Pure water manufacturing device

Abstract

In a pure water production device (3), a reverse osmosis membrane system (12) has three reverse osmosis membranes (12A, 12B, 12C) arranged in parallel, and a water supply pump (11A) can be controlled by a control means so as to supply pre-treated water (W0) in an amount corresponding to the required amount of water to be treated (W5) in the pure water production device (3). A flow meter (32) is provided in the front section of the water supply pump (11A), and the number of water passing through the reverse osmosis membranes (12A, 12B, 12C) can be controlled by a control means on the basis of a detection value of the flow meter (32). According to the pure water manufacturing device, the water quality can be stabilized even if the flow rate changes along with the water use amount and the like, and energy conservation can be achieved.

Description

Technical Field

[0001] The present invention relates to a pure water production device having a reverse osmosis membrane system, and more particularly to a pure water production device having a reverse osmosis membrane system whose flow rate can be changed according to the amount of water used, etc. Background Art

[0002] In the past, for example, Figure 1 As shown, raw water is treated by an ultrapure water production device 1 composed of three stages of devices, namely, a pre-treatment device 2, a primary pure water device 3, and a secondary pure water device (subsystem) 4, thereby producing ultrapure water used in the semiconductor and other electronic industries. Specifically, in the pre-treatment device 2, the raw water W is pre-treated by filtration, coagulation and sedimentation, and by using a precision filtration membrane, etc., mainly to remove suspended matter.

[0003] The primary pure water device 3 includes, for example, a tank 11 for pre-treated water W0, a water supply pump 11A, a reverse osmosis membrane system 12, an ultraviolet (UV) oxidation device 13, a regenerative ion exchange device (mixed bed type or four-bed five-tower type, etc.) 14, and a membrane degassing device 15. In addition, 16 is a preheater. Here, most of the electrolytes, particles, live bacteria, etc. in the pre-treated water W0 are removed, and organic matter is decomposed.

[0004] The subsystem 4 is composed of, for example, a subtank 21 for storing the primary pure water W1 produced in the aforementioned primary pure water device 3, a water supply pump 22 for conveying the primary pure water W1 stored in the subtank 21, an ultraviolet oxidation device 24 for treating the primary pure water W1, a platinum group metal catalyst resin tower 25, a membrane degassing device 26, a reverse osmosis membrane system 27, a non-regenerative mixed bed ion exchange device 28, and an ultrafiltration (UF) membrane 29 as a membrane filtration device. In addition, 23 is a heat exchanger. In the subsystem 4, the trace organic matter (TOC component) contained in the primary pure water W1 is oxidized and decomposed by ultraviolet rays in the ultraviolet oxidation device 24, and the hydrogen peroxide generated by the irradiation of the ultraviolet rays is decomposed in the platinum group metal catalyst resin tower 25, and the dissolved gas such as DO (dissolved oxygen) mixed in is removed by the membrane degassing device 26 in the subsequent stage. Then, the residual carbonate ions, organic acids, and anionic substances are removed by the reverse osmosis membrane system 27 and the non-regenerative ion exchange device 28. Then, the particles are removed by the ultrafiltration (UF) membrane 29 to become ultrapure water (secondary pure water) W2, which is supplied to the water point 5 from the delivery pipe 30, and the unused ultrapure water is returned to the sub-tank 21 from the return pipe 31.

[0005] In the ultrapure water production apparatus 1 as described above, the reverse osmosis membrane constituting the reverse osmosis membrane system 12 has the following Fig.17That is, it can be seen that in the reverse osmosis membrane, the effective pressure on the membrane surface ((water supply + concentrated water volume) / 2-treated water) is correlated with the removal rate of various removal target substances (here, boron), and when the effective pressure on the membrane surface decreases, the removal rate of various removal target substances shows a tendency to decrease. Here, the most suitable effective pressure on the membrane surface for removing various removal target substances varies depending on the type of reverse osmosis membrane, and there are significant differences, but when the effective pressure on the membrane surface decreases, the removal rate of various removal target substances shows a tendency to decrease.

[0006] Taking this characteristic into consideration, in order to always supply treated water with stable water quality, the reverse osmosis membrane system 12 is controlled so that the amount of treated water is roughly constant. Specifically, (constant amount of treated water) = (constant effective pressure on the membrane surface). However, depending on the long-term operating conditions, the clogging and degradation of the RO membrane may cause the relationship to change, so adjustments need to be made in the operation management.

[0007] However, Figure 2 The pure water manufacturing device 41 schematically shown in FIG. 4 includes: a first tank 42 storing pre-treated water W0; a first water supply pump 43; a reverse osmosis membrane system 44; a supply line 48A for conveying treated water WR of the reverse osmosis membrane treatment system 44 to a second tank 45; a second water supply pump 46 for supplying primary pure water W1 to the auxiliary system; a return line 49A for returning treated water WR of the permeation membrane treatment system 44 to the first tank 42; and a flow path 50 for concentrated water W3 of the reverse osmosis membrane treatment system 44. In addition, 48B and 49B are automatic flow control valves. In the pure water manufacturing device 41, the primary pure water W1 of the maximum usage amount of the water point (POU) 47 is produced and supplied to the second tank 45, and the excess water is recycled. Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the pure water manufacturing device 41, the water delivery rate of the first water supply pump 43 that delivers water to the reverse osmosis membrane system 44 is constant (110%), so a specified amount of electricity is normally consumed. In addition, even if the amount of water used at the water point (POU) 47 varies within the range of 0 to 80% or even no water is used, 90% of the treated water WR is returned from the return line 49A to the first tank 42 for recycling. In addition, the concentrated water W3 is 20% and remains constant. In recent years, measures to reduce CO2 and save energy are being promoted. In the pure water manufacturing device 41, it is important to reduce the operating energy of the first water supply pump 43 that supplies pre-treated water W0 to the reverse osmosis membrane system 44, which consumes a lot of electricity.

[0010] Therefore, it is considered to use an inverter or the like to reduce the water delivery rate of the first water supply pump 43 at the water use point (POU) 47. However, if the water delivery rate of the first water supply pump 43 is reduced only according to the required water supply rate at the water use point (POU) 47, it will lead to a decrease in the effective pressure on the membrane surface, and there is a problem of deterioration in the water quality of the water treated by the reverse osmosis membrane.

[0011] The present invention has been made in view of the above problems, and an object of the present invention is to provide a pure water production apparatus including a reverse osmosis membrane system capable of stabilizing water quality and achieving energy saving even when the flow rate varies due to changes in the amount of water used.

[0012] Means for solving problems

[0013] In view of the above-mentioned purpose, the present invention provides a pure water production device, which is a pure water production device having a reverse osmosis membrane system equipped with more than two reverse osmosis membranes, wherein a detection mechanism for detecting an index that can calculate the membrane surface effective pressure of the reverse osmosis membrane of the reverse osmosis membrane system is provided in the front section or the rear section of the reverse osmosis membrane system, and the pure water production device is provided with a control mechanism, which controls the number of reverse osmosis membranes passing water in the reverse osmosis membrane system based on the detection value of the detection mechanism to adjust the membrane surface effective pressure (Invention 1).

[0014] According to the above invention (Invention 1), the amount of treated water supplied to the reverse osmosis membrane system of the pure water manufacturing device is increased or decreased according to the required water amount of the water supply destination (water use point) of the pure water manufacturing device. In order to stably maintain the water quality of the treated water under the condition that the flow rate of the treated water supplied to the reverse osmosis membrane system changes, it is necessary to operate the membrane surface effective pressure within a specified range. When the membrane surface effective pressure is constant, the amount of water obtained by each reverse osmosis membrane depends on the number of reverse osmosis membranes through which water passes. Therefore, an index that can calculate the membrane surface effective pressure of the reverse osmosis membrane is detected, and the number of water passing through the reverse osmosis membranes arranged in parallel is increased or decreased so that the membrane surface effective pressure is within a specified range when the amount of treated water increases or decreases, thereby stabilizing the water quality.

[0015] In the above invention (Invention 1), preferably, the pure water production device includes a water supply pump for supplying the water to be treated to the reverse osmosis membrane system, and the control means is configured to be able to perform inverter control on the water supply pump (Invention 2).

[0016] According to the above invention (Invention 2), by controlling both the inverter of the water supply pump that supplies treated water to the reverse osmosis membrane system and the number of water passing through the reverse osmosis membrane, the membrane surface effective pressure can be appropriately maintained within a specified range, and the operating energy of the water supply pump can be efficiently improved.

[0017] In addition, in the above invention (Invention 2), it is preferred that the pure water production device has a flow meter for detecting the amount of concentrated water in the reverse osmosis membrane system, and has a control valve capable of adjusting the flow rate of the concentrated water, and the control mechanism is formed to be capable of adjusting the opening of the control valve based on the detection value of the flow rate of the concentrated water obtained by the flow meter (Invention 3).

[0018] According to the above invention (Invention 3), when the amount of water to be treated increases or decreases, the number of water passing through the parallel reverse osmosis membranes is increased or decreased, and the flow rate of concentrated water is adjusted, thereby enabling more appropriate control so that the membrane surface effective pressure is within a predetermined range.

[0019] Furthermore, in the above inventions (Inventions 1 to 3), it is preferred that the reverse osmosis membrane system is a structure filled with 2 to 6 reverse osmosis membranes or a structure formed of a plurality of reverse osmosis membrane containers filled with 1 to 6 reverse osmosis membranes (Invention 4).

[0020] According to the above invention (Invention 4), the reverse osmosis membrane system can be suitably applied regardless of whether it is a structure in which a plurality of reverse osmosis membranes are arranged in parallel or a structure in which a plurality of series of reverse osmosis membrane containers are arranged in parallel.

[0021] Effects of the Invention

[0022] According to the pure water manufacturing device of the present invention, a detection mechanism for detecting an index that can calculate the effective pressure of the membrane surface of the reverse osmosis membrane of the reverse osmosis membrane system is set in the pure water manufacturing device having a reverse osmosis membrane system with more than two reverse osmosis membranes arranged in parallel to detect the increase or decrease of the effective pressure of the membrane surface of the reverse osmosis membrane system, and based on the detection value, the number of reverse osmosis membranes passing water of the reverse osmosis membrane system is controlled, so that when the amount of treated water treated by the reverse osmosis membrane system increases or decreases, the number of reverse osmosis membranes passing water is increased or decreased so that the effective pressure of the membrane surface of the reverse osmosis membrane is within a specified range, thereby stabilizing the water quality. Furthermore, the operating energy of the water supply pump can be made efficient according to the amount of treated water treated by the reverse osmosis membrane system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart showing an ultrapure water production apparatus to which the pure water apparatus of the present invention can be applied.

[0024] Figure 2 This is a flow chart schematically showing the main parts of the pure water production apparatus.

[0025] Figure 3 This is a flow chart schematically showing the main part of the pure water production apparatus according to the first embodiment of the present invention.

[0026] Figure 4 Yes means Figure 3A flow chart showing an example of the operation process of the pure water production apparatus shown.

[0027] Figure 5 Yes means Figure 3 A flow chart of another example of the operating process of the pure water production apparatus shown.

[0028] Figure 6 FIG. 1 is a flow chart schematically showing a pure water production apparatus according to a second embodiment of the present invention.

[0029] Figure 7 It means according to Figure 6 A flow chart showing an example of an operation process of a pure water production apparatus according to the embodiment shown.

[0030] Figure 8 It means according to Figure 6 A flow chart of another example of the operation process of the pure water production apparatus according to the illustrated embodiment.

[0031] Fig. 9 This is a flow chart showing the reverse osmosis membrane treatment system in Example 1.

[0032] Fig.10 This is a graph showing the temporal changes in the water supply pressure (membrane surface effective pressure) and the permeate water pressure in Example 1.

[0033] Fig.11 This is a graph showing the changes in the concentrated water flow rate and the permeated water flow rate over time in Example 1.

[0034] Fig.12 This is a graph showing the relationship between the change in the number of reverse osmosis membranes in Example 1 and the water quality (electrical conductivity) of the permeated water.

[0035] Fig.13 This is a flow chart showing the reverse osmosis membrane treatment system in Example 2.

[0036] Fig.14 This is a graph showing the temporal changes in the water supply pressure (membrane surface effective pressure) and the permeate water pressure in Example 2.

[0037] Fig.15 This is a graph showing the changes in the concentrated water flow rate and the permeated water flow rate over time in Example 2.

[0038] Fig.16 This is a graph showing the elapsed time and the quality of the permeated water in Example 2.

[0039] Fig.17 This is a graph showing the relationship between the membrane effective pressure of the reverse osmosis membrane and the boron removal rate. DETAILED DESCRIPTION

[0040] Hereinafter, a pure water production apparatus including a reverse osmosis membrane system according to the present invention will be described with reference to the drawings.

[0041] [First embodiment]

[0042] (Pure water production equipment)

[0043] Figure 3 The main parts of a pure water production device equipped with a reverse osmosis membrane system according to a first embodiment of the present invention are schematically shown. The present invention has a feature in the control of the reverse osmosis membrane system, and therefore, in this embodiment, the reverse osmosis membrane system 12 is mainly shown in the figure. Figure 3 In the pure water manufacturing device shown, the reverse osmosis membrane system 12 is a structure in which three reverse osmosis membranes 12A, 12B, and 12C are arranged in parallel, and the water supply pump 11A can be controlled by a control mechanism not shown in the figure to supply the amount of treated water (pre-treated water) W4 corresponding to the required amount of primary pure water W1 in the pure water manufacturing device 3. In addition, a flow meter 32 for the treated water W4 is provided at the front section of the water supply pump 11A, and the number of water passing through the reverse osmosis membranes 12A, 12B, and 12C can be controlled by the control mechanism based on the detection value of the flow meter 32. In addition, 121 is a flow path for the concentrated water W6 of the reverse osmosis membranes 12A, 12B, and 12C.

[0044] (Reverse Osmosis Membrane System)

[0045] In this embodiment, the reverse osmosis membrane system 12 is a system in which two or more reverse osmosis membranes are arranged in parallel. The reverse osmosis membrane system 12 may be a reverse osmosis membrane-based structure in which 2 to 6 reverse osmosis membranes are filled in parallel, or may be a structure in which a plurality of reverse osmosis membrane containers filled with 1 to 6 reverse osmosis membranes are arranged in parallel. The reverse osmosis membrane system 12 is basically composed of the same reverse osmosis membrane.

[0046] The reverse osmosis membranes 12A, 12B, and 12C constituting the reverse osmosis membrane system 12 as described above are not particularly limited, and reverse osmosis membrane devices known in the art can be used. Various organic polymer membranes or ceramic membranes composed of cellulose acetate, aliphatic polyamide systems, aromatic polyamide systems, or composite systems thereof can be used. Ultra-low pressure reverse osmosis membranes, ultra-low pressure reverse osmosis membranes, low pressure or medium pressure reverse osmosis membranes can all be applicable, but low pressure reverse osmosis membranes or ultra-low pressure reverse osmosis membranes can be appropriately applied.

[0047] (Control method of pure water production device equipped with reverse osmosis membrane system)

[0048] based on Figure 3 to Figure 5 A method of controlling the reverse osmosis membrane system 12 in a pure water production apparatus including such a reverse osmosis membrane system 12 will be described.

[0049] First, if Figure 3 As shown, the basic state is to set the water volume (water production volume) of the treated water W5 to 80m 3 / h and fix the concentrated water W6 of the reverse osmosis membrane system 12 to 20m 3 / h, it can 3 / h of treated water W4 is supplied from the water supply pump 11A to the three reverse osmosis membranes 12A, 12B, and 12C constituting the reverse osmosis membrane system 12. At this time, the membrane surface effective pressure of the reverse osmosis membranes 12A, 12B, and 12C is 0.7 MPa, and it is assumed that an appropriate ion removal rate is achieved under this membrane surface effective pressure condition.

[0050] And, when the required water volume (treated water W5) of the water point is reduced to 40m 3 / h, such as Figure 4 As shown, control is performed to reduce the output of the water supply pump 11A to 60m 3 / h, the treated water W4 is supplied to the three reverse osmosis membranes 12A, 12B, and 12C constituting the reverse osmosis membrane system 12. At this time, since the concentrated water W6 of the reverse osmosis membrane system 12 is 20m 3 / h, therefore, the membrane surface effective pressure of the reverse osmosis membranes 12A, 12B, and 12C is 0.35 MPa. In this case, the decrease in the membrane surface effective pressure of the reverse osmosis membranes 12A, 12B, and 12C leads to the deterioration of the water quality of the treated water W5.

[0051] Therefore, in this embodiment, when the required water volume (treated water W5) of the water point is reduced to 40m 3 / h, such as Figure 5 As shown in FIG. 1 , water flow to one reverse osmosis membrane (reverse osmosis membrane 12C) is stopped. In this state, control is performed so that the output of the water supply pump 11A is reduced to 60 m / s. 3 / h, if the treated water W4 is supplied to the reverse osmosis membrane system 12, it is supplied to the reverse osmosis membranes 12A and 12B respectively. At this time, since the concentrated water W6 of the reverse osmosis membrane system 12 is 20m 3 / h, so the membrane surface effective pressure of the reverse osmosis membranes 12A and 12B is 0.52 MPa. In this way, the decrease in the membrane surface effective pressure of the reverse osmosis membranes 12A and 12B is suppressed, and the deterioration of the water quality of the treated water W5 can be prevented.

[0052] In the control as described above, as a method for judging the switching of the number of membranes of the reverse osmosis membrane, in the present embodiment, a flow meter 32 of the treated water W4 is provided, but it is not limited thereto, and a flow meter of the treated water W5, a calculation of the effective pressure of the membrane surface using a pressure gauge of the treated water W4 / treated water W5 / concentrated water W6, a water quality (conductivity, TOC (total organic carbon)) measurement mechanism of the treated water 5, etc. can also be used. In addition, the timing of the number switching can be arbitrarily set according to the type of membrane of the reverse osmosis membrane. Further, the start-stop mechanism can be an automatic valve or a water supply pump for each series.

[0053] [Second embodiment]

[0054] (Pure water production equipment)

[0055] This embodiment basically has the same Figure 2 The structure is the same as that of the pure water production device 41 shown in the figure. That is, the pure water production device 41 is equipped with: a reverse osmosis membrane system 44, which has a first tank 42 for storing pre-treated water W0, a first water supply pump 43, and a plurality of parallel reverse osmosis membranes; a supply line 48A, which transports the treated water WR of the reverse osmosis membrane treatment system 44 to the second tank 45; a second water supply pump 46, which supplies primary pure water W1 to the water point 47; a return line 49A, which returns the treated water WR of the permeation membrane treatment system 44 to the first tank 42; and a flow path 50 for the concentrated water W3 of the reverse osmosis membrane treatment system 44. In addition, 48B and 49B are automatic valves for flow adjustment.

[0056] (Control method of pure water production device)

[0057] based on Figure 6 to Figure 8 A method of controlling the reverse osmosis membrane system 44 in the pure water production apparatus 41 will be described.

[0058] (Conventional operation control method of pure water production device)

[0059] First, for previous controls, such as Figure 6 As shown in FIG. 1 , when the water treatment volume (water production volume) of the reverse osmosis membrane system 44 is set to 90 m 3 / h and fix the concentrated water W3 of the reverse osmosis membrane system 44 to 20m 3 / h, it will be 110m 3 / h of pre-treated water W0 of the treated water is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. As a result, the amount of treated water WR produced by the reverse osmosis membrane system 44 is 90m 3 / h, keep constant.

[0060] At this time, when the usage of water point 47 is 80m 3 / h, 80m3 / h of treated water WR is delivered from the supply line 48A to the second tank 45, while 10m 3 / h treated water WR is sent from return line 49A at 10m 3 / h is returned to the first tank 42 ((1) in the figure).

[0061] Then, when the usage of water point 47 is reduced to 55m 3 / h, 55m 3 / h of treated water WR is delivered from the supply line 48A to the second tank 45, while at 35m 3 / h is returned from the return line 49A to the first tank 42 ((2) in the figure).

[0062] Further, when the usage of water point 47 is reduced to 40m 3 / h, 40m 3 / h of treated water WR is delivered from the supply line 48A to the second tank 45, while on the other hand, the treated water WR is delivered at 50m 3 / h is returned from the return line 49A to the first tank 42 ((3) in the figure).

[0063] In this conventional operation control method, as the amount of water used at the water point 47 decreases, the membrane effective pressure of the reverse osmosis membrane constituting the reverse osmosis membrane system 44 decreases, and the quality of the treated water WR may deteriorate. Furthermore, the operating energy of the first water supply pump 43 is excessive.

[0064] (First Flow Rate Variation Operation Control Method for Pure Water Production Apparatus)

[0065] like Figure 7 As shown, the initial state of the first flow rate variation operational control is the same as (1) of the aforementioned "basic operational control".

[0066] That is, when the water treatment volume (water production volume) of the reverse osmosis membrane system 44 is set to 90m 3 / h and fix the concentrated water W3 of the reverse osmosis membrane system 44 to 20m 3 / h, 110m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. As a result, the amount of treated water WR produced by the reverse osmosis membrane system 44 is 90m 3 / h.

[0067] At this time, when the usage of water point 47 is 80m 3 / h, the treated water WR is supplied from the supply line 48A at 80m 3 / h is transported to the second tank 45, on the other hand, at 10m 3 / h is returned from the return line 49A to the first tank 42 ((1) in the figure).

[0068] Then, when the usage of water point 47 is reduced to 55m 3 / h, 90m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. As a result, the concentrated water of the reverse osmosis membrane system 44 is 20m 3 / h, therefore, the water production capacity of treated water WR is 75m 3 / h. At this time, as in the first embodiment described above, the number of reverse osmosis membranes constituting the reverse osmosis membrane system is reduced. Then, the treated water WR is supplied from the supply line 48A at 55m 3 / h is transported to the second tank 45, on the other hand, at 15m 3 / h is returned from the return line 49A to the first tank 42 ((2) in the figure).

[0069] Further, when the usage of water point 47 is reduced to 40m 3 / h, 80m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. As a result, the amount of treated water WR produced is 60m 3 / h. At this time, as in the first embodiment described above, the number of reverse osmosis membranes constituting the reverse osmosis membrane system is reduced. Then, the treated water WR is supplied from the supply line 48A at 40m 3 / h is transported to the second tank 45, on the other hand, at 20m 3 / h is returned from the return line 49A to the first tank 42 ((1) in the figure).

[0070] In this first flow rate variation operation control method, the decrease in the effective pressure of the membrane surface of the reverse osmosis membrane constituting the reverse osmosis membrane system 44 accompanying the decrease in the amount of water used at the water point 47 can be reduced, so that the water quality of the treated water WR can be suppressed. However, since the control is performed by increasing or decreasing the number of water passing through the reverse osmosis membrane, it is a step-by-step control, and therefore fine adjustment cannot be performed.

[0071] (Second Flow Rate Variation Operation Control Method for Pure Water Production Apparatus)

[0072] like Figure 8 As shown, in the second flow variation operation control, a water level gauge 51 is provided in the second tank 45, and the opening of the flow regulating automatic valves 48B and 49B can be controlled based on the measurement value of the water level gauge using a control mechanism not shown in the figure. In addition, a pressure gauge 52 is provided for measuring the pressure of the treated water WR, and an inverter 53 is provided in the first water supply pump 43, and the output of the first water supply pump 43 can be inverter-controlled based on the measurement value of the pressure gauge 52.

[0073] In the initial state of the second flow rate variation operation control, when the usage of the water point 47 is 80m 3 / h, 100m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. The concentrated water of the reverse osmosis membrane system 44 is fixed at 20m 3 Therefore, the water production rate of the treated water WR of the reverse osmosis membrane system 44 is 80m 3 In this embodiment, the flow rate regulating automatic valve 49B is closed, and the return line 49A does not return the flow rate to the first tank 42 (0m 3 / h) ((1) in the figure). The return line 49A is used as an emergency line when a pure water production device fails or the quality of the supplied water changes suddenly.

[0074] Then, when the usage of water point 47 is reduced to 55m 3 / h, 75m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. Thus, the water production capacity of the reverse osmosis membrane system 44 is set to 55m 3 / h, and, as in the first embodiment described above, the number of reverse osmosis membranes constituting the reverse osmosis membrane system is reduced. 3 / h treated water WR is delivered from the supply line 48A to the second tank 45. At this time, the pressure of the treated water WR changes due to the decrease in the amount of water produced, the change in the number of water passing through the reverse osmosis membrane, and the opening of the flow rate adjustment automatic valve 48B. Therefore, the pressure is measured using a pressure gauge 52, and the first water supply pump 43 is controlled using an inverter 53 to keep it substantially constant. In addition, the flow rate adjustment automatic valve 49B is closed, and no water is returned from the return line 49A to the first tank 42 (0m 3 / h)((2) in the figure).

[0075] Further, when the usage of water point 47 is reduced to 40m 3 / h, 60m 3 / h of treated water W0 is supplied from the first water supply pump 43 to the reverse osmosis membrane system 44. Thus, the amount of treated water WR produced is set to 40m 3 / h, and, as in the first embodiment described above, the number of reverse osmosis membranes constituting the reverse osmosis membrane system is reduced. 3 / h treated water WR is delivered from the supply line 48A to the second tank 45. At this time, the pressure of the treated water WR changes due to the decrease in the amount of water produced, the change in the number of water passing through the reverse osmosis membrane, and the opening of the flow rate adjustment automatic valve 48B. Therefore, the pressure is measured using a pressure gauge 52, and the first water supply pump 43 is controlled using an inverter 53 to keep it substantially constant. In addition, the flow rate adjustment automatic valve 49B is closed, and no water is returned from the return line 49A to the first tank 42 (0m 3 / h)((3) in the figure).

[0076] In this second flow rate variation operation control method, the decrease in the effective pressure of the membrane surface of the reverse osmosis membrane constituting the reverse osmosis membrane system 44 accompanying the decrease in the amount of water used at the water point 47 can be reduced, and thus the deterioration of the water quality of the treated water WR can be suppressed. In addition, the output of the first water supply pump 43 can be finely adjusted according to the pressure of the treated water WR of the reverse osmosis membrane system 44, and thus the power of the first water supply pump 43 can be suppressed to the minimum according to the amount of water used at the water point 47. In this way, by combining the operation control of maintaining the effective pressure of the membrane surface of the reverse osmosis membrane and minimizing the change in water quality, the operation control of the reverse osmosis membrane system 44 can be performed more appropriately.

[0077] The present invention has been described above based on the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments and can be implemented in various modified forms. For example, the configuration of the reverse osmosis membrane system is not particularly limited, and it can be applied to pure water production devices of various configurations with variable flow rates.

[0078] Example

[0079] Hereinafter, the present invention will be described in more detail based on specific examples, but the present invention is not limited to the following examples.

[0080] [Example 1]

[0081] (Test on switching the number of reverse osmosis membranes)

[0082] like Fig. 9As shown in FIG. 1 , a test device is prepared, which includes a reverse osmosis membrane system 62 having a water supply pump 61 and reverse osmosis membranes 62A and 62B, and a reverse osmosis membrane 63, and a sampling point 64 is provided on the downstream side of the reverse osmosis membrane 63. The reverse osmosis membrane system 62 includes a water supply pump 61 and reverse osmosis membranes 62A and 62B, and the reverse osmosis membrane 63 processes the concentrated water of these reverse osmosis membranes 62A and 62B. In this test device, the water supply pressure of the water supply pump 61 and the flow rate of the permeated water (processed water) of the reverse osmosis membrane system 62 are changed, and the water supply / stop to the reverse osmosis membranes 62A, 62B and the reverse osmosis membrane 63 are controlled accordingly. Specifically, the number of water supply is changed, and a water supply test for 4000 seconds is performed in the order of the flow rate from the largest to the smallest, respectively, for the reverse osmosis membranes 62A, 62B and the reverse osmosis membrane 63 (3 pieces), the reverse osmosis membrane 62A and the reverse osmosis membrane 63 (2 pieces), and the reverse osmosis membrane 62A (1 piece) only. In addition, as the reverse osmosis membranes 62A and 62B and the reverse osmosis membrane 63, a membrane is used in which one reverse osmosis membrane is respectively filled in one container and a high performance is exhibited at a membrane surface effective pressure of about 0.4 to 1.0 MPa.

[0083] The flow rates of permeated water and concentrated water in the water flow test are shown in FIG. Fig.10 , the water supply pressure and the permeate pressure are shown in Fig.11 The results of measuring the conductivity (EC) of the permeate water of the reverse osmosis membrane system 62 and the change in the number of water passing through the reverse osmosis membrane are shown in FIG. Fig.12 .

[0084] according to Figure 10 to Figure 12 It can be seen that the effective pressure of the membrane surface (≒water supply pressure (in this embodiment, the amount of concentrated water is constant, and the permeate water ≒0Ma)) of the reverse osmosis membranes 62A and 62B and the reverse osmosis membrane 63 can be controlled in the range of approximately 0.8 to 0.5 MPa. In addition, the conductivity of the treated water (permeate water) can be stably maintained at a low level. In addition, it temporarily increases when the number of reverse osmosis membranes is increased, but it is believed that this is because the water quality of the water retained on the permeate water side deteriorates when the water flow through the reverse osmosis membrane is stopped. When the reverse osmosis membrane starts to flow water again, the deteriorated retained water will be released. It can be seen that it is preferably washed before starting again.

[0085] [Example 2]

[0086] (Test to confirm the effect of flow rate fluctuation on the treated water of reverse osmosis membrane)

[0087] Prepared Fig.13 For this test setup, Fig. 9 In the device shown, an inverter 65 is provided in the water supply pump 61, and a flow control valve 66 is provided on the downstream side of the reverse osmosis membrane 63 to control the permeate water pressure and the concentrated water flow rate to be constant, and the number of water passing is fixed to three for treatment.

[0088] The flow rates of permeate water and concentrate water in this test are shown in Fig.14 , the water supply pressure and the permeate pressure are shown in Fig.15 The results of measuring the conductivity (EC), Na concentration, SiO2 concentration, TOC concentration and boron concentration of the permeated water measured at the sampling point 64 are shown together with the change in the number of water passing through the reverse osmosis membrane. Fig.16 .

[0089] according to Figure 14 to Figure 16 It can be seen that as the permeate flow rate and water supply pressure decrease, the water quality decreases, and the water quality of the permeate water depends on the water supply pressure (membrane surface effective pressure). Therefore, it can be said that by applying the control of Example 1, operation with more stable water quality can be performed.

[0090] Description of Reference Numerals

[0091] 1: Ultrapure water production device.

[0092] 2: Pre-processing device.

[0093] 3: Primary pure water device.

[0094] 4: Secondary pure water device (auxiliary system).

[0095] 5: Use water points.

[0096] 11: Can.

[0097] 11A: Water supply pump.

[0098] 12: Reverse osmosis membrane system.

[0099] 12A, 12B, 12C: Reverse osmosis membrane.

[0100] 32: Flow meter.

[0101] 41: Pure water production device.

[0102] 42: The first can.

[0103] 43: First water supply pump.

[0104] 44: Reverse osmosis membrane system.

[0105] 45: The second can.

[0106] 46: Second water supply pump.

[0107] 47: Use water.

[0108] 48A: Supply line.

[0109] 48B: Automatic flow control valve.

[0110] 49A: Return line.

[0111] 49B: Automatic flow adjustment valve.

[0112] 50: Concentrated water flow path.

[0113] 51: Water level gauge.

[0114] 52: Pressure gauge.

[0115] 53: Inverter.

[0116] 61: Water supply pump.

[0117] 62: Reverse osmosis membrane system.

[0118] 62A, 62B, 63: Reverse osmosis membrane.

[0119] 64: Sampling point.

[0120] 65: Inverter.

[0121] 66: Flow control valve.

[0122] W: raw water.

[0123] W0: pre-treated water (treated water). W1: primary pure water.

[0124] W2: secondary pure water (ultrapure water). W3, W6: concentrated water.

[0125] W4: Treated water.

[0126] W5: Treated water.

[0127] W6: Concentrated water.

[0128] W5, WR: treated water from reverse osmosis membrane system.

Claims

1. A pure water production device, comprising a reverse osmosis membrane system having two or more reverse osmosis membranes, wherein: A detection mechanism for detecting an index capable of calculating the membrane surface effective pressure of the reverse osmosis membrane of the reverse osmosis membrane system is provided at the front section or the rear section of the reverse osmosis membrane system. The pure water production device includes a control mechanism that controls the number of reverse osmosis membranes through which water flows in the reverse osmosis membrane system based on the detection value of the detection mechanism to adjust the membrane surface effective pressure.

2. The pure water production device according to claim 1, wherein: The pure water production device includes a water supply pump for supplying the water to be treated to the reverse osmosis membrane system, and the control mechanism is configured to be able to perform inverter control on the water supply pump.

3. The pure water production device according to claim 2, wherein: The pure water production device has a flow meter for detecting the amount of concentrated water in the reverse osmosis membrane system, and has a control valve capable of adjusting the flow of the concentrated water. The control mechanism is formed to be able to adjust the opening of the control valve based on the detection value of the flow of concentrated water obtained by the flow meter.

4. The pure water production device according to any one of claims 1 to 3, wherein The reverse osmosis membrane system is a structure filled with 2 to 6 reverse osmosis membranes or a structure formed by a plurality of reverse osmosis membrane containers filled with 1 to 6 reverse osmosis membranes.

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