Membrane separation device

Abstract

A membrane separation device according to at least one embodiment of the present disclosure comprises a plurality of separation stages including: a first separation stage that includes a separation membrane module having a separation membrane, a primary-side flow path, and a secondary-side flow path, in a quantity of one or in a quantity of at least two in which the primary-side flow paths are connected in parallel to each other; and a second separation stage that includes the separation membrane module in a quantity of one or in a quantity of at least two in which the primary-side flow paths are connected in parallel to each other. The primary-side flow path of the separation membrane module in the second separation stage is connected in series to the primary-side flow path of the separation membrane module in the first separation stage on the downstream side of the flow of a fluid to be treated. The flow rate of the fluid to be treated flowing through the primary-side flow path of the separation membrane module in the second separation stage is higher than the flow rate of the fluid to be treated flowing through the primary-side flow path of the separation membrane module in the first separation stage.

Description

Membrane separation apparatus

[0001] The present disclosure relates to a membrane separation apparatus. The present application claims priority based on Japanese Patent Application No. 2025-056092 filed with the Japan Patent Office on March 28, 2025, the content of which is incorporated herein by reference.

[0002] Separation of some components from a fluid containing a plurality of components is performed by using a separation membrane module having a separation membrane (see, for example, Patent Document 1).

[0003] Japanese Patent No. 4929269

[0004] In a membrane separation apparatus in which a plurality of separation membrane modules are connected in series, the concentration of a component to be permeated is lower in the separation membrane module on the downstream side of the flow of the fluid to be treated than in the separation membrane module on the upstream side of the flow of the fluid to be treated. Therefore, the separation membrane module on the downstream side of the flow of the fluid to be treated is more susceptible to concentration polarization than the separation membrane module on the upstream side of the flow of the fluid to be treated, so that the permeation amount of the component to be permeated tends to be further reduced.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to reduce the influence of concentration polarization in a membrane separation apparatus.

[0006] A membrane separation apparatus according to at least one embodiment of the present disclosure comprises a plurality of separation stages, each including one separation membrane module or two or more separation stages, each having the primary side passages connected in parallel to one another, the separation membrane module having a separation membrane for separating a permeate fluid from a supplied fluid to be treated, a primary side passage configured for the flow of the fluid to be treated, and a secondary side passage separated from the primary side passage by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane, wherein the plurality of separation stages includes: a first separation stage including one separation membrane module or two or more separation stages, each having the primary side passages connected in parallel to one another; and a second separation stage including one separation membrane module or two or more separation stages, each having the primary side passages connected in parallel to one another, wherein the primary side passage of the separation membrane module in the second separation stage is connected in series downstream of the flow of the fluid to be treated with respect to the primary side passage of the separation membrane module in the first separation stage. The flow velocity of the fluid to be processed flowing through the primary channel of the separation membrane module in the second separation stage is faster than the flow velocity of the fluid to be processed flowing through the primary channel of the separation membrane module in the first separation stage.

[0007] According to at least one embodiment of this disclosure, the effect of concentration polarization can be reduced in a membrane separation apparatus.

[0008] This is a diagram showing the overall configuration of the membrane separation apparatus according to the first embodiment. This is a diagram showing the conceptual overall configuration of the membrane separation apparatus according to the second embodiment.

[0009] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of this disclosure, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only describe such arrangements strictly, but also represent states of relative displacement with tolerances, or angles or distances to the extent that the same function is achieved. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" should not only describe states of being strictly equal, but also represent states where tolerances, or differences to the extent that the same function is achieved, exist. For example, expressions describing shapes such as square shapes or cylindrical shapes should not only describe geometrically precise square shapes or cylindrical shapes, but also represent shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.

[0010] Figure 1 is a diagram showing the overall configuration of the membrane separation apparatus according to the first embodiment. Figure 2 is a diagram showing the conceptual overall configuration of the membrane separation apparatus according to the second embodiment.

[0011] As shown in Figures 1 and 2, a membrane separation apparatus 1 according to several embodiments has a plurality of separation membrane modules 3, each having a separation membrane 11 for separating a permeate fluid F2 from a supplied fluid to be processed F1, a primary side flow path 13 configured for the flow of the fluid to be processed F1, and a secondary side flow path 15 separated from the primary side flow path 13 by the separation membrane 11 and configured for the flow of the permeate fluid F2 that has permeated through the separation membrane 11. Each of the plurality of separation membrane modules 3 has a primary side inlet 13i which is the inlet for the fluid to be processed F1 to the primary side flow path 13, a primary side outlet 13o which is the outlet for the fluid to be processed F1 after it has flowed through the primary side flow path 13, and a secondary side outlet 15o which is the outlet for the permeate fluid F2 from the secondary side flow path 15.

[0012] Some embodiments of the membrane separation apparatus 1 include a first-stage separation stage 31 which includes one separation membrane module 3 or two or more separation membrane modules 3 which are connected in parallel with each other by primary flow channels 13, and a second-stage separation stage 32 which includes one separation membrane module 3 or two or more separation membrane modules 3 which are connected in parallel with each other by primary flow channels 13.

[0013] The membrane separation apparatus 1 according to the first embodiment comprises a third separation stage 33 which includes one separation membrane module 3, or two or more separation membrane modules 3 whose primary side flow paths are connected in parallel to each other. For example, in the example shown in Figure 1, the membrane separation apparatus 1 according to the first embodiment comprises three separation stages 30, with three separation membrane modules 3 provided in the first separation stage 31, two separation membrane modules 3 provided in the second separation stage 32, and one separation membrane module 3 provided in the third separation stage 33.

[0014] For example, in the example shown in Figure 2, the membrane separation apparatus 1 according to the second embodiment is equipped with two separation stages 30, with one separation membrane module 3 provided in the first separation stage 31 and one separation membrane module 3 provided in the second separation stage 32. Note that the number of separation stages 30 and the number of separation membrane modules 3 in each separation stage 30 in the membrane separation apparatus 1 shown in Figures 1 and 2 are illustrative examples and are not limited to the number of separation stages 30 and the number of separation membrane modules 3 in each separation stage 30 in the membrane separation apparatus 1 shown in Figures 1 and 2, as long as they do not contradict the content described below.

[0015] In the example shown in Figure 1, the three separation membrane modules 3 of the first separation stage 31 have their primary flow paths 13 connected in parallel to each other, and the two separation membrane modules 3 of the second separation stage 32 have their primary flow paths 13 connected in parallel to each other. In the example shown in Figure 1, the primary flow paths 13 of the two separation membrane modules 3 of the second separation stage 32 are connected in series downstream of the flow of the fluid to be processed F1 to the primary flow paths 13 of the three separation membrane modules 3 of the first separation stage 31. In the example shown in Figure 1, the primary flow path 13 of one separation membrane module 3 of the third separation stage 33 is connected in series downstream of the flow of the flow of the fluid to be processed F1 to the primary flow paths 13 of the two separation membrane modules 3 of the second separation stage 32. In the membrane separation apparatus 1 according to the first embodiment, for example, the specifications of all separation membrane modules 3 are the same. Therefore, if the flow rate of the fluid to be processed F1 supplied to the separation membrane modules 3 is the same, the flow velocity of the fluid to be processed F1 in the primary flow paths 13 will also be the same.

[0016] In other words, in the example shown in Figure 1, the fluid to be processed F1 supplied from the fluid to be processed supply channel 21 to the first separation stage 31 flows through one of the primary side channels 13 of the three separation membrane modules 3 in the first separation stage 31, and then flows through one of the primary side channels 13 of the two separation membrane modules 3 in the second separation stage 32. After flowing through one of the primary side channels 13 of the two separation membrane modules 3 in the second separation stage 32, the fluid to be processed F1 flows through one of the primary side channels 13 of the separation membrane module 3 in the third separation stage 33 and is led to the fluid to be processed outlet channel 22. The fluid to be processed outlet channel 22 is a channel for leading the fluid to be processed F1 from the primary side channels 13 of the separation membrane module 3 in the downstreammost separation stage 30 to the outside (outside the system) of the membrane separation device 1.

[0017] The membrane separation apparatus 1 according to the first embodiment includes, in the downstream separation stage 30 (third separation stage 33) of the flow of the fluid to be processed F1, a primary side outlet 13o which is the outlet of the primary side flow path 13, a recycling flow path 24 connecting the primary side inlet 13i which is the inlet of the primary side flow path 13, and a pressurizing device 25 provided in the recycling flow path 24 that sucks in the fluid to be processed F1 from the primary side outlet 13o of the primary side flow path 13 and pressurizes it. The pressurizing device 25 is, for example, a pump. Therefore, a portion of the fluid to be processed F1 that has flowed through the primary side flow path 13 in the separation membrane module 3 of the downstream separation stage 30 (third separation stage 33) of the flow of the fluid to be processed F1 is supplied back to the primary side flow path 13 via the recycling flow path 24.

[0018] In the example shown in Figure 2, the primary channel 13 of one separation membrane module 3 in the second separation stage 32 is connected in series downstream of the flow of the fluid to be treated F1 to the primary channel 13 of one separation membrane module 3 in the first separation stage 31. In the example shown in Figure 2, the fluid to be treated F1 supplied from the fluid to be treated supply channel 21 to the first separation stage 31 flows through the primary channel 13 of one separation membrane module 3 in the first separation stage 31, then flows through the primary channel 13 of one separation membrane module 3 in the second separation stage 32, and is led to the fluid to be treated outlet channel 22.

[0019] In several embodiments of the membrane separation apparatus 1, the permeate fluid F2 from the secondary flow path 15 of each separation membrane module 3 is guided to a permeate fluid outlet flow path 23 for guiding the permeate fluid F2 to the outside (outside the system) of the membrane separation apparatus 1.

[0020] In the following explanation, of two adjacent separation stages 30 along the flow of the fluid F1 to be treated, the separation stage 30 upstream of the flow of the fluid F1 to be treated will be referred to as the first separation stage 5, and the separation stage 30 downstream will be referred to as the second separation stage 6. For example, in the example shown in Figure 1, if the first separation stage 31 is the first separation stage 5, then the second separation stage 32 becomes the second separation stage 6, and if the second separation stage 32 is the first separation stage 5, then the third separation stage 33 becomes the second separation stage 6. For example, in the example shown in Figure 2, if the first separation stage 31 is the first separation stage 5, then the second separation stage 32 becomes the second separation stage 6.

[0021] Accordingly, a membrane separation apparatus 1 according to some embodiments comprises a first separation stage 5 including one separation membrane module 3 or two or more separation membrane modules 3 whose primary flow paths 13 are connected in parallel with each other, and a second separation stage 6 including one separation membrane module 3 or two or more separation membrane modules 3 whose primary flow paths 13 are connected in parallel with each other. In a membrane separation apparatus 1 according to some embodiments, the primary flow paths 13 of the separation membrane module 3 in the second separation stage 6 are connected in series with respect to the primary flow paths 13 of the separation membrane module 3 in the first separation stage 5, downstream of the flow of the fluid to be processed F1.

[0022] Furthermore, in some embodiments of the membrane separation apparatus 1, as described below, the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the second separation stage 6 is configured to be faster than the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0023] In the separation membrane module 3 of the second separation stage 6, the concentration of the target component is lower compared to the separation membrane module 3 of the first separation stage 5. Therefore, the separation membrane module 3 of the second separation stage 6 is more susceptible to the effects of concentration polarization than the separation membrane module 3 of the first separation stage 5, and the amount of target component that permeates tends to be smaller. According to several embodiments of the membrane separation apparatus 1, by making the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 of the second separation stage 6 faster than the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 of the first separation stage 5, the effect of concentration polarization can be reduced in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the effects of concentration polarization compared to the separation membrane module 3 of the first separation stage 5. As a result, the effect of concentration polarization can be reduced in the membrane separation apparatus 1.

[0024] In the membrane separation apparatus 1 according to the first embodiment, the number of separation membrane modules 3 in the second separation stage 6 is less than the number of separation membrane modules 3 in the first separation stage 5. By reducing the number of separation membrane modules 3 in the second separation stage 6 compared to the number of separation membrane modules 3 in the first separation stage 5, it becomes easier to make the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane modules 3 in the second separation stage 6 faster than the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane modules 3 in the first separation stage 5. If multiple separation membrane modules 3 are simply connected in series, the pressure loss of the fluid to be processed F1 passing through the multiple separation membrane modules 3 increases, and the power of the pump to supply the fluid to be processed F1 increases. In addition, because the supply pressure of the fluid to be processed F1 needs to be increased in response to the increased pressure loss of the fluid to be processed F1 passing through the multiple separation membrane modules 3, the requirements for sealing on the inlet side of the membrane separation apparatus 1 become higher. According to the membrane separation apparatus 1 of the first embodiment, the pressure loss of the fluid to be processed F1 is reduced compared to the case where multiple separation membrane modules 3 are simply connected in series, so the power of the pump for supplying the fluid to be processed F1 can be reduced. According to the membrane separation apparatus 1 of the first embodiment, the pressure loss of the fluid to be processed F1 is reduced compared to the case where multiple separation membrane modules 3 are simply connected in series, so the requirements for sealing on the inlet side of the membrane separation apparatus 1 can be relaxed.

[0025] In the membrane separation apparatus 1 according to the first embodiment, a recycling channel 24 and a pressurizing device 25 are provided, so that a portion of the fluid to be processed F1 that has flowed through the primary channel 13 in the separation membrane module 3 of the downstream separation stage 30 (third separation stage 33) of the fluid to be processed F1 can be supplied back to the primary channel 13 via the recycling channel 24. As a result, the effect of concentration polarization can be reduced in the downstream separation stage 30 of the fluid to be processed F1, which is susceptible to the effects of concentration polarization, and the amount of permeation target components can be increased. Therefore, for example, if the fluid in the secondary channel 15 contains components that are useful in later processes, such as components of the product (hereinafter also referred to as useful components), the recovery rate of useful components can be improved. Also, for example, if the fluid in the primary channel 13 contains useful components, the purity of the useful components can be improved.

[0026] In the example shown in Figure 1, for example, the number of separation membrane modules 3 included in each separation stage 30 may be the same in the first separation stage 31 and the second separation stage 32, and the number of separation membrane modules 3 included in the third separation stage 33 may be less than the number of separation membrane modules 3 included in the second separation stage 32. In this case, if the second separation stage 32 is designated as the first separation stage 5 and the third separation stage 33 as the second separation stage 6, the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the second separation stage 6 will be faster than the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0027] Similarly, in the example shown in Figure 1, for example, the number of separation membrane modules 3 included in each separation stage 30 may be the same in the second separation stage 32 and the third separation stage 33, and the number of separation membrane modules 3 included in the first separation stage 31 may be greater than the number of separation membrane modules 3 included in the second separation stage 32. In this case, if the first separation stage 31 is designated as the first separation stage 5 and the second separation stage 32 as the second separation stage 6, the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the second separation stage 6 will be faster than the flow velocity of the fluid to be processed F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0028] A membrane separation apparatus 1 according to the second embodiment will be described further. In the membrane separation apparatus 1 according to the second embodiment, the separation membrane module 3 includes a separation section 3s which includes a separation membrane 11, a primary channel 13 and a secondary channel 15, and a casing (not shown) which houses the separation section 3s. Multiple primary channels 13 are formed in the separation section 3s which extend in a certain direction. Each of the multiple primary channels 13 has an opening at one end 13a and another end 13b in the direction of extension.

[0029] In the membrane separation apparatus 1 according to the second embodiment, in the first separation stage 31, for all of the multiple primary flow paths 13 of the separation section 3s, a primary inlet 13i and a primary outlet 13o are set up so that the fluid to be processed F1 flows from one end 13a in the extending direction of the primary flow path 13 (for example, the left side shown in Figure 2) to the other end 13b (for example, the right side shown in Figure 2).

[0030] In the membrane separation apparatus 1 according to the second embodiment, in the second separation stage 32, a portion 13c of the plurality of primary flow paths 13 of the separation section 3s is configured with a primary inlet 13i so that the fluid to be processed F1 flows from one end 13a in the extending direction of the primary flow path 13 (for example, the left side in Figure 2) to the other end 13b (for example, the right side in Figure 2), and the remaining portion 13d of the plurality of primary flow paths 13 is configured with a primary outlet 13o so that the fluid to be processed F1 flows from the other end 13b in the extending direction of the primary flow path 13 (for example, the right side in Figure 2) to the one end 13a (for example, the left side in Figure 2). Then, in the second separation stage 32, the separation membrane module 3 has a return channel 26 formed therein that connects the other end 13b (for example, the right side in Figure 2) of a portion 13c of the plurality of primary channel 13 of the separation section 3s with the other end 13b (for example, the right side in Figure 2) of the remaining portion 13d of the plurality of primary channel 13.

[0031] As a result, the fluid to be processed F1 supplied to the primary side inlet 13i of the separation membrane module 3 in the second separation stage 32 flows through a portion 13c of the multiple primary side channels 13 from one end 13a in the direction of extension of the primary side channel 13 (for example, the left side in Figure 2) to the other end 13b (for example, the right side in Figure 2), and then flows into the remaining portion 13d of the multiple primary side channels 13 from the other end 13b (for example, the right side in Figure 2) via the return channel 26. The fluid to be processed F1 that has flowed into the remaining portion 13d of the multiple primary side channels 13 flows through the remaining portion 13d of the multiple primary side channels 13 from the other side (for example, the right side in Figure 2) to the one side (for example, the left side in Figure 2), and flows out from one end 13a (for example, the left side in Figure 2) of the remaining portion 13d of the multiple primary side channels 13.

[0032] In the membrane separation apparatus 1 according to the second embodiment, for example, the separation section 3s of the first separation stage 31 and the separation section 3s of the second separation stage 32 are separation sections 3s of the same specifications. Therefore, the flow path cross-sectional area of ​​each primary side flow path 13, the number of primary side flow paths 13, and the membrane area of ​​the separation membrane 11 are the same for the separation section 3s of the first separation stage 31 and the separation section 3s of the second separation stage 32. Consequently, by forming the folded flow path 26, the flow path cross-sectional area of ​​the primary side flow path 13 can be reduced compared to when the folded flow path 26 is not formed.

[0033] The number of portions 13c of the primary flow path 13 and the number of portions 13d of the remaining portion 13d may be equal, or the number of portions 13d may be less than the number of portions 13c. If the number of portions 13d is less than the number of portions 13c, even if the flow rate of the fluid to be treated F1 decreases due to the permeation of the permeation target component during the process of flowing through the primary flow path 13, the decrease in the flow velocity of the fluid to be treated F1 flowing through the remaining portion 13d can be reduced.

[0034] Thus, in the membrane separation apparatus 1 according to the second embodiment, the number of separation membrane modules 3 in the second separation stage 6 may be equal to the number of separation membrane modules 3 in the first separation stage 5. The membrane area of ​​each separation membrane 11 in the second separation stage 6 may be equal to the membrane area of ​​each separation membrane 11 in the first separation stage 5. The cross-sectional area of ​​the primary flow path 13 of the separation membrane module 3 in the second separation stage 6 is preferably smaller than the cross-sectional area of ​​the primary flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0035] This makes it possible to make the flow velocity of the fluid to be treated F1 flowing through the primary channel 13 of the separation membrane module 3 of the second separation stage 6 faster than the flow velocity of the fluid to be treated F1 flowing through the primary channel 13 of the separation membrane module 3 of the first separation stage 5. Therefore, in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the effects of concentration polarization compared to the separation membrane module 3 of the first separation stage 5, the effects of concentration polarization can be reduced and the amount of permeation target components can be increased.

[0036] In the membrane separation apparatus 1 according to the second embodiment, the separation membrane module 3 in the first separation stage 5 may have a primary side inlet portion 13i, which is the inlet for the fluid to be processed F1, on one side in the extending direction of the primary side flow path 13, and a primary side outlet portion 13o, which is the outlet for the fluid to be processed F1, on the other side in the extending direction. In the separation membrane module 3 in the second separation stage 6, the primary side inlet portion 13i, which is the inlet for the fluid to be processed F1, and the primary side outlet portion 13o, which is the outlet for the fluid to be processed F1, are provided on one side in the extending direction of the primary side flow path 13, and a return flow path 26 may be formed on the other side in the extending direction to change the flow of the fluid to be processed F1 from a direction toward the other side to a direction toward the one side.

[0037] As described above, by forming a return channel 26 in the separation membrane module 3 in the second separation stage 6, the cross-sectional area of ​​the primary channel 13 per unit flow rate can be reduced compared to when the return channel 26 is not formed, thereby increasing the flow velocity of the fluid to be processed F1. This reduces the effect of concentration polarization in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the effects of concentration polarization than the separation membrane module 3 of the first separation stage 5, and increases the amount of permeation target components. According to the membrane separation apparatus 1 of the second embodiment, for example, even if there is a limit to the supply amount of the fluid to be processed F1 and a sufficient flow velocity of the fluid to be processed F1 cannot be secured even if the number of separation membrane modules 3 in the downstream separation stage 30 is reduced to one, the flow velocity of the fluid to be processed F1 can be increased by forming a return channel 26.

[0038] In the second embodiment described above, a separation membrane module 3 having the same configuration as the separation membrane module 3 in the first separation stage 31 may be connected in series upstream of the first separation stage 31. In this case, the flow path cross-sectional area of ​​the primary flow path 13 is the same for the separation membrane module 3 in the first separation stage 31 and the separation membrane module 3 connected in series upstream of the first separation stage 31. In the second embodiment described above, a separation membrane module 3 having the same configuration as the separation membrane module 3 in the second separation stage 32 may be connected in series downstream of the second separation stage 32. In this case, the flow path cross-sectional area of ​​the primary flow path 13 is the same for the separation membrane module 3 in the second separation stage 32 and the separation membrane module 3 connected in series downstream of the second separation stage 32.

[0039] In the second embodiment described above, in the second separation stage 6, the multiple primary flow paths 13 of the separation section 3s are divided into two groups: a part 13c and the remainder 13d of the multiple primary flow paths 13. The two groups are connected in series by connecting the part 13c and the remainder 13d of the multiple primary flow paths 13 with a return flow path 26 at the other end 13b in the extending direction of the primary flow paths 13. In other words, in the second embodiment described above, the number of returns of the multiple primary flow paths 13 of the separation section 3s in the second separation stage 6 is 1. However, in the second embodiment, the multiple primary flow paths 13 of the separation section 3s in the second separation stage 6 may be divided into three or more groups, and each group may be connected in series. In other words, the number of returns of the multiple primary flow paths 13 of the separation section 3s in the second separation stage 6 may be two or more. Even in this case, the flow path cross-sectional area of ​​the primary flow paths 13 of the separation membrane module 3 in the second separation stage 6 is smaller than the flow path cross-sectional area of ​​the primary flow paths 13 of the separation membrane module 3 in the first separation stage 5.

[0040] For example, if the multiple primary flow paths 13 of the separation section 3s are divided into three groups, for the first group of primary flow paths 13, a primary inlet 13i is provided at one end 13a so that the fluid to be processed F1 flows from one end 13a to the other end 13b in the extending direction of the primary flow path 13. For the second group of primary flow paths 13, a return flow path 26 is provided at the other end 13b so that the fluid to be processed F1 flows from the other end 13b to the one end 13a in the extending direction of the primary flow path 13. For the third group of primary flow paths 13, a return flow path 26 is provided at one end 13a so that the fluid to be processed F1 flows from one end 13a to the other end 13b in the extending direction of the primary flow path 13, and a primary outlet 13o is provided at the other end 13b.

[0041] If the multiple primary flow paths 13 of the separation section 3s are divided into four or more groups, it is preferable to connect each group in series with a return flow path 26, similar to the case where they are divided into three groups as described above.

[0042] The present disclosure is not limited to the embodiments described above, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0043] The content described in each of the above embodiments can be understood, for example, as follows. (1) A membrane separation device 1 according to at least one embodiment of the present disclosure includes: a first separation stage 5 including one separation membrane module 3, or two or more separation membrane modules 3 whose primary-side flow paths 13 are connected in parallel with each other; and a second separation stage 6 including one separation membrane module 3, or two or more separation membrane modules 3 whose primary-side flow paths 13 are connected in parallel with each other, wherein the separation membrane module 3 includes: a separation membrane 11 for separating a permeated fluid F2 from a supplied fluid F1 to be treated; a primary-side flow path 13 configured to allow the fluid F1 to be treated to flow therethrough; and a secondary-side flow path 15 separated from the primary-side flow path 13 by the separation membrane 11 and configured to allow the permeated fluid F2 that has permeated through the separation membrane 11 to flow therethrough. The primary-side flow path 13 of the separation membrane module 3 in the second separation stage 6 is connected in series on the downstream side of the flow of the fluid F1 to be treated with respect to the primary-side flow path 13 of the separation membrane module 3 in the first separation stage 5. The flow velocity of the fluid F1 to be treated flowing through the primary-side flow path 13 of the separation membrane module 3 in the second separation stage 6 is higher than the flow velocity of the fluid F1 to be treated flowing through the primary-side flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0044] In the separation membrane module 3 of the second separation stage 6, the concentration of the component to be permeated is lower than that in the separation membrane module 3 of the first separation stage 5. Therefore, the separation membrane module 3 of the second separation stage 6 is more susceptible to the influence of concentration polarization than the separation membrane module 3 of the first separation stage 5, so that the permeation amount of the component to be permeated tends to be further reduced. According to the configuration of (1) above, by setting the flow velocity of the fluid F1 to be treated flowing through the primary-side flow path 13 of the separation membrane module 3 in the second separation stage 6 to be higher than the flow velocity of the fluid F1 to be treated flowing through the primary-side flow path 13 of the separation membrane module 3 in the first separation stage 5, the influence of concentration polarization can be reduced in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the influence of concentration polarization than the separation membrane module 3 of the first separation stage 5. Thereby, in the membrane separation device 1, the influence of concentration polarization can be reduced.

[0045] (2) In some embodiments, in the configuration of (1) above, the number of separation membrane modules 3 in the second separation stage 6 is less than the number of separation membrane modules 3 in the first separation stage 5.

[0046] According to the configuration in (2) above, by reducing the number of separation membrane modules 3 in the second separation stage 6 to the number of separation membrane modules 3 in the first separation stage 5, it becomes easy to make the flow velocity of the fluid to be treated F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the second separation stage 6 faster than the flow velocity of the fluid to be treated F1 flowing through the primary side flow path 13 of the separation membrane module 3 in the first separation stage 5. When multiple separation membrane modules 3 are simply connected in series, the pressure loss of the fluid to be treated F1 passing through the multiple separation membrane modules 3 increases, and the power of the pump to supply the fluid to be treated F1 increases. In addition, when the pressure loss of the fluid to be treated F1 passing through the multiple separation membrane modules 3 increases, the requirements for sealing on the inlet side of the membrane separation device 1 increase. According to the configuration in (2) above, the pressure loss of the fluid to be treated F1 is reduced compared to when multiple separation membrane modules 3 are simply connected in series, so the power of the pump to supply the fluid to be treated F1 can be reduced. According to the configuration described in (2) above, the pressure loss of the fluid to be processed F1 is reduced compared to the case where multiple separation membrane modules 3 are simply connected in series, thus easing the requirements for sealing on the inlet side of the membrane separation device 1.

[0047] (3) In some embodiments, the configuration of (1) or (2) above may include a recycling channel 24 connecting the outlet (primary outlet portion 13o) of the primary channel 13 of the separation membrane module 3 in the second separation stage 6 to the inlet (primary inlet portion 13i) of the primary channel 13, and a pressurizing device 25 provided in the recycling channel 24 that sucks in the fluid to be processed F1 from the outlet (primary outlet portion 13o) of the primary channel 13 and pressurizes it.

[0048] According to the configuration of (3) above, in the second separation stage 6, which is susceptible to the influence of concentration polarization, the influence of concentration polarization can be reduced, and the permeation amount of the target permeation component can be increased. Thereby, for example, when the fluid in the secondary-side flow path 15 contains a useful component, the recovery rate of the useful component can be improved. Further, for example, when the fluid in the primary-side flow path 13 contains a useful component, the purity of the useful component can be improved.

[0049] (4) In some embodiments, in the configuration of (1) above, the number of separation membrane modules 3 in the second separation stage 6 may be equal to the number of separation membrane modules 3 in the first separation stage 5. The membrane area of the separation membrane 11 of the separation membrane module 3 in the second separation stage 6 may be equal to the membrane area of the separation membrane 11 of the separation membrane module 3 in the first separation stage 5. The flow path cross-sectional area of the primary-side flow path 13 of the separation membrane module 3 in the second separation stage 6 is preferably smaller than the flow path cross-sectional area of the primary-side flow path 13 of the separation membrane module 3 in the first separation stage 5.

[0050] According to the configuration of (4) above, the flow velocity of the fluid to be treated F1 flowing through the primary-side flow path 13 of the separation membrane module 3 in the second separation stage 6 can be made higher than the flow velocity of the fluid to be treated F1 flowing through the primary-side flow path 13 of the separation membrane module 3 in the first separation stage 5. Thereby, in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the influence of concentration polarization compared to the separation membrane module 3 of the first separation stage 5, the influence of concentration polarization can be reduced, and the permeation amount of the target permeation component can be increased.

[0051] (5) In some embodiments, in the configuration of (4) above, the separation membrane module 3 in the first separation stage 5 may be provided with an inlet for the fluid to be treated F1 (primary-side inlet portion 13i) on one side in the extending direction of the primary-side flow path 13, and an outlet for the fluid to be treated F1 (primary-side outlet portion 13o) on the other side in the extending direction. The separation membrane module 3 in the second separation stage 6 is provided with an inlet for the fluid to be treated F1 (primary-side inlet portion 13i) and an outlet for the fluid to be treated F1 (primary-side outlet portion 13o) on one side in the extending direction of the primary-side flow path 13, and a folded flow path 26 that changes the flow direction of the fluid to be treated F1 from the direction toward the other side to the direction toward the one side may be formed on the other side in the extending direction.

[0052] According to the configuration of (5) above, by forming a return channel 26 in the separation membrane module 3 in the second separation stage 6, the cross-sectional area of ​​the primary channel 13 per unit flow rate can be reduced compared to the case where the return channel 26 is not formed, so that the flow velocity of the fluid to be treated F1 can be increased. As a result, the effect of concentration polarization can be reduced in the separation membrane module 3 of the second separation stage 6, which is more susceptible to the effect of concentration polarization than the separation membrane module 3 of the first separation stage 5, and the amount of permeation target components can be increased. According to the configuration of (5) above, for example, even if there is a limit to the supply amount of the fluid to be treated F1 and even if the number of separation membrane modules 3 in the downstream separation stage 30 is one, the flow velocity of the fluid to be treated F1 can be increased by forming a return channel 26.

[0053] 1 Membrane separation device 3 Separation membrane module 3s Separation section 5 First separation stage 6 Second separation stage 11 Separation membrane 13 Primary channel 13i Primary inlet 13o Primary outlet 15o Secondary outlet 15 Secondary channel 21 Fluid to be processed supply channel 22 Fluid to be processed outlet channel 23 Permeate fluid outlet channel 24 Recycling channel 25 Pressure booster 26 Reversal channel 30 Separation stage 31 First separation stage 32 Second separation stage 33 Third separation stage

Claims

1. A plurality of separation stages, each comprising one separation membrane module or two or more separation stages, each having the primary side passages connected in parallel to one another, the separation stage comprising one separation membrane module having a separation membrane for separating a permeate fluid from a supplied fluid to be treated, a primary side passage configured for the flow of the fluid to be treated, and a secondary side passage separated from the primary side passage by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane, wherein the plurality of separation stages comprises: a first separation stage comprising one separation membrane module or two or more separation stages comprising one separation membrane module or two or more separation stages comprising one separation membrane module or two or more separation stages comprising the primary side passages connected in parallel to one another, the primary side passage of the separation membrane module in the second separation stage being connected in series downstream of the flow of the fluid to be treated with respect to the primary side passage of the separation membrane module in the first separation stage, A membrane separation apparatus in which the flow velocity of the fluid to be processed flowing through the primary channel of the separation membrane module in the second separation stage is faster than the flow velocity of the fluid to be processed flowing through the primary channel of the separation membrane module in the first separation stage.

2. The membrane separation apparatus according to claim 1, wherein the number of separation membrane modules in the second separation stage is less than the number of separation membrane modules in the first separation stage.

3. The membrane separation apparatus according to claim 1 or 2, comprising: a recycling channel connecting the outlet of the primary channel of the separation membrane module in the second separation stage to the inlet of the primary channel; and a pressurizing device provided in the recycling channel for drawing in the fluid to be processed from the outlet of the primary channel and pressurizing it.

4. The membrane separation apparatus according to claim 1, wherein the number of separation membrane modules in the second separation stage is equal to the number of separation membrane modules in the first separation stage, the membrane area of ​​the separation membrane in the separation membrane module in the second separation stage is equal to the membrane area of ​​the separation membrane in the separation membrane module in the first separation stage, and the flow path cross-sectional area of ​​the primary side flow path of the separation membrane module in the second separation stage is smaller than the flow path cross-sectional area of ​​the primary side flow path of the separation membrane module in the first separation stage.

5. The membrane separation apparatus according to claim 4, wherein the separation membrane module in the first separation stage has an inlet for the fluid to be processed on one side in the extending direction of the primary flow path and an outlet for the fluid to be processed on the other side in the extending direction, and the separation membrane module in the second separation stage has an inlet for the fluid to be processed and an outlet for the fluid to be processed on one side in the extending direction of the primary flow path, and a return flow path is formed on the other side in the extending direction that changes the flow of the fluid to be processed from a direction toward the other side to a direction toward the one side.

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