JPH0780252A - Pervaporation membrane separator and method for stopping operation thereof - Google Patents

Abstract

PURPOSE:To stop the operation of a pervaporation membrane separator especially for a short period of time by relatively simple operation in order to prevent the swelling of a separation membrane. CONSTITUTION:In a pervaporation membrane separator, a membrane module having the function of cooling the liquid coming into contact with a membrane at the time of the stop of operation, pref. constituted so that a cooling jacket cooling the liquid coming into contact with the membrane is formed to the periphery of a module can body is installed and, further, function passing a cooling medium through the cooling jacket at the time of the stop of operation to cool the liquid coming into contact with the membrane is formed. A method for stopping the operation of the pervaporation membrane separator is characterized by that the liquid coming into contact with the membrane is cooled without extracting the raw soln. on the supply side of the pervaporation membrane module at the time of the stop of operation and the vacuum degree on the transmission side of the pervaporation membrane module is kept and a supply soln. is heated while the vacuum degree on the transmission side is kept at the time of the resumption of operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pervaporation membrane separation apparatus, a membrane module used therein, and a method for stopping the operation of the pervaporation membrane separation apparatus. More specifically, the present invention relates to a permeation vaporization membrane separation device having a mechanism suitable for performing a method of stopping the operation of the pervaporation membrane separation device suitable for an emergency or a short period of suspension, and the like.

[0002]

2. Description of the Related Art As one of methods for separating a mixed liquid, a separation membrane having a special affinity with a component of the mixed liquid is used.
The mixed liquid is supplied to one side (primary side) of the separation membrane, and the other side (secondary side) is decompressed so that the vapor partial pressure of the permeated component on the secondary side is smaller than the equilibrium vapor pressure on the primary side. There is known a pervaporation method (pervaporation method) in which a specific component in a liquid mixture is vaporized and permeated from the primary side to the secondary side while being retained to be separated.

When performing the pervaporation method, the primary side of the separation membrane is in contact with the supply liquid (mixture to be separated), and the secondary side (permeation component side) is depressurized. The supply liquid (primary side) is heated because the permeation component takes heat of vaporization when permeating from the primary side to the secondary side. Further, since the permeation component (secondary side) is vaporized, it is general to provide a cooling device on the secondary side to condense and liquefy.

Conventionally, when the operation of the pervaporation membrane separator is stopped, all of the equipment on the primary side (supply side) and the secondary side (permeate side) are stopped, or the cooling device on the secondary side is stopped. Everything except the (condenser) was stopped, and the liquid to be separated was left in contact with the membrane. In this operation stop method, the separation membrane swells due to the liquid to be separated, which causes deterioration of the membrane, which is a problem.

As a method for solving the above-mentioned problems, only the operation of the equipment on the supply side is stopped and the operation on the permeation side is continued to supply a dry gas to the separation membrane or a liquid having no affinity to the separation membrane. A method has been proposed (JP-A-5-571).
No. 56). Further, as another method, a method has been proposed in which the stock solution on the supply side is drained during operation stoppage, the supply side is opened to atmospheric pressure air, and the permeate side is dried after operation stoppage and / or before restarting operation. (Japanese Patent Laid-Open No. 4-243527).

However, these methods require a labor-intensive operation such as supplying a dry gas or the like to the supply side or draining the stock solution, and the operation is stopped particularly for a short period (several hours to several tens of hours). It was not suitable for emergency stop.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a method for stopping the operation of a pervaporation membrane separation apparatus which is suitable for short-term operation stoppage and the like, which does not cause swelling of the separation membrane at the time of operation stoppage and is relatively easy to operate, It is an object of the present invention to provide a pervaporation membrane separation device suitable for that purpose.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that, in a pervaporation membrane separator, in order to cool the liquid in contact with the membrane around the permeation membrane module can body. By providing a cooling jacket for the above, cooling the liquid contacting the membrane without removing the stock solution on the supply side of the pervaporation membrane module when the operation is stopped, and keeping the degree of vacuum on the permeation side of the pervaporation membrane module The inventors have found that the problems can be solved and arrived at the present invention.

That is, the gist of the present invention is, in a pervaporation membrane separation device for bringing a liquid mixture to be separated into contact with a pervaporation membrane and selectively permeating the liquid component to separate the liquid component,
A permeation membrane separator having a function of cooling the liquid in contact with the membrane when the operation is stopped, and a cooling jacket for cooling the liquid in contact with the membrane are provided around the module can body. In the operation of the pervaporative membrane module characterized and the pervaporative membrane separation device, when the operation is stopped, the liquid in contact with the membrane is cooled without draining the stock solution on the supply side of the pervaporative membrane module and the permeate side of the pervaporative membrane module is removed. In the method for stopping the operation of the pervaporation membrane separation device, the supply liquid is heated while maintaining the vacuum degree on the permeate side when the operation is restarted.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram for explaining one embodiment of the present invention. The pervaporation membrane separator is operated as follows during steady operation. The supply liquid is supplied from the undiluted liquid supply unit 1 via the liquid feed pump 2 and is heated by the heater 3 and then the pervaporation membrane module 6
Is supplied to the supply section (primary side) of the. The permeation side (secondary side) of the pervaporation membrane module 6 is decompressed by the vacuum pump 11. Components that do not pass through the pervaporation film are discharged as liquid from the line 8 to the outside of the system. The component that permeates the pervaporation membrane permeates the separation membrane while vaporizing and is sent to the condenser 10 via the line 9. The condenser 10 is cooled and condensed, and the condensate is discharged from the line 13 and the non-condensed component is discharged to the outside of the system from the line 14.

Here, the supply liquid may be any liquid mixture separated by the pervaporation method, for example, ethanol-water mixed liquid, isopropyl alcohol (IPA) -water mixed liquid, ethanol-benzene mixed liquid, acetic acid. -Water-mixed liquids are possible. The pervaporation film is not particularly limited, but polysulfone film, polyimide film,
Pervaporation membranes such as silicone-based membranes, xaton-based membranes, and cellulose-based membranes are used. The shape of the membrane is a hollow fiber membrane,
Examples thereof include spiral film shape.

The temperature heated by the heater 3 varies depending on the supply liquid, but in the alcohol-water system, for example, 60 to 12
It is 0 ° C. Depending on the temperature of the supply liquid, it is necessary to pressurize the primary side to prevent boiling. The pressure on the secondary side can be arbitrarily determined within a range smaller than the equilibrium vapor pressure on the primary side,
Usually, it is 0.1 to 100 Torr.

In the present invention, as the membrane module used in such a pervaporation membrane separator, a membrane module can is provided with a cooling jacket for cooling the liquid in contact with the membrane, and the operation is stopped. Sometimes, a coolant is passed through the jacket to cool the liquid in contact with the membrane. This allows
The operation of pervaporation membrane separation can be stopped while maintaining the degree of vacuum on the permeate side without removing the stock solution to be supplied to the membrane module.

The operation stopping method for pervaporation membrane separation of the present invention is performed in the following procedure. First, the liquid feed pump 2 is stopped and the heating by the heater 3 is stopped. Next, the valve 16
Is opened and the cooling medium is supplied to the cooling jacket 17 to cool the supply liquid in contact with the pervaporation film. As the cooling jacket, a normal cooling jacket having a distance between the inner cylinder and the outer cylinder of 5 mm or more is used. Water is usually used as the refrigerant.

In the operation stop method of the present invention,
The method for cooling the supply liquid is not limited to this. For example, when the heater 3 is a heat exchanger, a method of switching the heating medium to the cooling medium can be exemplified. Cooling is performed until a temperature at which pervaporation does not substantially occur. The specific temperature depends on the type of permeation component and the secondary pressure.
The supply of the refrigerant may be stopped when the temperature of the supply liquid in contact with the film becomes equal to or lower than a predetermined temperature.

At this time, the vacuum pump 11 is continuously operated and the degree of vacuum on the secondary side is maintained. Next, a method of restarting operation will be described. The valve 16 is closed to stop the supply of the refrigerant, and then the refrigerant is extracted from the cooling jacket. Next, heating is started by the heater 3, and the operation of the liquid feed pump 2 is started. Since the degree of vacuum on the secondary side is maintained, the operation can be promptly restarted by the above operation.

Further, in the above apparatus of the present invention, a back pressure valve is provided in the pipe for supplying the liquid mixture to the pervaporation membrane module, and a check valve is provided at the liquid side outlet (primary side outlet) of the pervaporation membrane module. It is preferable to provide the liquid crystal to prevent backflow or inflow of the liquid when cooled. FIG. 2 is a schematic diagram illustrating a mode in which a back pressure valve is provided in the liquid mixture supply pipe and a check valve is provided in the liquid side outlet pipe.

When the temperature of the liquid in contact with the pervaporation membrane is lowered by supplying the refrigerant, the pressure of the liquid is reduced. If no measures are taken to reduce the liquid pressure, the liquid flows into the pervaporation membrane module 6 from the liquid mixture supply pipe and / or the liquid side outlet pipe. This may lead to an unfavorable situation during an emergency stop. When the liquid mixture flows into the pervaporation membrane module 6, after the operation is restarted,
There is also a risk that liquid that has not been sufficiently separated exits from the primary outlet.

Therefore, as shown in FIG. 2, a back pressure valve 21 is provided in the liquid mixture supply pipe, and a check valve 20 is provided in the liquid side outlet pipe.
Is provided to contain the liquid in the pervaporation membrane module when the operation is stopped, so that the inflow of the liquid can be prevented and the inside of the pervaporation membrane module can have a negative pressure. As a result, for example, in the event of an emergency stop at the time of leakage, it is possible to stop the amount of leaked liquid to a minimum.

Further, in the above apparatus of the present invention, it is also a preferable embodiment that a back pressure valve is provided in the refrigerant outlet pipe of the cooling jacket to prevent a rapid evaporation and vaporization of the refrigerant supplied to the jacket. FIG. 3 is a schematic diagram for explaining a mode in which a back pressure valve is provided in the refrigerant outlet pipe of the cooling jacket.

When the operating temperature of pervaporation is higher than the boiling point of the refrigerant, the refrigerant supplied to the cooling jacket is rapidly vaporized and the volume becomes several hundred times or more. Exhausting this as it is requires a large-diameter exhaust line, which is not preferable. Therefore, when the operating temperature of the pervaporation membrane is higher than the boiling point of the refrigerant, as shown in FIG. 3, the refrigerant outlet pipe is discharged at a pressure higher than the vapor pressure of the refrigerant at the operating temperature of the pervaporation membrane. It is a preferred embodiment to provide the back pressure valve 22. In this case, the refrigerant is supplied to the cooling jacket at a pressure higher than the setting of the back pressure valve.

As described above, in the operation stop method of the present invention, since the liquid temperature on the primary side is lowered by cooling, there is no driving force for pervaporation, and pervaporation is stopped.
On the other hand, the degree of vacuum on the secondary side is maintained, and vaporization of the permeated component condensate occurs on the surface of the separation membrane in contact with the secondary side. Therefore, although the separation membrane is in contact with the supply liquid, the separation membrane is in a substantially dry state except the surface on the primary side, and it is possible to avoid swelling or the like due to the separation target liquid.

[0023]

EXAMPLES The present invention will now be described in more detail based on the examples shown in FIG. 1, but the present invention is not limited to these examples without departing from the gist thereof. <Example 1> Using the pervaporation membrane separator shown in FIG. 1, water was separated from this liquid mixture by a pervaporation method using a feed liquid as an IPA (isopropyl alcohol) -water mixture system. As the pervaporative membrane, a hollow fiber pervaporative membrane that selectively permeates water was used.

(1) During steady operation, the operation was as follows.
First, the supply liquid is supplied from the raw liquid supply unit 1 via the liquid feed pump 2,
After being heated to near the boiling point (about 83 ° C. at 1 atm) by the heater 3, it was supplied to the supply part (primary side) of the pervaporation membrane module 6. The permeation side (secondary side) of the pervaporation membrane module 6 was depressurized to about 5 to 10 Torr by the vacuum pump 11. The component (IPA) that does not pass through the pervaporation membrane was discharged from the system through line 8 as a liquid. The component (water) that permeated through the pervaporation membrane permeated the separation membrane while being vaporized, and was sent to the condenser 10 via the line 9. The water was cooled and condensed in the condenser 10, and the condensed liquid was discharged from the line 13 and the non-condensed component was discharged from the line 14 to the outside of the system.

(2) Next, the operation was stopped as follows. First, the liquid feed pump 2 was stopped and the heating by the heater 3 was stopped. Next, the valve 16 was opened, and cooling water (about 20 ° C.) was supplied to the cooling jacket 17 at a flow rate of about 2 to 3 l / min to cool the supply liquid in contact with the pervaporation membrane. The temperature of the feed liquid in contact with the membrane is 4 after about 5 minutes
At 0 ° C, pervaporation substantially stopped.

Cooling water was supplied for 30 minutes and then stopped. The vacuum pump 11 was continuously operated, and the degree of vacuum on the secondary side was maintained at about 5 to 10 Torr.

[0027]

The pervaporation membrane separation device and the method for stopping the operation thereof according to the present invention can be implemented by a relatively simple operation.
Moreover, swelling of the separation membrane can be prevented. It is especially useful for short-term shutdown.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for explaining one embodiment of the present invention.

FIG. 2 is a schematic view of an apparatus for explaining another aspect of the present invention.

FIG. 3 is a schematic view of an apparatus for explaining yet another aspect of the present invention.

[Explanation of symbols]

 1: undiluted solution supply part 2: solution delivery pump 3: heater 4: valve 5: supply line 6: permeation vaporization membrane module 7: valve 8: non-permeate extraction line 9: permeation component extraction line 10: condenser 11: vacuum Pump 12: Condensate discharge pump 13: Condensate discharge line 14: Non-condensate discharge line 15: Refrigerant supply source 16: Valve 17: Cooling jacket 18: Refrigerant supply line 19: Refrigerant discharge line 20: Non-permeate discharge line Check valve 21: Supply line back pressure valve 22: Refrigerant outlet line back pressure valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Moriyoshi Kudo Inventor Moriyoshi Kudo 370 Enzo, Chigasaki City, Kanagawa Mitsubishi Kasei Engineering Co., Ltd. Shonan Technology Center (72) Inventor Yuji Tanaka 4-2-1-12 Sendagaya, Shibuya-ku, Tokyo Ryosei Engineering Co., Ltd.

Claims (6)

[Claims] 1. A pervaporation membrane separation device in which a liquid mixture to be separated is brought into contact with a pervaporation membrane to selectively permeate and separate the liquid component, and a function of cooling the liquid in contact with the membrane when the operation is stopped. A pervaporative membrane separation device, comprising: 2. A membrane module having a cooling jacket for cooling the liquid in contact with the membrane is provided around the module can, and has a function of cooling the liquid in contact with the membrane by passing a refrigerant through the cooling jacket when the operation is stopped. The pervaporation membrane separation device according to claim 1, characterized in that it has. 3. The pervaporative membrane separation device according to claim 2, wherein a back pressure valve is provided in the refrigerant outlet pipe of the cooling jacket. 4. A back pressure valve is provided in a pipe for supplying a liquid mixture to a pervaporation membrane module, and a check valve is provided in a pipe connected to a liquid side (primary side) outlet of the pervaporation membrane module. The pervaporation membrane separation device according to any one of claims 1 to 3, characterized in that. 5. A membrane module used in the pervaporation membrane separation device according to claim 1, wherein a cooling jacket for cooling the liquid in contact with the membrane is provided around the membrane module can body. The feature is a pervaporation membrane module. 6. The operation of the pervaporation membrane separation device according to claim 1, wherein when the operation is stopped, the liquid in contact with the membrane is cooled without draining the stock solution on the supply side of the pervaporation membrane module and the permeation membrane module A method for stopping operation of a pervaporation membrane separation device, characterized in that the supply liquid is warmed while maintaining the vacuum on the permeate side when the operation is restarted while maintaining the vacuum on the permeate side.