Degassing membrane device, ultrapure water production device, and ultrapure water production method

Abstract

To provide a deaeration membrane device capable of confirming the degree of vacuum on the secondary side of the deaeration membrane device.SOLUTION: Feed water is supplied into a water phase chamber 3a of a deaeration membrane module. A pipeline 5, branch pipelines 10, 20, and vacuum pumps 14, 24 are installed so as to decompress a vapor phase chamber 3b, and valves 11, 21 are installed on the pipelines 10, 20. When switching actuation of the vacuum pumps 14, 24, the valves 11, 21 are switched by a controller 6. Vacuum gauges 13, 23 are installed on pipelines 12, 22 between the valves 11, 21 and the vacuum pumps 14, 24.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a degassing membrane device, and more particularly to a degassing membrane device having a plurality of vacuum pumps. The present invention also relates to an ultrapure water production system and method using the degassing membrane device. [Background technology]

[0002] Conventionally, systems for producing ultrapure water used for semiconductor washing and the like include those that treat raw water such as industrial water, city water, or well water in a pretreatment system using coagulation, flotation (sedimentation), filtration (membrane filtration), or the like to remove suspended solids, colloidal substances, polymeric organic matter, hydrophobic organic matter, and the like from the raw water, and then treat the water in a primary pure water system consisting of a membrane degasser, a reverse osmosis (RO) membrane separator, and an ion exchanger, or a membrane degasser and a two-stage RO membrane separator, or the like.

[0003] The RO membrane separation unit removes salts as well as ionic and colloidal TOC, while the ion exchange unit removes salts as well as TOC components that are adsorbed or ion-exchanged by ion exchange resins.

[0004] A membrane degassing device divides the interior into an aqueous phase chamber and a gas phase chamber using a hydrophobic polymer gas-permeable membrane (degassing membrane), and by reducing the pressure in the gas phase chamber using a vacuum pump, gases such as oxygen contained in the water being treated that has flowed into the aqueous phase chamber are removed by passing them through the membrane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-309566 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-355683 Summary of the Invention [Problem to be solved by the invention]

[0006] The vacuum pump of the degassing membrane device in the ultrapure water system must be operated continuously to maintain a vacuum in the primary piping at all times in order to keep the dissolved oxygen concentration, which is the required water quality for ultrapure water, below the standard value. For this reason, a backup machine (backup vacuum pump) is installed in case of a malfunction such as a trip of the vacuum pump. The backup machine and the main machine (vacuum pump) are connected to the degassing membrane device via a selector valve.

[0007] However, if switching from the main unit to the standby unit is performed before the standby unit's vacuum level has risen (becomes sufficiently high), a drop in vacuum will occur on the secondary side (pressure reduction side) of the degassing membrane unit, reducing the functionality of the degassing membrane unit and resulting in the required water quality of the ultrapure water DO (dissolved oxygen) concentration not being achieved.

[0008] Furthermore, even when manually switching the pump during vacuum pump maintenance, the switching operation is performed without being able to confirm that the vacuum level has risen, which may result in the water quality not being achieved.

[0009] The present invention is characterized by providing a degassing membrane device that allows confirmation of the degree of vacuum on the secondary side of the degassing membrane device.

[0010] One aspect of the present invention aims to provide a degassing membrane device that can switch between a main vacuum pump and a standby vacuum pump when the degree of vacuum on the secondary side of the degassing membrane device is sufficiently high.

[0011] An object of one aspect of the present invention is to provide an ultrapure water production apparatus and an ultrapure water production method using such a degassing membrane device. [Means for solving the problem]

[0012] The gist of the present invention is as follows.

[0013] [1] A degassing membrane module having an aqueous phase chamber and a gas phase chamber separated by a degassing membrane; a vacuum pump for reducing the pressure inside the gas phase chamber; In a degassing membrane device having A plurality of the vacuum pumps are installed, Pipes and valves are provided to connect each vacuum pump to the gas phase chamber, A vacuum gauge is provided to detect the degree of vacuum between the valve and the vacuum pump. A degassing membrane device characterized by:

[0014] [2] A control means is provided for controlling the valve so that one vacuum pump is in operation while the other vacuum pump is stopped, and the operating vacuum pump is connected to the gas phase chamber; When switching between vacuum pumps to be operated, the control means starts the other vacuum pump before stopping the vacuum pump currently in operation; After the degree of vacuum in the pipe connecting the other vacuum pump to the gas phase chamber reaches or exceeds the specified degree of vacuum, Ta A degassing membrane device [1] that stops a vacuum pump and blocks communication with the gas phase chamber, and connects the other vacuum pump to the gas phase chamber.

[0015] [3] An extraction pipe is provided for extracting degassed treated water from the aqueous phase chamber of the degassing membrane module, The degassing membrane device of [2] has a means for discharging the degassed treated water flowing out of the aqueous phase chamber of the degassing membrane module into a discharge pipe separate from the extraction pipe when the vacuum level in the pipe connecting the other vacuum pump to the gas phase chamber does not reach the specified vacuum level even after a predetermined time has elapsed after starting the other vacuum pump.

[0016] [4] An ultrapure water production system equipped with any one of the degassing membrane devices [1] to [3].

[0017] [5] An ultrapure water production apparatus equipped with the degassing membrane device of [3], wherein the discharge piping is arranged to allow the degassed water to flow into the primary pure water tank of the ultrapure water production apparatus.

[0018] [6] A method for producing ultrapure water using the ultrapure water production apparatus of [4] or [5]. [Effects of the Invention]

[0019] The degassing membrane device of the present invention is equipped with a vacuum meter, which can detect the degree of vacuum on the secondary membrane side (decompression side) of the degassing membrane device. Therefore, when switching the vacuum pump from the main unit to the standby unit, the switching can be performed after the degree of vacuum in the standby unit has become sufficiently high.

[0020] According to the ultrapure water production system and ultrapure water production method of the present invention, ultrapure water with a low DO (dissolved oxygen) concentration can be stably produced. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a configuration diagram of a degassing membrane device according to an embodiment. [Figure 2] 1 is a configuration diagram of an ultrapure water production system according to an embodiment. [Figure 3] FIG. 10 is a diagram showing the configuration of a degassing membrane device according to another embodiment. [Figure 4] FIG. 10 is a configuration diagram of an ultrapure water production system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment will be described with reference to the drawings.

[0023] FIG. 1 shows the configuration of a degassing membrane device 1 according to an embodiment.

[0024] Water is supplied to an aqueous phase chamber 3a of a degassing membrane module 3 through a water supply pipe 2. The degassing membrane module 3 has an aqueous phase chamber 3a and a gas phase chamber 3b separated by a degassing membrane 3m. The gas phase chamber 3b is depressurized by a vacuum pump 14 or 24 described below.

[0025] As the water flows through the aqueous phase chamber 3a, gas components in the water permeate the degassing membrane 3m. The degassed water is extracted through a pipe 4. Although not shown, a means for supplying nitrogen gas to the degassing membrane module is provided to reduce the oxygen partial pressure and further reduce the DO concentration of the degassed water.

[0026] A pipe 5 is connected to the gas phase chamber 3b to reduce the pressure inside the gas phase chamber 3b. The pipe 5 branches into pipes 10 and 20. Vacuum pumps 14 and 24 are installed at the ends of the pipes 10 and 20.

[0027] Valves 11 and 21 are provided in the pipes 10 and 20. Vacuum gauges 13 and 23 are provided to detect the pressure in the pipes 12 and 22 between the valves 11 and 21 and the vacuum pumps 14 and 24. The detection signals of the vacuum gauges 13 and 23 are input to a controller 6, which controls the valves 11 and 21 and the vacuum pumps 14 and 24.

[0028] During normal operation of the degassing membrane device 1, one of the vacuum pumps 14, 24 is operating and the other is stopped. When the vacuum pump 14 is operating, the valve 11 is open and the valve 21 is closed. When the vacuum pump 24 is operating, the valve 11 is closed and the valve 21 is open.

[0029] When the vacuum pump 14 is operating, the controller 6 monitors the pressure detected by the vacuum gauge 13. If the degree of vacuum in the pipe 12 detected by the vacuum gauge 13 drops below a predetermined value, it is assumed that a malfunction has occurred in the vacuum pump 14, and the controller stops the vacuum pump 14 and operates the vacuum pump 24.

[0030] In this case, before closing valve 11, opening valve 21, and stopping vacuum pump 14, vacuum pump 24 is started and waits until the degree of vacuum in pipe 22 detected by vacuum meter 23 reaches or exceeds a specified value. After the degree of vacuum in pipe 22 reaches or exceeds the specified value, valve 21 is opened, valve 11 is closed, and vacuum pump 14 is stopped.

[0031] This allows the vacuum pumps 14 and 24 to be switched without any or almost no decrease in the degree of vacuum in the gas phase chamber 3b of the degassing membrane module 3. The same procedure is used to switch the operating vacuum pump from the vacuum pump 24 to the vacuum pump 14.

[0032] In the above description, the vacuum pump is switched in response to a failure of the vacuum pump, but the same procedure is also used when switching the vacuum pump in response to periodic inspection of the vacuum pump.

[0033] FIG. 2 shows an example of the configuration of a subsystem (secondary pure water system) of an ultrapure water production system equipped with the above-mentioned degassing membrane device 1.

[0034] The primary pure water in the primary pure water tank 30 is pumped by a pump 31, and after organic matter is decomposed by UV oxidation in a UV oxidation device 32, ionic impurities are removed in an ion exchange device 33, and then the water is passed through a degassing membrane device 1 for degassing treatment. Fine impurities are removed from the degassed water in a UF membrane device 34, and the degassed water becomes ultrapure water, which is then sent to a point of use (not shown).

[0035] In this ultrapure water production system, the above-mentioned degassing membrane device 1 is used as the degassing membrane device, so that degassed treated water of a specified quality or higher is sent from the degassing membrane device 1 to the UF membrane device 34, thereby producing ultrapure water of stable quality.

[0036] 3 shows a degassing membrane apparatus 1A in which a pipe 7 is provided for discharging degassed treated water from the degassing membrane module 3 when the quality of the degassed treated water is poor, in addition to the degassing membrane apparatus 1 shown in FIG. 1. A valve 8 is provided on the pipe 7. A valve 9 is also provided on the pipe 4.

[0037] When switching from one vacuum pump to another, if for some reason the degree of vacuum in the pipe of the newly operated vacuum pump does not become sufficiently high even after a predetermined time has elapsed, the controller 6 closes valve 9 and opens valve 8, and the degassed water with a high concentration of dissolved gases is discharged from the system through pipe 7.

[0038] Valves 8 and 9 of Alternatively, a three-way valve may be installed.

[0039] 4 shows an example of an ultrapure water production system equipped with this degassing membrane device 1 A. In this ultrapure water production system, the discharged water from the pipe 7 is returned to the primary pure water tank 30 for reuse.

[0040] Other configurations in FIGS. 3 and 4 are the same as those in FIGS. 1 and 2, and the same reference numerals denote the same parts.

[0041] The above embodiment is one example of the present invention, and the present invention may have other configurations. For example, in the above embodiment, valves 11 and 21 are provided on pipes 10 and 20, respectively, but a three-way valve may be provided at the branch point from pipe 4 to pipes 10 and 20. In the above embodiment, two vacuum pumps are installed in parallel, but three or more may be installed in parallel. Furthermore, the ultrapure water production system may include equipment other than those described above. [Explanation of symbols]

[0042] 1,1A Degassing membrane device 3. Degassing membrane module 6 Controller 11,12 Valves 13,23 Vacuum gauge 14,24 Vacuum pump 32 UV oxidation equipment 33 Ion exchange device

Claims

1. a degassing membrane module having an aqueous phase chamber and a gas phase chamber separated by a degassing membrane; a vacuum pump for reducing the pressure inside the gas phase chamber; In a degassing membrane device having A plurality of the vacuum pumps are installed, Pipes and valves are provided to connect each vacuum pump to the gas phase chamber, A degassing membrane device provided with a vacuum gauge for detecting the degree of vacuum between the valve and the vacuum pump, a control means for controlling the valve so that one vacuum pump is in operation while the other vacuum pump is in a stopped state and the operating vacuum pump is in communication with the gas phase chamber; When switching between vacuum pumps to be operated, the control means starts the other vacuum pump before stopping the vacuum pump currently in operation; a degassing membrane device that stops the vacuum pump that was in operation and cuts off communication with the gas phase chamber after the degree of vacuum in the pipe that connects the other vacuum pump to the gas phase chamber reaches a specified degree of vacuum or more, and connects the other vacuum pump to the gas phase chamber; an extraction pipe is provided for extracting degassed water from the aqueous phase chamber of the degassing membrane module; a degassing membrane device having a means for causing the degassed treated water flowing out of the aqueous phase chamber of the degassing membrane module to flow into an exhaust pipe separate from the extraction pipe when the vacuum level in the pipe connecting the other vacuum pump to the gas phase chamber does not reach a specified vacuum level even after a predetermined time has elapsed after starting the other vacuum pump.

2. An ultrapure water production system comprising the degassing membrane device of claim 1.

3. 2. An ultrapure water production system equipped with the degassing membrane device of claim 1, wherein the discharge pipe is provided so as to allow the degassed water to flow into a primary pure water tank of the ultrapure water production system.

4. 4. A method for producing ultrapure water using the ultrapure water production system of claim 2 or 3.

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