Liquid circulation system

Abstract

To provide a liquid circulation system capable of suppressing fluctuation in a flow rate of liquid supplied to a use point, regardless of whether or not the liquid is used at the use point.SOLUTION: A liquid circulation system includes a circulation path with supply piping that supplies liquid in a tank to a use point via a plurality of treatment parts and return piping that returns liquid from the use point to the tank, a first pump installed in the middle of the plurality of treatment parts in the supply piping, a pressure detection part installed in the return piping, an adjustment valve installed downstream of the pressure detection part in the return piping to adjust the pressure inside the return piping according to the pressure detected by the pressure detection part, a flow rate flow detection part installed between the most downstream treatment part in the supply piping and the use point to detect the flow rate of the liquid inside the supply piping, and a first pump control part that controls the first pump so that the liquid flowing in the supply piping reaches a predetermined flow rate according to the flow rate detected by the flow rate detection part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a liquid circulation system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, devices for producing pure water are known.

[0003] The following Patent Document 1 discloses a pure water production apparatus including a pump that circulates pure water in a tank through a circulation line, and a water supply line that branches off from the circulation line downstream of the pump and is connected to a use point. This pure water production apparatus is provided with a control means that switches the rotation speed of the pump based on the results of detecting the presence or absence of pure water flowing through the water supply line or a change in the flow rate of pure water flowing through the water supply line.

[0004] Patent Document 2 below discloses a liquid supplying device that includes a pump that supplies liquid in a tank to a use point, a pipe that returns liquid returned from the use point to the tank, a pressure gauge that measures the return pressure in the pipe, and a flow meter that measures the return flow rate in the pipe. This liquid supplying device is provided with a control unit that controls a pressure adjustment means for adjusting the return pressure based on the return pressure and the return flow rate. The control unit determines a target value for the return pressure based on the return flow rate, and controls the pressure adjustment means so that the return pressure becomes the target value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-8823 A [Patent Document 2] Patent No. 7011958 Summary of the Invention [Problem to be solved by the invention]

[0006] The amount of ultrapure water used at a use point varies depending on the operating status of the semiconductor manufacturing equipment installed at the use point. Furthermore, semiconductor manufacturing equipment requires ultrapure water to be supplied at a constant pressure, and fluctuations in pressure can affect the yield of the semiconductors being manufactured. Therefore, ultrapure water production equipment is required to supply water at a constant pressure even if the flow rate fluctuates. In particular, 50m 3 In the case of ultrapure water production systems with a treatment flow rate of 1000000000 / h or more, the scale of the ultrapure water production system itself becomes large, and in many cases multiple ultrapure water production systems are installed in parallel. Furthermore, the scale of the use point, i.e., the factory, becomes large, so the distance of the supply piping from the end (UF) of the ultrapure water production system to the use point becomes long. At the same time, the return piping also becomes long, resulting in large pressure losses in the supply and return piping.

[0007] The pure water production apparatus described in Patent Document 1 is equipped with a water supply line that branches off from the circulation line downstream of the pump and is connected to a use point. For this reason, the configuration of the pure water production apparatus described in Patent Document 1 cannot be applied to an apparatus equipped with a circulation path that returns pure water that has passed through a use point to a tank, and there is room for improvement. In addition, since there are usually multiple water supply lines to the use point, the flow rate of each of these must be accurately measured, necessitating the installation of multiple flow meters. Increasing the number of measuring devices also increases the sources of water quality deterioration.

[0008] Furthermore, in the liquid supply device described in Patent Document 2, a target value for the return pressure is determined based on the return flow rate, and the pressure adjustment means is controlled so that the return pressure becomes the target value. For example, in a configuration in which the rotation speed of a pump is controlled based on the pressure in a supply pipe that supplies liquid to a use point, changing the target value for the return pressure when controlling the pressure adjustment means may change the flow rate of the liquid supplied to the use point, resulting in a deterioration in water quality. In addition, the control system becomes complicated, making it difficult to be practical.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a liquid circulation system that can suppress fluctuations in the flow rate of liquid supplied to a point of use, regardless of whether or not liquid is being used at the point of use. [Means for solving the problem]

[0010] As a result of careful investigation, the inventors discovered that fluctuations in flow rate in the supply piping and return piping from the end of the ultrapure water system to the point of use are the cause of pressure fluctuations at the point of use, and completed the technology of the present disclosure. In order to solve the above problems, the liquid circulation system according to a first aspect has a circulation path including a tank for storing liquid, a plurality of processing sections each performing different processing on the liquid supplied from the tank, a supply pipe that supplies the liquid in the tank to a use point that is a supply destination via the plurality of processing sections, and a return pipe that returns the liquid from the use point to the tank, a first pump that is provided midway between the plurality of processing sections in the supply pipe and supplies the liquid to the use point, a first pressure detection unit that is provided in the return pipe and detects the pressure inside the return pipe, a regulation valve that is provided downstream of the first pressure detection unit in the return pipe and adjusts the pressure inside the return pipe in accordance with the pressure detected by the first pressure detection unit, a flow rate detection unit that is provided in the supply pipe between the use point and the most downstream processing section of the plurality of processing sections, and a first pump control unit that controls the first pump so that the liquid flowing through the supply pipe is at a predetermined flow rate in accordance with the flow rate detected by the flow rate detection unit.

[0011] According to the liquid circulation system of the first aspect, a liquid circulation path including a supply pipe and a return pipe is provided, and the liquid in the tank is supplied to a destination point of use by the supply pipe via a plurality of processing units. In the plurality of processing units, different processing is performed on the liquid supplied from the tank. Furthermore, the liquid is returned from the point of use to the tank by the return pipe. In this way, the liquid is circulated through the circulation path. A first pressure detector is provided in the return pipe, and the first pressure detector detects the pressure inside the return pipe. A regulator valve is provided downstream of the first pressure detector in the return pipe, and the regulator valve regulates the pressure inside the return pipe in response to the pressure detected by the first pressure detector. Furthermore, a flow rate detection unit is provided between the most downstream processing unit among the multiple processing units in the supply pipe and the use point, and the flow rate detection unit detects the flow rate of the liquid inside the supply pipe. Then, the first pump control unit controls the first pump so that the liquid flowing through the supply pipe is at a predetermined flow rate according to the flow rate detected by the flow rate detection unit. This suppresses fluctuations in the flow rate supplied from the flow rate detection unit to the use point. Therefore, regardless of whether or not the liquid is used at the use point, it is possible to suppress fluctuations in the flow rate of the liquid supplied to the use point. Furthermore, because the fluctuations in the flow rate are small, deterioration of the quality of the ultrapure water due to fluctuations in the flow rate is suppressed to a minimum.

[0012] The liquid circulation system described in the second aspect is the liquid circulation system described in the first aspect, further comprising: a second pump provided on the supply piping downstream of the tank for supplying the liquid in the tank to the side of the plurality of processing units; a second pressure detection unit provided on the supply piping upstream of the first pump for detecting the pressure inside the supply piping; and a second pump control unit for controlling the second pump in accordance with the pressure detected by the second pressure detection unit so that the pressure inside the supply piping becomes a predetermined pressure.

[0013] According to the liquid circulation system of the second aspect, a second pump is provided on the supply pipe downstream of the tank, and the second pump supplies the liquid in the tank to the side of the multiple processing units. A second pressure detection unit is provided on the supply pipe upstream of the first pump, and the second pressure detection unit detects the pressure inside the supply pipe. Then, the second pump control unit controls the second pump in response to the pressure detected by the other pressure detection unit so that the pressure inside the supply pipe becomes a predetermined pressure. Therefore, when the second pump supplies the liquid in the tank to the side of the multiple processing units through the supply pipe, it is possible to suppress fluctuations in the pressure inside the supply pipe at the position of the second pressure detection unit.

[0014] The liquid circulation system of the third aspect is the liquid circulation system of the first aspect, wherein the first pressure detection unit is provided at a location less than 20% of the length of the return piping between the final stage of the branch with the use point in the return piping and the tank.

[0015] According to the liquid circulation system of the third aspect, the first pressure detection unit is provided at a position less than 20% of the length of the return pipe between the tank and the last stage from the last stage of the branch of the return pipe to the use point. For example, when the length of the return pipe between the tank and the use point is long, in a configuration in which the first pressure detection unit is provided at a position more than 20% of the length of the return pipe between the last stage and the tank from the last stage of the branch of the return pipe to the use point, when the liquid begins to be used at the use point, if the diameter of the return pipe is the same, the flow rate of the liquid in the return pipe decreases, and pressure loss decreases. Therefore, in a first pressure detection unit provided at a position more than 20% of the length of the return pipe from the last stage of the branch of the use point, there is a possibility that the pressure inside the return pipe will not be appropriately adjusted by the adjustment valve. In contrast, if the first pressure detection unit is provided less than 20% of the length of the return piping from the final stage of the branch with the use point in the return piping, the reduction in pressure loss can be neglected even if the flow rate of the liquid in the return piping decreases. Therefore, the pressure inside the return piping can be appropriately adjusted by the adjustment valve according to the pressure detected by the first pressure detection unit.

[0016] The liquid circulation system of the fourth aspect is the liquid circulation system of the first aspect, wherein the first pressure detection unit is provided on a side of the return piping closer to the final stage of the branch with the use point than the tank, and at a location where the pressure difference is within 9.8 kPa when comparing the pressure difference when the flow rate of the liquid in the return piping is maximum and minimum.

[0017] According to the liquid circulation system of the fourth aspect, the first pressure detection unit is provided on the return pipe closer to the last stage of the branch with the use point than the tank, at a location where the pressure difference between the maximum and minimum flow rates of the liquid in the return pipe is within 9.8 kPa. For example, in a case where the length of the return pipe between the tank and the use point is long, in a configuration where the first pressure detection unit is provided on the return pipe closer to the tank than the last stage of the branch with the use point, at a location where the pressure difference between the maximum and minimum flow rates of the liquid in the return pipe is greater than 9.8 kPa, when the liquid begins to be used at the use point, if the diameter of the return pipe is the same, the flow rate of the liquid in the return pipe decreases, and pressure loss decreases. Therefore, in a first pressure detection unit provided near the tank, there is a possibility that the pressure inside the return pipe will not be appropriately adjusted by the adjustment valve. In contrast, if the first pressure detection unit is located on the return piping closer to the final stage of the branch with the use point than the tank, and the differential pressure when the flow rate of the liquid in the return piping is maximum and minimum is within 9.8 kPa, the return piping is less susceptible to the effect of reduced pressure loss even if the flow rate of the liquid in the return piping decreases. Therefore, the pressure inside the return piping can be appropriately adjusted by the adjustment valve according to the pressure detected by the first pressure detection unit.

[0018] A liquid circulation system according to a fifth aspect is the liquid circulation system according to the first aspect, wherein the first pump is a booster pump that pressurizes the supply pipe to compensate for a pressure deficiency and supplies the liquid.

[0019] According to the liquid circulation system of the fifth aspect, the first pump provided in the supply pipe between the multiple treatment sections is a booster pump that supplies liquid by pressurizing the supply pipe to compensate for the pressure deficiency. This makes it easier to control the flow rate of liquid on the outlet side of the booster pump according to the flow rate of liquid inside the supply pipe detected by a flow rate detector between the most downstream treatment section among the multiple treatment sections in the supply pipe and the use point. This makes it possible to more reliably suppress fluctuations in the flow rate of liquid supplied to the use point.

[0020] The liquid circulation system according to a sixth aspect is the liquid circulation system according to the first aspect, wherein the multiple processing sections constitute the most downstream processing section and include a filtration device equipped with an ultrafiltration membrane, and an ion exchange device equipped with an ion exchange resin and provided upstream just before the filtration device, and the ion exchange device has two or more ion exchange resin processing sections connected in parallel to the supply piping and into which liquid is respectively introduced and discharged.

[0021] According to the liquid circulation system of the sixth aspect, the ion exchange device has two or more ion exchange resin treatment sections connected in parallel to a supply pipe, and liquid is introduced into each of the two or more ion exchange resin treatment sections, and liquid treated with each ion exchange resin is discharged. This makes it possible to stop one of the two or more ion exchange resin treatment sections, perform maintenance on that ion exchange resin treatment section, and pass liquid through the other ion exchange resin treatment sections. This makes it possible to perform maintenance on one of the two or more ion exchange resin treatment sections while continuing the operation of the liquid circulation system.

[0022] The liquid circulation system described in a seventh aspect is the liquid circulation system described in the sixth aspect, and is configured such that, during maintenance of the ion exchange device, one of the ion exchange resin treatment units is stopped and liquid that has passed through the other ion exchange resin treatment unit is supplied to the filtration device.

[0023] According to the liquid circulation system of the seventh aspect, during maintenance of the ion exchange device, one ion exchange resin treatment section is stopped, and the liquid that has passed through the other ion exchange resin treatment section is supplied to the filtration device. For example, in a configuration in which the first pump is controlled according to the pressure inside the supply pipe detected by a pressure gauge installed between the most downstream treatment section in the supply pipe and the use point, if the amount of liquid used at the use point is changed and one of the ion exchange resin treatment sections is stopped at the same time, it is necessary to control the first pump by the pressure gauge and control the adjustment valve by the first pressure detection section.In this case, since there are two pressure controls, the flow rate and pressure of the liquid cannot be predicted, and the operating flow rate of the liquid changes depending on the timing, which may make it impossible to return to the original state (the operating flow rate of the liquid in the liquid circulation system may become unstable). In contrast, in the above liquid circulation system, when the amount of liquid used at the point of use is changed and one of the ion exchange resin treatment units is stopped at the same time, the first pump is controlled according to the flow rate of liquid detected by a flow rate detection unit between the most downstream treatment unit in the supply piping and the point of use. Therefore, since the first pump is controlled by the flow rate detection unit and the regulating valve is controlled by the first pressure detection unit, the operating flow rate of the liquid in the liquid circulation system can be stabilized.

[0024] The liquid circulation system described in the eighth aspect is configured in the liquid circulation system described in the sixth aspect, such that, during maintenance of the ion exchange device, liquid is introduced into one of the ion exchange resin treatment sections to wash the ion exchange resin, the washed liquid is discharged into a drainage path other than the supply piping, liquid is introduced into the other ion exchange resin treatment section, and the liquid that has passed through the other ion exchange resin treatment section is supplied to the filtration device.

[0025] According to the liquid circulation system described in the eighth aspect, during maintenance of the ion exchange device, liquid is introduced into one ion exchange resin treatment section to wash the ion exchange resin, the washed liquid is discharged into the drain, and the liquid that has passed through the other ion exchange resin treatment section is supplied to the filtration device. For example, in a configuration in which the first pump is controlled according to the pressure inside the supply pipe detected by a pressure gauge installed between the most downstream treatment section in the supply pipe and the use point, if the amount of liquid used at the use point is changed and the ion exchange resin in one ion exchange resin treatment section is cleaned at the same time, it is necessary to control the first pump by the pressure gauge and the adjustment valve by the first pressure detection section. In this case, since there are two pressure controls, the flow rate and pressure of the liquid cannot be predicted, and the operating flow rate of the liquid changes depending on the timing, which may make it impossible to return to the original state (the operating flow rate of the liquid in the liquid circulation system may become unstable). In contrast, in the above liquid circulation system, when the amount of liquid used at the point of use is changed and the ion exchange resin in one ion exchange resin treatment section is cleaned at the same time, the first pump is controlled according to the flow rate of the liquid detected by a flow rate detection section between the most downstream treatment section in the supply piping and the point of use. Therefore, the first pump is controlled by the flow rate detection section and the regulating valve is controlled by the first pressure detection section, so that the operating flow rate of the liquid in the liquid circulation system can be stabilized. Effect of the Invention

[0026] According to the liquid circulation system of the present disclosure, fluctuations in the flow rate of liquid supplied to a point-of-use can be suppressed regardless of whether or not the liquid is being used at the point-of-use.

[0027] The technology of the present disclosure is widely applicable to liquid supply devices and liquid supply systems having a circulation system, but is particularly applicable to ultrapure water production devices and ultrapure water production systems. 3 The present invention is particularly suitable for use in ultrapure water production apparatuses and ultrapure water production systems with a supply rate of 1000 sulphur / h or more, and / or ultrapure water production apparatuses and ultrapure water production systems in which a plurality of such apparatuses and systems are provided in parallel. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a configuration diagram showing a liquid circulation system according to a first embodiment. [Diagram 2] FIG. 2 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first embodiment, and a use point. [Diagram 3] 1 is a block diagram showing a hardware configuration of a liquid circulation system according to a first embodiment. FIG. [Figure 4] FIG. 2 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first embodiment, and a use point, showing a state in which liquid has been used at the use point. [Diagram 5] FIG. 2 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first embodiment, and a use point, showing a state in which a first ion exchange resin treatment section is stopped. [Figure 6] FIG. 2 is a schematic diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first embodiment, and a use point, illustrating a state in which resin cleaning is being performed on the first ion exchange resin treatment section. [Figure 7] FIG. 2 is a configuration diagram showing a liquid circulation system of a first comparative example. [Figure 8] FIG. 2 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first comparative example, and a use point. [Figure 9] FIG. 2 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of the liquid circulation system of the first comparative example, and a use point, showing a state in which liquid has been used at the use point. [Figure 10] FIG. 11 is a configuration diagram showing a second ion exchange device and an ultrafiltration membrane of a liquid circulation system of a second comparative example, and a use point, showing a state in which liquid has been used at the use point. [Figure 11]FIG. 1 is a schematic diagram showing a second ion exchange device and an ultrafiltration membrane of a liquid circulation system of a first comparative example, and a use point, illustrating a state in which no liquid is being used at the use point and the first ion exchange resin treatment unit is stopped. [Figure 12] FIG. 1 is a schematic diagram showing a second ion exchange device and an ultrafiltration membrane of a liquid circulation system of a first comparative example, and a use point, illustrating a state in which liquid is used at the use point and the first ion exchange resin treatment unit is stopped. [Figure 13] FIG. 1 is a schematic diagram showing a second ion exchange device and an ultrafiltration membrane of a liquid circulation system of a first comparative example, and a use point, illustrating a state in which resin cleaning of a first ion exchange resin treatment section is being performed without using liquid at the use point. [Figure 14] FIG. 1 is a schematic diagram showing a second ion exchange device and an ultrafiltration membrane of a liquid circulation system of a first comparative example, and a use point, illustrating a state in which liquid is being used at the use point and resin cleaning is being performed on a first ion exchange resin treatment section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, elements that are less relevant to the present disclosure are omitted.

[0030] [Overall configuration of liquid circulation system] 1 shows the overall configuration of a liquid circulation system according to the first embodiment. In the liquid circulation system according to the first embodiment, an example will be described in which ultrapure water is supplied and recovered as an example of liquid.

[0031] 1, the liquid circulation system 10 includes a pretreatment device 12, a primary pure water device 14, a pure water tank 16, a secondary pure water device 20, and a point of use 50. Furthermore, the secondary pure water device 20 includes a circulation pump (P1) 22, a heat exchanger (HEX) 24, an ultraviolet ray irradiation device (UV) 26, a first ion exchange device (polisher-1) 28, a membrane degasser (MDG) 30, a booster pump (P2) 32, a second ion exchange device (polisher-2) 34, and an ultrafiltration device (UF) 36.

[0032] The liquid circulation system 10 also includes a supply pipe 62 that supplies the liquid in the pure water tank 16 (primary pure water, which will be described later in the first embodiment) to a use point 50, which is a supply destination, via the secondary pure water apparatus 20, and a return pipe 64 that returns the liquid from the use point 50 to the pure water tank 16. In the liquid circulation system 10, the supply pipe 62 and the return pipe 64 form a circulation path 60 that circulates the liquid in the pure water tank 16. The heat exchanger 24, the ultraviolet irradiator 26, the first ion exchanger 28, the membrane degassing apparatus 30, the second ion exchanger 34, and the ultrafiltration apparatus 36 inside the secondary pure water apparatus 20 are examples of a plurality of processing sections that perform different processes on the liquid.

[0033] The liquid circulation system 10 also includes a control device 80 that controls each part of the liquid circulation system 10. Although one control device 80 is shown in Fig. 1, the control device 80 may be composed of multiple control units arranged at separate locations.

[0034] The liquid circulation system 10 also includes a pressure detector (PT1) 40 provided in the supply piping 62 between the membrane degassing device 30 and the second ion exchange device 34, and a flow rate detector (FT1) provided in the supply piping 62 between the most downstream ultrafiltration device 36 and the point of use 50. The liquid circulation system 10 also includes a pressure detector (PT2) 66 provided in the return piping 64, and an adjustment valve 68 provided in the return piping 64 downstream of the pressure detector 66.

[0035] (Pretreatment device) Raw water is supplied to the pretreatment device 12. The pretreatment device 12 clarifies the supplied raw water using a coagulation settling means, a sand filtration means, a membrane filtration means, etc., to obtain pretreated water from which suspended solids and a part of organic matter have been removed. Examples of raw water include industrial water, tap water, groundwater, river water, etc.

[0036] (Primary pure water equipment) The primary pure water system 14 further purifies the pretreated water obtained by treatment in the pretreatment system 12 to remove impurities from the pretreated water and obtain primary pure water. Specifically, the system has various devices such as a demineralizer that removes impurity ions, a reverse osmosis membrane device that removes inorganic ions, organic matter, fine particles, etc., a vacuum degassing device or membrane degassing device that removes dissolved gases such as dissolved oxygen, and a regenerative mixed-bed demineralizer or electrical regenerative demineralizer that removes remaining ions, etc.

[0037] (Pure water tank) The primary pure water obtained in the primary pure water device 14 is sent to the pure water tank 16. The pure water tank 16 is an example of a tank, and is a container for temporarily storing the primary pure water obtained in the primary pure water device 14. The material and shape of the pure water tank 16 are not particularly limited as long as the tank can stably store the primary pure water without causing component elution or rusting from the container. For example, materials such as fiber reinforced plastics (FRP), polyethylene, SUS304, SUS316, and materials lined with fluororesin such as polytetrafluoroethylene are preferably used. In addition, the upper part of the pure water tank 16 is preferably purged with pure nitrogen to prevent the absorption of impurity gases such as carbon dioxide and oxygen.

[0038] As described below, the pure water tank 16 stores unused ultrapure water mixed with the above-mentioned primary pure water when the unused ultrapure water among the produced ultrapure water is circulated and collected at the use point 50. The mixture of the primary pure water stored in the pure water tank 16 and the ultrapure water returned from the use point will also be referred to as "primary pure water" hereinafter.

[0039] (Secondary pure water device) 1, in the secondary pure water system 20, a circulation pump 22 provided downstream of the pure water tank 16 in the supply piping 62 supplies primary pure water from the pure water tank 16 to a heat exchanger 24. The circulation pump 22 is an example of a second pump. A power source 44 is connected to the circulation pump 22.

[0040] In the secondary pure water system 20, the ultrapure water produced by the secondary pure water system 20 is supplied to the point of use 50 by a booster pump 32 provided in the supply piping 62 between the membrane degassing device 30 and the second ion exchange device 34. The booster pump 32 is a pump that pressurizes the supply piping 62 to compensate for any pressure deficiency, thereby supplying primary pure water. The booster pump 32 is an example of a first pump. A power source 46 is connected to the booster pump 32.

[0041] The heat exchanger 24 of the secondary pure water device 20 adjusts the temperature of the primary pure water by heat exchange (heating or cooling) with the primary pure water. As the heat exchanger 24, for example, a plate-type heat exchanger can be used, but the specific structure is not particularly limited.

[0042] The primary pure water whose temperature has been adjusted by the heat exchanger 24 is sent to the ultraviolet irradiation device 26. In the ultraviolet irradiation device 26, the primary pure water is irradiated with ultraviolet light to decompose organic matter in the primary pure water and sterilize live bacteria. If the ultraviolet irradiation device 26 is equipped with an ultraviolet lamp capable of irradiating a wavelength of about 185 nm or about 254 nm, for example, it is possible to reliably decompose and sterilize organic matter in the primary pure water. There is no particular limitation on the ultraviolet lamp used, but a low-pressure mercury lamp is preferred in terms of ease of handling.

[0043] The first ion exchange device 28 is a device that uses an ion exchange resin to remove impurity ions such as hydrogen peroxide and organic acids generated in the ultraviolet irradiation device 26. As the ion exchange resin, for example, an anion resin or a mixed bed resin in which an anion resin and a cation resin are mixed is used. The first ion exchange device 28 has a structure in which an ion exchange resin is filled in, for example, a cylindrical sealed container.

[0044] The membrane degassing device 30 is a device that removes gas, particularly dissolved oxygen, from primary pure water using a gas separation membrane that does not allow water to pass through but allows gas to pass through. The primary pure water treated by the membrane degassing device 30 has a low concentration of dissolved oxygen. The primary pure water whose dissolved oxygen concentration has been reduced by the membrane degassing device 30 is sent to a second ion exchange device 34 by a booster pump 32.

[0045] The second ion exchange device 34 is a device that removes impurity ions such as organic acids using an ion exchange resin, similar to the first ion exchange device 28. As the ion exchange resin, for example, an anion resin or a mixed bed resin in which an anion resin and a cation resin are mixed is used. Although the secondary pure water system 20 is provided with the first ion exchange device 28, the system may be configured to include only the second ion exchange device 34 without providing the first ion exchange device 28. The primary pure water from which the impurity ions have been removed by the second ion exchange device 34 is sent to the ultrafiltration device 36. The configuration of the second ion exchange device 34 will be described later.

[0046] The ultrafiltration device 36 is equipped with an ultrafiltration membrane and is a device that produces ultrapure water by removing fine particles using the ultrafiltration membrane. The ultrafiltration device 36 is an example of a filtration device. The ultrafiltration device 36 is disposed at the end of the supply pipe 62 in the secondary pure water system 20 in the supply direction, and constitutes the most downstream processing section inside the secondary pure water system 20. The ultrapure water obtained by the secondary pure water system 20 is supplied to a use point 50, which is the place of use, via the supply pipe 62. The configuration of the ultrafiltration device 36 will be described later. In this disclosure, the outlet side of the ultrafiltration device is the end of the ultrapure water system.

[0047] In addition, the secondary water purification system 20 may be provided with an oxidant removal device provided with a catalytic resin carrying Pt or Pd metal, or a reducing resin carrying sulfite groups, hydrogen sulfite groups, nitrite groups, etc., and a boron-selective ion exchange device. The resins of these devices may also be packed in the first ion exchange device or the second ion exchange device.

[0048] The pressure detector 40 detects the pressure inside the supply pipe 62 between the membrane degassing device 30 and the booster pump 32. The pressure detector 40 is an example of a second pressure detection unit. For example, a pressure transmitter is used as the pressure detector 40. The pressure transmitter is a communication device that converts pressure data into a signal and transmits it as a radio wave. The control device 80 controls the circulation pump 22 according to the pressure detected by the pressure detector 40 so that the pressure inside the supply pipe 62 becomes a predetermined pressure. The control of the circulation pump 22 will be described later.

[0049] The flow rate detector 42 detects the flow rate of ultrapure water inside the supply pipe 62 between the ultrafiltration device 36 at the most downstream position in the secondary pure water system 20 and the point of use 50. The flow rate detector 42 is an example of a flow path detection unit. For example, a flow rate transmitter is used as the flow rate detector 42. The flow rate transmitter is a communication device that converts flow rate data into a signal and transmits it as a radio wave. The control device 80 controls the booster pump 32 according to the flow rate detected by the flow rate detector 42 so that the ultrapure water flowing through the supply pipe 62 is at a predetermined flow rate. The control of the booster pump 32 will be described later.

[0050] 2 shows the configuration of the second ion exchange device 34, the ultrafiltration device 36, and the vicinity of the point of use 50. As shown in FIG. 2, the second ion exchange device 34 includes a first ion exchange resin treatment section (polisher 2-1) 102 and a second ion exchange resin treatment section (polisher 2-2) 104 connected in parallel to a supply pipe 62. Specifically, the supply pipe 62 is branched into two inlet pipes 106A and 106B, the inlet pipe 106A is connected to the first ion exchange resin treatment section 102, and the inlet pipe 106B is connected to the second ion exchange resin treatment section 104. As a result, primary pure water is introduced from the supply pipe 62 through the inlet pipes 106A and 106B into the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104, respectively. The inlet pipes 106A and 106B are provided with valves 107A and 107B for opening and closing the flow paths, respectively.

[0051] A discharge pipe 108A is connected to the first ion exchange resin treatment section 102, and a discharge pipe 108B is connected to the second ion exchange resin treatment section 104. The discharge pipes 108A and 108B are joined to the downstream supply pipe 62. The discharge pipes 108A and 108B are provided with valves 109A and 109B for opening and closing the flow paths, respectively.

[0052] Discharge lines 110A and 110B are connected to the middle of the discharge pipes 108A and 108B, respectively. The discharge lines 110A and 110B are provided with valves 111A and 111B for opening and closing the flow paths, respectively. During normal use of the secondary pure water apparatus 20, the valves 111A and 111B are closed (see FIG. 2). As a result, the primary pure water treated in the first ion exchange resin treatment section 102 is supplied to the supply pipe 62 via the discharge pipe 108A, and the primary pure water treated in the second ion exchange resin treatment section 104 is supplied to the supply pipe 62 via the discharge pipe 108B.

[0053] In addition, the second ion exchange device 34 is provided with two first ion exchange resin treatment sections 102 and two second ion exchange resin treatment sections 104, but instead of this, a configuration including three or more ion exchange resin treatment sections may be used.

[0054] 2, the ultrafiltration device 36 is configured as a unit equipped with two ultrafiltration membrane processing sections 120A and 120B. The primary pure water treated by the second ion exchange device 34 is introduced into the two ultrafiltration membrane processing sections 120A and 120B via a supply pipe 62, and filtered by the ultrafiltration membranes. The ultrapure water filtered by the two ultrafiltration membrane processing sections 120A and 120B is supplied to the point of use 50 via the supply pipe 62.

[0055] (Use points) 1 and 2, the supplied ultrapure water is used at the point of use 50. Any unused ultrapure water supplied to the point of use 50 is circulated and collected in the pure water tank 16 via the return piping 64, and is stored in the pure water tank 16 together with the primary pure water. Furthermore, when the ultrapure water is not used at the point of use 50, the ultrapure water supplied from the secondary pure water device 20 to the point of use 50 is returned directly to the pure water tank 16 via the return piping 64 (see FIG. 2).

[0056] As an example, the point of use 50 is provided in a clean room 52 located away from the secondary pure water system 20. The supply pipe 62 from the most downstream end of the secondary pure water system 20 to the connection to the point of use 50, and the return pipe 64 from the branch to the point of use 50 to the pure water tank 16, form a relatively long flow path. For example, the length L1 of the supply pipe 62 from the downstream end of the secondary pure water system 302 to the connection to the point of use 50 is, for example, 0.1 km or more and 1.5 km or less. In addition, the length of the return pipe 64 from the branch to the point of use 50 to the pure water tank 16 is, for example, 0.1 km or more and 1.5 km or less.

[0057] The material for the supply pipe 62 and the return pipe 64 is not particularly limited, but may be PVDF (polyvinylidene fluoride), PVC (polyvinyl chloride), stainless steel such as SUS304 or SUS316, etc., and when the liquid is ultrapure water, it is preferable to use PVDF.

[0058] The pressure detector 66 is provided in the return pipe 64 connected to the point of use 50, and detects the pressure inside the return pipe 64. The pressure detector 66 is an example of a first pressure detection unit. For example, a pressure transmitter is used as the pressure detector 66. An adjustment valve 68 provided downstream of the pressure detector 66 in the return pipe 64 adjusts the pressure inside the return pipe 64.

[0059] The pressure detector 66 is preferably provided at a position from the branch of the return pipe 64 to the use point 50 to less than 20% of the length of the return pipe 64 between the branch and the pure water tank 16, more preferably at a position less than 10% of the length of the return pipe 64, and even more preferably at a position less than 5% of the length of the return pipe 64. Here, the length of the return pipe 64 refers to the length from the branch of the return pipe 64 to the use point 50 to the connection with the pure water tank 16.

[0060] Although not shown in the drawings, in the liquid circulation system 10, the circulation path 60 may be provided with a plurality of branch points to the use point 50. In this case, it is preferable that the pressure detector 66 is provided at a position from the last stage of the branch to the use point 50 in the return piping 64 to less than 20% of the length of the return piping 64 between the last stage and the pure water tank 16.

[0061] (Hardware configuration of liquid circulation system) Fig. 3 shows a block diagram of the hardware configuration of the liquid circulation system 10. As shown in Fig. 3, the control device 80 has components including a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a storage 84, and an input / output interface 85. Each component is connected to each other via a bus 86.

[0062] The CPU 81 is a central processing unit, and executes various programs and controls each part. That is, the CPU 81 reads a program from the ROM 82 or the storage 84, and executes the program using the RAM 83 as a working area. The CPU 81 controls each of the above components and performs various arithmetic processing according to the program recorded in the ROM 82 or the storage 84. In the first embodiment, the ROM 82 or the storage 84 stores a liquid circulation processing program.

[0063] The ROM 82 stores various programs and various data. The RAM 83 temporarily stores programs or data as a working area. The storage 84 is configured with an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including an operating system and various data.

[0064] The input / output interface 85 is connected to the pressure detector 40, the flow rate detector 42, the pressure detector 66, and the adjustment valve 68. Furthermore, the input / output interface 85 is connected to the circulation pump 22 via a power supply 44, and to the booster pump 32 via a power supply 46.

[0065] The control device 80 receives an input of a pressure value detected by the pressure detector 40 of the supply pipe 62. The control device 80 controls the frequency of electricity supplied from the power source 44 to the circulation pump 22 according to the pressure detected by the pressure detector 40. This adjusts the pressure and flow rate at the outlet of the circulation pump 22. The control device 80 is an example of a second pump control unit. The control device 80 controls the frequency of electricity supplied from the power source 44 to the circulation pump 22 so that the pressure of the pressure detector 40 becomes a preset pressure.

[0066] The controller 80 receives as input the value of the flow rate of ultrapure water detected by the flow rate detector 42 of the supply pipe 62. The controller 80 controls the frequency of electricity supplied from the power source 46 to the booster pump 32 in accordance with the flow rate of ultrapure water detected by the flow rate detector 42. The booster pump 32 is a pump that pressurizes the supply pipe 62 to compensate for any pressure deficiency, thereby supplying primary pure water. This adjusts the pressure and flow rate at the outlet of the booster pump 32. The controller 80 is an example of a first pump control section. For example, when the flow rate of ultrapure water detected by the flow rate detector 42 is 80m 3 / h (see FIG. 2).

[0067] The value of the pressure detected by the pressure detector 66 of the return pipe 64 is input to the control device 80. The control device 80 adjusts the pressure inside the return pipe 64 by controlling the opening state of the regulating valve 68 in accordance with the pressure detected by the pressure detector 66. For example, when the pressure detected by the pressure detector 66 is 343 kPa (i.e., 3.5 kgf / cm 2 ) (see FIG. 2).

[0068] [Actions and Effects of the First Embodiment] Next, the operation and effects of the first embodiment will be described.

[0069] 1, the liquid circulation system 10 is provided with a circulation path 60 having a supply pipe 62 and a return pipe 64, and primary pure water in a pure water tank 16 is supplied to a point of use 50 via a secondary pure water device 20 through the supply pipe 62. In the secondary pure water device 20, the primary pure water is treated by a heat exchanger 24, an ultraviolet irradiation device 26, a first ion exchange device 28, a membrane degassing device 30, a second ion exchange device 34, and an ultrafiltration device 36 to obtain ultrapure water. The ultrapure water obtained by the secondary pure water device 20 is supplied to the point of use 50. Furthermore, ultrapure water not used at the point of use 50 is returned to the pure water tank 16 through the return pipe 64.

[0070] 1 and 2, a pressure detector 66 is provided in the return pipe 64, and the pressure inside the return pipe 64 is detected by the pressure detector 66. A regulating valve 68 is provided downstream of the pressure detector 66 in the return pipe 64, and the pressure inside the return pipe 64 is adjusted by the regulating valve 68 in accordance with the pressure detected by the pressure detector 66.

[0071] 1 and 2, a flow rate detector 42 is provided in the supply pipe 62 between the ultrafiltration device 36 at the most downstream of the secondary pure water system 20 and the point of use 50, and the flow rate detector 42 detects the flow rate of the liquid inside the supply pipe 62. Then, in accordance with the flow rate detected by the flow rate detector 42, the control device 80 controls the booster pump 32 so that the primary pure water flowing through the supply pipe 62 is at a predetermined flow rate. This suppresses fluctuations in the flow rate of the ultrapure water supplied from the flow rate detector 42 in the supply pipe 62 to the point of use 50. Therefore, regardless of whether or not ultrapure water is used at the point of use 50, it is possible to suppress fluctuations in the flow rate of the ultrapure water supplied to the point of use 50.

[0072] 1, in the liquid circulation system 10, a circulation pump 22 is provided downstream of the pure water tank 16 in the supply pipe 62, and the primary pure water in the pure water tank 16 is supplied to the heat exchanger 24 side of the secondary pure water system 20 by the circulation pump 22. A pressure detector 40 is provided upstream of the booster pump 32 in the supply pipe 62, and the pressure inside the supply pipe 62 is detected by the pressure detector 40. Then, the control device 80 controls the circulation pump 22 in accordance with the pressure detected by the pressure detector 40 so that the pressure inside the supply pipe 62 becomes a predetermined pressure. Therefore, when the primary pure water in the pure water tank 16 is supplied to the heat exchanger 24 side of the secondary pure water system 20 through the supply pipe 62 by the circulation pump 22, the fluctuation in the pressure inside the supply pipe 62 at the position of the pressure detector 40 can be suppressed.

[0073] Furthermore, in the liquid circulation system 10, a booster pump 32 is provided between the membrane degassing device 30 and the second ion exchange device 34 in the supply piping 62. This makes it easier to control the flow rate of the primary pure water on the outlet side of the booster pump 32 in accordance with the flow rate of ultrapure water detected by a flow detector 42 between the most downstream ultrafiltration device 36 in the supply piping 62 and the point of use 50. This makes it possible to more reliably suppress fluctuations in the flow rate of ultrapure water supplied to the point of use 50.

[0074] (Example of not using ultrapure water at the point of use) Here, an example will be described in which ultrapure water is not used at the use point 50 in the liquid circulation system 10. FIG. 2 shows a case where ultrapure water is not used at the use point 50 (when the amount of ultrapure water used is 0 ml). 3 / h) is shown.

[0075] As shown in FIG. 2, the control device 80 detects that the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. At this time, at the point of use 50, for example, the required pressure is 343 kPa (i.e., 3.5 kgf / cm 2 ), whereas the actual pressure is 343kPa (i.e., 3.5kgf / cm 2 The pressure at the use point 50 is measured by a pressure gauge (not shown). As a result, the flow rate of ultrapure water supplied to the use point 50 by the supply pipe 62 is 80 m 3 / h, and the pressure difference (ΔP) between the pressure of the pressure detector 40 and the pressure of the use point 50 is 49 kPa (i.e., 0.5 kgf / cm 2 )

[0076] In this example, since there is no use of ultrapure water at the use point 50, the flow rate of ultrapure water returned to the pure water tank 16 through the return pipe 64 is 80 m 3 The control device 80 detects that the pressure of the pressure detector 66 provided on the side of the return pipe 64 branching off from the use point 50 is 343 kPa (i.e., 3.5 kgf / cm 2The pressure inside the return pipe 64 is controlled by the adjusting valve 68 so that the pressure becomes equal to or larger than the pressure in the return pipe 64 .

[0077] (Example of using ultrapure water at the point of use) Next, an example in which ultrapure water is used at a point-of-use 50 in the liquid circulation system 10 will be described with reference to FIG.

[0078] As shown in FIG. 4, the control device 80 detects that the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. At this time, the required pressure at the point of use 50 is 343 kPa (i.e., 3.5 kgf / cm 2 ), whereas the actual pressure is 343kPa (i.e., 3.5kgf / cm 2 Therefore, the flow rate of the ultrapure water supplied to the point of use 50 through the supply pipe 62 is 80 m 3 / h, and the pressure difference (ΔP) between the internal pressure of the supply pipe 62 (the pressure near the flow detector 42) and the pressure at the use point 50 is 49 kPa (i.e., 0.5 kgf / cm 2 )

[0079] At use point 50, for example, the amount of ultrapure water used is 50m 3 / h, the flow rate of the ultrapure water returned to the pure water tank 16 through the return pipe 64 is 30 m 3 The control device 80 detects that the pressure of the pressure detector 66, which is provided on the return pipe 64 near the branch with the use point 50, is 343 kPa (i.e., 3.5 kgf / cm 2 The pressure inside the return pipe 64 is controlled by the adjusting valve 68 so that the pressure becomes equal to or larger than the pressure in the return pipe 64 .

[0080] As described above, in the liquid circulation system 10, fluctuations in the flow rate of ultrapure water supplied to the point of use 50 can be suppressed regardless of whether ultrapure water is used at the point of use 50. Furthermore, in the liquid circulation system 10, fluctuations in the flow rate of ultrapure water are small, so deterioration of the quality of the ultrapure water due to fluctuations in flow rate is minimized.

[0081] (Pressure detector position) In the liquid circulation system 10, the pressure detector 66 is provided at a position from the branch of the return pipe 64 to the use point 50, which is less than 20% of the length of the return pipe 64 between the branch and the pure water tank 16.

[0082] For example, in a configuration in which the length of the return piping between the pure water tank and the use point is long and the pressure detection unit is provided at a position that is 20% or more of the length of the return piping 64 from the branch of the return piping to the use point to the pure water tank 16, when ultrapure water begins to be used at the use point, if the diameter of the return piping is the same, the flow rate of ultrapure water in the return piping decreases, and pressure loss decreases. Therefore, with a pressure detection unit provided at a position that is 20% or more of the length of the return piping 64 from the branch of the return piping to the use point, there is a possibility that the pressure inside the return piping will not be appropriately adjusted by the adjustment valve 68.

[0083] In contrast, in the liquid circulation system 10, the pressure detector 66 is provided at a position that is less than 20% of the length of the return piping 64 from the branch with the use point 50 in the return piping 64, so that even if the flow rate of ultrapure water in the return piping 64 decreases, the reduction in pressure loss can be ignored. Therefore, the pressure inside the return piping 64 can be appropriately adjusted by the adjustment valve 68 in accordance with the pressure detected by the pressure detector 66. There is no particular restriction on where the adjustment valve 68 can be installed, so long as it is downstream of the pressure detector 66 in the return piping 64.

[0084] [Liquid Circulation System of First Comparative Example] Here, a liquid circulation system of Comparative Example 1 will be described. Note that the same components as those in the above-described first embodiment are given the same reference numerals and the description thereof will be omitted.

[0085] As shown in FIG. 7, the liquid circulation system 300 of the first comparative example includes a secondary pure water apparatus 302 and a control device 320 as configurations different from those of the liquid circulation system 10 of the first embodiment. The secondary pure water apparatus 302 includes a second pressure detector 310 for detecting the pressure inside the supply pipe 62 between the most downstream ultrafiltration device 36 and the point of use 50. The control device 320 controls the frequency of the power source 46 that supplies power to the booster pump 32 based on the pressure detected by the second pressure detector 310. That is, the liquid circulation system 300 does not include the flow rate detector 42 (see FIG. 1) as in the liquid circulation system 10 of the first embodiment. In the liquid circulation system 300, the length L2 of the supply pipe 62 from the downstream end of the secondary pure water apparatus 302 to the connection part of the point of use 50 is, for example, 0.5 km or more and 1.5 km or less.

[0086] Furthermore, the liquid circulation system 300 differs from the liquid circulation system 10 of the first embodiment in that a third pressure detector 312 for detecting the pressure inside the return pipe 64 is provided on the upstream side of the adjustment valve 68 in the return pipe 64 and closer to the pure water tank 16. The control device 320 adjusts the pressure inside the return pipe 64 by controlling the opening state of the adjustment valve 68 in accordance with the pressure detected by the third pressure detector 66. The control device 320, for example, detects the pressure inside the return pipe 64 when the pressure detected by the third pressure detector 312 is 294 kPa (i.e., 3 kgf / cm 2 ), thereby adjusting the pressure inside the return piping 64. In the liquid circulation system 300, the length of the return piping 64 from the branching of the return piping 64 with the use point 50 to the third pressure detector 312 is, for example, 0.5 km or more and 1.5 km or less. The third pressure detector 312 is provided, for example, at a position 80% or more of the length of the return piping 64 from the branching of the return piping 64 with the use point 50.

[0087] (Example of not using ultrapure water at the point of use) As shown in FIG. 8, in the liquid circulation system 300 of the first comparative example, no ultrapure water is used at the use point 50 (the amount of ultrapure water used is 0 m 3 / h), the control device 320 detects, for example, that the pressure of the second pressure detector 310 is 392 kPa (i.e., 4 kgf / cm 2 At this time, the frequency of the power source 46 that supplies power to the booster pump 32 is controlled so that the required pressure at the point of use 50 is 343 kPa (i.e., 3.5 kgf / cm 2 ), whereas the actual pressure is 343kPa (i.e., 3.5kgf / cm 2 The flow rate of the ultrapure water supplied to the point of use 50 through the supply pipe 62 is 80 m 3 / h, and the pressure difference (ΔP) between the pressure of the second pressure detector 310 and the pressure of the use point 50 is 49 kPa (i.e., 0.5 kgf / cm 2 )

[0088] Since no ultrapure water is used at use point 50 (the amount of ultrapure water used is 0m 3 / h), the flow rate of ultrapure water flowing to the pure water tank 16 side through the return pipe 64 is 80 m 3 The controller 320 detects that the pressure of the third pressure detector 312 in the return pipe 64 is 343 kPa (i.e., 3.5 kgf / cm 2 The pressure inside the return pipe 64 is controlled by the adjustment valve 68 so that the pressure difference (ΔP) between the pressure at the use point 50 and the pressure at the third pressure detector 312 is 49 kPa (i.e., 0.5 kgf / cm 2 )

[0089] (Example of using ultrapure water at the point of use) FIG. 9 shows a liquid circulation system 300 in which 50 ml of ultrapure water is pumped to a use point 50. 3 9, in the return pipe 64, the third pressure detector 312 detects that the set pressure of the regulating valve 68 is 294 kPa (i.e., 3 kgf / cm 2) when the use point 50 starts to use ultrapure water, if the diameter of the return pipe 64 remains the same, the flow rate of ultrapure water in the return pipe 64 decreases, and the pressure loss decreases. For example, the pressure difference (ΔP) between the pressure at the use point 50 and the pressure at the third pressure detector 312 is 49 kPa (i.e., 0.5 kgf / cm 2 ) to 29.4kPa (i.e., 0.3kgf / cm 2 )

[0090] At use point 50, the required pressure is 343 kPa (i.e., 3.5 kgf / cm 2 ), whereas the actual pressure is 323.4kPa (i.e., 3.3kgf / cm 2 At this time, the pressure of the second pressure detector 310 is 392 kPa (i.e., 4 kgf / cm 2 ), and the pressure difference (ΔP) between the pressure of the second pressure detector 310 and the pressure of the use point 50 is 68.6 kPa (i.e., 0.7 kgf / cm 2 ), the pressure loss increases and the supply flow rate increases. For example, the supply flow rate of ultrapure water in the supply pipe 62 is actually 80 m 3 / h, but the supply flow rate is 100m 3 / h. In other words, the actual supply flow rate of ultrapure water increases relative to the design flow rate of ultrapure water in the supply pipe 62. This means that the change in pressure may affect the quality of the ultrapure water. In addition, the operating conditions of the semiconductor manufacturing equipment and the like installed at the point of use will change, which may affect the product yield.

[0091] For the convenience of maintenance, the third pressure detector 312 and the regulating valve 68 are generally installed near the pure water tank 16. That is, if the third pressure detector 312 and the regulating valve 68 were installed near the point of use, they would be installed, for example, in a building different from the building in which the pure water system is installed, on a different floor, and further inside or near a clean room, which would significantly impair maintainability, and is therefore not generally done.

[0092] [Liquid Circulation System of the Second Comparative Example] Next, a liquid circulation system of Comparative Example 2 will be described. Note that the same components as those in the first embodiment and Comparative Example 1 described above are given the same reference numerals and the description thereof will be omitted.

[0093] (Example of using ultrapure water at the point of use) FIG. 10 shows a liquid circulation system 330 of the second comparative example. For example, 50 ml of ultrapure water is 3 10 shows an example in which the setting of the third pressure detector 312 is changed immediately after the state of FIG. 9 is reached. That is, as shown in FIG. 10, in the liquid circulation system 330 of the second comparative example, the set pressure of the third pressure detector 312 is manually changed to 323.4 kPa (i.e., 3.3 kgf / cm 2 ) and narrow the opening of the adjustment valve 68. As a result, the flow rate of the ultrapure water returned by the return pipe 64 is increased by 50 m compared to the liquid circulation system 330 of the first comparative example. 3 / h to 30m 3 / h, and the pressure loss in the return pipe 64 is reduced. The pressure at the use point 50 is 343 kPa (i.e., 3.3 + 0.2 = 3.5 kgf / cm 2 Furthermore, the pressure difference (ΔP) between the second pressure detector 310 of the supply pipe 62 and the use point 50 is 49 kPa (i.e., 0.5 kgf / cm 2 ) and the supply volume of ultrapure water from the supply pipe 62 is also 80 m 3 Return to / h.

[0094] However, in the liquid circulation system 330, the set pressure of the third pressure detector 312 is manually and suddenly changed to 323.4 kPa (i.e., 3.3 kgf / cm 2 ), the quality of the ultrapure water may deteriorate. In addition, the control device 320 needs to control two pressures: the control of the booster pump 32 by the second pressure detector 310, and the control of the regulating valve 68 by the third pressure detector 312, which complicates the control of the operating system.

[0095] In contrast, in the liquid circulation system 10 of the first embodiment, the control device 80 controls the frequency of the power source 46 that supplies power to the booster pump 32 in accordance with the flow rate of ultrapure water of the flow detector 42 between the ultrafiltration device 36 and the point of use 50 in the supply piping 62. This suppresses fluctuations in the flow rate of ultrapure water supplied to the point of use 50 through the supply piping 62. Therefore, regardless of whether ultrapure water is used at the point of use 50, it is possible to suppress fluctuations in the flow rate of ultrapure water supplied to the point of use 50 through the supply piping 62.

[0096] Furthermore, in the liquid circulation system 10, the pressure detector 66 is provided at a position that is less than 20% of the length of the return piping 64 from the branch point with the use point 50 in the return piping 64. Therefore, even if the flow rate of ultrapure water in the return piping 64 decreases, the reduction in pressure loss can be neglected. Therefore, the pressure inside the return piping 64 can be appropriately adjusted by the adjustment valve 68 according to the pressure detected by the pressure detector 66.

[0097] [First example of maintenance in the liquid circulation system of the first embodiment] Next, a first example of maintenance of the liquid circulation system 10 of the first embodiment will be described.

[0098] 5 shows a state in which the first ion exchange resin treatment section 102 of the second ion exchange device 34 is stopped during maintenance of the liquid circulation system 10. As shown in FIG. 5, in the liquid circulation system 10, the change in the amount of ultrapure water used at the point of use 50 and the operation of the first ion exchange resin treatment section 102 are performed simultaneously. At the point of use 50, the amount of ultrapure water used is changed to 50 m 3 / h.

[0099] In the liquid circulation system 10, the valve 107A of the inlet pipe 106A is closed and the valve 109A of the outlet pipe 108A is closed, so that the primary pure water does not flow to the first ion exchange resin treatment section 102. This stops the first ion exchange resin treatment section 102, and the maintenance of the first ion exchange resin treatment section 102 can be performed. The valves 111A and 111B are also closed. Furthermore, the valve 107B of the inlet pipe 106B is opened and the valve 109B of the outlet pipe 108B is opened, so that the primary pure water flows only to the second ion exchange resin treatment section 104. The primary pure water treated in the second ion exchange resin treatment section 104 is supplied to the ultrafiltration device 36 from the outlet pipe 108B through the supply pipe 62.

[0100] The control device 80 detects that the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. As a result, the supply amount of ultrapure water supplied to the point of use 50 through the supply pipe 62 is increased to 80 m 3 / h.

[0101] Here, the operation and effects of the configuration of the second ion exchange device 34 of the liquid circulation system 10 of the first embodiment will be described.

[0102] In the liquid circulation system 10, the second ion exchange device 34 has a first ion exchange resin treatment section 102 and a second ion exchange resin treatment section 104 connected in parallel to the supply pipe 62. When the valves 107A and 107B of the first ion exchange resin treatment section 102 are opened and the valves 107B and 109B of the second ion exchange resin treatment section 104 are opened, primary pure water is introduced into the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104, respectively, and primary pure water treated in the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104 is discharged (see FIG. 4). In this configuration, one of the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104 can be stopped for maintenance and primary pure water can be passed through the other of the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104. Therefore, maintenance of either the first ion exchange resin treatment section 102 or the second ion exchange resin treatment section 104 can be performed while the liquid circulation system 10 continues to operate.

[0103] Furthermore, in the liquid circulation system 10, during maintenance of the second ion exchange device 34, one of the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104 is stopped, and the primary pure water that has passed through the other of the first ion exchange resin treatment section 102 and the second ion exchange resin treatment section 104 is supplied to the ultrafiltration device 36. For example, the first ion exchange resin treatment section 102 is stopped, and the primary pure water that has passed through the second ion exchange resin treatment section 104 is supplied to the ultrafiltration device 36 (see FIG. 5).

[0104] 5, in the liquid circulation system 10, the booster pump 32 is controlled in accordance with the flow rate of ultrapure water detected by a flow rate detector 42 between the most downstream ultrafiltration device 36 in the supply piping 62 and the point of use 50. For example, when the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. This controls the booster pump 32 by two controls, the flow rate detector 42 and the pressure detector 66, and therefore the operating flow rate of ultrapure water in the liquid circulation system 10 can be stabilized. Therefore, in the liquid circulation system 10, even if the amount of ultrapure water used at the point of use 50 is changed and the first ion exchange resin treatment unit 102 is stopped at the same time, the flow rate of ultrapure water supplied to the point of use 50 and the pressure at the point of use 50 can be kept almost constant.

[0105] [First example of maintenance for the liquid circulation system of the first comparative example] Next, a first example of maintenance of the liquid circulation system 300 of the first comparative example will be described.

[0106] 11 shows an example of maintenance of the second ion exchange device 34 in the liquid circulation system 300 of the first comparative example when there is no change in the amount of ultrapure water used at the point of use 50 (when ultrapure water is not used). As shown in Fig. 11, when the first ion exchange resin treatment section 102 of the second ion exchange device 34 is stopped, the pressure loss in the second ion exchange resin treatment section 104 increases. This increase in pressure loss is compensated for by increasing the frequency of the power source 46 that supplies power to the booster pump 32.

[0107] FIG. 12 shows a case where the amount of ultrapure water used at the point of use 50 is changed (for example, when 50 ml of ultrapure water is used) in the liquid circulation system 300 of the first comparative example. 312 shows an example of maintenance of the second ion exchange device 34 in a liquid circulation system 300 (when the amount of ultrapure water used at the point of use 50 is changed and the first ion exchange resin treatment section 102 is stopped at the same time). As shown in FIG. 12, in the liquid circulation system 300, when the amount of ultrapure water used at the point of use 50 is changed and the first ion exchange resin treatment section 102 is stopped, it is necessary to control the booster pump 32 by the second pressure detector 310 and the regulating valve 68 by the third pressure detector 312. At this time, since there are two automatic pressure controls in the same system, fluctuations in the flow rate and pressure of ultrapure water cannot be predicted. For this reason, depending on the timing, the operating flow rate of the liquid circulation system 300 may change, making it impossible to return the operating flow rate to its original state, and the operating state of the liquid circulation system 300 becomes unstable.

[0108] In contrast, in the liquid circulation system 10 of the first embodiment, the booster pump 32 is controlled in response to the flow rate of ultrapure water detected by a flow rate detector 42 between the ultrafiltration device 36 at the most downstream position in the supply piping 62 and the point of use 50. As a result, the booster pump 32 is controlled by the flow rate detector 42 and the regulating valve 68 is controlled by the pressure detector 66. Therefore, in the liquid circulation system 10, even if the amount of ultrapure water used at the point of use 50 is changed and the first ion exchange resin treatment unit 102 is stopped at the same time, the flow rate of ultrapure water supplied to the point of use 50 and the pressure at the point of use 50 can be kept approximately constant.

[0109] [Second Example of Maintenance in the Liquid Circulation System of the First Embodiment] Next, a first example of maintenance of the liquid circulation system 10 of the first embodiment will be described.

[0110] 6 shows a state in which the ion exchange resin in the first ion exchange resin treatment section 102 of the second ion exchange device 34 is being washed during maintenance of the liquid circulation system 10. As shown in FIG. 6, in the liquid circulation system 10, the amount of ultrapure water used at the point of use 50 is changed and the ion exchange resin in the first ion exchange resin treatment section 102 is washed at the same time. At the point of use 50, the amount of ultrapure water used is changed to 50 m 3 / h.

[0111] In the liquid circulation system 10, the valve 107A of the inlet pipe 106A is opened, the valve 109A of the outlet pipe 108A is closed, and the valve 111A of the outlet passage 110A is opened, whereby the primary pure water that has passed through the first ion exchange resin treatment section 102 is discharged to the outlet passage 110A. This allows the ion exchange resin of the first ion exchange resin treatment section 102 to be washed. In addition, the valve 107B of the inlet pipe 106B is opened, the valve 109B of the outlet pipe 108B is opened, and the valve 111B is closed, whereby the primary pure water that has passed through the second ion exchange resin treatment section 104 is supplied to the ultrafiltration device 36 from the outlet pipe 108B via the supply pipe 62. The flow rate during washing of the ion exchange resin of the first ion exchange resin treatment section 102 is 10 m 3 / h.

[0112] The control device 80 detects that the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. As a result, the supply amount of ultrapure water supplied to the point of use 50 through the supply pipe 62 is increased to 80 m 3 / h.

[0113] In the above-described liquid circulation system 10, during maintenance of the second ion exchange device 34, primary pure water is introduced into the first ion exchange resin treatment section 102 to wash the ion exchange resin, and the washed liquid is discharged into the discharge path 110A. At the same time, the primary pure water that has passed through the second ion exchange resin treatment section 104 is supplied to the ultrafiltration device 36. At that time, the booster pump 32 is controlled in accordance with the flow rate of ultrapure water detected by a flow rate detector 42 between the most downstream ultrafiltration device 36 and the point of use 50 in the supply piping 62. For example, when the flow rate of ultrapure water detected by the flow rate detector 42 is 80 m 3 / h. As a result, the booster pump 32 is controlled by the flow detector 42 and the regulating valve 68 is controlled by the pressure detector 66, so that the operating flow rate of ultrapure water in the liquid circulation system 10 can be stabilized. Therefore, in the liquid circulation system 10, even if the amount of ultrapure water used at the point of use 50 is changed and the ion exchange resin in the first ion exchange resin treatment section 102 is cleaned at the same time, the flow rate of ultrapure water supplied to the point of use 50 and the pressure at the point of use 50 can be kept almost constant.

[0114] [Second example of maintenance in the liquid circulation system of the first comparative example] Next, a second example of the maintenance of the liquid circulation system 300 of the first comparative example will be described.

[0115] 13 shows an example of maintenance of the second ion exchange device 34 in the liquid circulation system 300 of the first comparative example when there is no change in the amount of ultrapure water used at the point of use 50 (when ultrapure water is not used). As shown in Fig. 13, when the ion exchange resin in the first ion exchange resin treatment section 102 is washed, the washing flow rate discharged to the discharge path 110A increases. This increase in the washing flow rate is compensated for by increasing the frequency of the power source 46 that supplies power to the booster pump 32.

[0116] FIG. 14 shows a case where the amount of ultrapure water used at the point of use 50 is changed (for example, when 50 ml of ultrapure water is used) in the liquid circulation system 300 of the first comparative example. 3 14 shows an example of maintenance of the second ion exchange device 34 in a liquid circulation system 300 (when the amount of ultrapure water used at the point of use 50 is changed and the ion exchange resin in the first ion exchange resin treatment section 102 is washed at the same time). As shown in Fig. 14, in the liquid circulation system 300, when the amount of ultrapure water used at the point of use 50 is changed and the ion exchange resin in the first ion exchange resin treatment section 102 is washed at the same time, it is necessary to control the booster pump 32 by the second pressure detector 310 and the regulating valve 68 by the third pressure detector 312. In this case, since there are two automatic pressure controls in the same system, fluctuations in the flow rate and pressure of ultrapure water cannot be predicted, and the operating state of the liquid circulation system 300 becomes even more unstable.

[0117] In contrast, in the liquid circulation system 10 of the first embodiment, the booster pump 32 is controlled according to the flow rate of ultrapure water detected by a flow rate detector 42 between the ultrafiltration device 36 at the most downstream position in the supply piping 62 and the point of use 50. This results in two controls: control of the booster pump 32 by the flow rate detector 42, and control of the regulating valve 68 by the pressure detector 66. Therefore, in the liquid circulation system 10, even if the amount of ultrapure water used at the point of use 50 is changed and the ion exchange resin in the first ion exchange resin treatment section 102 is washed at the same time, the flow rate of ultrapure water supplied to the point of use 50 and the pressure at the point of use 50 can be kept approximately constant.

[0118] [others] Instead of the configuration of the liquid circulation system 10 of the first embodiment, the position of the pressure detector 66 may be changed under the following conditions. The pressure detector 66 is located on the side of the return pipe 64 closer to the point of use 50 than the pure water tank 16, and when comparing the differential pressure when the flow rate of the ultrapure water in the return pipe 64 is maximum and minimum, the differential pressure is 9.8 kPa (i.e., 0.1 kgf / cm 2 ), and the pressure difference is preferably within 4.9 kPa (i.e., 0.05 kgf / cm 2 It is more preferable that the pressure difference is within 2.94 kPa (i.e., 0.03 kgf / cm 2 ) or less.

[0119] For example, the pressure detector 66 is located on the side of the return pipe 64 closer to the use point 50 than the pure water tank 16, and detects that the differential pressure between the maximum and minimum flow rates of the ultrapure water in the return pipe 64 is 9.8 kPa (i.e., 0.1 kgf / cm 2 ), even if the flow rate of ultrapure water in the return pipe 64 decreases, it is less likely to be affected by a decrease in pressure loss. Therefore, the pressure inside the return pipe 64 can be appropriately adjusted by the adjustment valve 68 in accordance with the pressure detected by the pressure detector 66.

[0120] In a configuration in which a plurality of branch points to the use point 50 are provided in the circulation path 60, the pressure detector 66 is located closer to the final stage of the branch to the use point than the pure water tank 16 in the return piping, and when comparing the differential pressure when the liquid flow rate in the return piping is maximum and minimum, the differential pressure is 9.8 kPa (i.e., 0.1 kgf / cm 2 ) or less.

[0121] Although the present disclosure has been described in detail with respect to a specific embodiment, the present disclosure is not limited to such embodiment, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present disclosure.

[0122] [Preferred embodiment of the present disclosure] Preferred aspects of the present disclosure will be described below.

[0123] [Additional note 1] A tank for storing liquid; A plurality of processing units each performing a different process on the liquid supplied from the tank; a circulation path including a supply pipe that supplies the liquid in the tank to a use point that is a supply destination via the multiple processing units, and a return pipe that returns the liquid from the use point to the tank; a first pump provided in the supply pipe between the plurality of processing sections and configured to supply liquid to the point of use; A first pressure detection unit provided in the return pipe and detecting a pressure inside the return pipe; a regulator valve provided downstream of the first pressure detection unit in the return pipe and regulating the pressure inside the return pipe in response to the pressure detected by the first pressure detection unit; a flow rate detection unit that is provided between the use point and a most downstream processing unit among the plurality of processing units in the supply pipe and detects a flow rate of liquid inside the supply pipe; a first pump control unit that controls the first pump in accordance with the flow rate detected by the flow rate detection unit so that the liquid flowing through the supply pipe is at a predetermined flow rate; A liquid circulation system having

[0124] [Additional note 2] a second pump provided on the supply pipe downstream of the tank and configured to supply the liquid in the tank to a side of the processing units; a second pressure detection unit provided on the supply pipe upstream of the first pump and configured to detect a pressure inside the supply pipe; a second pump control unit that controls the second pump in response to the pressure detected by the second pressure detection unit so that the pressure inside the supply pipe becomes a predetermined pressure; The liquid circulation system according to claim 1, comprising:

[0125] [Additional note 3] The liquid circulation system according to claim 1 or 2, wherein the first pressure detection unit is provided at a location from the final stage of the return piping where the return piping branches off to the use point to less than 20% of the length of the return piping between the final stage and the tank.

[0126] [Additional note 4] The liquid circulation system according to claim 1 or 2, wherein the first pressure detection unit is provided on a side of the return piping closer to the final stage of the branch with the use point than the tank, and at a location where the pressure difference is within 9.8 kPa when comparing the pressure difference when the flow rate of the liquid in the return piping is maximum and minimum.

[0127] [Additional note 5] 5. The liquid circulation system according to claim 1, wherein the first pump is a booster pump that pressurizes the supply pipe to compensate for a pressure deficiency and supplies the liquid.

[0128] [Additional note 6] The plurality of processing units include A filtration device that constitutes the most downstream processing section and is equipped with an ultrafiltration membrane; an ion exchange device provided immediately upstream of the filtration device and equipped with an ion exchange resin; The ion exchange device is connected in parallel to the supply piping, and has two or more ion exchange resin treatment sections into which liquid is introduced and into which liquid is discharged, respectively.

[0129] [Additional note 7] The liquid circulation system according to claim 6, wherein, during maintenance of the ion exchange device, one of the ion exchange resin treatment sections is stopped and the liquid that has passed through the other ion exchange resin treatment section is supplied to the filtration device.

[0130] [Additional note 8] During maintenance of the ion exchange device, A liquid is introduced into one of the ion exchange resin treatment sections to wash the ion exchange resin, and the washed liquid is discharged to a discharge path other than the supply pipe; 7. The liquid circulation system according to claim 6, wherein the liquid is introduced into another of the ion exchange resin treatment sections, and the liquid that has passed through the other of the ion exchange resin treatment sections is supplied to the filtration device. [Explanation of symbols]

[0131] 10 Liquid Circulation System 16 Pure water tank (tank) 20 Secondary water purification device 22 Circulation pump (second pump) 24 Heat exchanger (multiple processing sections) 26 UV irradiation device (multiple processing sections) 28 First ion exchange device (multiple processing sections) 30 Membrane degassing device (multiple treatment sections) 32 Booster pump (first pump) 32 Return piping 34 Second ion exchange device (multiple processing sections) 36 Ultrafiltration membrane (filtration device, downstream processing section) 40 Pressure detector (second pressure detector) 42 Flow detector (flow detector) 50 Use Points 60 Circulation Route 62 Supply piping 64 Return piping 66 Pressure detection unit 66 Pressure detector (first pressure detector) 68 Regulating valve 80 control device (first pump control unit, second pump control unit) 102 First ion exchange resin treatment section (ion exchange resin treatment section) 104 Second ion exchange resin treatment section (ion exchange resin treatment section)

Claims

1. A tank for storing liquid; A plurality of processing units each performing a different process on the liquid supplied from the tank; a circulation path including a supply pipe that supplies the liquid in the tank to a use point that is a supply destination via the plurality of processing units, and a return pipe that returns the liquid from the use point to the tank; a first pump provided in the supply pipe between the plurality of processing sections and configured to supply liquid to the point of use; A first pressure detection unit provided in the return pipe and detecting a pressure inside the return pipe; a regulator valve provided downstream of the first pressure detection unit in the return pipe and regulating the pressure inside the return pipe in response to the pressure detected by the first pressure detection unit; a flow rate detection unit that is provided between the use point and a most downstream processing unit among the plurality of processing units in the supply pipe and detects a flow rate of liquid inside the supply pipe; a first pump control unit that controls the first pump in response to the flow rate detected by the flow rate detection unit so that the liquid flowing through the supply pipe is at a predetermined flow rate; A liquid circulation system having

2. a second pump provided on the supply pipe downstream of the tank and configured to supply the liquid in the tank to a side of the processing units; a second pressure detection unit provided on the supply pipe upstream of the first pump and configured to detect a pressure inside the supply pipe; a second pump control unit that controls the second pump in response to the pressure detected by the second pressure detection unit so that the pressure inside the supply pipe becomes a predetermined pressure; 2. The liquid circulation system of claim 1, comprising:

3. 2. The liquid circulation system according to claim 1, wherein the first pressure detection unit is provided at a location less than 20% of the length of the return piping between the final stage of the branch to the use point in the return piping and the tank.

4. 2. The liquid circulation system according to claim 1, wherein the first pressure detection unit is provided on a side of the return piping closer to the final stage of the branch with the use point than the tank, and at a location where the differential pressure is within 9.8 kPa when comparing the differential pressure when the liquid flow rate in the return piping is maximum and minimum.

5. 2. The liquid circulation system according to claim 1, wherein the first pump is a booster pump that pressurizes the supply pipe to compensate for a pressure deficiency and supplies the liquid.

6. The plurality of processing units include A filtration device that constitutes the most downstream processing section and is equipped with an ultrafiltration membrane; an ion exchange device provided immediately upstream of the filtration device and equipped with an ion exchange resin; 2. The liquid circulation system according to claim 1, wherein the ion exchange device has two or more ion exchange resin treatment sections connected in parallel to the supply pipe, the two or more treatment sections receiving and discharging the liquid, respectively.

7. The liquid circulation system according to claim 6, wherein, during maintenance of the ion exchange device, one of the ion exchange resin treatment sections is stopped and liquid that has passed through the other ion exchange resin treatment section is supplied to the filtration device.

8. During maintenance of the ion exchange device, A liquid is introduced into one of the ion exchange resin treatment sections to wash the ion exchange resin, and the washed liquid is discharged to a discharge path other than the supply pipe; 7. The liquid circulation system according to claim 6, wherein the liquid is introduced into another of the ion exchange resin treatment sections, and the liquid that has passed through the other of the ion exchange resin treatment sections is supplied to the filtering device.

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