WO2018180726A1 - Method for manufacturing sodium hydroxide and/or chlorine and 2 chamber type saltwater electrolytic cell - Google Patents

Abstract

Provided is a method for manufacturing sodium hydroxide and/or chlorine wherein, in a 2 chamber method for an oxygen negative electrode method, water is supplied to the negative electrode chambers and overheating of the electrolytic cell is suppressed without requiring additional energy. The present invention is a method for manufacturing sodium hydroxide and/or chlorine by electrolysis of saltwater using a 2 chamber saltwater electrolytic cell having one or more unit cells provided with a positive electrode chamber incorporating a positive electrode and a negative electrode chamber incorporating a gas-diffusion negative electrode with an ion exchange membrane therebetween, wherein the method is characterized in that the unit cells also has a humidification chamber for generating a gas that includes oxygen to which moisture is added for supply to the negative electrode chamber, and the humidification chamber is adjacent to the positive electrode chamber or negative electrode chamber within the unit cell or in an adjacent unit cell such that heat exchange is possible and adds moisture to the gas containing oxygen by generating water vapor by means of heat from the positive electrode chamber or the negative electrode chamber.

Description

Sodium hydroxide and / or chlorine production method, and two-chamber saline electrolyzer

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

Sodium hydroxide and chlorine are important as industrial materials, and conventionally a method of electrolyzing saline using an ion exchange membrane, using a metal electrode as a cathode, It has been produced by a method of electrolysis.
2NaCl + 2H ₂ O → Cl ₂ + 2NaOH + H ₂ (1)

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

In the oxygen cathode method, a three-chamber method in which the electrolytic cell is divided into three chambers, ie, an anode chamber, a catholyte chamber, and a cathode gas chamber, has been adopted. Recently, as described in Patent Document 1, for example, an anode, A two-chamber method in which the ion exchange membrane and the gas diffusion electrode are brought into close contact with each other, the catholyte chamber is substantially eliminated, and the electrolytic cell is divided into two chambers, an anode chamber and a cathode gas chamber, has been studied. As shown in the above reaction formula, water is required for the electrolytic reaction of the saline solution, and the presence of water is also necessary to prevent the sodium hydroxide produced from becoming too concentrated. In the three-chamber method, there is a liquid chamber in which a sodium hydroxide aqueous solution circulates in the cathode chamber, from which sufficient moisture is supplied. On the other hand, in the two-chamber method, since there is no liquid chamber in the cathode chamber, the water supply is only electroosmotic water supplied through the ion exchange membrane from the anode chamber side. It is necessary to supply moisture. In Patent Document 1, it is described that a deficient amount of water is supplied via a gas chamber. Specifically, water heated to 90 ° C. is prepared and introduced from an oxygen gas inlet. ing. Patent Document 2 also discloses supplying a moist oxygen-containing gas to the cathode compartment. Specifically, the oxygen-containing gas is provided by bubbling oxygen into water heated to 80 ° C. It is described that a gas is prepared and introduced into the cathode compartment.

Japanese Patent Laid-Open No. 2001-3188 Japanese Patent Laid-Open No. 11-152591

However, the water supply methods described in Patent Documents 1 and 2 require energy for heating water to 80 ° C. or 90 ° C. Furthermore, in Patent Document 1, when the temperature of the electrolytic cell becomes too high, the anolyte is circulated through an external heat exchanger, and the temperature of the anolyte is lowered using cooling water or the like, and cooling water is prepared. Energy is also needed.

Accordingly, the present invention provides an oxygen cathode method in which the water is efficiently supplied by supplying moisture to the cathode chamber and suppressing overheating of the electrolytic cell without requiring extra energy other than that required for the electrolytic reaction. An object is to provide a method capable of producing sodium oxide and / or chlorine.

The present invention is as follows.
[1] A two-chamber saline electrolyzer having at least one unit cell having an anode chamber with an anode and a cathode chamber with a gas diffusion cathode sandwiched between ion exchange membranes is used in the anode chamber. Is a method of producing sodium hydroxide and / or chlorine by supplying salt water and supplying a humidified oxygen-containing gas to the cathode chamber and electrolyzing the salt solution,
The unit cell further includes a humidification chamber that generates a humidified oxygen-containing gas to be supplied 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 an adjacent unit cell so that heat can be exchanged, and water vapor is generated by heat from the anode chamber or cathode chamber. A method for producing sodium hydroxide and / or chlorine for humidifying the oxygen-containing gas.

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

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

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

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

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

[7] The manufacturing method according to [5], wherein the flow paths provided outside the humidification 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 that the order of the anode chamber, the cathode chamber, and the humidifying chamber is repeated. The manufacturing method of crab.

[9] A two-chamber type saline electrolyzer having one or more unit cells each having an anode chamber and a cathode chamber with an ion exchange membrane interposed therebetween,
The anode chamber has a built-in anode and is provided with a raw material salt water supply port and an electrolyzed salt water discharge port and a chlorine discharge port, and the cathode chamber has a gas diffusion cathode and is a humidified oxygen-containing gas. Supply section and electrolysis reaction product outlet,
The unit cell further includes a humidification chamber that generates an oxygen-containing gas to be supplied to the cathode chamber,
The humidifying chamber is adjacent to the anode chamber or the cathode chamber in the unit cell, or to the anode chamber or the cathode chamber of an adjacent unit cell so that heat exchange is possible, and is provided with an oxygen-containing gas supply port. Legal saline electrolyzer.

[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 humidification chamber is adjacent to the anode chamber or the cathode chamber so that heat exchange is possible, the oxygen-containing gas can be humidified 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 the opening for supplying the humidified oxygen-containing gas. FIG. 3 is a schematic cross-sectional view illustrating an example of a unit cell including a connection pipe that supplies a humidified oxygen-containing gas. FIG. 4 is a schematic cross-sectional view showing an example of a monopolar electrolytic cell. FIG. 5 is a schematic cross-sectional view showing an example of a bipolar electrolytic cell.

Hereinafter, a two-chamber type saline electrolyzer 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 within a range that can be adapted to the purpose described above and below.

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. This anode chamber 3 is provided with an anode 3a in close contact with the side of the anode chamber of the ion exchange membrane 2, and the anode chamber 3 is provided with a supply port 3b for the raw material saline solution at the lower part thereof. And a chlorine discharge port 3c at the top thereof. On the other hand, the cathode chamber 4 includes a liquid holding layer 4b in close contact with the side of the cathode chamber of the ion exchange membrane 2, a gas diffusion cathode 4a, and a gas diffusion cathode support 4c and a cushioning material 4d as necessary. .

The unit cell 1 of the present invention includes a humidification chamber 5 separated from the cathode chamber 4 by a partition wall 6, and the humidification chamber 5 can exchange heat with the cathode chamber 4. In addition, the partition wall 6 in the illustrated example has a planar shape as shown in FIG. 2A, and the upper portion of the partition wall 6 has an opening 7 throughout. For this reason, the humidified oxygen-containing gas can be supplied from the humidification chamber 5 to the cathode chamber 4. The cathode chamber 4 is also provided with a pressure equalizing line 4e for making 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.

Note that the water in the humidification chamber may or may not be circulated to the outside. When circulating to the outside, a line for passing water from the outside to the humidification chamber and discharging hot water can be separately provided (not shown). When water is passed from the outside, the flow rate and temperature of the water can be set as appropriate so that the temperature of the water in the humidification chamber satisfies a predetermined condition (for example, 80 ° C. or higher). Even if the water is passed through, it is preferable from the viewpoint of energy efficiency that the temperature is set to a predetermined temperature using only the heat of the electrolytic reaction.

In the unit cell 1, raw material saline is supplied to the anode chamber 3 from the raw salt water supply port 3b, and oxygen-containing gas is bubbled from the oxygen-containing gas supply port 5a into the water stored in the humidifying chamber 5, By generating a humidified oxygen-containing gas (oxygen concentration is, for example, 90% or more, preferably 93% or more) and supplying the cathode chamber 4 with electricity, chlorine is generated in the anode 3a. Sodium hydroxide is formed in 4a. Then, the electrolytic reaction of the saline solution proceeds and the heat generated at the cathode is transmitted to the humidification chamber 5 so that the temperature of the water stored in the humidification chamber 5 can be raised, and the vaporization of the water in the humidification chamber is promoted. . If the oxygen-containing gas is subsequently supplied to the humidification chamber 5 by bubbling or the like, an oxygen-containing gas containing an amount of water vapor approximately equal to the amount saturated at the temperature of the water in the humidification 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. Moreover, when oxygen-containing gas containing high-concentration water vapor is supplied to each unit cell from a humidifier provided outside the electrolytic cell as disclosed in Patent Document 1, moisture is supplied through a pipe in the middle of supply. In particular, in an electrolytic cell having a plurality of unit cells, the degree of moisture condensation may vary from unit cell to unit cell, and the water supply amount varies from unit cell to unit cell. 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. In addition, by transmitting the heat of the cathode chamber to the humidification 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 humidification 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 (in this way, the humidification chamber 5). The unit cell having the respective chambers 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 the respective chambers in the order of the anode chamber 3, the cathode chamber 4 and the humidifying chamber 5 Hereinafter referred to as A-type 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, the humidification chamber 5 can be heated by using the heat to increase the steam generation efficiency. It is. As will be described later, a plurality of B-type unit cells may be used side by side. 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 steam generation efficiency in the humidification chamber 5 can be increased by the exothermic reaction in the cathode chamber 4 of the adjacent unit cell.

In addition, the chlorine produced | generated in the anode chamber 3 is discharged | emitted with the salt solution after electrolysis from the discharge port 3c. The sodium hydroxide produced in the cathode chamber 4 is a sodium hydroxide aqueous solution having a concentration of about 32.0 to 34.0% due to electroosmotic water from the anode chamber 3 and moisture in the oxygen-containing gas sent to the cathode chamber. Thus, it flows under the cathode chamber under its own weight and is discharged together with the exhaust gas of the oxygen-containing gas from the electrolysis reaction product discharge port 4g. 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 6 in the unit cell 1 may have various shapes of openings 7 as long as the oxygen-containing gas humidified from the humidification chamber 5 to the cathode chamber 4 can flow through the upper part of the partition 6. . For example, as shown in FIG. 2 (b), 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 surface of the partition wall 6 as shown in FIG. 2A, or may be a part of the upper surface as shown in FIG. Good. Further, the number of openings is not particularly limited, and may be one or plural, and the shape of the openings is not particularly limited.

Furthermore, the partition wall 6 may not have the opening 7 as long as the humidified oxygen-containing gas can be circulated from the humidifying chamber 5 to the cathode chamber 4. For example, as shown in FIG. 3, a humidified oxygen-containing gas may be supplied to the cathode chamber 4 through an external flow path such as the communication 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 is possible. When a plurality of B-type unit cells are arranged, an opening 7 is formed between the humidifying chamber 5 and the cathode chamber 4 of the adjacent unit cell, or connected by a connecting pipe 8 so as to be adjacent to the humidifying chamber 5. The oxygen-containing gas may be supplied to the cathode chamber 4 of the unit cell.

In the unit cell as described above (including both A-type unit cell and B-type unit cell; hereinafter the same), the anode 3a is not particularly limited as long as it is an insoluble anode used for brine electrolysis. An expanded metal composed of a metal such as titanium, or a base having a mesh structure such as fine mesh coated with a metal oxide including a ruthenium oxide, titanium oxide, iridium oxide, or platinum group metal oxide. 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 carboxylic acid and / or sulfonic acid as an ion exchange group.

The gas diffusion cathode 4a is not particularly limited as long as it is used for saline electrolysis by the oxygen cathode method. For example, a metal mesh material, carbon cloth and / or hydrophobic resin is used as a base material, A reaction layer on which a hydrophilic catalyst is supported can be used on one surface, and a sheet-like electrode having a three-layer structure in which a water-repellent gas diffusion layer is bonded to the other surface can be used. Examples of the catalyst include silver, platinum, gold, metal oxide, and carbon. The gas diffusion cathode may be permeable to liquid or may not be permeable to liquid.

In the cathode chamber 4, no current can flow unless there is a liquid between the ion exchange membrane 2 and the gas diffusion cathode 4 a. 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 by capillarity, but in order to hold the liquid more reliably, the ion exchange membrane 2 and the gas diffusion cathode It is preferable that the liquid holding layer 4b exists between 4a. The liquid holding layer 4b can uniformly hold a liquid such as an aqueous sodium hydroxide solution 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 needs to hold a sodium hydroxide aqueous 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, the ion exchange membrane and the cathode are in contact with each other, and the electric resistance between the electrodes is small, so that the electrolysis voltage can be reduced. In order to adhere to 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 on the cushion material, and the reaction force is used to make the gas diffusion cathode 4a. It is preferable to adhere to the ion exchange membrane 2. In the two-chamber method, a liquid pressure due to a saline solution acts on the anode chamber with the ion exchange membrane as a boundary, and a gas pressure acts on the cathode chamber. The reaction force of the cushion material is designed according to the differential pressure between the fluid pressure and the gas pressure, but the fluid pressure increases as the depth of the saline solution increases. By making it larger, it is possible to equalize the pressure applied to the ion exchange membrane and the anode. As such a cushioning material 4d, it is possible to use a coil material or a woven mat material. The coil has elasticity in the diametrical direction, and a reaction force is generated in this direction. Therefore, the coil axis can be used in parallel with the back plate of the cathode gas chamber, and the coil diameter, coil system, and laying density can be reduced. By adjusting, the reaction force of the cushion material may be made larger in the lower part than in the upper part. In addition, the woven mat material can be a demister mesh woven knitted metal wire, and the cushion material can be adjusted by adjusting the wire diameter, the number of wires to be bundled, and the number of mat layers laminated. It is sufficient to make the reaction force of the lower part larger than the upper part.

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

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

As a material for 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. Moreover, as a material of the wall surface which comprises the cathode chamber 4 and the humidification chamber 5, it is preferable to use Ni or Ni alloy whose Ni content is 20 weight% or more, and also what plated this with silver.

In the present invention, the electrolytic cell may be configured by arranging a plurality of the above-described unit cells (A type unit cell or B type unit cell, preferably A type unit cell). When arranging a plurality of unit cells, each unit cell may be a monopolar electrolytic cell electrically connected in parallel, or each unit cell may be a bipolar electrolytic cell electrically connected in series, A bipolar electrolytic cell is preferred. Hereinafter, taking as an example the case where the A-type single cells having the openings 7 described above are arranged as means for circulating the oxygen-containing gas between the humidification chamber 5 and the cathode chamber 4, a monopolar electrolytic cell and The bipolar electrolytic cell will be described, but the following example can also be applied to an example in which the connection pipe 8 is used and a B-type single cell is arranged.

FIG. 4 is a schematic cross-sectional view showing an example of a monopolar electrolytic cell in which three A-type unit cells 1 having openings 7 are arranged. 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 (the anode chamber 3, the cathode chamber 4, and the humidifying chamber 5 in this order). , In reverse order (in order of humidification chamber 5, cathode chamber 4 and anode chamber 3), normal order, reverse order, etc., a plurality (three in the illustrated example) are arranged while alternately reversing the order of the chambers in the unit cell. . The anode of each unit cell is connected in parallel to an external power supply, and the cathode is also connected in parallel to the external power supply. 9 is a water storage tank for adjusting the water surface height of the humidification chamber. Even in such an example, the heat of the cathode chamber 4 is transmitted to the humidification chamber 5, and the oxygen-containing gas can be humidified efficiently. In the example in which the arrangement order of the chambers in the unit cell is alternately reversed 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, both unit cells (1) and (2) may share one humidification chamber 5.

FIG. 5 is a schematic cross-sectional view showing an example of a bipolar electrolytic cell in which four A-type unit cells having openings 7 are arranged. In the bipolar 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 therein 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) can be electrically connected to the cathode 4a in the adjacent unit cell (2) ( The cathode 4a at one end and the anode 3a at the other end are connected to an external power source, so that the unit cells are connected in series. Moreover, the raw material salt water supply ports 3b of each unit cell, the electrolyzed salt water 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 The pressure equalization lines 4e are connected to each other by piping, and the water supply port 5b and the pressure equalization line 4e are connected to the water storage tank 9. The mechanism of the electrolytic reaction in each unit cell of the bipolar electrolytic cell 20 is the same as that of the unit cell described above. However, by arranging the unit cells, one humidifying chamber 5 can be used as a cathode chamber in the same unit cell. 4 is adjacent to the anode chamber 3 in the adjacent unit cell. Therefore, the humidification chamber 5 can be humidified using 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 during humidification can be further increased. Further, since the heat of the anode chamber 3 is transferred to the humidification chamber 5, the anode chamber 3 can also be cooled.

In the case of configuring a bipolar electrolytic cell by arranging a plurality of B-type unit cells (unit cells arranged in the order of a humidifying chamber, an anode chamber, and a cathode chamber) without changing the order of each chamber, as in the example of FIG. The humidification chamber 5 is sandwiched between the anode chamber 3 and the cathode chamber 4. 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 humidification chamber 5.

This application claims the benefit of priority based on Japanese Patent Application No. 2017-0608057 filed on Mar. 30, 2017. The entire content of the specification of Japanese Patent Application No. 2017-0608057 filed on March 30, 2017 is incorporated herein by reference.

Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by the following examples, and can of course be implemented with appropriate modifications within a range that can be adapted to the above-described gist. Included in the range.

Example 1
As shown in FIG. 5, five unit cells having the structure shown in FIG. 1 (but not having a gas diffusion cathode support) are arranged so that the anode chamber, the cathode chamber, and the humidifying chamber are repeated in this order. Specifically, it was connected in series to assemble a bipolar two-chamber saline electrolyzer. The anode is DSE manufactured by Permerek Electrode Co., Ltd. (insoluble metal coated with a Pt group metal or its oxide as a main component on a metal substrate), and the cathode is a gas-liquid permeable carbon-silver electrode (GDE2013) manufactured by Permerek Electrode Co. ), 4403D manufactured by Asahi Kasei Chemicals Co., Ltd. for the ion exchange membrane, a carbon fiber woven fabric having a thickness of 0.45 mm for the liquid holding layer, and a spiral nickel wire after silver plating for the cushioning 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 rate of 183 L / m ² / h, and water is stored in the humidifying chamber, and the temperature is 25 ° C. and the concentration is 93.0. %, 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 in the humidification chamber. Since the temperature of the humidification chamber is 84.0 ° C., the temperature of the humidified oxygen-containing gas is about 84.0 ° C. when 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
The unit cell does not have a humidifying chamber, but the other materials such as the anode, cathode, ion exchange membrane, etc., and the size of the cathode chamber, anode chamber, etc. are the same as in Example 1, but the anode cell, cathode Five sheets were arranged so that the order of the chambers was repeated, and electrically connected in series to assemble a bipolar type conventional two-chamber saline electrolyzer (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 cell. In the humidifier, the oxygen-containing gas having a concentration of 93.0% and 1.5 times the required theoretical amount of oxygen-containing gas is connected. A humidified oxygen-containing gas was generated by bubbling in water (25 ° C.) in a humidifier, 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 contrast to Example 1, Comparative Example 1 does not have a humidifying chamber in the unit cell and supplies an oxygen-containing gas humidified from an external humidifier. "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 water temperature of 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) Except that, various values at the time of 10 days were measured in the same manner as in Comparative Example 1.

Comparative Example 3
In the same configuration as that of Comparative Example 2, the temperature of the humidified oxygen-containing gas is prevented from decreasing by keeping the surroundings of the pipe connecting the humidifier and the cathode chamber of each unit cell intensified. 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 after operating the same electrolytic cell as in Example 1 for 300 days were measured.

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

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 and the difference between the value of each unit cell and the average value for the concentration of the aqueous sodium hydroxide solution and the current efficiency.

In Example 1, the temperature of the humidification chamber is equal to the temperature of the anode chamber due to the reaction heat of the electrolytic reaction, and the concentration of the generated aqueous sodium hydroxide solution is not too high at 32.2%. It can be seen that a sufficient amount of water vapor can be supplied (Table 1). Moreover, since the dispersion | variation between five unit cells is restrained small about the density | concentration of produced | generated sodium hydroxide aqueous solution, and current efficiency, it turns out that the dispersion | variation in the amount of water vapor supplied to the cathode chamber of each unit cell is small. (Table 2). In addition, in Example 2 in which Example 1 was operated for a long period of time, a good current efficiency of 96.3% was exhibited even after 300 days had passed, and the other results were as good as those in Example 1. Is obtained. Further, in Example 2, since a sufficient amount of water vapor can be supplied, the generated sodium hydroxide concentration can be kept low, and damage to the gas diffusion cathode is suppressed, so that the gas after 300 days has elapsed since the operation of the electrolytic cell. The change in the voltage of the diffusion cathode was as small as 45 mV as an average value of the five unit cells. In addition, the change of the voltage of the gas diffusion cathode in each unit cell was 78 mV, 15 mV, 45 mV, 33 mV, and 54 mV, respectively.

On the other hand, in Comparative Example 1 in which the humidified oxygen-containing gas was supplied from the external humidifier, 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 supply amount of water vapor 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 increasing the water temperature in the external humidifier is required. The average value of the concentration of the generated aqueous sodium hydroxide solution is 32.2%, and on average, a sufficient amount of water vapor can be supplied. As shown in Table 2, both the sodium hydroxide concentration and the current efficiency are obtained. The variation for each unit cell is large. This is presumably because moisture was condensed during the introduction of the humidified oxygen-containing gas from the external humidifier to the cathode chamber of each unit cell, and the degree of condensation differed for each unit cell. Further, a high-temperature oxygen-containing gas is supplied from the outside of the electrolytic cell, and it is necessary to make the supply saline solution to the anode low in order to prevent overheating of the electrolytic cell (supply in Example 1) The temperature of the salt solution is 53.8 ° C., which is a general temperature range in a salt electrolysis factory, whereas the temperature of the salt solution supplied in Comparative Example 2 is 47.0 ° C.) Extra energy for is needed.

Comparative Example 3 is an example in which heat insulation is strengthened on the pipe from the external humidifier in Comparative Example 2, and, like Comparative Example 2, energy for heating in the external humidifier is required. In Comparative Example 3, as a result of suppressing the condensation of water in the piping, the variation in the generated sodium hydroxide concentration and current efficiency from cell to cell was suppressed. Extra energy for is needed.

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 was the average value of five unit cells. It was 108 mV, which was much 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 sodium hydroxide aqueous solution concentration produced in Comparative Example 4 is 34.6%, which is 2% higher than the sodium hydroxide aqueous solution concentration of 32.2% in Examples 1 and 2. Therefore, it is considered that the gas diffusion cathode is damaged. Note that 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 Humidifying Chamber 6 Partition 7 Opening 8 Connection Pipe 10 Monopolar Electrolyzer 20 Bipolar Electrolyzer

Claims (10)

A two-chamber type saline electrolyzer having at least one unit cell having an anode chamber with an anode and a cathode chamber with a gas diffusion cathode sandwiched between ion exchange membranes is used. A method of producing sodium hydroxide and / or chlorine by supplying a humidified oxygen-containing gas to the cathode chamber and electrolyzing a saline solution,
The unit cell further includes a humidification chamber that generates a humidified oxygen-containing gas to be supplied 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 an adjacent unit cell so that heat can be exchanged, and water vapor is generated by heat from the anode chamber or cathode chamber. The method for producing sodium hydroxide and / or chlorine, characterized in that the oxygen-containing gas is humidified. The humidification chamber is adjacent to the cathode chamber, and the humidified oxygen-containing gas generated in the humidification chamber is supplied from the humidification chamber to the cathode chamber through an opening provided in a partition wall between the humidification chamber and the cathode chamber. The manufacturing method according to claim 1. The manufacturing method according to claim 2, wherein the opening provided in the partition wall between the humidification chamber and the cathode chamber is a single opening. The manufacturing method according to claim 2, wherein the opening provided in the partition wall between the humidification chamber and the cathode chamber is a plurality of openings. The manufacturing method according to claim 1, wherein the humidified oxygen-containing gas generated in the humidification chamber is supplied from the humidification chamber to the cathode chamber through a channel provided outside the humidification chamber and the cathode chamber. The manufacturing method according to claim 5, wherein the flow path provided outside the humidification chamber and the cathode chamber is a single flow path. The manufacturing method according to claim 5, wherein the channels provided outside the humidification chamber and the cathode chamber are a plurality of channels. The production according to claim 1, 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. Method. A two-chamber type saline electrolyzer having one or more unit cells each having an anode chamber and a cathode chamber with an ion exchange membrane interposed therebetween,
The anode chamber has a built-in anode and is provided with a raw material salt water supply port and an electrolyzed salt water discharge port and a chlorine discharge port, and the cathode chamber has a gas diffusion cathode and is a humidified oxygen-containing gas. Supply section and electrolysis reaction product outlet,
The unit cell further includes a humidification chamber that generates an oxygen-containing gas to be supplied to the cathode chamber,
The humidifying chamber is adjacent to the anode chamber or the cathode chamber in the unit cell, or to the anode chamber or the cathode chamber of an adjacent unit cell so that heat exchange is possible, and is provided with an oxygen-containing gas supply port. Legal saline electrolyzer. The electrolytic cell according to claim 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.

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