Control method for pure water production system

Abstract

When the amount of water used at each point of use is reduced and the amount of water supplied to the subsystems (4A, 4B, 4C) is reduced than a reference value, the control valves (60A, 60B, 60C) are respectively reduced to reduce the amount of water supplied, and the water supply pressure of the pressure gauge (59) is increased. Therefore, the control means reduces the output of the high-pressure pump (52B) by inverter control so that the measured value of the pressure gauge (59) becomes substantially constant with respect to a predetermined value on the basis of the measured value of the pressure gauge (59). Furthermore, when the amount of water used at each point of use increases and the amount of water supplied to the subsystems (4A, 4B, 4C) increases than the reference value, the control valves (60A, 60B, 60C) are opened, and the amount of water supplied is increased. Therefore, the water supply pressure of the pressure gauge (59) is reduced. Therefore, the control means increases the output of the high-pressure pump (52B) by inverter control on the basis of the measured value of the pressure gauge (59) such that the measured value of the pressure gauge (59) becomes substantially constant with respect to a predetermined value. As long as the control method of the pure water production system is adopted, the water supply amount can be controlled according to the water use amount.

Description

Technical Field

[0001] The present invention relates to a control method for a pure water production system for producing ultrapure water used in the electronic industry such as semiconductors and liquid crystals, and in particular to a control method for a pure water production system capable of controlling the water supply amount according to the water usage amount. Background Art

[0002] Conventionally, ultrapure water used in the semiconductor and other electronics industries has been produced by treating raw water in an ultrapure water production system consisting of a pretreatment system, a primary pure water device, and a subsystem for treating the primary pure water.

[0003] For example, Figure 1 As shown, the ultrapure water production system 1 consists of three stages: a pretreatment unit 2, a primary pure water unit (pure water production system) 3, and a secondary pure water production unit (subsystem) 4, which is a pure water-using device. In the pretreatment unit 2 of the ultrapure water production system 1, raw water W is pretreated by filtration, coagulation and sedimentation, and microfiltration membranes, primarily to remove suspended matter.

[0004] The primary pure water device 3 includes a treated water tank 31 for storing pretreated water (treated water) W1, a high-pressure pump 32 for delivering the pretreated water W1, a reverse osmosis membrane device 33, a first degassing membrane device 34A for removing dissolved gases using air, a second degassing membrane device 34B for further degassing dissolved gases using nitrogen, an ultraviolet oxidation device 35, an electrodeionization device 36, and a water supply pump 37 for supplying water to the electrodeionization device 36. The primary pure water device 3 removes most electrolytes, particulates, and live bacteria from the pretreated water W1 and decomposes organic matter.

[0005] Subsystem 4 consists of a sub-tank 41, located after the electrodeionization unit, that stores primary pure water W2 produced by the primary pure water unit 3. It serves as a pure water tank; an ultraviolet oxidation unit 42, which treats the primary pure water W2 supplied from sub-tank 41 by a pump (not shown); a non-regenerative mixed-bed ion exchange unit 43; and an ultrafiltration (UF) membrane 44, which serves as a membrane filtration unit. Furthermore, an RO (reverse osmosis) membrane separation unit may be provided as needed. In subsystem 4, trace organic matter (TOC (total organic carbon)) contained in the primary pure water W2 is oxidatively decomposed by the ultraviolet oxidation unit 42. Subsequently, the water is treated in the non-regenerative mixed-bed ion exchange unit 43 to remove residual carbonate ions, organic acids, anionic substances, and metal ions or cationic substances through ion exchange. Particles are then removed by the ultrafiltration (UF) membrane 44, resulting in ultrapure water W3, which is then supplied to the point of use 5. Unused ultrapure water is returned to sub-tank 41.

[0006] In the ultrapure water production system 1 , in order to stably supply primary pure water of a predetermined quality, an excess of primary pure water W2 is produced in advance, only the required amount is supplied to the sub-tank 41 , and the remaining amount is circulated and used.

[0007] However, in the conventional control method for ultrapure water production system 1 described above, since more water than required is supplied to electrodeionization device 36 and the like for treatment, there is room for improvement in energy efficiency. Therefore, it is possible to adjust the processing capacity of electrodeionization device 36 based on the usage at point of use 5, with respect to the processing capacity of primary pure water device 3. However, this not only makes it difficult to track changes in usage at point of use 5, but also leads to a decrease in the quality of the desalted water during the electrodeionization process.

[0008] Therefore, as a control method for an ultrapure water production system that can produce primary pure water according to the usage amount at the usage point, the applicant has obtained a patent for a control method for an ultrapure water production system, wherein the ultrapure water production system comprises: a primary pure water system having a reverse osmosis membrane, an electrodeionization device, and a water supply pump arranged at the front end of the electrodeionization device; a water storage tank (sub-tank) equipped with a water level measuring unit arranged at the rear end of the electrodeionization device; a subsystem that further processes the primary pure water produced in the primary pure water system, wherein the supply pump of the electrodeionization device is inverter-controlled in such a manner that the water level of the water storage tank measured by the water level measuring unit is kept approximately constant (patent document 1).

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent No. 6863510. Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, the control method for an ultrapure water production system described in Patent Document 1 controls the water level of a water storage tank (sub-tank) or other tank to maintain a substantially constant level. Therefore, the control method is not applicable to water supply systems that do not include sub-tanks or other tanks. In particular, in large-scale ultrapure water production systems with multiple sub-systems, a control method for a pure water production system that can more reliably supply water to the sub-systems through simple control is ideal for efficient operation of the ultrapure water production system.

[0014] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a control method for a pure water production system capable of controlling the amount of water supplied according to the amount of water used.

[0015] Means for solving problems

[0016] In view of the above-mentioned purpose, the present invention provides a control method for a pure water manufacturing system, which supplies pure water manufactured by a pure water manufacturing system having a treated water supply source, a water supply mechanism connected to the treated water supply source, a water supply pressure gauge arranged at the rear end of the water supply mechanism, and one or more water treatment equipment arranged between the water supply mechanism and the pressure gauge to a pure water-using device at the rear end of the pressure gauge, wherein a flow regulating mechanism for supplying pure water to the pure water-using device is provided between the pressure gauge and the pure water-using device, and the supply amount of pure water is regulated by the flow regulating mechanism according to the water consumption of the pure water-using device, and the water supply output of the water supply mechanism is controlled in such a way that the measured value of the pressure gauge becomes approximately constant (Invention 1).

[0017] According to this invention (Invention 1), the flow rate regulating mechanism is controlled so that the amount of pure water supplied to the pure water-using equipment increases or decreases according to the increase or decrease in pure water usage. Without any control, the water supply pressure decreases or increases with this increase or decrease in supply volume. Therefore, the water supply output of the water supply mechanism is controlled so that the water supply pressure remains approximately constant relative to a predetermined value. This allows for independent control of the pure water supply and the output of the water supply mechanism. This allows for simple and highly versatile control even when the pure water supply system does not include a tank.

[0018] In the above invention (Invention 1), preferably, the pure water using equipment is provided in a plurality of series in parallel at a downstream stage of the pressure gauge (Invention 2).

[0019] According to this invention (Invention 2), in controlling the flow rate regulating mechanism for supplying pure water to a plurality of series, the water supply pressure is increased or decreased according to the increase or decrease in the total supply amount of pure water. Therefore, the water supply output of the water supply mechanism is controlled so that the water supply pressure remains substantially constant relative to a predetermined value. This allows the control of the pure water supply and the control of the water supply mechanism output to be independent. Thus, even when pure water is supplied to a plurality of series at different supply amounts, simple and highly versatile control can be achieved.

[0020] In the above inventions (Inventions 1 and 2), preferably, the water treatment equipment is one or more selected from a reverse osmosis membrane, an ultraviolet oxidation device, a degassing membrane, an electrodeionization device, a regenerative ion exchange device, and a non-regenerative ion exchange device (Invention 3).

[0021] According to this invention (Invention 3), it is applicable to various general-purpose primary pure water devices.

[0022] Effects of the Invention

[0023] According to the present invention, the flow rate regulating mechanism adjusts the pure water supply according to the amount of water used by the pure water-using equipment. Furthermore, even if the pure water supply (usage) increases or decreases, the water supply output of the water supply mechanism is controlled so that the pressure gauge measurement value remains approximately constant relative to a predetermined value. Therefore, the control of the pure water supply and the control of the water supply mechanism output can be independent. Thus, even in the case where the pure water supply system does not include a tank, simple and highly versatile control can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a flow chart showing an ultrapure water production system including a pure water production system.

[0025] Figure 2 This is a flowchart showing a pure water production system (primary pure water device) to which a control method of a pure water production system according to one embodiment of the present invention can be applied.

[0026] Figure 3 This is a schematic diagram illustrating a control method for the pure water production system according to the above embodiment.

[0027] Figure 4 Graphs showing the amount of water used at the use point, the amount of water treated by the electrodeionization device, and the water level in the water storage tank in the pure water production systems (primary pure water devices) of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0028] Hereinafter, a control method of a pure water production system according to the present invention will be described with reference to the accompanying drawings.

[0029] (Pure water production system)

[0030] The present embodiment is characterized in controlling a pure water production system (primary pure water device) constituting an ultrapure water production system.

[0031] There are no special restrictions on the pure water manufacturing system (primary pure water device). As long as it has a water supply pump for supplying treated water, a water supply pressure gauge installed at the rear of the water supply pump, a pure water using device installed at the rear of the pressure gauge and using the produced pure water, and one or more water treatment devices between the water supply pump and the pressure gauge, it can be applied to various pure water manufacturing systems. Then, it can be preferably applied to Figure 1 The ultrapure water production system shown does not include the sub-tank 41 .

[0032] exist Figure 2In the embodiment, the primary pure water device (pure water manufacturing system) 3 has a treated water tank 51 for storing pretreated water W1 as a treated water supply source, a water supply pump 52A for the pretreated water W1, a high-pressure pump 52B that can be controlled by an inverter for controlling the water supply output of the water supply pump 52A, a reverse osmosis membrane device 53, a first degassing membrane device 54A based on air, a second degassing membrane device 54B based on nitrogen, an ultraviolet oxidation device 55, an electrodeionization device (CDI) 56, and a water supply pump 57 for supplying water to the electrodeionization device 56. The treated water of the electrodeionization device 56 is transported to the boron chelate resin tower 58 and treated, and then can be supplied to the subsystem 4 with primary pure water W2. It should be noted that in this embodiment, the subsystem 4 as a pure water use device is Figure 1 The illustrated configuration does not include the sub-tank 41 , and the sub-system 4 consumes the pure water W2 in accordance with the usage amount at the usage point 5 .

[0033] In the primary pure water device 3, a water supply pressure gauge 59 and a control valve 60 as a flow regulating mechanism are provided at the rear section of the boron chelate resin tower 58. The pressure gauge 59 can transmit information to a control mechanism (not shown) that can perform inverter control on the high-pressure pump 52B in a manner such that the measured value of the pressure gauge 59 becomes approximately constant (e.g., ±5%) relative to a predetermined value, and can control the opening of the control valve 60 based on the usage of the primary pure water W2 in the subsystem 4. The supply of the primary pure water W2 can be controlled by, for example, measuring the supply of ultrapure water W3 supplied from the subsystem 4 to the use point 5 using a flow meter, determining the usage of the primary pure water W2 based on the supply, and controlling the opening of the control valve 60. Alternatively, the supply of ultrapure water W3 supplied from the subsystem 4 to the use point 5 and the return amount sent back from the use point 5 to the subsystem 4 can be measured using a flow meter, determining the usage of the primary pure water W2 based on the difference between the two, and controlling the opening of the control valve 60.

[0034] It should be noted that reference numeral 71 denotes the recovery line for concentrated water from the reverse osmosis membrane device 53. This recovery line 71 is equipped with a flow control valve 72, a flow meter 73, a concentrated water tank 74, a water supply pump 75, and a recovery reverse osmosis membrane 76, thereby returning the treated water from the recovery reverse osmosis membrane 76 to the treated water tank 51. Furthermore, reference numeral 81 denotes the recovery line for concentrated water from the electrodeionization device 56. This recovery line 81 is equipped with a flow control valve 82 and a flow meter 83. The concentrated water from the electrodeionization device 56 is transported to a dilute system recovery reverse osmosis membrane (not shown) for treatment.

[0035] (Control method of pure water production system)

[0036] Next, explain Figure 2 A control method for a pure water production system is shown.

[0037] exist Figure 2 In the process, the water supply pump 52A and the high-pressure pump 52B with an inverter are started to supply pretreated water (treated water) W1 from the treated water tank 1, and the pretreated water (treated water) W1 is treated in the reverse osmosis membrane device 53, the first degassing membrane device 54A, the second degassing membrane device 54B, the ultraviolet oxidation device 55 and the electrodeionization device (CDI) 56, and then transported to the boron chelating resin tower 58 and treated, and then sent to the subsystem 4, and ultrapure water is prepared in the subsystem 4 according to the usage at the use point, and the required amount is supplied to the use point.

[0038] In the water production process of the primary pure water device 3 as described above, the pressure gauge 59 for water supply, the control valve 60 and the high-pressure pump 52B which can be controlled by the inverter become as follows. Figure 3 The control system shown in Figure 1. Figure 3 In the embodiment, the rear section of the boron chelate resin tower 58 branches into three series, supplying pure water W2 to subsystems 4A, 4B, and 4C respectively, and each water supply pipe is provided with a control valve 60A, 60B, and 60C. That is, there are three control valves. It should be noted that, in Figure 3 For the sake of convenience, other components are omitted.

[0039] In the primary pure water device 3, first, a reference value (which may be a value within a specified range) for the water supply to subsystems 4A, 4B, and 4C is determined in advance. Then, flow meters 61A, 61B, and 61C measure the water supply to subsystems 4A, 4B, and 4C based on the water usage of each point of use (POU) 5A, 5B, and 5C of subsystems 4A, 4B, and 4C. When the measured value decreases compared to the reference value, control means (not shown) reduce the control valves 60A, 60B, and 60C, respectively, to reduce the water supply to subsystems 4A, 4B, and 4C. As a result, the water supply pressure of the pressure gauge 59 increases due to the decrease in the total water supply of the three systems. Therefore, based on the measured value of the pressure gauge 59, the control means reduces the output of the high-pressure pump 52B through inverter control in a manner such that the measured value of the pressure gauge 59 becomes approximately constant relative to the predetermined value. Meanwhile, flow meters 61A, 61B, and 61C measure the water flow rates supplied to subsystems 4A, 4B, and 4C, corresponding to the water usage at each point of use (POU) 5A, 5B, and 5C of subsystems 4A, 4B, and 4C. When these measured values ​​increase above a reference value, control means (not shown) opens control valves 60A, 60B, and 60C, respectively, increasing the water flow rates to subsystems 4A, 4B, and 4C. This increases the total water flow rate across the three systems, and the water supply pressure measured by pressure gauge 59 decreases. Therefore, based on the measured value of pressure gauge 59, the control means increases the output of high-pressure pump 52B through inverter control, ensuring that the measured value of pressure gauge 59 remains approximately constant relative to a predetermined value.

[0040] Although the above describes the case where the water supply volume to subsystems 4A, 4B, and 4C increases or decreases compared to the prescribed reference value, even in the case of a combination of an increasing series and a decreasing series, as long as the total water supply volume of the three series increases or decreases, the increase or decrease in the total water supply volume can be controlled in the same manner based on the control of control valves 60A, 60B, and 60C.

[0041] For example, in Figure 3 In the control system shown, three series are constructed using the same equipment. When the pressure gauge 59 is controlled to be 0.1 MPa, the water supply volume (water consumption at the use point) to the three series is changed in the manner that the opening of the control valve 60A becomes 20%→40%→60%→20%, the opening of the control valve 60B becomes 20%→20%→40%→40%, and the opening of the control valve 60C becomes 20%→40%→60%→20%. An example of frequency control of the inverter of the high-pressure pump 52B of the four processes at this time is shown in the following Table 1.

[0042] [Table 1]

[0043]

[0044] Although the present invention has been described above based on the above-mentioned embodiment, the present invention is not limited to the embodiment and can be implemented in various modified forms. For example, as a pure water manufacturing system 3 to which the present invention can be applied, there is no particular limitation as long as it is a pure water manufacturing system 3 having a treated water tank 51, a water supply pump 52A and a high-pressure pump 52B as a water supply mechanism connected to the treated water tank 51, a pressure gauge 59 provided at the rear section of the water supply pump 52A and the high-pressure pump 52B capable of inverter control, and one or more water treatment equipment provided between the water supply pump 52A and the high-pressure pump 52B and the pressure gauge 59. Based on the water supply amount (pure water usage) supplied to the pure water using equipment by the pressure gauge 59 and the subsystem 4, the output of the high-pressure pump 52B is controlled in such a way that the measured value of the pressure gauge 59 becomes approximately constant. For example, the one or more water treatment devices disposed between the water supply pump 52A, the high-pressure pump 52B, and the pressure gauge 59 are not particularly limited and can be composed of one or two selected from a reverse osmosis membrane, an ultraviolet oxidation device, a degassing membrane, an electrodeionization device, a regenerative ion exchange device, and a non-regenerative ion exchange device. Alternatively, the water supply mechanism may consist solely of the inverter-controlled high-pressure pump 52B. Furthermore, in the case where primary pure water (pure water) W2 is continuously supplied to the sub-tank 41 based on the usage at the point of use 5, the sub-tank 41 may also be provided.

[0045] [Example]

[0046] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[0047] [Example 1 and Comparative Example 1]

[0048] As a test device, we prepared Figure 2 The pure water production system 3 of the structure shown in the figure is shown in the figure. In this test device, the maximum water treatment capacity of the electrodeionization device 56 is set to 23m 3 / h, the amount of water treated by the electrodeionization device 56 was measured when the output of the high-pressure pump 52B was manually controlled (manual control) so that the supply amount of primary pure water (pure water) W2 was changed according to the change in the supply amount of water supplied to the use point of the subsystem 4 (the amount of water used at the use point) (Comparative Example 1). The results are shown together with the amount of water used at the use point. Figure 4 .

[0049] Then, the opening of the control valve 60 was adjusted according to the change in the amount of water supplied to the point of use by the subsystem 4 (the amount of water used at the point of use), and the amount of water treated by the electrodeionization device 56 was measured when the output of the high-pressure pump 52B was controlled by the inverter so that the measured value of the pressure gauge 59 became approximately constant (Example 1). The results are shown together with the amount of water used at the point of use. Figure 4 .

[0050] from Figure 4 As can be seen, according to Example 1 using inverter control, the amount of water used at the point of use can be tracked to adjust the amount of water treated by the electrodeionization device 56 (equivalent to the amount of primary pure water W2 produced), thereby reducing the operating power of the high-pressure pump 52B. In contrast, in Comparative Example 1 using manual control, only simple step-by-step control can be performed based on the amount of water used at the point of use. This results in an excess of water treated by the electrodeionization device 56, and excessive power consumption by the high-pressure pump 52B.

[0051] Explanation of symbols

[0052] 1: Ultrapure water production system.

[0053] 2: Pretreatment device.

[0054] 3: Primary pure water device (pure water manufacturing system).

[0055] 31: Processed water tank.

[0056] 32: High pressure pump.

[0057] 33: Reverse osmosis membrane device.

[0058] 34A: First degassing membrane device.

[0059] 34B: Second degassing membrane device.

[0060] 35: Ultraviolet oxidation device.

[0061] 36: Electrodeionization device.

[0062] 37: Water supply pump.

[0063] 4, 4A, 4B, 4C: Secondary pure water production device (subsystem).

[0064] 41: Sub-jar.

[0065] 42: Ultraviolet oxidation device.

[0066] 43: Non-regenerative mixed bed ion exchange unit.

[0067] 44: Ultrafiltration (UF) membrane.

[0068] 5, 5A, 5B, 5C: Point of use.

[0069] 51: Treated water tank (treated water supply source).

[0070] 52A: Water supply pump (water supply mechanism).

[0071] 52B: High pressure pump (water supply mechanism).

[0072] 53: Reverse osmosis membrane device.

[0073] 54A: First degassing membrane device.

[0074] 54B: Second degassing membrane device.

[0075] 55: Ultraviolet oxidation device.

[0076] 56: Electrodeionization device (CDI).

[0077] 57: Water supply pump.

[0078] 58: Boron chelating resin tower.

[0079] 59: Pressure gauge.

[0080] 60, 60A, 60B, 60C: Control valve (flow regulating mechanism). 61A, 61B, 61C: Flow meter.

[0081] 71: Recycling line.

[0082] 72: Flow control valve.

[0083] 73: Flow meter.

[0084] 74: Concentrated water tank.

[0085] 75: Water supply pump.

[0086] 76: Recover reverse osmosis membrane device.

[0087] 81: Recycling line.

[0088] 82: Flow control valve.

[0089] 83: Flow meter.

[0090] W: raw water.

[0091] W1: pretreated water (treated water).

[0092] W2: primary pure water (pure water).

[0093] W3: secondary pure water (ultrapure water).

Claims

1. A method for controlling a pure water production system, wherein pure water produced by the pure water production system, comprising a treated water supply source, a water supply mechanism connected to the treated water supply source, a water supply pressure gauge provided at a downstream stage of the water supply mechanism, and one or more water treatment devices provided between the water supply mechanism and the pressure gauge, is supplied to a pure water user device at a downstream stage of the pressure gauge, wherein: There is a flow regulating mechanism for supplying pure water to the pure water using equipment between the pressure gauge and the pure water using equipment. The supply amount of pure water is adjusted by the flow regulating mechanism according to the water consumption of the pure water using equipment, and the water supply output of the water supply mechanism is controlled in such a way that the measured value of the pressure gauge becomes approximately constant.

2. The control method of the pure water production system according to claim 1, wherein: The pure water using equipment is provided in a plurality of series in parallel at the downstream stage of the pressure gauge.

3. The control method for a pure water production system according to claim 1 or 2, wherein: The water treatment equipment is one or more selected from a reverse osmosis membrane, an ultraviolet oxidation device, a degassing membrane, an electrodeionization device, a regenerative ion exchange device, and a non-regenerative ion exchange device.

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