WO2022118849A1

WO2022118849A1 - Gas separation system, and method for producing gas

Info

Publication number: WO2022118849A1
Application number: PCT/JP2021/043900
Authority: WO
Inventors: 洋帆広沢; 耀介水野
Original assignee: 東レ株式会社
Priority date: 2020-12-02
Filing date: 2021-11-30
Publication date: 2022-06-09
Also published as: JPWO2022118849A1

Abstract

The present invention relates to a gas separation system provided with a specific gas separating membrane unit, wherein: a feed gas pipe is connected to a feed gas inlet of the specific gas separating membrane unit; a permeated gas discharge pipe is connected to a permeated gas discharge port; a concentrated gas discharge pipe is connected to a concentrated gas discharge port; the permeated gas discharge pipe or the concentrated gas discharge pipe has a branched portion; a pipe positioned upstream of the pipe having the branched portion has a merging portion; and the branched portion and the merging portion are linked by a branch pipe.

Description

Gas separation system and gas manufacturing method

The present invention relates to a gas separation system provided with a gas separation membrane and a method for producing a gas using the gas separation system.

In recent years, hydrogen has been attracting attention as a clean energy source. Hydrogen is obtained by gasifying fossil fuels such as natural gas and coal and removing carbon dioxide from a mixed gas containing hydrogen and carbon dioxide as main components. The gas to be treated has undergone steam reforming and an aqueous gas shift, and is characterized by high temperature and high pressure. In addition, hydrogen is also used in the Haber-Bosch process, which synthesizes ammonia. This is a method of synthesizing ammonia by reacting hydrogen and nitrogen at high temperature and high pressure, but a process of separating and recovering unreacted hydrogen and nitrogen in a production plant is required.

As a method of concentrating a specific gas from a mixed gas at low cost, a membrane separation method that selectively permeates a target gas by utilizing the difference in gas permeability of the material is attracting attention.

Regarding a gas separation system including a separation membrane, for example, Patent Document 1 includes one gas separation membrane unit in the front stage and two gas separation membrane units in the rear stage, and the total amount of gas obtained from one gas separation membrane unit in the rear stage is separated into the gas in the front stage. A technique for circulating in a membrane unit is disclosed.

Patent Documents 2 and 3 disclose a technique in which one gas separation membrane unit is provided in the front stage and one gas separation membrane unit is provided in the rear stage, and the entire amount of gas obtained from the rear stage is circulated to the gas separation membrane unit in the front stage. There is.

Further, Patent Document 4 discloses a technique for recovering helium while circulating helium that has passed through the separation membrane unit in a supply gas.

Japanese Patent Application Laid-Open No. 2016-187770 Japanese Patent Application Laid-Open No. 51-147480 Japanese Patent Application Laid-Open No. 09-066217 Japanese Patent Application Laid-Open No. 2019-072658

However, in the conventional gas separation system provided with a gas separation membrane, it is difficult to enrich both high recovery rate and high purity, and the purification efficiency may not be sufficient.

Therefore, it is an object of the present invention to provide a gas separation system capable of purifying a component to be enriched with a high recovery rate and a high purity.

The present invention for achieving the above object includes the following 1 to 15.
A gas separation system that enriches at least one component from a mixed gas containing 1.2 or more components.
The gas separation system includes a specific gas separation membrane unit and is equipped with a specific gas separation membrane unit.
The specific gas separation membrane unit includes an inlet for a supply gas, an outlet for a permeated gas, and an outlet for a concentrated gas.
A supply gas pipe is connected to the inlet of the supply gas.
A permeated gas discharge pipe is connected to the permeated gas discharge port.
A concentrated gas discharge pipe is connected to the concentrated gas discharge port.
The permeated gas discharge pipe or the concentrated gas discharge pipe has a branch portion, a pipe located upstream of the pipe having the branch portion has a merging portion, and the branch portion and the merging portion are connected by a branch pipe. Has been a gas separation system.
2. 2. There is only one specific gas separation membrane unit in the gas separation system,
The gas separation system according to 1 above, wherein the supply gas pipe has the confluence and does not include another gas separation membrane unit.
3. 3. A method for producing a gas using the gas separation system according to 1 or 2 above.
A method for producing a gas, which comprises a step of controlling the concentration of enriched components in the supplied gas supplied to the specific gas separation membrane unit to 30 mol% or less.
4. Another gas separation membrane unit is further provided upstream of the specific gas separation membrane unit, and a permeated gas or a concentrated gas that has passed through the other gas separation membrane unit is supplied to the specific gas separation membrane unit. The gas separation system described.
5. Another gas separation membrane unit is further provided downstream of the specific gas separation membrane unit, and the permeated gas or concentrated gas that has passed through the specific gas separation membrane unit is supplied to the other gas separation membrane unit. The gas separation system described.
6. The gas separation system according to any one of 1, 2, 4 or 5, wherein the separation membrane in the specific gas separation membrane unit is a polyamide membrane.
7. The gas separation system according to any one of 1, 2, 4, 5 or 6, wherein the enriched component in the supply gas supplied to the specific gas separation membrane unit is hydrogen.
8. A gas separation system that enriches at least one component from a mixed gas containing two or more components.
The gas separation system includes a first gas separation membrane unit and a second gas separation membrane unit connected by a connecting pipe.
The first gas separation membrane unit includes a first inlet, a first permeation outlet, and a first concentration outlet.
The second gas separation membrane unit includes a second inlet, a second permeation outlet, and a second concentration outlet.
A first supply gas pipe is connected to the first inlet.
The connecting pipe connects the first permeation outlet or the first concentration outlet with the second inlet.
A second permeation gas discharge pipe is connected to the second permeation outlet.
A second concentrated gas discharge pipe is connected to the second concentration outlet.
The second permeated gas discharge pipe or the second concentrated gas discharge pipe has a branch portion, the first supply gas pipe or the connecting pipe has a merging portion, and the branch portion and the merging portion have a merging portion. A gas separation system connected by a branch pipe.
9. 8. The gas separation system according to 8, wherein the connecting pipe has the confluence.
10. 8. The gas separation system according to 8 or 9, wherein the separation membrane in the first gas separation membrane unit and the separation membrane in the second gas separation membrane unit is a polyamide membrane.
11. The connecting pipe connects the first concentration outlet and the second inlet.
The gas separation system according to any one of 8 to 10, wherein the branch portion is provided in the second permeated gas discharge pipe.
12. The connecting pipe connects the first permeation outlet and the second inlet.
The gas separation system according to any one of 8 to 10, wherein the branch portion is provided in the second concentrated gas discharge pipe.
13. 11. The gas separation system according to 11 or 12, wherein the second permeated gas discharge pipe or the second concentrated gas discharge pipe is connected to the branch pipe and the recovery device via the branch portion.
14. 11. The gas separation system according to 11 above, wherein the enriched component in the supply gas supplied to the first gas separation membrane unit and the second gas separation membrane unit is hydrogen.
15. A method for producing a gas using the gas separation system according to 11 or 12 above.
The amount of gas of the enriched component contained in the gas discharged from the first gas separation membrane unit and not supplied to the second gas separation membrane unit is supplied to the first gas separation membrane unit. A method for producing a gas, which comprises a step of controlling 30% by volume or more and 80% by volume or less of the enriched components in the gas.

According to the present invention, at least one gas can be enriched from a mixed gas containing two or more components while achieving both high recovery rate and high purity.

FIG. 1 is a flow chart of a gas separation system according to the first embodiment. FIG. 2 is a flow chart of the gas separation system in Examples 2 to 7. FIG. 3 is a flow chart showing an example of a gas separation system according to an embodiment of the present invention. FIG. 4 is a flow chart of the gas separation system in Examples 8 to 12. FIG. 5 is a flow chart of the gas separation system in Examples 13 to 16. FIG. 6 is a flow chart of the gas separation system in Comparative Examples 3 to 6.

The present invention is a gas separation system that enriches at least one component from a mixed gas containing two or more components, wherein the gas separation system includes a specific gas separation membrane unit, and the specific gas separation membrane unit is The supply gas is provided with an inlet for the supply gas (hereinafter also referred to as "inlet"), an outlet for the permeated gas (hereinafter also referred to as the "permeation outlet"), and an outlet for the concentrated gas (hereinafter also referred to as the "concentrated outlet"). A supply gas pipe is connected to the inlet of the gas, a permeated gas discharge pipe is connected to the permeated gas discharge port, and a concentrated gas discharge pipe is connected to the concentrated gas discharge port. The pipe or the concentrated gas discharge pipe has a branch portion, the pipe located upstream of the pipe having the branch portion has a merging portion, and the branch portion and the merging portion are connected by a branch pipe. Regarding gas separation system.

The gas separation system according to the embodiment of the present invention includes a specific gas separation membrane unit. Here, the gas separation membrane unit refers to a portion having the ability to enrich at least one component from a mixed gas containing two or more components by providing the separation membrane, and a specific preferable configuration will be described later. do. The specific gas separation membrane unit is a gas separation membrane unit having the above-mentioned configuration. The gas separation system according to the embodiment of the present invention may include a specific gas separation membrane unit and another gas separation membrane unit. That is, the other gas separation membrane unit refers to a gas separation membrane unit further included in the gas separation membrane system in addition to the specific gas separation membrane unit included in at least the gas separation membrane system. The other gas separation membrane unit may not have the above configuration as the specific gas separation membrane unit, but does not exclude the case where the other gas separation membrane unit has the above configuration as the specific gas separation membrane unit. In the present specification, the specific gas separation membrane unit and other gas separation membrane units may be collectively referred to simply as a gas separation membrane unit.

In the gas separation membrane unit, the inlet (inlet) of the supplied gas is the inlet of the gas supplied to the gas separation membrane unit. The supplied gas is supplied through a supply gas pipe connected to the inlet. The supply gas pipe may be a connecting pipe connecting the inlet and the permeation outlet or the concentration outlet of another gas separation membrane unit.
The permeated gas discharge port (permeation outlet) is an outlet from which the gas (permeated gas) that has permeated the separation membrane in the gas separation membrane unit is discharged. The permeated gas is discharged from the gas separation membrane unit through the permeated gas discharge pipe connected to the permeation outlet. On the other hand, the concentrated gas discharge port (concentrated outlet) is an outlet from which the remaining gas (concentrated gas) that does not permeate the separation membrane in the gas separation membrane unit is discharged. The concentrated gas is discharged from the gas separation membrane unit through a concentrated gas discharge pipe connected to the concentration outlet. The concentrated gas discharge pipe and the permeated gas discharge pipe may be connecting pipes connected to the inlets of different gas separation membrane units, respectively.
Further, in the specific gas separation membrane unit, the permeated gas discharge pipe or the concentrated gas discharge pipe has a branch portion, and the pipe located upstream of the pipe having the branch portion has a confluence portion. The branch portion and the merging portion are connected by a branch pipe. The pipe located upstream of the pipe having the branch portion is, in other words, the gas flow through the gas separation membrane unit (specific separation membrane unit) to which the pipe having the branch portion is connected when viewed from the branch portion. A pipe located on the upstream side. The branch pipe is a pipe that branches the flowing gas in different directions, and the merging part flows to the gas that has flowed from the branch part to the pipe that is located upstream of the pipe that has the branch part. It is a pipe where gas merges. The merging portion may be provided with a mixer that efficiently mixes the gas.

The gas discharged from the specific gas separation membrane unit is divided into a circulating flow that reaches the confluence from the branching part through the branching pipe and a recovery flow that is recovered as a gas containing the target component with high purity. By providing the circulating flow, in the gas separation membrane unit to which the circulating flow is supplied, the concentration of the component to be permeated through the separation membrane becomes high, and the partial pressure affecting the filtration increases, so that the permeation is promoted. By repeating this operation until the gas concentration in the gas separation membrane unit becomes equilibrium, the selective separability in the gas separation membrane unit can be further improved, and the components to be enriched as a gas separation membrane unit can be obtained with high recovery rate and high purity. Can be done. The above description is for the case where the separation membrane mounted on the gas separation membrane unit selectively permeates the components to be enriched, but the separation membrane selectively selects the components to be enriched. The above-mentioned "permeation" can be read as "concentration", and the effect of the present invention can be obtained in the same manner. Hereinafter, the portion that can be read in the same manner may be referred to as "permeation or concentration".

The gas separation system according to the embodiment of the present invention includes the following first and second embodiments.
The gas separation system according to the embodiment of the present invention may include at least one gas separation membrane unit, and at least one of the gas separation membrane units may be a specific gas separation membrane unit. Here, as a configuration example when the gas separation system includes two or more gas separation membrane units, the following (a) or (b) can be mentioned.
(A) A gas separation system in which another gas separation membrane unit is further provided upstream of the specific gas separation membrane unit, and a permeated gas or a concentrated gas that has passed through the other gas separation membrane unit is supplied to the specific gas separation membrane unit. ..
(B) Another gas separation membrane unit is further provided downstream of the specific gas separation membrane unit, and the permeated gas or concentrated gas that has passed through the specific gas separation membrane unit is supplied to the other gas separation membrane unit. system.

Among them, in the case of (a) above, the first gas separation system is provided with a first gas separation membrane unit as another gas separation membrane unit and a second gas separation membrane unit as a specific gas separation membrane unit. The gas separation system according to the embodiment of the above is specifically exemplified. That is, the gas separation system according to the first embodiment of the present invention includes a first gas separation membrane unit and a second gas separation membrane unit connected by a connecting pipe, and the first gas separation membrane unit is , A first inlet, a first permeation outlet, and a first concentration outlet, the second gas separation membrane unit comprises a second inlet, a second permeation outlet, and a second concentration outlet. A first supply gas pipe is connected to the first inlet, and the connecting pipe connects the first permeation outlet or the first concentration outlet to the second inlet, and the first. A second permeated gas discharge pipe is connected to the permeation outlet of 2, a second concentrated gas discharge pipe is connected to the second enrichment outlet, and the second permeate gas discharge pipe or the second is said. The concentrated gas discharge pipe of No. 1 has a branch portion, the first supply gas pipe or the connecting pipe has a merging portion, and the branch portion and the merging portion are connected by a branch pipe.
That is, the first embodiment is characterized in that it has at least two gas separation membrane units in the embodiment of the present invention.

In the gas separation system of the second embodiment, there is only one specific gas separation membrane unit in the gas separation system, the supply gas pipe has a confluence, and the gas separation system is another gas separation membrane unit. Not equipped. That is, the second embodiment is characterized in that it has only one gas separation membrane unit in the embodiment of the present invention.

Hereinafter, embodiments of the present invention including the first embodiment and the second embodiment will be described in detail.

<Gas separation system and gas separation membrane unit>
(First Embodiment: Gas separation system having a plurality of gas separation membrane units)
The gas separation system 100 according to the first embodiment includes a first gas separation membrane unit 1 and a second gas separation membrane unit 2 connected by a connecting pipe 8. Here, the first gas separation membrane unit 1 is another gas separation membrane unit, and the second gas separation membrane unit 2 is a specific gas separation membrane unit. This will be described below.

FIGS. 1 to 4 are diagrams schematically illustrating the gas system according to the first embodiment of the present invention, respectively. In FIGS. 1 to 4, the first gas separation membrane unit 1 includes a first inlet 11, a first permeation outlet 12, and a first concentration outlet 13. The second gas separation membrane unit 2 includes a second inlet 21, a second permeation outlet 22, and a second concentration outlet 23. A first supply gas pipe 41 is connected to the first inlet 11.

The connecting pipe 8 connects the first permeation outlet 12 or the first concentration outlet 13 and the second inlet 21. At this time, the connecting pipe 8 also serves as a supply gas pipe connected to the second inlet 21. Further, the connecting pipe 8 also serves as a permeated gas discharge pipe connected to the first permeation outlet 12 or a concentrated gas discharge pipe connected to the first concentrating outlet 13. Of the first permeation outlet 12 or the first concentration outlet 13, the outlet to which the connecting pipe 8 is not connected is the permeation gas discharge pipe or the first permeation gas discharge pipe 51 or the first as the concentrated gas discharge pipe. Concentrated gas discharge pipe 61 is connected. Here, as shown in FIGS. 1 to 4, the first permeated gas discharge pipe 51 may merge with the second permeated gas discharge pipe 52, if necessary. Alternatively, the first concentrated gas discharge pipe 61 may merge with the second concentrated gas discharge pipe 62.

A second permeated gas discharge pipe 52 is connected to the second permeation outlet 22, and a second concentrated gas discharge pipe 62 is connected to the second concentration outlet 23. The second permeated gas discharge pipe 52 or the second concentrated gas discharge pipe 62 has a branch portion 9, and the first supply gas pipe 41 or the connecting pipe 8 has a merging portion. Here, the branch portion 9 and the merging portion 10 are connected by a branch pipe 7. The merging portion 10 is provided in the first supply gas pipe 41 or the connecting pipe 8 which is a pipe located upstream of the pipe having the branching portion in the aspects of FIGS. 1 to 4, but the merging portion has the branching portion. It may be provided in a pipe located upstream of the flow of the supply gas. That is, the merging portion may be provided at least on the upstream side via the second gas separation membrane unit 2 when viewed from the branching portion.

The branch pipe 7 is a pipe that branches the flowing gas in different directions, and the merging portion 10 connects the gas flowing through the branch pipe 7 from the branch portion 9 to the first supply gas pipe 41 or the connecting pipe 8. It is a pipe where the flowing gas joins. The merging portion 10 may include a mixer that efficiently mixes the gas.

Here, in the configuration exemplified in FIG. 1, the connecting pipe 8 connects the first concentration outlet 13 and the second inlet 21, the second permeated gas discharge pipe 52 has the branch portion 9, and the second The supply gas pipe 41 of No. 1 has a confluence portion 10.

In the configuration exemplified in FIG. 2, the connecting pipe 8 connects the first concentration outlet 13 and the second inlet 21, the second permeated gas discharge pipe 52 has a branch portion 9, and the connecting pipe 8 has a branch portion 9. It has a structure having a merging portion 10.

In the configuration exemplified in FIG. 3, the connecting pipe 8 connects the first permeation outlet 12 and the second inlet 21, the second concentrated gas discharge pipe 62 has the branch portion 9, and the first supply. The gas pipe 41 has a confluence portion 10.

In the configuration exemplified in FIG. 4, the connecting pipe 8 connects the first permeation outlet 12 and the second inlet 21, the second concentrated gas discharge pipe 62 has a branch portion 9, and the connecting pipe 8 has a branch portion 9. It has a structure having a merging portion 10.

The gas discharged from the second gas separation membrane unit 2 is recovered together with the circulating flow reaching the confluence portion 10 from the branch portion 9 through the branch pipe 7 and the gas discharged from the first gas separation membrane unit 1. It is divided into recovery streams. By providing the circulating flow, in the gas separation membrane unit to which the circulating flow is supplied, the concentration of the component to be permeated or concentrated in the separation membrane is increased, and the partial pressure affecting the filtration is increased, so that the permeation or concentration is promoted. By repeating this operation until the gas concentration in the gas separation membrane unit becomes equilibrium, the selective separability in the gas separation membrane unit can be further improved, and the components to be enriched as a gas separation membrane unit can be obtained with high recovery rate and high purity. Can be done.

In particular, in the gas discharged from the first gas separation membrane unit 1 to the second gas separation membrane unit 2, that is, the gas passing through the connecting pipe 8, the concentration of the component to be permeated or concentrated in the separation membrane is relatively low. is doing. Therefore, in the configuration having the merging portion 10 in the connecting pipe 8 as exemplified in FIGS. 2 and 4, the effect of improving the partial pressure by supplying the circulating flow to the second gas separation membrane unit 2 is shown in FIG. And as illustrated in FIG. 3, the first supply gas pipe 41 is higher than the configuration having the merging portion 10.

Therefore, in the first embodiment, the merging portion 10 may be provided at least on the upstream side via the second gas separation membrane unit 2 when viewed from the branching portion, and is concrete in the embodiments exemplified in FIGS. 1 to 4. It may be provided in either the first supply gas pipe 41 or the connecting pipe 8, but it is more preferable that the merging portion 10 is provided in the connecting pipe 8.

When the separation membrane mounted on the first gas separation membrane unit 1 and the second gas separation membrane unit 2 selectively permeates the component to be enriched, that is, the component to be enriched is better than the component to be enriched. When the permeability of the component to be converted is high, the connecting pipe 8 connects the first concentration outlet 13 of the first gas separation membrane unit 1 and the second inlet 21 of the second gas separation membrane unit 2. It is provided in. Further, the branch portion 9 is provided in the second permeated gas discharge pipe 52. 1 and 2 are diagrams showing a configuration example in this case. In such a configuration, since the component to be enriched is contained in the permeated gas with high purity, the permeated gas is recovered. That is, in such a configuration, it is preferable that the second permeated gas discharge pipe 52 is connected to the branch pipe 7 and the recovery device via the branch portion 9.

On the other hand, when neither the separation membrane mounted on the first gas separation membrane unit 1 and the second gas separation membrane unit 2 selectively permeates the component to be enriched, the connecting pipe 8 is the first. Is provided so as to connect the first permeation outlet 12 of the gas separation membrane unit 1 and the second inlet 21 of the second gas separation membrane unit 2. Further, the branch portion 9 is provided in the second concentrated gas discharge pipe 62. 3 and 4 are diagrams showing a configuration example in this case. In such a configuration, since the component to be enriched is contained in the concentrated gas with high purity, the concentrated gas is recovered. That is, in such a configuration, it is preferable that the second concentrated gas discharge pipe 62 is connected to the branch pipe 7 and the recovery device via the branch portion 9.

A part of the permeated gas discharged from the second gas separation membrane unit 2 is recovered as an enriched gas by using a gas separation system equipped with a membrane that selectively permeates the components to be enriched, and the permeation that is not recovered. By merging the gas with the supply gas of the second gas separation membrane unit 2, the partial pressure of the component to be enriched on the supply side of the second gas separation membrane unit 2 is increased, and the permeation of the component to be enriched is increased. Since the amount is increased, the component to be enriched can be obtained with high recovery rate and high purity.

Further, in a gas separation system having the same configuration as the case where a membrane for selectively permeating a component to be enriched is mounted, conversely, when the same operation is performed using a membrane for selectively permeating a component to be enriched, the same operation is performed. The partial pressure of the non-rich component on the supply side of the gas separation membrane unit 2 of 2 is increased, and the permeation amount of the non-rich component is increased. That is, it is possible to obtain a component that is deprived on the permeation side with a high recovery rate and high purity.

Here, each gas separation membrane unit in the gas separation system may be composed of one gas separation membrane module, or may be configured by arranging a plurality of gas separation membrane modules in parallel or in series. A flat membrane or a hollow fiber membrane can be used as the form of the membrane mounted on the gas separation membrane module, and the membrane is modularized and stored in a pressure vessel for use.

Although the configuration in which the first gas separation membrane unit and the second gas separation membrane unit are combined is described in detail here as a configuration example of the first embodiment, the gas separation system of the first embodiment is described in detail. The number of gas separation membrane units inside is not particularly limited as long as it is two or more, and there may be three or more gas separation membrane units. For example, the second permeation outlet 22 or the second concentration outlet 23 of the second gas separation membrane unit and the inlet of another gas separation membrane unit that may be further contained may be connected by a connecting pipe. The first supply gas pipe may be a connecting pipe connected to a permeation outlet or a concentration outlet of another gas separation membrane unit that may be further contained. Further, even when the gas separation membrane unit is composed of three or more, as described above, the merging portion may be provided at least on the upstream side via the second gas separation membrane unit 2 when viewed from the branch portion. For example, when another gas separation membrane unit is included upstream of the first gas separation membrane unit, the confluence may be provided in a supply gas pipe or a connecting pipe connected to the inlet of the other gas separation membrane unit. good.

Similarly, here, the case where the first gas separation membrane unit and the second gas separation membrane unit are combined is described in detail as a configuration example of the first embodiment, but the gas separation system of the first embodiment is described in detail. In the above, by forming a structure in which a plurality of gas separation systems are connected, a mode may be provided in which a plurality of branch portions, merging portions, and connecting pipes are provided. In this way, a plurality of gas separation systems of the first embodiment are combined. Can also obtain the same effect. Alternatively, the first gas separation membrane unit and other gas separation membrane units that may be further contained may have a configuration corresponding to the specific separation membrane unit together with the second gas separation membrane unit.

(Second Embodiment: Gas Separation System with Only One Gas Separation Membrane Unit)
The gas separation system according to the second embodiment of the present invention is a gas separation system that enriches at least one component from two or more kinds of gases, and the gas separation system includes a specific gas separation membrane unit. The specific gas separation membrane unit includes an inlet for a supply gas (hereinafter, also referred to as an inlet), an outlet for a permeated gas (hereinafter, also referred to as a permeation outlet), and an outlet for a concentrated gas (hereinafter, also referred to as a concentrated outlet). A supply gas pipe is connected to the inlet, a permeated gas discharge pipe is connected to the permeation outlet, a concentrated gas discharge pipe is connected to the concentrated outlet, and the permeated gas discharge pipe or the concentrated gas is connected. The discharge pipe has a branch portion, and the pipe located upstream of the pipe having the branch portion has a merging portion, and the branch portion and the merging portion are connected by a branch pipe. The gas separation system according to the second embodiment has only one specific gas separation membrane unit in the gas separation system, the supply gas pipe has a confluence, and the gas separation system has another gas separation membrane. It is characterized by not having a unit. That is, the gas separation system 200 according to the second embodiment of the present invention includes a gas separation membrane unit in which one module or a plurality of modules are connected in parallel or in series as a specific separation membrane unit. This will be described below.

As illustrated in FIG. 5, the specific gas separation membrane unit 2 includes an inlet 21, a permeation outlet 22, and a concentration outlet 23, and a supply gas pipe 4 is connected to the inlet 21. Further, a permeation gas discharge pipe 5 is connected to the permeation outlet 22, and a concentrated gas discharge pipe 6 is connected to the concentration outlet 23.

Further, the permeated gas discharge pipe 5 or the concentrated gas discharge pipe 6 has a branch portion 9. FIG. 5 is a configuration example in which the permeated gas discharge pipe 5 has a branch portion. The supply gas pipe 4, which is a pipe having a branch portion, that is, a pipe located upstream of the permeated gas discharge pipe 5 or the concentrated gas discharge pipe 6, has a confluence portion 10. The branch portion 9 and the merging portion 10 are connected by a branch pipe 7. The branch pipe 7 is a pipe that branches the flowing gas in different directions, and the merging portion 10 is a pipe in which the gas flowing through the branch pipe 7 from the branch portion 9 and the gas flowing in the supply gas pipe 4 merge. Is. The merging portion 10 may include a mixer that efficiently mixes the gas.

The gas discharged from the specific gas separation membrane unit 2 is divided into a circulating flow that reaches the confluence portion 10 from the branch portion 9 through the branch pipe 7 and a recovery flow that is recovered as a gas containing the target component with high purity. By providing the circulating flow, in the gas separation membrane unit to which the circulating flow is supplied, the concentration of the component to be permeated or concentrated in the separation membrane is increased, and the partial pressure affecting the filtration is increased, so that the permeation or concentration is promoted. By repeating this operation until the gas concentration in the gas separation membrane unit becomes equilibrium, the selective separability in the gas separation membrane unit can be further improved, and the components to be enriched as a gas separation membrane unit can be obtained with high recovery rate and high purity. Can be done.

When the separation membrane mounted on the specific gas separation membrane unit 2 selectively permeates the component to be enriched, that is, when the permeation of the component to be enriched is higher than that of the component to be enriched, the branch portion Reference numeral 9 is provided in the permeated gas discharge pipe 5. In such a configuration, since the component to be enriched is contained in the permeated gas with high purity, the permeated gas is recovered. That is, in such a configuration, it is preferable that the permeated gas discharge pipe 5 is connected to the branch pipe 7 and the recovery device via the branch portion 9.

When the separation membrane mounted on the specific gas separation membrane unit 2 does not selectively permeate the components to be enriched, the branch portion 9 is provided in the concentrated gas discharge pipe 6. In such a configuration, since the component to be enriched is contained in the concentrated gas with high purity, the concentrated gas is recovered. That is, in such a configuration, it is preferable that the concentrated gas discharge pipe 6 is connected to the branch pipe 7 and the recovery device via the branch portion 9.

<Gas separation membrane module>
The gas separation membrane unit in the gas separation system according to the embodiment of the present invention includes a separation membrane. The separation membrane is provided in the gas separation membrane unit, preferably in the form of a gas separation membrane module. The gas separation membrane unit may be composed of one gas separation membrane module, or may be configured by arranging a plurality of gas separation membrane modules in parallel or in series.

In the gas separation membrane module, filtration is continuously performed from the inlet to the concentration outlet. As the filtration progresses, the partial pressure of the components that permeate the membrane decreases, so the closer to the concentration outlet of the gas separation membrane module, the more difficult it is for the gas to permeate. In particular, in the first embodiment, the second gas separation membrane unit is more difficult to permeate because the filtration is more advanced than that of the first gas separation membrane unit. Therefore, it is preferable to eliminate the concentration polarization on the membrane surface, which is a permeation resistance, by increasing the flow velocity of the supply gas. Examples of the means include a method of thinning the flow path material on the supply side, and a method of sending the supply gas from the end face of the gas separation membrane module and discharging it from the outer peripheral portion in the case of a flat membrane.

<Circulation ratio>
The ratio of the circulating flow rate to the recovered flow rate is called the circulation ratio. The larger the circulation ratio, the easier it is to increase the amount of permeation in the gas separation membrane unit to which the circulating flow is supplied, but the smaller the amount of recovered flow, the smaller the flow rate of the obtained enriched gas tends to be. Therefore, the circulation ratio can be adjusted according to the desired recovery rate and purity of the enriched gas. For example, the circulation ratio is preferably adjusted in the range of 1 to 15. Since the more preferable range of the circulation ratio varies depending on the composition of the supply gas, it can be appropriately adjusted in this range.

As a means for adjusting the circulation ratio, it is possible to change the opening degree of the valve provided in the connecting pipe or the recovery flow pipe. The recovery rate is the ratio of the recovered enriched components to the enriched components in the supplied gas, and the closer the recovery rate is to 100%, the more efficiently the gas separation is performed.

<Separation membrane>
The separation membrane in the first gas separation membrane unit and the separation membrane in the second gas separation membrane unit in the gas separation membrane unit of the first embodiment can be appropriately selected depending on the type of gas to be enriched. As the separation membrane, the same ones used so far in the art can be used without particular limitation. Examples thereof include rubber-like polymer materials such as silicone resin and polybutadiene resin, polymer films such as polyimide, polyetherimide, polyamide, polyamideimide, polysulfone, polycarbonate, cellulose and carbon, and inorganic films such as zeolite, silica and palladium. ..

The separation membrane mounted on the gas separation membrane unit may be a homogeneous membrane, an asymmetric membrane composed of a homogeneous layer and a porous layer, a microporous membrane, or the like. The form of storing the separation membrane in the pressure vessel may be any of a plate and frame type, a spiral type, a hollow fiber type and the like. When a relatively small gas such as hydrogen or helium is permeated, a polyamide membrane, a silica membrane, a zeolite membrane, or a graphene membrane can be used. In particular, the polyamide film is preferable because it can be highly filled in the module and the amount of gas permeation can be increased. Therefore, in the first embodiment of the present invention, the separation membrane in the first gas separation membrane unit and the separation membrane in the second gas separation membrane unit are preferably polyamide films.

As for the separation membrane in the gas separation membrane unit in the gas separation system according to the second embodiment, the same one as that used in the first embodiment can be selected. The same applies to the separation membrane in each gas separation membrane unit including the specific gas separation membrane unit in the other embodiment, and a polyamide membrane is preferably used.

<Improvement of filtration efficiency by pump>
The gas separation system according to the embodiment of the present invention can be used for methods such as hydrogen purification and recovery of methane from exhaust gas from a plant or biogas. That is, in the gas separation system, the enriched components in the supply gas supplied to the gas separation membrane unit are not particularly limited, but hydrogen and methane are preferable, and hydrogen is more preferable. The gas separation system may be any one that enriches at least one component from a mixed gas containing two or more components, for example, enriches two or more components from a mixed gas containing three or more components. It may be a thing. In the gas separation system according to the embodiment of the present invention, a pressure pump and a decompression pump can be provided before and after the gas separation membrane unit in order to improve the filtration efficiency.

<Enrichment method (gas production method)>
A method for producing a gas using the gas separation system according to the present embodiment will be described. Such a gas production method includes, for example, a step of supplying a mixed gas containing two or more components to the gas separation system according to the present embodiment, and a permeated gas or a concentrated gas that has passed through a gas separation membrane unit in the gas separation system. Including the step of recovering.

(Gas separation system with multiple gas separation membrane units)
In the method for producing a gas using the gas separation system according to the first embodiment, the enriched components contained in the gas discharged from the first gas separation membrane unit and not supplied to the second gas separation membrane unit. It is preferable to have a step of controlling the amount of the gas to be 30% by volume or more and 80% by volume or less of the enriched components in the supply gas supplied to the first gas separation membrane unit. The gas discharged from the first gas separation membrane unit 1 and not supplied to the second gas separation membrane unit 2 is a case where the connecting pipe 8 connects the first concentration outlet 13 and the second inlet 21. Refers to the permeated gas discharged from the first permeation outlet. Further, when the connecting pipe 8 connects the first permeation outlet 12 and the second inlet 21, it means the concentrated gas discharged from the first enrichment outlet. The ratio of the amount of gas is more preferably 40% by volume or more, further preferably 50% by volume or more. The proportion of the amount of gas is preferably 70% by volume or less, more preferably 60% by volume or less. The amount of enriched components contained in the gas discharged from the first gas separation membrane unit and not supplied to the second gas separation membrane unit is controlled by, for example, changing the supply gas amount, operating pressure, and temperature. can.

By doing so, the concentration of the enriched component in the supply gas supplied to the second gas separation membrane unit is increased, and as a result, the partial pressure is increased and the performance related to permeation or concentration is improved. Therefore, while the separation in the first gas separation membrane unit is performed with high recovery rate and high purity, the separation in the second gas separation membrane unit can also be performed with high recovery rate and high purity.

(Gas separation system with only one gas separation membrane unit)
In the method for producing a gas using the gas separation system according to the second embodiment, a step of controlling the concentration of enriched components contained in the supply gas supplied to the specific gas separation membrane unit to 30 mol% or less. That is, it is preferable to have a step of keeping the concentration of the enriched component in the supplied gas to be low. The concentration of the enriched component contained in the feed gas is more preferably 10 mol% or less, further preferably 5 mol% or less. The concentration of the enriched component contained in the feed gas can be controlled by using, for example, an adsorption method or an absorption method.

When the gas separation system according to the second embodiment is used, it is possible to increase the concentration of enriched components in the supplied supply gas in the specific gas separation membrane unit in which the supply gas is first treated by the separation membrane. can. Therefore, a higher effect can be exhibited when the concentration of the enriched component in the supply gas is low than when the concentration is high. It should be noted that such an embodiment is suitable in both the case where the separation membrane mounted on the specific gas separation membrane unit selectively permeates the component to be enriched and the case where the component to be enriched is not selectively permeated. be.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

(Preparation of gas separation membrane)
An 18% by mass dimethylformamide (DMF) solution of polysulfone was cast at room temperature (25 ° C.) and a coating thickness of 190 μm on a non-woven fabric made of polyester fibers (air permeability 1.0 cc / cm ² / sec) produced by the papermaking method. Immediately after that, the porous support layer was formed on the non-woven fabric as the base material by immediately immersing it in pure water for 5 minutes.
Next, the porous support layer was added to an aqueous solution in which 2-ethylpiperazine was dissolved at 5.5% by mass, sodium dodecyldiphenyl ether disulfonate was 500 ppm (mass basis), and trisodium phosphate was 2.0% by mass. After immersing the formed substrate for 10 seconds, nitrogen was blown from an air nozzle to remove excess aqueous solution. Subsequently, an n-decane solution containing 0.2% by mass of trimesic acid chloride heated to 70 ° C. was uniformly applied to the surface of the porous support and held at a film surface temperature of 60 ° C. for 3 seconds. The film surface temperature was cooled to 10 ° C. and left for 1 minute in an air atmosphere while maintaining this temperature to form a separation functional layer (polyamide film). The obtained separation membrane was held vertically, drained, and washed with pure water at 60 ° C. for 2 minutes to obtain a separation membrane.

(Helium permeability of gas separation membrane to oxygen)
A separation film air-dried under a greenhouse at 25 ° C. was cut into a circle with an effective film area of 25 cm ² and attached to a transmission cell separated by two chambers on the supply side and the permeation side, containing 60 mol% helium and 40 mol% oxygen. The supplied gas was supplied at a pressure of 0.1 MPa, a temperature of 25 ° C., and 100 mL / min, and the permeation side was reduced to −0.05 MPa for operation. After 30 minutes from the start of operation, the permeated gas is sampled, the permeated gas is sent to gas chromatography having a TCD (thermal conductivity detector), the concentration of the permeated gas in this mixed gas is analyzed, and the permeability of helium and oxygen is determined. Calculated. In addition, helium / oxygen selectivity was calculated by dividing the helium permeability by the oxygen permeability. As a result, the helium permeability was 10 nmol / m ² / s / Pa, the oxygen permeability was 0.5 nmol / m ² / s / Pa, and the helium / oxygen selectivity was 20.

(Helium permeability of gas separation membrane to methane)
The permeability of helium and methane and the selectivity of helium / methane were calculated in the same manner as the evaluation of helium permeability to oxygen of the gas separation membrane except that the type of gas was changed from oxygen to methane. As a result, the helium permeability was 10 nmol / m ² / s / Pa, the methane permeability was 0.25 nmol / m ² / s / Pa, and the helium / methane selectivity was 40.

In this example, the prepared separation membrane was used to separate the mixed gas containing helium, but the separation membrane is a polyamide membrane that can selectively permeate relatively small gas such as hydrogen and helium. be. Therefore, when a mixed gas containing hydrogen is used for each gas separation system used in this example, the separation can be performed in the same manner, and the effect of the present invention can be obtained in the same manner. Further, as described above, the effect of the present invention can be obtained in the same manner even when the type of the separation membrane is appropriately changed according to the type of the enriched gas.

(Gas separation membrane module)
After cutting the gas separation membrane to a width of 300 mm, it was air-dried in a greenhouse at 25 ° C. and then folded, and a supply-side flow path material (Diomesh PET-Screen 100-55PT (manufactured by innovex)) was sandwiched between the folded separation membranes. A permeation side flow path material (Diomesh PET-Screen 100-55PT (manufactured by innovex)) is placed on the permeation side surface of the gas separation membrane, and an adhesive is applied to the three ends of the permeation side flow path material. The laminate (number of leaves: 5 sheets, effective membrane area 1.0 m ² ) is spirally surrounded by an ABS resin water collecting pipe (width: 300 mm, diameter: 17 mm, number of holes 80 x 2 rows of straight lines). A separation membrane module with a diameter of 2.5 inches was produced.

(Helium recovery rate and helium purity)
The mixed gas containing helium and oxygen was separated by the gas separation system under the conditions shown in the table. The operating temperature was 30 ° C., and the operating pressure of each gas separation membrane unit was 0.1 MPa.
The permeated gas 1 hour after the start of operation was sampled with a mass spectrometer (CGM2-051 manufactured by ULVAC SOLUTIONS), the volumes of helium and oxygen were analyzed, and the helium purity was calculated from the following formula.
Helium purity (% by volume) = permeated helium amount (L / min) / permeated gas (total of helium and oxygen) amount (L / min) x 100
Subsequently, the permeated gas was sent to a soap membrane type flow meter (VP-1U manufactured by Horiba STEC), and the obtained measured value was taken as the permeated gas amount (L / min), and the helium recovery rate was calculated from the following formula.
Helium recovery rate (% by volume) = supply helium amount (L / min) / permeated gas (total of helium and oxygen) amount (L / min) x (helium purity / 100) x 100
The amount of supplied helium is a value obtained by dividing the product of the supply flow rate and the volume% of helium in each embodiment by 100.

(Methane recovery rate and methane purity)
The gas type was changed to a mixed gas containing 60 mol% of methane and 40 mol% of helium, and the methane purity and recovery rate were calculated by the same method as the helium purity and recovery rate. It was evaluated in the same way.

(Example 1)
In the gas separation system having the configuration shown in FIG. 1, a mixed gas (7 L / min) containing 60 mol% of helium and 40 mol% of oxygen was separated by the gas separation system. The results are shown in Table 1.

(Examples 2 to 7)
The performance of the gas separation system was evaluated in the same manner as in Example 1 except that the configuration of the gas separation system was changed to that shown in FIG. 2 and the number of modules and the circulation ratio were changed as shown in the table. The results are shown in Table 1.

(Examples 8 to 12)
The supply gas was 60 mol% of methane and 40 mol% of helium, the configuration of the gas separation system was changed to that shown in FIG. 4, and the number of modules and the circulation ratio were changed as shown in Table 2. Similarly, the performance of the gas separation system was evaluated. The results are shown in Table 2.

(Examples 13 to 16)
The supply gas was a mixed gas (3 L / min) prepared to have the composition shown in Table 4 containing helium and oxygen, the configuration of the gas separation system was changed to that shown in FIG. 5, and the number of modules and the circulation ratio were changed to those shown in Table 4. The performance of the gas separation system was evaluated in the same manner as in Example 1 except that the changes were made as per. The results are shown in Table 4.

(Comparative Example 1)
In the configuration of the gas separation system shown in FIG. 1, all the same as in Example 1 except that the second permeation gas discharge pipe in the second gas separation membrane unit is not provided and the second permeation outlet is sealed. The gas separation system was operated. The results are shown in Table 3. That is, although the partial pressure of helium in the first gas separation membrane unit increased, the filtration in the first gas separation membrane unit was not sufficiently performed, and the recovery rate of helium deteriorated.

(Comparative Example 2)
In the configuration of the gas separation system shown in FIG. 2, the gas separation system is provided in the same manner as in the second embodiment except that the second permeation gas discharge pipe is not provided with a branch portion in the second gas separation membrane unit. I drove. The results are shown in Table 3. That is, the partial pressure of helium in the second gas separation membrane unit decreased, and the amount of helium permeated deteriorated, so that the purity of helium recovered by the gas separation system deteriorated.

(Comparative Examples 3 to 6)
The gas separation system was operated in the same manner as in Examples 13 to 16, except that the configuration of the gas separation system was such that no branch portion was provided as shown in FIG. The gas separation membrane unit 1 in the gas separation system 300 of FIG. 6 has an inlet 11 to which the supply gas pipe 4 is connected, a permeation outlet 12 to which the permeation gas discharge pipe 5 is connected, and a concentration outlet to which the concentrated gas discharge pipe 6 is connected. 13 is provided. The results are shown in Table 4. That is, the partial pressure of helium in the gas separation membrane unit decreased, and the amount of helium permeation deteriorated, so that the purity of helium recovered by the gas separation system deteriorated.

As is clear from the results shown in Tables 1 to 4, the gas separation system in Examples 1 to 16 was able to achieve both high recovery rate and high purity for the components to be enriched. It can be said that such a gas separation system is excellent in separation for enriching at least one component from a mixed gas containing two or more components.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on December 2, 2020 (Japanese Patent Application No. 2020-1999) and a Japanese patent application filed on December 23, 2020 (Japanese Patent Application No. 2020-21307). It is taken here as a reference.

Since the gas separation system of the present invention can purify the components to be enriched with high recovery rate and high purity, it can be suitably used for separation of enriching at least one of two or more kinds of gases.

100, 200, 300 Gas Separation System 1 Gas Separation Membrane Unit (1st Gas Separation Membrane Unit)
11 Supply gas inlet (first inlet)
12 Permeated gas discharge port (first permeated outlet)
13 Concentrated gas discharge port (first concentrated gas outlet)
2 Specific gas separation membrane unit (second gas separation membrane unit)
21 Supply gas inlet (second inlet)
22 Permeated gas discharge port (second permeation outlet)
23 Concentrated gas outlet (second concentrated outlet)
4 Supply gas pipe 41 First supply gas pipe 5 Permeated gas discharge pipe 51 First permeated gas discharge pipe 52 Second permeated gas discharge pipe 6 Concentrated gas discharge pipe 61 First concentrated gas discharge pipe 62 Second enrichment Gas discharge pipe 7 Branch pipe 8 Connecting pipe 9 Branching part 10 Confluence part

Claims

A gas separation system that enriches at least one component from a mixed gas containing two or more components.
The gas separation system includes a specific gas separation membrane unit and is equipped with a specific gas separation membrane unit.
The specific gas separation membrane unit includes an inlet for a supply gas, an outlet for a permeated gas, and an outlet for a concentrated gas.
A supply gas pipe is connected to the inlet of the supply gas.
A permeated gas discharge pipe is connected to the permeated gas discharge port.
A concentrated gas discharge pipe is connected to the concentrated gas discharge port.
The permeated gas discharge pipe or the concentrated gas discharge pipe has a branch portion, a pipe located upstream of the pipe having the branch portion has a merging portion, and the branch portion and the merging portion are connected by a branch pipe. Has been a gas separation system.
There is only one specific gas separation membrane unit in the gas separation system,
The gas separation system according to claim 1, wherein the supply gas pipe has the confluence and does not include another gas separation membrane unit.
A method for producing a gas using the gas separation system according to claim 1 or 2.
A method for producing a gas, which comprises a step of controlling the concentration of enriched components in the supplied gas supplied to the specific gas separation membrane unit to 30 mol% or less.
Claim 1 in which another gas separation membrane unit is further provided upstream of the specific gas separation membrane unit, and a permeated gas or a concentrated gas that has passed through the other gas separation membrane unit is supplied to the specific gas separation membrane unit. The gas separation system described in.
Claim 1 in which another gas separation membrane unit is further provided downstream of the specific gas separation membrane unit, and a permeated gas or a concentrated gas that has passed through the specific gas separation membrane unit is supplied to the other gas separation membrane unit. The gas separation system described in.
The gas separation system according to any one of claims 1, 2, 4 or 5, wherein the separation membrane in the specific gas separation membrane unit is a polyamide membrane.
The gas separation system according to any one of claims 1, 2, 4, 5 or 6, wherein the enriched component in the supply gas supplied to the specific gas separation membrane unit is hydrogen.
A gas separation system that enriches at least one component from a mixed gas containing two or more components.
The gas separation system includes a first gas separation membrane unit and a second gas separation membrane unit connected by a connecting pipe.
The first gas separation membrane unit includes a first inlet, a first permeation outlet, and a first concentration outlet.
The second gas separation membrane unit includes a second inlet, a second permeation outlet, and a second concentration outlet.
A first supply gas pipe is connected to the first inlet.
The connecting pipe connects the first permeation outlet or the first concentration outlet with the second inlet.
A second permeation gas discharge pipe is connected to the second permeation outlet.
A second concentrated gas discharge pipe is connected to the second concentration outlet.
The second permeated gas discharge pipe or the second concentrated gas discharge pipe has a branch portion, the first supply gas pipe or the connecting pipe has a merging portion, and the branch portion and the merging portion have a merging portion. A gas separation system connected by a branch pipe.
The gas separation system according to claim 8, wherein the connecting pipe has the confluence portion.
The gas separation system according to claim 8 or 9, wherein the separation membrane in the first gas separation membrane unit and the separation membrane in the second gas separation membrane unit is a polyamide membrane.
The connecting pipe connects the first concentration outlet and the second inlet.
The gas separation system according to any one of claims 8 to 10, wherein the branch portion is provided in the second permeated gas discharge pipe.
The connecting pipe connects the first permeation outlet and the second inlet.
The gas separation system according to any one of claims 8 to 10, wherein the branch portion is provided in the second concentrated gas discharge pipe.
The gas separation system according to claim 11 or 12, wherein the second permeated gas discharge pipe or the second concentrated gas discharge pipe is connected to the branch pipe and the recovery device via the branch portion.
The gas separation system according to claim 11, wherein the enriched component in the supply gas supplied to the first gas separation membrane unit and the second gas separation membrane unit is hydrogen.
A method for producing a gas using the gas separation system according to claim 11 or 12.
The amount of gas of the enriched component contained in the gas discharged from the first gas separation membrane unit and not supplied to the second gas separation membrane unit is supplied to the first gas separation membrane unit. A method for producing a gas, which comprises a step of controlling 30% by volume or more and 80% by volume or less of the enriched components in the gas.