JPH03109904A - Permeable gasifying membrane module and degassing method - Google Patents

Abstract

PURPOSE:To efficiently remove a material to be treated by fitting a carrier gas introducing means to the reduced pressure side of a permeable gasifying membrane module. CONSTITUTION:A liq. introducing inlet 4 and a liq. discharging outlet 5 are separately fitted to spice parts leading to the insides of hollow fibers 1 in module housing 2. An air breeder composed of a needle valve 6 and a gas introducing inlet 7 and an exhaust port 8 connected to a vacuum pump are fitted to a space part leading to the outsides of the hollow fibers 1. For example, distilled water contg. 2-methylisoborneol is passed through the module and the 2- methylisoborneol in the water is removed. A mixture having a low b.p. can be efficiently separated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a new and useful pervaporation membrane module and a degassing method. More specifically, the present invention provides an improved pervaporation membrane module (hereinafter also referred to as a membrane module or module) provided with a new means of introducing a carrier gas, and an improved pervaporation membrane module (hereinafter also referred to as a membrane module or module) provided with a new means of introducing a carrier gas. An improved degassing method comprising the use of a membrane module.

The present invention provides an improved pervaporation deaerator and a pervaporation deaeration method,
In other words, we provide an improved pervaporation membrane module and degassing method that efficiently removes the target (liquid to be treated) that should be removed, such as gases, malodorous substances, or volatile substances contained in the liquid. It is something to do.

[Conventional technology]

By the way, so far, we have used a selectively permeable membrane as a diaphragm.
By introducing the liquid to be treated into one side of this diaphragm and reducing the pressure on the other side of the membrane, gases and volatile substances dissolved in the liquid are removed, which is called pervaporation. Diaphragm deaeration using this method is known.

Under these current technological conditions, for example, when purifying tap water, that is, removing volatile harmful substances such as foul-smelling substances and low-boiling halogen compounds contained in water, the amount remaining in the treated water must be extremely small. is required.

Incidentally, it is said that 2-methylisoborneol, which is considered to be the causative agent of moldy odor, gives off an odor at 10 ppt (ppt = 10-12), and therefore it is required to remove the odor to an order of magnitude lower than that.

However, with conventional diaphragm degassing, it is difficult to completely remove dissolved substances even if they are gases, and it is difficult to completely remove dissolved substances when they are liquids at room temperature and have low vapor pressure. was particularly difficult. That is, in removing volatile dissolved substances from a liquid by pervaporation,
The residual concentration of a substance that is liquid at room temperature is ○, t p
There was no known method for removing it to below pm.

In addition, when a water ring type vacuum pump is used as a vacuum pump in an application to remove oxygen from water, due to restrictions on the degree of pressure reduction, the dissolved oxygen concentration may be reduced to 0.5 ppm at room temperature, for example. If you try to make the remaining amount as low as below,
There was a drawback that the processing flow rate became significantly small.

[Problems to be Solved by the Invention] However, in view of the various problems and various drawbacks in the prior art as described above, the inventors of the invention have attempted to solve these problems, and have attempted to eliminate the various drawbacks. With this goal in mind, we began earnest research.

Therefore, the problem to be solved by the present invention is to provide an effective method for purifying clean water by pervaporation, that is, to develop a method for effectively purifying clean water by permeating volatile harmful substances such as trihalomecune and I-lichloroethylene contained in clean water. A method for almost completely removing odors such as mold, a method for removing odor such as mold to a level below the sensory darkness level, and a method for removing oxygen from water while keeping the residual oxygen concentration low.
The object of the present invention is to provide a method for increasing the throughput, and also to provide an extremely useful pervaporation membrane module that is suitable for purification methods in such various cases.

In other words, the problem to be solved by the present invention is to provide an improved pervaporation type deaerator and a deaeration method using the pervaporation type.

[Means for Solving the Problems] Therefore, the inventors of the present invention focused on the problems to be solved by the invention as described above, and as a result of intensive studies,
An improved pervaporation membrane module comprising a new means for introducing a carrier gas, and an improved method of degassing comprising using a membrane module provided with such a means for introducing a carrier gas. Thus, we have completed the present invention.

That is, the present invention provides, in part, a pervaporation membrane module comprising means for introducing a carrier gas, that is, by introducing a liquid into one side of the diaphragm and reducing the pressure of the gas phase on the other side. The present invention provides a pervaporation membrane module that removes gas or volatile substances contained in a liquid to the gas phase side, in which a carrier gas introducing means is provided on the pressure reduction side of the membrane module. The second method is a degassing method which consists of using a pervaporation membrane module equipped with a III gas feed introduction means; By depressurizing the gas phase on one side,
In a degassing method using a pervaporation method, which involves removing gases or volatile substances contained in the liquid to the gas phase side, a carrier gas is introduced into the gas phase side of the membrane module to increase the removal effect. The purpose of this invention is to provide a method for degassing the air in a manner that will encourage the user to do so.

Here, first, the pervaporation membrane module of the present invention,
In other words, the deaeration membrane module introduces the liquid to be treated into one side of the diaphragm, and reduces the pressure on the other side of the diaphragm using a conventional pressure reduction means such as a vacuum Honda, and then 1 A small amount of carrier gas is introduced by the general gas introduction means.

Air bleeders are a particularly typical means of introducing the carrier gas, but the main point of the Gagaru air bleeder is to introduce air or other gases from outside the module to the decompression section of the module. It should be understood that it is equipped with minute ventilation holes that have the function of introducing air.

The air bleeder with such minute ventilation holes may have a mechanism such as an orifice, a valve, or a gas flow rate regulating device.

Among these, a needle valve mechanism is preferable because it is inexpensive, easy to handle, and allows the flow rate to be adjusted.

Further, as the carrier gas introducing means, a metered gas supply device equipped with a gas pump may be used.

Typical examples of the carrier gas to be introduced include air, nitrogen, carbon dioxide, and inert gas, which may be selected as appropriate depending on the purpose.
-1- When the purpose is to purify water, it is desirable to use air because it is simple.

It is also desirable for air breeders to be equipped with a filter to remove dust, oil, etc.

In the following, unless otherwise specified, the carrier gas introduction means will be described as being represented by an air bleeder.

The air bleeder may be installed at any location on the membrane module, as long as the streamline of the gas introduced from the air bleeder comes into contact with the diaphragm. The most efficient method is to install the air bleeder at the farthest position from the connection port (not shown), so that the volumetric flow of gas introduced from this air bleeder carries away the volatile substances that have passed through the diaphragm. is good and desirable.

Incidentally, a preferred embodiment of the pervaporation membrane module of the present invention is shown in FIG. 2, which shows an external perfusion type membrane module, in which the diaphragm is a hollow fiber type membrane module. When the inside of the hollow fiber 1 is in a gas phase, it is desirable to have a structure in which the gas is introduced into the hollow fiber end opposite to the hollow fiber end facing the gas outlet 8.

On the other hand, another preferred embodiment of the pervaporation membrane module of the present invention is a membrane module in which the diaphragm is of a hollow fiber type, as shown in FIG. When the outside of the hollow fiber 1 is in the gas phase, the hollow fiber itself is sealed in the form of a braided body, or the module is It is also possible to provide a special structure, such as a neck flow path diversion means such as a baffle plate, so that the gas introduced from the air bleeder efficiently carries away the volatile substances that have passed through the diaphragm.

In the present invention, it is also possible to use a carrier gas introducing means in which the gas flow rate adjustment mechanism is integrated with the module, or the gas flow rate adjustment mechanism and the seven wheels may be combined together. It is also possible to use carrier gas introduction means in the form of a separate carrier gas introduction means, thus allowing the gas to be introduced by connecting the carrier gas introduction means to the gas phase side of the module.

The amount of gas introduced from the conical reader depends on the type of pressure reduction means, degree of pressure reduction and displacement, pressure loss on the pressure reduction side of the module, type of volatile substance to be removed, vapor pressure, membrane permeability and permeation amount, etc. In the present invention, the flow rate is set to be 0.01 to 50 Torr higher than the degree of vacuum measured at the exhaust port 8 when no air bleeder is provided, although each is different.

If the amount of introduced gas is outside this range, the removal effect will be reduced or a large capacity decompression means will be required.

The optimal amount of gas to be introduced can be determined by conducting a simple experiment by varying the amount of gas introduced as appropriate and measuring the amount of residual gas or residual low-volatile substances in the treated water. can.

The pressure of the gas supplied to the air bleeder is but not limited to.

In addition, the degree of vacuum on the gas phase side of the module in the present invention is
The level normally used in the pervaporation method may be used; for example, at the outlet 8, the pressure may be 0.01 to 20 Torr.
A degree of vacuum can be employed.

The present invention can be applied to all systems for removing volatile substances from liquids, but especially when the volatile substance to be removed is a substance with a low vapor pressure and a boiling point of 35 to 250°C. effective. For example, trihalomecun,
halogen compounds such as trichloroethylene, tetrachloroconylene, dichloroethane, trichloroethane;) hydrocarbons such as luene or henzene or gasoline; water-soluble organic solvents such as methanol, ethanol or acetone; or fluorine-containing compounds such as freon. These include various organic solvents such as 2-methylisoborneol and diosmin, and various malodorous substances such as 2-methylisoborneol and diosmin. It also includes volatile malodorous substances and volatile harmful substances contained in tap water, even if they are not identified.

1 The present invention is also particularly effective in applications where volatile substances are highly degassed from liquids. For example, it is effective in removing harmful substances such as malodorous substances and i-rehalomethane from water used for drinking or eating. According to the present invention, it is possible to remove low boiling point halogen compounds such as goloform and trichloroethylene contained in water to 0.1 ppm or less, and it is also possible to remove high boiling point compounds such as 2-methylisoborneol. It is possible to remove odor to below the detection limit of odor (referred to as 10 ρρ).

There are no particular limitations on the liquid to which the present invention can be applied. In other words, the present invention can be applied by selecting a diaphragm suitable for the target liquid. However, it is particularly useful when the liquid is water. For example, tap water, gray water, washing water or waste water.

The present invention is also effective in deoxidizing water.

In particular, by introducing air as a carrier gas], it is possible to reduce the residual oxygen concentration if the treatment is constant, and increase the treatment flow rate if the residual oxygen concentration is constant. becomes possible.

The degree of increase in throughput at this time is due to the low vacuum of 5 to 200 Torr on the reduced pressure side of the membrane module.
Moreover, the residual oxygen concentration is at the equilibrium value (
The effect of the present invention is particularly large when it is as low as 4 times or less the convergence value of the residual oxygen concentration when the processing flow rate is extrapolated to an infinitesimal value, and the effect of the present invention is maximized.

Furthermore, it is truly surprising that by using so-called air containing oxygen as the carrier gas, rather than nitrogen or inert gas, the effect of increasing the processing flow rate or reducing the residual oxygen concentration increases. That's true.

Therefore, in the present invention, there is no need to limit the type or structure of the diaphragm, and any diaphragm can be used as long as it is suitable for the intended system.
Among these, the most representative ones are asymmetric membranes with non-porous layers, non-porous homogeneous membranes, porous membranes, flat membranes, hollow fiber membranes, and tubular membranes. Any material such as a membrane can be applied.

There are no restrictions on the pressure reducing means, and it can be selected as appropriate depending on the purpose and application.

(Effects of the Invention) First, the present invention makes it possible to remove volatile substances dissolved in a liquid to an extremely low residual amount. In addition, it is also possible to remove harmful substances such as low boiling point halogen compounds contained in tap water down to 0.1 ppm or less. This is what I did.

In this way, by deaeration using the pervaporation method, low vapor pressure substances that are liquid at room temperature can be converted to 0.1. Up to now, no method has been known that can remove the residual amount to a level as low as ppm or less.

The present invention is also applicable to the deoxidation of water, and according to the present invention, treated water with a low residual oxygen concentration can be reliably obtained in a large throughput.

Moreover, to deoxidize this water, it is possible to use a filtration seal vacuum pump that is small, lightweight, and easy to maintain, and it is also possible to use air, which is inexpensive and simple, as the carrier gas. There is a Meriso I. that says it can be done.

Furthermore, the present invention can realize the various effects described above with an extremely simple mechanism, and therefore can be used in existing pervaporation devices without introducing any special and costly mechanism. It also has Merino I., in which the degassing effect can be further increased by simply modifying only the extreme <- part.

The pervaporation membrane module and deaeration method of the present invention are useful, for example, for deodorizing and purifying tap water.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A hollow fiber heterogeneous membrane manufactured by a melt molding method using poly 4 methylpentene 1 as a material has an outer diameter of 253 pm and an inner diameter of 199 μm, and the gas permeation rate measured according to IIsTM old 434 is as follows. Oxygen permeation rate 2, 4 x 1.
0-”cm3(STP) 7cm2.sec, c
mllIX and the nitrogen permeation rate is 6.2XIO”
'cm' (STP) 7 cm2.sec, cmllg. 1,0000 of these hollow fiber membranes were loaded into a module housing in a parallel bundle, and the effective hollow fiber length was 500 mm.
An internal perfusion type module as shown in FIG. 1 was fabricated. A space connected to the inside of the hollow fiber 1 of the module housing 2 includes a liquid inlet 4 and a liquid discharge port 4.
Further, in the space connected to the outside of the hollow fiber, an air bleeder consisting of a needle valve 6 and a gas introduction lower, and an exhaust port 8 to which a vacuum pump is connected are provided.

To this module, add 0.51% of distilled water to which 2-methylisoborneol has been added, or distilled water to which chloroborum and 6-trichlorethylene have been added. /
It flows at min, and the displacement is 50 at the exhaust port, i'! /m
An oil rotary vacuum pump was connected to reduce the pressure, and the amount of air introduced was adjusted using a needle valve. The amounts of volatile substances in the raw water and the discharged water at this time are shown in Table 1 along with a comparative example when the needle valve was fully closed. Note that the gas phase pressure in the table is a value measured at the exhaust port 8.

Comparative Example 1 An experiment was carried out in exactly the same manner as in Example 1, except that the needle valve was completely closed so that no air was introduced at all. The results are shown in Table 1.

Example 2 The outer diameter is 28271 m, the inner diameter is 217 μm, and the oxygen permeation rate is 3.4 X IF 'cm' (STP)/c
m2. sec, cmtlg, nitrogen permeation rate is 3.
1 Xl0-'cm'(STP)/cm", seccm
The hollow fiber membrane was fabricated in the same manner as in Example 1, except that it was changed to 12 filaments of 30 denier, and the hollow fiber density was 25 using the twine weaving method.
A force 1] was applied to a blind-like sheet called CT11. This hollow fiber sheet was wrapped around a hard polyhinyl chloride pipe 9 with a diameter of 13 mm and an inner diameter of 10 mm.
-[Joule Housing 2] made of hard PVC
The effective membrane area (based on the hollow fiber outer surface) of the shape shown in FIG. 2 is 5. We have created an external perfusion type module.

Distilled water added with 2-methylisoborneol, distilled water added with chloroborum, and trichloroethylene was flowed through the module at 2.0 A/min, and a water ring vacuum with an exhaust volume of 45 Of2/min was applied to the exhaust port. A pump was connected to reduce the pressure, and the amount of air introduced was adjusted using a needle 9 valve. At this time, the amount of volatile substances in the raw water and the discharged water is
The results are shown in Table 1 along with a comparative example in which Leharbe is fully closed. Note that the gas phase pressure in the table is a value measured at 1-1-8.

Comparative Example 2 An experiment was carried out in exactly the same manner as in Example 2, except that the needle valve was completely closed so that no air was introduced at all. The results are shown in Table 1.

Example 3 Using the same hollow fiber membrane as in Example 1, a module having the same shape as in Example 1 and a membrane area (inner surface area) of 130τ was produced. Tap water is run through this module, a water ring vacuum pump with a displacement of 450β/min is connected to the exhaust port to reduce the pressure, and the amount of air introduced is adjusted using a needle valve so that the pressure at the exhaust port 8 is 29 torr. adjusted. At this time, the dissolved oxygen concentration of the raw water introduced into the module is 8.5 ppm, and the dissolved oxygen concentration of the treated water is:
o when the water flow rate is extremely low (0, l l /min)
, ssppm. Treatment 0 The dissolved oxygen concentration of treated water increases with the increase in water flow rate, and
,! The flow rate to reach 5 ppm was 7.41/min.

Furthermore, under conditions where the amount of air introduced was adjusted so that the pressure was 33 torr, the dissolved oxygen concentration of the treated water was as low as the water flow rate of 0. 0.38 pp when I Q /m1nO
m, which was slightly worse than Comparative Example 3, but the flow rate at which the dissolved oxygen concentration of the treated water reached 0.5ρρm was 8.31
/min.

Comparative Example 3 The same test as in Example 3 was conducted except that the needle valve was changed to be fully closed. The pressure at the exhaust port 8 is 2
At 8 torr, the dissolved oxygen concentration in raw water is 8.5 ppm
So, when the flow rate of water is 0.11/min, the dissolved oxygen concentration in the treatment is 0.35 ppm, and the flow rate at which the dissolved oxygen concentration of the treated water becomes 0.5 ppm is 7, OR/m.
It was tn.

[Brief explanation of drawings]

Each drawing shows a preferred embodiment of the present invention, and FIG. 1 is a partial vertical cross-sectional front view of the membrane module used in Example 1, and FIG. FIG. 3 is a longitudinal sectional front view of the membrane module. In the figure, 1 is a hollow fiber, 2 is a housing, 3 is a resin sealing part,
4 is a liquid inlet, 5 is a liquid outlet, 6 is a needle valve, '1 is a gas inlet, 8 is an outlet, and 9 is a porous pipe. agent

Claims (1)

[Scope of Claims] 1. A pervaporation membrane module, characterized in that a carrier gas introduction means is provided on the pressure reduction side of the pervaporation membrane module. 2. A deaeration method characterized by using a pervaporation membrane module provided with a carrier gas introduction means on the pressure reduction side of the pervaporation membrane module. 3. Claim 3 or 4, wherein the carrier gas is air.
Deaeration method described in. 4. Claim 4, wherein the liquid is water or an aqueous solution.
Deaeration method described in. 5. The degassing method according to claim 4, wherein the volatile substances are trihalomethane, trichloroethylene, tetrachloroethylene, and trichloroethane. 6. The deaeration method according to claim 4, wherein the target to be removed is oxygen.