JPH025824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying an alkaline chloride electrolytic cell. More specifically, the present invention relates to a method of modifying a diaphragm method monopolar type rigid electrolytic cell to make it into an ion exchange membrane method electrolytic cell.

There are three methods for producing caustic soda by electrolysis of alkali chloride, especially salt water: the mercury method, the diaphragm method, and the ion exchange membrane method. The mercury method was at its peak in Japan for a time because it produced a high concentration of caustic soda and a low salt content, but it is now destined to be completely abolished due to environmental pollution issues.
As an alternative, the conversion to the diaphragm method rapidly progressed. However, in this diaphragm method, the electrolyte obtained is dilute, so it must be concentrated to about 50% caustic soda, and it usually contains about 1% salt. It may cause an adverse effect on.
The ion-exchange membrane method has been attracting attention in recent years as a method that improves these shortcomings.In place of a diaphragm made of asbestos, a cation-exchange membrane is installed between the negative and anode electrodes, and high-purity caustic soda is This is a method of obtaining concentration.

Therefore, currently the best way to obtain high-quality caustic soda is to use the ion exchange membrane method, but if you have already installed a diaphragm method electrolyzer, it is not recommended to completely switch over. becomes a big burden. Therefore, on the one hand, efforts are being made to refine and improve the quality of caustic soda obtained by the diaphragm method, and on the other hand, studies are being made to modify existing diaphragm electrolytic cells into ion-exchange membrane electrolytic cells. The present invention relates to a method for converting the diaphragm method electrolytic cell into an ion exchange membrane electrolytic cell.

An example of converting a diaphragm electrolytic cell into an ion exchange membrane electrolytic cell is the method disclosed in Japanese Patent Application Laid-Open No. 10399/1983. This method is used as an ion exchange membrane electrolytic cell by replacing the diaphragm with a cation exchange membrane and changing the electrolyte and gas flow paths, and has the advantage that it can be used as an ion exchange membrane electrolytic cell without any modification. On the other hand, it has the disadvantage that no consideration is given to the distance between the electrodes, and no efforts have been made in terms of efficiency (the diaphragm and the cation exchange membrane have different thicknesses).

The inventors of the present invention have arrived at the present invention as a result of extensive research to find a reasonable method for modifying an alkali chloride electrolytic cell that eliminates the above-mentioned drawbacks and also requires low modification costs. That is, the present invention provides a monopolar diaphragm electrolytic cell in which the cathode has a flat tube shape, and each cathode tube is electrically connected to a plurality of conductive plates inside the cell, and the conductive plates penetrate through the flat cathode tube. Both ends of the tubes are directly connected to both tank walls, which are cathode tank busbar connection walls, and both ends of each flat cathode tube connect adjacent cathode tubes with the same conductive material as the cathode tank to form a common cathode chamber. An electrolytic cell in which the anode is formed and the anode is supported at the bottom of the electrolytic cell (specifically, the electrolytic cell described in Japanese Patent Publication No. 49-27749 can be mentioned) is modified into an ion-exchange membrane method electrolytic cell. To do this, the anode is wrapped in a bag-shaped cation exchange membrane, each forming a plurality of anode chambers, each flat tubular cathode is separated individually, and the tubular upper and lower ends are cut to form two sheets. A plate-shaped cathode is obtained by cutting out the conductive plate, changing its orientation so that its plane is parallel to the plane of the plate-shaped cathode, and inserting an elastic conductive substance between the plate-shaped cathode and the plate-shaped cathode. A method for remodeling an alkali chloride electrolytic cell, which comprises electrically connecting a conductive plate and a plate-shaped cathode and simultaneously adjusting the distance between the electrodes by welding the elastic conductive substance and the cathode active surface. It provides:

Conventionally, pole spacing adjustment has normally been performed using an anode, but the anode is made of expensive metal such as titanium, and the electrical resistance at the connection between the support rod and the spring is large, resulting in voltage loss. It has the disadvantages of being large and difficult to process. On the other hand, in the present invention, since the cathode, which is usually made of mild steel, is processed, welding and assembly are simple, and the electric resistance is low, so there is little voltage loss during operation, and a large voltage drop can be obtained. It has the advantage of

Typical embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a diaphragm electrolytic cell before remodeling, and shows a vertical cross-sectional view.
FIG. 2 shows a horizontal sectional view from part A thereof. In the figure, 1 is a cathode, which usually has a network structure. A brown film 3 is deposited or coated on this surface. The cathode is electrically connected to the conductive plate 4 at several points. 2 indicates an anode. FIG. 3 shows an example of an ion exchange membrane electrolytic cell after modification by the method of the present invention in the same part as FIG. 2. That is, the cathode 1 is cut out from the section a in FIG. 1 and the section b in FIG. The mouth part of the exchange membrane is located at the upper part and forms an individual anode chamber in which one or a plurality of anodes arranged in parallel are enclosed. The cation exchange membrane may be any membrane normally used for alkali chloride. The conductive plate 4 may be left in its installed state before modification, but it is better to rotate it 90 degrees as shown in the figure, change its orientation so that its plane is parallel to the plane of the plate cathode, and connect it to the tank body. This is preferable because the electrode spacing can be easily adjusted. Then, an elastic conductive material 5 is inserted between the cathode 1 and the conductive plate 4 to adjust the distance between the electrodes and bring the cathode closer to the anode. That is, in an electrolytic cell in which the anode is surrounded by a cation exchange membrane, the distance between the electrodes can be adjusted by the cathode, which has the advantage that the entire cell can be assembled easily. The elastic conductive substance is not particularly limited in terms of material, but is preferably the same material as the conductive plate. Further, the shape is not particularly limited, and the effects of the present invention can be obtained even if the shape is a semicylindrical shape or a spring shape as shown in the drawings, however, the shape should be determined in consideration of electrical resistance.

The cation exchange membrane is fixed by providing a support frame on the top of the electrolytic cell, but there are no particular limitations on the format. This can be done by interposing it between the two. FIG. 4 is a partial plan view of the support frame, and FIG. 5 is a partial sectional view at section B thereof. In the figure, numeral 10 is a space, and numeral 11 is a part into which a cap for guiding anode gas with an ion exchange membrane interposed (see Fig. 6) is slightly opened upward. Further, 12 is a part that rides on the side wall of the electrolytic cell body.

The support frame 6 and cap 7 configured as described above provide a sixth
As shown in the figure, a cation exchange membrane 3' is fixed to form a cathode chamber. In addition, cover this with a tank lid.
These include conductive substances with an elasticity of 5,
All of these examples are given as examples, and do not limit the present invention.

As described above, according to the present invention, it is possible to modify a diaphragm method electrolytic cell into an ion exchange membrane method electrolytic cell relatively inexpensively and without much modification, and by using this modified electrolytic cell, efficiency can be improved. Electrolysis of aqueous alkali chloride can be carried out well, and a high-quality aqueous alkali hydroxide solution can be obtained.

[Brief explanation of drawings]

Fig. 1 is a vertical partial cross-sectional view of the diaphragm method electrolytic cell before modification, Fig. 2 is a horizontal partial cross-sectional view at part A, and Fig. 3 is a horizontal partial cross-section of the electrolytic cell after modification by the method of the present invention. 4 is a partial plan view of the support frame, FIG. 5 is a partial cross-sectional view at part B thereof, and FIG. 6 is a vertical partial cross-sectional view of the electrolytic cell after modification by the method of the present invention. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Anode, 3... Diaphragm, 3'... Cation exchange membrane, 4... Conductive plate, 5... Elastic conductive material, 6... Support frame, 7... Cap.

Claims (1)

[Scope of Claims] 1. A monopolar diaphragm electrolytic cell, wherein the cathode has a flat tube shape, and each cathode tube is electrically connected to a plurality of conductive plates inside the cathode tube, and the conductive plates are connected to the flat cathode tubes. The two ends of each cathode tube are directly connected to the two tank walls, which are the cathode tank busbar connection walls, and the two ends of each cathode tube connect adjacent cathode tubes with the same conductive material to form a cathode chamber. When converting an electrolytic cell in which the anode is supported at the bottom of the electrolytic cell to an ion-exchange membrane electrolytic cell, the anode is wrapped in a bag-shaped cation-exchange membrane, each forming a plurality of anode chambers, and each flat tubular cathode Separate the conductive plates individually, and then cut the upper and lower ends of the tubular shape to obtain two plate-shaped cathodes. Cut the conductive plate and orient it so that its plane is parallel to the plane of the plate-shaped cathode. By changing the conductive plate and rearranging the conductive plate, inserting an elastic conductive material between the conductive plate and the plate-shaped cathode, and welding the elastic conductive substance and the cathode active surface, the conductive plate and the plate-shaped cathode are A method for modifying an alkaline chloride electrolytic cell, which comprises electrically connecting the electrodes and adjusting the distance between the electrodes at the same time. 2. The method according to claim 1, wherein a cation exchange membrane support frame is provided above the electrolytic cell.