Ultra-pure water production apparatus, ultra-pure water production method, operation management method of ultra-pure water production apparatus, and method for measuring colloidal particles

Abstract

Provided are an ultrapure water production apparatus, an ultrapure water production method, an operation management method of the ultrapure water production apparatus, and a colloidal particle measurement method that can be used for the measurement of colloidal particles. 【Solution means】The ultrapure water production apparatus includes a water supply pump, an ion exchange apparatus, and an ultrafiltration membrane apparatus in this order, and is an ultrapure water production apparatus including a secondary pure water apparatus that removes impurities from primary pure water. On the downstream side of the ultrafiltration membrane apparatus, at least one combination of a first combination of an acoustic particle counter and an optical particle counter and a second combination of an acoustic particle counter and a TOC meter is arranged.

Description

Technical Field

[0001] The technology of the present disclosure relates to an ultrapure water production apparatus and a method for measuring colloidal particles.

[0002] The ultrapure water used in the semiconductor manufacturing process is produced by an ultrapure water production apparatus including a primary pure water apparatus and a secondary pure water apparatus in this order. In the ultrapure water production apparatus, the primary pure water apparatus removes total organic carbon (TOC) components and ion components in raw water or pretreated water using a reverse osmosis membrane apparatus or an ion exchange apparatus to produce primary pure water. The secondary pure water apparatus removes extremely minute impurities in the primary pure water to produce ultrapure water. And it is common to install an ultrafiltration membrane (UF) apparatus at the end of the secondary pure water apparatus to remove nanoparticlesize fine particles.

[0003] In such an ultrapure water production apparatus, a particle counter for measuring the number of fine particles in water is arranged on the downstream side of the ultrafiltration membrane apparatus, and the water quality is managed based on the measurement value of the particle counter (see, for example, Patent Document 1). Patent Document 1 discloses a configuration in which a plurality of optical particle counters are arranged for the purpose of improving the measurement accuracy of fine particles. Further, in the ultrapure water production apparatus described in Patent Document 2, the flow rate of the water to be treated flowing through the ion exchange apparatus is controlled in order to efficiently remove fine particles.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the semiconductor manufacturing process, ultrapure water is used for cleaning semiconductor wafers. If impurities contained in the ultrapure water adhere to the semiconductor wafers, it may have an adverse effect on the quality of the semiconductor. In recent years, with the remarkable progress of miniaturization and high integration of semiconductor circuits, the required water quality for ultrapure water used in the semiconductor manufacturing process has become increasingly strict.

[0006] Among the impurities adhering to the semiconductor wafers, in addition to fine particles, colloidal particles are included. A colloid refers to a state in which particles much smaller than fine particles are dispersed in a liquid while having a certain degree of aggregation and floating like a cloud. Here, the aggregation of particles in such a state is called colloidal particles.

[0007] In an ultrapure water production device, various sources of colloidal particles can be considered, and one of the sources is considered to be the ion exchange device. For example, the bond of unstable functional groups is broken from the surface of the ion exchange resin, and the broken functional groups desorb from the ion exchange resin and aggregate, or aggregate on the surface of the ion exchange resin to form colloidal particles, which float in water.

[0008] Colloidal particles do not completely dissolve in a liquid like ions, and have both non-particle properties such as ions and particle properties such as fine particles. Also, colloidal particles can be considered to have a smaller particle diameter compared to fine particles. Since colloidal particles are not complete fine particles with a clearly defined outer edge, the refractive index of light is very low compared to fine particles, and it was difficult to measure with a known optical particle counter.

[0009] However, it is known that colloidal particles can be confirmed to exist by using an SEM (Scanning Electron Microscope) etc. when they are attached to a semiconductor wafer, and may have an adverse effect on the quality of the semiconductor as described above. Therefore, in the process of producing ultrapure water, it has been desired to measure colloidal particles, such as quantitatively grasping the colloidal particles in the water to be treated or at least grasping the tendency of increase or decrease.

[0010] The technology of the present disclosure provides an ultrapure water production apparatus, an ultrapure water production method, an operation management method of the ultrapure water production apparatus, and a colloidal particle measurement method that can be used for measuring colloidal particles.

Means for Solving the Problems

[0011] The ultrapure water production apparatus according to the technology of the present disclosure is an ultrapure water production apparatus including a secondary pure water apparatus that removes impurities from primary pure water, and includes a water supply pump, an ion exchange apparatus, and an ultrafiltration membrane apparatus in this order, and at least one of a first combination of an acoustic particle counter and an optical particle counter and a second combination of an acoustic particle counter and a TOC meter is arranged on the upstream side and / or the downstream side of the ultrafiltration membrane apparatus.

[0012] It may have a processor for controlling the water recovery rate of the ultrafiltration membrane apparatus.

[0013] The ultrapure water production method according to the technology of the present disclosure is an ultrapure water production method using the above-described ultrapure water production apparatus.

[0014] The operation management method of the ultrapure water production apparatus according to the technology of the present disclosure is an operation management method of an ultrapure water production apparatus including a secondary pure water apparatus that removes impurities from primary pure water, and includes a water supply pump, an ion exchange apparatus, and an ultrafiltration membrane apparatus in this order. It is arranged on the downstream side of the ultrafiltration membrane apparatus and uses at least one of a first combination of an acoustic particle counter and an optical particle counter and a second combination of an acoustic particle counter and a TOC meter, and performs operation management based on the measurement values obtained from the combination.

[0015] The method for measuring colloidal particles according to the technology of the present disclosure is a method for measuring colloidal particles in a secondary pure water device that includes a water supply pump, an ion exchange device, and an ultrafiltration membrane device in this order to remove impurities from primary pure water. It is arranged on the downstream side of the ultrafiltration membrane device and uses at least one of a first combination of an acoustic particle counter and an optical particle counter or a second combination of an acoustic particle counter and a TOC meter. Based on the measurement values obtained from the combination, colloidal particles are measured.

Advantages of the Invention

[0016] According to the technology related to the present disclosure, it is possible to provide an ultrapure water production device, an ultrapure water production method, an operation management method for an ultrapure water production device, and a method for measuring colloidal particles that can be used for measuring colloidal particles.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0018] [Ultra-pure Water Production Apparatus] Hereinafter, an ultra-pure water production apparatus according to the technology of the present disclosure will be described. As shown in FIG. 1, the ultra-pure water production apparatus 10 according to the present embodiment includes a pretreatment apparatus 11, a primary pure water apparatus 12, and a secondary pure water apparatus 13. The ultra-pure water produced by the ultra-pure water production apparatus 10 is sent to a use point (POU) 14 and used here. The use point 14 is, for example, a semiconductor manufacturing apparatus, and the ultra-pure water is used for washing a semiconductor wafer in a semiconductor manufacturing process.

[0019] Among the ultra-pure water sent to the use point 14, the unused ultra-pure water is returned to the secondary pure water apparatus 13 through the circulation line LC. Also, although one use point 14 is shown in FIG. 1, the ultra-pure water production apparatus 10 may supply ultra-pure water to two or more use points 14. Further, the used ultra-pure water used at the use point 14 is returned to the pretreatment apparatus 11 through the recovery line LR. The circulation line LC and the recovery line LR are pipelines for flowing liquid and are composed of piping or the like.

[0020] (Pretreatment Apparatus) Raw water is supplied to the pretreatment device 11. The pretreatment device 11 is equipped with a coagulation sedimentation device, a sand filtration device, a membrane filtration device, etc., and uses these to clarify the raw water and produce pretreated water with turbidity removed and a part of the suspended substances and organic substances removed. As the raw water, industrial water, tap water, groundwater, river water, etc. can be used. In addition, if the pretreatment device 11 is configured with a combination of a high-pressure reverse osmosis membrane device, hypobromous acid addition, and an ultraviolet irradiation device for urea removal, or if a boron removal device such as a boron-selective ion exchange device is added to the high-pressure reverse osmosis membrane device, etc., seawater or sewage can also be used as the raw water. As the raw water, one of these may be used, or two or more may be used in combination.

[0021] (Primary pure water device) The primary pure water device 12 performs primary pure water treatment to turn raw water into primary pure water. The primary pure water device 12 performs purification treatment of the raw water to remove impurities from the raw water and produce primary pure water. Specifically, the primary pure water device 12 has various devices such as a desalination device for removing impurity ions, a reverse osmosis membrane device for removing inorganic ions, organic substances, fine particles, etc., a vacuum degassing device or a membrane degassing device for removing dissolved gases such as dissolved oxygen, and a regenerative mixed bed type desalination device and an electrodeionization device for removing remaining ions, etc. Note that instead of raw water, primary pure water treatment may be performed on the pretreated water.

[0022] (Secondary pure water device) The secondary pure water device 13 is a device that performs secondary pure water treatment to remove extremely trace amounts of impurities in the primary pure water and produce ultrapure water.

[0023] As shown in Fig. 2, the secondary pure water device 13 includes a pure water tank (TK) 21, a water supply pump P1 provided at the downstream of the pure water tank 21, an ultraviolet irradiation device (UV) 22, a membrane degassing device (MDG) 23, a non-regenerative mixed bed ion exchange resin device (Polisher) 24, a booster pump P2, and an ultrafiltration membrane device (UF) 25 in this order. In the secondary pure water device 13, the primary pure water stored in the pure water tank 21 is sequentially supplied to each device from the ultraviolet irradiation device 22 to the ultrafiltration membrane device 25 at the downstream by the water supply pump P1 and the booster pump P2, and is processed by each device to produce ultrapure water. Note that the booster pump P2 may be provided at the upstream of the non-regenerative mixed bed ion exchange resin device 24.

[0024] The material, shape, etc. of the pure water tank 21 are not particularly limited as long as it does not generate rust, etc., and there is almost no component elution from the container, and it can stably store primary pure water. The material of the pure water tank 21 is preferably, for example, fiber reinforced plastic (FRP), polyethylene, SUS304, or those lined with a fluororesin such as Teflon (registered trademark).

[0025] (Ultraviolet irradiation device) In the ultraviolet irradiation device 22, ultraviolet rays are irradiated onto the primary pure water to decompose organic substances in the primary pure water and perform sterilization treatment (sterilization) of live bacteria, etc. The ultraviolet irradiation device 22 includes, for example, an ultraviolet lamp capable of irradiating a wavelength near 185 nm or a wavelength near 254 nm, and can reliably decompose organic substances and sterilize in the primary pure water. The ultraviolet lamp of the ultraviolet irradiation device 22 is not particularly limited, but a low-pressure mercury lamp is preferable in terms of ease of handling. Further, examples of the ultraviolet irradiation device 22 include a flow-through type in which an ultraviolet lamp is arranged inside the housing along the flow path of the water to be treated, or an immersion type in which the ultraviolet lamp is immersed in a tank for storing the water to be treated. The flow-through type is preferable from the viewpoint of treatment efficiency.

[0026] (Membrane degassing device) The membrane degassing device 23 removes gases, particularly dissolved oxygen, in primary pure water, using a gas separation membrane that allows gases to permeate but does not allow water to permeate.

[0027] (Non-regenerable mixed-bed ion exchange resin device) The primary pure water with the dissolved oxygen concentration removed by the membrane degassing device 23 is sent to the non-regenerable mixed-bed ion exchange resin device 24. The non-regenerable mixed-bed ion exchange resin device 24 adsorbs and removes impurity ions such as organic acids generated by the decomposition of organic substances by the ultraviolet irradiation device 22 and metal ions remaining in the water. The non-regenerable mixed-bed ion exchange resin device 24 has, for example, a structure in which a cylindrical sealed container is filled with a mixed-bed ion exchange resin. The mixed-bed ion exchange resin is usually a mixture of a cation exchange resin and an anion exchange resin. The non-regenerable mixed-bed ion exchange resin device 24 is an example of the "ion exchange device" of the present disclosure.

[0028] (Booster pump) The booster pump P2 is a pump that additionally applies pressure assistively to increase the water passing pressure. By ensuring the water pressure on the outlet side of the ultrafiltration membrane device 25 with the booster pump P2, the water pressure required at the use point 14 can be properly maintained.

[0029] (Ultrafiltration membrane device) The ultrafiltration membrane device 25 includes one or more ultrafiltration membrane modules or one or more ultrafiltration membrane cartridges. The ultrafiltration membrane module is formed by providing an ultrafiltration membrane inside a housing having a water inlet for feed water, a permeate outlet, and a concentrate outlet, and by connecting each opening of the module to a pipe, the water to be treated is passed through the ultrafiltration membrane. In the ultrafiltration membrane module, when the clogging of the ultrafiltration membrane progresses and the filtration performance deteriorates, the entire module can be replaced, and the deteriorated ultrafiltration membrane can be cleaned for each module. The ultrafiltration membrane installed in the ultrafiltration membrane module is sometimes called an ultrafiltration membrane cartridge. In the case of an ultrafiltration membrane cartridge, only the cartridge inside the ultrafiltration membrane module can be replaced. The ultrafiltration membrane is composed of, for example, a hollow fiber membrane.

[0030] The ultrafiltration membrane device 25 removes fine particles in water, for example, fine particles with a particle size of 50 nm or more (preferably 10 nm or more). The ultrafiltration membrane device is composed of one or more ultrafiltration membrane modules. The type of the ultrafiltration membrane provided in the ultrafiltration membrane module is not particularly limited, and usually, it is a hollow fiber membrane, and it may also be a spiral membrane, a tubular membrane, a flat membrane, etc. The material of the ultrafiltration membrane is polysulfone, polyvinylidene fluoride, polyethylene, polypropylene, etc., and it is preferably that the nominal molecular weight cut-off is 3000 to 8000, and more preferably 4000 to 6000. The ultrafiltration membrane module may use either an internal pressure type or an external pressure type. Further, the ultrafiltration membrane device 25 may be a cross-flow type or an all-filtration type. Also, the ultrafiltration membrane device 25 can be set in multiple stages in series.

[0031] In the ultrafiltration membrane device 25, the water inlet is connected to the water flow line on the side of the booster pump P2, the outlet on the permeate side is connected to the circulation line LC, and the outlet on the concentrate side is connected to the drain line LB. A valve VA is provided in the path of the circulation line LC. Further, the circulation line LC branches on the upstream side of the valve VA, and the branched water supply line LA is connected to the use point 14. The ultrapure water not used at the use point 14 is returned to the pure water tank 21.

[0032] A measuring device 31 for measuring impurities in the water to be treated is arranged in the pipeline on the downstream side of the ultrafiltration membrane device 25. The measuring device 31 is composed of, as an example, an acoustic particle counter 31A, an optical particle counter 31B, and a TOC meter 31C. The measured values of the measuring device 31 are output to the processor 26. The processor 26 manages the water quality based on the measured values.

[0033] The water to be treated is subjected to impurity removal in the ultrafiltration membrane device 25, but the ultrafiltration membrane device 25 cannot completely remove the impurities. Based on the measured values obtained from the measuring device 31, the processor 26 monitors whether the amount of impurities contained in the water to be treated is within a preset allowable range. Then, the processor 26 repeatedly removes the impurities by means of the ultrafiltration membrane device 25 or the like until the measured value falls within the allowable range. When the measured value has decreased to within the allowable range, the ultrapure water produced at the use point 14 is sent. That is, on the downstream side of the measuring device 31, a bypass line LD that returns to the pure water tank 21 is connected before branching into the water supply line LA. And by means of a valve (not shown), it is possible to switch the destination of the water to be treated that has passed through the ultrafiltration membrane device 25 to either the bypass line LD or the water supply line LA. When the water quality is outside the allowable range, the water to be treated of the ultrafiltration membrane device 25 is directly returned to the pure water tank 21 using the bypass line LD that returns to the pure water tank 21, and when the measured value falls within the allowable range, it is switched to the water supply line LA that supplies the use point 14. The impurities include, in addition to fine particles, dissolved organic carbon (DOC: Dissolved Organic Carbon), colloidal particles, metals such as iron, copper, calcium, and boron dissolved in the water to be treated.

[0034] The acoustic particle counter 31A sends out sound waves of energy specific to the fine particles to be detected into the water to be treated, and a piezoelectric element detects the cavitation pressure caused by the fine particles that have received the sound waves. Then, when a pressure equal to or higher than a certain pressure is detected, it is counted as a fine particle, and the number of counted fine particles is output as a measured value to the processor 26. As the acoustic particle counter 31A, for example, "NanoPULS" (registered trademark) manufactured by OVIVO is used.

[0035] The optical particle counter 31B emits laser light into the water to be treated, condenses the scattered light of the laser light irradiated on the particles with a condensing optical system, and detects the condensed light with a photoelectric conversion element. Then, it counts the number of particles according to the detected light reception amount, and outputs the counted number of particles as a measured value to the processor 26. As the optical particle counter 31B, for example, "Ultra DI (registered trademark) 20Plus" manufactured by PMS is used.

[0036] The TOC meter 31C is a device that measures the total carbon content (TOC: Total Organic Carbon) contained in the organic substances present during the treatment. The total carbon content includes, in addition to the dissolved organic carbon content (DOC), a small proportion of particulate or colloidal organic carbon content (the amount of organic carbon that does not dissolve in the water to be treated). As is well known, the TOC meter 31C decomposes the organic substances in the water to be treated using ultraviolet irradiation or an oxidizing agent, and measures the amount of generated carbon dioxide (CO 2 ) by methods such as infrared absorption method or conductivity method. Since the amount of generated carbon dioxide is proportional to the total carbon content contained in the organic substances, the total carbon content contained in the water to be treated can be quantified by measuring the amount of generated carbon dioxide. The TOC meter 31C outputs the measured total carbon content as a measured value. As the TOC meter 31C used here, any TOC meter for ultrapure water, such as Anatel A1000-XP manufactured by Beckman Coulter, Accura SXII manufactured by T & C Technical Co., Ltd., Sievers M500e, Sievers 500RL, Sievers 900, and 6000TOC manufactured by METTLER TOLEDO, can be used without particular limitation.

[0037] Furthermore, the processor 26 can measure colloidal particles, which are impurities in the water to be treated, based on the measurement values of the acoustic particle counter 31A and the optical particle counter 31B.

[0038] FIG. 3 is a schematic diagram conceptually showing colloidal particles CL. The ion exchange resin RE schematically shows a cation exchange resin and an anion exchange resin provided in the non-regenerative mixed bed type ion exchange resin device 24. From the surface of the ion exchange resin RE, ions IO of an organic substance derived from the functional group of the ion exchange resin may be peeled off, and when these ions IO aggregate in the liquid, they may become colloidal particles CL. Note that the colloidal particles CL may be formed in water after the ions IO are desorbed from the ion exchange resin RE, but they may be formed on the ion exchange resin RE or at the contact portion with water in the secondary water purification device 13, for example, on the filtration membrane of the ultrafiltration membrane device 25, on the surface of a pipe, or the like. Here, the colloidal particles CL are a concept including monomers, dimers, trimers, and polymers. The particle size of the colloidal particles CL is considered to be in the range from approximately several nanometers to several tens of nanometers or more, and those of the same degree as the size of the fine particles MP are also included. As described above, the colloidal particles CL do not completely dissolve in the liquid like the ions IO, and have both non-particle properties such as the ions IO and particle properties such as the fine particles MP.

[0039] In view of the properties of such colloidal particles CL, the inventors have found that it is possible to measure colloidal particles based on the measurement values of the optical particle counter 31B and the acoustic particle counter 31A. That is, the inventors have found, through experiments based on a hypothesis, that the acoustic particle counter 31A can detect colloidal particles CL in addition to the fine particles MP, and that by combining the optical particle counter 31B and the acoustic particle counter 31A, it is possible to quantitatively grasp the colloidal particles CL.

[0040] FIG. 4 is a diagram conceptually showing the reason why it is difficult to detect the colloidal particles CL in the optical particle counter 31B. As shown in FIG. 4(A), in the optical particle counter 31B, the laser light DL is irradiated onto the microparticles MP, and the microparticles MP are detected by detecting the scattered light SL scattered by the microparticles MP. However, the colloidal particles CL strongly exhibit optically non-particle-like properties and have a very small refractive index compared to the microparticles MP. Therefore, as shown in FIG. 4(B), even when the laser light DL is irradiated onto the colloidal particles CL, scattering hardly occurs. In the optical particle counter 31B, it is considered that the microparticles MP can be detected for such reasons, but the colloidal particles CL cannot be detected.

[0041] On the other hand, FIG. 5 is a diagram conceptually showing the reason why the colloidal particles CL can be detected in the acoustic particle counter 31A. As shown in FIG. 5(A), in the acoustic particle counter 31A, the sound wave SW is irradiated onto the microparticles MP, and the pressure based on the cavitation CV of the liquid generated by the vibration of the microparticles MP that have received the sound wave SW is detected. The colloidal particles CL do not dissolve in the liquid and exist as a solid with an outer edge similar to the microparticles MP. Therefore, as shown in FIG. 5(B), when the sound wave SW is irradiated onto the colloidal particles CL, the colloidal particles CL also vibrate in the same manner as the microparticles MP, and cavitation CV of the liquid occurs. The acoustic particle counter 31A is considered to be able to detect the colloidal particles CL by detecting the pressure based on this cavitation CV.

[0042] Figures 6 and 7 show the experimental results for verifying the above hypothesis. The experiment was conducted by adding gold colloid standard particles and PSL (polystyrene latex) standard microparticles online to ultrapure water and measuring the amount of microparticles with a particle counter installed at the downstream of the ultrafiltration membrane device 25. The gold colloid standard particles used were the standard gold colloid manufactured by BBI Solutions, and the PSL standard microparticles used were the standard latex particles manufactured by Thermo Fisher. The gold colloid standard particles are a model of microparticle MP, and the PSL standard microparticles are a model of colloidal particles. Hereinafter, the gold colloid standard particles are referred to as gold colloid particles and are denoted by AU in the figures. The PSL standard microparticles are referred to as latex spheres and are denoted by PSL in the figures. The acoustic particle counter 31A and the optical particle counter 31B used were the products described above.

[0043] Figure 6 is a graph showing the experimental results of an experiment in which the optical particle counter 31B detects gold colloid particles (Au), which are a model of microparticle MP, and latex spheres (PSL), which are a model of colloidal particles CL. Figure 7 is a graph showing the experimental results of an experiment in which the acoustic particle counter 31A detects gold colloid particles (Au) and latex spheres (PSL). In Figures 6 and 7, the horizontal axis represents the particle diameter [nm], and the vertical axis represents the detection rate. In Figures 6 and 7, there is no data with a particle diameter of less than 20 nm because the detection limit of each of the acoustic particle counter 31A and the optical particle counter 31B is 20 nm. The acoustic particle counter 31A and the optical particle counter 31B used were the products described above.

[0044] The latex sphere (PSL) is an organic substance, and it is presumed that the finer the particle size, the more the colloidal properties increase. On the other hand, it is presumed that the gold colloidal particles (Au) are less likely to exhibit this tendency due to their metallic properties. As shown in Fig. 6, in the optical particle counter 31B, there is a deviation in the detection rates of the gold colloidal particles (Au) and the latex spheres (PSL), and it can be seen that the detection rate of the latex spheres (PSL) is lower than that of the gold colloidal particles (Au). Since the difference widens as the particle size decreases, it can be understood that in the optical particle counter 31B, the more non-particle-like the properties become, the more difficult it is to detect. This experimental result is consistent with the hypothesis that for colloidal particles CL with a refractive index lower than that of the fine particles MP, as shown in Fig. 4, scattered light SL is less likely to occur, making detection difficult.

[0045] On the other hand, as shown in Fig. 7, in the acoustic particle counter 31A, there is no deviation in the detection rates of the gold colloidal particles (Au) and the latex spheres (PSL), and it can be seen that the latex spheres (PSL) can be detected to the same extent as the gold colloidal particles (Au). This experimental result is consistent with the hypothesis that, as shown in Fig. 5, the colloidal particles CL exhibit particle-like properties acoustically and generate cavitation CV when receiving the sound wave SW.

[0046] When these contents are organized, it becomes as shown in Fig. 8. That is, as shown in Fig. 8(A), in the acoustic particle counter 31A, both the fine particles MP and the colloidal particles CL can be detected, while in the optical particle counter 31B, the fine particles MP can be detected, but the colloidal particles CL cannot be detected. Therefore, as shown in Fig. 8(B), the measured value Xa of the acoustic particle counter 31A includes both the measured value of the fine particles MP and the measured value of the colloidal particles CL. In contrast, the measured value Xb of the optical particle counter 31B does not include the measured value of the colloidal particles CL and only includes the measured value of the fine particles MP.

[0047] Therefore, as shown in FIG. 9, in the processor 26, the measured value X_CL of the colloidal particles CL can be obtained by subtracting the measured value Xb of the optical particle counter 31B from the measured value Xa of the acoustic particle counter 31A. Similar to Xa and Xb, the measured value X_CL is the number of colloidal particles CL per unit volume. In this way, the processor 26 can quantitatively grasp the colloidal particles CL.

[0048] Next, a method for removing the colloidal particles CL measured in this way will be described. Since many of the colloidal particles CL have a smaller particle size than the fine particles MP, it has been considered difficult to remove them by the ultrafiltration membrane device 25. Also, focusing on the fact that the colloidal particles CL are aggregates of the ions IO, attempts have been made to remove them by capturing them by an electrical method. However, since the concentration of the colloidal particles CL is low, the contact probability of the ions IO with the substance that captures the ions IO is low, and it has been difficult to capture them by an electrical method.

[0049] Therefore, the inventors have found a method for removing the colloidal particles CL from the water to be treated by controlling the operating conditions of the ultrafiltration membrane device 25. Specifically, it is a method of setting the operating conditions of the ultrafiltration membrane device 25 to have a water recovery rate of less than 80% and operating. By this method, as will be described below, it has become possible to suppress the colloidal particles CL smaller than the pore size of the ultrafiltration membrane from passing through the ultrafiltration membrane. The control of the water recovery rate is performed by the processor 26 controlling the opening degrees of the valves VA and VB, and the driving conditions of the water supply pump P1 and the booster pump P2.

[0050] First, conventionally, in an ultrafiltration membrane device, it was considered that fine particles MP larger than the pore diameter of the ultrafiltration membrane were captured and removed from water, that is, the filtration mainly proceeded by the mechanism of surface filtration. However, colloid particles CL observed in ultrapure water at the end are often smaller than the pore diameter of the ultrafiltration membrane, and for this reason, it is considered that the colloid particles CL cannot be removed by the above-described surface filtration. As a result of investigations, the inventors hypothesized that the colloid particles CL proceed by the mechanism of depth filtration rather than surface filtration, and conducted experiments. As a result, it was found that the colloid particles CL are removed by the ultrafiltration membrane device 25 by filtering in a crossflow manner and under the conditions of the water recovery rate described above. The reason is not necessarily clear, but it is considered as follows.

[0051] FIG. 10 is a diagram for explaining the state of capture of fine particles MP and colloid particles CL on the membrane during membrane filtration in the present embodiment, and is a schematic diagram showing (A) the initial stage of filtration, (B) when the filtration has progressed (mid-stage), and (C) when the filtration has further progressed (final stage) from the top.

[0052] In FIG. 10, the rectangle represents the membrane surface 41 and the pore inner wall 42 of the filtration membrane, the solid small circles represent the fine particles MP, and the broken small circles represent the colloid particles CL. The thick arrow indicates the water flow, and the thin arrow indicates the movement of the fine particles MP.

[0053] First, the mechanism by which the fine particles MP are captured in the filtration membrane will be described. The places where the fine particles MP are captured and adsorbed are considered to be two, namely, the membrane surface 41 and the pore inner wall 42 of the filtration membrane. When the filtration membrane is new or in a state close to new, the number of fine particles MP already adsorbed on the membrane surface 41 or the pore inner wall 42 of the filtration membrane is small. Therefore, both the membrane surface 41 and the pore inner wall 42 can adsorb the fine particles MP. Since the water to be treated first contacts the membrane surface 41, as shown in FIG. 10(A), mainly the membrane surface 41 adsorbs the fine particles MP. After that, as the adsorption of the fine particles MP on the membrane surface 41 progresses, as shown in FIG. 10(B), the adsorption of the fine particles MP on the pore inner wall 42 gradually progresses.

[0054] Furthermore, as membrane filtration progresses and adsorption of the fine particles MP onto the ultrafiltration membrane proceeds, the amount of the fine particles MP adsorbed on the membrane surface 41 or the inner wall 42 of the pores increases. As a result, it becomes difficult for the fine particles MP to be newly adsorbed onto the membrane, and thus, as shown in FIG. 10(C), the fine particles MP start to permeate through the membrane. When this happens, the removal rate of the fine particles MP decreases.

[0055] Here, during the process of membrane filtration, the fine particles MP repeat adsorption onto and desorption from the membrane surface 41 of the ultrafiltration membrane. Therefore, if cross-flow membrane filtration is used and the flow velocity along the membrane surface 41 is increased to suppress the increase in the concentration of the fine particles MP on the membrane surface 41, the initial state as shown in FIG. 10(A) can be maintained. As a result, it is considered that the fine particles MP smaller than the pore diameter of the ultrafiltration membrane can be prevented from passing through the pores of the ultrafiltration membrane, and thus a high removal rate can be maintained.

[0056] The behavior of the colloidal particles CL is similar to that of the fine particles MP smaller than the pore diameter of the ultrafiltration membrane, and it is considered that during the process of membrane filtration, the colloidal particles CL repeat adsorption onto and desorption from the membrane surface 41 of the ultrafiltration membrane. Therefore, by suppressing the increase in the concentration of the colloidal particles CL adhering to the membrane surface 41, it is possible to suppress the colloidal particles CL smaller than the pore diameter of the ultrafiltration membrane from passing through the pores of the ultrafiltration membrane, and as a result, it is considered that the colloidal particles CL can be removed.

[0057] And, as an example, a method of operating by setting the water recovery rate to less than 80% is a method of maintaining the initial state shown in FIG. 10(A). Usually, the water recovery rate is often set to 80% or more, but by deliberately lowering the water recovery rate to less than 80%, that is, by increasing the flow velocity on the concentration side, the flow velocity along the membrane surface 41 can be increased. As a result, the amount of deposition of the fine particles MP and the colloidal particles CL deposited on the membrane surface 41 decreases, and thus it is considered that the initial state shown in FIG. 10(A) can be maintained.

[0058] FIG. 11 shows, as an example of a method of using the ultrapure water production apparatus 10 having the measuring apparatus 31 of the above embodiment, the experimental results of attempting to remove the colloidal particles CL by controlling the water recovery rate. The operating condition 1 of the ultrafiltration membrane apparatus 25 of Example 1 is that the water recovery rate is 55%, and the operating condition 2 of Example 2 is that the water recovery rate is 85%. The transmembrane differential pressure between the permeate side and the concentrate side of the filtration membrane is 1 kgf / cm 2 is. Also, as the filtration membrane, Microza (registered trademark) OAT6036 (molecular weight cut-off 6000) manufactured by Asahi Kasei Corporation was used. Further, as the mixed bed ion exchange resin of the non-regenerative mixed bed type ion exchange resin apparatus 24, "N-Lite (registered trademark) MBSP" manufactured by Nomura Micro Science was used, and the space velocity (SV) was set to 40 (1 / h). In the experiment, first, the water recovery rate of the ultrafiltration membrane apparatus 25 was set to 85%, and the secondary pure water apparatus 13 was operated under this setting to measure data. Then, the water recovery rate was set to 55%, and after the secondary pure water apparatus 13 was operated for 30 days until the data stabilized, measurement was performed to obtain measurement results. As the secondary pure water apparatus 13 used in the experiment, a secondary pure water apparatus 13 having the same configuration as that in FIG. 2 was used except that the ultraviolet irradiation apparatus 22 and the membrane degassing apparatus 23 were not installed.

[0059] In Example 1, the measured value of the acoustic particle counter 31A is Xa1, the measured value of the optical particle counter 31B is Xb1, and the difference therebetween is ΔX1, which is the number of colloidal particles CL per unit volume in Example 1. In Example 2, the measured value of the acoustic particle counter 31A is Xa2, the measured value of the optical particle counter 31B is Xb2, and the difference therebetween is ΔX2, which is the number of colloidal particles CL per unit volume in the comparative example. More specific numerical values are shown in Table 1 below.

[0060]

Table 1

[0061] As shown in Table 1, ΔX1, which is the amount of colloidal particles CL in Example 1, has decreased to 1 / 10 or less compared to ΔX2 in Example 2.

[0062] It was verified that the colloidal particles CL were removed by setting the water recovery rate to less than 80% as in Example 1.

[0063] Although the water recovery rate was set to less than 80%, if it is less than 50%, the water recovery rate becomes too low, resulting in a decrease in practicality. In terms of improving the removal rate of the colloidal particles CL and efficiently obtaining ultrapure water, the water recovery rate in the ultrafiltration membrane device 25 is preferably 50% or more and less than 80%.

[0064] As described above, the ultrapure water production apparatus 10 according to the technology of the present disclosure includes a water supply pump P1 (an example of a water supply pump), a non-regenerative mixed bed type ion exchange resin apparatus 24 (an example of an ion exchange apparatus), and an ultrafiltration membrane apparatus 25 in this order, and is an ultrapure water production apparatus 10 including a secondary pure water apparatus 13 that removes impurities from primary pure water. A combination of an acoustic particle counter 31A and an optical particle counter 31B (corresponding to the first combination) is arranged on the downstream side of the ultrafiltration membrane apparatus 25. Such an ultrapure water production apparatus 10 can be used for measuring the colloidal particles CL.

[0065] As the water supply pump, only the water supply pump P1 may be used, or a booster pump P2 may be further provided as in the above embodiment.

[0066] Further, since the ultrapure water production apparatus 10 according to the technology of the present disclosure has a combination of an acoustic particle counter 31A and an optical particle counter 31B, as described with reference to FIGS. 8 and 9, the colloidal particles CL in the water to be treated can be quantitatively grasped.

[0067] Further, the ultrapure water production apparatus 10 according to the technology of the present disclosure has a processor 26 that controls the water recovery rate of the ultrafiltration membrane apparatus 25. Therefore, as shown in FIGS. 10 and 11, by controlling the water recovery rate, the colloidal particles CL contained in the ultrapure water can be removed.

[0068] In this embodiment, the acoustic particle counter 31A and the optical particle counter 31B were compared at the same detection limit. However, they do not necessarily have to be the same with respect to the detection limit. In the case of different detection limits, it is not possible to take the difference between the measured value of the acoustic particle counter 31A and the measured value of the optical particle counter 31B. However, it is possible to grasp the trend of the increase or decrease of the colloidal particles CL from the trends of the measured values of both. Also, it is possible to estimate the amount of the colloidal particles CL in advance using the conversion coefficient between the measured value of the acoustic particle counter 31A and the measured value of the optical particle counter 31B. For example, if latex spheres (PSL) of various particle sizes are used to obtain the same trend as in FIG. 6 in advance for each particle size, it is possible to obtain the amount of the colloidal particles CL even when the detection limits are different by using a conversion method using the conversion coefficient and the like.

[0069] [Modification Example] The modification example shown in FIG. 12 is different from the combination of measuring instruments used for measuring the colloidal particles CL in FIG. 9 of the above embodiment. Since the other configurations are the same as those of the above embodiment, only the differences will be described below.

[0070] This modification example is based on the result of examination under the hypothesis that it is possible to use the TOC meter 31C to measure the amount of the colloidal particles CL. That is, the TOC meter 31C is a measuring instrument that measures the total amount of carbon of organic substances in water. Since the colloidal particles CL contain organic substances, at least part of the measured value of the TOC meter 31C should correspond to the amount of the colloidal particles CL. Also, in ultrapure water, for example, it is not the case that colloidal particles of single elements such as silica colloids, iron colloids, and organic substance colloids are mixed and present, but rather colloidal particles CL composed of a plurality of elements are present. Furthermore, it is possible to hypothesize that the component ratio in the colloidal particles CL does not change depending on the individual colloidal particles CL and is generally constant. Then, the hypothesis that there should be some relationship between the value of the TOC meter 31C and the amount of the colloidal particles CL obtained by the method of the above embodiment (that is, ΔX = Xa - Xb) holds. This modification example is the finding found under this hypothesis.

[0071] In the above-described embodiment, the colloidal particles CL were measured based on the measurement values of the acoustic particle counter 31A and the optical particle counter 31B. However, in the modified example shown in FIG. 12, a combination of measuring instruments of the acoustic particle counter 31A and the TOC meter 31C (corresponding to the second combination) is used, and the colloidal particles CL are measured based on two measurement values, i.e., the measurement value of the acoustic particle counter 31A and the measurement value of the TOC meter 31C. However, in the case of the modified example, it is difficult to quantify the colloidal particles CL, but it is possible to perform measurement to the extent of grasping the trend of increase or decrease of the colloidal particles CL.

[0072] In FIG. 13, as shown in FIG. 13(A), the acoustic particle counter 31A can detect both the fine particles MP and the colloidal particles CL, but cannot detect the dissolved organic carbon (DOC: Dissolved Organic Carbon) dissolved in water. On the other hand, the TOC meter 31C can detect DOC. Further, as described above, the TOC meter 31C can detect the amount of particulate organic carbon (the amount of particulate organic carbon that does not dissolve in the water to be treated) in addition to DOC. Although the proportion of this amount of particulate organic carbon contained in the total carbon amount (TOC) is very small, most of it is considered to be colloidal particles CL. Thus, it is also possible to detect the colloidal particles CL with the TOC meter 31C.

[0073] Then, as shown in FIG. 13(B), the measured value Xa of the acoustic particle counter 31A includes the fine particles MP and the colloidal particles CL, and the measured value Xc of the TOC meter 31C includes the DOC and the colloidal particles CL. As a result of examining the relationship between the amount of colloidal particles CL (Xa - Xb) obtained from the difference between the measured value Xa of the acoustic particle counter 31A and the measured value Xb of the optical particle counter 31B and Xc, the following relationship was generally found. That is, when there is no change in Xc and only Xa increases or decreases, it is considered that the fine particles MP have increased or decreased. And when there is no change in Xa and only Xc increases or decreases, it is considered that the DOC has increased or decreased. Further, when both the values of Xa and Xc increase or decrease, it is considered highly likely that the colloidal particles CL have increased or decreased. The processor 26 can grasp the tendency of increase or decrease of the colloidal particles CL based on the fluctuations of Xa and Xc. Thus, in the technology of the present disclosure, the concept of "measuring colloidal particles" includes not only quantitatively grasping the colloidal particles CL but also grasping the tendency of increase or decrease of the colloidal particles CL.

[0074] Hitherto, it has been difficult not only to quantitatively grasp the colloidal particles CL but also to grasp the tendency of increase or decrease. Therefore, even if it is not possible to quantitatively grasp them, it is practically sufficient to be able to grasp only the tendency of increase or decrease of the colloidal particles CL.

[0075] Also, for example, when the amount of DOC is decreased until it becomes almost constant and then the ultrafiltration membrane device 25 is operated under the condition of a water recovery rate of 55% as shown in FIG. 11, if it can be confirmed that both the values of Xa and Xc have decreased, it is considered highly likely that the colloidal particles CL have decreased. In this case, the processor 26 may be able to quantitatively grasp the amount of the colloidal particles CL by executing a predetermined calculation based on the two measured values of Xa and Xc.

[0076] Here, the measured value of the TOC meter 31C is the concentration, and the unit is [ppb]. On the other hand, the measured value of the acoustic particle counter 31A is the number per unit volume, and the unit is [particles / L]. Therefore, it is not possible to quantify the colloidal particles CL simply by taking the difference between the measured value Xa of the acoustic type and the measured value Xb of the optical type, such as in the combination of the acoustic particle counter 31A and the optical particle counter 31B. However, it is possible to estimate the approximate amount of the colloidal particles CL by using an arithmetic expression that includes the measured value Xc of the TOC meter and the coefficient for converting the concentration to the number.

[0077] Even in the case of the modification example, a method of removing the colloidal particles CL by setting the water recovery rate of the ultrafiltration membrane device 25 to less than 80% can be applied.

[0078] The experimental results in the case of the modification example are shown in Table 2 below. Example 1 in Table 2 is the measurement of TOC using the TOC meter 31C at the same timing as the measurement in Example 1 of Table 1. Example 2 is similarly the measurement of TOC using the TOC meter 31C at the same timing as the measurement in Example 2 above. As the TOC meter, Sievers M500e manufactured by Suez was used.

[0079]

Table 2

[0080] In Table 2, when comparing Example 1 and Example 2, it can be seen from the differences (ΔX1 and ΔX2) between the measured value Xa of the acoustic particle counter 31A and the measured value Xb of the optical particle counter 31B that the colloidal particles CL have decreased in Example 1. However, the measured value Xa1 in Example 1 has decreased more than the measured value Xa2 in Example 2, and the measured value Xa2 in Example 1 has also decreased more than the measured value Xc2 in Example 2. Since both the values of Xa and Xc have decreased in this way, it can be determined from this tendency that the colloidal particles CL have decreased.

[0081] Table 3 for comparing Example 3, which is different from Example 2, is shown below. In Table 3, Example 2 is the same as in Table 2. Example 3 is the same as Example 2 except that the space velocity (SV) of the non-regenerative mixed-bed ion exchange resin device 24 among the conditions of Example 2 is changed from 24 (1 / h) to 200 (1 / h). Example 3 is the case where the decrease of total organic carbon (TOC) is attempted by increasing the SV.

[0082]

Table 3

[0083] When comparing Example 2 and Example 3, there is no significant increase or decrease in the size of the colloidal particles CL, and they are equivalent. Also, the measured values Xa2 and Xa3 of the acoustic particle counter 31B are almost equivalent. On the other hand, when comparing the measured values Xc2 and Xc3 of the TOC meter 31C, Xc3 has decreased compared to Xc2. Therefore, Table 3 corresponds to the case where there is no change in Xa and only Xc has decreased. In this case, from the relationship between the increase and decrease of Xa and Xc, it can be determined that the decrease of TOC is due to the decrease of dissolved organic carbon (DOC).

[0084] As described above, as shown in Table 2 and Table 3, it can be seen that there is a correlation between the amount of colloidal particles CL (Xa - Xb) obtained from the difference between the measured value Xa of the acoustic particle counter 31A and the measured value Xb of the optical particle counter 31B, and the combination of the measured value Xa of the acoustic particle counter 31A and the measured value Xc of the TOC meter 31C. Therefore, by using the combination of the acoustic particle counter 31A and the TOC meter 31C, it is possible to grasp at least the trend of the increase and decrease of the colloidal particles CL.

[0085] In addition, in Modification 1, when the optical particle counter 31B is used instead of the acoustic particle counter 31A, the same results as in Modification 1 cannot be obtained, and no clear relationship is found between the amount of colloidal particles CL (Xa - Xb) and the measured value Xc of the TOC meter 31C. Therefore, it is confirmed that when measuring the colloidal particles CL using the present invention, the acoustic particle counter 31A is essential, and it is effective to use the optical particle counter 31B or the TOC meter 31C in a complementary manner to this measuring instrument.

[0086] As described above, the ultrapure water production apparatus 10 according to the modified example of the technology of the present disclosure has a combination of an acoustic particle counter 31A and a TOC meter 31C (corresponding to the second combination). The TOC meter 31C is an essential measuring instrument in the field of ultrapure water production and has been widely used so far. Therefore, according to the modified example, the TOC meter 31C that has been used so far can be effectively utilized for measuring colloidal particles CL. Of course, in the case of the modified example, the optical particle counter 31B may be omitted.

[0087] In addition, the measuring device 31 of the first combination or the second combination included in the ultrapure water production apparatus 10 according to the technology of the present disclosure can be used for the operation management of the ultrapure water production apparatus 10 in addition to measuring colloidal particles CL. That is, when it is determined by the measuring device 31 that the amount of colloidal particles CL has changed or is likely to have changed, it is considered that there is some cause in the ultrapure water production apparatus 10. For example, in the case of an increase in the amount of colloidal particles CL, if it is due to a change in the operating conditions, the deterioration of the water quality can be improved by restoring the operating conditions. Also, if it can be determined that it is due to a malfunction of some device, it can be dealt with by eliminating the malfunction of the device. Further, if the amount of colloidal particles CL changes when the operating conditions of the ultrapure water production apparatus 10 are changed, it is also possible to find the optimum operating conditions. This tendency can be grasped by monitoring the change in the measured value over time using the first combination of the acoustic particle counter 31A and the optical particle counter 31B or the second combination of the acoustic particle counter 31A and the TOC meter 31C, and thus has an excellent effect of being very easily achievable.

[0088] When providing the first combination of the two measuring instruments, i.e., the acoustic particle counter 31A and the optical particle counter 31B, in the above-described embodiment, or the second combination of the two measuring instruments, i.e., the acoustic particle counter 31A and the TOC meter 31C, in the modification, the arrangement of the two measuring instruments can be changed in various ways. For example, the two measuring instruments may be arranged in series, or may be arranged in parallel in two branch paths obtained by branching one pipeline.

[0089] Also, the installation positions of the two measuring instruments may be on the downstream side or the upstream side of the ultrafiltration membrane device 25. If it is on the downstream side of the ultrafiltration membrane device 25, the amount of colloidal particles CL in the treated water of the ultrafiltration membrane device 25, that is, the produced ultrapure water, can be directly measured. On the other hand, if it is on the upstream side of the ultrafiltration membrane device 25, it is also possible to measure the amount of colloidal particles CL in the supply water to the ultrafiltration membrane device 25. Furthermore, if installed on both the upstream side and the downstream side of the ultrafiltration membrane device 25, it becomes possible to directly measure the removal amount of colloidal particles CL by the ultrafiltration membrane device 25.

[0090] In the above-described embodiment, the processor 26 may be constituted by one or more pieces of hardware, and the type of hardware is not limited. For example, the processor may be constituted by a programmable logic device such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), or a dedicated circuit for executing specific processing such as an ASIC (Application Specific Integrated Circuit).

[0091] The technology of the present disclosure can also be appropriately combined with the above-described various embodiments and / or various modifications. Also, of course, various configurations can be adopted without departing from the gist, not limited to the above-described embodiments.

[0092] The above-described content and the illustrated content are detailed descriptions of the part related to the technology of the present disclosure and are only examples of the technology of the present disclosure. For example, the descriptions regarding the above configurations, functions, operations, and effects are descriptions of examples of the configurations, functions, operations, and effects of the part related to the technology of the present disclosure. Therefore, it goes without saying that within the scope not departing from the gist of the technology of the present disclosure, the above-described content and the illustrated content may be deleted of unnecessary parts, added with new elements, or replaced. Also, in order to avoid complication and facilitate the understanding of the part related to the technology of the present disclosure, the descriptions regarding common technical knowledge and the like that do not particularly require explanation for enabling the implementation of the technology of the present disclosure are omitted in the above-described content and the illustrated content.

Explanation of Signs

[0093] 10 Ultra-pure water production device 11 Pretreatment device 12 Primary pure water device 13 Secondary pure water device 14 Use point 21 Pure water tank 22 Ultraviolet irradiation device 23 Membrane degassing device 24 Non-regenerable mixed-bed ion exchange resin device 25 Ultrafiltration membrane device 26 Processor 31 Measuring device 31A Acoustic particle counter 31B Optical particle counter 31C TOC meter 41 Membrane surface 42 Pore inner wall CL Colloidal particle CV Cavitation DL Laser light IO Ion LA Water supply line LB Drain line LC Circulation line LD Bypass line LR Recovery line MP Particle P1 Water supply pump P2 Booster Pump RE Ion Exchange Resin SL Scattered Light SW Sound Wave VA, VB Valves Measured Values of Xa, Xb, Xc, X_CL

Claims

1. An ultrapure water production apparatus including a secondary pure water device that removes impurities from primary pure water, the secondary pure water device comprising a water pump, an ion exchange device, and an ultrafiltration membrane device in this order, An ultrapure water producing apparatus in which at least one combination of a first combination of an acoustic particle meter and an optical particle meter, and a second combination of the acoustic particle meter and a TOC meter are arranged upstream and / or downstream of the ultrafiltration membrane device.

2. 2. The ultrapure water production system according to claim 1, further comprising a processor for controlling the water recovery rate of said ultrafiltration membrane device.

3. 3. A method for producing ultrapure water using the ultrapure water producing apparatus according to claim 1 or 2.

4. A method for managing the operation of an ultrapure water production system including a secondary pure water system that removes impurities from primary pure water, the method comprising: A method for detecting a particle size distribution in a sample by a filter using at least one of a first combination of an acoustic particle size meter and an optical particle size meter and a second combination of an acoustic particle size meter and a TOC meter, the method being disposed downstream of the ultrafiltration membrane device; The method for managing operation of an ultrapure water production system performs management of operation based on the measurement values ​​obtained from the combination.

5. A method for measuring colloidal particles in a secondary pure water system that removes impurities from primary pure water, the method comprising: A method for detecting a particle size distribution in a sample by a TOC meter using a ... A method for measuring colloid particles, comprising the steps of: measuring the colloid particles based on a measurement value obtained from the combination.

Images