JPH0714467B2 - Liquid separation element - Google Patents

Description

The present invention relates to a liquid separation element using a liquid separation membrane. More specifically, the liquid separation element is generally used for various liquid separations such as pure water production, seawater desalination, recovery of valuables, and concentration. The present invention provides the liquid separation element. By improving the liquid flow path material, the liquid can be more uniformly supplied to the membrane surface, and the pressure loss that occurs when the liquid passes can be greatly reduced.

[Prior Art] First, the structure of a liquid separation element will be described with reference to the drawings. As shown in FIG. 4, the first liquid separation membrane 2 and the second liquid separation membrane 3
The separated liquid flow path member 5 is sandwiched between
A supply liquid flow path member 6 in which the remaining three directions of the first liquid separation film and the second liquid separation film are sealed in an envelope shape with an adhesive or the like so as to open only in the direction of the central tube 1 having 1a. And are treated as one unit, and the single or plural units are wound around the central tube to form the liquid separation element. Separation liquid that has permeated the liquid separation membranes 2 and 3 while the supply liquid 9 is supplied from the end face of the liquid separation element and discharged as the concentrated liquid 11 from the other end face.
10 is taken out from the central tube 1 via the separated liquid flow path member 5.

Generally, the function required of the supply liquid flow path member is to supply the liquid uniformly on the film surface and to have a small flow resistance.
In response to such a demand, conventionally, a net, which is commercially available under the trade name "Netron Net" (manufactured by Nippon Netron Co., Ltd.), made of polypropylene or polyethylene is used. A schematic diagram of the conventional net is shown in FIG. Further, the sectional structure is shown in FIG.

[Problems to be Solved by the Invention] When such a conventional net is used for the feed liquid flow path member, the feed liquid flows in a zigzag manner so as to avoid the net intersection point, so that the pressure loss inevitably increases. . There is also a method of widening the pitch as a method of reducing the pressure loss, but if it is too large, there is a drawback that the concentration is partially increased at a portion where the liquid is difficult to flow, so-called concentration polarization occurs, and the separation performance is deteriorated. Another method is to increase the net thickness. The net thickness is the intersection point thickness of the strands 13 and 14, but since the strands 13 and 14 are bonded in the molten state immediately after spinning in the net manufacturing process, the intersection point thickness is always smaller than twice the strand diameter. Is normal. Therefore, since the opening where the liquid actually flows is the intersection thickness minus the strand diameter, the opening area does not increase simply in proportion to the net thickness. Moreover, although the pressure loss is somewhat reduced by thickening the net, the thicker the net, the smaller the filling amount of the liquid separation membrane, and therefore the smaller the membrane area, and the liquid separated from the liquid separation element of a predetermined size. The amount decreases.

Further, since the net thickness is increased, the net rigidity is increased and the workability in the liquid separation element manufacturing process is deteriorated. Furthermore, since the net edge of the conventional net is sharp, the liquid separation membrane is often scratched by the net edge in the liquid separation element assembling process. Therefore, a protective tape is often attached to the surface of the liquid separation membrane at the portion in contact with the net edge in order to protect the membrane.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a liquid separation element having a supply liquid flow path member that reduces pressure loss and has less uneven flow.

[Means for Solving the Problems] The above-mentioned objects of the present invention are as follows: (1) A first liquid separation membrane, a separation liquid flow path member, and a second liquid around a hollow central tube having holes on the surface. In a liquid separation element formed by winding a single set or multiple sets of a unit having a separation membrane and a supply liquid flow path member as one set, the supply liquid flow path member is a net formed by Russell knitting having the following configuration, Liquid separating element The thickness obtained by subtracting the thickness of the needle loop portion from the thickness of the needle loop portion is 0.2 mm to 1.0 mm.

The width obtained by subtracting the width of the needle loop portion from the pitch of the needle loop portion is 2 mm to 10 mm.

The pitch of the weft yarn bundle that forms the sinker loop is 2 mm to 10 mm in the warp direction.

(2) Thread diameter of the yarn that composes the net by Russell knitting is 0.1 m
The liquid separation element according to claim 1, wherein the liquid separation element has a diameter of m to 0.5 mm.

Is achieved by.

The details will be described below.

In the conventional feed liquid flow path material, the feed liquid flows in a zigzag manner, whereas in the flow path material of the present invention, the feed liquid flows straight and evenly. That is, the supply liquid flow path material of the present invention is composed of a Russell knitting net and is arranged so as to supply the supply liquid in the weaving direction of the net. The pitch of the weft yarn bundle that forms the sinker loop part of the Russell knitting net must be 2 mm or more and 10 mm or less in the warp direction, and 3 mm
-6 mm is particularly preferred. Because, if it is less than 2 mm, the number of times the supply liquid is disturbed by the weft yarn bundle increases and the pressure loss increases. If it is larger than 10 mm, the net loses rigidity and cannot be used. Also, the thickness obtained by subtracting the thickness of the sinker loop from the thickness of the needle loop is 0.2 mm to 1.0 mm.
mm is required, and the width obtained by subtracting the width of the needle loop portion from the pitch of the needle loop portion is required to be 2 mm to 10 mm, preferably 3 mm to 7 mm. Because the thickness is 0.2mm
If the thickness is less than 2 mm and the width is less than 2 mm, the pressure loss lowering effect becomes less, and if the thickness exceeds 1.0 mm and the width exceeds 10 mm, a drift occurs and the separation performance deteriorates. As the thread material, polyethylene or vinyl thread is preferred because it is preferable that the membrane is not damaged, and the thread diameter is preferably 0.1 to 0.5 mm in order to satisfy the above requirements.

Here, the net made of Russell knitting is a net made by warp knitting using a Russell knitting machine as described in publicly known documents such as "Basic knowledge of Russell" published by Textile Journal Co., Ltd. Say that.

[Examples] Example 1 and Comparative Example 1 A Russell knitting net made of polyethylene yarn having a wire diameter of 0.2 mm was used to warp a knitting composition having a weft pitch of 5 mm x 5 mm and a thickness of 0.8 mm to supply liquid to a liquid separation element. It was used as a channel material, and was arranged so that the groove direction of the recess and the supply direction of the supply liquid were substantially coincident with each other.
That is, they were arranged so as to supply the liquid in the knitting direction (Example 1).

On the other hand, as Comparative Example 1, the conventional net has a pitch of 3.8 mm × 3.8 mm
A 0.8 mm thick one was used.

The flow resistance value at that time and the separation performance result of the liquid separation element are summarized in Table 1. That is, compared with the case where the conventional net is used, the net of the present invention shows that the separation performance does not change even if the supply amount is reduced, and thus the flow is uniform with less uneven flow. Moreover, it was confirmed that the pressure loss was reduced to about 1/2.

Comparative Example 2 As shown in FIG. 1, a channel material of a 250 μm-thick polyester stretched film in which triangular grooves having a groove width of 5 mm and a height of 1 mm were formed was used as the channel material for the liquid supply, and the channel was supplied in the groove direction. Table 2 shows the results of evaluations similar to those of Example 1 in which the samples were arranged so as to substantially match the directions. As a result, as with the Russell knitted net of Example 1, good results were obtained in terms of pressure loss and exclusion performance.

However, under the conditions of the raw water NaCl concentration of 5000 ppm and the pressure of 20 kg / cm ² , as shown in Table 3, the film of Comparative Example 2 was inferior in the salt removal rate as compared with the Russell knitted net of Example 1. .

[Effects of the Invention] The following effects are achieved by providing the supply liquid flow path member of the present invention.

(1) The pressure loss of the liquid molecule element could be reduced to half.

(2) Even if the pressure loss was halved, uneven flow did not occur and good separation performance could be obtained even at the bottom flow rate.

[Brief description of drawings]

FIG. 1 is a film cross-sectional view schematically showing an example of a groove shape of a film having concave and convex grooves on the surface, which is preferable as a supply liquid flow path material for a liquid separation element of the present invention, and the cross-sectional direction is the groove. It is perpendicular to the direction. FIG. 2 is a film cross-sectional view schematically showing another example of the groove shape of the film having concave and convex grooves on the surface, which is preferable as the supply liquid flow path material of the liquid separation element of the present invention, and the cross-sectional direction is It is a direction perpendicular to the groove direction. FIG. 3 is a film cross-sectional view schematically showing still another example of the groove shape of the film having concave and convex grooves on the surface, which is preferable as the supply liquid flow path material of the liquid separation element of the present invention, and the cross-sectional direction. Is a direction perpendicular to the groove direction. FIG. 4 is an external view of a conventional liquid separation element, showing a state in which a part thereof is cut and unwound. Figure 5 shows
FIG. 11 is a top view of a net that has been used as a supply liquid flow path member of a conventional liquid separation element. FIG. 6 is a sectional view taken along the line AA of FIG. In the figure, 1: Central office 1a: Hole 2: First liquid separation membrane 3: Second liquid separation membrane 5: Separation liquid flow path material 6: Supply liquid flow path material 7a: End plate 7b: End plate 8: Sealing material 9: supply liquid 10: separation liquid 11: concentrated liquid 12: filament windowing 13: strand 1 14: strand 2 are shown respectively.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-151304 (JP, A) JP-A-50-160178 (JP, A) JP-A-53-23875 (JP, A) Actual development Sho-56- 54904 (JP, U) Actual public Sho 61-25841 (JP, Y2)

Claims (2)

[Claims] 1. A unit in which a first liquid separation membrane, a separated liquid flow path member, a second liquid separation membrane and a supply liquid flow path member are provided as a set around a hollow central tube having holes on its surface. A liquid separation element in which a single set or a plurality of sets are wound, wherein the supply liquid flow path member is a net by Russell knitting having the following configuration. The thickness obtained by subtracting the thickness of the sinker loop from the thickness of the needle loop is 0.2 mm to 1.0 mm. The width obtained by subtracting the width of the needle loop portion from the pitch of the needle loop portion is 2 mm to 10 mm. The pitch of the weft yarn bundle that forms the sinker loop is 2 mm to 10 mm in the warp direction. 2. The liquid separation element according to claim 1, wherein the diameter of the thread forming the net by the Russell knitting is 0.1 mm to 0.5 mm.