JP7204597B2 - Ultrapure water production system and ultrapure water production method - Google Patents

Description

The present invention relates to an ultrapure water production system and an ultrapure water production method that produce ultrapure water while circulating the ultrapure water with a tank that stores ultrapure water and supply the ultrapure water to the tank. .

Ultrapure water is used in various applications, and depending on the application, it is necessary to store ultrapure water in a large tank. An example of such an application is the use of ultrapure water as a medium of physical measurement while stored in a tank. Ultrapure water stored in a tank generally becomes impure gradually. Therefore, the ultrapure water production system, which produces ultrapure water by an ultrapure water production system and stores this ultrapure water in a tank, has the function of recovering and repurifying the ultrapure water from the tank, which is the point of use. is required. Patent Document 1 shows an example of an ultrapure water production system in which ultrapure water collected from a point of use is added to primary pure water, and then subjected to various purification processes to produce ultrapure water and supply the ultrapure water to the point of use. there is

JP 2009-106831 A

If the top surface of the tank is open to the atmosphere due to reasons such as when the tank is not full, contamination of the ultrapure water stored in the tank with impurities can be caused by the ultrapure water near the liquid surface. becomes particularly noticeable in Therefore, when ultrapure water is recovered from a tank, which is a point of use, and repurified, it is desirable to preferentially recover ultrapure water near the liquid surface. In addition, even when ultrapure water is supplied to a tank that is almost empty and the ultrapure water is stored in the tank, the ultrapure water near the liquid level in the tank is circulated to the ultrapure water production device for repurification. By doing so, the overall water quality of the ultrapure water stored in the tank (for example, water quality represented by specific resistance) can reach the specified value more quickly. When the capacity of the tank is about 100 tons or 200 tons, a pump provided outside the tank can easily circulate ultrapure water from the tank to the ultrapure water production apparatus. However, when the capacity of the tank increases to, for example, several tens of thousands of tons, and the height of the tank increases accordingly, due to limitations such as the suction capacity of the pump, i. Therefore, it becomes difficult to circulate the ultrapure water, especially the ultrapure water near the liquid surface, to the ultrapure water production apparatus side. As a result, it takes a long time for the quality of the ultrapure water stored in the tank to reach the specified value.

An object of the present invention is an ultrapure water production system and method used to store ultrapure water in a large tank while circulating ultrapure water in this tank, wherein the ultrapure water is stored in the tank. An object of the present invention is to provide an ultrapure water production system and method capable of shortening the time required for pure water to reach a specified value.

The ultrapure water production system of the present invention includes an ultrapure water production apparatus for producing ultrapure water and a tank for storing the ultrapure water produced by the ultrapure water production apparatus. In an ultrapure water production system that recovers at least part of water and circulates it to an ultrapure water production device, a pump for recovering ultrapure water from a tank and a suction position of the ultrapure water in the pump are stored in the tank It is characterized by having a variable mechanism that changes according to the position of the liquid surface of the ultrapure water.

In the ultrapure water production method of the present invention, ultrapure water produced by an ultrapure water production apparatus is supplied to a tank for storage, and at least part of the ultrapure water stored in the tank is recovered to obtain ultrapure water. In a method for producing ultrapure water that circulates in a production apparatus, the ultrapure water suction position of a pump for recovering ultrapure water from the tank is changed according to the position of the liquid surface of the ultrapure water stored in the tank. It is characterized by

According to the present invention, ultrapure water is produced using an ultrapure water production apparatus, stored in a large tank, and at least part of the ultrapure water stored in the tank is circulated through the ultrapure water production apparatus. By changing the position of the ultrapure water suction by the pump according to the position of the ultrapure water level in the tank, the time required to reach the specified value for the quality of the ultrapure water stored in the tank is shortened. can do.

1 is a flow sheet showing the configuration of an ultrapure water production system according to an embodiment of the present invention; It is a flow sheet which shows the structure of water supply equipment. FIG. 4 shows an arrangement for varying the position of the pump within the tank;

Preferred embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an ultrapure water production system according to one embodiment of the present invention. The ultrapure water production system shown in FIG. and an ultrapure water production device 20 for repurifying the ultrapure water by circulating at least part of the ultrapure water stored in. Furthermore, ultrapure water is supplied to this ultrapure water production system from a water supply facility 40 provided outside in order to make up for the shortage of ultrapure water in the ultrapure water production system. . Even when the tank 10 is newly charged with ultrapure water, the ultrapure water from the water supply equipment 40 is used. Assuming that the capacity of the tank 10 is 50,000 tons, the height of the tank 10 will be, for example, 40 m, and the level of the liquid level L will differ by 40 m between when the tank 10 is empty and when it is full. . The suction lift of a normal pump is at most several meters, and it is impossible to pump up ultrapure water from the inside of the tank 10 by the pump provided above the tank 10 when the tank 10 is not full or nearly full. The height of the tank is the distance from the bottom of the tank to the liquid surface when the tank is full.

The ultrapure water production system 20 includes a subtank 21 that temporarily stores circulating ultrapure water, a pump 22 that feeds the ultrapure water stored in the subtank 21, and ultraviolet rays to remove organic matter in the water. An ultraviolet (UV) oxidation device 23 that decomposes and oxidizes, a heat exchanger 35 that cools ultrapure water to a desired temperature or temperature range, and an ion exchange device that is filled with ion exchange resin and removes ion components in water. (IER) 24, a filter (F) 25, an ultraviolet (UV) sterilization device 26 for sterilizing fungi contained in water, and an ultrafiltration device (UF) 27 having an ultrafiltration membrane. . To the secondary or outlet of the pump 22 are connected in series a UV oxidation device 23, a heat exchanger 35, an ion exchange device 24, a filter 25, a UV disinfector 26 and an ultrafiltration device 27, in that order. Circulating purified ultrapure water is obtained from the outlet of the ultrafiltration device 27 , and this ultrapure water is temporarily stored in the subtank 28 . The ultrapure water stored in the sub-tank 28 is supplied to the tank 10 via a pipe 41 via a pump 29 and a heat exchanger 30 . The heat exchanger 30 is for cooling the ultrapure water, whose temperature has risen in the course of flowing through pipes, to a desired temperature or temperature range. The pump 29 and the heat exchanger 30 also constitute the ultrapure water production device 20 . The configuration of the ultrapure water production apparatus 20 shown here is one of the configurations generally used in the production of ultrapure water by circulation purification.

A pipe 41 for supplying ultrapure water from the ultrapure water production apparatus 20 to the tank 10 includes a valve V2, a membrane deaerator (MD) 42, and a heat exchanger for cooling ultrapure water from the ultrapure water production apparatus 20 side. 43 are provided in series in this order, and a pipe 45 extending from the top of the tank 10 toward the bottom of the tank 10 is connected to the outlet of the heat exchanger 43 . The ultrapure water that has flowed out of the heat exchanger 43 is supplied into the tank 10 from the bottom side of the tank 10 via the pipe 45 . The reason why the heat exchanger 43 is provided here is to maintain the ultrapure water in the tank 10 at a relatively low temperature, eg, 13.5°C to 13.8°C. In the example shown here, in addition to the heat exchanger 43, the ultrapure water production apparatus 20 is provided with the heat exchangers 30 and 35 as described above so as to improve the accuracy of temperature control of the ultrapure water supplied to the tank 10. I have to. Ultrapure water supplied from the water supply system 40 is injected into the pipe 41 via the valve V1 at a position between the valve V2 and the membrane deaerator . Therefore, the ultrapure water from the water supply system 40 is supplied to the tank 10 via the membrane degassing device 42 and the heat exchanger 43 without passing through the ultrapure water production device 20 .

FIG. 2 shows the configuration of the water supply facility 40. As shown in FIG. The water supply facility 40 produces ultrapure water from supply water such as tap water, city water, well water, and spring water. It has a sub-tank 82 that temporarily stores the supply water treated by the reverse osmosis device 81 and a pump 83 that feeds the supply water in the sub-tank 82 . A safety filter (not shown) is provided at the front stage of the reverse osmosis device 81 . At the outlet of the pump 83, a heat exchanger 84, an ion exchange device 85 for removing ion components in water, and an ultraviolet sterilization device 86 for sterilizing fungi contained in water are connected in series in this order. Outlet water of device 86 is temporarily stored in sub-tank 87 . A pump 88 is connected to the sub-tank 87, and a reverse osmosis device 89, a heat exchanger 90, a vacuum degassing device (VD) 91 for removing dissolved gas, and a pump 92 are connected in this order to the outlet of the pump 88. are connected in series with A non-regenerative ion exchange device (CP; cartridge polisher) 93 for removing ion components in water and an ultrafiltration device 94 are connected in series in this order to the outlet of the pump 92 . Outlet water of the ultrafiltration device 94 is supplied as ultrapure water from the water supply system 40 toward the valve V1. The heat exchangers 84, 90 cool the passing water so that the tank 10 can be supplied with ultrapure water having a constant water temperature within the desired range.

As shown in FIG. 1, the ultrapure water production system of the present embodiment further electrically drives the pump 50 and the pump 50 to return the ultrapure water in the tank 10 to the ultrapure water production device 20. It has an inverter unit (INV) 51 to be controlled, a pipe 52, a booster pump 53 connected to the pipe 52, and a pipe 54 connecting the secondary side of the booster pump 53 and the ultrapure water production apparatus 20. . In this embodiment, the pump 50 is arranged inside the tank 10 and is provided so that the pump 50 is positioned in the ultrapure water stored in the tank 10 when the pump 50 is in operation. The ultrapure water sucked by the pump 50 is supplied to the booster pump 53 through the pipe 52 . Pump 50 is placed in ultrapure water stored in tank 10 , but booster pump 53 is provided outside tank 10 . The inverter unit 51 and the pump 50 are electrically connected by a wiring cable 55 , and the pump 50 is configured to feed water at a constant pressure by the inverter unit 51 . As long as the pump 50 is provided in water, a portion of the distribution cable 55 is also submerged in water, so that the distribution cable 55 should be water resistant. The reason why the booster pump 53 is provided in the present embodiment is that the pump 50 provided in the water in the tank 10 alone does not provide enough pressure to send the ultrapure water from the tank 10 to the ultrapure water production apparatus 20, and as a result, the tank 10 to the ultrapure water production apparatus 20 may drop and the specified value of the circulation flow rate to the ultrapure water production apparatus 20 may not be met. This is to pressurize the water and send it to the ultrapure water production device 20 .

The ultrapure water production apparatus 20 is provided with a circulation pipe 32 for circulating ultrapure water to the sub-tank 21, and a pipe 54 from the tank 10 side is connected to the circulation pipe 32 via a valve V3. Connected. In the circulation pipe 32 , a filter (F) 33 for removing fine particles and the like contained in the circulating ultrapure water is provided immediately before the ultrapure water introduction position to the sub-tank 21 . Furthermore, in order to enable circulation of ultrapure water inside the ultrapure water production apparatus 20, a pipe 31 branching from the outlet of the heat exchanger 30 is provided. It is connected to the circulation pipe 32 at a position between the valve V3 and the filter 33 in the circulation pipe 32 .

With the configuration described above, a path for circulating ultrapure water is formed between the tank 10 and the ultrapure water production apparatus 20. By opening the valves V2 and V3 and closing the valve V4, the tank 10 and the ultrapure water production device 20, and the circulating ultrapure water is repurified by the ultrapure water production device 20, so that the water quality of the ultrapure water stored in the tank 10 gradually increases. will improve. When ultrapure water is not supplied to the tank 10 for maintenance of the tank 10 or the like, the valves V1, V2 and V3 are closed and the valve V4 is opened to supply ultrapure water inside the ultrapure water production apparatus 20. It can be circulated, and the quality of the ultrapure water produced by the ultrapure water production device 20 can be maintained.

In the above description, the ultrapure water from the water supply facility 40 is directly supplied to the tank 10 via the valve V1 and the pipe 41. , for example, the sub-tank 21 or the sub-tank 28 .

The ultrapure water returned from the tank 10 to the ultrapure water production apparatus 20 is preferably ultrapure water in the vicinity of the liquid surface L in the tank 10 . On the other hand, when ultrapure water is being supplied from the water supply equipment 40 to the tank 10, the liquid level L of ultrapure water in the tank 10 gradually rises. When the ultrapure water is drained from the tank 10 for some reason, the liquid level L gradually drops. Therefore, in the present embodiment, the position of the pump 50 in the tank 10 can be raised and lowered as the liquid level L in the tank 10 rises and falls. The suction position is variable. FIG. 3 shows an example of a configuration for raising and lowering the position of the pump 50 provided underwater in the tank 10. As shown in FIG.

A sturdy top plate 11 is provided on the upper surface of the tank 10.例文帳に追加The inverter unit 51 is provided on the top plate 11, for example. An end of the pipe 52 connected to the booster pump 53 extends to a position above the top plate 11 . In this embodiment, the pump 50 and the end of the pipe 52 are connected by connecting one or more pipe members 61 in series, and the ultrapure water sucked from the suction port 56 of the pump 50 flows into the pipe member. 61 to pipe 52 . The pipe members 61 connected in series extend vertically as a link of pipe members 61 . The pump 50 is placed in the ultrapure water stored in the tank 10 , preferably in the vicinity of the liquid surface L of the tank 10 . The vicinity of the liquid surface L of the ultrapure water in the tank 10 is, for example, a first position where only the suction port 56 of the pump 50 is submerged in the ultrapure water in the tank 10. The second position is the position where the pump 10 is submerged in the ultrapure water so that the upper end position is on the same horizontal plane as the liquid level L of the ultrapure water in the tank 10. The range up to the position of The height of the liquid level L changes according to the amount of ultrapure water stored in the tank 10, and the distance from the top plate 11 to the liquid level L also changes. Therefore, in the present embodiment, the distance between the pump 50 and the top plate 11 can be changed by increasing or decreasing the number of pipe members 61 connecting the pump 50 and the ends of the pipes 52 .

The pipe member 61 is a pipe having a certain length, for example, several tens of cm to 2 m, provided with flanges at both ends, and is configured to be detachably connected in series with each other. A fixing device 62 for fixing the pipe member 61 is provided on the upper surface of the top plate 11 so that the pipe member 61 does not fall from the top plate 11 into the tank 10 . If the distance between the top plate 11 and the pump 50 changes, the length of the portion of the wiring cable 55 located inside the tank 10 also changes. Therefore, a storage device 63 for storing the wiring cable 55 is also provided on the upper surface of the top plate 11 . In the drawing, a spare pipe member 61 is also drawn on top plate 11 .

The procedure for raising or lowering the position of the pump 50 in the tank 10 is as follows. First, if the pump 50 is operating, the pump 50 is stopped. If the position of the pump 50 is to be raised as the liquid level L rises, the connecting body of the pipe member 61 is lifted upward from the fixing device 62, the connecting body is removed from the end of the pipe 52, and then the pump 50 is The number of pipe members 61 corresponding to the distance to be raised is removed from the upper end side of the connecting body. Then, the end of the pipe 52 is attached to the new upper end of the connector, and the upper end of the connector is fixed to the fixing device 62 . In accordance with this, the loose portion of the wiring cable is stored in the storage device 63. - 特許庁After that, the pump 50 is restarted. When the liquid level L in the tank 10 is lowered due to reasons such as draining the ultrapure water in the tank 10, the required number of pipe members 61 are removed instead of removing the pipe members 61 from the connecting body in the above procedure. The upper end of the connecting body is further connected, and the distribution cable 55 of the required length is pulled out from the storage device 63 .

According to the present embodiment, the ultrapure water in the tank 10 cannot be sent to the ultrapure water production apparatus 20 side because the distance to the liquid surface L is long and the suction capacity of a normal pump provided outside the tank 10 is limited. Even if it is not possible, by arranging the pump 50 so as to be submerged in the ultrapure water in the tank 10, the ultrapure water in the tank 10, especially the liquid Ultrapure water in the vicinity of the plane L can now be sent to the Zhao pure water production apparatus 20 side. In the case of a general pump arranged outside the tank, the practical suction lift is about 2 m. Especially effective. Since the ultrapure water near the liquid surface L tends to contain impurities, according to the present embodiment, the ultrapure water that seems to contain a large amount of impurities can be preferentially sent to the ultrapure water production apparatus 20. , the quality of the ultrapure water in the tank 10 can be rapidly increased.

Using the ultrapure water production system shown in FIGS. 1, 2 and 3, for the tank 10 having a capacity of 50,000 tons, the target water quality of the ultrapure water in the tank 10 is expressed as a specific resistance of 5 MΩ cm. As described above, ultrapure water is circulated between the tank 10 and the ultrapure water production apparatus 20 while supplying ultrapure water from the water supply equipment 40 so that the tank 10 is filled from an empty state, and the tank 10 is filled with ultrapure water. The quality of the ultrapure water was improved. The circulation amount to the ultrapure water production device 20 is 60 m ³ /h, the ultrapure water quality at the outlet of the ultrapure water production device 20 is 17.5 MΩ·cm or more, and the average water temperature is 13.5°C. Met. Since the inside of the tank 10 is open to the atmosphere when the ultrapure water is being charged into the tank 10, the water quality of the ultrapure water near the liquid surface L in the tank 10 is from 1 MΩ·cm to 3 MΩ·cm. It was about As described above, the position of the pump 50 in the tank 10 is raised along with the rise of the liquid level L, and when the ultrapure water near the liquid level L is preferentially fed to the ultrapure water production apparatus 20 by the pump 10, the tank When the tank 10 was filled with water, the quality of the ultrapure water in the tank 10 was 7 MΩ·cm, exceeding the target water quality.

On the other hand, without using the pump arranged in the water in the tank 10, the ultrapure water in the tank 10 is produced by using the pump provided outside the tank 10 to suck up the ultrapure water from the tank 10. In the case of a configuration in which water is sent to the device 20, the ultrapure water cannot be sent to the ultrapure water production device 20 until the liquid level L is nearly full. In such a configuration, when the same ultrapure water production apparatus 20 is used for the same tank 10 and the ultrapure water is charged into the tank 10, the ultrapure water in the tank 10 when the tank 10 is full The water quality was 2.5 MΩ·cm. After the tank 10 is full, the pump is operated to circulate the ultrapure water in the vicinity of the liquid level L to the ultrapure water production device 20. Two months after the tank is full, the quality of the ultrapure water in the tank 10 is finally changed. It reached 7 MΩ·cm.

10 Tank 11 Top Plate 20 Ultrapure Water Production Device 21, 28, 82, 87 Sub Tank 22, 29, 50, 83, 88, 92 Pump 23 Ultraviolet Oxidation Device 24, 85 Ion Exchange Device 25, 33 Filter 26, 86 Ultraviolet Sterilization Device 27, 94 Ultrafiltration device 31, 41, 45, 52, 54 Piping 32 Circulation pipe 40 Water supply equipment 30, 35, 43, 84, 90 Heat exchanger 42 Membrane degassing device 51 Inverter unit 53 Booster pump 55 Wiring cable 56 suction port 61 pipe member 62 fixing device 63 storage device 81, 89 reverse osmosis device 91 vacuum degassing device 93 non-regenerative ion exchange device L liquid level V1 to V4 valve

Claims (7)

An ultrapure water production apparatus for producing ultrapure water, and a tank for storing the ultrapure water produced by the ultrapure water production apparatus, wherein at least part of the ultrapure water stored in the tank is recovered. In the ultrapure water production system that circulates to the ultrapure water production device,
a pump for recovering ultrapure water from the tank;
An ultrapure water system, comprising: a variable mechanism for varying a suction position of the ultrapure water in the pump according to a position of a liquid surface of the ultrapure water stored in the tank. The pump is arranged to be submerged in ultrapure water stored in the tank,
2. The ultrapure water production system according to claim 1, wherein said variable mechanism varies a length in said tank of a conduit for supplying ultrapure water from said pump to said ultrapure water production apparatus. 3. The ultrapure water production system according to claim 2, wherein said pipeline in said tank is configured by one or more detachable pipe members connected in series. The ultrapure water production system according to any one of claims 1 to 3, wherein the tank has a height of 2 m or more. Further comprising a booster pump provided outside the tank,
The pump sends ultrapure water to the booster pump,
5. The ultrapure water production system according to any one of claims 1 to 4, wherein said booster pump supplies ultrapure water sent from said pump to said ultrapure water production apparatus. Ultrapure water that supplies ultrapure water produced by an ultrapure water production apparatus to a tank and stores it, collects at least part of the ultrapure water stored in the tank, and circulates the ultrapure water in the ultrapure water production apparatus In the manufacturing method,
A method for producing ultrapure water, characterized by changing a suction position of ultrapure water in a pump for recovering ultrapure water from the tank according to the position of the liquid surface of the ultrapure water stored in the tank. . 7. The ultrapure water production method according to claim 6, wherein said pump is arranged so as to be submerged in ultrapure water stored in said tank.

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