JP2898080B2 - Operation method of degassing membrane device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operation method of a degassing membrane device for separating a gas (gas) dissolved in a liquid or a low-boiling volatile organic substance in a liquid, Specifically, condensate (mainly solvent) of the evaporation component of the stock solution accumulated on the permeate side of the degassing membrane module during operation
Is removed after the operation is stopped and / or before the operation is restarted, and the operation is always started in a state where there is no condensate on the permeation side.

[Problems to be solved by conventional technology and invention]

In order to separate the gas (gas) dissolved in the liquid or the low-boiling volatile organic substance in the liquid, the pressure of the substance to be separated on the permeation side is adjusted to the concentration of the substance to be separated in the feed liquid (stock solution). It is necessary to make the pressure lower than the equilibrium pressure (Henry's law). As a specific method, a method of reducing the pressure on the permeate side with a vacuum pump, or sending (sweeping) a gas different from the substance to be separated to the permeate side, etc. Has been proposed. However, when a degassing membrane device based on such a principle is actually operated, on the permeate side of the degassing membrane module, some of the evaporated components (mainly a solvent) evaporated on the supply side are condensed, and as a result, the membrane of the substance to be separated is condensed. There is a problem that the resistance of permeation is caused and the separation speed gradually decreases, that is, the membrane performance gradually decreases.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when the membrane deaerator is operated intermittently, by adopting a specific operation method, the dissolved gas or dissolved low boiling point The inventors have found that volatile organic substances can be efficiently separated, and have reached the present invention.

That is, the present invention relates to a degassing membrane device equipped with a degassing membrane module for bringing a dissolved gas or a liquid containing a low-boiling volatile organic substance into contact with a permeable membrane and selectively permeating and separating them. After the stock solution on the supply side of the degassing membrane module is drained, the supply side is opened to atmospheric pressure air, and the permeate side of the degassing membrane module is dried after the degassing operation is stopped and / or before the degassing operation is restarted. And removing the condensate on the permeate side to recover the performance of the degassing membrane module, and then restarting the operation of the degassing membrane device.

In the present invention, the method for drying the permeate side of the degassing membrane module and removing the condensate on the permeate side is not particularly limited as long as the performance of the degassing membrane module can be recovered, but preferably the following method can be adopted.

The first method is a method in which the permeate side is reduced in pressure by a vacuum pump and the entire amount of room temperature or heated atmospheric pressure air is permeated through the membrane, thereby evaporating and removing the condensate on the permeate side. The operating conditions at this time are generally such that the pressure on the permeate side is 5 to 30.
The pressure may be 0 mmHg and atmospheric pressure air at room temperature to 80 ° C. may be completely permeated through the membrane for 0.5 to 5 hours.

The second method is a method in which condensate on the permeate side is removed by evaporation by sending room temperature or heated atmospheric air from one side of the supply side to the other side.

The operating condition at this time may be that air at room temperature to 80 ° C. is normally blown at a flow rate of 40 Nl / min or more for 0.5 to 6 hours.

The third method is to open the permeate side to atmospheric pressure air, send room temperature or heated pressurized air to the supply side, and perform permeation through the entire membrane to evaporate and remove condensate on the permeate side. How to The operating conditions at this time are usually from room temperature to
Pressurized air at 80 ° C. and a pressure of 1 kgf / cm ² or more may be permeated through the membrane for 0.5 to 5 hours.

As another method, a method of evaporating and removing the condensate on the permeation side by leaving it to stand naturally for a predetermined time can be used.

The liquid to which the operation method of the present invention is applied is not particularly limited as long as the liquid in which gas is dissolved or the liquid in which low-boiling volatile organic substances are dissolved. For example, boilers used for liquid chromatography, automated clinical chemistry analysis, analytical instruments such as medical spectrophotometers, ion-exchanged water processes, ultrapure water systems for semiconductor production, power generation, general industry, marine boilers, etc. Liquids and wastewaters used in connection with industrial uses such as water for use, nuclear power, water for turbines, and the like can be given. These liquids usually include river water, well water, tap water, industrial water, local water, etc., and are generally Ca, Mg, N
It is a liquid containing cations such as a and K, anions such as chlorine ions, sulfate ions and hydrogen carbonate ions, and organic substances decomposed and decomposed by living organisms. Further, a liquid containing a substance that does not dissolve in water, such as colloid particles and suspended particles, is also included.

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

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

The gases dissolved in the various aqueous solutions described above include oxygen,
Carbon dioxide, nitrogen, chlorine, ammonia and the like.

In addition, a low-boiling volatile organic substance is a substance having a boiling point lower than that of water and having a high vapor pressure at the same temperature. For example, methanol, ethanol, butanol, lower alcohols such as propanol, carbon tetrachloride, chloroform,
Halogen hydrocarbons such as Freon, other methyl ethers
Ethers such as ethyl ether, methyl ethyl ketone,
And ketones such as acetone.

The operation method according to the present invention can be applied to any type of degassing membrane device equipped with a degassing membrane module, and is not limited to any particular type.

〔The invention's effect〕

According to the method of the present invention, in an intermittently operated degassing membrane device, during operation, a condensate of an evaporating component (mainly a solvent) accumulates on the permeate side of the degassing membrane module, and a film of the substance to be separated is formed. Even if the performance of the degassing membrane device deteriorates as a result of permeation resistance, the condensate can be removed by the evaporating operation while the operation is stopped, so that operation in which the performance in a predetermined range is always maintained is possible. There are advantages.

〔Example〕

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

Example 1 A permselective composite membrane having an active thin film of about 1.5 μm thick crosslinkable silicone resin on an aromatic polysulfone porous membrane formed on a nonwoven fabric was obtained. Of such composite membrane
The oxygen transmission rate at 25 ° C. was 1.1 Nm ³ / m ² · h · atm. Using this membrane, the raw water side spacer is 0.35 mm thick, the transmission side spacer is 0.3 mm thick, the element diameter is 60 mm, and the length is 1
m, a spiral module having a membrane area of 3.2 m ² was molded. FIG. 1 shows a degassing membrane device equipped with such a module.

In this degassing membrane device, city water (dissolved oxygen concentration (DD
7.9 ppm) at a flow rate of 0.35 m ³ / h, and the deaeration operation (operation 1) was performed for 20 hours while maintaining the permeate pressure at 15 ± 2 mmHg.

At the end of operation, valves 6, 9 are closed and valves 7,
8 was opened to remove raw water from the supply side of the degassing membrane module 5, and the supply side of the module was opened to atmospheric pressure air. After a lapse of 3 hours, the heaters 11 and 12 were turned on, and the vacuum pump 4 was operated at a pressure of 50 mmHg to allow the entire amount of air at 60 ° C. to pass through the membrane for 1 hour. Thereafter, a degassing operation was performed for 20 hours under the same conditions as in Operation 1 (Operation 2).

Table 1 shows the concentration (DO value) of the dissolved oxygen in the treated water in the initial and final stages of Runs 1 and 2.

COMPARATIVE EXAMPLE A degassing membrane device equipped with the same spiral type degassing membrane module as in Example 1 was supplied with city water (dissolved oxygen concentration (DO
7.9 ppm) at a flow rate of 0.35 m ³ / h, and the deaeration operation (operation 1) was performed for 20 hours while maintaining the permeate pressure at 15 ± 2 mmHg.

After the operation, the raw water was left on the supply side of the degassing membrane module for 4 hours. Thereafter, a degassing operation was performed for 20 hours under the same conditions as in Operation 1 (Operation 2). Operation 1 and Operation 2
Table 1 shows the treated water DO values in the initial and final stages of the process.

Example 2 City air at 26 ° C (dissolved oxygen concentration (DO value) is 7.9 ppm) was flowed at a flow rate of 0.35 m into a degassing membrane device equipped with the same spiral type degassing membrane module as in Example 1 (Fig. 2). Dewatering operation (operation 1) was performed for 20 hours while passing water at ³ / h and maintaining the permeate pressure at 15 ± 2 mmHg.

At the end of operation, valves 6, 9 are closed and valves 7,
By opening 8 and 10, the raw water entering the supply side of the degassing membrane module was drained, and the supply side of the module was opened to atmospheric pressure air. After 2 hours, the valve 10 was closed, the heater 11 and the blower 13 were turned on, and air at 50 ° C. was blown at a flow rate of 150 Nl / min for 2 hours.

Thereafter, a degassing operation was performed for 20 hours under the same conditions as in Operation 1 (Operation 2). Table 1 shows the DO values of the treated water in the initial and final stages of the operation 1 and the operation 2.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are schematic views of an apparatus for carrying out an operation method of a degassing membrane apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Undiluted solution supply part, 2 ... Processing liquid outflow part, 3 ... Liquid supply pump, 4 ... Vacuum pump, 5 ... Degassing membrane module, 6
… 10 …… Valve, 11 ～ 12 …… Heater, 13 …… Blower

Claims (1)

(57) [Claims] 1. A degassing membrane device equipped with a degassing membrane module for contacting a liquid containing a dissolved gas or a volatile organic substance with a low boiling point with a permeable membrane to selectively permeate and separate them, and the operation is stopped. After the stock solution on the supply side of the degassing membrane module is drained, the supply side is opened to atmospheric pressure air, and the permeate side of the degassing membrane module is dried after the degassing operation is stopped and / or before the degassing operation is restarted. Removing the condensate on the permeate side to recover the performance of the degassing membrane module and restarting the operation of the degassing membrane module.