JP2024162818A - Concentration System - Google Patents

Abstract

The present invention provides a concentration system that increases the recovery rate of a target component contained in a target solution when separating and concentrating water from the target solution by brine concentration using a multi-stage membrane separation system including a plurality of semipermeable membrane modules.
[Solution] The concentration system includes a plurality of semipermeable membrane modules 1 to 4, a concentration flow path formed by connecting first chambers 11, 21, 31, 41 of the modules, and a dilution flow path formed by connecting second chambers 12, 22, 32, 42 of the plurality of semipermeable membrane modules, a target solution is flowed through the concentration flow path and an auxiliary solution having an osmotic pressure is flowed through the dilution flow path, and the target solution is concentrated as the target solution has a higher pressure than the auxiliary solution, and at least one of the concentration flow path and the dilution flow path includes switches 50a, 50b, 51a, 51b, etc. that switch the flow path so that at least one of the target solution and the auxiliary solution does not flow through at least one of the plurality of semipermeable membrane modules.
[Selected Figure] Figure 1

Description

The present invention relates to a concentration system.

For the purpose of reducing the energy required for desalination using reverse osmosis (RO), a membrane separation method (brine concentration) has been investigated 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 (concentrated liquid) from the first chamber and a diluted target solution (diluted liquid) from the second chamber.

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 multi-stage membrane separation system in which multiple semipermeable membrane modules are connected in series for brine concentration (BC).

International Publication No. 2018/084246 JP 2019-188330 A Special table 2018-515340 publication

In such a multi-stage membrane separation (concentration) system that includes multiple semipermeable membrane modules, the multiple semipermeable membrane modules must be periodically cleaned to prevent clogging of the semipermeable membranes. In addition, if it becomes difficult to restore the performance of the semipermeable membranes even after cleaning, the semipermeable membrane module must be replaced.

Here, in order to clean or replace the semipermeable membrane module, it is necessary to stop the operation of the concentration system or remove the semipermeable membrane module from the concentration system. This causes problems such as a decrease in the operating efficiency of the concentration system and increased effort in operation.

Therefore, the present invention aims to easily clean and replace semipermeable membrane modules in a multi-stage concentration system (membrane separation system) that includes multiple semipermeable membrane modules used to separate and concentrate water from a target solution by brine concentration (BC).

[1] 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:
A plurality of semipermeable membrane modules are provided,
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 in which the first chambers of the plurality of semipermeable membrane modules are connected to each other,
A dilution flow path is provided in which the second chambers of the plurality of semipermeable membrane modules are connected to each other,
The target solution is flowed through the concentration flow path,
An auxiliary solution having an osmotic pressure is caused to flow through the dilution flow path;
Since the target solution has a higher pressure than the auxiliary solution, in each of the plurality of semipermeable membrane modules, a solvent contained in the target solution in the first chamber is transferred to the auxiliary solution in the second chamber through the semipermeable membrane, and the target solution is concentrated to obtain the concentrated liquid;
At least one of the concentration flow path and the dilution flow path further includes a switch for switching the flow path so that the target solution and the auxiliary solution do not flow through at least one of the plurality of semipermeable membrane modules.
Concentration system.

[2] At least one of the concentration flow path and the dilution flow path is provided with a bypass flow path that directly connects the upstream side and downstream side of at least one of the plurality of semipermeable membrane modules,
The switch is a switch for switching the flow path to the bypass flow path.
The concentration system according to [1].

[3] The bypass flow path is provided in both the concentration flow path and the dilution flow path.
The concentration system according to [2].

[4] The apparatus further includes a reverse osmosis module having a reverse osmosis membrane and a first chamber and a second chamber separated by the reverse osmosis membrane,
In the reverse osmosis module, the target solution is supplied to the first chamber at a pressure higher than that of the second chamber, a solvent contained in the target solution in the first chamber permeates through the reverse osmosis membrane into the second chamber and the target solution is concentrated, the concentrated target solution is discharged from the first chamber, and a permeated liquid, which is the solvent that has permeated the reverse osmosis membrane, is discharged from the second chamber,
The target solution concentrated in the reverse osmosis module is supplied to the concentration flow path;
The switch is a switch for switching a flow path so as to flow the permeate through at least one of the plurality of semipermeable membrane modules.
The concentration system according to any one of [1] to [3].

[5] The concentration system according to any one of [1] to [4], in which a portion of the concentrated solution is used as the auxiliary solution.

[6] The concentration system according to any one of [1] to [5], further comprising a pressurizing device for pressurizing the target solution to a pressure higher than that of the auxiliary solution.

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

According to the present invention, in a multi-stage concentration system (membrane separation system) including multiple semipermeable membrane modules used to separate and concentrate water from a target solution by brine concentration (BC), the semipermeable membrane modules can be easily cleaned and replaced.

FIG. 1 is a schematic diagram showing an example of a concentration system according to an embodiment. FIG. 2 is a schematic diagram showing another state of the concentration system shown in FIG. 1 . FIG. 13 is a schematic diagram showing a modified example of the concentration system of the embodiment. FIG. 13 is a schematic diagram showing another modified example of the concentration system of the embodiment. FIG. 2 is a schematic diagram showing another example of a concentration system according to an embodiment. FIG. 6 is a schematic diagram showing another state of the concentration system shown in FIG. 5 .

Embodiments of the present invention will now be described with reference to the drawings. Note that in the drawings, the same reference numerals represent the same or corresponding parts.

<Concentration system>
The concentration system of the present embodiment is a system for obtaining a concentrated solution in which the target component is concentrated by separating a solvent from a target solution containing the target component.

1 and 2, the concentration system of this embodiment is a multi-stage concentration system (membrane separation system) including a plurality of semipermeable membrane modules 1, 2, 3, and 4.
Fig. 1 is a diagram showing a normal operating state in which the target solution is concentrated, and Fig. 2 is a diagram showing a temporary state in which the semipermeable membrane module is cleaned or replaced. Similarly, Fig. 5 is a diagram showing a normal operating state in which the target solution is concentrated, and Fig. 6 is a diagram showing a temporary state in which the semipermeable membrane module or the like is cleaned.
1, 2, 5 and 6, flow paths indicated by dotted lines indicate flow paths through which no liquid flows.
In FIG. 1, four semipermeable membrane modules 1, 2, 3, and 4 are depicted as the "plurality of semipermeable membrane modules", but the "plurality of semipermeable membrane modules" may be, for example, any number of semipermeable membrane modules greater than or equal to two.

Each of the multiple semipermeable membrane modules 1, 2, 3, 4 has a semipermeable membrane 10, 20, 30, 40, and a first chamber 11, 21, 31, 41 and a second chamber 12, 22, 32, 42 separated by the semipermeable membrane.

A concentration flow path is provided in which the first chambers 11, 21, 31, and 41 of multiple semipermeable membrane modules 1, 2, 3, and 4 are connected. That is, the concentration flow path is composed of the first chambers 11, 21, 31, and 41 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.

A dilution flow path is provided in which the second chambers 12, 22, 32, and 42 of the multiple semipermeable membrane modules 1, 2, 3, and 4 are connected. That is, the dilution flow path is composed of the second chambers 12, 22, 32, and 42 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.

The target solution is passed through the concentration flow path. The target solution flows through the first chamber 11 of semipermeable membrane module 1, the first chamber 21 of semipermeable membrane module 2, the first chamber 31 of semipermeable membrane module 3, and the first chamber 41 of semipermeable membrane module 4 in that order.

1, an auxiliary solution having an osmotic pressure is flowed through the dilution flow path. The auxiliary solution flows in the order of the second chamber 42 of the semipermeable membrane module 4, 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 flows in the reverse order to the target solution in the connection of the semipermeable membrane modules.
However, the auxiliary solution is not limited to the embodiment shown in FIG. 1, and may flow in the order of the second chamber 12 of the semipermeable membrane module 1, the second chamber 22 of the semipermeable membrane module 2, the second chamber 32 of the semipermeable membrane module 3, and the second chamber 42 of the semipermeable membrane module 4.

In each semipermeable membrane module, the flow direction of the liquid on either side of the semipermeable membrane (between the first and second chambers) may be in any direction, and may be in opposing directions (counterflow method) or in parallel directions (parallel flow method).

The target solution has a higher pressure (hydrostatic pressure) than the auxiliary solution. That is, 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).

The target solution is pressurized by a pressurizing device or the like. An example of the pressurizing device is a high-pressure pump (not shown) that can pressurize the target solution while sending it into the first chamber. The pressurizing device may be a device other than a pump, and may be, for example, a device that pressurizes the liquid in the first chamber from outside the semipermeable membrane module.

Because the target solution has a higher pressure than the auxiliary solution, in each of the multiple semipermeable membrane modules, the solvent (such as water) contained in the target solution in the first chamber transfers 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.

(Switch)
The concentration system of this embodiment further includes a switch that can switch the flow path in at least one of the concentration flow path and the dilution flow path so that neither the target solution nor the auxiliary solution flows through at least one of the multiple semipermeable membrane modules.
That is, in the concentration flow path, the switch can switch the flow path of the target solution so that the target solution does not flow into at least one first chamber of the plurality of semipermeable membrane modules, and in the dilution flow path, the switch can switch the flow path of the auxiliary solution so that the auxiliary solution does not flow into at least one second chamber of the plurality of semipermeable membrane modules.

The concentration system of this embodiment, which has such characteristics, can easily clean and replace the semipermeable membrane modules in a multi-stage concentration system (membrane separation system) that includes multiple semipermeable membrane modules used to separate and concentrate water from a target solution by brine concentration (BC).

The concentration system may include a switch in only one of the concentration flow path or the dilution flow path, in which case cleaning of only one of the concentration flow path or the dilution flow path in which the switch is provided can be easily performed.
When it is desired to clean both the concentrate flow path and the dilution flow path or to replace the semipermeable membrane module, the concentrate system is preferably provided with switches in both the concentrate flow path and the dilution flow path.

As an example of this embodiment, a bypass flow path (see dotted line in FIG. 1 ) that directly connects the upstream side and downstream side of at least one of the multiple semipermeable membrane modules (without passing through a semipermeable membrane module) may be provided in at least one of the concentration flow path and the dilution flow path. In this case, the above-mentioned switch may be a switch (S in FIG. 1 : symbols 50a to 57b) for switching the flow path to the bypass flow path.
In this case, by switching the flow path to the bypass flow path, at least one of the multiple semipermeable membrane modules can be cleaned or replaced without stopping the flow of at least one of the concentration flow path (target solution) and the dilution flow path (auxiliary solution).

For example, as shown in Fig. 1, a bypass flow path (dotted line portion) may be provided in both the concentration flow path and the dilution flow path for all the semipermeable membrane modules. Here, the above-mentioned switch is a switch for switching the flow path to the bypass flow path.
In this case, by switching the flow path to a bypass flow path, any of the multiple semipermeable membrane modules can be easily cleaned or replaced as necessary without stopping the flow in both the concentration flow path and the dilution flow path.
For example, as shown in FIG. 2, the flow path on the first chamber 31 side of the semipermeable membrane module 3 is switched from the concentration flow path to the bypass flow path by switches 52a, 52b, and similarly, the flow path on the second chamber 32 side of the semipermeable membrane module 3 is switched from the dilution flow path to the bypass flow path by switches 55a, 55b. This makes it possible to easily clean or replace only the semipermeable membrane module 3 out of the multiple semipermeable membrane modules, without stopping the flows in both the concentration flow path and the dilution flow path in the entire system.

3, for example, a flow path (a flow path indicated by a thin line in the figure in which a switching valve 72 is provided) for a cleaning liquid (such as a permeate liquid described later) may be provided so that the first chambers 11, 21, 31, and 41 of the semipermeable membrane modules 1, 2, 3, and 4 can be individually washed. In Fig. 3, the flow path for the cleaning liquid can be individually opened and closed by the switching valve 72.
The cleaning liquid may be tap water, pure water, a chemical cleaning liquid, etc., in addition to the permeate liquid described below. Therefore, a cleaning liquid other than the permeate liquid may be separately prepared or stored in the tank 7. A cleaning liquid may be supplied from a source other than the tank 7.
4, for example, a flow path (a flow path indicated by a thin line in the figure in which a switching valve 72 is provided) for a cleaning liquid (such as a permeate liquid described later) may be provided so that the first chambers 11, 21, 31, and 41 of the semipermeable membrane modules 1, 2, 3, and 4 can be individually cleaned. In Fig. 4, the flow path for the cleaning liquid can be individually opened and closed by the switching valve 72.
In addition, by switching the concentration flow path and the dilution flow path for any semipermeable membrane module to a bypass flow path (a flow path indicated by a dotted line in the figure) and instead opening the switching valve 72 to switch to a path through which the cleaning liquid flows, it is possible to supply only the cleaning liquid into any semipermeable membrane module. The destination of the cleaning liquid discharged from the semipermeable membrane module is not particularly limited, and it may be appropriately treated as industrial waste or reused as the target solution.
Both of the cleaning fluid flow paths shown in FIG. 3 and FIG. 4 may be provided.
By providing such a flow path for the cleaning liquid, any of the semipermeable membrane modules can be easily cleaned while the concentration system is operating.

As another example of this embodiment, the concentration system shown in FIG. 5 further includes a reverse osmosis module 9 having a reverse osmosis membrane 90 and a first chamber 91 and a second chamber 92 separated by the reverse osmosis membrane 90 .
In the reverse osmosis module 9, the target solution is supplied to the first chamber 91 at a higher pressure than the second chamber 92, and the solvent (such as water) contained in the target solution in the first chamber 91 permeates through the reverse osmosis membrane 90 into the second chamber 92 while the target solution is concentrated. The concentrated target solution is discharged from the first chamber 91, and the permeated liquid, which is the solvent that has permeated the reverse osmosis membrane, is discharged from the second chamber 92.
The target solution concentrated in the reverse osmosis module 9 is supplied to the concentration flow path (the first chamber 11 of the semipermeable membrane module 1).
The concentration system shown in FIG. 5 includes switches 61, 62, and 63 for switching the flow paths so that the permeate discharged from the second chamber 92 of the reverse osmosis module 9 flows through the concentration flow paths and the dilution flow paths of the multiple semipermeable membrane modules 1 and 2, and flow paths for this purpose (dotted line portions in FIG. 5).
This allows the flow path to be switched so that the permeate flows through the concentration flow path and the dilution flow path (i.e., the flow path is switched as shown in FIG. 6 ), thereby making it possible to use the permeate to clean the concentration flow path and the dilution flow path (the first chamber side and the second chamber side of the semipermeable membrane).
In addition, the present invention is not limited to the embodiment shown in Fig. 5, and a switch or the like may be provided so that only one of the concentration flow path or the dilution flow path can be cleaned. For example, a switch or the like may be provided so that only the concentration flow path (the first chamber side of the semipermeable membrane) in which contamination of the semipermeable membrane is particularly likely to occur is cleaned.

Of the switches shown in FIG. 5, switches 62 and 63 are switches that switch the flow paths so that the target solution and auxiliary solution do not flow through the multiple semipermeable membrane modules 1 and 2.

In addition, if it is desired to clean the first chamber 91 of the reverse osmosis module 9 (the first chamber 91 side of the reverse osmosis membrane 90), as shown in FIG. 5, switches 61, 62, and 63 for switching the flow path so that the permeate flows into the first chamber 91 of the reverse osmosis module 9, and a flow path for this purpose (dotted line portion in FIG. 5: the flow path between switch 61 and switch 64) may be provided. Note that there is no need to increase the pressure of the permeate when flowing it into the first chamber 91 of the reverse osmosis module 9.

In the concentration system shown in FIG. 5, the permeate is temporarily stored in tank 7, and the permeate stored in tank 7 is supplied to the concentration flow path and the dilution flow path by pump 8. As a result, in the state shown in FIG. 6, even if the permeate is not discharged from the second chamber 92 of the reverse osmosis module 9, the above-mentioned cleaning can be performed using the permeate stored in tank 7.

When cleaning with the permeate, the chemical in the chemical tank 71 may be mixed with the permeate to enhance the cleaning effect.

The above-described switch is not particularly limited as long as it has the above-described function. An example of the switch is a switching valve such as a three-way valve.
The switch may also be automated by a control device, etc. In this case, the switch is electrically connected to the control device (not shown) or the like.

(Target solution and auxiliary solution)
The target solution and the auxiliary solution are not particularly limited, and may be, for example, salt water (brine, seawater, brackish water, etc.), industrial wastewater, etc. The above-mentioned concentration system can be suitably used to further concentrate the target solution, particularly when the target solution is a high-concentration (high osmotic pressure) solution such as brine.

The target solution may be pretreated to remove fine particles, microorganisms, scale components, etc. contained in the solution. Pretreatment may involve various known pretreatments used in seawater desalination technology, such as filtration using NF membranes, UF membranes, MF membranes, etc., addition of sodium hypochlorite, addition of coagulants, 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.

In theory, membrane separation using BC 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 pressure of the target solution and the osmotic pressure of the auxiliary solution is 30% or less of the pressure of the target solution.

The auxiliary solution is not particularly limited as long as it is a liquid having an osmotic pressure, but a part of the target solution (concentrate) concentrated in the concentration flow paths of the multiple semipermeable membrane modules may be used as the auxiliary solution in the multiple semipermeable membrane modules. For example, in Fig. 1, a part of the target solution discharged from at least one of the first chambers 11, 21, 31, 41 of the semipermeable membrane modules 1, 2, 3, 4 can be used as the auxiliary solution.
In addition, a flow path for supplying a part of the concentrated liquid 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. Examples of such a mechanism include a device such as an automatic adjustment valve that keeps the pressure high on the upstream side and reduces the pressure on the downstream side, and an energy recovery device that has a mechanism for converting energy recovered from a pressurized supply liquid into auxiliary energy for driving a pump or the like.

The diluted solution may also be supplied to the concentration flow path together with the target solution. The concentrated solution obtained by concentrating the target solution may then be used as an auxiliary solution, and the diluted solution obtained by diluting the auxiliary solution may be supplied to the concentration flow path together with the target solution.

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.

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

In addition, in concentration by the RO method, the osmotic pressure of the concentrated target liquid on one side of the semipermeable membrane is generated in the opposite direction to the pressing force of the pump. Therefore, when the osmotic pressure of the concentrated target liquid reaches the pressure of the pump, the pressing force of the pump and the osmotic pressure of the target liquid acting in the opposite direction are counterbalanced, and water does not pass through the semipermeable membrane any more, and concentration does not proceed.
In contrast, in the membrane separation process (concentration method) using the BC method, the concentration difference (osmotic pressure difference) between the liquids supplied to the first and second chambers in each semipermeable membrane module is small, and the osmotic pressure that inhibits the concentration process, as in the RO method, is unlikely to occur. Therefore, in the concentration system using the BC method, the final concentration of the target solution can be increased more than in the concentration system using only the RO method. In principle, it is considered that the target solution can be concentrated to a saturated concentration.

In this embodiment, as in the multi-stage concentration system 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 connected in parallel to each of the multiple semipermeable membrane modules 1a, 1b, 1x, and 1y connected in series.

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 on the upstream side of the concentration flow path (downstream side of the dilution flow path). In this case, it is considered that the cross-sectional area of the flow path increases downstream of the dilution flow path, reducing the liquid flow resistance. Since 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 liquid passing increases and the liquid flow resistance tends to increase downstream of the dilution flow path. For this reason, reducing the liquid flow resistance downstream of the dilution flow path is effective in reducing the liquid flow resistance of the dilution flow path in the entire concentration system.

In addition, in a multi-stage concentration system such as that of this embodiment, the target solution flowing through the first chamber (concentration flow path) is concentrated sequentially in multiple semipermeable membrane modules, and the flow rate of the target solution decreases as the concentration progresses. 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.

In addition, the configuration disclosed in Japanese Patent Publication No. 7020512 can be applied to the concentration system of this embodiment.

The semipermeable membrane used in this embodiment may be, for example, a semipermeable membrane called a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), a nanofiltration membrane (NF membrane), or an ultrafiltration membrane (UF membrane). 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.

Typically, the pore size of RO and FO membranes is approximately 2 nm or less, and the pore size of UF membranes is approximately 2 to 100 nm. Among RO membranes, NF membranes have a relatively low rejection rate for ions and salts, and typically the pore size of NF membranes is 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 more.

The material constituting the semipermeable membrane is not particularly limited, but examples include cellulose-based resin, polysulfone-based resin, polyamide-based resin, etc. It is preferable that the semipermeable membrane is composed of a material containing at least one of cellulose-based resin and polysulfone-based resin.

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, is more preferably cellulose triacetate.

The polysulfone-based resin is preferably a polyethersulfone-based resin. The polyethersulfone-based resin is preferably a sulfonated polyethersulfone.

In the drawings, the semipermeable membrane of the semipermeable membrane module is drawn as a flat membrane 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 have a smaller membrane thickness than flat membranes, and are advantageous in that they can increase the membrane area per module and increase the permeation efficiency.

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 the hollow fiber membrane (hollow portion). Even if the solution flowing inside the hollow fiber membrane is pressurized, pressure loss may increase and it may be difficult to apply sufficient pressure, and while hollow fiber membranes generally tend to maintain their structure against external pressure, the hollow fiber membrane may be damaged if the internal pressure becomes too high.

One example of a specific hollow fiber membrane is a membrane with a single layer structure made entirely of cellulose resin. However, the single layer structure referred to here does not necessarily mean that the entire layer is a uniform membrane, and may be, for example, a membrane that is non-uniform in the thickness direction. Specifically, the membrane may have a dense layer on the outer surface, which is essentially a separation active layer that 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 is essentially 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 makes it possible to accurately control the movement of molecules from the outside to the inside of the hollow fiber membrane.

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

1, 2, 3, 4 Semipermeable membrane module, 10, 20, 30, 40 Semipermeable membrane, 11, 21, 31, 41 First chamber, 12, 22, 32, 42 Second chamber, 50a, 50b, 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b, 55a, 55b, 56a, 56b, 57a, 57b, 61, 62, 63, 64, 65 Switch, 7 Tank, 71 Chemical tank, 72 Switching valve, 8 Pump, 9 Reverse osmosis module, 90 Reverse osmosis membrane, 91 First chamber, 92 Second chamber.

Claims (7)

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:
A plurality of semipermeable membrane modules are provided,
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 in which the first chambers of the plurality of semipermeable membrane modules are connected to each other,
A dilution flow path is provided in which the second chambers of the plurality of semipermeable membrane modules are connected to each other,
The target solution is flowed through the concentration flow path,
An auxiliary solution having an osmotic pressure is caused to flow through the dilution flow path;
Since the target solution has a higher pressure than the auxiliary solution, in each of the plurality of semipermeable membrane modules, a solvent contained in the target solution in the first chamber is transferred to the auxiliary solution in the second chamber through the semipermeable membrane, and the target solution is concentrated to obtain the concentrated liquid;
At least one of the concentration flow path and the dilution flow path further includes a switch for switching the flow path so that the target solution and the auxiliary solution do not flow through at least one of the plurality of semipermeable membrane modules.
Concentration system. At least one of the concentration flow path and the dilution flow path is provided with a bypass flow path that directly connects the upstream side and downstream side of at least one of the plurality of semipermeable membrane modules,
The switch is a switch for switching the flow path to the bypass flow path.
The concentrating system of claim 1 . The bypass flow path is provided in both the concentration flow path and the dilution flow path.
The concentrating system of claim 2. a reverse osmosis module having a reverse osmosis membrane and a first chamber and a second chamber separated by the reverse osmosis membrane;
In the reverse osmosis module, the target solution is supplied to the first chamber at a pressure higher than that of the second chamber, a solvent contained in the target solution in the first chamber permeates through the reverse osmosis membrane into the second chamber and the target solution is concentrated, the concentrated target solution is discharged from the first chamber, and a permeated liquid, which is the solvent that has permeated the reverse osmosis membrane, is discharged from the second chamber,
The target solution concentrated in the reverse osmosis module is supplied to the concentration flow path;
The switch is a switch for switching a flow path so as to flow the permeate through at least one of the plurality of semipermeable membrane modules.
The concentrating system of claim 1 . The concentration system according to claim 1, in which a portion of the concentrated solution is used as the auxiliary solution. The concentration system of claim 1, further comprising a pressurizing device for pressurizing the target solution to a pressure higher than that of the auxiliary solution. The concentration system according to claim 1, wherein the semipermeable membrane is a hollow fiber membrane.

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