JP2007301477A - Electric softening system, softening system, and soft water manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric softening system capable of freely removing a hardness component in hard water from a desired conversion rate to a significantly high conversion rate corresponding to a purpose without causing the phenomenon of a decrease in electric current efficiency, a softening system, and a soft water manufacturing method. <P>SOLUTION: The method comprises placing a monovalent cation permselective membrane and a cation exchange membrane reciprocally between an anode chamber and a cathode chamber to make the gap as a water passing chamber, passing water to be treated containing a hardness component through a water passing chamber (softening chamber) located on the cathode side of the monovalent cation permselective membrane and replacement water containing a monovalent cation is passed through a water passing chamber (replacement chamber) located on the anode side of the monovalent cation permselective membrane, and replacing the hardness component in the water to be treated with the monovalent cation in replacement water by applying a direct current potential. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrosoftening device that softens hard water, a softening device, and a soft water production method.

  Water containing a large amount of divalent cations (hardness components) such as calcium ions and magnesium ions is called hard water and is unsuitable for use in boiler feed water or cooling water. For this reason, a hard water softening process is performed in order to remove divalent cations. As a method for removing the divalent cations and performing the water softening treatment, a salt softening method in which soft water is passed through the packed bed of Na-type strongly acidic cation exchange resin, or a reverse osmosis membrane method in which soft water is passed through the hard water into the reverse osmosis membrane There is.

  The salt softening method using Na-type strongly acidic cation exchange resin is a regeneration method in which saline solution is passed because the hardness component leaks into the treated water when the amount of ion exchanged hardness component exceeds the exchange capacity of the cation exchange resin. There is a problem that a process is required and continuous processing cannot be performed. In the reverse osmosis membrane method, although continuous softening treatment can be performed, there is a risk that calcium carbonate scale may be generated on the membrane surface, and there is a problem that the water recovery rate cannot be increased. In this reverse osmosis membrane apparatus, by adding an acid to the water to be treated, precipitation of calcium carbonate scale can be avoided, but a dangerous acid becomes a problem in use.

On the other hand, in JP-A-8-108184, raw water in which monovalent cations and divalent cations are mixed is supplied to an electrodialysis cell, and a monovalent ion selective permeable cation exchange membrane and a non-selective permeable cation exchange membrane are used. A water treatment system that simultaneously obtains treated water rich in valence ions and less divalent ions and treated water rich in divalent ions and less monovalent ions is disclosed.
JP-A-8-108184 (Claim 1, FIG. 1)

  However, in the electrodialysis cell of JP-A-8-108184, the cations of the water to be treated that have flowed into the concentration chamber permeate the non-selective cation exchange membrane by a direct current potential and are carried to the desalting chamber. On the other hand, the anion in the water to be treated cannot permeate through the non-selective cation exchange membrane or the stainless partition, and remains in the concentration chamber. As a result, the concentration chamber becomes anion-rich and the pH is lowered. When pH decreases, the proportion of hydrogen ions in the cations that move through the non-selective cation exchange membrane increases, so the rate of movement of calcium ions and magnesium ions decreases, so-called current efficiency decreases. There is a problem of inviting a phenomenon.

  Therefore, an object of the present invention is to provide an electric softening device, a softening device, and a softening device that can freely remove a hardness component in hard water from a desired softening rate to a significantly high softening rate depending on the purpose without causing a phenomenon of current efficiency reduction. The object is to provide a method for producing soft water.

  In such a situation, the present inventor has conducted intensive studies, and as a result, the monovalent cation selective permeation membrane and the cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber, and a water passage is provided between them. Water to be treated containing hardness components is passed through a water flow chamber (softening chamber) located on the cathode side of the permeable membrane, and monovalent in the water flow chamber (substitution chamber) located on the anode side of the monovalent cation selective permeable membrane. By passing substitution water containing cations and applying a DC potential to the cathode and anode to replace the hardness component in the water to be treated with monovalent cations in the substitution water, without causing a decrease in current efficiency, It has been found that the hardness component in hard water can be freely removed from a desired softening rate to a remarkably high softening rate depending on the purpose, and the present invention has been completed.

  That is, according to the present invention, a monovalent cation selective permeable membrane and a cation exchange membrane are alternately arranged between an anode chamber and a cathode chamber, and a water passage is provided between them. The water chamber is a softening chamber, and the water flow chamber located on the anode side of the monovalent cation selective permeation membrane is a replacement chamber. The softening chamber is provided with an introduction path for treated water containing hardness components and a soft water discharge path. The replacement chamber has an introduction path for substitution water containing monovalent cations and a hardness component concentrated water discharge path, and each of the anode chamber and the cathode chamber has a water introduction path and a discharge path. A device is provided.

  The present invention also includes a pre-demineralization device and the electrosoftening device located at the subsequent stage of the pre-demineralization device, and the treated water discharge path of the pre-demineralization device and the treated water introduction of the electrosoftening device. The present invention provides a softening device in which a path is connected and a concentrate discharge path of the pre-demineralization apparatus and a replacement water introduction path of the electrosoftening apparatus are connected.

  Further, the present invention includes the electrosoftening device and a post-desalination device located at a subsequent stage of the electrosoftening device, and a treated water discharge path of the electrosoftening device and a treated water introduction path of the post-desalination device. And a softening device in which the concentrate discharge path of the demineralizer and the replacement water introduction path of the electrosoftening device are connected.

  In the present invention, a monovalent cation selective permeable membrane and a cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber, and a water passage is provided between them, and a passage located on the cathode side of the monovalent cation selective permeable membrane is provided. Water to be treated containing hardness components is passed through the water chamber (softening chamber), and replacement water containing monovalent cations is passed through the water passage chamber (substitution chamber) located on the anode side of the monovalent cation selective permeation membrane. The present invention provides a method for producing soft water in which a direct current potential is applied to a cathode and an anode to replace a hardness component in water to be treated with a monovalent cation in substitution water.

  When water is passed through the electrosoftening device of the present invention and energized, monovalent cations and divalent cations in the treated water pass through the cation exchange membrane in the softening chamber and move to the substitution chamber. At the same time, in the substitution chamber, mainly monovalent cations in the substitution water permeate the monovalent cation selective permeation membrane and move to the softening chamber. For this reason, soft water can be obtained by substituting the monovalent cation for the hardness component in the water to be treated. In the electrosoftening device of the present invention, the cation transport rate is the same in any of the softening chambers and the replacement chambers, and the pH does not decrease, so that the current efficiency is not reduced. In addition, if the substitution water containing monovalent cations equal to or more than the equivalent hardness component to be removed in the water to be treated is passed, the scale of the monovalent cation selective permeation membrane of the substitution chamber is less likely to be generated, and more Since a large amount of current can flow, the amount of ions moved per unit time increases, and the softening efficiency improves. Further, by adjusting the current voltage value and the amount of monovalent cation in the substitution water, the hardness component in the hard water can be freely removed from a desired softening rate to a remarkably high softening rate. Further, according to the softening device of the present invention, since the monovalent cation is concentrated in the concentrated water obtained from the pre-demineralizer, it is not necessary to add a monovalent cation salt separately to the replacement water. Since the pre-demineralized treated water is treated water, soft water with lower hardness can be obtained. The softening device of the present invention is suitable particularly when the hardness and salt concentration of raw water are high. Further, according to another softening device of the present invention, since the monovalent cation is concentrated in the concentrated water obtained from the post-desalting device, it is necessary to add a monovalent cation salt separately to the replacement water. Disappear. In addition, the former-stage electrosoftening device can be operated at a lower current value, and the capacity of the DC power supply can be reduced. Moreover, when a reverse osmosis membrane apparatus is used in the latter stage, scale adhesion on the membrane surface can be suppressed. In addition, the anode outlet water can be used as acidic functional water because cations are reduced to lower the pH, and hypochlorous acid is generated by the anodic reaction and has oxidizing power and sterilizing power. Further, the cathode outlet water can be used as alkaline functional water having a reducing power because cations increase to increase the pH and hydrogen gas is generated by the cathode reaction.

  An electrosoftening device according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view of the electrosoftening device of this example. In the electrosoftening device 10, the monovalent cation selective permeable membrane 4 and the cation exchange membrane 3 are alternately arranged between the anode chamber 6 adjacent to the anode 7 and the cathode chamber 5 adjacent to the cathode 8, and a water passage is provided therebetween. The water flow chamber located on the cathode 8 side of the monovalent cation selective permeable membrane 4 is the softening chamber 1, the water flow chamber located on the anode 7 side of the monovalent cation selective permeable membrane 4 is the replacement chamber 2, and the softening chamber 1 Is provided with an introduction pipe a and a soft water discharge pipe b containing hardness components, and a substitution water introduction pipe c and a hardness component concentrated water discharge pipe d containing monovalent cations are arranged in the replacement chamber 2. The anode chamber 6 is provided with an anode water introduction pipe e and an anode water drain pipe f connected to the hardness component concentrated water discharge pipe d, and the cathode water introduction pipe g connected to the anode water drain pipe f in the cathode chamber 5. And a cathode water drain pipe h. The ion exchange membrane adjacent to the anode chamber 6 is a monovalent cation selective permeable membrane 4 as in this example, so that the hardness component from entering the electrosoftening device from the water flowing through the anode chamber 6 can be prevented. It is preferable in that it can be performed.

  In addition, a monovalent cation salt supply means may be connected to the replacement water introduction pipe c of the electrosoftening device 10 (not shown). Thereby, the monovalent cation concentration in the substitution water can be appropriately adjusted to an arbitrary amount. Examples of the monovalent cation salt supply means include a device composed of a monovalent cation salt storage tank, a monovalent cation salt supply pump, piping, valves and the like.

  Although the monovalent cation selective permeable membrane 4 is not particularly limited, a cation exchange membrane in which a thin layer of polycation is completely fixed on the membrane surface can be used. Since the electrostatic repulsion between the polycation, which is a positively charged barrier existing on the membrane surface, and the ion to be permeated is larger for the divalent cation than for the monovalent cation, Permeation of the membrane is hindered. As such a monovalent cation selective permeable membrane, a commercially available one can be used.

  Next, a method for producing soft water using the electric softening device 10 will be described. To the softening chamber 1 located on the cathode 8 side of the monovalent cation selective permeation membrane, the water to be treated containing hardness components is passed through the water to be treated introduction pipe a, and on the anode 7 side of the monovalent cation selective permeation membrane 4. The substitution water containing monovalent cations is passed through the substitution chamber 2 located through the substitution water introduction pipe c, and a DC potential is applied to the cathode 8 and the anode 7.

  When water is passed through the electrosoftening device 10 and energized, in the softening chamber 1, monovalent cations and divalent cations (hardness components) of the water to be treated permeate the cation exchange membrane 3 and move to the substitution chamber 2. At the same time, in the substitution chamber 2, mainly monovalent cations in the substitution water permeate the monovalent cation selective permeable membrane 4 and move to the softening chamber 1. Thus, in the softening chamber 1, soft water is obtained continuously by sequentially substituting the divalent cations in the water to be treated with monovalent cations, and in the replacement chamber 2, the monovalent cations in the substitution water are converted into divalent cations. By successively substituting, the concentrated water in which the hardness component is continuously concentrated can be obtained. Further, in the electrosoftening device 10, the cation transport rate is the same in any of the softening chamber 1 and the substitution chamber 2, and the pH does not decrease, so that the current efficiency is not reduced.

  In the electrosoftening device of the present invention, the flow direction of the water to be treated in the softening chamber 1 and the flow direction of the replacement water in the replacement chamber 2 are not particularly limited. However, as shown in FIG. Is preferred. If the flow direction of the water to be treated in the softening chamber 1 and the flow direction of the water to be substituted in the replacement chamber 2 are counterflowing, the hardness component in the water to be treated introduced into the softening chamber 1 is higher than that of the monovalent cation. Since it is an electric charge and easily moves through the cation exchange membrane 3 on the discharge side of the substitution chamber 2, it is quickly discharged out of the system from the softening chamber 1. This makes it difficult for scale to occur on the membrane surface of the monovalent cation selective permeable membrane 4 on the substitution chamber 2 side.

  In the electric softening device 10, the replacement chamber outlet water discharged from the replacement chamber 2 is passed through the anode chamber 6, and the anode chamber outlet water is further passed through the cathode chamber 5. Thereby, the monovalent cation that has passed through the cation exchange membrane 3 from the softening chamber 1 and moved to the replacement chamber 2 can be returned to the anode chamber 6 and used again for replacement, and the cation moves and decreases in the anode chamber 6. By passing the anode outlet water having a lowered pH through the cathode chamber 5, the risk of hardness scale deposition in the cathode chamber 5 can be reduced. Such a water flow method for electrode water is particularly suitable when treating water to be treated having a high hardness component. In this example, all of the replacement chamber outlet water is passed through the anode chamber 6. However, the present invention is not limited to this, and a portion of the replacement chamber outlet water may be passed through the anode chamber 6. Moreover, the electrode water in the anode chamber 6 and the cathode chamber 5 may be separately passed.

  In the electrosoftening device 10, the cathode outlet water discharged from the cathode water discharge pipe h is used as alkaline functional water having a reducing power because cations increase and pH rises and hydrogen gas is generated by the cathode reaction. be able to.

  In the present invention, the water to be treated is hard water, and specific examples include tap water and well water. The treated water usually contains impurities such as divalent cations such as calcium ions and magnesium ions, strong electrolytes such as sodium ions, potassium ions, chloride ions and sulfate ions, weak electrolytes such as carbonate ions and silica. May be included. Moreover, when processing water with high hardness, a pre-demineralization apparatus can be installed in the front | former stage of the electrosoftening apparatus 10 (refer FIG. 3), and the treated water which flows out out of this pre-demineralization apparatus can be made into to-be-processed water. . Thereby, the treated water of lower hardness can be obtained.

  In the substituted water containing the monovalent cation of the present invention (hereinafter also simply referred to as “substituted water”), the amount of the monovalent cation in the substituted water is preferably equal to or greater than the equivalent of the hardness component to be removed. When the amount of monovalent cation in the substitution water is less than the equivalent of the hardness component to be removed, soft water is temporarily obtained, but the removal of the hardness component becomes insufficient, and the membrane of the monovalent cation selective permeation membrane 4 in the substitution chamber 2 Scale tends to occur on the surface. When the amount of monovalent cations is large, a larger amount of current flows, so that the amount of ions moved per unit time increases and the softening efficiency is improved.

  The replacement water may contain a divalent cation. Specific examples of the replacement water include water to be treated, water prepared by adding a monovalent cation salt to the water to be treated, and the like. When the amount of monovalent cation in the water to be treated is less than the equivalent of the hardness component to be removed, it is preferable to add a monovalent cation salt separately from the viewpoint of improving the removal rate of the hardness component. The monovalent cation salt added to the water to be treated is usually sodium chloride. When the monovalent cation equivalent is less than the divalent cation equivalent, for example, the replacement water flow rate may be flowed in a large amount with respect to the treated water flow rate, but this is not preferable because the utilization rate of water decreases.

  Moreover, when processing water with high hardness, a pre-demineralizer can be installed in the front | former stage of the electrosoftening apparatus 10 (refer FIG. 3), and the concentrated water discharged | emitted from this pre-demineralizer can also be used as substitution water. Monovalent cations are also concentrated in the concentrated water discharged from the pre-demineralizer, which is preferable in that it can be used without adding a monovalent cation salt and the softening efficiency is increased. Moreover, when processing water with high hardness, a post-desalination apparatus can be installed in the back | latter stage of the electrosoftening apparatus 10 (refer FIG. 4), and the concentrated water discharged | emitted from this post-desalination apparatus can also be used as replacement water. The concentrated water discharged from the desalting apparatus after that contains monovalent cations, which is preferable in that it can be used without adding a monovalent cation salt and the softening efficiency is increased. The pre-demineralization device and the post-desalination device are both known types of devices that concentrate rejected ions in concentrated water, and examples thereof include an electrodialysis device, an electric deionized water production device, and a reverse osmosis membrane device. It is done.

  In the present invention, at least the softening chamber, preferably the softening chamber and the replacement chamber, more preferably all of the softening chamber, the substitution chamber, the anode chamber, and the cathode chamber of the electrosoftening device may be filled with a cation exchanger. it can. By filling the softening chamber 1 with a cation exchanger, divalent cations with high ion exchange selectivity can be more selectively excluded into the substitution chamber 2. In addition, since the cation exchanger itself has conductivity, filling the softening chamber, the replacement chamber, the cathode chamber, or the anode chamber can lower the energization resistance value of the device stack and reduce the power consumption. In the present invention, the cation exchanger is not particularly limited, and examples thereof include cation exchange resins, cation exchange fibers, and organic porous cation exchangers.

In the method for producing soft water according to the present invention, it is preferable to operate so as to satisfy R ≦ 1 as an operating condition in which a hardness scale is not generated. R represents (current value (A) × 3600 seconds / 96500 coulomb) / ((monovalent cation concentration of substitution water (mgCaCO ₃ / l) × substitution water flow rate (l / h)) / number of substitution chambers)) . When R exceeds 1, that is, when a current exceeding a monovalent cation is passed, the monovalent cation becomes insufficient, and water deviates between H ⁺ and OH ⁻ . In this case, although H ⁺ permeates the monovalent cation selective permeation membrane, OH ⁻ remains, so that the pH becomes high and the membrane surface on the cathode side of the substitution chamber can be easily scaled. A practical R value is 0.7 to 0.9. When R is less than 0.7, the softening ability is lowered, so that the efficiency is deteriorated when it is desired to increase the hardness component removal rate.

  In the method for producing soft water of the present invention, examples of a method for obtaining soft water having a low hardness component removal rate include a method of flowing a small current and a method of flowing substitution water having a low monovalent cation concentration. Soft water with a low hardness component removal rate can be used as water to be treated in desalination equipment such as reverse osmosis membrane equipment and electrical deionized water production equipment, as well as the amount of monovalent cation salt added to replacement water. It can be reduced and power saving operation can be performed. On the other hand, as a method of obtaining soft water having a high hardness component removal rate, a method of passing substitution water containing a monovalent cation equivalent to or higher than the hardness component to be removed in the water to be treated, a substitution containing a monovalent cation higher than the equivalent In addition to the method of passing water, a method of flowing a current value such that the R value is in the range of 0.7 to 1.0 can be mentioned. In the method for producing soft water of the present invention, substituted water containing a monovalent cation having an electric current value such that the R value is in the range of 0.7 to 1.0 and having an equivalent or higher equivalent of the hardness component to be removed in the water to be treated. A method of passing water is preferable in that a high hardness component removal rate of 90% or more, particularly 95% or more can be obtained.

  Next, an electrosoftening device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram of the electrosoftening device of this example. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, description thereof will be omitted, and different points will be mainly described. That is, the electrosoftening device 10a in FIG. 2 is different from the electrosoftening device 10 in FIG. 1 in the electrode water path. In the electrosoftening device 10a, the substitution chamber 2 is provided with a substitution water introduction pipe c containing monovalent cations and a hardness component concentrated water discharge pipe d, and the cathode chamber 5 is connected to the hardness component concentrated water discharge pipe d. A cathode water introduction pipe g and a cathode water drain pipe h are arranged, and an anode water introduction pipe e and an anode water drain pipe f connected to the cathode water drain pipe h are arranged in the anode chamber 6.

  According to the electrosoftening device 10a, in addition to the same effect as the electrosoftening device 10, the monovalent cations that have moved through the cation exchange membrane 3 from the softening chamber 1 are returned to the most upstream anode chamber 6 for cation movement. Can be used again for replacement. As a result, since the monovalent cation concentration in the system can be maintained high, the monovalent cation salt added to the replacement water can be saved and the softening efficiency can be increased. Further, in the electrosoftening device 10a, the anode outlet water has a reduced cation and pH, and hypochlorous acid is generated by the anodic reaction and has oxidizing power and sterilizing power. Can do.

  Next, the softening device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic view of the softening device of this example. In FIG. 3, the softening device 20 includes a pre-demineralization device 21 and the electric softening device 10 located at the rear stage of the pre-desalination device 21, and the treated water discharge pipe k of the pre-desalination device 21 and the electric softening The treated water introduction pipe a of the apparatus 10 is connected, and the concentrate discharge pipe j of the pre-demineralizer 21 and the replacement water introduction pipe c of the electrosoftening apparatus 10 are connected. In the softening device 20 of FIG. 3, the electrosoftening device 10 may be the electrosoftening device 10a. The pre-demineralization device 21 is a known device that concentrates excluded ions in concentrated water, and examples thereof include an electrodialysis device, an electric deionized water production device, and a reverse osmosis membrane device. In the softening device 20, the pre-demineralization device 21 roughly removes the hardness components of raw water and impurity components such as monovalent cations, and then removes the remaining hardness components using the electric softening device 10. Desalination of the desalting apparatus is performed under mild conditions. For this reason, for example, when a reverse osmosis membrane device is used, scale generation on the membrane surface can be suppressed. The softening device 20 is particularly suitable when the hardness and salt concentration of raw water are high.

  In the method of producing soft water using the softening device 20 of this example, in the electrosoftening device 10, the treated water of the pre-demineralizer 21 is used as the water to be treated, and the concentrated water of the pre-demineralizer 21 is used as the replacement water. Since it is the same as the case where it uses, description is abbreviate | omitted.

  Next, a softening device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram of the softening device of this example. In the softening device 20a of FIG. 4, the same components as those of the softening device 20 of FIG. 3 are denoted by the same reference numerals, description thereof is omitted, and different points are mainly described. In FIG. 4, the softening device 20 a includes an electrosoftening device 10 and a post-desalination device 22 positioned at the rear stage of the electrosoftening device 10. The treated water discharge pipe b of the electrosoftening device 10 and the post-desalination device 22 The treated water introduction pipe i is connected, and the concentrate discharge pipe j of the post-desalination apparatus 22 and the replacement water introduction pipe c of the electric softening apparatus are connected. In the softening device 20a of FIG. 4, the electrosoftening device 10 may be the electrosoftening device 10a. The post-desalting device 22 is a known device that concentrates excluded ions in concentrated water, and examples thereof include an electrodialysis device, an electrical deionized water production device, and a reverse osmosis membrane device. In the softening device 20a, the electrosoftening device 10 operates with a low hardness component removal rate, roughens the raw water hardness component, and then removes the remaining hardness components and other impurity ions with the post-desalination device 22. do it. Since the electrosoftening device 10 in the previous stage can be operated with a low hardness component removal rate, the amount of the monovalent cation salt added to the replacement water can be reduced, or the operation can be performed at a lower current value. The capacity of the power supply can be reduced. Moreover, when a reverse osmosis membrane device is used as the desalting device 22 in the subsequent stage, for example, the generation of scale on the membrane surface can be suppressed because the hardness component concentration in the water to be treated is reduced. The softening device 20 is particularly suitable when the hardness and salt concentration of raw water are high.

  Next, the present invention will be described more specifically with reference to examples. However, this is merely an example and does not limit the present invention.

The treated water was continuously operated for 500 hours under the operating conditions shown in Table 1 in the electrosoftening apparatus shown in FIG. 1 to obtain treated water. After continuous operation for 500 hours, the treated water was analyzed, and the apparatus was stopped and disassembled to visually check the generation of scale inside the apparatus. The treated water was made by passing tap water through an activated carbon filter (PF-CB, manufactured by Organo) into the softening chamber of the electric softening device, and the treated water sample and operation data were collected 500 hours after the start of operation. In addition, the replacement water is obtained by filtering tap water through an activated carbon filtration filter in the same manner as the water to be treated, adding 25% saline using a metering pump so that the alkali metal concentration becomes a predetermined concentration, and then replacing the replacement chamber of the electrosoftening device. Water was passed through. In Example 1, the concentration of hardness of the water to be treated is 60.1mgCaCO ₃ / l, substituted water was cation concentration 100mgCaCO ₃ / l of equivalent or more monovalent the hardness components. R was 0.75. As a result, the hardness of the treated water was 3.0 mgCaCO ₃ / L, and the hardness removal rate was 95.0%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

The same operation as in Example 1 was performed except that the energization current value was set to 0.1 A instead of 0.2 A, and the average applied voltage was set to 9.7 V instead of 16 V. R in this operating condition was 0.37. That is, in Example 2, the energizing current value and the average applied voltage are changed and set to a low softening force. The results are shown in Table 1. The hardness of the treated water was 29.6 mg CaCO ₃ / L, and the hardness component removal rate was 50.7%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

The replacement water is tap water (Example 1) (treated water) instead of the salt-added prepared water, 0.06 A instead of the energization current value of 0.2 A, and 12 V instead of the average applied voltage of 16 V. The same procedure as in Example 1 was performed. R in this operating condition was 0.84. That is, Example 3 uses water whose substitutional water has a monovalent cation concentration below the equivalent of the hardness component in the water to be treated. The results are shown in Table 1. The hardness of the treated water was 49.8 mg CaCO ₃ / L, and the hardness component removal rate was 17.2%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

As the water to be treated, tap water (Example 2) is used instead of tap water (Example 1), and as the replacement water, tap water (Example 2) is used instead of the salt-added prepared water. The procedure was the same as Example 1 except that 0.12 A was used instead of 2 A, and 22 V was used instead of the average applied voltage of 16 V. R in this operating condition was 0.86. That is, Example 4 uses the tap water which is to-be-processed water different from Examples 1-3 as substitution water, and the monovalent cation density | concentration of the said tap water exceeds the equivalent of the hardness component contained in the same tap water. It uses water. The results are shown in Table 1. The hardness of the treated water was 3.1 mg CaCO ₃ / L, and the hardness component removal rate was 92.5%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

Without filling the softening chamber and the replacement chamber with a cation exchanger, a polypropylene mesh spacer is placed as a route material, and the replacement water is replaced with salt-added prepared water to make tap water (Example 2) (treated water). The same operation as in Example 1 was performed except that 0.03 A was substituted for the current value of 0.2 A, 34 V was substituted for the average applied voltage of 16 V, and 300 hours were substituted for the continuous operation time of 500 hours. In addition, since the thickness of the softening chamber and the replacement chamber was set to 1 mm each, the number of chambers was set to 20 chambers, and the volumes of Examples 1 to 4 and the water flow space were combined. R in this operating condition was 0.86. That is, in Example 5, the softening chamber and the replacement chamber are not filled with a cation exchange resin, and tap water that is to be treated is water having a monovalent cation concentration exceeding the equivalent of the hardness component contained in the tap water with the same tap water. Is used. The results are shown in Table 1. The hardness of the treated water was 5.0 mg CaCO ₃ / L, the hardness component removal rate was 88.0%, and no scale was observed on the film surface on the cathode side of the substitution chamber.

The water to be treated was continuously operated for 500 hours in the following softening apparatus under the operating conditions shown in Table 2 to obtain treated water with less hardness. After continuous operation for 500 hours, the treated water was analyzed, and the apparatus was stopped and disassembled to visually check the generation of scale inside the apparatus. In Example 6, the concentration of hardness of the water to be treated is 60.1mgCaCO ₃ / l, substituted water was cation concentration 327mgCaCO ₃ / l of equivalent or more monovalent the hardness components. R was 0.82. As a result, the hardness of the treated water was 0.017 mg CaCO ₃ / l, and the hardness removal rate was 99.97%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

<Softening device>
The treated water (intermediate soft water) of the same electrosoftening device as in Example 1 is connected so as to pass through a reverse osmosis membrane (element; “ES-20-D4” manufactured by Nitto Denko Corporation) through an intermediate soft water tank and a high-pressure pump. Then, the reverse osmosis membrane concentrated water is connected through a concentrated water tank and a concentrated water pump so as to be passed to the replacement chamber of the electrosoftening device.

  In Example 6, since the optimum flow rates of the electric softening part and the reverse osmosis membrane part did not match, the intermediate soft water and the reverse osmosis membrane concentrated water were temporarily stored in the intermediate soft water tank and the concentrated water tank and pumped. Although the method of feeding water was used, the intermediate soft water tank, the concentrated water tank, and the concentrated water pump can be omitted by making the intermediate soft water flow rate of the electric softening unit and the supply water flow rate of the reverse osmosis membrane unit coincide.

The water to be treated was continuously operated for 500 hours in the following softening apparatus under the operating conditions shown in Table 2 to obtain treated water with less hardness. After continuous operation for 500 hours, the treated water was analyzed, and the apparatus was stopped and disassembled to visually check the generation of scale inside the apparatus. In Example 7, the concentration of the treated water of the former-stage electric deionized water production apparatus (hereinafter also referred to as an electrodeionization apparatus or an electrodeionization part) is 17.9 mg CaCO ₃ / l, and the replacement water has the hardness. The monovalent cation concentration equal to or greater than the equivalent of the component was 45.3 mg CaCO ₃ / l. R was 0.82. As a result, the hardness of the treated water was 0.36 mg CaCO ₃ / l, and the hardness removal rate was 98.0%. Further, no scale was observed on the film surface on the cathode side of the replacement chamber.

<Softening device>
The water to be treated is passed through an electrodeionization device, the treated water is passed through a softening chamber of an electric softening device similar to that of the first embodiment, and the concentrated water of the electrodeionization device is replaced with a replacement chamber of the electric softening device. A device connected to allow water to pass through. The electrodeionization device is a known electrodeionization device, and a deionization chamber partitioned by a cation exchange membrane and an anion exchange membrane is filled with a mixed bed ion exchange resin, and the anion exchange membrane and the cation exchange membrane. The concentrating compartment partitioned by 1 was also filled with mixed bed ion exchange resin.

  The energization current value 0.2A of the electrodeionization part of Example 7 corresponds to about 80% with respect to the ion load in the water to be treated flowing in a unit time. The capacity was about 70% in terms of ion removal rate. As can be seen from Table 2, under these operating conditions, even if water to be treated containing a large amount of hardness component is passed through the electrodeionization section and energized to deionize, the hardness scale is deposited inside the stack. I didn't.

It is a schematic diagram of the electrosoftening apparatus in the 1st Embodiment of this invention. It is a schematic diagram of the electrosoftening apparatus in the 2nd Embodiment of this invention. It is a schematic diagram of the softening apparatus in the 1st Embodiment of this invention. It is a schematic diagram of the softening apparatus in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Softening chamber 2 Replacement chamber 3 Cation exchange membrane 4 Monovalent cation selective permeation membrane 5 Cathode chamber 6 Anode chamber 7 Anode 8 Cathode 10, 10a Electrosoftening device a-k piping 20, 20a Softening device 21 Pre-demineralization device 22 Post-desalting device Salt equipment

Claims (16)

  A monovalent cation selective permeable membrane and a cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber to serve as a water passage, and a water passage located on the cathode side of the monovalent cation selective permeable membrane as a softening chamber. The water passage chamber located on the anode side of the monovalent cation selective permeation membrane is used as a replacement chamber, and the softening chamber is provided with an introduction path and a soft water discharge path for water to be treated containing a hardness component. An electrosoftening device characterized in that a substitution water introduction path containing monovalent cations and a hardness component concentrated water discharge path are arranged, and a water introduction path and a discharge path are arranged in the anode chamber and the cathode chamber, respectively. .   2. The electrosoftening device according to claim 1, wherein a monovalent cation salt supply means is connected to the introduction path of the replacement water.   The hardness chamber concentrated water discharge path of the replacement chamber is connected to the introduction path of the cathode chamber, and the discharge path of the cathode chamber is connected to the introduction path of the anode chamber. The electrosoftening device according to 1 or 2.   The hardness chamber concentrated water discharge path of the replacement chamber is connected to the introduction path of the anode chamber, and the discharge path of the anode chamber is connected to the introduction path of the cathode chamber. The electrosoftening device according to 1 or 2.   The electrosoftening device according to any one of claims 1 to 3, wherein a cation exchanger is filled in at least the softening chamber among the softening chamber, the replacement chamber, the anode chamber, and the cathode chamber.   A pre-demineralization device and an electrosoftening device according to any one of claims 1 to 5 located at a stage subsequent to the pre-demineralization device are disposed, and the treated water discharge path of the pre-demineralization device and the electrosoftening device The softening device is characterized in that the treated water introduction route is connected, and the concentrate discharge route of the pre-demineralization device and the replacement water introduction route of the electrosoftening device are connected.   An electrosoftening device according to any one of claims 1 to 5 and a post-desalination device located at a subsequent stage of the electrosoftening device are disposed, and a treated water discharge path of the electrosoftening device and the post-desalination device A softening apparatus comprising: a treated water introduction path connected; and a concentrate discharge path of the post-desalting apparatus and a replacement water introduction path of the electrosoftening apparatus.   The softening device according to claim 6, wherein the pre-desalting device is an electrodialysis device, an electric deionized water production device, or a reverse osmosis membrane device.   The softening apparatus according to claim 7, wherein the post-desalting apparatus is an electrodialysis apparatus, an electric deionized water production apparatus, or a reverse osmosis membrane apparatus.   A monovalent cation selective permeable membrane and a cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber, and a water passage is formed between them, and a water passage chamber (softening chamber) located on the cathode side of the monovalent cation selective permeable membrane. The water to be treated containing the hardness component is passed through, and the water containing the monovalent cation is passed through the water flow chamber (substitution chamber) located on the anode side of the monovalent cation selective permeation membrane. A method for producing soft water, comprising applying a position to replace a hardness component in water to be treated with a monovalent cation in substitution water.   The method for producing soft water according to claim 10, wherein the amount of monovalent cations in the substitution water is equal to or more than the equivalent of the hardness component to be removed.   The method for producing soft water according to claim 10 or 11, wherein the replacement water is water to be treated or water prepared by adding a monovalent cation salt to the water to be treated.   The said to-be-processed water is the treated water which flows out from a pre-demineralizer, The said replacement water is the concentrated water discharged | emitted from this pre-demineralizer, The any one of Claims 10-12 characterized by the above-mentioned. The soft water manufacturing method as described.   The method for producing soft water according to any one of claims 10 to 13, wherein a cation exchanger is filled in at least the softening chamber among the softening chamber, the substitution chamber, the anode chamber, and the cathode chamber.   15. All or part of the replacement chamber outlet water discharged from the replacement chamber is passed through the cathode chamber, and further, the cathode chamber outlet water is passed through the anode chamber. The soft water manufacturing method of description.   15. All or part of the replacement chamber outlet water discharged from the replacement chamber is passed through the anode chamber, and further, the anode chamber outlet water is passed through the cathode chamber. The soft water manufacturing method of description.

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