Ammonia combustion driven ammonia cracking hydrogen production system and its application in cascade cracking process

Abstract

The present invention belongs to the technical field of hydrogen production by cracking, and in particular, relates to an ammonia combustion-driven ammonia cracking hydrogen production system and its application in a cascade cracking process. The design of the ammonia combustion-driven ammonia cracking hydrogen production system is based on the characteristics of the ammonia cracking reaction. During the ammonia cracking process, two crackers are provided, and hydrogen and nitrogen are separated before entering the second cracker to reduce the hydrogen partial pressure, improve the ammonia cracking efficiency, and increase hydrogen production. This accelerates the cracking reaction and reduces the investment in cracking equipment. At the same time, the system uses a mixture of ammonia and air as the combustion source, effectively reducing fossil energy consumption and carbon emissions. The intermediate heat exchanger is used to effectively preheat the combustion source and the ammonia to be cracked, thereby improving the system's thermal efficiency and ammonia cracking rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by cracking, and in particular relates to an ammonia cracking hydrogen production system driven by ammonia combustion and its application in a cascade cracking process. Background Art

[0002] To address the threat of climate change caused by global warming, the development and commercialization of clean and sustainable energy technologies is necessary. The necessity of energy transformation is well understood, and hydrogen energy offers advantages such as being green, efficient, carbon-free, and widely applicable. The entire hydrogen energy industry chain encompasses hydrogen production, storage and transportation, and application. The primary challenge in achieving large-scale application of the hydrogen energy industry lies in safe and efficient hydrogen storage and transportation technologies.

[0003] Currently, my country's hydrogen storage and transportation methods primarily involve high-pressure gaseous hydrogen storage and cryogenic liquid hydrogen storage. High-pressure gaseous hydrogen storage, which pressurizes hydrogen to 35-70 MPa for storage and transportation, is widely used domestically. However, hydrogen's low volumetric energy density leads to high storage and transportation costs, and high-pressure storage and transportation safety is poor. Cryogenic liquid hydrogen storage, which liquefies hydrogen to an ultra-low temperature of -253°C for storage and transportation, has a high volumetric hydrogen storage density, but the liquefaction process is energy-intensive and costly. Furthermore, contact between cryogenic hydrogen and metal containers can cause hydrogen embrittlement, resulting in poor safety.

[0004] Ammonia (NH3) is a fundamental chemical raw material crucial to national economy and people's livelihoods, widely used in fertilizers, environmental protection, military, refrigeration, and other fields. Furthermore, as a highly efficient hydrogen storage medium, ammonia offers significant technical advantages, including low storage and transportation costs, high hydrogen content per unit volume, and enhanced safety. Hydrogen-ammonia fusion technology (i.e., converting hydrogen into ammonia at the production end, transporting the ammonia to the application end, and then converting it back into hydrogen for use) is an effective way to address the major bottlenecks in hydrogen storage and transportation, effectively enabling the long-distance, low-cost storage and transportation of hydrogen energy. Countries around the world are actively developing ammonia energy industry layouts, with Japan and South Korea leading the global research and development of the entire "hydrogen-ammonia" energy industry chain.

[0005] The process of converting hydrogen into ammonia is quite mature at the production end. Ammonia utilization requires cracking and separation. Ammonia can achieve high cracking rates using metal catalysts at high temperatures of 400°C to 750°C. To improve the efficiency of ammonia crackers, continuous optimization efforts are underway, focusing primarily on catalyst selection and cracker structure. In addition to its use as a hydrogen carrier, ammonia can also be used directly as a fuel. Research in this area is growing, but this has led to a rapid increase in initial investment.

[0006] The patent documents searched by the applicant include:

[0007] Patent publication number CN217895148U discloses a device for accelerating the contact reaction of ammonia cracking to produce hydrogen. By adding a filter and a stirring mechanism to the cracker, the device increases the contact area and improves the ammonia cracking efficiency. However, this prior art suffers from the technical drawback of a complex internal structure of the cracker. Patent publication number CN201512408U discloses an ammonia cracking furnace hydrogen production device that uses diesel or natural gas combustion to provide heat for cracking. However, this device suffers from uneven temperature distribution and insufficient contact between ammonia and the catalyst, potentially leading to reduced ammonia cracking efficiency. Therefore, a simple and efficient method to improve cracking efficiency is needed.

[0008] The applicant has not found any patent document that is identical or similar to the present application. Summary of the Invention

[0009] The present invention provides an ammonia cracking hydrogen production system driven by ammonia combustion and its application in a cascade cracking process. Based on the characteristics of the ammonia cracking reaction, the system provides two crackers during the ammonia cracking process, and separates hydrogen and nitrogen before entering the second cracker to reduce the hydrogen partial pressure, improve the ammonia cracking efficiency and increase the hydrogen yield; at the same time, it accelerates the cracking reaction and reduces the investment in cracking equipment.

[0010] The overall technical concept of the present invention is:

[0011] The ammonia combustion-driven ammonia cracking hydrogen production system includes a cracking device that can catalytically crack ammonia into hydrogen and nitrogen at high temperature. The mixed gas produced by the cracking device is denitrified to produce hydrogen; and a heat supply device that provides a heat source for the cracking device, wherein:

[0012] A. The heat supply device includes a combustion furnace, an intermediate heat exchanger, and an external heater. The combustion furnace uses a mixture of ammonia and air as a combustion source. The combustion source passes through the first cold end of the intermediate heat exchanger and the external heater, and then connects to the combustion furnace. The high-temperature flue gas generated by the combustion furnace is output to the first hot end of the intermediate heat exchanger to provide heat for the cracking unit.

[0013] B. The cracking device includes a first cracker and a second cracker connected in series via a pipeline. The ammonia to be cracked is connected to the first cracker via the second cold end of the intermediate heat exchanger. The cracked gas output end of the first cracker is connected to a gas-liquid separator via a cooler. The gas-liquid separator has two outputs, one of which is a nitrogen-hydrogen mixed gas output that is passed through a pressure swing adsorption device to remove nitrogen and produce hydrogen, and the other is ammonia output to the second cracker for cracking. The cracked gas output end of the second cracker is connected to the gas-liquid separator via the second hot end of the intermediate heat exchanger and a cooler;

[0014] C. The pipeline connecting the combustion furnace and the first cold end output of the intermediate heat exchanger and the cooler output pipeline are equipped with control valves, which are controlled to start and stop by a central processing unit connected to the temperature sensor signal output.

[0015] Application of ammonia combustion driven ammonia cracking hydrogen production system in cascade cracking process.

[0016] The specific technical concept of the present invention is:

[0017] In order to simplify the pipeline structure and effectively utilize the waste heat of the cracked gas, the preferred technical implementation means is that the cracked gas output end of the first cracker is correspondingly connected to the cracked gas output end of the second cracker.

[0018] To simplify the system structure, the preferred technical implementation method is that the ammonia has two outputs after passing through the splitter, one of which is the ammonia to be cracked, and the other is the ammonia for combustion and is mixed with compressed air through the first mixer as a combustion source.

[0019] In order to make full use of the heat of high-temperature flue gas, the preferred technical implementation method is that the high-temperature flue gas generated by the combustion furnace passes through the first cracker and the second cracker in sequence and then connects to the first hot end of the intermediate heat exchanger to provide a heat source for it.

[0020] In order to simplify the pipeline layout and facilitate a more compact system structure, the preferred technical implementation means is that the cracked gas output end of the second cracker and the cracked gas output end of the first cracker are connected to the second hot end input of the intermediate heat exchanger through the second mixer.

[0021] In order to facilitate the control of the materials transported in the pipeline, the preferred technical implementation method is to provide a third gate valve in the pipeline for transporting the ammonia to be cracked output by the diverter, a second gate valve in the other pipeline for transporting the ammonia for combustion; and a first gate valve in the pipeline for transporting the compressed air.

[0022] In order to facilitate the automatic control of the working temperature of the devices in the system, the preferred technical implementation method is that a first temperature sensor and a fourth gate valve are provided in the pipeline connecting the combustion furnace and the first cold end output of the intermediate heat exchanger, and the fourth gate valve is controlled to start and stop by a central processing unit connected to the signal output of the first temperature sensor; a second temperature sensor and a seventh gate valve are provided in the output pipeline of the cooler, and the seventh gate valve is controlled to start and stop by a central processing unit connected to the signal output of the second temperature sensor.

[0023] In order to achieve effective switching between system startup and normal working conditions, the preferred technical implementation method is that the first cold end of the intermediate heat exchanger has two outputs connected to the combustion source input end of the combustion furnace through the first temperature sensor and the fourth gate valve. One of them is connected to the fourth gate valve after passing through the sixth gate valve, the external heater, the first temperature sensor, and the other is connected to the fourth gate valve after passing through the fifth gate valve, the first temperature sensor.

[0024] In order to meet the cracking reaction requirements of the cracker and improve the cracking efficiency, the preferred technical implementation is that the volume ratio of the first cracker to the second cracker is 20% to 40%.

[0025] The application of ammonia combustion driven ammonia cracking hydrogen production system in the cascade cracking process includes the following steps:

[0026] A. Close the pipeline for ammonia to be cracked and the pipeline connecting the combustion furnace and the first cold end output of the intermediate heat exchanger, open the pipeline for conveying ammonia for combustion and compressed air, and mix the ammonia for combustion and the compressed air to generate a mixed gas;

[0027] B. The mixed gas is connected to an external heater through the first cold end of the intermediate heat exchanger for heating. When the mixed gas is heated to 425°C to 525°C, the control valve in the pipeline connecting the combustion furnace and the output of the first cold end of the intermediate heat exchanger is opened under the control of the central processing unit. The heated mixed gas enters the combustion furnace for combustion. The generated high-temperature flue gas is output to the cracking unit and the first hot end of the intermediate heat exchanger to provide a heat source. When the temperature of the high-temperature flue gas in the combustion furnace reaches 1127°C to 2027°C and the pressure reaches 100kPa to 1000kPa, the external heater is turned off.

[0028] C. After the heat supply is stable, the ammonia gas to be cracked is connected to the pipeline. The ammonia gas to be cracked is output to the first cracker after heat exchange at the second cold end of the intermediate heat exchanger for the first high-temperature catalytic cracking;

[0029] D. Close the control valve on the cooler output pipeline. When the first cracked gas output from the first cracker is cooled to 25°C-30°C through the cooler, open the control valve on the cooler output pipeline under the control of the central processing unit. The cooled first cracked gas is separated through the gas-liquid separator and two outputs are generated. One of the nitrogen-hydrogen mixed gas outputs is nitrogen-removed and hydrogen-produced through the pressure swing adsorption device, and the other ammonia gas is output to the second cracker for a second high-temperature catalytic cracking. The cracked gas output from the second cracker is heat exchanged through the second hot end of the intermediate heat exchanger and then output to the cooler for cooling. The cooled second cracked gas is separated through the gas-liquid separator, and the cycle is repeated.

[0030] In order to facilitate the switching of the working pipeline between the on and off states, the preferred technical implementation method is that the step A is to close the third gate valve and the fourth gate valve, open the first gate valve and the second gate valve, and mix the ammonia for combustion with the air compressed by the compressor in the first mixer to generate a mixed gas.

[0031] In order to improve the ammonia cracking efficiency while effectively reducing fuel consumption, the preferred technical implementation means is that the volume ratio of the ammonia for combustion in step A to the ammonia to be cracked in step C is 8-10:90-92.

[0032] In order to improve the thermal utilization rate of high-temperature flue gas, the preferred technical implementation method is that the high-temperature flue gas generated by the combustion furnace in step B is output in sequence to the first cracker, the second cracker and the first hot end of the intermediate heat exchanger to provide them with a heat source.

[0033] In order to facilitate effective control of the switching of the working state of the external heater, the preferred technical implementation method begins with that in step B, turning off the external heater is to close the sixth gate valve and open the fifth gate valve.

[0034] In order to achieve effective high-temperature catalytic cracking and improve the cracking efficiency, the preferred technical implementation method is that the catalyst used for the first high-temperature catalytic cracking and the second high-temperature catalytic cracking in steps C and D is Fe2O3 and a metal catalyst with Fe2O3 as the main component combined with Ru, wherein ruthenium accounts for 4% of the total mass of the catalyst. Since it belongs to the existing technology, the applicant will not elaborate on it here.

[0035] A more preferred technical implementation method is that the temperature of the first high-temperature catalytic cracking and the second high-temperature catalytic cracking in steps C and D is 400°C to 750°C, and the pressure is 100kPa to 1000kPa.

[0036] In order to effectively utilize the heat in the cracked gas, the preferred technical implementation method is that the first cracked gas output from the first cracker in step D is cooled by the second hot end of the intermediate heat exchanger and the cooler.

[0037] In the description of the present invention, the terms "first", "second", "third", "fourth", "fifth", "sixth" and "seventh" are only used to express distinctions and should not be understood as implying or indicating importance.

[0038] The substantial features and significant technical advancements of the present invention are:

[0039] 1. The cracking device of the present invention uses two crackers connected in series as the main structure for ammonia cascade cracking. First, since most of the ammonia cracking reaction occurs at the cracker inlet, the cracking efficiency is high and the overall length of the cracker is short. Only 75% to 80% of the length of the existing cracker is required to achieve the same cracking efficiency, effectively reducing the footprint and equipment investment. Second, there is no need to modify the structure of the existing cracker, and the structure of the cracker is simple. Third, the first cracker and the second cracker are designed with different volume specifications, which not only effectively meets the needs of cascade cracking, but also effectively improves the cracking efficiency during the second cracking process.

[0040] 2. The present invention adopts a gas-liquid separator structure design, which separates hydrogen and nitrogen through the gas-liquid separator before the cracking gas undergoes the second cracking. Firstly, it reduces the hydrogen partial pressure to ensure stable operation of the equipment; secondly, it improves the ammonia cracking efficiency and increases the hydrogen production.

[0041] 3. The present invention adopts the structural design of the intermediate heat exchanger. Firstly, it can effectively realize the preheating of the combustion source and the ammonia to be cracked, laying a structural foundation for the rapid and stable operation of the combustion furnace and the heat guarantee of the system. At the same time, after the ammonia to be cracked is preheated, the temperature rise time during the cracking process is reduced, thereby accelerating the cracking reaction. Secondly, it can effectively absorb the waste heat of the first cracked gas and high-temperature flue gas, reducing heat loss and further improving the thermal efficiency of the system and the ammonia cracking rate.

[0042] 4. The present invention adopts a second cracker, an intermediate heat exchanger, a cooler, a gas-liquid separator and corresponding pipelines to form a circulation loop, which further improves the ammonia cracking rate and thermal efficiency.

[0043] 5. The present invention adopts the structural design of temperature sensor and central processing unit, which can dynamically control the system working conditions according to the temperature changes of combustion source and cooled cracked gas, thereby improving the degree of system automation.

[0044] 6. Except for the short-term operation of the external heater during startup, the cracking reaction in the present invention does not require additional heat from the outside during operation. It only relies on the heat generated by the combustion of ammonia to meet the needs of the system. First, it reduces fossil energy consumption and improves environmental protection problems caused by carbon emissions caused by the use of fossil fuels; second, it effectively simplifies the system structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings of the present invention include:

[0046] Figure 1 It is a structural schematic diagram of the ammonia cracking hydrogen production system driven by ammonia combustion in the present invention.

[0047] The reference numerals in the accompanying drawings are as follows:

[0048] 1. Cooler; 2. First gate valve; 3. Second gate valve; 4. Third gate valve; 5. Fourth gate valve; 6. First mixer; 7. Diverter; 8. Intermediate heat exchanger; 9. Combustion furnace; 10. First cracker; 11. Second cracker; 12. Gas-liquid separator; 13. Pressure swing adsorption device; 14. Compressor; 15. Second mixer; 16. Fifth gate valve; 17. Sixth gate valve; 18. External heater; 19. First temperature sensor; 20. Second temperature sensor; 21. Seventh gate valve. DETAILED DESCRIPTION

[0049] The accompanying drawings show embodiments of the present invention. The embodiments of the present invention are further described below in conjunction with the accompanying drawings, but should not be understood as limiting the present invention. The scope of protection of the present invention is based on the contents recorded in the claims. Any replacement of equivalent technical means made according to the description does not depart from the scope of protection of the present invention.

[0050] Example

[0051] The overall structure of this embodiment is shown in the figure. The ammonia combustion-driven ammonia cracking hydrogen production system includes a cracking device that can catalytically crack ammonia into hydrogen and nitrogen at high temperature. The mixed gas produced by the cracking device is denitrified to produce hydrogen. The system also includes a heat supply device that provides a heat source for the cracking device, wherein:

[0052] A. The heat supply device includes a combustion furnace 9, an intermediate heat exchanger 8, and an external heater 18. The combustion furnace 9 uses a mixture of ammonia and air as a combustion source. The combustion source passes through the first cold end of the intermediate heat exchanger 8 and the external heater 18, and then connects to the combustion furnace 9. The high-temperature flue gas generated by the combustion furnace 9 is output to the first hot end of the intermediate heat exchanger 8 to provide heat for the cracking unit.

[0053] B. The cracking device includes a first cracker 10 and a second cracker 11 connected in series through a pipeline. The ammonia to be cracked is connected to the first cracker 10 through the second cold end of the intermediate heat exchanger 8. The cracked gas output end of the first cracker 10 is connected to the gas-liquid separator 12 through the cooler 1. The gas-liquid separator 12 has two outputs, one of which is a nitrogen-hydrogen mixed gas output that is removed from nitrogen and produced by a pressure swing adsorption device 13, and the other ammonia is output to the second cracker 11 for cracking. The cracked gas output end of the second cracker 11 is connected to the gas-liquid separator 12 after passing through the second hot end of the intermediate heat exchanger 8 and the cooler 1. The cracked gas output end of the first cracker 10 is correspondingly connected to the cracked gas output end of the second cracker 11;

[0054] C. The pipeline connecting the combustion furnace 9 and the first cold end output of the intermediate heat exchanger 8 and the output pipeline of the cooler 1 are provided with control valves, which are controlled to start and stop by a central processing unit connected to the temperature sensor signal output.

[0055] After passing through the diverter 7, the ammonia gas is output in two ways, one of which is the ammonia gas to be cracked, and a third gate valve 4 is provided in the ammonia gas delivery pipeline to be cracked. The other is ammonia gas for combustion and is mixed with compressed air through the first mixer 6 as a combustion source. A second gate valve 3 is provided in the ammonia gas delivery pipeline for combustion, and a first gate valve 2 is provided in the air delivery pipeline compressed by the compressor 14.

[0056] The high-temperature flue gas generated by the combustion furnace 9 passes through the first cracker 10 and the second cracker 11 in sequence and is connected to the first hot end of the intermediate heat exchanger 8 to provide a heat source therefor.

[0057] The cracked gas output end of the second cracker 11 and the cracked gas output end of the first cracker 10 are connected to the second hot end input of the intermediate heat exchanger 8 through the second mixer 15.

[0058] A first temperature sensor 19 and a fourth gate valve 5 are provided in the pipeline connecting the combustion furnace 9 and the first cold end output of the intermediate heat exchanger 8. The fourth gate valve 5 is controlled to start and stop by a central processing unit connected to the signal output of the first temperature sensor 19; a second temperature sensor 20 and a seventh gate valve 21 are provided in the output pipeline of the cooler 1. The seventh gate valve 21 is controlled to start and stop by a central processing unit connected to the signal output of the second temperature sensor 20.

[0059] The first cold end of the intermediate heat exchanger 8 has two outputs connected to the combustion source input end of the combustion furnace 9 through the first temperature sensor 19 and the fourth gate valve 5. One of them is connected to the fourth gate valve 5 after passing through the sixth gate valve 17, the external heater 18, the first temperature sensor 19, and the other is connected to the fourth gate valve 5 after passing through the fifth gate valve 16 and the first temperature sensor 19.

[0060] The total length of the first cracker 10 and the second cracker 11 is 4.0 to 6.4 meters and the diameters of the two are the same. The length ratio of the first cracker 10 to the second cracker 11 is 20:100.

[0061] The application of ammonia combustion driven ammonia cracking hydrogen production system in the cascade cracking process includes the following steps:

[0062] A. Close the third gate valve 4 and the fourth gate valve 5, open the first gate valve 2 and the second gate valve 3, and mix the ammonia gas for combustion with the air compressed by the compressor 14 in the first mixer 6 to generate a mixed gas. The pressure of the compressed air is 1000 kPa.

[0063] B. The mixed gas is heated by connecting the first cold end of the intermediate heat exchanger 8 to the external heater 18. When the mixed gas is heated to 425°C to 525°C, the control valve in the pipeline connecting the combustion furnace 9 to the output of the first cold end of the intermediate heat exchanger 8 is opened under the control of the central processing unit. The heated mixed gas enters the combustion furnace 9 and is burned. The generated high-temperature flue gas is output to the cracking unit and the first hot end of the intermediate heat exchanger 8 to provide a heat source. When the temperature of the high-temperature flue gas in the combustion furnace reaches 1127°C and the pressure reaches 1000 kPa, the sixth gate valve 17 is closed and the fifth gate valve 16 is opened.

[0064] C. After the heat supply is stabilized, the ammonia gas to be cracked is connected to the pipeline. The ammonia gas to be cracked is output to the first cracker 10 after heat exchange at the second cold end of the intermediate heat exchanger 8 for the first high-temperature catalytic cracking.

[0065] D. Close the control valve on the output pipeline of cooler 1. When the first cracked gas output by the first cracker 10 is cooled to 28° C. through the second hot end of the intermediate heat exchanger 8 and the cooler 1, open the control valve on the output pipeline of cooler 1 under the control of the central processing unit. The cooled first cracked gas is separated by the gas-liquid separator 12 and two outputs are generated. One of the outputs is a nitrogen-hydrogen mixed gas that is output through the pressure swing adsorption device 13 to remove nitrogen and produce hydrogen, and the other is an ammonia gas that is output to the second cracker 11 for a second high-temperature catalytic cracking. The cracked gas output of the second cracker 11 is heat exchanged through the second hot end of the intermediate heat exchanger 8 and then output to the cooler 1 for cooling. The cooled second cracked gas is separated by the gas-liquid separator 12, and the cycle is repeated.

[0066] The volume ratio of the ammonia gas for combustion in step A to the ammonia gas to be cracked in step C is 10:90.

[0067] The high-temperature flue gas generated by the combustion furnace 9 in step B is sequentially output to the first cracker 10, the second cracker 11 and the first hot end of the intermediate heat exchanger 8 to provide a heat source therefor.

[0068] The catalysts used for the first high-temperature catalytic cracking and the second high-temperature catalytic cracking in steps C and D are Fe2O3 and a metal catalyst mainly composed of Fe2O3 and Ru, wherein Ru accounts for 4% of the total mass of the catalyst.

[0069] In steps C and D, the temperature of the first high-temperature catalytic cracking and the second high-temperature catalytic cracking is 400° C. to 750° C., and the pressure is 100 kPa to 1000 kPa.

[0070] The applicant performed a process simulation in Aspen Plus based on the data settings in the examples. The amount of ammonia introduced into the system was 234.92 kmol / h, which could produce 256.49 kmol / h of hydrogen.

Claims

1. Ammonia combustion driven ammonia cracking hydrogen production system, including a cracking device that can catalytically crack ammonia into hydrogen and nitrogen at high temperature. The mixed gas produced by the cracking device is denitrified to produce hydrogen; it is characterized by It also includes a heat supply device that provides a heat source for the cracking device, wherein: A. The heat supply device includes a combustion furnace (9), an intermediate heat exchanger (8), and an external heater (18); the combustion furnace (9) uses a mixture of ammonia and air as a combustion source, and the combustion source is connected to the combustion furnace (9) through the first cold end of the intermediate heat exchanger (8) and the external heater (18). The high-temperature flue gas generated by the combustion furnace (9) is output to the cracking device and the first hot end of the intermediate heat exchanger (8) to provide a heat source for it; B. The cracking device comprises a first cracker (10) and a second cracker (11) connected in series through a pipeline. The ammonia to be cracked is connected to the first cracker (10) via the second cold end of the intermediate heat exchanger (8). The cracked gas output end of the first cracker (10) is connected to the gas-liquid separator (12) via the cooler (1). The gas-liquid separator (12) has two outputs, one of which is a nitrogen-hydrogen mixed gas output to remove nitrogen and produce hydrogen through a pressure swing adsorption device (13). The other ammonia is output to the second cracker (11) for cracking. The cracked gas output end of the second cracker (11) is connected to the gas-liquid separator (12) after passing through the second hot end of the intermediate heat exchanger (8) and the cooler (1); C. The pipeline connecting the combustion furnace (9) and the first cold end output of the intermediate heat exchanger (8) and the output pipeline of the cooler (1) are provided with a control valve, which is controlled to start and stop by a central processing unit connected to the signal output of the temperature sensor.

2. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 1, characterized in that The cracked gas output end of the first cracker (10) is correspondingly connected to the cracked gas output end of the second cracker (11).

3. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 1, characterized in that After passing through the splitter (7), the ammonia is output in two ways, one of which is the ammonia to be cracked, and the other is the ammonia for combustion, which is mixed with the compressed air through the first mixer (6) and used as a combustion source.

4. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 1, characterized in that The high-temperature flue gas generated by the combustion furnace (9) passes through the first cracker (10) and the second cracker (11) in sequence and then connects to the first hot end of the intermediate heat exchanger (8) to provide a heat source for it.

5. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 2, characterized in that The cracked gas output end of the second cracker (11) and the cracked gas output end of the first cracker (10) are connected to the second hot end input of the intermediate heat exchanger (8) through the second mixer (15).

6. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 3, characterized in that A third gate valve (4) is provided in the pipeline for delivering the ammonia gas to be cracked outputted from the diverter (7), a second gate valve (3) is provided in the pipeline for delivering the ammonia gas for combustion, and a first gate valve (2) is provided in the pipeline for delivering the compressed air.

7. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 1, characterized in that A first temperature sensor (19) and a fourth gate valve (5) are provided in the pipeline connecting the combustion furnace (9) and the first cold end output of the intermediate heat exchanger (8), and the fourth gate valve (5) is controlled to start and stop by a central processing unit connected to the signal output of the first temperature sensor (19); a second temperature sensor (20) and a seventh gate valve (21) are provided in the output pipeline of the cooler (1), and the seventh gate valve (21) is controlled to start and stop by a central processing unit connected to the signal output of the second temperature sensor (20).

8. The ammonia combustion driven ammonia cracking hydrogen production system according to claim 7, characterized in that The first cold end of the intermediate heat exchanger (8) has two outputs connected to the combustion source input end of the combustion furnace (9) through the first temperature sensor (19) and the fourth gate valve (5). One of the outputs passes through the sixth gate valve (17), the external heater (18), the first temperature sensor (19) and then the fourth gate valve (5), and the other passes through the fifth gate valve (16), the first temperature sensor (19) and then the fourth gate valve (5).

9. The ammonia combustion-driven ammonia cracking hydrogen production system according to any one of claims 1 to 8, characterized in that The volume ratio of the first cracker (10) to the second cracker (11) is 20% to 40%.

10. Use of the ammonia cracking hydrogen production system according to any one of claims 1 to 9 in cascade cracking hydrogen production.

11. Application of the ammonia combustion driven ammonia cracking hydrogen production system according to claim 10 in a cascade cracking process, characterized in that The steps include: A. Close the pipeline for ammonia to be cracked and the pipeline connecting the combustion furnace (9) and the first cold end output of the intermediate heat exchanger (8), open the pipeline for conveying ammonia for combustion and compressed air, and mix the ammonia for combustion and the compressed air to generate a mixed gas; B. The mixed gas is connected to the external heater (18) through the first cold end of the intermediate heat exchanger (8) and heated. When the mixed gas is heated to 425°C to 525°C, the control valve in the pipeline connecting the combustion furnace (9) and the first cold end output of the intermediate heat exchanger (8) is opened under the control of the central processing unit. The heated mixed gas enters the combustion furnace (9) and burns. The generated high-temperature flue gas is output to the cracking device and the first hot end of the intermediate heat exchanger (8) to provide a heat source. When the temperature of the high-temperature flue gas in the combustion furnace reaches 1127°C to 2027°C and the pressure reaches 100kPa to 1000kPa, the external heater (18) is turned off. C. After the heat supply is stabilized, the pipeline for delivering the ammonia gas to be cracked is opened, and the ammonia gas to be cracked is output to the first cracker (10) after heat exchange at the second cold end of the intermediate heat exchanger (8) for the first high-temperature catalytic cracking; D. Close the control valve on the output pipeline of the cooler (1). When the first cracked gas output by the first cracker (10) is cooled to 25°C-30°C through the cooler (1), the control valve on the output pipeline of the cooler (1) is opened under the control of the central processing unit. The first cracked gas after cooling is separated by the gas-liquid separator (12) and two outputs are generated. One of the nitrogen-hydrogen mixed gas outputs is passed through the pressure swing adsorption device (13) to remove nitrogen and produce hydrogen, and the other ammonia gas is output to the second cracker (11) for a second high-temperature catalytic cracking. The cracked gas output of the second cracker (11) is subjected to heat exchange at the second hot end of the intermediate heat exchanger (8) and then output to the cooler (1) for cooling. The second cracked gas after cooling is separated by the gas-liquid separator (12), and the cycle is repeated.

12. Application of the ammonia combustion driven ammonia cracking hydrogen production system according to claim 11 in a cascade cracking process, characterized in that The step A is to close the third gate valve (4) and the fourth gate valve (5), open the first gate valve (2) and the second gate valve (3), and mix the ammonia gas for combustion with the air compressed by the compressor (14) in the first mixer (6) to generate a mixed gas.

13. Application of the ammonia combustion driven ammonia cracking hydrogen production system according to claim 11 in a cascade cracking process, characterized in that The volume ratio of the ammonia gas for combustion in step A to the ammonia gas to be cracked in step C is 8-10:90-92.

14. Application of the ammonia combustion driven ammonia cracking hydrogen production system in a cascade cracking process according to claim 11, characterized in that The high-temperature flue gas generated by the combustion furnace (9) in step B is sequentially output to the first cracker (10), the second cracker (11) and the first hot end of the intermediate heat exchanger (8) to provide a heat source for them.

15. Application of the ammonia combustion driven ammonia cracking hydrogen production system in a cascade cracking process according to claim 11, characterized in that In step B, closing the external heater (18) is performed by closing the sixth gate valve (17) and opening the fifth gate valve (16).

16. Application of the ammonia combustion driven ammonia cracking hydrogen production system according to claim 11 in a cascade cracking process, characterized in that The catalysts used for the first high-temperature catalytic cracking and the second high-temperature catalytic cracking in steps C and D are Fe2O3 and a metal catalyst composed mainly of Fe2O3 and Ru, wherein Ru accounts for 4% of the total mass of the catalyst.

17. Application of the ammonia combustion driven ammonia cracking hydrogen production system in a cascade cracking process according to any one of claims 11 or 16, characterized in that The temperature of the first high-temperature catalytic cracking and the second high-temperature catalytic cracking in steps C and D is 400° C. to 750° C., and the pressure is 100 kPa to 1000 kPa.

18. Application of the ammonia combustion driven ammonia cracking hydrogen production system in a cascade cracking process according to claim 11, characterized in that In the step D, the first cracked gas output from the first cracker (10) is cooled through the second hot end of the intermediate heat exchanger (8) and the cooler (1).

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