JPS6311434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic method suitable for electrolyzing an aqueous alkali metal salt solution using a monopolar vertical electrolytic cell.
In general, various types of electrolysis methods are known depending on the shape of the electrode, the presence or absence of a diaphragm, etc., and are used in various fields. In recent years, vertical membrane electrolytic cells using asbestos or ion exchange membranes have been widely adopted in industry.

This type of electrolytic cell is roughly divided into monopolar type and bipolar type, but in monopolar vertical electrolytic cells, the anode has a plate-shaped electrode formed into a frame shape. structure is known.

Conventionally, the shape of this type of electrode structure has been such that the electrode plate 1 is configured in a box shape as shown in FIG. Generally, as shown in A and B, a conductive plate 3 is provided and welded to the inner surface of the electrode plate 1 and the outer surface of the lead bar 2 to conduct electricity. (Refer to Japanese Patent Publication No. 50-35031) Although the method shown in Figure 1 has a relatively low electrode body manufacturing cost, the method shown in Figure 2 A or B is superior in terms of current distribution during electrolysis, and the power cost is high. At present, the latter method is advantageous.

On the other hand, the electrical resistance due to the gas generated between the electrodes causes an increase in the electrolytic voltage and increases to an extent that cannot be ignored, especially in high current density operations using metal-insoluble electrodes. For this purpose, it is common practice to make the electrode a mesh, rod, or perforated plate so that it passes through the back side of the electrode surface. In this case, the electrolytic solution containing a large amount of generated gas will have a small apparent specific gravity and will cause an upward flow, but the upper part of the liquid, where the gas has been discharged outside, will cause a downward flow, especially around the electrode. Flows into internal parts where gas is not generated. However, in the conventional electrode structure shown in FIGS. 1 and 2A and 2B, the entire inside of the electrode serves as an upward passage for the generated gas, so that it collides with the above-mentioned downward flow and weakens the flow. Therefore, the internal circulation of the electrolyte that pushes out the generated gas and supplies new electrolyte is weakened, resulting in a disadvantage that the electrolysis voltage increases and the current efficiency decreases.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and is an electrolytic cell using a monopolar vertical electrolytic cell in which at least one electrode is constituted by an electrode frame having electrode plates on both sides. In the method, a cylindrical conductive dispersion having a length sufficient to cause convection of the electrolyte is used to form a region where the generated gas does not pass around the outer periphery of the electrode lead bar in the electrode frame, and the generated gas does not pass through the area. area to act as a downward flow path for the electrolyte, promoting internal circulation within the electrode chamber, and increasing the current density.
The object of the present invention is to provide a new electrolysis method for electrolyzing an aqueous alkali metal salt solution at 14 A/dm ² or higher.

That is, in the present invention, a cylindrical body having a length sufficient to cause convection of an electrolytic solution surrounding an electrode lead bar forms a space in which generated gas is not mixed inside, and the space is defined as an area through which the generated gas does not pass. This becomes a passage for the downward flow mentioned above, and forms a convection current in correspondence with the upward flow outside the cylindrical body, so that the flow of the electrolyte inside the electrode body is good, and the removal of the generated gas is smooth, so the electrolytic voltage This has the effect of reducing current efficiency and improving current efficiency.

Further, the cylindrical dispersion forming the generated gas impermeable region is made of a conductive material, and is bonded to the inner surface of the electrode plate and the outer circumferential surface of the electrode lead bar.
At the same time, the effect of improving current distribution in electrolysis and increasing the strength of the electrode body is achieved.

Further, in the present invention, the cylindrical body surrounding the electrode lead bar is composed of two symmetrical conductive dispersion plates, and both ends of each dispersion plate are overlapped at the middle part of the electrode plate to constitute the electrode body. It can be implemented by

This facilitates manufacturing, assembly and maintenance of the electrolytic cell. Further, the electrode body of the present invention has
It can be applied to both an anode frame and a cathode frame, and can be applied to a monopolar vertical electrolytic cell in which one or more pairs of these frames are provided. Furthermore, the present invention also relates to a monopolar electrolytic cell in which a large number of anode frames and cathode frames are arranged vertically in parallel with a liquid- or ion-permeable diaphragm in between, and these are integrated in a liquid-tight manner into a filter press type. Applicable.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Figures 3A and 3B are cross-sectional views of the electrode structure used to carry out the method of the present invention, in which 1 is a mesh-shaped metal-insoluble electrode, 2 is an electrode lead bar, and 3' is a cylindrical structure surrounding the electrode lead bar. Conductive dispersion, 4 is an electrolyte supply port. Gas generated by electrolysis is generated on the surface of the electrode plate 1, guided into the interior of the electrode body through the mesh, and ascends through regions A and B.

On the other hand, since the region C is surrounded by the cylindrical conductive dispersion body 3', this region C becomes a region through which the generated gas does not pass through which the generated gas does not flow.
forms an electrolyte downward flow path.

FIG. 3B shows an example in which the cylindrical body is composed of two symmetrical conductive dispersion plates, which are overlapped at the intermediate overlapping portion 5 of the electrode plates. On the other hand, in the conventional configuration shown in FIGS. 2A and 2B, all regions A and B within the electrode serve as upward paths for the generated gas, and the downward flow is obstructed.

4 and 5 show the case where the method of the present invention is applied to an ion-exchange membrane method salt electrolyzer, where 11 is an anode plate, 13 is an anode lead bar, and 15 is an anode plate.
is an anode dispersion, 17 is an anode element frame, and the anode lead bar 13 is connected to an anode bus bar 21 via a stud bolt nut 19 and a connector 20. Reference numeral 12 denotes a cathode plate, which is composed of a cathode lead bar 14, a cathode dispersion body 16, a cathode element frame 18, etc., similar to the anode side. The cathode lead bar 14 has a stand bolt nut 19',
It has a connector 20' and is connected to the cathode bus bar 22. As shown in the figure, the cylindrical dispersion elements 15 and 16 are made of a fluid-impermeable conductive plate made of titanium or the like with openings at the top and bottom so as to surround the lead bars 13 and 14, and have a cylindrical shape, and are made of a conductive plate made of titanium or the like that is open at the top and bottom so as to surround the lead bars 13 and 14. The length should be sufficient to prevent contamination and to achieve a convection effect for electrolyte, etc.

The salt water is supplied from the header (not shown) into the anode element frame 17 via the salt water branch 24, the salt water manifold 25, and the salt water supply pipe 30, and the recycled caustic soda aqueous solution is supplied from the header (not shown) to the caustic soda branch 26. , the caustic soda manifold 27 and the caustic soda supply pipe 31 into the cathode element frame 18 for electrolysis. Anode element frame 17
Chlorine gas is generated in the anode chamber in the cathode element frame 18, and sodium ions from the anolyte pass through the ion exchange membrane 23 and move to the cathode chamber in the cathode element frame 18. Hydrogen gas and hydroxide ions are generated in the cathode chamber, and caustic soda is generated in the catholyte.

The chlorine gas generated in the anode chamber flows out from the nozzle 28 together with the saline solution, separating the saline solution and the chlorine gas. On the other hand, the hydrogen gas generated in the cathode chamber flows out from the nozzle 29 together with the generated caustic soda and is separated into hydrogen gas and caustic soda, and the separated caustic soda is recycled back to the cathode chamber for use.

Figure 6 shows the results of measuring the influence of electrolytic voltage due to generated gas in ion-exchange membrane salt electrolysis, where line a is an example when a conventional electrode body is used, and line b is an example when the method of the present invention is used. It shows the case,
Line c shows an ideal case without the influence of generated gas. As is clear from the figure, the effect of preventing the electrolytic voltage rise by the present invention is greater than that of the conventional one.
Recognized at current density of approximately 8A/dm2 ^or higher, especially 14A/dm2
It is noticeable at dm ² or higher.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional electrode structure, FIG. 2 A and B are cross-sectional views of the conventional electrode structure, and FIGS. FIG. 4 is an explanatory diagram showing the inside of an electrolytic cell to which the present invention is applied. FIG. 5 is a schematic diagram showing the entire structure when the present invention is applied to an ion exchange membrane salt electrolytic cell. The figure is an electrolytic voltage measurement diagram showing the effects of the present invention. 1: Electrode plate, 2: Electrode lead bar, 3, 3':
Conductive dispersion, 4: Electrolyte supply port, 5: Intermediate overlapping portion, A, B: Generated gas passing region, C: Generated gas non-passing region, 11: Anode plate, 12: Cathode plate,
13: Anode lead bar, 14: Cathode lead bar,
15: anode dispersion element, 16: cathode dispersion element, 17: anode element frame, 18: cathode element frame, 19, 19': stud bolt nut,
20, 20': Connector, 21: Anode busbar,
22: Cathode bus bar, 23: Ion exchange membrane, 2
4: Salt water branch, 25: Salt water manifold, 2
6: Caustic soda branch, 27: Caustic soda manifold, 28, 29: Nozzle, 30: Salt water supply pipe, 31: Caustic soda supply pipe.

Claims (1)

[Scope of Claims] 1. In an electrolysis method using a monopolar vertical electrolytic cell in which at least one electrode is constituted by an electrode frame having electrode plates on both sides, a length sufficient to cause convection of the electrolyte solution. A cylindrical conductive dispersion is used to form a region through which the generated gas does not pass around the outer periphery of the electrode lead bar in the electrode frame, and the region through which the generated gas does not pass is used as a downward flow path for the electrolytic solution to prevent the passage of the generated gas through the electrode chamber. An electrolysis method characterized by promoting internal circulation and electrolyzing an aqueous alkali metal salt solution at a current density of 14 A/dm ² or more. 2. A filter press in which a large number of anode frames with anode plates on both sides and cathode frames with cathode plates on both sides are installed vertically with a liquid- or ion-permeable diaphragm in between, and these are integrated in a liquid-tight manner. In an electrolysis method using a monopolar vertical electrolytic cell, a cylindrical conductive dispersion with a length sufficient to cause convection of the electrolyte is used to coat the outer periphery of the electrode lead bar in the electrode frame. A region through which the generated gas does not pass is formed, and the region through which the generated gas does not pass acts as a downward flow path for the electrolytic solution to promote internal circulation of the electrode chamber, and to increase the current density.
The electrolytic method according to claim 1, characterized in that an aqueous alkali metal salt solution is electrolyzed at 14 A/dm ² or more.