Method for producing pure water and apparatus for producing pure water

Abstract

The present invention provides a method and apparatus for producing pure water that suppresses the rate of increase of viable bacteria and other microorganisms in the water within a heat exchanger. [Solution] 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 medical 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, 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 more.

Description

Technical Field

[0001] The present invention relates to a method for producing pure water and a pure water production apparatus.

Background Art

[0002] Primary pure water used for semiconductor manufacturing and the like is produced by treating raw water or pretreated water with a pure water apparatus having a reverse osmosis membrane or a decomposition device. For example, in order to obtain treated water of sufficient quality in a reverse osmosis membrane or a decomposition device, the water temperature may be adjusted, and a heat exchanger may be installed in the front stage of the reverse osmosis membrane or the decomposition device (see, for example, Patent Documents 1 and 2). In addition, pharmaceutical water, particularly purified water, is produced by treating raw water with a pharmaceutical water production apparatus including a reverse osmosis membrane and an EDI (electrical deionization device). In this pharmaceutical water production apparatus, periodic heat sterilization may be performed to sterilize live bacteria and endotoxins in the apparatus. Also in this case, the treated water is heated by a heat exchanger (see, for example, Patent Document 3). Similarly, in an injection water production apparatus for producing injection water among pharmaceutical waters, the treated water is heated by a heat exchanger to perform heat sterilization in the system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the production of primary pure water and pharmaceutical water, reverse osmosis membranes made of polyamide composite membranes are often used because they produce highly purified treated water. However, reverse osmosis membranes made of polyamide composite membranes have the problem of being severely degraded by hypochlorite-based disinfectants. Therefore, hypochlorite-based disinfectants cannot be used to kill live bacteria originating from the raw water. In such cases, antibacterial agents are sometimes used instead of hypochlorite-based disinfectants, but sufficient effects are not always observed. In addition, it has been considered to install germicidal UV (ultraviolet irradiation device) or pre-filters (microfilters or activated carbon towers) in front of the reverse osmosis membrane device to prevent the supply of bacteria to the reverse osmosis membrane, but neither method is always sufficiently effective, and the problem of the reverse osmosis membrane becoming clogged with bacteria (called biofouling) often occurs. Furthermore, in decomposition equipment used in the production of primary pure water, although rare, biofouling can occur within the decomposition unit, inhibiting the progress of the decomposition reaction. In addition, if a reverse osmosis membrane system is installed downstream of the decomposition unit, the same biofouling problem may occur.

[0005] Furthermore, in the production of water for pharmaceutical use, it is strictly required that no live bacteria or endotoxins (hereinafter also referred to as "live bacteria, etc.") are generated or mixed into the water for pharmaceutical use. For this reason, in conventional water for injection production processes, water for injection was circulated in a circulation system at 80°C or higher to prevent contamination with live bacteria and endotoxins, and the required amount of water for injection was supplied from there to the place of use. In contrast to this, in the production of water for injection using ultrafiltration, the circulation of water for injection at room temperature or near room temperature before use (sometimes called cold WFI) is beginning to be considered. In cold WFI, water for injection at room temperature is circulated within the production equipment system, so there are concerns about an increase in live bacteria and endotoxins in the water. Therefore, some measures are needed to address concerns about an increase in live bacteria and endotoxins, and currently, this has not yet been put into practical use.

[0006] The present invention was made to solve the above-mentioned problems, and aims to provide a method and apparatus for producing pure water that suppresses the increase of live bacteria and other microorganisms in water. [Means for solving the problem]

[0007] The inventors conducted thorough research and discovered that the rate of increase of viable bacteria within the heat exchanger differs depending on the heat exchanger's structure, and consequently, the rate of bacterial growth in subsequent devices differs significantly. They confirmed that this is due to the fact that the likelihood of viable bacteria originating from the raw water proliferating in the heat exchanger and being supplied to subsequent devices differs depending on the heat exchanger's structure, and thus completed the invention.

[0008] Embodiments of the present invention have the following configurations. [1] A method for producing pure water, comprising the steps 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 aforementioned pure water is medicinal water or primary pure water. The aforementioned water treatment equipment includes a 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. In the process 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. The differential pressure between the inlet pressure and outlet 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. A method for producing pure water. [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] A method for producing pure water according to [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, and at least a portion of the treated water from the electro-deionizer is circulated back into the tank. [5] A method for producing pure water according to [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 that has one or more water treatment devices for treating water to be treated and produces pure water, The aforementioned pure water is medicinal water or primary pure water. The aforementioned water treatment equipment includes a plate-type heat exchanger, The plate-type heat exchanger comprises a first frame and a second frame, and a plurality of heat transfer plates between the first frame and the second frame, The plate-type heat exchanger has an inlet for introducing the heat transfer medium, and an outlet for discharging the heat transfer medium from the plate-type heat exchanger. The first frame has an inlet for the water to be treated, and the second frame has an outlet for the water to be treated. A pure water production apparatus in which the differential pressure between the inlet pressure and outlet 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. [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, in this order, a tank, the plate heat exchanger, a reverse osmosis membrane device, and an electrodeionizer, and having a circulation pipe for circulating at least a portion of the treated water from the electrodeionizer back to the tank. [9] The pure water production apparatus according to [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. The "~" symbol indicates a numerical range that includes the numbers before and after it.

Advantages of the Invention

[0009] According to the method and apparatus for producing pure water of the present invention, pure water can be produced by suppressing the growth rate of viable bacteria and the like in water in a heat exchanger.

Brief Description of the Drawings

[0010] [Figure 1] It is a diagram schematically showing a plate-type heat exchanger. [Figure 2] It is a diagram schematically showing the heat transfer plate of the present embodiment. [Figure 3] It is a diagram schematically showing another heat transfer plate of the present embodiment. [Figure 4] It is an elevation view schematically showing the plate-type heat exchanger of the embodiment. [Figure 5] It is an elevation view schematically showing a conventional plate-type heat exchanger. [Figure 6] It is a diagram schematically showing a pure water apparatus having the plate-type heat exchanger of the embodiment. [Figure 7] It is a diagram schematically showing another pure water apparatus having the plate-type heat exchanger of the embodiment. [Figure 8] It is a diagram schematically showing an apparatus for producing pharmaceutical water (purified water) having the plate-type heat exchanger of the embodiment. [Figure 9] It is a diagram schematically showing an apparatus for producing water for injection having the plate-type heat exchanger of the embodiment. [Figure 10] It is a graph showing an example of the decrease in permeation flux due to the growth of viable bacteria and the like in the subsequent reverse osmosis membrane apparatus when using the plate-type heat exchanger of the embodiment and the plate-type heat exchanger of the comparative example.

Embodiments for Carrying Out the Invention

[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 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 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. 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, inlets 5a and outlets 5b are located at two diagonally opposite corners, and inlets 13a and outlets 13b are located at two diagonally opposite 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 while Figure 2 shows an configuration where inlets 5a and outlets 5b are located at two diagonally opposite corners, Figure 1 shows a configuration where inlets 5a and outlets 5b are located at adjacent corners for the sake of explanation.

[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 1-3, 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 within 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 and the inner diameter of the gasket 3 surrounding them be approximately the same 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 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 of the plate-type heat exchanger 1 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 shaded line represents 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 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 inlet 2a is increased, making it possible to miniaturize the plate 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 about 2 to 10 times compared to conventional plate 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 4, the dotted line represents 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 are 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 is 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 be 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 downstream. 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 at 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 showing 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 temperature control system 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 biodecomposition treatment using a biological treatment tank. 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 tank 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 treats the water to be treated or a device that treats the water in a batch manner. In order to improve 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 treats 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 treats 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 equipment 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 its other configurations are the same as those of the primary pure water system 20 shown in Figure 5. Therefore, components that perform the same function are given the same reference numerals 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 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 produces primary pure water by treating raw water. In the primary pure water system 200 shown in Figure 7, the accumulation of viable bacteria and other microorganisms within the plate-type heat exchanger 1 does not occur. Therefore, biofouling in the reverse osmosis membrane system (RO) 25 can be prevented for a long period of time. Depending on the operating conditions, for example, the flux of the plate-type heat exchanger can be increased by four times, i.e., the differential pressure between the inlet and outlet before the plate-type heat exchanger can be increased by about four times, compared to a conventional plate-type heat exchanger. In this case, the impact on the reverse osmosis membrane 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 1 day to 6 months, meaning that sterilization is performed once every 1 day to 6 months. To effectively prevent contamination by bacteria, etc., it is more preferable to sterilize once every 1 day to 2 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 between 60°C and 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 device 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. If the sterilization temperature is 60°C, the time required to lower the water temperature to room temperature is 30 to 120 minutes, and if 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 for injection production apparatus 70 maintains, for example, a water temperature of 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 water for injection. [Examples]

[0043] Next, examples will be described. The present invention is not limited to the following examples.

[0044] (Example 1) A primary pure water system similar to the primary pure water system 200 shown in Figure 7 was prepared, and pure water was produced. The raw water quality and operating conditions of the various systems were as follows.

[0045] [Raw water quality] Conductivity: 200μS / cm Live bacteria: 200 pieces / mL Water temperature: 15℃ [Heat exchanger] Water flow differential pressure (difference between inlet pressure and outlet pressure): 0.25 MPa Treated water temperature (water temperature after passing through the heat exchanger): 25℃ [Reverse osmosis membrane device] Film type: TM710 (manufactured by Toray Industries, Inc.) 1 roll Water recovery rate: 75%

[0046] Under the above conditions, the change in permeate flux of the reverse osmosis membrane system was recorded while producing primary pure water. Approximately 50 days after the installation of the primary pure water system, the permeate flux of the reverse osmosis membrane system began to decrease. The relationship between the permeate flux of the reverse osmosis membrane system and the elapsed time after this decrease began is shown in the graph of Figure 10, as a relative value with the permeate flux value immediately after the installation of the primary pure water system set to 1.

[0047] (Comparative Example 1) In place of the plate-type heat exchanger in the example, a plate-type heat exchanger was used in which the water to be treated was introduced from the first frame side and discharged from the first frame side. The number of plates in 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 introduction pressure and discharge pressure of the water to be treated into the plate-type heat exchanger was 0.02 MPa. In Comparative Example 1, the permeation flux of the reverse osmosis membrane device began to decrease approximately 7 days after the installation of the primary pure water device. The relationship between the permeation flux of the reverse osmosis membrane device and the elapsed time after this decrease in permeation flux began is shown in the graph of Figure 10 as a relative value with the permeation flux value immediately after the installation of the primary pure water device in the comparative example set to 1.

[0048] The number of viable bacteria in the treated water of the reverse osmosis membrane system was measured during continuous water flow for 50 days from the start of water flow in Example 1 and Comparative Example 1. The maximum value is shown in Table 1, "Viable Bacteria Count (Steady State)". During this period, the pump was not turned on or off, and water treatment operation was performed steadily. In addition, immediately after repeating the operation of stopping and starting the pump installed upstream of the plate heat exchanger five times, the number of viable bacteria in the feed water and treated water of the plate heat exchanger was measured, and the results are shown in Table 1, "Viable Bacteria Count (Immediately After On / Off)". Viable bacteria were measured using the sampling-culture method.

[0049] [Table 1]

[0050] Table 1 shows that during steady-state operation without pump on / off cycles, the amount of viable bacteria in the reverse osmosis membrane supply water is approximately the same for both Example 1 and Comparative Example 1. Similarly, the amount of viable bacteria in the heat exchanger supply water when the pump is switched on and off is also approximately the same for both Example 1 and Comparative Example 1. However, when the pump is switched on and off, the amount of viable bacteria in the heat exchanger treated water increases. This increase is particularly significant in Comparative Example 1. This indicates that when the flow rate and pressure fluctuate due to the pump being switched on and off, viable bacteria that have proliferated inside the heat exchanger are discharged. [Explanation of Symbols]

[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 treatment 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, comprising the steps 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 aforementioned pure water is medicinal water or primary pure water. The aforementioned water treatment equipment includes a 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. In the process 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 discharged from the second frame side, and heat exchange is performed with the heat transfer medium. The differential pressure between the inlet pressure and outlet 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. A method for producing pure water.

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. A method for producing pure water according to claim 1 or 2, wherein the water treatment equipment used in this order is a tank, a plate-type 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 into the tank.

5. A method for producing pure water according to claim 1 or 2, wherein the water treatment equipment used is 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. In a pure water production apparatus that has one or more water treatment devices for treating water to be treated and produces pure water, The aforementioned pure water is medicinal water or primary pure water. The aforementioned water treatment equipment includes a plate-type heat exchanger, The plate-type heat exchanger comprises a first frame and a second frame, and a plurality of heat transfer plates between the first frame and the second frame, The plate-type heat exchanger has an inlet for introducing the heat transfer medium, and an outlet for discharging the heat transfer medium from the plate-type heat exchanger. The first frame has an inlet for the water to be treated, and the second frame has an outlet for the water to be treated. A pure water production apparatus in which the differential pressure between the inlet pressure and outlet 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.

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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