JPH0747112B2 - Spiral type liquid separation element - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a spiral type liquid separation element, and more specifically, the structure of a permeate side flow path member which is one of the members of the spiral type liquid separation element. And regarding the improvement of the material.

[Prior Art] Conventionally, a spiral type liquid separation element has mainly used a reverse osmosis membrane or an ultrafiltration membrane. The spiral type liquid separation element using a general reverse osmosis membrane has a first semipermeable membrane and a permeate side flow path around a central tube where a large number of water collecting holes are arranged in a row in the axial direction of the tube. The material, the second semipermeable membrane, and the supply liquid side flow path material are wound around a single set or multiple sets of units. In liquid separation using a reverse osmosis membrane, a pressure difference is usually applied between the feed liquid side and the permeate side in order to improve the separation performance of the reverse osmosis membrane and allow the processing fluid to flow smoothly. cm ²
Operating pressure of about 60 kg / cm ² is applied,
Among the above-mentioned flow channel materials, particularly the permeate side flow channel material, retains the membrane without impairing the function of the reverse osmosis membrane against operating pressure,
Rigidity is required to properly hold the permeate flow path. In addition, in order to improve the separation performance of the reverse osmosis membrane, it is desirable that the resistance of the flow path formed by the permeate-side flow path material be suppressed to a minimum. In order to reduce the flow path resistance, it is necessary to increase the open area ratio of the flow path material in the cross section in the flow path direction. In order to increase the membrane packing density, it is basically desirable for the channel material to be as thin as possible, but this conflicts with the requirement for low channel resistance. It is set to the optimum thickness.

In response to such characteristics, a knitted fabric is used as the permeate-side flow path material of the conventional spiral type liquid separation element using a reverse osmosis membrane, and a typical example is a tricot knitted fabric in which a polyester fiber is knitted with a double Denbi structure. Is hardened by resin impregnation or heat fusion processing, or the tricot knitted fabric is further calendered to have a smooth surface, and a thickness of about 0.2 to 0.3 mm is generally used (for example, Japanese Patent Publication No. 62-35802). FIG. 3 shows a cross-sectional view of the tricot knitted fabric 4a as the permeate side flow path material. A groove 8 which is a flow path for the permeated liquid and a projection 9 for holding the reverse osmosis membrane and securing the flow path are formed on the surface thereof.

In recent years, as the degree of integration of semiconductors has increased, the required water quality of ultrapure water used as cleaning water has become strict. Fifth
The figure shows a general ultrapure water production system. In the primary pure water system (11 to 19), the coagulant 11 and the bactericide 12 are injected into the raw water, the sand is filtered 13 and the liquid separator 16 using the reverse osmosis membrane is used.
And the ion-exchange resin tower 19 to obtain primary pure water. In the secondary pure water system (20 to 23, also called subsystem), the primary pure water is sterilized by ultraviolet light 21 and then treated by the polisher 22 (ion exchange treatment), and then the module 23 using the ultrafiltration membrane. By processing at, ionic substances, TOC, fine particles, etc. are eliminated and ultrapure water is produced.

In order to satisfy the required water quality of ultrapure water, which is becoming more stringent with the increasing integration of semiconductors, recently, a liquid separation device using a reverse osmosis membrane has been used in place of the ultrafiltration membrane in the subsystem immediately before the point of use. Is being considered.

In this case, not only the separation performance, which is a required characteristic of the spiral type liquid separation device using a reverse osmosis membrane, but also the elution of ionic substances and TOC components from the device itself, and the removal of fine particles, etc. It is important that no abnormal retention of liquid occurs inside the liquid separation element.
In order to satisfy these characteristics, the member that comes into contact with the permeated liquid in the liquid separation element is made of a material with very little elution of ionic substances and TOC components, and has a structure that does not drop out fine particles or have abnormal retention parts. There is a need. Examples of the member that comes into contact with the permeated liquid include the above-mentioned permeated liquid-side channel material. The tricot knitted fabric of polyester fiber that has been used in the past has been subjected to heat-sealing and calendering, so fine particles and TOC satisfy the water quality within the range of the current measurement technology, but have higher sensitivity. There was a problem with the specific resistance, which is a water quality indicator for ionic substances. That is, although the elution of the ionic substance is small from the initial stage, this elution rate is maintained for a long period of time, and an abnormal retention part is generated in the permeated liquid channel. Therefore, the cleaning property of the member was also very inefficient. Moreover, even if the conventional spiral type liquid separation element using this flow path material is used and treated with ultrapure water as the feed water, the specific resistance of the permeated liquid is greatly increased to reach the level of the feed water. It took a long time, and the so-called rising characteristics were extremely poor. Poor rising characteristics lead to a decrease in water yield, which in turn increases the production cost of ultrapure water.

Here, the abnormal retention portion of the tricot will be described with reference to the drawings. FIG. 2 is a plan development view of one embodiment of the first semipermeable membrane 2, the permeate-side channel material 4 (tricot knitted fabric), and the second semipermeable membrane 3 attached to the central tube 1. In the process of manufacturing the spiral type liquid separation element, the first and second semipermeable membranes are opened only in the central tube 1, and the other three sides are sealed with the adhesive 6 to form an envelope. Since it is wrapped around the central tube before the resin hardens, the adhesive width near the central tube becomes wider. FIG. 3 is a sectional view taken along line XX in FIG. As shown in the figure, water flows well in the groove direction of the tricot knitted fabric (toward the central tube), but there is more than 10 times the resistance in the direction perpendicular to the groove. Therefore, when the permeate collected in the central tube through the tricot groove blocks the flow path with the adhesive as described above, the entire area becomes the abnormal retention section 7 as shown in FIG. . Due to the above-mentioned phenomenon, the effective membrane area of the spiral type liquid separation element becomes smaller than the actual membrane area (adhesive uncoated part) in addition to the decrease of the specific resistance, which reduces the amount of permeated liquid. However, it was feared that the microorganisms would propagate in the abnormal retention area.

[Problems to be Solved by the Invention] In order to improve the defects of the prior art as described above, the present invention uses a mesh-shaped woven net as the permeate-side channel material to improve the internal permeate-side channel material. Eliminates abnormal stagnation areas, exhibits excellent performance in resistivity, TOC, and rising characteristics of fine particles in the ultrapure water subsystem, and exhibits and maintains excellent separation performance for a long period of time without damaging the reverse osmosis membrane. The present invention is intended to provide a spiral type liquid separation element that can be used.

[Means for Solving the Problem] The present invention is directed to a first semipermeable membrane, a permeated liquid channel material, a second semipermeable membrane, and a supply liquid channel around a hollow central tube having a hole on the surface. In a spiral type liquid separation element formed by winding a single set or a plurality of sets of units, the permeated liquid flow path material of the unit has a thickness of 0.1 to 2.0 mm and a mesh of 0.15 to 3.0 m.
The present invention relates to a spiral type liquid separation element characterized by using a net made of a mesh plain plain fabric of m.

Any net may be used as long as it is a mesh-shaped woven fabric, but a sieve net (bolting cloth), and / or a filter cloth (filter cloth) and the like are preferable.

The woven fabric structure of the net may be any structure as long as it has a structure that secures a flow path for the permeated liquid and that the permeated liquid is dispersed and flows in all directions, but a plain weave structure is required. There is.

The material (fiber) of the woven fabric may be any as long as it has a mechanical strength sufficient to maintain the shape against an operating pressure, but preferably, a polyamide fiber (nylon, etc.), a polyester fiber, a poly fiber. Acrylonitrile fiber, polyolefin fiber such as polyethylene and polypropylene, polyvinyl chloride fiber, polyvinylidene chloride fiber, fluorine fiber (polyfluoroethylene fiber, etc.),
Carbon fiber etc. are mentioned. Especially when the liquid separation element is applied to the ultrapure water subsystem, low elution of ionic substances and organic substances and heat resistance sufficient to withstand hot water sterilization are taken into consideration in consideration of the resistivity and the rising characteristics of TOC. Polypropylene fiber and / or fluorine-based fiber are more preferable in consideration of the possession and economy.

The type of thread is generally a multifilament, a monofilament, or a mixture of both, but when applied to an ultrapure water subsystem, a monofilament is more preferable in consideration of cleaning efficiency of members and rising characteristics of fine particles.

Next, a detailed description will be given with reference to the drawings. FIG. 4 is the same as FIG. 3, showing the first semipermeable membrane 2 attached to the central tube 1, the permeate flow path material 4b (monofilament plain weave net), and the second semipermeable membrane 3 of FIG. A cross-sectional view in the XX direction as shown in FIG.

The thickness a of the net is determined by the thickness b of the monofilament, and can be arbitrarily set by changing the thickness b of the monofilament. The mesh (pitch) c can be set arbitrarily,
The minimum value of the mesh size is limited by the rigidity of the fiber and the thickness b of the monofilament.

The net thickness a, monofilament thickness b, and filament mesh c are set according to the operating conditions of the element (operating pressure, amount of water produced), the rigidity or mechanical strength of the monofilament, the flow path resistance depending on the fabric structure, etc. It is also necessary to consider that the membrane packing density and the function of the semipermeable membrane can be maintained and the permeate flow channel can be stably maintained for a long period of time. Considering the above-mentioned required functions, the net used for the spiral type liquid separation element used in the ultrapure water subsystem has a net thickness a of 0.1 to 2.0 mm and a filament mesh c of 0.15 to
It should be in the range of 3.0 mm.

Since the net made of mesh-shaped fabric has the above-mentioned advantages, it is possible to provide a liquid separation element having an extremely excellent start-up characteristic in an ultrapure water subsystem, and at the same time, a conventional spiral type liquid separation element can be provided. It is possible to improve the separation performance and durability of the device and to facilitate the cleaning and sterilization of the device.

[Example] Example 1 A net having a thickness of 0.2 mm and a monofilament mesh of 50 x 50 Mesh / inch, in which a monofilament made of polypropylene as a raw material was plain-woven, was used as a comparative example from the past as a permeate side flow path material. A multi-filament of polyester fiber was knitted into a double-denbi structure, and a tricot knitted fabric, which was hardened by heat treatment, was further calendered to produce a spiral type liquid separation element with an outer diameter of 4 inches. In the ultrapure water production system shown in FIG. 5, a spiral type liquid separation device was installed after the polisher of the subsystem, and the rising characteristics of the specific resistance of the separation elements were compared. The specific resistance of supply water is 18.20M
Ω · cm, operating pressure 10kg / cm ² , temperature 25 ℃, water production 4T
Figure 6 shows the results of operation at a recovery rate of 90% / day. The spiral type liquid separation element manufactured using the conventional flow path material does not reach the level of the supply water even after operating for about 100 hours, and reaches a peak at 18,10 MΩ · cm. On the other hand, the spiral type liquid separation element manufactured by using the monofilament plain weave net for the flow path material reached the supply water level (18.20 MΩ · cm) 2 hours after the start of operation.
The start-up time has been greatly reduced. After a further 10 hours, the specific resistance of theoretical pure water reached 18.25 MΩ · cm.

Example 2 With respect to the permeate-side channel material used in Example 1, the flow resistance up to 300 hours was measured at a pressure of 15 kg / cm ² , and the results are shown in Table 1.
Shown in. Although the thickness of the flow path material of the tricot knitted fabric used conventionally is 0.25 mm and the thickness of the plain weave net is 20% thinner, the initial value of the flow resistance is 10%.
I was able to make it smaller. The rate of change in flow resistance after 300 hours is 5%, which is as durable as the tricot fabric.

Example 3 A spiral type liquid separation element was manufactured in the same manner as in Example 1, and the separation performance of 0.15% saline solution was compared at an operating pressure of 15 kg / cm ² and a temperature of 25 ° C. The results are shown in Table 2. The separation element using the plain weave net increased the amount of water produced by about 10% and improved the water quality of the permeate by about 40% compared to the one using the tricot knitted fabric.

[Effects of the Invention] The present invention has the following effects by improving the prior art as described above.

(1) The flatness of the surface of the flow path material is improved and the deformation of the membrane is suppressed to a minimum, so that the performance of the liquid separation element is prevented from deteriorating and the life is greatly extended.

(2) The flow channel material can be made thinner, and the film packing density can be increased accordingly, and by eliminating the decrease in the effective film area due to the spread of the adhesive, the liquid separation element per unit volume can be reduced. The amount of permeate increases.

(3) The rise characteristics when applied to the ultrapure water subsystem are extremely high due to the elimination of abnormal retention in the permeate side flow path and the use of low elution type fiber as the flow path material. It contributes to the improvement of water quality and yield of ultrapure water.

(4) By using a monofilament, it is possible to reduce the number of fine particles dropped when applied to the ultrapure water subsystem to below the detection limit value of the current measurement technology, and improve the water quality of ultrapure water. To do.

(5) Propagation of microorganisms in the permeate side channel can be prevented, and hot water sterilization and washing can be facilitated, and therefore, it can be suitably used in the food field.

The device according to the present invention can be applied not only to the spiral type liquid separation element applied to the ultrapure water subsystem but also to all spiral type liquid separation elements, and its application field is extremely wide.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a spiral type liquid separation element according to the present invention. FIG. 2 is a plan development view of an embodiment of a spiral type liquid separation element according to the prior art, showing an abnormal retention part of the conventional element. FIG. 3 is a cross-sectional view taken along the line XX in FIG. 2 in the case where a tricot knitted fabric is used as the permeate liquid flow path material in the liquid separation element according to the prior art. FIG. 4 shows the X of the liquid separation element when a monofilament plain weave net is used as the permeate liquid flow path material according to the present invention.
It is a -X sectional view. FIG. 5 is an example of a schematic diagram of an ultrapure water production system. FIG. 6 is a diagram showing the rising characteristics of the specific resistance in the ultrapure water subsystem of the spiral liquid separation element according to the present invention and the spiral liquid separation element according to the prior art. 1: Central tube, 1b: Water collecting hole, 2: First semipermeable membrane, 4: Permeate side flow path material, 4a: Tricot knitted fabric, 4b: Permeate flow path material, 5: Supply liquid side flow path Material, 6: Adhesive, 7: Abnormal retention area, 8: Groove, 9: Protrusion, 1
0: Textile, 11: Flocculant, 12: Bactericide, 13: Sand filter, 14: Security filter, 15: High pressure pump, 16: Liquid separator, 17: Permeate tank, 18: Degassing tower, 19: Ion Exchange resin tower, 20: 1 primary pure water tank

Claims (1)

[Claims] 1. A unit comprising a set of a first semipermeable membrane, a permeated liquid channel material, a second semipermeable membrane, and a supply liquid channel material around a hollow central tube having a hole on the surface. In a spiral type liquid separation element formed by winding a single set or multiple sets, the permeated liquid flow path material of the unit has a thickness of 0.1 to 2.0 mm and a mesh of 0.15 to 3.
A spiral type liquid separation element characterized by using a net made of 0 mm mesh plain weave fabric.