JP2009050759A - Spiral type separation membrane element - Google Patents

Abstract

A spiral separation membrane element capable of suppressing concentration polarization without increasing pressure loss on the supply side is provided.
In a spiral separation membrane element in which one or more of a separation membrane, a supply-side flow channel material, and a permeation-side flow channel material are wound around a perforated hollow central tube, the supply-side flow The road material includes a net formed by crossing a plurality of threads (1, 2) in a lattice shape, and a protrusion (3) provided on at least a part of the plurality of threads (1, 2), The protrusion (3) is a spiral separation membrane element characterized by protruding into the unit cell (4) surrounded by the threads (1, 2).
[Selection] Figure 1

Description

  The present invention relates to a spiral separation membrane element that separates components suspended and dissolved in a liquid.

  Conventionally, as a structure of a spiral type separation membrane element, one or more of a separation membrane, a supply side flow channel material and a permeate side flow channel material is wound around a perforated hollow central tube. (For example, Patent Documents 1 to 3).

  A net-like material is usually used for the supply side channel material. The supply-side flow path material is required to have a function of suppressing concentration polarization by ensuring the flow path of the supply liquid and at the same time promoting the surface renewal of the separation membrane surface. When concentration polarization occurs, the osmotic pressure on the membrane surface may increase, which may cause problems such as a decrease in the amount of permeate.

In order to suppress concentration polarization, there is a method of increasing the linear velocity of the supply liquid on the membrane surface by reducing the thickness of the supply-side flow path material. The pressure loss on the supply side may increase due to the blockage. When the pressure loss on the supply side increases, the required power of the pump for supplying the supply liquid increases, resulting in an increase in power cost and damage to the element.
Japanese Patent Laid-Open No. 02-273520 Japanese Patent Laid-Open No. 08-332489 JP-A-10-005554

  In order to solve the above problems, an object of the present invention is to provide a spiral separation membrane element capable of suppressing concentration polarization without increasing pressure loss on the supply side.

  As a result of intensive studies, the present inventor has found that the above object can be achieved by the spiral separation membrane element shown below, and has completed the present invention.

  That is, the spiral separation membrane element of the present invention is a spiral separation in which one or more of the separation membrane, the supply-side channel material, and the permeation-side channel material are wound around a perforated hollow central tube. In the membrane element, the supply-side channel material includes a net formed by crossing a plurality of yarns in a lattice shape, and a protrusion provided on at least a part of the plurality of yarns, And protruding in a unit cell surrounded by the yarn.

  In the spiral separation membrane element of the present invention, since the protrusions provided on the yarn protrude into the unit cell surrounded by the yarn, the turbulent flow is promoted on the membrane surface and the surface renewal of the membrane surface is promoted. Is done. In addition, since the protrusions are not provided continuously like a thread, the supply liquid flow is not obstructed and the flow path is not easily blocked by a floating component in the supply liquid. Thereby, concentration polarization can be suppressed without increasing the pressure loss on the supply side.

  In the present invention, when the net has a two-layer structure including a first layer composed of a first thread and a second layer composed of a second thread, the protrusion is formed of the net It is preferable that it is provided on at least one of the first yarn exposed on the second layer side and the second yarn exposed on the first layer side of the net. Since an increase in the thickness of the entire supply-side channel material can be prevented, a decrease in the linear velocity of the supply liquid on the membrane surface can be prevented. Thereby, concentration polarization can be easily suppressed. In this case, it is preferable that the protrusion has a thickness in a direction orthogonal to the supply liquid flow surface substantially equal to or less than the yarn diameter of the yarn intersecting with the yarn provided with the protrusion. This is because the thickness of the supply-side channel material can be made substantially equal to the thickness of the net made of the yarn, so that concentration polarization can be more easily suppressed.

  Moreover, it is preferable that the protrusions are provided at substantially equal intervals along the supply liquid flow direction. This is because the portion where the resistance of the supply liquid flow increases can be dispersed, and the effect of suppressing the increase in pressure loss is more effectively exhibited.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a partial plan view showing an example of a supply-side channel material used in the spiral separation membrane element of the present invention. FIG. 1B is a cross-sectional view taken along the line I-I in FIG.

  The spiral separation 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 permeation-side channel material are wound around a perforated hollow central tube. Such membrane elements are also described in detail in the above-mentioned Patent Documents 1 to 3, and regarding configurations other than the supply-side channel material, conventionally known separation membranes, permeation-side channel materials, hollow central tubes, etc. Either can be adopted. 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.

  As shown in FIG. 1A, the supply-side flow path material used in the present invention includes a plurality of yarns 1 extending from the lower left to the upper right in FIG. And a plurality of protrusions 3 provided on the yarn 1. That is, the supply-side channel material used in the present invention includes a net formed by the threads 1 and 2 and a plurality of protrusions 3. Further, as shown in FIG. 1B, the net formed by the threads 1 and 2 is a two-layer structure including a first layer 11 composed of the thread 1 and a second layer 12 composed of the thread 2. have. The protrusion 3 is provided on the thread 1 exposed on the second layer 12 side of the net and protrudes into the unit cell 4 (see FIG. 1A) surrounded by the threads 1 and 2. Yes. According to the present invention, since the protrusion 3 protrudes into the unit cell 4, turbulence is promoted on the separation membrane surface (not shown), and the surface renewal of the membrane surface is promoted. Further, since the protrusions 3 are not provided continuously like the yarns 1 and 2, the flow of the supply liquid is not obstructed and the flow path is not easily blocked by the floating component in the supply liquid. Thereby, concentration polarization can be suppressed without increasing the pressure loss on the supply side. Moreover, since the protrusion 3 is provided in the thread | yarn 1 exposed to the 2nd layer 12 side of the said net | network, the increase in the thickness of a supply side flow-path material can be prevented. Thereby, since the fall of the linear velocity of the supply liquid on a film surface can be prevented, concentration polarization can be suppressed easily.

  The material for the threads 1 and 2 is not particularly limited, and examples thereof include plastic materials such as polyethylene resin and polypropylene resin. Further, the thickness of the net formed by the yarns 1 and 2 is preferably 0.5 mm or more and 2.0 mm or less. When the thickness of the net is reduced, the linear velocity of the supply liquid on the film surface increases, so that concentration polarization can be suppressed. On the other hand, when the thickness of the net is increased, blockage of the flow path due to floating components in the supply liquid can be prevented, so that the required power of the pump that supplies the supply liquid can be reduced. In the example shown in FIG. 1 (A), the thickness of the net is the thickness at the intersection 5 where the yarns 1 and 2 intersect, and is preferably an average thickness measured at least 10 points. As a method for measuring the thickness, there are a method using a thickness gauge and a method using a magnifier such as an optical microscope or a CCD camera. The following numerical values (yarn pitch, yarn crossing angle, protrusion protrusion length) are preferably average values obtained by measuring at least 10 points.

Pitch _{P 2} of the pitch _{P 1} and thread 2 thread 1 are all 1~15mm are preferred. When the pitch is reduced, turbulent flow is promoted on the film surface, and surface renewal of the film surface is promoted. Thereby, concentration polarization can be suppressed. On the other hand, when the pitch is increased, the pressure loss can be reduced. The pitch P ₂ of the pitch P ₁ and thread 2 thread 1 may be the same or different.

  The crossing angle θ between the yarn 1 and the yarn 2 is preferably 50 to 120 degrees. Generally, when the crossing angle θ is small, the pressure loss of the flow path can be reduced (see Japanese Patent No. 3230490). On the other hand, when the crossing angle θ is large, turbulent flow is promoted on the film surface, and surface renewal of the film surface is promoted. Thereby, concentration polarization can be suppressed.

The ratio between the protrusion length L of the protrusion 3 and the pitch of the yarn provided with the protrusion 3 (L / P _{1 in} the case of FIG. 1A) is, for example, in the range of 0.1 to 0.8. Preferably, it is the range of 0.2-0.6. If the value of the ratio is reduced, the pressure loss can be reduced. On the other hand, when the value of the ratio is increased, concentration polarization can be suppressed.

  The yarns 1 and 2 may be multifilaments or monofilaments, but monofilaments that are unlikely to hinder the supply liquid flow are preferable. Further, the yarns 1 and 2 are preferably fixed to each other by fusion, adhesion, or the like in order to stably maintain the supply liquid flow. In particular, in order to achieve both suppression of concentration polarization and reduction of pressure loss on the supply side, it is preferable that the yarns 1 and 2 are extruded and integrally formed by a fusion method, a shearing method, or the like.

  In the example shown in FIGS. 1 (A) and 1 (B), the protrusion 3 is provided only on the thread 1, but may be provided only on the thread 2, and may be provided on both the threads 1 and 2. Also good. Further, the number of the protrusions 3 is not limited, and may be one, or may be plural as in the examples shown in FIGS. Further, as shown in FIG. 1 (B), the protrusion 3 has a thickness T in a direction orthogonal to the supply liquid flow surface substantially equal to the yarn diameter of the yarn 2 intersecting the yarn 1 provided with the protrusion 3. It is preferable that they are equivalent (or less). This is because the thickness of the supply-side channel material can be made substantially equal to the thickness of the net composed of the yarns 1 and 2, so that concentration polarization can be more easily suppressed. “The thickness T of the projection 3 is substantially equal to the yarn diameter” means that the thickness T of the projection 3 and the yarn diameter of the yarn 2 intersecting the yarn 1 provided with the projection 3 are randomly selected. 10 points are measured to calculate an average value, and the average value of the thickness T of the protrusion 3 is within ± 15% of the average value of the yarn diameter of the yarn 2. As a measuring method at this time, a method of measuring with an enlargement device such as an optical microscope or a CCD camera is preferable.

  The intervals of the protrusions 3 may be provided at substantially equal intervals along the supply liquid flow direction as in the example shown in FIG. 1A, or may be provided irregularly. However, when the intervals between the protrusions 3 are provided at substantially equal intervals along the supply liquid flow direction, the portions where the resistance of the supply liquid flow increases can be dispersed, so that the effect of suppressing an increase in pressure loss is more effective. Effectively demonstrated. Here, the “interval between the protrusions 3” refers to an interval between the central portions of the protrusions 3 adjacent in the supply liquid flow direction. The “substantially equidistant spacing” refers to a case where the spacing of the protrusions 3 is measured at 10 random locations and all values at the measurement locations are within ± 15% of the average value. As a measuring method at this time, a method of measuring with an enlargement device such as an optical microscope or a CCD camera is preferable.

  With respect to the method of providing the protrusion 3 shown in FIG. 1A, first, a thread for forming the protrusion 3 (hereinafter referred to as “projection forming thread”), the thread 2, and the thread 1 are in a lattice shape. Form a net that intersects At this time, the protrusion forming yarn is arranged between the yarns 2. Next, the protrusion 3 can be provided by cutting and removing a part 6 of the protrusion-forming yarn (a portion indicated by a broken line between the protrusions 3 in FIG. 1A). In the present invention, the method of providing the protrusion is not limited to the above method. For example, after forming the net, a method of fixing the protrusion to the desired position of the yarn constituting the net with an adhesive or the like is used. Also good. In this case, the material and shape of the protrusion are not particularly limited. Moreover, each protrusion may be the same or different.

As mentioned above, although the example of the supply side channel material used by this invention was demonstrated, this invention is not limited to the said example. For example, in FIG. 1 (A), the although the installation pitch of protrusions 3 along the yarn 2 is illustrated for the case same as the pitch P ₁ of the thread 1, as in the example shown in FIG. 2, the projections 3 the installation pitch, and the multiple of the pitch P ₁ of the thread 1, and may be protrusions 3 with respect to the column 7 of the projection 3 adjacent are alternately arranged. As a modification of FIG. 2, two rows of protrusions 3 may be arranged between adjacent yarns 2 as in the example shown in FIGS. 3A and 3B, or FIG. ), (B), three rows of protrusions 3 may be arranged between adjacent yarns 2. Here, FIG. 3 (B) and FIG. 4 (B) are respectively a sectional view taken along line II-II in FIG. 3 (A) and a sectional view taken along line III-III in FIG. 4 (A). A part 6 of the yarn remains. In addition, if the method etc. which adhere a protrusion with an adhesive agent etc. are used, the supply side channel material in which a part of protrusion formation thread | yarn will not remain can be formed.

  Although not shown, four or more rows of protrusions 3 may be disposed between adjacent yarns 2, or one or more rows of protrusions 3 may be disposed between adjacent yarns 1. Good. Further, as in the example shown in FIG. 5, the protrusions 3 may be arranged at all points between the intersection portions 5 of the yarns 1 and 2. In FIG. 5, the protrusions 3 are formed on both the yarn 1 exposed on the second layer 12 (see FIG. 1B) side and the yarn 2 exposed on the first layer 11 (see FIG. 1B) side. Is provided. Also in this example, since the decrease in the linear velocity of the supply liquid on the film surface can be prevented, concentration polarization can be easily suppressed.

  The spiral separation membrane element of the present invention can be used for any filtration method such as reverse osmosis filtration, ultrafiltration, and microfiltration, and its use is not limited. In particular, this effect is particularly effective when filtering turbid water with a reverse osmosis membrane or desalinating seawater or brine.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Supply channel material)
As Examples 1 and 2 and Comparative Examples 1 to 3, the polypropylene resin supply side flow path materials shown in Table 1 were prepared and set in parallel plate cells (C10-T; flow path width 35 mm, flow path length 135 mm), respectively. FIG. 6 shows the relationship between the flow rate when pure water is flowed and the pressure loss. Here, Example 1 and Example 2 are the supply-side flow path materials shown in FIGS. 3 (A) and 3 (B) and FIGS. 4 (A) and 4 (B), respectively. , A supply-side flow path material provided with no protrusions (that is, made of a conventional net). When forming the protrusion 3 in Examples 1 and 2, as described above, a method of cutting and forming a desired portion using the protrusion forming yarn was used. In Examples 1 and 2, the thickness T of the protrusion 3 in the direction orthogonal to the supply liquid flow surface was substantially equal to the yarn diameter (0.32 mm) of the yarns 1 and 2. Moreover, in Table 1, the average value of the value measured 10 places at random is shown about any item.

  As shown in FIG. 6, the pressure loss values of the supply side channel materials of Examples 1 and 2 were 20% or more lower than those of Comparative Examples 1 and 3.

(Spiral reverse osmosis membrane element)
A spiral reverse osmosis membrane element having a length of 1016 mm and an effective membrane area of 37.0 m ² was prepared using the supply-side channel material of Example 1 and Comparative Examples 1 and 2, and pure water in a state where it was loaded in a pressure vessel. FIG. 7 shows the relationship between the flow rate of the supply water (pure water) and the pressure loss when the water is passed. The decrease in pressure loss confirmed with C10-T was also confirmed with actual elements. Table 2 shows the results of element performance confirmation using the aqueous NaCl solution (concentration: 1500 ppm) for each spiral reverse osmosis membrane element described above. The evaluation conditions at this time were an operating pressure of 1.55 MPa and a recovery rate of 15%.

  The element using the supply-side channel material of Comparative Example 2 has a low pressure loss as shown in FIG. 7, but the element performance (NaCl rejection and permeated water amount) shown in Table 2 is also low, and concentration polarization occurs. It is thought that. On the other hand, the element using the supply side channel material of Example 1 had low pressure loss, and the element performance had a value equivalent to that of Comparative Example 1. That is, according to Example 1, it turned out that pressure loss can be reduced rather than Comparative Examples 1 and 3, and element performance can be maintained equal to Comparative Example 1. Furthermore, since the element performance was higher than that of Comparative Example 2, it was found that a turbulent flow effect sufficient to suppress concentration polarization was obtained. From this result, it was found that according to the present invention, it is possible to provide a spiral separation membrane element capable of suppressing concentration polarization without increasing the pressure loss on the supply side.

(A) is a partial top view which shows an example of the supply side flow path material used for the spiral type separation membrane element of this invention, (B) is the II sectional view taken on the line of (A). It is a fragmentary top view which shows another example of the supply side channel material used for the spiral type separation membrane element of this invention. (A) is a fragmentary top view which shows another example of the supply side flow path material used for the spiral separation membrane element of this invention, (B) is the II-II sectional view taken on the line of (A). (A) is a partial top view which shows another example of the supply-side flow path material used for the spiral type separation membrane element of this invention, (B) is the III-III sectional view taken on the line of (A). It is a fragmentary top view which shows another example of the supply side channel material used for the spiral type separation membrane element of this invention. It is a graph which shows the relationship between the flow volume and pressure loss when flowing pure water through the supply side channel material of Examples 1, 2 and Comparative Examples 1-3. It is a graph which shows the relationship between the flow rate of supply water, and a pressure loss when flowing pure water through the spiral type reverse osmosis membrane element using the supply side channel material of Example 1 and Comparative Examples 1 and 2.

Explanation of symbols

1, 2 Thread 3 Projection 4 Unit lattice 5 Intersection part 11 First layer 12 Second layer L Projection length P _1, P ₂ Pitch T Projection thickness θ Crossing angle

Claims (4)

In a spiral type separation membrane element in which one or more of a separation membrane, a supply-side flow passage material and a permeation-side flow passage material are wound around a perforated hollow central tube,
The supply-side channel material includes a net formed by crossing a plurality of yarns in a lattice shape, and a protrusion provided on at least a part of the plurality of yarns,
The spiral separation membrane element, wherein the protrusion protrudes into a unit cell surrounded by the thread. The net has a two-layer structure including a first layer composed of a first thread and a second layer composed of a second thread,
The protrusion is provided on at least one of the first yarn exposed on the second layer side of the net and the second yarn exposed on the first layer side of the net. Spiral separation membrane element.   3. The spiral separation membrane according to claim 2, wherein the protrusion has a thickness in a direction orthogonal to a supply liquid flow surface substantially equal to or less than a yarn diameter of a yarn that intersects the yarn provided with the protrusion. element.   The spiral projection membrane element according to any one of claims 1 to 3, wherein the protrusions are provided at substantially equal intervals along a supply liquid flow direction.

Images