JP2000144467A - Electrolytic cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic cell by which the interelectrode distance and bath voltage are decreased, and an ion-exchange membrane is not damaged. SOLUTION: A movable electrode connecting an electrode 4 and a rib 5 or the electrode 4 and a partition wall through a bent leaf spring member 2 is provided in an electrolytic cell. In this case, when the length between the leaf spring bend part 3 and the rib and a leaf spring connection part or between the partition wall and the leaf spring connection part is expressed by L2 and the length between the bend part and the electrode and leaf spring connection part by L1, L1/L2=0.2 to 0.9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic cell using an ion exchange membrane method, and more particularly, to an electrolytic cell that reduces the distance between electrodes to reduce the electrolytic voltage.

[0002]

2. Description of the Related Art An ion-exchange membrane electrolytic cell is widely used for the production of salt by electrodialysis of seawater and the production of caustic soda and chlorine by electrolysis of salt. Among these, taking a chlor-alkali salt electrolysis method for obtaining caustic soda and chlorine by electrolysis of salt as an example, as shown in FIG. 7, a cathode 12 and an anode 14 are provided with an ion exchange membrane 11 interposed therebetween, and a cathode 12 and an anode 14 are provided. A cathode rib 13 and a partition wall 6 are provided on the side of
Is provided with an anode rib 15 and a partition 6.
In the electrolytic cell, a very large current of usually 3 to 5 kA / m ² is supplied between the anode and the cathode with the ion exchange membrane interposed therebetween to electrolyze the salt solution.

One of the functions required of an electrolytic cell using an ion-exchange membrane method is to reduce the power consumption of electrolysis consumed by electrolysis. For this purpose, it is necessary to reduce the electrolysis voltage as much as possible. Electrolysis voltage mainly depends on electrode material,
It depends on the electric resistance of the ion exchange membrane, the structural resistance of the electrolytic cell, the distance between the anode and the cathode, and the like. Of these, various proposals have been made so far, particularly regarding the distance between the electrodes, which greatly contributes to the reduction of the electrolytic voltage.

[0004] In order to reduce the electrolysis voltage, it is desirable to minimize the distance between the electrodes with the ion exchange membrane interposed therebetween. However, the manufacturing accuracy of both cathode and anode electrodes,
The average distance between the electrodes, which does not cause damage to the ion exchange membrane installed between the anode and the cathode due to the limit of the assembly accuracy of the electrolytic chamber frame and the thermal deformation distortion caused by heating during operation, is 2 mm. Usually, it is ３3 mm or more. Therefore, if the average interelectrode distance is particularly reduced to 2 mm or less in order to reduce the electrolysis voltage, the electrodes are locally pressed against the ion exchange membrane, and the ion exchange membrane is locally crushed or the electrodes are rubbed with the ion exchange membrane. In many cases, damage such as cuts and pinholes is caused on the ion exchange membrane, and the operation becomes impossible in many cases. For this reason, the electrode and the ion exchange membrane are substantially brought into contact with each other, or the electrode and the rib of the electrolytic cell or the electrode and the partition are joined by a leaf spring member in order to keep the electrode at a very short distance. A method has been proposed. For example, as shown in JP-A-5-306484, a method of connecting an electrode and a partition or rib of an electrolytic cell with a comb-shaped leaf spring member, or as shown in JP-A-58-37183, A method of forming a flat flexible pressing member having a tip portion that is pierced and bent outward,
As disclosed in Japanese Patent Publication No. 62-3236, there has been proposed a method of supporting a flexible porous electrode with a conductive support such as a leaf spring.

[0005] When the electrode and the ion exchange membrane are brought into contact with each other using such a leaf spring member, the ion exchange membrane is not pressed in the vertical direction by the elastic effect of the leaf spring member. Although it is not easily damaged, the electrode is displaced not only vertically but also horizontally with respect to the membrane, so that the electrode and the ion exchange membrane are rubbed. Problems such as critical defects, such as the formation of through holes, or damage to the ion exchange membrane surface or the core material of the ion exchange membrane, shortening the life of the ion exchange membrane. there were.

[0006]

SUMMARY OF THE INVENTION The present invention reduces the electrolysis voltage without causing damage to the ion exchange membrane even when the distance between the electrodes is shortened and the electrodes are substantially brought into contact with the ion exchange membrane. An object of the present invention is to provide an electrolytic cell that can be used.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an electrolytic cell provided with a movable electrode for connecting between an electrode and a rib or between an electrode and a partition by a bent leaf spring member. When the length from the bent portion to the electrode and the leaf spring connection portion is L1 and the length from the bent portion to the electrode and the leaf spring connection portion is L2, the value of L1 / L2 is 0.2. The present invention relates to an electrolytic cell having an average electrode-to-electrode distance of 2 mm or less.

[0008] By setting the value of L1 / L2 within the above range,
When the electrode and the ion exchange membrane are pressed, the electrode is displaced only in the pressing direction (vertical direction) against the ion exchange membrane,
Horizontal displacement is substantially eliminated, and damage to the ion exchange membrane due to rubbing between the electrode and the ion exchange membrane can be prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a part of an electrolytic cell connected by a leaf spring member having a bent portion between an electrode and a rib by the method of the present invention. The electrode 4 and the rib 5 are connected by the leaf spring 2. FIG. 2 is a cross-sectional view of a part of the electrolytic cell of the present invention. FIG. 3 is a sectional view showing an embodiment of the electrolytic cell of the present invention.
Are directly connected by a leaf spring 2. For example, when a leaf spring is provided on the cathode side, current flows from the electrode (cathode) 4 through the leaf spring 2 to the partition 6.

FIG. 4 is a sectional view of a leaf spring member, in which the leaf spring is bent at a bending angle θ. The length from the leaf spring bent portion 3 to the rib and the leaf spring connecting portion 8 or the partition and the leaf spring connecting portion 9 is L2, and the length from the bent portion 3 to the electrode and the leaf spring connecting portion 7 is L2.
Assuming that the length of L1 / L2 is 0.2,
It is preferably set to a range of 0.9, and more preferably set to a range of 0.4 to 0.6. Most preferably, by setting the value of L1 / L2 to 0.53, the horizontal displacement of the electrode with respect to the ion exchange membrane can be completely eliminated in this case.

By setting the value of L1 / L2 within the above range,
Even when the electrode and the ion exchange membrane are pressed, displacement of the electrode in the horizontal direction with respect to the ion exchange membrane can be substantially eliminated, and damage to the ion exchange membrane due to rubbing between the electrode and the ion exchange membrane can be prevented.

The thickness of the leaf spring member used in the present invention is determined from the viewpoint of minimizing the electric resistance loss when an electric current passes through the leaf spring member and securing the elastic effect of the leaf spring member. The thickness is preferably set to 0.05 to 2 mm, more preferably 0.1 to 0.7 mm. Further, a length L1 from the electrode and the leaf spring connecting portion 7 to the leaf spring bent portion 3 and a length L from the bent portion 3 to the rib and the leaf spring connecting portion 8 or from the partition wall to the leaf spring connecting portion 9 are shown.
2 is preferably 10 to 200 mm, more preferably 20 to 100 mm, from the viewpoint of reducing the electric resistance loss of the leaf spring member and securing the elasticity effect of the leaf spring member. It is good to be in the range.

The leaf spring member used in the present invention is not limited to a non-perforated flat plate as shown in FIG. 1, but is provided with a plurality of holes as shown in FIG. 5 or as shown in FIG. It may be an expanded metal, or may be a perforated plate having a circular or square hole formed by punching. By providing the leaf spring member with the opening as described above, it is possible to secure the inflow and outflow of liquid between adjacent chambers partitioned by the leaf spring member.

The contact pressure when the electrode is contacted with the ion exchange membrane, is necessary to maintain the level that does not damage the ion exchange membrane, an apparent electrode area reference 10 × 10 ³ g /
cm ² or less, preferably 100 g / cm ²
It is better to do the following. By setting the length L1 + L2 of the leaf spring member and the thickness of the leaf spring member within the above ranges and selecting a combination of the length and the thickness of the leaf spring member, it is possible to cope with such a condition of a small contact pressure. it can.

In the electrolytic cell of the present invention, the electrode connecting the leaf spring member may be an anode, a cathode, or both. Generally, in an electrolytic cell using an ion exchange membrane method, the pressure on the cathode chamber side is kept higher than that on the anode chamber side,
Since the ion exchange membrane is pressed against the anode side by this pressure difference, when the leaf spring member is connected to only one of the electrodes, it is preferable to connect it to the cathode side.

As the cathode shape used in the present electrolytic cell, an expanded metal is used. However, the shape of the cathode is not limited to the expanded metal, and it can also be applied to a punched metal having a hole such as a circular or square punched out or a wire mesh. . When an expanded metal is used, it is preferable to use a rolled and smoothed shape in order to prevent damage to the ion exchange membrane.

As the anode, an expanded metal is used as in the case of the cathode. However, the shape of the anode is not limited to the expanded metal. The invention can also be applied to a punched metal having a circular or square hole and a wire mesh. When an expanded metal is used, it is preferable to use a rolled and smoothed shape in order to prevent damage to the ion exchange membrane.

Next, it is desirable that the thickness of the electrode base material be as thin as possible so as to enhance flexibility and easily follow local elastic deformation of the leaf spring. In order to follow the deformation due to more local contact, the thickness of the electrode base material should be 0.1 to 1 m.
m, preferably in the range of 0.1 to 0.7 mm.

[0020]

EXAMPLES Hereinafter, the electrolytic cell of the present invention will be described with reference to examples.

Example 1 An electrode element having an electrolysis area of 1.2 m × 2.4 m was manufactured and an electrolyzer was assembled. The anode is made of titanium, and a roll of rolled and smoothed expanded metal coated with a coating solution composed of ruthenium, iridium, and titanium is used, and a titanium rib (wall thickness: 1.5 mm) is used.
Was fixed by electrical resistance spot welding. The rib interval was set to 95 mm. The cathode was made of nickel, and an active cathode in which a 0.5 mm-thick expanded metal rolled with a roll and smoothed and coated with a powder mainly containing nickel oxide by thermal spraying was used. As shown in the embodiment of FIG. 3, the cathode and the cathode chamber partition were joined by electric resistance spot welding with a leaf spring member made of nickel. The thickness of the leaf spring is 0.2 mm, the length from the cathode / leaf spring connection to the leaf spring bend is 17 mm, and the length from the bend to the cathode chamber partition / leaf spring connection is 32 mm, ie, the plate The spring total length was 49 mm, and the leaf spring bending angle was 59 degrees. In the leaf spring, holes having a diameter of 10 mm were provided at a pitch of 50 mm between the bent portion of the leaf spring and the joint between the partition and the leaf spring. The pressure in the cathode chamber was maintained 30 cm higher than the pressure in the anode chamber, and the anode and the ion exchange membrane were in close contact with each other. The cathode and the ion exchange membrane were also in close contact with each other, and the distance between the electrodes was 0 mm. Ion exchange membrane is Aciplex F420 of Asahi Kasei Corporation
3 was used. Electrolysis temperature 90 ° C, caustic soda concentration 3
Electrolysis was performed under the conditions of 2% and a current density of 4.0 kA / m ² . Electrolysis voltage as a result of performing electrolysis for 14 days is
2.940V. After the electrolysis was completed, the electrolytic cell was disassembled and the ion exchange membrane was observed. As a result, no damage was observed.

Comparative Example 1 Example 1 was repeated except that only the distance between the electrodes was 2 mm.
An electrolytic cell was constructed under the same conditions as described above. The electrolysis voltage as a result of performing electrolysis for 14 days was 2.990 V, and the voltage of 50 mV was higher than that in Example 1.

COMPARATIVE EXAMPLE 2 The cathode and the rib, and the rib and the cathode chamber partition were connected and fixed by electric resistance spot welding using a nickel rib (thickness: 1.5 mm) without using a leaf spring as the cathode side configuration. . The average distance between the ion-exchange membrane and the cathode was 0.5 mm, and the other conditions were the same as in Example 1 to form an electrolytic cell. Immediately after the start of electrolysis, it was found that the ion exchange membrane had a pinhole, and the electrolysis was stopped.

[0024]

According to the present invention, the length from the bent portion of the leaf spring to the connecting portion between the rib and the leaf spring or between the partition and the leaf spring is L.
2. The length from the bent portion to the electrode and leaf spring connection portion is L1.
The electrolytic cell is characterized in that the value of L1 / L2 is in the range of 0.2 to 0.9 when the electrode is pressed against the ion exchange membrane even when the electrode is pressed against the ion exchange membrane. Since the displacement in the direction can be substantially eliminated, it is possible to reduce the distance between the electrodes and reduce the electrolysis voltage without damaging the ion exchange membrane due to rubbing between the electrodes and the ion exchange membrane.

[Brief description of the drawings]

FIG. 1 is a perspective view of a part of an electrode mounting portion of an electrolytic cell in which an electrode and a rib are bent by a leaf spring member bent by the method of the present invention.

FIG. 2 is a cross-sectional view of a part of an electrode mounting portion of the electrolytic cell of the present invention.

FIG. 3 is a cross-sectional view showing a part of an electrode mounting portion showing one embodiment of the electrolytic cell of the present invention.

FIG. 4 is a sectional view of a leaf spring member.

FIG. 5 is a specific example of a leaf spring member used in the electrolytic cell of the present invention, and is a perspective view of a leaf spring provided with a plurality of holes.

FIG. 6 is a specific example of a leaf spring member used in the electrolytic cell of the present invention, and is a perspective view of a leaf spring made of expanded metal.

FIG. 7 is an explanatory view of a conventional ion exchange method electrolytic cell.

[Explanation of symbols]

 1: Electrolyte cell pole room 2: Leaf spring 3: Leaf spring bent part 4: Electrode 5: Rib 6: Partition wall 7: Electrode-leaf spring coupling part 8: Rib-leaf spring coupling part 9: Partition-leaf spring coupling part 10 : Leaf spring bending angle 11: ion exchange membrane 12: cathode 13: cathode rib 14: anode 15: anode rib

Claims (2)

[Claims] In an electrolytic cell provided with a movable electrode for connecting between an electrode and a rib or between an electrode and a partition by a bent leaf spring member, a rib and a leaf spring connection portion or a partition are formed from a bent portion of the leaf spring. When the length from the bent portion to the electrode and the leaf spring connecting portion is L1, the value of L1 / L2 is in the range of 0.2 to 0.9. Electrolyzer characterized by that 2. The electrolytic cell according to claim 1, wherein the average distance between the electrodes is 2 mm or less.