Lithium desorption unit

Abstract

Provided are a positive electrode, a negative electrode, an adsorption layer provided between the positive electrode and the negative electrode and supplied with an adsorbent adsorbing lithium ions, a substance layer provided between the adsorption layer and the negative electrode and supplied with a substance to be electrolyzed, a bonding layer provided between the adsorption layer and the substance layer, a first permeable membrane provided between the adsorption layer and the bonding layer to pass lithium ions separated from the adsorbent in the adsorption layer, and a second permeable membrane provided between the substance layer and the bonding layer to pass negative ions ionized from the substance layer in the substance layer and not to pass positive ions. The bonding layer is supplied with the lithium ions having passed through the first permeable membrane and the negative ions having passed through the second permeable membrane to produce a lithium compound in which the lithium ions and the negative ions bond to each other.

Description

DESCRIPTION TITLE OF THE INVENTION: LITHIUM DESORPTION UNIT Field

[0001] The present disclosure relates to a lithium desorption unit. Background

[0002] Disclosed are techniques for recovering resources contained in seawater from seawater. For example, in Patent Literature 1, lithium in seawater is adsorbed by an adsorbent, and the adsorbent is passed through a weak acid solution to desorb lithium as ions from the adsorbent. Disclosed are techniques for recovering lithium by blowing and bubbling carbon dioxide gas emitted from power plants and recovering it as lithium carbonate. Citation List Patent Literature

[0003] Patent Literature 1: Japanese Patent Application Laid-open No. H01-313323 Summary Technical Problem

[0004] It is known that weak acid treatment degrades the adsorbent, and there is room for improvement to increase the reuse rate of the adsorbent in order to properly recover a target component contained in seawater.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide a lithium desorption unit that can properly desorb lithium contained in seawater. Solution to Problem

[0006] A lithium desorption unit according to the present disclosure includes: a positive electrode; a negative electrode; an adsorption layer provided between the positive electrode and the negative electrode and supplied with an adsorbent adsorbing lithium ions; a substance layer provided between the adsorption layer and the negative electrode and supplied with a substance to be electrolyzed; a bonding layer provided between the adsorption layer and the substance layer; a first permeable membrane provided between 2 the adsorption layer and the bonding layer to pass lithium ions separated from the adsorbent in the adsorption layer to the bonding layer; and a second permeable membrane provided between the substance layer and the bonding layer to pass negative ions ionized from the substance layer in the substance layer and not to pass positive ions. The bonding layer is supplied with the lithium ions having passed through the first permeable membrane and the negative ions having passed through the second permeable membrane to produce a lithium compound in which the lithium ions and the negative ions bond to each other. Advantageous Effects of Invention

[0007] The present disclosure can properly desorb lithium. Brief Description of Drawings

[0008] FIG. 1 is a schematic diagram of an entire configuration of a target component recovery system according to a first embodiment. FIG. 2 is a schematic diagram of a flow of a target component contained in seawater. FIG. 3 is a schematic diagram of a structure of a lithium desorption unit. FIG. 4 is a schematic diagram of a structure of the lithium desorption unit. FIG. 5 is a schematic diagram of an entire configuration of a target component recovery system according to a second embodiment. Description of Embodiments

[0009] The following describes suitable embodiments of the present disclosure in detail with reference to the accompanying drawings. Note that the present disclosure is not limited by these embodiments and, when there are a plurality of embodiments, also includes ones configured by combining the embodiments. The components in the embodiments include ones that can be readily assumed by those skilled in the art, substantially the same ones, and ones that are in what is called the range of equivalence. Furthermore, the components in the embodiments described below can be omitted, replaced, or modified in various ways without departing from the gist of the present invention.

[0010] First Embodiment The following describes a target component recovery system 1 according to the present embodiment using FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of an entire configuration of a target component recovery system according to a first embodiment. FIG. 2 is a schematic diagram of a flow of a target component contained in seawater.

[0011] Target Component Recovery System As illustrated in FIG. 1 and FIG. 2, the target component recovery system 1 includes a plant 100, water intake equipment 10, an adsorbent storage tank 20, a mixing tank, an adsorbent separation unit, an adsorption unit 30, a waste liquid processing unit 43, a lithium desorption unit 40, a target component recovery unit 50, and a controller 90. The target component recovery system 1 is a system performing certain treatment on a target component (a resource) contained in a solution to recover the target component. The solution in this example is preferably any of seawater, concentrated wastewater of seawater desalination equipment producing fresh water from seawater, and saline lake brine. Examples of the target component include lithium, uranium, and magnesium, but these target components are not limiting so long as it is a target component that can be recovered using the system of the present disclosure. Note that the following description will be given with seawater as the solution and with lithium as the target component. That is, the target component recovery system according to the present disclosure is a system recovering lithium contained in seawater.

[0012] Plant The plant 100 is equipment producing resources and / or goods required for industrial activities. The plant 100 preferably utilizes seawater taken in from the water intake equipment 10, which will be described later. The plant 100 discharges an exhausted heat medium, which is a heated medium produced during operation. The exhausted heat medium may be any medium, and, for example, when the plant 100 is provided with a steam turbine, the exhausted heat medium may be steam after driving the steam turbine. For example, when the plant 100 is provided with a boiler, the exhausted heat medium may be steam after being used in the boiler. The plant 100 may discharge the exhausted heat medium from a plurality of places. The plant 100 may be any equipment utilizing seawater and discharging the exhausted heat medium, and examples thereof include nuclear power generation equipment, thermal power generation equipment, and chemical plants. The present embodiment describes the plant 100 with nuclear power generation equipment as an example. In addition, in the present embodiment, the plant 100 is preferably a plant in operation.

[0013] Nuclear Power Generation Equipment The following describes an outline of the nuclear power generation equipment (nuclear power equipment). The nuclear power equipment has, for example, a pressurized water reactor (PWR). The nuclear power equipment uses heat generated by the pressurized water reactor to perform, for example, power generation. The nuclear power equipment uses light water as a nuclear reactor coolant and a neutron moderator and makes it high-temperature, high-pressure water that is not boiled across the entire reactor core of the nuclear reactor. This high-temperature, high-pressure water (a primary coolant) is sent to a steam generator to generate steam through heat exchange. This steam (a secondary coolant) is then sent to a turbine generator to perform power generation. The secondary coolant becomes steam through the heat of the high- temperature, high-pressure primary coolant from the nuclear reactor in the steam generator, drives a steam turbine, is cooled by seawater in a condenser 101 to become condensed water, and is returned to the steam generator again by a condensed water pump. Note that the nuclear power equipment may be nuclear power equipment in which a boiling water reactor (BWR) is used.

[0014] After the secondary coolant drives the steam turbine to perform power generation, the condenser 101 cools the secondary coolant with seawater from sea S to produce condensed water. The steam as the secondary coolant passes through a steam channel 101a to be sent to the condenser 101. The condenser 101 supplies the produced condensed water to the steam generator with a condensed water channel 101b.

[0015] Water Intake Equipment The water intake equipment 10 is used for the plant 100 to take in seawater. The water intake equipment 10 takes in seawater from a water intake target to which the plant 100 (the nuclear power equipment) is adjacent, which is the sea S in the present embodiment, supplies the seawater taken in to the condenser 101, and discharges the seawater discharged from the condenser 101 to the adsorption unit 30. The water intake equipment 10 includes a water intake channel 12, a screen 14, a water discharge channel 16, and a pump P.

[0016] The water intake channel 12 is a water channel one end of which connects to the sea S and the other end of which connects to the condenser 101. The water intake channel 12, into which the seawater from the sea S flows, supplies the seawater to the condenser 101. The water intake channel 12 in its certain range from the side connected to the condenser 101 is a duct. The water intake channel 12 in its part connected to the sea S may be, for example, a water channel the upper face of which is open.

[0017] The screen 14 is provided midway in the water intake channel 12. The screen 14 is a mesh-like member. The screen 14 removes foreign matter contained in the seawater. The seawater passes through the screen 14 and flows into the condenser 101 by the pump P provided over there.

[0018] One end of the water discharge channel 16 connects to the condenser 101, and the other end thereof connects to the adsorption unit 30. The water discharge channel 16 has, for example, a hollow cylindrical shape in its part connected to the condenser 101, and the seawater having cooled the secondary coolant in the condenser 101 flows toward the adsorption unit 30. In other words, the water discharge channel 16 is said to be a pipe connecting the water intake equipment 10 and the adsorption unit 30 to each other.

[0019] The pump P causes the seawater taken in from the water intake channel 12 to flow to the condenser 101. The pump P connects to a drive unit (not illustrated). When the drive unit is driven, the pump P operates.

[0020] Adsorbent Storage Tank The adsorbent storage tank 20 stores therein an adsorbent adsorbing the target component in the solution (the seawater). The adsorbent storage tank 20 supplies the adsorbent to the mixing tank. The adsorbent storage tank 20, under the control of the controller 90, supplies the stored adsorbent to the mixing tank. For example, the adsorbent storage tank 20 is provided with a pipe connected to the mixing tank and a valve provided in the pipe, and the controller 90 controls the opening and closing of the valve to control the supply of the adsorbent inside the adsorbent storage tank 20 to the mixing tank. In the present embodiment, the adsorbent storage tank 20 stores therein the adsorbent and liquid in a mixed manner. That is, the adsorbent storage tank 20 stores therein the adsorbent with the adsorbent contained in the liquid. The liquid in this example may be any liquid and may be, for example, water.

[0021] The following describes the adsorbent. The adsorbent is a substance adsorbing the target component (the resource) contained in the solution (for example, the seawater). The adsorbent adsorbs, for example, the target component contained in the seawater in ionic form. The adsorbent may be, for example, powdery. The adsorbent may be any substance that can adsorb the target component. For example, when the target component to be recovered is lithium, manganese oxide may be used as the adsorbent. For example, in this case, the adsorbent is preferably a manganese oxide formed with an opening large enough to cause lithium ions to enter so that lithium ions can be collected. For example, the adsorbent is preferably a spinel-type manganese oxide (<semantics>λ<annotation encoding="application / x-tex">\lambda< / annotation>< / semantics>-MnO2) or iron phosphate (FePO4). For example, when the target component is uranium, an adsorbent (braid) different from manganese oxide may be used. For the adsorbent, a plurality of the adsorbents may be used. However, the adsorbent is not limited to the manganese oxide exclusive for recovering lithium or the braid for recovering uranium and may be an adsorbent having a structure suitable for the resource to be recovered. For example, the adsorbent may be a general manganese oxide, not the manganese oxide exclusive for recovering lithium. This can also adsorb resources other than lithium with manganese oxide.

[0022] Adsorption Unit The adsorption unit 30 is a unit adding the adsorbent to the solution (the seawater) to produce an adsorption liquid containing the solution and the adsorbent.

[0023] The adsorption unit 30 is supplied with the seawater as the solution taken in to the water intake equipment 10 via the water discharge channel 16. That is, the seawater taken in to the water intake equipment 10 is subjected to heat exchange in the condenser 101 and then flows into the adsorption unit 30 through the water discharge channel 16. The adsorption unit 30 is also supplied with the adsorbent from the adsorbent storage tank 20. With this, inside the adsorption unit 30, the adsorbent is added to the seawater, and the adsorption liquid containing the seawater and the adsorbent is produced. Note that, for example, a stirring machine stirring the seawater and the adsorbent may be provided inside the adsorption unit 30.

[0024] Note that inside the adsorption unit 30, with the adsorbent added to the seawater, the seawater to which the adsorbent is added (the adsorption liquid) is preferably stored for a certain period (for example, about a few days to 14 days). By thus storing the adsorption liquid for the certain period, the target component can properly be adsorbed to the adsorbent. When the seawater is thus stored for the certain period, while the seawater is stored in one adsorption unit 30, the seawater can be taken in to another adsorption unit 30, to which the adsorbent can be added. That is, the target component recovery system 1 can efficiently perform recovery processing by taking in the seawater also to the other adsorption unit 30 while taking in the seawater to the one adsorption unit 30. Thus, the target component recovery system 1 is preferably provided with a plurality of the adsorption units 30. More specifically, after the seawater is taken in to the adsorption unit 30, to which the adsorbent is added, while the supply of the seawater to the adsorption unit 30 is stopped, the seawater may be taken in to the other adsorption unit 30. By performing this operation to the adsorption units 30, the target component can efficiently be recovered.

[0025] Lithium Desorption Unit In the lithium desorption unit 40, one end is connected to the adsorption unit 30, and another end is connected to the target component recovery unit 50. The lithium desorption unit 40 is supplied with the adsorption liquid produced in the adsorption unit 30 from the adsorption unit 30.

[0026] FIG. 3 is a schematic diagram of a structure of the lithium desorption unit. The lithium desorption unit 40, when a current passes therethrough, desorbs lithium ions (Li+) from the adsorbent through electrolysis. The lithium desorption unit 40 produces a lithium compound from the desorbed lithium ions. The electrolysis and the production of the lithium compound will be described later. The lithium desorption unit 40 includes a power source unit 410 and a main body 420.

[0027] The power source unit 410 includes an electric wire 411 and a power source 412. The electric wire 411 connects a positive electrode 421 and a negative electrode 422 of the main body 420 to each other. The power source 412 is provided midway in the electric wire 411. The positive side of the power source 412 connects to the positive electrode 421 of the main body 420, and the negative side thereof connects to the negative electrode 422 of the main body 420. The power source unit 410, when a current passes therethrough, divides the voltage applied to the power source 412 to the main body 420.

[0028] The main body 420 includes the positive electrode 421, the negative electrode 422, an adsorption layer 424, a substance layer 428, a bonding layer 440, a first permeable membrane 450, and a second permeable membrane 460.

[0029] The positive electrode 421 and the negative electrode 422 are the electrodes of the lithium desorption unit 40 and have a plate shape. When voltage is applied to the positive electrode 421 and the negative electrode 422, the voltage is applied to the layers of the main body 420.

[0030] The adsorption layer 424 is provided between the positive electrode 421 and the negative electrode 422. The adsorption layer 424 is provided in contact with the positive electrode 421. The adsorption layer 424 is supplied with the adsorbent adsorbing lithium ions. The adsorption layer 424 is supplied with liquid. This enables the adsorbent to flow inside the adsorption layer 424. The adsorption layer 424 moves lithium ions from manganese oxide contained in the adsorbent to the bonding layer 440. The lithium ions desorbed from the adsorbent in the adsorption layer 424 are attracted toward the negative electrode 422 through the force of an electric field formed between the positive electrode 421 and the negative electrode 422 and passed through the first permeable membrane 450 to move toward the negative electrode 422 (the bonding layer 440). In other words, in the adsorption layer 424, when each voltage is applied to the positive electrode 421 and the negative electrode 422 of the lithium desorption unit 40, the lithium ions adhering to the adsorbent move to the bonding layer 440.

[0031] The substance layer 428 is provided between the adsorption layer 424 and the negative electrode 422. The substance layer 428 is supplied with a substance to be electrolyzed. The substance layer 428 electrolyzes the supplied substance when each voltage is applied to the positive electrode 421 and the negative electrode 422. Hydrogen ions generated by the electrolysis become hydrogen gas in the negative electrode 422, and a gas recovery unit 429 recovering unwanted hydrogen gas may be connected to the substance layer 428.

[0032] The bonding layer 440 is provided between the adsorption layer 424 and the substance layer 428. The bonding layer 440 is supplied with an electrolytic solution. The bonding layer 440 is supplied with the lithium ions having passed through the first permeable membrane 450 and negative ions having passed through the second permeable membrane 460. The bonding layer 440 produces a lithium compound in which the lithium ions and the negative ions bond to each other in the electrolytic solution.

[0033] The first permeable membrane 450 is provided between the adsorption layer 424 and the bonding layer 440. The first permeable membrane 450 is a separator passing the target component (lithium ions). The first permeable membrane 450 is preferably a membrane selectively passing a target substance and inhibiting other substances from moving toward the positive electrode 421. The first permeable membrane 450 is, for example, a cation exchange membrane passing positive ions and not passing negative ions. The first permeable membrane 450 of the present embodiment includes a lithium separator 452 separating lithium ions from the adsorbent. For the lithium separator 452, various separators disposed between a positive electrode and a negative electrode of lithium-ion secondary batteries can be used. The first permeable membrane 450 includes the lithium separator 452 and can thereby, when positive ions other than the lithium ions generated inside the adsorption layer 424, or more precisely, positive ions larger than the lithium ions are generated, inhibit the generated positive ions from moving to the bonding layer 440. For the first permeable membrane 450, any membrane can be used so long as it is a membrane that can selectively pass lithium, and it may be either the lithium separator 452 alone or the cation exchange membrane alone.

[0034] The second permeable membrane 460 is provided between the substance layer 428 and the bonding layer 440. The second permeable membrane 460 is a membrane passing negative ions and not passing positive ions. The second permeable membrane 460 is an anion exchange membrane. The second permeable membrane 460 passes generated ions from the negative electrode 422 toward the positive electrode 421. In other words, the second permeable membrane 460 passes negative ions ionized in the substance layer 428 to the bonding layer 440 and does not pass positive ions ionized in the substance layer 428 to the bonding layer 440.

[0035] The substance layer 428 has a separation membrane 430. The separation membrane 430 is disposed between the negative electrode 422 of the substance layer 428 and the second permeable membrane 460. The separation membrane 430 separates the substance layer 428 into two areas between the negative electrode 422 and the second permeable membrane 460. The separation membrane 430 is a laminated membrane with an anion exchange membrane disposed closer to the positive electrode 421 with a cation exchange membrane disposed closer to the negative electrode 422, and with the two membranes being in contact with each other. The separation membrane 430 is, for example, a bipolar membrane, which passes hydrogen ions toward the negative electrode, passes hydroxide ions toward the positive electrode, and does not pass water molecules. In the separation membrane 430, the electrolysis of water occurs even without an ionic component for electric conduction. The separation membrane 430 enables hydroxide ions to move toward the positive electrode 421 and enables hydrogen ions to move toward the negative electrode 422 among the ions of water electrolyzed by the separation membrane 430. The separation membrane 430 separates the electrolyzed ions of the substance layer 428 so as to be unevenly present in their respective areas.

[0036] Electrolysis and Production of Lithium Compound The following describes the electrolysis and the production of the lithium compound executed by the lithium desorption unit 40. The lithium desorption unit 40 according to the present disclosure produces, for example, lithium hydroxide. The following describes processing for producing it.

[0037] Production of Lithium Hydroxide In the lithium desorption unit 40, the adsorption layer 424 is supplied with a substance containing lithium to be separated. In the present embodiment, the adsorbent adsorbing lithium contained in seawater is filled. The lithium desorption unit 40 supplies water as the substance to be electrolyzed to the substance layer 428.

[0038] The lithium desorption unit 40 applies a certain voltage to the positive electrode 421 and the negative electrode 422 of the main body 420. In the lithium desorption unit 40, by applying the certain voltage to the positive electrode 421 and the negative electrode 422, lithium desorption from the adsorbent occurs in the adsorption layer 424 and electrolysis occurs in the substance layer 428. In the adsorption layer 424, lithium becomes lithium ions, which pass through the first permeable membrane 450 and move to the bonding layer 440.

[0039] The substance layer 428 electrolyzes water into hydroxide ions (OH-) and hydrogen ions (H+). The hydroxide ions (OH-) produced by the electrolysis by the substance layer 428 move to the bonding layer 440 via the second permeable membrane 460. The hydrogen ions (H+) produced in the substance layer 428 become hydrogen gas in the negative electrode 422, which is recovered by the gas recovery unit 429.

[0040] The bonding layer 440 of the lithium desorption unit 40 is supplied with the lithium ions having passed through the first permeable membrane 450 and the 11 hydroxide ions having passed through the second permeable membrane 460. In the bonding layer 440, the lithium ions and the hydroxide ions bond to each other to produce lithium hydroxide.

[0041] Adsorbent Recovery Unit An adsorbent recovery unit 42 is connected to the lithium desorption unit 40. The adsorbent recovery unit 42 recovers the adsorbent contained in waste liquid, which is the adsorption liquid after the target component of the seawater has been desorbed by the lithium desorption unit 40. The adsorbent recovery unit 42 has, for example, a tank, in which a filter for filtering the adsorbent and a mechanism for supplying the filtered adsorbent to the adsorbent storage tank 20 are provided. The adsorbent recovery unit 42 supplies the filtered adsorbent to the adsorbent storage tank 20. This enables the adsorbent to be used again. The adsorbent recovery unit 42 supplies filtered waste liquid to the waste liquid processing unit 43. Note that the adsorbent recovery unit 42 is not necessarily provided.

[0042] Waste Liquid Processing Unit In the waste liquid processing unit 43, one end is connected to the adsorbent recovery unit 42, and another end is connected to the sea S. The waste liquid processing unit 43 processes the waste liquid after the adsorbent has been recovered by the adsorbent recovery unit 42 to a state of being able to be returned to the sea S and discharges the processed waste liquid into the sea S. Note that when the adsorption unit 30 processes the waste liquid, one end of the waste liquid processing unit 43 is connected to the adsorption unit 30, and another end is connected to the sea S. In this case, the waste liquid flows from the adsorption unit 30 to the waste liquid processing unit 43, and the waste liquid processing unit 43 processes the waste liquid and discharges the processed waste liquid into the sea S.

[0043] Controller The controller 90 is an arithmetic unit including a central processing unit (CPU), a storage unit, and the like. The controller 90 connects to the adsorbent storage tank 20, the adsorption unit 30, the adsorbent recovery unit 42, the waste liquid processing unit 43, the lithium desorption unit 40, the target component recovery unit 50, and the pump P. The controller 90 controls the functions of the connected units.

[0044] As described above, the lithium desorption unit 40 according to the present embodiment is provided with the positive electrode 421 and the negative electrode 422. The lithium desorption unit 40 also has the adsorption layer 424 provided between the positive electrode 421 and the negative electrode 422 and supplied with the adsorbent adsorbing lithium ions, the substance layer 428 provided between the adsorption layer 424 and the negative electrode 422 and supplied with the substance to be electrolyzed, and the bonding layer 440 provided between the adsorption layer 424 and the substance layer 428. Furthermore, the lithium desorption unit 40 has the first permeable membrane 450 provided between the adsorption layer 424 and the bonding layer 440 to pass the lithium ions separated from the adsorbent in the adsorption layer 424 and the second permeable membrane 460 provided between the substance layer 428 and the bonding layer 440 to pass the negative ions ionized from the substance layer 428 in the substance layer 428. In the lithium desorption unit 40, the lithium ions having passed through the first permeable membrane 450 and the negative ions having passed through the second permeable membrane 460 are supplied in the bonding layer 440 to produce the lithium compound in which the lithium ions and the negative ions bond to each other. This can properly desorb lithium.

[0045] In addition, the lithium desorption unit 40 can vary the lithium compound that can be produced in the bonding layer 440 by varying the substance to be supplied to the substance layer 428.

[0046] Production of Lithium Carbonate FIG. 4 is a schematic diagram of another example of the structure of the lithium desorption unit. The above embodiment has been described as a case in which lithium hydroxide is produced, but the present disclosure is not limited to this example. The lithium desorption unit illustrated in FIG. 4 produces lithium carbonate. In the lithium desorption unit illustrated in FIG. 4, carbonic acid (H2CO3) is supplied to the substance layer 428 as the substance to be electrolyzed. The substance layer 428 is supplied with an electrolytic solution. In the substance layer 428, when a current is passed through the main body 420, carbonate ions (CO3-) are produced by the electrolysis of the electrolytic solution. The substance layer 428 supplies hydrogen gas to the gas recovery unit 429 (closer to the negative electrode 422) while generating carbonate ions (CO3-) reacting with lithium ions. The substance layer 428 supplies the carbonate ions generated by the electrolysis to the bonding layer 440 via the second permeable membrane 460.

[0047] The bonding layer 440 is supplied with the lithium ions having passed through the first permeable membrane 450 and the carbonate ions having passed through the second permeable membrane 460. The bonding layer 440 produces lithium carbonate in which the lithium ions and the carbonate ions bond to each other.

[0048] The product produced in the bonding layer 440 of the lithium desorption unit 40 is supplied to the target component recovery unit 50 and is recovered by the target component recovery unit 50.

[0049] Second Embodiment FIG. 5 is a schematic diagram of an entire configuration of a target component recovery system according to a second embodiment. In the present embodiment, by heating the adsorption liquid and the like utilizing the exhausted heat of the plant 100, the efficiency of recovering lithium as the target component is improved. In the second embodiment, the same components as those of the first embodiment are denoted by the same symbols, and detailed descriptions thereof are omitted.

[0050] This target component recovery system 1A includes the plant 100, the water intake equipment 10, the adsorbent storage tank 20, the adsorbent separation unit, the adsorption unit 30, the adsorbent recovery unit 42, the waste liquid processing unit 43, the lithium desorption unit 40, the target component recovery unit 50, a heat exchanger 80, and a controller 90A. The target component recovery system 1A is a system performing certain treatment on a target component (a resource) contained in a solution to recover the target component.

[0051] Heat Exchanger The temperature of the seawater taken in from the water intake equipment 10 is not always constant due to seasonal and other effects. Thus, the temperature of the seawater may be lowered, and even when the adsorbent is added, the efficiency of recovering the target component may be reduced. Given this, in the present embodiment, by heating the seawater using the heat exchanger 80, the reduction in the efficiency of recovering the target component is inhibited, and the target component can properly be recovered. The following describes the heat exchanger 80.

[0052] The heat exchanger 80 performs heat exchange between the exhausted heat medium from the plant 100 and the seawater taken in to the water intake equipment 10 to heat the seawater taken in to the water intake equipment 10. The heat exchanger 80 is connected to a pipe through which the exhausted heat medium from the plant 100 flows and is supplied with the exhausted heat medium from the pipe. The heat exchanger 80 is disposed at a position at which the seawater taken in to the water intake equipment 10 can be heated. This enables the heat exchanger 80 to heat the seawater taken in to the water intake equipment 10 with the exhausted heat medium from the plant 100. The seawater taken in to the water intake equipment 10 in this example refers to the seawater (or the adsorption liquid) after being taken in to the water intake equipment 10 and before being supplied to the lithium desorption unit 40. That is, the heat exchanger 80 heats the seawater (or the adsorption liquid) between the position at which the water intake equipment 10 is provided and the position at which the lithium desorption unit 40 is provided in a direction in which the seawater (or the adsorption liquid) flows inside the target component recovery system 1A. The heat exchanger 80 more preferably heats the seawater (or the adsorption liquid) after being discharged from the condenser 101 and before being supplied to the lithium desorption unit 40. Thus, by heating the seawater (or the adsorption liquid) by the heat exchanger 80, the seawater can properly be heated utilizing the exhausted heat from the plant 100, and the target component can properly be recovered.

[0053] In the present embodiment, the heat exchanger 80 preferably heats the seawater (the adsorption liquid) inside the adsorption unit 30. That is, the heat exchanger 80 is disposed at a position at which the seawater inside the adsorption unit 30 can be heated. For example, the heat exchanger 80 is disposed within a certain distance range of the adsorption unit 30 (within a distance range sufficient to enable heating of the seawater inside the adsorption unit 30). For example, the heat exchanger 80 may be disposed at a position in contact with an outer wall of the adsorption unit 30 or inside the adsorption unit 30.

[0054] The heat exchanger 80 preferably heats the seawater taken in to the water intake equipment 10 (in this example, the seawater inside the adsorption unit 30) to maintain the temperature of the seawater within a proper temperature range. The proper temperature range of the seawater in this example may be set as appropriate. For example, the heat exchanger 80 controls the degree of heating in accordance with the flow rate of the seawater taken in by the pump P to perform heating so as to maintain the proper temperature range of the seawater. For example, the heat exchanger 80 may be provided with a valve that can control the amount of the exhausted heat medium supplied to the heat exchanger 80, and the controller 90A may control the amount of the exhausted heat medium supplied by controlling the opening and closing of the valve in accordance with the flow rate of the seawater taken in by the pump P to control the degree of heating. For example, when the exhausted heat medium is discharged from a plurality of places of the plant 100, pipes from the respective places of the plant 100 may be able to be connected to the heat exchanger 80. In this case, for example, the controller 90A selects a pipe to be connected to the heat exchanger 80 among the pipes from the respective places of the plant 100 in accordance with the flow rate of the seawater taken in by the pump P and connects the selected pipe and the heat exchanger 80 to each other. This can supply the exhausted heat medium having a heat value corresponding to the flow rate of the seawater, and thus the seawater can properly be heated.

[0055] Note that the heat exchanger 80 is not limited to heating the seawater inside the adsorption unit 30 and may, for example, heat the seawater flowing through the pipe (the water discharge channel) 16 connected between the water intake equipment 10 and the adsorption unit 30 to each other. In this case, the heat exchanger 80 is disposed at a position at which the seawater inside the water discharge channel 16 can be heated. For example, the heat exchanger 80 is disposed within a certain distance range of the water discharge channel 16 (within a distance range sufficient to enable heating of the seawater inside the water discharge channel 16). For example, the heat exchanger 80 may be disposed at a position in contact with the outer periphery of the water discharge channel 16.

[0056] A plurality of heat exchangers may be provided. In this case, for example, a heat exchanger 80 heating the seawater (the adsorption liquid) inside the adsorption unit 30 and a heat exchanger 80 heating the seawater inside the water discharge channel 16 may be provided.

[0057] Controller The controller 90A is an arithmetic unit including a central processing unit (CPU), a storage unit, and the like. The controller 90A connects to the adsorbent storage tank 20, the mixing tank, the adsorbent separation unit, the adsorption unit 30, the adsorbent recovery unit 42, the waste liquid processing unit 43, the lithium desorption unit 40, the heat exchanger 80, and the pump P. The controller 90A controls the functions of the connected units. For example, the controller 90A controls heat exchange (the amount of exhausted heat) by the heat exchanger 80.

[0058] The adsorbent recovery unit 42 may be connected to the adsorption unit 30. Thus, the target component recovery system 1A can properly recover the target component contained in the seawater by performing heat exchange by the heat exchanger 80.

[0059] Effects A lithium desorption unit according to a first aspect of the present disclosure includes the positive electrode 421, the negative electrode 422, the adsorption layer 424 provided between the positive electrode 421 and the negative electrode 422 and supplied with an adsorbent adsorbing lithium ions, the substance layer 428 provided between the adsorption layer 424 and the negative electrode 422 and supplied with a substance to be electrolyzed, the bonding layer 440 provided between the adsorption layer 424 and the substance layer 428, the first permeable membrane 450 provided between the adsorption layer 424 and the bonding layer 440 and passing lithium ions separated from the adsorbent in the adsorption layer 424, and the second permeable membrane 460 provided between the substance layer 428 and the bonding layer 440 and passing negative ions ionized from the substance layer 428 in the substance layer 428. The bonding layer 440 is supplied with the lithium ions having passed through the first permeable membrane 450 and the negative ions having passed through the second permeable membrane 460 to produce a lithium compound in which the lithium ions and the negative ions bond to each other. In this way, lithium can be desorbed from the adsorbent without using any acid, and a reduction in the absorption rate of the adsorbent can be inhibited. Thus, lithium can properly be desorbed.

[0060] A lithium desorption unit according to a second aspect of the present disclosure is the lithium desorption unit according to the first aspect, in which the substance layer 428 is supplied with water, and the bonding layer 440 is supplied with hydroxide ions having passed through the second permeable membrane 460 to produce lithium hydroxide. This can recover lithium from lithium hydroxide.

[0061] A lithium desorption unit according to a third aspect of the present disclosure is the lithium desorption unit according to the first aspect or the second aspect, in which the substance layer 428 is supplied with carbonic acid, and the bonding layer 440 is supplied with carbonate ions having passed through the second permeable membrane 460 to produce lithium carbonate. This can recover lithium from lithium carbonate.

[0062] A lithium desorption unit according to a fourth aspect of the present disclosure is the lithium desorption unit according to any one of the first aspect to the third aspect, in which the adsorbent is a spinel-type manganese oxide and iron phosphate. This can properly desorb lithium.

Claims

1. A lithium desorption unit comprising: a positive electrode; a negative electrode; an adsorption layer provided between the positive electrode and the negative electrode and supplied with an adsorbent adsorbing lithium ions; a substance layer provided between the adsorption layer and the negative electrode and supplied with a substance to be electrolyzed; a bonding layer provided between the adsorption layer and the substance layer; a first permeable membrane provided between the adsorption layer and the bonding layer to pass lithium ions separated from the adsorbent in the adsorption layer to the bonding layer; and a second permeable membrane provided between the substance layer and the bonding layer to pass negative ions ionized from the substance layer in the substance layer and not to pass positive ions, the bonding layer being supplied with the lithium ions having passed through the first permeable membrane and the negative ions having passed through the second permeable membrane to produce a lithium compound in which the lithium ions and the negative ions bond to each other.

2. The lithium desorption unit according to claim 1, wherein the substance layer is supplied with water, and the bonding layer is supplied with hydroxide ions having passed through the second permeable membrane from the substance layer to produce lithium hydroxide.

3. The lithium desorption unit according to claim 1 or 2, wherein the substance layer is supplied with carbonic acid, and the bonding layer is supplied with carbonate ions having passed through the second permeable membrane from the substance layer to produce lithium carbonate.

4. The lithium desorption unit according to claim 1 or 2, wherein the adsorbent is a spinel-type manganese oxide and iron phosphate.