Two-stage water supply system for electrolytic cell and general water tank thereof

Abstract

The application is suitable for the field of hydrogen production by electrolysis of water, and provides a two-stage water supply system for an electrolytic cell and a universal water tank thereof, which comprises: the universal water tank, which is used for parameter adjustment of the electrolytic cell, is provided with a water supply port, an anode outlet, an oxygen outlet, a water replenishing port, a cathode outlet and a hydrogen outlet; the electrolytic cell, which is used for electrolysis of water to produce hydrogen and oxygen, is provided with a water inlet, an anode water outlet and a cathode water outlet; and the expansion water tank, which is used for water replenishment of the universal water tank; wherein the water replenishing port of the universal water tank is connected with the expansion water tank and is used for water replenishment of the universal water tank; the water supply port of the universal water tank is connected with the water inlet of the electrolytic cell and is used for water supply of the electrolytic cell; and the anode outlet and the cathode outlet of the universal water tank are connected with the anode water outlet and the cathode water outlet of the electrolytic cell, respectively. The application realizes control of the gas pressure of the two-stage outlet of the electrolytic cell through the universal water tank, and the electrolytic cell can work at an optimal temperature of 65-85 DEG C by controlling the water pumping rate to the electrolytic cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen production by water electrolysis, and particularly relates to a two-stage water supply system for an electrolytic cell and a universal water tank thereof. BACKGROUND

[0002] Hydrogen production by water electrolysis is a process of separating water molecules in water or solution into hydrogen and oxygen by electrolysis under the condition of inputting direct current. Therefore, in the process of electrolytic cell operation, the water supply provided by the water tank and the timely water-gas separation function are guarantees for ensuring the stability of the electrolysis process. As proton exchange membrane electrolytic cells are increasingly widely used in hydrogen energy storage fields, the pressure of the hydrogen outlet often needs to reach 1 Mpa or more.

[0003] The existing electrolytic cell system often uses an expansion water tank and a water-gas separator to supply water to the electrolytic cell and separate water and gas, respectively. The gas separated by the water-gas separator enters a storage module, and the water at the distribution point is circulated back to the expansion water tank. The one-stage water supply has a simple structure and low prices of system accessories.

[0004] However, the pressure is difficult to control when the water is supplied in one stage, and the purity of the obtained hydrogen is not high. The expansion water tank is large, and the water supplied to the electrolytic cell has a low temperature, which reduces the electrolysis efficiency and even damages the electrolytic cell. SUMMARY

[0005] The purpose of the embodiments of the present application is to provide a two-stage water supply system for an electrolytic cell, which aims to solve the problems of difficult pressure control when the water is supplied in one stage, low purity of the obtained hydrogen, large expansion water tank, low temperature of the water supplied to the electrolytic cell, reduced electrolysis efficiency, and even damaged electrolytic cell.

[0006] The embodiments of the present application are implemented in the following manner. A two-stage water supply system for an electrolytic cell includes:

[0007] A universal water tank is used for electrolytic cell parameter adjustment. The parameters include at least water replenishment flow, water replenishment temperature, and gas pressure. The universal water tank is provided with a water supply port, an anode outlet, an oxygen outlet, a water replenishment port, a cathode outlet, and a hydrogen outlet.

[0008] The electrolytic cell is used for electrolysis of water to produce hydrogen and oxygen. The electrolytic cell is provided with a water inlet, an anode water outlet, and a cathode water outlet.

[0009] An expansion water tank is used for water replenishment of the universal water tank.

[0010] The water replenishment port of the universal water tank is connected to the expansion water tank, and is used for water replenishment of the universal water tank.

[0011] The water supply port of the universal water tank is connected to the water inlet of the electrolytic cell, and is used for water supply to the electrolytic cell.

[0012] The anode outlet of the general water tank is connected with the anode water outlet of the electrolytic tank, and the cathode outlet of the general water tank is connected with the cathode water outlet of the electrolytic tank, for water and gas to flow from the electrolytic tank to the general water tank.

[0013] Another purpose of the embodiment of the present application is to provide a general water tank for a two-stage water supply system of an electrolytic tank, which comprises:

[0014] an anode box body, which is provided with a water supply port, an anode outlet, an oxygen outlet, a first pressure sensor, a temperature liquid level sensor and an anode box body flange;

[0015] a cathode box body, which is provided with a water replenishment port, a cathode outlet, a hydrogen outlet, a second pressure sensor, a temperature liquid level sensor and a cathode box body flange;

[0016] The anode box body flange of the anode box body and the cathode box body flange of the cathode box body are communicated;

[0017] A diaphragm is clamped between the anode box body flange and the cathode box body flange.

[0018] The embodiment of the present application provides a two-stage water supply system for an electrolytic tank, which utilizes the general water tank to monitor the oxygen and hydrogen gas pressure generated by the electrolytic tank, realizes the control of the gas pressure of the two-pole outlets of the electrolytic tank, solves the pressure control problem in the original one-stage water supply, and effectively alleviates the gas purity problem caused by gas penetration; the small-sized general water tank can improve the water supply temperature entering the electrolytic tank, and through the water inlet rate of the electrolytic tank, the electrolytic tank can always work at the optimal temperature of 65-85℃; the two-stage water supply mode combining the small-sized general water tank and the large-sized expansion water tank can quickly adjust the temperature supplied to the electrolytic tank by adjusting the water inlet rate of the expansion water tank to the general water tank. Meanwhile, the expansion water tank no longer needs to bear pressure, and the use safety thereof can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The structure schematic diagram of the two-stage water supply system for the electrolytic tank provided by the embodiment of the present application;

[0020] Figure 2 The structure schematic diagram of the general water tank of the two-stage water supply system for the electrolytic tank provided by the embodiment of the present application;

[0021] Figure 3 The sectional view of the general water tank of the two-stage water supply system for the electrolytic tank provided by the embodiment of the present application.

[0022] In the attached diagram: 1. General-purpose water tank; 2. Electrolytic cell; 3. Expansion tank; 4. First water pump; 5. First check valve; 6. Second check valve; 7. Second water pump; 8. First electric needle valve; 9. Second electric needle valve; 10. Radiator; 101. Water supply port; 102. Anode outlet; 103. Oxygen outlet; 104. Water replenishment port; 105. Cathode outlet; 106. Hydrogen outlet; 107. First pressure sensor; 108. Second pressure sensor; 109. Temperature and level sensor; 110. Level sensor; 111. Anode housing flange; 112. Cathode housing flange; 113. Diaphragm; 114. Anode housing; 115. Cathode housing; 201. Electrolytic cell inlet; 202. Electrolytic cell anode outlet; 203. Electrolytic cell cathode outlet. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0024] The specific implementation of this application will be described in detail below with reference to specific embodiments.

[0025] like Figure 1 The diagram shown is a structural schematic of a secondary water supply system for an electrolyzer provided in an embodiment of this application, comprising:

[0026] A general-purpose water tank 1 is used for parameter adjustment of the electrolytic cell 2. The parameters include at least water supply flow rate, water supply temperature and gas pressure. The general-purpose water tank 1 is provided with a water supply port 101, an anode outlet 102, an oxygen outlet 103, a water supply port 104, a cathode outlet 105 and a hydrogen outlet 106.

[0027] The electrolytic cell 2 is used to electrolyze water to produce hydrogen and oxygen. The electrolytic cell is provided with a water inlet 201, an anode water outlet 202 and a cathode water outlet 203.

[0028] Expansion tank 3 is used to replenish water to the general-purpose water tank 1;

[0029] The water inlet 104 of the general-purpose water tank 1 is connected to the expansion tank 1 and is used to replenish water to the general-purpose water tank 1.

[0030] The water supply port 101 of the general-purpose water tank 1 is connected to the water inlet 201 of the electrolytic cell and is used to supply water to the electrolytic cell;

[0031] The anode outlet 102 of the general water tank 1 is connected with the anode water outlet 202 of the electrolytic tank, and the cathode outlet 105 of the general water tank is connected with the cathode water outlet 203 of the electrolytic tank, for water and gas to flow from the electrolytic tank 2 to the general water tank 1.

[0032] In the embodiment of the present application, the general water tank 1 is used to monitor the oxygen and hydrogen gas pressure generated by the electrolytic tank 2, to realize the control of the gas pressure at the two outlets of the electrolytic tank 2, to solve the pressure control problem of the original primary water supply, and to effectively alleviate the gas purity problem caused by gas permeation; the small volume of the general water tank 1 can improve the water supply temperature into the electrolytic tank 2, and through the water inlet rate of the electrolytic tank 2, the electrolytic tank 2 can always work at the optimal temperature of 65-85℃; the secondary water supply mode combining the small volume of the general water tank 1 and the large volume of the expansion water tank 3 can quickly adjust the temperature supplied to the electrolytic tank 2 by adjusting the water supply rate of the expansion water tank 3 to the general water tank 1. At the same time, the expansion water tank 3 no longer needs to bear pressure, which can improve its safety in use.

[0033] In one example of the present application, the general water tank 1 is a newly added structural device in the traditional expansion water tank 3 and the electrolytic tank 2, which has the functions of water supply and water-gas separation, provides water supply with appropriate temperature and controllable flow rate for the electrolytic tank 2, separates the wet hydrogen and oxygen generated by the electrolytic tank 2, optimizes the original primary water supply mode of the electrolytic tank 2 directly supplied by the expansion water tank 3 to the secondary water supply mode through the general water tank 1, can monitor the gas pressure in the general water tank 1 in real time by setting sensors in the general water tank 1, realize the control of the gas pressure at the two outlets of the electrolytic tank 2, the water supply flow rate and the liquid temperature, quickly adjust the temperature supplied to the electrolytic tank 2 by adjusting the water supply rate of the general water tank 1 to the electrolytic tank 2; under the condition of inputting direct current, the electrolytic tank 2 electrolyzes the water molecules in water or solution into hydrogen and oxygen, in the process of working of the electrolytic tank 2, the water supply provided by the general water tank 1 and the timely water-gas separation function are the guarantee to ensure the stability of the electrolysis process, the optimal working temperature of the electrolytic tank 2 is between 65-85℃, the expansion water tank 3 is generally made of materials that can produce certain deformation, and is usually circular or rectangular, due to the change of water temperature in the secondary water supply system, the secondary water supply mode combining the small volume of the general water tank 1 and the large volume of the expansion water tank 3, the expansion water tank 3 no longer needs to bear the stress caused by the large circulating water temperature difference. The devices in the system are connected through pipelines, can flow materials between each other, the expansion water tank 3 supplies water to the general water tank 1, the general water tank 1 supplies water to the electrolytic tank 2, and the gas carrying water generated by the electrolytic tank 2 flows to the electrolytic tank 2.

[0034] As Figure 1As shown, as a preferred embodiment of the present application, the water replenishing port 104 of the general water tank 1 and the expansion water tank 3 are further provided with a first check valve 5 and a first water pump 4, for controlling the flow of water replenishing the general water tank.

[0035] In an embodiment of the present application, the water replenishing port 104 of the general water tank 1 is connected with the first check valve 5, the first water pump 4 and the expansion water tank 3 in series through a pipeline. The check valve only allows the medium to flow in one direction and prevents the reverse direction, which can be a lift check valve, swing check valve and butterfly check valve, and the specific type is not limited. The water pump increases the energy of the liquid, transports the liquid and controls the flow rate of the liquid, thereby controlling the amount of water entering the general water tank 1, and the type of pump is not limited. When the liquid level in the general water tank 1 is higher than 75% of the maximum allowable liquid level, the amount of water entering the general water tank 1 from the expansion water tank 3 is reduced, and when the liquid level in the general water tank 1 is lower than the minimum allowable liquid level, the amount of water entering the general water tank 1 from the expansion water tank 3 is increased. The liquid level in the general water tank 1 can be effectively maintained at an appropriate height.

[0036] As shown, Figure 1 As another preferred embodiment of the present application, the water supply port 101 of the general water tank 1 and the water inlet 201 of the electrolytic tank are further provided with a second check valve 6 and a second water pump 7, for controlling the flow of water entering the electrolytic tank 2.

[0037] In an embodiment of the present application, the water supply port 101 of the general water tank 1 is connected with the second check valve 6, the second water pump 7 and the water inlet 201 of the electrolytic tank through a pipeline, for supplying water or lye to the electrolytic tank 2. The second check valve 6 can be the same or different type as the first check valve 5, and the second water pump 7 can be the same or different type as the first water pump 4. The amount of water entering the electrolytic tank 2 can be adjusted by the second water pump 7.

[0038] As shown, Figure 1 As another preferred embodiment of the present application, the anode outlet 102 of the general water tank 1 and the anode water outlet 202 of the electrolytic tank are further provided with a radiator 10, for controlling the temperature of the water and gas entering the general water tank 1.

[0039] In an embodiment of the present application, a radiator 10 is further arranged between the anode outlet 102 of the general water tank 1 and the anode water outlet 202 of the electrolytic tank, and the oxygen generated by the anode of the electrolytic tank 2 and the water or alkali solution which is not completely reacted are led into the general water tank 1 through the pipeline from the anode water outlet 202 of the electrolytic tank, the anode outlet 102 of the general water tank. Further, the water or alkali solution which is not completely reacted falls back into the general water tank 1, and the oxygen is discharged through the oxygen outlet 103 of the general water tank 1. The radiator 10 changes the heat dissipation effect according to the water temperature in the general water tank 1, and can be in the form of a combination of a radiator pipe and a radiator fan. The liquid temperature in the general water tank 1 is maintained, and then the liquid level temperature entering the electrolytic tank 2 is controlled, so that the liquid temperature in the electrolytic tank 2 is maintained at 65-85°C.

[0040] As shown in Figure 1 , as another preferred embodiment of the present application, the oxygen outlet 103 of the general water tank 1 is connected with a first electric needle valve 8 for controlling the pressure of the oxygen in the general water tank 1.

[0041] The hydrogen outlet 106 of the general water tank 1 is connected with a second electric needle valve 9 for controlling the pressure of the hydrogen in the general water tank 1.

[0042] In an embodiment of the present application, by controlling the opening degree of the first electric needle valve 8 and the second electric needle valve 9, the gas pressure in the general water tank 1 can be adjusted, and the purity of the hydrogen can be maintained under the condition of a higher outlet pressure.

[0043] As another preferred embodiment of the present application, the first-stage water supply mode of the two-stage water supply system is that the expansion water tank 3 supplies water to the general water tank 1 through the first water pump 4 and the first check valve 5.

[0044] In an embodiment of the present application, the first-stage water supply makes the expansion water tank 3 no longer need to bear the stress caused by the large circulating water temperature difference, and the use safety can be improved.

[0045] As another preferred embodiment of the present application, the second-stage water supply mode of the two-stage water supply system is that the general water tank 1 supplies water to the electrolytic tank 2 through the second check valve 6 and the second water pump 7.

[0046] In an embodiment of the present application, the second-stage water supply realizes the control of the gas pressure at the two-pole outlets of the electrolytic tank 2, solves the pressure control problem in the original first-stage water supply, and effectively alleviates the problem of gas purity caused by gas permeation.

[0047] As shown in Figure 2 , the embodiment of the present application further provides a general water tank of a two-stage water supply system for an electrolytic tank, which comprises:

[0048] An anode box 114 is provided with a water inlet 101, an anode outlet 102, an oxygen outlet 103, a first pressure sensor 107, a temperature liquid level sensor 109, and an anode box flange 111;

[0049] A cathode box 115 is provided with a water supplement inlet 104, a cathode outlet 105, a hydrogen outlet 106, a second pressure sensor 108, a liquid level sensor 110, and a cathode box flange 112;

[0050] The anode box flange 111 of the anode box 114 and the cathode box flange 112 of the cathode box 115 are communicated;

[0051] The anode box flange 111 and the cathode box flange 112 are clamped with a diaphragm 113.

[0052] In the embodiment of the present application, the gas pressure sensor in the universal water tank 1 is used to control the gas pressure of the two electrode outlets of the electrolytic tank 2, and effectively alleviate the problem of gas purity caused by gas permeation; the small volume of the universal water tank 1 can improve the water temperature entering the electrolytic tank 2, and by controlling the water pump rate, the electrolytic tank 2 can always work at the optimal temperature of 65-85℃.

[0053] In one embodiment of the present application, the anode box 114 and the cathode box 115 are cylindrical boxes with the same height and the same inner diameter, the anode outlet 102 is arranged at the middle position of the anode box 114, the water inlet 101 is arranged at the bottom position of the anode box 114, the oxygen outlet 103, the first pressure sensor 107, and the temperature liquid level sensor 109 are arranged at the top position of the anode box 114, the anode box flange 112 is arranged at one side of the water inlet 101, and similarly, the cathode box 115 is provided with the cathode outlet 105, the water supplement inlet 104, the hydrogen outlet 106, the second pressure sensor 108, the liquid level sensor 110, and the cathode box flange 112 at the same positions as the anode box 114, and the positions of the anode outlet 102 and the cathode outlet 105 are at least above half of the height of the box.

[0054] In one embodiment of the present application, the installation of the entire universal water tank 1 is realized by the butt sealing of the anode box flange 111 and the cathode box flange 112, a piece of diaphragm 113 is clamped between the two flange interfaces, if the electrolytic tank 2 is a PEM electrolytic tank, the diaphragm is a proton exchange membrane; if the electrolytic tank 2 is an alkaline water electrolytic tank, the diaphragm 113 is a polyphenylene sulfide membrane (PPS). Further, the diaphragm 113 plays a role of isolating bubbles and water-soluble gases, and only allows water or alkaline solution to pass through. Through the action of the diaphragm, even under an operating pressure of 3MPa, the purity of hydrogen can still be maintained at 99.98%

[0055] The oxygen and water or alkali produced by the anode of the electrolytic cell 2 are introduced into the anode tank 114 through the pipe from the anode water outlet 202 of the electrolytic cell, the anode outlet 102 of the general water tank, and further, the water or alkali are returned to the anode tank 114, and the oxygen is discharged through the oxygen outlet 103.

[0056] The oxygen and water or alkali produced by the cathode of the electrolytic cell 2 are introduced into the cathode tank 115 through the pipe from the cathode water outlet 203 of the electrolytic cell, the cathode outlet 105 of the general water tank, and further, the water or alkali are returned to the cathode tank 115 from the anode through the proton exchange membrane, and the hydrogen is discharged through the hydrogen outlet 106.

[0057] The first pressure sensor 107 measures the gas pressure in the anode tank 114.

[0058] The second pressure sensor 108 measures the gas pressure in the cathode tank 115.

[0059] The temperature and liquid level sensor 109 measures the temperature and liquid level of the liquid in the anode tank 114.

[0060] The liquid level sensor 110 measures the liquid level in the cathode tank 115.

[0061] By controlling the opening of the first and second electric needle valves 8 and 9, the gas pressure in the anode tank 114 and the cathode tank 115 can be adjusted. The water added to the general water tank 1 from the expansion water tank 3 enters the anode tank 114 from the cathode tank 115 through the diaphragm 113 in the communicating vessel, and the gas pressure in the anode tank 114 should be slightly lower than that in the cathode tank 115, and the control range is 20-150 kPa.

[0062] Preferably, the pressure difference is 20 kPa when the gas pressure in the anode tank 114 is 1 MPa.

[0063] Preferably, the pressure difference is 50 kPa when the gas pressure in the anode tank 114 is 2 MPa.

[0064] Preferably, the pressure difference is 100 kPa when the gas pressure in the anode tank 114 is 3 MPa.

[0065] Preferably, when the temperature in the anode tank 114 exceeds 85 degrees or the temperature rising rate is greater than 5°C / min under a gas pressure of 0-3 MPa, the pressure difference is adjusted to 150 kPa, and the water supply rate into the cathode tank 115 is also increased accordingly, so that the liquid entering the anode tank 114 is increased to achieve the effect of cooling.

[0066] The replenishment rate (v) is adjusted according to the temperature in the anode tank 114, the liquid level D1 and the liquid level D2 in the cathode tank 115. The specific adjustment method is as follows:

[0067] Under normal replenishment, D min ≤ D1 ≤ 0.5D max and D min ≤ D2 ≤ 0.25D max , where D max is the maximum allowable liquid level, and D min is the minimum allowable liquid level. If the liquid level is higher than D max , the liquid will overflow the tank; if the liquid level is lower than D min , the cathode tank cannot replenish the anode tank.

[0068] The total liquid level in the anode tank 114 and the cathode tank 115 of the general water tank 1 is controlled to be equal to 0.75D max , and the expression of the replenishment rate is as follows:

[0069]

[0070] In the formula, v is the replenishment rate, mL / s; R is the radius of the anode tank 114 and the cathode tank 115, cm; x is the sum of the liquid levels in the anode tank 114 and the cathode tank 115, cm; D max is the maximum allowable liquid level, which is a constant, cm; and t is time, s.

[0071] The temperature control conforms to the following four states:

[0072] State 1: The radiator 10 rotates at variable speed according to the water temperature in the anode tank 114 to maintain the water temperature at 60-65°C, and the water supply rate of the second water pump 7 is a fixed value.

[0073] State 2: When the water temperature is 65-75°C, the rotation speed of the radiator 10 is adjusted to the highest, and the water supply rate of the second water pump 7 is twice the original fixed value.

[0074] State 3: When the water temperature is 75-85°C, the rotation speed of the radiator 10 is adjusted to the highest, the water supply rate of the second water pump 7 is twice the original fixed value, and the replenishment amount of the first water pump 4 is increased to twice the normal replenishment rate. Cold water passes through the diaphragm 113 into the anode tank 114 until the liquid level in the anode tank 114 reaches 0.75D max .

[0075] State 4: When the water temperature is higher than 85°C, the entire system is closed in an emergency.

[0076] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A two-stage water supply system for an electrolytic cell, characterized in that, The system comprises: a general water tank for adjusting parameters of an electrolytic cell, the parameters at least including water supplement flow rate, water supplement temperature and gas pressure, the general water tank is provided with a water supply port, an anode outlet, an oxygen outlet, a water supplement port, a cathode outlet and a hydrogen outlet; the electrolytic cell is used for electrolyzing water to generate hydrogen and oxygen, and is provided with a water inlet, an anode water outlet and a cathode water outlet; an expansion water tank is used for supplementing water to the general water tank; the water supplement port of the general water tank is connected with the expansion water tank, and is used for supplementing water to the general water tank; the water supply port of the general water tank is connected with the water inlet of the electrolytic cell, and is used for supplying water to the electrolytic cell; the anode outlet of the general water tank is connected with the anode water outlet of the electrolytic cell, and the cathode outlet of the general water tank is connected with the cathode water outlet of the electrolytic cell, and are used for water and gas flowing from the electrolytic cell to the general water tank; a radiator is further arranged between the anode outlet of the general water tank and the anode water outlet of the electrolytic cell, and is used for controlling the temperature of water and gas input into the general water tank; the general water tank comprises: an anode tank body, which is provided with a water supply port, an anode outlet, an oxygen outlet, a first pressure sensor, a temperature liquid level sensor and an anode tank body flange; a cathode tank body, which is provided with a water supplement port, a cathode outlet, a hydrogen outlet, a second pressure sensor, a liquid level sensor and a cathode tank body flange; the anode tank body flange of the anode tank body and the cathode tank body flange of the cathode tank body are communicated; a diaphragm is clamped between the anode tank body flange and the cathode tank body flange, and the diaphragm plays a role of isolating gas bubbles and water-soluble gas; the gas pressure in the anode tank body is less than the gas pressure in the cathode tank body, and the control range is 20-150 kPa; The water replenishment rate is adjusted based on the temperature and liquid level in the anode tank and the liquid level in the cathode tank; under normal water replenishment conditions, D min ≤D1≤0.5D max And D min ≤D2≤0.25D max Where D1 is the liquid level in the anode tank; D2 is the liquid level in the cathode tank; D max For the maximum permissible liquid level, D min Minimum allowable liquid level; controlling the sum of the liquid levels in the anode tank and the cathode tank of the general water tank to be equal to 0.75D max The expression of the make-up rate is as follows, in the formula, v is the water supplement rate, mL / s; R is the radius of the anode tank body and the cathode tank body, cm; x is the sum of the liquid level heights in the anode tank body and the cathode tank body, cm; D max is the maximum allowable liquid level height, which is a constant, cm; and t is the time, s.

2. A two-stage water supply system for an electrolytic cell according to claim 1, wherein a first check valve and a first water pump are further arranged between the water supplement port of the general water tank and the expansion water tank, and are used for controlling the flow rate of water supplement to the general water tank.

3. A two-stage water supply system for an electrolytic cell according to claim 1, wherein a second check valve and a second water pump are further arranged between the water supply port of the general water tank and the water inlet of the electrolytic cell, and are used for controlling the flow rate of water input to the electrolytic cell.

4. A two-stage water supply system for an electrolytic cell according to claim 1, wherein a first electric needle valve is connected with the oxygen outlet of the general water tank, and is used for controlling the pressure of oxygen in the general water tank; and a second electric needle valve is connected with the hydrogen outlet of the general water tank, and is used for controlling the pressure of hydrogen in the general water tank.

5. A two-stage water supply system for an electrolytic cell according to claim 1, wherein the first-stage water supply mode of the two-stage water supply system is that the expansion water tank supplies water to the general water tank through the first water pump and the first check valve.

6. A two-stage water supply system for an electrolytic cell according to claim 1, wherein the second-stage water supply mode of the two-stage water supply system is that the general water tank supplies water to the electrolytic cell through the second check valve and the second water pump.

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