Nitrogen supplementing and hydrogen discharging device of liquid flow energy storage system

Abstract

The invention discloses a nitrogen supplementing and hydrogen discharging device of a liquid flow energy storage system, which comprises a galvanic pile, two electrolyte tanks, four pipelines, a pump, a nitrogen tank and a gas discharging assembly, the two electrolyte tanks are respectively connected to a positive electrode cavity and a negative electrode cavity of the galvanic pile, the four pipelines are connected between the electrolyte tanks and the galvanic pile, so that electrolyte circulates in the galvanic pile and the electrolyte tanks; the pump is installed on the pipeline and drives electrolyte to circulate, the nitrogen tank is installed on one side of the electrolyte tank and discharges nitrogen into the electrolyte tank, and the exhaust assembly is installed on the top of the electrolyte tank and discharges nitrogen and hydrogen on the top of the electrolyte tank. According to the nitrogen supplementing and hydrogen discharging device of the liquid flow energy storage system, separated hydrogen is taken away in time through cooperation of the circulation loop, the nitrogen tank and the exhaust assembly, the concentration of hydrogen on the top of the tank is prevented from being increased, and the explosion risk is remarkably reduced; the gas collecting bin is combined with the liquid seal hydrogen discharging pipe, efficient gathering and one-way guiding-out of hydrogen are achieved, and dissolving residues of the hydrogen in electrolyte are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid flow energy storage safety, in particular to a nitrogen supplementing and hydrogen discharging device for a liquid flow energy storage system. BACKGROUND

[0002] As one of the mainstream routes of grid-level long-time energy storage, the large-scale deployment of liquid flow batteries has strategic significance for improving the proportion of new energy consumption. During the operation of the all-vanadium system, hydrogen evolution occurs on the negative side for a long time. If hydrogen accumulates in the top space of the storage tank, the concentration will reach the explosion limit, which will directly threaten the safety of the power station. Therefore, the standards of various countries have strict limits on the hydrogen concentration in the tank, forcing enterprises to seek more reliable hydrogen management solutions.

[0003] Currently, the industry generally uses continuous nitrogen dilution and intermittent manual exhaust mode: nitrogen source is continuously injected into the tank top after decompression to maintain a slight positive pressure and dilute hydrogen. When the pressure reaches the set upper limit, the mechanical breathing valve or solenoid valve is opened for a short time to release. This scheme is simple in structure and low in cost, and has been applied to many energy storage products. Some newly built projects introduce online hydrogen meters and PLC linkage. When the hydrogen content exceeds the standard, the exhaust valve is automatically opened to try to reduce the frequency of manual intervention through automation.

[0004] However, the above two methods are based on "passive dilution and centralized discharge", which cannot block hydrogen accumulation from the source: continuous purging causes nitrogen waste, and the breathing valve may still have a local hydrogen concentration that is too high at the moment of opening. The service life of the sensor is shortened in the acidic mist environment, resulting in false negatives or false operations. How to achieve real-time separation and controllable discharge of hydrogen with low nitrogen consumption and maintenance-free structure has become an urgent need for the safe operation of liquid flow energy storage systems. SUMMARY

[0005] To solve the problem of hydrogen accumulation in the electrolyte tank top and delayed discharge in the prior art, the present application provides a nitrogen supplementing and hydrogen discharging device for a liquid flow energy storage system.

[0006] To achieve the above purpose, the present application provides a nitrogen supplementing and hydrogen discharging device for a liquid flow energy storage system, which adopts the following technical scheme: A nitrogen supplementing and hydrogen discharging device for a liquid flow energy storage system, comprising an electric pile; two electrolyte tanks connected to the positive and negative electrode cavities of the electric pile; four pipelines connected between the electrolyte tanks and the electric pile to form an electrolyte circulation loop; a pump installed on the pipeline; a nitrogen tank in communication with the electrolyte tank through a main nitrogen supply pipe; and an exhaust assembly communicated with the electrolyte tank for discharging gas in the electrolyte tank.

[0007] By adopting the technical scheme, closed circulation is formed between the stack and the electrolyte tank, the electrolyte is driven to flow by the pump, the nitrogen tank provides nitrogen to the electrolyte tank through the main nitrogen conveying pipe, the exhaust assembly timely discharges the gas in the tank, thereby suppressing hydrogen accumulation and reducing the risk of explosion.

[0008] Further, the application further comprises: a gas collection bin fixed to the top of the electrolyte tank and communicated with the electrolyte tank through a hydrogen discharge pipe, the bottom end of the hydrogen discharge pipe extends below the liquid level of the electrolyte, and the exhaust assembly is located on the gas collection bin.

[0009] By adopting the technical scheme, the gas collection bin collects the hydrogen gas floating in the electrolyte, the hydrogen discharge pipe extends below the liquid level to form a liquid seal, preventing hydrogen backflow, and the hydrogen discharge assembly is located on the top of the gas collection bin to realize directional discharge of hydrogen, thereby improving exhaust efficiency and safety.

[0010] Further, the bottom end of the hydrogen discharge pipe is connected with a gas collection cover, and the gas collection cover is located below the liquid level of the electrolyte and has a downward opening.

[0011] By adopting the technical scheme, the gas collection cover enlarges the hydrogen collection area, making it easier for gas bubbles to enter the hydrogen discharge pipe, reducing hydrogen residue in the electrolyte, and improving collection efficiency.

[0012] Further, the hydrogen discharge assembly comprises a connecting pipe, a first cover, a floating ball and a connecting rod, the connecting pipe is fixed to the top of the gas collection bin and communicated with the inside of the gas collection bin, the first cover is arranged in the connecting pipe in a lifting manner, the floating ball is located in the gas collection bin, and the connecting rod is connected between the floating ball and the first cover.

[0013] By adopting the technical scheme, the hydrogen gas aggregation causes the floating ball to rise, driving the first cover to open and realizing automatic exhaust, and when the hydrogen gas decreases, the floating ball falls, the cover resets, and unnecessary nitrogen loss is avoided.

[0014] Further, a first bolt is screwed to the top of the connecting pipe, one end of the first bolt extending into the connecting pipe is rotationally provided with a first piston, and a first spring is arranged between the first piston and the first cover.

[0015] By adopting the technical scheme, rotating the first bolt can adjust the spring pre-tightening force, thereby setting the floating ball starting threshold value, adapting to exhaust requirements under different working conditions, and improving control accuracy.

[0016] Further, a Venturi tube is arranged on the main nitrogen conveying pipe in communication, and a throat interface of the Venturi tube is communicated with the connecting pipe.

[0017] By adopting the technical scheme, when nitrogen gas flows through the throat, negative pressure is generated, hydrogen gas in the connecting pipe is sucked in and mixed with the nitrogen gas, and then is sent back to the tank, and is uniformly discharged by the exhaust assembly, so that hydrogen gas circulation dilution is realized, and instantaneous emission concentration is reduced.

[0018] Further, the exhaust assembly comprises a valve body and a second cover; the valve body is fixedly installed on the gas collection chamber and is provided with an air inlet and an air outlet, the air inlet is communicated with the inside of the electrolyte tank through an exhaust pipe; and the second cover is arranged in the valve body in a lifting manner.

[0019] By adopting the technical scheme, when the pressure in the tank rises, the gas pushes the second cover to rise, the exhaust passage is automatically opened, the cover falls back after the pressure drops, air backflow is prevented, and self-stable pressure emission is realized.

[0020] Further, a second bolt is screwed on the top of the valve body, a second piston is arranged on the end of the second bolt extending into the valve body in a rotating manner, and a second spring is arranged between the second piston and the second cover.

[0021] By adopting the technical scheme, the second bolt can be adjusted to change the spring compression amount, set the valve body opening pressure, and be compatible with different system pressure grades, so that the universality and safety are improved.

[0022] Further, the air outlet is communicated with a mixing tank through a conveying pipe.

[0023] By adopting the technical scheme, the discharged nitrogen-hydrogen mixed gas is collected in the mixing tank, which is convenient for subsequent unified treatment or nitrogen gas recovery, reduces resource waste and reduces environmental risk.

[0024] Further, a pressure reducing valve and a one-way valve are arranged on the main nitrogen conveying pipe; and stop valves are arranged on the pipeline and the main nitrogen conveying pipe respectively.

[0025] By adopting the technical scheme, the pressure reducing valve stabilizes the nitrogen pressure, the one-way valve prevents gas backflow, and the stop valves realize segmented maintenance and emergency shutdown, so that the system operation safety and maintenance convenience are ensured.

[0026] Compared with the prior art, the present application has the following beneficial effects: The nitrogen supplementing and hydrogen discharging device of the liquid flow energy storage system of the application timely takes away the separated hydrogen through the cooperation of the circulation loop, the nitrogen tank and the exhaust assembly, avoids the increase of the hydrogen concentration on the tank top, and significantly reduces the explosion risk; the gas collection bin is combined with the liquid seal hydrogen discharge pipe to realize efficient hydrogen gathering and one-way discharge, and reduce the hydrogen dissolution residue in the electrolyte; the float-cover structure realizes pure mechanical automatic exhaust without external energy and sensors, and is reliable in operation and small in maintenance amount; the Venturi negative pressure injection pre-mixes the hydrogen into the nitrogen to reduce the instantaneous hydrogen concentration of the discharge and reduce the nitrogen consumption; the pressure self-opening valve body is matched with the adjustable spring to flexibly set the exhaust pressure according to the system requirement, prevent excessive discharge or pressure out of control; and the mixed tank centrally collects the nitrogen-hydrogen mixed gas to provide conditions for subsequent separation or recovery, improve the gas utilization rate and simplify the tail gas treatment process. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The whole structure schematic view of the nitrogen supplementing and hydrogen discharging device of the liquid flow energy storage system described in the embodiment of the application; Figure 2 The partial connection schematic view of the electrolyte tank and the nitrogen tank described in the embodiment of the application; Figure 3 The cross-sectional view of the electrolyte tank described in the embodiment of the application; Figure 4 The connection schematic view of the hydrogen discharge assembly and the Venturi tube described in the embodiment of the application; Figure 5 The schematic view of the hydrogen discharge assembly described in the embodiment of the application; Figure 6 The cross-sectional view of the hydrogen discharge assembly described in the embodiment of the application; Figure 7 The connection schematic view of the exhaust assembly and the mixed tank described in the embodiment of the application; Figure 8 The cross-sectional view of the exhaust assembly described in the embodiment of the application; Figure 9 The exploded schematic view of the exhaust assembly described in the embodiment of the application.

[0028] Explanation of reference signs: 1, stack; 2, electrolyte tank; 3, pipeline; 4, pump; 5, nitrogen tank; 6, main nitrogen conveying pipe; 7, exhaust assembly; 701, valve body; 702, second cover; 703, gas inlet; 704, gas outlet; 705, second bolt; 706, second piston; 707, second spring; 8, gas collection bin; 9, hydrogen discharge pipe; 10, hydrogen discharge assembly; 1001, connecting pipe; 1002, first cover; 1003, float; 1004, connecting rod; 1005, first bolt; 1006, first piston; 1007, first spring; 11, gas collecting hood; 12, venturi; 13, pressure reducing valve; 14, check valve; 15, stop valve; 16, delivery pipe; 17, mixing tank; 18, exhaust pipe. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other manners different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit and scope of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0030] As shown in Figure 1 and Figure 2 The nitrogen supplementing and hydrogen discharging device of the liquid flow energy storage system of the present application is shown, which comprises an electric pile 1, an electrolyte tank 2, a pipeline 3, a pump 4, a nitrogen tank 5, and an exhaust assembly 7.

[0031] The number of the electrolyte tanks 2 is two, which are connected to the positive and negative electrode cavities of the electric pile 1 respectively, the number of the pipelines 3 is four, which are connected between the electrolyte tanks 2 and the electric pile 1 to make the electrolyte circulate in the electric pile 1 and the electrolyte tanks 2, the pump 4 is installed on the pipeline 3 to drive the electrolyte to circulate, the nitrogen tank 5 is installed on one side of the electrolyte tank 2 to discharge nitrogen into the electrolyte tank 2, and the exhaust assembly 7 is installed on the top of the electrolyte tank 2 to discharge the nitrogen and hydrogen on the top of the electrolyte tank 2.

[0032] It is worth mentioning that the electric pile 1 is a common electric pile in the full vanadium battery in the prior art, which will not be described here again, the two electrolyte tanks 2 are for the positive and negative electrodes respectively, the electrolyte in the electrolyte tanks 2 circulates in the electric pile 1 to contact the electrodes in the electric pile 1 to realize charging and discharging, the four pipelines 3 are divided into two groups to connect the two electrolyte tanks 2 and one electric pile 1, and the pump 4 can ensure the electrolyte to circulate in the electric pile 1 and the electrolyte tanks 2, thereby improving the charging and discharging efficiency.

[0033] In addition, hydrogen is generated after the vanadium electrolyte and the electrode react, especially on the negative electrode, because the potential is too negative or the electrode catalytic activity is high, a hydrogen evolution side reaction occurs to generate hydrogen, the hydrogen rises and gathers on the top of the electrolyte tank 2, the nitrogen is discharged into the top of the electrolyte to form a nitrogen seal, and the hydrogen and part of the nitrogen are discharged from the exhaust assembly 7, so that the safety of the electrolyte tank 2 is improved, and explosion caused by too high hydrogen concentration is avoided.

[0034] Based on the above overall introduction, an exemplary structure of the present embodiment is shown in Figure 3As shown, the electrolyte tank 2 is provided with a gas collection chamber 8 at the top, the gas collection chamber 8 is communicated with the electrolyte tank 2 through a hydrogen discharge pipe 9, the exhaust assembly 7 is provided with an exhaust pipe 18 communicated with the electrolyte tank 2, and the nitrogen tank 5 is communicated with the electrolyte tank 2 through the main nitrogen conveying pipe 6.

[0035] It should be noted that the gas collection chamber 8 is used to store hydrogen, the hydrogen generated in the electrolyte tank 2 flows into the gas collection chamber 8 through the hydrogen discharge pipe 9, the hydrogen discharge pipe 9 extends downward into the electrolyte, that is, the liquid level of the electrolyte is higher than the bottom end of the hydrogen discharge pipe 9, and a gas collection cover 11 can be arranged at the bottom of the hydrogen discharge pipe 9, when the hydrogen bubbles generated by the stack 1 enter the electrolyte tank 2 with the electrolyte, the hydrogen floats up, most of the hydrogen bubbles will enter the gas collection cover 11, and then flow into the gas collection chamber 8 through the gas collection cover 11 and the hydrogen discharge pipe 9, and a small amount of hydrogen will mix with the nitrogen in the upper part of the electrolyte, but the amount is small and will not be dangerous, and the hydrogen discharge assembly 10 can be arranged at the top of the gas collection chamber 8, when the hydrogen concentration reaches a set value, the hydrogen discharge assembly 10 releases hydrogen, the exhaust pipe 18 passes through the gas collection chamber 8 and is partially communicated with the nitrogen in the nitrogen tank 5, when the preset pressure is reached, the exhaust assembly 7 is opened to discharge the nitrogen and hydrogen, the main nitrogen conveying pipe 6 is connected to the nitrogen part at one end of the electrolyte tank 2 to ensure that the nitrogen can be directly discharged into the nitrogen sealed space, and a flame arrester can be communicated with the hydrogen discharge assembly 10 to directly discharge the hydrogen into the air.

[0036] As a preferred embodiment, as shown in Figure 5 and Figure 6 The hydrogen discharge assembly 10 of the embodiment includes a connecting pipe 1001 arranged at the top of the gas collection chamber 8, a first cover 1002 is arranged in the connecting pipe 1001 in a lifting manner, the bottom of the first cover 1002 is connected with a floating ball 1003, and the floating ball 1003 extends into the gas collection chamber 8. It should be noted that the top space of the connecting pipe 1001 is large, the bottom space is small, the first cover 1002 can be blocked at the connection between the large space and the small space, the floating ball 1003 and the first cover 1002 are connected through a connecting rod 1004, the connecting rod 1004 extends downward out of the connecting pipe 1001 and into the gas collection chamber 8, and the floating ball 1003 is located at the bottom end of the connecting rod 1004, when the hydrogen concentration gradually increases, the hydrogen floats up to lift the floating ball 1003, the first cover 1002 rises, and the hydrogen is discharged from the connecting pipe 1001, thereby realizing the discharge of hydrogen.

[0037] In addition, the first bolt 1005 is screwed on the top of the connecting pipe 1001, the first piston 1006 is rotatably arranged at one end of the first bolt 1005 in the connecting pipe 1001, and the first spring 1007 is arranged between the first piston 1006 and the first cover 1002. Specifically, the pressure of the first spring 1007 can be adjusted by rotating the first bolt 1005, so as to control the pressure at which the floating ball 1003 floats, the first piston 1006 can prevent hydrogen from being discharged from the first bolt 1005, and the first spring 1007 can be adjusted by abutting against the first piston 1006.

[0038] As preferred, as shown in Figure 4 In the embodiment, the Venturi tube 12 is arranged in communication with the main nitrogen conveying pipe 6, and the throat interface of the Venturi tube 12 is in communication with the hydrogen discharge assembly 10. Specifically, according to the basic principle of the Venturi tube 12, negative pressure is generated at the throat during the conveying of nitrogen, the hydrogen discharge assembly 10 conveys hydrogen into the Venturi tube 12 to mix with nitrogen, and then the nitrogen-hydrogen mixture is discharged into the nitrogen-sealed space through the main nitrogen conveying pipe 6. Since the throat interface of the Venturi tube 12 is small, the concentration of nitrogen is higher than that of hydrogen, and no danger occurs. The nitrogen-hydrogen mixture is discharged until the hydrogen in the gas collection bin 8 is completely discharged.

[0039] As a preferred embodiment, as shown in Figure 7 and Figure 8 The exhaust assembly 7 of the embodiment includes the valve body 701 fixedly installed on the gas collection bin 8 and the second cover 702 arranged in the valve body 701 in a lifting manner. The valve body 701 is provided with the gas inlet 703 and the gas outlet 704, and the gas inlet 703 is in communication with the exhaust pipe 18. It should be noted that the valve body 701 is divided into the upper cavity and the lower cavity by the second cover 702. The connecting pipe 1001 extends into the nitrogen-sealed space in the electrolyte tank 2, the nitrogen-hydrogen mixture conveyed by the main nitrogen conveying pipe 6 increases, the nitrogen-hydrogen mixture in the tank is conveyed to the lower cavity in the valve body 701 through the exhaust pipe 18, the pressure increases to lift the second cover 702, the nitrogen-hydrogen mixture enters the upper cavity of the valve body 701 and is discharged from the gas outlet 704. The mixing tank 17 can be arranged on one side of the nitrogen tank 5, the mixing tank 17 is connected with the gas outlet 704 through the conveying pipe 16, the discharged nitrogen-hydrogen mixture is collected for hydrogen removal treatment. The arrangement ensures that the nitrogen can be used again, and the hydrogen removal treatment is a common mode in the prior art, which will not be described here.

[0040] In addition, as shown in Figure 2 and Figure 9As shown, the second bolt 705 is screwed on the top of the valve body 701, the second bolt 705 extends into one end of the valve body 701 and is rotationally arranged with the second piston 706, the second spring 707 is arranged between the second piston 706 and the second cover 702, the second piston 706 is lifted by rotating the second bolt 705, so as to adjust the pressure of the second spring 707, and thus the second cover 702 is opened only when the pressure in the electrolyte tank 2 reaches the preset value. In order to ensure the safety of the equipment, a pressure reducing valve 13 and a one-way valve 14 are arranged at the connection between the nitrogen tank 5 and the main nitrogen conveying pipe 6, the pressure reducing valve 13 can reduce and maintain the pressure, and the one-way valve 14 can avoid the backflow of nitrogen, in application, the stop valve 15 is arranged at the pipeline 3 and the main nitrogen conveying pipe 6 respectively, so as to facilitate the start and stop of the equipment, the impact base is connected to the bottom of the second cover 702, the connecting plate is arranged between the impact base and the second cover 702, the exhaust pipe 18 extends into the valve body 701 and the pipe opening is directed to the impact base, so that the gas flow is directly aligned with the impact base, the pressure is concentrated on the impact base, and the second cover 702 is easily pushed away, so as to realize the discharge of the nitrogen-hydrogen mixed gas.

[0041] The nitrogen supplementing and hydrogen discharging device of the liquid flow energy storage system in the embodiment can timely take away the separated hydrogen by the cooperation of the circulating loop, the nitrogen tank 5 and the exhaust assembly 7, avoid the increase of the hydrogen concentration on the tank top, and significantly reduce the explosion risk; the gas collection bin 8 and the liquid seal hydrogen discharge pipe 9 are combined to realize the efficient gathering and one-way discharge of hydrogen, and reduce the residual dissolution of hydrogen in the electrolyte; the float ball 1003 and the cover structure realize pure mechanical automatic exhaust without external energy and sensors, and are reliable in operation and small in maintenance amount; the Venturi negative pressure injection pre-mixes hydrogen into nitrogen, reduces the instantaneous hydrogen concentration of discharge, and reduces the nitrogen consumption; the pressure self-opening valve body 701 is matched with the adjustable spring, so that the exhaust pressure can be flexibly set according to the system requirement, and the excessive discharge or pressure out of control is prevented; the mixed tank 17 collects the nitrogen-hydrogen mixed gas, provides conditions for subsequent separation or recovery, improves the gas utilization rate, and simplifies the tail gas treatment process.

[0042] Although the application discloses the preferred embodiments to achieve the above-mentioned purpose, it is not intended to limit the structural features of the application, and any person skilled in the art should know that any easily thought change or modification is possible under the technical spirit of the application, and is covered by the patent application scope of the application.

Claims

1. A device for nitrogen supplement and hydrogen removal of a liquid flow energy storage system, characterized in that, The device comprises: a stack (1); two electrolyte tanks (2) connected to the positive and negative electrode cavities of the stack (1) respectively; four pipelines (3) connected between the electrolyte tanks (2) and the stack (1) to form an electrolyte circulation loop; a pump (4) installed on the pipeline (3); a nitrogen tank (5) in communication with the electrolyte tank (2) through a main nitrogen delivery pipeline (6); an exhaust assembly (7) arranged in communication on the electrolyte tank (2) for discharging gas in the electrolyte tank (2).

2. The device for nitrogen supplement and hydrogen removal of liquid flow energy storage system according to claim 1, characterized in that, The device further comprises: a gas collection bin (8) fixed to the top of the electrolyte tank (2) and in communication with the electrolyte tank (2) through a hydrogen discharge pipeline (9), the bottom end of the hydrogen discharge pipeline (9) extending below the electrolyte liquid level, and the exhaust assembly (7) being arranged on the gas collection bin (8); a hydrogen discharge assembly (10) arranged in communication on the top of the gas collection bin (8) for discharging hydrogen in the gas collection bin (8).

3. The device for supplementing nitrogen and discharging hydrogen of the liquid flow energy storage system according to claim 2, characterized in that: the bottom end of the hydrogen discharge pipeline (9) is connected with a gas collection cover (11), and the gas collection cover (11) is located below the electrolyte liquid level and opens downward.

4. The device for supplementing nitrogen and discharging hydrogen of the liquid flow energy storage system according to claim 2, characterized in that: the hydrogen discharge assembly (10) comprises a connecting pipeline (1001), a first cover (1002), a floating ball (1003), and a connecting rod (1004), the connecting pipeline (1001) is fixed to the top of the gas collection bin (8) and in communication with the inside of the gas collection bin (8), the first cover (1002) is arranged in the connecting pipeline (1001) in a lifting manner, the floating ball (1003) is located in the gas collection bin (8), and the connecting rod (1004) is connected between the floating ball (1003) and the first cover (1002).

5. The device for supplementing nitrogen and discharging hydrogen of the liquid flow energy storage system according to claim 4, characterized in that: a first bolt (1005) is screwed to the top of the connecting pipeline (1001), the end of the first bolt (1005) extending into the connecting pipeline (1001) is rotationally provided with a first piston (1006), and a first spring (1007) is arranged between the first piston (1006) and the first cover (1002).

6. The device for supplementing nitrogen and discharging hydrogen of the liquid flow energy storage system according to claim 4, characterized in that: a Venturi tube (12) is arranged in communication on the main nitrogen delivery pipeline (6), and the throat interface of the Venturi tube (12) is in communication with the connecting pipeline (1001).

7. The device for supplementing nitrogen and discharging hydrogen of the liquid flow energy storage system according to claim 2, characterized in that: the exhaust assembly (7) comprises a valve body (701) and a second cover (702), the valve body (701) is fixedly installed on the gas collection bin (8) and is provided with an air inlet (703) and an air outlet (704), the air inlet (703) is in communication with the inside of the electrolyte tank (2) through an exhaust pipeline (18), and the second cover (702) is arranged in the valve body (701) in a lifting manner. 8.The nitrogen supplementing and hydrogen discharging device for liquid flow energy storage system according to claim 7, characterized in that: The top of the valve body (701) is screwed with a second bolt (705), the end of the second bolt (705) extending into the valve body (701) is rotationally provided with a second piston (706), and the second piston (706) is provided with a second spring (707) between the second piston (706) and the second cover (702). 9.The nitrogen supplementing and hydrogen discharging device for liquid flow energy storage system according to claim 7, characterized in that: The gas outlet (704) is connected with a mixing tank (17) through a conveying pipe (16). 10.The nitrogen supplementing and hydrogen discharging device for liquid flow energy storage system according to any one of claims 1-9, characterized in that: The main nitrogen conveying pipe (6) is provided with a pressure reducing valve (13) and a one-way valve (14), and the pipeline (3) and the main nitrogen conveying pipe (6) are respectively provided with stop valves (15).

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