Water electrolysis method and electrolysis system

Abstract

This invention provides an electrolysis method that can contribute to improving the lifespan of a PEM-type electrolytic device. [Solution] According to one aspect of the present invention, there is a method for electrolyzing water, comprising: a control step of controlling the content of water to be less than 100 μg / L in terms of cation equivalent weight, which is selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms; and a supply step of supplying water with controlled cation content to a PEM type electrolytic device.

Description

Technical Field

[0001] The present invention relates to a method for electrolyzing water and an electrolysis system.

Background Art

[0002] Currently, renewable energy that can be continuously used, such as wind power generation, hydroelectric power generation, and solar power generation, has attracted attention. A system (Power to Gas) that stores and utilizes the power of this renewable energy in the form of hydrogen or methane has been said to be attracting attention. As a method of Power to Gas, there are a method of electrolyzing water with electricity to produce hydrogen and a method of producing methane using hydrogen and CO2 produced by electrolyzing water. Thus, it can be said that the technology of converting water into hydrogen by electrolyzing water is the core technology in Power to Gas. Water electrolysis is roughly classified into three categories. 1) Polymer Electrolyte Membrane (PEM) type water electrolysis, 2) alkaline water electrolysis, and 3) Solid Oxide Electrolysis Cell (SOEC) water electrolysis.

[0003] PEM type water electrolysis is typically carried out using a Membrane Electrode Assembly (MEA). Usually, an MEA is composed of an anode, which is an electrode part, a cathode, and an electrolyte membrane sandwiched between them. When water is supplied to the anode side of the MEA and a potential difference occurs between the electrodes, water is decomposed on the anode side, generating oxygen and protons (H + ). The protons move to the cathode side through sulfonic acid groups in the PEM and combine with electrons at the cathode to generate hydrogen. Technologies related to such PEM type water electrolysis systems are disclosed in, for example, Patent Document 1 and the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, our inventors have found that there is room for improvement to extend the lifespan of the above-mentioned PEM-type water electrolysis system (PEM-type water electrolysis device).

[0006] In view of the above circumstances, the present invention aims to provide an electrolysis method and the like that can contribute to improving the lifespan of a PEM-type electrolytic device. [Means for solving the problem]

[0007] According to one aspect of the present invention, an electrolysis method for water is provided, comprising: a control step of controlling the content of water of one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms, so that the content is less than 100 μg / L in terms of cation equivalent weight; and a supply step of supplying water with controlled cation content to a PEM type electrolytic device.

[0008] According to the above embodiment, an electrolysis method and the like that can contribute to improving the lifespan of a PEM-type electrolytic device are provided.

[0009] Furthermore, they may be provided in the following embodiments.

[0010] (1) A method for electrolyzing water, comprising: a control step of controlling the content of one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms in the water, so that the content is less than 100 μg / L in terms of cation weight; and a supply step of supplying the water with the controlled cation content to a PEM type electrolytic device.

[0011] (2) An electrolysis method according to (1) above, wherein in the control step, the content of the metal cation in the water is controlled to be less than 100 μg / L in terms of cation equivalent weight.

[0012] (3) An electrolysis method according to (2) above, wherein in the control step, the content of one or more cations selected from the group consisting of sodium ions, potassium ions, calcium ions, magnesium ions, zinc ions, iron ions, copper ions, aluminum ions, nickel ions, chromium ions, platinum ions, iridium ions, and zirconium ions in the water is controlled to be less than 100 μg / L in terms of cation equivalent weight.

[0013] (4) An electrolysis method according to (2) or (3) above, wherein in the control step, the content of polyvalent metal ions in the water is controlled to be less than 100 μg / L in terms of cation weight.

[0014] (5) An electrolysis method according to any one of (1) to (4) above, wherein the content of the cation in the water supplied to the PEM type electrolytic device is 0.01 μg / L or more in terms of cation equivalent weight.

[0015] (6) An electrolysis method according to any one of (1) to (5) above, further comprising a purification step for purifying the water, wherein the purification step involves contacting the water with a cation exchange resin, and the water that has passed through the purification step is supplied to the PEM type electrolytic device.

[0016] (7) An electrolytic method according to (6) above, wherein the purification step is carried out without contact between the water and the anion exchange resin.

[0017] (8) An electrolysis system for electrolyzing water, comprising a measurement unit, a control unit, and a PEM electrolysis device. The measurement unit measures the content of one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms in the water. The control unit supplies the water to the PEM electrolysis device on the condition that the content of the cations is less than 100 μg / L in terms of the weight of the cations in terms of cation conversion.

[0018] (9) In the electrolysis system according to (8) above, further comprising a purification unit, the purification unit has a cation exchange resin in the system and is configured to perform a process of bringing the water into contact with the cation exchange resin, and the water purified by the purification unit is supplied to the PEM electrolysis device.

[0019] (10) In the electrolysis system according to (9) above, the purification unit does not have an anion exchange resin in the system. Of course, this is not the limit.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic diagram showing an example of the PEM electrolysis device in the present embodiment. [Figure 2] It is a conceptual diagram showing an example of the electrolysis system of the present embodiment. [Figure 3] It is a graph showing the observation results of Test Example 2.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described. Note that the various characteristic matters shown in the embodiments below can be combined with each other. Also, in this specification, "~" represents from above to below unless otherwise specified.

[0022] [Method for Electrolyzing Water] That is, the method for electrolyzing water in the present embodiment is as follows. A method for electrolyzing water, A control step to ensure that the water contains one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms, is less than 100 μg / L in terms of cation equivalent weight, A supply step of supplying the water, whose cation content is controlled, to a PEM-type electrolytic device, An electrolysis method comprising the following: The following describes the apparatus used in the water electrolysis method of this embodiment (hereinafter also simply referred to as the "electrolysis method") and the processes included in the electrolysis method of this embodiment.

[0023] (PEM type electrolyzer) In the electrolysis method of this embodiment, water that has undergone predetermined control is supplied to a PEM-type electrolytic device. This specification will first describe the details of this PEM-type electrolytic device.

[0024] Figure 1 is a schematic diagram showing an example of a PEM-type electrolytic device in this embodiment. The PEM-type electrolytic device 1 shown in Figure 1 has a laminate in which an anode 2, an electrolyte membrane 3, and a cathode 4 are stacked in that order. Such a laminate may also be called a membrane electrode assembly (MEA). Furthermore, the PEM-type electrolytic device 1 of this embodiment has an anode-side cavity 20 on the side where the anode 2 is located, and a cathode-side cavity 40 on the side where the cathode 4 is located. These two cavities are isolated via the aforementioned MEA. The anode-side cavity 20 is provided with an anode-side inlet 21 and an anode-side outlet 22, and the cathode-side cavity 40 is provided with a cathode-side outlet 41. Although not shown in detail in Figure 1, the anode 2 and cathode 4 are electrically connected, and a potential difference is generated between the anode 2 and cathode 4.

[0025] The PEM-type electrolytic device 1 of this embodiment generates oxygen molecules (oxygen gas) and hydrogen molecules (hydrogen gas) by electrolyzing the supplied water. When such electrolysis of water is performed, in the PEM-type electrolytic device 1 of this embodiment, the anode 2 functions as the anode and the cathode 4 functions as the cathode. As shown in the background art section, when water is supplied to the anode side (anode side cavity 20) of the PEM-type electrolytic device 1 and a potential difference is created between the electrodes, the water decomposes at the anode 2, producing oxygen molecules (oxygen gas) and protons (H + This results in the formation of ) . In the PEM-type electrolytic device 1 shown in Figure 1, water is typically supplied from the anode inlet 21. The oxygen molecules (oxygen gas) produced at anode 2 are typically recovered from the anode outlet 22. Meanwhile, the protons produced at anode 2 move to cathode 4 via the electrolyte membrane 3, where they combine with electrons to produce hydrogen molecules (hydrogen gas). In this way, the hydrogen molecules (hydrogen gas) produced at cathode 4 are recovered from the cathode outlet 41.

[0026] Furthermore, the anode 2, electrolyte membrane 3, and cathode 4 of the PEM-type electrolytic device 1 are appropriately selected and constructed from materials that enable the electrolysis of water as described above. Specifically, the anode 2 and cathode 4 can be selected from materials that function as electrodes. Here, the electrodes may have a metal catalyst or the like that which promotes the gasification reaction described above supported on their surface. Such metal catalysts may include various metal atoms such as nickel, copper, palladium, zinc, platinum, gold, silver, ruthenium, and iridium. The electrolyte membrane 3 can be constructed from a membrane that allows the movement of protons from the anode 2 to the cathode 4. Such an electrolyte membrane 3 can typically be constructed from a resin material, but the resin material may have acidic groups in its structure. Examples of acidic groups include sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, and phosphoric acid groups. The resin material constituting the electrolyte membrane 3 may be a so-called fluororesin. Furthermore, because it is a readily available material, the electrolyte membrane 3 may be constructed from a fluororesin having perfluorosulfonic acid groups. In particular, Nafion® (manufactured by DuPont), a copolymer of polymerizable perfluorosulfonic acid units and tetrafluoroethylene units, is a typical example of a material that is suitably used as the electrolyte membrane 3.

[0027] Next, various steps that may be included in the electrolysis method of this embodiment will be described.

[0028] (Management process) The electrolysis method of this embodiment includes a control step to ensure that the content of water with one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms is less than 100 μg / L in terms of cation equivalent weight.

[0029] In other words, in the control process of this embodiment, the water supplied to the PEM-type electrolytic device 1 is controlled so that the content of the various cations described above is below a predetermined amount. The number of cations controlled in the control process may be one or two or more. Typically, the cations controlled in the control process are controlled as control items. The number of these control items may be one, two or more, three or more, five or more, seven or more, or ten or more. There is no particular upper limit on the number of control items, but from the viewpoint of efficiently executing the electrolysis method of this embodiment, the number of control items may be 50 or less, 40 or less, 30 or less, 20 or less, 15 or less, 10 or less, 8 or less, or 5 or less.

[0030] The following are examples of cations that correspond to the control items mentioned above.

[0031] The metal ions controlled in the control process may be cations corresponding to metals selected from the group consisting of alkali metals, alkaline earth metals, transition metals, lanthanides, and actinides. The metal cations here may be monovalent or polyvalent.

[0032] Furthermore, cations containing nitrogen atoms that are controlled in the control process typically refer to cations in which the nitrogen atom is positively charged. A more specific example is the ammonium cation (NH4). + Examples of cations containing a nitrogen atom include organic ammonium cations. Examples of organic ammonium cations used here include linear ammonium cations such as tetraethylammonium cation, tetraoctylammonium cation, and diethylmethyl(2-methoxyethyl)ammonium cation (DEME); cyclic ammonium cations such as N-ethyl-N-methylpyrrolidium cation, N-methoxyethyl-N-methylpyrrolidium cation, and N-methoxyethyl-N-methylpiperidium cation (which include so-called pyrrolidium cations and piperidium cations); imidazolium cations such as 1-ethyl-3-methylimidazolium (EMI) and 1-butyl-3-methylimidazolium (BMI); and pyridinium cations such as butylpyridinium.

[0033] Furthermore, cations containing phosphorus atoms that are controlled in the control process typically refer to cations in which the phosphorus atom is positively charged. More specific examples include linear phosphonium cations such as tetraethylphosphonium; and cyclic phosphonium cations such as phosphoniaspiro[4.4]nonane.

[0034] Furthermore, cations containing sulfur atoms that are controlled in the control process typically refer to cations in which the sulfur atom is positively charged. More specific examples include linear sulfonium cations such as triethylsulfonium; and cyclic sulfonium cations such as S-methyltetrahydrothiophenium and S-methyl-4-oxasulfoniacyclohexane.

[0035] The inventors have found that limiting the cation content of the water supplied to the PEM-type electrolytic device 1 contributes to improving the lifespan of the PEM-type electrolytic device 1. The reason for this is not entirely clear, but the following possibilities can be considered. Specifically, it is assumed that the cations contained in the water degrade the anode 2 and cathode 4 (for example, the metal catalyst supported on the anode 2 and cathode 4), and that reducing the amount of cations in the water can suppress such degradation. Furthermore, it is assumed that the cations contained in the water have an adverse effect on certain sites (typically functional groups) on the electrolyte membrane 3, and that reducing the amount of cations in the water can suppress the occurrence of such adverse effects. As an example of such adverse effects, it is assumed that the acidic groups of the electrolyte membrane 3 coordinate (complex) with the cations.

[0036] In this embodiment, "managing" may include quantifying (measuring) a predetermined component contained in water, or confirming that the content of the predetermined component is within a predetermined value (which may be interpreted as being within a predetermined range or less than a predetermined value). In other words, the management process in this embodiment may be carried out by quantifying (measuring) the amount of cations contained in water using a predetermined analytical device, or, for water introduced from an external source, by confirming that the amount of cations contained in the water is within a predetermined value using a quality assurance certificate or the like.

[0037] The analytical method used here should be appropriately determined depending on the type of cation being controlled. For example, if the controlled item is a metal cation, the content of metal cations in water can be quantified using methods such as ICP-MS (Inductively Coupled Plasma Mass Spectrometry). If the controlled item is an organic substance, it can also be quantified using methods such as HPLC (High Performance Liquid Chromatography). Of course, these methods are not the only ones that can be used, and various known analytical methods may be employed.

[0038] Regarding this control process, the cation content of the water supplied to the PEM-type electrolytic device 1 is less than 100 μg / L in terms of cation equivalent weight. However, this cation content may be less than 90 μg / L, less than 80 μg / L, less than 70 μg / L, less than 60 μg / L, less than 50 μg / L, less than 40 μg / L, less than 30 μg / L, less than 20 μg / L, less than 10 μg / L, or less than 5 μg / L. In other words, in the control process of this embodiment, it is possible to control that one or more control items (one or more cations) are below the above-mentioned content. When controlling water using two or more control items, the control values ​​(upper limits) for each may be different. For example, for water to be supplied to the PEM-type electrolytic device 1, it is possible to control cation A to have a cation equivalent weight of less than 100 μg / L and cation B to have a cation equivalent weight of less than 50 μg / L.

[0039] Furthermore, with respect to this control process, there is no particular limit on the lower limit of the cation content of the water supplied to the PEM-type electrolytic device 1. On the other hand, from the perspective of constructing an industrially advantageous process without setting excessive specifications for the water used, the cation content of the water supplied to the PEM-type electrolytic device 1 may be 0.01 μg / L or more, 0.02 μg / L or more, 0.03 μg / L or more, 0.05 μg / L or more, 0.1 μg / L or more, 0.3 μg / L or more, 0.5 μg / L or more, or 1 μg / L or more, in terms of cation equivalent weight. When water is controlled using two or more control items, the lower limits may also be different for each control item, similar to the upper limits mentioned above.

[0040] Furthermore, in the control process, it is preferable that the content of metal cations in water be controlled to be below a predetermined value in terms of cation-equivalent weight. According to the inventors' studies, such metal cations have a significant impact on the aforementioned PEM-type electrolytic apparatus 1, and it has been confirmed that more appropriate control is required. Regarding such metal cations, in addition to 100 μg / L, various upper and lower limits mentioned earlier can be used as the control value (predetermined value) (the same applies to the following explanation regarding the control process).

[0041] In a more typical embodiment, in the control step of this embodiment, it is preferable that the content of one or more cations selected from the group consisting of sodium ions, potassium ions, calcium ions, magnesium ions, zinc ions, iron ions, copper ions, aluminum ions, nickel ions, chromium ions, platinum ions, iridium ions, and zirconium ions in the water is controlled to be below a predetermined value. Since quantitative methods for these metal cations have been established, it is easy to appropriately control the electrolysis method of this embodiment.

[0042] From another perspective, the control process may also be controlled to ensure that the content of polyvalent metal ions in water is below a predetermined value in terms of cation weight. In certain systems, polyvalent metal ions (polyvalent metal cations) may have a more adverse effect on the PEM-type electrolytic device 1 than monovalent metal ions such as sodium ions and potassium ions. From this perspective, it is preferable that the control process in this embodiment controls the content of the above-mentioned polyvalent metal ions to be below a predetermined value.

[0043] (Supply process) Furthermore, the electrolysis method of this embodiment includes a supply step of supplying water with a controlled cation content to a PEM-type electrolytic device.

[0044] In other words, in this supply process, water controlled by the aforementioned control process is supplied from the anode-side inlet 21 of the PEM-type electrolytic device 1. A potential difference is then created between the anode 2 and the cathode 4, and the supplied water is electrolyzed (in other words, this supply process may also include the process of decomposing the supplied water using the PEM-type electrolytic device 1 to generate oxygen molecules (oxygen gas) and hydrogen molecules (hydrogen gas)).

[0045] The generated oxygen gas and hydrogen gas may be collected in designated containers. Furthermore, the collected gases may be subjected to a predetermined purification process, and may be used for various purposes (industrial applications, fuel, etc.).

[0046] (purification process) Furthermore, the electrolysis method of this embodiment may further include a purification step for purifying water. That is, such a purification step may be performed prior to the control step and supply step described above, and in the supply step described above, water that has gone through such a purification step may be supplied to the PEM type electrolytic device 1.

[0047] The purification process described here may include various purification treatments to satisfy the control items in the aforementioned control process. Typical examples of purification treatments include treatment using reverse osmosis (RO) membrane separators, degassing devices, ion exchange devices (such as mixed-bed or 4-bed 5-column types), electrodeionizers, and oxidation devices such as ultraviolet (UV) irradiation oxidation devices. These treatments remove ions and organic components from the raw water (which may be tap water, etc.). More typical treatments include a combination of treatment using an activated carbon (AC) device to treat the raw water and treatment using a reverse osmosis membrane (RO) device equipped with a reverse osmosis membrane to treat the outlet water of the activated carbon device.

[0048] In this embodiment, it is preferable that the purification process may involve contacting water with a cation exchange resin. As mentioned above, in the control process of this embodiment, the amount of a predetermined cation is controlled to be at a predetermined value. That is, from the viewpoint of efficiently reducing the content of such metal cations, it is preferable to contact water with a cation exchange resin in the purification process. The contact with the cation exchange resin here may be carried out by contacting water with a cation exchange resin filled in a cartridge, or by passing water through an electrodeionizer (CDI). It is preferable that the cations that become contained in the water by contacting water with the cation exchange resin are cations other than the control items. In a typical embodiment, by contacting water with the cation exchange resin described above, the predetermined cations contained in the water may be exchanged for protons (that is, the cation exchange resin may be a resin having a proton-donating group (acid group), etc.).

[0049] Furthermore, the purification process in this embodiment may be carried out without contact between water and the anion exchange resin. According to the inventors' studies, the anions contained in water have a relatively small effect on the PEM-type electrolytic device 1. In other words, by not contacting water with the anion exchange resin in the purification process, it is possible to perform efficient electrolysis without complicating the process.

[0050] In the electrolysis method described above, the water supplied to the PEM-type electrolytic device 1 is subject to specific control. This can contribute to improving the lifespan of the PEM-type electrolytic device 1.

[0051] [Electrolytic System] In addition, in this embodiment, the following electrolytic system may also be provided. An electrolysis system for electrolyzing water, It comprises a measurement unit, a control unit, and a PEM-type electrolytic device. The measuring unit measures the content of one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms in the water. The control unit supplies the water to the PEM type electrolytic device on the condition that the cation content is less than 100 μg / L in terms of cation equivalent weight, in an electrolytic system.

[0052] A typical example of the electrolysis system described above will be explained with reference to Figure 2. Figure 2 is a conceptual diagram showing an example of the electrolysis system of this embodiment. The electrolysis system 100 shown in Figure 2 includes the PEM-type electrolytic device 1 described earlier, a measurement unit 6, and a control unit 7. The various components shown in Figure 2 may be connected by pipes or the like that through which water can pass. In the example of the electrolysis system 100 shown in Figure 2, water stored in a predetermined location (for example, a raw material tank) is first supplied to the purification unit 5. The water purified in the purification unit 5 is then measured by the measurement unit 6. Here, the measurement unit 6 is electrically connected to the control unit 7. In a typical embodiment, the control unit 7 determines whether or not to supply water to the PEM-type electrolytic device 1 according to the measurement results of the measurement unit 6. That is, the control unit 7 is configured to control the supply of water to the PEM-type electrolytic device 1 on the condition that the water measurement results satisfy predetermined requirements. More specifically, the control unit 7 receives water measurement data from the measurement unit 6 and determines whether the measurement data exceeds a predetermined threshold. The control unit 7 then controls the supply to the PEM electrolytic device 1 based on the determination result.

[0053] Details of each component that may be provided in the electrolysis system 100 of this embodiment are as follows. Note that the PEM type electrolysis apparatus 1 is the same as the apparatus shown in Figure 1, so its description is omitted here.

[0054] (Refining Department 5) The purification unit 5 provided in the electrolysis system 100 may have various means for purifying water. In the electrolysis system 100 of this embodiment, the water purified by the purification unit 5 in this manner is supplied to the PEM type electrolytic device 1.

[0055] Here, the purification unit 5 may be configured to perform the various processes described above as purification steps. In a typical embodiment, the purification unit 5 may be equipped with various purification means (purification devices) such as a reverse osmosis (RO) membrane separator, a degasser, an ion exchange device (such as a mixed-bed type or a 4-bed 5-column type), an electrodeionizer, and an oxidation device such as an ultraviolet (UV) irradiation oxidation device. In this embodiment, the purification unit 5 can be arbitrarily configured (combined as appropriate) according to the specifications and processing volume of the electrolysis system 100 to be constructed.

[0056] The purification unit 5 may be configured to perform a process of bringing water into contact with a cation exchange resin (i.e., at least a part of the purification unit 5 may include an ion exchange device containing a cation exchange resin). In the electrolysis system 100 of this embodiment, the control unit 7 supplies water to the PEM type electrolytic device 1 on the condition that the cation content of the water is below a predetermined level. Therefore, from the viewpoint of efficiently reducing the cations contained in the water, it is preferable to include such a cation exchange resin in the system of the purification unit 5.

[0057] On the other hand, the purification unit 5 may be configured so as not to have an anion exchange resin in its system (i.e., the purification unit 5 may not include an ion exchange device containing an anion exchange resin). According to the inventors' studies, anions contained in water have a relatively small effect on the PEM type electrolytic device 1. Therefore, by not including an anion exchange resin in the system of the purification unit 5 in this way, it is possible to construct an efficient electrolytic system 100 without complicating the configuration of the electrolytic system 100.

[0058] (Measurement unit 6) Furthermore, the measurement unit 6 of this embodiment is configured to measure the content of water, one or more cations selected from the group consisting of metal cations, cations containing nitrogen atoms, cations containing phosphorus atoms, and cations containing sulfur atoms.

[0059] The specific configuration of the measurement unit 6 can be set appropriately according to the type of cation to be controlled. In other words, the measurement unit 6 can be selected from among the means capable of quantifying the cation content listed above. Examples of specific equipment include the equipment shown in the control process section above.

[0060] (Control Unit 7) The control unit 7 controls the supply of water to the PEM-type electrolytic device 1 on the condition that the cation content measured by the measurement unit 6 is less than a predetermined value in terms of cation equivalent weight (typically less than 100 μg / L, but other values ​​may also be used). The conditions for supplying water here may be the same as the conditions for control in the management process described above, but the explanation is omitted here.

[0061] Specifically, the control unit 7 controls the supply of water to the PEM-type electrolytic device 1 when the cation content measured by the measurement unit 6 meets predetermined conditions. The water supply port in the PEM-type electrolytic device 1 may be the anode-side inlet 21 shown in Figure 1. The control here may be exemplified by valve control for the piping connecting each component. Although the details of such a valve are not shown in Figure 2, for example, the valve here may be provided upstream of the PEM-type electrolytic device 1 and is configured to communicate with the control unit 7. That is, if the measurement result of the measurement unit 6 for the water that has passed through the purification unit 5 meets predetermined conditions, the control unit 7 operates the valve to allow the inflow of water into the PEM-type electrolytic device 1. On the other hand, if the measurement result of the measurement unit 6 does not meet the predetermined conditions, the control unit 7 can operate the valve to prohibit the inflow of water into the PEM-type electrolytic device 1. When the control unit 7 operates the valve, for example, the control unit 7 transmits a signal to the valve to control its opening and closing. Furthermore, if the inflow of water into the PEM-type electrolytic device 1 is prohibited, control may be implemented to discard the water that has passed through the purification unit 5, or control may be implemented to circulate the water so that purification is performed again in the purification unit 5.

[0062] As described above, in the electrolysis system 100, the control unit 7 supplies water that satisfies predetermined conditions to the PEM-type electrolytic device 1, which can contribute to improving the lifespan of the PEM-type electrolytic device 1.

[0063] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0064] The present invention will be described in more detail below with reference to examples (each test example). However, the present invention is not limited to the following examples.

[0065] <Test Example 1> First, a PEM-type electrolytic apparatus 1 similar to the configuration shown in Figure 1 was prepared. Meanwhile, various salt compounds corresponding to aluminum(III) ions, zinc(II) ions, iron(II) ions, copper(II) ions, and manganese(II) ions were prepared and added to ultrapure water to obtain a test solution with a metal ion concentration of 1 mg / L.

[0066] For each test solution obtained, water was passed through the anode-side inlet 21 to the anode-side outlet 22 of the PEM-type electrolytic device 1, and water electrolysis was started under room temperature conditions. In this test example 1, voltage logging was performed simultaneously with the start of electrolysis, and the voltage increase over time was observed.

[0067] The results are shown in Table 1 below, and an increase in voltage during electrolysis was observed in water containing various metal ions. Table 1 also shows the "concentration limit," which is the concentration at which the electrolysis efficiency decreases by 10% assuming the PEM electrolysis apparatus operates for 15 years.

[0068] [Table 1]

[0069] <Test Example 2> In Test Example 2, silicate ions (SiO3) were used as the anionic component. 2- A test solution containing 40 mg / L of ) was prepared. In this test solution, metal ions contained in the water were removed to an undetectable level using an ion exchange resin beforehand (protons are present as countercations of silicate ions). In Test Example 2, the test solution was passed through a PEM-type electrolytic device, and voltage logging was performed while electrolysis was carried out.

[0070] Figure 3 is a graph showing the observation results of Test Example 2. As shown in Figure 3, it was confirmed that even if the anionic components contained in the water supplied to the PEM-type electrolytic device were at a relatively high concentration, the effect on electrolysis was minimal.

[0071] These test examples suggest that certain cationic components adversely affect the operation of PEM-type electrolytic devices. In other words, by identifying inhibitory factors in the electrolysis process that had not been considered in the past, the present invention enables long-term and safe operation of electrolysis using PEM-type electrolytic devices. [Explanation of Symbols]

[0072] 1:PEM type electrolyzer 2: Anode 3: Electrolyte membrane 4: Cathode 5:Refining department 6: Measurement Unit 7: Control Unit 20: Anode side cavity 21: Anode side entrance 22: Anode side exit 40: Cathode side cavity 41: Cathode side outlet 100: Electrolytic System

Claims

1. A method for electrolyzing water, A control process for controlling the cation content of the water, A supply step of supplying the water, whose cation content is controlled, to a PEM type electrolytic device, Equipped with, The electrolysis method wherein, in the aforementioned control process, one or more of the following (1) to (5) are controlled as control items. (1) The aluminum(III) ion content shall be less than 0.014 μg / L. (2) The zinc(II) ion content shall be less than 0.113 μg / L. (3) The iron(II) ion content shall be less than 1.704 μg / L. (4) The copper(II) ion content shall be less than 0.453 μg / L. (5) The manganese(II) ion content shall be less than 2.157 μg / L.

2. In the electrolysis method described in claim 1, An electrolysis method wherein the water supplied to the PEM type electrolytic apparatus contains 0.01 μg / L or more of aluminum(III) ions, zinc(II) ions, iron(II) ions, copper(II) ions, or manganese(II) ions, which are controlled as the control items.

3. In the electrolysis method described in claim 1, The process further comprises a purification step for purifying the aforementioned water, The purification process involves bringing the water into contact with the cation exchange resin. An electrolysis method in which water that has gone through the purification process is supplied to the PEM type electrolytic apparatus.

4. In the electrolysis method described in claim 3, The purification step is performed by an electrolytic method without contact between the water and the anion exchange resin.

5. An electrolysis system for electrolyzing water, It comprises a measuring unit, a control unit, and a PEM-type electrolytic device. The measuring unit measures the content of one or more cations selected from the group consisting of aluminum(III) ions, zinc(II) ions, iron(II) ions, copper(II) ions, and manganese(II) ions in the water. The control unit supplies the water to the PEM type electrolytic device on the condition that the cation content satisfies one or more of the following conditions (1) to (5). (1) The aluminum(III) ion content is less than 0.014 μg / L. (2) The zinc(II) ion content is less than 0.113 μg / L. (3) The iron(II) ion content is less than 1.704 μg / L. (4) The copper(II) ion content is less than 0.453 μg / L. (5) The manganese(II) ion content is less than 2.157 μg / L.

6. In the electrolytic system according to claim 5, Furthermore, it is equipped with a purification unit, The purification unit has a cation exchange resin in the system, The system is configured to perform a process of bringing the water and the cation exchange resin into contact, An electrolysis system in which water purified by the purification unit is supplied to the PEM type electrolytic device.

7. In the electrolysis system according to claim 6, The purification unit is an electrolytic system that does not contain anion exchange resin in the system.

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