JPS59208087A - Electrolytic cell for halogen generation and method therefor - Google Patents

Abstract

Halogen is produced by electrolyzing an aqueous halide in a specially designed cell. The cell comprises an analyte chamber and a catholyte chamber separated by a permeable membrane or diaphragm, notably an ion exchange (generally cation exchange) polymer. At least one electrode comprises at least two sections. One section comprises a gas and electrolyte permeable layer, sheet or mat having a catalytic surtace, i.e. one having a low overvoltage, (low hydrogen overvoltage if the cathode and low halogen overvoltage if the anode). This layer is spaced from themembrane by a second portion comprising an electroconductive resiliently compressible layer or mat, which is in contact with the membrane on one side thereof, the other side thereof being in contact with the main cathode. This second or spacer section advantageously has an electrode surface having a higher overvoltage than the first electrode surface. Preferably the cathode has the above construction. Upon electrolysis of alkali metal chloride or other halide in such a cell and with a cathode of the type described above, a low voltage is obtained even at high current densities and the cathode efficiency is high.

Description

DETAILED DESCRIPTION OF THE INVENTION By electrolyzing an aqueous halide solution in a specially designed electrolytic cell... halogen is produced. The cell consists of an anode and a cathode compartment separated by a permeable membrane or diaphragm, in particular an ion exchange (generally cation exchange) polymer. At least one electrode consists of at least two parts. One part is a catalytic surface, i.e. a gas and electrolyte permeable surface with a low hydrogen overvoltage (low hydrogen overvoltage for the cathode and low halogen overvoltage for the anode). consisting of layers, sheets or mats. This layer is separated from the membrane by a second part consisting of an electrically conductive, elastically compressible layer or sheet, which is in contact with the membrane on one side and with the main cathode on the other side. .

It is disadvantageous that this second or spacer part has an electrode surface with a higher overvoltage than the first electrode surface.

Preferably, the cathode has the above configuration. In such a cell and with a cathode of the type described above, low voltages are obtained even at high current densities when using alkali metal chlorides or other halides. and high cathode efficiency.

Prior Art Ion exchange (usually cation exchange) to separate aqueous solutions of alkali metals, halogenides or similar into anodes and cathodes.
It is known to conduct electrolysis in membrane cells with membranes. Since the membrane itself is generally impermeable or substantially impermeable to gas or liquid flow, the electrolysis produces chlorine at the anode and alkali at the anode;
This alkali is of high purity and contains very low chlorine concentrations Q. One type of cell that has been proposed for this type of electrolysis is the solid polymer electrolyte cell.

The solid polymer electrolyte cell is characterized by an ion exchange membrane separating the electrodes of the cell and characterized by one electrode, b6, or preferably both electrodes being in contact with the membrane. A solid polymeric solute cell (with respect to a conventional one-return cell in which the cathode and often both the anode and cathode are separated from the membrane)
, offers several advantages that are useful in various electrolytic processes. More precisely: (1) the overall potential between the electrodes is lower because the distance between the electrodes is reduced to virtually the same extent as the membrane;

2) The so-called "foam effect" is eliminated or at least reduced. That is, the difficulties normally encountered during electrolysis processes in which the gases generated at the electrodes accumulate in the zone between the electrodes are avoided, since the gases generated can be discharged behind the electrodes into the interior of the cell chamber.

3) The cell is of highly compressed form, thus reducing ohmic drops in the current distribution groove.

Ion permeable membranes are cation exchange polymers in the form of thin flexible membranes. Generally, they are nonporous and do not allow the flow of anolyte into the cathode chamber, but such membranes 5 may also be provided with some small pores to allow a small amount of water to pass through it. It has also been suggested that flow may be allowed, although the majority of research appears to have been done with non-porous membranes.

Typical polymers that may be used for this purpose include polymers of hatrifluoroethylene or tetrafluoro1 ethylene or copolymers thereof, which contain ion exchange groups used for this purpose. This ion exchange group is usually sulfonic acid, sulfonamide, carboxylic acid, or phosphorus. , etc., which is bonded through carbon to the fluorocarbon polymer to exchange cations. However, they may also contain anion exchange groups. A typical membrane of this type has the general formula %. Such membranes typically include fluorocarbon ion exchange polymers manufactured by DuPont under the trade name "Nafion" and manufactured by Asahi Glass Company of Japan under the trade name "Flemion". Patents describing membranes of this type include British Patent No. 1,184,821 and US Patent No. 3,282.
&7'5 and U.S. Pat. No. 4,075,405.

These membranes are ion permeable, but impermeable to the electrolyte, so...the chloride ions migrate through the membrane or this type of material in alkaline salt cells, and therefore are The alkali produced in this way contains little or no chloride ions. Additionally, more concentrated alkali metal hydroxides can be produced, with the resulting catholyte containing 15 to 45% or more Na0 by weight.
It is possible to include IJ. Patents describing this seeding method include U.S. Pat. Nos. 4,111,779 and 4,1
00°050 and many others. The application of ion exchange membranes as ion permeable membranes has been proposed for other applications such as in water electrolysis.

In the contemplated type of cell, the cathode is in close proximity or in direct contact with the ion exchange membrane. The membrane 4 is sufficiently permeable to allow the generated scum to escape rapidly from its point of origin and to facilitate the access of the liquid electrolyte to these points while at the same time allowing the formed alkali or other electrolytic products to rapidly escape from these points. must be able to be removed by The electrodes are therefore usually quite porous.

One difficulty encountered with permeable cathodes in direct contact or bonding with this membrane is that the cathode efficiency is relatively low, e.g. 85% or less, and that oxygen is present in significant concentrations e.g. It is to be contained in the generated chlorine in an amount of .5 to 1% or more.

Apparently, some portion of the alkali metal hydroxide produced at the cathode tends to migrate through the membrane.

This may be due to the fact that the caustic soda formed at the interface is not sufficiently and uniformly diluted by the catholyte in the catholyte chamber of the cell.

High alkalinity induces dehydration of the membrane, resulting in reduced electrical conductivity, and, moreover, large concentration gradients increase back-diffusion of hydroxide ions toward the anode, resulting in a loss of faradaic efficiency.

The development of various gradients on or within the membrane gives rise to contraction and swelling of the membrane in localized areas and constant changes in these facts, which can result in delamination and/or loss of the cathode layer or cathode material. It can be. Whatever the actual mechanism, the adverse consequences mentioned above occur.

BEST MODES AND MODES OF CARRYING OUT THE INVENTION In accordance with the present invention, halogens are removed in an electrolytic cell having a pair of opposing electrodes separated by an ion permeable separator, preferably an ion exchange polymer. It is effectively generated by electrolyzing aqueous compound solution,
In this case, at least one electrode, preferably the electrode, has two layers. This first layer is resistant to chemical and electrochemical attack and has a low overpotential, and is easily capable of functioning as an electrode and deploying the electrolyte by electrolysis. The second layer has a higher overvoltage (hydrogen overvoltage in the case of the negative ridge surface or one element overvoltage i in the case of the anodic surface)
between the low overvoltage surface and the membrane, typically in direct contact with the membrane.

Of course, both surfaces are electrically conductive and can be polarized as electrodes. Furthermore, the two surfaces are in direct electrical contact so that there is little or substantially no potential difference between them.

The first or rearmost part of the cathode I has a lower overvoltage than that of the previous part which engages the membrane, so that the main part or even substantially all of the cathodic electrolysis is separated from the membrane by a spacer or barrier. Occurs at a location that is separate and distinct from the membrane surface or its adjacent location.

The cathode, where this main electrolytic reaction takes place, is easily porous and therethrough facilitates the lateral flow of the anhydrous liquid. The cathode may therefore be in the form of a flexible electrically conductive metal screen with 3 to 10 mesh openings per centimeter, or a corrugated wire screen, or a silk composite of these materials. It's good. These openings are relatively large and thus provide a waterway adjacent to the point of contact between the conductive second layer spacer and the main catalytic cathode, thereby allowing the catholyte to flow into the catalytic cathode. It flows along the edge Vc along the surface and adjacent to these points, thereby scavenging the generated alkali from the part in front of the cathode and also from the region remote from the membrane.

For example, more active cathode layers have surfaces consisting of platinum group metals or their oxides, which have very low hydrogen overpotentials. In that case, the intermediate spacer of the layer may have an electrically conductive surface of a metal or arsenic with a higher overpotential. Porous St or stainless steel or nickel screens may be used for this purpose. As can be appreciated, other conductive materials that are susceptible to corrosion in the alkaline cathode region may also be used.

In any case, this intermediate portion is porous and permeable to the electrolyte. Since it is completely electrically conductive,
It acts cooperatively to conduct current to the more distant, active cathode region without increasing the overall voltage.

According to a preferred embodiment of the invention, the intermediate layer or spacer layer of this multilayer cathode consists of an electrically conductive, elastically compressible wire mat, which has a higher hydrogen content than the surface of the main cathode layer or the catalytic cathode layer. Has an overvoltage surface.

The resiliently compressible wire mantle forming the intermediate layer or spacer layer of the cathode is advantageously compressed during cell assembly between the membrane and the active layer or catalyst layer of the cathode. This intermediate resilient layer therefore exerts an elastic reaction force on the membrane and active layer during operation to effectively keep the membrane surface and the active cathode surface apart. In this way, the elastically compressible wire mat forming the interlayer or spacer layer, besides serving to maintain a certain separation between the main active layer of the electrode and the membrane surface, also The flexible membrane is restrained from wobbling under the action of scum bubbles induced by the turbulence of both the liquid and the catholyte, or from bending towards the anode or cathode under the action of fluctuating water pressure differences. This is of great importance because membranes that are assembled in cells without elastic or other means that can hold the membrane firmly in place do not adhere to the porous metal electrodes. This is because they often suffer from scratches due to constant rubbing against them.

Rigid mechanical restraint of this compressed mat is provided on one side by substantially rigid perforated positive cords to which the flexible membrane touches, and on the other side substantially rigid perforated pressure. It may be provided by a plate cathode or it may be a current distributor touched by the apertured catalyst layer of the cathode.

In the latter case, the elastically compressed mat has a dual function. One is a certain degree of isolation. Preferably 1 to 4 leakage isolation is provided and ensured between the membrane surface and the active monopolar layer during cell operation, and the other is a rigid current distribution for satisfactory operation of the cathode. The active cathode layer is pressed against the means.

The active cathode layer is made of noble metals (PtXRh, Ru, Ir,
a cathode such as iron, stainless steel, nickel, copper, or alloys thereof coated with a catalytic material having a low hydrogen overpotential, such as conductive oxides of Pti) or their alloys or other metals thereof; These coach inks, which are most advantageously made of metals that are resistant to liquids and which impart low hydrogen overvoltage properties to the main cathode layer, are rarely permanent and need to be renewed after a period of operation. In view of the need, this preferred embodiment of the present invention replaces a woven active cathode layer without the need to remove or cut the weld and weld or connect a newly coated cathode back in its place. It is clear that great benefits can be gained from the possibilities offered by reification.

Indeed, in the cell of the present invention, the active cathode layer is a thin perforated coated metal screen, which acts as a current distribution means to the elastically compressed spacer layer or mat and the active cathode layer. (simply sandwiched between a substantially rigid pressure plate or a series of spaced ribs or stubs).

The elastically compressible mat forming the relatively high hydrogen overpotential spacer layer is pliable, spring-like in character, and can be compressed up to 60% or more of its uncompressed thickness by application of pressure from compression means. Although it can be compressed against the membrane until it is small, it can also rebound substantially to its initial thickness when the pressure is released.

Thus, its elastic response memory applies and maintains a substantially uniform pressure on the membrane. This is because pressure can be distributed and compensated for irregularities in the adjacent surfaces. It is sufficiently flexible to bend in all directions and take on the contours of the membrane. The compressible mat should also facilitate circulation of electrolyte to and from the membrane surface.

Thus, the compressible layer is open in its structure and contains a large free volume. This elastically compressible cloak is inherently electrically conductive at its surface, is generally made of a metal that resists the electrochemical attack of the contacting electrolyte, and thus covers the entire main active electrode layer. Helps spread polarization and current.

A preferred embodiment of the resilient spacer layer of the present invention consists of a substantially open mesonically planar electrically conductive metal wire article or screen with an open mesh structure and is resistant to electrolyte and electrolysis products. consisting of a resistive wire or fabric, and that some or all of the wire has a diameter or amplitude substantially equal to or less than the thickness of the wire along at least one directrix parallel to the plane of the article; It is characterized by the formation of a series of coils, waves, rips or other corrugations that correspond to the thickness of the article and preferably correspond to the thickness of the article. Of course, such creases or wrinkles are placed across the thickness of the screen.

These wrinkles, in the form of wrinkles, coils, waves, etc., have sides that are sloped or curved with respect to an axis perpendicular to the thickness of the wrinkled fabric, thus compressing the layer. Sometimes some deflection and pressure is transmitted laterally to make the pressure distribution more uniform over the electrode area or electrode surface.

A coil or loop of wire in one section that is subjected to a compressive force greater than that acting on the adjacent area but does not twist due to irregularities in the flatness or parallelism of the surfaces compressing this fabric, By transmitting excess force to the wire, it can be deflected more to release it. Therefore, the fabric acts to a substantial extent as a pressure equalizer and prevents the elastic response forces acting on a single point of contact from being exceeded and thereby over-tightening or penetrating the membrane. It is effective for. Of course, such self-adjusting ability of the elastic layer also helps to obtain a good and uniform contact distribution over the entire electrode surface.

One highly effective embodiment preferably consists of a series of helical cylindrical spirals, the coils interlocking with the coils of adjacent spirals in mutual meshing or mutual looping relationship. It's wrapped. The diameter of the spiral is 5 to 10 times or more the diameter of the wire in the spiral. According to this preferred arrangement, the wire helix itself represents a very small portion of the volume enclosed by the helix, so that the helix is open when viewed from the distal side, thereby providing an internal waterway to allow circulation of the electrolyte. do.

However, this helical cylindrical spiral does not need to be wound with adjacent spirals in a mutual mesh-forming relationship as described above; It's okay. In that case, these spirals are juxtaposed next to each other and each coil is only involved in one alternation I-.

According to another embodiment, the spacer layer consists of a crimped mesonue or fabric of metal wires, in which case each single wire has a maximum height of the crimps of the woven mesh or fabric. It forms a series of amplitudes corresponding to his. In one variant, two or more knitted pieces or fabrics are shredded individually by molding and then layered on top of each other to obtain a single layer of desired thickness. You can.

Crinkling the metal mesh or fabric imparts a high compressibility and significant compressive resilience under a load of at least about 50-2000 mm per square centimeter of the surface to which pressure is applied. It can be 9.

The mat can be compressed to a much smaller thickness and volume. For example, about 50 to 90% of its initial volume and/or thickness
Alternatively, it may be compressed to an even smaller degree, and therefore compressed between the membrane and the active cathode layer.

The mat is mobile or sliding with respect to the adjacent surfaces IK of the membrane and active cathode layer between which it is compressed.

When clamping applies pressure, the loops or coils of wire that make up the resilient mat shift laterally to distribute the pressure evenly over the surfaces in sliding contact.

Most of the cell clamping pressure is stored elastically by each individual coil or wire of metal wire forming the spacer layer.

Preferably, the resilient periphery mat is compressed to about 80 to 30 factors of its original uncompressed thickness under a compression pressure of between 5 and 200 degrees per square centimeter of projected area. Even in its compressed state, this elastic mantle must be highly porous, such that the ratio between the hollow volume of the compressed mat and its apparent volume, expressed as a percentage, is at least a factor of 75 (in rare cases 50% or less), preferably 8
Advantageously, it consists of between 5% and 96%.

The diameter of the wire used may vary within wide limits depending on the type of molding or weaving, and is still sufficiently small to obtain the desired elasticity and deformation properties at cell assembly pressures. 50 and 5009/cm of electrode surface
An assembly pressure corresponding to a load of between 2 and 2 is typically required to obtain good electrical contact between the active negative r+ layer and the cooperating current distribution structure or current collector. However, higher pressures may also be used.

By providing a further deformation of the elastic spacer of the present invention of about 1.5 to 3 mm, corresponding to a compression of not more than 60q6 of the thickness of the uncompressed article at a pressure of about 400 g/m2 for the projected area, the active cathode Contact pressures in the layers can be obtained within the above limits or alternatively with deviations from the plane of up to 2 mml/m.

The diameter of the metal wire is preferably between 0,1 mm or even less and 0-8 mm, - the force, the thickness of the uncompressed article, i.e. the coil diameter or amplitude when tightening is the wire 5 times the diameter or more,
Preferably it is in the range of 4 to 10 powers. Thus, the compressible portion encloses a large free or occupied volume portion, which is free and open to electrolyte flow and gas flow.

In the wrinkled fabric described above (which includes compressed wire helices), this percentage of free volume is approximately 75% of the total volume occupied by the fabric.
, and this free volume percentage should not be less than 25 parts, and preferably should not be less than 50 parts. The pressure drop in the flow of scum and electrolyte through such a fabric is negligible.

The failure rule 1 contemplated here may be applied to electrolytic cells such as those depicted in the +1 genus diagram.

1 is a diagrammatic horizontal cross-section of a cell with a double layer electrode therein, and FIG. 2 is a diagrammatic vertical cross-section of the cell of FIG.

As shown, the cell consists of an anode end plate 1 and a cathode end plate 2, both of which are mounted in one vertical plane, with each end plate in the form of a water channel forming an anode space 3 and a cathode space 4. It has a side wall that encloses each. Each endplate also has one peripheral sealing surface on the sidewall projecting from the plane of the respective endplate to each side of the cell, 5 anode/-
6 is a cathode sealing surface. These surfaces touch the membrane or diaphragm 7 by means of the insertion of suitable gaskets, not shown in the figure, which membrane or diaphragm,...
The anode and cathode are separated by crossing the space between the side walls.

The anode 8 consists of a relatively rigid, incompressible piece of expanded titanium metal or other anodically resistant substrate, preferably a non-passivated metal or oxide or mixed oxide of a platinum group metal. It also has a sex coating on it. This seam 1- is sized to fit within the side wall of the anode backing plate and is rather fixed by spaced electrically conductive ribs 9 fixed to the web or base of the anode plate 1 and projecting therefrom. Rigidly supported. The spaces between the ribs provide easy flow of anolyte, which is supplied from the bottom and withdrawn from the top.

The entire end plate and ribs may be graphite or may be titanium clad steel or other suitable material. positive i/-
) 8 may or may not be coated, for example with platinum or a similar metal, to improve the electrical contact, and the anodic sort 8 may be welded to the rib 9 if necessary. good.

The rigid perforated sort 8 of the anode is held firmly in a vertical position. This sort may be made of expanded metal with an opening 1o sloping upwardly and outwardly from the membrane, deflecting rising gas bubbles into the space 90 force and away from the membrane.

On the cathode side, the ribs 11 extend outwardly from the base of the cathode plate 2 by a distance of a fraction of the total depth of the cathode space 4. These ribs are spaced across the cell to provide parallel space for vertical electrolyte flow from bottom to top, and are interlocked with the sheet or layered cathode. The cathode plate and ribs may be made of steel or nickel-iron alloy or other cathodically resistive electrically conductive material. A relatively rigid pressure plate 12 is welded onto this conductive rib 11, which is perforated to facilitate circulation of electrolyte from one side thereof to the other.

Typically these openings or shutters are directed into space 4.
(See Figure 2).

The pressure plate is electrically conductive and serves to impart cathodic polarity to the electrode and apply pressure to it, and may be made of expanded metal or steel, nickel, copper or alloys thereof. It may be made with a heavy screen.

The main or active cathode layer is an implicitly resistive material such as nickel, stainless steel, iron, copper, or alloys thereof coated with an implicitly resistive catalytic material having a low hydrogen overpotential. A tiny amount of electrically conductive material? It is advantageous to make it with +l110J sacrificial screen 13. Many catalytic materials for hydrogen evolution in caustic solutions are known in the art, and particularly suitable materials include noble metals such as platinum, ruthenium, palladium, rhodium, iridium, and osmium, their alloys and acid f metal, Raney nickel, molybdenum and tungsten alloys. Any of these materials can be successfully used to coat the cathode screen.

The elastically compressible spacer layer 14 inserted between the membrane 7 and the main active layer 13 is a compressible wire mesh fabric with crimped corrugations or wrinkles, which fabric is disclosed in US Pat. Advantageously, open mesh braided wire strands of the type described in No. 4,343,690,
In that patent, wire strands are woven into a relatively flat fabric with interlocking loops. This fabric is then tightened or wrinkled into a single corrugation, which is spaced close together, say 0.3 to 2 centimeters apart, and this compressible texture gives a total length of 2 to 10 millimeters. This crimp has a rippled or herringbone pattern, and the menonille of the fabric is coarser, that is, it has a larger pore size than the pore size of the screen 13.

In this preferred embodiment, the resiliently compressible spacer layer 14 is connected to the pressure plate 12 and the main or active cathode 1.
The cathode layer 13 is connected to the current distribution pressure plate 1 by the spacer layer 14, which serves to provide good electrical contact between the
2 evenly over the entire surface of the electrode.

The resiliently compressible spacer layer 14 also keeps the flexible membrane 7 pressed against the rigid apertured anode 8 as it moves in and out of the cell. prevent things.

Layer 14 effectively separates the main or active cathode layer from the membrane at a readily predetermined distance, which distance may be between 1 and 4.

Since the spacer layer 14 has a higher hydrogen overpotential than the active layer 3, the electrode reaction is substantially reduced by the catalytic screen 130.
This occurs at the surface, which is also due to the highly anomalous structure of the compressed layer 14 of thin metal wires.

The products of the electrode reaction are easily diluted and quickly removed from the membrane surface, thus effectively preventing high concentration gradients at the membrane surface.

In operation of this embodiment, a substantially saturated aqueous solution of thorium chloride is fed into the bottom of the anode chamber of the cell and
Acupuncture water with reduced concentration and generated chlorine flow in two directions in the waterway or space 3, and exit from the top of the cell. Water or dilute sodium hydroxide is fed into the bottom of the cathode chamber and rises through the conduit 4 as well as the cavity of the compression spacer layer 14, and the evolved hydrogen and alkali are removed from the top of the cell.

Electrolysis is caused by applying a direct current electrical potential between the anode and cathode plates.

As shown in FIG. 2, the openings in the pressure plate 12 are windowed to provide an angled outlet oriented upwardly away from the compressed material layer 14, thereby allowing the generated hydrogen and or the electrolyte exits behind the electrolyte chamber 4. The space occupied by the Ti vertical space behind the pressure plate 12 and the compressed fabric 14 is therefore provided for the upward flow of electrolyte and scum. Ru.

According to the improved method of the present invention for sodium chloride electrolysis, 14
Acupuncture water containing 0 to aooy/l of sodium chloride is circulated into the anode chamber of the cell. Chlorine: is generated at the anode, while the hydrated ions migrate through the cation membrane to the cathode, where a substantial concentration of caustic powder and hydrogen of 15-20% by weight or more is produced. Alkali metal hydroxides with a weight ratio of 25 to 40% are more than 90%, often 94%
can be produced with anode efficiencies and cathode efficiencies of two.

The following examples are for illustrative purposes only.

A laboratory-sized electrolytic cell with an effective electrode area of 100 mm in height and 100 mm in width was constructed.

The frame and back plate of the cell were made of titanium for the anode part and stainless steel (Al5I816) for the cathode part L.

As mentioned above, the anode is coated with a mixture of ruthenium and titanium oxides in a 1:1 ratio of each with a non-passivating catalytic coating obtained by pyrolysis of salt solutions of these metals. It was an expanded titanium plate with a thickness of 1.5.

The depth of the anode chamber behind the anode was 12 mm.

The membrane is a laminate sheet approximately 0.25+nm thick, consisting of two layers of cation exchange resin laminated together with an interlayer of polytetrafluoroethylene screen as mechanical support. The two layers are made of a copolymer of tetrafluoroethylene and perfluorovinyl ether, one carrying sulfonic groups and the other containing carboxyl groups.

The membrane was assembled in the cell with its carboxyl layer facing the cathode chamber.

The cathode structure consisted of a) 5m+ welded onto the vertical rift of AISI 316;
Holes with a diameter of 8.0 m + n are drilled at ++ intervals, and the thickness is 2.
Current collector in the shape of a notebook with a hole of 0mm Al51 316. The depth of the cathode chamber behind this current collector screen is 1
I got 8m1.

b) A 25 M/U nickel screen plated with an alloy of ruthenium (80 to 85%) and nickel (15 to 20%) at 7-89/m2 to give a particularly low hydrogen overvoltage. shaped, main or catalytic cathode layer.

C) One layer of elastically compressed spacer in the form of a mat made of three double layers of loosely woven nickel wire with a diameter of 0.11 mm.

A catalytic cathode layer b) is inserted between a rigid current collector a) and an elastic spacer layer C), which when tightening the cells together compresses the elastic mat into the li plane. , this membrane will touch the rigid one-field pole. Approximately 400 g
/cm2 pressure ((the corresponding compression reduces the thickness of the elastic mat inserted between the active cathode screen and the membrane to about 6y
The initial uncompressed thickness force of nm was reduced to approximately 2.7 m+π. Therefore, the distance between the anode surface and the surface of the active cathode layer was about 2.7 mm plus the film thickness, ie practically comprised between 2.7 mm and 2.8yo++.

The cell was operated under the following conditions.

Current rating: 3000A/m' Anode concentration: NaC (l l 76g/11Catholyte concentration 30% by weight Na01in quality,
90°C ± 1°C Cell voltage: 3.121/' ± 0.02 Cathode current efficiency: 94.5% α element in chlorine scum: 0.1% by volume Reference Example Same as that described in Example 1 The cell is dismantled and the nickel-coated (b) main (or catalytic) cathode screen is placed against the surface of the membrane, and the braided nickel wire (C) elastic mesh is used as the rigid current collector a). and an active cathode screen.

When reassembling the cell, this elastic cloak should be approximately 2.7 m long.
The active cathode screen was compressed to a thickness of 1 m, thereby applying a pressure of 11 m against the membrane surface. Therefore, the distance between the anode and cathode surfaces depends on the thickness of the film. Zunawachi approx. 0
．． It was 25 mm.

The cell was operated under exactly the same conditions as described in the previous experiment and the following results were obtained.

Cell voltage: 3.19T/'±0.02 Cathode current efficiency: 93% Oxygen in chlorine gas: 0.5 volume ratio The method of the present invention can be applied to any type of ion permeation l! It may also be implemented with a negative value.

The membrane may be of the single-layer type, or it may be a laminated membrane consisting of different layers made of ion-exchange resins (or the membrane may contain reinforcing O-fibers or fabrics). It's okay to stay.

The surface of the membrane may be modified either in its chemical composition or in its physical form, for example the membrane may have a rough surface.

The membrane may also have a porous layer over the entire surface of the membrane, either of resin or of particulate material forming a microporous layer, which layer is either conductive or non-conductive in nature.

As will be clear to the expert, the current distribution means, which are depicted in the preferred embodiment in the accompanying drawings in the form of a substantially rigid perforated plate 12, may be of a different nature, for example: The active cathode screen 13 may be pressed by elastic wires directly against the vertical ribs 11 extending from the cathode end plate.

Preferably in the latter case, the active cathode 13 may be made of a heavier gauge screen and the distribution of vertical ribs may be closer, i.e. there may be a large number of vertical ribs between the active screen and the current distribution means. To provide electrical contact, the cell chamber should be closely spaced with a number of ribs per unit width (
・.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic horizontal sectional view of a cell with a double layer electrode therein, and FIG. 2 is a cross-sectional view of the cell diagram II'1 of FIG. 1: Anode end plate 2: Cathode end plate 3: Anode chamber 4: Cathode chamber 7: Membrane 8: Rigid perforated notebook 9. 11: Rib 10: Opening 12: Rigid pressure plate 13 2. Flexible screen 14: Resilient Compressible Spearer ~ 47 Procedural Amendments 1. Indication of the case Showa Gen δ Year Patent Application No. 1131OL No. 2, Name of the Invention No. 34 Part 1 YO・SI゛ Large L6 Amendment Person Relationship with the Case Patent Applicant Address 4 agent 5 subject of amendment 478-

Claims (1)

[Scope of Claims] 1° An ion permeable membrane dividing the electrolytic cell into an anode chamber and a cathode chamber; substantially rigid current distribution means and a high hydrogen overvoltage screen between the membrane and a low hydrogen overvoltage screen; consisting of one screen with a low hydrogen overvoltage in direct contact with a resiliently compressible wire mat, and maintaining the low hydrogen overvoltage screen separated from the membrane while the low overvoltage screen is connected to the current distribution means. consisting of a cloak that is pressed with
A method of chlorine generation consisting of electrolyzing an alkali metal chloride in an electrolytic cell with a cathode in a cathode chamber. 2. The method according to claim 1, wherein the membrane is pressed against the anode surface by the above-mentioned elastically compressible wire mat. 8. Consisting of an ion exchange membrane that divides the electrolytic cell into an anode chamber and a cathode chamber, a perforated anode in the anode chamber, and a porous cathode in the cathode chamber; consisting of a screen with a low hydrogen overpotential surface separated from the surface of the membrane by a resiliently compressed wire cloak with a high hydrogen overpotential surface, and which screen is connected to the current distribution means mounted in the cathode chamber by Diaphragm electrolytic cell, characterized in that it is compressed by an elastically compressed wire cloak; 4. The electrolytic cell according to claim 3, wherein the membrane is in direct contact with the surface of the porous anode.