Gas separation system

Abstract

A gas separation system (1) separates NH3 from a mixed gas containing NH3, CO2 and N2. The gas separation system (1) is provided with a first separation membrane (10) and a second separation membrane (20) disposed downstream of the first separation membrane (10). The first separation membrane (10) selectively transmits NH3, thereby generating a first enriched gas enriched in NH3 and a first depleted gas depleted in NH3. The second separation membrane (20) separates the CO2, thereby generating a second enriched gas enriched in CO2 and a second depleted gas depleted in CO2.

Description

Gas Separation Systems

[0001] The present invention relates to a gas separation system.

[0002] Conventionally, methods for separating a specific component contained in a mixed gas have been known that combine pressure swing adsorption (PSA), temperature swing adsorption (TSA), or absorption methods with a separator using a membrane separation method or the like (e.g., Patent Document 1).

[0003] The technique described in Patent Document 1 involves separating a mixed gas into an exhaust gas (hydrogen sulfide, water vapor, and heavy hydrocarbons) and a concentrated gas (carbon dioxide and light hydrocarbons) in an adsorption tower, and then separating the concentrated gas into carbon dioxide and light hydrocarbons using a separation membrane.

[0004] According to the technique described in Patent Document 1, water vapor and heavy hydrocarbons can be separated as exhaust gas (impurities). Water vapor and heavy hydrocarbons are both condensable gases. Condensable gases are a general term for gases that, when supplied to a separation membrane with a high partial pressure, may condense on a subsequent separation membrane, thereby reducing the separation performance of the separation membrane.

[0005] US Patent Application Publication No. 2009 / 0151562

[0006] However, since the pressure and temperature of the enriched gas flowing out of the adsorption tower or absorption tower are prone to fluctuations, it is necessary to constantly monitor and control the pressure and temperature of the enriched gas supplied to a separator such as a separation membrane, which is cumbersome.

[0007] An object of the present invention is to provide a gas separation system that can easily separate condensable gases.

[0008] A gas separation system according to a first aspect of the present invention is a gas separation system for separating a second non-condensable gas from a mixed gas containing a first condensable gas, a first non-condensable gas, and a second non-condensable gas. The gas separation system includes a first separation membrane and a first separator disposed downstream of the first separation membrane. The first separation membrane selectively allows the first condensable gas to permeate therethrough, thereby producing a first enriched gas enriched in the first condensable gas and a first lean gas depleted in the first condensable gas. The first separator separates the first non-condensable gas, thereby producing a second enriched gas enriched in the first non-condensable gas and a second lean gas depleted in the first non-condensable gas.

[0009] A gas separation system according to a second aspect of the present invention is related to the first aspect, wherein the first separator is a second separation membrane that selectively allows the second condensable gas to permeate.

[0010] A gas separation system according to a third aspect of the present invention is related to the second aspect, and the configuration of the second separation membrane is different from the configuration of the first separation membrane.

[0011] A fourth aspect of the present invention relates to the gas separation system of any one of the first to third aspects, and includes a second separator disposed upstream of the first separation membrane. The mixed gas further includes a second condensable gas. At the operating temperature of the first separator, the saturated vapor pressure of the second condensable gas is lower than the saturated vapor pressure of the first condensable gas.

[0012] A gas separation system according to a fifth aspect of the present invention is related to the fourth aspect, in which the second separator is a third separation membrane that selectively allows the first non-condensable gas to permeate.

[0013] A gas separation system according to a sixth aspect of the present invention relates to the fifth aspect, and the configuration of the third separation membrane is different from the configuration of the first separation membrane.

[0014] A gas separation system according to a seventh aspect of the present invention relates to any one of the first to sixth aspects, wherein the concentration of the first condensable gas in the gas supplied to the first separator is lower than the concentration of the first condensable gas in the gas supplied to the first separation membrane.

[0015] A gas separation system according to an eighth aspect of the present invention relates to any one of the first to seventh aspects, wherein the first condensable gas is NH ３ is.

[0016] A gas separation system according to a ninth aspect of the present invention relates to any one of the first to seventh aspects, wherein the first condensable gas is H ２ O, and the first non-condensable gas is N ２ and the second non-condensable gas is CH ４ is.

[0017] A gas separation system according to a tenth aspect of the present invention relates to any one of the first to seventh aspects, wherein the first condensable gas is H ２ O and the first non-condensable gas is H ２ and the second non-condensable gas is N ２ , CO ２ and CH ４ Either:

[0018] A gas separation system according to an eleventh aspect of the present invention relates to any one of the first to seventh aspects, wherein the first condensable gas is H ２ O, and the first non-condensable gas is CO ２ and the second non-condensable gas is CH ４ and H ２ Either:

[0019] A gas separation system according to a twelfth aspect of the present invention relates to any one of the first to seventh aspects, wherein the first condensable gas is H ２ O, and the first non-condensable gas is CO ２ and the second non-condensable gas is N ２ and each of the first separation membrane and the first separator is a zeolite membrane.

[0020] According to the present invention, a gas separation system capable of easily separating condensable gases can be provided.

[0021] Schematic diagram showing the configuration of a gas separation system according to an embodiment. Schematic diagram showing the configuration of a gas separation system according to Modification 2.

[0022] (Gas Separation System 1) FIG. 1 is a schematic diagram showing the configuration of a gas separation system 1. As shown in FIG.

[0023] The gas separation system 1 includes a first separation membrane 10 and a second separation membrane 20 .

[0024] The first separation membrane 10 is an example of a "first separation membrane" according to the present invention. The second separation membrane 20 is an example of a "first separator" according to the present invention.

[0025] [First Separation Membrane 10] The first separation membrane 10 is disposed upstream of the second separation membrane 20. The first separation membrane 10 contains NH ３ , H ２ , CO ２ and N ２ The mixed gas supplied to the first separation membrane 10 is preferably pressurized.

[0026] NH ３ is an example of the "first condensable gas" according to the present invention. ３ The kinetic diameter of CO is 0.265 nm. ２ is an example of the "first non-condensable gas" according to the present invention. ２ The kinetic molecular diameter of N is 0.33 nm. ２ is an example of the "second non-condensable gas" according to the present invention. ２ The kinetic diameter of H is 0.364 nm. ２ is an example of the "third non-condensable gas" according to the present invention. ２ The kinetic molecular diameter of is 0.289 nm.

[0027] As described above, the mixed gas according to this embodiment contains one type of condensable gas (NH ３ ) and three types of non-condensable gases (H ２ , CO ２ and N ２ ) and

[0028] Condensable gas is a general term for gases whose saturated vapor pressure is less than 2 MPaG at the operating temperature of a separator (in this embodiment, second separation membrane 20) for separating non-condensable gases arranged in a subsequent stage. Non-condensable gas is a general term for gases other than condensable gases.

[0029] Preferably, the condensable gas has a saturated vapor pressure of less than 1 MPaG at the operating temperature of the separator (in this embodiment, second separation membrane 20) for separating the non-condensable gases arranged in the subsequent stage. When the condensable gas is more likely to condense in this way, the effect of easily separating the condensable gases and suppressing performance degradation of the "separator", which is a feature of the present invention, becomes more pronounced.

[0030] The mixed gas according to the present embodiment includes one condensable gas and three non-condensable gases, but is not limited to this. The mixed gas may include at least one condensable gas and at least two non-condensable gases. The mixing ratio of each gas in the mixed gas can be set as appropriate.

[0031] In this embodiment, the first separation membrane 10 is a membrane that separates NH ３ and H, a non-condensable gas. ２ However, the first separation membrane 10 only needs to be capable of separating condensable gases, and does not necessarily have to be incapable of separating non-condensable gases.

[0032] The first separation membrane 10 separates NH ３ and H ２ The first separation membrane 10 is a separation membrane that can selectively permeate NH ３ and H ２ The constituent material of the first separation membrane 10 is not particularly limited as long as it is a membrane that can selectively permeate the above-mentioned components. For example, a zeolite membrane, a carbon membrane, a silica membrane, a synthetic resin membrane, or the like can be used as the first separation membrane 10. In particular, a zeolite membrane is preferred because it can exhibit high separation performance even under high-temperature conditions.

[0033] In this specification, selective permeation means that the desired component is enriched in the permeate side space of the separation membrane.

[0034] The first separation membrane 10 is formed by separating NH ３ and H ２ By selectively permeating ３ and H ２ a first enriched gas enriched in NH ３ and H ２ is depleted and CO２ and N ２ and a first depleted gas enriched with .

[0035] The first enriched gas is discharged to the outside from the permeate side space of the first separation membrane 10. NH ３ and H ２ Although the concentration of each is not particularly limited, the first enrichment gas is mainly NH ３ and H ２ It is preferable that the compound contains mainly NH ３ and H ２ "Containing" means that the first enriched gas contains NH ３ and H ２ The total concentration of NH in the first enriched gas represents the maximum concentration. ３ and H ２ The mixing ratio is not particularly limited.

[0036] The first lean gas flows out from the non-permeation side space of the first separation membrane 10 and is supplied to the second separation membrane 20. The first lean gas is CO ２ and N ２ The first lean gas includes NH ３ and H ２ It is preferable that the compound is substantially free of NH ３ and H ２ One or both of these may be included.

[0037] [Second Separation Membrane 20] The second separation membrane 20 is disposed downstream of the first separation membrane 10. The second separation membrane 20 is provided with a ２ and N ２ A first depleted gas is supplied, the first gas comprising:

[0038] NH in the first depleted gas supplied to the second separation membrane 20 ３ The concentration of NH in the mixed gas supplied to the first separation membrane 20 is ３ Lower than the concentration of

[0039] The second separation membrane 20 separates the first non-condensable gas, CO ２ The second separation membrane 20 separates CO from the first depleted gas. ２ selectively permeable to CO ２ The second separation membrane 20 is a CO２ The material of the second separation membrane 20 is not particularly limited as long as it is a membrane that can selectively permeate the above. As the second separation membrane 20, for example, a zeolite membrane, a carbon membrane, a silica membrane, a synthetic resin membrane, or the like can be used.

[0040] The configuration of the second separation membrane 20 is preferably different from the configuration of the first separation membrane 10. The second separation membrane 20 is ２ For example, the pore size of the second separation membrane 20 is ２ and N ２ It is preferable that the kinetic diameter is smaller than that of the molecular weight of the polymer.

[0041] The second separation membrane 20 separates the CO contained in the first depleted gas. ２ By selectively permeating ２ a second enriched gas enriched in CO; ２ is impoverished and N ２ and a second depleted gas enriched with .

[0042] The second enriched gas is discharged to the outside from the permeate side space of the second separation membrane 20. ２ The concentration of the second enriched gas is not particularly limited, but the second enriched gas is mainly CO ２ It is preferable that the mixture contains mainly CO. ２ The term "containing" means that the maximum concentration component in the second enriched gas is CO ２ This means that

[0043] The second depleted gas is discharged to the outside from the non-permeation side space of the second separation membrane 20. The second depleted gas is mainly N ２ The second depleted gas contains NH ３ Preferably, the first lean gas is substantially free of NH ３ If the second depleted gas also contains NH ３ may also include:

[0044] (Features) (1) The gas separation system 1 is ３ (first condensable gas), CO ２ (first non-condensable gas) and N ２ (second non-condensable gas) from a mixed gas containing NH ３The gas separation system 1 includes a first separation membrane 10 (first separation membrane) and a second separation membrane 20 (first separator) disposed downstream of the first separation membrane 10. The first separation membrane 10 separates NH ３ By selectively permeating ３ a first enriched gas enriched in NH ３ is depleted and CO ２ and N ２ The second separation membrane 20 generates a first depleted gas enriched with CO ２ By separating CO ２ a second enriched gas enriched in CO; ２ and a second depleted gas in which the first depleted gas is depleted.

[0045] In this way, according to the gas separation system 1, NH ３ is separated by a separation membrane in advance, and then CO ２ and N ２ Therefore, since the condensable gas can be separated in advance before the non-condensable gas is separated, the second separation membrane 20 can separate NH ３ The PSA method can prevent the separation performance of the second separation membrane 20 from being reduced by condensation and liquefaction of NH ３ Compared to the case where an adsorption tower for separating NH is used, it is possible to suppress pressure fluctuations in the first lean gas supplied to the second separation membrane 20. Therefore, there is no need to perform complicated control of the pressure of the first lean gas. Also, it is possible to reduce the energy required to increase the pressure of the first lean gas by the amount of pressure drop. Furthermore, when the gas separation system 1 separates NH by temperature swing adsorption (TSA) or absorption, ３ In comparison with the case of separating the first lean gas, there is no need for complicated temperature control of the first lean gas. Furthermore, in the case of the TSA method or the absorption method, the gas temperature may be lowered to more effectively perform adsorption or absorption. Therefore, the energy required to heat the first lean gas can be reduced.

[0046] (2) The gas separation system 1 is ２ Therefore, the gas separation system 1 is provided with a second separation membrane 20 as a "first separator" that selectively permeates CO ２Compared to the case where an adsorption tower or absorption tower is provided as a separator, it is possible to accurately separate CO with a simple configuration. ２ Furthermore, since the membrane separation method is a continuous process, it is more susceptible to pressure and temperature fluctuations than the adsorption and absorption methods, which are batch processes. Therefore, when a separation membrane is used as the "separator," the effect of the present invention, which can suppress pressure and temperature fluctuations in the first depleted gas, becomes more pronounced.

[0047] (3) The second separation membrane 20 preferably has a different configuration from the first separation membrane 10. This allows the first non-condensable gas, CO ２ A separation membrane suitable for separating the above can be used as the second separation membrane 20.

[0048] (4) NH in the first depleted gas (an example of the "gas supplied to the first separator"). ３ The concentration of NH in the mixed gas (an example of the "gas supplied to the first separation membrane") ３ This is because the concentration of CO, a non-condensable gas contained in the first lean gas, is lower than that of CO. ２ and N ２ Before separating the condensable gas NH ３ This means that CO is removed from the first depleted gas. ２ can be separated with high accuracy.

[0049] (Modifications of the embodiment) Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0050] [Variation 1] In the above embodiment, the gas separation system 1 includes the second separation membrane 20 as an example of the first separator, but the first separator is not limited to a separation membrane. The first separator may be any structure capable of separating the first non-condensable gas. For example, a structure that separates the first non-condensable gas by a PSA method, a TSA method, or an absorption method may be used as the first separator.

[0051] [Modification 2] In the above embodiment, NH 4 is used as an example of the first condensable gas. ３However, the condensable gas is not limited to this. ３ , H ２ O and the like can be used.

[0052] Furthermore, in the above embodiment, CO is used as an example of the first non-condensable gas. ２ and N as an example of the second non-condensable gas. ２ and H as an example of the third non-condensable gas. ２ However, the first to third non-condensable gases include, for example, CO ２ , N ２ , H ２ , C.H. ４ etc. can be used.

[0053] Table 1 shows typical examples of combinations of the first condensable gas, the first non-condensable gas, and the second non-condensable gas contained in the mixed gas.

[0054]

[0055] The combination of gases is determined depending on the composition of the mixed gas to be treated, but the gas separation system according to the present invention can be particularly effectively used in the following cases.

[0056] First, the mixed gas contains NH as the first condensable gas. ３ In this case, it is preferable to include NH ３ Since the concentration of can be preferentially reduced, deterioration of the separation membrane and the device can be suppressed.

[0057] The mixed gas contains H as the first condensable gas. ２ It is also preferable that the gas contains O. In this case, H, which has a low vapor pressure and is easily condensed, is used. ２ By separating O first, H ２ This can prevent O from condensing and causing a decrease in membrane performance.

[0058] The mixed gas contains H as the first condensable gas. ２ When O is contained, N is used as the first non-condensable gas. ２ and CH as the second non-condensable gas. ４ It is more preferable to include H２ By removing O, the performance of the first separator in the subsequent stage is improved. ２ This can prevent the decrease due to swelling or blockage caused by O. ２ N, the second most inert gas after O ２ By removing the non-permeable gas CH ４ The purity of CH ４ This reduces the risk of explosion.

[0059] The mixed gas contains H as the first condensable gas. ２ When O is contained, H is used as the first non-condensable gas. ２ and N as the second non-condensable gas. ２ , CO ２ and CH ４ It is more preferable that the catalyst contains one of the following: By removing molecules in order of decreasing kinetic molecular diameter, it is possible to prevent these molecules from mixing with each gas separated in the subsequent stage, thereby obtaining a high-purity gas.

[0060] The mixed gas contains H as the first condensable gas. ２ When O is contained, CO is used as the first non-condensable gas. ２ and CH as the second non-condensable gas. ４ and H ２ It is more preferable that the compound contains either of the following: ２ By removing O, the performance of the first separator in the subsequent stage is improved. ２ This can prevent the decrease due to swelling or blockage caused by O. ２ CO, the second most inert gas after O ２ By removing the non-permeable gas CH ４ and H ２ The purity of CH ４ and H ２ This reduces the risk of explosion.

[0061] Furthermore, the mixed gas contains H as the first condensable gas. ２ When O is contained, CO is used as the first non-condensable gas. ２ and N as the second non-condensable gas. ２It is particularly preferable that the first and second separation membranes 10 and 20 each contain a zeolite membrane. ２ By first removing O, H ２ O followed by CO ２ When separating CO ２ This allows for effective separation because the affinity between the catalyst and zeolite can be effectively utilized.

[0062] [Modification 3] In the above embodiment, the mixed gas contains one type of condensable gas and three types of non-condensable gases, but this is not limiting. The mixed gas may contain at least one type of condensable gas and at least two types of non-condensable gases.

[0063] When the mixed gas contains two or more condensable gases, the gas separation system according to the present invention may separate each of the two or more condensable gases separately or may separate the two or more condensable gases together, as long as separation of at least the second non-condensable gas is achieved. For example, each of the two or more condensable gases may permeate at least one of the first separation membrane and the first separator.

[0064] For example, if the mixed gas is NH ３ (first condensable gas), H ２ O (second condensable gas), CO ２ (first non-condensable gas), N ２ (second non-condensable gas) and H ２ When the gas separation system 1 includes the third non-condensable gas, it is sufficient that the gas separation system 1 includes a third separation membrane 30 disposed upstream of the first separation membrane 10, as shown in FIG.

[0065] The third separation membrane 30 is disposed upstream of the first separation membrane 10. The third separation membrane 30 is ２ O, N.H. ３ , H ２ , CO ２ and N ２ A mixed gas containing

[0066] The third separation membrane 30 separates H, one of the condensable gases, from the mixed gas. ２ The third separation membrane 30 separates H from the mixed gas.２ H that can selectively permeate O ２ The third separation membrane 30 is a H ２ The constituent material of the third separation membrane 30 is not particularly limited as long as it is a membrane that is selectively permeable to O. For example, the third separation membrane 30 can be a zeolite membrane, a carbon membrane, a silica membrane, a synthetic resin membrane, or the like.

[0067] The configuration of the third separation membrane 30 is preferably different from the configurations of the first and second separation membranes 10 and 20. Specifically, the third separation membrane 30 is ２ A membrane capable of adsorbing O is preferred.

[0068] The third separation membrane 30 is an example of the "second separator" according to the present invention. ２ By providing the third separation membrane 30, which selectively allows O to permeate, as the "second separator," H ２ Compared to a case where an adsorption tower for separating O is provided as the second separator, pressure fluctuations in the third depleted gas supplied to the first separation membrane 10 can be suppressed. Therefore, there is no need to perform complicated control of the pressure of the third depleted gas. In addition, the energy required to increase the pressure of the third depleted gas can be reduced.

[0069] The third separation membrane 30 separates H contained in the mixed gas. ２ By selectively allowing O to pass through, ２ a third enriched gas enriched in O; and H ２ A third depleted gas is generated, which is depleted in O.

[0070] The third enriched gas flows out from the permeate side space of the third separation membrane 30. The third enriched gas mainly contains H ２ The third depleted gas flows out from the non-permeation side space of the third separation membrane 30 and is supplied to the first separation membrane 10. The third depleted gas contains NH ３ , H ２ , CO ２ and N ２ The third depleted gas contains H ２ It is preferable that the composition is substantially free of O, but H ２ O may be included.

[0071] In this modification, the configurations and functions of the first separation membrane 10 and the second separation membrane 20 are the same as those described in the above embodiment. ２ The concentration of O is determined by the H ２ The concentration is lower than that of O.

[0072] Here, at the operating temperature of the second separation membrane 20, H ２ The saturated vapor pressure of O is NH ３ That is, when the second separation membrane 20 is in operation, the saturated vapor pressure of H ２ O is NH ３ It's easier to condense.

[0073] In this modification, H ２ O to NH ３ Therefore, the condensable gas can be more reliably prevented from condensing on the second separation membrane 20 .

[0074] In this modification, the gas separation system 1 includes the third separation membrane 30 as an example of the second separator. However, the second separator is not limited to the separation membrane. The second separator may be any structure capable of separating the second condensable gas. For example, an adsorption tower that separates the second condensable gas by the PSA method may be used as the second separator.

[0075] [Variation 4] In the above embodiment, the non-condensable gas is separated after the condensable gas is separated from the mixed gas, but some of the non-condensable gas may be separated before the condensable gas is separated from the mixed gas.

[0076] For example, a CO ２ CO ２ A part of the above may be separated in advance.

[0077] 1 Gas separation system 10 First separation membrane 20 Second separation membrane 30 Third separation membrane

Claims

1. A gas separation system for separating a second non-condensable gas from a mixed gas containing a first condensable gas, a first non-condensable gas, and a second non-condensable gas, comprising: a first separation membrane; and a first separator disposed downstream of the first separation membrane, wherein the first separation membrane selectively allows the first condensable gas to permeate, thereby producing a first enriched gas enriched in the first condensable gas, and a first depleted gas depleted in the first condensable gas and enriched in the first non-condensable gas and the second non-condensable gas, and wherein the first separator separates the first non-condensable gas, thereby producing a second enriched gas enriched in the first non-condensable gas, and a second depleted gas depleted in the first non-condensable gas.

2. The gas separation system according to claim 1, wherein the first separator is a second separation membrane that selectively allows the second non-condensable gas to permeate.

3. The gas separation system according to claim 2, wherein the second separation membrane has a different configuration from the first separation membrane.

4. A gas separation system according to any one of claims 1 to 3, comprising a second separator arranged upstream of the first separation membrane, the mixed gas further containing a second condensable gas, and the saturated vapor pressure of the second condensable gas being lower than the saturated vapor pressure of the first condensable gas at the operating temperature of the first separator.

5. The gas separation system according to claim 4, wherein the second separator is a third separation membrane that selectively allows the second condensable gas to permeate.

6. The gas separation system according to claim 5, wherein the third separation membrane has a different configuration from the first separation membrane.

7. The gas separation system according to claim 1, wherein the concentration of the first condensable gas in the gas supplied to the first separator is lower than the concentration of the first condensable gas in the gas supplied to the first separation membrane.

8. The first condensable gas is NH ３ The gas separation system according to any one of claims 1 to 3, wherein 9. The first condensable gas is H ２ O, and the first non-condensable gas is N ２ and the second non-condensable gas is CH ４ The gas separation system according to any one of claims 1 to 3, wherein 10. The first condensable gas is H ２ O, and the first non-condensable gas is H ２ and the second non-condensable gas is N ２ , CO ２ and CH ４ The gas separation system according to any one of claims 1 to 3, wherein the gas separation system is one of the following:

11. The first condensable gas is H ２ O, and the first non-condensable gas is CO ２ and the second non-condensable gas is CH ４ and H ２ The gas separation system according to any one of claims 1 to 3, wherein the gas separation system is one of the following:

12. The first condensable gas is H ２ O, and the first non-condensable gas is CO ２ and the second non-condensable gas is N ２ The gas separation system according to claim 1 , wherein each of the first separation membrane and the first separator is a zeolite membrane.

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