JPS58185786A - Method for electrolyzing alkali chloride - Google Patents

Abstract

PURPOSE:To reduce the rise of voltage due to the shielding effect of a generated gas, by using expanded metal obtd. by stretching a metallic plate after cutting many notches in the plate as each electrode body and by specifying the thickness of the frames of the metal, the width of the notches and the tilt angle between the frames and a diaphragm. CONSTITUTION:A metallic plate is stretched after cutting many notches in the plate to obtain expanded metal 1 having openings 2 corresponding to the notches and frames 3 twisted slightly in the stretching direction, and the metal 1 is used as each electrode body. The thickness T of the frames 3 of the metal 1 is specified to >=0.5mm., and the width W of the notches is made 1.5-3 times the thickness T. When the metal 1 is attached to an electrolytic cel, the tilt angle theta between the frames 3 and a diaphragm 4 is set to 20-60 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolyzing an aqueous alkali chloride solution using a vertical diaphragm type electrolytic cell.

Conventionally, it has been common practice to use expanded metal as the electrode body in vertical diaphragm electrolytic cells.
The sliding voltage is significantly reduced by coating this with an active layer, but when measuring the actual voltage balance, the voltage valve due to the anolyte gas and membrane resistance is 20A/dm t in terms of current density.
The voltage is about 0.8 to 1.2V, among which liquid resistance,
The resistance increases due to gas dispersion, the resistance increases due to poor current distribution, and the resistance due to the diaphragm is about 0.6 to 0. IV.
The remaining 0.2 to 0.5 V is considered to be due to the effect of blocking the generated gas. In particular, it is known that as the distance between the electrodes is reduced in order to reduce the sliding voltage, this blocking effect becomes even greater.

The inventors of the present invention have conducted various studies to solve these problems, and as a result, we have determined the thickness and width of the expanded metal, and the angle of the opening formed by the diaphragm when it is installed as an electrode body. The method of the present invention was completed based on the knowledge that maintaining the voltage within a specific range is extremely effective in reducing the voltage rise due to the blocking effect of generated gas.

That is, the present invention provides an alkali chloride electrolysis method using a vertical electrolytic cell having a diaphragm and electrode bodies disposed on both sides of the diaphragm, in which the electrode body is an expanded metal made by stretching a metal plate with many notches. For extended metal frames, the plate thickness should be 0.5 m or more, and the increments should be 1.5 to 1.5 m thick.
This is an alkali chloride electrolysis method characterized in that the angle of inclination of the frame with respect to the diaphragm is 20 to 60 degrees in the upper and outer direction.

The structure of the present invention will be explained with reference to the drawings. When a large number of notches are bored in a metal plate in a staggered manner and the plate is stretched in a direction perpendicular to the notches, as shown in Fig. 1, openings (2) corresponding to the number of notches are formed. , a frame with a shape slightly twisted in the pull-stretch direction (
Extended metal (1) having 3) is obtained. Figure 2 is a partially enlarged view of the same, where the thickness of the frame (3) is T, the increments width is W, and the length of the opening (2) in the short direction is S.
W, and the length in the long direction is expressed as LW. Figure 3 is a side sectional view when the expanded metal (1) is installed as an electrode body in an electrolytic cell (not shown).
placed on both sides of the

In the present invention, the expanded metal (1) has a plate thickness T of the frame (3) of 0.5. As described above, the increments width W is set to 1.5 to 3 times the plate thickness, and the inclination angle θ of the frame (3) with respect to the diaphragm (4) is set to 20 to 60°. The generally used expanded metal has a thickness T and a width W of 1.0 to 1.58, and when such an electrode body is used, the gas generated from the electrode during electrolysis is separated by the gap 11 (4) and the expanded band. The proportion of gas escaping above 1 itu (5) of metal (1) increases, and the blocking effect of this gas increases.

In the present invention, it is difficult to make the plate thickness (T) less than 0.5n in terms of processing, and if the W/T ratio is less than 1.5, gas will flow from the opening (2) to the expanded metal (1). It is difficult to remove the back side (the surface not facing the diaphragm), and if the W/T ratio exceeds 3, the inclination angle θ□ will be less than 20° or the gas will spread to the space 11 (5) of the present invention. cannot achieve the goal.

Furthermore, if the inclination angle θ is less than 20' or more than 60'', it becomes difficult for the upward flow of the generated gas to escape through the opening (2) due to the interaction with the plate thickness T and the increment width W. In this way, the plate thickness T
When an expanded metal processed to maintain the ratio of the increments width W and the inclination angle θ to a certain range is used as an electrode, most of the gas generated from the electrode will flow through the opening (2) directed upward and outward. The gas is guided to the surface not facing the diaphragm (4), and the gas lift effect becomes even better, and the above-mentioned blocking effect is significantly reduced. Therefore, when electrolyzing an aqueous alkali chloride solution, the voltage increase due to the gas blocking effect can be significantly reduced. In addition, as shown in Figure 4, the frame (3
) is more effective in guiding the generated gas if the edge of the diaphragm (4) is cut out as shown in (6). In addition, a micromesh-like metal plate coated with a platinum group metal is placed on the expanded metal surface facing the diaphragm on the anode side (one pore area is 9 Wt or less).

By stacking layers with a porosity of about 20 to 85%, the effect of the present invention can improve gas dispersion.

Example 1 Plate thickness Im, increments width 211, LW 14n.

swzw, θ==40° length and width 70X 70m titanium expanded band metal with Ft:Ir weight ratio of 7
Lavender oil containing chloroplatinic acid and iridium chloride was applied so as to have a coating thickness of :3, and after drying, it was heated and sintered at 450° C. This operation was repeated until the coating thickness became 0.1 μm to prepare an anode body.

On the other hand, a cathode body was fabricated by applying black nickel plating to stainless steel expanded metal having the same dimensions as the anode body using a conventional method.

The above anode body and cathode body were attached to a small alkaline chloride electrolytic cell via a cation exchange membrane (trade name Nafion 214, manufactured by DuPont), and the distance between the anode and the exchange membrane was approximately 1n, and the distance between the li electrode and the exchange membrane was approximately 1n. 3 m, and supplying saturated saline to the anode chamber and pure water to make a 20 wt% Na011 aqueous solution to the cathode chamber, at a bath temperature of 80°C and a current density of 20 A/dat.
Continuous operation was performed for 0 days.

During this period, the average current efficiency was 91%, and the sliding voltage was 3.0% on average.
It was 5V.

Comparative Example 1 Anode body: plate thickness 1.5wI, increments width 1.5ws, L
W14w, SW 7n, θ=40° length and width 70X
Except that a 70M titanium expanded metal plated with F'i-Ir was used, and a stainless steel expanded metal plated with nickel black plating of the same size as the anode body was used as the cathode body. When saturated saline solution was electrolyzed for 10 days under exactly the same conditions as in Example 1, the current efficiency was 91% on average and the sliding voltage was 3.34 V on average.

Example 2. Comparative Example 2 Five types each of titanium expanded band metal and stainless steel expanded band metal were manufactured in which the thickness of the anode body and the cathode body were 1n, and the increments width was varied between 1 and 4n. Electrolysis of saturated saline solution was carried out under the same conditions as in Example 1, with anodes and cathodes having the same plating treatment and the same increment width facing each other. The relationship between the W/T ratio and the average sliding voltage in this case is shown in FIG. From this figure, W/T=1.5~
A decrease in sliding voltage is observed in the range of 3.0.

Example 3. Comparative Example 3 The thickness of both the anode body and the cathode body was 1n, and the increment width was 2. Five types each of titanium expanded band metal and stainless steel expanded band metal were manufactured in which the inclination angle θ of the frame was changed between 10 and 70 degrees by adjusting the tension level during binding and expanded banding. The same plating treatment as in Example 1 was applied, and saturated saline solution was electrolyzed under the same conditions as in Example 1, with anodes and cathodes having the same inclination angle facing each other. θ and sliding voltage i in this case
Figure 6 shows the relationship between

From this figure, it is observed that the sliding voltage decreases in the range of θ from 20 to 60°.

[Brief explanation of drawings]

Fig. 1 is a front view showing the shape of the expanded metal used in the present invention, Fig. 2 is a partially enlarged view thereof, and Fig. 3 shows expanded metal arranged on both sides of the diaphragm as an anode body and a cathode body. FIG. 4 is a schematic cross-sectional view showing the deformed expanded metal, and FIG. 5 is a schematic cross-sectional view of the expanded metal of Example 2. A graph showing the relationship between W/T and sliding voltage of Comparative Example 2, and FIG. 6 is that of Example 3. 3 is a graph showing the relationship between θ and sliding voltage in Comparative Example 3. (1): Extended band metal, (2): Opening, (3)
: Frame, (4): Diaphragm, T: Plate thickness, W: Notch width,
θ: Inclination angle Applicant Osaka Soda Co., Ltd. Agent Patent attorney Touya Monta 1 stroke 7! L@γ31,4 ga41jl!

Claims (1)

[Claims] In an alkali chloride electrolysis method using a vertical type 1 electrolytic cell in which a diaphragm and electrode bodies are arranged on both sides of the membrane, the electrode body is an expanded metal made by making a large number of notches in a metal plate and stretching it. The frame has a plate thickness of 0.
．． 5W or more, the increment width is 1.5 to 3.0 times the board thickness,
An alkali chloride electrolysis method characterized in that the angle of inclination of the frame with respect to the diaphragm is 20 to 60 degrees toward the side of the upper body.