JPH01224011A - Degassing separation module and degassing separation using said module - Google Patents

Abstract

PURPOSE:To enhance an effect in separating a gas from a liq. by embedding a hollow yarn membrane with both ends opened into a partition wall of a high molecular polymer, and liquid-tightly fixing both ends of the hollow yarn membrane to the partition wall. CONSTITUTION:Many porous hollow yarn membranes 11 made of polyolefin are arranged in an outer cylinder 10, and both ends of the membrane 11 are liquid-tightly supported by a potting material 12. Raw water is introduced into the hollow part of the membrane 11 from a raw water inlet 13. The outside of the membrane 11 is depressurized. The raw water introduced into the hollow part of the membrane 11 is passed through the hollow part, and the gas dissolved in the raw water is permeated through the peripheral wall of the membrane 11 to the outside of the membrane 11 and discharged through a reduced-pressure line connecting port 15. The treated water freed of dissolved gas is discharged from a treated water outlet 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] Endkanyo provides a degassing separation module that can be suitably used to separate and remove oxygen, carbon dioxide, etc. dissolved or contained in a liquid. The present invention relates to the degassing separation method used.

[Prior Art] Conventionally, when separating and removing a gas dissolved in a liquid, particularly water, it has generally been done to heat the liquid.

[Issue to be Solved by the Invention 21 However, the conventional degassing method by heating requires thermal energy to heat the steam to the saturated steam temperature, and the equipment is large and requires a large space for installation. It has drawbacks such as many problems from an economic point of view.

[Means for Solving the Problems] Therefore, in view of the problems with conventional degassing methods, the present inventors continued intensive studies and developed a porous hollow fiber membrane with a unique fibrillar state for degassing separation. It has been found that it is extremely effective when used, and the present invention has been achieved.

That is, according to the present invention, there is provided a porous hollow fiber membrane of polyolefin, the peripheral wall of which has a group of relatively thick rods running approximately perpendicularly to the length direction of the hollow fiber membrane, and a group of relatively thick rods between the rods. and a group of microfibrils running in the length direction of the hollow fiber membrane and connected between each rod, and a group of strip-shaped micropores is formed by these rods and microfibrils. is used as a liquid degassing separation membrane, a plurality of these are bundled, and both ends of the hollow fiber membrane are embedded in a polymer partition wall with both ends open, and the partition wall connects both ends of the hollow fiber membrane to the housing. A degassing separation module characterized by being liquid-tightly sealed, and
A liquid is introduced into the degassing separation module, and the degree of vacuum is 50.
Provided is a degassing separation method characterized in that the liquid is degassed under reduced pressure of c++*Hg or less.

In a preferred embodiment of the porous hollow fiber membrane used in the present invention, the rod groups run approximately at right angles to the length direction of the hollow fiber membrane, and the average length (a) of microfibrils formed between each rod group is 3. At least twice the length, the rod forms a closed circuit.
2 and 3), preferably at least 5 times the average length (a) of the microfibrils, more preferably 10
It is characterized by forming a closed circuit with more than twice the length. Here, the average length (a) of the microfibrils is taken as an arbitrary point on any of the rods and expressed as the average length of 20 arbitrary microfibrils around the point.

In the present invention, various molding conditions were carefully studied, and relatively thick rod-shaped portions were formed only in a direction substantially perpendicular to the length direction of the hollow fiber membrane. This is a special hollow fiber membrane that is not formed in the longitudinal direction of the hollow fiber membrane.

By forming it in this way, the number of pores per the same area could be increased by 20 to 30%, and the strength could be maintained, making it possible to significantly improve the porosity.

In addition, a preferred embodiment of the hollow fiber membrane used in the module of the present invention is a membrane having a thickness of 50 to 150 JLm, particularly 50 to 10 JLm.
0gm, inner diameter 250-1000m, especially 270-4
When the pore diameter was measured using the bubble point method at 00pm,
Pore size is 0.005-1.0gm, especially 0.05-0.5
It is within the range of gm.

If a hollow fiber membrane having such physical properties is used in a degassing separation module from a liquid, gas dissolved in the liquid can be efficiently removed.

In the hollow fiber membrane used in the degassing separation module of the present invention, preferably an average length (a) of microfibrils starting from any one point on the rod (20 microfibrils surrounding the starting point) (expressed in average length), said rods form a closed circuit. In other words, this means that the length of the microfibrils is approximately constant over the above range.

Note that the term "rod" used in the present invention refers to the shape exhibited on the outer wall surface of the hollow fiber membrane (see Figures 1 and 2), and does not particularly mean a "rod-like" shape, but a hollow fiber membrane. The cross section of the fiber membrane is shown in Figure 3 (Figure 3 is an electron micrograph showing a part of the hollow fiber membrane together with its cut surface. In detail, the upper part of the hollow fiber membrane shown in the figure is hollow). The right side of the lower half of the hollow fiber membrane shown in the same figure shows the vertical cross section of the hollow fiber membrane, and the left side of the lower half of the hollow fiber membrane shown in the same figure. indicates the inner wall surface of the hollow fiber membrane), as shown in the upper part of the hollow fiber membrane. Therefore,
The "rod thickness" in the present invention also means the "thickness" (thickness) exhibited on the outer wall surface of the hollow fiber membrane. As is clear from FIG. 3, the "rod" exhibits the same form on the inner wall surface and longitudinal section of the hollow fiber membrane as on the outer wall surface.

In addition, the density of microfibrils (microreticular fibrils) is determined by the average length of fibrils (
Taking the width of a), it is preferable that the number of microfibrils within the range d above the mouth/throat is 3 or more and 30 or less.

As shown in FIG. 3, the wall portion constituting the peripheral wall of the porous hollow fiber membrane has minute fibrils running between rods running approximately in parallel. That is, in FIG. 3, the rods do not form a closed circuit over 50 d or more with respect to the average length (a) of the microfibrils. This shows that the porosity is dramatically improved, and in other words, the porosity of the same membrane area is dramatically improved.

Such a porous hollow fiber membrane can be manufactured by using a known stretching method at a low temperature as described above.

In addition, the degassing separation module of the present invention, which is used as a porous hollow fiber membrane for degassing separation from a liquid, has a plurality of porous hollow fiber membranes bundled together, with both ends of the hollow fiber membranes in an open state. A high molecular weight polymer (so-called potting material) is embedded in the partition wall, and both ends of the porous hollow fiber membrane are liquid-tightly sealed in the housing by the partition wall. Note that polyurethane resin or the like is generally used as the botting material constituting the partition wall.

As the polyolefin used in producing the porous hollow fiber membrane in the present invention, crystalline polyolefins such as polyethylene, polypropylene, and poly-4-methylpentene-1 are used, and polyethylene and polypropylene are particularly preferred. used. Moreover, polypropylene is preferable especially when heat resistance is required.

Next, an example of separating dissolved gas from a liquid using the degassing separation module of the present invention will be described with reference to FIG.

In FIG. 4, a large number of porous hollow fiber membranes 11 are disposed within the outer cylinder 10, and both ends of the hollow fiber membranes 11 are supported in a fluid-tight manner by a botch ink material 12. Further, at both ends of the hollow fiber membrane 11, an inlet 13 for raw water containing dissolved gas such as oxygen gas and an outlet 14 for treated water from which the dissolved gas has been removed are provided. Roughly the outer cylinder 10 has an outer cylinder 10
A pressure reduction line connection port 15 and a safety valve 16 are provided for reducing the pressure inside the tank.

In the above configuration, raw water is introduced into the hollow portion of the hollow fiber membrane 11 through the raw water inlet 13. The outside part of the hollow fiber membrane 11 is under reduced pressure, and while the raw water introduced into the hollow part of the hollow fiber membrane 11 passes through the hollow part of the hollow fiber membrane 11, the dissolved gas in the raw water is absorbed by the peripheral wall of the hollow fiber membrane 11. It exits to the outside of the hollow fiber membrane 11 through the vacuum line connection port 15 and is discharged through the vacuum line connection port 15. The treated water from which dissolved gas has been removed is then taken out from the treated water outlet 14.

In addition, in the present invention, the degassing separation method using the degassing separation module is preferably carried out at a liquid temperature of 10°C or higher, particularly preferably 25 to so"c. If the liquid temperature is lower than lOoC, Degassing efficiency decreases.

Furthermore, the degree of reduced pressure is 50 csHg or less, preferably 70 cst1g or less. Decompression degree 50c
If it is smaller than o+Hg, degassing will not be carried out effectively.

In addition, the flow rate of the liquid flowing through the hollow part of the porous hollow fiber membrane installed in the degassing separation module is correlated with the membrane area of the module. is preferably 5.0 sentences/win or less, and when the membrane area is preferably in the range of 0.2 to 0.8 m2, the liquid flow rate is 0.2 m2 to 0.8 m2. 1 to 0.5 sentences/win is preferable. When the liquid flow rate exceeds 5.0 sentences/win, the degassing efficiency deteriorates.

Further, since the degassing separation module of the present invention has a structure that can be dried and regenerated by nearing, it is extremely convenient and economical to use.

A method for measuring the pore diameter using the baffle point method will be described next.

The bubble point method is A, S, T, M, (American
5 standard Te5t Method), and is used to determine the maximum pore diameter of a porous material (in this case, a hollow fiber membrane).

That is, pressure by air is gradually applied to the inside of the hollow fibers of a hollow fiber membrane wetted with a solvent, and the maximum pore diameter is determined by the following formula from the pressure when air bubbles first appear on the outside of the hollow fibers.

r=2σ/p where r is the radius of the maximum pore diameter (cm), p is the pressure (dy
ne/cm), cr is the surface tension (dyne/cm
).

Note that the pore size in the present invention is not the maximum pore size, but is determined from the pressure at which bubbles emerge simultaneously.

[Examples] Hereinafter, the present invention will be explained in more detail based on Examples, but it will be clear that the present invention is not limited to these Examples.

(Example 1) Polypropylene (product name: UBE-PP-J 109
G Manufactured by Ube Industries ■, MFI=9g/10min) with a diameter of 3
Using a 0 mm circular slit nozzle, the mixture was melted and spun in a conventional manner, and a hollow fiber membrane was spun at a winding speed of 116 m/min.

After heat treating this hollow fiber membrane at 160°C for 5 minutes, -
Stretched by 15% in a cold bath (liquid nitrogen) at 196°C, then heat-set by treating at a temperature of 150°C for 45 seconds, and further stretched by 300% in a heating medium at 135°C.
After stretching and fibrillation, it was heated to 80℃ at the same temperature.
% shrinkage (based on that before being stretched by 300%) and heat treatment was performed.

An electron micrograph of the outer wall surface of the hollow fiber membrane obtained is shown in FIG.

This hollow fiber membrane has an inner diameter of 320 gm, a membrane thickness of 55 μm,
The pore diameter is 0.25 pm (measured by the bubble point method). Using this hollow fiber membrane, degassing separation modules with various specifications shown in Table 1 were fabricated. Under the conditions shown in Table 1, the degassing separation module was A performance test for deoxidizing oxygen dissolved in water was conducted according to the outlined flowchart shown below.

In FIG. 5, the raw water enters the degassing separation module 17, is degassed, and the treated water JP! The amount of dissolved oxygen was measured using a dissolved oxygen (DO) meter 19. Note that 20 indicates a needle valve.

The results are shown in Table-1.

(The following is a blank space) Table 1 [Effects of the invention] As explained above, according to the degassing separation module of the present invention and the degassing separation method using the same, porous hollow fibers having the above-described specific structure Since a membrane is used, degassing can be efficiently separated from the liquid.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph showing the shape of a part of the outer wall surface of the porous hollow fiber membrane used in the degassing separation module of the present invention, and FIG. Electron wJ micrograph showing the shape of the fibers in the area further enlarged, No. 3
The figure is an electron micrograph showing the shape of some fibers of a porous hollow fiber membrane along with their cut surfaces. FIG. 4 is a schematic diagram showing an example of the degassing separation module of the present invention, and FIG. 5 is a schematic flow diagram showing an example of degassing using the degassing separation module. - 10... Outer cylinder, 11... Porous hollow fiber membrane, 12...
・Potting material, 13...Raw water inlet, 14...
Treated water outlet, 15...reduction line connection port. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A porous hollow fiber membrane of polyolefin, the peripheral wall of which is comprised of a group of relatively thick rods running approximately perpendicularly to the length direction of the hollow fiber membrane, and between each rod the hollow fiber membrane A porous hollow fiber membrane consisting of a group of microfibrils running in the length direction and connected between each rod, and a group of strip-shaped micropores formed by these rods and microfibrils is used to degas the liquid. Used as a separation membrane, a plurality of these are bundled, and both ends of the hollow fiber membrane are embedded in a polymer partition wall in an open state, and both ends of the hollow fiber membrane are liquid-tightly sealed in a housing by the partition wall. A degassing separation module characterized by: (2) A porous hollow fiber membrane of polyolefin, the peripheral wall of which is comprised of a group of relatively thick rods running approximately perpendicular to the length direction of the hollow fiber membrane, and between each rod the hollow fiber membrane A porous hollow fiber membrane consisting of a group of microfibrils running in the length direction and connected between each rod, and a group of strip-shaped micropores formed by these rods and microfibrils is used to degas the liquid. Used as a separation membrane, a plurality of these are bundled, and both ends of the hollow fiber membrane are embedded in a polymer partition wall in an open state, and both ends of the hollow fiber membrane are liquid-tightly sealed in a housing by the partition wall. A degassing separation method characterized by introducing a liquid into a degassing separation module made of a degassing separation module, and degassing the liquid under a reduced pressure of 50 cmHg or less.