JPS6145160Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to an electrolytic cell for an aqueous alkali metal halide solution, particularly an aqueous alkali chloride solution.

Specifically, the present invention relates to an apparatus for efficiently obtaining mainly high-quality caustic alkali at a low electrolytic voltage in a horizontal electrolytic cell using a cation exchange membrane as an electrolytic diaphragm.

Horizontal electrolytic cells are divided into an upper anode chamber and a lower cathode chamber by a horizontally stretched diaphragm, and generally have the advantage that the target electrolytic product, e.g., caustic alkali, is produced in the cathode chamber and does not move through the diaphragm to the anode chamber. For this reason, horizontal electrolytic cells have been widely used industrially.

In addition, the most typical example of a horizontal electrolyzer is
There is a mercury electrolyzer, but because the mercury used in the cathode is an environmental pollutant, it is destined to be discontinued in the near future. If such a mercury cathode electrolyzer is to be converted to a mercury-free diaphragm electrolyzer at the lowest possible cost, it will inevitably be converted to a horizontal diaphragm electrolyzer, and such a horizontal diaphragm The development of a method for producing an electrolytic product of a quality equivalent to that of the mercury method with high current efficiency in a method electrolyzer is an important issue facing the industry.

A method of converting the above-mentioned mercury method electrolytic cell to a horizontal diaphragm method electrolytic cell is disclosed in Japanese Patent Publication No. 53-25557, but the electrolytic cell obtained by this method uses a filter diaphragm, The filtration membrane has a high water permeability, so that the anolyte fluid permeates through the membrane hydraulically and has the drawback that the anolyte fluid is mixed into, for example, caustic alkali produced in the cathode compartment, reducing its purity.

On the other hand, a cation exchange membrane called a dense diaphragm does not allow the electrolyte to permeate hydraulically, but only allows water molecules coordinated with electrically moving alkali metal ions to pass through. On the other hand, the small amount of water that permeated evaporates, causing poor conductivity between the cation exchange membrane and the cathode, and eventually stopping the electrolytic reaction.

In order to solve this problem, Japanese Patent Laid-Open Nos. 49-126596 and 50-55600 disclose a method in which a water retainer is present between the cation exchange membrane and the cathode, and a method in which a caustic alkaline solution is sprayed on the cathode. Methods have been proposed in which electrolysis is carried out while supplying water in the form of water or water in the form of a fountain.

However, the method proposed in Japanese Patent Application Laid-Open No. 49-126596 not only has problems in the number of steps involved in intervening a water retainer and the durability of the water retainer, but also When a water retaining body is interposed between the electrodes, the distance between the electrodes increases and the increase in resistance due to the water retaining body increases the electrolytic voltage, so this method cannot be said to be advantageous in terms of performance. Also, JP-A-50-
The method proposed in Publication No. 55600 has difficulty in practical application because it is difficult to spray and supply water uniformly in large-scale electrolyzers such as commercial electrolyzers.

The present invention was made to eliminate the drawbacks of the prior art as described above, and the present invention enables a relatively easy conversion from a mercury method electrolyzer to a horizontal cation exchange membrane electrolyzer, and has a high cost. This makes it possible to produce high quality caustic alkali with high current efficiency. Furthermore, it goes without saying that the electrolytic cell according to the present invention can be newly constructed using new materials.

That is, an object of the present invention is to obtain high quality caustic alkali with high efficiency using a horizontal diaphragm electrolytic cell. Another object is to provide an improved type of horizontal diaphragm electrolyzer that uses a cathode of new construction and has increased performance. Still another object is to provide a high performance horizontal diaphragm electrolyzer, particularly a horizontal cation exchange membrane electrolyzer, which is a conversion from a mercury electrolyzer. Other purposes will become clear in the following description.

To achieve the above object, the present invention is divided into an upper anode chamber and a lower cathode chamber by a cation exchange membrane stretched substantially horizontally, and the anode chamber has a substantially horizontal anode. It is surrounded by a lid, an anode chamber side wall surrounding the anode, and the upper surface of the cation exchange membrane, and has an anolyte inlet and outlet as well as an anode gas exhaust. The cathode chamber is surrounded by a cathode bottom plate, a side wall of the cathode chamber provided around the periphery of the bottom plate, and a lower surface of the cation exchange membrane, and the cathode chamber is surrounded by a support portion on the cathode bottom plate. A novel device characterized in that it has a cathode installed at an appropriate distance from the bottom plate via a catholyte, and an inlet for a catholyte and an outlet for a multiphase flow of cathode gas and catholyte. It contains an electrolytic cell.

Aspects of the invention will now be described in detail with reference to the accompanying drawings. In the following explanation, sodium chloride, which is currently most commonly used in industry, will be used as a representative example of the alkali metal halide, and caustic soda will be used as the electrolyzed product thereof. It goes without saying that the invention is not intended to be limited to these, and can be applied to other inorganic salt aqueous solutions, water electrolysis, etc.

1 to 3 are a side view, a vertical longitudinal cross-sectional view, and a vertical cross-sectional view, respectively, of an electrolytic cell according to the present invention.

In FIGS. 1 and 2, the device of the present invention consists of a rectangular anode chamber 1 whose length is larger than its width, preferably several times the length, and a cathode chamber 2 located directly below the rectangular anode chamber 1. The anode chamber 1 and the cathode chamber 2 are partitioned by a cation exchange membrane 3 stretched substantially horizontally between the side walls. In this document, "substantially horizontal" includes a case where the object is slightly inclined as necessary (a case where a slope of up to about 1/10 is applied).

Examples of cation exchange membranes suitable for the present invention include membranes made of perfluorocarbon polymers having cation exchange groups. Membranes made of perfluorocarbon polymers with sulfonic acid groups as exchange groups are manufactured by E.I.
It is commercially available under the trade name "Nafion" from Pont de Nemours & Company, and its chemical structure is as shown in the following formula.

The preferred equivalent weight of such a cation exchange membrane is 1000
It is between 2000 and 2000, preferably between 1100 and 1500. The equivalent weight here is the weight (g) of the dry membrane per equivalent of exchange group. Further, cation exchange membranes in which part or all of the sulfonic acid groups in the above exchange membranes are replaced with carboxylic acid groups and other commonly used cation exchange membranes can also be applied to the present invention. These cation exchange membranes have extremely low water permeability and only allow sodium ions with 3 to 4 water molecules to pass through without allowing hydraulic flow.

The anode chamber 1 includes a lid 4 and an anode chamber side wall 5 extending to surround an anode 6 suspended from the lid 4.
The anode 6 is defined by the upper surface of the cation exchange membrane 3, and the anode suspension device 7 is provided upright on the lid 4.
The anodes 6 are connected to each other by an anode bus bar 8. The lid body 4 has a hole 10 through which the anode conductive rod 9 is inserted, and the hole 10 is hermetically sealed by a sheet 11. An anode plate 12 is attached to the lower end of the anode conductive rod 9, and since the anode plate 12 is connected to the anode suspension device 7, it can be adjusted up and down by operating the anode suspension device 7, and the positive ions It can be arranged so as to be in contact with the exchange membrane 3. Of course, the anode is not limited to being suspended from an anode suspension device installed upright on the lid.
Suspension support may be provided by other methods. Furthermore, the anode chamber has at least one anolyte inlet 13, which can be provided on the lid 4 or on the side wall 5 of the anode chamber. On the other hand, at least one anolyte outlet 14 is provided, and these can be provided on the side wall 5. Moreover, the lid body 4
Alternatively, the side wall 5 is provided with an anode gas (chlorine gas) outlet 15 at an appropriate location.

As the lid body 4 and the anode chamber side wall 5 constituting the above-mentioned anode chamber 1, the lid body and the anode chamber side wall constituting the mercury method electrolyzer can be used, and there are no particular restrictions as long as they are made of materials that can withstand chlorine. It can be used suitably. For example, chlorine-resistant metals such as titanium and titanium alloys, fluorine-based polymers, hard rubber, etc. can be used. Furthermore, iron lined with the above-mentioned metals, fluorine-based polymers, hard rubber, etc. can also be used.

Although a graphite anode can be used as the anode plate 12 for carrying out the anode reaction, an insoluble anode made of a metal such as titanium or tantalum coated with, for example, a platinum group metal, an oxidized platinum group metal, or a mixture thereof is preferable. . Of course, the anode plate used in the mercury method electrolyzer can be used with the same dimensions and shape.

Next, the cathode chamber 2 is defined by the lower surface of the cation exchange membrane 3, a cathode bottom plate 16, and a cathode chamber side wall 17 standing upright along the edge of the cathode bottom plate so as to surround the cathode bottom plate.

The cathode 24 is fixed to the cathode 24 by one or more supports 25 . The support portion 25 is made of iron, nickel, stainless steel, copper, or the like, and is conductive in itself, and can electrically connect the cathode bottom plate 16 and the cathode 24 as well as support the cathode 24 . There are no particular restrictions on the fixing method; welding,
Examples include screws, bolts and nuts. Further, the support portion 25 may be made of a non-conductive material such as heat-resistant plastic such as polytetrafluoroethylene or chlorinated vinyl chloride, or hard rubber such as natural rubber. The support portion can be fixed using adhesive, bolts, or the like. The cathode 24 is made of a non-conductive material such as those described above.
When supporting the cathode on the cathode bottom plate 16, the cathode bottom plate 16 and the cathode 24 are electrically connected with a conductive material such as iron, nickel, copper, stainless steel, etc., or the conductive material connected to the cathode 24 is placed in the cathode chamber. It may be taken out from the side wall 17 and connected to the anode bus bar 8 of an adjacent electrolytic cell. The cathode is made of a corrosion-resistant material such as iron, nickel, or stainless steel, and its shape is a rod such as a round bar or a square bar.
It is also possible to fix a porous sheet such as expanded metal or punched metal on top of the support part 25. Furthermore, a tanzak-shaped plate may be arranged on the support portion 25 to form a louver-shaped electrode. It is preferable to use a cathode whose surface is coated with nickel or silver spraying, nickel alloy plating, etc. to reduce the hydrogen overvoltage. The material of the support portion may be the same as that of the cathode, or may be different.

The cathode of the present invention is particularly advantageous when converting a mercury electrolyzer into a horizontal cation exchange membrane electrolyzer. In other words, if a rod-shaped, porous sheet-shaped, louver-shaped electrode, etc. of approximately the same size as the cathode bottom plate is manufactured in advance, and this is fixed on the cathode bottom plate via a support, the cathode bottom plate can be easily removed from the line. A cathode can be easily formed. Also, when applying low hydrogen overvoltage treatment to the cathode by thermal spraying, plating, etc., the cathode that has been previously treated can be connected to the bottom plate without removing the cathode bottom plate from the production line, which is very convenient for construction. It's advantageous. Furthermore, when performing reprocessing with low hydrogen overvoltage, only the cathode can be removed and reprocessing can be performed.

The cathode chamber side wall 17 can be made of something like a rigid frame edge, or can be made of a packing-like material made of elastic rubber, plastic, or the like.

The material for forming the cathode chamber side wall 17 is not particularly limited as long as it is resistant to caustic alkalis such as caustic soda, and iron, stainless steel, nickel,
Nickel alloy etc. can be used. Furthermore, a material obtained by lining an alkali-resistant material on an iron base material can also be suitably used. Furthermore, materials such as rubber, plastic, etc. can also be used. Examples of such materials include rubber-based materials such as natural rubber, butyl rubber, and ethylene propylene rubber (EPR), poly(tetrafluoroethylene), and poly(tetrafluoroethylene).
Examples include fluorine-based polymer materials such as propylene hexafluoride), poly(ethylene-tetrafluoroethylene), polyvinyl chloride, and reinforced plastics (FRP).

Next, the catholyte inlet and the outlet for the mixed phase liquid of cathode gas and catholyte are connected to the cathode chamber 2, that is, the cathode chamber 2 surrounded by the cation exchange membrane 3, the cathode chamber side wall 17, and the cathode bottom plate 16. It is only necessary to generate a flow of a mixed phase liquid of catholyte and cathode gas. Therefore, it can be provided at an appropriate location on the cathode bottom plate 16 or the cathode chamber side wall 17. The cross-sectional structure of the catholyte inlet is not particularly limited as long as it can cause the catholyte to flow as described above, but it is preferable that the catholyte flows uniformly. The mouth is a preferred embodiment. The direction of the multiphase liquid flow may be either the longitudinal direction of the electrolytic cell or the direction perpendicular thereto.

FIG. 3 is a vertical cross-sectional view of an electrolytic cell according to the present invention, showing a rod-shaped cathode as an example of the cathode. The horizontal beam 26 is connected to the cathode bottom plate 16 by a plurality of conductive support portions 25 .

FIG. 4 is a cross-sectional view and a schematic diagram showing a catholyte circulation system of a horizontal cation exchange membrane electrolytic cell in which a mercury electrolytic cell is converted into a cation exchange membrane electrolytic cell according to the present invention.

In the figure, the anode chamber 1 includes a lid 4 and a lid 4.
An anode chamber side wall 5 is erected to surround the plurality of anodes 6 and anode plate 12 suspended from the anode chamber, and a clamp is provided between the lower flange of the anode chamber side wall 5 and the cathode chamber side wall (not shown). The upper surface of the cation exchange membrane 3 is defined by the upper surface of the cation exchange membrane 3. The anode 6 is the lid 4
The anodes are suspended by an anode suspension device 7 installed upright, and each anode is interconnected by a bus bar 8. Further, the anode chamber 1 is provided with an anolyte inlet 13, an anolyte outlet, and an anode gas outlet 15. However, when the anode gas and the anolyte are extracted as a mixed phase liquid and separated into gas and liquid outside the anode chamber, the anode gas outlet 13 is not necessary.

On the other hand, the cathode chamber 2 is defined by a cathode bottom plate 16 which is the same as the bottom plate of a mercury electrolyzer, a side wall of the cathode chamber installed on the periphery of the cathode plate, and the lower surface of the cation exchange membrane 3. has been completed. Cathode bottom plate 1
6 is connected to a cathode busbar 18. The cathode chamber 2 is provided with a catholyte inlet 19 and a mixed phase liquid outlet 20 of catholyte and cathode gas. Cathode 24
is electrically connected to the cathode bottom plate 16 via the conductive support portion 25 .

Saturated salt water is supplied to the anode chamber 1 from the anolyte inlet 13, chlorine gas generated by electrolysis is taken out from the anode gas outlet 15, and fresh salt water is discharged from the anolyte outlet.

The catholyte is supplied from the catholyte inlet 19, becomes a multiphase flow with hydrogen gas generated in the cathode chamber 2, and is taken out from the multiphase liquid outlet 20, and the hydrogen gas and catholyte are separated by a separator 21. . The substantially gas-free catholyte from which the gas has been separated is circulated into the cathode chamber 2 through the catholyte inlet 19 by a pump 22 . The separator 21 and the pump 22 may be provided one for a plurality of electrolytic cells, or may be provided for each electrolytic cell.

Current is supplied from the anode busbar 8 and the cathode chamber 2
It passes through the cathode 24 , the conductive support part 25 , and the cathode bottom plate 16 , and is taken out from the cathode bus bar 18 .

In the anode chamber 1, the formula A reaction occurs, and the sodium ions in the anode chamber 1 pass through the cation exchange membrane 3 and reach the cathode chamber 2.
On the other hand, in cathode chamber 2, the formula A reaction occurs, producing hydrogen gas, and
Caustic soda is generated by receiving sodium ions that have migrated from the anode chamber 1 through the cation exchange membrane 3.

Therefore, the greatest feature of the present invention is that by supplying catholyte into the cathode chamber and forming a multiphase flow of catholyte and cathode gas that fills the cathode chamber and flows through it,
The lower surface of the cation exchange membrane 3 is sufficiently moistened with this flow to allow the electrolytic reaction to proceed smoothly, and the caustic soda and hydrogen gas generated between the cation exchange membrane 3 and the cathode 24 are immediately introduced into this flow after generation. The cathode chamber 2 is rolled up and dispersed between the cathode and the cathode bottom plate.
It has a structure that allows it to be discharged outside.

The catholyte that is supplied into the cathode chamber and flows through it is carried to the outside of the cathode chamber together with hydrogen gas and generated caustic soda. After the hydrogen gas is separated by the separator 21, the catholyte is returned to the catholyte inlet 19. It is advantageous to use a circulating fluid in which at least a portion of the sodium hydroxide is refluxed, since the concentration of caustic soda can be increased as appropriate, and the concentration can also be adjusted by diluting it with water midway through.

As described above, according to the present invention, high quality caustic alkali can be efficiently produced at low voltage in a horizontal cation exchange membrane electrolytic cell.
Furthermore, the electrolytic cell of the present invention can be easily manufactured by converting a mercury method electrolytic cell, and can be used not only for electrolytic cells but also for almost all existing equipment such as busbars, rectifiers, fresh salt water treatment equipment, salt water system equipment, etc. Since the mercury electrolyzer can be reused without having to be scrapped, conversion of the mercury electrolyzer can be carried out with great economic advantage.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are side views, vertical longitudinal cross-sectional views, and vertical cross-sectional views, respectively, showing one embodiment of the electrolytic cell according to the present invention, and Figure 4 is a mercury method electrolytic cell for cation exchange. FIG. 1 is a vertical cross-sectional view of a horizontal cation exchange membrane electrolytic cell converted to a membrane electrolytic cell and a schematic diagram showing a catholyte circulation system. 1... Anode chamber, 2... Cathode chamber, 3... Cation exchange membrane, 4... Lid, 5... Anode chamber side wall, 6...
Anode, 7... Anode suspension device, 8... Anode bus bar, 9... Anode conductive rod, 10... Hole, 11... Sheet, 12... Anode plate, 13... Anolyte inlet,
14...Anolyte discharge port, 15...Anode gas discharge port, 16...Cathode bottom plate, 17...Cathode chamber side wall, 1
8... Cathode busbar, 19... Cathode fluid inlet, 2
0...Cathode mixed phase liquid outlet, 21...Separator, 22
... Pump, 23 ... Packing, 24 ... Cathode, 24a ... Rod-shaped cathode, 25 ... Support part, 26
...Horizontal beam.

Claims (1)

[Claims for Utility Model Registration] 1. An upper anode chamber and a lower cathode chamber are divided by a cation exchange membrane stretched substantially horizontally, and the anode chamber has a substantially horizontal anode. It is surrounded by a lid, an anode chamber side wall surrounding the anode, and the upper surface of the cation exchange membrane, and has an anolyte inlet and outlet as well as an anode gas outlet. The cathode chamber is surrounded by a cathode bottom plate, a side wall of the cathode chamber provided around the periphery of the bottom plate, and a lower surface of the cation exchange membrane, and the cathode chamber is surrounded by a support part on the cathode bottom plate. A horizontal type, characterized in that it has a cathode installed at an appropriate distance from the bottom plate via the bottom plate, and is also equipped with an inlet for catholyte and an outlet for a mixed phase liquid of cathode gas and catholyte. electrolytic cell. 2. The electrolytic cell according to claim 1, wherein the supporting portion is conductive. 3. The electrolytic cell according to claim 1, wherein the electrolytic cell is converted from a mercury method electrolytic cell.