Method and apparatus for membrane treatment of solution

Abstract

To provide a device for membrane treatment of a solution which enables the solution to be highly concentrated in an efficient manner at low costs.SOLUTION: A device 1 for membrane treatment of a solution includes a first membrane treatment unit 10 having a high pressure chamber 12 and a low pressure chamber 13 partitioned by a semi-permeable membrane 11. The device 1 divides a processed solution that has passed through the high pressure chamber 12 into a first solution and a second solution and causes the first solution to pass through the low pressure chamber 13 to move water contained in the processed liquid in the high pressure chamber 12 to the first solution in the low pressure chamber 13 and thereby concentrate the processed liquid. The device 1 includes: a heating device 20 which heats the processed liquid with an external heat source before the processed liquid is supplied to the first membrane treatment unit 10; and heat recovery devices 31, 30 which conduct heat exchange between at least one of the first solution and the second solution, which has been subject to membrane treatment in the first membrane treatment unit 10, and the processed liquid before heating by the heating device 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for membrane treatment of a solution. [Background technology]

[0002] Patent Document 1 discloses a method for membrane treatment of a solution such as seawater, in which a target solution that has undergone a precipitation process to cool the target solution is supplied to a high-pressure chamber of a semipermeable membrane module, and a portion of the target solution that has passed through the high-pressure chamber is supplied to a low-pressure chamber, thereby transferring water contained in the target solution in the high-pressure chamber to the low-pressure chamber via the semipermeable membrane and concentrating the target solution in the high-pressure chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 158456 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described membrane treatment method, the target solution cooled in the precipitation step is heated and then supplied to the semipermeable membrane module, thereby preventing the precipitation of saturated components and clogging of the semipermeable membrane.

[0005] However, since the temperature of the target solution after heating is approximately the same as the temperature before cooling in the precipitation process, in order to achieve high concentration in the semipermeable membrane module, it is necessary to increase the membrane area of ​​the semipermeable membrane, which could lead to an increase in the size and cost of the semipermeable membrane module.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and apparatus for membrane treatment of a solution that can efficiently and inexpensively concentrate the solution. [Means for solving the problem]

[0007] The object of the present invention is to provide a membrane treatment method for a solution, which comprises a first membrane concentration step in which a solution to be treated that has passed through a high-pressure chamber of a first membrane treatment unit having a high-pressure chamber and a low-pressure chamber separated by a semipermeable membrane is divided into a first solution and a second solution, and the first solution is passed through the low-pressure chamber to move water contained in the solution to be treated in the high-pressure chamber to the first solution in the low-pressure chamber, thereby concentrating the solution to be treated, and which comprises a heating step in which the solution to be treated before the first membrane concentration step is heated by an external heat source, and a heat recovery step in which at least one of the first solution and the second solution that have been subjected to the first membrane concentration step is heat-exchanged with the solution to be treated before the heating step. The method further comprises a confluence step of converging the first solution that has been subjected to the first membrane concentration step with the solution to be treated, and a second membrane concentration step of supplying the solution to be treated that has been subjected to the confluence step to a second membrane treatment unit having a reverse osmosis membrane and concentrating it by reverse osmosis membrane treatment, wherein the first membrane concentration step is performed on the solution to be treated that has been concentrated in the second membrane concentration step, and further comprises a pretreatment step of supplying the solution to be treated to a pretreatment unit having a nanofiltration membrane, wherein the second membrane concentration step is performed on the solution to be treated that has permeated the nanofiltration membrane in the pretreatment step. This is achieved by a membrane treatment method of the solution.

[0009] before The heating step can be performed on the solution to be treated before the second membrane concentration step is performed, and the heat recovery step can further include a step of exchanging heat between the permeate of the solution to be treated that has been subjected to the second membrane concentration step and the solution to be treated before the second membrane concentration step is performed.

[0011] before The heating step and the heat recovery step can be performed on the liquid to be treated after the pretreatment step and before the second membrane concentration step. Alternatively, the heating step can be performed on the liquid to be treated before the pretreatment step, and the heat recovery step can further include a step of exchanging heat between the retentate of the liquid to be treated that has been subjected to the pretreatment step and the liquid to be treated before the pretreatment step.

[0012] before The heat recovery step can perform heat exchange between at least one of the first solution and the second solution that have been subjected to the first membrane concentration step and the liquid to be treated that has been concentrated in the second membrane concentration step.

[0013] Another object of the present invention is to provide a membrane treatment device for a solution, which comprises a first membrane treatment unit having a high-pressure chamber and a low-pressure chamber separated by a semipermeable membrane, and which divides a solution to be treated that has passed through the high-pressure chamber into a first solution and a second solution, and passes the first solution through the low-pressure chamber, thereby transferring water contained in the solution to be treated in the high-pressure chamber to the first solution in the low-pressure chamber and concentrating the solution to be treated, and which comprises a heating device that heats the solution to be treated in the first membrane treatment unit by an external heat source, and a heat recovery device that exchanges heat between at least one of the first solution and the second solution that has been subjected to membrane treatment in the first membrane treatment unit and the solution to be treated before being heated by the heating device. The system further comprises a second membrane treatment unit having a reverse osmosis membrane, wherein the second membrane treatment unit concentrates the solution to be treated, which is a mixture of the first solution that has been membrane-treated in the first membrane treatment unit, by reverse osmosis membrane treatment; the first membrane treatment unit concentrates the solution to be treated concentrated in the second membrane treatment unit; and the system further comprises a pretreatment unit having a nanofiltration membrane, wherein the second membrane treatment unit concentrates the solution to be treated that has permeated the nanofiltration membrane of the pretreatment unit. This is achieved by a membrane treatment device for the solution. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method and apparatus for membrane treatment of a solution that can efficiently and inexpensively concentrate the solution. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a film treatment apparatus for a solution according to an embodiment of the present invention. [Figure 2] FIG. 10 is a schematic configuration diagram of a film treatment apparatus for a solution according to another embodiment of the present invention. [Figure 3] FIG. 10 is a schematic configuration diagram of a film treatment apparatus for a solution according to still another embodiment of the present invention. [Figure 4] FIG. 10 is a schematic configuration diagram of a film treatment apparatus for a solution according to still another embodiment of the present invention. [Figure 5] FIG. 10 is a schematic configuration diagram of a film treatment apparatus for a solution according to still another embodiment of the present invention. [Figure 6] FIG. 10 is a schematic configuration diagram of a film treatment apparatus for a solution according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Fig. 1 is a schematic diagram of a membrane treatment device for a solution (hereinafter simply referred to as "membrane treatment device") according to one embodiment of the present invention. The membrane treatment device 1-1 shown in Fig. 1 includes a first membrane treatment unit 10, a heating device 20, and heat recovery devices 30 and 31.

[0017] In the first membrane treatment unit 10, a chamber is divided by a semipermeable membrane 11 to form a high-pressure chamber 12 and a low-pressure chamber 13. A raw solution, which is a solution to be treated, is introduced into the high-pressure chamber 12. The raw solution is, for example, seawater, and can be concentrated by the membrane treatment device 1 to produce salt, etc. However, the raw solution is not particularly limited, and may be a solution of inorganic salt other than seawater, an organic solution, etc.

[0018] The stock solution that has passed through the high-pressure chamber 12 is divided into a first solution and a second solution, and the first solution passes through the low-pressure chamber 13. Because the stock solution in the high-pressure chamber 12 is at a higher pressure than the first solution in the low-pressure chamber 13, this pressure difference causes water contained in the stock solution in the high-pressure chamber 12 to move to the first solution in the low-pressure chamber 13, and the stock solution that has passed through the first membrane treatment unit 10 is concentrated. In other words, the second solution is a highly concentrated solution, while the first solution that has passed through the low-pressure chamber 13 becomes diluted water.

[0019] The heating device 20 is a heat exchanger that exchanges heat between the stock solution and a backup heat source such as steam before it is supplied to the first membrane treatment unit 10, and the amount of heating can be adjusted by adjusting the aperture of a flow control valve 23. The heating device 20 is equipped with a temperature sensor 21 that detects the temperature of the stock solution after heating, and a controller 22 that controls the aperture of the flow control valve 23 so that the temperature detected by the temperature sensor 21 becomes a set temperature, and the temperature of the stock solution supplied to the first membrane treatment unit 10 can be maintained at a desired temperature. The configuration of the heating device 20 is not particularly limited as long as it is configured to heat the stock solution using an external heat source, and may be a heater or the like.

[0020] The heat recoverers 30 and 31 are both heat exchangers, into which a portion of the raw solution before being supplied to the heating device 20 is introduced via the branch flow paths 2 and 3, and heat is exchanged with the second solution and the first solution, respectively, that have been subjected to membrane treatment in the first membrane treatment unit 10. The raw solution from which heat has been recovered in the heat recoverers 30 and 31 is merged with the remainder of the raw solution downstream of the branch points of the branch flow paths 2 and 3, and the merged raw solution is supplied to the heating device 20. The branch points and merge points of the branch flow paths 2 and 3 can be any points upstream of the heating device 20.

[0021] Next, a membrane treatment method for a solution using the membrane treatment device 1-1 having the above configuration (hereinafter simply referred to as the "membrane treatment method") will be described. First, a heating step is performed in which the raw solution is heated by the heating device 20, and then the raw solution is supplied to the high-pressure chamber 12 of the first membrane treatment unit 10, where a first membrane concentration step is performed in which the raw solution is concentrated. A portion of the concentrated raw solution passes through the low-pressure chamber 13 as a first solution to become dilution water, while the remainder is sent to the next step, such as a salt production step, as a second solution, which is a highly concentrated solution.

[0022] The first solution and the second solution that have been subjected to the first membrane concentration step pass through the heat recovery devices 31 and 30, respectively, and exchange heat with a part of the raw solution before being supplied to the heating device 20. This performs a heat recovery step in which the heat of the first solution and the second solution is recovered to raise the temperature of the raw solution.

[0023] As described above, according to the membrane treatment device and membrane treatment method of this embodiment, the stock solution can be heated to a desired temperature using an external heat source and concentrated in the first membrane treatment unit. This increases the concentration rate in the first membrane treatment unit, and reduces the membrane area of ​​the semipermeable membrane, thereby enabling the first membrane treatment unit to be made smaller and less expensive. Furthermore, the heat required to heat the stock solution is recovered through heat exchange between the stock solution and the first and second solutions, thereby reducing the heat required from the external heat source and reducing running costs. Therefore, the stock solution can be highly concentrated efficiently and at low cost.

[0024] In this embodiment, heat recovery is performed by exchanging heat between both the first solution and the second solution and the stock solution, but it is sufficient that at least one of the first solution and the second solution is heat exchanged with the stock solution before being heated by the heating device 20. That is, the heat recovery devices 30 and 31 shown in FIG. 1 may be configured to include only one of them, and this also applies to each embodiment described later.

[0025] Although one embodiment of the present invention has been described in detail above, the specific aspects of the present invention are not limited to the above embodiment and various modifications are possible. Figure 2 is a schematic diagram of a membrane treatment device for a solution according to another embodiment of the present invention. The membrane treatment device 1-2 shown in Figure 2 is the membrane treatment device 1-1 shown in Figure 1, with a second membrane treatment unit 40 disposed between the heating device 20 and the first membrane treatment unit 10. Note that in the following figures, similar components are designated by the same reference numerals.

[0026] The second membrane treatment unit 40 is equipped with a reverse osmosis membrane 41 within a casing, and concentrates the stock solution by supplying it under pressure and subjecting it to reverse osmosis membrane treatment. The concentrated stock solution is supplied to the high-pressure chamber 12 of the first membrane treatment unit 10. The reverse osmosis membrane 41 may be any semipermeable membrane capable of reverse osmosis membrane treatment, and may be an NF membrane other than an RO membrane. The dilution water (first solution) that has passed through the low-pressure chamber 13 of the first membrane treatment unit 10 is merged with the stock solution at the junction 5. The second membrane treatment unit 40 may be configured in multiple stages instead of a single stage.

[0027] In the membrane treatment device 1-2 shown in Fig. 2, a portion of the raw solution before being supplied to the heating device 20 is supplied to heat recovery devices 30 and 31 via branch flow paths 2 and 3, where it exchanges heat with the second solution and the first solution, respectively, and is also supplied to a heat exchanger 32 via a branch flow path 4, where it exchanges heat with permeated water that has permeated through a reverse osmosis membrane 41 in a second membrane treatment unit 40. Note that some of the branch flow paths 2, 3, and 4 are omitted from the illustration in Fig. 2.

[0028] The membrane treatment method using the membrane treatment device 1-2 shown in Figure 2 is the membrane treatment method using the membrane treatment device 1-1 shown in Figure 1, and further includes a confluence step in which diluted water (first solution) that has been subjected to the first membrane concentration step is merged with the raw liquid at the confluence section 5, and a second membrane concentration step in which the raw liquid that has been subjected to the confluence step is concentrated in the second membrane treatment unit 40, thereby making it possible to easily increase the concentration rate of the highly concentrated liquid (second solution).

[0029] Furthermore, the heating step by the heating device 20 is performed on the raw liquid before the second membrane concentration step is performed, and in the heat recovery step, the heat required to heat the raw liquid is recovered in the heat recovery devices 30 and 31 and also in the heat recovery device 32, so that the raw liquid can be concentrated efficiently at low cost. In particular, when the reverse osmosis membrane 41 of the second membrane treatment unit 40 is an RO membrane, the flow rate of the permeate through the reverse osmosis membrane 41 is high, so that heat recovery in the heat recovery device 32 is more effective.

[0030] Figure 3 is a schematic diagram of a membrane treatment device for a solution according to yet another embodiment of the present invention. The membrane treatment device 1-3 shown in Figure 3 is the same as the membrane treatment device 1-2 shown in Figure 2, except that instead of arranging the heating device 20 upstream of the second membrane treatment unit 40, it is arranged between the second membrane treatment unit 40 and the first membrane treatment unit 10. The heat recovery process in the heat recovery devices 30, 31 is performed using the stock solution concentrated in the second membrane treatment unit 40. The membrane treatment device 1-3 shown in Figure 3 is effective when heating the second membrane treatment unit 40 is not necessary or desired, because the stock solution heated by the heating device 20 is not directly supplied to the second membrane treatment unit 40.

[0031] The membrane treatment device 1-4 shown in FIG. 4 is the membrane treatment device 1-3 shown in FIG. 3, further including a pretreatment unit 50 that pretreats the raw water before it is supplied to the second membrane treatment unit 40. The pretreatment unit 50 can perform a pretreatment step before the second membrane concentration step. The pretreatment unit 50 includes an NF membrane 51 in a casing. By passing the raw water through the NF membrane 51, scale components of seawater and the like are discharged to the outside as brine (non-permeated liquid). In the configuration shown in FIG. 4, the reverse osmosis membrane of the second membrane treatment unit 40 is preferably an RO membrane. The pretreatment unit 50 may be configured in multiple stages instead of a single stage. In the membrane treatment device 1-4 shown in FIG. 4, the second membrane treatment unit 40 and the pretreatment unit 50 can be excluded from the heating device 20.

[0032] 4, the membrane treatment device 1-5 shown in Fig. 5 is configured such that the heating device 20 is disposed between the pretreatment unit 50 and the second membrane treatment unit 40 instead of between the second membrane treatment unit 40 and the first membrane treatment unit 10. After the pretreatment step, the raw liquid is subjected to a heating step and a heat recovery step before being subjected to the second membrane concentration step. This membrane treatment device 1-5 can recover the heat of the permeate from the second membrane treatment unit 40 using a heat recovery device 32.

[0033] 5, the membrane treatment device 1-6 shown in Fig. 6 is configured such that the heating device 20 is disposed upstream of the pretreatment unit 50 instead of being disposed between the pretreatment unit 50 and the second membrane treatment unit 40. In the membrane treatment device 1-6 shown in Fig. 6, a portion of the raw liquid before being supplied to the heating device 20 is also supplied to the heat exchanger 33 via the branch flow path 5 and undergoes heat exchange with the brine (non-permeated liquid) of the pretreatment unit 50. Therefore, in the heat recovery step, the heat required to heat the raw liquid can be recovered not only by the heat recovery devices 30 and 32 but also by the heat recovery device 33. [Explanation of symbols]

[0034] 1. Membrane treatment equipment 10 First membrane treatment unit 11 Semi-permeable membrane 12 Hyperbaric Chamber 13 Low pressure chamber 20 Heating device 30, 31, 32, 33 Heat recovery unit 40 Second membrane treatment unit 41 Reverse osmosis membrane 50 Pre-treatment Unit 51 Nanofiltration Membrane

Claims

1. A membrane treatment method for a solution, comprising a first membrane concentration step of dividing a solution to be treated that has passed through a high-pressure chamber of a first membrane treatment unit having a high-pressure chamber and a low-pressure chamber separated by a semipermeable membrane into a first solution and a second solution, and passing the first solution through the low-pressure chamber, thereby transferring water contained in the solution to be treated in the high-pressure chamber to the first solution in the low-pressure chamber, thereby concentrating the solution to be treated, a heating step of heating the solution to be treated by an external heat source before the first membrane concentration step is performed; a heat recovery step of exchanging heat between at least one of the first solution and the second solution that has been subjected to the first membrane concentration step and the solution to be treated before the heating step, a confluence step of converging the first solution that has been subjected to the first membrane concentration step with the solution to be treated; a second membrane concentration step of supplying the solution to be treated that has been subjected to the joining step to a second membrane treatment unit having a reverse osmosis membrane and concentrating the solution by reverse osmosis membrane treatment, the first membrane concentration step is performed on the solution to be treated that has been concentrated in the second membrane concentration step; A pretreatment step of supplying the solution to be treated to a pretreatment unit having a nanofiltration membrane is further provided, The second membrane concentration step is a membrane treatment method for a solution, which is performed on the solution to be treated that has permeated the nanofiltration membrane in the pretreatment step.

2. the heating step is performed on the solution to be treated before the second membrane concentration step is performed, 2. The membrane treatment method for a solution according to claim 1, wherein the heat recovery step further comprises a step of exchanging heat between the permeate of the solution to be treated that has been subjected to the second membrane concentration step and the solution to be treated that has not yet been subjected to the second membrane concentration step.

3. 2. The membrane treatment method for a solution according to claim 1, wherein the heating step and the heat recovery step are performed on the solution to be treated after the pretreatment step and before the second membrane concentration step.

4. The heating step is performed on the liquid to be treated before the pretreatment step is performed, 2. The membrane treatment method for a solution according to claim 1, wherein the heat recovery step further comprises a step of exchanging heat between the non-permeated liquid of the solution to be treated that has been subjected to the pretreatment step and the solution to be treated that has not yet been subjected to the pretreatment step.

5. 2. The membrane treatment method for a solution according to claim 1, wherein the heat recovery step involves heat exchange of at least one of the first solution and the second solution that have been subjected to the first membrane concentration step with the liquid to be treated that has been concentrated in the second membrane concentration step.

6. A membrane treatment device for a solution, comprising a first membrane treatment unit having a high-pressure chamber and a low-pressure chamber separated by a semipermeable membrane, wherein a solution to be treated that has passed through the high-pressure chamber is divided into a first solution and a second solution, and the first solution is passed through the low-pressure chamber, thereby transferring water contained in the solution to be treated in the high-pressure chamber to the first solution in the low-pressure chamber, thereby concentrating the solution to be treated, a heating device that heats the solution to be treated by an external heat source before being supplied to the first membrane treatment unit; a heat recovery device that exchanges heat between at least one of the first solution and the second solution that has been subjected to membrane treatment in the first membrane treatment unit and the solution to be treated before being heated by the heating device; a second membrane treatment unit having a reverse osmosis membrane; the second membrane treatment unit concentrates the solution to be treated, which is obtained by joining the first solution that has been subjected to membrane treatment in the first membrane treatment unit, by reverse osmosis membrane treatment; the first membrane treatment unit concentrates the solution to be treated that has been concentrated in the second membrane treatment unit; further comprising a pretreatment unit having a nanofiltration membrane; The second membrane treatment unit is a membrane treatment device for a solution that concentrates the solution to be treated that has permeated the nanofiltration membrane of the pretreatment unit.

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