Hydrogen production system and hydrogen production method

Abstract

This hydrogen production system and hydrogen production method are provided with: a heat exchanger for heating water vapor using a heat medium that has been heated by thermal energy at 600 DEG C or higher; a high-temperature water vapor electrolysis device that applies a voltage to the high-temperature water vapor electrolysis tank, said voltage being lower than the potential of a thermal neutral point in which Joule heating accompanying the application of current and endothermic equilibrium accompanying the electrolysis reaction are performed, and electrolyzes water vapor at 600 DEG C or higher to produce hydrogen; and a heating device for heating the high-temperature water vapor electrolysis device with water vapor.

Description

Technical Field

[0001] The present disclosure relates to a hydrogen production system and a hydrogen production method. Background Art

[0002] As one of the hydrogen production technologies, there is a high-temperature steam electrolysis method. The electrolysis method has the advantages of cheap raw materials and no carbon dioxide (CO2) is produced in the hydrogen production process. However, the electrolysis method generates hydrogen by electrolysis, so there is a problem of high cost of electricity. Therefore, the high-temperature steam electrolysis method is considered to reduce the electricity required for electrolysis by electrolyzing high-temperature steam above 700°C.

[0003] However, it is difficult to generate high-temperature steam above 700°C. In the past, water was heated by boilers, electric furnaces, etc. to generate steam, and the steam was electrolyzed to generate hydrogen. In addition, the decomposition of water is an endothermic reaction. When 1 mol of water is electrolyzed, 286 kilojoules of heat must be supplied from the outside. Therefore, in the past, the water vapor was electrolyzed at 700°C to 900°C while the Joule heat of the high-temperature steam electrolyzer was used to supplement the heat absorbed by the water during electrolysis and the sensible heat of the steam. As such an existing hydrogen manufacturing device, there is, for example, a device described in the following Patent Document 1.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-041202 Summary of the invention

[0007] Problems to be solved by the invention

[0008] A hydrogen manufacturing device using high-temperature steam electrolysis can reduce the electric energy consumed by the electrolysis of water by using high-temperature steam. However, in reality, the existing hydrogen manufacturing device uses the necessary electric energy to provide the energy for generating high-temperature steam at a temperature equivalent to the operating temperature of the electrolysis of water, and also uses electric energy to provide the endothermic reaction of the electrolysis of water. That is, the existing high-temperature steam electrolyzer operates at a potential of the thermoneutral point or a potential above the thermoneutral point, which achieves a balance between the endothermic absorption of water electrolysis and the heat release of the water electrolyzer, and consumes a lot of electric energy. Most of the cost of hydrogen production using high-temperature steam electrolysis is electricity. If most of this electricity can be provided by renewable energy, carbon dioxide can be reduced. However, the power supply of renewable energy is unstable, and therefore, it is difficult to apply to large-scale and stable hydrogen production. On the other hand, the electric energy generated by the thermal power generation system is accompanied by the generation of carbon dioxide.

[0009] The present disclosure aims to solve the above-mentioned problems and to provide a hydrogen production system and a hydrogen production method that can reduce the electric energy cost when producing hydrogen and suppress the generation of carbon dioxide.

[0010] Solutions to the problem

[0011] The hydrogen manufacturing system disclosed in the present invention for achieving the above-mentioned purpose comprises: a heat exchanger, which heats a heat medium by heat energy above 600°C, and uses the above-mentioned heat medium after the heating to heat water vapor; and a high-temperature steam electrolysis device, which applies a voltage lower than the voltage of the thermal neutral point to the high-temperature steam electrolysis cell, and electrolyzes the above-mentioned water vapor above 600°C to produce hydrogen, wherein the voltage of the thermal neutral point is the voltage when the thermal equilibrium is 0 due to the balance between the Joule heating accompanied by the application of current and the endothermic equilibrium accompanied by the electrolysis reaction.

[0012] In addition, the hydrogen production method disclosed in the present invention includes: a process of generating thermal energy above 600°C; a process of superheating water vapor to above 600°C using a heat medium heated by the above thermal energy; a process of heating a high-temperature water vapor electrolyzer with the above water vapor; and a process of electrolyzing the above water vapor to produce hydrogen by applying a voltage lower than the voltage of the thermal neutral point to the above-mentioned high-temperature water vapor electrolyzer, wherein the voltage of the thermal neutral point is the voltage when the thermal equilibrium is 0 due to the balance between the Joule heating accompanied by the application of current and the endothermic heat accompanied by the electrolysis reaction in the above-mentioned high-temperature water vapor electrolyzer.

[0013] Effects of the Invention

[0014] According to the hydrogen production system and hydrogen production method of the present disclosure, it is possible to reduce the electric energy cost when producing hydrogen and suppress the generation of carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram showing the configuration of the hydrogen manufacturing system according to the first embodiment.

[0016] Figure 2 It is a graph showing the relationship between the voltage and thermal energy of a high-temperature steam electrolysis device.

[0017] Figure 3 This is a graph showing the temperature change of the high-temperature steam electrolysis cell when the high-temperature steam electrolysis device is switched from no-load operation to operation at 1.1 V, which is lower than the potential of the thermal neutral point.

[0018] Figure 4 This is a graph showing the voltage change of the high-temperature steam electrolysis cell when the high-temperature steam electrolysis device is switched from no-load operation to operation at 1.1 V, which is lower than the potential of the thermal neutral point.

[0019] Figure 5This is a graph showing changes in the current flowing in the high-temperature steam electrolysis cell when the conditions of the fluid flowing to the air electrode of the high-temperature steam electrolysis device are changed.

[0020] Figure 6 This is a table showing the relationship between OCV, which is the steam utilization rate of a high-temperature steam electrolysis device, and the potential difference between OCV and a voltage, for example, 1.1 V, which is a voltage lower than the potential of the thermal neutral point.

[0021] Figure 7 This is a graph showing changes in current when the concentration of water vapor supplied to the hydrogen electrode of the high-temperature water vapor electrolysis device is changed.

[0022] Figure 8 It is a schematic diagram showing the configuration of a hydrogen manufacturing system according to a second embodiment.

[0023] Fig. 9 It is a schematic diagram showing the configuration of a hydrogen manufacturing system according to a third embodiment.

[0024] Explanation of symbols

[0025] 10, 10A, 10B Hydrogen Manufacturing System

[0026] 11 Heat Source

[0027] 12 Heat exchanger

[0028] 13 High temperature steam electrolysis device

[0029] 14 Heating device

[0030] 21 Intermediate heat exchanger

[0031] 22 Supply head

[0032] 23 Reflux Head

[0033] 24 Circulation Machine

[0034] 31 Steam generator

[0035] 321st heat exchanger

[0036] 33 2nd heat exchanger

[0037] 34 Hydrogen side heat exchanger

[0038] 35 Oxygen side heat exchanger

[0039] 36, 38 Heat recovery device

[0040] 37, 39 Condenser

[0041] 41 Circulation Machine

[0042] 51 High temperature steam electrolyzer

[0043] 51a Electrolyte layer

[0044] 51b Porous hydrogen electrode layer

[0045] 51c Porous oxygen electrode layer

[0046] 61, 62, 63, 64 flow control valve

[0047] 65 Hydrogen side temperature regulator

[0048] 66 Oxygen side temperature regulator

[0049] 67 Temperature Sensor

[0050] 71 Steam Head

[0051] 72 Check valve

[0052] L11 loop path

[0053] L12 Supply Path

[0054] L13 Return path

[0055] L14, L15, L16, L17, L18 heat medium supply path

[0056] L31 Water supply path

[0057] L32 1st water vapor supply path

[0058] L33 Second water vapor supply path

[0059] L34 Hydrogen side water vapor supply path

[0060] L35 Hydrogen exhaust path

[0061] L36 Circulation Route

[0062] L41, L42 gas supply path

[0063] L43 Oxygen side water vapor supply path

[0064] L44 Oxygen exhaust path

[0065] L45 Circulation Route

[0066] L51 Power supply path

[0067] L71 Hydrogen side steam branch

[0068] L72 Oxygen side steam branch DETAILED DESCRIPTION

[0069] Hereinafter, the preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the embodiments, and in addition, when there are multiple embodiments, embodiments formed by combining the embodiments are also included. In addition, the constituent elements in the embodiments include constituent elements that can be easily thought of by those skilled in the art, substantially the same constituent elements, and so-called constituent elements in the equivalent range.

[0070] [First embodiment]

[0071] <Hydrogen production system>

[0072] Figure 1 It is a schematic diagram showing the configuration of the hydrogen manufacturing system according to the first embodiment.

[0073] In the first embodiment, if Figure 1 As shown, the hydrogen production system 10 includes a heat source 11 , a heat exchanger 12 , a solid electrolyte high temperature steam electrolysis device (SOEC) 13 , and a heating device 14 .

[0074] The heat source 11 is a high temperature gas-cooled reactor, which can generate heat energy above 900° C. It should be noted that the heat source 11 is not limited to a high temperature gas-cooled reactor, as long as it can generate heat energy above 600° C. As the heat source, for example, an electric furnace, a heliostat solar concentrator, a boiler and boiler exhaust heat, a gas turbine exhaust heat, etc. can be used.

[0075] The high temperature gas-cooled reactor as the heat source 11 is a nuclear reactor that uses ceramic materials for the coating of the fuel, uses helium as the coolant, and uses graphite as the moderator. The high temperature gas-cooled reactor can generate helium gas as a heat medium above 900°C. The high temperature gas-cooled reactor as the heat source 11 is connected to the circulation path L11. In addition to the heat source 11, the circulation path L11 is also connected to the intermediate heat exchanger 21. The intermediate heat exchanger 21 connects one end of the supply path L12 and one end of the return path L13.

[0076] The intermediate heat exchanger 21 performs heat exchange between the primary helium (primary heat medium) flowing in the circulation path L11 and the secondary helium (secondary heat medium) flowing in the supply path L12 and the return path L13. That is, the intermediate heat exchanger 21 heats the secondary helium flowing in the supply path L12 and the return path L13 to, for example, 900°C by using the primary helium of, for example, 950°C flowing in the circulation path L11.

[0077] The supply path L12 is connected to the supply head 22 at the other end. The return path L13 is connected to the return head 23 at the other end. The return path L13 is provided with a circulator 24. The hydrogen manufacturing system 10 manufactures hydrogen using secondary helium as a heat medium, which is heated by heat energy of 900° C. or more generated by the heat source 11.

[0078] The high-temperature steam electrolysis device 13 produces hydrogen by electrolyzing water at a high temperature of about 700° C. to 900° C. using a high-temperature steam electrolysis cell 51 which is a solid electrolyte electrolysis cell. The high-temperature steam electrolysis device 13 includes an electrolyte layer 51 a , a porous hydrogen electrode layer 51 b , and a porous oxygen electrode layer 51 c .

[0079] The steam generator 31 generates water vapor by heating water with the heat energy of the secondary helium. The steam generator 31 is connected to the water supply path L31 and is connected to one end of the first water vapor supply path L32. The heat exchanger 12 includes a first heat exchanger 32 and a second heat exchanger 33. The second heat exchanger 33 includes a hydrogen side heat exchanger 34 and an oxygen side heat exchanger 35. The first heat exchanger 32 is connected to the other end of the first water vapor supply path L32 and is connected to one end of the second water vapor supply path L33. The other end of the second water vapor supply path L33 is connected to the hydrogen side heat exchanger 34. The hydrogen side heat exchanger 34 is connected to one end of the hydrogen side water vapor supply path L34.

[0080] The first heat exchanger 32 superheats the water vapor by the heat energy of the secondary helium to generate superheated water vapor. The hydrogen side heat exchanger 34 constituting the second heat exchanger 33 further superheats the superheated water vapor by the heat energy of the secondary helium. In addition, the oxygen side heat exchanger 35 constituting the second heat exchanger 33 further heats the heated air by the heat energy of the secondary helium. In the water vapor supply paths L32 and L33, the first heat exchanger 32 is arranged on the upstream side of the flow direction of the water vapor, and the second heat exchanger 33 is arranged on the downstream side closer to the first heat exchanger 32. The hydrogen side heat exchanger 34 as the second heat exchanger 33 is arranged adjacent to the oxygen side heat exchanger 35. Since high-temperature water vapor is supplied from the hydrogen side heat exchanger 34 and the oxygen side heat exchanger 35 to the porous hydrogen electrode layer 51b and the porous oxygen electrode layer 51c of the high-temperature water vapor electrolyzer, heat generation can be reduced by arranging them adjacently. The hydrogen-side heat exchanger 34 superheats the superheated water vapor by the thermal energy of the secondary helium, and the oxygen-side heat exchanger 35 heats the heating air by the thermal energy of the secondary helium.

[0081] In the high-temperature steam electrolysis device 13, the high-temperature steam electrolysis cell 51 is connected to the other end of the hydrogen-side steam supply path L34 and the oxygen-side steam supply path L43. The hydrogen-side steam supply path L34 is connected to the inlet side of the porous hydrogen electrode layer 51b, and the oxygen-side steam supply path L43 is connected to the inlet side of the porous oxygen electrode layer 51c. The porous hydrogen electrode layer 51b is heated by the superheated steam supplied from the hydrogen-side steam supply path L34. The high-temperature steam electrolysis device 13 is connected to the hydrogen exhaust path L35 and the oxygen exhaust path L44. The high-temperature steam electrolysis device 13 is connected to the hydrogen exhaust path L35 on the outlet side of the porous hydrogen electrode layer 51b, and is connected to the oxygen exhaust path L44 on the outlet side of the porous oxygen electrode layer 51c. The hydrogen exhaust path L35 is provided with a heat recovery device 36 and a condenser 37. The heat recovery device 36 recovers the heat of the generated hydrogen and heats the water vapor flowing in the first water vapor supply path L32, for example. The heat recovery device 38 recovers the heat of the generated oxygen and heats the air. The condenser 37 cools the remaining water vapor discharged from the high-temperature water vapor electrolyzer 51 together with the hydrogen into water. Since hydrogen is generated by the porous hydrogen electrode layer 51b of the high-temperature water vapor electrolyzer 51, the water vapor is condensed by the condenser 37, thereby separating the water vapor and the hydrogen, and purifying the high-purity hydrogen. It should be noted that the water generated in the condenser 37 is returned to the steam generator 31 through the circulation path L36.

[0082] In addition, the heat recovery device 38 is connected to one end of the gas supply path L41. The other end of the gas supply path L41 is open to the atmosphere. The gas supply path L41 is provided with a circulation machine 41. The heat recovery device 38 is connected to the oxygen side heat exchanger 35 through the gas supply path L42. When the circulation machine 41 is driven, the gas (air) is supplied to the heat recovery device 38 through the gas supply path L41, and is heated by the gas flowing in the oxygen exhaust path L44. The heated gas is further heated in the oxygen side heat exchanger 35 through the gas supply path L42 and is supplied to the porous oxygen electrode layer 51c. The heated gas is supplied to the porous oxygen electrode layer 51c for heating, and the generated oxygen is discharged to the oxygen exhaust path L44.

[0083] In addition, the high-temperature steam electrolysis device 13 is connected to the power supply path L51, and can supply power (electric energy) from the outside. The details will be described later. The high-temperature steam electrolysis device 13 applies a voltage lower than the potential of the thermal neutral point where the heat release and heat absorption based on Joule heat reach a balance from the power supply path L51 to electrolyze the steam to produce hydrogen.

[0084] The high-temperature steam electrolysis device 13 uses steam heated by the thermal energy of the secondary helium and uses the electric energy supplied from the power supply path L51 to produce hydrogen. The heating device 14 uses steam superheated by the thermal energy of the secondary helium to heat the high-temperature steam electrolysis cell 51 of the high-temperature steam electrolysis device 13. The details will be described later. The heating device 14 heats the high-temperature steam electrolysis device 13 with superheated steam at a temperature higher than the operating temperature of the high-temperature steam electrolysis device 13, thereby replenishing the heat energy lost by the endothermic reaction when the high-temperature steam electrolysis device 13 produces hydrogen.

[0085] The supply header 22 is connected to the second heat exchanger 33 via the heat medium supply path L14. The downstream end of the heat medium supply path L14 is branched into two, one is connected to the hydrogen side heat exchanger 34, and the other is connected to the oxygen side heat exchanger 35. The second heat exchanger 33 is connected to the steam generator 31 via the heat medium supply path L15. The upstream end of the heat medium supply path L15 is branched into two, one is connected to the hydrogen side heat exchanger 34, and the other is connected to the oxygen side heat exchanger 35. The steam generator 31 is connected to the return header 23 via the heat medium supply path L16. That is, the secondary helium supplied to the head 22 is supplied to the second heat exchanger 33 (hydrogen side heat exchanger 34, oxygen side heat exchanger 35) through the heat medium supply path L14 to heat water vapor and the like, is supplied from the second heat exchanger 33 to the steam generator 31 through the heat medium supply path L15 to heat water, and returns from the steam generator 31 to the reflux head 23 through the heat medium supply path L16.

[0086] In addition, the supply header 22 is connected to the first heat exchanger 32 through the heat medium supply path L17. The first heat exchanger 32 is connected to the return header 23 through the heat medium supply path L18. That is, the secondary helium of the supply header 22 is supplied to the first heat exchanger 32 through the heat medium supply path L17 to superheat the water vapor, and returns to the return header 23 through the heat medium supply path L18.

[0087] The heating device 14 is composed of at least a heat exchanger 12 for heating water vapor and a circulation machine 24. In particular, the heating device 14 is composed of a hydrogen side heat exchanger 34 and an oxygen side heat exchanger 35 as the second heat exchanger 33. The heating device 14 circulates the secondary helium through the circulation machine 24, thereby supplying the superheated water vapor heated by the second heat exchanger 33 (hydrogen side heat exchanger 34, oxygen side heat exchanger 35) to the high-temperature water vapor electrolyzer 51 (porous hydrogen electrode layer 51b, porous oxygen electrode layer 51c), and heating the high-temperature water vapor electrolyzer 51.

[0088] The high-temperature steam electrolyzer 51 supplies high-temperature superheated steam from the hydrogen-side steam supply path L34 to the porous hydrogen electrode layer 51b. The high-temperature steam electrolyzer 51 applies voltage to the porous hydrogen electrode layer 51b and the porous oxygen electrode layer 51c by supplying power from the power supply path L51. The high-temperature steam electrolyzer 51 electrolyzes water vapor in the porous hydrogen electrode layer 51b by applying voltage to generate hydrogen. The generated hydrogen is discharged to the hydrogen discharge path L35. On the other hand, oxygen ions generated by electrolysis in the porous hydrogen electrode layer 51b pass through the electrolyte layer 51a, and oxygen is generated in the porous oxygen electrode layer 51c, and the generated oxygen is discharged to the oxygen gas discharge path L44.

[0089] The high-temperature steam electrolysis device 13 generates hydrogen and oxygen by an electrolysis reaction according to the following formula.

[0090] H2O→H2+1 / 2O2

[0091] In addition, one of the two branches of the heat medium supply path L14 is connected to the hydrogen side heat exchanger 34, and the other is connected to the oxygen side heat exchanger 35. The heat medium supply path L14 is provided with flow control valves 61 and 62 at each branch pipe reaching the hydrogen side heat exchanger 34 and the oxygen side heat exchanger 35. The second steam supply path L33 is provided with a flow control valve 63, and the gas supply path L42 is provided with a flow control valve 64. The hydrogen side temperature regulator 65 controls the opening of the flow control valves 61 and 63 so that the temperature of the superheated water vapor (heat medium) flowing in the hydrogen side steam supply path L34 reaches a predetermined temperature. The oxygen side temperature regulator 66 controls the opening of the flow control valves 62 and 64 so that the temperature of the heating gas (heat medium) flowing in the oxygen side steam supply path L43 reaches a predetermined temperature. The temperature sensor 67 measures the temperature of the high-temperature steam electrolyzer 51 and outputs it to the hydrogen side temperature regulator 65 and the oxygen side temperature regulator 66. The hydrogen-side temperature regulator 65 and the oxygen-side temperature regulator 66 control the openings of the flow regulating valves 61 , 62 , 63 , and 64 based on the temperature of the high-temperature steam electrolysis cell 51 measured by the temperature sensor 67 .

[0092] <Principles of hydrogen production method>

[0093] Figure 2 is a graph showing the relationship between voltage and thermal energy of a high-temperature steam electrolysis device. Figure 3 is a graph showing the temperature change of the high-temperature steam electrolysis tank when the high-temperature steam electrolysis device is switched from no-load operation to operation at 1.1 V, which is lower than the potential of the thermal neutral point. Figure 4 This is a graph showing the voltage change of the high-temperature steam electrolysis cell when the high-temperature steam electrolysis device is switched from no-load operation to operation at 1.1 V, which is lower than the potential of the thermal neutral point.

[0094] The high-temperature steam electrolysis device 13 is a reverse reaction of the reaction of the fuel cell (SOFC), and generates hydrogen and oxygen by electrolyzing steam through the reaction represented by the following formulas (1), (2-1), and (2-2).

[0095] ΔH=ΔG+TΔS·····(1)

[0096] ΔH: Enthalpy [kJ / mol]

[0097] ΔG: Gibbs free energy [kJ / mol] (equivalent to electrical energy)

[0098] TΔS: Entropy [kJ / mol] (equivalent to thermal energy)

[0099] SOEC hydrogen pole: H2O+2e - →H2+O 2- ····(2-1)

[0100] SOEC oxygen pole: O 2- →1 / 2O2+2e - ·····(2-2)

[0101] E=ΔH / 2F (3)

[0102] F: Faraday constant

[0103] The electrolysis of water is an endothermic reaction, so a general high-temperature steam electrolysis device operates at a voltage (potential) of 1.3 V or more, which is equivalent to the potential of the thermal neutral point based on Joule heat, which is a balance between heat release and heat absorption. The thermal neutral point is obtained by the above formula (3) and changes according to the enthalpy. The thermal neutral point at 800°C is about 1.29 V in theoretical terms. The actual high-temperature steam electrolysis device operates at a voltage higher than the potential of the thermal neutral point in order to achieve a balance with heat absorption due to heat loss caused by heat release. It should be noted that if the temperature of the water increases, the potential of the thermal neutral point also increases.

[0104] like Figure 2 As shown, the heat absorption accompanying the electrolysis of high-temperature steam decreases in a linear function (proportion) in accordance with the increase in voltage. The Joule heating accompanying the electrolysis increases in accordance with the increase in voltage in a quadratic function. Therefore, the heat balance obtained by combining the Joule heating and the heat absorption decreases first and then increases in accordance with the increase in voltage.

[0105] Since the existing hydrogen production system does not have a high-temperature heat source (high-temperature gas-cooled reactor) 11, the endothermic reaction when water is electrolyzed by Joule heating using a high-temperature steam electrolysis device is supplemented by a potential above the thermal neutral point. That is, the existing high-temperature steam electrolysis device operates at a voltage above the thermal neutral point N.

[0106] On the other hand, the hydrogen manufacturing system 10 of the first embodiment has a heat source (high temperature gas-cooled reactor) 11, so the high temperature helium heated by the heat energy of 600°C or more generated by the heat source 11 is used to heat the water vapor and the high temperature water vapor electrolysis device 13 (high temperature water vapor electrolysis cell 51), and the endothermic reaction when the water is electrolyzed can be supplemented. Therefore, the hydrogen manufacturing system 10 is operated at a voltage of the operating point NL below the thermal neutral point N. At the operating point NL, since high temperature heat is supplied from the heat source 11, there is no need to excessively convert electrical energy into thermal energy (Joule heating), and the electrical energy used for the electrolysis of water can be reduced.

[0107] Specifically, the hydrogen manufacturing system 10 heats the high-temperature steam electrolysis device 15 with steam having a temperature higher than the operating temperature of the high-temperature steam electrolysis device 15, and applies a voltage lower than the thermal neutral point of heat release and heat absorption equilibrium to the high-temperature steam electrolysis device 13 (high-temperature steam electrolysis cell 51), thereby electrolyzing the steam to produce hydrogen. That is, the heating device 14 replenishes the heat energy lost due to the endothermic reaction when the high-temperature steam electrolysis device 15 produces hydrogen.

[0108] Here, the voltage lower than the thermal neutral point refers to a voltage within a range from a no-load voltage (OCV=Open circuit voltage) for the high-temperature steam electrolysis device 15 to a voltage (N) lower than the thermal neutral point. A voltage within a range of 1.0V to 1.2V is preferred.

[0109] That is, the hydrogen manufacturing system 10 supplies the heat absorption represented by TΔS of the above-mentioned formula (1) with the water vapor produced by the secondary helium of the heat source 11, thereby reducing the consumption of electric energy. Figure 3 and Figure 4 As shown, if the high-temperature steam electrolysis device 15 is switched from no-load operation to 1.1V operation at time t1, the high-temperature steam electrolysis device 15 is at a voltage below the potential of the thermal neutral point, so the Joule heat consumed by the resistance of the high-temperature steam electrolysis cell 51 is reduced. However, if the Joule heat of the high-temperature steam electrolysis cell 51 is reduced, heat absorption is dominant, and therefore, from time t1 to time t2, the temperature of the high-temperature steam electrolysis cell 51 is reduced, and the current flowing through the high-temperature steam electrolysis cell 51 becomes smaller (refer to Figure 4 ), the amount of hydrogen produced decreases in proportion to the current flowing through the high-temperature steam electrolyzer 51. Figure 3 and Figure 4 This is an embodiment when the high-temperature steam electrolysis device is operated at a potential below the thermal neutral point, such as when the high-temperature steam electrolysis device is operated at a potential below the thermal neutral point. Figure 3 As shown, the water vapor temperature may be subsequently increased, or water vapor having a temperature higher than that of the high-temperature water vapor electrolysis device 13 may be supplied in advance.

[0110] Therefore, for the hydrogen manufacturing system 10, when the high-temperature steam electrolysis device 15 is operated at a voltage below the thermal neutral point where more heat is absorbed, steam at a temperature higher than the operating temperature of the high-temperature steam electrolysis cell 51 is supplied to the high-temperature steam electrolysis cell 51 at time t2. As a result, the high-temperature steam electrolysis cell 51 performs operation to thermally compensate for the heat absorbing portion from time t2 to time t3, suppressing the temperature drop of the high-temperature steam electrolysis cell 51, and the current flowing through the high-temperature steam electrolysis cell 51 returns to the initial current, thereby suppressing the reduction in the amount of hydrogen produced. Compared with the conventional method, the hydrogen manufacturing system 10 of the first embodiment supplies the energy of the heat absorbing portion of TΔS from the heat source 11 among the consumed electric energy, so that the electric energy consumed by the high-temperature steam electrolysis cell 51 is reduced.

[0111] Figure 5 This is a graph showing changes in the current flowing in the high-temperature steam electrolysis cell when the conditions of the fluid flowing to the air electrode of the high-temperature steam electrolysis device are changed.

[0112] As described above, a general hydrogen production system operates at a voltage higher than the potential of the thermal neutral point, thereby providing the heat absorption caused by the self-heating of the high-temperature steam electrolyzer itself through the Joule heat generated by the resistor, so it is not necessary to supply heat to the oxygen electrode. Here, although air is conventionally supplied to the oxygen electrode of the high-temperature steam electrolyzer, the purpose of supplying air is not to supply heat, but to discharge the oxygen generated by the oxygen electrode of the high-temperature steam electrolyzer.

[0113] The hydrogen manufacturing system 10 of the first embodiment needs to supplement the heat absorbed during the electrolysis of water by high-temperature steam or the like, and needs to supply heat to the oxygen electrode of the high-temperature steam electrolyzer 51. It can be considered that this is because, in the above-mentioned formula (2-2), the reaction at the oxygen electrode is an entropy increase reaction, and therefore, the endothermic reaction at the oxygen electrode is large. Therefore, for the high-temperature steam electrolyzer 51 operating at a voltage lower than the potential of the thermal neutral point, by supplying the oxygen electrode with steam or air above the operating temperature of the high-temperature steam electrolyzer 51, heat is actively supplied, and the oxygen generated on the surface of the oxygen electrode is discharged, thereby reducing the oxygen partial pressure, and according to the Nernst equation, the current flows easily.

[0114] That is, Figure 5 As shown, the current of the high-temperature steam electrolyzer 51 varies depending on the type of heat medium supplied to the oxygen electrode. For example, when the heat medium is superheated steam (rich steam / steam, oxygen, nitrogen), the current increases. On the other hand, when the heat medium is heated air (zero steam / oxygen, nitrogen), the current is lower than that of superheated steam. Moreover, when there is no heat medium (zero heat medium), the current is further lower than that of heated air. Figure 5The change in electrolysis current is caused by the partial pressure of oxygen flowing on the oxygen electrode side. The oxygen partial pressure is low on the steam-rich side, and the heat medium zero is the high oxygen partial pressure side containing only oxygen. According to the Nernst equation of formula (4), when the oxygen partial pressure decreases, the potential also decreases. Therefore, the potential difference with the potential applied to the high-temperature steam electrolyzer increases, and the electrolysis current increases.

[0115] Figure 6 This is a table showing the relationship between OCV, which is the steam utilization rate of a high-temperature steam electrolysis device, and the potential difference between OCV and a voltage lower than the potential of the thermal neutral point, for example, 1.1 V. Figure 7 This is a graph showing changes in current when the concentration of water vapor supplied to the hydrogen electrode of the high-temperature water vapor electrolysis device is changed.

[0116] In a conventional hydrogen manufacturing system, the amount of water vapor supplied to the high-temperature water vapor electrolyzer is set to a minimum in order to reduce the energy supplied, and the goal is to produce hydrogen with as little water vapor as possible. In a conventional hydrogen manufacturing system, the target water vapor utilization rate of water vapor used to produce hydrogen relative to the supplied water vapor is 80% or more.

[0117] On the other hand, the hydrogen manufacturing system 10 of the first embodiment can supply a large amount of high-temperature heat to the high-temperature steam electrolyzer 51 through the heat source 11, so there is no need to increase the water vapor utilization rate. Therefore, the hydrogen manufacturing system 10 can supply water vapor to the high-temperature steam electrolyzer 51 in moles more than the number required for hydrogen production. When a large amount of water vapor is supplied to the high-temperature steam electrolyzer 51, according to the Nernst equation of the following formula (4), the water vapor partial pressure increases, thereby reducing the OCV, and increasing the potential difference with the voltage applied to the high-temperature steam electrolyzer 51, which has the effect of making the current flow easily.

[0118] E=E0+RT / zF·LN(aH2×aO21 / 2 / aH2O)·····(4)

[0119] Figure 6 The relationship between the hydrogen partial pressure and oxygen partial pressure, the water partial pressure and OCV when the temperature of the steam supplied to the high-temperature steam electrolyzer 51 is 750°C, and the potential difference between OCV and 1.1V when the voltage applied to the high-temperature steam electrolyzer 51 is 1.1V are summarized. Figure 6 As shown, the lower the water vapor utilization rate, the lower the OCV, and therefore the greater the potential difference from the voltage 1.1V applied to the high-temperature steam electrolyzer 51. As the potential difference increases, the current flowing through the high-temperature steam electrolyzer 51 also increases, resulting in an increase in the amount of hydrogen produced.

[0120] In addition, if Figure 7As shown, the lower the water vapor concentration supplied to the hydrogen electrode of the high-temperature water vapor electrolyzer 51, the lower the current. For example, when the water vapor concentration is 65% (H2O / N2+H2+H2O: 65%), the current is high. When the water vapor concentration is reduced to 50% (H2O / N2+H2+H2O: 50%), 30% (H2O / N2+H2+H2O: 30%), 20% (H2O / N2+H2+H2O: 20%), 10% (H2O / N2+H2+H2O: 10%), and 5% (H2O / N2+H2+H2O: 5%), the current also decreases.

[0121] <Hydrogen production method>

[0122] The hydrogen manufacturing method of this embodiment includes: a process of generating thermal energy above 600°C; a process of superheating water vapor to above 600°C using secondary helium (heat medium) heated by thermal energy; a process of heating the high-temperature water vapor electrolyzer 51 with water vapor; and a process of electrolyzing water vapor to manufacture hydrogen by applying a voltage to the high-temperature water vapor electrolyzer 51 that is lower than the potential of the thermal neutral point at which heat release and heat absorption are balanced in the high-temperature water vapor electrolyzer 51.

[0123] Specifically explain, such as Figure 1 As shown, the high temperature gas-cooled reactor as the heat source 11 generates primary helium at, for example, 950° C. The high temperature primary helium flows in the circulation path L11, and exchanges with the secondary helium flowing in the return path L13 in the intermediate heat exchanger 21, and the secondary helium is heated to, for example, 890° C. The secondary helium after the heat exchange in the intermediate heat exchanger 21 flows in the supply path L12, and is supplied to the supply head 22 at, for example, about 890° C.

[0124] When the circulation machine 24 is driven, the high-temperature secondary helium circulates while being heated in the intermediate heat exchanger 21. The secondary helium supplied to the head 22 is supplied to the second heat exchanger 33 through the heat medium supply path L14, superheats the water vapor, and is supplied from the second heat exchanger 33 to the steam generator 31 through the heat medium supply path L15. The steam generator 31 heats the water supplied from the water supply path L31 and the like with the high-temperature secondary helium to generate water vapor. In addition, the secondary helium supplied to the head 22 is supplied to the first heat exchanger 32 through the heat medium supply path L17, and the first heat exchanger 32 superheats the water vapor supplied from the steam generator 31.

[0125] That is, the steam generator 31 heats the water supplied from the water supply path L31 to, for example, 180° C. to generate water vapor. The water vapor is supplied to the first heat exchanger 32 through the first water vapor supply path L32, where it is superheated to 600° C., and supplied to the hydrogen side heat exchanger 34 through the second water vapor supply path L33. The water vapor is superheated to, for example, 850° C. through the hydrogen side heat exchanger 34, and is supplied to the porous hydrogen electrode layer 51b of the high-temperature water vapor electrolyzer 51 through the hydrogen side water vapor supply path L34 in the form of high-temperature water vapor at 850° C.

[0126] On the other hand, when the circulation machine 41 is driven, the gas (air) is supplied to the heat recovery device 38 through the gas supply path L41. The heat recovery device 38 is heated by the high-temperature oxygen generated from the porous oxygen electrode layer 51c. The heated gas is supplied to the oxygen side heat exchanger 35 through the gas supply path L42. The gas is heated to, for example, 800°C by the oxygen side heat exchanger 35, and is supplied to the porous oxygen electrode layer 51c of the high-temperature steam electrolyzer 51 in the form of a high-temperature gas of 800°C.

[0127] In the high-temperature steam electrolyzer 51, the porous hydrogen electrode layer 51b is heated by the superheated steam supplied from the hydrogen-side heat exchanger 34, and the porous oxygen electrode layer 51c is heated by the high-temperature gas supplied from the oxygen-side heat exchanger 35. In addition, by applying a voltage with the power supplied from the power supply path L51 of the high-temperature steam electrolyzer 51, the superheated steam supplied to the porous hydrogen electrode layer 51b is electrolyzed to generate hydrogen and oxygen.

[0128] At this time, the high-temperature steam electrolyzer 51 is heated to a temperature (e.g., 800° C.) higher than the operating temperature (e.g., 750° C.) of the high-temperature steam electrolyzer 51 by the superheated steam and the heated gas. In addition, the high-temperature steam electrolyzer 51 is supplied with power from the power supply path L51, and a voltage lower than the potential of the thermal neutral point, specifically, a voltage of 1.0V to 1.2V is applied to the porous hydrogen electrode layer 51b and the porous oxygen electrode layer 51c. As a result, the superheated steam in the porous hydrogen electrode layer 51b is electrolyzed in the porous hydrogen electrode layer 51b to generate hydrogen, and the generated hydrogen is discharged to the hydrogen gas discharge path L35. On the other hand, the oxygen ions generated by the electrolysis in the porous hydrogen electrode layer 51b pass through the electrolyte layer 51a, and oxygen is generated in the porous oxygen electrode layer 51c, and the generated oxygen is discharged to the oxygen gas discharge path L44.

[0129] Since the high-temperature steam electrolyzer 51 can supply more than the number of moles of steam required for the production of hydrogen, the remaining steam is discharged to the hydrogen discharge path L35 together with the generated hydrogen. In addition, the high-temperature steam electrolyzer 51 discharges the supplied gas (air) and the generated oxygen to the oxygen discharge path L44. The condenser 37 cools the steam and high-temperature gas to form water, which is supplied to the steam generator 31 through the circulation path L36. Since the steam is condensed by the condenser 37, the purity of the hydrogen can be improved.

[0130] In addition, the heating device 14 needs to heat the high-temperature steam electrolyzer 51 with superheated steam and heating gas at a temperature higher than the operating temperature of the high-temperature steam electrolyzer 51 (for example, 750°C). Therefore, the temperature sensor 67 measures the temperature of the high-temperature steam electrolyzer 51 and outputs it to the hydrogen-side temperature regulator 65 and the oxygen-side temperature regulator 66. The hydrogen-side temperature regulator 65 controls the opening of the flow regulating valves 61 and 63 so that the temperature of the steam flowing in the hydrogen-side steam supply path L34 reaches, for example, 800°C or more. In addition, the oxygen-side temperature regulator 66 controls the opening of the flow regulating valves 62 and 64 so that the temperature of the gas flowing in the oxygen-side steam supply path L43 reaches, for example, 800°C or more.

[0131] Here, the temperature of the water vapor flowing in the hydrogen side water vapor supply path L34 and the temperature of the gas flowing in the oxygen side water vapor supply path L43 are controlled to reach the assumed operating temperature of the high-temperature water vapor electrolyzer 51 (for example, 750°C), which are measured by the temperature sensor 67 and output to the hydrogen side temperature regulator 65 and the oxygen side temperature regulator 66, and the openings of the flow regulating valves 61, 63 and the flow regulating valves 62, 64 are adjusted respectively, thereby controlling the operating temperature of the high-temperature water vapor electrolyzer 51.

[0132] [Second embodiment]

[0133] Figure 8 2 is a schematic diagram showing the configuration of a hydrogen manufacturing system according to a second embodiment. It should be noted that the same reference numerals are used for components having the same functions as those of the first embodiment described above, and detailed descriptions thereof will be omitted.

[0134] like Figure 8 As shown, the hydrogen manufacturing system 10A includes a heat source 11, a heat exchanger 12, a high-temperature steam electrolysis device 13, and a heating device 14 in the same manner as the first embodiment. Compared with the first embodiment, the hydrogen manufacturing system 10A of the second embodiment changes the supply structure of the heat medium to the porous oxygen electrode layer 51c constituting the high-temperature steam electrolysis device 13.

[0135] The other end of the second water vapor supply path L33 is connected to the water vapor header 71. The water vapor header 71 connects one end of the hydrogen side water vapor branch L71 and the oxygen side water vapor branch L72. The hydrogen side heat exchanger 34 connects the other end of the hydrogen side water vapor branch L71 and connects one end of the hydrogen gas discharge path L35. The oxygen side heat exchanger 35 connects the other end of the oxygen side water vapor branch L72 and connects one end of the oxygen gas discharge path L44. In addition, the hydrogen gas discharge path L35 is provided with a heat recovery device 36 and a condenser 37. The oxygen gas discharge path L44 is provided with a heat recovery device 38 and a condenser 39. The water generated in the condensers 37 and 39 is returned to the steam generator 31 through the circulation paths L36 and L45.

[0136] The first heat exchanger 32 superheats the water vapor by the heat energy of the secondary helium to generate superheated water vapor. The hydrogen side heat exchanger 34 in the second heat exchanger 33 further superheats the superheated water vapor by the heat energy of the secondary helium. In addition, the oxygen side heat exchanger 35 in the second heat exchanger 33 further superheats the superheated water vapor by the heat energy of the secondary helium. In the water vapor supply paths L32 and L33, the first heat exchanger 32 is arranged on the upstream side of the flow direction of the water vapor, the water vapor header 71 is arranged on the downstream side of the first heat exchanger 32, and the second heat exchanger 33 is arranged on the downstream side of the water vapor header 71. The hydrogen side heat exchanger 34 and the oxygen side heat exchanger 35 as the second heat exchanger 33 are arranged in parallel on the downstream side of the water vapor supply path L33.

[0137] In the high-temperature steam electrolysis device 13, the high-temperature steam electrolysis cell 51 is connected to the other ends of the hydrogen discharge path L35 and the oxygen discharge path L44. The hydrogen discharge path L35 is connected to the inlet side of the porous hydrogen electrode layer 51b, and the oxygen discharge path L44 is connected to the inlet side of the porous oxygen electrode layer 51c. Therefore, the porous hydrogen electrode layer 51b and the porous oxygen electrode layer 51c are supplied with superheated steam.

[0138] The hydrogen manufacturing system 10A branches the steam superheated in the first heat exchanger 32 through the steam header 71 and supplies it to the hydrogen side heat exchanger 34 and the oxygen side heat exchanger 35 to superheat it, and supplies it to the high-temperature steam electrolyzer 51. Therefore, the high-temperature steam electrolyzer 51 is heated by the superheated steam at a temperature (e.g., 800° C.) higher than the operating temperature (e.g., 750° C.) of the high-temperature steam electrolyzer 51. In the hydrogen manufacturing system 10A, the system configuration can be simplified.

[0139] The heat medium supplied to the oxygen side heat exchanger 35 by the hydrogen manufacturing system 10A of this embodiment is superheated water vapor. Therefore, unlike the first embodiment, a condenser 39 is arranged downstream of the heat recovery device 38. The supplied water vapor is discharged to the hydrogen discharge path L35 together with the hydrogen generated from the porous hydrogen electrode layer 51b of the high-temperature water vapor electrolyzer, and the supplied water vapor is discharged to the oxygen discharge path L44 together with the oxygen generated from the porous oxygen electrode layer 51c. By cooling and condensing the steam with the condensers 37 and 39, the purity of hydrogen and oxygen can be increased respectively. In particular, high-purity oxygen can be recovered by the condenser 39. It should be noted that the other components in the hydrogen manufacturing system 10A are the same as those of the hydrogen manufacturing system 10 of the first embodiment, and the description is omitted.

[0140] [Third embodiment]

[0141] Fig. 9 1 is a schematic diagram showing the configuration of a hydrogen manufacturing system according to a third embodiment. It should be noted that the same reference numerals are used for components having the same functions as those of the first and second embodiments described above, and detailed descriptions thereof will be omitted.

[0142] like Fig. 9 As shown, the hydrogen manufacturing system 10B includes a heat source 11, a heat exchanger 12, a high-temperature steam electrolysis device 13, and a heating device 14 in the same manner as the first embodiment. Compared with the first embodiment, the hydrogen manufacturing system 10B of the third embodiment changes the supply structure of the heat medium to the porous oxygen electrode layer 51c constituting the high-temperature steam electrolysis device 13.

[0143] The other end of the second water vapor supply path L33 is connected to the water vapor header 71. The water vapor header 71 connects one end of the hydrogen-side water vapor branch L71 and the oxygen-side water vapor branch L72. The hydrogen-side heat exchanger 34 connects the other end of the hydrogen-side water vapor branch L71 and connects one end of the hydrogen gas discharge path L35. The oxygen-side heat exchanger 35 connects the other end of the oxygen-side water vapor branch L72 and connects one end of the oxygen gas discharge path L44. In addition, the oxygen-side water vapor branch L72 is connected to the other end of the gas supply path L42 on the upstream side of the flow control valve 64. In addition, the oxygen-side water vapor branch L72 is provided with a check valve 72 on the upstream side of the connection portion of the gas supply path L42. The check valve 72 prevents the heated air from flowing back from the oxygen-side heat exchanger 35 side to the water vapor header 71 side.

[0144] In the high-temperature steam electrolysis device 13, the high-temperature steam electrolysis cell 51 is connected to the other ends of the hydrogen discharge path L35 and the oxygen discharge path L44. The hydrogen discharge path L35 is connected to the inlet side of the porous hydrogen electrode layer 51b, and the oxygen discharge path L44 is connected to the inlet side of the porous oxygen electrode layer 51c. Therefore, the porous hydrogen electrode layer 51b can supply superheated water vapor, and the porous oxygen electrode layer 51c can supply superheated water vapor and heated air.

[0145] The hydrogen manufacturing system 10B branches the steam superheated in the first heat exchanger 32 through the steam header 71 and supplies it to the hydrogen side heat exchanger 34 and the oxygen side heat exchanger 35 to superheat it, and supplies it to the high-temperature steam electrolyzer 51, and supplies gas (air) to the oxygen side heat exchanger 35 to heat it, and supplies it to the porous oxygen electrode layer 51c of the high-temperature steam electrolyzer 51. Therefore, the high-temperature steam electrolyzer 51 is heated at a temperature (e.g., 800°C) higher than the operating temperature (e.g., 750°C) of the high-temperature steam electrolyzer 51 by the superheated steam and the heated gas.

[0146] It should be noted that the other configurations of the hydrogen manufacturing system 10B are the same as those of the hydrogen manufacturing system 10 of the first embodiment and the hydrogen manufacturing system 10A of the second embodiment, and thus description thereof will be omitted.

[0147] [Effects of this embodiment]

[0148] The first type of hydrogen manufacturing system comprises: a heat exchanger 12, which uses secondary helium (heat medium) heated by thermal energy above 600°C to heat water vapor; a high-temperature water vapor electrolysis device 13, which applies a voltage lower than the potential of the thermal neutral point of the thermal equilibrium between Joule heating accompanied by the application of electric current and the endothermic equilibrium accompanied by the electrolysis reaction to the high-temperature water vapor electrolysis cell 51, and electrolyzes water vapor above 600°C to produce hydrogen; and a heating device 14, which heats the high-temperature water vapor electrolysis device 13 with water vapor.

[0149] According to the hydrogen manufacturing system of the first embodiment, a voltage lower than the potential of the thermal neutral point is applied to the high-temperature steam electrolysis cell 51, and the high-temperature steam electrolysis device 13 is heated by steam heated by secondary helium at 600° C. or above, thereby manufacturing hydrogen. Therefore, the amount of electric energy generated by a thermal power generation system or the like can be reduced, the generation of carbon dioxide can be suppressed, and the electric energy cost when manufacturing hydrogen can be reduced.

[0150] The hydrogen manufacturing system of the second embodiment is the hydrogen manufacturing system of the first embodiment, and further, the heating device 14 heats the high-temperature steam electrolysis device 15 with steam having a temperature higher than the operating temperature of the high-temperature steam electrolysis device 15. As a result, the high-temperature steam electrolysis cell 51 performs a heat compensation operation for the heat absorbing part, and the temperature drop of the high-temperature steam electrolysis cell 51 can be suppressed, the current drop can be suppressed, and the reduction in the amount of hydrogen production can be suppressed, and as a result, the consumed electric energy can be suppressed.

[0151] The third embodiment of the hydrogen manufacturing system is the first embodiment or the second embodiment of the hydrogen manufacturing system, and further, the heating device 14 supplements the heat energy lost by the endothermic reaction when the high-temperature steam electrolysis device 13 produces hydrogen. Thus, the amount of heat energy supplied from the outside to the high-temperature steam electrolysis device 13 can be reduced.

[0152] The hydrogen manufacturing system of the fourth embodiment is a hydrogen manufacturing system of any one of the first to third embodiments, and further, the high-temperature steam electrolysis device 13 applies a voltage higher than the OCV and lower than the potential of the thermal neutral point to the high-temperature steam electrolysis cell 51, thereby electrolyzing water vapor to produce hydrogen. This can reduce the amount of electric energy used and achieve a reduction in energy cost.

[0153] The hydrogen manufacturing system of the fifth embodiment is a hydrogen manufacturing system of any one of the first to fourth embodiments, and further, the high-temperature steam electrolysis device 15 supplies a number of moles of steam greater than the number of moles required for hydrogen production. As a result, the steam utilization rate of the high-temperature steam electrolysis device 15 is reduced, and the reduction in the amount of hydrogen production can be suppressed.

[0154] The hydrogen manufacturing system of the sixth embodiment is a hydrogen manufacturing system of any one of the first to fifth embodiments, and further, the high-temperature steam electrolysis device 15 has an electrolyte layer 51a, a porous hydrogen electrode layer 51b, and a porous oxygen electrode layer 51c, and the heating device 14 heats the porous hydrogen electrode layer 51b with steam and heats the porous oxygen electrode layer 51c with at least one of steam and heated air. Thus, the high-temperature steam electrolysis device 15 can be heated with good efficiency.

[0155] The hydrogen manufacturing system of the seventh embodiment is a hydrogen manufacturing system of any one of the first to sixth embodiments, wherein the heating device 14 controls at least one of the flow rate of water vapor and the flow rate of secondary helium so that the operating temperature of the high-temperature steam electrolyzer 13 reaches the expected temperature and the temperature of the water vapor supplied to the high-temperature steam electrolyzer 13 reaches a temperature higher than the operating temperature of the high-temperature steam electrolyzer 15. Thus, the heating device 14 can appropriately heat the high-temperature steam electrolyzer 13.

[0156] The hydrogen manufacturing system of the eighth embodiment is a hydrogen manufacturing system of any one of the first to seventh embodiments, which has a high temperature gas-cooled reactor as a heat source 11 capable of generating thermal energy, and a heat exchanger 12 heats water vapor using a heat medium heated by the thermal energy of high temperature helium generated in the high temperature gas-cooled reactor. Thus, the amount of carbon dioxide generated can be reduced.

[0157] The hydrogen production method of the ninth embodiment includes: a step of generating heat energy of 600°C or higher; a step of superheating water vapor to 600°C or higher using secondary helium (heat medium) heated by heat energy; a step of heating the high-temperature water vapor electrolyzer 51 by water vapor; and a step of electrolyzing water vapor to produce hydrogen by applying a voltage lower than the potential of the thermal neutral point where the Joule heating accompanying the application of current and the endothermic balance accompanying the electrolysis reaction in the high-temperature water vapor electrolyzer 51. Thus, the amount of electric energy generated by a thermal power generation system or the like can be reduced, the generation of carbon dioxide can be suppressed, and the energy cost can be reduced.

Claims

1. A hydrogen production system comprising: a heat exchanger that heats a heat medium with heat energy of 600° C. or higher and heats the steam using the heated heat medium; and A high-temperature steam electrolysis device applies a voltage lower than the voltage of the thermal neutral point to the high-temperature steam electrolysis cell, electrolyzes the steam above 600°C to produce hydrogen, and the voltage of the thermal neutral point is the voltage when the thermal equilibrium is 0 due to the balance between the Joule heating accompanied by the application of current and the endothermic equilibrium accompanied by the electrolysis reaction.

2. The hydrogen production system according to claim 1, wherein: The heat exchanger has: a first heat exchanger provided in the water vapor supply path, and A second heat exchanger is provided on a downstream side of the first heat exchanger in the water vapor supply path.

3. The hydrogen production system according to claim 1 or 2, wherein: The heat exchanger heats the high-temperature steam electrolysis device using the steam having a temperature higher than an operating temperature of the high-temperature steam electrolysis device.

4. The hydrogen production system according to claim 1, wherein: The heat exchanger replenishes the heat energy lost by the high-temperature steam electrolysis device due to the endothermic reaction when producing hydrogen.

5. The hydrogen production system according to claim 1, wherein: The high-temperature steam electrolysis device applies a voltage higher than OCV and lower than the voltage of the thermal neutral point to the high-temperature steam electrolysis cell, thereby electrolyzing the steam to produce hydrogen.

6. The hydrogen production system according to claim 1, wherein: The high-temperature steam electrolysis device supplies steam in a number of moles equal to or greater than the number of moles required for the production of hydrogen.

7. The hydrogen production system according to claim 1, wherein: The high-temperature steam electrolysis device has an electrolyte layer, a hydrogen diffusion electrode layer, and an oxygen diffusion electrode layer. The heat exchanger heats the hydrogen diffusion electrode layer with the steam and heats the oxygen diffusion electrode layer with at least one of the steam and heated air.

8. The hydrogen production system according to claim 1, wherein: The heat exchanger controls at least one of a flow rate of the steam and a flow rate of the heat medium so that a temperature of the steam supplied to the high-temperature steam electrolysis device reaches a temperature higher than an operating temperature of the high-temperature steam electrolysis device.

9. The hydrogen manufacturing system according to claim 1 has a high temperature gas-cooled reactor as a heat source capable of generating the thermal energy, and the heat exchanger heats the water vapor using a heat medium heated by the thermal energy of high temperature helium generated in the high temperature gas-cooled reactor.

10. A method for producing hydrogen, comprising: Processes that generate heat above 600°C; A step of superheating the steam to 600° C. or higher using the heat medium heated by the heat energy; A step of heating a high-temperature steam electrolyzer with the steam; and A process of producing hydrogen by electrolyzing the water vapor by applying a voltage lower than the voltage of the thermal neutral point to the high-temperature steam electrolyzer, wherein the voltage of the thermal neutral point is the voltage when the thermal equilibrium is 0 due to the Joule heating accompanying the application of current and the endothermic equilibrium accompanying the electrolysis reaction in the high-temperature steam electrolyzer.

Images