Capacitive deionization water purification system using citric circulation water in circulation tank for desorption process, and control method therefor

Abstract

Provided are a capacitive deionization (CDI) water purification system using citric circulation water in a circulation tank for a desorption process, and a control method therefor, the CDI water purification system being implemented to separately include a circulation tank capable of supplying circulation water used only for ion desorption in a desorption mode during CDI water purification in which an adsorption process and a desorption process are repeatedly performed, and using a citric acid solution so as to prevent heavy metals having low solubility from being precipitated in a CDI cell and, simultaneously, enable same to be enriched in the circulation tank at a high concentration.

Description

Capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process and its control method

[0001] The present invention relates to a capacitive deionization water treatment system, and more particularly, to a capacitive deionization water treatment system having a circulation tank for a desorption process to circulate treated water only in a desorption mode during capacitive deionization (CDI) water treatment in which an adsorption process and a desorption process are repeatedly performed, and a control method thereof, in which a citric acid solution is used to prevent heavy metals with low solubility from being precipitated in a CDI cell, using citric acid circulating water in a circulation tank for a desorption process.

[0002] In general, desalination water treatment technology refers to a technology that removes salt components such as nitrates and heavy metals from water with high electrical conductivity and uses it for domestic or industrial purposes.

[0003] Because these salt components are dissolved in water in the form of ions, they are difficult to remove through water purification using a general filter.

[0004] Therefore, a desalination technology capable of effectively removing these salt components was needed.

[0005] Conventional desalination technologies include reverse osmosis and distillation.

[0006] However, in the case of reverse osmosis membranes, there are disadvantages such as high energy consumption due to the use of high-pressure pumps and difficulty in maintenance due to membrane fouling.

[0007] Additionally, the evaporation method has the disadvantage of requiring high heat and taking up a large area for installation.

[0008] To address these shortcomings, capacitive deionization (CDI) technology, which removes ionic substances using electrochemical methods, has been developed in earnest since the 1990s.

[0009] Specifically, this capacitive deionization (CDI) technology is a technology that removes ionic substances in influent water by utilizing ion adsorption and desorption reactions in the electric double layer (EDL) formed at the interface of charged electrodes.

[0010] When explaining the adsorption and desorption processes of a typical capacitive desalination technology, first, when a voltage is applied within a potential range where no electrolytic reaction of water occurs, a certain amount of charge is charged to the electrode.

[0011] At this time, when brine water containing ions is passed through the charged electrodes, ions with opposite charges to the charged electrodes move to each electrode by electrostatic force and are adsorbed on the electrode surface, and the water passing through the electrodes becomes desalinated water with the ions removed.

[0012] In particular, since the amount of ions adsorbed on the electrode is determined by the capacitance of the electrode used, a porous carbon electrode with a large specific surface area is typically used as the electrode used for capacitive desalination.

[0013] Additionally, when the adsorption capacity of the electrode becomes saturated, it cannot adsorb any more ions, and the ions in the influent are discharged as they are into the effluent.

[0014] At this time, in order to desorb the ions adsorbed on the electrodes, the electrodes are short-circuited or a potential opposite to the adsorption potential is applied to the electrodes, so that the electrodes lose charge or acquire an opposite charge, and thereafter, the ions adsorbed in the adsorption process are quickly desorbed, resulting in regeneration of the electrodes.

[0015] Additionally, the desorption of ions from each CDI cell within a capacitive deionization (CDI) module can be broadly divided into two mechanisms.

[0016] For example, one is the movement of ions from the CDI electrode where adsorption has occurred to the spacer, and the other is the movement of ions from the spacer out of the CDI module.

[0017] However, in the case of the capacitive deionization (CDI) process, a problem may arise that reduces efficiency because ions do not completely separate.

[0018] Meanwhile, Figure 1 is a drawing showing a general MCDI process.

[0019] As a form in which an ion exchange membrane is combined with an electrode to compensate for the disadvantage of reducing efficiency due to the aforementioned ions not being completely separated, membrane capacitive deionization (MCDI) has been actively researched since the mid-2000s to the present, as shown in Fig. 1.

[0020] As mentioned above, the capacitive deionization (CDI) technology is very easy to operate because adsorption and desorption occur by changing only the potential of the electrode.

[0021] Additionally, it is known as an environmentally friendly desalination process because it does not emit environmental pollutants during the desalination process.

[0022] In addition, this capacitive desalination technology is easy to maintain because it does not require separate chemicals for adsorption and desorption, unlike other existing desalination technologies.

[0023] In terms of operating method, it has the advantage of low energy consumption because it can be operated at a low voltage, for example, below 1.5 V, where water hydrolysis does not occur.

[0024] However, the conventional capacitive desalination (CDI) process requires continuous supply of feed water because it repeats adsorption and desorption using the same feed water.

[0025] This causes a problem in that the product water recovery rate, which indicates the amount of product water compared to the supply water, is low.

[0026] This is very disadvantageous for operating the capacitor discharge desalination (CDI) process in cases where the amount of water supply is limited, such as groundwater.

[0027] To solve these problems, there are efforts to increase the recovery rate by operating the process by reducing the flow rate and velocity during ion desorption in the capacitive deionization (CDI) process. However, there is a limitation in that the recovery rate does not increase significantly because the desorption is performed using the same feed water.

[0028] Meanwhile, as a prior art related to the aforementioned CDI water treatment device, an invention entitled “Capacitive deionization water treatment device and its control method” is disclosed in Korean Patent No. 10-2275921, which will be described with reference to FIGS. 2 to 4.

[0029] Figure 2 is a schematic diagram showing a conventional capacitive deionization water treatment device.

[0030] Figure 3 is a drawing for explaining the adsorption process and desorption process of the capacitive deionization water treatment device illustrated in Figure 2.

[0031] Figure 4 is an operational flow chart for explaining a control method of a capacitive deionization water treatment device according to a conventional technology.

[0032] Referring to FIGS. 2 and 3, a conventional capacitive deionization water treatment device may include a CDI module (30), a purified water supply valve (40), a concentrated water discharge valve (50), an electrical conductivity meter (10), a control unit (20), and a treated water circulation unit (60).

[0033] The CDI module (30) purifies water by adsorbing and removing ions in the inflow water as shown in a) of Fig. 5 in the case of the water purification mode (adsorption mode) by the capacitive deionization method.

[0034] In addition, in the case of regeneration mode (desorption mode), ions adsorbed on the electrode can be desorbed and regenerated, as shown in b) of Fig. 3.

[0035] That is, the CDI module (30) may include an anode to which a positive voltage (+) is applied, a cathode to which a negative voltage (-) is applied, and a spacer provided between the anode and the cathode to allow inflow water to flow.

[0036] Specifically, as shown in a) of Fig. 3, in the water purification process, water purification is performed by utilizing the adsorption reaction of ions by electrical attraction in the electric double layer formed on the electrode surface as an electrostatic potential is applied, and purified water (or product water), which is the treated water, is discharged.

[0037] In addition, as shown in b) of Fig. 3, in the regeneration process consisting of steps S1 to S5, regeneration proceeds by desorbing ions adsorbed on the electrode as OV or reverse potential is applied, and concentrated wastewater, which is treated water, is discharged.

[0038] In other words, purified water discharged as treated water in the water purification process in the CDI module (30) flows into the water purification tank (70) and is stored, and also, concentrated wastewater in the regeneration process flows into the concentrated wastewater tank through the concentrated water discharge valve (50) and is stored.

[0039] The purified water supply valve (40) can block the inflow of purified water from the inflow tank to the CDI module (30) and allow purified water in the purified water tank (70) to flow into the CDI module (30).

[0040] The concentrated water discharge valve (50) changes the path of the treated water from the CDI module (30), and in the purification process, the treated water flows to the purification tank (70), and in the regeneration process,

[0041] As shown in b) of Fig. 3, the treated water can be blocked or diverted to a concentrated wastewater tank to allow the concentrated wastewater to be discharged.

[0042] The electrical conductivity meter (10) can determine the end of the regeneration process by measuring the electrical conductivity of the treated water in the CDI module (30) and providing it to the control unit (20).

[0043] The treated water circulation unit (60) can recirculate the treated water discharged from the CDI module (30) into the CDI module (30) to allow the treated water to circulate.

[0044] Here, the treated water circulation unit (60) can circulate the treated water by including a blocking valve (62) for blocking the treated water discharged from the CDI module (30) and a circulation pump (61) for introducing the treated water discharged from the CDI module (30) into the CDI module (30), as shown in b) of FIG. 3.

[0045] The control unit (20) operates the purified water supply valve (40) in the regeneration process consisting of steps S1 to S5 in b) of FIG. 3 to supply a set amount of purified water to the CDI module (30) and operates the CDI module (30) in regeneration mode.

[0046] Afterwards, if the increase in electrical conductivity according to the electrical conductivity input from the electrical conductivity meter (10) is below the set value, the concentrated water discharge valve (50) is operated to discharge the treated water, and then the mode can be switched to the water purification mode.

[0047] In addition, the control unit (20) controls the water supply valve (40) to be blocked in the water purification process illustrated in a) of FIG. 3 so that the inflow water flows into the CDI module (30), controls the concentrated water discharge valve (50) to be blocked so that the treated water flows into the water purification tank (70), and operates the CDI module (30) in the water purification mode for a set time.

[0048] When examining the electrical conductivity of the treated water in this CDI module (30), the conductivity of the influent water is maintained constant, and when the purification process is performed for a set time, the electrical conductivity initially drops and then remains constant.

[0049] Afterwards, if the change in the electrical conductivity of the concentrated wastewater in the regeneration process is below the set value after the set time has elapsed,

[0050] That is, when there is little change, the concentrated wastewater is discharged, and after a sharp drop, the water is returned to the inflow stream, and the purification process is performed, thereby repeating the aforementioned process.

[0051] According to the conventional capacitive deionization water treatment device, the amount of purified water used is minimized by circulating a set amount of purified water in the regeneration process using the capacitive deionization method and performing the regeneration process.

[0052] Not only can productivity be improved by reducing the amount of concentrated wastewater, but operating efficiency can also be improved by optimizing the regeneration time by performing the regeneration process based on electrical conductivity.

[0053] Also, referring to FIG. 4, the control method of the conventional capacitive deionization water treatment device is as follows:

[0054] First, the control unit (20) operates the purified water supply valve (40) in the regeneration process (or desorption process) to supply a set amount of purified water to the CDI module (30) (S11).

[0055] Afterwards, after supplying water to the CDI module (30), the control unit (20) operates the CDI module (30) in regeneration mode (S12).

[0056] Next, after operating the CDI module (30) in regeneration mode, the control unit (20) can cause the treated water to circulate to the CDI module (30) through the treated water circulation unit (60) (S13).

[0057] Next, while operating the CDI module (30) in regeneration mode, the control unit (20) receives the electrical conductivity of the treated water from the electrical conductivity meter (10) and determines whether the increase in the electrical conductivity is below the set value (S14).

[0058] Thereafter, the control unit (20) determines whether the increase in electrical conductivity is less than or equal to the set value, and if the increase in electrical conductivity exceeds the set value, the control unit (20) returns to step S12 and repeats the aforementioned process to perform the regeneration process.

[0059] On the other hand, if it is determined that the increase in electrical conductivity is less than or equal to the set value, the control unit (20) operates the concentrated water discharge valve (50) to discharge the concentrated wastewater, which is the treated water (S15).

[0060] Next, after discharging the concentrated wastewater, the control unit (20) stops the operation of the purified water supply valve (40) so that the inflow water flows into the CDI module (30) (S16).

[0061] Afterwards, after switching the inflow water to flow into the CDI module, the control unit (20) operates the CDI module (30) in water purification mode (S17).

[0062] Next, after operating the CDI module (30) in the purification mode, the control unit (20) stops the operation of the concentrated water discharge valve (50) to allow the treated water to flow into the purification tank (70) (S18).

[0063] Next, after switching the treated water to flow into the water purification tank (70), the control unit (20) returns to step S16 for a set time and performs the water purification process (or adsorption process) while repeating the aforementioned process (S19).

[0064] In other words, the water purification process of the CDI module according to the conventional technology is a process of continuously circulating the effluent of the CDI module, and when the effluent is continuously circulated and the electrical conductivity is measured and reaches a certain value, the circulated water is discharged as concentrated wastewater through a discharge line.

[0065] The water purification process of a CDI module according to conventional technology repeats the process of taking water from a water purification tank and circulating it through the desorption process of the CDI module n times each time the CDI module is operated in desorption mode (purification mode).

[0066] However, there was a problem that the water recovery rate of the product was reduced because the water was taken from the water purification tank each time, the electrical conductivity was measured, and the circulating water was discarded as concentrated wastewater. Accordingly, the same supply water was used in the CDI module to continuously perform the adsorption and desorption modes.

[0067] As a prior art for solving the problems of the aforementioned capacitor-type deionized water treatment device, the applicant of the present invention has filed a patent application and registered in the Republic of Korea Patent No. 10-2333809, which discloses an invention entitled "Capacitor-type deionized water treatment system having a circulation tank for desorption process and a control method thereof."

[0068] Referring to FIGS. 5 and 6, the present invention is described and incorporated herein by reference.

[0069] Figure 5 is a configuration diagram of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to a conventional technology.

[0070] Figure 6 is a flow chart showing a control method of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to a conventional technology.

[0071] Referring to FIG. 5, a desalination water treatment system (80) having a circulation tank for a desorption process according to a conventional technology repeatedly performs the adsorption process and desorption process shown in a) and b) of FIG. 5.

[0072] As shown in a) of Fig. 5, the adsorption process of the desalination water treatment system having a circulation tank for the desorption process according to the conventional technology is as follows:

[0073] The first switching valve (83) is switched to supply the inflow water to the CDI module (84), and the adsorption mode treated water is discharged in the adsorption mode according to the constant voltage operation of the CDI module (84) to first fill the circulation tank (87) to the full water level.

[0074] Afterwards, the second switching valve (85) is switched to store the production water, which is the adsorption mode treated water flowing out from the CDI module (84) for the preset adsorption time, in the production water tank (86).

[0075] At this time, a water level gauge can be installed in the circulation tank (87) to check the water level of the adsorption mode treated water.

[0076] According to a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to conventional technology, when treating influent containing highly soluble ions such as sodium chloride (NaCl), the operation of the capacitive desalination device is possible while achieving a high recovery rate of produced water through continuous circulation.

[0077] Also, referring to FIG. 6, a control method of a capacitive desalination water treatment system having a circulation tank for a desorption process according to a conventional technology is as follows.

[0078] First, as an adsorption process, the influent stored in the influent tank is supplied to a capacitor deionization (CDI) module (84), and ion adsorption is performed according to the constant voltage operation of the CDI module (84) to discharge adsorption mode treated water (S21).

[0079] At this time, the CDI module (84) is provided with an anode to which a positive voltage (+) is applied, a cathode to which a negative voltage (-) is applied, and a spacer provided between the anode and the cathode to allow the inflow water to flow.

[0080] A positive voltage or a reverse voltage can be applied to the CDI module (84) by a voltage variable corresponding to a CDI drive signal generated from the administrator terminal.

[0081] Next, after the adsorption mode treated water is fully filled in the circulation tank (87), the adsorption mode treated water is introduced into the production water tank (86) and stored for a preset adsorption time (S22).

[0082] Next, when the preset adsorption time has elapsed, as a desorption process, the circulation pump (89) is driven to supply the adsorption mode treated water in the circulation tank (87) to the CDI module (84) (S23).

[0083] Next, ion desorption is performed by reverse voltage operation of the CDI module (84) to discharge desorption mode treated water (S24).

[0084] Next, the concentrated water, which is the desorption mode treatment water, is introduced into the circulation tank (87) (S25).

[0085] Next, the preset desorption time and the electrical conductivity of the concentrated water, which is the ion desorption treatment water, are checked using an electrical conductivity meter (88) (S26). At this time, when the preset desorption time has elapsed and the electrical conductivity has reached the set value, the desorption mode according to the reverse voltage operation of the CDI module (84) is terminated.

[0086] Next, when the electrical conductivity of the concentrated water reaches the set value, the concentrated water in the circulation tank (87) is discharged or released (S27).

[0087] Accordingly, the recovery rate of produced water can be increased by minimizing the discharge of concentrated water by discharging the concentrated water only when the electrical conductivity of the concentrated water, which is the desorption mode treated water introduced into the circulation tank (87), reaches the set value.

[0088] In the case of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to conventional technology,

[0089] In the adsorption mode, the influent is supplied to the CDI module (84), and after adsorption is performed by constant voltage operation of the CDI module (84), the treated water adsorbed in the CDI module (84) is first filled in the circulation tank (87), and then the treated water adsorbed in the CDI module, which is the produced water, is stored in the produced water tank (86).

[0090] Afterwards, in the desorption mode, the adsorbed treated water filled in the circulation tank (87) is supplied again to the CDI module (84), and desorption is performed according to the reverse voltage operation of the CDI module (84).

[0091] By refilling the treated water removed from the CDI module (84) into the circulation tank (87) and discharging the concentrated water filled in the circulation tank only when the electrical conductivity of the concentrated water, which is the removed treated water, reaches a set value, the recovery rate of the produced water through the circulation tank can be increased.

[0092] However, in the case of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to conventional technology, in the case of influent water containing heavy metals with low solubility in addition to highly soluble ions such as sodium chloride (NaCl),

[0093] During the water treatment process, precipitation may occur in each CDI cell of the CDI module (84), and at this time, the liquid may crystallize, making it impossible to operate the equipment.

[0094] Figure 7 is a photograph illustrating a CDI cell in which Ca and Mg are precipitated through a treatment water circulation process according to a conventional technology.

[0095] When a treatment water circulation process according to conventional technology is performed, as shown by reference numeral A in FIG. 7, heavy metals with low solubility, such as calcium (Ca) or magnesium (Mg), may crystallize and precipitate in each CDI cell of the CDI module (84).

[0096] Therefore, when treating influent containing heavy metals with low solubility in addition to highly soluble ions such as sodium chloride (NaCl), a fundamental solution is needed to resolve the problem of heavy metal precipitation occurring in the CDI module (84).

[0097] Meanwhile, as another prior art, Korean Patent Publication No. 2015-61323 discloses an invention entitled “Method for regenerating an electro-absorbing deionizing electrode,” which will be described with reference to FIG. 8.

[0098] The conventional electrosorption deionization electrode regeneration method is a method for treating a fluid containing dissolved solids,

[0099] First, a flow-through capacitor is formed, comprising at least one pair of porous electrodes, each comprising a first electrode and a second electrode, each comprising an electrode material having a surface for electrostatic adsorption of dissolved solids; and a flow path present between the first electrode and the second electrode.

[0100] Next, a fluid containing dissolved solids is supplied through a flow path into a fluid-passing capacitor.

[0101] Next, a potential difference is applied between the first and second electrodes so that the first electrode becomes the anode and the second electrode becomes the cathode, thereby allowing dissolved solids from the fluid in the channel to be adsorbed onto the porous electrodes.

[0102] Next, the potential difference applied between the first electrode and the second electrode is removed, or a first reverse potential difference is applied between the first and second electrodes so that the first electrode becomes a cathode and the second electrode becomes an anode, thereby allowing the dissolved solids adsorbed on the porous electrodes to be desorbed.

[0103] Next, while supplying an acid solution through a flow path into the fluid-flow capacitor, a second reverse potential difference is applied between the first and second electrodes so that the first electrode becomes a cathode and the second electrode becomes an anode, thereby removing the deposits formed inside the fluid-flow capacitor.

[0104] Specifically, FIG. 8 is a schematic diagram showing a sediment removal process in a fluid flow capacitor of an electrosorption deionization unit cell according to a conventional technology, and shows a scale removal mechanism through acid washing under voltage application in an electrosorption deionization system including a charge barrier (ion exchange membrane).

[0105] As shown in Fig. 8, by allowing the acid solution to flow through the flow path and applying a reverse potential difference, electrolysis of water can occur simultaneously at the electrode.

[0106] Since a reverse potential difference is applied under acidic conditions, electrolysis of water can occur at a lower voltage.

[0107] In this way, when an acid solution is allowed to flow while applying a reverse potential, scale can be easily removed even by an acid solution with a relatively low hydrogen ion concentration.

[0108] In addition, since hydrogen ions can be generated by electrolysis of water between the cation exchange membrane and the second electrode, scale deposited on the second electrode, etc. can also be effectively removed.

[0109] Accordingly, according to the conventional electrosorption deionization electrode regeneration method, electrosorption deionization treatment can be performed for a longer period of time without a decrease in ion adsorption efficiency.

[0110] Meanwhile, as another prior art, Republic of Korea Publication Patent No. 2017-2047 discloses an invention entitled “Drinking water and ultrapure water-grade cooling water manufacturing system,” which will be described with reference to FIG. 9.

[0111] Figure 9 is a configuration diagram of a drinking water and ultrapure water-grade cooling water manufacturing system according to conventional technology.

[0112] Referring to Figure 9, the drinking water and ultrapure water-grade cooling water manufacturing system according to the conventional technology is,

[0113] It includes a pre-processing means (91), a CDI means (92) and a post-processing means (94), and the pre-processing means (91) and the post-processing means (94) can be selectively configured with the CDI means (92) as the main component.

[0114] In addition, the detailed configuration of the preprocessing means (91) and the postprocessing means (94) can be appropriately modified as needed.

[0115] The CDI means (92) of the drinking water and ultrapure water-grade cooling water manufacturing system according to the conventional technology comprises a plurality of CDI stacks (91a1, 91a2, 91a3, …, 91ad) connected in parallel to form a CDI device (91), wherein each CDI stack (91a1, 91a2, 91a3, …, 91ad) performs a CDI (Capacitive Deionization) process of a capacitive deionization method.

[0116] At this time, the CDI process is a water treatment method that removes cations and anions using an electrodynamic technique as a technology for desalination and removal and treatment of ionic substances using a non-Faraday electrode.

[0117] The internal configuration of the CDI stack (91a1, 91a2, 91a3, …, 91ad) may include various configurations proposed for the CDI water treatment process,

[0118] This presents a technical idea for effectively utilizing the CDI process, and the detailed configuration for performing the CDI process itself can be selectively modified as needed.

[0119] In addition, in the case of a drinking water and ultrapure water-grade cooling water production system according to a conventional technology, a control valve (91b1, 91b2, 91b3, …, 91bd) for controlling the inflow of seawater or brackish water into each CDI stack (91a1, 91a2, 91a3, …, 91ad) is provided at the front end of each CDI stack (91a1, 91a2, 91a3, …, 91ad), and a control unit (93) for controlling the control valve (91b) is included.

[0120] Specifically, as the CDI stack undergoes an electrical adsorption and desorption process, fouling or scale occurs on the electrodes and ion exchange membranes within the cells stacked within it.

[0121] To remove such contamination, a periodic cleaning process is introduced, in which a cleaning means that supplies a cleaning solution when cleaning the CDI means is connected to the front and rear ends of the CDI means and cleans one or more CDI stacks selected from among the CDI means in a circulating CIP (Cleaning In Place) manner.

[0122] To this end, a CIP tank and CIP pump are installed, and when performing the cleaning process, citric acid, etc. is introduced to remove scale, and also, when performing the cleaning process, sodium hypochlorite (NaOCl), etc. is introduced to control biofouling.

[0123] According to the conventional drinking water and ultrapure water production system, a high-efficiency desalination process can be performed while reducing the power consumption of the seawater desalination process by applying the low-energy desalination technology, capacitor desalination (CDI).

[0124] In particular, by having multiple CDI stacks in parallel and having some CDI stacks and the remaining CDI stacks alternately and continuously perform water treatment processes, the water treatment process can be continuously performed even when some process equipment is being cleaned or repaired.

[0125] As described above, according to conventional technology, when cleaning a CDI cell using citric acid, a predetermined cleaning water is used intermittently rather than circulating water.

[0126] Specifically, as illustrated in FIG. 8, a configuration is separately included for removing internal deposits (scale) of a capacitor while supplying a weak acid solution (pH 3 or lower) containing citric acid into the CDI capacitor.

[0127] In addition, as shown in FIG. 9, a configuration is disclosed for removing biofouling generated in a CDI stack by introducing citric acid during a CDI stack cleaning process.

[0128] According to the conventional technology, a configuration is disclosed for applying citric acid to a CDI water treatment module to clean and wash foreign substances, scale, fouling, precipitation, etc. deposited inside the CDI module.

[0129] However, in the case of conventional technology, a configuration is disclosed in which a citric acid solution is intermittently injected as a cleaning solution only when a single or cleaning is required.

[0130] According to conventional technology, by utilizing the desorption water as circulating water, most of the influent water can be purified as product water, thereby increasing the recovery rate of product water. However, in the case of heavy metals with low solubility, there is a problem in that heavy metals such as calcium (Ca) or magnesium (Mg) are precipitated in the CDI cell, making facility operation impossible.

[0131] The technical problem to be solved by the present invention for solving the above-mentioned problem is to provide a capacitive deionization (CDI) water treatment system having a circulation tank for a desorption process so as to circulate treated water only in a desorption mode during a capacitive deionization (CDI) water treatment in which an adsorption process and a desorption process are repeatedly performed, a capacitive deionization water treatment system using citric acid circulating water in a desorption process circulation tank, which can prevent heavy metals with low solubility from being precipitated in a CDI cell and at the same time concentrate them in a high concentration in the circulation tank, and a control method therefor.

[0132] In order to achieve the above task, the present invention provides a capacitive deionization (CDI) water treatment system having a circulation tank for the desorption process so that treated water is circulated only in the desorption mode during the capacitive deionization (CDI) water treatment in which the adsorption process and the desorption process are repeatedly performed, and uses a citric acid solution to prevent heavy metals with low solubility from being precipitated in the CDI cell.

[0133] According to the present invention, in a capacitive deionization (CDI) water treatment system in which adsorption and desorption processes are repeatedly performed, a circulation tank for the desorption process is provided to circulate treated water only in the desorption mode, and a citric acid solution is used to prevent heavy metals with low solubility from being precipitated in each CDI cell of the CDI module, while at the same time concentrating them at a high concentration in the circulation tank.

[0134] Figure 1 is a diagram showing a typical MCDI process.

[0135] Figure 2 is a schematic diagram showing a conventional capacitive deionization water treatment device.

[0136] Figure 3 is a drawing for explaining the adsorption process and desorption process of the capacitive deionization water treatment device illustrated in Figure 2.

[0137] Figure 4 is an operational flow chart for explaining a control method of a capacitive deionization water treatment device according to a conventional technology.

[0138] Figure 5 is a drawing for explaining the adsorption process and desorption process of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to a conventional technology.

[0139] Figure 6 is a flow chart showing a control method of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to a conventional technology.

[0140] Figure 7 is a photograph illustrating a CDI cell in which Ca and Mg are precipitated through a treatment water circulation process according to a conventional technology.

[0141] Figure 8 is a schematic diagram showing a sediment removal process in a fluid flow capacitor of an electrosorption deionization unit cell according to a conventional technology.

[0142] Figure 9 is a configuration diagram of a drinking water and ultrapure water-grade cooling water manufacturing system according to conventional technology.

[0143] FIG. 10 is a drawing for explaining the adsorption process and desorption process of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0144] FIG. 11 is a drawing specifically explaining the adsorption process of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0145] FIG. 12 is a drawing specifically explaining a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0146] Figure 13 is a configuration diagram of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0147] Figure 14 is a specific configuration diagram of an administrator terminal in a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0148] FIG. 15 is a photograph showing a CDI module circulating with citric acid circulating water in a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0149] Figure 16 is an operation flow diagram showing a control method of a capacitive desalination water treatment system equipped with a circulation tank for a desorption process according to an embodiment of the present invention.

[0150] [ Explanation of symbols ]

[0151] 100: Capacitive desalination water treatment system

[0152] 110: Influent tank 120: Influent supply pump

[0153] 130: First switching valve 140: CDI module (or MCDI module)

[0154] 150: Second switching valve 160: Production water tank

[0155] 170: Circulation tank 171: Water level gauge 172: Citric acid solution supply unit 180: Electrical conductivity meter

[0156] 190: Circulation pump 200: Administrator terminal

[0157] 201: Control unit 202: Pump drive signal generation unit

[0158] 203: Valve switching signal generation unit 204: CDI drive signal generation unit

[0159] 205: Water level check section 206: Adsorption and desorption time check section

[0160] 207: Electrical conductivity check unit 210: Potentiostat

[0161] As a means for achieving the above-mentioned technical task, the capacitive deionization water treatment system using citric acid circulation water in a desorption process circulation tank according to the present invention is a capacitive deionization water treatment system that treats influent water by repeating an adsorption process and a desorption process, the system comprising: a capacitive deionization (CDI) module that adsorbs ions in influent water by a capacitive deionization method through a constant voltage operation in an adsorption mode and discharges adsorption mode treated water, and desorbs ions adsorbed on an electrode through a reverse voltage operation in a desorption mode and discharges desorption mode treated water; a circulation tank in which adsorption mode treated water discharged from the CDI module in the adsorption mode is stored, the adsorption mode treated water is supplied to the CDI module in the desorption mode, and the desorption mode treated water is introduced from the CDI module; a citric acid solution supply unit that supplies a citric acid solution so that the adsorption mode treated water stored in the circulation tank forms citric acid circulating water; And it includes a circulation pump driven to supply the adsorption mode treated water and the desorption mode treated water introduced into the circulation tank to the CDI module, wherein the adsorption mode treated water is used as citric acid circulation water by the citric acid solution to clean the CDI module; and it is characterized in that the concentrated water is discharged only when the electrical conductivity of the concentrated water, which is the desorption mode treated water introduced into the circulation tank, reaches a set value, thereby minimizing the discharge of the concentrated water, thereby increasing the product water recovery rate.

[0162] Meanwhile, as another means for achieving the aforementioned technical task, a control method of a capacitive desalination water treatment system using citric acid circulating water in a desorption process circulation tank according to the present invention is a control method of a capacitive desalination water treatment system that treats influent water by repeating an adsorption process and a desorption process, comprising the steps of: a) supplying influent water to a capacitive desalination (CDI) module, performing ion adsorption by constant voltage operation according to an adsorption mode of the CDI module, and discharging adsorption mode treated water; b) fully charging the adsorption mode treated water into a circulation tank, and then storing the water in the product water tank for a preset adsorption time; c) mixing a citric acid solution with the adsorption mode treated water in the circulation tank to form citric acid circulating water; d) supplying the citric acid circulating water in the circulation tank to the CDI module by driving a circulation pump when the preset adsorption time has elapsed; e) performing ion desorption by reverse voltage operation according to a desorption mode of the CDI module, and discharging the desorption mode treated water; f) a step of introducing concentrated water, which is the desorption mode treated water, into the circulation tank; g) a step of checking a preset desorption time and the electrical conductivity of the concentrated water, which is the desorption mode treated water; and h) a step of discharging the concentrated water in the circulation tank when the electrical conductivity of the concentrated water reaches a set value, wherein in step c), the adsorption mode treated water is used as citric acid circulation water by the citric acid solution to clean the CDI module; and the concentrated water is discharged only when the electrical conductivity of the concentrated water, which is the desorption mode treated water introduced into the circulation tank, reaches a set value, thereby minimizing the discharge of the concentrated water, thereby increasing the product water recovery rate.

[0163] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description are omitted to clearly explain the present invention, and similar parts are designated with similar reference numerals throughout the specification.

[0164] Throughout the specification, when a part is said to "include" a component, this does not exclude other components, but rather implies the inclusion of other components, unless otherwise specifically stated. Furthermore, terms such as "part" or "part" used in the specification refer to a unit that processes at least one function or operation, which may be implemented using hardware, software, or a combination of hardware and software.

[0165] Hereinafter, with reference to FIGS. 10 to 15, a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention will be described.

[0166] Referring to FIG. 16, a control method of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention is described.

[0167] [Capacitive desalination water treatment system (100) using citric acid circulating water in a circulation tank for the desorption process]

[0168] First, according to the results confirmed through actual experiments on the capacitive desalination water treatment system, as mentioned above,

[0169] The second mechanism of the capacitive deionization water treatment system, the spacer, is the factor that has a greater influence on the desorption efficiency as ions move out of the CDI module, and the ion concentration of the feed water used for ion desorption does not have a significant influence.

[0170] Accordingly, as an embodiment of the present invention, a capacitive desalination water treatment system was configured to include a circulation tank capable of supplying recycled water used only for ion desorption, and as a result, it was confirmed that the production water recovery rate can be effectively increased.

[0171] Meanwhile, the general CDI process is a water treatment process that fundamentally involves repetition of adsorption and desorption, and thus, the desorption process inevitably results in process interruption and the generation of concentrated water.

[0172] In response to this, according to the embodiment of the present invention, a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process generates less concentrated water and has a high recovery rate.

[0173] In particular, it can be applied to the water purification of semiconductor cleaning water containing high concentrations of specific ions, heat circulation water of district heating companies, and groundwater contaminated with iron, fluorine, manganese, etc.

[0174] In addition, in the case of groundwater, there is a limitation in that a process with a low production water recovery rate cannot be applied due to insufficient water quantity, but this can be solved through a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0175] FIG. 10 is a drawing for explaining the adsorption process and desorption process of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention. FIG. 10 a) is a drawing for explaining the adsorption process, and FIG. 10 b) is a drawing for explaining the desorption process.

[0176] In a capacitive desalination water treatment system (100) using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention, the adsorption process and desorption process shown in a) and b) of FIG. 10 are repeatedly performed.

[0177] As shown in a) of Fig. 10, the adsorption process of the capacitive desalination water treatment system using citric acid circulating water in the circulation tank for the desorption process according to the embodiment of the present invention is,

[0178] Switch the first switching valve (130) to supply the inflow water to the CDI module (140),

[0179] After the adsorption mode treatment water is discharged in the adsorption mode according to the constant voltage operation of the above CDI module (140) and the circulation tank (170) is first filled to the full water level,

[0180] By switching the second switching valve (150), the production water, which is the adsorption mode treated water flowing out from the CDI module (140) for a preset adsorption time, is introduced into the production water tank (160) and stored.

[0181] At this time, a water level gauge can be installed in the circulation tank (170) to check the water level of the adsorption mode treated water.

[0182] In addition, a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention,

[0183] By using a weak acid solution such as citric acid instead of general distilled water or treated water as the circulating water in the circulation tank (170), not only can low-solubility heavy metal ions be concentrated in a much higher concentration in the circulation tank (170), but also the problem of precipitation in each CDI cell of the CDI module (140) can be solved.

[0184] That is, by using (mixing) a 1 to 2% citric acid solution instead of using general distilled water or treated water as the circulating water in the circulation tank (170), it is possible to prevent heavy metal ions with low solubility from being precipitated in each CDI cell of the CDI module (140) and to concentrate them at a high concentration in the circulation tank (170).

[0185] Specifically, FIG. 11 is a drawing for specifically explaining the adsorption process of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0186] In Fig. 11 a), the first switching valve (130) is switched according to the first valve switching signal in the adsorption process to supply inflow water to the CDI module (140).

[0187] Afterwards, it is shown that the adsorption mode treated water flowing out according to the constant voltage operation of the CDI module (140) is first charged into the circulation tank (170).

[0188] At this time, the adsorption mode treated water filled in the circulation tank (170) is used as citric acid circulation water by the citric acid solution supplied from the citric acid solution supply unit (172).

[0189] b) of Fig. 11 shows that after the adsorption mode treated water is filled in the circulation tank (170), the second switching valve (150) is switched in accordance with the second valve switching signal to allow the adsorption mode treated water flowing out of the CDI module (140) to be stored in the production water tank (160).

[0190] At this time, the production water stored in the production water tank (160) is not supplied to the CDI module (140) again.

[0191] In addition, as shown in b) of FIG. 11, the desorption process of the capacitive desalination water treatment system using citric acid circulating water in the desorption process circulation tank according to the embodiment of the present invention first switches the first switching valve (130) according to the first valve switching signal, and supplies the citric acid circulating water filled in the circulation tank (170) to the CDI module (140) by driving the circulation pump (190) according to the pump driving signal.

[0192] The desorption mode treatment water is discharged in the desorption mode according to the reverse voltage operation of the above CDI module (140).

[0193] In addition, the desorption mode treated water is reintroduced into the circulation tank (170), and only when the electrical conductivity of the desorption mode treated water, which is the concentrated water, reaches a set value is the concentrated water introduced into the circulation tank (170) discharged or released.

[0194] Specifically, FIG. 12 is a drawing for specifically explaining the desorption process of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0195] Figure 12a) shows that in the desorption process, the adsorption mode treated water in the circulation tank (170) is supplied to the CDI module (140) and the concentrated water, which is the desorption mode treated water, is discharged.

[0196] b) of Fig. 12 shows that when the electrical conductivity of the concentrated water reaches the set value, the first switching valve (130) and the second switching valve (150) are switched and the concentrated water stored in the circulation tank (170) is discharged or discharged.

[0197] Afterwards, after discharging the above-mentioned concentrated water, the citric acid circulation water is recharged into the circulation tank (170) in the next adsorption process and supplied to the CDI module (140) in the desorption process.

[0198] Accordingly, in the case of a capacitive desalination water treatment system (100) using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention, the problem of a low recovery rate of produced water compared to supplied water can be solved by performing adsorption mode and desorption mode using the same citric acid circulating water in the CDI module (140).

[0199] That is, by supplying feed water to the CDI module (140) to carry out the adsorption process and desorption process, and adding a circulation tank (170) that supplies citric acid circulation water used only for desorption, the feed water used in the adsorption process and desorption process is configured separately, thereby increasing the production water recovery rate.

[0200] In other words, the capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention is a zero liquid discharge (ZLD) system that can reduce the amount of concentrated water discharged, and can purify most of the inflow water into product water.

[0201] Here, the zero-discharge system does not mean a technology that produces zero concentrated wastewater, but rather a system that can recover more than 98%.

[0202] Meanwhile, Fig. 13 is a configuration diagram of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0203] Referring to FIG. 13, a capacitive desalination water treatment system (100) using citric acid circulation water in a circulation tank for a desorption process according to an embodiment of the present invention,

[0204] It is a capacitive desalination water treatment system that treats influent water by repeating the adsorption and desorption processes.

[0205] It comprises an influent tank (110), an influent supply pump (120), a first switching valve (130), a CDI module (140), a second switching valve (150), a product water tank (160), a circulation tank (170), an electrical conductivity meter (180), a circulation pump (190), a manager terminal (200), and a potentiostat (210), and further includes a citric acid solution supply unit (172) installed in the circulation tank (170).

[0206] The influent tank (110) stores influent or raw water for storage desalination water treatment.

[0207] The inflow water supply pump (120) supplies the inflow water or raw water stored in the inflow water tank (110) to the CDI module (140).

[0208] At this time, the inflow water supply pump (120) can be controlled to operate according to the first pump driving signal generated under the control of the administrator terminal (200).

[0209] The first switching valve (130) is installed at the front end of the CDI module (140) and is switched under the control of the manager terminal (200) so that the inflow water or raw water supplied by the inflow water supply pump (120) in the adsorption mode is supplied to the CDI module (140).

[0210] In the detachment mode, the treated water circulating in the circulation tank (170) is switched to be supplied to the CDI module (140) under the control of the manager terminal (200).

[0211] Here, it is preferable that the first switching valve (130) is a three-way valve, one side is connected to the inflow water supply pump (120), the other side is connected to the front end of the CDI module (140), and the three-way side is connected to the circulation pump (190).

[0212] For example, in the adsorption mode, the three-way side connected to the circulation pump (190) is turned off according to the first valve switching signal, and in the desorption mode, the one-way side connected to the inflow water supply pump (120) is turned off according to the first valve switching signal.

[0213] The CDI module (140) is driven by a positive voltage applied from a potential variable (210) to perform an adsorption mode, or is driven by a reverse voltage applied from the potential variable (210) to perform a desorption mode.

[0214] Here, the CDI module (140) is provided with an anode to which a positive voltage (+) is applied, a cathode to which a negative voltage (-) is applied, and a spacer provided between the anode and the cathode so that the inflow water can flow.

[0215] Additionally, it is obvious to those skilled in the art that the CDI module (140) may be a membrane capacitive deionization (MCDI) module as described above.

[0216] The second switching valve (150) is installed at the rear end of the CDI module (140), and is first switched so that the adsorption mode treated water flowing out of the CDI module (140) is fully filled in the circulation tank (170) under the control of the manager terminal (200) in the adsorption mode, and then, when the adsorption mode treated water is fully filled in the circulation tank (170), it is switched again so that it is stored in the produced water tank (160).

[0217] In addition, in the detachment mode, the detachment mode treatment water flowing out from the CDI module (140) is switched to be stored in the circulation tank (170) under the control of the administrator terminal (200).

[0218] Here, it is preferable that the second switching valve (150) is a three-way valve, one side of which is connected to the rear end of the CDI module (140), the other side is connected to the front end of the production water tank (160), and the third side is connected to the circulation tank (170).

[0219] For example, in the adsorption mode, the second valve switching signal turns off the other side connected to the production water tank (160), and then the circulation tank (170) is filled with the adsorption mode treated water.

[0220] The three-way side connected to the above circulation tank (170) is turned off, and the two-way side connected to the above production water tank (160) is turned on.

[0221] Additionally, in the detachment mode, the other side connected to the production water tank (160) is turned off according to the second valve switching signal.

[0222] The production water tank (160) stores the production water (or purified water) which is the adsorption mode treated water discharged by the CDI module (140).

[0223] Accordingly, in the existing CDI system, the produced water stored in the produced water tank in the desorption mode is supplied to the CDI module, but in the case of the capacitive desalination water treatment system using citric acid circulation water in the circulation tank for the desorption process according to the embodiment of the present invention,

[0224] The production water stored in the production water tank (160) does not need to be supplied to the CDI module (140), and instead, the adsorption mode treated water that is fully filled in the circulation tank (170) is used as citric acid circulation water and supplied to the CDI module (140).

[0225] The circulation tank (170) stores the adsorption mode treated water discharged by the CDI module (140) in the adsorption mode, and uses the adsorption mode treated water as citric acid circulating water in the desorption mode to circulate and supply it to the CDI module (140), thereby converting the citric acid circulating water into concentrated water, which is desorption mode treated water.

[0226] At this time, the circulation tank (170) is controlled to operate according to a second pump driving signal generated under the control of the administrator terminal (200).

[0227] The citric acid solution supply unit (172) supplies citric acid solution so that the adsorption mode treated water stored in the circulation tank (170) forms citric acid circulation water.

[0228] Accordingly, the above adsorption mode treated water can be used as citric acid circulation water by the above citric acid solution to clean the CDI module (140).

[0229] Specifically, the citric acid solution supply unit (172) can be installed in the circulation tank (170) to supply 1 to 2% citric acid solution.

[0230] At this time, the citric acid solution can prevent the low-solubility heavy metal ions from being precipitated from each CDI cell of the CDI module (140).

[0231] Here, the heavy metal ion with low solubility is calcium (Ca) or magnesium (Mg), and can be concentrated to a high concentration within the circulation tank (170).

[0232] An electrical conductivity meter (180) is installed in the circulation tank (170) to measure the electrical conductivity of the concentrated water, which is the desorption mode treatment water, and the end of the desorption mode is determined based on the electrical conductivity. At this time, when the electrical conductivity reaches the set value, the concentrated water is discharged.

[0233] The circulation pump (190) circulates and supplies the citric acid circulation water stored in the circulation tank (170) to the CDI module (140) in the desorption mode.

[0234] The administrator terminal (200) controls the constant voltage or reverse voltage operation of the CDI module (140) so that the CDI module (140) performs the adsorption mode and the desorption mode.

[0235] The completion of the desorption process is determined based on the electrical conductivity measured by the above-mentioned electrical conductivity meter (180), and the operation of the circulation tank (170) and circulation pump (190) is controlled.

[0236] For example, the above administrator terminal (200) may be implemented as a laptop PC, desktop PC, etc., but is not limited thereto.

[0237] The voltage regulator (210) applies a positive voltage to the CDI module (140) to perform an adsorption mode under the control of the manager terminal (200) or applies a reverse voltage to the CDI module (140) to perform a desorption mode.

[0238] Specifically, a positive or reverse voltage is applied to the CDI module (140) by the voltage variable (210) according to the CDI driving signal generated from the administrator terminal (200).

[0239] In other words, in the case of a capacitive desalination water treatment system (100) using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention, in the adsorption process, the influent water (or raw water) of the influent water tank (110) is moved to a CDI module (140) through an influent water supply pump (120), and then ions are adsorbed in the CDI module (140) to produce product water from which ionic substances have been removed.

[0240] Afterwards, in the desorption mode, the CDI module (140) desorbs ions, and when the concentrated water, which is the desorption mode treated water containing ionic substances, is discharged, it is moved to the circulation tank (170), and then, in the desorption mode again, the concentrated water containing ionic substances can be used as the supply water circulated to be used in the desorption mode.

[0241] That is, when the above circulation pump (190) is applied to the desorption mode, ions are desorbed only from the concentrated water, which is the desorption mode treated water that already contains ionic substances, and ultimately, the production water recovery rate can be increased by differentiating the supply water for the adsorption mode and the desorption mode.

[0242] Meanwhile, FIG. 14 is a specific configuration diagram of an administrator terminal in a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0243] As shown in Fig. 14, in a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention,

[0244] The administrator terminal (200) may include a control unit (201), a pump driving signal generation unit (202), a valve switching signal generation unit (203), a CDI driving signal generation unit (204), a water level confirmation unit (205), an adsorption and desorption time confirmation unit (206), and an electrical conductivity confirmation unit (207).

[0245] The control unit (201) controls the constant voltage or reverse voltage operation of the CDI module (140) so that the CDI module (140) performs the adsorption mode and desorption mode, and controls the operation of the circulation tank (170) and the circulation pump (190) in the desorption mode.

[0246] The pump drive signal generating unit (202) generates pump drive signals for driving the inflow water supply pump (120) and the circulation pump (190) according to the control of the control unit (201). That is, the pump drive signal generating unit (202) generates a first pump drive signal for driving the inflow water supply pump (120) in the adsorption process, and also generates a second pump drive signal for driving the circulation pump (190) in the desorption process.

[0247] The valve switching signal generation unit (203) generates valve switching signals for switching the first switching valve (130) and the second switching valve (150) according to the control of the control unit (201).

[0248] The CDI drive signal generation unit (204) generates a CDI drive signal for driving the CDI module (140) with a positive voltage or a reverse voltage according to the control of the control unit (201).

[0249] The water level confirmation unit (205) receives and confirms the water level data measured by the water level gauge (171) installed in the circulation tank (170).

[0250] The adsorption and desorption time confirmation unit (206) confirms the preset adsorption time and desorption time, respectively.

[0251] The electrical conductivity verification unit (207) verifies whether the electrical conductivity measured by the electrical conductivity meter (180) reaches the set value.

[0252] Meanwhile, in the case of a capacitive desalination water treatment system (100) using citric acid circulation water in a circulation tank for a desorption process according to an embodiment of the present invention, the concentrated water, which is the desorption mode treatment water, is circulated once to proceed with the desorption mode in the CDI module (140).

[0253] At this time, the used concentrated water is stored in the circulation tank (170) and reused in the desorption mode of the next CDI module (140), so that the concentrated water is not continuously discharged.

[0254] Specifically, a process in which an adsorption process and a desorption process are performed is called a 1-cycle process, and assuming that 100 L of product water can be produced from the influent water through this, in the 1-cycle process, 50 L is stored in the circulation tank (170) in the adsorption mode according to the constant voltage operation of the CDI module (140), and then 100 L is produced in the product water tank (160).

[0255] In addition, in the discharging mode of the CDI module (140), after the circulation tank (170) filled with 50 L is returned to the circulation tank (170) after the first, second, and third discharging modes, 100 L of product water is produced, and no concentrated water is discarded.

[0256] Accordingly, in the case of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention,

[0257] By recovering the concentrated water from the circulation tank (170) and reusing it repeatedly instead of discharging it for each cycle, the recovery rate of produced water is increased.

[0258] In addition, since the concentrated water, which is the desorption mode treatment water, can be continuously used in the desorption mode of the CDI module, there is no unnecessarily discarded concentrated water, so the capacitive desalination water treatment system can be operated economically.

[0259] Meanwhile, FIG. 15 is a photograph showing a CDI module circulated with citric acid circulating water in a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0260] In the case of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention,

[0261] Rather than a configuration that cleans the CDI module (140) by adding a citric acid solution once or intermittently when necessary,

[0262] The citric acid solution supply unit (172) installed in the above circulation tank (170) supplies citric acid to form its own citric acid circulation water.

[0263] Accordingly, as shown by reference numeral B in FIG. 15, the problem of heavy metal ions having low solubility being precipitated as crystallized heavy metals in each CDI cell of the CDI module (140) can be solved.

[0264] In addition, in the case of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention, heavy metal ions can be concentrated into the circulation tank (170) at a high concentration.

[0265] That is, by forming a citric acid circulation water using a 1 to 2% citric acid solution, heavy metals can be prevented from being deposited and concentrated at a high concentration within the circulation tank (170).

[0266] Accordingly, the capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention can continuously perform CDI water treatment even when applying heavy metals with low solubility such as calcium (Ca) or magnesium (Mg) in addition to heavy metal ions with high solubility such as sodium chloride (NaCl) by utilizing citric acid solution as circulating water in a CDI module equipped with an existing circulation tank, and can be applied to water treatment of a wide range of heavy metal ions.

[0267] [Control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for the desorption process]

[0268] Figure 16 is a flowchart showing a control method of a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process according to an embodiment of the present invention.

[0269] Referring to FIG. 16, a control method of a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process according to an embodiment of the present invention is as follows.

[0270] First, as an adsorption process, the influent stored in the influent tank (110) is supplied to a capacitor deionization (CDI) module (140), and ion adsorption is performed according to the constant voltage operation of the CDI module (140) to discharge adsorption mode treated water (S110).

[0271] At this time, the CDI module (140) is provided with an anode to which a positive voltage (+) is applied, a cathode to which a negative voltage (-) is applied, and a spacer provided between the anode and the cathode so that the inflow water can flow, and a positive voltage or a reverse voltage can be applied to the CDI module (140) by a voltage variable (210) corresponding to a CDI driving signal generated from the manager terminal (200).

[0272] Next, after the above adsorption mode treated water is fully filled in the circulation tank (170), the adsorption mode treated water is introduced into the production water tank (160) and stored for a preset adsorption time (S120).

[0273] At this time, a water level gauge (171) is installed in the circulation tank (170) to check whether the water level of the ion-adsorbed treated water flowing out of the CDI module (140) is full.

[0274] Next, a citric acid solution is mixed with the adsorption mode treated water in the circulation tank (170) to form citric acid circulation water (S130).

[0275] Accordingly, the above adsorption mode treated water can be used as citric acid circulation water by the above citric acid solution to clean the CDI module (140).

[0276] Specifically, a citric acid solution supply unit (172) is installed in the circulation tank (170) to supply 1 to 2% citric acid solution.

[0277] The above citric acid solution can prevent the low solubility heavy metal ions from being precipitated in each CDI cell of the CDI module (140).

[0278] Here, the heavy metal ion with low solubility is calcium (Ca) or magnesium (Mg), and can be concentrated to a high concentration within the circulation tank (170).

[0279] Next, when the above-described preset adsorption time has elapsed, the circulation pump (190) is driven to supply the citric acid circulation water in the circulation tank (170) to the CDI module (140) (S140).

[0280] Next, ion desorption is performed by reverse voltage operation of the CDI module (140) to discharge desorption mode treated water (S150).

[0281] Next, concentrated water, which is desorption mode treatment water, is introduced into the circulation tank (170) (S160).

[0282] Next, the preset desorption time and the electrical conductivity of the concentrated water, which is the ion desorption treatment water, are checked (S170).

[0283] At this time, when the preset detachment time has elapsed and the electrical conductivity has reached the set value, the detachment mode according to the reverse voltage operation of the CDI module (140) is terminated.

[0284] Next, when the electrical conductivity of the concentrated water reaches a set value, the concentrated water in the circulation tank (170) is discharged or released (S180).

[0285] At this time, if the electrical conductivity of the concentrated water does not reach the set value, steps S110 to S170 described above are repeated.

[0286] Accordingly, the recovery rate of the produced water can be increased by minimizing the discharge of the concentrated water by discharging the concentrated water only when the electrical conductivity of the concentrated water, which is the desorption mode treated water introduced into the circulation tank (170), reaches a set value.

[0287] Ultimately, according to an embodiment of the present invention, since the concentrated water, which is the desorption mode treated water, can be continuously used in the desorption mode of the CDI module, there is no unnecessarily discarded concentrated water, so the capacitive desalination water treatment system can be operated economically, and furthermore, since it generates little concentrated water and has a high recovery rate, it can be applied to the purification of semiconductor cleaning water in which specific ions are present in high concentrations, thermal circulation water of district heating companies, and groundwater contaminated with iron, fluorine, manganese, etc.

[0288] In addition, according to an embodiment of the present invention, in a capacitive deionization (CDI) water treatment system in which an adsorption process and a desorption process are repeatedly performed, a separate circulation tank capable of supplying circulation water used only for ion desorption in the desorption mode is implemented, thereby purifying most of the influent water into product water, thereby increasing the product water recovery rate.

[0289] In particular, by using a citric acid solution, heavy metals with low solubility can be prevented from being precipitated in each CDI cell of the CDI module, while at the same time being concentrated in a high concentration within the circulation tank.

[0290] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner. The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A capacitive deionization (CDI) module (140) that adsorbs ions of influent water using a constant voltage operation in adsorption mode and discharges adsorption mode treated water, and desorbs ions adsorbed on an electrode using a reverse voltage operation in desorption mode and discharges desorption mode treated water; A circulation tank (170) in which the adsorption mode treated water flowing out from the CDI module (140) in the adsorption mode is stored, the adsorption mode treated water is supplied to the CDI module (140) in the desorption mode, and the desorption mode treated water flows in from the CDI module (140); A citric acid solution supply unit (172) that supplies a citric acid solution so that the adsorption mode treated water stored in the circulation tank (170) forms citric acid circulation water; and Including a circulation pump (190) driven to supply the adsorption mode treated water and the desorption mode treated water introduced into the circulation tank (170) to the CDI module (140), The above adsorption mode treated water is used as citric acid circulation water by the above citric acid solution to clean the CDI module (140); and A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that the concentrated water is discharged only when the electrical conductivity of the concentrated water, which is the desorption mode treatment water introduced into the circulation tank (170), reaches a set value, thereby minimizing the discharge of the concentrated water, thereby increasing the recovery rate of the produced water.

2. In paragraph 1, The above citric acid solution supply unit (172) is A capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process, characterized in that it is installed in the circulation tank (170) to supply 1 to 2% citric acid solution.

3. In paragraph 2, The above citric acid solution, A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that the low solubility heavy metal ions are prevented from being precipitated in each CDI cell of the CDI module (140).

4. In paragraph 3, The above low solubility heavy metal ions are, A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that calcium (Ca) or magnesium (Mg) is concentrated at a high concentration in the circulation tank (170).

5. In paragraph 1, The above circulation tank (170) is A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a water level gauge (171) is installed to check whether the water level of the adsorption mode treated water flowing out of the CDI module (140) is full.

6. In paragraph 1, A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, which further includes a manager terminal (200) that controls the constant voltage or reverse voltage operation of the CDI module (140) so that the CDI module (140) performs an adsorption mode and a desorption mode, determines the end of the desorption process based on the electrical conductivity measured by the electrical conductivity meter (180), and controls the operation of the circulation tank (170) and the circulation pump (190).

7. In paragraph 6, A desalination treatment system using citric acid circulation water in a circulation tank for a desorption process, which further includes a first switching valve (130) installed in front of the CDI module (140) and switched under the control of a manager terminal (200) so that inflow water or raw water supplied by the inflow water supply pump (120) in adsorption mode is supplied to the CDI module (140), and switched under the control of a manager terminal (200) so that treated water circulated in a circulation tank (170) in desorption mode is supplied to the CDI module (140).

8. In paragraph 7, The above first switching valve (130) is A three-way valve having one side connected to the inflow water, the other side connected to the front end of the CDI module (140), and the third side connected to the circulation pump (190), wherein the three-way valve is turned off in the adsorption mode in response to a first valve switching signal, and the one-way valve is turned off in response to the first valve switching signal in the desorption mode. A desalination treatment system using citric acid circulation water in a circulation tank for a desorption process.

9. In paragraph 6, A capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, which is installed at the rear end of the CDI module (140) and, in the adsorption mode, first switches so that the adsorption mode treated water flowing out from the CDI module (140) is fully filled in the circulation tank (170) under the control of the administrator terminal (200), and then switches again so that the adsorption mode treated water is stored in the production water tank (160) when the adsorption mode treated water is fully filled in the circulation tank (170).

10. In paragraph 9, The above second switching valve (150) is A three-way valve having one side connected to the rear end of a CDI module (140), the other side connected to the front end of a product water tank (160), and the third side connected to a circulation tank (170), wherein the second switching valve (150) is characterized in that in the adsorption mode, the other side connected to the product water tank (160) is turned off in accordance with a second valve switching signal, and after the adsorption mode treated water is filled in the circulation tank (170), the three-way side connected to the circulation tank (170) is turned off and the other side connected to the product water tank (160) is turned on, and in the desorption mode, the other side connected to the product water tank (160) is turned off in accordance with the second valve switching signal. 11.a) A step of supplying influent water to a capacitor discharge deionization (CDI) module (140), performing ion adsorption through constant voltage operation according to the adsorption mode of the CDI module (140), and discharging adsorption mode treated water; b) A step of fully filling the circulation tank (170) with the above adsorption mode treatment water and then storing it by flowing it into the production water tank (160) for a preset adsorption time; c) A step of forming citric acid circulation water by mixing a citric acid solution into the adsorption mode treated water in the circulation tank (170); d) When the preset adsorption time has elapsed, a step of driving the circulation pump (190) to supply the citric acid circulation water in the circulation tank (170) to the CDI module (140); e) A step of performing ion desorption by reverse voltage operation according to the desorption mode of the CDI module (140) and discharging desorption mode treated water; f) A step of introducing the concentrated water, which is the desorption mode treatment water, into the circulation tank (170); g) a step of checking the preset desorption time and the electrical conductivity of the concentrated water, which is the desorption mode treatment water; and h) When the electrical conductivity of the concentrated water reaches a set value, a step of discharging the concentrated water in the circulation tank (170) is included. In the above step c), the adsorption mode treatment water is used as citric acid circulation water by the citric acid solution to clean the CDI module (140); and A control method for a capacitive desalination water treatment system using citric acid circulating water in a desorption process circulation tank, characterized in that the concentrated water is discharged only when the electrical conductivity of the concentrated water, which is the desorption mode treatment water introduced into the circulation tank (170), reaches a set value, thereby minimizing the discharge of the concentrated water, thereby increasing the recovery rate of the produced water.

12. In paragraph 11, The citric acid solution supply unit (172) of the above circulation tank (170) is A control method for a capacitive desalination water treatment system using citric acid circulating water in a circulation tank for a desorption process, characterized in that the circulation tank (170) is installed to supply a 1 to 2% citric acid solution.

13. In paragraph 12, The above citric acid solution, A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that the low solubility heavy metal ions are prevented from being precipitated in each CDI cell of the CDI module (140).

14. In paragraph 13, A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that the heavy metal ion with low solubility is calcium (Ca) or magnesium (Mg) and is concentrated at a high concentration in the circulation tank (170).

15. In paragraph 11, The above circulation tank (170) is A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a water level gauge (171) is installed to check whether the water level of the adsorption mode treatment water flowing out from the CDI module (140) is full.

16. In paragraph 11, The above CDI module (140) is A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that it comprises an anode to which a positive voltage (+) is applied, a cathode to which a negative voltage (-) is applied, and a spacer provided between the anode and the cathode so that inflow water can flow, and a positive voltage or a reverse voltage is applied to the CDI module (140) by a potential variable (210) corresponding to a CDI driving signal generated from the manager terminal (200).

17. In paragraph 16, A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a first switching valve (130) is installed at the front end of the CDI module (140), and the first switching valve (130) is switched under the control of a manager terminal (200) so that inflow water or raw water supplied by an inflow water supply pump (120) in an adsorption mode is supplied to the CDI module (140), and is switched under the control of a manager terminal (200) so that treated water circulated in a circulation tank (170) in a desorption mode is supplied to the CDI module (140).

18. In paragraph 17, The above first switching valve (130) is A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a three-way valve having one side connected to the inflow water, the other side connected to the front end of a CDI module (140), and the third side connected to the circulation pump (190) is turned off in accordance with a first valve switching signal in an adsorption mode, and a one-way side connected to the inflow water supply pump (120) is turned off in accordance with the first valve switching signal in a desorption mode.

19. In paragraph 17, A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a second switching valve (150) is installed at the rear end of the CDI module (140), and the second switching valve (150) is first switched so that the adsorption mode treated water flowing out of the CDI module (140) in the adsorption mode is fully filled in the circulation tank (170) under the control of the manager terminal (200), and then switched again so that the adsorption mode treated water is stored in the product water tank (160) when the adsorption mode treated water is fully filled in the circulation tank (170).

20. In paragraph 19, The above second switching valve (150) is A control method for a capacitive desalination water treatment system using citric acid circulation water in a circulation tank for a desorption process, characterized in that a three-way valve is connected on one side to the rear end of a CDI module (140), on the other side to the front end of a product water tank (160), and on the third side to a circulation tank (170), wherein the second switching valve (150) is characterized in that in the adsorption mode, the other side connected to the product water tank (160) is turned off in accordance with a second valve switching signal, and after the adsorption mode treated water is filled in the circulation tank (170), the three-way side connected to the circulation tank (170) is turned off and the other side connected to the product water tank (160) is turned on, and in the desorption mode, the other side connected to the product water tank (160) is turned off in accordance with the second valve switching signal.

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