JPH0425351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing galvanic corrosion of a hydrogen separator in an ion exchange membrane salt electrolyzer.

Conventionally, mercury electrolysis has been used as a common salt electrolysis method because the purity and concentration of the resulting caustic soda aqueous solution can be increased, but this has been changed to diaphragm or ion exchange membrane electrolysis due to mercury pollution problems. Among them, the ion-exchange membrane electrolysis method is currently becoming mainstream because a highly purified caustic soda aqueous solution can be obtained, and the diaphragm electrolysis method is also being converted to the ion-exchange membrane method.

By the way, in an ion-exchange membrane type electrolytic cell, hydrogen and caustic soda are generated on the cathode side, and this aqueous caustic soda solution and hydrogen are separated by a hydrogen separator following the electrolytic cell, and the aqueous caustic soda solution is sent to a concentration step. The hydrogen separator used here is usually made of metal, and is bolted to the electrolytic cell via a flange via packing.

With this structure, and the electrolytic cell and hydrogen separator are connected by bolts, they should normally be at equal potential, but unexpectedly the bolts generate heat and burn out. It was also found that corrosion occurred in the hydrogen separator.

The present inventors have discovered that the cause of the burning and corrosion of the bolt portion of the hydrogen separator is the potential difference between the electrolytic cell and the hydrogen separator, and have completed the present invention.

That is, the present invention provides a method for electrolytic corrosion of a hydrogen separator, characterized in that a metal part of a device (hydrogen separator) for separating hydrogen from a mixture of hydrogen and caustic soda in an ion-exchange membrane salt electrolyzer is connected to the electrolytic cell by a metal wire. It is a prevention method.

The present invention will be explained below with reference to the drawings.

There is an ion exchanger 4 between the anode 2 and the cathode 3 of the electrolytic cell 1, and purified saline (normal concentration is
26%) is introduced, and chlorine and diluted salt water are discharged from the anode side. On the other hand, a low concentration caustic soda aqueous solution is usually introduced to the cathode side.
Sodium ions are taken in through the ion exchange membrane 4, and as the concentration of the introduced caustic soda aqueous solution increases, hydrogen is generated at the cathode. This highly concentrated caustic soda is discharged together with hydrogen and introduced into a hydrogen separator 5 following the electrolytic cell. Here, hydrogen is separated, and the separated hydrogen is sent to a hydrogen storage tank (not shown) or a hydrogen consumption process (not shown) through a pipe 6 provided at the top of the hydrogen separator 5. On the other hand, the caustic soda from which hydrogen has been separated passes through a pipe 7 provided in the hydrogen separator 5, and a portion is sent to a concentration step, and the remainder is added with water and circulated to the electrolytic cell 1.

Here, in order to prevent electrical leakage from the hydrogen separator 5, the end of the pipe 7 is usually connected to a pipe made of an insulating material such as rubber.

In addition, the hydrogen piping 6 from the hydrogen separator 5 is also equipped with measures to prevent leakage from the electrolytic cell 1, so the leakage prevention should be almost complete. It is presumed that the caustic soda aqueous solution becomes conductive and is grounded elsewhere, causing burning or electrolytic corrosion of the hydrogen separator 5 and the bolts used to attach it.

In the present invention, a wire 8 made of a metal that is a good conductor, such as copper, is connected between the hydrogen separator 5 and the cathode chamber portion of the electrolytic cell to equalize the potential between the cathode chamber portion of the electrolytic cell and the hydrogen separator 5. The cathode chamber portion is a cathode of the electrolytic cell and a portion of the electrolytic cell structure that always maintains the same stable potential as the cathode.

Note that it is preferable to connect each flange with a metal wire in the same manner as the connection between the electrolytic cell 1 and the hydrogen separator 5, since this will improve the effect of preventing burning of the bolt portion.

The method of preventing electrolytic corrosion of a hydrogen separator according to the present invention is extremely efficient because it can be achieved simply by connecting the cathode chamber with the electrolytic cell and the hydrogen separator with a metal wire.

Furthermore, since the hydrogen separator will not be destroyed by electrolytic corrosion, safety is also improved.

However, in the method of the present invention, the tip of the metal part of the pipe 7 of the hydrogen separator 5 gradually corrodes, so it is preferable to connect this part with a flange so that it can be easily replaced. .

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the main parts of an ion exchange membrane type salt electrolyzer and a hydrogen separator. Each symbol in the figure has the following meaning. DESCRIPTION OF SYMBOLS 1... Electrolytic cell, 2... Anode, 3... Cathode, 4... Ion exchange membrane, 5... Hydrogen separator, 6... Hydrogen piping, 7... Caustic soda aqueous solution piping, 8... Metal wire.

Claims (1)

[Claims] 1. An electric hydrogen separator characterized in that the metal part of the device (hydrogen separator) for separating hydrogen from a mixture of hydrogen and caustic soda in an ion-exchange membrane salt electrolyzer is connected to the cathode chamber part of the electrolyzer with a metal wire. Erosion prevention method.