Concentration system

Abstract

The present invention is a concentration system for obtaining, by separating a solvent from a target solution containing a target component, a concentrated liquid in which the target component is concentrated, the concentration system comprising a plurality of semipermeable membrane modules, and a pressurizing device for increasing the pressure of the target solution. Each of the plurality of semipermeable membrane modules has a semipermeable membrane, and a first chamber and a second chamber partitioned by the semipermeable membrane, wherein a concentration flow path formed by connecting the first chambers of the plurality of semipermeable membrane modules is provided, and a dilution flow path formed by connecting the second chambers of the plurality of semipermeable membrane modules is provided. The target solution is caused to flow through the concentration flow path, and an auxiliary solution having osmotic pressure is caused to flow through the dilution flow path. The concentration system comprises at least one selected from a group consisting of a concentrated liquid measuring device and an auxiliary solution measuring device, and an adjusting device. The adjusting device includes at least one selected from a group consisting of a concentrated liquid adjusting device and an auxiliary solution adjusting device. The concentrated liquid measuring device is provided downstream of the concentration flow path, and the auxiliary solution measuring device is provided downstream of the dilution flow path. The concentrated liquid measuring device measures at least one selected from a group consisting of the flow rate and the concentration of the concentrated liquid. The auxiliary solution measuring device measures at least one selected from a group consisting of the flow rate and the concentration of the auxiliary solution. The concentrated liquid adjusting device controls the pressurizing device such that a measured value of the concentrated liquid measuring device falls within a predetermined range. The auxiliary solution adjusting device controls the pressurizing device such that a measured value of the auxiliary solution measuring device falls within a predetermined range.

Description

Concentration System

[0001] The present invention relates to a concentration system.

[0002] With the aim of reducing the energy required for desalination using reverse osmosis (RO), etc., studies have been conducted on an osmotically assisted reverse osmosis (OARO) method or a brine concentration (BC) method, which is a membrane separation method in which a high-pressure target solution is passed through the first chamber of a semipermeable membrane module having a semipermeable membrane and a first and second chamber separated by the semipermeable membrane, and a low-pressure target solution is passed through the second chamber, causing the solvent (water, etc.) contained in the target solution in the first chamber to migrate through the semipermeable membrane to the target solution in the second chamber, thereby discharging a concentrated target solution (concentrate) from the first chamber and a diluted target solution (diluted solution) from the second chamber.

[0003] For example, Patent Document 1 (WO 2018 / 084246), Patent Document 2 (JP 2019-188330 A), and Patent Document 3 (JP 2018-515340 A) disclose the use of a multistage membrane separation system in which a plurality of semipermeable membrane modules are connected in series in a brine concentration method.

[0004] International Publication No. 2018 / 084246 Japanese Patent Application Laid-Open No. 2019-188330 Japanese Patent Application Laid-Open No. 2018-515340

[0005] In such a multistage membrane separation (concentration) system including a plurality of semipermeable membrane modules, the target solution is sequentially concentrated in a flow path (concentration flow path) formed by connecting the first chambers of a plurality of semipermeable membrane modules.

[0006] The concentration system is designed to obtain a concentrated solution of a desired concentration according to the concentration, flow rate, pressure, temperature, etc. of the target solution. However, if the concentration, flow rate, pressure, temperature, etc. of the target solution differ from or fluctuate from the designed values, it is not possible to obtain a concentrated solution of the desired concentration or flow rate. Furthermore, the design of such a concentration system is complex, and when actually operated, a concentrated solution of the desired concentration or flow rate is not necessarily obtained as designed.

[0007] Therefore, an object of the present invention is to stably obtain a concentrated solution of a predetermined concentration or flow rate when separating and concentrating a solvent from a target solution by osmotic pressure-assisted reverse osmosis or brine concentration using a multistage concentration system (membrane separation system) including a plurality of semipermeable membrane modules.

[0008] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention has the following configuration.

[0009] [1] A concentration system for separating a solvent from a target solution containing a target component to obtain a concentrated solution in which the target component is concentrated, comprising: a plurality of semipermeable membrane modules; and a pressurizing device for pressurizing the target solution, wherein each of the plurality of semipermeable membrane modules has a semipermeable membrane and a first chamber and a second chamber separated by the semipermeable membrane, a concentration flow path is provided to which the first chambers of the plurality of semipermeable membrane modules are connected, and a dilution flow path is provided to which the second chambers of the plurality of semipermeable membrane modules are connected, the target solution is flowed through the concentration flow path, and an auxiliary solution having an osmotic pressure is flowed through the dilution flow path, the concentration system comprises at least one selected from the group consisting of a concentrated solution meter and an auxiliary solution meter, and an adjuster, wherein the adjuster includes at least one selected from the group consisting of a concentrated solution adjuster and an auxiliary solution adjuster, the concentrated solution meter is provided downstream of the concentration flow path, and the auxiliary solution meter is provided downstream of the dilution flow path, A concentration system, wherein the concentrated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid, the auxiliary solution measuring device measures at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution, the concentrated liquid adjuster controls the pressurizing device so that the measurement value of the concentrated liquid measuring device falls within a predetermined range, and the auxiliary solution adjuster controls the pressurizing device so that the measurement value of the auxiliary solution measuring device falls within a predetermined range.

[0010] [2] The concentration system according to [1], wherein the pressurizing device is a high-pressure pump for pumping the target solution, and the regulator controls the frequency of the high-pressure pump.

[0011] [3] The concentration system according to [1], wherein the pressurizing device is a pressure regulating valve for regulating the pressure in at least one of the plurality of semipermeable membrane modules, and the regulator controls the pressure regulating valve.

[0012] [4] A system including at least one reverse osmosis module and a pre-stage pressurizing device for pressurizing the target solution, upstream of the plurality of semipermeable membrane modules, wherein the at least one reverse osmosis module has a reverse osmosis membrane and a first pre-stage chamber and a second pre-stage chamber separated by the reverse osmosis membrane, wherein a pre-stage concentration flow path is provided connecting the first pre-stage chamber of the at least one reverse osmosis module and a first chamber of the most upstream semipermeable membrane module of the plurality of semipermeable membrane modules, wherein the solvent contained in the target solution supplied to the first pre-stage chamber at a pressure higher than that of the second pre-stage chamber migrates through the reverse osmosis membrane into the second pre-stage chamber, and the target solution is diluted, thereby discharging a pre-concentrated solution from the first pre-stage chamber and obtaining a permeated solution from the second pre-stage chamber, and wherein a permeate flow path is provided for discharging the permeated solution, and the concentration system includes at least one selected from the group consisting of a pre-concentrated solution meter and a permeated solution meter, and a pre-stage regulator, The concentration system according to any one of [1] to [3], wherein the pre-stage adjuster includes at least one selected from the group consisting of a pre-concentrated liquid adjuster and a permeated liquid adjuster, the pre-concentrated liquid measuring device is provided in the pre-concentration flow path, the permeated liquid measuring device is provided downstream of the permeation flow path, the pre-concentrated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the pre-concentrated liquid, the permeated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the permeated liquid, the pre-concentrated liquid adjuster controls the pre-stage pressurizing device so that the measurement value of the pre-concentrated liquid measuring device falls within a predetermined range, and the permeated liquid adjuster controls the pre-stage pressurizing device so that the measurement value of the permeated liquid measuring device falls within a predetermined range.

[0013] [5] The concentration system according to [4], wherein the pre-stage pressurizing device is a high-pressure pump for pumping the target solution, and the pre-stage regulator controls the frequency of the high-pressure pump.

[0014] [6] The concentration system according to [4], wherein the pre-stage pressurizing device is a pressure regulating valve for regulating the pressure in the at least one reverse osmosis module, and the pre-stage regulator controls the pressure regulating valve.

[0015] [7] The concentration system according to any one of [1] to [6], wherein the semipermeable membrane is a hollow fiber membrane.

[0016] [8] The concentration system according to any one of [4] to [6], wherein the reverse osmosis membrane is a hollow fiber membrane.

[0017] [9] A concentration system for obtaining a concentrated solution in which a target component is concentrated by separating a solvent from a target solution containing the target component, comprising: at least one reverse osmosis module, a plurality of semipermeable membrane modules, and a front-stage pressurizing device for pressurizing the target solution, wherein the at least one reverse osmosis module has a reverse osmosis membrane and a front-stage first chamber and a front-stage second chamber separated by the reverse osmosis membrane, and each of the plurality of semipermeable membrane modules has a semipermeable membrane and a first chamber and a second chamber separated by the semipermeable membrane, a front-stage concentration flow path is provided in which the front-stage first chamber of the at least one reverse osmosis module is connected to the first chamber of the semipermeable membrane module located most upstream of the plurality of semipermeable membrane modules, a concentration flow path is provided in which the first chambers of the plurality of semipermeable membrane modules are connected, and a dilution flow path is provided in which the second chambers of the plurality of semipermeable membrane modules are connected, the solvent contained in the target solution supplied to the first upstream chamber at a pressure higher than that of the second upstream chamber migrates through the reverse osmosis membrane into the second upstream chamber, diluting the target solution and thereby discharging a pre-concentrated solution from the first upstream chamber and obtaining a permeated solution from the second upstream chamber; a permeation flow path is provided for discharging the permeated solution; the pre-concentrated solution is caused to flow through the concentration flow path; and an auxiliary solution having an osmotic pressure is caused to flow through the second chamber; the concentration system comprises at least one selected from the group consisting of a pre-concentrated solution meter and a permeated solution meter, and a pre-adjuster; the pre-adjuster includes at least one selected from the group consisting of a pre-concentrated solution adjuster and a permeated solution adjuster; the pre-concentrated solution meter is provided in the pre-concentration flow path; and the permeated solution meter is provided downstream of the permeation flow path; the pre-concentrated solution meter measures at least one selected from the group consisting of a flow rate and a concentration of the pre-concentrated solution; and the permeated solution meter measures at least one selected from the group consisting of a flow rate and a concentration of the permeated solution. A concentration system in which the pre-concentrated liquid adjuster controls the upstream pressurizing device so that the measurement value of the pre-concentrated liquid measuring device falls within a predetermined range, and the permeated liquid adjuster controls the upstream pressurizing device so that the measurement value of the permeated liquid measuring device falls within a predetermined range.

[0018]

[10] The concentration system according to [9], wherein the pre-stage pressurizing device is a high-pressure pump for pumping the target solution, and the pre-stage regulator controls the frequency of the high-pressure pump.

[0019]

[11] The concentration system according to [9], wherein the pre-stage pressurizing device is a pressure regulating valve for regulating the pressure in the at least one reverse osmosis module, and the pre-stage regulator controls the pressure regulating valve.

[0020]

[12] A concentration system according to any of [9] to

[11] , comprising: a pressurizing device for pressurizing the pre-concentrated liquid; at least one selected from the group consisting of a concentrated liquid measuring device and an auxiliary solution measuring device; and an adjuster, wherein the adjuster includes at least one selected from the group consisting of a concentrated liquid adjuster and an auxiliary solution adjuster, the concentrated liquid measuring device is provided downstream of the concentration flow path, and the auxiliary solution measuring device is provided downstream of the dilution flow path, the concentrated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid, and the auxiliary solution measuring device measures at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution, the concentrated liquid adjuster controls the pressurizing device so that the measurement value of the concentrated liquid meter falls within a predetermined range, and the auxiliary solution adjuster controls the pressurizing device so that the measurement value of the auxiliary solution meter falls within a predetermined range.

[0021]

[13] The concentration system according to

[12] , wherein the pressurizing device is a high-pressure pump for pumping the pre-concentrated liquid, and the regulator controls the frequency of the high-pressure pump.

[0022]

[14] The concentration system according to

[12] , wherein the pressurizing device is a pressure regulating valve for regulating the pressure in at least one of the plurality of semipermeable membrane modules, and the regulator controls the pressure regulating valve.

[0023]

[15] The concentration system according to any one of [9] to

[14] , wherein the semipermeable membrane and the reverse osmosis membrane are hollow fiber membranes.

[0024]

[16] The concentration system according to any one of [1] to

[15] , wherein a part of the concentrated solution is used as the auxiliary solution.

[0025] According to the present invention, when a solvent is separated from a target solution and concentrated by osmotic pressure-assisted reverse osmosis or brine concentration using a multistage concentration system (membrane separation system) including a plurality of semipermeable membrane modules, a concentrated solution of a predetermined concentration or flow rate can be stably obtained.

[0026] FIG. 1 is a schematic diagram showing an example of a concentration system of embodiment 1. FIG. 2 is a schematic diagram showing another example of the concentration system of embodiment 1. FIG. 3 is a schematic diagram showing another example of the concentration system of embodiment 1. FIG. 4 is a schematic diagram showing another example of the concentration system of embodiment 1. FIG. 5 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 6 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 7 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 8 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 9 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 10 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 11 is a schematic diagram showing another example of the concentration system of embodiment 2. FIG. 12 is a schematic diagram showing another example of the concentration system of embodiment 3. FIG. 13 is a schematic diagram showing another example of the concentration system of embodiment 3. FIG. 14 is a schematic diagram showing another example of the concentration system of embodiment 3. FIG. 15 is a schematic diagram showing another example of the concentration system of embodiment 4. FIG. 16 is a schematic diagram showing another example of the concentration system of embodiment 4. Fig. 1 is a schematic diagram showing another example of the concentration system of embodiment 4. Fig. 2 is a schematic diagram showing another example of the concentration system of embodiment 4. Fig. 3 is a schematic diagram showing another example of the concentration system of embodiment 4. Fig. 4 is a schematic diagram showing another example of the concentration system of embodiment 4. Fig. 5 is a schematic diagram showing another example of the concentration system of embodiment 4.

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals denote the same or corresponding parts.

[0028] <Concentration System> The concentration system of this embodiment is a system for obtaining a concentrated liquid in which the target component is concentrated by separating the solvent from a target solution (liquid to be treated) containing the target component.

[0029] (Embodiment 1) Figures 1 to 4 are diagrams schematically showing the configuration of a concentration system of this embodiment. The concentration system of this embodiment is a multistage concentration system (membrane separation system). Note that although three semipermeable membrane modules 1, 2, and 3 are depicted as the multiple semipermeable membrane modules in Figures 1 to 4, the multiple semipermeable membrane modules may be, for example, any number of semipermeable membrane modules greater than or equal to two.

[0030] Each of the plurality of semipermeable membrane modules 1, 2, 3 has a semipermeable membrane 1A, 2A, 3A, and a first chamber 11, 21, 31 and a second chamber 12, 22, 32 separated by the semipermeable membrane.

[0031] A concentration flow path is provided in which the first chambers 11, 21, 31 of multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the concentration flow path is composed of the first chambers 11, 21, 31 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules, the first chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the first chambers may be connected in parallel.

[0032] A dilution flow path is provided in which the second chambers 12, 22, 32 of the multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the dilution flow path is composed of the second chambers 12, 22, 32 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules, the second chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the second chambers may be connected in parallel.

[0033] The target solution is passed through the concentration flow path, passing through the first chamber 11 of the semipermeable membrane module 1, the first chamber 21 of the semipermeable membrane module 2, and the first chamber 31 of the semipermeable membrane module 3 in this order.

[0034] An auxiliary solution having osmotic pressure is flowed through the dilution flow path. The auxiliary solution is flowed in the order of the second chamber 32 of the semipermeable membrane module 3, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 12 of the semipermeable membrane module 1. That is, the auxiliary solution is flowed in the reverse order of the target solution when the semipermeable membrane modules are connected. However, the auxiliary solution is not limited to the embodiments shown in Figures 1 to 4, and may be flowed in the order of the second chamber 12 of the semipermeable membrane module 1, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 32 of the semipermeable membrane module 3.

[0035] In each semipermeable membrane module, the flow directions on both sides of the semipermeable membrane (in the first and second chambers) may be in any direction, and may be opposite directions (counterflow system) or parallel directions (parallel flow system).

[0036] In multiple semipermeable membrane modules, the flow directions on both sides of the semipermeable membrane (in the first and second chambers) may be in any direction, and may be opposite directions (counterflow method) or parallel directions (parallel flow method).

[0037] The target solution has a higher pressure (hydrostatic pressure) than the auxiliary solution, i.e., in each of the multiple semipermeable membrane modules, the liquid in the first chamber (target solution) has a higher pressure than the liquid in the second chamber (auxiliary solution).

[0038] Because the target solution has a higher pressure than the auxiliary solution, in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the target solution in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated solution is discharged from the first chamber and the diluted solution, which is the diluted auxiliary solution, is discharged from the second chamber.

[0039] Here, the pressure of the target solution is increased by a pressurizing device, such as a high-pressure pump 51 and a pressure adjusting valve 52.

[0040] The high-pressure pump 51 is a device that can pressurize the target solution and pump it into the first chamber. The high-pressure pump 51 is provided upstream of at least one of the first chambers of the multiple semipermeable membrane modules. For example, in FIG. 1 , the high-pressure pump 51 is provided upstream of the first chamber 11. For example, the high-pressure pump 51 may be provided between the first chamber 11 and the first chamber 21, or between the first chamber 21 and the first chamber 31.

[0041] The pressure regulating valve 52 is a device capable of regulating the pressure in at least one of the plurality of semipermeable membrane modules. At least one pressure regulating valve 52 is provided in the concentration system. For example, in FIG. 2 , the pressure regulating valve 52 is provided between the first chamber 11 and the first chamber 21. For example, the pressure regulating valve 52 may be provided upstream of the first chamber 11, or may be provided between the first chamber 21 and the first chamber 31.

[0042] At least one pressurizing device may be provided in the concentration system, but multiple pressurizing devices may also be provided. Note that the pressurizing device may be a device other than those described above, for example, a device that pressurizes the liquid in the first chamber from outside the semipermeable membrane module.

[0043] The concentration system includes at least one selected from the group consisting of a concentrate measuring device 61 and an auxiliary solution measuring device 62, and an adjuster. The adjuster includes at least one selected from the group consisting of a concentrate adjuster 71 and an auxiliary solution adjuster 72. Note that the adjusters may be integrated into the entire concentration system.

[0044] 1 and 2, the concentrated liquid measuring device 61 is provided on the most downstream side of the concentration flow path (downstream of the first chamber 31 of the semipermeable membrane module 3). The concentrated liquid measuring device 61 measures at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid. The concentrated liquid measuring device 61, the concentrated liquid adjuster 71, and the pressurizing device are electrically connected. The concentrated liquid adjuster 71 controls the pressurizing device so that the measurement value of the concentrated liquid measuring device 61 (at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid) falls within a predetermined range.

[0045] When the pressurizing device is the high-pressure pump 51, the concentrated liquid adjuster 71 controls the frequency (number of rotations) of the high-pressure pump 51. For example, when the measurement value of the concentrated liquid meter 61 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid adjuster 71 lowers the frequency of the high-pressure pump 51 to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the concentrated liquid meter 61 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid adjuster 71 increases the frequency of the high-pressure pump 51 to increase the pressure in the semipermeable membrane module. In this way, the concentrated liquid adjuster 71 controls the high-pressure pump 51 so that the measurement value of the concentrated liquid meter 61 falls within a predetermined range.

[0046] When the pressurizing device is the pressure regulating valve 52, the concentrated liquid adjuster 71 controls the aperture of the pressure regulating valve 52. For example, when the measurement value of the concentrated liquid measuring device 61 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid adjuster 71 increases the aperture of the pressure regulating valve 52 to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the concentrated liquid measuring device 61 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid adjuster 71 decreases the aperture of the pressure regulating valve 52 to increase the pressure in the semipermeable membrane module. In this way, the concentrated liquid adjuster 71 controls the pressure regulating valve 52 so that the measurement value of the concentrated liquid measuring device 61 falls within a predetermined range.

[0047] 3 and 4, the auxiliary solution measuring device 62 is provided on the most downstream side of the dilution flow path (downstream of the second chamber 12 of the semipermeable membrane module 1). The auxiliary solution measuring device 62 measures at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution. The auxiliary solution measuring device 62, the auxiliary solution adjuster 72, and the pressurizing device are electrically connected. The auxiliary solution adjuster 72 controls the pressurizing device so that the measurement value of the auxiliary solution measuring device 62 (at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution) falls within a predetermined range.

[0048] When the pressurizing device is the high-pressure pump 51, the auxiliary solution adjuster 72 controls the frequency (number of rotations) of the high-pressure pump 51. For example, when the measurement value of the auxiliary solution meter 62 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution adjuster 72 lowers the frequency of the high-pressure pump 51, thereby reducing the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution adjuster 72 increases the frequency of the high-pressure pump 51, thereby increasing the pressure in the semipermeable membrane module. In this way, the auxiliary solution adjuster 72 controls the high-pressure pump 51 so that the measurement value of the auxiliary solution meter 62 falls within a predetermined range.

[0049] When the pressurizing device is the pressure regulating valve 52, the auxiliary solution adjuster 72 controls the opening degree of the pressure regulating valve 52. For example, when the measurement value of the auxiliary solution meter 62 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution adjuster 72 increases the opening degree of the pressure regulating valve 52, thereby reducing the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution adjuster 72 decreases the opening degree of the pressure regulating valve 52, thereby increasing the pressure in the semipermeable membrane module. In this way, the auxiliary solution adjuster 72 controls the pressure regulating valve 52 so that the measurement value of the auxiliary solution meter 62 falls within a predetermined range.

[0050] (Embodiment 2) Figures 5 to 12 are diagrams schematically illustrating the configuration of a concentration system according to another embodiment of the present invention. The concentration system according to this embodiment is a multistage concentration system (membrane separation system). Note that in Figures 5 to 12, one reverse osmosis module 4 is depicted as the reverse osmosis module, and three semipermeable membrane modules 1, 2, and 3 are depicted as the multiple semipermeable membrane modules. The multiple semipermeable membrane modules may be any number of semipermeable membrane modules, for example, two or more. Furthermore, although one reverse osmosis module (reverse osmosis module 4) is depicted in Figures 5 to 12, multiple (n) reverse osmosis modules may be provided.

[0051] The reverse osmosis module 4 has a reverse osmosis membrane 4A and a first front-stage chamber 41 and a second front-stage chamber 42 separated by the reverse osmosis membrane 4A.

[0052] A pre-concentration flow path is provided, which is formed by connecting the pre-stage first chamber 41 of the reverse osmosis module 4 and the first chamber 11 of the most upstream semipermeable membrane module 1 of the multiple semipermeable membrane modules. That is, the pre-concentration flow path is made up of the pre-stage first chamber 41, the first chamber 11, and a flow path connecting them.

[0053] A permeate flow path is provided which is connected to the second front chamber 42 of the reverse osmosis module 4 .

[0054] In the reverse osmosis module 4, the target solution is pressurized at high pressure, causing the solvent (water, etc.) contained in the target solution in the first upstream chamber 41 to migrate through the reverse osmosis membrane 4A into the second upstream chamber 42, and the concentrated target solution, a pre-concentrated liquid, is discharged from the first upstream chamber 41, and the permeated liquid is discharged from the second upstream chamber 42.

[0055] Each of the plurality of semipermeable membrane modules 1, 2, 3 has a semipermeable membrane 1A, 2A, 3A, and a first chamber 11, 21, 31 and a second chamber 12, 22, 32 partitioned by the semipermeable membrane.

[0056] A concentration flow path is provided in which the first chambers 11, 21, 31 of multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the concentration flow path is composed of the first chambers 11, 21, 31 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules, the first chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the first chambers may be connected in parallel.

[0057] A dilution flow path is provided in which the second chambers 12, 22, 32 of the multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the dilution flow path is composed of the second chambers 12, 22, 32 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules 1, 2, 3, the second chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the second chambers may be connected in parallel.

[0058] A pre-concentrated liquid is passed through the concentration flow path. The pre-concentrated liquid flows through the first chamber 11 of the semipermeable membrane module 1, the first chamber 21 of the semipermeable membrane module 2, and the first chamber 31 of the semipermeable membrane module 3 in this order.

[0059] An auxiliary solution having osmotic pressure is flowed through the dilution flow path. The auxiliary solution is flowed in the order of the second chamber 32 of the semipermeable membrane module 3, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 12 of the semipermeable membrane module 1. That is, the auxiliary solution is flowed in the reverse order of the target solution when the semipermeable membrane modules are connected. However, the auxiliary solution is not limited to the embodiments shown in Figures 5 to 12, and may be flowed in the order of the second chamber 12 of the semipermeable membrane module 1, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 32 of the semipermeable membrane module 3.

[0060] In each semipermeable membrane module, the flow directions on both sides of the semipermeable membrane (in the first and second chambers) may be in any direction, and may be opposite directions (counterflow system) or parallel directions (parallel flow system).

[0061] In each of the multiple semipermeable membrane modules, the target solution has a higher pressure than the auxiliary solution, so that in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the target solution in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated solution is discharged from the first chamber and the diluted solution is discharged from the second chamber.

[0062] The pre-concentrated liquid has a higher pressure (hydrostatic pressure) than the auxiliary solution, i.e., in each of the multiple semipermeable membrane modules, the liquid in the first chamber (pre-concentrated liquid) has a higher pressure than the liquid in the second chamber (auxiliary solution).

[0063] Because the pre-concentrated liquid has a higher pressure than the auxiliary solution, in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the pre-concentrated liquid in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated liquid is discharged from the first chamber and the diluted liquid, which is the diluted auxiliary solution, is discharged from the second chamber.

[0064] Here, the target solution is pressurized by a pre-stage pressurizing device. Examples of the pre-stage pressurizing device include a high-pressure pump and a pressure regulating valve. The pre-concentrated solution is also pressurized by a pressurizing device. The pressurizing device used is the same as the pre-stage pressurizing device. In this embodiment, the high-pressure pump serving as the pressurizing device is referred to as the "first high-pressure pump," the pressure regulating valve serving as the pressurizing device is referred to as the "first pressure regulating valve," the high-pressure pump serving as the pre-stage pressurizing device is referred to as the "second high-pressure pump," and the pressure regulating valve serving as the pre-stage pressurizing device is referred to as the "second pressure regulating valve." The first and second high-pressure pumps are collectively referred to as the "high-pressure pump," and the first and second pressure regulating valves are collectively referred to as the "pressure regulating valve."

[0065] The first high-pressure pump 51 (second high-pressure pump 53) is a device that can pressurize the pre-concentrated solution (target solution) and pump it into the first chamber (first chamber at the front stage). The first high-pressure pump 51 (second high-pressure pump 53) is provided upstream of at least one of the first chambers of the multiple semipermeable membrane modules (upstream of at least one reverse osmosis module). For example, in FIG. 5 , the first high-pressure pump 51 (second high-pressure pump 53) is provided upstream of the first chamber 11 (upstream of the first chamber at the front stage 41). For example, the first high-pressure pump 51 may be provided between the first chamber 11 and the first chamber 21, or between the first chamber 21 and the first chamber 31.

[0066] The first pressure regulating valve 52 (second pressure regulating valve 54) is a device capable of regulating the pressure in at least one of the multiple semipermeable membrane modules (at least one reverse osmosis membrane module). At least one first pressure regulating valve 52 (second pressure regulating valve 54) is provided in the concentration system. For example, in FIG. 6 , the first pressure regulating valve 52 (second pressure regulating valve 54) is provided between the first chamber 11 and the first chamber 21 (between the upstream first chamber 41 and the first chamber 11). For example, the first pressure regulating valve 52 may be provided upstream of the upstream first chamber 41 and the first chamber 11, or may be provided between the first chamber 21 and the first chamber 31. For example, the second pressure regulating valve 54 may be provided upstream of the upstream first chamber 41.

[0067] The upstream pressurizing device and the pressurizing device may be provided in the concentration system at least one at a time, or may be provided in multiple numbers. Note that the upstream pressurizing device and the pressurizing device may be devices other than those described above, for example, devices that pressurize the liquid in the upstream first chamber from outside the reverse osmosis module and the liquid in the first chamber from outside the semipermeable membrane module.

[0068] The concentration system includes at least one selected from the group consisting of a concentrate measuring device 61 and an auxiliary solution measuring device 62, and an adjuster. The adjuster includes at least one selected from the group consisting of a concentrate adjuster 71 and an auxiliary solution adjuster 72. The concentration system includes at least one selected from the group consisting of a pre-concentrated solution measuring device 63 and a permeated solution measuring device 64, and an upstream adjuster. The upstream adjuster includes at least one selected from the group consisting of a pre-concentrated solution adjuster 73 and a permeated solution adjuster 74. Note that the adjusters, upstream adjusters, and the adjusters and upstream adjusters may be integrated into the entire concentration system.

[0069] 5 and 6 , the concentrated liquid measuring device 61 is provided on the most downstream side of the concentration flow path (downstream of the first chamber 31 of the semipermeable membrane module 3), and the pre-concentrated liquid measuring device 63 is provided on the upstream concentration flow path (downstream of the upstream first chamber 41 of the reverse osmosis module 4 and upstream of the first chamber 11 of the semipermeable membrane module 1). The concentrated liquid measuring device 61 measures at least one parameter selected from the group consisting of the flow rate and concentration of the concentrated liquid. The pre-concentrated liquid measuring device 61, the concentrated liquid adjuster 71, and the pressurizing device are electrically connected. The pre-concentrated liquid measuring device 63, the pre-concentrated liquid adjuster 73, and the upstream pressurizing device are electrically connected. The concentrated liquid adjuster 71 controls the pressurizing device so that the measurement value of the concentrated liquid measuring device 61 (at least one parameter selected from the group consisting of the flow rate and concentration of the concentrated liquid) falls within a predetermined range. The pre-concentrated liquid adjuster 73 controls the front-stage pressurizing device so that the measurement value of the pre-concentrated liquid measuring device 63 (at least one selected from the group consisting of the flow rate and concentration of the pre-concentrated liquid) falls within a predetermined range.

[0070] When the pressurizing device (pre-stage pressurizing device) is the first high-pressure pump 51 (second high-pressure pump 53), the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) controls the frequency (rotation speed) of the first high-pressure pump 51 (second high-pressure pump 53). For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) lowers the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to reduce the pressure in the semipermeable membrane module (reverse osmosis module). For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) increases the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to increase the pressure in the semipermeable membrane module (reverse osmosis module). In this way, the first high-pressure pump 51 (second high-pressure pump 53) is controlled by the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) so that the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is within a specified range.

[0071] When the pressurizing device (pre-stage pressurizing device) is the first pressure regulating valve 52 (second pressure regulating valve 54), the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) controls the aperture of the pressure regulating valve 52. For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) increases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) decreases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to increase the pressure in the semipermeable membrane module. In this way, the first pressure regulating valve 52 (second pressure regulating valve 54) is controlled by the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) so that the measurement value of the concentrated liquid measuring instrument 61 (pre-concentrated liquid measuring instrument 63) is within a predetermined range.

[0072] 7 and 8 , the auxiliary solution meter 62 is provided at the most downstream side of the dilution flow path (downstream of the second chamber 12 of the semipermeable membrane module 1), and the permeate meter 64 is provided at the most downstream side of the permeation flow path (downstream of the upstream second chamber 42 of the reverse osmosis module 4). The auxiliary solution meter 62 measures at least one parameter selected from the group consisting of the flow rate and concentration of the auxiliary solution. The permeate meter 64 measures at least one parameter selected from the group consisting of the flow rate and concentration of the permeate. The auxiliary solution meter 62, auxiliary solution adjuster 72, and pressurizing device are electrically connected. The permeate meter 64, permeate adjuster 74, and upstream pressurizing device are electrically connected. The auxiliary solution adjuster 72 controls the pressurizing device so that the measurement value of the auxiliary solution meter 62 (at least one parameter selected from the group consisting of the flow rate and concentration of the auxiliary solution) falls within a predetermined range. The permeate adjuster 74 controls the pre-stage pressurizing device so that the measurement value of the permeate measuring device 64 (at least one selected from the group consisting of the flow rate and concentration of the permeate) falls within a predetermined range.

[0073] When the pressurizing device (preceding stage pressurizing device) is the first high-pressure pump 51 (second high-pressure pump 53), the auxiliary solution adjuster 72 (permeate adjuster 74) controls the frequency (rotation speed) of the first high-pressure pump 51 (second high-pressure pump 53). For example, when the measurement value of the auxiliary solution meter 62 (permeate adjuster 64) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution adjuster 72 (permeate adjuster 74) lowers the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 (permeate adjuster 64) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution adjuster 72 (permeate adjuster 74) increases the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to increase the pressure in the semipermeable membrane module. In this way, the first high-pressure pump 51 (second high-pressure pump 53) is controlled by the auxiliary solution adjuster 72 (permeate adjuster 74) so ​​that the measurement value of the auxiliary solution meter 62 (permeate meter 64) falls within a predetermined range.

[0074] When the pressurizing device (pre-stage pressurizing device) is the first pressure regulating valve 52 (second pressure regulating valve 54), the auxiliary solution regulator 72 (permeate regulator 74) controls the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54). For example, when the measurement value of the auxiliary solution meter 62 (permeate meter 64) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution regulator 72 (permeate regulator 74) increases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 (permeate meter 64) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution regulator 72 (permeate regulator 74) decreases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to increase the pressure in the semipermeable membrane module. In this way, the pressure regulating valve 52 is controlled by the auxiliary solution adjuster 72 (permeate adjuster 74) so ​​that the measurement value of the auxiliary solution meter 62 (permeate meter 64) falls within a predetermined range.

[0075] Figures 9 to 12 show a concentration system that is composed of a combination of the arrangement and control points of each instrument, each measuring device, and each regulator in multiple semipermeable membrane modules described in Figures 5 to 8, and the arrangement and control points of each instrument, each measuring device, and each regulator in at least one reverse osmosis module.

[0076] In the concentration system shown in Figure 9, the concentrate adjuster 71 controls the first high-pressure pump 51 so that the measurement value of the concentrate meter 61 falls within a predetermined range, and the permeate adjuster 74 controls the second high-pressure pump 53 so that the measurement value of the permeate meter 64 falls within a predetermined range. In the concentration system shown in Figure 10, the concentrate adjuster 71 controls the first pressure regulating valve 52 so that the measurement value of the concentrate meter 61 falls within a predetermined range, and the permeate adjuster 74 controls the second pressure regulating valve 54 so that the measurement value of the permeate meter 64 falls within a predetermined range. In the concentration system shown in Figure 11, the auxiliary solution adjuster 72 controls the first high-pressure pump 51 so that the measurement value of the auxiliary solution meter 62 falls within a predetermined range, and the pre-concentrate adjuster 73 controls the second high-pressure pump 53 so that the measurement value of the pre-concentrate meter 63 falls within a predetermined range. In the concentration system shown in Figure 12, the auxiliary solution adjuster 72 controls the first pressure regulating valve 52 so that the measurement value of the auxiliary solution measuring instrument 62 falls within a predetermined range, and the pre-concentrated liquid adjuster 73 controls the second pressure regulating valve 54 so that the measurement value of the pre-concentrated liquid measuring instrument 63 falls within a predetermined range.

[0077] In the concentration system of this embodiment, the arrangement and control locations of the instruments, measuring instruments, and regulators in the multiple semipermeable membrane modules may be different from the arrangement and control locations of the instruments, measuring instruments, and regulators in at least one reverse osmosis module. For example, the concentration system may be configured to control the frequency of the first high-pressure pump in the multiple semipermeable membrane modules and control the second pressure regulation valve in at least one reverse osmosis module. For example, the concentration system may be configured to control the frequency of the first pressure regulation valve in the multiple semipermeable membrane modules and control the second high-pressure pump in at least one reverse osmosis module.

[0078] (Embodiment 3) Figures 13 to 16 are diagrams schematically showing the configuration of a concentration system according to another embodiment of the present invention. The concentration system according to this embodiment is a multistage concentration system (membrane separation system). Note that in Figures 13 to 16, one reverse osmosis module 4 is depicted as the reverse osmosis module, and three semipermeable membrane modules 1, 2, and 3 are depicted as the multiple semipermeable membrane modules. The multiple semipermeable membrane modules may be any number of semipermeable membrane modules, for example, two or more. Furthermore, although one reverse osmosis module (reverse osmosis module 4) is depicted in Figures 13 to 16, multiple (n) reverse osmosis modules may be provided.

[0079] The reverse osmosis module 4 has a reverse osmosis membrane 4A and a first front-stage chamber 41 and a second front-stage chamber 42 separated by the reverse osmosis membrane 4A.

[0080] A pre-concentration flow path is provided, which is formed by connecting the pre-stage first chamber 41 of the reverse osmosis module 4 and the first chamber 11 of the most upstream semipermeable membrane module 1 of the multiple semipermeable membrane modules. That is, the pre-concentration flow path is made up of the pre-stage first chamber 41, the first chamber 11, and a flow path connecting them.

[0081] A permeate flow path is provided which is connected to the second front chamber 42 of the reverse osmosis module 4 .

[0082] In the reverse osmosis module 4, the target solution is pressurized at high pressure, causing the solvent (water, etc.) contained in the target solution in the first upstream chamber 41 to migrate through the reverse osmosis membrane 4A into the second upstream chamber 42, and the concentrated target solution, a pre-concentrated liquid, is discharged from the first upstream chamber 41, and the permeated liquid is discharged from the second upstream chamber 42.

[0083] Each of the plurality of semipermeable membrane modules 1, 2, 3 has a semipermeable membrane 1A, 2A, 3A, and a first chamber 11, 21, 31 and a second chamber 12, 22, 32 partitioned by the semipermeable membrane.

[0084] A concentration flow path is provided in which the first chambers 11, 21, 31 of multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the concentration flow path is composed of the first chambers 11, 21, 31 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules, the first chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the first chambers may be connected in parallel.

[0085] A dilution flow path is provided in which the second chambers 12, 22, 32 of the multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the dilution flow path is composed of the second chambers 12, 22, 32 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules 1, 2, 3, the second chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the second chambers may be connected in parallel.

[0086] A pre-concentrated liquid is passed through the concentration flow path. The pre-concentrated liquid flows through the first chamber 11 of the semipermeable membrane module 1, the first chamber 21 of the semipermeable membrane module 2, and the first chamber 31 of the semipermeable membrane module 3 in this order.

[0087] An auxiliary solution having osmotic pressure is flowed through the dilution flow path. The auxiliary solution is flowed in the order of the second chamber 32 of the semipermeable membrane module 3, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 12 of the semipermeable membrane module 1. That is, the auxiliary solution is flowed in the reverse order of the target solution when the semipermeable membrane modules are connected. However, the auxiliary solution is not limited to the embodiments shown in Figures 13 to 16, and may be flowed in the order of the second chamber 12 of the semipermeable membrane module 1, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 32 of the semipermeable membrane module 3.

[0088] In each semipermeable membrane module, the flow directions on both sides of the semipermeable membrane (in the first and second chambers) may be in any direction, and may be opposite directions (counterflow system) or parallel directions (parallel flow system).

[0089] In each of the multiple semipermeable membrane modules, the target solution has a higher pressure than the auxiliary solution, so that in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the target solution in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated solution is discharged from the first chamber and the diluted solution is discharged from the second chamber.

[0090] The pre-concentrated liquid has a higher pressure (hydrostatic pressure) than the auxiliary solution, i.e., in each of the multiple semipermeable membrane modules, the liquid in the first chamber (pre-concentrated liquid) has a higher pressure than the liquid in the second chamber (auxiliary solution).

[0091] Because the pre-concentrated liquid has a higher pressure than the auxiliary solution, in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the pre-concentrated liquid in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated liquid is discharged from the first chamber and the diluted liquid, which is the diluted auxiliary solution, is discharged from the second chamber.

[0092] Here, the pressure of the target solution is increased by a pre-stage pressurizing device, such as a high-pressure pump or a pressure adjusting valve.

[0093] The high-pressure pump 53 is a device that can pressurize the target solution and send it into the first pre-stage chamber. The high-pressure pump 53 is provided upstream of at least one reverse osmosis module. For example, in FIG. 13 , the high-pressure pump 53 is provided upstream of the first pre-stage chamber 41.

[0094] The pressure regulating valve 54 is a device that can regulate the pressure in at least one reverse osmosis membrane module. At least one pressure regulating valve 54 is provided in the concentration system. For example, in FIG. 14 , the pressure regulating valve 54 is provided between the first upstream chamber 41 and the first chamber 11. For example, the pressure regulating valve 54 may be provided upstream of the first upstream chamber 41.

[0095] The upstream pressurizing device may be at least one, or may be multiple, in the concentration system. Note that the upstream pressurizing device may be a device other than those described above, such as a device that pressurizes the liquid in the upstream first chamber from outside the reverse osmosis module.

[0096] The concentration system includes at least one selected from the group consisting of a preconcentrated liquid measuring device 63 and a permeated liquid measuring device 64, and a pre-adjuster. The pre-adjuster includes at least one selected from the group consisting of a preconcentrated liquid adjusting device 73 and a permeated liquid adjusting device 74. Note that the pre-adjusters may be integrated into the entire concentration system.

[0097] 13 and 14 , the preconcentrated liquid measuring device 63 is provided in the preconcentration flow path (downstream of the first preconcentration chamber 41 of the reverse osmosis module 4 and upstream of the first chamber 11 of the semipermeable membrane module 1). The preconcentrated liquid measuring device 63 measures at least one parameter selected from the group consisting of the flow rate and concentration of the preconcentrated liquid. The preconcentrated liquid measuring device 63, the preconcentrated liquid adjuster 73, and the preconcentrated liquid pressurizing device are electrically connected. The preconcentrated liquid adjuster 73 controls the preconcentrated liquid pressurizing device so that the measurement value of the preconcentrated liquid measuring device 63 (at least one parameter selected from the group consisting of the flow rate and concentration of the preconcentrated liquid) falls within a predetermined range.

[0098] When the upstream pressurizing device is the high-pressure pump 53, the preconcentrate adjuster 73 controls the frequency (number of rotations) of the high-pressure pump 53. For example, if the measurement value of the preconcentrate meter 63 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the preconcentrate adjuster 73 lowers the frequency of the high-pressure pump 53, thereby reducing the pressure in the reverse osmosis module. For example, if the measurement value of the preconcentrate meter 63 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the preconcentrate adjuster 73 increases the frequency of the high-pressure pump 53, thereby increasing the pressure in the reverse osmosis module. In this way, the preconcentrate adjuster 73 controls the high-pressure pump 53 so that the measurement value of the preconcentrate meter 63 falls within a predetermined range.

[0099] When the upstream pressurizing device is the pressure regulating valve 54, the preconcentrated liquid adjuster 73 controls the aperture of the pressure regulating valve 54. For example, when the measurement value of the preconcentrated liquid measuring device 63 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the preconcentrated liquid adjuster 73 increases the aperture of the pressure regulating valve 54 to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the preconcentrated liquid measuring device 63 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the preconcentrated liquid adjuster 73 decreases the aperture of the pressure regulating valve 54 to increase the pressure in the semipermeable membrane module. In this way, the preconcentrated liquid adjuster 73 controls the pressure regulating valve 54 so that the measurement value of the preconcentrated liquid measuring device 63 falls within a predetermined range.

[0100] 15 and 16 , the permeate measuring device 64 is provided at the most downstream side of the permeate flow path (downstream of the first-stage second chamber 42 of the reverse osmosis module 4). The permeate measuring device 64 measures at least one selected from the group consisting of the flow rate and concentration of the permeate. The permeate measuring device 64, the permeate adjusting device 74, and the first-stage pressurizing device are electrically connected. The permeate adjusting device 74 controls the first-stage pressurizing device so that the measurement value of the permeate measuring device 64 (at least one selected from the group consisting of the flow rate and concentration of the permeate) falls within a predetermined range.

[0101] When the upstream pressurizing device is the high-pressure pump 53, the permeate adjuster 74 controls the frequency (rotation speed) of the high-pressure pump 53. For example, when the measurement value of the permeate meter 64 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the permeate adjuster 74 lowers the frequency of the high-pressure pump 53 to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the permeate meter 64 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the permeate adjuster 74 increases the frequency of the high-pressure pump 53 to increase the pressure in the semipermeable membrane module. In this way, the permeate adjuster 74 controls the high-pressure pump 53 so that the measurement value of the permeate meter 64 falls within a predetermined range.

[0102] When the upstream pressurizing device is the pressure regulating valve 54, the permeate adjuster 74 controls the aperture of the pressure regulating valve 54. For example, when the measurement value of the permeate meter 64 is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the permeate adjuster 74 increases the aperture of the pressure regulating valve 54 to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the permeate meter 64 is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the permeate adjuster 74 decreases the aperture of the pressure regulating valve 54 to increase the pressure in the semipermeable membrane module. In this way, the permeate adjuster 74 controls the pressure regulating valve 52 so that the measurement value of the permeate meter 64 falls within a predetermined range.

[0103] (Embodiment 4) Figures 17 to 24 are diagrams schematically showing the configuration of a concentration system according to another embodiment of the present invention. The concentration system according to this embodiment is a multistage concentration system (membrane separation system). Note that in Figures 17 to 24, one reverse osmosis module 4 is depicted as the reverse osmosis module, and three semipermeable membrane modules 1, 2, and 3 are depicted as the multiple semipermeable membrane modules. The multiple semipermeable membrane modules may be any number of semipermeable membrane modules, for example, two or more. Furthermore, although one reverse osmosis module (reverse osmosis module 4) is depicted in Figures 17 to 24, multiple (n) reverse osmosis modules may be provided.

[0104] The reverse osmosis module 4 has a reverse osmosis membrane 4A and a first front-stage chamber 41 and a second front-stage chamber 42 separated by the reverse osmosis membrane 4A.

[0105] A pre-concentration flow path is provided, which is formed by connecting the pre-stage first chamber 41 of the reverse osmosis module 4 and the first chamber 11 of the most upstream semipermeable membrane module 1 of the multiple semipermeable membrane modules. That is, the pre-concentration flow path is made up of the pre-stage first chamber 41, the first chamber 11, and a flow path connecting them.

[0106] A permeate flow path is provided which is connected to the second front chamber 42 of the reverse osmosis module 4 .

[0107] In the reverse osmosis module 4, the target solution is pressurized at high pressure, causing the solvent (water, etc.) contained in the target solution in the first upstream chamber 41 to migrate through the reverse osmosis membrane 4A into the second upstream chamber 42, and the concentrated target solution, a pre-concentrated liquid, is discharged from the first upstream chamber 41, and the permeated liquid is discharged from the second upstream chamber 42.

[0108] Each of the plurality of semipermeable membrane modules 1, 2, 3 has a semipermeable membrane 1A, 2A, 3A, and a first chamber 11, 21, 31 and a second chamber 12, 22, 32 partitioned by the semipermeable membrane.

[0109] A concentration flow path is provided in which the first chambers 11, 21, 31 of multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the concentration flow path is composed of the first chambers 11, 21, 31 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules, the first chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the first chambers may be connected in parallel.

[0110] A dilution flow path is provided in which the second chambers 12, 22, 32 of the multiple semipermeable membrane modules 1, 2, 3 are connected. That is, the dilution flow path is composed of the second chambers 12, 22, 32 and a flow path connecting them. In at least some of the multiple semipermeable membrane modules 1, 2, 3, the second chambers are preferably connected in series. In some of the multiple semipermeable membrane modules, the second chambers may be connected in parallel.

[0111] A pre-concentrated liquid is passed through the concentration flow path. The pre-concentrated liquid flows through the first chamber 11 of the semipermeable membrane module 1, the first chamber 21 of the semipermeable membrane module 2, and the first chamber 31 of the semipermeable membrane module 3 in this order.

[0112] An auxiliary solution having osmotic pressure is flowed through the dilution flow path. The auxiliary solution is flowed in the order of the second chamber 32 of the semipermeable membrane module 3, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 12 of the semipermeable membrane module 1. That is, the auxiliary solution is flowed in the reverse order of the target solution when the semipermeable membrane modules are connected. However, the auxiliary solution is not limited to the embodiments shown in Figures 17 to 24, and may be flowed in the order of the second chamber 12 of the semipermeable membrane module 1, the second chamber 22 of the semipermeable membrane module 2, and the second chamber 32 of the semipermeable membrane module 3.

[0113] In each semipermeable membrane module, the flow directions on both sides of the semipermeable membrane (in the first and second chambers) may be in any direction, and may be opposite directions (counterflow system) or parallel directions (parallel flow system).

[0114] In each of the multiple semipermeable membrane modules, the target solution has a higher pressure than the auxiliary solution, so that in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the target solution in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated solution is discharged from the first chamber and the diluted solution is discharged from the second chamber.

[0115] The pre-concentrated liquid has a higher pressure (hydrostatic pressure) than the auxiliary solution, i.e., in each of the multiple semipermeable membrane modules, the liquid in the first chamber (pre-concentrated liquid) has a higher pressure than the liquid in the second chamber (auxiliary solution).

[0116] Because the pre-concentrated liquid has a higher pressure than the auxiliary solution, in each of the multiple semipermeable membrane modules, the solvent (water, etc.) contained in the pre-concentrated liquid in the first chamber migrates through the semipermeable membrane to the auxiliary solution in the second chamber, and the concentrated liquid is discharged from the first chamber and the diluted liquid, which is the diluted auxiliary solution, is discharged from the second chamber.

[0117] Here, the target solution is pressurized by a pre-stage pressurizing device. Examples of the pre-stage pressurizing device include a high-pressure pump and a pressure regulating valve. The pre-concentrated solution is also pressurized by a pressurizing device. The pressurizing device used is the same as the pre-stage pressurizing device. In this embodiment, the high-pressure pump serving as the pressurizing device is referred to as the "first high-pressure pump," the pressure regulating valve serving as the pressurizing device is referred to as the "first pressure regulating valve," the high-pressure pump serving as the pre-stage pressurizing device is referred to as the "second high-pressure pump," and the pressure regulating valve serving as the pre-stage pressurizing device is referred to as the "second pressure regulating valve." The first and second high-pressure pumps are collectively referred to as the "high-pressure pump," and the first and second pressure regulating valves are collectively referred to as the "pressure regulating valve."

[0118] The first high-pressure pump 51 (second high-pressure pump 53) is a device that can pressurize the pre-concentrated solution (target solution) and pump it into the first chamber (first chamber at the front stage). The first high-pressure pump 51 (second high-pressure pump 53) is provided upstream of at least one of the first chambers of the multiple semipermeable membrane modules (upstream of at least one reverse osmosis module). For example, in FIG. 17 , the first high-pressure pump 51 (second high-pressure pump 53) is provided upstream of the first chamber 11 (upstream of the first chamber at the front stage 41). For example, the first high-pressure pump 51 may be provided between the first chamber 11 and the first chamber 21, or between the first chamber 21 and the first chamber 31.

[0119] The first pressure regulating valve 52 (second pressure regulating valve 54) is a device capable of regulating the pressure in at least one of the multiple semipermeable membrane modules (at least one reverse osmosis membrane module). At least one first pressure regulating valve 52 (second pressure regulating valve 54) is provided in the concentration system. For example, in FIG. 18 , the first pressure regulating valve 52 (second pressure regulating valve 54) is provided between the first chamber 11 and the first chamber 21 (between the upstream first chamber 41 and the first chamber 11). For example, the first pressure regulating valve 52 may be provided upstream of the upstream first chamber 41 and the first chamber 11, or may be provided between the first chamber 21 and the first chamber 31. For example, the second pressure regulating valve 54 may be provided upstream of the upstream first chamber 41.

[0120] The upstream pressurizing device and the pressurizing device may be provided in the concentration system at least one at a time, or may be provided in multiple numbers. Note that the upstream pressurizing device and the pressurizing device may be devices other than those described above, for example, devices that pressurize the liquid in the upstream first chamber from outside the reverse osmosis module and the liquid in the first chamber from outside the semipermeable membrane module.

[0121] The concentration system includes at least one selected from the group consisting of a concentrate measuring device 61 and an auxiliary solution measuring device 62, and an adjuster. The adjuster includes at least one selected from the group consisting of a concentrate adjuster 71 and an auxiliary solution adjuster 72. The concentration system includes at least one selected from the group consisting of a pre-concentrated solution measuring device 63 and a permeated solution measuring device 64, and an upstream adjuster. The upstream adjuster includes at least one selected from the group consisting of a pre-concentrated solution adjuster 73 and a permeated solution adjuster 74. Note that the adjusters, upstream adjusters, and the adjusters and upstream adjusters may be integrated into the entire concentration system.

[0122] 17 and 18 , the concentrated liquid measuring device 61 is provided on the most downstream side of the concentration flow path (downstream of the first chamber 31 of the semipermeable membrane module 3), and the pre-concentrated liquid measuring device 63 is provided on the upstream concentration flow path (downstream of the upstream first chamber 41 of the reverse osmosis module 4 and upstream of the first chamber 11 of the semipermeable membrane module 1). The concentrated liquid measuring device 61 measures at least one parameter selected from the group consisting of the flow rate and concentration of the concentrated liquid. The pre-concentrated liquid measuring device 61, the concentrated liquid adjuster 71, and the pressurizing device are electrically connected. The pre-concentrated liquid measuring device 63, the pre-concentrated liquid adjuster 73, and the upstream pressurizing device are electrically connected. The concentrated liquid adjuster 71 controls the pressurizing device so that the measurement value of the concentrated liquid measuring device 61 (at least one parameter selected from the group consisting of the flow rate and concentration of the concentrated liquid) falls within a predetermined range. The pre-concentrated liquid adjuster 73 controls the front-stage pressurizing device so that the measurement value of the pre-concentrated liquid measuring device 63 (at least one selected from the group consisting of the flow rate and concentration of the pre-concentrated liquid) falls within a predetermined range.

[0123] When the pressurizing device (pre-stage pressurizing device) is the first high-pressure pump 51 (second high-pressure pump 53), the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) controls the frequency (rotation speed) of the first high-pressure pump 51 (second high-pressure pump 53). For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) lowers the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to reduce the pressure in the semipermeable membrane module (reverse osmosis module). For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) increases the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to increase the pressure in the semipermeable membrane module (reverse osmosis module). In this way, the first high-pressure pump 51 (second high-pressure pump 53) is controlled by the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) so that the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is within a specified range.

[0124] When the pressurizing device (pre-stage pressurizing device) is the first pressure regulating valve 52 (second pressure regulating valve 54), the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) controls the aperture of the pressure regulating valve 52. For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is sufficiently concentrated, and the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) increases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the concentrated liquid meter 61 (pre-concentrated liquid meter 63) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is not sufficiently concentrated, and the concentrated liquid regulator 71 (pre-concentrated liquid regulator 73) decreases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to increase the pressure in the semipermeable membrane module. In this way, the first pressure regulating valve 52 (second pressure regulating valve 54) is controlled by the concentrated liquid adjuster 71 (pre-concentrated liquid adjuster 73) so that the measurement value of the concentrated liquid measuring instrument 61 (pre-concentrated liquid measuring instrument 63) is within a predetermined range.

[0125] 19 and 20 , the auxiliary solution measuring device 62 is provided at the most downstream side of the dilution flow path (downstream of the second chamber 12 of the semipermeable membrane module 1), and the permeate measuring device 64 is provided at the most downstream side of the permeation flow path (downstream of the upstream second chamber 42 of the reverse osmosis module 4). The auxiliary solution measuring device 62 measures at least one parameter selected from the group consisting of the flow rate and concentration of the auxiliary solution. The permeate measuring device 64 measures at least one parameter selected from the group consisting of the flow rate and concentration of the permeate. The auxiliary solution measuring device 62, the auxiliary solution adjuster 72, and the pressurizing device are electrically connected. The permeate measuring device 64, the permeate adjuster 74, and the upstream pressurizing device are electrically connected. The auxiliary solution adjuster 72 controls the pressurizing device so that the measurement value of the auxiliary solution measuring device 62 (at least one parameter selected from the group consisting of the flow rate and concentration of the auxiliary solution) falls within a predetermined range. The permeate adjuster 74 controls the pre-stage pressurizing device so that the measurement value of the permeate measuring device 64 (at least one selected from the group consisting of the flow rate and concentration of the permeate) falls within a predetermined range.

[0126] When the pressurizing device (preceding stage pressurizing device) is the first high-pressure pump 51 (second high-pressure pump 53), the auxiliary solution adjuster 72 (permeate adjuster 74) controls the frequency (rotation speed) of the first high-pressure pump 51 (second high-pressure pump 53). For example, when the measurement value of the auxiliary solution meter 62 (permeate adjuster 64) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution adjuster 72 (permeate adjuster 74) lowers the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 (permeate adjuster 64) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution adjuster 72 (permeate adjuster 74) increases the frequency of the first high-pressure pump 51 (second high-pressure pump 53) to increase the pressure in the semipermeable membrane module. In this way, the first high-pressure pump 51 (second high-pressure pump 53) is controlled by the auxiliary solution adjuster 72 (permeate adjuster 74) so ​​that the measurement value of the auxiliary solution meter 62 (permeate meter 64) falls within a predetermined range.

[0127] When the pressurizing device (pre-stage pressurizing device) is the first pressure regulating valve 52 (second pressure regulating valve 54), the auxiliary solution regulator 72 (permeate regulator 74) controls the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54). For example, when the measurement value of the auxiliary solution meter 62 (permeate meter 64) is higher than the upper limit flow rate or lower than the lower limit concentration, it is determined that the target solution is sufficiently concentrated, and the auxiliary solution regulator 72 (permeate regulator 74) increases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to reduce the pressure in the semipermeable membrane module. For example, when the measurement value of the auxiliary solution meter 62 (permeate meter 64) is lower than the lower limit flow rate or higher than the upper limit concentration, it is determined that the target solution is not sufficiently concentrated, and the auxiliary solution regulator 72 (permeate regulator 74) decreases the aperture of the first pressure regulating valve 52 (second pressure regulating valve 54) to increase the pressure in the semipermeable membrane module. In this way, the pressure regulating valve 52 is controlled by the auxiliary solution adjuster 72 (permeate adjuster 74) so ​​that the measurement value of the auxiliary solution meter 62 (permeate meter 64) falls within a predetermined range.

[0128] Figures 21 to 24 show a concentration system that is composed of a combination of the arrangement and control points of each instrument, each measuring device, and each regulator in multiple semipermeable membrane modules described in Figures 17 to 20, and the arrangement and control points of each instrument, each measuring device, and each regulator in at least one reverse osmosis module.

[0129] In the concentration system shown in Figure 21, the concentrate adjuster 71 controls the first high-pressure pump 51 so that the measurement value of the concentrate measuring instrument 61 falls within a predetermined range, and the permeate adjuster 74 controls the second high-pressure pump 53 so that the measurement value of the permeate measuring instrument 64 falls within a predetermined range. In the concentration system shown in Figure 22, the concentrate adjuster 71 controls the first pressure regulating valve 52 so that the measurement value of the concentrate measuring instrument 61 falls within a predetermined range, and the permeate adjuster 74 controls the second pressure regulating valve 54 so that the measurement value of the permeate measuring instrument 64 falls within a predetermined range. In the concentration system shown in Figure 23, the auxiliary solution adjuster 72 controls the first high-pressure pump 51 so that the measurement value of the auxiliary solution measuring instrument 62 falls within a predetermined range, and the pre-concentrate adjuster 73 controls the second high-pressure pump 53 so that the measurement value of the pre-concentrate measuring instrument 63 falls within a predetermined range. In the concentration system shown in Figure 24, the auxiliary solution adjuster 72 controls the first pressure regulating valve 52 so that the measurement value of the auxiliary solution measuring device 62 falls within a predetermined range, and the pre-concentrated liquid adjuster 73 controls the second pressure regulating valve 54 so that the measurement value of the pre-concentrated liquid measuring device 63 falls within a predetermined range.

[0130] In the concentration system of this embodiment, the arrangement and control locations of the instruments, measuring instruments, and regulators in the multiple semipermeable membrane modules may be different from the arrangement and control locations of the instruments, measuring instruments, and regulators in at least one reverse osmosis module. For example, the concentration system may be configured to control the frequency of the first high-pressure pump in the multiple semipermeable membrane modules and control the second pressure regulation valve in at least one reverse osmosis module. For example, the concentration system may be configured to control the frequency of the first pressure regulation valve in the multiple semipermeable membrane modules and control the second high-pressure pump in at least one reverse osmosis module.

[0131] In the first to fourth embodiments, at least one selected from the group consisting of a flow meter and a concentration meter is used as each measuring instrument from the viewpoint of ease of control and accuracy. However, a pressure meter may be used instead of the flow meter and concentration meter to perform similar control.

[0132] According to the concentration systems of the first to fourth embodiments, when a solvent is separated from a target solution and concentrated by the OARO method or the BC method using a multistage concentration system (membrane separation system) including a plurality of semipermeable membrane modules, a concentrated solution at a predetermined flow rate or concentration can be stably obtained.

[0133] (Target Solution and Auxiliary Solution) The target solution and auxiliary solution are not particularly limited, and examples thereof include salt water (brine, seawater, brackish water, etc.), industrial wastewater, etc. The concentration system described above can be suitably used to further concentrate a target solution, particularly when the target solution is a highly concentrated (high osmotic pressure) solution such as brine.

[0134] The target solution or the like may be subjected to pretreatment to remove fine particles, microorganisms, scale components, etc. contained in the solution. As the pretreatment, various known pretreatments used in seawater desalination technology or the like can be carried out, and examples thereof include filtration using an NF membrane, UF membrane, MF membrane, etc., addition of sodium hypochlorite, addition of a coagulant, activated carbon adsorption treatment, ion exchange resin treatment, etc. Such pretreatment is preferably carried out before the target solution and auxiliary solution are supplied to the semipermeable membrane module.

[0135] Theoretically, membrane separation by the BC method is possible if the osmotic pressure difference (absolute value) between the target solution (liquid to be concentrated) flowing through the first chamber (high-pressure side) and the auxiliary solution (liquid to be diluted) flowing through the second chamber (low-pressure side) is smaller than the pressure of the target solution. In this case, it is preferable that the difference between the osmotic pressures of the target solution and the auxiliary solution be 30% or less of the pressure of the target solution.

[0136] The auxiliary solution is not particularly limited as long as it is a liquid having osmotic pressure, but a portion of the target solution (concentrate) concentrated in the concentration flow paths of multiple semipermeable membrane modules may be used as the auxiliary solution in multiple semipermeable membrane modules. For example, in FIG. 1, a portion of the target solution discharged from at least one of the first chambers 11, 21, and 31 of multiple semipermeable membrane modules 1, 2, and 3 may be used as the auxiliary solution. Also, in FIG. 5, a portion of the target solution (concentrate) discharged from at least one of the first chambers 11, 21, and 31 of multiple semipermeable membrane modules 1, 2, and 3, or a portion of the target solution (pre-concentrate) discharged from the first chamber 41 of the reverse osmosis module 4 may be used as the auxiliary solution. Note that a flow path for supplying a portion of the concentrate as an auxiliary solution to the dilution flow path (the second chamber of the semipermeable membrane module) is preferably provided with a mechanism (not shown) for reducing the pressure of the liquid. Such mechanisms include devices such as automatic control valves that maintain high pressure on the upstream side and reduce pressure on the downstream side, and energy recovery devices that have a mechanism for recovering energy from pressurized supply liquid and converting it into auxiliary energy for driving a pump or the like.

[0137] Alternatively, a dilute solution may be supplied to the concentration flow path together with the target solution, and the target solution may be concentrated to obtain a concentrate, which may then be used as an auxiliary solution, and the auxiliary solution may be diluted to obtain a dilute solution, which may then be supplied to the concentration flow path together with the target solution.

[0138] In this way, when the target solution is circulated in the concentration system, the recovery rate of the concentrated liquid (target component) from the target solution can be increased.

[0139] In addition, when the diluent and the target solution are combined in a tank and the resulting combined solution is supplied to the concentration flow path, the liquids of different concentrations mix together in the tank, creating a concentration gradient in the tank, which can cause the concentration of the liquid supplied to the concentration flow path to become unstable. For this reason, it is preferable that the diluent and the target solution are thoroughly mixed in the tank. Here, for example, by returning a portion of the liquid sent from the pump to the tank to stir the liquid in the tank, the diluent and the target solution can be thoroughly mixed without the need for a separate stirring device.

[0140] Furthermore, a temperature regulator such as a heat exchanger may be provided to ensure a stable temperature when the temperature of the target solution rises due to heat generated by the pump or when the temperature of the target solution itself becomes high or low. In particular, when the target solution circulates through a concentration system, the liquid temperature may gradually rise and exceed the heat resistance temperature of the semipermeable membrane, or in the case of a target solution whose viscosity changes significantly depending on the liquid temperature, the amount of permeate water and the amount of auxiliary solution passing through may be affected, and the desired concentration performance may not be achieved. For this reason, it is particularly important to provide a temperature regulator in a concentration system in which the target solution circulates.

[0141] (Multiple Semipermeable Membrane Modules) In a concentration process (membrane separation process) by the OARO method or the BC method using multiple semipermeable membrane modules, osmotic pressure acting in the opposite direction to the direction in which the solvent moves from the first chamber to the second chamber is unlikely to occur, so concentration can be carried out at a lower pressure (pump pressure) than in the RO method. Therefore, in the concentration system of this embodiment, which mainly performs concentration by the OARO method, the power consumption of pumps, etc. can be reduced, and the energy efficiency of concentration can be improved.

[0142] In RO concentration, the osmotic pressure of the concentrated target solution on one side of the semipermeable membrane is generated in the opposite direction to the pump pressure. Therefore, when the osmotic pressure of the concentrated target solution reaches the pump pressure, the pump pressure and the osmotic pressure of the target solution acting in the opposite direction are balanced, preventing further water from passing through the semipermeable membrane and preventing concentration.

[0143] In contrast, in membrane separation treatment (concentration method) using the OARO method or the BC method, the difference in concentration (osmotic pressure difference) between the liquids supplied to the first and second compartments in each semipermeable membrane module is small, and the osmotic pressure that inhibits concentration treatment as in the RO method is unlikely to occur. Therefore, in a concentration system using the OARO method or the BC method, the final concentration of the target solution can be increased more than in a concentration system using only the RO method. In principle, it is thought that the target solution can be concentrated to a saturated concentration.

[0144] In this embodiment, as in the multistage concentration systems shown in FIG. 2 of Patent Document 1 (WO 2018 / 084246) and FIG. 4 of Patent Document 2 (JP 2019-188330 A), one or more other semipermeable membrane modules may be further connected in parallel to each of a plurality of semipermeable membrane modules 1a, 1b, 1x, and 1y connected in series.

[0145] As shown in FIG. 2 of Patent Document 1 and FIG. 4 of Patent Document 2, it is preferable to have a larger number of semipermeable membrane modules connected in parallel toward the upstream side of the concentration flow path (downstream side of the dilution flow path). In this case, it is thought that the cross-sectional area of ​​the flow path increases downstream of the dilution flow path, reducing the flow resistance. Because water migrates from the first chamber (concentration flow path side) to the second chamber (dilution flow path side) through a semipermeable membrane, the amount of flow increases toward the downstream side of the dilution flow path, and the flow resistance tends to increase. Therefore, reducing the flow resistance downstream of the dilution flow path is effective in reducing the flow resistance of the dilution flow path throughout the entire concentration system.

[0146] Furthermore, in a multistage concentration system such as that of this embodiment, the target solution flowing through the first chamber (concentration flow path) is sequentially concentrated, and as the concentration progresses, the flow rate of the target solution decreases. If the flow rate per semipermeable membrane module decreases, the concentration efficiency decreases. In order to suppress such a decrease in the flow rate of the target solution downstream of the concentration flow path, it is preferable that the number of semipermeable membrane modules connected in parallel is greater upstream of the concentration flow path.

[0147] In addition, in the concentration system of this embodiment, the configuration disclosed in Japanese Patent Application Laid-Open No. 2022-011711 can be applied.

[0148] (Semipermeable Membrane) Examples of the semipermeable membrane used in this embodiment include semipermeable membranes called reverse osmosis membranes (RO membranes), forward osmosis membranes (FO membranes), nanofiltration membranes (NF membranes), and ultrafiltration membranes (UF membranes). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane. When a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane is used as the semipermeable membrane, the pressure of the liquid (target solution) in the first chamber is preferably 0.5 to 10.0 MPa.

[0149] Typically, RO membranes and FO membranes have pore sizes of approximately 2 nm or less, and UF membranes have pore sizes of approximately 2 to 100 nm. NF membranes have a relatively low rejection rate for ions and salts compared to RO membranes, and typically have pore sizes of approximately 1 to 2 nm. When an RO membrane, FO membrane, or NF membrane is used as the semipermeable membrane, the salt rejection rate of the RO membrane, FO membrane, or NF membrane is preferably 90% or higher.

[0150] The material constituting the semipermeable membrane is not particularly limited, but examples thereof include cellulose-based resins, polysulfone-based resins, polyamide-based resins, etc. The semipermeable membrane is preferably made of a material containing at least one of a cellulose-based resin and a polysulfone-based resin.

[0151] The cellulose-based resin is preferably a cellulose acetate-based resin. Cellulose acetate-based resins are resistant to chlorine, a disinfectant, and have the characteristic of being able to inhibit the growth of microorganisms. The cellulose acetate-based resin is preferably cellulose acetate, and from the viewpoint of durability, more preferably cellulose triacetate.

[0152] The polysulfone-based resin is preferably a polyethersulfone-based resin. The polyethersulfone-based resin is preferably a sulfonated polyethersulfone.

[0153] 1 to 4, the semipermeable membranes of the semipermeable membrane modules are depicted as flat membranes for simplification, but the shape of the semipermeable membrane is not particularly limited. The semipermeable membrane may be, for example, a flat membrane such as a spiral membrane (spiral-type semipermeable membrane) or a hollow fiber membrane (hollow fiber-type semipermeable membrane), but is preferably a hollow fiber membrane. Hollow fiber membranes are advantageous in that they have a smaller membrane thickness than flat membranes and can further increase the membrane area per module, thereby increasing the permeation efficiency.

[0154] In each of the multiple semipermeable membrane modules, it is preferable that the first chamber is outside the hollow fiber membrane and the second chamber is inside (hollow portion) of the hollow fiber membrane, because even if the solution flowing inside the hollow fiber membrane is pressurized, the pressure loss may become large and it may be difficult to apply pressure sufficiently, and further, although hollow fiber membranes generally easily maintain their structure against external pressure, high internal pressure may damage the hollow fiber membrane.

[0155] A specific example of a hollow fiber membrane is a membrane with a single layer structure composed entirely of a cellulose-based resin. However, the single layer structure referred to here does not necessarily mean a membrane with a uniform layer throughout; for example, it may be a membrane that is non-uniform in the thickness direction. Specifically, the membrane may have a dense layer on the outer surface, which serves as a separation active layer that essentially determines the pore size of the hollow fiber membrane, and the inner surface side may have a lower density than the dense layer. Since the dense layer essentially serves as a separation active layer that determines the pore size of the hollow fiber membrane, when the solution outside the hollow fiber membrane is pressurized, having a dense layer on the outer surface of the hollow fiber membrane allows for more accurate control of the movement of molecules from the outside to the inside of the hollow fiber membrane.

[0156] Another specific example of a hollow fiber membrane is a two-layer membrane having a dense layer of a polyphenylene resin (e.g., sulfonated polyethersulfone) on the outer surface of a support layer (e.g., a layer made of polyphenylene oxide). Another example is a two-layer membrane having a dense layer of a polyamide resin on the outer surface of a support layer (e.g., a layer made of polysulfone or polyethersulfone).

[0157] The above-disclosed embodiments, modifications, and examples are all illustrative and not restrictive. Furthermore, appropriate combinations of the embodiments, modifications, and examples are also included within the scope of the present invention. In other words, the technical scope of the present invention is defined by the claims, and includes all changes, modifications, substitutions, etc. within the meaning and scope of the claims.

[0158] The present invention achieves stable production of a concentrated solution at a predetermined flow rate or concentration when separating and concentrating a solvent from a target solution by the OARO method or the BC method using a multistage concentration system (membrane separation system) including multiple semipermeable membrane modules, thereby making a significant contribution to the industrial world.

[0159] 1, 2, 3 Semipermeable membrane module, 1A, 2A, 3A Semipermeable membrane, 4 Reverse osmosis module, 4A Reverse osmosis membrane, 5 Concentration flow path, 6 Dilution flow path, 7 Pre-stage concentration flow path, 8 Permeation flow path, 11, 21, 31 First chamber, 12, 22, 32 Second chamber, 41 Pre-stage first chamber, 42 Pre-stage second chamber, 51 High-pressure pump (first high-pressure pump), 52 Pressure adjustment valve (first pressure adjustment valve), 53 High-pressure pump (second high-pressure pump), 54 Pressure adjustment valve (second pressure adjustment valve), 61 Concentrate measuring device, 62 Auxiliary solution measuring device, 63 Pre-concentrate measuring device, 64 Permeate measuring device, 71 Concentrate adjuster, 72 Auxiliary solution adjuster, 73 Pre-concentrate adjuster, 74 Permeate adjuster.

Claims

1. A concentration system for separating a solvent from a target solution containing a target component to obtain a concentrated solution in which the target component is concentrated, comprising: a plurality of semipermeable membrane modules; and a pressurizing device for pressurizing the target solution, wherein each of the plurality of semipermeable membrane modules has a semipermeable membrane and a first chamber and a second chamber separated by the semipermeable membrane, a concentration flow path is provided to which the first chambers of the plurality of semipermeable membrane modules are connected, and a dilution flow path is provided to which the second chambers of the plurality of semipermeable membrane modules are connected, the target solution is flowed through the concentration flow path, and an auxiliary solution having an osmotic pressure is flowed through the dilution flow path, the concentration system comprises at least one selected from the group consisting of a concentrated solution meter and an auxiliary solution meter, and an adjuster, wherein the adjuster includes at least one selected from the group consisting of a concentrated solution adjuster and an auxiliary solution adjuster, the concentrated solution meter is provided downstream of the concentration flow path, and the auxiliary solution meter is provided downstream of the dilution flow path, A concentration system, wherein the concentrated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid, the auxiliary solution measuring device measures at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution, the concentrated liquid adjuster controls the pressurizing device so that the measurement value of the concentrated liquid measuring device falls within a predetermined range, and the auxiliary solution adjuster controls the pressurizing device so that the measurement value of the auxiliary solution measuring device falls within a predetermined range.

2. The concentration system according to claim 1, wherein the pressurizing device is a high-pressure pump for pumping the target solution, and the regulator controls the frequency of the high-pressure pump.

3. The concentration system according to claim 1, wherein the pressurizing device is a pressure regulating valve for regulating the pressure in at least one of the plurality of semipermeable membrane modules, and the regulator controls the pressure regulating valve.

4. A system comprising at least one reverse osmosis module upstream of the plurality of semipermeable membrane modules and a pre-stage pressurizing device for pressurizing the target solution, wherein the at least one reverse osmosis module has a reverse osmosis membrane and a first pre-stage chamber and a second pre-stage chamber separated by the reverse osmosis membrane, wherein a pre-stage concentration flow path is provided connecting the first pre-stage chamber of the at least one reverse osmosis module and the first chamber of the semipermeable membrane module located most upstream of the plurality of semipermeable membrane modules, wherein the solvent contained in the target solution supplied to the first pre-stage chamber at a pressure higher than that of the second pre-stage chamber migrates through the reverse osmosis membrane into the second pre-stage chamber, and the target solution is diluted, thereby discharging a pre-concentrated solution from the first pre-stage chamber and obtaining a permeated solution from the second pre-stage chamber, and wherein a permeated flow path is provided for discharging the permeated solution, wherein the concentration system comprises at least one selected from the group consisting of a pre-concentrated solution meter and a permeated solution meter, and a pre-stage adjuster, 4. The concentration system according to claim 1, wherein the pre-stage adjuster includes at least one selected from the group consisting of a pre-concentrated liquid adjuster and a permeated liquid adjuster, the pre-concentrated liquid measuring device is provided in the pre-concentration flow path, the permeated liquid measuring device is provided downstream of the permeation flow path, the pre-concentrated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the pre-concentrated liquid, the permeated liquid measuring device measures at least one selected from the group consisting of the flow rate and concentration of the permeated liquid, the pre-concentrated liquid adjuster controls the pre-stage pressurizing device so that the measurement value of the pre-concentrated liquid measuring device falls within a predetermined range, and the permeated liquid adjuster controls the pre-stage pressurizing device so that the measurement value of the permeated liquid measuring device falls within a predetermined range.

5. The concentration system according to claim 4, wherein the pre-stage pressurizing device is a high-pressure pump for pumping the target solution, and the pre-stage regulator controls the frequency of the high-pressure pump.

6. The concentration system of claim 4, wherein the pre-pressurizing device is a pressure regulating valve for regulating the pressure in the at least one reverse osmosis module, and the pre-regulator controls the pressure regulating valve.

7. The concentration system according to any one of claims 1 to 6, wherein the semipermeable membrane is a hollow fiber membrane.

8. The concentration system according to any one of claims 4 to 6, wherein the reverse osmosis membrane is a hollow fiber membrane.

9. A concentration system for separating a solvent from a target solution containing a target component to obtain a concentrated solution in which the target component is concentrated, comprising at least one reverse osmosis module, a plurality of semipermeable membrane modules, and a front-stage pressurizing device for pressurizing the target solution, wherein the at least one reverse osmosis module has a reverse osmosis membrane and a first front-stage chamber and a second front-stage chamber separated by the reverse osmosis membrane, and each of the plurality of semipermeable membrane modules has a semipermeable membrane and a first chamber and a second chamber separated by the semipermeable membrane, a front-stage concentration flow path is provided that connects the first front-stage chamber of the at least one reverse osmosis module to the first chamber of the semipermeable membrane module that is most upstream of the plurality of semipermeable membrane modules, a concentration flow path is provided that connects the first chambers of the plurality of semipermeable membrane modules, and a dilution flow path is provided that connects the second chambers of the plurality of semipermeable membrane modules, the solvent contained in the target solution supplied to the first upstream chamber at a pressure higher than that of the second upstream chamber migrates through the reverse osmosis membrane into the second upstream chamber, diluting the target solution and thereby discharging a pre-concentrated solution from the first upstream chamber and obtaining a permeated solution from the second upstream chamber; a permeation flow path is provided for discharging the permeated solution; the pre-concentrated solution is caused to flow through the concentration flow path; and an auxiliary solution having an osmotic pressure is caused to flow through the second chamber; the concentration system comprises at least one selected from the group consisting of a pre-concentrated solution meter and a permeated solution meter, and a pre-adjuster; the pre-adjuster includes at least one selected from the group consisting of a pre-concentrated solution adjuster and a permeated solution adjuster; the pre-concentrated solution meter is provided in the pre-concentration flow path; and the permeated solution meter is provided downstream of the permeation flow path; the pre-concentrated solution meter measures at least one selected from the group consisting of a flow rate and a concentration of the pre-concentrated solution; and the permeated solution meter measures at least one selected from the group consisting of a flow rate and a concentration of the permeated solution. A concentration system in which the pre-concentrated liquid adjuster controls the upstream pressurizing device so that the measurement value of the pre-concentrated liquid measuring device falls within a predetermined range, and the permeated liquid adjuster controls the upstream pressurizing device so that the measurement value of the permeated liquid measuring device falls within a predetermined range.

10. The concentration system according to claim 9, wherein the pre-stage pressurizing device is a high-pressure pump for pumping the target solution, and the pre-stage regulator controls the frequency of the high-pressure pump.

11. The concentration system of claim 9, wherein the pre-pressurization device is a pressure regulating valve for regulating the pressure in the at least one reverse osmosis module, and the pre-regulator controls the pressure regulating valve.

12. A concentration system according to any one of claims 9 to 11, comprising a pressurizing device for pressurizing the pre-concentrated liquid, at least one selected from the group consisting of a concentrated liquid meter and an auxiliary solution meter, and an adjuster, wherein the adjuster includes at least one selected from the group consisting of a concentrated liquid adjuster and an auxiliary solution adjuster, the concentrated liquid meter is provided downstream of the concentration flow path, the auxiliary solution meter is provided downstream of the dilution flow path, the concentrated liquid meter measures at least one selected from the group consisting of the flow rate and concentration of the concentrated liquid, the auxiliary solution meter measures at least one selected from the group consisting of the flow rate and concentration of the auxiliary solution, the concentrated liquid adjuster controls the pressurizing device so that the measurement value of the concentrated liquid meter falls within a predetermined range, and the auxiliary solution adjuster controls the pressurizing device so that the measurement value of the auxiliary solution meter falls within a predetermined range.

13. The concentration system according to claim 12, wherein the pressurizing device is a high-pressure pump for pumping the pre-concentrated liquid, and the regulator controls the frequency of the high-pressure pump.

14. The concentration system according to claim 12, wherein the pressurizing device is a pressure regulating valve for regulating the pressure in at least one of the plurality of semipermeable membrane modules, and the regulator controls the pressure regulating valve.

15. The concentration system according to any one of claims 9 to 14, wherein the semipermeable membrane and the reverse osmosis membrane are hollow fiber membranes.

16. A concentration system according to any one of claims 1 to 15, wherein a portion of the concentrate is used as the auxiliary solution.

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