JPH0418921A - Liquid separation element - Google Patents

Abstract

PURPOSE:To reduce the pressure loss or uneven flow by forming a liquid separation element by winding a unit of flow passage member comprising Russell cord nets for supplying a liquid around a hollow center tube having pores on its surface. CONSTITUTION:The liquid separation element is formed by winding a unit comprising a first liquid separation membrane, flow passage member for the separated liquid, second liquid separation membrane and flow passage member for supplying liquid comprising Russell cord net around a hollow-type center tube having pores on its surface. In this liquid separation membrane, a film having a rugged pattern on its surface is preferably used instead of the Russell cord net for the flow passage member for supplying the liquid. The Russelle cord net is a longitudinally knitted net by using a Russell knitting machine as shown by well-known technique. The film having a rugged pattern on its surface is formed by subjecting a film to embossing, laser working or etching, etc., to form continuous rugged pattern on its surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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, valuable material recovery, and concentration. By improving the liquid channel material, it is possible to supply liquid more uniformly to the membrane surface and to significantly reduce the pressure loss that occurs when liquid passes through it.

[Conventional technology] First, the structure of the liquid separation element will be explained using diagrams. .

As shown in FIG. 4, it has a structure in which a separated liquid channel material 5 is sandwiched between a first liquid separation membrane 2 and a second liquid separation membrane 3, and only in the direction of the central pipe 1 having holes 1a. The remaining three directions of the first liquid separation membrane and the second liquid separation membrane are sealed with adhesive or the like in an envelope shape so as to open, and the supply liquid channel material 6 is assembled into one unit. One or more units are wrapped around a central tube to form a liquid separation element. The separated liquid 10 that has permeated the liquid separation membrane 2.3 while supplying the feed liquid 9 from one end face of the liquid separation element and discharging it as a concentrated liquid 11 from the other end face is transferred to the central pipe via the separated liquid channel material 5.] −
taken out from

In general, the functions required of the feed liquid channel material are to uniformly supply the liquid onto the membrane surface and to have little flow resistance.

In response to such demands, conventional nets made of polypropylene or polyethylene, which are commercially available under the trade name "Netron Net" (manufactured by Nippon Netron Co., Ltd.), have been used.

A schematic diagram of the conventional network is shown in FIG. Furthermore, the cross-sectional configuration is shown in FIG.

[Problem to be solved by the invention] When such a conventional net is used as a feed liquid channel material, the feed liquid flows in a zigzag pattern avoiding the net intersections, which inevitably increases pressure loss. . One way to reduce pressure loss is to widen the pitch, but if the pitch is made too large, it causes polarized flow, causing concentration polarization, where the concentration locally becomes high in areas where it is difficult for the liquid to flow, and this has the disadvantage of reducing separation performance. Another method is to increase the thickness of the net. Net thickness is 13 strands
The thickness at the intersection of the strands 13 and 14 is usually smaller than twice the strand diameter because the strands 13 and 14 are bonded in a melted state immediately after spinning in the net manufacturing process. Therefore, the actual opening through which the liquid flows is the area obtained by subtracting the strand diameter from the intersection thickness, so the opening area does not increase simply in proportion to the net thickness. In addition, although increasing the thickness of the net will reduce the pressure loss to some extent, the amount of liquid separation membrane filled will be reduced by the thicker net, and the membrane area will also be reduced, allowing the liquid to be separated from a liquid separation element of a predetermined size. quantity or decrease.

In addition, the increased net thickness increases the net rigidity, resulting in disadvantages such as deterioration of workability in the liquid separation element manufacturing process. Furthermore, since the net edges of conventional nets are sharp, the net edges often damage the liquid separation membrane during the liquid separation element assembly process. Therefore, protective tape is often attached to the surface of the liquid separation membrane where it comes into contact with NetEdge to protect the membrane.

An object of the present invention is to solve the above-mentioned conventional problems and provide a liquid separation element having a feed liquid channel material that reduces pressure loss and causes 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 separated liquid channel material, and a second liquid are arranged around a hollow central tube having holes on its surface. A liquid separation element formed by winding a single or double unit consisting of a separation membrane and a feed liquid channel material, characterized in that the feed liquid channel material is a net made of raschel knitting. , and (2) the liquid separation element described in (1) above, characterized in that the feed liquid channel material is a film having uneven grooves on the surface instead of a raschel knitted net. It is something to do.

This will be explained in detail below.

In contrast to conventional feed liquid channel materials in which the feed liquid flows in a zigzag pattern, the channel material of the present invention is characterized in that the feed liquid flows straight and uniformly. In other words, the feed liquid channel material of the present invention is made of a raschel knitted net and is arranged so that the feed liquid is supplied in the weaving direction of the net. The pitch of the weft yarn bundles constituting the sinker loop portion of the raschel knitted net is particularly preferably 2 mm or more and 10 mm or less, preferably 3 mm to 6 mm, in the knitting direction. This is because when the thickness is less than 2 mm, the number of times the supply liquid is disturbed by the weft yarn bundle increases, resulting in a large pressure loss. If it is larger than 10 mm, the net will lose its rigidity and become unusable. Further, the thickness obtained by subtracting the thickness of the sinker loop from the thickness of the needle loop is 0.2 mm to 1. ．． The pitch of the needle loop part minus the width of the needle loop part is preferably 2 mm to 1.0 mm, preferably 3 mm to 7 m.
M is good. Because the above thickness is less than 0.2mm and the width is 2
If the thickness is less than 1 mm, the effect of reducing pressure loss will be reduced, and the thickness will be less than 1. This is because if the width exceeds 10 mm, 0 mm, or 10 mm, drifting occurs and the separation performance deteriorates. As the thread material, polyethylene or vinyl thread is preferable since it is preferable to use a material that does not scratch the membrane, and the thread diameter is preferably 0.1 to 0.5 mm in order to satisfy the above requirements.

What is a net made of raschel knitting here?■ A net made by warp knitting using a raschel knitting machine, as described in the well-known literature such as ``Basic Knowledge of Russell'' published by Textile Journal Publishing and ``braiding'' by Jikkyo Publishing. says.

Next, as part of the present invention, a film having uneven grooves on its surface is also provided as a feed liquid channel material having the same effect as the above-mentioned Rassel knitted net. In other words, a film having uneven grooves on its surface is one in which continuous uneven grooves are formed on the surface of the film by a method such as embossing, laser processing, or etching. Specific shapes include those shown in FIGS. 1 to 3. As the material, polyester, polypropylene, etc. are preferable, and a stretched film is more preferable in terms of strength. The thickness is 100 μm to 30 μm in order to have uneven grooves with the above requirements and firmly maintain the groove shape.
0 lt m is preferred.

[Example Example 1, Comparative Example 1 A warp knitted net made of a raschel knitted net using polyethylene yarn with a wire diameter of 0.2 mm, a horizontal pitch of 5 mm x 5 mm, and a thickness of 0.8 mm was subjected to liquid separation. It was used as a supply liquid channel material of an element, and was arranged so that the direction of the recessed groove and the supply liquid supply direction were substantially aligned. That is, the arrangement was such that the liquid was supplied in the knitting direction (Example 1).

On the other hand, as Comparative Example 1, the conventional net has a pitch of 3°8mm x
A piece of 3.8 mm and 0.8 mm thick was used.

Table 1 summarizes the flow resistance values and separation performance results of the liquid separation element at that time. In other words, compared to when a conventional net was used, the separation performance of the net of the present invention did not change even if the supply amount was reduced, indicating that the flow was uniform with less uneven flow. Furthermore, it was confirmed that the pressure loss was reduced to approximately %.

Example 2 As shown in Fig. 1, the feed liquid channel material was 250 μm thick.
Groove width 5 mm, height 1 m on polyester stretched film
Table 2 shows the results of the same evaluation as in Example 1, using a channel material in which m triangular grooves were formed, and arranging the grooves so that the direction of the grooves roughly coincided with the supply liquid supply direction. As a result, similar to the Russell knitted net of Example 1, good results were obtained in terms of pressure loss and displacement performance.

[Effects of the Invention] By providing the feed liquid channel material of the present invention, the following effects can be achieved.

(1) The pressure loss of the liquid molecular device could be reduced to 1.

(2) Pressure loss is 1. Even at low flow rates, we were able to obtain good separation performance even at low flow rates without causing drift.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a film schematically showing an example of the groove shape of a film having uneven grooves on its surface, which is preferable as a feed liquid channel material of a liquid separation element of the present invention, and the cross-sectional direction is The direction is perpendicular to the direction. FIG. 2 is a cross-sectional view of a film schematically showing another example of the groove shape of a film having uneven grooves on its surface, which is preferable as a feed liquid channel material of a liquid separation element of the present invention, and the cross-sectional direction is The direction is perpendicular to the groove direction. FIG. 3 is a cross-sectional view of a film schematically showing still another example of the groove shape of a film having uneven grooves on its surface, which is preferable as a feed liquid channel material of a liquid separation element of the present invention, and is a cross-sectional view of a film in the cross-sectional direction. is a direction perpendicular to the groove direction. FIG. 4 is an exploded view showing a conventional liquid separation element in a partially cut and unrolled state. FIG. 5 is a top view of a net that has been used for IH as a feed liquid channel material of a conventional liquid separation element. FIG. 6 is a sectional view in the direction A of FIG. 5. In the figure, a a b central hole, hole. First liquid separation membrane Second liquid separation membrane: Separated liquid channel material: Feed liquid channel material End plate End plate: Seal material: Feed liquid, separated liquid concentrate, filament winding, strand 1 and strand 2, respectively show.

Claims (2)

[Claims] (1) A single set of units including a first liquid separation membrane, a separated liquid channel material, a second liquid separation membrane, and a supply liquid channel material around a hollow central tube with holes on its surface. Alternatively, a liquid separation element formed by winding multiple sets, wherein the supply liquid channel material is a net made of raschel knitting. (2) The liquid separation element according to claim (1), wherein the feed liquid channel material is a film having uneven grooves on the surface instead of a raschel knitted net.