Seawater treatment device and seawater treatment method

Abstract

This seawater treatment device comprises: an electrolytic cell which includes an ion exchange membrane, an anode disposed so as to face one surface of the ion exchange membrane, and a cathode disposed so as to face the other surface of the ion exchange membrane, wherein seawater is supplied to an anode chamber accommodating the anode; and a recycle line through which anode discharge water discharged from the anode chamber is supplied to a cathode chamber accommodating the cathode.

Description

Seawater treatment apparatus and seawater treatment method

[0001] The present invention relates to a seawater treatment apparatus and a seawater treatment method.

[0002] Power plants such as thermal power plants and nuclear power plants require large amounts of cooling water to cool the equipment inside the plant, so they are mainly built in locations facing the sea and use seawater as cooling water. When seawater is used as cooling water for the cooling equipment inside a power plant, precipitates containing components such as magnesium and calcium contained in the seawater can form inside the cooling equipment, causing problems such as a decrease in the cooling performance of the cooling equipment. Therefore, to remove the components contained in the seawater, seawater treatment equipment that electrolyzes seawater is used, for example.

[0003] As a seawater treatment device, for example, a magnesium recovery device has been disclosed in which an electrolytic cell having an anode and a cathode is divided into an anode-side tank and a cathode-side tank by a cation exchange membrane. In this magnesium recovery device, seawater is introduced into the cathode-side tank, and electrolysis is performed while restricting the movement of hydroxide ions from the cathode-side tank to the anode-side tank, thereby increasing the hydroxide ion concentration in the cathode-side tank and generating magnesium hydroxide (see, for example, Patent Document 1).

[0004] Japanese Patent No. 7538489

[0005] However, when using a conventional seawater treatment device that electrolyzes seawater, such as the technology described in Patent Document 1, the pH of the seawater used in the treatment device may change to either acidic or alkaline. When the pH of seawater changes, precipitates containing components such as magnesium and calcium may form. Therefore, from the perspective of protecting the marine environment, it is desirable to return the used seawater to the sea with a pH close to that of the seawater before use.

[0006] One aspect of the present invention aims to provide a seawater treatment apparatus that can easily bring the pH of used seawater closer to the pH of seawater before use.

[0007] In view of the above points, the inventors conducted extensive research and found that when seawater is electrolyzed, the pH of the seawater discharged from the anode chamber containing the anode is more acidic, and the pH of the seawater discharged from the cathode chamber containing the cathode is more alkaline, resulting in a more acidic pH for the seawater. Therefore, the inventors found that by first electrolyzing the seawater in the anode chamber to lower the pH, and then electrolyzing the now pH-lowered seawater in the cathode chamber, the pH of the seawater used can be neutralized, bringing it closer to the pH of the seawater before use.

[0008] One aspect of the present invention is a seawater treatment apparatus comprising: an electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber housing the anode; and a recycling line that supplies anode wastewater discharged from the anode chamber to a cathode chamber housing the cathode.

[0009] One aspect of the present invention is a seawater treatment method in an electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber containing the anode, and the anode wastewater discharged from the anode chamber is supplied to a cathode chamber containing the cathode, thereby electrolyzing the seawater.

[0010] One aspect of the present invention makes it possible to easily bring the pH of the used seawater closer to the pH of the seawater before use, and also removes the CO2 dissolved in the seawater before use. ２ It can be easily recovered.

[0011] This figure shows a simplified example of the configuration of a seawater treatment system using the seawater treatment apparatus according to the first embodiment of the present invention. This figure shows a simplified example of the configuration of a seawater treatment system using the seawater treatment apparatus according to the second embodiment of the present invention.

[0012] Embodiments of the present invention will be described in detail below. For ease of understanding, the same reference numerals are used for identical components in each drawing, and redundant explanations are omitted. Also, the scale of each component in the drawings may differ from the actual scale. In this specification, the "~" indicating a numerical range means that the values ​​before and after it are included as the lower and upper limits, respectively, unless otherwise specified. Furthermore, if only the upper limit of a numerical range represented by "~" has a unit specified, it means that the lower limit also has the same unit.

[0013] <First Embodiment> [Seawater Treatment System] A seawater treatment system applying the seawater treatment apparatus according to the first embodiment of the present invention (hereinafter sometimes simply referred to as "this embodiment") will be described. Figure 1 is a simplified diagram showing an example of the configuration of a seawater treatment system applying the seawater treatment apparatus according to this embodiment. As shown in Figure 1, the seawater treatment system 1A comprises a power supply unit 10, a seawater treatment apparatus 20A, and a cooling system 30, and uses the power supplied from the power supply unit 10 to perform electrolysis of seawater W1 in the seawater treatment apparatus 20A. In the seawater treatment system 1A, the seawater used for electrolysis in the seawater treatment apparatus 20A is either returned directly to the ocean or supplied to the cooling system 30 as cooling water and then returned to the ocean. The power supply unit 10 and the cooling system 30 that constitute the seawater treatment system 1A will be described below, followed by a description of the seawater treatment apparatus 20A.

[0014] (Power supply unit) The power supply unit 10 is a power supply device that supplies power in DC to the power supply unit 22 of the seawater treatment device 20A, and has at least one of a first power supply unit 11 and a second power supply unit 12, and may have a power conversion unit 13.

[0015] The first power supply unit 11 generates electricity derived from renewable energy. The first power supply unit 11 can be any power generation device that uses renewable energy, and can consist of, for example, a wind power generator, a solar power generator, a hydroelectric power generator, a geothermal power generator, a wave power generator, a thermoelectric power generator, and a biomass power generator.

[0016] The second power supply unit 12 can consist of power plants such as thermal power plants and nuclear power plants that burn fossil fuels such as natural gas or coal.

[0017] The power supply unit 10 may also be equipped with a storage battery, which stores the electricity generated by at least one of the first power supply unit 11 and the second power supply unit 12, and supplies power from the storage battery to the seawater treatment device 20A as needed. The power supply unit 10 is charged by receiving power from at least one of the first power supply unit 11 and the second power supply unit 12, thereby reducing the CO2 generated from the power supply unit 10. ２ Emissions can be reduced.

[0018] The power conversion unit 13 converts the output voltage of the first power supply unit 11 to a predetermined voltage. For example, a DC / DC converter can be used as the power conversion unit 13. When power is input in AC from the first power supply unit 11, the power conversion unit 13 converts the voltage using a transformer, rectifies it using a bridge diode, smooths it using a smoothing electrolytic capacitor, and supplies power to the electrolytic cell 21 from its output terminal. The power conversion unit 13 may also convert the output voltage of the second power supply unit 12 to a predetermined voltage.

[0019] (Cooling Equipment) The cooling equipment 30 is a cooling system installed in various plants such as petroleum refining plants and power generation plants. The cooling equipment 30 has piping through which cathode wastewater W3 discharged from the cathode chamber 216B of the seawater treatment device 20A passes, and heat exchange is performed between the cathode wastewater W3 and the heat transfer medium generated in the various plants via the piping. As a result, the cathode wastewater W3 is used as cooling water for the heat transfer medium, and the heat transfer medium is cooled.

[0020] The cooling equipment 30 only needs to have piping through which the cathode drainage W3 passes. Examples of cooling equipment 30 include heat exchangers.

[0021] (Seawater treatment device) The seawater treatment device 20A consists of an electrolysis tank (hereinafter simply referred to as "electrolytic tank") 21, a power supply unit 22, a storage unit 23, a recovery unit 25, a measurement unit 26, a control unit 27, a seawater supply line L11, a recycling line L12 and CO ２It has a gas discharge line L13. The seawater treatment device 20A uses electricity supplied from the power supply unit 10 to continuously or intermittently electrolyze the seawater W1 supplied to the electrolytic cell 21.

[0022] ((Electrolytic Cell)) The electrolytic cell 21 has a cation exchange membrane 211, which is an example of an ion exchange membrane, an anode 212 and a cathode 213, a plate member 214 and a gasket 215. In the electrolytic cell 21, the anode chamber 216A is defined by the cation exchange membrane 211, the anode 212 and the gasket 215, and the cathode chamber 216B is defined by the cation exchange membrane 211, the cathode 213 and the gasket 215. In the anode chamber 216A and the cathode chamber 216B, the electrolytic cell 21 uses seawater W1 supplied to the anode chamber 216A and anode wastewater W2B supplied to the cathode chamber 216B as electrolytes to simultaneously perform electrolysis of seawater W1 and anode wastewater W2B.

[0023] In the electrolytic cell 21, a cation exchange membrane 211 is used as an example of an ion exchange membrane, but an anion exchange membrane may also be used.

[0024] The cation exchange membrane 211 is positioned between the anode 212 and the cathode 213, separating the anode 212 and the cathode 213. Depending on the valence of the cation to be passed through, any type of cation exchange membrane can be used as appropriate. As an example of a cation exchange membrane, a monovalent cation such as sodium ion (Na) is used. ＋ A cation exchange membrane can be used that allows only ions to pass through.

[0025] The anode 212 is positioned opposite one of the main surfaces of the cation exchange membrane 211 (the left main surface in Figure 2). The seawater W1 supplied to the anode chamber 216A is seawater stored in the seawater tank 231. In the electrolysis of the seawater W1, the anode 212 electrolyzes the water in the seawater W1 to produce oxygen (O). ２ ) gas, hydrogen ions (H ＋ ) and electronic (e － This causes (the event).

[0026] There is no particular limitation on the material for forming the anode 212, as long as it is a conductive material that can be generally used as an electrode (hereinafter referred to as "conductive material"). Examples of usable conductive materials include copper (Cu), nickel (Ni), iron (Fe), titanium (Ti), tungsten (W), molybdenum (Mo), chromium (Cr), platinum (Pt), aluminum (Al), zinc (Zn), cadmium (Cd), gold (Au), alloys of these materials, and carbon (C). These may be used alone in one type, or two or more types may be used in combination. Among these, it is preferable to use Au, Pt, or Pt from the viewpoints of high chemical stability and no dissolution into the anode drainage W2A even by electrolysis.

[0027] Furthermore, the above material may be dispersed and supported on a conductive base material, or may coat a conductive base material. The base material may be composed of, for example, a material mainly containing metals such as Ti, Zr, Nb, Mo, Hf, Ta and W, oxides thereof, or metals such as stainless steel (SUS). Examples of the form of the base material include plates, woven or non-woven sheets, meshes, porous bodies and foams. As the anode 212, for example, a Ti plate coated with Pt may be used. A Ti plate coated with Pt is preferable from the viewpoints that it is not eroded by electrolysis of the anode drainage W2A, has high electrical conductivity, excellent mechanical strength, and is low in cost.

[0028] The cathode 213 is provided to face the other main surface of the cation exchange membrane 211 (the main surface on the right side in FIG. 2). That is, the cathode 213 is provided to face a main surface of the cation exchange membrane 211 different from the main surface facing the anode 212. The anode drainage W2B supplied to the cathode chamber 216B is generated by electrolysis of seawater W1 in the anode chamber 216A, and dissolved CO ２ is removed seawater, and is acidic. In the electrolysis of the anode drainage W2B, the cathode 213 electrolyzes water in the anode drainage W2B to produce hydrogen (H ２ ) gas and hydroxide ions (OH － ).

[0029] The cathode 213 can be made of the same material as the material used to form the anode 212.

[0030] The plate member 214 is a plate-shaped member provided on the anode 212 and cathode 213. The plate member 214 may be made of, for example, a metal such as stainless steel and titanium, a carbon material, or a corrosion-resistant alloy such as a Cr-Ni-Fe system. The plate member 214 has a pair of plate members 214A and 214B.

[0031] Plate member 214A is provided on a main surface different from the main surface of the anode 212 that faces the cation exchange membrane 211. Plate member 214B is provided on a main surface different from the main surface of the cathode 213 that faces the cation exchange membrane 211.

[0032] The gasket 215 is provided between the cation exchange membrane 211 and the anode 212, and between the cation exchange membrane 211 and the cathode 213. The gasket 215 is a frame-shaped member positioned between the cation exchange membrane 211 and the anode 212 or cathode 213. That is, the gasket 215 has a cylindrical shape with an open surface that contacts the cation exchange membrane 211 and the anode 212 or cathode 213. The gasket 215 seals the space between the cation exchange membrane 211 and the anode 212 or cathode 213.

[0033] The gasket 215 has a pair of gaskets 215A and 215B. Gasket 215A is provided so as to be sandwiched between the cation exchange membrane 211 and the anode 212, sealing the space between the cation exchange membrane 211 and the anode 212. Gasket 215B is provided so as to be sandwiched between the cation exchange membrane 211 and the cathode 213, sealing the space between the cation exchange membrane 211 and the cathode 213.

[0034] The material used to form the gasket 215 can be any material capable of sealing the space between the cation exchange membrane 211 and the anode 212 or cathode 213. For example, silicone rubber and natural rubber can be used.

[0035] The gasket 215A has a first anode opening 221A that connects the inside and outside of the anode chamber 216A, and second anode openings 222A and 223A.

[0036] The first anode opening 221A is a supply port for supplying seawater W1 to the anode chamber 216A. The first anode opening 221A is provided at one end of the anode chamber 216A and may be located at the bottom of the anode chamber 216A or at the bottom surface of the anode chamber 216A.

[0037] The second anode opening 222A is an outlet for discharging anode drainage W2B from the anode chamber 216A. The second anode opening 222A is provided at the other end of the anode chamber 216A and may be provided at the top of the anode chamber 216A or on the upper surface of the anode chamber 216A.

[0038] The second anode opening 223A is located within the anode chamber 216A, where O2 is produced in the anode 212 by the electrolysis of seawater W1. ２ This is an outlet for discharging gas. The second anode opening 223A, like the second anode opening 222A, is provided at the other end of the anode chamber 216A in a different position from the second anode opening 222A.

[0039] The gasket 215B has a first cathode opening 221B that connects the inside and outside of the cathode chamber 216B, and second cathode openings 222B and 222C.

[0040] The first cathode opening 221B is a supply port for supplying anode drainage W2A to the cathode chamber 216B. The first cathode opening 221B is preferably located at the bottom of the cathode chamber 216B, and may also be located on the bottom surface of the cathode chamber 216B.

[0041] The second cathode opening 222B is an outlet for discharging cathode drainage W3 from the cathode chamber 216B. The second cathode opening 222B is preferably located in the upper part of the cathode chamber 216B, and may also be located on the upper surface of the cathode chamber 216B.

[0042] The second cathode opening 223B is located within the cathode chamber 216B, where H is generated in the cathode 213 by the electrolysis of anode wastewater W2B.２ This is an outlet for discharging gas. The second cathode opening 223B, like the second cathode opening 222B, is located at the other end of the cathode chamber 216B and is in a different position from the second cathode opening 222B.

[0043] The anode chamber 216A is partitioned by a cation exchange membrane 211, an anode 212, and a gasket 215, and is a space through which seawater W1 passes. Seawater W1 is supplied to the anode chamber 216A from the seawater tank 231 through the seawater supply line L11.

[0044] The cathode chamber 216B is partitioned by the cation exchange membrane 211, the cathode 213, and the gasket 215, and is the space through which the anode wastewater W2B passes. The anode wastewater W2B sent from the first storage unit 232 through the recycling line L12 is supplied to the cathode chamber 216B.

[0045] In the electrolytic cell 21, with seawater W1 supplied to the anode chamber 216A and cathode chamber 216B of the electrolytic cell 21, power is supplied to the power supply unit 22, and when a DC current flows through the anode 212 and cathode 213 of the electrolytic cell 21, the electrode reaction at the anode 212 and the electrode reaction at the cathode 213 proceed in parallel. That is, electrolysis of the seawater W1 supplied to the anode chamber 216A and the anode wastewater W2B supplied to the cathode chamber 216B occur simultaneously.

[0046] In the anode chamber 216A, the electrolysis reaction shown in the following formula (1-1) occurs. That is, the electrode reaction at anode 212 causes the water in the seawater W1 supplied to the anode chamber 216A to be electrolyzed, resulting in O ２ Gas, hydrogen ions (H ＋ ) and electronic (e － ) occurs. Electrolysis reaction occurring at anode 212: 2H ２ O→O ２ +4H ＋ +4e － ... (1-1)

[0047] Due to the electrolysis of water by the electrode reaction at anode 212, the anode wastewater W2A discharged from anode chamber 216A contains more H than seawater W1. ＋Because it contains a large amount of [unclear], the pH of the anode wastewater W2A is lower than that of the seawater W1, and the pH of the anode wastewater W2A is, for example, around 2.0 to 5.0.

[0048] The lower limit of the pH of the anode wastewater W2A discharged from the anode chamber 216A is preferably 2.5 or higher, more preferably 3.0 or higher, and even more preferably 3.5 or higher. The upper limit of the pH of the anode wastewater W2A is preferably 4.5 or lower, more preferably 4.3 or lower, and even more preferably 4.0 or lower.

[0049] Seawater W1 contains carbon dioxide (CO2). ２ ) is dissolved, and CO2 is dissolved in this seawater W1. ２ The lower the pH of the seawater W1 in the anode chamber 216A, that is, the more acidic the seawater W1 becomes, the more CO2 dissolved in the seawater W1 is lost. ２ CO is a gas ２ CO ２ It becomes a gas and is easily generated in the seawater W1. Therefore, in the anode chamber 216A, the electrolysis of water in the seawater W1 generates H in the seawater W1. ＋ As a result, the more acidic the seawater W1 becomes, the more CO2 dissolved in the seawater W1 is produced. ２ CO ２ It is easily generated as a gas in seawater W1. In this case, CO ２ The gas is contained in the anode wastewater W2A, for example, in the form of bubbles, and is discharged along with the anode wastewater W2A that is discharged from the anode chamber 216A.

[0050] Also, calcium ions (Ca) contained in seawater W1 ２＋ ) and magnesium ions (Mg ２＋ ) is generally the hydroxide ions produced by the electrolysis of water, or hydroxide ions that make up CO2 ２ The carbonate ions produced by the reaction with the following equations (1-2) to (1-5) are then reacted with the carbonate ions. This results in the formation of calcium carbonate (CaCO3). ３ ) and magnesium hydroxide (Mg(OH) ２ ) is generated. － +CO ２ →HCO ３－ ...(1-2) OH － +HCO ３ － →HCO ３ ２－ +H ２ O...(1-3) Ca ２＋ +CO ３ ２－ →CCO ３ ...(1-4) Mg ２＋ +2OH － →Mg(OH) ２ ... (1-5)

[0051] In the anode chamber 216A, the pH of seawater W1 becomes, for example, around 2.0 to 5.0, and seawater W1 becomes strongly acidic, causing the CO2 dissolved in seawater W1 to be absorbed. ２ It vaporizes into CO ２ The proportion of CO2 dissolved in seawater W1 increases. ２ This is a reaction between calcium ions or magnesium ions and bicarbonate ions (HCO3). ３ － ) and carbonate ions (CO ３ ２－ This makes it less likely for ) to occur. Therefore, the formation of calcium carbonate and magnesium hydroxide in seawater W1 is suppressed.

[0052] In the cathode chamber 216B, the following electrolysis reaction occurs: (2-1) electrons supplied from the cathode output terminal of the power supply unit 22 and water in the anode wastewater W2B react at the cathode 213, causing the water to be electrolyzed and hydrogen (H) to be produced. ２ ) gas and hydroxide ions (OH － ) occurs. Electrolysis reaction occurring at cathode 213: 2H ２ O + 2e － →H ２ +2OH － ... (2-1)

[0053] H produced in the electrolysis reaction ２The gas is discharged from the cathode chamber 216B to the hydrogen gas discharge line L16 and recovered in the hydrogen recovery unit 252. Due to the electrolysis of water by the electrode reaction in the cathode 213, the cathode wastewater W3 discharged from the cathode chamber 216B contains more OH than the anode wastewater W2B. － Because it contains a large amount of [unclear], the pH of the anode wastewater W2B is neutralized in the cathode chamber 216B, and the pH of the cathode wastewater W3 becomes neutral or slightly alkaline. The pH of the cathode wastewater W3 is, for example, around 5.5 to 8.0.

[0054] The lower limit of the pH of the cathode wastewater W3 discharged from the cathode chamber 216B is preferably 6.0 or higher, more preferably 6.3 or higher, and even more preferably 6.5 or higher. The upper limit of the pH of the cathode wastewater W3 is preferably 7.8 or lower, more preferably 7.5 or lower, and even more preferably 7.3 or lower.

[0055] Furthermore, the cathode chamber 216B contains sodium ions (Na) generated by the electrolysis of seawater W1 in the anode chamber 216A. ＋ ) are supplied through the cation exchange membrane 211. The sodium ions undergo the reaction shown in formula (2-2) below, and hydroxide ions (OH) are generated at the cathode 213. － ) combines with to produce sodium hydroxide (NaOH). 2Na ＋ +2H ２ 0 + 2e － → 2NaOH + H ２ ... (2-2)

[0056] Although Figure 1 shows only one electrolytic cell 21, the seawater treatment device 20A may have multiple electrolytic cells 21. In this case, each electrolytic cell 21 may be arranged in parallel, for example, so that the arrangement of the anode 212 and cathode 213 is the same.

[0057] (Power supply unit) The power supply unit 22 is a DC power supply that receives power from the power supply unit 10 and supplies power to the electrolytic cell 21, supplying power for electrolysis (electrolytic power) to the anode 212 and cathode 213 provided in the electrolytic cell 21. The anode output terminal of the power supply unit 22 is connected to the anode 212 of the electrolytic cell 21. The cathode output terminal of the power supply unit 22 is connected to the cathode 213 of the electrolytic cell 21. As a result, a predetermined electrolytic voltage is applied between the anode 212 and cathode 213 of the electrolytic cell 21, and an electrolytic current flows.

[0058] The voltage applied by the power supply unit 22 can be adjusted as appropriate, as long as the electrode reaction proceeds at both electrodes, anode 212 and cathode 213, while suppressing the generation of chlorine or chlorine compounds. For example, by setting the electrode potential of anode 212 to less than the potential for the generation of chlorine or chlorine compounds, the electrode potential at anode 212 to be greater than or equal to the oxygen generation potential, and the electrode potential at cathode 213 to be greater than or equal to the hydrogen generation potential, the electrolysis reaction of water can proceed between anode 212 and cathode 213.

[0059] (Storage section) The storage section 23 includes a seawater tank 231, a first storage section 232, and a second storage section 233.

[0060] The seawater tank 231 is installed in the seawater supply line L11 and is a tank for storing seawater W1 supplied to the electrolytic cell 21. Impurities contained in the seawater W1 may be removed from the seawater tank 231.

[0061] The first storage section 232 is provided in the recycling line L12 and is a storage tank for storing anode wastewater W2A discharged from the anode chamber 216A of the electrolytic cell 21. In the first storage section 232, CO2 contained in the anode wastewater W2A in a dissolved state is stored. ２ The substance is vaporized and released into the space within the first storage section 232.

[0062] CO2 dissolved in anode wastewater W2A ２ The method of releasing the CO into the space within the first storage section 232 is not particularly limited, and a method of vaporizing and releasing the substance dissolved in the liquid can be used.２ Methods for releasing CO2 include, for example, a depressurization method, a spraying method, and a heating method. In the depressurization method, for example, when supplying anode wastewater W2A into the first storage section 232, the pressure inside the first storage section 232 is reduced by controlling a pressure reducing valve, etc., thereby releasing the CO2 dissolved in the anode wastewater W2A. ２ CO2 is released. In the spraying method, for example, anode wastewater W2A is sprayed into the first storage section 232 using a liquid sprayer or the like and supplied, and the pressure of the anode wastewater W2A is reduced, thereby releasing the CO2 dissolved in the anode wastewater W2A. ２ CO is released. In the heating method, for example, the anode wastewater W2A supplied to the first storage section 232 is heated, ２ By reducing the solubility of CO2 dissolved in anode wastewater W2A, ２ It releases.

[0063] Furthermore, CO2 is contained within the anode drainage W2A. ２ Even if gas is being generated, CO generated in the anode wastewater W2A ２ The gas is CO2 dissolved in the anode wastewater W2A. ２ The substance can be released into the space within the first storage section 232 using a method similar to the method used to release the substance.

[0064] In this embodiment, the CO2 dissolved in the anode wastewater W2A is stored in the first storage section 232. ２ Although it is releasing CO2, the CO2 contained in the anode wastewater W2A ２ CO2 can be separated. ２ The recovery section is provided between the anode chamber 216A and the first storage section 232 of the recycling line L12, CO ２ CO dissolved in the anode wastewater W2A in the recovery section ２ CO2 may be released. ２ For the recovery section, for example, a desorption tower commonly used for treating wastewater can be used.

[0065] The second storage section 233 is provided in the seawater discharge line L15 and is a storage tank for storing cathode wastewater W3 discharged from the cathode chamber 216B of the electrolytic cell 21.

[0066] ((Recovery Section)) The recovery section 25 comprises CO ２ recovery section 251 and a hydrogen recovery section 252.

[0067] CO ２ recovery section 251 is a CO ２ gas provided in the discharge line L13, which recovers O ２ gas contained in anode drainage W2A. The CO ２ recovery section 251 is not particularly limited, as long as it is a gas recovery device capable of recovering CO ２ gas.

[0068] Note that in the present embodiment, the CO ２ recovery section 251 is provided in the CO ２ gas discharge line L13, but it may be provided in the recycle line L12, or may be provided in the anode chamber 216A.

[0069] The hydrogen recovery section 252 is connected to a hydrogen gas discharge line L16, and recovers H ２ gas generated by electrolysis of seawater W1 in the cathode chamber 216B. The hydrogen recovery section 252 is not particularly limited, as long as it is a gas recovery device capable of recovering hydrogen gas.

[0070] ((Measurement Section)) The measurement section 26 comprises a first pH measurement section 261A to a fourth pH measurement section 261D, and a first flow rate measurement section 262A to a third flow rate measurement section 262C.

[0071] The first pH measuring unit 261A is installed in the seawater supply line L11 and measures the pH of seawater W1. The second pH measuring unit 261B is installed in the recycling line L12 and measures the pH of anode wastewater W2A. The third pH measuring unit 261C is installed in the seawater discharge line L15 and measures the pH of cathode wastewater W3. The fourth pH measuring unit 261D is installed in the seawater replenishment line L17 and measures the pH of auxiliary seawater W11. The first to fourth pH measuring units 261A to 261D only need to be able to measure the pH of seawater W1, anode wastewater W2A, cathode wastewater W3, or auxiliary seawater W11, and for the first to fourth pH measuring units 261A to 261D, for example, commonly used pH meters may be used. The first pH measuring unit 261A to the fourth pH measuring unit 261D transmit a signal indicating the measured pH to the control unit 27.

[0072] The first flow rate measuring unit 262A is installed in the seawater supply line L11 and measures the flow rate of seawater W1 flowing through the seawater supply line L11. The second flow rate measuring unit 262B is installed in the recycling line L12 and measures the flow rate of anode wastewater W2B flowing through the anode wastewater W2B. The third flow rate measuring unit 262C is installed in the hydrogen gas discharge line L16 and measures the flow rate of H discharged from the cathode chamber 216B to the hydrogen gas discharge line L16. ２ The gas flow rate is measured. The first to third flow rate measuring units 262A to 262C measure seawater W1, anode wastewater W2B, or H ２ It is sufficient to measure the gas flow rate, and for the first flow rate measuring unit 262A to the third flow rate measuring unit 262C, for example, a commonly used flow rate measuring device such as a flow sensor can be used. The first flow rate measuring unit 262A to the third flow rate measuring unit 262C measure the measured seawater W1, anode wastewater W2B and H ２ A signal indicating the gas flow rate is transmitted to the control unit 27.

[0073] ((Control Unit)) The control unit 27 controls each component that makes up the seawater treatment device 20A, including the electrolytic cell 21, power supply unit 22, measuring unit 26, pumps P1 to P3 and control valves V11 to V17. The control unit 27 has a storage means for storing a control program or various stored information, and a calculation means that operates based on the control program. The control unit 27 realizes the control function of each component that makes up the seawater treatment device 20A by having the calculation means execute the control program stored in the storage means.

[0074] The control unit 27 controls the power supplied from the power supply unit 22 to the electrolytic cell 21 to control the potentials of the anode 212 and cathode 213. Based on the measurement results of the measurement unit 26, the control unit 27 may control the output of the power supply unit 22 to control the potentials of the anode 212 and cathode 213, or it may control the driving of pumps P1 to P3, the opening and closing of control valves V11 to V17, etc.

[0075] The control unit 27 may control the voltage applied to the anode 212 and cathode 213 based on the pH of the anode wastewater W2A flowing through the recycling line L12, which is measured by the second pH measuring unit 261B, so that the pH of the cathode wastewater W3 discharged from the anode chamber 216A is within a predetermined range.

[0076] The specified range should be equal to or close to the pH of seawater W1, and the pH of cathode wastewater W3 is preferably 5.5 to 8.0, more preferably 6.0 to 7.8, and even more preferably 6.5 to 7.5.

[0077] (Various Lines) The seawater supply line L11 is connected to the anode chamber 216A of the electrolytic cell 21 and is a line that supplies seawater W1 taken in from the sea as anode liquid to the anode chamber 216A of the electrolytic cell 21. Specifically, the seawater supply line L11 is connected to the first anode opening 221A of the anode chamber 216A. A seawater tank 231 may be provided in the middle of the seawater supply line L11. The seawater supply line L11 may supply seawater W1 directly from the sea to the anode chamber 216A, or it may supply seawater W1 stored in a seawater tank 231 provided in the middle of the seawater supply line L11 to the anode chamber 216A.

[0078] A pump P1 is provided in the seawater supply line L11, and the pump P1 supplies seawater W1 from the seawater tank 231 to the anode chamber 216A of the electrolytic cell 21.

[0079] The recycling line L12 connects the second anode opening 222A of the anode chamber 216A of the electrolytic cell 21 to the first cathode opening 221B of the cathode chamber 216B, and supplies the anode wastewater W2A discharged from the anode chamber 216A to the cathode chamber 216B as cathode liquid. Since the recycling line L12 has a first storage section 232 along its course, CO2 is released from the anode wastewater W2A in the first storage section 232. ２ The anode wastewater W2B from which the gas has been removed is supplied as cathode liquid from the first storage unit 232 to the cathode chamber 216B.

[0080] Furthermore, gaseous CO2 is present in the anode wastewater W2A discharged from the anode chamber 216A. ２ If the gas can be recovered through the recycling line L12 or in the anode chamber 216A, the anode wastewater W2A may not be stored in the first storage section 232 but supplied to the cathode chamber 216B.

[0081] A pump P2 is provided in the recycling line L12, and the pump P2 supplies anode wastewater W2B from the first storage section 232 to the cathode chamber 216B of the electrolytic cell 21. A control valve V11 is also provided in the recycling line L12, and by controlling the control valve V11, the flow rate of anode wastewater W2A supplied to the first storage section 232 is adjusted.

[0082] CO ２ The gas discharge line L13 is connected to the first storage section 232 and CO ２ The recovery unit 251 is connected, and the CO discharged from the first storage unit 232 ２ CO2 ２ This is the line that supplies the recovery unit 251.

[0083] CO ２ A control valve V13 is provided in the gas discharge line L13, and by controlling the control valve V13, the CO discharged from the first storage unit 232 is controlled. ２ The gas flow rate is adjusted.

[0084] The oxygen gas discharge line L14 is connected to the anode chamber 216A of the electrolytic cell 21, and the oxygen produced by electrolyzing the anode wastewater W2B is discharged. ２ This is a line for discharging gas from the anode chamber 216A. Specifically, the oxygen gas discharge line L14 is connected to the second anode opening 223A of the anode chamber 216A, and discharges O from the anode chamber 216A. ２ The gas is released to the outside.

[0085] A control valve V14 is provided in the oxygen gas discharge line L14, and by controlling the control valve V14, the oxygen gas discharged from the oxygen gas discharge line L14 is controlled. ２ The gas flow rate is adjusted.

[0086] The seawater discharge line L15 is a line that discharges cathode wastewater W3 from the cathode chamber 216B. Specifically, the seawater discharge line L15 is connected to the second cathode opening 222B of the cathode chamber 216B and discharges cathode wastewater W3 from the cathode chamber 216B.

[0087] A control valve V15 is provided in the seawater discharge line L15, and the flow rate of the cathode wastewater W3 flowing through the seawater discharge line L15 is adjusted by controlling the control valve V15.

[0088] The seawater discharge line L15 comprises seawater discharge lines L15-1 to L15-3. Seawater discharge line L15-1 connects the cathode chamber 216B and the second storage section 233, supplying the cathode wastewater W3 discharged from the cathode chamber 216B to the second storage section 233. One end of seawater discharge line L15-2 is connected to the second storage section 233, and it is a line that directly discharges the cathode wastewater W3 stored in the second storage section 233 into the ocean. Seawater discharge line L15-3 connects the second storage section 233 and the cooling equipment 30, supplying the cathode wastewater W3 stored in the second storage section 233 to the cooling equipment 30, and then discharging it into the ocean.

[0089] The control valve V15 includes control valve V151 installed in seawater discharge line L15-1, control valve V152 installed in seawater discharge line L15-2, and control valve V153 installed in seawater discharge line L15-3. By controlling these control valves V151 to V153, the flow rate of cathode wastewater W3 flowing through each line of seawater discharge line L15 is adjusted.

[0090] The hydrogen gas discharge line L16 connects the cathode chamber 216B of the electrolytic cell 21 to the hydrogen recovery unit 252, and generates H by electrolyzing the anode wastewater W2B. ２ This is a line that supplies gas from the cathode chamber 216B to the hydrogen recovery unit 252. Specifically, the hydrogen gas discharge line L16 is connected to the second cathode opening 223B of the cathode chamber 216B and supplies the hydrogen gas discharged from the cathode chamber 216B. ２ The gas is supplied to the hydrogen recovery unit 252.

[0091] A control valve V16 is provided in the hydrogen gas discharge line L16, and by controlling the control valve V16, the hydrogen gas discharged from the hydrogen gas discharge line L16 is controlled. ２ The gas flow rate is adjusted.

[0092] The seawater replenishment line L17 is a line that supplies seawater W1 from the seawater tank 231 to the cathode chamber 216B as auxiliary seawater W11. Specifically, the seawater replenishment line L17 is connected to the seawater tank 231 and the first cathode opening 222D of the cathode chamber 216B, and supplies auxiliary seawater W11 from the seawater tank 231 to the cathode chamber 216B.

[0093] A pump P3 is provided in the seawater supply line L17, and the pump P3 supplies seawater W1 from the seawater tank 231 to the cathode chamber 216B of the electrolytic cell 21. In addition, a control valve V17 is provided in the seawater supply line L17, and by controlling the control valve V17, the flow rate of auxiliary seawater W11 supplied from the seawater tank 231 to the cathode chamber 216B of the electrolytic cell 21 is adjusted.

[0094] Next, the method of electrolysis using seawater W1 in the seawater treatment device 20A will be explained. In the seawater treatment device 20A, seawater W1 pumped from the sea flows in the following order: through the anode chamber 216A of the electrolytic cell 21, the recycling line L12, and the cathode chamber 216B of the electrolytic cell 21. In the electrolytic cell 21, seawater W1 is supplied to the anode chamber 216A, and anode wastewater W2B is supplied to the cathode chamber 216B, and electrolysis of seawater W1 and anode wastewater W2B is performed. By electrolyzing seawater W1 in the anode chamber 216A, the CO2 dissolved in seawater W1 is removed. ２ CO2 is released from seawater W1, and CO2 released from seawater W1 ２ Collect it.

[0095] Seawater W1 pumped from the sea is supplied to the seawater tank 231 via the seawater supply line L11, where it is processed as needed, such as removing impurities. The seawater W1 discharged from the seawater tank 231 is supplied to the cathode chamber 216B of the electrolytic cell 21 via the seawater supply line L11 through the first cathode opening 221B.

[0096] In the electrolytic cell 21, with seawater W1 supplied to the anode chamber 216A and cathode chamber 216B of the electrolytic cell 21, power is supplied to the power supply unit 22 from the power supply unit 10, and a DC current is passed through the anode 212 and cathode 213 of the electrolytic cell 21. The seawater W1 supplied to the anode chamber 216A is electrolyzed within the anode chamber 216A. As the seawater W1 is electrolyzed in the anode chamber 216A, O ２ CO ２ , hydrogen ions (H ＋ ), sodium ions (Na ＋ ) and electronic (e － ) and other things occur. The pH of seawater W1 is, for example, around 8 to 10, but the anode wastewater W2A discharged from the anode chamber 216A contains hydrogen ions, so the pH of the anode wastewater W2A is, for example, around 2.0 to 5.0. Furthermore, if the pH of seawater W1 drops to, for example, 3.0 or lower due to the electrolysis of seawater W1 in the anode chamber 216A, the CO2 dissolved in the seawater W1 will be released. ２ CO ２It can be released as a gas, but in this case, CO ２ The gas is present in seawater W1 in the form of bubbles.

[0097] Sodium ions generated in the anode chamber 216A pass through the cation exchange membrane 211 and move to the cathode chamber 216B. ２ The gas is discharged to the outside via the oxygen gas discharge line L14 through the second anode opening 223A of the anode chamber 216A. Electrons generated in the anode chamber 216A move to the anode output terminal of the power supply unit 22 via the plate member 214A, and are supplied from the cathode output terminal of the power supply unit 22 to the cathode 213 via the plate member 214B.

[0098] The anode wastewater W2A is discharged to the recycling line L12 through the second anode opening 222A of the anode chamber 216A and stored in the first storage unit 232.

[0099] In the first storage section 232, the CO2 dissolved in the anode wastewater W2A in the anode chamber 216A ２ By vaporizing it, CO2 is released from the anode drainage W2A into the space of the first storage section 232. ２ It is released as a gas. Furthermore, the CO generated in the seawater W1 within the anode chamber 216A ２ The gas is also released into the space of the first storage section 232. CO released into the first storage section 232 ２ Gas is CO ２ CO is discharged into gas exhaust line L13. ２ It is collected in the recovery unit 251.

[0100] In the first storage section 232, CO ２ The anode wastewater W2B from which the gas has been removed is supplied into the cathode chamber 216B through the first cathode opening 221B of the cathode chamber 216B via the recycling line L12.

[0101] The anode wastewater W2B supplied into the cathode chamber 216B is electrolyzed in the cathode chamber 216B, and as a result, H ２ Gas, hydroxide ion (OH －), sodium hydroxide and magnesium hydroxide are produced.

[0102] Specifically, hydroxide ions combine with sodium ions that have moved from the anode chamber 216A through the cation exchange membrane 211 to the cathode chamber 216B to produce NaOH. Furthermore, hydroxide ions react with sodium and magnesium ions to produce sodium hydroxide and magnesium hydroxide. Also, CO2 dissolved in the seawater W1 is present in the anode wastewater W2. ２ Since these are almost completely removed, hydroxide ions remain unreacted in the anode wastewater W2B, except for being used to produce sodium hydroxide and magnesium hydroxide.

[0103] The anode wastewater W2B is neutralized by the hydroxide ions produced by the electrolysis of water in the cathode chamber 216B, and the pH of the cathode wastewater W3 discharged from the cathode chamber 216B becomes approximately 5.5 to 8.0.

[0104] Furthermore, the CO2 dissolved in the seawater W1 was present in the anode wastewater W2. ２ Since it is almost completely removed, the unreacted hydroxide ions remaining in the anode wastewater W2B are CO ２ This reduces the amount of bicarbonate ions or carbonate ions produced by the reaction. Therefore, it reduces the generation of calcium carbonate and magnesium carbonate, etc.

[0105] H generated in cathode chamber 216B ２ The gas is discharged from the second cathode opening 223B into the hydrogen gas discharge line L16 and recovered in the hydrogen recovery unit 252.

[0106] The cathode wastewater W3 is discharged from the second anode opening 222A of the anode chamber 216A into the seawater discharge line L15-1 and stored in the second storage section 233. The cathode wastewater W3 stored in the second storage section 233 is discharged through the seawater discharge line L15-3 and used as cooling water in the cooling equipment 30 of various plants such as oil refineries and power plants before being released into the ocean. Alternatively, the cathode wastewater W3 stored in the second storage section 233 is discharged through the seawater discharge line L15-2 into the ocean without supplying cooling equipment 30.

[0107] Thus, the seawater treatment device 20A has an electrolytic cell 21 and a recycling line L12. In the electrolytic cell 21, electrolysis of seawater W1 is performed in the anode chamber 216A, and electrolysis of anode wastewater W2B is performed in the cathode chamber 216B. The seawater treatment device 20A uses the recycling line L12 to remove CO2 contained in the anode wastewater W2A discharged from the anode chamber 216A of the electrolytic cell 21. ２ Drainage that supplies the anode drainage W2B, from which the contaminants have been removed, to the cathode chamber 216B.

[0108] The pH of the seawater W1 supplied to the anode chamber 216A is, for example, about 5.5 to 8.0, but the water in the seawater W1 is electrolyzed in the anode chamber 216A, and the H in the seawater W1 ＋ As the amount of OH increases, the seawater W1 becomes more acidic in the anode chamber 216A, and the pH of the seawater W1 in the anode chamber 216A drops to, for example, 3 to 5. The pH of the anode wastewater W2B supplied from the anode chamber 216A to the cathode chamber 216B through the recycling line L12 is acidic, but by using the anode wastewater W2B as an electrolyte in the cathode chamber 216B and electrolyzing the water in the anode wastewater W2B, OH is added to the anode wastewater W2B. － As the amount of [unclear element] increases, the anode wastewater W2B is neutralized, and the pH of the anode wastewater W2B rises. The pH of the anode wastewater W2B discharged from the cathode chamber 216B becomes, for example, around 6.0 to 8.0. Therefore, even if the seawater treatment device 20A uses seawater W1 as the electrolyte of the electrolytic cell 21, it can adjust the pH of the cathode wastewater W3 discharged from the cathode chamber 216B of the electrolytic cell 21 to be close to the pH of the seawater W1 before use by adjusting the pH of the seawater W1 and anode wastewater W2B used in the electrolytic cell 21.

[0109] Furthermore, the seawater treatment device 20A can adjust the pH of the cathode wastewater W3 discharged from the electrolytic cell 21 to near neutral simply by performing electrolysis of seawater W1 in the anode chamber 216A of the electrolytic cell 21 and electrolysis of the anode wastewater W2B in the cathode chamber 216B. Therefore, the pH of the cathode wastewater W3 can be easily adjusted to a state close to the pH of the seawater W1 before use.

[0110] Therefore, the seawater treatment device 20A can easily bring the pH of the cathode wastewater W3 discharged from the cathode chamber 216B of the electrolytic cell 21 closer to the pH of the seawater W1 before use.

[0111] Furthermore, the seawater treatment device 20A has H in the cathode chamber 216B. ２ Because gas can be generated, the generated H ２ Gas can be used for sales and other purposes.

[0112] The seawater treatment device 20A uses CO ２ The recycling line L12 has a recovery unit 251, and CO2 released from the anode wastewater W2A ２ CO2 produced by electrolyzing seawater W1 in the anode chamber 216A ２ CO2 ２ It is preferable to recover it in the recovery unit 251. As a result, the seawater treatment device 20A can recover CO ２ CO that was dissolved in the anode wastewater W2A in the recovery unit 251 ２ And the CO generated in the anode chamber 216A ２ The gas can be easily recovered.

[0113] Also, CO ２ CO recovered in the recovery unit 251 ２ CO2 contained in the ocean ２ Therefore, the seawater treatment device 20A uses CO2 from the natural environment. ２ This means that it is absorbing CO2, and thus is having the effect of reducing greenhouse gases. The seawater treatment device 20A absorbs CO2. ２ CO recovered in the recovery unit 251 ２ By trading the amount of CO2 absorbed as credits and using the proceeds to cover hydrogen production costs, the selling price of the produced hydrogen can be reduced. In other words, when electricity is obtained from renewable energy sources, the cost of producing the electricity is high, making it difficult to produce hydrogen cheaply. The seawater treatment device 20A produces hydrogen and CO2 simultaneously. ２ By recovering and crediting hydrogen, the profits earned can be used to lower the price of hydrogen, thereby keeping the price of hydrogen down.

[0114] Furthermore, the anode wastewater W2B supplied to the cathode chamber 216B is CO２ Because it contains almost no CO, the cathode wastewater W3 discharged from the cathode chamber 216B is similarly CO ２ It contains almost no CO2. Also, the pH of the cathode wastewater W3 discharged from the cathode chamber 216B is lower than the pH of the seawater W1 before use. The anode wastewater W2B is CO2. ２ Because it contains almost no CaCO3 and has a low pH, the cathode wastewater W3 contains CaCO3. ３ It is less likely to precipitate. Therefore, even if the cathode wastewater W3 stored in the second storage section 233 is supplied as cooling water to the cooling equipment 30 of a plant, marine organisms such as barnacles and mussels that are floating in the cathode wastewater W3 will not attach to the piping of the cooling equipment 30 and reproduce, thereby preventing blockages in the piping of the cooling equipment 30.

[0115] In other words, since the pH of seawater W1 is around 8.0 to 10.0, marine organisms present in seawater W1 can easily grow in it. When seawater W1 is used as cooling water for cooling equipment 30 such as a power plant, if it adheres to the piping of the cooling equipment 30, CaCO2 precipitates in the seawater W1. ３ It reproduces by taking in CaCO3 as a nutrient source. In this embodiment, CaCO3 precipitates in the cathode wastewater W3. ３ Because the amount can be significantly reduced, when cathode wastewater W3 is used as cooling water for cooling equipment 30 such as a power plant, marine organisms can attach to the piping of the cooling equipment 30 but their reproduction can be suppressed. Therefore, even when the cathode wastewater W3 is used as cooling water for cooling equipment 30 such as a power plant, the seawater treatment device 20A can suppress blockages in the piping of the cooling equipment 30 caused by marine organisms contained in the cathode wastewater W3.

[0116] The seawater treatment device 20A has a first storage section 232 in the recycling line L12, and CO ２ The recovery unit 251 recovers CO2 released from the first storage unit 232. ２ It is preferable to recover the CO2 dissolved in the anode wastewater W2A in the first storage section 232. ２ Or CO contained in anode wastewater W2A２ It can release gas. The seawater treatment device 20A is CO ２ In the recovery unit 251, CO2 released from the first storage unit 232 ２ By recovering the CO2 contained in the anode wastewater W2A discharged from the anode chamber 216A, ２ This allows for efficient recovery. Furthermore, by providing a first storage section 232 in the recycling line L12, the seawater treatment device 20A can easily adjust the amount of anode wastewater W2B supplied to the cathode chamber 216B, thereby allowing for appropriate control of the flow rate of cathode wastewater W3 discharged from the cathode chamber 216B.

[0117] The seawater treatment apparatus 20A preferably has a hydrogen recovery unit 252. This allows the seawater treatment apparatus 20A to recover the H produced in the cathode chamber 216B. ２ Because the gas can be easily recovered, H ２ It allows for the easy sale of gas and other related services.

[0118] In the seawater treatment apparatus 20A, it is preferable that the control unit 27 controls the voltage applied to the anode 212 and cathode 213 based on the pH of the anode wastewater W2B and the pH of the cathode wastewater W3. This allows the seawater treatment apparatus 20A to appropriately control the pH of the cathode wastewater W3 discharged from the cathode chamber 216B so that it is within a predetermined range, for example, 5.5 to 8.0. Therefore, the seawater treatment apparatus 20A can bring the pH of the cathode wastewater W3 closer to the pH of the seawater W1 before use with greater accuracy.

[0119] The seawater treatment device 20A may be equipped with a second pH measuring unit 261B in the recycling line L12 and a third pH measuring unit 261C in the seawater discharge line L15. The pH of the anode wastewater W2B discharged from the anode chamber 216A and the pH of the cathode wastewater W3 discharged from the cathode chamber 216B can be confirmed from the second pH measuring unit 261B and the third pH measuring unit 261C. Therefore, the control unit 27 can appropriately control the voltage applied to the anode 212 and cathode 213 based on the second pH measuring unit 261B and the third pH measuring unit 261C. Thus, the seawater treatment device 20A can appropriately bring the pH of the cathode wastewater W3 closer to the pH of the seawater W1 before use.

[0120] The seawater treatment device 20A may be equipped with a second flow rate measuring unit 262B in the recycling line L12. By measuring the flow rate of the anode wastewater W2B supplied from the cathode chamber 216B, the amount of hydroxide ions generated in the cathode chamber 216B can be predicted. This makes it easier to control the voltage applied to the anode 212 and cathode 213 so that the pH of the cathode wastewater W3 discharged from the cathode chamber 216B is within a predetermined range, for example, 5.5 to 8.0. Therefore, the seawater treatment device 20A can bring the pH of the cathode wastewater W3 closer to the pH of the seawater W1 before use with greater accuracy.

[0121] The seawater treatment device 20A may be provided with a seawater replenishment line L17. The seawater treatment device 20A can supply auxiliary seawater W11 from the seawater tank 231 to the cathode chamber 216B via the seawater replenishment line L17. Controlling only the voltage applied to the anode 212 and cathode 213 may not be sufficient to adequately control the pH of the cathode wastewater W3 discharged from the cathode chamber 216B to a predetermined range, such as 5.5 to 8.0, relative to the flow rate of the anode wastewater W2B supplied to the cathode chamber 216B. The pH of the anode wastewater W2B is about 2.0 to 5.0, while the pH of the seawater W1 is about 6.0 to 8.0. The seawater treatment device 20A can easily control the pH of the cathode wastewater W3 to be within a predetermined range by replenishing the cathode chamber 216B with auxiliary seawater W11 from the seawater replenishment line L17 as an electrolyte, in addition to the anode wastewater W2B. Therefore, the seawater treatment device 20A can easily bring the pH of the cathode wastewater W3 closer to the pH of the seawater W1 before use.

[0122] The seawater treatment system 1A preferably comprises the seawater treatment device 20A described above and a cooling device 30. The seawater treatment system 1A uses the cathode wastewater W3 discharged from the seawater treatment device 20A as cooling water in the cooling device 30, thereby enabling stable cooling of heat transfer fluids generated in various plants such as petroleum refining plants and power generation plants, while also reducing the cost burden required for cooling the heat transfer fluid.

[0123] The seawater treatment system 1A may include a power supply unit 10 and the seawater treatment device 20A described above. In this way, the seawater treatment system 1A can use the power supplied from the power supply unit 10 to electrolyze seawater W1 and anode wastewater W2B in the electrolytic cell 21 in the seawater treatment device 20A.

[0124] Furthermore, in the seawater treatment system 1A, it is preferable that the power supply unit 10 has at least one of a first power supply unit 11 and a second power supply unit 12. This allows the seawater treatment system 1A to stably operate the seawater treatment device 20A by supplying at least one of the renewable energy-derived power supplied from the first power supply unit 11 and the power generated by the second power supply unit 12 to the electrolytic cell 21. In addition, in the seawater treatment device 20A, the seawater treatment system 1A uses the renewable energy-derived power supplied from the first power supply unit 11 to electrolyze seawater W1 and anode wastewater W2B, thereby reducing the consumption of fossil fuels associated with hydrogen production and CO2 reduction. ２ Emissions can be reduced. Furthermore, the seawater treatment system 1A supplies power generated in the second power supply unit 12 to the electrolytic cell 21, so that even if the power supplied from the first power supply unit 11 to the electrolytic cell 21 of the seawater treatment device 20A is insufficient, the seawater treatment device 20A can be operated stably. As a result, the seawater treatment system 1A can stably perform electrolysis of seawater W1 and anode wastewater W2B in the seawater treatment device 20A.

[0125] In the seawater treatment system 1A, it is preferable that the power supply unit 10 has a first power supply unit 11 and a second power supply unit 12. This allows the seawater treatment system 1A to perform electrolysis of seawater W1 and anode wastewater W2B in the seawater treatment apparatus 20A more stably.

[0126] In this embodiment, the operation of the seawater treatment apparatus 20A is controlled by the control unit 27, which controls the power supplied from the power supply unit 22 to the electrolytic cell 21, based on the measurement results of the measurement unit 26. However, the operation of the seawater treatment apparatus 20A may be controlled as appropriate and as needed by an operator or other person.

[0127] <Second Embodiment> [Seawater Treatment System] A seawater treatment system equipped with a seawater treatment apparatus according to the second embodiment of the present invention (hereinafter sometimes simply referred to as "this embodiment") will be described. Note that the description of the configuration of the seawater treatment system according to this embodiment that is common with the seawater treatment system 1A according to the first embodiment shown in Figure 1 will be omitted.

[0128] Figure 2 is a simplified diagram showing an example of the configuration of a seawater treatment system equipped with the seawater treatment apparatus according to this embodiment. As shown in Figure 2, the seawater treatment system 1B equipped with the seawater treatment apparatus according to this embodiment has CO2 added to the seawater treatment apparatus 20A shown in Figure 1. ２ It is equipped with an absorption section 28 and a separation section 29. That is, the seawater treatment system 1B comprises a power supply section 10, a seawater treatment device 20B and a cooling device 30, and the seawater treatment device 20B is CO ２ It has an absorption section 28 and a separation section 29.

[0129] CO ２ The absorption unit 28 is located in the seawater supply line L11 and absorbs seawater W1 and CO2 supplied to the anode chamber 216A. ２ The contained gas G1 is brought into gas-liquid contact. ２ In the absorption section 28, seawater W1 and CO ２ The contained gas G1 is brought into gas-liquid contact, CO ２ CO2 is included in gas G1 ２ By absorbing it into seawater W1, CO ２ CO2 is included in gas G1 ２ CO can be recovered in seawater W1. Seawater W1 is CO ２ By including this, the CO2 recovered from the anode wastewater W2A discharged from the anode chamber 216A in the first storage unit 232 ２ The quantity can be increased. Also, CO ２ In the absorption section 28, CO ２ CO in gas G1 ２ CO2 is absorbed by seawater W1. ２ The contained gas G1 is CO ２ It is released to the outside as free gas.

[0130] CO ２ The absorption section 28 absorbs seawater W1 and CO2. ２The contained gas G1 is brought into gas-liquid contact, CO ２ CO in gas G1 ２ Any device that can absorb CO into seawater W1 is sufficient. ２ As the absorption section 28, for example, an absorption tower commonly used for treating exhaust gases can be used. ２ CO2 is released into the contained gas G1 by a spraying or injection method. ２ CO may be supplied into the absorption section 28. ２ If the absorption section 28 is an absorption tower, CO will enter the absorption tower. ２ Alternatively, the contained gas G1 may be sprayed in a spray form and brought into contact with seawater W1. ２ Alternatively, the contained gas G1 may be injected using a nozzle or other injection device to bubble the seawater W1.

[0131] CO ２ As the contained gas G1, for example, exhaust gas discharged from plant facilities such as oil refineries may be used. The exhaust gas is CO ２ It is sufficient that it contains CO ２ Exhaust gas with a concentration of 5 to 20 wt% can be used.

[0132] The separation unit 29 is located in the seawater discharge line L15-1 and contains Mg(OH) contained in the cathode wastewater W3 discharged from the cathode chamber 216B. ２ The following is separated: In the separation section 29, Mg(OH) contained in the cathode wastewater W3 ２ By separating it, Mg(OH) in cathode wastewater W3 ２ It can be recovered.

[0133] The separation unit 29 contains Mg(OH) contained in the cathode wastewater W3. ２ Any device capable of separating the substances is acceptable, and as the separation unit 29, for example, a centrifuge or other separation device commonly used for separating impurities such as salts contained in wastewater can be used.

[0134] Next, a method for electrolyzing seawater W1 using the seawater treatment device 20B will be described. The treatment of seawater W1 in the seawater treatment device 20B is performed in the seawater treatment system 1A according to the first embodiment described above, where CO2 is applied to the seawater treatment device 20A. ２ Since it is the same as the seawater treatment apparatus 20A except for the presence of an absorption section 28 and a separation section 29, only the main differences will be explained.

[0135] Seawater W1 discharged from seawater tank 231 is treated with CO2 in seawater supply line L11. ２ CO is supplied to the absorption section 28. ２ In the absorption section 28, seawater W1 and CO ２ The contained gas G1 is brought into gas-liquid contact. ２ In the absorption section 28, CO ２ CO2 is included in gas G1 ２ The seawater W1 that has absorbed CO is supplied to the anode chamber 216A of the electrolytic cell 21 and electrolyzed in the anode chamber 216A. The anode wastewater W2A discharged from the anode chamber 216A is supplied to the first storage unit 232 via the recycling line L12. In the first storage unit 232, the CO dissolved in the anode wastewater W2A in the anode chamber 216A is electrolyzed. ２ By vaporizing it, CO2 is released from the anode drainage W2A into the space of the first storage section 232. ２ It is released as a gas. CO released into the first storage unit 232 ２ Gas is CO ２ CO is discharged into gas exhaust line L13. ２ It is collected in the recovery unit 251. In the first storage unit 232, CO ２ The anode wastewater W2B, from which the gas has been removed, is supplied to the cathode chamber 216B via the recycling line L12.

[0136] The cathode wastewater W3 discharged from the cathode chamber 216B of the seawater treatment device 20B to the seawater discharge line L15-1 is supplied to the separation unit 29, where the Mg(OH) contained in the cathode wastewater W3 is separated. ２ After being separated and removed, it is stored in the second storage section 233.

[0137] Thus, the seawater treatment device 20B further CO２ By having an absorption section 28, CO2 is absorbed into the seawater W1. ２ CO in gas G1 ２ It can absorb CO2. And the CO2 absorbed by seawater W1 ２ CO2 is supplied to the first storage unit 232 in a dissolved state in the anode wastewater W2A discharged from the anode chamber 216A, and vaporized in the first storage unit 232, thereby adding CO2 to the seawater W1. ２ CO absorbed from contained gas G1 ２ Therefore, the seawater treatment device 20B can recover CO from the seawater W1. ２ In addition, CO ２ CO in gas G1 ２ Because it can also be recovered, for example, CO2 contained in exhaust gases emitted from plant facilities such as oil refineries. ２ Therefore, the seawater treatment device 20B can recover naturally occurring CO2 contained in seawater W1. ２ CO ２ CO2 originating from plant equipment is contained in gas G1. ２ They can be collected simultaneously.

[0138] Furthermore, the seawater treatment device 20B is designed to absorb CO2 contained in exhaust gases discharged from plant equipment and the like. ２ This reduces the amount of waste released to the outside.

[0139] Furthermore, the seawater treatment device 20B absorbs CO2 into the seawater W1. ２ Since CO can be recovered simply by dissolving it in the anode wastewater W2A and vaporizing it in the first storage section 232, ２ CO in gas G1 ２ Without installing new equipment for recovery, CO2 contained in exhaust gases emitted from plant equipment, etc. ２ CO2 can be recovered. In addition, the seawater treatment device 20B can recover CO2 absorbed into the seawater W1 in the first storage section 232. ２ CO derived from contained gas G1 ２ Without generating any additional energy required for CO absorption, ２ It is possible to collect them.

[0140] Furthermore, the seawater treatment device 20B has a separation unit 29 in addition to the seawater treatment device 20A, so that the Mg(OH) generated in the cathode chamber 216B ２ CO can be recovered. In the seawater treatment device 20B, ２ The absorption unit 28 absorbs the CO2 contained in the seawater W1 supplied to the anode chamber 216A. ２ CO in gas G1 ２ And the CO that moved from cathode chamber 216B to anode chamber 216A ２ Since it is recovered, CaCO3 is placed in the cathode chamber 216B ３ This suppresses the generation of salt. For this reason, the seawater treatment device 20B removes the salt generated in the cathode chamber 216B almost entirely from Mg(OH) ２ It can be made into only Mg(OH) ２ Since it is useful as a valuable material, the seawater treatment device 20B uses high-purity Mg(OH) as a valuable material. ２ It can be recovered efficiently.

[0141] As described above, various embodiments of the present invention have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, or modifications are possible without departing from the spirit of the invention. The above embodiments and their variations are included in the scope or spirit of the invention, as well as in the claims of the invention and its equivalents.

[0142] The embodiments of the present invention disclosed above are further specified by, for example, the following embodiments: [1] An electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber housing the anode; and a recycling line supplying anode wastewater discharged from the anode chamber to a cathode chamber housing the cathode. [2] CO2 discharged from the anode wastewater to the anode chamber or the recycling line. ２Alternatively, by electrolyzing the seawater in the anode chamber, CO2 is released from the seawater. ２ CO2 recovery ２ [1] A seawater treatment apparatus having a recovery unit. [3] The recycling line has a first storage unit for storing the anode wastewater, and the CO ２ The recovery unit recovers the CO2 discharged from the first storage unit. ２ [1] or [2] seawater treatment apparatus for recovering [4] A seawater treatment apparatus according to any one of [1] to [3], comprising a hydrogen gas recovery unit for recovering hydrogen gas generated in the cathode chamber. [5] A seawater treatment apparatus according to any one of [1] to [4], comprising a control unit for controlling the voltage applied to the anode and the cathode so that the pH of the cathode wastewater discharged from the cathode chamber is within a predetermined range, based on the pH of the anode wastewater flowing through the recycling line and the cathode wastewater discharged from the cathode chamber. [6] A seawater treatment apparatus according to any one of [1] to [5], comprising a second pH measuring unit for measuring the pH of the anode wastewater discharged from the anode chamber, and a third pH measuring unit for measuring the pH of the cathode wastewater discharged from the cathode chamber. [7] A seawater treatment apparatus according to any one of [1] to [6], comprising a flow rate measuring unit for measuring the flow rate of the anode wastewater in the recycling line. [8] A seawater treatment apparatus according to any one of [1] to [7], having a seawater supply line for supplying the seawater to the cathode chamber. [9] CO2 supplied to the seawater supplied to the electrolytic cell. ２ CO2 contained in the gas ２ CO2 absorbed into the seawater ２A seawater treatment apparatus according to any one of [1] to [8], comprising: an absorption unit; and a separation unit for separating magnesium hydroxide contained in the cathode wastewater discharged from the cathode chamber.

[10] A seawater treatment system comprising: a seawater treatment apparatus according to any one of [1] to [9]; and a cooling system having piping through which the cathode wastewater discharged from the cathode chamber of the seawater treatment apparatus passes.

[11] A seawater treatment system comprising: a seawater treatment apparatus according to any one of [1] to [9]; and a power supply unit for supplying at least one of renewable energy-derived electricity and fossil fuel-derived electricity to the seawater treatment apparatus.

[12] An electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber containing the anode, and the anode wastewater discharged from the anode chamber is supplied to a cathode chamber containing the cathode to electrolyze the seawater, and CO2 is released from the seawater by electrolyzing the seawater in the anode chamber. ２ A method for treating seawater to recover waste products.

[0143] This application claims priority based on Japanese Patent Application No. 2025-39593, filed with the Japan Patent Office on 12 March 2025, and incorporates all the contents of the said application.

[0144] 1A, 1B Seawater treatment system 10 Power supply unit 20A, 20B Seawater treatment device 21 Electrolytic cell 22 Power supply unit 23 Storage unit 25 Recovery unit 26 Measurement unit 27 Control unit 28 CO ２ Absorption section 29 Separation section 30 Cooling equipment 211 Cation exchange membrane 212 Anode 213 Cathode 216A Anode chamber 216B Cathode chamber 231 Seawater tank 232 First storage section 233 Second storage section 251 CO ２Recovery Unit 252 Hydrogen Recovery Unit 261A First pH Measurement Unit 261B Second pH Measurement Unit 261C Third pH Measurement Unit 261D Fourth pH Measurement Unit 262A First Flow Rate Measurement Unit 262B Second Flow Rate Measurement Unit 262C Third Flow Rate Measurement Unit L11 Seawater Supply Line L12 Recycling Line L13 CO ２ Gas discharge line L14 Oxygen gas discharge line L15 Seawater discharge line L16 Hydrogen gas discharge line W1 Seawater W2A, W2B Anode wastewater W3 Cathode wastewater

Claims

1. A seawater treatment apparatus comprising: an electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber housing the anode; and a recycling line that supplies anode wastewater discharged from the anode chamber to a cathode chamber housing the cathode.

2. CO2 released from the anode wastewater into the anode chamber or the recycling line. ２ Alternatively, by electrolyzing the seawater in the anode chamber, CO2 is released from the seawater. ２ CO2 recovery ２ The seawater treatment apparatus according to claim 1, comprising a recovery unit.

3. The recycling line has a first storage section for storing the anode wastewater, and the CO ２ The recovery unit recovers the CO2 discharged from the first storage unit. ２ A seawater treatment apparatus according to claim 2, for recovering [the substance].

4. The seawater treatment apparatus according to claim 1 or 2, further comprising a hydrogen gas recovery unit for recovering hydrogen gas generated in the cathode chamber.

5. The seawater treatment apparatus according to claim 1 or 2, further comprising a control unit that controls the voltage applied to the anode and the cathode based on the pH of the anode wastewater flowing through the recycling line and the cathode wastewater discharged from the cathode chamber, such that the pH of the cathode wastewater discharged from the cathode chamber falls within a predetermined range.

6. The seawater treatment apparatus according to claim 1 or 2, comprising: a second pH measuring unit for measuring the pH of the anode wastewater discharged from the anode chamber; and a third pH measuring unit for measuring the pH of the cathode wastewater discharged from the cathode chamber.

7. The seawater treatment apparatus according to claim 1 or 2, wherein the recycling line has a flow rate measuring unit for measuring the flow rate of the anode wastewater.

8. The seawater treatment apparatus according to claim 1 or 2, further comprising a seawater supply line for supplying seawater to the cathode chamber.

9. CO2 is added to the seawater supplied to the electrolytic cell. ２ CO2 contained in the gas ２ CO2 absorbed into the seawater ２ The seawater treatment apparatus according to claim 1 or 2, comprising: an absorption unit; and a separation unit for separating magnesium hydroxide contained in the cathode wastewater discharged from the cathode chamber.

10. A seawater treatment system comprising: a seawater treatment apparatus according to claim 1 or 2; and a cooling apparatus having piping through which cathode wastewater discharged from the cathode chamber of the seawater treatment apparatus passes.

11. A seawater treatment system comprising: a seawater treatment device according to claim 1 or 2; and a power supply unit that supplies at least one of electricity derived from renewable energy and electricity derived from fossil fuels to the seawater treatment device.

12. A method for treating seawater in an electrolytic cell having an ion exchange membrane, an anode installed facing one side of the ion exchange membrane, and a cathode installed facing the other side of the ion exchange membrane, wherein seawater is supplied to an anode chamber containing the anode, and the anode wastewater discharged from the anode chamber is supplied to a cathode chamber containing the cathode, thereby electrolyzing the seawater.

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