JPH0429751B2 - - Google Patents

Description

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

BACKGROUND ART Conventionally, as a common salt electrolysis method, a mercury electrolysis method has been used because the purity and concentration of the resulting caustic soda aqueous solution can be increased. However, due to mercury pollution problems, the method has been changed to a diaphragm type or ion exchange membrane type electrolysis method.

Among these, 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 replaced by the ion-exchange membrane electrolysis method.

By the way, in the ion exchange membrane electrolysis method, hydrogen and caustic soda are generated on the cathode side, and the caustic soda aqueous solution and hydrogen are separated by a hydrogen separator following the electrolytic cell, and the caustic soda aqueous solution is sent to a concentration step.

The hydrogen separator used here is usually made of metal and is connected to the electrolytic cell through packing with flange bolts.

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

The present inventors discovered that the cause of the burning and corrosion of the bolt portion of the hydrogen separator is that the caustic soda aqueous solution is a conductor, and finally completed the present invention.

That is, the present invention separates hydrogen from a mixture of hydrogen and caustic soda in an ion-exchange membrane salt electrolyzer using a hydrogen separator, and then the caustic soda aqueous solution is placed inside a dropping device made of an electrically insulating material. Introduced onto a dispersion plate to form a drop,
This is a method for preventing corrosion of a hydrogen separator of a salt electrolytic cell, characterized in that the caustic soda aqueous solution is dripped in the dripping device.

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

There is an ion exchange membrane 4 between the anode 2 and the cathode 3 of the electrolytic cell 1, and purified saline (usually at a concentration of 25 to 26 wt%) is introduced to the anode side, and the concentration is lowered to chlorine from the anode side. The saline solution is drained out.

On the other hand, a low-concentration caustic soda aqueous solution (sometimes only water) is introduced to the cathode side, and sodium ions are taken in through the ion exchange membrane 4, and the concentration of the introduced caustic soda aqueous solution increases. Hydrogen is generated. 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 aqueous solution from which hydrogen has been separated is passed from the hydrogen separator 5 through the pipe 7 to the dropping device 11.
leading to.

A dispersion plate 12 for an aqueous caustic soda solution made of an electrically insulating material and having a suitable number of holes of a suitable size is provided in the dropping device.

The caustic soda aqueous solution that has arrived here passes through this dispersion plate 12 and is dripped in the form of a drip.
Since the continuity as a liquid is broken, an electric circuit related to the hydrogen separator 5 is no longer formed, and therefore, there is no current that causes corrosion, and corrosion due to the current in the hydrogen separator 5 is no longer formed. Prevented.

The corrosion prevention method of the hydrogen separator of the present invention is achieved by dropping the generated caustic soda aqueous solution using a simple dripping device, and also,
The hydrogen separator will not be destroyed due to corrosion and will be safe, which will greatly contribute to the industrial field.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an electrolytic cell, a hydrogen separator, and a caustic soda dropping device for carrying out the method of the present invention. Each symbol has the following meaning. 1... Electrolytic cell, 2... Anode, 3... Cathode, 4... Ion exchange membrane, 5... Hydrogen separator, 6... Hydrogen discharge piping, 7
...Hydrogen separator caustic soda aqueous solution discharge piping, 8
... Caustic soda aqueous solution, 9... Caustic soda aqueous solution introduction pipe of hydrogen separator, 10... Pressure equalization pipe, 11...
A dropping device for a caustic soda aqueous solution, 12... A dispersion plate for a caustic soda aqueous solution, 13... A droplet-like caustic soda aqueous solution, 14... A caustic soda aqueous solution.

Claims (1)

[Claims] 1. After separating the mixture of hydrogen and caustic soda aqueous solution discharged from the ion-exchange membrane type salt electrolyzer using a hydrogen separator, the caustic soda aqueous solution is placed inside a dripping device made of an electrically insulating material. A method for preventing corrosion of a hydrogen separator of a salt electrolytic cell, characterized in that the caustic soda aqueous solution is introduced onto a dispersion plate in which the caustic soda is dissolved, and the caustic soda aqueous solution is dripped in the dripping device.