JP2000024442A - Nitrogen enriching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the temporary performance degradation of a separation membrane module generated during the stoppage of operation and to shorten the time required for the recovery of the performance of the membrane at the time of starting the operation again by mounting a means for cutting-off the outside air during the stoppage of the operation at each of an air supply port, a permeation side discharge port and a non-permeation side discharge. SOLUTION: A nitrogen enriching device is constituted so that an ionization membrane module composed of a bundle of hollow fiber membranes 24 selectively permeating oxygen is incorporated in a vessel 20 provided with a supply port 21 for supplying at least dried air, a discharge port 22 for recovering and discharging non-permeated nitrogen enriched air and a discharge port 23 for recovering oxygen enriched air permeated through the hollow fiber membranes. In such a case, each of the cut-off means 6, 8 and 9 is respectively mounted to each of openings 21-23. Then, at the time of stopping the operation of the device, the cut-off means is closed to prevent the outside air from flowing into the module. As the cut-off means, any of valves having a cut-off function can be used and one small in air flow resistance to prevent the lowering of the nitrogen enriching function is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing nitrogen-enriched air from air using a hollow fiber separation membrane. The present invention relates to a nitrogen enrichment apparatus for shortening the time required to start.

[0002]

2. Description of the Related Art Nitrogen-enriched air is used in the fields of food processing such as packaging and preservation, in the field of food such as fungicide and insect repellent of cereals, preservation of fruits and vegetables, and in the field of chemistry such as purging of pipes and tanks and explosion proof. It is widely used in the fields of fuels, electronics, chemicals, metals, etc. In recent years, with the development of separation membrane technology such as a hollow fiber membrane and its production technology, and a production technology of a separation membrane module, a method for producing nitrogen-enriched air or oxygen-enriched air from air using a separation membrane has been developed. Kaisho 56-91
Various proposals have been made in JP-A-802-802, JP-A-57-82105, JP-A-2-252609 and the like.

[0003] In the nitrogen enrichment apparatus, raw material air which is usually dried in advance using a freezing dehumidifier or a separation membrane module is supplied, and the raw material air is supplied to the non-permeate side of the separation membrane module to remove oxygen or the like. The gas having a high permeation rate permeates through the membrane and is recovered or removed from the permeation side, and the nitrogen-enriched air is recovered from the non-permeation side. The nitrogen enrichment unit is usually operated periodically or intermittently.

However, in general, in a nitrogen enrichment apparatus using a polymer material as a separation membrane material, when the operation is stopped for a certain period and restarted, a predetermined separation performance cannot be obtained immediately after starting, and a predetermined separation performance cannot be obtained. However, there is a problem that useless operation is forced due to a long time until the recovery of the separation membrane performance.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to prevent a temporary decrease in the performance of a separation membrane module during a suspension of operation in a nitrogen enrichment apparatus, and to reduce the time until the performance of the membrane recovers when the operation is restarted. It is an object of the present invention to provide a method and an apparatus for reducing the time.

[0006]

Means for Solving the Problems The present inventors have studied various causes of the deterioration of the air separation performance of the separation membrane module, and found that the cause of the contamination of the air, such as atmospheric contaminants entering the module during the downtime. The present inventors have found that the influence of water is present, and have led to the creation of the present invention.

That is, the present invention is a nitrogen-enriching apparatus having an air supply port, a permeate outlet and a non-permeate outlet,
Compressed dry air is supplied to the inside of the hollow fiber of the nitrogen enrichment device incorporating a separation membrane module comprising a bundle of hollow fiber membranes, and oxygen in the air is selectively permeated to the outside of the hollow fiber membrane. In the nitrogen enrichment apparatus for generating non-permeate nitrogen-enriched air inside, the air supply port, the permeate-side outlet and the non-permeate-side outlet are each provided with a means for shutting off the outside air during the suspension of operation. The present invention relates to a characteristic nitrogen enrichment apparatus.

[0008] As means for shutting off the outside air during the operation stoppage of the present invention, a valve or a check valve is preferable.

Further, the present invention is a nitrogen enrichment apparatus having an air supply port, a permeate side discharge port and a non-permeate side discharge port,
Compressed dry air is supplied to the inside of the hollow fiber of the nitrogen enrichment device incorporating a separation membrane module comprising a bundle of hollow fiber membranes, and oxygen in the air is selectively permeated to the outside of the hollow fiber membrane. In a nitrogen enrichment apparatus that generates non-permeate nitrogen-enriched air inside, an air supply port, a permeate-side outlet, and a non-permeate-side outlet are provided so as to prevent outside air from entering the inside of the separation membrane module during operation suspension. The present invention relates to a method for maintaining performance of a separation membrane, which is characterized in that the performance is maintained.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The nitrogen enrichment apparatus of the present invention
This will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a method for producing nitrogen-enriched air. FIG. 2 is a sectional view showing an example of the nitrogen enrichment device. The raw material air containing water is supplied to a pressurizing machine (compressor) 1 and stored in a tank 2. The pressurized air stored in the tank 2 passes through a dehumidifier 3 such as a separation membrane module or a refrigeration dehumidifier, passes through an air filter 4 (if necessary, a mist separator), and is pressure-adjusted by a pressure reducing valve 5, After passing through the blocking means 6 of the present invention, oxygen or moisture is introduced into the inside of one hollow fiber membrane of the separation membrane module 7, that is, into the hollow (hole), and while flowing and passing through the hollow fiber, oxygen or moisture is passed through the hollow fiber membrane. And exits the apparatus through the blocking means 9 of the present invention from the transmission side outlet of the module. On the other hand, the non-permeated nitrogen-enriched air passing through the inside of the hollow fiber passes through the shut-off means 8 of the present invention from the other outlet of the hollow fiber, and comes out of the apparatus via the flow control valve 10.

As shown in FIG. 2, the nitrogen enrichment device includes a supply port 21 for supplying at least dried air;
Oxygen is selectively permeated to a container 20 having an outlet 22 for collecting and discharging non-permeated nitrogen-enriched air and an outlet 23 for collecting oxygen-enriched air that has passed through the hollow fiber membrane. The one having a built-in separation membrane module consisting of a bundle of hollow fiber membranes 24 is used, and is configured by providing shut-off means 6, 8, and 9 at the supply port and the discharge port of the container, respectively. Both ends of the hollow fiber membrane 24 are integrally fixed with a resin such as an epoxy resin so that the hollows (holes) at both ends are not closed.

When the apparatus is operating, the shut-off means
In the open state, when the operation is stopped, the shut-off means is closed, so that no outside air enters the module.

Any means for shutting off the outside air may be used as long as it has a shutoff function, such as a valve, a check valve, or a breather valve. However, it is preferable that the airflow resistance is as small as possible in order not to reduce the nitrogen enrichment function.

As a shut-off means, a check valve or the like which opens the shut-off plate by the pressure of the gas when gas comes, and closes the cut-off plate by gravity when the gas stops, is used every time the operation is stopped or restarted. There is no need to perform the work of opening and closing the blocking means.

Although the present invention has been described with respect to a nitrogen enriching apparatus, the present invention is applied to an oxygen generating apparatus if attention is paid to the permeation side of the membrane, and the present invention can be applied to an oxygen generating apparatus.

[0017]

EXAMPLE 1 According to the process shown in FIG. 1, the film thickness was 100 μm and the outer diameter was 500 μm.
And a diameter of 40 mm consisting of a hollow fiber module in which asymmetric hollow fiber membranes of aromatic polyimide having a length of 450 mm are bundled,
The following operation was performed using a separation membrane module having a length of 500 mm and using, as the shutoff means 6, 8, and 9, check valves having a function of shutting off when the supply of gas was stopped.

First, the pressure of the raw material air entering the module was adjusted to 7 kg / cm ² G, the temperature was adjusted to 25 ° C., and the flow rate of the nitrogen-enriched air was adjusted to 15 NL / min, and the module was operated for 24 hours. Thereafter, the operation was stopped. When the operation is stopped, the temperature of the atmosphere is 25 to 31 ° C, and the humidity is 60.
７０70%. 24 hours after stopping driving,
The operation was started again under the same conditions as above (this operation is referred to as the first operation after stopping). The operation for 24 hours and the stop for 24 hours were repeated, and the oxygen concentration of the air emerging from the non-permeate side of the membrane was measured. The oxygen concentration meter was provided immediately after the flow control valve 10 on the non-permeate side in FIG. Table 1 shows changes over time in the oxygen concentration when the operation is restarted. Oxygen concentration, immediately after the start of operation,
The concentration was almost 4.9%, almost at the end of the operation.

[0019]

[Table 1]

Comparative Example 1 The check valve connected to the entrance and the two outlets to the module of Example 1 was removed, and the operation and stop were repeated under the same conditions as in Example 1 without the shut-off means, and the membrane was removed. The oxygen concentration of the air coming out of the non-permeate side of was measured. Table 2 shows changes over time when the operation is restarted. Immediately after the restart of the operation, the oxygen concentration showed 5.4 to 6.0%, and reached the stable value of 4.9% in about 5 to 6 hours. FIG. 3 is a graph showing the average values of the measurement results of Example 1 and Comparative Example 1. It can be seen that the time required to reach steady operation at the time of restart of operation is greatly reduced by the present invention.

[0021]

[Table 2]

[0022]

According to the nitrogen enrichment apparatus, by providing a shielding means for allowing outside air to enter the inside of the module at each of the air supply port and the air discharge port, it is possible to prevent a temporary decrease in performance of the separation membrane module which occurs at the time of suspension of operation. Further, it is possible to save time until the performance of the membrane is restored when the operation is restarted.

[Brief description of the drawings]

FIG. 1 is a process for producing nitrogen-enriched air for explaining the nitrogen-enriched apparatus of the present invention.

FIG. 2 is a nitrogen enrichment apparatus having the shut-off means of the present invention.

FIG. 3 is a diagram showing a change with time of the oxygen concentration at the non-permeate side outlet when the operation is restarted in the case where the outside air is shut off during the operation suspension and when the operation is not performed.

[Description of Signs] 1; pressurizer (compressor) 2; tank 3; dehumidifier 4; air filter (and mist separator) 5; pressure reducing valve 6; Shut-off means 9; permeate-side outlet shut-off means 10; flow rate control valve 20; module container 21; module inlet 22; module non-permeate side outlet 23; module permeate side outlet 24; hollow fiber membrane

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Kusunoki 8-1 Goi-minamikaigan, Ichihara-shi, Chiba Ube Industries, Ltd. Polymer Research Laboratory F-term (reference) 4D006 GA41 HA02 HA05 HA18 HA25 JA18A JA64Z KA64 KB12 KE04Q MA01 MA25 MC58 PA02 PB17 PB62 PB63 PC01 PC71

Claims (4)

[Claims] 1. A nitrogen-enriching apparatus having an air supply port, a permeate-side outlet, and a non-permeate-side outlet.
It is supplied to the inside of a hollow fiber of a nitrogen enrichment device incorporating a separation membrane module comprising a bundle of hollow fiber membranes, and oxygen in the air is selectively permeated to the outside of the hollow fiber membrane and is not permeated to the inside. A nitrogen-enriched apparatus for producing nitrogen-enriched air according to claim 1, wherein each of the air supply port, the permeate-side exhaust port and the non-permeate-side exhaust port is provided with means for shutting off the outside air during operation suspension. Device. 2. The nitrogen enrichment apparatus according to claim 1, wherein the means for shutting off the outside air is a valve. 3. The nitrogen enrichment apparatus according to claim 1, wherein the means for shutting off the outside air is a check valve. 4. A nitrogen-enriching apparatus having an air supply port, a permeate-side outlet and a non-permeate-side outlet, wherein compressed dry air is
It is supplied to the inside of a hollow fiber of a nitrogen enrichment device incorporating a separation membrane module comprising a bundle of hollow fiber membranes, and oxygen in the air is selectively permeated to the outside of the hollow fiber membrane and is not permeated to the inside. In the nitrogen enrichment apparatus that generates nitrogen-enriched air, shut off the air supply port, the permeate-side exhaust port, and the non-permeate-side exhaust port to prevent outside air from entering the inside of the separation membrane module during operation suspension. A method for maintaining the performance of a separation membrane, characterized in that: