Water electrolysis device

Abstract

To provide a water electrolysis device capable of reducing the load of a water supply side route while preventing the degradation of a water electrolysis cell.SOLUTION: A water electrolysis device comprises a water electrolysis stack with a plurality of water electrolysis cells stacked therein, a water supply side route for supplying the water electrolysis stack with water, and a hydrogen side route for recovering hydrogen generated in the water electrolysis stack, which water supply side route comprises a pump, i.e., a power source for supplying the water electrolysis stack with water, an ion exchanger disposed between the pump and the water electrolysis stack, a bypass, i.e., a route flowing water from the pump to the water electrolysis stack without passing through the ion exchanger, a valve for adjusting the flow rate of water flowing in the bypass, and a controller for controlling to adjust the degree of the valve opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a water electrolysis apparatus. [Background technology]

[0002] In water electrolysis devices that generate hydrogen and oxygen by electrolyzing water, if the water supplied to the water electrolysis cell contains ions, the deterioration of the water electrolysis cell may be accelerated. Therefore, it is desirable to remove these ions.

[0003] Patent Document 1 discloses that when a water electrolysis device is left unused for a long period of time, water is circulated to remove ions from the system before starting water electrolysis. For this purpose, ions are removed from the pure water supplied to the water electrolysis stack (each water electrolysis cell) by an ion exchanger provided downstream of the circulation pump. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-048506 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The technology described in Patent Document 1 suffers from problems such as high pressure loss, heavy load on the pump, the need for a large ion exchanger, and frequent maintenance such as replacement.

[0006] In view of the prior art, this disclosure aims to provide a water electrolysis device that can reduce the load on the water supply path while suppressing the deterioration of the water electrolysis cell. [Means for solving the problem]

[0007] After careful consideration, the inventors discovered that while passing the entire volume of water supplied to the water electrolysis stack through an ion exchanger is one way to minimize the deterioration of the water electrolysis stack, there are also many instances during the operation of the water electrolysis device where there are few or no ions. The inventors reasoned that passing water through the ion exchanger in such conditions wasted power in pumping the water and led to an increase in the size of the ion exchanger. Therefore, they solved the above problem by the specific means described below.

[0008] The present invention discloses a water electrolysis apparatus for obtaining hydrogen and oxygen by supplying water to a water electrolysis cell and applying voltage, comprising a water electrolysis stack in which water electrolysis cells are stacked, a water supply path for supplying water to the water electrolysis stack, and a hydrogen path for recovering hydrogen produced from the water electrolysis stack, wherein the water supply path comprises a pump which is a power source for supplying water to the water electrolysis stack, an ion exchanger disposed between the pump and the water electrolysis stack, a bypass which is a path for allowing water from the pump to flow to the water electrolysis stack without passing through the ion exchanger, a valve for adjusting the amount of water flowing through the bypass, and a controller for adjusting the valve, wherein the controller controls the opening of the valve based on the discharge pressure of the pump or the pressure in the piping between the pump and the ion exchanger.

[0009] The present invention discloses a water electrolysis apparatus for obtaining hydrogen and oxygen by supplying water to a water electrolysis cell and applying voltage, comprising a water electrolysis stack in which water electrolysis cells are stacked, a water supply path for supplying water to the water electrolysis stack, and a hydrogen path for recovering hydrogen produced from the water electrolysis stack, wherein the water supply path comprises a pump which is a power source for supplying water to the water electrolysis stack, an ion exchanger disposed between the pump and the water electrolysis stack, a bypass which is a path for allowing water from the pump to flow to the water electrolysis stack without passing through the ion exchanger, a valve for adjusting the amount of water flowing through the bypass, and a controller for adjusting the valve, wherein the controller controls the opening of the valve based on the amount of ions contained in the water supplied to the water electrolysis stack.

[0010] In the above water electrolysis device, the controller may obtain the conductivity of the water supplied to the water electrolysis stack to obtain the ion amount, and adjust the opening degree of the valve based on the conductivity threshold value.

[0011] In the above water electrolysis device, the controller may obtain the conductivity difference of the water on the upstream side and the downstream side across the ion exchanger to obtain the ion amount, and adjust the opening degree of the valve based on the conductivity difference threshold value.

Advantages of the Invention

[0012] According to the present disclosure, at least a part of the ions can be removed to suppress the deterioration of the water electrolysis cell, and a path that does not pass through the ion exchanger can be utilized to reduce the load on the water supply side path.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a conceptual diagram for explaining the configuration of the water electrolysis device 10. [Figure 2] FIG. 2 is a cross-sectional view for explaining the layer configuration of the water electrolysis cell 11. [Figure 3] FIG. 3 is a conceptual diagram for explaining the configuration of the controller 30. [Figure 4] FIG. 4 is a diagram for explaining the water supply control S10 according to Form 1. [Figure 5] FIG. 5 is a conceptual diagram for explaining the configuration of the water electrolysis device 50. [Figure 6] FIG. 6 is a diagram for explaining the water supply control S20 according to Form 2. [Figure 7] FIG. 7 is a diagram for explaining the water supply control S30 according to Form 3.

Modes for Carrying Out the Invention

[0014] 1. Configuration and Control of Water Electrolysis Device (Form 1) FIG. 1 conceptually shows the water electrolysis device 10 according to Form 1. The basic principles and concepts regarding the generation of hydrogen and oxygen by water electrolysis performed by the water electrolysis device 10 can follow those known in the art. In this embodiment, the water electrolysis device 10 includes a water electrolysis stack 20 formed by stacking a plurality of water electrolysis cells 11 and sandwiching both ends thereof with end plates, a water supply side path (oxygen side path) on one side sandwiching the water electrolysis stack 20, and a hydrogen side path on the other side. In the water electrolysis device 10, water is supplied to the water electrolysis cells 11 provided in the water electrolysis stack 20 from the water supply side path and energized by the power source 19, thereby decomposing water into hydrogen and oxygen. The obtained hydrogen is discharged into the hydrogen side path and recovered and stored.

[0015] 1.1. Water electrolysis stack As described above, the water electrolysis stack 20 is configured by stacking a plurality of water electrolysis cells 11 and sandwiching both ends thereof with end plates arranged at both ends.

[0016] FIG. 2 shows a partial cross section of a site where water electrolysis is performed in one water electrolysis cell 11. As can be seen from FIG. 2, the water electrolysis cell 11 has a stacked structure composed of a plurality of layers. The layer configuration is as known and is not particularly limited. For example, as shown in FIG. 2, the water electrolysis cell 11 has a hydrogen electrode catalyst layer 13, a hydrogen electrode diffusion layer 15, and a hydrogen electrode separator 17 stacked on one side of the electrolyte membrane 12, and an oxygen electrode catalyst layer 14, an oxygen electrode diffusion layer 16, and an oxygen electrode separator 18 stacked on the other side of the electrolyte membrane 12. The hydrogen electrode separator 17 is wave-shaped in the cross section, forms a groove-shaped hydrogen electrode flow path 17a between the hydrogen electrode diffusion layer 15, and hydrogen and accompanying water flow through the hydrogen electrode flow path 17a and are discharged into the hydrogen side path. On the other hand, the oxygen electrode separator 18 is also wave-shaped in the cross section and forms a groove-shaped oxygen electrode flow path 18a between the oxygen electrode diffusion layer 16. Water is supplied from the water supply side path to the oxygen electrode flow path 18a, and oxygen and the remaining water are discharged from the oxygen electrode flow path 18a into the water supply side path.

[0017] A power source 19 is connected between both electrodes of the water electrolysis stack 20 via a power line. By applying a voltage from this power source 19 to the water electrolysis stack 20, water electrolysis is performed in the water electrolysis cell 11. Here, the power source 19 is as known, and a normal power source used for water electrolysis can be applied.

[0018] 1.2. Water supply path (oxygen path) The water supply path (oxygen path) has a route through which tap water is purified by passing it through an ion exchanger and stored in a tank 21, and the purified water is supplied to the water electrolysis stack 20 via a water pump 22 through a cooler 23 and an ion exchanger 24. The oxygen and water that come out of the water electrolysis stack 20 are returned to a gas-liquid separator 25 to separate the gas and liquid, the gas (oxygen) is discharged, and the liquid (water) is returned to the tank 21 to be used again for water electrolysis. These components are connected by piping and configured so that water and oxygen can flow through the necessary paths.

[0019] Furthermore, in this configuration, there are piping branches to the upstream and downstream sides of the ion exchanger 24, and a bypass A is provided, which is a path that can supply water to the water electrolysis stack 20 without passing through the ion exchanger 24. A valve 26 is provided in this bypass A, and the flow rate can be changed by the opening of the valve 26, so that the amount of water flowing through bypass A can be adjusted. The type of valve 26 is not particularly limited, but as will be described later, the opening degree of valve 26 is controlled by the controller 30, so a control valve that is electrically connected to the controller 30 and whose opening degree is operated by a signal can be used.

[0020] Furthermore, in this configuration, a pressure gauge 27 capable of measuring the pressure in the piping is placed between the pump 22 and the ion exchanger 24 in the water supply path. While a known pressure gauge 27 can be used, from the viewpoint of obtaining pressure, which is one of the pieces of information used to adjust the opening degree of the valve 26 as described later, it is electrically connected to the controller 30 and configured to transmit the obtained pressure information to the controller 30.

[0021] Furthermore, a controller 30 is provided in the water supply path. The controller 30 is a controller that controls the water electrolysis apparatus 10 in this embodiment. More specifically, in this embodiment, it is a controller that controls the opening degree of the valve 26 based on pressure information from at least the pressure gauge 27. However, it does not have to be a controller solely for that purpose and may have other functions for controlling the water electrolysis apparatus 10. The configuration of the controller 30 is not particularly limited, but it can typically be configured as a computer. Figure 3 conceptually shows an example of the configuration of a computer 30 as the controller 30.

[0022] The computer 30 includes a CPU (Central Processing Unit) 31 which is a processor, RAM (Random Access Memory) 32 which functions as a work area, ROM (Read-Only Memory) 33 as a storage medium, a receiving unit 34 which is an interface for receiving information into the computer 30 whether wired or wireless, and an output unit 35 which is an interface for sending information from the computer 30 to the outside whether wired or wireless. A pressure gauge 27 is electrically connected to the receiving unit 34, and it is configured to receive pressure information via a signal. On the other hand, a valve 26 is electrically connected to the output unit 35, and the opening degree of the valve 26 can be controlled.

[0023] Computer 30 stores computer programs that define each control process performed by the water electrolysis apparatus 10 in this embodiment as specific commands and execute these commands. In computer 30, the CPU 31, RAM 32, and ROM 33, which are hardware resources, work together with the computer programs. Specifically, the CPU 31 realizes the function by executing the computer program recorded in ROM 33 in RAM 32, which functions as a work area, based on pressure information from the pressure gauge 27 acquired via the receiving unit 34. The information acquired or generated by the CPU 31 is stored in RAM 32. Then, based on the obtained results, commands are sent to the valve 26 via the output unit 35 as needed. The specific details of the control performed by the water electrolysis device 10 will be explained later.

[0024] 1.3. Hydrogen-side pathway In the hydrogen-side path, as can be seen in Figure 1, hydrogen and associated water from the water electrolysis stack 20 are collected in the gas-liquid separator 28, where the gas and liquid are separated. The gas (hydrogen) is then sent to the hydrogen tank 29 for storage via a dehumidifier and the like. Meanwhile, the water (associated water) separated in the gas-liquid separator 28 is returned to the tank 21 in the water supply path by a pump (not shown) or the like. These components are also connected by piping, and the system is configured to allow water and hydrogen to flow through the necessary paths.

[0025] 1.4 Control by Controllers As mentioned above, in water electrolysis devices, the water supplied to the water electrolysis stack may contain ions. This is partly due to the leaching of metal from the piping into the water by the generated hydrogen, etc. Therefore, an ion exchanger is installed to remove ions before supplying water to the water electrolysis stack. On the other hand, after diligent research, the inventor found that while passing the entire amount of water supplied to the water electrolysis stack through an ion exchanger is one way to minimize the deterioration of the water electrolysis stack, there are also many instances in the operation of the water electrolysis device where there are few or no ions. The inventor believed that passing water through an ion exchanger even in such conditions would result in wasted power on the water pump and lead to an increase in the size of the ion exchanger. Therefore, in this configuration, although it is ideal to remove all ions, considering the above and taking into account the relationship with the pump capacity and the capacity of the ion exchanger, it was thought that there would be an overall benefit to the water electrolysis apparatus even if some of the ions were removed to reduce the amount of ions and supply water to the water electrolysis stack. In this configuration, control is performed by the controller 30 as follows. Figure 4 shows the flow of the water supply control S10 by the controller 30.

[0026] As shown in Figure 4, in this embodiment, the water supply control S10 includes processes S11 to S15. Each of these processes can be performed by information acquisition, calculation, and command by the controller 30. Each process is described below.

[0027] In process S11, the controller 30 obtains the value of pressure P from the pressure gauge 27. This pressure P represents the load on the pump 22.

[0028] In process S12, the pressure P obtained in process S11 becomes the specified upper limit pressure P H Determine if it is greater than the specified upper limit pressure P. H This is a pressure value determined based on the upper limit of the discharge capacity of pump 22. This specified upper limit pressure P H If this value is exceeded, the load on pump 22 becomes too large, increasing the likelihood of malfunction. This determination is made by the controller 30. In process S12, P > P H If it is determined that (Yes), proceed to process S13, and in process S12, P > P H Not (No, i.e., P ≤ P) H If it is determined that this is the case, proceed to process S14.

[0029] In process S13, when the result in process S12 is determined to be Yes, the controller 30 commands valve 26 to increase its opening. This increases the flow rate of water through bypass A and decreases the flow rate of water through ion exchanger 24, thereby reducing pressure loss and thus lowering pressure P. At this time, there are no particular limitations on how to determine the degree to which the opening of valve 26 is increased, but for example, it can be done as follows. In Example 1 of valve opening determination, control is performed using pre-obtained functions or maps. Specifically, a calibration test is conducted beforehand to determine the relationship between the opening of valve 26 and the hydrogen production amount (load current) and pressure P. This relationship is then expressed as a function or map, and used as a database in calculations performed by the controller 30. In Example 2 of valve opening determination, the valve opening is controlled by feedback control (PI control, PID control) so that the pressure P (or the discharge pressure of the pump, as described later) reaches the target value. That is, the controller 30 controls the valve opening by comparing the measured value of pressure P (or discharge pressure) with the target value. After adjusting the opening degree of valve 26 in process S13, the process returns to S11.

[0030] In process S14, when the result in process S12 is determined to be No, the controller 30 sets P to the specified target pressure P. LDetermine whether it is not less than the specified target pressure P L is a pressure value determined based on the target pressure during normal operation (efficient operation) in view of the discharge capacity of the pump 22. By maintaining the operation at this specified target pressure P L efficient water supply by the pump 22 is performed. In process S14, when it is determined that P < P L (Yes), the process proceeds to process S15. When it is determined in process S14 that P < P L is not true (No, that is, P ≥ P L ), the process returns to process S11.

[0031] In process S15, when it is determined Yes in process S14, the controller 30 instructs the valve 26 to reduce the opening degree of the valve 26. As a result, the flow rate of water flowing through the bypass A can be reduced and the flow rate of water flowing through the ion exchanger 24 can be increased, so that as much water as possible within the allowable range of the capacity of the pump 22 can be passed through the ion exchanger 24. At this time, the method for determining the degree of reduction of the opening degree of the valve 26 is not particularly limited, but the above-described example 1 of opening degree determination and example 2 of opening degree determination can be used. After adjusting the opening degree of the valve 26 in process S15, the process returns to process S11.

[0032] 1.5. Effects, etc. According to the water electrolysis apparatus 10 of the present embodiment, by control, the frequency of water passing through the ion exchanger can be increased as much as possible by making the most of the power performance of the pump. On the other hand, since the pump 22 is suppressed from being in an overloaded state, it is possible to avoid malfunctions of the apparatus and to avoid using a pump with an unnecessarily high capacity.

[0033] In the present embodiment, an example of performing control based on the pressure P in the pipe by the pressure gauge 27 is shown, but the present invention is not limited thereto. Instead, the discharge pressure of the pump 23 can be acquired and the same control can be performed using this discharge pressure.

[0034] Also, in the present embodiment, the pressure P of the pressure gauge 27 is compared with P H and P LAn example was shown in which the relationship between the two values ​​is calculated to determine whether to change the opening degree of valve 26. However, the method is not limited to this. Alternatively, the value of pressure P, the discharge pressure of pump 22, and at least one of the values ​​of water electrolysis amount (hydrogen production amount), along with the opening degree of valve 26, may be investigated in advance and created in a database (so-called mapping), and the opening degree of valve 26 may be obtained based on that database.

[0035] 2. Configuration and control of a water electrolysis apparatus (Form 2) 2.1. Configuration of a water electrolysis device Figure 5 schematically shows the configuration of the water electrolysis apparatus 50 according to the second form. In the water electrolysis apparatus 50, a conductivity meter 51 is installed instead of a pressure gauge 27 compared to the water electrolysis apparatus 10. The other components can be considered in the same way as those of the water electrolysis apparatus 10, so their explanation is omitted here.

[0036] The conductivity meter 51 is an instrument that measures the conductivity of water flowing through the piping downstream of bypass A up to the water electrolysis stack 20. The obtained conductivity is configured to be transmitted as a signal to the controller 30. Since the conductivity of water is related to the amount of ions in the water, in this embodiment, the amount of ions can be obtained by measuring the conductivity.

[0037] 2.2. Water supply control In this configuration as well, as mentioned above, while it is ideal to remove all ions, considering that there are often states where there are almost no (or few) ions, and taking into account the relationship with the pump capacity and the capacity of the ion exchanger, it was thought that there would be benefits to the water electrolysis apparatus as a whole even if some of the ions were removed to reduce the ion content and supply water to the water electrolysis stack. In this configuration, the controller 30 performs the control as follows. Figure 6 shows the flow of the water supply control S20 by the controller 30 of the water electrolysis apparatus 50.

[0038] As shown in Figure 6, in this embodiment, the water supply control S20 includes processes S21 to S24. Each of these processes can be performed by information acquisition, calculation, and command by the controller 30. Each process is described below.

[0039] In process S21, the controller 30 obtains the conductivity value S from the conductivity meter 51. This conductivity S represents the amount of ions contained in the water supplied to the water electrolysis stack 20.

[0040] In process S22, it is determined whether the conductivity S obtained in process S21 is below a specified value. The specified value of conductivity S is not particularly limited, but is determined considering the effect of ions on the water electrolysis stack, the performance of the ion exchanger, and the performance of the pump, etc. Specifically, for example, 1 μS / m can be cited. If the conductivity S is greater than the specified value, if this high state continues for a long time, it may have a significant impact on the water electrolysis stack. If it is determined in process S22 that the conductivity is below the specified value (Yes), proceed to process S23. If it is determined in process S22 that the conductivity is not below the specified value (No, i.e., the conductivity is greater than the specified value), proceed to process S24.

[0041] In process S23, when the result in process S22 is determined to be Yes, the controller 30 commands valve 26 to increase its opening. This increases the flow rate of water through bypass A and decreases the flow rate of water through ion exchanger 24, thereby reducing pressure loss and thus reducing the load on the pump. Here, since the conductivity is determined to be below the specified value in process S22, it is possible to increase the amount of water that does not pass through ion exchanger 24, making this type of control possible. The method for determining the degree of increase in the opening of valve 26 at this time is not particularly limited, but it can be done as follows, for example. In Example 3 of valve opening determination, control is performed using pre-obtained functions or maps. Specifically, a compatibility test is conducted beforehand to determine the relationship between the opening degree of valve 26 and the hydrogen production amount (load current) and conductivity S. This relationship is then expressed as a function or map, and used as a database in calculations by the controller 30. In Example 4 of valve opening determination, feedback control (PI control, PID control) is used to control the valve opening to achieve the required conductivity S. That is, the controller 30 controls the valve opening to change based on a comparison of the measured conductivity S with the target value. After the opening of valve 26 is adjusted in process S23, the process returns to S21.

[0042] In process S24, when the result in process S22 is determined to be No, the controller 30 commands the valve 26 to reduce the opening of the valve 26. This reduces the flow rate of water flowing through bypass A and increases the flow rate of water flowing through the ion exchanger 24, thereby promoting ion removal by the ion exchanger 24. In this case, since the conductivity S was greater than the specified value in process S22, it is necessary to remove ions, and this control can be performed. At this time, there are no particular limitations on the method for determining the degree to which the opening of the valve 26 is reduced, but the opening determination examples 3 and 4 described above can be used. After the opening of valve 26 is adjusted in process S24, the process returns to S21.

[0043] 2.3. Effects, Others According to this embodiment of the water electrolysis apparatus 50, control makes it possible to pass as much water as possible through the ion exchanger while minimizing the burden on the pump and ion exchanger, thereby suppressing the supply of ions to the water electrolysis stack.

[0044] In this embodiment, an example is shown in which the relationship between the conductivity S of the conductivity meter 51 and a predetermined value is calculated each time to determine whether to change the opening degree of the valve 26. However, the invention is not limited to this, and at least one of the values ​​of conductivity S, the discharge pressure of the pump 22, and the amount of water electrolysis (hydrogen production) and the opening degree of the valve 26 may be investigated in advance and created in a database (so-called mapping), and the opening degree of the valve 26 may be obtained based on the database.

[0045] In this embodiment, a conductivity meter and its measured conductivity were used to obtain the amount of ions contained in the supply water. However, the means and measurement method are not particularly limited as long as the amount of ions contained in the supply water can be obtained, and other means may be used.

[0046] 3. Configuration and control of a water electrolysis apparatus (Form 3) 3.1. Configuration of a water electrolysis apparatus In the water electrolysis apparatus according to Embodiment 3, an additional conductivity meter is placed between the upstream side of bypass A and the pump 22, compared to the water electrolysis apparatus 50 according to Embodiment 2. This allows the controller 30 to obtain the difference between the conductivity upstream of bypass A and the conductivity downstream of the ion exchanger 24. The other components can be considered in the same way as in the water electrolysis apparatus 50, so their explanation is omitted here.

[0047] 3.2. Water supply control Figure 7 shows the flow of the water supply control S30 by the controller 30 of this water electrolysis apparatus. As shown in Figure 7, the water supply control S30 in this embodiment includes processes S31 to S34. Each of these processes can be performed by information acquisition, calculation, and command by the controller 30. Each process will be described below.

[0048] In process S31, the controller 30 obtains the conductivity value S from the two conductivity meters and calculates the conductivity difference of the water across bypass A and ion exchanger 24.

[0049] In process S32, it is determined whether the conductivity difference ΔS obtained in process S31 is less than or equal to a specified value. The specified value of the conductivity difference ΔS is not particularly limited, but is determined by considering the effect of ions on the water electrolysis stack, the performance of the ion exchanger, and the performance of the pump, etc. Specifically, for example, 1 μS / m can be cited. If the conductivity difference ΔS is greater than the specified value, it means that there are many ions that need to be removed. If it is determined in process S32 that the conductivity difference is less than or equal to the specified value (Yes), the process proceeds to process S33. If it is determined in process S32 that the conductivity difference is not less than or equal to the specified value (No, i.e., the conductivity difference is greater than the specified value), the process proceeds to process S34.

[0050] In process S33, when it is determined that the result is Yes in process S32, the controller 30 commands the valve 26 to increase its opening. This increases the flow rate of water through bypass A and decreases the flow rate of water through the ion exchanger 24, thereby reducing pressure loss and thus reducing the load on the pump. Here, since it is determined in process S32 that the conductivity difference is below a specified value, there are few ions to be removed, and it is possible to increase the amount of water that does not pass through the ion exchanger, making this type of control possible. At this time, the method for determining the degree of increase in the opening of valve 26 is not particularly limited, but it can be done as follows, for example. In Example 5 of valve opening determination, control is performed using pre-obtained functions or maps. Specifically, a compatibility test is conducted beforehand to determine the relationship between the opening of valve 26 and the hydrogen production amount (load current) and conductivity difference ΔS. This relationship is then expressed as a function or map, and used as a database in calculations by the controller 30. In Example 6 of valve opening determination, feedback control (PI control, PID control) is used to control the valve opening to achieve the required conductivity difference ΔS. That is, the controller 30 controls the valve opening to change based on a comparison with the target value using the measured conductivity difference ΔS. After the opening degree of valve 26 is adjusted in process S33, the process returns to S31.

[0051] In process S34, when the result in process S32 is determined to be No, the controller 30 commands the valve 26 to reduce the opening of the valve 26. This reduces the flow rate of water flowing through bypass A and increases the flow rate of water flowing through the ion exchanger 24, thereby promoting ion removal by the ion exchanger 24. In this case, since the conductivity difference ΔS in process S32 was greater than the specified value, this control can be performed because there are many ions to be removed. At this time, there are no particular limitations on the method for determining the degree to which the opening of the valve 26 is reduced, but the above-described examples 5 and 6 for determining the opening can be used. After the opening degree of valve 26 is adjusted in process S34, the process returns to S31.

[0052] 3.3 Effects, Others According to this water electrolysis apparatus, control mechanisms make it possible to minimize the load on the pump and ion exchanger while suppressing the supply of ions to the water electrolysis stack through the ion exchanger as much as possible.

[0053] In this embodiment, an example is shown in which the relationship between the conductivity difference ΔS of two conductivity meters and a predetermined value is calculated each time to determine whether to change the opening degree of valve 26. However, this is not limited to this, and at least one of the conductivity difference ΔS, the discharge pressure of pump 22, and the water electrolysis amount (hydrogen production amount), along with the opening degree of valve 26, may be investigated in advance and created in a database (so-called mapping), and the opening degree of valve 26 may be obtained based on this database.

[0054] 4. Others Although each of the above embodiments 1 to 3 was described separately, the device and control system may be configured using a combination of embodiment 1 and embodiment 2, or a combination of embodiment 1 and embodiment 3. In that case, if pump capacity is prioritized as in Form 1, control can be performed to satisfy the conductivity S of Form 2 or the conductivity difference ΔS of Form 3 as much as possible within the range that satisfies the conditions of Form 1 (a predetermined threshold is set, but situations where it is not met are also tolerated). On the other hand, if prioritizing reducing the burden on the water electrolysis stack by limiting the amount of ions, control can be performed to satisfy the pressure of Form 1 as much as possible within the range that satisfies the conditions of Form 2 or Form 3 (a predetermined threshold is set, but situations where it is not met are also tolerated). Furthermore, in order to satisfy both the limitations on pump capacity and ion quantity that place a burden on the water electrolysis device, the amount of hydrogen produced by water electrolysis and the water flow rate can be changed to satisfy both Form 1 and Form 2, or Form 2 and Form 3. [Explanation of Symbols]

[0055] 10...Water electrolysis unit, 11...Water electrolysis cell, 20...Water electrolysis stack, 21...Tank, 22...Pump, 23...Cooler, 24...Ion exchanger, 25...Gas-liquid separator, 26...Valve, 27...Pressure gauge, 28...Gas-liquid separator, 29...Hydrogen tank, 30...Controller

Claims

[Claim 1] A water electrolysis apparatus that supplies water to a water electrolysis cell and applies voltage to obtain hydrogen and oxygen, A water electrolysis stack in which the aforementioned water electrolysis cells are stacked, A water supply path for supplying water to the water electrolysis stack, It has a hydrogen side path for recovering hydrogen generated from the water electrolysis stack, The aforementioned water supply route includes: A pump which is a power source that supplies water to the water electrolysis stack, An ion exchanger is placed between the pump and the water electrolysis stack. A bypass is a path that allows water from the pump to flow to the water electrolysis stack without passing through the ion exchanger. A valve for adjusting the amount of water flowing through the bypass, The system comprises a controller for adjusting the valve, The controller controls the opening of the valve based on the discharge pressure of the pump or the pressure in the piping between the pump and the ion exchanger. Water electrolysis equipment.

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