JP2007209956A - Spiral type separation membrane element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spiral type separation membrane element capable of suppressing pressure loss in a channel in the supply side and giving high operation efficiency and good filtered water quality owing to a sufficient effect for suppressing concentration polarization. <P>SOLUTION: The spiral type separation membrane element comprises a separation membrane, a channel material in the supply side, and a channel material in the filtered side which are rolled around a hollow center pipe having holes. The channel material in the supply side is composed of warp yarns 1 parallel to the flow direction of the supplied liquid and weft yarns 2 crossing the flow direction of the supplied liquid, wherein both yarns are entwisted at a crossing angle θ of 20 to 80° and have the ratio (L1/L2) of the intervals L1 of the warp yarns and the intervals L2 of the weft yarns in a range from 1.3 to 2.0, and the intervals L1 of the warp yarns is 5 mm or wider. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spiral-type separation membrane element that separates components suspended and dissolved in a liquid. More specifically, the pressure loss on the supply side can be made smaller than before, and concentration polarization on the membrane surface can be suppressed. The present invention relates to a spiral-type separation membrane element having a built-in supply-side channel material having a structure having a stirring effect required for the purpose.

  Conventionally, as a structure of a spiral separation membrane element (hereinafter sometimes referred to as “membrane element”), a single or a plurality of separation membranes, supply-side flow channel materials, and permeate-side flow channel materials are perforated hollow central tubes. What is wrapped around is known. As the supply-side channel material, a diamond net with diamond-shaped constituent yarn is usually used, and at the same time as securing the channel on the element supply side, the surface renewal of the membrane surface is promoted to promote concentration polarization. There is a function to suppress.

  In recent years, spiral-type reverse osmosis membrane elements used for ultrapure water production have been reduced in operating pressure, and high-performance elements with low pressure loss are desired in order to increase operating efficiency.

  In addition, in order to suppress concentration polarization, there is a method of increasing the linear velocity of the membrane surface by reducing the thickness of the supply-side channel material, but this method increases pressure loss, and the supply liquid is supplied to the water supply. There is a problem that the required power of the pump to be increased.

  As a diamond-type net, the following Patent Document 1 proposes a raw water spacer in which the angle of the net legs is within a range of ± 15 to 40 ° with respect to the raw water flow. However, the diamond-type net generally has a large pressure loss, so that it cannot sufficiently cope with a reduction in the operating pressure of the membrane element.

  Therefore, as spacers having a pressure loss lower than that of the diamond net, the following Patent Documents 2 to 3 describe that the warp yarns parallel to the flow direction of the supply liquid and the weft yarns crossing the supply liquid flow direction have an acute angle of intersection. A connected ladder net has been proposed. Specifically, a ladder type net is proposed in which the ratio (L1 / L2) of the warp yarn interval L1 and the weft yarn interval L2 is in the range of 1.0 to 0.77.

  However, these ladder-type nets are too important to reduce pressure loss, so they become channel materials with little effect of concentration polarization suppression, and when used for spiral type reverse osmosis membrane elements, they have sufficient salt blocking performance. It was difficult to get.

Japanese Patent Laid-Open No. 2000-042378 Japanese Patent No. 3098600 JP 2005-319454 A

  Accordingly, an object of the present invention is to provide a spiral separation membrane element that can reduce the pressure loss of the supply-side flow path and has a sufficient operation effect and permeated water quality because the effect of suppressing concentration polarization is sufficient. is there.

  In order to achieve the above-mentioned object, the present inventors diligently studied the warp yarn interval, the weft yarn interval, etc. of the ladder-shaped net-like channel material, and set the ratio and length of the warp yarn interval to the weft yarn interval within a certain range. As a result, the inventors have found that the above object can be achieved, and have completed the present invention.

  That is, the spiral separation membrane element of the present invention is a spiral separation membrane element in which a separation membrane, a supply-side channel material and a permeation-side channel material are wound around a perforated hollow central tube. In the supply side channel material, warp yarns parallel to the flow direction of the supply liquid and weft yarns intersecting the supply liquid flow direction are connected at an intersecting angle of 20 to 80 °, and the ratio of the warp yarn interval L1 to the weft yarn interval L2 ( L1 / L2) is in the range of 1.3 to 2.0, and the warp interval L1 is 5 mm or more.

  According to the spiral separation membrane element of the present invention, the ratio (L1 / L2) between the warp yarn interval L1 and the weft yarn interval L2 is in the range of 1.3 to 2.0, and the warp yarn interval L1 is 5 mm or more. The effect of reducing the pressure loss of the supply-side channel material and the effect of suppressing the concentration polarization can both be achieved, and the operating efficiency and permeated water quality can be improved. Moreover, since the crossing angle between the warp and the weft is 20 to 80 °, both the effect of reducing the pressure loss and the effect of suppressing the concentration polarization are improved.

  The spiral separation membrane element of the present invention is preferably used for producing ultrapure water. In that case, the rejection performance of a 500 ppm NaCl solution at 25 ° C. under the conditions of an operating pressure of 0.5 MPa and a recovery rate of 15%. Is preferably 99.0% or more.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The membrane element of the present invention has a structure in which one or more of a separation membrane, a supply-side channel material, and a permeate-side channel material are wound around a perforated hollow central tube (not shown). . As for the membrane element, conventionally known separation membranes, permeation side flow channel materials, hollow central tubes, etc. can be adopted except for the supply side flow channel materials. For example, when a plurality of supply-side channel materials and permeation-side channel materials are used, a plurality of membrane leaves are wound around a hollow central tube.

  FIG. 1 is a diagram showing an example of a supply-side channel material of a membrane element according to the present invention. The supply-side channel material has a structure in which warp yarns 1 parallel to the flow direction of the supply liquid are connected to weft yarns 2 that intersect the supply liquid flow direction.

  The membrane element of the present invention can be applied to any filtration method such as reverse osmosis filtration, ultrafiltration, microfiltration, etc., but the supply side channel material as described above is mainly reverse osmosis using a reverse osmosis membrane. The effect is exhibited in the case of filtration, and it is particularly preferable to use for ultrapure water production.

  Examples of the material of the warp 1 or the weft 2 constituting the supply-side channel material include resins such as polypropylene, polyethylene, polyethylene terephthalate (PET), and polyamide, as well as natural polymers and rubbers. Is preferred.

  The warp yarn 1 and the weft yarn 2 may be multifilaments or monofilaments, but monofilaments that do not obstruct the flow path are preferred. The warp yarn 1 and the weft yarn 2 may be fixed to each other by fusion or adhesion, or may be a woven fabric. However, in order to maintain the flow path stably, it is preferable that the warp 1 and the weft 2 are fixed.

  Furthermore, the crossing angle θ of the weft 2 with respect to the warp 1 may be 20 to 80 °, but is preferably 30 ° to 70 ° and more preferably 40 ° to 50 ° from the viewpoint of reducing the flow resistance due to the weft 2. When the crossing angle θ is smaller than 20 °, the effect of suppressing the concentration polarization is reduced, and the net is easily deformed and handling becomes difficult. When the crossing angle θ is larger than 80 °, production becomes difficult, production cost is greatly increased, and pressure loss is also increased.

  Further, the arrangement of the warp yarn 1 and the weft yarn 2 is preferably a structure in which all the weft yarns 2 are arranged on one side of the plurality of warp yarns 1 arranged as shown in FIG. According to such a structure, an effect that the resistance of the supply-side channel material can be reduced is obtained.

  The interval L1 between the warp yarns 1 constituting the supply-side channel material is preferably 5 mm or more. If the interval is narrower than this, the effect of suppressing concentration polarization is reduced. That is, in the ladder type spacer, there is a tendency that the turbulence in the vicinity of the warp yarn 1 tends to be less, and when the warp interval L1 is narrow and the warp yarn 1 is increased, the flow path material is less effective in suppressing concentration polarization due to the raw water flow. End up. Moreover, there is also an effect of reducing the pressure loss by increasing the warp interval L1. However, if the warp interval L1 is too wide, the channel material is stiff and difficult to handle, so 10 mm or less is preferable.

  The ratio (L1 / L2) between the warp interval L1 and the weft interval L2 is in the range of 1.3 to 2.0, preferably 1.3 to 1.8, and more preferably 1.3 to 1.5. When L1 / L2 is smaller than this range, the distance L2 between the wefts 2 is widened and the pressure loss is reduced, but the flow path material is less effective in suppressing concentration polarization. On the other hand, if it exceeds the above range, the net pressure loss will increase.

  Further, if the thickness of the net is reduced, the linear velocity of the film surface increases and concentration polarization can be suppressed. However, if the thickness of the net is too thin, there arises a problem that the required power of the pump for feeding the supply liquid increases. For this reason, the thickness of the net is preferably 0.5 mm or greater and 1.0 mm or less. The net thickness referred to here is preferably an average thickness obtained by measuring at least 10 points. As a measuring method, there are a method using a thickness gauge or a method using a magnifier such as an optical microscope or a CCD camera.

  Further, as shown in FIG. 2 (a), for the problem of reducing the pressure loss due to the flow of the supply liquid, the weft thread 2 intersecting the supply liquid flow direction is thinned to cut off the supply liquid flow path. The area can be increased, which is effective for obstructing or blocking the flow of the supply side flow path, and the pressure loss of the flow path can be reduced.

  In other words, in the conventional supply-side channel material, the weft and the warp are formed with substantially the same diameter, and the actual channel cross-sectional area of the supply-side channel cross-sectional area is less than 1/2. Absent. In the supply-side channel material of the present invention, by reducing the diameter ratio of the weft yarn 2 to the warp yarn 1, the channel cross-sectional area increases and the pressure loss can be reduced as compared with the conventional one. Specifically, the yarn diameter of the warp 1 is preferably 50% or more of the thickness of the net, and more preferably 70% or more and 75% or less. If the yarn diameter of the warp 1 becomes smaller than this, the yarn diameter of the weft 2 will eventually become larger and the pressure loss tends to increase. On the other hand, if the yarn diameter of the warp yarn 1 becomes too large, the yarn diameter of the weft yarn 2 becomes small and the effect of suppressing concentration polarization tends to be reduced.

  As for the cross-sectional shapes of the warp yarn 1 and the weft yarn 2, as shown in FIG. 2B, the warp yarn 1 is circular or substantially circular, and the weft yarn 2 has a major axis parallel to the plane of the supply-side channel material. An elliptical shape may be used.

  The spiral separation membrane element of the present invention preferably has a rejection rate performance of 500 ppm NaCl solution at 0.5 MPa and a performance of 99.0% or more. The higher the performance of the element operating at low pressure, the greater the effect of the present invention. Specifically, it is preferably used for reverse osmosis filtration performed at an operating pressure of 0.2 to 0.5 MPa.

  Moreover, the spiral-type separation membrane element of the present invention does not limit the application at all, but the effect is particularly exerted when used mainly for the production of ultrapure water.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. Needless to say, the present invention is not limited to such examples.

<Example 1>
As shown in Table 1, the supply-side channel material used in the present invention has a thickness of 0.66 mm, a warp diameter of 0.48 mm, a weft diameter of 0.18 mm, a weft interval of 5.4 mm, and a weft interval of 4. A ladder-type (see FIG. 1) polypropylene net with a warp-weft crossing angle of 43 ° and a warp-to-weft spacing ratio (L1 / L2) of 1.35 and a membrane area of 6.5 m ² was used. A membrane element having a diameter of 4 inches was produced.

  Using this membrane element, a pure water permeation test was performed while changing the operating pressure, and the pressure loss of the membrane element at each flow rate was measured. The results are shown in FIG. Further, reverse osmosis filtration was performed under the conditions of operating pressure: 0.50 MPa, raw water: 500 ppm NaCl solution (25 ° C., pH 6.7), and recovery rate: 15%, and the NaCl rejection and the amount of permeated water were measured. The results are shown in Table 2.

<Example 2>
In Example 1, as shown in Table 1, a membrane element was produced and evaluated in the same manner as in Example 1 except that a polypropylene net having a weft interval L2 changed to 3.0 mm was used. . The results are shown in Table 2 and FIG.

<Comparative Example 1>
As shown in Table 1, the supply-side channel material has a supply-side channel material thickness of 0.68 mm, warp diameter 0.29 mm, weft diameter 0.29 mm, warp interval 3.0 mm, weft interval 3.0 mm, warp and Using a diamond-shaped polypropylene net (see Fig. 4) with a weft crossing angle of 90 ° and a ratio between the warp and weft spacing (L1 / L2) of 1.00 (see Fig. 4), the membrane area is 6.5 m ² and 4 inches in diameter. A membrane element was prepared. Using this membrane element, the membrane element was evaluated in the same manner as in Example 1. The results are shown in Table 2 and FIG.

<Comparative example 2>
In Example 1, as shown in Table 1, a membrane element was produced and evaluated in the same manner as in Example 1 except that a polypropylene net having a weft interval L2 changed to 2.0 mm was used. . The results are shown in Table 2 and FIG.

<Comparative Example 3>
In Example 1, as shown in Table 1, a membrane element was produced and evaluated in the same manner as in Example 1 except that a polypropylene net having a weft interval L2 changed to 6.0 mm was used. . The results are shown in Table 2 and FIG.

<Result>
The ladder-type channel material of the present invention has a NaCl loss of 40% or more compared to the diamond-type channel material (Comparative Example 1) used for a normal spiral-type reverse osmosis membrane element. The blocking performance was 99.3% or more, and it was confirmed that a turbulent flow effect sufficient to maintain concentration polarization was obtained. On the other hand, in Comparative Example 2 in which the ratio (L1 / L2) is too large, the pressure loss is increased, the amount of permeated water is reduced, and in Comparative Example 3 in which the ratio (L1 / L2) is too small, the blocking performance of NaCl is increased. The turbulence effect sufficient to maintain concentration polarization was not obtained, and the amount of permeated water was also reduced.

Explanatory drawing which shows an example of the supply side channel material of the spiral type separation membrane element of this invention Explanatory drawing which illustrates the relationship between the weft and warp of the supply side channel material The graph which shows the relationship between the flow volume and pressure loss in an Example and a comparative example Explanatory drawing which shows an example of the supply side channel material of the conventional spiral type separation membrane element

Explanation of symbols

1 warp 2 weft L1 warp spacing L2 weft spacing θ Crossing angle of weft with warp

Claims (2)

In the spiral-type separation membrane element in which the separation membrane, the supply-side channel material, and the permeation-side channel material are wound around a perforated hollow central tube,
In the supply side channel material, the warp yarn parallel to the flow direction of the supply liquid and the weft yarn crossing the supply liquid flow direction are connected at an intersecting angle of 20 to 80 °, and the ratio of the warp yarn interval L1 to the weft yarn interval L2 ( L1 / L2) is in the range of 1.3 to 2.0, and the warp yarn spacing L1 is 5 mm or more.   2. The rejection performance of a 25 ppm, 500 ppm NaCl solution is 99.0% or more under the conditions of an operating pressure of 0.5 MPa and a recovery rate of 15%, which is used for production of ultrapure water. Spiral type separation membrane element.

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