JP7061997B2 - Method for producing sodium hydroxide and / or chlorine, and 2-chamber saline electrolytic cell - Google Patents

Description

The present invention relates to a method for producing sodium hydroxide and / or chlorine, and a two-chamber saline electrolytic cell.

Sodium hydroxide and chlorine are important as industrial materials, and conventionally, it is a method of electrolyzing a saline solution using an ion exchange membrane. A metal electrode is used as a cathode, and the saline solution is prepared by the reaction of the following formula (1). It has been manufactured by a method of electrolysis.
2NaCl + 2H ₂ O → Cl ₂ + 2NaOH + H ₂ (1)

However, since the electrolysis of the saline solution according to the above formula (1) requires a large amount of electric power, in recent years, in anticipation of significant energy saving, a method of reducing oxygen with a cathode using a gas diffusion electrode (hereinafter referred to as oxygen). (Called the cathode method) is being considered. The reaction at the anode is an oxidation reaction of chloride ions as in the conventional method, and in the oxygen cathode method, the reaction of the following formula (2) occurs as a whole.
2NaCl + 1 / 2O ₂ + H ₂ O → Cl ₂ + 2 NaOH (2)

In the oxygen cathode method, a three-chamber method has been adopted in which the electrolytic cell is divided into three chambers, an anode chamber, a cathode liquid chamber, and a cathode gas chamber. A two-chamber method is being studied in which the ion exchange film and the gas diffusion electrode are brought into close contact with each other, the cathode liquid chamber is substantially eliminated, and the electrolytic cell is divided into two chambers, an anode chamber and a cathode gas chamber. As shown in the above reaction formula, the electrolytic reaction of the saline solution requires water, and also requires the presence of water so that the sodium hydroxide produced does not become too thick. In the three-chamber method, the cathode chamber has a liquid chamber in which the sodium hydroxide aqueous solution circulates, and sufficient water is supplied from this chamber. On the other hand, in the two-chamber method, since there is no liquid chamber in the cathode chamber, the water is supplied only to the electroosmotic water supplied from the anode chamber side through the ion exchange membrane, but this alone is not sufficient and the cathode is supplied by some method. It is necessary to supply water. In Patent Document 1, it is described that the insufficient water is supplied via the gas chamber. Specifically, water heated to 90 ° C. is prepared and introduced from the inlet of oxygen gas. ing. Further, Patent Document 2 also discloses that a moist oxygen-containing gas is supplied to the cathode compartment. Specifically, the oxygen-containing gas obtained by bubbling oxygen in water heated to 80 ° C. It is stated that a gas is prepared and introduced into the cathode compartment.

Japanese Unexamined Patent Publication No. 2001-3188 Japanese Unexamined Patent Publication No. 11-152591

However, the water supply method described in Patent Documents 1 and 2 requires energy for heating water to 80 ° C. or 90 ° C. Further, in Patent Document 1, when the temperature of the electrolytic cell becomes too high, the anolyte is circulated in an external heat exchanger and the temperature of the anolyte is lowered by using cooling water or the like, and cooling water is prepared. You also need the energy to do it.

Therefore, according to the present invention, in the two-chamber method of the oxygen cathode method, water is efficiently supplied to the cathode chamber and the overheating of the electrolytic cell is suppressed without requiring extra energy other than the energy required for the electrolytic reaction. It is an object of the present invention to provide a method capable of producing sodium oxide and / or chlorine.

The present invention is as follows.
[1] Using a two-chamber method saline electrolytic cell having one or more unit cells including an anode chamber with a built-in anode and a cathode chamber with a built-in gas diffusion cathode across an ion exchange membrane, the anode chamber is used. Is a method of supplying a saline solution and a humidified oxygen-containing gas to the cathode chamber to electrolyze the saline solution to produce sodium hydroxide and / or chlorine.
The unit cell further comprises a humidifying chamber that produces a humidified oxygen-containing gas to supply to the cathode chamber.
The humidifying chamber is adjacent to the anode chamber or the cathode chamber in the unit cell, or the anode chamber or the cathode chamber of the adjacent unit cell so as to be heat exchangeable, and generates water vapor by the heat from the anode chamber or the cathode chamber. A method for producing sodium hydroxide and / or chlorine that humidifies the oxygen-containing gas by allowing the gas to be heated.

[2] The humidifying chamber is adjacent to the cathode chamber, and the humidified oxygen-containing gas generated in the humidifying chamber is transferred from the humidifying chamber to the cathode through an opening provided in the partition wall between the humidifying chamber and the cathode chamber. The manufacturing method according to [1] supplied to the chamber.

[3] The manufacturing method according to [2], wherein the opening provided in the partition wall between the humidifying chamber and the cathode chamber is a single opening.

[4] The manufacturing method according to [2], wherein the openings provided in the partition wall between the humidifying chamber and the cathode chamber are a plurality of openings.

[5] The production method according to [1], wherein the humidified oxygen-containing gas generated in the humidifying chamber is supplied from the humidifying chamber to the cathode chamber through a flow path provided outside the humidifying chamber and the cathode chamber.

[6] The manufacturing method according to [5], wherein the flow path provided outside the humidifying chamber and the cathode chamber is a single flow path.

[7] The manufacturing method according to [5], wherein the flow paths provided outside the humidifying chamber and the cathode chamber are a plurality of flow paths.

[8] In the electrolytic cell, a plurality of unit cells are connected, and the plurality of unit cells are arranged so as to repeat the order of the anode chamber, the cathode chamber, and the humidification chamber [1] to [7]. The manufacturing method described in Crab.

[9] A two-chamber saline electrolytic cell having one or more unit cells having an anode chamber and a cathode chamber with an ion exchange membrane interposed therebetween.
The anode chamber has a built-in anode and includes a supply port for raw saline solution, a discharge port for electrolyzed saline solution, and a chlorine discharge port. The cathode chamber has a built-in gas diffusion cathode and is a humidified oxygen-containing gas. Equipped with a supply unit and an outlet for electrolyzed reactants
The unit cell further comprises a humidifying chamber that produces an oxygen-containing gas to supply to the cathode chamber.
The humidifying chamber is adjacent to the anode chamber or cathode chamber in the unit cell, or the anode chamber or cathode chamber of the adjacent unit cell so as to be heat exchangeable, and is provided with an oxygen-containing gas supply port. Legal saline electrolytic cell.

[10] The electrolytic cell according to [9], wherein a plurality of unit cells are connected in the electrolytic cell, and the plurality of unit cells are arranged so that the order of the anode chamber, the cathode chamber, and the humidifying chamber is repeated.

According to the present invention, since the humidifying chamber is adjacent to the anode chamber or the cathode chamber so as to be heat exchangeable, the oxygen-containing gas can be humidified by using the heat of the anode chamber or the cathode chamber, and the electrolytic cell is overheated. Can be prevented.

FIG. 1 is a schematic cross-sectional view showing an example of a unit cell. FIG. 2 is a schematic cross-sectional view showing an example of the shape of an opening for supplying a humidified oxygen-containing gas. FIG. 3 is a schematic cross-sectional view showing an example of a unit cell provided with a connecting pipe for supplying a humidified oxygen-containing gas. FIG. 4 is a schematic cross-sectional view showing an example of a unipolar electrolytic cell. FIG. 5 is a schematic cross-sectional view showing an example of a multi-pole electrolytic cell.

Hereinafter, a two-chamber saline electrolytic cell according to the present invention and a method for producing sodium hydroxide and / or chlorine using the same will be described with reference to the drawings, but the present invention is not limited to the following drawings. , The design may be changed to the extent that it fits the purpose of the above and the following.

FIG. 1 is a diagram showing an example of a unit cell in the electrolytic cell of the present invention. The unit cell 1 has an anode chamber 3 and a cathode chamber 4 with an ion exchange membrane 2 interposed therebetween. The anode chamber 3 is provided with an anode 3a in close contact with the side surface of the anode chamber of the ion exchange membrane 2, and the anode chamber 3 is provided with a raw material saline supply port 3b below the anode chamber 3 and is provided with a saline solution after electrolysis. And a chlorine discharge port 3c is provided on the upper part thereof. On the other hand, the cathode chamber 4 is provided with a liquid holding layer 4b in close contact with the side surface of the cathode chamber of the ion exchange membrane 2, a gas diffusion cathode 4a, a gas diffusion cathode support 4c and a cushioning material 4d in this order, if necessary. ..

The unit cell 1 of the present invention is provided with a humidifying chamber 5 separated from the cathode chamber 4 by a partition wall 6, and the humidifying chamber 5 can exchange heat with the cathode chamber 4. Further, the partition wall 6 of the illustrated example has a planar shape as shown in FIG. 2A, and has a shape in which the upper portion of the partition wall 6 becomes an opening 7 over the entire surface. Therefore, the humidified oxygen-containing gas can be supplied from the humidifying chamber 5 to the cathode chamber 4. The cathode chamber 4 is also provided with a pressure equalizing line 4e for keeping the water surface height of the humidifying chamber constant. However, in the present invention, the pressure equalizing line 4e is not essential if the same function can be performed by other means.

The water in the humidifying chamber may or may not be distributed to the outside. When distributing to the outside, a separate line can be provided to allow water to flow from the outside to the humidifying chamber and discharge hot water (not shown). When water is passed from the outside, the flow rate and temperature of the water can be appropriately set so that the temperature of the water in the humidifying chamber satisfies a predetermined condition (for example, 80 ° C. or higher), but as will be described later, water is passed from the outside. From the viewpoint of energy efficiency, it is preferable to use only the heat of the electrolytic reaction to bring the temperature to a predetermined temperature, even if water is passed through the temperature.

In the unit cell 1, the raw material saline solution is supplied to the anode chamber 3 from the raw material saline supply port 3b, and the oxygen-containing gas is bubbled into the water stored in the humidifying chamber 5 from the oxygen-containing gas supply port 5a. By generating a humidified oxygen-containing gas (oxygen concentration is, for example, 90% or more, preferably 93% or more) and energizing while supplying this to the cathode chamber 4, chlorine is generated in the anode 3a and the gas diffusion cathode. Sodium hydroxide is produced in 4a. Then, the electrolytic reaction of the saline solution proceeds and the heat generated at the cathode is transferred to the humidifying chamber 5, so that the water stored in the humidifying chamber 5 can be heated, and the vaporization of the water in the humidifying chamber is promoted. .. If the oxygen-containing gas is continuously supplied to the humidifying chamber 5 by bubbling or the like, an oxygen-containing gas containing water vapor in an amount substantially equal to the amount saturated at the temperature of the water in the humidifying chamber can be generated. Therefore, the humidification efficiency of the oxygen-containing gas can be increased without using extra external energy other than the energy required for the electrolytic reaction. Further, when an oxygen-containing gas containing a high concentration of water vapor is supplied to each unit cell from a humidifier provided outside the electrolytic tank as disclosed in Patent Document 1, water is contained in a pipe or the like in the middle of supply. In addition to being unable to supply a sufficient amount of water vapor due to condensation, the degree of water condensation may differ from unit cell to unit cell, especially in an electrolytic tank with multiple unit cells, and the amount of water supply varies from unit cell to unit cell. However, in the present invention, since each unit cell has a humidifying chamber, a sufficient amount of water can be supplied to each unit cell without variation. Further, by transferring the heat of the cathode chamber to the humidifying chamber, it is possible to prevent overheating of the unit cell, that is, overheating of the electrolytic cell without requiring extra energy for cooling.

In the example of FIG. 1 described above, the humidifying chamber 5 is adjacent to the cathode chamber 4 in the unit cell 1, but may be adjacent to the anode chamber 3 in the unit cell 1 (as described above, the humidifying chamber 5). The unit cell having each chamber in the order of the anode chamber 3 and the cathode chamber 4 is hereinafter referred to as a B-type unit cell, and the unit cell having each chamber in the order of the anode chamber 3, the cathode chamber 4, and the humidifying chamber 5 is referred to as a B-type unit cell. Hereinafter referred to as type A unit cell). Even in the case of such a B-type unit cell, since the electrolysis reaction of the anode chamber 3 is an exothermic reaction, it is possible to heat the humidifying chamber 5 and increase the steam generation efficiency by using the heat. Is. Further, as will be described later, a plurality of B-type unit cells may be used side by side, and in such a case, the humidifying chamber 5 may be adjacent to the cathode chamber 4 of the adjacent unit cell. In that case, the exothermic reaction in the cathode chamber 4 of the adjacent unit cell can increase the efficiency of water vapor generation in the humidifying chamber 5.

The chlorine generated in the anode chamber 3 is discharged from the discharge port 3c together with the saline solution after electrolysis. The sodium hydroxide produced in the cathode chamber 4 is an aqueous solution of sodium hydroxide having a concentration of about 32.0 to 34.0% due to the water content in the electroosmotic water from the anode chamber 3 and the oxygen-containing gas sent to the cathode chamber. Then, it flows downward under the cathode chamber by its own weight, and is discharged together with the exhaust gas of the oxygen-containing gas from the discharge port 4 g of the electrolysis reaction product. As described above, since a sufficient amount of water can be supplied to the cathode in the present invention, the concentration of the sodium hydroxide aqueous solution does not become too high, and damage to the gas diffusion cathode 4a and the ion exchange membrane 2 can be prevented. ..

The partition wall 6 in the unit cell 1 may have openings 7 having various shapes as long as the oxygen-containing gas humidified from the humidifying chamber 5 to the cathode chamber 4 can flow through the upper part of the partition wall 6. .. For example, as shown in FIG. 2B, a plurality of openings may be provided in the upper part of the partition wall 6. The opening provided in the upper part of the partition wall 6 may extend over the entire upper part of the partition wall 6 as shown in FIG. 2A, or may be a part of the upper surface as shown in FIG. 2B. good. Further, the number of openings is not particularly limited, and the number of openings may be one or a plurality, and the shape of the openings is not particularly limited.

Further, the partition wall 6 does not have to have the opening 7 as long as the humidified oxygen-containing gas can flow from the humidifying chamber 5 to the cathode chamber 4. For example, as shown in FIG. 3, the humidified oxygen-containing gas may be supplied to the cathode chamber 4 through an external flow path such as the connecting pipe 8. The unit cell 1 in FIG. 3 is the same as the unit cell shown in FIG. 1 except that it has a connecting pipe 8 instead of the opening 7 in FIG.

When the B-type unit cell described above is used, the humidified oxygen-containing gas is supplied from the humidifying chamber 5 to the cathode chamber 4 by connecting the humidifying chamber 5 and the cathode chamber 4 with the connecting pipe 8 as described above. This makes it possible. When arranging a plurality of B-type unit cells, an opening 7 may be formed between the humidifying chamber 5 and the cathode chamber 4 of the adjacent unit cell, or the connecting pipe 8 may be connected to the humidifying chamber 5 next to the humidifying chamber 5. The oxygen-containing gas may be supplied to the cathode chamber 4 of the unit cell of the above.

In the unit cell as described above (including both the A type unit cell and the B type unit cell; the same applies hereinafter), the anode 3a is not particularly limited as long as it is an insoluble anode used for salt solution electrolysis, for example. An expanded metal composed of a metal such as titanium, a substrate having a mesh structure such as a fine mesh, coated with an oxide of a metal including ruthenium oxide, titanium oxide, iridium oxide, or an oxide of a platinum group metal. Can be used.

The ion exchange membrane 2 is not particularly limited as long as it can be used for saline electrolysis, and examples thereof include a perfluorocarbon type cation exchange membrane having a carboxylic acid and / or a sulfonic acid as an ion exchange group.

The gas diffusion cathode 4a is not particularly limited as long as it is used for salt solution electrolysis by the oxygen cathode method, but for example, a metal mesh material, a carbon cloth and / or a hydrophobic resin is used as a base material, and the base material is used. A reaction layer on which a hydrophilic catalyst is supported can be used on one surface, and a three-layered sheet-like electrode or the like bonded with a water-repellent gas diffusion layer can be used on the other surface. Examples of the catalyst include silver, platinum, gold, metal oxides, carbon and the like. The gas diffusion cathode may be one that permeates the liquid or may not permeate the liquid.

In the cathode chamber 4, if there is no liquid between the ion exchange membrane 2 and the gas diffusion cathode 4a, no current can flow. If the ion exchange membrane 2 and the gas diffusion cathode 4a are in close contact with each other, it is possible to hold the liquid between them due to the capillary phenomenon, but in order to hold the liquid more reliably, the ion exchange membrane 2 and the gas diffusion cathode are held. It is preferable that the liquid holding layer 4b is present between the 4a. The liquid holding layer 4b can uniformly hold a liquid such as an aqueous solution of sodium hydroxide between the ion exchange membrane 2 and the gas diffusion cathode 4a, and can prevent an increase in current density and an increase in voltage. The liquid holding layer is required to have hydrophilicity and corrosion resistance because it is necessary to hold an aqueous sodium hydroxide solution (concentration is about 30% and temperature is about 80 to 90 ° C.) generated by an electrolytic reaction. Therefore, a porous structure made of a carbon material such as carbon fiber or a resin is preferably used.

The advantage of the two-chamber method is that the anode, ion exchange membrane, and cathode are in contact with each other, and the electrical resistance between the electrodes is small, so the electrolytic voltage can be reduced. In order to bring the cushion material 4d into close contact with the ion exchange membrane 2 (via the liquid holding layer 4b), the cushion material 4d is accommodated in a compressed state to generate a reaction force in the cushion material, and the reaction force is used to make the gas diffusion cathode 4a. It is preferable to bring it into close contact with the ion exchange membrane 2. In the two-chamber method, the hydraulic pressure of the saline solution acts on the anode chamber and the gas pressure acts on the cathode chamber with the ion exchange membrane as the boundary. The reaction force of the cushion material is designed according to the differential pressure between the hydraulic pressure and the gas pressure, but since the hydraulic pressure increases as the depth of the saline solution increases, the reaction force of the cushion material is lower than the upper part of the cathode chamber. By making the value larger, it is possible to equalize the pressure applied to the ion exchange membrane and the anode. As such a cushion material 4d, a coil material or a wave-processed mat material can be used. Since the coil has elasticity in the radial direction and a reaction force is generated in this direction, the coil shaft can be used by arranging it in parallel with the back plate of the cathode gas chamber, and the wire diameter of the coil material, coil system, and laying density can be adjusted. By adjusting, the reaction force of the cushion material may be made larger in the lower part than in the upper part. As the wave-processed mat material, a demister mesh made by knitting metal wires can be used as a wave-processed material. By adjusting the wire diameter, the number of wires to be bundled, and the number of laminated mat materials, a cushioning material can be used. The reaction force of the lower part should be larger than that of the upper part.

A gas diffusion cathode support 4c can be interposed between the cushion material 4d and the gas diffusion cathode 4a, if necessary. The gas diffusion cathode support 4c can receive the reaction force of the cushion material 4d, homogenize it, and transmit it to the gas diffusion cathode 4a, the liquid holding layer 4b, and the ion exchange membrane 2. As the gas diffusion cathode support 4c, a mesh material such as a wire mesh may be used.

Both the cushioning material 4d and the gas diffusion cathode support 4c are housed in the cathode chamber, and the cathode chamber is a highly corrosive environment in which a high concentration oxygen and a high concentration sodium hydroxide aqueous solution are present at a high temperature. Therefore, it is preferable to use a Ni alloy having a Ni or Ni content of 20% by weight or more, or a silver-plated alloy thereof.

As the material of the wall surface constituting the anode chamber 3, it is preferable to use Ti or a Ti alloy having a Ti content of 20% by weight or more. Further, as the material of the wall surface constituting the cathode chamber 4 and the humidifying chamber 5, it is preferable to use Ni or a Ni alloy having a Ni content of 20% by weight or more, or a silver-plated material thereof.

In the present invention, a plurality of the above-mentioned unit cells (A type unit cell or B type unit cell, preferably A type unit cell) may be arranged side by side to form an electrolytic cell. When arranging a plurality of unit cells, a single-pole electrolytic cell in which each unit cell is electrically connected in parallel may be used, or a multi-pole electrolytic cell in which each unit cell is electrically connected in series may be used. A multi-pole electrolytic cell is preferable. Hereinafter, the unipolar electrolytic cell and the unipolar electrolytic cell will be described as an example in which a single cell of type A having the above-mentioned opening 7 is arranged as a means for circulating oxygen-containing gas between the humidification chamber 5 and the cathode chamber 4. Although the multi-pole type electrolytic cell will be described, the following examples can be applied to an example using the connecting pipe 8 and a case where B-type single cells are arranged side by side.

FIG. 4 is a schematic cross-sectional view showing an example of a unipolar electrolytic cell in which three A-type unit cells 1 having an opening 7 are arranged side by side. In the unipolar electrolytic cell 10 of FIG. 4, the A-type unit cells arranged in the order of the anode chamber 3, the cathode chamber 4, and the humidifying chamber 5 are arranged in the normal order (in the order of the anode chamber 3, the cathode chamber 4, and the humidifying chamber 5). , Reverse order (humidification chamber 5, cathode chamber 4, anode chamber 3), forward order, reverse order, and so on. .. The anode of each unit cell is connected to the external power supply in parallel, and the cathode is also connected to the external power supply in parallel. Reference numeral 9 is a water storage tank for adjusting the water surface height of the humidifying chamber. Even in such an example, the heat of the cathode chamber 4 is transferred to the humidifying chamber 5, and the oxygen-containing gas can be efficiently humidified. In the example of arranging the rooms in the unit cell while alternately reversing the order as described above, the humidifying chamber 5 of one unit cell (1) is adjacent to the humidifying chamber 5 of the adjacent unit cell (2). Sometimes. In such a case, one humidifying chamber 5 may be shared by both unit cells (1) and (2).

FIG. 5 is a schematic cross-sectional view showing an example of a bipolar electrolytic cell in which four A-type unit cells having an opening 7 are arranged side by side. In the multi-pole electrolytic cell 20 of FIG. 5, the unit cell 1 having the anode chamber 3 and the cathode chamber 4 having the humidifying chamber 5 inside repeats the order of the anode chamber 3, the cathode chamber 4, and the humidifying chamber 5. In addition, a large number (four in the illustrated example) are arranged, and the anode 3a in one unit cell (1) is electrically conductive with the cathode 4a in the adjacent unit cell (2) ( (Not shown), the cathode 4a at one end and the anode 3a at the other end are connected to an external power source, so that each unit cell is connected in series. In addition, the raw salt solution supply ports 3b of each unit cell, the electrolyzed saline and chlorine discharge ports 3c, the oxygen-containing gas supply ports 5a, the water supply ports 5b, and the electrolysis reaction product discharge ports 4g each other. The pressure equalizing lines 4e are connected to each other by pipes, and the water supply port 5b and the pressure equalizing line 4e are connected to the water storage tank 9. The mechanism of the electrolytic reaction in each unit cell of the multipolar electrolytic cell 20 is the same as the unit cell described above, but by arranging the unit cells, one humidifying chamber 5 becomes a cathode chamber in the same unit cell. Not only adjacent to 4, but also adjacent to the anode chamber 3 in the adjacent unit cell. Therefore, the humidifying chamber 5 can be humidified by utilizing both the heat generated by the electrolytic reaction of the anode chamber 3 and the heat generated by the electrolytic reaction of the cathode chamber 4, and the thermal efficiency at the time of humidification can be further improved. Further, since the heat of the anode chamber 3 is transferred to the humidifying chamber 5, it can also be used for cooling the anode chamber 3.

In addition, as shown in the example of FIG. 5, a plurality of B-type unit cells (unit cells arranged in the order of a humidifying chamber, an anode chamber, and a cathode chamber) may be arranged side by side without changing the order of each chamber to form a multi-pole electrolytic cell. The humidifying chamber 5 is sandwiched between the anode chamber 3 and the cathode chamber 4. Even in such a case, the heat from the anode chamber 3 and the heat from the cathode chamber 4 can be used for humidification in the humidifying chamber 5.

This application claims the benefit of priority based on Japanese Patent Application No. 2017-08857 filed on March 30, 2017. The entire contents of the specification of Japanese Patent Application No. 2017-08857 filed on March 30, 2017 are incorporated herein by reference.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by the following examples, and it is of course possible to carry out the present invention with appropriate modifications within a range that can be adapted to the above-mentioned purpose, and all of them are technical of the present invention. Included in the range.

Example 1
Five unit cells having the structure shown in FIG. 1 (however, they do not have a gas diffusion cathode support) are arranged so that the anode chamber, the cathode chamber, and the humidifying chamber repeat in this order as shown in FIG. In particular, they were connected in series to assemble a bipolar two-chamber type saline electrolytic cell. The anode is DSE manufactured by Permerek Electrode Co., Ltd. (an insoluble metal in which a metal substrate is coated with a Pt group metal or its oxide as a main component), and the cathode is a gas-liquid permeation type carbon-silver electrode manufactured by Permerek Electrode Co., Ltd. (GDE2013). ), 4403D manufactured by Asahi Kasei Chemicals Co., Ltd. was used for the ion exchange film, a carbon fiber woven fabric having a thickness of 0.45 mm was used for the liquid holding layer, and a silver-plated spiral nickel wire was used for the cushion material.

A saline solution having a concentration of 218 g / L and a temperature of 53.8 ° C. is supplied to the anode chamber at a ratio of 183 L / m ² / h, and water is stored in the humidifying chamber to a temperature of 25 ° C. and a concentration of 93.0 ° C. %, 1.5 times the required theoretical amount of oxygen-containing gas (corresponding to "oxygen-containing gas supplied to the electrolytic cell" shown in Table 1 below) was bubbled into the water of the humidifying chamber and supplied. Since the temperature of the humidifying chamber is 84.0 ° C., the temperature of the humidified oxygen-containing gas is about 84.0 ° C. at the time of being supplied to the cathode chamber. Electrolysis was performed at a current density of 5.65 kA / m ² , and various values were measured after 10 days.

Comparative Example 1
Although there is no humidifying chamber in the unit cell, other materials such as the anode, cathode, and ion exchange membrane, and the size of the cathode chamber, anode chamber, etc. are the same as in Example 1, and the unit cell is used in the anode chamber and cathode. Five sheets were arranged so that the order of the chambers was repeated, and electrically connected in series to assemble a multi-pole conventional two-chamber cathode electrolyte electrolytic cell (not shown).

A saline solution having a concentration of 219 g / L and a temperature of 51.4 ° C. was supplied to the anode chamber at a rate of 183 L / m ² / h. The cathode chamber of each unit cell is connected to one humidifier provided outside the electrolytic tank, and the humidifier contains an oxygen-containing gas at a concentration of 93.0% and 1.5 times the required theoretical amount of oxygen-containing gas. The humidifier was bubbled in water (25 ° C.) to generate a humidified oxygen-containing gas at 25 ° C., and the humidified oxygen-containing gas was supplied to the cathode chamber at the same temperature. Electrolysis was performed at a current density of 5.65 kA / m ² , and various values were measured after 10 days. In addition, unlike Example 1, Comparative Example 1 does not have a humidifying chamber in the unit cell and supplies oxygen-containing gas humidified from an external humidifier, so that it is supplied to the electrolytic cell shown in Table 1 below. "Oxygen-containing gas" and "oxygen-containing gas supplied to the cathode chamber" mean the same thing (the same applies to Comparative Examples 2 to 4 below).

Comparative Example 2
The temperature of the water in the external humidifier in Comparative Example 1 was set to 84 ° C., and the humidified oxygen-containing gas generated at 84 ° C. was supplied to the cathode chamber as it was (heat input to the humidifier was about 5.2 MJ / m ² /). h) Various values were measured after 10 days in the same manner as in Comparative Example 1 except for the above.

Comparative Example 3
In the same configuration as in Comparative Example 2, the temperature around the pipe connecting the humidifier and the cathode chamber of each unit cell is further strengthened to keep the temperature of the humidified oxygen-containing gas from dropping, and various types after 10 days have passed. The value was measured. The heat input to the humidifier was about 5.2 MJ / m ² / h, as in Comparative Example 2.

Example 2
Various values were measured after operating the same electrolytic cell as in Example 1 for 300 days.

Comparative Example 4
Various values were measured after operating the same electrolytic cell as in Comparative Example 1 for 300 days.

The measurement results of Examples and Comparative Examples are shown in Tables 1 and 2. Table 2 shows the average value of the five unit cells for the concentration of the generated sodium hydroxide aqueous solution and the current efficiency, and shows the difference between the value and the average value of each unit cell.

In Example 1, the temperature of the humidifying chamber is equal to the temperature of the anode chamber due to the heat of reaction of the electrolytic reaction, and the concentration of the generated sodium hydroxide aqueous solution is 32.2%, which is not too high. It can be seen that a sufficient amount of water vapor can be supplied (Table 1). Further, since the variation between the five unit cells is kept small in terms of the concentration of the generated sodium hydroxide aqueous solution and the current efficiency, it can be seen that the variation in the amount of water vapor supplied to the cathode chamber of each unit cell is small. (Table 2). Further, in Example 2 in which Example 1 was operated for a long period of time, a good current efficiency of 96.3% was shown even after 300 days had passed, and other values were almost the same as those in Example 1. Has been obtained. Further, in Example 2, since a sufficient amount of water vapor can be supplied, the concentration of sodium hydroxide produced can be kept low, and damage to the gas diffusion cathode is suppressed. Therefore, the gas 300 days after the operation of the electrolytic cell is performed. The change in the voltage of the diffusion cathode was as small as 45 mV on average of the five unit cells. The changes in the voltage of the gas diffusion cathode in each unit cell were 78 mV, 15 mV, 45 mV, 33 mV, and 54 mV, respectively.

On the other hand, in Comparative Example 1 in which the oxygen-containing gas humidified from the external humidifier was supplied, since the temperature of the external humidifier was 25.0 ° C., the water vapor pressure in the gas was low, and the generated sodium hydroxide aqueous solution Since the concentration is as high as 34.6%, it can be seen that the amount of water vapor supplied is insufficient (Table 1).

Comparative Example 2 is an example in which the temperature of the external humidifier is changed to 84 ° C. in order to increase the water vapor pressure in the oxygen-containing gas, and energy for raising the water temperature in the external humidifier is required. The average concentration of the generated sodium hydroxide aqueous solution is 32.2%, and a sufficient amount of water vapor can be supplied on average. However, as shown in Table 2, both the sodium hydroxide concentration and the current efficiency are both. , The variation for each unit cell is large. It is considered that this is because the moisture condenses during the introduction of the humidified oxygen-containing gas from the external humidifier into the cathode chamber of each unit cell, and the degree of condensation differs for each unit cell. Further, a high-temperature oxygen-containing gas is supplied from the outside of the electrolytic cell, and in order to prevent overheating of the electrolytic cell, it is necessary to use a low-temperature saline solution supplied to the anode (supply in Example 1). The temperature of the saline solution is 53.8 ° C., which is a general temperature range in a salt electrolytic cell, whereas the temperature of the supplied saline solution in Comparative Example 2 is 47.0 ° C.), and the cooling of the supplied saline solution is performed. Extra energy is needed for.

Comparative Example 3 is an example in which the piping from the external humidifier in Comparative Example 2 is heat-insulated, and requires energy for heating by the external humidifier as in Comparative Example 2. In Comparative Example 3, as a result of suppressing the condensation of water in the pipe, the variation in the generated sodium hydroxide concentration and the current efficiency from cell to cell was suppressed, but the cooling of the supplied saline solution was suppressed as in Comparative Example 2. Extra energy is needed for.

Comparative Example 4 is an example in which the electrolytic cell was operated for 300 days under the same conditions as Comparative Example 1, and the change in the voltage of the gas diffusion cathode after 300 days from the operation of the electrolytic cell is the average value of the five unit cells. The voltage was 108 mV, which was considerably higher than that of Example 2, and the current efficiency was 96.0%, which was lower than that of Example 2. As in Comparative Example 1, the concentration of the sodium hydroxide aqueous solution produced in Comparative Example 4 is 34.6%, which is more than 2% higher than the concentration of the sodium hydroxide aqueous solution of Examples 1 and 2 of 32.2%. Therefore, it is considered that the cause is that the gas diffusion cathode is damaged. The changes in the voltage of the gas diffusion cathode in each unit cell were 123 mV, 66 mV, 114 mV, 108 mV, and 129 mV, respectively.

1 Unit cell 2 Ion exchange membrane 3 Anode chamber 3a Anode 4 Cathode chamber 4a Gas diffusion cathode 5 Humidity chamber 6 Partition 7 Opening 8 Connecting pipe 10 Single pole type electrolytic cell 20 Multipolar type electrolytic cell

Claims (12)

A two-chamber method salt solution electrolytic cell having one or more unit cells having an anode chamber with a built-in anode and a cathode chamber with a built-in gas diffusion cathode across an ion exchange membrane is used, and the anode chamber is a saline solution. A method of supplying a humidified oxygen-containing gas to the cathode chamber and electrolyzing a saline solution to produce sodium hydroxide and / or chlorine.
The unit cell further comprises a humidifying chamber that produces a humidified oxygen-containing gas to supply to the cathode chamber.
The humidifying chamber has a partition wall between the humidifying chamber and the cathode chamber.
The humidifying chamber is heat-exchangeably adjacent to the anode chamber or the cathode chamber in the unit cell, or the anode chamber or the cathode chamber of the adjacent unit cell, and generates water vapor by the heat from the anode chamber or the cathode chamber. A method for producing sodium hydroxide and / or chlorine, which comprises humidifying the oxygen-containing gas by allowing it to be heated. The production method according to claim 1, wherein the oxygen-containing gas supplied to the humidifying chamber is humidified by vaporizing the water stored in the humidifying chamber to generate water vapor. The humidifying chamber is adjacent to the cathode chamber, and the humidified oxygen-containing gas generated in the humidifying chamber is supplied from the humidifying chamber to the cathode chamber through an opening provided in the partition wall according to claim 1 or 2 . The manufacturing method described. The manufacturing method according to claim 3 , wherein the opening provided in the partition wall is a single opening. The manufacturing method according to claim 3 , wherein the openings provided in the partition wall are a plurality of openings. The production method according to claim 1 or 2 , wherein the humidified oxygen-containing gas generated in the humidifying chamber is supplied from the humidifying chamber to the cathode chamber through a flow path provided outside the humidifying chamber and the cathode chamber. The manufacturing method according to claim 6 , wherein the flow path provided outside the humidifying chamber and the cathode chamber is a single flow path. The manufacturing method according to claim 6 , wherein the flow paths provided outside the humidifying chamber and the cathode chamber are a plurality of flow paths. The production according to any one of claims 1 to 8 , wherein a plurality of unit cells are connected in the electrolytic cell, and the plurality of unit cells are arranged so that the order of the anode chamber, the cathode chamber, and the humidification chamber is repeated. Method. A two-chamber saline electrolytic cell having one or more unit cells having an anode chamber and a cathode chamber with an ion exchange membrane in between.
The anode chamber has a built-in anode and includes a supply port for raw saline solution, a discharge port for electrolyzed saline solution, and a chlorine discharge port. The cathode chamber has a built-in gas diffusion cathode and is a humidified oxygen-containing gas. Equipped with a supply unit and an outlet for electrolyzed reactants
The unit cell further comprises a humidifying chamber that produces an oxygen-containing gas to supply to the cathode chamber.
The humidifying chamber has a partition wall between the humidifying chamber and the cathode chamber.
The humidifying chamber is adjacent to the anode chamber or cathode chamber in the unit cell, or the anode chamber or cathode chamber of the adjacent unit cell so as to be heat exchangeable, and is provided with an oxygen-containing gas supply port. Legal saline electrolytic cell. The two-chamber saline electrolytic cell according to claim 10, wherein the oxygen-containing gas supplied to the humidifying chamber is humidified by vaporizing the water stored in the humidifying chamber to generate water vapor. The electrolytic cell according to claim 10 or 11 , wherein a plurality of unit cells are connected in the electrolytic cell, and the plurality of unit cells are arranged so that the order of the anode chamber, the cathode chamber, and the humidifying chamber is repeated.

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