Hydrogen Production System

Abstract

To provide a hydrogen production system capable of producing high-purity hydrogen gas at low cost, which is applicable for the production of hydrogen by the decomposition of formic acid.SOLUTION: A hydrogen production system (S) comprises: a formic acid reaction tank (1) that produces a mixed fluid (M) of non-solid state carbon dioxide (CD), and hydrogen gas (HG) by catalytic decomposition of a hydrogen storage agent containing formic acid, in which a cyclone separator (3) is provided for the separation of the mixed gas (M) into the non-solid state carbon dioxide (CD), and hydrogen gas (HG).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a system for producing hydrogen. [Background technology]

[0002] In recent years, in order to realize a so-called low-carbon society, technologies have been proposed that utilize hydrogen as a fuel, such as fuel cells and hydrogen gas turbines. Various technologies have also been proposed as hydrogen sources, and one of them is known to produce high-pressure hydrogen gas by decomposing formic acid using a catalyst (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-124730 Summary of the Invention [Problem to be solved by the invention]

[0004] Formic acid not only has excellent storage and transportability as a hydrogen carrier, but can also be produced inexpensively from biogas, so the formic acid decomposition technology described above is expected to enable low-cost production of hydrogen fuel. On the other hand, in order to actually use the hydrogen gas obtained by this technology as fuel, it is further required to separate the carbon dioxide that is produced simultaneously with the hydrogen gas with high accuracy and at low cost. Although Patent Document 1 mentions gas-liquid separation of a mixed gas of hydrogen and carbon dioxide, it does not disclose a specific method for producing high-purity hydrogen at low cost.

[0005] Therefore, in order to solve the above problems, an object of the present disclosure is to provide a hydrogen production system that can inexpensively produce high-purity hydrogen gas, which is applicable to a method of producing hydrogen by formic acid decomposition. [Means for solving the problem]

[0006] In order to achieve the above object, the hydrogen production system according to the present disclosure comprises: a formic acid reactor that generates a fluid mixture of non-solid carbon dioxide and hydrogen gas by catalytically decomposing a hydrogen storage agent containing formic acid; a cyclone separator that separates the mixed fluid into the non-solid carbon dioxide and the hydrogen gas; Equipped with. [Effects of the Invention]

[0007] According to the hydrogen production system according to the present disclosure, it is possible to inexpensively produce high-purity hydrogen gas in a method for producing hydrogen by formic acid decomposition. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic configuration of a hydrogen production system according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a block diagram showing a schematic configuration of a hydrogen production system according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] A preferred embodiment of the present disclosure will now be described with reference to the drawings. Fig. 1 shows a hydrogen production system S according to one embodiment of the present disclosure. The hydrogen production system S includes a formic acid reaction vessel 1 and a cyclone separator 3.

[0010] The formic acid reaction vessel 1 generates a mixture fluid M of non-solid carbon dioxide CD and hydrogen gas HG (hereinafter simply referred to as "mixture fluid") by catalytically decomposing a hydrogen storage agent containing formic acid. In this specification, "hydrogen storage agent containing formic acid" refers to formic acid, formate, or a mixture thereof. In the formic acid reaction vessel 1, high-temperature and high-pressure hydrogen and carbon dioxide CD are generated by the following reaction: HCOOH → H2+ CO2

[0011] Specifically, in this embodiment, the reaction in the formic acid reaction tank 1 generates a high-pressure mixture fluid M of approximately several tens of MPa to 200 MPa. Therefore, the formic acid reaction tank 1 is configured as a pressure-resistant container that can withstand such pressure. There are no particular limitations on the material from which the pressure-resistant container of the formic acid reaction tank 1 is made, and for example, metal, resin, ceramics, etc. can be used.

[0012] The catalyst used in the reaction in the formic acid reaction tank 1 is not particularly limited as long as it can generate a high-pressure mixture fluid M, but is preferably an organometallic complex made of a transition metal. Examples of transition metal species used in this catalyst include iridium, rhodium, ruthenium, and cobalt. In this embodiment, an iridium-based catalyst is used.

[0013] The hydrogen storage agent containing formic acid used in the formic acid reaction tank 1 can be obtained by any method, and examples of such materials that can be used include processed materials containing a solution obtained by decomposing plant biomass, processed materials obtained by processing feces and urine, processed materials obtained by decomposing waste plastics, processed materials obtained by hydrocarbon reforming, coal dry distillation, coal gasification, etc.

[0014] As described above, in this embodiment, the carbon dioxide CD generated in the formic acid reaction tank 1 is in a non-solid state. In this specification, "non-solid state" carbon dioxide CD refers to carbon dioxide CD in a gaseous state, a liquid state, or a supercritical state. The hydrogen production system S according to this embodiment generates a mixture fluid M of carbon dioxide CD in a supercritical state and hydrogen gas HG in the formic acid reaction tank 1, and introduces this mixture fluid M into a cyclone separator 3, which will be described later, while maintaining the supercritical state of the carbon dioxide CD in the mixture fluid M.

[0015] In the illustrated example, a heat dissipation device 5 is disposed upstream of the cyclone separator 3. The heat dissipation device 5 dissipates heat from the mixture fluid M discharged from the formic acid reaction tank 1. In this embodiment, the mixture fluid M produced in the formic acid reaction tank 1 has a high temperature of approximately 50°C to 80°C and a high pressure of approximately 20 MPa to 150 MPa. The heat dissipation device 5 is equipped with a fluid pipe 7 that passes such high-temperature mixture fluid M. The heat dissipation device 5 exposes the fluid pipe 7 to the outside air to cool the mixture fluid M, thereby lowering the temperature of the mixture fluid M to a temperature close to the ambient temperature of the heat dissipation device 5. For example, in the heat dissipation device 5, the temperature of the mixture fluid M is lowered to approximately 20°C to 40°C. Note that the mixture fluid M described above is at a high pressure of at least 1 MPa at normal temperature or 35°C, and the fluid pipe 7 of the heat dissipation device 5 is pressure-resistant to the high pressure of the mixture fluid M described above.

[0016] The heat dissipation device 5 can adjust the temperature of the mixture fluid M that passes through the heat dissipation device 5 and is supplied to the cyclone separator 3 by appropriately setting the diameter, length, material, etc. of the fluid pipe 7 through which the mixture fluid M passes. Therefore, by passing the mixture fluid M through the heat dissipation device 5 while maintaining the pressure of the mixture fluid M within a predetermined range, it is possible to control the state of carbon dioxide CD in the mixture fluid M that is supplied to the cyclone separator 3, i.e., whether it is in a gaseous, liquid, or supercritical fluid state.

[0017] The cyclone separator 3 is a device that separates particles of different densities by centrifugal force generated by rotating the fluid to be separated. The cyclone separator 3 used in this embodiment separates the mixture fluid M into carbon dioxide CD and hydrogen gas HG in a non-solid state.

[0018] In this embodiment, the cyclone separator 3 is configured as a multi-stage type (two-stage type in this example). That is, the cyclone separator 3 has a first cyclone separator (hereinafter simply referred to as the "first separator") 3A arranged on the upstream side and a second cyclone separator (hereinafter simply referred to as the "second separator") 3B arranged on the downstream side. Specifically, the first separator 3A separates the mixture fluid M into non-solid carbon dioxide CD and hydrogen gas HG. The second separator 3B separates the solid carbon dioxide CD from the hydrogen gas HG obtained by the first separator 3A.

[0019] In this specification, the "hydrogen gas" after passing through the cyclone separator 3 includes hydrogen gas HG as the main component mixed with impurities. Similarly, in this specification, the "carbon dioxide" after passing through the cyclone separator 3 includes carbon dioxide CD as the main component mixed with impurities.

[0020] A mixture fluid M of carbon dioxide CD in a non-solid state (supercritical state in this example) and hydrogen gas HG is introduced into the first separator 3A, and this mixture fluid M is separated into carbon dioxide CD and hydrogen gas HG by the first separator 3A. The hydrogen gas HG separated in the first separator 3A has a purity of, for example, about 90% to 99%. As will be described later, this hydrogen gas HG is introduced into the second separator 3B. Note that a portion of the hydrogen gas HG separated in the first separator 3A may be supplied via the first hydrogen supply channel 9 to a hydrogen consumption facility (first hydrogen consumption facility 11 in the same figure) that can utilize the hydrogen gas HG with the purity after separation in the first separator 3A. The carbon dioxide CD in a non-solid state (supercritical state in this example) separated in the first separator 3A is recovered, for example, in a tank (first tank 13 in the same figure) that can store it in a non-solid state, and then supplied for an appropriate purpose.

[0021] As described above, in this embodiment, the carbon dioxide CD in the mixture fluid M introduced into the cyclone separator 3 (first separator 3A in this example) is a supercritical fluid. Because a supercritical fluid has a viscosity similar to that of a gas, it can be easily introduced into the cyclone separator 3 as a mixture fluid M with hydrogen gas HG from the formic acid reaction vessel 1. Furthermore, a supercritical fluid has a density similar to that of a liquid. Because the densities of carbon dioxide CD and hydrogen gas HG in the supercritical state differ by approximately 2,000 to 10,000 times, the cyclone separator 3 can easily separate the carbon dioxide CD from the hydrogen gas HG by utilizing this density difference. The mixture fluid M swirling inside the cyclone separator 3 is separated into carbon dioxide CD and hydrogen gas HG by the action of centrifugal force, with carbon dioxide CD moving toward the outside of the swirl and hydrogen gas HG moving toward the center of the swirl. For example, the cyclone separator 3 is provided with an outlet for carbon dioxide CD on the outside of the swirl and an outlet for hydrogen gas HG on the center of the swirl.

[0022] However, the carbon dioxide CD in the mixture fluid M introduced into the cyclone separator 3 does not need to be in a supercritical state as long as it is in a non-solid state. Even when the carbon dioxide CD is gaseous, the density difference between it and the hydrogen gas HG is about 20 times, so high-purity (for example, about 90% to 99%) hydrogen gas HG can be easily and inexpensively produced using the cyclone separator 3 without providing any cooling equipment to solidify the carbon dioxide CD. Furthermore, when the carbon dioxide CD is liquid, the density difference between it and the hydrogen gas HG is about 10,000 times, so hydrogen gas HG can be produced in a similar manner.

[0023] The hydrogen gas HG separated by the first separator 3A flows into the decompressed second separator 3B. In this embodiment, the second separator 3B is set to a pressure at which the swirled carbon dioxide CD solidifies. When the carbon dioxide CD in the mixture fluid M is in a solid state, its density is approximately 15,000 times different from that of the carbon dioxide CD. Due to this density difference, the second separator 3B produces hydrogen gas HG of even higher purity (for example, approximately 99.99%). The hydrogen gas HG separated by the second separator is supplied via the second hydrogen supply path 14 to, for example, a second hydrogen consumption facility 15 that uses hydrogen gas of higher purity than the first hydrogen consumption facility 11. Note that the produced hydrogen gas HG may be stored in a storage tank and then transported to each consumption facility instead of being directly supplied to the first hydrogen consumption facility 11 and the second hydrogen consumption facility 15. On the other hand, the solid carbon dioxide CD (dry ice) separated in the second separator 3B is subjected to, for example, a decompression treatment, and then recovered in a second tank 17 capable of storing the carbon dioxide CD in a solid state, and thereafter supplied for an appropriate use. However, the carbon dioxide CD recovered from the second separator 3B does not have to be solid.

[0024] The hydrogen production system S described above may further include a reciprocating expander (hereinafter referred to as the "downstream expander") 18 downstream of the cyclone separator 3 (on the first hydrogen supply channel 9 and / or the second hydrogen supply channel 14). The hydrogen gas HG separated by the cyclone separator 3 may be at a high pressure of 1 MPa or more. In this case, the downstream expander 18 extracts work from the pressure of the hydrogen gas HG, thereby reducing the pressure of the hydrogen gas HG to the pressure required by each hydrogen consumption facility, such as the first hydrogen consumption facility 11 and the second hydrogen consumption facility 15. The work extracted by the downstream expander 18 can be used as power for other facilities, for example by converting it into electricity using a generator or the like.

[0025] It is not essential that the cyclone separator 3 be configured as a two-stage type as illustrated. The cyclone separator 3 may be a multi-stage type with three or more stages, or a single-stage type. The number of stages of the cyclone separator 3 can be appropriately selected taking into consideration the purity of the hydrogen gas HG required for the application of the hydrogen gas HG, the separation performance of the cyclone separator 3 itself, the installation space, etc.

[0026] The hydrogen production system S described above may additionally include a separator other than the cyclone separator 3. For example, when supplying hydrogen gas HG to an application requiring higher purity than that obtained by the final-stage cyclone separator 3 (in this example, the second separator 3B), a separation membrane 19 may be provided in the hydrogen gas supply path from the final-stage cyclone separator 3, as shown by the dashed line in Fig. 1. Furthermore, the separation membrane 19 may be provided upstream of the cyclone separator 3, or the separation membrane 19 may be provided between the first separator 3A and the second separator 3B.

[0027] The hydrogen gas HG produced by the hydrogen production system S is used, for example, in hydrogen-fueled prime movers such as gas turbines and boilers, and in hydrogen-fueled stationary fuel cells, automobile fuel cells, and other power generation devices.

[0028] Next, another embodiment of the present disclosure will be described with reference to Fig. 2. In the following description, elements that are the same as or similar to those in the above-described embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof may be omitted.

[0029] The hydrogen production system S according to this embodiment is provided with a reciprocating expander (hereinafter referred to as the "upstream expander") 21 that is disposed upstream of the cyclone separator 3 and extracts work from the mixture fluid M discharged from the formic acid reaction tank 1.

[0030] In the illustrated example, a heating device 23 is provided upstream of the upstream expander 21. The mixture fluid M generated in the formic acid reaction tank 1 is introduced into the heating device 23 while the carbon dioxide CD in the mixture fluid M is maintained in a supercritical state.

[0031] In this embodiment, the mixture fluid M produced in the formic acid reaction tank 1 has a high temperature of about 50°C to 80°C and a high pressure of about 20 MPa to 150 MPa. The heating device 23 is equipped with a fluid pipe 7 that passes such high-temperature mixture fluid M. The heating device 23 exposes the fluid pipe 7 to a heat source to heat the mixture fluid M, thereby increasing the temperature of the mixture fluid M to, for example, about 100°C to 330°C and the pressure to, for example, about 20 MPa to 50 MPa.

[0032] The mixture fluid M heated by the heating device 23 flows into the upstream expander 21. The upstream expander 21 extracts work from the pressure of the mixture fluid M and reduces the pressure to about 1 MPa. The mixture fluid M discharged from the upstream expander 21 is introduced into the cyclone separator 3, which will be described later, while maintaining the supercritical state of carbon dioxide CD in the mixture fluid M. Note that the work extracted by the upstream expander 21 can be used as power for other equipment, for example, by converting it into electricity using a generator or the like.

[0033] In this embodiment, the cyclone separator 3 is configured as a multi-stage system (two-stage system in this example) consisting of a first separator 3A and a second separator 3B. The first separator 3A separates the mixture fluid M into non-solid carbon dioxide CD and hydrogen gas HG. The second separator 3B separates solid carbon dioxide CD (dry ice) from the hydrogen gas HG obtained by the first separator 3A. The carbon dioxide CD separated by the first separator 3A and the carbon dioxide CD separated by the second separator 3B are subjected to, for example, a decompression treatment, and then recovered as solid carbon dioxide in a second tank 17 capable of storing carbon dioxide CD in a solid state, and then supplied for an appropriate purpose. However, the carbon dioxide CD recovered from the first separator 3A and the second separator 3B does not have to be solid.

[0034] The hydrogen production system S according to this embodiment may include a heat dissipation device 5 downstream of the upstream expander 21. The heat dissipation device 5 cools the mixture fluid M by exposing the fluid pipe 7 to the outside air. The heat dissipation device 5 can adjust the temperature of the mixture fluid M that passes through the heat dissipation device 5 and is supplied to the cyclone separator 3 by appropriately setting the diameter, length, material, etc. of the fluid pipe 7 through which the mixture fluid M passes. Therefore, by passing the mixture fluid M through the heat dissipation device 5 while maintaining the pressure of the mixture fluid M within a predetermined range, it is possible to control the state of carbon dioxide CD in the mixture fluid M that is supplied to the cyclone separator 3, i.e., whether it is in a gaseous, liquid, or supercritical fluid state.

[0035] It should be noted that either or both of the heating device 23 and the heat dissipation device 5 described in this embodiment may be omitted.

[0036] As described above, according to the hydrogen production system S according to each embodiment of the present disclosure, as described above, the large density difference between the non-solid carbon dioxide CD and the hydrogen gas HG can be utilized to produce high-purity hydrogen gas HG using the cyclone separator 3. Therefore, high-purity hydrogen gas HG can be produced easily and inexpensively without providing any cooling equipment for solidifying the carbon dioxide CD.

[0037] In each embodiment of the present disclosure, as described above, the cyclone separator 3 may include a first separator 3A (first cyclone separator) that separates the mixture fluid M into non-solid carbon dioxide CD and hydrogen gas HG, and a second separator 3B (second cyclone separator) that is disposed downstream of the first separator 3A and separates the solid carbon dioxide CD from the hydrogen gas HG obtained by the first separator 3A. This configuration allows for the production of hydrogen gas HG with a higher purity than when only one cyclone separator 3 is provided. It also makes it possible to produce hydrogen gas HG with different purities depending on the application. It also makes it possible to produce carbon dioxide CD in different states.

[0038] Each embodiment of the present disclosure may include a heat dissipation device 5 that is disposed upstream of the cyclone separator 3 and dissipates heat from the mixture fluid M discharged from the formic acid reaction tank 1. With this configuration, it is possible to control the state of carbon dioxide CD in the mixture fluid M supplied to the cyclone separator 3, i.e., whether it is in a gaseous, liquid, or supercritical fluid state.

[0039] In each embodiment of the present disclosure, the non-solid carbon dioxide CD in the mixture fluid M may contain carbon dioxide CD in a supercritical state. According to this configuration, as described above, the mixture fluid M with hydrogen gas HG can be easily introduced from the formic acid reaction tank 1 to the cyclone separator 3, and can be easily separated from the hydrogen gas HG by the cyclone separator 3, which utilizes the difference in density.

[0040] Each embodiment of the present disclosure may include a separation membrane 19 that further separates carbon dioxide CD contained in the hydrogen gas HG supplied from the cyclone separator 3. With this configuration, it is possible to produce hydrogen gas HG that is suitable for applications requiring extremely high-purity hydrogen gas HG.

[0041] As shown in each embodiment, when a reciprocating expander (downstream expander 18 in FIG. 1, upstream expander 21 in FIG. 2) is provided downstream or upstream of the cyclone separator 3, it becomes possible to effectively utilize the high pressure of the mixture fluid M generated in the formic acid reaction tank 1 to drive other devices such as a generator. However, these expanders 18 and 21 may be omitted.

[0042] As described above, the preferred embodiments of the present disclosure have been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present disclosure. Therefore, such additions, modifications, and deletions are also included in the scope of the present disclosure. [Explanation of symbols]

[0043] 1 Formic Acid Reactor 3 Cyclone Separator 3A First Cyclone Separator 3B Second cyclone separator 5. Heat dissipation device 18 Downstream Expander 19 Separation membrane 21 Upstream expander 23 Heating device CD Carbon dioxide in non-solid state S Hydrogen Production System HG Hydrogen Gas M mixture fluid

Claims

1. a formic acid reactor that generates a fluid mixture of non-solid carbon dioxide and hydrogen gas by catalytically decomposing a hydrogen storage agent containing formic acid; a cyclone separator that separates the mixed fluid into the non-solid carbon dioxide and the hydrogen gas; A hydrogen production system comprising:

2. 2. The hydrogen production system according to claim 1, The cyclone separator is a first cyclone separator for separating the mixed fluid into the non-solid carbon dioxide and the hydrogen gas; a second cyclone separator disposed downstream of the first cyclone separator for separating solid carbon dioxide from the hydrogen gas obtained by the first cyclone separator; having Hydrogen production system.

3. 3. The hydrogen production system according to claim 1, a heat dissipation device disposed upstream of the cyclone separator to dissipate heat from the mixture fluid discharged from the formic acid reaction tank; Hydrogen production system.

4. The hydrogen production system according to any one of claims 1 to 3, The non-solid state carbon dioxide includes carbon dioxide in a supercritical state. Hydrogen production system.

5. The hydrogen production system according to any one of claims 1 to 4, A separation membrane is provided which further separates carbon dioxide contained in the hydrogen gas supplied from the cyclone separator. Hydrogen production system.

6. The hydrogen production system according to any one of claims 1 to 5, The system further includes a reciprocating downstream expander disposed downstream of the cyclone separator to extract work from the hydrogen gas discharged from the cyclone separator. Hydrogen production system.

7. The hydrogen production system according to any one of claims 1 to 5, The system further includes a reciprocating upstream expander disposed upstream of the cyclone separator for extracting work from the mixture fluid discharged from the formic acid reactor. Hydrogen production system.

8. The hydrogen production system according to claim 7, The system further includes a heating device disposed upstream of the upstream expander and configured to heat the mixture fluid discharged from the formic acid reaction tank. Hydrogen production system.

9. The hydrogen production system according to claim 7 or 8, The system further includes a heat dissipation device disposed upstream of the cyclone separator to dissipate heat from the mixture fluid discharged from the upstream expander. Hydrogen production system.

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