JPS6067685A - Electrolytic cell for aqueous solution of alkali chloride - Google Patents

Abstract

PURPOSE:To perfectly prevent corrosion generated in an electrolytic cell, by respectively providing insulating insert pipes in the anode solution supply and discharge nozzles of the anode chamber of a unit electrolytic cell, and arranging an auxiliary electrode in the vicinity of the opening part of each insert pipe. CONSTITUTION:A solution supply pipe 2 and a formed solution withdrawal pipe 3, both of which are made of a fluorine contained resin, are provided to the nozzles of the anode chamber main body 1 of an electrolytic cell and respectively connected to passages 5, 6. Insert pipes 7 made of a fluorine contained resin are respectively provided in the solution supply nozzle and the formed solution withdrawal nozzle and auxiliary electrodes 8 are respectively provided in the vicinity of the opening parts of the insert pipes 7 or within said pipes 7. By providing the insulating insert pipes 7 in the electrolytic cell 1, a part of leak resistance is formed in the electrolytic cell 1 and a leak current is suppressed and anodic oxidizing corrosion reaction or hydrogen generating reaction generated in the vicinity of the opening parts of the inserts pipes by a minute leak current can be further suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an 'if decomposition tank for an aqueous alkali chloride solution, and more specifically, to an electrolytic cell which completely prevents corrosion occurring in each unit KWll tank in a plurality of electrolytic cells electrically connected in series. This is what we provide.

As a method for producing caustic alkali and chlorine by electrolyzing an aqueous alkali chloride solution, for example, an ion exchange membrane is sandwiched between
There is a so-called ion exchange de-alkali chloride electrolysis method in which an anode is provided, a negative and anode chamber is formed, and alkali chloride is dissolved to obtain a caustic alkali solution. An electrolytic cell plant using this method is a monopolar electrolytic cell constructed by electrically connecting a plurality of single monopolar cells each having a monopolar cathode and an anode across an ion exchange membrane. J! is formed by connecting it in series with J!, or bipolar J! is formed by sandwiching an ion exchange membrane. 11j A single bipolar electrolytic cell equipped with a negative and anode is used as a unit rli electrolytic cell 2, which can be electrically connected in series to form a plurality of bipolar electrolytic cells electrically connected in parallel and/or in 1α array. is formed by connecting to.

When electrolyzing an aqueous alkali chloride solution using such an electrolyzer plant, regarding the supply of liquid to the unit electrolyzer chamber,
A plurality of units +tl, 11''Ni'! However, since the unit electrolytic cells are electrically connected in series, the potentials in each unit electrolytic cell are at an angle, and during electrolysis, the liquid supply to the unit electrolytic cell II! C. When the liquid from the inner electrode chamber of the electrolytic cell is extracted into a common passage, a part of the electrolytic current leaks through the liquid. The area around the supply nozzle and drain nozzle acts as a so-called electrode, and the electrolytic reaction occurs in this area.'The chlorine gas extraction nozzle attached to the electrolytic cell body also depends on the usage. 'L' as anode material
High-grade metals such as 1% NbXTa are used, but these types of materials act as anodes at points where such current leaks out and are severely susceptible to anodic oxidation phenomena under extreme current values. In addition, this type of material is a metal that easily absorbs hydrogen, and acts as a cathode at locations where such current leaks in and out, causing severe hydrogen embrittlement. -1 Conventionally, in order to prevent corrosion of the electrolytic cell body, 1
, a method of increasing the piping resistance by changing the inner diameter, length, etc. of the liquid supply/drainage pipe (Japanese Patent Application Laid-open Nos. 12742/1982 and 14696/1983), and a method of increasing the piping resistance by changing the inner diameter, length, etc. board,
Many attempts have been proposed to minimize leakage current by increasing piping resistance by arranging valves or the like to locally cut off the flow of liquid (% 1973-30279)
No., Japanese Patent Publication No. 53-45698). In addition, the layout resistance IU trial model is proposed (lr! J, open B (35717
No. 4479)0 However, even if such a method is adopted, the anode chamber liquid supply nozzle, liquid drain nozzle, chlorine gas extraction nozzle, and a part of the 114ik chamber main body will still be damaged for a certain period of time due to corrosion damage. 'f(1, mate♀((After the transfer,
This requires a replacement operation or l+applied serving nli i's, etc., and it is not possible to completely prevent 15 meals.

In addition, attempts have been made to add hydrochloric acid or the like to the anolyte to increase the PL+ and to suppress the contamination of oxygen in the generated chlorine gas as much as possible. The electrical conductivity of the liquid increases/the applied current increases 0 In addition, as the pH decreases, the degree of corrosion and hydrogen absorption of the anode chamber material also tends to increase, and the combination of these two causes extremely severe corrosion damage. In particular, the ion exchange membrane used in ion exchange desorption electrolysis has a strong ability to adsorb metal ions. If ions are present, they will be adsorbed and deposited on the surface of the ion exchange membrane, lowering the desorption voltage.Furthermore, membranes whose performance has deteriorated will hardly recover their performance even if the concentration of phlegm ions in the lysate is low. Therefore, this also creates a need to completely prevent corrosion of the anode chamber body.

In view of the above points, the present inventor has arrived at the present invention as a result of extensive research.

That is, the present invention provides an insulating insertion tube in the liquid supply nozzle and/or produced liquid extraction nozzle installed in the anode chamber of the electrolytic cell, and further provides an insulating insertion tube in the vicinity of the opening of the insertion tube in the anode chamber and/or in the insertion tube. The present invention provides an electrolytic cell for an aqueous alkali chloride solution, characterized in that 4it 1JJJ electrodes are installed inside the tube.

The present invention provides an insulating tube inside the electrolytic cell, so that part of the leakage resistance is formed within the electrolytic cell, minimizing the leakage current, and furthermore, the leakage resistance is minimized. !Small
A means of completely suppressing M% corrosion damage in the 4'r'+"i tank by installing an auxiliary electrode to prevent the anodic oxidation corrosion reaction and hydrogen generation reaction near the opening of the insertion tube caused by the current. It provides a 4JA power supply tank with a

The auxiliary electrode in this case is an electrode that does not act as an internal dissolution reaction at all, but acts as a gas generation reaction, a solution oxidation reaction, or a solution orphan reaction.

In the present invention, the electrolytic cell main body is a member having an angle of +1η; for example, in the case of a pole-chamber boule type tome M cell, the box body corresponds to this; in the case of a filter press type electrolytic cell, the ♀ frame corresponds to this. Titanium, titanium alloy, tantalum, zirconium, niobium, etc. are generally used as materials for the anode chamber and the nozzles attached to the anode chamber, which are the members that make up the tank. As for iron,
Soft force 1, cast iron, stainless steel, Ni-based alloy, old etc. are used.

The nozzles attached to the anode and cathode chambers are generally connected by welding or the like. Pipe-shaped nozzles are often used as liquid supply and liquid discharging nozzles, but various other shapes can also be used.

In the present invention, it is desirable that the insertion tube installed in the liquid supply/discharge nozzle be electrically insulating. This is because if it is electrically conductive, there is a risk that a corrosive current will flow through the insertion tube. The insertion tube material may be electrically insulative as long as it can withstand an aqueous alkali chloride solution, chlorine gas, etc. at an electric temperature.

For example, Teflon, asbestos, and vinyl chloride.

Examples include acrylic resin, EPDM rubber, and other rubbers.

Pipe-shaped insertion tubes are often used,
It has at least one opening.

The auxiliary electrode of the present invention operates both as an anode and as a cathode. That is, the auxiliary electrode in the electrolytic cell from which a part of the electrolytic current leaks out acts as an anode, and the auxiliary IE shuttle in the electrolytic cell from which part of the electrolytic current leaks out acts as a cathode.

As auxiliary electrodes which act as anodes, so-called coated metal electrodes, such as metals of the platinum group coated on titanium or tantalum, graphite blocks, and also pure Zr)Ag can be used.
etc. are used.

Auxiliary electrodes that act as cathodes include, for example, platinum group metals or platinum group coated areas, graphite blocks, pure N
+ -, Zr%Ag, etc. are used, but when acting as a cathode, the m-reaction reaction hardly occurs, so even if hydrogen embrittlement is caused by sacrificially attaching Ti, Ta, etc. If it is replaced regularly, it can be used as an auxiliary electrode.

The locations for installing the auxiliary electrodes of the present invention are not particularly limited, but from the operational point of view, the anolyte supply nozzle and the produced liquid drain should be selected from the viewpoint of efficiency in preventing corrosion. It is preferable to provide it near the opening of the insulating insertion tube installed in the exit nozzle and/or within the Jr. 11 group.

The shapes of the auxiliary electrodes for the present invention include wires, rods, wire mesh, plates, etc.
All embodiments may be adopted as long as they are used for each product and act as electrodes. Especially when using plate materials,
Direct attachment to the anode chamber main body or a part of the main body made of a material that acts as an auxiliary electrode are effective means for carrying out the present invention.

According to the present invention, an insulating insertion tube is provided in the liquid supply nozzle and/or the produced liquid extraction nozzle which are inserted into the anode chamber of the electrolytic cell, and furthermore, an insulating insertion tube is provided near the opening of the insertion tube and/or inside the insertion tube. By installing the auxiliary electrode, it is possible to completely prevent corrosion of the stain decomposition tank body and the gold kA nozzle attached to the AT decomposition body. The life of this electrolytic cell is significantly longer, and it is extremely effective when operating at low pH by adding acid to the anolyte.Compared to conventional methods, maintenance is reduced by 4 dlL. With an economically superior electrolytic cell;

Since the electrolytic cell of the present invention has almost no eluted metal ions in the anode chamber supply liquid and the anode chamber extraction liquid, it does not cause any adverse effect on the ion exchange membrane, that is, a decrease in the performance of the ion exchange membrane, and can be used as a fishing gear. The lifespan can be maintained.

Next, examples of the present invention will be described.

(Example 1) The anode has a bipolar electrode made of expanded titanium metal coated with ruthenium oxide and titanium oxide, and the cathode is made of N1 expanded metal.The main body has an anode chamber made of titanium and a cathode chamber made of SU8304.
Current-carrying area 200 am” (width 2
A unit with a size of 1 m x height 1 n 7) was used.

An approximate m3 diagram of the anode chamber of a unit electrolytic cell is shown in Figure O1. A liquid supply pipe 2 and a product liquid extraction pipe 3 made of fluorocarbon resin were installed in the nozzle of the electrolytic cell anode chamber main body 1, and the product liquid extraction pipe 3 was connected to a dropper 4. A passage 5.6 common to the cell unit was connected to the saliva supply pipe 2 and the dropper 4, and an insertion pipe 7 made of fluororesin was provided in the liquid supply nozzle and the produced liquid extraction nozzle.Furthermore, An auxiliary '+13' pole was installed near the opening of the insertion tube or inside the insertion tube.

As an auxiliary electrode, a titanium auxiliary electrode coated with ruthenium oxide and titanium oxide is used for the cell unit where part of the electrolytic current leaks out on the high potential side. An auxiliary electrode made by TI was installed in the cell unit located at , that is, through which such current leaks and flows.

A cation exchange membrane Na day was applied to 25 pairs of the above cell units.
901 (trade name, manufactured by DuPont) was inserted as a separator to make a bipolar electrolytic cell.

Next, salt was electrolyzed at a current density of 30 A/am'' and an electrolysis temperature of 9.
It was carried out at 0°C. The concentration of electrolyzed brine is 200 t/l
,, and p)l was set to 4.

At that time, the Ti7i degree in the salt water was measured every month.
Even after two years of operation, all concentrations are below the detection limit of 0.01p.
The electrolytic cell was disassembled and the corrosion condition was examined, but no corrosion was observed inside the electrolytic cell.

(Example 2) Salt was electrolyzed under the same conditions as in Example 1, except that the method of installing the auxiliary electrode in Example 1 was changed as shown in FIGS. 2 to 4.

Figure 2 shows the insertion tube 7 installed in the product liquid extraction nozzle when a mesh supporter is installed near the opening of the insertion tube 7, and Figure 3 shows the insertion tube 7 installed in the liquid supply nozzle. In the case where several side holes are made in the liquid supply nozzle and mesh auxiliary electrodes 8 are arranged around them, FIG.
This is an example in which a rod-shaped auxiliary electrode 8 is placed inside the insertion '1.

As for the auxiliary electrode material, as in Example 1, the cell unit located on the high potential side is made of titanium coated with ruthenium-AA-side and titanium oxide, and the cell unit located on the low potential side is made of titanium coated with ruthenium-AA-side and titanium oxide. The unit is made of Ti.

The results showed that, as in Example 1, no corrosion was observed even after two years of operation. It was proven that.

(Example 3) In Example 1, salt was added to the electrolytically supplied brine, and p
Electrolysis of 1 jiK of food was carried out under the same conditions as in Example 1 except that H was lowered from 4 to 2.

As a result, after −1 year of electrolysis operation, the tank was dismantled and
We investigated the corrosion situation, but no corrosion was observed inside the electrolytic cell, and no deposits were detected on the ion exchange membrane.

(Comparative Example 1) In Example 3, the auxiliary voltage (V8) was removed, and salt electrolysis was performed under the same conditions as in Example 3. After a period of time, leakage from the T'i can was detected.After about 15 months of electrolytic operation, I disassembled the electrolytic cell and found that the insertion tube 7 was inserted into the liquid supply nozzle and liquid discharge nozzle.
Severe rt< eclipse occurred in the high-potential side cell unit of the T1 tank near the opening A1, and hydrogen embrittlement occurred in the low'tE side cell unit.

From this, it is clear that the electrolytic cell according to the present invention is not only equipped with a means for completely preventing corrosion, but is also an excellent electrolytic cell that can maintain excellent corrosion resistance from the viewpoint of energy saving.

[Brief explanation of the drawing]

FIGS. 1 to 4 are auxiliary ttt 4? in the present invention. FIG. 2 is an explanatory diagram schematically showing various aspects of a unit electrolytic cell for an alkali chloride solution provided with an insertion tube. In each figure, 1 is a unit electrolytic cell, 2 is an anode chamber liquid supply f'', 'rs is an anode chamber produced liquid extraction pipe, 4 is a dropper, 5 is a frame.
A common passage of the liquid supply pipe, 6 a common passage of the anode chamber produced liquid drain 1 former t1, 7 an insertion pipe, 8 an auxiliary: (1, analysis patent applicant Toyoso; 'AI Industry I'l : Shikisha Figure 1 Figure 2 Figure 6

Claims (1)

[Scope of Claims] 1) An insulating insertion tube is provided in the liquid supply nozzle and/or the produced liquid extraction nozzle installed in the anode chamber of the unit electrolytic cell, and further in the vicinity of the opening of the insertion tube in the anode chamber. and/
or an auxiliary electrode is installed in the insertion tube.2) The electrolysis according to claim 1, wherein the unit electrolytic cell is an electrolytic cell having an ion exchange membrane as a diaphragm. tank