Hydrogen liquefaction system and hydrogen liquefaction process

Abstract

This invention discloses a hydrogen liquefaction system powered by photovoltaic and wind power generation. The system includes: an electrolytic hydrogen production unit, a first cold box, a second cold box, and a third cold box. The hydrogen outlet of the electrolytic hydrogen production unit is connected to the inlet of a cooler, a compressor, and a hydrogen storage tank via a first pipeline. The hydrogen output from the hydrogen storage tank is cooled by the first, second, and third cold boxes and then stored in a liquid hydrogen storage tank. The system includes a propane circulation loop providing cooling for the first cold box, cooler, and compressor; a liquid nitrogen circulation loop providing cooling for the first and second cold boxes; and a low-temperature hydrogen circulation loop providing cooling for the first, second, and third cold boxes. This invention also discloses a hydrogen liquefaction process. This system uses solar and wind power to produce hydrogen energy and achieves energy storage through methods such as reservoir water storage and increasing the capacity of the hydrogen storage tank, overcoming the volatility of renewable energy sources and ensuring the normal and stable operation of the hydrogen liquefaction system.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy production technology, and in particular to a hydrogen liquefaction system and hydrogen liquefaction process. Background Technology

[0002] Hydrogen energy is classified into three categories based on its production source: gray hydrogen, blue hydrogen, and green hydrogen.

[0003] Gray hydrogen is primarily produced through the combustion of fossil fuels (such as oil, natural gas, and coal). Gray hydrogen has lower production costs, simpler production technology, and requires less equipment and space. However, its production scale is smaller, and it generates emissions such as carbon dioxide during the production process. Currently, the vast majority of hydrogen on the market is gray hydrogen, accounting for approximately 95% of global hydrogen production.

[0004] Blue hydrogen is produced by reforming natural gas through steam methane reforming or autothermal steam reforming. Natural gas is a fossil fuel, and greenhouse gases are generated during the production of blue hydrogen. However, thanks to the use of advanced technologies such as carbon capture, utilization, and storage (CCUS), the greenhouse gases are captured, reducing the impact on the Earth's environment and achieving low-carbon, low-emission hydrogen production.

[0005] Green hydrogen is hydrogen produced using renewable energy sources such as solar, wind, and nuclear power. For example, hydrogen is produced by electrolyzing water through renewable energy power generation. There are no carbon emissions during the production of green hydrogen, and only water vapor is produced during its use. Therefore, green hydrogen is considered to be the most environmentally friendly type of hydrogen.

[0006] In summary, although hydrogen energy is a clean and renewable energy source with no carbon emissions during energy release, current hydrogen production primarily uses grey hydrogen, making it not 100% carbon-free. The future trend for hydrogen energy is towards low-carbon and carbon-free production, transitioning from grey hydrogen to blue hydrogen, and ultimately achieving green hydrogen.

[0007] The development of the blue-green hydrogen industry faces a series of challenges: technical difficulties (such as how to overcome the volatility of renewable energy), high costs, etc. At present, the blue-green hydrogen industry does not have a relatively complete hydrogen liquefaction system and corresponding hydrogen liquefaction process. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a hydrogen liquefaction system that uses solar and wind power to produce hydrogen energy, and a hydrogen liquefaction process based on the hydrogen liquefaction system.

[0009] The technical solution of this invention is as follows: the hydrogen liquefaction system includes: an electrolytic hydrogen production device, a first cold box, a second cold box, and a third cold box; the first cold box has a first hydrogen liquefaction pipeline, a first propane circulation pipeline, a second propane circulation pipeline, a first liquid nitrogen circulation pipeline, a second liquid nitrogen circulation pipeline, a first hydrogen circulation pipeline, and a second hydrogen circulation pipeline; the second cold box has a second hydrogen liquefaction pipeline, a third liquid nitrogen circulation pipeline, a fourth liquid nitrogen circulation pipeline, a third hydrogen circulation pipeline, and a fourth hydrogen circulation pipeline; the third cold box has a third hydrogen liquefaction pipeline, a fifth hydrogen circulation pipeline, and a sixth hydrogen circulation pipeline.

[0010] The hydrogen outlet of the electrolytic hydrogen production equipment is connected in sequence to the inlet of the cooler, the compressor, and the hydrogen storage tank via a first pipeline; the outlet of the hydrogen storage tank is connected in sequence to the inlet of the first hydrogen liquefaction pipeline, the second hydrogen liquefaction pipeline, the third hydrogen liquefaction pipeline, and the liquid hydrogen storage tank via a second pipeline.

[0011] The outlet of the propane storage tank is connected in sequence to the first propane circulation pipeline, the compressor cooling pipeline, the cooler cooling pipeline, the second propane circulation pipeline, the propane refrigerator, and the inlet of the propane storage tank through the third pipeline, forming a propane circulation loop;

[0012] The outlet of the liquid nitrogen storage tank is connected in sequence to the third liquid nitrogen circulation pipeline, the first liquid nitrogen circulation pipeline, the nitrogen compressor, the second liquid nitrogen circulation pipeline, the fourth liquid nitrogen circulation pipeline, the liquid nitrogen expander, and the inlet of the liquid nitrogen storage tank through the fourth pipeline, forming a liquid nitrogen circulation loop; one end of the first branch pipeline is connected to the fourth pipeline at the outlet of the liquid nitrogen expander, and the other end of the first branch pipeline is connected to the fourth pipeline at the inlet of the liquid nitrogen expander, and a first circulation switch is installed on the first branch pipeline;

[0013] The outlet of the cryogenic hydrogen storage tank is connected in sequence to the fifth hydrogen circulation pipeline, the third hydrogen circulation pipeline, the first hydrogen circulation pipeline, the hydrogen compressor, the second hydrogen circulation pipeline, the fourth hydrogen circulation pipeline, the sixth hydrogen circulation pipeline, the hydrogen expander, and the inlet of the cryogenic hydrogen storage tank through the fifth pipeline, forming a cryogenic hydrogen circulation loop; one end of the second branch pipeline is connected to the fifth pipeline at the outlet of the hydrogen expander, and the other end of the second branch pipeline is connected to the fifth pipeline at the inlet of the hydrogen expander. A second circulation switch is installed on the second branch pipeline.

[0014] The liquid hydrogen storage tank's gas outlet is connected to the fifth pipeline between the third cold box and the cryogenic hydrogen storage tank via the sixth pipeline; the power supply for the hydrogen liquefaction system comes from photovoltaic power generation and wind power generation.

[0015] Furthermore, in the aforementioned hydrogen liquefaction system, to overcome the volatility of renewable energy, the following measures are adopted: a seventh pipeline is connected to the outlet of the hydrogen storage tank, and the seventh pipeline is connected to the hydrogen inlet of the hydrogen fuel cell; the electrical energy generated by the hydrogen fuel cell is supplied to the hydrogen liquefaction system through grid connection and / or by the hydrogen grid.

[0016] Furthermore, in the aforementioned hydrogen liquefaction system, to overcome the volatility of renewable energy, the following measures can also be adopted: a reservoir capable of hydroelectric power generation and a pump to draw water from the water source into the reservoir are also provided. The inlet of the electrolytic hydrogen production equipment is connected to the outlet of the reservoir through an eighth pipeline. The power supply for the pump comes from photovoltaic power generation and wind power generation. The electricity generated by the hydroelectric power generation in the reservoir is supplied to the hydrogen liquefaction system and / or connected to the grid.

[0017] Furthermore, in the aforementioned hydrogen liquefaction system, the first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline; the outlet of the pump is connected in sequence to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline; the outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve; the third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank.

[0018] This invention also includes a hydrogen liquefaction process using the hydrogen liquefaction system described in this application. The power supply for the hydrogen liquefaction system comes from photovoltaic power generation and wind power generation. The hydrogen produced by the electrolytic hydrogen production equipment is cooled by a cooler, compressed by a compressor, and then stored in a hydrogen storage tank. The pressure range of the compressor is 0 to 45 MPa. The hydrogen in the storage tank enters the first hydrogen liquefaction pipeline of the first cold box for the first cooling, then enters the second hydrogen liquefaction pipeline of the second cold box for the second cooling, and then enters the third hydrogen liquefaction pipeline of the third cold box for the third cooling before being stored in a liquid hydrogen storage tank.

[0019] The cryogenic propane in the propane storage tank enters the first cold box through the first propane circulation pipeline, providing cooling capacity to the first cold box. Then, it sequentially enters the cooling pipeline of the compressor and the cooling pipeline of the cooler, providing cooling capacity to the compressor and cooler. After that, it enters the first cold box through the second propane circulation pipeline for cooling before entering the propane refrigeration machine. The cryogenic propane obtained by the propane refrigeration machine returns to the propane storage tank. The cryogenic propane circulates along the above path. The temperature range of the cryogenic propane obtained by the propane refrigeration machine is -20℃ to -42℃.

[0020] When the first circulation switch is closed, the liquid nitrogen in the liquid nitrogen storage tank enters the second cold box through the third liquid nitrogen circulation pipeline, providing cooling capacity to the second cold box. Then, it enters the first cold box through the first liquid nitrogen circulation pipeline, providing cooling capacity to the first cold box, and then enters the nitrogen compressor. The pressure range of the nitrogen compressor is 0-10 MPa. Then, it enters the first cold box through the second liquid nitrogen circulation pipeline for the first cooling, and then enters the second cold box through the fourth liquid nitrogen circulation pipeline for the second cooling. Finally, it returns to the liquid nitrogen storage tank after passing through the liquid nitrogen expander. The liquid nitrogen circulates along the above path. The inlet temperature of the liquid nitrogen expander is -120℃ to -150℃, and the temperature of the liquid nitrogen returning to the liquid nitrogen storage tank is -195℃.

[0021] When the second circulation switch is closed, the cryogenic hydrogen in the cryogenic hydrogen storage tank and the BOG gas in the liquid hydrogen storage tank enter the third cold box through the fifth hydrogen circulation pipeline, providing cooling for the third cold box. Then, it enters the second cold box through the third hydrogen circulation pipeline, providing cooling for the second cold box. Next, it enters the first cold box through the first hydrogen circulation pipeline, providing cooling for the first cold box, and then enters the hydrogen compressor. The pressure range of the hydrogen compressor is 0 to 5 MPa. Then, it enters the first cold box through the second hydrogen circulation pipeline for the first cooling, then through the fourth hydrogen circulation pipeline for the second cooling, then through the sixth hydrogen circulation pipeline for the third cooling, and finally returns to the cryogenic hydrogen storage tank after passing through the hydrogen expander. The cryogenic hydrogen circulates along the above path. The inlet temperature of the hydrogen expander is -210℃ to -230℃, and the temperature of the cryogenic hydrogen returning to the cryogenic hydrogen storage tank is -253℃.

[0022] When the hydrogen liquefaction system is in standby mode, turn on the first and second circulation switches to shut down the liquid nitrogen expander and the hydrogen expander.

[0023] Furthermore, in the aforementioned hydrogen liquefaction process, to overcome the volatility of renewable energy, the following measures are adopted: the hydrogen liquefaction system also includes a reservoir capable of hydroelectric power generation and a pump to draw water from the water source into the reservoir. The power supply for the pump comes from photovoltaic and wind power generation. The inlet of the electrolytic hydrogen production equipment is connected to the outlet of the reservoir through an eighth pipeline, and the water in the reservoir provides a water source for the electrolytic hydrogen production equipment. During periods of abundant sunshine and wind, the surplus electricity generated during the normal operation of the hydrogen liquefaction system is directly connected to the grid and / or supplied to the pump. The water stored in the reservoir can generate hydroelectric power when the power supply to the hydrogen liquefaction system is insufficient, supplying power to the hydrogen liquefaction system and ensuring its normal operation.

[0024] Furthermore, in the aforementioned hydrogen liquefaction process, to overcome the volatility of renewable energy, the following measures can also be adopted: a seventh pipeline is connected to the outlet of the hydrogen storage tank, and the seventh pipeline is connected to the hydrogen inlet of the hydrogen fuel cell; the electricity generated by the hydrogen fuel cell is connected to the grid and / or supplied to the hydrogen liquefaction system; during periods of abundant sunshine and wind, the hydrogen storage capacity of the hydrogen storage tank is increased, the storage capacity of the liquid nitrogen storage tank is increased, and the rest of the hydrogen liquefaction system operates at full load; when the hydrogen liquefaction system is in a state of no power supply or insufficient power supply, the electricity generated by the hydrogen fuel cell is supplied to the hydrogen liquefaction system, and the surplus electricity after supplying the hydrogen liquefaction system is directly connected to the grid.

[0025] Furthermore, in the aforementioned hydrogen liquefaction process, the first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline; the outlet of the pump is connected sequentially to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline; the outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve; the third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank; outside air enters the first cold box through the pump, air filter, and first air separation pipeline for the first cooling, and then enters the second cold box through the second air separation pipeline for the second cooling, to obtain a gas-liquid mixture containing liquid oxygen and liquid nitrogen, which is stored in the air separation product collection tank and / or the liquid nitrogen storage tank.

[0026] The beneficial effects of this invention are: it develops a hydrogen liquefaction system that uses renewable energy sources—solar and wind power—to produce hydrogen energy; when solar and wind power generation is excessive or abundant, energy storage is achieved through methods such as reservoir water storage and increasing the capacity of hydrogen storage tanks; when solar and wind power generation is insufficient or nonexistent, electricity can be generated through reservoir hydropower and hydrogen fuel cells to supply the hydrogen liquefaction system, thereby overcoming the volatility of renewable energy sources, ensuring the normal and stable operation of the hydrogen liquefaction system, and improving the efficiency of the hydrogen liquefaction system. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the hydrogen liquefaction system described in this invention.

[0028] Figure 2 yes Figure 1 A magnified view of a section of the first cold box.

[0029] Figure 3 yes Figure 1 A magnified view of a portion of the second cold box section.

[0030] Figure 4 yes Figure 1 A magnified view of a portion of the third cold box section. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. Example 1

[0032] The hydrogen liquefaction system described in this invention, such as Figure 1 As shown, it includes: an electrolytic hydrogen production device, a first cold box 1, a second cold box 2, and a third cold box 3.

[0033] The first cold box 1 includes a first hydrogen liquefaction pipeline 12, a first propane circulation pipeline 17, a second propane circulation pipeline 18, a first liquid nitrogen circulation pipeline 15, a second liquid nitrogen circulation pipeline 16, a first hydrogen circulation pipeline 13, and a second hydrogen circulation pipeline 14, as follows: Figure 2 As shown.

[0034] The second cold box 2 includes a second hydrogen liquefaction pipeline 22, a third liquid nitrogen circulation pipeline 25, a fourth liquid nitrogen circulation pipeline 26, a third hydrogen circulation pipeline 23, and a fourth hydrogen circulation pipeline 24, as follows: Figure 3 As shown.

[0035] The third cold box 3 contains a third hydrogen liquefaction pipeline 31, a fifth hydrogen circulation pipeline 32, and a sixth hydrogen circulation pipeline 33, such as... Figure 4 As shown.

[0036] like Figure 1 As shown, the hydrogen outlet of the electrolytic hydrogen production equipment is connected sequentially to the inlet of the cooler, compressor, and hydrogen storage tank via the first pipeline 4; the outlet of the hydrogen storage tank is connected sequentially to the inlet of the first hydrogen liquefaction pipeline 12, the second hydrogen liquefaction pipeline 22, the third hydrogen liquefaction pipeline 31, and the liquid hydrogen storage tank via the second pipeline 5. At this time, the hydrogen produced by the electrolytic hydrogen production equipment is sequentially cooled by the cooler, compressed by the compressor, and then stored in the hydrogen storage tank. The hydrogen in the storage tank is then sequentially cooled by the first cold box 1, the second cold box 2, and the third cold box 3, becoming liquid hydrogen, which is then stored in the liquid hydrogen storage tank.

[0037] In this embodiment, a propane circulation loop provides cooling capacity to the first cold box 1, the compressor, and the cooler, such as... Figure 1 and Figure 2 As shown, the outlet of the propane storage tank is connected sequentially to the first propane circulation pipeline 17, the compressor cooling pipeline, the cooler cooling pipeline, the second propane circulation pipeline 18, the propane refrigerator, and the inlet of the propane storage tank via the third pipeline 6, forming a propane circulation loop. The propane, having provided its cooling capacity, first enters the first cold box 1 for cooling before entering the propane refrigerator. This is to lower the temperature of the propane and allow the propane refrigerator to operate more effectively.

[0038] In this embodiment, a liquid nitrogen circulation loop provides cooling for the first cold box 1 and the second cold box 2, such as... Figure 1 and Figure 3 As shown, the outlet of the liquid nitrogen storage tank is connected in sequence to the third liquid nitrogen circulation pipeline 25, the first liquid nitrogen circulation pipeline 15, the nitrogen compressor, the second liquid nitrogen circulation pipeline 16, the fourth liquid nitrogen circulation pipeline 26, the liquid nitrogen expander, and the inlet of the liquid nitrogen storage tank through the fourth pipeline 7, forming a liquid nitrogen circulation loop; one end of the first branch pipeline is connected to the fourth pipeline at the outlet of the liquid nitrogen expander, and the other end of the first branch pipeline is connected to the fourth pipeline at the inlet of the liquid nitrogen expander. A first circulation switch is installed on the first branch pipeline; when the hydrogen liquefaction system is operating normally, the first circulation switch is in the normally closed state.

[0039] Before entering the nitrogen expander, the liquid nitrogen that has been supplied with cooling capacity first enters the first cold box 1 for cooling, and then enters the second cold box 2 for cooling. The purpose is to reduce the temperature of the liquid nitrogen so that the nitrogen expander can operate better.

[0040] In this embodiment, a low-temperature hydrogen circulation loop provides cooling for the first cold box 1, the second cold box 2, and the third cold box 3. Figure 1 and Figure 4 As shown, the outlet of the cryogenic hydrogen storage tank is connected in sequence via the fifth pipeline 8 to the fifth hydrogen circulation pipeline 32, the third hydrogen circulation pipeline 23, the first hydrogen circulation pipeline 13, the hydrogen compressor, the second hydrogen circulation pipeline 14, the fourth hydrogen circulation pipeline 24, the sixth hydrogen circulation pipeline 33, the hydrogen expander, and the inlet of the cryogenic hydrogen storage tank, forming a cryogenic hydrogen circulation loop; one end of the second branch pipeline is connected to the fifth pipeline at the outlet of the hydrogen expander, and the other end of the second branch pipeline is connected to the fifth pipeline at the inlet of the hydrogen expander. A second circulation switch is installed on the second branch pipeline; when the hydrogen liquefaction system is operating normally, the second circulation switch is in the normally closed state.

[0041] Before entering the hydrogen expander, the cryogenic hydrogen, after being supplied with cooling capacity, first enters the first cold box 1 for cooling, then enters the second cold box 2 for cooling, and then enters the third cold box 3 for cooling. The purpose is to reduce the temperature of the cryogenic hydrogen so that the expander can operate better.

[0042] The outlet of the liquid hydrogen storage tank is connected to the fifth pipeline 8 between the third cold box 3 and the cryogenic hydrogen storage tank via the sixth pipeline 9. At this time, the gas in the liquid hydrogen storage tank can be combined with the cryogenic hydrogen output from the cryogenic hydrogen storage tank to provide cooling energy for the third cold box 3, the second cold box 2, and the first cold box 1.

[0043] The power supply for the hydrogen liquefaction system described in this invention comes from photovoltaic power generation and wind power generation.

[0044] To overcome the volatility of renewable energy, the present invention also incorporates the following design:

[0045] Firstly, a seventh pipeline 10 is connected to the outlet of the hydrogen storage tank, and this pipeline 10 is connected to the hydrogen inlet of the hydrogen fuel cell. The electricity generated by the hydrogen fuel cell is connected to the grid and / or supplied to the hydrogen liquefaction system. During periods of abundant sunshine and wind, after wind and solar power supply to the hydrogen liquefaction system, there may be a surplus of electricity. In this case, the hydrogen storage capacity of the hydrogen storage tank can be increased, and the remaining parts can operate at full load. When electricity is scarce or there is an emergency power shortage, the hydrogen fuel cell can generate electricity to supply the hydrogen liquefaction system, ensuring its normal operation. In addition, any surplus electricity after supplying the liquefaction system can also be connected to the grid.

[0046] Secondly, a reservoir capable of hydroelectric power generation and pumps to draw water from the water source into the reservoir are installed. The inlet of the electrolysis hydrogen production equipment is connected to the outlet of the reservoir via the eighth pipeline 20, providing water for the equipment. During periods of abundant sunshine and wind, after wind and solar power supply the hydrogen liquefaction system, a surplus of electricity will occur. This surplus electricity will power the pumps, enabling water storage in the reservoir. In case of power shortages or emergencies, hydroelectric power can provide electricity to the hydrogen liquefaction system, ensuring its normal operation. Furthermore, the electricity generated by hydroelectric power can be connected to the grid.

[0047] Thirdly: A first air separation pipeline 11 is installed in the first cold box 1, and a second air separation pipeline 21 is installed in the second cold box 2. The outlet of the air extractor is connected sequentially to an air filter, an air compressor, the first air separation pipeline 11, and the second air separation pipeline 21 via a ninth pipeline 30. The outlet of the second air separation pipeline 21 is connected to a third branch pipeline 40 with a first valve and a fourth branch pipeline 50 with a second valve. The third branch pipeline 40 is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline 50 is connected to the inlet of the liquid nitrogen storage tank. By utilizing the cooling capacity of the first cold box 1 and the second cold box 2, compressed air is converted into a gas-liquid mixture containing liquid oxygen and liquid nitrogen. The gas-liquid mixture is stored in the air separation product collection tank and / or the liquid nitrogen storage tank.

[0048] In summary, the hydrogen liquefaction system described above utilizes renewable energy sources—solar and wind power—to produce hydrogen. When solar and wind power generation is abundant or plentiful, energy storage is achieved through methods such as reservoir water storage and increasing hydrogen storage tank capacity. When solar and wind power generation is scarce or nonexistent, electricity can be generated from reservoir hydropower and hydrogen fuel cells to supply the hydrogen liquefaction system. This overcomes the volatility of renewable energy sources, ensures the normal and stable operation of the hydrogen liquefaction system, and improves its efficiency. Example 2

[0049] The hydrogen liquefaction process described in this invention employs a hydrogen liquefaction system according to any of the schemes described in this application. The power supply for the hydrogen liquefaction system comes from photovoltaic power generation and wind power generation. Hydrogen produced by the electrolytic hydrogen production equipment is cooled by a cooler, compressed by a compressor, and then stored in a hydrogen storage tank. The temperature range of the hydrogen after cooling is 20℃-40℃, and the pressure range of the compressor is 0 to 45 MPa. The hydrogen in the storage tank enters the first hydrogen liquefaction pipeline 12 of the first cold box 1 for the first cooling. After the first cooling, the temperature of the hydrogen is between -30℃ and -42℃, and it is in a gaseous state. Then, it enters the second hydrogen liquefaction pipeline 22 of the second cold box 2 for the second cooling. After the second cooling, the temperature of the hydrogen is between -190℃ and -200℃, and it is still in a gaseous state. Then, it enters the third hydrogen liquefaction pipeline 32 of the third cold box 3 for the third cooling. After the third cooling, liquid hydrogen is formed, with a temperature between -252℃ and -253℃, and it is in a liquid state. Finally, it is stored in a liquid hydrogen storage tank.

[0050] The working process of the propane circulation loop that provides cooling capacity to the first cold box 1, compressor, and cooler is as follows: Low-temperature propane from the propane storage tank enters the first cold box 1 via the first propane circulation pipeline 17, providing cooling capacity to the first cold box 1. Then, it sequentially enters the cooling pipelines of the compressor and cooler, providing cooling capacity to the compressor and cooler. Finally, it enters the first cold box 1 via the second propane circulation pipeline 18 for cooling. The cooled propane has a temperature between -10℃ and -20℃, and then enters the propane refrigeration unit. The low-temperature propane obtained by the propane refrigeration unit returns to the propane storage tank. The temperature range of the low-temperature propane obtained by the propane refrigeration unit is -40℃ to -42℃.

[0051] The working process of the liquid nitrogen circulation loop providing cooling capacity to the first cold box 1 and the second cold box 2 is as follows: First, the first circulation switch is closed. Liquid nitrogen in the liquid nitrogen storage tank enters the second cold box 2 through the third liquid nitrogen circulation pipe 25, providing cooling capacity to the second cold box 2. Then, it enters the first cold box 1 through the first liquid nitrogen circulation pipe 15, providing cooling capacity to the first cold box 1 before entering the nitrogen compressor. The pressure range of the nitrogen compressor is 0 to 10 MPa. Then, it enters the first cold box 1 through the second liquid nitrogen circulation pipe 16 for the first cooling. The nitrogen temperature after the first cooling is between -35℃ and -42℃. Then, it enters the second cold box 2 through the fourth liquid nitrogen circulation pipe 26 for the second cooling. The nitrogen temperature after the second cooling is between -120℃ and -150℃. Finally, it returns to the liquid nitrogen storage tank after passing through the liquid nitrogen expander. The inlet temperature of the liquid nitrogen expander is -120℃ to -150℃, and the temperature of the liquid nitrogen returning to the liquid nitrogen storage tank is -195℃.

[0052] The operation of the cryogenic hydrogen circulation loop providing cooling for the first cold box 1, the second cold box 2, and the third cold box 3 is as follows: First, the second circulation switch is closed. The cryogenic hydrogen in the cryogenic hydrogen storage tank and the BOG gas in the liquid hydrogen storage tank enter the third cold box 3 through the fifth hydrogen circulation pipeline 32 to provide cooling for the third cold box 3. Then, it enters the second cold box 2 through the third hydrogen circulation pipeline 23 to provide cooling for the second cold box 2. Then, it enters the first cold box 1 through the first hydrogen circulation pipeline 13 to provide cooling for the first cold box 1, and then enters the hydrogen compressor. The pressure range of the hydrogen compressor is 0 to 5 MPa. Then, it enters the first cold box 1 through the second hydrogen circulation pipeline 14 for the first cooling. After the first cooling, the cryogenic hydrogen temperature is -35℃ to -42℃. Then, it enters the second cold box 2 through the fourth hydrogen circulation pipeline 24 for the second cooling. After the second cooling, the cryogenic hydrogen temperature is -190℃ to -200℃. Then, it enters the third cold box 3 via the sixth hydrogen circulation pipeline 33 for a third cooling. After the third cooling, the temperature of the cryogenic hydrogen is between -210℃ and -230℃. Finally, it returns to the cryogenic hydrogen storage tank after passing through the hydrogen expander. The inlet temperature of the hydrogen expander is -210℃ to -230℃, and the temperature of the cryogenic hydrogen returning to the cryogenic hydrogen storage tank is -253℃.

[0053] When the hydrogen liquefaction system is in standby mode, the first and second circulation switches are turned on, and the liquid nitrogen expander and hydrogen expander are shut down. This can minimize the use of electrical energy and maintain the overall cold energy of the first cold box 1, the second cold box 2, and the third cold box 3, thereby reducing energy loss.

[0054] Due to the volatility of renewable energy sources, in situations where grid power is unavailable, there are four modes of renewable energy power supply, depending on the actual circumstances: surplus power, abundant power, insufficient power, and no power. To overcome the volatility of renewable energy, this invention also incorporates the following design:

[0055] Firstly, a seventh pipeline 10 is connected to the outlet of the hydrogen storage tank, and this pipeline 10 is connected to the hydrogen inlet of the hydrogen fuel cell. The electricity generated by the hydrogen fuel cell is connected to the grid and / or supplied to the hydrogen liquefaction system. During periods of abundant sunshine and wind, after wind and solar power supply the hydrogen liquefaction system, there may be a surplus of electricity. In this case, the hydrogen storage capacity of the hydrogen storage tank can be increased, as can the storage capacity of the liquid nitrogen storage tank, with the remaining parts operating at full load. When electricity is scarce or there is an emergency power shortage, the hydrogen fuel cell can generate electricity to supply the hydrogen liquefaction system, ensuring its normal operation. Furthermore, any surplus electricity supplied to the liquefaction system can also be connected to the grid.

[0056] Secondly, a reservoir capable of hydroelectric power generation and pumps to draw water from the water source into the reservoir are installed. The inlet of the electrolysis hydrogen production equipment is connected to the outlet of the reservoir via the eighth pipeline 20, providing water for the equipment. During periods of abundant sunshine and wind, after wind and solar power supply the hydrogen liquefaction system, a surplus of electricity will occur. This surplus electricity will power the pumps, enabling water storage in the reservoir. In case of power shortages or emergencies, hydroelectric power can provide electricity to the hydrogen liquefaction system, ensuring its normal operation. Furthermore, the electricity generated by hydroelectric power can be connected to the grid.

[0057] Thirdly: A first air separation pipeline 11 is installed in the first cold box 1, and a second air separation pipeline 21 is installed in the second cold box 2. The outlet of the air extractor is connected sequentially to an air filter, an air compressor, the first air separation pipeline 11, and the second air separation pipeline 21 via a ninth pipeline 30. The outlet of the second air separation pipeline 21 is connected to a third branch pipeline 40 with a first valve and a fourth branch pipeline 50 with a second valve. The third branch pipeline 40 is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline 50 is connected to the inlet of the liquid nitrogen storage tank. By utilizing the cooling capacity of the first cold box 1 and the second cold box 2, compressed air is converted into a gas-liquid mixture containing liquid oxygen and liquid nitrogen. The gas-liquid mixture is stored in the air separation product collection tank and / or the liquid nitrogen storage tank.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A hydrogen liquefaction system, including: The electrolytic hydrogen production equipment is characterized by further comprising: a first cold box, a second cold box, and a third cold box; The first cold box has a first hydrogen liquefaction pipeline, a first propane circulation pipeline, a second propane circulation pipeline, a first liquid nitrogen circulation pipeline, a second liquid nitrogen circulation pipeline, a first hydrogen circulation pipeline, and a second hydrogen circulation pipeline; The second cold box contains a second hydrogen liquefaction pipeline, a third liquid nitrogen circulation pipeline, a fourth liquid nitrogen circulation pipeline, a third hydrogen circulation pipeline, and a fourth hydrogen circulation pipeline; The third cold box contains a third hydrogen liquefaction pipeline, a fifth hydrogen circulation pipeline, and a sixth hydrogen circulation pipeline; The hydrogen outlet of the electrolytic hydrogen production equipment is connected in sequence to the inlet of the cooler, the compressor, and the hydrogen storage tank via a first pipeline; the outlet of the hydrogen storage tank is connected in sequence to the inlet of the first hydrogen liquefaction pipeline, the second hydrogen liquefaction pipeline, the third hydrogen liquefaction pipeline, and the liquid hydrogen storage tank via a second pipeline. The outlet of the propane storage tank is connected in sequence to the first propane circulation pipeline, the compressor cooling pipeline, the cooler cooling pipeline, the second propane circulation pipeline, the propane refrigerator, and the inlet of the propane storage tank through the third pipeline, forming a propane circulation loop; The outlet of the liquid nitrogen storage tank is connected in sequence to the third liquid nitrogen circulation pipeline, the first liquid nitrogen circulation pipeline, the nitrogen compressor, the second liquid nitrogen circulation pipeline, the fourth liquid nitrogen circulation pipeline, the liquid nitrogen expander, and the inlet of the liquid nitrogen storage tank through the fourth pipeline, forming a liquid nitrogen circulation loop; one end of the first branch pipeline is connected to the fourth pipeline at the outlet of the liquid nitrogen expander, and the other end of the first branch pipeline is connected to the fourth pipeline at the inlet of the liquid nitrogen expander, and a first circulation switch is installed on the first branch pipeline; The outlet of the cryogenic hydrogen storage tank is connected in sequence to the fifth hydrogen circulation pipeline, the third hydrogen circulation pipeline, the first hydrogen circulation pipeline, the hydrogen compressor, the second hydrogen circulation pipeline, the fourth hydrogen circulation pipeline, the sixth hydrogen circulation pipeline, the hydrogen expander, and the inlet of the cryogenic hydrogen storage tank through the fifth pipeline, forming a cryogenic hydrogen circulation loop; one end of the second branch pipeline is connected to the fifth pipeline at the outlet of the hydrogen expander, and the other end of the second branch pipeline is connected to the fifth pipeline at the inlet of the hydrogen expander. A second circulation switch is installed on the second branch pipeline. The liquid hydrogen storage tank's gas outlet is connected to the fifth pipeline between the third cold box and the cryogenic hydrogen storage tank via the sixth pipeline; the power supply for the hydrogen liquefaction system comes from photovoltaic power generation and wind power generation.

2. The hydrogen liquefaction system according to claim 1, characterized in that: A seventh pipeline is also connected to the outlet of the hydrogen storage tank, and the seventh pipeline is connected to the hydrogen inlet of the hydrogen fuel cell; the electrical energy generated by the hydrogen fuel cell is connected to the power grid and / or supplied to the hydrogen liquefaction system.

3. The hydrogen liquefaction system according to claim 1 or 2, characterized in that: The system also includes a reservoir capable of generating hydroelectric power and a pump to draw water from the water source into the reservoir. The inlet of the electrolytic hydrogen production equipment is connected to the outlet of the reservoir via an eighth pipeline. The pump is powered by photovoltaic and wind power generation. The electricity generated by the hydroelectric power generation in the reservoir is supplied to the hydrogen liquefaction system and / or connected to the grid.

4. The hydrogen liquefaction system according to claim 1 or 2, characterized in that: The first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline. The outlet of the air pump is connected in sequence to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline. The outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve. The third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank.

5. The hydrogen liquefaction system according to claim 3, characterized in that: The first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline. The outlet of the air pump is connected in sequence to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline. The outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve. The third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank.

6. A hydrogen liquefaction process, characterized in that: The hydrogen liquefaction system described in any one of claims 1 to 5 is powered by photovoltaic power generation and wind power generation. The hydrogen produced by the electrolytic hydrogen production equipment is cooled by a cooler, compressed by a compressor, and then stored in a hydrogen storage tank. The pressure range of the compressor is 0-45 MPa. The hydrogen in the storage tank enters the first hydrogen liquefaction pipeline of the first cold box for the first cooling, then enters the second hydrogen liquefaction pipeline of the second cold box for the second cooling, and then enters the third hydrogen liquefaction pipeline of the third cold box for the third cooling before being stored in a liquid hydrogen storage tank. The cryogenic propane in the propane storage tank enters the first cold box through the first propane circulation pipeline, providing cooling capacity to the first cold box. Then, it sequentially enters the cooling pipeline of the compressor and the cooling pipeline of the cooler, providing cooling capacity to the compressor and cooler. After that, it enters the first cold box through the second propane circulation pipeline for cooling before entering the propane refrigeration machine. The cryogenic propane obtained by the propane refrigeration machine returns to the propane storage tank. The cryogenic propane circulates along the above path. The temperature range of the cryogenic propane obtained by the propane refrigeration machine is -20℃ to -42℃. When the first circulation switch is closed, the liquid nitrogen in the liquid nitrogen storage tank enters the second cold box through the third liquid nitrogen circulation pipeline, providing cooling capacity to the second cold box. Then, it enters the first cold box through the first liquid nitrogen circulation pipeline, providing cooling capacity to the first cold box, and then enters the nitrogen compressor. The pressure range of the nitrogen compressor is 0-10 MPa. Then, it enters the first cold box through the second liquid nitrogen circulation pipeline for the first cooling, and then enters the second cold box through the fourth liquid nitrogen circulation pipeline for the second cooling. Finally, it returns to the liquid nitrogen storage tank after passing through the liquid nitrogen expander. The liquid nitrogen circulates along the above path. The inlet temperature of the liquid nitrogen expander is -120℃ to -150℃, and the temperature of the liquid nitrogen returning to the liquid nitrogen storage tank is -195℃. When the second circulation switch is closed, the cryogenic hydrogen in the cryogenic hydrogen storage tank and the BOG gas in the liquid hydrogen storage tank enter the third cold box through the fifth hydrogen circulation pipeline, providing cooling for the third cold box. Then, it enters the second cold box through the third hydrogen circulation pipeline, providing cooling for the second cold box. Next, it enters the first cold box through the first hydrogen circulation pipeline, providing cooling for the first cold box, and then enters the hydrogen compressor. The pressure range of the hydrogen compressor is 0 to 5 MPa. Then, it enters the first cold box through the second hydrogen circulation pipeline for the first cooling, then through the fourth hydrogen circulation pipeline for the second cooling, then through the sixth hydrogen circulation pipeline for the third cooling, and finally returns to the cryogenic hydrogen storage tank after passing through the hydrogen expander. The cryogenic hydrogen circulates along the above path. The inlet temperature of the hydrogen expander is -210℃ to -230℃, and the temperature of the cryogenic hydrogen returning to the cryogenic hydrogen storage tank is -253℃. When the hydrogen liquefaction system is in standby mode, turn on the first and second circulation switches to shut down the liquid nitrogen expander and the hydrogen expander.

7. A hydrogen liquefaction process according to claim 6, characterized in that: The hydrogen liquefaction system also includes a reservoir capable of generating hydroelectric power and a pump that draws water from the water source into the reservoir. The pump is powered by photovoltaic and wind power. The inlet of the electrolytic hydrogen production equipment is connected to the outlet of the reservoir through an eighth pipeline, and the water in the reservoir provides the water source for the electrolytic hydrogen production equipment. During periods of abundant sunshine and wind, surplus electricity generated during normal operation of the hydrogen liquefaction system is directly connected to the grid and / or supplied to the pumps; water stored in the reservoir can generate hydroelectric power to supply electricity to the hydrogen liquefaction system when its power supply is insufficient, ensuring the normal operation of the hydrogen liquefaction system.

8. A hydrogen liquefaction process according to claim 6 or 7, characterized in that: A seventh pipeline is also connected to the outlet of the hydrogen storage tank, which is connected to the hydrogen inlet of the hydrogen fuel cell; the electricity generated by the hydrogen fuel cell is connected to the grid and / or supplied to the hydrogen liquefaction system. During periods of abundant sunshine and wind, the hydrogen storage capacity of the hydrogen storage tank is increased, the liquid nitrogen storage capacity is increased, and the rest of the hydrogen liquefaction system operates at full load. When the hydrogen liquefaction system is without power supply or has insufficient power supply, electricity is generated by hydrogen fuel cells to supply the hydrogen liquefaction system, and any surplus electricity after supplying the hydrogen liquefaction system is directly connected to the grid.

9. A hydrogen liquefaction process according to claim 6 or 7, characterized in that: The first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline; the outlet of the air pump is connected in sequence to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline; the outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve; the third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank; Outside air enters the first cold box through an air pump, air filter, and first air separation pipeline for the first cooling, and then enters the second cold box through the second air separation pipeline for the second cooling, resulting in a gas-liquid mixture containing liquid oxygen and liquid nitrogen. The gas-liquid mixture is stored in an air separation product collection tank and / or a liquid nitrogen storage tank.

10. A hydrogen liquefaction process according to claim 8, characterized in that: The first cold box has a first air separation pipeline, and the second cold box has a second air separation pipeline; the outlet of the air pump is connected in sequence to an air filter, an air compressor, the first air separation pipeline, and the second air separation pipeline via a ninth pipeline; the outlet of the second air separation pipeline is connected to a third branch pipeline with a first valve and a fourth branch pipeline with a second valve; the third branch pipeline is connected to the inlet of the air separation product collection tank, and the fourth branch pipeline is connected to the inlet of the liquid nitrogen storage tank; Outside air enters the first cold box through an air pump, air filter, and first air separation pipeline for the first cooling, and then enters the second cold box through the second air separation pipeline for the second cooling, resulting in a gas-liquid mixture containing liquid oxygen and liquid nitrogen. The gas-liquid mixture is stored in an air separation product collection tank and / or a liquid nitrogen storage tank.

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