Secondary water purification unit

Abstract

To provide a secondary pure water system that can reduce environmental impact and maintain the quality of ultrapure water. [Solution] A secondary pure water production device in an ultrapure water production system comprising a primary pure water production device and a secondary pure water production device, wherein the secondary pure water production device has a non-regenerative ion exchange device and an ultrafiltration membrane in that order, and at least the downstream side of the non-regenerative ion exchange device is connected by non-fluorine and non-chlorine synthetic resin piping. As the non-fluorine and non-chlorine synthetic resin piping, polyolefin resin piping such as polypropylene or polyethylene is used.

Description

[Technical Field]

[0001] This invention relates to a secondary pure water system for an ultrapure water production apparatus. [Background technology]

[0002] Ultrapure water used for semiconductor cleaning is produced by treating raw water (industrial water, city water, well water, etc.) in an ultrapure water production system consisting of a pretreatment system, a primary pure water system, and a secondary pure water system (subsystem).

[0003] Pretreatment systems consisting of coagulation, pressurized flotation (sedimentation), and filtration devices remove suspended solids and colloidal substances from the raw water. Primary pure water systems equipped with reverse osmosis (RO) membrane separators, degassing devices, and ion exchange devices (mixed-bed, 2-bed 3-column, or 4-bed 5-column) remove ions and organic components from the raw water. In addition to salt removal, RO membrane separators remove ionic and colloidal total organic oxygen (TOC). In addition to salt removal, ion exchange devices remove TOC components that are adsorbed or ion-exchanged by ion exchange resins. Degassing devices (nitrogen degassing or vacuum degassing) remove dissolved oxygen.

[0004] In a secondary pure water system (subsystem) equipped with a heat exchanger, low-pressure ultraviolet (UV) oxidation device, mixed-bed ion exchange device, and ultrafiltration (UF) membrane separation device, the purity of the water is further increased to produce ultrapure water. In the low-pressure UV oxidation device, ultraviolet light with a wavelength of 185 nm emitted from a low-pressure UV lamp decomposes TOC into organic acids and then CO2. The decomposed organic acids and CO2 are removed by the ion exchange resin in the subsequent stage. In the UF membrane separation device, fine particles are removed, as well as particles leached out of the ion exchange resin.

[0005] Patent Document 1 describes using synthetic resin for the water-contacting surfaces of equipment in a secondary pure water system. Examples of synthetic resins include fluororesins such as polytetrafluoroethylene and polyvinyl difluoride, as well as polyethylene, polypropylene, polyetheretherketone, polyvinyl chloride, and polysulfone. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-167308 [Overview of the project] [Problems that the invention aims to solve]

[0007] In semiconductor factories, maintaining ultrapure water quality is essential, which limits the materials that can be used in various components. On the other hand, the materials used often contain substances subject to environmental regulations (such as fluorine and chlorine).

[0008] For example, in the case of fluoropolymer piping, organic fluorine compounds are released into the environment during the manufacturing and disposal of the piping material, or when ultrapure water is passed through it. In the case of chlorine-based piping, harmful chlorine-based gases (such as dioxins) are generated during the manufacturing and disposal of the piping material, and during installation (heat fusion).

[0009] While polyolefin resin piping, such as polypropylene and polyethylene, can reduce environmental impact for ultrapure water, it has inferior gas barrier properties compared to fluororesin and chlorine resin piping, making it difficult to maintain the quality of ultrapure water. (For example, dissolved oxygen (DO) levels tend to rise.)

[0010] Furthermore, polyolefin resin piping exhibits inferior surface smoothness compared to fluorine-based resin piping and chlorine-based resin piping.

[0011] The present invention aims to provide a secondary pure water system that can reduce environmental impact and maintain the quality of ultrapure water. [Means for solving the problem]

[0012] The gist of this invention is as follows:

[0013] [1] A secondary pure water production device in an ultrapure water production system equipped with a primary pure water production device and a secondary pure water production device, where the secondary pure water production device has a non-regenerative ion exchange device and an ultrafiltration membrane in this order, and at least the downstream side of the non-regenerative ion exchange device is connected by a non-fluorine and non-chlorine synthetic resin pipe, a secondary pure water device.

[0014] [2] The secondary pure water device according to [1], wherein the DO concentration of the ultrapure water produced by the ultrapure water production system is 1 μg / L or less.

[0015] [3] The secondary pure water device according to [1], wherein the non-fluorine and non-chlorine synthetic resin pipe is a polyolefin resin pipe.

[0016] [4] The secondary pure water device according to [3], wherein the polyolefin resin pipe is a polypropylene pipe or a polyethylene pipe.

[0017] [5] The secondary pure water device according to [4], wherein the polypropylene pipe or the polyethylene pipe has a gas barrier layer of 480 [cc·20 μm / (m 2 ·24 hr·atm)] or less.

[0018] [6] The secondary pure water device according to [5], wherein the polypropylene pipe or the polyethylene pipe is a multilayer pipe having a gas barrier layer on the outermost layer.

[0019] [7] The secondary pure water device according to any one of [4] to [6], wherein the elution amount of the cation component from the inner peripheral surface of the pipe is 30 μg / m 2 or less. [Effect of the Invention]

[0020] In the secondary pure water device of the present invention, since at least the equipment on the downstream side of the non-regenerative ion exchange device is connected by a non-fluorine and non-chlorine synthetic resin pipe, it is possible to reduce the environmental load and maintain the water quality of ultrapure water.

Brief Description of the Drawings

[0021] [Figure 1] It is a flowchart of an ultrapure water production device equipped with a secondary pure water device according to an embodiment. [Figure 2] It is a flowchart of a secondary pure water device according to an embodiment. [Figure 3] It is a configuration diagram of piping used in a secondary pure water device according to an embodiment. [Figure 4] It is a flowchart of a secondary pure water device according to an example.

Modes for Carrying Out the Invention

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

[0023] FIG. 1 is a flowchart of an ultrapure water production device equipped with a secondary pure water device, and FIG. 2 is a configuration diagram of the secondary pure water device (subsystem).

[0024] Raw water composed of industrial water, well water, tap water, etc. is sent from the raw water tank 1 to the pretreatment device 2 and processed. The pretreatment device 2 includes a coagulation device, a pressure flotation (sedimentation) device, a filtration device, etc., and removes suspended substances and colloidal substances in the raw water.

[0025] The treated water of the pretreatment device 2 is sent to the primary pure water device 4 through the filtration water tank 3 and processed. As the primary pure water device 4, (a) Multi-bed ion exchange device + RO (reverse osmosis membrane) device (b) RO device + high purity type ion exchange device (c) RO device + decarbonation device + electro-deionization device etc. can be used, but not limited thereto. The RO device in (b) and (c) may be a two-stage RO device.

[0026] The pure water obtained from the primary pure water system 4 is introduced into the pure water tank 5. The pure water in the pure water tank 5 is sent through piping 6 to the deaeration membrane system 7, where it is deaerated. The deaerated water is sent through piping 8 to the TOC decomposition unit 10 for further treatment.

[0027] In this embodiment, the TOC decomposition unit 10 includes a UV oxidizer 11 and an ion exchanger (which may be a mixed-bed type, a 2-bed 3-column type, or a 4-bed 5-column type, etc.) 12 located after it.

[0028] A bypass line consisting of pipe 13, valve 14, and pipe 15 is provided to bypass the degassing membrane device 7 described above. Pipe 13 connects pipe 6 to valve 14, and pipe 15 connects valve 14 to pipe 8.

[0029] A DO meter 9 is installed downstream of the confluence point with pipe 15 in pipe 8. The detection signal from the DO meter 9 is input to a valve controller (not shown). The valve controller controls the opening of valve 14 so that the DO detected by the DO meter 9 is 10 ppb or less.

[0030] The high-purity (low TOC) primary pure water processed in the TOC decomposition unit 10 is sent to the sub-tank 17 through piping 16. A branch pipe 16A branches off from piping 16, allowing a portion of the high-purity (low TOC) primary pure water from the TOC decomposition unit 10 to be returned to the pure water tank 5. A flow control valve (not shown) is provided downstream of the branch of piping 16A in piping 16, and the opening of this valve is controlled so that the water level in the sub-tank 17 is within a predetermined range.

[0031] Ultrapure water from use point 36 is also introduced into sub-tank 17 via piping 37.

[0032] The water in the sub-tank 17 is sent through the piping 18 to the secondary pure water system (hereinafter sometimes referred to as the subsystem) 20. The ultrapure water produced by processing in the subsystem 20 is sent through the piping 35 to the use point 36, and the unused ultrapure water is returned to the sub-tank 17 through the piping 37.

[0033] Subsystem 20, as shown in Figure 2, includes a sub-pump 19, a cooler (heat exchanger) 21, a low-pressure ultraviolet (UV) oxidizer 22, a non-regenerative ion exchanger 23, a degassing membrane device 24, and an ultrafiltration membrane (UF) device 25. These devices are connected by piping 31-34.

[0034] In this embodiment, at least the piping 33, 34, and 35 downstream of the non-regenerative ion exchange device 23 is made of non-fluorine and non-chlorine synthetic resin piping, and preferably all the piping 18, 31-35 is made of non-fluorine and non-chlorine synthetic resin piping.

[0035] For this non-fluorine and non-chlorine synthetic resin piping, polyolefin resin piping is preferred.

[0036] The polyolefin resin can be any polymer containing monomer units derived from olefins. Examples include polypropylene resins, polyethylene resins, ethylene-carboxylic acid alkenyl ester copolymer resins, ethylene-α-olefin copolymer resins, polybutene resins, and poly(4-methyl-1-pentene) resins. These polyolefin resins may be used individually or in combination of two or more. Among these polyolefin resins, polyethylene resins and polypropylene resins are preferred from the viewpoint of improving the strength of ultrapure water piping.

[0037] Examples of polyethylene resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). Among these, high-density polyethylene (HDPE) is preferred from the viewpoint of suppressing the elution of organic components into ultrapure water.

[0038] Examples of carboxylic acid alkenyl esters in ethylene-carboxylic acid alkenyl ester copolymer resins include vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, and allyl acetate, with vinyl acetate being preferred.

[0039] Examples of ethylene-α-olefin copolymers include copolymers obtained by copolymerizing ethylene with α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, or 1-octene in a proportion of several mole percent.

[0040] Examples of polypropylene resins include homopolypropylene, block polypropylene, and random polypropylene. Ethylene is typically used as the copolymer component in block polypropylene and random polypropylene. Among these, random polypropylene is preferred from the viewpoint of achieving a good balance of rigidity and strength in ultrapure water piping. Examples of polybutene resins include polybutene-1.

[0041] As described above, polypropylene or polyethylene pipes are preferred as polyolefin resin pipes, and these polypropylene or polyethylene pipes have a density of 480cc·20μm / (m 2 It is preferable to have a gas barrier layer of 24hr·atm or less, and for this reason, it is preferable to provide a gas barrier layer on the outermost layer of polypropylene or polyethylene piping.

[0042] Furthermore, for polypropylene or polyethylene piping, the amount of cation components eluted from the inner surface of the piping is 30 μg / m³.2 The following are preferred:

[0043] The subsystem shown in Figure 2 is an example of the present invention, and the secondary pure water system of the present invention may have at least a sub-tank, a sub-pump, a non-regenerative ion exchange device, and an ultrafiltration membrane device (UF device). That is, the secondary pure water system of the present invention may have other equipment in the subsystem shown in Figure 2, some equipment may be omitted, and some equipment may be arranged differently. For example, a hydrogen peroxide removal device may be provided downstream of the UV oxidizer 22. Also, the non-regenerative ion exchange device 23 may be placed downstream of the degassing membrane device 24.

[0044] As mentioned above, polyolefin resin piping is suitable as a non-fluorine and non-chlorine synthetic resin piping, but this polyolefin resin piping generally has a low gas permeability coefficient (high gas permeability). The gas permeability coefficient can be calculated using the following formula.

[0045] Gas permeability coefficient [cc·20μm / (m 2 (24hrs·atm) = Gas permeation rate (volume) × Film thickness / (Pressure difference × Permeation area × Time)

[0046] Gas permeability can be calculated using the following formula.

[0047] Gas permeability [cc / (m³) 2 (24hr·atm) = Gas permeation rate (volume) / (pressure difference × permeation area × time)

[0048] In the present invention, in order to improve the gas barrier properties of polyolefin-based synthetic resin piping, which has poor gas barrier properties, it is preferable to have one of the following configurations (1), (2), or (3).

[0049] (1) It has a single-layer or multi-layer structure and has at least one gas barrier layer. This gas barrier layer has a gas permeability coefficient of 480 [cc·20 μm / (m 2·24hrs·atm)] or less, and a synthetic resin gas barrier layer having a thickness of 150 μm or less, particularly 50 to 150 μm, is suitable.

[0050] As this synthetic resin, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinylidene chloride resin, polyacrylonitrile, etc. are suitable.

[0051] This synthetic resin gas barrier layer may be provided on the outer circumference of the pipe as shown in Fig. 3(a). Also, as shown in Fig. 3(b), it is preferable to provide a high-density polyethylene (HDPE) layer with a reduced elution amount of Ca or the like on the inner circumference of the pipe. These layers may be formed integrally with the pipe by extrusion molding.

[0052] (2) A substance having a gas permeability coefficient of 480 [cc·20μm / (m 2 ·24hrs·atm)] or less is provided on the outside of the pipe. Such substances include metal pipes such as SUS, gas barrier resins (polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinylidene chloride resin, and polyacrylonitrile, etc.), or pipe materials gas barrier processed with a gas barrier resin.

[0053] (3) The resin pipe is thickened to lower the gas permeability. In this case, it is preferable that the ratio of the outer diameter of the pipe to the resin thickness is 15% or more.

[0054] In the present invention, the elution amount of metal ions (for example, Ca, Zn, Al, Fe, Ni, Mg, k, Na, Ba, B, etc.) from the inner circumferential surface of the pipe is preferably 30 μg / m 2 or less.

Example

[0055] [Example 1] Using the subsystem having the configuration shown in Fig. 4, primary pure water having the water quality shown in Table 1 was treated to produce ultrapure water. In the subsystem of Fig. 4, as the pipe at least on the downstream side of the ion exchange device, the gas permeability coefficient is 480 [cc·20μm / (m 2The gas barrier layer has a thickness of 150 μm or less on its outer periphery and is less than 24 hours atm. The metal ion elution concentration from the inner surface is 30 μg / m³. 2 The following polyethylene piping was used. The water quality of the produced ultrapure water is shown in Table 1.

[0056] [Table 1]

[0057] As shown in Table 1, the water quality of the produced ultrapure water was good, and the DO concentration of the ultrapure water was 1 μg / L or less. [Explanation of symbols]

[0058] 1. Raw water tank 2 Pre-treatment device 4 Primary water purifier 5. Pure water tank 7 Degassing membrane 10 TOC disassembly units 17 Sub-tank 20. Secondary pure water system (subsystem) 21 Cooler 22 UV oxidizer 23 Non-regenerative ion exchange device 24 Degassing membrane device 25 Ultrafiltration membrane device 36 Youth Points

Claims

1. A secondary pure water production device in an ultrapure water production system comprising a primary pure water production device and a secondary pure water production device, The aforementioned secondary pure water production apparatus has a non-regenerative ion exchange device and an ultrafiltration membrane in this order, A secondary pure water system, wherein at least the downstream side of the non-regenerative ion exchange device is connected by non-fluorine and non-chlorine synthetic resin piping.

2. The secondary pure water apparatus according to claim 1, wherein the DO concentration of the ultrapure water produced by the ultrapure water production system is 1 μg / L or less.

3. The secondary pure water apparatus according to claim 1, wherein the non-fluorine and non-chlorine synthetic resin piping is made of polyolefin resin.

4. The secondary pure water apparatus according to claim 3, wherein the polyolefin resin piping is polypropylene piping or polyethylene piping.

5. The polypropylene or polyethylene piping has a capacity of 480 [cc・20 μm / (m ２ A secondary pure water apparatus according to claim 4, having a gas barrier layer of 24hr·atm or less.

6. The secondary pure water apparatus according to claim 5, wherein the polypropylene or polyethylene piping is a multilayer piping having a gas barrier layer as its outermost layer.

7. The polypropylene or polyethylene piping has an elution amount of cation components from the inner surface of the piping of 30 μg / m³. ２ The secondary pure water apparatus according to any one of claims 4 to 6, which is as follows:

Images