JPS59182984A - Electrolytic cell - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION SUMMARY OF THE DISCLOSURE A dimensionally stable anode, a nonporous ion-selective diaphragm separating said anode from a cathode chamber, and a diaphragm extending between a conductive wall of the cathode chamber and the diaphragm and a wall of the cathode chamber. An electrolytic cell is disclosed comprising a porous stationary bed of loose cathode material within a cathode chamber that conducts electrical current between said diaphragm. This electrolytic cell reduces the electrode gap to substantially the thickness of the diaphragm and forces the diaphragm against the anode. Therefore, the current density should be largely uniform over the entire electrode area, and local differences in current density that may cause a decrease in diaphragm performance due to local mechanical and electrical stresses that occur in other types of electrolytic cells are avoided. The present invention provides a method for conducting current from the effective cathode surface to the chamber wall of the cathode chamber.

[Prior art and purpose of this invention]

Briefly, this invention is an electrolytic cell equipped with an anode coated with an ion-selective diaphragm, the cathode comprising a static porous bed of small electrically conductive particles, the bed interfacing with the chamber wall of the cathode chamber. It extends between the diaphragm wall and presses the diaphragm against the anode. More specifically, this invention relates to an electrolytic cell for aqueous solutions of alkali metal halides, but also for electrolysis of salts undergoing decomposition under electrolytic conditions, such as electrolysis of HCI solutions, water electrolysis, organic and inorganic oxidation and reduction. It can also be used to perform other electrolytic functions such as electrolysis.

Recently, electrolytic cells using ion exchange membranes instead of conventional asbestos diaphragms have been developed, especially for electrolysis of plines. Ion exchange membranes are electrically conductive in operation, but are impermeable to the hydrodynamic flow of liquids and gases. In operation, when an alkali metal halide is introduced into the anode chamber, gaseous halogen is produced at the surface of the anode.

The alkali metal ions selectively pass through the cation membrane, and the alkali metal ions combine with hydroxyl groups generated at the cathode by electrolysis of water to form alkali metal hydroxide.

Electrolysers with cationic membranes offer many benefits over traditional diaphragm electrolysers. Electrolysers with cationic membranes produce relatively pure solutions of alkali metal hydroxides that do not require subsequent separation and purification of the hydroxides, as is the case with porous membranes. It does not need to be diluted with brine and can be performed more effectively and easily than electrolytic methods.

In order to take full advantage of the properties of a non-porous diaphragm, it is desirable to reduce the distance between the electrodes (i.e. the electrode gap) to a minimum; such a reduction has a significant effect on the operating voltage, and eventually has a remarkable effect on the energy efficiency of electrolytic treatment.

Commercially available diaphragms are sensitive to current density, which must be kept within certain desirable limits for their effective operation. - The current density should be almost constant over the entire surface to avoid creating mechanical and electrical stresses that would damage the diaphragm.

In the well-known diaphragm type electrolytic cell, the parameters listed above are largely influenced by the structural tolerance limits, and considering the dimensions of the electrode surface of the electrolytic cell on the market, the electrode space (
Regarding extremely small objects (about a few millimeters),
Unavoidable deviations from the strict parallelism of the anode and cathode surfaces also lead to some fluctuations in the current density on the surface of the diaphragm. As a result, previous attempts to correct current density locally in various regions of the diaphragm have been unsuccessful.

According to this inventive embodiment, a cation diaphragm electrolytic cell is provided which is particularly suitable for the electrolysis of aqueous solutions of alkali metal halides, the electrode space of which is much smaller than that of known electrolytic cells, The spacing is constant across the entire IC across the electrode surface, and these characteristics do not impose tight mechanical tolerances on the electrolytic cell, but rather render traditional tight mechanical tolerances unnecessary.

An object of the present invention is to provide a diaphragm type electrolytic cell in which the ratio of the electrode surface to the volume of the electrolytic cell is extremely high.

The purpose of this invention is to maintain electrical conductivity on the cathode side of the diaphragm by introducing a controlled amount of moisture into the cathode chamber.

Another object of the invention is to control the concentration of alkali metal hydroxide in the cathode chamber by adjusting the amount of water fed into the cathode chamber.

Other objects and benefits of the invention will be further elucidated as follows.

A preferred embodiment of the electrolytic cell of this invention comprises a cathode vessel made of steel or other conductive material that does not corrode in the catholyte environment, the upper end of which is made of titanium or other conductive material that is passive under anodic polarization conditions. The titanium bar plate is closed with a pulp metal plate or cover and has at least one hole, preferably a series of tubular anodes, welded to the hole. Extending the entire height of the vessel, the tube wall of the tubular anode is perforated (except for the upper portion of the tube wall in the immediate vicinity, which is welded to the titanium plate) to permit liquid and gas permeation.

The anode is dimensionally stable, typically made of titanium or other valve metal, and has at least a portion of its active surface coated with a conductive electrocatalyst, preferably platinum, that tolerates the anodic conditions and is non-passive.
coated with palladium, rhodium, ruthenium and iridium, or their oxides or mixed oxides,
The lower end of the tubular anode is closed with a plug of inert material, preferably plastic, and is drilled with a concentric threaded hole.

The permeable wall of the tubular anode is covered on the outside with a diaphragm, forming the inside of the tubular anode into an anode chamber; the lower end of the cathode vessel is covered with a plate, preferably an inert plastic plate. Inside the numerous tubular anodes there is a prine or other device for supplying the anolyte, mainly a plastic inlet tube, the flange of which is provided with a flange for sealing against the bottom plate of the container. There is. The anolyte is delivered through a tubular fitting threaded into a threaded hole in the plug of the tubular anode.

In a preferred embodiment, the vessel is provided with an outlet in its upper part for discharging the cathode gas, and an outlet in its lower part for discharging the catholyte and an inlet for recycling diluted catholyte or water into the cathode chamber. The anode welded to the cover of the container communicates with the upper chamber of the container through the hole in the cover, and the anode gas is separated from the electrolyte in this upper chamber, escapes from the outlet, and is sent to the gas recovery system. , the electrolyte is recycled to a resaturation system before being pumped back into the electrolytic cell. The cathode of the electrolytic cell is made of loose conductive particles such as small pieces, globules, balls, cylinders, Raschig rings, metal wool, or other particles. It consists of a porous stationary bed of solid material, the particles of which are tightly packed into the container and reach at least the height of the permeable wall of the tubular anode covered with a diaphragm. A charge of cathode material contacts and presses against the inner wall of the vessel and the outer surface of the membrane on the numerous tubular anodes. Conductive cathode fill materials are graphite, lead, iron, nickel, cobalt, vanadium, molybdenum, or their alloys, intermetallic compounds, metal hydrides, carbides, and nitrides, or other materials that have good conductivity and tolerate cathodic conditions. It can be a substance.

On the contrary, materials exhibiting low hydrogen overpotentials such as iron, nickel and their alloys are particularly suitable for brine electrolysis.
For example, high hydrogen overpotential particulate materials such as lead and lead alloys are preferred for reducing Fem to FeTT using an acidic sulfate catholyte with an anion diaphragm and oxygen generation at the anode. The cathode fill material can also include plastics, ceramics, and other non-conductive materials coated with a layer of conductive, cathodically resistant materials as described above.

The titanium plate or cover to which the tubular anode is welded is insulated from the cathode chamber by an insulating gasket. It is connected to the positive terminal of the current distribution network and the cathode chamber is connected to the negative terminal of the current distribution network.

The cathode fill is cathodically polarized and acts as a cathode, and the porosity of the stationary bed of cathode material facilitates the rapid evacuation of cathode gas and cathodically protects the interior walls of the cathode vessel. contributes to

The electrode space is defined by the geometry of the cathode material represented by the particles of the bed adjacent to the diaphragm surface, and the geometrically uncertain electrolyte flow of the mesh of the permeable wall of the tubular anode to which the diaphragm is attached. It is narrowed by the thickness of the diaphragm due to the local deflection of the east line.

The spacing between the cathode fill material and the anode remains essentially constant during the electrolytic process.

The electrolytic cell configuration described above ensures that the current density is uniform over the entire electrode volume, without causing sudden local current density differences that could cause mechanical and electrical stresses that could destroy the diaphragm. will occur.

Although the preferred embodiment of the electrolytic cell of the present invention with a plurality of tubular anodes has a much greater ratio of electrode surface to volume occupied by the electrolytic cell than conventional commercially available diaphragm electrolysers, It has the advantage of being extremely small.

The drawings of the preferred embodiment of the invention show a circular tube anode in a rectangular vessel, which is preferred because of its highly uniform current density and low cost. However, the anode tube may have other shapes, such as oval, rectangular, hexagonal, or other polygonal shapes, and these shapes fall within the scope of the term "tube" in this specification. The containers can also be rectangular, cylindrical, or other shapes. Although a single concentric cylindrical anode housed within a cylindrical container is not a very good example for practicing this invention, it is possible to achieve the desired capacity by using a large number of cells in this embodiment as well. Be able to do it.

The electrolytic cell of the present invention will be explained in connection with the production of chlorine;
It can also be applied to electrolysis for producing other products.

As shown in FIG. 1, the electrolytic cell consists of a rectangular cathode vessel 1 made of steel or nickel, or alloys thereof, or other conductive cathode-resistant materials. container 1
An insulating gasket 3 is provided between the cathode vessel 1 and the titanium cover 2, with a 1C bolted titanium or other anodically passive valve metal cap 2 closing the vessel at the top.

A titanium tubular anode 4 is welded to a hole in the cover 2 and protrudes to both sides of the cover as shown in the drawing. The tube wall of the tubular anode 4 is provided with holes and other perforations, which are provided in the bottom of the anode 4 from slightly below the cover 2. The perforations 6 of the anode are formed by welding a reticular or expanded titanium plate to the solid top, or they can alternatively be constructed integrally with the top. The surface of the perforation 6 of the tubular anode 4 is suitably coated with an electrocatalytic coating, which is non-passive and resistant to the anodic conditions and mainly contains noble metals or oxides of noble metals. The lower end of the tubular anode 4 is closed by welding a titanium stopper or a closure body 7, or as shown in FIG. It is preferable that

A preferably tubular cation diaphragm 8 is placed over the anode 4 and connects the unperforated top of the anode with a plastic band 9.
It is tightened to the cylindrical outer surface of the stopper 7. This mounting method easily and completely achieves a fluid seal between the diaphragm and the perforated part of the anode 4, which is troublesome in ordinary filter press electrolyzers.The cation diaphragm 8 is permeable to cations. , is preferably impermeable to hydrodynamic flow of liquids and gases. Suitable membrane materials are fluorinated polymers or copolymers containing sulfonic acid groups. This type of material is extremely flexible and can be extruded or hot glued from flat sheets into tubular shapes.

The thickness of this type of diaphragm is on the order of one-tenth of a millimeter.

Rotate the container by 180° to facilitate filling, and remove the cathode material 1.
Fill with 0. The vessel is then closed with a rectangular plate 11 having a perforation at the base of each of the anodes 4. Preferably, this plate is made of inert plastics. A rectangular brine distribution box 12, also made of inert plastic, is welded to the plate 11 and closed by a closing plate 13 with a brine introduction opening [4].
A gasket can be provided between the bottoms of the flanges 27. The flange 27 of the plate 1 can be bolted to the bottom flange of the vessel 1, the closure plate 13 can be attached to the bottom of the distribution box 12, the brine distribution box is connected to the anode 4 with a tubular connector 15. has been contacted internally. One end of this connector is equipped with a flange, and has a screw hole 7a of the plug 7.
It is screwed into. A seal or gasket is provided between the flange of the connector 15 and the brine distribution box 2, and the cathode chamber is filled with particulate matter up to the top of the permeable portion 6 of the tubular anode.

The cathode chamber is provided with one or more outlets 17 for discharging hydrogen at a location higher than the height of the granular layer 10, and an adjustable gooseneck outlet 18 for discharging catholyte is provided below. .

Above the top surface of the particulate matter 10, a water sprinkler or spray tube 24 extends horizontally the length of the container and is provided with a series of holes to remove the alkali metal hydroxide formed in the cathode chamber. Water or catholyte is added to the cathode chamber to adjust the concentration.

In order to dilute the hydroxide generated at the cathode and maintain the hydroxide concentration in the catholyte flowing out from the electrolytic cell within the range of 25% (by weight) to 43% (by weight), water is introduced into the cathode chamber through the water sprinkler pipe 24. It is desirable to constantly add ℃λ.

The top of each tubular anode 4 is connected to a rectangular tank 19 extending over the entire top of the electrolyzer vessel 1 . The level of the electrolyte in the tank 19 is maintained constant by a gooseneck type discharge pipe 20 for discharging the electrolyte. The electrolyte discharged from the tube 20 is recirculated into the electrolytic cell via the electrolyte inlet tube 14 and sent to a resaturation system before being sent to the resaturation system. and is discharged via outlet 21.

The plate or cover 2 to which the tubular anode 4 is welded is directly connected to the positive terminal of the power source by a connecting member 22, and is connected to the cathode container 1.
is connected to the negative terminal by the connecting member 23.

FIG. 2 is a sectional view taken along line Tl in FIG. 1, in which the elements of the electrolytic cell described in connection with FIG. 1 are designated by the same reference numerals. The position of the water sprinkler tube 24 is indicated by a broken line at a point higher than the height of the cathode material particles 10 of the cathode container 1.

The electrolytic cell shown in the drawing has 6 parts in a rectangular casing.
It is equipped with a regular tubular anode, but the number of anodes can be changed laterally, multiple rows can be used, and the shape of the electrolytic cell and the anode can be different from those shown in the drawing. and other embodiments may be made within the spirit and scope of the invention.

The cylindrical surface of the tubular anode 4 is much wider than the volume of the container 1, and when compared with electrolytic cells used in the general market, although the current density for the electrolytic cells is the same, a small electrolytic cell has a high current density. The rate of production can be mentioned. Depending on the operation, for example NaCl concentrated brine (120-310 g/1
1) was sent to the distribution box 12 through the inlet 14, passed through each anode of the tubular anode 4, and rose over the electrocatalyst coated surface producing chlorine.

n) The I+ ion passes through the cation membrane and mixes with hydroxide, which is released to the cathode by water electrolysis, to form sodium hydroxide. The chlorine rises in the electrolyte contained inside the tubular anode 4 and enters the tank 19, where it is separated from the liquid and discharged through the outlet 21. The rising chlorine bubbles cause the electrolyte within the tubular anode 4 to rapidly flow upwards.

The prine that did not rise passes through the discharge port 20 at a constant liquid level,
It is recycled to the resaturation system before being reintroduced into the cell via inlet 14.

The hydrogen released on the surface of the porous cathode bed adjacent to the diaphragm 8 passes through the granular bed 10 and collects on the top surface of the cathode vessel, from where it is discharged via the outlet 17. hydroxide) IJ
The solution is discharged via an adjustable Gooseneck type outlet 8. An adjustable gooseneck outlet 8 maintains the catholyte level at the same level as the top of the cathode bed 10.

The catholyte is a hydroxide solution located outside the electrolytic cell.
The diluted hydroxide solution, which is circulated through the Jum recovery system and flows out, is reintroduced into the cathode chamber via the sprinkler pipe 24.

The operating temperature can vary between 30° and 100°C, but is preferably kept at about 85°C. The pH value of the anolyte can be varied between 1 and 6, and the current density is 1000
Between 5000 m and 5000 m.

I can do it.

Although the electrolytic cell of this invention has been described with reference to the drawings, it is understood that many modifications may be made within the spirit of the invention, that other electrolytic treatments may be performed on the electrolytic cell described above, that titanium may be replaced by tantalum, zirconium, etc. Please note that other valve metals such as molybdenum, niobium, tungsten, and yttrium can be used to construct electrolytic cells, and that static conductive particulate materials can be used in other types of electrolytic cells.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a preferred embodiment of the invention;
The figure is a sectional view taken along the line II--I in FIG. 1, and various parts on the cross section are indicated by dotted lines. In the drawings, main parts are indicated by the following symbols.

Claims (1)

[Claims] 1. An anode chamber containing an electrolyte and a gas-permeable anode;
a cathode compartment containing an electrolyte and a gas-permeable cathode separated by a liquid-impermeable ion exchange membrane; an electrolyte supplied to the anode compartment and water to the cathode compartment; in an electrolytic cell comprising a device for recovering the liquid or gaseous products produced by the electrolytic cell and a device for applying an electric current to the electrolytic cell, the electrolyte and the gas permeable cathode are separated by a porous filling material which is electrically conductive and corrosion resistant for the catholyte. An electrolytic cell comprising a stationary bed, wherein the gas-permeable anode and the diaphragm are in contact with each other, and the diaphragm and the cathode are in contact with each other. 2. The electrolytic cell according to claim 1, wherein the porous filling material is in the shape of a sphere, a small sphere, a saddle, a Raschig ring, a cylinder, a small piece, a metal strand, or a metal cotton. B. The electrolytic cell according to claims 1 and 2, wherein the anode is made of porous pulp metal electrocatalytically coated. 4. The electrolytic cell according to any of the preceding claims, wherein the diaphragm is a cation-permeable polymer film and is made of a fluorinated hydrocarbon polymer having a sulfone group. 5. Porous filled cathode materials graphite, lead, iron, nickel, cobalt, vanadium, molybdenum, zinc, their alloys, intermetallic compounds, metal hydrogenation, carbonization, nitride compounds and/or low hydrogen overvoltage An electrolytic cell according to any of the preceding claims, which belongs to the category consisting of substances.