Control method applied to hydrogen liquefier gas management system

Abstract

The invention discloses a control method applied to a hydrogen liquefier gas management system. The gas management system comprises a high-pressure pipeline, a low-pressure pipeline, a compressor, a buffer tank and a cold box, an unloading valve is arranged on a pipeline between an inlet of the buffer tank and the high-pressure pipeline, a loading valve is arranged on a pipeline between an outlet of the buffer tank and the low-pressure pipeline, and a first bypass valve is arranged between the high-pressure pipeline and the low-pressure pipeline; the buffer tank is used for storing and releasing hydrogen; the method comprises the steps that the rotating speed of the compressor and the opening degree of the loading valve and the opening degree of the first bypass valve are adjusted based on the air consumption of the cold box; the pressure of the high-pressure pipeline is adjusted by adjusting the opening degree of the loading valve and the opening degree of the unloading valve; and the pressure of the low-pressure pipeline is adjusted by adjusting the opening degree of the first bypass valve. The pressure of the gas management system can be ensured to be stable, and gas can be stably supplied to the liquefaction cold box.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen liquefaction, and in particular to a control method applied to a gas management system of a hydrogen liquefier. Background Art

[0002] A hydrogen liquefier is a device that converts gaseous hydrogen into liquid hydrogen. A complete hydrogen liquefier mainly includes a gas management system, a liquefied cold box, a liquid hydrogen storage and transportation system, utilities, and a control system. Among them, the control system is equivalent to the "brain" of the hydrogen liquefier, directing the system to operate flexibly, carefully, safely and reliably according to the predetermined control logic. Among these controls, the control of the gas management system is a key link in the entire control. Only by ensuring that the control of the gas management system meets expectations can the normal operation of the subsequent liquefaction process be effectively maintained.

[0003] However, when controlling the gas management system, the relevant technology mainly aims to ensure a stable gas supply to the liquefied cold box, but ignores the stability of the high and low pressure pipeline pressures during the gas supply process, resulting in the continuous superposition of various interference factors, causing fluctuations to expand and thus affecting the normal operation of subsequent liquefaction processes.

[0004] Therefore, there is an urgent need for a control method for a hydrogen liquefier gas management system. Summary of the invention

[0005] The present invention provides a control method for a hydrogen liquefier gas management system, which can ensure the stable pressure of the gas management system and the stable gas supply to the liquefied cold box. The technical solution is as follows:

[0006] On the one hand, the present application provides a control method for a hydrogen liquefier gas management system, the gas management system comprising: a high-pressure pipeline, a low-pressure pipeline, a compressor, a buffer tank and a cold box; an unloading valve is provided on the pipeline between the inlet of the buffer tank and the high-pressure pipeline, a loading valve is provided on the pipeline between the outlet of the buffer tank and the low-pressure pipeline, and a first bypass valve is provided between the high-pressure pipeline and the low-pressure pipeline; the buffer tank is used to store and release hydrogen; the method comprises:

[0007] Based on the gas consumption of the cold box, adjusting the speed of the compressor, and the openings of the loading valve and the first bypass valve;

[0008] By adjusting the opening of the loading valve and the unloading valve, the pressure of the high-pressure pipeline is adjusted;

[0009] The pressure of the low-pressure pipeline is adjusted by adjusting the opening of the first bypass valve.

[0010] On the other hand, the present application provides a gas management system for a hydrogen liquefier, comprising: a high-pressure pipeline, a low-pressure pipeline, a compressor, a buffer tank and a cold box; an unloading valve is provided on the pipeline between the inlet of the buffer tank and the high-pressure pipeline, a loading valve is provided on the pipeline between the outlet of the buffer tank and the low-pressure pipeline, and a first bypass valve is provided between the high-pressure pipeline and the low-pressure pipeline; the buffer tank is used to store and release hydrogen.

[0011] The embodiment of the present invention provides a control method for a hydrogen liquefier gas management system. First, by adjusting the rotation speed of the compressor, and the opening of the loading valve and the first bypass valve, the stability of the gas consumption of the cold box can be maintained. In addition, by setting the unloading valve and the pressurizing valve, when the pressure of the high-pressure pipeline fluctuates, the opening of the two valves can be adjusted to maintain the stability of the high-pressure pressure. When the pressure of the low-pressure pipeline fluctuates, the stability of the low-pressure pressure is maintained by adjusting the pressure of the first bypass valve. Since the high-pressure pressure and the low-pressure pressure are controlled separately, when the pressure of one of the pipelines is adjusted, the stability of the pressure of the other pipeline will not be affected, and the two do not interfere with each other, thereby ensuring the stability of the system as a whole. It can be seen that the present application can ensure the stability of the pressure of the gas management system and provide a stable gas supply to the liquefied cold box. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 is a flow chart of a control method applied to a hydrogen liquefier gas management system provided by one embodiment of the present invention;

[0014] Figure 2 is a schematic diagram of a hydrogen liquefier gas management system provided by an embodiment of the present invention;

[0015] Figure 3 It is a high pressure control logic schematic diagram provided by an embodiment of the present invention.

[0016] Reference numerals:

[0017] 1- high-pressure pipeline; 2- low-pressure pipeline; 3- compressor; 4- buffer tank; 5- cold box; 6- unloading valve; 7- loading valve; 8- first bypass valve; 9- second bypass valve; 10- first pressure gauge; 11- second pressure gauge. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] The main function of the gas management system is to provide stable high-pressure raw gas to the liquefied cold box, receive low-pressure gas returned from the liquefied cold box, and maintain the pressure stability of the low-pressure gas. Therefore, the control core of the entire gas management system is to maintain the stability of high-pressure and low-pressure pressures to ensure the smooth progress of subsequent liquefaction work. However, when the existing method is used for control, once the operating conditions fluctuate, each circuit will act independently, which seriously affects the stability of the system.

[0020] Based on this, the inventor proposes a new control method to solve the above problems.

[0021] The specific implementation of the above concept is described below.

[0022] Please refer to Figure 1 and Figure 2 The embodiment of the present invention provides a control system simulation method for on-orbit operation, wherein the gas management system comprises: a high-pressure pipeline 1, a low-pressure pipeline 2, a compressor 3, a buffer tank 4 and a cold box 5; an unloading valve 6 is arranged on the pipeline between the inlet of the buffer tank 4 and the high-pressure pipeline 1, a loading valve 7 is arranged on the pipeline between the outlet of the buffer tank 4 and the low-pressure pipeline 2, and a first bypass valve 8 is arranged between the high-pressure pipeline 1 and the low-pressure pipeline 2; the buffer tank 4 is used to store and release hydrogen; the method comprises:

[0023] Step 100, adjusting the speed of the compressor 3, and the openings of the loading valve 7 and the first bypass valve 8 based on the gas consumption of the cold box 5;

[0024] Step 102, adjusting the pressure of the high-pressure pipeline 1 by adjusting the opening of the loading valve 7 and the unloading valve 6;

[0025] Step 104 , adjusting the pressure of the low-pressure pipeline 2 by adjusting the opening of the first bypass valve 8 .

[0026] In this embodiment, first, the gas consumption of the cold box 5 can be maintained stable by adjusting the rotation speed of the compressor 3, as well as the opening of the loading valve 7 and the first bypass valve 8. In addition, by setting the unloading valve 6 and the pressurizing valve, when the pressure of the high-pressure pipeline 1 fluctuates, the opening of the two valves can be adjusted to maintain the stability of the high-pressure pressure. When the pressure of the low-pressure pipeline 2 fluctuates, the stability of the low-pressure pressure is maintained by adjusting the pressure of the first bypass valve 8. Since the high-pressure pressure and the low-pressure pressure are controlled separately, when the pressure of one of the pipelines is adjusted, the stability of the pressure of the other pipeline will not be affected, and the two will not interfere with each other, thereby ensuring the overall stability of the system. It can be seen that the present application can ensure the stability of the pressure of the gas management system and provide a stable gas supply to the liquefied cold box 5.

[0027] It should be noted that the loading valve 7 is used to increase the pressure value of the high-pressure pipeline 1, and the unloading valve 6 is used to reduce the pressure value of the high-pressure pipeline 1. The compressor 3 outputs the gas from the low-pressure pipeline 2 to the high-pressure pipeline 1 after suction compression, providing high pressure to the gas.

[0028] During operation, the main material circulation paths are as follows:

[0029] 1) The raw gas in the gas buffer tank 4 enters the low-pressure pipeline 2 through the loading valve 7;

[0030] 2) The compressor 3 sucks in low-pressure gas and compresses and pressurizes it to convert it into high-pressure gas and discharge it into the high-pressure pipeline 1;

[0031] 3) The high-pressure gas discharged from the compressor 3 is the high-pressure raw gas required for the operation of the liquefied cold box 5. The gas enters the cold box 5 through the high-pressure air inlet pipeline and is cooled and liquefied in the cold box 5;

[0032] 4) The gas that has not been liquefied after passing through the cold box 5 is returned to the low-pressure suction pipeline of the gas management system. When the gas in the low-pressure pipeline 2 is insufficient, the loading valve 7 is opened to supply gas from the buffer tank 4 to the low-pressure pipeline 2.

[0033] With respect to step 100, in some embodiments, adjusting the speed of the compressor 3 and the openings of the loading valve 7 and the first bypass valve 8 based on the gas consumption of the cold box 5 includes:

[0034] When the gas consumption of the cold box 5 decreases, the opening of the first bypass valve 8 is increased, the opening of the loading valve 7 is decreased, and the rotation speed of the compressor 3 is reduced;

[0035] When the gas consumption of the cold box 5 increases, the opening of the first bypass valve 8 is reduced, the opening of the loading valve 7 is increased, and the rotation speed of the compressor 3 is increased.

[0036] In this embodiment, the speed of the compressor 3 adopts an automatic adjustment mode. After the hydrogen liquefier is running, the compressor 3 runs at a set speed. At this time, the loading valve 7 is slowly opened to release the gas in the buffer tank 4 to the low-pressure pipeline 2, and then the gas is compressed to the high-pressure pipeline 1 through the operation of the compressor 3. Under this effect, the pressure of the low-pressure pipeline 2 will drop rapidly. When it is lower than the low-pressure setting value, in order to maintain the stability of the low-pressure pressure, it is necessary to open the bypass valve and add part of the gas in the high-pressure pipeline 1 to the low-pressure pipeline 2 for a constant low-pressure pressure. On the contrary, if the pressure is higher than the low-pressure setting value, the bypass valve opening will be reduced accordingly.

[0037] In the initial stage of operation, since the amount of gas required in the cold box 5 is small, the compressor 3 can run at a relatively low speed to ensure the gas demand of the cold box 5. However, as the system runs deeper, a large amount of gas is liquefied, forcing the cold box 5 to use more gas, and the control system will gradually increase the operating speed of the compressor 3 to ensure that more raw gas is quickly provided to the cold box 5. On the contrary, if the gas consumption of the cold box 5 decreases, the control system will automatically reduce the operating speed of the compressor 3.

[0038] In some embodiments, the gas consumption demand of the cold box 5 is determined based on the opening of the first bypass valve 8: when the opening of the first bypass valve 8 continues to decrease, it is determined that the gas consumption of the cold box 5 increases; when the opening of the first bypass valve 8 continues to increase, it is determined that the gas consumption of the cold box 5 decreases.

[0039] In this step, the control system uses the opening of the first bypass valve 8 as an indicator for determining the gas demand of the cold box 5. When the valve opening continues to decrease, it means that there is already a lot of gas in the low-pressure pipeline 2, and the pressure of the low-pressure pipeline 2 increases, indicating that the gas consumption of the cold box 5 has increased. At this time, a large amount of gas in the low-pressure pipeline 2 needs to be sent to the cold box 5. At this time, the compressor 3 starts to increase speed and quickly extracts the low-pressure gas. When the opening of the first bypass valve 8 continues to increase, it means that the gas consumption of the cold box 5 has decreased, and there is a lot of gas retained in the high-pressure pipeline 1. At this time, it is necessary to reduce the speed of the compressor 3 and reduce the gas supply to the high-pressure pipeline 1. In addition, the opening setting value of the first bypass valve is determined according to the equipment performance and user requirements, and this application does not make specific restrictions on its opening value.

[0040] For step 102, if Figure 3 As shown, in some embodiments, the pressure of the high-pressure pipeline 1 is adjusted by adjusting the opening of the loading valve 7 and the unloading valve 6, including:

[0041] Get the pressure value of high pressure pipeline 1;

[0042] If the obtained pressure value is lower than the high pressure setting value, the opening of the loading valve 7 is gradually increased until the pressure value of the high pressure pipeline 1 rises to the high pressure setting value;

[0043] If the acquired pressure value is higher than the high pressure setting value, the opening of the unloading valve 6 is gradually increased until the pressure value of the high pressure pipeline 1 is reduced to the high pressure setting value.

[0044] In this embodiment, maintaining the high pressure stable near the high pressure setting value is an important indicator of the operation of the liquefier. In actual work, the high pressure setting value is determined according to the process requirements, such as 15 kg, etc., and this application does not make specific limitations. After the compressor 3 is running, the loading valve 7 is gradually opened to start releasing the raw gas in the buffer tank 4 to the low-pressure pipeline 2. The larger the loading valve 7 is opened, the higher the pressure released will be, and the higher the high pressure pressure compressed and discharged by the compressor 3 will be. Therefore, the main function of the loading valve 7 is to increase the pressure of the high-pressure pipeline 1. After the high pressure pressure is higher than the set high pressure setting value, the unloading valve 6 will gradually open to discharge the excess gas in the high-pressure pipeline 1 back to the gas buffer tank 4. Therefore, the main function of the unloading valve 6 is to reduce the pressure of the high-pressure pipeline 1. It can be seen that the use of the loading valve 7 and the unloading valve 6 in combination can stabilize the high pressure and low pressure near the set value.

[0045] When the cold box 5 is running, if the gas consumption increases, a large amount of gas in the high-pressure pipeline 1 will enter the cold box 5, causing the high-pressure pressure to decrease. In order to maintain the high-pressure pressure, the opening of the loading valve 7 will increase to send more gas into the system pipeline. Similarly, if the gas consumption of the cold box 5 decreases, the pressure of the high-pressure pipeline 1 will increase. At this time, the loading valve 7 stops loading, and the unloading valve 6 gradually opens to return the excess gas to the buffer tank 4 to maintain a constant high-pressure pressure.

[0046] The loading valve 7 and the unloading valve 6 are controlled in reverse coordination in real time according to the actual gas consumption of the cold box 5, and the two valves cannot be opened or closed at the same time.

[0047] With respect to step 104, in some embodiments, adjusting the pressure of the low-pressure pipeline 2 by adjusting the opening of the first bypass valve 8 includes:

[0048] Get the pressure value of low-pressure pipeline 2;

[0049] If the obtained pressure value is lower than the low pressure setting value, the opening of the first bypass valve 8 is gradually increased to increase the pressure value of the low pressure pipeline 2;

[0050] If the acquired pressure value is higher than the low pressure setting value, the opening of the first bypass valve 8 is gradually closed to reduce the pressure value of the low pressure pipeline 2 .

[0051] In this embodiment, maintaining the pressure of the low-pressure pipeline 2 stable near the low-pressure set value is an important indicator for the operation of the hydrogen liquefier. In actual work, the low-pressure set value of the low-pressure pipeline 2 can be 1 kg, etc., and this application does not make specific limitations.

[0052] Usually, the control system mainly adjusts the low pressure through the first bypass valve 8. However, when the pressure control range of the gas is wide, one bypass valve cannot meet the requirements of the adjustment range and the adjustment accuracy at the same time.

[0053] Therefore, in some embodiments, a second bypass valve 9 is further provided between the high-pressure pipeline 1 and the low-pressure pipeline 2; the second bypass valve 9 and the first bypass valve 8 are provided in parallel, and the caliber of the second bypass valve 9 is larger than the caliber of the first bypass valve 8; the method further comprises:

[0054] In response to the opening of the first bypass valve 8 being higher than its set opening value, the opening of the second bypass valve 9 is gradually increased until the opening of the first bypass valve 8 is reduced to its set opening value;

[0055] In response to the opening of the first bypass valve 8 being lower than its set opening value, the opening of the second bypass valve 9 is gradually reduced until the opening of the first bypass valve 8 increases to its set opening value.

[0056] In this embodiment, compared with the traditional single-valve low-pressure control mode, the present application adopts a dual-valve-fine and coarse adjustment control method. Since the first bypass valve 8 has a small caliber, its ability to adjust the low pressure is limited, and it is only suitable for precise adjustment under the condition of a small range of low pressure fluctuations. The second bypass valve 9 has a larger caliber and a wider pressure control range for the gas, and can achieve a wide range of coarse adjustment. Therefore, when the low pressure range fluctuates greatly and the first bypass valve 8 cannot complete the pressure regulation, the second bypass valve 9 will participate in the control. In this way, the low pressure can be controlled near the specified target through the cooperation of the two valves, and the control accuracy of the low pressure can be further improved through fine adjustment to meet the working conditions with relatively strict process requirements.

[0057] It should be noted that, in order to prevent the first bypass valve 8 and the second bypass valve 9 from acting independently, the second bypass valve 9 uses the opening of the first bypass valve 8 as the basis for control and regulation. That is, when the opening of the first bypass valve 8 deviates from the set opening value, it means that the regulating capacity of the valve has reached a saturated state. At this time, the second bypass valve 9 participates in the control until the opening of the first bypass valve 8 returns to the set opening value. If the pressure of the low-pressure pipeline 2 still deviates from the low-pressure set value after the opening of the first bypass valve 8 returns to the set opening value, the opening of the first bypass valve 8 continues to increase or decrease, and at the same time, the second bypass valve 9 continues to participate in the regulation according to the change trend of the first bypass valve 8. By analogy, the real-time control of the pressure of the low-pressure pipeline 2 is achieved to maintain the stability of the low-pressure pressure.

[0058] The specific working process of the first bypass valve 8 and the second bypass valve 9 is as follows:

[0059] After the compressor 3 is running, the control system immediately starts the control of the first bypass valve 8 and the second bypass valve 9. The first bypass valve 8 is opened to the set opening value according to the actual value of the low pressure in the pipeline at startup, and then automatically adjusted and controlled according to the actual change of the low pressure.

[0060] When the opening of the first bypass valve 8 is lower than the set opening value, it means that the low pressure is higher than the upper limit of the valve's regulating capacity. At this time, the second bypass valve 9 will gradually reduce the opening to reduce the pressure from the high pressure pipeline 1 to the low pressure pipeline 2. After the pressure of the low pressure pipeline 2 is reduced, the first bypass valve 8 will gradually increase the opening to restore the pressure of the low pressure pipeline 2.

[0061] When the opening of the first bypass valve 8 is higher than the set opening value, it means that the low pressure is lower than the lower limit of the valve's regulating capacity. At this time, the second bypass valve 9 will gradually increase its opening to increase the pressure from the high-pressure pipeline 1 to the low-pressure pipeline 2. After the pressure of the low-pressure pipeline 2 increases, the first bypass valve 8 will gradually reduce its opening to restore the pressure of the low-pressure pipeline 2.

[0062] In some embodiments, the second bypass valve 9 can also be used to adjust the gas consumption of the cold box 5. Specifically, the gas consumption of the cold box 5 can be reduced by increasing the opening of the second bypass valve 9, and the gas consumption of the cold box 5 can be increased by decreasing the opening of the second bypass valve 9.

[0063] In some embodiments, a first pressure gauge 10 is provided on the high-pressure pipeline 1 to detect the pressure of the high-pressure pipeline 1 .

[0064] In some embodiments, a second pressure gauge 11 is provided on the low-pressure pipeline 2 to detect the pressure of the low-pressure pipeline 2 .

[0065] It should also be noted that during the operation of the control system, in order to respond to emergencies and protect the safe operation of equipment and processes, the gas management system is also equipped with compressor interlock shutdown protection.

[0066] The conditions for triggering interlock protection are:

[0067] (1) The high pressure is higher than the interlock protection setting value;

[0068] (2) The low pressure is higher than the interlock protection setting value;

[0069] (3) The low pressure is lower than the interlock protection setting value;

[0070] (4) Compressor failure alarm;

[0071] If any of the above conditions are met, the interlock protection function of the compressor will be triggered.

[0072] When the chain protection is triggered, the corresponding chain actions are:

[0073] (1) Compressor shutdown

[0074] (2) Loading valve closed

[0075] (3) Unloading valve closed

[0076] (4) The first bypass valve is closed

[0077] (5) The second bypass valve is closed

[0078] After the interlock action occurs, the hydrogen liquefier will remain in the interlock shutdown state permanently until the operator confirms that it can be restored.

[0079] like Figure 2 As shown, an embodiment of the present invention further provides a gas management system for a hydrogen liquefier, comprising: a high-pressure pipeline 1, a low-pressure pipeline 2, a compressor 3, a buffer tank 4 and a cold box 5; an unloading valve 6 is arranged on the pipeline between the inlet of the buffer tank 4 and the high-pressure pipeline 1, a loading valve 7 is arranged on the pipeline between the outlet of the buffer tank 4 and the low-pressure pipeline 2, and a first bypass valve 8 is arranged between the high-pressure pipeline 1 and the low-pressure pipeline 2; the buffer tank 4 is used to store and release hydrogen.

[0080] In some embodiments, a second bypass valve 9 is further provided between the high-pressure pipeline 1 and the low-pressure pipeline 2 ; the second bypass valve 9 and the first bypass valve 8 are arranged in parallel, and the caliber of the second bypass valve 9 is larger than the caliber of the first bypass valve 8 .

[0081] In addition, the equipment mentioned in this application is only the components necessary to realize the hydrogen liquefaction function. In other embodiments, the gas management system of the hydrogen liquefier may also include more or fewer equipment, such as valves, flow meters, etc., and this application does not make specific limitations.

[0082] Finally, it should be noted that, in this article, relational terms such as first, second, third and fourth are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0083] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A control method for a hydrogen liquefier gas management system, characterized in that: The gas management system comprises: a high-pressure pipeline (1), a low-pressure pipeline (2), a compressor (3), a buffer tank (4) and a cold box (5); an unloading valve (6) is arranged on the pipeline between the inlet of the buffer tank (4) and the high-pressure pipeline (1), a loading valve (7) is arranged on the pipeline between the outlet of the buffer tank (4) and the low-pressure pipeline (2), and a first bypass valve (8) is arranged between the high-pressure pipeline (1) and the low-pressure pipeline (2); the buffer tank (4) is used to store and release hydrogen; the method comprises: Based on the gas consumption of the cold box (5), adjusting the rotation speed of the compressor (3) and the openings of the loading valve (7) and the first bypass valve (8); By adjusting the openings of the loading valve (7) and the unloading valve (6), the pressure of the high-pressure pipeline (1) is adjusted; The pressure of the low-pressure pipeline (2) is adjusted by adjusting the opening of the first bypass valve (8).

2. The method according to claim 1, characterized in that The adjusting of the rotation speed of the compressor (3) and the openings of the loading valve (7) and the first bypass valve (8) based on the gas consumption of the cold box (5) comprises: When the gas consumption of the cold box (5) decreases, the opening of the first bypass valve (8) is increased, the opening of the loading valve (7) is decreased, and the rotation speed of the compressor (3) is reduced; When the gas consumption of the cold box (5) increases, the opening of the first bypass valve (8) is reduced, the opening of the loading valve (7) is increased, and the rotation speed of the compressor (3) is increased.

3. The method according to claim 1, characterized in that The method of adjusting the pressure of the high-pressure pipeline (1) by adjusting the openings of the loading valve (7) and the unloading valve (6) comprises: Obtaining the pressure value of the high-pressure pipeline (1); If the acquired pressure value is lower than the high pressure setting value, the opening of the loading valve (7) is gradually increased until the pressure value of the high pressure pipeline (1) rises to the high pressure setting value; If the acquired pressure value is higher than the high pressure setting value, the opening of the unloading valve (6) is gradually increased until the pressure value of the high pressure pipeline (1) is reduced to the high pressure setting value.

4. The method according to claim 1, characterized in that: The step of adjusting the pressure of the low-pressure pipeline (2) by adjusting the opening of the first bypass valve (8) comprises: Obtaining the pressure value of the low-pressure pipeline (2); If the acquired pressure value is lower than the low pressure setting value, gradually increasing the opening of the first bypass valve (8) to increase the pressure value of the low pressure pipeline (2); If the acquired pressure value is higher than the low pressure setting value, the opening of the first bypass valve (8) is gradually closed to reduce the pressure value of the low pressure pipeline (2).

5. The method according to claim 4, characterized in that A second bypass valve (9) is further arranged between the high-pressure pipeline (1) and the low-pressure pipeline (2); the second bypass valve (9) and the first bypass valve (8) are arranged in parallel, and the diameter of the second bypass valve (9) is larger than the diameter of the first bypass valve (8); the method further comprises: In response to the opening of the first bypass valve (8) being higher than its set opening value, gradually increasing the opening of the second bypass valve (9) until the opening of the first bypass valve (8) is reduced to its set opening value; In response to the opening of the first bypass valve (8) being lower than its set opening value, the opening of the second bypass valve (9) is gradually reduced until the opening of the first bypass valve (8) increases to its set opening value.

6. The method according to claim 5, characterized in that Also includes: The gas consumption of the cold box (5) is reduced by increasing the opening of the second bypass valve (9), and the gas consumption of the cold box (5) is increased by decreasing the opening of the second bypass valve (9).

7. The method according to claim 1, characterized in that The gas consumption demand of the cold box (5) is determined according to the opening degree of the first bypass valve (8): When the opening of the first bypass valve (8) continues to decrease, it is determined that the gas consumption of the cold box (5) increases; when the opening of the first bypass valve (8) continues to increase, it is determined that the gas consumption of the cold box (5) decreases.

8. The method according to claim 1, characterized in that The high-pressure pipeline (1) is provided with a first pressure gauge (10) for detecting the pressure of the high-pressure pipeline (1).

9. The method according to claim 1, characterized in that: The low-pressure pipeline (2) is provided with a second pressure gauge (11) for detecting the pressure of the low-pressure pipeline (2).

10. A gas management system for a hydrogen liquefier, characterized in that: include: A high-pressure pipeline (1), a low-pressure pipeline (2), a compressor (3), a buffer tank (4) and a cold box (5); an unloading valve (6) is provided on the pipeline between the inlet of the buffer tank (4) and the high-pressure pipeline (1), a loading valve (7) is provided on the pipeline between the outlet of the buffer tank (4) and the low-pressure pipeline (2), and a first bypass valve (8) is provided between the high-pressure pipeline (1) and the low-pressure pipeline (2); the buffer tank (4) is used to store and release hydrogen.

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