Hydrogen production device, controller of hydrogen production device, and hydrogen production method

Abstract

To provide a hydrogen production device capable of decreasing heat energy necessary for heating gas supplied to a fuel electrode.SOLUTION: A hydrogen production device (1) comprises: an electrochemical cell (50) that comprises a fuel electrode (51) including Ni, a solid electrolyte layer (53) and an air electrode (52) and in which the fuel electrode is supplied with hydrogen and steam, steam supplied to the fuel electrode is electrolyzed to generate hydrogen at the fuel electrode and generate oxygen at the air electrode, fuel electrode exhaust including hydrogen is discharged from the fuel electrode and air electrode exhaust including oxygen is discharged from the air electrode; and a recycle unit (60) recycling a portion of hydrogen included in the fuel electrode exhaust to the fuel electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a hydrogen production device, a control device for the hydrogen production device, and a hydrogen production method. [Background technology]

[0002] Utilizing hydrogen produced by high-temperature steam electrolysis can contribute to the realization of a low-carbon or carbon-free society.

[0003] Electrochemical cells are sometimes used to produce hydrogen by high-temperature steam electrolysis. Patent Document 1 discloses a hydrogen production device that uses a solid oxide electrolysis cell (SOEC), which is one type of electrochemical cell.

[0004] According to the hydrogen production device disclosed in Patent Document 1, hydrogen and water vapor are supplied to the fuel electrode of an SOEC. The water vapor supplied to the fuel electrode is electrolyzed at the fuel electrode to generate hydrogen and oxygen. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-143131 A Summary of the Invention

[0006] (Problem to be solved by the invention) In order to efficiently generate high-temperature steam electrolysis in an electrochemical cell, high-temperature steam is supplied to the fuel electrode. In addition, hydrogen is supplied to the fuel electrode as a reducing agent to suppress deterioration (oxidation) of the fuel electrode. The hydrogen supplied to the fuel electrode does not contribute to the high-temperature steam electrolysis reaction at the fuel electrode, but needs to be at a high temperature when supplied to the fuel electrode so as not to inhibit the high-temperature steam electrolysis reaction. Therefore, in order to supply high-temperature hydrogen and steam to the fuel electrode, they need to be heated before being supplied to the fuel electrode, but if the thermal energy required for heating is large, a problem occurs in that energy efficiency decreases. Therefore, an object of the present disclosure is to provide a hydrogen production device, a control device thereof, and a hydrogen production method that can reduce the thermal energy required for heating the gas supplied to the fuel electrode. [Means for solving the problem]

[0007] The hydrogen production device (1) according to the present disclosure includes an electrochemical cell (50) that includes a fuel electrode (51) containing Ni, a solid electrolyte layer (53), and an air electrode (52), and that supplies hydrogen and water vapor to the fuel electrode, electrolyzes the water vapor supplied to the fuel electrode to generate hydrogen at the fuel electrode and oxygen at the air electrode, discharges a fuel electrode exhaust gas containing hydrogen from the fuel electrode, and discharges an air electrode exhaust gas containing oxygen from the air electrode, and a reflux section (60) that refluxes a portion of the hydrogen contained in the fuel electrode exhaust gas to the fuel electrode.

[0008] According to the hydrogen production device of the present disclosure, a portion of the high-temperature hydrogen generated by electrolysis of water vapor (high-temperature steam electrolysis) at the fuel electrode is returned to the fuel electrode via the return section. Since the hydrogen returned to the fuel electrode is at a high temperature, thermal energy for heating it is not required or only a small amount of thermal energy is required for heating it. This makes it possible to reduce the thermal energy required for heating the gas supplied to the fuel electrode. Furthermore, by using a portion of the hydrogen contained in the fuel electrode exhaust gas as hydrogen for preventing deterioration of the fuel electrode, the amount of hydrogen separately required for preventing deterioration of the fuel electrode can be reduced.

[0009] In one aspect of the hydrogen production device according to the present disclosure, the fuel electrode exhaust gas contains water vapor, and the reflux section refluxes a portion of the fuel electrode exhaust gas containing hydrogen and water vapor to the fuel electrode. In this manner, in addition to high-temperature hydrogen, water vapor that has not reacted at the fuel electrode is also supplied to the fuel electrode via the reflux section, making it possible to effectively utilize the unreacted water vapor and to reduce the thermal energy required to generate the water vapor and the thermal energy required to heat the water vapor. This makes it possible to further reduce the thermal energy required to heat the gas supplied to the fuel electrode.

[0010] The hydrogen production device according to the present disclosure includes a hydrogen supply unit (10) configured to be able to supply hydrogen from a hydrogen supply source to the fuel electrode, a water vapor supply unit (40) configured to receive water, vaporize the supplied water to generate water vapor, and supply the generated water vapor to the fuel electrode, and a ratio R of the sum of the flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and the flow rate of hydrogen returned from the reflux unit to the fuel electrode to the sum of the flow rate of water vapor generated in the water vapor supply unit and the flow rate of water vapor returned from the reflux unit to the fuel electrode. in is the predetermined target flow rate R in * and a control unit (70) that controls the flow rate of hydrogen supplied from the hydrogen supply unit to the anode and the flow rate of water supplied to the water vapor supply unit so that the ratio R of the flow rate of hydrogen to the flow rate of water vapor supplied to the anode is regulated to be equal to or larger than the ratio R of the flow rate of hydrogen to the flow rate of water vapor supplied to the anode, while part of the hydrogen and water vapor contained in the anode exhaust gas is returned to the anode. in The target flow rate R in * can be maintained.

[0011] The control unit of the hydrogen production device according to the present disclosure controls the ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the fuel electrode exhaust gas. out Estimate the estimated ratio R out Based on the ratio R in is the target flow rate R in *The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and the flow rate of water supplied to the water vapor supply unit can be controlled so as to achieve the above.

[0012] The control unit of the hydrogen production device according to the present disclosure calculates a ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the condensed water amount of the anode exhaust gas. out The method may be configured to estimate

[0013] The temperature of the fuel electrode exhaust gas returned from the return section of the hydrogen production device according to the present disclosure to the fuel electrode is preferably 100° C. or higher. This allows water vapor that has not reacted at the fuel electrode to be supplied to the fuel electrode as water vapor without condensing.

[0014] The hydrogen production device according to the present disclosure may be configured to include a thermal insulation container in which the electrochemical cells are housed. In this case, a hot module may be configured by housing the electrochemical cells in the thermal insulation container. In this case, the thermal insulation container may be configured to house a cell stack in which a plurality of electrochemical cells are stacked.

[0015] The control device for a hydrogen production device according to the present disclosure includes an electrochemical cell (50) that includes a fuel electrode (51) containing Ni, a solid electrolyte layer (53), and an air electrode (52), in which hydrogen and water vapor are supplied to the fuel electrode, the water vapor supplied to the fuel electrode is electrolyzed to generate hydrogen at the fuel electrode and oxygen at the air electrode, and the fuel electrode exhaust gas containing hydrogen and water vapor is discharged from the fuel electrode and the air electrode exhaust gas containing oxygen is discharged from the air electrode, a hydrogen supply unit (10) configured to be able to supply hydrogen from a hydrogen supply source to the fuel electrode, and A control device for a hydrogen production device (1) including a water vapor supply unit (40) configured to generate water vapor by vaporizing the supplied water and to supply the generated water vapor to an anode, and a reflux unit (60) that refluxes a portion of an anode exhaust gas to the anode, the control device (70) controlling a ratio R of the sum of the flow rate of hydrogen supplied from the hydrogen supply unit to the anode and the flow rate of hydrogen refluxed from the reflux unit to the anode, to the sum of the flow rate of water vapor generated in the water vapor supply unit and the flow rate of water vapor refluxed from the reflux unit to the anode. in is the predetermined target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and the flow rate of water supplied to the water vapor supply unit are controlled so as to satisfy the above condition.

[0016] According to the control device for the hydrogen production device of the present disclosure, a portion of the hydrogen and water vapor contained in the fuel electrode exhaust gas is returned to the fuel electrode, and the ratio R of the flow rate of hydrogen to the water vapor supplied to the fuel electrode is set to 0.05. in The target flow rate R in * can be maintained.

[0017] The control device according to the present disclosure is a control device for controlling a ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the anode exhaust gas. out Estimate the estimated ratio R out Based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and the flow rate of water supplied to the water vapor supply unit can be controlled so as to achieve the above.

[0018] The control device according to the present disclosure calculates a ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. out The method may be configured to estimate

[0019] Furthermore, the hydrogen production method according to the present disclosure is a hydrogen production method using an electrochemical cell (50) that includes a fuel electrode (51) containing Ni, a solid electrolyte layer (53), and an air electrode (52), and that generates hydrogen by electrolyzing water vapor at the fuel electrode and generates oxygen at the air electrode, discharges a fuel electrode exhaust gas containing hydrogen and water vapor from the fuel electrode, and discharges an air electrode exhaust gas containing oxygen from the air electrode, and includes a water vapor supply step of vaporizing water to generate water vapor and supplying the generated water vapor to the fuel electrode, a hydrogen supply step of supplying hydrogen from a hydrogen supply source to the fuel electrode, an electrolysis step of electrolyzing the water vapor supplied to the fuel electrode to generate hydrogen and oxygen, and a reflux step of refluxing a portion of the fuel electrode exhaust gas to the fuel electrode.

[0020] According to the hydrogen production method of the present disclosure, high-temperature hydrogen generated by electrolysis of water vapor (high-temperature water vapor electrolysis) at the fuel electrode and a portion of the water vapor that did not react at the fuel electrode are returned to the fuel electrode via the return section. Since the hydrogen returned to the fuel electrode is at a high temperature, thermal energy for heating it is not necessary, or only a small amount of thermal energy is required for heating it. Furthermore, by returning the unreacted water vapor to the fuel electrode, the water vapor can be effectively utilized, and the thermal energy for generating water vapor and the thermal energy for heating the water vapor can also be reduced. Therefore, the thermal energy required for heating the gas supplied to the fuel electrode can be reduced.

[0021] In one embodiment of the hydrogen production method according to the present disclosure, the hydrogen production method includes a ratio R of the sum of the flow rate of hydrogen supplied to the anode in the hydrogen supplying step and the flow rate of hydrogen returned to the anode in the refluxing step to the sum of the flow rate of water vapor supplied to the anode in the water vapor supplying step and the flow rate of water vapor returned to the anode in the refluxing step. in is the predetermined target flow rate R in * The method includes a flow rate control step of controlling the flow rate of hydrogen supplied to the fuel electrode in the hydrogen supply step and the flow rate of water vaporized in the water vapor supply step so that the flow rate of hydrogen supplied to the fuel electrode is equal to or greater than the flow rate of water vaporized in the water vapor supply step.

[0022] According to this, while part of the hydrogen and water vapor contained in the fuel electrode exhaust gas is returned to the fuel electrode, the ratio R of the flow rate of hydrogen to the flow rate of water vapor supplied to the fuel electrode is in The target flow rate R in * can be maintained.

[0023] In another embodiment of the hydrogen production method according to the present disclosure, the hydrogen production method includes: out The flow rate control step includes a step of estimating the ratio R out Based on the ratio R in is the target flow rate R in * This is a process of controlling the flow rate of hydrogen supplied to the fuel electrode in the hydrogen supply process and the flow rate of water vaporized in the water vapor supply process so that the above-mentioned condition is satisfied.

[0024] In another aspect of the hydrogen production method according to the present disclosure, the anode exhaust gas flow rate ratio estimation step is performed by estimating a ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the condensed water amount of the anode exhaust gas. out This is a process of estimating the following. [Brief description of the drawings]

[0025] [Figure 1]1 is a block diagram showing a schematic configuration of a hydrogen production device according to an embodiment. [Diagram 2] 2 is a schematic diagram showing the types of gas supplied to the fuel electrode and the air electrode, and the types of gas discharged from the fuel electrode and the air electrode. FIG. [Diagram 3] 4 is a flowchart showing a flow of a hydrogen / water flow rate control process routine executed by a CPU of a control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0027] Fig. 1 is a block diagram showing a schematic configuration of a hydrogen production device according to this embodiment. As shown in Fig. 1, the hydrogen production device 1 according to this embodiment includes a hydrogen supply unit 10, a water supply unit 20, an air supply unit 30, a water vapor supply unit 40, a solid oxide electrolysis cell (hereinafter, SOEC) 50 as an electrochemical cell, a reflux unit 60, a control unit 70 (control device), and a flow rate sensor 93.

[0028] The hydrogen supply unit 10 is configured to be able to supply hydrogen from a hydrogen supply source to the fuel electrode 51 described below. The hydrogen supply unit 10 includes a hydrogen flow rate regulator 11 and a hydrogen supply path 12. A hydrogen supply source is connected to one end of the hydrogen supply path 12. An example of the hydrogen supply source is a hydrogen cylinder. Hydrogen supplied from the hydrogen supply source flows through the hydrogen supply path 12. The hydrogen flow rate regulator 11 is interposed midway through the hydrogen supply path 12. The hydrogen flow rate regulator 11 is configured to be able to regulate the flow rate of hydrogen flowing through the hydrogen supply path 12. An example of the hydrogen flow rate regulator 11 is a hydrogen pump capable of changing the output flow rate of hydrogen. The hydrogen flow rate regulator 11 may be a flow rate regulator valve capable of regulating the flow rate of hydrogen flowing through the hydrogen supply path 12.

[0029] The water supply unit 20 includes a water flow rate adjustment device 21 and a water supply path 22. A water supply source is connected to one end of the water supply path 22. An example of the water supply source is a water storage tank in which pure water is stored. Water supplied from the water supply source flows through the water supply path 22. The water flow rate adjustment device 21 is interposed midway through the water supply path 22. The water flow rate adjustment device 21 is configured to be able to adjust the flow rate of water flowing through the water supply path 22. An example of the water flow rate adjustment device 21 is a water pump that is able to change the water delivery flow rate.

[0030] The other end of the hydrogen supply path 12 and the other end of the water supply path 22 are connected to the water vapor supply unit 40. Therefore, hydrogen flowing through the hydrogen supply path 12 and water flowing through the water supply path 22 are supplied to the water vapor supply unit 40. The water vapor supply unit 40 is configured to vaporize the supplied water to generate water vapor and supply the generated water vapor to the fuel electrode 51 described later. Specifically, the water vapor supply unit 40 includes a heater 41 and a mixed gas discharge path 42. Water and hydrogen are supplied to the heater 41. The heater 41 heats the supplied water to vaporize it and generate water vapor. In addition, the heater 41 heats the supplied hydrogen and the generated water vapor to a temperature within a predetermined reaction temperature range. Here, the reaction temperature range is a temperature range required for water vapor to cause high-temperature steam electrolysis at the fuel electrode 51, and is a temperature range of about 600°C to 800°C. The heater 41 may be divided into an evaporator for vaporizing water to generate steam, and a temperature increaser for heating the supplied hydrogen and the steam generated by the evaporator to a temperature within a predetermined reaction temperature range. The hydrogen and steam heated by the heater 41 are introduced into the mixed gas discharge path 42, and further introduced from the mixed gas discharge path 42 into the SOEC 50.

[0031] The SOEC 50 includes an anode 51, an air electrode 52, and a solid electrolyte layer 53. Hydrogen and water vapor heated by a heater 41 are supplied to the anode 51 via a mixed gas exhaust path 42. The anode 51 is a reaction field where the supplied water vapor causes an electrolysis reaction (high-temperature water vapor electrolysis reaction) represented by the following formula (1): (1)H2O+2e- →H2+O 2-

[0032] Water vapor is electrolyzed at the fuel electrode 51 as shown in formula (1), whereby hydrogen and oxygen ions are generated at the fuel electrode 51. The fuel electrode 51 is made of a material that has porosity, electronic conductivity, and catalytic properties for the reaction of formula (1) above. In this embodiment, the fuel electrode 51 is made of a material that contains nickel (Ni). For example, a Ni-YSZ cermet electrode, a Ni-GDC cermet electrode, or the like can be used for the fuel electrode 51.

[0033] The solid electrolyte layer 53 serves to transfer oxygen ions generated at the fuel electrode 51 by the reaction of formula (1) to the air electrode 52. The solid electrolyte layer 53 is made of a material that is dense, has no electronic conductivity, and has high ionic conductivity. For example, the material of the solid electrolyte layer 53 can be YSZ (yttria-stabilized zirconia).

[0034] The air electrode 52 is a reaction field where oxygen ions cause the reaction of the following formula (2). (2)O 2- →(1 / 2)O2+2e -

[0035] The reaction of formula (2) occurs at the air electrode 52, whereby oxygen is produced at the air electrode 52. The air electrode 52 is made of a material that is porous, electronically conductive, and stable against oxygen. For example, La 1-x Sr x MnO 3-δ , La 1-x Sr x Chief of Staff 3-δ , La 1-x Sr x Co 1-Y Fe Y O 3-δ ,Pr 1-x Sr x MnO 3-δAn example of the material of the air electrode 52 is a perovskite oxide represented by the following formula: An air supply unit 30 is connected to this air electrode 52. The air supply unit 30 includes an air flow regulator 31 and an air supply path 32. One end of the air supply path 32 is connected to an air supply source, and the other end of the air supply path 32 is connected to the air electrode 52. Thus, air from the air supply source is supplied to the air electrode 52 via the air supply path 32. An air flow regulator 31 is interposed in the air supply path 32. The air flow regulator 31 regulates the flow rate of air flowing through the air supply path 32 and supplied to the air electrode 52.

[0036] The SOEC 50 is constructed by stacking an anode 51, a solid electrolyte layer 53, and an air cathode 52 in this order in a predetermined direction. A cell stack is constructed by stacking a plurality of SOECs 50 (single cells) in the above-mentioned predetermined direction. The cell stack and the water vapor supply unit 40 are housed in an insulating container 80. This provides thermal insulation for the components exposed to high temperatures from the outside. The insulating container 80 and the components housed therein (a cell stack consisting of the water vapor supply unit 40 and a plurality of SOECs 50) form a hot module.

[0037] The hydrogen production device 1 also includes a voltage application device 55. The voltage application device 55 is electrically connected to the SOEC 50 so as to be able to apply a predetermined voltage between the fuel electrode 51 and the air electrode 52 of the SOEC 50.

[0038] An anode exhaust gas path 91 is connected to the anode 51, and an anode exhaust gas path 92 is connected to the cathode 52. An anode exhaust gas path 91 flows with an anode exhaust gas discharged from the anode 51. An anode exhaust gas path 92 flows with an anode exhaust gas discharged from the cathode 52.

[0039] The reflux unit 60 includes a blower 61 and a reflux path 62. One end of the reflux path 62 is connected to the middle of the anode exhaust gas path 91, and the other end of the reflux path 62 is connected to the heater 41 of the water vapor supply unit 40. The blower 61 is interposed in the middle of the reflux path 62 and configured to be able to move the fluid inside from one end side to the other end side of the reflux path 62. The blower 61 may be configured to have a variable rotation speed, for example, so that the flow rate of the fluid flowing through the reflux path 62 can be adjusted.

[0040] A flow rate sensor 93 is attached to the air electrode exhaust gas path 92. The flow rate sensor 93 detects the flow rate of the air electrode exhaust gas flowing through the air electrode exhaust gas path 92. Flow rate information detected by the flow rate sensor 93 is passed to the control unit 70.

[0041] The control unit 70 includes a microcomputer equipped with a CPU, a ROM, a RAM, and an interface. The control unit 70 is electrically connected to the hydrogen flow rate regulator 11 and the water flow rate regulator 21. The control unit 70 is configured to be able to control the hydrogen flow rate regulator 11 and the water flow rate regulator 21.

[0042] When the hydrogen production device 1 having the above configuration is operated, water is supplied from the water supply source to the water supply path 22, and the water flows through the water supply path 22. At this time, the flow rate of the water flowing through the water supply path 22 is adjusted by the water flow rate regulator 21. The water flowing through the water supply path 22 is supplied to the heater 41 of the water vapor supply unit 40. The water supplied to the heater 41 is vaporized by heating, generating water vapor.

[0043] Furthermore, hydrogen is supplied from the hydrogen supply source to hydrogen supply path 12, and hydrogen flows through hydrogen supply path 12. At this time, the flow rate of hydrogen flowing through hydrogen supply path 12 is adjusted by hydrogen flow rate regulator 11. The hydrogen flowing through hydrogen supply path 12 is introduced into heater 41 and mixed with water vapor. Then, the mixed gas of hydrogen and water vapor is heated to a temperature of about 700° C. by heater 41. The heated hydrogen and water vapor are supplied to fuel electrode 51 of SOEC 50 via mixed gas discharge path 42 (water vapor supply process, hydrogen supply process).

[0044] In addition, air is supplied from an air supply source to air supply path 32, and the air flows through air supply path 32. At this time, the flow rate of the air flowing through air supply path 32 is adjusted to a predetermined flow rate by air flow regulator 31. The air flowing through air supply path 32 is supplied to air electrode 52 of SOEC 50.

[0045] Furthermore, the voltage application device 55 is operated to apply a predetermined voltage between the fuel electrode 51 and the air electrode 52 of the SOEC 50. At this time, the voltage is applied so that the fuel electrode 51 serves as the cathode (positive electrode) and the air electrode 52 serves as the anode (negative electrode). This causes the high-temperature steam electrolysis reaction shown in the above formula (1), and the steam supplied to the fuel electrode 51 is electrolyzed to generate hydrogen and oxygen ions at the fuel electrode 51 (electrolysis process).

[0046] The hydrogen generated at the fuel electrode 51 is discharged from the fuel electrode 51 as anode exhaust gas together with water vapor that was not subjected to the reaction of the above formula (1) at the fuel electrode 51 (hereinafter, unreacted water vapor). The anode exhaust gas discharged from the fuel electrode 51 flows through anode exhaust gas passage 91 and is discharged to the outside. The oxygen ions generated at the fuel electrode 51 pass through the solid electrolyte layer 53 and are supplied to the air electrode 52. Then, the reaction shown in the above formula (2) occurs at the air electrode 52, and oxygen is generated at the air electrode 52 (electrolysis process). The oxygen generated at the air electrode 52 is discharged from the air electrode 52 as anode exhaust gas together with the air supplied to the air electrode 52. The air electrode exhaust gas discharged from the air electrode 52 flows through the air electrode exhaust gas passage 92 and is discharged to the outside. The flow rate of the air electrode exhaust gas discharged from the air electrode 52 is measured by a flow rate sensor 93 provided in the air electrode exhaust gas passage 92.

[0047] As a result of the hydrogen production device 1 operating as described above, hydrogen is produced in the SOEC 50. The produced hydrogen is discharged to the outside together with unreacted water vapor as anode exhaust gas from anode exhaust gas path 91. The anode exhaust gas discharged to the outside is separated into water and hydrogen by an operation such as condensation. The separated hydrogen is then stored in a specified container.

[0048] Incidentally, the hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 is at room temperature while flowing through the hydrogen supply path 12, but must be at a high temperature of about 700° C. when it is supplied to the fuel electrode 51. Therefore, the hydrogen at room temperature supplied from the hydrogen supply unit 10 is supplied to the water vapor supply unit 40 and heated to about 700° C. together with water vapor by the heater 41 of the water vapor supply unit 40. However, a large amount of thermal energy is required to heat the hydrogen at room temperature together with water vapor to about 700° C. In this regard, in the hydrogen production device 1 according to this embodiment, the blower 61 of the reflux unit 60 is driven during operation. Therefore, a part of the fuel electrode exhaust gas containing hydrogen and water vapor discharged from the fuel electrode 51 to the fuel electrode exhaust gas path 91 flows through the reflux path 62 branched off from the fuel electrode exhaust gas path 91. The fuel electrode exhaust gas flowing through the reflux path 62 is pressure-fed by the blower 61 and introduced into the heater 41 of the water vapor supply unit 40. A portion of the anode exhaust gas introduced into the heater 41 is mixed with water vapor generated in the heater 41 and hydrogen supplied from the hydrogen supply unit 10, heated together with these in the heater 41, and then returned from the heater 41 to the anode 51 of the SOEC 50 (return process).

[0049] By carrying out the reflux process, a portion of the hydrogen contained in the anode exhaust gas is refluxed by reflux section 60 to anode 51 via heater 41. The anode exhaust gas refluxed to anode 51 is already at a high temperature, at least 100°C, before being introduced into heater 41. Therefore, the hydrogen contained in the anode exhaust gas refluxed to anode 51 is also at a high temperature, and does not require much thermal energy to reheat it in heater 41. Therefore, the thermal energy can be reduced compared to the case where the hydrogen contained in the anode exhaust gas is not refluxed to anode 51.

[0050] Furthermore, by carrying out the reflux process, a portion of the unreacted water vapor contained in the anode exhaust gas is also refluxed by the reflux section 60 to the anode 51 via the heater 41. The unreacted water vapor refluxed to the anode 51 is also already at a high temperature, at least 100°C, before being introduced into the heater 41. Therefore, the refluxed unreacted water vapor is supplied to the anode 51 as water vapor without condensing, so that no thermal energy is required to vaporize it in the heater 41, and no significant thermal energy is required for reheating it. This makes it possible to reduce the thermal energy required to generate water vapor and the thermal energy required to heat the water vapor.

[0051] The ratio of hydrogen and water vapor supplied to the fuel electrode 51 is determined to be an appropriate ratio taking into consideration the suppression of deterioration (oxidation) of the fuel electrode 51 and the efficiency of hydrogen production at the fuel electrode 51. In general, the flow rate F of water vapor supplied to the fuel electrode 51 is H2O_in Hydrogen flow rate F H2_in Ratio R in (=F H2_in / F H2O_in In the case where a part of the fuel electrode exhaust gas is returned to the fuel electrode 51 as in the hydrogen production device 1 according to the present embodiment, the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied from the water supply unit 20 to the water vapor supply unit 40 must be controlled so as to be (for example, 0.1 to 0.2).

[0052] Here, the molar flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 via the water vapor supply unit 40 (hereinafter simply referred to as flow rate) is X H2 The flow rate of water vapor generated by vaporizing water supplied from the water supply unit 20 to the water vapor supply unit 40 and supplied to the fuel electrode 51 is X H2O The flow rate of hydrogen (reflux hydrogen) returned from the reflux section 60 to the fuel electrode 51 via the water vapor supply section 40 is Y H2The flow rate of water vapor (recirculated water vapor) returned from the reflux section 60 to the fuel electrode 51 via the water vapor supply section 40 is Y H2O In addition, the flow rate F of hydrogen supplied to the fuel electrode 51 is H2_in and the water vapor flow rate F H2O_in The sum of the total flow rate F in In this case, the following formula holds: (3)F in =(X H2 +X H2O )+(Y H2 +Y H2O ) (4)R in =(X H2 +Y H2 ) / (X H2O +Y H2O )

[0053] From equation (4), X H2 is expressed by the following equation (5). (5)X H2 =R in X H2O +R in Y H2O -Y H2 Substituting equation (5) into equation (3), we obtain equation (6). (6)F in =(R in X H2O +R in Y H2O -Y H2 )+X H2O +Y H2 +Y H2O =R in X H2O +R in Y H2O +X H2O +Y H2O =(R in +1)X H2O +(R in +1)Y H2O

[0054] By transforming equation (6), we get X H2O is obtained as shown in equation (7). (7)X H2O=(F in -(R in +1)Y H2O ) / (R in +1) =F in / (R in +1)-Y H2O

[0055] Substituting equation (7) into equation (5) and rearranging it, we get X H2 is expressed as equation (8). (8)X H2 =R in (F in / (R in +1)-Y H2O )+R in Y H2O -Y H2 =R in F in / (R in +1)-Y H2

[0056] As shown in equations (7) and (8), the flow rate X H2 and flow rate X H2O is the total flow rate F in , ratio R in , flow rate of reflux hydrogen Y H2 , flow rate of reflux steam Y H2O Therefore, the total flow rate F in The target total flow rate F in * and the ratio R in The target flow rate R in * If you set it to Y, the flow rate of reflux hydrogen will be H2 and the flow rate of reflux steam Y H2O Depending on the flow rate X H2 and flow rate X H2O The control unit 70 determines the flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 as the uniquely determined flow rate X H2 The hydrogen flow rate regulator 11 is controlled so that the flow rate of the water vapor generated in the water vapor supply unit 40 is uniquely determined to be the flow rate X H2OIn this way, even when a part of the fuel electrode exhaust gas is returned from the return section 60 to the fuel electrode 51, the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above condition. In this specification, the flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 is sometimes referred to as the flow rate of added hydrogen, and the flow rate of water vapor generated in the water vapor supply unit 40 is sometimes referred to as the flow rate of generated water vapor.

[0057] However, since the temperature of the anode exhaust gas is very high, the flow rate of reflux hydrogen Y H2 and the flow rate of reflux steam Y H2O Therefore, the control unit 70 of the hydrogen production device 1 according to this embodiment determines the flow rate Y of the reflux hydrogen based on the flow rate of the air electrode exhaust gas. H2 and the flow rate of reflux steam Y H2O Estimate the flow rate of reflux hydrogen Y H2 and the flow rate of reflux steam Y H2O Based on flow rate x H2 and flow rate X H2O Then, the control unit 70 determines whether the flow rate of the additional hydrogen is equal to or smaller than the estimated flow rate X H2 The hydrogen flow rate regulator 11 is controlled so that the flow rate of the generated water vapor coincides with the estimated flow rate X H2O The water flow rate regulator 21 is controlled so as to match the above.

[0058] Specifically, the control unit 70 of the hydrogen production device 1 according to this embodiment calculates the ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the fuel electrode exhaust gas based on the detection information of the flow rate sensor 93 attached to the air electrode exhaust gas path 92. out (anode exhaust gas flow rate ratio estimation step). The control unit 70 estimates the estimated ratio R out Based on the flow rate Y H2 and Y H2O Furthermore, the control unit 70 estimates the estimated flow rate Y H2 and Y H2O Based on flow rate xH2 and X H2O Then, the control unit 70 determines whether the flow rate of the additional hydrogen is equal to or smaller than the estimated flow rate X H2 The hydrogen flow rate regulator 11 is controlled so that the flow rate of the generated water vapor coincides with the estimated flow rate X H2O The water flow rate regulator 21 is controlled so as to match the above.

[0059] 2 is a schematic diagram showing the types of gas supplied to the fuel electrode 51 and the air electrode 52, and the types of gas discharged from the fuel electrode 51 and the air electrode 52. In FIG. 2, the flow rate of hydrogen (hydrogen for reduction) supplied to the fuel electrode 51 is F H2_in The flow rate of the water vapor (water vapor for electrolysis) supplied to the fuel electrode 51 is represented by F H2O_in It is expressed by:

[0060] In addition, the flow rate of hydrogen (produced hydrogen) generated at the fuel electrode 51 in the fuel electrode exhaust gas is F H2_out2 The flow rate of the water vapor that has not reacted at the fuel electrode 51 (unreacted water vapor) is represented by F H2O_out In addition, since the reducing hydrogen does not contribute to the reaction at the fuel electrode 51, the hydrogen supplied to the fuel electrode 51 is discharged from the fuel electrode 51 as is. Therefore, the flow rate F of hydrogen other than the generated hydrogen among the hydrogen discharged from the fuel electrode 51 is H2_out1 F H2_in (F H2_in =F H2_out1 ).

[0061] In addition, in FIG. 2, the flow rate of air supplied to the air electrode 52 is F air_in In addition, the flow rate of oxygen (generated oxygen) generated at the air electrode 52 in the air electrode exhaust gas is expressed by F O2_out The flow rate of the air discharged from the air electrode 52 is represented by F air_out Here, since the air supplied to the air electrode 52 does not contribute to the reaction at the air electrode 52, the air supplied to the air electrode 52 is discharged from the air electrode 52 as it is. For this reason, F air_in is F air_out (F air_in =F air_out ).

[0062] The flow rate sensor 93 detects the flow rate of the air electrode exhaust gas, i.e., the flow rate F of the air exhausted from the air electrode 52. air_out and the flow rate F of oxygen generated at the air electrode 52 O2_out The flow rate Z (=F air_out +F O2_out ) is detected. In addition, since the oxygen generated at the air electrode 52 is generated by electrolysis of water, the flow rate of hydrogen generated at the fuel electrode 51 is twice the flow rate of the generated oxygen. Therefore, the flow rate F of hydrogen (generated hydrogen) generated at the fuel electrode 51 is H2_out2 can be expressed by the following equation (9). (9)F H2_out2 =2F O2_out =2(ZF air_out )=2(ZF air_in ) In the above formula (9), F air_in is a known quantity that can be set in advance. Therefore, the flow rate F of the generated hydrogen is calculated from equation (9). H2_out2 can be estimated.

[0063] Flow rate of unreacted water vapor F H2O_out is the flow rate of water vapor for electrolysis F H2O_in Flow rate of hydrogen produced from F H2_out2 Therefore, the following equation (10) holds: (10)F H2O_out =F H2O_in -F H2_out2 =F H2O_in -2(ZF air_in )

[0064] Also, F H2O_in isX H2O +Y H2O and F H2_in isX H2 +Y H2 Therefore, the following equations (11) and (12) hold. (11)F H2O_in +F H2_in =F in (12)F H2_in / F H2O_in =Rin

[0065] From equations (11) and (12), F H2O_in and F H2_in can be expressed as equations (13) and (14). (13)F H2O_in =F in / (R in +1) (14)F H2_in =R in F in / (R in +1)

[0066] Using the above relationship, the ratio R of the flow rate of hydrogen to the flow rate of water vapor in the anode exhaust gas is out can be expressed as the following equation (15). (15)R out =(F H2_out1 +F H2_out2 ) / F H2O_out =(F H2_in +2(ZF air_in )) / (F H2O_in -2(ZF air_in )) =(R in F in / (R in +1)+2Δ) / (F in / (R in +1)-2Δ) =(R in F in +2(R in +1)Δ) / (F in -2(R in +1)Δ) Here, Δ=ZF air_in

[0067] If the ratio of the gas flowing into the reflux section 60 to the total fuel electrode exhaust gas is a constant ratio α, the flow rate of reflux hydrogen Y H2 and the flow rate of reflux steam Y H2O are expressed as the following equations (16) and (17), respectively. (16)Y H2 =α(F H2_out1 +F H2_out2 ) =αR out F H2O_out =αR out (F H2O_in -2Δ) =αR out (F in / (R in +1)-2Δ) (17)Y H2O =α(F H2_out1 +F H2_out2 ) / R out =α(F H2_in +2Δ) / R out =α(R in F in / (R in +1)+2Δ) / R out

[0068] In equations (16) and (17), the total flow rate F in The target total flow rate F in * and the ratio R in The target flow rate R in * By setting (fixing) Y H2 and Y H2O Therefore, the estimated Y H2 and Y H2O By substituting into equations (7) and (8), the ratio R in The target flow rate R in * Flow rate of additional hydrogen required to maintain H2 and the flow rate of generated steam X H2O Then, the control unit 70 determines whether the flow rate of the additional hydrogen is equal to or smaller than the estimated flow rate X H2 The hydrogen flow rate regulator 11 is controlled so that the flow rate of the generated water vapor is equal to or smaller than the estimated flow rate X H2O In this way, the water flow rate regulator 21 is controlled so that the ratio R in is the target flow rate R in *The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirement. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0069] Also, as can be seen from equation (15), the ratio R out is estimated based on the flow rate Z detected by the flow rate sensor 93. Furthermore, as can be seen from equations (16) and (17), the flow rate Y H2 and the flow rate of reflux steam Y H2O is the ratio R out The flow rate is estimated based on the flow rate X H2 and flow rate X H2O is the flow rate Y H2 and flow rate Y H2O Therefore, the control unit 70 estimates the ratio R based on the flow rate of the air electrode exhaust gas detected by the flow rate sensor 93. out Estimate the estimated ratio R out Based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirement.

[0070] FIG. 3 is a flowchart showing the flow of a hydrogen / water flow rate control processing routine executed by the CPU of the control unit 70 to control the flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40. The routine shown in FIG. 3 is repeatedly executed when it is determined that the operation of the hydrogen production device 1 has stabilized after its operation. When the routine shown in FIG. 3 is started, the CPU of the control unit 70 (hereinafter, CPU) first acquires the flow rate Z of the air electrode exhaust gas from the flow rate sensor 93 in step (hereinafter, step will be abbreviated as S) 11 in FIG. 3. Next, in S12, the CPU calculates the flow rate F of the generated hydrogen using the above formula (9). H2_out2 In step S13, the flow rate F of unreacted water vapor is estimated (calculated) using the above formula (10). H2O_outNext, in S14, the CPU estimates (calculates) the ratio R of the flow rate of hydrogen to the flow rate of water vapor in the anode exhaust gas using the above formula (15). out Estimate (calculate).

[0071] Next, in S15, the CPU calculates the flow rate Y of reflux hydrogen using the above formula (16). H2 In step S16, the flow rate of reflux steam Y is calculated using the above formula (17). H2O Next, in S17, the CPU estimates (calculates) the flow rate X H2 In step S18, the flow rate X is calculated using the above formula (8). H2O Estimate (calculate).

[0072] Next, the CPU executes hydrogen flow rate control in S19. In this hydrogen flow rate control, the CPU determines whether the flow rate of hydrogen flowing through the hydrogen supply path 12 (i.e., hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51) is equal to or greater than the flow rate X calculated in S17. H2 The hydrogen flow rate regulator 11 is controlled so that the flow rate X H2 of hydrogen can be flowed.

[0073] In addition, the CPU executes water flow rate control in S20. In this water flow rate control, the CPU determines whether the flow rate of the water vapor generated in the water vapor supply unit 40 is equal to or smaller than the flow rate X calculated in S18. H2O The water flow rate regulator 21 is controlled so that the flow rate X H2O After that, the CPU ends this routine.

[0074] The CPU executes the above-mentioned hydrogen / water flow rate control process to return a portion of the anode exhaust gas from the return section 60 to the anode 51 at a ratio R in is the target flow rate R in *The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 are controlled so as to satisfy the above requirement. This makes it possible to reduce thermal energy while preventing deterioration of the fuel electrode 51 and improving the efficiency of hydrogen production.

[0075] (Variation 1) In this example, instead of the flow rate sensor 93, an oxygen concentration sensor is attached to the air electrode exhaust gas passage 92. When the oxygen concentration sensor is attached to the air electrode exhaust gas passage 92, the oxygen concentration sensor measures the oxygen concentration S (%) of the air electrode exhaust gas. In addition, the flow rate F of the air supplied to the air electrode 52 is air_in The oxygen concentration S0 (%) of the air supplied to the air electrode 52 is a known amount that can be set to a predetermined value in advance, so the flow rate F of the generated oxygen O2_out is expressed by the following equation (18). (18)F O2_out =F air_in (S-S0) / (100-S)

[0076] In this modification, the control unit 70 calculates the flow rate F of the generated oxygen according to the formula (18). O2_out The control unit 70 estimates (calculates) the flow rate F of the generated oxygen. O2_out Using the above equation (9), the flow rate of generated hydrogen F H2_out2 The flow rate of unreacted water vapor F is estimated (calculated) from the above equations (10) and (13). H2O_out Furthermore, the control unit 70 estimates (calculates) the flow rate F H2_out1 The flow rate of hydrogen for reduction F H2_out1 is the flow rate F estimated by the above equation (14). H2_in is equal to.

[0077] In this way, the flow rate F of the produced hydrogen in the anode exhaust gas is O2_out , the flow rate of unreacted water vapor F H2O_out , and the flow rate of hydrogen for reduction F H2_out1 The control unit 70 uses the flow rates thus obtained to obtain the ratio R out The control unit 70 estimates (calculates) the estimated ratio Rout and the flow rate of unreacted water vapor F H2O_out Using Eq. (16), the flow rate of reflux hydrogen Y H2 Estimate the ratio R out , the flow rate of hydrogen produced H 2_out2 and the flow rate of hydrogen for reduction F H2_out1 Using equation (17), the flow rate of reflux steam Y H2O Furthermore, the control unit 70 estimates the flow rate Y H2 and the flow rate of reflux steam Y H2 Using equations (7) and (8), the flow rate X H2 and flow rate X H2O Then, the control unit 70 estimates (calculates) the estimated flow rate X H2 and X H2O In this way, the hydrogen flow rate control and the water flow rate control are performed based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirements. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0078] (Variation 2) In this example, no sensor is provided in the cathode exhaust gas path 92, and instead an electrolysis current measuring device is attached to the SOEC 50. The electrolysis current measuring device measures the current flowing through the SOEC 50 when a voltage is applied to the SOEC 50.

[0079] At the fuel electrode 51 of SOEC 50, H2O+2e - →H2+O 2- The larger the current (electrolysis current) flowing through the SOEC 50 during this electrolysis reaction, the greater the amount of hydrogen generated. H2_out2 The relationship between the electrolysis current and the flow rate of the produced hydrogen F H2_out2The control unit 70 then acquires the electrolytic current detected by the electrolytic current measuring device, and compares the acquired electrolytic current, the stored electrolytic current, and the flow rate F of the generated hydrogen. H2_out2 From the relationship, the flow rate of the produced hydrogen F H2_out2 The control unit 70 estimates the estimated flow rate F H2_out2 Using the above equations (10) and (13), the flow rate of unreacted water vapor F H2O_out Then, the flow rate F is calculated using the above formula (14). H2_in Estimate (calculate) the estimated flow rate F H2_in Flow rate F H2_out1 (=Flow rate F H2_in ) is estimated (calculated) from the above formula (15) in the same manner as in the first modification. out Estimate (calculate) the estimated ratio R out Based on this, the flow rate X of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 is H2 and the flow rate X of the water vapor generated in the water vapor supply unit 40 H2O Then, the control unit 70 estimates (calculates) the estimated flow rate X H2 and flow rate X H2O In this way, the hydrogen flow rate control and the water flow rate control are performed based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirements. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0080] (Variation 3) In this example, instead of flow rate sensor 93, a temperature sensor for measuring the temperature of SOEC 50 and a voltage sensor for measuring the voltage applied between fuel electrode 51 and air electrode 52 of SOEC 50 are used.

[0081] The IV characteristics of the SOEC 50 depend on the temperature of the SOEC 50 and the mixture ratio of hydrogen and water vapor supplied to the anode 51 (= ratio Rin ) depends on the ratio R in The target flow rate R in * and by investigating the IV characteristics of the SOEC 50 in advance using the temperature of the SOEC 50 as a parameter, it is possible to obtain the relationship between the applied voltage and the electrolysis current. This relationship between the applied voltage and the electrolysis current is stored in the control unit 70. The control unit 70 then acquires the temperature of the SOEC 50 from the temperature sensor while the hydrogen production device 1 is in operation, and acquires the voltage applied to the SOEC 50 from the voltage sensor. The control unit 70 can estimate the electrolysis current from the acquired temperature of the SOEC 50, the voltage applied to the SOEC 50, and the stored relationship between the applied voltage and the electrolysis current. Thereafter, in the same manner as in the second modification, the ratio R out Estimate (calculate) the estimated ratio R out The flow rate X of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 based on H2 and the flow rate X of the water vapor generated in the water vapor supply unit 40 H2O Then, the control unit 70 estimates (calculates) the calculated flow rate X H2 and X H2O In this way, the hydrogen flow rate control and the water flow rate control are performed based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirements. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0082] (Variation 4) In this example, a dew point meter (for example, a capacitance type dew point meter) is used instead of flow sensor 93. Also, in this example, a portion of the anode exhaust gas is sampled, and the dew point temperature of the sampled anode exhaust gas is measured by the dew point meter.

[0083] The dew point temperature of the anode exhaust gas is the ratio of the flow rate of hydrogen and water vapor in the anode exhaust gas, R outTherefore, the dew point temperature and ratio R out The relationship between the dew point temperature of the anode exhaust gas and the ratio R out The control unit 70 stores the relationship between the dew point temperature measured by the dew point meter and the stored dew point temperature and the ratio R out From the relationship, the ratio R out Estimate (calculate).

[0084] In addition, the control unit 70 calculates the estimated ratio R out From this, using equation (15), Δ(=ZF air_in The control unit 70 calculates the obtained ratio R out Using and Δ, the flow rate of reflux hydrogen Y is calculated using equation (16). H2 The flow rate of reflux steam Y H2 Then, the flow rate X is calculated using equations (7) and (8). H2 and flow rate X H2O Then, the control unit 70 estimates (calculates) the calculated flow rate X H2 and X H2O In this way, the hydrogen flow rate control and the water flow rate control are performed based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirements. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0085] (Variation 5) In this example, the ratio R outIn this example, a gas-liquid separator is used instead of flow sensor 93. Also, in this example, a portion of the anode exhaust gas is sampled, and the sampled anode exhaust gas is separated into gas and liquid by the gas-liquid separator. Thereafter, the weight of the separated water (amount of condensed water) is measured, and the flow rate of the separated gas (hydrogen) is measured by a mass flow meter or the like. Control unit 70 calculates ratio R from the measured weight of water and flow rate of gas (hydrogen). out After that, the flow rate X of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 is estimated (calculated) in the same manner as in the fourth modification. H2 and the flow rate X of the water vapor generated in the water vapor supply unit 40 H2O Then, the control unit 70 estimates (calculates) the calculated flow rate X H2 and X H2O In this way, the hydrogen flow rate control and the water flow rate control are performed based on the ratio R in is the target flow rate R in * The flow rate of hydrogen supplied from the hydrogen supply unit 10 to the fuel electrode 51 and the flow rate of water supplied to the water vapor supply unit 40 can be controlled so as to satisfy the above requirements. As a result, it is possible to prevent deterioration of the fuel electrode 51 and improve the efficiency of hydrogen production while reducing thermal energy.

[0086] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, an example in which the anode exhaust gas from the reflux section 60 is introduced into the heater 41 of the water vapor supply section 40 has been described, but when the heater 41 is configured to be divided into a vaporizer and a heater, the anode exhaust gas may be introduced into the vaporizer or into the heater. In addition, the anode exhaust gas from the reflux section 60 may be directly supplied to the anode 51 without passing through the water vapor supply section 40. In addition, if only hydrogen in the anode exhaust gas in the reflux section 60 can be extracted, only the hydrogen may be refluxed to the anode 51. In addition, the present invention can also be applied to the hydrogen production part of an SOEC co-electrolysis device that generates hydrogen and CO by co-electrolyzing water vapor and CO2 using an SOEC, and further synthesizes CH4. Furthermore, the present invention can also be applied to the SOEC mode of an r-SOC system. In this way, the present invention can be modified without departing from the spirit of the invention.

[0087] The present invention may include the following configurations. [1] an electrochemical cell including an anode containing Ni, a solid electrolyte layer, and an air electrode, in which hydrogen and water vapor are supplied to the anode, the water vapor supplied to the anode is electrolyzed to generate hydrogen at the anode and oxygen at the air electrode, anode exhaust gas containing hydrogen is discharged from the anode, and air electrode exhaust gas containing oxygen is discharged from the air electrode; a reflux section that refluxes a portion of hydrogen contained in the fuel electrode exhaust gas to the fuel electrode; A hydrogen production device comprising:

[0088] [2] The hydrogen production apparatus according to [1], the anode exhaust gas contains water vapor; The hydrogen generating device, wherein the reflux section recirculates a portion of the fuel electrode exhaust gas containing hydrogen and water vapor to the fuel electrode.

[0089] [3] The hydrogen production apparatus according to [2], a hydrogen supply unit configured to supply hydrogen from a hydrogen supply source to the fuel electrode; a water vapor supply unit configured to receive water, vaporize the water, generate water vapor, and supply the generated water vapor to the fuel electrode; Ratio R of the sum of the flow rate of hydrogen supplied from the hydrogen supply unit to the anode and the flow rate of hydrogen returned from the reflux unit to the anode to the sum of the flow rate of water vapor generated in the water vapor supply unit and the flow rate of water vapor returned from the reflux unit to the anode in is the predetermined target flow rate R in * a control unit that controls a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so as to satisfy the above condition; A hydrogen production device comprising:

[0090] [4] The hydrogen production apparatus according to [3], The control unit is configured to calculate a ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the anode exhaust gas. out Estimate the estimated ratio R out Based on the ratio R in is the target flow rate R in * a flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and a flow rate of water supplied to the water vapor supply unit so as to satisfy the above condition.

[0091] [5] The hydrogen production apparatus according to [4], The control unit calculates a ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. out A hydrogen production device that estimates the capacity of the hydrogen storage tank.

[0092] [6] The hydrogen production device according to any one of [1] to [5], A hydrogen production device, wherein the temperature of the fuel electrode exhaust gas returned from the return section to the fuel electrode is 100°C or higher.

[0093] [7] The hydrogen production device according to any one of [1] to [6], A hydrogen production device comprising an insulated container in which the electrochemical cell is housed.

[0094] [8] The hydrogen production apparatus according to [7], The hydrogen production device, wherein a cell stack in which a plurality of the electrochemical cells are stacked is housed in the thermal insulation container.

[0095] [9] an electrochemical cell including an anode containing Ni, a solid electrolyte layer, and an air electrode, in which hydrogen and water vapor are supplied to the anode, the water vapor supplied to the anode is electrolyzed to generate hydrogen at the anode and oxygen at the air electrode, an anode exhaust gas containing hydrogen and water vapor is discharged from the anode, and an air electrode exhaust gas containing oxygen is discharged from the air electrode; a hydrogen supply unit configured to supply hydrogen from a hydrogen supply source to the fuel electrode; a water vapor supply unit configured to receive water, vaporize the water, generate water vapor, and supply the generated water vapor to the fuel electrode; a reflux section that refluxes a portion of the anode exhaust gas to the anode; A control device for a hydrogen production device comprising: The control device is configured to calculate a ratio R of a sum of a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of hydrogen returned from the reflux unit to the anode, to a sum of a flow rate of water vapor generated in the water vapor supply unit and a flow rate of water vapor returned from the reflux unit to the anode. in is the predetermined target flow rate R in *a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so that the above-mentioned condition is satisfied.

[0096]

[10] A control device for a hydrogen production device according to [9], The control device controls a ratio R of a flow rate of hydrogen to a flow rate of water vapor contained in the anode exhaust gas. out Estimate the estimated ratio R out Based on the ratio R in is the target flow rate R in * a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so that the above-mentioned

[0097]

[11] A control device for a hydrogen production apparatus according to

[10] , The control device calculates the ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. out A control device for a hydrogen production device that estimates the above.

[0098]

[12] A method for producing hydrogen using an electrochemical cell comprising an anode containing Ni, a solid electrolyte layer, and an air electrode, the method comprising: generating hydrogen by electrolyzing water vapor at the anode and generating oxygen at the air electrode; discharging an anode exhaust gas containing hydrogen and water vapor from the anode; and discharging an air electrode exhaust gas containing oxygen from the air electrode, the method comprising the steps of: a water vapor supplying step of vaporizing water to generate water vapor and supplying the generated water vapor to the anode; a hydrogen supply step of supplying hydrogen from a hydrogen supply source to the fuel electrode; an electrolysis step of generating hydrogen and oxygen by electrolyzing water vapor supplied to the fuel electrode; a reflux step of refluxing a portion of the anode exhaust gas to the anode; A method for producing hydrogen comprising the steps of:

[0099]

[13]

[12] A method for producing hydrogen according to the present invention, A ratio R of the sum of the flow rate of hydrogen supplied to the fuel electrode in the hydrogen supplying step and the flow rate of hydrogen returned to the fuel electrode in the refluxing step to the sum of the flow rate of water vapor supplied to the fuel electrode in the water vapor supplying step and the flow rate of water vapor returned to the fuel electrode in the refluxing step in is the predetermined target flow rate R in * a flow rate control step of controlling the flow rate of hydrogen supplied to the anode in the hydrogen supply step and the flow rate of water vaporized in the water vapor supply step so that the hydrogen production method is achieved.

[0100]

[14]

[13] A method for producing hydrogen according to the present invention, The ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the anode exhaust gas out a step of estimating an anode exhaust gas flow rate ratio, The flow rate control step is performed by controlling the ratio R out Based on the ratio R in is the target flow rate R in * a step of controlling a flow rate of hydrogen supplied to the anode in the hydrogen supply step and a flow rate of water vaporized in the water vapor supply step so that

[0101]

[15]

[14] A method for producing hydrogen according to the present invention, The anode exhaust gas flow rate ratio estimation step is a step of estimating the ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. out A method for producing hydrogen, comprising the step of estimating [Explanation of symbols]

[0102] 1...hydrogen production device, 10...hydrogen supply section, 11...hydrogen flow rate regulator, 12...hydrogen supply path, 20...water supply section, 21...water flow rate regulator, 22...water supply path, 30...air supply section, 31...air flow rate regulator, 32...air supply path, 40...water vapor supply section, 41...heater, 42...mixed gas exhaust path, 50...SOEC (electrochemical cell), 51...fuel electrode, 52...air electrode, 53...solid electrolyte layer, 55...voltage application device, 60...reflux section, 61...blower, 62...reflux path, 70...control section (control device), 80...insulating container, 91...fuel electrode exhaust gas path, 92...air electrode exhaust gas path, 93...flow rate sensor

Claims

1. an electrochemical cell including an anode containing Ni, a solid electrolyte layer, and an air electrode, in which hydrogen and water vapor are supplied to the anode, the water vapor supplied to the anode is electrolyzed to generate hydrogen at the anode and oxygen at the air electrode, anode exhaust gas containing hydrogen is discharged from the anode, and air electrode exhaust gas containing oxygen is discharged from the air electrode; a reflux section that refluxes a portion of hydrogen contained in the fuel electrode exhaust gas to the fuel electrode; A hydrogen production device comprising:

2. The hydrogen production device according to claim 1, the anode exhaust gas contains water vapor; The hydrogen generating device, wherein the reflux section recirculates a portion of the fuel electrode exhaust gas containing hydrogen and water vapor to the fuel electrode.

3. The hydrogen production device according to claim 2, A hydrogen supply unit configured to supply hydrogen from a hydrogen supply source to the fuel electrode; a water vapor supply unit configured to receive water, vaporize the water, generate water vapor, and supply the generated water vapor to the fuel electrode; A ratio R of the sum of the flow rate of hydrogen supplied from the hydrogen supply unit to the anode and the flow rate of hydrogen returned from the reflux unit to the anode, to the sum of the flow rate of water vapor generated in the water vapor supply unit and the flow rate of water vapor returned from the reflux unit to the anode ｉｎ is a predetermined target flow rate ratio R ｉｎ ＊ a control unit that controls a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so as to satisfy the above condition; A hydrogen production device comprising:

4. The hydrogen production device according to claim 3, The control unit is configured to calculate a ratio R of a flow rate of hydrogen to a flow rate of water vapor contained in the anode exhaust gas. ｏｕｔ Estimate the estimated ratio R ｏｕｔ Based on this, the ratio R ｉｎ is the target flow rate R ｉｎ ＊ a flow rate of hydrogen supplied from the hydrogen supply unit to the fuel electrode and a flow rate of water supplied to the water vapor supply unit so as to satisfy the above condition.

5. The hydrogen production device according to claim 4, The control unit calculates a ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. ｏｕｔ A hydrogen production device that estimates the capacity of the hydrogen storage tank.

6. The hydrogen production device according to any one of claims 1 to 5, A hydrogen generating device, wherein the temperature of the anode exhaust gas returned from the reflux section to the anode is 100° C. or higher.

7. The hydrogen production device according to any one of claims 1 to 5, A hydrogen production device comprising an insulated container in which the electrochemical cell is housed.

8. The hydrogen production device according to claim 7, The hydrogen production device, wherein a cell stack in which a plurality of the electrochemical cells are stacked is housed in the thermal insulation container.

9. an electrochemical cell including an anode containing Ni, a solid electrolyte layer, and an air electrode, in which hydrogen and water vapor are supplied to the anode, the water vapor supplied to the anode is electrolyzed to generate hydrogen at the anode and oxygen at the air electrode, an anode exhaust gas containing hydrogen and water vapor is discharged from the anode, and an air electrode exhaust gas containing oxygen is discharged from the air electrode; a hydrogen supply unit configured to supply hydrogen from a hydrogen supply source to the fuel electrode; a water vapor supply unit configured to receive water, vaporize the water, generate water vapor, and supply the generated water vapor to the fuel electrode; a reflux section that refluxes a portion of the anode exhaust gas to the anode; A control device for a hydrogen production device comprising: The control device is configured to determine a ratio R of a sum of a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of hydrogen returned from the reflux unit to the anode, to a sum of a flow rate of water vapor generated in the water vapor supply unit and a flow rate of water vapor returned from the reflux unit to the anode. ｉｎ is a predetermined target flow rate ratio R ｉｎ ＊ a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so that the above-mentioned condition is satisfied.

10. The control device for a hydrogen production device according to claim 9, The control device controls a ratio R of a flow rate of hydrogen to a flow rate of water vapor contained in the anode exhaust gas. ｏｕｔ Estimate the estimated ratio R ｏｕｔ Based on this, the ratio R ｉｎ is the target flow rate R ｉｎ ＊ a flow rate of hydrogen supplied from the hydrogen supply unit to the anode and a flow rate of water supplied to the water vapor supply unit so that the above-mentioned

11. The control device for the hydrogen production device according to claim 10, The control device calculates the ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. ｏｕｔ A control device for a hydrogen production device that estimates the above.

12. A method for producing hydrogen using an electrochemical cell comprising an anode containing Ni, a solid electrolyte layer, and an air electrode, the method comprising: generating hydrogen by electrolyzing water vapor at the anode and generating oxygen at the air electrode; discharging an anode exhaust gas containing hydrogen and water vapor from the anode; and discharging an air electrode exhaust gas containing oxygen from the air electrode, the method comprising the steps of: a water vapor supplying step of vaporizing water to generate water vapor and supplying the generated water vapor to the anode; a hydrogen supply step of supplying hydrogen from a hydrogen supply source to the fuel electrode; an electrolysis step of generating hydrogen and oxygen by electrolyzing water vapor supplied to the fuel electrode; a reflux step of refluxing a portion of the anode exhaust gas to the anode; A method for producing hydrogen comprising the steps of:

13. 13. The method for producing hydrogen according to claim 12, A ratio R of the sum of the flow rate of hydrogen supplied to the fuel electrode in the hydrogen supplying step and the flow rate of hydrogen returned to the fuel electrode in the refluxing step to the sum of the flow rate of water vapor supplied to the fuel electrode in the water vapor supplying step and the flow rate of water vapor returned to the fuel electrode in the refluxing step ｉｎ is a predetermined target flow rate ratio R ｉｎ ＊ a flow rate control step of controlling the flow rate of hydrogen supplied to the anode in the hydrogen supply step and the flow rate of water vaporized in the water vapor supply step so that the hydrogen production method is achieved.

14. The method for producing hydrogen according to claim 13, The ratio R of the flow rate of hydrogen to the flow rate of water vapor contained in the anode exhaust gas ｏｕｔ a step of estimating an anode exhaust gas flow rate ratio, The flow rate control step is performed by controlling the ratio R ｏｕｔ Based on this, the ratio R ｉｎ is the target flow rate R ｉｎ ＊ a step of controlling a flow rate of hydrogen supplied to the anode in the hydrogen supply step and a flow rate of water vaporized in the water vapor supply step so that

15. 15. The method for producing hydrogen according to claim 14, The anode exhaust gas flow rate ratio estimation step estimates the ratio R based on any one of the flow rate of the air electrode exhaust gas, the oxygen concentration of the air electrode exhaust gas, the electrolysis current of the electrochemical cell, the voltage applied to the electrochemical cell, the dew point of the anode exhaust gas, and the amount of condensed water in the anode exhaust gas. ｏｕｔ A method for producing hydrogen, comprising the step of estimating

Images