Mixed gas separation apparatus and mixed gas separation method

Abstract

To separate high-purity gas from a mixed gas with high efficiency and low cost. [Solution] The mixed gas separation apparatus comprises a compression unit that compresses a mixed gas in which multiple types of gases including hydrogen are mixed; a hydrogen storage unit equipped with a hydrogen storage alloy that absorbs hydrogen and absorbs the hydrogen contained in the mixed gas compressed by the compression unit into the hydrogen storage alloy; an oxidation unit that performs oxidation treatment on the gas that has passed through the hydrogen storage unit; and a gas storage unit that stores the gas after oxidation treatment by the oxidation unit.

Description

Technical Field

[0001] The present invention relates to a mixed gas separation apparatus and a mixed gas separation method.

Background Art

[0002] In recent years, naturally occurring natural hydrogen has attracted attention as a supply source of hydrogen, which is a clean energy resource. Natural hydrogen exists underground, on the seabed, and the like, and has been observed all over the world. Such natural hydrogen often exists in the form of a mixed gas with other gases such as helium and methane, which causes difficulties in utilization.

[0003] For example, as a method of utilizing a mixed gas of hydrogen and helium, if the hydrogen content is sufficiently high, the mixed gas may be directly used as a fuel without separating hydrogen and helium. Further, if the helium content is sufficiently high, hydrogen may be removed by an oxidation reaction, and the resulting gas may be used as a helium source.

[0004] Further, it is also conceivable to separate hydrogen and helium from the mixed gas to obtain respective high-purity gases. In general, methods for separating various high-purity gases from a mixed gas in which a plurality of types of gases are mixed include cryogenic separation, molecular sieve separation, membrane separation, and the like.

Prior Art Literature

Patent Literature

[0005]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] However, separating high-purity gases from a mixture of hydrogen and other gases presents problems such as low separation efficiency and increased costs. For example, in the case of a mixture of hydrogen and helium, both hydrogen and helium have very small molecular sizes, making it difficult to separate them by molecular sieving or membrane separation. Even if separation of hydrogen and helium were possible by molecular sieving or membrane separation, it would require numerous separation stages, increasing costs. Furthermore, both hydrogen and helium have very low liquefaction temperatures (helium: -269°C, hydrogen: -253°C), and the freezing point of hydrogen is -259°C. Because these temperatures are close together, separating hydrogen and helium by cryogenic separation accompanied by rectification is difficult.

[0007] While separating hydrogen and helium is difficult, hydrogen can be used as an energy carrier, and helium is a noble gas used in its gaseous state for applications such as leak testing and lasers. Therefore, it is desirable to recover both hydrogen and helium from a gas mixture.

[0008] This disclosure has been made in view of the above, and aims to provide a mixed gas separation apparatus and a mixed gas separation method that can separate high-purity gas from a mixed gas with high efficiency and low cost. [Means for solving the problem]

[0009] According to one aspect of the present disclosure, a mixed gas separation apparatus includes a compression unit for compressing a mixed gas comprising a mixture of several types of gases including hydrogen; a hydrogen storage unit equipped with a hydrogen storage alloy for storing hydrogen, which stores hydrogen contained in the mixed gas compressed by the compression unit into the hydrogen storage alloy; an oxidation unit for performing an oxidation treatment on the gas that has passed through the hydrogen storage unit; and a gas storage unit for storing the gas after the oxidation treatment by the oxidation unit. [Effects of the Invention]

[0010] According to this disclosure, high-purity gas can be separated from a mixed gas with high efficiency and low cost. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing the configuration of a mixed gas separation apparatus according to one embodiment. [Figure 2] Figure 2 is a diagram illustrating the structure of the hydrogen storage section. [Figure 3] Figure 3 is a flowchart showing a mixed gas separation method according to one embodiment. [Modes for carrying out the invention]

[0012] An embodiment of the present invention will be described below with reference to the attached drawings. The embodiment described below is illustrative and should not be interpreted as limiting.

[0013] Figure 1 shows the configuration of a mixed gas separation apparatus 100 according to one embodiment. This mixed gas separation apparatus 100 is intended to separate hydrogen and helium from a mixed gas of hydrogen and helium, but the mixed gases targeted in this disclosure are not limited to a mixed gas of hydrogen and helium. That is, for example, when separating hydrogen and methane from a mixed gas of hydrogen and methane, it is possible to use a mixed gas separation apparatus with a configuration similar to the mixed gas separation apparatus 100 shown in Figure 1.

[0014] The mixed gas separation apparatus 100 shown in Figure 1 includes a compression section 110, a hydrogen storage section 120-1 to 120-N (where N is an integer of 1 or more), a heating section 130-1 to 130-N, a hydrogen storage section 140, an oxidation section 150, a drying section 160, and a helium storage section 170.

[0015] The compression unit 110 is equipped with a compressor that compresses the mixed gas taken into the mixed gas separation device 100, and sends the compressed, high-pressure mixed gas to the hydrogen storage unit 120-1.

[0016] Each hydrogen storage unit 120-1 to 120-N has a hydrogen storage alloy and stores hydrogen contained in the mixed gas. That is, each hydrogen storage unit 120-1 to 120-N stores hydrogen contained in the mixed gas by passing the mixed gas around the hydrogen storage alloy. Then, hydrogen storage units 120-1 to 120-(N-1) send the mixed gas that has passed around the hydrogen storage alloy to the next stage hydrogen storage units 120-2 to 120-N. Also, hydrogen storage unit 120-N sends the off-gas after passing around the hydrogen storage alloy to the oxidation treatment unit 150. The number of stages N of hydrogen storage units 120-1 to 120-N is appropriately determined according to the hydrogen concentration in the mixed gas taken into the mixed gas separation device 100 and the desired purity of the hydrogen or helium obtained by separation.

[0017] Furthermore, after hydrogen is absorbed by the hydrogen storage alloy in the hydrogen storage sections 120-1 to 120-N, they are heated by the corresponding heating sections 130-1 to 130-N, and the hydrogen released from the hydrogen storage alloy is sent to the hydrogen storage section 140. In other words, when the hydrogen storage alloy is heated, it releases the absorbed hydrogen molecules, so the hydrogen storage sections 120-1 to 120-N send the hydrogen released from the hydrogen storage alloy to the hydrogen storage section 140.

[0018] The hydrogen storage sections 120-1 to 120-N include a hydrogen storage alloy 121 composed of metal atoms 122 arranged in a lattice pattern, as shown in Figure 2(a). When this hydrogen storage alloy 121 comes into contact with a high-pressure mixed gas, the hydrogen molecules 201 contained in the mixed gas combine with the metal atoms 122 to form a metal hydride, as shown in Figure 2(b). Furthermore, as shown in Figure 2(b), when the hydrogen storage alloy 121 that has become a metal hydride is heated, it releases the absorbed hydrogen molecules 201.

[0019] The heating units 130-1 to 130-N heat the corresponding hydrogen storage units 120-1 to 120-N, respectively. Specifically, after the mixed gas passes through the hydrogen storage units 120-1 to 120-N and the off-gas is delivered to the oxidation treatment unit 150, when the mixed gas and the off-gas are purged, the heating units 130-1 to 130-N heat the hydrogen storage units 120-1 to 120-N respectively, so as to release hydrogen from the hydrogen storage alloy. The heating temperature for releasing hydrogen stored in the hydrogen storage alloy varies depending on the types of metal atoms constituting the hydrogen storage alloy. However, considering that flammable hydrogen is released, it is preferable to use, for example, a hydrogen storage alloy that releases hydrogen at a heating temperature of less than 100°C. Therefore, the heating units 130-1 to 130-N heat the hydrogen storage units 120-1 to 120-N respectively to a heating temperature at which the hydrogen storage alloy releases hydrogen, for example, 150°C or lower.

[0020] The hydrogen storage unit 140 stores hydrogen delivered from the hydrogen storage units 120-1 to 120-N. That is, the hydrogen storage unit 140 stores hydrogen released when the hydrogen storage alloy is heated. The hydrogen stored in the hydrogen storage unit 140 is high-purity hydrogen separated from helium in the mixed gas. The hydrogen stored in the hydrogen storage unit 140 can be used directly as hydrogen energy, or can be further purified to obtain higher-purity hydrogen before use.

[0021] The oxidation treatment unit 150 includes an oxidation catalyst. When off-gas after hydrogen storage is delivered from the hydrogen storage unit 120-N, the oxidation treatment unit 150 takes in oxygen gas to perform oxidation treatment on the off-gas. Specifically, since helium-rich off-gas is delivered from the hydrogen storage unit 120-N, the oxidation treatment unit 150 oxidizes hydrogen remaining in the off-gas into water, thereby removing hydrogen remaining in the off-gas. Accordingly, the off-gas becomes high-purity helium gas.

[0022] The drying treatment section 160 is provided with a desiccant, absorbs moisture from the off-gas oxidized by the oxidation treatment section 150, and removes moisture generated by the oxidation of hydrogen. That is, since the off-gas contains moisture through the oxidation treatment performed by the oxidation treatment section 150, the drying treatment section 160 removes the moisture, which is an impurity, from the off-gas that has become helium gas.

[0023] The helium storage section 170 stores the helium gas that has been dried by the drying treatment section 160. That is, the helium storage section 170 stores high-purity helium gas separated from hydrogen. The helium gas stored in the helium storage section 170 can be used in its gaseous state as it is for leak tests, lasers, or the like, or can be cooled to a temperature close to absolute zero to be liquefied and used in an ultra-low temperature region.

[0024] Next, a mixed gas separation method performed by the mixed gas separation apparatus 100 configured as described above will be described with reference to the flowchart shown in FIG. 3.

[0025] When the mixed gas is taken into the mixed gas separation apparatus 100, the mixed gas is compressed by the compression section 110 (step S101). The mixed gas is, for example, a mixed gas of hydrogen and helium, and may be mined from the ground or the seabed as natural hydrogen, which is also called white hydrogen or gold hydrogen. Alternatively, the mixed gas may be exhaust gas generated from, for example, factories, laboratories, or the like.

[0026] The compressed mixed gas that has reached a high pressure sequentially flows into the hydrogen storage sections 120-1 to 120-N, and passes around the hydrogen storage alloys provided in the hydrogen storage sections 120-1 to 120-N, whereby hydrogen in the mixed gas is stored in the hydrogen storage alloys (step S102). Accordingly, the mixed gas that has passed through the hydrogen storage sections 120-1 to 120-N becomes helium-rich off-gas. When the hydrogen storage sections 120-1 to 120-N are provided in multiple stages (that is, when N is 2 or more), the amount of hydrogen remaining in the mixed gas decreases as the mixed gas proceeds to the downstream hydrogen storage sections 120-1 to 120-N, thereby obtaining helium-rich off-gas.

[0027] Then, when the helium-rich off-gas is sent from the final stage hydrogen storage unit 120-N to the oxidation treatment unit 150, the oxidation treatment unit 150 performs an oxidation treatment on the off-gas (step S103). That is, the oxidation by the oxidation catalyst oxidizes the hydrogen remaining in the helium-rich off-gas, generating water, and producing a high-purity helium gas containing water.

[0028] The off-gas containing moisture is sent to the drying section 160, where it is dried (step S104). That is, the moisture contained in the off-gas is removed by drying with a desiccant, and high-purity helium gas is produced. The produced high-purity helium gas is stored in the helium storage section 170 (step S105). This makes it possible to recover high-purity helium from the mixed gas.

[0029] Then, the mixed gas and off-gas remaining inside the mixed gas separation device 100 are scavenged (step S106), and the hydrogen storage alloys of the corresponding hydrogen storage units 120-1 to 120-N are heated by the heating units 130-1 to 130-N (step S107). As a result, the hydrogen that was absorbed by the hydrogen storage alloy is released, and the released hydrogen is stored in the hydrogen storage unit 140 (step S108). Since the hydrogen released from the hydrogen storage alloy is high-purity hydrogen separated from helium, high-purity hydrogen can be recovered from the mixed gas.

[0030] In this example, it is assumed that after the mixed gas has passed through all hydrogen storage sections 120-1 to 120-N, the mixed gas and off-gas are scavenged, and the hydrogen storage sections 120-1 to 120-N are simultaneously heated by the heating sections 130-1 to 130-N. However, the timing of scavenging and heating is not limited to this. For example, as the mixed gas passes through each of the hydrogen storage sections 120-1 to 120-N, the hydrogen storage sections 120-1 to 120-N that the mixed gas has passed through are sequentially scavenged, and the hydrogen storage alloy is sequentially heated in the hydrogen storage sections 120-1 to 120-N after scavenging is complete.

[0031] As described above, according to this embodiment, hydrogen in a mixed gas is absorbed by a hydrogen storage alloy, and residual hydrogen is removed by oxidation and drying treatment of the helium-rich off-gas after hydrogen absorption, thereby storing the resulting high-purity helium. Subsequently, the hydrogen storage alloy is heated to release the absorbed hydrogen, and the resulting high-purity hydrogen is stored. Therefore, hydrogen and helium can be separated from a mixed gas of hydrogen and helium using simple equipment, and high-purity gas can be separated from the mixed gas with high efficiency and low cost.

[0032] In the above embodiment, the mixed gas taken into the mixed gas separation device 100 is compressed by the compression unit 110. However, as a pretreatment before compression, a process to remove impurities dissolved in the mixed gas, for example, by using a filter, may be performed.

[0033] Furthermore, the hydrogen storage unit 140 and the helium storage unit 170 may store hydrogen and helium in a gaseous state, or they may store hydrogen and helium in a liquid state. In addition, the hydrogen and helium may be purified by various methods before being stored in the hydrogen storage unit 140 and the helium storage unit 170.

[0034] The following is further disclosed regarding the above-described embodiment. [1] A compression section for compressing a mixed gas containing hydrogen and several other types of gases, A hydrogen storage unit comprising a hydrogen storage alloy that absorbs hydrogen, wherein hydrogen contained in the mixed gas compressed by the compression unit is absorbed into the hydrogen storage alloy, An oxidation treatment unit that performs oxidation treatment on the gas that has passed through the hydrogen storage unit, A gas storage unit for storing the gas after oxidation treatment by the oxidation treatment unit, A mixed gas separation apparatus having the following features.

[0035] [2] A heating section for heating the hydrogen storage alloy provided in the hydrogen storage section, A hydrogen storage unit for storing hydrogen released from a hydrogen storage alloy heated by the aforementioned heating unit, The mixed gas separation apparatus described above [1] further having the following:

[0036] [3] The heating section is After the gas is stored in the gas storage unit and the inside of the mixed gas separator is scavenged, the hydrogen storage alloy is heated. The mixed gas separation apparatus described in [2] above.

[0037] [4] The heating section is After the gas passes through the hydrogen storage section and is scavenged, the hydrogen storage alloy provided in the hydrogen storage section is heated. The mixed gas separation apparatus described in [2] above.

[0038] [5] The hydrogen storage unit is The system comprises multiple hydrogen storage alloys arranged in multiple stages, and the mixed gas is passed sequentially around the multiple hydrogen storage alloys. A mixed gas separation apparatus as described in any one of the above [1] to [3].

[0039] [6] Drying treatment to remove moisture generated by the oxidation of hydrogen by the oxidation treatment. A mixed gas separation apparatus according to any one of the above [1] to [3], further comprising:

[0040] [7] The compression section is Compress a mixed gas of hydrogen and helium. A mixed gas separation apparatus as described in any one of the above [1] to [3].

[0041] [8] Compressing a mixed gas containing hydrogen and several other types of gases, By passing a compressed mixed gas around a hydrogen-absorbing alloy that absorbs hydrogen, hydrogen contained in the mixed gas is absorbed by the hydrogen-absorbing alloy. The process involves performing an oxidation treatment on the gas that has passed around the hydrogen storage alloy, Storing the gas after oxidation treatment, A method for separating mixed gases having the following characteristics. [Explanation of Symbols]

[0042] 110 Compression section 120-1~120-N Hydrogen storage section 130-1~130-N Heating section 140 Hydrogen Storage Unit 150 Oxidation treatment 160 Drying treatment process 170 Helium storage section

Claims

1. A compression unit that compresses a mixed gas containing hydrogen and several other types of gases, A hydrogen storage unit comprising a hydrogen storage alloy that absorbs hydrogen, wherein hydrogen contained in the mixed gas compressed by the compression unit is absorbed into the hydrogen storage alloy, An oxidation treatment unit that performs oxidation treatment on the gas that has passed through the hydrogen storage unit, A gas storage unit for storing the gas after oxidation treatment by the oxidation treatment unit, A mixed gas separation apparatus having the following features.

2. The hydrogen storage section includes a heating section for heating the hydrogen storage alloy, A hydrogen storage unit for storing hydrogen released from a hydrogen storage alloy heated by the aforementioned heating unit, The mixed gas separation apparatus according to claim 1, further comprising:

3. The aforementioned heating section is After the gas is stored in the gas storage unit and the inside of the mixed gas separator is scavenged, the hydrogen storage alloy is heated. The mixed gas separation apparatus according to claim 2.

4. The aforementioned heating section is After the gas passes through the hydrogen storage section and is scavenged, the hydrogen storage alloy provided in the hydrogen storage section is heated. The mixed gas separation apparatus according to claim 2.

5. The hydrogen storage unit is The system comprises multiple hydrogen storage alloys arranged in multiple stages, and the mixed gas is passed sequentially around the multiple hydrogen storage alloys. The mixed gas separation apparatus according to claim 1.

6. Drying section that removes moisture generated by the oxidation of hydrogen by the oxidation section. The mixed gas separation apparatus according to claim 1, further comprising:

7. The compression section is Compress a mixed gas of hydrogen and helium. The mixed gas separation apparatus according to claim 1.

8. Compressing a mixed gas containing hydrogen and several other types of gases, By passing a compressed mixed gas around a hydrogen-absorbing alloy that absorbs hydrogen, hydrogen contained in the mixed gas is absorbed by the hydrogen-absorbing alloy. The process involves performing an oxidation treatment on the gas that has passed around the hydrogen storage alloy, Storing the gas after oxidation treatment, A method for separating mixed gases having the following characteristics.

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