JP2020012146A - Electrolytic cell and method of using the same - Google Patents

Abstract

To prevent an increase of an excessive voltage caused by the degradation of an electrode resulting from a reverse current generated when electrolysis is suspended.SOLUTION: There are provided an electrolysis tank comprising an electrode chamber and a flow path communicating with the electrode chamber, which is characterized by comprising a current cutoff valve disposed in the flow path, and a method of using the electrolysis tank.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrolytic cell and a method for using the same.

The application of electrolysis technology to industry has been practiced for a long time.For example, the production of caustic soda / chlorine by electrolysis of saline, the production of hypochlorous acid, the production of alkaline ionized water, the production of ozone water, etc. are wide-ranging. . Until now, various proposals have been made aiming at reduction of equipment cost, improvement of electrolysis efficiency and improvement of durability of the apparatus.
In recent years, technologies such as wind power generation and solar power generation using renewable energy have been attracting attention in order to solve problems such as global warming due to greenhouse gases such as carbon dioxide and a decrease in reserves of fossil fuels.

  Renewable energy has the property that its output varies depending on climatic conditions, and its fluctuations are very large. As a result, it is not always possible to transport the power obtained from renewable energy generation to the general power system, and there are concerns about social implications such as imbalance in power supply and demand and instability of the power system. I have.

  Therefore, research has been conducted to use electric power generated from renewable energy instead of storing and transporting the electric power. Specifically, it has been studied to generate hydrogen that can be stored and transported by electrolysis (electrolysis) of water using electric power generated from renewable energy, and to use hydrogen as an energy source and a raw material. I have.

  Hydrogen is widely used industrially in the fields of petroleum refining, chemical synthesis, metal refining, etc. In recent years, hydrogen can be used in hydrogen stations for fuel cell vehicles (FCV), smart communities, hydrogen power plants, and the like. Sex is also spreading. For this reason, there is high expectation for the development of a technique for obtaining particularly high-purity hydrogen from renewable energy.

  As a method of electrolysis of water, there are a solid polymer water electrolysis method, a high temperature steam electrolysis method, an alkaline water electrolysis method and the like. Among them, alkaline water electrolysis is one of the most promising ones because it has been industrialized for more than several decades, it can be implemented on a large scale, and it is cheaper than other water electrolysis devices. Have been.

  However, in order to adapt alkaline water electrolysis as a means for storing and transporting energy in the future, water electrolysis can be performed efficiently and stably using electric power whose output fluctuates greatly as described above. There is a need to. Therefore, it is required to solve various problems of an electrolytic cell and an apparatus for alkaline water electrolysis.

  In order to solve the problem of reducing the electrolysis voltage in alkaline water electrolysis and improving the power consumption of hydrogen production, the structure of the electrolytic cell, particularly, the structure in which the gap between the diaphragm and the electrode is substantially eliminated It is well known that adopting a structure called a zero gap structure is effective (see Patent Documents 1 and 2). In the zero-gap structure, the generated gas quickly escapes through the pores of the electrode to the side opposite to the diaphragm side of the electrode, thereby reducing the distance between the electrodes and minimizing the generation of gas accumulation near the electrodes, and The voltage is kept low. The zero gap structure is extremely effective in suppressing the electrolytic voltage, and has been adopted in various electrolytic devices.

U.S. Pat. No. 4,530,743 JP-A-59-173281

However, for example, in the case of use under a fluctuating power supply, electrolysis is frequently stopped. Therefore, there is a need for an improved electrolysis cell so that the electrode can be used for a longer period.
Therefore, an object of the present invention is to suppress an increase in overvoltage caused by deterioration of an electrode due to a reverse current generated when electrolysis is stopped.

  The inventors have found that in a conventional electrolytic cell, when electrolysis is stopped, a leakage current circuit is formed by a flow path for supplying an electrolytic solution to an electrode chamber, and self-discharge occurs. Such self-discharge is also referred to as a reverse current because the direction of the current flowing through the conducting surface is opposite to the direction of the current during electrolysis. It has been found that in the process in which the reverse current is generated, the electrodes (cathode and anode) are redox-oxidized, activated dissolution and volume expansion / contraction occur, and the electrodes may be deactivated to increase the overvoltage.

The gist of the present invention is as follows.
[1]
An electrolytic cell comprising: an electrode chamber; and a flow path communicating with the electrode chamber, wherein a current cutoff valve is provided in the flow path.
[2]
The electrolytic cell according to [1], wherein the current cutoff valve is provided so as to shut off the flow path.
[3]
The electrolytic cell according to [1] or [2], further comprising at least one selected from the group consisting of a header having the flow path and communicating with the electrode chamber, and a conduit having the flow path and communicating with the header.
[4]
The electrolytic cell according to any one of [1] to [3], wherein the current cutoff valve includes an insulating material.
[5]
The electrolytic cell according to any one of [1] to [4], wherein a portion of the flow path corresponding to a location where the current cutoff valve is provided includes an insulating material.
[6]
The electrolytic cell according to any one of [1] to [5], wherein the current cutoff valve is provided in a portion of the flow passage having a smallest cross-sectional area.
[7]
The electrolytic cell according to any one of [1] to [6], wherein the current cutoff valve is driven by at least one selected from the group consisting of manual operation, gas pressure, and electric energy.
[8]
The electrolytic cell according to any one of [1] to [7], wherein the current cutoff valve is at least one selected from the group consisting of a ball valve, a globe valve, a gate valve, a butterfly valve, a diaphragm valve, and a check valve.
[9]
The method for using an electrolytic cell according to any one of [1] to [8], wherein the current cutoff valve is closed before or after the electrolytic stop.
[10]
The use of the electrolytic cell according to [9], wherein the current cutoff valve is closed within 2 hours after the electrolysis is stopped.
[11]
The use of the electrolytic cell according to [10], wherein the current cutoff valve is closed within 30 seconds after stopping the electrolysis.
[12]
The use of the electrolytic cell according to [10] or [11], wherein the current cutoff valve is opened within 60 seconds after restarting the electrolysis.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that an electrode deteriorates and overvoltage rises by the reverse current which arises at the time of electrolysis stop.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view shown about the whole example of the bipolar electrode type electrolytic cell for alkaline water electrolysis of this embodiment. It is a perspective view showing an electrolysis room, a header, and a conduit of an example of a bipolar electrolyzer for alkaline water electrolysis of this embodiment. It is a top view which shows the example of the bipolar electrode type electrolytic cell for alkaline water electrolysis of the external header type of this embodiment. FIG. 2 is a cross-sectional view showing a part of a side view of an external header type bipolar electrolytic cell of the present embodiment together with a flow of an electrolytic solution. It is a figure showing the outline of the electrolysis device for alkaline water electrolysis of this embodiment. The results of electrode degradation evaluation for Examples 1 to 5 and Comparative Example 1 are shown. The vertical axis shows the voltage rise value, and the horizontal axis shows the number of repetitions of energization / stop.

  Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

(Electrolyzer)
FIG. 1 is a side view showing an example of a bipolar electrolyzer for alkaline water electrolysis according to the present embodiment.
The bipolar electrolyzer 50 for alkaline water electrolysis of the present embodiment is not particularly limited. For example, as shown in FIG. 1, an anode 2a, a cathode 2c, a partition wall 1 for separating the anode 2a and the cathode 2c, The bipolar electrolytic cell 50 may include a plurality of bipolar elements 60 including the outer frame 3 surrounding the partition wall 1 and stacked with the diaphragm 4 interposed therebetween.

The bipolar type is one of the methods of connecting a large number of cells to a power source. A plurality of bipolar elements 60 having one side serving as an anode 2a and one side serving as a cathode 2c are arranged in the same direction and connected in series. This is the method of connecting to the power supply.
The bipolar electrolyzer 50 has a feature that the current of the power supply can be reduced, and a compound, a predetermined substance, or the like can be mass-produced in a short time by electrolysis. If the output of the power supply equipment is the same, low current and high voltage are cheaper and more compact, so a double pole type is more preferable than a single pole type industrially.

FIG. 2 is a perspective view showing an electrolytic chamber, a header, and a conduit of an example of the bipolar electrolytic cell for alkaline water electrolysis of the present embodiment.
In the bipolar electrolytic cell 50 according to the present embodiment, the electrode chamber 5 through which the electrolytic solution passes is defined in the electrolytic cell 50. Although not particularly limited, for example, as shown in FIG. The electrode chamber 5 may be defined by the and the diaphragm 4.
Further, the bipolar electrolytic cell 50 in the present embodiment includes a header 10 communicating with the electrode chamber 5, and is not particularly limited. For example, as illustrated in FIG. 2, the header 10 is provided outside the outer frame 3. May be.
Further, the bipolar electrolytic cell 50 in the present embodiment may be provided with the conduit 20 which is a pipe for collecting gas or electrolyte solution distributed or collected on the header 10.

As shown in FIG. 2, the bipolar electrolyzer 50 for alkaline water electrolysis according to the present embodiment includes an electrode chamber and a flow path communicating with the electrode chamber, and a current cutoff valve is provided in the flow path. It is characterized by.
With the above configuration, when the power supply to the electrolytic cell 65 of the electrolytic cell 50 is stopped, by closing the current cutoff valve, the leakage current circuit formed by the flow path for supplying the electrolytic solution to the electrode chamber can be easily formed. It is possible to shut off quickly, reliably, and to prevent the occurrence of reverse current as much as possible. Therefore, according to the electrolytic cell 50 of the present embodiment, it is possible to suppress the electrode from being deteriorated due to the reverse current generated when the electrolysis is stopped.

In the present embodiment, as shown in FIG. 2, the current cutoff valve is provided so as to be able to cut off the flow path.
Here, "blocking the flow path" means eliminating or minimizing the generation of the reverse current, and specifically, setting the current density of the leakage current to 0.1 mA / m ² or less. That means.

FIG. 3 is a plan view showing an example of the external header type bipolar electrolytic cell for alkaline water electrolysis of the present embodiment.
In this embodiment, as shown in FIGS. 2 and 3, the electrolytic cell 50 may further include a header 10 having a flow path and communicating with the electrode chamber, and a conduit 20 having a flow path and communicating with the header 10. The current cutoff valve may be provided on the header 10 and the conduit 20, as shown in FIGS.

  In the present embodiment, the current cutoff valve preferably includes an insulating material.

In the present embodiment, the header portion corresponding to the location where the current cutoff valve is provided preferably contains an insulating material.
As the insulating material, specifically, fluorine rubber (FKM), nitrile rubber (NBR), tetrafluoroethylene propylene rubber (FEPM), perfluoro rubber (FFKM), ethylene propylene rubber (EPDM), ethylene tetrafluoride resin (PTFE) ), Polyvinylidene fluoride (PVDF), polypropylene (PP), polyphenylene sulfide (PPS), and the like.

  Insulating materials used for the current cutoff valve and the above-mentioned header portion include fluoro rubber (FKM), nitrile rubber (NBR), tetrafluoroethylene propylene rubber (FEPM), perfluoro rubber (FFKM), and ethylene propylene rubber (EPDM). , Fluorotetrafluoroethylene resin (PTFE), polyvinylidene fluoride (PVDF) and the like, and fluororubber (FKM), tetrafluoroethylene resin (PTFE), polypropylene (PP), and polyphenylene sulfide (PPS) are preferable.

In the present embodiment, it is preferable that the current cutoff valve is provided at a location where the cross-sectional area is the smallest in the flow path of the header. According to such a configuration, the cost for installing the valve can be reduced.
In the example shown in FIG. 2, the cross-sectional area of the flow path of the header is constant over the extension length of the header, and the current cutoff valve is provided at an arbitrary position with respect to the extension length of the header.

  In the present embodiment, the drive of the current cutoff valve may be performed manually, by gas pressure, by electric energy, or the like.

In the present embodiment, examples of the current cutoff valve include a ball valve, a globe valve, a gate valve, a butterfly valve, a diaphragm valve, a check valve, and the like, and a ball valve and a gate valve are preferable.
These may be used alone or in combination of two or more.

The resistance of each of the current cutoff valves is preferably 1 Ω or more, more preferably 1 kΩ or more, and further preferably 1 MΩ or more.
The resistivity of each of the current cutoff valves is at least 10 ⁻¹ Ω · m, preferably at least 10 ⁴ Ω · m, more preferably at least 10 ⁶ Ω · m.
The resistance and the resistivity are measured according to JIS K6911.

  Hereinafter, a main configuration of the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment will be described in detail.

((Double pole element))
As shown in FIG. 1, a bipolar element 60 used in a bipolar electrolyzer 50 for alkaline water electrolysis includes, as shown in FIG. 1, a partition 1 that separates an anode 2 a and a cathode 2 c, and an outer frame that borders the partition 1. 3 is provided. More specifically, the partition 1 has conductivity, and the outer frame 3 is provided so as to surround the partition 1 along the outer edge of the partition 1.

  Note that, in the present embodiment, the bipolar element 60 may be used so that a given direction D1 along the partition wall 1 is generally a vertical direction. Specifically, FIG. 2 and FIG. When the shape of the partition wall 1 in a plan view is rectangular as shown in the drawing, the partition wall 1 is used such that a given direction D1 along the partition wall 1 is the same as the direction of one set of two opposite sides. (See FIGS. 1 to 3). In this specification, the vertical direction is also referred to as an electrolyte passage direction.

In this embodiment, as shown in FIG. 1, the bipolar electrolytic cell 50 is configured by laminating a required number of bipolar elements 60.
In the example shown in FIG. 1, the bipolar electrolytic cell 50 has a fast head 51g, an insulating plate 51i, and an anode terminal element 51a arranged in this order from one end, and further includes an anode-side gasket portion 7, a diaphragm 4, and a cathode-side gasket portion. 7. The bipolar element 60 is arranged in this order. At this time, the bipolar element 60 is arranged so that the cathode 2c faces the anode terminal element 51a. From the anode side gasket portion 7 to the bipolar element 60, the number required for the design production amount is repeatedly arranged. After the necessary number of the anode side gasket portion 7 to the bipolar element 60 are repeatedly arranged, the anode side gasket portion 7, the diaphragm 4, and the cathode side gasket portion 7 are arranged again, and finally, the cathode terminal element 51c, the insulation The plate 51i and the loose head 51g are arranged in this order. The bipolar electrolytic cell 50 is formed into a body by tightening the whole by a tie rod type 51r (see FIG. 1) or a hydraulic cylinder type tightening mechanism.
The arrangement of the bipolar electrolytic cell 50 can be arbitrarily selected from either the anode 2a side or the cathode 2c side, and is not limited to the above order.

  As shown in FIG. 1, in the bipolar electrolytic cell 50, the bipolar element 60 is disposed between the anode terminal element 51a and the cathode terminal element 51c. The diaphragm 4 is arranged between the anode terminal element 51a and the bipolar element 60, between the adjacent bipolar elements 60, and between the bipolar element 60 and the cathode terminal element 51c. .

  In the bipolar electrolytic cell 50 according to the present embodiment, as shown in FIGS. 2 and 3, an electrode chamber 5 through which the electrolytic solution passes is defined by the partition wall 1, the outer frame 3, and the diaphragm 4.

  In the present embodiment, in particular, in the bipolar electrolytic cell 50, a portion between the two partition walls 1 between two adjacent bipolar elements 60, and a portion between the adjacent bipolar element 60 and the terminal element The portion between the partitions 1 is referred to as an electrolytic cell 65. The electrolytic cell 65 includes a partition 1, an anode chamber 5a, an anode 2a, and a diaphragm 4 of one element, and a cathode 2c, a cathode chamber 5c, and the partition 1 of the other element.

  Specifically, the electrode chamber 5 has an electrolyte inlet 5 i for introducing an electrolyte into the electrode chamber 5 and an electrolyte outlet 5 o for leading the electrolyte from the electrode chamber 5 at the boundary with the outer frame 3. More specifically, the anode chamber 5a is provided with an anode electrolyte inlet 5ai for introducing an electrolyte into the anode chamber 5a and an anode electrolyte outlet 5ao for leading an electrolyte derived from the anode chamber 5a. Similarly, the cathode chamber 5c is provided with a cathode electrolyte inlet 5ci for introducing an electrolyte into the cathode chamber 5c and a cathode electrolyte outlet 5co for extracting an electrolyte derived from the cathode chamber 5c.

  The bipolar electrolytic cell 50 in the present embodiment includes a header 10 that communicates with the electrode chamber 5 outside the outer frame 3 (see FIGS. 2 and 3).

In an example shown in FIGS. 2 and 3, a header 10 which is a pipe for distributing or collecting a gas or an electrolytic solution is attached to a bipolar electrolytic cell 50. Specifically, the header 10 includes an inlet header for putting the electrolyte into the electrode chamber 5 and an outlet header for taking out the gas and the electrolyte from the electrode chamber 5.
In one example, below the outer frame 3 at the edge of the partition 1, an anode inlet header 10Oai for putting the electrolyte in the anode chamber 5a and a cathode inlet header 10Oci for putting the electrolyte in the cathode chamber 5c are provided. Similarly, on the side of the outer frame 3 at the edge of the partition 1, an anode outlet header 10Oao for discharging the electrode solution from the anode chamber 5a and a cathode outlet header 10Oco for discharging the electrolyte from the cathode chamber 5c are provided. .
In one example, in the anode chamber 5a and the cathode chamber 5c, the inlet header and the outlet header are provided so as to face each other with the central portion of the electrode chamber 5 interposed therebetween.

In particular, the bipolar electrolytic cell 50 of this example employs an external header 100 type in which the bipolar electrolytic cell 50 and the header 10 are independent.
FIG. 4 shows a part of a side view of the external header type bipolar electrolytic cell for alkaline water electrolysis of the present embodiment together with the flow of the electrolytic solution.

  In addition, as a disposition mode of the header 10 attached to the bipolar electrolytic cell shown in FIGS. 1 to 3, typically, there are an internal header 10I type and an external header 10O type. A mold may be adopted, and there is no particular limitation.

Further, in one example shown in FIGS. 2 and 3, a conduit 20 which is a pipe for collecting gas or electrolyte solution distributed or collected in the header 10 is attached to the header 10. Specifically, the conduit 20 is composed of a liquid distribution pipe communicating with the inlet header and a liquid collecting pipe communicating with the outlet header.
In one example, a lower part of the outer frame 3 is provided with an anode liquid distribution pipe 20Oai communicating with the anode inlet header 100ai and a cathode liquid distribution pipe 20Oci communicating with the cathode inlet header 100ci. An anode liquid collecting tube 20Oao communicating with the anode outlet header 10Oao and a cathode liquid collecting tube 20Oco communicating with the cathode outlet header 10Oco are provided on the side of the outer frame 3.

  In the present embodiment, in the anode chamber 5a and the cathode chamber 5c, the inlet header and the outlet header are preferably provided at separate positions from the viewpoint of water electrolysis efficiency, and face each other with the central portion of the electrode chamber 5 interposed therebetween. When the shape of the partition wall 1 in a plan view is rectangular as shown in FIGS. 2 and 3, it is preferable that the partition wall 1 be provided symmetrically with respect to the center of the rectangle.

Usually, as shown in FIGS. 2 and 3, the anode inlet header 10 Oai, the cathode inlet header 10 Oci, the anode outlet header 10 Oao, and the cathode outlet header 10 Oco are provided one by one in each electrode chamber 5. The present invention is not limited to this, and a plurality of electrode chambers 5 may be provided.
Usually, the anode liquid distribution pipe 20Oai, the cathode liquid distribution pipe 20Oci, the anode liquid collection pipe 20Oao, and the cathode liquid collection pipe 20Oco are provided one by one in each electrode chamber 5, but in the present embodiment, The present invention is not limited to this, and a plurality of electrode chambers 5 may also be used.

  In the illustrated example, a rectangular partition wall 1 in a plan view and a rectangular diaphragm 4 in a plan view are arranged in parallel, and a rectangular parallelepiped outer frame provided on an edge of the partition wall 1 on the partition 1 side. Is perpendicular to the partition 1, the shape of the electrode chamber 5 is a rectangular parallelepiped. However, in the present invention, the shape of the electrode chamber 5 is not limited to the rectangular parallelepiped in the illustrated example, and the shape of the partition 1 and the diaphragm 4 in a plan view and the inner surface of the outer frame 3 on the partition 1 side and the partition 1 are formed. The shape may be appropriately changed depending on the angle or the like, and may have any shape as long as the effects of the present invention can be obtained.

  In the present embodiment, the extending direction of the header 10 is not particularly limited.

  In the present embodiment, the extending direction of the conduit 20 is not particularly limited. However, from the viewpoint of easily obtaining the effects of the present invention, as shown in an example shown in FIGS. The liquid tube 20Oai, the liquid distribution tube 20Oci for the cathode, and the liquid collection tube 20Oo (the liquid collection tube 20Oao for the anode, the liquid collection tube 20Oco for the cathode) preferably extend in a direction perpendicular to the partition wall 1, respectively. More preferably, each of the conduits 20 extends in a direction perpendicular to the partition wall 1.

In the present embodiment, one or a plurality of current cutoff valves 90 may be provided at any one or a plurality of locations in the flow path in the electrolytic cell 50, and more specifically, one location of the header 10O. Alternatively, one or more current cutoff valves 90 may be provided at a plurality of locations, and one or more current cutoff valves 90 may be provided at one or more locations of the conduit 20O.
In the example shown in FIGS. 2 and 3, a plurality of current cutoff valves 90 are provided at a plurality of locations of the header 100 and a plurality of locations of the conduit 200.

In the present embodiment, among the flow paths in the electrolytic cell 50, the current cutoff valve 90 may be provided in the flow path on the inlet side and / or the flow path on the outlet side. A current cutoff valve 90 may be provided in the outlet header 10Oo, and a current cutoff valve 90 may be provided in the liquid distribution pipe 20Oi and the liquid collection pipe 20Oo of the conduit 20O. One or more may be provided, and one or more may be provided between adjacent liquid distribution pipes 20Oi of the header 20O.
In the examples shown in FIGS. 2 and 3, among the headers 100, the current cutoff valve 90 is provided at the inlet header 100i (the anode inlet header 100ai and the cathode inlet header 100ci), and the outlet header 100oo (the anode outlet header 100oo). And a cathode exit header 10Oco) is provided with a current cutoff valve 90.

  In the present embodiment, it is desirable that a plurality of current cutoff valves 90 be provided so that each electrolysis cell 65 can be electrically independent.

Hereinafter, the components of the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment will be described in detail.
Hereinafter, preferred embodiments for enhancing the effects of the present invention will be described in detail.

-Partition wall-
The shape of the partition wall 1 in the present embodiment may be a plate-like shape having a predetermined thickness, but is not particularly limited.
The shape of the partition wall 1 in plan view is not particularly limited, and may be a rectangle (square, rectangle, etc.) or a circle (circle, ellipse, etc.). Here, the rectangle may have rounded corners.

  The partition 1 may be used so that a given direction D1 along the partition 1 may be a vertical direction. Specifically, as shown in FIGS. If the shape is rectangular, it may be used such that a given direction D1 along the partition 1 is the same as the direction of one of the two opposing sides. In this specification, the vertical direction is also referred to as an electrolyte passage direction.

  The material of the partition wall 1 is preferably a conductive material from the viewpoint of realizing uniform supply of electric power, and is nickel-plated on nickel, nickel alloy, mild steel, nickel alloy from the viewpoint of alkali resistance and heat resistance. Are preferred.

−electrode−
In the hydrogen production by alkaline water electrolysis according to the present embodiment, reduction of energy consumption, specifically, reduction of electrolysis voltage is a major problem. Since the electrolysis voltage greatly depends on the electrodes 2, the performance of both electrodes 2 is important.

  The electrolysis voltage of the alkaline water electrolysis is, in addition to the voltage required for the electrolysis of water theoretically determined, the overvoltage of the anodic reaction (oxygen generation), the overvoltage of the cathodic reaction (hydrogen generation), and the voltage between the anode 2a and the cathode 2c. And a voltage depending on the distance between the electrodes 2. Here, the overvoltage refers to a voltage that needs to be applied excessively beyond the theoretical decomposition potential when a certain current flows, and its value depends on the current value. When the same current flows, power consumption can be reduced by using the electrode 2 having a low overvoltage.

  In order to realize a low overvoltage, requirements for the electrode 2 include high conductivity, high oxygen generating ability (or hydrogen generating ability), and high wettability of the electrolyte on the surface of the electrode 2. No.

  Even if an unstable current such as renewable energy is used as the electrode 2 for alkaline water electrolysis in addition to low overvoltage, corrosion of the base material and the catalyst layer of the electrode 2, falling off of the catalyst layer, and Dissolution, adhesion of inclusions to the diaphragm 4, and the like are unlikely to occur.

  The structure of the conductive substrate of the anode and the cathode is preferably a mesh structure from the viewpoint of securing a specific surface area as a carrier and achieving both defoaming properties. The material of the conductive substrate may be at least one selected from the group consisting of nickel iron, vanadium, molybdenum, copper, silver, manganese, platinum group, graphite, chromium, and the like. An alloy composed of two or more metals or a mixture of two or more conductive substances may be used for the conductive substrate. Preferably, nickel metal is used for the conductive substrate.

−−Anode−−
The anode 2a includes a conductive substrate and a catalyst layer that covers the conductive substrate, and the catalyst layer is preferably a porous body. The catalyst layer preferably covers the entire surface of the conductive substrate.

  The catalyst layer of the anode preferably contains nickel as an element in terms of durability against alkali and high activity against oxygen generation. The catalyst layer preferably contains at least one nickel compound selected from nickel oxide, nickel metal, nickel hydroxide, and a nickel alloy.

−−Cathode−−
The cathode 2c is not particularly limited. Ru-La-Pt-based, Ru-Ce-based, Pt-Ce-based, and at least one Pt-group compound selected from the group consisting of Pt-Ir-based, Ir-Pt-Pd-based, and Pt-Ni-based Is preferred. Further, it is preferable to use a pyrolytic active cathode. The structure of the base material of the cathode is preferably a mesh structure from the viewpoint of securing a specific surface area as a carrier and achieving both defoaming properties.

  The catalyst layer of the cathode preferably contains nickel as an element in terms of durability against alkali and high activity against hydrogen generation. The catalyst layer preferably contains at least one nickel compound selected from nickel oxide, nickel metal, nickel hydroxide, and a nickel alloy.

−Outer frame−
The shape of the outer frame 3 in the present embodiment is not particularly limited as long as the partition 1 can be bordered.

-Diaphragm-
As the diaphragm 4 used in the bipolar electrolyzer 50 for alkaline water electrolysis according to the present embodiment, an ion-permeable diaphragm 4 is used to isolate generated hydrogen gas and oxygen gas while conducting ions. You. As the ion-permeable diaphragm 4, an ion-exchange membrane having an ion-exchange ability and a porous membrane that can penetrate an electrolyte can be used. The ion-permeable diaphragm 4 preferably has low gas permeability, high ionic conductivity, low electron conductivity, and high strength.

−Electrode room−
In the bipolar electrolytic cell 50 of the present embodiment, as shown in FIG. 2, the partition 1, the outer frame 3, and the diaphragm 4 define an electrode chamber 5 through which the electrolytic solution passes.

-Gasket-
In the bipolar electrolyzer 50 for alkaline water electrolysis of the present embodiment, it is preferable that the gasket 7 having the diaphragm 4 is sandwiched between the outer frames 3 bordering the partition 1.
The gasket 7 is used for sealing between the bipolar element 60 and the diaphragm 4 and between the bipolar element 60 with respect to the electrolytic solution and the generated gas. Gas mixing between the two electrode chambers can be prevented.

−header−
The bipolar electrolyzer 50 for alkaline water electrolysis has a cathode chamber 5c and an anode chamber 5a for each electrolytic cell 65. In order to continuously perform the electrolysis reaction in the electrolytic cell 50, it is necessary to continuously supply the cathode solution 5c and the anode compartment 5a of each electrolysis cell 65 with an electrolytic solution sufficiently containing raw materials consumed by electrolysis. There is.

  The electrolytic cell 65 is connected to an electrolyte supply / discharge pipe called a header 10 common to the plurality of electrolytic cells 65. In general, the liquid distributor for the anode is called the anode inlet header 10ai, the liquid distributor for the cathode is called the cathode inlet header 10ci, the liquid collector for the anode is called the anode outlet header 10ao, and the liquid collector for the cathode is called the cathode outlet header 10co. The electrolytic cell 65 is connected to a liquid distribution pipe for each electrode and a liquid collection pipe for each electrode through a hose or the like.

  The material of the header 10 is not particularly limited, but it is necessary to adopt a material that can sufficiently withstand operating conditions such as the corrosiveness of the electrolytic solution used, pressure and temperature. The material of the header 10 may be iron, nickel, cobalt, PTFE, ETFE, PFA, polyvinyl chloride, polyethylene, or the like.

  In the present embodiment, the range of the electrode chamber 5 varies depending on the detailed structure of the outer frame 3 provided at the outer end of the partition wall 1. It may differ depending on the disposition mode of the pipe for distributing or collecting the liquid). As a mode of disposing the header 10 of the bipolar electrolytic cell 50, an inner header 10I type and an outer header 100 type are typical.

  In the present embodiment, the external header 100 type is preferable because the installation of the current cutoff valve is easy.

−External header−
The external header 100 type refers to a type in which the bipolar electrolytic cell 50 and the header 10 (a pipe for distributing or collecting an electrolytic solution) are independent.

  The external header 10O type bipolar electrolytic cell 50 is configured such that the anode inlet header 10Oai and the cathode inlet header 10Oci run in parallel with the electrolytic cell 50 in a direction perpendicular to the energizing surface of the electrolytic cell 65. Provided. The anode inlet header 10Oai and the cathode inlet header 10Oci are connected to the respective electrolytic cells 65 by hoses.

The anode header 100 Oai, the cathode inlet header 100 Oci, the anode outlet header 100 Oao, and the cathode outlet header 100 Oco which are externally connected to the external header 10 O type bipolar electrolytic cell 50 are collectively referred to as an external header 10 O. Call.
In the example of the external header 100 type, a luminal member is installed in a header 10 through hole provided in a portion located below the outer frame 3 at the edge of the partition wall 1, and the luminal member is Are connected to the anode inlet header 10Oai and the cathode inlet header 10Oci, and similarly, in the through hole for the header 10 provided in the upper portion of the outer frame 3 at the edge of the partition 1, A lumen member (for example, a hose or a tube) is installed, and the lumen member is connected to the anode outlet header 100Oao and the cathode outlet header 10Oco.

(Electrolysis device for alkaline water electrolysis)
FIG. 5 shows an outline of the electrolysis apparatus for alkaline water electrolysis of the present embodiment.
By using the bipolar water electrolysis tank of this embodiment as an electrolysis device including other components and using it as a hydrogen production device, a hydrogen production device with high electrolysis efficiency can be provided.
The electrolytic apparatus for alkaline water electrolysis of the present embodiment includes at least the bipolar water electrolysis tank 50, the gas-liquid separation tank 72 (hydrogen separation tank 72h, oxygen separation tank 72o), the electrolyte circulation pump 71, and the water A charging pump 73 and a rectifier 74 for supplying power for electrolysis are provided.
In addition to the above, the alkaline water electrolysis apparatus 70 of the present embodiment may include an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure gauge 78, a heat exchanger 79, and a pressure control valve 80.

According to the electrolysis apparatus 70 for alkaline water electrolysis of the present embodiment, the effect of the bipolar electrolyzer 50 for alkaline water electrolysis of the present embodiment can be obtained.
That is, according to the present embodiment, during operation with a variable power supply such as renewable energy, it is possible to realize high-efficiency hydrogen production, reduce self-discharge that occurs when power supply is stopped, The electric control system can be stabilized.

(How to use the electrolytic cell)
The method for using the electrolytic cell according to the present embodiment is characterized in that, in the electrolytic cell according to the present embodiment, the current cutoff valve is closed before or after the electrolysis is stopped.

In this embodiment, since a reverse current flows before the electrolysis is stopped, it is preferable to close the current cutoff valve before or immediately after the electrolysis is stopped in order to suppress the reverse current. It is preferred that the current cutoff valve be closed within an hour.
Here, “electrolysis stop” refers to a point in time when the electric current to be supplied becomes 0.1 mA / m ² or less, and preferably a point in time when it becomes 0 (zero).
The timing for closing the current cutoff valve is more preferably within 5 minutes after the electrolysis is stopped, and even more preferably within 5 seconds after the electrolysis is stopped.
In addition, in order to suppress the water hammer phenomenon caused by closing the current cutoff valve while the electrolyte is circulated, the current cutoff valve is stopped at the timing when the circulation of the electrolyte is stopped and the internal state of the electrolyte is stabilized. Is preferably closed.

In the present embodiment, it is preferable to open the current cut-off valve within 2 hours after resuming the electrolysis, since overheating of the electrolytic solution is caused unless the valve is opened after the energization is restarted.
Here, the “restart of electrolysis” is preferably a point in time when the current to be supplied has exceeded 0 (zero).
The timing for opening the current cutoff valve is more preferably within one hour after the restart of electrolysis, more preferably within 30 minutes, and even more preferably within 5 seconds.
The timing for opening the current cutoff valve may be before the electrolysis is restarted.

  In the present embodiment, from the viewpoint of enhancing the effect of the present invention, the operation of closing the current cutoff valve 90 is preferably performed simultaneously on a plurality of current cutoff valves 90 provided in the electrolytic cell 50. More preferably, it is performed simultaneously for all the provided current cutoff valves 90.

The electrolytic solution used in the present embodiment may be an alkaline aqueous solution in which an alkali salt is dissolved, and examples thereof include an NaOH aqueous solution and a KOH aqueous solution.
The concentration of the alkali salt is preferably from 20% by mass to 50% by mass, more preferably from 25% by mass to 40% by mass.
In the present embodiment, an aqueous solution of 25% by mass to 40% by mass of KOH is particularly preferable from the viewpoints of ionic conductivity, kinematic viscosity, and freezing during cooling.

In the method of using the electrolytic cell of the present embodiment, the flow rate Q of the electrolytic solution per electrode chamber is controlled according to the size of the electrode chamber 5 from the viewpoint of enhancing the effect of the present invention. It is preferably from 10 ⁻⁷ m ³ / sec to 1 × 10 ⁻² m ³ / sec, more preferably from 1 × 10 ⁻⁶ m ³ / sec to 1 × 10 ⁻³ m ³ / sec.
The kinematic viscosity ν of the electrolytic solution is determined by the type, concentration, and temperature of the electrolytic solution.

  In the method for using the electrolytic cell of the present embodiment, from the viewpoint of suitably obtaining the effects of the present invention, the temperature of the electrolytic solution in the electrolytic cell 65 is preferably room temperature to 150 ° C, and 80 ° C to 130 ° C. It is more preferred that there be.

In the method of using the electrolytic cell according to the present embodiment, the current density applied to the electrolytic cell 65 may be usually 30 kA / m ² or less. Operation may be performed at a constant current density or an operation in which the current density fluctuates.

  In the method of using the electrolytic cell according to the present embodiment, the pressure in the electrolytic cell 65 can be set within the range of the design pressure of the electrolytic cell 65.

  Above, with reference to the drawings, the method of using the bipolar electrolyzer for alkaline water electrolysis of the present embodiment and the bipolar electrolyzer for alkaline water electrolysis of the present embodiment has been described by way of example. The method of using the bipolar electrolyzer for alkaline water electrolysis and the bipolar electrolyzer for alkaline water electrolysis is not limited to the above examples, and the above embodiment can be appropriately modified.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

(Configuration of electrolysis device)
The configuration of the electrolyzer was as shown in FIG.

The electrolytic cell was an external header 100 type electrolytic cell shown in FIGS. 3 and 4 and had 10 cells.
The header used for the electrolytic cell had the same cross-sectional area of the flow path, and the conduit used for the electrolytic cell had the same cross-sectional area of the flow path.

The type of the current cutoff valve was a diaphragm valve or a ball valve, and the material constituting the diaphragm valve or the ball valve was polypropylene (PP) or polyphenylene sulfide (PPS).
For the ball valve, the resistance was 1 MΩ or more and the resistivity was 10 ⁶ Ω · m.
With respect to the diaphragm valve, the resistance was 1 MΩ or more, and the resistivity was 10 ⁶ Ω · m.
The installation method of the current cutoff valve was as described later.
The current cutoff valve is provided in each of an anode inlet header (anode inlet side hose) 100 Oai, an anode outlet header (anode outlet side hose) 100 Oao, a cathode inlet header (a cathode inlet side hose) 100 Oci, and a cathode outlet header (a cathode outlet side hose) 100 Oco. One hose was installed at each location (see FIG. 3).
In addition, the current cutoff valves are provided at the inlet and the center of the liquid distribution pipe, and at the liquid collection pipe in the anode liquid distribution pipe 20Oai, the anode liquid collection pipe 20Oao, the cathode liquid distribution pipe 20Oci, and the cathode liquid collection pipe 20Oco. One piece was installed at each of the outlet and the center (see FIG. 4).

<Operation of electrolyzer>
The electrolytic apparatus was operated by adjusting the electrolytic solution circulation pump shown in FIG. 5 so that the flow rate of the electrolytic solution per electrode chamber was 1 × 10 ⁻³ m ³ / sec with a 25% by mass KOH aqueous solution. The liquid temperature during circulation of the electrolytic solution was maintained at 80 ° C. using the heat exchanger of FIG.
Electrolysis was performed on the bipolar element 60 shown in FIG. 3 by passing a current from the rectifier 74 shown in FIG. 5 at a current density of 8 kA / m ² . The energization was performed by repeating the continuous energization for 12 hours and the energization stop for 12 hours. The continuous energization and the stop of the energization were performed by opening (closing) and closing (stopping) the installed shut-off valves, respectively, as necessary. .

<Conditions of the current cutoff valve in the embodiment>
The type of the current cutoff valve used in the embodiment, the place where the cutoff was actually opened and closed, and the timing of opening and closing the current cutoff valve are as shown in Table 1 below.
In this example, the electrolysis was stopped when the current to be supplied was 0 (zero).

<Evaluation of electrode deterioration>
Next, a method of evaluating electrode deterioration will be described.
In the bipolar element 60, terminals for voltage measurement are attached to the anode and the cathode for each element, and the voltage of each element was measured 10 hours after the start of energization every time the energization was performed, and the average value was calculated. . Each time the continuous energization and the energization stop were repeated, the calculated voltage continued to increase little by little. Based on the rise value, the degree of deterioration of the electrodes (anode and cathode) of the electrolytic cell was evaluated according to the following evaluation criteria.
：: Voltage rise value of less than 30 mV, no electrode deterioration ×: Voltage rise value of 30 mV or more, electrode deterioration

Table 2 below shows the measurement results of the voltage rise value (the unit of the numerical value is mV) for each of the repetitions for Examples 1 to 5.
Further, as Comparative Example 1, the measurement results of the voltage rise value when continuous energization and energization stop were repeated without opening and closing all the installed shutoff valves were also shown.
FIG. 6 shows the results of the electrode degradation evaluation for Examples 1 to 5 and Comparative Example 1. The vertical axis shows the voltage rise value, and the horizontal axis shows the number of repetitions of energization / stop.

  Table 3 below shows the results of the voltage rise values shown in Table 2 evaluated according to the evaluation criteria described above.

  As shown in Table 3, in Comparative Example 1, deterioration of the electrode was observed when the number of times of continuous energization and energization stop exceeded 400 times. Since the comparative example 1 does not use the shutoff valve, it can be said that the effect of opening and closing the current shutoff valve is large in the repeated operation of energizing / stopping the water electrolysis device.

  Also, from Table 3, when the repetitive operation of energization and stop is performed for a long period of time, the timing of closing the current cutoff valve is set to 2 seconds earlier than to 60 seconds later to deteriorate the electrode. Is small.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that an electrode deteriorates and overvoltage rises by the reverse current which arises at the time of electrolysis stop.

Reference Signs List 1 partition 2 electrode 2a anode 2c cathode 2e conductive elastic body 2r current collector 3 outer frame 4 diaphragm 5 electrode chamber 5a anode chamber 5c cathode chamber 5i electrolyte inlet 5o electrolyte outlet 5ai anode electrolyte inlet 5ao anode electrolyte outlet 5ci Cathode electrolyte inlet 5co Cathode electrolyte outlet 6 Rectifier plate 6a Anode rectifier plate (anode rib)
6c Cathode rectifier (cathode rib)
7 gasket 10 header 10I inner header 100 outer header 100ai anode inlet header (anode inlet side hose)
10Oao anode outlet header (anode outlet side hose)
10Oci cathode inlet header (cathode inlet side hose)
10Oco cathode outlet header (cathode outlet side hose)
DESCRIPTION OF SYMBOLS 20 Conduit 20Oai Anode distribution pipe 20Oao Anode collection pipe 20Oci Cathode distribution pipe 20Oco Cathode collection pipe 50 Bipolar electrolytic cell 51g Fast head, loose head 51a Anode terminal element 51c Cathode terminal element 51i Insulating plate 51r Tie rod 60 Bipolar element 65 Electrolysis cell 70 Electrolyzer 71 Electrolyte circulation pump 72 Gas-liquid separation tank 72 h Hydrogen separation tank 72 o Oxygen separation tank 73 Water injection pump 74 Rectifier 75 Oxygen analyzer 76 Hydrogen analyzer 77 Flowmeter 78 Pressure gauge 79 heat exchanger 80 pressure control valve 90 current cutoff valve D1 given direction along partition wall (electrolyte passage direction)
S1 Area of the conducting surface of the bipolar element S2 Cross-sectional area of the flow path of the header L2 Length of the flow path of the header Z Zero gap structure d Thickness of the electrolytic cell

Claims (12)

  An electrolytic cell comprising: an electrode chamber; and a flow path communicating with the electrode chamber, wherein a current cutoff valve is provided in the flow path.   The electrolytic cell according to claim 1, wherein the current cutoff valve is provided so as to be able to cut off the flow path.   3. The electrolytic cell according to claim 1, further comprising at least one selected from the group consisting of a header having the flow path and communicating with the electrode chamber, and a conduit having the flow path and communicating with the header. 4.   The electrolytic cell according to any one of claims 1 to 3, wherein the current cutoff valve includes an insulating material.   The electrolytic cell according to any one of claims 1 to 4, wherein a portion of the flow path corresponding to a location where the current cutoff valve is provided includes an insulating material.   The electrolytic cell according to any one of claims 1 to 5, wherein the current cutoff valve is provided at a portion of the flow passage having a smallest cross-sectional area.   The electrolytic cell according to any one of claims 1 to 6, wherein the current cutoff valve is driven by at least one selected from the group consisting of manual operation, gas pressure, and electric energy.   The electrolytic cell according to any one of claims 1 to 7, wherein the current cutoff valve is at least one selected from the group consisting of a ball valve, a globe valve, a gate valve, a butterfly valve, a diaphragm valve, and a check valve.   The method according to any one of claims 1 to 8, wherein the current cutoff valve is closed before or after the electrolysis is stopped.   The use of the electrolytic cell according to claim 9, wherein the current cutoff valve is closed within 2 hours after stopping the electrolysis.   The use of the electrolytic cell according to claim 10, wherein the current cutoff valve is closed within 30 seconds after stopping the electrolysis.   The use of the electrolytic cell according to claim 10 or 11, wherein the current cutoff valve is opened within 60 seconds after restarting the electrolysis.

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