JPH05168865A - Method for dehydrating water solution of organic matter - Google Patents

Abstract

PURPOSE:To make treatment with high dehydration and concentration efficiencies in a method for dehydrating water solution of organic matter where the water solution of organic matter is brought into contact with a pervaporation membrane and vapor permeating through the membrane is condensed and separated by keeping the secondary pressure sufficiently low. CONSTITUTION:A water soluble organic solvent or its water solution is injected as vapor into the permeation side of a pervaporation membrane 2a. By injecting the water soluble solvent as vapor into the permeated vapor side, the freezing point of the permeated vapor is decreased, to prevent solidification in a condenser 3. Thereby, even if the secondary pressure is reduced to a high degree, the condensate is smoothly discharged to outside the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating an aqueous solution of an organic matter, and more particularly to a method for separating water in an aqueous solution of an organic matter such as an ethanol aqueous solution or an isopropyl alcohol aqueous solution by using a pervaporation membrane to enhance the dehydration efficiency. The present invention relates to a method for dehydrating an organic matter aqueous solution, which has a significantly low water content and is capable of recovering highly concentrated organic matter.

[0002]

2. Description of the Related Art Conventionally, a pervaporation method has been known as a method for dehydrating and removing water from an aqueous solution to concentrate dissolved components. This method uses a pervaporation membrane having a special affinity for water, and water in an aqueous solution supplied to one side (primary side) of this membrane permeates and permeates the membrane to the other side of the membrane. (Secondary side)
It is a method of concentrating components that are difficult to permeate by separating water by evaporating with.

A method of performing a conventional general pervaporation method will be described below with reference to FIG.

FIG. 2 is a system diagram of a conventional aqueous solution dehydration / concentration apparatus using a pervaporation membrane. In the figure, 1 is an aqueous solution heater, 2a is a pervaporation membrane that selectively permeates water,
2 is a membrane module unit, 3 is a permeated vapor condenser,
4 is a vacuum pump on the secondary side.

In the illustrated conventional method, the aqueous solution to be treated supplied from the pipe 7 is heated by the heater 1 and then supplied to the primary side of the membrane module unit 2 via the pipe 9. The secondary side of the membrane module unit 2 is decompressed by the vacuum pump 4. Moisture having an affinity for the pervaporation membrane 2a in the aqueous solution supplied to the primary side of the membrane module unit 2 permeates and permeates the pervaporation membrane 2a and evaporates on the secondary side. Then, the water introduced into the condenser 3 through the pipe 13 and condensed in the condenser 3 is
It is discharged from the system after passing 5. In addition, the non-condensable gas and vapor that does not condense in the condenser 3 is connected to the pipe 14 and the vacuum pump 4.
And discharged through the pipe 16 to the outside of the system. On the other hand, the residual liquid that has not permeated through the pervaporation membrane 2a of the membrane module unit 2 becomes a concentrated liquid in which the water concentration is reduced and the components in the aqueous solution are concentrated due to the permeation of water, and the concentrated liquid goes out of the system through the pipe 10. Is discharged.

In such a pervaporation method, the aqueous solution is highly treated, for example, the aqueous solution to be treated has a water concentration of 1000 pp.
In order to dehydrate and concentrate to a low water concentration such as m or less, the water vapor partial pressure of the aqueous solution on the primary side needs to be maintained at a value higher than the water vapor partial pressure on the secondary side. Therefore, the following operations are required. The temperature of the primary side aqueous solution is raised to increase the water vapor partial pressure. In order to reduce the water vapor partial pressure on the secondary side, the secondary side is decompressed as much as possible. That is, it is generally important to set the operating temperature as high as possible and the secondary pressure as low as possible.

Therefore, in the method shown in FIG. 2, the heater 1 heats the aqueous solution to be treated to a temperature close to the heat resistant temperature of the pervaporation membrane 2a, and the vacuum pump 4 further presses the secondary side pressure (hereinafter "2"). It is necessary to evacuate the secondary pressure) to as low a pressure as possible, that is, to a high vacuum.

[0008]

By the way, the pressure on the condensation side of the condenser 3 is substantially equal to the secondary pressure. Therefore, when the secondary pressure is lowered, the pressure on the condensation side of the condenser 3 is lowered, and unless the operating temperature is lowered, the permeated vapor enters the vacuum pump 4 without being condensed. As a result, the vacuum pump 4 becomes overloaded and the secondary pressure cannot be maintained at a low set value, making it impossible to operate the process.

In order to solve such a problem, it is necessary to lower the operating temperature of the condenser 3 in order to sufficiently condense the permeated vapor. However, it has been found that when the operating temperature of the condenser 3 is lowered, the permeated vapor freezes (freezes) immediately after the condensation when the water content in the permeated vapor is high.

When the condensate is solidified and solidified in the condenser 3, it cannot be extracted from the pipe 15. Therefore, even if an attempt is made to lower the operating temperature of the condenser in order to improve the reduction of the condensation rate of the permeated vapor due to the low secondary pressure and increase the condensation rate, the condensation temperature cannot be lowered to below the freezing point of the condensate. It was difficult to raise the rate sufficiently.

The present invention solves the above-mentioned conventional problems, and in the dehydration and concentration treatment of an aqueous solution by the pervaporation method, the secondary pressure is kept sufficiently low, and the condensate is prevented from coagulating to ensure stable operation. In addition, it is an object of the present invention to provide a method for dehydrating an aqueous solution of an organic matter, which can be processed with high dehydration and concentration efficiency.

[0012]

A method for dehydrating an aqueous solution of organic matter according to claim 1 is to bring the aqueous solution of organic matter into contact with a pervaporation membrane,
In a method for dehydrating an aqueous solution of an organic matter in which vapor permeating the membrane is condensed and separated, a water-soluble organic solvent or its aqueous solution is injected into the permeate side of the membrane by vapor.

The method for dehydrating an aqueous solution of organic matter according to a second aspect is characterized in that, in the method for the first aspect, a part of the aqueous solution of the organic matter to be treated is injected into the permeate side of the membrane by vapor.

The method for dehydrating an aqueous solution of organic matter according to claim 3 is the method according to claim 1 or 2, wherein the aqueous solution of organic matter to be treated is an aqueous ethanol solution, and the water-soluble organic solvent injected into the permeation side of the membrane by steam is ethanol. It is characterized by

The method for dehydrating an aqueous solution of organic matter according to claim 4 is the method according to claim 1 or 2, wherein the aqueous solution of organic matter to be treated is an isopropyl alcohol aqueous solution, and the water-soluble organic solvent injected into the permeation side of the membrane by vapor is isopropyl alcohol. Is characterized in that

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing one embodiment of a method for dehydrating an aqueous solution of organic matter according to the present invention. In addition, in FIG.
Members having the same functions as those shown in FIG. 2 are designated by the same reference numerals.

In the illustrated embodiment, the pipe 13 for feeding the permeated vapor of the pervaporation membrane 2 to the condenser 3 is connected to the pipe 17,
An evaporation supply means for the water-soluble organic solvent (or an aqueous solution thereof) consisting of the heating evaporator 5 and the pipe 18 was connected.

In the method of this embodiment, the aqueous organic substance solution to be treated supplied from the pipe 7 is heated by the heater 1 and then supplied to the primary side of the membrane module unit 2. Of the aqueous solution supplied to the primary side, water having an affinity for the pervaporation membrane 2a selectively permeates and permeates 2a, is evaporated on the secondary side, and is depressurized by the vacuum pump 4,
The steam is extracted from the pipe 13.

On the other hand, the water-soluble organic solvent supplied from the pipe 17 evaporates in the heating evaporator 5, merges with the secondary vapor in the pipe 13 through the pipe 18, and is fed to the condenser 3. It is cooled and condensed in the condenser 3. At the time of cooling and condensation in the condenser 3, since the vapor of the water-soluble organic solvent is mixed with the permeated vapor, the mixed vapor has a lower freezing point than that in the case where only the permeated vapor is contained.

Here, the composition of the mixed vapor supplied to the condenser 3 can be easily adjusted to an arbitrary value by controlling the amount of the water-soluble organic solvent supplied from the pipe 17. Therefore, the composition of the liquid cooled and condensed in the condenser 3 can be arbitrarily adjusted.

Therefore, the composition of the condensate can be adjusted so as to obtain a desired freezing point, and the freezing point can be lowered so that a desired saturated vapor pressure can be obtained. That is, the moisture concentration of the condenser 3 can be sufficiently lowered without coagulating (freezing) the condensate, and the saturated vapor pressure of the condensate corresponding thereto can be lowered, so that the permeation vaporization membrane 2a 2 It is possible to sufficiently lower the secondary pressure to perform a high degree of membrane permeation, prevent solidification in the condenser 3, and smoothly discharge the condensate from the pipe 15.

On the other hand, the non-condensable gas and vapor that are not condensed in the condenser 3 are discharged to the outside of the system through the pipe 14, the vacuum pump 4 and the pipe 16.

The non-permeable component of the pervaporative membrane 2 is extracted from the pipe 10.

In the present invention, as the water-soluble organic solvent to be injected into the permeated vapor, it is advantageous to use the same kind as the organic substance in the aqueous solution of the organic substance to be treated.

Particularly, in the present invention, it is most economical and preferable to separate a part of the aqueous solution of the organic substance to be treated and inject it into the permeated vapor. In this case, for example, in FIG.
A branch pipe 20 is provided in the pipe 7, and a part of the aqueous solution of the organic substance to be treated is passed through the pipe 20, the heating evaporator 5 and the pipe 18 to form the pipe 13
Should be injected into.

In the present invention, the amount of the water-soluble organic solvent to be injected into the permeated vapor may be any amount as long as it can lower the freezing point to the extent that coagulation of the permeated vapor can be prevented in the condenser. It is appropriately determined depending on the components, the water concentration, the degree of the secondary pressure, the temperature of the condenser, the type of water-soluble organic solvent to be injected, and the like.

The method of the present invention as described above is particularly effective for dehydration treatment of an aqueous ethanol solution or an isopropyl alcohol solution. In this case, ethanol or isopropyl alcohol is vaporized and injected into the permeated vapor, or This can be easily carried out by collecting a part of the aqueous solution of the organic substance to be treated and injecting it by evaporation.

[0029]

By mixing the water-soluble organic solvent with water, the freezing point of the obtained mixture becomes lower than the freezing point of water.

Therefore, according to the method of the present invention, by injecting the water-soluble organic solvent as vapor into the permeate vapor side, the freezing point of the permeate vapor is lowered, and the coagulation in the condenser is prevented.

Therefore, when the secondary pressure is set to a high degree of reduced pressure, even if the temperature of the condenser is lowered in order to improve the condensation efficiency, solidification does not occur in the condenser and the permeated vapor is efficiently condensed. Thus, the condensate can be smoothly discharged out of the system.

In particular, as the water-soluble organic solvent, it is preferable to use the same kind of organic substance as the aqueous solution of the organic substance to be treated, and in particular, a part of the aqueous solution of the organic substance to be treated is collected and evaporated to be industrially used. It can be economically implemented.

The method of the present invention is particularly effective for dehydrating an aqueous ethanol solution or an isopropyl alcohol solution.

[0034]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 An isopropyl alcohol aqueous solution was dehydrated according to the method shown in FIG.

[0036] Note that the pervaporation membrane 2a, using a composite film which code the polyvinyl alcohol polyimide resin, permeation area was fabricated membrane module unit 2 to be 10 m ^2.

The aqueous solution of the organic substance to be treated is an aqueous solution containing 99% by weight of isopropyl alcohol, and the supply amount is 1
It was supplied to the membrane module unit at 0 kg / h and a supply temperature of 110 ° C.

The secondary side of the pervaporation membrane 2a is provided with a vacuum pump 4
The temperature of the condenser 3 was set to -20 ° C. 96.4 g / h of 99 wt% isopropyl alcohol aqueous solution was supplied from the pipe 17 so that the permeated vapor of the pervaporation membrane 2a would not solidify.

In this case, the amount of vapor permeated through the pervaporation membrane 2a is 105 g / h, and the isopropyl alcohol concentration is 5
% By weight. This vapor was evaporated in the heating evaporator 5 and merged with the isopropyl alcohol vapor injected through the pipe 18 to become vapor having an isopropyl alcohol concentration of 50% by weight. The vapor was in a liquid state and smoothly extracted from the pipe 15 without solidifying in the condenser 3.

In this example, the water concentration of the residual liquid that did not pass through the membrane, which was extracted from the membrane module unit 2 through the pipe 10, was 30 ppm, and it was confirmed that the water was highly dehydrated.

Incidentally, in the method of this embodiment, the conventional method in which isopropyl alcohol vapor is not injected into the permeated vapor is
Moisture concentration of the residual liquid obtained in Comparative Example 1 below 440 ppm
On the other hand, a dehydration effect as much as 15 (440 ppm / 30 ppm) times was obtained.

Comparative Example 1 According to the conventional method shown in FIG. 2, dehydration was performed in the same manner as in Example 1 except that the permeated vapor was directly introduced into the condenser 3 and cooled.

In the condenser 3, the permeation vaporization membrane 2a was kept at a secondary pressure of 7 TORR by cooling with a 0 ° C. refrigerant so that the permeated vapor would not solidify. The amount of permeated vapor is 1
The concentration of isopropyl alcohol was 00.6 g / h, and the concentration was 5.0% by weight.

As a result, the water concentration of the residual liquid obtained from the membrane module unit 2 was 440 ppm, and it was not possible to carry out a high degree of dehydration.

[0045]

As described in detail above, according to the method for dehydrating an aqueous solution of organic matter of the present invention, it is possible to highly dehydrate and concentrate the aqueous solution of organic matter under stable operation of the apparatus.

[0046]

[Brief description of drawings]

FIG. 1 is a system diagram showing a method for carrying out a method for dehydrating an organic matter aqueous solution of the present invention.

FIG. 2 is a system diagram showing a conventional example.

[Explanation of symbols]

 1 Heater 2 Membrane Module Unit 2a Pervaporation Membrane 3 Condenser 4 Vacuum Pump 5 Heating Evaporator

Claims (4)

[Claims] 1. An organic aqueous solution is brought into contact with a pervaporation membrane,
A method for dehydrating an aqueous solution of organic matter, comprising condensing and separating vapor that has permeated through the membrane, comprising injecting a water-soluble organic solvent or an aqueous solution thereof with vapor into the permeate side of the membrane. 2. The method for dehydrating an organic matter aqueous solution according to claim 1, wherein a part of the organic matter aqueous solution to be treated is injected into the permeate side of the membrane with steam. 3. The method for dehydrating an aqueous solution of organic matter according to claim 1, wherein the aqueous solution of organic matter to be treated is an aqueous solution of ethanol, and the water-soluble organic solvent injected into the permeate side of the membrane by steam is ethanol. .. 4. The organic substance aqueous solution according to claim 1, wherein the organic substance aqueous solution to be treated is an isopropyl alcohol aqueous solution, and the water-soluble organic solvent injected into the permeate side of the membrane by vapor is isopropyl alcohol. Dehydration method.