JP3105610B2 - Spiral type membrane separation module and its cleaning method. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spiral type separation membrane module capable of backwashing with a permeate.

[0002]

2. Description of the Related Art Separation membrane modules are used to separate a specific liquid from a solution, a specific gas from a mixed gas, a solid from a liquid or gas, a gas from a gas-containing liquid, and the like. Widely used.

[0003] Various types of separation membrane modules are used, and one type of the separation membrane module is a spiral type separation membrane module.

In this spiral-type separation membrane module, a sponge-like semipermeable membrane having a skin layer on the surface is formed in a envelope-like membrane with a backing of a support such as a nonwoven fabric, and a permeate passage is formed in the membrane envelope. The member is put in, the open end of this membrane envelope is communicated with the permeate collection tube, and the membrane envelope is wound around the permeate collection tube together with the stock solution passage member, the outside of the membrane envelope is used as the stock solution and the inside of the membrane envelope is permeated Liquid side.

[0005] Regarding the separation membrane module, regardless of the type, it is unavoidable that the permeation flow rate decreases with time due to clogging or the like, and it is necessary to recover the permeation performance by performing washing appropriately. It is.

[0006]

Conventionally, chemical cleaning is usually used for cleaning a spiral separation membrane module. However, in chemical cleaning, there is a concern that the membrane may be deteriorated, and it takes a long time to discharge the chemical after the cleaning and replace it with the undiluted solution, so that the operation of the separation membrane module must be stopped for a long time. . Further, there is an uneconomical effect that the drug is expensive and the washing cost is high.

However, in the cleaning of the hollow fiber membrane module, a so-called backwashing method is known in which the permeate in the permeate tank is pumped to the permeate side of the membrane. Problems such as the deterioration of the membrane, the long stoppage of the separation membrane module, and the cleaning cost can be solved.

However, according to the experimental results of the present inventors, when the spiral type separation membrane module is backwashed, peeling occurs between the semipermeable membrane and the support, and the membrane portion at the peeling position is reversed. The membrane is in an unsupported state with respect to the washing pressure, and damage to the membrane cannot be avoided.

The above-mentioned support is required by a tension member.
It has enough strength.

In the present inventor, however, the above support
Embed body in sponge layer, skin on back of sponge layer
If a layer or a dense layer is provided, even if a liquid pressure acts on the permeated liquid side, the support can effectively act as a tension member against the pressure, and the pressure between the semipermeable membrane and the support can be increased. It was experimentally confirmed that peeling could be prevented and backwashing with a permeate could be performed safely.

[0011] The object of the present invention is based on the above experimental results,
It is an object of the present invention to provide a spiral-type separation membrane module capable of backwashing with a permeate.

[0012]

Means for Solving the Problems The present invention first spiral membrane separation module according to - le embeds the support cloth sponge layer, the film having a skin layer on the support fabric on both sides of the sponge layer surface The configuration is characterized by being used. In another spiral type membrane separation module according to the present invention, a support cloth is embedded in a sponge layer, a skin layer is provided on the surface of the sponge layer in contact with the liquid to be treated, and the sponge layer is formed on the back of the sponge layer.
The structure is characterized in that a membrane provided with a dense layer having a smaller hole diameter than the hole diameter of the portion is used.

[0013]

The sponge layer can be present also on the back side of the membrane, and the sponge layer surface becomes sufficiently dense. Therefore, the liquid pressure can be sufficiently received also on the back side of the membrane, and the support acts as a tension member. Can be done. Therefore, backwashing can be performed while the membrane is held safely.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is an explanatory sectional view showing a film used in the present invention. In FIG. 1, reference numeral 1 denotes a sponge layer of a semipermeable membrane. Reference numeral 2 denotes a woven fabric embedded in a sponge layer, and the gap between the fibers is filled with a sponge-like substance 10 having a semipermeable membrane. 1
Reference numerals 1 and 12 denote sponge layer portions on both sides of the woven fabric 2, and the sponge layer 1 is composed of these portions 11, 12 and an intermediate portion 10 in which the woven fabric 2 is embedded. Reference numerals 31 and 32 denote skin layers formed on the surfaces of the sponge layer portions 11 and 12, respectively. The skin layer in contact with the permeated liquid may have a coarser density than the skin layer in contact with the undiluted solution.

FIG. 2 is a cross-sectional explanatory view showing another example of the membrane used in the present invention. The skin 33 is not formed on the surface 33 of the sponge layer portion 12 on the side in contact with the permeated liquid.
The pore diameter is made smaller than the inside of the sponge layer 1 so as to be sufficiently dense. In FIG. 2, the same reference numerals as those in FIG.
The same constituent elements as those of FIG.

In the embodiment using the membrane shown in FIG. 1, the membrane is formed into an envelope shape with the dense skin layer on the surface side, and the permeate passage member is placed in the envelope. Is connected to the permeate collection pipe, and the membrane envelope is wound around the permeate collection pipe together with the stock solution passage member, and has a stock solution inlet at one end and a stock solution outlet at the other end.
The above-mentioned wound membrane envelope is accommodated in a casing, and the end of the permeate collection pipe of the wound body is drawn out of the cylindrical case.
In the embodiment using the film (1), the skin layer is on the surface side of the film envelope.

As the semipermeable membrane used in the present invention, a reverse osmosis membrane, an ultrafiltration membrane, or a microfiltration membrane can be used depending on the polymer material used.

As the membrane used in the present invention, a reverse osmosis composite membrane, a gas separation membrane, or a pervaporation membrane obtained by using the above-mentioned membrane as a support membrane and forming a thin separation layer on the surface thereof is used. Can also.

The film material used in the present invention is not particularly limited as long as it is a polymer having film forming properties.
For example, polysulfone-based polymers, hydrophilic polyolefin-based polymers, polyvinylidene fluoride, polyacrylonitrile-based polymers, cellulose acetate, polyimide, mixtures thereof, or sulfonic acid groups, carboxyl groups, amino groups, etc. Those into which a charged group has been introduced can be used.

In the film forming solution, a polymer polymer is used as a material.
Is dissolved in a solvent. The polymer concentration varies depending on the molecular weight and type of the polymer.
%, Preferably 10 to 30%.

As the solvent used as the film forming solution, it is necessary to use a solvent which dissolves the polymer and can be mixed with water. N, N-dimethylacetamide, N, N-dimethylformamide, N- An aprotic polar solvent such as methyl-2-pyrrolidone, dimethylsulfoxide, acetone, THF, dioxane and the like can be used.

As the additives to be added to the film forming solution, for example, inorganic salts such as lithium chloride and magnesium perchlorate, and organic substances such as ethylene glycol, polyethylene glycol and polyvinylpyrrolidone formamide can be used. The concentration of the additive varies depending on the type of the polymer and the type of the additive, but is usually 1 to 200 parts by weight, preferably 5 to 150 parts by weight, per 100 parts by weight of the polymer.

The woven fabric used in the present invention must be capable of being impregnated with a film-forming solution, have excellent tensile strength, and be capable of forming a film when the impregnated film-forming solution solidifies in a coagulating liquid. Requirements such as being able to withstand shrinkage are required.

The fibers of the woven fabric are long fibers of a monofilament and preferably have a wire diameter of 30 to 200 μm. The material of the fiber is not particularly limited as long as it has mechanical strength and resistance to the solvent of the film forming solution. For example,
Polyester, polypropylene, polyethylene, polyamide and the like can be used.

In the method for producing the membrane used in the present invention, in the case of the membrane shown in FIG. 1, a woven fabric is impregnated with a membrane forming solution, and the woven fabric is vertically interposed between two rolls with a gap adjusted. To adjust the thickness of the film forming solution layer on both sides of the woven fabric to approximately the same thickness,
A skin layer is formed by solvent evaporation from the film forming solution surface,
Next, a method of immersing in a coagulation liquid to solidify a solution portion containing a solvent inside the film and causing a phase transition to a sponge layer can be used. Further, a method of forming a skin layer and a sponge layer in a coagulating liquid without evaporating the solvent can also be used.

In the case of the membrane shown in FIG. 2, when the solvent is evaporated from the surface of the film forming liquid layer of the woven fabric impregnated with the film forming solution by the above method,
The method of adjusting the generation of the skin layer by changing the atmosphere such as temperature, humidity, presence or absence of organic solvent vapor between the front and back surfaces, and when immersing the woven fabric impregnated with the film forming solution in the coagulating liquid,
A method of shifting the solidification time between the front surface and the back surface can be used. For example, a woven cloth placed on a glass plate or a sheet-like film is impregnated with a film-forming solution, a solvent is evaporated from the surface of the film-forming solution layer to form a skin layer on one side, and then these are combined together. A method of immersing in a coagulation liquid to coagulate a part in a solution state containing a solvent therein and causing a phase transition to a sponge layer can be used. Further, a method of forming a skin layer and a sponge layer in a coagulating liquid without evaporating the solvent can also be used.

The above-mentioned coagulation liquid contains water as a main component, but may contain an inorganic salt such as bow glass, a water-soluble organic solvent such as alcohol, and a surfactant.

In the spiral type separation membrane module of the present invention, the support is embedded in the sponge layer of the semipermeable membrane, and even if the permeate is pressurized and backwashed, it comes into contact with the permeate. Since the back surface of the semipermeable membrane receives the pressure of the permeated liquid and the support acts as a tension member, backwashing can be performed while the membrane is stably supported by the support.

In this case, the denser the back surface of the semipermeable membrane which receives the pressure of the permeated liquid, the more effectively the liquid pressure can be received. However, the pressure may not be as dense as the skin layer on the stock solution side.

In the spiral separation membrane module of the present invention, backwashing can be performed safely without causing damage to the membrane. This is clear from the backwash test of the following Examples and Comparative Examples.

Example 1 18% by weight of polysulfone was dissolved in N-methyl-2-pyrrolidone to prepare a film forming solution. A 110-mesh polyester woven fabric was placed on a polyester film, and the above-mentioned film forming solution was poured onto the polyester film and impregnated. This was passed vertically between two rolls with the gap adjusted to 200 μm with the film attached, immersed in water and solidified to form a film having a thickness of 18 μm.
A 0 μm film was obtained. The woven fabric was embedded in the sponge layer. This membrane exhibited performance as an ultrafiltration membrane, and the rejection of polyethylene glycol 20,000 on the front and back sides (the side in contact with the polyester film) was 74% and 6%, respectively. Using this membrane, a spiral type separation membrane module was assembled.

Example 2 22% by weight of a saponified ethylene-vinyl acetate copolymer was added to 42% by weight of isopropyl alcohol and 36% by weight of water to give 80%.
It melt | dissolved at ℃, and adjusted as a film-forming solution. This film-forming solution was impregnated into a 110-mesh polyester woven fabric, passed between two rolls with a gap adjusted to 180 μm, immersed in water and solidified to obtain a 210 μm-thick film. The woven fabric was embedded in the sponge layer, and skin layers were formed on both sides of the semipermeable membrane. This membrane exhibits the performance as an ultrafiltration membrane, with polyethylene glycol 50,0 on the front and back.
The rejection of 00 was 90% and 88%, respectively. Using this membrane, a spiral type separation membrane module was assembled.

Comparative Example 1 The same membrane-forming solution as in Example 1 was applied on a 220-mesh polyester woven fabric. The film forming solution remained on the woven fabric surface without being impregnated to the back surface. This was passed vertically between two rolls with a gap adjusted to 200 μm, immersed in water and solidified to obtain a 190 μm thick film.
The woven fabric was exposed on the back of the membrane. This membrane exhibits the performance as an ultrafiltration membrane, and the rejection of polyethylene glycol 20,000 on the front and back sides is 76% and 15%, respectively.
Met. Using this membrane, a spiral type separation membrane module was assembled.

Comparative Example 2 The procedure of Comparative Example 1 was repeated except that the same film forming solution as in Example 2 was used.

Each of the above-mentioned Examples and Comparative Examples was operated at a pressure of 2 kg / cm ^{2 using} tap water as raw water. During this operation, a pressure of 3 kg / cm ² was applied to the permeate side once a day for 30 seconds.
After 30 days, the amount of permeated water was at least 80% of the initial permeated water after 30 days (30% to 35% when backwashing was not performed), and backwashing was performed without damage to the membrane. did it.

On the other hand, in the comparative example, the initial 105
% To 110%, and when the film was taken out and observed,
The sponge layer and the woven fabric were locally peeled, and the film was damaged at some of the peeled portions.

[0037]

The spiral separation membrane module of the present invention has the above-described configuration, and can be safely backwashed with a permeated solution without damaging the membrane. Therefore, unlike the conventional chemical cleaning, it is possible to eliminate the problems such as deterioration of the membrane, long-term operation stop of the separation membrane module, and high cost, and keep the permeated water amount high by backwashing.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an example of a film used in the present invention.

FIG. 2 is an explanatory sectional view showing another example of a film used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sponge layer 2 Support cloth 31 Skin layer 32 Skin layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 63 / 10,65 / 02

Claims (4)

(57) [Claims] 1. A buried supporting cloth sponge layer, the supporting cloth
A spiral type membrane separation module, wherein a membrane having a skin layer provided on both surfaces of a sponge layer is used. 2. The spiral type membrane separation module according to claim 1.
-Spiral characterized by backwashing the filter with a permeate
Method for cleaning a membrane separation module. Wherein embedding a supporting cloth sponge layer, providing a skin layer on the sponge layer surface contacting the liquid to be treated, the sponge
A spiral type membrane separation module using a membrane provided with a dense layer having a pore size smaller than the pore size inside the sponge layer on the back surface of the layer . 4. The spiral type membrane separation module according to claim 3.
-Spiral characterized by backwashing the filter with a permeate
Method for cleaning a membrane separation module.