Method for controlling electrolysis system and electrolysis system

Abstract

To protect an anode and a cathode while suppressing deterioration of the quality of hydrogen as a product.SOLUTION: The electrolysis system comprises an electrolytic cell including an anode chamber having an anode and a cathode chamber having a cathode, and a rectifier capable of supplying current to the anode and the cathode in an energization direction in which electrolysis of an electrolyte in the electrolytic cell proceeds. The method for controlling the electrolysis system comprises supplying a protective current to the anode and the cathode in the energization direction by the rectifier during stoppage of operation of the electrolysis system, and supplying hydrogen gas to the cathode chamber and supplying oxygen gas to the anode chamber during stoppage of operation of the electrolysis system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for controlling an electrolysis system and an electrolysis system. [Background technology]

[0002] In recent years, in order to realize a decarbonized society, power generation using renewable energy such as wind power or solar power has been actively carried out. Furthermore, electrolysis systems that produce hydrogen and oxygen by electrolyzing water using electricity generated using such renewable energy have attracted attention. Commercial electrolysis systems use a current of several thousand to several tens of thousands of amperes to produce hydrogen and oxygen.

[0003] Here, power generation using renewable energy may be stopped due to constant fluctuations in the renewable energy. For example, solar power generation using sunlight stops at night. Furthermore, wind power generation using wind power stops during strong winds. When power generation using renewable energy stops in this way, it is necessary to stop the operation of the electrolysis system. However, stopping the operation of the electrolysis system may cause a reverse current to occur in the anode and cathode of the electrolysis system. When such a reverse current occurs, there is a risk that the anode and cathode may deteriorate.

[0004] Therefore, a method is known in which a protective current is supplied to the anode and cathode while the electrolysis system is stopped, thereby maintaining the potential of the anode and cathode at or above the theoretical decomposition voltage, thereby preventing the generation of reverse current in the anode and cathode. For example, Patent Document 1 describes a method in which, prior to stopping electrolysis, the current density is set to 0 A / cm within a range in which electrolysis does not stop. 2 The method for producing hydrogen gas described in Patent Document 1 involves maintaining the current density for at least one second while introducing gas into the hydrogen generating electrode, and then reducing the current density to a value at which electrolysis does not occur, thereby stopping the electrolysis. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 210578 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, Patent Document 1 describes that the gas introduced into the hydrogen generating electrode is at least one selected from the group consisting of nitrogen and rare gases. When nitrogen gas or the like is introduced into the hydrogen generating electrode, the concentration of hydrogen as a product decreases, and the quality of the hydrogen as a product may decrease.

[0007] In view of the above, an object of the present disclosure is to protect the anode and cathode while suppressing deterioration in the quality of hydrogen as a product. [Means for solving the problem]

[0008] That is, the present disclosure is as follows. [1] A method for controlling an electrolysis system including an electrolytic cell having an anode chamber having an anode and a cathode chamber having a cathode, and a rectifier capable of supplying current to the anode and the cathode in a current flow direction in which electrolysis of an electrolytic solution in the electrolytic cell proceeds, comprising: supplying a protective current to the anode and the cathode in the current-carrying direction by the rectifier during shutdown of the electrolysis system; supplying hydrogen gas to the cathode chamber and oxygen gas to the anode chamber while operation of the electrolysis system is stopped. [2] the electrolysis system further includes a hydrogen tank that stores hydrogen gas generated by electrolysis of the electrolyte in the electrolytic cell; [1] The method for controlling an electrolysis system according to [1], wherein supplying hydrogen gas to the cathode chamber while operation of the electrolysis system is stopped includes supplying hydrogen gas stored in the hydrogen tank to the cathode chamber. [3] the electrolysis system further includes an oxygen tank that stores oxygen gas generated by electrolysis of the electrolyte in the electrolytic cell; [3] The method for controlling an electrolysis system according to [1] or [2], wherein supplying oxygen gas to the anode chamber while operation of the electrolysis system is stopped includes supplying oxygen gas stored in the oxygen tank to the anode chamber. [4] supplying hydrogen gas to the cathode chamber during shutdown of the electrolysis system, detecting an oxygen concentration in hydrogen of the hydrogen gas in the cathode chamber; determining whether or not the oxygen concentration in the detected hydrogen gas exceeds a first threshold value; and when it is determined that the oxygen concentration in hydrogen of the detected hydrogen gas exceeds a first threshold, controlling the supply of hydrogen gas to the cathode chamber. [5] The method for controlling an electrolysis system according to any one of [1] to [4], further comprising adjusting the air pressure in the cathode chamber after supplying hydrogen gas to the cathode chamber. [6] supplying oxygen gas to the anode chamber during shutdown of the electrolysis system, detecting a hydrogen concentration in oxygen of the oxygen gas in the anode chamber; determining whether or not the concentration of hydrogen in oxygen in the detected oxygen gas exceeds a second threshold; and when it is determined that a hydrogen-in-oxygen concentration of the detected oxygen gas exceeds a second threshold, performing control so that oxygen gas is supplied to the anode chamber. [7] The method for controlling an electrolysis system according to any one of [1] to [6], further comprising adjusting the air pressure in the anode chamber after supplying oxygen gas to the anode chamber. [8] an electrolytic cell including an anode chamber having an anode and a cathode chamber having a cathode; a rectifier capable of supplying current to the anode and the cathode in a current flow direction in which electrolysis of the electrolyte in the electrolytic cell proceeds; a control device that controls the current flow direction so that a protective current is supplied to the anode and the cathode by the rectifier while the electrolysis system is not operating, the control device controls so that hydrogen gas is supplied to the cathode chamber and oxygen gas is supplied to the anode chamber while operation of the electrolysis system is stopped. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, it is possible to protect the anode and the cathode while suppressing deterioration in the quality of hydrogen as a product. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram illustrating a configuration of an electrolysis system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a side view of the electrolytic cell shown in FIG. [Figure 3] FIG. 3 is a perspective view of the electrolytic cell shown in FIG. 2. [Figure 4] FIG. 3 is a plan view of the electrolytic cell shown in FIG. [Figure 5] 1 is a flowchart illustrating an example of a procedure for a control method for an electrolysis system according to an embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating a simulation result. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0012] (Electrolysis system configuration) As shown in Fig. 1 , an electrolysis system 1 according to this embodiment includes an electrolytic cell 2, an anode tank 3, a sensor 4, an oxygen tank 5, a fan 6, a cathode tank 7, a sensor 8, a scrubber 9, a compressor 10, a hydrogen gas purification device 11, and a hydrogen tank 12. The electrolysis system 1 further includes a rectifier 13 and a control device 16. The electrolysis system 1 may also include a liquid feed pump that feeds an electrolytic solution to the electrolytic cell 2, etc.

[0013] As shown in FIGS. 2 and 3 (described later), the electrolytic cell 2 includes an anode chamber 27a having an anode 21a and a cathode chamber 27c having a cathode 21c. An electrolytic solution passes through the anode chamber 27a and the cathode chamber 27c. The electrolytic solution is, for example, an alkaline aqueous solution in which an alkaline salt is dissolved. Examples of the electrolytic solution include an aqueous NaOH solution and an aqueous KOH solution. A current is supplied to the anode 21a and the cathode 21c from the rectifier 13. When a current is supplied to the anode 21a and the cathode 21c, the electrolytic solution in the anode chamber 27a and the cathode chamber 27c is electrolyzed. When the electrolytic solution is electrolyzed, hydrogen gas is generated in the cathode chamber 27c and oxygen gas is generated in the anode chamber 27a.

[0014] The anode tank 3 is connected to the anode chamber 27a of the electrolytic cell 2 via an anolyte outlet 27ao and an anode collection pipe header 30Oao, which will be described later and are shown in FIG. 3 . The anode tank 3 is supplied with the electrolyte and oxygen gas from the anode chamber 27a of the electrolytic cell 2. The anode tank 3 separates the supplied electrolyte and oxygen gas. The separated oxygen gas is supplied to the oxygen tank 5.

[0015] The sensor 4 is disposed in a supply path of oxygen gas from the anode tank 3 to the oxygen tank 5. The supply path includes, for example, piping and valves.

[0016] The sensor 4 includes a concentration sensor. The sensor 4 detects the concentration of hydrogen in oxygen in the oxygen gas in the supply path from the anode tank 3 to the oxygen tank 5. The sensor 4 transmits the detection result of the concentration of hydrogen in oxygen to the control device 16.

[0017] The sensor 4 includes an air pressure sensor. The sensor 4 detects the air pressure in the supply path of oxygen gas from the anode tank 3 to the oxygen tank 5. The sensor 4 transmits the detected air pressure to the control device 16.

[0018] Oxygen gas is supplied to the oxygen tank 5 from the anode tank 3. The oxygen tank 5 stores the oxygen gas.

[0019] The oxygen tank 5 is connected to an anode collection pipe header 30Oao (shown in FIG. 3 ) via a supply path. The supply path includes a fan 6, piping, and a valve (described below). While the electrolysis system 1 is not operating, oxygen gas stored in the oxygen tank 5 is supplied to the electrolytic cell 2 via the anode collection pipe header 30Oao (shown in FIG. 3 ) under the control of the control device 16.

[0020] The fan 6 is disposed in the supply path of oxygen gas from the oxygen tank 5 to the electrolytic cell 2. The fan 6 rotates based on a control signal received from the control device 16. When the fan 6 rotates, oxygen gas is supplied from the oxygen tank 5 to the electrolytic cell 2.

[0021] The cathode tank 7 is connected to the cathode chamber 27c of the electrolytic cell 2 via a cathode electrolyte outlet 27io and a cathode collection pipe header 30Oco shown in FIG. 3 (described later). The cathode tank 7 is supplied with the electrolyte and hydrogen gas from the cathode chamber 27c of the electrolytic cell 2. The cathode tank 7 separates the electrolyte and the hydrogen gas. The separated hydrogen gas is supplied to a scrubber 9.

[0022] The sensor 8 is disposed in a supply path of hydrogen gas from the cathode tank 7 to the scrubber 9. The supply path includes, for example, piping and valves.

[0023] The sensor 8 includes a concentration sensor. The sensor 8 detects the oxygen concentration in hydrogen of the hydrogen gas in the supply path from the cathode tank 7 to the scrubber 9. The sensor 8 transmits the detection result of the oxygen concentration in hydrogen to the control device 16.

[0024] The sensor 8 includes an air pressure sensor. The sensor 8 detects the air pressure in the supply path of hydrogen gas from the cathode tank 7 to the scrubber 9. The sensor 8 transmits the detected air pressure to the control device 16.

[0025] Hydrogen gas is supplied to the scrubber 9 from the cathode tank 7. The scrubber 9 removes mist contained in the hydrogen gas during operation of the electrolysis system 1. The scrubber 9 supplies the hydrogen gas from which the mist has been removed to the compressor 10. As will be described later, during shutdown of the electrolysis system 1, a protective current is supplied to the anode 21a and cathode 21c of the electrolytic cell 2 by the electrode protection rectifier 15. The scrubber 9 releases hydrogen gas into the atmosphere while a protective current is supplied to the anode 21a and cathode 21c of the electrolytic cell 2 during shutdown of the electrolysis system 1.

[0026] Hydrogen gas is supplied to the compressor 10 from the scrubber 9. The compressor 10 compresses the hydrogen gas to a predetermined pressure. The predetermined pressure may be set based on the capacity of the hydrogen tank 12, etc. The compressor 10 supplies the compressed hydrogen gas to a hydrogen gas purification device 11.

[0027] Hydrogen gas is supplied from the compressor 10 to the hydrogen gas purifier 11. The hydrogen gas purifier 11 removes impurities from the supplied hydrogen gas to purify the hydrogen gas. The hydrogen gas purifier 11 supplies the purified hydrogen gas to the hydrogen tank 12.

[0028] Hydrogen gas is supplied to the hydrogen tank 12 from the hydrogen gas refinery device 11. The hydrogen tank 12 stores the hydrogen gas. The hydrogen gas stored in the hydrogen tank 12 is shipped as a product.

[0029] The hydrogen tank 12 is connected to a cathode collection pipe header 30Oco shown in FIG. 3 via a supply path. The supply path includes piping and valves. When the electrolysis system 1 is not operating, the hydrogen gas stored in the hydrogen tank 12 is supplied to the electrolytic cell 2 via the cathode collection pipe header 30Oco shown in FIG. 3 under the control of the control device 16.

[0030] The rectifier 13 is configured to be able to supply current to the anode 21a and the cathode 21c of the electrolytic cell 2 in a current flow direction that advances the electrolysis of the electrolyte in the electrolytic cell 2. The rectifier 13 includes a main rectifier 14 and an electrode protection rectifier 15.

[0031] During operation of the electrolysis system 1, the main rectifier 14 supplies current to the anode 21a and cathode 21c of the electrolytic cell 2 in a current flow direction that promotes electrolysis of the electrolyte in the electrolytic cell 2, based on a control signal received from the control device 16. The current supplied by the main rectifier 14 is supplied to the anode 21a and cathode 21c via an anode terminal element 25a and a cathode terminal element 25c of the electrolytic cell 2, as shown in Figure 2, which will be described later. When operation of the electrolysis system 1 is stopped, the main rectifier 14 stops supplying current to the anode 21a and cathode 21c of the electrolytic cell 2.

[0032] While the electrolysis system 1 is out of operation, the electrode protection rectifier 15 supplies a protective current to the anode 21a and cathode 21c of the electrolytic cell 2 in the current flow direction in which electrolysis of the electrolyte in the electrolytic cell 2 progresses, based on a control signal received from the control device 16. The protective current supplied by the electrode protection rectifier 15 is supplied to the anode 21a and cathode 21c via an anode terminal element 25a and a cathode terminal element 25c of the electrolytic cell 2 shown in FIG. 2 (described below). The protective current is a current for protecting the anode 21a and cathode 21c of the electrolytic cell 2. The magnitude of the protective current is small compared to the magnitude of the current supplied from the main rectifier 14 to the anode 21a and cathode 21c during operation of the electrolytic system 1. The magnitude of the protective current may be such that the potentials of the anode 21a and cathode 21c can be maintained at or above the theoretical decomposition voltage. Supplying a protective current to the anode 21a and the cathode 21c while the electrolysis system 1 is out of operation can prevent reverse current from occurring in the anode 21a and the cathode 21c. Preventing reverse current from occurring in the anode 21a and the cathode 21c can prevent deterioration of the anode 21a and the cathode 21c.

[0033] The control device 16 is, for example, a computer. The control device 16 controls each component of the electrolysis system 1. The control device 16 includes a communication unit 17, a storage unit 18, and a control unit 19.

[0034] The communication unit 17 includes at least one communication module capable of communicating with each component of the electrolysis system 1. The communication module may comply with a standard for communication between the control device 16 and each component of the electrolysis system 1. Communication between the control device 16 and each component of the electrolysis system 1 may be wired or wireless.

[0035] The storage unit 18 is configured to include at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or a combination of at least two of these. The semiconductor memory is, for example, a random access memory (RAM) or a read-only memory (ROM). The RAM is, for example, a static random access memory (SRAM) or a dynamic random access memory (DRAM). The ROM is, for example, an electrically erasable programmable read-only memory (EEPROM). The storage unit 18 may function as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 18 stores data used in the operation of the control device 16 and data obtained by the operation of the control device 16.

[0036] The control unit 19 is configured to include at least one processor, at least one dedicated circuit, or a combination of these. The processor is, for example, a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The control unit 19 controls each part of the control unit 16 and executes processes related to the operation of the control unit 16.

[0037] The control unit 19 controls the operation of the electrolysis system 1. The processing by the control unit 19 will be described in detail later.

[0038] (Electrolytic cell configuration) As shown in Fig. 2, the electrolytic cell 2 according to this embodiment is a bipolar type. However, the electrolytic cell 2 is not limited to a bipolar type. The electrolytic cell 2 may also be a monopolar type.

[0039] The bipolar system is one method of connecting a large number of cells to a power source. As shown in Fig. 2, the bipolar system according to this embodiment is a method in which multiple bipolar elements 20 are arranged in the same direction and directly connected, and only both ends of the elements are connected to the power source, i.e., to the rectifier 13 in this embodiment. Of the two surfaces included in the bipolar element 20, one surface serves as the anode 21a and the other surface serves as the cathode 21c.

[0040] The bipolar electrolytic cell 2 can reduce the current of power supply equipment such as the rectifier 13. Furthermore, the bipolar electrolytic cell 2 can produce a large amount of a compound or a predetermined substance through electrolysis in a short period of time. If the power output is the same, a low-current, high-voltage power supply equipment is cheaper and more compact. Therefore, from an industrial perspective, the bipolar type is preferable to the monopolar type.

[0041] In the electrolytic cell 2 according to this embodiment, as shown in FIG. 2, a plurality of bipolar elements 20 are stacked with a diaphragm 24 sandwiched between them.

[0042] (Multi-pole element configuration) As shown in Fig. 2, the bipolar element 20 according to this embodiment includes an anode 21a, a cathode 21c, a partition wall 22, and an outer frame 23. The partition wall 22 separates the anode 21a from the cathode 21c. The partition wall 22 is conductive. The outer frame 23 frames the partition wall 22. The outer frame 23 is provided along the outer edge of the partition wall 22 so as to surround the partition wall 22.

[0043] The bipolar element 20 may be used such that the predetermined direction D1 along the partition wall 22 is the vertical direction, as shown in Figures 3 and 4. In other words, when the partition wall 22 has a rectangular shape in a plan view as shown in Figure 4, the bipolar element 20 may be used such that the predetermined direction D1 along the partition wall 22 is the same direction as the direction of one of two pairs of opposing sides, as shown in Figures 3 and 4.

[0044] As shown in FIG. 2 , a bipolar electrolytic cell 2 is constructed by stacking the required number of bipolar elements 20. In the stacked structure of the electrolytic cell 2, a fast head 25g, an insulating plate 25i, and an anode terminal element 25a are arranged in this order from one end of the electrolytic cell 2. Furthermore, in the electrolytic cell 2, an anode side gasket portion 26, a diaphragm 24, a cathode side gasket portion 26, and a bipolar element 20 are arranged in this order. At this time, the bipolar element 20 is arranged so that its cathode 21c faces the anode terminal element 25a. The anode side gasket portion 26 to the bipolar element 20 are arranged repeatedly as many times as necessary for the designed production volume. After the required number of anode side gasket portions 26 to the bipolar element 20 are arranged repeatedly, the anode side gasket portion 26, the diaphragm 24, and the cathode side gasket portion 26 are again arranged in this order. Finally, the cathode terminal element 25c, insulating plate 25i, and loose head 25g are arranged in this order. The electrolytic cell 2 is assembled by clamping the entire assembly using a clamping mechanism such as a tie rod system 25r (see FIG. 2) or a hydraulic cylinder system.

[0045] The stacked structure of the electrolytic cell 2 can be arbitrarily selected from either the anode 21a side or the cathode 21c side. The arrangement of the elements in the stacked structure of the electrolytic cell 2 is not limited to the order described above.

[0046] 2, in the electrolytic cell 2, the bipolar element 20 is disposed between the anode terminal element 25a and the cathode terminal element 25c. Diaphragms 24 are disposed between the anode terminal element 25a and the bipolar element 20, between adjacent bipolar elements 20, and between the bipolar element 20 and the cathode terminal element 25c.

[0047] 3 and 4, in the electrolytic cell 2, an electrode chamber 27 is defined by a partition wall 22, an outer frame 23, and a diaphragm 24. An electrolyte passes through the electrode chamber 27. The electrode chamber 27 is an anode chamber 27a or a cathode chamber 27c.

[0048] Hereinafter, the portion of the electrolytic cell 2 between the partition walls 22 of two adjacent bipolar elements 20, and the portion between the partition walls 22 of an adjacent bipolar element 20 and a terminal element, will be referred to as the "electrolytic cell 28."

[0049] The electrolytic cell 28 includes the partition wall 22, anode chamber 27a, and anode 21a of one of two adjacent bipolar elements 20, and the cathode 21c, cathode chamber 27c, and partition wall 22 of the other bipolar element 20. The electrolytic cell 28 employs a zero-gap structure Z. The zero-gap structure Z is a structure in which there is substantially no gap between the diaphragm 24 and the electrode 21. The electrode 21 is the anode 21a or the cathode 21c.

[0050] The electrode chambers 27 have an electrolyte inlet 27i and an electrolyte outlet 27o at the boundary with the outer frame 23. The electrolyte inlet 27i introduces the electrolyte into the electrode chambers 27. The electrolyte outlet 27o discharges the electrolyte from the electrode chambers 27. For example, the anode chamber 27a has an anolyte inlet 27ai through which the electrolyte is introduced into the anode chamber 27a and an anolyte outlet 27ao through which the electrolyte discharged from the anode chamber 27a is discharged. Similarly, the cathode chamber 27c has a catholyte inlet 27ci through which the electrolyte is introduced into the cathode chamber 27c and a catholyte outlet 27co through which the electrolyte discharged from the cathode chamber 27c is discharged.

[0051] The anode chamber 27a and the cathode chamber 27c may have an internal distributor for uniformly distributing the electrolyte solution across the electrode surface inside the electrolytic cell 2. The electrode chamber 27 may also have a baffle plate that has the function of restricting the flow of the solution inside the electrolytic cell 2. Furthermore, the anode chamber 27a and the cathode chamber 27c may have protrusions for creating Karman vortices in order to uniformize the concentration or temperature of the electrolyte solution inside the electrolytic cell 2 and to promote degassing of gas adhering to the electrode 21 or the diaphragm 24.

[0052] 3 and 4, the electrolytic cell 2 according to this embodiment is provided with a conduit hose 29 outside the outer frame 3. The conduit hose 29 communicates with the electrode chamber 27.

[0053] 3 and 4, a conduit hose 29, which is a pipe for distributing or collecting gas or electrolyte, is attached to the electrolytic cell 2. The conduit hose 29 includes an inlet conduit hose for introducing electrolyte into the electrode chamber 27 and an outlet conduit hose for discharging the gas or electrolyte from the electrode chamber 27.

[0054] As an example, the electrolytic cell 2 is provided with an anode inlet conduit hose 29Oai and a cathode inlet conduit hose 29Oci below the outer frame 23 at the edge of the partition 22. The anode inlet conduit hose 29Oai introduces electrolyte into the anode chamber 27a. The cathode inlet conduit hose 29Oci introduces electrolyte into the cathode chamber 27c. In the same or similar manner, the electrolytic cell 2 is provided with an anode outlet conduit hose 29Oao and a cathode outlet conduit hose 29Oco at the side of the outer frame 23 at the edge of the partition 22. The anode outlet conduit hose 29Oao extracts electrolyte from the anode chamber 27a. The cathode outlet conduit hose 29Oco extracts electrolyte from the cathode chamber 27c.

[0055] As another example, the inlet conduit hose and the outlet conduit hose may be provided in the anode chamber 27a and the cathode chamber 27c so as to face each other across the center of the electrode chamber 27.

[0056] An external header 30O type is employed in the electrolytic cell 2 according to this embodiment. The external header 30O type is a type in which the electrolytic cell 2 and the external header 30 are independent of each other.

[0057] 4 shows a plan view of an example of an external header 30O type electrolytic cell 2 according to this embodiment. However, an internal header type may also be attached to the electrolytic cell 2.

[0058] 3 and 4, an external header 30 is attached to the conduit hose 29. The external header 30 is a pipe that collects the gas or electrolyte distributed or collected in the conduit hose 29. The external header 30 includes a distribution pipe that communicates with the inlet conduit hose and a collection pipe that communicates with the outlet conduit hose.

[0059] As an example, the electrolytic cell 2 is provided with an anode distribution pipe header 30Oai and a cathode distribution pipe header 30Oci at the bottom of the outer frame 23. The anode distribution pipe header 30Oai communicates with an anode inlet conduit hose 29Oai. The cathode distribution pipe header 30Oci communicates with a cathode inlet conduit hose 29Oci. In the same or similar manner, the electrolytic cell 2 is provided with an anode collection pipe header 30Oao at the side of the outer frame 23, which is communicated with an anode outlet conduit hose 29Oao, and a cathode collection pipe header 30Oco which is communicated with a cathode outlet conduit hose 29Oco.

[0060] In this embodiment, in the anode chamber 27a and the cathode chamber 27c, the inlet conduit hose and the outlet conduit hose are preferably provided at positions apart from each other in terms of water electrolysis efficiency. Furthermore, the inlet conduit hose and the outlet conduit hose are preferably provided to face each other across the center of the electrode chamber 27. Furthermore, when the shape of the partition wall 22 in a plan view is rectangular as shown in Figures 3 and 4, the inlet conduit hose and the outlet conduit hose are preferably provided symmetrically with respect to the center of the rectangle.

[0061] 3 and 4 , each electrode chamber 27 is typically provided with one anode inlet conduit hose 29Oai, one cathode inlet conduit hose 29Oci, one anode outlet conduit hose 29Oao, and one cathode outlet conduit hose 29Oco. However, this is not limited to this embodiment. For example, each electrode chamber 27 may be provided with a plurality of these elements.

[0062] 3 and 4 , each electrode chamber 27 is typically provided with one anode distribution pipe header 30Oai, one cathode distribution pipe header 30Oci, one anode collection pipe header 30Oao, and one cathode collection pipe header 30Oco. However, this is not limited to this embodiment. For example, these elements may be shared by multiple electrode chambers 27.

[0063] In the illustrated example, the partition wall 22, which is rectangular in plan view, and the diaphragm 24, which is also rectangular in plan view, are arranged parallel to each other, and the inner surface of the rectangular outer frame 23, which is provided at the edge of the partition wall 22 and faces the partition wall 22, is perpendicular to the partition wall 22. Therefore, the shape of the electrode chamber 27 is rectangular. However, in the present disclosure, the shape of the electrode chamber 27 is not limited to the rectangular parallelepiped shape of the illustrated example. The shape of the electrode chamber 27 may be any shape as long as the effects of the present disclosure are obtained. The shape of the electrode chamber 27 may be modified as appropriate depending on the shape of the partition wall 22 or the diaphragm 24 in plan view, the angle between the inner surface of the outer frame 23 facing the partition wall 22 and the partition wall 22, etc.

[0064] In this embodiment, the positional relationship between the electrode chamber 27 and the conduit hose 29 is not particularly limited. As shown in Figures 3 and 4, when the bipolar element 20 is used so that the predetermined direction D1 along the partition wall 22 is vertical, the inlet conduit hose may be located below or to the side of the electrode chamber 27 (below in the illustration). The outlet conduit hose may be located above or to the side of the electrode chamber 27 (lateral in the illustration). The distribution pipe header communicating with the inlet conduit hose may be located below or to the side of the electrode chamber 27 (below in the illustration). The collection pipe header communicating with the outlet conduit hose may be located above or to the side of the electrode chamber 27 (lateral in the illustration).

[0065] In this embodiment, the extending direction of the conduit hose 29 is not particularly limited.

[0066] In the present embodiment, the extension direction of the external headers 30 is not particularly limited. However, as shown in Figures 3 and 4, the distribution pipes (anode distribution pipe header 30Oai and cathode distribution pipe header 30Oci) and the collection pipes (anode collection pipe header 30Oao and cathode collection pipe header 30Oco) preferably extend in a direction perpendicular to the partition wall 22. It is more preferable that all of the headers 30 extend in a direction perpendicular to the partition wall 22.

[0067] As shown in Fig. 4, the electrolytic cell 2 according to this embodiment may include a plurality of rectifying plates 31. The rectifying plates 31 are arranged parallel to a predetermined direction D1 along the partition wall 22. Such rectifying plates 31 can reduce convection that occurs in the electrode chamber 27 due to turbulence in the gas-liquid flow within the electrode chamber 27. As a result, a local increase in the temperature of the electrolyte can be suppressed.

[0068] (Electrolysis system control) The control device 16 controls the electrolysis system 1. The control unit 19 controls the operation of the electrolysis system 1. That is, the control unit 19 controls the operation of the electrolysis system 1 and the operation stop of the electrolysis system 1.

[0069] <Operation control of electrolysis system> The control unit 19 controls the liquid feed pump to feed the electrolyte to the electrolytic cell 2 by sending a control signal to the liquid feed pump via the communication unit 17. In other words, the control unit 19 controls the liquid feed pump to feed the electrolyte to the anode chamber 27a via the anode inlet conduit hose 29Oai and to feed the electrolyte to the cathode chamber 27c via the cathode inlet conduit hose 29Oci.

[0070] The control unit 19 sends a control signal to the main rectifier 14 via the communication unit 17, causing the main rectifier 14 to supply current to the anode 21a and the cathode 21c in the current flow direction that advances the electrolysis of the electrolyte in the electrolytic cell 2. With this configuration, oxygen gas is generated in the anode chamber 27a, and hydrogen gas is generated in the cathode chamber 27c.

[0071] <Shutdown control of electrolysis system> During operation stoppage of the electrolysis system 1, the control unit 19 supplies a protective current to the anode 21a and the cathode 21c via the electrode protection rectifier 15 in the current flow direction in which electrolysis of the electrolyte in the electrolytic cell 2 progresses. With this configuration, as described above, it is possible to prevent reverse current from occurring in the anode 21a and the cathode 21c, and to prevent deterioration of the anode 21a and the cathode 21c.

[0072] In a bipolar electrolytic cell 2, the protective current from the electrode protection rectifier 15 is supplied to an anode terminal element 25a and a cathode terminal element 25c at both ends, as shown in Fig. 2. The anode terminal element 25a is connected to an anode collection pipe header 30Oao and an anode distribution pipe header 30Oai via a conduit hose 29 as shown in Fig. 3. The cathode terminal element 25c is connected to a cathode collection pipe header 30Oco and a cathode distribution pipe header 30Oci via a conduit hose 29 as shown in Fig. 3.

[0073] Here, the conduit hose 29 is conductive due to the electrolyte flowing through it. The external header 30 is also grounded. Meanwhile, the anode terminal element 25a, the cathode terminal element 25c, and each bipolar element 20 each have a potential other than 0 V. This configuration generates a potential difference between the anode terminal element 25a, the cathode terminal element 25c, and each bipolar element 20 and the external header 30. This potential difference causes a leakage current to flow between the anode terminal element 25a, the cathode terminal element 25c, and each bipolar element 20 and the header 30. Because the conduit hose 29 is conductive as described above, this leakage current is separated from the current flowing through the electrolytic reaction surfaces in each bipolar element 20. Due to this leakage current, the current flowing through the electrolytic reaction surfaces becomes smaller in the central portion of the electrolytic cell 2.

[0074] Furthermore, the potential of each of the anode terminal element 25a and the cathode terminal element 25c of the electrolytic cell 2 becomes equal to or greater than the theoretical decomposition voltage due to the supply of a protective current. Therefore, for example, if the bipolar element 20 has 300 pairs of anode and cathode terminal elements 25a and 25c, the potential difference between each of the anode and cathode terminal elements 25a and 25c and the header 30 is approximately +180 V at the anode terminal element 25a and approximately −180 V at the cathode terminal element 25c. As a result, the potential at the center of the electrolytic cell 2 becomes 0 V.

[0075] Here, the leakage current described above is distributed and discharged from the current supplied to the electrolytic reaction surface as a protective current in proportion to the potential difference between each bipolar element 20 and the external header 30. Therefore, the protective current from the electrode protection rectifier 15 is small in the central part of the electrolytic cell 2. With this configuration, in the central part of the electrolytic cell 2, the leakage current of the bipolar element 20 becomes relatively large compared to the current flowing through the electrolytic reaction surface.

[0076] Thus, in the central portion of the electrolytic cell 2, the leakage current of the bipolar element 20 becomes relatively large relative to the current flowing through the electrolysis reaction surface. As a result, the hydrogen-in-oxygen concentration becomes high in the anode chamber 27a, and the oxygen-in-hydrogen concentration becomes high in the cathode chamber 27c. Therefore, unless the value of the protective current from the electrode protection rectifier 15 is increased during shutdown of the electrolysis system 1, there is a risk of detonation gas being generated. However, from the perspective of reducing equipment costs and effectively utilizing renewable energy, it is desirable to keep the value of the protective current from the electrode protection rectifier 15 small. One possible method for suppressing the generation of detonation gas while reducing the value of the protective current from the electrode protection rectifier 15 is to supply nitrogen gas to the electrolytic cell 2 during shutdown of the electrolysis system 1. However, supplying nitrogen gas to the electrolytic cell 2 may reduce the concentration of hydrogen as a product, thereby potentially reducing the quality of the hydrogen product. Therefore, hydrogen gas must be discarded until the nitrogen concentration in the hydrogen gas falls within a predetermined range.

[0077] Therefore, while the electrolysis system 1 is shut down, the control unit 19 supplies a protective current to the anode 21a and the cathode 21c via the electrode protection rectifier 15 in the current flow direction in which electrolysis of the electrolyte in the electrolytic cell 2 progresses, while supplying hydrogen gas to the cathode collection pipe header 30Oco and oxygen gas to the anode collection pipe header 30Oao. By supplying hydrogen gas to the cathode collection pipe header 30Oco while the electrolysis system 1 is shut down, the oxygen gas generated in the cathode chamber 27c can be diluted. Furthermore, by supplying oxygen gas to the anode collection pipe header 30Oao while the electrolysis system 1 is shut down, the hydrogen gas generated in the anode chamber 27a can be diluted. By diluting the oxygen gas generated in the cathode chamber 27c and the hydrogen gas generated in the anode chamber 27a in this way, the generation of detonation gas can be suppressed without supplying nitrogen gas to the electrolytic cell 2 or increasing the protective current from the electrode protection rectifier 15. With this configuration, in this embodiment, it is possible to protect the anode 21a and the cathode 21c while suppressing a decrease in the quality of the hydrogen product. An example of the processing by the control unit 19 will now be described with reference to FIG.

[0078] 5 is a flowchart showing an example of the procedure of the method for controlling the electrolysis system 1 according to an embodiment of the present disclosure. The control unit 19 starts the process of step S1 when, for example, the control unit 19 receives a signal instructing the electrolysis system 1 to stop operation from an external device via the communication unit 17.

[0079] The control unit 19 sends a control signal to the electrode protection rectifier 15 via the communication unit 17, thereby causing the electrode protection rectifier 15 to supply a protective current to the anode 21a and the cathode 21c in the current flow direction in which electrolysis of the electrolyte in the electrolytic cell 2 progresses (step S1). The maximum value of the protective current is smaller than the value of the current supplied from the main rectifier 14 to the anode 21a and the cathode 21c during operation of the electrolysis system 1. The minimum value of the protective current may be set in advance based on the structure of the electrolytic cells 28 in the electrolytic cell 2, the number of stacked bipolar elements 20, etc.

[0080] The control unit 19 receives the detection result of the oxygen concentration in hydrogen gas from the sensor 8 via the communication unit 17 (step S2). This detection result of the oxygen concentration in hydrogen gas is the detection result of the oxygen concentration in hydrogen gas in the supply path of hydrogen gas from the cathode tank 7 to the scrubber 9. This detection result of the oxygen concentration in hydrogen gas changes when the oxygen concentration in hydrogen gas in the cathode chamber 27c changes. Therefore, this detection result of the oxygen concentration in hydrogen gas can be treated as the detection result of the oxygen concentration in hydrogen gas in the cathode chamber 27c.

[0081] The control unit 19 determines whether the oxygen concentration in the hydrogen of the hydrogen gas received in the processing of step S2 exceeds a first threshold (step S3). The first threshold may be set based on the maximum value of the protective current from the electrode protection rectifier 15. For example, the larger the protective current from the electrode protection rectifier 15, the smaller the contribution of the leakage current in the central portion of the electrolytic cell 2 described above, and the more likely it is that the generation of oxygen gas in the cathode chamber 27c due to the leakage current will be reduced. Therefore, the larger the protective current from the electrode protection rectifier 15, the smaller the first threshold may be set.

[0082] If the control unit 19 determines that the oxygen concentration in the hydrogen gas exceeds the first threshold value (step S3: YES), the control unit 19 proceeds to the process of step S4. On the other hand, if the control unit 19 determines that the oxygen concentration in the hydrogen gas is equal to or less than the first threshold value (step S3: NO), the control unit 19 proceeds to the process of step S6.

[0083] In the process of step S4, the control unit 19 controls the supply of hydrogen gas stored in the hydrogen tank 12 to the cathode chamber 27c. For example, as described above, the hydrogen tank 12 is connected to the cathode collection pipe header 30Oco via a supply path including piping and a valve. The control unit 19 then controls the valve to open, for example, by sending a control signal to the valve via the communication unit 17. When the valve opens, the compressed hydrogen gas stored in the hydrogen tank 12 is supplied to the cathode collection pipe header 30Oco. This allows the generated oxygen gas to be diluted with the hydrogen gas. The flow rate of the hydrogen gas supplied to the cathode chamber 27c may be set in advance depending on the structure of the electrolytic cell 2, etc.

[0084] Here, when hydrogen gas is supplied to the cathode chamber 27c in the process of step S4, the air pressure in the cathode chamber 27c increases, so the control unit 19 executes the process of step S5.

[0085] In the process of step S5, the control unit 19 adjusts the air pressure in the cathode chamber 27c. In this embodiment, the control unit 19 causes the scrubber 9 to release hydrogen gas into the atmosphere by sending a control signal to the scrubber 9 via the communication unit 17. The amount of hydrogen gas released into the atmosphere by the scrubber 9 is, for example, the sum of the amount of hydrogen gas supplied to the cathode chamber 27c in the process of step S4 and the amount of hydrogen gas generated in the cathode chamber 27c due to the supply of a protective current in the process of step S1. By releasing hydrogen gas into the atmosphere using the air pressure control system of the scrubber 9 in this manner, the air pressure in the cathode chamber 27c is controlled.

[0086] In the processing of steps S4 and S5, the control unit 19 may receive, from the sensor 8, a detection result of the air pressure in the supply path of hydrogen gas from the cathode tank 7 to the scrubber 9 via the communication unit 17. The control unit 19 may adjust the flow rate of hydrogen gas supplied to the cathode chamber 27c based on the received detection result of the air pressure. The control unit 19 may adjust the flow rate of hydrogen gas supplied to the cathode chamber 27c by adjusting the flow rate of hydrogen gas released into the atmosphere by the scrubber 9.

[0087] In the processing of step S6, the control unit 19 receives the detection result of the hydrogen concentration in oxygen gas from the sensor 4 via the communication unit 17. This hydrogen concentration in oxygen gas is the hydrogen concentration in oxygen in the oxygen gas supply path from the anode tank 3 to the oxygen tank 5. This detection result of the hydrogen concentration in oxygen gas changes when the hydrogen concentration in oxygen gas in the anode chamber 27a changes. Therefore, this detection result of the hydrogen concentration in oxygen gas can be treated as the detection result of the hydrogen concentration in oxygen gas in the anode chamber 27a.

[0088] In the process of step S7, the control unit 19 determines whether the hydrogen concentration in oxygen of the oxygen gas received in the process of step S6 exceeds a second threshold. The second threshold may be set based on the maximum value of the protective current. For example, the larger the protective current from the electrode protection rectifier 15, the smaller the contribution of the leakage current in the central portion of the electrolytic cell 2 described above, and the more likely it is that hydrogen gas will be generated in the anode chamber 27a due to the leakage current. Therefore, the larger the protective current from the electrode protection rectifier 15, the smaller the second threshold may be set.

[0089] If the control unit 19 determines that the hydrogen concentration in oxygen of the oxygen gas exceeds the second threshold (step S7: YES), the control unit 19 proceeds to the process of step S8. On the other hand, if the control unit 19 determines that the hydrogen concentration in oxygen of the oxygen gas is equal to or less than the second threshold (step S7: NO), the control unit 19 returns to the process of step S2.

[0090] In the process of step S8, the control unit 19 controls the supply of oxygen gas stored in the oxygen tank 5 to the anode chamber 27a. For example, as described above, the oxygen tank 5 is connected to the anode collection pipe header 30Oao via a supply path including a pipe and a valve. The control unit 19 controls the valve to open, for example, by sending a control signal to the valve via the communication unit 17. Furthermore, the control unit 19 rotates the fan 6 by sending a control signal to the fan 6 via the communication unit 17. When the valve opens and the fan 6 rotates, the oxygen gas stored in the oxygen tank 5 is supplied to the anode collection pipe header 30Oao. By supplying the oxygen gas in this manner, the generated hydrogen gas can be diluted with the oxygen gas. The flow rate of the oxygen gas supplied to the anode chamber 27a may be set in advance depending on the structure of the electrolytic cell 2, etc.

[0091] Here, when oxygen gas is supplied to the anode chamber 27a in the process of step S8, the air pressure in the anode chamber 27a increases, so the control unit 19 executes the process of step S9.

[0092] In the process of step S9, the control unit 19 adjusts the air pressure in the anode chamber 27a. In this embodiment, the control unit 19 causes the oxygen tank 5 to release oxygen gas into the atmosphere by sending a control signal to the oxygen tank 5 via the communication unit 17. The amount of oxygen gas released from the oxygen tank 5 into the atmosphere is, for example, the sum of the amount of oxygen gas supplied to the anode chamber 27a in the process of step S8 and the amount of oxygen gas generated in the anode chamber 27a by supplying a protective current in the process of step S1. By performing the process of step S9, the air pressure in the anode chamber 27a is controlled by releasing oxygen gas into the atmosphere using the air pressure control system of the oxygen tank 5.

[0093] In the processing of steps S8 and S9, the control unit 19 may receive, from the sensor 4, a detection result of the air pressure in the supply path of oxygen gas from the anode tank 3 to the oxygen tank 5, via the communication unit 17. The control unit 19 may adjust the flow rate of oxygen gas supplied to the anode chamber 27a based on the received detection result of the air pressure. The control unit 19 may adjust the flow rate of oxygen gas released from the oxygen tank 5 into the atmosphere, thereby adjusting the flow rate of oxygen gas supplied to the anode chamber 27a.

[0094] After the process of step S, the control unit 19 returns to the process of step S2. In the processes of steps S2 to S9, for example, when a signal instructing operation of the electrolysis system 1 is received from an external device via the communication unit 17, the control unit 19 may stop the processes of steps S2 to S9. After stopping the processes of steps S2 to S9, the control unit 19 may perform operation control of the electrolysis system 1.

[0095] <Simulation results> The inventors performed a simulation to confirm the effects of the present disclosure under the following conditions: Number of electrolytic cells: 300 [cells] Reaction area of ​​electrolytic cell 28: 2.72 [m] Resistance of cathode inlet conduit hose 29Oci: 410[Ω] Resistance of anode inlet conduit hose 29 Ω: 410 Ω Resistance of cathode outlet hose 290co: 1095 [Ω] Resistance of anode outlet conduit hose 29Oao: 1095 [Ω] Electrolyte circulation volume: 24L / cell / hour NaOH concentration of electrolyte: 21 [wt%] The inventors calculated the voltage applied to the electrolytic cell 28 based on the theoretical decomposition voltage of 1.23 [V].

[0096] The simulation results are shown in Figure 6. When the protective current value is 93 [A] or less, electrolysis does not occur and the anode 21a and the cathode 21c cannot be protected. Therefore, the lower limit of the protective current value was set to 93 [A].

[0097] As shown in FIG. 6, the flow rate of hydrogen gas to the cathode chamber 27c, i.e., the supply rate, is 0 [Nm 3 / hr], and the flow rate of oxygen gas to the anode chamber 27a, i.e., the supply rate, is 0 [Nm 3 / hr], the protective current value was 175 [A]. On the other hand, when the flow rate of hydrogen gas to the cathode chamber 27c, i.e., the supply rate, was 1.44 [Nm 3 / hr], and the flow rate of oxygen gas to the anode chamber 27a, i.e., the supply rate, was 5.12 [Nm 3 / hr], the protective current value was 93 [A]. From this result, it can be seen that if oxygen gas is supplied to the anode chamber 27a and hydrogen gas is supplied to the cathode chamber 27c, the protective current value can be reduced to about half of the value when oxygen gas is not supplied to the anode chamber 27a and hydrogen gas is not supplied to the cathode chamber 27c.

[0098] As described above, in the control device 16 according to this embodiment, while the electrolysis system 1 is stopped, the control unit 19 supplies protective currents to the anode 21a and the cathode 21c via the electrode protection rectifier 15 in the current flow direction in which electrolysis of the electrolyte in the electrolytic cell 2 progresses. Furthermore, while the electrolysis system 1 is stopped, the control unit 19 supplies hydrogen gas to the cathode chamber 27c and oxygen gas to the anode chamber 27a. With this configuration, as described above, the generation of detonation gas can be suppressed without supplying nitrogen gas to the electrolytic cell 2. Furthermore, the generation of detonation gas can be suppressed without increasing the protective currents supplied to the anode 21a and the cathode 21c by the electrode protection rectifier 15. As a result, the anode 21a and the cathode 21c can be protected while preventing a decrease in the quality of the hydrogen product.

[0099] Although the above-described embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present disclosure should not be construed as being limited by the above-described embodiments, and various modifications or alterations are possible without departing from the scope of the claims.

[0100] For example, in the above-described embodiment, it has been described that hydrogen gas stored in the hydrogen tank 12, i.e., hydrogen gas generated in the electrolysis system 1, is supplied to the cathode chamber 27c of the electrolytic cell 2. However, as long as hydrogen gas can be supplied to the cathode collection pipe header 30co of the electrolytic cell 2, hydrogen gas stored in the hydrogen tank 12, i.e., hydrogen gas other than hydrogen gas generated in the electrolysis system 1, may also be supplied to the cathode collection pipe header 30co of the electrolytic cell 2. As another example, hydrogen gas generated by a device other than the electrolysis system 1 may be supplied to the cathode collection pipe header 30co of the electrolytic cell 2.

[0101] For example, in the above-described embodiment, it has been described that oxygen gas stored in the oxygen tank 5, i.e., oxygen gas generated in the electrolysis system 1, is supplied to the anode collection pipe header 30ao of the electrolytic cell 2. However, as long as oxygen gas can be supplied to the anode collection pipe header 30ao of the electrolytic cell 2, oxygen gas stored in the oxygen tank 5, i.e., oxygen gas other than oxygen gas generated in the electrolysis system 1, may be supplied to the anode collection pipe 30ao of the electrolytic cell 2. As another example, oxygen gas generated by a device other than the electrolysis system 1 may be supplied to the anode collection pipe header 30ao of the electrolytic cell 2. [Explanation of symbols]

[0102] 1: Electrolysis system, 2: Electrolytic cell, 3: Anode tank, 4: Sensor, 5: Oxygen tank, 6: Fan, 7: Cathode tank, 8: Sensor, 9: Scrubber, 10: Compressor, 11: Hydrogen gas purification device, 12: Hydrogen tank, 13: Rectifier, 14: Main rectifier, 15: Electrode protection rectifier, 16: Control device, 17: Communication unit, 18: Memory unit, 19: Control unit, 20: Bipolar element, 21: Electrode, 21a: Anode, 21c: Cathode, 22: Partition wall, 23: Outer frame, 24: Diaphragm, 25a: Anode terminal element, 25g: Fast head, loose head, 25c: Cathode terminal element, 25i: Insulating plate, 25r: Tie rod system, 26: Gasket part, 27: electrode chamber, 27a: anode chamber, 27c: cathode chamber, 27ai: anolyte inlet, 27ao: anolyte outlet, 27ci: catholyte inlet, 27co: catholyte outlet, 27i: electrolyte inlet, 27o: electrolyte outlet, 28: electrolytic cell, 29: anode inlet conduit hose, 29Oai: anode inlet conduit hose, 29Oci: cathode inlet conduit hose, 29Oao: anode outlet conduit hose, 29Oco: cathode outlet conduit hose, 30: header, 30Oai: anode distribution pipe header, 30Oci: cathode distribution pipe header, 30Oao: anode collection pipe header, 30Oco: cathode collection pipe header, 31: rectifier plate, Z: zero gap structure

Claims

1. A method for controlling an electrolysis system including an electrolytic cell having an anode chamber having an anode and a cathode chamber having a cathode, and a rectifier capable of supplying current to the anode and the cathode in a current flow direction in which electrolysis of an electrolytic solution in the electrolytic cell proceeds, comprising: supplying a protective current to the anode and the cathode in the current-carrying direction by the rectifier during shutdown of the electrolysis system; supplying hydrogen gas to the cathode chamber and oxygen gas to the anode chamber while operation of the electrolysis system is stopped.

2. the electrolysis system further includes a hydrogen tank that stores hydrogen gas generated by electrolysis of the electrolyte in the electrolytic cell; 2. The method for controlling an electrolysis system according to claim 1, wherein supplying hydrogen gas to the cathode chamber while operation of the electrolysis system is stopped includes supplying hydrogen gas stored in the hydrogen tank to the cathode chamber.

3. the electrolysis system further includes an oxygen tank that stores oxygen gas generated by electrolysis of the electrolyte in the electrolytic cell; 2. The method for controlling an electrolysis system according to claim 1, wherein supplying oxygen gas to the anode chamber while operation of the electrolysis system is stopped comprises supplying oxygen gas stored in the oxygen tank to the anode chamber.

4. supplying hydrogen gas to the cathode chamber during shutdown of the electrolysis system, detecting an oxygen concentration in hydrogen of the hydrogen gas in the cathode chamber; determining whether or not the oxygen concentration in the detected hydrogen gas exceeds a first threshold; and performing control so that hydrogen gas is supplied to the cathode chamber when it is determined that the oxygen concentration in hydrogen of the detected hydrogen gas exceeds a first threshold value.

5. The method for controlling an electrolysis system according to claim 4, further comprising adjusting the air pressure in the cathode chamber after supplying hydrogen gas to the cathode chamber.

6. supplying oxygen gas to the anode chamber during shutdown of the electrolysis system, detecting a hydrogen concentration in oxygen of the oxygen gas in the anode chamber; determining whether or not the concentration of hydrogen in oxygen in the detected oxygen gas exceeds a second threshold; and performing control so that oxygen gas is supplied to the anode chamber when it is determined that the hydrogen-in-oxygen concentration of the detected oxygen gas exceeds a second threshold value.

7. The method for controlling an electrolysis system according to claim 6, further comprising adjusting the air pressure in the anode chamber after supplying oxygen gas to the anode chamber.

8. 1. An electrolysis system comprising: an electrolytic cell including an anode chamber having an anode and a cathode chamber having a cathode; a rectifier capable of supplying current to the anode and the cathode in a current flow direction in which electrolysis of the electrolyte in the electrolytic cell proceeds; a control device that controls the current flow direction so that a protective current is supplied to the anode and the cathode by the rectifier while the electrolysis system is not operating, the control device controls so that hydrogen gas is supplied to the cathode chamber and oxygen gas is supplied to the anode chamber while the operation of the electrolysis system is stopped.

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