Method for controlling pure water production system, and pure water production system

Abstract

In a method for controlling a pure water production system according to the present invention, when the water storage amount for a pure water tank 111 as measured by a level sensor 112 is increased from a reference value, a control means reduces the water supply amount of primary pure water W2 to the pure water tank 111 by narrowing a flow rate adjustment valve 113. On the basis of a measurement value from a second pressure gauge 115 in the stage preceding the flow rate adjustment valve 113, the output of a booster pump 109 is controlled so as to reduce the output of an inverter 110 so that the measurement value from the second pressure gauge 115 becomes almost constant at a predetermined pressure. Additionally, the output of an inverter 103 of a water feed pump 102 is controlled so as to be reduced so that the pressure in the stage preceding the booster pump 109 is also almost constant. This makes it possible to avoid the risk of cavitation in the booster pump 109, stably operate the booster pump 109, and supply the necessary amount of the primary pure water W2 to the pure water tank 111. According to such a method for controlling a pure water production system, it is possible, in a pure water production system having a booster pump between water treatment apparatuses, to control a water supply amount in accordance with the amount of water used.

Description

Control method for pure water production system and pure water production system

[0001] The present invention relates to a control method for a pure water production system for producing ultrapure water used in the electronics industry, such as semiconductors and liquid crystal displays, and to the pure water production system, and more particularly to a control method for a pure water production system capable of controlling the amount of water supply according to the amount of water used, and to the pure water production system.

[0002] Conventionally, ultrapure water used in the semiconductor and other electronics industries is produced by treating raw water in an ultrapure water production system that is composed of a pretreatment system, a primary pure water equipment, and a subsystem that treats the primary pure water.

[0003] 2, an ultrapure water production system 1 is composed of three stages of equipment: a pretreatment device 2, a primary pure water production system (pure water production system) 3, and a secondary pure water production system (subsystem) 4, which uses pure water. In the pretreatment device 2 of this ultrapure water production system 1, raw water W is subjected to pretreatment using filtration, coagulation sedimentation, microfiltration membranes, etc., and mainly suspended solids are removed.

[0004] The primary deionization system 3 includes a water tank 31 for storing pretreated water (water to be treated) W1, a water pump 32 for pumping the pretreated water W1, a reverse osmosis membrane device 33, a membrane deaeration device 34 for removing dissolved gases with air, an ultraviolet oxidation device 35, an electrodeionization device 36, a regenerative ion exchange device 37, and a booster pump 38 for supplying water to the electrodeionization device 36. The primary deionization system 3 removes most of the electrolytes, fine particles, live bacteria, etc. from the pretreated water W1 and also decomposes organic matter.

[0005] Subsystem 4 comprises a subtank 41 (a pure water tank) downstream of the regenerative ion exchanger 38 for storing the primary pure water W2 produced by the primary pure water system 3, an ultraviolet oxidation device 42 (a non-regenerative mixed-bed ion exchanger 43), and an ultrafiltration (UF) membrane 44 (a membrane filtration device) for treating the primary pure water W2 delivered from the subtank 41 via a pump (not shown). Subsystem 4 may also include an RO membrane separator, etc. In this subsystem 4, the ultraviolet oxidation device 42 oxidizes and decomposes trace amounts of organic matter (TOC components) contained in the primary pure water W2. The non-regenerative mixed-bed ion exchanger 43 then processes the water to remove residual carbonate ions, organic acids, anionic substances, and even metal ions and cationic substances by ion exchange. The ultrafiltration (UF) membrane 44 then removes particulates to produce ultrapure water W3, which is then supplied to the point of use 5, with unused ultrapure water returning to the subtank 41.

[0006] In this ultrapure water production system 1, in order to stably supply primary pure water of a specified water quality, an excess amount of primary pure water W2 is produced in advance, and only the required amount is supplied to the sub-tank 41, with the excess being recycled and reused.

[0007] However, in the conventional control method for the ultrapure water production system 1 described above, more feedwater than necessary is supplied to the electrodeionization device 36 and other devices for treatment, leaving room for improvement in terms of energy efficiency. Therefore, it is conceivable to vary the treatment volume of the electrodeionization device 36 in accordance with the amount of water used at the point of use 5. However, this not only makes it difficult to follow the fluctuations in the amount of water used at the point of use 5, but also leads to a deterioration in the quality of the water deionized by electrodeionization.

[0008] Therefore, as a control method for an ultrapure water production system capable of producing primary pure water according to the amount of water used at the point of use, the applicant has filed an application for a control method for a pure water production system (Japanese Patent Application No. 2023-035557), in which pure water produced in a pure water production system comprising a source of water to be treated, a water supply mechanism connected to the source of water to be treated, a water supply pressure gauge installed downstream of the water supply mechanism, and one or more types of water treatment equipment installed between the water supply mechanism and the pressure gauge is supplied to a pure water-using device downstream of the pressure gauge, and a flow rate adjustment mechanism for the pure water supplied to the pure water-using device is provided between the pressure gauge and the pure water-using device, the flow rate adjustment mechanism adjusts the amount of pure water supplied according to the amount of water used by the pure water-using device, and the water supply output of the water supply mechanism is controlled so that the measurement value of the pressure gauge remains approximately constant.

[0009] This method for controlling a pure water production system can be implemented, for example, in a primary pure water system (pure water production system) 3 as shown in Fig. 3. In Fig. 3, the primary pure water system (pure water production system) 3 includes a water tank 51 to be treated as a water supply source for storing pretreated water W1, a feed pump 52A for the pretreated water W1, an inverter-controllable high-pressure pump 52B for controlling the water supply output of the feed pump 52A, a reverse osmosis membrane device 53, a first degassing membrane device 54A using air, a second degassing membrane device 54B using nitrogen gas, an ultraviolet oxidation device 55, an electrodeionization device (CDI) 56, and a feed pump (boost pump) 57 for supplying water to the electrodeionization device 56. Treated water from the electrodeionization device 56 is sent to a boron chelate resin tower 58 for treatment, and the primary pure water W2 can then be supplied to the subsystem 4.

[0010] In this primary pure water system 3, a pressure gauge 59 for the primary pure water W2 supplied to the subsystem 4 and a flow control valve 60 as a flow control mechanism are provided downstream of the boron chelate resin tower 58. This pressure gauge 59 is capable of transmitting information to a control mechanism (not shown). This control mechanism is capable of inverter-controlling the high-pressure pump 52B so that the value measured by the pressure gauge 59 remains approximately constant (for example, within ±5%) of a predetermined value, and is also capable of controlling the opening of the flow control valve 60 based on the amount of primary pure water W2 used in the subsystem 4. The supply amount of primary pure water W2 can be controlled, for example, by measuring the supply amount of ultrapure water W3 from subsystem 4 to use point 5 using a flow meter or the like, determining the amount of primary pure water W2 to be used based on this supply amount, and controlling the opening of flow control valve 60; alternatively, by measuring the supply amount of ultrapure water W3 from subsystem 4 to use point 5 and the return amount from use point 5 to subsystem 4 using flow meters, determining the amount of primary pure water W2 to be used based on the difference between the two, and controlling the opening of flow control valve 60.

[0011] Reference numeral 61 denotes a recovery line for concentrated water from the reverse osmosis membrane device 53, which is equipped with a flow control valve 62, a flow meter 63, a concentrated water tank 64, a water supply pump 65, and a recovery reverse osmosis membrane device 66, and the treated water from the recovery reverse osmosis membrane device 66 is returned to the treated water tank 51. Reference numeral 67 denotes a recovery line for concentrated water from the electrodeionization device 56, which is equipped with a flow control valve 68 and a flow meter 69, and the concentrated water from the electrodeionization device 56 is sent to a dilute system recovery reverse osmosis membrane (not shown) for treatment.

[0012] In such a primary pure water device (pure water manufacturing system) 3, the output of the high-pressure pump 52B is controlled based on the pressure gauge 59 and the amount of water supplied (amount of pure water used) to pure water-using equipment such as subsystem 4, so that the measured value of the pressure gauge 59 remains approximately constant, thereby controlling the amount of water supplied in accordance with the amount of primary pure water W2 used in subsystem 4, etc.

[0013] The control method for a pure water production system described in Japanese Patent Application No. 2023-035557 makes it possible to produce primary pure water according to the amount of use at the point of use. However, as a result of subsequent studies by the present applicants, when water treatment equipment requiring water supply pressure is connected without an intervening tank, as shown in Figure 3, in addition to a feed water pump 52A and a high-pressure pump 52B from a tank 51 of water to be treated, one or more series of booster pumps 57 may be arranged between consecutive water treatment equipment. In this case, if the water supply flow rate of only the feed water pump 52A or the high-pressure pump 52B is controlled by an inverter, the pressure of the water supplied to the inlet side of the booster pump 57 decreases, causing cavitation in the booster pump 57 and potentially causing a malfunction.

[0014] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control method for a pure water production system having a booster pump between water treatment devices, which can control the amount of water supplied depending on the amount of water used, and a pure water production system capable of implementing this method.

[0015] In view of the above-mentioned object, firstly, the present invention provides a control method for a pure water producing system which supplies pure water produced in the system to the pure water-using equipment, the system comprising a source of water to be treated, a water supply mechanism connected to the source of water to be treated, two or more types of water treatment equipment provided downstream of the water supply mechanism, and a first pressure gauge provided intermediate the water treatment equipment, a boost pump provided downstream of the first pressure gauge and intermediate the two or more types of water treatment equipment, a flow rate adjustment mechanism for pure water supplied to the pure water-using equipment provided upstream of the pure water-using equipment, and a second pressure measuring means provided downstream of the water treatment equipment and upstream of the flow rate adjustment mechanism, the method comprising: adjusting the amount of pure water supplied by the pure water-using equipment using the flow rate adjustment mechanism in accordance with the amount of water used by the pure water-using equipment; controlling the water flow rate of the boost pump so that the measurement value of the second pressure measuring means remains approximately constant; and controlling the water supply output of the water supply mechanism so that the measurement value of the first pressure gauge remains approximately constant (Invention 1).

[0016] According to this invention (Invention 1), the flow rate of pure water supplied is adjusted by the flow rate adjustment mechanism in accordance with the amount of water used by the pure water-using equipment, and the water flow rate of the boost pump is controlled so that the measurement value of the second pressure measurement means remains approximately constant, and the water supply output of the water supply mechanism is controlled so that the measurement value of the first pressure gauge remains approximately constant. This reduces fluctuations in the pressure of the water supplied to the inlet side of the boost pump, thereby reducing the risk of cavitation in the boost pump. Furthermore, the operating pressure of the water treatment equipment located downstream of the boost pump can be stabilized.

[0017] In the above invention (Invention 1), it is preferable that the water treatment equipment is one or more selected from a reverse osmosis membrane device, a membrane degassing device, an ultraviolet oxidation device, an electrical regenerative deionization device, a non-regenerative ion exchange device, and a UF membrane device (Invention 2).

[0018] According to this invention (Invention 2), it is possible to apply the invention to various general-purpose pure water production systems.

[0019] In the above inventions (Inventions 1 and 2), it is preferable that the water flow rate of the boost pump is controlled by the frequency output from the inverter, and that the lower limit of the fluctuation value of the water consumption amount of the pure water-using equipment is 50% or more of the maximum value (Invention 3).

[0020] According to this invention (Invention 3), by controlling the water flow rate of the booster pump with an inverter, it is possible to quickly respond to a wide range of water amounts in accordance with fluctuations in the amount of water used by the pure water-using equipment.

[0021] In a second aspect, the present invention provides a pure water production system comprising a source of water to be treated, a water supply mechanism connected to the source of water to be treated, two or more types of water treatment equipment provided downstream of the water supply mechanism, and a first pressure gauge provided between the water treatment equipment, a boost pump provided downstream of the first pressure gauge and between the two or more types of water treatment equipment, a flow rate adjustment mechanism for pure water supplied to a pure water-using equipment provided downstream of the water treatment equipment and upstream of the pure water-using equipment, and a second pressure measuring means provided downstream of the water treatment equipment and upstream of the flow rate adjustment mechanism, wherein the pure water supply rate is adjusted by the flow rate adjustment mechanism according to the amount of water used by the pure water-using equipment, the water flow rate of the boost pump is controlled so that the measurement value of the second pressure measuring means remains approximately constant, and the water supply output of the water supply mechanism is controlled so that the measurement value of the first pressure gauge remains approximately constant (Invention 4).

[0022] According to this invention (Invention 4), the flow rate of pure water supplied is adjusted by the flow rate adjustment mechanism in accordance with the amount of water used by the pure water-using equipment, and the water flow rate of the boost pump is controlled so that the measurement value of the second pressure measurement means remains approximately constant, and the water supply output of the water supply mechanism can be controlled so that the measurement value of the first pressure gauge remains approximately constant. This reduces fluctuations in the pressure of the water supplied to the inlet side of the boost pump, thereby reducing the risk of cavitation occurring during boosting. Furthermore, the operating pressure of water treatment equipment located downstream of the boost pump can be stabilized.

[0023] In the above invention (Invention 4), it is preferable that the water treatment equipment is one or more selected from a reverse osmosis membrane device, a membrane degassing device, an ultraviolet oxidation device, an electrical regenerative deionization device, a non-regenerative ion exchange device, and a UF membrane device (Invention 5).

[0024] According to this invention (Invention 5), it is possible to apply the invention to various general-purpose pure water production systems.

[0025] In the above inventions (Inventions 4 and 5), it is preferable that the water flow rate of the boost pump is controlled by the frequency output from the inverter, and that the lower limit of the fluctuation value of the water consumption rate of the pure water-using equipment is 50% or more of the maximum value (Invention 6).

[0026] According to this invention (Invention 6), by controlling the water flow rate of the boost pump with an inverter, it is possible to quickly respond to a wide range of water amounts in accordance with fluctuations in the amount of water used by the pure water-using equipment.

[0027] According to the control method for a water production system of the present invention, the flow rate of pure water is adjusted by the flow rate adjustment mechanism in accordance with the amount of water used by the pure water-using equipment, the water flow rate of the boost pump is controlled so that the measurement value of the second pressure measurement means remains approximately constant, and the water supply output of the water supply mechanism is controlled so that the measurement value of the first pressure gauge remains approximately constant, thereby reducing the risk of cavitation occurring during pressure increase.Furthermore, the operating pressure of water treatment equipment located downstream of the boost pump can be stabilized.

[0028] It is a flow diagram showing a pure water producing system according to an embodiment of the present invention, a flow diagram showing an ultrapure water producing system including the pure water producing system, and a flow diagram showing a conventional pure water producing system.

[0029] The pure water producing system and its control method of the present invention will be described below with reference to the accompanying drawings.

[0030] (Pure Water Production System) The pure water production system (primary pure water apparatus) of this embodiment can be applied to various pure water production systems as long as it includes a water pump for supplying water to be treated, two or more types of water treatment equipment, a booster pump installed between the water treatment equipment, and a pure water-using equipment installed downstream of the two or more types of water treatment equipment for using the produced pure water. For example, it can be suitably applied to an ultrapure water production system as shown in FIG.

[0031] 1 , the primary pure water system (pure water production system) 3 includes a water tank 101 serving as a water supply source for storing pretreated water W1, a water pump 102 for the pretreated water W1, an inverter 103 for controlling the water supply output of the water pump 102, and water treatment equipment including a reverse osmosis membrane device (RO membrane device) 104, a membrane degasser 105, an ultraviolet oxidation device 106, an electrodeionization (CDI) device 107, and a regenerative ion-exchange resin tower 108. A booster pump 109 equipped with an inverter 110 is provided upstream of the electrodeionization device 107, i.e., midway through the water treatment equipment, to supply water to the electrodeionization device 107. Primary pure water W2 treated in the ion-exchange resin tower 108 is stored in a pure water tank 111, such as a sub-tank.

[0032] In this primary pure water system 3, a level sensor 112 is attached to the pure water tank 111, and a flow rate adjustment valve 113 is provided upstream of the pure water tank 111. The level sensor 112 is capable of transmitting information to control means (not shown), and this control means is able to control the flow rate adjustment valve 113 in accordance with the measurement value of the level sensor 112 to adjust the amount of water fed to the pure water tank 111. A first pressure gauge 114 is provided upstream of the boost pump 109, and this first pressure gauge 114 is capable of transmitting information to a control mechanism (not shown), and this control mechanism is able to inverter-control the water feed pump 102 so that the measurement value of the first pressure gauge 114 remains approximately constant (for example, within ±5%) of a predetermined value. Furthermore, a second pressure gauge 115 is provided upstream of the flow control valve 113, and this second pressure gauge 115 is capable of transmitting information to a control mechanism (not shown), and this control mechanism is capable of inverter-controlling the boost pump 109 so that the measurement value by the second pressure gauge 115 becomes approximately constant (for example, within ±5%) of a predetermined value.

[0033] (Method of Controlling the Pure Water Production System) Next, a method of controlling the pure water production system shown in Fig. 1 will be described. In Fig. 1, a water pump 102 equipped with an inverter 103 is started to supply pretreated water (water to be treated) W1 from a water tank 101 to be treated. The pretreated water is treated in a reverse osmosis membrane device 104, a membrane degassing device 105, and an ultraviolet oxidation device 106. The water is pressurized by a booster pump 109 and treated in an electrodeionization device (CDI) 107 and a regenerative ion exchange resin tower 108. The resulting primary pure water W2 is then stored in a pure water tank 111.

[0034] At this time, a reference value (which may be a value within a predetermined range) for the water level of the subtank 11 is set in advance, and this increase or decrease is related to the amount of water used by the pure water-using equipment. In addition, the water supply pressure upstream of the flow control valve 113 (measured value by the second pressure gauge 115) and the pressure upstream of the booster pump 109 (measured value by the first pressure gauge 114) are also set in advance.

[0035] When the amount of water stored in the pure water tank 111 measured by the level sensor 112 increases above a reference value due to a decrease in water usage at points of use, a control means (not shown) throttles the flow control valve 113 to reduce the amount of primary pure water W2 supplied to the pure water tank 111. As a result, the water supply pressure measured by the second pressure gauge 115 tends to increase. However, the output of the boost pump 109 is controlled by reducing the output (frequency: Hz; the same applies below) of the inverter 110 so that the measurement value of the second pressure gauge 115 remains approximately constant at a predetermined pressure. The inverter 103 of the water supply pump 102 is also controlled by reducing the output so that the pressure upstream of the boost pump 109 (measurement value of the first pressure gauge 114) remains approximately constant. This prevents a decrease in the water supply pressure at the inlet of the boost pump 109, thereby avoiding the risk of cavitation in the boost pump 109. The boost pump 109 can then be stably operated to supply the required amount of primary pure water W2 to the pure water tank 111.

[0036] On the other hand, if the amount of water used at the point of use or the like increases and the amount of water stored in the pure water tank 111 measured by the level sensor 112 falls below the reference value, a control means (not shown) opens the flow control valve 113 to increase the amount of primary pure water W2 supplied to the pure water tank 111. As a result, the water supply pressure measured by the second pressure gauge 115 tends to decrease, but the inverter 110 controls the output of the boost pump 109 to increase so that the measurement value of the second pressure gauge 115 remains approximately constant at a predetermined pressure. The inverter 103 is also controlled to increase the output of the water supply pump 102 so that the pressure upstream of the boost pump 109 (measurement value of the first pressure gauge 114) remains approximately constant. This allows the water supply pressure of the boost pump 109 to be maintained approximately constant, allowing the boost pump 109 to operate stably and supply the required amount of primary pure water W2 to the pure water tank 111. In this method for controlling a pure water production system, the lower limit of the fluctuation value of the amount of water used by the pure water-using equipment is preferably 50% or more of the maximum value (100%).

[0037] While the present invention has been described above based on the above-described embodiment, various modifications are possible. For example, the two or more types of water treatment equipment are not particularly limited and may be configured using two or more types selected from the group consisting of 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. In the above-described embodiment, control is performed based on the water level in the pure water tank 111. However, a flow meter may be provided at the outlet of the pure water tank 111 to control the flow rate of the primary pure water W2 from the pure water tank 111. Furthermore, while the water supply mechanism in this embodiment is configured solely with the water supply pump 102, it may also be configured as a two-stage system consisting of a water supply pump and an inverter-controllable high-pressure pump for controlling the water supply output of the water supply pump.

[0038] The present invention will be described in more detail based on the following examples, but the present invention is not limited to the following examples.

[0039] Example 1 Using the pure water production system shown in FIG. ３The pretreated water W1 was sent from a water tank (pretreatment tank) 101 capable of holding a liquid volume of about 0.7 m to a reverse osmosis membrane device 104 by a water pump 102 equipped with an inverter 103. The reverse osmosis membrane device 104 had a membrane surface effective pressure of about 0.6 MPa and a flow rate of about 0.7 m. ３ / m ２ An ultra-low pressure membrane capable of achieving a permeate rate of 1 / day was used. The permeate obtained in the reverse osmosis membrane device 104 had dissolved gases removed in a membrane degassing device 105, and organic components were decomposed in an ultraviolet oxidation device 106. The water pressure was then increased by a booster pump 109, and the water was passed through an electrodeionization device 107. Residual ions in the treated water from the electrodeionization device 107 were removed in a regenerative ion exchange resin tower 108 to produce primary pure water W2, which was then passed through a flow control valve 113 to a flow rate of 3 m ３ The primary pure water W2 was then pumped from the pure water tank 111 to a polishing process by a water pump to be converted into ultrapure water, which was then used at the point of use.

[0040] The flow rate adjusting valve 113 was controlled so that the level of the pure water tank 111 was constant. The water supply rate of the water supply pump 102 was set to a maximum of 30 m ３ The frequency output from the inverter 103 was set to 50 Hz so that the brine volume from the reverse osmosis membrane device 104 was about 6 m ３ A constant flow valve was installed on the brine supply line to keep the brine supply rate constant at 1 / hr. The booster pump 109 was of a type with a required suction head of 0.1 MPa, and the maximum water supply rate of the booster pump 109 was 24 m ３ The frequency output from the inverter 110 was adjusted to 48 Hz so that the pressure (measured by the second pressure gauge 115) upstream of the flow control valve 113 was 0.1 MPa at 1000 rpm / hr. The inlet pressure of the boost pump 109 was 0.2 MPa. The amount of brine in the electrodeionization device 107 was approximately 1 m ３ A constant flow valve was installed on the brine supply line so that the brine flow rate was 1 / hr.

[0041] In such a pure water production system, the inverter 110 of the boost pump 109 is controlled so that the pressure in the upstream stage of the flow rate adjustment valve 113 (measurement value of the second pressure gauge 115) is kept substantially constant at 0.1 MPa, and the inverter 103 of the water supply pump 102 is controlled so that the pressure in the upstream stage of the boost pump 109 (measurement value of the first pressure gauge 114) is kept substantially constant at 0.2 MPa. This reduces the amount of ultrapure water used at the point of use, and increases the amount of water supplied from the pure water tank 111 to a maximum of approximately 23 m ３ / hr, about 12m ３ / hr (52%). As a result, the input frequency of booster pump 109 was reduced to approximately 26 to 30 Hz, and the input frequency of water pump 102 was reduced to approximately 32 to 36 Hz. At this time, the upstream pressure of booster pump 109 was maintained at 0.2 MPa, so the risk of cavitation in booster pump 109 was avoided.

[0042] Comparative Example 1 In Example 1, the inverter 103 of the water pump 102 was controlled so that the pressure (measured value of the second pressure gauge 115) in the upstream stage of the flow rate adjustment valve 113 was kept substantially constant at 0.1 MPa, and the boost pump 109 was not controlled by the inverter 110 but operated at a constant 48 Hz, reducing the amount of ultrapure water used at the point of use and limiting the amount of water sent from the pure water tank 111 to a maximum of approximately 23 m ３ / hr, about 12m ３ / hr (52%). As a result, the input frequency of the water pump 102 was reduced to about 32 to 36 Hz, but the upstream pressure of the booster pump 109 was reduced to about 0.1 MPa, putting the booster pump 109 in an operating state with a risk of cavitation occurring.

[0043] 1 Ultrapure water production system 2 Pretreatment device 3 Primary pure water device (pure water production system) 4 Secondary pure water production device (subsystem) 5 Point of use (equipment using pure water) 101 Treated water tank (treated water supply source) 102 Water pump (water supply mechanism) 103 Inverter 104 Reverse osmosis membrane device (water treatment equipment) 105 Membrane degassing device (water treatment equipment) 106 Ultraviolet oxidation device (water treatment equipment) 107 Electrodeionization device (CDI) (water treatment equipment) 108 Regenerative ion exchange resin tower (water treatment equipment) 109 Booster pump 110 Inverter 111 Pure water tank 112 Level sensor 113 Flow rate adjustment valve (flow rate adjustment mechanism) 114 First pressure gauge 115 Second pressure gauge W Raw water W1 Pretreated water (treated water) W2 Primary pure water (pure water) W3 Secondary pure water (ultra pure water)

Claims

1. A control method for a pure water production system that supplies pure water produced in a pure water production system comprising a source of water to be treated, a water supply mechanism connected to the source of water to be treated, two or more types of water treatment equipment installed downstream of the water supply mechanism, and a first pressure gauge installed intermediate the water treatment equipment, a boost pump installed downstream of the first pressure gauge and intermediate the two or more types of water treatment equipment, a flow rate adjustment mechanism for pure water supplied to a pure water-using equipment installed upstream of the water treatment equipment, and a second pressure measurement means installed downstream of the water treatment equipment and upstream of the flow rate adjustment mechanism, wherein the control method adjusts the amount of pure water supplied by the pure water-using equipment using the pure water, controls the water flow rate of the boost pump so that the measurement value of the second pressure measurement means remains approximately constant, and controls the water supply output of the water supply mechanism so that the measurement value of the first pressure gauge remains approximately constant.

2. The method for controlling a pure water production system according to claim 1, wherein the water treatment equipment is one or more selected from the group consisting of a reverse osmosis membrane device, a membrane degasser, an ultraviolet oxidation device, an electrical regenerative deionizer, a non-regenerative ion exchange device, and a UF membrane device.

3. A method for controlling a pure water production system as described in claim 1 or 2, wherein the water supply flow rate of the boost pump is controlled by the frequency output from the inverter, and the lower limit of the fluctuation value of the water consumption amount of the pure water-using equipment is 50% or more of the maximum value.

4. A pure water production system comprising a source of water to be treated, a water supply mechanism connected to the source of water to be treated, two or more types of water treatment equipment installed downstream of the water supply mechanism, and a first pressure gauge installed midway between the water treatment equipment, with a boost pump installed downstream of the first pressure gauge and midway between the two or more types of water treatment equipment, a flow rate adjustment mechanism for pure water supplied to a pure water-using equipment installed downstream of the water treatment equipment and upstream of the pure water-using equipment, and a second pressure measurement means installed downstream of the water treatment equipment and upstream of the flow rate adjustment mechanism, wherein the pure water production system has a control means for adjusting the amount of pure water supplied by the flow rate adjustment mechanism according to the amount of water used by the pure water-using equipment, controlling the water flow rate of the boost pump so that the measurement value of the second pressure measurement means remains approximately constant, and controlling the water supply output of the water supply mechanism so that the measurement value of the first pressure gauge remains approximately constant.

5. The pure water production system according to claim 4, wherein the water treatment equipment is one or more selected from the group consisting of a reverse osmosis membrane device, a membrane degasser, an ultraviolet oxidation device, an electrical regenerative deionizer, a non-regenerative ion exchange device, and a UF membrane device.

6. A pure water production system as described in claim 4 or 5, wherein the water supply flow rate of the boost pump is controlled by the frequency output from the inverter, and the lower limit of the fluctuation value of the water consumption amount of the pure water-using equipment is 50% or more of the maximum value.

Images