Hydrogen production system

Abstract

We provide a hydrogen production system that reduces the cost of the blower used to return hydrogen gas to the steam electrolysis device. [Solution] The hydrogen production system comprises a steam electrolytic device including an electrolytic cell configured to generate hydrogen gas from steam, a hydrogen gas supply line for guiding the hydrogen gas discharged from the steam electrolytic device to a hydrogen supply target, a cooler positioned on the hydrogen gas supply line for cooling the hydrogen gas, a dehumidifier positioned downstream of the cooler in the hydrogen gas supply line and containing an adsorbent for recovering moisture from the hydrogen gas flowing downstream of the cooler, a regeneration gas supply line for extracting the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line and returning it to the dehumidifier as a regeneration gas for the adsorbent, and a regeneration gas blower for sending the regeneration gas discharged from the dehumidifier to the steam electrolytic device.

Description

Technical Field

[0001] The present disclosure relates to a hydrogen production system for producing hydrogen gas using a solid oxide electrolysis cell.

Background Art

[0002] The hydrogen production system disclosed in Patent Document 1 includes a sweep gas supply line for supplying a sweep gas such as dry air to the anode electrode of a solid oxide electrolysis cell, a raw material gas supply line for supplying a raw material gas containing water vapor to the cathode electrode of the solid oxide electrolysis cell, and a product gas supply line for guiding the product gas (more specifically, hydrogen gas) generated in the solid oxide electrolysis cell to a product gas recovery section (see FIG. 3 of the same document).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For the purpose of maintaining the reducing atmosphere in the above cathode electrode, it is conceivable to install a line in the hydrogen production system for returning the hydrogen gas extracted from the product gas supply line to the solid oxide electrolysis cell. Further, it is further conceivable to install a blower for sending out hydrogen gas toward the solid oxide electrolysis cell on the line. Furthermore, it is conceivable to install a dehumidifier for recovering moisture from the hydrogen gas on the above product gas supply line. A dehumidifying agent is disposed in the dehumidifier.

[0005] The hydrogen gas discharged from solid oxide electrolytic cells is a high-temperature gas well over 100°C, requiring a high heat resistance temperature for the blower. Furthermore, because the high-temperature hydrogen gas flowing into the blower is low-density, the power required by the blower to return a predetermined mass flow rate of hydrogen gas to the solid oxide electrolytic cell becomes high. This could lead to increased blower costs.

[0006] Furthermore, it is conceivable to return a portion of the dehumidified hydrogen gas discharged from the dehumidifier to the dehumidifier as a gas for regenerating the desiccant. However, releasing the regenerating gas discharged from the dehumidifier 16 outside the system would mean a loss of hydrogen gas generated in the solid oxide electrolytic cell.

[0007] The purpose of this disclosure is to provide a hydrogen production system that reduces the cost of the blower used to return hydrogen gas to the steam electrolysis device, and also reduces hydrogen gas loss. [Means for solving the problem]

[0008] A hydrogen production system according to at least one embodiment of this disclosure is A steam electrolysis apparatus including an electrolytic cell configured to generate hydrogen gas from water vapor, A hydrogen gas supply line for guiding the hydrogen gas discharged from the steam electrolysis apparatus to a hydrogen supply target, A cooler is placed on the hydrogen gas supply line for cooling the hydrogen gas, A dehumidifier located downstream of the cooler in the hydrogen gas supply line, comprising an adsorbent for recovering moisture from the hydrogen gas flowing downstream of the cooler, A regeneration gas supply line for extracting the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line and returning it to the dehumidifier as a regeneration gas for the adsorbent, A regeneration gas blower for supplying the regeneration gas discharged from the dehumidifier to the water vapor electrolysis device, It is equipped with. [Effects of the Invention]

[0009] According to this disclosure, a hydrogen production system is provided that reduces the cost of the blower used to return hydrogen gas to the steam electrolysis device and also reduces hydrogen gas loss. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a hydrogen production system according to one embodiment. [Figure 2] This is a schematic diagram of the hydrogen gas supply system according to the first embodiment. [Figure 3] This is a schematic diagram of the hydrogen gas supply system according to the second embodiment. [Figure 4] This is a schematic diagram of the hydrogen gas supply system according to the third embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components. Note that similar configurations may be denoted by the same reference numerals and their explanations may be omitted.

[0012] <Configuration of the hydrogen production system in this disclosure> Referring to Figure 1, a hydrogen production system 310 according to one embodiment of the present disclosure will be described. The hydrogen production system 310 is a pressurized solid oxide electrolytic cell (pressurized SOEC) system as an example, and includes a steam electrolytic device 201. The steam electrolytic device 201 is provided with an electrolytic cell 105 for electrolyzing steam and a power supply device 650 for applying voltage to the electrolytic cell 105. Furthermore, the hydrogen production system 310 includes a steam generator 343 for recovering excess heat from the electrolytic cell 105 and generating and heating steam to be supplied to the electrolytic cell 105, and an oxidizing gas cooler 512, etc.

[0013] The electrolytic cell 105 is a solid oxide electrolytic cell (SOEC) configured to generate hydrogen gas from water vapor. In this embodiment, the supplied water vapor is pressurized water vapor, and the electrolytic cell 105 is a pressurized SOEC. The electrolytic cell 105 comprises a hydrogen electrode 109, an oxygen electrode 113, and a solid electrolyte 111 provided between the hydrogen electrode 109 and the oxygen electrode 113. Although only one electrolytic cell 105 is schematically depicted in Figure 1, a configuration in which multiple electrolytic cells 105 are housed in the water vapor electrolytic device 201 is also possible. The power supply device 650 is configured to apply a voltage between the hydrogen electrode 109 and the oxygen electrode 113.

[0014] The hydrogen electrode 109 is connected to a steam supply header 207 through which steam supplied to the hydrogen electrode 109 flows, and a generated hydrogen discharge header 209 through which hydrogen gas discharged from the hydrogen electrode 109 flows. The steam supply header 207 is connected to a water supply line 340 via a raw material gas supply line 346 and a steam supply line 344, and a water supply pump 341 is provided in the water supply line 340. A flow control valve 342 (or a flow control device) for controlling the water supply flow rate is provided downstream of the water supply pump 341. The steam generator 343 is connected to the steam supply line 344 in parallel with the flow control valve 342 in series.

[0015] A hydrogen gas return line L is connected to the connection point Q between the steam supply line 344 and the raw material gas supply line 346. The return line L corresponds to a hydrogen gas recirculation line 9 (see FIG. 2) or a regeneration gas discharge line 10B (see FIGS. 3 and 4) described later. The hydrogen gas extracted from the hydrogen gas supply line 410 and flowing through the return line L merges with the steam from the steam supply line 344 at the connection point Q. The raw material gas containing steam and hydrogen gas is supplied to the hydrogen electrode 109 in the water vapor electrolyzer 201 via the raw material gas supply line 346. The temperature of the raw material gas flowing into the water vapor electrolyzer 201 is approximately 200 to 350°C. A superheater may be arranged on the raw material gas supply line 346, and the steam contained in the raw material gas may be superheated in the superheater. The hydrogen gas generated at the hydrogen electrode 109 is taken out from the hydrogen gas supply line 410 via the generated hydrogen discharge header 209. The temperature of the hydrogen gas discharged from the generated hydrogen discharge header 209 is approximately 300°C to 400°C. The hydrogen gas supply line 410 is configured to guide hydrogen gas to the hydrogen supply target 3. The hydrogen supply target 3 is a facility that stores or consumes hydrogen, which may be hydrogen gas or liquid hydrogen. Although it is only an example, the hydrogen supply target 3 may be a hydrogen gas tank that stores hydrogen gas.

[0016] The oxygen electrode 113 is connected to an oxidizing gas supply line 513 through which an oxidizing gas (e.g., air) containing oxygen supplied to the oxygen electrode 113 flows, and an oxidizing gas discharge line 514 through which the exhaust gas of the oxidizing gas discharged from the oxygen electrode 113 flows. The oxidizing gas intake line 510 includes an oxidizing gas compressor 511 that compresses the oxidizing gas and an oxidizing gas cooler 512 that cools the pressurized oxidizing gas. The oxidizing gas intake line 510 is connected to the oxidizing gas supply line 513 and supplies the water vapor electrolysis device 201 with an oxidizing gas at a desired temperature, pressure, and flow rate. A steam generator 343 is provided in the oxidizing gas discharge line 514 and is connected to an expander (power turbine) 515 driven by the exhaust oxidizing gas after heat recovery. The exhaust oxidizing gas from which power has been recovered by the expander 515 is discharged to the outside through the exhaust oxidizing gas discharge line 516 from a vent stack 517.

[0017] <Operation (Operating Method) of Hydrogen Production System 310> Next, the operation (operating method) of the hydrogen production system 310 according to the embodiment of the present disclosure will be described. Water from a water supply source flows through a water supply line 340 by a water supply pump 341 and is heated in a steam generator 343 by an operation described later to become pressurized steam. The water supply amount is determined based on the system steam utilization rate Uss, which is the ratio of the amount of water vapor electrolyzed to the water (water vapor) externally supplied to the electrolysis system. The pressurized steam generated in the steam generator 343 flows through a steam supply line 344 and merges with hydrogen gas at a connection point Q. The raw material gas containing hydrogen gas and steam flows through a raw material gas supply line 346 and is supplied to the oxygen electrode 109. Since hydrogen gas is contained in the raw material gas, it can be adjusted to a desired hydrogen concentration to prevent oxidation of the metal on the hydrogen electrode side of the raw material gas supply line 346 and the water vapor electrolysis device 201. On the other hand, the oxidizing gas compressed by the oxidizing gas compressor 511 is adjusted to a desired temperature by an oxidizing gas cooler 512 provided in the oxidizing gas intake line 510, then flows through the oxidizing gas supply line 513 and is supplied to the oxygen electrode 113 to maintain the operating temperature of the water vapor electrolysis device 201 at an appropriate value.

[0018] The power supply unit 650 applies a DC voltage between the hydrogen electrode 109 and the oxygen electrode 113, causing the water vapor in the hydrogen electrode 109 to be electrolyzed, generating hydrogen and oxygen ions (O2-) (see reaction equation (1) below). The oxygen ions pass through the solid electrolyte 111 and become oxygen at the oxygen electrode 113 (see reaction equation (2) below). The hydrogen gas flowing out of the hydrogen electrode 109 contains water vapor, and this water vapor-containing hydrogen gas flows through the hydrogen gas supply line 410. A portion of the hydrogen gas flowing through the hydrogen gas supply line 410 flows through the return line L and returns to the raw material gas supply line 346, while the remaining hydrogen gas is supplied to the hydrogen supply target 3. The oxidizing gas discharge line 514 is connected to the heating side line of the steam generator 343 and is used as a heating medium for the steam generator 343. Since the heat-recovered exhaust oxidizing gas is pressurized, it is supplied to the expander (power turbine) 515, and power recovery for driving the oxidizing gas compressor 511 can be performed, thereby reducing power consumption. H2O + 2e- → H2 + O2- ... (1) 2O2- → O2 + 4e- ···(2)

[0019] Hereinafter, the supply system for hydrogen gas (generated hydrogen) extracted from the steam electrolysis apparatus 201 will be referred to as "hydrogen gas supply system 2". Although several specific configurations are applicable to hydrogen gas supply system 2, the following description will illustrate hydrogen gas supply system 2A(2) according to the first embodiment, hydrogen gas supply system 2B(2) according to the second embodiment, and hydrogen gas supply system 2C(2) according to the third embodiment.

[0020] <Hydrogen gas supply system 2A(2) according to the first embodiment> Figure 2 is a schematic diagram of the hydrogen gas supply system 2A(2) according to the first embodiment. The hydrogen gas supply system 2A includes a hydrogen gas supply line 410 for guiding hydrogen gas discharged from the hydrogen discharge main pipe 209 of the steam electrolysis device 201 to the hydrogen supply target 3, a cooler 15 located on the hydrogen gas supply line 410, a gas-liquid separator 15A located downstream of the cooler 15 in the hydrogen gas supply line 410, a dehumidifier 16 located downstream of the gas-liquid separator 15A in the hydrogen gas supply line 410, and a hydrogen compressor 6 located downstream of the dehumidifier 16 in the hydrogen gas supply line 410.

[0021] The cooler 15 is configured to cool the hydrogen gas using a refrigerant, such as cooling water. As just one example, the temperature of the hydrogen gas discharged from the cooler 15 is approximately 50°C. The gas-liquid separator 15A separates condensed water from the hydrogen gas discharged from the cooler 15. The dehumidifier 16 contains an adsorbent 14 to further remove moisture from the hydrogen gas from which condensed water has been separated in the gas-liquid separator 15A. This moisture originates from saturated water vapor that was not separated into gas and liquid by the cooler 15 and the gas-liquid separator 15A, among the water vapor accompanying the hydrogen gas discharged from the generated hydrogen discharge main pipe 209. Note that the cooler 15 and the gas-liquid separator 15A may be integrated into a single structure. Furthermore, the water recovered by the gas-liquid separator 15A can be returned to the water supply line 340 and used as a raw material for steam supply, thereby reducing the amount of water supplied from outside the system.

[0022] The hydrogen gas supply line 410 includes a first hydrogen gas supply line 41 connected to the steam electrolyzer 201 and the cooler 15, and a second hydrogen gas supply line 42 connected to the cooler 15 and the hydrogen supply target 3. The dehumidifier 16 and the hydrogen compressor 6 are located on the second hydrogen gas supply line 42.

[0023] The adsorbent 14 of the dehumidifier 16 needs to be regenerated to remove moisture from the adsorbent 14. The hydrogen gas supply system 2A according to this embodiment further includes a first regeneration gas supply line 18. The first regeneration gas supply line 18 is configured to return the dehumidified hydrogen gas discharged from the dehumidifier 16 to the dehumidifier 16 as a regeneration gas for the adsorbent 14. The term "regeneration gas" is synonymous with "dehumidified hydrogen gas."

[0024] Although Figure 2, which is a schematic diagram, shows a single dehumidifier 16 on the second hydrogen gas supply line 42, this disclosure does not exclude a configuration in which multiple dehumidifiers 16 are arranged in parallel on the second hydrogen gas supply line 42. Therefore, a configuration in which multiple first regeneration gas supply lines 18 are connected to multiple dehumidifiers 16 may also be adopted.

[0025] The hydrogen gas supply system 2A further includes a regeneration gas discharge line 10A (10) for guiding the regeneration gas (regeneration gas after it has been used to regenerate the adsorbent 14) discharged from the dehumidifier 16 to the steam electrolysis device 201. The regeneration gas flowing through the regeneration gas discharge line 10A originates from the hydrogen gas discharged from the cooler 15 and therefore has a relatively low temperature.

[0026] The hydrogen gas supply system 2A further includes a first heat exchanger 8. The first heat exchanger 8 is configured to exchange heat between the regeneration gas flowing through the regeneration gas discharge line 10A and the hydrogen gas flowing through the first hydrogen gas supply line 41. The hydrogen gas flowing through the first hydrogen gas supply line 41 is at a higher temperature than the regeneration gas flowing through the regeneration gas discharge line 10A. The first heat exchanger 8 according to this embodiment is configured to lower the temperature of the hydrogen gas flowing through the first hydrogen gas supply line 41 and to raise the temperature of the regeneration gas flowing through the regeneration gas discharge line 10A.

[0027] The regeneration gas discharge line 10A includes a first regeneration gas discharge line 11 for guiding the regeneration gas discharged from the dehumidifier 16 to the hydrogen gas recirculation line 9 described later. On the first regeneration gas discharge line 11, in addition to the first heat exchanger 8 described above, there is a regeneration gas blower 21 for pressurizing the regeneration gas, a buffer tank 30A(30) configured to store the regeneration gas, and a regeneration gas valve 29A(29) positioned between the buffer tank 30A and the first heat exchanger 8. The regeneration gas valve 29A(29) may be, for example, a solenoid valve (PCV). On the first regeneration gas discharge line 11, the regeneration gas blower 21 is located upstream of the first heat exchanger 8, and the buffer tank 30A(30) is located upstream of the regeneration gas blower 21.

[0028] The hydrogen gas supply system 2A further includes a hydrogen gas recirculation line 9 that branches off from the first hydrogen gas supply line 41 upstream of the cooler 15. The hydrogen gas recirculation line 9 is configured to guide the hydrogen gas extracted from the first hydrogen gas supply line 41 to the steam electrolysis unit 201. More specifically, the inlet of the hydrogen gas recirculation line 9 is connected to the first hydrogen gas supply line 41, and the outlet of the hydrogen gas recirculation line 9 is connected to the connection point Q between the steam supply line 344 and the raw material gas supply line 346. The hydrogen gas extracted by the hydrogen gas recirculation line 9 merges with steam from the steam supply line 344 at the connection point Q. The hydrogen gas and the raw material gas containing the hydrogen gas are guided to the steam electrolysis unit 201 via the raw material gas supply line 346.

[0029] The hydrogen gas supply system 2A further includes a recirculation blower 20 for guiding hydrogen gas extracted from the first hydrogen gas supply line 41 and regenerative gas discharged from the dehumidifier 16 to the steam electrolysis device 201. In the first embodiment, the recirculation blower 20 is located on the hydrogen gas recirculation line 9. More specifically, the recirculation blower 20 is located downstream of the connection point S where the first regenerative gas discharge line 11 connects to the hydrogen gas recirculation line 9.

[0030] The operation overview of the hydrogen gas supply system 2A(2) is described below. Hydrogen gas flowing through the first hydrogen gas supply line 41 flows into the cooler 15 via the first heat exchanger 8. In addition, a portion of the hydrogen gas flowing through the same line flows into the hydrogen gas recirculation line 9 upstream of the first heat exchanger 8. Hydrogen gas discharged from the cooler 15 flows through the second hydrogen gas supply line 42. The hydrogen gas separates condensed water in the gas-liquid separator 15A, is dehumidified in the dehumidifier 16, and then compressed in the hydrogen compressor 6. The hydrogen compressor 6 sends the compressed hydrogen gas to the hydrogen supply target 3.

[0031] A portion of the hydrogen gas discharged from the dehumidifier 16 flows through the first regeneration gas supply line 18 as regeneration gas. After the regeneration gas has dehydrated the adsorbent 14 in the dehumidifier 16, it is discharged into the buffer tank 30A. When the regeneration gas valve 29A is opened, the regeneration gas stored in the buffer tank 30A flows towards the hydrogen gas recirculation line 9 by the regeneration gas blower 21. At this time, since the recirculation blower 20 is located downstream of the connection point S between the hydrogen gas recirculation line 9 and the first hydrogen gas supply line 41, it sends the hydrogen gas flowing through the hydrogen gas recirculation line 9 and the regeneration gas discharged from the dehumidifier 16 to the raw material gas supply line 346.

[0032] The hydrogen gas flowing through the hydrogen gas recirculation line 9 and the regenerative gas flowing through the first regenerative gas discharge line 11 merge at connection point S. Both gases pass through the recirculation blower 20 and flow into the raw material gas supply line 346. The raw material gas supply line 346 leads the raw material gas, which contains hydrogen gas and water vapor, to the water vapor electrolysis device 201. The proportion of hydrogen gas in the raw material gas is approximately 3% to 50%.

[0033] According to the above configuration, the regeneration gas flowing into the regeneration gas blower 21 is a low-temperature gas of about 50°C discharged from the dehumidifier 16. The gas temperature after the regeneration gas flowing through the return line L merges with the regeneration gas is lower than the gas discharged from the steam electrolysis device 201 (flowing upstream of the cooler 15). Therefore, the heat resistance temperature of the regeneration gas blower 21 can be lowered. As a result, the cost of the blower that returns hydrogen gas to the steam electrolysis device 201 can be reduced. In addition, since the hydrogen gas discharged from the dehumidifier 16 is returned to the raw material gas supply line 346 and reused as raw material gas without being released outside the system, the loss of hydrogen gas produced in the steam electrolysis device 201 can be reduced. Therefore, the amount of hydrogen gas supplied to the hydrogen supply target 3 can be increased. Furthermore, in a configuration in which a recirculation blower 20 is provided in addition to the regeneration gas blower 21, the recirculation blower 20 is responsible for sending the regeneration gas supplied from the first regeneration gas discharge line 11 to the steam electrolysis device 201. This reduces the pressure boosted by the regeneration gas blower 21, thereby reducing the power required for the regeneration gas blower 21. Note that the recirculation blower 20 is not an essential component of this disclosure (details will be described later using Figure 3).

[0034] Furthermore, with the configuration that includes the first heat exchanger 8, the temperature of the hydrogen gas flowing from the first hydrogen gas supply line 41 into the cooler 15 can be lowered, thereby reducing the cooling capacity required by the cooler 15. Furthermore, the temperature of the regenerating gas flowing through the first regenerating gas discharge line 11 can be increased, and as long as it is below the heat resistance temperature of the recirculation blower 20, the temperature of the hydrogen gas returning to the steam electrolysis device 201 can be increased. Here, in order to increase the conductivity of oxygen ions in the solid electrolyte 111 of the steam electrolysis device 201, it is necessary to raise the temperature of the steam electrolysis chamber (not shown) inside the steam electrolysis device 201, so it is preferable that the temperature of the raw material gas flowing through the raw material gas supply line 346 is also higher. In this embodiment, by increasing the temperature of the regenerating gas returning from the first regenerating gas discharge line 11 to the raw material gas supply line 346, the heat input to the superheater installed in the raw material gas supply line 346 can be suppressed, and the thermal efficiency of the hydrogen production system 310 can be increased.

[0035] Furthermore, in a configuration that includes a hydrogen gas recirculation line 9, in addition to the regeneration gas discharged from the dehumidifier 16, hydrogen gas flowing through the hydrogen gas recirculation line 9 returns to the steam electrolysis device 201. Therefore, even if the flow rate of regeneration gas required for the regeneration of the adsorbent 14 is small, the amount of hydrogen gas returning to the electrolytic cell 105 can be secured. Thus, the reducing atmosphere of the hydrogen electrode 109 of the electrolytic cell 105 can be secured more reliably, and damage to the hydrogen electrode 109 can be avoided. Furthermore, the higher the pressure of the raw material gas in the raw material gas supply line 346, the less regeneration gas flow is required to regenerate the adsorbent 14. The higher the pressure, the greater the pressure difference between the partial pressure of water vapor in the dehumidifier 16 and the pressure in the first regeneration gas discharge line 11. As a result, the desorption effect of the water contained in the adsorbent 14 can be enhanced, and the amount of adsorbent 14 required can be reduced.

[0036] Furthermore, with the buffer tank 30A(30) located in the first regeneration gas discharge line 11, the regeneration gas can be intermittently supplied to the steam electrolysis device 201 at a desired timing.

[0037] <Hydrogen gas supply system 2B(2) according to the second embodiment> Figure 3 is a schematic diagram of the hydrogen gas supply system 2B(2) according to the second embodiment. In Figure 3, the same reference numerals are used for the same components as in the hydrogen gas supply system 2A according to the first embodiment.

[0038] The hydrogen gas supply system 2B is equipped with a regenerative gas discharge line 10B (10) in place of the regenerative gas discharge line 10A (see Figure 2). The regenerative gas discharge line 10B is connected to the dehumidifier 16 and the steam supply line 344. The regenerative gas discharge line 10B includes a second regenerative gas discharge line 12 for guiding the regenerative gas discharged from the dehumidifier 16 to the first heat exchanger 8, and a third regenerative gas discharge line 13 for guiding the regenerative gas discharged from the first heat exchanger 8 to connection point Q.

[0039] The second regeneration gas discharge line 12 includes a buffer tank 30B(30) and a regeneration gas valve 29B(29). Furthermore, in the second embodiment, a regeneration gas blower 21 is also located on the second regeneration gas discharge line 12. The regeneration gas blower 21 is located between the buffer tank 30B(30) and the first heat exchanger 8.

[0040] In the second embodiment, the regeneration gas discharged from the dehumidifier 16 flows through the second regeneration gas discharge line 12 and is stored in the buffer tank 30B. When the regeneration gas valve 29B(29) is opened, the regeneration gas in the buffer tank 30B is pressurized by the regeneration gas blower 21 to a pressure higher than the connection point Q with the steam supply line 344 and sent towards the raw material gas supply line 346. The sent regeneration gas passes through the first heat exchanger 8, reaches the connection point Q, and merges with the water vapor from the steam supply line 344.

[0041] In the second embodiment, the regeneration gas blower 21 is positioned on the second regeneration gas discharge line 12. With this configuration, the recirculation blower 20 (see Figure 2) is unnecessary. That is, the only blower positioned on the regeneration gas discharge line 10B is the regeneration gas blower 21. Furthermore, the temperature of the regeneration gas flowing into the regeneration gas blower 21 is, for example, around 50°C, which is lower than the temperature of the hydrogen gas flowing through the first hydrogen gas supply line 41. As a result, the gas density of the regeneration gas increases, making it possible to pressurize the regeneration gas more efficiently.

[0042] With the buffer tank 30B positioned on the second regeneration gas discharge line 12, pressure fluctuations caused by the intermittently discharged regeneration gas from the dehumidifier 16 can be mitigated, and the regeneration gas can be stably and continuously supplied to the steam electrolysis device 201.

[0043] Furthermore, the hydrogen gas supply system 2B according to the second embodiment does not include a hydrogen gas recirculation line 9 (see Figure 1). This is because, if a sufficient flow rate of regenerating gas can be secured through the regenerating gas discharge line 10B, the hydrogen gas returned to the raw material gas supply line 346 can be supplied solely by the regenerating gas flowing through the regenerating gas discharge line 10B. For example, if the pressure of the raw material gas in the raw material gas supply line 346 is relatively low, the flow rate of regenerating gas required for the regeneration of the adsorbent 14 increases, and this can be supplied solely by the regenerating gas flowing through the regenerating gas discharge line 10B.

[0044] <Hydrogen gas supply system 2C(2) according to the third embodiment> Figure 4 is a schematic diagram of the hydrogen gas supply system 2C(2) according to the third embodiment. In Figure 4, the same reference numerals are used for the same components as in the hydrogen gas supply system 2B according to the second embodiment.

[0045] The hydrogen gas supply system 2C includes a second regenerative hydrogen gas supply line 18A in place of the first regenerative gas supply line 18 (see Figure 3). The second regenerative hydrogen gas supply line 18A is configured to extract hydrogen gas discharged from the hydrogen compressor 6 from the second hydrogen gas supply line 42 and return it to the dehumidifier 16 as regenerative gas. The second regenerative hydrogen gas supply line 18A includes a line connected to the outlet of the hydrogen compressor 6 and the second heat exchanger 8A, and a regenerative hydrogen gas valve 28 is located on this line. The second heat exchanger 8A is configured to raise the temperature of the regenerative gas by exchanging heat between the regenerative gas flowing through the second regenerative hydrogen gas supply line 18A and the hydrogen gas flowing upstream of the cooler 15 in the hydrogen gas supply line 410. The regenerative gas heated in the second heat exchanger 8A flows into the dehumidifier 16.

[0046] The regeneration gas discharge line 10C(10) according to the third embodiment differs from the regeneration gas discharge lines 10A and 10B according to the first and second embodiments in that it is not equipped with a blower (recirculation blower 20 and regeneration gas blower 21). The regeneration gas discharge line 10C is equipped with a buffer tank 30B(30) similar to that of the second embodiment.

[0047] In the third embodiment, if the desiccant in the dehumidifier 16 is of a type that is regenerated by heating, the regenerating hydrogen gas is heated in the second heat exchanger 8A to the temperature necessary for the regeneration of the adsorbent 14 before being supplied to the dehumidifier 16. If the pressure ratio of the hydrogen compressor 6 is high and the hydrogen temperature at the outlet of the hydrogen compressor 6 becomes sufficiently high due to compression, the hydrogen gas may be supplied directly to the dehumidifier 16 without being heated in the second heat exchanger 8A. An electric heater may also be provided for use when the system is started up. Since the regenerating hydrogen gas is extracted from the outlet of the hydrogen compressor 6, the regenerating hydrogen gas discharged from the dehumidifier 16 is supplied to the buffer tank 30B while maintaining a pressure higher than the connection point Q with the steam supply line 344, and after the pressure fluctuations are mitigated, it is sent to the raw material gas supply line 346.

[0048] In the third embodiment, the hydrogen gas discharged from the outlet of the hydrogen compressor 6 is supplied to the dehumidifier 16 as the regeneration gas. With this configuration, the pressure of the regeneration hydrogen gas can be made higher than the pressure at connection point Q, so the regeneration gas can be supplied to the dehumidifier 16 by opening and closing the regeneration hydrogen gas valve 28 without using the regeneration gas blower 21 and the recirculation blower 20. Eliminating the need for the regeneration gas blower 21 and the recirculation blower 20 means reducing the cost of the blower that returns the hydrogen gas to the steam electrolysis device 201 to zero. Furthermore, since the hydrogen gas whose temperature has risen due to compression by the hydrogen compressor 6 is directly supplied to the dehumidifier 16 as a regeneration gas, it is possible to miniaturize the second heat exchanger 8A by reducing the amount of heat required for heating, or to remove the second heat exchanger 8A if the pressure ratio is high and the hydrogen gas temperature is above the temperature required for regeneration of the adsorbent. Furthermore, by returning the regeneration gas discharged from the dehumidifier 16 to the steam supply line 344 of the steam electrolysis device 201, the release of generated hydrogen outside the system is eliminated, and the raw material gas supply line 346 can be kept in a reduced state. In other words, the loss of hydrogen gas can be reduced.

[0049] Furthermore, with the buffer tank 30B(30) positioned in the regeneration gas discharge line 10C, the regeneration gas can be intermittently and stably delivered to the steam electrolysis device 201 at the desired timing.

[0050] <Summary> The contents described in some of the embodiments above can be understood, for example, as follows:

[0051] 1) A hydrogen production system (310) according to at least one embodiment of the present disclosure is A steam electrolysis apparatus (201) including a solid oxide type electrolytic cell (105) configured to generate hydrogen gas from water vapor, A hydrogen gas supply line (410) for guiding the hydrogen gas discharged from the steam electrolysis apparatus to the hydrogen supply target (3), A cooler (15) for cooling the hydrogen gas is placed on the hydrogen gas supply line, A dehumidifier located downstream of the cooler in the hydrogen gas supply line, comprising a dehumidifier (16) containing an adsorbent (14) for recovering moisture from the hydrogen gas flowing downstream of the cooler, A regeneration gas supply line (18) for extracting the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line and returning it to the dehumidifier as a regeneration gas for the adsorbent, A regeneration gas blower (21) for supplying the regeneration gas discharged from the dehumidifier to the water vapor electrolysis device, It is equipped with.

[0052] According to the configuration described in 1) above, the regeneration gas flowing into the regeneration gas blower is the regeneration gas at approximately 50°C used to regenerate the adsorbent in the dehumidifier, and has a relatively lower temperature compared to the hydrogen gas flowing into the cooler. Therefore, the heat resistance temperature of the regeneration gas blower can be lowered. As a result, the cost of the regeneration gas blower can be reduced.

[0053] 2) In some embodiments, the hydrogen production system described in 1) above, The hydrogen gas supply line includes a first hydrogen gas supply line (41) connected to the steam electrolysis apparatus and the cooler, The aforementioned hydrogen production system A regeneration gas discharge line (10) for guiding the regeneration gas discharged from the dehumidifier to the water vapor electrolysis device, The system further includes a first heat exchanger (8) configured to lower the temperature of the hydrogen gas flowing through the first hydrogen gas supply line by exchanging heat between the regenerating gas flowing through the regenerating gas discharge line and the hydrogen gas flowing through the first hydrogen gas supply line.

[0054] According to the configuration described in 2) above, the temperature of the hydrogen gas flowing into the cooler from the first hydrogen gas supply line can be lowered, thereby reducing the heat loss discharged from the cooler to the outside of the system. In addition, the temperature of the regenerating gas flowing through the regenerating gas discharge line can be increased. Since the temperature of the hydrogen gas returning to the steam electrolysis device can be increased, the efficiency of hydrogen gas generation by the steam electrolysis device can also be improved.

[0055] 3) In some embodiments, the hydrogen production system is as described in 2) above, It includes a second regenerative gas discharge line (12) for guiding the regenerative gas discharged from the dehumidifier to the heat exchanger, The regeneration gas blower is positioned on the second regeneration gas discharge line.

[0056] According to the configuration described in 3) above, the temperature of the regenerated gas flowing into the regenerated gas blower is sufficiently low because it is the gas that has been regenerated from the dehumidifier, and a circulation gas blower for recirculating hydrogen gas is not required, thus reducing the number of blowers.

[0057] 4) In some embodiments, the hydrogen production system is as described in 3) above, The system further includes a buffer tank (30) located on the second regeneration gas discharge line for storing the regeneration gas.

[0058] According to the configuration described in 4) above, pressure fluctuations caused by regeneration gas from the dehumidifier, which is discharged intermittently, can be mitigated, and regeneration gas can be stably and continuously supplied to the steam electrolysis device.

[0059] 5) In some embodiments, the hydrogen production system is as described in any of 1) to 4) above, A hydrogen gas recirculation line that branches off from the hydrogen gas supply line upstream of the cooler, further comprising a hydrogen gas recirculation line (9) for guiding the hydrogen gas extracted from the hydrogen gas supply line to the steam electrolysis device.

[0060] According to the configuration described in 5) above, in addition to the regeneration gas discharged from the dehumidifier, hydrogen gas flowing through the hydrogen gas recirculation line returns to the steam electrolysis device. Therefore, even if the flow rate of regeneration gas required for adsorbent regeneration is low, the amount of hydrogen gas returning to the solid oxide electrolytic cell can be secured. Thus, a reducing atmosphere can be more reliably secured for the hydrogen electrode of the solid oxide electrolytic cell, and damage to the hydrogen electrode can be avoided.

[0061] 6) In some embodiments, the hydrogen production system is as described in 5) above, A first regenerative gas discharge line (11) for guiding the regenerative gas discharged from the dehumidifier to the hydrogen gas recirculation line, In the hydrogen gas recirculation line, a recirculation blower (20) is located downstream of the point where the first regenerative gas discharge line connects to the hydrogen gas recirculation line (connection point S). To further prepare.

[0062] According to the configuration described in 6) above, the recirculation blower is responsible for supplying the hydrogen gas extracted by the hydrogen gas recirculation line and the regenerative gas discharged from the dehumidifier to the steam electrolysis device. The recirculation blower reduces the pressure increase required by the regenerative gas blower, thus reducing the power required by the regenerative gas blower. Furthermore, by mixing hydrogen gas extracted from the hydrogen gas supply line with low-temperature regeneration gas, the gas temperature at the recirculation blower inlet is reduced, which lowers the heat resistance temperature of the recirculation blower. Additionally, the density of the gas increases, which reduces the cost and power required for the recirculation blower that returns the gas to the steam electrolysis device.

[0063] 7) In some embodiments, the hydrogen production system is as described in 6) above, The system further includes a buffer tank (30) located on the first regeneration gas discharge line for storing the regeneration gas.

[0064] According to the configuration described in 7) above, pressure fluctuations caused by the regeneration gas from the dehumidifier, which is discharged intermittently, can be mitigated, and the regeneration gas can be stably and continuously supplied to the steam electrolysis device.

[0065] 8) A hydrogen production system (310) according to one embodiment of the present disclosure is A steam electrolysis apparatus (201) including an electrolytic cell (105) configured to generate hydrogen gas from water vapor, A hydrogen gas supply line (410) for guiding the hydrogen gas discharged from the steam electrolysis apparatus to the hydrogen supply target, A cooler (15) for cooling the hydrogen gas is placed on the hydrogen gas supply line, A dehumidifier located downstream of the cooler in the hydrogen gas supply line, comprising a dehumidifier (16) containing an adsorbent (14) for recovering moisture from the hydrogen gas flowing downstream of the cooler, A hydrogen compressor (6) is positioned on the hydrogen gas supply line and compresses the dehumidified hydrogen gas discharged from the dehumidifier and sends it to the hydrogen supply target, A second regeneration gas supply line (18A) extracts the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line downstream of the hydrogen compressor and returns it to the dehumidifier as a regeneration gas for the adsorbent, A regeneration gas discharge line (10C) for guiding the regeneration gas discharged from the dehumidifier to the steam electrolysis device, and It is equipped with.

[0066] According to the configuration described in 8) above, the regenerative gas extracted by the second regenerative gas supply line using the power of the hydrogen compressor can pass through the dehumidifier and return to the steam electrolysis device. Since there is no need to place a blower on the regenerative gas discharge line, the cost of a blower to return the hydrogen gas to the steam electrolysis device can be reduced to zero. In addition, since the regenerative gas discharged from the dehumidifier is returned to the steam electrolysis device, hydrogen gas loss can be reduced.

[0067] 9) In some embodiments, the hydrogen production system is as described in 8) above, The system further includes a second heat exchanger (8A) for raising the temperature of the regenerating gas by exchanging heat between the regenerating gas flowing through the second regenerating gas supply line (18A) and the hydrogen gas flowing upstream of the cooler in the hydrogen gas supply line.

[0068] According to the configuration in 9) above, a heat source can be secured for the regeneration gas flowing into the dehumidifier, thus preventing insufficient regeneration of the adsorbent.

[0069] 10) In some embodiments, the hydrogen production system is as described in 9) above, The system is further equipped with a buffer tank (30) located on the regeneration gas discharge line for storing the regeneration gas.

[0070] According to the configuration described in 10) above, pressure fluctuations caused by regeneration gas from the dehumidifier, which is discharged intermittently, can be mitigated, and regeneration gas can be stably and continuously supplied to the steam electrolysis device.

[0071] 11) In some embodiments, a hydrogen production system according to any one of 1) to 10) above, The system further includes a gas-liquid separator (15A) positioned between the cooler and the dehumidifier on the hydrogen gas supply line for separating condensed water from the hydrogen gas discharged from the cooler.

[0072] According to the configuration described in 11) above, condensed water in the cooler can be recovered from hydrogen gas. [Explanation of symbols]

[0073] 2A, 2B, 2C(2): Hydrogen gas supply system 3: Target of hydrogen supply 6: Hydrogen gas compressor 8 :1st heat exchanger 8A: 2nd heat exchanger 9: Hydrogen gas recirculation line 10A, 10B, 10C (10): Regeneration gas discharge line 11: First regeneration gas discharge line 12: Second regeneration gas discharge line 13: Third regenerative gas discharge line 14: Adsorbent 15:Cooler 15A: Gas-liquid separator 16:Dehumidifier 18: Regeneration gas supply line 18A: Hydrogen gas supply line for regeneration 20: Recirculation blower 21: Gas blower for regeneration 28: Gas valve for regeneration 29A, 29B (29): Gas valve for regeneration 30A, 30B (30): Buffer Tank 41: First hydrogen gas supply line 42: Second hydrogen gas supply line 105: Electrolytic cell 109: Hydrogen electrode 111: Solid electrolyte 113: Oxygen electrode 201: Steam electrolysis apparatus 207: Steam supply main pipe 209: Hydrogen-generated discharge main pipe 310: Hydrogen production system 340: Water supply line 341: Water supply pump 342: Flow control valve 343: Steam generator 344: Steam supply line 346: Raw material gas supply line 410: Hydrogen gas supply line 510: Oxidizing gas intake line 511: Oxidizing gas compressor 512: Oxidizing gas cooler 513: Oxidizing gas supply line 514: Oxidizing gas emission line 515: Expander 516: Oxidizing gas emission line 517: Vent Stack 650: Power supply L: Return line Q,S: Connection point

Claims

1. A steam electrolysis apparatus including an electrolytic cell configured to generate hydrogen gas from water vapor, A hydrogen gas supply line for guiding the hydrogen gas discharged from the steam electrolysis apparatus to a hydrogen supply target, A cooler is placed on the hydrogen gas supply line for cooling the hydrogen gas, A dehumidifier located downstream of the cooler in the hydrogen gas supply line, comprising an adsorbent for recovering moisture from the hydrogen gas flowing downstream of the cooler, A regeneration gas supply line for extracting the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line and returning it to the dehumidifier as a regeneration gas for the adsorbent, A regeneration gas blower for supplying the regeneration gas discharged from the dehumidifier to the water vapor electrolysis device, Equipped with Hydrogen production system.

2. The hydrogen gas supply line includes a first hydrogen gas supply line connected to the steam electrolysis apparatus and the cooler, The aforementioned hydrogen production system A regeneration gas discharge line for guiding the regeneration gas discharged from the dehumidifier to the steam electrolysis device, The system further comprises a first heat exchanger configured to lower the temperature of the hydrogen gas flowing through the first hydrogen gas supply line by exchanging heat between the regenerating gas flowing through the regenerating gas discharge line and the hydrogen gas flowing through the first hydrogen gas supply line. The hydrogen production system according to claim 1.

3. The system includes a second regenerative gas discharge line for guiding the regenerative gas discharged from the dehumidifier to the first heat exchanger, The regeneration gas blower is positioned on the second regeneration gas discharge line. The hydrogen production system according to claim 2.

4. The system is located on the second regeneration gas discharge line and further comprises a buffer tank for storing the regeneration gas. The hydrogen production system according to claim 3.

5. A hydrogen gas recirculation line that branches off from the hydrogen gas supply line upstream of the cooler, further comprising a hydrogen gas recirculation line for guiding the hydrogen gas extracted from the hydrogen gas supply line to the steam electrolysis apparatus. A hydrogen production system according to claim 1 or 2.

6. A first regenerative gas discharge line for guiding the regenerative gas discharged from the dehumidifier to the hydrogen gas recirculation line, In the hydrogen gas recirculation line, a recirculation blower is located downstream of the point where the first regenerative gas discharge line connects to the hydrogen gas recirculation line, Furthermore, it is equipped with The hydrogen production system according to claim 5.

7. The system is located on the first regeneration gas discharge line and further comprises a buffer tank for storing the regeneration gas. The hydrogen production system according to claim 6.

8. A steam electrolysis apparatus including an electrolytic cell configured to generate hydrogen gas from water vapor, A hydrogen gas supply line for guiding the hydrogen gas discharged from the steam electrolysis apparatus to a hydrogen supply target, A cooler is placed on the hydrogen gas supply line for cooling the hydrogen gas, A dehumidifier located downstream of the cooler in the hydrogen gas supply line, comprising an adsorbent for recovering moisture from the hydrogen gas flowing downstream of the cooler, A hydrogen compressor is positioned on the hydrogen gas supply line and compresses the dehumidified hydrogen gas discharged from the dehumidifier and sends it to the hydrogen supply target. A second regeneration gas supply line for extracting the dehumidified hydrogen gas discharged from the dehumidifier from the hydrogen gas supply line downstream of the hydrogen compressor and returning it to the dehumidifier as a regeneration gas for the adsorbent, A regeneration gas discharge line for guiding the regeneration gas discharged from the dehumidifier to the steam electrolysis device, A hydrogen production system equipped with the following features.

9. The system further includes a second heat exchanger for raising the temperature of the regenerating gas by exchanging heat between the regenerating gas flowing through the second regenerating gas supply line and the hydrogen gas flowing upstream of the cooler in the hydrogen gas supply line. The hydrogen production system according to claim 8.

10. The regeneration gas discharge line is positioned and further comprises a buffer tank for storing the regeneration gas. The hydrogen production system according to claim 9.

11. The hydrogen gas supply line further comprises a gas-liquid separator positioned between the cooler and the dehumidifier for separating condensed water from the hydrogen gas discharged from the cooler. A hydrogen production system according to claim 1 or 8.

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