Water electrolysis hydrogen production system

Abstract

The utility model discloses a water electrolysis hydrogen production system, and relates to the technical field of water electrolysis hydrogen production, the water electrolysis hydrogen production system comprises a liquid circulation flow path, and the liquid circulation flow path comprises a gas-liquid separator, a circulation pump and an electrolytic bath which are sequentially distributed in the direction from upstream to downstream; the water electrolysis hydrogen production system further comprises a backflow branch, the liquid inlet end of the backflow branch is connected into the liquid circulation flow path between the circulation pump and the electrolytic bath, the liquid outlet end of the backflow branch is connected into the liquid circulation flow path on the upstream of the circulation pump, and the backflow branch is provided with a first valve. The first valve member has an opening pressure. According to the technical scheme, the circulating pump is prevented from working below the minimum working flow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water electrolysis hydrogen production, and particularly relates to a water electrolysis hydrogen production system. BACKGROUND

[0002] In the water electrolysis hydrogen production system, the alkali liquor is circulated in the equipment such as the gas-liquid separator, the pump and the electrolytic cell. In order to adapt to the low power load condition, the circulation amount of the alkali liquor needs to be adjusted to a very small flow rate. However, for a certain circulation pump, the flow rate range is certain, and there is a long-term minimum flow rate requirement. If the circulation pump works below the minimum working flow rate for a long time, the pump will be damaged. CONTENT OF THE UTILITY MODEL

[0003] The main purpose of the present application is to provide a water electrolysis hydrogen production system, which aims to avoid the circulation pump working below the minimum working flow rate.

[0004] To achieve the above purpose, the water electrolysis hydrogen production system provided by the present application comprises a liquid circulation flow path, which comprises a gas-liquid separator, a circulation pump and an electrolytic cell distributed in sequence in the direction from upstream to downstream.

[0005] The water electrolysis hydrogen production system further comprises a backflow branch, the liquid inlet end of the backflow branch is connected to the liquid circulation flow path between the circulation pump and the electrolytic cell, the liquid outlet end of the backflow branch is connected to the liquid circulation flow path upstream of the circulation pump, the backflow branch is provided with a first valve, and the first valve has an opening pressure.

[0006] In an embodiment, the first valve is configured as a back pressure valve or an adjustable one-way valve.

[0007] In an embodiment, the backflow branch is further provided with a second valve between the liquid outlet end and the first valve, and the opening degree of the second valve is adjustable.

[0008] In an embodiment, the second valve is configured as at least one of a stop valve and a butterfly valve.

[0009] In an embodiment, the second valve is configured as a manual valve.

[0010] In an embodiment, the liquid outlet end of the backflow branch is connected to the liquid circulation flow path between the circulation pump and the gas-liquid separator.

[0011] In an embodiment, the liquid circulation flow path further comprises a heat exchanger located between the gas-liquid separator and the circulation pump, and the liquid outlet end of the backflow branch is connected to the liquid circulation flow path between the circulation pump and the heat exchanger.

[0012] In an embodiment, the gas-liquid separator includes a hydrogen-side gas-liquid separator and an oxygen-side gas-liquid separator, which are arranged in parallel in the liquid circulation flow path upstream of the heat exchanger.

[0013] In an embodiment, the liquid circulation flow path includes a first flow section downstream of the access position of the liquid inlet end, which is provided with a regulating valve.

[0014] In an embodiment, the first flow section is further provided with a flow detection device.

[0015] In an embodiment, the liquid circulation flow path includes a second flow section between the access position of the liquid inlet end and the circulation pump, which is provided with a pressure detection device.

[0016] In the technical solution of the present application, when the required amount of lye circulation is lower than the minimum working flow rate of the circulation pump, the circulation pump can still be operated at the minimum working flow rate, at which time, the pressure at the liquid inlet end can be greater than or equal to the opening pressure of the first valve element to guide the return branch to be open, and the liquid discharged from the circulation pump can be divided into two parts, one part flows to the electrolytic cell through the liquid circulation flow path according to the required amount of lye circulation of the system, and the remaining part can be shunted through the return branch to return to the liquid circulation flow path upstream of the circulation pump, and thus can be utilized. In this way, the circulation pump can continue to operate at the minimum working flow rate under the minimum load of the system, thereby ensuring the service life of the circulation pump.

[0017] When the required amount of lye circulation is greater than the minimum working flow rate of the circulation pump, the circulation pump operates according to the required amount of lye circulation of the system, at which time, due to the increase in the flow rate of the circulation pump, the pressure at the liquid inlet end will decrease and cannot meet the opening pressure of the first valve element, and the return branch can be closed, and the liquid discharged from the circulation pump will flow to the electrolytic cell through the liquid circulation flow path only, to ensure the stable operation of the system. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in these drawings without creative labor for those skilled in the art.

[0019] Figure 1 The system schematic diagram of an embodiment of the water electrolysis hydrogen production system provided by the present application.

[0020] BRIEF DESCRIPTION OF DRAWINGS

[0021] 100, electrolytic cell;

[0022] 200, gas-liquid separator; 201, hydrogen-side gas-liquid separator; 202, oxygen-side gas-liquid separator;

[0023] 300, circulating pump;

[0024] 410, reflux branch; 411, liquid inlet end; 412, liquid outlet end;

[0025] 420, first flow section; 421, regulating valve; 422, flow detection device;

[0026] 430, second flow section; 431, pressure detection device;

[0027] 510, first valve; 520, second valve; 600, heat exchanger.

[0028] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0030] It should be noted that if the present application has a directional indication (such as up, down, left, right, front, back, etc.) in the embodiments, the directional indication is only used to explain the relative position relationship, movement condition, etc. between the components in a certain posture, and if the certain posture changes, the directional indication also changes accordingly.

[0031] In addition, if the present application has a description of "first", "second" and the like in the embodiments, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appears throughout the text, which means that the three parallel schemes include A scheme, or B scheme, or A and B schemes are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection claimed by the present application.

[0032] The application provides a water electrolysis hydrogen production system.

[0033] Referring to Figure 1 The water electrolysis hydrogen production system comprises a gas-liquid separator 200 and an electrolytic tank 100, and has an electrolysis product flow path. In the electrolysis product flow path, the gas-liquid separator 200 is located downstream of the electrolytic tank 100. The gas electrolysis product generated by the electrolytic tank 100 carries the alkali liquor into the gas-liquid separator 200, and then gas-liquid separation occurs in the gas-liquid separator 200. The gas continues to flow downstream of the electrolysis product flow path, and the alkali liquor remains in the gas-liquid separator 200.

[0034] The water electrolysis hydrogen production system also has a liquid circulation flow path. The gas-liquid separator 200, the circulation pump 300 and the electrolytic tank 100 are arranged in the upstream-to-downstream direction of the liquid circulation flow path. That is, after the circulation pump 300 is operated, the alkali liquor in the gas-liquid separator 200 can be recycled to the electrolytic tank 100 through the liquid circulation flow path and participate in the electrolysis reaction again.

[0035] The circulation pump 300 has a minimum working flow rate. It can be understood that the minimum working flow rate of the pump refers to the minimum flow rate at which the pump can effectively work under normal operating conditions. This parameter is very important to ensure the safe and efficient operation of the pump. If the pump is operated below its minimum working flow rate, it may cause some problems and affect the service life of the pump. For example, when the pump is operated below the minimum working flow rate, the fluid cannot effectively carry away the heat generated by the motor and the bearing, which may cause the pump to overheat and damage the internal components of the pump.

[0036] In an embodiment of the application, the water electrolysis hydrogen production system further comprises a backflow branch 410. The liquid inlet end 411 of the backflow branch 410 is connected to the liquid circulation flow path between the circulation pump 300 and the electrolytic tank 100. The liquid outlet end 412 of the backflow branch 410 is connected to the liquid circulation flow path upstream of the circulation pump 300. The backflow branch 410 is provided with a first valve 510, and the first valve 510 has an opening pressure.

[0037] In the technical solution of the present application, when the required amount of lye circulation is lower than the minimum working flow rate of the circulation pump 300, the circulation pump 300 can still be operated at the minimum working flow rate, at this time, the pressure at the liquid inlet end 411 can be greater than or equal to the opening pressure of the first valve 510, so as to open the return branch 410, and the liquid flowing out of the circulation pump 300 can be divided into two parts, one part flows to the electrolytic tank 100 through the liquid circulation flow path according to the required amount of lye circulation, and the remaining part can be branched off through the return branch 410, so as to be returned to the liquid circulation flow path upstream of the circulation pump 300 and be utilized again. In this way, when the system is operated at the minimum load power, even if the required amount of lye circulation is lower than the minimum working flow rate of the circulation pump 300, the circulation pump 300 can still be continuously operated at the minimum working flow rate, so as to guarantee the service life of the circulation pump 300.

[0038] When the required amount of lye circulation is greater than the minimum working flow rate of the circulation pump 300, the circulation pump 300 is operated according to the required amount of lye circulation, at this time, since the flow rate of the circulation pump 300 is increased, and the flow rate and the pressure are inversely proportional, the pressure at the liquid inlet end 411 will decrease, and cannot meet the opening pressure of the first valve 510, so the return branch 410 can be closed, and the liquid flowing out of the circulation pump 300 will flow to the electrolytic tank 100 through the liquid circulation flow path only, so as to guarantee the stable operation of the system.

[0039] In an embodiment, the first valve 510 is configured as a back pressure valve or an adjustable check valve. These three types of valves all have an opening pressure, and the valve can be opened only when the pressure at the liquid inlet end 411 is greater than or equal to the opening pressure, and the opening pressure can be adjusted, and can be adjusted adaptively according to the minimum working flow rate of the circulation pump 300 and the required amount of lye circulation under the minimum load of the system.

[0040] Among them, the back pressure valve is also called back pressure regulating valve or pressure maintaining valve, the back pressure valve usually includes a valve body, a movable valve clack (or valve core), a spring and an adjusting mechanism, the valve clack is installed in the valve body and is subjected to a certain closing force by the spring, and the adjusting mechanism (such as adjusting screw or knob) is used to adjust the pre-tightening force of the spring, so as to set the required back pressure value (i.e. opening pressure). When the pressure at the inlet is lower than the set back pressure value, the pre-tightening force of the spring keeps the valve clack in the closed state, and prevents the fluid from passing through, so the return branch 410 is cut off. Once the pressure at the inlet rises and exceeds the set back pressure value, the valve clack will be pushed open, allowing part of the fluid to pass through the valve and be discharged, so the return branch 410 is opened. The pre-tightening force of the spring can be changed through the adjusting mechanism, so as to adjust the opening pressure of the back pressure valve.

[0041] An adjustable check valve, also known as an adjustable non-return valve or adjustable backstop valve, is a special type of check valve that not only prevents fluid from flowing in the reverse direction, but also allows a specific opening pressure to be set through adjustment. This valve combines the basic function of a check valve with the additional ability to adjust the pressure. An adjustable check valve typically includes a valve body, a valve disc (or valve core), a spring, and an adjustment mechanism. The valve disc is installed in the valve body and can move freely to allow forward flow and prevent reverse flow. The spring is used to apply closing force to the valve disc, ensuring that it remains closed in the absence of sufficient forward pressure. The adjustment mechanism allows the user to adjust the pre-tightening force of the spring, thereby changing the minimum pressure required for the valve disc to open. When fluid flows from the inlet to the outlet, if the pressure exceeds the set opening pressure, the valve disc will be pushed open, allowing fluid to pass through, and the backflow branch 410 is turned on. Once the fluid stops flowing or the pressure drops below the set value, the spring will push the valve disc back to the closed position, preventing fluid from flowing in the reverse direction, and the backflow branch 410 is turned off. The user can increase or decrease the pre-tightening force of the spring through the adjustment mechanism (such as a knob or screw). Increasing the pre-tightening force will increase the pressure required for the valve disc to open, and decreasing the pre-tightening force will decrease this pressure.

[0042] In an embodiment, the backflow branch 410 further comprises a second valve 520 between the outlet 412 and the first valve 510, and the opening degree of the second valve 520 is adjustable. In this way, the maximum flow capacity of the backflow branch 410 can be adjusted by adjusting the opening degree of the second valve 520. That is, the first valve 510 is used to switch the on-off of the backflow branch 410, and the second valve 520 is used to adjust the flow load that the backflow branch 410 can withstand.

[0043] Specifically, when the first valve 510 and the second valve 520 are initialized, the first valve 510 can be in a closed state, and the flow of the liquid circulation flow path is just the minimum working flow of the circulation pump 300. At this time, the opening pressure of the first valve 510 is adjusted through the adjustment mechanism of the first valve 510, so that the pressure of the inlet 411 at this time is just enough to make the first valve 510 open. That is, the opening pressure of the first valve 510 will correspond to the pressure of the inlet 411 when the circulation pump 300 operates at the minimum working flow. Therefore, when the flow at the inlet 411 is less than the minimum working flow of the circulation pump 300, the pressure of the inlet 411 will be greater than the opening pressure of the first valve 510, that is, the backflow branch 410 can be turned on.

[0044] Then, the access position of the liquid inlet end 411 and the flow of the liquid circulation flow path (i.e., the first flow section 420) between the electrolytic tank 100 are adjusted to the required amount of lye flow at the minimum load power of the system, and the opening of the second valve 520 is adjusted so that the outlet flow of the circulation pump 300 is adjusted to the minimum working flow. In this way, when the system is running at the minimum load power, the flow of the liquid inlet end 411 is less than the minimum working flow of the circulation pump 300, the first valve 510 can be kept in the open state, and the opening of the second valve 520 can ensure that the return branch 410 can bear the remaining part of the minimum working flow of the circulation pump 300 after the required lye flow of the system, which is also the maximum flow carrying capacity required by the return branch 410.

[0045] When the system is running at a power slightly greater than the minimum load power, but the required lye flow of the system is still less than the minimum working flow of the circulation pump 300, at this time, the flow of the liquid inlet end 411 is still less than the minimum working flow of the circulation pump 300, the first valve 510 can still be kept in the open state, and the required lye flow returned by the return branch 410 is smaller, and the opening of the second valve 520 can meet the flow load.

[0046] When the circulation pump 300 is running at a flow greater than the minimum working flow, the flow of the liquid inlet end 411 is increased, and the pressure is reduced to less than the opening pressure of the first valve 510, i.e., the first valve 510 is switched to the closed state, thereby cutting off the return branch 410 to ensure the stable circulation of the lye.

[0047] Further, in the embodiment, the second valve 520 is configured as at least one of a stop valve and a butterfly valve. The second valve 520 can be a single valve or can be composed of multiple valves, which can be of the same type or different types. In the case of multiple valves, the openings of the multiple valves can be adjusted in a gradient to avoid the formation of a flow sudden change point in the return branch 410, thereby ensuring smooth and smooth liquid flow in the return branch 410.

[0048] The stop valve is usually composed of a cylindrical valve body, a movable valve disc (or valve disc) and a valve seat. The valve disc moves up and down through the valve stem to control the flow of fluid. When the valve disc rises, the fluid can pass through the valve body; when the valve disc descends and contacts the valve seat, the fluid is cut off. The stop valve has good flow regulation ability and can accurately control the flow by adjusting the position of the valve disc.

[0049] A butterfly valve is mainly composed of a valve body, a butterfly plate and a valve stem. The valve body is usually a cylindrical or circular pipe section. The butterfly plate (or valve disc) is located inside the valve body and controls the flow of fluid by rotating. The butterfly plate is usually circular with a diameter slightly smaller than the inner diameter of the valve body. The valve stem connects the butterfly plate to an external handle or other actuator, which is used to rotate the butterfly plate. When the butterfly plate is rotated 90 degrees so that it is parallel to the direction of fluid flow, the valve is fully open and fluid can pass freely. When the butterfly plate is rotated 90 degrees so that it is perpendicular to the direction of fluid flow, the valve is fully closed and fluid is completely blocked. By rotating the butterfly plate to any angle between 0 and 90 degrees, partial adjustment of the flow can be achieved. For example, rotating 45 degrees can reduce the flow by about half.

[0050] Therefore, in this embodiment, the opening degree can be adjusted by any one of the two valves, so as to change the flow load that the return branch 410 can bear, so as to match the demand of the system. Of course, in other embodiments, the second valve 520 can also be configured as a plug valve or an angle valve, etc.

[0051] Further, in this embodiment, the second valve 520 is configured as a manual valve. The manual valve has simple structure, is usually composed of basic mechanical components, has high reliability and low failure rate. The configuration cost of the manual valve is low, the manual valve usually does not need complex installation process, does not need additional wiring or power connection, has simple and fast installation process, and can be quickly put into use. And the maintenance cost of the manual valve is also relatively low, because there is no complex electronic or mechanical system to be checked and repaired regularly, usually only needs regular lubrication and inspection of sealing parts. In addition, in the case of power interruption or other emergency, the manual valve can still work normally, and is not affected by external power supply, and since the manual valve does not involve electrical components, there is no risk of electrical fire or short circuit. Of course, in other embodiments, the second valve 520 can also be an electrically controlled valve, so that the opening degree of the valve can be electrically controlled, and remote control can be realized.

[0052] Without loss of generality, the first valve 510 is configured as a back pressure valve, and the second valve 520 is configured as a manual stop valve, so that the structures of the first valve 510 and the second valve 520 are relatively simple, the operation of adjusting is convenient, and the costs of the two are low, which is conducive to reducing the system modification cost.

[0053] In an embodiment, the liquid outlet end 412 of the reflux branch 410 is connected to the liquid circulation flow path between the circulation pump 300 and the gas-liquid separator 200. In this way, the reflux path of the reflux branch 410 is short, which can reduce the friction loss and local resistance loss, reduce the total pressure loss of the system, facilitate to reduce the required head of the circulation pump 300, at the same time, can accelerate the circulation speed of the fluid, improve the response speed of the system to the flow change, reduce the pressure fluctuation, and improve the stability of the system. In addition, the shorter reflux branch 410 is beneficial to reduce the material and installation workload of the pipeline, reduce the initial installation cost and maintenance cost, and can save installation space. Of course, in other embodiments, the liquid outlet end 412 of the reflux branch 410 can also be connected to the liquid circulation flow path at other positions, such as being connected to the inner cavity of the gas-liquid separator 200, or being connected to the liquid circulation flow path upstream of the gas-liquid separator 200.

[0054] In an embodiment, the liquid circulation flow path further comprises a heat exchanger 600 located between the gas-liquid separator 200 and the circulation pump 300, and the liquid outlet end 412 of the reflux branch 410 is connected to the liquid circulation flow path between the circulation pump 300 and the heat exchanger 600. In this way, the caustic lye flowing out of the gas-liquid separator 200 can be cooled by the heat exchanger 600 to ensure that the caustic lye can maintain a suitable reaction temperature after returning to the electrolytic cell 100, thereby avoiding affecting the electrolysis reaction of the electrolytic cell 100 by the recycled caustic lye. In this embodiment, the connection position of the liquid outlet end 412 of the reflux branch 410 is between the circulation pump 300 and the heat exchanger 600, which is beneficial to further shorten the path length of the reflux branch 410. Of course, in other embodiments, the heat exchanger 600 can not be provided, and the temperature of the caustic lye circulating can be controlled by mixing the caustic lye of the scrubber and the gas-liquid separator 200.

[0055] In an embodiment, the gas-liquid separator 200 comprises a hydrogen-side gas-liquid separator 201 and an oxygen-side gas-liquid separator 202, and the hydrogen-side gas-liquid separator 201 and the oxygen-side gas-liquid separator 202 are connected in parallel in the liquid circulation flow path and arranged upstream of the heat exchanger 600. In this way, the caustic lye of the hydrogen-side gas-liquid separator 201 and the oxygen-side gas-liquid separator 202 can be cooled simultaneously by a heat exchanger 600, and the caustic lye recovery processes of the hydrogen side and the oxygen side can share the liquid circulation flow path at the rear end of the heat exchanger 600, which is beneficial to simplify the structure of the system and save costs. Of course, in other embodiments, two independent liquid circulation flow paths can be formed corresponding to the hydrogen-side gas-liquid separator 201 and the oxygen-side gas-liquid separator 202.

[0056] In an embodiment, the liquid circulation flow path comprises a first flow section 420 downstream of the access position of the liquid inlet end 411, and the first flow section 420 is provided with an adjusting valve 421. In this way, the flow rate of the first flow section 420 can be adjusted by controlling the opening degree of the adjusting valve 421, so as to match the required amount of lye circulation of the system. Of course, in other embodiments, a three-way valve can be provided at the access position of the liquid inlet end 411, and the flow rate of the first flow section 420 and the flow rate of the return branch 410 can be distributed by the three-way valve.

[0057] In an embodiment, the first flow section 420 is further provided with a flow detection device 422. In this way, the flow rate of the first flow section 420 can be monitored by the flow detection device 422, so as to ensure stable operation of the system, and facilitate adjustment of the opening degree of the adjusting valve 421.

[0058] In an embodiment, the liquid circulation flow path comprises a second flow section 430 between the access position of the liquid inlet end 411 and the circulation pump 300, and the second flow section 430 is provided with a pressure detection device 431. In this way, the pressure of the second flow section 430 can be monitored by the pressure detection device 431, so as to ensure stable operation of the system.

[0059] In addition, when adjusting the opening pressure of the first valve member 510 and the opening degree of the second valve member 520, the detection values of the flow detection device 422 and the pressure detection device 431 can be referred to, so as to ensure the accuracy of the initial configuration of the first valve member 510 and the second valve member 520. Specifically, when adjusting the opening pressure of the first valve member 510, the flow rate of the first flow section 420 is first detected by the flow detection device 422, so that the flow rate of the liquid circulation flow path corresponds to the minimum working flow rate of the circulation pump 300, and the pressure value of the pressure detection device 431 at this time is recorded, which is the pressure value corresponding to the minimum working flow rate. Then, when adjusting the opening degree of the second valve member 520, the detection value of the pressure detection device 431 reaches the above-mentioned pressure value, which means that the flow rate of the liquid circulation flow path corresponds to the minimum working flow rate of the circulation pump 300, and the opening degree of the second valve member 520 is adjusted to the right position. Of course, when no related detection device is provided, the initial adjustment of the first valve member 510 and the second valve member 520 can also be performed by externally connecting a related detection device, so as to provide a basis for adjustment by the detection value.

[0060] The above-described embodiments are merely exemplary embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structural transformation made by referring to the content of the present application and the drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A hydrogen production system by water electrolysis, characterized by, The water electrolysis hydrogen production system comprises a liquid circulation flow path, which comprises, in an upstream-to-downstream direction, a gas-liquid separator, a circulating pump and an electrolytic cell arranged in sequence. The water electrolysis hydrogen production system further comprises a backflow branch, an inlet end of the backflow branch being connected to the liquid circulation flow path between the circulating pump and the electrolytic cell, an outlet end of the backflow branch being connected to the liquid circulation flow path upstream of the circulating pump, the backflow branch being provided with a first valve, the first valve having an opening pressure.

2. The water electrolysis hydrogen generation system of claim 1, wherein, The first valve is configured as a back pressure valve or an adjustable one-way valve.

3. The water electrolysis hydrogen generation system of claim 1, wherein, The backflow branch is further provided with a second valve between the outlet end and the first valve, the second valve being adjustable in opening degree.

4. The water electrolysis hydrogen generation system of claim 3, wherein, The second valve is configured as at least one of a stop valve and a butterfly valve. And / or, the second valve is configured as a manual valve.

5. The water electrolysis hydrogen generation system of claim 1, wherein, The outlet end of the backflow branch is connected to the liquid circulation flow path between the circulating pump and the gas-liquid separator.

6. The water electrolysis hydrogen generation system of claim 5, wherein, The liquid circulation flow path further comprises a heat exchanger between the gas-liquid separator and the circulating pump, the outlet end of the backflow branch being connected to the liquid circulation flow path between the circulating pump and the heat exchanger.

7. The water electrolysis hydrogen generation system of claim 6, wherein, The gas-liquid separator comprises a hydrogen-side gas-liquid separator and an oxygen-side gas-liquid separator, the hydrogen-side gas-liquid separator and the oxygen-side gas-liquid separator being arranged in parallel in the liquid circulation flow path upstream of the heat exchanger.

8. The water electrolysis hydrogen generation system of claim 1, wherein, The liquid circulation flow path comprises a first flow section downstream of the connection position of the inlet end, the first flow section being provided with an adjusting valve.

9. The water electrolysis hydrogen generation system of claim 8, wherein, The first flow section is further provided with a flow detection device.

10. The water electrolysis hydrogen generation system of claim 1, wherein, The liquid circulation flow path comprises a second flow section between the connection position of the inlet end and the circulating pump, the second flow section being provided with a pressure detection device.

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