Evaluation system, program for evaluation system, and evaluation method

Abstract

An evaluation system according to the present invention evaluates the performance of an electrolysis cell that electrolyzes supplied steam to generate hydrogen gas or a test piece that is a portion thereof and comprises a steam supply line that supplies steam to the test piece, a hydrogen gas extraction line that extracts hydrogen gas that is generated from the test piece by electrolysis, a generated hydrogen information acquisition unit that acquires generated hydrogen information that directly or indirectly indicates the hydrogen gas content of a fluid that flows along the hydrogen gas extraction line, and a steam control unit that controls the flow rate of the steam supplied to the test piece from the steam supply line on the basis of the acquired generated hydrogen information.

Description

Evaluation system, evaluation system program, and evaluation method

[0001] The present invention relates to an evaluation system, a program for the evaluation system, and an evaluation method for evaluating an electrolytic cell that generates hydrogen gas by electrolyzing water vapor.

[0002] An electrolytic cell, such as a solid oxide electrolysis cell (SOEC), which generates hydrogen gas by electrolyzing supplied water vapor, is configured to include an electrolytic cell main body that performs electrolysis to generate hydrogen, and a hot module that houses the electrolytic cell main body and maintains it at a high temperature. An evaluation system for evaluating the performance of such an electrolytic cell is configured to supply water vapor and a small amount of hydrogen to the electrolytic cell main body via the hot module, and to measure the concentration and flow rate of hydrogen gas discharged from the electrolytic cell main body after passing through the hot module, thereby evaluating the performance.

[0003] Japanese Patent Application Laid-Open No. 2020-041202

[0004] However, such an evaluation system has a problem in that it is difficult to stably control the steam supplied to the steam electrolysis cell in a transient state after various electrolysis conditions, such as the temperature of the hot module or the applied voltage and current, change, and it takes time for hydrogen to be generated stably from the electrolysis cell.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to enable, in an electrolytic cell evaluation system, stable control of water vapor supplied to an electrolytic cell even in a transient state after a change in conditions.

[0006]

[0006] The present inventors conducted extensive research to solve the above-mentioned problems and found that not only hydrogen gas but also a small amount of unreacted water vapor flows in the hydrogen gas outlet line from which hydrogen gas generated in the electrolytic cell is extracted, and that in the transient state of the evaluation system, the viscosity fluctuates due to fluctuations in the ratio of hydrogen gas to water vapor in the fluid flowing through the hydrogen gas outlet line, and that such fluctuations in viscosity are the main factor hindering stable control of the flow rate of water vapor supplied to the electrolytic cell. Further extensive research led to the discovery that by using information on the hydrogen gas content in the fluid flowing through the hydrogen gas outlet line, the flow rate of water vapor supplied to the electrolytic cell can be controlled taking into account the viscosity of the fluid flowing through the line, and thus conceived the present invention.

[0007] That is, the evaluation system according to the present invention evaluates the performance of a test specimen which is an electrolytic cell or a part thereof that generates hydrogen gas by electrolyzing supplied water vapor, and is characterized by comprising: a water vapor supply line that supplies water vapor to the test specimen; a hydrogen gas extraction line that extracts the hydrogen gas generated from the test specimen by electrolysis; a produced hydrogen information acquisition unit that acquires produced hydrogen information that directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line; and a water vapor control unit that controls the flow rate of water vapor supplied to the test specimen from the water vapor supply line based on the acquired produced hydrogen information.

[0008] In this case, the flow rate of water vapor supplied to the electrolytic cell is controlled based on produced hydrogen information indicating the content of hydrogen gas in the fluid generated in the electrolytic cell under test, and therefore the water vapor supplied to the electrolytic cell can be controlled taking into account the viscosity of the fluid flowing through the line. This allows stable control of the water vapor supplied to the electrolytic cell even in a transient state in which the content of hydrogen gas generated fluctuates, thereby enabling appropriate testing to evaluate the performance of the electrolytic cell.

[0009] In a specific embodiment of the evaluation system, the water vapor control unit controls the flow rate of water vapor supplied from the water vapor supply line to the specimen so as to be constant.

[0010] In order to more appropriately conduct tests to evaluate the performance of the electrolytic cell, it is preferable that the evaluation system further controls the pressure or temperature of the steam supplied to the test piece from the steam supply line by the steam control unit based on the obtained information on the produced hydrogen.

[0011] Specific embodiments of the evaluation system include those in which the generated hydrogen information includes at least one of information regarding the voltage applied to the test specimen during electrolysis, information regarding the current applied to the test specimen during electrolysis, information regarding the flow rate of the hydrogen gas extraction line, information regarding the pressure of the hydrogen gas extraction line, information regarding the hydrogen concentration in the hydrogen gas extraction line, and information regarding the pressure of the water vapor supply line.

[0012] In addition, an embodiment in which the effects of the present invention are particularly pronounced is one in which the hydrogen gas extraction line carries a mixed gas of hydrogen gas produced in the test specimen and unreacted water vapor supplied to the test specimen.

[0013] In an embodiment in which the effects of the present invention are particularly pronounced, the electrolytic cell is a solid oxide electrolytic cell.

[0014] Furthermore, the evaluation system program of the present invention is a program for an evaluation system that evaluates the performance of a test specimen, the program comprising a steam supply line that supplies steam to a test specimen, which is an electrolytic cell or part thereof that generates hydrogen gas by electrolyzing supplied steam, and a hydrogen gas extraction line that extracts the hydrogen gas generated from the test specimen by electrolysis, and is characterized in that it causes a computer to function as a produced hydrogen information acquisition unit that acquires produced hydrogen information that directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line, and a steam control unit that controls the flow rate of steam supplied from the steam supply line to the test specimen based on the acquired produced hydrogen information.

[0015] The evaluation method of the present invention is an evaluation method using an evaluation system for evaluating the performance of a test specimen, the system comprising a steam supply line for supplying steam to a test specimen that is an electrolytic cell or part thereof that generates hydrogen gas by electrolyzing supplied steam, and a hydrogen gas extraction line for extracting the hydrogen gas generated from the test specimen by electrolysis, and is characterized by including a produced hydrogen information acquisition step for acquiring produced hydrogen information that directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line, and a steam control step for controlling the flow rate of steam supplied to the test specimen from the steam supply line based on the acquired produced hydrogen information.

[0016] Such an evaluation system program and evaluation method can achieve the same effects as the evaluation system of the present invention described above.

[0017] According to the present invention as described above, in the electrolytic cell evaluation system, it becomes possible to stably control the steam supplied to the electrolytic cell even in a transient state after a change in conditions.

[0018] 1 is a diagram schematically illustrating the configuration of an evaluation system according to an embodiment of the present invention, and is a flowchart illustrating the operation of the evaluation system according to the embodiment.

[0019] An evaluation system 100 according to an embodiment of the present invention will be described below with reference to the drawings.

[0020] The evaluation system 100 of this embodiment evaluates the performance of an electrolytic cell (in this embodiment, a solid oxide electrolytic cell (SOEC)) that electrolyzes supplied water vapor to produce hydrogen gas and oxygen gas, or a part thereof, as a specimen T. The electrolytic cell includes an anode, a cathode, and a solid oxide electrolyte, and ions move within the solid oxide electrolyte when a voltage and a current are applied, generating oxygen gas at the anode through an oxidation reaction and hydrogen gas at the cathode through a reduction reaction.

[0021] Specifically, this evaluation system 100 includes a water vapor supply line 1 that supplies water vapor to the test specimen T, a hydrogen gas extraction line 3 that extracts hydrogen gas generated from the test specimen T by electrolysis, an oxygen gas extraction line 4 that extracts oxygen gas generated from the test specimen T by electrolysis, a power supply unit 5 that supplies power to the test specimen T to apply voltage, and a control unit 6.

[0022] The specimen T of this embodiment comprises an electrolysis cell body (also referred to as a cell stack) having an anode, a cathode, and a solid oxide electrolyte, and a hot module HM that houses the electrolysis cell body and maintains it at a predetermined temperature.

[0023] The hot module HM includes a heater and a heat insulator and maintains the electrolytic cell body at an appropriate operating temperature, for example, maintaining the electrolytic cell body at a temperature of about 500° C. to about 850° C. The exterior of the hot module HM is provided with a water vapor inlet port P1 for introducing water vapor into the housed electrolytic cell body, a hydrogen gas outlet port P2 for discharging hydrogen gas generated in the electrolytic cell body, an oxygen gas outlet port P3 for discharging oxygen gas generated in the electrolytic cell body, and a power supply port P4 for supplying power to the electrolytic cell body.

[0024] The steam supply line 1 has an upstream end connected to a steam generation source and a downstream end connected to a steam introduction port P1 of the test specimen T, and supplies steam with adjusted flow rate, pressure, and temperature to the test specimen T. The steam supply line 1 is provided with a flow meter 11 that measures the flow rate of the steam to be supplied, a flow control valve 12 that controls the flow rate of the steam to be supplied, a pressure meter 13 that measures the pressure of the steam to be supplied, and a thermometer 14 that measures the temperature of the steam to be supplied. Note that a mass flow controller may be provided instead of the flow meter 11 and the flow control valve 12.

[0025] A hydrogen gas supply line 2, through which hydrogen flows to be supplied to the test piece T, is connected to the downstream side of the fluid control valve in the water vapor supply line 1. The upstream end of the hydrogen gas supply line 2 is connected to a hydrogen gas source. A flow meter 21 for measuring the flow rate of the hydrogen gas flowing, and a flow control valve 22 for controlling the flow rate of the hydrogen gas flowing are provided in the hydrogen gas supply line 2. Note that a mass flow controller may be provided instead of the flow meter 21 and the flow control valve 22.

[0026] The hydrogen gas extraction line 3 has an upstream end connected to the hydrogen gas outlet port P2 of the specimen T and extracts hydrogen gas generated at the cathode of the specimen T. The ratio of the hydrogen gas generated at the cathode and the mixed gas containing unreacted water vapor flowing through the hydrogen gas extraction line 3 changes depending on the state of the electrolysis reaction at the cathode of the specimen T. The water vapor supply line 1 is equipped, in this order, with a pressure gauge 31 that measures the pressure of the fluid extracted from the specimen T and a flow meter 32 (specifically, a mass flow meter) that measures the flow rate. In this embodiment, the hydrogen gas extraction line 3 is further equipped with a gas analyzer 33 (e.g., a gas chromatograph) that measures the hydrogen concentration in the extracted fluid, downstream of the flow meter 32. Note that instead of the flow meter 32, a flow meter that measures the flow rate of the flowing mixed gas and a flow control valve that controls the flow rate of the flowing mixed gas may be provided, or a mass flow controller that measures and controls the flow rate of the flowing mixed gas may be provided.

[0027] The oxygen gas extraction line 4 has its upstream end connected to the oxygen gas outlet port P3 of the test specimen T, and extracts the oxygen gas generated at the anode of the test specimen T. The oxygen gas extraction line 4 is provided with a pressure gauge 41 for measuring the pressure of the extracted oxygen gas and a thermometer for measuring the temperature.

[0028] The control device 6 is a general-purpose or dedicated computer equipped with a CPU, memory, input / output interface, etc., and controls the state of the steam supplied from the steam supply line 1 to the test specimen T to generate hydrogen gas at a stable concentration and flow rate from the test specimen T. The control device 6 performs at least the functions of a produced hydrogen information acquisition unit 61 and a steam control unit 62 by causing the CPU and peripheral devices to cooperate in accordance with a predetermined program stored in a predetermined area of ​​the memory.

[0029] The produced hydrogen information acquisition unit 61 acquires produced hydrogen information that directly or indirectly indicates the content of hydrogen gas in the fluid flowing through the hydrogen gas extraction line 3. The produced hydrogen information includes, for example, at least one of information on the voltage applied to the test piece T during electrolysis, information on the current applied to the test piece T during electrolysis, information on the flow rate of the hydrogen gas extraction line 3, information on the pressure of the hydrogen gas extraction line 3, information on the hydrogen concentration in the hydrogen gas extraction line 3, and information on the pressure of the water vapor supply line 1.

[0030] The produced hydrogen information acquisition unit 61 acquires information regarding the voltage and current applied to the test piece T during electrolysis from the power supply device 5. The produced hydrogen information acquisition unit 61 also acquires information regarding the flow rate and pressure of the hydrogen gas extraction line 3 from the flowmeter 32 and the pressure gauge 31, respectively, and acquires information regarding the hydrogen concentration in the hydrogen gas extraction line 3 from the gas analyzer 33. The produced hydrogen information acquisition unit 61 also acquires information regarding the pressure of the water vapor supply line 1 from the pressure gauge 13.

[0031] The steam control unit 62 controls the flow rate of steam supplied from the steam supply line 1 to the test piece T based on the obtained information on produced hydrogen. Specifically, the steam control unit 62 adjusts the aperture of the flow control valve 12 provided in the steam supply line 1, for example, based on the obtained information on produced hydrogen, to control the flow rate of steam supplied to the test piece T to be constant. The steam control unit 62 may adjust the aperture of the flow control valve 12 by PID control or predictive control based on the obtained information on produced hydrogen.

[0032] In addition, the steam control unit 62 of this embodiment is configured to control not only the flow rate of the supplied steam but also the temperature and pressure based on the acquired information on the produced hydrogen. Specifically, the steam control unit 62 controls the temperature and pressure of the steam supplied to the test piece T so that they are constant.

[0033] The control device 6 also functions as a hydrogen gas control unit 63 that controls the flow rate of hydrogen gas supplied from the hydrogen gas supply line 2 to the test piece T based on the obtained generated hydrogen information. The hydrogen gas control unit 63 adjusts, for example, the mass flow controller 21 provided in the hydrogen gas supply line 2 so as to follow the flow rate of water vapor, and controls the flow rate of hydrogen supplied to the test piece T so that it is constant.

[0034] The water vapor control unit 62 and the hydrogen gas control unit 63 of this embodiment control the flow control valve 12 and the flow control valve 22, respectively, so that the water vapor concentration becomes a predetermined value (e.g., 86% hydrogen gas, 14% water vapor gas) in the mixed gas extracted from the test specimen T through the hydrogen gas extraction line 3. Furthermore, since the response speed of the water vapor flow control is slower than the response speed of the hydrogen gas flow control, this embodiment may be configured such that the water vapor control unit 62 controls the flow control valve 12 to adjust the flow rate of water vapor supplied to the test specimen T, and then the hydrogen gas control unit 63 controls the opening of the on-off valve 22 to adjust the flow rate of hydrogen gas supplied to the test specimen T.

[0035] Furthermore, the control device 6 functions as a calculation unit 64 that calculates measurement values ​​based on each measurement signal, and a display unit 65 that outputs and displays each measurement value and the temperature, pressure, flow rate, etc. that are the objects of control on a display (not shown), etc. Examples of measurement values ​​include the temperature, pressure, and flow rate of the water vapor flowing through the water vapor supply line 1, the temperature, pressure, and flow rate of the hydrogen gas flowing through the hydrogen gas supply line 2, and the temperature, pressure, and flow rate of the mixed gas flowing through the hydrogen gas extraction line 3.

[0036] Next, the operation of the evaluation system 100 of this embodiment will be described with reference to FIG.

[0037] The evaluation system 100 first heats the heater of the hot module HM to raise the temperature of the test piece T, and supplies water vapor and hydrogen gas from the water vapor supply line 1 and the hydrogen gas supply line 2, respectively, to place the hot module HM in an evaluation standby state (step S1). Specifically, for example, the temperature of the hot module HM is set to about 800°C, and a mixed gas composed of 95% water vapor and 5% hydrogen gas is supplied to the hot module HM.

[0038] Next, the power supply device 5 supplies power to the test piece T to start electrolysis (step S2). As a result, hydrogen gas is generated at the hydrogen electrode of the test piece T, and oxygen gas is generated at the oxygen electrode. Furthermore, the viscosity of the fluid flowing through the hydrogen gas extraction line 3 changes as the ratio of hydrogen gas to water vapor changes.

[0039] Next, the water vapor control unit 62 and the hydrogen gas control unit 63 control the flow control valve 12 and the flow control valve 22, respectively, based on the acquired generated hydrogen information, so that the hydrogen gas concentration and water vapor concentration in the mixed gas flowing through the hydrogen gas extraction line 3 become predetermined values ​​(e.g., 86% hydrogen gas, 14% water vapor gas) (step S3).

[0040] Then, when the hydrogen flow rate, hydrogen gas concentration, and water vapor concentration in the mixed gas flowing through the hydrogen gas extraction line 3 reach predetermined values ​​and the test specimen T reaches a stable electrolytic state (step S4), evaluation of the test specimen begins (step S5).

[0041] According to the evaluation system 100 of this embodiment configured as described above, the flow rate of water vapor supplied to the electrolytic cell is controlled based on the produced hydrogen information indicating the content of hydrogen gas in the fluid generated in the electrolytic cell, which is the test specimen T, and therefore the water vapor supplied to the electrolytic cell can be controlled taking into account the viscosity of the fluid flowing through the line. This allows stable control of the water vapor supplied to the electrolytic cell even in a transient state in which the content of hydrogen gas generated fluctuates, enabling appropriate testing to evaluate the performance of the electrolytic cell.

[0042] The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the water vapor control unit 62 controls the temperature and pressure in addition to the flow rate of the water vapor to be supplied, but this is not limiting. In other embodiments, the water vapor control unit 62 may control at least only the flow rate of the water vapor to be supplied.

[0043] In the above embodiment, the hydrogen gas extraction line 3 is provided with the gas analyzer 33, but this is not limiting. In other embodiments, the hydrogen gas extraction line 3 does not necessarily need to be provided with the gas analyzer 33.

[0044] Furthermore, the evaluation system 100 of the above embodiment evaluates the performance of a solid oxide electrolysis cell (SOEC) or a part thereof as the specimen T, but is not limited to this. The evaluation system 100 may use an electrolysis cell other than a solid oxide electrolysis cell as the specimen T, as long as the electrolysis cell electrolyzes supplied water vapor to produce hydrogen gas and oxygen gas.

[0045] In the above embodiment, the evaluation of the specimen T is started when the specimen T reaches an electrolytically stable state, but this is not limited thereto. In other embodiments, the evaluation of the specimen T may be started before the specimen T reaches an electrolytically stable state.

[0046] In another embodiment, a dew point meter may be provided in the hydrogen gas extraction line 3 to measure the humidity of the fluid flowing through the hydrogen gas extraction line 3, and the measured humidity may be used as the generated hydrogen information.

[0047] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention.

[0048] According to the above-described evaluation system of the present invention, in the electrolytic cell evaluation system, the water vapor supplied to the electrolytic cell after a change in conditions can be stably controlled.

[0049] REFERENCE SIGNS LIST 100: Evaluation system 1: Steam supply line 3: Hydrogen gas extraction line 4: Oxygen gas extraction line 61: Produced hydrogen information acquisition unit 62: Steam control unit T: Test piece

Claims

1. An evaluation system for evaluating the performance of a test specimen which is an electrolytic cell or a part thereof which generates hydrogen gas by electrolyzing supplied water vapor, comprising: a water vapor supply line which supplies water vapor to the test specimen; a hydrogen gas extraction line which extracts the hydrogen gas generated from the test specimen by electrolysis; a produced hydrogen information acquisition unit which acquires produced hydrogen information which directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line; and a water vapor control unit which controls the flow rate of water vapor supplied to the test specimen from the water vapor supply line based on the acquired produced hydrogen information.

2. The evaluation system according to claim 1, wherein the water vapor control unit controls the flow rate of water vapor supplied from the water vapor supply line to the specimen so as to be constant.

3. An evaluation system as described in claim 1 or 2, wherein the steam control unit further controls the pressure or temperature of the steam supplied to the test piece from the steam supply line based on the acquired information on the produced hydrogen.

4. An evaluation system according to any one of claims 1 to 3, wherein the produced hydrogen information includes at least one of information regarding the voltage applied to the test specimen during electrolysis, information regarding the current applied to the test specimen during electrolysis, information regarding the flow rate of the hydrogen gas extraction line, information regarding the pressure of the hydrogen gas extraction line, information regarding the hydrogen concentration in the hydrogen gas extraction line, and information regarding the pressure of the water vapor supply line.

5. An evaluation system according to any one of claims 1 to 4, wherein the hydrogen gas extraction line is a line through which a mixture of hydrogen gas generated in the test specimen and unreacted water vapor supplied to the test specimen flows.

6. The evaluation system according to any one of claims 1 to 5, wherein the electrolytic cell is a solid oxide electrolytic cell.

7. A program for an evaluation system for evaluating the performance of a test specimen, the test specimen comprising a steam supply line that supplies steam to a test specimen, which is an electrolytic cell or part thereof that generates hydrogen gas by electrolyzing supplied steam, and a hydrogen gas extraction line that extracts the hydrogen gas generated from the test specimen by electrolysis, the program for an evaluation system causing a computer to function as a generated hydrogen information acquisition unit that acquires generated hydrogen information that directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line, and a steam control unit that controls the flow rate of steam supplied to the test specimen from the steam supply line based on the acquired generated hydrogen information.

8. An evaluation method using an evaluation system for evaluating the performance of a test specimen, the system comprising a steam supply line for supplying steam to a test specimen which is an electrolytic cell or part thereof that generates hydrogen gas by electrolyzing supplied steam, and a hydrogen gas extraction line for extracting the hydrogen gas generated from the test specimen by electrolysis, the evaluation method comprising: a produced hydrogen information acquisition step for acquiring produced hydrogen information that directly or indirectly indicates the hydrogen gas content in the fluid flowing through the hydrogen gas extraction line; and a steam control step for controlling the flow rate of steam supplied to the test specimen from the steam supply line based on the acquired produced hydrogen information.

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