JP2929690B2 - Deoxidizer for pure water production equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deoxidizer for a pure water producing apparatus, and more particularly to pure water for removing dissolved oxygen in treated water by passing nitrogen gas through the treated water. The present invention relates to a deoxidizer for a manufacturing apparatus.

[Conventional technology]

In recent years, in the process of manufacturing semiconductors such as ICs and LSIs, pure water has been used to clean the semiconductors. With respect to the pure water, the demand for the quality of the water is becoming stricter as the degree of integration of the semiconductor is increased.

Conventionally, a vacuum deaerator has been used as an apparatus for producing the pure water.

The vacuum deaerator is a device that removes dissolved oxygen in the water to be treated by spraying the water to be treated into a deaeration tower whose inside is evacuated by a steam ejector or a water ring pump.

However, in order to satisfy the above-mentioned required water quality, the vacuum deaerator needs to have a height of the deaeration tower of 10 m or more. The deaeration tower of such a height must be installed outdoors, and therefore the length of the pipe from the pure water production equipment installed indoors to the deaeration tower becomes longer, which causes the pipe to lose organic matter, etc. Is eluted or bacteria are generated in the piping, so that high-quality pure water cannot be obtained.

Further, the vacuum deaerator has a drawback that the deaeration performance is low. That is, even if many steam ejectors and water seal pumps are installed in the vacuum degassing tower and all these are operated, the DO (oxygen content) value in the treated water can be reduced only to about 50 to 100 ppb. Can not. Recently, it has been found that the DO value must be 10 ppb or less so that dissolved oxygen in pure water does not adversely affect the semiconductor. Therefore, there is a drawback that pure water produced by a vacuum degassing tower cannot be used for cleaning semiconductors.

Therefore, as a deoxidizer for producing such high-quality pure water, there is a deoxidizer using nitrogen gas.

The deoxygenation apparatus using nitrogen gas blows nitrogen gas from the bottom of the tank in which the water to be treated is stored through a diffuser plate to allow bubbles of the nitrogen gas to flow through the water to be treated, thereby dissolving the water in the water to be treated. In some cases, oxygen is taken into bubbles and removed.

FIG. 10 shows an embodiment of a deoxygenating apparatus using the nitrogen gas.

The treated water 12 is stored in the storage tank 10, and the storage tank 10
A nitrogen gas blowing device 14 is attached near the bottom of the device. A diffuser plate 16 is laid on the upper surface of the nitrogen gas blowing device 14, and the diffuser plate 16 blows nitrogen gas sent through a valve 18 and a duct 20 into the water to be treated in a bubble form. Can be.

A treated water feed pipe 22 is attached above the diffuser plate 16, and the treated water fed to the lower surface of the treated water feed pipe 22 is blown out toward the diffuser plate 16. Outlet
Are formed. Therefore, the outlets 22a, 22a
Is mixed with nitrogen gas blown out from the diffuser plate 16 in a bubble form, and dissolved oxygen in the water to be treated is taken in the bubbles of the nitrogen gas. And evaporates in the direction of the arrow, and is exhausted to the outside from the ceiling surface exhaust port 24 of the storage tank 10. The treated water from which dissolved oxygen has been removed in this way flows in from the opening 26a of the trough 26 attached near the water surface of the storage tank 10, and the side opening 2a of the storage tank 10
It is sent to a pure water removal device (not shown) via 8.

Specifically, when nitrogen gas having a purity of 99.9995% or more is passed through the water to be treated having a dissolved oxygen concentration of 8 to 9 mg /, the oxygen concentration of the treated water after deoxygenation is reduced to about 0.5 mg /.
As a result, the DO value can be reduced to 10 ppb or less, which is the required quality of pure water.

By the way, the principle of the deoxygenation device using nitrogen gas is based on the solubility of gas in water (Henry's lane shown in FIG. 11).
As is clear from the illustration in w), the purity of nitrogen gas is 99.
If the concentration is 99% or more, the dissolved oxygen in the water to be treated is sufficiently 10ppb
It can be:

[Problems to be solved by the invention]

However, when the volume of nitrogen gas (hereinafter referred to as a gas-liquid ratio) with respect to the volume of the water to be treated stored in the storage tank is reduced, the conventional deoxygenating apparatus has the required water quality of 10 ppb.
The following cannot be achieved: Therefore, in order to satisfy the above 10 ppb or less, a large amount of nitrogen gas must be blown out, which has a disadvantage that the running cost of the deoxidizer increases.

Further, if the number of the degassing towers is increased, the DO value of the water to be treated is decreased, but the total amount of nitrogen gas blown out increases as the number of the degassing towers is increased, so that the initial cost of the deoxygenating apparatus is increased. There are drawbacks.

The present invention has been made in view of such circumstances, and provides a deoxygenation apparatus of a pure water production apparatus capable of efficiently using nitrogen gas to reduce running costs and initial costs in the deoxygenation apparatus. The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a deionized water purification apparatus for removing dissolved oxygen in the water to be treated by blowing nitrogen gas from the bottom of the tank in which the water to be treated is stored and passing the gas through the water to be treated. In the oxygen device, a plurality of the tanks (30, 32) are provided so that the water to be treated is sequentially communicated so that the water to be treated can flow therethrough, and the nitrogen gas is supplied through the water to be treated stored in the downstream tank (32). Are sequentially connected so that they can be supplied to the adjacent upstream tank (30).

[Action]

According to the present invention, a nitrogen gas is blown into a downstream tank (32) to aerate a plurality of tanks (30, 32) in which the water to be treated is sequentially communicated so that the water to flow can flow the water to be treated. Is collected and supplied to the upstream tank (30) adjacent to the downstream tank (32), and this nitrogen gas is collected and supplied to the adjacent upstream tank sequentially. In this way, the tanks (30, 3) are supplied so that nitrogen gas is sequentially supplied from the downstream tank (32) to the upstream tank.
Since 2) is connected, even if the number of installed tanks increases, nitrogen gas can be efficiently used to contribute to deoxygenation of the water to be treated.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a deoxidizer for a pure water production apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of a deoxidizer of a pure water production apparatus according to the present invention.

In FIG. 1, the deaeration tower 30 on the right side in the figure is installed on the upstream side in the flow direction of the water to be treated, and the deaeration tower 32 on the left side in the figure is installed on the downstream side.

In the degassing tower 30, partition plates 34, 36, 38 are installed at equal intervals. The partition plate 34 has a communication port 34 near its water surface.
a is formed, and the partition plate 36 is formed with a communication port 36a near the bottom. A communication port 38a is formed in the partition plate 38 near the water surface. Further, an inlet 40 is formed near the right bottom portion of the degassing tower 30 in the drawing, and an outlet 42 is formed near the left bottom portion in the drawing.

The inflow port 40 is communicated with a treated water storage tank 104 via a water distribution pipe 100 and a water supply pump 102, and the treated water 106 stored in the treated water storage tank 104 is operated by operating the water supply pump 102. The water is supplied to the deaeration tower 30 via the water distribution pipe 100.
The outlet 42 is connected to the above-described deaerator 32 via a water pipe 44, a pump 46, and a water pipe 48.

Therefore, the water to be treated supplied from the inflow port 40 flows through the flow path 50 defined between the inner wall surface of the deaeration tower 30 and the partition plate 34 in the direction of the arrow in the drawing, and It is fed into the passage 52 defined by the partition plate 34 and the partition plate 36 from the communication port 34a.
The water to be treated that has been sent into the flow path 52 is
a into the flow path 54 defined by the partition plate 36 and the partition plate 38, and further from the communication port 38a of the partition plate 38, the flow path 56 defined by the partition plate 38 and the inner wall surface of the degassing tower 30. Sent to. Channel
The water to be treated fed into 56 is pumped from the outlet 42
The outlet of the degassing tower 32 is sucked by the pipe 46 through a water pipe 48.
From 58, it is sent into the degassing tower 32.

A drain pipe 108 is communicated near the water surface of the deaeration tower 30, and the level of the water to be treated flowing in the deaeration tower 30 is controlled by the communication port.
When the water rises above 34a and 38a, excess water to be treated is circulated to the water to be treated storage tank 104 through the drain pipe 108.

On the other hand, a nitrogen gas blowing device 60 is provided at the bottom of the degassing tower 30.
Is attached. On the upper surface of the nitrogen gas blowing device 60,
A diffuser plate 62 is provided to foam the nitrogen gas blown from the nitrogen gas blower 60. The nitrogen gas blowing device 60
Is a ceiling opening of the degassing tower 32 described above through a duct 64.
Communicated to 66.

By the way, in the deaeration tower 32, partition plates 68, 70, 72,
74 will be installed. A communication port is provided near the water surface of the partition plate 68.
68a are formed, and a communication port 70a is formed near the bottom of the partition plate 70. A communication port 72a is provided near the water surface of the partition plate 72.
A communication port 74a is formed near the water surface of the partition plate 74.
Is formed. Accordingly, the water to be treated from the degassing tower 30 flows from the inlet 58 of the degassing tower 32 through the flow path 76 defined by the inner wall surface of the degassing tower 32 and the partition plate 68 in the direction of the arrow in the figure. The flow path 7 defined by the partition plate 68 and the partition plate 70 from the communication port 68a of the partition plate 68.
Sent to 8. The water to be treated sent into the flow path 78 is
The flow is sent from the communication port 70a of the partition plate 70 to the flow path 80 defined by the partition plate 70 and the partition plate 72, and the flow defined by the partition plate 72 and the partition plate 74 from the communication port 72a of the partition plate 72. It is sent to the road 82. Further, the water to be treated fed into the flow path 82 is
From the communication port 74a of the deaerator 32 and the flow path 84 defined by the partition plate 74 and the inner wall surface of the degassing tower 32, and is sent to the level controller 88 from the inlet 86.

As shown in FIG. 2, the level controller 88 includes a float 110, a connecting rod 112, and a taper valve 114. The taper valve 114 is formed in a tapered shape capable of opening and closing the drain port 116, and the lower end of the connecting rod 112 is connected to the upper end thereof. The float 110 is inserted into the upper end of the connecting rod 112, and the float 110 is sandwiched and fixed by a pair of bolts 118,118. Further, the distance between the float 110 and the taper valve 114 can be adjusted by changing the screwing position of the bolts 118, 118 with the connecting rod 112. Furthermore, a level controller
88, the connecting rod 112 is a pair of upper and lower guide plates 120, 12
By being supported by 2, it can move only in the vertical direction according to a change in water level.

Therefore, when the level of the treated water in the degassing tower 32 exceeds a certain level, the float 110 of the level controller 88 floats as the level of the treated water rises, and the taper valve 114 opens the drain port 116. . That is, when the water level exceeds a predetermined water level, treated water is sent from the inflow port 86 to the level controller 88, and the treated water is discharged from the drain port 116 to the water distribution pipe 90 and the first
It is stored in the treated water tank 126 via the back pressure valve 124 shown in the figure. Further, the distance between the float 110 and the taper valve 114 can be changed as described above.
The water level inside can be adjusted appropriately.

At the bottom of the degassing tower 32, a nitrogen gas blowing device 92 is provided. A diffuser plate is provided on the upper surface of the nitrogen gas blower 92.
94 will be laid. The diffuser plate 94 is provided with a nitrogen gas blowing device 92.
It is attached to diffuse the nitrogen gas blown out of the deaeration tower 32 and supply the bubbled nitrogen gas to the entire treated water in the degassing tower 32. The nitrogen gas blowing device 92 is connected to a nitrogen gas supply device (not shown) via a duct 96.

Next, the operation of the deoxidizer of the pure water producing apparatus configured as described above will be described.

First, the water to be treated is supplied from the inlet 40 of the degassing tower 30,
By the suction operation of the pump 46, the flow paths 50, 52, 54, 56
From the outlet 42 through the water pipes 44 and 48 to the deaeration tower 32
Sent to. A predetermined amount of oxygen dissolved in the water to be treated is removed from the water to be treated passing through the flow paths 50, 52, 54, and 56 by the nitrogen gas from the nitrogen gas blowing device 60. The removed oxygen is taken in the bubbles of the nitrogen gas, evaporates from the surface of the water to be treated, and is exhausted to the outside through an outlet 98 opened on the ceiling surface of the degassing tower 30. As a result, the water to be treated is passed through the flow paths 50, 52, 54, and 56 in the degassing tower 30 and is passed through the nitrogen gas, so that the partition plates 34, 36,
Compared to a conventional degassing tower without 38, more nitrogen gas is supplied by the length of the flow path. Therefore, the nitrogen gas can be used efficiently.

The nitrogen gas blown from the nitrogen gas blowing device 60 is supplied from the outlet 66 of the degassing tower 32 via a pipe 64.

The water to be treated fed into the degassing tower 32 (to which dissolved oxygen has been removed to some extent) flows into the above-described flow channels 76, 78, 80, 8
The water flows into the level controller 88 from the inflow port 86 via the inlet 84 and the treated water tank 12 via the water distribution pipe 90 and the back pressure valve 12.
Stored in 6. The water to be treated is supplied to the flow paths 76, 78, 8
When passing through O, 82, and 84, dissolved oxygen in the water to be treated is further removed by nitrogen gas sent from the nitrogen gas supply device 90 via the diffuser plate 94, and purified into treated water, that is, purified water. As described above, the channels 76, 78, 80, 82, 94
And the nitrogen gas is efficiently passed through the water to be treated, so that the dissolved oxygen in the water to be treated can be removed more efficiently than in a conventional degassing tower.

Further, the nitrogen gas blown out from the nitrogen gas blowing device 92 rises in the direction of the arrow from the water surface together with the dissolved oxygen, and flows through the discharge port 66 of the degassing tower 32 or the duct 64.
Supplied to Therefore, according to the present embodiment, it is possible to significantly reduce the consumption of nitrogen gas as compared with a conventional deoxidizer in which nitrogen gas is supplied and exhausted for each degassing tower.

FIG. 3 is an explanatory diagram comparing the amount of deoxidation between the deoxidizer according to the present invention and the conventional deoxygenator.

According to FIG. 3, by using the deoxidizer according to the present invention shown in FIG. 1, it is possible to treat water to be treated having a dissolved oxygen of 8.5 ppm to a required water quality of 10 ppb at a gas-liquid ratio of 0.75. . Further, when the conventional deoxygenation apparatus shown in FIG. 10 is used, in order to achieve the above 10 ppb at a gas-liquid ratio of 0.75, 10 degassing towers are required, and in order to reduce the number of degassing towers. It was found that the gas-liquid ratio had to be greatly increased. Therefore, according to the deoxidizer of the present invention, the number of degassing towers and the gas-liquid ratio are reduced as compared with the conventional deoxygenator, that is, the dissolved oxygen in the water to be treated is efficiently removed with a small amount of nitrogen gas. It turns out that it can be done.

Table 1 shows the results of performance comparison tests between the oxygen scavenger of the present invention and the conventional oxygen scavenger.

According to Table 1, when the gas-liquid ratio is kept constant at 0.75, the conventional deoxygenation apparatus A requires 10 columns, although the deoxygenation apparatus of the present invention can cover two degassing towers. Become. Also,
It was found that the running cost ratio was the same, but the initial cost ratio was increased by a factor of 5. Next, when deoxygenation was performed with the gas-liquid ratio of the conventional deoxidizer B set to 1.0, the number of degassing towers was increased. Can be reduced from 10 towers to 8 towers, but the running cost ratio increases by 1.33 times. Next, if the gas-liquid ratio is set to 2.0 in the conventional deoxygenator C, the number of degassing towers is 5
The tower can be reduced, but the running cost ratio increases to 2.67 times.

Therefore, according to the oxygen scavenger according to the present invention, the number of degassing towers can be reduced as compared with the conventional oxygen scavenger, and the gas-liquid ratio can be greatly reduced. In addition, running costs and initial costs can be significantly reduced.

By the way, according to the deoxidizer of the present invention, as shown in FIG. 4, even if the DO value of the supplied water to be treated fluctuates, the DO value in the treated water from which dissolved oxygen has been removed is made substantially constant. Can be.

The pump 46 is installed between the deaeration towers 30 and 32 shown in FIG. 1 because the flow of the nitrogen gas and the water to be treated is changed by the fluctuation of the supplied water and the pressure of the nitrogen gas. This is to prevent the water to be treated from varying in depth and not being constant, and the water quality of the to-be-treated water being thereby unstable. Therefore,
By installing the pump 46, a constant amount of water to be treated can be supplied to the degassing tower 32 even when the gas pressure of the nitrogen gas fluctuates.

The feature of the present embodiment is also to obtain required dissolved oxygen by arranging the deaeration towers 30 and 32 in multiple stages and performing multistage processing. In such a multi-stage degassing tower, in order to supply a common nitrogen gas to each of the degassing towers 30 and 32 equally,
The head of the water to be treated stored in each of the deaeration towers 30 and 32 must be set to the same value while keeping the water levels of the 30 and 32 constant. For this purpose, it is necessary to set the flow rate such that the pressure loss due to the rise or fall of the water level of the water to be treated in each of the degassing towers 30 and 32 is minimized.

Therefore, in order to satisfy such demands, in the deaeration tower 30, the supply amount from the water to be treated storage tank 104 is made larger than the supply amount from the deaeration tower 30 to the deaeration tower 32. It is devised that excess treated water in the gas tower 30 always returns from the drain pipe 108 to the to-be-treated water storage 104.

In order to reuse the nitrogen gas from the degassing tower 32 as the gas for aeration of the degassing tank 30, the upper space in the degassing tower 32 is maintained at a pressure sufficient to aerate the degassing tower 30. There must be. That is, the pressure in the upper space in the degassing tower 32 is
The pressure must be equal to or greater than the sum of the head pressure of 30 and the pressure loss at the diffuser plate 62. Therefore, when the same exhaust pipe 108 as the degassing tower 30 is provided in the degassing tower 32 to obtain treated water, the degassing tower 3
The nitrogen gas discharged from 2 does not flow toward the degassing tower 30 and the drain pipe 90
And flows to the treated water tank 126, so that the object of the present invention cannot be achieved.

Therefore, such a problem is solved and the degassing tower 32
In order to keep the water level constant, a level controller 88 and a back pressure valve 124 are installed in the treated water passage line to apply back pressure to the treated water passage line, and the nitrogen gas does not flow to the drain pipe 90,
And it is devised to keep the water level constant.

In this embodiment, the partition plates 34 and 38 (the partition plates of the degassing tower 32) are used.
The communication ports 34a, 38a (68a, 72a) are formed at the communication ports 34a, 38a (including 68, 72). However, the invention is not limited to this, and the partition plates 34, 38 are connected to the partition plate 36 as shown in FIG. It may be attached with a step.

Also, as shown in FIGS. 6 and 7, the upper opening 12
The inner cylinder 132 having the 8, 130 formed therein is installed inside the degassing tower 30 (including the degassing tower 32), and a partition plate 134 is further mounted inside the inner cylinder 132, and the water to be treated is indicated by an arrow in the figure. You may make it flow as shown.

Further, as shown in FIG. 8 and FIG.
8, 140, and 142 may be connected in a cross shape and installed inside the degassing tower 30 (including the degassing tower 32) so that the water to be treated flows counterclockwise in the figure.

〔The invention's effect〕

As described above, according to the deoxygenating apparatus of the pure water production apparatus according to the present invention, the water to be treated is sequentially communicated with the tank so that the water can flow, and the nitrogen gas that has passed through the water to be treated in the downstream tank is adjacent to the tank. The nitrogen gas can be efficiently contributed to the deoxygenation of the water to be treated, and the number of degassing towers can be greatly reduced.

Moreover, according to the oxygen scavenger according to the present invention, the running cost and initial cost can be significantly reduced as compared with the conventional oxygen scavenger.

In addition, a level controller was installed at the treatment outlet of the downstream tank, and a back pressure valve was attached to the treated water passage line connected to this level controller, so that each tank on the nitrogen gas upstream side from the downstream side was stable. Can be supplied.

[Brief description of the drawings]

FIG. 1 is a first deoxygenator of a pure water production apparatus according to the present invention.
FIG. 2 is an explanatory view showing an embodiment, FIG. 2 is a cross-sectional view showing an embodiment of a level controller installed in the pure water producing apparatus according to the present invention, and FIG. 3 is a deoxygenating apparatus of the pure water producing apparatus according to the present invention. FIG. 4 is an explanatory diagram comparing the deoxidation performance with a conventional deoxidizer, FIG. 4 is an explanatory diagram showing the relationship between the DO fluctuation of the water to be treated and the DO of the treated water, and FIG. 5 is the pure water production according to the present invention. FIG. 6 is an explanatory view showing a second embodiment of the deoxidizer of the apparatus, FIG. 6 is a top view showing a third embodiment of the deoxidizer of the pure water production apparatus according to the present invention, and FIG. 8 is a top view showing a fourth embodiment of the deoxidizer of the pure water producing apparatus according to the present invention, FIG. 9 is a front view in FIG. 8, and FIG. FIG. 11 is an explanatory view showing an embodiment of a deoxygenating apparatus of a water producing apparatus, and FIG. 11 is an explanatory view showing a relationship between solubility of gas in water. 30, 32 ... degassing tower, 34, 36, 38, 68, 70, 72, 74 ... partition plate, 46 ... pump, 50, 52, 54, 56, 76, 78, 80, 8
2, 84… Flow path, 60, 92… Nitrogen gas blowing device, 62, 94
... diffuser plate, 88 ... level controller, 104 ... treated water storage tank, 110 ... float, 114 ... taper valve, 124
…… Back pressure valve, 126 …… Treatment water tank.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuko Hashimoto 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Plant Construction Co., Ltd. (72) Inventor, etc. 1-11-1 Uchikanda, Chiyoda-ku, Tokyo No. Hitachi Plant Construction Co., Ltd. (72) Inventor Yasuyuki Yagi 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Hitachi Plant Construction Co., Ltd. (56) References JP-A-59-154109 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) B01D 19/00

Claims (5)

(57) [Claims] 1. A deoxygenating apparatus for a pure water producing apparatus, wherein nitrogen gas is blown out from a bottom portion of a tank in which water to be treated is stored and aerated through the water to be treated to remove dissolved oxygen in the water to be treated. A plurality of tanks were installed, and the water to be treated was sequentially communicated so as to be able to flow, and the nitrogen gas that had passed through the water to be treated stored in the downstream tank was sequentially communicated so that it could be supplied to the adjacent upstream tank. A deoxygenation device for a pure water production device, characterized in that: 2. The tank has a plurality of partition plates disposed at predetermined intervals in the tank and divided into a plurality of flow paths. The plurality of partition plates have a communication port near a bottom and a communication port near a water surface. The deoxygenating apparatus for a pure water production apparatus according to claim 1, wherein the plurality of flow paths are formed alternately and a plurality of flow paths are sequentially communicated. 3. The nitrogen gas which has passed the water to be treated in the upstream tank through the flow path of the water to be treated, which communicates the tanks, does not flow back through the flow path to the tank in the downstream side. The deoxygenating apparatus for a pure water producing apparatus according to claim 1, wherein the back pressure valve is mounted as described above. 4. The supply amount of the water to be treated supplied to the most upstream tank is made larger than the flow amount from the most upstream tank to the downstream tank. A drain pipe is attached, and it is desired that excess treated water obtained by subtracting a flow rate from the supply rate be drained from the drain pipe so as to maintain a constant water level in the uppermost stream side tank. 19) The deoxidizer of the pure water production apparatus described in the above. 5. The apparatus according to claim 3, wherein a level controller capable of appropriately adjusting the level of the water to be treated is provided in each of the downstream tanks, and the level controller is connected to the back pressure valve. ).