JP2020138196A - Separation membrane element - Google Patents

Abstract

To provide a separation membrane element allowing for materialization of a stable and highly reliable separation operation even in operation under high pressure.SOLUTION: The separation membrane element is provided that includes a water collection pipe and a separation membrane leaf. The separation membrane leaf is wound around the circumference of the water collection pipe, the separation membrane leaf is composed of a separation membrane pair in which a surface A1 of a separation membrane and a surface A2 of the separation membrane are arranged opposite to each other and a plurality of sheet-shaped materials arranged between the surface A1 of the separation membrane and the surface A2 of the separation membrane, the sheet-shaped material has smooth surface and/or a projection formation surface with projections formed thereon, the surface A1 and the surface A2 are in contact with the smooth surface, the projection formation surfaces are opposite to each other and, upon observation from a thickness direction of the separation membrane pair, the separation membrane element has such a portion that longitudinal directions of the projections intersect each other.SELECTED DRAWING: Figure 3

Description

The present invention relates to a separation membrane element.

In the technique for removing ionic substances contained in seawater and brackish water, the use of the separation method using a separation membrane element has been expanding in recent years as a process for energy saving and resource saving. Separation membranes used in the separation membrane element separation method are classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes in terms of their pore size and separation function. These separation membranes are used, for example, for the production of drinking water from seawater, brackish water, water containing harmful substances, etc., the production of industrial ultrapure water, wastewater treatment, and recovery of valuable resources. It is used properly according to the separation component and separation performance.

There are various forms of the separation membrane element, but they are common in that raw water is supplied to one surface of the separation membrane and permeated water is obtained from the other surface. Since the separation membrane element includes a large number of bundled separation membranes, the membrane area per separation membrane element is large, that is, the amount of permeated water obtained per separation membrane element is large. It is formed to be. As the separation membrane element, various shapes such as a spiral type, a hollow fiber type, a plate and frame type, a rotary flat membrane type, and a flat membrane integrated type have been proposed according to the application and purpose.

For example, spiral separation membrane elements are widely used for reverse osmosis filtration. The spiral type separation membrane element includes a water collecting pipe and a separating membrane leaf surrounded by the water collecting pipe. The separation membrane leaf is a supply-side flow path material that supplies raw water to the surface of the separation membrane, and / or the separation membrane that separates the components contained in the raw water and the permeated water that permeates the separation membrane and is separated from the raw water to the water collection pipe. The permeation side flow path material for guiding the above is formed by laminating. The spiral type separation membrane element is preferably used because it can apply a high pressure to the raw water and can take out a large amount of permeated water.

However, when a high pressure is applied to the raw water, not only stress is applied to the permeation side flow path material that supports the separation membrane, but also the separation membrane falls between the permeation side flow path materials, and the separation membrane is damaged or damaged. , The problem that the permeation side flow path is blocked occurs. In order to suppress such a problem, a plurality of permeation side flow path materials are arranged to widen the permeation side flow path (Patent Document 1), or a smooth sheet is sandwiched between the separation membrane and the permeation side flow path material (Patent Document 1). Techniques such as Patent Document 2) have been devised.

Special Table 2015-064752 Japanese Unexamined Patent Publication No. 09-141067

However, with the conventional technology, the reliability in operation under high pressure is still insufficient, and the risk of the above-mentioned problems becoming apparent has not been eliminated.

Therefore, an object of the present invention is to provide a separation membrane element capable of realizing a stable and highly reliable separation operation even in operation under high pressure.

In order to achieve the above object, the present invention includes a water collecting pipe and a separation membrane leaf, and the separation membrane leaf is surrounded around the water collecting pipe, and the separation membrane leaf is a separation membrane. the surface a _1, and the surface a ₂ of the separation membrane, are arranged so as to face each other, and the separation membrane pair, disposed between the surface a ₁ and the surface a _2, a plurality of sheet-like material If made, the sheet-like material, smooth surface and / or projections forming surface projections are formed, have, the surfaces a ₁ and the surface a ₂ is in contact with the smooth surface, Provided is a separation membrane element having a portion where the protrusion forming surfaces face each other and the longitudinal directions of the protrusions intersect when observed from the thickness direction of the separation membrane pair.

According to the present invention, blockage of the permeation side flow path can be effectively suppressed even in operation under high pressure, and a stable and highly reliable separation operation can be achieved.

It is a schematic diagram which shows one aspect of the sheet-like material provided in the separation membrane element of this invention. It is a schematic diagram which shows another aspect of the sheet-like material provided in the separation membrane element of this invention. It is a developed perspective view which shows one aspect of the separation membrane element of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

The separation membrane element of the present invention includes a water collecting pipe and a separation membrane leaf, and the separation membrane leaf is surrounded by the water collecting pipe.

FIG. 3 is a developed perspective view showing one aspect of the separation membrane element of the present invention. In the separation membrane element 5 in FIG. 1, a separation membrane in which a supply-side flow path material 1 and a separation membrane 2 which are sheet-like materials and a transmission-side flow path material 3 which is a sheet-like material are laminated around a water collecting pipe 4. The reef is surrounded.

The water collecting pipe included in the separation membrane element of the present invention is a hollow tubular member and has a plurality of holes on its side surface. Examples of the material of the water collecting pipe include resin and metal, but resins such as noryl resin, modified polyphenylene ether resin, and ABS resin are preferable because of their excellent cost and durability.

Separation membrane leaf separation membrane element of the present invention is provided has a surface A ₁ of the separation membrane, and the surface A ₂ of the separation membrane, are arranged so as to face each other, and the separation membrane pair, the surfaces A ₁ and the It disposed between the surface a _2, a plurality of sheet-like material, consisting of.

The type of the separation membrane constituting the separation membrane leaf included in the separation membrane element of the present invention may be appropriately selected according to the separation target, for example, a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane or a microfiltration membrane. Examples of the reverse osmosis membrane include a composite semipermeable membrane including a base material, a porous support, and a separation functional layer.

Examples of the above-mentioned base material include fabrics containing polyester or aromatic polyamide as a main component.

Examples of the porous support include polysulfones, polyether sulfones, polyamides, polyesters, cellulose-based polymers, vinyl polymers, polyphenylene sulfides, polyphenylene sulfide sulfones, polyphenylene sulfones, and polyphenylene oxides formed on a substrate. A polymer layer can be mentioned.

Examples of the above-mentioned separation function layer include a separation function layer containing polyamide as a main component, which is dense enough to sufficiently separate ions and the like and has a high affinity with water. The separation functional layer containing polyamide as a main component can be formed, for example, by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide.

The above-mentioned separation membrane pair may be formed by combining two separation membranes independent of each other, may be formed by folding one separation membrane, or may surround one separation membrane. when, the surface a ₁ of the separation membrane, and a surface a ₂ of the separation membrane, may be formed by Maki囲while facing each other.

Sheet material constituting the separation membrane leaf separation membrane element of the present invention is provided is between the surface A ₁ and the surface A _2, the plurality are arranged so as to be sandwiched. The ends of the separation membrane sandwiching the sheet-like material are appropriately sealed. Examples of the "sealing" method include bonding with an adhesive or hot melt, fusion with heating or laser, or sandwiching a rubber sheet. Sealing by simple bonding is possible. preferable.

Sheet material in the flow path formed in the gap between the surface A ₁ and the surface A _2, but is intended to function as a so-called feed-side passage material or permeation-side passage material, the specific Such embodiments include porous sheets such as nets, tricots, non-woven fabrics or films.

Sheet material constituting the separation membrane leaf separation membrane element of the present invention is provided, the smooth surface and / or projections are protrusions formed surface formed has, the surfaces A ₁ and the surface A ₂ is It needs to be in contact with the smooth surface. That is, it is necessary that at least one of the plurality of sheet-like materials constituting the separation membrane leaf included in the separation membrane element of the present invention has a smooth surface.

Here sheet material has a "smooth surface" is the average height difference of the surface of the sheet material in the opposing direction of the said surface A ₁ and the surface A ₂ is refers to the surface is within 20 [mu] m. The average height difference between the surface of the sheet-like material, the cross section of the sheet material in the opposing direction of the said surface A ₁ and the surface A ₂ (hereinafter, "cross-sectional C") was observed with a microscope, the surface of interest The height difference of 30 randomly selected points is measured, and the average value is used.

On the other hand, the "projection-forming surface" of the sheet-like material means a surface other than the above-mentioned "smooth surface" and a surface on which protrusions are formed. The term "projection" as used herein refers to a portion where the maximum height difference in the cross section C is 50 μm or more.

For example, when raw water is supplied to the separation membrane leaf surrounded by the separation membrane element and a high pressure is applied, the separation membrane falls into the difference in height between the flow path materials or the surface of the flow path material, and the flow path is blocked. It contributes to being done. The separation membrane element of the present invention contrast, the sheet-like material has a very small smooth surface height difference, by being placed in contact respectively with the surfaces A ₁ and the surface A _2, under high pressure It is possible to significantly suppress the depression of the separation membrane.

On the other hand, a plurality of sheet-like material disposed between the surfaces A ₁ and the surface A ₂ are those of the projections formed faces face each other, and the separation membrane pairs in the thickness direction (i.e., the when viewed from the opposing direction) of the surface a ₁ and the surface a _2, the projections each other, each longitudinal is required to have a portion in contact so as to intersect. By adopting such a configuration, not only the deformation of the sheet-like material is significantly suppressed by the appropriate contact between the protrusions, but also the blockage is less likely to occur, and a wider flow path can be secured. The angle at which the protrusions come into contact with each other so that their longitudinal directions intersect is preferably 80 to 100 °, more preferably 85 to 95 °. The angle at which the longitudinal directions of the protrusions intersect means the angle of the acute angle and the obtuse angle formed by the intersection of the longitudinal directions of the protrusions, including the direction perpendicular to the longitudinal direction of the water collecting pipe.

As a mode for opposing the protrusions forming surfaces of the sheet material, one side only two sheet-like material projections forming surface (the other surface smooth surface), and the surface A ₁ and the surface A ₂ It may be arranged between them so that the projection forming surfaces face each other, and one or more sheet-like materials having protrusion forming surfaces on both sides or one side are arranged between such two sheet-like materials. It doesn't matter.

Separation membrane drop between the flow path member under high pressure, the separation membrane is damaged, or because the problem permeation-side passage is closed, tends to occur particularly in the permeation-side passage, the surfaces A ₁ and the surface When A ₂ is the surface on the transmission side, the separation membrane element of the present invention can more preferably exert its effect.

If the surface A ₁ and the surface A ₂ is a surface of the permeate side, the feed-side passage to arranged the passage materials, other than the sheet-like material constituting the separation membrane leaf separation membrane element of the present invention comprises Materials may be used. Examples of such a material include a net, an uneven sheet, and a protrusion directly fixed to the surface of the separation membrane on the transmission side. Further, as the material of such a material, a thermoplastic resin that can be easily molded is preferable, and polyethylene or polypropylene is more preferable because it is inexpensive and does not easily cause damage to the separation membrane.

In the case the surface A ₁ and the surface A ₂ is a surface of the permeate side, the resistance of the permeation-side passage since it is possible considerably suppressed, the thickness of the supply-side flow path (the thickness of the supply-side passage material) Even if the thickness is reduced, the amount of water produced by the separation membrane element can be maintained at a high level, and the number of separation membrane leaves that can be filled in the separation membrane, that is, the membrane area per separation membrane element can be increased. it can.

As the mode of the protrusions formed on the sheet-like material constituting the separation membrane leaf included in the separation membrane element of the present invention, for example, a dot shape as shown in FIG. 1 or a stripe shape as shown in FIG. 2 is used. Can be mentioned. The thickness H0 of the sheet-like material exemplified in FIG. 1 or FIG. 2 can be measured by observing the sheet-like material with a microscope. Note thickness H0 of the sheet-like material is a thickness in the opposing direction between the surface A ₁ and the surface A _2. In particular, the striped shape is preferable because the protrusions can secure a wide flow path when the protrusion forming surfaces face each other.

The maximum height difference of the protrusions formed on the sheet-like material exemplified in FIG. 1 or FIG. 2, that is, the height H1, needs to be 50 μm or more as described above, but the thickness of the permeation side flow path (permeation). In order to reduce the thickness of the side flow path material and increase the membrane area per separation membrane element, it is preferably 800 μm or less. Further, the distance between the plurality of protrusions formed on the sheet-like material exemplified in FIG. 1 or FIG. 2, that is, the groove width D is 0.02 to 0.80 mm in order to maintain an appropriate space as a flow path. It is preferable to have. The height H1, the groove width D, the groove length E, and the length of the protrusion in the longitudinal direction, that is, the length X of the protrusion are measured by observing the sheet-like material with a microscope. be able to. Note the height H1 of the projections is the length in the opposing direction between the surface A ₁ and the surface A _2, said groove width D, the length X of the groove length E and projections, said It is the length in the direction perpendicular to the facing direction between the surface A ₁ and the surface A ₂ .

The maximum length in the direction perpendicular to the longitudinal direction of the protrusions formed on the sheet-like material exemplified in FIG. 1 or FIG. 2, that is, the width W of the protrusions, keeps an appropriate space as a flow path. In order to maintain the shape of the protrusion even under high pressure, 0.1 to 1.0 mm is preferable, and 0.3 to 0.7 mm is more preferable. The width W of the protrusions can also be measured by observing the sheet-like material with a microscope.

Examples of the method of forming the protrusions on the sheet-like material included in the separation membrane element of the present invention include a method of discharging the molten resin onto the surface of the sheet-like non-woven fabric into a predetermined shape to solidify the resin. Further, the surface of the non-woven fabric, film or the like may be unevenly molded by embossing or imprinting to form protrusions.

(Adhesion of protrusions to the permeable side surface of the separation membrane)
The molten resin may be discharged into a predetermined shape on the permeable side surface of the separation membrane to be solidified. In this case, since the sheet-like material is not required, the protrusions can be increased by the thickness of the sheet-like material, and the permeation-side flow path can be widened to further improve the water-forming property of the element. That is, if the projections are formed on the surface A ₂ of surface A ₁ and the separation membrane of the separation membrane, without arranged a plurality of sheet-like material between the surfaces A ₁ and the surface A ₂ passage Can be stably secured and water production can be enhanced.

The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

(Shape of sheet material)
The thickness H0 of the sheet-like material and the height H1, width W, length X, groove width D, and groove length E of the protrusions formed on the sheet-like material make the sheet-like material a microscope (Keyence). It was observed and measured with a high-precision shape measuring system KS-1100) manufactured by Mfg. Co., Ltd.

(Judgment of smooth surface / protrusion forming surface)
The cross section C of the sheet-like material is exposed, and the cross section C is observed with a microscope (manufactured by KEYENCE; one-shot 3D measurement macroscope (VR-3000)) under the following conditions to form a smooth surface / protrusion. The surface was judged.

Measurement magnification: 40 times Measurement range: 5 mm x 5 mm
Filter: Gaussian termination effect correction: Effective S filter: None L filter: 0.8 mm
(Amount of water production)
For the separation membrane element, a NaCl aqueous solution having a pH of 6.5 and 10.6% by mass was used as raw water, and after operating for 15 minutes under the conditions of an operating pressure of 12.5 MPa and a temperature of 25 ° C., permeated water was sampled for 1 minute. The sampling amount was converted into the permeated water amount (gallon) per day and expressed as the water production amount (GPD (gallon / day)).

(Recovery rate)
In the measurement of the fresh water amount, the raw water volume V _F supplied to the predetermined time, the transmission amount of water at the same time as the V _P, and the recovery rate is calculated the value of V P _/ V _F × 100.

(TDS removal rate)
For raw water used for 1-minute sampling and sampled permeated water in the measurement of water production, the concentration of total dissolved solids (hereinafter, "TDS") was measured by conductivity measurement, and the TDS removal rate was calculated from the following formula. did.

TDS removal rate (%) = 100 × {1- (TDS concentration in permeated water / TDS concentration in raw water)}
(Preparation of sheet-shaped material A)
Using an applicator loaded with a comb-shaped shim with a slit width of 0.4 mm and a pitch of 0.8 mm, while adjusting the temperature of the backup roll to 20 ° C., the surface of the non-woven fabric having a thickness of 0.06 mm and a grain size of 32 g / m ² is high. A composition pellet composed of 60% by mass of crystalline polypropylene (MFR 1000 g / 10 minutes, melting point 161 ° C.) and 40% by mass of low stereoregular polypropylene (manufactured by Idemitsu Kosan Co., Ltd .; L-MODU · S400) at a resin temperature of 205 ° C. A sheet-like material A was prepared by applying in a striped shape composed of a plurality of straight lines under the condition of a traveling speed of 10 m / min.

(Preparation of sheet-shaped material B)
A sheet-like material B having imprint processing and CO ² laser processing on the surface of an unstretched polypropylene film (manufactured by Toray Industries, Inc .; Trefan (registered trademark)) and having striped protrusions and through holes consisting of a plurality of straight lines. Was produced.

In the above imprinting process, an unstretched polypropylene film was sandwiched between metal dies having grooves formed by cutting, held at 140 ° C./15 MPa for 2 minutes, cooled to 40 ° C., and then taken out of the die.

Further, as the above-mentioned CO ² laser processing, a 3D-Axis CO ² laser marker (MLZ9500) is used to perform laser processing from the smooth surface of the sheet-like material to the recesses between the striped protrusions on the protrusion forming surface. Then, a through hole was provided.

(Example 1)
A 15% by mass dimethylformamide solution of polysulfone was cast at room temperature (25 ° C.) to a thickness of 180 μm on a non-woven fabric (porosity 1.0 cc / cm ² / sec) made of polyester fibers manufactured by the papermaking method, and immediately. It was immersed in pure water and left to stand for 5 minutes to prepare a porous support having a porous support layer formed on a substrate.

The porous support was immersed in an aqueous solution in which 2-ethylpiperazine was 2.0% by mass, sodium dodecyldiphenyl ether disulfonate was 100 ppm, and trisodium phosphate was 1.0% by mass for 10 seconds. Nitrogen was blown from the air nozzle to remove excess aqueous solution from the surface of the porous support. Subsequently, a 0.2% by mass n-decane solution of trimesic acid chloride heated to 70 ° C. was uniformly applied to the surface of the porous support, held at a film surface temperature of 60 ° C. for 3 seconds, and then the film. The surface temperature was cooled to 10 ° C. and left as it was in an air atmosphere for 1 minute to form a separation functional layer, which was then held vertically and drained. The obtained separation membrane was washed with pure water at 60 ° C. for 2 minutes.

The separation membrane thus obtained is cut and folded so that the surfaces on the supply side are on the inside, and a net (thickness 0.52 mm, pitch 2.2 mm × 2.2 mm) is passed between them. It was placed as a road material. Sheet-like materials I and II shown in Table 1 were arranged on the surface (transmission side surface) of the separation membrane so that the protrusion forming surfaces face each other as the permeation side flow path material.

This was wound around a stainless steel water collecting pipe (width: 1000 mm, diameter: 18 mm, number of holes 40 x linear 1 row) in a spiral shape, and finally edge cuts at both ends were performed to prepare a separation membrane element. ..

The prepared separation membrane element was placed in a pressure vessel, and the amount of water produced and the TDS removal rate were evaluated under the condition of a recovery rate of 5%. The results were shown in Table 1.

(Examples 2 to 7)
The separation membrane element was prepared in the same manner as in Example 1 except that the sheet-like material was as shown in Table 1.

When the prepared separation membrane element was placed in a pressure vessel and evaluated under the same conditions as in Example 1, the results were as shown in Table 1.

(Example 8)
The separation membrane element was provided in the same manner as in Example 1 except that a sheet-like material was not used as the transmission side flow path material but was provided on the transmission side surface of the separation membrane and the height of the protrusion was 0.3 mm. Made.

When the prepared separation membrane element was placed in a pressure vessel and evaluated under the same conditions as in Example 1, the results were as shown in Table 1.

(Comparative Examples 1 to 3)
The separation membrane element was prepared in the same manner as in Example 1 except that the sheet-like material was as shown in Table 1.

When the prepared separation membrane element was placed in a pressure vessel and evaluated under the above conditions, the results were as shown in Table 1.

In Comparative Examples 1 to 3, since any of the permeation-side surfaces of the separation membrane pair was not in contact with the smooth surface of the sheet-like material, the separation membrane fell between the flow path materials under high pressure, and the permeation-side flow path was formed. Clogged and the amount of water produced decreased significantly.

The separation membrane element of the present invention can be suitably used for the treatment of industrial water, etc., in addition to desalting seawater, brackish water and tap water.

1 Supply side flow path material 2 Separation film 3 Permeation side flow path material 4 Water collecting pipe 5 Separation film element 6 Protrusions 7 Recesses 8 Sheet-like material D Groove width E Groove length H0 Sheet-like material thickness H1 Sheet-like material protrusions Height of object W Width of protrusion of sheet-like material X Length of protrusion of sheet-like material

Claims (3)

Equipped with a water collection pipe and a separation membrane leaf,
The separation membrane leaf is surrounded around the water collecting pipe.
The separation membrane leaf, the surface A ₁ of the separation membrane, and the surface A ₂ of the separation membrane, are arranged so as to face each other, and the separation membrane pair, between the surface A ₁ and the surface A ₂ Consists of multiple sheet-like materials arranged,
The sheet-like material has a smooth surface and / or a protrusion-forming surface on which protrusions are formed.
The surface A ₁ and the surface A ₂ are in contact with the smooth surface.
The protrusion forming surfaces face each other and
A separation membrane element having a portion where the protrusions come into contact with each other so that their longitudinal directions intersect when observed from the thickness direction of the separation membrane pair. The separation membrane element according to claim 1, wherein the surface A ₁ and the surface A ₂ are surfaces on the transmission side. Equipped with a water collection pipe and a separation membrane leaf,
The separation membrane leaf is surrounded around the water collecting pipe.
The separation membrane leaf, the surface A ₁ of the separation membrane protrusion is formed, likewise the surface A ₂ of the separation membrane protrusion is formed is disposed so as to face each other, made from the separation membrane pairs ,
A separation membrane element having a portion where the protrusions come into contact with each other so that their longitudinal directions intersect when observed from the thickness direction of the separation membrane pair.