Secondary pure water production equipment for ultrapure water production systems

Abstract

To provide a secondary pure water production apparatus of an ultrapure water production system which is easy in temperature control and is capable of suppressing operation energy.SOLUTION: An ultrapure water production system 1 is composed of a pretreatment system 2, a primary pure water production apparatus 3, and a secondary pure water production apparatus (subsystem) 4 for treatment of primary pure water. The secondary pure water production apparatus 4 is provided with a sub-tank 21, a pump 22, a heat exchanger 23, a temperature sensor 24 communicating with cooling means (not shown in the figure) of the heat exchanger, a low pressure ultraviolet oxidation device (UV oxidation device) 25, a pressure gauge 26, a pressure-elevation pump 27, a reverse osmosis membrane (RO membrane) 28, and a non-regeneration type ion exchanger 29. The reverse osmosis membrane (RO membrane) 28 has a transmission flow flux of 2.0 m3 / (m2 day) or over per 1 MPa of membrane surface effective pressure (water temperature 25°C, pure water (RO permeable water)).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary pure water production apparatus for an ultrapure water production system that produces ultrapure water used in the electronics industry, such as semiconductors and liquid crystal displays, and in particular to a secondary pure water production apparatus that allows for easy temperature control and reduces operating energy. [Background technology]

[0002] Conventionally, ultrapure water used in the semiconductor and other electronics industries is produced by treating raw water (industrial water, city water, well water, etc.) W in an ultrapure water production system 1, which is composed of a pretreatment system 2, a primary pure water production apparatus 3, and a secondary pure water production apparatus (subsystem) 4 that treats the primary pure water, as shown in Figure 1.

[0003] In the pretreatment system 2, which is comprised of coagulation, flotation (sedimentation), and filtration (membrane filtration) devices, suspended solids and colloidal substances are removed from the raw water W to obtain pretreated water W0. This process also makes it possible to remove polymeric organic matter, hydrophobic organic matter, and the like.

[0004] The primary pure water production system 3 includes a tank 11 for pretreated water W0, a preheater 15, a reverse osmosis (RO) membrane 12, a heat exchanger 16, an ion exchanger (e.g., mixed-bed or four-bed, five-tower type) 13, and a degasser 14. The primary pure water production system 3 removes ions and organic components from the pretreated water W0. Note that the higher the water temperature, the lower the viscosity and the higher the permeability of membrane devices. For this reason, as shown in FIG. 1 , the preheater 15 and heat exchanger 16 are installed upstream of the reverse osmosis membrane 12. By controlling the outlet water of the heat exchanger 16 to a predetermined temperature, the viscosity of the water is reduced, and the water is heated so that the temperature of the water supplied to the reverse osmosis membrane 12, the ion exchanger 13, and the degasser 14 is above the predetermined temperature. The primary pure water W1, which is the water supplied to the secondary pure water production system 4, is also controlled to a predetermined temperature. Steam is supplied to the primary side of the heat exchanger 16 as a heat source fluid. The reverse osmosis membrane 12 treats the water to be treated at a predetermined recovery rate to remove salts, as well as ionic and colloidal TOC, and discharges concentrated water. The ion exchanger 13 removes salts and TOC components that are adsorbed or ion-exchanged by ion exchange resin. The degasser 14 removes inorganic carbon (IC) and dissolved oxygen.

[0005] The primary pure water W1 produced in the primary pure water production system 3 is delivered to the secondary pure water production system 4 via piping 17. This secondary pure water production system 4 includes a sub-tank 21, a pump 22, a heat exchanger 23, a temperature sensor 24 connected to the heat exchanger's cooling means (not shown), a low-pressure ultraviolet oxidation system (UV oxidation system) 25, a pressure gauge 26, a boost pump 27, a reverse osmosis (RO) membrane 28, and a non-regenerative ion exchanger 29. The low-pressure ultraviolet oxidation system 25 uses 185 nm ultraviolet light emitted from a low-pressure ultraviolet lamp to decompose TOC into organic acids and further CO2 levels. Next, the boost pump 27 boosts the primary pure water W1 to a predetermined pressure corresponding to the membrane surface pressure of the reverse osmosis (RO) membrane 28, and supplies it to the system. The reverse osmosis (RO) membrane 28 removes particulates and ionic impurities. The organic matter and CO2 produced by decomposition in the low-pressure ultraviolet oxidation device 25 are removed in a non-regenerative ion exchange device 29 in the subsequent stage.

[0006] The ultrapure water W2 produced in this secondary pure water production system 4 is sent to the use point 5 via piping 30, and unused ultrapure water W2 is returned to the sub-tank 21 via return piping 31. If necessary, a particle removal means such as an ultrafiltration membrane may be provided downstream of the ion exchange system 29.

[0007] The heat exchanger 23 adjusts the temperature of the ultrapure water W2 delivered from the secondary pure water production system 4 to a predetermined temperature (e.g., approximately 25°C). Generally, the ultrapure water W2 produced in the secondary pure water production system 4 is supplied to the point of use 5, and the surplus ultrapure water W2 (unused) is returned from the point of use 5 to the sub-tank 21, where it is treated again in the secondary pure water production system 4 and circulated while maintaining a constant ultrapure water quality. The repeated circulation prevents the water from stagnating and suppresses the growth of microorganisms. During this circulation, the temperature of the circulating ultrapure water W2 increases due to heat from the pump 22 and the ultraviolet irradiation lamp of the low-pressure ultraviolet oxidation device 25, but this heat is removed by the heat exchanger 23, and the temperature of the water delivered to the point of use 5 is adjusted to within ±1°C of the set temperature, for example. Summary of the Invention [Problem to be solved by the invention]

[0008] However, when a reverse osmosis membrane (RO membrane) 28 is provided in the secondary pure water production system 4, high pressure must be applied to the water to be treated to cause it to pass through the reverse osmosis membrane (RO membrane) 28, which necessitates a booster pump 27 provided upstream. However, the drive energy of this booster pump 27 also contributes to an increase in water temperature, which may result in hunting in water temperature control. Furthermore, in recent years, energy conservation has also been required in ultrapure water production systems, and it is desirable to be able to reduce the operating energy of the secondary pure water production system 4 itself.

[0009] The present invention has been made in view of the above problems, and has as its object to provide a secondary pure water production device in an ultrapure water production system that allows easier temperature control and reduces operating energy than conventional systems. [Means for solving the problem]

[0010] In view of the above object, the present invention provides a secondary pure water production system for an ultrapure water production system comprising a primary pure water production system equipped with at least an ion exchange device and a secondary pure water production system for further treating the primary pure water treated in the primary pure water production system, the secondary pure water production system having a permeation flux of 2.0 m per membrane surface effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 The present invention provides a secondary pure water production system comprising a reverse osmosis membrane (1000 times or more), and a booster pump for feeding the water to be treated to the reverse osmosis membrane.

[0011] According to this invention (Invention 1), by using a reverse osmosis membrane with a large permeation flux per 1 MPa of effective membrane surface pressure, the same amount of water can be supplied at a low operating pressure, which reduces the workload of the boost pump that delivers water to the reverse osmosis membrane, thereby significantly reducing operating energy compared to when a general-purpose reverse osmosis membrane with a lower permeation flux is used. Furthermore, by reducing operating energy, heat generation from the boost pump can be suppressed, which suppresses temperature rise in the secondary pure water and reduces energy required for cooling the secondary pure water, thereby enabling stable control of the temperature of the secondary pure water.

[0012] In the above invention (Invention 1), it is preferable that the secondary pure water production apparatus comprises a storage tank for the primary pure water, a heat exchanger, an ultraviolet oxidation device, a booster pump, the reverse osmosis membrane and an ion exchange device provided in a water supply pipe communicating with a use point connected to the storage tank, and a return pipe for returning water from the use point to the storage tank (Invention 2).

[0013] According to this invention (Invention 2), an ion exchange device is provided downstream of the reverse osmosis membrane, so even if ion components leak from the reverse osmosis membrane, which has a large permeation flux per 1 MPa of effective membrane surface pressure, they can be removed. In addition, by providing a return pipe, it is possible to efficiently use secondary pure water, reduce operating energy, and efficiently adjust temperature.

[0014] In the above inventions (Inventions 1 and 2), the reverse osmosis membrane has a permeation flux of 0.6 m under the condition of an effective membrane surface pressure of 0.3 MPa (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 It is preferable that the membrane surface pressure is 0.3 MPa (water temperature 25°C, feed water 500 mg / L at NaCl) or more, the salt rejection rate is 95% or more (membrane surface effective pressure 0.3 MPa (water temperature 25°C, feed water 500 mg / L at IPA) and the IPA rejection rate is 60% or more (membrane surface effective pressure 0.3 MPa (water temperature 25°C, feed water 500 mg / L at IPA) (Invention 3).

[0015] According to this invention (Invention 3), by selecting a reverse osmosis membrane with such performance, which has a large permeation flux per 1 MPa of effective membrane surface pressure, it is possible to produce secondary pure water with stable water quality while reducing the operating energy of the secondary pure water production equipment and efficiently controlling the temperature. [Effects of the Invention]

[0016] In the secondary pure water production system of the present invention, by using a reverse osmosis membrane with a high permeation flux per 1 MPa of effective membrane surface pressure, the workload of the booster pump that pumps water to the reverse osmosis membrane is reduced, resulting in a significant reduction in operating energy compared to when a general-purpose reverse osmosis membrane with a lower permeation flux is used, thereby suppressing temperature increases in the secondary pure water. These combined effects make it possible to stably control the temperature of the secondary pure water. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flow diagram showing an ultrapure water producing system to which a secondary pure water producing apparatus according to a first embodiment of the present invention can be applied. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of a secondary pure water production apparatus according to the present invention will be described with reference to the accompanying drawings.

[0019] (Ultra pure water production equipment) The ultrapure water production system using the secondary pure water production apparatus of this embodiment has the same configuration as the ultrapure water production system shown in Figure 1 described above, except that the reverse osmosis membrane (RO membrane) 28 of the secondary pure water production apparatus 4 has the following performance.

[0020] <Reverse osmosis membrane> - Permeation flux of 0.6m under the condition of membrane surface effective pressure of 0.3MPa (water temperature 25℃, pure water (RO permeate)) 3 / (m 2 permeation flux of 2.0 m per membrane effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 (days) or more Salt rejection rate: 95% or more (membrane surface effective pressure 0.3 MPa (water temperature 25°C, feed water 500 mg / L at NaCl) IPA removal rate: 60% or more (membrane surface effective pressure 0.3 MPa (water temperature 25°C, feed water 500 mg / L at IPA)

[0021] (Operation method of ultrapure water production system) The following describes the operation method of the above-described ultrapure water production system 1. First, raw water W is supplied to the pretreatment system 2, where suspended solids and colloidal substances in the raw water W are removed using coagulation, flotation (sedimentation), filtration (membrane filtration), etc., to obtain pretreated water W0. During this process, polymeric organic matter, hydrophobic organic matter, etc. are also removed to a certain extent.

[0022] This pretreated water W0 is supplied to a primary pure water production system 3 and temporarily stored in a tank 11, after which it is supplied by a pump (not shown). It is preheated in a preheater 15 to reduce the viscosity of the pretreated water W0, and then supplied to a reverse osmosis membrane 12. The reverse osmosis membrane 12 processes the water to be treated at a predetermined recovery rate, removing salts as well as ionic and colloidal TOC. Subsequently, an ion exchanger 13 removes salts and TOC components adsorbed or ion-exchanged by the ion exchange resin. Finally, a degasser 14 removes inorganic carbon (IC) and dissolved oxygen, producing primary pure water W1.

[0023] This primary pure water W1 is sent to the secondary pure water production system 4 via a pipe 17. In the secondary pure water production system 4, the primary pure water W1 is sent by a pump 22, and in a low-pressure ultraviolet oxidation system 25, TOC is converted into organic acids and further CO by ultraviolet light of 185 nm emitted from a low-pressure ultraviolet lamp. 2 The primary pure water W1 is then boosted by a booster pump 27 to a predetermined pressure corresponding to the membrane surface pressure of the reverse osmosis membrane (RO membrane) 28, and supplied, and fine particles are removed by the reverse osmosis membrane (RO membrane) 28. The organic matter and CO2 produced by decomposition in the low-pressure ultraviolet oxidation device 25 are then removed in a non-regenerative ion exchange device 29 in the subsequent stage, producing ultrapure water (secondary pure water) W2.

[0024] In the conventional ultrapure water production system 1 described above, the reverse osmosis membrane (RO membrane) 28 was responsible for removing both ionic components and particulates. However, in the present embodiment, the reverse osmosis membrane 28 with a predetermined effective membrane surface pressure is intended to remove particulates originating from the upstream boost pump 27 rather than ionic components. The reverse osmosis membrane 28 is generally capable of removing most components with a molecular weight of 200 or more, and particulates are subject to removal. In this embodiment, an ion exchange device 29 is used downstream of the reverse osmosis membrane (RO membrane) 28, which can remove ionic components. Therefore, even if a reverse osmosis membrane 28 with a high permeation flux per 1 MPa effective membrane surface pressure is used, the quality of the ultrapure water W2 is not degraded.

[0025] The ultrapure water W2 produced in this secondary pure water production system 4 is sent to the point of use 5 via piping 30, and unused ultrapure water is returned to the sub-tank 21 via return piping 31 for circulating use. As this circulating use increases the temperature of the ultrapure water W2 due to the transmission of energy from the pump 22, low-pressure ultraviolet oxidation device 25, boost pump 27, etc., the ultrapure water W2 sent from the secondary pure water production system 4 to the point of use 5 is cooled by the heat exchanger 23 to a predetermined temperature (for example, 25±0.5°C).

[0026] In the process for producing ultrapure water W2 as described above, in this embodiment, the secondary pure water production apparatus 4 uses a reverse osmosis membrane with a permeation flux of 2.0 m per membrane effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 Since the boost pump 27 employs a pump having a pump pressure of 1000 psi or more, the operating energy of the boost pump 27 is reduced. In addition, the boost pump 27 does not provide much heat to the ultrapure water W2, so the temperature rise of the secondary pure water W2 can be suppressed. These combined effects enable the temperature of the secondary pure water W2 to be stably controlled.

[0027] The above has described the secondary pure water system 4 in the ultrapure water producing system 1 of this embodiment, but the present invention is not limited to the above embodiment and can be applied to various aspects of the primary pure water system 3. Furthermore, the ion exchange device in the secondary pure water system 4 is generally a non-regenerative ion exchange device 29, but it may also be an electrodeionization device. [Example]

[0028] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0029] Example 1 In the ultrapure water production system 1 shown in FIG. 1, the reverse osmosis membrane 28 has a flux (permeation flow rate) of 0.76 m at an effective membrane surface pressure of 0.3 MPa. 3 / (m 2 The secondary water purification system 4 was operated using a membrane (at 25°C). The circulating water volume was 100 m 3 / h(0.028m 3 / h), the water supply pressure by the booster pump 27 was 0.3 MPa (head 30 m), and the pump efficiency η of the booster pump 27 was 0.7.

[0030] First, to find the hydraulic power (Pw) under these operating conditions, the hydraulic power Pw can be calculated using the following formula (1). Pw(kW)=ρgHQ / 1000 (1) (where ρ is the density of water (kg / m 3 ) and g is the acceleration due to gravity (9.8m / s 2 ), H is the total head (m), and Q is the discharge rate (m 3 / S)

[0031] According to the above formula (1), the hydraulic power (Pw) is 1000 (kg / m 3 )×9.8(m / s 2 )×30(m)×0.028(m 3 / S) = 8.2kW.

[0032] Next, the shaft power (Pa) of the boost pump 27 can be calculated from the following equations (2) and (3). η=Pw / Pa (2) Pa=Pw / 0.7 (3)

[0033] According to the above formula (3), the shaft power (Pa) of the boost pump 27 is 8.2 (kW) / 0.7=11.7 Kw.

[0034] Then, the loss energy (ΔP) can be calculated from the hydraulic power (Pw) and the shaft power (Pa) of the boost pump 27 using the following formula (4). ΔP (kW) = Pa - Pw = 11.7 (kW) - 8.2 (kW) = 3.5 kW.

[0035] Comparative Example 1 In the ultrapure water production system 1 shown in FIG. 1, a general-purpose reverse osmosis membrane 28 with a high flux is used, which has a flux (permeation flow rate) of 1.00 m at an effective membrane surface pressure of 0.75 MPa. 3 / (m 2 The secondary water purification system 4 was operated using a membrane (at 25°C). The circulating water volume was 100 m 3 / h(0.028m 3 / h), the water supply pressure by the booster pump 27 was 0.75 MPa (head 75 m), and the pump efficiency η of the booster pump 27 was 0.7.

[0036] First, when the hydraulic power (Pw) under these operating conditions is calculated in the same manner as in Example 1, the hydraulic power Pw is 1000 (kg / m 3 )×9.8(m / s 2 )×75(m)×0.028(m 3 / S) = 20.6kW.

[0037] Next, the shaft power (Pa) of the boost pump 27 is calculated in the same manner as in Example 1. Pa = 20.6 (kW) / 0.7 = 29.4 kW.

[0038] Then, the loss energy (ΔP) is calculated from the hydraulic power (Pw) and the shaft power (Pa) of the boost pump 27. ΔP (kW) = Pa - Pw = 29.4 (kW) - 20.6 (kW) = 8.8 kW.

[0039] As is clear from the above Example 1 and Comparative Example 1, the secondary pure water production apparatus 4 has a permeation flux of 2.0 m per membrane effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 In Example 1, which uses a reverse osmosis membrane 28 of the above 1000-150 ... [Explanation of symbols]

[0040] 1. Ultrapure water production system 2 Pretreatment System 3 Primary water purification equipment 4 Secondary pure water production equipment (subsystem) 5 Use Points 11. Tank 12 Reverse osmosis membrane (RO) 13 Ion exchange device 14 Degassing device 15 Preheater 16 Heat exchanger 17 Piping 21 Subtank 22 Pump 23 Heat exchanger 24 Temperature Sensor 25 Low-pressure ultraviolet oxidation equipment (UV oxidation equipment) 26 Pressure gauge 27 Booster pump 28 Reverse osmosis membrane (RO membrane) 29 Non-regenerative ion exchanger 30 Piping 31 Return piping W Raw Water W0 Pretreated water W1 Primary pure water W2 Ultrapure water (secondary pure water)

Claims

1. A secondary pure water production system for an ultrapure water production system comprising a primary pure water production system equipped with at least an ion exchange device and a secondary pure water production system for further treating the primary pure water treated in the primary pure water production system, The secondary pure water production apparatus has a permeation flux of 2.5 m per membrane surface effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)). ３ / (m ２ A secondary pure water production system comprising a reverse osmosis membrane having a diameter of 100 mm or more and a booster pump for feeding the water to be treated to the reverse osmosis membrane.

2. 2. The secondary pure water production system according to claim 1, comprising a storage tank for the primary pure water, a heat exchanger, an ultraviolet oxidation device, a booster pump, a reverse osmosis membrane, and an ion exchange device provided in a water supply pipe connected to a use point connected to the storage tank, and a return pipe for returning water from the use point to the storage tank.

3. The reverse osmosis membrane has a permeation flux (flux) of 0.6 m under the condition of an effective membrane surface pressure of 0.3 MPa (water temperature 25°C, pure water (RO permeate)). ３ / (m ２ 3. The secondary pure water production apparatus according to claim 1, wherein the water temperature is 25°C, the feed water has a salt rejection rate of 95% or more (effective membrane surface pressure of 0.3 MPa (water temperature 25°C, feed water 500 mg / L at NaCl) and the IPA rejection rate is 60% or more (effective membrane surface pressure of 0.3 MPa (water temperature 25°C, feed water 500 mg / L at IPA)).

4. A secondary pure water manufacturing apparatus as described in Claim 2, wherein the heat exchanger cools the temperature of the secondary pure water supplied from the secondary pure water manufacturing apparatus to the use point to 25±0.5°C.

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