Water softening device and method for regenerating same

Abstract

A water softening device comprising: a water softening tank in which raw water is softened with a weakly acidic cation-exchange resin; a pH adjustment tank; an electrolysis tank in which acid electrolysis water is generated; a conductivity measurement unit S1 that measures the conductivity of the raw water; a conductivity measurement unit S2 that measures the conductivity of the soft water obtained by passing through the water softening tank and the pH adjustment tank; a passed water amount detection unit that detects the cumulative amount of raw water passed through the water softening tank in a predetermined period; and a control unit that controls the passing of acid electrolysis water to the water softening tank. The control unit calculates the regeneration time for the weakly acidic cation-exchange resin on the basis of the amount of hard component adsorbed to the weakly acidic cation-exchange resin calculated from the difference between the conductivity of the raw water and the conductivity of the soft water and the cumulative amount of passing raw water, and executes a process of regenerating the weakly acidic cation-exchange resin by passing acid electrolysis water to the water softening tank during the calculated regeneration time.

Description

[Technical Field]

[0001] The present invention relates to a water softening device and a method for regenerating the same. [Background technology]

[0002] Many water softeners have been proposed that use cation exchange resins. For example, a known device uses a cation exchange resin with sodium ions as functional groups (strongly acidic cation exchange resin) to exchange calcium ions and magnesium ions, which are hardness components in raw water, for sodium ions to obtain soft water.

[0003] Cation exchange resins lose or even lose their ion exchange capacity with continued use. That is, once all of the sodium ions, which are functional groups of the cation exchange resin, have been exchanged for calcium ions and magnesium ions, which are hardness components, the resin is no longer capable of ion exchange. Therefore, to make the resin capable of ion exchange again, it is necessary to regenerate the cation exchange resin. The regeneration process involves passing regenerated water, such as saturated salt water, through the cation exchange resin. This regeneration process requires the periodic replenishment of salt depending on the amount of soft water used, which is time-consuming. Furthermore, the use of a large amount of salt poses environmental problems.

[0004] Therefore, as a method for regenerating cation exchange resins without using table salt, a method has been proposed in which weakly acidic cation exchange resins are used and the weakly acidic cation exchange resins are regenerated with acidic electrolyzed water produced by electrolysis (see, for example, Patent Documents 1 and 2). This method has been successful to a certain extent in that it does not use table salt and does not cause environmental problems. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-30973 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-165954 Summary of the Invention

[0006] In conventional water softeners using the above-mentioned weakly acidic cation exchange resin, it is not possible to quantify the amount of hardness components attached to the weakly acidic cation exchange resin. Therefore, when regenerating the weakly acidic cation exchange resin, the amount of acidic electrolyzed water required for the regeneration is unknown, which poses a problem. That is, to ensure a perfect regeneration process, an excessive amount of acidic electrolyzed water must be passed through, which wastes the power, time, and water required for producing the acidic electrolyzed water. Conversely, passing a small amount of acidic electrolyzed water shortens the regeneration process time, but the regeneration of the weakly acidic cation exchange resin is insufficient.

[0007] The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a water softener that uses acidic electrolyzed water to regenerate weakly acidic cation exchange resins, and a regeneration method thereof that can prevent excess or deficiency in the amount of acidic electrolyzed water used in the regeneration treatment of weakly acidic cation exchange resins.

[0008] In order to solve the above problems, a water softening device according to a first aspect of the present invention comprises a water softening tank that softens raw water containing hardness components with a weakly acidic cation exchange resin, a pH adjustment tank that adjusts the pH of the softened water produced in the water softening tank to a neutral range, an electrolysis tank that produces alkaline electrolyzed water and acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin, (1) a conductivity measuring unit S1 that measures the conductivity of raw water and a conductivity measuring unit S2 that measures the conductivity of softened water obtained by passing through the water softening tank and the pH adjustment tank, and (2) at least one of a hardness detecting unit that detects the hardness of raw water or a hardness storing unit that stores the hardness of raw water measured in advance, and a conductivity measuring unit S1 that measures the conductivity of raw water and a conductivity measuring unit S2 that measures the conductivity of softened water obtained by passing through the water softening tank and the pH adjustment tank. a conductivity measuring unit S2, a water flow rate detecting unit that detects the cumulative amount of raw water passing through the water softening tank in a predetermined period, and a control unit that at least controls the flow of acidic electrolyzed water generated by the electrolytic tank into the water softening tank. The control unit calculates a regeneration time for the weakly acidic cation exchange resin based on the amount of hardness components adsorbed on the weakly acidic cation exchange resin, which is calculated from the difference between the conductivity of the raw water measured by the conductivity measuring unit S1 and the conductivity of the softened water measured by the conductivity measuring unit S2, or the hardness of the raw water detected by the hardness detecting unit or the hardness of the raw water stored in the hardness memory unit, and the cumulative amount of raw water passed through the water flow rate detecting unit, and controls the weakly acidic cation exchange resin to be regenerated by passing acidic electrolyzed water through the water softening tank for the calculated regeneration time.

[0009] A method for regenerating a water softener according to a second aspect of the present invention includes a water softening tank that softens raw water containing hardness components with a weakly acidic cation exchange resin, a pH adjustment tank that adjusts the pH of the softened water produced in the water softening tank to a neutral range, an electrolytic tank that produces alkaline electrolyzed water and acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin, (1) a conductivity measuring unit S1 that measures the conductivity of the raw water and a conductivity measuring unit S2 that measures the conductivity of the softened water obtained by passing through the water softening tank and the pH adjustment tank, and (2) at least one of a hardness detecting unit that detects the hardness of the raw water or a hardness storing unit that stores the hardness of the raw water measured in advance, and a conductivity measuring unit S1 that measures the conductivity of the raw water and the water softening tank. and a pH adjustment tank, and a water flow rate detection unit that detects the amount of raw water passing through the water softening tank. The method calculates a regeneration time for the weakly acidic cation exchange resin based on the difference between the conductivity of the raw water measured by the conductivity measurement unit S1 and the conductivity of the softened water measured by the conductivity measurement unit S2, or the hardness of the raw water detected by the hardness detection unit or the hardness of the raw water stored in the hardness memory unit, and the cumulative amount of raw water passed through the water flow rate detection unit, and then passes acidic electrolyzed water through the water softening tank for the calculated regeneration time to regenerate the weakly acidic cation exchange resin. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram showing an example of a water softening device according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating the relationship between the amount of change in hardness ions and the amount of change in electrical conductivity. [Figure 3] FIG. 3 is a conceptual diagram showing a modified example of the water softening device according to this embodiment. [Figure 4] FIG. 4 is a conceptual diagram showing a modified example of the water softening device according to this embodiment. [Figure 5] FIG. 5 is a conceptual diagram showing an example of an electrolytic cell according to this embodiment. [Figure 6] FIG. 6 is a graph showing the change in pH on the weakly acidic cation exchange resin side versus the regeneration time of the weakly acidic cation exchange resin. [Figure 7] FIG. 7 is a graph showing the change in pH on the weakly basic anion exchange resin side versus the regeneration time of the weakly basic anion exchange resin. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a water softening device and a regeneration method thereof according to the present embodiment will be described with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of convenience and may differ from the actual proportions.

[0012] <Water softener> The water softening device of this embodiment includes a water softening tank that softens raw water containing hardness components using a weakly acidic cation exchange resin. It also includes a pH adjustment tank that adjusts the pH of the softened water produced in the water softening tank to a neutral range. It also includes an electrolytic tank that produces alkaline electrolyzed water and acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin. It also includes at least one of the following (1) and (2). (1) A conductivity measuring unit S1 that measures the conductivity of raw water, and a conductivity measuring unit S2 that measures the conductivity of softened water obtained by passing through the water softening tank and the pH adjustment tank. (2) A hardness detection unit that detects the hardness of raw water or a hardness storage unit that stores the hardness of raw water measured in advance. The apparatus further includes a water flow rate detector that detects the cumulative amount of raw water passing through the water softening tank over a predetermined period. It also includes a control unit that controls the flow of acidic electrolyzed water generated by the electrolytic tank into the water softening tank. The control unit calculates a regeneration time for the weakly acidic cation exchange resin based on the amount of hardness components adsorbed on the weakly acidic cation exchange resin, and controls the water softening tank to regenerate the weakly acidic cation exchange resin by passing acidic electrolyzed water through the water softening tank for the calculated regeneration time. The amount of hardness components adsorbed on the weakly acidic cation exchange resin is calculated from the difference between the conductivity of the raw water measured by the conductivity measuring unit S1 and the conductivity of the softened water measured by the conductivity measuring unit S2, and the cumulative amount of raw water flow detected by the water flow rate detector. Alternatively, the ... is calculated from the raw water hardness detected by the hardness detecting unit or the raw water hardness stored in the hardness memory unit, and the cumulative amount of raw water flow detected by the water flow rate detector.

[0013] 1 conceptually illustrates each element of a water softening device 10 of this embodiment. The water softening device 10 includes a water softening tank 12, a pH adjustment tank 13, and an electrolytic tank 14. The water softening tank 12 is connected to a flow path 20 for passing raw water W1 containing hardness components, and a flow path 22 for leading softened water obtained by passing through the water softening tank 12 and the pH adjustment tank 13 to the outside. The flow path 20 includes a water flow rate detection unit Sw for detecting the cumulative amount of raw water W1 passing through the water softening tank 12 over a predetermined period, and a conductivity measurement unit S1 for measuring the conductivity of the raw water. The flow path 22 also includes a conductivity measurement unit S2 for measuring the conductivity of the softened water obtained by passing through the water softening tank 12 and the pH adjustment tank 13. The water softening tank 12 is further connected to a flow path 24 for passing the acidic electrolyzed water produced in the electrolytic tank 14 and a flow path 26 for discharging the acidic electrolyzed water containing hardness components after regenerating the weakly acidic cation exchange resin in the water softening tank 12. The electrolytic tank 14 is connected to a flow path 28 for introducing water W2 for producing electrolyzed water, and to a flow path 27 for discharging alkaline electrolyzed water produced simultaneously with the production of acidic electrolyzed water.

[0014] A control unit 40 is connected to the electrolytic bath 14, and the control unit 40 controls the flow of acidic electrolyzed water generated by the electrolytic bath 14 to the water softening bath 12. More specifically, when regenerating the weakly acidic cation exchange resin in the water softening bath 12, the control unit 40 calculates the amount of hardness components adsorbed on the weakly acidic cation exchange resin based on the difference between the conductivity of the raw water and the conductivity of the softened water and the cumulative amount of water passed. Then, based on the calculated amount of hardness components and the pH or flow rate of the acidic electrolyzed water being passed, the control unit 40 calculates the flow time of the acidic electrolyzed water, i.e., the regeneration time. The control unit controls the flow of acidic electrolyzed water through the weakly acidic cation exchange resin for the calculated time.

[0015] In the water softening device 10 shown in FIG. 1, when raw water containing hardness components is softened to produce soft water, the raw water first passes through a weakly acidic cation exchange resin provided in the water softening tank 12. At this time, the cations that are hardness components in the raw water are exchanged for hydrogen ions by the weakly acidic cation exchange resin, thereby softening the water. Next, the softened water obtained passes through a pH adjustment tank 13 to + The pH is adjusted to a neutral range by decreasing the pH. Here, the pH in the neutral range is in the range of 5.8 to 8.6.

[0016] On the other hand, when regenerating the weakly acidic cation exchange resin, the acidic electrolyzed water produced in the electrolytic cell 14 is passed through the water softening cell 12 and passes through the weakly acidic cation exchange resin therein. That is, by passing through the weakly acidic cation exchange resin, the cations (hardness components) adsorbed on the weakly acidic cation exchange resin undergo an ion exchange reaction with the hydrogen ions contained in the acidic electrolyzed water, thereby regenerating the weakly acidic cation exchange resin. Then, the acidic electrolyzed water containing the cations after passing through the weakly acidic cation exchange resin is discharged through the flow path 26. During the above-described regeneration process, the acidic electrolyzed water flows through the electrolytic cell 14, the flow path 24, the water softening cell 12, and the flow path 26 in this order by a pump (not shown).

[0017] In this embodiment, the control unit 40 controls the electrolytic bath 14 to regenerate the weakly acidic cation exchange resin, and sets the time for passing acidic electrolyzed water through the water softening bath 12, i.e., the regeneration time. More specifically, the control unit 40 preferably calculates the regeneration time for the weakly acidic cation exchange resin as follows. Specifically, the control unit 40 ... based on the relationship between the difference (ΔC) between the amount of hardness components in the raw water and the amount of hardness components in the softened water obtained by passing through the water softening bath and the pH adjustment bath, relative to the difference (ΔS) between the conductivity of the raw water and the conductivity of the softened water obtained by passing through the water softening bath and the pH adjustment bath. This relationship is expressed as ΔC / ΔS=α (α: proportionality constant). Specifically, the change in the amount of hardness components before and after water softening is calculated from the difference between the conductivity of the raw water measured by the conductivity measuring unit S1 and the conductivity of the softened water measured by the conductivity measuring unit S2. The regeneration time for the weakly acidic cation exchange resin is then calculated from the calculated change in the hardness components. The difference ΔS between the conductivity of raw water and the conductivity of softened water that has passed through the water softening tank and pH adjustment tank is also called the conductivity change ΔS. The difference ΔC between the amount of hardness components in raw water and the amount of hardness components in softened water that has passed through the water softening tank and pH adjustment tank is also called the hardness ion change ΔC. The method for calculating the regeneration time of the weakly acidic cation exchange resin will be described in detail below.

[0018] To prevent the excess or deficiency of the amount of acidic electrolyzed water required for regenerating the weakly acidic cation exchange resin, it is necessary to know the amount of hardness components (hardness ions) adhering to the weakly acidic cation exchange resin. In this embodiment, the conductivity of the raw water before passing through the water softening tank 12 and the conductivity of the softened water after passing through the water softening tank 12 and the pH adjustment tank are measured, and the amount of hardness components adhering to the weakly acidic cation exchange resin is calculated based on the difference between the conductivity. In other words, by using a weakly acidic cation exchange resin for water softening and measuring the conductivity of the water before and after the water softening treatment, the amount of hardness components can be quantified in-line. The principle behind this is explained below. When water containing hardness components is softened using a weakly acidic cation exchange resin (represented by RCOOH), the following ion exchange reaction occurs: Ca 2+ + 2RCOOH → (RCOO - )2Ca 2+ + 2H+ In addition, water generally contains the alkalinity component HCO3 - Contains HCO3 - When hardness components are present, H released by ion exchange reaction of hardness components + is HCO3 - The H2CO3 produced by the reaction immediately changes to dissolved CO2. H + + HCO3 - → H2CO3 → CO2 + H2O where HCO3 - The ratio of HCO3 to hardness ions varies depending on the water quality, i.e., the location where the raw water is taken. If there is a lot of alkalinity in the raw water, - Since the amount of H released from the weakly acidic cation exchange resin is more than twice that of hardness ions, + is HCO3 - When the alkalinity component in the raw water is low, HCO3 - is less than twice the hardness ion, and HCO3 - without being consumed by H + In this case, the pH adjustment tank adjusts the pH of the soft water to a neutral range, and the remaining H + Reduce.

[0019] As mentioned above, when the raw water contains a large amount of alkalinity components, if weakly acidic cation exchange resin is used for water softening, the H released by the ion exchange reaction + is HCO3 - The pH adjustment tank reacts with the alkaline component, which reduces the ion concentration in the water. + Therefore, in the water softening device of this embodiment, the difference in conductivity of water before and after the softening process and the amount of hardness ions reduced are in an equivalent relationship. In addition, since the difference in conductivity and the amount of hardness ions reduced are in a proportional relationship, Ca 2+ and HCO3 -If the correlation between the change in hardness ion concentration and the change in conductivity is clarified in advance, the change in hardness ion concentration can be calculated based on the change in conductivity. Then, the amount of hardness components adsorbed on the weakly acidic cation exchange resin is calculated from the change in hardness ion concentration and the cumulative amount of water passed, and the regeneration time using acidic electrolyzed water is set according to the amount of hardness components.

[0020] Further explanation will be given with reference to Figure 2. As shown in Figure 2(a), if the relationship between the amount of change in hardness ions ΔC and the amount of change in conductivity ΔS is as shown in the bar graph, the two are proportional to each other, and therefore the relational expression ΔC / ΔS=α (α: proportionality constant) is given. Also, as shown in Figure 2(b), if the amount of change in conductivity ΔS1 before and after softening treatment for a certain raw water is obtained, the amount of change in hardness ions ΔC1 can be calculated from the above relational expression. The difference between the amount of change in hardness ions ΔC1 and the hardness of the raw water is the hardness of the softened water obtained by the softening treatment.

[0021] As described above, the amount of hardness components (i.e., hardness) in the softened water can be calculated by measuring the conductivity of water before and after softening. The hardness ion change ΔC1 represents the reduction in hardness components during softening and is equivalent to the amount of hardness components adsorbed onto the weakly acidic cation exchange resin. Therefore, the amount of hardness components adsorbed onto the weakly acidic cation exchange resin can be calculated from the difference in conductivity between water before and after softening. On the other hand, the hardness components adsorbed onto the weakly acidic cation exchange resin are components that should be removed by regeneration, and the regeneration time of the weakly acidic cation exchange resin depends on the amount of the components. Therefore, the regeneration time can be calculated based on the amount of acidic electrolyzed water appropriate for removing the hardness components.

[0022] The control unit 40 preferably calculates the regeneration time using the following formula 1, where C (mol) is the total change in hardness components before and after softening, x is the pH of the acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin, and v (L / min) is the flow rate of the acidic electrolyzed water. A previously measured value can also be used for the pH. Playback time (minutes) = C × 2 / (10 -x ×v) [Formula 1] Below are three examples of how to calculate the regeneration time of a weakly acidic cation exchange resin.

[0023] (1) The total amount of adsorption of hardness components is calculated from the cumulative amount of water flow and the average amount of adsorbed hardness components, and the regeneration time is calculated from the calculated total amount of adsorption of hardness components. The cumulative water flow rate is the total amount of raw water used in the water softening treatment. More specifically, it is the total amount of water flowing from the time raw water is passed through a weakly acidic cation exchange resin that has undergone regeneration treatment (or a new one) until just before the start of regeneration treatment. The average amount of adsorption hardness is the value obtained by dividing the amount of adsorption hardness of the weakly acidic cation exchange resin measured at predetermined intervals by the number of measurements. In other words, the adsorption capacity of weakly acidic cation exchange resins decreases as the water softening treatment continues, and the amount of hardness components adsorbed is not constant, so an average value is used. Furthermore, the total amount of hardness components adsorbed is the total amount of hardness components adsorbed from the time raw water is passed through the weakly acidic cation exchange resin (or a new one) that has undergone regeneration treatment until just before the start of regeneration treatment. The total amount of hardness components adsorbed can be calculated using the following formula. Total amount of adsorbed hardness components (mol) = "Cumulative amount of water passed" (L) x "Average amount of adsorbed hardness" (mol / L)

[0024] The regeneration time of the weakly acidic cation exchange resin can be calculated from the total amount of adsorption of hardness components calculated as above. That is, if the total change in the amount of hardness components before and after softening is C (mol), the pH of the acidic electrolyzed water used for regeneration treatment is x, and the flow rate is V (L / min), the regeneration time can be calculated using the following formula. In the following formula, the hardness components are the divalent cation calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) is assumed. Playback time (minutes) = C × 2 / (10 -x ×V)

[0025] (2) The total amount of hardness adsorption is calculated from the cumulative amount of water flow, the amount of adsorbed hardness immediately before the start of regeneration treatment, and the correction coefficient, and the regeneration time is calculated from the calculated total amount of hardness adsorption. In the above (1), the "average adsorption hardness amount" in calculating the total amount of hardness component adsorption is obtained through multiple measurements, but in (2), it is calculated by multiplying the adsorption hardness amount immediately before the start of regeneration treatment by a correction coefficient. In this respect, it differs from the above (1). That is, the total amount of hardness component adsorption can be calculated using the following formula. The correction coefficient a can be obtained by accumulating experimental data. That is, experimental data on the adsorption hardness amount immediately before the regeneration treatment and the average adsorption hardness amount can be accumulated, and the average adsorption hardness amount / adsorption hardness amount immediately before the regeneration treatment can be used as the correction coefficient a from a large amount of experimental data. Total amount of adsorbed hardness components (mol) = "Cumulative amount of water passed" (L) x "Amount of adsorbed hardness immediately before regeneration treatment" (mol / L) x a (a>0) Then, based on the calculated total amount of adsorption of hardness components, the regeneration time can be calculated in the same manner as in (1) above.

[0026] The water softening device of this embodiment may include a hardness detection unit that detects the hardness of raw water or a hardness storage unit that stores previously measured raw water hardness, instead of or in addition to the conductivity measurement units S1 and S2. That is, if the hardness of raw water passed through the water softening tank is known, the total amount of hardness adsorption by the weakly acidic cation exchange resin can be calculated from the hardness of the raw water and the cumulative amount of water passed through the water softening tank. The regeneration time of the weakly acidic cation exchange resin can then be calculated from the calculated total amount of hardness adsorption as follows. Note that when a hardness detection unit or a hardness storage unit is provided along with the conductivity measurement units S1 and S2, the regeneration time of the weakly acidic cation exchange resin is calculated using either one of them, rather than using both at the same time.

[0027] (3) The total amount of hardness adsorption is calculated from the cumulative amount of water flow and the hardness of the raw water, and the regeneration time is calculated from the calculated total amount of hardness adsorption. If we consider that the total amount of hardness components in the raw water being passed through is equal to the total amount of hardness components adsorbed by the weakly acidic cation exchange resin, the total amount of adsorbed hardness components can be calculated using the following formula. Total amount of hardness components adsorbed (mol) = "Cumulative amount of water passed" (L) x "Hardness of raw water" (mol / L) Then, based on the calculated total amount of adsorption of hardness components, the regeneration time can be calculated in the same manner as in (1) above.

[0028] As described above, the total amount of hardness components adsorbed by the weakly acidic cation exchange resin can be calculated by measuring the conductivity of water before and after softening and calculating the difference between them, or by knowing the hardness of the raw water. Then, the regeneration time can be calculated from the calculated total amount of hardness components adsorbed, and the weakly acidic cation exchange resin can be regenerated for that regeneration time, thereby preventing excess or deficiency in the amount of acidic electrolyzed water. Consequently, the weakly acidic cation exchange resin can be sufficiently regenerated, while reducing the power and time required for producing acidic electrolyzed water and the waste of water used to produce the acidic electrolyzed water. Each element of the water softening device of this embodiment will be described in detail below.

[0029] [Water softening tank] Water softening tank 12 contains a weakly acidic cation exchange resin therein, which softens raw water containing hardness components. Water containing hardness components flows into water softening tank 12 via flow path 20, passes through the weakly acidic cation exchange resin, and is discharged as softened water from flow path 22. In other words, flow paths 20 and 22 are used when softening raw water passed through flow path 22. Note that the water softening tank can also exchange ions other than hardness components (e.g., potassium ions, sodium ions, ammonium ions, etc.), and is not limited to use for water softening.

[0030] On the other hand, the water softening tank 12 is connected to a flow path 24 extending from the electrolytic tank 14 through which acidic electrolyzed water is passed, and a flow path 26 which introduces the acidic electrolyzed water that has passed through the weakly acidic cation exchange resin to the mixing tank 16. The flow paths 24 and 26 are used when regenerating the weakly acidic cation exchange resin.

[0031] As described above, in the water softening tank 12, different flow paths are used when softening raw water and when regenerating the weakly acidic cation exchange resin, and the required flow path is selected and used by a valve (not shown). In other words, the water softening tank 12 is provided with a main water path through which raw water flows and a regeneration water path through which acidic electrolyzed water generated by the electrolytic tank 14 flows. The main water path is a flow path that runs within the water softening tank 12 from flow path 20 to flow path 22, and the regeneration water path is a flow path that runs within the water softening tank 12 from flow path 24 to flow path 26.

[0032] There are no particular limitations on the weakly acidic cation exchange resin, and any general-purpose one can be used. For example, one with a carboxyl group (-COOH) as the exchange group can be used. In addition, hydrogen ions (H + ) is a metal ion, ammonium ion (NH4 + ) or other cations may also be used.

[0033] [pH adjustment tank] As mentioned above, the pH adjustment tank adjusts the pH of the soft water to a neutral range and removes the remaining H + That is, the pH adjustment tank may be any tank that has the function of reducing the hydrogen ion concentration, and examples thereof include a weakly basic anion exchange resin, which will be described later, as well as carbon dioxide degassing and capacitive deionization.

[0034] [Electrolytic cell] The electrolytic cell 14 electrolyzes the water W2 introduced thereinto into acidic electrolyzed water and alkaline electrolyzed water. The acidic electrolyzed water produced in the electrolytic cell 14 is discharged through a flow path 24 and introduced into the water softening cell 12 for regeneration of the weakly acidic cation exchange resin. The alkaline electrolyzed water produced in the electrolytic cell 14 is discharged through a flow path (not shown).

[0035] There are no particular limitations on the electrolytic cell used in the water softening device 10 of this embodiment as long as it can produce acidic electrolyzed water and alkaline electrolyzed water. An example of the electrolytic cell 14 will be described with reference to FIG.

[0036] The electrolytic cell shown in Fig. 5 comprises an electrolysis chamber 50 for electrolyzing water, a power supply 54, an anode 62 connected to the anode of the power supply 54 via a wiring 56, and a cathode 60 connected to the cathode of the power supply 54 via a wiring 58. The inside of the electrolysis chamber 50 is partitioned by a partition wall 64 through an ion permeable membrane, with the anode chamber on the right side of Fig. 5 and the cathode chamber on the left side. Water flows into the cathode chamber and the anode chamber from a flow path 52, and the water in the cathode chamber is discharged as alkaline electrolyzed water from the flow path 66, and the water in the anode chamber is discharged as acidic electrolyzed water from the flow paths 68, 69, respectively.

[0037] Water introduced into the cathode chamber and the anode chamber of the electrolysis chamber 50 is electrolyzed by applying a voltage between the cathode 60 and the anode 62. In the electrolysis chamber 50, the electrolysis of water generates hydroxide ions (OH - ) and hydrogen gas in the anode chamber, and hydrogen ions (H + ) and oxygen gas are generated. Then, alkaline electrolyzed water is generated in the cathode chamber, and acidic electrolyzed water is generated in the anode chamber. The alkaline electrolyzed water is discharged from the flow path 66, and the acidic electrolyzed water is discharged from the flow path 68.

[0038] The acidic electrolyzed water generated in the electrolytic cell 14 should have a lower pH because the more hydrogen ions it contains, the more efficiently it can regenerate the weakly acidic cation exchange resin.

[0039] [Conductivity measurement section S1, S2] The conductivity measuring unit S1 measures the conductivity of raw water flowing upstream of the water softening tank 12. On the other hand, the conductivity measuring unit S2 measures the conductivity of softened water flowing downstream of the water softening tank 12. Both the conductivity measuring units S1 and S2 may be any device capable of measuring conductivity, and for example, a conductivity meter may be used. The conductivities measured by the conductivity measuring units S1 and S2 are sent to the control unit 40 as electrical signals.

[0040] [Hardness detection unit, hardness storage unit] The hardness detection unit has a function of detecting the hardness of the raw water W1, and may use, for example, a known water hardness meter that electrically measures water hardness. Alternatively, the hardness of the raw water may be calculated based on the conductivity of the raw water measured by the conductivity measurement unit S1. Furthermore, if the hardness of the raw water is known in advance, a hardness memory unit that stores the hardness of the raw water may be provided. The hardness memory unit may be provided in a memory unit within the control unit, which will be described later.

[0041] [Water flow detection unit] The water flow rate detection unit Sw detects the amount of raw water passed through the water softening tank 12. The water flow rate detection unit Sw may be any device capable of detecting the amount of raw water passed through, such as a flow rate sensor. The water flow rate detected by the water flow rate detection unit is sent to the control unit 40 as an electrical signal. The control unit 40 is configured to accumulate and store the amount of water flow over a predetermined period of time. The predetermined period is, for example, the period from when the raw water is passed through a weakly acidic cation exchange resin that has undergone regeneration treatment (or a new one) until immediately before the regeneration treatment is performed.

[0042] [Control Unit] The control unit 40 plays a role in controlling the entire water softening apparatus 10. The control unit 40 receives inputs such as conductivity signals from the conductivity measuring units S1 and S2 and a water flow rate signal from the water flow rate detecting unit Sw. The control unit 40 also includes, for example, an input / output unit that outputs predetermined control signals, a memory unit that stores a calibration curve map showing the relationship between conductivity and hardness, a RAM that is used as a work area and stores calculation results, and a CPU that controls the entire apparatus. In this embodiment, as described above, the regeneration time required to regenerate the weakly acidic cation exchange resin is calculated, and the acidic electrolyzed water generated in the electrolytic cell 14 is controlled to flow through the water softening cell 12 for the calculated regeneration time.

[0043] Next, another embodiment of the water softener of this embodiment will be described with reference to FIG. 3. This water softener differs from the water softener 10 shown in FIG. 1 in that it includes a mixing tank for mixing alkaline electrolyzed water generated in an electrolytic cell with acidic electrolyzed water used for regenerating a weakly acidic cation exchange resin. Specifically, as shown in FIG. 3, a water softener 10A includes a mixing tank 16 for mixing alkaline electrolyzed water generated in an electrolytic cell 14 with acidic electrolyzed water used for regenerating a weakly acidic cation exchange resin. A control unit 40 controls the mixing tank 16 to supply mixed water generated by mixing alkaline electrolyzed water and acidic electrolyzed water to the electrolytic cell 14 during regeneration of the weakly acidic cation exchange resin. The mixed water generated in the mixing tank 16 is passed through the electrolytic cell 14, where it is decomposed into acidic electrolyzed water and alkaline electrolyzed water. Therefore, the water softener 10 shown in FIG. 1 can reuse water that would otherwise be discharged, thereby reducing water consumption.

[0044] The water softening apparatus 10A shown in Fig. 3 includes a water softening tank 12, a pH adjusting tank 13, an electrolytic tank 14, and a mixing tank 16. Of these, the water softening tank 12, the pH adjusting tank 13, and the electrolytic tank 14 are the same as those in the water softening apparatus 10 shown in Fig. 1, so the same reference numerals are used to denote the peripheral members, and a description thereof will be omitted. The mixing tank 16 and its periphery will be described below.

[0045] As shown in Fig. 3, the water softening tank 12 is connected to a flow path 24 for passing the acidic electrolyzed water produced in the electrolytic tank 14, and a flow path 31 for passing the acidic electrolyzed water containing hardness components after the weak acid cation exchange resin has been regenerated in the water softening tank 12, to the mixing tank 16. The mixing tank 16 is further connected to a flow path 34 for passing the alkaline electrolyzed water produced in the electrolytic tank 14, a flow path 30 for passing the mixed water produced in the mixing tank 16 to the electrolytic tank 14, and a water supply path 32 for supplying water when the water level decreases due to the regeneration of the weak acid cation exchange resin. The mixing tank 16 is also connected to a drainage path 33 for discharging the mixed water. If the flow path 31 is sufficiently long and can accommodate the amount of water required for the regeneration treatment, the flow path 31 can be directly connected to the electrolytic cell 14 without providing the mixing tank 16. In this case, the flow path 34 and the water supply channel 32 are also directly connected to the flow path 31.

[0046] On the other hand, when regenerating the weakly acidic cation exchange resin, acidic electrolyzed water generated in the electrolytic cell 14 is passed through the water softening cell 12 and the weakly acidic cation exchange resin therein. Then, the acidic electrolyzed water containing cations (hardness components) after passing through the weakly acidic cation exchange resin is passed through the flow path 31 into the mixing cell 16. Also, alkaline electrolyzed water generated in the electrolytic cell 14 is passed through the flow path 34 into the mixing cell 16. That is, the acidic electrolyzed water containing cations and the alkaline electrolyzed water are mixed in the mixing cell 16. At this time, the hardness components as cations in the acidic electrolyzed water react with the alkaline electrolyzed water in the mixing cell 16. For example, when the hardness component in the acidic electrolyzed water is calcium ion, calcium hydroxide is generated by the alkaline electrolyzed water, or calcium carbonate is generated by combining with carbonate ions normally present in the water. Then, the water in the mixing cell 16 after the reaction (treated water) is passed through the electrolytic cell 14. That is, the water in the mixing tank 16 is passed through the electrolytic tank 14 to generate acidic electrolyzed water, which is then used to regenerate the weakly acidic cation exchange resin. Therefore, the acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin is reused as acidic electrolyzed water after its hardness components are diluted or converted into reaction products by alkaline electrolyzed water in the mixing tank 16. Furthermore, the reused acidic electrolyzed water is treated in the mixing tank 16 to reduce the hardness components, thereby preventing a decrease in regeneration efficiency. Furthermore, alkaline electrolyzed water is generated simultaneously with the generation of acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin, eliminating the need for a separate device for generating alkaline electrolyzed water. In the water softener 10A shown in FIG. 3, the control unit 40 controls the supply of mixed water, generated by mixing alkaline electrolyzed water and acidic electrolyzed water in the mixing tank 16, to the electrolytic tank 14 during the regeneration of the weakly acidic cation exchange resin. During the above regeneration process, the acidic electrolyzed water is pumped by a pump (not shown) through the electrolytic cell 14, flow path 24, water softening cell 12, flow path 31, mixing cell 16, and flow path 30, and then flows back into the electrolytic cell 14.

[0047] Next, another embodiment of the water softening device of this embodiment will be described with reference to Fig. 4. This water softening device differs from the water softening device 10 shown in Fig. 1 in that it uses a pH adjustment tank containing a weakly basic anion exchange resin and has a flow path for passing alkaline electrolyzed water generated in an electrolytic cell through the pH adjustment tank. That is, a water softening device 10B shown in Fig. 4 includes a water softening tank 12, an electrolytic cell 14, and a pH adjustment tank 18, and a flow path 35 for passing alkaline electrolyzed water generated in the electrolytic cell 14 is connected to the pH adjustment tank 18. Of these, the water softening tank 12 and the electrolytic cell 14 are the same as those in the water softening device 10 shown in Fig. 1, so the same reference numerals are used to designate the peripheral components and a description thereof will be omitted. The pH adjustment tank 18 and its surroundings will be described below.

[0048] As shown in Fig. 4, the water softening tank 12 is connected to a flow path 20 for passing raw water W1 containing hardness components, and a flow path 29 for leading the softened water obtained by passing through the water softening tank 12 to the pH adjustment tank 18. As in the water softening device 10 shown in Fig. 1, the flow path 20 is equipped with a water flow rate detection unit Sw that detects the cumulative amount of raw water W1 passing through the water softening tank over a predetermined period of time, and a conductivity measurement unit S1 that measures the conductivity of the raw water. On the other hand, the pH adjusting tank 18 is further connected to a flow path 35 for passing the alkaline electrolyzed water generated in the electrolytic tank 14, and a flow path 36 for leading the soft water after pH adjustment to the outside. The flow path 36 is equipped with a conductivity measuring unit S2 for measuring the conductivity of the soft water that has passed through the pH adjusting tank 18. In addition, the pH adjusting tank 18 is connected to a flow path 37 for discharging basic electrolyzed water containing anions such as chloride ions and sulfate ions after the weakly basic anion exchange resin has been regenerated.

[0049] In the water softening device 10B shown in Figure 4, raw water W1 flows into the water softening tank 12, where hardness components are ion-exchanged by the weakly acidic cation exchange resin inside, turning it into soft water. In this state, the soft water has a low pH, in the acidic range, due to the influence of hydrogen ions generated by the ion exchange. The soft water is then guided through the flow path 29 to the pH adjustment tank 18, where anions are exchanged for hydroxide ions by the weakly basic anion exchange resin inside, raising the pH to a neutral range. Therefore, the raw water W1 becomes soft water in the neutral range by passing through the water softening tank 12 and the pH adjustment tank 18.

[0050] On the other hand, like the weakly acidic cation exchange resin, the weakly basic anion exchange resin also loses its ion exchange capacity with continued water flow, necessitating regeneration. Therefore, the water softener 10B shown in FIG. 4 is preferably regenerated using alkaline electrolyzed water supplied from the electrolytic cell 14 via the flow path 35. That is, the control unit 40 controls the supply of alkaline electrolyzed water produced in the electrolytic cell 14 to the pH adjustment tank 18 to regenerate the weakly basic anion exchange resin during regeneration of the acidic cation exchange resin. Since the electrolytic cell 14 simultaneously produces acidic electrolyzed water and alkaline electrolyzed water, the weakly acidic cation exchange resin in the water softening tank 12 and the weakly basic anion exchange resin in the pH adjustment tank 18 can be simultaneously regenerated. Therefore, the control unit 40 preferably controls the supply of alkaline electrolyzed water produced in the electrolytic cell 14 to the pH adjustment tank 18 to regenerate the weakly basic anion exchange resin during regeneration of the acidic cation exchange resin.

[0051] During water softening in the water softening device 10B shown in Figure 4, raw water W1 flows in through flow path 20, passes through water flow rate detection unit Sw and conductivity measurement unit S1, and flows into the water softening tank 12. The softened water obtained by passing through the weakly acidic cation exchange resin in the water softening tank 12 is discharged from flow path 29. The softened water further flows into flow path 29 and is passed through pH adjustment tank 18. In pH adjustment tank 18, the pH of the softened water rises to a neutral range, and the softened water passes through conductivity measurement unit S2 and is discharged from flow path 36. That is, softened water in the neutral range is discharged from flow path 36 of the water softening device 10B and is used as drinking water, etc.

[0052] On the other hand, in the water softening device 10B, when regenerating the weakly acidic cation exchange resin in the water softening tank 12, acidic electrolyzed water flows by a pump (not shown) through the electrolytic tank 14, flow path 24, water softening tank 12, and flow path 22 in this order, thereby regenerating the weakly acidic cation exchange resin in the water softening tank 12. On the other hand, when regenerating the weakly basic anion exchange resin in the pH adjusting tank 18, alkaline electrolyzed water flows through the electrolytic tank 14, flow path 35, pH adjusting tank 18, and flow path 38 in this order, thereby regenerating the weakly basic anion exchange resin in the pH adjusting tank 18.

[0053] In the water softening apparatus 10B, the weakly acidic cation exchange resin in the water softening tank 12 is regenerated, and at the same time, the weakly basic anion exchange resin in the pH adjustment tank 18 is regenerated using alkaline electrolyzed water. The regeneration time of the weakly basic anion exchange resin will be explained below. As described above, the H in the softened water obtained by passing through the weakly acidic cation exchange resin + The concentration of depends on the amount of alkalinity component that is insufficient relative to the hardness ions. (molar concentration of hardness ions adsorbed on weakly acidic cation exchange resin) × 2 - (HCO3 - (molar concentration of H) = (molar concentration of H ion exchanged by weakly basic anion exchange resin + (molar concentration of This results in the following relationship. Therefore, (molar concentration of hardness ions adsorbed on weakly acidic cation exchange resin) × 2 > (molar concentration of hardness ions adsorbed on weakly basic anion exchange resin) + (molar concentration of ) (1) This results in the following relationship. To regenerate a weakly acidic cation exchange resin, 1 mole of hardness ions is required. + Since 2 moles are required, (H required for regeneration of weakly acidic cation exchange resin + (Number of moles) = (Molar concentration of hardness ions adsorbed on the weakly acidic cation exchange resin) × 2 × (Cumulative amount of water passed) (2) This becomes: To regenerate weakly basic anion exchange resin, ion-exchanged H + For 1 mole, OH - Since 1 mole of is required, (OH necessary for regeneration of weakly basic ion-anion exchange resin - (number of moles of H ion exchanged with weakly basic anion exchange resin) = (number of moles of H ion exchanged with weakly basic anion exchange resin) + (molar concentration of water) × (cumulative water flow rate) (3) From the relationship in equation (1), the H required for regeneration of the weakly acidic cation exchange resin is + (number of moles of OH required for regeneration of weakly basic anion exchange resin) - In other words, the number of moles of OH required for regeneration of the weakly basic anion exchange resin is - The number of moles of H required to regenerate the weakly acidic cation exchange resin is + In the electrolytic cell 14, the number of moles of OH - and H + Since the weakly basic anion exchange resin is generated in equal amounts, the time required for regeneration of the weakly basic anion exchange resin with alkaline electrolyzed water is shorter than the time required for regeneration of the weakly acidic cation exchange resin with acidic electrolyzed water. Therefore, in the water softener 10B, the control unit 40 controls the regeneration time of the weakly acidic cation exchange resin, and it is possible to complete the regeneration of the weakly basic anion exchange resin within the controlled regeneration time.

[0054] The weakly basic anion exchange resin used in the pH adjusting tank 18 preferably has a tertiary amino group as the anion exchange group.

[0055] The water softening device of this embodiment may further include a display unit that compares and displays the hardness of raw water calculated based on the conductivity of the raw water measured by the conductivity measuring unit S1 and the hardness of softened water calculated based on the conductivity of the softened water measured by the conductivity measuring unit S2. This aspect will be described below.

[0056] As explained in FIG. 2(b), once the change in electrical conductivity ΔS1 between before and after softening of raw water is obtained, the change in hardness ions ΔC1 can be calculated from the relationship ΔC / ΔS=α (α: proportionality constant). The difference between the change in hardness ions ΔC1 and the hardness of the raw water is the hardness of the softened water obtained by the softening process. In other words, by measuring the change in electrical conductivity ΔS1 between before and after softening of raw water, the hardness of the softened water can be calculated from the measured value. Thus, there is a correlation between the electrical conductivity and hardness of water before and after softening. Therefore, by storing calibration curves in the memory of the control unit 40 for the raw water hardness relative to the raw water conductivity and the softened water hardness relative to the softened water conductivity, the hardness of each can be detected by measuring the electrical conductivity of the raw water and the softened water. The detected hardness can then be displayed on the display, allowing a comparison between the hardness of the raw water and the hardness of the softened water obtained by the softening process.

[0057] <Method for regenerating weakly acidic cation exchange resin in a water softener> The method for regenerating a weakly acidic cation exchange resin in a water softener of this embodiment is the same as the method for regenerating a weakly acidic cation exchange resin in a water softener of this embodiment. That is, the water softener includes a water softening tank that softens raw water containing hardness components with a weakly acidic cation exchange resin. It also includes a pH adjustment tank that adjusts the pH of the softened water produced in the water softening tank to a neutral range. It also includes an electrolytic tank that produces alkaline electrolyzed water and acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin. It also includes at least one of the following (1) and (2). (1) A conductivity measuring unit S1 that measures the conductivity of raw water, and a conductivity measuring unit S2 that measures the conductivity of softened water obtained by passing through the water softening tank and the pH adjustment tank. (2) A hardness detection unit that detects the hardness of raw water or a hardness storage unit that stores the hardness of raw water measured in advance. The apparatus further includes a water flow rate detector that detects the flow rate of raw water passing through the water softening tank. The regeneration time of the weak acid cation exchange resin is calculated based on the difference between the conductivity of the raw water measured by the conductivity measuring unit S1 and the conductivity of the softened water measured by the conductivity measuring unit S2, and the cumulative flow rate of raw water detected by the water flow rate detector. Alternatively, the regeneration time of the weak acid cation exchange resin is calculated based on the raw water hardness detected by the hardness detecting unit or the raw water hardness stored in the hardness memory unit, and the cumulative flow rate of raw water detected by the water flow rate detector. Furthermore, the acidic electrolyzed water is passed through the water softening tank for the calculated regeneration time to regenerate the weak acid cation exchange resin. The water softener in the method for regenerating the weakly acidic cation exchange resin of the water softener of this embodiment corresponds to the water softener of this embodiment described above. The water softener has already been described, so a detailed description thereof will be omitted.

[0058] As explained in the water softening device of the present embodiment, the total amount of hardness components adsorbed by the weakly acidic cation exchange resin can be calculated by measuring the conductivity of water before and after softening and calculating the difference between them, or by knowing the hardness of the raw water. Then, the regeneration time is calculated from the calculated total amount of hardness components adsorbed, and the weakly acidic cation exchange resin is regenerated during that regeneration time, thereby preventing excess or deficiency in the amount of acidic electrolyzed water. Consequently, the weakly acidic cation exchange resin can be sufficiently regenerated, while reducing the waste of electricity, time, and water required for producing acidic electrolyzed water.

[0059] Below, verification data will be used to demonstrate that the water softening device of this embodiment is capable of calculating the regeneration time of the weakly acidic cation exchange resin from the amount of hardness components based on the difference between the conductivity of the raw water and the conductivity of the softened water.

[0060] (1) Changes in conductivity due to softening and the relationship between conductivity and hardness ion concentration The changes in hardness ion concentration and electrical conductivity associated with water softening were measured using the water softener 10B shown in Figure 4. Specifically, artificial hard water was passed through the water softener 10B as raw water, and the electrical conductivity and cation concentration of the resulting soft water were measured after 10, 20, 40, and 48 minutes. The results are shown in Table 1. The weakly acidic cation exchange resin used was C104 manufactured by Purolite Co., Ltd. The weakly basic anion exchange resin used was A845S manufactured by Purolite Co., Ltd. The raw water used was artificial hard water with a Na concentration of 1.86 mmol / L, a Mg concentration of 1.26 mmol / L, and a Ca concentration of 2.52 mmol / L.

[0061] [Table 1]

[0062] From Table 1, it can be seen that by passing water through the weakly acidic cation exchange resin and the weakly basic anion exchange resin, the Na concentration, Mg concentration, and Ca concentration are reduced compared to the raw water. It can also be seen that the conductivity is reduced compared to the raw water. Furthermore, while the hardness of the raw water is 378 mg / L, the hardness of the treated water is about 40 mg / L, and the water is softened by the water softener 10B.

[0063] On the other hand, Na + is a monovalent cation, Mg 2+ and Ca 2+ are divalent cations, and the valence of each cation is different. Therefore, when evaluating the change in conductivity, it is necessary to consider the contribution of the valence to the conductivity. Therefore, a conductivity contribution coefficient was introduced to take into account the difference in the valence of each cation. The contribution coefficient of each cation is + is set to 0.1, and Mg 2+ is set to 0.2, and Ca 2+ was set to 0.2. Because Ca and Mg are divalent cations, their contribution coefficients are twice that of Na. The conductivity can be calculated using the following formula: Conductivity (mS / cm) = Cation concentration (mmol / L) x Contribution factor The conductivity was calculated using the above formula based on the values ​​shown in Table 1. The calculation results are shown in Table 2 below.

[0064] [Table 2]

[0065] Table 2 shows that the calculated conductivity and the measured value are almost identical, indicating that it is possible to calculate the concentration of adsorbed cations from the change in conductivity.

[0066] (2) Calculation of regeneration time of weakly acidic cation exchange resin First, the regeneration reaction of weakly acidic cation exchange resin for each cation is as follows: (2RCOO - )Ca 2+ + 2H + → 2(RCOO - H + ) + Ca 2+ (2RCOO - )Mg 2+ + 2H + → 2(RCOO - H + ) + Mg 2+ R COO - N a + + H + → RCOO - H + + Na + From the above reaction formula, in the regeneration reaction of weakly acidic cation exchange resin, 1 mole of proton is required for 1 mole of cation to regenerate monovalent cation, and 2 moles of proton are required for 1 mole of cation to regenerate divalent cation. In other words, the adsorption amount equivalent to monovalent cation is important for calculating the regeneration time of weakly acidic cation exchange resin. Therefore, for example, if a weakly acidic cation exchange resin is used to regenerate Na + 1 mole of Ca 2+ When 2 moles of protons are adsorbed, the amount of monovalent cations adsorbed is 5 moles, and the required protons are 5 moles.

[0067] Next, we will consider estimating the amount of cation adsorption from the change in conductivity. 2+ and Ca 2+ The contribution coefficient of Na + Therefore, Ca 2+ Concentration of Na + When converting to equivalent, Ca 2+ Multiply the concentration by 2. This gives us the following formula:

[0068]

number

[0069] From the above formula, we can see that the total cation concentration in terms of sodium ions can be calculated by dividing the conductivity by the sodium contribution coefficient. Furthermore, as mentioned above, the amount of monovalent cation adsorption is important when calculating the regeneration time of a weakly acidic cation exchange resin. Therefore, the cation concentration in terms of sodium ions is important. The change in cation concentration in terms of sodium ions can be calculated from the difference in conductivity using the following formula:

[0070]

number

[0071] Next, the regeneration time of the weakly acidic cation exchange resin is calculated from the sodium ion equivalent adsorption concentration. The conductivity of the 4.4 L of water passed through the resin is 0.919 mS / cm for the raw water and 0.208 mS / cm for the soft water produced. From these conductivities, the sodium ion equivalent adsorption concentration can be calculated as follows: (0.919-0.208)(mS / cm) / 0.1(mS / cm / mmol / L)=7.1mmol / L Since the amount of water passed was 4.4 L, the total number of moles of adsorption converted to Na = 7.1 mmol / L x 4.4 L = 31.2 mmol. On the other hand, the pH of the acidic water used in the regeneration treatment is 2.1, and the flow rate is 0.1 (L / min), so according to the above formula (1), the time required to regenerate the weakly acidic cation exchange resin is 39.4 minutes.

[0072] Furthermore, the regeneration time was measured when the regeneration treatment was actually carried out. Figure 6 shows the change in pH of the water before and after treatment with the weakly acidic cation exchange resin versus the regeneration time. The regeneration is complete when the pH of the water before and after treatment is the same, and Figure 6 shows that regeneration was completed after approximately 40 minutes. In other words, the time required for regeneration of the weakly acidic cation exchange resin calculated as above was 39.4 minutes, which is almost the same as the measured value. This shows that the regeneration time can be calculated using the above-mentioned method.

[0073] On the other hand, Figure 7 shows the change in pH of water before and after treatment with a weakly basic anion exchange resin. The time when the pH of the water before and after treatment is the same is the end of regeneration, which is about 30 minutes. That is, as mentioned above, it was also shown that the time required for regeneration of a weakly basic anion exchange resin with alkaline electrolyzed water is shorter than the time required for regeneration of a weakly acidic cation exchange resin with acidic electrolyzed water. Therefore, the weakly acidic cation exchange resin again It is possible to complete the regeneration of the weakly basic anion exchange resin within the reaction time.

[0074] The entire contents of Patent Application No. 2020-158748 (filing date: September 23, 2020) are incorporated herein by reference. [Industrial Applicability]

[0075] According to the present disclosure, in a water softening device that uses acidic electrolyzed water to regenerate a weakly acidic cation exchange resin, it is possible to provide a water softening device and a regeneration method thereof that can prevent excess or deficiency in the amount of acidic electrolyzed water required for the regeneration treatment of the weakly acidic cation exchange resin. [Explanation of symbols]

[0076] 10 10A 10B Water softener 12 Water softening tank 14 Electrolyzer 16 Mixing tank 18 pH adjustment tank 40 Control Unit S1S2 conductivity detector Sw Water flow rate detector

Claims

1. a water softening tank that softens raw water containing hardness components using a weakly acidic cation exchange resin; a pH adjusting tank for adjusting the pH of the softened water produced in the water softening tank to a neutral range; an electrolytic cell for producing alkaline electrolyzed water and acidic electrolyzed water for regenerating the weakly acidic cation exchange resin; (1) A conductivity measuring unit S for measuring the conductivity of the raw water １ and a conductivity measuring unit S for measuring the conductivity of the softened water obtained by passing through the water softening tank and the pH adjusting tank. ２ and (2) at least one of a hardness detection unit that detects the hardness of the raw water or a hardness storage unit that stores the hardness of the raw water measured in advance; a water flow rate detection unit that detects an integrated amount of raw water passing through the water softening tank over a predetermined period of time; a control unit that controls at least the flow of acidic electrolyzed water generated by the electrolytic cell to the water softening cell; The control unit is configured to １ The conductivity of the raw water measured by the conductivity measuring unit S ２ or the amount of hardness components adsorbed on the weakly acidic cation exchange resin, which is calculated from the difference in conductivity of water before and after the water softening treatment measured by the method (2), or the hardness of the raw water detected by the hardness detection unit or the hardness of the raw water stored in the hardness storage unit, and the cumulative amount of raw water passed by the water passing amount detection unit; and control is performed so that the weakly acidic cation exchange resin is regenerated by passing the acidic electrolyzed water through the water softening tank for the calculated regeneration time, The water softening device, wherein the pH adjustment tank contains a weakly basic anion exchange resin.

2. The control unit calculates the conductivity of the conductivity measuring unit S based on a relational expression (ΔC / ΔS=α (α: proportionality constant)) between the difference (ΔS) between the conductivity of the raw water and the conductivity of the softened water obtained by passing through the water softening tank and the pH adjustment tank and the difference (ΔC) between the amount of hardness components in the raw water and the amount of hardness components in the softened water softened by the water softening tank. １ The conductivity of the raw water measured by the conductivity measuring unit S ２ 2. The water softening device according to claim 1, wherein the change in hardness components before and after softening the water is calculated from the difference in conductivity of the softened water measured by the above method, and the regeneration time of the weakly acidic cation exchange resin is calculated from the calculated change in hardness components.

3. 3. The water softening device according to claim 2, wherein the control unit calculates the regeneration time by the following formula 1, where C (mol) is the total change in the hardness components before and after the softening, x is the pH of the acidic electrolyzed water used for regenerating the weakly acidic cation exchange resin, and v (L / min) is the flow rate of the acidic electrolyzed water. Regeneration time (min) = C × 2 / (10 －ｘ ×v) [Formula 1]

4. The water softening apparatus according to any one of claims 1 to 3, further comprising a mixing tank for mixing the alkaline electrolyzed water produced in the electrolytic tank with the acidic electrolyzed water used for regenerating the weakly acidic cation exchange resin, wherein the control unit controls to supply mixed water produced by mixing the alkaline electrolyzed water and the acidic electrolyzed water in the mixing tank to the electrolytic tank during regeneration of the weakly acidic cation exchange resin.

5. 2. The water softening device according to claim 1, wherein the control unit controls the alkaline electrolyzed water produced in the electrolytic cell to be supplied to the pH adjustment cell during regeneration of the weakly acidic cation exchange resin to regenerate the weakly basic anion exchange resin.

6. Furthermore, the conductivity measuring unit S １ The hardness of the raw water calculated based on the conductivity of the raw water measured by the conductivity measuring unit S ２ The water softening device according to any one of claims 1 to 5, further comprising a display unit for comparing and displaying the hardness of the softened water calculated based on the conductivity of the softened water measured by the above method.

7. A water softening tank that softens raw water containing hardness components with a weakly acidic cation exchange resin, a pH adjusting tank that adjusts the pH of the softened water produced in the water softening tank to a neutral range, an electrolytic tank that produces alkaline electrolyzed water and acidic electrolyzed water used to regenerate the weakly acidic cation exchange resin, and (1) a conductivity measuring unit S that measures the conductivity of the raw water. １ and a conductivity measuring unit S for measuring the conductivity of the softened water obtained by passing through the water softening tank and the pH adjusting tank. ２ (2) at least one of a hardness detection unit for detecting the hardness of the raw water or a hardness storage unit for storing the hardness of the raw water measured in advance, and a conductivity measurement unit S for measuring the conductivity of the raw water １ and a conductivity measuring unit S for measuring the conductivity of the softened water obtained by passing through the water softening tank and the pH adjusting tank. ２ and a water flow rate detection unit that detects the amount of raw water passing through the water softening tank, The conductivity measuring unit S １ The conductivity of the raw water measured by the conductivity measuring unit S ２ or the hardness of the raw water detected by the hardness detection unit or the hardness of the raw water stored in the hardness storage unit, and the accumulated amount of raw water passed through the water passing amount detection unit, and for the calculated regeneration time, the acidic electrolyzed water is passed through the water softening tank to perform regeneration treatment of the weakly acidic cation exchange resin; A method for regenerating a weakly acidic cation exchange resin in a water softening device, wherein the pH adjustment tank contains a weakly basic anion exchange resin.

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