JPS627885A - Multipair electrolytic cell for alkali chloride using ion-exchange membrane method - Google Patents

Abstract

PURPOSE:To obtain the title pressure electrolytic cell easy to assemble, having small contact electric resistance and whose current density is made uniform by arranging plural unit cells obtained by arranging a unit anode chamber and a unit cathode chamber on both sides of a cation-exchange membrane so that the anode and the cathode are faced to the membrane and electrically connecting the cells with an inelastic platy body. CONSTITUTION:A unit anode chamber 14 is formed by a frame-shaped peripheral wall 1, a metallic platy side wall 2, an anode 4 which is welded to the side wall 2 through plural conductive ribs 3 and nozzles 5 and 6 for supplying and discharging an electrolyte, and a unit cathode 16 having the same structure as the unit 14 with the sole exception of the electrode 4 as the cathode is formed. Plural unit cells 17 wherein both units 14 and 16 are arranged on both sides of a cation-exchange membrane 12 so that the anode and the cathode are faced to the membrane 12 are placed in order, and the cell 17 and the cell 17 and/or the cell 17 and a current lead plate 19 are electrically connected by an inelastic body having many protruded parts. The electrolytic cell thus formed is operated under pressure. Besides, an electrically conductive sheet 18 consisting of the platy body is preferably inserted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic cell for producing chlorine and alkali metal hydroxide by electrolyzing an aqueous alkali metal chloride solution.

More specifically, the present invention relates to electrolysis of an aqueous alkali metal chloride solution that is operated under pressure and includes a cation exchange membrane between an anode and a cathode.

Examples of alkali metal chlorides include common salt, potassium chloride, lithium chloride, and the like, and common salt is important from an industrial standpoint. Although a description will be given below using common salt as an example, the present invention is not limited to the electrolysis of common salt.

BACKGROUND OF THE INVENTION There are two types of ion exchange membrane electrolytic cells for electrolyzing saline solutions: a bipolar type and a unipolar type, and a large number of electrolytic cells for each type have been proposed in the past.

For example, in bipolar electrolytic cells, electrical connections between adjacent cells are made using titanium-iron explosive crimping plates (Japanese Patent Laid-Open No. 51-43377), and electrical connections between adjacent cells are made using elastic connectors. Irumono (Unexamined Japanese Patent Publication No. 53-1
No. 49174) An electrolytic cell in which plastic is used as the material and electrical connections between adjacent cells are made using bolts and nuts (
JP-A No. 51-72973), etc.

In addition, as a monopolar electrolytic cell, there is one in which current is distributed by multiple lead rods inserted into the electrolytic cell (Japanese Patent Application Laid-open No. 153877/1987), and a type in which current is distributed through a plurality of lead rods inserted into the electrolytic cell (Japanese Patent Application Laid-Open No. 52-153877). JP-A 1973, which directly connects busbars.
-108899@) etc.

Problems to be Solved by the Invention Various improvements have been made to the above-mentioned conventional electrolytic cells to make them suitable for ion-exchange decomposition salt electrolysis, but they are complicated to assemble and have problems with electrical contact resistance between adjacent cells. However, they are still not completely satisfactory because they are large, the current density within the electrolytic cell is non-uniform, or they are expensive.

Furthermore, the conventional electrolytic cell described above is not compatible with the bipolar type to the monopolar type, and in order to prepare both types of electrolytic cells, it is necessary to prepare a large number of units. .

It is also known that when the cell is operated with a high internal pressure, the power consumption rate is extremely reduced (Special Publication No. 56-431
No. 16). However, even in such pressurized electrolysis, conventional electrolytic cells that still require improvement are used as they are, and no electrolytic cell that fully takes advantage of the advantages of pressurization has yet been proposed.

An object of the present invention is to provide a pressurized ion exchange membrane salt electrolytic cell that is easy to assemble, has low electrical contact resistance between adjacent cells, has a uniform current density in the electrolytic cell, and is inexpensive.

Means for Solving the Problems To achieve the above object, the present invention has a frame-shaped peripheral wall;
An anode chamber unit consisting of a metal plate-shaped side wall and an anode welded to the plate-shaped side wall via a plurality of conductive ribs, a frame-shaped peripheral wall, a metal plate-shaped side wall, and a plurality of A cathode chamber unit consisting of a cathode welded through conductive ribs is arranged on both sides of a cation exchange membrane with a plurality of unit cells arranged with the anode and cathode facing the membrane, and the space between the unit cells and/or This is an ion exchange membrane alkali iodochloride multi-pair electrolytic cell operated under pressure, in which the electrical connection between the unit cell and the current lead plate is made by an inelastic plate-like body having a large number of protrusions. .

In order to make electrical connections between the unit cells and/or between the unit cells and the current lead plate using an inelastic plate-like body having a large number of protrusions, it is necessary to connect the unit cells and/or between the unit cells and the current lead plate. A conductive sheet made of a non-elastic plate having a large number of protrusions may be inserted between the lead plate and the lead plate.1. A large number of protrusions may be provided on the plate-like side wall of the anode chamber unit and/or the cathode chamber unit.

The inelastic plate-like body having a large number of protrusions used in the present invention may have any shape as long as it satisfies the purpose of the present invention, but generally the height of the protrusions is 1. ．． O~4.0mm, preferably 1.5~3.0mm
The size of the protrusion is 2 to 1 mmφ, preferably 3 to 5 mmφ. The protrusions are present at a pitch of 5 to 30 mm, preferably 10 to 20 mm. Also,
When such a plate-like body is provided separately from the side wall, its thickness is 0.3 to 2.0 mm, preferably 0.5 to 1.5 mm.

When providing a protrusion directly on the side wall, it is important to be careful not to make a hole in the side wall.

When using a conductive sheet, it is not subject to such restrictions and processing is simple.

In the present invention, a plate-like body without elasticity means a plate-like body whose thickness does not substantially change when this plate-like body is sandwiched between two flat plates and pressure is applied from both sides.

To use the electrolytic cell of the present invention as a bipolar electrolytic cell, the anode chamber units and cathode chamber units of adjacent cells are arranged back to back, current lead plates are placed at both ends, and fastening frames are attached from both sides. Just tighten it.

In addition, to use it as a monopolar electrolytic cell, insert a current lead plate between adjacent cells and arrange the anode chamber unit and anode chamber unit and the cathode chamber unit and cathode chamber unit of the adjacent cells so that they are back to back. However, a current may be placed at both ends and the fastening frame may be used to tighten from both ends.

Since the electrolytic cell of the present invention is operated under pressure, the internal pressure causes the side walls to bulge outward. Therefore, the side walls of adjacent cells and the current lead plates and side walls are in full contact with each other.

At this time, in order to reduce the contact electrical resistance, it is important to increase the contact pressure.

In the present invention, since the contact is made by a non-elastic plate-like body having a large number of protrusions, the pressure at the contact point becomes very large.

Therefore, the contact current resistance between adjacent cells and/or between the current lead plate and each cell becomes extremely small, and the current density distribution within the electrolytic cell is made uniform.

In addition, the anode chamber unit and the cathode chamber unit may be connected via a cation exchange membrane, or via a current lead plate, or
Since they have a simple structure in which they are arranged without intervening and tightened from both ends with fastening frames, assembly is extremely easy and the manufacturing cost is extremely low.

Hereinafter, the electrolytic cell of the present invention will be explained in detail with reference to the drawings, but the electrolytic cell of the present invention is not limited only to these drawings.

1 and 2 are a front view and a sectional view of the anode chamber unit and the cathode chamber unit constituting the electrolytic cell of the present invention, respectively, and a sectional view taken along the line A-A'' in the direction of the arrow, and FIGS. The figures are a front view and a cross-sectional view of the anode chamber unit and cathode chamber unit of another embodiment, taken along the line BB in the direction of the arrow.

FIG. 5 shows one embodiment of the side wall used in the electrolytic cell of the present invention.

FIG. 6 is an assembled diagram of a bipolar electrolytic cell of the present invention, and FIG. 7 is an assembled diagram of a monopolar electrolytic cell of the present invention. The numbers in the figures correspond to each other, and the same numbers indicate the same thing.

1 is a peripheral wall, 2 is a side wall, 3 is a conductive rear, and 4 is an electrode.

The peripheral wall 1 has an electrolytic solution supply nozzle 5 at the lower part and an electrolytic solution and electrolysis product discharge nozzle 6 at the upper part. These nozzles are connected to an electrolytic solution supply header and an electrolytic solution and electrolytic product discharge header by flexible hoses, and are used for supplying and discharging the electrolytic solution and electrolytic products.

The thickness of the peripheral wall is not particularly limited as long as it is provided with a nozzle and has sufficient strength, and is generally 0.5 to 5.0 cm.
Preferably, 1.0 to 3.0 cm is suitable.

In the case of a large frame in which the length of one side of the peripheral wall is 1 m or more, it is preferable to provide a reinforcing rib 7 in the center because the thickness of the wall and the width of the frame can be reduced.

An embodiment in which reinforcing ribs are provided is shown in FIGS. 3 and 4. The reinforcing ribs 7 are welded or bolted to the upper and lower sides of the peripheral wall 1, and have holes 8 that serve as passages for the electrolyte and generated gas. It is preferable that the reinforcing rib 7 and the side wall 2 are not welded. If welded, the side walls will not swell sufficiently due to internal pressure, resulting in poor adhesion between the side walls and between the current lead plates and the side walls.

As the material for the peripheral wall, metals such as iron, nickel, titanium, and alloys thereof, and plastics such as polyethylene, polypropylene, and polyvinyl chloride can be used without any restrictions. If it is made of metal, it can be integrated with the side wall by welding, which is preferable for preventing electrolyte leakage and improving the strength of the electrolytic cell. In this case, titanium or a titanium alloy is preferable for the anode chamber unit, and iron, nickel, or an alloy thereof for the cathode chamber unit.

A conductive rib 3 is welded to the side wall 2, and an electrode 4 is welded to the conductive rib 3.

The materials for making the side walls and conductive ribs may be any material that is inert under electrolytic conditions, for example titanium or titanium alloy for the anode chamber unit, iron, nickel or their like for the cathode chamber unit. Alloys can be used.

The outer surface 9 of the side wall has high electrical conductivity in order to reduce the electrical resistance of contact with the adjacent side wall and current lead plate.
In addition, it is preferable to provide a coating made of a metal with low hardness, such as copper, tin, or aluminum. Especially when the sidewall material is titanium, it also prevents the formation of an oxide film.
Such coatings are effective.

As a means for coating these metals, for example, ordinary means such as electroless plating, electroplating, thermal spraying, vapor deposition, etc. can be applied.

The thickness of the side wall swells appropriately due to the internal pressure of the cell, and
The thickness may be 1 to 3 mm as long as the conductive rib can be welded.
degree is preferred.

Preferably, the side wall and the peripheral wall are integrated by welding, bolting, adhesion, or the like.

In addition, if the peripheral wall is made of a material with insufficient resistance to electrolytes and electrolytic substances, such as plastic, the side wall may be press-molded into a dish shape as shown in FIG.
0 may be fitted with a peripheral wall.

Similarly to the reinforcing ribs 7, the conductive ribs 3 are also provided with holes 11 that serve as passages for the electrolytic solution and electrolytic products. The height of the conductive rib is the height of the peripheral wall 1 and the sealing gasket 1.
3.15, the thickness of the electrode 4, etc., the membrane-electrode distance is adjusted to be O or around O. At this time, it is preferable that the conductive ribs of the anode chamber unit and the conductive ribs of the cathode chamber unit are arranged in alternating positions. If they are placed in the same position,
If the height of the conductive ribs is too high, there is a risk that the membrane may be cut by the electrode at the conductive ribs or that the current may be short-circuited. If they are arranged alternately, even if the height of the conductive ribs is slightly higher than the calculated value, the difference in height will be adjusted by deforming the electrode and/or side wall into a wave shape. The membrane is not cut by the electrode, and the membrane-electrode distance can be completely set to 0.

For the electrode 4, a normal porous electrode such as an expanded metal, a perforated flat plate, a rod shape, a net shape, etc. can be used, but a perforated flat plate electrode can reduce the membrane-electrode distance without damaging the membrane. It is preferable because it can be done.

A perforated plate electrode is an electrode in which a circular, oval, square, rectangular, or cross-shaped opening is provided in a flat plate. Holes are generally created by punching, and the shape of the opening is preferably circular, making it easy to punch.The hole diameter is:
The diameter is 0.5 to 6 mm, preferably 1 to 5 mm, and the aperture ratio is 10 to 70%, preferably 15 to 60%.

If the pore size and aperture ratio are too small, gas handling will be poor, and if they are too large, the current density in the cation exchange membrane will become non-uniform, which is not preferable.

As the anode material, those used for the electrolysis of ordinary aqueous alkali metal chloride solutions may be used. That is, an electrode is used in which the base material is titanium, zirconium, tantalum, niobium, or an alloy thereof, and the surface thereof is coated with an anode active material mainly composed of a platinum metal oxide such as ruthenium oxide.

As the cathode material, iron, nickel, or an alloy thereof may be used as it is, or its surface may be coated with a cathode active material such as Raney nickel, Rodan nickel, or nickel oxide.

Next, a method of assembling the electrolytic cell of the present invention using the above-mentioned anode chamber unit and cathode chamber unit will be explained.

FIG. 6 is an example of a bipolar electrolytic cell of the present invention. A cathode chamber unit 14 is connected to one side of the cation exchange membrane 12 via an anode chamber gasket 13, and a cathode chamber gasket 15 is connected to the other side of the cation exchange membrane 12.
The cathode chamber unit 16 is arranged through the
．． 13, 14, 15, and 16 constitute a unit cell 17.

A large number of these unit cells are arranged with conductive sheets 18 interposed so that the anode chamber unit and cathode chamber unit are back to back, and current lead plates 19 are arranged at both ends.The electrolytic cell is assembled by tightening with a filter press type fastening frame. Can be assembled.

When the plate-like side wall of the anode chamber unit and/or the cathode chamber unit has a large number of protrusions, the conductive sheet 18 is not necessarily required.

The conductive sheet 18 is made of an inelastic plate-like body having a large number of protrusions. It is important not to have elasticity because if it has elasticity, the contact pressure will not increase due to the buffering effect, and as a result, the electrical contact resistance will increase.

The conductive sheet is preferably a flat plate with a thickness of about 0.1 to 3 mm with protrusions on one or both sides, an expanded sheet, and a burring because they can further reduce the electrical contact resistance.

The size of the conductive sheet is the same as that of the side wall, and a large number of protrusions are provided over the entire surface.

The material of the conductive sheet may be any metal having high electrical conductivity, such as copper, tin, aluminum, iron, nickel, and alloys thereof.

The anode chamber gasket 13 and the cathode chamber gasket 15 are for sealing the electrolyte, and if the surface of the cation exchange membrane is flat and the membrane itself has sealing properties, these gaskets may be omitted. , only one of them is acceptable.

The material of the anode chamber gasket may be any material as long as it is resistant to chlorine gas and has elasticity; for example, chloroprene rubber, fluororubber, silicone rubber, etc. are preferable. Examples of materials for the cathode chamber gasket include ethylene/propylene rubber, chloroprene rubber, and butyl rubber.

Fluororubber etc. are preferred. Additionally, the gasket may be lined with a reinforcing fabric.

The thickness of the gasket only needs to be thick enough to completely seal the electrolyte, and although it varies depending on the hardness, it is usually 0.5
It is approximately 3 mm.

The ion exchange membrane 12 used in the present invention is not particularly limited, and those generally used in aqueous alkali metal chloride solutions can be used.

The ion exchange group may be of the sulfonic acid type, carboxylic acid type or sulfonic acid amide type, but a combination type of carboxylic acid and sulfonic acid with a high alkali metal transfer number is most suitable. In this case, it is most preferable to use the side where the sulfonic acid group is present as the anode side and the side where the carboxylic acid group is present as the cathode side. As the resin matrix, fluorocarbon resin is excellent in terms of chlorine resistance. Further, it may be lined with cloth, net, etc. to improve strength.

In order to equalize the current density in the electrolytic cell, the current lead plate 19 has the same size as the outer shape of the peripheral wall so as to contact the entire side wall, and has a connection part 21 of a bus bar from the rectifier on its upper part. have. The thickness of the current lead plate should be selected in consideration of the current carrying area and current density so that the ohmic loss in the current lead plate does not become too large.

The materials for the current lead plate are metals with high electrical conductivity,
For example, copper and aluminum are preferred.

FIG. 7 shows an example of a monopolar electrolytic cell of the present invention. The configuration of the unit cell 17 is the same as in the case of a bipolar electrolytic cell. By arranging the conductive sheet 18 and the current lead plate 19 so that the anode chamber unit and the cathode chamber unit, and the cathode chamber unit and the cathode chamber unit are back to back, this unit cell is tightened with a filter press type fastening frame 20. The electrolyzer is assembled.

The electrolytic cell of the present invention must be operated under pressure. There are no particular restrictions on the method of applying pressure. For example, a pressure regulating valve may be installed in the discharge system of generated chlorine gas and hydrogen gas to apply gas pressure, or the pressure inside the electrolytic cell may be controlled by controlling the circulating flow rate of the anolyte and catholyte supplied to the electrolytic cell. You may. The degree of pressurization is 0.2-3.0kMCm
G is preferably 0.5 to 2.0 kg/cm G. If this is too small, the surface pressure between the side walls of adjacent cells and between the side walls and the current lead plate will be insufficient, and the electrical contact resistance will increase. On the other hand, if it is too large, the electrolytic cell must be constructed to withstand high pressure, making the electrolytic cell expensive.

Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 The bipolar electrolytic cell shown in Fig. 6 was assembled using two unit cells, three conductive sheets, and two current lead plates, and the peripheral wall had a width of 2400 mm, a height of 1200 mm, and a thickness. is 20 mm, the width of the frame portion is 20 mm, and the central portion has a reinforcing rib with a height of 20 mm and a width of 5 mm.

The reinforcing ribs are provided with ten holes with a diameter of 8 mm for passage of the electrolyte and electrolysis products. The peripheral wall for the anode chamber unit was made of titanium, and the peripheral wall for the cathode chamber unit was made of stainless steel.

The side wall has a thickness of 2 mm, has the same external shape as the fusion wall, and is welded to the peripheral wall at its outer and inner peripheries.

Conductive ribs are welded to the side wall at intervals of 12 cm, and the conductive ribs for the anode and the conductive ribs for the cathode are at alternate positions.

The anode conductive rib has a height of 20 mm and a width of 5 mm, and the cathode conductive rib has a height of 22 mm and a width of 5 mm. These conductive ribs are also provided with 10 holes each having a diameter of 8 mm for passage of the electrolytic solution and electrolytic products. The material of the side walls and conductive ribs is the same as that of the peripheral wall, titanium for the anode chamber unit and stainless steel for the cathode chamber unit.

The outside of the side wall of the anode chamber was electrolessly plated with copper.

The anode was manufactured by drilling holes of 2 mm diameter in a zigzag pattern at a pitch of 3 mm in a titanium plate having a thickness of 1 mm, and coating the surface with an oxygen-containing solid solution containing ruthenium, iridium, titanium, and zirconium.

The cathode is a 1mm thick stainless steel plate with 3 2mmφ holes.
The openings were made in a staggered manner with a mm pitch.

As the conductive sheet, an expanded sheet with a short axis of 7 mm and a long axis of 14 mm made from a stainless steel plate with a thickness of 1.5 mm was used. Its size is the same as the outer shape of the surrounding wall.

A 4 mm thick copper plate was used as the current lead plate.

The anode chamber gasket was made of 0.5 mm thick fluororubber, and the cathode chamber gasket was made of 2.5 mm thick ethylene/propylene rubber. Their shape is frame-like with the same dimensions as the surrounding wall.

The cation exchange membrane was manufactured in the following steps.

Tetrafluoroethylene and perfluoro-4,7-dioxy-5-methyl-8-nonenesulfonyl fluoride were copolymerized to produce a polymer with an equivalent weight of 1300 (polymer 1) and a polymer with an equivalent weight of 1130 (polymer 2). Obtained.

These polymers were heat molded to a thickness of 35 mm each.
A two-layer laminate of μ (polymer 1) and 100 μ-polymer 2) was prepared, and a Teflon (registered trademark) woven fabric was embedded from the surface of polymer 2 by a vacuum lamination method. Only the surface of the polymer 1 of the sulfonic acid type cation exchange membrane obtained by saponifying the laminate was subjected to reduction treatment to convert it into carboxylic acid groups.

The electrolytic cell shown in Figure 6 is assembled so that the carboxylic acid of the cation exchange membrane is on the cathode side, and 310 g/I is placed in the anode chamber so that the salt concentration at the outlet is 175 CI/1.
A dilute caustic soda aqueous solution was supplied to the cathode chamber so that the caustic soda concentration at the outlet was 30% by weight, and electrolysis was carried out at an electrolysis temperature of 90° C. and a current density of 40 A/cdm. As a result, the current efficiency was 96.0% and the sliding voltage was 6.7V.

Example 24 Under the same conditions as Example 1, only the conductive sheet was made with a thickness of 0.8
On one side of a mm stainless steel plate, with a pitch of 20 mm in the row direction and 17.5 mm in the column direction, an inner diameter of 3 mm and a depth of 2
Electrolysis was performed using a burring with a recess of 1 mm in diameter and a hole with an inner diameter of 1 mm at the tip. The result is a current efficiency of 96,
0%, and the sliding voltage was 6.6V.

Effects of the Invention As described above, the electrolytic cell of the present invention has low contact electrical resistance between adjacent cells and between the current lead plate and the cell, and the current density within the electrolytic cell is uniform, so that the electrolytic cell of the present invention has a current density of 30A.
It can be operated at a relatively high current density of /Cdm or higher. In order to reduce the electrical contact resistance, it is important to increase the contact pressure, but if the material has elasticity, the contact pressure will not increase due to the buffering effect. Furthermore, it is easy to assemble and disassemble and is inexpensive. Furthermore, it can be constructed as either a bipolar type or a single-polar type depending on the location conditions.

[Brief explanation of the drawing]

1 and 2 are front views of an anode chamber unit and a cathode chamber unit constituting the electrolytic cell of the present invention, and their A-A
= sectional view, FIGS. 3 and 4 are front views of another embodiment of the anode chamber unit and cathode chamber unit, and a BB sectional view thereof, FIG. 5 is one embodiment of the side wall used in the electrolytic cell of the present invention A cross-sectional view of . FIG. 6 is an assembled diagram of a bipolar electrolytic layer of the present invention, and FIG. 7 is an assembled diagram of a monopolar electrolytic cell of the present invention. 1... Peripheral wall 2... Side wall 3... Conductive rib 4... Electrode 5... Supply nozzle 6... Discharge nozzle 7... Reinforcing rib 8... Hole 9... Outer wall surface 10... Corner 11... Hole 12... Cation exchange membrane 13
・15... Gasket 1/1... Anode chamber unit 16... Cathode chamber unit 17... Unit cell 18... Conductive sheet 19.
・Lead plate 20-...Tightening rod 21...
・Connection part

Claims (3)

[Claims] (1) An anode chamber unit consisting of a picture frame-shaped peripheral wall, a metal plate-shaped side wall, and an anode welded to the plate-shaped side wall via a plurality of conductive ribs; A cathode chamber unit consisting of a cathode welded to the plate-shaped side wall via a plurality of conductive ribs, and a plurality of unit cells arranged on both sides of the cation exchange membrane so that the anode and cathode face the membrane. , operated under pressure, characterized in that electrical connections between unit cells and/or between unit cells and current lead plates are made by inelastic plate-like bodies having a large number of protrusions. Ion exchange membrane method alkaline chloride multi-pair electrolyzer (2) A patent in which the plate-shaped side wall of the anode chamber unit and/or cathode chamber unit has a large number of protrusions, and the plate-shaped side wall also acts as an inelastic plate-like body having a large number of protrusions. An electrolytic cell according to claim (1). (3) Claims (
1) The electrolytic cell described.