JPH0440432B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an ion-exchange membrane salt electrolyzer that includes an electrolytic cell and a hydrogen separator that separates hydrogen from a mixture of hydrogen obtained in the electrolytic cell and a caustic soda aqueous solution. The present invention relates to a method for preventing galvanic corrosion of connected caustic soda aqueous solution introduction pipes.

[Conventional technology]

Recently, the salt electrolysis method has been converted from mercury electrolysis method to diaphragm type or ion exchange membrane type electrolysis method due to the problem of mercury pollution. Among them, ion exchange membrane type electrolysis method is used because it can obtain a high purity caustic soda aqueous solution. is now becoming mainstream.

By the way, in an ion-exchange membrane electrolytic cell, hydrogen and caustic soda are generated on the cathode side, and this hydrogen and caustic soda aqueous solution are sent to a hydrogen separator following the electrolytic cell to separate hydrogen, and the caustic soda aqueous solution is sent to a concentration process. . The hydrogen separator used here is
It is usually made of metal or synthetic resin, and is connected to the electrolytic cell through a hydrogen separator introduction pipe, and both ends of the introduction pipe are bolted to flanges via packing. With this structure, if the hydrogen separator is made of metal, the electrolytic cell and hydrogen separator are connected with bolts through the metal introduction pipe, so they should normally be at equal potential. However, there is an unexpected problem in that corrosion occurs in the hydrogen separator, the hydrogen separator inlet pipe, and the bolts. Furthermore, even when the hydrogen separator is made of synthetic resin in order to improve insulation and avoid corrosion, corrosion of the hydrogen separator inlet pipe and bolts remains a problem.

[Problem that the invention seeks to solve]

The object of the present invention is to solve the above-mentioned problems by providing a hydrogen separator inlet pipe section when the hydrogen separator is made of synthetic resin;
That is, it is an object of the present invention to provide a method for preventing electrolytic corrosion of the bolt portion that fastens the introduction pipe and its flange.

[Means for solving problems]

The present inventors have discovered that the cause of this corrosion in the hydrogen separator inlet pipe is electrolytic corrosion caused by a potential difference between the electrolytic cell, the hydrogen separator inlet pipe, and the discharged caustic soda aqueous solution. , we have completed the present invention.

That is, the present invention is an ion-exchange membrane type salt electrolyzer, characterized in that a caustic soda aqueous solution in a hydrogen separator that separates hydrogen from a mixture of hydrogen and caustic soda in an electrolytic cell is electrically connected to a cathode chamber portion of the electrolytic cell. This is a method for preventing galvanic corrosion of the hydrogen separator inlet pipe of a salt electrolyzer.

In the method of the present invention, a conductor such as an iron rod or iron piece is brought into contact with the caustic soda solution by immersing the conductor in the caustic soda solution in the hydrogen separator, and the conductor and the cathode chamber of the electrolytic cell are Connect with a conductor such as copper wire. Therefore, the caustic soda aqueous solution in the electrolytic cell and the hydrogen separator becomes equipotential, and the electrolytic corrosion mentioned above is prevented.

At this time, it is more preferable to connect the flanges with copper wire or the like in the same way, since this will improve the effect of preventing electrolytic corrosion of the bolt portions.

〔Example〕

The present invention will be explained in detail below using examples.

Embodiment FIG. 1 is a conceptual diagram of an example of implementing the present invention.

There is an ion exchange membrane 4 between the anode 2 and cathode 3 of the electrolytic cell 1, and purified saline 5 (normal concentration is 25 to 26% by weight) is introduced to the anode side, and chlorine 6 and chlorine 6 are introduced from the anode side. The saline solution 7 whose concentration has become diluted is discharged. On the other hand, a caustic soda aqueous solution 8 of usually low concentration is introduced to the cathode side, and sodium ions are taken in through the ion exchange membrane 4 to increase the concentration of the caustic soda aqueous solution and hydrogen is generated at the cathode.
This highly concentrated caustic soda is discharged from the electrolytic cell together with hydrogen and introduced into a synthetic resin hydrogen separator 10 connected via a hydrogen separator introduction pipe 9.
The separated hydrogen 11 is passed through a pipe 12 provided at the top of the hydrogen separator inlet pipe to a hydrogen storage tank (not shown).
Or sent to a hydrogen consuming process (not shown). On the other hand, the caustic soda 13 from which hydrogen has been separated passes through a pipe 14 provided in the hydrogen separator, and a part thereof is sent to a concentration step, and the remainder is added with water and circulated to the electrolytic cell.

Here, in order to prevent electrical leakage from the hydrogen separator inlet pipe, the hydrogen separator is made of synthetic resin.
In addition, the hydrogen pipe 12 from the top of the hydrogen separator introduction pipe is also equipped with measures to prevent electrical leakage from the electrolytic cell, so the electrical leakage prevention should be almost complete. The caustic soda aqueous solution becomes a conductive substance and is grounded elsewhere, causing electrolytic corrosion on the hydrogen separator inlet pipe and the bottle to which it is attached.

In order to avoid this electrolytic corrosion, an iron rod 15 is immersed in the hydrogen separator, and this iron rod is attached to the cathode chamber part 1 of the electrolytic cell.
6 and a copper wire 17 to make the caustic soda aqueous solution in the electrolytic cell and the hydrogen separator equipotential.

As a result, it was possible to prevent electrolytic corrosion of the hydrogen separator inlet pipe and bolt parts.

〔Effect of the invention〕

The method for preventing electrolytic corrosion of the hydrogen separator inlet pipe section of the present invention is as follows:
This is extremely efficient because it can be achieved simply by electrically connecting the electrolytic cell and the caustic soda aqueous solution in the hydrogen separator with a conductor such as a metal wire.

Further, since the hydrogen separator inlet pipe section is not destroyed by electrolytic corrosion, safety is also extremely improved.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the main parts of an ion exchange membrane salt electrolyzer and a hydrogen separator. 1... Electrolytic cell, 2... Anode, 3... Cathode, 4...
...Ion exchange membrane, 9...Hydrogen separator introduction pipe, 10
...Hydrogen separator, 15...iron rod, 17...copper wire.

Claims (1)

[Claims] 1. In an ion-exchange membrane type salt electrolyzer, the caustic soda aqueous solution in the hydrogen separator that separates hydrogen from the mixture of hydrogen and caustic soda in the electrolytic cell is electrically connected to the cathode chamber portion of the electrolytic cell. Method for preventing electrolytic corrosion of the hydrogen separator inlet pipe of a tank.