JPH032237B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high purity hydrogen by electrolysis.

Hydrogen is widely used as a synthetic raw material such as methanol, ammonia, and chlorine, as fuel, and as a raw material for ICs, etc. In recent years, demand has increased particularly in specific fields that require high added value for ICs. . In line with this, the hydrogen used in these applications is required to be highly pure, with a low content of impurities such as nitrogen, oxygen, and unsaturated hydrocarbons, especially with a low nitrogen content.

Common industrial methods for producing hydrogen include water electrolysis and alkali metal chloride electrolysis (by-product hydrogen), but the hydrogen obtained by these conventional methods is limited by the gas concentration of impurities. It was difficult to use it in the above-mentioned specific field because of its high value. For example, hydrogen obtained by electrolysis of alkali metal chlorides using an ion exchange membrane electrolyzer generally has a nitrogen content of 30 to 40 ppm, so further purification is required if high purity hydrogen gas is required, such as for IC use. And so.

The present inventors found that the concentration of impurity gases in hydrogen obtained by electrolysis is extremely related to the concentration of dissolved gases in the water mainly supplied to the electrolysis. The inventors have discovered that the above-mentioned problem can be solved by reducing .

That is, the present invention is a method for producing hydrogen by electrolysis, which is characterized in that water supplied to the electrolysis step is degassed in advance.

The electrolysis method for producing hydrogen in the present invention can be applied without particular limitation to, for example, a method using water electrolysis, an ion exchange membrane method, or an alkali metal chloride electrolysis method using a mercury method. Suitable for electrolytic method.

That is, in the electrolysis of alkali metal chlorides using the ion-exchange membrane method, by supplying previously degassed water to the cathode chamber of an electrolytic cell using an ion-exchange membrane as a diaphragm, caustic alkali is produced and high purity is produced. of hydrogen gas can be obtained. Furthermore, in water electrolysis, high purity hydrogen gas can be produced by degassing the electrolytic solution supplied to the electrolytic cell in advance. Furthermore, in mercury electrolysis,
The amalgam produced in the electrolytic tank is reacted by supplying previously degassed water in the demolition tank,
High purity hydrogen can be obtained together with caustic alkali. Therefore, in the present invention, the water supplied to the electrolytic process differs depending on the electrolytic method for producing hydrogen as described above, but in any case water or aqueous solution supplied to react to produce hydrogen gas is used. means.

The degassing method of the present invention is not particularly limited as long as it is a method for removing dissolved gas, especially nitrogen gas, from water supplied during the electrolysis process, but generally, dissolved gas in water has a gas partial pressure. Since the higher the water temperature and the lower the water temperature, the higher the solubility, the degassing method may be performed in the opposite manner to the above. That is, as a degassing method, a method of degassing under reduced pressure is preferable, and a method of flushing the supplied water under reduced pressure is particularly preferably used. The pressure (degree of vacuum) and water temperature at this time may be selected appropriately based on the relationship between the water supply temperature and the capacity of the pressure reducing device, but in general,
A pressure of around 110 mmHg at a temperature of 45-60°C is used. Dissolved gases in water after deaeration, especially nitrogen gas, show values close to zero.

Since the hydrogen gas obtained by the method of the present invention can reduce the nitrogen content to almost zero, it can be used as is for any purpose.

In addition, the method of the present invention can more effectively remove gases other than nitrogen from hydrogen by also using other gas removal methods such as commonly used deoxidizing methods. Therefore, it is preferable.

EXAMPLES Hereinafter, examples will be shown to specifically explain the present invention, but the present invention is not particularly limited to the following examples.

Example 1 Pure water (temperature 25°C) from which cations and anions in engineering water were removed using an ion exchange resin was heated to 50°C using an exhaust heat recovery device.

The purified water after heating is supplied to the degassing tower, and the operating pressure is 80 mm.
Flash evaporated with Hg. The pure water temperature after flashing was 47°C.

Flash-treated pure water is supplied to the cathode chamber of the ion-exchange membrane salt electrolyzer at a rate of 185/Hr, and saline water (NaCl concentration 300 g/Hr) is supplied to the anode chamber at a rate of 1.7
It was fed at a rate of m ³ /Hr. Electrolysis was performed with a current of 100 KA, and the generated hydrogen gas was analyzed using gas chromatography (JIS K 0512 method). Nitrogen in hydrogen was less than 1 ppm.

Example 1 Pure water whose temperature was raised by exhaust heat recovery was supplied to the cathode chamber of an electrolytic cell without flash evaporation. Other conditions were the same as in Example 1 for electrolysis. Analysis of the generated hydrogen gas by gas chromatography revealed that the nitrogen concentration in the hydrogen was 30 ppm.

Claims (1)

[Scope of Claims] 1. A method for producing high-purity hydrogen, characterized in that water supplied to an electrolysis step in a method for producing hydrogen by electrolysis is degassed in advance. 2. The manufacturing method according to claim 1, wherein hydrogen is produced by electrolysis of an alkali metal chloride. 3. The manufacturing method according to claims 1 and 2, wherein the water is supplied to the cathode chamber of an ion exchange membrane electrolytic cell. 4. The manufacturing method according to claim 1, which comprises flashing and degassing under reduced pressure.