JPS5927393B2 - Electrode and electrolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific embodiment of an electrode for electrolyzing a solution to be electrolyzed and a method for electrolyzing a solution to be electrolyzed using the electrode.

Conventionally, a solution to be electrolyzed, such as an alkali metal halide solution, is electrolyzed using an electrolytic cell in which a diaphragm is placed between a cathode and an anode and is divided into an anode chamber and a cathode chamber, and... halogenated gas and alkali metal hydroxide are generated. It is a known technology to manufacture.

In particular, electrolysis of aqueous sodium chloride solutions should be carried out in large-scale industrial facilities, since the resulting chlorine and caustic soda are of great industrial importance. Until now, there have been two methods for electrolyzing aqueous alkali chloride solutions: the diaphragm method and the mercury method.
At present, due to the toxicity of mercury and pollution regulations, among the diaphragm methods, diaphragm methods using ion exchange membranes are being developed and adopted.

In this method, even the longest one must be operated under a high electrolytic voltage of 4.0 or more. For this reason, the electrolytic power cost accounts for a large proportion;
How to lower the electrolytic voltage and maintain high current efficiency remains a question for the future. There are various possible causes for the increase in electrolytic voltage in this method.

One is due to deposits on the surface of the diaphragm, and the other is due to deterioration of the membrane itself and the influence of electrolytic conditions.

In addition, due to the generation of gas bubbles at the cathode and anode,
The presence of gas bubbles in the vicinity of the electrodes, especially between the electrodes and the diaphragm, causes a large voltage increase due to accumulation, which is the biggest obstacle in the electrolysis of sodium chloride aqueous solutions and the like. For this reason, porous electrodes, such as expanded metal or wire mesh electrodes, are generally used as electrode shapes to improve gas release and liquid mixing.

However, these electrodes have not yet provided a fundamental solution to the problem. Therefore, JP-A-52-11457
1. JP-A-5316371 and JP-A-53-1028
74, etc., in order to suppress the voltage increase caused by gas bubbles, measures such as installing the expanded metal electrode at a specific angle, providing vertical grooves on the electrode surface, and providing a guide plate are used. Various efforts have been made, including: On the other hand, when an ion exchange membrane is used to electrolyze an aqueous sodium chloride solution, for example, the ion exchange membrane undergoes a
Usually 1.8 to 2.501 in the longitudinal direction to the original film before use.
), it is known that there is a 2.0-3.0% dimensional change in the lateral direction.

In addition, in conventional filter press type electrolytic cells, in order to prevent electrolyte leakage, the outer periphery of the ion exchange membrane is sufficiently surrounded by a gasket made of a suitable material such as chloroprene rubber or EPDM. Fixed. Therefore, dimensional changes in both directions of the ion exchange membrane become absorbed by the membrane as vertical and horizontal wrinkles with no escape. In particular, when performing electrolysis using a vertical electrolytic cell with electrodes and diaphragms installed in the vertical direction, gas bubbles generated in the horizontal direction (horizontal direction) and accumulated in the creases have a long retention time. Since it is long and the bubbles are large, it is a major cause of the increase in electrolytic voltage. Furthermore, the accumulation of gas bubbles due to the generation of these wrinkles makes the current density of the membrane higher than the apparent current density, and as the amount of gas generated increases due to the increase in current density, the apparent current density becomes higher and the electrolytic The effect on voltage will increase.

For example, if the current density is higher than 30K/DTrI, the voltage increase due to the presence of gas bubbles will be 0.5 to 0.
．． It is large at 8V and cannot be ignored from an economical point of view. In order to suppress the occurrence of wrinkles in this membrane, research has been conducted on ways to prevent wrinkles by modifying and improving the membrane itself, and methods for reducing the voltage rise caused by gas bubbles by circulating the liquid in each electrode chamber. However, nothing satisfactory has yet been developed.

The present invention was completed as a result of research to improve these problems.

That is, the present invention absorbs vertical and horizontal wrinkles due to elongation and dimensional changes of the diaphragm during electrolysis as unidirectional wrinkles, thereby reducing the residence time of gas bubbles caused by membrane wrinkles and improving the membrane surface and membrane surface. By using an electrolytic electrode having a specific structure, which can effectively raise gas bubbles on the electrode surface, and also achieve extremely good degassing and liquid mixing on the electrode surface, and the electrode. The present invention provides a method for electrolyzing a solution to be electrolyzed. According to the present invention, the potential drop can be reduced and the increase in the voltage between the cathode and the anode can be significantly reduced. The present invention will be explained in detail below.

The present invention provides an electrode for electrolyzing a solution to be electrolyzed, which has a W-shaped continuous wave structure when viewed in plan and in cross section, and a method for electrolyzing a solution to be electrolyzed using the electrode. It is a perforated plate having unevenness on the surface, and has a W-shaped continuous shape in which the wavy lines of valleys m1...Mn... and peaks n1...NT,... are parallel to each other in the vertical direction, and Provided are electrodes for electrolyzing a solution to be electrolyzed, each of which has a W-shaped continuous wave shape in longitudinal and transverse cross-sections in the thickness direction, and a method for electrolyzing a solution to be electrolyzed using the electrode.

In the electrode structure of the present invention, when viewed in plan and in cross section, "W-shaped continuous waveform" means that when the electrode surface of the electrode is viewed in plan, as shown in [A] in FIG. , peaks m1...-Nln... and valleys n1 on both the front and back sides of the electrode.
...Nn... A collection of continuous waveforms in which the wavy lines M and n are parallel to each other and have a W-shaped continuous shape is called a W-shaped continuous waveform in a plan view, and a W-shaped continuous waveform in a cross-sectional view is: As shown in [B] in FIG. 1 and [C] in FIG. 1, when viewed in cross-section (x-xl view, y-y' view) in the electrode thickness direction,
Both have a W-shaped continuous wave cross section, which is the most distinctive feature of the present invention.

Various shapes can be used for the electrode plate of the electrode structure of the present invention, including porous shapes that allow gas to escape, such as wire mesh, mesh, and expanded metal.

In particular, it is preferable to use expanded metal in which the holes have a rhombic or long hexagonal shape. The material is not particularly limited, but when used as a cathode, iron, mild steel, nickel, etc. are used, and when used as an anode, a commonly used metal electrode such as titanium, tungsten, etc. coated with platinum, palladium, etc. is used. Ru. The electrode of the present invention is effective when used as an electrode for electrolyzing a solution to be electrolyzed in an electrolytic cell divided into an anode chamber and a cathode chamber, with a diaphragm disposed between the cathode and anode.

Furthermore, as a diaphragm, a diaphragm having water permeability, a neutral porous membrane, a porous membrane having a charge, a cation exchange membrane, especially a cation exchange membrane having a sulfone group, a carboxyl group, a phosphate group, etc., especially a fluorine-based membrane are used. When the cation exchange membrane is used as an electrode for electrolyzing a solution to be electrolyzed, especially an aqueous solution of sodium chloride or potassium chloride, the effect is great. Moreover, there are various modes of carrying out electrolysis.

A mode in which electrolysis is performed by applying an electrolytic voltage between a pair of cathodes and anodes, an anode chamber consisting of a bipolar electrode in which the cathode and anode are integrated, a partition wall separating the cathode and anode, and a cathode. A plurality of cell units consisting of chambers are arranged in series in a filter press format, and each end is provided with only an anode chamber or only a cathode chamber, and an electrolytic voltage is applied to the cathode and anode at both ends of the resulting battery cell. There are various modes of performing electrolysis. Although the present invention may have any of these embodiments, it is particularly effective to use it as an electrode for a vertical electrolytic cell in which the cathode and anode are installed substantially vertically.

FIG. 2 shows a partial sectional view of an example of a vertical electrolytic cell to which the present invention is applied. The electrolysis method of the present invention will be described with reference to FIG. 2, taking as an example the case where an aqueous sodium chloride solution is electrolyzed. In FIG. 2, an electrolytic cell containing a cathode 1 and an anode 2 having a W-type continuous wave structure according to the present invention is
Separated by a diaphragm 3 fixed in place by suitable means, a cathode chamber 4 and an anode chamber 5 are formed. ).

The electrolytic cell is provided with an electrolyte or saturated brine solution inlet 6 in the anode chamber 5, a brine overflow port 7, and a produced chlorine gas outlet 8 formed on the back side of the anode 2, and the brine is continuously circulated. Let them use it.

The cathode chamber 4 is also provided with a companion inlet 9 for introducing water or a dilute caustic soda solution, an outlet 10 for discharging the concentrated caustic soda produced from the cathode chamber 4, and a hydrogen gas discharge outlet 11 formed by one surface of the cathode. It will be done. The product, ie caustic soda, formed in the cathode compartment 14 is submitted to a suitable recovery device for concentration of the desired product. When electrolyzing a liquid to be electrolyzed using the electrode with the W-type continuous wave structure of the present invention, it is particularly important to install the electrode surface of one or both of the electrodes in contact with the diaphragm. As shown in Figure 2, either the peaks or valleys of the cathode 1 and anode 2 are connected to the diaphragm 3.
It is desirable to do this in close contact with the

This is because it is important to absorb wrinkles in both directions that occur in the diaphragm 3 as uniform wrinkles in each direction. As a means for bringing the diaphragm 3 into contact with the electrode, for example, in order to contact the anode 2, there is a method in which the diaphragm is installed at a position where the diaphragm is in contact with the anode, and a method in which the liquid level in the cathode chamber of both chambers adjacent to the diaphragm is A method in which the gas pressure in the cathode chamber is made higher than that in the anode chamber, or a method in which a fixed anode support 12 and a variable cathode support are used, as shown in FIG. There are methods such as forcing contact using 13.
These methods can be used alone or in combination. When the diaphragm is brought into contact with the cathode, a similar combination of the above means may be employed. The cathode support 13 shown in FIG. 2 has a cathode terminal portion 14 in close contact with the cathode 1, and is equipped with a cathode variable mechanism using a bimetal 17.

As the method for bringing the cathode into contact with the diaphragm, in addition to the method using a bimetal, a method using a spring or the like may be adopted as appropriate. In short, the effects of the present invention can be achieved by selecting a means for bringing the W-type continuous wave structure electrode of the present invention into contact with the diaphragm. Reference numeral 15 indicates an electrode stopper for adjusting the minimum width between the electrodes to prevent the cathode 1 from coming too close to the anode 2, 16 an adjustment bolt for adjusting the stopper, and 18 a rubber gasket.

When using the electrode of the present invention in a vertical electrolytic cell, it is preferable to form a longitudinally wavy shape as shown in the plan view of [A] in Fig. 1, in order to facilitate the escape of gas bubbles, suppress the residence time of gas bubbles, and suppress the voltage rise. It is necessary to use the electrode in this manner. When the present invention is applied,
0 compared to the electrolysis voltage when electrolysis is performed using normal electrodes.
．． A voltage drop of 4 to 1.2v can be expected. Further, in a preferred embodiment of the electrode of the present invention, when the W-shaped waveform in the thickness direction is viewed in cross section, the waveform angle (hereinafter referred to as cross-sectional angle) of the W-shaped continuous waveform with respect to the horizontal or vertical direction is 10 to 50.
It is desirable to maintain the temperature preferably between 20 and 35 degrees.

The cross-sectional view angle is the a-
Angle α connecting d-c and c-a-d and C in Figure 1
(y-y' sectional view) d-e-d/ and fe-fl
It is a general term for the angle β connecting the .

Furthermore, when the w-shaped wavy line of the electrode is viewed from above, the waveform angle of the w-shaped continuous waveform with respect to the horizontal direction or the vertical direction (hereinafter referred to as the planar viewing angle) is 20 to 60 degrees, preferably 30 to
It is desirable to maintain the temperature at 45 degrees. The plane view angle is the first
A in the figure (refers to the angle γ connecting Dab-c and b-de. This means that if the cross-sectional and planar viewing angles are not maintained within this range, wrinkles in the diaphragm will be absorbed in one direction. This is because the effect of the present invention cannot be fully exhibited.The interval between the W-shaped continuous waveforms when viewed from above, that is, A(7)h in Fig. 1, may be arbitrarily selected. However, in view of the need to fully satisfy the effects of the present invention, it is desirable to configure the spacing within the range of 10 to 30 [NOl] and to maintain the anode to 2.0 to 4.0 m101.

As the electrolytic conditions for carrying out the electrolysis of, for example, an alkali metal/logenide aqueous solution according to the present invention, already known conditions of this type can be appropriately employed.

For example, the electrolysis temperature can be from room temperature to 90°C. Further, although it is possible to operate at a current density of 5 to 50 A/d, a current density of 50 A/d or higher is not necessarily advantageous since the bath voltage becomes extremely high. These conditions are:
bath. It is desirable to decide on conditions that are economically advantageous by comprehensively considering voltage, current efficiency, etc. As described above, the present invention relates to a specific embodiment of an electrode and an electrolysis method using the electrode, and by applying the present invention, vertical and horizontal wrinkles due to elongation and dimensional changes of the diaphragm during electrolysis can be reduced to uniform wrinkles in all directions. As a result, the residence time of gas bubbles caused by wrinkles can be reduced, gas can be vented on the electrode surface, and the liquid can be mixed very efficiently.

As a result, it is possible to effectively prevent voltage rise and reduce membrane deterioration due to deposits on the diaphragm. In this way, the electrode of the present invention alone provides an effective means for solving problems that have hitherto been a problem, and has extremely great practical significance in this field. The present invention will be explained in more detail below using Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited only to these Examples.

Example 1 A perfluorosulfonic acid type cation exchange membrane (DuPont, trade name NaffiOnMemb) was used as a diaphragm.
rane3l5), using electrodes with a W-shaped continuous wave structure (h width 10n101) as shown in FIG. Pure water is supplied to the cathode chamber of a vertical electrolytic cell installed so as to be connected to each other, while 1500 m of saturated salt water with a concentration of 0.1 to 〆l of impurity ions as calcium oxide, which has been passed through a chelate ion exchange resin, is supplied to the anode chamber. Electrolysis was carried out under the conditions shown below while feeding with 1000 hr. and without circulating the liquid in each electrode chamber.

The bath voltage immediately after the start of energization was 4.00 to 4.12 V, and the bath voltage after 2000 hrs was also 3.90 to 4.15 V, with no voltage increase over time being observed at all.

Further, after 2000 hours had elapsed, the electrolytic cell was disassembled and the used membrane was observed for wrinkles, and it was found that almost no horizontal wrinkles had occurred, and only vertical wrinkles had occurred. Further, there was no deposit or discoloration on the membrane, and it was equivalent to the membrane before use. Examples 2 to 7, Comparative Examples 1 to 2 Saturated salt water was electrolyzed under the same conditions as in Example 1, except that electrodes with a W-type continuous wave structure having various angles as shown in Table 1 were used. .

Table 1 shows the results of observing the bath voltage and the condition of the membrane used 1000 hrs after the start of current application. Comparative example
3 Electrolysis of saturated salt water was carried out under the same conditions as in Example 1, except that a commonly used electrode was used instead of the W-type continuous wave structure electrode and the liquid in each electrode chamber was circulated.

The bath voltage immediately after the start of energization is 3.99 to 4.15 V, and 1
After 000 hrs, a significant increase in bath voltage over time was observed, ranging from 4.24 to 4.34.

After 1500 hrs, the membrane was removed from the container and observed, and it was found that the membrane had white spots and was slightly discolored.

[Brief explanation of drawings]

FIG. 1 is a plan view A and cross-sectional views B and C of an electrode showing one example of the present invention. (However, holes are omitted.) FIG. 2 shows a partial sectional view of an example of a vertical electrolytic cell to which the electrode of the present invention is applied. In Figure 2,
1... cathode, 2... anode, 3...
...Diaphragm, 4...Cathode chamber, 5...Anode chamber, 6...Brine inlet, 7...
Brine overflow port, 8... Chlorine gas outlet, 9...
...Water or dilute caustic soda inlet, 10...
... Outlet of generated caustic soda, 11 ... Hydrogen gas discharge port, 12 ... Anode support, 13 ...
...Cathode support, 14...Cathode terminal, 15.
... Electrode stopper 1, 16 ... Adjustment bolt, 17 ... Bimetal, 18 ... Packing.

Claims (1)

[Scope of Claims] 1. A porous plate having unevenness on the electrode surface, which has valleys m_1.
...m_n..., the wavy lines of the peaks n_1...n_n... take a W-shaped continuous shape in which they are parallel to each other in the longitudinal direction, and the longitudinal and cross-sectional shapes in the thickness direction are all W-shaped continuous. An electrode for electrolysis of the electrolyte solution that takes a waveform shape. 2. The electrode according to claim 1, wherein the W-shaped wavy line on the electrode surface has a planar angle γ of 20 to 60 degrees, and the cross-sectional angles α and β of the W-shaped wave in the thickness direction are 10 to 50 degrees. . 3 A perforated plate having unevenness on the electrode surface when electrolyzing a solution to be electrolyzed in an electrode tank divided into an anode chamber and a cathode chamber with a diaphragm arranged between the cathode and anode, with valleys m_1...m_
n..., peaks n_1...n_n... have a W-shaped continuous wave shape in which the wavy lines are parallel to each other in the longitudinal direction, and the longitudinal and cross-sectional shapes in the thickness direction have a W-shaped continuous wave shape. An electrolytic method characterized in that the electrode is used as either or both cathode and anode electrodes. 4. The electrolysis method according to claim 3, in which at least one electrode having a W-shaped continuous waveform is installed on the diaphragm so that the peaks or valleys of the electrode surface are in contact with the diaphragm. 5. Claim No. 5 using an electrode in which the angle γ of the W-shaped wavy line on the electrode surface in plan view is in the range of 20 to 60 degrees, and the cross-sectional angles α and β of the W-shaped wave in the thickness direction are in the range of 10 to 50 degrees. The electrolysis method according to item 3 or 4.