JPH0371166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid separation device using a semipermeable membrane. More specifically, the present invention relates to the structure of a channel material through which a permeated liquid passes and a base material holding a semipermeable membrane in a liquid separation device using a reverse osmosis membrane. [Prior art and its problems] Conventionally, liquid separation devices using reverse osmosis method have two semipermeable membranes shaped like an envelope, the open end of the envelope is communicated with the hollow part of a hollow shaft tube, and the envelope is There is a so-called spiral type which is wound around a hollow shaft tube and has a structure in which the permeated liquid flows inside the envelope and the stock liquid flows outside the envelope. This liquid separation device passes a high-pressure stock solution that is higher than the reverse osmosis pressure of the membrane through the outside of the envelope, and the permeate that has passed through the membrane is taken out through the inside of the envelope, but the envelope itself is pressurized from the outside at high pressure. This will crush the channel material inserted as a flow path for the permeate and impede the flow of the liquid, so generally speaking, even if the outside of the envelope is pressurized inside the envelope, it will not form a flow path for the permeate. In order to prevent the channel material from being crushed, the channel material itself is made rigid and resistant to deformation. The channel materials used were porous fabrics such as woven and knitted fabrics that had minute grooves extending inside them, especially those with grooves on the surface. These fabrics were impregnated with melamine resin or the like to make them rigid so that they would not be easily deformed by the pressure applied to the stock solution through the membrane. On the other hand, since the semipermeable membrane itself is easily torn by pressure, it was supported by a fabric as a base material to increase its durability. Conventionally, the above-mentioned woven or knitted fabric B as a channel material has been used.
The difference in thread density between the fabric A and Fabric A as a base material for supporting the semipermeable membrane was at most about 5 to 6 threads/25 mm. However, the conventional structure has the disadvantage that although there is no problem when used at low temperatures, the purity of permeated water tends to decrease during long-term operation at high temperatures and high pressures.
Also, there was a drawback that the flow path resistance became large and the amount of purified water taken out decreased. [Object of the present invention] The present invention improves the drawbacks of the conventional examples and provides a device that ensures stable pure water permeability over a long period of time even when used at high temperatures and high pressures. More specifically, the thread density of the fabric A as the base material supporting the semipermeable membrane, that is, the weft thread density Na, and the thread density of the woven or knitted fabric B as the channel material, that is, the weft thread density or the course density Nb By specifying the relationship between [Structure of the present invention] The present invention consists of the following structure. "Providing fabric A as a base material that supports the semipermeable membrane,
In a liquid separation device provided with a woven or knitted fabric B as a channel material, the weft yarn density or course density Nb (strands/25 mm) of the woven or knitted fabric B and the weft yarn density Na of the woven fabric A are determined.
A liquid separation device characterized in that the relationship between Nb≦Na−13 or Na+8≦Nb (pieces/25 mm). ” The present invention will be further explained in detail. As the fabric A used as the base material of the semipermeable membrane according to the present invention, taffeta, twill, etc. can be used.
It is preferable that the surface be as smooth as possible, as thin as possible, and that there is little change in shape, and a high-density plain fabric (such as taffeta) made of synthetic fiber filaments is preferable. The woven and knitted fabric B used as the channel material is preferably one with a texture that has ridges and adzes in the length direction, and in the case of knitted fabrics, it is preferable to use double denbi or tricotto, which has a variable texture using three layers, which is a combination of this and chain stitch, etc. can be used. In particular, the woven and knitted fabric B, which serves as the channel material, has a large number of fine grooves and mutually communicating holes necessary for flowing the permeate that has passed through the semipermeable membrane toward the permeate outlet such as a hollow shaft tube. be. The groove width is large,
A large number of grooves per unit length is good for allowing permeated water to flow without resistance, but if the grooves are too wide or there are too many grooves, the semipermeable membrane becomes pressurized. When this happens, the semipermeable membrane deforms and falls into the groove, blocking the groove that was originally intended to be used as a flow path for the permeate, and reducing the liquid separation capacity of the device, such as the amount of water produced. Needless to say, there are limits. The channel material structure that satisfies the above conditions has a groove width of 100μm.
~500μm, thickness of about 150μm ~ 500μm is preferable. The number of grooves may be 4/cm to 40/cm. Furthermore, the woven or knitted fabric B that serves as the channel material needs to be made rigid, but this can be done by adding a resin or the like to it and solidifying it at the stage of finishing the greige of the woven or knitted fabric B into the channel material. It may be something that gives rigidity to the knitted fabric B, or a mixture of synthetic fiber yarns made of two types of polymers with different melting points may be used as the yarn forming the woven or knitted fabric B, or a low melting point polymer may be used as a sheath. Woven or knitted fabric B is made by using core-sheath composite yarns of two types of polymers with different melting points arranged on the sides, and then by melting and solidifying only the low melting point polymer by heat setting or other means. It may be something that makes the whole rigid. Next, the thread density relationship between the woven fabric A and the woven or knitted fabric B according to the present invention will be explained. The woven or knitted fabric B constitutes a channel material, and preferably has ridges and ridges in the length direction. That is, the woven or knitted fabric B needs to form a flow path, and the shape and size of the flow path greatly influences the performance of the liquid separation device. For this reason, sufficient consideration has been given to the yarn arrangement in the flow path direction of the woven or knitted fabric B, especially the yarn density of the woven or knitted fabric. On the other hand, little consideration is given to the yarn arrangement in the direction perpendicular to the flow path of the woven or knitted fabric B, that is, the horizontal or course direction of the woven or knitted fabric B, and the ease of forming the woven or knitted fabric B or the general nature of clothing for the woven or knitted fabric is not considered. It was decided based on common sense. Fabric A is used as a base material for holding a semipermeable membrane, and the thread arrangement of the fabric A is determined not only by the smoothness, thickness, and dimensional stability of the woven or knitted fabric surface, but also by the application of the semipermeable membrane. It was determined solely by ease of use.
From the above perspective, we have repeatedly studied improvements to woven fabric A and woven/knitted fabric B, and have improved the temperature and pressure of the stock solution to 40°C and 30°C.
Almost satisfactory results were obtained within about Kg/cm ² . However, when the temperature and pressure of the stock solution were raised to even higher temperatures, a serious problem arose in that the purity of the permeate decreased significantly, and it became clear that a satisfactory liquid separation device could not be obtained with the above considerations alone. The present invention was obtained through various studies to solve this problem.
Nb (strands/25 mm) and thread density Na (strands/25 mm) in the direction perpendicular to the flow path in the liquid separation device of fabric A.
It was discovered that the parameters (mm) are related to each other and greatly influence the performance of the liquid separation device.
That is, the thread density Na (threads/25 mm) and Nb (threads/25 mm)
25mm) must satisfy the relationship of Nb≦Na−13 or Na+8≦Nb. This means that the weft yarn density of fabric A and the weft yarn density or course density of woven or knitted fabric B must be at least -13 or more than +8 threads/25 mm apart in the direction perpendicular to the flow path of the permeate in the liquid separator. It means that. More preferably, the relationship Nb≦Na−15 or Na+12≦Nb is satisfied. In addition, the thread density Na of the basic fabric A is 60 to 80.
A length of about 25 mm is preferable. Next, it will be explained using drawings. FIG. 1 is a longitudinal sectional view showing an example of the device according to the present invention, and FIG. 2 is a sectional view taken along the line XX shown in FIG. The apparatus shown in FIGS. 1 and 2 has a liquid separation element 8 built into a cylindrical container 5, which is sealed using side lids 6 and 7. Further, the cylindrical container 5 is provided with a supply pipe 9 and a stock solution discharge pipe 10 for the stock solution, which is the liquid to be separated, and the liquid separation element 8 is provided with a permeate pipe for taking out the permeate separated by the liquid separation element. A discharge pipe 11 is connected. Furthermore, sealing members 13 are provided at both ends of the liquid separation element 8 to close off the stock liquid between the liquid separation element 8 and the cylindrical container 5. The stock solution is fed from the stock solution supply pipe 9 at a pressure higher than the osmotic pressure of the stock solution, and after filling the space 15 of the cylindrical container 5, an opening 12 is formed on the outer peripheral generatrix of the liquid separation element 8 in a direction perpendicular to the generatrix. The liquid flows into the stock solution passage 19 which extends in a spiral shape. As shown in FIG. 2, the liquid separation element includes a hollow tube 16 having a small hole 14 in the center, and two semipermeable membranes 17, 17' are placed at one end of the hollow tube with the small hole 14 in between. It is attached by adhesive. A stock solution passage 19 is formed on the side of the hollow tube of the semipermeable membrane that does not sandwich the small hole 14, and a porous sheet-like material is used as the stock solution passage material to allow the stock solution to flow smoothly in the stock solution passage. It is inserted as 22. On the other hand, semipermeable membrane 1
A permeate channel 23 was formed on the side of the membranes 7 and 17' that sandwiched the small holes, and a channel material 24 was inserted into the permeate channel 23 and bonded to the hollow tube 16 of the semipermeable membranes 17 and 17'. Join the opposite ends together. After the semipermeable membranes 17, 17' arranged in this way, the passage material 22 for the stock solution, and the passage material 24 for the permeated liquid are wound together around the hollow tube 16, seal portions are attached at both ends as shown in FIG. 20 and 21 are formed. Therefore, the obtained liquid separation element 8 has a spiral-shaped stock liquid passage 19 and a permeated liquid passage 23, and the stock liquid passage 19 is connected to the liquid separation element 8 as described above.
An opening 12 is provided on the outer peripheral generatrix. Further, a stock solution passage hole 18 is provided near the hollow tube 16 in the seal portion 21 (on the side where the stock solution discharge pipe 10 is located).
The structure is such that the raw liquid flows out from the liquid separation element from here. FIG. 3 is a sectional view showing a different aspect of the device from FIG. 2. The one in Fig. 2 has one stock liquid passage 19 and one permeate passage 23 for one hollow tube, whereas the one in Fig. 3 has small holes 14.
are provided at three locations, including a stock solution passage 19 and a permeate passage 23.
Three channels are provided in each channel, and the length of each channel is shortened. FIGS. 4 and 5 show semipermeable membranes 17, 17', permeate channel 23, channel material 24, and base materials 25, 2.
5' is a cross-sectional view schematically showing the positional relationship of 5';
4 is a sectional view taken along the Z-Z line in FIG. 5, and FIG. 5 is a sectional view taken along the Y-Y line in FIG. 4. In addition, the direction of the liquid flow of the permeated liquid in both figures is a direction that three-dimensionally penetrates the permeated liquid flow path 23 shown in the cross-sectional view in FIG. In this case, the water flows in the left and right directions of the permeation channel 23 shown in the cross-sectional view. The semipermeable membranes 17, 17' are made of a base material 25,
25', and the base materials 25, 25' are overlapped at positions sandwiching the channel material 24 from both sides. The channel material 24 has a structure having ridges of appropriate height, and the space formed by the groove between the ridges and the base material 25 serves as a channel 23 through which the permeated liquid flows.
The stock solution flows on both sides of the outside of the semipermeable membranes 17, 17'.
In the present invention, the woven fabric A forms the base materials 25, 25', and the woven or knitted fabric B becomes the channel material 24. Therefore, the yarn density in the direction perpendicular to the flow path of the woven or knitted fabric B in the present invention, that is, the weft yarn density or course density Nb
(thread/25 mm) and the yarn density Na in the direction perpendicular to the flow path in the liquid separation device of fabric A is the fifth
In the case of the figure, each thread b, b, b...
...and the number of threads a, a, a... between 25 mm. Furthermore, it is common for the length direction of both the base material and the channel material to match the direction of the channel when used as a liquid separator. Weft yarn density, Nb is woven and knitted fabric B
This is the weft density or course density. [Operations and Effects of the Present Invention] The liquid separation device of the present invention allows the purity of the permeate to be maintained at a sufficiently high level even when the stock solution is at high temperature and high pressure. The most important characteristic of a liquid separation device is how much highly purified permeate it can extract, and in addition to this is the economic efficiency and durability of the device. A typical example is seawater desalination, and the most effective way to increase the amount of permeate extracted is to apply high pressure to the raw solution. This requirement is strong in areas in the Middle East that are not blessed with fresh water, and in such areas it is often necessary to operate liquid separation equipment at high pressure using high-temperature seawater as the raw liquid. Under such conditions, a phenomenon called "slumping of the semipermeable membrane" occurs. To explain this with reference to FIG. 4, the semipermeable membranes 17, 17', the base materials 25, 2
5', this is a phenomenon in which high temperature and high pressure are applied to the channel material 24, reducing the rigidity of each member, and the semipermeable membrane and base material are deformed by the high pressure and fall into the channel 23 portion of the channel material 24. When such a phenomenon occurs, the cross-sectional area of the flow path 23 decreases, and the amount of permeated liquid taken out decreases. Further, a depression is formed on the surface of the semipermeable membrane 17 depending on the degree of "depression". While such dents are minor, there is no major problem, but as the depth of the dent increases, fine cracks occur in the semipermeable membrane near the dent, causing leakage of the stock solution to the permeate side, which prevents permeation. Significantly reduces liquid purity. This "dropping" phenomenon is an extremely important problem for liquid separation devices, and this problem becomes especially serious when the temperature and pressure of the stock solution are increased. The liquid separation device of the present invention has the remarkable effect of providing a solution to this problem. In other words, even when used at high temperatures and high pressures, such as seawater desalination in the Middle East, there is a "depression".
We were able to prevent this phenomenon and enable stable water purification operation for a long period of time. Next, the present invention will be explained in more detail with reference to examples. Example 1 A 37.5 denier, 18 filament yarn made of polyethylene terephthalate and a 37.5 denier, 18 filament yarn made of a polymer obtained by copolymerizing polyethylene terephthalate with 10 mol % of isophthalic acid were prepared by a conventional method. Both yarns were aligned and mixed to obtain a mixed yarn of 75 denier and 36 filaments, and the mixed yarn was fed to a 32 gauge tricot knitting machine with a course density of 43, 54, 73 (strands/25 mm). A gray fabric was created. After the knitted fabric was relaxed and refined, the course density after heat treatment was 48, 50, 54, 60, 68,
The tenter conditions were determined so that the wale density was 73, 76, and 80 lines/25 mm, and the wale density was 40 lines/25 mm, and thermal fusion processing was performed at 250°C for 1 minute. These eight types of tricotally fused products were used as channel materials. On the other hand, Taffeter 1 (warp thread density: 89 threads/25 mm, weft thread density: 66 threads/25 mm) was used as the base material, using 150 denier, 48 filament threads made of polyethylene terephthalate as the warp and weft threads, and the same threads. Taffeter 2 (warp thread density 93/25mm, weft thread density 76)
book/25mm) was used. Synthetic composite membranes were coated on these base materials and combined with eight types of channel materials to create 16 types of liquid separation devices and performance evaluation tests were conducted. In this example, the flow path was parallel to the length direction of the tricot, and the liquid separation device was created by making the length direction of the base material coincide with the length direction of the flow path material. Therefore, Na is the weft density of taffeta, and Nb is the course density of tricot. Examples of performance test results are shown in FIGS. 6 and 7. FIG. 6 shows the change over time in the purity of the permeate, and FIG. 7 shows the change over time in the amount of permeate taken out, and these are test examples of a liquid separation device with poor performance. It can be seen that the purity of the permeate decreases with the passage of operating time. It can be seen that the amount of permeate removed (expressed as the daily amount removed per m ² of semipermeable membrane) varies considerably. Table 1 summarizes the presence or absence of a decrease in permeate purity over time and the stability of the amount taken out for 16 types of liquid separation devices. It can be seen that in the liquid separation device of the present invention, there is almost no decrease in the purity of the permeated liquid over time, and the stability of the amount of permeated liquid taken out is also stable without any problems. 【table】

[Brief explanation of drawings]

Figures 1 to 3 illustrate the structure of the liquid separation device according to the present invention, with Figure 2 being a front view, and Figures 3 and 4.
The figure shows a cross section taken along line XX in FIG. 4 and 5 are cross-sectional views showing the positional relationships among the semipermeable membrane, channel material, and base material in model form. A YY cross section of the figure is shown. 6th
7 and 7 respectively show changes in the permeate purity and the amount of permeate taken out over the course of operation time. 17, 17': Semi-permeable membrane, 19: Stock solution passage, 2
3: Permeate channel, 24: Channel material, 25, 25':
Base material.

Claims (1)

[Claims] 1. Fabric A is provided as a base material supporting a semipermeable membrane,
In a liquid separation device provided with a woven or knitted fabric B as a channel material, the weft yarn density or course density Nb (strands/25 mm) of the woven or knitted fabric B and the weft yarn density Na of the woven fabric A are determined.
A liquid separation device characterized in that the relationship between Nb≦Na−13 or Na+8≦Nb (pieces/25 mm). 2. Claim 1, characterized in that the relationship between the weft yarn density Na of the woven fabric A and the weft yarn density or course density Nb of the woven or knitted fabric B is Nb≦Na−15 or Na+12≦Nb. Liquid separation equipment. 3. The liquid separation device according to claim 1, wherein the fabric A is taffeta, and the woven or knitted fabric B is tricot.