Filtration device

Abstract

To provide a filtration device which can increase of an amount of a filtrate.SOLUTION: A filtration device includes a spiral membrane module 10. The membrane module includes: an element in which a filtration membrane is wound around a winding axis extending in a predetermined direction; and a container which houses the element. The container includes a first container 110 and a second container 210 disposed at one side in the predetermined direction of the first container. The element includes: a first element 120 housed in the first container; and a second element 220 housed in the second container. The first container includes: a first outlet 114b of a filtrate, and the second container includes a second outlet 214b of the filtrate.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a filtration device.

Background Art

[0002] Patent Document 1 discloses a configuration in which units with a membrane element covered with resin are joined by a joint, and a permeate fluid outlet is perforated in an end plate of the downstream unit.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a configuration where two units are joined as in Patent Document 1 above, the flow path through which the permeate fluid flows becomes longer, resulting in an increase in the resistance when the permeate fluid flows, and there is a risk that the amount of filtrate will decrease.

[0005] The present invention has been made by the inventors of the present application newly paying attention to the above problems, and an object thereof is to provide a filtration device capable of increasing the amount of filtrate.

Means for Solving the Problems

[0006] A filtration device according to an aspect of the present invention includes a spiral membrane module, the membrane module including an element in which a filtration membrane is wound around a winding shaft extending in a predetermined direction, and a container that houses the element, the container including a first container and a second container disposed on one side of the first container in the predetermined direction, the element including a first element housed in the first container and a second element housed in the second container, the first container including a first outlet for filtrate, and the second container including a second outlet for filtrate.

Advantages of the Invention

[0007] According to the filtration device of the present invention, the filtrate volume can be increased.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0009] (1) The filtration device according to an embodiment of the present invention includes a spiral membrane module. The membrane module includes an element in which a filtration membrane is wound around a winding axis extending in a predetermined direction, and a container for housing the element. The container includes a first container and a second container disposed on one side of the first container in the predetermined direction. The element includes a first element housed in the first container and a second element housed in the second container. The first container has a first outlet for filtrate, and the second container has a second outlet for filtrate.

[0010] According to the filtration device according to an embodiment of the present invention, the container of the spiral membrane module includes a first container and a second container. The first container has a first outlet for filtrate, and the second container has a second outlet for filtrate. In this way, in the configuration where the container includes a first container and a second container, each of the first container and the second container has an outlet for filtrate, so that the filtrate can be taken out from two outlets (the first outlet and the second outlet). Thereby, the distance that the filtrate flows can be shortened and the resistance when the filtrate flows can be reduced, so that the amount of filtrate can be increased. Furthermore, since the area of the outlet of the filtrate is large, the resistance when the filtrate flows can be reduced and the amount of filtrate can be increased.

[0011] (2) In the filtration device described in (1) above, the first outlet may be disposed at an end portion on the other side of the first container in the predetermined direction, and the second outlet may be disposed at an end portion on the one side of the second container in the predetermined direction.

[0012] According to the filtration device described in (2) above, by disposing the first outlet at an end portion on the other side of the first container in the predetermined direction and disposing the second outlet at an end portion on the one side of the second container in the predetermined direction, two outlets (the first outlet and the second outlet) for filtrate can be disposed at both end portions of the container in the predetermined direction. Thereby, since the filtrate is taken out from both end portions of the container in the predetermined direction, an outlet for filtrate can be provided without a complicated structure. Also, when the outlet for filtrate is provided at an end portion excluding the end face of the container, it becomes easy to connect three or more containers such as a third container for housing a third element in addition to the first container and the second container.

[0013] (3) In the filtering device according to (2) above, the first outlet may be formed on the end face on the other side of the first container in the predetermined direction, and the second outlet may be formed on the end face on the one side of the second container in the predetermined direction.

[0014] According to the filtering device described in (3) above, by forming the first outlet on the end face on the other side of the first container in the predetermined direction and the second outlet on the end face on the one side of the second container in the predetermined direction, two outlets (the first outlet and the second outlet) of the filtrate can be formed on both end faces of the container in the predetermined direction. Thereby, since the outlet of the filtrate and the path of the filtrate can be directly connected, the structure of the container can be simplified.

[0015] (4) In the filtering device according to any one of (1) to (3) above, the container may be formed by connecting the end face on the one side of the first container in the predetermined direction and the end face on the other side of the second container in the predetermined direction, so that the flow path of the stock solution in the first container and the flow path of the stock solution in the second container are connected.

[0016] According to the filtration device described in (4) above, a container can be formed with a simple configuration in which the flow path of the stock solution in the first container and the flow path of the stock solution in the second container are connected by connecting the end face on one side in the predetermined direction of the first container and the end face on the other side in the predetermined direction of the second container. When a plurality of containers (hereinafter also referred to as individual containers), such as the first container and the second container, in which elements such as the first element and the second element (hereinafter also referred to as individual elements) are accommodated, are integrally connected in series such that their respective end faces are connected, rather than via piping, if the filtrate flow paths of these individual elements are connected at the connection surface of the individual containers and the filtrate is configured to be taken out only from the downstream individual container, the inventors have newly found a problem that no filtrate comes out in the downstream membrane module, and in some cases, the filtrate flows back to the stock solution side. When connecting a plurality of individual containers in series by piping instead of connecting the end faces of the respective individual containers, since the filtrate in each individual element also necessarily converges through the piping passing outside the individual containers, the above phenomenon is less likely to become a major problem, and thus such a problem is not recognized. When a plurality of individual containers in which individual elements are accommodated are integrally connected in series such that their respective end faces are connected, rather than via piping, such a problem can be solved by taking out the filtrate individually from these individual containers. Further, the above problem can be solved more effectively if the filtrate flow paths are not connected by blocking the filtrate flow paths of the individual elements accommodated in the individual containers at the connection surface of the plurality of individual containers.

[0017] (5) In the filtration device described in (4) above, it is also possible that the end of the filtrate flow path at the end on the one side in the predetermined direction of the first container is blocked, and the end of the filtrate flow path at the end on the other side in the predetermined direction of the second container is blocked.

[0018] According to the filtration device described in (5) above, by blocking the end of the filtrate flow path at one end of the first container in a predetermined direction and blocking the end of the filtrate flow path at the other end of the second container in the predetermined direction, the filtrate flow paths of the individual elements can be made independent of each other. The pressure of the filtrate depends on the average of the inlet pressure and the outlet pressure of each individual element. Therefore, when a plurality of individual elements are connected in series and the filtrate flow paths are also connected at the connection points of the individual elements, the inlet pressure of the stock solution of the downstream individual element may be equal to or lower than the pressure of the filtrate of that individual element. In this case, there arises a problem that no filtrate flows out from the individual element, and in some cases, a situation occurs where the filtrate flows backward to the stock solution side. By blocking the end of the filtrate flow path at one end of the first container in a predetermined direction and blocking the end of the filtrate flow path at the other end of the second container in the predetermined direction, the pressure of the filtrate of the downstream individual element is suppressed from being affected by the pressure of the filtrate of the upstream individual element. As a result, the phenomenon that the difference between the pressure of the stock solution and the pressure of the filtrate in the downstream individual element becomes small is less likely to occur. Consequently, the risk of deterioration of the filtration performance is reduced.

[0019] (6) In the filtration device according to any one of (1) to (5) above, the first container further includes a first opening that serves as an inlet or an outlet of the stock solution at the other end in the predetermined direction, and the second container further includes a second opening that serves as an outlet or an inlet of the stock solution at the one end in the predetermined direction. When the first opening is an inlet of the stock solution, the second opening may be an outlet of the stock solution, and when the first opening is an outlet of the stock solution, the second opening may be an inlet of the stock solution.

[0020] According to the filtration device described in (6) above, since the first container includes a first opening at the other end in the predetermined direction and the second container includes a second opening at the one end in the predetermined direction, two openings (the first opening and the second opening) that serve as the inlet and the outlet of the stock solution can be arranged at both ends of the container in the predetermined direction. Thereby, since the stock solution can be made to flow from one end to the other end of the container in the predetermined direction, a flow path for the stock solution can be efficiently secured in a limited space.

[0021] (7) In the filtering device described in (6) above, the first opening may be formed on the end face on the other side of the first container in the predetermined direction, and the second opening may be formed on the end face on the one side of the second container in the predetermined direction.

[0022] According to the filtering device described in (7) above, by forming the first opening on the end face on the other side of the first container in the predetermined direction and the second opening on the end face on the one side of the second container in the predetermined direction, two openings (the first opening and the second opening) serving as the inlet and outlet of the stock solution can be formed on both end faces of the container in the predetermined direction. As a result, the stock solution can flow from one end face to the other end face of the container in the predetermined direction, so that the length of the stock solution path can be ensured while shortening the length of the container in the predetermined direction. Therefore, the effect of (6) above can be made more remarkable. Further, since the inlet and outlet of the stock solution are on the end faces of the container, it is easy to connect three or more containers at their respective end faces.

[0023] (8) In the filtering device described in any one of (1) to (7) above, at least one of the first element and the second element may have a length in the predetermined direction of 800 mm or less.

[0024] According to the filtering device described in (8) above, at least one of the first element and the second element has a length in the predetermined direction, that is, the winding axis direction, of 800 mm or less. This reduces the influence of the pressure loss in the winding axis direction of the element and can mitigate the difference in filtering efficiency due to the location in the winding axis direction. Therefore, for example, when the second container is arranged on one side of the first container in the predetermined direction in a manner such as connecting the first container containing the first element and the second container containing the second element in series, the problem of a difference in filtering efficiency between the first element and the second element is less likely to occur. Further, since an element with a short length in the winding axis direction is applicable to any of the modes of single, series connection, and parallel connection, it is easy to perform equipment design according to the installation environment, the properties of the substance to be removed, and the like.

[0025] (9) In the filtration device according to any one of (1) to (8) above, the inlet pressure of the stock solution flowing into the membrane module may be less than 0.2 MPa.

[0026] According to the filtration device described in (9) above, the inlet pressure of the stock solution flowing into the membrane module is less than 0.2 MPa. Here, the filtration device is configured to reduce the resistance when the filtrate flows by shortening the distance that the filtrate flows by taking out the filtrate from two outlets (the first outlet and the second outlet). For this reason, even if the length of the container becomes long by connecting the first container and the second container, the resistance when the filtrate flows can be reduced, so that the inlet pressure of the stock solution flowing in can be operated at a low pressure. Therefore, since it is possible to perform a low-pressure operation in which the inlet pressure of the stock solution flowing into the membrane module is made less than 0.2 MPa, the power required for pressurization can be reduced, and as a result, the power consumption can be reduced.

[0027] When the container is formed by connecting the end face on one side in the predetermined direction of the first container and the end face on the other side in the predetermined direction of the second container, so that the flow path of the stock solution in the first container and the flow path of the stock solution in the second container are connected, it is more preferable that the inlet pressure of the stock solution flowing into the membrane module is less than 0.2 MPa. In the above aspect (the end face on one side of the first container and the end face on the other side of the second container are connected + the flow paths of the stock solution are connected in series), when the inlet pressure of the stock solution flowing into the membrane module is low, the possibility that the inlet pressure of the stock solution in the downstream individual element becomes equal to or lower than the pressure of the filtrate is increased compared to the case of high-pressure operation. To address this problem, the filtrate flow paths of a plurality of individual elements are made independent, and the first container that houses the first element and the second container that houses the second element are arranged along a predetermined direction. The first container is provided with a first outlet for the filtrate, and the second container is provided with a second outlet for the filtrate. By adopting such a configuration, it is possible to suppress the situation where it becomes difficult for the filtrate to come out in the downstream individual element, that is, to suppress a decrease in the filtration efficiency.

[0028] Hereinafter, a filtration device according to an embodiment (including its modifications) of the present invention will be described with reference to the drawings. Note that all the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, processes, order of processes, etc. shown in the following embodiments are merely examples and are not intended to limit the present invention. In each figure, the dimensions and the like are not shown precisely. In each figure, the same or similar components are denoted by the same reference numerals.

[0029] In the following description and drawings, the height direction (vertical direction), longitudinal direction of the membrane module, longitudinal direction of the element of the membrane module, the direction in which the winding axis of the element extends (predetermined direction), or the arrangement direction of the first membrane module and the second membrane module in the filtration device is defined as the X-axis direction. The front-rear direction of the membrane module in the filtration device is defined as the Y-axis direction. The left-right direction of the membrane module in the filtration device is defined as the Z-axis direction. These X-axis direction, Y-axis direction and Z-axis direction are directions that intersect (orthogonal in this embodiment) with each other. Depending on the usage mode, the X-axis direction may not be the height direction (vertical direction), but hereinafter, for the sake of convenience of explanation, the X-axis direction will be described as the height direction (vertical direction).

[0030] In the following description, the X-axis plus direction indicates the arrow direction of the X-axis, and the X-axis minus direction indicates the direction opposite to the X-axis plus direction. When simply referring to the X-axis direction, it indicates the bidirectional or either one of the X-axis plus direction and the X-axis minus direction. The same applies to the Y-axis direction and the Z-axis direction. Expressions indicating relative directions or postures such as parallel and orthogonal include cases where they are not strictly in that direction or posture. That two directions are parallel (or orthogonal) means not only that the two directions are completely parallel (or orthogonal), but also that they are substantially parallel (or orthogonal), that is, for example, including a difference of about several percent.

[0031] (Embodiment) [Explanation of Filtration Device 1] First, the schematic configuration of the filtration device 1 in the present embodiment will be described. FIG. 1 is a schematic diagram showing the schematic configuration of the filtration device 1 according to the present embodiment.

[0032] As shown in FIG. 1, the filtration device 1 includes a membrane module 10, a stock solution tank 20, and a pump 30.

[0033] The membrane module 10 is a cross-flow filtration type filter that filters the solid content in the stock solution by flowing the supplied stock solution parallel to the filtration membrane. The membrane module 10 is a spiral type membrane module in which the filtration membrane is wound. In the membrane module 10, the stock solution is supplied from the first opening 114a of the first membrane module 100, and the stock solution (concentrate) is taken out from the second opening 214a of the second membrane module 200. At this time, in the membrane module 10, the filtrate (permeate) is taken out from the first outlet 114b of the first membrane module 100 and the second outlet 214b of the second membrane module 200. In the present embodiment, the filtration device 1 includes two membrane modules 10 connected in parallel. A detailed description of the configuration of the membrane module 10 will be described later.

[0034] The stock solution tank 20 is a container (storage tank) for storing the stock solution 21. That is, the stock solution 21 to be filtered by the membrane module 10 is stored in the stock solution tank 20. In the present embodiment, the stock solution 21 circulating through the membrane module 10 (the stock solution 21 before being filtered by the membrane module 10 and the stock solution 21 after being filtered by the membrane module 10) is stored in the stock solution tank 20.

[0035] The pump 30 is a pump that supplies the stock solution to the membrane module 10. The pump 30 feeds the stock solution 21 stored in the stock solution tank 20 and supplies it to the membrane module 10. Specifically, the pump 30 takes out the stock solution 21 from the stock solution tank 20, discharges the taken-out stock solution 21 at a discharge pressure P1, and feeds it to the two membrane modules 10 through the pipe 41.

[0036] The stock solution 21 discharged from the pump 30 is supplied to the two membrane modules 10 from the first opening 114a of the first membrane module 100 provided in each of the two membrane modules 10. Specifically, the stock solution 21 flows into one of the two membrane modules 10 (in the +Z-axis direction) at the inlet pressure P2, and the stock solution 21 flows into the other membrane module 10 (in the -Z-axis direction) at the inlet pressure P3. The inlet pressure P3 is slightly different from the inlet pressure P2 due to the pressure loss when the stock solution 21 passes through the pipe 41, but it may be the same pressure as the inlet pressure P2 without considering the pressure loss.

[0037] The inlet pressures P2 and P3 of the stock solution 21 flowing into the membrane module 10 are less than 0.2 MPa. The inlet pressures P2 and P3 are preferably 0.1 MPa or less, more preferably 0.07 MPa or less (or less than 0.07 MPa), and even more preferably 0.05 MPa or less (or less than 0.05 MPa). The inlet pressures P2 and P3 are preferably 0.001 MPa or more, more preferably 0.01 MPa or more, and even more preferably 0.05 MPa or more.

[0038] Since the inlet pressures P2 and P3 of the stock solution 21 flowing into the membrane module 10 are less than 0.2 MPa, the discharge pressure P1 of the pump 30 may be small. In this embodiment, the upper limit value of the discharge pressure P1 of the pump 30 is less than 0.45 MPa. The upper limit value of the discharge pressure P1 of the pump 30 is preferably 0.3 MPa or less, more preferably 0.2 MPa or less, and even more preferably 0.1 MPa or less. The lower limit value of the discharge pressure P1 of the pump 30 is preferably 0.0014 MPa or more, more preferably 0.014 MPa or more, and even more preferably 0.07 MPa or more. The discharge pressure P1 of the pump 30 is adjusted by inverter control so as to match the set values of the inlet pressures P2 and P3 of the stock solution 21 flowing into the membrane module 10. The discharge pressure P1 of the pump 30 may be adjusted by a valve for flow rate adjustment (not shown).

[0039] The stock solution 21 is filtered (the filtrate is removed) and concentrated by the two membrane modules 10, discharged from the second openings 214a of the second membrane modules 200 provided in each of the two membrane modules 10, and returned to the stock solution tank 20 through the pipe 42. Specifically, the stock solution 21 is discharged from one of the two membrane modules 10 (in the +Z-axis direction) at the outlet pressure P4, and the stock solution 21 is discharged from the other membrane module 10 (in the -Z-axis direction) at the outlet pressure P5. The outlet pressure P4 is lower than the inlet pressure P2, and the outlet pressure P5 is lower than the inlet pressure P3. That is, the outlet pressures P4 and P5 are less than 0.2 MPa. The outlet pressures P4 and P5 are preferably 0.1 MPa or less, more preferably 0.07 MPa or less (or less than 0.07 MPa), and even more preferably 0.05 MPa or less (or less than 0.05 MPa). The outlet pressure P4 and the outlet pressure P5 may be the same pressure or different pressures. The stock solution 21 may be taken out of the filtration device 1 through a pipe or the like instead of being returned to the stock solution tank 20.

[0040] The filtrate (permeate) from which the solid content has been removed by filtering the stock solution 21 with the two membrane modules 10 is discharged from the first outlet 114b of the first membrane module 100 and the second outlet 214b of the second membrane module 200 provided in each of the two membrane modules 10. The filtrate discharged from the first outlet 114b of the first membrane module 100 is taken out of the membrane module 10 through the pipes 43 and 45. The filtrate discharged from the second outlet 214b of the second membrane module 200 is taken out of the membrane module 10 through the pipes 44 and 45.

[0041] [Description of the two membrane modules 10] Next, the configuration of the membrane module 10 will be described in detail. Since the two membrane modules 10 included in the filtration device 1 have the same configuration, the configuration of one membrane module 10 will be described in detail below. FIG. 2 is a perspective view showing the configuration of the membrane module 10 according to the present embodiment. FIG. 2 is an enlarged perspective view showing one membrane module 10 shown in FIG. 1 removed from the filtration device 1. FIG. 3 is a front view, a bottom view, and a top view showing the configuration of the membrane module 10 according to the present embodiment. Specifically, FIG. 3(a) is a front view showing the configuration of the membrane module 10 shown in FIGS. 1 and 2 when viewed from the negative Y-axis direction. FIG. 3(b) is a bottom view showing the configuration of the membrane module 10 shown in FIGS. 1 and 2 when viewed from the negative X-axis direction. FIG. 3(c) is a top view showing the configuration of the membrane module 10 shown in FIGS. 1 and 2 when viewed from the positive X-axis direction.

[0042] As shown in FIGS. 2 and 3, the membrane module 10 includes a first membrane module 100 and a second membrane module 200. The first membrane module 100 and the second membrane module 200 are spiral membrane modules of a cross-flow filtration method. The first membrane module 100 and the second membrane module 200 are arranged side by side in a predetermined direction (in the present embodiment, the X-axis direction). Specifically, the second membrane module 200 is arranged on one side in the predetermined direction of the first membrane module 100 (in the present embodiment, the positive X-axis direction).

[0043] The first membrane module 100 includes a first container 110 and a first element 120 accommodated in the first container 110. The second membrane module 200 includes a second container 210 and a second element 220 accommodated in the second container 210. Here, the first container 110 and the second container 210 are referred to as container 11, and the first element 120 and the second element 220 are referred to as element 12. That is, the membrane module 10 includes an element 12 in which a filtration membrane is wound around a winding axis A (see FIG. 4) extending in a predetermined direction (X-axis direction), and a container 11 that accommodates the element 12. The container 11 includes a first container 110 and a second container 210 disposed on one side (X-axis positive direction) in a predetermined direction of the first container 110. The element 12 includes a first element 120 accommodated in the first container 110 and a second element 220 accommodated in the second container 210. Each of these components will be described in detail below.

[0044] [2.1 Explanation of the first container 110 of the first membrane module 100] First, the configuration of the first container 110 included in the first membrane module 100 will be described in detail. As shown in FIGS. 2 and 3, the first container 110 is a cylindrical (tubular) container extending in the X-axis direction in which a space (hollow) extending in the X-axis direction is formed inside. The material of the first container 110 is not particularly limited, and examples of the first container 110 include resin containers such as polyvinyl chloride and engineering plastics, or metal containers. The first container 110 includes a first container body 111 and flange portions 112, 113, and 114.

[0045] The first container body 111 is a cylindrical (circular tubular) portion extending in the X-axis direction that constitutes the main body of the first container 110, and accommodates the first element 120 inside. The shape of the first container body 111 is not particularly limited as long as it can accommodate the first element 120 inside, and it may be an elliptical cylinder, an oblong cylinder, a polygonal cylinder such as a square cylinder, or the like.

[0046] The flange portion 112 is an annular and plate-shaped part located at the end of the first container 110 in the positive X-axis direction and connected to the end of the first container body 111 in the positive X-axis direction. The flange portion 112 has a portion protruding outward from the first container body 111, and a plurality of circular through-holes 112a, which are circular through-holes penetrating the flange portion 112 in the X-axis direction, are provided in this portion. The shape of the flange portion 112 is not particularly limited as long as it has a portion protruding outward from the first container body 111, and the outer shape viewed from the X-axis direction may be an elliptical shape, an oval shape, or a polygonal shape such as a square shape.

[0047] The connection portion 112a is disposed at a position facing the connection portion 212a provided on the flange portion 212 included in the second membrane module 200 described later, and is connected to the connection portion 212a. Specifically, a connection member (not shown) such as a bolt is inserted into the connection portion 112a and the connection portion 212a and coupled to a connection member (not shown) such as a nut, whereby the connection portion 112a and the connection portion 212a are connected. Thereby, the flange portion 112 and the flange portion 212 are connected (fixed) in a state of being in contact with each other. The shape of the connection portion 112a is not particularly limited as long as it can be connected to the connection portion 212a, and it may be a through-hole having a polygonal shape such as an elliptical shape, an oval shape, or a square shape, or may not be a through-hole. The connection portion 112a may be a portion connected by a connection member other than a bolt and a nut.

[0048] The flange portion 113 is an annular and plate-shaped part located at the end of the first container 110 in the negative X-axis direction and connected to the end of the first container body 111 in the negative X-axis direction. The flange portion 113 has a portion protruding outward from the first container body 111, and a plurality of circular through-holes 113a, which are circular through-holes penetrating the flange portion 113 in the X-axis direction, are provided in this portion. The shape of the flange portion 113 is not particularly limited as long as it has a portion protruding outward from the first container body 111, and the outer shape viewed from the X-axis direction may be an elliptical shape, an oval shape, or a polygonal shape such as a square shape.

[0049] The connecting portion 113a is disposed at a position facing the connecting portion 114c provided on the flange portion 114 to be described later, and is connected to the connecting portion 114c. Specifically, a connecting member (not shown) such as a bolt is inserted into the connecting portion 113a and the connecting portion 114c and coupled to a connecting member (not shown) such as a nut, whereby the connecting portion 113a and the connecting portion 114c are connected. Thereby, the flange portion 113 and the flange portion 114 are connected (fixed) in a state of being in contact with each other. The shape of the connecting portion 113a is not particularly limited as long as it can be connected to the connecting portion 114c, and may be a through hole such as an elliptical shape, an oval shape, or a polygonal shape such as a square shape, or may not be a through hole. The connecting portion 113a may be a portion connected by a connecting member other than a bolt and a nut.

[0050] The flange portion 114 is a disk-shaped member that is disposed in the negative X-axis direction of the flange portion 113 and is connected to the flange portion 113. The flange portion 114 has the same outer shape as the flange portion 113 when viewed in the X-axis direction. The outer shape of the flange portion 114 when viewed in the X-axis direction may be an elliptical shape, an oval shape, or a polygonal shape such as a square shape, or may have an outer shape different from that of the flange portion 113. The flange portion 114 is provided with a first opening 114a, a first outlet 114b, and a plurality of connecting portions 114c.

[0051] The first opening 114a is a circular through hole that penetrates the flange portion 114 in the X-axis direction, and is disposed in the positive Z-axis direction with respect to the central position (first outlet 114b) of the flange portion 114. The first opening 114a is an opening that serves as an inlet or an outlet for the stock solution. In the present embodiment, the first opening 114a is an opening that serves as an inlet for the stock solution, and is formed to have a size larger than that of the first outlet 114b. The shape of the first opening 114a is not particularly limited as long as it is an opening that serves as an inlet or an outlet for the stock solution, and may be a through hole such as an elliptical shape, an oval shape, or a polygonal shape such as a square shape. The arrangement position and size of the first opening 114a are not particularly limited either. The first opening 114a may be disposed in the negative Z-axis direction with respect to the central position of the flange portion 114, or may be disposed in the positive Y-axis direction or the negative Y-axis direction with respect to the central position, and may be disposed at any position of the flange portion 114.

[0052] The first outlet 114b is a circular through-hole that penetrates the flange portion 114 in the X-axis direction and is disposed at the center position of the flange portion 114. The first outlet 114b is an opening that serves as an outlet for the filtrate and is directly connected to the liquid collecting pipe 130 of the first element 120 described later. The shape of the first outlet 114b is not particularly limited as long as it is an opening that serves as an outlet for the filtrate, and it may be a through-hole such as an elliptical shape, an oval shape, or a polygonal shape such as a square shape. The arrangement position and size of the first outlet 114b are also not particularly limited.

[0053] The connection portion 114c is a circular through-hole that penetrates the flange portion 114 in the X-axis direction and is disposed at a position facing the connection portion 113a of the flange portion 113. As described above, the connection portion 114c is connected to the connection portion 113a, whereby the flange portion 114 is connected (fixed) to the flange portion 113. The shape of the connection portion 114c is not particularly limited as long as it can be connected to the connection portion 113a, and it may be a through-hole such as an elliptical shape, an oval shape, or a polygonal shape such as a square shape, or it may not be a through-hole. The connection portion 114c may be a portion connected by a connection member other than a bolt and a nut.

[0054] [2.2 Explanation of the First Element 120 of the First Membrane Module 100] Next, the configuration of the first element 120 included in the first membrane module 100 will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is a perspective view showing the configuration of the first element 120 according to the present embodiment. FIG. 5 is a plan view and a cross-sectional view showing the configuration of the leaf 121 according to the present embodiment. FIG. 5(a) is a plan view showing the configuration when one leaf 121 is unfolded and spread flat, and FIG. 5(b) is a cross-sectional view showing the cross-section when the leaf 121 is cut in the thickness direction. In FIG. 5, the illustration of components other than one leaf 121 and the liquid collecting pipe 130 is omitted.

[0055] The first element 120 is a columnar part extending in the X-axis direction, which is housed in the first container 110 and filters the stock solution flowing into the first container 110. As shown in FIGS. 3 and 4, the first element 120 includes a leaf 121, a liquid collecting pipe 130, and a closing member 140.

[0056] The leaf 121 is provided with a filtration membrane 122. A plurality of leaves 121 are wound around the liquid collecting pipe 130 around the winding axis A (see FIG. 4), thereby constituting a spiral-shaped first element 120. In the present embodiment, the number of leaves 121 of the first element 120 is 16 or more. That is, 16 or more leaves 121 are wound around the liquid collecting pipe 130, thereby constituting a spiral-shaped first element 120. The number of leaves 121 is preferably 18 or more, more preferably 20 to 40, and even more preferably 20 to 26 from the viewpoint of easy manufacturing.

[0057] As shown in FIGS. 4 and 5, the leaf 121 includes filtration membranes 122a and 122b as the filtration membrane 122, a filtrate net 123, and a stock solution net 124. In the present embodiment, in the leaf 121, the filtration membrane 122a, the filtrate net 123, the filtration membrane 122b, and the stock solution net 124 are laminated in this order.

[0058] The filtration membrane 122 (122a and 122b) is a microfiltration membrane (MF membrane). Specifically, the filtration membrane 122 has a large number of micropores, and is a microfiltration membrane with the pore diameter of the micropores being 0.1 μm or more and 0.4 μm or less. The pore diameter is measured by measuring the average flow pore diameter using a pore size distribution measuring device capable of measuring the pore diameter by the bubble point method (the maximum pore diameter evaluation method of the filter defined in JIS K 3832). The filtration membrane 122 preferably has a pore diameter of the micropores of 0.15 μm or more and 0.35 μm or less, more preferably 0.2 μm or more and 0.3 μm or less, and even more preferably 0.23 μm or more and 0.27 μm or less. As the filtration membrane 122, those in which a polymer membrane having a large number of micropores is formed on the surface of a base material made of a non-woven fabric made of synthetic resin can be used.

[0059] The filter membranes 122 (122a and 122b) are wound around a winding shaft A (see Fig. 4) extending in a predetermined direction (X-axis direction), and are sheet-like members that become rectangular (rectangular or square) when the wound state is developed and spread out flat. In Fig. 5(a), the length in the winding direction of the filter membrane 122 (leaf 121) is defined as length L1, and the length in the winding shaft direction of the filter membrane 122 (leaf 121) is defined as length L2. The winding direction of the filter membrane 122 is the direction in which the filter membrane 122 is wound, and is illustrated as the Y-axis direction in Fig. 5(a). The winding shaft direction of the filter membrane 122 is the direction in which the winding shaft A extends when the filter membrane 122 is wound, and in the present embodiment, it is the X-axis direction.

[0060] The length L1 in the winding direction of the filter membranes 122 (122a and 122b) is 800 mm or less. The length L1 in the winding direction of the filter membrane 122 is preferably 700 mm or less, more preferably 600 mm or less, and even more preferably 500 mm or less. The length L1 in the winding direction of the filter membrane 122 is preferably 300 mm or more, more preferably 400 mm or more, and even more preferably 420 mm or more. The length L2 in the winding shaft direction (X-axis direction) of the filter membranes 122 (122a and 122b) is 800 mm or less. The length L2 in the winding shaft direction of the filter membrane 122 is preferably 700 mm or less, more preferably 600 mm or less, and even more preferably 500 mm or less. The length L2 in the winding shaft direction of the filter membrane 122 is preferably 300 mm or more, more preferably 400 mm or more, and even more preferably 420 mm or more.

[0061] The above length L2 is also the length of the first element 120 (excluding the liquid collecting pipe 130) in the winding axis direction. That is, the first element 120 has a length L2 in a predetermined direction, namely the winding axis direction (X-axis direction), of 800 mm or less. The length L2 of the first element 120 in the winding axis direction is preferably 700 mm or less, more preferably 600 mm or less, and even more preferably 500 mm or less. The length L2 of the first element 120 in the winding axis direction is preferably 300 mm or more, more preferably 400 mm or more, and even more preferably 420 mm or more.

[0062] With a filter membrane 122 of such a size, the effective filtration area per leaf 121 of the first element 120 is 1.3 m 2 or less. The effective filtration area per leaf 121 is the total area of the filter membrane 122 in one leaf 121, that is, the total area of the filter membrane 122a and the filter membrane 122b. The effective filtration area per leaf 121 is 1.0 m 2 or less is preferable, 0.8 m 2 or less is more preferable, and 0.4 m 2 or less is even more preferable.

[0063] The filter membranes 122a and 122b form a bag body with three sides closed with the filtrate net 123 sandwiched therebetween, and the other one side communicates with the liquid collecting pipe 130. As the method for manufacturing the bag body by the filter membranes 122a and 122b, various methods similar to those of a conventional spiral type membrane module can be used. The bag body may be manufactured by welding or adhering three sides of the leaf-shaped filter membrane 122, or the bag body may be manufactured by folding a strip-shaped filter membrane 122 in a zigzag manner and welding or adhering two sides.

[0064] The filtrate net 123 is a member (filtrate flow path forming member) that forms the flow path of the filtrate. The filtrate net 123 is disposed between the filtration membranes 122a and 122b, maintains the interval between the filtration membranes 122a and 122b, and ensures the flow of the filtrate. The filtrate net 123 communicates with the liquid collection pipe 130, and the filtrate filtered by the filtration membranes 122a and 122b is sent to the liquid collection pipe 130 through the filtrate net 123.

[0065] As the filtrate net 123, various materials and shapes can be used as long as the interval between the filtration membranes 122a and 122b can be maintained and the flow path of the filtrate can be ensured. As the filtrate net 123, a net using synthetic resin fibers such as polyolefin-based, polyester-based, and polyamide-based can be used. As the filtrate net 123, a net having a structure in which filaments forming a mesh are three-dimensionally crossed can be used.

[0066] The mesh size of the net used for the filtrate net 123 is preferably such that the density of the filaments arranged in parallel (the number per unit length) is 30 or more filaments per inch, more preferably 35 or more filaments per inch, and even more preferably 40 or more filaments per inch. If the density of the filaments is small, there is a risk that the filtration membrane 122 may bite into the filtrate net 123, but by setting the density of the filaments within the above range, it is possible to suppress the filtration membrane 122 from biting into the filtrate net 123.

[0067] The thickness of the filtrate net 123 is 0.2 mm or more. That is, the interval between the filtration membranes 122a and 122b is 0.2 mm or more. The thickness of the filtrate net 123 is preferably 0.21 mm or more, more preferably 0.22 mm or more, and even more preferably 0.23 mm or more. The thickness of the filtrate net 123 is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.4 mm or less. This is because if the thickness of the filtrate net 123 is too small, the flow path of the filtrate becomes narrow and it becomes difficult to ensure the flow of the filtrate, and if the thickness of the filtrate net 123 is too large, the first element 120 becomes larger.

[0068] The stock solution net 124 is a member (stock solution flow path forming member) that forms the flow path of the stock solution. The stock solution net 124 is arranged so as to sandwich the filtration membrane 122a or the filtration membrane 122b with the filtrate net 123. As a result, the stock solution net 124 is disposed between the filtration membrane 122a and the filtration membrane 122b, maintains the interval between the filtration membrane 122a and the filtration membrane 122b, and secures the flow of the stock solution.

[0069] As the stock solution net 124, various materials and shapes can be used as long as the interval between the filtration membrane 122a and the filtration membrane 122b can be maintained and the flow path of the stock solution can be secured. As the stock solution net 124, those having the same material and structure as the filtrate net 123 can be used. In the present embodiment, the density of the filaments of the stock solution net 124 is the same as or smaller than the density of the filaments of the filtrate net 123. The thickness of the stock solution net 124 is the same as or larger than the thickness of the filtrate net 123.

[0070] The liquid collection pipe 130 is a tubular member that collects the filtrate. The liquid collection pipe 130 is disposed at the central position of the first element 120 when viewed in the X-axis direction, and is a cylindrical member extending in the X-axis direction. The liquid collection pipe 130 includes a plurality of holes 131 arranged in the X-axis direction. The plurality of holes 131 are through holes through which the filtrate passes. The liquid collection pipe 130 communicates with the flow path of the filtrate formed by the filtrate net 123, and collects the filtrate filtered by the filtration membrane 122 from the plurality of holes 131 into the interior of the liquid collection pipe 130. The liquid collection pipe 130 flows the collected filtrate in the X-axis direction along the flow path inside the liquid collection pipe 130. The shape of the liquid collection pipe 130 is not particularly limited as long as it can collect the filtrate, and may be an elliptical cylinder shape, an oval cylinder shape, a polygonal cylinder shape such as a square cylinder shape, or the like. The liquid collection pipe 130 is formed of a resin or the like, but the material is not particularly limited, and any material that can be used for the liquid collection pipe provided in a conventional spiral type membrane module may be used. The number, size, shape, etc. of the holes 131 provided in the liquid collection pipe 130 are not particularly limited.

[0071] The blocking member 140 is a member (insert plug) that blocks the opening of the liquid collecting pipe 130. The blocking member 140 is formed of resin or the like, but its material is not particularly limited and may be the same as that of the liquid collecting pipe 130 or different from that of the liquid collecting pipe 130. In the present embodiment, the blocking member 140 is disposed at the end of the liquid collecting pipe 130 in the +X-axis direction, inserted into the opening (the filtrate outlet) at the end of the liquid collecting pipe 130 in the +X-axis direction, and blocks the opening (the filtrate outlet). Thereby, the liquid collecting pipe 130 causes the collected filtrate to flow in the -X-axis direction and discharges it from the opening 132 at the end of the liquid collecting pipe 130 in the -X-axis direction.

[0072] [2.3 Description of the second membrane module 200] The second membrane module 200 has the same configuration as that obtained by inverting the first membrane module 100 in the X-axis direction and inverting it in the Z-axis direction. In other words, the second membrane module 200 has the same configuration as that obtained by rotating the first membrane module 100 180° about the Y-axis. For this reason, the second container 210 of the second membrane module 200 has the same configuration as the first container 110 of the first membrane module 100, and the second element 220 of the second membrane module 200 has the same configuration as the first element 120 of the first membrane module 100. For this reason, the description of each component included in the second membrane module 200 will be simplified or omitted.

[0073] The second container 210 includes a second container body 211 having the same configuration as the first container body 111, and flange portions 212, 213, and 214 having the same configuration as the flange portions 112, 113, and 114. The flange portion 212 is provided with a plurality of connecting portions 212a having the same configuration as the plurality of connecting portions 112a of the flange portion 112. The flange portion 213 is provided with a plurality of connecting portions 213a having the same configuration as the plurality of connecting portions 113a of the flange portion 113. The flange portion 214 is provided with a second opening 214a having the same configuration as the first opening 114a of the flange portion 114, a second outlet 214b having the same configuration as the first outlet 114b, and a plurality of connecting portions 214c having the same configuration as the plurality of connecting portions 114c. The second opening 214a is an opening that serves as an outlet for the stock solution and is arranged in the negative Z-axis direction with respect to the central position (second outlet 214b) of the flange portion 214. The second opening 214a may be arranged in the positive Z-axis direction with respect to the central position of the flange portion 214, or may be arranged in the positive Y-axis direction or the negative Y-axis direction with respect to the central position, and may be arranged at any position of the flange portion 214.

[0074] The second element 220 includes a leaf 221 having the same configuration as the leaf 121, a liquid collecting pipe 230 having the same configuration as the liquid collecting pipe 130, and a closing member 240 having the same configuration as the closing member 140. The closing member 240 is arranged at the end of the liquid collecting pipe 230 in the negative X-axis direction and is inserted into the opening (outlet for the filtrate) at the end of the liquid collecting pipe 230 in the negative X-axis direction to close the opening (outlet for the filtrate). Thereby, the liquid collecting pipe 230 flows the collected filtrate in the positive X-axis direction and discharges it from the opening at the end of the liquid collecting pipe 230 in the positive X-axis direction.

[0075] [2.4 Overall Description of the Membrane Module 10] As described above, the first container 110 of the first membrane module 100 is provided with a first outlet 114b for the filtrate, and the second container 210 of the second membrane module 200 is provided with a second outlet 214b for the filtrate. That is, the container 11 is provided with outlets for the filtrate in each of the first container 110 and the second container 210. In the present embodiment, the first outlet 114b is provided in the flange portion 114 of the first container 110, and the second outlet 214b is provided in the flange portion 214 of the second container 210. For this reason, the first outlet 114b is disposed at the end portion on the other side (the negative X-axis direction) in the predetermined direction of the first container 110. The end portion of the first container 110 is the portion between the end surface in the negative X-axis direction of the leaf 121 of the first element 120 and the end surface in the negative X-axis direction of the flange portion 114. The second outlet 214b is disposed at the end portion on one side (the positive X-axis direction) in the predetermined direction of the second container 210. The end portion of the second container 210 is the portion between the end surface in the positive X-axis direction of the leaf 221 of the second element 220 and the end surface in the positive X-axis direction of the flange portion 214. That is, the container 11 is provided with outlets for the filtrate at both end portions in the predetermined direction (the X-axis direction). Specifically, the first outlet 114b is formed at the end surface on the other side (the negative X-axis direction) in the predetermined direction of the first container 110. The second outlet 214b is formed at the end surface on one side (the positive X-axis direction) in the predetermined direction of the second container 210. That is, the container 11 is provided with outlets for the filtrate at both end surfaces in the predetermined direction (the X-axis direction).

[0076] A closing member 140 is disposed at an opening (the filtrate outlet) at the end of the liquid collecting pipe 130 disposed in the first container 110 in the +X-axis direction, and a closing member 240 is disposed at an opening (the filtrate outlet) at the end of the liquid collecting pipe 230 disposed in the second container 210 in the -X-axis direction. As a result, in the first container 110, the end of the filtrate flow path at one end in a predetermined direction (the +X-axis direction) is blocked. In the second container 210, the end of the filtrate flow path at the other end in the predetermined direction (the -X-axis direction) is blocked. The flange portion 112 of the first container 110 and the flange portion 212 of the second container 210 are connected in a state of being in contact with each other. For this reason, the container 11 is formed by connecting the end face on one side in a predetermined direction (the +X-axis direction) of the first container 110 and the end face on the other side in the predetermined direction (the -X-axis direction) of the second container 210. Thereby, the stock solution flow path in the first container 110 and the stock solution flow path in the second container 210 are connected.

[0077] The first container 110 of the first membrane module 100 further includes a first opening 114a that serves as an inlet or an outlet for the stock solution (in this embodiment, it is an inlet). The second container 210 of the second membrane module 200 further includes a second opening 214a that serves as an outlet or an inlet for the stock solution (in this embodiment, it is an outlet). That is, the container 11 is provided with an inlet for the stock solution at one of the first container 110 and the second container 210, and an outlet for the stock solution at the other. When the first opening 114a is the inlet for the stock solution, the second opening 214a is the outlet for the stock solution. When the first opening 114a is the outlet for the stock solution, the second opening 214a is the inlet for the stock solution. In this embodiment, the first opening 114a is provided in the flange portion 114 of the first container 110, and the second opening 214a is provided in the flange portion 214 of the second container 210. For this reason, the first container 110 is provided with the first opening 114a at the end on the other side (negative X-axis direction) in the predetermined direction. The second container 210 is provided with the second opening 214a at the end on one side (positive X-axis direction) in the predetermined direction. That is, the container 11 is provided with an inlet for the stock solution at one end in the predetermined direction (X-axis direction), and an outlet for the stock solution at the other end. Specifically, the first opening 114a is formed on the end face on the other side (negative X-axis direction) in the predetermined direction of the first container 110. The second opening 214a is formed on the end face on one side (positive X-axis direction) in the predetermined direction of the second container 210. That is, the container 11 is provided with an inlet for the stock solution at one end face in the predetermined direction (X-axis direction), and an outlet for the stock solution at the other end face.

[0078] [Explanation of the filtration method in the filtration device 1] Next, the filtration method in the filtration device 1 using the membrane module 10 configured as described above will be described. FIG. 6 is a flowchart showing each step of the filtration method in the filtration device 1 according to this embodiment.

[0079] As shown in FIG. 6, first, the stock solution is caused to flow into the membrane module 10 at an inlet pressure smaller than 0.2 MPa (S102: Stock solution inflow step).

[0080] Specifically, the pump 30 extracts the stock solution 21 from the stock solution tank 20, and supplies the extracted stock solution 21 to the membrane module 10 at an inlet pressure (inlet pressures P2 or P3 in FIG. 1) smaller than 0.2 MPa through the first opening 114a of the first container 110 included in the first membrane module 100 of the membrane module 10.

[0081] Next, the stock solution that has flowed into the membrane module 10 is filtered by the filtration membrane, and a cake layer is formed on the filtration membrane (S104: filtration and cake layer formation step).

[0082] Specifically, the stock solution flowing in from the first opening 114a flows through the stock solution net 124 of each leaf 121 of the first element 120. As a result, a part of the stock solution is filtered by the filtration membrane 122, flows through the filtrate net 123, and flows into the liquid collection pipe 130. At this time, a part of the solid content contained in the stock solution is captured and deposited on the surface of the filtration membrane 122, and a cake layer (filtration membrane surface deposit) is formed on the surface of the filtration membrane 122. The stock solution that has passed through the first element 120 flows through the stock solution net of each leaf 221 of the second element 220. As a result, a part of the stock solution is filtered by the filtration membrane and flows through the filtrate net, and flows into the liquid collection pipe 230. Also in the second element 220, a cake layer is formed on the surface of the filtration membrane in the same manner as in the first element 120. These cake layers may be removed periodically or irregularly by flushing or the like. In this way, the first membrane module 100 and the second membrane module 200 are cross-flow filtration type filters that perform cross-flow operation in which the supplied stock solution is made to flow parallel to the filtration membrane 122 or the like to filter the solid content in the stock solution.

[0083] Next, the stock solution (concentrate) and the filtrate (permeate) are discharged from the membrane module 10 (S106: Stock solution and filtrate discharge step). Specifically, the stock solution (concentrate) that has passed through the second element 220 is discharged from the second opening 214a of the second container 210 of the second membrane module 200. The filtrate (permeate) that has flowed into the liquid collection pipe 130 is discharged from the first outlet 114b of the first container 110 of the first membrane module 100. The filtrate (permeate) that has flowed into the liquid collection pipe 230 is discharged from the second outlet 214b of the second container 210 of the second membrane module 200. The stock solution (concentrate) discharged from the membrane module 10 is returned to the stock solution tank 20. The filtrate (permeate) discharged from the membrane module 10 is supplied to a filtrate tank (not shown) or the like.

[0084] [Explanation of the manufacturing process of the 4 membrane module 10] Next, the manufacturing process of the membrane module 10 will be described. FIG. 7 is a front view, a bottom view, and a top view showing the configuration of the membrane module 50 that forms a part of the membrane module 10 according to the present embodiment. FIG. 7(a) is a front view of the membrane module 50 viewed from the negative Y-axis direction, FIG. 7(b) is a bottom view of the membrane module 50 viewed from the negative X-axis direction, and FIG. 7(c) is a top view of the membrane module 50 viewed from the positive X-axis direction. FIGS. 7(a) to 7(c) correspond to FIGS. 3(a) to 3(c). FIG. 8 is a front view showing the process of manufacturing the membrane module 10 according to the present embodiment. FIG. 8(a) shows the membrane module 50 and the membrane module 60 that form a part of the membrane module 10. FIG. 8(b) shows a state in which the first membrane module 100 is separated from the membrane module 50 and the second membrane module 200 is separated from the membrane module 60. FIG. 8(c) shows the membrane module 10 in which the first membrane module 100 and the second membrane module 200 are connected.

[0085] As shown in FIG. 7, the membrane module 50 is a spiral membrane module of a cross-flow filtration type including one container (first container 110) and one element (first element 120). The membrane module 50 has a configuration in which a flange portion 115 is connected to the end portion of the first membrane module 100 in the positive X-axis direction described above. The flange portion 115 has the same configuration as the flange portion 214 of the second membrane module 200 described above, but does not include an outlet for the filtrate.

[0086] Specifically, the flange portion 115 is a disk-shaped member disposed in the positive X-axis direction of the flange portion 112 and connected to the flange portion 112. The flange portion 115 is provided with a third opening 115a and a plurality of connection portions 115c. The third opening 115a is an opening that serves as an inlet or an outlet for the stock solution. The third opening 115a may be disposed at any position of the flange portion 115. In the membrane module 50, the third opening 115a serves as the inlet for the stock solution and the first opening 114a serves as the outlet for the stock solution, but the first opening 114a may serve as the inlet for the stock solution and the third opening 115a may serve as the outlet for the stock solution. The connection portion 115c is disposed at a position facing the connection portion 112a of the flange portion 112 and is connected to the connection portion 112a, whereby the flange portion 115 is connected (fixed) to the flange portion 112.

[0087] When manufacturing the membrane module 10, as shown in FIG. 8(a), the membrane module 50 and the membrane module 60 are prepared. The membrane module 60 has the same configuration as that obtained by inverting the membrane module 50 in the X-axis direction and inverting it in the Z-axis direction. In other words, the membrane module 60 has the same configuration as that obtained by rotating the membrane module 50 by 180° about the Y-axis. That is, in FIG. 8(a), it is sufficient to prepare two membrane modules 50. In the membrane module 60, the portion corresponding to the first membrane module 100 in the membrane module 50 is used as the second membrane module 200, and the portion corresponding to the flange portion 115 is used as the flange portion 215. That is, the membrane module 60 has a configuration in which a flange portion 215 is connected to the end portion of the second membrane module 200 in the negative X-axis direction.

[0088] Then, as shown in FIG. 8(b), the flange portion 115 is removed from the membrane module 50, and the first membrane module 100 is separated from the membrane module 50. Similarly, the flange portion 215 is removed from the membrane module 60, and the second membrane module 200 is separated from the membrane module 60.

[0089] Then, as shown in FIG. 8(c), the first membrane module 100 and the second membrane module 200 are connected by connecting the flange portion 112 of the first membrane module 100 and the flange portion 212 of the second membrane module 200. Thereby, the membrane module 10 is manufactured.

[0090] [Description of Effects] As described above, according to the filtration device 1 according to the present embodiment, the container 11 of the spiral membrane module 10 includes the first container 110 and the second container 210. The first container 110 includes the first outlet 114b for the filtrate, and the second container 210 includes the second outlet 214b for the filtrate. In such a configuration where the container 11 includes the first container 110 and the second container 210, since each of the first container 110 and the second container 210 has an outlet for the filtrate, the filtrate can be taken out from the two outlets (the first outlet 114b and the second outlet 214b). As a result, the distance through which the filtrate flows can be shortened and the resistance when the filtrate flows can be reduced, so that the amount of filtrate can be increased. Further, since the area of the outlet of the filtrate is large, the resistance when the filtrate flows can be reduced and the amount of filtrate can be increased.

[0091] In particular, in a wastewater treatment device or the like, while it is required to reduce the installation area, the requirements regarding the height direction (the above-described predetermined direction, the X-axis direction) are often not strict. From this perspective, in some cases, it may be required to arrange the first membrane module 100 and the second membrane module 200 in series (arrange the first container 110 and the second container 210 in a predetermined direction) rather than in parallel in the membrane module 10. Even in such a case, in order to reduce the resistance when the filtrate flows and increase the amount of filtrate, it is preferable to adopt this configuration.

[0092] The first outlet 114b is disposed at the end portion on the other side (negative X-axis direction) in a predetermined direction of the first container 110, and the second outlet 214b is disposed at the end portion on one side (positive X-axis direction) in a predetermined direction of the second container 210. Thereby, the two outlets (the first outlet 114b and the second outlet 214b) of the filtrate can be disposed at both end portions in a predetermined direction of the container 11. Therefore, since the filtrate is taken out from both end portions in the predetermined direction (X-axis direction) of the container 11, an outlet for the filtrate can be provided without a complicated structure. Further, when the outlet of the filtrate is provided at an end portion excluding the end face of the container 11, it becomes easy to connect three or more containers, such as a third container that houses a third element, in addition to the first container 110 and the second container 210.

[0093] The first outlet 114b is formed on the end face on the other side (negative X-axis direction) in a predetermined direction of the first container 110, and the second outlet 214b is formed on the end face on one side (positive X-axis direction) in a predetermined direction of the second container 210. Thereby, the two outlets (the first outlet 114b and the second outlet 214b) of the filtrate can be formed on both end faces in a predetermined direction (X-axis direction) of the container 11. Therefore, since the outlet of the filtrate and the path of the filtrate can be directly connected, the structure of the container 11 can be simplified. By connecting the end face of the first container 110 or the second container 210 to another member (not shown), the first outlet 114b or the second outlet 214b can be easily connected to the other member.

[0094] By connecting the end face on one side (in the +X-axis direction) of the first container 110 in a predetermined direction and the end face on the other side (in the -X-axis direction) of the second container 210 in a predetermined direction, a simple structure can form the container 11 by connecting the flow path of the stock solution in the first container 110 and the flow path of the stock solution in the second container 210. As a result, a configuration in which the stock solution passes between the first container 110 and the second container 210 can be easily realized. When a plurality of individual containers such as the first container 110 and the second container 210, which house individual elements such as the first element 120 and the second element 220, are integrally connected in series such that their respective end faces are connected, rather than via piping, and the filtrate flow paths of these individual elements are connected at the connection surface of the individual containers and configured to extract filtrate only from the downstream individual container, the inventors newly found a problem that in the downstream membrane module, no filtrate is produced, and in some cases, the filtrate flows back to the stock solution side. When connecting a plurality of individual containers in series by piping instead of connecting the end faces of each individual container, since the filtrate in each individual element also inevitably merges through piping passing outside the individual containers, the above phenomenon is less likely to become a major problem, and thus such a problem is not recognized. When a plurality of individual containers that house individual elements are integrally connected in series such that their respective end faces are connected, rather than via piping, such a problem can be solved by individually extracting filtrate from these individual containers. Furthermore, when the filtrate flow paths are not connected by blocking the filtrate flow paths of the individual elements housed in the individual containers at the connection surface of the plurality of individual containers, the above problem can be solved more effectively.

[0095] By blocking the filtrate outlet at one end of the first container 110 in a predetermined direction (the positive X-axis direction) and blocking the filtrate outlet at the other end of the second container 210 in the predetermined direction (the negative X-axis direction), it is possible to suppress one filtrate from affecting the other filtrate. For example, it is possible to suppress the high-pressure side filtrate from inhibiting the flow of the low-pressure side filtrate. In particular, when the membrane module 10 is operated at low pressure, since the flow of the low-pressure side filtrate is easily inhibited by the high-pressure side filtrate, the effect of the above configuration is high. Since the path can be divided between the filtrate in the first container 110 and the filtrate in the second container 210, the resistance when the filtrate flows can be reduced. When connecting the first membrane module 100 and the second membrane module 200, there is no need to remove the insert plug and attach a connector for connecting the liquid collection pipe 130 and the liquid collection pipe 230, and the first membrane module 100 and the second membrane module 200 can be easily connected.

[0096] Specifically, by blocking the filtrate outlet at one end of the first container 110 in a predetermined direction and blocking the filtrate outlet at the other end of the second container 210 in the predetermined direction, the filtrate flow paths of the individual elements can be made independent of each other. The pressure of the filtrate depends on the average of the inlet pressure and the outlet pressure of each individual element. Therefore, when a plurality of individual elements are connected in series and the filtrate flow paths are also connected at the connection points of the individual elements, the inlet pressure of the stock solution of the downstream individual element may be equal to or lower than the pressure of the filtrate of the individual element. In this case, there arises a problem that no filtrate comes out of the individual element, and in some cases, the filtrate flows backward to the stock solution side. By blocking the filtrate outlet at one end of the first container 110 in a predetermined direction and blocking the filtrate outlet at the other end of the second container 210 in the predetermined direction, the pressure of the filtrate of the downstream individual element is suppressed from being affected by the pressure of the filtrate of the upstream individual element, so that the phenomenon that the difference between the pressure of the stock solution and the pressure of the filtrate in the downstream individual element becomes small is less likely to occur. As a result, the risk of deterioration of the filtration performance is reduced.

[0097] The first container 110 is provided with a first opening 114a at the end on the other side (the minus X-axis direction) in a predetermined direction, and the second container 210 is provided with a second opening 214a at the end on one side (the plus X-axis direction) in a predetermined direction. Thereby, the two openings (the first opening 114a and the second opening 214a) serving as the inlet and outlet of the stock solution can be arranged at both ends in the predetermined direction (the X-axis direction) of the container 11. Therefore, since the stock solution can flow from one end to the other end in the predetermined direction (the X-axis direction) of the container 11, a flow path for the stock solution can be efficiently secured in a limited space.

[0098] The first opening 114a is formed on the end face on the other side (the minus X-axis direction) in a predetermined direction of the first container 110, and the second opening 214a is formed on the end face on one side (the plus X-axis direction) in a predetermined direction of the second container 210. Thereby, the two openings (the first opening 114a and the second opening 214a) serving as the inlet and outlet of the stock solution can be formed on both end faces in the predetermined direction (the X-axis direction) of the container 11. Therefore, since the stock solution can flow from one end face to the other end face in the predetermined direction (the X-axis direction) of the container 11, furthermore, the length in the predetermined direction (the X-axis direction) of the container 11 can be shortened while ensuring the length of the path of the stock solution. Further, since the inlet and outlet of the stock solution are on the end face of the container 11, it is easy to connect three or more containers at their respective end faces. That is, by connecting the end face of the first container 110 or the second container 210 to a member such as another container (not shown), the first opening 114a or the second opening 214a can be easily connected to the member such as the other container.

[0099] At least one of the first element 120 and the second element 220 has a length of 800 mm or less in a predetermined direction, that is, the winding axis direction. Thereby, the influence of the pressure loss in the winding axis direction of the element can be reduced, and the difference in the filtration efficiency due to the location in the winding axis direction can be mitigated. Therefore, for example, in a mode such as connecting in series the first container 110 containing the first element 120 and the second container 210 containing the second element 220, when the second container 210 is arranged on one side in the predetermined direction of the first container 110, the problem that a difference occurs in the filtration efficiency between the first element 120 and the second element 220 is less likely to occur. Furthermore, since an element with a short length in the winding axis direction is applicable to any of the modes of being alone, in series connection, and in parallel connection, equipment design according to the installation environment, the properties of the substance to be removed, etc. can be easily performed.

[0100] When the container 11 is formed by connecting the end face on one side in the predetermined direction of the first container 110 and the end face on the other side in the predetermined direction of the second container 210, so that the flow path of the stock solution in the first container 110 and the flow path of the stock solution in the second container 210 are connected, it is more preferable that the inlet pressure of the stock solution flowing into the membrane module 10 is less than 0.2 MPa. In the above mode (the end face on one side of the first container 110 and the end face on the other side of the second container 210 are connected + the flow paths of the stock solution are connected in series), when the inlet pressure of the stock solution flowing into the membrane module 10 is low, the possibility that the inlet pressure of the stock solution in the downstream individual element becomes equal to or lower than the pressure of the filtrate is increased compared with the case of high-pressure operation. To address this problem, the filtrate flow paths of a plurality of individual elements are made independent, and the first container 110 containing the first element 120 and the second container 210 containing the second element 220 are arranged along a predetermined direction. The first container 110 is provided with a first filtrate outlet 114b, and the second container 210 is provided with a second filtrate outlet 214b. By adopting such a configuration, it is possible to suppress the situation where it becomes difficult for the filtrate to flow out in the downstream individual element, that is, the filtration efficiency decreases.

[0101] The inlet pressure of the stock solution flowing into the membrane module 10 is less than 0.2 MPa. Here, the filtration device 1 is configured to reduce the resistance when the filtrate flows by shortening the distance that the filtrate flows by taking out the filtrate from two outlets (the first outlet 114b and the second outlet 214b). For this reason, even if the length of the container 11 is increased by connecting the first container 110 and the second container 210, the resistance when the filtrate flows can be reduced, so that the inlet pressure at which the stock solution flows in can be operated at a low pressure. Therefore, since it is possible to perform low-pressure operation in which the inlet pressure of the stock solution flowing into the membrane module 10 is made less than 0.2 MPa, the power required for pressurization can be reduced, and as a result, the power consumption can be reduced.

[0102] The filtration membranes of the elements 12 provided in the spiral-type membrane module 10 (the filtration membrane 122 of the first element 120, the filtration membrane of the second element 220) are microfiltration membranes. Here, in conventional spiral-type membrane modules, since an RO membrane (reverse osmosis membrane) or a UF membrane (ultrafiltration membrane) with a relatively small pore diameter was used, a sufficient amount of filtrate could not be obtained unless it was used in high-pressure operation where the inlet pressure of the stock solution was a high pressure. For spiral-type membrane modules using microfiltration membranes (MF membranes) as well, high-pressure operation was performed in the same manner as those using RO membranes or UF membranes. In the process of considering the application of spiral-type membrane modules to the filtration and concentration of biological systems such as microalgae, the inventors found the problem that cells may break and organisms may die in high-pressure operation. As a result of intensive studies, it was newly found that if the operation is at a sufficiently low pressure (low-pressure operation) of the inlet pressure of the stock solution, the cells do not break and microalgae and the like can be filtered and concentrated alive. Further studies revealed that when the membrane module 10 using a microfiltration membrane was operated at low pressure, it could be practically used with low power even for applications other than the filtration and concentration of biological systems.

[0103] The pore diameter of the microfiltration membrane provided in the spiral membrane module 10 is 0.1 μm or more and 0.4 μm or less. Here, the microfiltration membrane is used when filtering substances with an average particle diameter of about 0.05 μm to 10 μm, particularly substances with an average particle diameter exceeding 0.4 μm. When the inlet pressure of the stock solution is high, that is, in the case of high-pressure operation, substances having a particle diameter slightly larger than the pore diameter of the micropores of the microfiltration membrane are deformed by the application of pressure and are thus pushed into the micropores of the microfiltration membrane, and as a result, clogging of the micropores may occur. On the other hand, in low-pressure operation, since the inlet pressure of the stock solution is low, the problem of clogging of the micropores by substances having a particle diameter slightly larger than the pore diameter of the micropores is less likely to occur. On the other hand, when the pore diameter of the micropores is less than 0.1 μm, it is difficult to obtain the required amount of filtrate in low-pressure operation. From the above, when the spiral membrane module 10 using the microfiltration membrane is operated at low pressure, it is preferable that the pore diameter of the microfiltration membrane be 0.1 μm or more and 0.4 μm or less, whereby clogging of the micropores is less likely to occur and a sufficient amount of filtrate can be obtained.

[0104] The inlet pressure of the stock solution flowing into the spiral membrane module 10 is 0.1 MPa or less. In this way, by performing low-pressure operation with the inlet pressure of the stock solution flowing into the membrane module 10 being 0.1 MPa or less, the power required for pressurizing the stock solution can be further reduced, and thus the power consumption can be further reduced. Further, by performing further low-pressure operation, clogging of the micropores by the substance to be filtered can be made less likely to occur. In the process of considering the application of the spiral membrane module to the filtration and concentration of biological systems such as microalgae, the inventors have found the problem that cells may break and organisms may die in high-pressure operation. By performing low-pressure operation with the inlet pressure of the stock solution flowing into the membrane module 10 being 0.1 MPa or less, the cells do not break, and microalgae and the like can be filtered and concentrated while alive. Under the low-pressure operation where the inlet pressure of the stock solution is 0.1 MPa or less, compared with the case of using an RO membrane or a UF membrane in the membrane module 10, a sufficient amount of filtrate can be obtained and the filtration efficiency can be improved. Therefore, it is preferable to use a microfiltration membrane in the membrane module 10, whereby it is possible to filter and concentrate with high filtration efficiency while suppressing the breakage of cells such as microalgae.

[0105] The element 12 included in the spiral membrane module 10 is provided with a filtrate collecting pipe (the collecting pipe 130 of the first element 120, the collecting pipe 230 of the second element 220). Since the filtration device 1 performs a low-pressure operation to make the inlet pressure of the raw liquid flowing into the membrane module 10 less than 0.2 MPa, a configuration that can reduce the resistance when the filtrate flows is preferable. For this reason, by adopting a configuration in which the filtrate is collected and flowed through the collecting pipe, the resistance when the filtrate flows can be reduced.

[0106] In the element 12 included in the spiral membrane module 10, the length in the winding direction of the filtration membrane (the filtration membrane 122 of the first element 120, the filtration membrane of the second element 220) is 800 mm or less. The thickness of the filtrate net (the filtrate net 123 of the first element 120, the filtrate net of the second element 220) is 0.2 mm or more. Here, in a conventional spiral membrane module, as a general cross-flow filtration, it is often used for the purpose of performing "cake-free filtration" that does not form a membrane surface deposit (cake layer). In this case, a high-pressure operation is performed. In a high-pressure operation, since the resistance due to the pressure loss in the winding direction of the filtration membrane can be ignored, there is almost no merit in shortening the length in the winding direction of the filtration membrane. Therefore, the length in the winding direction of the filtration membrane is relatively long. On the other hand, since the filtration device 1 performs a low-pressure operation to make the inlet pressure of the raw liquid flowing into the membrane module 10 less than 0.2 MPa, if the length in the winding direction of the filtration membrane (such as the filtration membrane 122) is increased, the filtrate volume will decrease. For this reason, the length in the winding direction of the filtration membrane (such as the filtration membrane 122) is shortened to 800 mm or less to reduce the resistance due to the pressure loss in the winding direction of the filtration membrane (such as the filtration membrane 122). Furthermore, the thickness of the filtrate net (such as the filtrate net 123) is set to 0.2 mm or more to ensure a space for the filtrate to flow. By adopting these configurations, the overall pressure loss can be reduced and the filtrate volume can be increased. Thus, setting this configuration to increase the filtrate volume under specific conditions of low-pressure operation is not predictable from the prior art assuming high-pressure operation.

[0107] The effective filtration area per leaf (leaf 121 of the first element 120, leaf 221 of the second element 220) of the element 12 included in the spiral membrane module 10 is 1.3 m 2 is as follows. Thus, in the filtration device 1 using a filtration membrane (such as the filtration membrane 122) with a short length in the winding direction, by setting the effective filtration area per leaf (such as leaf 121) to 1.3 m 2 or less, in addition to the pressure loss of the filtrate flow path, the circulation pressure loss can also be reduced. Here, the "pressure loss of the filtrate flow path" means the pressure loss of the path through which the filtrate passing through the filtration membrane flows. Also, the "circulation pressure loss" means the pressure loss of the path through which the stock solution flows. The pressure loss of the filtrate flow path and the circulation pressure loss do not pose a problem during high-pressure operation (generally high-circulation operation), but have a great impact in the case of low-pressure operation (which inevitably becomes low-circulation operation). Therefore, in the case of low-pressure operation, by setting the effective filtration area per leaf (such as leaf 121) to 1.3 m 2 or less, the pressure loss of the filtrate flow path and the circulation pressure loss in one leaf (such as leaf 121) can be reduced.

[0108] The number of leaves (leaf 121 of the first element 120 or leaf 221 of the second element 220) of the element 12 included in the spiral membrane module 10 is 16 or more. Here, by shortening the length in the winding direction of the filtration membrane (such as the filtration membrane 122) and reducing the effective filtration area per leaf (such as leaf 121), it is possible to reduce the pressure loss of the filtrate flow path and the circulation pressure loss in the case of low-pressure operation. However, when the effective filtration area of the entire element becomes small, a sufficient amount of filtrate cannot be obtained. Therefore, when the length in the winding direction of the filtration membrane (such as the filtration membrane 122) is 800 mm or less and the effective filtration area per leaf (such as leaf 121) is 1.3 m 2 or less, by setting the number of leaves (such as leaf 121) to 16 or more, it is possible to ensure a larger amount of filtrate while keeping the pressure loss of the filtrate flow path and the circulation pressure loss low during low-pressure operation.

[0109] In the spiral membrane module 10, the upper limit value of the discharge pressure of the pump 30 that supplies the raw liquid to the membrane module 10 is less than 0.45 MPa. In this way, by making the upper limit value of the discharge pressure of the pump 30 less than 0.45 MPa, the power required for pressurizing the raw liquid can be reduced, so that the power consumption can be reduced. Here, a filtration device equipped with a conventional spiral membrane module had to be operated under high pressure conditions where the inlet pressure of the raw liquid flowing into the membrane module was 0.45 MPa or higher in order to obtain a sufficient amount of filtrate even when an RO membrane or a UF membrane was used for the membrane module. Therefore, in the conventional device, a pump with sufficiently high discharge pressure performance was adopted as the pump for supplying the raw liquid. For example, a pump with an upper limit value of the discharge pressure of 0.45 MPa or higher was adopted. In the conventional device, there was no reason to make the upper limit value of the discharge pressure of the pump less than 0.45 MPa, and such an attempt was not made. On the other hand, as described above, the inventors, in the process of considering the application of a spiral membrane module to the filtration and concentration of biological substances such as microalgae, noticed the phenomenon that cells may break and organisms may die during high-pressure operation. Based on this, they focused on operating the filtration device under low pressure conditions (low-pressure operation) with a low inlet pressure of the raw liquid flowing into the membrane module. As a result of studying the practical application of a filtration device suitable for such low-pressure operation, they found that a pump 30 with an upper limit value of the discharge pressure less than 0.45 MPa should be used as the pump for supplying the raw liquid to the spiral membrane module 10. They also found that the power consumption during operation can be reduced by using such a pump 30. Such a filtration device 1 is suitable for performing a filtration treatment operation under the condition that the inlet pressure of the raw liquid supplied to the spiral membrane module 10 is lower than 0.2 MPa. It is preferable to use a pump 30 with an upper limit value of the discharge pressure of 0.3 MPa or less or 0.14 MPa for this device, as the power consumption can be further reduced. These upper limit values are respectively suitable for performing a filtration treatment operation under the conditions that the inlet pressure of the raw liquid is 0.15 MPa or less and 0.1 MPa.

[0110] According to the filtration method according to this embodiment, the raw liquid is caused to flow into the spiral membrane module 10 at an inlet pressure lower than 0.2 MPa. In this way, by performing low-pressure operation with the inlet pressure of the raw liquid flowing into the membrane module 10 being lower than 0.2 MPa, the power required for pressurizing the raw liquid can be reduced, so that the power consumption can be reduced.

[0111] [6. Description of Modification Examples] As described above, the filtration device 1 according to this embodiment has been described, but the present invention is not limited to the above embodiment. The embodiments disclosed this time are illustrative in all respects and not restrictive, and the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

[0112] (Modification Example 1) In the above embodiment, the membrane module 10 is provided with outlets for the filtrate (the first outlet 114b and the second outlet 214b) at both ends (both end faces) of the container 11, but the present invention is not limited to this. The membrane module 10 only needs to be provided with outlets for the filtrate in both the first container 110 and the second container 210. FIG. 9 is a front view showing the configuration of the membrane module 10a according to Modification Example 1 of this embodiment. FIG. 9 corresponds to FIG. 3(a).

[0113] As shown in FIG. 9, the membrane module 10a in this modification example includes a first membrane module 101 and a second membrane module 201 instead of the first membrane module 100 and the second membrane module 200 included in the membrane module 10 in the above embodiment.

[0114] The first membrane module 101 is provided with a first outlet 133 for filtrate that is connected to the liquid collection pipe 130 on the side surface of the end portion of the first container 110 (first container main body 111) in the minus X-axis direction. As described above, the end portion of the first container 110 is the portion between the minus X-axis end surface of the leaf 121 of the first element 120 and the minus X-axis end surface of the flange portion 114. Therefore, the first outlet 133 is arranged in the X-axis direction between the minus X-axis end surface of the leaf 121 of the first element 120 and the minus X-axis end surface of the flange portion 114 (in this modification, the plus X-axis end surface of the flange portion 113). The flange portion 114 is not provided with an outlet for filtrate (the first outlet 114b in the above embodiment).

[0115] The second membrane module 201 is provided with a second outlet 233 for filtrate that is connected to the liquid collection pipe 230 on the side surface of the end portion of the second container 210 (second container main body 211) in the plus X-axis direction. As described above, the end portion of the second container 210 is the portion between the plus X-axis end surface of the leaf 221 of the second element 220 and the plus X-axis end surface of the flange portion 214. Therefore, the second outlet 233 is arranged in the X-axis direction between the plus X-axis end surface of the leaf 221 of the second element 220 and the plus X-axis end surface of the flange portion 214 (in this modification, the minus X-axis end surface of the flange portion 213). The flange portion 214 is not provided with an outlet for filtrate (the second outlet 214b in the above embodiment).

[0116] In the membrane module 10a according to this modification, the same effects as those in the above embodiment can also be achieved. In particular, in this modification, since it is not necessary to provide outlets for filtrate on both end faces of the container 11, the degree of freedom in arranging the outlets for filtrate can be improved. Since the outlet for filtrate is provided at a position other than the end face of the container 11, in addition to the first container 110 and the second container 210, it becomes easier to connect three or more containers such as a third container that houses a third element.

[0117] In this modification example, a first outlet for the filtrate may be provided on the side surface of the end portion of the first container 110 in the +X-axis direction. A second outlet for the filtrate may be provided on the side surface of the end portion of the second container 210 in the -X-axis direction. A first outlet for the filtrate may be provided at the central portion of the first container 110 in the X-axis direction. A second outlet for the filtrate may be provided at the central portion of the second container 210 in the X-axis direction. That is, at least one of the first outlet and the second outlet may be arranged at the central portion of at least one of the first container 110 and the second container 210 in a predetermined direction (X-axis direction).

[0118] (Modification Example 2) In the above embodiment, the filtration device 1 is provided with two membrane modules 10 connected in parallel, but it is not limited thereto. The filtration device 1 may be provided with three or more membrane modules 10 connected in parallel, or may be provided with only one membrane module 10. The filtration device 1 may be provided with a plurality of membrane modules 10 connected in series. FIG. 10 is a schematic diagram showing a schematic configuration of a filtration device 2 according to a modification example 2 of the present embodiment. FIG. 10 is a figure corresponding to FIG. 1.

[0119] As shown in FIG. 10, in this modification example, in the filtration device 2, two membrane modules 10 are connected in series. Among the two membrane modules 10, for the membrane module 10 in the -Z-axis direction, the first membrane module 100 is arranged in the -X-axis direction, and the second membrane module 200 is arranged in the +X-axis direction. For the membrane module 10 in the +Z-axis direction, the first membrane module 100 is arranged in the +X-axis direction, and the second membrane module 200 is arranged in the -X-axis direction.

[0120] In such a configuration, the stock solution 21 discharged from the pump 30 is supplied to the membrane module 10 at an inlet pressure P6 through the pipe 41 from the first opening 114a of the membrane module 10 in the negative Z-axis direction. The inlet pressure P6 has a pressure in the same range as the inlet pressure P2 or P3 in the above embodiment, such as being less than 0.2 MPa. The stock solution 21 is filtered by the membrane module 10 in the negative Z-axis direction and discharged from the second opening 214a of the membrane module 10 at an outlet pressure P7, and then passes through the pipe 46 and is supplied to the membrane module 10 at an inlet pressure P8 from the first opening 114a of the membrane module 10 in the positive Z-axis direction. The outlet pressure P7 and the inlet pressure P8 have a pressure in the same range as the outlet pressure P4 or P5 in the above embodiment, such as being less than 0.2 MPa. The stock solution 21 is filtered by the membrane module 10 in the positive Z-axis direction and discharged from the second opening 214a of the membrane module 10 at an outlet pressure P9, and then returned to the stock solution tank 20 through the pipe 47. The filtrate (permeate) from which the solid content has been removed by filtering the stock solution 21 with the two membrane modules 10 is discharged from the first outlet 114b and the second outlet 214b provided in each of the two membrane modules 10 through the pipes 43, 44, and 45.

[0121] Also in the filtration device 2 according to this modification, the same effects as those in the above embodiment can be achieved. As in this modification, since a plurality of membrane modules 10 can be connected in series, the plurality of membrane modules 10 can be connected in various forms.

[0122] (Other modifications) In the above embodiment, the membrane module 10 is provided with an inlet and an outlet (the first opening 114a and the second opening 214a) for the stock solution at both end faces of the container 11, but it is not limited to this. The opening serving as the inlet or outlet for the stock solution may be provided on the side surface such as the end portion or the central portion in the X-axis direction of the first container 110 or the second container 210, and may be provided at any position of the container 11 of the membrane module 10.

[0123] In the above-described embodiment, the flange portion 112 is provided with a connection portion 112a at a portion protruding outward from the first container body 111, and the flange portion 212 is provided with a connection portion 212a at a portion protruding outward from the second container body 211, and it is assumed that the connection portion 112a and the connection portion 212a are connected. However, the flange portion 112 may not be provided with a portion protruding outward from the first container body 111, and the flange portion 212 may not be provided with a portion protruding outward from the second container body 211. In this case, the flange portion 112 and the flange portion 212 may be connected by a joint. The same applies to the connection between the flange portion 113 and the flange portion 114, the connection between the flange portion 213 and the flange portion 214, and the connection between other flange portions.

[0124] In the above-described embodiment, the filtration membrane provided in the membrane module 10 is a microfiltration membrane (MF membrane) having a pore diameter of 0.1 μm or more and 0.4 μm or less, but a microfiltration membrane having a different pore diameter or a filtration membrane other than the microfiltration membrane may also be used.

[0125] In the above-described embodiment, the upper limit value of the discharge pressure of the pump 30 is set to be less than 0.45 MPa, but it may be 0.45 MPa or more.

[0126] In the above-described embodiment, the length in the winding direction of the filtration membrane provided in the membrane module 10 is 800 mm or less, and the thickness of the filtrate net is 0.2 mm or more, but it is not limited thereto. The length in the winding direction of the filtration membrane may be greater than 800 mm, and the thickness of the filtrate net may be less than 0.2 mm.

[0127] In the above-described embodiment, in both the first element 120 (excluding the liquid collection pipe 130) and the second element 220 (excluding the liquid collection pipe), the length in the predetermined direction (the winding axis direction) is set to 800 mm or less, but it is not limited thereto. The length of the first element 120 or the second element 220 in the predetermined direction (the winding axis direction) may be greater than 800 mm. That is, at least one of the first element 120 and the second element 220 may have a length in the predetermined direction (the winding axis direction) of 800 mm or less. Or, both the first element 120 and the second element 220 may have a length in the predetermined direction (the winding axis direction) greater than 800 mm.

[0128] In the above-described embodiment, the effective filtration area per leaf of the elements included in the membrane module 10 is 1.3 m 2 or less, but it may be greater than 1.3 m 2

[0129] In the above-described embodiment, the number of leaves of the elements included in the membrane module 10 is set to 16 or more, but it may be less than 16.

[0130] In the above-described embodiment, in the first container 110 of the first membrane module 100, the end of the filtrate flow path at one end in the predetermined direction is blocked, and in the second container 210 of the second membrane module 200, the end of the filtrate flow path at the other end in the predetermined direction is blocked, but it is not limited thereto. The end of the filtrate flow path being blocked is not limited to this combination. The end of the filtrate flow path at the other end in the predetermined direction of the first container 110 may be blocked, or the end of the filtrate flow path at one end in the predetermined direction of the second container 210 may be blocked. That is, a configuration in which neither end on one side in the predetermined direction of both the first container 110 and the second container 210 is blocked, and the filtrate is taken out from the outlets at both ends of the first container 110 and the second container 210 may be used. At least one of the first container 110 and the second container 210 may have a configuration in which the end of the filtrate flow path is not blocked.

[0131] ​In the above-described embodiment, the first container 110 of the first membrane module 100 and the second container 210 of the second membrane module 200 are directly connected to each other at their end faces. However, the present invention is not limited to this, and they may be connected via other members such as pipes.

[0132] In the above-described embodiment, the first membrane module 100 and the second membrane module 200 have the same configuration. However, they may have different configurations.

[0133] In the above-described embodiment, a cake layer is formed on the filtration membrane provided in the membrane module 10. However, a cake layer may not be formed.

[0134] In the above-described embodiment, the filtration device 1 includes the membrane module 10 composed of a plurality of membrane modules. However, it may include the membrane module 50 composed of one membrane module. In this case, the number of membrane modules 50 included in the filtration device 1 may be one or a plurality. When the filtration device 1 includes a plurality of membrane modules 50, the plurality of membrane modules 50 may be connected in series or in parallel. In this case, the inlet pressure of the stock solution flowing into the membrane module 50 has a pressure in the same range as the inlet pressure P2 or P3 in the above-described embodiment, such as less than 0.2 MPa. By connecting a plurality of membrane modules 50 in parallel, the pressure applied to each membrane module 50 can be equalized. Therefore, compared with the case of connecting in series, the filtration efficiency can be improved, and operation at low power may be possible. Thus, since the elements are respectively accommodated in the containers of each membrane module 50, it is possible to correspond to any form, such as using the membrane module 50 alone (without performing parallel connection and series connection), using it in parallel connection, using it in series connection, or using a combination of parallel connection and series connection, and the configuration can be changed according to the use environment or use situation. Furthermore, since the length in the winding axis direction of the element (the above-described length L2) is not too long, i.e., 800 mm or less, it is easy to change the membrane module 50 into various forms described above.

[0135] In the above-described embodiment, the inlet pressure of the stock solution flowing into the membrane module 10 was set to be less than 0.2 MPa, but it may be 0.2 MPa or more.

[0136] In the above-described embodiment, it was assumed that all the membrane modules 10 have the above-described configuration, but any one of the membrane modules 10 may not have the above-described configuration.

[0137] A configuration constructed by arbitrarily combining the above-described embodiment and its modified examples is also included within the scope of the present invention.

Explanation of Reference Numerals

[0138] 1, 2 Filtration device 10, 10a, 50, 60 Membrane module 11 Container 12 Element 20 Stock solution tank 21 Stock solution 30 Pump 41, 42, 43, 44, 45, 46, 47 Pipe 100, 101 First membrane module 110 First container 111 First container body 112, 113, 114, 115, 212, 213, 214, 215 Flange portion 112a, 113a, 114c, 115c, 212a, 213a, 214c Connection portion 114a First opening 114b, 133 First outlet 115a Third opening 120 First element 121, 221 Leaf 122, 122a, 122b Filter membrane 123 Filtrate net 124 Stock solution net 130, 230 Liquid collection pipe 131 Hole 132 Opening 140, 240 Blocking member 200, 201 Second membrane module 210 Second container 211 Second container body 214a Second opening 214b, 233 Second outlet 220 Second element

Claims

1. A filtration device comprising a spiral membrane module, wherein the membrane module comprises: an element in which a filtration membrane is wound around a winding shaft extending in a predetermined direction; and a container for housing the element, the container comprising a first container and a second container disposed on one side of the first container in the predetermined direction, the element comprising a first element housed in the first container and a second element housed in the second container, the first container comprising a first outlet for filtrate, the second container comprising a second outlet for filtrate. Filtration device.

2. The first outlet is disposed at an end of the first container on the other side in the predetermined direction, and the second outlet is disposed at an end of the second container on the one side in the predetermined direction. The filtration device according to Claim 1.

3. The first outlet is formed on an end face of the first container on the other side in the predetermined direction, and the second outlet is formed on an end face of the second container on the one side in the predetermined direction. The filtration device according to Claim 2.

4. The container is formed by connecting an end face of the first container on the one side in the predetermined direction and an end face of the second container on the other side in the predetermined direction, so that a raw liquid flow path in the first container and a raw liquid flow path in the second container are connected. The filtration device according to any one of Claims 1 to 3.

5. An end of the filtrate flow path at the one side end of the first container in the predetermined direction is blocked, and an end of the filtrate flow path at the other side end of the second container in the predetermined direction is blocked. The filtration device according to Claim 4.

6. The first container further comprises a first opening serving as an inlet or outlet for raw liquid at the other side end in the predetermined direction, the second container further comprises a second opening serving as an outlet or inlet for raw liquid at the one side end in the predetermined direction, wherein when the first opening is an inlet for raw liquid, the second opening is an outlet for raw liquid, and when the first opening is an outlet for raw liquid, the second opening is an inlet for raw liquid. The filtration device according to any one of Claims 1 to 3.

7. The first opening is formed on an end face of the first container on the other side in the predetermined direction, and the second opening is formed on an end face of the second container on the one side in the predetermined direction. The filtration device according to Claim 6.

8. At least one of the first element and the second element has a length in the predetermined direction of 800 mm or less. The filtration device according to any one of Claims 1 to 3.

9. The inlet pressure of the stock solution flowing into the membrane module is less than 0.2 MPa The filtration device according to any one of claims 1 to 3.

Images