Hydrogen energy equipment leak detection system and leak detection method

Abstract

The invention discloses a leakage detection system and a leakage detection method for hydrogen energy equipment, which are used for solving the problems of resource waste, high leakage detection cost and low efficiency of the hydrogen energy equipment caused by direct nitrogen emission of the existing LNG equipment by recovering nitrogen of the LNG equipment and taking a hydrogen-nitrogen mixed gas with a specific concentration as a leakage detection medium of the hydrogen energy equipment. By recycling the waste nitrogen after detection of the LNG equipment, the problem of waste of liquid nitrogen resources in traditional LNG testing can be effectively solved, the liquid nitrogen can be directly used for subsequent detection operation of the hydrogen energy equipment after being recycled and pressurized, and the purchase cost of the liquid nitrogen in the detection process of the hydrogen energy equipment is reduced. Besides, nitrogen and hydrogen mixed gas with a specific mixing ratio is adopted as a detection medium of the hydrogen energy equipment, high efficiency which cannot be achieved by conventional nitrogen leakage detection can be achieved while the safety of detection operation is guaranteed, the leakage detection time of the hydrogen energy equipment is shortened, and meanwhile the problem of high cost during detection of a conventional helium pressure maintaining method can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogenation equipment, and in particular to a hydrogen energy equipment leak detection system and a leak detection method. Background Art

[0002] LNG is a colorless, odorless, non-toxic, and flammable cryogenic liquid formed by liquefying natural gas after purification (removing impurities such as CO2, sulfides, moisture, and solid particles) and deep cooling to approximately -162°C under normal pressure. It is widely used in urban gas peak-shaving, industrial fuel, power generation, and transportation (such as LNG vehicles and ships). Before commissioning, LNG equipment requires low-temperature and pressure testing. During this testing, liquid nitrogen is typically used in large quantities as a testing fluid. After the test is completed, a large amount of liquid nitrogen vaporizes and cannot be recovered. Directly discharging it would waste resources. The existing liquid nitrogen recovery devices known to the inventors primarily recover nitrogen cold energy during LNG testing and operation. After the cold energy is recovered, the nitrogen is directly discharged into the air.

[0003] Furthermore, as the global energy mix shifts toward a low-carbon economy, hydrogen, as a clean secondary energy source, presents broad application prospects in the transportation sector. Hydrogen energy equipment, as core infrastructure of the hydrogen energy industry, requires leak detection, fundamental to its safety and performance, directly impacting the efficiency of hydrogen storage and transportation, as well as its commercialization. Currently, leak detection for hydrogen energy equipment relies on helium pressure maintenance (GB50516-2021 standard requires a one-hour leakage rate of ≤0.5%), but helium is expensive and in short supply. Traditional nitrogen leak detection, on the other hand, requires over 24 hours to meet leak detection requirements, resulting in low efficiency.

[0004] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] The inventor calculated the critical value of the explosion risk based on: C GH =C H / (C H +K∙C N ×100%), it is known that when the hydrogen concentration in the hydrogen-nitrogen mixed gas is less than 5.5%, the hydrogen-nitrogen mixed gas can be considered as a non-flammable gas. H is the volume concentration of hydrogen, C N is the volume concentration of nitrogen, and K is the equivalent dilution factor of nitrogen (K for nitrogen = 1). Considering the high cost of helium leak detection and the low efficiency of nitrogen leak detection in existing technologies, the inventors proposed adding 0-5% hydrogen to nitrogen as a leak detection medium for hydrogen energy equipment.

[0006] In view of at least one of the above technical problems, the present disclosure provides a hydrogen energy equipment leak detection system and leak detection method. By recovering nitrogen from LNG equipment and using a hydrogen-nitrogen mixture of a specific concentration as the leak detection medium for the hydrogen energy equipment, the problems of direct nitrogen discharge from existing LNG equipment polluting the environment and high cost and low efficiency of hydrogen energy equipment leak detection are solved.

[0007] According to one aspect of the present disclosure, a hydrogen energy equipment leak detection system is provided, which includes a nitrogen recovery unit connected to the liquid nitrogen outlet of the LNG equipment and provided with a nitrogen container, a hydrogen container for storing hydrogen, and a gas mixing unit respectively connected to the nitrogen container and the hydrogen container and provided with a gas mixer; the nitrogen recovery unit includes a nitrogen recovery pipeline provided between the liquid nitrogen outlet of the LNG equipment and the nitrogen container, and the nitrogen recovery pipeline is sequentially connected in series from upstream to downstream with a liquid nitrogen collection tank, a liquid nitrogen vaporizer, and a low-pressure buffer tank. , a booster pump and an air cooler; the gas mixing unit includes a nitrogen pipeline connected between the nitrogen inlet of the gas mixer and the nitrogen container, a hydrogen pipeline connected between the hydrogen inlet of the gas mixer and the hydrogen container, a concentration control pipeline connected between the mixed gas outlet of the gas mixer and the downstream of the hydrogen pipeline, and a mixed gas pipeline connected to the mixed gas outlet and connected in series with a gas analyzer; the nitrogen pipeline and the hydrogen pipeline are respectively connected in series with a flow meter and a gas control valve for controlling the conductivity of the corresponding pipeline.

[0008] In some embodiments of the present disclosure, the hydrogen energy equipment leak detection system also includes a purge pipeline with its two ends respectively connected to the nitrogen pipeline and the corresponding position upstream of the hydrogen pipeline; the purge pipeline is serially connected with a purge one-way valve that conducts one-way from the nitrogen pipeline to the hydrogen pipeline and a purge control valve for controlling the on and off of the purge pipeline.

[0009] In some embodiments of the present disclosure, the hydrogen energy equipment leak detection system also includes a main discharge line connected to the discharge port, and a discharge branch line connected to the nitrogen recovery pipeline at a position downstream of the liquid nitrogen collection tank, liquid nitrogen vaporizer and air cooler through a safety valve and a discharge valve respectively.

[0010] In some embodiments of the present disclosure, the driving air inlet of the booster pump is correspondingly connected to the compressed air source; the air cooler includes a nitrogen inlet correspondingly connected to the nitrogen recovery pipeline and an air inlet correspondingly connected to the driving air outlet of the booster pump.

[0011] In some embodiments of the present disclosure, corresponding on-off valves and one-way valves are respectively provided between the air inlet of the nitrogen recovery pipeline, the liquid nitrogen collection tank, the liquid nitrogen vaporizer, the low-pressure buffer tank, and the booster pump.

[0012] According to another aspect of the present disclosure, a hydrogen energy equipment leak detection method is provided, which is implemented based on the above-mentioned hydrogen energy equipment leak detection system and specifically includes the following steps: (1) After the LNG equipment has completed the leak test, connect the inlet of the nitrogen recovery unit to the liquid nitrogen outlet of the LNG equipment; (2) The nitrogen recovery pipeline is opened accordingly, and the recovered liquid nitrogen is vaporized into nitrogen in the liquid nitrogen vaporizer and then enters the low-pressure buffer tank. At the same time, the booster pump is started to pressurize the nitrogen to a corresponding degree and then cooled by the air cooler and then transported to the nitrogen container for storage; (3) When there is a need for leak detection of hydrogen energy equipment, the hydrogen pipeline is connected to the hydrogen container in which hydrogen is pre-stored, and at the same time, the nitrogen pipeline is connected and the flow meters and gas control valves in the nitrogen pipeline and hydrogen pipeline are used to control the volume of nitrogen and hydrogen entering the gas mixer; (4) The difference between the actual hydrogen concentration in the mixed gas and the set hydrogen concentration is determined according to the output result of the gas analyzer in the mixed gas pipeline, and used as the basis for regulating the degree of conductivity of the nitrogen pipeline and the hydrogen pipeline; (5) When the hydrogen pipeline is fully connected and still cannot meet the mixed concentration requirement output by the mixed gas pipeline, the concentration control pipeline is correspondingly connected to control the hydrogen concentration.

[0013] In some embodiments of the present disclosure, in step (3), before the gas mixing unit operates, the nitrogen pipeline and the purge pipeline connected to the nitrogen pipeline and the corresponding position upstream of the hydrogen pipeline are opened, and the nitrogen in the nitrogen container is used for purge operation.

[0014] One or more technical solutions provided in the embodiments of this application have at least any of the following technical effects or advantages: 1. By recycling the waste nitrogen after LNG equipment testing, the problem of liquid nitrogen resource waste in traditional LNG testing can be effectively solved. The liquid nitrogen can be directly used in subsequent hydrogen energy equipment testing after recovery and pressurization, eliminating the liquid nitrogen procurement cost during the hydrogen energy equipment testing process, with good economic benefits and large-scale application prospects.

[0015] 2. Using a nitrogen-hydrogen mixture with a specific blending ratio as the detection medium for hydrogen energy equipment can achieve high efficiency that cannot be achieved by conventional nitrogen leak detection while ensuring the safety of the detection operation, reducing the leak detection time of hydrogen energy equipment and solving the high cost problem of conventional helium pressure maintenance method detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structural principle of a hydrogen energy equipment leak detection system in one embodiment of the present application.

[0017] Figure 2 This is a comparison curve diagram of nitrogen-hydrogen mixed gas and conventional nitrogen detection in one embodiment of the present application.

[0018] In the above figures, 1 is a nitrogen recovery unit, 10 is a recovery inlet, 11 is a nitrogen container, 12 is a liquid nitrogen collection tank, 13 is a liquid nitrogen vaporizer, 14 is a low-pressure buffer tank, 15 is a booster pump, 150 is a compressed gas pipeline, 16 is an air cooler, 17 is a venting pipeline, 2 is a gas mixing unit, 21 is a hydrogen container, 22 is a gas mixer, 23 is a nitrogen pipeline, 24 is a hydrogen pipeline, 25 is a concentration control pipeline, 26 is a mixed gas pipeline, and 3 is a purge pipeline. DETAILED DESCRIPTION

[0019] The procedures involved or relied upon in the following embodiments are all conventional or simple procedures in the art, and those skilled in the art can make conventional selections or adaptive adjustments based on specific application scenarios. The devices involved in the following embodiments, unless otherwise specified, are all conventional commercially available products.

[0020] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0021] In order to solve the technical problems that the leak detection cost of hydrogen energy equipment is high due to the helium pressure maintenance method, and the traditional nitrogen leak detection method is time-consuming and inefficient, this example discloses a hydrogen energy equipment leak detection system. Figure 1 , which includes a nitrogen recovery unit 1 and a gas mixing unit 2.

[0022] Specifically, in this embodiment, taking the test of a certain LNG pump skid as an example, the LNG equipment test uses a total of 20 to 30 kg of liquid nitrogen. In order to avoid the waste of resources and environmental pollution caused by its direct release, in this embodiment, the liquid nitrogen is recovered and used for leak detection of hydrogen energy equipment.

[0023] See also Figure 1 Nitrogen recovery unit 1 includes a nitrogen recovery pipeline with a nitrogen container 11 connected to its terminal end. A recovery inlet 10 of the nitrogen recovery pipeline is connected to the liquid nitrogen outlet of the LNG equipment, thereby collecting liquid nitrogen and nitrogen gas discharged from the LNG equipment. To ensure the safety and reliability of this device, a breakaway valve and a hose are provided at recovery inlet 10. These valves connect to the corresponding liquid nitrogen outlet of the LNG equipment, thereby increasing the flexibility of the connection through the hose. Furthermore, the breakaway valve allows the nitrogen recovery pipeline to be promptly disconnected and sealed from the liquid nitrogen delivery pipeline when subjected to external forces such as pulling, thereby improving the safety of liquid nitrogen recovery.

[0024] Liquid nitrogen enters the nitrogen recovery pipeline through the recovery inlet 10 and the inlet valve. Since liquid nitrogen cannot be used directly, in this embodiment, see Figure 1 , a liquid nitrogen vaporizer 13 is set upstream of the nitrogen recovery pipeline to vaporize the liquid nitrogen. However, considering that the processing capacity of the liquid nitrogen vaporizer 13 per unit time is limited, the liquid nitrogen vaporization capacity in this example is 25Nm 3 / h, so in this embodiment, a liquid nitrogen collection tank 12 is installed upstream of the liquid nitrogen vaporizer 13. In this embodiment, the liquid nitrogen collection tank 12 has a capacity of 50L. The liquid nitrogen entering the nitrogen recovery unit 1 is temporarily stored in the liquid nitrogen collection tank 12, which can serve as a buffer. At the same time, a ball valve and a one-way valve are connected in series in the pipeline between the liquid nitrogen collection tank 12 and the liquid nitrogen vaporizer 13 to prevent backflow.

[0025] Liquid nitrogen is vaporized into nitrogen gas and then transported to the nitrogen container 11 for storage, and is used when the hydrogen energy equipment is leak tested. However, the nitrogen gas pressure after vaporization by the liquid nitrogen vaporizer 13 is limited, and it cannot be effectively stored in the nitrogen container 11, resulting in a limited storage capacity in the nitrogen container 11. Therefore, in this embodiment, see Figure 1 A booster pump 15 is provided downstream of the liquid nitrogen vaporizer 13, thereby pressurizing the nitrogen through the booster pump 15 to increase the nitrogen storage capacity in the nitrogen container 11. In this example, the rated flow rate of the booster pump 15 is 24Nm 3 / h. Considering that the boosting flow rate of the boosting pump 15 per unit time is limited, and to avoid the problem of its boosting flow rate not matching the vaporization volume of the liquid nitrogen vaporizer 13, in this embodiment, a low-pressure buffer tank 14 is provided in the pipeline between the liquid nitrogen vaporizer 13 and the boosting pump 15. The low-pressure buffer tank 14 temporarily stores the nitrogen that cannot be promptly pressurized by the boosting pump 15. In this embodiment, the low-pressure buffer tank 14 is connected to the outlet of the liquid nitrogen vaporizer 13 and the nitrogen inlet of the boosting pump 15 via ball valves, respectively, to control the on-off of the corresponding parts of the pipeline, facilitating system control and subsequent maintenance.

[0026] Considering that the nitrogen gas will be pressurized by the booster pump 15, the gas temperature will rise. In order to avoid the nitrogen container from accumulating temperature as the nitrogen is continuously filled, thus causing safety risks, in this embodiment, see Figure 1 , an air cooler 16 is provided in the pipeline between the booster pump 15 and the nitrogen container 11 to cool down the high-pressure and high-temperature nitrogen output by the booster pump 15. Figure 1 In this embodiment, the driving air inlet of the booster pump 15 is connected to the compressed air source through the compressed air pipeline 150, thereby providing corresponding power for the operation of the booster pump 15. In addition, in this embodiment, in order to improve the cooling efficiency of the air cooler 16, see Figure 1In this example, the driving air outlet of the booster pump 15 is connected to the air inlet of the air cooler 16, so as to take away the heat from the air cooler 16 to the greatest extent by utilizing the high-speed flow characteristics of the compressed air when it is discharged, thereby accelerating the heat dissipation and cooling process of the nitrogen in the air cooler 16.

[0027] In order to ensure the recovery safety of the nitrogen recovery unit 1, avoid overpressure and facilitate the release of nitrogen in maintenance scenarios, in this embodiment, the nitrogen recovery unit 1 also includes a release pipeline 17, see Figure 1 In this example, the vent pipeline includes a vent main line connected to the vent port, and also includes a vent branch line in which one end is connected to the vent main line and the other end is connected to the nitrogen recovery pipeline between the liquid nitrogen collection tank 12 and the liquid nitrogen vaporizer 13, the liquid nitrogen vaporizer 13 and the low-pressure buffer tank 14, and the air cooler 16 and the nitrogen container 11, and each vent branch line is respectively provided with a vent safety valve and a vent manual valve arranged in parallel. Furthermore, the vent safety valve is used to realize automatic venting when the corresponding part of the system is overpressured, and the vent manual valve is used to achieve the purpose of manual venting on demand.

[0028] Therefore, the nitrogen recovery unit of the hydrogen energy equipment leak detection system in this example can recover 20 kg of liquid nitrogen at a time. According to the conventional specification of nitrogen cylinders of 40L (12-15 MPa), the nitrogen storage capacity of a single nitrogen cylinder is about 0.46 kg. Therefore, the nitrogen recovery unit in this example can recover about 43 bottles of high-pressure nitrogen at a time, thereby saving about 5,160 yuan in nitrogen procurement costs and achieving good economic benefits.

[0029] In addition, in order to obtain the nitrogen-hydrogen mixed gas required for leak detection of hydrogen energy equipment, in this embodiment, see Figure 1 The hydrogen energy equipment leak detection system also includes a gas mixing unit 2. The gas mixing unit 2 is provided with a hydrogen container 21. In order to achieve effective mixing of nitrogen and hydrogen, a gas mixer 22 is provided at the downstream position of the gas mixing unit 2 in this example. The gas mixer 22 is a static mixer with a nitrogen inlet and a hydrogen inlet. Figure 1 The nitrogen inlet of the gas mixer 22 is connected to the nitrogen container 11 through the nitrogen pipeline 23. Similarly, the hydrogen inlet of the gas mixer 22 is connected to the hydrogen container 21 through the hydrogen pipeline 24. In this way, nitrogen and hydrogen are obtained from the nitrogen container 11 and the hydrogen container 21 respectively and mixed in the gas mixer 22.

[0030] See also Figure 1Because the nitrogen-hydrogen gas mixture used for leak detection in hydrogen energy equipment has strict concentration requirements, in order to ensure that the mixed gas output by the system meets the required concentration of 5% hydrogen mixed with 95% nitrogen set in this example, flow meters and gas control valves are installed in series in nitrogen pipeline 23 and hydrogen pipeline 24, respectively. The gas control valves in this example are air-operated valves, and each flow meter and gas control valve is connected to a PLC controller for dynamic adjustment of the set mixing ratio based on the PID control program preset in the PLC controller. Since PID control is a conventional control program, it will not be described in detail in this example.

[0031] In addition, in order to avoid the problem that the hydrogen concentration in the mixed gas cannot reach the set requirement even if the hydrogen pipeline is fully connected during the hydrogen mixing process, in this embodiment, see Figure 1 A concentration control pipeline 25 is set between the mixed gas outlet of the gas mixer 22 and the downstream of the hydrogen pipeline 24. A concentration control valve is connected in series in the concentration control pipeline 25. The opening degree of the valve is correspondingly regulated to adjust the hydrogen concentration in the downstream mixed gas to meet the required hydrogen concentration setting requirements.

[0032] See also Figure 1 The outlet of the gas mixer 22 is connected to a mixed gas pipeline 26. In order to verify whether the mixed concentration in the output mixed gas meets the requirements, in this embodiment, a gas analyzer is connected in series in the mixed gas pipeline 26. The gas analyzer is connected to the PLC controller, so as to determine whether the gas mixing meets the preset requirements based on the analysis value of the gas analyzer.

[0033] In addition, in this embodiment, considering that the gas mixing unit 2 is filled with impurity air in its pipeline before operation, in order to prevent the gas initially output from containing impurities and failing to meet the gas standard required for leak detection, see Figure 1 In this example, a purge line 3 is connected and installed upstream of the nitrogen line 23 and the hydrogen line 24. Specifically, a one-way valve and a purge control valve are connected in series in the purge line 3, and a ball valve is provided between the purge line 3 and the hydrogen container 21. Therefore, when purging, the nitrogen in the nitrogen container 11 is used as the purge gas source. At the same time, the ball valve between the purge line and the hydrogen container 21 is closed, and the purge control valve in the purge line 3 is opened to connect the purge line. Since the one-way valve in the purge line only allows nitrogen to flow from the nitrogen line 23 to the hydrogen line 24, and the purge line 3 is located upstream of the gas mixing unit 2, it can achieve the purpose of purging impurities and air in the pipelines and various components of the gas mixing unit 2.

[0034] This example also discloses a hydrogen energy equipment leak detection method, which is implemented based on the above-mentioned hydrogen energy equipment leak detection system and specifically includes the following steps: (1) After the LNG equipment has completed the leak test, the inlet of the nitrogen recovery unit is connected to the liquid nitrogen outlet of the LNG equipment. Specifically, in this embodiment, the upstream hose of the nitrogen recovery pipeline is connected to the liquid nitrogen outlet of the LNG equipment, thereby obtaining the liquid nitrogen discarded by the LNG and inputting it into the nitrogen recovery unit for recovery and storage.

[0035] (2) Control the ball valves in the nitrogen recovery pipeline to ensure that the nitrogen recovery pipeline is open. The recovered liquid nitrogen is vaporized into nitrogen gas in the liquid nitrogen vaporizer and then enters the low-pressure buffer tank for buffering. In this embodiment, when the nitrogen recovery pipeline is open, the PLC controller controls the start of the booster pump. After the nitrogen is pressurized to a certain degree, it is transported to the air cooler for cooling and then enters the nitrogen container for storage and standby use.

[0036] (3) When there is a need to detect leaks in hydrogen energy equipment, in this case, the ball valve between the purge line and the hydrogen container is closed first, and the purge line, nitrogen line, hydrogen line, concentration control line and mixed gas line are opened at the same time. The high-pressure nitrogen in the nitrogen container is used to purge the gas mixing unit pipeline equipment to avoid interference from impurity air. After the purge is closed, the purge line is closed, and the hydrogen line is connected to the hydrogen container in which hydrogen is pre-stored. At the same time, the nitrogen line is opened, so that nitrogen and hydrogen enter the gas mixing unit respectively and are mixed in the gas mixer. At the same time, the initial opening of the gas transmission control valve in the nitrogen and hydrogen pipelines is controlled by the PLC through the monitoring values ​​of the flow meters in the nitrogen and hydrogen pipelines.

[0037] (4) The PLC controller receives the analysis data from the gas analyzer in real time and controls the opening of the gas control valves in the nitrogen pipeline and hydrogen pipeline based on the PID algorithm according to the difference between the set value and the analysis value and the flow data fed back by the flow meters in the nitrogen pipeline and hydrogen pipeline, so as to regulate the volume of nitrogen and hydrogen entering the gas mixer so that the output mixed gas concentration can meet the mixing requirements.

[0038] (5) When the hydrogen pipeline is fully opened and still cannot meet the mixed concentration requirement output by the mixed gas pipeline, the concentration control valve in the concentration control pipeline is opened to a corresponding degree to control the amount of hydrogen entering the mixed gas pipeline, thereby achieving regulation of the hydrogen concentration in the mixed gas pipeline.

[0039] To verify the effectiveness of the leak detection system based on nitrogen and hydrogen mixed gas for hydrogen energy equipment leak detection, see Figure 2 Under the pressure of 15MPa, pure nitrogen and 5% hydrogen / 95% nitrogen mixed gas were used to perform sealing tests with the same leakage rate. Figure 2Test data showed that when using pure nitrogen, it took an average of 180.78 minutes to achieve a 5% pressure drop (from 15 MPa to 14.25 MPa). Using a 5% hydrogen / 95% nitrogen mixture, the same 5% pressure drop took an average of only 108.31 minutes. This comparison of the two groups showed that the 5% hydrogen / 95% nitrogen mixture saved 72.47 minutes of testing time compared to pure nitrogen, increasing detection efficiency by 40.1%, significantly optimizing the leak detection process.

[0040] Based on the test results, the time formula t(c) for the equivalent standard test time based on nitrogen standard test time and nitrogen-hydrogen ratio was established as follows: .

[0041] Where, t N2 is the standard detection time of nitrogen; c is the integral fraction of hydrogen gas; α is the system volume correction coefficient, which defaults to 1; k(S) is the detector correction coefficient, and t(c) is the detection time of mixed gas.

[0042] Although some preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0043] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A hydrogen energy equipment leak detection system, characterized in that: It includes a nitrogen recovery unit connected to the liquid nitrogen outlet of the LNG equipment and provided with a nitrogen container, a hydrogen container for storing hydrogen, and a gas mixing unit respectively connected to the nitrogen container and the hydrogen container and provided with a gas mixer; The nitrogen recovery unit includes a nitrogen recovery pipeline provided between the liquid nitrogen outlet of the LNG equipment and the nitrogen container, wherein the nitrogen recovery pipeline is sequentially connected with a liquid nitrogen collection tank, a liquid nitrogen vaporizer, a low-pressure buffer tank, a booster pump and an air cooler from upstream to downstream; The gas mixing unit includes a nitrogen pipeline connected between the nitrogen inlet of the gas mixer and the nitrogen container, a hydrogen pipeline connected between the hydrogen inlet of the gas mixer and the hydrogen container, a concentration control pipeline connected between the mixed gas outlet of the gas mixer and the downstream of the hydrogen pipeline, and a mixed gas pipeline connected to the mixed gas outlet and connected in series with a gas analyzer; the nitrogen pipeline and the hydrogen pipeline are respectively connected in series with a flow meter and a gas control valve for controlling the conductivity of the corresponding pipeline.

2. The hydrogen energy equipment leak detection system according to claim 1, characterized in that: It also includes a purge pipeline with its two ends respectively connected to the nitrogen pipeline and the corresponding position upstream of the hydrogen pipeline; the purge pipeline is serially connected with a purge one-way valve for unidirectional conduction from the nitrogen pipeline to the hydrogen pipeline and a purge control valve for controlling the on and off of the purge pipeline.

3. The hydrogen energy equipment leak detection system according to claim 1 or 2, characterized in that: It also includes a discharge main line connected to the discharge port, and a discharge branch line connected to the nitrogen recovery pipeline at a position downstream of the liquid nitrogen collection tank, the liquid nitrogen vaporizer and the air cooler through a safety valve and a discharge valve.

4. The hydrogen energy equipment leak detection system according to claim 1, characterized in that: The driving air inlet of the boost pump is correspondingly connected to the compressed air source; the air cooler includes a nitrogen inlet correspondingly connected to the nitrogen recovery pipeline and an air inlet correspondingly connected to the driving air outlet of the boost pump.

5. The hydrogen energy equipment leak detection system according to claim 1, characterized in that: Corresponding on-off valves and one-way valves are respectively provided between the air inlet of the nitrogen recovery pipeline, the liquid nitrogen collection tank, the liquid nitrogen vaporizer, the low-pressure buffer tank, and the booster pump.

6. A method for leak detection of hydrogen energy equipment, characterized in that: The hydrogen energy equipment leak detection system according to claim 1 is implemented, specifically comprising the following steps: (1) After the LNG equipment has completed the leak test, connect the inlet of the nitrogen recovery unit to the liquid nitrogen outlet of the LNG equipment; (2) The nitrogen recovery pipeline is opened accordingly, and the recovered liquid nitrogen is vaporized into nitrogen in the liquid nitrogen vaporizer and then enters the low-pressure buffer tank. At the same time, the booster pump is started to pressurize the nitrogen to a corresponding degree and then cooled by the air cooler and then transported to the nitrogen container for storage; (3) When there is a need for leak detection of hydrogen energy equipment, the hydrogen pipeline is connected to the hydrogen container in which hydrogen is pre-stored, and at the same time, the nitrogen pipeline is connected and the flow meters and gas control valves in the nitrogen pipeline and hydrogen pipeline are used to control the volume of nitrogen and hydrogen entering the gas mixer; (4) The difference between the actual hydrogen concentration in the mixed gas and the set hydrogen concentration is determined according to the output result of the gas analyzer in the mixed gas pipeline, and used as the basis for regulating the degree of conductivity of the nitrogen pipeline and the hydrogen pipeline; (5) When the hydrogen pipeline is fully connected and still cannot meet the mixed concentration requirement output by the mixed gas pipeline, the concentration control pipeline is correspondingly connected to control the hydrogen concentration.

7. The hydrogen energy equipment leak detection method according to claim 6, characterized in that: In the step (3), before the gas mixing unit is operated, the nitrogen pipeline and the purge pipeline connected to the nitrogen pipeline and the corresponding position upstream of the hydrogen pipeline are opened, and the nitrogen in the nitrogen container is used for purge operation.

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