WO2018173331A1

WO2018173331A1 - Piperidine and piperazine compounds as drawing agents and switchable polarity solvents in direct osmosis

Info

Publication number: WO2018173331A1
Application number: PCT/JP2017/033662
Authority: WO
Inventors: Akiko Suzuki; Toshihiro Imada; Takashi Kuboki; Kenji Sano
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 2017-03-23
Filing date: 2017-09-19
Publication date: 2018-09-27
Also published as: JP6649310B2; JP2018158303A

Abstract

Embodiments provide a water treatment system capable of separating water at low cost and a working medium. A water treatment system of an embodiment includes: an osmotic pressure generator including a first treatment container having an osmosis membrane to partition a first chamber for accommodating water to be treated and a second chamber for accommodating a working medium to induce osmotic pressure; and a concentrator including a carbon dioxide releasing unit for releasing carbon dioxide from the working medium, a phase separating unit for separating the phase-separated working medium, and a carbon dioxide introducing unit for absorbing carbon dioxide into the working medium, wherein the working medium contains an amine compound, wherein the amine compound is a compound expressed by Formula (1) or (2).

Description

[Title established by the ISA under Rule 37.2] PIPERIDINE AND PIPERAZINE COMPOUNDS AS DRAWING AGENTS AND SWITCHABLE POLARITY SOLVENTS IN DIRECT OSMOSIS

Embodiments described herein relate to a water treatment system and a working medium.

When a solution having a low solute concentration and a solution having a high solute concentration are isolated from each other by an osmosis membrane, the solvent of the low concentration solution permeates through the osmosis membrane and moves to the high concentration solution side. A desalination system which performs desalination such as seawater desalination and an osmotic power generation system which generates power by turning a turbine are known, and both of them utilize a phenomenon that the solvent moves. In addition, concentration systems which concentrate foods and sludge by utilizing this phenomenon are also known. At this time, the solution to be used on the higher concentration side is the working medium (draw solution), and various kinds of working mediums have been proposed so far.

As the solute of the draw solution, kitchen salt is generally used. Organic salts are also used as the solute of the draw solution. However, a draw solution of an organic salt has an inferior permeate flux of water to a draw solution of kitchen salt.

A draw solution in which two or more kinds of solutes are mixed has been proposed. A synergistic effect is observed in a mixture of plural inorganic salts, but the flux passing through the osmosis membrane may decrease due to an adverse effect in the case of a mixture of an inorganic salt with saccharose.

Patent JP2013-518718A

Embodiments provide a water treatment system capable of separating water at low cost and a working medium.

A water treatment system of an embodiment includes: an osmotic pressure generator including a first treatment container having an osmosis membrane to partition a first chamber for accommodating water to be treated and a second chamber for accommodating a working medium to induce osmotic pressure; and a concentrator including a carbon dioxide releasing unit for releasing carbon dioxide from the working medium, a phase separating unit for separating the phase-separated working medium, and a carbon dioxide introducing unit for absorbing carbon dioxide into the working medium, wherein the working medium contains an amine compound, wherein the amine compound is a compound expressed by Formula (1) or (2) of Fig.2, wherein R¹¹ and R¹⁴ in Formula (1) are a linear or branched alkyl chain having 1 or more and 5 or less carbon atoms and optionally contain at least one kinds selected from the group consisting of a tertiary amine, a cyclic tertiary amine, a carboxyl group, and a hydroxyl group, R¹², R¹³, R¹⁵, and R¹⁶ in Formula (1) are H or a linear alkyl group having 1 or more and 3 or less carbon atoms and optionally contain a hydroxyl group, a halogen, or a hydroxyl group and a halogen, R²¹ in Formula (2) is a linear or branched alkyl chain having 2 or more and 10 or less carbon atoms and optionally contains one or more tertiary amines, and R²² and R²³ in Formula (2) are CH₂, O, or CH-COOR²⁴ (R²⁴ is linear or branched and has 0 or more and 4 or less carbon atoms).

Fig. 1 is a schematic diagram of a water treatment system according to an embodiment; Fig. 2 is chemical formulas of a solute according to an embodiment; Fig. 3 is a schematic diagram of a water treatment system according to an embodiment; and Fig. 4 is a schematic diagram of a water treatment system according to an embodiment.

Hereinafter, water treatment systems and working mediums to be used in the water treatment systems of embodiments will be described.
(First Embodiment)
A water treatment system according to a first embodiment will be described with reference to the schematic diagram illustrated in Fig. 1. In an osmotic pressure generator 1 including a first treatment container 11 having an osmosis membrane 12 to partition a first chamber 13 for accommodating water to be treated A and a second chamber 14 for accommodating a working medium B and a concentrator 2 of a water treatment system 100 according to the first embodiment illustrated in Fig. 1, the working medium B induces osmotic pressure in the osmotic pressure generator 1 and the absorption of carbon dioxide gas into the working medium B and the release of carbon dioxide from the working medium B are performed in the concentrator 2.

According to such a water treatment system 100, water C in the water to be treated A in the first chamber 13 permeates through the osmosis membrane 12 and moves to the working medium B in the second chamber 14 by the osmotic pressure difference generated between the water to be treated A in the first chamber 13 and the working medium B in the second chamber 14.

The working medium B easily induces the osmotic pressure by absorbing carbon dioxide gas. Moreover, the working medium B is separated from water by releasing the carbon dioxide gas, and the working medium B is thus concentrated. For the concentration of the working medium B, solid-liquid separation or liquid-liquid separation is performed. It is possible to form the working medium B into a medium which easily induces the osmotic pressure again by absorbing carbon dioxide gas into the concentrated working medium B. Hence, the water treatment is performed at low cost in the embodiment.

The water treatment system of the embodiment is preferable from the viewpoint of being able to permeate the water C in the water to be treated A in the first chamber 13 through the osmosis membrane and to move the water C to the working medium B in the second chamber 14 at a high permeate flux by using the working medium B of the embodiment. The working medium B of the embodiment is used in a water treatment system which can be operated at low cost and a water treatment system.

The first treatment container 11 is partitioned into the first chamber 13 and the second chamber 14 by the osmosis membrane 12. The first treatment container 11 is a resin or metal container which accommodates the water to be treated A in the first chamber 13 and the working medium B in the second chamber 14.

The osmosis membrane 12 may be, for example, a forward osmosis membrane (FO membrane) or a reverse osmosis membrane (RO membrane). A preferred osmosis membrane is a FO membrane.

As the osmosis membrane 12, for example, a cellulose acetate membrane, a polyamide membrane, or the like can be used. The osmosis membrane preferably has a thickness of 45 micrometre or more and 250 micrometre or less.

The first chamber 13 is a region in the first treatment container 11 for accommodating the water to be treated A, and it is partitioned by the osmosis membrane 12. The first chamber 13 may be provided with an introduction and discharge path (not illustrated) through which the water to be treated A is introduced and discharged.

The water to be treated A is a liquid having a lower solute concentration than the working medium. Examples of the water to be treated A may include a salt water (seawater and the like), lake water, river water, marsh water, domestic wastewater, industrial wastewater, or a mixture thereof. When the water to be treated A is a salt water, the salt (sodium chloride) concentration of the salt water may be, for example, from 0.05% to 8%. The water to be treated A contains salts such as sodium chloride, magnesium chloride, magnesium sulfate, calcium sulfate, and potassium chloride and suspended substances, and substances other than water are concentrated.

The second chamber 14 is a region in the first treatment container 11 for accommodating the working medium B, and it is partitioned by the osmosis membrane 12.

The concentrator 2 includes a carbon dioxide releasing unit for releasing carbon dioxide from the working medium B, a phase separating unit for separating the phase-separated working medium B, and a carbon dioxide introducing unit for absorbing carbon dioxide into the working medium B. In addition, the concentrator 2 may further include a storage unit for storing the concentrated working medium B. As the phase separating unit, a three-phase separation type centrifugal separator or the like can be utilized. As the carbon dioxide introducing unit, a carbon dioxide bubbling device or the like may be utilized, or dry ice (solid carbon dioxide) may be added to the working medium B. As the carbon dioxide releasing unit, a warming device, an inert gas bubbling device, or the like can be utilized. It is preferable to employ a heat exchanger utilizing exhaust heat as the warming device from the viewpoint of energy cost. In addition, carbon dioxide released by the carbon dioxide releasing unit may be utilized as the carbon dioxide to be utilized in the carbon dioxide introducing unit, or gas obtained by purifying carbon dioxide in the exhaust gas from a power plant using fossil fuel may be utilized.

The working medium B of the first embodiment contains an amine compound which becomes a liquid of which the properties change depending on the concentration of carbon dioxide in the solution. In the working medium B of the embodiment, the valence of the amine compound increases to induce osmotic pressure as the concentration of carbon dioxide increases. Moreover, when the concentration of carbon dioxide in the working medium B is decreased, the amine compound is separated from water and it is thus possible to concentrate the working medium B. Moreover, the working medium B becomes a medium exhibiting excellent osmotic pressure inducting property again by increasing the concentration of carbon dioxide in the working medium B.

It is possible to operate the water treatment at low cost since the process of changing the concentration of carbon dioxide in the working medium B and the separation of the working medium B from water require low energy.

Water produced by the concentration of working medium B may contain an amine compound at a low concentration in some cases. This is the loss of amine compound. In addition, the amine compound is an impurity of water produced by the concentration of working medium B when the water treatment is desalination. Hence, in a case in which water produced by the concentration of working medium B may contain an amine compound at a low concentration, the water produced by the concentration of working medium B is treated by using a reverse osmosis membrane separator to concentrate the liquid containing the amine compound, the concentrated liquid is returned to the working medium B, and water thus produced can be obtained. In the operation by the reverse osmosis membrane separator, the concentration of the amine compound in the liquid to be treated is low, and it is thus possible to perform the water treatment by only using the reverse osmosis membrane separator with lower energy than in the concentration treatment. In the concentrator 2, there is a large difference in cost between the case of performing the reverse osmosis membrane separation and the case of performing the concentration of the embodiment, and the water treatment of the embodiment is excellent from the viewpoint of cost.

The solubility of the amine compound of the embodiment in water changes depending on the concentration of carbon dioxide in the medium. The concentration of working medium B is performed by utilizing this property. As a method for absorbing carbon dioxide into the working medium B, for example, a gas containing carbon dioxide may be blown into the working medium B. At this time, carbon dioxide may be blown into the working medium B at 80 degrees C. or lower since carbon dioxide is released when the temperature is too high. In addition, an inert gas such as nitrogen gas may be blown into the working medium B in order to release carbon dioxide in the working medium B. At this time, the release rate of carbon dioxide increases as the working medium B is heated to a temperature lower than the boiling point thereof. The concentration of carbon dioxide in the working medium B when being introduced into the osmotic pressure generator 1 is 1 or more and 3 or less when the molar concentration of the working medium B is 1. The concentration of carbon dioxide introduced can be confirmed by 13C quantitative NMR measurement of the working medium B. For the measurement, a double tube capable of isolating the deuterated solvent from the working medium B is utilized. The molar concentration ratio of the amount of carbon dioxide introduced to the amine compound contained in working medium B can be calculated from the integral value ratio of the peaks obtained.

When the concentration of carbon dioxide in the working medium B increases, the solubility of the amine compound in the working medium B (water) increases and the working medium B becomes an aqueous solution. Meanwhile, when the concentration of carbon dioxide in the working medium B decreases, the solubility of the amine compound in the working medium B (water) decreases and the working medium B becomes in a solid-liquid separated state or a liquid-liquid separated state.

In a case in which the working medium B becomes in the solid-liquid separated state, it is possible to obtain a concentrated working medium B by recovering the solid by filtration or the like of the liquid and dissolving the solid in water. When dissolving the solid, the solid is dissolved by blowing carbon dioxide or the like into the solution and thus increasing the concentration of carbon dioxide in the solution.

In addition, in a case in which the working medium B becomes in the liquid-liquid separated state, it is possible to obtain a concentrated working medium B by recovering the upper phase or the lower phase by using decantation, a separating funnel, or a liquid-liquid extractor and dissolving the phase containing an amine compound at a high concentration in water. When dissolving the phase containing an amine compound at a high concentration in water, the phase containing an amine compound at a high concentration is dissolved in water by blowing carbon dioxide into the solution and thus increasing the concentration of carbon dioxide in the solution.

The concentration of the working medium B is easy when the solubility of an amine compound in the working medium B (water) greatly changes depending on the concentration of carbon dioxide. Hence, it is preferable to use an amine compound the solubility of which after absorption of carbon dioxide in water is four or more times the solubility of which after release of carbon dioxide in water.

Consequently, in the embodiment, it is possible to provide a water treatment system which can be operated at low cost and can efficiently perform a treatment such as desalination and concentration of the water to be treated A and a working medium B for a water treatment system. The water treatment system of the embodiment is also preferably utilized as a water treatment system which further includes a body of rotation and generates electricity by generating a water flow by induction of osmotic pressure and rotating the body of rotation by the water flow.

The solute contained in the working medium B is a compound of which the affinity for water changes depending on the concentration of carbon dioxide. The working medium B of the embodiment can generate a high permeate flux (Jw L/m²h) when the water in the water to be treated A in the first chamber 13 permeates through the osmosis membrane 12 and moves to the working medium B in the second chamber 14. A specific amine compound is a compound expressed by Formula (1) or (2) in Fig. 2. The structure of compound is measured by 1H-NMR and 13C-NMR analysis.

R¹¹ and R¹⁴ in Formula (1) are a linear or branched alkyl chain having 1 or more and 5 or less carbon atoms and optionally contain at least one kinds selected from the group consisting of a tertiary amine, a cyclic tertiary amine, a carboxyl group, and a hydroxyl group. R¹², R¹³, R¹⁵, and R¹⁶ in Formula (1) are H or a linear alkyl group having 1 or more and 3 or less carbon atoms and optionally contain a hydroxyl group, a halogen, or a hydroxyl group and a halogen. The halogen of the amine compound expressed by Formula (1) is any one of Cl, Br, or F. Specific compounds expressed by Formula (1) in Fig. 2 is preferably at least one kinds of amine compounds selected from the group consisting of 4-(1,1-dimethylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-β,β-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,α-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,β-dimethyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-propanone, 4-(1,1-dimethylethyl)-α-ethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-3-methyl-1-piperazineethanol, 4-(2-hydroxyethyl)-α,α-dimethyl-1-piperazineacetic acid, 3-(4-(1,1-dimethylethyl)-1-piperazinyl)-1,2-propanediol, 4-(2-hydroxy-1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-α-(1-methylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-ethyl-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineacetic acid, 3,(4-(1,1-dimethylethyl)-1-piperazinyl)-2-butanone, 4-(1,1-dimethylethyl)-α-ethyl-α-methyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-butanone, and 1,4-bis[2-(1-piperazinyl)ethyl]-piperazine.

R²¹ in Formula (2) is a linear or branched alkyl chain having 2 or more and 10 or less carbon atoms and optionally contains one or more tertiary amines. R²² and R²³ in Formula (2) are CH₂, O, or CH-COOR²⁴ (R²⁴ is linear or branched and has 0 or more and 4 or less carbon atoms, and for example, R²⁴ is a linear or branched alkyl chain). CH-COOR²⁴ is CH-COOH when the number of carbon atoms of R²⁴ is 0. The compound having a structure expressed by Formula (2) in Fig. 2 is preferably at least one kinds of amine compounds selected from the group consisting of 1,1'-(1,2-ethanediyl)-bis-piperidine, 1,1'-(1,3-propanediyl)bis-4-piperidinecarboxylic acid diethyl ester, 1,1'-(1-methyl-1,2-ethanediyl)-bis-piperidine, 4-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 3-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 2-methyl-1-[2-(1-piperidinyl)ethyl]piperidine, 1,1-(1,2-dimethyl-1,2-ethanediyl)piperidine, 1,1'-(1,2-ethanediyl)-bis-4-methylpiperidine, 1,1'-(1,2-ethanediyl)bis-2-methylpiperidine, 1-[2-(1-piperidinyl)ethyl]4-piperidinone, 1,1'-(1,3-propanediyl)-bis-piperidine, 1,1'-(2-methyl-1,3-propanediyl)bis-piperidine, and 1,1'-(1,4-butanediyl)-bis-piperidine.

Accordingly, the amine compound contained in the working medium of the embodiment is preferably at least one kinds selected from the group consisting of 4-(1,1-dimethylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-β,β-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,α-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,β-dimethyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-propanone, 4-(1,1-dimethylethyl)-α-ethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-3-methyl-1-piperazineethanol, 4-(2-hydroxyethyl)-α,α-dimethyl-1-piperazineacetic acid, 3-(4-(1,1-dimethylethyl)-1-piperazinyl)-1,2-propanediol, 4-(2-hydroxy-1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-α-(1-methylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-ethyl-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineacetic acid, 3,(4-(1,1-dimethylethyl)-1-piperazinyl)-2-butanone, 4-(1,1-dimethylethyl)-α-ethyl-α-methyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-butanone, 1,4-bis[2-(1-piperazinyl)ethyl]-piperazine, 1,1'-(1,2-ethanediyl)-bis-piperidine, 1,1'-(1,3-propanediyl)bis-4-piperidinecarboxylic acid diethyl ester, 1,1'-(1-methyl-1,2-ethanediyl)-bis-piperidine, 4-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 3-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 2-methyl-1-[2-(1-piperidinyl)ethyl]piperidine, 1,1-(1,2-dimethyl-1,2-ethanediyl)piperidine, 1,1'-(1,2-ethanediyl)-bis-4-methylpiperidine, 1,1'-(1,2-ethanediyl)bis-2-methylpiperidine, 1-[2-(1-piperidinyl)ethyl]4-piperidinone, 1,1'-(1,3-propanediyl)-bis-piperidine, 1,1'-(2-methyl-1,3-propanediyl)bis-piperidine, and 1,1'-(1,4-butanediyl)-bis-piperidine.

The concentration of the compound expressed by Formula (1) or Formula (2) of the solute in the working medium is desirably adjusted based on the concentration of the solute in the water to be treated which is used, the properties of the compound expressed by Formula (1) or Formula (2). In general, it is desirable that the concentration of the amine compound in the working medium is set to 10% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and still more preferably 50% by mass or more and 70% by mass or less. However, when a trouble such as an increase in the viscosity occurs, the adjustment is performed to decrease the concentration. The upper limit of the concentration depends on the specific solubility of the substance when being ionized.

(Second Embodiment)
Next, a desalination system which is one example of a water treatment system will be described with reference to the schematic diagram illustrated in Fig. 3. In the second embodiment, the first chamber 13, the water to be treated A, the second chamber 14, the working medium B, and the osmosis membrane 12 are common to those in the first embodiment and the second embodiment. The water to be treated A is a salt water (aqueous solution of sodium chloride) such as seawater. The working medium B to be used in the second embodiment is the working medium B of the first embodiment or the second embodiment. In Fig. 3 and subsequent figures, the reference numerals of water to be treated, working medium, and water in the water treatment system are not illustrated, but the reference numerals thereof are common to those in the water treatment system in Fig. 1. The second embodiment is a desalination system, and the water to be treated A is thus a salt water, but the water to be treated A is not limited to a salt water but the water to be treated A described in the first embodiment A or the like is used in the case of a concentration system or the like.

A desalination system 200 is equipped with an osmotic pressure generator 1, a concentrator 2, a concentrated working medium tank 3, a purified water tank 4, and a reverse osmosis membrane separator 5. The osmotic pressure generator 1, the concentrator 2, the reverse osmosis membrane separator 5, and the concentrated working medium tank 3 are connected in this order to form a loop. The working medium B (draw solution) to induce osmotic pressure circulates through this loop. In other words, the working medium B circulates through the osmotic pressure generator 1, the concentrator 2, the reverse osmosis membrane separator 5, and the concentrated working medium tank 3 in this order. Incidentally, the upper and the lower are the directions illustrated in the drawings, and for example, the concentrated working medium tank 3 is on the upper side of the concentrator 2 and the osmotic pressure generator 1 is on the left side of the reverse osmosis membrane separator 5.

A tank of water to be treated 15 is connected to the upper part of a treatment container 10 in which the first chamber 13 is located through a pipeline 101a. A first pump 16 is provided to the pipeline 101a. A pipeline 101b for discharging the concentrated water to be treated A is connected to the lower part of the first treatment container 11 in which the first chamber 13 is located.

The concentrator 2 is connected to the lower part of the first treatment container 11 in which the second chamber 14 is located through a pipeline 101e. Furthermore, the concentrator 2 is connected to the concentrated working medium tank 3 through a pipeline 101d. A third pump 18 is provided to the pipeline 101d. The concentrator 2 is connected to the upper part of the second treatment container 21 in which the third chamber 53 is located through a pipeline 101f and to the lower part of the second treatment container 21 in which the third chamber 53 is located through a pipeline 101g. The third pump 18 is provided to the pipeline 101e.

The concentrated working medium tank 3 is connected to the upper part of the first treatment container 11 in which the second chamber 13 is located through a pipeline 101c. A second pump 17 is provided to the pipeline 101c.

The purified water tank 4 is connected to the reverse osmosis membrane separator 5 through a pipeline 101h. A pipeline 101i for delivering the purified water in the purified water tank 4 to the outside and recovering the purified water is connected to the purified water tank 4. An on-off valve 41 is provided to the pipeline 101i. The on-off valve 41 is opened, for example, when the purified water in the purified water tank 4 exceeds a certain amount. In the case of omitting the reverse osmosis membrane separator 5, the concentrator 2 and the purified water tank are connected to each other through the pipeline 101h.

The reverse osmosis membrane separator 5 is equipped with, for example, an airtight second treatment container 1. The second treatment container 51 is partitioned in, for example, the horizontal direction, for example, by a reverse osmosis membrane (RO membrane or NF membrane) 52, and a third chamber 53 is formed on the left side of the reverse osmosis membrane 52 and a fourth chamber 54 is formed on the right side thereof. The reverse osmosis membrane separator 5 is connected to the purified water tank 4 through the pipeline 101i. In the purified water tank 4, water (purified water) moved to the fourth chamber through the reverse osmosis membrane 52 when concentrating the working medium B is accommodated.

Next, the operation of desalination by the desalination system 200 illustrated in Fig. 3 will be described.

The first pump 16 is driven to supply the water to be treated A (for example, seawater) from the tank of water to be treated 15 into the first chamber 13 of the osmotic pressure generator 1 through the pipeline 101a. Before and after the supply of seawater, the second pump 17 is driven to supply the concentrated working medium B from the concentrated working medium tank 4 into the second chamber 14 of the osmotic pressure generator 1 through the pipeline 101c. At this time, the solute concentration of the concentrated working medium B supplied to the second chamber 14 is higher than the salt concentration of the seawater supplied to the first chamber 13. Hence, an osmotic pressure difference is generated between the seawater in the first chamber 13 and the concentrated working medium B in the second chamber 14, and water in the seawater permeates through the osmosis membrane 12 and moves into the second chamber 14. The concentrated working medium B in the second chamber 14 is an aqueous solution containing the solute of the first embodiment or the second embodiment and exhibits a high osmotic pressure inducing action. Hence, a high permeate flux is generated when water in the seawater in the first chamber 13 permeates through the osmosis membrane 12 and moves to the concentrated working medium B in the second chamber 14. As a result, it is possible to move a large amount of water in the seawater in the first chamber 13 to the concentrated working medium B in the second chamber 14 and thus to perform a highly efficient desalination treatment for extracting water (pure water) from a salt water.

In the osmotic pressure generator 1, the seawater is discharged as condensed seawater from the first chamber 13 through the pipeline 101b and the concentrated working medium B is diluted with the water moved as the water in the seawater moves from the first chamber 13 to the concentrated working medium B in the second chamber 14. In a case in which the water treatment system of the embodiment performs the concentration of the liquid to be treated A, the wastewater discharged through the pipeline 101b is recovered.

The diluted working medium B in the second chamber 14 is delivered to the concentrator 2 through the pipeline 101d. In the concentrator 2, carbon dioxide is released from the diluted working medium B by, for example, heating the diluted working medium B. The working medium B which has released carbon dioxide is phase-separated. The phase-separated working medium B is subjected to solid-liquid separation or liquid-liquid separation to recover water. The recovered water moves to the third chamber 53 of the reverse osmosis membrane separator 5 through the pipeline 101f. The amine compound used as a solute is contained in the water moved to the third chamber 53 in a small amount in some cases, and this is concentrated in the reverse osmosis membrane separator 5. The water containing the concentrated amine compound passes through the pipeline 101g and is mixed with the concentrated working medium B. The purified water moved to the fourth chamber 4 in the reverse osmosis membrane separator 5 passes through the pipeline 101h and moves to the purified water tank 4.

In the concentrator 2, carbon dioxide is absorbed into the concentrated working medium B and the amine compound is dissolved in water again. In the case of performing solid-liquid separation, the concentration of the working medium B may be adjusted to a public concentration by, for example, adding water if necessary. The concentrated working medium B that has become an aqueous solution of amine is delivered from the third chamber 23 to the concentrated working medium tank 3. The concentrated working medium B in the concentrated working medium tank 3 is supplied into the second chamber 14 of the osmotic pressure generator 1 by driving the second pump 17, and it is utilized in the desalination treatment for extracting water (pure water) from a salt water as described above.

Meanwhile, the water (pure water) moved to the fourth chamber 24 is delivered to the pure water tank 26 through the pipeline 101i. When the amount of water in the purified water tank 26 exceeds a certain amount, the on-off valve 27 is opened to deliver the water to the outside through the pipeline 101h and to recover the water.

Consequently, it is possible to provide a desalination system which can be operated at low cost and can efficiently perform a desalination treatment of seawater (recovery of pure water). Such a system can be operated at low cost even in a water treatment system which performs concentration.

Incidentally, in the desalination system 200 illustrated in Fig. 3, the first treatment container 11 of the osmotic pressure generator is partitioned in the horizontal direction by an osmosis membrane to form the first chamber 13 and the second chamber 14, but the first treatment container may be partitioned into upper and lower parts by an osmosis membrane to form the first chamber 13 and the second chamber 14.

It is preferable to add the solute to the concentrated working medium tank 4 and the like when the solute concentration in the working medium B is decreased by the desalination treatment.

In the desalination system 200 illustrated in Fig. 3, the concentration of the diluted working medium B is not only performed by using the reverse osmosis membrane separator 5 equipped with a reverse osmosis membrane (RO membrane, NF membrane) but also may be performed by using any device as long as it can remove the water in the diluted working medium B.

(Third Embodiment)
Next, an osmotic power generation system 300 which is one example of the water treatment system according to the third embodiment will be described with reference to the schematic diagram illustrated in Fig. 4. Incidentally, in Fig. 4, the same members as those in Fig. 3 are denoted by the same reference numerals, and the description thereon is omitted. The working medium to be used in the third embodiment is the working medium B of the first embodiment.

The water treatment system according to the third embodiment is a power generation system. The power generation system 300 is equipped with an osmotic pressure generator 1 for generating a water flow and a body of rotation 6 for generating electricity by the water flow generated by the osmotic pressure generator 1.

The osmotic power generation system 300 is equipped with the first chamber 13 for accommodating water, the second chamber 14 for accommodating the working medium B (draw solution) which induces osmotic pressure, the osmosis membrane 12 for partitioning the first chamber 13 and the second chamber 14, a pressure exchanger 7 connected to the second chamber 14, and the body of rotation 6 connected to the pressure exchanger 7. According to such a water treatment system, by the osmotic pressure difference generated between the water in the first chamber 13 and the working medium B in the second chamber 14, the water in the first chamber 14 permeates through the osmosis membrane 12 and moves to the working medium B in the second chamber 44. The body of rotation 62 is rotated by the water flow accompanying the movement of water to the working medium B to generate electricity.

In the third embodiment, the working medium B is an aqueous solution containing the solute of the embodiment and exhibits a high osmotic pressure inducing action. Hence, it is possible to generate a high permeate flux when the water in the first chamber 13 permeates through the osmosis membrane 12 and moves to the working medium B in the second chamber 14. As a result, the working medium B containing water thus moved forms a water flow having a high pressure, and it is thus possible to rotate the body of rotation 6 at a higher speed to generate electricity. Consequently, it is possible to provide a water treatment system which can be operated at low cost and can efficiently rotate the body of rotation 6 to generate electricity.

As the body of rotation 82, for example, a turbine or a water wheel can be used.

In the osmotic power generation system 400, the pressure exchanger 7 and the body of rotation 6 are provided to the pipeline 101e connected to the lower part (the exit side of the working medium B) of the first treatment container 11 in which the second chamber 14 of the osmotic pressure generator 1 is located along the flow direction of the working medium B in this order. In addition, in the pipeline 101c which connects the concentrated working medium tank 3 with the upper part of the first treatment container 11 in which the second chamber 14 is located, the portion of the pipeline 101c on the downstream side in the flowing direction of the working medium B of the second pump 17 is connected to the upper part of the first treatment container 11 in which the second chamber 14 is located via the pressure exchanger 7. In other words, in the osmotic pressure generator 1, the diluted working medium B having a flux generated when water has moved from the first chamber 13 to the second chamber 14 through the osmosis membrane 12 is allowed to flow out from the lower part of the first treatment container 11 in which the second chamber 14 is located through the pipeline 101e provided with the pressure exchanger 7. During this time, the pipeline 101c through which the concentrated working medium B flowed out from the concentrated working medium tank 3 flows passes through the pressure exchanger 7. Hence, the pressure of the diluted working medium B is lowered and the pressure of the concentrated working medium B to flow to the body of rotation 6 is raised by pressure exchange between the concentrated working medium B and the diluted working medium B flowed out from the second chamber 14 in the pressure exchanger 7.

Incidentally, in the osmotic power generation system 300, water is accommodated in the tank of water to be treated 15.

Next, the operation of power generation by the osmotic power generation system 300 illustrated in Fig. 4 will be described. The first pump 16 is driven to supply water from the tank of water to be treated 15 into the first chamber 13 of the osmotic pressure generator 1 through the pipeline 101a. Before and after the supply of water, the second pump 17 is driven to supply the concentrated working medium B from the concentrated working medium tank 3 into the second chamber 14 of the osmotic pressure generator 1 through the pipeline 101c. The concentrated working medium B supplied to the second chamber 14 has a sufficiently higher concentration compared to the water only of the solvent supplied to the first chamber 13. Hence, the osmotic pressure difference is generated between the water in the first chamber 13 and the concentrated working medium B in the second chamber 14, and the water permeates through the osmosis membrane 12 and moves into the second chamber 14. At this time, the working medium B in the second chamber 14 is an aqueous solution containing the solute of the embodiment and exhibits a high osmotic pressure inducing action. Hence, a high permeate flux is generated when water in the first chamber 13 permeates through the osmosis membrane 12 and moves to the working medium B in the second chamber 14. As a result, a large amount of water in the first chamber 13 can move to the concentrated working medium B in the second chamber 14 and a diluted working medium B which has a high pressure and is diluted with water is produced. Incidentally, the water in the first chamber 13 is discharged through the pipeline 101b.

The diluted working medium B having a high pressure in the second chamber 14 is delivered to the concentrator 2 through the pipeline 101e and stored therein. The pressure exchanger 7 and the body of rotation 6 are provided to the pipeline 101e along the flow direction of the working medium B in this order.

Hence, the pressure of the diluted working medium B is lowered and the pressure of the concentrated working medium B is raised by pressure exchange between the concentrated working medium B which flows from the concentrated working medium tank 3 through the pipeline 101c and the diluted working medium B which has a high pressure and flows from the second chamber 14 (through the body of rotation 6) through the pipeline 101e in the pressure exchanger 7 as described above. The diluted working medium B having an appropriate pressure by pressure exchange flows to the body of rotation 6 and efficiently rotates it to generate electricity. In addition, the concentrated working medium B having an appropriate pressure by pressure exchange is supplied to the second chamber 14.

In the concentrator 2, the same concentration of the working medium B and purification by the reverse osmosis membrane separator 5 as those in the second embodiment are performed, and the concentrated working medium B of an aqueous solution of amine is stored in the concentrated working medium tank 3.

Incidentally, in the osmotic power generation system 300 illustrated in Fig. 4, the first treatment container 11 of the osmotic pressure generator is partitioned in the horizontal direction by an osmosis membrane 12 to form the first chamber 13 and the second chamber 14, but the first treatment container 11 may be partitioned into upper and lower parts by an osmosis membrane to form the first chamber 13 and the second chamber 14.

In the osmotic power generation system 300 illustrated in Fig. 4, the water in the first chamber 13 of the osmotic pressure generator 1 is delivered to the outside through the pipeline 101b, but the pipeline 101b may be connected to the tank of water to be treated 15 to form a loop by the tank of water to be treated 15, the pipeline 101a, the first chamber 13 of the osmotic pressure generator 1, and the pipeline 101b.

Hereinafter, Examples will be described.

A forward osmosis test was performed as follows. The CTA-ES membrane manufactured by HTI Corporation was set in a FO cell, pure water was placed on the active face side of the membrane as water to be treated, and the working medium was then placed on the support layer side. The working medium placed on the support layer side is in the state of an aqueous solution of amine as a sufficient amount of carbon dioxide has bubbled in the working medium in advance. The time when the working medium was completely placed was counted as 0 minute, and this state was left to stand for 20 minutes. After the test, the weight of the liquid on the active face side was measured, and the permeate flux (Jw) was calculated from the difference before and after the test by taking the specific gravity of the liquid as 1. In addition, the total organic carbon concentration in the liquid on the active face side after the test was measured by using a total organic carbon meter and the cation concentration was measured by ion chromatography to calculate the loss of solute (Js). In addition, the working medium was concentrated by allowing nitrogen gas to bubble in the working medium after the test while heating the working medium at 80 degrees C. The solute contained in the working medium and the concentration thereof and the experimental results are presented in Table 1.

From Table 1, it has been confirmed that it is possible to concentrate the working medium by adjusting the concentration of carbon dioxide in the working medium in Examples in which the compounds expressed by Formulas (1) and (2). It is possible to decrease the energy required for concentrating the working medium since Js/Jw in Examples is each 0.5 or less, and it is thus possible to separate water at low cost. In addition, it is possible to generate electricity at low cost by using the water flow generated by the osmotic pressure inducing action of these to generate electricity.
Here, some elements are expressed only by element symbols thereof.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

A Water to be treated,
B Working medium,
C Water
1 Osmotic pressure generator,
2 Concentrator,
3 Concentrated working medium tank,
4 Purified water tank,
5 Reverse osmosis membrane separator,
11 First treatment container,
12 Osmosis membrane,
13 First chamber,
14 Second chamber,
15 Tank of water to be treated,
16 First pump,
17 Second pump,
18 Third pump,
41 On-off valve,
51 Second treatment container,
52 Reverse osmosis membrane (RO membrane, NF membrane),
53 Third chamber,
54 Fourth chamber,
100 Water treatment system,
101 Pipeline,
200 Desalination system,
300 Osmotic power generation system

Claims

A water treatment system comprising:
an osmotic pressure generator including a first treatment container having an osmosis membrane to partition a first chamber for accommodating water to be treated and a second chamber for accommodating a working medium to induce osmotic pressure; and
a concentrator including a carbon dioxide releasing unit for releasing carbon dioxide from the working medium, a phase separating unit for separating the phase-separated working medium, and a carbon dioxide introducing unit for absorbing carbon dioxide into the working medium, wherein
the working medium contains an amine compound, wherein
the amine compound is a compound expressed by Formula (1) or (2), wherein
R¹¹ and R¹⁴ in Formula (1) are a linear or branched alkyl chain having 1 or more and 5 or less carbon atoms and optionally contain at least one kinds selected from the group consisting of a tertiary amine, a cyclic tertiary amine, a carboxyl group, and a hydroxyl group,
R¹², R¹³, R¹⁵, and R¹⁶ in Formula (1) are H or a linear alkyl group having 1 or more and 3 or less carbon atoms and optionally contain a hydroxyl group, a halogen, or a hydroxyl group and a halogen,
R²¹ in Formula (2) is a linear or branched alkyl chain having 2 or more and 10 or less carbon atoms and optionally contains one or more tertiary amines, and
R²² and R²³ in Formula (2) are CH₂, O, or CH-COOR²⁴ (R²⁴ is linear or branched and has 0 or more and 4 or less carbon atoms):

.
The water treatment system according to claim 1, wherein the amine compound contained in the working medium is at least one kinds selected from the group consisting of 4-(1,1-dimethylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-β,β-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,α-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,β-dimethyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-propanone, 4-(1,1-dimethylethyl)-α-ethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-3-methyl-1-piperazineethanol, 4-(2-hydroxyethyl)-α,α-dimethyl-1-piperazineacetic acid, 3-(4-(1,1-dimethylethyl)-1-piperazinyl)-1,2-propanediol, 4-(2-hydroxy-1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-α-(1-methylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-ethyl-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineacetic acid, 3,(4-(1,1-dimethylethyl)-1-piperazinyl)-2-butanone, 4-(1,1-dimethylethyl)-α-ethyl-α-methyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-butanone, 1,4-bis[2-(1-piperazinyl)ethyl]-piperazine, 1,1'-(1,2-ethanediyl)-bis-piperidine, 1,1'-(1,3-propanediyl)bis-4-piperidinecarboxylic acid diethyl ester, 1,1'-(1-methyl-1,2-ethanediyl)-bis-piperidine, 4-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 3-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 2-methyl-1-[2-(1-piperidinyl)ethyl]piperidine, 1,1-(1,2-dimethyl-1,2-ethanediyl)piperidine, 1,1'-(1,2-ethanediyl)-bis-4-methylpiperidine, 1,1'-(1,2-ethanediyl)bis-2-methylpiperidine, 1-[2-(1-piperidinyl)ethyl]4-piperidinone, 1,1'-(1,3-propanediyl)-bis-piperidine, 1,1'-(2-methyl-1,3-propanediyl)bis-piperidine, and 1,1'-(1,4-butanediyl)-bis-piperidine.
The water treatment system according to claim 1 or 2, wherein a concentration of the amine compound in the working medium is 10% by mass or more and 70% by mass or less.
The water treatment system according to any one of claims 1 to 3, wherein the amine compound in the working medium undergoes solid-liquid separation or liquid-liquid separation when a concentration of carbon dioxide decreases.
The water treatment system according to any one of claims 1 to 4, wherein a solubility of the amine compound after absorption of carbon dioxide in water is four or more times a solubility of the amine compound after release of carbon dioxide in water.
The water treatment system according to any one of claims 1 to 5, further comprising a body of rotation, wherein
a water flow is generated by the induction of osmotic pressure, and
the body of rotation is rotated by the water flow to generate electricity.
A working medium to be used in the water treatment system according to any one of claims 1 to 6.
A working medium comprising an amine compound, wherein
the amine compound is a compound expressed by Formula (1) or (2), wherein
R¹¹ and R¹⁴ in Formula (1) are a linear or branched alkyl chain having 1 or more and 5 or less carbon atoms and optionally contain at least one kinds selected from the group consisting of a tertiary amine, a cyclic tertiary amine, a carboxyl group, and a hydroxyl group,
R¹², R¹³, R¹⁵, and R¹⁶ in Formula (1) are H or a linear alkyl group having 1 or more and 3 or less carbon atoms and optionally contain a hydroxyl group, a halogen, or a hydroxyl group and a halogen,
R²¹ in Formula (2) is a linear or branched alkyl chain having 2 or more and 10 or less carbon atoms and optionally contains one or more tertiary amines, and
R²² and R²³ in Formula (2) are CH₂, O, or CH-COOR²⁴ (R²⁴ is linear or branched and has 0 or more and 4 or less carbon atoms):

.
The working medium according to claim 8, wherein
the amine compound is at least one kinds selected from the group consisting of 4-(1,1-dimethylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-β,β-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,α-dimethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α,β-dimethyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-propanone, 4-(1,1-dimethylethyl)-α-ethyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-3-methyl-1-piperazineethanol, 4-(2-hydroxyethyl)-α,α-dimethyl-1-piperazineacetic acid, 3-(4-(1,1-dimethylethyl)-1-piperazinyl)-1,2-propanediol, 4-(2-hydroxy-1,1-dimethylethyl)-1-piperazineacetic acid, 4-(1,1-dimethylethyl)-α-(1-methylethyl)-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-ethyl-β-methyl-1-piperazineethanol, 4-(1,1-dimethylethyl)-α-methyl-1-piperazineacetic acid, 3,(4-(1,1-dimethylethyl)-1-piperazinyl)-2-butanone, 4-(1,1-dimethylethyl)-α-ethyl-α-methyl-1-piperazineethanol, 1-[4-(1,1-dimethylethyl)-1-piperazinyl]-2-butanone, 1,4-bis[2-(1-piperazinyl)ethyl]-piperazine, 1,1'-(1,2-ethanediyl)-bis-piperidine, 1,1'-(1,3-propanediyl)bis-4-piperidinecarboxylic acid diethyl ester, 1,1'-(1-methyl-1,2-ethanediyl)-bis-piperidine, 4-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 3-methyl-1[2-(1-piperidinyl)ethyl]piperidine, 2-methyl-1-[2-(1-piperidinyl)ethyl]piperidine, 1,1-(1,2-dimethyl-1,2-ethanediyl)piperidine, 1,1'-(1,2-ethanediyl)-bis-4-methylpiperidine, 1,1'-(1,2-ethanediyl)bis-2-methylpiperidine, 1-[2-(1-piperidinyl)ethyl]4-piperidinone, 1,1'-(1,3-propanediyl)-bis-piperidine, 1,1'-(2-methyl-1,3-propanediyl)bis-piperidine, and 1,1'-(1,4-butanediyl)-bis-piperidine,
a concentration of the amine compound in the working medium is 10% by mass or more and 70% by mass or less,
the amine compound in the working medium undergoes solid-liquid separation or liquid-liquid separation when a concentration of carbon dioxide decreases, and
a solubility of the amine compound after absorption of carbon dioxide in water is four times or more a solubility of the amine compound after release of carbon dioxide in water.