JP7777821B2 - membrane separation equipment - Google Patents

Description

The present invention relates to a membrane separation device.

Water treatment systems have been proposed that treat water such as industrial wastewater through multiple processes, recovering the purified water for reuse. Water treatment systems typically include a reverse osmosis membrane separator that uses reverse osmosis, increasing the pressure on the pretreated water to a level higher than the osmotic pressure, forcing the water in the water to pass through the reverse osmosis membrane for separation. Furthermore, from the perspective of efficient water utilization and environmental conservation, the introduction of ZLD (Zero Liquid Discharge), which eliminates liquid discharge, is being promoted. In this case, a distillation process is required in the final stage to evaporate and recover the wastewater, which poses the problem of high energy consumption.

To reduce the burden on the distillation process, it is necessary to highly concentrate the wastewater in the upstream membrane separation process. However, with 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 reverse osmosis membranes 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 will be important to increase the purification efficiency of the water to be treated.

Increasing the processing area of the separation membrane is an effective way to improve purification efficiency. Known methods for this include devices in which flat membranes are spirally wound into a multi-layer structure, and devices in which flat membranes are stacked into a flat laminate structure. An example of the former, as described in Patent Document 1, is a cylindrical device in which a long, thin membrane foil is folded over a predetermined length and wound around a support tube, with a spacer positioned between the two foil layers to form a flow path. Specifically, the spacer comprises a resin mesh layer, both ends of which are held by tubular supports, applying tension to the membrane foil and allowing fluid to flow throughout the entire flow path. An example of the latter is a device in which flat membranes held by a frame are stacked to form a flow path between the layers, with each device having a processing capacity that corresponds to the number of windings or layers.

International Publication No. 2013/144004

The device described in Patent Document 1 generally uses a resin material that is easy to process in order to process it into the specified 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 it is made by processing a soft thin film, it is prone to deformation due to fluid flow, etc., which raises concerns about localized stress and the inability to perform stable treatment. As a result, durability decreases, or treatment capacity cannot be fully utilized, resulting in reduced purification efficiency. Alternatively, attempts to improve durability or treatment capacity result in the device configuration becoming more complex and larger.

The present invention was made in consideration of these issues, and aims to provide a membrane separation device that can improve the durability and processing capacity of separation membranes that use membrane distillation, thereby improving the recovery rate of purified water.

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 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 hydrophobic porous wall 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 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 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) 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 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 hydrophobic porous wall 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 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 the purified water and concentrated water (d).
Yet another aspect of the present invention is a method for producing a semiconductor device comprising:
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 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 hydrophobic porous wall 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 a 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 the 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. Because 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.

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.

1A and 1B are a front view and a cross-sectional view of a membrane distillation section constituting a membrane separation device in embodiment 1. FIG. 2 is a perspective view of a membrane distillation unit constituting a membrane separation device in the first embodiment. 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. 1 is a schematic configuration diagram of a membrane separation device according to a first embodiment. FIG. 1 is an explanatory diagram of a water treatment system to which a membrane separation device is applied in a first embodiment. FIG. 4 is a schematic diagram showing another configuration example of the membrane separation device in the first embodiment. FIG. 10 is a schematic diagram showing another example of the cell shape of the membrane distillation section in the first embodiment. FIG. 10 is a schematic diagram showing another example of the slit position of the membrane distillation section in the first embodiment. FIG. 10 is a front view and a cross-sectional view of a membrane distillation unit in a second embodiment. 10 is an enlarged cross-sectional view of part A in FIG. 9 and a cross-sectional view taken along line XX. FIG. 10 is a schematic configuration diagram of a membrane separation device according to a second embodiment. 10 is an enlarged cross-sectional view of part B in FIG. 9 and a partially enlarged view thereof. 11A and 11B are cross-sectional views taken along the lines YY and ZZ in FIG. 10. FIG. 11 is an enlarged cross-sectional view of part C in FIG. 10 . FIG. 15 is an enlarged cross-sectional view of part D in FIG. 14 . FIG. 10 is a diagram illustrating the flow of water to be treated in the membrane distillation unit in the second embodiment. FIG. 10 is a diagram illustrating the flow of refrigerant in the membrane distillation section in the second embodiment. 17 is a cross-sectional view taken along the line S-S in FIG. 16. FIG. 10 is a schematic configuration diagram of a membrane separation device according to a third embodiment. FIG. 10 is an explanatory diagram of the flow path configuration of the membrane distillation section in embodiment 3 and a partially enlarged view thereof. 10 is a schematic diagram showing the plugging structure of the end face of the membrane distillation section in embodiment 3. FIG. FIG. 10 is a schematic configuration diagram of a membrane separation device according to a fourth embodiment. 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. 10 is a schematic diagram showing the plugging structure of the end face of the membrane distillation section in embodiment 4. FIG.

(Embodiment 1)
An embodiment of a membrane separation device will be described with reference to FIGS. 1 to 8. FIG.
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 therebetween. 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 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.

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 arranged adjacent to each other via a hydrophobic porous wall 3 that serves as the 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 the cell wall, except for the vicinity of the outer skin 21, and have the same cross-sectional shape.

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 the vapor pressure difference, separating the water to be treated d0 into purified water c and concentrated water d. The hydrophobic porous wall 3 preferably has a ceramic substrate 31 with numerous pores 32 and a hydrophobic membrane 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 material of the ceramic structure 2 and is configured with a predetermined porosity that does not hinder the permeation of water vapor v while maintaining its shape. The numerous pores 32 connect adjacent cells 22, forming paths for the permeating water vapor v.

In this way, the first and second flow paths 41, 42 and hydrophobic porous wall 3 of the membrane distillation section 10 are constructed from the ceramic structure 2, which improves pressure resistance and reduces the risk of deterioration due to reactions with chemicals, etc. Furthermore, the interiors of the numerous cells 22 of the ceramic structure 2 serve as flow paths, and the hydrophobic porous wall 3 that separates them serves as a separation membrane, increasing the distillation area and improving durability and processing capacity.

The hydrophobic film 33 coats at least the surface of the ceramic substrate 31 facing the first flow path 41, imparting hydrophobic properties 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 surface of the ceramic particles that make up the ceramic substrate 31 is coated 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.

The ceramic substrate 31 can be made of a ceramic material such as alumina, silica, SiC, zirconia, or cordierite. The hydrophobic membrane 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 a hydrophobic membrane 33 made of a hydrophobic material with a large contact angle is formed on its surface, so the pressure required for liquid penetration is high. As a result, the water to be treated d0 penetrates the hydrophobic porous wall 3 in a liquid state and does not permeate to the other side.

Preferably, in Figure 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, resulting in 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 is hotter than the refrigerant r, to permeate the hydrophobic porous wall 3 (see the left diagram in Figure 3). When the water vapor v reaches the wall surface adjacent to the third flow path 43 in the second flow path 42, it is cooled by the wall surface cooled by the low-temperature refrigerant r and condenses into liquid water w.

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. 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, causing the water vapor v, which exceeds the saturated vapor amount at the cooled air temperature, to condense and become liquid water w.

As a result, water vapor v is separated from the water to be treated d0 as it passes through the first flow path 41, turning it into more concentrated water d. The liquid water w in the second flow path 42 moves along the wall surface and is recovered. This method, in which the second flow path 42, which acts as an air gap, is arranged 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).

Specifically, in the ceramic structure 2, for example, the cells 22 that form the first flow path 41 or the third flow path 43 can be open cells with both ends open, while the cells 22 that form the second flow path 42 can be plugged cells with both ends closed. At one end face of the ceramic structure 2, a supply flow path 11 is connected to one end opening of the first flow path 41. The water to be treated d0 supplied from the supply flow path 11 flows from one end face of the ceramic structure 2 to the other end face, 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, for example, flow in the opposite direction to the first flow path 41. One end opening provided on the discharge side of the water to be treated d0 can serve 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.

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

In addition, in a second direction (here, the vertical direction z) perpendicular to the first direction, the cells 22 that become the first flow path 41 or the third flow path 43 are arranged alternately, sandwiching the cells 22 that become the second flow path 42, and only the cells 22 that become the second flow path 42 are plugged at both ends. In the horizontal direction y, the multiple cells 22 that become the second flow path 42 are aligned adjacent to one another, and similarly, the multiple cells 22 that become the third flow path 43 are aligned adjacent to one another.

Cells 22 forming the second flow paths 42 are in communication with other adjacent cells 22, for example, via slits 23 formed in the cell walls between the adjacent cells 22 as communication ports. A configuration can be adopted in which multiple adjacent cells 22 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, are in communication with each other via the slits 23. Specifically, the slits 23 are provided through the cell walls so that condensed water can flow between adjacent cells 22 in each row. Preferably, the slits 23 are formed to an appropriate size that can maintain the strength of the cell walls.

The slits 23 of the second flow path 42 are provided in each row of multiple cells 22 at equivalent positions in the axial direction x, with equivalent widths and lengths, and serve as flow paths for conducting 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 outlet side of the water to be treated d0). By locating 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.

In Figure 2, the outer skin 21, which forms the outer peripheral side of the ceramic structure 2, has first openings 24 consisting of slits of approximately the same shape at positions corresponding to each row of slits 23. Liquid water w condensed in the second flow path 42 passes through each row of slits 23 and is discharged from the first openings 24 and 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, where it is warmed to a certain extent and discharged to the outside of the ceramic structure 2.

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 positioned 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, increasing the temperature difference with 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 through 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 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 hollow 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.

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 flow in opposite directions. A pump P2 that sends out purified water c is provided in the recovery flow path 12 connected to the second flow path 42.

The heating unit 5 is located 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 creates the desired temperature difference between the first flow path 41 and the second flow path 42 required for membrane distillation. Specific configuration examples 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 using an air gap membrane distillation method, allowing for efficient recovery of purified water c. Here, the desired temperature difference is the 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 the desired amount of liquid water w.

Such a membrane separation device 1 can be applied to the water treatment system 100 shown in Figure 5 to form a ceramic membrane separation device 300 used in the membrane separation process. In the membrane separation process, a reverse osmosis membrane separation device 200 is provided upstream of the ceramic membrane separation device 300. The water treatment system 100 is configured as a system for purifying industrial wastewater discharged from a factory F, for example, and the ceramic membrane separation device 300 is supplied with primary concentrated water d1 treated in the reverse osmosis membrane separation device 200 as water to be treated d0. Note that the system can also be applied to systems for separating and recovering cleaning solutions used in various processes in the factory F, as well as systems for desalination of seawater, in addition to industrial wastewater.

Water to be treated d0, such as industrial wastewater, is pretreated in a pretreatment device 101 and then supplied to a reverse osmosis membrane separation device 200 as pretreated water dp. The 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 placed between the reverse osmosis membrane separation device 200 and the ceramic membrane separation device 300. This is for convenience; as shown in Figure 4, it can be incorporated into the ceramic membrane separation device 300. In either case, the heated primary concentrated water d1 is supplied to a membrane distillation unit 10 as water to be treated d0, and second purified water c2 is recovered in the membrane distillation unit 10. The concentrated water d, obtained by separating the second purified water c2 from the water to be treated d0, is then sent sequentially to a downstream evaporator 400 and crystallizer 500 as secondary concentrated water d2.

The pretreatment device 101 is a device for removing various substances contained in 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. Substances contained in industrial wastewater include, for example, oil, high COD substances, heavy metals, fluoride, phosphate compounds, Cl, SO ₄ , Na, Mg, and CaCO ₃ (calcium carbonate). High COD substances refer to 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 pretreated water dp is supplied to the reverse osmosis membrane separation device 200. This pretreated water dp mainly contains salt, which is removed in processes following the reverse osmosis membrane separation device 200.

The reverse osmosis membrane separation device 200 uses 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 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 (e.g., approximately 8%).

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 allows water vapor v evaporated from the primary concentrated water d1 to pass through the hydrophobic porous wall 3, obtaining second purified water c2. By using the cells 22 of the ceramic structure 2 as a flow path and using the hydrophobic porous wall 3 as the cell walls that separate the cells 22, a membrane separation device with excellent pressure resistance and a large treatment area can be achieved.

This increases the concentration of the secondary concentrated water d2, reducing the burden on the subsequent evaporation process. 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.

The first purified water c1, second purified water c2, distilled water c3, and distilled water c4 extracted from each device in 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 resources or disposed of as industrial waste.

As shown as a modified example in Figure 6, the membrane separation device 1 shown in Figure 4 above can preferably be configured as a circulating air-gap membrane distillation system in which the concentrated water d (secondary concentrated water d2) extracted from the membrane distillation section 10 is circulated. Specifically, between the valve V1 and pump P1 in the flow path to which the water to be treated d0 (primary concentrated water d1) is supplied, a tank T1 for storing the water to be treated d0 and a chiller C1 for converting the water to be treated d0 into a predetermined low-temperature refrigerant r are provided. 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.

As a result, before sending the water to be treated d0 to the membrane distillation unit 10, the chiller C1 maintains the water at a constant temperature lower than room temperature, allowing it to be 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 the heat of condensation when the water vapor v condenses, and is then heated to the 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 may be 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 back to the first flow path 41 and functions as the water to be treated d0.

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 increasing the recovery efficiency of 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 increasing the recovery efficiency of purified water c.

In this way, the membrane separation device 1 of this embodiment is configured as an air-gap membrane distillation device, and uses 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 the second flow path 42, which serves as an air gap. 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, performing membrane distillation. This allows for stable, continuous treatment and improves purification efficiency.

In addition, this embodiment uses a circulation-type membrane separation device 1 that cools the water to be treated d0 to function as 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. Because the temperature of the water to be treated d0 decreases as it passes through the first flow path 41, less cooling energy needs to be added to the water to be treated d0 to enable it to function as refrigerant r. Furthermore, because the temperature of the refrigerant r rises to a certain extent due to latent heat as it passes through the third flow path 43, less heating energy needs to be added to the refrigerant r to enable it to function as the water to be treated d0. This reduces energy consumption in the water treatment system 100 that recovers purified water c.

7, the flow path shapes of the first to third flow paths 41 to 43 formed in the membrane distillation unit 10 are not limited to a rectangle, but can also be, for example, a hexagon. In this case, water vapor v can be passed through the hydrophobic porous wall 3 between the first flow path 41 and the second flow path 42 and recovered by membrane distillation. In this way, the flow path shape of the membrane distillation unit 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 rectangle or hexagon, or a circle.

Furthermore, 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. Slits 23 are also arranged at equivalent positions in the adjacent second flow paths 42 across the third flow path 43. Note that 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, with an opening area equivalent to that of the slits 23. In this way, the shape and number of the communication openings can be set as desired to connect adjacent cells 22 and ensure the desired opening area or flow rate. In this case, the first openings 24 provided in the outer skin 21 can also be of the same shape.

For each row of multiple second flow paths 42 that communicate with each other via the slits 23, the slits 23 are positioned at equal positions in the axial direction x. This arrangement ensures that the slits 23 are not unevenly positioned, or the number of slits 23 positioned in the axial direction x can be increased, allowing for efficient recovery of purified water c from the first openings 24 formed on the outer circumferential side of the ceramic structure 2. The slits 23 may be positioned so that a through flow path is formed between a pair of first openings 24, or they may be positioned so that no flow path penetrates through. In the latter case, the slits 23 are positioned 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 central position in the horizontal direction y, two flow paths will be formed through which liquid water w condensed in the second flow paths 42 flows to both sides of the central position. These two flow paths do not necessarily need to be positioned in a straight line and may be positioned at different positions in the axial direction x. In this case, the cell wall without the slit 23 may not be located in the middle position, and the two flow paths may be arranged so that they 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 that the purified water c can be recovered into the recovery flow path 12.

(Embodiment 2)
This embodiment is an example of a 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. Here, as an example of application to the circulation-type apparatus configuration shown in Figure 6, 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.

As shown in Figures 9 and 10, in this embodiment, the ceramic structure 2 constituting the membrane distillation unit 10 has flow paths formed therein, and only the first flow path 41 is composed of open cells with both ends open. The second flow path 42 and the third flow path 43 are composed of plugged cells with both ends closed. In addition to a first opening 24 communicating with the second flow path 42, a second opening 25 communicating with the third flow path 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 flow path 42, multiple slits 26 are provided in the cells 22 that form the third flow path 43.

As shown in Figure 11, the entire ceramic structure 2 that constitutes the membrane distillation section 10 is housed in a casing 6. The casing 6 consists of 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 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 multiple 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.

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, communicating with the outlet side of the first flow path 41 at an opening that penetrates the center. The main body 61 is provided with a flow path 15 that opens on the outer periphery of the closed end and communicates with the second flow path 42 (not shown) via the first opening 24, and is connected to the 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.

A pair of pipes that form the refrigerant flow path 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 that communicates 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 that communicates with the third flow path 43 and the space that communicates with the first flow path 41 are liquid-tightly separated 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.

Specifically, in Figure 10, 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 path 41. On the opposite side of the second flow path 42 from the first flow path 41, plugged cells that become third flow paths 43 are arranged. The positional relationship of the three flow paths is, for example, as shown in Figure 12. 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 Figure 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.

Furthermore, the third flow paths 43 have slits 26 extending in the axial direction x evenly spaced at multiple locations in the axial direction x, with second openings 25 arranged at opposing positions (for example, five locations in Figure 9). This allows the third flow paths 43 in the same row to communicate with each other via the slits 26 (for example, see the left diagram in Figure 13). They also communicate with the refrigerant flow path 13 via the second openings 25 and spaces. 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 consisting of through-holes of any shape may be provided, and the shape of the second openings 25 can be similarly modified.

12, the ceramic structure 2 is composed of cells 22 each having a roughly square rectangular cross section, excluding the portion adjacent to the cylindrical outer skin 21. The plugs sealing 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 (e.g., about 2 mm) that will not peel off and will ensure a sufficient processing area for membrane distillation. The sizes of the ceramic structure 2 and the cells 22 are, for example, as follows:
Ceramic structure 2: cylindrical 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)
Length of one side of cell 22 a:c-b

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 greater than 1/2 of the length a (e.g., 0.5 mm). If it is smaller than 1/2 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 is set appropriately to achieve both of these goals (e.g., 20 mm), as a wider slit reduces strength and a narrower slit makes it difficult to ensure a sufficient flow path area. The spacing (length in the axial direction x) between multiple slits 26 is set appropriately to achieve both of these goals (e.g., 10 mm), as a wider slit reduces the flow path area of the slit 26 and a narrower slit reduces strength. When multiple slits 23 are provided, the spacing between the slits 23 and 26 is set similarly.

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 in 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 it should be set appropriately (for example, 10 mm) to ensure a sufficient area for fluid flow. In this way, if the slits 23 and slits 26 are the same size, a maximum of six slits can be arranged along the length of the ceramic structure 2. The slits 23 through which liquid water w, formed by condensation of water vapor v, flows generally have a lower flow rate than the slits 26 through which the refrigerant r flows, so they can be set to fewer in number.

In this embodiment, as shown in Figures 14 and 15, membrane distillation can be achieved by using the temperature difference between the hot water side and the cold water side as a driving force, thereby performing 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 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. This allows the cooled refrigerant r flowing through the second flow path 42 to cool almost the entire wall surface adjacent to the first flow path 41.

In Figure 14, the second flow path 42, which serves as an air gap, is located between the first flow path 41, which communicates with the supply flow path 11, and the third flow path 43, which communicates 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 cooled refrigerant r flows through the third flow path 43 via slits 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.

As shown in Figure 15, the hydrophobic porous wall 3 is made of a porous ceramic substrate 31. The inner and outer surfaces are coated with a hydrophobic material, allowing water vapor (v) to pass through while preventing liquid from entering the pores 32. As shown in the movement of water vapor (v) in the figure, water vapor (v) generated on the first flow path 41 side passes through the pores 32 and moves toward 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) to a low temperature, where the water vapor (v) is cooled and condenses into liquid water (w) (see Figure 14, for example). 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 periphery of the ceramic structure 2, and moves to the external recovery flow path 12.

In this way, 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 makes it possible to realize an air-gap type membrane separation device 1 with a compact configuration and improve purification efficiency.

(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 device 1 and the flow path connected to the membrane distillation unit 10. In particular, this embodiment will be described for the case where the membrane separation device 1 uses vacuum membrane distillation (VMD). In vacuum membrane distillation, the membrane separation device 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 depressurizing the second flow path 42 that communicates with the recovery flow path 12. The basic configuration of the membrane separation device 1 is otherwise the same as in the above embodiment, and it is suitable for use as the ceramic membrane separation device 300 in the water treatment system 100 described above. The following will focus on the differences.

In Figure 19, in this embodiment of the membrane separation device 1, the entire ceramic structure 2 that constitutes the membrane distillation section 10 is housed in a casing 6. The casing 6 and 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 chamber is the atmospheric pressure chamber 63, and the vertically lower chamber is the reduced pressure chamber 64. Between the two chambers, a seal member 65 is placed around the outer periphery of the ceramic structure 2, providing a liquid-tight seal between the two chambers.

The top surface of the casing 6 on the normal pressure chamber 63 side is provided with an inlet 66 for the water to be treated d0 (primary concentrated water d1) that has been heated by passing through the heating section 5. The casing 6 on the reduced pressure chamber 64 side is provided with an outlet 67 for the concentrated water d (secondary concentrated water d2) on the end side wall 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 feed pump P3 is connected between the outlet 67 for the water to be treated d0 and the outlet flow path 11a, circulating the water to be treated d0 back to the supply flow path 11. By repeating this process, the desired concentrated water d is obtained, which is then sent to the next process. This concentration process can be performed batchwise or continuously.

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 recovery flow path 12a leading to the outlet 68 for the water vapor v and the supply flow path 11, 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).

In Figure 20, the ceramic structure 2 has a first flow path 41 consisting of open cells that open on the end faces facing the atmospheric pressure chamber 63 and the reduced pressure chamber 64, and a second flow path 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 Figure 21, on one end face of the ceramic structure 2 facing the atmospheric pressure chamber 63, the cells 22 that become the first flow path 41 and the second flow path 42 are arranged alternately in a staggered pattern, for example, so that the open and closed portions alternate. On the other end face facing the reduced pressure chamber 64, none of the cells 22 are plugged.

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 is connected to the reduced pressure chamber 64, and a pressure difference occurs between the surface of the hydrophobic porous wall 3 between the two flow paths on the first flow path 41 side and the surface on the second flow path 42 side. As a result, water vapor v that has 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.

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 preferably located 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 sufficient space is created on the bottom side of the casing 6 to store the concentrated water d (secondary concentrated water d2).

In this way, 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 the high-temperature water to be treated d0 flows, and the reduced-pressure second flow path 42, as the driving force when water vapor v passes 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 way, stable processing can be performed continuously with a compact configuration, and purification efficiency can be improved.

(Embodiment 4)
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. The basic configuration of the membrane separation apparatus 1 is otherwise the same as in the above embodiment, and the following description will focus on the differences.

In Figure 22, the membrane separation device 1 has the entire ceramic structure 2 that constitutes the membrane distillation section 10 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 atmospheric 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.

An outlet 67 for the water to be treated d0 is provided on the side wall near the bottom of the atmospheric 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, forming a circulation flow path 11b that circulates 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.

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

At this time, when 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, which 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. 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 open reduced pressure chamber 64. It is then sucked by the vacuum pump P4 and discharged 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).

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

In the above embodiment, the membrane separation device 1 is configured with a membrane distillation section 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 pressure difference can be generated by circulating a sweep gas through the second flow path 42 using sweep gas membrane distillation (SGMD).

When using refrigerant r, it is not limited to the water to be treated d0 before heating, and can be any liquid such as water or oil. For example, in a system to which membrane separation device 1 is applied, fluids used in other processes can also be used. Furthermore, while an example of application to a water treatment system 100 for treating industrial wastewater has been described, it is not limited to this, and can be used for treating any wastewater or other water.

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 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 adjacently disposed with a cell wall made of a hydrophobic porous wall (3) interposed therebetween,
The membrane separation device is configured to separate the water to be treated into the purified water and the concentrated water (d) by allowing water vapor (v) to permeate through 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. The membrane separation device described in [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 cell that becomes the first flow path is an open cell with both ends open, and is connected to the supply flow path at one end face of the ceramic structure, and the water to be treated that is supplied to the first flow path is circulated toward the other end face of the ceramic structure,
The membrane separation device according to [3] or [4], wherein the cells that form 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) that opens to 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 to a side surface of the ceramic structure.
[6] The cell is a quadrangular cell having a quadrangular shape as viewed from the axial direction, and a plurality of the cells that become the first flow path are aligned adjacent to each other in a first direction (y) 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 that forms the second flow path and the row of cells that forms the third flow path, adjacent cells are in communication with each other via communication ports (23, 26) that penetrate cell walls. The membrane separation device according to any one of [3] to [5].
[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 distillation section is configured such that the cell serving as the second flow path 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 a pressure difference between the side facing the first flow path and the side facing the second flow path. [1] or [2] The membrane separation device described in [1] or [2].
[9] The ceramic structure is housed in a casing (6),
The membrane separation apparatus 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 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 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 the closed parts are staggered on the end face facing the atmospheric pressure chamber.
[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.

REFERENCE SIGNS LIST 1 membrane separation device 10 membrane distillation section 11 supply flow path 12 recovery flow path 2 ceramic structure 21 outer shell 22 cell 3 hydrophobic porous wall 41 first flow path 42 second flow path

Claims (6)

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. 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 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. The membrane separation device according to claim 1 or 2, 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 . 3. The membrane separation apparatus according to claim 1, 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 . 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 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. The membrane separation device according to claim 5, 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) that connects the outlet flow path to the supply flow path and circulates the water to be treated .