JPH02131112A - Gas concentration apparatus - Google Patents

Abstract

PURPOSE:To raise a recovery factor of gas by supplying gas from a apace on the primary side of a first module to a second module and further providing a pressure reducing means for concurrently reducing pressures of each of the spaces on the secondary sides of the first and second modules. CONSTITUTION:The outside air is supplied under pressure through a line 36 to a primary side space 31a of a first module 33A from an inlet port 38 by means of a compressor 37. The air in the space 31a of the module 33A is fed to a primary side space 32a of a second module 33B through a connection line. 38. Nitrogen enriched air is obtained in the primary side space 32a, whereby said nitrogen enriched air is delivered from a delivery port 39 through a valve 40 and a line 35. And the pressure reducing means 34 includes a pressure reducing pump 43 and a valve 44. In this manner, optimum conditions corresponding to the concentration of non-permeation gas in the primary side space can be determined.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses a selectively permeable membrane that can selectively permeate at least one type of gas from a mixed gas, such as an oxygen selectively permeable membrane. The present invention relates to a gas concentrator for concentrating a gas having a relatively low permeation rate through the selectively permeable membrane (for example, nitrogen relative to the oxygen selectively permeable membrane).

In this specification, the term "permeable gas" means "a gas that easily permeates the selectively permeable membrane (that is, the permeation rate is relatively high)", and the term "non-permeable gas" means "the gas that permeates the selectively permeable membrane". It is used to mean a gas that is difficult to permeate through a membrane (that is, has a relatively low permeation rate).

[Conventional technology]

Conventionally, an oxygen selectively permeable membrane is used, in which oxygen has a higher permeation rate than nitrogen, and a pressure difference is created across the oxygen selectively permeable membrane to obtain oxygen-enriched air on one side of the membrane and on the other side. Gas concentrators are used to obtain nitrogen-enriched air. The nitrogen-enriched air obtained as described above is widely used, for example, for preventing oxidation in chemical reaction systems and maintaining the freshness of fresh foods.

A typical prior art technique in which nitrogen, which is a non-permeable gas to the oxygen selectively permeable membrane, is concentrated using an oxygen selectively permeable membrane to obtain nitrogen-enriched air is shown in FIG.

A space 1a on one side partitioned by the oxygen selectively permeable membrane 1 in an oxygen selectively permeable membrane module (hereinafter referred to as "module") 2 which is modularized by accommodating the oxygen selectively permeable membrane 1 (
Hereinafter, it will be referred to as "primary space 1a." ) is supplied with pressurized air from the outside via an air introduction pipe 6 by a compressor 3. The space 1b on the other side (hereinafter referred to as "secondary space lb") partitioned by the oxygen selectively permeable membrane 1 is depressurized by a vacuum pump 8 from the discharge port 4, whereby the secondary space 1b Oxygen-enriched air having an increased oxygen concentration is passed through the oxygen selectively permeable membrane 1 and is discharged from the outlet 10 by the vacuum pump 8.

Air remaining in the primary space 1a in the module 2 (
Nitrogen-enriched air (with a high nitrogen concentration) is supplied for use from the outlet pipe 5 via the valve 9. Reference numeral 7 denotes a valve, and the pressure in the secondary space 1b can be adjusted by adjusting its opening degree. Further, depending on the adjustment of the valve 9, the pressure in the primary space 1a is changed.

In the module 2, as a result of the oxygen selectively permeable membrane 1 extracting oxygen as a permeate gas from the air in the primary space 1a, the oxygen concentration on both sides of the oxygen selectively permeable membrane 1 changes from the upper side to the lower side in FIG. It gradually decreases as the direction increases. That is, in the primary space 1a, the nitrogen concentration increases from the air inlet to the air outlet. Therefore, in this prior art, nitrogen-enriched air in which the nitrogen concentration in the primary space la is averaged is led out to the outlet pipe 5, and therefore there is a problem in that the yield of nitrogen-enriched air is poor.

Another prior art that improves on the prior art described above is shown in FIG. In this prior art, first and second modules 13.14 each having an oxygen selectively permeable membrane 11.12 having the same characteristics are connected in series by a connecting pipe 15 connecting each primary side space 11a, 12a. The air in the secondary space 12b of the second module 14 is returned by the vacuum pump 16 to the pipe 19 that introduces external air from the pipe 18 through the valve 17, and the mixed air of this returned air and the external air is The compressor 20 supplies the air to the primary space 11a of the first module 13 from the inlet 21.

Furthermore, the air in the secondary space 11b of the first module 13 is discharged from the discharge port 22 via the valve 24 by the vacuum pump 23. Furthermore, the air in the primary space 11a 12a of the second module 14 is supplied for use from the outlet pipe 25 via the valve 26.

The primary space 11 a of the first module 13 , the secondary space 11 b , and the primary space 12 a of the second module 14
, and the pressure in the secondary space 12b is
6.17 etc.

In the first module 13, the pressure difference and pressure ratio between the primary space 11a and the secondary space 11b are determined by the valve 24.
The oxygen concentration of the air on the secondary side space 11b side of the oxygen selective permeable membrane 11 in the entire area from the inlet to the outlet of the module 13 is adjusted by adjusting the opening degree of the oxygen selectively permeable membrane 11 and the membrane area of the oxygen selectively permeable membrane 11. It is set to be higher than the outside air. On the other hand, the primary space 11 of the first module 13 is connected to the second module 14 from the connecting pipe 15.
In this second module 14, the valve 17.26 and the membrane area of the oxygen selectively permeable membrane 12 provide a gap between the primary space 12a and the secondary space 12b. If the pressure difference and pressure ratio of
It is set to be lower than that of the external air from 9.

According to such a configuration, the primary space 11a of the first module 13 is supplied with mixed air of external air and air with a lower oxygen concentration than the external air, and
In the primary space 11a of the module 11, the nitrogen concentration is higher than that of the outside air in the entire region from the inlet to the outlet, and in this way, the yield of nitrogen-enriched air is improved.

[Problem to be solved by the invention]

In an oxygen selectively permeable membrane, the oxygen permeation rate (cc/
If the scrnHgc) is large, the nitrogen selection coefficient [nitrogen permeation rate (cc/scmHgcIa)/oxygen permeation rate (cc/scmHgcdl)] is low, and if the permeation rate is small, the nitrogen selection coefficient is high.

In the above-mentioned prior art, oxygen selective permeation membranes 11.12 having the same characteristics are used in modules 13.14.
Primary space 11a, 1 in each module 13.14
Each pressure difference and pressure ratio between 2a and the secondary spaces 11b and 12b are individually controlled, and the permeation rate is set so that the desired oxygen concentration is obtained in each of the secondary spaces 11b and 12b. I have to.

However, the first and second modules 13°14
In order to set the pressure difference and pressure ratio to be different from each other and to prevent air having different oxygen concentrations from the secondary spaces 11b and 12b from being mixed,
Air with a relatively high oxygen concentration is discharged from the secondary space 11b of the first module 13, and the second module 1
In order to return air with relatively low oxygen concentration from the secondary space 12b of No. 4, separate vacuum pumps 23 and 16 are provided for each, resulting in a complicated configuration and a small amount of nitrogen-enriched air recovered. There was also the problem that the recovery rate was not improved much.

An object of the present invention is to provide a gas concentrator that has a simple configuration and improves the amount and rate of recovery of concentrated gas.

[Means to solve the problem]

The gas concentrator of the present invention includes a first module in which the internal space is partitioned into a primary side space and a secondary side space by a first selectively permeable membrane; and a secondary side space, the primary side space being supplied with gas from the primary side space of the first module, and each secondary side of the first and second module. a pressure reducing means for commonly reducing the pressure in a space, the permeation rate of the permeate gas in the second selectively permeable membrane is lower than the permeation rate of the permeable gas in the first selectively permeable membrane, and the second
The non-permeable gas selectivity coefficient (permeation rate of non-permeable gas/permeation rate of permeable gas) of the selectively permeable membrane is set higher than the non-permeable gas selectivity coefficient of the first selectively permeable membrane.

[Effect]

According to the configuration of the present invention, concentrated gas with an increased concentration of non-permeable gas is obtained in the primary space partitioned by the first selectively permeable membrane in the first module, and this concentrated gas is transferred to the second module.
is supplied to the primary side space partitioned by the second permselective membrane of the module. Therefore, gas having a relatively high concentration of non-permeable gas is supplied to the primary side space of the second module, but the second selectively permeable membrane of this second module has a permeation rate of the permeable gas of the second module. The permeation rate of the permeate gas of the first selectively permeable membrane of the first module is selected to be lower than that of the first module, and the non-permeate gas selectivity coefficient of the first module is selected to be higher than that of the first module. The pressure difference and pressure ratio between each primary space and secondary space in the first and second modules are reduced by commonly reducing the pressure in each secondary space partitioned by a selectively permeable membrane using a pressure reducing means. Even if set equal, it is possible to set optimal conditions for further increasing the concentration of non-permeable gas in the concentrated gas from the first module in the second module.

Moreover, since a highly concentrated concentrated gas can be obtained without returning the permeated gas as in the conventional method, the flow rate of this concentrated gas can be increased and the recovery amount and recovery rate can be significantly improved.

[Embodiment 1] FIG. 1 is a conceptual diagram showing the basic configuration of a gas concentrator according to an embodiment of the present invention. This gas concentrator has a first gas concentrator that can selectively permeate oxygen. They each have second oxygen selectively permeable membranes 31 and 32, respectively. Each one-way space 3 partitioned by a second oxygen selectively permeable membrane 31°32
1a, 32a (hereinafter referred to as "primary side spaces 31a, 32a, etc.") are connected by a connecting pipe 38 to first and second oxygen selectively permeable membrane modules (hereinafter referred to as "modules") 33A, 33B; The first . of the first and second modules 33A, 33B. Second oxygen selectively permeable membrane 3
The spaces 31b (hereinafter referred to as "secondary side space 31b") and 32b (hereinafter referred to as "secondary side space 31b") on the other side partitioned by 1.32
"Secondary side space 31b". ) to obtain nitrogen-enriched air with an increased concentration of nitrogen, which is a non-permeable gas, in the pipe 35. External air is supplied to the primary space 31a of the first module 33A through a pipe 36 under pressure by a compressor 37 from an inlet 38 thereof.

The air in the primary space 31a of this first module 33A is transferred to the second module 3 through the connecting pipe 38.
It is supplied to the primary side space 32a of 3B. Nitrogen-enriched air is obtained in this primary space 32a as will be described later, and this nitrogen-enriched air is supplied from the outlet 39 through the valve 40 and through the pipe 35 for use.

The pressure reducing means 34 includes first and second modules 33A,
Pipe 41 connected to each secondary side space 31b, 32b of 33B
and the respective secondary spaces 31b, 32 via this pipe 41.
A pressure reducing pump 43 that commonly reduces the pressure of the air and exhausts it from the discharge pipe 42, and a valve 44 provided between the pipe 41 and the pressure reducing pump 43.
Equipped with.

In the first and second modules 33A and 33B, the oxygen permeation rate of the second oxygen selectively permeable membrane 32 of the second module 33B is higher than that of the first oxygen selectively permeable membrane 32 of the first module 33A. Nitrogen selection coefficient α of the second oxygen selectively permeable membrane 32 is smaller than the permeation rate.
is set larger than the nitrogen selection coefficient α of the first oxygen selectively permeable membrane 31. However, the nitrogen selection coefficient α is defined by the following equation.

(Nitrogen permeation rate) In this embodiment, as the second oxygen selectively permeable membrane 31, 32, the first oxygen selectively permeable membrane 31 is made of polydimethyl on a porous support membrane of Duraguard Z400 (trade name: manufactured by Polyplastics Co., Ltd.). Two layers of siloxane formed by a water surface development method are used. The characteristics of this oxygen selectively permeable membrane 31 are shown in Table 1. However, in this Table 1, "pressure" refers to the oxygen selectively permeable membrane 3.
It shows the pressure on the other surface side when one surface side of No. 1 is at atmospheric pressure (760 mmHg).

Table 1 Next, as the second oxygen selective permeation membrane 32, a polyethersulfone porous support membrane is used in which one layer of poly4methylpentene-1 and two layers of polydimethylsiloxane are formed by a water surface development method. . The characteristics of this second oxygen selectively permeable membrane 32 are shown in Table 2.

Table 2, Figure 2 shows the first and second oxygen selectively permeable membranes 3 as described above.
In the gas concentrator of this example using 1.32,
The measurement result of the relationship between the nitrogen concentration of the nitrogen-enriched air obtained from the pipe 35 and the flow rate of the nitrogen-enriched air is shown by the curve kIAfil. This measurement is performed by adjusting the valve 40 in the first and second modules 33A.

The pressure in each primary side space 31a, 32a of 33B is 760m
mHg, and by adjusting the pressure reducing pump 42 and valve 41, the pressure in each secondary space 31b, 32b is set to 1536 inches.
These are the measurement results when IIHg is used.

FIG. 2 also shows the above-mentioned section 1. Second oxygen selectively permeable membrane 3
1.32 as the selectively permeable oxygen membrane 1 having the configuration shown in FIG.
．． It is indicated by ff3. In this case, the pressure in the primary space 1a of the module 2 is atmospheric pressure (760 mm 1 g)
The pressure in the secondary space 1b was -536 mmHg.

Curve I! in this figure 2! , 2 and the curve jI! 3, when the nitrogen concentration is high, the first oxygen selectively permeable membrane 3
It is understood that it is more advantageous to use 1, and when it is low, it is more advantageous to use the second oxygen selectively permeable membrane 32. In the gas concentrator of this embodiment shown in FIG. The second oxygen selectively permeable membranes 31 and 32 are used in the manner described above, and good characteristics as shown by curve 1 in FIG. 2 are obtained.

[Example 2] In another example of the present invention, in the configuration shown in FIG. Mixture N1 in which dimethylsiloxane is mixed in a ratio of 1=1
A layer and one layer of polydimethylsiloxane are formed by a water surface spreading method. The characteristics of this first oxygen selectively permeable membrane 31 are shown in Table 3.

Table 3 In addition, as the second oxygen selective permeation membrane 32, one layer of a mixture of poly(4-methylpentene-1) and polydimethylsiloxane (1:1) was added to a polyethersulfone porous support membrane.
One layer of polydimethylsiloxane and one layer of poly4methylpentene-1 were formed by a water surface spreading method. The characteristics of this second oxygen selectively permeable membrane 32 are shown in Table 4.

(Left space below) Table 4, Figure 3 shows the above-mentioned 1. Second oxygen selectively permeable membrane 3
A curve 14 shows the measurement result of the relationship between the nitrogen concentration of the nitrogen-enriched air obtained from the pipe 35 and the flow rate of the nitrogen-enriched air in the gas concentrator of this embodiment using the 1.32. This measurement is performed by adjusting the valve 40 in the first and second modules 33A.

The pressure in each primary side space 31a, 32a of 33B is 2083
mmHg, and by adjusting the pressure reducing pump 42 and valve 41, the pressure in each secondary space 31b, 32b is -550mHg.
These are the measurement results when expressed as mHg.

FIG. 3 also shows the above-mentioned section 1. Second oxygen selectively permeable membrane 3
1.32 as the oxygen selectively permeable membrane 1 having the configuration shown in FIG.
! 5. It is shown as ff16. In this case, the pressure in the primary space 1a of the module 2 is 2083 mm.
Hg, and the pressure in the secondary space 1b was -550 mmHg.

From the curve 15 and the curve t6 in FIG. 3, as in the case of the first embodiment described above, it is advantageous to use the first oxygen selectively permeable membrane 31 when the nitrogen concentration is high. It is understood that when the oxygen permeability is low, it is more advantageous to use the second oxygen selectively permeable membrane 32. In the gas concentrator of this embodiment having the configuration shown in FIG. 1, the first and second oxygen selectively permeable membranes 31 and 32 are used in the manner described above, and the curve 14 shown in FIG. It has obtained good characteristics as shown in .

[Example 3] In yet another embodiment of the invention, the outer diameter is 2000 μm.

This is a hollow fiber type oxygen selective permeation membrane module with a membrane area of 50M, in which composite hollow membranes coated with polydimethylsiloxane are arranged in parallel in a cylindrical shape on the outer surface of a polysulfone hollow fiber porous support with an inner diameter of 1650 μm and a thickness of 175 pm. It is used as one module. In addition, as a second module, the outer diameter is 2000 μm, the inner diameter is 1650 μm, and the thickness is 17 μm.
4 on the outer surface of a 5 μm polysulfone hollow fiber porous support.
A hollow fiber type oxygen selective permeation membrane module with a membrane area of 50 holes is used, in which composite hollow fiber membranes coated with methylpentene-1 are arranged in parallel in a columnar manner. This first and second
Each primary space of the module is interconnected,
External air is supplied to the primary space of the first module, and the secondary spaces of the first and second modules are commonly reduced in pressure by a vacuum pump or the like. Nitrogen-enriched air for use is taken out from the primary space of the second module. That is, the gas concentrator of this embodiment realizes a configuration comparable to the configuration shown in FIG. 1 (FIG. 1 type) using the first and second modules as described above.

Table 5 shows the characteristics of the gas concentrator of this example, as well as the gas concentrator (type 6) shown in FIG. 6 using the first and second modules as described above, and At the same time, characteristics of the respective configurations of the gas concentrator shown in FIG. 7 (FIG. 7 type) are also shown.

Table 5 As is clear from this Table 5, when the membrane area, the pressure in the primary space, and the pressure in the secondary space are set to the same conditions, nitrogen-enriched air when a nitrogen concentration of 97% is obtained. The amount of recovery is 120 in Figure 6 and Figure 7, respectively.
, 130 (bo/)I), whereas in the case of the type 1 shown in this example, it becomes 150<rrr/H), and it can be seen that the recovery rate is also greatly improved.

[Embodiment 4] The basic configuration of yet another embodiment of the present invention is shown in FIG. The gas concentrator of this embodiment has four modules 55A and 55B each having oxygen selective permeation membranes 51, 52, and 53°54.

Equipped with 55C and 55D. Air from the outside is supplied by the compressor 56 to the primary space 51a of the module 55A. Between the primary space 51a and the primary space 52a of the module 55B, this primary space 52a
and the primary space 53a of the module 55C, and the primary space 53a and the primary space 54a of the module 55D are connected by connecting pipes 57, respectively. Further, each secondary side space 51b, 52b, 53b, 54b of the modules 55A, 55B, 55C, 55D has a pipe 58
It is depressurized and exhausted by a decompression pump 59 via the decompression pump 59. The pipe 58 is provided with a valve 60, which allows the secondary spaces 51b, 52b, 53b to be closed.

The pressure of 54b can be adjusted.

The nitrogen enriched air is the primary space 54a of the module 55D.
It is taken out through a valve 62 from an outlet 61 provided in the pipe 6.
Supplied for use from 3.

By adjusting the opening degree of the valve 62, the primary space 51a
, 52a, 53a, and 54a are adjusted.

In the oxygen selectively permeable membranes 51, 52, 53, 54,
Each nitrogen selection coefficient is set to increase in order, and each oxygen permeation rate is set to decrease in order. The characteristics of each oxygen selectively permeable membrane are shown in curves in Figure 5. ! , 8, 19. ff1lo.

I! 11. Kono Takkyoku IIaj2B, 19
゜110.41!11 is the oxygen selectively permeable membrane 51, 52
53.54 is applied to the conventional configuration shown in FIG. 6, the measurement result of the (nitrogen enriched air flow rate) vs. (nitrogen concentration) characteristic is shown. A similar characteristic in the gas concentrator of this embodiment shown in FIG. 4 is shown by curve 17. As is clear from FIG. 5, in the gas concentrator of this embodiment, the amount of nitrogen-concentrated air recovered is significantly improved. In this example, we will focus on the module consisting of
When this module is defined as a first module, a module whose primary space is supplied with air from the primary space of this module corresponds to a second module. Further, a pressure reducing means includes a pipe 58, a pressure reducing pump 59, and the like.

In the above embodiment, an oxygen selectively permeable membrane was taken as an example of the selectively permeable membrane to increase the nitrogen concentration to obtain nitrogen-enriched air. , and CHa.

(such as those that separate H, O and air, and N2 and CO)
This method can be widely implemented in gas concentrators that condense gases whose permeation rate through the selectively permeable membrane is relatively low.

Furthermore, in the above-mentioned embodiment, the external air is pressurized and supplied to the primary space of the module, but if at least a pressure reducing means is provided to reduce the pressure of the secondary space,
Non-permeable gas can be condensed well.

〔Effect of the invention〕

According to the gas concentrator of the present invention, the first module and the second module have mutually different characteristics. By using second selectively permeable membranes, the first and second modules of the first and second modules are each provided with a second selectively permeable membrane. The pressure difference and pressure ratio between each primary side space and each secondary side space which are partitioned by the second permselective membrane are reduced in common by a pressure reducing means in each of the secondary side spaces. Even though the value is set to
In each module, optimal conditions can be set corresponding to the concentration of non-permeable gas in each of the primary spaces. Therefore, there is no need to provide separate means for reducing the pressure in the secondary spaces of the first and second modules, which is advantageous in simplifying the configuration and reducing costs.

Furthermore, since a highly concentrated concentrated gas can be obtained without returning the permeated gas as in the conventional method, the flow rate of this concentrated gas can be increased and the recovery amount and recovery rate can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the basic configuration of a gas concentrator according to an embodiment of the present invention, and FIG. 2 is a graph showing the (nitrogen enriched air flow rate) versus (nitrogen concentration) characteristics of the gas concentrator.
FIG. 3 is a graph showing the (nitrogen-concentrated air flow rate) versus (nitrogen concentration) characteristics of a gas concentrator according to another embodiment of the present invention.
FIG. 4 is a conceptual diagram showing the basic configuration of a gas concentrator according to still another embodiment of the present invention, FIG. 5 is a graph showing its (nitrogen enriched air flow rate) versus (nitrogen concentration) characteristics, etc. 7 and 7 are conceptual diagrams showing the basic configuration of a conventional gas concentrator. 31... First oxygen selectively permeable membrane, 32... Second oxygen selectively permeable membrane, 51, 52.53.54... Oxygen selectively permeable membrane, 33A... First module, 33B.・・・
Second module, 34... Pressure reduction means, 42.59 Pressure reduction pump, 55A, 55B, 55C, 55D... Module 31 - - First selection statement communication 32 - Aya 2 encounter connection 33A--Ichika 1's low juice) and 33B-$2 module 34-Lower pressure means, Jigo 9°'! i! ! , 1m air residue t (j!/m1n) - Nitrogen thin cotton air flow rate (f/min) Figure Figure

Claims (1)

[Claims] A first module in which an internal space is partitioned into a primary space and a secondary space by a first permselective membrane; a second module partitioned into a downstream space and into which gas is supplied from the primary space of the first module; and a secondary space of each of the first and second modules. a pressure reducing means for reducing the pressure in common, the permeation rate of the permeate gas in the second selectively permeable membrane is lower than the permeation rate of the permeable gas in the first selectively permeable membrane, and the second selectively permeable membrane A gas concentrator in which a non-permeable gas selection coefficient (permeation rate of non-permeable gas/permeation rate of permeable gas) is higher than a non-permeable gas selectivity coefficient of the first selectively permeable membrane.