Pure water production method, pure water production apparatus, and ultrapure water supply system

Abstract

To provide a pure water production method capable of stabilizing the quality of terminal water.SOLUTION: In the method for producing pure water, water to be treated is subjected to activated carbon treatment by an activated carbon device 5, and the activated carbon-treated water is desalted by a desalting device to produce pure water. In the active carbon device 5, a plurality of active carbon towers 51 to 5n filled with active carbon are arranged in parallel, and in the demineralizer, at least a plurality of demineralizers are arranged in parallel. The pure water production method includes a water collecting step of passing water to be treated through all of the plurality of active carbon towers 51 to the 5n, and a regenerating step of stopping water passing through at least one tower of the plurality of active carbon towers 51 to the 5n or regenerating at least a part of the plurality of desalination devices, wherein a water passing space speed of the active carbon tower in the regenerating step is 10 / h or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pure water manufacturing method and apparatus for manufacturing pure water, and an ultrapure water supply system. [Background technology]

[0002] In the manufacturing processes of semiconductor devices and liquid crystal display devices, ultrapure water, from which organic matter, ionic components, fine particles, bacteria, etc. have been highly removed, is used as cleaning water, etc. In particular, when manufacturing electronic components including semiconductor devices, a large amount of ultrapure water is used as cleaning water in the cleaning process, and the demands for water quality are increasing year by year. For example, if organic matter is contained in ultrapure water used in a cleaning process, the organic matter may be carbonized in the subsequent heat treatment process, resulting in poor insulation, etc. Therefore, there is a demand for ultrapure water with an extremely low level of total organic carbon (TOC), and more preferably, ultrapure water from which persistent organic matter such as urea has been removed with high efficiency.

[0003] As shown in FIG. 1, ultrapure water is generally produced in an ultrapure water production system 100, which is composed of a primary pure water system 101 that produces pure water and a subsystem 102 that further removes impurities from the pure water produced in the primary pure water system. The primary pure water system 101 is primarily composed of an activated carbon unit 105, a 2B3T (two-bed, three-tower ion exchange unit) 106, a reverse osmosis membrane unit 107, an ultraviolet irradiation unit 108, a double-bed pure water system (SBP) 109, and a degassing unit 110. The subsystem 102 is primarily composed of an ultraviolet irradiation unit 111, an ion exchange unit 112, a degassing unit 113, and an ultrafiltration membrane unit 114. It is preferable to remove persistent organic substances such as TOC and urea in the primary pure water system as much as possible. In some cases, a pretreatment unit 104, such as a filtration unit, is provided upstream of the primary pure water system. In addition, the primary pure water system 101 may be equipped with an EDI (electrodeionized water production device) downstream of the reverse osmosis membrane device 107 instead of the 2B3T 106, and the configuration of each component technology varies depending on the properties of the impurities in the raw water and the required treated water quality.

[0004] Patent Document 1 describes a water treatment method that uses biological treatment to remove urea from water to be treated in the production of primary pure water. This water treatment method uses activated carbon as a carrier for supporting organisms, so-called biological activated carbon. Patent Documents 2 and 3 describe a method for producing pure water in which water containing organic matter (e.g., urea) is treated biologically to remove some of the organic matter. This method uses an activated carbon tower filled with biological activated carbon. For ease of maintenance, multiple activated carbon towers are arranged in parallel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-230093 [Patent Document 2] Japanese Patent Publication No. 2022-187347 [Patent Document 3] Japanese Patent Publication No. 2022-30031 Summary of the Invention [Problem to be solved by the invention]

[0006] In the operation of pure water production equipment, multiple activated carbon towers are arranged in parallel, and some of the activated carbon towers may be replaced or cleaned while water is being sampled. To prevent bacterial growth on the activated carbon inside the activated carbon towers, water to be treated is usually passed through the activated carbon towers when they are not being cleaned or replaced. Therefore, when the activated carbon towers are not being cleaned or replaced, water is passed through all of them. Therefore, when some of the activated carbon towers are being cleaned or replaced, the water flow conditions for the activated carbon towers change, and this changes the end water quality, i.e., the water quality (TOC) of the pure water (or ultrapure water) being sampled. For this reason, stabilizing the end water quality is a challenge.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for producing pure water that can solve the above problems and stabilize the quality of water at the end of the process. [Means for solving the problem]

[0008] In order to achieve the above object, according to one aspect of the present invention, A method for producing pure water, comprising: treating water to be treated with activated carbon in an activated carbon device; and desalination of the activated carbon-treated water in a desalination device to produce pure water, The activated carbon device includes a plurality of activated carbon towers filled with activated carbon arranged in parallel, The desalination device includes at least a plurality of desalination devices arranged in parallel, a water sampling step in which the water to be treated is passed through all of the activated carbon towers; a regeneration step of stopping the flow of water through at least one of the activated carbon towers or regenerating at least a part of the demineralization equipment, The method for producing pure water is provided, wherein the space velocity of water passing through the activated carbon tower in the regeneration step is 10 / h or less.

[0009] According to another aspect of the present invention, A pure water production system comprising: an activated carbon device that treats water to be treated with activated carbon; and a demineralization device that demineralizes the activated carbon-treated water from the activated carbon device to produce pure water, wherein the activated carbon device has a plurality of activated carbon towers that are arranged in parallel, each of which is filled with activated carbon; and the demineralization device has at least a plurality of demineralization devices that are arranged in parallel, a control means for performing a water sampling step in which the water to be treated is passed through all of the activated carbon towers, and a regeneration step in which the water passing through at least one of the activated carbon towers is stopped or at least a part of the demineralization equipment is regenerated; The pure water production apparatus is provided in which the space velocity of water passing through the activated carbon tower in the regeneration step is 10 / h or less.

[0010] According to yet another aspect of the present invention, a primary pure water system having at least the pure water manufacturing apparatus; a subsystem for producing ultrapure water by removing impurities from the pure water produced in the primary pure water system; and a recovery system that recovers the ultrapure water used at the point of use where the ultrapure water produced in the subsystem is used and returns it to the primary pure water system. [Effects of the Invention]

[0011] According to the present invention, the quality of water at the end of the pure water production system can be stabilized. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing the configuration of an ultrapure water production apparatus. [Figure 2] 1 is a block diagram showing the configuration of a pure water manufacturing apparatus to which a pure water manufacturing method according to a first embodiment of the present invention is applied, and FIG. 2 is a schematic diagram for explaining an example of an operating process performed in the pure water manufacturing method according to the first embodiment of the present invention. [Figure 3] FIG. 1 is a diagram for explaining an operating process when there are three activated carbon towers. [Figure 4] FIG. 1 is a diagram for explaining an operating process when there are five activated carbon towers. [Figure 5] FIG. 1 is a diagram for explaining an operating process when there are seven activated carbon towers. [Figure 6] FIG. 10 is a block diagram showing the configuration of a pure water producing apparatus to which a pure water producing method according to a second embodiment of the present invention is applied. [Figure 7] FIG. 4 is a diagram for explaining an example of an operating process performed in a pure water producing method according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a block diagram showing the configuration of a pure water producing apparatus to which a pure water producing method according to a third embodiment of the present invention is applied. [Figure 9A] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. [Figure 9B] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. [Figure 9C] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. [Figure 9D] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. [Figure 9E] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. [Figure 9F] FIG. 2 is a schematic diagram for explaining an operation process including a regeneration / cleaning process of an ion exchange resin. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the components described in the embodiments are merely examples and are not intended to limit the scope of the present invention.

[0014] (First embodiment) 2 is a block diagram showing the configuration of a pure water production system (primary pure water system) to which the pure water production method according to the first embodiment of the present invention is applied. Referring to FIG. 2, the pure water production system 1 has a raw water tank 2, a filtration device 3, a filtered water tank 4, an activated carbon device 5, a 2B3T device 6, and downstream equipment 13. The activated carbon device 5 has a plurality of activated carbon towers 51 to 5 n are arranged in parallel, and the water to be treated in the filtration tank is treated and supplied to the 2B3T device 6. The number of activated carbon towers arranged in parallel can be set appropriately.

[0015] The raw water tank 2 stores the water to be treated. The water to be treated may be, for example, industrial water, well water, city water, surface water, wastewater provided inside or outside a customer's factory, treated sewage, or desalinated seawater, and one or more of these waters are stored in the raw water tank 2. The filtration device 3 is connected to the raw water tank 2 via piping. The water to be treated stored in the raw water tank 2 is supplied to the filtration device 3. The filtration device 3 filters the water to be treated using, for example, sand as a filter medium. The filtered water tank 4 is connected to the filtration device 3 via piping. The filtration device 3 is stored in the filtered water tank 4. Note that the filtration device 3 may be considered a pre-treatment device installed upstream of the primary pure water system, but here the filtration device 3 is included in the primary pure water system.

[0016] Multiple activated carbon towers 51-5 n The activated carbon towers 51 to 5 are connected to the filtered water tank 4 via piping. n Both of these are filled with activated carbon with a porous structure, and the filtered water supplied from the filtered water tank 4 is passed through the activated carbon. The activated carbon adsorbs and removes organic matter from the filtered water. In addition, the organic matter is decomposed by attaching microorganisms to the activated carbon and by the microorganisms growing in the activated carbon layer.

[0017] The activated carbon treated water is treated in a 2B3T device (desalting device) 6. The 2B3T device 6 is a two-bed, three-tower pure water device, and is composed of a cation exchange resin tower (K ​​tower), a decarbonation tower (D tower), and an anion exchange resin tower (A tower). m and multiple D Towers 111-11 m and multiple A towers 121-12 m Here, Tower K is an ion exchange resin tower packed with a strongly acidic cation exchange resin (cation exchange resin). Tower D is a decarbonation tower. Tower A is an ion exchange resin tower packed with a strongly basic anion exchange resin (anion exchange resin). Multiple K towers 101-10 m is connected to multiple activated carbon towers 51-5 through piping. n It is connected to several K towers 101-10 m are multiple activated carbon towers 51 to 5 n Activated carbon treated water is supplied from the K tower, and the cations in the activated carbon treated water are ion-exchanged using a strongly acidic cation exchange resin. The number of K towers connected in parallel can be set appropriately.

[0018] Multiple D Towers 111-11 m is connected to multiple K towers 101-10 through piping. m It is connected to several D Towers 111-11 m are multiple K towers 101-10 mIon-exchange treated water is supplied from the tower D, and carbon dioxide and the like in the ion-exchange treated water are removed. For example, carbon dioxide gas in the treated water can be degassed (removed) using a decarbonation membrane that allows gas to pass through. The number of parallel D towers can be set as appropriate.

[0019] Multiple A Towers 121-12 m is connected to multiple D towers 111-11 through piping. m It is connected to several Towers A 121-12 m are multiple D towers 111-11 m The decarbonated water is supplied from the column A, and the anions in the decarbonated water are ion-exchanged using a strong basic anion exchange resin. The number of columns A arranged in parallel can be set appropriately.

[0020] In the method for producing pure water according to the present embodiment, the activated carbon towers 51 to 5 n The space velocity (SV) when water is passed through the activated carbon towers in parallel is set as the reference value, and when water is not being taken from some of the activated carbon towers due to cleaning or replacement of the activated carbon towers (a partial water taking stop process, hereinafter also referred to as the "regeneration process", including the case where the ion exchange resin towers described below are regenerated), that is, when the space velocity of the activated carbon tower through which water is passed increases, the activated carbon tower is operated so that the space velocity of the activated carbon tower through which water is passed is 1.5 times or less of the reference value. By operating in this manner, it is possible to stabilize the terminal water quality.

[0021] Here, the water collection process is carried out in all activated carbon towers 51 to 5 n The partial water sampling stop step is performed by operating multiple activated carbon towers 51 to 55. n This is an operating process carried out when some of the activated carbon towers are not used for water sampling. The space velocity indicates how many times the volume of water is passed through a unit volume of activated carbon (in other words, how many times the volume of activated carbon is treated per unit time). The operating process, including the water sampling process and the partial water sampling stop process, is carried out by a control means (also called a control device) not shown. Note that this operating process may also be carried out manually.

[0022] Generally, the space velocity is expressed as the flow rate of filtrate water supplied to activated carbon per unit time divided by the volume of activated carbon. When n activated carbon towers are arranged in parallel, the "flow rate of filtrate water supplied to activated carbon" refers to the total flow rate of the water being treated passing through the n activated carbon towers, and the "volume of activated carbon" refers to the total volume of activated carbon in the n activated carbon towers. However, when arranged in parallel, the same activated carbon towers are usually arranged, so even if the space velocity is calculated using the "flow rate of filtrate water supplied to activated carbon" and "volume of activated carbon" per tower, it will be the same value as when calculated for all towers.

[0023] Normally, the specifications of the activated carbon equipment (such as the amount of activated carbon packed, the number of towers, and the water flow rate) are designed based on the water quality of the water to be treated and the required water quality at the end, taking into account the cleaning and replacement of the activated carbon towers. n In a water collection system including the above, when a part of the activated carbon tower is cleaned (backwashed) or replaced, or when the ion exchange resin tower (tower K or tower A) in the downstream 2B3T device 6 is regenerated, the water flow conditions for the activated carbon tower change, which can cause the organic matter treatment in the activated carbon tower to be inappropriate, resulting in a deterioration of the activated carbon-treated water and ultimately the quality of the end water (the quality of the pure water (or ultrapure water) being collected). In particular, when the activated carbon in the activated carbon tower is biologically activated carbon, biological treatment is performed in addition to the adsorption effect of the activated carbon in organic matter treatment, making the organic matter treatment mechanism by activated carbon complex. Therefore, when the water flow conditions for the activated carbon tower change, the activated carbon treatment may not be performed as designed, which is thought to result in a deterioration of the end water quality. Based on this knowledge, the inventors have discovered that when a partial water sampling stop process (cleaning (backwashing), replacement, regeneration, etc.) is performed in which the spatial velocity of the activated carbon tower through which water passes increases, the terminal water quality can be stabilized by operating the activated carbon device so that the fluctuations in the spatial velocity fall within a certain range based on the spatial velocity of the activated carbon device during the water sampling process.

[0024] An application example of the pure water producing method of this embodiment will be described below as an example of the partial water withdrawal stop step.

[0025] (Application example 1: When there are three activated carbon towers) 3A and 3B are diagrams illustrating the operation steps performed in the method for producing pure water according to the present embodiment when there are three activated carbon towers. In Fig. 3, (a) is a schematic diagram showing the water flow during the water sampling step, and (b) is a schematic diagram showing the water flow during the cleaning step. In this operation step, one of the three activated carbon towers 51 to 53 is operated separately.

[0026] In the water collection process shown in Figure 3(a), the flow rate of the filtered water at the inlet side of the three activated carbon towers 51 to 53 is Q [m 3 / h]. Normally, activated carbon towers 51 to 53 are each set to the same capacity V [m 3 ] is packed in the activated carbon, so the flow rate of each of the three activated carbon towers 51 to 53 is Q / 3 [m 3 / h] and the space velocity SV is Q / 3V [ / h]. 3(b), the activated carbon tower 53 of the three activated carbon towers 51 to 53 is isolated from the water sampling system, and water is sampled using the two activated carbon towers 51 and 52 while backwashing is performed on the activated carbon tower 53. Cleaning water is supplied from outside the water sampling system and is passed in the opposite direction to the direction of flow of the filtered water.

[0027] During the cleaning process, the flow rate of the activated carbon towers 51 and 52, which continue to collect water, is Q / 3 [m 3 / h] to Q / 2 [m 3 / h]. That is, the space velocity is 1.5 times that during the water sampling process. When the SV during the partial water sampling stop process is 1.5 times or less than the SV during the water sampling process, the quality of the activated carbon-treated water, and ultimately the terminal water quality, remains stable. In this way, when water sampling is stopped from one of the three activated carbon towers due to cleaning or the like, the SV ratio is theoretically 1.5 times, but in reality, the SV ratio may exceed 1.5 times due to pressure loss or one-sided flow within the activated carbon tower. In such cases, the terminal water quality becomes unstable, so the SV ratio is set to 1.5 times or less by adjusting the flow rate according to the second embodiment described below.

[0028] (Application example 2: When there are five activated carbon towers) 4 is a diagram illustrating the operating steps performed in the method for producing pure water of this embodiment when there are five activated carbon towers. In FIG. 4, (a) is a schematic diagram showing the water flow state during the water sampling step, (b) is a schematic diagram showing the water flow state during the cleaning step, and (c) is a schematic diagram showing the water flow state when the water flow is stopped to replace some of the activated carbon towers during the cleaning step.

[0029] In the water collection process shown in Figure 4(a), the flow rate of the filtered water at the inlet side of the five activated carbon towers 51 to 55 is Q [m 3 / h]. Normally, activated carbon towers 51 to 55 are each set to the same capacity V [m 3 ] is packed in the activated carbon, so the flow rate of each of the five activated carbon towers 51 to 55 is Q / 5 [m 3 / h] and the space velocity SV is Q / 5V [ / h]. In the cleaning process (partial water sampling stop process) shown in Fig. 4(b), of the five activated carbon towers 51 to 55, activated carbon tower 55 is isolated from the water sampling system, and water is sampled using the four activated carbon towers 51 to 54 while backwashing is performed on activated carbon tower 55. Cleaning water is supplied from outside the water sampling system and is passed in the opposite direction to the flow direction of the filtered water. In the cleaning and replacement process (partial water sampling stop process) shown in Figure 4(c), of the five activated carbon towers 51 to 55, activated carbon tower 55 is disconnected from the water sampling system for cleaning, and activated carbon tower 54 is disconnected from the water sampling system for replacement, and water is sampled using the three activated carbon towers 51 to 53.

[0030] During the cleaning process, the flow rate of the activated carbon towers 51 to 54, which continue to collect water, is Q / 5 [m 3 / h] to Q / 4[m 3 / h]. In other words, the space velocity is 1.25 times that during the water sampling process. In this way, if the SV during the partial water sampling stop process is 1.5 times or less than the SV during the water sampling process, the quality of the activated carbon treated water, and ultimately the terminal water quality, remains stable. In addition, during the cleaning and replacement process, the flow rate of the activated carbon towers 51 to 53, which continue to collect water, is Q / 5 [m 3 / h] to Q / 3 [m 3 / h]. That is, the spatial velocity is 1.67 times that during the water sampling process. When the SV during the partial water sampling stop process exceeds 1.5 times the SV during the water sampling process, the quality of the activated carbon treated water, and ultimately the terminal water quality, becomes unstable. When the SV ratio exceeds 1.5 times, the SV ratio is set to 1.5 times or less by adjusting the flow rate according to the second embodiment described below. Furthermore, even if the SV ratio theoretically exceeds 1.5 times, if the SV ratio during actual operation is 1.5 times or less, flow rate adjustment is not necessary.

[0031] In addition, it is preferable that the SV of the activated carbon tower during normal operation (during the water sampling process) is 10 / h or less. If the SV of the activated carbon tower during normal operation (during the water sampling process) exceeds 10 / h, the terminal water quality may become unstable even if the SV during the partial water sampling stop process is about 1.5 times.

[0032] Furthermore, it is preferable that the SV of the activated carbon tower during the partial water collection stop step is 10 / h or less.

[0033] (Application example 3: When there are 7 activated carbon towers) 5 is a diagram illustrating the operating steps performed in the method for producing pure water of this embodiment when there are seven activated carbon towers. In FIG. 5, (a) is a schematic diagram showing the water flow state during the water sampling step, (b) is a schematic diagram showing the water flow state during the cleaning step, and (c) is a schematic diagram showing the water flow state when the water flow is stopped to replace some of the activated carbon towers during the cleaning step.

[0034] In the water collection process shown in Figure 5(a), the flow rate of the filtered water at the inlet side of the seven activated carbon towers 51 to 57 is Q [m 3 / h]. Normally, activated carbon towers 51 to 57 are each set to the same capacity V [m 3 ] is packed with activated carbon, so the flow rate of each of the seven activated carbon towers 51 to 57 is Q / 7 [m 3 / h] and the space velocity SV is Q / 7V [ / h]. 5(b), activated carbon tower 57, one of the seven activated carbon towers 51 to 57, is isolated from the water sampling system, and water is sampled using the six activated carbon towers 51 to 56 while backwashing is performed on activated carbon tower 57. Cleaning water is supplied from outside the water sampling system and is passed in the opposite direction to the direction of flow of the filtered water. In the cleaning and replacement process (partial water sampling stop process) shown in Figure 5(c), of the seven activated carbon towers 51 to 57, activated carbon tower 57 is disconnected from the water sampling system for cleaning, and activated carbon tower 56 is disconnected from the water sampling system for replacement, and water is sampled using the five activated carbon towers 51 to 55.

[0035] During the cleaning process, the flow rate of the activated carbon towers 51 to 56, which continue to collect water, is Q / 7 [m 3 / h] to Q / 6[m 3 / h]. In other words, the space velocity is 1.17 times that during the water sampling process. In this way, if the SV during the partial water sampling stop process is 1.5 times or less than the SV during the water sampling process, the quality of the activated carbon treated water, and ultimately the terminal water quality, remains stable. In addition, during the cleaning and replacement process, the flow rate of the activated carbon towers 51 to 55, which continue to collect water, is Q / 7 [m 3 / h] to Q / 5[m 3 / h]. That is, the spatial velocity is 1.4 times that during the water sampling process. In this way, when the SV during the partial water sampling stop process is 1.5 times or less than the SV during the water sampling process, the terminal water quality remains stable. Note that if the SV ratio exceeds 1.5 due to pressure loss or one-sided flow within the activated carbon tower, the terminal water quality becomes unstable, so the SV ratio is set to 1.5 times or less by adjusting the flow rate according to the second embodiment described below. Also, when three or more activated carbon towers are separated from the water sampling system, the SV exceeds 1.5 times the SV during the water sampling process, making the terminal water quality unstable, so the SV ratio is set to 1.5 times or less by adjusting the flow rate.

[0036] In addition, it is preferable that the SV of the activated carbon tower during normal operation (during the water sampling process) is 10 / h or less. If the SV of the activated carbon tower during normal operation (during the water sampling process) exceeds 10 / h, the terminal water quality may become unstable even if the SV during the partial water sampling stop process is about 1.5 times.

[0037] Furthermore, it is preferable that the SV of the activated carbon tower during the partial water collection stop step is 10 / h or less.

[0038] As described above, according to the method for producing pure water of this embodiment, the terminal water quality can be stabilized by operating the activated carbon tower so that fluctuations in the space velocity fall within a certain range based on the space velocity in the activated carbon tower during the water sampling process.

[0039] The above-mentioned flow rate values ​​and the number of activated carbon towers are merely examples and can be changed as appropriate. For example, if the activated carbon towers used for water sampling can be operated so that the space velocity is 1.5 times or less the reference value, the number of activated carbon towers separated from the water sampling system may be two or more. The terminal water quality may be determined based on urea, which is one of the TOC components, or may be determined based on other persistent TOC components.

[0040] (Second embodiment) Fig. 6 is a block diagram showing the configuration of a pure water production system to which a pure water production method according to a second embodiment of the present invention is applied. The pure water production system 1A shown in Fig. 6 differs from the pure water production system 1 described in the first embodiment in that it has a flow control valve 7. The components other than the flow control valve 7 are basically the same as those of the pure water production system 1, so a description of these components will be omitted here.

[0041] The flow control valve 7 is connected to the plurality of activated carbon towers 51 to 55. n The filtered water stored in the filtered water tank 4 is supplied to the activated carbon towers 51-5 via the flow control valve 7. n The flow control valve 7 is connected to the activated carbon towers 51 to 55. n The flow rate on the inlet side can be adjusted.

[0042] In the method for producing pure water of this embodiment, similarly to the first embodiment, the activated carbon towers 51 to 5 nThe reference value is the space velocity when water is passed through the activated carbon towers in parallel, but unlike the first embodiment, when a partial water sampling stop step is performed, the flow rate on the inlet side is adjusted by the flow control valve 7 so that the space velocity of the activated carbon tower used for water sampling is 1.5 times or less the reference value. This adjustment makes it possible to stabilize the terminal water quality.

[0043] As an example, an operating process will be described below in which the flow rate is adjusted in a water sampling system equipped with two activated carbon towers 51 and 52 so that the space velocity of the activated carbon tower used for water sampling becomes 1.3 times the reference value.

[0044] 7A and 7B are diagrams illustrating an example of an operating process performed in the pure water production method of this embodiment. In Fig. 7A, (a) is a schematic diagram showing the water flow state during the water sampling process, and (b) is a schematic diagram showing the water flow state during the cleaning process. In this operating process, one of the two activated carbon towers 51 and 52 is operated separately.

[0045] In the water collection process shown in FIG. 7(a), the flow rate of the filtered water at the inlet side of the two activated carbon towers 51 and 52 is controlled by the flow control valve 7. 3 In this case, the flow rates of the activated carbon towers 51 and 52 are set to Q / 2 [m 3 / h]. The activated carbon packing capacity of each activated carbon tower is V [m 3 ], then SV is Q / 2V[ / h]. In the cleaning process shown in Fig. 7(b), of the two activated carbon towers 51 and 52, the activated carbon tower 52 is separated from the water collection system, and water is collected using the activated carbon tower 51 while backwashing is performed on the activated carbon tower 52. The flow rate of the filtered water at the inlet side of the two activated carbon towers 51 and 52 is Q [m 3 / h], the SV of the activated carbon tower 51 that collects water is Q / V [ / h], and the SV ratio is doubled, exceeding 1.5. Therefore, here, the flow rate of the filtered water on the inlet side of the activated carbon tower 51 is controlled to q [m 3 / h]( <Q[m 3 / h) so that the SV ratio is 1.5 or less. This will stabilize the water quality at the terminal.

[0046] The above-mentioned flow rate values ​​and the number of activated carbon towers are merely examples and can be changed as appropriate. For example, as long as the flow rate can be adjusted so that the space velocity of the activated carbon tower used for water sampling is 1.5 times or less the reference value, the number of activated carbon towers connected in parallel may be three or more, and the number of activated carbon towers separated from the water sampling system may be two or more.

[0047] (Third embodiment) Fig. 8 is a block diagram showing the configuration of a pure water production system to which a pure water production method according to a third embodiment of the present invention is applied. The pure water production system 1B shown in Fig. 8 differs from the pure water production system 1A described in the second embodiment in that it includes a replenishment device 8. The components other than the replenishment device 8 are basically the same as those of the pure water production system 1A, so a description of these components will be omitted here.

[0048] When the flow control valve 7 adjusts the flow rate on the inlet side, it may not be possible to ensure the amount of water supplied to the 2B3T device 6. In this embodiment, when the amount of water supplied to the 2B3T device 6 cannot be ensured, the supply device 8 supplies the shortage to the 2B3T device 6. For example, the supply device 8 can supply surplus water, such as recovered water obtained from the 2B3T device 6, to the activated carbon-treated water or treated water obtained by treating the activated carbon-treated water.

[0049] Although not shown in FIG. 8, if a reverse osmosis (RO) membrane device or an electrodeionization (EDI) device is provided downstream of the A tower in the 2B3T device 6, the surplus water can be the concentrated water from the RO membrane device, the concentrated water from the EDI, or even the circulating surplus water from the equipment that treats the permeate from the RO membrane device. The surplus water can be supplied not only to the outlet of the activated carbon tower, but also to the inlet of the K tower or an RO tank provided upstream of the RO membrane device. Supplying the surplus water to the inlet of the K tower allows the desalination process to be performed on the make-up water as well, allowing for more efficient use of the surplus water.

[0050] Furthermore, the quality of the surplus water (make-up water) from the replenishing device 8 may be analyzed by an analyzer (not shown), and surplus water with a predetermined component below a threshold value may be replenished to the primary pure water system. The predetermined components are, for example, conductivity, residual salt concentration, TOC value, urea concentration, etc. The threshold value differs depending on the replenishing point, but it is desirable that it is equivalent to the water quality at the replenishing point during steady operation.

[0051] This allows the quality of surplus water (make-up water) to be managed and only water that meets the standards to be used for make-up, making it possible to further stabilize the water quality at the terminal.

[0052] Alternatively, for example, a water tank may be provided downstream of the 2B3T device 6, and the supply of makeup water from the makeup device 8 may be controlled according to the water level in the water tank. Upper and lower limits for the water level in the water tank may be set in advance, and makeup may begin when the water level reaches the lower limit, and may stop when the water level reaches the upper limit. This allows excess water to be replenished with the minimum necessary amount of makeup water.

[0053] Alternatively, the amount of excess water required for replenishment may be calculated based on the rate of water level decrease and the remaining time of the activated carbon backwashing process, and the amount of replenishment may be adjusted based on the calculated value. This method also allows replenishment of excess water with the minimum necessary amount. For example, when the cleaning process shown in Figure 7(b) is performed, the minimum necessary amount of excess water can be replenished based on the measured water level, which not only stabilizes the terminal water quality but also enables the excess water to be replenished efficiently.

[0054] (Fourth embodiment) A pure water production method according to a fourth embodiment of the present invention will now be described. As mentioned above, the 2B3T device 6 provided downstream of the activated carbon device 5 typically has multiple K towers. All of the multiple activated carbon towers in the activated carbon device 5 are used for water sampling during normal operation, but at least one K tower is generally kept in a standby state and is not used for water sampling.

[0055] 9A to 9F are schematic diagrams illustrating the operation process including the regeneration / cleaning process of the ion exchange resin. In Fig. 9A to 9F, there are five activated carbon towers (activated carbon towers 51 to 55), and three K towers, D towers, and A towers (K towers 101 to 103, D towers 111 to 113, and A towers 121 to 123) respectively.

[0056] In the water sampling process, one of the three K towers 101 to 103 is put into standby mode, and the remaining two K towers are used to sample water. When regeneration / cleaning of the ion exchange resin of one of the two operating K towers is required, the standby K tower is operated to perform regeneration / cleaning of the target K tower.

[0057] Specifically, as shown in FIG. 9A, K tower 101 is in a standby state, and water is sampled using K towers 102 and 103. K tower 101 is isolated from the water sampling system, and the ion exchange resin has been regenerated. Components other than K tower 101 are in operation (driving) for water sampling. A flow rate Q [m 3 / h] of water is supplied. Therefore, the flow rate of each of the activated carbon towers 51 to 55 is Q / 5 [m 3 / h]. The activated carbon treated water is supplied to the K towers 102 and 103, and the flow rate is Q / 2 [m 3 / h]. K Tower 103 is the next target for regeneration.

[0058] Next, as shown in FIG. 9B, the K tower 101 is idled (prepared for water collection). Specifically, the activated carbon treated water is passed through the K tower 101 in the same amount as the K towers 102 and 103, and the treated water from the K tower 101 is returned to the filtered water tank 4. Therefore, the flow rate of the produced pure water is Q [m 3 / h], the flow rate of water supplied to the entire K column is 3Q / 2 [m 3 / h], and the flow rate of each of the five activated carbon towers 51 to 55 is 3Q / 10 [m 3 / h]. Therefore, the flow rate of each of the activated carbon towers 51 to 55 is Q / 5 [m 3 / h] to 3Q / 10[m 3 / h], the SV ratio is 1.5 times. If the SV ratio is 1.5 times or less, the terminal water quality will be stable.

[0059] Next, as shown in FIG. 9C, a chemical passing step is performed on the K tower 103. Specifically, the K tower 103 is separated from the water sampling system, and the ion exchange resin is regenerated using, for example, hydrochloric acid. In this regeneration (chemical passing) step, the components other than the K tower 103 are in operation (operating) for water sampling. The flow rate of each of the activated carbon towers 51 to 55 is set to Q / 5 [m 3 / h]. The activated carbon treated water is supplied to the K towers 101 and 102, and the flow rate of each is Q / 2 [m 3 / h].

[0060] Next, as shown in FIG. 9D, the pushing step of the K tower 103 is carried out. Specifically, the hydrochloric acid remaining in the K tower 103 is pushed out using clear water. In this pushing step, the components other than the K tower 103 are in operation (operating) for collecting water. The flow rate of each of the activated carbon towers 51 to 55 is Q / 5 [m 3 / h]. The activated carbon treated water is supplied to K towers 101 and 102, and the flow rate is Q / 2 [m 3 / h].

[0061] Next, as shown in FIG. 9E, a cleaning step of the K tower 103 is carried out. Specifically, the K tower 103 is cleaned using activated carbon treated water. Specifically, the activated carbon treated water is passed through the K tower 103 in the same amount as the water in the K towers 101 and 102, and the water used to clean the K tower 103 is discharged outside the system. The flow rate of each of the K towers 101 to 103 is Q / 2 [m 3 / h]. Therefore, the flow rate of the pure water produced is Q [m 3 / h], the flow rate of water supplied to the entire K column is 3Q / 2 [m 3 / h], and the flow rate of each of the five activated carbon towers 51 to 55 is 3Q / 10 [m 3 / h]. Therefore, the flow rate of each of the activated carbon towers 51 to 55 is Q / 5 [m 3 / h] to 3Q / 10[m 3 / h], the SV ratio is 1.5 times. If the SV ratio is 1.5 times or less, the terminal water quality will be stable.

[0062] Next, as shown in FIG. 9F, the K tower 103 is placed on standby, and the remaining two K towers 101 and 102 are used to collect water. The components other than the K tower 103 are in operation (driving) for collecting water. The flow rate of each of the activated carbon towers 51 to 55 is Q / 5 [m 3 / h]. The activated carbon treated water is supplied to K towers 101 and 102, and the flow rate is Q / 2 [m 3 / h]. Tower K 102 is the next target for regeneration.

[0063] In the operation process including the above-mentioned ion exchange resin regeneration / cleaning process, the space velocity of the activated carbon towers 51 to 55 increases during the idling operation (preparation for water sampling) shown in Figure 9B and the cleaning process shown in Figure 9E, which may result in a deterioration in the terminal water quality. In the method for producing pure water according to the present embodiment, a plurality of K towers 101 to 10 m One of the K towers is separated from the water passage for activated carbon-treated water, and water other than activated carbon-treated water is passed through the separated K tower. This suppresses an increase in the space velocity of the activated carbon tower and the deterioration of the terminal water quality.

[0064] In any of the above-described first to fourth embodiments of the pure water production method, during the partial water sampling stop step, it is possible to operate the activated carbon tower used for water sampling so that the space velocity is 1.5 times or less the reference value, thereby stabilizing the terminal water quality. The following describes the results of measuring the urea concentration by changing the space velocity of one activated carbon tower.

[0065] Example 1 In an ultrapure water production system equipped with three activated carbon towers arranged in parallel, filtered water with a raw water urea concentration of 10 ppb was passed through the activated carbon towers. The space velocity of the activated carbon towers was 6h -1 The urea concentration at the outlet of the activated carbon tower was 1 ppb, and the TOC concentration at the POU (Point-of-Use) (TOC concentration in ultrapure water) was 0.2 ppb.

[0066] Next, one of the three activated carbon towers was backwashed for 30 minutes, and the remaining activated carbon towers were backwashed at a space velocity of 1.5 times (space velocity 9h -1 In this case, the urea concentration at the outlet of the activated carbon tower was 1.3 ppb, and the TOC concentration at the POU was 0.26 ppb (see the table below).

[0067] (Comparative Example 1) Next, one activated carbon tower was backwashed for 30 minutes, and the space velocity in the remaining activated carbon towers was doubled (space velocity 12 h -1 The activated carbon tower was operated under the following conditions: In this case, the urea concentration at the outlet of the activated carbon tower was 3.5 ppb, and the TOC concentration at the POU was 0.5 ppb (see the table below).

[0068] [Table 1]

[0069] From the results of Example 1 and Comparative Example 1 described above, it can be seen that when water flow through one tower is stopped, the terminal water quality can be stabilized by operating the activated carbon tower through which water is flowing so that the space velocity is 1.5 times or less the reference value (SV value when water is flowing through all towers).

[0070] (Comparative Example 2) In an ultrapure water production system equipped with three activated carbon towers arranged in parallel, filtered water with a raw water urea concentration of 10 ppb was passed through the activated carbon towers. The space velocity of the activated carbon towers was 11.0 h -1 (>10h -1 The TOC concentration of the POU (TOC concentration of ultrapure water) was 0.2 ppb. After that, one tower was backwashed and water was passed through the remaining two towers. The space velocity of the activated carbon tower at this time was 16.5 h -1 (SV ratio = 1.5), and the TOC concentration of the POU (TOC concentration of ultrapure water) was 0.5 ppb (see the table below).

[0071] [Table 2]

[0072] From the results of the above-mentioned Comparative Example 2, it was found that when water flow through one tower is stopped, even if the spatial velocity of the activated carbon tower through which water flows is 1.5 times the standard value (SV value when water flows through all towers), if the SV value during the water sampling process is high (exceeding 10 / h), the terminal water quality becomes unstable during the partial water sampling stop process.

[0073] Example 2 In an ultrapure water production system equipped with five activated carbon towers arranged in parallel, filtered water with a raw water urea concentration of 10 ppb was passed through the activated carbon towers. The space velocity of the activated carbon towers was 4.0 h -1 The TOC concentration of the POU (TOC concentration of ultrapure water) was 0.2 ppb. After that, one tower was backwashed and water was passed through the remaining four towers. The space velocity of the activated carbon tower at this time was 5.0 h -1 (SV ratio = 1.25), and the TOC concentration of the POU (TOC concentration of ultrapure water) was 0.25 ppb (see the table below).

[0074] (Comparative Example 3) One more tower was replaced and water was passed through the remaining three towers. The space velocity of the activated carbon tower was 7.0 h -1 (SV ratio = 1.75), and the TOC concentration of the POU (TOC concentration of ultrapure water) was 0.28 ppb (see the table below).

[0075] [Table 3]

[0076] In each of the pure water producing methods of the first to fourth embodiments described above, components described in other embodiments may be combined, provided that the operation is not impaired. In each embodiment, the collected pure water may be further treated to produce ultrapure water of even higher purity. For example, additional treatments such as RO treatment, EDI treatment, ultraviolet oxidation treatment, degassing treatment, regenerative ion exchange treatment, non-regenerative ion exchange treatment, temperature adjustment treatment, and final filtration treatment may be performed to remove ionic components, metals, organic matter, dissolved gases, fine particles, live bacteria, and the like, thereby improving the final water quality.

[0077] Furthermore, in the first to fourth embodiments, a case has been described in which a plurality of K towers and A towers are installed in parallel as demineralization equipment. However, the demineralization equipment may be changed to a plurality of RO membrane devices installed in parallel. For example, the demineralization equipment may be a so-called RO-EDI, which is composed of an RO membrane device and an EDI (electrodeionized water production system) that treats RO membrane permeate water. The regeneration process regenerates at least one of the plurality of RO membrane devices. Here, regeneration refers to cleaning or replacement of the RO membrane device. For example, when multiple RO membrane devices are installed in parallel, water may be passed through all of the RO membrane devices in the water sampling process, as with the activated carbon tower. Alternatively, as with the resin tower (K ​​tower), one (or some) of the RO membrane devices may be placed on standby, and the remaining RO membrane devices may be used to sample water. In the former case, at least one of the RO membrane devices is isolated and regenerated in the regeneration process. The activated carbon device is operated so that the fluctuation in space velocity falls within a certain range, based on the space velocity of the activated carbon device during the water sampling process. In the latter case, the standby RO membrane device is operated in the regeneration process, and the RO membrane device to be cleaned or replaced is cleaned or replaced. The RO membrane device to be cleaned or replaced is isolated from the water passage for activated carbon-treated water, and water other than the activated carbon-treated water is passed through the isolated RO membrane device. This prevents an increase in the space velocity of the activated carbon tower.

[0078] The pure water production method of the present invention can be applied to existing ultrapure water production apparatus (e.g., ultrapure water production apparatus 100 shown in FIG. 1). Furthermore, an ultrapure water supply system can also be configured using a pure water production apparatus to which the pure water production method of the present invention is applied. The ultrapure water supply system includes, for example, a primary pure water system having at least any of the pure water production apparatuses described in the first to fourth embodiments, a subsystem that produces ultrapure water by removing impurities from the pure water produced in the primary pure water system, and a recovery system that recovers ultrapure water used at a point-of-use where the ultrapure water produced in the subsystem is used and returns it to the primary pure water system. In this ultrapure water supply system, activated carbon control in the primary pure water system eliminates the need to provide activated carbon in the recovery system. [Explanation of symbols]

[0079] 1 Pure water production equipment 2 Raw Water Tank 3. Filtration equipment 4 Filtration tank 51~5 n activated carbon tower 6 2B3T device 13 Post-processing equipment 101~10 m K tower 111~11 m D tower 121~12 m A tower

Claims

1. A method for producing pure water, comprising: treating water to be treated with activated carbon in an activated carbon device; and desalination of the activated carbon-treated water in a desalination device to produce pure water, The activated carbon device includes a plurality of activated carbon towers filled with activated carbon arranged in parallel, The desalination device includes at least a plurality of desalination devices arranged in parallel, a water sampling step in which the water to be treated is passed through all of the activated carbon towers; a regeneration step of stopping water flow through at least one of the activated carbon towers or regenerating at least a part of the demineralization equipment, The method for producing pure water, wherein the space velocity of water passing through the activated carbon tower in the regeneration step is 10 / h or less.

2. 2. The method for producing pure water according to claim 1, wherein the space velocity of water passing through the activated carbon tower in the water sampling step is 10 / h or less.

3. The activated carbon device has five or more activated carbon towers arranged in parallel, 3. The method for producing pure water according to claim 1, wherein the regeneration step stops water flow through one or two of the activated carbon towers.

4. 4. The method for producing pure water according to claim 3, wherein the regeneration step is performed while water is stopped from passing through two of the activated carbon towers, one of which is stopped for replacement, and the other is stopped for backwashing.

5. 3. The method for producing pure water according to claim 1, wherein water is passed through the activated carbon tower so that the ratio of the space velocity of water passing through the activated carbon tower in the regeneration step to the space velocity of water passing through the activated carbon tower in the water sampling step is 1.5 or less.

6. 3. The method for producing pure water according to claim 1, wherein, when a ratio of the water space velocity through the activated carbon tower in the regeneration step to the water space velocity through the activated carbon tower in the water sampling step exceeds 1.5, the water flow rate through each activated carbon tower in the regeneration step is adjusted to make the ratio 1.5 or less.

7. the demineralization devices are ion exchange devices filled with ion exchange resin, and at least some of the ion exchange devices are in a standby state in which water sampling is not performed; The regeneration step includes a water sampling preparation step of passing treated water from the activated carbon tower through all of the plurality of ion exchange devices before a next water sampling step is performed. a chemical supplying step in which the ion exchange device in the standby state is used for water collection in the next water collection step, and at least one of the ion exchange devices used for water collection in the water collection step is separated from the water collection and regenerated by supplying a chemical; and 3. The method for producing pure water according to claim 1, wherein the water sampling preparation step comprises sending the water passed through the ion exchange device in the standby state to a stage preceding the activated carbon device.

8. the desalination equipment is a reverse osmosis membrane device, 3. The method for producing pure water according to claim 1, wherein the regeneration step regenerates at least one of the plurality of demineralization devices.

9. A pure water production system comprising: an activated carbon device that treats water to be treated with activated carbon; and a demineralization device that demineralizes the activated carbon-treated water from the activated carbon device to produce pure water, wherein the activated carbon device has a plurality of activated carbon towers that are arranged in parallel, each of which is filled with activated carbon; and the demineralization device has at least a plurality of demineralization devices that are arranged in parallel, a control means for performing a water sampling step in which the water to be treated is passed through all of the activated carbon towers, and a regeneration step in which the water passing through at least one of the activated carbon towers is stopped or at least a part of the demineralization equipment is regenerated; The pure water production apparatus, wherein the space velocity of water passing through the activated carbon tower in the regeneration step is 10 / h or less.

10. 10. The water purification system according to claim 9, wherein the space velocity of water passing through the activated carbon tower in the water sampling step is 10 / h or less.

11. a primary pure water system having at least the pure water producing apparatus according to claim 9 or 10; a subsystem for producing ultrapure water by removing impurities from the pure water produced in the primary pure water system; and a recovery system that recovers the ultrapure water used at a point of use that uses the ultrapure water produced in the subsystem and returns it to the primary pure water system.

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