JPH05168874A - Leak detection for pervaporation - Google Patents

Abstract

PURPOSE:To promptly detect the leak of supply liquid from the liquid supply side to the reduced pressure side in a pervaporation method by measuring the temp. of permeated vapor. CONSTITUTION:In a pervaporation method (permeation vaporization method) wherein, by reducing the pressure on one side of a separation membrane and supplying a liquid mixture (water/alcohol, water/isopropylalcohol, water/ allylalcohol, etc.) to on the other side, priority is given to passing of a specified component through the separation membrane to separate (concentrate) the component, when the leak of the liquid mixture due to pinholes, rupture, etc., of the separation membrane to the reduced pressure side is detected, the temp. of permeated vapor is measured on the reduced pressure side to detect the leak of the liquid mixture to the reduced pressure side from the change of the permeated vapor temp. Thereby the leak of the liquid mixture is promptly detected and the reliability of separation treatment is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting leakage of a supply liquid from a supply liquid side to a decompression side in a pervaporation method (pervaporation method) for separating a specific liquid component from a liquid mixture. ..

[0002]

2. Description of the Related Art A pervaporation method is known as an effective technique for concentrating a specific liquid component from an organic liquid mixture or a mixture of water and an organic liquid, especially a compound having a boiling point close to it, or an azeotropic mixture.

The pervaporation method is a method in which one side of a separation membrane is decompressed and a liquid mixture is supplied to the other side so that only a specific liquid component is preferentially passed through the separation membrane for separation. Therefore, pinholes and breaks in the separation membrane,
Alternatively, when a crack occurs between the separation membrane and the fixing means, the liquid mixture leaks to the decompression side, and there is a problem that only a specific liquid component cannot be sufficiently separated.

[0004]

After assembling the pervaporation apparatus using the separation membrane, it is possible to find pinholes, breakages, etc. of the separation membrane by performing a pressure test or a pressure reduction test. .. On the other hand, pinholes and breakage of the separation membrane that occur during the operation of the pervaporation device are currently detected due to an increase in the amount of permeate, a decrease in the concentration of permeate, or a deterioration in the degree of vacuum on the pressure reducing side. There is.

However, the above-mentioned increase in the amount of permeated liquid,
The phenomenon that the concentration of permeated liquid and the concentration of permeate do not decrease does not appear immediately after the occurrence of pinholes in the separation membrane, so that there is a problem that the discovery is delayed. Further, the phenomenon that the degree of vacuum on the depressurization side deteriorates does not appear prominently when the volume on the depressurization side of the pervaporation apparatus is large, so it is not suitable as a means for detecting the occurrence of pinholes in the separation membrane.

For this reason, there has been a demand for a method of quickly detecting the leakage of the liquid mixture to the depressurization side due to pinholes, breakage, etc. of the separation membrane.

[0007]

As a result of various studies to solve the above problems, the inventors of the present invention have found that a change in permeated vapor temperature on the reduced pressure side is an index for detecting a leakage phenomenon of a liquid mixture to the reduced pressure side. Therefore, they have come to propose the present invention.

That is, according to the present invention, in the pervaporation method, the leak detection method of the pervaporation method is characterized by detecting the leakage of the supply liquid from the supply liquid side to the decompression side by measuring the permeated vapor temperature. Is.

As the separation membrane used in the pervaporation method of the present invention, known separation membranes can be used without any limitation. Examples thereof include polymers such as cellulose, polyvinyl alcohol, polyamide, polyester, polysulfone, polycarbonate, polyimide and chitosan. Can be mentioned. Examples of the shape of the separation membrane include, but are not limited to, a plate-and-frame type in which flat membranes are laminated, a spiral type, and a module type in which hollow fibers are potted.

As the liquid mixture separated by the pervaporation method, an organic liquid mixture or a mixture of water and an organic liquid can be used without any limitation. Specifically, water / ethyl alcohol, water / isopropyl alcohol,
Water / n-propyl alcohol, water / allyl alcohol,
Water / 2,3-dichloro-1-propanol, water / 2-methoxyethanol, water / isobutyl alcohol, water / 1
-Butanol, water / 2-butanol, water / furfuryl alcohol, water / pentanol, water / 2-pentanol,
Water / water / alcohol-based mixture such as 4-methyl-1-butanol: water / tetrahydrofuran, water / methyl ethyl ketone, and the like.

The leakage of the supply liquid from the supply liquid side to the decompression side in the present invention mainly occurs from the separation membrane. There are pinholes, spots, cracks, and the like in the form of leakage points. The flat membrane-like one in which the separation membrane is pressed with a gasket or the like has leakage that occurs from the sealing surface of the gasket, and the hollow fiber membrane-like one that is potted with an adhesive is fixed with an adhesive. There is also a leak from the part.

In the present invention, it is possible to immediately detect the leakage of the feed liquid by measuring the temperature of the permeated vapor. Generally, the permeated vapor temperature is a value obtained by subtracting the latent heat consumed by the vapor on the separation membrane from the temperature of the supplied liquid. The inventors of the present invention have repeated the experiment by paying attention to the fact that the amount of liquid that permeates when the separation membrane leaks is remarkably large, and as a result, a very large amount of heat is generated when the leaked liquid evaporates on the reduced pressure side. It was discovered that the permeated vapor temperature drops extremely as it is consumed. Therefore, the leakage of the separation membrane can be easily found by measuring the permeated vapor temperature. Here, the permeated vapor temperature naturally changes when the separation membrane type, the feed liquid concentration, and the feed liquid temperature differ, but the permeated vapor amount is always constant during steady-state operation where these conditions are constant, so the permeated vapor temperature is The temperature is always constant. Therefore, it is possible to detect the leakage of the supply liquid because the permeated vapor temperature is lower than the constant temperature during the steady operation.

The range of decrease in the permeated vapor temperature when the mixed liquid leaks varies depending on the above operating conditions, but is generally 5 ° C.
It can be determined that the leakage of the mixed liquid has occurred when the width of the decrease is within the above range.

In the present invention, the permeated vapor temperature is the temperature on the reduced pressure side of the separation membrane. This temperature varies depending on the separation membrane and the liquid mixture, but is generally somewhat lower than the temperature of the feed liquid. The location for measuring the temperature of the permeated vapor is preferably near the separation membrane, which is less susceptible to heat transfer from the outside.

[0015]

According to the leakage detection method of the pervaporation method of the present invention, it is possible to detect the leakage that has occurred in the separation membrane and its surroundings irrespective of the separation membrane species, the supply liquid concentration, the supply liquid temperature and the like. Therefore, when a leak occurs, it is possible to immediately stop the separation, find the leaked portion, and repair it.

[0016]

EXAMPLES The contents of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Water contained in isopropyl alcohol was dehydrated by a pervaporation device using a module having 150 modules of a polyimide-based hollow fiber membrane having an inner diameter of 0.8 mm and a total length of 30 cm as potting. The mixed liquid of isopropyl alcohol and water heated to 60 ° C. was supplied to the inside of the hollow fiber membrane, and the outside was pulled to a reduced pressure and kept at 7 mmHg. The amount of the supply liquid at the start was 50 l, and the concentration was isopropyl alcohol: water = 90: 10 (mass%), and the concentration of isopropyl alcohol was increased by performing batch operation. When the permeated vapor temperature with respect to the feed liquid concentration during operation was measured, the values shown in Table 1 were obtained. Supply liquid concentration is isopropyl alcohol: water = 99.5: 0.5
When (wt%) was reached, water was added until the concentration became isopropyl alcohol: water = 90: 10 (wt%), and dehydration was continued again. When this operation was repeated, 8
At the 02nd time, the supply liquid concentration was isopropyl alcohol: water =
At 90:10 (% by weight), the permeation vapor temperature dropped sharply to 32 ° C., so when dehydration was stopped and the module was examined, pinholes were found in one hollow fiber.

[0018]

[Table 1]

Claims (1)

[Claims] 1. A leak detection method of the pervaporation method, characterized in that the leak of the supply liquid from the supply liquid side to the decompression side is detected by measuring the permeation vapor temperature in the pervaporation method.