JP3150796B2 - Carbon dioxide-free separation membrane module and storage method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of preserving a membrane module having a gas permeable performance or temporarily suspending its function. In particular, the present invention relates to a method for storing or temporarily stopping functions of a membrane module for the purpose of degassing from a liquid.

[0002]

2. Description of the Related Art Conventionally, various membrane modules have been used for reverse osmosis, ultrafiltration, or gas separation. These modules are typically spiral modules, tubular modules, hollow fiber modules, plate and frame modules, and the like. Among them, hollow fiber modules have been used in various fields because of their compactness and low dead volume.

[0003] In recent years, membrane modules have been used for degassing in liquids for module applications.
In general, the liquid to be treated is flowed on one side of the membrane, the other side of the membrane is depressurized, and gas dissolved in the liquid is discharged to the decompression side via the membrane. In this case, the properties of the membrane generally have a property of allowing gas to permeate and a property of not allowing the liquid to be treated to pass through the membrane when the liquid to be treated is in a liquid state. Of these uses, a popular one is degassing in water.
For example, by removing dissolved oxygen from water and reducing the oxidizing ability of water, corrosion of piping and the like can be prevented. In addition, by removing the gas in the water, it is possible to prevent the generation of bubbles when the water is used.

[0004] Thus, the use of membrane modules for degassing liquids is expanding. Among these uses, application of the membrane module to degassing of pure water or ultrapure water has been considered.

However, in such a module,
When the degassing function of the module is stopped or the membrane module is stored, a trouble occurs that the original function is not exhibited in a short time even if the function of the module is to be obtained again.

For example, a membrane module installed for the purpose of degassing on the secondary pure water side of an ultrapure water apparatus stops the function of the membrane module together with the ultrapure water apparatus, for example, for about one night, and then returns When the apparatus is operated, the quality of the ultrapure water deteriorates, and it takes time to recover. or,
Even when the function of only the membrane module attached to the ultrapure water device is stopped, a problem that the water quality is deteriorated occurs.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that such deterioration of water quality is due to the influence of carbon dioxide present in the membrane module, and that the deterioration of the water quality substantially occurs in the membrane module. The above problem has been solved by keeping carbon dioxide free.

[0008] That is, the present invention relates to a separation membrane module in which a membrane has a property of allowing gas to permeate, wherein the carbon dioxide-free separation membrane module has substantially no carbon dioxide in the membrane module. It is desirable that the separation membrane module is a hollow fiber membrane module in which at least one end between hollow fibers is sealed. The present invention also provides a separation membrane module having a gas-permeable property, in which an inert gas is sealed in the membrane module or the membrane module is depressurized to keep substantially no carbon dioxide. A method for storing a carbon dioxide-free separation membrane module is provided. In particular, the present invention, in a pure water or ultrapure water supply device having a separation membrane module for the purpose of degassing in water, when or after stopping the function of the membrane module, inert gas to the membrane module The present invention relates to a method for storing a carbon dioxide-free separation membrane module that keeps substantially no carbon dioxide in the membrane module by enclosing or reducing the pressure of the membrane module and sealing the module in that state.

[0009] The point of the present invention is to avoid the adverse effects of contact dissolution of gas on the liquid to be treated. In a commonly used microfiltration membrane or ultrafiltration membrane device, even when the device is stopped, liquid and gas do not generally come into contact with each other, but have a gas permeable membrane used in the present invention. In a module, the effect of the present invention is great. Further, in such a module for the purpose of degassing in water, since the contact area between the liquid and the gas is kept large in order to increase the degassing efficiency, it is more effective to use the method of the present invention. It is.

[0010] The method of the present invention may be any method as long as carbon dioxide is not substantially present in the space within the membrane module. An effective method is to reduce the pressure in the space. In this method, even if, for example, the enclosed processing liquid evaporates and the degree of pressure reduction is reduced after the pressure is reduced, there is no problem since carbon dioxide does not enter from the outside. Further, this state is preferable because the risk of mixing in the module is reduced. Further, this method is particularly effective because a device for degassing in water is provided with a device for reducing the pressure, and this device can be used to easily reduce the pressure in the space of the membrane module.

It is also effective to fill a space with a gas inert to water, such as nitrogen gas, helium, neon or argon. According to this method, the inside of the module can be kept at the same pressure as the outside air or at a pressure higher than the outside air, so that there is almost no danger of carbon dioxide mixing from the outside of the module.

The membrane module to which the method of the present invention is applied may be of any type as long as the membrane has gas permeability. For example, spiral type, plate,
There are an and frame type, a tube type, a pleated type, a hollow fiber type and the like. Among them, a hollow fiber type membrane module is particularly effective for applying the present method. This is because the contact area between the processing liquid and the gas is particularly large because the membrane area filling amount per module volume is large, and it is easily affected by carbon dioxide in a short time. In addition, since the hollow fiber membrane module has a small dead space in the space where the processing liquid flows, the method is effective because it is often used for applications that dislike a trace amount of impurities, such as ultrapure water applications. .

[0013]

EXAMPLES The effects of the present invention will be described with reference to the following examples, but the present invention is not limited by these examples.

Example of making a module Hollow fiber made of polypropylene having an inner diameter of 240 μm and an outer diameter of 300 μm
43200 pieces were filled into a polysulfone case having an inner diameter of 82 mmφ, an outer diameter of 89 mmφ and a length of about 1 m, and both ends were centrifugally sealed with an epoxy adhesive.

Example 1 Ultrapure water having a specific resistance of 18.1 MΩ · cm was passed through the inside of the hollow fiber of the hollow fiber module obtained in the module preparation example at a rate of 310 liter / hr, and the outside of the hollow fiber was sealed with water. The pressure was reduced by a pump to deaerate ultrapure water, and water was passed until the difference between the specific resistance at the module outlet and the specific resistance at the inlet of the ultrapure water became 0.1 or less. After that, the water flow was stopped and the pressure was stopped,
The inside of the module was kept under reduced pressure, and the nozzle port was sealed and left as it was for 10 minutes so as not to touch the carbon dioxide in the outside air. Thereafter, the pressure reduction and water flow were resumed. Eight minutes after water flow was resumed, the difference in specific resistance between the ultrapure water module inlet and outlet became 0.1 or less, returning to the state before water flow was stopped.

Example 2 The procedure was exactly the same as in Example 1 except that the time of once stopping the depressurization and the water stop was 20 hours. The specific resistance difference at the outlet is 0.1
It was as follows.

COMPARATIVE EXAMPLE 1 The procedure was the same as that of Example 1 except that the pressure was stopped when the ultrapure water stopped, the outer side of the hollow fiber of the hollow fiber module was returned to normal pressure, and was kept in contact with the outside air. However, the difference in specific resistance between the inlet and outlet of the ultrapure water module was 0.5 even after 20 minutes had passed after resuming water flow.

COMPARATIVE EXAMPLE 2 The procedure was the same as in Example 2 except that the pressure was stopped when the ultrapure water stopped, the outer side of the hollow fiber of the hollow fiber module was returned to normal pressure, and the hollow fiber module was kept in contact with the outside air. Then, three hours after resuming water flow, the specific resistance difference between the inlet and outlet of the ultrapure water module became 0.1 or less.

Example 3 After reducing the pressure and stopping the water once, nitrogen gas was blown into the depressurized portion of the hollow fiber module so as not to touch the outside air, and the hollow fiber module space was filled with nitrogen gas. In the same manner as in Example 2, the specific resistance difference between the inlet and the outlet of the ultrapure water module was reduced to 0.1 or less 50 minutes after water flow was resumed.

[0020]

According to the preservation method of the present invention for keeping substantially no carbon dioxide in the space within the membrane module, the module is not affected by carbon dioxide when the module is restarted after storage. Thus, the time required for starting up can be shortened. In particular, a great effect is brought about for use in ultrapure water, which dislikes a decrease in specific resistance due to the influence of carbon dioxide.

Claims (5)

(57) [Claims] 1. A separation membrane module in which a membrane has a gas-permeating property, wherein carbon dioxide is substantially absent in the membrane module. 2. The carbon dioxide-free separation membrane module according to claim 1, wherein the separation membrane module is a hollow fiber membrane module in which at least one end between hollow fibers is sealed. 3. A separation membrane module in which a membrane has a gas-permeating property. By keeping an inert gas in the membrane module or depressurizing the membrane module, the membrane module is kept substantially free of carbon dioxide. How to store carbon dioxide-free separation membrane module. 4. In a pure water or ultrapure water supply device having a separation membrane module for degassing in water, when or after stopping the function of the membrane module, an inert gas is supplied to the membrane module. A method for preserving a carbon dioxide-free separation membrane module that maintains substantially no carbon dioxide in the membrane module by enclosing or reducing the pressure of the membrane module and sealing the module in that state. 5. The method for storing a carbon dioxide-free separation membrane module according to claim 4, wherein the separation membrane module is a hollow fiber membrane module in which at least one end between hollow fibers is sealed.