JPH06327905A - Degassing membrane module and its operation - Google Patents

Abstract

PURPOSE:To reduce a pressure drop and to remarkably improve the amt. of treated water by using a degassing membrane with a spacer arranged between hollow-fiber membranes, allowing raw water to flow outside the membrane and evacuating the inside. CONSTITUTION:One end of a hollow-fiber membrane 2 is connected to a vacuum line 3, and the other end is sealed by a sealing part 5. Raw water is supplied from a raw water inlet 1, passed outside the membrane 2 and sent to a degassed water outlet 4. In this case, the gas dissolved in the raw water is moved into the membrane 2, and the raw water is degassed. Since the raw water is passed outside the membrane 2, the pressure drop due to flow resistance is not increased, and a large amt. of raw water is treated. Meanwhile, as the inside of the membrane 2 is evacuated and the membrane is surrounded by the raw water, the raw water is kept at the same temp., and steam is not condensed on the surface of the membrane 2. Further, the channeling of raw water is obviated by arranging a spacer 14 between the membranes 2, and the raw water is efficiently degassed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degassing membrane module which uses a hydrophobic gas permeable membrane to remove the dissolved gas in the raw water by flowing the raw water into one of the membranes and depressurizing the other. More specifically, the present invention relates to a hollow fiber type degassing membrane module.

[0002]

2. Description of the Related Art Recently, a so-called degassing process for removing gases such as oxygen, nitrogen and carbon dioxide dissolved in water using a hydrophobic gas separation membrane has recently been put into practical use. (Actual exploitation Sho 57-35795, Japanese Unexamined Patent Publication No. 62-273095) In this method, raw water is applied to the front or back surface of a membrane made of silicone or the like, which has a gas permeation function and a water impermeable property. By flowing and reducing the pressure on the opposite surface, only the dissolved gas in the raw water is removed through the membrane and degassed. By removing the dissolved gas in the water, it is possible to prevent, for example, corrosion of the inner surface of the liquid contacting the pipe due to dissolved oxygen in the water circulation line and deterioration of the water quality of the ultrapure water due to carbon dioxide. With this method, there are no problems such as chemical residual components found in the conventional chemical addition method, the apparatus is simpler than the vacuum degassing method, etc., and the operating cost is reduced. There is.

Currently used degassing membrane modules include a spiral type and a hollow fiber type. The hollow fiber type is a system in which raw water is caused to flow inside the hollow fiber membrane and pressure is reduced outside to remove dissolved gas in the raw water flowing inside the hollow fiber. In the case of the hollow fiber type, the membrane area per module volume can be made large, so the dissolved gas concentration can be sufficiently reduced in a small module, and highly efficient degassing treatment is possible. is doing.

[0004]

However, in the conventional methods of flowing raw water inside the hollow fiber and depressurizing the outside,
It was easy to suppress the concentration film development that occurs in the raw water flow, and it was possible to degas with high efficiency.However, if the raw water contained dust, etc., due to the thin hollow fiber, the hollow fiber inlet would be clogged. May occur. Further, when an attempt is made to increase the amount of treated water, an increase in pressure loss due to the flow resistance of raw water causes a significant increase in required power, making it difficult to process a large amount of water. In addition, when the outside temperature of the module is low, water vapor is likely to condense on the outer surface of the hollow fiber membrane and block the membrane surface, so that the membrane area effective for deaeration is reduced and the treatment efficiency is likely to be lowered. Had.

Further, when it is intended to remove a specific gas such as oxygen or carbon dioxide, it is known to flow a carrier gas other than the degassing target to the depressurization side for the purpose of improving the degassing efficiency. As described in (Japanese Patent Laid-Open No. 3-249907), this method is a technique established by a flat film stacking type or a spiral type, and it is necessary that the carrier gas flows evenly on the depressurized side. In the case of the hollow fiber type, the arrangement of the hollow fiber membrane has a slight deviation, or the condensed steam generated when the temperature is low as described above becomes an obstacle, and the effect of flowing the carrier gas cannot be sufficiently exerted.

[0006]

The object of the present invention is basically achieved by a degassing membrane module characterized in that a spacer is arranged between hollow fiber hydrophobic gas permeable membranes.

By using the raw water flow path outside the hollow fiber, it is possible to prevent an increase in pressure loss due to flow resistance, and it is possible to enable large-scale processing without requiring the hollow fiber membrane to have such a high pressure resistance. it can. Further, since the depressurized side is inside the hollow fiber membrane and is surrounded by raw water, it is kept at the same temperature as the raw water, water vapor can be prevented from condensing on the surface of the hollow fiber membrane, and the treatment efficiency can be sufficiently maintained. However, this method has a problem that the raw water flowing outside the hollow fiber membrane is likely to have a drift.
Therefore, by arranging a spacer between the hollow fiber membranes, it is possible to prevent uneven flow of raw water and perform highly efficient degassing treatment.

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

1 and 2 are side sectional views showing the structure of an example of the degassing membrane module of the present invention using a spacer having a cross-shaped cross section, and FIG. 3 is a cross sectional view thereof. is there. FIG. 1 shows one end of a hollow fiber degassing membrane 2 connected to a vacuum line 3 and the other end sealed. FIG. 2 shows the hollow fiber membrane 2 arranged in a U-shape, and both ends of which are on the same side. It is glued and released to. As a result, the raw water supplied from the raw water supply port 1 passes through the outside of the hollow fiber degassing membrane 2, and at that time, the dissolved gas in the raw water moves inside the hollow fiber membrane to degas the raw water. .

The number, position and orientation of the raw water supply port 1 and the degassed water outlet 4 and the shape, material, size and number of the spacers in the present invention are not particularly limited.
It is desirable that it is arranged so as to prevent uneven flow and sufficiently pass through the membrane surface. For example, as shown in FIG. 4, the raw water supply port 1 is provided at a plurality of locations, or as shown in FIGS. 5 and 6, the raw water supply port 1 and the degassed water outlet 4 are connected to the central pipe 6, the raw water pipe 7, and the degassed water. It is also possible to supply and drain raw water and degassed water from the module end plate by the pipe 8, and it is possible to flexibly deal with the installation location, conditions and shape. Furthermore, the vacuum line 3 has no problem from either end of the hollow fiber degassing membrane 2 as long as it communicates with the inside of the hollow fiber membrane. Especially, when pressure distribution is generated inside the hollow fiber, As shown in FIG. 7, both ends of the hollow fiber degassing membrane 2 can be connected to the vacuum line 3. Further, if it is desired to simplify the piping of the vacuum line 3, as shown in FIG. 8, a vacuum line pipe 10 may be arranged inside the module so that the vacuum line is unified.

When a carrier gas is flowed to the depressurized side to remove a specific gas such as oxygen or carbon dioxide, as shown in FIG. 9, the opposite side of the end of the hollow fiber membrane connected to the vacuum line 3 is opened. Then, the carrier gas can be introduced by forming the carrier gas supply port 12. The carrier gas is not particularly limited as long as it is a gas different from the specific gas to be removed, but an inert gas that does not affect the raw water is desirable, and nitrogen that is contained in a large amount in the air is preferable. By passing the carrier gas through the hollow fiber membrane as described above, the specific gas partial pressure on the depressurizing side, that is, the permeating side can be sufficiently reduced, and the degassing efficiency can be greatly improved.

Further, in the degassing membrane module of the present invention, raw water is made to flow to the outside of the hollow fiber. However, if there is a problem in the shape of the raw water supply port or the module case, or if there is a bias in the arrangement of the hollow fiber membrane, Residence tends to occur on the outer surface of the hollow fiber membrane, and concentration polarization of the dissolved gas in the raw water occurs, so that degassing efficiency decreases. In order to prevent such uneven flow that tends to occur in the vicinity of the raw water inlet, as described above, in addition to the method of using a plurality of raw water supply ports or diffusing the raw water into the module by a porous pipe, as shown in FIG. First, there is a method in which the raw water distribution plate 13 is provided in the module so that the raw water can sufficiently flow between the hollow fiber membranes.

Further, as a very effective means for preventing unbalanced flow of raw water and preventing concentration polarization as a type of spacer, it is intended to improve the treatment efficiency of a liquid separation membrane module for dialysis, etc. Sho 53-35683, JP-A-3-27
As described in 8821, there is known a method of winding a spacer yarn around a hollow fiber membrane to obtain a certain gap between the hollow fiber membranes. It was found that the deaeration efficiency can be greatly improved by winding the spacer yarn around one or more hollow fiber membranes to prevent the concentration polarization of the raw water flowing outside the hollow fibers. The method of winding the spacer yarn around the hollow fiber membrane can be used alone instead of the above-mentioned spacer or can be used in combination with other spacers. The type and winding method of the spacer yarn used for the hollow fiber degassing membrane in the present invention are not particularly limited, but it is desirable to be able to sufficiently prevent uneven distribution of raw water flowing outside the hollow fiber and concentration film of dissolved gas. . The material of the spacer yarn is not particularly limited, but nylon, polyester, polypropylene, fluororesin and the like are preferable. Suitable spacer yarns are slightly different depending on the diameter of the hollow fiber and the thickness of the module, but it is generally effective to use a processed yarn obtained by twisting one or more single yarns of 5 to 150 denier. The most effective winding method is to bundle 2 to 4 hollow fibers and wrap the spacer yarn at a pitch of 1 to 10 cm / roll.

FIG. 11 shows a schematic view of an example in which a spacer yarn is wound around a hollow fiber membrane, and FIGS. 12 and 13 show an example of a hollow fiber membrane module around which a spacer yarn is wound.

The hollow fiber membrane used in the degassing membrane module of the present invention is not particularly limited to the shape of the hollow fiber, and is generally called tubular type (hollow fiber diameter of several mm or more), capillary type (hollow fiber). The diameter of the hollow fiber is about 1 mm) and the diameter of the hollow fiber (hollow fiber diameter is less than 1 mm) and the shape of the cross section of the hollow fiber are not limited, but the hollow fiber type can have a large membrane area. Also,
The state of the pores is also not particularly limited, but in order to exhibit degassing performance, the membrane surface on the side where the raw water flows is sufficiently dense to prevent the raw water from entering the pores. Things are good. Further, in order to have sufficient gas permeability, it is desirable that the inside of the hollow fiber membrane and the surface of the pressure reducing side are sparse. This reduces the gas permeation resistance,
Further, since the pore area on the depressurization side becomes large, it becomes easy to sufficiently depressurize the film surface. By the way, the membrane material should be hydrophobic and can be formed into the shape of a hollow fiber,
Polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, poly (4-methylpentene), etc. are preferable, but considering the pore structure, polyvinylidene fluoride or poly (4-methylpentene) rather than fibril holes represented by polyethylene, polypropylene, etc. It is particularly preferable that the polymer has ultrafine uniform pores. Further, in order to improve the hydrophobicity of the membrane, it is possible to form a hydrophobic membrane such as a cross-linking silicone-based or fluororesin-based one or both of the inner and outer surfaces of the hollow fiber to form a composite membrane. In particular, the crosslinkable silicone-based composite film is a film characterized by forming a crosslinkable silicone-based thin film on the surface of the base material film, and the surface state is so dense that it is generally called a non-porous film. There are many things we are doing. For this reason, in addition to the hydrophobic property of silicone itself, it has the excellent property of being able to suppress the adsorption of dirt components.

[0016]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to this.

Example 1 A degassing membrane module of the type shown in FIG. 1, which is an example of the present invention, was produced. This module is made by wet-spinning polyvinylidene fluoride (HYLAR460 manufactured by Ausimont Co., USA) and has 24,000 hollow fiber membranes (total length 450 mm, effective length 420 mm) with inner diameter 180 μm and outer diameter 225 μm, diameter 50 mm, length 500 mm. The hollow fiber membrane was loaded in a case of No. 1, one of the hollow fiber membranes was sealed, the other was opened, and the hollow fiber membrane was connected to a vacuum line. Using this module, the vacuum line is set to 50 torr and the raw water is
A degassing test was conducted using pure water with a water temperature of 25 ° C and a dissolved oxygen concentration of 8.0 ppm at a treatment flow rate of 2 liters / minute. The dissolved oxygen concentration at the module outlet was 0.8 ppm, and the pressure loss was 0.03 kgf / cm.
^{Was 2} .

Example 2 A degassing membrane module shown in FIG. 9 was produced under the same conditions as in Example 1 except that it had a carrier gas supply port. Using this module, 20 ml of nitrogen was used as carrier gas / When a degassing test was conducted under the same conditions, the dissolved oxygen concentration at the module outlet was 0.6 ppm, and the pressure loss was 0.04 kgf / cm ² .

Comparative Example 1 A conventional degassing membrane module having no spacer as shown in FIG. 14 was produced. This module is loaded with the same 24,000 hollow fiber membranes as in Example 1 in the same case, but the conventional method in which both ends of the hollow fiber membrane are opened to allow raw water to flow inside the hollow fiber membrane and depressurize the outside It is a module. When a deaeration test was conducted using this module under the same conditions as in Example 1, the dissolved oxygen concentration at the module outlet was 0.4 ppm and the pressure loss was 0.3 kgf / cm ² .

Comparative Example 2 Under the same conditions as in Comparative Example 1 except that a carrier gas supply port is provided, FIG.
When a conventional degassing membrane module as shown in Fig. 4 was produced and a degassing test was conducted using this module under the same conditions as in Example 2, the dissolved oxygen concentration at the module outlet was 0.
The pressure loss was 1 ppm and the pressure loss was 0.3 kgf / cm ² .

[0021]

INDUSTRIAL APPLICABILITY In the present invention, a spacer is arranged between the hollow fiber hydrophobic gas permeable membranes, and while the raw water is allowed to flow outside the hollow fiber membranes, the inside pressure is reduced to remove the dissolved gas in the raw water. In the degassing membrane module described above, raw water is caused to flow to the outside of the hollow fiber membrane and the inside pressure is reduced, whereby the pressure loss can be reduced and a large amount of treatment is possible.

[Brief description of drawings]

FIG. 1 is a side sectional view of an example of a degassing membrane module with one end sealed according to the present invention.

FIG. 2 is a side sectional view of an example of a U-shaped degassing membrane module according to the present invention.

FIG. 3 is a cross-sectional view of an example of a degassing membrane module according to the present invention.

FIG. 4 is a cross-sectional view of an example of a degassing membrane module having a plurality of raw water supply ports according to the present invention.

FIG. 5 is a cross-sectional view of an example of a degassing membrane module having a central pipe according to the present invention.

FIG. 6 is a cross-sectional view of an example of a degassing membrane module having a raw water and degassing water pipe according to the present invention.

FIG. 7 is a cross-sectional view of an example of a degassing membrane module having vacuum lines at both ends of a hollow fiber membrane according to the present invention.

FIG. 8 is a cross-sectional view of an example of a degassing membrane module in which a vacuum line is assembled by a central pipe according to the present invention.

FIG. 9 is a cross-sectional view of another example of a degassing membrane module having a carrier gas supply port according to the present invention.

FIG. 10 is a cross-sectional view of an example of a degassing membrane module having a raw water distribution plate according to the present invention.

FIG. 11 is a schematic view of an example of a hollow fiber membrane element wound with a spacer yarn according to the present invention.

FIG. 12 is a schematic view of an example of a degassing membrane module in which a spacer yarn is wound around a hollow fiber membrane according to the present invention.

FIG. 13 is a schematic view of an example of a degassing membrane module having a spacer and having a spacer yarn wound around a hollow fiber membrane according to the present invention.

FIG. 14 is a cross-sectional view of an example of a conventional degassing membrane module.

FIG. 15 is a cross-sectional view of an example of a conventional degassing membrane module having a carrier gas introduction port.

[Explanation of symbols]

1: Raw water supply port 2: Hollow fiber degassing membrane 3: Vacuum line 4: Degassing water outlet 5: Sealing part 6: Central pipe 7: Raw water pipe 8: Degassing water pipe 9: Hole 10: Vacuum line pipe 11 : Spacer yarn 12: Carrier gas supply port 13: Raw water distribution plate 14: Spacer 15: Hollow fiber membrane element in which two spacer yarns are wound crosswise around one single yarn 16: One spacer yarn per single yarn 17: Hollow fiber membrane element in which one spacer yarn is wound around two single yarns

Claims (7)

[Claims] 1. A degassing membrane module comprising a spacer disposed between hollow fiber hydrophobic gas permeable membranes. 2. The degassing membrane module according to claim 1, wherein the spacer is a filament yarn spirally wound around one or more hollow fiber membranes. 3. The degassing membrane module according to claim 1, wherein the hollow fiber membrane has a structure in which the outer surface is dense and the inner surface is sparse. 4. The hollow fiber membrane material is polyvinylidene fluoride,
Alternatively, the degassing membrane module according to claim 1, which is a polymer composed of 4-methylpentene. 5. Dissolution in raw water by using a degassing membrane module in which a spacer is arranged between hollow fiber hydrophobic gas permeable membranes, while depressurizing the inside while flowing raw water to the outside of the hollow fiber membranes. A method for operating a degassing membrane module, which comprises removing gas. 6. The method for operating a degassing membrane module according to claim 5, wherein a gas supply port is provided in a portion communicating with the inside of the hollow fiber membrane, and a carrier gas other than a removal target is flowed. 7. The method for operating a degassing membrane module according to claim 6, wherein the carrier gas is nitrogen or air.