JPH034243B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for producing oxygen using a pressure swing adsorption type oxygen production apparatus, and is designed to increase the purge efficiency of an adsorption tower and improve the product oxygen gas yield. This is what I did.

The pressure swing adsorption method (hereinafter referred to as
It is abbreviated as PSA method. ). For example, there is a method for producing oxygen using this PSA method as shown in FIG. That is, raw air is sent from pipe 1 to compressor 2, where it is pressurized to approximately 5 kg/cm ² , and then passes through pipe 3 to three adsorption units, which are switched and used by switching valves 4, 4, and so on. One adsorption tower 5 among the towers 5a, 5b, 5c
sent to a. The adsorption tower 5a is filled with zeolite or the like that selectively adsorbs nitrogen as an adsorbent, and nitrogen in the air introduced under pressure is adsorbed, and at the outlet of the adsorption tower 5a, a gas containing oxygen as the main component is filled. The product oxygen gas is obtained. This product oxygen gas is sent to a supply destination via a switching valve 4, a pipe 6, and a pressure regulating valve 7. On the other hand, a part of the product oxygen gas is branched from a pipe 8 to another adsorption tower 5b which is in the regeneration process after being saturated by adsorbing nitrogen and being depressurized.
The gas is brought to a pressure of about 1 Kg/cm ² and then flows back through the pipe 10 and the switching valve 4 as a purge gas. This purge gas desorbs nitrogen from the adsorbent, regenerates the adsorbent, and becomes nitrogen-containing waste gas, which is discharged into the atmosphere via the switching valve 4 and the pipe 11. This operation means that the adsorption tower 5b has been purged. In addition, after the adsorption tower 5c has been purged as described above, a part of the product oxygen gas is further introduced, and the adsorption tower 5c is in a state where it is repressurized to about 5 kg/cm ² and is waiting for the next adsorption step. are doing.

In this way, the PSA type oxygen production device is configured so that product oxygen gas can be obtained continuously by sequentially switching the three adsorption towers 5a, 5b, and 5c to the adsorption, depressurization purge, and repressurization steps. has been done.

Incidentally, in such a PSA type oxygen production apparatus, as described above, a part of the product oxygen gas is used for purging and repressurizing the adsorption tower 5, and thus the oxygen yield is determined by this. Therefore, reducing the amount of purge gas as much as possible is an important factor in improving the performance of the device, particularly in improving the oxygen yield and reducing costs. Further, the pressure regulating valve 9 for obtaining purge gas has a complicated structure and frequently fails, which hinders stable operation of the apparatus.

This invention was made in view of the above circumstances,
The amount of purge gas can be reduced, the oxygen yield and oxygen purity of the entire device can be improved, and the purge gas flow rate can be maintained constant without using a pressure regulating valve, making it easy to achieve stable operation of the device. The purpose is to provide a method for producing oxygen using the PSA method, and the feature is that an oxygen enrichment membrane unit is provided in the product oxygen gas flow path to obtain a certain amount of purge gas with high oxygen purity. .

Embodiments of the invention will be described below with reference to the drawings.

FIG. 2 shows a first embodiment of the oxygen production method using the PSA method of the present invention, and the same components as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. In the embodiment shown in FIG. 2, an oxygen-enriching membrane unit 12 is provided in the middle of the pipe 6 for delivering the product oxygen gas to the supply destination in the method shown in FIG. 1, and the purge gas is obtained from this oxygen-enriching membrane unit 12. The points are distinctive. The oxygen enrichment membrane unit 12 is made of a thin polymer film such as cellulose acetate or silicone rubber, and selectively permeates oxygen gas, and gas containing oxygen is supplied to the primary side of the unit 12 under pressure. Then, a certain amount of oxygen gas permeates to the secondary side. By providing this oxygen enrichment membrane unit 12 in the product oxygen gas flow path, a certain amount of gas having a higher oxygen concentration than the product oxygen gas can be obtained on the secondary side of this unit 12. This gas is sent to the adsorption tower 5 as a purge gas for the adsorption tower 5 through the valve 13 and the pipe 10, and is used for purging and repressurization. Also, unit 12
Most of the remainder of the product oxygen gas supplied to the primary side is sent to the supply destination via the pressure regulating valve 7, as in the conventional case.

In such an oxygen production method using the PSA method, since the oxygen purity of the purge gas is high, a predetermined purge is performed in a short time in the purge process of the adsorption tower 5, and therefore the total amount of purge gas is reduced. Ru. Also, in the repressurization step, since high-purity oxygen gas is sealed in the adsorption tower 5, the rise in oxygen purity of the product oxygen gas in the next adsorption step is accelerated. Therefore, the product oxygen yield is substantially increased and the production cost of the product oxygen gas is reduced. Furthermore, the oxygen enrichment membrane unit 12 acts as a resistor against the flow of product oxygen gas, and if the pressure on the primary side is constant, the flow rate of the purge gas appearing on the secondary side will be constant. The valve 9 becomes unnecessary, and failures caused by the pressure regulating valve 9 are eliminated.

FIG. 3 shows a second embodiment of this invention.
Components that are the same as those shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. In the second embodiment, the oxygen enrichment membrane unit 12 is applied to an oxygen production method using the PSA method in which the adsorption tower 5 is regenerated under reduced pressure by a vacuum pump 14, and the other parts are the same as those in the first embodiment. It is similar to In this device, since the adsorption tower 5 is regenerated by the vacuum pump 14, the product oxygen yield of the entire device is further improved.

As explained above, in the oxygen production method using the PSA method of the present invention, an oxygen enrichment membrane is provided in the product oxygen gas flow path to obtain a constant amount of purge gas with higher oxygen purity. The oxygen yield and oxygen purity can be improved, and the cost of oxygen production can be reduced. Furthermore, since a fixed amount of purge gas can be obtained without using a pressure regulating valve, there are advantages such as eliminating failures caused by the pressure regulating valve, which are common in conventional devices, and enabling stable operation of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram showing a conventional oxygen production method using the PSA method, and FIGS. 2 and 3 are both schematic system diagrams showing examples of the oxygen production method using the PSA method of the present invention. 2...Compressor, 4...Switching valve, 5a, 5b, 5
c... Adsorption tower, 10... Tube, 12... Oxygen enrichment membrane unit.

Claims (1)

[Claims] 1. Oxygen by the pressure swing method, which continuously produces oxygen gas by switching a plurality of adsorption towers that selectively adsorb nitrogen gas in raw air to each step of adsorption and regeneration. In the production method, the oxygen gas obtained is flowed through an oxygen enrichment membrane unit, and the oxygen gas that has permeated through the unit is flowed into the adsorption tower in the regeneration step. Production method. 2. The pressure swing according to claim 1, wherein the pressure of the oxygen gas flowing into the oxygen enrichment membrane unit is kept constant, and the amount of gas passing through the unit is kept constant. Oxygen production method by method.