Molten Salt Tower Type Solar Hydrogen Production System by Ammonia Decomposition and Its Process

Abstract

The present invention discloses a molten salt tower solar ammonia decomposition hydrogen production system and process thereof, belonging to the technical field of ammonia decomposition hydrogen production. The system includes a solar heat absorption system, a molten salt heat storage system, a molten salt reheating system, an ammonia reaction generation system, and a molten salt storage system; the solar heat absorption system, the molten salt heat storage system, the molten salt reheating system, and the ammonia reaction generation system are connected in sequence via a hot salt pipeline, and the ammonia reaction generation system, the molten salt storage system, and the solar heat absorption system are connected via a cold salt pipeline. The present invention converts solar energy into thermal energy, heats the molten salt, and then transfers the heat of the molten salt to ammonia to decompose the ammonia to produce hydrogen. The heat storage system of the present invention can maintain the system for 24 hours of stable operation, which is conducive to the efficient use of solar energy. With the repeated use of molten salt, the material loss efficiency during operation can be greatly reduced, making the economic cost lower than the existing water electrolysis hydrogen production, while having the advantages of being more efficient and more environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of ammonia decomposition hydrogen production, and in particular relates to a molten salt tower solar ammonia decomposition hydrogen production system and a process thereof. Background Art

[0002] Since the beginning of the Industrial Revolution, the development and utilization of traditional fossil energy has reached a very mature stage. Large-scale mining and utilization has not only led to resource shortages but also caused environmental pollution and damage. In recent years, the research and development of hydrogen has been ongoing, and countries around the world have given a certain degree of attention to hydrogen energy research. Hydrogen in nature is mostly composed of hydrogen atoms, and hydrogen is extremely rare. Therefore, the development and utilization of hydrogen can only begin with hydrogen production, which is artificially produced.

[0003] Currently, most hydrogen production processes utilize water electrolysis. A more novel approach utilizes wind or solar power to produce hydrogen. This is primarily due to the "wind and power curtailment" phenomenon in the wind and solar power generation industries. Water electrolysis can effectively address this issue. However, this method requires specialized materials such as electrolytes and is also subject to the intermittent nature of wind and solar power, resulting in suboptimal hydrogen production. Ammonia decomposition hydrogen production, on the other hand, theoretically enables 24 / 7 hydrogen production. Using molten salt tower technology, molten salt is used to store solar energy and store it in a hot salt tank. The hot salt tank also utilizes insulation technology to maintain a relatively stable temperature, minimizing energy losses. During the day, the molten salt absorbs heat and performs its work, while a reserve molten salt flows into the hot salt tank to release heat at night.

[0004] Using the reversible thermochemical reaction 2NH3+ΔH 3H2+N2, energy is stored through the conversion of thermal energy and chemical energy. The NH3 system energy storage has the advantages of high density, easy to control reversible reaction without side reactions, mature technology, reliable application, simple storage and separation, making it the preferred thermochemical energy storage material for solar thermal power generation. Experimental research on the use of ammonia decomposition reaction as solar thermal storage power generation has been carried out abroad, and its efficiency is mostly above 0.6. Therefore, this system has certain practical prospects. Summary of the Invention

[0005] In view of the above situation, the object of the present invention is to provide a molten salt tower solar ammonia decomposition hydrogen production system and process.

[0006] In order to achieve the above objectives, the following technical solutions are proposed:

[0007] A molten salt tower solar ammonia decomposition hydrogen production system includes a solar heat absorption system, a molten salt heat storage system, a molten salt reheating system, an ammonia reaction generation system and a molten salt storage system; the solar heat absorption system, the molten salt heat storage system, the molten salt reheating system and the ammonia reaction generation system are connected in sequence through a hot salt pipeline, and the ammonia reaction generation system, the molten salt storage system and the solar heat absorption system are connected through a cold salt pipeline.

[0008] Furthermore, the molten salt reheating system includes a superheater and a reheater, the hot salt pipeline is divided into two pipelines connected to the inlets of the superheater and reheater respectively, and the outlets of the superheater and reheater are merged into one pipeline and connected to the ammonia reaction system.

[0009] Furthermore, the ammonia reaction generation system includes an ammonia decomposition reactor, an ammonia storage tank, a hydrogen storage tank and a nitrogen storage tank. The outlets of the superheater and the reheater are merged into a pipeline and connected to the inlet of the internal channel of the ammonia decomposition reactor. The external channel of the ammonia decomposition reactor is connected to the ammonia storage tank, the hydrogen storage tank and the nitrogen storage tank respectively through a gas pipeline. The outlet of the internal channel of the ammonia decomposition reactor is connected to the molten salt storage system through a cold salt pipeline.

[0010] Furthermore, the molten salt storage system includes a cold salt tank and a cold salt pump, the outlet of the internal channel of the ammonia decomposition reactor is connected to the cold salt tank through a cold salt pipe, the cold salt tank is connected to the cold salt pump, and the cold salt pump is connected to the solar heat absorption system through the cold salt pipe.

[0011] Furthermore, the solar heat absorption system includes a heliostat field, a heat absorption tube and a heat absorption tower. The heliostat field absorbs solar energy to the heat absorption tube, the heat absorption tube is arranged on the heat absorption tower, the cold salt pump is connected to the heat absorption tube through a cold salt pipeline, and the heat absorption tube is connected to the molten salt heat storage system through a hot salt pipeline.

[0012] Furthermore, the molten salt heat storage system includes a hot salt tank and a hot salt pump, the heat absorption pipe is connected to the hot salt tank through a hot salt pipeline, the hot salt tank is connected to the hot salt pump, and the outlet of the hot salt pump is connected to the inlet of the superheater and the reheater respectively.

[0013] A molten salt tower solar ammonia decomposition hydrogen production process specifically comprises the following steps:

[0014] 1) The heliostat field reflects sunlight onto the heat absorbing tubes, where the molten salt absorbs the heat. After heating, the hot molten salt flows from the heat absorbing tubes along the hot salt pipeline into the hot salt tank for storage and insulation.

[0015] 2) The hot salt pump extracts the molten salt from the hot salt tank, and the molten salt enters the superheater and reheater through the hot salt pipeline, where the molten salt is heated again to further increase its temperature.

[0016] 3) The high-temperature molten salt flowing out of the superheater and reheater enters the internal channel of the ammonia decomposition reactor through the hot salt pipeline, providing temperature conditions for the ammonia decomposition and hydrogen production process;

[0017] 4) Ammonia flows from the ammonia storage tank into the external channel of the ammonia decomposition reactor for decomposition, producing H2 and N2 gases, which then enter the hydrogen storage tank and nitrogen storage tank respectively. After heat exchange, the temperature of the molten salt will drop to a cold salt state, and it will enter the cold salt tank through the cold salt pipeline for storage. When there is sunlight, the cold molten salt will be pumped into the heat absorption tube on the heat absorption tower through the cold salt pipeline by the cold salt pump. This cycle is repeated to continuously provide heat for ammonia decomposition.

[0018] Furthermore, the temperature of the hot molten salt in the hot salt tank is 540-560°C, and the temperature of the high-temperature molten salt flowing out of the superheater and the reheater is above 600°C.

[0019] Furthermore, ammonia flows from the ammonia storage tank into the external channel of the ammonia decomposition reactor for decomposition, producing H2 and N2 gases, which are purified through membrane separation and then enter the hydrogen storage tank and nitrogen storage tank respectively.

[0020] Furthermore, the temperature of the molten salt in the cold salt tank (12) is 220-240°C.

[0021] This system primarily utilizes binary molten salt, composed of 60% NaNO3 and 40% KNO3 by mass, commonly known as solar salt. This salt has a maximum temperature resistance of 620°C, and its actual operating temperature is 260-565°C.

[0022] The beneficial results of the present invention are:

[0023] 1. A molten salt tower solar ammonia decomposition hydrogen production system based on solar thermal storage. Due to the intermittent nature of solar energy, the thermal storage system can maintain 24-hour stable operation of the system, which is conducive to the efficient use of solar energy.

[0024] 2. The amino system has abundant and cheap raw materials, can provide energy continuously around the clock, has high energy storage density, easy-to-control reversible reactions without side reactions, mature technology, reliable application, and simple storage and separation.

[0025] 3. The molten salt tower ammonia decomposition hydrogen production system based on solar thermal storage can greatly reduce the material loss efficiency during operation with the help of repeated use of molten salt, making the economic cost lower than the existing water electrolysis hydrogen production. At the same time, it has the advantages of being more efficient and more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a system flow chart of the present invention;

[0027] In the figure: 1—heliostat field; 2—heat absorption pipe; 3—heat absorption tower; 4—hot salt pipeline; 5—superheater; 6—reheater; 7—ammonia decomposition reactor; 8—ammonia storage tank; 9—gas pipeline; 10—hydrogen storage tank; 11—nitrogen storage tank; 12—cold salt tank; 13—cold salt pump; 14—hot salt tank; 15—hot salt pump; 16—cold salt pipeline. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention is not limited thereto.

[0029] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0030] like Figure 1 As shown, the molten salt tower solar ammonia decomposition hydrogen production system includes a heliostat field 1, a heat absorption pipe 2, a heat absorption tower 3, a superheater 5, a reheater 6, an ammonia decomposition reactor 7, an ammonia storage tank 8, a hydrogen storage tank 10, a nitrogen storage tank 11, a cold salt tank 12, a cold salt pump 13, a hot salt tank 14 and a hot salt pump 15. The heliostat field 1 absorbs sunlight to the heat absorption pipe 2, which is arranged on the heat absorption tower 3. The heat absorption pipe 2 is connected to the hot salt tank 14 through a hot salt pipeline 4. The hot salt tank 14 is connected to the hot salt pump 15. The hot salt pipeline 4 at the outlet of the hot salt pump 15 is divided into two pipelines. They are respectively connected to the inlets of the superheater 5 and the reheater 6. The outlets of the superheater 5 and the reheater 6 merge into one and are connected to the inlet of the internal pipeline of the ammonia decomposition reactor 7. The ammonia storage tank 8, the hydrogen storage tank 10 and the nitrogen storage tank 11 are connected to the external pipeline of the ammonia decomposition reactor 7 through the gas pipeline 9. The outlet of the internal pipeline of the ammonia decomposition reactor 7 is connected to the inlet of the cold salt tank 12 through the cold salt pipeline 16. The outlet of the cold salt tank 12 is connected to the cold salt pump 13. The cold salt pump 13 is connected to the heat absorption pipe 2 through the cold salt pipeline 16 to complete the connection of the circulation loop.

[0031] Sunlight shines down from the sky, and after being reflected by the heliostat field 1, the light will be reflected into the heat absorption tube 2. The molten salt in the heat absorption tube 2 will absorb heat, and the molten salt will be heated from about 220℃ to above 550℃. After the heating is completed, the hot molten salt will flow from the heat absorption tube 2 to the hot salt pipe 4. The molten salt in the hot salt pipe 4 will flow into the hot salt tank 14 for storage and insulation. The molten salt temperature will be maintained at about 550℃. The hot molten salt is extracted from the hot salt tank 14 by using the hot salt pump 15. The molten salt is taken out from the hot salt tank 14, and then the molten salt is transported to the molten salt reheating system by means of the hot salt pipeline 4. The molten salt enters the superheater 5 and the reheater 6 respectively through the hot salt pipeline 4. The two heaters reheat the molten salt to further increase the temperature of the molten salt. That is, after the molten salt coming out of the superheater 5 and the reheater 6 is coupled, the temperature will be increased from about 550°C to above 600°C, which is more in line with the conditions for ammonia decomposition and hydrogen production, and will also improve the reaction rate and working efficiency of the entire system. The high-temperature molten salt flowing out of the superheater 5 and the reheater 6 enters the internal channel of the ammonia decomposition reactor 7 through the hot salt pipeline 4, providing temperature conditions for the ammonia decomposition and hydrogen production process. Then, ammonia flows from the ammonia storage tank 8 into the external channel of the ammonia decomposition reactor 7 for decomposition, and will proceed according to the reaction of 2NH3+DH——N2+3H2 to obtain two gases, H2 and N2. Due to the difference in properties, the generated N2 and H2 will not fuse after production, and then the N2 will be separated by membrane. After being screened and separated from the H2, the molten salt enters the hydrogen storage tank 10 and the nitrogen storage tank 11. After heat exchange, the molten salt cools to a cold salt state and enters the cold salt tank 12 through the cold salt pipeline 16 for storage. When sunlight arrives, the cold molten salt is pumped through the cold salt pipeline 16 by the cold salt pump 13 into the heat absorption tube 2 on the heat absorption tower 3. After being reflected by the heliostat field 1, the sunlight is concentrated in the heat absorption tube 2, where the cold molten salt absorbs heat again, raising its temperature to become hot molten salt. The hot molten salt then passes through the hot salt pipeline 4 for subsequent processes, completing the cycle over and over again, continuously providing heat for ammonia decomposition.

Claims

1. A hydrogen production process using a molten salt tower solar ammonia decomposition hydrogen production system, characterized in that: The molten salt tower solar ammonia decomposition hydrogen production system comprises a solar heat absorption system, a molten salt heat storage system, a molten salt reheating system, an ammonia reaction generation system and a molten salt storage system; the solar heat absorption system, the molten salt heat storage system, the molten salt reheating system and the ammonia reaction generation system are connected in sequence through a hot salt pipeline (4), and the ammonia reaction generation system, the molten salt storage system and the solar heat absorption system are connected through a cold salt pipeline (16); The molten salt reheating system includes a superheater (5) and a reheater (6), the hot salt pipeline (4) is divided into two pipelines connected to the inlets of the superheater (5) and the reheater (6) respectively, and the outlets of the superheater (5) and the reheater (6) are combined into one pipeline and connected to the ammonia reaction system; The ammonia reaction generating system comprises an ammonia decomposition reactor (7), an ammonia storage tank (8), a hydrogen storage tank (10) and a nitrogen storage tank (11); the outlets of the superheater (5) and the reheater (6) are connected to the inlet of the internal channel of the ammonia decomposition reactor (7) after being merged into a pipeline; the external channel of the ammonia decomposition reactor (7) is connected to the ammonia storage tank (8), the hydrogen storage tank (10) and the nitrogen storage tank (11) respectively through a gas pipeline (9); and the outlet of the internal channel of the ammonia decomposition reactor (7) is connected to the molten salt storage system through a cold salt pipeline (16); The molten salt storage system includes a cold salt tank (12) and a cold salt pump (13), the outlet of the internal channel of the ammonia decomposition reactor (7) is connected to the cold salt tank (12) through a cold salt pipe (16), the cold salt tank (12) is connected to the cold salt pump (13), and the cold salt pump (13) is connected to the solar heat absorption system through the cold salt pipe (16); The solar heat absorption system comprises a heliostat field (1), a heat absorption pipe (2) and a heat absorption tower (3); the heliostat field (1) absorbs solar energy and supplies it to the heat absorption pipe (2); the heat absorption pipe (2) is arranged on the heat absorption tower (3); a cold salt pump (13) is connected to the heat absorption pipe (2) through a cold salt pipeline (16); and the heat absorption pipe (2) is connected to a molten salt heat storage system through a hot salt pipeline (4); The molten salt heat storage system includes a hot salt tank (14) and a hot salt pump (15), the heat absorption pipe (2) is connected to the hot salt tank (14) through the hot salt pipeline (4), the hot salt tank (14) is connected to the hot salt pump (15), and the outlet of the hot salt pump (15) is connected to the inlet of the superheater (5) and the inlet of the reheater (6); The hydrogen production process using the molten salt tower solar ammonia decomposition hydrogen production system specifically includes the following steps: 1) The heliostat field (1) reflects sunlight into the heat absorbing tube (2), and the molten salt in the heat absorbing tube (2) absorbs heat. After the heating is completed, the hot molten salt flows from the heat absorbing tube (2) along the hot salt pipeline (4) into the hot salt tank (14) for storage and heat preservation; 2) The hot salt pump (15) extracts the hot molten salt from the hot salt tank (14), and the molten salt enters the superheater (5) and the reheater (6) through the hot salt pipe (4) to heat the molten salt again and further increase the temperature of the molten salt; 3) The high-temperature molten salt flowing out of the superheater (5) and the reheater (6) enters the internal channel of the ammonia decomposition reactor (7) through the hot salt pipeline (4), providing temperature conditions for the ammonia decomposition hydrogen production process; 4) Ammonia flows from the ammonia storage tank (8) into the external channel of the ammonia decomposition reactor (7) for decomposition, producing H2 and N2 gases, which then enter the hydrogen storage tank (10) and the nitrogen storage tank (11) respectively. After heat exchange, the molten salt temperature drops to a cold salt state, and enters the cold salt tank (12) through the cold salt pipe (16) for storage. When there is sunlight, the cold molten salt is pumped through the cold salt pipe (16) by the cold salt pump (13) into the heat absorption pipe (2) on the heat absorption tower (3). This cycle is repeated to continuously provide heat for ammonia decomposition; The temperature of the hot molten salt in the hot salt tank (14) is 540-560°C, and the temperature of the high-temperature molten salt flowing out of the superheater (5) and the reheater (6) is above 600°C.

2. A hydrogen production process using a molten salt tower solar ammonia decomposition hydrogen production system according to claim 1, characterized in that: Ammonia flows from the ammonia storage tank (8) into the external channel of the ammonia decomposition reactor (7) for decomposition, producing two gases, H2 and N2, which are purified through membrane separation and then enter the hydrogen storage tank (10) and nitrogen storage tank (11) respectively.

3. The hydrogen production process using a molten salt tower solar ammonia decomposition hydrogen production system according to claim 1, characterized in that: The temperature of the molten salt in the cold salt tank (12) is 220~240℃.

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