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) includes: a first separation membrane (10); and a second separation membrane (20) disposed on a downstream side of the first separation membrane (10). The first separation membrane (10) generates a first enriched gas in which NH3 is enriched and a first depleted gas in which NH3 is depleted and CO2 and N2 are enriched, by selectively permeating NH3. The second separation membrane (20) generates a second enriched gas in which CO2 is enriched and a second depleted gas in which CO2 is depleted, by separating CO2.

Description

Technical Field

[0001] This invention relates to gas separation systems. Background Technology

[0002] Conventionally, methods for separating specified components contained in a gas mixture include: combining pressure variation adsorption (PSA), temperature variation adsorption (TSA), or absorption methods, as well as methods using membrane separation methods (e.g., Patent Document 1).

[0003] Regarding the method described in Patent Document 1, after separating the mixed gas into waste gas (hydrogen sulfide, water vapor, and heavy hydrocarbons) and concentrated gas (carbon dioxide and light hydrocarbons) in an adsorption tower, the concentrated gas is then separated into carbon dioxide and light hydrocarbons in a separation membrane.

[0004] According to the method described in Patent Document 1, hydrogen sulfide and water vapor can be separated as waste gases (impurities). Hydrogen sulfide and water vapor are both types of deteriorating gases. Deteriorating gases refer to gases that are corrosive to metals, gases that cause brittleness in metals, and gases that exhibit alkalinity when dissolved in aqueous solution.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: U.S. Patent Application Publication No. 2009 / 0151562 Summary of the Invention

[0008] However, the concentrated gas flowing out of the adsorption tower and absorption tower is prone to pressure and temperature fluctuations. Therefore, it is necessary to constantly monitor and control the pressure and temperature of the concentrated gas supplied to the separation membrane and other separators, which is quite complicated.

[0009] The purpose of this invention is to provide a gas separation system that can easily separate out deteriorating gases.

[0010] The first aspect of the present invention relates to a gas separation system that separates a deteriorating gas from a mixture of a deteriorating gas, a first non-deteriorating gas, and a second non-deteriorating gas. The gas separation system includes: a first separation membrane; and a separator disposed downstream of the first separation membrane. The first separation membrane selectively permeates the deteriorating gas to generate a first enriched gas rich in the deteriorating gas and a first depleted gas that is depleted in the deteriorating gas and enriched in both the first and second non-deteriorating gases. The separator separates the first non-deteriorating gas to generate a second enriched gas rich in the first non-deteriorating gas and a second depleted gas that is depleted in the first non-deteriorating gas.

[0011] The gas separation system of the second aspect of the present invention is based on the first aspect described above, wherein the separator is a second separation membrane that allows the first non-deteriorating gas to selectively permeate.

[0012] The gas separation system involved in the third aspect of the present invention is based on the second aspect described above, but the composition of the second separation membrane is different from that of the first separation membrane.

[0013] The gas separation system according to the fourth aspect of the present invention is based on any one of the first to third aspects described above, wherein the concentration of deteriorating gas in the gas supplied to the separator is lower than the concentration of deteriorating gas in the gas supplied to the first separation membrane.

[0014] The fifth aspect of the present invention relates to a gas separation system based on any one of the first to fourth aspects described above, wherein the deteriorating gas is NH3.

[0015] The sixth embodiment of the present invention involves a gas separation system based on any one of the first to fourth embodiments described above, wherein the deteriorating gas is H2, the first non-deteriorating gas is N2, and the second non-deteriorating gas is CH4.

[0016] The gas separation system involved in the seventh embodiment of the present invention is based on any one of the first to fourth embodiments described above, wherein the deteriorating gas is H2, the first non-deteriorating gas is CO2, and the second non-deteriorating gas is N2.

[0017] The gas separation system involved in the eighth embodiment of the present invention is based on any one of the first to fourth embodiments described above, wherein the deteriorating gas is H2, the first non-deteriorating gas is CO2, the second non-deteriorating gas is CH4, and the first separation membrane and the separation body are zeolite membranes.

[0018] The gas separation system involved in the ninth embodiment of the present invention is based on any one of the first to fourth embodiments described above, wherein the deteriorating gas is H2O, the first non-deteriorating gas is CO2, and the second non-deteriorating gas is CH4.

[0019] The gas separation system involved in the tenth aspect of the present invention is based on any one of the first to fourth aspects described above, wherein the deteriorating gas is H2O, the first non-deteriorating gas is N2, and the second non-deteriorating gas is CH4.

[0020] The gas separation system involved in the eleventh aspect of the present invention is based on any one of the first to fourth aspects described above, wherein the deteriorating gas is H2O, the first non-deteriorating gas is CO2, the second non-deteriorating gas is N2, and the first separation membrane and the separation body are zeolite membranes.

[0021] Invention Effects

[0022] According to the present invention, a gas separation system capable of easily separating out deteriorating gases can be provided. Attached Figure Description

[0023] Figure 1 This is a schematic diagram showing the configuration of the gas separation system according to the embodiment. Detailed Implementation

[0024] (Gas separation system 1)

[0025] Figure 1 This is a schematic diagram showing the configuration of gas separation system 1.

[0026] The gas separation system 1 includes a first separation membrane 10 and a second separation membrane 20.

[0027] The first separation membrane 10 is an example of the "first separation membrane" involved in this invention. The second separation membrane 20 is an example of the "separator" involved in this invention.

[0028] [First separation membrane 10]

[0029] The first separation membrane 10 is disposed upstream of the second separation membrane 20. The first separation membrane 10 is supplied with a mixed gas containing NH3, CO2 and N2.

[0030] NH3 is an example of a "deteriorating gas" according to the present invention. The dynamic molecular diameter of NH3 is 0.265 nm. CO2 is an example of a "first non-deteriorating gas" according to the present invention. The dynamic molecular diameter of CO2 is 0.33 nm. N2 is an example of a "second non-deteriorating gas" according to the present invention. The dynamic molecular diameter of N2 is 0.364 nm.

[0031] Degrading gases refer to gases that are corrosive to metals, gases that cause brittleness in metals, and gases that exhibit alkalinity when dissolved in aqueous solution. Examples of gases that are corrosive to metals include NH3. Examples of gases that cause brittleness in metals include H2. Examples of gases that exhibit alkalinity when dissolved in aqueous solution include NH3. Furthermore, from the viewpoint that it can dissolve other components to form an aqueous solution, H2O is also considered a degrading gas.

[0032] Non-deteriorating gases refer to all gases other than deteriorating gases.

[0033] It should be noted that the mixed gas involved in this embodiment includes one deteriorating gas and two non-deteriorating gases, but is not limited to this. The mixed gas may include at least one deteriorating gas and at least two non-deteriorating gases. The mixing ratio of each gas in the mixed gas can be appropriately set.

[0034] As described above, the mixed gas involved in this embodiment includes NH3 as a deteriorating gas and CO2 and N2 as non-deteriorating gases. The mixed gas supplied to the first separation membrane 10 is preferably pressurized.

[0035] The first separation membrane 10 separates NH3, which is a deteriorating gas, from the mixed gas. The first separation membrane 10 is an NH3 separation membrane capable of selectively permeating NH3 from the mixed gas. The material of the first separation membrane 10 is not particularly limited; it can be any membrane capable of selectively permeating NH3. For example, zeolite membranes, carbon membranes, silica membranes, and synthetic resin membranes can be used as the first separation membrane 10. In particular, zeolite membranes exhibit high separation performance even under high temperature conditions, and are therefore preferred.

[0036] It should be noted that, in this specification, selective permeation means that the desired component is enriched in the permeation space of the separation membrane.

[0037] The first separation membrane 10 generates a first enriched gas enriched with NH3 and a first depleted gas enriched with CO2 and N2 by selectively permeating NH3 contained in the mixed gas.

[0038] The first enriched gas is discharged to the outside through the permeate side space of the first separation membrane 10. The concentration of NH3 in the first enriched gas is not particularly limited; however, the first enriched gas preferably mainly contains NH3. "Mainly contains NH3" means that the highest concentration of NH3 in the first enriched gas is NH3. The first enriched gas may contain CO2.

[0039] A first lean gas flows out from the non-permeable side space of the first separation membrane 10 and is supplied to the second separation membrane 20. The first lean gas contains CO2 and N2. The first lean gas may contain NH3.

[0040] [Second separation membrane 20]

[0041] The second separation membrane 20 is disposed downstream of the first separation membrane 10. A first lean gas containing CO2 and N2 is supplied from the first separation membrane 10 to the second separation membrane 20.

[0042] The concentration of NH3 in the first depleted gas supplied to the second separation membrane 20 is lower than the concentration of NH3 in the mixed gas supplied to the first separation membrane 10.

[0043] The second separation membrane 20 separates CO2, which is the first non-deteriorating gas, from the first depleted gas. The second separation membrane 20 is a CO2 separation membrane capable of selectively permeating CO2 from the first depleted gas. The material of the second separation membrane 20 is not particularly limited; it can be any membrane capable of selectively permeating CO2. Examples of materials that can be used for the second separation membrane 20 include zeolite membranes, carbon membranes, silica membranes, and synthetic resin membranes.

[0044] The second separation membrane 20 is preferably composed differently from the first separation membrane 10. The second separation membrane 20 is preferably composed of a structure suitable for CO2 separation. For example, it is preferable that the pore size of the second separation membrane 20 is larger than the dynamic molecular diameter of CO2 and smaller than the dynamic molecular diameter of N2.

[0045] The second separation membrane 20 generates a second enriched gas enriched with CO2 and a second depleted gas enriched with N2 by selectively permeating CO2 contained in the first depleted gas.

[0046] The second enriched gas is discharged to the outside through the permeate side space of the second separation membrane 20. The concentration of CO2 in the second enriched gas is not particularly limited; however, it is preferable that the second enriched gas mainly contains CO2. "Mainly contains CO2" means that the highest concentration of CO2 in the second enriched gas is CO2.

[0047] The second depleted gas is discharged to the outside from the non-permeable side space of the second separation membrane 20. The concentration of N2 in the second depleted gas is not particularly limited; however, it is preferable that the second depleted gas mainly contains N2. "Mainly contains N2" means that the highest concentration of N2 in the second depleted gas is N2. If the first depleted gas contains NH3, the second depleted gas may also contain NH3.

[0048] (feature)

[0049] (1) Gas separation system 1 separates NH3 from a mixture of NH3 (a first deteriorating gas), CO2 (a first non-deteriorating gas), and N2 (a second deteriorating gas). Gas separation system 1 includes: a first separation membrane 10 (first separation membrane); and a second separation membrane 20 (separator), which is disposed downstream of the first separation membrane 10. The first separation membrane 10 generates a first enriched gas enriched with NH3 and a first depleted gas enriched with CO2 and N2 by selectively permeating NH3. The second separation membrane 20 generates a second enriched gas enriched with CO2 and a second depleted gas by separating CO2.

[0050] Thus, according to gas separation system 1, CO2 and N2 can be separated after NH3 has been pre-separated by passing it through the separation membrane. Therefore, deteriorating gases can be separated by passing them through the separation membrane before non-deteriorating gases are separated. Thus, compared to the case where NH3 is separated by PSA, pressure fluctuations in the first lean gas supplied to the second separation membrane 20 can be suppressed. Accordingly, complex control of the pressure and temperature of the first lean gas is unnecessary. Furthermore, the energy required to pressurize the first lean gas by reducing its pressure can be reduced. Moreover, compared to the case where NH3 is separated by temperature variation adsorption (TSA) or absorption, gas separation system 1 does not require complex temperature control of the first lean gas. In addition, in the case of TSA or absorption, the gas temperature is sometimes lowered due to more efficient adsorption or absorption. Therefore, the energy required to heat the first lean gas can be reduced.

[0051] (2) The gas separation system 1 includes a second separation membrane 20 that selectively allows CO2 to pass through, serving as a "separator". Therefore, compared to cases where adsorption towers or absorption towers are used as separators to separate CO2 by adsorption or absorption methods, the gas separation system 1 can separate CO2 with good accuracy with a simple configuration. In addition, membrane separation is a continuous process, and therefore, compared to adsorption and absorption methods, which are batch processes, it is more susceptible to pressure or temperature fluctuations. Therefore, when a separation membrane is used as a "separator", the effect of the present invention, which can suppress pressure or temperature fluctuations of the first depleted gas, is more significant.

[0052] The "separator" is preferably configured to degrade due to deteriorating gases. For example, in this embodiment, the second separation membrane 20 is preferably degraded by NH3. That is, the second separation membrane 20 is preferably configured such that its lifespan is shorter in the presence of NH3 compared to when NH3 is not present. With such a configuration, the feature of the present invention, which allows for easy removal of deteriorating gases, becomes more effective.

[0053] (3) The composition of the second separation membrane 20 is preferably different from that of the first separation membrane 10. Accordingly, a separation membrane suitable for separating CO2, which is a first non-degrading gas, can be used as the second separation membrane 20.

[0054] (4) The concentration of NH3 in the first lean gas (an example of "gas supplied to the separator") is lower than the concentration of NH3 in the mixed gas (an example of "gas supplied to the first separation membrane"). This means that NH3, which is a deteriorating gas, is removed before CO2 and N2, which are non-deteriorating gases contained in the first lean gas, are separated. Accordingly, CO2 can be separated from the first lean gas with good precision.

[0055] (Modifications of the implementation method)

[0056] The above describes one embodiment of the present invention. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention.

[0057] [Variation Example 1]

[0058] In the above embodiments, NH3 is cited as an example of a deteriorating gas, but it is not limited to this. For example, NH3, H2, H2O, etc. can be used as deteriorating gases.

[0059] Furthermore, in the above embodiments, CO2 is cited as an example of the first non-deteriorating gas, and N2 is cited as an example of the second non-deteriorating gas, but the embodiments are not limited thereto. For example, CO2, N2, CH4, etc., can be used as the first and second non-deteriorating gases.

[0060] Here, representative examples of combinations of deteriorating gases, first non-deteriorating gases, and second non-deteriorating gases contained in the gas mixture are summarized in Table 1.

[0061] [Table 1]

[0062]

[0063] The combination of gases is determined by the composition of the mixed gas to be treated; however, the gas separation system of the present invention can be used particularly effectively in the following cases.

[0064] First, the mixed gas preferably contains NH3 as a deteriorating gas. In this case, the concentration of corrosive NH3 can be preferentially reduced, thus suppressing the deterioration of the separation membrane or the device.

[0065] Furthermore, it is preferable that the mixed gas contains H2 as a deteriorating gas. In this case, the concentration of H2 in the first enriched gas can be increased, thus making it easier to fully utilize the first enriched gas as an H2 source (e.g., a raw material for MeOH synthesis).

[0066] In the case where the mixed gas contains H2 as a deteriorating gas, it is more preferable to contain N2 as the first non-deteriorating gas and CH4 as the second non-deteriorating gas. Accordingly, by removing H2, which has a smaller molecular size and is easily permeable, it is possible to suppress H2 from mixing into the gases separated in the subsequent stages, thus obtaining a gas of high purity. By removing N2, which is an inactive gas, immediately after H2, the purity of CH4, which is an impermeable gas, gradually increases, thereby reducing the risk of CH4 explosion in an emergency.

[0067] Furthermore, if the mixed gas contains H2 as a deteriorating gas, it is more preferable to contain CO2 as the first non-deteriorating gas and N2 as the second non-deteriorating gas. Accordingly, by removing molecules sequentially starting from those with smaller dynamic molecular diameters, it is possible to suppress the mixing of these molecules into the gases separated in the subsequent stages, thus obtaining a gas of high purity.

[0068] Furthermore, when the mixed gas contains H2 as a deteriorating gas, it is particularly preferable to contain CO2 as the first non-deteriorating gas and CH4 as the second non-deteriorating gas, and the first and second separation membranes 10 and 20 are zeolite membranes. This way, by removing H2, which has a smaller molecular size and is easily permeable, H2 mixing into the gases separated in the subsequent stage can be suppressed, thus obtaining a gas of high purity. When separating CO2 immediately after H2, the affinity between CO2 and zeolite can be effectively utilized, thus enabling efficient separation.

[0069] Furthermore, H2O is preferably included in the gas mixture as a deteriorating gas. In this case, by separating H2O, which has a low vapor pressure and is easily condensable, it is possible to prevent H2O from condensing in the subsequent separation membrane and thus reducing membrane performance.

[0070] In the case where the mixed gas contains H2O as a deteriorating gas, it is more preferable to contain CO2 as the first non-deteriorating gas and CH4 as the second non-deteriorating gas. Therefore, by removing H2O first, the performance of the subsequent separator can be prevented from decreasing due to swelling or blockage caused by H2O. By removing CO2, which is an inactive gas, immediately after H2O, the purity of CH4, which is a non-permeable gas, gradually increases, thus reducing the risk of CH4 explosion in an emergency.

[0071] Furthermore, if the mixed gas contains H2O as a deteriorating gas, it is more preferable to contain N2 as the first non-deteriorating gas and CH4 as the second non-deteriorating gas. This way, by removing H2O first, the performance of the subsequent separator can be prevented from decreasing due to swelling or blockage caused by H2O. By removing N2, which is an inactive gas, immediately after H2O, the purity of CH4, which is a non-permeable gas, gradually increases, thus reducing the risk of CH4 explosion in an emergency.

[0072] Furthermore, when the mixed gas contains H2O as a deteriorating gas, it is particularly preferable to contain CO2 as the first non-deteriorating gas and N2 as the second non-deteriorating gas, and the first and second separation membranes 10 and 20 are zeolite membranes. Thus, by first removing H2O, which has a particularly high affinity for zeolite, and then separating CO2 immediately after H2O, the affinity between CO2 and zeolite can be effectively utilized, thereby enabling highly efficient separation.

[0073] [Variation Example 2]

[0074] In the above embodiments, the mixed gas comprises one deteriorating gas and two non-deteriorating gases, but is not limited thereto. The mixed gas may comprise at least one deteriorating gas and at least two non-deteriorating gases.

[0075] [Variation Example 3]

[0076] In the above embodiment, the second separation membrane 20, as an example of a separator, separates CO2, which is an example of a first non-deteriorating gas, contained in the first depleted gas, but is not limited thereto. The separator can separate the deteriorating gas and the first non-deteriorating gas together.

[0077] For example, if the mixed gas supplied to the first separation membrane 10 contains NH3, CO2, N2 and H2, the first depleted gas supplied to the second separation membrane 20 contains CO2, N2 and H2.

[0078] In this case, the second separation membrane 20 can separate the CO2 and H2 contained in the first depleted gas. This generates a first enriched gas containing CO2 and H2, and a second depleted gas containing N2.

[0079] [Variation Example 4]

[0080] The first separation membrane 10 can separate various deteriorating gases. For example, in the above modified example 2, the first separation membrane 10 can generate a first enriched gas enriched with NH3 and H2, and a first depleted gas depleted with NH3 and H2 and enriched with CO2 and N2.

[0081] [Variation Example 5]

[0082] In the above embodiments, the gas separation system 1 includes a second separation membrane 20 as an example of a separator; however, the separator is not limited to a separation membrane. The separator can be any structure capable of separating the first non-deteriorating gas. For example, a structure capable of separating the first non-deteriorating gas by PSA, TSA, or absorption methods can be used as the separator.

[0083] [Variation Example 6]

[0084] In the above embodiments, the first enriched gas, containing the deteriorated gas separated by the first separation membrane 10, is discharged to the outside from the permeate side space of the first separation membrane 10. The deteriorated gas can be reused for the synthesis of desired substances or as fuel. Furthermore, in the above-described variation 2, H2, which is one of the non-deteriorated gases, can be reused.

[0085] [Variation Example 7]

[0086] In the above embodiments, after the deteriorating gas is separated from the mixed gas, the non-deteriorating gas is then separated. However, a portion of the non-deteriorating gas can be separated before the deteriorating gas is separated from the mixed gas.

[0087] For example, a portion of the CO2 can be pre-separated by a CO2 separation membrane configured on the upstream side of the first separation membrane 10.

[0088] Explanation of reference numerals in the attached figures

[0089] 1 Gas separation system

[0090] 10 First separation membrane

[0091] 20 Second separation membrane

Claims

1. A gas separation system for separating the deteriorating gas from a mixture comprising a deteriorating gas, a first non-deteriorating gas, and a second non-deteriorating gas, characterized in that, The gas separation system comprises: First separation membrane; as well as A separator, disposed downstream of the first separation membrane. The first separation membrane selectively permeates the deteriorating gas to generate a first enriched gas in which the deteriorating gas is enriched, and a first depleted gas in which the deteriorating gas is depleted and the first non-deteriorating gas and the second non-deteriorating gas are enriched. The separator generates a second enriched gas (enriched by the first non-deteriorating gas) and a second depleted gas (depleted by the first non-deteriorating gas) by separating the first non-deteriorating gas.

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

3. The gas separation system according to claim 2, characterized in that, The second separation membrane has a different structure than the first separation membrane.

4. The gas separation system according to any one of claims 1 to 3, characterized in that, The concentration of the deteriorating gas in the gas supplied to the separator is lower than the concentration of the deteriorating gas in the gas supplied to the first separation membrane.

5. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is NH3.

6. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2. The first non-degrading gas is N2. The second non-degrading gas is CH4.

7. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2. The first non-degrading gas is CO2. The second non-degrading gas is N2.

8. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2. The first non-degrading gas is CO2. The second non-degrading gas is CH4. The first separation membrane and the separation body are both zeolite membranes.

9. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2O. The first non-degrading gas is CO2. The second non-degrading gas is CH4.

10. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2O. The first non-degrading gas is N2. The second non-degrading gas is CH4.

11. The gas separation system according to any one of claims 1 to 3, characterized in that, The deteriorating gas is H2O. The first non-degrading gas is CO2. The second non-degrading gas is N2. The first separation membrane and the separation body are both zeolite membranes.

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