Patent Application
20200010963
The present disclosure relates to production of hydrogen gas.
There is an increased demand for hydrogen gas as fuel for power generation by a fuel cell or as raw industrial materials. The hydrogen gas produced by hydrogen production plants or the like may be compressed at the plants or hydrogen gas stations, stored in containers, and supplied to fuel consumption devices of fuel cell vehicles or the like via dispensers. JP 2017-131862A discloses a configuration in which the hydrogen gas produced by a gas manufacturing apparatus is compressed by a compressor, temporarily stored in a pressure accumulator, and then filled in a vehicle via a dispenser.
As disclosed in JP 2017-131862A, when the hydrogen gas is stored, in general, it is compressed so as to be high pressure gas of, for example, 70 MPa (mega Pascal) so that a large quantity of the hydrogen gas can be stored. Accordingly, a compressor is needed, which unfortunately results in high compression costs for suppling the hydrogen gas. Therefore, a technique for producing the hydrogen gas that can reduce the costs of compressing the hydrogen gas is desired.
According to an aspect of the present disclosure, a system for producing hydrogen gas is provided. This system for producing the hydrogen gas comprises a pair of electrodes that are disposed at a predetermined water depth under water and configured to be connected to a power supply for electrolysis of water, a gas storage chamber that is disposed at the water depth, has communication holes through which surrounding water can flow in, and stores the hydrogen gas generated at a cathode of the pair of electrodes due to the electrolysis, a hydrogen recovery device disposed above the water depth, and piping configured to lead the hydrogen gas stored in the gas storage chamber to the hydrogen recovery device.
The pair of electrodes 10 include a cathode 11 and an anode 12. The pair of electrodes 10 are used for the electrolysis of water. The pair of electrodes 10 are disposed in a vicinity of a bottom of the sea B1 at a predetermined water depth D1 and exposed to surrounding water. The water depth D1 is about 7000 m (meter) in this embodiment. The pair of electrodes 10 are disposed in the gas storage chamber 20. The pair of electrodes 10 are supplied with a direct current by a power supply device 510 described later via the wiring 50. This causes a chemical reaction represented by the following formula (1) at the cathode 11, which generates the hydrogen gas. Meanwhile, a chemical reaction represented by the following formula (2) is caused at the anode 12, which generates oxygen gas.
2H2O+2e−→H2+2OH− (1)
2OH−→½O2+H2O+2e− (2)
The gas storage chamber 20 is disposed and fixed on the bottom of the sea B1. The gas storage chamber 20 stores the hydrogen gas generated at the cathode 11 of the pair of the electrodes 10 by the flow of the electric current through the cathode 11, that is to say, the hydrogen gas generated at the cathode 11 due to the electrolysis of water. The gas storage chamber 20 has an exterior wall 21 and a partition wall 22. The exterior wall 21 and the partition wall 22 are both formed of a resin with excellent corrosion resistance such as polyethylene (PE). As will be described later, an inside and an outside of the gas storage chamber 20 communicate with each other, so that differential pressure between internal pressure and external pressure of the gas storage chamber 20 is small. Therefore, durability that is so high as to withstand the water pressure at the water depth D1 is not necessary to a material of the gas storage chamber 20.
The exterior wall 21 forms a outer envelope of the gas storage chamber 20. In this embodiment, the exterior wall 21 includes a lower part 211 approximately in a cylindrical shape and an upper part 212 extending upward from the lower part 211. The upper part 212 has a hollow conical outer shape. The lower part 211 has a plurality of communication holes 26 aligned in the vicinity of the bottom of the sea B1 with a predetermined distance to each other in a circumferential direction. Each of the plurality of communication holes 26 is formed as a through hole penetrating in a thickness direction of the lower part 211. Thus, the surrounding seawater flows into the gas storage chamber 20 through each of the communication holes 26. In other words, the inside and the outside of the gas storage chamber 20 communicate with each other.
The partition walls 22 is formed with a plate-like member protruding vertically downward from a top wall surface 29 of the upper part 212 to the inside of the gas storage chamber 20. The partition wall 22 divides the upper space in the gas storage chamber 20 into a pair of gas storage sections 23. The pair of gas storage sections 23 include a hydrogen storage section 24 and an oxygen storage section 25. The hydrogen storage section 24 is a storage chamber for the cathode 11. More specifically, the hydrogen storage section 24 is located above the cathode 11 so as to store the hydrogen gas generated at the cathode 11. The oxygen storage section 25 is a storage chamber for the anode 12. More specifically, the oxygen storage section 25 is located above the anode 12 so as to store the oxygen gas generated at the anode 12.
As described above, since the inside of the gas storage chamber 20 communicates with the surrounding water, the hydrogen gas generated by the chemical reaction of the formula (1) in the gas storage chamber 20 is the hydrogen gas of the pressure equivalent to the water pressure at the water depth D1 that is about 70.9 MPa (mega Pascal). Accordingly, the hydrogen storage section 24 stores the hydrogen gas of about 70.9 MPs (mega Pascal).
Meanwhile, support portions that are formed on the exterior wall 21 of the gas storage chamber 20 so as to fix the pair of electrodes 10 at locations corresponding to the respective storage sections 24 and 25. Note that the support portions may be disposed on the bottom of the sea B1 as an independent member from the exterior wall 21.
In the area corresponding to the oxygen storage section 25 in the upper part 212 of the exterior wall 21, an exhaust opening 27 is formed. The exhaust opening 27 is formed as a through hole penetrating in a thickness direction of the upper part 212. Therefore, the oxygen storage section 25 is configured such that the surrounding water can flow in through the plurality of communication holes 26 and the exhaust opening 27. The exhaust opening 27 discharges the oxygen gas generated by the chemical reaction of the formula (2) at the anode 12 and accumulated in the gas storage chamber 20 to the outside of the gas storage chamber 20.
The hydrogen recovery device 30 is loaded on a ship 500 and recovers the hydrogen gas sent through the piping 40. The hydrogen recovery device 30 includes a shutoff valve 31 and a hydrogen processing unit 32. The shutoff valve 31 is an electromagnetic valve, and opens and closes the piping 40 based on control signals sent by a controller. The hydrogen processing unit 32 processes the hydrogen gas sent from the gas storage chamber 20 through the piping 40. The processing includes, for example, inspection processing of the hydrogen gas, filling processing of the hydrogen gas into a gas tank, and so forth.
The piping 40 connects the inside of the gas storage chamber 20 and the hydrogen recovery device 30 in a communicating manner so as to lead the hydrogen gas in the gas storage chamber 20 to the hydrogen recovery device 30. Most part of the piping 40 is disposed along a vertical direction under the sea. One end of the piping 40 is fixed to the gas storage chamber 20 with a metal fixing part while the other end is connected to the shutoff valve 31. An inside of the piping 40 communicates with the hydrogen storage section 24. The piping 40 is designed to withstand differential pressure between internal pressure and external pressure. More specifically, the internal pressure of the piping 40 is equivalent to the pressure of the hydrogen gas in the gas storage chamber 20, which is about 70.9 MPa. On the other hand, the external pressure of the piping 40 is lowest above the water, which is about 0.1 MPa, and is highest at an installation part to the gas storage chamber 20, which is about 70.9 MPa. Accordingly, the piping 40 is designed to withstand the maximum differential pressure (70.8 MPa) between 70.9 MPa and 0.1 MPa. In the present embodiment, the piping 40 is formed of alloy including nickel and titanium. The piping 40 may be formed by joining a multiple piping parts, for example.
The wiring 50 electrically connects the power supply device 510 and the pair of electrodes 10. The wiring 50 is disposed along the piping 40 and fixed to the piping 40 by fasteners 45 at multiple places. With this configuration, damages to the wiring 50 due to displacement by tidal currents and waves can be suppressed. The wiring 50 is covered with a coating layer made of material with excellent corrosion resistance such as polyethylene. The power supply device 510 is a direct current power supply loaded on the ship 500.
In the state where the ship 500 is not in a place shown in
The pair of electrodes 10 connected to the power supply are disposed at the predetermined water depth D1 such that they are exposed to the surrounding water (procedure P105). The procedure P105 includes several steps. More specifically, it includes a step for disposing the gas storage chamber 20 and the pair of electrodes 10 on the bottom of the sea B1, a step for connecting the piping 40 to the gas storage chamber 20, a step for disposing the wiring 50 along the piping 40 and fixing the wiring 50 to the piping 40 by the fasteners 45, a step for attaching the ends of the wiring 40 and piping 50 above the sea surface to the buoy not shown in the drawings, a step for disposing the ship 500 loaded with the power supply device 510 and the hydrogen recovery device 30 above the gas storage chamber 20, a step for connecting the end of the wiring 50 attached to the buoy to the power supply device 510, and a step for connecting the end of the piping 40 attached to the buoy to the shutoff valve 31. Note that many of these steps may be performed using, for example, a submarine with a working arm.
The electric current is applied to the pair of electrodes 10 so as to generate the hydrogen gas at the cathode 11 (procedure P110). The hydrogen gas generated by the procedure P110 is stored in the gas storage chamber 20, more specifically in the hydrogen storage section 24 (procedure P115). The hydrogen gas stored in the gas storage chamber 20 is led to the hydrogen recovery device 30 through the piping 40 (procedure P120). This is how the hydrogen gas of about 70.9 MPa generated at the cathode 11 of the pair of the electrodes 10 disposed at the water depth D1 is stored in the gas storage chamber 20 and led to the hydrogen processing unit 32 through the piping 40.
According to the hydrogen gas producing system 100 in the embodiment described above, the hydrogen gas is generated by the electrolysis of water using the pair of electrodes 10 disposed at the predetermined water depth D1 under the sea. Therefore, the hydrogen gas of the pressure equivalent to the water pressure at the water depth D1, that is, the hydrogen gas of the pressure of about 70.9 MPa can be generated. Consequently, compared with a configuration for producing the hydrogen gas above the water depth D1, the high pressure hydrogen gas can be generated without any facilities such as a compressor, which reduces the costs of compressing the hydrogen gas to produce the hydrogen gas. In addition, since the generated hydrogen gas is stored in the gas storage chamber 20 into which the surrounding water flows, the hydrogen gas can be stored as the hydrogen gas of the pressure equivalent to the water pressure at the predetermined water depth. Therefore, no large facilities that can withstand the pressure of the hydrogen gas are necessary, which can reduce costs of storing the hydrogen gas. Consequently, since no storage facilities that can withstand the high pressure are necessary for the storage of the hydrogen gas, the costs of storing the hydrogen gas can be reduced.
Moreover, the wiring 50 configured to electrically connect the power supply device 510 and the pair of electrodes 10 is disposed along the piping 40 that connects the inside of the gas storage chamber 20 and the hydrogen recovery device 30 in a communicating manner and fixed to the piping 40 at multiple places. Therefore, displacement by tidal currents and waves can be suppressed so as to suppress damages to the wiring 50, compared with a configuration in which the wiring 50 is disposed without any supports under the sea.
Furthermore, since the upper space in the gas storage chamber 20 is divided into the hydrogen storage section 24 and the oxygen storage section 25, the cathode 11 is disposed under the hydrogen storage section 24 while the anode 12 is disposed under the oxygen storage section 25, and the piping 40 communicates with the hydrogen storage section 24, the oxygen gas generated at the anode 12 by the electrolysis of water can be restrained from being led to the hydrogen recovery device 30 through the piping 40 and highly-concentrated hydrogen gas can be led to the hydrogen recovery device 30.
In the foregoing embodiment, the power supply device 510 is loaded on the ship 500, but the present disclosure is not limited to this. For example, it may be loaded on a rig or a platform used to extract crude oil from an offshore oil field, or on a rig or a platform for an exclusive use of producing the hydrogen gas. Alternatively, the power supply device 510 may be disposed on land, for example. In such a configuration, the wiring configured to connect the power supply device 510 and the pair of electrodes 10 may be disposed such that it runs along the bottom of the sea B1 to a place close to the land and, at a vicinity of the location of the power supply device 510, goes up vertically to connect with the power supply device 510. Alternatively, the power supply device 510 may be disposed under the sea, for example. In such a configuration, the power supply device 510 may be configured with a secondary battery or the like and the charged power supply device 510 may be disposed on the bottom of the sea B1. In such a configuration, the power supply device 510 may be configured as a submarine equipped with a screw and a rudder. In the case in which a charging amount falls equal to or below a predetermined threshold, the power supply device 510 may be made to emerge to the sea surface. Then, after the power supply device 510 is charged, it may be submerged to a vicinity of the gas storage chamber 20.
In the foregoing embodiments, the partition wall 22 may be omitted. In such a configuration, the exhaust opening 27 may be omitted. In such a configuration, the gas storage chamber 20 stores both hydrogen gas and oxygen gas. However, since a specific gravity of the hydrogen gas is lower than that of the oxygen gas, the hydrogen gas is stored above in the gas storage chamber 20. Moreover, the piping 40 is connected to the upper part 212 of the gas storage chamber 20. Accordingly, the hydrogen gas stored in the gas storage chamber 20 can be led to the hydrogen recovery device 30 through the piping 40 in preference to the oxygen gas in this configuration as well.
In the foregoing embodiments, the hydrogen gas is generated by the electrolysis of water. However, the hydrogen gas may be generated by other methods. For example, liquid hydrogen may be filled in an insulating container having an exhaust opening that is to be opened by the water pressure at the water depth D1 and the insulating container may be dropped from the ship 500 to submerge toward the gas storage chamber 20. Moreover, in such a configuration, a guiding may be prepared in advance to guide the insulating container into the gas storage chamber 20. In such a configuration, the exhaust opening of the submerging insulating container will open when it reaches the bottom of the sea B1. At this time, the liquid hydrogen filled in the insulating container quickly vaporizes to generate the hydrogen gas that is discharged outside the insulating container. In the configuration in which the insulating container is guided into the gas storage chamber 20, the hydrogen gas discharged from the insulating container is to be stored in the gas storage chamber 20. As to the insulating container, for example, a double structure container made of material that can withstand the pressure (differential pressure) of about 70.9 MPa may be used. In addition, the container may have an approximately spherical appearance shape. This configuration enables the insulating container to withstand higher pressure. Moreover, as to the exhaust opening that is to be opened by the water pressure at the water depth D1, for example, it may be configured so as to include a valve unit with a valve body and a spring energizing the valve body toward the outside from the inside of the insulating container. In this configuration, energizing power of the spring is set smaller than the water pressure at the water depth D1 so that the exhaust opening can be opened by the water pressure at the water depth Dl.
In the foregoing embodiments, the gas storage chamber 20 is fixed to the bottom of the sea B1. However, the gas storage chamber 20 may be configured to be a movable room. More specifically, the gas storage chamber 20 may be normally loaded on the ship 500 and dropped into the sea from the ship 500 so as to be submerged to a vicinity of the bottom of the sea B1 in the procedure P105 of the processing for producing the hydrogen gas. At this time, the gas storage chamber 20 may be submerged using the piping 40 as a guiding. For example, a through hole may be preliminarily formed in addition to the exhaust opening 27 in the upper part 212 so that the piping 40 is inserted in the through hole, and with the piping 40 left inserted therein, the gas storage chamber 20 may be submerged while being guided by the piping 40. In this configuration, in order to prevent the piping 40 from coming out of the through hole when the gas storage chamber 20 is most submerged, an end of the piping 40 may be formed in a large flange shape. Moreover, in such a configuration, the pair of electrodes 10 may be fixed to the gas storage chamber 20 in advance and submerged with it.
In each of the foregoing embodiments, the gas storage chamber 20 is disposed at the bottom of the sea at a water depth of 7000 meters. However, the present disclosure is not limited to this. For example, it may be disposed at any water depth ranging from 10 to 8000 meters. More preferably, it may be disposed at any water depth ranging from 100 to 7000 meters. In this configuration, the place at this water depth does not have to be the bottom of the sea. Furthermore, the gas storage chamber 20 may be disposed not only in the sea but also in any water environment such as a lake and a pond.
The configurations of the hydrogen gas producing system 100 in the
US140A5202-AO_English_spec_for_filing.docx foregoing embodiments are only examples and may be modified in various ways. For example, only the exhaust opening 27 may be omitted without omitting the partition wall 22. Moreover, although the hydrogen recovery device 30 is described to be loaded on the ship 500, it may be disposed on land or under the sea. In the configuration in which the hydrogen recovery device 30 is disposed under the sea, the hydrogen recovery device 30 may be disposed above a water depth of a location of the pair of the electrodes 10. This configuration enables to recover the hydrogen gas of higher pressure, compared with a configuration in which the hydrogen gas is generated at a water depth of a location of the hydrogen recovery device 30. Moreover, in the foregoing embodiments, the exterior wall 21 and the partition wall 22 are formed of polyethylene; however, they may be formed of any material such as other kinds of resins, metal, and ceramics, instead of polyethylene. Furthermore, the hydrogen recovery device 30 may be equipped with a compressor. In this configuration, for example, in the case in which the gas storage chamber 20 is disposed at a certain water depth shallower than 7000 meters, the hydrogen gas of the pressure lower than 70.9 MPa can be further compressed so as to have the pressure of 70.9 MPa by the compressor. Even in this configuration, compared with a configuration in which the hydrogen gas of the pressure lower than the water pressure at that water depth is compressed so as to have the pressure of 70.9 MPa, the following effects are exhibited: some of compressors used for multistage compression can be omitted, or electric power needed for the compression can be reduced, for example. Moreover, in the foregoing embodiments, the procedure P120 may be omitted. In other words, a recovery procedure may be omitted from the processing for producing the hydrogen gas and the recovery processing may be executed as a separate processing. Moreover, in the foregoing embodiments, the hydrogen recovery device 30 may include a pump for initiatively sending the hydrogen gas in the gas storage chamber 20 to the hydrogen processing unit 32 through the piping 40. Furthermore, in the forgoing embodiments, the whole wiring 50 under the sea may be fixed to the piping 40.
The present disclosure is not limited to the foregoing embodiments and can be implemented in various ways without departing from the spirit and scope of the present disclosure. For example, the technical features of the embodiments may be replaced or combined as appropriate, in order to solve part or all of the problems described above or in order to achieve part or all of the advantageous effects described above. Some technical features that are not described as being essential herein may be omitted as appropriate. For example, the present disclosure may be implemented in the following aspects.
(1) According to an aspect of the present disclosure, a system for producing hydrogen gas is provided. This system for producing the hydrogen gas comprises a pair of electrodes that are disposed at a predetermined water depth under water and configured to be connected to a power supply for electrolysis of water, a gas storage chamber that is disposed at the water depth, has communication holes through which surrounding water can flow in, and stores the hydrogen gas generated at a cathode of the pair of electrodes due to the electrolysis, a hydrogen recovery device disposed above the water depth, and piping configured to lead the hydrogen gas stored in the gas storage chamber to the hydrogen recovery device.
According to the system for producing the hydrogen gas in this aspect, since the hydrogen gas is generated by the electrolysis of water using the pair of electrodes disposed at the predetermined water depth under water, the hydrogen gas of the pressure equivalent to the water pressure at the predetermined water depth can be generated. Therefore, compared with a configuration for producing the hydrogen gas above the predetermined water depth, the hydrogen gas of higher pressure can be generated without any facilities such as a compressor. As a result, the hydrogen gas can be generated with costs of compressing the hydrogen gas reduced. In addition, since the generated hydrogen gas is stored in the gas storage chamber into which the surrounding water flows, the hydrogen gas can be stored as the hydrogen gas of the pressure equivalent to the water pressure at the predetermined water depth. Therefore, no large facilities that can withstand the pressure of the hydrogen gas are necessary, which can reduce costs of storing the hydrogen gas. Consequently, since no storage facilities that can withstand the high pressure are necessary for the storage of the hydrogen gas, the costs of storing the hydrogen gas can be reduced.
(2) In the system for producing the hydrogen gas in the foregoing aspect, the power supply may be located above the water depth. The system may be further provided with wiring configured to electrically connect the power supply and the pair of electrodes. The wiring may be disposed along the piping and at least part of the wiring may be fixed to the piping. According to the system for producing the hydrogen gas in this aspect, the wiring configured to electrically connect the power supply and the pair of electrodes is disposed along the piping that connects the inside of the gas storage chamber and the hydrogen recovery device in a communicating manner and at least part of the wiring is fixed to the piping. Therefore, displacement of the wiring can be suppressed and damages to the wiring due to the displacement can be also suppressed, compared with a configuration in which the wiring is disposed without any supports under water.
(3) In the system for producing the hydrogen gas in the foregoing aspect, the gas storage chamber may include an exterior wall forming a contour of the gas storage chamber and a partition wall protruding from a top wall surface of the exterior wall into the gas storage chamber so as to divide upper space in the gas storage chamber into a hydrogen storage section and an oxygen storage section. The cathode of the pair of electrodes may be disposed under the hydrogen storage section while the anode of the pair of electrodes may be disposed under the oxygen storage section, and the piping may communicate with the hydrogen storage section. According to the system for producing the hydrogen gas in this aspect, the upper space in the gas storage chamber is divided into the hydrogen storage section and the oxygen storage section, the cathode is disposed under the hydrogen storage section while the anode is disposed under the oxygen storage section, and the piping communicates with the hydrogen storage section. Therefore, the oxygen gas generated at the anode by the electrolysis of water can be restrained from being led to the hydrogen recovery device through the piping and highly-concentrated hydrogen gas can be led to the hydrogen recovery device.
The present disclosure can be implemented in various aspects. For example, it can be implemented in the aspects such as a hydrogen gas storage system, a hydrogen gas producing method, a hydrogen gas compressing method, and a hydrogen gas storage method.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-129920 | Jul 2018 | JP | national |
The present application claims priority from Japanese patent application 2018-129920, filed Jul. 9, 2018, the entirety of the content of which is hereby incorporated by reference into this application.
