JPH04171002A - Recovering method for performance of film module - Google Patents

Abstract

PURPOSE:To recover efficiently the performance of a film module with lowered performance by removing water solution on one side in the case that the performance of the film module is lower than the initial performance, reducing the pressure of water solution on the other side and retaining its pressure-reduced state. CONSTITUTION:In a film module for removing a permeating dissolved component, by bringing a water solution on one side, in which gas or low boiling volatile organic material (example: methanol) is dissolved, into contact with a film module and making the vapor pressure of said water solution component close to zero on the other side through a water non-permeable film interposed between both sides, when the performance is its initial performance, the water solution on one side is removed, while the pressure on the other side is reduced and said pressure reduced state is retained. As a result, the film module can be dried simply and quickly to remove the water vapor, and the performance of the film module can be recovered efficiently to reduce the operation cost, maintenance cost and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for restoring the performance of a membrane module, and particularly to a method for restoring performance that is effective in the field of membrane modules used in degassing processes.

[Prior Art and Problems to be Solved by the Invention] When using an aqueous solution, there are many fields in which it is necessary to remove gases or organic substances dissolved therein. In this field, a membrane module has been proposed that uses a water-impermeable membrane to remove dissolved components that permeate through the membrane from an aqueous solution in which gas or low-boiling volatile organic substances are dissolved.

However, the components that permeate through the membrane are not as large as the above-mentioned dissolved components, and some water also permeates as vapor molecules. As a result, the permeated water vapor has a significantly higher boiling point than other dissolved components, so it condenses easily, and this condensed water accumulates on the support layer of the membrane, on the permeation side, and in a part of the ventilation spacer. There is. Although the presence of this water had no effect on separation performance in the initial state, it became a factor in permeation resistance. Therefore, when operating at high temperatures, continuously for long periods of time, or in places where the outside temperature changes drastically, condensate formation becomes noticeable and the initial performance deteriorates.

Previously, it was not clear what the cause of this was, so no effective countermeasures had been taken.Currently, there was no countermeasure other than replacing the module after the performance deteriorated.

[Means to solve the problem]

As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered that the performance of a membrane module whose initial performance has deteriorated can be restored by the following method, leading to the present invention.

That is, the first method of the present invention involves contacting one side with an aqueous solution in which a gas or a low-boiling volatile organic substance is dissolved through a water-impermeable membrane, and bringing the vapor pressure of the aqueous solution components close to zero on the other side. In a membrane module for removing permeated dissolved components, if its performance is lower than the initial performance, remove the aqueous solution on one side and maintain the other under reduced pressure with a vacuum pump to remove the water vapor inside. This is a method of forcibly exhausting the air to the outside. The operating conditions at this time are preferably -300 mmHg or less and maintaining the reduced pressure state for 1 minute or more, particularly preferably -600 mmHg.
The vacuum state is maintained for 30 minutes or more. If the conditions are outside this range, only a small amount of moisture will be exhausted, so it will take a long time to dry, which is not practical. The vacuum pump used is not particularly limited as long as it can meet the above conditions; for example, water ring type, diaphragm type, dry rotary type, oil rotary type, etc. can be used.

According to this method, there is no need to heat the module to a high temperature, and a vacuum pump used for removing gases or low-boiling volatile organic substances can be used, so operations such as attaching and detaching the module are not necessary.

Further, in the present invention, a condenser can be installed in front of the vacuum pump to supplement water vapor. Furthermore, by applying external heat within the module's allowable temperature range, performance can be restored in a shorter time.

The second method of the present invention is a method of forcibly removing water vapor inside the module by flowing dry gas to the water passage side after removing water inside the module. The operating conditions at this time are to ventilate for at least 1 minute at a temperature of room temperature or above, at a rate of INl/min or above (preferably at a temperature of 40°C or above, at a temperature of 5ON).
i! It is desirable to ventilate the room at a rate of at least /min for at least 300 minutes. If such conditions are outside the above range, the drying gas will take a long time to dry because only a small amount of moisture will accompany the drying gas, which is practically undesirable. The dry gas to be vented is preferably dry air, and the active gas is N2, Ar, He.
etc. can also be used.

According to this method, the amount of ventilation can be freely changed, and the ventilation temperature can also be changed freely within the range of the heat-resistant temperature of the module, so the drying time can be shorter than that of the first method. It is possible.

Furthermore, since no water vapor condensation occurs, there is no need to use a condenser.

The third method of the present invention is to remove water inside the module and then supply dry gas (air or inert gas) at atmospheric pressure or higher to the water passage side, allowing water vapor to flow outside while permeating the membrane. This is a method to remove. The operating conditions at this time are to hold the pressure at room temperature or higher and atmospheric pressure or higher for 1 minute or more, preferably at 40°C or higher and 3 kg/cd or higher.
It is desirable to apply pressure for 0 minutes or more. When such conditions are outside the above range, gas permeation does not occur or is only slight, so that only a small amount of moisture is entrained, which is not preferred in practice.

According to this method, unlike the ventilation method described above, since dry gas is forced to flow through the membrane, it is possible to exhaust moisture condensed in the membrane support layer and the permeation side ventilation spacer to the outside as water vapor. It is.

Further, as with other methods, it is possible to shorten the drying time by heating within the allowable temperature range of the module.
Furthermore, since the pressure can be applied within the range up to the withstand pressure of the module, the amount of permeated gas can also be changed to shorten the drying time.

The aqueous solution to which the present invention is applied is not particularly limited as long as it is an aqueous solution in which a gas is dissolved or a low-boiling volatile organic substance is dissolved therein.

For example, liquid chromatography, automated clinical chemistry analysis,
Industrial applications such as analytical instruments such as medical spectrophotometers, ion exchange water processes, ultrapure water systems for semiconductor manufacturing, power generation, general industry, boiler water used in ship boilers, nuclear power plant water, turbine water, etc. Examples include liquids and wastewater used in connection with this. These liquids usually include river water, well water, tap water, industrial water, pharmacopoeia ordinary water, etc., and generally contain cations such as Ca, Mg, Na, etc., chloride ions, sulfate ions, bicarbonate ions, etc. It is a liquid that contains anions, living organisms, or decayed and decomposed organic matter. It also includes liquids containing substances that are not soluble in water, such as colloidal particles and suspended particles.

The present invention can also be applied to drinking water flowing inside general household water pipes, building water supply pipes, cooling towers, circulating water pipes, etc. and building water supply.

The present invention can also be applied to water used in the production of soy sauce, raw water used in the production of beverages such as beer, alcohol, juice, coffee, and water used in the production process.

The gases dissolved in the various aqueous solutions mentioned above include oxygen, carbon dioxide, nitrogen, chlorine, and ammonia.

In addition, low-boiling volatile organic substances refer to substances that have a boiling point lower than that of water and have a vapor pressure or the same temperature. For example, lower alcohols such as methanol, ethanol, butanol, propatool, carbon tetrachloride, cloiform,
Halogen hydrocarbons such as chlorofluorocarbons, other methyl ethers,
Ethers such as ethyl ether, methyl ethyl ketone,
Examples include ketones such as acetone.

The performance recovery method of the present invention can be applied to any type of membrane module and is not limited to that type in any way.

〔Effect of the invention〕

According to the method of the present invention, since water vapor can be removed by simply and quickly drying a membrane module, the performance of a membrane module whose performance has deteriorated can be efficiently restored, reducing operating costs and
This has the advantage of reducing maintenance costs, etc.

〔Example〕

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 A composite membrane was obtained by forming silicone to a thickness of 1.5 μm on a polysulfone porous membrane formed on a nonwoven fabric.

The nitrogen gas permeation rate of this composite membrane at 30'C was 0.75 Nm/rrl'-h-atm.
Using this membrane, the raw water side spacer has a thickness of 0.35 aun,
Permeation side spacer 〇, 3[[1 thickness, membrane area 2.2rrl]
'A spiral module was molded.

With the permeate side of the module under a vacuum of -745 mmHg, ultrapure water with dissolved oxygen of 8.111) pm (25°C) was supplied at a flow rate of 1. As a result of water passing at a rate of 0.000 t/h, the dissolved oxygen concentration at the outlet was 1.01 ppm.

This module was installed at room temperature and at a flow rate of 0.72 t/h.
After passing water for 2 hours, the outlet dissolved oxygen concentration measured under the above conditions was 2
．． It became 70 ppm, and the performance deteriorated.

Using this module with degraded performance, after draining the water remaining on the raw water side, the permeate side was brought to a vacuum of -710 mIIHg, and after being held at room temperature for 1 hour, the outlet dissolved oxygen concentration measured under the above conditions was 1.46 ppm. The recovery rate was 73%. Here, the recovery rate is: Performance decrease D〇 - DO after recovery Recovery rate = lOOX (96)
Performance decrease D〇 - Initial DO. (DO = dissolved oxygen) Example 2 A module with the same specifications as the module used in Example 1 was run at 60°C and at a flow rate of 0.72 t/h for 2 hours, resulting in a performance drop to the same extent as in Example 1. I got the module.

Using this module, performance recovery was performed under the conditions shown in the table below. The results are also shown in the table.

Claims (3)

[Claims] (1) By contacting one side with an aqueous solution in which a gas or a low-boiling volatile organic substance is dissolved through a water-impermeable membrane, and bringing the vapor pressure of the aqueous solution components close to zero on the other side,
The performance of a membrane module for removing permeating dissolved components, which is characterized in that when its performance is lower than its initial performance, one aqueous solution is removed, the other is reduced in pressure, and the reduced pressure state is maintained. Recovery method. (2) A method for restoring the performance of a membrane module according to claim (1), characterized in that instead of reducing the pressure on the other side, dry gas at room temperature or higher is passed through the side from which the aqueous solution has been removed. (3) A method for restoring the performance of a membrane module according to claim (1), characterized in that instead of reducing the pressure on the other side, the side from which the aqueous solution has been removed is kept under pressure with dry gas at room temperature or higher.