JP7454428B2 - Electrolyzer, electrolyzer, electrolysis method - Google Patents

Description

The present invention relates to a bipolar electrolytic cell for alkaline water electrolysis, a bipolar electrolytic device for alkaline water electrolysis, and an alkaline water electrolysis method.

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 caused by greenhouse gases such as carbon dioxide and decreasing fossil fuel reserves.

The nature of renewable energy is that its output is highly variable, as it depends on climatic conditions. For this reason, it is not always possible to transport the electricity obtained from renewable energy generation to the general power grid, and there are concerns about social impacts such as an imbalance in power supply and demand and instability of the power grid. There is.

Therefore, research is being conducted to use electricity generated from renewable energy in a form that can be stored and transported instead. Specifically, consideration is being given to generating hydrogen that can be stored and transported through electrolysis (electrolysis) of water using electricity generated from renewable energy, and using hydrogen as an energy source or raw material. There is.

Hydrogen is widely used industrially in petroleum refining, chemical synthesis, metal refining, etc., and in recent years, it has become possible to use it in hydrogen stations for fuel cell vehicles (FCV), smart communities, hydrogen power plants, etc. Gender is also expanding. For this reason, expectations are high for the development of technology to obtain particularly high-purity hydrogen from renewable energy.

Examples of water electrolysis methods include solid polymer water electrolysis, high-temperature steam electrolysis, and alkaline water electrolysis. Among these, alkaline water electrolysis is one of the most promising because it has been industrialized for several decades, can be implemented on a large scale, and is inexpensive compared to other water electrolysis devices. has been done.

However, in order to adapt alkaline water electrolysis as a means of storing and transporting energy in the future, it will be possible to perform water electrolysis by efficiently and stably using electricity, which has large output fluctuations, as mentioned above. There is a need to. Therefore, there is a need to solve various problems with electrolytic cells and devices for alkaline water electrolysis.

For example, in a bipolar electrolyzer for alkaline water electrolysis, by adjusting the length and cross-sectional area of the flow path, cross-sectional area, and area of the current-carrying surface of the header (manifold), which is a pipe that distributes or collects electrolyte, the device can be adjusted. It has been reported that the durability of the device is improved by adjusting the electrical resistance and suppressing electrode deterioration due to leakage current (reverse current) (Patent Documents 1 and 2).
Depending on how the header is installed, there are typically internal header types that are integrated with the electrolytic cell (provided inside the electrolytic cell), and internal header types that are independent of the electrolytic cell (provided inside the electrolytic cell). There is also an external header type (provided externally).

Japanese Patent Application Publication No. 2019-019379 International Publication No. 2018/139597

In the case of an internal header type bipolar electrolyzer for alkaline water electrolysis, leakage current tends to increase, and this leakage current may generate oxygen gas in addition to hydrogen gas on the cathode side, or generate oxygen gas as well as oxygen gas on the anode side. Since hydrogen gas is also generated, a mixed gas of hydrogen gas and oxygen gas is generated, resulting in a problem of deterioration of gas purity. Further, since a mixed gas of hydrogen gas and oxygen gas is an explosive gas, it is also a safety problem.
One way to reduce this leakage current is to increase electrical resistance. Electrical resistance is determined by the cross-sectional area of the header's flow path and the thickness of the electrolytic cell, so to increase the electrical resistance, you can reduce the cross-sectional area of the header's flow path or increase the thickness of the electrolytic cell. It may be possible to make design adjustments. However, in the internal header type bipolar electrolyzer for alkaline water electrolysis, these design adjustments are difficult due to its structure.
Furthermore, in order to obtain uniform flow distribution in the piping of the internal header, it is required that the fluid resistance at each electrolytic cell inlet of the piping of the internal header is large. The piping of the internal header has holes (notches) for the inflow and outflow of electrolyte and generated gas, and by increasing the number of these holes or reducing their size, the fluid at the inlet of each electrolytic cell can be reduced. However, due to the structure of the internal header, these adjustments can only be made within a very narrow range and are difficult. Furthermore, if the holes are too small, they may become clogged with foreign matter, but due to the structure of the internal header, it is difficult to see if the holes are clogged, so it is necessary to disassemble the electrolytic cell to clear the clogs. There is.

On the other hand, in an external header type bipolar electrolyzer for alkaline water electrolysis, the outlet header (hose) must be thicker than the inlet header (hose) in consideration of the volume of generated gas to be collected. However, if the nozzles for connecting the outlet headers are made too thick as the diameter of the outlet headers increases, there is a problem that interference between the nozzles occurs. Furthermore, if the thickness of the electrolytic cell is increased in order to eliminate interference between the nozzles, a problem arises in that the entire electrolytic cell becomes enlarged.
In addition, the larger the diameter of the outlet header (hose), the weaker its pressure resistance becomes, and in order to withstand pressurized operation, it is necessary to thicken the outlet header to improve its pressure resistance. .

Therefore, the present invention provides a bipolar electrolytic cell for alkaline water electrolysis, which suppresses the occurrence of leakage current, prevents deterioration of gas purity, makes the electrolytic cell thinner, and enables pressurized operation, and a bipolar electrolytic cell for alkaline water electrolysis. The present invention aims to provide a type electrolyzer and an alkaline water electrolysis method.

That is, the present invention is as follows.
[1]
Comprising an anode terminal element and a cathode terminal element,
A plurality of bipolar elements are provided between the anode terminal element and the cathode terminal element, each of which includes an anode, a cathode, a partition separating the anode and the cathode, and an outer frame that frames the partition. are superimposed across the
an inlet header that communicates with an electrode chamber defined by the partition wall, the outer frame, and the partition film on the outside of the outer frame; and an entrance header that communicates with the electrode chamber defined by the partition wall, the outer frame, and the partition film; and an outlet header communicating with an electrode chamber defined by the diaphragm and the diaphragm.
[2]
The area of the conductive surface of the bipolar element is S1, the cross-sectional area of the flow path of the inlet header is S2i, the cross-sectional area of the flow path of the outlet header is S2o, the length of the flow path of the inlet header is L2i, and the cross-sectional area of the flow path of the inlet header is S2o. As described in [1], where the length of the outlet header flow path is L2o, ((S2i/S1)/L2i)/((S2o/S1)/L2o) is 0.0001 to 0.5. A bipolar electrolyzer for alkaline water electrolysis.
[3]
The bipolar electrolytic cell for alkaline water electrolysis according to [1] or [2], which has 50 to 500 bipolar elements.
[4]
The bipolar electrolytic cell for alkaline water electrolysis according to [2] , wherein the S1 is 0.1 to 10 m ² .
[5]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [4], wherein the electrolytic cell has a thickness d of 5 to 100 mm.
Here, the thickness d of the electrolytic cell is defined as the distance between the partition walls of two adjacent bipolar elements in the direction perpendicular to the partition walls, and the distance between the partition walls of the adjacent bipolar elements and the anode terminal element. It means the distance between the partition wall in the direction perpendicular to the partition wall, or the distance between the partition wall of the adjacent bipolar element and the partition wall of the cathode terminal element in the direction perpendicular to the partition wall.
[6]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [5], wherein the inlet header has a withstand pressure of 0.1 to 10 MPa.
[7]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [6], wherein at least a portion of the inlet header is made of a flexible material.
[8]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [7], wherein at least a portion of the inlet header is insulating.
[9]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [8], which has an electrically insulating layer between the inlet header and the outer frame.
[10]
The bipolar electrolytic cell for alkaline water electrolysis according to [9], wherein the electrical insulating layer has a resistance value of 0.1 MΩ or more.
[11]
The bipolar electrolyzer for alkaline water electrolysis according to any one of [1] to [10], wherein the outlet header includes at least one selected from the group consisting of nickel, resin, and resin-coated metal. Tank.
[12]
The bipolar electrolytic cell for alkaline water electrolysis according to any one of [1] to [11],
A liquid pump for circulating the electrolyte,
a gas-liquid separation tank that separates the electrolyte from hydrogen and/or oxygen;
A bipolar electrolyzer for alkaline water electrolysis, comprising a water replenisher for replenishing water.
[13]
The method according to [12], further comprising a detector that detects the stoppage of the power supply when the power supply to the bipolar electrolyzer for alkaline water electrolysis is stopped, and a controller that automatically stops the liquid feeding pump. Bipolar electrolyzer for alkaline water electrolysis.
[14]
An alkaline water electrolysis method, characterized in that the liquid feeding pump is stopped when power supply to the electrolyzer for alkaline water electrolysis according to [12] or [13] is stopped.
[15]
[12] or [13], when the power supply to the electrolyzer for alkaline water electrolysis is stopped, the liquid level of the electrolyte is controlled to be lower than the communication port to the electrode chamber of the outlet header. Alkaline water electrolysis method.

According to the present invention, a bipolar electrolytic cell for alkaline water electrolysis, which suppresses the occurrence of leakage current, prevents deterioration of gas purity, and enables thinner electrolytic cells and pressurized operation, and a bipolar electrolytic cell for alkaline water electrolysis. A type electrolyzer and an alkaline water electrolysis method can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which shows the whole example of the bipolar electrolytic cell for alkaline water electrolysis of this embodiment. FIG. 2 is a diagram illustrating a cross section of a zero-gap structure inside the electrolytic cell in a portion surrounded by a broken rectangular frame in FIG. 1. FIG. It is a perspective view showing a part of a bipolar element, a header, and a conduit of an example of a bipolar electrolytic cell for alkaline water electrolysis of this embodiment. FIG. 1 is a plan view showing an example of a bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment. 4 is a diagram showing a part of a cross section of the bipolar electrolytic cell for alkaline water electrolysis shown in FIG. 4 taken along the line AA in FIG. 4. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline of the electrolyzer for alkaline water electrolysis of this embodiment.

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

(Bipolar electrolyzer for alkaline water electrolysis)
The bipolar electrolytic cell for alkaline water electrolysis of this embodiment includes a plurality of bipolar elements including an anode, a cathode, a partition separating the anode and the cathode, and an outer frame that frames the partition. an inlet header that is stacked with a diaphragm in between and communicates with an electrode chamber defined by the diaphragm, the outer frame, and the diaphragm on the outside of the outer frame; and the diaphragm on the inside of the outer frame. and an outlet header communicating with an electrode chamber defined by the outer frame and the diaphragm.
Hereinafter, the configuration of an example of a bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment will be described with reference to the drawings.

FIG. 1 shows a side view of an entire example of a bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment.
FIG. 2 shows a side view of a zero-gap structure of an example of a bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment, with respect to a portion surrounded by a broken line rectangular frame shown in FIG. 1.
FIG. 3 shows a perspective view of a part of the bipolar element, header, and conduit of an example of the bipolar electrolytic cell for alkaline water electrolysis of this embodiment.
As shown in FIGS. 1 and 2, the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment includes an anode 2a, a cathode 2c, a partition wall 1 separating the anode 2a and the cathode 2c, and a partition wall 1 that borders the partition wall 1. This is a bipolar electrolytic cell 50 in which a plurality of bipolar elements 60 each having a detachable outer frame 3 are stacked with a diaphragm 4 in between.
In the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, although not particularly limited, it is preferable that a zero-gap structure Z is formed in which the diaphragm 4 is in contact with the anode 2a and the cathode 2c (see FIG. 2).

The bipolar type is one of the methods of connecting a large number of cells to a power supply, and is a method in which a plurality of bipolar elements 60, one side of which is an anode 2a and one side of which is a cathode 2c, are arranged in the same direction and connected in series, and only both ends are connected. This is the way to connect the power supply.
The bipolar electrolytic cell 50 has the feature that the current of the power source can be made small, and can produce compounds, predetermined substances, etc. in large quantities in a short time by electrolysis. For power equipment with the same output, constant current and high voltage power supplies are cheaper and more compact, so bipolar power supplies are industrially preferable to single-pole power supplies.

((Bipolar element))
As shown in FIGS. 1 and 2, a bipolar element 60 used in an example of a bipolar electrolytic cell 50 for alkaline water electrolysis includes a partition wall 1 that separates an anode 2a and a cathode 2c. It is equipped with an outer frame 3 that can be removed. 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.

In addition, in this embodiment, the bipolar element 60 may be used so that the given direction D1 along the partition wall 1 is a vertical direction, and specifically, as shown in FIG. 1 is rectangular in plan view, it may be used so that the given direction D1 along the partition wall 1 is the same direction as the direction of one of the two pairs of opposing sides (see FIG. 3 to Figure 5). In this specification, the vertical direction is also referred to as the electrolyte passing direction.

In this embodiment, as shown in FIG. 1, the bipolar electrolytic cell 50 is configured by stacking a required number of bipolar elements 60.
In the example shown in FIGS. 1 and 2, the bipolar electrolytic cell 50 includes 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 gasket portion 7, a diaphragm 4, and a cathode. The side gasket portion 7 and the bipolar element 60 are arranged side by side in this order. At this time, the bipolar element 60 is arranged so that the cathode 2c faces the anode terminal element 51a side. The parts from the anode side gasket part 7 to the bipolar element 60 are repeatedly arranged as many times as necessary for the designed production volume. After repeatedly arranging the anode side gasket part 7 to the bipolar element 60 as many times as necessary, the anode side gasket part 7, the diaphragm 4, and the cathode side gasket part 7 are arranged side by side 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 assembled into a body by tightening the entire structure using a tightening mechanism such as a tie rod 51r (see FIG. 1) or a hydraulic cylinder type, thereby forming the bipolar electrolytic cell 50.
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-mentioned order.

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

Furthermore, in the bipolar electrolytic cell 50 of this embodiment, as shown in FIGS. 2 to 5, the partition wall 1, the outer frame 3, and the partition membrane 4 define an electrode chamber 5 through which the electrolyte passes.

In this embodiment, in particular, the portion between two adjacent bipolar elements 60 in the bipolar electrolytic cell 50 between the partition walls 1, and the portion between the adjacent bipolar elements 60 and the terminal element. The portion between the partition walls 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 partition 4 of one element, and a cathode 2c, a cathode chamber 5c, and a partition 1 of the other element.

Specifically, the electrode chamber 5 has an electrolyte inlet 5i that introduces the electrolyte into the electrode chamber 5 and an electrolyte outlet 5o that leads out 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 the electrolyte into the anode chamber 5a, and an anode electrolyte outlet 5ao for discharging the electrolyte from the anode chamber 5a. Similarly, the cathode chamber 5c is provided with a catholyte inlet 5ci for introducing the electrolyte into the cathode chamber 5c, and a catholyte outlet 5co for leading out the electrolyte from the cathode chamber 5c.

In this embodiment, the anode chamber 5a and the cathode chamber 5c may be provided with an internal distributor for uniformly distributing the electrolytic solution within the electrode surface inside the electrolytic cell 50. Further, the electrode chamber 5 may include a baffle plate having a function of restricting the flow of liquid inside the electrolytic cell 50. Further, in the anode chamber 5a and the cathode chamber 5c, a Karman vortex is generated in order to equalize the concentration and temperature of the electrolytic solution inside the electrolytic cell 50 and to promote degassing of gas adhering to the electrodes 2 and the diaphragm 4. It may also be provided with a protrusion for making.

The bipolar electrolytic cell 50 in this embodiment includes an inlet header 10 that communicates with the electrode chamber 5 on the outside of the outer frame 3, and an inlet header 10 that communicates with the electrode chamber 5 on the inside of the partition wall 1 and/or the outer frame 3. and an outlet header 11 (see FIG. 3).

The bipolar electrolytic cell 50 of this embodiment is attached with a header, which is a pipe that distributes or collects gas or electrolyte. In detail, the header consists of an inlet header 10 for introducing electrolyte into the electrode chamber 5 and an outlet header 11 for discharging gas and electrolyte from the electrode chamber 5.
In the bipolar electrolytic cell 50 of this embodiment, the inlet header 10 is of an external header type, and the outlet header 11 is of an internal header type.
By making the inlet header 10 an external header type, the leakage current path can be shortened compared to the case where an internal header is used, and deterioration in gas purity caused by leakage current can be reduced. Furthermore, since the length and diameter of the header can be adjusted regardless of the structure of the electrolytic cell, it is easy to adjust the electrical resistance and fluid resistance. Furthermore, if the header is an external header, even if the header becomes clogged due to foreign matter, it can be easily dealt with by removing the external header.
In addition, by making the outlet header 11 an internal header type, unlike an external header, there is no need to use a nozzle, so there is no problem of nozzles interfering with each other, and the enlargement of the electrolytic cell to solve this problem is also avoided. Therefore, the electrolytic cell can be made thinner. Furthermore, since it has higher pressure resistance than an external header, it can also be used in pressurized operation.
The external header type refers to a type in which the header is independent of the bipolar electrolytic cell (located outside the electrolytic cell), and is separated from the bipolar electrolytic cell by an insulating member. etc., may be electrically insulated from the bipolar electrolytic cell. In addition, the internal header type is a type in which the header is integrated with the bipolar electrolytic cell (provided inside the electrolytic cell), and may not be electrically insulated from the bipolar electrolytic cell. .
In the example shown in FIGS. 3 to 5, below the outer frame 3 at the edge of the partition wall 1, there is an anode inlet header 10Oai of an external header type for introducing the electrolyte into the anode chamber 5a, and an anode inlet header 10Oai for introducing the electrolyte into the cathode chamber 5c. It is equipped with an external header type cathode inlet header 10Oci. Further, above the outer frame 3 at the edge of the partition wall 1, there is an internal header type anode outlet header 11Iao for discharging the electrode solution from the anode chamber 5a, and an internal header type cathode outlet for discharging the electrolyte from the cathode chamber 5c. It is equipped with a header 11Ico.
Further, in the example shown in FIGS. 3 to 5, in the anode chamber 5a and the cathode chamber 5c, an inlet header 10 and an outlet header 11 are provided to face each other with the center portion of the electrode chamber 5 interposed therebetween.

Furthermore, as shown in FIGS. 3 and 4, a conduit (liquid distribution pipe) 20 is attached to the inlet header 10 and is a pipe that collects gas and electrolyte distributed to the inlet header 10. It's communicating.
In the example shown in FIGS. 3 and 4, a lower part of the outer frame 3 is provided with an anode liquid distribution pipe 20Oai that communicates with the anode inlet header 10Oai, and a cathode liquid distribution pipe 20Oci that communicates with the cathode inlet header 10Oci. ing.

In this embodiment, in the anode chamber 5a and the cathode chamber 5c, the inlet header 10 and the outlet header 11 are preferably provided at separate positions from the viewpoint of water electrolysis efficiency, and are placed on both sides of the central part of the electrode chamber 5. They are preferably provided so as to face each other, and when the partition wall 1 has a rectangular shape in plan view as shown in FIGS. 3 and 4, they are preferably provided symmetrically with respect to the center of the rectangle.

Normally, as shown in FIGS. 3 and 4, one anode inlet header 10Oai, one cathode inlet header 10Oci, one anode outlet header 11Iao, and one cathode outlet header 11Ico are provided in each electrode chamber 5, but in this embodiment, The present invention is not limited to this, and each electrode chamber 5 may be provided with a plurality of electrodes.
Further, normally, one anode liquid distribution pipe 20Oai and one cathode liquid distribution pipe 20Oci are provided in each electrode chamber 5, but in the present embodiment, they are not limited to this, and are shared in a plurality of electrode chambers 5. You can.

The material of the inlet header 10 in this embodiment is not particularly limited, but it is necessary to adopt a material that can sufficiently withstand the corrosivity of the electrolyte used and operating conditions such as pressure and temperature. The material of the inlet header 10 may be metals such as iron, nickel, cobalt, etc., resins such as PTFE, ETFE, PFA, polyvinyl chloride, polyethylene, etc.
Furthermore, it is preferable that at least a portion of the material of the inlet header 10 is a flexible material because it is easy to connect to the electrolytic cell 50, the conduit 20, etc. and handle it. Examples of the flexible material include PFA, PTFE, and bellows-shaped metals (nickel, stainless steel).
Moreover, it is preferable that at least a part of the material of the inlet header 10 in this embodiment is insulating from the viewpoint of cutting off electrical continuity with the electrolytic cell 50. Examples of the insulating material include PFA and PTFE.

Furthermore, in this embodiment, from the viewpoint of interrupting electrical continuity between the entrance header 10 and the electrolytic cell 50, it is preferable to provide an electrical insulating layer between the entrance header 10 and the outer frame 3. Examples of the electrically insulating layer include layers containing PFA, PTFE, EPDM, and the like.
The resistance value of the electrical insulating layer is preferably 0.1 MΩ or more, more preferably 0.4 MΩ or more, still more preferably 1.0 MΩ or more, from the viewpoint of blocking electrical continuity with the electrolytic cell 50. It is. Further, since the higher the resistance value of the electrical insulating layer is, the more preferable it is, the upper limit is not particularly limited, but it is usually preferably 100 MΩ or less.

The material of the outlet header 11 in this embodiment is not particularly limited, but it is necessary to adopt a material that can sufficiently withstand the corrosivity of the electrolyte used and operating conditions such as pressure and temperature. The material of the outlet header 11 may be a metal such as iron, nickel, or cobalt, a resin such as PTFE, ETFE, PFA, polyvinyl chloride, or polyethylene, or the metal coated with the resin. Among these, from the viewpoint of alkali resistance, it is preferable to include at least one selected from the group consisting of nickel, resin, and metal coated with resin.

In the illustrated example, the partition wall 1 which is rectangular in plan view and the partition membrane 4 which is rectangular in plan view are arranged in parallel, and the partition wall 1 side of the rectangular parallelepiped-shaped outer frame provided at the edge of the partition wall 1. Since the inner surface of the electrode chamber 5 is perpendicular to the partition wall 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, but may be formed by the shape of the partition wall 1 or the partition film 4 in plan view, or the shape of the inner surface of the outer frame 3 on the partition wall 1 side and the partition wall 1. It may be modified as appropriate depending on the angle, etc., and may have any shape as long as the effects of the present invention can be obtained.

In this embodiment, the positional relationship between the electrode chamber 5 and the inlet header 10 and outlet header 11 is not particularly limited, and as shown in FIGS. When used so that the direction D1 is vertical, the inlet header 10 is located below or to the side of the electrode chamber 5 (lower in the illustration), and the outlet header 11 is located below or to the side of the electrode chamber 5. Further, the liquid distribution pipe 20 communicating with the inlet header 10 may be located below or to the side of the electrode chamber 5 (in the illustration, below).

In this embodiment, the direction in which the inlet header 10 extends is not particularly limited.
Further, in this embodiment, the extending direction of the liquid distribution pipe 20 communicating with the inlet header 10 is not particularly limited, but as shown in the example shown in FIGS. 3 and 4, it is possible to easily obtain the effects of the present invention. Therefore, it is preferable that the conduits 20 (anode liquid distribution pipe 20Oai, cathode liquid distribution pipe 20Oci) extend in a direction perpendicular to the partition wall 1; It is further preferred that all of the tubes 20Oci) extend in a direction perpendicular to the partition wall 1.

In this embodiment, the direction in which the outlet header 11 extends is not particularly limited, but from the viewpoint of easily obtaining the effects of the present invention, the direction in which the outlet header 11 extends is perpendicular to the partition wall 1, as shown in the example shown in FIGS. 3 and 4. Preferably, some of the outlet headers 11 extend, and more preferably, both of the outlet headers 11 extend in a direction perpendicular to the bulkhead 1.

In addition, in the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, convection generated in the electrolytic chamber 5 due to disturbance of the flow of gas and liquid in the electrolytic chamber 5 is reduced, and a local temperature increase of the electrolytic solution is prevented. In order to suppress this, a plurality of rectifying plates 6 may be provided that are arranged parallel to a given direction D1 along the partition wall 1 (see FIG. 4).
The number and length of the rectifying plates 6, the angles formed with the partition wall 1, and the fixed spacing (pitch) in the direction perpendicular to the given direction D1 along the partition wall 1 may be determined as appropriate as long as the effects of the present invention can be obtained. It may be fixed or may not be fixed. Further, the current plate 6 may have through holes, and the number of through holes and the constant interval (pitch) in a given direction D1 along the partition wall 1 may be set as long as the effect of the present invention is obtained. It may be determined as appropriate and may not be constant.

Sometimes, the electrolytic cell 65 causes a self-discharge reaction through the leakage current circuit formed by the electrolyte supply piping when electrolysis is stopped. The self-discharge reaction is called a reverse current because the direction of the current flowing through the current-carrying surface is opposite to that during electrolysis.
The cathode 2c or the anode 2a may be deactivated due to activation dissolution or volume expansion/contraction due to oxidation/reduction during the process of generating a reverse current.

A structure with a very large surface area that consumes reverse current preferentially by itself being redoxed than the cathode 2c or the anode 2a is called a reverse charge absorber.
The reverse electric absorber is electrically connected to the cathode 2c or the anode 2a inside the cathode chamber 5c or the anode chamber 5a, and the electrochemical potential of the cathode 2c or anode 2a is maintained at the potential of the reverse electric absorber. Thus, the cathode 2c or the anode 2a can be protected.

In this embodiment, the cathode 2c or the anode 2a is composed of a catalyst layer and a base material that supports the catalyst layer, and this catalyst layer and base material have the function of a reverse electricity absorber.

In the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, the area of the current-carrying surface of the bipolar element 60 is S1, the cross-sectional area of the flow path of the inlet header 10 is S2i, and the cross-sectional area of the flow path of the outlet header 11 is S1. When S2o is the length of the flow path of the inlet header 10, L2i is the length of the flow path of the outlet header 11, and L2o is the length of the flow path of the outlet header 11, ((S2i/S1)/L2i)/((S2o/S1)/L2o) is preferably from 0.0001 to 0.5, more preferably from 0.0001 to 0.03, even more preferably from 0.0001 to 0.01, and even more preferably from 0.0001 to 0.001. Even more preferably.

The area S1 of the current-carrying surface of the bipolar element 60 refers to the area of the electrodes (anode 2a and cathode 2c) of the bipolar element 60 in a plane parallel to the partition wall 1. In addition, when the said area differs between the anode 2a and the cathode 2c, it shall mean the average.
The cross-sectional area S2i of the flow path of the inlet header 10 refers to the cross-sectional area of the internal space of the inlet header 10 through which the electrolyte passes. In addition, when there is a change in the cross-sectional area in the extending direction of the entrance header 10, the average of the cross-sectional area is used. Furthermore, when the above-mentioned cross-sectional area is different between the anode inlet header 10Oai and the cathode inlet header 10Oci, the average thereof is used.
S2o, the cross-sectional area of the flow path of the outlet header 11, refers to the cross-sectional area of the internal space of the outlet header 11 through which the electrolyte passes. In addition, when there is a change in the cross-sectional area in the extending direction of the outlet header 11, the average of the cross-sectional area is used. Furthermore, when the above-mentioned cross-sectional area is different between the anode outlet header 11Iao and the cathode inlet header 11Ico, the average thereof is used.
The length L2i of the flow path of the inlet header 10 refers to the extended length of the internal space of the inlet header 10 through which the electrolyte passes. In particular, when a conduit (liquid distribution pipe) 20 communicating with the inlet header 10 is provided, this refers to the length from the electrolyte inlet 5i of the inlet header 10 to the connection part with the conduit (liquid distribution pipe) 20. . In addition, when the above-mentioned lengths differ between the anode inlet header 10Oai and the cathode inlet header 10Oci, the average length is used.
The length L2o of the flow path of the outlet header 11 refers to the extended length of the internal space of the outlet header 11 through which the electrolyte passes. Furthermore, when the lengths are different between the anode outlet header 11Iao and the cathode outlet header 11Ico, the length is the average of the lengths.

When ((S2i/S1)/L2i)/((S2o/S1)/L2o) is within the above range, leakage current generated during electrolysis is reduced, and deterioration in gas purity due to leakage current is reduced. becomes possible.

Furthermore, in the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment, the area S1 of the current-carrying surface of the bipolar element 60 is preferably 0.1 to 10 m ² , and preferably 0.15 to 8 m ² . It is more preferable that the area is 0.2 to 5 m ² .
If the current-carrying surface is too small, the electrolyte supply header will also be small, making it difficult to manufacture the electrolytic cell 50. Furthermore, if the current-carrying surface is too large, the sealing surface pressure tends to become uneven, which may cause electrolyte leakage or gas leakage.

Furthermore, in the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, from the viewpoint of further increasing the gas purity and from the viewpoint of suppressing flow path blockage due to solid matter existing in the circulation flow path, the inlet header is The cross-sectional area S2i of the flow path is preferably 7.00×10 ⁻⁷ to 3.14×10 ⁻⁴ m ² , and preferably 1.0×10 ⁻⁶ to 2.0×10 ⁻⁴ m ² . It is more preferable that there be.
Furthermore, in the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment, the length L2i of the flow path of the inlet header is set from the same viewpoint as the preferable range of S2i, although it is not particularly limited. , preferably 0.2 to 10 m, more preferably 0.4 to 8 m.

Furthermore, in the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, from the viewpoint of further increasing the gas purity and from the viewpoint of suppressing flow path blockage due to solid matter existing in the circulation flow path, the outlet header is The cross-sectional area S2o of the flow path is preferably 1.0×10 ⁻⁴ to 1.0×10 ⁻¹ m ² , and preferably 1.0×10 ⁻³ to 5.0×10 ⁻¹ m ² . It is more preferable that there be.
In addition, in the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, since the outlet header is an internal header, the length L2o of the flow path is determined by the thickness d, number, etc. of the electrolytic cells 65. good.

Furthermore, in the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment, the thickness d of the electrolytic cell 65 is preferably 5 to 100 mm, more preferably 10 to 70 mm, and more preferably 20 to 60 mm. It is even more preferable that there be.
The thickness d of the electrolytic cell 65 is the thickness of the portion between two adjacent bipolar elements 60 and the thickness of the portion between the partition walls 1, and the thickness of the portion between the adjacent bipolar elements 60 and the terminal elements 51a, 51c. The distance between the partition walls 1 of two adjacent bipolar elements 60 in the direction perpendicular to the partition walls 1, and the distance between the partition walls 1 of two adjacent bipolar elements 60, respectively. This refers to the distance in the direction perpendicular to the partition wall 1 between the partition wall 1 of the element 60 and the partition wall 1 of the terminal elements 51a, 51c. If the thickness d is not constant throughout the bipolar electrolytic cell 50, it may be the average value.
If the thickness d of the electrolytic cell is too small, the gas ratio in the gas-liquid chamber of the electrolytic cell 65 tends to increase, and the cell voltage tends to increase. Furthermore, if the thickness d is too large, uniform distribution becomes difficult due to the influence of pressure loss in the header 10, and the installation area becomes too large.

In the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment, from the viewpoint of pressure resistance compatible with pressurized operation, the pressure resistance of the inlet header 10 is preferably 0.1 to 10 MPa, and preferably 0.3 to 5 MPa. It is more preferably 0.3 to 1.5 MPa, even more preferably 0.3 to 0.9 MPa, and particularly preferably 0.5 to 0.7 MPa.
The pressure resistance of the inlet header 10 can be adjusted by changing the material and thickness of the inlet header 10.
The pressure resistance of the inlet header 10 can be confirmed by the fact that there is no damage or deformation as a result of a pressure resistance test, and more specifically, it can be determined by the method described in Examples described later.

The bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment preferably has 50 to 500 bipolar elements 60, more preferably 70 to 300 bipolar elements 60, and more preferably 100 to 200 bipolar elements 60. It is further preferable to have a bipolar element 60 of.
As the number (logarithm) of bipolar elements 60 decreases, the influence of leakage current on gas purity is alleviated, but as the logarithm increases, it becomes difficult to uniformly distribute the electrolyte to each electrolytic cell 65. .
Furthermore, if the number of logarithms increases too much, it may become difficult to manufacture the electrolytic cell 50, and if a large number of bipolar elements 60 with poor manufacturing accuracy are stacked, the seal surface pressure tends to be uneven, and the electrolyte leakage and gas leakage easily occur.

Hereinafter, the constituent elements of the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment will be explained in detail.
Further, preferred embodiments for enhancing the effects of the present invention will also be described in detail below.

-Bulkhead-
The shape of the partition wall 1 in this 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 rectangular (square, rectangle, etc.) or circular (circle, ellipse, etc.), and the rectangle may have rounded corners.
In one embodiment, the partition wall 1 and the outer frame 3 may be integrated by welding or other methods. For example, the partition wall 1 has a flange portion ( An anode flange portion projecting to the anode 2a side and a cathode flange portion projecting to the cathode 2c side) may be provided, and the flange portion may be made a part of the outer frame 3.

Note that the partition wall 1 may normally be used so that a given direction D1 along the partition wall 1 is a vertical direction. Specifically, as shown in FIGS. 3 and 4, the partition wall 1 is When the shape is rectangular, the given direction D1 along the partition wall 1 may be used so as to be the same direction as the direction of one of the two pairs of opposing sides. In this specification, the vertical direction is also referred to as the electrolyte passing direction.

The material for the partition wall 1 is preferably a conductive material from the viewpoint of realizing a uniform supply of electric power, and from the viewpoint of alkali resistance and heat resistance, nickel, nickel alloy, mild steel, nickel plating on nickel alloy is preferable. Preferably.

-electrode-
In hydrogen production by alkaline water electrolysis of this embodiment, reducing energy consumption, specifically reducing electrolysis voltage, is a major issue. Since this electrolytic voltage largely depends on the electrodes 2, the performance of both electrodes 2 is important.

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

In order to achieve a low overvoltage, the requirements for the electrode 2 include high conductivity, high oxygen generation ability (or hydrogen generation ability), and high wettability of the electrolyte on the electrode 2 surface. Can be mentioned.

In addition to its low overvoltage, the electrode 2 for alkaline water electrolysis does not cause corrosion of the base material and catalyst layer of the electrode 2, drop-off of the catalyst layer, or damage to the electrolyte even when unstable current from renewable energy is used. One example of this is that dissolution, adhesion of contained substances to the diaphragm 4, etc. are less likely to occur.

The electrode 2 in this embodiment is preferably a porous body in order to increase the surface area used for electrolysis and to efficiently remove gas generated by electrolysis from the surface of the electrode 2. In particular, in the case of a zero-gap electrolytic cell, it is necessary to degas the gas generated from the back side of the surface in contact with the diaphragm 4, so the surface of the electrode 2 opposite to the surface in contact with the membrane must be penetrated. is preferred.

Examples of porous bodies include plain woven mesh, punched metal, expanded metal, and metal foam.

The electrode 2 in this embodiment may be the base material itself, or may have a catalyst layer with high reaction activity on the surface of the base material, but it is preferable that the electrode 2 has a catalyst layer with high reaction activity on the surface of the base material. .

The material of the base material is not particularly limited, but mild steel, stainless steel, nickel, and nickel-based alloys are preferable from the viewpoint of resistance to the usage environment.

The catalytic layer of the anode 2a is preferably one with high oxygen generation capacity, and nickel, cobalt, iron, platinum group elements, etc. can be used. In order to achieve the desired activity and durability, the catalytic layer can be formed as a simple metal, a compound such as an oxide, a composite oxide or alloy made of multiple metal elements, or a mixture of these. Organic substances such as polymers may be included to improve durability and adhesion to the substrate.

The catalyst layer of the cathode 2c preferably has a high hydrogen generation ability, and nickel, cobalt, iron, or platinum group elements can be used. In order to achieve desired activity and durability, these catalyst layers can be formed as a single metal, a compound such as an oxide, a composite oxide or alloy consisting of a plurality of metal elements, or a mixture thereof. An organic substance such as a polymeric material may be included in order to improve durability and adhesion to the base material.

Methods for forming the catalyst layer on the substrate include plating, thermal spraying such as plasma spraying, thermal decomposition in which a precursor layer solution is applied onto the substrate and then heated, and a catalyst material is mixed with a binder component. Examples of methods include a method of fixing the film on a base material, and a vacuum film forming method such as a sputtering method.

-Outer frame-
The shape of the outer frame 3 in this embodiment is not particularly limited as long as it can frame the partition wall 1, but it may have a shape that includes an inner surface along the direction perpendicular to the plane of the partition wall 1 over the outer extent of the partition wall 1. .
The shape of the outer frame 3 is not particularly limited, and may be determined as appropriate depending on the shape of the partition wall 1 in plan view.

The material for the outer frame 3 is preferably a conductive material, and from the viewpoint of alkali resistance and heat resistance, nickel, nickel alloy, mild steel, or nickel plated on a nickel alloy is preferable.

-diaphragm-
As the diaphragm 4 used in the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, an ion-permeable diaphragm 4 is used in order to conduct ions while separating generated hydrogen gas and oxygen gas. Ru. As the ion-permeable diaphragm 4, an ion exchange membrane having ion exchange ability and a porous membrane capable of permeating an electrolytic solution can be used. The ion-permeable diaphragm 4 preferably has low gas permeability, high ionic conductivity, low electronic conductivity, and high strength.

--Porous membrane--
The porous membrane has a plurality of fine through holes and has a structure that allows the electrolyte to permeate through the diaphragm 4 . Since ion conduction occurs when the electrolyte permeates into the porous membrane, control of the porous structure such as pore size, porosity, and hydrophilicity is extremely important. On the other hand, it is required that not only the electrolyte but also the generated gas pass through, that is, it must have gas barrier properties. Control of the pore structure is also important from this point of view.

Porous membranes have a plurality of fine through-holes, and include porous polymer membranes, porous inorganic membranes, woven fabrics, non-woven fabrics, and the like. These can be produced using known techniques.
Examples of methods for producing porous polymer membranes include a phase inversion method (microphase separation method), an extraction method, a stretching method, a wet gel stretching method, and the like.

The porous membrane preferably contains a polymer material and hydrophilic inorganic particles, and the presence of the hydrophilic inorganic particles can impart hydrophilicity to the porous membrane.

---Polymer materials---
Examples of polymeric materials include polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene/ethylene copolymer, and polyvinylidene fluoride. , polytetrafluoroethylene, perfluorosulfonic acid, perfluorocarboxylic acid, polyethylene, polypropylene, polyphenylene sulfide, polyparaphenylenebenzobisoxazole, polyketone, polyimide, polyetherimide, and the like. Among these, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, and polytetrafluoroethylene are preferable, and polysulfone is more preferable. These may be used alone or in combination of two or more.

The pore diameter of the porous membrane is preferably controlled in order to obtain appropriate membrane properties such as separation ability and strength. Furthermore, when used in alkaline water electrolysis, the pore diameter of the porous membrane may be controlled in order to prevent mixing of oxygen gas generated from the anode 2a and hydrogen gas generated from the cathode 2c, and to reduce voltage loss during electrolysis. preferable.
The larger the average pore diameter of the porous membrane, the larger the amount of permeation through the porous membrane per unit area. Particularly in electrolysis, the ion permeability of the porous membrane becomes better, and voltage loss tends to be reduced more easily. Furthermore, the larger the average pore diameter of the porous membrane, the smaller the surface area of contact with alkaline water, which tends to suppress the deterioration of the polymer.
On the other hand, the smaller the average pore diameter of the porous membrane, the higher the separation accuracy of the porous membrane, and the better the gas barrier properties of the porous membrane tend to be in electrolysis. Furthermore, when hydrophilic inorganic particles with a small particle size, which will be described later, are supported on a porous membrane, they can be firmly held without falling off. Thereby, the high retention ability of the hydrophilic inorganic particles can be imparted, and the effect can be maintained over a long period of time.

From this point of view, in the porous membrane of this embodiment, the average pore diameter is preferably in the range of 0.1 to 1.0 μm. If the porous membrane has a pore diameter within this range, it can have both excellent gas barrier properties and high ion permeability. Further, it is preferable that the pore diameter of the porous membrane is controlled within the temperature range in which it is actually used. Therefore, for example, when used as a diaphragm 4 for electrolysis in an environment of 90°C, it is preferable that the above-mentioned pore diameter range be satisfied at 90°C. Further, the porous membrane preferably has an average pore diameter of 0.1 to 0.5 μm, which is a range in which the diaphragm 4 for alkaline water electrolysis can exhibit better gas barrier properties and high ion permeability.

The average pore diameter of a porous membrane can be measured by the following method.
The average pore diameter of the porous membrane refers to the average water permeation pore diameter measured by the following method using an integrity tester (Sartorius Stedim Japan, "Sartocheck Junior BP-Plus"). First, a porous membrane including the core material is cut into a predetermined size, and this is used as a sample. Set this sample in any pressure-resistant container and fill the container with pure water. Next, the pressure container is held in a constant temperature bath set at a predetermined temperature, and measurement is started after the inside of the pressure container reaches the predetermined temperature. When measurement begins, the upper surface of the sample is pressurized with nitrogen, and the pressure and permeation flow rate when pure water permeates from the lower surface of the sample are recorded. The average water permeation pore diameter can be determined from the following Hagen-Poiseuille equation using the gradient between the pressure and the permeation flow rate when the pressure is between 10 kPa and 30 kPa.
Average permeable pore diameter (m) = {32ηLμ ₀ /(εP)} ^0.5
Here, η is the viscosity of water (Pa・s), L is the thickness of the porous membrane (m), μ ₀ is the apparent flow velocity, and μ ₀ (m/s) = flow rate (m ³ /s)/flow It is the road area (m ² ). Further, ε is the porosity, and P is the pressure (Pa).

The diaphragm 4 for alkaline water electrolysis is porous from the viewpoint of maintaining gas barrier properties, hydrophilicity, preventing reduction in ion permeability due to adhesion of air bubbles, and obtaining stable electrolytic performance (low voltage loss, etc.) over a long period of time. It is preferred to control the porosity of the membrane.
From the viewpoint of achieving both high levels of gas barrier properties and low voltage loss, the lower limit of the porosity of the porous membrane is preferably 30% or more, more preferably 35% or more, and 40% or more. More preferably. Further, the upper limit of the porosity is preferably 70% or less, more preferably 65% or less, and even more preferably 55% or less. If the porosity of the porous membrane is below the above upper limit, ions can easily permeate through the membrane, and voltage loss in the membrane can be suppressed.

The porosity of a porous membrane refers to the open porosity determined by the Archimedes method, and can be determined by the following formula.
Porosity P (%) = ρ / (1 + ρ) × 100
Here, ρ=(W3-W1)/(W3-W2), W1 is the dry mass of the porous membrane (g), W2 is the mass of the porous membrane in water (g), and W3 is the saturated mass of the porous membrane ( g).

As a method for measuring porosity, a porous membrane washed with pure water is cut into three pieces of 3 cm x 3 cm and used as measurement samples. First, W2 and W3 of the sample are measured. Thereafter, the porous membrane is left to dry for 12 hours or more in a dryer set at 50° C., and W1 is measured. Then, the porosity is determined from the values of W1, W2, and W3. The porosity is determined for the three samples, and the arithmetic mean value thereof is defined as the porosity P.

The thickness of the porous membrane is not particularly limited, but is preferably 100 to 700 μm, more preferably 100 to 600 μm, even more preferably 200 to 600 μm.
When the thickness of the porous membrane is equal to or greater than the above lower limit, it is less likely to be torn by puncture or the like, and short-circuits between the electrodes are less likely to occur. In addition, gas barrier properties are improved. Moreover, if it is below the above upper limit, voltage loss is unlikely to increase. Furthermore, the influence of variations in the thickness of the porous membrane is reduced.
Moreover, when the thickness of the diaphragm is 100 μm or more, it is difficult to tear due to puncture or the like, and short-circuit between the electrodes is difficult to occur. In addition, gas barrier properties are improved. If it is 600 μm or less, voltage loss is unlikely to increase. Furthermore, the influence of variations in the thickness of the porous membrane is reduced.
When the thickness of the porous membrane is 250 μm or more, even better gas barrier properties can be obtained, and the strength of the porous membrane against impact is further improved. From this viewpoint, the lower limit of the thickness of the porous membrane is more preferably 300 μm or more, still more preferably 350 μm or more, and even more preferably 400 μm or more. On the other hand, if the thickness of the porous membrane is 700 μm or less, ion permeability is less likely to be inhibited by the resistance of the electrolyte contained in the pores during operation, and even better ion permeability can be maintained. From this viewpoint, the upper limit of the thickness of the porous membrane is more preferably 600 μm or less, even more preferably 550 μm or less, and even more preferably 500 μm or less.

--- Hydrophilic inorganic particles ---
The porous membrane preferably contains hydrophilic inorganic particles in order to exhibit high ion permeability and high gas barrier properties. The hydrophilic inorganic particles may be attached to the surface of the porous membrane, or may be partially embedded in the polymeric material constituting the porous membrane. Furthermore, when the hydrophilic inorganic particles are encapsulated in the voids of the porous membrane, they become difficult to detach from the porous membrane, and the performance of the porous membrane can be maintained for a long time.

Examples of the hydrophilic inorganic particles include oxides or hydroxides of zirconium, bismuth, and cerium; oxides of elements of group IV of the periodic table; nitrides of elements of group IV of the periodic table; and nitrides of elements of group IV of the periodic table. At least one inorganic substance selected from the group consisting of carbides of group elements can be mentioned. Among these, from the viewpoint of chemical stability, oxides of zirconium, bismuth, and cerium, and oxides of Group IV elements of the periodic table are more preferred, oxides of zirconium, bismuth, and cerium are even more preferred, and zirconium oxide is more preferred. Even more preferred.

The hydrophilic inorganic particles preferably have a fine particle shape.

--Porous support--
When a porous membrane is used as the diaphragm 4, the porous membrane may be used together with a porous support. Preferably, the structure is such that the porous membrane includes a porous support, and more preferably, the structure is such that the porous membrane is laminated on both sides of the porous support. Alternatively, it may have a structure in which porous membranes are laminated symmetrically on both sides of a porous support.

Examples of the porous support include meshes, porous membranes, nonwoven fabrics, woven fabrics, composite fabrics containing nonwoven fabrics, and woven fabrics inherent in the nonwoven fabrics. These may be used alone or in combination of two or more. More preferable embodiments of the porous support include, for example, a mesh base material composed of monofilaments of polyphenylene sulfide, or a composite fabric containing a nonwoven fabric and a woven fabric inherent in the nonwoven fabric.

--Ion exchange membrane--
Ion exchange membranes include cation exchange membranes that selectively allow cations to pass through, and anion exchange membranes that selectively allow anions to pass through, and either of these membranes can be used.
The material of the ion exchange membrane is not particularly limited, and known materials can be used. For example, fluorine-containing resins and modified resins such as polystyrene/divinylbenzene copolymers can be suitably used. In particular, fluorine-containing ion exchange membranes are preferred because they have excellent heat resistance, chemical resistance, and the like.

Examples of the fluorine-containing ion-exchange membrane include those containing a fluorine-containing polymer that has the function of selectively permeating ions generated during electrolysis and has an ion exchange group. The fluorine-containing polymer having an ion-exchange group as used herein refers to a fluorine-containing polymer having an ion-exchange group or an ion-exchange group precursor that can become an ion-exchange group by hydrolysis. Examples include polymers that have a main chain of fluorinated hydrocarbon, have functional groups as pendant side chains that can be converted into ion exchange groups by hydrolysis, etc., and can be melt processed.

The molecular weight of the fluorine-containing copolymer is not particularly limited. It is preferably 0.05 to 50 (g/10 minutes), more preferably 0.1 to 30 (g/10 minutes).

Examples of the ion exchange groups that the ion exchange membrane has include cation exchange groups such as sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups, and anion exchange groups such as quaternary ammonium groups.

The ion exchange membrane can be provided with excellent ion exchange ability and hydrophilicity by adjusting the equivalent mass EW of the ion exchange groups. Furthermore, it can be controlled to have many smaller clusters (tiny portions in which ion exchange groups coordinate and/or adsorb water molecules), which tends to improve alkali resistance and ion selective permselectivity.
This equivalent mass EW can be measured by replacing the ion exchange membrane with salt and back titrating the solution with an alkali or acid solution. The equivalent mass EW can be adjusted by the copolymerization ratio of monomers as raw materials, selection of monomer species, etc.
The equivalent mass EW of the ion exchange membrane is preferably 300 or more from the viewpoint of hydrophilicity and water resistance of the membrane, and preferably 1300 or less from the viewpoint of hydrophilicity and ion exchange ability.

The thickness of the ion exchange membrane is not particularly limited, but from the standpoint of ion permeability and strength, a thickness in the range of 5 to 300 μm is preferable.

For the purpose of improving the hydrophilicity of the surface of the ion exchange membrane, surface treatment may be performed. Specifically, examples include a method of coating with hydrophilic inorganic particles such as zirconium oxide, and a method of providing fine irregularities on the surface.

From the viewpoint of membrane strength, it is preferable to use the ion exchange membrane together with a reinforcing material. The reinforcing material is not particularly limited, and examples include common nonwoven fabrics, woven fabrics, and porous membranes made of various materials. The porous membrane in this case is not particularly limited, but a PTFE membrane that has been stretched and made porous is preferred.

((Zero gap structure))
In the bipolar element 60 in the zero-gap cell, a spring, which is an elastic body, is arranged between the electrode 2 and the partition wall 1, and the electrode 2 is supported by this spring, as a means to reduce the distance between the electrodes. It is preferable. For example, in the first example, a spring made of a conductive material may be attached to the partition wall 1, and the electrode 2 may be attached to this spring. In the second example, a spring may be attached to the electrode rib attached to the partition wall 1, and the electrode 2 may be attached to the spring. In addition, when adopting a configuration using such an elastic body, the strength of the springs, the number of springs, the shape, etc., etc. may be adjusted as necessary to prevent uneven pressure between the electrode 2 and the diaphragm 4. There is a need to.

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

In this embodiment, the inlet header 10 and outlet header 11 of the bipolar electrolytic cell are arranged in an external header 10O type and an internal header 10I type, respectively, and the space occupied by the anode 2a and the cathode 2c is also It may be a space inside the chamber 5. Further, particularly when a gas-liquid separation box is provided, the space occupied by the gas-liquid separation box may also be a space inside the electrode chamber 5.

-rectifier-
In the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, a rectifier plate 6 (an anode rectifier plate 6a, a cathode rectifier plate 6c) is attached to the partition wall 1, and the rectifier plate 6 is physically connected to the electrode 2. Preferably. According to this configuration, the current plate 6 serves as a support for the electrode 2, and the zero gap structure Z can be easily maintained.
Here, the current plate 6 may be provided with the electrode 2, or the current collector 2r, the conductive elastic body 2e, and the electrode 2 may be provided in this order.
In the above-mentioned bipolar electrolytic cell 50 for alkaline water electrolysis, a structure is adopted in which the rectifying plate 6, the current collector 2r, the conductive elastic body 2e, and the electrode 2 are stacked in this order in the cathode chamber 5c, and the anode In the chamber 5a, a structure is adopted in which the rectifier plate 6 and the electrode 2 are stacked in this order.

In addition, in the bipolar electrolytic cell 50 for alkaline water electrolysis of the above-mentioned example, the structure of "straightening plate 6-current collector 2r-conductive elastic body 2e-electrode 2" is adopted in the cathode chamber 5c, and the anode chamber 5a employs the above-mentioned "straightening plate 6-electrode 2" structure, but the present invention is not limited to this, and the anode chamber 5a also employs the "straightening plate 6-current collector 2r-conductive elastic body" structure. 2e-electrode 2'' structure may be adopted.

It is preferable that the rectifying plate 6 (anode rectifying plate 6a, cathode rectifying plate 6c) not only has the role of supporting the anode 2a or the cathode 2c but also has the role of transmitting current from the partition wall 1 to the anode 2a or the cathode 2c.

In the bipolar electrolytic cell 50 for alkaline water electrolysis of the present embodiment, it is preferable that at least a part of the rectifying plate 6 is electrically conductive, and it is more preferable that the entire rectifying plate 6 is electrically conductive. According to this configuration, an increase in cell voltage due to electrode deflection can be suppressed.

As a material for the current plate 6, a conductive metal is generally used. For example, nickel-plated mild steel, stainless steel, nickel, etc. can be used.

The interval between adjacent anode rectifier plates 6a or the interval between adjacent cathode rectifier plates 6c is determined by taking into consideration electrolytic pressure, pressure difference between anode chamber 5a and cathode chamber 5c, and the like.

The length of the current plate 6 (anode current plate 6a, cathode current plate 6c) may be determined as appropriate depending on the size of the partition wall 1.
The height of the current plate 6 depends on the distance from the partition wall 1 to each flange, the thickness of the gasket 7, the thickness of the electrodes 2 (anode 2a, cathode 2c), the distance between the anode 2a and the cathode 2c, etc. may be determined as appropriate.
Further, the thickness of the current plate 6 may be 0.5 to 5 mm in consideration of cost, manufacturability, strength, etc., and a thickness of 1 to 2 mm is easily used, but is not particularly limited.

-gasket-
In the bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, it is preferable that the gasket 7 having the diaphragm 4 is sandwiched between the outer frames 3 that frame the partition 1 .
The gasket 7 is used to seal between the bipolar element 60 and the diaphragm 4 and between the bipolar element 60 against electrolyte and generated gas, and prevents electrolyte and generated gas from leaking out of the electrolytic cell. Gas mixing between the two electrode chambers can be prevented.

The general structure of the gasket 7 is a rectangular or annular shape in which the electrode surface is hollowed out to match the surface in contact with the frame of the element. The diaphragm 4 can be stacked between elements by sandwiching the diaphragm 4 between two such gaskets. Further, the gasket 7 includes a slit portion that can accommodate the diaphragm 4 so as to hold the diaphragm 4, and an opening that allows the accommodated diaphragm 4 to be exposed on both surfaces of the gasket 7. It is also preferable. Thereby, the gasket 7 has a structure in which the edge of the diaphragm 4 is accommodated in the slit portion and covers the end face of the edge of the diaphragm 4 . Therefore, leakage of the electrolytic solution and gas from the end face of the diaphragm 4 can be more reliably prevented.

The material of the gasket 7 is not particularly limited, and any known insulating rubber material, resin material, etc. can be selected.
Specific examples of rubber materials and resin materials include natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), and silicone rubber (SR). ), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), fluororubber (FR), isobutylene-isoprene rubber (IIR), urethane rubber (UR), chlorosulfonated polyethylene rubber (CSM), etc. Materials such as polytetrafluoroethylene (PTFE), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene/ethylene copolymer (ETFE), chlorotrifluoroethylene/ethylene copolymer (ECTFE), etc. Resin materials such as fluororesin materials, polyphenylene sulfide (PPS), polyethylene, polyimide, and polyacetal can be used. Among these, ethylene-propylene-diene rubber (EPDM) and fluororubber (FR) are particularly preferred from the viewpoint of elastic modulus and alkali resistance.

The gasket 7 may have a reinforcing material embedded therein. Thereby, when the gasket 7 is sandwiched and pressed between the frames during stacking, it is possible to suppress the gasket 7 from being crushed, and it is possible to easily prevent damage.
Such reinforcing materials can be made of known metal materials, resin materials, carbon materials, etc. Specifically, metals such as nickel and stainless steel, resins such as nylon, polypropylene, PVDF, PTFE, and PPS, carbon particles and carbon Examples include carbon materials such as fibers.

The size of the gasket 7 is not particularly limited and may be designed according to the dimensions of the electrode chamber 5 and the membrane, but it is preferable that the width is 10 to 40 mm.
In this case, if the gasket 7 has a slit portion, the size of the slit portion is preferably such that the internal dimensions of the slit are 0.5 to 5 mm larger in length and width than the size of the membrane.

The thickness of the gasket 7 is not particularly limited, and is designed depending on the material, elastic modulus, and cell area of the gasket 7. The preferred thickness range is preferably 1.0 to 10 mm, more preferably 3.0 to 10 mm.
Further, when the gasket 7 includes a slit portion, the opening width of the slit portion may be set to 0.5 to 1.0 times the thickness of the membrane.

The elastic modulus of the gasket 7 is not particularly limited, and is designed depending on the material of the electrode 2 and the cell area. The preferred elastic modulus range is more preferably 0.20 to 20 MPa in terms of tensile stress at 100% deformation, and more preferably 1.0 to 10 MPa from the viewpoint of sealing properties and cell strength during stacking. .
Note that the tensile stress can be measured in accordance with JIS K6251. For example, Autograph AG manufactured by Shimadzu Corporation may be used.

In particular, in this embodiment, the thickness of the gasket 7 is 3.0 to 10 mm, and the tensile stress at 100% deformation is 1.0 to 10 MPa, from the viewpoint of suppressing the increase in cell voltage due to electrode deflection. It is also preferable from the viewpoint of sealing properties and cell strength during stacking.

In this embodiment, it is preferable to cover the surface of the gasket 7 with an insulating resin sheet (for example, a fluororesin such as polytetrafluoroethylene). By doing this, the plurality of elements 60 are insulated from each other, so that the charge accumulated in each element 60 during the energization process (the process in which electrolytic solution is electrolyzed) is transferred during the stop process. It is possible to prevent the other elements 60 from being affected in the process (in which the electrolysis of the electrolytic solution is stopped).

-header-
The bipolar electrolytic cell 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 continue supplying an electrolytic solution containing enough raw materials to be consumed by electrolysis to the cathode chamber 5c and anode chamber 5a of each electrolytic cell 65. There is.

The electrolytic cell 65 is connected to an electrolytic solution supply pipe called an inlet header 10 that is common to the plurality of electrolytic cells 65 . Generally, the anode liquid distribution pipe is called an anode inlet header 10ai, and the cathode liquid distribution pipe is called a cathode inlet header 10ci. The electrolytic cell 65 is connected to each electrode liquid distribution pipe through a hose or the like.
Furthermore, the electrolytic cell 65 is connected to an electrolytic solution collection pipe called an outlet header 11 that is common to the plurality of electrolytic cells 65 . Generally, the anode liquid collection pipe is called an anode outlet header 11ao, and the cathode liquid collection pipe is called a cathode outlet header 11co.

The materials for the inlet header 10 and the outlet header 11 are not particularly limited, but it is necessary to adopt materials that can sufficiently withstand the corrosive nature of the electrolyte used and operating conditions such as pressure and temperature. The material of the header 10 may be iron, nickel, cobalt, PTFE, ETFE, PFA, polyvinyl chloride, polyethylene, or the like.

In this 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. This may vary depending on the arrangement of the outlet header 11.

In the bipolar electrolytic cell 50 for alkaline water electrolysis, the outlet header 11 is an internal header integrated with the bipolar electrolytic cell 50, and the anode outlet header 11Iao and the cathode outlet header 11Ico are located inside the partition wall 1 and/or It is provided in the upper part of the outer frame 3.
In the example shown in FIGS. 3 to 5, a part of the upper portion of the outer frame 3 at the edge of the partition wall 1 is provided with an anode outlet header 11Iao and a cathode outlet header 11Ico.

Further, in the bipolar electrolytic cell 50 for alkaline water electrolysis, the inlet header 11 is an external header independent of the bipolar electrolytic cell 50, and the anode inlet header 10Oai and the cathode inlet header 10Oci are the electrolytic cell. The electrolytic cell 65 is provided independently in a direction perpendicular to the current-carrying surface of the electrolytic cell 65 and running in parallel with the electrolytic cell 50 . The anode inlet header 10Oai and the cathode inlet header 10Oci are connected to each electrolytic cell 65 with a hose.
In the example shown in FIGS. 3 and 4, a tubular member is installed in the through hole for the inlet header 10 provided in the lower part of the outer frame 3 at the edge of the partition wall 1, and A shaped member is connected to the anode inlet header 10Oai and the cathode inlet header 10Oci.

-Gas-liquid separation box-
The bipolar electrolytic cell 50 may include a gas-liquid separation box for separating the electrolyte from the gas generated by electrolysis. The installation position of the gas-liquid separation box is not particularly limited, but it may be installed between the anode chamber 5a and the anode outlet header 11Iao or between the cathode chamber 5c and the cathode outlet header 11Ico.

The surface of the gas-liquid separation box may be coated with a coating material that is sufficiently resistant to the corrosivity of the electrolytic solution and operating conditions such as pressure and temperature. The coating material may be insulating for the purpose of increasing the electrical resistance of the leakage current circuit inside the electrolytic cell. EPDM, PTFE, ETFE, PFA, polyvinyl chloride, polyethylene, etc. may be used as the coating material.

(Electrolyzer for alkaline water electrolysis)
FIG. 6 shows an outline of the electrolyzer for alkaline water electrolysis of this embodiment.
The electrolyzer 70 for alkaline water electrolysis of this embodiment includes a bipolar electrolytic cell 50 for alkaline water electrolysis of this embodiment, a liquid feed pump 71 for circulating an electrolyte, and an electrolyte and hydrogen and/or oxygen. and a water replenisher 73 for replenishing water consumed by electrolysis.

According to the electrolyzer 70 for alkaline water electrolysis of this embodiment, the effects of the bipolar electrolytic cell for alkaline water electrolysis of this embodiment can be obtained.
In other words, according to this embodiment, the occurrence of leakage current is suppressed to prevent deterioration of gas purity, and the electrolytic cell can be made thinner and operated under pressure, so that it can be operated under variable power sources such as renewable energy. High energy conversion efficiency can be maintained over a long period of time.

Hereinafter, the constituent elements of the electrolyzer 70 for alkaline water electrolysis of this embodiment will be explained.

-Feed pump-
The liquid feeding pump 71 used in this embodiment is not particularly limited and may be determined as appropriate.

-Gas-liquid separation tank-
The gas-liquid separation tank 72 used in this embodiment includes a hydrogen separation tank 72h that separates an electrolytic solution and hydrogen gas, and an oxygen separation tank 72o that separates an electrolytic solution and oxygen gas.
The hydrogen separation tank 72h is connected to the cathode chamber 5c, and the oxygen separation tank 72o is connected to the anode chamber 5a.

The gas-liquid separation tank 72 of the alkaline water electrolysis system includes an oxygen separation tank 72o used for the anode chamber 5a and a hydrogen separation tank 72h used for the cathode chamber 5c.

The gas-liquid separation tank 72 for the anode chamber 5a separates the oxygen gas and electrolyte generated in the anode chamber 5a, and the gas-liquid separation tank 72 for the cathode chamber 5c separates the hydrogen gas and electrolyte generated in the cathode chamber 5c. Separate.

A mixture of electrolytic solution and generated gas discharged from the electrolytic cell 65 is made to flow into the gas-liquid separation tank 72. If gas-liquid separation is not performed appropriately, when the electrolyte in the cathode chamber 5c and the anode chamber 5a are mixed, oxygen gas and hydrogen gas will be mixed, resulting in a decrease in the purity of the gas. In the worst case, there is a risk of an explosive atmosphere forming.

The gas and electrolyte flowing into the gas-liquid separation tank 72 are separated into a gas phase in the upper layer of the tank and a liquid phase in the lower layer of the tank. The degree of gas-liquid separation is determined by the flux of the electrolyte in the gas-liquid separation tank 72, the floating speed of the generated gas bubbles, and the residence time in the gas-liquid separation tank 72.

After the gas has been separated, the electrolytic solution flows out from the outlet at the bottom of the tank and flows into the electrolytic cell 65 again, thereby forming a circulation path. The oxygen and hydrogen gas discharged from the discharge port above the tank both contain alkaline mist, so a mist separator or cooler is installed downstream of the discharge port to liquefy the excess mist and separate the gas and liquid. It is preferable to install a device that can be returned to the tank 72.

The gas-liquid separation tank 72 may be equipped with a liquid level gauge in order to ascertain the level of the electrolytic solution stored therein.

Moreover, it is preferable that the gas-liquid separation tank 72 includes a pressure release valve. This makes it possible to safely lower the pressure if it exceeds the design pressure, even if the pressure increases due to the gas generated during electrolysis.

The inlet to the gas-liquid separation tank 72 is preferably located above the electrolyte level in order to improve gas-liquid separation, but is not limited thereto.
In order to prevent a drop in the liquid level in the electrolytic cell when circulation is stopped, it is preferable that the electrolytic liquid level in the gas-liquid separation tank 72 is higher than the top surface of the electrolytic cell, but the present invention is not limited thereto.
Although it is preferable to provide a shutoff valve between the electrolytic cell 65 and the gas-liquid separation tank 72, the present invention is not limited thereto.

The material for the gas-liquid separation tank 72 is an alkali-resistant metal such as nickel. On the other hand, when a general-purpose metal such as iron is used as the tank housing material, the surface in contact with the electrolyte inside the tank may be coated with a fluorine-based resin, etc. The material of the separation tank 72 is not limited.

Considering the installation volume, the capacity of the gas-liquid separation tank 72 is preferably small, but if the capacity is too small, the pressure difference between the cathode 2c and the anode 2a may become large or the electrolytic current value may fluctuate. , since the liquid level in the tank fluctuates, it is necessary to take this fluctuation into account.
Similarly, if the height of the tank is low, it is likely to be affected by the above-mentioned fluctuations, so it is preferable to increase the height of the tank.

-Water supply device-
The water supply device 73 used in this embodiment is not particularly limited and may be determined as appropriate.
As the water, general tap water may be used, but in consideration of long-term operation, it is preferable to use ion exchange water, RO water, ultrapure water, or the like.

-others-
In addition to the bipolar electrolyzer 50, the gas-liquid separation tank 72, and the water supply device 73, the electrolyzer 70 for alkaline water electrolysis of this embodiment includes a rectifier 74, an oxygen concentration meter 75, a hydrogen concentration meter 76, and a flow meter 77. , a pressure gauge 78, a heat exchanger 79, and a pressure control valve 80.

Moreover, it is preferable that the electrolyzer 70 for alkaline water electrolysis of the present embodiment further includes a detector that detects the stoppage of the power supply and a controller that automatically stops the liquid pump when the power supply is stopped. . By providing a detector and a controller, it becomes possible to efficiently reduce the effects of self-discharge without manual operation even under a power source that fluctuates widely, such as renewable energy.

(Alkaline water electrolysis method)
The alkaline water electrolysis method of this embodiment can be implemented using the electrolyzer 70 for alkaline water electrolysis of this embodiment.
Preferred conditions for the method are described below.

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

In the alkaline water electrolysis method of this embodiment, the temperature of the electrolytic solution in the electrolytic cell 65 is preferably 80 to 130°C.
With the above temperature range, it is possible to effectively suppress deterioration of the members of the electrolyzer 70 such as the gasket 7 and the diaphragm 4 due to heat while maintaining high electrolysis efficiency.
The temperature of the electrolytic solution is more preferably 85 to 125°C, particularly preferably 90 to 115°C.

In the alkaline water electrolysis method of this embodiment, the current density applied to the electrolytic cell 65 is preferably 0.5 to 20 kA/m ² , more preferably 1 to 15 kA/m ² .
In particular, when using a variable power source, it is preferable to set the lower and upper limits of the current density to the above ranges.

In the alkaline water electrolysis method of this embodiment, the pressure inside the electrolytic cell 65 is preferably 0.1 to 10 MPa, more preferably 0.3 to 5 MPa, and 0.3 to 1.5 MPa. It is more preferably 0.3 to 0.9 MPa, even more preferably 0.5 to 0.7 MPa.

In this embodiment, for example, an electrolytic device 70 for alkaline water electrolysis having a configuration as shown in FIG. 6 can be manufactured using the components of the electrolytic device 70 for alkaline water electrolysis described above, but the present invention is not limited to this. It's not something you can do.

Moreover, in this embodiment, it is preferable to stop the liquid feeding pump when power supply to the bipolar electrolytic cell for alkaline water electrolysis is stopped. In a configuration in which the electrolyte is distributed from one circulation path to the cathode chamber and anode chamber of the electrolytic cell, stopping the liquid pump allows mixing of hydrogen and oxygen dissolved in the electrolyte and release of the mixed hydrogen and oxygen. can be prevented. This makes it possible to suppress deterioration of gas purity within the apparatus during shutdown.

Above, the bipolar electrolyzer for alkaline water electrolysis, the electrolyzer for alkaline water electrolysis, and the alkaline water electrolysis method according to the embodiments of the present invention have been exemplified with reference to the drawings. The type electrolyzer, the electrolyzer for alkaline water electrolysis, and the alkaline water electrolysis method are not limited to the above examples, and changes can be made to the above embodiments as appropriate.

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

The measurement methods and evaluation methods used in Examples and Comparative Examples will be explained below.

(Inlet header pressure resistance)
The pressure resistance (MPa) of the inlet header was confirmed by making the inlet header airtight, pressurizing it with liquid or gas, and evaluating that there was no damage, deformation, or leakage of the enclosed liquid or gas.
(Inlet leakage current and outlet leakage current)
The inlet leak current and outlet leak current were obtained by enclosing a part of the header with a clamp meter and measuring the current value (A) flowing through the header during electrolysis or while the electrolytic cell voltage remained. .
If it is difficult to measure with a clamp meter due to the structure, the potential difference V in the header is determined by measuring the potential with respect to the reference electrode in the header at two or more points in the stacking direction of the electrolytic cell (direction perpendicular to the partition wall 1). The value divided by the electrical resistance R of the electrolytic solution in the header was defined as the leakage current value.

(Oxygen concentration in hydrogen O ₂ /H ₂ )
The oxygen concentration in hydrogen (O ₂ /H ₂ (ppm by volume), which is an indicator of the purity of hydrogen gas generated by electrolysis, is measured by collecting a portion of the generated hydrogen gas and using a galvanic oxygen sensor, gas chromatograph, and thermal conductivity detection. The measurement was carried out using a device combined with a device (TCD).

(Hydrogen concentration in oxygen H ₂ /O ₂ )
A portion of the generated oxygen gas was sampled, and the hydrogen concentration in oxygen H ₂ /O ₂ (ppm by volume), which is an index of the purity of the oxygen gas generated by electrolysis, was measured using a catalytic combustion sensor.

[Example 1, 2]
As the electrolytic cell, a bipolar electrolytic cell 50 in which the number of bipolar elements 60 (11 zero-gap electrolytic cells 65, FIG. 2) shown in Table 1 were arranged as shown in FIG. 1 was used. Nickel (catalyst layer cobalt) was used as the anode 2a, and nickel (catalyst layer platinum/palladium) was used as the cathode 2c. Further, the electrolytic solution was a potassium hydroxide aqueous solution.
Regarding the header and the conduit, as shown in FIGS. 3 and 4, an anode liquid distribution pipe 20Oai and a cathode liquid distribution pipe 20Oci are provided outside the case of the electrolytic cell 50 for distributing the electrolyte. Ta. Further, hoses (anode inlet header 10Oai, cathode inlet header 10Oci) as inlet headers 10 for passing the electrolyte from these conduits 20 to the electrode chamber 5 were attached from the outside.
Here, as shown in FIGS. 3 and 4, both of the inlet headers 10 (anode inlet header 10Oai, cathode inlet header 10Oci) extend outward from below the partition wall 1 of the bipolar element 60. Placed. Moreover, as shown in FIGS. 3 and 4, both the anode liquid distribution pipe 20Oai and the cathode liquid distribution pipe 20Oci were arranged so as to extend in a direction perpendicular to the partition wall 1 of the bipolar element 60.
Further, as shown in FIGS. 3 to 5, the outlet headers 11 (anode outlet header 11Iao, cathode outlet header 11Ico) are arranged parallel to the two lateral sides of the partition wall 1 of the bipolar element 60. They were arranged so as to extend (extend perpendicularly to the upper and lower sides of the partition wall 1).
Further, as shown in FIGS. 3 to 5, both the anode liquid collection tube 20Iao and the cathode liquid collection tube 20Ico were arranged so as to extend in a direction perpendicular to the partition wall 1 of the bipolar element 60.
The material of the inlet header 10 was PFA, and the material of the anode liquid distribution pipe 20Oai, the cathode liquid distribution pipe 20Oci, the outlet header 11, the anode liquid collection pipe 20Iao, and the cathode liquid collection pipe 20Ico was nickel.

Electrolyte flows into the anode chamber 5a and cathode chamber 5c from the inlet hoses of the anode chamber 5a and cathode chamber 5c, and the electrolyte and generated gas flow from the anode outlet header 11Iao and cathode outlet header 11Ico of the anode chamber 5a and cathode chamber 5c. The structure is such that the liquid flows out of the electrolytic cell 50.
The electrolytic solution was flowed into the cathode chamber 5c via the cathode inlet header 10Oci, and from the cathode chamber 5c to the outside of the electrolytic cell 50 via the cathode outlet header 11Ico. Further, the electrolytic solution was flowed into the anode chamber 5a via the anode inlet header 10Oai, and from the anode chamber 5a to the outside of the electrolytic cell 50 via the anode outlet header 11Iao. The electrolyte flowed vertically from below to above and rose along the electrode surface.
In the cathode chamber 5c, hydrogen gas is generated by electrolysis, and in the anode chamber 5a, oxygen gas is generated by electrolysis. Therefore, a multiphase flow of electrolyte and hydrogen gas occurs in the cathode outlet header 11Ico, and the electrolyte and hydrogen gas flow in the anode outlet header 11Iao. This resulted in a multiphase flow of gas and oxygen gas.

The area S1 of the electrodes (anode 5a and cathode 5c) attached to the bipolar element 60, the cross-sectional area S2i of the flow path of the inlet header 10 (anode inlet header 10Oai, cathode inlet header 10Oci), the outlet header 11 (anode outlet header 11Iao) , the cross-sectional area S2o of the channel of the cathode outlet header 11Ico), the length L2i of the channel of the inlet header 10, the length L2o of the channel of the outlet header 11, and the thickness d of the electrolytic cell 65 are shown in Table 1, respectively. adjusted to the value.

As shown in Figure 6, the liquid pump circulates the anode chamber, the oxygen separation tank (gas-liquid separation tank for the anode), the anode chamber, and the cathode chamber, the hydrogen separation tank (gas-liquid separation tank for the cathode), The cathode chamber was circulated.
A current of 6 kA/m ² was applied to the area S1 of each cathode and anode from the rectifier to the bipolar electrolytic cell.
The measurement results are shown in Table 1.

[Comparative Examples 1 and 2]
A bipolar electrolytic cell and an electrolytic device for alkaline water electrolysis were produced in the same manner as in the example except that the inlet header 10 and the outlet header 11 were both of internal header type.
The inlet header 10 (anode inlet header 10Iai, cathode inlet header 10Ici) and the outlet header 11 (anode outlet header 11Iao, cathode outlet header 11Ico) are connected to the two lateral sides of the partition wall 1 of the bipolar element 60. The partition walls 1 were arranged so as to extend parallel to each other (orthogonally to the upper and lower sides of the partition wall 1).
Further, all of the conduits 20 (anode liquid distribution pipe 20Iai, cathode liquid distribution pipe 20Ici, anode liquid collection pipe 20Iao, and cathode liquid collection pipe 20Ico) are arranged in a direction perpendicular to the partition wall 1 of the bipolar element 60. It was arranged so that it extended to .
Further, the inlet header 10 and the outlet header 11 are provided to face each other across the center of the electrode chamber 5 in the electrode chamber 5, which is rectangular in plan view, and the anode inlet header 10Iai and the cathode inlet of the anode chamber 5a and the cathode chamber 5c are provided. The electrolyte flows into the anode chamber 5a and the cathode chamber 5c from the header 10Ici, and the electrolyte and generated gas flow out of the electrolytic cell 50 from the anode outlet header 11Iao and cathode outlet header 11Ico of the anode chamber 5a and cathode chamber 5c. Structure.
The electrolytic solution was flowed into the cathode chamber 5c via the cathode inlet header 10Ici, and from the cathode chamber 5c to the outside of the electrolytic cell 50 via the cathode outlet header 11Ico. Further, the electrolytic solution was flowed into the anode chamber 5a via the anode inlet header 10Iai, and from the anode chamber 5a to the outside of the electrolytic cell 50 via the anode outlet header 11Iao. The electrolyte flowed vertically from below to above and rose along the electrode surface.
In the cathode chamber 5c, hydrogen gas is generated by electrolysis, and in the anode chamber 5a, oxygen gas is generated by electrolysis. Therefore, a multiphase flow of electrolyte and hydrogen gas occurs in the cathode outlet header 11Ico, and the electrolyte and hydrogen gas flow in the anode outlet header 11Iao. This resulted in a multiphase flow of gas and oxygen gas.

The area S1 of the electrodes (anode 5a and cathode 5c) attached to the bipolar element 60, the cross-sectional area S2i of the flow path of the inlet header 10 (anode inlet header 10Iai, cathode inlet header 10Ici), the outlet header 11 (anode outlet header 11Iao) , the cross-sectional area S2o of the channel of the cathode outlet header 11Ico), the length L2i of the channel of the inlet header 10, the length L2o of the channel of the outlet header 11, and the thickness d of the electrolytic cell 65 are shown in Table 1, respectively. adjusted to the value.
The measurement results are shown in Table 1.

[Comparative Examples 3 to 5]
A bipolar electrolytic cell and an electrolytic device for alkaline water electrolysis were produced in the same manner as in the example except that the inlet header 10 and the outlet header 11 were both external header types.
Conduits 20 for distributing and collecting electrolyte (anode liquid distribution pipe 20Oai, cathode liquid distribution pipe 20Oci, anode liquid collection pipe 20Oao, cathode A liquid collection pipe 20Oco) was provided. Furthermore, in this electrolytic cell 50, hoses (anode inlet header 10Oai, cathode inlet header 10Oci, anode outlet header 11Oao, cathode outlet Header 11Oco) was attached from the outside.
Here, both the inlet header 10 and the outlet header 11 (anode inlet header 10Oai, cathode inlet header 10Oci, anode outlet header 11Oao, cathode outlet header 11Oco) are directed outward from the side of the partition wall 1 of the bipolar element 60. It was arranged so that it extended to . In addition, all of the conduits 20 (anode liquid distribution pipe 20Oai, cathode liquid distribution pipe 20Oci, anode liquid collection pipe 20Oao, and cathode liquid collection pipe 20Oco) are arranged in a direction perpendicular to the partition wall 1 of the bipolar element 60. It was arranged so that it extended to .

Further, an inlet hose and an outlet hose are provided to face each other across the center of the electrode chamber 5 in the electrode chamber 5, which is rectangular in plan view. The electrolytic solution flows into the chamber 5c, and the electrolytic solution and generated gas flow out of the electrolytic cell 50 from the outlet hoses of the anode chamber 5a and the cathode chamber 5c.
The electrolytic solution was flowed into the cathode chamber 5c via the cathode inlet header 10Oci, and from the cathode chamber 5c to the outside of the electrolytic cell 50 via the cathode outlet header 11Oco. Further, the electrolytic solution was flowed into the anode chamber 5a via the anode inlet header 10Oai, and from the anode chamber 5a to the outside of the electrolytic cell 50 via the anode outlet header 11Oao. The electrolyte flowed vertically from below to above and rose along the electrode surface.
In the cathode chamber 5c, hydrogen gas is generated by electrolysis, and in the anode chamber 5a, oxygen gas is generated by electrolysis. Therefore, a multiphase flow of electrolyte and hydrogen gas occurs in the cathode outlet header 11Oco, and the electrolyte flows in the anode outlet header 11Oao. This resulted in a multiphase flow of gas and oxygen gas.

Area S1 of the electrodes (anode 5a and cathode 5c) attached to the bipolar element 60, cross-sectional area S2i of the flow path of the inlet header 10 (anode inlet header 10Oai, cathode inlet header 10Oci), outlet header 11 (anode outlet header 11Oao) , the cross-sectional area S2o of the channel of the cathode outlet header 11Oco), the length L2i of the channel of the inlet header 10, the length L2o of the channel of the outlet header 11, and the thickness d of the electrolytic cell 65 are shown in Table 1, respectively. adjusted to the value.
The measurement results are shown in Table 1.

In Examples 1 and 2, since the inlet header was an external header, compared to Comparative Examples 1 and 2, the leakage current of the inlet header could be significantly suppressed, and the gas purity was improved.
Furthermore, in Examples 1 and 2, since the outlet header was an internal header, the withstand voltage of the inlet header (withstand voltage of the electrolyzer) was improved compared to Comparative Examples 3 to 5.

According to the bipolar electrolyzer for alkaline water electrolysis, the bipolar electrolyzer for alkaline water electrolysis, and the alkaline water electrolysis method of the present invention, the occurrence of leakage current is suppressed, the gas purity is good, and the electrolytic cell is thin. Since it is possible to operate under reduced pressure and pressure, stable operation over a wide output range and highly efficient electrolysis are possible even when operating under fluctuating power sources such as renewable energy.

1 Partition wall 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 Current plate 6a Anode current plate (anode rib)
6c Cathode rectifier plate (cathode rib)
7 Gasket 10, 11 Header 10O External header 10Oai 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)
11I Internal header 11Iai Anode inlet header 11Iao Anode outlet header 11Ici Cathode inlet header 11Ico Cathode outlet header 20 Conduit 20Oai, 20Iai Anode liquid distribution pipe 20Oao, 20Iao Anode liquid collection tube 20Oci, 20Ici Cathode liquid distribution pipe 20Oco, 20I co for cathode Liquid collecting pipe 50 Bi-polar electrolytic cell 51g Fast head, loose head 51i Insulating plate 51a Anode terminal element 51c Cathode terminal element 51r Tie rod 60 Bi-polar element 65 Electrolytic cell 70 Electrolyzer 71 Liquid pump 72 Gas-liquid separation tank 72h Hydrogen Separation tank 72o Oxygen separation tank 73 Water supply device 74 Rectifier 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve D1 Given direction along the partition wall (electrolyte passage direction)
S1 Area of conductive surface of bipolar element S2i Cross-sectional area of inlet header flow path S2o Cross-sectional area of outlet header flow path L2i Length of inlet header flow path L2o Length of outlet header flow path Z Zero gap structure d Thickness of electrolytic cell

Claims (15)

Comprising an anode terminal element and a cathode terminal element,
A plurality of bipolar elements are provided between the anode terminal element and the cathode terminal element, each of which includes an anode, a cathode, a partition separating the anode and the cathode, and an outer frame that frames the partition. are superimposed across the
an inlet header that communicates with an electrode chamber defined by the partition wall, the outer frame, and the partition film on the outside of the outer frame; and an entrance header that communicates with the electrode chamber defined by the partition wall, the outer frame, and the partition film; and an outlet header communicating with an electrode chamber defined by the diaphragm and the diaphragm. The area of the conductive surface of the bipolar element is S1, the cross-sectional area of the flow path of the inlet header is S2i, the cross-sectional area of the flow path of the outlet header is S2o, the length of the flow path of the inlet header is L2i, and the cross-sectional area of the flow path of the inlet header is S2o. According to claim 1, where the length of the flow path of the outlet header is L2o, ((S2i/S1)/L2i)/((S2o/S1)/L2o) is 0.0001 to 0.5. A bipolar electrolyzer for alkaline water electrolysis. The bipolar electrolytic cell for alkaline water electrolysis according to claim 1 or 2, having 50 to 500 bipolar elements. The bipolar electrolytic cell for alkaline water electrolysis according to claim 2 , wherein the S1 is 0.1 to 10 m ² . The bipolar electrolytic cell for alkaline water electrolysis according to any one of claims 1 to 4, wherein the electrolytic cell has a thickness d of 5 to 100 mm.
Here, the thickness d of the electrolytic cell is defined as the distance between the partition walls of two adjacent bipolar elements in the direction perpendicular to the partition walls, and the distance between the partition walls of the adjacent bipolar elements and the anode terminal element. It means the distance between the partition wall in the direction perpendicular to the partition wall, or the distance between the partition wall of the adjacent bipolar element and the partition wall of the cathode terminal element in the direction perpendicular to the partition wall. The bipolar electrolytic cell for alkaline water electrolysis according to any one of claims 1 to 5, wherein the inlet header has a withstand pressure of 0.1 to 10 MPa. The bipolar electrolytic cell for alkaline water electrolysis according to any one of claims 1 to 6, wherein at least a portion of the inlet header is made of a flexible material. The bipolar electrolytic cell for alkaline water electrolysis according to any one of claims 1 to 7, wherein at least a portion of the inlet header is insulating. The bipolar electrolytic cell for alkaline water electrolysis according to claim 1, further comprising an electrically insulating layer between the inlet header and the outer frame. The bipolar electrolytic cell for alkaline water electrolysis according to claim 9, wherein the electrical insulating layer has a resistance value of 0.1 MΩ or more. The bipolar electrolyzer for alkaline water electrolysis according to any one of claims 1 to 10, wherein the outlet header includes at least one selected from the group consisting of nickel, resin, and resin-coated metal. Tank. A bipolar electrolytic cell for alkaline water electrolysis according to any one of claims 1 to 11,
A liquid pump for circulating the electrolyte,
a gas-liquid separation tank that separates the electrolyte from hydrogen and/or oxygen;
A bipolar electrolyzer for alkaline water electrolysis, comprising a water replenisher for replenishing water. 13. The electrolyzer according to claim 12, further comprising a detector that detects a stop in the power supply when the power supply to the bipolar electrolyzer for alkaline water electrolysis is stopped, and a controller that automatically stops the liquid pump. Bipolar electrolyzer for alkaline water electrolysis. An alkaline water electrolysis method, characterized in that the liquid feeding pump is stopped when power supply to the electrolyzer for alkaline water electrolysis according to claim 12 or 13 is stopped. When power supply to the electrolyzer for alkaline water electrolysis according to claim 12 or 13 is stopped, the liquid level of the electrolytic solution is controlled to be lower than the communication port to the electrode chamber of the outlet header, Alkaline water electrolysis method.

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