Membrane separation device

Abstract

A membrane separation device according to at least one embodiment of the present disclosure comprises: a plurality of separation membrane modules which each have a separation membrane, a primary-side flow path and a secondary-side flow path; a changing device for changing the number of separation membrane modules that supply a fluid to be treated; a detection device for specifying the recovery rate or purity of a useful component; and a control device for controlling the changing device so as to change the number of separation membrane modules that supply the fluid to be treated on the basis of the detection results from the detection device. The changing device is configured such that the primary-side flow paths of the separation membrane modules that supply the fluid to be treated can be connected in series when the number of separation membrane modules that supply the fluid to be treated is two or more.

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. 2025-056064 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 an apparatus configured to separate some components from a fluid containing a plurality of components by a separation membrane, the substantial membrane area (hereinafter also referred to as effective membrane area) decreases due to deterioration of the separation membrane caused by use. Among the primary side flow path and the secondary side flow path separated by the separation membrane, for example, when a component useful in subsequent steps (hereinafter also referred to as a useful component), such as a product component, is contained in the fluid of the secondary side flow path that has permeated through the separation membrane, a decrease in the effective membrane area leads to a decrease in the recovery rate of the useful component. Further, for example, when the useful component is contained in the fluid of the primary side flow path, a decrease in the effective membrane area leads to a decrease in the purity of the useful component.

[0005] For this reason, spare separation membranes are sometimes arranged in anticipation of a decrease in effective membrane area, but the membrane area tends to be excessive in the initial operation stage of the apparatus. When the membrane area is excessive relative to the required membrane area, there is an increased tendency for components that are not desired to permeate through the separation membrane to permeate through the separation membrane. Therefore, when the membrane area is excessive relative to the required membrane area, for example, if a useful component is contained in the fluid of the secondary side flow path that has permeated through the separation membrane, the purity of the useful component will decrease, and for example, if a useful component is contained in the fluid of the primary side flow path, the recovery rate of the useful component will decrease.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a membrane separation apparatus capable of reducing a decrease in the recovery rate and purity of components obtained in the membrane separation apparatus.

[0007] A membrane separation apparatus according to at least one embodiment of the present disclosure comprises: a plurality of separation membrane modules each having a separation membrane for separating a permeate from a supplied fluid to be treated; a primary side flow path configured for the fluid to be treated to flow through; and a secondary side flow path separated from the primary side flow path by the separation membrane and configured for the permeate that has permeated through the separation membrane to flow through; a changing device for changing the number of separation membrane modules that supply the fluid to be treated; a detection device for identifying the recovery rate or purity of useful components; and a control device for controlling the changing device to change the number of separation membrane modules that supply the fluid to be treated based on the detection result of the detection device, wherein the changing device is configured to connect the primary side flow paths of the separation membrane modules that supply the fluid to be treated in series when the number of separation membrane modules that supply the fluid to be treated is two or more.

[0008] According to at least one embodiment of this disclosure, the recovery rate and purity of components obtained in a membrane separation apparatus can be reduced.

[0009] This figure shows the overall configuration of the membrane separation apparatus according to the first embodiment. This figure illustrates the case where there is one separation membrane module to which the fluid to be processed is supplied in the membrane separation apparatus according to the first embodiment. This figure illustrates the case where there are two separation membrane modules to which the fluid to be processed is supplied in the membrane separation apparatus according to the first embodiment. This figure illustrates the case where there are three separation membrane modules to which the fluid to be processed is supplied in the membrane separation apparatus according to the first embodiment. This figure illustrates the case where there are four separation membrane modules to which the fluid to be processed is supplied in the membrane separation apparatus according to the first embodiment. This figure shows the overall configuration of the membrane separation apparatus according to the second embodiment. This figure shows the overall configuration of an example of the membrane separation apparatus according to the third embodiment. This figure shows the overall configuration of another example of the membrane separation apparatus according to the third embodiment. This figure shows the overall configuration of the membrane separation apparatus according to the fourth embodiment. This figure illustrates the processing in the membrane separation apparatus according to the fourth embodiment.

[0010] 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.

[0011] Figure 1 is a diagram showing the overall configuration of a membrane separation apparatus according to the first embodiment. Figure 2A is a diagram illustrating the case in the membrane separation apparatus according to the first embodiment where there is one separation membrane module to which the fluid to be processed is supplied. Figure 2B is a diagram illustrating the case in the membrane separation apparatus according to the first embodiment where there are two separation membrane modules to which the fluid to be processed is supplied. Figure 2C is a diagram illustrating the case in the membrane separation apparatus according to the first embodiment where there are three separation membrane modules to which the fluid to be processed is supplied. Figure 2D is a diagram illustrating the case in the membrane separation apparatus according to the first embodiment where there are four separation membrane modules to which the fluid to be processed is supplied. Figure 3 is a diagram showing the overall configuration of a membrane separation apparatus according to the second embodiment. Figure 4 is a diagram showing the overall configuration of an example of a membrane separation apparatus according to the third embodiment. Figure 5 is a diagram showing the overall configuration of another example of a membrane separation apparatus according to the third embodiment. Figure 6 is a diagram showing the overall configuration of a membrane separation apparatus according to the fourth embodiment. Figure 7 is a diagram illustrating the processing in the membrane separation apparatus according to the fourth embodiment.

[0012] (Regarding configurations common to each embodiment) As shown in Figures 1 to 7, the membrane separation apparatus 1 according to some embodiments includes a plurality of separation membrane modules 3, a changing device 5 for changing the number of separation membrane modules 3 that supply the fluid to be processed F1, a detection device 7, and a control device 9. The membrane separation apparatus 1 according to some embodiments is connected to a fluid to be processed supply channel 21 for supplying the fluid to be processed F1 to the membrane separation apparatus 1. The membrane separation apparatus 1 according to some embodiments includes a fluid to be processed discharge channel 22 for discharging the fluid to be processed F1 from the primary side channel 13 of the separation membrane module 3 (described later) to the outside (outside the system) of the membrane separation apparatus 1, and a permeate fluid discharge channel 23 for discharging the permeate fluid F2 from the secondary side channel 15 of the separation membrane module 3 (described later) to the outside (outside the system) of the membrane separation apparatus 1.

[0013] (Separation Membrane Module 3) Each of the plurality of separation membrane modules 3 includes 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.

[0014] Multiple separation membrane modules 3 are configured such that their respective primary flow paths 13 can be connected in series. Specifically, the primary inlet 13i of the first-stage separation membrane module 3A, located furthest upstream in the flow of the fluid to be processed F1, is connected to a fluid supply flow path 21 for supplying the fluid to be processed F1 to the membrane separation device 1. The primary outlet 13o of the first-stage separation membrane module 3A and the primary inlet 13i of the second-stage separation membrane module 3B, which is related to the flow of the fluid to be processed F1, are connected via a primary-side first switching valve 5A, which will be described later. The primary outlet 13o of the second-stage separation membrane module 3B and the primary inlet 13i of the third-stage separation membrane module 3C, which is related to the flow of the fluid to be processed F1, are connected via a primary-side second switching valve 5B, which will be described later. The primary outlet 13o of the third-stage separation membrane module 3C and the primary inlet 13i of the fourth-stage separation membrane module 3D, which is related to the flow of the fluid to be processed F1, are connected via a primary-side third switching valve 5C, which will be described later.

[0015] In Figure 3, for illustrative purposes, the third separation membrane module 3C and the fourth separation membrane module 3D are omitted from the description. In some embodiments of the membrane separation apparatus 1, the number of separation membrane modules 3 is four, but the number of separation membrane modules 3 is not limited to four; it can be two or more. In the following description, when referring to the first to fourth separation membrane modules 3A through 3D collectively, or when there is no need to distinguish between each of the first to fourth separation membrane modules 3D, they will simply be referred to as separation membrane modules 3.

[0016] The primary side outlet 13o of the first stage separation membrane module 3A is also connected to the fluid to be processed outlet channel 22 via the primary side first switching valve 5A. The primary side outlet 13o of the second stage separation membrane module 3B is also connected to the fluid to be processed outlet channel 22 via the primary side second switching valve 5B. The primary side outlet 13o of the third stage separation membrane module 3C is also connected to the fluid to be processed outlet channel 22 via the primary side third switching valve 5C. The primary side outlet 13o of the fourth stage separation membrane module 3D is connected to the fluid to be processed outlet channel 22 via the primary side on / off valve 5D, which will be described later.

[0017] The secondary outlet 15o of the first-stage separation membrane module 3A is connected to the permeate fluid outlet channel 23 via a channel 41. The secondary outlet 15o of the second-stage separation membrane module 3B is connected to the permeate fluid outlet channel 23 via a channel 42. The secondary outlet 15o of the third-stage separation membrane module 3C is connected to the permeate fluid outlet channel 23 via a channel 43. The secondary outlet 15o of the fourth-stage separation membrane module 3D is connected to the permeate fluid outlet channel 23 via a channel 44.

[0018] (Changing device 5) In some embodiments of the membrane separation apparatus 1, the changing device 5 includes a primary side first switching valve 5A, a primary side second switching valve 5B, a primary side third switching valve 5C, and a primary side on / off valve 5D. The primary side first switching valve 5A is a switching valve positioned between the primary side outlet 13o of the first stage separation membrane module 3A and the flow path 31 connecting the fluid to be processed outlet flow path 22. The primary side first switching valve 5A is a switching valve for switching whether the fluid to be processed F1 from the primary side flow path 13 of the first stage separation membrane module 3A flows to the fluid to be processed outlet flow path 22 or to the primary side flow path 13 of the second stage separation membrane module 3B.

[0019] The primary-side second switching valve 5B is a switching valve positioned between the primary-side outlet 13o of the second-stage separation membrane module 3B and the flow path 32 connecting the fluid to be processed outlet 22. The primary-side second switching valve 5B is a switching valve for switching whether the fluid to be processed F1 from the primary-side flow path 13 of the second-stage separation membrane module 3B flows to the fluid to be processed outlet 22 or to the primary-side flow path 13 of the third-stage separation membrane module 3C.

[0020] The primary-side third switching valve 5C is a switching valve positioned between the primary-side outlet 13o of the third-stage separation membrane module 3C and the flow path 33 connecting the fluid to be processed outlet 22. The primary-side third switching valve 5C is a switching valve for switching whether the fluid to be processed F1 from the primary-side flow path 13 of the third-stage separation membrane module 3C flows to the fluid to be processed outlet 22 or to the primary-side flow path 13 of the fourth-stage separation membrane module 3D.

[0021] The primary side on-off valve 5D is an on-off valve positioned between the primary side outlet portion 13o of the fourth stage separation membrane module 3D and the flow path 34 connecting the fluid to be processed outlet flow path 22. In the following description, when referring to the primary side first switching valve 5A to the primary side third switching valve 5C and the primary side on-off valve 5D collectively, or when there is no need to particularly distinguish between the primary side first switching valve 5A to the primary side third switching valve 5C and the primary side on-off valve 5D, they will simply be referred to as the changing device 5.

[0022] In some embodiments of the membrane separation apparatus 1, the changing device 5 is configured to connect the primary side flow paths 13 of the separation membrane modules 3 that supply the fluid to be processed F1 in series, as described later, when the number of separation membrane modules 3 that supply the fluid to be processed F1 is two or more. In some embodiments of the membrane separation apparatus 1, the changing device 5 is controlled by a control device 9, which will be described later, based on the detection result of a detection device 7, which will be described later.

[0023] (Detection device 7) In some embodiments of the membrane separation apparatus 1, the detection device 7 is a sensor for determining the recovery rate or purity of useful components, and includes a primary flow rate detection device 71, a primary concentration detection device 72, a secondary flow rate detection device 73, and a secondary concentration detection device 74. Useful components will be explained later. The primary flow rate detection device 71 is a sensor for detecting the flow rate of the fluid to be treated F1 after it has flowed through the entire separation membrane module 3 to which the fluid to be treated F1 is supplied, and is located downstream of the fluid to be treated outlet channel 22, beyond the connection points with all the channels from channel 31 to channel 34 in the fluid to be treated outlet channel 22. The primary concentration detection device 72 is a sensor for detecting the concentration of the target component in the fluid to be treated F1 after it has flowed through the entire separation membrane module 3 to which the fluid to be treated F1 is supplied, and is located downstream of the fluid to be treated outlet channel 22, beyond the connection points with all the channels from channel 31 to channel 34 in the fluid to be treated outlet channel 22.

[0024] The secondary flow rate detection device 73 is a sensor for detecting the flow rate of permeate fluid F2 from all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied, and is located downstream of the permeate fluid outlet channel 23, beyond the connection points with all of the channels from channel 41 to channel 44 in the permeate fluid outlet channel 23. The secondary concentration detection device 74 is a sensor for detecting the concentration of the target component in the permeate fluid F2 from all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied, and is located downstream of the permeate fluid outlet channel 23, beyond the connection points with all of the channels from channel 41 to channel 44 in the permeate fluid outlet channel 23.

[0025] (Control device 9) In some embodiments of the membrane separation apparatus 1, the control device 9 is a device for controlling the changing device 5 to change the number of separation membrane modules 3 that supply the fluid to be processed F1 based on the detection result of the detection device 7. The control device 9 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example, and the CPU reads this program into the RAM and executes information processing and calculations to realize various functions. The program may be pre-installed in the ROM or other storage medium, provided in a state where it is stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memory.

[0026] (When the number of separation membrane modules 3 supplying the fluid to be processed F1 is 1) As shown in Figure 2A, when the number of separation membrane modules 3 supplying the fluid to be processed F1 is 1, the control device 9 controls the change device 5 as follows. In Figures 2A to 2D, for each valve of the change device 5, open ports are represented by white triangles, and closed ports are represented by black triangles.

[0027] When the number of separation membrane modules 3 supplying the fluid to be processed F1 is 1, the control device 9 controls the primary side first switching valve 5A to connect the primary side outlet 13o of the first stage separation membrane module 3A to the fluid to be processed outlet channel 22, and to block the connection between the primary side outlet 13o of the first stage separation membrane module 3A and the primary side inlet 13i of the second stage separation membrane module 3B. As a result, the fluid to be processed F1 from the primary side channel 13 of the first stage separation membrane module 3A is allowed to flow into the fluid to be processed outlet channel 22 by the primary side first switching valve 5A, while flow into the primary side channel 13 of the second stage separation membrane module 3B is prohibited. Consequently, the fluid to be processed F1 supplied from the fluid to be processed supply channel 21 flows through the primary side channel 13 of the first stage separation membrane module 3A and flows into the fluid to be processed outlet channel 22. The control device 9 controls the primary side second switching valve 5B to block communication between the primary side outlet 13o of the second stage separation membrane module 3B and the fluid to be processed discharge channel 22, and to block communication between the primary side outlet 13o of the second stage separation membrane module 3B and the primary side inlet 13i of the third stage separation membrane module 3C.

[0028] The control device 9 controls the primary third switching valve 5C to block communication between the primary outlet 13o of the third stage separation membrane module 3C and the fluid to be processed discharge channel 22, and to block communication between the primary outlet 13o of the third stage separation membrane module 3C and the primary inlet 13i of the fourth stage separation membrane module 3D. The control device 9 controls the primary on / off valve 5D to block communication between the primary outlet 13o of the fourth stage separation membrane module 3D and the fluid to be processed discharge channel 22.

[0029] (When the number of separation membrane modules 3 supplying the fluid to be processed F1 is 2) As shown in Figure 2B, when the number of separation membrane modules 3 supplying the fluid to be processed F1 is 2, the control device 9 controls the change device 5 as follows. That is, the control device 9 blocks communication between the primary side outlet 13o of the first stage separation membrane module 3A and the fluid to be processed outlet channel 22, and controls the primary side first switching valve 5A to connect the primary side outlet 13o of the first stage separation membrane module 3A and the primary side inlet 13i of the second stage separation membrane module 3B. As a result, the fluid to be processed F1 from the primary side channel 13 of the first stage separation membrane module 3A is prohibited from flowing to the fluid to be processed outlet channel 22 by the primary side first switching valve 5A, and is permitted to flow to the primary side channel 13 of the second stage separation membrane module 3B.

[0030] Furthermore, the control device 9 controls the primary side second switching valve 5B to connect the primary side outlet 13o of the second stage separation membrane module 3B to the fluid to be processed outlet channel 22, and to block the communication between the primary side outlet 13o of the second stage separation membrane module 3B and the primary side inlet 13i of the third stage separation membrane module 3C. As a result, the fluid to be processed F1 supplied from the fluid to be processed supply channel 21 flows sequentially through the primary side channel 13 of the first stage separation membrane module 3A and the primary side channel 13 of the second stage separation membrane module 3B, and flows into the fluid to be processed outlet channel 22.

[0031] The control device 9 controls the primary third switching valve 5C to block communication between the primary outlet 13o of the third stage separation membrane module 3C and the fluid to be processed discharge channel 22, and to block communication between the primary outlet 13o of the third stage separation membrane module 3C and the primary inlet 13i of the fourth stage separation membrane module 3D. The control device 9 controls the primary on / off valve 5D to block communication between the primary outlet 13o of the fourth stage separation membrane module 3D and the fluid to be processed discharge channel 22.

[0032] (When the number of separation membrane modules 3 supplying the fluid to be processed F1 is 3) As shown in Figure 2C, when the number of separation membrane modules 3 supplying the fluid to be processed F1 is 3, the control device 9 controls the change device 5 as follows. That is, the control device 9 blocks communication between the primary side outlet 13o of the first stage separation membrane module 3A and the fluid to be processed outlet channel 22, and controls the primary side first switching valve 5A to connect the primary side outlet 13o of the first stage separation membrane module 3A and the primary side inlet 13i of the second stage separation membrane module 3B. As a result, the fluid to be processed F1 from the primary side channel 13 of the first stage separation membrane module 3A is prohibited from flowing to the fluid to be processed outlet channel 22 by the primary side first switching valve 5A, and is permitted to flow to the primary side channel 13 of the second stage separation membrane module 3B.

[0033] Furthermore, the control device 9 blocks communication between the primary side outlet 13o of the second stage separation membrane module 3B and the fluid to be processed outlet channel 22, and controls the primary side second switching valve 5B to connect the primary side outlet 13o of the second stage separation membrane module 3B and the primary side inlet 13i of the third stage separation membrane module 3C. As a result, the fluid to be processed F1 from the primary side channel 13 of the second stage separation membrane module 3B is prohibited from flowing into the fluid to be processed outlet channel 22 by the primary side second switching valve 5B, while flow into the primary side channel 13 of the third stage separation membrane module 3C is permitted.

[0034] The control device 9 controls the primary side third switching valve 5C to connect the primary side outlet 13o of the third stage separation membrane module 3C to the fluid to be processed outlet channel 22, and to block the connection between the primary side outlet 13o of the third stage separation membrane module 3C and the primary side inlet 13i of the fourth stage separation membrane module 3D. As a result, the fluid to be processed F1 supplied from the fluid to be processed supply channel 21 flows sequentially through the primary side channel 13 of the first stage separation membrane module 3A, the primary side channel 13 of the second stage separation membrane module 3B, and the primary side channel 13 of the third stage separation membrane module 3C, before flowing into the fluid to be processed outlet channel 22.

[0035] The control device 9 controls the primary side on / off valve 5D to block communication between the primary side outlet 13o of the fourth stage separation membrane module 3D and the fluid to be processed discharge channel 22.

[0036] (When the number of separation membrane modules 3 supplying the fluid to be processed F1 is 4) As shown in Figure 2D, when the number of separation membrane modules 3 supplying the fluid to be processed F1 is 4, the control device 9 controls the change device 5 as follows. That is, the control device 9 blocks communication between the primary side outlet 13o of the first stage separation membrane module 3A and the fluid to be processed outlet channel 22, and controls the primary side first switching valve 5A to connect the primary side outlet 13o of the first stage separation membrane module 3A and the primary side inlet 13i of the second stage separation membrane module 3B. As a result, the fluid to be processed F1 from the primary side channel 13 of the first stage separation membrane module 3A is prohibited from flowing to the fluid to be processed outlet channel 22 by the primary side first switching valve 5A, and is permitted to flow to the primary side channel 13 of the second stage separation membrane module 3B.

[0037] Furthermore, the control device 9 blocks communication between the primary side outlet 13o of the second stage separation membrane module 3B and the fluid to be processed outlet channel 22, and controls the primary side second switching valve 5B to connect the primary side outlet 13o of the second stage separation membrane module 3B and the primary side inlet 13i of the third stage separation membrane module 3C. As a result, the fluid to be processed F1 from the primary side channel 13 of the second stage separation membrane module 3B is prohibited from flowing into the fluid to be processed outlet channel 22 by the primary side second switching valve 5B, while flow into the primary side channel 13 of the third stage separation membrane module 3C is permitted.

[0038] The control device 9 blocks communication between the primary outlet 13o of the third-stage separation membrane module 3C and the fluid to be processed outlet channel 22, and controls the primary-side third switching valve 5C to connect the primary outlet 13o of the third-stage separation membrane module 3C and the primary inlet 13i of the fourth-stage separation membrane module 3D. As a result, the fluid to be processed F1 from the primary-side channel 13 of the third-stage separation membrane module 3C is prohibited from flowing into the fluid to be processed outlet channel 22 by the primary-side third switching valve 5C, while flow into the primary-side channel 13 of the fourth-stage separation membrane module 3D is permitted.

[0039] The control device 9 controls the primary side opening / closing valve 5D such that the primary side outlet portion 13o of the 4th-stage separation membrane module 3D communicates with the fluid-to-be-treated outlet flow path 22. As described above, the fluid to be treated F1 supplied from the fluid-to-be-treated supply flow path 21 sequentially flows through the primary side flow path 13 of the 1st-stage separation membrane module 3A, the primary side flow path 13 of the 2nd-stage separation membrane module 3B, the primary side flow path 13 of the 3rd-stage separation membrane module 3C, and the primary side flow path 13 of the 4th-stage separation membrane module 3D, and flows into the fluid-to-be-treated outlet flow path 22.

[0040] (Regarding Permeation Amount of Permeation Target Component in Separation Membrane) The permeation amount of a permeation target component in a separation membrane will be described. The permeation amount Qx of the permeation target component in the separation membrane can be obtained by the following formula (1) or formula (2). Note that formula (1) corresponds to the case of membrane separation by the VP method (VP: Vapor permeation), and formula (2) corresponds to the case of membrane separation by the PV method (PV: Pervaporation). Qx = f・kx・(px1-px2)・A ・・・(1) Qx = f・kx・(p ＊ x-px2)・A ・・・(2)

[0041] The coefficients and parameters in formula (1) and formula (2) are as follows. kx: Permeation coefficient of permeation target component x [kg / (m ２ ・h・kPa)] Qx: Permeation amount of permeation target component x [kg / h] px1: Partial pressure [kPa] of permeation target component x on the primary side (non-permeation side) px2: Partial pressure [kPa] of permeation target component x on the secondary side (permeation side) p ＊ x: Saturated vapor pressure [kPa] of permeation target component x on the primary side A: Membrane area of the separation membrane [m ２ f: Deterioration coefficient of the separation membrane [-]

[0042] The deterioration coefficient f of a separation membrane is a dimensionless coefficient where the deterioration coefficient f of an unused separation membrane is set to 1, and its value gradually becomes smaller than 1 as deterioration progresses due to use of the separation membrane.

[0043] In a device configured to separate some components from a fluid containing multiple components using a separation membrane, as the separation membrane deteriorates with use, the deterioration coefficient f decreases, resulting in a decrease in the amount Qx of the target component that permeates through the separation membrane. In other words, as the separation membrane deteriorates with use, the effective membrane area (hereinafter also referred to as the effective membrane area) decreases due to the deterioration of the separation membrane. Here, the effective membrane area corresponds to the product of the membrane area A of the separation membrane and the deterioration coefficient f of the separation membrane (f・A).

[0044] (Regarding the effects of deterioration of the separation membrane 11 and countermeasures) In the membrane separation apparatus 1 according to several embodiments, if it is desired to separate components useful in subsequent processes after processing by the membrane separation apparatus 1 according to several embodiments, such as product components, into the secondary channel 15, which has permeated through the separation membrane 11, the recovery rate of the useful components in the secondary channel 15 will decrease if the separation membrane 11 deteriorates. Also, if it is desired to leave the useful components in the primary channel 13, for example, if the separation membrane 11 deteriorates, the purity of the useful components in the primary channel 13 will decrease.

[0045] Therefore, in the membrane separation apparatus 1 according to some embodiments, for example, if it is desired to separate useful components to the secondary flow path 15, the number of separation membrane modules 3 supplied with the fluid to be processed F1 is increased by one if the recovery rate of useful components in the secondary flow path 15 falls below a specified recovery rate. Here, when it is desired to separate useful components to the secondary flow path 15, the degree of decrease in the recovery rate of useful components in the secondary flow path 15 can be determined by the flow rate of the permeate fluid F2 from all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied. Therefore, in the membrane separation apparatus 1 according to some embodiments, the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 supplied with the fluid to be processed F1 by one if the flow rate of the permeate fluid F2 detected by the secondary flow rate detection device 73 is below a specified flow rate Q1. This makes it possible to increase the recovery rate of useful components, for example, when it is desired to include useful components in the permeate fluid F2 of the secondary flow path 15. The specified flow rate Q1 is a predetermined value depending on the composition of the fluid to be treated F1 before processing by the membrane separation apparatus 1 according to several embodiments, the supply flow rate of the fluid to be treated F1 supplied to the membrane separation apparatus 1, the supply pressure, the supply temperature, etc.

[0046] In the membrane separation device 1 according to some embodiments, for example, when it is desired to leave useful components on the primary side flow path 13 side, if the separation membrane 11 deteriorates, it becomes difficult to remove components to be removed from the fluid to be treated F1, so the flow rate of the permeated fluid F2 detected by the secondary side flow rate detection device 73 decreases, and the purity of the useful components on the primary side flow path 13 side decreases. That is, when it is desired to leave useful components on the primary side flow path 13 side, the degree of decrease in the purity of the useful components on the primary side flow path 13 side can be determined by the flow rate of the permeated fluid F2 from all of the separation membrane modules 3 supplied with the fluid to be treated F1. Therefore, in the membrane separation device 1 according to some embodiments, the control device 9 controls the changing device 5 to increase the number of separation membrane modules 3 supplied with the fluid to be treated F1 by one when the flow rate of the permeated fluid F2 detected by the secondary side flow rate detection device 73 is equal to or lower than a specified flow rate Q2. Accordingly, for example, when it is desired to leave useful components on the primary side flow path 13 side, the purity of the useful components on the primary side flow path 13 side can be increased. Note that the specified flow rate Q2 is a value predetermined in accordance with the composition of the fluid to be treated F1 before treatment by the membrane separation device 1 according to some embodiments, the supply flow rate, supply pressure, supply temperature, etc. of the fluid to be treated F1 supplied to the membrane separation device 1, and is a value different from the aforementioned specified flow rate Q1.

[0047] As described above, in the membrane separation device 1 according to some embodiments, when the flow rate of the permeated fluid F2 detected by the secondary side flow rate detection device 73 is equal to or lower than a specified flow rate (specified flow rate Q1 or specified flow rate Q2), the control device 9 controls the changing device 5 to increase the number of separation membrane modules 3 supplied with the fluid to be treated F1 by one, thereby reducing the decrease in recovery rate and purity of useful components.

[0048] Furthermore, if it is desired to separate useful components to the secondary flow path 15, a decrease in the recovery rate of useful components on the secondary flow path 15 will increase the flow rate of the fluid to be treated F1 after it has flowed through all of the separation membrane modules 3 to which it is supplied. Therefore, if it is desired to separate useful components to the secondary flow path 15, the degree of decrease in the recovery rate of useful components on the secondary flow path 15 can be determined by the flow rate of the fluid to be treated F1 after it has flowed through all of the separation membrane modules 3 to which it is supplied. Accordingly, in some embodiments of the membrane separation apparatus 1, the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be treated F1 is supplied by one if the flow rate of the fluid to be treated F1 detected by the primary flow rate detection device 71 is equal to or greater than a specified flow rate Q3. This makes it possible to increase the recovery rate of useful components on the secondary flow path 15, for example, if it is desired to separate useful components to the secondary flow path 15. The specified flow rate Q3 is a value predetermined according to the composition of the fluid to be treated F1 before processing by the membrane separation apparatus 1 according to several embodiments, the supply flow rate of the fluid to be treated F1 supplied to the membrane separation apparatus 1, the supply pressure, the supply temperature, etc., and is a different value from the specified flow rate Q1 and specified flow rate Q2 mentioned above.

[0049] In some embodiments of the membrane separation apparatus 1, if it is desired to leave useful components on the primary flow path 13 side, the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 increases because if the separation membrane 11 deteriorates, it becomes difficult to remove the components that should be removed from the fluid to be processed F1. In other words, if it is desired to leave useful components on the primary flow path 13 side, the degree of decrease in the purity of the useful components on the primary flow path 13 side can be determined by the flow rate of the fluid to be processed F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied. Therefore, in some embodiments of the membrane separation apparatus 1, if the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is equal to or greater than a specified flow rate Q4, the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be processed F1 is supplied by one. This makes it possible to increase the purity of the useful components on the primary flow path 13 side, for example, if it is desired to leave useful components in the fluid of the primary flow path 13. The specified flow rate Q4 is a value predetermined according to the composition of the fluid to be treated F1 before processing by the membrane separation apparatus 1 according to several embodiments, the supply flow rate of the fluid to be treated F1 supplied to the membrane separation apparatus 1, the supply pressure, the supply temperature, etc., and is a different value from the specified flow rate Q1, specified flow rate Q2, and specified flow rate Q3.

[0050] Thus, in the membrane separation apparatus 1 according to some embodiments, when the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is equal to or greater than a specified flow rate (specified flow rate Q3 or specified flow rate Q4), the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 that supply the fluid to be processed F1 by one, thereby reducing the recovery rate and purity of useful components.

[0051] Furthermore, in some embodiments of the membrane separation apparatus 1, if it is desired to leave useful components on the primary flow path 13 side, the number of separation membrane modules 3 supplying the fluid to be processed F1 is increased by one when the purity of the useful components on the primary flow path 13 side falls below a specified purity. Here, when it is desired to leave useful components on the primary flow path 13 side, the degree of decrease in the purity of the useful components on the primary flow path 13 side can be determined by the concentration of the target component, i.e., the useful component, in the fluid to be processed F1 after it has flowed through all of the separation membrane modules 3 to which it was supplied. Therefore, in some embodiments of the membrane separation apparatus 1, the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 supplying the fluid to be processed F1 by one when the concentration of the useful components detected by the primary concentration detection device 72 is below a specified concentration C1. This makes it possible to increase the purity of the useful components, for example, when it is desired to leave useful components on the primary flow path 13 side. The specified concentration C1 is a predetermined value.

[0052] In some embodiments of the membrane separation apparatus 1, when it is desired to separate useful components to the secondary flow path 15, a decrease in the recovery rate of useful components in the secondary flow path 15 leads to an increase in the concentration of useful components in the fluid to be processed F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied. That is, when it is desired to separate useful components to the secondary flow path 15, the degree of decrease in the recovery rate of useful components in the secondary flow path 15 can be determined by the concentration of the target component, i.e., the useful component, in the fluid to be processed F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied. Therefore, in some embodiments of the membrane separation apparatus 1, the control device 9 controls the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be processed F1 is supplied by one if the concentration of useful components detected by the primary side concentration detection device 72 is equal to or greater than a specified concentration C2. This makes it possible to increase the recovery rate of useful components in the secondary flow path 15, for example, when it is desired to separate useful components to the secondary flow path 15. Note that the specified concentration C2 is a predetermined value and is different from the specified concentration C1 mentioned above.

[0053] To increase the number of separation membrane modules 3 supplying the fluid to be processed F1 by one, the control device 9 controls the modification device 5 as follows: For example, if the number of separation membrane modules 3 supplying the fluid to be processed F1 is 1 as shown in Figure 2A, the control device 9 controls the modification device 5 as described above so that the number of separation membrane modules 3 supplying the fluid to be processed F1 becomes 2 as shown in Figure 2B. For example, if the number of separation membrane modules 3 supplying the fluid to be processed F1 is 2 as shown in Figure 2B, the control device 9 controls the modification device 5 as described above so that the number of separation membrane modules 3 supplying the fluid to be processed F1 becomes 3 as shown in Figure 2C. For example, if the number of separation membrane modules 3 supplying the fluid to be processed F1 is 3 as shown in Figure 2C, the control device 9 controls the modification device 5 as described above so that the number of separation membrane modules 3 supplying the fluid to be processed F1 becomes 4 as shown in Figure 2D.

[0054] As described above, according to several embodiments of the membrane separation apparatus 1, the control device 9 can determine the degree of decrease in the recovery rate or purity of useful components due to deterioration of the separation membrane 11 in the separation membrane module 3 to which the fluid to be processed F1 is supplied, based on the detection result of the detection device 7 for determining the recovery rate or purity of useful components, and change the number of separation membrane modules 3 to which the fluid to be processed F1 is supplied. This makes it possible to reduce the decrease in the recovery rate or purity of useful components.

[0055] (Regarding the effects of excessive membrane area A of the separation membrane 11 and countermeasures) If a spare separation membrane module 3 is connected in anticipation of the deterioration of the separation membrane 11 as described above, and the fluid to be processed F1 is flowed through the spare separation membrane module 3 from the beginning, the membrane area A will be excessive in the initial stages of operation of the membrane separation device 1. When the membrane area A is excessive compared to the required membrane area A, there is a higher tendency for components that are not desired to permeate the separation membrane 11 to permeate the separation membrane 11. Therefore, when the membrane area A is excessive compared to the required membrane area A, for example, if it is desired to separate useful components to the secondary flow path 15, the purity of the useful components will decrease, and for example, if it is desired to leave useful components on the primary flow path 13, the recovery rate of the useful components will decrease.

[0056] According to several embodiments of the membrane separation apparatus 1, the effect of the excessive membrane area A of the separation membrane 11 can be reduced by setting the specified flow rates Q1, Q2, Q3, Q4 and specified concentrations C1, C2 described above so as to increase the number of separation membrane modules 3 after the deterioration of the separation membrane 11 has progressed to a certain extent.

[0057] In some embodiments of the membrane separation apparatus 1, the total area of ​​the membrane surface A through which the fluid to be processed F1 flows increases by the amount of one separation membrane module 3 immediately after increasing the number of separation membrane modules 3 through which the fluid to be processed F1 flows, as described above. Therefore, immediately after increasing the number of separation membrane modules 3 through which the fluid to be processed F1 flows, the total area of ​​the membrane surface A through which the fluid to be processed F1 flows may exceed the appropriate membrane surface area A. To address this, the membrane separation apparatus 1 according to the second embodiment reduces the influence of the excess membrane surface area A as follows.

[0058] As shown in Figure 3, the membrane separation apparatus 1 according to the second embodiment includes, in addition to the configuration of the membrane separation apparatus 1 according to the first embodiment shown in Figure 1, a secondary pressure regulating device 50 provided in the flow path 42 connecting the secondary outlet 15o of the second stage separation membrane module 3B and the permeate fluid outlet flow path 23. The secondary pressure regulating device 50 provided in the flow path 42 is a device for regulating the pressure of the secondary flow path 15 of the second stage separation membrane module 3B. The secondary pressure regulating device 50 provided in the flow path 42 includes, for example, a flow control valve 51 for regulating the flow rate of the permeate fluid F2 flowing through the flow path 42, and a booster device 52 configured to suck in the permeate fluid F2 from the secondary flow path 15 and discharge it to the permeate fluid outlet flow path 23. The secondary pressure regulating device 50 provided in the flow path 42 can control the partial pressure px2 of the permeate target component x in the second stage separation membrane module 3B as follows.

[0059] In the membrane separation apparatus 1 according to the second embodiment, the flow path 42 is provided with a secondary pressure detection device 75 for detecting the pressure in the secondary flow path 15 of the second stage separation membrane module 3B. The secondary pressure detection device 75 is a pressure sensor for detecting the pressure in the secondary flow path 15 of the second stage separation membrane module 3B.

[0060] Although not shown in Figure 3, the membrane separation apparatus 1 according to the second embodiment includes, similar to the case of the second-stage separation membrane module 3B, a secondary pressure regulating device 50 (not shown) provided in the flow path 43 connecting the secondary outlet 15o of the third-stage separation membrane module 3C and the permeable fluid outlet flow path 23, and a secondary pressure detection device 75 (not shown) for detecting the pressure in the secondary flow path 15 of the third-stage separation membrane module 3C. Furthermore, the membrane separation apparatus 1 according to the second embodiment includes, similar to the case of the second-stage separation membrane module 3B, a secondary pressure regulating device 50 (not shown) provided in the flow path 44 connecting the secondary outlet 15o of the fourth-stage separation membrane module 3D and the permeable fluid outlet flow path 23, and a secondary pressure detection device 75 (not shown) for detecting the pressure in the secondary flow path 15 of the fourth-stage separation membrane module 3D.

[0061] For example, consider the case where the number of separation membrane modules 3 that supply the fluid to be processed F1 is changed from 1 to 2, as shown in Figure 2B.

[0062] (Immediately after changing the number of separation membrane modules 3 that supply the fluid to be processed F1) Immediately after changing the number of separation membrane modules 3 that supply the fluid to be processed F1 from 1 to 2, the total area of ​​membrane A through which the fluid to be processed F1 flows may exceed the appropriate membrane area A.

[0063] Therefore, when the number of separation membrane modules 3 supplying the fluid to be processed F1 is changed from 1 to 2, it is possible to increase the pressure in the secondary flow path 15 of the second-stage separation membrane module 3B by narrowing the opening of the flow control valve 51 provided in the flow path 42. When the pressure in the secondary flow path 15 of the second-stage separation membrane module 3B is increased, the value of px2 in equation (1) or (2) above increases, so the amount Qx of the permeation target component x in the second-stage separation membrane module 3B decreases. In other words, this is equivalent to a decrease in the apparent membrane area A in the second-stage separation membrane module 3B. For this reason, even if the total area of ​​the membrane area A through which the fluid to be processed F1 flows exceeds the appropriate membrane area A immediately after changing the number of separation membrane modules 3 supplying the fluid to be processed F1 from 1 to 2, the apparent membrane area A in the second-stage separation membrane module 3B can be reduced by increasing the pressure in the secondary flow path 15 of the second-stage separation membrane module 3B.

[0064] This allows for a reduction in the recovery rate of useful components, even if the membrane area A is excessive compared to the required membrane area A, when, for example, it is desired to leave useful components on the primary channel 13 side. Furthermore, when, for example, it is desired to separate useful components on the secondary channel 15 side, a reduction in the purity of the useful components can be reduced even if the membrane area A is excessive compared to the required membrane area A.

[0065] Furthermore, whether the total area of ​​the membrane A through which the fluid to be processed F1 flows exceeds the appropriate membrane area A can be determined by the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71. Specifically, if the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is less than or equal to a specified flow rate Q5, the control device 9 should determine that the total area of ​​the membrane A through which the fluid to be processed F1 flows exceeds the appropriate membrane area A. In other words, if the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is less than or equal to a specified flow rate Q5, the control device 9 should control the secondary pressure regulator 50 (flow rate control valve 51) to increase the pressure in the secondary flow path 15 of the second stage separation membrane module 3B. The specified flow rate Q5 is a value predetermined by tests or other means.

[0066] (If the separation membrane 11 deteriorates after changing the number of separation membrane modules 3 that supply the fluid to be processed F1) If the separation membrane 11 deteriorates after changing the number of separation membrane modules 3 that supply the fluid to be processed F1 from 1 to 2, as described above, a decrease in the recovery rate of useful components and a decrease in the purity of useful components will occur.

[0067] Therefore, if the separation membrane 11 deteriorates after changing the number of separation membrane modules 3 that supply the fluid to be processed F1 from 1 to 2, it is conceivable to lower the pressure in the secondary channel 15 of the second-stage separation membrane module 3B by using a pressure booster 52 provided in the channel 42 to suck in the permeate fluid F2 from the secondary channel 15. Lowering the pressure in the secondary channel 15 of the second-stage separation membrane module 3B reduces the value of px2 in equation (1) or (2) described above, so that the amount Qx of the permeate target component x in the second-stage separation membrane module 3B increases. In other words, it is the same as increasing the apparent membrane area A in the second-stage separation membrane module 3B. For this reason, even if the separation membrane 11 deteriorates after changing the number of separation membrane modules 3 that supply the fluid to be processed F1 from 1 to 2, the apparent membrane area A in the second-stage separation membrane module 3B can be increased by lowering the pressure in the secondary channel 15 of the second-stage separation membrane module 3B.

[0068] As a result, for example, if it is desired to leave the useful components on the primary channel 13 side, even if the purity of the useful components decreases due to the deterioration of the separation membrane 11, the decrease in the purity of the useful components can be reduced by lowering the pressure in the secondary channel 15. Also, for example, if it is desired to separate the useful components on the secondary channel 15 side, even if the recovery rate of the useful components decreases due to the deterioration of the separation membrane 11, the decrease in the recovery rate of the useful components can be reduced by lowering the pressure in the secondary channel 15.

[0069] Whether or not the separation membrane 11 is deteriorating can be determined by the concentration of the target component in the fluid to be processed F1 detected by the primary concentration detection device 72, or by the flow rate of the permeate fluid F2 detected by the secondary flow rate detection device 73. Specifically, if the concentration of the target component in the fluid to be processed F1 detected by the primary concentration detection device 72 is below a specified concentration C3, or if the flow rate of the permeate fluid F2 detected by the secondary flow rate detection device 73 is below a specified flow rate Q6, it should be determined that the separation membrane 11 is deteriorating. In other words, if the concentration of the target component in the fluid to be processed F1 detected by the primary concentration detection device 72 is below a specified concentration C3, or if the flow rate of the permeate fluid F2 detected by the secondary flow rate detection device 73 is below a specified flow rate Q6, the control device 9 should control the secondary pressure regulator 50 (pressure booster 52) to lower the pressure in the secondary flow path 15 of the second stage separation membrane module 3B. The specified concentration C3 and specified flow rate Q6 are values ​​predetermined through testing or other means.

[0070] The above description explained the control of the secondary pressure regulator 50 installed in the flow path 42 after changing the number of separation membrane modules 3 supplying the fluid to be processed F1 from 1 to 2. The same applies to the control of the secondary pressure regulator 50 (not shown) installed in the flow path 43 after changing the number of separation membrane modules 3 supplying the fluid to be processed F1 from 2 to 3, and to the control of the secondary pressure regulator 50 (not shown) installed in the flow path 44 after changing the number of separation membrane modules 3 supplying the fluid to be processed F1 from 3 to 4.

[0071] Thus, in the membrane separation apparatus 1 according to the second embodiment, the pressure of the secondary flow path 15 in the separation membrane modules 3 other than the first-stage separation membrane module 3A is adjusted by the secondary pressure adjustment device 50. As a result, the pressure of the permeate fluid F2 from the secondary flow path 15 of the separation membrane modules 3 other than the first-stage separation membrane module 3A, which has a relatively smaller flow rate than the flow rate of the permeate fluid F2 from the secondary flow path 15 of the first-stage separation membrane module 3A, is adjusted, thus reducing the energy consumed compared to adjusting the pressure of the permeate fluid F2 from the secondary flow path 15 of the separation membrane module 3 of the first-stage separation membrane module 3A.

[0072] Here, among the multiple separation membrane modules 3 to which the fluid to be treated F1 is supplied, the separation membrane module 3 furthest downstream in the flow of the fluid to be treated F1 is designated as the second separation membrane module 3Y, and the separation membrane module 3 one stage upstream of the second separation membrane module 3Y in relation to the flow of the fluid to be treated F1 is designated as the first separation membrane module 3X. That is, when the fluid to be treated F1 is supplied to the first stage separation membrane module 3A and the second stage separation membrane module 3B, the first separation membrane module 3X is the first stage separation membrane module 3A, and the second separation membrane module 3Y is the second stage separation membrane module 3B. When the fluid to be treated F1 is supplied from the first stage separation membrane module 3A to the third stage separation membrane module 3C, the first separation membrane module 3X is the second stage separation membrane module 3B, and the second separation membrane module 3Y is the third stage separation membrane module 3C. When the fluid to be processed F1 is supplied from the first separation membrane module 3A to the fourth separation membrane module 3D, the first separation membrane module 3X is the third separation membrane module 3C, and the second separation membrane module 3Y is the fourth separation membrane module 3D.

[0073] In the membrane separation apparatus 1 according to the second embodiment, the control device 9 may control the secondary pressure regulator 50 for the second separation membrane module 3Y to adjust the pressure in the secondary flow path 15 of the second separation membrane module 3Y based on the detection result of the detection device 7. This allows control of the partial pressure (partial pressure px1) in the primary flow path 13 and the partial pressure (partial pressure px2) in the secondary flow path 15 of the permeate target component in the second separation membrane module 3Y, thereby controlling the flow rate of the permeate fluid F2 in the second separation membrane module 3Y. Therefore, as described above, the effects of the deterioration of the separation membrane 11 and the effects of the excessive membrane area A of the separation membrane 11 can be reduced. Furthermore, the membrane separation apparatus 1 according to the second embodiment can reduce energy consumption compared to the case in which the apparent membrane area A is changed by controlling the temperature of the fluid to be processed F1 supplied to the second separation membrane module 3Y.

[0074] (Regarding other examples of partial pressure control of the permeate target component x in the secondary channel 15) In the membrane separation apparatus 1 according to the second embodiment shown in Figure 3, the partial pressure px2 of the permeate target component x in the secondary channel 15 can be controlled by the secondary pressure regulator 50, or a secondary pressure regulator 50 not shown. In the membrane separation apparatus 1 according to the third embodiment shown in Figures 4 and 5, the partial pressure px2 of the permeate target component x in the secondary channel 15 can be reduced as follows.

[0075] In the membrane separation apparatus 1 according to the third embodiment shown in Figures 4 and 5, at least some of the separation membrane modules 3 have a supply channel 60 connected to the secondary channel 15 for guiding fluid from outside the secondary channel 15.

[0076] For example, the membrane separation apparatus 1 shown in Figure 4, in addition to the configuration of the membrane separation apparatus 1 according to the first embodiment shown in Figure 1, is equipped with an external fluid supply channel 61 as a supply channel 60 for introducing fluid from outside the membrane separation apparatus 1 into the secondary channel 15. In the membrane separation apparatus 1 shown in Figure 4, the external fluid supply channel 61 is connected to the secondary channel 15 of all separation membrane modules 3. In the membrane separation apparatus 1 shown in Figure 4, fluid from outside the membrane separation apparatus 1 can be supplied to the secondary channel 15 of all separation membrane modules 3 via the external fluid supply channel 61. In the membrane separation apparatus 1 shown in Figure 4, by supplying fluid from outside the membrane separation apparatus 1 to the secondary channel 15 via the external fluid supply channel 61, the partial pressure px2 of the permeate target component x in the secondary channel 15 can be reduced. This makes it possible to increase the amount Qx of permeate target component x.

[0077] For example, the membrane separation apparatus 1 shown in Figure 5, in addition to the configuration of the membrane separation apparatus 1 according to the first embodiment shown in Figure 1, includes, as a supply channel 60, a connecting channel 62 that connects the secondary side channels 15 of the first stage separation membrane module 3A and the second stage separation membrane module 3B, a connecting channel 63 that connects the secondary side channels 15 of the second stage separation membrane module 3B and the third stage separation membrane module 3C, and a connecting channel 64 that connects the secondary side channels 15 of the third stage separation membrane module 3C and the fourth stage separation membrane module 3D.

[0078] The partial pressure px2 of the permeate target component x in the secondary channel 15 of the second-stage separation membrane module 3B is lower than the partial pressure px2 of the permeate target component x in the secondary channel 15 of the first-stage separation membrane module 3A. Therefore, by supplying the permeate fluid F2 from the secondary channel 15 of the second-stage separation membrane module 3B to the secondary channel 15 of the first-stage separation membrane module 3A via the connecting channel 62, the partial pressure px2 of the permeate target component x in the secondary channel 15 of the first-stage separation membrane module 3A can be reduced. This makes it possible to increase the amount Qx of the permeate target component x in the secondary channel 15 of the first-stage separation membrane module 3A.

[0079] Similarly, the partial pressure px2 of the permeate target component x in the secondary channel 15 of the third-stage separation membrane module 3C is lower than the partial pressure px2 of the permeate target component x in the secondary channel 15 of the second-stage separation membrane module 3B. Therefore, by supplying the permeate fluid F2 from the secondary channel 15 of the third-stage separation membrane module 3C to the secondary channel 15 of the second-stage separation membrane module 3B via the connecting channel 63, the partial pressure px2 of the permeate target component x in the secondary channel 15 of the second-stage separation membrane module 3B can be reduced. This makes it possible to increase the amount Qx of the permeate target component x in the secondary channel 15 of the second-stage separation membrane module 3B.

[0080] The partial pressure px2 of the permeate target component x in the secondary channel 15 of the fourth-stage separation membrane module 3D is lower than the partial pressure px2 of the permeate target component x in the secondary channel 15 of the third-stage separation membrane module 3C. Therefore, by supplying the permeate fluid F2 from the secondary channel 15 of the fourth-stage separation membrane module 3D to the secondary channel 15 of the third-stage separation membrane module 3C via the connecting channel 64, the partial pressure px2 of the permeate target component x in the secondary channel 15 of the third-stage separation membrane module 3C can be reduced. This makes it possible to increase the amount Qx of the permeate target component x in the secondary channel 15 of the third-stage separation membrane module 3C.

[0081] Here, among the multiple separation membrane modules 3 to which the fluid to be processed F1 is supplied, the separation membrane module 3 furthest downstream of the flow of the fluid to be processed F1 is designated as the second separation membrane module 3Y, and the separation membrane module 3 one stage upstream of the second separation membrane module 3Y with respect to the flow of the fluid to be processed F1 is designated as the first separation membrane module 3X. In the membrane separation apparatus 1 shown in Figure 5, the supply flow path 60 consists of connecting flow paths 62, 63, and 64 that connect the secondary flow path 15 of the second separation membrane module 3Y and the secondary flow path 15 of the first separation membrane module 3X.

[0082] (Other examples for improving purity or recovery rate) As shown in Figures 6 and 7, the membrane separation apparatus 1 according to the fourth embodiment includes, in addition to the configuration of the membrane separation apparatus 1 according to the first embodiment shown in Figure 1, a permeate return flow path 24 that connects the secondary flow path 15 of at least one separation membrane module 3 to a treated fluid supply flow path 21 for supplying the treated fluid F1 to the first stage separation membrane module 3A located at the upstream end of the flow of the treated fluid F1. In the example shown in Figures 6 and 7, the permeate return flow path 24 is configured to connect the secondary flow paths 15 of all separation membrane modules 3 to the treated fluid supply flow path 21.

[0083] As shown in Figures 6 and 7, the membrane separation apparatus 1 according to the fourth embodiment further includes, in addition to the configuration of the membrane separation apparatus 1 according to the first embodiment shown in Figure 1, secondary switching valves 6 provided in each of the passages 41, 42, 43, and 44 connecting the secondary outlet portion 15o of each separation membrane module 3 to the permeate fluid discharge passage 23, and a pressure booster 25 provided in the permeate fluid return passage 24. The secondary switching valves 6 and the pressure booster 25 are controlled by a control device 9.

[0084] The secondary switching valve 6 includes a secondary first switching valve 6A located in the flow path 41, a secondary second switching valve 6B located in the flow path 42, a secondary third switching valve 6C located in the flow path 43, and a secondary fourth switching valve 6D located in the flow path 44. The secondary first switching valve 6A is a switching valve for switching whether the permeate fluid F2 from the secondary outlet 15o of the first stage separation membrane module 3A flows through the permeate fluid outlet flow path 23 or through the permeate fluid return flow path 24. The secondary second switching valve 6B is a switching valve for switching whether the permeate fluid F2 from the secondary outlet 15o of the second stage separation membrane module 3B flows through the permeate fluid outlet flow path 23 or through the permeate fluid return flow path 24. The secondary third switching valve 6C is a switching valve for switching whether the permeate fluid F2 from the secondary outlet 15o of the third stage separation membrane module 3C flows through the permeate fluid outlet channel 23 or through the permeate fluid return channel 24. The secondary fourth switching valve 6D is a switching valve for switching whether the permeate fluid F2 from the secondary outlet 15o of the fourth stage separation membrane module 3D flows through the permeate fluid outlet channel 23 or through the permeate fluid return channel 24.

[0085] The pressure boosting device 25 is a device for increasing the pressure of the permeate fluid F2 so that the permeate fluid F2 from the secondary side flow path 15 of each separation membrane module 3 can be returned to the fluid to be processed supply flow path 21, and is, for example, a pump. In the membrane separation apparatus 1 according to the fourth embodiment configured in this way, purity or recovery rate is improved in the following manner.

[0086] (When it is desired to leave useful components on the primary flow path 13 side) When it is desired to leave useful components on the primary flow path 13 side, a certain amount of membrane surface area is required through which the fluid to be treated F1 flows in order to ensure the purity of the useful components in the fluid to be treated F1 that is discharged from the fluid to be treated outlet flow path 22 to the outside (outside the system) of the membrane separation device 1. However, a small amount of useful components will permeate through the separation membrane 11. If the absolute amount or concentration of useful components mixed into the permeate fluid F2 is relatively small, in the first to third embodiments described above, there is a risk that the absolute amount or concentration of useful components mixed into the permeate fluid F2 will exceed the permeate value.

[0087] Therefore, in the membrane separation apparatus 1 according to the fourth embodiment, if the flow rate of the fluid to be treated F1 detected by the primary flow rate detection device 71 is less than or equal to a specified flow rate, the control device 9 controls the secondary switching valve 6 to allow the permeate fluid F2 to flow through the permeate fluid return channel 24 in the separation membrane module 3 that is the furthest downstream of the flow of the fluid to be treated F1 among the separation membrane modules 3 to which the fluid to be treated F1 is supplied.

[0088] For example, consider the case where the fluid to be processed F1 is supplied to all separation membrane modules 3, and the permeate fluid F2 from all separation membrane modules 3 flows into the permeate fluid outlet channel 23. In this case, when the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is found to be less than or equal to a specified flow rate Q7, the control device 9 controls the secondary fourth switching valve 6D to block communication between the secondary outlet 15o of the fourth stage separation membrane module 3D and the permeate fluid outlet channel 23, as shown in Figure 7, and to connect the secondary outlet 15o of the fourth stage separation membrane module 3D with the permeate fluid return channel 24. In Figure 7, for each secondary switching valve 6, open ports are represented by white triangles, and closed ports are represented by black triangles. As a result, the flow of the permeate fluid F2 from the secondary channel 15 of the fourth stage separation membrane module 3D to the permeate fluid outlet channel 23 is prohibited by the secondary fourth switching valve 6D, while flow to the permeate fluid return channel 24 is permitted. Therefore, the permeate fluid F2 from the secondary channel 15 of the fourth stage separation membrane module 3D is returned to the fluid to be processed supply channel 21 via the permeate fluid return channel 24 and the pressurizing device 25. Thus, the useful components mixed in the permeate fluid F2 can be supplied back to the first stage separation membrane module 3A as the fluid to be processed F1 and purified again, thereby reducing the decrease in the recovery rate of useful components.

[0089] For example, consider a case where there are three separation membrane modules 3 supplying the fluid to be processed F1, and all of the permeate fluid F2 from the three separation membrane modules 3 flows into the permeate fluid outlet channel 23. In this case, when the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is found to be less than or equal to a specified flow rate Q8, the control device 9 blocks the communication between the secondary outlet 15o of the third stage separation membrane module 3C and the permeate fluid outlet channel 23, and controls the secondary third switching valve 6C to connect the secondary outlet 15o of the third stage separation membrane module 3C with the permeate fluid return channel 24. As a result, the flow of permeate fluid F2 from the secondary flow channel 15 of the third stage separation membrane module 3C to the permeate fluid outlet channel 23 is prohibited by the secondary third switching valve 6C, and the flow to the permeate fluid return channel 24 is permitted. Therefore, the permeate fluid F2 from the secondary channel 15 of the third-stage separation membrane module 3C is returned to the fluid to be processed supply channel 21 via the permeate fluid return channel 24 and the pressurizing device 25.

[0090] For example, consider a case where there are two separation membrane modules 3 supplying the fluid to be processed F1, and all of the permeate fluid F2 from the two separation membrane modules 3 flows into the permeate fluid outlet channel 23. In this case, when the flow rate of the fluid to be processed F1 detected by the primary flow rate detection device 71 is found to be less than or equal to a specified flow rate Q9, the control device 9 blocks the communication between the secondary outlet 15o of the second stage separation membrane module 3B and the permeate fluid outlet channel 23, and controls the secondary second switching valve 6B to connect the secondary outlet 15o of the second stage separation membrane module 3B with the permeate fluid return channel 24. As a result, the flow of permeate fluid F2 from the secondary flow channel 15 of the second stage separation membrane module 3B to the permeate fluid outlet channel 23 is prohibited by the secondary second switching valve 6B, and the flow to the permeate fluid return channel 24 is permitted. Therefore, the permeate fluid F2 from the secondary flow path 15 of the second-stage separation membrane module 3B is returned to the fluid to be processed supply flow path 21 via the permeate fluid return flow path 24 and the pressurizing device 25. This makes it easier to reduce the absolute amount and concentration of useful components mixed in the permeate fluid F2 to below the permeate fluid F2 limit, even when the permissible values ​​for the absolute amount and concentration of useful components mixed in the permeate fluid F2 are relatively small. Note that the specified flow rates Q7 to Q9 are values ​​predetermined by tests or other means.

[0091] Furthermore, for example, when discharging the permeate fluid F2 into the external environment, if an emission standard value is set for the useful components when discharging them into the external environment, if the permeate fluid F2 from the separation membrane module 3 downstream of the flow of the fluid to be treated F1 is allowed to flow directly into the permeate fluid outlet channel 23, there is a risk that permeate fluid F2 containing useful components at concentrations exceeding the emission standard value will be discharged into the external environment.

[0092] Therefore, in the membrane separation apparatus 1 according to the fourth embodiment, if the concentration of useful components in the permeate fluid F2 detected by the secondary concentration detection device 74 is equal to or greater than the specified concentration C4, the control device 9 controls the secondary switching valve 6 to allow the permeate fluid F2 to flow through the permeate fluid return channel 24 in the separation membrane module 3 furthest downstream of the flow of the fluid to be treated F1, as described above. In the fourth embodiment, the secondary concentration detection device 74 is assumed to be a sensor capable of detecting the concentration of useful components in the permeate fluid F2. As a result, the permeate fluid F2, which has a relatively high concentration of useful components, can be supplied again to the first stage separation membrane module 3A as the fluid to be treated F1 and purified again, thereby reducing the concentration of useful components discharged into the external environment. The specified concentration C4 is a value predetermined by tests or the like.

[0093] (When you want to separate the useful components on the secondary flow path 15 side) When you want to separate the useful components on the secondary flow path 15 side, as the flow of the fluid to be treated F1 moves from the upstream separation membrane module 3 to the downstream separation membrane module 3, the partial pressure of components other than the useful components in the fluid to be treated F1 remains approximately constant, while the partial pressure of the useful components to be separated decreases. Therefore, as the flow of the fluid to be treated F1 moves from the upstream separation membrane module 3 to the downstream separation membrane module 3, the purity of the useful components in the permeate fluid F2 in the secondary flow path 15 decreases.

[0094] Therefore, in the membrane separation apparatus 1 according to the fourth embodiment, if the concentration of useful components in the permeate fluid F2 detected by the secondary concentration detection device 74 is less than or equal to a specified concentration C5, the control device 9 controls the secondary switching valve 6 to allow the permeate fluid F2 to flow through the permeate fluid return channel 24 from the downstream separation membrane module 3 to which the fluid to be treated F1 is supplied, similar to the case where the fluid in the primary flow path 13 described above contains useful components. As a result, the permeate fluid F2 from the downstream separation membrane module 3, which contains a relatively large amount of components other than useful components, is supplied again to the first stage separation membrane module 3A as the fluid to be treated F1 and purified again, while the permeate fluid F2 from the upstream separation membrane module 3, which contains a relatively small amount of components other than useful components, can flow through the permeate fluid outlet channel 23, thereby reducing the decrease in the purity of useful components in the permeate fluid F2 discharged from the permeate fluid outlet channel 23. The specified concentration C5 is a value predetermined by tests or the like.

[0095] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, and forms that combine these forms as appropriate. That is, the second embodiment described above may be combined with at least one of the third, fourth, and fifth embodiments described above. Similarly, the third embodiment described above may be combined with at least one of the second, fourth, and fifth embodiments described above. The fourth embodiment described above may be combined with at least one of the second, third, and fifth embodiments described above. The fifth embodiment described above may be combined with at least one of the second, third, and fourth embodiments described above.

[0096] The contents of each of the above embodiments can be understood, for example, as follows: (1) A membrane separation apparatus 1 according to at least one embodiment of the present disclosure comprises a plurality of separation membrane modules 3 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, a changing device 5 for changing the number of separation membrane modules 3 that supply the fluid to be processed F1, a detection device 7 for identifying the recovery rate or purity of useful components, and a control device 9 for controlling the changing device 5 to change the number of separation membrane modules 3 that supply the fluid to be processed F1 based on the detection result of the detection device 7. The changing device 5 is configured to connect the primary side flow paths 13 of the separation membrane modules 3 that supply the fluid to be processed F1 in series when the number of separation membrane modules 3 that supply the fluid to be processed F1 is two or more.

[0097] According to the configuration described in (1) above, the control device 9 can determine the degree of decrease in the recovery rate or purity of useful components due to the deterioration of the separation membrane 11 in the separation membrane module 3 to which the fluid to be processed F1 is supplied, based on the recovery rate or purity of useful components, and change the number of separation membrane modules 3 to which the fluid to be processed F1 is supplied. This makes it possible to reduce the decrease in the recovery rate or purity of useful components.

[0098] (2) In some embodiments, in the configuration of (1) above, the detection device 7 may include a secondary flow rate detection device 73 for detecting the flow rate of the permeate fluid F2 from all of the separation membrane modules 3 to which the fluid to be processed F1 is supplied. The control device 9 may control the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be processed F1 is supplied if the flow rate detected by the secondary flow rate detection device 73 is less than or equal to a specified flow rate (specified flow rate Q1 or specified flow rate Q2).

[0099] According to the configuration described in (2) above, for example, if it is desired to leave the useful components on the primary channel 13 side, the purity of the useful components can be increased, and if it is desired to separate the useful components on the secondary channel 15 side, the recovery rate of the useful components can be increased.

[0100] (3) In some embodiments, in the configuration of (1) above, the detection device 7 may include a primary flow rate detection device 71 for detecting the flow rate of the fluid to be treated F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be treated F1 is supplied. The control device 9 may control the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be treated F1 is supplied if the flow rate of the fluid to be treated F1 detected by the primary flow rate detection device 71 is equal to or greater than a specified flow rate (specified flow rate Q3 or specified flow rate Q4).

[0101] According to the configuration described in (3) above, for example, if it is desired to leave the useful components on the primary channel 13 side, the purity of the useful components can be increased, and if it is desired to separate the useful components on the secondary channel 15 side, the recovery rate of the useful components can be increased.

[0102] (4) In some embodiments, in the configuration of (1) above, the detection device 7 may include a primary-side concentration detection device 72 for detecting the concentration of the target component in the fluid to be treated F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be treated F1 is supplied. The control device 9 may control the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be treated F1 is supplied if the concentration detected by the primary-side concentration detection device 72 is less than or equal to a specified concentration C1.

[0103] According to the configuration described in (4) above, for example, if it is desired to leave useful components on the primary flow path 13 side, the purity of the useful components can be increased.

[0104] (5) In some embodiments, in the configuration of (1) above, the detection device 7 may include a primary concentration detection device 72 for detecting the concentration of the target component in the fluid to be treated F1 after it has flowed through all of the separation membrane modules 3 to which the fluid to be treated F1 is supplied. The control device 9 may control the modification device 5 to increase the number of separation membrane modules 3 to which the fluid to be treated F1 is supplied if the concentration detected by the primary concentration detection device 72 is equal to or greater than a specified concentration C2.

[0105] According to the configuration described in (5) above, for example, if it is desired to separate the useful components into the secondary flow path 15, the recovery rate of the useful components can be increased.

[0106] (6) In some embodiments, in the configuration of (1) above, the plurality of separation membrane modules 3 include a first separation membrane module 3X (for example, the first-stage separation membrane module 3A) having a separation membrane 11, a first primary side channel (for example, the primary side channel 13 in the first-stage separation membrane module 3A) configured for the flow of the fluid to be processed F1, and a first secondary side channel (for example, the secondary side channel 15 in the first-stage separation membrane module 3A) separated from the first primary side channel (for example, the primary side channel 13 in the first-stage separation membrane module 3A) by the separation membrane 11 and configured for the flow of the permeate fluid F2 that has permeated through the separation membrane 11, and a second primary side channel (for example, the second-stage separation membrane module 3B) configured for the flow of the fluid to be processed F1 The device may include a primary channel 13, a separation membrane 11, and a second secondary channel 15 (for example, a secondary channel 15 in the second stage separation membrane module 3B) which is separated from a second primary channel 13 (for example, a primary channel 13 in the second stage separation membrane module 3B) by the separation membrane 11 and configured for the flow of permeate fluid F2 that has permeated through the separation membrane 11, wherein the second primary channel 13 (for example, a primary channel 13 in the second stage separation membrane module 3B) is connected in series with the first primary channel (for example, a primary channel 13 in the first stage separation membrane module 3A) downstream of the first primary channel 13 (for example, a primary channel 13 in the first stage separation membrane module 3A), and the device may also include a second separation membrane module 3Y (for example, a second stage separation membrane module 3B). In some embodiments, the system may include a secondary pressure detection device 75 for detecting the pressure in a second secondary flow path (for example, a secondary flow path 15 in the second stage separation membrane module 3B) and a secondary pressure adjustment device 50 for adjusting the pressure in the second secondary flow path (for example, a secondary flow path 15 in the second stage separation membrane module 3B). The control device 9 may control the secondary pressure adjustment device 50 to adjust the pressure in the second secondary flow path (for example, a secondary flow path 15 in the second stage separation membrane module 3B) based on the detection result of the detection device 7.

[0107] According to the configuration of (6) above, by adjusting the pressure of the second secondary side channel (for example, the secondary side channel 15 in the second stage separation membrane module 3B), the partial pressure of the permeate target component in the second primary side channel (for example, the primary side channel 13 in the second stage separation membrane module 3B) and the partial pressure in the second secondary side channel (for example, the secondary side channel 15 in the second stage separation membrane module 3B) can be controlled, thereby controlling the flow rate of the permeate fluid F2 in the second separation membrane module 3Y (for example, the second stage separation membrane module 3B).

[0108] (7) In some embodiments, in the configuration of (6) above, the detection device 7 may include a primary flow rate detection device 71 for detecting the flow rate of the fluid to be treated F1 after it has flowed through the entire separation membrane module 3 to which the fluid to be treated F1 has been supplied. The control device 9 may control the secondary pressure regulator 50 to increase the pressure of the second secondary flow path (for example, the secondary flow path 15 in the second stage separation membrane module 3B) if the flow rate of the fluid to be treated F1 detected by the primary flow rate detection device 71 is less than or equal to a specified flow rate Q5.

[0109] According to the configuration of (7) above, for example, if it is desired to leave the useful components on the primary channel 13 side, even if the membrane area is excessive compared to the required membrane area, the decrease in the recovery rate of the useful components can be reduced. According to the configuration of (7) above, for example, if it is desired to separate the useful components on the secondary channel 15 side, even if the membrane area is excessive compared to the required membrane area, the decrease in the purity of the useful components can be reduced.

[0110] (8) In some embodiments, in the configuration of (6) above, the detection device 7 may include a primary side concentration detection device 72 for detecting the concentration of the target component in the fluid to be treated F1 after it has flowed through the second separation membrane module 3Y (for example, the second stage separation membrane module 3B). The control device 9 may control the secondary side pressure regulator 50 to reduce the pressure in the second secondary side flow path (for example, the secondary side flow path 15 in the second stage separation membrane module 3B) if the concentration of the target component in the fluid to be treated F1 detected by the primary side concentration detection device 72 is less than or equal to a specified concentration C3.

[0111] According to the configuration described in (8) above, for example, if it is desired to leave useful components on the primary channel 13 side, even if the purity of the useful components decreases due to deterioration associated with the use of the separation membrane 11, the decrease in the purity of the useful components can be reduced by lowering the pressure in the second secondary channel (for example, the secondary channel 15 in the second stage separation membrane module 3B).

[0112] (9) In some embodiments, in the configuration of (6) above, the detection device 7 may include a secondary flow rate detection device 73 for detecting the flow rate of the permeate fluid F2 from the first separation membrane module 3X (e.g., the first stage separation membrane module 3A) and the second separation membrane module 3Y (e.g., the second stage separation membrane module 3B). The control device 9 may control the secondary pressure regulating device 50 to reduce the pressure in the second secondary flow path (e.g., the secondary flow path 15 in the second stage separation membrane module 3B) if the flow rate of the permeate fluid F2 detected by the secondary flow rate detection device 73 is less than or equal to a specified flow rate Q6.

[0113] According to the configuration described in (9) above, for example, if it is desired to separate the useful components to the secondary flow path 15, even if the recovery rate of the useful components decreases due to deterioration associated with the use of the separation membrane 11, the decrease in the recovery rate of the useful components can be reduced by lowering the pressure in the second secondary flow path (for example, the secondary flow path 15 in the second stage separation membrane module 3B).

[0114] (10) In some embodiments, in any of the configurations (1) to (5) above, the plurality of separation membrane modules 3 may have a supply channel 60 connected to the secondary channel 15 for guiding fluid from outside the secondary channel 15.

[0115] According to the configuration of (10) above, by introducing fluid from outside the secondary channel 15 to the secondary channel 15 via the supply channel 60, the partial pressure of the components that have permeated through the separation membrane 11 in the secondary channel 15 can be reduced, thereby increasing the amount of components that permeate through the separation membrane 11. As a result, for example, if it is desired to leave the useful components on the primary channel 13 side, the purity of the useful components can be improved. Also, for example, if it is desired to separate the useful components on the secondary channel 15 side, the recovery rate of the useful components can be improved.

[0116] (11) In some embodiments, in the configuration of (10) above, the supply channel 60 may be configured to allow fluid from outside the system to be introduced into the secondary channel 15.

[0117] According to the configuration described in (11) above, by introducing a fluid from outside the system into the secondary channel 15, the partial pressure of the component that has permeated through the separation membrane in the secondary channel 15 can be reduced, thereby increasing the amount of the component that permeates through the separation membrane 11.

[0118] (12) In some embodiments, in the configuration of (10) above, the plurality of separation membrane modules 3 include a first separation membrane module 3X (for example, a first-stage separation membrane module 3A) having a separation membrane 11, a first primary side flow path (for example, a primary side flow path 13 in the first-stage separation membrane module 3A) configured for the flow of the fluid to be processed F1, and a first secondary side flow path (for example, a secondary side flow path 15 in the first-stage separation membrane module 3A) separated from the first primary side flow path (for example, a primary side flow path 13 in the first-stage separation membrane module 3A) by the separation membrane 11 and configured for the flow of the permeate fluid F2 that has permeated through the separation membrane 11, and a second primary side flow path (for example, a second-stage separation membrane module 3A) configured for the flow of the fluid to be processed F1 The system may include a primary channel 13 in Joule 3B and a second secondary channel 15 in the second stage separation membrane module 3B, which is separated from a second primary channel 13 in the second stage separation membrane module 3B by a separation membrane 11 and configured for the flow of permeate fluid F2 that has permeated through the separation membrane 11, and a second separation membrane module 3Y (e.g., second stage separation membrane module 3B) in which the second primary channel 13 in the second stage separation membrane module 3B is connected in series with the first primary channel 13 in the first stage separation membrane module 3A downstream of the first primary channel 13 in the first stage separation membrane module 3A. In some embodiments, the system may include a discharge channel (permeate fluid outlet channel 23) for guiding the permeate fluid F2 in the first secondary channel 15 in the first stage separation membrane module 3A to the outside of the system. The supply channel 60 may also be a connecting channel (e.g., a connecting channel 62) that connects the second secondary channel (e.g., the secondary channel 15 in the second stage separation membrane module 3B) and the first secondary channel (e.g., the secondary channel 15 in the first stage separation membrane module 3A).

[0119] In the configuration of (12) described above, the partial pressure in the second secondary channel (for example, the secondary channel 15 in the second stage separation membrane module 3B) of the component that has permeated through the separation membrane 11 is lower than the partial pressure in the first secondary channel (for example, the secondary channel 15 in the first stage separation membrane module 3A) of the component that has permeated through the separation membrane 11. According to the configuration of (12) described above, by introducing the permeate fluid F2 in the second secondary channel (for example, the secondary channel 15 in the second stage separation membrane module 3B) into the first secondary channel (for example, the secondary channel 15 in the first stage separation membrane module 3A) via a connecting channel (for example, a connecting channel 62), the partial pressure in the first secondary channel (for example, the secondary channel 15 in the first stage separation membrane module 3A) of the component that has permeated through the separation membrane 11 can be reduced, and the amount of the component that permeates through the separation membrane 11 can be increased.

[0120] (13) In some embodiments, the configuration of (1) to (12) above may include a permeate return channel 24 that connects a secondary channel 15 of at least one separation membrane module 3 to a channel (a channel for supplying the fluid to be treated to a separation membrane module 3 (the first stage separation membrane module 3A) located at the upstream end of the flow of the fluid to be treated F1.

[0121] According to the configuration described in (13) above, the permeate fluid F2 in the secondary channel 15 of the relatively downstream separation membrane module 3 can be returned via the permeate fluid return channel 24 to a channel (processed fluid supply channel 21) for supplying the processed fluid F1 to the separation membrane module 3 (first stage separation membrane module 3A) located at the upstream end of the flow of the processed fluid F1. This reduces the decrease in the purity of the useful components when, for example, it is desired to separate the useful components into the secondary channel 15, and reduces the decrease in the recovery rate of the useful components when, for example, it is desired to leave the useful components in the primary channel 13.

[0122] 1 Membrane Separation Device 3 Separation Membrane Modules 3A First Stage Separation Membrane Module 3B Second Stage Separation Membrane Module 3C Third Stage Separation Membrane Module 3D Fourth Stage Separation Membrane Module 3X First Separation Membrane Module 3Y Second Separation Membrane Module 5 Change Device 6 Secondary Side Switching Valve 7 Detection Device 9 Control Device 11 Separation Membrane 13 Primary Side Flow Channel 15 Secondary Side Flow Channel 21 Fluid to be Processed Supply Flow Channel 22 Fluid to be Processed Outlet Flow Channel 23 Permeate Fluid Outlet Flow Channel 24 Permeate Fluid Return Flow Channel 50 Secondary Side Pressure Regulator 60 Supply Flow Channel 61 External Fluid Supply Flow Channel 62 Connecting Flow Channel 63 Connecting Flow Channel 64 Connecting Flow Channel 71 Primary Side Flow Rate Detection Device 72 Primary Side Concentration Detection Device 73 Secondary Side Flow Rate Detection Device 74 Secondary Side Concentration Detection Device 75 Secondary Side Pressure Detection Device

Claims

1. A membrane separation apparatus comprising: a plurality of separation membrane modules, each having a separation membrane for separating a permeate from a supplied fluid to be treated; a primary side flow path configured for the flow of the fluid to be treated; and a secondary side flow path separated from the primary side flow path by the separation membrane and configured for the flow of the permeate that has permeated through the separation membrane; a changing device for changing the number of separation membrane modules that supply the fluid to be treated; a detection device for determining the recovery rate or purity of useful components; and a control device for controlling the changing device to change the number of separation membrane modules that supply the fluid to be treated based on the detection result of the detection device, wherein the changing device is configured to connect the primary side flow paths of the separation membrane modules that supply the fluid to be treated in series when the number of separation membrane modules that supply the fluid to be treated is two or more.

2. The membrane separation apparatus according to claim 1, wherein the detection device includes a secondary flow detection device for detecting the flow rate of the permeate fluid from all of the separation membrane modules to which the fluid to be processed is supplied, and the control device controls the modification device to increase the number of separation membrane modules to which the fluid to be processed is supplied if the flow rate detected by the secondary flow detection device is less than or equal to a specified flow rate.

3. The membrane separation apparatus according to claim 1, wherein the detection device includes a primary flow detection device for detecting the flow rate of the fluid to be treated after it has flowed through all of the separation membrane modules to which the fluid to be treated is supplied, and the control device controls the changing device to increase the number of separation membrane modules to which the fluid to be treated is supplied if the flow rate of the fluid to be treated detected by the primary flow detection device is equal to or greater than a specified flow rate.

4. The membrane separation apparatus according to claim 1, wherein the detection device includes a primary concentration detection device for detecting the concentration of a target component in the fluid to be treated after it has flowed through all of the separation membrane modules to which the fluid to be treated is supplied, and the control device controls the changing device to increase the number of separation membrane modules to which the fluid to be treated is supplied if the concentration detected by the primary concentration detection device is less than or equal to a specified concentration.

5. The membrane separation apparatus according to claim 1, wherein the detection device includes a primary concentration detection device for detecting the concentration of a target component in the fluid to be treated after it has flowed through all of the separation membrane modules to which the fluid to be treated is supplied, and the control device controls the modification device to increase the number of separation membrane modules to which the fluid to be treated is supplied if the concentration detected by the primary concentration detection device is equal to or greater than a specified concentration.

6. The membrane separation apparatus according to claim 1, comprising: a first separation membrane module having a separation membrane, a first primary side channel configured for the flow of the fluid to be processed, and a first secondary side channel separated from the first primary side channel by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane; a second separation membrane module having a separation membrane, a second primary side channel configured for the flow of the fluid to be processed, and a second secondary side channel separated from the second primary side channel by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane, wherein the second primary side channel is connected in series with the first primary side channel downstream of the first primary side channel; a secondary side pressure detection device for detecting the pressure of the second secondary side channel; and a secondary side pressure adjustment device for adjusting the pressure of the second secondary side channel, wherein the control device controls the secondary side pressure adjustment device to adjust the pressure of the second secondary side channel based on the detection result of the detection device.

7. The membrane separation apparatus according to claim 6, wherein the detection device includes a primary flow detection device for detecting the flow rate of the fluid to be treated after it has flowed through all of the separation membrane modules to which the fluid to be treated has been supplied, and the control device controls the secondary pressure regulating device to increase the pressure of the second secondary flow path if the flow rate of the fluid to be treated detected by the primary flow detection device is less than or equal to a specified flow rate.

8. The membrane separation apparatus according to claim 6, wherein the detection device includes a primary concentration detection device for detecting the concentration of a target component in the fluid to be processed after it has flowed through the second separation membrane module, and the control device controls the secondary pressure regulating device to reduce the pressure in the second secondary flow path when the concentration of the target component in the fluid to be processed detected by the primary concentration detection device is below a specified concentration.

9. The membrane separation apparatus according to claim 6, wherein the detection device includes a secondary flow rate detection device for detecting the flow rate of the permeate fluid from the first separation membrane module and the second separation membrane module, and the control device controls the secondary pressure regulating device to reduce the pressure in the second secondary flow path when the flow rate of the permeate fluid detected by the secondary flow rate detection device is less than or equal to a specified flow rate.

10. The membrane separation apparatus according to any one of claims 1 to 5, wherein the plurality of separation membrane modules are connected to a supply channel for introducing fluid from outside the secondary channel into the secondary channel.

11. The membrane separation apparatus according to claim 10, wherein the supply channel is configured to allow fluid from outside the system to be introduced into the secondary channel.

12. The membrane separation apparatus according to claim 10, comprising: a first separation membrane module having a separation membrane, a first primary side channel configured for the flow of the fluid to be processed, and a first secondary side channel separated from the first primary side channel by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane; a second separation membrane module having a separation membrane, a second primary side channel configured for the flow of the fluid to be processed, and a second secondary side channel separated from the second primary side channel by the separation membrane and configured for the flow of the permeate fluid that has permeated through the separation membrane, wherein the second primary side channel is connected in series with the first primary side channel downstream of the first primary side channel; and further comprising a discharge channel for guiding the permeate fluid in the first secondary side channel out of the system, wherein the supply channel is a connecting channel connecting the second secondary side channel and the first secondary side channel.

13. A membrane separation apparatus according to any one of claims 1 to 4, comprising: a secondary flow path of at least one separation membrane module and a permeate return flow path connecting to a flow path for supplying the fluid to be treated to the separation membrane module located furthest upstream in the flow of the fluid to be treated.

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