Water electrolysis system and control method

Abstract

The invention provides a water electrolysis system and a control method. The system comprises an electrolytic bath, a hydrogen-water separation system and a hydrogen drainage system, the hydrogen-water separation system comprises a hydrogen discharge branch and a water distribution branch; the hydrogen discharge branch comprises a secondary pressure regulating valve, a primary pressure regulating valve and a hydrogen-water separator; the water distribution branch comprises a hydrogen-water separator and a hydrogen-water separator drain valve; the hydrogen drainage system comprises a water collecting branch and at least one pressurizing branch; the water collecting branch comprises a water collector; the pressurizing branch comprises a pressurizing valve, one end of the pressurizing valve is connected with the water collector through a pipeline, and the other end of the pressurizing valve is connected to the pipeline between the second-stage pressure regulating valve and the first-stage pressure regulating valve through a pipeline. The pressure of the whole system can be kept unchanged in the drainage process, system pressure fluctuation caused by action lag of the hydrogen side pressure regulating valve and the oxygen side pressure regulating valve is avoided, and the situation that the service life of the electrolytic cell is affected by pressure impact on the electrolytic cell is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic cells for electrolysis, and in particular to a water electrolysis system and a control method. Background Art

[0002] The core structure of the electrolyzer is an electrolytic chamber unit composed of bipolar plates, conductive plates and proton exchange membranes. The specific structure of the electrolytic chamber unit includes a proton exchange membrane and a catalyst attached to both sides, and conductive plates are arranged on both sides. Two bipolar plates press the above structure together through a sealing ring. Multiple electrolytic chamber units are connected in series to form an electrolyzer. Voltage is applied on both sides and water is provided to the anode. The anode water is decomposed to produce hydrogen ions, which are combined with electrons on the cathode side to form hydrogen after passing through the proton exchange membrane. In this process, part of the water at the anode migrates to the cathode side following the hydrogen ions, and the oxygen produced on the anode side is mixed with the remaining unreacted water and discharged from the electrolytic unit.

[0003] As an essential equipment for hydrogen production in electrolyzers, the functional stability of the electrolysis system has a very important impact on the electrolyzer. In terms of electrolyzer performance testing and industrial application, the electrolysis system needs to ensure the pressure stability of the electrolysis system during operation, which has a positive impact on the stability and life of the electrolyzer. The pressure control of the hydrogen and oxygen sides of the existing electrolysis system is based on the opening of the pressure regulating valve. The pressure will change dramatically at the moment of hydrogen side drainage, and the action of the pressure regulating valve is delayed, resulting in large pressure fluctuations in the system. This problem will become more obvious as the pressure on the hydrogen side increases. Therefore, it is necessary to design a new water electrolysis system to avoid pressure fluctuations at the moment of hydrogen side drainage. Summary of the invention

[0004] Based on the technical problem that drainage of the hydrogen side of the electrolyzer causes system pressure fluctuations as mentioned above, a water electrolysis system and control method are provided. The present invention mainly adds a water collection branch and a pressure charging branch to the hydrogen-water separation system to ensure that the water collection branch is isolated from other containers and pipelines on the hydrogen side at the moment of drainage on the hydrogen side, thereby not causing pressure changes; after the drainage is completed, the pressure charging branch raises the pressure of the water collection branch to the pressure setting value of the hydrogen-water separation system again, and then connects the water collection branch and the entire hydrogen side without causing system pressure changes. The hydrogen-water separation system is directly connected to the electrolyzer, thereby avoiding pressure shocks to the electrolyzer.

[0005] The technical means adopted by the present invention are as follows:

[0006] The present invention provides a water electrolysis system, characterized in that it comprises: an electrolytic cell, a hydrogen-water separation system and a hydrogen drainage system;

[0007] The hydrogen-water separation system comprises a hydrogen discharge branch and a water separation branch;

[0008] The hydrogen discharge branch includes a secondary pressure regulating valve, a primary pressure regulating valve and a hydrogen-water separator, the inlet of the hydrogen-water separator is connected to the hydrogen outlet of the electrolyzer through a pipeline, and the gas outlet of the hydrogen-water separator is connected to the primary pressure regulating valve and the secondary pressure regulating valve through pipelines in sequence;

[0009] The water diversion branch includes a hydrogen-water separator and a hydrogen-water separator drain valve, and the liquid outlet of the hydrogen-water separator is connected to the hydrogen-water separator drain valve through a pipeline;

[0010] The hydrogen drainage system includes a water collection branch and at least one charging branch;

[0011] The water collecting branch includes a water collector, and the inlet of the water collector is connected to the liquid outlet of the hydrogen-water separator through a pipeline via a drain valve of the hydrogen-water separator;

[0012] The pressure charging branch includes a pressure charging valve, one end of which is connected to the water collector through a pipeline, and the other end of which is connected to the pipeline between the secondary pressure regulating valve and the primary pressure regulating valve through a pipeline.

[0013] Furthermore, the water electrolysis system also includes an oxygen-water separation system for discharging oxygen generated by the electrolytic cell and unreacted water.

[0014] Furthermore, the water collection branch also includes a water collector drain valve and a liquid level switch, the water collector drain valve is connected to the water collector, and the liquid level switch is installed on the water collector.

[0015] Furthermore, the oxygen-water separation system comprises an oxygen discharge branch and a water circulation branch, wherein the oxygen discharge branch is connected to the electrolyzer, and the water circulation branch is connected to the oxygen discharge branch and the electrolyzer.

[0016] Furthermore, the oxygen exhaust branch includes an oxygen-water separator and an oxygen pressure regulating valve, the oxygen-water separator is connected to the electrolyzer, and the oxygen pressure regulating valve is connected to the oxygen-water separator.

[0017] Furthermore, the water circulation branch includes a circulation pump, and the circulation pump is respectively connected to the electrolyzer and the oxygen-water separator of the oxygen exhaust branch.

[0018] The present invention also provides a control method for a water electrolysis system, comprising the following steps:

[0019] Step 1: The circulating pump is running to send the electrolyte into the electrolytic cell for electrolysis. The generated oxygen and unreacted water enter the oxygen-water separator. The separated oxygen is regulated by the oxygen pressure regulating valve to reach the set value to ensure constant pressure in the oxygen-water separation system.

[0020] Step 2: The hydrogen and a small amount of water produced in the electrolyzer enter the hydrogen-water separator, and the separated hydrogen is pressure-regulated by a primary regulating valve to reach a set value, thereby ensuring a constant pressure in the hydrogen-water separation system and the hydrogen drainage system;

[0021] Step 3: As the liquid level in the water collector continues to rise and reaches the liquid level switch position, close the hydrogen-water separator drain valve and open the water collector drain valve to drain water. At this time, the charging valve is in a closed state and the secondary pressure regulating valve is in an open state;

[0022] Step 4: When the drainage reaches the preset time, close the water collector drainage valve, adjust the pressure of the secondary pressure regulating valve to be equal to that of the primary pressure regulating valve, open the charging valve, and charge the water collector with pressure;

[0023] Step 5. When the pressure in the water collector is equal to that in the hydrogen-water separation system, close the charging valve, open the water collector drain valve and the secondary pressure regulating valve. At this time, the water in the hydrogen-water separator flows into the water collector under the action of gravity, and the water collector and the hydrogen-water separator are at the same pressure. At the moment the water collector drain valve is opened, the pressure fluctuations in the hydrogen-water separation system and the hydrogen drainage system are extremely small.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The hydrogen-water separation system of the present invention is isolated from the water collector during drainage, and the internal effective space remains unchanged, which can ensure that the pressure of the entire system remains unchanged during the drainage process.

[0026] 2. After the drainage is completed in the present invention, the generated hydrogen is refilled into the water collector to make the pressure of the water collector equal to the pressure of the hydrogen-water separation system, and then the hydrogen-water separator and the water collector are connected, so that the pressure of the entire system remains unchanged after the drainage is completed.

[0027] 3. The pressure of the electrolysis system of the present invention is maintained unchanged during the whole process, which can avoid the system pressure fluctuation caused by the action lag of the hydrogen-side pressure regulating valve and the oxygen-side pressure regulating valve, and avoid the pressure shock to the electrolytic cell that affects its life.

[0028] 4. The method for ensuring accurate pressure control in the system of the present invention is achieved through the opening and closing or adjustment of the electric valve, and the control logic is easy to implement.

[0029] Based on the above reasons, the present invention can be widely promoted in the fields of electrolysis and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 It is a system principle diagram in a specific implementation manner of the present invention.

[0032] In the figure: 1. electrolytic cell; 2. circulation pump; 3. oxygen-water separator; 4. oxygen pressure regulating valve; 5. secondary pressure regulating valve; 6. primary pressure regulating valve; 7. hydrogen-water separator; 8. hydrogen-water separator drain valve; 9. water collector; 10. water collector drain valve; 11. charging valve; 12. liquid level switch. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0037] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0038] Example 1

[0039] The present invention provides a water electrolysis system, comprising an electrolyzer 1, an oxygen-water separation system, a hydrogen-water separation system, and a hydrogen drainage system. The oxygen-water separation system comprises an oxygen discharge branch and a water circulation branch. The hydrogen-water separation system comprises a hydrogen discharge branch and a water distribution branch. The hydrogen drainage system comprises a water collection branch and a pressurizing branch. The oxygen discharge branch is connected to the electrolyzer 1, the water circulation branch is connected to the oxygen discharge branch and the electrolyzer 1, the hydrogen discharge branch is connected to the electrolyzer 1, the water distribution branch is connected to the hydrogen discharge branch, the water collection branch is connected to the water distribution branch, and the pressurizing branch is connected to the hydrogen discharge branch and the water collection branch.

[0040] The oxygen exhaust branch consists of an oxygen-water separator 3, an oxygen pressure regulating valve 4 and a pipeline, and the water circulation branch consists of a circulation pump 2 and a pipeline. The oxygen-water separator 3 is connected to the electrolyzer 1 through a pipeline, the oxygen pressure regulating valve 4 is connected to the oxygen-water separator 3 through a pipeline, the circulation pump 2 is connected to the oxygen-water separator 3 through a pipeline, and is also connected to the electrolyzer 1 through a pipeline.

[0041] The hydrogen discharge branch is composed of a primary pressure regulating valve 6, a secondary pressure regulating valve 5, a hydrogen-water separator 7 and a pipeline, and the water distribution branch is composed of a hydrogen-water separator drain valve 8 and a pipeline. The inlet of the hydrogen-water separator 7 is connected to the hydrogen outlet of the electrolyzer 1 through a pipeline, the primary pressure regulating valve 6 is connected to the hydrogen outlet of the hydrogen-water separator 7 through a pipeline, and the secondary pressure regulating valve 5 is connected to the primary pressure regulating valve 6 through a pipeline. The hydrogen-water separator drain valve 8 is connected to the liquid outlet of the hydrogen-water separator 7 through a pipeline.

[0042] The water collecting branch is composed of a water collector 9, a water collector drain valve 10, a liquid level switch 12 and a pipeline, and a pressure charging branch is provided, which is composed of a pressure charging valve 11 and a pipeline. The inlet of the water collector 9 is connected to the hydrogen-water separator drain valve 8 through a pipeline, the water collector drain valve 10 is connected to the water collector 9 through a pipeline, the liquid level switch 12 is installed on the water collector 9, one end of the pressure charging valve 11 is connected to the water collector drain valve 10 through a pipeline, and the other end is connected to the pipeline between the secondary pressure regulating valve 5 and the primary pressure regulating valve 6 through a pipeline.

[0043] The electrolytic cell 1 is connected to direct current, and the oxygen and water generated by electrolysis enter the oxygen-water separator 3. The circulating pump 2 in the water circulation branch absorbs water from the oxygen-water separator 3 and then pumps the separated water into the electrolytic cell 1. The generated oxygen and unreacted water flow back to the oxygen-water separator 3, and the separated oxygen flows into the oxygen pressure regulating valve 4 in the oxygen discharge branch and is then discharged.

[0044] The hydrogen and a small amount of water produced by the electrolyzer 1 flow into the hydrogen-water separator 7 in the hydrogen discharge branch, wherein the separated hydrogen flows into the primary pressure regulating valve 6 and the secondary pressure regulating valve 5 in the hydrogen discharge branch and then is discharged; the water separated in the hydrogen-water separator 7 flows through the hydrogen-water separator drain valve 8 and enters the water collector 9 in the water collection branch; the water in the water collector 9 is discharged through the water collector drain valve 10 after the liquid level switch 12 sends a signal; the hydrogen discharged from the primary pressure regulating valve 6 can enter the water collector 9 through the charging valve 11 of the charging branch before the secondary pressure regulating valve 5.

[0045] The system separates the hydrogen-water separation system from the water collector during drainage, avoiding pressure fluctuations in the system; after drainage is completed, the generated hydrogen is returned to the water collector, and after the pressure is equal to that of the hydrogen-water separation system, the hydrogen-water separation and the water collector are connected, avoiding pressure fluctuations in the hydrogen-water separation system, and thus avoiding pressure shocks to the electrolyzer. This method precisely controls the constant pressure during the entire drainage process.

[0046] Example 2

[0047] like Figure 1 As shown, the present invention provides a water electrolysis system, and the system includes an electrolytic cell 1, a circulation pump 2, an oxygen-water separator 3, an oxygen pressure regulating valve 4, a secondary pressure regulating valve 5, a primary pressure regulating valve 6, a hydrogen-water separator 7, a hydrogen-water separator drain valve 8, a water collector 9, a water collector drain valve 10, a charging valve 11 and a liquid level switch 12; in addition, it includes some necessary connecting pipelines.

[0048] A control method for a water electrolysis system of the present invention comprises the following steps:

[0049] Step 1: The circulating pump 2 is operated to feed the electrolyte into the electrolytic cell 1 for electrolysis. The generated oxygen and unreacted water enter the oxygen-water separator 3. The separated oxygen is pressure-regulated by the oxygen pressure regulating valve 4 to reach the set value, thereby ensuring a constant pressure in the oxygen-water separation system.

[0050] Step 2: The hydrogen and a small amount of water generated in the electrolyzer 1 enter the hydrogen-water separator 7, and the separated hydrogen is pressure-regulated by the primary regulating valve 6 to reach the set value, thereby ensuring that the pressure in the hydrogen-water separation system and the hydrogen drainage system is constant;

[0051] Step 3: As the liquid level in the water collector 9 continues to rise and reaches the position of the liquid level switch 12, the hydrogen-water separator drain valve 8 is closed and the water collector drain valve 10 is opened to drain water. At this time, the charging valve 11 is in a closed state and the secondary pressure regulating valve 5 is in an open state;

[0052] Step 4: When the drainage reaches the preset time, close the water collector drainage valve 10, adjust the pressure of the secondary pressure regulating valve 5 to be equal to that of the primary pressure regulating valve 6, open the charging valve 11, and charge the water collector 9;

[0053] Step 5. When the pressure in the water collector 9 is equal to that in the hydrogen-water separation system, close the charging valve 11, and open the water collector drain valve 10 and the secondary pressure regulating valve 5. At this time, the water in the hydrogen-water separator 7 flows into the water collector 9 under the action of gravity. Since the water collector 9 and the hydrogen-water separator 7 are at the same pressure, at the moment when the water collector drain valve 10 is opened, the pressure fluctuation of the hydrogen-water separation system and the hydrogen drainage system is extremely small.

[0054] When the system is working, the oxygen side pipeline pressure P 氧 Use oxygen pressure regulating valve 4 to set. Hydrogen side pipeline pressure P 氢 Use the first-stage pressure regulating valve 6 to set, the second-stage pressure regulating valve 5 is fully opened, the hydrogen-water separator drain valve 8 is opened, and the water collector drain valve 10 and the pressure charging valve 11 are closed. The water in the hydrogen-water separator 7 flows into the water collector 9 through the hydrogen-water separator drain valve 8. When the liquid level reaches the set value of the liquid level switch 12, the hydrogen-water separator drain valve 8 is closed, and the water collector drain valve 10 and the pressure charging valve 11 are opened. At this time, the water collector 9 is drained, but the pressure P before the first-stage pressure regulating valve 6 is 氢 After the water collector 9 is drained, close the water collector drain valve 10 and set the pressure of the secondary pressure regulating valve 5 to P 氢 , open the charging valve 11, and then rush hydrogen into the water collector 9. When the pressure reaches the set value, close the charging valve 11, open the hydrogen-water separator drain valve 8 and the secondary pressure regulating valve 5. At this time, the hydrogen-water separator 7 and the water collector 9 are equal in pressure, and water flows into the water collector 9 by gravity, maintaining the hydrogen side pipeline pressure P 氢 Keep it constant.

[0055] During operation, there is no pressure fluctuation in front of the first-stage pressure regulating valve 6 during the moment of drainage of the hydrogen side pipeline and the pressure increase of the water collector 9, and the pressure stabilization effect is obvious especially under high system pressure (≥3.5MPa).

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water electrolysis system, characterized in that: include: An electrolyzer (1), a hydrogen-water separation system and a hydrogen drainage system; The hydrogen-water separation system comprises a hydrogen discharge branch and a water separation branch; The hydrogen discharge branch comprises a secondary pressure regulating valve (5), a primary pressure regulating valve (6) and a hydrogen-water separator (7); the inlet of the hydrogen-water separator (7) is connected to the hydrogen outlet of the electrolyzer (1) via a pipeline; and the gas outlet of the hydrogen-water separator (7) is connected to the primary pressure regulating valve (6) and the secondary pressure regulating valve (5) via pipelines in sequence; The water diversion branch comprises a hydrogen-water separator (7) and a hydrogen-water separator drain valve (8), and the liquid outlet of the hydrogen-water separator (7) is connected to the hydrogen-water separator drain valve (8) via a pipeline; The hydrogen drainage system includes a water collection branch and at least one charging branch; The water collecting branch comprises a water collector (9), the inlet of the water collector (9) is connected to the liquid outlet of the hydrogen-water separator (7) through a pipeline via a hydrogen-water separator drain valve (8); The pressure charging branch comprises a pressure charging valve (11), one end of which is connected to the water collector (9) via a pipeline, and the other end of which is connected to the pipeline between the secondary pressure regulating valve (5) and the primary pressure regulating valve (6) via a pipeline.

2. The water electrolysis system according to claim 1, characterized in that: The water electrolysis system also includes an oxygen-water separation system for discharging the oxygen generated by the electrolytic cell (1) and unreacted water.

3. The water electrolysis system according to claim 1, characterized in that: The water collection branch further comprises a water collector drain valve (10) and a liquid level switch (12); the water collector drain valve (10) is connected to the water collector (9); and the liquid level switch (12) is installed on the water collector (9).

4. The water electrolysis system according to claim 2, characterized in that: The oxygen-water separation system comprises an oxygen discharge branch and a water circulation branch, wherein the oxygen discharge branch is connected to the electrolytic cell (1), and the water circulation branch is connected to the oxygen discharge branch and the electrolytic cell (1).

5. The water electrolysis system according to claim 4, characterized in that: The oxygen exhaust branch comprises an oxygen-water separator (3) and an oxygen pressure regulating valve (4); the oxygen-water separator (3) is connected to the electrolytic cell (1); and the oxygen pressure regulating valve (4) is connected to the oxygen-water separator (3).

6. The water electrolysis system according to claim 4, characterized in that: The water circulation branch comprises a circulation pump (2), and the circulation pump (2) is respectively connected to the electrolytic cell (1) and the oxygen-water separator (3) of the oxygen exhaust branch.

7. A method for controlling a water electrolysis system according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: The circulation pump (2) is operated to feed the electrolyte into the electrolytic cell (1) for electrolysis, and the generated oxygen and unreacted water enter the oxygen-water separator (3). The separated oxygen is pressure-regulated by the oxygen pressure regulating valve (4) to reach the set value, thereby ensuring that the pressure in the oxygen-water separation system is constant. Step 2, the hydrogen and a small amount of water generated in the electrolyzer (1) enter the hydrogen-water separator (7), and the separated hydrogen is pressure-regulated by the primary regulating valve (6) to reach the set value, thereby ensuring that the pressure in the hydrogen-water separation system and the hydrogen drainage system is constant; Step 3: As the liquid level in the water collector (9) continues to rise and reaches the position of the liquid level switch (12), the hydrogen-water separator drain valve (8) is closed and the water collector drain valve (10) is opened to drain water. At this time, the charging valve (11) is in a closed state and the secondary pressure regulating valve (5) is in an open state; Step 4: When the drainage reaches the predetermined time, close the water collector drainage valve (10), adjust the pressure of the secondary pressure regulating valve (5) to be equal to that of the primary pressure regulating valve (6), open the pressure charging valve (11), and charge the water collector (9); Step 5. When the pressure in the water collector (9) is equal to that in the hydrogen-water separation system, close the charging valve (11), open the water collector drain valve (10) and the secondary pressure regulating valve (5), and the water in the hydrogen-water separator (7) flows into the water collector (9) under the action of gravity. The water collector (9) and the hydrogen-water separator (7) are at the same pressure. At the moment when the water collector drain valve (10) is opened, the pressure fluctuation of the hydrogen-water separation system and the hydrogen drainage system is extremely small.

Images