buffer tank 22 is located between the fourth-stage heat exchanger 20 and the separation and purification unit, and its outlet is connected to the inlet of the molecular sieve purifier 23 via a cracked gas pipeline.

[0036] Furthermore, the hot-side inlet of the tertiary heat exchanger 19 is connected to the flue gas outlet of the hot blast furnace 11 via a flue gas pipeline, and the hot-side outlet of the tertiary heat exchanger 19 is connected to the hot-side inlet of the primary heat exchanger 17 via a flue gas pipeline. The hot-side outlet of the primary heat exchanger 17 is connected to the second hot-side inlet of the quaternary heat exchanger 20 via a flue gas pipeline. The second hot-side outlet of the quaternary heat exchanger 20 is connected to a tail gas treatment device for purifying and discharging the heat-exchanged flue gas.

[0037] The cold side inlet of the fourth-stage heat exchanger 20 is connected to the gaseous ammonia outlet of the evaporator 9, i.e., the second path, through a bypass pipeline. The cold side outlet of the fourth-stage heat exchanger 20 is connected to the fuel inlet of the hot blast stove 11, i.e., the ammonia-hydrogen mixture inlet 32 ​​of the plasma stabilizer 28, through an ammonia pipeline, so as to send the preheated gaseous ammonia into the hot blast stove 11 to participate in combustion.

[0038] The catalytic cracker 21 contains a catalyst bed, which can be filled with Ru-based, Ni-based, Fe-based, or other catalysts suitable for ammonia cracking reactions to improve hydrogen generation efficiency. The temperature sensor of the catalytic cracker 21 is electrically connected to the control system 5 for real-time monitoring of the cracking reaction temperature.

[0039] The second stream of gaseous ammonia output from evaporator 9 first enters primary heat exchanger 17, where it undergoes a first heat exchange with the flue gas output from tertiary heat exchanger 19, achieving initial preheating. It then enters secondary heat exchanger 18, where it undergoes a second heat exchange with the high-temperature cracked gas mixture output from catalytic cracker 21, further increasing the ammonia temperature. Afterward, it enters tertiary heat exchanger 19, where it undergoes a third heat exchange with the high-temperature flue gas output from hot blast furnace 11, bringing the ammonia entering catalytic cracker 21 to the temperature required for the cracking reaction. The high-temperature ammonia after three heat exchanges enters catalytic cracker 21, where it undergoes a catalytic cracking reaction under the action of the catalyst bed, generating a cracked gas mixture containing hydrogen, nitrogen, and unreacted ammonia.

[0040] The cracked mixture first enters the secondary heat exchanger 18 to exchange heat with the ammonia gas to be cracked, transferring heat to the ammonia gas; then it enters the quaternary heat exchanger 20 for further cooling, and transfers the remaining heat to the gaseous ammonia from the liquid ammonia pressurization and evaporation system 1; the cooled cracked mixture enters the buffer tank 22 to stabilize the gas flow and pressure, providing a stable gas source for the subsequent purification process.

[0041] The waste heat recovery process for the flue gas is as follows: The high-temperature flue gas generated by the hot blast stove 11 first enters the tertiary heat exchanger 19, where it exchanges heat with the ammonia output from the secondary heat exchanger 18; then, the flue gas enters the primary heat exchanger 17, where it exchanges heat with the ammonia output from the evaporator 9; finally, it enters the quaternary heat exchanger 20, where the gaseous ammonia output from the evaporator 9 is further preheated. The flue gas after the four-stage heat exchange is then discharged after denitrification and purification treatment.

[0042] The four-stage heat exchanger 20 simultaneously performs comprehensive heat exchange between the three streams of flue gas, pyrolysis mixture, and ammonia. On the one hand, it recovers the waste heat of the high-temperature flue gas, and on the other hand, it recovers the heat of the pyrolysis mixture. At the same time, it uses the heat from both parts to preheat the ammonia, thereby increasing the temperature of the ammonia entering the hot blast furnace 11 and the catalytic cracker 21, thus reducing the overall energy consumption of the system and improving thermal efficiency.

[0043] like Figure 1 and Figure 2In this embodiment, the separation, purification, and power generation system 4 includes a molecular sieve purifier 23, a separation purifier 24, a hydrogen booster 25, a fuel cell 26, and an electrical load 27. The inlet of the molecular sieve purifier 23 is connected to the outlet of the buffer tank 22 via a pyrolysis gas pipeline. The hydrogen outlet of the molecular sieve purifier 23 is connected to the inlet of the hydrogen booster 25 via a hydrogen pipeline. The tail gas outlet of the molecular sieve purifier 23 is connected to the inlet of the separation purifier 24 via a tail gas pipeline. The control terminal of the molecular sieve purifier 23 is electrically connected to the control system 5. The hydrogen booster 25 is located between the molecular sieve purifier 23 and the fuel cell 26. The outlet of the hydrogen booster 25 is connected to the anode inlet of the fuel cell 26 via a high-pressure hydrogen pipeline. The control terminal of the hydrogen booster 25 is also electrically connected to the control system 5. The anode inlet of fuel cell 26 is connected to the outlet of hydrogen booster 25, and the cathode inlet of fuel cell 26 is connected to the atmosphere or connected to an air supply pipeline. The power output terminal of fuel cell 26 is electrically connected to the external electrical load 27 and the input terminal of battery 16, respectively. The control terminal of fuel cell 26 is electrically connected to control system 5. Separator 24 is located downstream of molecular sieve purifier 23. The gas outlet of separator 24 is connected to the ammonia-hydrogen mixture inlet 32 ​​of plasma stabilizer 28 of hot blast furnace 11 through an ammonia-containing tail gas pipeline, for returning the separated ammonia-containing gas to hot blast furnace 11 for recycling and combustion. The tail gas outlet of separator 24 is connected to tail gas treatment device. The output terminal of battery 16 is electrically connected to the power supply terminal of electric heater 8, plasma power supply 12, fan 14 and molecular sieve purifier 23, respectively, for supplying power to these electrical devices.

[0044] Furthermore, the pyrolysis mixture enters the molecular sieve purifier 23 after passing through the buffer tank 22, where high-purity hydrogen is extracted using pressure swing adsorption (PSA). The high-purity hydrogen is then pressurized by the hydrogen booster 25 and enters the fuel cell 26, where the chemical energy of the hydrogen is directly converted into electrical energy to power the external electrical load 27. A portion of the electrical energy can be supplied to the storage battery 16, which further powers the electric heater 8, plasma power supply 12, fan 14, and molecular sieve purifier 23, enabling the system to operate self-powered.

[0045] The exhaust gas purified by the molecular sieve purifier 23 enters the separation purifier 24, where it is further separated to obtain an ammonia-hydrogen mixture. This mixture is then fed back to the hot blast stove 11 as the main fuel for combustion, achieving the recycling of pyrolysis exhaust gas, improving fuel utilization, and reducing hydrogen loss and unpyrolyzed ammonia emissions.

[0046] In this embodiment, the control system 5 is electrically connected to the liquid ammonia pressurization and evaporation system 1, the PSA tail gas combustion and heating system 2, the heat exchange and cracking system 3, and the separation, purification and power generation system 4 via signal lines. It monitors and automatically controls operating parameters such as liquid ammonia pressure, air flow rate, ammonia flow rate, cracking temperature, combustion temperature, fuel cell output power, and system pressure in real time to ensure stable, safe, and efficient operation of the system.

[0047] like Figure 3 As shown, the hot blast stove 11 consists of a plasma flame stabilizer 28 and a burner 29. The plasma flame stabilizer 28 includes a ground electrode 30, a high-voltage electrode 31, an ammonia-hydrogen mixture inlet 32, a high-voltage line 33, and a swirling gas ring 34. The ammonia-hydrogen mixture includes a first-path gaseous ammonia and ammonia-containing tail gas from the separator 24. It enters the swirling gas ring 34 through the ammonia-hydrogen mixture inlet 32, forming a rotating airflow under the action of swirling. Under the action of high-voltage alternating current, plasma discharge is generated between the high-voltage electrode 31 and the ground electrode 30, forming a plasma jet.

[0048] The burner 29 includes an air inlet 35, a swirling gas ring 36, and an arc-shaped nozzle 37. Compressed air enters the air inlet 35 through the air pressure reducing valve 13 and then enters the swirling gas ring 36. Under the action of the swirling flow, a stable swirling flow is formed, which is fully mixed with the high-temperature active gas flow ejected from the plasma burner 28. The arc-shaped nozzle 37 is located at the outlet of the burner 29. Its arc-shaped contraction structure can enhance the rotation intensity of the gas flow, improve the uniformity of air-ammonia mixing, and prolong the residence time of high-temperature flue gas, thereby improving combustion stability and combustion efficiency. The mixed gas flow ejected through the arc-shaped nozzle 37 is ignited at the outlet of the burner 29, forming a stable ammonia flame 38, which provides a continuous and stable high-temperature heat source for the catalytic cracker 21.

[0049] During operation, the ammonia-hydrogen mixture first enters the plasma stabilizer 28, forming a stable plasma discharge. After the plasma jet is ejected from the nozzle, it mixes with the air output from the air inlet 35, enabling the hot blast stove 11 to continuously and stably output high-temperature flue gas, providing a stable heat source for the catalytic cracker 21. Furthermore, the swirling gas ring 1 34 and the swirling gas ring 2 36 promote the formation of swirling currents between the ammonia-hydrogen mixture and the air, creating a stable internal recirculation zone. This not only facilitates thorough mixing of the plasma jet and fuel but also improves flame stability, reduces the risk of blow-out during combustion, and ensures the long-term stable operation of the hot blast stove 11.

[0050] The operation method of this device will be described in detail below.

[0051] (1) System Start-up Stage. The control system 5 is started, firstly by activating the liquid ammonia booster 7 to pressurize and transport the liquid ammonia in the liquid ammonia storage tank 6 to the evaporator 9; simultaneously, the electric heater 8 is activated to heat the evaporator 9, causing the liquid ammonia to gradually evaporate and form gaseous ammonia. The ammonia pressure reducing valve 10 is opened, allowing some of the gaseous ammonia, namely the first path and the ammonia-hydrogen mixture from the separator and purifier 24, to enter the plasma stabilizer 28. Subsequently, the plasma power supply 12 is activated to form a stable plasma discharge. After the discharge stabilizes, the battery 16 is activated to provide power to the blower 14. The blower 14 compresses air into the air storage tank 15, and the air in the air storage tank 15 is sent to the air pressure reducing valve 13, and after pressure adjustment, enters the burner 29. Ignition is completed under the assistance of plasma, and a stable flame is formed. As the temperature of the hot air furnace 11 continues to rise, it begins to provide heat to the catalytic cracker 21.

[0052] (2) Stable heating stage. After the hot air furnace 11 is stably burning, the high-temperature flue gas first enters the third-stage heat exchanger 19 to exchange heat with the ammonia gas to be cracked for the first time at high temperature; then the flue gas enters the first-stage heat exchanger 17 to preheat the ammonia gas output from the evaporator 9; finally, the flue gas enters the fourth-stage heat exchanger 20 to continue to release the remaining heat. After completing the staged waste heat recovery, the tail gas is treated and then discharged. At the same time, most of the gaseous ammonia output from the evaporator 9, i.e. the second path, passes through the first-stage heat exchanger 17, the second-stage heat exchanger 18 and the third-stage heat exchanger 19 in sequence to be heated step by step, so that it reaches the temperature required for the cracking reaction before entering the catalytic cracker 21.

[0053] (3) Ammonia cracking to hydrogen production stage. High-temperature ammonia gas, preheated by the three-stage heat exchanger 19, enters the catalytic cracker 21. The catalytic cracker 21 is filled with ammonia cracking catalyst. Under the condition of continuous heating by the hot blast furnace 11, the ammonia gas undergoes catalytic cracking reaction in the catalyst bed to generate a cracked mixture of hydrogen, nitrogen and ammonia. After leaving the catalytic cracker 21, the cracked mixture first enters the second-stage heat exchanger 18 to exchange heat with the ammonia gas to be cracked, transferring heat to the ammonia gas; then it enters the fourth-stage heat exchanger 20 for further cooling and to continue to recover the remaining heat, and finally enters the buffer tank 22.

[0054] (4) Fuel cell power generation stage. The cracked gas mixture output from the buffer tank 22 enters the molecular sieve purifier 23 for purification to obtain high-purity hydrogen. The purified high-purity hydrogen enters the hydrogen booster 25 and is then delivered to the fuel cell 26 after being pressurized. The fuel cell 26 uses the high-purity hydrogen to undergo an electrochemical reaction, directly converting the chemical energy in the hydrogen into electrical energy to provide a stable power supply for the external electrical load 27.

[0055] (5) Tail gas recycling stage. The tail gas purified by molecular sieve enters the separator 24 for further separation to obtain an ammonia-hydrogen mixture. The ammonia-hydrogen mixture is then fed back to the hot air furnace 11 as the main fuel and burned together with ammonia to achieve the recycling of pyrolysis tail gas. At the same time, the flue gas at the outlet of the fourth-stage heat exchanger 20 is purified and discharged in compliance with standards.

[0056] (6) Stable operation phase. The control system 5 monitors parameters such as the temperature of the hot air furnace 11, the temperature of the catalytic cracker 21, the liquid ammonia pressure, the air flow rate, the ammonia flow rate, the hydrogen purity, and the output power of the fuel cell 26 in real time, and automatically adjusts the operating status of the liquid ammonia booster 7, the blower 14, the plasma power supply 12, and the hydrogen booster 25 according to the monitoring results, so that the system always maintains stable operation.

[0057] It is worth noting that this invention uses ammonia as a zero-carbon fuel and a feedstock for hydrogen production. Liquid ammonia is converted into gaseous ammonia through a liquid ammonia pressurization and evaporation system 1 and output in two streams. The first stream of gaseous ammonia enters the hot blast furnace 11 as fuel via an ammonia pressure reducing valve 10, while the second stream enters the heat exchange and cracking system 3 as a cracking feedstock. The hot blast furnace 11 employs a plasma stabilizer 28 coupled with a burner 29. The plasma power supply 12 applies high-voltage alternating current to the high-voltage electrode 31 and the ground electrode 30 via a high-voltage line 33, generating a plasma jet. High-energy electrons and active particles are used to enhance the combustion reaction of ammonia fuel, broadening the combustion stability limit. This allows the hot blast furnace 11 to achieve stable combustion of pure ammonia and ammonia-containing tail gas without the need for auxiliary fuels such as natural gas or hydrogen. This solves the problems of low flame propagation speed and ignition difficulty in pure ammonia combustion. The high-temperature flue gas generated by the hot blast stove 11 flows sequentially through the three-stage heat exchanger 19, the first-stage heat exchanger 17, and the fourth-stage heat exchanger 20 for cascaded waste heat recovery. At the same time, the high-temperature hydrogen-containing cracked gas output from the catalytic cracker 21 flows sequentially through the second-stage heat exchanger 18 and the fourth-stage heat exchanger 20 for step-by-step cooling, transferring heat to the second gaseous ammonia. The waste heat of both the high-temperature flue gas and the hydrogen-containing cracked gas is recovered through the fourth-stage heat exchanger 20. The second gaseous ammonia is preheated to the cracking reaction temperature by passing sequentially through the first-stage heat exchanger 17, the second-stage heat exchanger 18, and the third-stage heat exchanger 19 before entering the catalytic cracker 21. This achieves synergistic cascaded utilization of combustion heat and cracking waste heat, significantly reducing external heating demand and improving the overall thermal efficiency of the system.

[0058] The hydrogen-containing cracked gas generated by the catalytic cracker 21 is pressurized by the buffer tank 22 and then enters the molecular sieve purifier 23. High-purity hydrogen is extracted by pressure swing adsorption. The high-purity hydrogen is then pressurized by the hydrogen booster 25 and enters the fuel cell 26 to generate electricity, supplying power to the external electrical load 27. This achieves the integrated production of hydrogen from ammonia cracking and power generation by the fuel cell. The tail gas purified by the molecular sieve purifier 23 enters the separation purifier 24 for further separation. The uncracked ammonia and residual hydrogen are returned to the hot air furnace 11 as the main fuel for recycling and combustion, effectively recovering the combustible components in the PSA tail gas, improving the overall utilization rate of ammonia fuel, and reducing the direct emission of uncracked ammonia. Part of the electrical energy output from the fuel cell 26 is sent to the storage battery 16, which supplies power to the electric heater 8, plasma power supply 12, fan 14, and molecular sieve purifier 23. The fan 14 compresses air to the air storage tank 15 and then enters the combustion chamber through the air pressure reducing valve 13. The electric heater 8 provides initial heat to the evaporator 9 during the system startup phase, thus forming a self-powered closed loop of fuel cell power generation, battery energy storage, and power supply to electrical equipment, reducing the system's dependence on external power grid. The control system 5 is communicatively connected to the liquid ammonia pressurization and evaporation system 1, the PSA tail gas combustion heating system 2, the heat exchange and cracking system 3, and the separation, purification, and power generation system 4, respectively, to monitor and adjust operating parameters such as liquid ammonia pressure, air flow, ammonia flow, cracking temperature, combustion temperature, and fuel cell output power in real time, ensuring coordinated operation of each unit. Through the above-mentioned multi-stage heat exchange network and multi-unit coupling and collaboration, this invention achieves zero-carbon operation of the entire process of ammonia cracking hydrogen production and hydrogen power generation without the need for external fossil fuel supplementation or continuous power supply from the external power grid. It effectively solves the problems of poor combustion stability, insufficient waste heat utilization, lack of tail gas recovery and utilization, and low system integration in the prior art, and improves the overall energy utilization rate of the system.

[0059] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A plasma-assisted PSA tail gas combustion heating ammonia cracking hydrogen production unit, characterized in that, It includes a liquid ammonia supply unit, a combustion heating unit, a heat exchange and pyrolysis unit, a separation and purification unit, and a control system; The liquid ammonia supply unit converts liquid ammonia into gaseous ammonia and then divides the gaseous ammonia into a first gaseous ammonia output and a second gaseous ammonia output. The combustion heating unit includes a hot air furnace and a plasma generator. The hot air furnace is connected to the liquid ammonia supply unit and the separation and purification unit respectively, and receives the first gaseous ammonia and the ammonia-containing tail gas returned by the separation and purification unit as fuel. The plasma generator is used to assist the combustion of the hot air furnace, and the hot air furnace generates high-temperature flue gas. The heat exchange pyrolysis unit includes a catalytic pyrolysis reactor and a heat exchange component. The heat exchange component is disposed between the liquid ammonia supply unit and the catalytic pyrolysis reactor, and between the catalytic pyrolysis reactor and the separation and purification unit. The second gaseous ammonia is preheated by the heat exchange component and then enters the catalytic pyrolysis reactor for pyrolysis reaction to generate hydrogen-containing pyrolysis gas. The hydrogen-containing pyrolysis gas is cooled by the heat exchange component and then enters the separation and purification unit. The separation and purification unit is used to separate hydrogen products from the hydrogen-containing cracked gas and to further separate the purified tail gas, returning the separated ammonia-containing gas to the hot blast furnace. The control system is communicatively connected to the liquid ammonia supply unit, the combustion heating unit, the heat exchange pyrolysis unit, and the separation and purification unit, respectively. The heat exchange assembly includes a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, and a quaternary heat exchanger; the second gaseous ammonia flows sequentially through the primary, secondary, and tertiary heat exchangers for preheating before entering the catalytic cracking reactor; the high-temperature flue gas flows sequentially from the hot blast furnace through the tertiary, primary, and quaternary heat exchangers before being discharged; the hydrogen-containing cracked gas flows sequentially from the catalytic cracking reactor through the secondary and quaternary heat exchangers for cooling before entering the separation and purification unit.

2. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 1, characterized in that, The liquid ammonia supply unit includes a liquid ammonia storage tank, a liquid ammonia booster, an evaporator, and an electric heater. The liquid ammonia in the liquid ammonia storage tank is pressurized by the liquid ammonia booster and then enters the evaporator, where it evaporates into gaseous ammonia with the assistance of the electric heater. The first stream of gaseous ammonia enters the hot air furnace through an ammonia pressure reducing valve, and the second stream of gaseous ammonia enters the heat exchange assembly.

3. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 2, characterized in that, The primary heat exchanger is used for heat exchange between the second-stage gaseous ammonia and the flue gas from the tertiary heat exchanger. The secondary heat exchanger is used for heat exchange between the gaseous ammonia preheated by the primary heat exchanger and the hydrogen-containing cracked gas from the catalytic cracking reactor. The tertiary heat exchanger is used for heat exchange between the gaseous ammonia heated by the secondary heat exchanger and the high-temperature flue gas from the hot blast furnace. The quaternary heat exchanger is used for comprehensive heat exchange between the flue gas from the primary heat exchanger, the hydrogen-containing cracked gas from the secondary heat exchanger, and the gaseous ammonia output from the liquid ammonia supply unit. The hydrogen-containing cracked gas cooled by the quaternary heat exchanger enters the separation and purification unit, and the gaseous ammonia heated by the heat exchange enters the hot blast furnace.

4. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 3, characterized in that, The hot air furnace includes a plasma stabilizer and a burner. The plasma stabilizer is equipped with a ground electrode, a high-voltage electrode, an ammonia-hydrogen mixture inlet, a high-voltage line, and a first swirling gas ring. The burner is equipped with an air inlet, a second swirling gas ring, and an arc-shaped nozzle. The plasma generating device is a plasma power supply, which is electrically connected to the high-voltage electrode via the high-voltage line. The first gaseous ammonia and the ammonia-containing tail gas returned from the separation and purification unit enter the plasma stabilizer through the ammonia-hydrogen mixture inlet. Under the high-voltage discharge between the high-voltage electrode and the ground electrode, a plasma jet is formed. Air forms a swirling flow through the air inlet and the second swirling gas ring and then mixes and burns with the plasma jet.

5. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 4, characterized in that, The combustion heating unit also includes a fan, an air storage tank, and an air pressure reducing valve. The fan compresses air into the air storage tank, and the air in the air storage tank enters the hot air furnace after being pressure-regulated by the air pressure reducing valve.

6. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 5, characterized in that, The separation and purification unit includes a molecular sieve purifier and a separation purifier. The molecular sieve purifier is used to adsorb and separate high-purity hydrogen from the hydrogen-containing cracked gas. The separation purifier is used to further separate uncracked ammonia and hydrogen from the tail gas purified by the molecular sieve purifier, and return the separated ammonia-containing gas to the hot blast furnace. The heat exchange cracking unit also includes a buffer tank disposed between the heat exchange component and the separation and purification unit to stabilize the flow rate and pressure of the hydrogen-containing cracked gas entering the separation and purification unit.

7. The ammonia cracking hydrogen production device for plasma-assisted PSA tail gas combustion heating according to claim 6, characterized in that, It also includes a power generation unit and an energy storage unit. The power generation unit includes a hydrogen booster and a fuel cell. The hydrogen booster pressurizes the hydrogen product separated by the separation and purification unit and sends it to the fuel cell. The fuel cell is electrically connected to an external electrical load. The energy storage unit is a battery. The fuel cell is also electrically connected to the battery. The battery is electrically connected to at least one of the plasma generator, the electric heater, the fan, and the molecular sieve purifier.

8. A method for producing hydrogen from ammonia by plasma-assisted PSA tail gas combustion heating, using the ammonia by plasma-assisted PSA tail gas combustion heating apparatus as described in claim 7, characterized in that... Includes the following steps: Liquid ammonia is converted into gaseous ammonia, and the gaseous ammonia is divided into a first gaseous ammonia stream and a second gaseous ammonia stream. The first gaseous ammonia is mixed with the separated and recovered ammonia-containing tail gas and then fed into a hot blast furnace for combustion under plasma assistance to produce high-temperature flue gas. The second gaseous ammonia is preheated by a heat exchanger and then fed into a catalytic cracking reactor to undergo a cracking reaction, generating hydrogen-containing cracked gas. The hydrogen-containing cracked gas is cooled by the heat exchange component and then purified and separated to obtain hydrogen products. The purified exhaust gas is further separated, and the ammonia-containing gas is recovered and returned to the hot blast stove for recycling and combustion.

9. The ammonia cracking hydrogen production method based on plasma-assisted PSA tail gas combustion heating according to claim 8, characterized in that, The specific process of preheating the second-path gaseous ammonia through the heat exchange components is as follows: the second-path gaseous ammonia flows sequentially through the first-stage heat exchanger, the second-stage heat exchanger, and the third-stage heat exchanger for step-by-step heat exchange and temperature increase, so that the temperature of the ammonia gas before entering the catalytic cracking reactor reaches the cracking reaction temperature; the specific process of cooling the hydrogen-containing cracked gas through the heat exchange components is as follows: the hydrogen-containing cracked gas flows sequentially through the second-stage heat exchanger and the fourth-stage heat exchanger for step-by-step heat exchange and temperature decrease; the waste heat recovery path of the high-temperature flue gas is as follows: the high-temperature flue gas flows sequentially through the third-stage heat exchanger, the first-stage heat exchanger, and the fourth-stage heat exchanger for tiered waste heat recovery before being discharged; The plasma-assisted combustion generates a plasma jet by applying a high-voltage discharge into the hot blast stove. The high-energy electrons and active particles in the plasma jet enhance the combustion reaction of ammonia fuel and broaden the combustion stability limit. It also includes a power generation step: the purified and separated hydrogen product is pressurized and sent to the fuel cell to generate electricity. Part of the generated electricity is supplied to external electrical loads, and the other part is supplied to the electrical equipment in the device for self-powered operation.

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