JPH0621006B2 - High-concentration oxygen gas production equipment by pressure fluctuation adsorption method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention uses a mixed gas such as air containing oxygen and nitrogen as a raw material and adsorbs and separates nitrogen by a pressure fluctuation adsorption method to produce a high concentration oxygen gas. Related to the device.

[Conventional technology]

An apparatus for producing oxygen gas having a higher concentration than air, for example, by a pressure fluctuation adsorption method is generally a plurality of adsorption columns filled with synthetic or natural zeolite that selectively adsorb nitrogen and a blower for supplying a raw material gas. And a vacuum pump for regenerating the adsorption cylinder is a main component. An outline of this will be described with reference to FIG. 3. 1 is a blower, 2a, 2b, 2
c is three adsorption cylinders that are used for switching, 3 is an oxygen compressor, 4 is a vacuum pump, the raw material gas is supplied from the blower 1, and the adsorption cylinder 2 is passed through the switching valves 5a, 5b, 5c.
Nitrogen gas is adsorbed and separated in the process of flowing in a, 2b, and 2c, and the remaining high-concentration oxygen gas is discharged to the outlet side switching valves 6a, 6b,
After entering the oxygen compressor 3 via 6c and the control valve 7 and increasing the pressure to a desired pressure, it is supplied to the consumer. Now, when the adsorption cylinder 2a is in the adsorption step, 2b is the charging step, and 2c is in the regeneration step, the raw material gas is supplied to the switching valve 5a and the adsorption cylinder 2a to produce high-concentration oxygen gas, and part of it is branched. The switching valve 9 which is one of the switching valves 9a, 9b, 9c from the pipe 8
It is introduced into the adsorption cylinder 2b via b. Also, the adsorption cylinder 2c separates the adsorbed nitrogen by the vacuum pump 4 and the switching valves 10a, 1
It is exhausted from the switching valve 10c which is one of 0b and 10c.

As described above, the adsorption step, the charging step and the regeneration step are sequentially repeated by each of the adsorption columns 2a, 2b and 2c to continuously obtain a high concentration of oxygen gas. Xerrite called Ca-Na-A type is generally used as shown in FIG. 4, and is generally used together with a water absorbing agent. That is, a water absorbing agent 50 that adsorbs and removes alumina-based or silica-based water from the raw material gas inlet side into the adsorption column 2, and Ca-Na- as the nitrogen adsorbent 51.
A type zeolite is filled.

[Problems to be solved by the invention]

However, the performance of the apparatus for producing a high-concentration oxygen gas having the above-described structure is deteriorated mainly due to the temperature change in the adsorption cylinder, especially the temperature decrease, due to two factors. This is Ca-Na- which is commonly used as a nitrogen adsorbent.
This is because the A-type zeolite has an increased nitrogen adsorption capacity at a temperature lower than room temperature, especially at a temperature below freezing point, but at the same time, an oxygen adsorption capacity also increases, which lowers the selectivity. Here, the cause of the temperature decrease in the adsorption cylinder is that the temperature of the raw material gas (especially air) flowing into the adsorption cylinder due to the decrease in the atmospheric temperature in the winter or in the cold region decreases.
As can be seen from the invention described in Japanese Patent Laid-Open Publication No. JP-A-2003-242, there is inevitably a low temperature region below room temperature in the adsorption cylinder of the adsorption device that employs the pressure fluctuation method. For this reason, various measures have been taken from the past, for example, by providing a heating device such as a heater before or after the blower and supplying the raw material gas after warming it or introducing the raw material gas into a machine room that houses a vacuum pump or the like. This is a method in which the temperature is raised by the heat generated by the electric motor or the like and then the temperature is supplied.
However, these measures are related to factors, and for the factors, methods such as averaging the in-cylinder temperature distribution with a heat conductor or reducing the low temperature with a gas pressure equalizing means have been proposed. However, it has the drawback of being poorly implemented.

Therefore, there is a proposal that the operating conditions of the apparatus are set to a low temperature range and, for example, Na-X type or Na-Y type zeolite having good selection performance at low temperature is used as an adsorbent, but the whole system is low. It cannot be denied that there is a disadvantage that the device becomes complicated because it is operated at a temperature.

Therefore, the present invention aims to improve the performance deterioration caused by the temperature decrease in the winter and the inevitable temperature decrease of the pressure fluctuation adsorption method without providing special equipment.

[Means for solving problems]

In order to achieve the above object, the present invention is configured such that a plurality of adsorption columns filled with an adsorbent that selectively adsorbs nitrogen are switched and used, and a mixed gas containing oxygen and nitrogen is mixed by a pressure fluctuation adsorption method. In a device for producing a high-concentration oxygen gas, the first invention as a nitrogen adsorbent for the adsorption column is Na-X type or Na-Y type or Ca on the raw material gas inlet side.
-X type zeolite is characterized in that Ca-Na-A type zeolite is filled on the outlet side, and the second invention is that Na-X type or Na-Y type zeolite is on the source gas inlet side and Ca is on the outlet side. -Na-A type zeolite is characterized in that each is filled with Ca-X type zeolite interposed.

That is, as described above, the oxygen production apparatus by the pressure fluctuation adsorption method inevitably brings about a temperature decrease in the adsorption cylinder, but the temperature distribution of this is not the entire one, but the lowest temperature in the portion near the raw material gas inlet side. There are departments. That is, in the nitrogen adsorbent filling portion, a low temperature region is generated in about 60% (capacity) from the raw material gas inlet side, and the adsorption / separation performance of each portion generally shows the overall performance according to the temperature distribution. In this low temperature region, especially in the lowest temperature region, the temperature is 30 to 60 ° C from the temperature of the raw material gas at the inlet of the adsorption cylinder.
When the temperature of the raw material gas is 20 ° C.
A temperature of -40 ° C is reached.

FIG. 5 shows the tendency of nitrogen adsorption capacity and oxygen / nitrogen selectivity coefficient with respect to the temperature of various nitrogen adsorbents.
As is clear from the figure, the Ca-Na-A type zeolite generally used in this type of device has a large nitrogen adsorption capacity under the temperature in the above-mentioned low temperature range, but the oxygen / nitrogen separation performance is deteriorated. Next, in the case of Na-X type zeolite, (N
The same applies to the a-Y type).
-Inferior to Na-A type zeolite, but the oxygen / nitrogen selectivity increases with decreasing temperature, and the overall separation performance is 0-
It exceeds the Ca-Na-A type in the range of 10 ° C.
In addition, Ca-X type zeolite is more than Ca-Na-A type,
The adsorption capacity is almost equal or higher, and the oxygen / nitrogen selectivity coefficient does not decrease even at low temperature. However, when the concentration of recovered oxygen is low, the recovery rate is higher than that of others, but when high concentration of oxygen is obtained, the effect is not so great, and due to the air flow, the adsorption breakthrough test shows that other adsorbents are used. It was found that the mass transfer zone in the high concentration oxygen region is long. Therefore, even though it has the above-mentioned characteristics, when it is used alone in the adsorption column, favorable results cannot be expected as an apparatus for obtaining high concentration oxygen.

Based on such knowledge, the present invention selects an adsorbent corresponding to the temperature distribution in the adsorption cylinder, and stacks and adsorbs it.

〔Example〕

 This will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a case where a water absorbing agent 20 and two kinds of nitrogen adsorbents (I) 21 and (II) 22 are laminated in an adsorption cylinder 2,
The water absorbing agent 20 is a well-known moisture absorbing agent such as alumina or silica. The nitrogen adsorbent (I) 21 is Na-X type (or Na-Y type) zeolite or Ca-X type zeolite, and the nitrogen adsorbent (II) 22 is Ca-Na.
-A type zeolite is used. That is, according to the temperature distribution in the adsorption column 2, an adsorbent having high selectivity at low temperature is filled in a low temperature region close to the inlet side of the raw material gas, and selectivity at high temperature in the high concentration oxygen region at the outlet side is maintained at room temperature. It is filled with Ca-Na-A type zeolite having good and large adsorption capacity. Here, the nitrogen adsorbent (I) 21 has a Na-X type (or Na-Y).
Type) zeolite, the filling amount thereof is 0.1 to 0.6 by weight ratio to the total nitrogen adsorbents (I) 21 and (II) 22, and preferably 0.2 to 0. .4. Further, Ca-X type zeolite is used as a nitrogen adsorbent (I) 21.
When adopted as, the weight ratio is 0.2 to 0.7,
It is preferably 0.2 to 0.5.

FIG. 2 shows a water absorbing agent 30 and three kinds of nitrogen adsorbents (I) 3
1, (II) 32 and (III) 33 are laminated in this order on the adsorption cylinder 2 from the raw material gas inlet side, and the water absorbing agent 30 and
The nitrogen adsorbents (I) 31 and (III) 33 are the same as above.
Alumina or silica based water adsorbents, Na-X type (or Na-Y type) zeolite and Ca-Na-A type zeolite. The nitrogen adsorbent (II) 32 is Ca-
The X-type zeolite is filled, the nitrogen adsorption region is divided into three, and an adsorbent suitable for each temperature distribution is selected and used. That is, in the lowest temperature range, the selection performance improves as the temperature decreases.
-X type (or Na-Y type) zeolite is a Ca-X type zeolite which has excellent selectivity and adsorption capacity in low temperature to normal temperature and low concentration oxygen region, but has long mass transfer zone in high concentration oxygen region. In addition, Ca-Na-A type zeolite, which has a high adsorption capacity at room temperature and a high concentration of oxygen and has a high adsorption capacity at room temperature, is filled. Here, the filling ratio of each nitrogen adsorbent is
The weight ratio of Na-X type (or Na
-Y type) zeolite is 0.1 to 0.3, and Ca-X type zeolite is 0.1 to 0.6.

In the above description, the water absorbing agent is filled in the adsorption cylinder,
It goes without saying that a separate water absorption cylinder may be provided and the adsorption cylinder may be filled with only the nitrogen adsorbent.

The third with three suction cylinders shown in FIG. 1 and FIG. 2 below
An experimental example using the apparatus shown in the figure is shown.

First Experimental Example Using the adsorption column 2 shown in FIG. 1, alumina gel was used as the water absorbing agent 20, Na-X type zeolite was used as the nitrogen adsorbent (I) 21, Ca-Na-A type was used as the nitrogen adsorbent (II) 22. Zeolite was loaded. Na-X type zeolite is Na-
The total weight of the X-type and Ca-Na-A type zeolite was 40%, and the total weight was 580 kg. The results are shown in Table 1 together with the case where only Ca-Na-A type zeolite was packed.

Operating conditions Adsorption pressure: 0.25 kgf / cm ² G Regeneration pressure: 200 Torr Inlet air temperature: 20 ° C One adsorption process time: 70 seconds Recovered oxygen purity: 93.5% O ₂ As a result, the amount of product oxygen collected was slightly reduced, but the oxygen yield was improved by about 7%. Improving the yield directly brings about a reduction in the electric power consumption rate, and in the long-term operation, the cost increase due to the increase in the adsorption column due to the decrease in the amount of product oxygen collected can be sufficiently compensated, and a great effect can be obtained.

Second Experimental Example Using the adsorption column 2 shown in FIG. 1, alumina gel was used as the water absorbing agent 20, Ca-X type zeolite was used as the nitrogen adsorbent (I) 21, Ca-Na-A type was used as the nitrogen adsorbent (II) 22. Zeolite was loaded. In addition, Ca-X type / (Ca-X type +
Ca-Na-A type) 50% by weight, total 580 kg
And The results are shown in Table 2.

Operating conditions Adsorption pressure: 0.25 kgf / cm ² G Regeneration pressure: 200 Torr Inlet air temperature: 20 ° C One adsorption process time: 70 seconds Recovered oxygen purity: 93.5% O ₂ As a result, the product oxygen collection amount was improved by about 4%, and the oxygen yield was improved by about 9%.

Third Experimental Example Using the adsorption column 2 shown in FIG. 2, alumina gel was used as the water absorbing agent 30, Na-X type zeolite was used as the nitrogen adsorbent (I) 31, Ca-X type zeolite was used as the nitrogen adsorbent (II) 32, Ca-Na-A type zeolite was filled as the nitrogen adsorbent (III) 33, and Na-X was added to the total nitrogen adsorbent weight.
Type is 20%, Ca-X type is 40%, total amount is 580kg
And The results are shown in Table 3.

Operating conditions Adsorption pressure: 0.25 kgf / cm ² G Regeneration pressure: 200 Torr Inlet air temperature: 20 ° C One adsorption process time: 70 seconds Recovered oxygen purity: 93.5% O ₂ As a result, the product oxygen collection amount was improved by about 2%, and the oxygen yield was improved by about 10%.

〔The invention's effect〕

As is clear from the above description, the high-concentration oxygen production apparatus according to the present invention is a stack of nitrogen adsorbents corresponding to the temperature distribution in the adsorption column, and therefore brings many effects. For example, as shown in the above-mentioned examples, the oxygen yield is improved by 7 to 10% as compared with the conventional method, but this means that the power source unit used is reduced by 7 to 10%, which is a large amount. The cost can be reduced. Further, when the second and third embodiments are adopted, the oxygen collection amount is also improved by 2 to 4%, so that further cost reduction can be expected.

Next, as described above, in order to cope with the low temperature characteristics of such a device, conventionally, the device is operated by a low temperature, or a special configuration is obliged to reduce the atmospheric temperature such as winter. Is completely unnecessary.

[Brief description of drawings]

FIG. 1 is a sectional view of a suction cylinder showing an embodiment of the present invention, and FIG.
FIG. 4 is a sectional view of an adsorption column showing another embodiment of the present invention, FIG. 3 is a system diagram of a high-concentration oxygen gas production apparatus by the pressure fluctuation adsorption method, FIG. 4 is a sectional view of a conventional adsorption column, and FIG. The figure shows the tendency of nitrogen adsorption capacity and oxygen / nitrogen selectivity with respect to the temperature of various nitrogen adsorbents. 2 ... Adsorption cylinder, 20,30 ... Water absorbing agent 21, 22, 3
1,32,33 ... Nitrogen adsorbent

Claims (6)

[Claims] 1. A plurality of adsorbing cylinders filled with an adsorbent for selectively adsorbing nitrogen are switched and used, and a high-concentration oxygen gas is mixed from a mixed gas containing oxygen and nitrogen by a pressure fluctuation adsorption method. In the apparatus for manufacturing the above, as a nitrogen adsorbent of the adsorption column, Na-X type or Na-
Y-type or Ca-X type zeolite is also used on the outlet side for Ca
A high-concentration oxygen gas production apparatus by a pressure fluctuation adsorption method, characterized in that each is filled with Na-A type zeolite. 2. The weight ratio of the zeolite charged on the inlet side of the raw material gas to the total nitrogen adsorbent is Na-X type or N type.
The pressure fluctuation adsorption according to claim 1, wherein the a-Y type is 0.1 to 0.6, and the Ca-X type is 0.2 to 0.7. High-concentration oxygen gas production equipment by the method. 3. A high-concentration oxygen gas according to the pressure fluctuation adsorption method according to claim 1 or 2, characterized in that a moisture adsorbent is filled in a preceding stage of the nitrogen adsorbent in the adsorption column. Manufacturing equipment. 4. A plurality of adsorbing cylinders filled with an adsorbent for selectively adsorbing nitrogen are switched and used, and a high-concentration oxygen gas is mixed from a mixed gas containing oxygen and nitrogen by a pressure fluctuation adsorption method. In the apparatus for manufacturing the above, as a nitrogen adsorbent of the adsorption cylinder, Na-X type or Na
-Y type zeolite, Ca-Na-A type zeolite on the outlet side, and Ca-X type zeolite interposed in the middle between them to provide high concentration oxygen by pressure fluctuation adsorption method Gas production equipment. 5. The weight ratio of the zeolite to the total nitrogen adsorbent is 0.1 to 0. 0 for the Na-X type or Na-Y type.
3. The high concentration oxygen gas production apparatus by the pressure fluctuation adsorption method according to claim 4, wherein the Ca-X type is 0.1 to 0.6. 6. A high-concentration oxygen gas according to the pressure fluctuation adsorption method according to claim 4 or 5, characterized in that a moisture adsorbent is filled in a preceding stage of the nitrogen adsorbent in the adsorption column. Manufacturing equipment.