Membrane separation device

Abstract

To provide a membrane separation device which improves durability of a separation membrane using membrane distillation and processing capacity to be capable of improving collection ratio of purification water.SOLUTION: A membrane separation device 1 includes a membrane distillation part 10 between a supply passage 11 to which water to be treated d0 is supplied and a recovery passage 12 where purification water c is recovered. The membrane distillation part 10 is a ceramic structure 2 where space in a cylindrical outer cover 21 is partitioned by a large number of cells 22 extending in an axial direction x. In the ceramic structure 2, a cell 22 communicating with the supply passage 11 to be a first passage 41 is arranged through a cell wall of a hydrophobic porous wall 3 adjacent to a cell 22 communicating with the recovery passage to be a second passage 42. Water vapor v penetrates the hydrophobic porous wall 3 from a side facing the first passage 41 to a side facing the second passage 42 by vapor pressure difference or pressure difference to separate the water to be treated d0 into the purification water c and concentrated water d.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a membrane separation device. [Background technology]

[0002] Water treatment systems have been proposed that treat water, such as industrial wastewater, through multiple processes in sequence, recovering the purified water for reuse. Water treatment systems typically include a reverse osmosis membrane separator that uses reverse osmosis, where the pressure on the pretreated water side is increased above the osmotic pressure, causing the water in the water to pass through the reverse osmosis membrane and separate. Furthermore, from the perspectives of efficient water utilization and environmental conservation, the introduction of zero liquid discharge (ZLD) technology is being promoted. In this case, a distillation process is required in the final stage to evaporate and recover the wastewater, which poses a problem of high energy consumption.

[0003] To reduce the burden on the distillation process, it is necessary to highly concentrate the wastewater in the membrane separation process that precedes it. However, in reverse osmosis, as the concentration of the water to be treated increases, the pressure applied to the reverse osmosis membrane must be increased, and there is a limit to the pressure that the reverse osmosis membrane can withstand. Therefore, it is possible to use different methods in combination in the membrane separation process to highly concentrate the water to be treated. For example, the use of membrane distillation, which is a heat-driven method with relatively low energy consumption, is being considered, and when it is put into practical use, it is important to increase the purification efficiency of the water to be treated.

[0004] Increasing the treatment area of ​​the separation membrane is an effective way to improve purification efficiency. Known methods for achieving this include devices in which flat membranes are spirally wound into a multilayer structure, and devices in which flat membranes are stacked into a flat laminate structure. As an example of the former, as described in Patent Document 1, a cylindrical device is formed by winding a thin membrane foil around a support tube while folding it over at a predetermined length, and a spacer is placed between the two foil layers to form a flow path. Specifically, the spacer includes a resin mesh layer, and both ends of the spacer are held by tubular supports to apply tension to the membrane foil, allowing fluid to flow throughout the entire flow path. As an example of the latter, there is a device in which flat membranes are held around a frame and stacked to form a flow path between the layers, each with a processing capacity that corresponds to the number of windings or stacking. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 144004 Summary of the Invention [Problem to be solved by the invention]

[0006] The device described in Patent Document 1 generally uses a resin material with good processability to be processed into a predetermined spiral shape. When the wastewater to be treated contains chemicals such as acids or alkalis, the resin material may deteriorate due to chemical reactions with the chemicals. Furthermore, because the device is made by processing a soft thin film, it is prone to deformation due to fluid flow, etc., which may cause localized stress and prevent stable treatment. As a result, durability may decrease or the device may not be able to fully utilize its treatment capacity, resulting in reduced purification efficiency. Alternatively, attempts to improve durability or treatment capacity may result in the device configuration becoming more complex and larger.

[0007] The present invention has been made in consideration of such problems, and aims to provide a membrane separation device that can improve the durability and processing capacity of separation membranes that use membrane distillation and can improve the recovery rate of purified water. [Means for solving the problem]

[0008] One aspect of the present invention is A membrane separation device (1) including a membrane distillation section (10) between a supply flow path (11) to which water to be treated (d0) is supplied and a recovery flow path (12) to which purified water (c) separated from the water to be treated is recovered, The membrane distillation section includes a ceramic structure (2) in which a cylindrical outer shell (21) is partitioned into a large number of cells (22) extending in an axial direction (x), In the ceramic structure, the cell that communicates with the supply flow path to form a first flow path (41) and the cell that communicates with the recovery flow path to form a second flow path (42) are adjacently disposed via a cell wall made of a hydrophobic porous wall (3). and the cell adjacent to the cell forming the second flow path on the opposite side to the cell forming the first flow path is defined as a third flow path (43) communicating with the refrigerant flow path (13). And, The hydrophobic porous wall has a ceramic substrate (31) having a large number of pores (32) and a hydrophobic film (33) covering the surface of the ceramic substrate, The ceramic structure has an open cell having both ends open as the cell that becomes the first flow path, and is connected to the supply flow path at one end face of the ceramic structure, so that the water to be treated is supplied from the one end face side to the other end face side of the ceramic structure, The cells that form the second flow path and the third flow path are plugged cells with both ends closed, and the second flow path and the recovery flow path are connected via a first opening (24) that opens into a side surface of the ceramic structure, and the third flow path and the refrigerant flow path are connected via a second opening (25) that opens into a side surface of the ceramic structure, In the hydrophobic porous wall, A vapor pressure difference caused by a temperature difference between the side facing the first flow path and the side facing the second flow path causes From the side facing the first flow path to the side facing the second flow path 、 The membrane separation device is configured to allow water vapor (v) to permeate and separate the water to be treated into the purified water and concentrated water (d). Another aspect of the present invention is A membrane separation device (1) including a membrane distillation section (10) between a supply flow path (11) to which water to be treated (d0) is supplied and a recovery flow path (12) from which purified water (c) is recovered, The membrane distillation section includes a ceramic structure (2) in which a cylindrical outer shell (21) is partitioned into a large number of cells (22) extending in an axial direction (x), In the ceramic structure, the cell that communicates with the supply flow path and forms a first flow path (41) and the cell that communicates with the recovery flow path and forms a second flow path (42) are disposed adjacent to each other with a cell wall made of a hydrophobic porous wall (3) interposed therebetween, and the cell that is adjacent to the cell that forms the second flow path on the opposite side to the cell that forms the first flow path is formed as a third flow path (43) that communicates with a refrigerant flow path (13), The hydrophobic porous wall has a ceramic substrate (31) having a large number of pores (32) and a hydrophobic film (33) covering the surface of the ceramic substrate, The cell is a quadrangular cell having a quadrangular shape as viewed from the axial direction, and a plurality of the cells that form the first flow path are aligned adjacent to each other in a first direction (y) that is parallel to one side of the quadrangular cell as viewed from the axial direction, A plurality of the cells that form the second flow path are aligned adjacent to each other in the first direction, a plurality of the cells that form the third flow path are aligned adjacent to each other in the first direction, When viewed from the axial direction, in a second direction (z) perpendicular to the first direction, rows of cells that become the second flow path are arranged on both sides of the row of cells that become the first flow path, and rows of cells that become the third flow path are arranged outside the rows of cells on both sides, In the row of cells forming the second flow path and the row of cells forming the third flow path, adjacent cells are in communication with each other via communication ports (23, 26) penetrating cell walls, The membrane separation device is configured such that the hydrophobic porous wall allows water vapor (v) to pass from the side facing the first flow path to the side facing the second flow path due to a vapor pressure difference generated by a temperature difference between the side facing the first flow path and the side facing the second flow path, thereby separating the water to be treated into purified water and concentrated water (d). Yet another aspect of the present invention is A membrane separation device (1) including a membrane distillation section (10) between a supply flow path (11) to which water to be treated (d0) is supplied and a recovery flow path (12) from which purified water (c) is recovered, The membrane distillation section is composed of a ceramic structure (2) in which the inside of a cylindrical outer shell (21) is partitioned into a number of cells (22) extending in the axial direction (x). The ceramic structure is housed in a casing (6), In the ceramic structure, the cell that communicates with the supply flow path to form a first flow path (41) and the cell that communicates with the recovery flow path to form a second flow path (42) are adjacently disposed with a cell wall formed of a hydrophobic porous wall (3) interposed therebetween, The inside of the casing is partitioned into an atmospheric pressure chamber (63) communicating with the supply flow path and a reduced pressure chamber (64) communicating with the recovery flow path, and the cell forming the first flow path is arranged to communicate with at least the atmospheric pressure chamber, and the cell forming the second flow path is arranged to communicate only with the reduced pressure chamber, the atmospheric pressure chamber is disposed vertically above the decompression chamber, In the ceramic structure, the cells that form the first flow paths are open cells that open at an end face facing the atmospheric pressure chamber and at an end face facing the reduced pressure chamber, and the cells that form the second flow paths are single-stoppered cells that close the end face facing the atmospheric pressure chamber and open the end face facing the reduced pressure chamber, and the cells that form the first flow paths and the cells that form the second flow paths are arranged adjacent to each other so that the openings and the closed portions are staggered on the end face facing the atmospheric pressure chamber, In the membrane distillation section, the cell serving as the second flow path is depressurized by a vacuum pump (P4) provided in the recovery flow path, In the hydrophobic porous wall, a side facing the first flow path and a side facing the second flow path Due to the pressure difference The membrane separation device is configured to allow water vapor (v) to pass from the side facing the first flow path to the side facing the second flow path, thereby separating the water to be treated into purified water and concentrated water (d). [Effects of the Invention]

[0009] In the membrane separation device configured as described above, when water to be treated is supplied to the first flow path of the membrane distillation unit, steam permeates the hydrophobic porous wall between the first flow path and the adjacent second flow path due to a vapor pressure difference or pressure difference, and is recovered as purified water from the second flow path. The water to be treated from which the steam has been separated is recovered as concentrated water. Since the first and second flow paths and the hydrophobic porous wall of the membrane distillation unit are constructed from a ceramic structure, pressure resistance is improved and there is little risk of deterioration due to reactions with chemicals or other substances contained in the water to be treated. Furthermore, the ceramic structure defines the internal spaces of numerous cells as the first and second flow paths, and the hydrophobic porous wall that separates them acts as a separation membrane, increasing the distillation area. These features improve the durability of the membrane distillation unit and the treatment capacity of the water to be treated, enabling increased purification efficiency.

[0010] As described above, according to the above-described aspect, it is possible to provide a membrane separation device that can improve the durability and processing capacity of a separation membrane that utilizes membrane distillation, and can improve the recovery rate of purified water. In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are a front view and a cross-sectional view of a membrane distillation unit constituting a membrane separation device in a first embodiment. [Figure 2] FIG. 2 is a perspective view of a membrane distillation unit constituting the membrane separation device in the first embodiment. [Figure 3] FIG. 2 is an explanatory diagram of the flow path configuration of the membrane distillation unit in the first embodiment and a partially enlarged view thereof. [Figure 4] FIG. 1 is a schematic configuration diagram of a membrane separation device according to a first embodiment. [Figure 5] FIG. 1 is an explanatory diagram of a water treatment system to which a membrane separation device is applied in a first embodiment. [Figure 6] FIG. 3 is a schematic diagram showing another example of the configuration of the membrane separation device in the first embodiment. [Figure 7] FIG. 4 is a schematic diagram showing another example of the cell shape of the membrane distillation section in the first embodiment. [Figure 8] FIG. 4 is a schematic diagram showing another example of the slit position of the membrane distillation section in the first embodiment. [Figure 9] 10A and 10B are a front view and a cross-sectional view of a membrane distillation unit in a second embodiment. [Figure 10] 10 is an enlarged cross-sectional view of part A in FIG. 9 and a cross-sectional view taken along line XX. [Figure 11] FIG. 10 is a schematic diagram of a membrane separation device according to a second embodiment. [Figure 12] 10 is an enlarged cross-sectional view of part B in FIG. 9 and a partially enlarged view thereof. [Figure 13] 11A and 11B are cross-sectional views taken along the lines YY and ZZ in FIG. 10 . [Figure 14] FIG. 11 is an enlarged cross-sectional view of part C in FIG. 10. [Figure 15] FIG. 15 is an enlarged cross-sectional view of part D in FIG. 14. [Figure 16] FIG. 10 is a diagram illustrating the flow of water to be treated in a membrane distillation unit in the second embodiment. [Figure 17] FIG. 10 is a diagram illustrating the flow of refrigerant in the membrane distillation section in the second embodiment. [Figure 18] 17 is a cross-sectional view taken along line SS in FIG. 16. [Figure 19] FIG. 10 is a schematic diagram of a membrane separation device according to a third embodiment. [Figure 20] FIG. 10 is an explanatory diagram of the flow path configuration of the membrane distillation section in the third embodiment, and a partially enlarged view thereof. [Figure 21] FIG. 10 is a schematic diagram showing the plugging structure of the end face of the membrane distillation section in embodiment 3. [Figure 22] FIG. 10 is a schematic diagram of a membrane separation device according to a fourth embodiment. [Figure 23]FIG. 10 is an explanatory diagram of the flow path configuration of the membrane distillation section in embodiment 4, and a partially enlarged view thereof. [Figure 24] FIG. 10 is a schematic diagram showing the plugging structure of the end face of the membrane distillation section in embodiment 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Embodiment 1) An embodiment of a membrane separation device will be described with reference to FIGS. As shown in Figure 2, the membrane separation device 1 of this embodiment is based on membrane distillation, which is one type of membrane separation method, and includes a supply flow path 11 to which water to be treated d0 is supplied, a recovery flow path 12 to which purified water c separated from the water to be treated d0 is recovered, and a membrane distillation unit 10 provided between them. The membrane distillation unit 10 is made of a ceramic structure 2 that constitutes a separation membrane and a flow path. The ceramic structure 2 has a cylindrical outer shell 21 that is partitioned into a large number of cells 22 extending in the axial direction x, and the internal space of each cell 22 forms a flow path through which a fluid such as the water to be treated d0 or the purified water c flows.

[0013] As shown in Fig. 1, in the ceramic structure 2, a large number of cells 22 form a first flow path 41 that communicates with the supply flow path 11 and a second flow path 42 that communicates with the recovery flow path 12. The cells 22 that form the first flow path 41 and the cells 22 that form the second flow path 42 are adjacently disposed with a hydrophobic porous wall 3 interposed therebetween, which serves as a cell wall. The hydrophobic porous wall 3 functions as a ceramic separation membrane for membrane distillation and also partitions the large number of cells 22. In the ceramic structure 2, the large number of cells 22 are surrounded by the hydrophobic porous wall 3 that serves as a cell wall, except for the vicinity of the outer skin 21, and have the same cross-sectional shape.

[0014] As shown in Figures 2 and 3, the hydrophobic porous wall 3 is configured to allow water vapor v to permeate from the side facing the first flow path 41 to the side facing the second flow path 42 due to a vapor pressure difference, separating the water to be treated d0 into purified water c and concentrated water d. The hydrophobic porous wall 3 preferably includes a ceramic substrate 31 having a large number of pores 32 and a hydrophobic film 33 covering the surface of the ceramic substrate 31, and is configured to allow water vapor v to permeate while not allowing liquid to permeate. The ceramic substrate 31 constitutes the base of the ceramic structure 2 and is configured to have a predetermined porosity that does not hinder the permeation of water vapor v while maintaining its shape. The large number of pores 32 communicate between adjacent cells 22, forming paths for the permeating water vapor v.

[0015] In this way, the first and second flow paths 41, 42 and the hydrophobic porous wall 3 of the membrane distillation section 10 are made of the ceramic structure 2, which improves pressure resistance and reduces the risk of deterioration due to reactions with chemical solutions, etc. Furthermore, the interiors of the many cells 22 of the ceramic structure 2 serve as flow paths, and the hydrophobic porous walls 3 that separate them serve as separation membranes, which increases the distillation area and improves durability and processing capacity.

[0016] The hydrophobic film 33 covers at least the surface of the ceramic substrate 31 facing the first flow path 41, imparting hydrophobicity to the ceramic substrate 31 and preventing liquid water (hereinafter referred to as liquid water) from penetrating into the pores 32. Preferably, almost the entire surfaces of the ceramic particles constituting the ceramic substrate 31 are covered with the hydrophobic film 33, thereby improving the hydrophobicity of the passages for water vapor v formed in the pores 32 of the ceramic substrate 31.

[0017] The ceramic substrate 31 can be made of a ceramic material such as alumina, silica, SiC, zirconia, or cordierite. The hydrophobic film 33 can be made of a hydrophobic material, preferably a hydrocarbon-based or fluorine-based water-repellent material. The hydrophobic porous wall 3 has fine pores in the ceramic material that forms the ceramic substrate 31, and the hydrophobic film 33 made of a hydrophobic material with a large contact angle is formed on the surface thereof, so the pressure required for liquid penetration is high. Therefore, the water to be treated d0 penetrates into the hydrophobic porous wall 3 in a liquid state and does not permeate to the other side.

[0018] 1, a third flow path 43 through which a refrigerant r having a lower temperature than the water to be treated d0 flows can be provided in the cell 22 adjacent to the cell 22 that forms the second flow path 42 on the opposite side from the cell 22 that forms the first flow path 41. This creates a temperature difference between the first flow path 41 and the second flow path 42, causing a vapor pressure difference on both sides of the hydrophobic porous wall 3 facing both flow paths. This vapor pressure difference causes water vapor v evaporated from the water to be treated d0, which has a higher temperature than the refrigerant r, to permeate the hydrophobic porous wall 3 (see the left diagram in FIG. 3). When the water vapor v reaches the wall surface of the second flow path 42 adjacent to the third flow path 43, it is cooled by the wall surface cooled by the low-temperature refrigerant r and condenses into liquid water w.

[0019] More specifically, when the high-temperature water to be treated d0 in the first flow path 41 heats the air in the second flow path 42 adjacent to the first flow path 41, a large amount of water vapor v is present therein. When the refrigerant r in the third flow path 43 cools the air in the second flow path 42 adjacent to the third flow path 43, the water vapor v, which exceeds the saturated vapor amount at the cooled air temperature, condenses and becomes liquid water w.

[0020] As a result, water vapor v is separated from the water to be treated d0 as it passes through the first flow path 41, resulting in more concentrated concentrated water d. The liquid water w in the second flow path 42 moves along the wall surface and is collected. This method, in which the second flow path 42 serving as an air gap is disposed between the first flow path 41 through which the water to be treated d0 flows and the third flow path 43 through which the refrigerant r flows, is called air gap membrane distillation (AGMD).

[0021] Specifically, in the ceramic structure 2, for example, the cells 22 that become the first flow path 41 or the third flow path 43 can be configured as open cells with both ends open, and the cells 22 that become the second flow path 42 can be configured as plugged cells with both ends closed. At one end face of the ceramic structure 2, the first flow path 41 has one end opening connected to a supply flow path 11. The water to be treated d0 supplied from the supply flow path 11 flows from one end face side to the other end face side of the ceramic structure 2, and concentrated water to be treated d0 (i.e., concentrated water d) is discharged from the other end opening of the first flow path 41 to the discharge flow path 11a. The third flow path 43 can be configured, for example, to flow in the opposite direction to that of the first flow path 41, with one end opening provided on the discharge side of the water to be treated d0 serving as the inlet side of the refrigerant flow path 13, and the refrigerant r can be supplied toward the other end opening connected to the discharge side of the refrigerant flow path 13.

[0022] More specifically, the cells 22 of the ceramic structure 2 can be, for example, quadrangular cells that are quadrangular when viewed from the axial direction x, and are arranged parallel to each other in directions corresponding to two adjacent sides of the quadrangle (for example, the horizontal direction y and the vertical direction z shown in FIG. 1). Specifically, the multiple cells 22 that form the first flow paths 41 are aligned adjacent to each other in a first direction (here, the horizontal direction y) parallel to one side of the quadrangular cell when viewed from the axial direction x. Note that "horizontal" here is a convenient expression and does not necessarily indicate that the ceramic structure 2 is used in a state where the horizontal direction y in FIG. 1 is horizontal.

[0023] In a second direction (here, the vertical direction z) perpendicular to the first direction, the cells 22 that become the first flow paths 41 or the third flow paths 43 are alternately arranged with the cells 22 that become the second flow paths 42 sandwiched between them, and only the cells 22 that become the second flow paths 42 are plugged at both ends. In the horizontal direction y, the multiple cells 22 that become the second flow paths 42 are aligned adjacent to one another, and similarly, the multiple cells 22 that become the third flow paths 43 are aligned adjacent to one another.

[0024] The cells 22 forming the second flow paths 42 communicate with adjacent cells 22 via, for example, slits 23 serving as communication ports formed in the cell walls between the adjacent cells 22. A configuration can be adopted in which multiple cells 22 adjacent to each other in the horizontal direction y, in other words, the cells 22 in each row sandwiched between the first flow path 41 and the third flow path 43, communicate with each other via the slits 23. Specifically, the slits 23 are provided penetrating the cell walls so that condensed water can flow between adjacent cells 22 in each row. Preferably, the slits 23 are formed to have an appropriate size that allows the strength of the cell walls to be maintained.

[0025] The slits 23 of the second flow path 42 are provided in the plurality of cells 22 in each row at the same position in the axial direction x, with the same width and length, and serve as flow paths for discharging the condensed liquid water w to the outside of the ceramic structure 2. Preferably, the slits 23 extending in the axial direction x can be formed by cutting out the cell wall at a position in the axial direction x of each cell 22 near the end on the supply side of the low-temperature refrigerant r (i.e., the discharge side of the water to be treated d0). By arranging the slits 23 at a position in contact with the supply-side refrigerant r, which has a lower temperature, the water vapor v can be efficiently condensed and recovered.

[0026] 2, first openings 24 consisting of slits of approximately the same shape are provided in the outer skin 21, which forms the outer peripheral side surface of the ceramic structure 2, at positions corresponding to the rows of slits 23. The liquid water w condensed in the second flow path 42 passes through the rows of slits 23 and is discharged from the first openings 24, and is recovered as purified water c into the recovery flow path 12. The heat of condensation of the liquid water w is received by the refrigerant r passing through the third flow path 43, and is warmed to a certain extent before being discharged to the outside of the ceramic structure 2.

[0027] As shown in FIG. 4, the membrane separation device 1 preferably further includes a heating unit 5 that heats the water to be treated d0. The heating unit 5 is arranged to heat the water to be treated d0 after it has passed through the third flow path 43 and before it is introduced into the first flow path 41. This allows the heated water to be treated d0 to be supplied to the supply flow path 11, thereby increasing the temperature difference between the water to be treated d0 and the refrigerant r. Furthermore, the water to be treated d0 before it is heated can be used as the refrigerant r. The figure schematically shows the fluid flow into the flow paths provided in the membrane distillation unit 10. The water to be treated d0 is first supplied to the refrigerant flow path 13 and used as the room-temperature refrigerant r in the third flow path 43 of the membrane distillation unit 10. After that, it is supplied to the supply flow path 11 via the heating unit 5. Note that, as indicated by the outline arrows in the figure, heat transfer occurs in the membrane distillation unit 10, and the refrigerant r is warmed by the heat of condensation generated when water vapor v condenses into liquid water w.

[0028] A valve V1 and a pump P1 are arranged in the refrigerant flow path 13 on the inlet side of the third flow path 43, and the water to be treated d0 is sent to the membrane distillation unit 10 while the flow rate is adjusted by the valve V1. As described above, in the membrane distillation unit 10, the first flow path 41 through which the water to be treated d0 flows and the third flow path 43 through which the refrigerant r flows are opposite each other across the second flow path 42, and their flow directions are opposite. A pump P2 that sends out purified water c is provided in the recovery flow path 12 connected to the second flow path 42.

[0029] The heating unit 5 is provided between the outlet side of the refrigerant flow path 13 and the supply flow path 11 and heats the water to be treated d0 to a desired temperature, for example, 40°C or higher. More preferably, the water to be treated d0 is heated to 60°C or higher. This provides a desired temperature difference between the first flow path 41 and the second flow path 42, which is necessary for membrane distillation to occur. A specific configuration example of the heating unit 5 will be described later. In this way, the water to be treated d0 supplied to the membrane separation device 1 is used to form a membrane distillation unit 10 of an air gap membrane distillation type, and purified water c can be efficiently recovered. Here, the desired temperature difference is a temperature difference at which the heated air in the second flow path 42 is cooled, causing the water vapor v in the air to condense and obtain a desired amount of liquid water w.

[0030] Such a membrane separation apparatus 1 can be applied to a water treatment system 100 shown in Fig. 5 to form a ceramic membrane separation apparatus 300 used in a membrane separation process. In the membrane separation process, a reverse osmosis membrane separation apparatus 200 is provided upstream of the ceramic membrane separation apparatus 300. The water treatment system 100 is configured as a system for purifying industrial wastewater discharged from a factory F, for example, and primary concentrated water d1 treated in the reverse osmosis membrane separation apparatus 200 is supplied to the ceramic membrane separation apparatus 300 as water to be treated d0. Note that the application is not limited to industrial wastewater, and the ceramic membrane separation apparatus 300 can also be used in systems for separating and recovering cleaning solutions used in various processes in the factory F, and even in systems for desalination of seawater.

[0031] Water to be treated d0, such as industrial wastewater, is pretreated in a pretreatment device 101 and then supplied as pretreated water dp to a reverse osmosis membrane separation device 200. First purified water c1 is recovered, and the separated primary concentrated water d1 is supplied to a ceramic membrane separation device 300. Here, a heating unit 5 is disposed between the reverse osmosis membrane separation device 200 and the ceramic membrane separation device 300. However, this is for convenience and can be incorporated into the ceramic membrane separation device 300, as shown in FIG. 4 . In either case, the heated primary concentrated water d1 is supplied as water to be treated d0 to a membrane distillation unit 10, where second purified water c2 is recovered. The concentrated water d, obtained by separating the second purified water c2 from the water to be treated d0, is then sent as secondary concentrated water d2 to a downstream evaporator 400 and a crystallizer 500, respectively.

[0032] The pretreatment device 101 removes various substances from the water to be treated d0. For example, in the case of industrial wastewater, various treatments such as oil separation, biological treatment, coagulation treatment, and membrane separation can be performed as appropriate. Examples of substances contained in industrial wastewater include oil, high-COD substances, heavy metals, fluoride, phosphate compounds, Cl, SO4, Na, Mg, and CaCO3 (calcium carbonate). High-COD substances are substances with a high chemical oxygen demand (COD). After removing a certain amount of substances from the industrial wastewater using the pretreatment device 101, the resulting pretreated water dp is supplied to the reverse osmosis membrane separation device 200. This pretreated water dp primarily contains salt, which is removed in processes following the reverse osmosis membrane separation device 200.

[0033] The reverse osmosis membrane separation device 200 includes an organic membrane such as cellulose acetate or aromatic polyamide as the reverse osmosis membrane. In the reverse osmosis membrane separation device 200, the pressure on the pretreated water dp side and the primary concentrated water d1 side is increased so that it is higher than the osmotic pressure, causing the water in the pretreated water dp to pass through the reverse osmosis membrane. This produces first purified water c1. However, as the concentration of the primary concentrated water d1 increases, the osmotic pressure also increases. Therefore, considering the pressure resistance strength of the reverse osmosis membrane, there is a limit to how much the primary concentrated water d1 can be concentrated. Therefore, the salt concentration in the primary concentrated water d1 can only be increased to a certain level (for example, approximately 8%).

[0034] Therefore, in the water treatment system 100, the membrane separation device 1 of this embodiment is provided as a ceramic membrane separation device 300 downstream of the reverse osmosis membrane separation device 200. As described above, the membrane separation device 1 uses the ceramic structure 2 in the membrane distillation section 10, and the water vapor v evaporated from the primary concentrated water d1 is passed through the hydrophobic porous wall 3 to obtain the second purified water c2. By using the inside of the cells 22 of the ceramic structure 2 as a flow path and using the hydrophobic porous wall 3 as the cell wall that separates the cells 22, it is possible to provide a membrane separation device that has excellent pressure resistance and a large treatment area.

[0035] This increases the concentration of the secondary concentrated water d2, reducing the burden on the subsequent evaporation step. The evaporation device 400 evaporates the secondary concentrated water d2 by heating or reducing the pressure, or by combining heating and reducing the pressure, and recovers it as distilled water c3. The crystallization device 500 heats and evaporates the tertiary concentrated water d3 remaining after the distilled water c3 has evaporated, and recovers it as distilled water c4.

[0036] The first purified water c1, second purified water c2, distilled water c3, and distilled water c4 extracted from each device of the water treatment system 100 can be recovered and reused. In the crystallization device 500, after the distilled water c4 evaporates, crystals of impurities d4 remain. Various substances can remain as impurities d4, and depending on the type, they can be used as valuable materials or disposed of as industrial waste.

[0037] As shown as a modified example in Figure 6, the membrane separation apparatus 1 shown in Figure 4 above can preferably be configured as a circulation-type air-gap membrane distillation type apparatus in which concentrated water d (secondary concentrated water d2) discharged from the membrane distillation section 10 is circulated. Specifically, a tank T1 for storing the water to be treated d0 (primary concentrated water d1) and a chiller C1 for converting the water to be treated d0 into a predetermined low-temperature refrigerant r are provided between a valve V1 and a pump P1 in a flow path to which the water to be treated d0 (primary concentrated water d1) is supplied. An outlet flow path 11a is connected to the tank T1, forming a circulation flow path 11b for the water to be treated d0. Separate tanks for storing the primary concentrated water d1 and the secondary concentrated water d2 can also be provided.

[0038] As a result, before sending the water to be treated d0 to the membrane distillation unit 10, it can be maintained at a constant temperature lower than room temperature in the chiller C1 and sent from the refrigerant flow path 13 to the third flow path 43 as a lower-temperature refrigerant r. In the membrane distillation unit 10, the refrigerant r cools the cell wall between the membrane distillation unit 10 and the second flow path 42, receives condensation heat when the water vapor v condenses, and is further heated to a desired temperature in the heating unit 5. The heating unit 5 is, for example, a heat exchanger 51 or a heater 52 such as an electric heater, and either one or both are provided. In the heat exchanger 51, the heat exchange medium that exchanges heat with the refrigerant r is, for example, a fluid containing waste heat generated in the water treatment system 100 or an external device. The heated refrigerant r is then supplied again to the first flow path 41 and functions as the water to be treated d0.

[0039] The liquid water w condensed in the second flow path 42 is recovered as purified water c (secondary purified water c2), and the water to be treated d0 is concentrated by the amount of the condensed liquid water w and returned to the tank T as concentrated water d (secondary concentrated water d2). In this way, the water to be treated d0 can be concentrated and circulated to the membrane distillation unit 10. By repeating this process, even more concentrated concentrated water d can be obtained, thereby improving the recovery efficiency of the purified water c. In addition, by cooling the refrigerant r with the chiller C1 when circulating it to the third flow path 43, the temperature difference with the water to be treated d0 that passes through the heating unit 5 and is supplied to the first flow path 41 can be further increased, thereby improving the recovery efficiency of the purified water c.

[0040] As described above, the membrane separation device 1 of this embodiment is configured as an air-gap membrane distillation device, and utilizes the difference in vapor pressure between the hot water side and the cold water side as the driving force when water vapor v passes through the hydrophobic porous wall 3. That is, a first flow path 41 through which high-temperature water to be treated d0 flows and a third flow path 43 through which refrigerant r (low-temperature water to be treated d0) flows are arranged on both sides of a second flow path 42, which serves as an air gap, and water vapor v generated at the interface on the first flow path 41 side of the hydrophobic porous wall 3 is permeated to the second flow path 42 side, thereby performing membrane distillation. This allows stable treatment to be performed continuously, and purification efficiency to be improved.

[0041] Furthermore, in this embodiment, the membrane separation device 1 is a circulation type that cools the water to be treated d0 to function as the refrigerant r, and then heats the refrigerant r to function as the water to be treated d0. This not only eliminates the need to prepare a refrigerant r separate from the water to be treated d0, but also provides the following advantages. That is, the temperature of the water to be treated d0 decreases as it passes through the first flow path 41, so that the amount of cooling energy additionally applied to the water to be treated d0 to function as the refrigerant r can be reduced. Furthermore, the temperature of the refrigerant r increases to a certain extent due to latent heat as it passes through the third flow path 43, so that the amount of heating energy additionally applied to the refrigerant r to function as the water to be treated d0 can be reduced. This reduces the energy consumption in the water treatment system 100 that recovers the purified water c.

[0042] As shown in Figure 7, the shape of the first to third flow paths 41 to 43 formed in the membrane distillation section 10 is not limited to a rectangle, but may be, for example, a hexagon. In this case, too, the water vapor v of In this way, the shape of the flow path of the membrane distillation section 10, i.e., the cross-sectional shape of the cells 22 of the ceramic structure 2, can be any cross-sectional shape, such as a polygon such as a square or hexagon, or a circle.

[0043] The arrangement of the slits 23 formed in the second flow path 42 of the membrane distillation unit 10 is not particularly limited. For example, as shown in FIG. 8, the slits 23 may be provided at multiple locations in the axial direction x. Here, as an example, an example is shown in which two notches are cut out at one end of the axial direction x and slits 23 of the same shape are arranged. The slits 23 are also arranged at equivalent positions in the adjacent second flow paths 42 across the third flow path 43. The communication openings are not limited to notched slits 23. For example, they may be through-holes of any shape, such as rectangular, elliptical, or circular holes, having an opening area equivalent to that of the slits 23. In this way, the shape and number of the communication openings can be arbitrarily set so as to connect adjacent cells 22 and ensure a desired opening area or flow rate. In this case, the first openings 24 provided in the outer skin 21 can also have an equivalent shape.

[0044] For the plurality of second flow paths 42 in each row that communicate with each other via the slits 23, the slits 23 are positioned at equal positions in the axial direction x. This arrangement of the slits 23 is not biased, or the number of slits 23 arranged in the axial direction x can be increased, allowing the purified water c to be efficiently collected from the first openings 24 formed on the outer peripheral side surface of the ceramic structure 2. The slits 23 may be arranged so that a through flow path is formed between a pair of first openings 24, or they may be arranged so that the flow path does not penetrate through. In the latter case, the slits 23 are arranged so that two flow paths are formed that communicate with one of the pair of first openings 24. For example, if a slit 23 is not provided in one of the cell walls at a middle position in the horizontal direction y, two flow paths will be formed through which the liquid water w condensed in the second flow paths 42 flows to both sides of the middle position. These two flow paths do not necessarily need to be arranged in a straight line and may be at different positions in the axial direction x. In this case, the cell wall without the slit 23 may not be provided at the intermediate position, and for example, the two flow paths may be arranged so as to overlap in the axial direction x. In this way, the flow path formed by the communication port and the first opening 24 only needs to be configured so as to be able to recover the purified water c to the recovery flow path 12.

[0045] (Embodiment 2) This embodiment is an example of the detailed configuration of a membrane separation apparatus 1, as shown in Figures 9 to 18. In this embodiment, the membrane separation apparatus 1 also includes a membrane distillation section 10 that utilizes an air gap membrane distillation method, and is suitable as the ceramic membrane separation apparatus 300 in the water treatment system 100 shown in Figure 5 described above. Here, as an example applied to the circulation-type apparatus configuration shown in Figure 6 described above, differences will be mainly described below. The rest of the basic configuration of the membrane separation apparatus 1 is the same as in embodiment 1. Note that, among the symbols used in the second and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components, etc. as those in the previous embodiments, unless otherwise specified.

[0046] As shown in Figures 9 and 10, in this embodiment, the ceramic structure 2 constituting the membrane distillation unit 10 has channels formed therein, and only the first channel 41 is configured as an open cell with both ends open. The second channel 42 and the third channel 43 are configured as plugged cells with both ends closed. In addition to a first opening 24 communicating with the second channel 42, a second opening 25 communicating with the third channel 43 is provided on the side of the ceramic structure 2. Inside the ceramic structure 2, in addition to slits 23 in the cells 22 that form the second channel 42, multiple slits 26 are provided in the cells 22 that form the third channel 43.

[0047] As shown in FIG. 11 , the entire ceramic structure 2 constituting the membrane distillation section 10 is housed in a casing 6. The casing 6 comprises a main body 61, which is a cylindrical body closed at one end, and a lid-like large-diameter section 62 that is fixed to cover the outer periphery of the open side of the main body 61. A tapered flow path 14 is formed inside the large-diameter section 62 on one end face of the ceramic structure 2. A pipe that serves as the supply flow path 11 is connected to the small-diameter side of the tapered flow path 14. The large-diameter side of the flow path 14 has a size that roughly matches the outer diameter of the ceramic structure 2, and the supply flow path 11 communicates with a number of first flow paths 41 (not shown) inside the ceramic structure 2 via the flow path 14. A seal member S1 is attached to the outer periphery of the connection end with the flow path 14 to provide a liquid-tight seal.

[0048] A main body 61 is attached to the outer periphery of the ceramic structure 2. An outlet flow path 11a is provided on the closed end surface of the main body 61 at an opening that penetrates the center and communicates with the outlet side of the first flow path 41. The main body 61 is provided with a flow path 15 that opens on the outer periphery of the closed end and communicates with a second flow path 42 (not shown) via a first opening 24, and is connected to a recovery flow path 12 (not shown). As a result, purified water c that is discharged from the first opening 24 of the second flow path 42 is recovered from the flow path 15 to the recovery flow path 12 via the space between the outer periphery of the ceramic structure 2 and the inner periphery of the main body 61.

[0049] A pair of pipes that form refrigerant flow paths 13 are attached to the outer periphery of the cylindrical portion of the main body 61 at opposing positions, and refrigerant r is supplied from one of the pipes to the other. A space communicating with the second opening 25 of the third flow path 43 is formed between the inner circumferential surface of the cylindrical portion and the outer circumferential surface of the ceramic structure 2, and the refrigerant r supplied to this space flows through the third flow path 43 and is discharged from the opposite side. The space communicating with the third flow path 43 and the space communicating with the first flow path 41 are liquid-tightly partitioned by a seal member S2 attached to the outer periphery of the ceramic structure 2. A seal member S3 is also attached to the outer periphery of the end face of the ceramic structure 2 on the outlet flow path 11a side, providing a liquid-tight seal.

[0050] 10, specifically, open cells that become first flow paths 41 are arranged every third row on the end face of the ceramic structure 2, and plugged cells that become second flow paths 42 are arranged on both sides of the first flow paths 41. A plugged cell that becomes a third flow path 43 is arranged on the opposite side of the second flow path 42 from the first flow path 41. The positional relationship of the three flow paths is as shown in FIG. 12, for example. Furthermore, each second flow path 42 has a slit 23 extending in the axial direction x at one end side in the axial direction x, and adjacent second flow paths 42 communicate with each other via the slit 23 (see, for example, the right diagram in FIG. 13). Furthermore, each second flow path 42 communicates with a flow path 15 that is connected to the recovery flow path 12 via a first opening 24 and a space.

[0051] Additionally, the third flow paths 43 have slits 26 extending in the axial direction x evenly arranged at a plurality of locations in the axial direction x, and second openings 25 are arranged at opposing positions (for example, five locations in FIG. 9 ). As a result, the third flow paths 43 in the same row communicate with each other via the slits 26 (for example, see the left diagram in FIG. 13 ). They also communicate with the refrigerant flow path 13 via the second openings 25 and spaces. Note that, in the axial direction x, the slits 26 of the third flow paths 43 are positioned so as not to overlap with the slits 23 of the second flow paths 42, facilitating separation of the fluid flow paths. Instead of the slits 26, communication ports formed of through-holes of any shape may be provided, and the shape of the second openings 25 can be similarly changed.

[0052] As shown in Figure 12, the ceramic structure 2 is made up of cells 22 each having a roughly square cross section, excluding the portion adjacent to the cylindrical outer skin 21. The plugs that seal the ends of the second and third flow paths 42, 43 are set to a certain depth inward from the end faces, and are set to a length that will not cause peeling or the like and will ensure a sufficient processing area for membrane distillation (for example, about 2 mm). The sizes of the ceramic structure 2 and the cells 22 are, for example, as follows: Ceramic structure 2: Cylinder with a diameter of 102 mm and a length of 200 mm Thickness of outer skin 21: 1 mm Wall thickness b of cell 22: 63.5 μm (2.5 mil; milli inch length) Cell pitch c: 0.847 mm (900 cpsi; cells per square inch) The length of one side of cell 22 is a:cb

[0053] In this case, the height (length in the vertical direction z) of the slits 23 provided in the second flow path 42 and the slits 26 provided in the third flow path 43 is preferably smaller than the height of the flow path, i.e., the length a of one side of the cell 22, and larger than ½ of the length a (e.g., 0.5 mm). If it is smaller than ½ of the length a, the pressure loss when the fluid passes through increases. Furthermore, the width (length in the axial direction x) of the slits 23 and 26 decreases in strength if they are wide, and it is difficult to ensure a sufficient flow path area if they are narrow. Therefore, the width is appropriately set to achieve both (e.g., 20 mm). The interval (length in the axial direction x) between the multiple slits 26 decreases in strength if they are wide, and it is difficult to ensure a sufficient flow path area if they are narrow. Therefore, the interval is appropriately set to achieve both (e.g., 10 mm). When multiple slits 23 are provided, the interval between the slits 23 and slits 26 is also set in a similar manner.

[0054] Furthermore, the distance (length in the axial direction x) between the end face of the ceramic structure 2 and the slits 23 and 26 is equal to or greater than the depth of the plugs of the plugged cells, and is preferably longer to ensure the strength of the end face. However, if the distance is too long, the number of slits will be limited, so the distance is appropriately set (e.g., 10 mm) so as to provide a sufficient area for the fluid to flow. In this way, if the slits 23 and 26 have the same dimensions, a maximum of six slits can be arranged along the length of the ceramic structure 2. The slits 23 through which liquid water w, which is condensed water vapor v, flows generally have a lower flow rate than the slits 26 through which the refrigerant r flows, and therefore can be set to a smaller number.

[0055] In this embodiment, as shown in Figures 14 and 15, the temperature difference between the hot water side and the cold water side is used as a driving force to induce membrane distillation, thereby enabling membrane separation. Also, in Figures 16 to 18, the flow direction in each flow path within the ceramic structure 2 is indicated by arrows. As shown in Figure 16, heated water to be treated d0 is supplied to the first flow path 41 from one end to the other end in the axial direction x. As shown in Figures 17 and 18, cooled refrigerant r is supplied to the third flow path 43 and flows in one direction through multiple slits 26 facing each flow path. As a result, the cooled refrigerant r flowing through the second flow path 42 can cool almost the entire wall surface adjacent to the first flow path 41.

[0056] In FIG. 14, a second flow path 42, which serves as an air gap, is located between a first flow path 41 communicating with the supply flow path 11 and a third flow path 43 communicating with the refrigerant flow path 13. Heated water to be treated d0 flows through the first flow path 41 in the direction indicated by the arrow in the figure, and a cooled refrigerant r flows through the third flow path 43 via a slit 26 in a direction intersecting the flow of the water to be treated d0. A hydrophobic porous wall 3 is located between the first flow path 41 and the second flow path 42 and functions as a ceramic separation membrane for membrane distillation. A temperature difference occurs between the opposing surfaces of the hydrophobic porous wall 3, i.e., the surface on the first flow path 41 side and the surface on the second flow path 42 side. The resulting vapor pressure difference causes water vapor v to permeate the hydrophobic porous wall 3, as indicated by the arrow in the figure.

[0057] As shown in FIG. 15 , the hydrophobic porous wall 3 is made of a porous ceramic substrate 31, and its inner and outer surfaces are coated with a hydrophobic material, thereby preventing liquid from entering the pores 32 while allowing water vapor v to pass through. As shown in the diagram, the movement of water vapor v is shown. Water vapor v generated on the first flow path 41 side passes through the pores 32 and moves to the second flow path 42 side. In the second flow path 42, the wall surface adjacent to the third flow path 43 is cooled by the refrigerant r and has a low temperature, where the water vapor v is cooled and condensed into liquid water w (see, for example, FIG. 14 ). This liquid water w moves along the wall surface, passes through the slits 23 opening into the second flow path 42, passes through the space around the ceramic structure 2, and moves to the external recovery flow path 12.

[0058] Thus, in this embodiment, the membrane separation device 1 performs membrane distillation by utilizing the difference in vapor pressure between the first flow path 41, through which the high-temperature water to be treated d0 flows, and the third flow path 43, through which the refrigerant r (low-temperature water to be treated d0) flows. This allows for continuous, stable treatment and improved purification efficiency. Furthermore, the ceramic structure 2 is housed within the casing 6, and the flow paths opening on the end face or outer peripheral side of the ceramic structure 2 are connected to external flow paths via flow paths provided on the end face or inner peripheral side of the casing 6. This allows for a compact configuration of the air-gap type membrane separation device 1, and improved purification efficiency.

[0059] (Embodiment 3) As shown in Figures 19 to 21, this embodiment is another example of the configuration of the membrane distillation unit 10 of the membrane separation apparatus 1 and the flow paths connected to the membrane distillation unit 10. In particular, this embodiment will be described for a case where the membrane separation apparatus 1 uses vacuum membrane distillation (VMD). In vacuum membrane distillation, the membrane separation apparatus 1 does not have a refrigerant flow path 13, and the membrane distillation unit 10 performs membrane distillation using a pressure difference as a driving force by reducing the pressure of the second flow path 42 that communicates with the recovery flow path 12. The basic configuration of the membrane separation apparatus 1 is otherwise the same as in the above embodiment, and it can be suitably used as the ceramic membrane separation apparatus 300 in the water treatment system 100 described above. The following will mainly describe the differences.

[0060] 19, in the membrane separation device 1 of this embodiment, the entire ceramic structure 2 constituting the membrane distillation section 10 is housed in a casing 6. The casing 6 and the ceramic structure 2 are arranged so that the axial direction x is vertical, and a supply flow path 11 is connected to the top surface of the casing 6. The interior of the casing 6 is partitioned in the axial direction x into two chambers: an atmospheric pressure chamber 63 and a reduced pressure chamber 64. Here, the vertically upper side is the atmospheric pressure chamber 63 and the vertically lower side is the reduced pressure chamber 64, and a seal member 65 is arranged around the outer periphery of the ceramic structure 2 between the two chambers to provide a liquid-tight seal between the two chambers.

[0061] An inlet 66 for water to be treated d0 (primary concentrated water d1) heated by passing through the heating section 5 is provided on the top surface of the casing 6 on the normal pressure chamber 63 side. An outlet 67 for concentrated water d (secondary concentrated water d2) is provided on the end side wall of the casing 6 on the reduced pressure chamber 64 side near the bottom, and an outlet 68 for steam v is provided above the outlet 67. A circulation flow path 11b equipped with a liquid transfer pump P3 is connected between the outlet 67 for the water to be treated d0 and the outlet flow path 11a, so that the water to be treated d0 is circulated to the supply flow path 11. By repeating this process, the desired concentrated water d is obtained, which is then sent to the next step. This concentration step can be performed batchwise or continuously.

[0062] The outlet 68 for the water vapor v is connected to a tank T2 equipped with a vacuum pump P4 via a condenser 53. The condenser 53 is configured as a heat exchanger that exchanges heat between the supply passage 11 and the recovery passage 12a continuing from the outlet 68 for the water vapor v, and the liquid water w obtained by condensing the water vapor v is recovered into the tank T2 as purified water c (secondary purified water c2).

[0063] 20, the ceramic structure 2 has first flow paths 41 consisting of open cells that open on the end faces facing the atmospheric pressure chamber 63 and the decompression chamber 64, and second flow paths 42 consisting of single-plugged cells that are plugged only on the end face facing the atmospheric pressure chamber 63. In this case, as shown in Fig. 21, on one end face of the ceramic structure 2 facing the atmospheric pressure chamber 63, the cells 22 that become the first flow paths 41 and the second flow paths 42 are alternately arranged in a staggered pattern, for example, so that the open and closed portions are alternately arranged. On the other end face facing the decompression chamber 64, none of the cells 22 are plugged.

[0064] At this time, when heated water to be treated d0 flows into the first flow path 41 from the normal pressure chamber 63 side, it passes through the first flow path 41 due to its own weight and flows out into the reduced pressure chamber 64. Meanwhile, the second flow path 42 adjacent to the first flow path 41 communicates with the reduced pressure chamber 64, and a pressure difference occurs between the surface on the first flow path 41 side and the surface on the second flow path 42 side in the hydrophobic porous wall 3 between the two flow paths. As a result, water vapor v evaporated at the interface on the first flow path 41 side permeates the hydrophobic porous wall 3 and moves to the second flow path 42.

[0065] The water vapor v that has moved to the second flow path 42 flows into the decompression chamber 64 from the opening side and is discharged to the recovery flow path 12a from the outlet 68. The outlet 68 is desirably provided at a position sufficiently far from the bottom surface of the casing 6, for example, near the end face of the ceramic structure 2. In this way, the water vapor v is quickly discharged from the decompression chamber 64, while a sufficient space is formed on the bottom side of the casing 6 in which the concentrated water d (secondary concentrated water d2) can be stored.

[0066] As described above, the membrane separation device 1 of this embodiment is configured as a vacuum membrane distillation device, and performs membrane distillation by utilizing the difference in vapor pressure between the first flow path 41, through which high-temperature water to be treated d0 flows, and the reduced-pressure second flow path 42, as the driving force for water vapor v passing through the hydrophobic porous wall 3. In this case, the refrigerant flow path 13 is not required in the membrane distillation section 10, and the third flow path 43 is not required inside the ceramic structure 2, so the flow path structure can be simplified. Even in this case, stable treatment can be continuously performed with a compact configuration, and purification efficiency can be improved.

[0067] (Embodiment 4) As shown in Figures 22 to 24, this embodiment is another configuration example of a membrane separation apparatus 1 that uses vacuum membrane distillation (VMD). In this embodiment, the arrangement of the flow paths connected to the casing 6 in the membrane distillation section 10 is changed, as in embodiment 3. Other than that, the basic configuration of the membrane separation apparatus 1 is the same as in the above embodiment, and the following description will focus on the differences.

[0068] 22, in the membrane separation apparatus 1, the entire ceramic structure 2 constituting the membrane distillation section 10 is housed in a casing 6 that is divided into two chambers. Inside the casing 6, the vertically upper section is a reduced pressure chamber 64 and the vertically lower section is an ordinary pressure chamber 63, and an outlet 68 for water vapor v is provided on the top surface of the casing 6. The outlet 68 for water vapor v is connected to the recovery flow path 12a and, via a condenser 53, to a tank T2 equipped with a vacuum pump P4.

[0069] An outlet 67 for the water to be treated d0 is provided on a side wall near the bottom of the normal pressure chamber 63, and a supply flow path 11 for the water to be treated d0 is connected above the outlet 67. The outlet 67 is connected to the supply flow path 11 upstream of the heating unit 5 via a liquid transfer pump P3, and a circulation flow path 11b is formed to circulate the concentrated water to be treated d0 to the supply flow path 11. After repeating this process, the concentrated water d (secondary concentrated water d2) is sent to the next process from the outlet flow path 11a.

[0070] 23, the ceramic structure 2 is configured with cells 22 (single-plugged cells) in which the first flow paths 41 are open to the lower atmospheric pressure chamber 63 and only the end face facing the reduced pressure chamber 64 is plugged, and the second flow paths 42 are open to the upper reduced pressure chamber 64 and only the end face facing the atmospheric pressure chamber 63 is plugged (single-plugged cells). In this case, as shown in FIG. 24, the ceramic structure 2 is configured such that, for example, on one end face facing the atmospheric pressure chamber 63, the cells 22 serving as the first flow paths 41 and the second flow paths 42 are alternately arranged in a staggered pattern so that the open and closed portions are alternated. In this case, on the other end face facing the reduced pressure chamber 64, the cells 22 are arranged in a staggered pattern so that the open and closed portions are reversed.

[0071] At this time, when the heated water to be treated d0 flows into the atmospheric pressure chamber 63 from the supply flow path 11, water vapor v is generated on the atmospheric pressure chamber 63 side and flows into the first flow path 41 that opens into the atmospheric pressure chamber 63. The second flow path 42 adjacent to the first flow path 41 opens into the reduced pressure chamber 64, and due to the difference in steam pressure between the first flow path 41 side and the reduced pressure chamber 64 side in the hydrophobic porous wall 3, the water vapor v permeates the hydrophobic porous wall 3 and moves to the second flow path 42. The water vapor v rises within the second flow path 42 and flows into the reduced pressure chamber 64 on the opening side, and is further sucked by the vacuum pump P4 and led from the outlet 68 to the recovery flow path 12a, passes through the condenser 53, and is recovered in the tank T2 for purified water c (secondary purified water c2).

[0072] In this embodiment, too, purified water c can be separated and recovered from the water to be treated d0 using vacuum membrane distillation. Furthermore, the direction of movement of the water vapor v is opposite to that of the water to be treated d0, and the water to be treated d0 does not flow inside the ceramic structure 2, so the water vapor v can be easily separated and recovered from the water to be treated d0. Even in this way, stable treatment can be continuously performed with a compact configuration, and purification efficiency can be improved.

[0073] In the above embodiment, the membrane separation device 1 is configured to include a membrane distillation unit 10 that utilizes air gap membrane distillation and vacuum membrane distillation. However, the membrane separation device 1 is not limited to these, and can also utilize other membrane distillation methods based on vapor pressure difference or pressure difference. For example, in direct contact membrane distillation (DCMD), a first flow path 41 communicating with the supply flow path 11 and a second flow path 42 communicating with the recovery flow path 12 are adjacent to each other via a hydrophobic porous wall 3, and a refrigerant r is circulated through the second flow path 42. This also creates a temperature difference on both sides of the hydrophobic porous wall 3, thereby generating a vapor pressure difference. Alternatively, a sweep gas membrane distillation (SGMD) method may be used to generate a pressure difference by circulating a sweep gas through the second flow path 42.

[0074] When using the refrigerant r, the refrigerant is not limited to the water to be treated d0 before heating, but may be any liquid such as water or oil. For example, in a system to which the membrane separation device 1 is applied, a fluid used in another process may also be used. Furthermore, although an example of application to the water treatment system 100 for treating industrial wastewater has been described, the present invention is not limited to this, and may be used for treating any wastewater or other water.

[0075] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the spirit of the present invention. In addition, the contents described in the embodiments can be combined. The features of the present invention are as follows. [1] A membrane separation device (1) including a membrane distillation section (10) between a supply flow path (11) to which water to be treated (d0) is supplied and a recovery flow path (12) to which purified water (c) is recovered, The membrane distillation section includes a ceramic structure (2) in which a cylindrical outer shell (21) is partitioned into a large number of cells (22) extending in an axial direction (x), In the ceramic structure, the cell that communicates with the supply flow path to form a first flow path (41) and the cell that communicates with the recovery flow path to form a second flow path (42) are adjacently disposed with a cell wall formed of a hydrophobic porous wall (3) interposed therebetween, The membrane separation device is configured to separate the water to be treated into purified water and concentrated water (d) by allowing water vapor (v) to permeate the hydrophobic porous wall from the side facing the first flow path to the side facing the second flow path due to a vapor pressure difference or a pressure difference. [2] The membrane separation device according to [1], wherein the hydrophobic porous wall has a ceramic substrate (31) having a large number of pores (32) and a hydrophobic membrane (33) covering the surface of the ceramic substrate (31). [3] The ceramic structure has a cell adjacent to the cell that forms the second flow path on the opposite side of the cell that forms the first flow path as a third flow path (43) that communicates with a refrigerant flow path (13), and the hydrophobic porous wall generates a vapor pressure difference due to a temperature difference between the side facing the first flow path and the side facing the second flow path, thereby allowing water vapor to pass through. [1] The membrane separation device according to [1] or [2]. [4] The membrane separation device according to [3], wherein the refrigerant in the refrigerant flow path is the water to be treated before being supplied from the supply flow path to the first flow path. [5] The cells that become the first flow paths are open cells with both ends open, and are connected to the supply flow path at one end face of the ceramic structure, so that the water to be treated that is supplied to the first flow path flows toward the other end face of the ceramic structure; The membrane separation device according to [3] or [4], wherein the cells forming the second flow path and the third flow path are plugged cells with both ends closed, the second flow path and the recovery flow path are connected via a first opening (24) opening into a side surface of the ceramic structure, and the third flow path and the refrigerant flow path are connected via a second opening (25) opening into a side surface of the ceramic structure. [6] The cell is a quadrangular cell having a quadrangular shape when viewed from the axial direction, and a plurality of the cells that form the first flow path are aligned adjacent to each other in a first direction (y) that is parallel to one side of the quadrangular cell when viewed from the axial direction, A plurality of the cells that form the second flow path are aligned adjacent to each other in the first direction, a plurality of the cells that form the third flow path are aligned adjacent to each other in the first direction, When viewed from the axial direction, in a second direction (z) perpendicular to the first direction, rows of cells that become the second flow path are arranged on both sides of the row of cells that become the first flow path, and rows of cells that become the third flow path are arranged outside the rows of cells on both sides, The membrane separation device according to any one of [3] to [5], wherein in the row of cells forming the second flow path and the row of cells forming the third flow path, adjacent cells are in communication with each other via communication ports (23, 26) penetrating the cell walls. [7] The membrane separation device according to any one of [1] to [6], further comprising a circulation flow path (11b) that connects an outlet flow path (11a) through which the concentrated water is discharged from the first flow path to the supply flow path and circulates the water to be treated. [8] The membrane separation device described in [1] or [2], wherein the cell serving as the second flow path in the membrane distillation section is depressurized by a vacuum pump (P4) provided in the recovery flow path, and the hydrophobic porous wall allows water vapor to pass through due to the pressure difference between the side facing the first flow path and the side facing the second flow path. [9] The ceramic structure is housed in a casing (6), The membrane separation device according to claim [8], wherein the inside of the casing is partitioned into an atmospheric pressure chamber (63) communicating with the supply flow path and a reduced pressure chamber (64) communicating with the recovery flow path, and the cell forming the first flow path is arranged to communicate with at least the atmospheric pressure chamber, and the cell forming the second flow path is arranged to communicate only with the reduced pressure chamber.

[10] the atmospheric pressure chamber is disposed vertically above the decompression chamber, The ceramic structure has the cells that form the first flow path as open cells that open on the end face facing the atmospheric pressure chamber and the end face facing the reduced pressure chamber, and the cells that form the second flow path as single-plugged cells that close the end face facing the atmospheric pressure chamber and open the end face facing the reduced pressure chamber, and the cells that form the first flow path and the cells that form the second flow path are arranged adjacent to each other so that the openings and closed parts are staggered on the end face facing the atmospheric pressure chamber. [9] The membrane separation device described in

[11] The membrane separation apparatus according to

[10] , further comprising: an outlet flow path (11a) through which the concentrated water is discharged connected to the bottom side of the decompression chamber; a recovery flow path connected vertically above the outlet flow path; and a circulation flow path (11b) connecting the outlet flow path to the supply flow path to circulate the water to be treated. [Explanation of symbols]

[0076] 1 Membrane separation device 10 Membrane distillation section 11 Supply channel 12 Recovery channel 2. Ceramic structure 21 Hull 22 cells 3 Hydrophobic porous wall 41 First Channel 42 Second Channel

Claims

1. A membrane separation device (1) including a membrane distillation section (10) between a supply flow path (11) to which water to be treated (d0) is supplied and a recovery flow path (12) to which purified water (c) is recovered, The membrane distillation section comprises a ceramic structure (2) in which a cylindrical outer shell (21) is partitioned into a large number of cells (22) extending in an axial direction (x), In the ceramic structure, the cell communicating with the supply flow path to form a first flow path (41) and the cell communicating with the recovery flow path to form a second flow path (42) are disposed adjacent to each other via a cell wall made of a hydrophobic porous wall (3), and the cell adjacent to the cell forming the second flow path on the opposite side to the cell forming the first flow path is formed as a third flow path (43) communicating with a refrigerant flow path (13), The hydrophobic porous wall has a ceramic substrate (31) having a large number of pores (32) and a hydrophobic film (33) covering the surface of the ceramic substrate, The ceramic structure has an open cell having both ends open as the cell that becomes the first flow path, and is connected to the supply flow path at one end face of the ceramic structure, so that the water to be treated is supplied from the one end face side to the other end face side of the ceramic structure, The cells that become the second flow path and the third flow path are plugged cells with both ends closed, and the second flow path and the recovery flow path are connected via a first opening (24) that opens into a side surface of the ceramic structure, and the third flow path and the refrigerant flow path are connected via a second opening (25) that opens into a side surface of the ceramic structure, The membrane separation device is configured to separate the water to be treated into purified water and concentrated water (d) by allowing water vapor (v) to pass from the side facing the first flow path to the side facing the second flow path in the hydrophobic porous wall due to a vapor pressure difference generated by a temperature difference between the side facing the first flow path and the side facing the second flow path.

2. A membrane separation device (1) having a membrane distillation section (10) between a supply flow path (11) through which treated water (d0) is supplied and a recovery flow path (12) through which purified water (c) is recovered, The membrane distillation section comprises a ceramic structure (2) in which a cylindrical outer shell (21) is partitioned into a large number of cells (22) extending in an axial direction (x), In the ceramic structure, the cell communicating with the supply flow path to form a first flow path (41) and the cell communicating with the recovery flow path to form a second flow path (42) are disposed adjacent to each other via a cell wall made of a hydrophobic porous wall (3), and the cell adjacent to the cell forming the second flow path on the opposite side to the cell forming the first flow path is formed as a third flow path (43) communicating with a refrigerant flow path (13), The hydrophobic porous wall has a ceramic substrate (31) having a large number of pores (32) and a hydrophobic film (33) covering the surface of the ceramic substrate, The cell is a quadrangular cell having a quadrangular shape as viewed from the axial direction, and a plurality of the cells that form the first flow path are aligned adjacent to each other in a first direction (y) that is parallel to one side of the quadrangular cell as viewed from the axial direction, A plurality of the cells that form the second flow path are aligned adjacent to each other in the first direction, a plurality of the cells that form the third flow path are aligned adjacent to each other in the first direction, When viewed from the axial direction, in a second direction (z) perpendicular to the first direction, rows of cells that become the second flow path are arranged on both sides of the row of cells that become the first flow path, and rows of cells that become the third flow path are arranged outside the rows of cells on both sides, In the row of cells forming the second flow path and the row of cells forming the third flow path, adjacent cells are in communication with each other via communication ports (23, 26) penetrating cell walls, The membrane separation device is configured to separate the water to be treated into purified water and concentrated water (d) by allowing water vapor (v) to pass from the side facing the first flow path to the side facing the second flow path in the hydrophobic porous wall due to a vapor pressure difference generated by a temperature difference between the side facing the first flow path and the side facing the second flow path.

3. A membrane separation device as described in claim 1 or 2, wherein the refrigerant in the refrigerant flow path is the treated water before it is supplied from the supply flow path to the first flow path.

4. A membrane separation device as described in claim 1 or 2, further comprising an outlet flow path (11a) through which the concentrated water is drawn off from the first flow path, and a circulation flow path (11b) which connects the supply flow path to circulate the treated water.

5. A membrane separation device (1) having a membrane distillation section (10) between a supply flow path (11) through which treated water (d0) is supplied and a recovery flow path (12) through which purified water (c) is recovered, The membrane distillation section comprises a ceramic structure (2) in which a cylindrical outer skin (21) is partitioned into a large number of cells (22) extending in an axial direction (x), and the ceramic structure is housed in a casing (6), In the ceramic structure, the cell communicating with the supply flow path to form a first flow path (41) and the cell communicating with the recovery flow path to form a second flow path (42) are adjacently disposed with a cell wall made of a hydrophobic porous wall (3) interposed therebetween, The inside of the casing is partitioned into an atmospheric pressure chamber (63) communicating with the supply flow path and a reduced pressure chamber (64) communicating with the recovery flow path, and the cell forming the first flow path is arranged so as to communicate with at least the atmospheric pressure chamber, and the cell forming the second flow path is arranged so as to communicate only with the reduced pressure chamber, the atmospheric pressure chamber is disposed vertically above the decompression chamber, In the ceramic structure, the cells that form the first flow paths are open cells that open on an end face facing the atmospheric pressure chamber and an end face facing the reduced pressure chamber, and the cells that form the second flow paths are single-stoppered cells that close the end face facing the atmospheric pressure chamber and open the end face facing the reduced pressure chamber, and the cells that form the first flow paths and the cells that form the second flow paths are arranged adjacent to each other so that the openings and the closed portions are staggered on the end face facing the atmospheric pressure chamber, In the membrane distillation section, the cell serving as the second flow path is depressurized by a vacuum pump (P4) provided in the recovery flow path, The membrane separation device is configured to separate the water to be treated into purified water and concentrated water (d) by allowing water vapor (v) to pass from the side facing the first flow path to the side facing the second flow path due to a pressure difference between the side facing the first flow path and the side facing the second flow path in the hydrophobic porous wall.

6. A membrane separation device as described in claim 5, wherein the pressure reduction chamber is connected to an outlet flow path (11a) on the bottom side from which the concentrated water is discharged, the recovery flow path is connected vertically above the outlet flow path, and the membrane separation device further has a circulation flow path (11b) that connects the outlet flow path to the supply flow path and circulates the treated water.

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