JP2774843B2 - Spiral type degassing module - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane module for separating a gas (gas) dissolved in a liquid, and more particularly, to a method for efficiently converting a gas dissolved in various liquids. The present invention relates to a spiral degassing membrane module that frequently degasses.

[Problems to be solved by conventional technology and invention]

There are many fields that require degassing in the use of liquids.
For example, liquid chromatography,
Degassing of automated clinical chemistry analysis, medical spectrophotometer, etc. Industrial applications include degassing of ion-exchanged water processes, ultrapure water systems, boiler water, nuclear power water, turbine water, and the like.

For example, in liquid chromatography, when air is dissolved in a solvent, air bubbles are generated in a pump, around a valve, and in a detector, causing a trouble. Also, dissolved oxygen may cause a chemical reaction with the solute. In automated clinical chemistry analysis, even with a small amount of sample, even a small amount of dissolved oxygen adversely affects the analysis accuracy. In a spectrophotometer, absorption by dissolved oxygen and the like in the ultraviolet short wavelength region has a large influence. On the other hand, in the ion exchange water process, dissolved oxygen and carbon dioxide in the liquid shorten the life of the ion exchange resin. Boiler water,
In nuclear power water, dissolved oxygen promotes corrosion of containers, piping, etc.

In addition, deaeration is required in fields such as drinking water, building water supply, raw material water for beverage production, and water for beverage production.

Conventionally, methods for degassing a dissolved gas in a liquid, such as a heating boiling method, a decompression method, an ultrasonic method, and a helium method, are known. However, the heating and boiling method has a high danger due to high temperature operation, the decompression method and the ultrasonic method have low degassing ability, and the helium method is not an effective and economical method because the operation cost is high.

As described above, there are so many fields that require degassing, and there has been no satisfactory degassing method in any field.

In recent years, a deaeration method using a tube (hollow fiber) membrane made of a synthetic resin such as silicone or polytetrafluoroethylene has been proposed (Japanese Patent Application Laid-Open No. Sho 60-25514, Japanese Utility Model Application Laid-Open No.
No. 3-43609).

For example, there is a method in which a liquid containing a dissolved gas is caused to flow inside the membrane while keeping the outside of the hollow fiber membrane in a reduced-pressure atmosphere, and the dissolved gas in the liquid is degassed.

However, what is called such a tube (hollow fiber) shape,
The membrane module made of a hollow fiber membrane does not have a so-called turbulence promoting mechanism that promotes the turbulence (renewal of the surface) of the liquid to be degassed inside the hollow fiber membrane and increases the degassing rate, so that the membrane module is practically degassed. For use as an air-permeable membrane, a method of reducing the inner diameter of a hollow fiber membrane has been adopted as a means for increasing the deaeration rate that determines economic efficiency. However, reducing the inner diameter of the hollow fiber membrane has the drawback of causing problems of high pressure loss when flowing the liquid, as well as problems of mechanical strength and molding.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above-mentioned problems in degassing gas (gas) dissolved in various liquids. As a result, the liquid containing the dissolved gas was converted into a sheet having a turbulence promoting mechanism. The inventors have found out that the dissolved gas can be efficiently degassed by treating with a so-called spiral-type membrane module formed by winding a sheet and a sheet-like membrane, and have reached the present invention.

That is, the present invention is a membrane module for contacting a liquid containing a dissolved gas with a permeable membrane, selectively permeating the dissolved gas and separating the same, wherein the permeable membrane is in the form of a sheet,
Provided is a spiral degassing membrane module, wherein the sheet-like membrane is wound in a spiral shape.

Due to its structure, the spiral type membrane module has a turbulent flow of the liquid to be degassed (stock solution) between the sheet-shaped permeable membranes (surface renewal)
And a spacer having a turbulence promoting mechanism for promoting the degassing speed. The spacer is not particularly limited, but a net-like or lattice-like channel material made of, for example, polypropylene or the like is used.

Although there is no particular limitation on the flow path material of the gas on the permeation side, a spacer such as polyester or polypropylene having pressure resistance is usually used.

The permeable membrane used in the present invention is not particularly limited as long as it is in the form of a sheet. Further, the mechanical strength can be increased by using a permeable membrane formed on a reinforcing material such as a nonwoven fabric.

In the present invention, a permselective composite membrane in which a non-porous active thin film of a synthetic resin is preferably formed on a porous support membrane can be used. Here, the activity means having a property of separating a dissolved gas from an existing gas. Since the active thin film has a small film thickness, the active thin film does not have resistance to dissolved gas permeation, and the degassing speed of the module can be increased.

Further, as a particularly preferred permeable membrane, although not limited to its structure, it has a specific membrane physical property value described later, for example, a homogeneous membrane made of a non-porous active thin film, or a dense layer or a porous layer which supports the active dense layer integrally with the same. An asymmetric film composed of a porous layer and a composite film formed by partially infiltrating a nonporous thin film into a dense layer of the asymmetric film are used.

One of the physical properties of the film is a nitrogen gas permeation rate at 30 ° C. of 7 × 10 ⁻⁴ to 2 × 10 ² Nm ³ / m ² · h · atm. If the nitrogen gas permeation rate is smaller than 7 × 10 ⁻⁴ Nm ³ / m ² · h · atm, the permeation rate of the dissolved gas, that is, the deaeration rate may be reduced, while 2 × 10 ² Nm ³ / m If it is larger than ² · h · atm, there is a possibility that the membrane permeation rate of the liquid molecules increases and the degassing efficiency decreases.

Yet another membrane property value is that the pressure on the permeate side is 40 mm.
When water at an atmospheric pressure of 20 ° C. is supplied to the membrane as Hg, the membrane permeation amount of water vapor is 100 g / m ² · h or less. When the water vapor permeation rate is greater than 100 g / m ² · h, the permeate pressure increases due to the water vapor pressure, and as a result, the deaeration rate decreases. It is not preferable because it must be equipped.

Using the degassing membrane module of the present invention, the dissolved gas concentration is reduced on the supply side of the membrane by bringing the liquid containing the dissolved gas into contact with the permeable membrane and selectively permeating the dissolved gas through the membrane. Liquid can be obtained. At this time, it is preferable to reduce the pressure on the permeation side, and a liquid having a lower dissolved gas concentration can be obtained on the supply side as the pressure is lower, and the pressure is usually 0 to 200 mmHg, preferably 20 mmHg.
~ 150mmHg.

〔The invention's effect〕

Since the degassing membrane module of the present invention is a spiral type having the above characteristics, the degassing rate can be increased, and the equipment cost and operation can be increased as compared with a conventional tube (hollow fiber) -shaped hollow fiber membrane module. There is an advantage that costs and maintenance costs can be reduced.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

In the following, parts and% mean parts by weight and% by weight, respectively.

Example 1 15 parts of an aromatic polysulfone ("Polysulfone P-1700" manufactured by Union Carbide Co., Ltd.) and 5 parts of polyethylene glycol having an average molecular weight of 600 were mixed with N-methyl-2-pyrrolidone.
Dissolved in 80 parts. This solution was applied on a nonwoven fabric and solidified in water to obtain a 150 μm sheet-like porous membrane.

This porous film was dried at 60 ° C. to obtain a dried film. As a result of observing the cross section of the dried porous membrane with a scanning electron microscope, the dried porous membrane has a dense layer on the surface, has a coarse porous structure toward the inside, and is partially referred to as a so-called greasy structure. Asymmetric membrane having a missing portion of the polymer. The nitrogen gas permeation rate at 30 ° C. of such a porous membrane is 60 Nm ³ / m ² · h
・ It was atm. Further, when the pressure on the permeate side of the membrane was set to 40 mmHg and water at an atmospheric pressure of 20 ° C. was supplied to the membrane, the water vapor permeating the membrane was 0.45 g / m ² · h.

A spiral-type membrane is formed by sandwiching a net-shaped spacer made of polypropylene for the flow path of the liquid to be degassed (raw liquid) and a tricot-woven polyester spacer for the flow path of the permeation side. Module. The diameter of such a spiral element is
The length was 90 mm, the length was 1 m, and the membrane area was 6.5 m ² .

Distilled water (dissolved oxygen gas concentration at 25 ° C. and the concentration of 8.11 ppm) saturated with air at atmospheric pressure was passed through the module, and the pressure on the permeate side was maintained at 40 mmHg.

The result of the deaeration, that is, the relationship between the flow rate of the treatment liquid and the concentration of dissolved oxygen in the permeate is shown in the figure.

Example 2 A solution comprising 90 parts of isooctane, 10 parts of a crosslinkable polydimethylsiloxane prepolymer having a vinyl group as a reactive group and 1 part of a crosslinking agent was heated at 70 ° C. for 7 hours to prepare a silicone resin solution. This was diluted with isooctane to obtain a solution having a resin concentration of 1.8%. On the porous membrane obtained in Example 1, the above crosslinkable silicone resin solution was applied to a thickness of 50 μm.
m. After heating this coating film to a temperature of 100 ° C. to evaporate isooctane from the coating film,
After allowing to stand for 24 hours, a permselective composite membrane having an active thin film of a crosslinkable silicone resin having a thickness of about 1 μm was obtained on the dense layer of the porous membrane. The nitrogen gas permeation rate at 30 ° C. of the composite membrane was 0.7 Nm ³ / m ² · h · atm. Further, when the pressure on the permeation side of the membrane was set to 40 mmHg and water at an atmospheric pressure of 20 ° C. was supplied to the membrane, the amount of water vapor permeating the membrane was 5.8 g / m ² · h.

A spiral type module similar to that of Example 1 was prepared except that the permselective composite membrane was used, and the degassing performance was measured. The degassing result is shown in the figure.

Comparative Example 1 The same aromatic polysulfone solution as in Example 1 was extruded into a hollow shape from an annular nozzle, and water was coagulated from the inner and outer surfaces as a coagulating liquid to form a hollow fiber porous membrane having an inner diameter of 0.55 mm and an outer diameter of 1.00 mm. Obtained.

This hollow fiber-shaped porous membrane was dried at 100 ° C. to obtain a dried membrane. As a result of observing the cross section of the dried hollow fiber-shaped porous membrane with a scanning electron microscope, it has a dense layer on the surface, has a coarse porous structure toward the inside, and has a so-called finger-like structure partially. This was an asymmetric membrane having a missing portion of the named polymer. The nitrogen gas permeation rate at 30 ° C. of the porous membrane was 26 Nm ³ / m ² · h · atm.

The same crosslinkable silicone resin solution as in Example 2 was uniformly applied on the dense layer inside (inner diameter side) of the porous membrane by an air doctor method. This coating film was heated to a temperature of 80 ° C. to remove isooctane from the coating film by evaporation, and then left at room temperature for 24 hours to form a composite film having an active thin film made of a crosslinkable silicone resin on a dense layer of a porous film. Obtained. The nitrogen gas permeation rate at 30 ° C. of such a composite membrane is 0.031 Nm ³ / m ² · h
・ It was atm. The amount of water vapor measured in the same manner as in Example 1 was 0.32 g / m ² · h.

The hollow fiber composite membrane thus obtained was bundled to form a hollow fiber membrane module. The number of membranes was 3,600, the module diameter was 90 mm, the length was 1 m, and the membrane area was 6.2 m ² .

Supply side of such module (inner diameter side of hollow fiber upper membrane)
Pour distilled water (dissolved oxygen gas concentration: 8.11 ppm at 25 ° C) saturated with air at atmospheric pressure through to the permeate side (outer diameter side) of 40 mmHg
Pressure.

The result of the deaeration, that is, the relationship between the flow rate of the treatment liquid and the concentration of dissolved oxygen in the non-permeate liquid is shown in the figure.

Comparative Example 2 In the same manner as in Comparative Example 1, a hollow fiber porous membrane of an aromatic polysulfone having an inner diameter of 0.3 mm and an outer diameter of 0.45 mm was obtained.
Drying at 0 ° C. gave a dried film. The nitrogen gas permeation rate at 30 ° C. of the porous membrane was 5 Nm ³ / m ² · h · atm.
The amount of water vapor measured in the same manner as in Example 1 was 0.3 g / g
² · h.

The membranes thus obtained were bundled to form a hollow fiber membrane module. Here, the number of membranes was 16,000, the diameter of the module was 90 mm, the length was 1 m, and the membrane area was 15.1 m ² .

The drawing shows the degassing results obtained in the same manner as in Comparative Example 1 except that such a module was used.

[Brief description of the drawings]

The figure is a graph showing the degassing results obtained in Examples and Comparative Examples.

Claims (3)

(57) [Claims] 1. A liquid containing a dissolved gas is brought into contact with a permeable membrane,
A spiral module, wherein the dissolved gas is selectively permeated and separated therefrom, wherein the permeable membrane is sheet-shaped, and the sheet-shaped membrane is wound in a spiral shape. Degassing membrane module. 2. The spiral degassing membrane module according to claim 1, wherein the permeable membrane is a permselective composite membrane formed by forming a non-porous active thin film of a synthetic resin on a porous support membrane. 3. The permeable membrane has a nitrogen gas permeation rate of 7 × 10 ^-4 to 2 × 10 ² Nm ³ / m ² · h · atm at 30 ° C. as a physical property value of the membrane.
When the pressure on the permeate side of the membrane is 40 mmHg and water at an atmospheric pressure of 20 ° C. is supplied to the membrane, the amount of water vapor permeating the membrane is 10
The spiral-type degassing membrane module according to claim 1, wherein the density is 0 g / m ² · h or less.