Pure water production equipment

Abstract

The present invention provides a pure water production system that minimizes damage to the deionized water production equipment and enables efficient transport of concentrated water discharged from the concentration chamber. [Solution] The pure water production apparatus is characterized by comprising a deionized water production apparatus 1 having a desalination chamber 1a and a concentration chamber 1b, and a booster pump 8 connected to the outlet of the concentration chamber 1b.

Description

Technical Field

[0001] The present invention relates to a pure water production apparatus.

Background Art

[0002] Conventionally, when manufacturing semiconductor devices and liquid crystal devices, pure water (including ultrapure water) with highly removed impurities such as organic substances, ionic components, fine particles, and bacteria has been used as washing water. In particular, regarding the pure water used in the washing process of electronic components including semiconductor devices, the requirements for water quality have been increasing year by year. In recent years, in particular, the reduction of boron has been strongly demanded. Boron, which is a weakly acidic component, is known to be removable using a reverse osmosis membrane device (hereinafter referred to as an "RO device") or an electrically regenerated deionized water production device (hereinafter referred to as an "EDI device").

[0003] In order to suppress the treatment cost of pure water production as low as possible while using an expensive EDI device, it is preferable to perform water passing treatment at a high flow rate to increase the amount of treated water per unit time. However, when the flow rate of the liquid passing through the EDI device is increased, the pressure difference (water passing differential pressure) between the upstream side and the downstream side of the liquid in the desalination chamber of the EDI device becomes large. If a pressure exceeding the pressure resistance performance is applied to the EDI device, there is a possibility of damage.

[0004] Patent Document 1 shows a method of reducing the boron concentration in treated water by multi-stage treatment using a plurality of EDI devices connected in series. In such multi-stage treatment, particularly, the pressure of the liquid supplied to the EDI device located in the previous stage increases. However, in the pure water production apparatus described in Patent Document 1, a liquid feeding pump is provided between the first-stage EDI device (first electric deionization device) and the second-stage EDI device (second electric deionization device). Thereby, while increasing the flow rate of the liquid passing through the EDI device to increase the amount of treated water per unit time, the EDI device can be operated in a state where the pressure is low enough that the EDI device is not damaged and water leakage or localization of the packing does not occur, and stable operation of the EDI device is possible.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-34103 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the pure water production apparatus described in Patent Document 1, the supply pressure to the desalination chamber of the first-stage EDI device can be reduced. However, the pressure of the concentrated water discharged from the concentration chamber is not considered. The concentrated water is either stored in a concentrated water tank or returned upstream and mixed with the treated water supplied to the EDI device for reuse. However, if the pressure (back pressure) of the concentrated water is insufficient, it may not be possible to transport it to the concentrated water tank or mix it with the treated water properly. In particular, in large-scale pure water production apparatuses, if the concentrated water tank, which is the destination for the concentrated water, or the mixing location with the treated water is located on a different floor from the EDI device, or at a distant location even if on the same floor, there is a risk that the concentrated water cannot be transported properly. In order to transport concentrated water properly, it is necessary to give the concentrated water sufficient pressure. If the pressure of the water supplied to the EDI device is increased to exceed the pressure resistance capacity of the EDI device, the EDI device may be damaged, and water leakage or localization of packing material may occur. In the configuration described in Patent Document 1, the supply pressure to the desalination chamber of the first-stage EDI device can be reduced, but the pressure of the concentrated water cannot be optimized. It is conceivable to provide protective members on the outside of the housing (cell) of the EDI device, which is made of plastic or the like and cannot withstand high hydraulic pressure, in order to suppress deformation and damage to the housing due to pressurization, but this would lead to the EDI device becoming larger and heavier.

[0007] The object of the present invention is to provide a pure water production apparatus that suppresses damage to the deionized water production apparatus and enables efficient transport of concentrated water discharged from the concentration chamber. [Means for solving the problem]

[0008] The present invention is characterized by comprising a deionized water production apparatus having a desalination chamber and a concentration chamber, and a booster pump connected to the outlet of the concentration chamber. [Effects of the Invention]

[0009] According to the pure water production apparatus of the present invention, damage to the deionized water production apparatus is suppressed, and concentrated water discharged from the concentration chamber can be transported efficiently. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic block diagram showing a pure water production apparatus according to the first embodiment of the present invention. [Figure 2] This is a schematic block diagram showing the pure water production apparatus of Comparative Example 1. [Figure 3] This is a schematic block diagram showing the pure water production apparatus of Comparative Example 2. [Figure 4] This is a schematic block diagram showing the internal structure of the EDI device in the pure water production apparatus of the present invention. [Figure 5] Figure 4 is a simplified block diagram showing the main internal structure of the EDI device. [Figure 6] This is a block diagram that simplifies and shows the main internal structure of other EDI devices. [Figure 7] Furthermore, this is a block diagram schematically showing the internal structure of other EDI devices. [Figure 8] This is a schematic block diagram showing a pure water production apparatus according to a second embodiment of the present invention. [Figure 9] This is a schematic block diagram showing a pure water production apparatus according to a third embodiment of the present invention. [Figure 10] (A) is a schematic block diagram showing a pure water production apparatus according to a fourth embodiment of the present invention, and (B) is a schematic block diagram showing a modified example thereof. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] Figure 1 is a schematic block diagram showing the basic configuration of a pure water production apparatus according to the first embodiment of the present invention. The pure water production apparatus of this embodiment includes an EDI device (electrically regenerative deionized water production apparatus) 1, which is an example of a deionized water production apparatus; a tank for treated water 2 located upstream of the EDI device 1 (upstream in the flow direction of the water to be treated and the treated water); a liquid transfer pump 3 located between the EDI device 1 and the tank for treated water 2; and a tank for treated water 4 located downstream of the EDI device 1 (downstream in the flow direction of the water to be treated and the treated water). The EDI device 1 includes a desalination chamber 1a, a concentration chamber 1b, and an electrode chamber 1c. However, although not shown, it is also possible to have a configuration in which the electrode chamber 1c is not provided separately from the concentration chamber 1b, and the concentration chamber 1b is used in conjunction with the electrode chamber 1c. The supply path 5 connecting the water treatment tank 2, the liquid transfer pump 3, and the EDI device 1 branches into three branch paths 5a, 5b, and 5c, connecting the water treatment tank 2 and the liquid transfer pump 3 to the desalination chamber 1a, the concentration chamber 1b, and the electrode chamber 1c, respectively. Valves 6a, 6b, and 6c are provided at each of the three branch paths 5a, 5b, and 5c. The water treatment tank 4 is connected to the outlet of the desalination chamber 1a. The recovery path 7, which returns to the water treatment tank 2, is connected to the outlet of the concentration chamber 1b. A booster pump 8 is provided in this recovery path 7, that is, between the outlet of the concentration chamber 1b and the water treatment tank 2.

[0012] In the EDI device 1, generally, the liquid transfer pump 3 operates to supply the water to be treated from the water to be treated tank 2 to the desalination chamber 1a, the concentration chamber 1b, and the electrode chamber 1c of the EDI device 1, respectively. Ions in the water to be treated supplied to the desalination chamber 1a move to the concentration chamber 1b via an ion exchange membrane. After the ions are removed from the water to be treated supplied to the desalination chamber 1a, it flows into the treated water tank 4 from the outlet of the desalination chamber 1a as treated water and is used as cleaning water for semiconductor devices, liquid crystal devices, etc. (not shown). At the same time, the water to be treated supplied to the concentration chamber 1b (also called the water supplied to the concentration chamber) has the ions that have moved from the desalination chamber 1a concentrated in the concentration chamber 1b, and is then discharged as concentrated water from the outlet of the concentration chamber 1b. In this embodiment, the concentrated water is pressurized by the booster pump 8, returned to the treated water tank 2 via the recovery path 7, mixed with the treated water stored in the treated water tank 2, and then supplied again to the EDI device 1 by the operation of the liquid transfer pump 3. In this way, the circulation path for the concentrated water is configured in this embodiment. In this embodiment, the liquid transfer pump 3 and the treated water tank 2 are located directly before the EDI device 1, and the concentrated water is recovered (circulated) to this treated water tank 2, but the configuration is not limited to this. For example, although not shown, if a reverse osmosis membrane device (RO device) is located before the EDI device 1, and a tank is located directly before this RO device, the concentrated water may be recovered (circulated) to the tank directly before the RO device. Alternatively, the concentrated water may be recovered (circulated) to a tank located before the EDI device 1 and the RO device. Thus, even if there is a tank 2 for water to be treated before the EDI device 1, a tank immediately before the RO device, and a tank located further upstream from these, or even if there is only one or two of these tanks, the concentrated water may be recovered (circulated) into any tank located upstream of the EDI device 1. However, the present invention is not limited to such a configuration in which concentrated water is circulated. Although not described in detail, the water to be treated supplied to the electrode chamber 1c (also called electrode chamber supply water) is discharged as electrode water from the outlet of the electrode chamber 1c and disposed of or stored.

[0013] In this embodiment, even if the outlet of the concentration chamber 1b and the tank for treated water 2 (the point where the concentrated water is mixed into the treated water) are far apart, a booster pump 8 is provided between the outlet of the concentration chamber 1b and the tank for treated water 2. Therefore, the concentrated water can be smoothly and efficiently transported to the tank for treated water 2 without increasing the pressure at the outlet of the concentration chamber 1b. The fact that there is no need to increase the pressure at the outlet of the concentration chamber 1b means that the concentrated water can be transported without increasing the pressure of the treated water supplied to the desalination chamber 1a. Furthermore, it is possible to transport the concentrated water regardless of the flow rate of the treated water. To explain this point, normally, ions in the treated water supplied to the desalination chamber 1a move to the adjacent concentration chamber 1b via the ion exchange membrane, and the treated water from which the ions have been removed is discharged from the outlet of the desalination chamber 1a. However, if the pressure inside the desalination chamber 1a is equal to or lower than the pressure inside the concentration chamber 1b, there is a risk that concentrated water containing ions will flow from the concentration chamber 1b into the desalination chamber 1a. Therefore, it is necessary to ensure that the pressure in the desalination chamber 1a is greater than the pressure in the concentration chamber 1b. For example, the pressure at the outlet of the desalination chamber 1a, where the pressure is lowest, should be higher than the pressure at the inlet of the concentration chamber 1b, where the pressure is highest. Consequently, if the pressure of the water supplied to the concentration chamber is increased, the pressure of the treated water at the outlet of the desalination chamber 1a must be increased accordingly, and furthermore, the differential pressure of the water flow (for example, a treated water flow rate of 20 m³) must be increased to ensure proper desalination treatment. 3In the case of / h, the pressure of the water to be treated at the inlet of the desalination chamber 1a is higher by about 0.22 MPa. Generally, when the flow rate of the treated water is small, the pressure difference for water flow in the desalination chamber 1a becomes small, so the pressure at the outlet of the concentration chamber 1b can be increased. However, when the flow rate of the treated water is large, in order to increase the pressure at the outlet of the concentration chamber 1b, it is necessary to increase the pressure at the inlet of the desalination chamber 1a. For example, in an example of the pressure resistance performance of a normal EDI device 1, the pressure at the inlet of the desalination chamber 1a is 0.6 MPa or less, and more preferably 0.5 MPa or less. In contrast, in this embodiment, concentrated water can be transported without increasing the pressure of the water to be treated supplied to the desalination chamber 1a too much. Therefore, the pressure applied to the EDI device can be kept low so as to be within a preferable range (for example, 0.5 MPa or less), there is no need to enhance the pressure resistance performance of the EDI device made of plastic or the like, and there is no need to provide a protective member or the like outside the housing (cell). Thus, the EDI device 1 does not become larger or heavier. Also, water leakage and localization of the packing can be suppressed. For example, when an ion exchange resin is used as the packing, if there is a bias in the ion exchange resin, the treatment performance will deteriorate. However, in this embodiment, the bias of the ion exchange resin can be suppressed, so a decrease in the treatment performance can be suppressed. Note that the flow rate of the concentrated water is 2.5% to 20% (more generally 2.5% to 10%) of the flow rate of the treated water. Since the flow rate is small, the pressure difference for water flow in the concentration chamber 1b (the pressure difference between the inlet and outlet of the concentration chamber 1b) does not pose a problem.

[0014] The pure water production device of this embodiment is compared with Comparative Example 1 shown in FIG. 2, Comparative Example 2 shown in FIG. 3, and Comparative Example 3 not shown in the drawings. In Comparative Examples 1 to 3, a booster pump 8 is not connected to the outlet of the concentration chamber 1b. In Comparative Example 1, as shown in Table 1, the pressure at the inlet (water to be treated) of the desalination chamber 1a is 0.32 MPa, the pressure at the outlet (treated water) of the desalination chamber 1a is 0.1 MPa, the pressure at the inlet (concentration chamber supply water) of the concentration chamber 1b is 0.05 MPa, and the pressure at the outlet of the concentration chamber 1b is 0.02 MPa. The pressure of the concentrated water sent out from the outlet of the concentration chamber 1b is 0.02 MPa or less. In Comparative Example 1, since the pressure of the concentrated water is low and it is difficult to recover it to the water-to-be-treated tank 2 or the like, it is discarded without reuse.

[0015] On the other hand, in Comparative Example 2, in order to return the concentrated water to the tank 2 for treated water via the recovery passage 7, the pressure at the outlet of the concentration chamber 1b (concentrated water) is increased, and accordingly, the pressure at the inlet of the concentration chamber 1b (concentration chamber supply water), the pressure at the outlet of the desalination chamber 1a (treated water), and the pressure at the inlet of the desalination chamber 1a (treated water) are increased sequentially. For example, the differential pressure between the outlet and inlet of the concentration chamber 1b is about 0.03 MPa (concentrated water flow rate 2 m³ 3 (At a rate of / h), the differential pressure between the outlet and inlet of desalination chamber 1a is approximately 0.22 MPa (at a flow rate of 20 m³ of treated water). 3 This is the case for / h). Therefore, in Comparative Example 2, as shown in Table 1, the pressure at the inlet of desalination chamber 1a (water to be treated) is 0.45 MPa, the pressure at the outlet of desalination chamber 1a (treated water) is 0.23 MPa, the pressure at the inlet of concentration chamber 1b (water supplied to concentration chamber) is 0.18 MPa, and the pressure at the outlet of concentration chamber 1b is 0.15 MPa. Because the pressure of the concentrated water is high, it can be smoothly returned to the tank 2 for water to be treated, but the pressure of the water to be treated supplied to desalination chamber 1a is high, which may cause water leakage or localization of packing material.

[0016] In Comparative Example 3, similar to Comparative Example 2, the pressure at the outlet of the concentration chamber 1b is increased to return the concentrated water to the raw water tank 2 via the recovery path 7, and similar to Comparative Example 1, the pressure at the inlet (raw water) of the desalination chamber 1a is decreased to prevent water leakage and localization of the packing. However, the pressure at the outlet of the desalination chamber 1a is lower than the pressure at the inlet of the concentration chamber 1b. That is, a part of the desalination chamber 1a is at a lower pressure than a part of the concentration chamber 1b. In this configuration, when troubles such as damage occur in the ion exchange membrane separating the desalination chamber 1a and the concentration chamber 1b, or when an ion exchange membrane of a type having a property of slightly permeating water is used, there is a risk that the concentrated water flows from the concentration chamber 1b into the desalination chamber 1a, deteriorating the quality of the treated water sent out from the desalination chamber 1a. To avoid such problems in Comparative Example 3, it is preferable to set the pressure balance between the desalination chamber 1a and the concentration chamber 1b so that the desalination chamber 1a has a higher pressure than the concentration chamber 1b. Theoretically, as long as the pressure at the outlet of the desalination chamber 1a is greater than the pressure at the inlet of the concentration chamber 1b, the pressure difference does not matter. However, considering the pressure fluctuations in the desalination chamber 1a and the concentration chamber 1b, if the pressure at the outlet of the desalination chamber 1a is 0.02 MPa or more greater than the pressure at the inlet of the concentration chamber 1b, there is a high reliability of preventing the inflow of the concentrated water into the desalination chamber 1a. Furthermore, it is more preferable that the pressure at the outlet of the desalination chamber 1a is 0.05 MPa or more greater than the pressure at the inlet of the concentration chamber 1b. And in order not to make the pressure at the inlet of the desalination chamber 1a too large, it is preferable that the difference between the pressure at the outlet of the desalination chamber 1a and the pressure at the inlet of the concentration chamber 1b is 0.1 MPa or less.

[0017] In the pure water production apparatus of the first embodiment of the present invention, the pressures at the inlet of the desalination chamber 1a, the outlet of the desalination chamber 1a, the inlet of the concentration chamber 1b, and the outlet of the concentration chamber 1b are the same as in Comparative Example 1. However, the action of the booster pump 8 connected to the outlet of the concentration chamber 1b makes it possible to increase the pressure of the concentrated water (for example, to 0.15 MPa) and send it to the tank for treated water 2. The pressure of the concentrated water in the first embodiment described in Table 1 is the pressure of the concentrated water in the recovery path 7 shown in Figure 1 and after passing through the booster pump 8. In this embodiment, the pressure of the treated water supplied to the EDI device 1 does not become too high as in Comparative Example 2, and the pressure in the concentration chamber 1b does not become higher than that in the desalination chamber 1a as in Comparative Example 3, and moreover, the concentrated water can be transported at a sufficient pressure. Thus, in this embodiment, the pressure of the treated water supplied to the EDI device 1 can be kept low, so it is particularly effective when adjusting the pressure balance between the desalination chamber 1a and the concentration chamber 1b to prevent the inflow of concentrated water into the desalination chamber 1a, similar to Comparative Example 2.

[0018] [Table 1]

[0019] The EDI apparatus 1 generally has a desalination chamber 1a separated by a pair of ion exchange membranes between the anode and the cathode, and the desalination chamber 1a is filled with ion exchange resin. A detailed configuration of an example of the EDI apparatus 1 shown in Figure 4 will be described. This EDI apparatus 1 has a single desalination chamber type configuration with a single desalination chamber 1a, and between the two electrode chambers, namely the anode chamber 1c1 equipped with an anode 9 and the cathode chamber 1c2 equipped with a cathode 10, a concentration chamber 1b1, a desalination chamber 1a, and a concentration chamber 1b2 are provided in order from the anode chamber 1c1 side. The anode chamber 1c1 and the concentration chamber 1b1 are adjacent to each other, separated by a cation exchange membrane (CEM) 11; the concentration chamber 1b1 and the desalination chamber 1a are adjacent to each other, separated by an anion exchange membrane (AEM) 12; the desalination chamber 1a and the concentration chamber 1b2 are adjacent to each other, separated by a cation exchange membrane 13; and the concentration chamber 1b2 and the cathode chamber 1c2 are adjacent to each other, separated by an anion exchange membrane 14. The desalination chamber 1a is filled with ion exchange resin (generally including anion exchange resin (AER) and cation exchange resin (CER)). The anode chamber 1c1 is filled with cation exchange resin, and the cathode chamber 1c2 is filled with anion exchange resin. This EDI device 1 performs desalination (deionization) treatment on the water to be treated when the water to be treated is supplied to the desalination chamber 1a with a DC voltage applied between the anode 9 and the cathode 10. As a result, water from which ionic components have been removed is discharged from the desalination chamber 1a as treated water. In the desalination chamber 1a, the anionic components removed from the treated water move to the concentration chamber 1b1 via the anion exchange membrane 12 located on the anode 9 side of the desalination chamber 1a. The cationic components move to the concentration chamber 1b2 via the cation exchange membrane 13 located on the cathode 10 side of the desalination chamber 1a. Concentration chambers 1b1 and 1b2 are supplied with concentration chamber supply water and discharged. Electrode chamber supply water is supplied to the cathode chamber 1c2. The electrode chamber supply water supplied to the cathode chamber 1c2 passes through the cathode chamber 1c2 and is then supplied to the anode chamber 1c1, where it is discharged as electrode water. It is also possible to omit the cation exchange membrane 11 and the anion exchange membrane 14, so that the concentration chambers 1b1 and 1b2 also serve as electrode chambers (anode chamber and cathode chamber).

[0020] Figure 5 is a simplified explanatory diagram of the EDI device 1 shown in Figure 4, illustrating the flow directions of the treated water and the water supplied to the concentration chamber and the concentrated water. In the examples shown in Figures 4 and 5, the flow directions of the treated water and the water supplied to the concentration chamber are opposite to those of the concentrated water and the concentrated water; this relationship of flow directions is called counterflow. On the other hand, Figure 6 schematically shows an EDI device 1 with a so-called parallel flow configuration, where the flow directions of the treated water and the water supplied to the concentration chamber and the concentrated water coincide. The present invention is applicable to both the pure water production apparatus including the EDI device 1 with the counterflow configuration shown in Figures 4 and 5, and the pure water production apparatus including the EDI device 1 with the parallel flow configuration shown in Figure 6. However, adopting the counterflow configuration shown in Figures 4 and 5 allows for better maintenance of the water quality of the treated water. One reason for this is that the water near the outlet of the concentration chamber 1b is more concentrated and has higher conductivity and is dirtier than the water near the inlet of the concentration chamber 1b. On the other hand, the water near the outlet of desalination chamber 1a is cleaner than the water near the inlet of desalination chamber 1a because desalination has been performed there. In a parallel flow configuration, the clean water (treated water) near the outlet of desalination chamber 1a is adjacent to the dirty water (concentrated water) near the outlet of concentration chamber 1b. However, in a counterflow configuration, the clean water (treated water) near the outlet of desalination chamber 1a is not adjacent to the dirty water (concentrated water) near the outlet of concentration chamber 1b, thus maintaining good water quality for the treated water. Furthermore, due to the relationship between the high ion concentration in concentration chamber 1b and the pH of the ion exchange membrane adjacent to concentration chamber 1b, a counterflow configuration also has the advantage of suppressing scale formation.

[0021] While the counterflow configuration has the advantages mentioned above, the pressure at the inlet of the desalination chamber 1a tends to be high. In a counterflow configuration, the outlet portion of the desalination chamber 1a, which has low pressure, and the inlet portion of the concentration chamber 1b, which has high pressure, are located adjacent to each other. In a parallel flow configuration, the outlet portions of the desalination chamber 1a and the concentration chamber 1b, which have low pressure, are located adjacent to each other, so it is not necessary to increase the pressure in the desalination chamber 1a in order to ensure that the pressure at the outlet portion of the adjacent desalination chamber 1a is higher than the pressure at the outlet portion of the concentration chamber 1b. However, in a counterflow configuration, in order to ensure that the pressure at the outlet portion of the desalination chamber 1a is higher than the pressure at the inlet portion of the adjacent desalination chamber 1b, the pressure at the outlet portion of the desalination chamber 1a must be increased, and consequently, the pressure at the inlet portion of the desalination chamber 1a must be increased even further. Therefore, the pressure of the water to be treated supplied to the desalination chamber 1a tends to be higher in a counterflow configuration than in a parallel flow configuration. If, in a counterflow configuration, it were necessary to further increase the pressure of the water to be treated supplied to the desalination chamber 1a in order to efficiently transport the concentrated water to the water to be treated tank 2, the pressure of the water to be treated would become extremely high, greatly increasing the possibility of exceeding the pressure resistance capacity of the EDI device 1. Therefore, in a counterflow configuration, as described above, adopting the configuration of the present invention, which does not require increasing the pressure of the water to be treated in order to efficiently transport the concentrated water to the water to be treated tank 2, is extremely effective.

[0022] Figure 7 shows yet another example of the EDI device 1 used in the present invention. This EDI device 1 has a two-chamber desalination configuration with two adjacent desalination chambers 1a1 and 1a2 separated by an ion exchange membrane (anion exchange membrane) 15. Between the anode chamber (one electrode chamber) 1c1 equipped with an anode 9 and the cathode chamber (the other electrode chamber) 1c2 equipped with a cathode 10, a concentration chamber 1b1, two desalination chambers 1a1 and 1a2, and a concentration chamber 1b2 are provided in order from the anode chamber 1c1 side. Of the two desalination chambers 1a1 and 1a2 located between the anode 9 and the cathode 10, the desalination chamber 1a1 on the anode 9 side is partitioned by anion exchange membranes 12 and 15 and filled with ion exchange resin (at least a portion of which is composed of anion exchange resin). The desalination chamber 1a2 on the cathode 10 side is partitioned by an anion exchange membrane 15 and a cation exchange membrane 13, and is filled with ion exchange resin (at least a portion of which is composed of cation exchange resin). The other configurations are the same as those of the single-chamber desalination type shown in Figure 4, so their explanation is omitted. In this EDI device 1, with a DC voltage applied between the anode 9 and the cathode 10, the water to be treated is supplied to the desalination chamber 1a1 on the anode 9 side for desalination (deionization), then moved to the desalination chamber 1a2 on the cathode 10 side for further desalination, and the water from which ionic components have been removed is discharged as treated water from the desalination chamber 1a2 on the cathode 10 side. The processing in the concentration chambers 1b1, 1b2, cathode chamber 1c2, and anode chamber 1c1 is the same as those of the single-chamber desalination type shown in Figure 4, so their explanation is omitted. In such a two-chamber desalination EDI device 1, the pressure difference between the water flowing through the desalination chambers 1a1 and 1a2, that is, the pressure difference between the inlet of one desalination chamber 1a1 and the outlet of the other desalination chamber 1a2, is large, resulting in a high pressure of the water to be treated supplied to the desalination chamber 1a1. Therefore, in a pure water production apparatus including this two-chamber desalination EDI device 1, adopting the configuration of the present invention, which eliminates the need to further increase the pressure of the water to be treated for the purpose of efficiently transporting the concentrated water to the water to be treated tank 2, etc., is particularly effective. Furthermore, in this configuration, one desalination chamber 1a1 and the adjacent concentration chamber 1b1 are in a parallel flow relationship, while the other desalination chamber 1a2 and the adjacent concentration chamber 1b2 are in a counterflow relationship. Because it is a partially counterflow configuration, the present invention is particularly effective as described above.Alternatively, the water flow direction can be reversed from the example shown in Figure 7, so that the water to be treated is supplied to the desalination chamber 1a2 on the cathode 10 side for desalination (deionization), and then moved to the desalination chamber 1a1 on the anode 9 side for further desalination, resulting in the water from which ionic components have been removed being discharged as treated water from the desalination chamber 1a1 on the anode 9 side. Furthermore, the ion exchange resin and ion exchange membrane of the EDI device 1 are not limited to the configuration shown, and various other configurations may be adopted.

[0023] [Second Embodiment] Figure 8 is a schematic block diagram showing the basic configuration of a pure water production apparatus according to a second embodiment of the present invention. Similar to the first embodiment, the pure water production apparatus of this embodiment includes an EDI device 1, a tank for water to be treated 2, a liquid transfer pump 3, a tank for treated water 4, and a booster pump 8. The booster pump 8, connected to the outlet of the concentration chamber 1b of the EDI device 1, is connected to a concentrated water tank 16, rather than the tank for water to be treated 2. The other configurations are substantially the same as those of the first embodiment shown in Figure 1, and therefore their description is omitted. In this embodiment, the concentrated water discharged from the outlet of the concentration chamber 1b of the EDI device 1 and pressurized by the booster pump is not mixed with the water to be treated, but is sent to the concentrated water tank 16 for storage or use in other applications. Even if the concentrated water tank 16 is installed on a different floor from the EDI device 1, or on the same floor but at a distant location, the booster pump 8 ensures that the concentrated water is delivered efficiently. Furthermore, while maintaining good transport of concentrated water, the pressure of the water to be treated supplied to the EDI device 1 can be kept low.

[0024] [Third Embodiment] Figure 9 is a schematic block diagram showing the basic configuration of a pure water production apparatus according to a third embodiment of the present invention. Similar to the first embodiment, the pure water production apparatus of this embodiment includes an EDI device 1, a tank for water to be treated 2, a liquid transfer pump 3, a tank for treated water 4, and a booster pump 8. A temporary storage tank 17 is located between the outlet of the concentration chamber 1b of the EDI device 1 and the booster pump 8, and the temporary storage tank 17 is connected to the tank for water to be treated 2 via a recovery path 7. Therefore, the booster pump 8 is located in the recovery path 7 between the temporary storage tank 17 and the tank for water to be treated 2. The temporary storage tank 17 is located near the EDI device 1 and is equipped with a sensor (not shown) for detecting the amount of water in the temporary storage tank 17. Therefore, concentrated water is sent from the concentration chamber 1b of the EDI device 1 to the temporary storage tank 17 for storage. Because the temporary storage tank 17 is close to the EDI device 1, concentrated water can be sent smoothly. If the sensor detects that the amount of water in the temporary storage tank 17 is less than the specified amount, the booster pump 8 will not operate, and concentrated water will not be sent from the temporary storage tank 17. When the sensor detects that the amount of water in the temporary storage tank 17 is equal to or greater than the specified amount, the booster pump 8 will operate and send concentrated water from the temporary storage tank 17 to the tank for treated water 2 via the recovery path 7. Even if the temporary storage tank 17 and the tank for treated water 2 are far apart, the booster pump 8 will pressurize the concentrated water, so the concentrated water will be smoothly sent from the temporary storage tank 17 to the tank for treated water 2. In this way, the flow of concentrated water can be controlled by switching the booster pump 8 on and off according to the detection result of the sensor that detects the amount of water in the temporary storage tank 17.

[0025] [Fourth Embodiment] Figure 10(A) is a schematic block diagram showing the basic configuration of a pure water production apparatus according to the fourth embodiment of the present invention, and Figure 10(B) is a schematic block diagram showing a modified example thereof. The pure water production apparatus of this embodiment, like the third embodiment, includes an EDI device 1, a tank for water to be treated 2, a liquid transfer pump 3, a tank for treated water 4, a booster pump 8, and a temporary storage tank 17. In the configuration shown in Figure 10(A), flow meters 18 are installed in the recovery path 7 between the booster pump 8 and the tank for water to be treated 2, and at the inlet of the concentration chamber 1b. In the configuration shown in Figure 10(B), flow meters 18 are installed in the recovery path 7 between the booster pump 8 and the tank for water to be treated 2, and at the outlet of the concentration chamber 1b. In these configurations, in addition to detecting the amount of water in the temporary storage tank 17 as in the third embodiment, one flow meter 18 detects the flow rate of concentrated water flowing through the recovery path 7, and another flow meter 18 detects the flow rate at the inlet or outlet of the concentration chamber 1b, and both flow rates are compared. If the sensor detects that the amount of water in the temporary storage tank 17 is less than a specified amount, the flow rate of concentrated water flowing through the recovery path 7 is made smaller than the flow rate at the inlet or outlet of the concentration chamber 1b. If the sensor detects that the amount of water in the temporary storage tank 17 is greater than or equal to a specified amount, the flow rate of concentrated water flowing through the recovery path 7 is made larger than the flow rate at the inlet or outlet of the concentration chamber 1b. This adjustment keeps the amount of water in the temporary storage tank within a certain range. This adjustment may be made by adjusting either the flow rate of concentrated water flowing through the recovery path 7 or the flow rate at the inlet or outlet of the concentration chamber 1b, or by adjusting both flow rates. However, since the flow rate at the inlet or outlet of the concentration chamber 1b may affect the flow rate of the treated water at the inlet of the desalination chamber 1a and the flow rate of the treated water at the outlet of the desalination chamber 1a, it is preferable to adjust the flow rate of the concentrated water flowing through the recovery path 7. Specifically, this can be done by controlling the inverter of the booster pump 8 or the valves provided in the recovery path 7.

[0026] If multiple EDI devices 1 are arranged in parallel, the flow rate of concentrated water flowing through the recovery path 7 should be controlled by comparing it with the sum of the flow rates at the inlets of the concentration chambers 1b of each EDI device 1. Alternatively, the outlets of the concentration chambers 1b of each EDI device 1 should be merged before reaching the temporary storage tank 17, the flow rate after the merge should be detected, and the flow rate of concentrated water flowing through the recovery path 7 should be controlled by comparing it with the flow rate after the merge.

[0027] In this embodiment as well, even if the temporary storage tank 17 and the tank for treated water 2 are separated, the concentrated water is pressurized by the booster pump 8, so the concentrated water is smoothly sent from the temporary storage tank 17 to the tank for treated water 2. Furthermore, in this embodiment, even if the temporary storage tank 17 is small, control is possible without frequently switching the booster pump 8 on and off. Also, the booster pump 8 and the temporary storage tank 17 do not need to be particularly large. Moreover, according to this embodiment, the ion concentration at the destination where the concentrated water is returned, i.e., the treated water mixed with the concentrated water, tends to remain constant, and the ion removal performance tends to be stable.

[0028] [Effects of the present invention] As described above, according to the present invention, concentrated water can be smoothly delivered to a concentrated water tank 16 or a location where it is mixed with the treated water (such as the treated water tank 2) at a distance, without increasing the pressure at the inlet of the desalination chamber 1a. A booster pump 8 is used, which is located at the outlet of the concentration chamber 1b, and is not directly related to the flow rate or performance of the treated water discharged from the desalination chamber 1a. This enables smooth transport of concentrated water regardless of the flow rate of the treated water. Furthermore, since it is not necessary to increase the pressure at the inlet of the desalination chamber 1a, this does not lead to an increase in the size of the EDI device 1 or an increase in the number of parts. In addition, by not increasing the pressure at the inlet of the desalination chamber 1a, the risk of water leakage is reduced, and uneven distribution of ion exchange resin can be prevented. The present invention is particularly effective in EDI devices 1 having multiple desalination chambers 1a, EDI devices 1 with a counterflow configuration where it is preferable to balance the pressures of the desalination chamber 1a and the concentration chamber 1b, and in devices including a large EDI device 1 where the destination of the concentrated water is located at a distance from the EDI device 1. Furthermore, even in a pure water production apparatus in which multiple EDI devices 1 are connected in series, the effects of the present invention can be achieved by installing a booster pump 8 at the outlet of the concentration chamber 1b of each EDI device 1.

[0029] When concentrated water is mixed with the water to be treated before being supplied to the desalination chamber 1a, or when it is introduced into the concentrated water tank 16, if the destination of the concentrated water requires a pressure of 0.1 MPa or higher, more preferably 0.2 MPa or higher, it is effective to pressurize the concentrated water using the booster pump 8 of the present invention. Similarly, pressurizing the concentrated water using the booster pump 8 of the present invention is effective when the destination of the concentrated water is a tank with a height of 10 m or more (such as the water to be treated tank 2 or the concentrated water tank 16), and is even more effective when the tank is 20 m or more in height (such as the water to be treated tank 2 or the concentrated water tank 16). Furthermore, the flow rate of the concentrated water is 5 m 3The present invention is effective when the pressure is 0.1 MPa or higher. To explain these points, as mentioned above, when the destination of the concentrated water is far from the concentration chamber 1b of the EDI device 1, it is necessary to give the concentrated water sufficient pressure in order to transport it well. The higher the required pressure of the concentrated water, the greater the effect of pressurizing the concentrated water with the booster pump 8 of the present invention. Specifically, when the destination of the concentrated water is a pipe with a pressure of 0.1 MPa or higher or a tank with a height of 10 m or more, pressurizing the concentrated water with the booster pump 8 of the present invention is particularly effective. Furthermore, when the destination of the concentrated water is a pipe with a pressure of 0.2 MPa or higher or a tank with a height of 20 m or more, pressurizing the concentrated water with the booster pump 8 in the present invention is even more effective. In the EDI device 1 used in the above-described examples and comparative examples of the present invention, if an attempt is made to secure a pressure of approximately 0.2 MPa as the outlet pressure (concentrated water) of the concentration chamber 1b, the inlet pressure of the desalination chamber 1a may exceed the operating upper limit pressure (0.5 MPa in one example) (see Comparative Example 2). Therefore, when it is necessary for the outlet pressure (concentrated water) of the concentration chamber 1b to be 0.2 MPa or higher, it is particularly desirable to adopt the present invention. Similarly, when the height of the tank to which the concentrated water is transported (e.g., the tank for treated water 2 or the tank for concentrated water 16) is high, or when the flow rate of the concentrated water is large, it is necessary to increase the pressure of the concentrated water. Therefore, the present invention is particularly effective in increasing the pressure of the concentrated water without increasing the inlet pressure of the desalination chamber 1a. Specifically, the present invention is particularly effective when the height of the tank to which the concentrated water is transported is 10 m or more, and the effect of the present invention is even greater when the height of the tank to which the concentrated water is transported is 20 m or more. 3 The present invention is particularly effective when the pressure is greater than or equal to / h. Furthermore, the present invention is particularly effective in a pure water production apparatus operated under operating conditions in which the inlet pressure of the desalination chamber 1a is less than 0.4 MPa. [Explanation of symbols]

[0030] 1. EDI device (electronically regenerative deionized water production device) 1a Desalination room 1b,1b1,1b2 Concentration room 1c electrode chamber 1c1 Anode chamber 1c2 cathode chamber 2. Tank for treated water 3. Liquid transfer pump 4. Tank for treated water 5. Supply routes 5a,5b,5c Branch road 6a, 6b, 6c valves 7 Recovery route 8. Booster pump 9 Anode 10 cathode 11,13 Cation exchange membrane (CEM) 12,14,15 Anion exchange membrane (AEM) 16. Tank for concentrated water 17 Temporary storage tanks 18 Flow meter

Claims

1. A pure water production apparatus comprising a deionized water production apparatus having a desalination chamber and a concentration chamber, and a booster pump connected to the outlet of the concentration chamber.

2. The pure water production apparatus according to claim 1, wherein the concentrated water that has passed through the concentration chamber is mixed with water before it is supplied to the desalination chamber.

3. The pure water production apparatus according to claim 1, wherein the concentrated water that has passed through the concentration chamber is sent to a tank for concentrated water.

4. The pure water production apparatus according to any one of claims 1 to 3, wherein the flow of water passing through the desalination chamber and the flow of water passing through the concentration chamber are in opposite directions.

5. The pure water production apparatus according to claim 4, wherein the pressure at the outlet of the desalination chamber is greater than the pressure at the inlet of the concentration chamber, and the pressure difference is 0.02 MPa or more and 0.1 MPa or less.

6. The deionized water production apparatus has two desalination chambers, according to any one of claims 1 to 3.

7. The pure water production apparatus according to any one of claims 1 to 3, further comprising a temporary storage tank located between the outlet of the concentration chamber and the booster pump, wherein the temporary storage tank includes a sensor for detecting the amount of water.

8. The pure water production apparatus according to claim 7, wherein the booster pump is controlled to maintain the amount of concentrated water in the temporary storage tank within a certain range.

9. The pure water production apparatus according to claim 8, further comprising a flow meter positioned downstream of the booster pump in the flow direction of the concentrated water supplied to the booster pump.

10. The pure water production apparatus according to claim 9, further comprising another flow meter connected to the inlet or outlet of the concentration chamber.

11. The pure water production apparatus according to any one of claims 1 to 3, which is operated under operating conditions such that the inlet pressure of the desalination chamber is less than 0.4 MPa.

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