KR840002296B1 - Method of electrolyzing halides - Google Patents

Abstract

An electrolytic cell, partic. for chlorine prodn. includes a flexible ion-permeable draphragm with a compliant electrode layer on one or both side and a current distributor bearing against the layer. The distributor or a counter-electrode on the other side of the diaphragm is a resiliently compressible mat coextensive with the electrode. The mat applies pressure at multiple points so that equalising pressure is made by transferring excess from one point to adjacent points. The mat is open to permit electrolyte flow.

Description

Electrolysis of Halides in Electrolyzers

1 is a photograph showing one example of a representative elastic compression mat used by the method of the present invention.

Figure 2 is a photograph showing another example of the elastic compression mat used by the method of the present invention.

Figure 3 is a photograph showing another example of the elastic compression mat used by the method of the present invention.

4 is an exploded horizontal sectional view of a solid electrolyte electrolyzer having a representative compressible electrode in which the compression section is composed of a screw wire in the electrolytic cell used by the method of the present invention.

5 is a horizontal cross-sectional view of the electrolytic cell of FIG.

6 is an exploded perspective view of another example showing the current collector of the electrolytic cell of FIG.

7 is an exploded perspective view of another example showing the current collector of the electrolytic cell of FIG.

8 is an exploded cross-sectional view showing another example of an electrolytic cell used by the method of the present invention.

9 is a horizontal cross-sectional view of the electrolytic cell of FIG.

Figure 10 is a horizontal sectional view showing another example of an electrolytic cell used by the method of the present invention.

FIG. 11 is a partial vertical sectional view of the electrolytic cell of FIG. 10. FIG.

Figure 12 is a schematic diagram showing the electrolyte circulation system used in the electrolytic cell according to the method of the present invention.

13 is a graph showing the voltage drop obtained when the pressure on the electrode and the diaphragm increases.

The present invention relates to a process for the electrolysis of halides to generate chlorine or other halogens by electrolysis of halide ion-containing aqueous solutions, such as hydrochloric acid and / or alkali metal chlorides or their corresponding other electrolytic halogen compounds in an electrolytic cell. It is about.

In particular, in the electrolysis method of a halide that generates chlorine or halogen by electrolysis of an aqueous halide ion-containing solution in an electrolytic cell, an ion-permeable membrane is formed by positively charged a halogen-containing electrolyte. contact with a parmeable membrane and electrolyze between a pair of electrodes formed along its opposite sides,

A relatively fine and flexible gas and electrolyte permeable screen having a surface in which at least one electrode has a direct contact with the diaphragm and a conductive surface supporting the diaphragm, supporting the flexible screen and being opened in the electrolyte and gas flow. opne) consisting of a coarser electro conductive compre ssible mat at the back and a harder part than the back of the mat, so that the mat and the harder part are made up of the major area and the substantial of the flexible screen. The flexible screen is held in the same space and supported against the diaphragm by the pressure applied to the harder part to supply the electrolyte to the flexible screen so that at least one of the electrodes is in contact with the halide electrolyte so as to contact the halide electrolyte. Electrolysis of halides in an electrolytic cell characterized by electrolysis of aqueous solution to generate halogen It relates how decomposition.

In particular, in a single electrolytic cell in which an anode and a cathode are separated by an ion permeable diaphragm and an electrolytic cell having a liquid permeable diaphragm, alkali metal chlorides or other halides are circulated through the anolyte chamber. Chlorine was generated for a long time by allowing some to flow through the diaphragm to catholyte and undergo electrolysis. In electrolysing an alkali metal chloride solution, chlorine is generated at the anode, and a solution of alkali, ie alkali metal carbonate or bicarbonate or generally alkali metal hydroxide, is formed at the cathode.

Such alkaline liquids also contain alkali metal chlorides, which must be separated from the alkali in the following operation, which is relatively diluted and rarely exceeds 12-15 wt% of alkali.

Generally, the concentration of commercial sodium hydroxide is about 15 wt% or more, so the water in the dilute solution must be evaporated to achieve this concentration.

Furthermore, considerable research has recently been made on the use of ion exchange resins or polymers in the form of thin sheets or membranes as ion permeable diaphragms.

In general, these ion permeable diaphragms do not have a hole, so the anolyte does not flow into the cathode chamber, but such a diaphragm has a few holes so that the anolyte flows through the diaphragm.

Most of the research, however, has been done on diaphragms without holes.

Representative polymers that can be used for this purpose include fluorocarbon polymers such as unsaturated fluorocarbons.

By way of example, trifluoro ethylene or tetrafluoro ethylene polymers or copolymers thereof comprising ion exchange groups are used for this purpose.

In general, ion exchange groups are anionic groups such as sulfonic acid, sulfonamide, carboxylic acid, and phosphoric acid, and a fluorocarbon polymer is bonded to carbon to exchange anions.

However, their groups also include cation exchange groups.

Therefore, the general formula of these groups is as follows.

Such diaphragms are mainly manufactured by DuPont, Saga, and Asahi Glass Co., Ltd. under the trade name " Nafion, " under the trade name " Flemion. &Quot; There is 4075405.

These diaphragms are ion permeable, but since the anolyte cannot flow through this diaphragm, halide ions are hardly transported through the diaphragm of these materials in the alkali chloride electrolytic cell, and thus the alkali obtained contains almost no chloride ions.

Furthermore, it is possible to produce thicker alkali metal hydroxides and the resulting catholyte comprises a concentration of 15-45 wt% or higher NaOH.

Patents for such treatments include US Pat. Nos. 4,1117,79 and 4100050 and many others.

The application of ion exchange membranes as ion permeable membranes has been proposed for other uses, such as electrolysis of water.

Such electrolysis is carried out between the anode and the cathode, separated by a membrane, in particular an ion exchange membrane, in which case the anode or cathode or both are in the form of a porous foil layer of a conductive material resistant to electrochemical attack or bonded to the surface of the membrane. It is a notice.

Similar electrode-diaphragm assemblies have long been used in fuel cells called "solid polymer electrolyte" cells.

Such a battery has been used for a long time as a gas fuel cell, and has recently been used for the electrolytic production of chlorine in hydrochloric acid or alkali metal chlorine.

When producing chlorine in a solid polymer electrolyzer, the electrode is a porous thin layer of conductive electrocatalyst material permanently bonded to the surface of the ion exchange membrane with a binder made of fluoroin polymer, eg polytetrafluoroethylene (PTEE). It is generally composed of.

According to a preferred treatment method for producing a gas permeable electrode as in US Patent No. 3297484, 1 g of polytetrafluoroethylene is mixed by mixing the powder with an aqueous dispersion of polytetrafluoroethylene powder with a conductive electrocatalyst. Obtain a doughy mixture containing 2-20 g of sugar powder.

The mixture thus treated is diluted, if necessary, distributed over a supporting metal sheet, dried, and then the powder layer is covered with aluminum foil and pressed to a temperature sufficient to sinter the polytetrafluoroethylene particles to obtain a thin adhesive film.

After the aluminum foil is removed by NaOH leaching, a perforated electrode is attached to the diaphragm surface and pressed to a temperature sufficient to sinter the polytetrafluoroethylene matrix to the diaphragm. After quenching, the support metal sheet is removed and the electrode is bonded to the diaphragm.

Since the electrodes of the electrolytic cell are in close contact with both surfaces of the diaphragm separating the anode and cathode chambers and are not supported by the metal structure, respectively, the most efficient method of transmitting and distributing the current to the electrode is the uniform distribution of the electrolyzer. This is due to a plurality of point contacts uniformly distributed over the entire surface of the electrode by a current-carrying structure that constitutes a series of protrusions or ribs in contact with the surface of the electrode.

A diaphragm having coupling electrodes on both surfaces thereof must be pressed between two current carrying structures, an anode and a cathode, respectively. Unlike those that occur in fuel cells where the reactants are gaseous, have low current densities, and do not cause side reactions at the electrodes, solutions, particularly solid electrolytes used for the electrolysis of sodium chloride brine, are difficult to solve.

In the electrolytic cell for electrolysis of sodium chloride brine, the following reaction takes place in each part of the tank.

State of the anode _{^{reaction: 2Cl - → Cl 2 + 2e}} -

Movement through the diaphragm: 2Na ⁺ + H ₂

Cathode _{reaction: 2H 2 O + 2e → 2OH} - + H 2

Of the anode side _{^{reaction: 2OH - → O 2 + 2H}} 2 O + 4e -

Total main reaction: 2NaCl + 2H ₂ O → 2HaOH + Cl ₂ + H ₂

Therefore, in addition to the main reaction of chlorine discharge, the oxidation of water occurs in the anode to some extent, and as a result, it is kept as low as possible, but oxygen is generated.

This tendency for corals to be generated is particularly high by the alkaline environment at the active side of the anode, which is made of catalytic particles in contact with the diaphragm.

In fact, cation exchange diaphragms suitable for the electrolysis of alkali metal halides have different transfer numbers per membrane, and under high alkaline conditions present in the catholyte, some of these diaphragms are anolyte in the catholyte through the diaphragm. As a result, there are some shifts in the anion of the hydroxyl group.

Furthermore, the conditions necessary for efficient movement and gas generation of the liquid electrolyte on the electrode active surface require a diaphragm of the anode and cathode characterized by the flow portion for the electrolyte and the gas being relatively larger than for the fuel cell.

The electrodes, on the contrary, have a minimum thickness, typically in the range of 40-150 μ, and should be an efficient mass exchange of large amounts of liquid electrolyte.

In addition to these requirements, the electrode, in particular the electrocatalytic conductive material constituting the anode, is often a mixed oxide having a platinum group metal oxide or powder metal bonded by a binder which is rarely conductive. It is slightly conductive in the size direction.

Therefore, in addition to high-density contact with the collector, a uniform contact pressure should limit the anti-lowering in the electrolytic cell and have a uniform current density over the entire active surface of the electrolytic cell.

It is extremely difficult to meet these demands, especially in electrolyzers characterized by large surface areas, e.

For economic reasons, industrial electrolysers require at least 0.5 m ² , preferably 1-3 m ² or more of electrode surface, and tie rods in a filter press arrangement with electrical connections in series. The electrolytic device comprises up to several dozen bipolar electrolytic cells assembled by a liquid or gas jack.

Electrolyzers of this size have a major technical problem in providing a current-carrying structure, that is, producing a current collector with an extremely low error on the contact plane and giving a uniform contact pressure to the electrode surface after assembly of the electrolyzer.

Moreover, the diaphragm used in such an electrolyzer should be very thin to limit the resistance drop through the solid electrolyte in the electrolyzer. The thickness of the diaphragm is less than 0.2 mm, most not less than 2 mm, and the diaphragm is high when the electrolyzer is closed. When voltage is applied, it easily breaks or becomes excessively thin at many points.

Thus, the two negative anode collectors must be nearly exactly parallel, in addition to being almost completely planar.

Smaller electrolyzers provide some degree of collector flexibility to maintain a high degree of planarity and parallelism while compensating for slight bias in accurate planarity and parallelism.

U.S. Patent Application No. 57255, filed July 12, 1979, describes a solid electrolyte monopolar electrolyzer for sodium chloride, in which the two negative current collectors are turned off. It consists of a screen or telescopic sheet welded to each set of vertical metal pits, which is turned off, and is configured to apply more even pressure on the diaphragm surface by bending the screen to some degree when assembling the electrolyzer.

In addition, in the solid electrolyte bipolar electrolyzer of US Patent Application No. 951984, filed October 16, 1978, electrolysis of sodium chloride is described. In this electrolysis, bipolar separators are described. On both sides and at portions corresponding to the electrodes having a series of ribs and protrusions.

In order to compensate for slight deviations in planarity and parallelism, the resilient means is considered positive, taking into account the insertion of resilient means of screens or stretch sheets of two or more valve metals coated with a non-passivatable material. It is compressed between the anode-side rib and the anode bonded to the anode side of the diaphragm.

However, the two patent application solutions exemplified above have significant drawbacks and limitations in electrolytic cells which are characterized by large electrode surfaces.

First, there is a lack of uniformity of contact pressure that is required, resulting in concentration of current at many points where contact pressure is larger, resulting in polarization, inactivation of the diaphragm and catalyst electrode, local breakage of the diaphragm, Local mechanical damage often occurs when assembling an electrolyzer.

Second, the highest planarity and parallelism should be provided on the dipole separator surface, but this requires precise and costly machining on the seal surface of the rib and dipole separator.

Moreover, the rigidity of each component is followed by a pressurization which tends to accumulate along the heat, limiting the number of components that can be assembled in a single filter press batch.

Due to this technical difficulty, the current distribution screen is not in contact with some of the electrode portions when pressed against the electrode or is in contact with the degree of inherent effect.

A comparative test in which the dispensing screen was pressed against a pressure-sensitive paper that could give a visible impression corresponding to the screen. Markings do not appear, indicating that their large surface area is not in contact.

It is clear that when this observation is applied to the electrode, the actual electrode surface area does not work, and in fact it is.

Accordingly, the present invention provides an ion permeable membrane in which the halide containing electrolyte is positively charged in the electrolysis method of a halide that generates chlorine or other halogen by electrolysis of a halide ion-containing aqueous solution in an electrolytic cell. (electrode) between a pair of electrodes formed in contact with an ion-permeable membrane and formed along the opposite sides thereof, the at least one electrode having a surface in direct contact with the diaphragm and having a conductive surface supporting the diaphragm. This flexible gas and electrolyte permeable screen, a coarser electro conductive compressible mat in the back that is open to the electrolyte and the gas rod supporting the flexible screen and harder than the back of the mat The mat and the harder part are the main parts of the flexible screen. The flexible screen is supported against the diaphragm by the pressure applied to the harder part so that the flexible screen is substantially in the same space as the major area so that the electrolyte is supplied to the flexible screen so that at least one of the electrodes is a halide electrolyte. It provides a method for the electrolysis of halides in an electrolytic cell, characterized in that to generate a halogen by electrolysis of an aqueous solution of a halide containing electrolyte by contact with.

It is also an object of the present invention to have an electrode in direct contact with the diaphragm, the electrode or part of which can be easily compressed, has high elasticity and effectively distributes the clamping pressure of the electrolytic cell to the entire electrode surface effectively and uniformly. Electrolyzing alkali metal chlorides with an electrolytic cell.

One preferred embodiment of a flexible current collector or electrode according to the method of the present invention consists of an opening mesh, a planar conductive metal wire product or a screen made of a wire fabric having an opening mesh and resistant to electrolyte and electrolytic products. And part or all of the wire forms a series of coils, waves or crimps or other wave contours, the diameter or amplitude of which is greater than the wire thickness and preferably at least parallel to the plane of the product. One feature is to match the thickness of the product with a directrix.

Of course, such a crimp or wrinkle is provided in the direction of passing through the thickness of the screen.

Their crimps, coils, ripples, and other forms of wrinkles have sides that are inclined or curved with respect to the axis perpendicular to the thickness of the corrugated fabric, and when the collector is compressed, some displacement and pressure are transmitted transversely to force the electrode portion. To distribute more evenly.

Since the flatness and parallelism of the surface compressing the fabric are irregular, some coils or wire loops that exert more compressive force than acting on the adjacent part deform further to transfer forces to the adjacent coil or wire loop. Releases excess power.

Thus, the fabric acts as a pressure equalizer to its practical extent and is effective in preventing elastic recoil forces acting on a single point of contact exceeding the limit. Because of this, the diaphragm is too pinched or penetrated.

Of course, the self-regulating ability of the resilient collector is good across the entire surface of the country and helps to obtain a uniform contact distribution.

One of the most preferred and effective examples is a series of spiral and cylindrical winding wires, with coils connected to adjacent windings and wound around each other.

This spiral is of a length that actually corresponds to the height or width of the electrode chamber and is at least 10 cm or more in length, and the number of interconnected windings is sufficient to join the full width and the diameter of the winding is equal to the wire diameter of the winding. 5 to 10 times or more.

According to a more preferred arrangement the wire winding itself occupies a very small part of the cross section of the electrode chamber enclosed by the winding, so that the winding is open at its front and thus the channel and the electrode chamber through which the electrolyte can circulate. This provides a riser for gas bubbles.

However, this spiral cylindrical winding does not need to be wound together with adjacent windings as above.

These windings may also consist of adjacent single metal wire windings. In this case, the windings are parallel to each other with each of the coils simply joined together.

By doing in this way, high contact point density is achieved and it has a cavity board represented by the counter positive or counter current collector and the electrolytic cell single plate.

In another embodiment, the current collector or distributor consists of crimped knitted mesh or metal wire fabric, each wire having a size corresponding to the highest height of the crimp of the knitted mesh or fabric. Form a wave;

Thus, each metal wire is in contact with an electrolytic monolayer that acts as an alternating pressure plate and a porous electrode plate bonded to the diaphragm surface, an electrode layer or an intermediate flexible screen interposed between the diaphragm and the compressive layer.

At least a portion of the mesh extends through the thickness of the fabric and is open to the electrolyte flowing in the end direction.

Alternatively, two or more knitted meshes or fabrics may be superimposed after each being crimped by forming to obtain a collector of the required thickness.

Crimping of the metal mesh or fabric gives the collector a high compressibility and good elasticity with a load application surface, i.e. at least 50-200 g load per cm ^{2 of} back or veneer.

It is preferable that the electrode according to the method of the present invention has a thickness that is different from the length of the electrode chamber after assembling the electrolytic cell, but the length of the electrode chamber is usually larger.

In this case, a porous and substantially hard screen or plate spaced from the rear wall surface of the electrode chamber serves as a compression surface for the compressible elastic collector mat.

In this case, the space in front of the screen, at least relative and rigid, is open and provides a channel through which the gases and electrolytes flow. The mat can be compressed to extremely low thickness and capacity.

As an example, the mat can compress to about 50-90% or less of its initial capacity and / or thickness, thereby compressing or compressing between the diaphragm and the thick plate by tightening the conductive thick plate of the diaphragm and electrolyzer. The compression sheet can move.

In other words, they are not welded or coupled to the electrolyzer single plate or the inserted screen, and are moved to the power source and the electrode to which the current is actually connected by the mechanical contact therewith.

The mat can move and slide about the adjacent surface of these elements in contact with the mat.

When applying tightening pressure, the wire loops or coils that make up the resilient mat deform and slide transversely, evenly distributing pressure across the entire surface in contact with it.

In this way, the mat performs better than the individual springs distributed throughout the electrode surface because there is no interaction between pressure points to compensate for the indeterminateness of the support surface on which the spring is fixed.

Most of the tightening pressure of the electrolytic cell is stored elastically by a single waveform of the metal wire forming the current collector or by the coil.

In practice, the elastic collector of the present invention has a large mechanical strain that causes elastic deformation in one or more coils or crimps, so that the elastic collector of the present invention penetrates the diaphragm at a larger point or minute when the electrolytic cell is assembled. Can be effectively prevented or avoided from becoming thin or excessively thin.

Thus, in addition to the high deviations in the planarity of the current carrying structure of the mass electrode, the deviation in parallelism between the structure and the electrolytic cell plate or the back pressure plate may be allowed.

The flexible electrode according to the method of the present invention is more advantageous in that the negative electrode is made of or is like the harder type of positive electrode or faces the positive electrode, which means that the electrode on the positive side (+) side is somewhat harder supported. do.

In the electrolytic cell for the electrolysis of sodium chloride salt solution, it is preferable that the negative electrode mat or the compressive sheet be composed of nickel or nickel alloy wire or stainless steel wire because of its high resistance to satellite embrittlement by NaOH and hydrogen environment. Do.

The mat is coated with a platinum group metal or a metal oxide thereof, cobalt or an oxide thereof, or another electrocatalyst to reduce hydrogen overvoltage.

Any other metal that can retain its elasticity in use, such as titanium, which is a non-passivating coating such as platinum group metals or oxides thereof, is used.

The latter is particularly useful when used in contact with acidic anolyte.

As above, the electrode layer of electrode group of platinum group metal or its oxide or other resistive electrode material is bonded to the diaphragm so that this layer is usually at least about 40-150μ thick, in fact as described in US Pat. No. 3,297,484. It can be produced and, if necessary, two layers can be applied to both sides of the diaphragm.

Since this layer is actually continuous, it protects the dorsal and electrolyte permeability or compressible mat, so that most of the electrolysis takes place in the second layer and, if any, electrolysis, i. Does not occur.

In particular, this phenomenon occurs when the particles in the bilayer have a lower hydrogen (or chlorine) overvoltage than the matte surface.

In this case, the mat acts as a current distributor or as a collector for distributing the current to the low-poison layer. On the other hand, when the compressible mat is directly bonded to the diaphragm or when a multi-porous, conductive screen or other porous conductor is interposed between the mat and the diaphragm, the opening mesh structure is entirely internal, including the rear of the compressive fabric, and the rear end away from the diaphragm. This ensures a passage free of electrolyte disturbances.

Thus, an open but not completely closed compression mat may provide an active electrode surface two to four times or more than the total protruding surface in direct contact with its diaphragm.

British Patent No. 1,267,182 describes an increase in the surface area of a multilayer electrode. The multilayer cathode consists of an outer layer of expanded metal, a thin layer of a knitted mesh and an inner layer of a small mesh to form a cation exchange diaphragm and an electrode. The contacting cathode flows in the end direction through the cathode.

According to the method of the present invention, it is possible to obtain low pressure by compressible mats having wire or conductor portions formed through at least some distance thickness of the mat thickness by crimping, wrinkling, curling or other design configuration. It was confirmed that the voltage could be achieved.

In general, their wires are curved to flex elastically when compressing the mat to disperse the pressure, and their transverse wires exert the same potential on their rear wires as they actually are on the wire in contact with the diaphragm.

When compressing such a mat with or without a sandwiched screen, the voltage drop is reduced by 5-150 mV with the same amount of current as would be achieved by simply contacting the septum with the mat or sandwiched screen. Can be achieved.

This represents a substantial saving of 1Kw-hr power consumption per tonne of generated chlorine.

When compressing the mat, the area away from the diaphragm is close, but stays away from the diaphragm, increasing the area of electrolysis and increasing the surface area to allow a large amount of electrolysis without excessive voltage rise.

The latter part of the mat has the advantage that the mat is better polarized against corrosion even when practically no electrolysis takes place.

As an example, when a nickel compressible mat is combined with a continuous layer of highly conductive electrode particles bonded to a diaphragm, the electrical shield is so large that electrolysis hardly occurs on the mat.

In such a case, the nickel mat tends to corrode, especially when the alkali metal hydroxy exceeds 15 wt% and there is some chlorine.

The space part and a sufficiently open passage on the rear side of the mat consist of a porous opening structure in direct contact with the diaphragm so that the exposed surface is negatively polarized or cathodic for corrosion.

This also applies to surfaces where gas evolution or other electrolysis does not occur.

This advantage is particularly pronounced at a current density of about 1000 A / m ² of the electrode surface, measured in full surface surrounded by the electrode end. The elastic mat is preferably compressed to an uncompressed thickness of about 80-30% at a compression pressure between 50-2000 g / cm ² of projecting area.

Even in this compressed state, the resilient mat should be a high porosity, such as the ratio (%) of the space volume to the apparent volume of the compressed mat, at least 75% (rarely 50% or less), preferably 85-96%. This (%) can be obtained by measuring the volume of the compressed mat to the extent necessary and by weighing the mat.

Knowing the metal specific gravity of the mat, the solid area can be calculated by dividing the volume by its specific gravity to obtain the volume of the solid mat structure and subtracting this char from the dedicated volume to obtain the spatial volume.

When this ratio is excessively reduced and, for example, the elastic mat is overcompressed to less than 30% of the uncompressed thickness, the electrolytic cell voltage begins to rise, which is partly due to the rate of mass transfer to the electrode active surface and /. Or due to a decrease in the ability of the electrode system to properly escape with the generated gas.

Representative characteristics of the electrolytic cell voltage as a function of the degree of compression and as a function of the pore ratio of the compressible mat are shown in the following examples.

The diameter of the wire used varies widely depending on the type formed or the woven type, but in any case is sufficiently small to obtain the elasticity and deformation characteristics required by the electrolytic assembly pressure.

Assembly pressure on the electrode surface corresponding to the load of 50-500g / cm ² is it is necessary to obtain good electrical contact between the electrode and the diaphragm coupling each of the current-carrying structure or collector, a higher pressure generally up to 2000g / cm ² Can also be used.

The contact surface with the electrode has a high surface area and 2 mm by giving a deformation of about 15 to 3 mm of the flexible electrode of the present invention corresponding to a compression of about 60% or less of the uncompressed product thickness at a pressure of about 400 g / cm ² on the projecting surface. For electrolyzers with displacements in planarity up to / m, these limits can be obtained.

The diameter of the metal wire is preferably 0.1 or less to 0.7 mm, but the thickness of the uncompressed product, i.e., the diameter of the coil or the size of the crimp, is preferably 5 times or more to 4 to 20 mm of the wire diameter. .

Thus, the compressible cross section contains a large glass volume, that is, a proportion of the occupied volume in which the flow of electrolyte and gas is freely open.

In the above wrinkled fabrics, including compressive wire windings, the percentage of glass volume is about 75% or more of the dedicated portion of the fabric.

If the pressure drop in the flow of gas and electrolyte through the fabric is neglected, the percentage of glass volume is rarely 25% or less, preferably 50% or less.

When considering the use of a particle electrode or other porous electrode layer directly bonded to the diaphragm surface, the elastic mat or fabric acts directly as its electrode in combination with the diaphragm.

Giving a satisfactory density of resilient contact points between the electrode surface and the diaphragm results in a negligible loss of electrolytic cell voltage for the use of the combined porous electrode layer.

The density of the contact points is at least about 30 contact points / cm ² and more preferably about 50 contact points / cm ² or more at the diaphragm surface. Conversely, the contact area of a single contact point should be as small as possible, and the ratio of the combined diaphragm area corresponding to the indirect contact area is 0.6 or less and preferably 0.4 or less.

In practice, metal screens with properties similar to those interleaved between the elastic compression mat and the diaphragm as expanded metals of at least 10, preferably 20 or more, generally 20-200 or preferably finer mesh numbers Easy to use Mesh numbers represent the number of threads or wires per inch.

Under such a flexible, fine and dense contact between the electrode screen and the diaphragm surface, the main electrode reaction occurs at the contact boundary between the electrode and the ion exchanger contained in the diaphragm material, and most of the ion conduction occurs in or through the diaphragm. Rarely occurs in the liquid electrolyte in contact with the electrode.

As an example, the electrolysis of two distilled pure waters with a resistivity of about 2,000,000 cm or more has been successful in an electrolytic cell of this type with a cation exchange diaphragm at surprisingly low electrolytic cell voltages.

Also, when electrolysis of alkali metal salt solution is carried out in the same electrolytic cell, there is no change in the degree of knowing the electrolytic voltage even if the direction of the electrolytic cell is changed from horizontal to vertical. Indicates that it can be ignored.

This behavior coincides well with the behavior of solid electrolytes with particle electrodes bound to the diaphragm, and the electrolyser is a coarse porous electrode that is in contact with or slightly spaced from a conventional diaphragm, so that its "effect of bubbles" The electrolytic cell voltage causes the gas-generating porous electrode to be horizontally below the head of the electrolyte because it contributes greatly to the electrolytic cell voltage and increases the coefficient of the gas bubble depending on the height of the electrode due to the decrease in gas separation rate and the accumulation of gas bubbles. Contrary to the behavior of conventional diaphragm electrolysers, which are degraded when held and maximized when their electrodes are vertical.

This unexpected behavior explanation is due to the major ionic conduction in the diaphragm, and the very small elastic contact between the tiny mesh screen electrode layer and the diaphragm easily releases the small amount of gas generated at the contact boundary. This is partly due to the fact that the electrolytic cell actually behaves like a solid electrolyte tank because the gas pressure is once again in contact with it immediately.

The elastic compression electrode mat has a substantially uniform contact pressure, and a high density of fine contact points between the electrode surface and the diaphragm is uniform and thus has a complete practical application range.

This compressed electrode mat is effective for acting as a gas release spring and maintains a substantially constant contact between the electrode surface and the functional ion exchanger on the diaphragm surface, which serves as the electrolyte of the electrolytic cell.

The two electrodes of the electrolyzer consist of a resilient compressible mat made of a resistive material to the anolyte and the catholyte, respectively, and a fine mesh screen giving a large number of contacts of at least 30 contact points / cm ² .

More preferably, only one electrode of the electrolytic cell is made of elastic compressible mat by the method of the present invention with a fine mesh electrode screen, and the other electrode is actually a rigid porous structure, preferably between the rough hard structure and the dura mater. It has a fine mesh screen interpolated.

It will be described below in detail according to the drawings for carrying out the method of the present invention.

1 is a series of intertwined spiral spirals of 0.6 mm (or less) nickel wire with a compressive electrode or a cross section thereof, the coils of which are wound into the adjacent coils The coil has a diameter of 15 mm.

A representative example of the construction of FIG. 2 constitutes actually a spiral winding 2 having a flat, elliptical cross section of 0.5 mm diameter nickel wire, whose coils are wound inside the coils adjacent to each other so that the short axis of the winding is 8 mm.

A representative example of the structure of FIG. 3 consists of a knitted mesh of nickel wire with a diameter of 0.15 mm, which is crimped by formation, and the size or height of the crimp is 5 mm between 5 mm waves. The crimp is composed of crossed parallel crimp rows in the form of a herring bone pattern as shown in FIG.

4 shows an embodiment incorporating the current collector used by the method of the present invention as a solid electrolyte electrolyzer, a particular type of electrolysis of sodium chloride brine.

The electrolyzer consists mainly of a horizontal anodized end-plate 3 with a seal surface 4 along its entire periphery, with the seal surface 4 sealingly contacting the periphery of the diaphragm 5 as necessary. It has an insert of a liquid-permeable insulating gasket (not shown).

The anode end plate 3 also has a central recess 6, which faces the seal surface having a surface corresponding to the area of the anode 7 coupled to the diaphragm surface.

The positive electrode plate 3 is made of iron, and is covered with a tip contacting with the anolyte and titanium or other non-passive valve metal, and is made of graphite, or a moldable mixture of graphite and a chemically resistant resin binder.

The anode current collector is preferably composed of titanium, nidium or other valve metal screens or expanded sheets 8 coated with a non-passive electrolytic resistance material such as a noble metal and / or a mixed oxide of its oxide and platinum group metal.

The screen or expanded sheet 8 may be welded to, or more simply installed on, a series of ribs or projections 9 made of titanium or other valve metal welded to the central recess 6 of the electrolytic cell end plate, or simply mounted to the seal surface 4 of the end plate. It is parallel to the plane of, and preferably to the common plane.

The vertical negative electrode plate 10 has a central recess 11 in its inner side with respect to the peripheral seal surface 12, which is actually flat, i.e. free of ribs and parallel to the seal surface 12 plane.

Inside the recess of the negative electrode plate is placed a resilient compressible current collector (or compressive electrode) 13, preferably of nickel alloy, in the method of the present invention.

The thickness of the uncompressed elastic collector is preferably 10 to 60% larger than the length of the center recess 11 with respect to the seal surface. When assembling the electrolytic cell, the collector compresses 10 to 60% of the thickness and preferably protrudes. Apply an elastic reaction force of 80 to 600 g / cm ^{2 at} the surface.

The anode plate 10 can be made of iron or other electrical material resistant to NaOH and hydrogen.

Diaphragm 5 is a fluid impermeable, cation-permeable ion exchange membrane, for example 0.3 mm thick copolymer of perfluorosulfonylethoxy vinyl ether having an ion exchange group such as tetrafluoro ethylene and sulfonic acid group, carboxylic acid group or sulfonamide group. It is preferable that it is comprised from the polymer film of.

Because this membrane is thin, the diaphragm is relatively flexible and liable to creep down and not creep or deform if not supported.

Such diaphragms are manufactured under the Nafion trademark by E.I Dupont. This price. On the anode side of the anode is bonded a conductive electrocatalyst, preferably an anode 7 consisting of a porous layer having a thickness of 20-150μ of particles of oxides or mixed oxides of at least one platinum group metal.

On the cathodic side of the diaphragm is a porous layer of 20-150μ thick of conductive material with low hydrogen overvoltage, preferably of graphite and platinum-black particles in a weight ratio of 1: 1-5: 1. The negative electrode 14 is bonded.

The binder used to bond the particles to the diaphragm surface is preferably pletetrafluoroethylene (PTEE) and the electrode is pressed into the diaphragm at a high temperature sufficient to sinter the mixture of PTEE and the conductive catalyst and to form a porous film and bond the film. Make it.

This bond is made by assembling the diaphragm into a sandwich form between the electrode materials and pressing the granules together to embed the electrode particles into the diaphragm.

In general, the diaphragm is hydrated by boiling in an electrolyte solution such as a salt solution, an acid or an alkali metal hydroxide solution, and thus highly hydrated to 10-20 wt% or more of hydrated water or simple It contains a large amount of bonded water as the adsorbed water.

In this case, care must be taken to prevent excessive loss of moisture during the lamination process.

This lamination is accomplished by applying a pressure other than heat to the laminate, so that water tends to evaporate, which is minimized by one or more of the following means.

That is, (1) surrounds the stack with an impermeable enclosure. That is, the edges are kept in an atmosphere saturated with water around the laminate between the pressed or sealed metal foils.

(2) With a suitable molding design, water is quickly returned to the laminate.

(3) Molded in a steam atmosphere.

The electrode coupled to the diaphragm surface actually has protrusions corresponding to the central recesses 6 and 11 of the two end plates.

FIG. 5 shows the electrolyzer of FIG. 4 in an assembled state, in which the respective corresponding elements in each of the two figures have the same reference numerals.

As in FIG. 5, the positive end plate 3 and the negative end plate 10 are simultaneously clamped to compress the compressive current collector 13 made of spiral coil sheets or mats against the negative electrode 14.

During operation of the electrolyzer, for example, anolyte with saturated sodium chloride salt is circulated through the anode chamber, and more preferably fresh anolyte is supplied through the inlet pipe (not shown) near the bottom of the chamber, The anolyte is discharged together with the generated chlorine through an outlet pipe (not shown) around the top of the chamber.

NaOH obtained by supplying water or NaOH through an inlet pipe (not shown) at the bottom of the chamber is recovered as a concentrated solution through an outlet pipe (not shown) at the upper end of the cathode chamber.

Hydrogen generated at the cathode is recovered along with NaOH concentrated solution through another outlet pipe in the upper portion of the cathode chamber.

Since the mesh of the elastic compressible current collector is open, there is little resistance to gas or electrolyte flow through the compressed collector.

Both ends of the anode and cathode plates are properly connected to an external power source, and current flows from the rib 9 to the anode current collector 8.

Here, current is delivered to anode 5 through a number of contacts between the expanded sheet, i.e., anode current collector 7 and anode 7.

Ion transfer occurs mainly through the diaphragm 5, the cation exchange membrane, and current is transmitted by sodium ions moving through the diaphragm 5, the cation exchange membrane from the anode 7 to the cathode 14 of the electrolytic cell.

The current collector 13 collects current through the multiple contact points between the nickel wire and the cathode at the cathode 14 and is thus transferred to the negative electrode plate 10 through the multiple contact points.

After assembling the electrolytic cell, the current collector 13, which is in a compressed state, deforms between the product thickness, ie between 10-60% of a single coil or its crimp, to the cathode 14 surface, i.e., a positive current collector 8 that is actually unmodified An elastic reaction force is applied to the suppressed surface.

This reaction force maintains the required pressure at the point of contact between each anode current collector 8 with cathode 14 and anode 7 and cathode collector ie compressible current collector 13.

Planarity between the positive current collector 8 and the cavity plane represented by the surface of the central recessed hole 11 of the cathode chamber, without the need for mechanical restraints on the elastic deformation between adjacent windings or adjacent crimps of the current collector that is elastic. Equally control the slight displacement that inevitably occurs in parallelism.

Thus, this slight displacement, which typically occurs in the reference assembly process, can be sufficiently compensated to a considerable extent.

6 and 7 schematically show some enlarged perspective views of two preferred embodiments of the flexible and compressible current collector 13 (mat) of the electrolytic cell shown in FIGS. 4 and 5.

For simplicity, only relevant parts are shown and the same parts have the same reference numerals as in FIGS. 4 and 5.

The elastic and compressible mat of FIG. 6 is a series of spiral cylindrical windings of nickel wire with a diameter of 0.6 mm, the coils of which are wound inside each other as shown in the picture of FIG. 1, and the diameter of the coil is 10 mm. It is preferable.

Between the flexible fabric or sheet 13a and the diaphragm 5 having the negative electrode 14 (layer) on the surface, a thin thin porous sheet 13b was formed when expanded with a thickness of 0.3 mm.

The porous sheet 13b is flexible and flexible, giving almost negligible resistance to bending and flexing due to the elastic reaction force exerted by the wire loop of the sheet 13a when compressed against the diaphragm 5. Thus there is little resistance.

FIG. 7 illustrates an embodiment similar to FIG. 6, wherein the elastic and compressible fabric or layer 13a is a crimp knitted fabric of nickel wire of 0.15 mm diameter, as in the photograph of FIG.

8 shows another embodiment according to the method of the present invention, in which the electrolytic cell of the electrolytic cell according to the method of the present invention is embodied, and the electrolyzer which is particularly useful for sodium chloride salt electrolysis is optionally liquid impermeable, It has a vertical positive electrode end plate 3 having a sealing surface 4 which is contacted along its entire circumference so as to seal the periphery of the diaphragm 5 into which an insulating peripheral gasket (not shown) is inserted.

The bipolar plate 3 constitutes a central recess 6 with respect to its seal surface having a surface formed of a top area for exhausting used brine or chlorine from the bottom into which the brine is introduced. Communicate with each other.

The end plates are of iron and their sides in contact with the anolyte are covered with titanium or other passive valve metals or with a formable mixture of graphite or graphite with a chemically resistant resin binder or other anodically resistant material.

The anode is a gas and electrolyte permeable titanium which is coated with a non-passive electrolysis resistant material such as a noble metal and / or a mixed oxide of its oxide and platinum group metal or with other electrocatalyst coating acting as the anode surface when deposited on a conductive substrate, It is preferred that it consists of a niobium or other valve metal screen or expanded sheet, i.e., an anodic current collector 8.

The anode is actually rigid and the screen is thick enough to move the electrolytic current in rib 9 without excessive resistive losses.

More preferably, a coarse screen, ie, a flexible mesh screen made of the same material as the anode current collector 8, is installed on the surface of the anode current collector 8 of the coarse screen so that the surface of the diaphragm is 30 or more, preferably 60-100 contact points / cm ^2. Make a fine contact with the diaphragm at a density of.

The fine mesh screen is spot welded to the coarse screen or sandwiched between the anode current collector 8 and the diaphragm of the screen.

The fine mesh screen is coated with a conductive oxide that is resistant to precious metal or anolyte.

The vertical negative electrode plate 10 has a central recess 11 in its inner side with respect to the peripheral seal surface 12, which recess 11 is actually on a plane without ribs and is parallel to the seal surface plane.

The current collector 13, which is a flexible and compressible electrode, which is a preferred nickel alloy agent according to the method of the present invention, is located inside the central recess 11 of the negative electrode plate 10.

In the embodiment of FIG. 8, the electrode is a wire winding or a plurality of intertwined windings, the windings of which may be directly coupled with the diaphragm 5.

However, it is preferable to insert the cathode 14, which is a screen, as shown between the wire winding and the diaphragm, and it is also desirable to slidably couple the winding and the screen to each other and to the diaphragm.

Adjacent spacing of the windings should be large enough to facilitate the flow or movement of gas and electrolyte between and between the windings, for example in and out of the central portion surrounded by the windings.

Their space is generally sufficiently large, 3-4 times or more than the diameter of the wire.

The thickness of the uncompressed winding wire coil is preferably 10-60% larger than the length of the center recess 11 with respect to the seal surface plane.

When assembling the electrolytic cell, the coil is preferably compressed in the range of 10-60% of the thickness to apply the elastic reaction force to the protruding surface in the range of 80 to 100 g / cm ² .

The negative electrode plate 10 is made of iron or other conductive material resistant to NaOH and hydrogen.

Diaphragm 5, as described above, is preferably an ion exchange membrane that is fluid impermeable and cation selective permeable.

Screen-cathode 14 is usually made of nickel wire or other material resistant to corrosion in the cathode state.

The cathode (screen) is rigid but preferably flexible and non-rigid.

Therefore, it can be easily bent to accommodate and match the indeterminateness of the cathode surface of the diaphragm.

Their non-determination is on the diaphragm surface itself, but more generally it is non-deterministic in the rigid anode supporting the diaphragm.

In general, the screen is more flexible than the winding.

For this purpose, the mesh size of the screen should be smaller than the size of the opening between the spirals of the thread, and screens with a hole size of 0.5 to 3 mm in width and length are suitable but finer mesh screens can be used. Particularly preferred in the examples.

The intermittent screen shows various functions.

First, the screen is conductive and has an active electrode surface.

Secondly, the screen prevents the winding or other compressive electrode member from abrasion, invading, or thinning the diaphragm locally, and when the compressed electrode is pressed against the screen in the local area, the screen is adjacent to the screen. It helps to distribute the pressure along the diaphragm surface between the pressure points and prevents the deformed winding portion from invading or abrading the diaphragm.

In the process of electrolysis, hydrogen and alkali metal hydroxides are generated on the screen and generally throughout the helix and throughout the helix.

When the winding is compressed, its back surface, ie the surface separated or spaced from the diaphragm surface, is closer to the screen and the diaphragm. Of course, the greater the compression, the smaller the average distance from the diaphragm to the winding and the negative polarization of the winding surface. Or the degree of electrolysis is greater.

Therefore, the compression effect increases the total effective surface area of the cathode.

It was confirmed that the compression of the electrode can effectively lower the total voltage required to support the current flow rate of 1000 A / m ² or more of the active diaphragm surface.

At the same time, compression may limit the compressive electrode to open to the flow of electrolyte and gas.

Thus, as in FIG. 9, the winding is open to have a central vertical passage through which electrolyte and gas can rise.

Furthermore, the space between the windings leaves room for the catholyte to access both sides of the diaphragm and the windings.

The wire of the winding is generally small and in the range of 0.05 to 0.5 mm in diameter.

Larger wires can also be used, but the use of wires larger than 1.5 mm in diameter is rare, as they are more rigid and less compressible.

FIG. 9 shows the electrolyzer of FIG. 4 in an assembled state, in which the corresponding parts in the two figures have the same reference numerals.

As shown in this figure, the positive electrode end plate 3 and the negative electrode end plate 10 are simultaneously tightened to compress the current collector 13, which is a threaded coil sheet or mat, with respect to the negative electrode 14.

During operation of the electrolyzer, the anolyte, for example saturated sodium chloride brine, is circulated through the anode chamber, and more preferably fresh anolyte is supplied through an inlet pipe (not shown) near the bottom of the chamber and used up. Anolyte is discharged through an outflow pipe (not shown) on the upper circumferential surface of the seal, such as chlorine generated.

In the cathode chamber, alkali obtained by supplying water or diluted alkaline aqueous solution from the inlet pipe (not shown) at the bottom of the chamber is recovered as a thick solution through the outlet pipe (not shown) at the upper end of the cathode chamber.

Hydrogen generated at the cathode is recovered in the cathode chamber together with concentrated NaOH solution or through another outflow pipe at the top of the chamber.

Both ends of the anode and cathode are properly connected to an external power source, and current flows through the series of ribs 9 to the anode 8.

The ion transfer is mainly through the diaphragm 5, which is the ion exchange membrane, and the current is actually transferred through the diaphragm 5, the amount of which is positive from the anode 8 to the cathode 14.

The two electrodes give a plurality of contact points to the diaphragm so that a current eventually flows through the plurality of contact points to the cathode plate 10.

After assembling the electrolytic cell, the current collector 13 in its compressed state with 10-60% deformation of the raw material's thickness, ie single coil or its crimp, is a relatively stiff and actually unmodified positive or positive current collector for the negative electrode 14. An elastic reaction force is applied to the suppression surface indicated by 8.

This reaction force maintains the required pressure at the point of contact between the screen portion and the winding portion of the cathode 14, in addition to the cathode and the diaphragm.

Since the thread winding and the screen can slide against each other and the candidate support wall besides the diaphragm, the center of the anode 8 and cathode chamber, respectively, without mechanical suppression of the elastic strain difference between the adjacent winding of the flexible electrode or the adjacent crimp, respectively. A slight deviation (displacement) inevitably occurring in parallelism or planarity between the co-operation planes represented by the groove 11 ground can be equally adjusted in the transverse direction.

Thus, such small deviations that typically occur in standard assembly processes are compensated to a considerable extent.

The advantage of the flexible electrode according to the method of the present invention can be fully realized by an industrial filter press type electrolytic apparatus in which a module of high production capacity is formed by clamping a plurality of unit electrolyzers in a direct heat arrangement.

In this case, the end plates of the intermediate electrolyzer are marked on the surfaces of bipolar seperators with current collectors of anode and cathode on their respective surfaces.

Therefore, the dipole separator electrically connects the positive electrode of one electrolytic vehicle to the negative electrode of the adjacent electrolytic chamber in series in addition to operating to form the wall of each electrode chamber.

Since the deformability of these electrodes is increased, the flexible and compressible electrode of the present invention gives more uniform distribution of the tightening pressure of the filter press type module to each single electrolytic bath.

This is especially true when the opposite side of each diaphragm is firmly supported by a relatively rigid anode 8.

In such direct heat baths, the use of a flexible gasket on the seal surface of a single electrolyzer is desirable to avoid limiting the elasticity of the compression filter ptest type module to its diaphragm elasticity.

Therefore, the elastic deformation of the elastic collector inside each electrolytic cell in series can be obtained, which has a great advantage.

FIG. 10 shows yet another embodiment, in which a crimp fabric of wires wound together instead of a screw winding is used as the compressible member of the electrode, and an additional electrolyte passage is configured for electrolyte circulation.

As shown in the figure, the electrolytic cell is composed of a positive electrode plate 103 and a negative electrode plate 110, both of which are installed in a vertical plane in the form of a channel (channel) having side walls surrounding the anode space 106 and the cathode space 111 in a vertical plane.

Each end plate also has a peripheral seal surface on the side wall protruding from the plane of each end plate, the end plate 104 is the anode seal surface, and the end plate 112 is the cathode seal surface.

These seal surfaces support the diaphragm 105 formed through the enclosing space between the side walls.

Anode 108 consists of a relatively rigid, incompressible sheet that is resistive based on expanded metals of titanium or other porous anodes, preferably with a non-passivated coating such as platinum group metal, oxides or mixed oxide coatings thereon.

The sheet is sized to fit inside the side wall of the anode plate and is firmly supported by a spaced conductive metal or graphite rib 109 that sticks and protrudes into the substrate or web of the anode plate 103.

The space between the ribs facilitates the flow of the anolyte supplied from the bottom of the space and discharged from the top of the space.

The whole of the plate and ribs is of iron or other suitable material coated with graphite or titanium.

The rib end portion supporting the sheet 108 as both countries may be coated with, for example, platinum to improve electrical contact, and may not be coated, and the sheet 108 of the anode may be welded to the rib 109.

The rigid, porous anode sheet 108 is firmly supported in an upright position.

The sheet is made of expanded metal with a hole inclined upwardly away from the diaphragm to direct the rising gas bubbles toward the space of the diaphragm 105 (see FIG. 11).

More preferably, screen 108a, which is a flexible mesh of titanium or other valve metals coated with a non-passive layer of noble metals or conductive oxides having a low overvoltage for chlorine evolution, ie chlorination, is characterized by a rigid and porous sheet 108; It is installed between the diaphragms 105.

The fine mesh screen 108a has a very small surface area density with a diaphragm of at least 30 contact points / cm ² and may or may not be spot welded on the screen 108a.

On the cathode side, ribs 120 are formed over the entire length of the cathode space 111 outward from the base of the anode plate 110.

These ribs are spaced through the electrolyzer to provide space parallel to the electrolyte flow.

As in the above-described embodiment, the negative electrode plate and the rib are made of iron or nickel iron alloy or other negative electrode resistant material.

The conductive rib 120 is welded to a relatively rigid pressure plate 122 that is porous and allows the electrolyte to circulate from one axis to the other.

In general, these openings are inclined upward and toward the space 111 (see FIG. 11) at the diaphragm or the compressive electrode.

The pressure plate 122 is electrically conductive, and acts to apply polarity to and pressure on the electrode, and is composed of an expanded metal or a thick screen made of iron, nickel, copper, or an alloy thereof.

The relatively fine and flexible screen 114 supports the cathode side of the active surface of the diaphragm 105, and is flexible and relatively thin, resulting in the outer appearance of the diaphragm and thus the outer appearance (screen) of the anode 108.

This screen actually acts as a cathode and therefore is a screen of conductive, ie nickel or other cathodic wire, and has a low hydrogen overvoltage surface.

The screen preferably has a very small area of contact density with a diaphragm of at least 30 contact points / cm ² or more.

The compressible mat 113 is provided between the negative electrode screen 114 and the pressure plate 122 as the negative electrode.

As in FIG. 10, the mat is a crimped or wrinkled wire-mesh fabric, and the fabric is preferably an open mesh knitted wire of the same type as in FIG. The wire strands are paired with a relatively flat fabric with intertwined loops.

At this time, the fabric is brought close to each other by 0.3 to 2 cm intervals so that the thickness of the compressible fabric itself is crimped or wrinkled into a wave shape of 5-10 mm.

The crimp is zigzag or unil patterned, as in Figure 3, making the fabric mesh coarser.

That is, it has a larger hole size than the screen 114.

As in FIG. 10, this wavy fabric 113 is provided in the space between the finer mesh screen 114 and the pressure plate 122 of the more rigid expanded metal.

This wavy shape is formed through the space and the space ratio of the compressive fabric is at least 57%, preferably 85 to 96% of the apparent volume occupied by the fabric.

As shown, the wave shape is formed in a vertical or oblique direction to constitute an upward free flow path of gas and electrolyte so that the passage is not actually obstructed by the wire of the fabric.

This fact occurs when the mesh holes on both sides of the wave are free to pass through the flow of fluid so that the wave forms through electrolysis from one side to the other.

As described in another embodiment, the negative electrode plate 110 and the positive electrode plate 103 are clamped together to support a gasket that blocks the diaphragm from the outside atmosphere provided between the diaphragm 105 or the single wall.

The tightening pressure compresses the compressible mat 113, which is a wavy fabric, into a fine screen 114, and then presses the diaphragm to the opposite anode 108a, which forces the voltage body low.

In the experiment where the total thickness of the compressible mat 113 as an uncompressed fabric was 6 mm, when compressing the compressible sheet to a thickness of 4.0 mm and 2.0 mm at a current density of 3000 A / m ² in the protruding electrode area, the same current density at 0 compression was obtained. In comparison, it was confirmed that the voltage drop of about 150mV.

A comparable voltage drop of 5-150 mV was observed between 0 and 4 mm at zero compression.

The electrolytic cell voltage actually remained constant up to a compression of about 2 mm and started to rise slightly when the compression was less than 2.0 mm, i.e., less than about 30% of the fabric thickness.

This fact represents substantial energy savings of 5% or more in saline electrolysis.

When operating this embodiment, the aqueous phhosodium chloride solution is actually supplied to the bottom of the electrolyzer to flow upward through the passage between the ribs 109 or the space of the diaphragm 105, and the consumed brine and the generated chlorine flow out of the top of the electrolyzer.

Water or dilute sodium hydroxide is fed to the bottom of the cathode chamber to ascend through the passageway (cathode space) 111 and the space of the compressed mesh sheet 113 and withdraw hydrogen and alkali from the top of the electrolyzer.

Electrolysis is carried out by applying a DC voltage between the anode and cathode plates.

11 is a vertical cross-sectional view showing the flow pattern of the electrolytic cell, wherein the upper hole of the pressure plate 122 is a louver structure to form an upward inclined outlet on the compressible mat 113, which is a compressed fabric, and a part of hydrogen or electrolyte generated It flows out into the passage 111 (FIG. 10) which is a posterior electrolyte chamber.

Thus, the vertical space on the back side of the pressure coal 122 and the space occupied by the compressible mat 113 which is the compressible mesh sheet provide the flow of the upward electrolyte and gas.

These two anode chambers reduce the gap between the pressure plate 122 and the diaphragm, increasing the compression of the compressible mat 113 and opening the compressive mat with respect to the flow of fluid to increase the total effective surface area of the active part of the cathode. .

12 shows how the electrolyzer works.

As shown, the vertical electrolytic cell 20 of the type shown in the cross-sectional view of the fifth, nineth or tenth degree has an anolyte inflow line 22 which enters the bottom of the anolyte chamber (positive part) of the electrolyzer and an anode from the top of the anode part. It consists of liquid outlet line 24.

Similarly, the catholyte inflow line 26 flows into the bottom of the catholyte chamber of the electrolytic cell 20, and the cathode portion has an outflow line 28 located above the cathode portion.

The anode portion was separated from the cathode portion by a diaphragm 5 with the anode 8 pressed on the anode side and the cathode 14 pressed on the cathode side.

The diaphragm-electrode is formed in an upward direction, and generally its height is about 0.4 to 1 m or more.

The anode chamber or anode portion is surrounded by a diaphragm and an anode end wall 6 (fifth, ninth or 105) on the other side and the anode on one side, and the cathode chamber or cathode portion is placed on an upright cathode end wall on the other side of the membrane and the cathode on one side. Surrounded by

When operating such a device, brine is supplied from the supply tank 30 to the anolyte inlet line 22 through the valve line 32, and a circulation tank 34 is installed to discharge the brine through the line 5 'from the bottom of the tank. .

The brine concentration in the solution entering the bottom of the anode adjusts the relative flow rate through line 32 to be close to saturation, and the brine entering the bottom of the anode flows upward and contacts the anode.

As a result, chlorine is generated and rises with the anolyte, which is discharged to tank 34 via line 24.

The chlorine is then separated off and discharged through outlet 36 as shown and the brine is collected in tank 34 and recycled.

A portion of this brine is depleted brins and is taken out through the over flow line 40 and sent to a solid alkali metal halide source for resaturation and stagnation.

Alkaline earth metals in the form of halogen compounds or other compounds are kept at a low concentration, less than 1 ppm of alkali metal halogen compounds, and are often maintained at a low concentration of 50 to 100 parts by weight of alkaline earth metal per billion parts by weight of alkali halogen compounds. .

On the cathode side, water is fed from tank or other source 42 to line 26 via line 44 and line 44 exits to circulation line 26 where it is mixed with circulating alkali metal hydroxide (NaOH) exiting line 26 from the circulation tank.

The water-alkali metal hydroxide mixture enters the cathode section or the bottom of the cathode chamber and ascends above the cathode chamber through a compressed gas-permeable compressive mat (5, 9 or 10,) or current collector 13.

While flowing, the compound contacts the cathode to generate alkali metal hydroxides in addition to hydrogen gas.

Catholyte is discharged to tank 46 via line 28 where hydrogen is separated through outlet 48.

The alkali metal hydroxide solution is withdrawn via line 50 and the water supplied through line 44 is adjusted to maintain the concentration of NaOH or other alkalis at the required concentration.

Such concentrations are 5 or 10 wt% of alkali metal hydroxide, but are generally at least about 15 wt%, more preferably 15 wt% to 40 wt%.

Since the gas is emitted from two electrodes, it is possible to take advantage of the gas rise characteristics of the generated gas, which can be achieved by operating the electrolyzer in the state of liquid flow and keeping the anode chamber and the cathode chamber relatively narrow, for example, 0.5-8 cm. .

Under these conditions, the generated gas rises rapidly, accompanied by sludge of the electrolyte and the electrolyte.

In addition, the gas is discharged into the circulation tank through the discharge pipe and this circulation is smoothed by a pump as necessary.

Woven metal fabrics suitable for use as the current collector of the present invention are manufactured in knit mesh limited of Surrey, South Croydon, England, and the dimensions and wires of the fabric There are several kinds of thickness.

Commonly used wires are 0.1-0.7 mm thicker and thinner, although thinner wires are used to knit them to about 1-4 stitches / cm, preferably about 2-4 stitches / cm.

Water can be converted to a wide range, and can be done with a 5-100 mesh wavy wire screen.

Crimping a blended, cross-woven or knitted metal sheet to form a repeating wavy splinter, or loosely knitting or otherwise arranged to form a fabric 5-10 times the wire diameter or more, making the sheet compressible do.

However, the structure is entangled with each other to assist the movement so that the elasticity of the fabric is maintained.

This is especially true when crimping into regular squarely spaced wavy shapes, for example when forming sludge patterns. If desired, the knit fabric may be stacked in several layers.

When using the winding structure as in FIG. 3, the wire winding should be elastically compressible.

The diameter of the wire and the diameter of the winding are both configured to give the necessary compressibility and elasticity.

The diameter of the winding is usually 10 times or more of the wire diameter without compression.

For example, a nickel wire having a diameter of 10 mm may be wound around a winding having a diameter of about 10 mm.

As above, nickel wire is suitable when the wire is negative.

However, other metals that can resist cathodic reaction attack or corrosion by electrolyte or hydrogen satellite may be used. These metals include stainless steel, copper and copper coated with silver.

In the above embodiment, the compressible collector is indicated as the cathode side, but the compressive collector can be made to the anode side by reversing the polarity of the electrolytic cell.

Of course, in this case the electrode wire must be resistant to chlorine and anodic reactions and the wire is a valve metal, i.e. titanium or nibonium, preferably platinum group metals or oxides thereof, bimettallic spinel, gray titanium ( It is coated with a conductive, non-passive passivation layer that resists anode attack such as peroskite. In some cases, the use of the compressive member on the anode side may cause problems since it restricts the supply of the electrolyte of the halogen compound to the electrode-diaphragm interface.

If the anode part does not have sufficient access to the anolyte flowing through the electrolytic cell, the concentration of the halogen compound decreases locally due to electrolysis, and when the concentration of the halogen compound decreases too much, oxygen is generated rather than halogen as a result of the electrolysis of water. .

This phenomenon can be avoided by keeping the area of the contact point of the electrode-diaphragm small, i.e., rarely 1.0 mm or more, generally 1/2 mm or less in width, and a relatively fine mesh between the compressive mat and the diaphragm surface, This can be avoided effectively by keeping 10 mesh or more screens.

This problem is also important in the cathode, but the cathode reaction generates hydrogen and even when the contact point is relatively large, water and alkali metal ions are moved through the diaphragm so that no side reaction occurs when the product is generated, so there is no technical difficulty.

Therefore, the amount of side reaction products is small, no matter what the negative electrode gives.

Therefore, it is advantageous to use a compressive mat on the cathode side.

Next, examples according to the method of the present invention will be described, but the present invention is not limited thereto.

Example 1

The first test bath A was constructed according to FIGS. 10 and 11.

The dimensions of the electrode were 500 mm wide and 500 mm high, and were made of iron coated with a negative electrode plate 110, a negative electrode rib 120, a porous pressure plate 122 of the negative electrode, and a nickel plated layer.

The porous pressure plate slit a 1.5 mm thick steel sheet to form a diamond shaped opening with dimensions 12 mm and 6 mm.

The anode plate 103 is made of titanium coated steel, and the anode rib 109 is made of titanium.

The anode was formed by cutting a titanium plate of 1.5 mm thickness to form a diamond-shaped opening having dimensions of 10 mm and 5 mm, the anode 108 of a rough screen of expanded metal of titanium, and a titanium sheet of 0.20 mm thickness. Titanium is a fine mesh screen 108a of spot welded on the inside and the surface of the coarse screen obtained by cutting the diamond openings of 1.75 and 3.00 mm.

Both screens were covered with a mixed oxide layer of ruthenium and titanium corresponding to a load of ruthenium (as metal) 12 g / m ² as the protruding surface.

The cathode consisted of three layers of crimped knitted nickel fabric constituting the resilient compressible mat 113, which was knitted with nickel wire 0.15 mm in diameter.

The crimp had a pattern of slits, the size of the wave was 4.5 mm, and the pitch between adjacent crests was 5 mm.

Three layers of the crimp fabric were overlaid and pre-packed with a medium pressure of 100-200 g / cm ² to give the mat an uncompressed thickness of about 5.6 mm.

That is, after releasing the pressure, the mat was elastically recovered to a thickness of about 5.6 mm.

The cathode also contained a 20 mesh nickel screen 114 formed of nickel wire with a diameter of 0.15 mm, which was pressed on the pressure sensitive paper sheet and contacted the 105 surface of the diaphragm to obtain about 64 contact points / cm ² proved.

The diaphragm was a perfluorocarbon sulfonic acid type diaphragm manufactured by DuPont, which was a hydrate film of a Nafion 315 cation exchange membrane having a thickness of 0.6 mm.

A control test electrolyzer (B) of the same dimensions was constructed and the electrode was formed from the electrode of a commercially available product.

In other words, as the two rough screens, which are sharp stiffnesses, the anode 108 and the cathode 122 were directly pressed on both surfaces of the diaphragm 105 without using the fine mesh screen 108 (and 114) and uniformly elastically compressed against the diaphragm (,, The use of mat 113).

The experimental circuit was the same as the circuit in FIG.

The operating conditions are as follows.

By operating the test cell (A), the elastic mat was gradually compressed in relation to the operation characteristics of the electrolytic cell, that is, the electrolytic cell voltage, the current efficiency, and the degree of compression.

In Fig. 13, curve 1 represents the relationship between the electrolytic cell voltage and the degree of compression or the applied pressure.

It was confirmed that the electrolytic cell voltage was decreased by increasing the compression of the elastic mat to a thickness corresponding to about 30% of the uncompressed raw thickness of the elastic mat.

When the compression degree was exceeded, the electrolytic cell voltage slightly increased.

When the thickness of the mat is reduced to 3 mm, the operation of the control electrolytic bath B performed in parallel with the operation of the electrolytic bath A is compared as follows.

In order to evaluate the contribution to the bubble effect of the electrolyzer voltage, the electrolyzer was first reversed to 45 ° and finally 90 ° to the anode and held horizontally at the top of the diaphragm.

The operation characteristics of the electrolytic cell are shown below.

Remarks (X): Electrolyte voltage started to rise slowly and stabilized at about 3.6V.

(XX): Electrolyte voltage soared above 12V, electrolysis stopped.

This result can be explained as follows.

(A) By rotating the cell vertically and horizontally, the bubble effect on the cell voltage decreases in the cell B, while the relatively insensitive nature of the cell A is due to the bubble effect, which is actually negligible. Partly explains that electrolyzer A has a lower electrolyzer voltage.

(B) When the horizontal position is reached, hydrogen gas begins to collect in the lower side of the diaphragm in the control electrolytic cell B, and further insulates the active surface of the negative electrode screen by ion current transfer through the catholyte, while in electrolytic cell A The direction is markedly low.

This phenomenon can be explained by the fact that most of the ion transfer is limited inside the diaphragm thickness so that the cathode provides sufficient contact point with the ion exchanger on the surface of the diaphragm to effectively maintain the electrolytic current.

Substituting the finer mesh screens 108a and 114 with a screen further passed through, the density of the contact point between the electrode and the diaphragm was gradually decreased, and it was confirmed that the behavior of the experimental cell A gradually approached the behavior of the control cell B.

In addition, the cathode 113, a flexible and compressible mat, is a diaphragm having a fine contact point that is densely distributed by more than 90% of the total surface and generally by 98% even though the plane and parallelism of the compression plates or screens 108 and 122 are practically displaced. Secure the cover on the surface.

Example 2

To prepare, the test cell A was opened and replaced with a similar diaphragm having a positive electrode combined with a negative electrode combined with the diaphragm 105.

The anode was a porous layer having a thickness of 80 μm of mixed oxide particles of ruthenium and tutan having a ratio of 45/55 Ru / Ti bonded to polytetrafluoroethylene on the diaphragm surface.

The negative electrode is a porous layer having a thickness of 50 mu of particles of platinum black and graphite having a weight ratio of 1/1 bonded to polytetrafluoroethylene on the opposite side of the diaphragm.

The electrolytic cell was operated under exactly the same conditions as in Example 1, and the step between the electrolytic cell voltage and the degree of compression of the negative electrode 113, which is the flexible current collector layer, is shown by curve 2 in FIG.

The electrolyzer voltage of this control electrolyte electrolyzer is only about 100-200mV lower than that of the experimental electrolyzer A under the same operating conditions.

Example 3

To demonstrate unpredictable results, all of the titanium anode structure was replaced with a contrast structure of nickel-coated steel (anode 103 and anode rib 109 and pure nickel (rough screen 108 and fine mesh screen 108a).

The membrane used was Dupont's 0.3mm thick cation exchange membrane Nafion 120.

It was circulated through the pure water, the anode chamber and the cathode chamber distilled twice with a specific resistance of 200,000 Ωcm or more.

A slowly rising potential difference was applied to the two end plates of the electrolytic cell and oxygen began to pass through the electrolysis current when oxygen was generated at the anode 108a of the nickel screen and hydrogen at the cathode 114 of the nickel screen, respectively.

After several hours of operation, the following voltage-current characteristics were obtained.

The conductivity of the electrolyte was remarkable and the electrolyzer proved to operate as a ture solid electropyte system.

The anode 108a and the cathode 114 of the fine mesh screen were replaced with a rough screen to reduce the contact density between the electrode and the diaphragm surface to 100 contact points / cm ² -16 contact points / cm ² .

A marked rise in electrolytic cell voltage was confirmed as follows.

As will be apparent to those skilled in the art, the contact point density between the electrode and the diaphragm can be increased in a variety of convenient ways.

For example, fine electrode mesh screens can be made more coarse by chemical reactions that spray metal particles by plasma jet deposition or control metal wires forming surfaces in contact with the diaphragm to increase contact point density. Let's do it.

The structure is, of course, flexible enough to give a uniform distribution across the entire surface of the diaphragm, and the elastic recoil pressure exerted on the electrode by the elastic mat is evenly distributed throughout the contact point.

Thus, the electrical contact of the interface between the electrode and the diaphragm can be improved by increasing the functionality, the density of the ion exchanger, or by reducing the equivalent weight of the copolymer on the elastic mat, the intermittent intermediate screen, or the diaphragm surface in contact with the particle electrode. have.

In this way, the ion exchangeability of the matrix is invariable, and the contact point density of the electrode and the site of ion migration to the membrane can be increased.

As an example, one or two thin films of a copolymer having a low equivalent weight of 0.05-0.15 mm may be used for the high equivalent weight or the thickness of the copolymer having a weight that optimizes the resistance reduction and selectivity of the diaphragm of 0.15-0.6 mm. The thick film is laminated on one or both surfaces to form a septum.

Claims (1)

In the method of electrolyzing a halide electrolyte in an electrolytic cell composed of at least one anode and a cathode separated by an ion permeable diaphragm, The two anodes and the cathodes are kept in contact with the surface of the diaphragm at a number of contact points such that the density of the contact points is at least 30 contact points / cm ² and the ratio of the total contact area and the projected area is less than 0.75. Elastically pressing at least one of the positive electrode and the negative electrode to the diaphragm and applying a resilient pressure of 50-2000 g / cm ² almost uniformly over the entire surface of the diaphragm to firmly support the diaphragm on the other of the positive electrode or the negative electrode. In the electrolytic cell characterized by preventing diaphragm displacement and supplying an aqueous halide solution to the positive electrode and water to the negative electrode at the point of contact with the diaphragm surface. Electrolysis method of halogen compound of.

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