Method and apparatus for producing pure water

Abstract

This method and apparatus for producing pure water suppress a proliferation rate of viable bacteria or the like in water in a heat exchanger. The method for producing pure water treats water to be treated with one or more water treatment devices and involves a step for adjusting the temperature of the water to be treated, wherein the pure water is for pharmaceutical use or primary pure water; the water treatment device includes a plate heat exchanger; the plate heat exchanger includes a first frame, a second frame, and a plurality of heat transfer plates between the first frame and the second frame; in the step for adjusting the temperature, a heat medium is supplied to the plate heat exchanger, the water to be treated is introduced from the first frame side, and the water to be treated is derived from the second frame side to perform heat exchange with the heat medium; and the differential pressure between an introduction pressure and a derivation pressure of the water to be treated in the plate heat exchanger is 0.05-0.3 MPa.

Description

Method for producing pure water and apparatus for producing pure water 【0001】 This invention relates to a method for producing pure water and a pure water production apparatus. 【0002】 Primary pure water used in semiconductor manufacturing and other applications is produced by treating raw water or pre-treated water using a pure water system equipped with a reverse osmosis membrane or decomposition device. For example, the water temperature may be adjusted to obtain treated water of sufficient quality in the reverse osmosis membrane or decomposition device, and a heat exchanger may be installed before the reverse osmosis membrane or decomposition device (see, for example, Patent Documents 1 and 2). Furthermore, pharmaceutical water, especially purified water, is produced by treating raw water in a pharmaceutical water production system that includes a reverse osmosis membrane or EDI (electrodeionization). In this pharmaceutical water production system, periodic thermal sterilization may be performed to sterilize live bacteria and endotoxins within the system, and in this case, the water to be treated is heated by a heat exchanger (see, for example, Patent Document 3). Similarly, in a water for injection production system that produces water for injection, the water to be treated is heated by a heat exchanger to perform thermal sterilization within the system. 【0003】 Japanese Patent Publication No. 2009-183800, Japanese Patent Publication No. 2015-100733, Japanese Patent Publication No. 2004-074109 【0004】In the production of primary pure water and pharmaceutical water, reverse osmosis membranes made of polyamide composite membranes are often used because high-purity treated water can be obtained. However, reverse osmosis membranes made of polyamide composite membranes have a problem of being severely deteriorated by hypochlorite-based disinfectants. Therefore, in order to sterilize live bacteria derived from raw water, hypochlorite-based disinfectants cannot be used. Therefore, in some cases, bactericides are used instead of hypochlorite-based disinfectants, but sufficient effects may not be observed. In addition, it has been considered to install a sterilizing UV (ultraviolet irradiation device) in the front stage of the reverse osmosis membrane device or to install a pre-filter (microfilter or activated carbon tower) to prevent the supply of bacteria to the reverse osmosis membrane. However, in any method, sufficient effects cannot always be obtained, and the problem that the reverse osmosis membrane becomes clogged with bacteria (referred to as biofouling) often occurs. In addition, in the decomposition device used in the production of primary pure water, although rare, there are cases where biofouling occurs in the decomposition device and the progress of the decomposition reaction is inhibited. Furthermore, when a reverse osmosis membrane device is installed in the latter stage of the decomposition device, the problem of biofouling may occur as described above. 【0005】 Furthermore, in the production of pharmaceutical water, it is strictly required that live bacteria and endotoxins (hereinafter also referred to as "live bacteria, etc.") do not occur or mix into the pharmaceutical water. Therefore, in the conventional production process of injection water, in order to prevent the mixing of live bacteria and endotoxins, the injection water is circulated in a circulation system at 80 °C or higher, and from there, the required amount of injection water is supplied to the place of use. On the other hand, in the production of injection water using ultrafiltration, the circulation of injection water before use at room temperature or near room temperature (sometimes called cold WFI) has begun to be studied. In cold WFI, since injection water at room temperature is circulated in the production equipment system, an increase in live bacteria and endotoxins in the water is a concern. Therefore, some countermeasures against the concern of an increase in live bacteria and endotoxins are necessary, and the current situation is that it has not yet reached practical use. 【0006】 This embodiment has been made to solve the above-described problems, and an object thereof is to provide a method and an apparatus for producing pure water in which an increase in live bacteria, etc. in water is suppressed. 【0007】The inventors conducted thorough research and found that the rate of increase of viable bacteria within the heat exchanger differs depending on the structure of the heat exchanger, and therefore the rate of generation of viable bacteria in the downstream equipment differs significantly. They confirmed that this is due to the fact that the possibility of viable bacteria originating from the raw water proliferating in the heat exchanger and being supplied to the downstream equipment differs depending on the structure of the heat exchanger, and thus completed the apparatus and method of the embodiment. 【0008】This embodiment has the following configuration: [1] A method for producing pure water, comprising a step of treating water to be treated with one or more water treatment devices and adjusting the temperature of the water to be treated, wherein the pure water is medicinal water or primary pure water, the water treatment device includes a plate-type heat exchanger, the plate-type heat exchanger has a first frame and a second frame and a plurality of heat transfer plates between the first frame and the second frame, in the step of adjusting the temperature, a heat transfer medium is supplied to the plate-type heat exchanger, the water to be treated is introduced from the first frame side and the water to be treated is discharged from the second frame side to perform heat exchange with the heat transfer medium, and the differential pressure between the introduction pressure and discharge pressure of the water to be treated in the plate-type heat exchanger is 0.05 MPa or more and 0.3 MPa or less. [2] The method for producing pure water according to [1], wherein a heat transfer medium is introduced into the plate-type heat exchanger from the second frame side and the heat transfer medium is discharged from the first frame side. [3] The method for producing pure water according to [1] or [2], wherein the flow direction of the water to be treated and the flow direction of the heat transfer medium in the plate heat exchanger are opposite flows. [4] The method for producing pure water according to [1] or [2], wherein the water treatment equipment consists of a tank, the plate heat exchanger, a reverse osmosis membrane device, and an electrodeionizer, and at least a portion of the treated water from the electrodeionizer is circulated back to the tank. [5] The method for producing pure water according to [1] or [2], wherein the water treatment equipment consists of an ultrafiltration membrane device, a tank, and the plate heat exchanger, and at least a portion of the treated water from the plate heat exchanger is circulated back to the tank.[6] A pure water production apparatus having one or more water treatment devices for treating water to be treated, wherein the pure water is medicinal water or primary pure water, the water treatment device includes a plate heat exchanger, the plate heat exchanger has a first frame and a second frame, a plurality of heat transfer plates between the first frame and the second frame, an inlet for introducing a heat transfer medium into the plate heat exchanger, an outlet for discharging a heat transfer medium from the plate heat exchanger, an inlet for water to be treated provided on the first frame, and an outlet for water to be treated provided on the second frame, the differential pressure between the introduction pressure and the discharge pressure of water to be treated in the plate heat exchanger is 0.05 MPa or more and 0.3 MPa or less. [7] The pure water production apparatus according to [6], wherein the plate heat exchanger has an inlet for a heat transfer medium in the second frame and an outlet for a heat transfer medium in the first frame. [8] The pure water production apparatus according to [6], comprising a tank, the plate-type heat exchanger, a reverse osmosis membrane device, and an electro-deionizer in that order as the water treatment equipment, and having circulation piping for circulating at least a portion of the treated water from the electro-deionizer to the tank. [9] The pure water production apparatus according to [6], comprising an ultrafiltration membrane device, a tank, and the plate-type heat exchanger in that order as the water treatment equipment, and having circulation piping for circulating at least a portion of the treated water from the plate-type heat exchanger to the tank. The symbol "~" indicates a numerical range including the numbers before and after it. 【0009】 According to the method and apparatus for producing pure water of this embodiment, it is possible to produce pure water while suppressing the rate of increase of viable bacteria and other microorganisms in the water within the heat exchanger. 【0010】This is a schematic diagram of a plate-type heat exchanger. This is a schematic diagram of the heat transfer plate of this embodiment. This is a schematic diagram of another heat transfer plate of this embodiment. This is a schematic elevation view of the plate-type heat exchanger of this embodiment. This is a schematic elevation view of a conventional plate-type heat exchanger. This is a schematic diagram of a pure water system having the plate-type heat exchanger of this embodiment. This is a schematic diagram of another pure water system having the plate-type heat exchanger of this embodiment. This is a schematic diagram of a medical water (purified water) production apparatus having the plate-type heat exchanger of this embodiment. This is a schematic diagram of a water for injection apparatus having the plate-type heat exchanger of this embodiment. This is a graph showing an example of the decrease in permeate flux due to the growth of viable bacteria etc. in the downstream reverse osmosis membrane apparatus when using the plate-type heat exchanger of this embodiment and the plate-type heat exchanger of the comparative example. 【0011】 Hereinafter, a method for producing pure water according to an embodiment of the present invention will be described with reference to the drawings. The method for producing pure water according to this embodiment includes a step of treating the water to be treated with one or more water treatment devices and adjusting the temperature of the water to be treated. The water treatment device includes a plate-type heat exchanger, and in the step of adjusting the temperature of the water to be treated, the water to be treated is made to flow in a specific direction in the plate-type heat exchanger. The plate-type heat exchanger has a first frame, a second frame, and a plurality of heat transfer plates between the first frame and the second frame, and in the step of adjusting the temperature, the water to be treated is introduced from the first frame side and discharged from the second frame side. The differential pressure between the introduction pressure and the discharge pressure of the water to be treated in the plate-type heat exchanger is 0.05 MPa or more and 0.3 MPa or less. Preferably, the differential pressure between the introduction pressure and the discharge pressure of the water to be treated is 0.1 MPa or more and 0.25 MPa or less, and more preferably 0.15 MPa or more and 0.23 MPa or less. Furthermore, pure water refers to either primary pure water or water for medicinal use, and water for medicinal use includes, for example, purified water and water for injection. 【0012】Figure 1 is a schematic diagram of a plate-type heat exchanger 1 used in the pure water production method of this embodiment, and is a side view when the plate-type heat exchanger 1 is placed on the ground or the like, with the surface of the first frame facing forward. The plate-type heat exchanger 1 has a first frame 11 and a second frame 12. The first frame 11 and the second frame 12 are spaced apart, and a plurality of heat transfer plates 4 are arranged between the first frame 11 and the second frame 12. The first frame 11 is provided with an inlet 2a for the water to be treated, and the second frame 12 is provided with an outlet 2b for the water to be treated. The heat transfer plates 4 of the plate-type heat exchanger 1 of this embodiment are substantially rectangular, and their surfaces are made up of irregularities that serve as fluid passages. As shown in Figure 2, the heat transfer plates 4 have passage holes 5a, 5b, 13a, and 13b at the four corners of their irregular heat transfer surface, which serve as fluid inlets and outlets (see Figure 2). Gaskets 3 are provided between the outer peripheries of the multiple heat transfer plates 4, and the first frame 11 and the second frame 12 are fixed from both sides with tightening bolts (not shown). Note that fixing is not limited to bolting; for example, welding may be used. Between the multiple heat transfer plates 4, alternating passages for water to be treated 21a, 22a, 23a, 24a, 25a, 26a and passages for heat transfer medium 21b, 22b, 23b, 24b, 25b, 26b, 27b are formed. The water to be treated passages 21a to 26a are connected to an inlet 2a and an outlet 2b provided on the first frame 11. Heat from the heat transfer medium flowing through the heat transfer medium passages 21b to 27b is transferred to the water to be treated flowing through the water to be treated passages 21a to 26a via the heat transfer plates 4, and the water to be treated is heated or cooled. 【0013】Figure 2 is a schematic diagram of the heat transfer plate 4 of this embodiment. The heat transfer plate 4 has irregularities (not shown) formed on its surface that serve as fluid passages, and is usually made of a metal material such as stainless steel or titanium. The heat transfer plate 4 has fluid passage holes 5a, 13a, 5b, and 13b around its outer circumference. The passage holes 5a and 5b are a pair of fluid inlets 5a and outlets 5b. The passage holes 13a and 13b are a pair of fluid inlets 13a and outlets 13b. The heat transfer plate 4 has two pairs of inlets and outlets: inlet 5a and outlet 5b and inlet 13a and outlet 13b. Preferably, the pairs of inlets and outlets are spaced apart so that the passage for the water to be treated or heat transfer medium flowing through the heat transfer plate is as long as possible. If the heat transfer plate 4 is substantially rectangular, the inlets and outlets are provided at two diagonal corners of the four corners of the rectangle. Specifically, the inlet 5a and outlet 5b are located at two diagonal corners, and the inlet 13a and outlet 13b are located at two diagonal corners. The heat transfer plate 4 has gaskets 3 near its outer circumference and near the outer circumferences of the passage holes 5a, 13a, 5b, and 13b. The heat transfer plate 4 shown in Figure 2 allows the water to be treated to flow through the flow path formed by the gaskets 3 and the heat transfer plate 4. The water to be treated flows in from the passage hole (inlet) 5a, flows in the direction of the dotted line in the figure, and flows out from the passage hole (outlet) 5b. Note that Figure 2 shows an configuration in which the inlet 5a and outlet 5b are located at two diagonal corners, but for the sake of explanation, Figure 1 shows an configuration in which the inlet 5a and outlet 5b are located at adjacent corners. 【0014】 Figure 3 is a schematic diagram showing one of the multiple heat transfer plates 4 of the plate-type heat exchanger 1 of this embodiment. The heat transfer plate 4 shown in Figure 3 allows a heat transfer medium to flow through the flow path formed by the gasket 3 and the heat transfer plate 4. The heat transfer medium flows in from the passage hole (inlet) 13a, flows in the direction of the dotted line in the figure, and flows out from the passage hole (outlet) 13b. 【0015】In Figures 1 to 3, the gasket 3 is positioned at the outer edge of the heat transfer plate 4. The gasket 3 is made of an elastic material having a predetermined width and thickness, and has a sealing function to prevent fluid leakage by liquid-tightly sealing the outer edge of the heat transfer plate 4. Preferably, the gasket 3 is sandwiched between the heat transfer plate 4 and in surface contact with the heat transfer plate 4. Furthermore, it is preferable that the shape of the gasket 3 is such that its cross-section, at least the cross-section perpendicular to the longitudinal direction of the heat transfer plate, is rectangular, and the outer edge of the gasket 3 facing the outside and inside of the plate-type heat exchanger 1 is a flat surface without curves. The rectangular cross-section minimizes the gap between the gasket 3 and the heat transfer plate 4, thereby suppressing water accumulation in the plate-type heat exchanger 1. Similarly, the flat outer edge minimizes the gap between the gasket 3 and the heat transfer plate 4, thereby suppressing water accumulation in the plate-type heat exchanger 1. Furthermore, in this embodiment, since the plate-type heat exchanger 1 introduces the water to be treated from the first frame side and discharges the water to be treated from the second frame side, air is less likely to accumulate inside. Also, since air outlet means can cause the accumulation of impurities, it is preferable that the heat exchanger does not have an air outlet means. In addition, by placing the inlet of the water to be treated at the bottom of the heat exchanger and the outlet at the top of the heat exchanger, and by having the water to be treated flow upward along the heat transfer plate 4 inside the heat exchanger, air accumulation can be easily prevented. 【0016】Furthermore, in Figures 1 to 3, it is preferable that the inner diameter of the inlet 2a and the inner diameter of the passage hole 5a be approximately the same as the inner diameter of the gasket 3 surrounding the inlet 2a and the passage hole 5a, thereby creating a shape that does not produce irregularities in the inflow path of the water to be treated flowing into the plate-type heat exchanger 1 that could cause the accumulation of impurities. Similarly, it is preferable that the inner diameter of the outlet 2b and the inner diameter of the passage hole 5b be approximately the same as the inner diameter of the gasket 3 surrounding them. In addition, it is preferable that the inner diameter of the passage hole 13b be approximately the same as the inner diameter of the gasket 3 surrounding them to suppress the accumulation of the water to be treated. The shape of the gasket 3 is preferably such that no accumulation areas such as irregularities are created between it and the passage hole provided on the heat transfer plate 4. The gasket 3 sandwiched between the two heat transfer plates 4 may be integrally molded, or multiple gaskets may be used. 【0017】 In the method for producing pure water according to this embodiment, the water to be treated is introduced into the plate-type heat exchanger 1 from the inlet 2a of the first frame 11, flows through the flow path on the surface of the heat transfer plate 4, and is discharged from the outlet 2b of the second frame 12. 【0018】 The material of the plate-type heat exchanger 1 in the embodiment is stainless steel, titanium, iron, Hastelloy®, copper, etc., and in order to avoid deterioration of the water quality of the pure water produced, it is preferable that it be made of stainless steel, and at least the wetted surfaces of the heat transfer plates and the first and second frames are made of stainless steel. 【0019】Figure 4 is a simplified schematic diagram showing the passage of water to be treated within the plate-type heat exchanger 1 shown in Figure 1. It is an elevation view when the plate-type heat exchanger 1 is placed on the ground or the like, with the surface of the first frame 11 facing forward. The plate-type heat exchanger 1 shown in Figure 4 has a first frame 11 and a second frame 12. Multiple heat transfer plates 4 are arranged between the first frame 11 and the second frame 12. The first frame 11 is provided with an inlet 2a, and the second frame 12 is provided with an outlet 2b. In Figure 4, the dotted line represents the flow path of the water to be treated. The diagonal lines represent the passage of the heat transfer medium. In the plate-type heat exchanger 1 shown in Figure 4, water to be treated is introduced from the inlet 2a on the first frame 11 side, and the water to be treated is discharged from the outlet 2b on the second frame 12 side. As a result, all of the multiple water passages to be treated, located between the heat transfer plates, have the same length. Therefore, the flow velocity in each of the multiple water passages to be treated does not differ, and a common flow velocity can be ensured across all of them. This makes it easier for the flow velocity of the water to be treated to be uniform within the plate-type heat exchanger 1, allowing for efficient heat exchange. Consequently, sufficient heat exchange can be achieved even if the number of heat transfer plates is reduced or the flow rate introduced from the inlet 2a is increased, making it possible to miniaturize the plate-type heat exchanger. Therefore, depending on the amount of water to be treated and the flow velocity of the entire system, the flow rate of water to be treated per unit of heat exchanger can be increased by two to ten times compared to conventional plate-type heat exchangers. In addition, because the flow velocity within the heat exchanger is increased, water stagnation inside is less likely to occur. Consequently, for example, impurity accumulation does not occur in areas where impurities are particularly likely to accumulate, such as the boundary between the heat transfer plate 4 and the gasket 3 in the heat exchanger shown in Figure 1, and bacterial growth is less likely to occur. In other words, the inventors have found that the plate-type heat exchanger 1 of this embodiment has significantly higher heat exchange efficiency than conventional plate-type heat exchangers, and can therefore be operated at high flow rates, i.e., high differential water pressure, which are not typically applied to conventional plate-type heat exchangers. Furthermore, they have found that under these conditions, the growth of bacteria inside the plate-type heat exchanger can be suppressed, thereby reducing the impact of live bacteria in the downstream stage. 【0020】Figure 5 is a simplified schematic diagram showing the passage of water to be treated in a conventional plate-type heat exchanger 100. The conventional plate-type heat exchanger 100 has both the inlet and outlet of water to be treated on the first frame 11 side, and other components are the same as the plate-type heat exchanger 1 shown in Figures 1 and 4. Therefore, components that perform the same function are given the same reference numerals and detailed explanations are omitted. Figure 5 is an elevation view of the plate-type heat exchanger 100 when it is placed on the ground or the like, with the surface of the first frame 11 facing forward. In Figure 5, the dotted lines represent the flow path of water to be treated. 【0021】 In the plate-type heat exchanger 100 shown in Figure 5, the water to be treated is introduced from an inlet 80a located on the first frame 11 side, and the water to be treated is discharged from an outlet 80b located on the first frame 11 side. As a result, the multiple water-to-treat passages located between the heat transfer plates become shorter the closer they are to the first frame 11 and longer the further they are from the first frame 11. This difference in length affects the flow velocity of the water to be treated. That is, the flow velocity in the multiple water-to-treat passages becomes higher the closer they are to the first frame 11 and lower the further they are from the first frame 11. As a result, heat exchange within the plate-type heat exchanger 100 tends to become inefficient. Consequently, in order to perform sufficient heat exchange, it is necessary to reduce the flow rate introduced from the inlet 2a, and reducing the flow rate slows down the flow velocity within the plate-type heat exchanger 100. This makes it easier for water to accumulate in areas where impurities are particularly likely to accumulate, such as the boundary between the heat transfer plate 4 and the gasket 3. When water stagnates, bacteria proliferate in the stagnant water. When the flow rate fluctuates due to pump starting or stopping, or valve switching during water flow, the proliferated bacteria flow out to the downstream stage. Furthermore, even if an antibacterial agent is added to the water being treated in a plate-type heat exchanger, the antibacterial component does not easily reach, or does not reach, the stagnant parts of the plate-type heat exchanger. Therefore, once bacterial growth begins, it is difficult to suppress this growth. Depending on the water treatment conditions, conventional plate-type heat exchangers generally operate with a water flow differential pressure of 0.01 to 0.03 MPa. Operating at a differential pressure higher than this is not practical because it increases the amount of heat source used, such as steam. 【0022】Figure 6 is a schematic diagram of the primary pure water system 20 of this embodiment. The primary pure water system 20 is equipped with an activated carbon unit 21, a cation exchange unit (SC) 22, a decarbonation tower (DG) 23, a plate heat exchanger 1, a decomposition unit 24, a reverse osmosis membrane unit (RO) 25, an ultraviolet irradiation unit (TOC-UV) 26, a mixed-bed ion exchange unit (MB) 27, and a degassing membrane unit (MDG) 28 in this order, and processes raw water to produce primary pure water. 【0023】 The raw water sources include city water, well water, groundwater, river water, industrial water, and spent ultrapure water (recovered water) from semiconductor manufacturing processes. The raw water may contain 0.01 to 0.2 mg / L of urea. 【0024】 In the primary pure water system 20, the activated carbon system 21 is equipped with activated carbon, which removes chromatic components such as humic substances and / or dissolved organic carbon (DOC) components derived from humic substances, suspended solids, etc., from the raw water. Humic substances refer to humic substances produced when plants and other materials are decomposed by microorganisms, and include humic acid, fulvic acid, etc. As the activated carbon, coconut shell-based or coal-based activated carbon can be used, molded into powder, granular, fibrous, plate-shaped, or honeycomb shape. The chromaticity of the treated water from the activated carbon system 21 is preferably reduced to 5 degrees or less, more preferably to 2 degrees or less. 【0025】 The cation exchange device 22 has a cation exchange resin, which exchanges and removes cation components from the raw water. Either a strongly acidic cation exchange resin or a weakly acidic cation exchange resin, or both, can be used as the cation exchange resin. To prevent scaling in the downstream reverse osmosis membrane device 25, it is preferable to use a strongly acidic cation exchange resin because it has excellent performance in removing alkaline earth metals. 【0026】 The decarboxylation device 23 performs decarboxylation treatment on cation exchange treated water. In the decarboxylation treatment, dissolved carbon dioxide is removed from the water to be treated, producing decarboxylated water with a reduced carbon dioxide concentration. This prevents scale formation in the downstream reverse osmosis membrane device 25. 【0027】The decomposition device 24 has, for example, one or more airtight treatment tanks, and the water to be treated is retained in the treatment tanks for a certain period of time to decompose and remove urea and other organic substances from the water to be treated. In the treatment tanks, chemicals are added to the water to be treated while the pH is adjusted to an appropriate value according to the substance to be decomposed. Oxidizing agents such as ozone, hydrogen peroxide, hypobromous acid, hypochlorous acid, and persulfuric acid are used as chemicals. Alternatively, the decomposition device may also use biological decomposition treatment using a biological treatment tank or the like. When the decomposition device 24 decomposes urea, for example, hypobromous acid can be added to the water to be treated while the pH of the water to be treated in the treatment tanks is adjusted to 9 or higher to decompose the urea in the water to be treated. 【0028】 Furthermore, in order to decompose the oxidizing agent remaining in the treated water of the decomposition device 24, reducing agents such as sulfites and sulfite salts may be added downstream of the decomposition device 24. In addition, antibacterial agents to suppress the growth of viable bacteria may be added downstream of the decomposition device 24. Antibacterial agents that contain active ingredients such as chloramines and chlorinated isocyanurates, combined chlorine agents obtained by the reaction of chlorine with amide sulfuric acid and compounds having an amide sulfuric acid group, such as monochlorosulfamic acid, combined brominated agents obtained by the reaction of bromine with amide sulfuric acid and compounds having an amide sulfuric acid group, brominated agents such as dibromohydantoin and dibromonitrillopropion acid (DBNPA), and isothiazoline-based organic agents such as benzoisothiazoline, isothiazoline, methylisothiazoline-5-chloro-2-methyl-4-isothiazoline-3-one (MIT) and 5-chloro-2-methyl-4-isothiazoline-3-one (CMIT). The location where the antibacterial agent is added is preferably between the activated carbon column 21 and the reverse osmosis membrane device 25. 【0029】The plate-type heat exchanger 1 heats the water to be treated supplied to the decomposition unit 24. The configuration of the plate-type heat exchanger 1 is the same as that of the plate-type heat exchanger 1 shown in Figure 1 above. The decomposition unit 24 may be either a device that continuously processes the water to be treated or a device that processes the water to be treated in a batch manner. In terms of improving the urea decomposition efficiency in the decomposition unit 24, the temperature of the water to be treated heated by the plate-type heat exchanger 1 is, for example, 20°C to 40°C, and the residence time of the water to be treated in the decomposition unit 24 is, for example, 10 minutes to 30 minutes. When processing in a batch manner, or when starting and stopping the operation of the primary pure water unit 20, the heating rate (rate of change in the temperature of the water to be treated) is preferably 1°C / min to 10°C / min. In the case of batch operation, the interval from the end of heating of the water to be treated by the plate-type heat exchanger 1 to the start of heating of the next batch of water to be treated is 5 minutes to 20 minutes. 【0030】 The reverse osmosis membrane apparatus 25 removes salts and impurities such as ionic and colloidal organic matter from the urea decomposition water to produce concentrated water and permeate. As the reverse osmosis membrane apparatus 25, a cellulose triacetate asymmetric membrane or a polyamide composite membrane can be used, and membrane modules such as sheet flat membranes, spiral membranes, tubular membranes, and hollow fiber membranes can be used. Among these, a polyamide composite membrane is preferred in order to increase the rate of impurity removal, and a spiral membrane shape is preferred. The rate of impurity removal may be improved by connecting two or three reverse osmosis membrane apparatuses 25 in series to form a reverse osmosis membrane apparatus with two or more stages. When using a reverse osmosis membrane apparatus with two or more stages, it is also possible to add an acid, alkali, etc. to the water to be treated immediately before any of the reverse osmosis membranes to adjust the pH of the water to be treated to a desired range. 【0031】The ultraviolet irradiation device 26 decomposes trace amounts of organic matter remaining in the treated water of the reverse osmosis membrane device 25 by irradiating it with ultraviolet light. The mixed-bed ion exchange device 27 adsorbs and removes organic acids and other substances produced by the decomposition of organic matter. The degassing membrane device 28 removes gases, especially dissolved oxygen, from the treated water of the mixed-bed ion exchange device using a gas separation membrane that does not allow water to pass through but allows gases to pass through. In the primary pure water device 20 shown in Figure 3, the degassing membrane device 28 processes the treated water of the mixed-bed ion exchange device 27, but the order of the degassing membrane device 28 and the mixed-bed ion exchange device 27 may be reversed, with the mixed-bed ion exchange device 27 being installed later so that it processes the treated water of the degassing membrane device 28. It is also possible to use an electrodeionizer (EDI) instead of the mixed-bed ion exchange device 27. 【0032】 In the primary pure water system 20 of this embodiment, the water to be treated is introduced from the first frame side of the plate-type heat exchanger 1, and the water to be treated is discharged from the second frame side opposite to the first frame side, and the differential pressure between the introduction pressure and discharge pressure of the water to be treated is 0.05 MPa or more and 0.3 MPa or less. As a result, the accumulation of live bacteria, etc., in the plate-type heat exchanger 1 does not occur. As a result, even if the primary pure water system 20 is used for a long period of time after installation, the possibility of the outflow of live bacteria, etc., to the downstream stage is significantly suppressed, and the impact on downstream equipment due to the increase in live bacteria can be reduced. Depending on the operating conditions, for example, the flow velocity in the heat exchanger can be increased fourfold, i.e., the differential pressure before and after the plate-type heat exchanger can be increased fourfold, compared to a conventional plate-type heat exchanger. In this case, the performance degradation such as the decomposition rate due to contamination by live bacteria inside the decomposition unit 24, and the impact on downstream equipment such as the rate of clogging of the reverse osmosis membrane unit 25 installed downstream, can be reduced by about half. 【0033】Figure 7 is a schematic diagram showing another embodiment of the primary pure water system 200. The primary pure water system 200 differs from the primary pure water system 20 shown in Figure 5 in that it does not have a decomposition unit 24, but the other configurations are the same as those of the primary pure water system 20 shown in Figure 5. Therefore, the same reference numerals are used for components that perform the same function, and detailed explanations are omitted. The primary pure water system 200 shown in Figure 7 is equipped with an activated carbon unit 21, a cation exchange unit (SC) 22, a decarbonation tower (DG) 23, a plate-type heat exchanger 1, a reverse osmosis membrane unit (RO) 25, an ultraviolet irradiation unit (TOC-UV) 26, a mixed-bed ion exchange unit (MB) 27, and a degassing membrane unit (MDG) 28 in this order, and processes raw water to produce primary pure water. In the primary pure water system 200 shown in Figure 7, the accumulation of live bacteria, etc., does not occur in the plate-type heat exchanger 1. Therefore, biofouling in the reverse osmosis (RO) system 25 can be prevented for a long period of time. Depending on the operating conditions, for example, the flow velocity of the plate heat exchanger can be increased fourfold compared to a conventional plate heat exchanger, meaning the differential pressure between the inlet and outlet before the plate heat exchanger can be increased by about four times. In this case, the impact on the reverse osmosis system (RO) 25, such as the rate of clogging of the reverse osmosis membrane, is reduced to about half. 【0034】 Figure 8 is a schematic diagram showing a pharmaceutical water production apparatus 30 using the plate-type heat exchanger 1 of the embodiment shown in Figure 1. The pharmaceutical water production apparatus 30 produces pharmaceutical water, particularly purified water. The pharmaceutical water production apparatus 30 is equipped with a raw water tank (TK) 31, the plate-type heat exchanger 1 of the above-described embodiment, a reverse osmosis membrane device (RO) 32, and an electrodeionizer (EDI) 33 in this order, and produces purified water by processing the raw water. The pharmaceutical water production apparatus 30 is equipped with a water supply pipe L1 that sequentially sends the raw water stored in the raw water tank (TK) 31 to each water treatment device provided in the pharmaceutical water production apparatus 30, and a circulation pipe L2 that circulates all or part of the produced pharmaceutical water back to the raw water tank (TK) 31. An ultrafiltration membrane for producing water for injection from purified water may be installed downstream of the branching point of the circulation pipe L2 in the water supply pipe L1. 【0035】The reverse osmosis membrane apparatus 32 is equipped with a reverse osmosis membrane (RO) and removes ionic components from the water to be treated by the reverse osmosis membrane. The reverse osmosis membrane apparatus 32 is composed of, for example, one or more reverse osmosis membrane modules. The reverse osmosis membrane module is composed of, for example, a casing containing a reverse osmosis membrane and a flow channel material for passing the water to be treated through the reverse osmosis membrane. The shape of the reverse osmosis membrane is preferably a hollow fiber membrane, but it may also be a spiral membrane, flat membrane, tubular membrane, etc. The material of the reverse osmosis membrane provided in the reverse osmosis membrane module is, for example, various organic polymer membranes or ceramic membranes made of cellulose acetate, aliphatic polyamide, aromatic polyamide, or composites thereof. In this embodiment, the reverse osmosis membrane is preferably a spiral membrane from the viewpoint of increasing pressure resistance and improving treatment efficiency. The reverse osmosis membrane may be an ultra-low pressure type, low pressure type, medium pressure type, or high pressure type reverse osmosis membrane, but from the viewpoint of reducing power consumption during operation, low pressure or ultra-low pressure is preferred. 【0036】 The electrodeionizer 33 has, for example, an anion exchange membrane and a cation exchange membrane alternately arranged between the anode and the cathode, and alternately comprises a desalination chamber separated by the anion exchange membrane and the cation exchange membrane, and a concentration chamber into which concentrated water containing the removed ionic components flows. The electrodeionizer 33 has a mixture of anion exchange resin and cation exchange resin filled in the desalination chamber, and electrodes for applying a DC voltage. By using the electrodeionizer 33 to remove ions from the water to be treated while simultaneously continuously regenerating the ion exchange resin using a DC current, ionic components in the water can be continuously removed, and high-quality treated water can be obtained. 【0037】In the pharmaceutical water production apparatus 30 shown in Figure 8, after producing pharmaceutical water for a predetermined time, the production of pharmaceutical water is interrupted and sterilization is performed inside the production apparatus. The period during which pharmaceutical water production is continued is usually from one day to six months, meaning that sterilization is performed once every one to six months. To effectively prevent contamination by bacteria, etc., it is more preferable to sterilize once every one to two months, and even more preferable to sterilize once a week. If the interval between sterilization treatments is too long, it becomes difficult to effectively prevent contamination by bacteria, etc. Conversely, if the interval between sterilization treatments is too short, the production time for pharmaceutical water becomes insufficient, and the production efficiency decreases. 【0038】 Sterilization of the pharmaceutical water production apparatus 30 is carried out as follows. First, valves and the like (not shown) inside the pharmaceutical water production apparatus 30 are closed to create a closed circulation system within the pharmaceutical water production apparatus 30 using a water supply pipe L1 and circulation pipe L2. Specifically, the supply of raw water to the raw water tank (TK) 31 and the supply of treated water from the electric deionizer 33 to the downstream stage are stopped. Next, the raw water in the raw water tank (TK) 31 is heated to the temperature of the sterilization heating water by the plate-type heat exchanger 1. The heating water is gradually heated to the desired temperature while circulating inside the pharmaceutical water production apparatus 30. The heating rate at this time is, for example, 1°C / min to 10°C / min. When the raw water reaches the temperature of the sterilization heating water, the heating water is circulated inside the pharmaceutical water production apparatus 30 to sterilize the system. Here, the temperature of the sterilization heating water is 60°C or higher, preferably 60°C to 90°C. Furthermore, the sterilization time (heated water circulation time) is the time required for sufficient sterilization, depending on the configuration of the manufacturing equipment. For example, it is 30 to 120 minutes at 60°C and 30 to 120 minutes at 80°C. 【0039】 After the sterilization of the medical water production apparatus 30 is completed, the amount of heat transfer medium supplied to the plate-type heat exchanger 1 is gradually reduced to gradually lower the water temperature in the system. When the sterilization temperature is 60°C, the time required to lower the water temperature to room temperature is 30 to 120 minutes, and when the sterilization temperature is 80°C, it is 30 to 120 minutes. 【0040】In the pharmaceutical water production apparatus 30 of this embodiment, during the cooling period within the system after sterilization is complete, and during the purified water production process at room temperature, the water to be treated is introduced from the first frame side of the plate-type heat exchanger 1, and the water to be treated is discharged from the second frame side opposite to the first frame side, and the differential pressure between the introduction pressure and discharge pressure of the water to be treated is 0.05 MPa or more and 0.3 MPa or less. For this reason, there is no risk of the accumulation of live bacteria, etc., inside the plate-type heat exchanger 1. 【0041】 Figure 9 is a schematic diagram of the water for injection production apparatus 70. The water for injection production apparatus 70 produces water for injection by processing purified water produced by the pharmaceutical water production apparatus 30. The water for injection production apparatus 70 has a water for injection production section 71 and a circulation section 72. The water for injection production section 71 is an ultrafiltration membrane apparatus or a distillation apparatus that produces water for injection from purified water. The circulation section 72 has a water treatment pipe 70a and, along the path of the water treatment pipe 70a, a water for injection tank 73 and the plate-type heat exchanger 1 of the above embodiment. A portion of the produced water for injection is supplied to the place of use (POU) 75, and the unused water for injection is returned to the water for injection tank 73 via the circulation pipe 70b. 【0042】 In general, during the steady production of water for injection, the water temperature in the water for injection production apparatus 70 is maintained at, for example, 80°C. However, when the water for injection production apparatus 70 is started and stopped, the water in the system may cool down to room temperature. In the water for injection production apparatus 70 of this embodiment, the water to be treated is introduced from the first frame side of the plate-type heat exchanger 1, and the water to be treated is discharged from the second frame side opposite to the first frame side, and the differential pressure between the introduction pressure and discharge pressure of the water to be treated is 0.05 MPa or more and 0.3 MPa or less. For this reason, while the system is maintained at room temperature, the accumulation of live bacteria, etc., in the plate-type heat exchanger 1 does not occur, and therefore there is no risk of live bacteria contamination in the water for injection produced. Furthermore, since there is no temporary increase in live bacteria, etc., in the plate-type heat exchanger 1, it is expected to be applicable to the production of cold WFI. 【0043】 Next, examples will be described. The present invention is not limited to the following examples. 【0044】(Example 1) A primary pure water device similar to the primary pure water device 200 shown in FIG. 7 was prepared to produce pure water. The water quality of the raw water and the operating conditions of various devices were as follows. 【0045】 [Raw water quality] Conductivity: 200 μS / cm Live bacteria: 200 cells / mL Water temperature: 15°C [Heat exchanger] Water passing differential pressure (differential pressure between the inlet pressure and the outlet pressure): 0.25 MPa Treated water temperature (water temperature after passing through the heat exchanger): 25°C [Reverse osmosis membrane device] Membrane type: TM710 (manufactured by Toray Industries, Inc.) 1 piece Water recovery rate: 75% 【0046】 Under the above conditions, while producing primary pure water, the change in the permeate flux of the reverse osmosis membrane device was recorded. Approximately 50 days after the primary pure water device was installed, the decrease in the permeate flux of the reverse osmosis membrane device began. The relationship between the permeate flux of the reverse osmosis membrane device and the elapsed time after the start of this decrease in the permeate flux is shown in the graph of FIG. 10 as a relative value with the value of the permeate flux immediately after the primary pure water device was installed set to 1. 【0047】 (Comparative Example 1) Instead of the plate type heat exchanger of the example, a plate type heat exchanger having a structure in which the water to be treated is introduced from the first frame side of the plate type heat exchanger and the water to be treated is discharged from the first frame side was used. The number of plates of the plate type heat exchanger used in the comparative example was approximately 10 times that of the plate type heat exchanger used in the example. In the comparative example, the differential pressure between the inlet pressure and the outlet pressure of the water to be treated to the plate type heat exchanger was passed through at 0.02 MPa. Also, in Comparative Example 1, approximately 7 days after the primary pure water device was installed, the decrease in the permeate flux of the reverse osmosis membrane device began. The relationship between the permeate flux of the reverse osmosis membrane device and the elapsed time after the start of this decrease in the permeate flux is shown in the graph of FIG. 10 as a relative value with the value of the permeate flux immediately after the primary pure water device of the comparative example was installed set to 1. 【0048】The viable count of the water to be treated in the reverse osmosis membrane device during continuous water flow for 50 days from the start of water flow in Example 1 and Comparative Example 1 was measured. The maximum value is shown as "Viable count (steady state)" in Table 1. During this period, the pump was not turned on or off, and the water treatment operation was carried out constantly. Also, immediately after repeating the operations of stopping and starting the pump installed in the front stage of the plate heat exchanger 5 times, the viable counts of the supply water and treated water of the plate heat exchanger were measured, and the results are shown as "Viable count (immediately after on / off)" in Table 1. The viable count measurement was performed using the sampling - culture method. 【0049】 【0050】 From Table 1, during the steady operation without pump on / off, the viable count of the supply water to the reverse osmosis membrane device is generally the same in both Example 1 and Comparative Example 1. Also, the viable count of the supply water in the heat exchanger when the pump is turned on and off is generally the same in both Example 1 and Comparative Example 1. However, when the pump is turned on and off, the viable count of the treated water in the heat exchanger increases. Particularly, it increases significantly in Comparative Example 1. This indicates that when the flow rate and pressure fluctuate due to the pump on / off, viable bacteria that have propagated inside are discharged from the heat exchanger. 【0051】1: Plate heat exchanger, 2a: Inlet, 2b: Outlet, 3: Gasket, 4: Heat transfer plate, 11: First frame, 12: Second frame, 5a: Through hole (inlet), 5b: Through hole (outlet), 13a: Through hole (inlet), 13b: Through hole (outlet), 21a, 22a, 23a, 24a, 25a, 26a: Water to be treated passage, 21b, 22b, 23b, 24b, 25b, 26b, 27b: Heat transfer medium passage, 20: Primary pure water system, 21: Activated carbon system, 22: Cation exchange system, 23: Decarbonation system, 24: Decomposition system, 25: Reverse osmosis membrane system (RO), 26: Ultraviolet irradiation system (TOC-UV), 27: 1: Mixed-bed ion exchange system (MB), 28: Degassing membrane system (MDG), 30: Pharmaceutical water production system, 31: Raw water tank (TK), 32: Reverse osmosis membrane system (RO), 33: Electrodeionization system (EDI), L1: Water supply pipe, L2: Circulation piping, 50: Secondary pure water system, 50a: Water treatment piping, 50b: Circulation piping, 51: Pure water tank, 52: Pump, 53: Degassing membrane system, 54: Ultraviolet irradiation system, 55: Non-regenerative ion exchange system (polisher), 55, 56: Ultrafiltration membrane system, 70: Water for injection production system, 70a: Water treatment piping, 70b: Circulation piping, 71: Water for injection production section, 72: Circulation section, 73: Water for injection tank

Claims

1. A method for producing pure water, wherein the pure water is medical-grade water or primary pure water, and the method includes a step of adjusting the temperature of the water to be treated using a plate-type heat exchanger, the plate-type heat exchanger having a first frame and a second frame and a plurality of heat transfer plates between the first frame and the second frame, and in the temperature adjustment step, a heat transfer medium is supplied to the plate-type heat exchanger, the water to be treated is introduced from the first frame side and the water to be treated is discharged from the second frame side to perform heat exchange with the heat transfer medium, and the differential pressure between the introduction pressure and discharge pressure of the water to be treated in the plate-type heat exchanger is 0.05 MPa or more and 0.3 MPa or less.

2. The method for producing pure water according to claim 1, wherein a heat transfer medium is introduced into the plate-type heat exchanger from the second frame side and the heat transfer medium is discharged from the first frame side.

3. The method for producing pure water according to claim 1 or 2, wherein the flow direction of the water to be treated and the flow direction of the heat transfer medium in the plate-type heat exchanger are opposite flows.

4. The method for producing pure water according to claim 1 or 2, wherein the water treatment equipment includes a tank, a plate-type heat exchanger, a reverse osmosis membrane device, and an electro-deionizer, in this order, and at least a portion of the treated water from the electro-deionizer is circulated back into the tank.

5. The method for producing pure water according to claim 1 or 2, wherein the water treatment equipment includes an ultrafiltration membrane device, a tank, and the plate-type heat exchanger, in that order, and at least a portion of the treated water from the plate-type heat exchanger is circulated to the tank.

6. A pure water production apparatus for producing pure water, wherein the pure water is medicinal water or primary pure water, and the apparatus has a plate-type heat exchanger having a first frame and a second frame, and a plurality of heat transfer plates between the first frame and the second frame, and the plate-type heat exchanger has an inlet for introducing a heat transfer medium into the plate-type heat exchanger, an outlet for discharging the heat transfer medium from the plate-type heat exchanger, an inlet for water to be treated provided on the first frame, and an outlet for water to be treated provided on the second frame, and the differential pressure between the introduction pressure and the discharge pressure of water to be treated in the plate-type heat exchanger is 0.05 MPa or more and 0.3 MPa or less.

7. The pure water production apparatus according to claim 6, wherein the plate-type heat exchanger has an inlet for a heat transfer medium in the second frame and an outlet for a heat transfer medium in the first frame.

8. The pure water production apparatus according to claim 6, comprising, in this order, a tank, a plate-type heat exchanger, a reverse osmosis membrane device, and an electro-deionizer, and having a circulation pipe for circulating at least a portion of the treated water from the electro-deionizer back to the tank.

9. The pure water production apparatus according to claim 6, comprising, in this order, an ultrafiltration membrane device, a tank, and the plate-type heat exchanger as the water treatment equipment, and having a circulation pipe for circulating at least a portion of the treated water from the plate-type heat exchanger to the tank.

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