Water production method, adsorbent regeneration method, and water production apparatus
By alternating steps of adsorbing and diffusing molecules using controlled gas conditions, the method addresses high energy consumption and adsorbent replacement issues, achieving cost-effective and stable production of deuterium-reduced water.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TAKAGI CO LTD
- Filing Date
- 2022-08-01
- Publication Date
- 2026-05-11
AI Technical Summary
Existing methods for producing deuterium-reduced water are costly due to high energy consumption for desorbing adsorbed molecules and require frequent adsorbent replacement to maintain separation performance, leading to instability in water quality.
A method involving two steps: first, adsorbing raw water vapor onto an adsorbent and recovering preferentially desorbed water molecules, followed by supplying a gas with controlled humidity and temperature to diffuse adsorbed isotopic molecules into the gas, thereby restoring adsorbent separation performance without frequent replacement.
This method reduces production costs and maintains stable water quality by suppressing separation performance decline, allowing continuous production of deuterium-reduced water with reduced isotopic molecules.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for producing water, a method for regenerating an adsorbent, and a water production apparatus.
Background Art
[0002] Tap water and natural water may contain semi-heavy water, heavy water, etc., and water used for reactor cooling water, etc., may contain tritiated water, etc. These semi-heavy water, heavy water, and tritiated water have different physical properties such as solubility, electrical conductivity, and ionization degree of substances, and reaction rates, etc., compared to light water. Therefore, if organisms ingest a large amount of water containing semi-heavy water, heavy water, and tritiated water, it may have an adverse effect on biological reactions. Therefore, in order to avoid such a situation, various methods for preparing water with a reduced content of semi-heavy water, heavy water, and tritiated water have been studied.
[0003] For example, by utilizing the fact that the adsorption and desorption performance of light water, semi-heavy water, and heavy water on an adsorbent is slightly different, raw water is adsorbed onto an adsorbent having a pore structure, and then a part of the adsorbed raw water is desorbed, a method for producing deuterium-reduced water with a reduced content of semi-heavy water and heavy water is known (for example, Patent Documents 1, 2, etc.). These technologies are useful in reducing the content of semi-heavy water and heavy water. However, as the ratio of semi-heavy water and heavy water adsorbed on the adsorbent increases, the performance of separating light water contained in the raw water from semi-heavy water and heavy water gradually decreases, so there is a concern that the quality of the produced water is not stable, such as the content of semi-heavy water and heavy water in the obtained deuterium-reduced water gradually increases. Therefore, generally, replacement of the adsorbent, etc., is required, and the production cost of deuterium-reduced water tends to increase.
[0004] Studies are also being considered to regenerate and reuse used adsorbents. As such regeneration methods, methods that have been considered mainly involve removing molecules adsorbed on the adsorbent by heating and volatilizing them. In addition, for example, Patent Document 3 discloses a method for activating and regenerating an adsorbent used in hydrogen isotope concentration and separation, characterized in that, when separating and concentrating hydrogen isotopes in water containing various hydrogen isotopes by adsorption, the adsorbent used for the concentration and separation is heated and regenerated, and the heated and regenerated adsorbent is brought into countercurrent contact with a water vapor-encompassing gas of hydrogen isotopes with a mass lighter than the heavier hydrogen isotopes remaining in the heated and regenerated adsorbent at a temperature near the regeneration temperature of the adsorbent in an activation and regeneration zone, thereby transferring the heavier mass components of the hydrogen isotopes remaining in the heated and regenerated adsorbent into the gas. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] International Publication No. 2017 / 209227 [Patent Document 2] International Publication No. 2019 / 004102 [Patent Document 3] Japanese Patent Application Publication No. 53-093294 [Overview of the project] [Problems that the invention aims to solve]
[0006] While the method of regenerating adsorbents by heating is useful, if the adsorbent has high adsorption performance, a lot of energy is required to desorb the adsorbed molecules. Therefore, there is room for improvement from the perspective of reducing the production cost of deuterium-reduced water, etc. Furthermore, in order to continuously produce deuterium-reduced water, etc. over a long period of time, it would be useful to have a method to suppress the decrease in separation performance associated with the use of adsorbents during the production process, or to restore the decreased separation performance.
[0007] This disclosure aims to provide a method for producing water with a reduced content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. This disclosure also aims to provide a production apparatus usable in the above production method. This disclosure also aims to provide a method for regenerating an adsorbent used to reduce the content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. [Means for solving the problem]
[0008] This disclosure provides the following [1] to
[14] .
[0009] [1] A method for producing water in which the content of the isotopically substituted molecules is reduced, from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, A first step involves supplying raw material steam from raw water to an adsorbent, adsorbing at least a portion of the raw material steam onto the adsorbent, and recovering steam containing water molecules that preferentially desorb from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent. The first step is followed by a second step of supplying a gas containing water vapor to the adsorbent, thereby diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas, and restoring the separation performance of the adsorbent. In the second step, The relative humidity of the gas supplied to the adsorbent is adjusted to be 0.0005 to 2.5% RH at the temperature of the gas when supplied to the adsorbent. A manufacturing method wherein the content of the molecule substituted with an isotopic element in the gas supplied to the adsorbent is less than the content of the molecule in the raw material vapor. [2] The manufacturing method according to [1], wherein the content of the molecules in the gas supplied to the adsorbent in the second step is 140 atoms ppm or less. [3] The manufacturing method according to [1] or [2], wherein the temperature of the gas supplied to the adsorbent in the second step is 60°C or higher. [4] The process further includes a third step of preparing water in which the molecular content is reduced by condensing a portion of the steam recovered in the first step, The manufacturing method according to any one of [1] to [3], wherein in the third step, a portion of the vapor that was not condensed is used as the gas supplied to the adsorbent in the second step. [5] A manufacturing method according to any one of [1] to [4], wherein the first step and the second step are repeated alternately to continuously produce water in which the content of the molecules has been reduced. [6] The manufacturing method according to any one of [1] to [5], wherein the adsorbent is at least one selected from the group consisting of polymer sorbents, activated carbon, and zeolites. [7] The manufacturing method according to any one of [1] to [6], wherein the adsorbent is contained in an adsorbent layer provided on at least a part of the surface of the cylindrical body. [8] The manufacturing method according to any one of [1] to [6], wherein the adsorbent is filled into a cylindrical body. [9] A method for regenerating an adsorbent used to reduce the content of molecules substituted with isotopes, from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is substituted with an isotope of hydrogen, This includes supplying a gas containing water vapor to the adsorbent and diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas, thereby restoring the separation performance of the adsorbent. The relative humidity of the gas supplied to the adsorbent is adjusted to be 0.0005 to 2.5% RH at the temperature of the gas when supplied to the adsorbent. A regeneration method in which the content of the molecule substituted with an isotope element in the gas supplied to the adsorbent is smaller than the content of the molecule in the raw material vapor generated from the raw material water.
[10] The regeneration method according to [9], wherein the content of the molecule in the gas supplied to the adsorbent is 140 atomic ppm or less. [[ID==66]]
[11] The regeneration method according to [9] or
[10] , wherein the temperature of the gas supplied to the adsorbent is 60°C or higher.
[12] A production apparatus for producing water with a reduced content of the molecule substituted with an isotope element from raw material water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is substituted with an isotope element of hydrogen, comprising: An adsorption / desorption unit for raw material vapor generated from the raw material water, having an adsorbent; A raw material supply unit for supplying the raw material vapor to the adsorption / desorption unit; A recovery unit for recovering vapor containing water molecules preferentially desorbed from the adsorbent due to the difference in the strength of hydrogen bonds formed with the adsorbent; A gas supply unit for supplying a gas with an adjusted content and humidity of the molecule to the adsorption / desorption unit. By supplying a gas whose humidity is adjusted so that the relative humidity at the temperature when supplied from the gas supply unit to the adsorbent is 0.0005 to 2.5%RH, and the content of the molecule substituted with an isotope element in the gas is smaller than the content of the molecule in the raw material vapor, at least a part of the molecule substituted with an isotope element adsorbed on the adsorbent is diffused into the gas, and the separation performance of the adsorbent is restored. The production apparatus, wherein the recovery unit has means for condensing the recovered vapor, and the gas supply unit supplies the vapor not condensed in the recovery unit as the gas to the adsorption / desorption unit.
[13] The recovery unit has means for condensing the recovered vapor. The production apparatus according to
[12] , wherein the gas supply unit supplies the vapor not condensed in the recovery unit as the gas to the adsorption / desorption unit.
[14] The raw material supply unit supplies the vapor of the raw material water in a direction parallel to the extending direction of the adsorption / desorption unit. The gas supply unit supplies the gas in a direction opposite to the vapor of the raw material water, and the manufacturing apparatus according to
[12] or
[13] .
[0010] One aspect of the present disclosure is a manufacturing method for obtaining water with a reduced content of the above-mentioned molecules substituted with isotope elements from raw material water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is substituted with an isotope element of hydrogen. The method includes a first step of supplying the raw material vapor of the raw material water to an adsorbent, adsorbing at least a part of the raw material vapor to the adsorbent, and recovering a vapor containing water molecules preferentially desorbed from the adsorbent due to the difference in the strength of the hydrogen bonds formed between the adsorbent and the raw material vapor; and a second step of, after the first step, supplying a gas containing water vapor to the adsorbent and diffusing at least a part of the molecules adsorbed on the adsorbent into the gas to recover the separation performance of the adsorbent. In the second step, the relative humidity of the gas supplied to the adsorbent is adjusted to be 0.0005 to 2.5%RH at the temperature of the gas when supplied to the adsorbent, and the content of the molecules substituted with isotope elements in the gas supplied to the adsorbent is smaller than the content of the molecules in the raw material vapor. A manufacturing method is provided.
[0011] In the first step of the above manufacturing method, the vapor of the raw material water containing molecules substituted with isotope elements of hydrogen and water molecules (H2O, light water) is once adsorbed to the adsorbent. Focusing on the fact that the strength of the hydrogen bonds formed between the adsorbent and the molecules substituted with isotope elements of hydrogen (for example, D2O, T2O, etc.) and water molecules (H2O, light water) is different, and by utilizing the difference in the adsorption / desorption performance based on this difference, it is possible to manufacture water with a reduced content of molecules substituted with isotope elements of hydrogen by recovering a vapor containing a large amount of light water molecules that preferentially desorb from the raw material vapor adsorbed on the adsorbent.
[0012] The above manufacturing method also includes a second step in addition to the first step. In the second step, a gas containing water vapor with a lower content of hydrogen isotope-substituted molecules than the raw material vapor generated from the raw water is supplied to the adsorbent at a predetermined humidity. This reduces the proportion of the aforementioned molecules (e.g., D2O) in the environment in contact with the adsorbent. Therefore, by utilizing the concentration equilibrium with the environment, it is possible to diffuse at least some of the hydrogen isotope-substituted molecules that were adsorbed onto the adsorbent in the first step and remain on the adsorbent into the gas, thereby removing them from the adsorbent.
[0013] The above manufacturing method has a second step, and through the aforementioned action of suppressing the decrease in separation performance associated with the use of adsorbents or restoring the decreased separation performance, it is not necessarily required to replace the adsorbent as in the case of conventional adsorbents, and at least it is possible to produce the target water without needing to replace it at the same frequency as conventional methods, and thus the target water can be produced at a lower cost. According to the above manufacturing method, it is possible to stabilize the composition of the steam obtained through adsorption and desorption to the adsorbent, so that water with a reduced content of the above molecules (e.g., D2O, etc.) can be produced in a stable quality state.
[0014] In the second step described above, the content of the above molecules in the gas supplied to the adsorbent may be 140 atoms ppm or less. If the content of molecules substituted with hydrogen isotopes in the gas is within the above range, the diffusion of the above molecules (e.g., D2O, etc.) from the adsorbent will be more efficient. Generally, the content of molecules substituted with hydrogen isotopes in natural water available on flat land is about 150 atoms ppm. Since much of the water used as raw material contains molecules substituted with hydrogen isotopes at a higher rate, the proportion of the above molecules (e.g., D2O, etc.) that adhere to and concentrate on the adsorbent in the first step will exceed 150 atoms ppm.
[0015] In the second step described above, the temperature of the gas supplied to the adsorbent may be 60°C or higher. By keeping the temperature of the gas supplied to the adsorbent within the above range in the second step, the ambient temperature in which the adsorbent is placed is increased, making the diffusion of the molecules adsorbed on the adsorbent (e.g., D2O, etc.) into the gas more efficient.
[0016] The process further includes a third step in which a portion of the steam recovered in the first step is condensed to prepare water with a reduced content of the above molecules. In the third step, a portion of the steam that was not condensed may be used as the gas supplied to the adsorbent in the second step. Since the content of the above molecules (e.g., D2O, etc.) in the steam recovered in the third step is sufficiently reduced in the first step, it is suitable as a gas for diffusing the above molecules (e.g., D2O, etc.) adsorbed on the adsorbent. Furthermore, by utilizing the steam that could not be recovered, the cost of separately preparing the above gas can be reduced, thereby further reducing the production cost of water with a reduced content of the above molecules (e.g., D2O, etc.).
[0017] The first step and the second step described above can be repeated alternately to continuously produce water with a reduced content of the above molecules. With the manufacturing method according to this disclosure, the deterioration of the separation performance of the adsorbent due to continuous use can be suppressed, or the deteriorated separation performance can be restored. Therefore, it is not always necessary to replace the adsorbent as in the case of conventional adsorbents, and it is possible to continue producing the target water continuously without having to replace it at least as frequently as in the conventional method.
[0018] The above-mentioned adsorbent may be at least one selected from the group consisting of polymer sorbents, activated carbon, and zeolites.
[0019] The above-mentioned adsorbent may be contained in an adsorbent layer provided on at least a portion of the surface of the cylindrical body.
[0020] The above-mentioned adsorbent material may be filled into a cylindrical body.
[0021] One aspect of this disclosure is a method for regenerating an adsorbent used to reduce the content of isotopically replaced molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, comprising supplying a gas containing water vapor to the adsorbent and diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas to restore the separation performance of the adsorbent, wherein the relative humidity of the gas supplied to the adsorbent is adjusted to 0.0005 to 2.5% RH at the temperature of the gas supplied to the adsorbent, and the regeneration method provides a regeneration method in which the content of isotopically replaced molecules in the gas supplied to the adsorbent is smaller than the content of the molecules in the raw vapor generated from the raw water.
[0022] The above regeneration method involves supplying a gas containing vapor with a lower content of the above-mentioned molecules (e.g., D2O, T2O, etc.) substituted with isotopic elements than the raw water, at a predetermined humidity, to the used adsorbent. This allows at least a portion of the above-mentioned molecules (e.g., D2O, etc.) attached to the adsorbent to diffuse into the gas and be removed from the adsorbent, thereby restoring the separation performance of the adsorbent and enabling its regeneration.
[0023] The content of the above molecules in the gas supplied to the above adsorbent may be 140 atoms ppm or less.
[0024] The temperature of the gas supplied to the adsorbent may be 60°C or higher.
[0025] One aspect of the present disclosure is a production apparatus for producing water in which the content of the isotopically substituted molecules is reduced from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced by an isotopic element of hydrogen, comprising: an adsorption / desorption unit for raw material steam generated from the raw water having an adsorbent; a raw material supply unit for supplying the raw material steam to the adsorption / desorption unit; a recovery unit for recovering steam containing water molecules preferentially desorbed from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent; and a unit for supplying the molecules to the adsorption / desorption unit. The present invention provides a manufacturing apparatus comprising: a gas supply unit that supplies a gas whose content and humidity have been adjusted; the humidity of the gas supply unit is adjusted so that the relative humidity at the temperature at which it is supplied to the adsorbent is 0.0005 to 2.5% RH; and the content of the molecules substituted with isotopic elements in the gas is less than the content of the molecules in the raw material vapor; thereby diffusing at least a portion of the molecules substituted with isotopic elements adsorbed on the adsorbent into the gas, thereby restoring the separation performance of the adsorbent.
[0026] The above-described manufacturing apparatus, by comprising an adsorption / desorption unit for raw material steam generated from raw water, a raw material supply unit, and a recovery unit, is capable of producing water with a reduced content of the above-described molecules (e.g., D2O, T2O, etc.) substituted with isotopic elements. Furthermore, the above-described manufacturing apparatus is equipped with a gas supply unit that supplies gas with adjusted molecular content and relative humidity to the adsorption / desorption unit having an adsorbent, thereby enabling both water production and regeneration of the adsorbent. For this reason, the above-described manufacturing apparatus is useful for the water production method described above.
[0027] The recovery unit may have means for condensing the recovered steam, and the gas supply unit may supply the steam that was not condensed in the recovery unit as the gas to the adsorption / desorption unit.
[0028] The raw material supply unit may supply the steam of the raw material water in a direction parallel to the extending direction of the adsorption / desorption unit, and the gas supply unit may supply the gas in the opposite direction to the steam of the raw material water. [Effects of the Invention]
[0029] This disclosure provides a method for inexpensively producing water with a reduced content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. This disclosure also provides a manufacturing apparatus usable in the above manufacturing method. This disclosure also provides a method for regenerating an adsorbent used to reduce the content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. [Brief explanation of the drawing]
[0030] [Figure 1] Figure 1 is a schematic diagram showing an example of a manufacturing apparatus. [Figure 2] Figure 2 is a schematic diagram of the evaluation apparatus used in the example. [Figure 3] Figure 3 is a graph showing the relationship between the deuterium concentration and yield in the deuterium-reduced water produced in the examples. [Figure 4] Figure 4 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water in the examples and the content of deuterium-containing components in the water vapor used to regenerate the adsorbent. [Figure 5] Figure 5 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water in the examples and the relative humidity of the water vapor used to regenerate the adsorbent. [Figure 6] Figure 6 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water in the examples and the relative humidity of the water vapor used to regenerate the adsorbent. [Figure 7] Figure 7 is a graph showing the relationship between the deuterium concentration and yield in the deuterium-reduced water produced in the examples. [Modes for carrying out the invention]
[0031] The embodiments of this disclosure will be described below, with reference to the drawings as appropriate. However, the embodiments described below are illustrative examples for illustrating this disclosure and are not intended to limit this disclosure to the following. Unless otherwise specified, positional relationships such as up, down, left, and right shall be based on the positional relationships shown in the drawings. The dimensional ratios of each element are not limited to the ratios shown in the drawings.
[0032] Unless otherwise specified, the materials exemplified herein may be used individually or in combination of two or more. The content of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.
[0033] One embodiment of a production method for obtaining water with a reduced content of isotopically substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, includes a first step of supplying raw water vapor of raw water to an adsorbent, adsorbing at least a portion of the raw water vapor onto the adsorbent, and recovering the vapor containing water molecules that preferentially desorb from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent; and a second step after the first step of supplying a gas containing water vapor (hereinafter, sometimes also referred to as a regeneration gas) to the adsorbent, and diffusing at least a portion of the molecules adsorbed onto the adsorbent into the gas, thereby restoring the separation performance of the adsorbent. In the second step, the relative humidity of the gas supplied to the adsorbent is adjusted to 0.0005 to 2.5% RH at the temperature of the gas when supplied to the adsorbent. Furthermore, in the second step described above, the content of the molecules substituted with isotopic elements in the gas supplied to the adsorbent is smaller than the content of the molecules in the raw material vapor.
[0034] The isotopic elements of hydrogen are deuterium (D) and tritium (T). In other words, in this specification, "a molecule in which at least one of the hydrogen atoms constituting a water molecule is replaced with an isotopic element of hydrogen" (hereinafter, sometimes also referred to as a specific molecule) means a molecule in which the hydrogen in a water molecule is replaced with at least one of the elements deuterium (D) and tritium (T), and means at least one selected from the group consisting of semi-heavy water (DHO), heavy water (D2O), and tritiated water (THO, T2O). These specific molecules have stronger hydrogen bonds formed with the adsorbent than water (H2O, hereinafter, sometimes also referred to as light water), and preferentially adsorb to the adsorbent and are difficult to detach from the adsorbent. For this reason, once these specific molecules are adsorbed onto an adsorbent, the rate at which they volatilize from the adsorbent is lower than that of light water. The manufacturing method according to this disclosure utilizes these differences in characteristics to produce water with a reduced content of specific molecules from raw water.
[0035] On the other hand, due to the strong hydrogen bonds formed between the adsorbent and the adsorbent, once a specific molecule is adsorbed onto the adsorbent, it is not easy to detach it even by drying methods such as applying heat to the adsorbent. If an adsorbent containing a specific molecule is used continuously, the amount of the specific molecule remaining on the adsorbent increases, and the effect of reducing the content of the specific molecule in the raw water tends to be impaired. In that case, in order to produce water with a reduced content of the specific molecule, it is necessary to replace the adsorbent or to repeatedly perform operations that bring the adsorbent into contact with the adsorbent multiple times in order to gradually reduce the content of the specific molecule to the target value. As a result, the cost of producing water tends to increase. On the other hand, in the production method according to this disclosure, by detaching the specific molecule that has remained on the adsorbent through diffusion using concentration equilibrium with the environment using the method described later, the separation performance of the adsorbent can be restored or maintained at a certain level, thereby enabling the efficient production of water with a reduced content of the target specific molecule.
[0036] When the specific molecule is mainly semi-heavy water and heavy water having deuterium (D) as a constituent element, the water obtained by the manufacturing method of this disclosure is so-called deuterium-reduced water, and the manufacturing method of this disclosure can also be called a method for producing deuterium-reduced water. The deuterium-reduced water obtained by the manufacturing method of this disclosure is also suitable for drinking. Although deuterium-reduced water with a low content of heavy water and semi-heavy water is not approved in Japan, it is approved in Hungary, for example, as an anticancer agent for animals, and is sometimes consumed by cancer patients. When the specific molecule is mainly tritium water having tritium as a constituent element, the manufacturing method of this disclosure can also be called a method for decontaminating tritium water.
[0037] The raw water used in the manufacturing method of this disclosure may include, for example, natural water such as rainwater, groundwater, freshwater, and seawater, tap water, and contaminated water that has been used for cooling nuclear reactors, etc. The content of specific molecules in the raw water is not particularly limited and can be used. The upper limit of the content of specific molecules may be, for example, 300 ppm or less, 250 ppm or less, or 200 ppm or less, based on the total amount of water vapor generated from the raw water. If the upper limit of the content of specific molecules is within the above range, the amount of specific molecules adsorbed onto the adsorbent will be small, which can extend the lifespan of the adsorbent. The lower limit of the content of specific molecules may be, for example, 10 ppm or more, 30 ppm or more, or 50 ppm or more, based on the total amount of water vapor generated from the raw water. As the raw water used in the manufacturing method of this disclosure, water with a specific molecule content within the above range can be used, for example, raw water with a content of 10 to 300 ppm or 50 to 200 ppm can be used.
[0038] In this specification, the content of the above-mentioned specific molecules contained in the raw water, etc. (the content of molecules in which at least one of the hydrogen atoms constituting the water molecule is replaced by an isotopic element of hydrogen) means a value determined by wavelength scan cavity ring-down spectroscopy.
[0039] The adsorbent used in the first step can be any adsorbent that has the ability to adsorb water molecules. Examples of adsorbents that have the ability to adsorb water molecules include compounds having hydrophilic groups such as hydroxyl groups and carboxyl groups, and compounds having pores of a size corresponding to water molecules within the molecule. The adsorbent may be at least one selected from the group consisting of polymer sorbents, activated carbon, and zeolites. A polymer sorbent is a polymer material in which a cross-linking structure is introduced between multiple polymer chains having hydrophilic functional groups, and polymer sorbents are capable of adsorbing and desorbing water or similar compounds. Examples of polymer sorbents include cross-linked poly(meth)acrylic acid polymers. Examples of activated carbon include fibrous activated carbon and granular activated carbon. Examples of zeolites include FAU-type zeolites and LTA-type zeolites. FAU and LTA are three-letter uppercase alphabetical framework type codes used to classify the framework topology of zeolites.
[0040] The adsorbent may include, for example, at least one selected from the group consisting of adsorbents classified as Type I, Type IV, and Type V in the IUPAC classification of adsorption / desorption isotherms when water vapor is used. Here, an adsorption / desorption isotherm is a graph showing the adsorption / desorption behavior of water vapor on a graph where the amount of water vapor adsorbed onto the adsorbent is on the vertical axis and the relative pressure of the water vapor supplied to the adsorbent is on the horizontal axis. IUPAC classifies adsorbents into six types, I to VI, based on the differences in their behavior. Of these, Type I, Type IV, and Type V are all adsorbents having pores, and exhibit the behavior shown by those with relatively small pore diameters. It should be noted that the adsorbent used in the manufacturing method in this disclosure may exhibit adsorption / desorption behavior similar to that of the adsorbents classified as Type I, Type IV, or Type V above, and is not necessarily intended to be limited to adsorbents that physically have pores.
[0041] The adsorbent can be used in any form as long as it can come into contact with the raw material vapor and the gas in the second step described later. The adsorbent may be, for example, a powder, or it may be formed into a film or layer, or it may be supported on another material. The adsorbent may be, for example, filled into a cylindrical body, included in an adsorption layer provided on at least a part of the surface of the cylindrical body, or it may constitute an adsorption layer provided on at least a part of the surface of the cylindrical body. The cross-sectional shape of the cylindrical body is not particularly limited and may be a polygon such as a circle, ellipse, triangle, or square. The cylindrical body may be a single cylinder or other component, or it may be part of another structure. If the cylindrical body is part of another structure, for example it may be part of a structure having a honeycomb cross-sectional shape. The material constituting the cylindrical body is not particularly limited as long as it can withstand water vapor and heat and may be a metal, an inorganic material such as ceramic, or an organic material such as paper.
[0042] When the adsorbent is filled into a cylindrical body or forms an adsorbent layer on the surface of a structure, the direction of extension of the cylindrical body and the structure may be parallel to the flow path of the steam of the raw water.
[0043] In the first step, the flow rate of the raw material steam generated from the raw water may be adjusted by the distance at which the adsorbent and the steam are in contact. The flow rate of the raw material steam may be adjusted using the space velocity, which indicates how many times the volume of water vapor relative to the volume of the adsorbent should be supplied per unit time, as an indicator. The upper limit of the space velocity when supplying the raw material steam is, for example, 5.00 s. -1 Below, 3.00s -1 Below, 1.00s -1 The following, or 0.50s -1 The following is acceptable. By setting the upper limit of the space velocity within the above range, the adsorbent can more effectively adsorb the raw material vapor. The lower limit of the space velocity is, for example, 0.05 s. -1 The above is 0.10s -1 More than 0.30s -1 Above, or 0.40s -1The above is acceptable. By setting the lower limit of the space velocity within the above range, the production rate of the target water (e.g., deuterium-reduced water) can be increased, thereby reducing the amount of adsorbent used. In this specification, space velocity refers to the value measured by a flow meter (flow rate at 20°C and 101.325 kPa) at the temperature at which the steam is supplied.
[0044] In the first step, the temperature at which the raw material steam generated from the raw material water is supplied may be around room temperature, for example, 5-45°C, 10-40°C, or 15-35°C.
[0045] In the first step, the degree of adsorption of the raw material steam onto the adsorbent can be adjusted by appropriately increasing the pressure when supplying the raw material steam generated from the raw material water. The above pressure may be, for example, 0.0020 to 0.0025 MPa. Pressure as used herein refers to absolute pressure.
[0046] In the first step, vapor containing water molecules that preferentially desorb from the adsorbent due to differences in the strength of hydrogen bonds formed with the adsorbent is recovered. The means for recovering the vapor are not particularly limited, but for example, it may be recovered by cooling and condensing the vapor.
[0047] The second step is performed after the first step. In the second step, a gas containing water vapor is supplied to the adsorbent, and at least a portion of the molecules adsorbed on the adsorbent are diffused into the gas, thereby restoring the separation performance of the adsorbent. In the second step, in the process of producing water with a reduced content of the specific molecules, at least a portion of the specific molecules adsorbed on the adsorbent can be removed from the adsorbent.
[0048] By having a moderate level of humidity, the above gas can promote the desorption of the specific molecules adsorbed on the adsorbent by utilizing the concentration equilibrium with the environment on the surface of the adsorbent. The relative humidity of the gas supplied to the adsorbent is adjusted to be 0.0005 to 2.5% RH at the temperature of the gas supplied to the adsorbent. The above relative humidity may be, for example, 0.1 to 2.3% RH, 0.2 to 2.0% RH, or 0.3 to 1.8% RH at the temperature of the gas supplied to the adsorbent. The relative humidity at the temperature of the gas supplied to the adsorbent refers to the value obtained by converting the relative humidity measured at 25°C to the relative humidity at the temperature of the gas.
[0049] The humidity of the above gas may be adjusted so that the relative humidity at 100°C is 2.5%RH or less. If the adsorbent is, for example, a polymer sorbent used at relatively low temperatures, the relative humidity at 100°C may be considered when making adjustments. The upper limit of the relative humidity of the above gas at 100°C may be, for example, 0.600%RH or less. By setting the upper limit of the relative humidity within the above range, the exchange between specific molecules adsorbed on the adsorbent and light water becomes easier. The lower limit of the relative humidity of the above gas at 100°C may be, for example, 0.300%RH or more. By setting the upper limit of the relative humidity within the above range, the exchange between specific molecules adsorbed on the adsorbent and light water becomes easier. The relative humidity of the above gas at 100°C may be adjusted within the above range, for example, 0.300 to 0.600%RH.
[0050] In this specification, relative humidity refers to the value measured by a capacitive hygrometer.
[0051] The content of the above-mentioned molecule substituted with an isotopic element in the above-mentioned gas should be less than the content of the above-mentioned molecule in the water used as the raw material water, but it is desirable to use a gas with an even lower content. The upper limit of the content of the above-mentioned molecule in the above-mentioned gas in the second step may be, for example, 140 atoms ppm or less, 120 atoms ppm or less, 100 atoms ppm or less, or 90 atoms ppm or less. By setting the upper limit of the content of the specific molecule in the above-mentioned gas within the above range, the desorption of the specific molecule adsorbed on the adsorbent can be made easier. The lower limit of the content of the above-mentioned molecule in the above-mentioned gas in the second step is not particularly limited and may be zero (i.e., does not contain the specific molecule), but may be, for example, 20 atoms ppm or more, 50 atoms ppm or more, 60 atoms ppm or more, or 70 atoms ppm or more. Since gases with a low content of the specific molecule are expensive, by setting the lower limit of the content of the specific molecule in the above-mentioned gas within the above range, the production cost of the target water (e.g., deuterium-reduced water) can be reduced. By setting the lower limit of the content of specific molecules in the above gas to the above range, the cost of water production can be further reduced. The content of the above molecules in the gas in the second step may be adjusted within the above range, for example, 20 to 140 atomic ppm, 50 to 100 atomic ppm, or 60 to 100 atomic ppm.
[0052] In the second step described above, the temperature of the gas supplied to the adsorbent may be set higher than the temperature of the raw material vapor in the first step described above. The lower limit of the gas temperature in the second step described above may be, for example, 60°C or higher, 70°C or higher, 80°C or higher, 85°C or higher, 90°C or higher, or 95°C or higher. By setting the lower limit of the gas temperature within the above range, the desorption of specific molecules adsorbed on the adsorbent can be made easier. The upper limit of the gas temperature in the second step described above may be, for example, 300°C or lower, 275°C or lower, 250°C or lower, 225°C or lower, 200°C or lower, 180°C or lower, or 150°C or lower. By setting the upper limit of the gas temperature within the above range, the deterioration of the adsorbent itself can be suppressed.
[0053] The gas in the second step may be a mixed gas containing the aforementioned water vapor, or it may consist solely of the water vapor. When a mixed gas is used, it may be, for example, a mixed gas with air, hydrogen gas, and argon gas.
[0054] As the steam source used when preparing the gas used in the second step, for example, natural water with a low content of the specific molecule, or water that has been treated to further reduce the content of the specific molecule, can be used. As the water that has been treated to further reduce the content of the specific molecule, for example, deuterium-reduced water and light water can be used. Deuterium-reduced water may be commercially available, or deuterium-reduced water recovered in the first step may be used, or steam that could not be recovered in the first step (for example, steam from deuterium-reduced water) may be used. That is, the manufacturing method according to this disclosure may further include a third step in which water with a reduced content of the molecule is prepared by condensing a portion of the steam recovered in the first step. In addition, a portion of the steam that was not condensed in the third step may be used as the gas in the second step.
[0055] The gas flow path described above may be parallel to or antiparallel to the raw material vapor flow path in the first step. When the gas flow path is antiparallel to the raw material vapor flow path, it is easier to control the ambient temperature where the adsorbent is placed, and the regeneration efficiency of the adsorbent is superior. When the adsorbent is filled into a cylindrical body or constitutes an adsorption layer provided on the surface of a structure, the direction of extension of the cylindrical body and the structure may be parallel to the gas flow path.
[0056] In the above explanation, an example was shown in which the first and second steps are performed once each. However, the first and second steps may be repeated alternately multiple times, or water with a reduced content of the specific molecule may be continuously produced by repeating the first and second steps alternately. If the first and second steps are considered as treatments for the adsorbent, the first and second steps can be performed by sequentially changing the composition of the atmosphere in contact with the adsorbent.
[0057] The second step in the manufacturing method described above can reduce specific molecules adhering to the adsorbent. In other words, an operation similar to the operation in the second step can be used as a method for regenerating the adsorbent. One embodiment of the method for regenerating the adsorbent is a method used to reduce the content of molecules substituted with isotopic elements from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is substituted with an isotopic element of hydrogen, and includes supplying a gas containing water vapor to the adsorbent and diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas to restore the separation performance of the adsorbent. The humidity of the gas supplied to the adsorbent is adjusted so that the relative humidity at the temperature at which it is supplied to the adsorbent is 0.0005 to 2.5% RH, and the content of molecules substituted with isotopic elements in the gas is smaller than the content of the molecules in the raw vapor generated from the raw water. Various conditions for the regeneration method can be those exemplified in the description of the manufacturing method described above.
[0058] One embodiment of the manufacturing apparatus is a manufacturing apparatus for producing water in which the content of the isotopically replaced molecules is reduced from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, and comprises: an adsorption / desorption unit for raw material vapor generated from the raw water having an adsorbent; a raw material supply unit for supplying the raw material vapor to the adsorption / desorption unit; a recovery unit for recovering vapor containing water molecules preferentially desorbed from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent; and a gas supply unit for supplying gas with adjusted molecular content and humidity to the adsorption / desorption unit.
[0059] Figure 1 is a schematic diagram showing an example of a manufacturing apparatus. The manufacturing apparatus 100 includes an adsorption / desorption unit 10 having an adsorbent, a raw material supply unit 20 that supplies water vapor from raw material water to the adsorption / desorption unit 10, a recovery unit 30 that recovers the above after the content of the specific molecules has been reduced, and a gas supply unit 40 that supplies gas to the adsorption / desorption unit 10 to restore the separation performance of the adsorbent.
[0060] The raw material supply unit 20 may have a control unit that controls the composition, temperature, flow rate, etc., of the raw material steam generated from the raw material water supplied to the adsorption / desorption unit 10.
[0061] The adsorption / desorption unit 10 has an adsorbent. The shape of the adsorption / desorption unit 10 is not limited as long as the adsorbent is in contact with the raw material steam generated from the raw material water supplied from the raw material supply unit 20, or with the gas supplied from the gas supply unit 40. For example, it may be a container filled with an adsorbent in the form of powder or granules, or it may be a container housing a structure having a support and an adsorption layer provided on the support. The structure composed of the support and the adsorption layer may be, for example, a structure having a honeycomb-shaped cross-section in which a plurality of independent gas flow channels are formed.
[0062] The adsorption / desorption unit 10 may have a means for rotating the container around its central axis, which is set parallel to the flow path of the raw material steam supplied from the raw material supply unit 20 or the gas supplied from the gas supply unit 40. The means for rotation may be, for example, a desiccant rotor. When such a means for rotation is provided, it becomes easier to continuously produce water with reduced content of specific molecules.
[0063] If the adsorption / desorption unit 10 includes, for example, a structure having a honeycomb-shaped cross-section composed of multiple independent gas flow paths, and the structure is housed without gaps so as to be in contact with the inner wall of the container, then, for example, the central axis of the structure may be positioned so that the gas flow paths are parallel to the flow paths of the raw material steam supplied from the raw material supply unit 20, and the structure may be rotated around this central axis. In this case, if the cross-section of the structure perpendicular to the gas flow paths is divided into four equal parts starting from the center point of the cross-section, then, for example, three-quarters of the area may be in contact with the raw material steam and one-quarter of the area may be in contact with the gas. When set in this way, the first step of the manufacturing method described above is performed in the three-quarters area, and the second step of the first manufacturing method described above is performed in the one-quarter area. That is, the first and second steps are performed during one rotation of the structure, and the reduction of specific molecules in the raw material steam via the adsorbent and the recovery of separation performance by desorption of the specific molecules adsorbed on the adsorbent are performed continuously.
[0064] The humidity of the gas supply unit 40 is adjusted so that the relative humidity at the temperature at which it is supplied to the adsorbent is 0.0005 to 2.5% RH, and the gas supplied to the adsorption / desorption unit 10 is such that the content of the specific molecule in the gas is less than the content of the specific molecule in the raw material vapor. This allows at least a portion of the specific molecule adsorbed on the adsorbent to diffuse into the gas, thereby restoring the separation performance of the adsorbent.
[0065] If the adsorbent is, for example, a polymer sorbent used at relatively low temperatures, the relative humidity at 100°C may be considered and adjusted. That is, the humidity may be adjusted from the gas supply unit 40 so that the relative humidity at 100°C is 2.5%RH or less, and a gas in which the content of the specific molecule is smaller than the content of the specific molecule in the raw material vapor may be supplied to the adsorption / desorption unit 10. This allows at least a portion of the specific molecule adsorbed on the adsorbent to diffuse into the gas, thereby restoring the separation performance of the adsorbent.
[0066] The recovery unit 30 may further include means for condensing the recovered steam. The means for condensing the steam are not particularly limited, but may include means for cooling and condensing the steam. The gas supply unit 40 may supply the steam that was not condensed in the recovery unit 30 as the gas to the adsorption / desorption unit 10. In this case, the gas supply unit 40 may include means for obtaining the steam that was not condensed from the recovery unit 30. The means for obtaining the above is not particularly limited, but may include a steam transport line, etc.
[0067] The gas supply unit 40 may have a control unit that adjusts the content of the specific molecule, relative humidity, temperature, etc., in the gas supplied to the adsorption / desorption unit 10 according to the content of the specific molecule in the vapor recovered in the recovery unit 30. The recovery unit 30 may be equipped with a detector that acquires information on the content of the specific molecule in the recovered vapor, and the control unit of the gas supply unit 40 may acquire information from the detector of the recovery unit 30.
[0068] In Figure 1, the raw material supply unit 20 supplies steam from the raw material water in a direction parallel to the extension direction of the adsorption / desorption unit 10, and the gas supply unit 40 supplies the gas in the opposite direction to the steam from the raw material water. In this case, it is easy to control the ambient temperature of the adsorbent inside the adsorption / desorption unit 10, and the regeneration efficiency of the adsorbent is superior. However, the supply direction of the raw material steam and the supply direction of the gas do not necessarily have to be opposite; they can flow in the same direction.
[0069] Although several embodiments have been described above, this disclosure is not limited in any way to the embodiments described above. Furthermore, the descriptions of the embodiments described above are applicable to each other. [Examples]
[0070] The contents of this disclosure will be described in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the following examples.
[0071] (Example 1) First, a desiccant material (manufactured by Nippon Exlan Industries Co., Ltd., product name: Exblock) was prepared, in which an adsorbent was applied to a support and the cross-section exhibited a honeycomb structure. The individual cylindrical paths constituting the honeycomb structure of the desiccant material were placed inside a cylinder so that they were parallel to the direction of extension of the cylinder. The adsorbent used was a polymer sorbent, which is a crosslinked polyacrylic acid polymer. The cylinder used had an inner diameter of 2.3 cm and a length of 40 cm.
[0072] The cylinder S1 described above was installed in the evaluation apparatus shown in Figure 2. First, valves V1 and V2 were opened, and a mixed gas containing raw material vapor generated from raw material water was humidified to a relative humidity of 90%RH at 25°C and introduced from valve V1 at a flow rate of 4.0 L / min in the direction of the arrow. The mixed gas discharged from valve V2 and recovered was condensed in a cooler adjusted to -10°C to obtain deuterium-reduced water (first step). The mixed gas containing raw material vapor was introduced for 60 minutes, after which valves V1 and V2 were closed in that order. During this time, the temperature of the mixed gas supplied to the adsorbent was set to 25°C. Next, valves V3 and V4 were opened, and a mixed gas containing water vapor with a lower heavy water and semi-heavy water content than the raw material water (regeneration gas) was humidified to a relative humidity of 0.30%RH at 100°C and introduced from valve V3 at a flow rate of 36 L / min (second step). The above-mentioned regeneration gas was introduced for 30 minutes, after which valves V3 and V4 were closed in that order. During this time, the temperature of the regeneration gas was set to 100°C. Next, under the same conditions as the first process, the mixed gas containing raw water was introduced again and the deuterium-reduced water was recovered.
[0073] In the first step, water with a heavy water and semi-heavy water content of 148 atomic ppm was used as the raw material. Dry air was used as the transport gas. A mixed gas, prepared by mixing steam and dry air in a volume ratio of 9:1, was introduced into the adsorbent as the raw material. In the second step, water vapor with a heavy water and semi-heavy water content of 130 atomic ppm was used as the water vapor. Dry air was used as the transport gas. Water vapor and dry air were mixed in a volume ratio of 9:1, and a mixed gas (gas containing a small amount of water vapor) humidified to a relative humidity of 0.15%RH at 100°C was introduced into the adsorbent as the raw material.
[0074] By adjusting the amount of gas (amount of water) passing through the adsorbent, the yield of deuterium-reduced water was changed, and similar experiments were conducted.
[0075] <Measurement of the content (deuterium concentration) of molecules containing deuterium as a constituent atom in deuterium-reduced water> The deuterium concentration of each of the deuterium-reduced waters obtained as described above was measured using the method described later. Using the obtained results, the relationship with the yield (=[Amount of water passing through (L) / Amount of water in the supplied mixed gas (L)] × 100) was investigated and is shown in Figure 3. Figure 3 is a graph showing the relationship between the deuterium concentration and the yield in the deuterium-reduced water produced in the example.
[0076] [Measurement of deuterium concentration] The deuterium concentration was measured using wavelength scan cavity ring-down spectroscopy with a water isotope ratio analyzer (PICARRO, product name: L2130-i).
[0077] (Comparative Example 1) In the second step, deuterium-reduced water was produced using the same procedure as in Example 1, except that the mixed gas (regeneration gas) introduced from valve V3 was changed to only dry air (dry gas) used as the transport gas. The deuterium concentration was measured for each of the resulting deuterium-reduced waters. The results are shown in Figure 3.
[0078] As shown in Figure 3, in Example 1, it was confirmed that by using a gas containing water vapor with a lower heavy water and semi-heavy water content than the raw water as the regeneration gas, the deuterium concentration in the resulting deuterium-reduced water could be reduced compared to Comparative Example 1, in which only the transport gas was used in the second step.
[0079] (Example 2) To confirm the effect of the content of specific molecules in the water vapor contained in the regeneration gas, deuterium-reduced water was produced using gases with adjusted content of specific molecules. Specifically, deuterium-reduced water was produced in the same manner as in Example 1, except that the content of the specific molecules was changed to 136 atomic ppm, 121 atomic ppm, 84 atomic ppm, or 62 atomic ppm, and the relative humidity of the regeneration gas at 100°C was changed to 0.30% RH. For each of the obtained deuterium-reduced waters, the relationship between the content of deuterium-containing components in the deuterium-reduced water and the content of deuterium-containing components in the water vapor used for regeneration of the adsorbent was investigated. The results are shown in Figure 4. Figure 4 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water and the content of deuterium-containing components in the water vapor used for regeneration of the adsorbent in the example.
[0080] As shown in Figure 4, it was confirmed that treating the adsorbent with a regeneration gas containing a lower amount of specific molecules in the water vapor resulted in a greater reduction in the amount of specific molecules in the deuterium-reduced water obtained afterward.
[0081] (Example 3) To confirm the effect of relative humidity at the supply temperature of the regeneration gas to the adsorbent (set to 100°C in this case), deuterium-reduced water was produced using gas with adjusted relative humidity. Specifically, deuterium-reduced water was produced in the same manner as in Example 1, except that the relative humidity of the regeneration gas at 100°C was changed as shown in Table 1. For each of the obtained deuterium-reduced waters, the relationship between the content of deuterium-containing components in the deuterium-reduced water and the relative humidity of the water vapor used for regenerating the adsorbent was investigated. The results are shown in Figure 5. Figure 5 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water and the relative humidity of the water vapor used for regenerating the adsorbent in the example.
[0082] (Example 4) Deuterium-reduced water was produced in the same manner as in Example 1, except that the content of a specific molecule in the regeneration gas was changed to 121 atoms ppm, and the relative humidity of the regeneration gas at 100°C was changed as shown in Table 1. For each of the obtained deuterium-reduced waters, the relationship between the content of deuterium-containing components in the deuterium-reduced water and the relative humidity of the water vapor used for regenerating the adsorbent was investigated. The results are shown in Figure 6. Figure 6 is a graph showing the relationship between the content of deuterium-containing components in the deuterium-reduced water in the example and the relative humidity of the water vapor used for regenerating the adsorbent.
[0083] [Table 1]
[0084] As shown in Figures 5 and 6, it was confirmed that using a regeneration gas with a higher relative humidity at the supply temperature to the adsorbent (100°C) tends to reduce the deuterium concentration in the deuterium-reduced water obtained thereafter. On the other hand, if the content of specific molecules in the water vapor contained in the regeneration gas is relatively high, the deuterium concentration in the deuterium-reduced water obtained thereafter may increase as the relative humidity at the supply temperature (100°C) of the regeneration gas to the adsorbent increases.
[0085] (Example 5) Zeolite (manufactured by Tosoh Corporation, product name: HSZ-320NAD1C) was prepared, filled to the inside of the cylinder, and placed inside. The cylinder used had an inner diameter of 2.3 cm and a length of 6 cm. Except for using the cylinder filled with zeolite instead of the cylinder containing the desiccant material, and using a mixed gas in the second step that was humidified to have a relative humidity of 0.63%RH at 100°C and contained 120 atoms of heavy water and semi-heavy water, the procedure was the same as in Example 1, and the evaluation was performed under the conditions shown in <Measurement of the content of molecules containing deuterium as a constituent element (deuterium concentration) in deuterium-reduced water>. The results are shown in Figure 7.
[0086] (Comparative Example 2) In the second step, deuterium-reduced water was produced using the same procedure as in Example 5, except that the mixed gas (regeneration gas) introduced from valve V3 was changed to only dry air (dry gas) used as the transport gas. The deuterium concentration was measured for each of the obtained deuterium-reduced waters. The results are shown in Figure 7.
[0087] As shown in Figure 7, in Example 5, by using a gas containing water vapor with a lower heavy water and semi-heavy water content than the raw water as the regeneration gas, it was confirmed that the deuterium concentration in the resulting deuterium-reduced water could be reduced compared to Comparative Example 2, in which only the transport gas was used in the second step. Thus, it was confirmed that the same trend as in Example 1, in which a high-fragmentation agent was used, was observed even when zeolite was used as the adsorbent. [Industrial applicability]
[0088] This disclosure provides a method for inexpensively producing water with a reduced content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. This disclosure also provides a manufacturing apparatus usable in the above manufacturing method. This disclosure also provides a method for regenerating an adsorbent used to reduce the content of isotope-substituted molecules from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotope of hydrogen. [Explanation of Symbols]
[0089] 10... Adsorption / desorption unit, 20... Raw material supply unit, 30... Recovery unit, 40... Gas supply unit, 100... Manufacturing equipment.
Claims
1. A method for producing water in which the content of the isotopically substituted molecule is reduced, from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, A first step involves supplying raw material steam from raw water to an adsorbent, adsorbing at least a portion of the raw material steam onto the adsorbent, and recovering steam containing water molecules that preferentially desorb from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent. The first step is followed by a second step of supplying a gas containing water vapor to the adsorbent, thereby diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas, and restoring the separation performance of the adsorbent. In the second step, The relative humidity of the gas supplied to the adsorbent is adjusted to be between 0.0005% and 2.5% RH at the temperature of the gas supplied to the adsorbent. A manufacturing method wherein the content of the molecule substituted with an isotopic element in the gas supplied to the adsorbent is less than the content of the molecule in the raw material vapor.
2. The manufacturing method according to claim 1, wherein the content of the molecules in the gas supplied to the adsorbent in the second step is 140 atoms ppm or less.
3. The manufacturing method according to claim 1 or 2, wherein the temperature of the gas supplied to the adsorbent in the second step is 60°C or higher.
4. The process further includes a third step of preparing water in which the molecular content is reduced by condensing a portion of the steam recovered in the first step, The manufacturing method according to claim 1 or 2, wherein in the third step, a portion of the vapor that was not condensed is used as the gas supplied to the adsorbent in the second step.
5. The manufacturing method according to claim 1 or 2, wherein the first step and the second step are repeated alternately to continuously produce water in which the content of the molecules has been reduced.
6. The manufacturing method according to claim 1 or 2, wherein the adsorbent is at least one selected from the group consisting of polymer sorbents, activated carbon, and zeolites.
7. The manufacturing method according to claim 1 or 2, wherein the adsorbent is included in an adsorbent layer provided on at least a portion of the surface of the cylindrical body.
8. The manufacturing method according to claim 1 or 2, wherein the adsorbent is filled into a cylindrical body.
9. A method for regenerating an adsorbent used to reduce the content of molecules substituted with isotopes, from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is substituted with an isotope of hydrogen, This includes supplying a gas containing water vapor to the adsorbent and diffusing at least a portion of the molecules adsorbed on the adsorbent into the gas, thereby restoring the separation performance of the adsorbent. The relative humidity of the gas supplied to the adsorbent is adjusted to be between 0.0005% and 2.5% RH at the temperature of the gas supplied to the adsorbent. A regeneration method wherein the content of the molecule substituted with an isotopic element in the gas supplied to the adsorbent is less than the content of the molecule in the raw material steam generated from the raw material water.
10. The regeneration method according to claim 9, wherein the content of the molecules in the gas supplied to the adsorbent is 140 atoms ppm or less.
11. The regeneration method according to claim 9 or 10, wherein the temperature of the gas supplied to the adsorbent is 60°C or higher.
12. A manufacturing apparatus for producing water in which the content of the isotopically substituted molecules is reduced, from raw water containing water molecules and molecules in which at least one of the hydrogen atoms constituting the water molecules is replaced with an isotopic element of hydrogen, An adsorption and desorption unit for raw material vapor generated from the raw material water, having an adsorbent, A raw material supply unit that supplies the raw material steam to the adsorption / desorption unit, A recovery unit that recovers steam containing water molecules preferentially detached from the adsorbent due to differences in the strength of hydrogen bonds formed between the adsorbent and the adsorbent, The system includes a gas supply unit that supplies gas with adjusted molecular content and humidity to the adsorption / desorption unit, A manufacturing apparatus that adjusts the humidity of the gas supply unit so that the relative humidity at the temperature at which it is supplied to the adsorbent is 0.0005 to 2.5% RH, and supplies a gas to the adsorption / desorption unit in which the content of the molecules substituted with isotopic elements in the gas is less than the content of the molecules in the raw material vapor, thereby diffusing at least a portion of the molecules substituted with isotopic elements adsorbed on the adsorbent into the gas, and restoring the separation performance of the adsorbent.
13. The recovery unit has means for condensing the recovered steam, The manufacturing apparatus according to claim 12, wherein the gas supply unit supplies the steam that was not condensed in the recovery unit as the gas to the adsorption / desorption unit.
14. The raw material supply unit supplies steam of the raw material water in a direction parallel to the extending direction of the adsorption / desorption unit. The manufacturing apparatus according to claim 12 or 13, wherein the gas supply unit supplies the gas in the opposite direction to the steam of the raw water.