Electrodialysis system and method of operating the electrodialysis system

Abstract

The present invention provides an electrodialysis system that prevents the ion exchange membrane from drying out, and prevents the saline solution and concentrated solution from mixing. [Solution] The electrodialysis system according to the embodiment includes an anode, a cathode, an electrodialysis tank, a processing liquid supply system, a processing liquid recovery system, a storage liquid supply system, a storage liquid recovery system, and a gas supply system. The storage liquid supply system supplies storage liquid to the saline treatment chamber and the concentrated liquid treatment chamber. The storage liquid recovery system recovers storage liquid from the saline treatment chamber and the concentrated liquid treatment chamber. The gas supply system supplies gas to the saline treatment chamber and the concentrated liquid treatment chamber.

Description

[Technical Field]

[0001] This embodiment relates to an electrodialysis system and a method for operating the electrodialysis system. [Background technology]

[0002] Electrodialysis is a widely used technique due to its various applications, including desalination, concentration, and purification, and because the operation of starting and stopping the electrodialysis machine is relatively easy. An electrodialysis machine includes a pair of electrodes and an electrodialysis cell interposed between the pair of electrodes. The electrodialysis cell is composed of alternately stacked ion exchange membranes and gaskets, the gaskets being formed to define the processing chambers (or cells) for ion exchange. By applying a voltage to the pair of electrodes, substances to be removed can be removed from the liquid to be processed supplied to the processing chamber via the ion exchange membranes.

[0003] Ion exchange membranes can lose performance if they dry out. Therefore, ion exchange membranes should be kept moist both during use and storage. For example, when temporarily stopping the operation of an electrodialysis system, draining the treatment fluid from the treatment chamber of the electrodialysis tank is undesirable because it will cause the ion exchange membrane to dry out.

[0004] Possible countermeasures to address this include (1) removing the ion exchange membrane and storing it outside the electrodialysis tank, (2) filling the processing chamber with processing solutions such as saline solution, concentrate, and electrode solution used in electrodialysis, and (3) filling the processing chamber and tank with a storage solution such as water instead of the processing solution and immersing the ion exchange membrane in the storage solution.

[0005] (1) The larger the size of the electrodialysis machine, the lower the work efficiency may be. (2) For example, if there is a large difference between the concentration of components in the saline solution and the concentration of components in the concentrate, diffusion may occur during shutdown, and components may move between processing chambers. In this case, for example, components that have been moved from the saline solution to the concentrate by electrodialysis may return to the saline solution.

[0006] Regarding (3), the problems described in (1) and (2) above can be resolved. However, when the processing solution and storage solution are exchanged in the processing chamber, there is a possibility that the storage solution may mix with the processing solution or that the processing solution may be recovered into the storage solution. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 4439771 [Patent Document 2] Japanese Patent Publication No. 2009-279525 [Overview of the project] [Problems that the invention aims to solve]

[0008] The embodiment aims to provide an electrodialysis system and a method for operating the electrodialysis system that can prevent the storage solution for preventing the drying of the ion exchange membrane from mixing with the saline solution and the concentrated solution. [Means for solving the problem]

[0009] The electrodialysis system according to this embodiment includes an anode, a cathode, an electrodialysis cell interposed between the anode and the cathode, an ion exchange membrane, and a saline treatment chamber and a concentrated treatment chamber partitioned by the ion exchange membrane, and performs electrodialysis of saline by supplying saline to the saline treatment chamber and concentrated liquid to the concentrated treatment chamber; a treatment liquid supply system; a treatment liquid recovery system; a storage liquid supply system; a storage liquid recovery system; and a gas supply system. The treatment liquid supply system supplies saline to the saline treatment chamber and concentrated liquid to the concentrated treatment chamber. The treatment liquid recovery system recovers saline from the saline treatment chamber and concentrated liquid from the concentrated treatment chamber. The storage liquid supply system supplies storage liquid to the saline treatment chamber and concentrated liquid treatment chamber. The storage liquid recovery system recovers storage liquid from the saline treatment chamber and concentrated liquid treatment chamber. The gas supply system supplies gas to the saline treatment chamber and concentrated liquid treatment chamber.

[0010] The method of operating an electrodialysis system according to the embodiment is a method of operating an electrodialysis system including an electrodialysis tank interposed between an anode and a cathode, which includes an ion exchange membrane and a saline treatment chamber and a concentrated liquid treatment chamber partitioned by the ion exchange membrane, and which supplies saline to the saline treatment chamber and concentrate to the concentrated liquid treatment chamber to perform electrodialysis of the saline. The method of operation includes the steps of supplying saline to the saline treatment chamber to perform electrodialysis of the saline, stopping the supply of saline to the saline treatment chamber and then supplying gas to the saline treatment chamber, and stopping the supply of gas to the saline treatment chamber and then supplying storage liquid to the saline treatment chamber. [Effects of the Invention]

[0011] According to this embodiment, it is possible to prevent the storage solution used to prevent the ion exchange membrane from drying out from mixing with the saline solution and the concentrate. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows an example of a carbon dioxide gas recovery device in the first embodiment. [Figure 2] Figure 2 shows the electrodialysis process of the electrodialysis system according to the first embodiment. [Figure 3] Figure 3 is a flowchart illustrating the operation method of the electrodialysis system according to the first embodiment. [Figure 4] Figure 4 shows the gas supply process of the electrodialysis system shown in Figure 2. [Figure 5] Figure 5 shows the storage process for the electrodialysis system shown in Figure 2. [Figure 6] Figure 6 shows the electrodialysis process of the electrodialysis system according to the second embodiment. [Figure 7] Figure 7 shows the electrodialysis process of an electrodialysis system according to the third embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments will be described with reference to the drawings.

[0014] (First Embodiment) The electrodialysis system according to the first embodiment and the operation method of the electrodialysis system will be described with reference to FIGS. 1 to 5. The electrodialysis system according to this embodiment can be used for various applications such as desalination, concentration, or purification. Hereinafter, as an example, the case of electrodialyzing the absorption liquid used in the carbon dioxide gas recovery device will be described, but this embodiment is not limited to this.

[0015] First, the carbon dioxide gas recovery device 200 will be described with reference to FIG. 1.

[0016] As shown in FIG. 1, the carbon dioxide gas recovery device 200 includes an absorber 201, a regenerator 202, a reboiler 203, and a heat exchanger 204. The absorber 201 is supplied with a processed gas G1 containing carbon dioxide gas from equipment not shown. The processed gas G1 may be cooled by a cooler not shown, subjected to treatment such as desulfurization or denitration, and then supplied to the absorber 201.

[0017] The absorber 201 may include an absorption section 205 that absorbs the carbon dioxide gas contained in the processed gas G1 into the lean liquid F1 (absorption liquid), and a washing section 206 that washes the decarbonated gas G2 from which the carbon dioxide gas has been removed in the absorption section 205 with the washing liquid F3.

[0018] The processed gas G1 is supplied to the absorber 201 and rises from the lower position of the absorption section 205 toward the absorption section 205. On the other hand, the lean liquid F1 discharged from the regenerator 202 is supplied to the absorber 201 and disperses and falls from a liquid disperser (not shown) located above the absorption section 205. The absorption section 205 may be composed of, for example, a packing material, and the processed gas G1 and the lean liquid F1 are in gas-liquid contact in the absorption section 205. As a result, the carbon dioxide gas contained in the processed gas G1 is absorbed into the lean liquid F1, and the lean liquid F1 becomes a rich liquid F2 (absorption liquid).

[0019] More specifically, when the gas to be treated G1 comes into gas-liquid contact with the lean liquid F1, reactions such as those shown in equations (1) and (2) below occur. This forms a pyrolytic salt (R3NH2CO3) and a thermally stable amine salt (R3NHX), and the carbon dioxide in the gas to be treated G1 is absorbed by the lean liquid F1. In this way, carbon dioxide is removed from the gas to be treated G1. Below, R represents hydrogen, a substituted or unsubstituted alkyl group (which may form a heterocycle). R3N+CO2+H2O→R3NH2CO3···(1) R3N+HX → R3NHX ···(2)

[0020] The lean solution absorbs carbon dioxide from the gas G1 being treated, becoming the rich solution. The rich solution contains pyrolytic salts and thermally stable amine salts. In addition to carbon dioxide gas, the rich solution F2 may contain organic acids produced by the reaction with oxygen in the gas G1 being treated, and thermally stable amine salts produced by the absorption of SOx, NOx, carbonyl sulfide, hydrogen cyanide, thiocyanic acid, thiosulfate, and other inorganic acids contained in the gas G1 being treated.

[0021] The decarbonated gas G2, from which carbon dioxide gas has been removed, rises from the absorption section 205 and reaches the washing section 206. The washing section 206 is supplied with a washing liquid F3 that is dispersed and dropped from a liquid disperser (not shown) located above the washing section 206. The washing section 206 may be composed of, for example, a packing material, and the decarbonated gas G2 and the washing liquid F3 come into gas-liquid contact in the washing section 206. As a result, the decarbonated gas G2, which carries absorbent liquid components (amines), is washed by the washing liquid F3, and the absorbent liquid components are recovered from the decarbonated gas G2. The decarbonated gas G2 washed with the washing liquid F3 rises from the washing section 206 and is discharged to the outside from the absorber 201. The washing liquid F3 falls from the washing section 206, is collected in a receiving section (not shown), and is supplied to the circulation line 207. A circulation pump 208 is provided in the circulation line 207, and the washing liquid F3 passes through the circulation line 207 and reaches the liquid disperser described above. In this way, the cleaning solution F3 is circulating.

[0022] The rich liquid F2 that has absorbed carbon dioxide gas in the absorption section 205 is supplied to the rich liquid line 209. The rich liquid line 209 is equipped with a pump (not shown), and the rich liquid F2 is supplied to the heat exchanger 204 located in the rich liquid line 209. The rich liquid F2 is supplied to the heat exchanger 204 from the regenerator 202, and heat exchange takes place between the rich liquid F2 and the lean liquid F1. The rich liquid F2 discharged from the heat exchanger 204 is supplied to the regenerator 202.

[0023] The regenerator 202 is supplied with rich liquid F2, as well as high-temperature lean liquid F1 from the reboiler 203. This heats the rich liquid F2 in the regenerator 202, causing carbon dioxide gas to be released from it. The released carbon dioxide gas G3 is discharged from the regenerator 202 along with water vapor, and is cooled in the cooler 210, where it condenses the water vapor and produces condensate. The carbon dioxide gas G3 accompanied by condensate is supplied to the gas-liquid separator 211, where the condensate is separated from the carbon dioxide gas G3. The carbon dioxide gas G3 with the condensate separated is discharged from the gas-liquid separator 211. The condensate F4 is returned to the regenerator 202.

[0024] Lean liquid F1, which has released carbon dioxide gas in the regenerator 202, is discharged from the regenerator 202. Some of the lean liquid F1 is supplied to the reboiler 203. High-temperature steam is supplied to the reboiler 203 from equipment (not shown) to heat the lean liquid F1. The heated lean liquid F1 is supplied to the regenerator 202 to heat the rich liquid F2.

[0025] The remaining lean liquid F1 discharged from the regenerator 202 is supplied to the lean liquid line 212. The lean liquid line 212 is equipped with a pump (not shown), and the lean liquid F1 is supplied to the cooler 213 after passing through the heat exchanger 204 described above. The lean liquid F1 cooled in the cooler 213 is dispersed and dropped from the liquid disperser and supplied to the absorption unit 205.

[0026] In this way, the carbon dioxide gas recovery device 200 is configured to recover carbon dioxide gas G3 from the gas to be treated G1 while the absorbent liquid circulates between the absorber 201 and the regenerator 202.

[0027] The absorbent solution may be an amine-based aqueous solution containing an amine compound (hereinafter referred to as "amine") and water. Examples of amines include primary amines such as monoethanolamine and 2-amino-2-methyl-1-propanol, secondary amines such as diethanolamine and 2-methylaminoethanol, tertiary amines such as triethanolamine and N-methyldiethanolamine, polyethylene polyamines such as ethylenediamine, triethylenediamine, and diethylenetriamine, cyclic amines such as piperazines, piperidines, and pyrrolidines, polyamines such as xylylenediamine, and amino acids such as methylaminocarboxylic acid. These can be used individually or in combination of two or more. The absorbent solution typically uses an aqueous solution containing 10% to 70% by weight of these amines. Furthermore, the absorbent solution may contain, as needed, reaction accelerators, nitrogen-containing compounds to improve the absorption performance of acidic gases such as carbon dioxide, corrosion inhibitors to prevent corrosion of plant equipment, defoaming agents to prevent foaming, antioxidants to prevent deterioration of the absorbent solution, pH adjusters, and other compounds in any proportion as long as they do not impair the effectiveness of the absorbent solution.

[0028] Examples of the treated gas G1 mentioned above include combustion exhaust gases discharged from boilers or gas turbines in thermal power plants, process exhaust gases generated in steel mills, or combustion exhaust gases generated in waste treatment plants. The absorbent liquid absorbs organic acids produced by the reaction with oxygen contained in the treated gas G1, as well as SOx, NOx, carbonyl sulfides, hydrogen cyanide, thiocyanic acid, thiosulfuric acid, and other inorganic acids contained in the treated gas G1, and heat-stable amine salts accumulate. As an example, equations (3) to (7) show the reaction equations in which alkanolamines react with SO2 to produce heat-stable amine salts. SO2 + H2O = H2SO3 ... (3) H2SO3 + 1 / 2O2 = H2SO4 ... (4) H2SO3+2RNHCHR'CH2OH =[RNH2CHR'CH2OH]2SO3···(5) [RNH2CHR'CH2OH]2SO3+1 / 2O2 =[RNH2CHR'CH2OH]2SO4···(6) H2SO4+2RNHCHR'CH2OH =[RNH2CHR'CH2OH]2SO4···(7)

[0029] Such heat-stable amine salts are not decomposed by heating during the regeneration of the absorbent solution in the regenerator 202 and are not separated from the absorbent solution, thus accumulating in the absorbent solution. This reduces the carbon dioxide gas absorption efficiency of the absorbent solution and can cause corrosion of the carbon dioxide gas recovery device 200. For this reason, it is desirable to remove the heat-stable amine salts from the absorbent solution. In the electrodialysis system 1 according to this embodiment, such heat-stable amine salts as impurities can be removed from the absorbent solution. The electrodialysis system 1 will be described below with reference to Figures 2 to 4.

[0030] As shown in Figure 2, the electrodialysis system 1 may include an electrodialysis apparatus 2, a processing fluid supply system 20, a processing fluid recovery system 40, an electrode solution supply system 60, an electrode solution recovery system 70, a storage fluid supply system 80, a storage fluid recovery system 90, a gas supply system 100, a gas discharge system 110, and a control device 120.

[0031] [Electrodialysis machine] The electrodialysis apparatus 2 may include an anode 3, a cathode 4, and an electrodialysis cell 10 interposed between the anode 3 and the cathode 4.

[0032] The anode 3 contains an anode chamber 5 (or electrode solution chamber), into which electrode solution is supplied from the electrode solution supply system 60. The anode chamber 5 is filled with electrode solution. Similarly, the cathode 4 contains a cathode chamber 6 (or electrode solution chamber), into which electrode solution is supplied from the electrode solution supply system 60. The cathode chamber 6 is filled with electrode solution.

[0033] The electrodialysis cell 10 may include an ion exchange membrane and a saline treatment chamber and a concentrated solution treatment chamber partitioned by the ion exchange membrane. The electrodialysis cell 10 is configured to perform electrodialysis of saline by supplying saline to the saline treatment chamber and concentrated solution to the concentrated solution treatment chamber. The electrodialysis cell 10 may include a plurality of ion exchange membranes. The plurality of ion exchange membranes may include an anion exchange membrane 11, a bipolar membrane 13, and a cation exchange membrane 12.

[0034] More specifically, the anion exchange membrane 11, bipolar membrane 13, and cation exchange membrane 12 are arranged in this order from anode 3 to cathode 4. These three membranes define four processing chambers. An acid collection chamber 16 is formed between anode 3 and anion exchange membrane 11, and an absorbent solution purification chamber 14 is formed between anion exchange membrane 11 and bipolar membrane 13. An amine removal chamber 17 is formed between bipolar membrane 13 and cation exchange membrane 12, and an amine collection chamber 15 is formed between cation exchange membrane 12 and cathode 4. The absorbent solution purification chamber 14 and the amine collection chamber 15 are examples of saline processing chambers to which the absorbent solution to be treated is supplied as a saline solution, while the acid collection chamber 16 and the amine removal chamber 17 are examples of concentrated solution processing chambers to which a concentrated solution is supplied.

[0035] Figure 2 shows an example in which the electrodialysis cell 10 is composed of the four processing chambers described above, for convenience. However, the number of processing chambers that make up the electrodialysis cell 10 is arbitrary. In Figure 2, the number of combinations of saline processing chambers and concentrated processing chambers is arbitrary, as long as there is at least one such combination. Furthermore, saline processing chambers and concentrated processing chambers may exist individually rather than in combination. For example, if the electrodialysis cell 10 is composed of four combinations of saline processing chambers and concentrated processing chambers, the anion exchange membrane 11, bipolar membrane 13, cation exchange membrane 12, bipolar membrane 13, anion exchange membrane 11, bipolar membrane 13, and cation exchange membrane 12 may be arranged in this order. However, the arrangement of the ion exchange membranes is not limited to this.

[0036] As the anion exchange membrane 11, a polymer membrane having anion exchange groups that can allow anions to pass through and block the passage of cations is used. As the anion exchange membrane 11, for example, a membrane made of a polymer having a strongly basic quaternary ammonium group and weakly basic functional groups such as a primary amino group, a secondary amino group, or a tertiary amino group can be used. Specifically, as preferred anion exchange membranes 11, known anion exchange membranes 11 such as NeoSepta AMX, NeoSepta AHA (manufactured by Astrom Co., Ltd., trade name); Celemion AMV, Celemion AMT, Celemion DSV, Celemion ASV, and Celemion AHO (manufactured by AGC Engineering Co., Ltd., trade name) can be used.

[0037] As the cation exchange membrane 12, a polymer membrane having a cation exchange group that can allow cations to pass through and block the passage of anions is used. As the cation exchange membrane 12, for example, a membrane made of a polymer having one or more sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, sulfate ester groups, and phosphate ester groups can be used. Specifically, as preferred cation exchange membranes 12, known cation exchange membranes 12 such as NeoSepta CMX, NeoSepta CMB (manufactured by Astrom Co., Ltd., trade name), Celemion CMV, Celemion CMD, Celemion CSO, and Celemion CMF (manufactured by AGC Engineering Co., Ltd., trade name) can be used.

[0038] The bipolar membrane 13 is a composite membrane in which an anion exchange membrane and a cation exchange membrane are stacked, with the anion exchange membrane located on the anode 3 side and the cation exchange membrane located on the cathode 4 side. When a voltage above the theoretical decomposition voltage of water is applied to the bipolar membrane 13 in the presence of water, water can be electrolyzed into hydrogen ions and hydroxide ions. Preferably, known bipolar membranes 13 such as NeoSepta BP-1E (manufactured by Astrom Co., Ltd., trade name) can be used as the bipolar membrane 13.

[0039] The absorption solution purification chamber 14 is located between the anion exchange membrane 11 and the bipolar membrane 13. The anion exchange membrane 11 is located on the anode 3 side of the absorption solution purification chamber 14, and the bipolar membrane 13 is located on the cathode 4 side.

[0040] The acid collection chamber 16 is located closer to the anode 3 than the absorption solution purification chamber 14. The acid collection chamber 16 is adjacent to the absorption solution purification chamber 14 via an anion exchange membrane 11.

[0041] The amine removal chamber 17 is located between the bipolar membrane 13 and the cation exchange membrane 12. The bipolar membrane 13 is located on the anode 3 side of the amine removal chamber 17, and the cation exchange membrane 12 is located on the cathode 4 side.

[0042] The amine collection chamber 15 is located on the cathode 4 side of the amine removal chamber 17. The amine collection chamber 15 is adjacent to the amine removal chamber 17 via a cation exchange membrane 12.

[0043] The absorbent liquid purification chamber 14 and the amine collection chamber 15 are each supplied with the absorbent liquid to be treated from the saline tank 22, which will be described later. The absorbent liquid to be treated is an example of a saline solution. The absorbent liquid to be treated may be lean liquid F1 or rich liquid F2 continuously or intermittently drawn during the operation of the carbon dioxide gas recovery device 200 described above, or it may be the absorbent liquid to be treated after use in the carbon dioxide gas recovery device 200. The absorbent liquid recovered from the carbon dioxide gas recovery device 200 may be stored in the saline tank 22, which will be described later. The absorbent liquid contains the acidic component (X) of a thermally stable amine salt. - ) contains this acid component (X - ) is an anion.

[0044] The acid collection chamber 16 and the amine removal chamber 17 are each filled with concentrated liquid supplied from the concentrated liquid tank 32, which will be described later. The concentrated liquid is also called the acid collection liquid.

[0045] When a potential difference is generated between anode 3 and cathode 4, the acidic component (X) of the thermally stable amine salt contained in the absorbent solution to be treated is generated in the absorption solution purification chamber 14.- Since ) is an anion, it is attracted to the anode 3. As a result, the acidic component (X) of the thermally stable salt in the absorption solution purification chamber 14 is removed. - The acidic component (X) of the thermally stable amine salt moves from the absorption solution purification chamber 14 through the anion exchange membrane 11 to the acid collection chamber 16. - The ) is removed, and the concentration of the acid component of the thermally stable amine salt in the acid collection chamber 16 increases.

[0046] In the bipolar membrane 13, electrolysis of water occurs internally. As a result, hydroxide ions generated by electrolysis pass through the anion exchange membrane 11 of the bipolar membrane 13 and move to the absorption solution purification chamber 14. Hydrogen ions pass through the cation exchange membrane 12 of the bipolar membrane 13 and move to the amine removal chamber 17.

[0047] The absorbent liquid discharged from the absorbent liquid purification chamber 14 is supplied to the saline tank 22, which will be described later. It may also be supplied again from the saline tank 22 to the absorbent liquid purification chamber 14. In this case, the acidic component of the thermally stable amine salt can be removed from the absorbent liquid while circulating it. Alternatively, the absorbent liquid discharged from the absorbent liquid purification chamber 14 may be supplied to the carbon dioxide gas recovery device 200 described above.

[0048] The concentrated liquid discharged from the acid collection chamber 16 is supplied to the concentrated liquid tank 32, which will be described later. The concentrated liquid tank 32 is then supplied back to the acid collection chamber 16 to remove the acid component (X) of the thermally stable amine salt. - ) may be collected.

[0049] As described above, in the electrodialysis apparatus 2 shown in Figure 2, the acidic component of the thermally stable amine salt is removed from the absorbent solution in the absorption solution purification chamber 14. However, some of the amine in the absorbent solution in the absorption solution purification chamber 14 also passes through the ion exchange membrane and moves to the acid collection chamber 16. As a result, amine accumulates in the concentrated solution, leading to amine loss.

[0050] As a mechanism for reducing amine loss, although not restricted by theory, the following mechanisms can be considered. It is considered that amine loss occurs when, for example, the anion of carbamic acid that has reacted with carbon dioxide remaining in the absorption liquid to be treated passes through the anion exchange membrane 11 as shown in formula (8). In the following, R represents hydrogen, a substituted or unsubstituted alkyl group. 2R2NH + CO2 → R2NH2 + + R2NCOO - ···(8)

[0051] On the other hand, in the amine removal chamber 17, among the amine components contained in the supplied concentrated liquid, the amine (R3NH + ) that has become a cation is attracted to the side of the cathode 4. Here, R represents hydrogen or a substituted or unsubstituted alkyl group. R may form a heterocycle. As a result, the amine (R3NH + ) in the amine removal chamber 17 moves from the amine removal chamber 17 through the cation exchange membrane 12 to the amine collection chamber 15. As a result, the amine (R3NH + ) accumulates in the absorption liquid to be treated, and the amine that has moved to the concentrated liquid and been lost is recovered, reducing the loss amount.

[0052] The concentrated liquid only needs to have an electric resistance that allows electrodialysis. An acid component may be added to the concentrated liquid in advance. As a result, as shown in the following formula (9), the amount of amine existing as a cation in the concentrated liquid increases, making it easier to recover the amine from the concentrated liquid. As the acid component to be added, for example, sulfuric acid, nitric acid, formic acid, acetic acid, etc. may be used. Also, during electrodialysis, if the concentrated liquid is circulated, the acid component removed from the absorption liquid to be treated accumulates in the concentrated liquid. Therefore, the acid component may be added to the concentrated liquid only at the initial stage of operation and not thereafter. In this case, it is also possible to reduce the addition amount of the acid component. R3N + HX → R3NH + + X - ···(9)

[0053] The concentrate may be discarded and replaced with a new concentrate after the acidic component of the heat-stable amine salt reaches a predetermined concentration. Alternatively, only a portion of the concentrate may be continuously withdrawn, and a new concentrate may be continuously supplied. In this case, the acidic component of the stable amine salt in the concentrate can be maintained at a predetermined concentration.

[0054] Next, each system of the electrodialysis system according to this embodiment will be described with reference to Figure 2.

[0055] [Processing liquid supply system] The processing liquid supply system 20 is configured to supply saline solution to the saline solution processing chamber and concentrate to the concentrate solution processing chamber. The processing liquid supply system 20 according to this embodiment may also include a saline solution supply system 21 and a concentrate solution supply system 31. The processing liquid is a liquid supplied to the electrodialysis tank 10 for electrodialysis, and saline solution and concentrate solution are examples of processing liquids.

[0056] The saline supply system 21 is configured to supply saline to the saline treatment chamber. The saline (or absorbent liquid to be treated) is indicated by the symbol F5 in Figure 2. The saline supply system 21 may include a saline tank 22, a saline supply line 23, a saline pump 24, and a saline supply valve 25. The saline tank 22 is configured to store the absorbent liquid to be treated as saline. The saline supply line 23 connects the saline tank 22 to the absorbent liquid purification chamber 14 and the amine collection chamber 15, which are saline treatment chambers. The saline supply line 23 has a branch point 23P in the middle. The saline pump 24 is provided on the saline supply line 23 and is located upstream of the branch point 23P on the saline supply line 23. By driving the saline pump 24, the saline stored in the saline tank 22 is supplied to the absorbent liquid purification chamber 14 and the amine collection chamber 15. The saline supply valve 25 is an on / off valve installed in the saline supply line 23, and is located between the saline pump 24 and the branching point 23P in the saline supply line 23.

[0057] The concentrate supply system 31 is configured to supply concentrate to the concentrate processing chamber. The concentrate is indicated by the symbol F6 in Figure 2. The concentrate supply system 31 may include a concentrate tank 32, a concentrate supply line 33, a concentrate pump 34, and a concentrate supply valve 35. The concentrate tank 32 is configured to store concentrate. The concentrate supply line 33 connects the concentrate tank 32 to the acid collection chamber 16 and the amine removal chamber 17, which serve as concentrate processing chambers. The concentrate supply line 33 has a branch point 33P in the middle. The concentrate pump 34 is provided on the concentrate supply line 33 and is located upstream of the branch point 33P in the concentrate supply line 33. By driving the concentrate pump 34, the concentrate stored in the concentrate tank 32 is supplied to the acid collection chamber 16 and the amine removal chamber 17. The concentrate supply valve 35 is an on / off valve provided in the concentrate supply line 33, and is located between the concentrate pump 34 and the branching point 33P in the concentrate supply line 33.

[0058] [Processing liquid recovery system] The processing liquid recovery system 40 is configured to recover saline solution from the saline solution treatment chamber and also recover concentrated liquid from the concentrated liquid treatment chamber. The processing liquid recovery system 40 according to this embodiment may also include a saline solution recovery system 41 and a concentrated liquid recovery system 51.

[0059] The saline recovery system 41 is configured to recover saline from the saline treatment chamber. The saline recovery system 41 may recover the absorbent liquid to be treated as saline from the saline treatment chamber to the saline tank 22 described above. The saline recovery system 41 may include a saline recovery line 42 and a saline recovery valve 43. The saline recovery line 42 connects the absorbent liquid purification chamber 14 and the amine collection chamber 15 to the saline tank 22. The saline recovery line 42 has a confluence point 42P in the middle. By driving the saline pump 24 described above, the absorbent liquid to be treated is recovered from the absorbent liquid purification chamber 14 and the amine collection chamber 15 to the saline tank 22. The saline recovery valve 43 is an on / off valve provided in the saline recovery line 42 and is located downstream of the confluence point 42P in the saline recovery line 42.

[0060] The concentrate recovery system 51 is configured to recover concentrate from the concentrate processing chamber. The concentrate recovery system 51 may recover concentrate from the concentrate processing chamber to the concentrate tank 32 described above. The concentrate recovery system 51 may include a concentrate recovery line 52 and a concentrate recovery valve 53. The concentrate recovery line 52 connects the acid collection chamber 16 and the amine removal chamber 17 to the concentrate tank 32. The concentrate recovery line 52 has a confluence point 52P in the middle. By driving the concentrate pump 34 described above, concentrate is recovered from the acid collection chamber 16 and the amine removal chamber 17 to the concentrate tank 32. The concentrate recovery valve 53 is an on / off valve provided in the concentrate recovery line 52 and is located downstream of the confluence point 52P in the concentrate recovery line 52.

[0061] [Electrolyte supply system] The electrode solution supply system 60 is configured to supply electrode solution to the electrode solution chamber. The electrode solution supply system 60 according to this embodiment may include an electrode solution tank 61, an electrode solution supply line 62, an electrode solution pump 63, and an electrode solution supply valve 64. The electrode solution tank 61 is configured to store electrode solution. The electrode solution supply line 62 connects the electrode solution tank 61 to the anode chamber 5 and cathode chamber 6, which serve as electrode solution chambers. The electrode solution supply line 62 has a branch point 62P in the middle. The electrode solution pump 63 is provided on the electrode solution supply line 62 and is located upstream of the branch point 62P in the electrode solution supply line 62. By driving the electrode solution pump 63, the electrode solution stored in the electrode solution tank 61 is supplied to the anode chamber 5 and cathode chamber 6. The electrode solution supply valve 64 is an on / off valve provided on the electrode solution supply line 62 and is located between the electrode solution pump 63 and the branch point 62P in the electrode solution supply line 62.

[0062] [Electrode fluid recovery system] The electrode solution recovery system 70 is configured to recover the electrode solution from the electrode solution chamber. The electrode solution is indicated by reference numeral F7 in Figure 2. The electrode solution recovery system 70 may recover the electrode solution into the electrode tank described above. The electrode solution recovery system 70 according to this embodiment may include an electrode solution recovery line 71 and an electrode solution recovery valve 72. The electrode solution recovery line 71 connects the anode chamber 5 and the cathode chamber 6 to the electrode solution tank 61. The electrode solution recovery line 71 has a confluence point 71P in the middle. By driving the electrode solution pump 63 described above, the electrode solution is recovered from the anode chamber 5 and the cathode chamber 6 into the electrode solution tank 61. The electrode solution recovery valve 72 is an on / off valve provided on the electrode solution recovery line 71 and is located downstream of the confluence point 71P on the electrode solution recovery line 71.

[0063] [Storage liquid supply system] The storage liquid supply system 80 is configured to supply storage liquid to the saline solution treatment chamber, the concentrated solution treatment chamber, and the electrode solution chamber. The storage liquid may be water. Alternatively, the storage liquid may be a solution consisting of a compound other than water, or an aqueous solution containing a compound other than water. The storage liquid is indicated by the symbol F8 in Figure 5, which will be described later.

[0064] The storage liquid supply system 80 according to this embodiment may include a storage liquid tank 81, a storage liquid supply line 82, a storage liquid pump 83, and a storage liquid supply valve 84. The storage liquid tank 81 is configured to store the storage liquid. The storage liquid supply line 82 connects the storage liquid tank 81 to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6. In this embodiment, the storage liquid supply line 82 connects the storage liquid tank 81 to the saline supply line 23, the concentrated liquid supply line 33, and the electrode liquid supply line 62. The storage liquid supply line 82 has two branching points 82P1 and 82P2. The portion of the storage liquid supply line 82 on the saline supply line 23 side branches off from branching point 82P1 located upstream. The portion of the storage liquid supply line 82 on the side of the concentrated liquid supply line 33 and the portion on the side of the electrode liquid supply line 62 branch off from a branching point 82P2 located downstream. The storage liquid pump 83 is installed on the storage liquid supply line 82 and is located upstream of the branching point 82P1 in the storage liquid supply line 82. By driving the storage liquid pump 83, the storage liquid stored in the storage liquid tank 81 is supplied to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6. The storage liquid supply valve 84 is an on / off valve installed on the storage liquid supply line 82 and is located between the storage liquid pump 83 and the branching point 82P1 in the storage liquid supply line 82. The storage liquid supply line 82 is shown with a dashed line for clarity.

[0065] The connection point 82P3 between the storage liquid supply line 82 and the saline supply line 23 is located downstream of the saline supply valve 25 in the saline supply line 23. The connection point 82P3 may also be located between the saline supply valve 25 and the branching point 23P in the saline supply line 23.

[0066] The connection point 82P4 between the storage liquid supply line 82 and the concentrated liquid supply line 33 is located downstream of the concentrated liquid supply valve 35 in the concentrated liquid supply line 33. The connection point 82P4 may also be located between the concentrated liquid supply valve 35 and the branching point 33P in the concentrated liquid supply line 33.

[0067] The connection point 82P5 between the storage fluid supply line 82 and the electrode fluid supply line 62 is located downstream of the electrode fluid supply valve 64 in the electrode fluid supply line 62. The connection point 82P5 may also be located between the electrode fluid supply valve 64 and the branching point 62P in the electrode fluid supply line 62.

[0068] As shown in Figure 2, the storage liquid supply system 80 according to this embodiment may include three supply switching valves 85. The supply switching valves 85 are located downstream of the branching points 82P1 and 82P2 in the storage liquid supply line 82. The supply switching valves 85 are located in the portion of the storage liquid supply line 82 on the side of the saline supply line 23, the portion on the side of the concentrated liquid supply line 33, and the portion on the side of the electrode liquid supply line 62, respectively. By controlling each of the supply switching valves 85, the destination of the storage liquid can be switched. For example, it is possible to supply the storage liquid to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17, but not to the anode chamber 5 and the cathode chamber 6. Furthermore, the destination of the gas supply from the gas supply system 100, which will be described later, can also be switched in the same way by the supply switching valves 85.

[0069] [Storage liquid recovery system] The storage liquid recovery system 90 is configured to recover the storage liquid from the saline treatment chamber, the concentrated liquid treatment chamber, and the electrode liquid chamber. The storage liquid recovery system 90 may also recover the storage liquid to the storage liquid tank 81 described above. The storage liquid recovery system 90 according to this embodiment may include a storage liquid recovery line 91 and a storage liquid recovery valve 92. The storage liquid recovery line 91 connects the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6 to the storage liquid tank 81. In this embodiment, the storage liquid recovery line 91 connects the saline recovery line 42, the concentrated liquid recovery line 52, and the electrode liquid recovery line 71 described above to the storage liquid tank 81. The storage liquid recovery line 91 has two confluence points 91P1 and 91P2 along its length. The portion of the storage liquid recovery line 91 on the side of the saline solution recovery line 42 and the portion on the side of the concentrated solution recovery line 52 merge at a confluence point 91P1 located upstream. The portion of the storage liquid recovery line 91 on the side of the electrode solution recovery line 71 merges at a confluence point 91P2 located downstream. By driving the storage liquid pump 83 described above, the storage liquid is recovered from the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, amine removal chamber 17, anode chamber 5, and cathode chamber 6 into the storage liquid tank 81. The storage liquid recovery valve 92 is an on / off valve provided in the storage liquid recovery line 91 and is located downstream of the confluence point 91P2 in the storage liquid recovery line 91. The storage liquid recovery line 91 is shown with a dashed line for clarity.

[0070] The connection point 91P3 between the storage liquid recovery line 91 and the saline recovery line 42 is located upstream of the saline recovery valve 43 in the saline recovery line 42. The connection point 91P3 may also be located upstream of the confluence point 42P in the saline recovery line 42. In this case, the connection point 91P3 may be located in the part of the saline recovery line 42 on the side of the absorption liquid purification chamber 14, or in the part on the side of the amine collection chamber 15. In the example shown in Figure 2, the connection point 91P3 is located in the part on the side of the amine collection chamber 15.

[0071] The connection point 91P4 between the storage liquid recovery line 91 and the concentrate recovery line 52 is located upstream of the concentrate recovery valve 53 in the concentrate recovery line 52. The connection point 91P4 may also be located upstream of the confluence point 52P in the concentrate recovery line 52. In this case, the connection point 91P4 may be located in the portion of the storage liquid recovery line 91 on the acid collection chamber 16 side, or on the portion on the amine removal chamber 17 side. In the example shown in Figure 2, the connection point 91P4 is located in the portion on the amine removal chamber 17 side.

[0072] The connection point 91P5 between the storage fluid recovery line 91 and the electrode fluid recovery line 71 is located upstream of the electrode fluid recovery valve 72 in the electrode fluid recovery line 71. The connection point 91P5 may also be located downstream of the confluence point 71P in the electrode fluid recovery line 71. In this case, the connection point 91P5 may be located between the confluence point 71P and the storage fluid recovery valve 92 in the storage fluid recovery line 91.

[0073] As shown in Figure 2, the storage liquid recovery system 90 according to this embodiment may include three recovery switching valves 93. The recovery switching valves 93 are located upstream of the confluence points 91P1 and 91P2 in the storage liquid recovery line 91. The recovery switching valves 93 are located in the portion of the storage liquid recovery line 91 on the side of the saline solution recovery line 42, the portion on the side of the concentrated solution recovery line 52, and the portion on the side of the electrode solution recovery line 71, respectively. By controlling each of the recovery switching valves 93, the destination of the storage liquid can be switched. For example, if the storage liquid is supplied to the absorption solution purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17, and not to the anode chamber 5 and the cathode chamber 6, the recovery switching valve 93 on the saline solution recovery line 42 side and the recovery switching valve 93 on the concentrated solution recovery line 52 side may be opened, and the recovery switching valve 93 on the electrode solution recovery line 71 side may be closed. Furthermore, the recovery switching valves 93 may be opened and closed in accordance with the destination of the gas supplied from the gas supply system 100, which will be described later.

[0074] [Gas supply system] The gas supply system 100 is configured to supply gas to the saline treatment chamber, the concentrated liquid treatment chamber, and the electrode liquid chamber. The gas is indicated by the symbol G4 in Figure 4, which will be described later. The gas supply system 100 according to this embodiment may include a gas supply unit 101, a gas supply line 102, and a gas supply valve 103. The gas supply unit 101 is configured to supply gas to the gas supply line 102. The gas supply unit 101 may be, for example, a cylinder for compressing and storing gas, or a connection to an external supply source (not shown) for supplying compressed gas. The gas may be an inert gas such as nitrogen, or it may be air. The gas supply line 102 connects the gas supply unit 101 to the absorbent liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6. In this embodiment, the gas supply line 102 connects the gas supply unit 101 to the storage liquid supply line 82. The gas supply valve 103 is an on / off valve provided on the gas supply line 102.

[0075] The connection point 102P between the gas supply line 102 and the storage liquid supply line 82 is located downstream of the storage liquid supply valve 84 in the storage liquid supply line 82. In the example shown in Figure 2, the connection point 102P is located between the storage liquid supply valve 84 and the branching point 82P1 in the storage liquid supply line 82.

[0076] [Gas discharge system] The gas discharge system 110 is configured to discharge gas from the saline treatment chamber, the concentrated liquid treatment chamber, and the electrode liquid treatment chamber. The gas discharge system 110 according to this embodiment may include a gas outlet (not shown), a gas discharge line 111, and a gas discharge valve 112. The gas discharge line 111 connects the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6 to the gas discharge outlet. In this embodiment, the gas discharge line 111 connects the storage liquid recovery line 91 to the gas discharge outlet. The gas discharge valve 112 is an on / off valve provided on the gas discharge line 111.

[0077] The connection point 102P between the gas discharge line 111 and the storage liquid recovery line 91 is located upstream of the storage liquid recovery valve 92 in the storage liquid recovery line 91. In the example shown in Figure 2, the connection point 102P is located between the confluence point 91P2 and the storage liquid recovery valve 92 in the storage liquid recovery line 91.

[0078] [Control device] The control device 120 is configured to control the processing liquid supply system 20, the processing liquid recovery system 40, the electrode liquid supply system 60, the electrode liquid recovery system 70, the storage liquid supply system 80, the storage liquid recovery system 90, the gas supply system 100, and the gas discharge system 110. In this embodiment, the control device 120 controls the saline pump 24, the saline supply valve 25, the saline recovery valve 43, the concentrate pump 34, the concentrate supply valve 35, the concentrate recovery valve 53, the electrode liquid pump 63, the electrode liquid supply valve 64, the electrode liquid recovery valve 72, the storage liquid pump 83, the storage liquid supply valve 84, the supply switching valve 85, the storage liquid recovery valve 92, the recovery switching valve 93, the gas supply valve 103, and the gas discharge valve 112.

[0079] More specifically, the control device 120 may control each system such that, after stopping the supply of the absorbent liquid to be treated to the absorbent liquid purification chamber 14 and the amine collection chamber 15, it supplies gas to the absorbent liquid purification chamber 14 and the amine collection chamber 15, and then, after stopping the supply of gas to the absorbent liquid purification chamber 14 and the amine collection chamber 15, it supplies the storage liquid to the absorbent liquid purification chamber 14 and the amine collection chamber 15. The control device 120 may also control each system such that, after stopping the supply of the storage liquid to the absorbent liquid purification chamber 14 and the amine collection chamber 15, it supplies gas to the absorbent liquid purification chamber 14 and the amine collection chamber 15, and then, after stopping the supply of gas to the absorbent liquid purification chamber 14 and the amine collection chamber 15, it supplies the absorbent liquid to be treated to the absorbent liquid purification chamber 14 and the amine collection chamber 15.

[0080] The control device 120 may control each system such that, after stopping the supply of concentrated liquid to the acid collection chamber 16 and the amine removal chamber 17, it supplies gas to the acid collection chamber 16 and the amine removal chamber 17, and then, after stopping the supply of gas to the acid collection chamber 16 and the amine removal chamber 17, it supplies storage liquid to the acid collection chamber 16 and the amine removal chamber 17. The control device 120 may control each system such that, after stopping the supply of storage liquid to the acid collection chamber 16 and the amine removal chamber 17, it supplies gas to the acid collection chamber 16 and the amine removal chamber 17, and then, after stopping the supply of gas to the acid collection chamber 16 and the amine removal chamber 17, it supplies concentrated liquid to the acid collection chamber 16 and the amine removal chamber 17.

[0081] The control device 120 may control each system such that, after stopping the supply of electrode liquid to the anode chamber 5 and cathode chamber 6, it supplies gas to the anode chamber 5 and cathode chamber 6, and then, after stopping the supply of gas to the anode chamber 5 and cathode chamber 6, it supplies storage liquid to the anode chamber 5 and cathode chamber 6. The control device 120 may control each system such that, after stopping the supply of storage liquid to the anode chamber 5 and cathode chamber 6, it supplies gas to the anode chamber 5 and cathode chamber 6, and then, after stopping the supply of gas to the anode chamber 5 and cathode chamber 6, it supplies electrode liquid to the anode chamber 5 and cathode chamber 6.

[0082] Next, the operation method of the electrodialysis system according to this embodiment, which has the above configuration, will be explained with reference to Figures 2 to 4. In the following, as an example, the operation method of an electrodialysis system equipped with an electrodialysis tank 10 for electrodialysis of the absorption solution used in the carbon dioxide gas recovery device 200 shown in Figure 1 will be explained, but this embodiment is not limited to this. Each of the following steps is performed under the control of each system by the control device 120 described above.

[0083] First, as shown in Figure 3, an electrodialysis process is performed, and the absorbent solution to be treated is subjected to electrodialysis (Step S1).

[0084] In the electrodialysis process, as shown in Figure 2, the saline supply valve 25 and the saline recovery valve 43 open, and the saline pump 24 is driven. As a result, the absorbent liquid to be treated is supplied from the saline tank 22 through the saline supply line 23 to the absorbent liquid purification chamber 14 and the amine collection chamber 15 of the electrodialysis cell 10. The absorbent liquid to be treated supplied to the absorbent liquid purification chamber 14 and the amine collection chamber 15 is recovered to the saline tank 22 through the saline recovery line 42. In this way, the absorbent liquid to be treated circulates between the saline tank 22 and the saline treatment chambers 14 and 15.

[0085] Similarly, in the electrodialysis process, as shown in Figure 2, the concentrate supply valve 35 and the concentrate recovery valve 53 open, and the concentrate pump 34 is driven. As a result, concentrate is supplied from the concentrate tank 32 through the concentrate supply line 33 to the acid collection chamber 16 and the amine removal chamber 17 of the electrodialysis cell 10. The concentrate supplied to the acid collection chamber 16 and the amine removal chamber 17 is recovered back into the concentrate tank 32 through the concentrate recovery line 52. In this way, the concentrate circulates between the concentrate tank 32 and the concentrate processing chambers 16 and 17.

[0086] Similarly, in the electrodialysis process, as shown in Figure 2, the electrode solution supply valve 64 and the electrode solution recovery valve 72 open, and the electrode solution pump 63 is driven. As a result, electrode solution is supplied from the electrode solution tank 61 to the anode chamber 5 and cathode chamber 6 through the electrode solution supply line 62. The electrode solution supplied to the anode chamber 5 and cathode chamber 6 is recovered back into the electrode solution tank 61 through the electrode solution recovery line 71. In this way, the electrode solution circulates between the electrode solution tank 61 and the electrode solution chambers 5 and 6.

[0087] When a potential difference is applied between anode 3 and cathode 4, electrodialysis of the absorbent solution to be treated is performed as described above, and the acidic component (X) of the thermally stable amine salt is extracted from the absorbent solution to be treated. - ) is removed. As the saline solution and concentrate are circulated, the acidic component of the thermally stable amine salt (X) is removed from the absorbent liquid being treated. - ) can be removed efficiently.

[0088] After the electrodialysis process, a process to stop the supply of the processing solution is performed (step S2), as shown in Figure 3. In the process to stop the supply of the processing solution, the supply of the absorbent solution to be processed to the absorption solution purification chamber 14 and the amine collection chamber 15 is stopped, and the supply of the concentrated solution to the acid collection chamber 16 and the amine removal chamber 17 is stopped. In this case, as shown in Figure 4, the saline supply valve 25 and the saline recovery valve 43 are closed and the saline pump 24 is stopped. The concentrated solution supply valve 35 and the concentrated solution recovery valve 53 are closed and the concentrated solution pump 34 is stopped. In addition, the supply of electrode solution to the anode chamber 5 and the cathode chamber 6 is stopped. In this case, the electrode solution supply valve 64 and the electrode solution recovery valve 72 are closed and the electrode solution pump 63 is stopped.

[0089] After the processing liquid supply stop step, the first gas supply step is performed as shown in Figure 3 (step S3). In the first gas supply step, gas is supplied to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6. In this case, as shown in Figure 4, the gas supply valve 103 and the gas discharge valve 112 are opened. As a result, gas is supplied from the gas supply unit 101 to the storage liquid supply line 82 through the gas supply line 102. In addition, each supply switching valve 85 and each recovery switching valve 93 are opened.

[0090] The gas is supplied from the storage liquid supply line 82 through the saline supply line 23 to the absorbent liquid purification chamber 14 and the amine collection chamber 15. The gas supplied to the absorbent liquid purification chamber 14 and the amine collection chamber 15 is supplied to the gas discharge line 111 through the saline recovery line 42 and the storage liquid recovery line 91, and discharged to the outside from the gas discharge port. In this way, the gas is continuously supplied to and passes through the absorbent liquid purification chamber 14 and the amine collection chamber 15, and discharges the absorbent liquid remaining in the absorbent liquid purification chamber 14 and the amine collection chamber 15. At this time, the absorbent liquid is also discharged from a portion of the saline supply line 23 and a portion of the saline recovery line 42.

[0091] Similarly, gas is supplied from the storage liquid supply line 82 through the concentrated liquid supply line 33 to the acid collection chamber 16 and the amine removal chamber 17. The gas supplied to the acid collection chamber 16 and the amine removal chamber 17 is supplied to the gas discharge line 111 through the concentrated liquid recovery line 52 and the storage liquid recovery line 91, and discharged to the outside from the gas discharge port. In this way, the gas is continuously supplied to and passes through the acid collection chamber 16 and the amine removal chamber 17, and the concentrated liquid remaining in the acid collection chamber 16 and the amine removal chamber 17 is discharged. At this time, concentrated liquid is also discharged from a portion of the concentrated liquid supply line 33 and a portion of the concentrated liquid recovery line 52.

[0092] Similarly, gas is supplied from the storage liquid supply line 82 through the electrode liquid supply line 62 to the anode chamber 5 and cathode chamber 6. The gas supplied to the anode chamber 5 and cathode chamber 6 is supplied to the gas discharge line 111 through the electrode liquid recovery line 71 and the storage liquid recovery line 91, and discharged to the outside from the gas discharge port. In this way, the gas is continuously supplied to and passes through the anode chamber 5 and cathode chamber 6, discharging any electrode liquid remaining in the anode chamber 5 and cathode chamber 6. At this time, electrode liquid is also discharged from a portion of the electrode liquid supply line 62 and a portion of the electrode liquid recovery line 71.

[0093] After the first gas supply step, the first gas supply stop step is performed as shown in Figure 3 (step S4). In the first gas supply stop step, the supply of gas to the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, amine removal chamber 17, anode chamber 5, and cathode chamber 6 is stopped. In this case, the gas supply valve 103 and the gas discharge valve 112 are closed as shown in Figure 5.

[0094] After the first gas supply cessation step, a storage step is performed as shown in Figure 3 (step S5). In the storage step, storage liquid is supplied to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17. In this case, as shown in Figure 5, the storage liquid supply valve 84 and the storage liquid recovery valve 92 are opened and the storage liquid pump 83 is driven. As a result, storage liquid is supplied from the storage liquid tank 81 to the storage liquid supply line 82. In addition, each supply switching valve 85 and each recovery switching valve 93 are opened.

[0095] The storage liquid is supplied from the storage liquid supply line 82 through the saline supply line 23 to the absorption liquid purification chamber 14 and the amine collection chamber 15. The storage liquid supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15 is supplied to the storage liquid recovery line 91 through the saline recovery line 42, and recovered from the storage liquid recovery line 91 to the storage liquid tank 81. In this way, the storage liquid is continuously supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15, and the absorption liquid purification chamber 14 and the amine collection chamber 15 are filled with the storage liquid.

[0096] Similarly, the storage liquid is supplied from the storage liquid supply line 82 through the concentrate supply line 33 to the acid collection chamber 16 and the amine removal chamber 17. The storage liquid supplied to the acid collection chamber 16 and the amine removal chamber 17 is supplied to the storage liquid recovery line 91 through the concentrate recovery line 52, and recovered from the storage liquid recovery line 91 to the storage liquid tank 81. In this way, the storage liquid is continuously supplied to the acid collection chamber 16 and the amine removal chamber 17, and the acid collection chamber 16 and the amine removal chamber 17 are filled with the storage liquid.

[0097] In this way, the ion exchange membranes 11-13 can be immersed in the storage solution, preventing them from drying out. Furthermore, the ion exchange membranes 11-13 can be washed. During this time, the storage solution continuously passes through the acid collection chamber 16 and the amine removal chamber 17, thereby enhancing the washing effect on the ion exchange membranes 11-13.

[0098] In the storage process, as described above, the storage solution may be continuously supplied to the absorption solution purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17. However, after immersing the ion exchange membranes 11-13 in the storage solution, the supply of the storage solution to the absorption solution purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17 may be stopped.

[0099] In the storage process according to this embodiment, the storage liquid is supplied from the storage liquid supply line 82 through the electrode liquid supply line 62 to the anode chamber 5 and cathode chamber 6. The storage liquid supplied to the anode chamber 5 and cathode chamber 6 is supplied to the storage liquid recovery line 91 through the electrode liquid recovery line 71, and recovered from the storage liquid recovery line 91 to the storage liquid tank 81. In this way, the storage liquid is continuously supplied to the anode chamber 5 and cathode chamber 6, and the anode chamber 5 and cathode chamber 6 are filled with the storage liquid. This allows the anode chamber 5 and cathode chamber 6 to be immersed in the storage liquid and cleaned. During this time, the storage liquid continuously passes through the anode chamber 5 and cathode chamber 6, thereby enhancing the cleaning effect of the anode chamber 5 and cathode chamber 6.

[0100] After the storage process, as shown in Figure 3, a storage liquid supply stoppage process is performed (step S6). In the storage liquid supply stoppage process, the supply of storage liquid to the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, amine removal chamber 17, anode chamber 5, and cathode chamber 6 is stopped. In this case, as shown in Figure 4, the storage liquid supply valve 84 and the storage liquid recovery valve 92 are closed and the drive of the storage liquid pump 83 is stopped.

[0101] After the storage liquid supply cessation process, a second gas supply process is performed as shown in Figure 3 (step S7). In the second gas supply process, gas is supplied to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17. The second gas supply process can be carried out in the same manner as the first gas supply process described above. By performing the second gas supply process, the gas discharges the storage liquid remaining in the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, the amine removal chamber 17, the anode chamber 5, and the cathode chamber 6. At this time, some storage liquid is also discharged from a portion of the saline supply line 23, a portion of the saline recovery line 42, a portion of the concentrated liquid supply line 33, and a portion of the concentrated liquid recovery line 52. Similarly, the gas discharges the storage liquid remaining in the anode chamber 5 and the cathode chamber 6. At this time, some storage liquid is also discharged from a portion of the electrode liquid supply line 62 and a portion of the electrode liquid recovery line 71.

[0102] After the second gas supply step, a second gas supply stop step is performed as shown in Figure 3 (step S8). In the second gas supply stop step, the supply of gas to the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, amine removal chamber 17, anode chamber 5, and cathode chamber 6 is stopped. The second gas supply stop step can be performed in the same manner as the first gas supply stop step described above.

[0103] After the second gas supply cessation process, the electrodialysis process is performed in the same manner as described above, as shown in Figure 3 (step S9).

[0104] As described above, according to this embodiment, the storage liquid is supplied to the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, and amine removal chamber 17 of the electrodialysis cell 10 by the storage liquid supply system 80, and gas is supplied by the gas supply system 100. This allows the ion exchange membranes 11-13 that partition the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, and amine removal chamber 17 to be immersed in the storage liquid, preventing the ion exchange membranes 11-13 from drying out. Furthermore, since gas can be supplied to the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, and amine removal chamber 17, any remaining liquid in the absorption liquid purification chamber 14, amine collection chamber 15, acid collection chamber 16, and amine removal chamber 17 can be discharged. Therefore, when replacing the absorption liquid with the storage liquid, mixing of the absorption liquid and the storage liquid can be prevented. Similarly, when replacing the concentrated liquid with the storage liquid, mixing of the concentrated liquid and the storage liquid can be prevented. As a result, it is possible to prevent the storage solution used to prevent the ion exchange membranes 11-13 from drying out from mixing with the absorbent liquid to be treated and the concentrated liquid.

[0105] Furthermore, according to this embodiment, after stopping the supply of the absorbent liquid to be treated to the absorbent liquid purification chamber 14 and the amine collection chamber 15, gas is supplied to the absorbent liquid purification chamber 14 and the amine collection chamber 15. Subsequently, after stopping the supply of gas to the absorbent liquid purification chamber 14 and the amine collection chamber 15, storage liquid is supplied to the absorbent liquid purification chamber 14 and the amine collection chamber 15. This allows the gas to discharge any absorbent liquid remaining in the absorbent liquid purification chamber 14 and the amine collection chamber 15. Therefore, mixing of the absorbent liquid to be treated with the storage liquid can be prevented.

[0106] Furthermore, according to this embodiment, after stopping the supply of storage liquid to the absorption liquid purification chamber 14 and the amine collection chamber 15, gas is supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15. Subsequently, after stopping the supply of gas to the absorption liquid purification chamber 14 and the amine collection chamber 15, the absorption liquid to be treated is supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15. This allows the gas to discharge any remaining storage liquid in the absorption liquid purification chamber 14 and the amine collection chamber 15. Therefore, mixing of the storage liquid with the absorption liquid to be treated can be prevented.

[0107] Furthermore, according to this embodiment, after stopping the supply of concentrated liquid to the acid collection chamber 16 and the amine removal chamber 17, gas is supplied to the acid collection chamber 16 and the amine removal chamber 17. Subsequently, after stopping the supply of gas to the acid collection chamber 16 and the amine removal chamber 17, storage liquid is supplied to the acid collection chamber 16 and the amine removal chamber 17. This allows the gas to discharge any concentrated liquid remaining in the acid collection chamber 16 and the amine removal chamber 17. Therefore, mixing of the concentrated liquid with the storage liquid can be prevented.

[0108] Furthermore, according to this embodiment, after stopping the supply of storage liquid to the acid collection chamber 16 and the amine removal chamber 17, gas is supplied to the acid collection chamber 16 and the amine removal chamber 17. Subsequently, after stopping the supply of gas to the acid collection chamber 16 and the amine removal chamber 17, concentrated liquid is supplied to the acid collection chamber 16 and the amine removal chamber 17. This allows the gas to discharge any remaining storage liquid in the acid collection chamber 16 and the amine removal chamber 17. Therefore, mixing of the storage liquid with the concentrated liquid can be prevented.

[0109] Furthermore, according to this embodiment, the storage liquid supply system 80 includes a storage liquid tank 81 for storing the storage liquid, and the storage liquid is recovered from the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17 into the storage liquid tank 81. This allows the recovered storage liquid to be reused. In addition, the storage liquid can be continuously supplied to the absorption liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17, thereby enhancing the cleaning effect of the ion exchange membranes 11-13.

[0110] Furthermore, according to this embodiment, gas is discharged from the absorbent liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17 by the gas discharge system 110. This allows for a continuous supply of gas to the absorbent liquid purification chamber 14, the amine collection chamber 15, the acid collection chamber 16, and the amine removal chamber 17. As a result, the absorbent liquid remaining in the absorbent liquid purification chamber 14 and the amine collection chamber 15 can be effectively discharged, as can the concentrated liquid remaining in the acid collection chamber 16 and the amine removal chamber 17.

[0111] Furthermore, according to this embodiment, the anode chamber 5 and the cathode chamber 6 are supplied with storage liquid by the storage liquid supply system 80, and gas is supplied by the gas supply system 100. This allows the anode chamber 5 and the cathode chamber 6 to be cleaned with the storage liquid.

[0112] Furthermore, according to this embodiment, after stopping the supply of electrode solution to the anode chamber 5 and cathode chamber 6, gas is supplied to the anode chamber 5 and cathode chamber 6. Subsequently, after stopping the supply of gas to the anode chamber 5 and cathode chamber 6, storage solution is supplied to the anode chamber 5 and cathode chamber 6. This allows the gas to discharge any electrode solution remaining in the anode chamber 5 and cathode chamber 6. Therefore, mixing of electrode solution with the storage solution can be prevented.

[0113] Furthermore, according to this embodiment, after stopping the supply of storage liquid to the anode chamber 5 and cathode chamber 6, gas is supplied to the anode chamber 5 and cathode chamber 6. Subsequently, after stopping the supply of gas to the anode chamber 5 and cathode chamber 6, electrode liquid is supplied to the anode chamber 5 and cathode chamber 6. This allows the gas to discharge any remaining storage liquid in the anode chamber 5 and cathode chamber 6. Therefore, mixing of the storage liquid with the electrode liquid can be prevented.

[0114] In the above-described embodiment, an example was given in which the electrodialysis system 1 includes a gas discharge system 110. However, this embodiment is not limited to this. For example, the electrodialysis system 1 does not have to include a gas discharge system 110. In this case, in the first gas supply step, the saline recovery valve 43 may be opened and the gas supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15 may be recovered in the saline tank 22. The saline tank 22 may be configured to prevent an increase in internal pressure so that the gas can be recovered. Similarly, in the first gas supply step, the concentrate recovery valve 53 may be opened and the gas supplied to the acid collection chamber 16 and the amine removal chamber 17 may be recovered in the concentrate tank 32. The concentrate tank 32 may be configured to prevent an increase in internal pressure so that the gas can be recovered. Similarly, in the first gas supply step, the electrode solution recovery valve 72 may be opened and the gas supplied to the anode chamber 5 and the cathode chamber 6 may be recovered in the electrode solution tank 61. The electrode liquid tank 61 may be configured to prevent an increase in internal pressure so that gas can be recovered. In the second gas supply process, the storage liquid recovery valve 92 may be opened to recover the gas into the storage liquid tank 81. The storage liquid tank 81 may be configured to prevent an increase in internal pressure so that gas can be recovered.

[0115] (Second Embodiment) Next, using Figure 6, we will describe the electrodialysis system and the operation method of the electrodialysis system in the second embodiment.

[0116] In the second embodiment shown in Figure 6, the gas supply system mainly differs in that it includes a first gas supply system that supplies gas to the saline treatment chamber and a second gas supply system that supplies gas to the concentrated liquid treatment chamber. Other configurations are substantially the same as those of the first embodiment shown in Figures 1 to 5. In Figure 6, the same reference numerals are used for parts identical to those of the first embodiment shown in Figure 5, and detailed descriptions are omitted.

[0117] As shown in Figure 6, the gas supply system 100 according to this embodiment includes a first gas supply system 100A, a second gas supply system 100B, and a third gas supply system 100C.

[0118] The first gas supply system 100A is configured to supply gas to the absorption liquid purification chamber 14 and the amine collection chamber 15, which serve as saline treatment chambers. The first gas supply system 100A may include a first gas supply unit 101A, a first gas supply line 102A, and a first gas supply valve 103A. The first gas supply unit 101A is configured to supply gas to the first gas supply line 102A and may be configured in the same manner as the gas supply unit 101 described above. The first gas supply line 102A connects the first gas supply unit 101A to the absorption liquid purification chamber 14 and the amine collection chamber 15. In this embodiment, the first gas supply line 102A connects the first gas supply unit 101A to the storage liquid supply line 82. The first gas supply valve 103A is an on / off valve provided on the first gas supply line 102A.

[0119] The connection point 102AP between the first gas supply line 102A and the storage liquid supply line 82 is located downstream of the branching point 82P1 in the storage liquid supply line 82. The connection point 102AP is located in the portion of the storage liquid supply line 82 that is on the side of the saline supply line 23.

[0120] The second gas supply system 100B is configured to supply gas to the acid collection chamber 16 and the amine removal chamber 17, which serve as concentrated liquid processing chambers. The second gas supply system 100B may include a second gas supply unit 101B, a second gas supply line 102B, and a second gas supply valve 103B. The second gas supply unit 101B is configured to supply gas to the second gas supply line 102B and may be configured in the same manner as the gas supply unit 101 described above. The second gas supply line 102B connects the second gas supply unit 101B to the acid collection chamber 16 and the amine removal chamber 17. In this embodiment, the second gas supply line 102B connects the second gas supply unit 101B to the storage liquid supply line 82. The second gas supply valve 103B is an on / off valve provided on the second gas supply line 102B.

[0121] The connection point 102BP between the second gas supply line 102B and the storage liquid supply line 82 is located downstream of the branching point 82P2 in the storage liquid supply line 82. The connection point 102BP is located in the portion of the storage liquid supply line 82 that is on the side of the concentrated liquid supply line 33.

[0122] The third gas supply system 100C is configured to supply gas to the anode chamber 5 and the cathode chamber 6, which serve as electrode liquid chambers. The third gas supply system 100C may include a third gas supply unit 101C, a third gas supply line 102C, and a third gas supply valve 103C. The third gas supply unit 101C is configured to supply gas to the third gas supply line 102C and may be configured in the same manner as the gas supply unit 101 described above. The third gas supply line 102C connects the third gas supply unit 101C to the anode chamber 5 and the cathode chamber 6. In this embodiment, the third gas supply line 102C connects the third gas supply unit 101C to the storage liquid supply line 82. The third gas supply valve 103C is an on / off valve provided on the third gas supply line 102C.

[0123] The connection point 102CP between the third gas supply line 102C and the storage liquid supply line 82 is located downstream of the branching point 82P2 in the storage liquid supply line 82. The connection point 102CP is located in the portion of the storage liquid supply line 82 that is on the side of the electrode liquid supply line 62.

[0124] As described above, according to this embodiment, the gas supply system 100 includes a first gas supply system 100A that supplies gas to the absorption liquid purification chamber 14 and the amine collection chamber 15, and a second gas supply system 100B that supplies gas to the acid collection chamber 16 and the amine removal chamber 17. This allows for separate control of the gas supply to the absorption liquid purification chamber 14 and the amine collection chamber 15, and the gas supply to the acid collection chamber 16 and the amine removal chamber 17. Therefore, it is possible to prevent the supply of gas to unnecessary processing chambers.

[0125] In this embodiment, the supply switching valve 85 and the recovery switching valve 93 may be opened and closed in accordance with the gas supply valves 103A to 103C. For example, when the first gas supply valve 103A is opened to supply gas to the absorption liquid purification chamber 14 and the amine collection chamber 15, the supply switching valve 85 located on the side of the saline supply line 23 of the storage liquid supply line 82 may be opened, and the other two supply switching valves 85 may be closed. Alternatively, the recovery switching valve 93 located on the side of the saline recovery line 42 of the storage liquid recovery line 91 may be opened, and the other two recovery switching valves 93 may be closed.

[0126] (Third embodiment) Next, using Figure 7, we will describe the electrodialysis system and the operation method of the electrodialysis system in the third embodiment.

[0127] In the third embodiment shown in Figure 7, the main difference is that the storage liquid supply system includes a first storage liquid supply system that supplies storage liquid to the saline treatment chamber and a second storage liquid supply system that supplies storage liquid to the concentrated liquid treatment chamber. Other configurations are substantially the same as those of the first embodiment shown in Figures 1 to 5. In Figure 7, the same reference numerals are used for parts identical to those of the first embodiment shown in Figure 5, and detailed descriptions are omitted.

[0128] [Storage liquid supply system] As shown in Figure 7, the storage liquid supply system 80 according to this embodiment includes a first storage liquid supply system 80A, a second storage liquid supply system 80B, and a third storage liquid supply system 80C.

[0129] The first storage liquid supply system 80A is configured to supply storage liquid to the absorption liquid purification chamber 14 and the amine collection chamber 15, which serve as saline treatment chambers. The first storage liquid supply system 80A may include a first storage liquid tank 81A, a first storage liquid supply line 82A, a first storage liquid pump 83A, and a first storage liquid supply valve 84A. The first storage liquid tank 81A is configured to store storage liquid. The first storage liquid supply line 82A connects the first storage liquid tank 81A to the absorption liquid purification chamber 14 and the amine collection chamber 15. The first storage liquid supply line 82A connects the first storage liquid tank 81A to the saline supply line 23. The first storage liquid pump 83A is provided on the first storage liquid supply line 82A. By driving the first storage liquid pump 83A, the storage liquid stored in the first storage liquid tank 81A is supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15. The first storage fluid supply valve 84A is an on / off valve installed in the first storage fluid supply line 82A, and is located downstream of the first storage fluid pump 83A in the first storage fluid supply line 82A.

[0130] The connection point 82AP between the first storage fluid supply line 82A and the saline supply line 23 is located downstream of the saline supply valve 25 in the saline supply line 23. The connection point 82AP may also be located between the saline supply valve 25 and the branching point 23P in the saline supply line 23.

[0131] The second storage liquid supply system 80B is configured to supply storage liquid to the acid collection chamber 16 and the amine removal chamber 17, which serve as concentrated liquid processing chambers. The second storage liquid supply system 80B may include a second storage liquid tank 81B, a second storage liquid supply line 82B, a second storage liquid pump 83B, and a second storage liquid supply valve 84B. The second storage liquid tank 81B is configured to store storage liquid. The second storage liquid supply line 82B connects the second storage liquid tank 81B to the acid collection chamber 16 and the amine removal chamber 17. The second storage liquid supply line 82B connects the second storage liquid tank 81B to the concentrated liquid supply line 33. The second storage liquid pump 83B is provided on the second storage liquid supply line 82B. By driving the second storage liquid pump 83B, the storage liquid stored in the second storage liquid tank 81B is supplied to the acid collection chamber 16 and the amine removal chamber 17. The second storage fluid supply valve 84B is an on / off valve installed in the second storage fluid supply line 82B, and is located downstream of the second storage fluid pump 83B in the second storage fluid supply line 82B.

[0132] The connection point 82BP between the second storage liquid supply line 82B and the concentrated liquid supply line 33 is located downstream of the concentrated liquid supply valve 35 in the concentrated liquid supply line 33. The connection point 82BP may also be located between the concentrated liquid supply valve 35 and the branching point 33P in the concentrated liquid supply line 33.

[0133] The third storage liquid supply system 80C is configured to supply storage liquid to the anode chamber 5 and cathode chamber 6, which serve as electrode liquid chambers. The third storage liquid supply system 80C may include a third storage liquid tank 81C, a third storage liquid supply line 82C, a third storage liquid pump 83C, and a third storage liquid supply valve 84C. The third storage liquid tank 81C is configured to store storage liquid. The third storage liquid supply line 82C connects the third storage liquid tank 81C to the anode chamber 5 and cathode chamber 6. The third storage liquid supply line 82C connects the third storage liquid tank 81C to the electrode liquid supply line 62. The third storage liquid pump 83C is provided on the third storage liquid supply line 82C. By driving the third storage liquid pump 83C, the storage liquid stored in the third storage liquid tank 81C is supplied to the anode chamber 5 and cathode chamber 6. The third storage fluid supply valve 84C is an on / off valve installed in the third storage fluid supply line 82C, and is located downstream of the third storage fluid pump 83C in the third storage fluid supply line 82C.

[0134] The connection point 82CP between the third storage fluid supply line 82C and the electrode fluid supply line 62 is located downstream of the electrode fluid supply valve 64 in the electrode fluid supply line 62. The connection point 82CP may also be located between the electrode fluid supply valve 64 and the branching point 62P in the electrode fluid supply line 62.

[0135] [Storage liquid recovery system] As shown in Figure 7, the storage liquid recovery system 90 according to this embodiment includes a first storage liquid recovery system 90A, a second storage liquid recovery system 90B, and a third storage liquid recovery system 90C.

[0136] The first storage liquid recovery system 90A is configured to recover the storage liquid from the absorption liquid purification chamber 14 and the amine collection chamber 15 and supply it to the first storage liquid supply system 80A. The first storage liquid recovery system 90A may also recover the storage liquid into the first storage liquid tank 81A described above. The first storage liquid recovery system 90A according to this embodiment may include a first storage liquid recovery line 91A and a first storage liquid recovery valve 92A. The first storage liquid recovery line 91A connects the absorption liquid purification chamber 14 and the amine collection chamber 15 to the first storage liquid tank 81A. The first storage liquid recovery line 91A connects the saline recovery line 42 described above to the first storage liquid tank 81A. By driving the first storage liquid pump 83A described above, the storage liquid is recovered from the absorption liquid purification chamber 14 and the amine collection chamber 15 into the first storage liquid tank 81A. The first storage liquid recovery valve 92A is an on / off valve provided in the first storage liquid recovery line 91A.

[0137] The connection point 91AP between the first storage liquid recovery line 91A and the saline recovery line 42 is located upstream of the saline recovery valve 43 in the saline recovery line 42. The connection point 91AP may also be located upstream of the confluence point 42P in the saline recovery line 42. In this case, the connection point 91AP may be located in the part of the saline recovery line 42 on the side of the absorption liquid purification chamber 14, or on the part on the side of the amine collection chamber 15. In the example shown in Figure 7, the connection point 91AP is located in the part on the side of the amine collection chamber 15.

[0138] The second storage liquid recovery system 90B is configured to recover the storage liquid from the acid collection chamber 16 and the amine removal chamber 17 and supply it to the second storage liquid supply system 80B. The second storage liquid recovery system 90B may also recover the storage liquid to the second storage liquid tank 81B described above. The second storage liquid recovery system 90B according to this embodiment may include a second storage liquid recovery line 91B and a second storage liquid recovery valve 92B. The second storage liquid recovery line 91B connects the acid collection chamber 16 and the amine removal chamber 17 to the second storage liquid tank 81B. The second storage liquid recovery line 91B connects the concentrated liquid recovery line 52 described above to the second storage liquid tank 81B. By driving the second storage liquid pump 83B described above, the storage liquid is recovered from the acid collection chamber 16 and the amine removal chamber 17 to the second storage liquid tank 81B. The second storage liquid recovery valve 92B is an on / off valve provided in the second storage liquid recovery line 91B.

[0139] The connection point 91BP between the second storage liquid recovery line 91B and the concentrated liquid recovery line 52 is located upstream of the concentrated liquid recovery valve 53 in the concentrated liquid recovery line 52. The connection point 91BP may also be located upstream of the confluence point 52P in the concentrated liquid recovery line 52. In this case, the connection point 91BP may be located in the part of the concentrated liquid recovery line 52 on the side of the acid collection chamber 16, or on the part on the side of the amine removal chamber 17. In the example shown in Figure 7, the connection point 91BP is located in the part on the side of the amine removal chamber 17.

[0140] The third storage liquid recovery system 90C is configured to recover the storage liquid from the anode chamber 5 and the cathode chamber 6 and supply it to the third storage liquid supply system 80C. The third storage liquid recovery system 90C may also recover the storage liquid into the third storage liquid tank 81C described above. The third storage liquid recovery system 90C according to this embodiment may include a third storage liquid recovery line 91C and a third storage liquid recovery valve 92C. The third storage liquid recovery line 91C connects the anode chamber 5 and the cathode chamber 6 to the third storage liquid tank 81C. The third storage liquid recovery line 91C connects the electrode liquid recovery line 71 described above to the third storage liquid tank 81C. By driving the third storage liquid pump 83C described above, the storage liquid is recovered from the anode chamber 5 and the cathode chamber 6 into the third storage liquid tank 81C. The third storage liquid recovery valve 92C is an on / off valve provided in the third storage liquid recovery line 91C.

[0141] The connection point 91CP between the third storage fluid recovery line 91C and the electrode fluid recovery line 71 is located upstream of the electrode fluid recovery valve 72 in the electrode fluid recovery line 71. The connection point 91CP may also be located downstream of the confluence point 71P in the electrode fluid recovery line 71. In this case, the third storage fluid recovery line 91C may be located between the confluence point 71P and the electrode fluid recovery valve 72 in the electrode fluid recovery line 71.

[0142] [Gas supply system]

[0143] As shown in Figure 7, the gas supply system 100 according to this embodiment includes a first gas supply system 100A, a second gas supply system 100B, and a third gas supply system 100C, similar to the gas supply system 100 shown in Figure 6.

[0144] In this embodiment, the first gas supply line 102A connects the first gas supply unit 101A to the first storage liquid supply line 82A. The connection point 102AP between the first gas supply line 102A and the first storage liquid supply line 82A is located downstream of the first storage liquid supply valve 84A in the first storage liquid supply line 82A.

[0145] In this embodiment, the second gas supply line 102B connects the second gas supply unit 101B to the second storage liquid supply line 82B. The connection point 102BP between the second gas supply line 102B and the second storage liquid supply line 82B is located downstream of the second storage liquid supply valve 84B in the second storage liquid supply line 82B.

[0146] In this embodiment, the third gas supply line 102C connects the third gas supply unit 101C to the third storage liquid supply line 82C. The connection point 102CP between the third gas supply line 102C and the third storage liquid supply line 82C is located downstream of the third storage liquid supply valve 84C in the third storage liquid supply line 82C.

[0147] [Gas discharge system] As shown in Figure 7, the gas discharge system 110 according to this embodiment includes a first gas discharge system 110A, a second gas discharge system 110B, and a third gas discharge system 110C.

[0148] The first gas discharge system 110A is configured to discharge gas from the saline treatment chamber. The first gas discharge system 110A according to this embodiment may include a first gas outlet (not shown), a first gas discharge line 111A, and a first gas discharge valve 112A. The first gas discharge line 111A connects the absorption liquid purification chamber 14 and the amine collection chamber 15 to the first gas outlet. In this embodiment, the first gas discharge line 111A connects the first storage liquid recovery line 91A to the first gas outlet. The first gas discharge valve 112A is an on / off valve provided on the first gas discharge line 111A.

[0149] The connection point 111AP between the first gas discharge line 111A and the first storage liquid recovery line 91A is located upstream of the first storage liquid recovery valve 92A in the first storage liquid recovery line 91A.

[0150] The second gas discharge system 110B is configured to discharge gas from the concentrated liquid processing chamber. The second gas discharge system 110B according to this embodiment may include a second gas outlet (not shown), a second gas discharge line 111B, and a second gas discharge valve 112B. The second gas discharge line 111B connects the acid collection chamber 16 and the amine removal chamber 17 to the second gas outlet. In this embodiment, the second gas discharge line 111B connects the second storage liquid recovery line 91B to the second gas outlet. The second gas discharge valve 112B is an on / off valve provided on the second gas discharge line 111B.

[0151] The connection point 111BP between the second gas discharge line 111B and the second storage liquid recovery line 91B is located upstream of the second storage liquid recovery valve 92B in the second storage liquid recovery line 91B.

[0152] The third gas discharge system 110C is configured to discharge gas from the concentrated liquid processing chamber. The third gas discharge system 110C according to this embodiment may include a third gas outlet (not shown), a third gas discharge line 111C, and a third gas discharge valve 112C. The third gas discharge line 111C connects the acid collection chamber 16 and the amine removal chamber 17 to the third gas outlet. In this embodiment, the third gas discharge line 111C connects the third storage liquid recovery line 91C to the third gas outlet. The third gas discharge valve 112C is an on / off valve provided on the third gas discharge line 111C.

[0153] The connection point 111CP between the third gas discharge line 111C and the third storage liquid recovery line 91C is located upstream of the third storage liquid recovery valve 92C in the third storage liquid recovery line 91C.

[0154] As described above, according to this embodiment, the storage liquid supply system 80 includes a first storage liquid supply system 80A and a second storage liquid supply system 80B, and the storage liquid recovery system 90 includes a first storage liquid recovery system 90A and a second storage liquid recovery system 90B. This prevents the storage liquid supplied to the absorption liquid purification chamber 14 and the amine collection chamber 15 from mixing with the storage liquid supplied to the acid collection chamber 16 and the amine removal chamber 17. For example, if the saline solution is alkaline and the concentrate is acidic, preventing the mixing of the storage liquids is effective.

[0155] Even when the storage liquid supply system 80 further includes a third storage liquid supply system 80C, and the storage liquid recovery system 90 further includes a third storage liquid recovery system 90C, it is possible to prevent the storage liquid supplied to the anode chamber 5 and cathode chamber 6 from mixing with the storage liquid supplied to the absorption liquid purification chamber 14 and amine collection chamber 15, and the storage liquid supplied to the acid collection chamber 16 and amine removal chamber 17. For example, if the electrode solution is acidic, preventing the mixing of each storage liquid is even more effective.

[0156] In this embodiment, the storage liquid supply systems 80A to 80C do not necessarily include the supply switching valve 85 shown in Figure 2, etc. The storage liquid recovery systems 90A to 90C do not necessarily include the recovery switching valve 93 shown in Figure 2, etc.

[0157] According to the embodiments described above, it is possible to prevent the storage solution used to prevent the ion exchange membrane from drying out from mixing with the saline solution and the concentrated solution.

[0158] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Naturally, these embodiments can also be combined in part as appropriate within the scope of the spirit of the invention. [Explanation of Symbols]

[0159] 1: Electrodialysis system, 3: Anode, 4: Cathode, 10: Electrodialysis cell, 11: Anion exchange membrane, 12: Cation exchange membrane, 13: Bipolar membrane, 14: Absorption solution purification chamber, 15: Amine collection chamber, 16: Acid collection chamber, 17: Amine removal chamber, 20: Processing solution supply system, 21: Salt solution supply system, 31: Concentrated solution supply system, 40: Processing solution recovery system, 41: Salt solution recovery system, 51: Concentrated solution recovery system, 80: Storage solution supply system, 80A: First storage solution supply system, 80B: Second storage solution supply system, 90: Storage solution recovery system, 90A: First storage solution recovery system, 90B: Second storage solution recovery system, 100: Gas supply system, 100A: First gas supply system, 100B: Second gas supply system, 110: Gas discharge system, 120: Control device

Claims

1. Anode and, Cathode and, An electrodialysis cell interposed between the anode and the cathode, comprising an ion exchange membrane and a saline treatment chamber and a concentrated liquid treatment chamber partitioned by the ion exchange membrane, wherein the electrodialysis cell supplies saline to the saline treatment chamber and concentrate to the concentrated liquid treatment chamber to perform electrodialysis of the saline, A processing liquid supply system that supplies the saline solution to the saline solution processing chamber and the concentrated liquid to the concentrated liquid processing chamber, A processing liquid recovery system that recovers the saline solution from the saline solution processing chamber and the concentrated liquid from the concentrated liquid processing chamber, A storage liquid supply system that supplies storage liquid to the saline treatment chamber and the concentrated liquid treatment chamber, A storage liquid recovery system for recovering the storage liquid from the saline treatment chamber and the concentrated liquid treatment chamber, A gas supply system that supplies gas to the saline treatment chamber and the concentrated liquid treatment chamber, An electrodialysis system equipped with [specific features / equipment].

2. Further equipped with a control device, The control device controls the processing liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the saline solution to the saline solution processing chamber, then supply the gas to the saline solution processing chamber, and then stop supplying the storage liquid to the saline solution processing chamber. The electrodialysis system according to claim 1.

3. The control device controls the processing liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the storage liquid to the saline treatment chamber, then supply the gas to the saline treatment chamber, and then stop supplying the gas to the saline treatment chamber, and then supply the saline to the saline treatment chamber. The electrodialysis system according to claim 2.

4. Further equipped with a control device, The control device controls the processing liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the concentrated liquid to the concentrated liquid processing chamber, then supply the gas to the concentrated liquid processing chamber, and then stop supplying the storage liquid to the concentrated liquid processing chamber. The electrodialysis system according to claim 1.

5. The control device controls the processing liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the storage liquid to the concentrated liquid processing chamber, then supply the gas to the concentrated liquid processing chamber, and then stop supplying the gas to the concentrated liquid processing chamber, and then supply the concentrated liquid to the concentrated liquid processing chamber. The electrodialysis system according to claim 4.

6. The storage liquid supply system includes a storage liquid tank for storing the storage liquid, The storage liquid recovery system recovers the storage liquid from the saline treatment chamber and the concentrated liquid treatment chamber into the storage liquid tank. The electrodialysis system according to any one of claims 1 to 5.

7. The system further includes a gas discharge system for discharging the gas from the saline treatment chamber and the concentrated liquid treatment chamber. The electrodialysis system according to any one of claims 1 to 5.

8. The gas supply system includes a first gas supply system that supplies the gas to the saline treatment chamber and a second gas supply system that supplies the gas to the concentrated liquid treatment chamber. The electrodialysis system according to any one of claims 1 to 5.

9. The storage liquid supply system includes a first storage liquid supply system that supplies the storage liquid to the saline treatment chamber, and a second storage liquid supply system that supplies the storage liquid to the concentrated liquid treatment chamber. The storage liquid recovery system includes a first storage liquid recovery system that recovers the storage liquid from the saline treatment chamber and supplies it to the first storage liquid supply system, and a second storage liquid recovery system that recovers the storage liquid from the concentrated liquid treatment chamber and supplies it to the second storage liquid supply system. The electrodialysis system according to any one of claims 1 to 5.

10. The anode includes an anode chamber, The cathode includes a cathode chamber, The aforementioned electrodialysis system is An electrode solution supply system for supplying electrode solution to the anode chamber and the cathode chamber, An electrode solution recovery system for recovering the electrode solution from the anode chamber and the cathode chamber, Furthermore, The storage liquid supply system supplies the storage liquid to the anode chamber and the cathode chamber. The storage liquid recovery system recovers the storage liquid from the anode chamber and the cathode chamber. The gas supply system supplies the gas to the anode chamber and the cathode chamber. The electrodialysis system according to claim 1.

11. Equipped with a control device, The control device controls the electrode liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the electrode liquid to the anode chamber and the cathode chamber, then supply the gas to the anode chamber and the cathode chamber, and then stop supplying the gas to the anode chamber and the cathode chamber, and then supply the storage liquid to the anode chamber and the cathode chamber. The electrodialysis system according to claim 10.

12. The control device controls the electrode liquid supply system, the storage liquid supply system, and the gas supply system so as to stop supplying the storage liquid to the anode chamber and the cathode chamber, then supply the gas to the anode chamber and the cathode chamber, and then stop supplying the gas to the anode chamber and the cathode chamber, and then supply the electrode liquid to the anode chamber and the cathode chamber. The electrodialysis system according to claim 11.

13. An electrodialysis system including an electrodialysis cell interposed between an anode and a cathode, comprising an ion exchange membrane, a saline treatment chamber and a concentrated liquid treatment chamber partitioned by the ion exchange membrane, wherein saline is supplied to the saline treatment chamber and concentrated liquid is supplied to the concentrated liquid treatment chamber to perform electrodialysis of the saline, and the electrodialysis of the saline is performed, A step of supplying the saline solution to the saline solution processing chamber and performing electrodialysis of the saline solution, The process of stopping the supply of the saline solution to the saline solution treatment chamber, and then supplying gas to the saline solution treatment chamber, The steps include: stopping the supply of the gas to the saline treatment chamber, and then supplying the storage liquid to the saline treatment chamber; A method for operating an electrodialysis system equipped with the necessary components.

14. The steps include: stopping the supply of the storage liquid to the saline treatment chamber, and then supplying the gas to the saline treatment chamber; The steps include: stopping the supply of the gas to the saline treatment chamber, and then supplying the saline to the saline treatment chamber; A method for operating an electrodialysis system according to claim 13, further comprising the above.

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