JP7039504B2 - Control device and control method for hydrogen production plant - Google Patents

Description

An embodiment of the present invention relates to a control device for a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell, and a control method for the hydrogen production plant.

Attention is being paid to the realization of a hydrogen energy society that uses hydrogen as the main energy medium. The high temperature steam electrolysis method is widely known as a technique for efficiently producing hydrogen. In this high-temperature steam electrolysis method, hydrogen and oxygen are generated by electrolyzing (electrolyzing) steam at a high temperature of 500 ° C. or higher (usually about 700 ° C.) using a solid oxide electrolyzer cell (SOEC). A feature of this method is that by electrolyzing water vapor in a high temperature environment, the electric power required for electrolysis can be reduced as compared with water electrolysis at room temperature. In addition, because the temperature is high, the reaction activity of the electrodes is high and the electrode overvoltage is small, and since the electrolytic reaction proceeds using the heat of the environment, the heat loss of electrolysis generated by the SOIC during electrolysis can be used for the electrolytic reaction. be. Due to these characteristics, water vapor can be electrolyzed without energy loss during electrolysis.

Japanese Unexamined Patent Publication No. 2016-37643 International Publication No. WO2018 / 033948A1

When considering the basic operation of a hydrogen production plant, it is necessary to consider the effects of initial deterioration of SOIC characteristics. When the SOIC is kept at a constant high temperature (about 700 ° C) and operated near the thermal neutral point voltage, the initial deterioration of the SOIC characteristics after the start of the high temperature operation is large, for example, when the resistance value increases by about 20% in 2500 hours. It has been reported.

When a constant voltage operation is performed, the resistance value increases with the lapse of the operation time, so that the current decreases and the amount of hydrogen produced decreases. Conversely, if a specified amount of hydrogen is to be produced in the stable period when the resistance value of SOEC is saturated, a larger steam flow rate and power supply capacity will be required immediately after the start of operation, and the initial equipment scale will be large. There is a problem of becoming.

Further, when the current constant operation is performed, the amount of hydrogen produced becomes constant, and therefore the steam flow rate and the amount of hydrogen produced also become constant. However, as the resistance value of the SOIC increases with the passage of operating time, the supply voltage to the cell stack composed of the SOIC rises, and the SOCC becomes overvoltage, resulting in an increase in the scale of the power supply equipment. do. If the current is reduced in order to suppress the voltage rise, there is a problem that the amount of hydrogen produced is reduced.

As a hydrogen production plant, we would like to design and manufacture equipment that allows a substantially constant flow of steam, hydrogen, etc. to flow through systems such as boilers, heat exchangers, and pipes from the initial stage of operation to the stable period. Also, as a power supply facility, we want to supply hydrogen by supplying a substantially constant voltage and current.

The embodiment of the present invention has been made in consideration of the above-mentioned circumstances, and even if there is a large change in the characteristics of the electrolytic cell as an initial deterioration, the scale of the plant equipment is not increased and hydrogen is used efficiently. It is an object of the present invention to provide a control device and a control method for a hydrogen production plant capable of producing well and stably.

The control device of the hydrogen production plant according to the embodiment of the present invention is a control device of a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell, and is a voltage for measuring a voltage value of an electrolytic current supplied to the electrolytic cell. A measuring means, a temperature measuring means for measuring the temperature of the electrolytic cell, a current setting value of the electrolytic current are output, and a temperature setting value changing logic is provided, and the temperature setting of the electrolytic cell is provided by this temperature setting value changing logic. The current value of the electrolytic current is controlled based on the first control means that changes the value and outputs, and the current operation signal obtained from the current set value from the first control means, and is measured by the temperature measuring means. It has a second control means for controlling the temperature of the electrolytic cell by performing a temperature control calculation so that the measured temperature value is matched with the temperature set value, and the temperature set value changing logic is provided at the initial stage of operation. When the temperature set value is set to a temperature lower than the maximum operating temperature of the electrolytic cell, and the voltage measured value measured by the voltage measuring means increases by a specified value from the thermal neutral point voltage of the electrolytic cell alone. It is characterized in that the temperature setting value is sequentially increased by a predetermined value and set.

The method for controlling a hydrogen production plant according to the embodiment of the present invention is a method for controlling a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell. At the initial stage of operation, the temperature set value of the electrolytic cell is set to the electrolytic cell. The temperature is set to a temperature lower than the maximum operating temperature of the electrolytic cell, the temperature of the electrolytic cell is controlled based on this temperature set value, and the voltage value of the electrolytic current supplied to the electrolytic cell is the thermal neutral point voltage of the electrolytic cell alone. When the temperature is increased by a specified value, the temperature setting value is sequentially increased by a predetermined value and set, and the temperature of the electrolytic cell is controlled based on the increased temperature setting value. be.

Further, the control method of the hydrogen production plant according to the embodiment of the present invention is the control method of the hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell, when the temperature measurement value reaches the maximum operating temperature of the electrolytic cell. , The temperature set value is fixed to the maximum operating temperature, and the voltage control calculation is performed so that the voltage measurement value matches the voltage set value to obtain the current operation signal, and the current value of the electrolytic current is controlled. This is a characteristic control method.

According to the embodiment of the present invention, even if there is a large change in the characteristics of the electrolytic cell as an initial deterioration, hydrogen can be efficiently and stably produced without increasing the scale of the plant equipment.

The system diagram which shows the hydrogen production plant which the control apparatus of the hydrogen production plant which concerns on 1st Embodiment controls. The block diagram which shows the inside of the electric furnace in which the cell stack of FIG. 1 is housed. The block diagram which shows the control device of the hydrogen production plant which controls the hydrogen production plant of FIG. The graph which shows the heat absorption characteristic of the solid oxide electrolyzer cell (SOEC) which comprises the cell stack of FIG. 1 and FIG. The graph which shows the current-voltage characteristic of SOEC. The graph which shows the initial deterioration characteristic of SOEC. The graph which shows each characteristic of the temperature, voltage, and current of SOEC controlled by the control device of FIG. The graph which shows the negative resistance temperature characteristic of SOEC. An explanatory diagram illustrating a control operation executed by the control device of FIG. 3 at the initial stage of operation of a hydrogen production plant. It is explanatory drawing explaining the control operation which the control device of FIG. 3 performs when SOEC reaches the operating maximum temperature. The block diagram which shows the control apparatus of the hydrogen production plant which concerns on 2nd Embodiment. The block diagram which omits a part of the control apparatus of the hydrogen production plant which concerns on 3rd Embodiment. The block diagram which shows the omitted part of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[A] First Embodiment (FIGS. 1 to 10)
FIG. 1 is a system diagram showing a hydrogen production plant to be controlled by the control device of the hydrogen production plant according to the first embodiment. The hydrogen production plant 10 is composed of a solid oxide electrolyzer cell (SOEC: Solid Oxide Electrolyzer Cell), and houses a cell stack 1 for producing hydrogen by electrolysis of steam and the cell stack 1, for example, about 700 ° C. The electric furnace 2 that keeps the cell stack 1 at a high temperature, the steam-hydrogen line 3 that supplies steam to the cell stack 1 and recovers hydrogen, and the air-oxygen line 4 that supplies air to the cell stack 1 and discharges the generated oxygen. And, it is composed of.

The steam-hydrogen line 3 includes a steam line 3A for supplying steam to the cell stack 1 and a hydrogen line 3B for recovering hydrogen generated in the cell stack 1. Further, the air-oxygen line 4 includes an air line 4A for supplying air to the cell stack 1 and an oxygen line 4B for discharging the oxygen generated in the cell stack 1.

Heat exchangers 5 and 6 are installed in the steam-hydrogen line 3 and the air-oxygen line 4, respectively, for heat recovery. The heat exchanger 5 raises the temperature of the steam supplied to the SOIC by using the energy of the hydrogen gas from the SOIC which has become hot in the atmosphere of the electric furnace 2. Further, the heat exchanger 6 raises the temperature of the air supplied to the SOIC by using the energy of the oxygen gas from the SOIC which has become hot in the atmosphere of the electric furnace 2.

A boiler 7 for producing steam used for electrolysis is installed in the steam line 3A of the steam-hydrogen line 3. The electric power used for electrolysis is supplied from the cell power supply device 8 to the cell stack 1. Electric power is supplied to the cell power supply device 8 from the outside of the hydrogen production plant 10. The electric power may be electric power generated by hydraulic power or thermal power, or may be electric power generated from renewable energy such as solar power or wind power.

Next, FIG. 2 shows the internal configuration of the electric furnace 2 in which the cell stack 1 is housed. Since the SOEC has a small capacity, a plurality of sheets (for example, 25 sheets) are stacked to form the cell stack 1. FIG. 2 shows an example in which 24 of the cell stacks 1 are housed in the electric furnace 2. Electric heaters 15 are installed on the top, bottom, left, right, front and back of the electric furnace 2 and are covered with a heat insulating material 16, and the inside of the electric furnace 2 is maintained at a high temperature of 500 ° C. or higher, for example, about 700 ° C.

The hydrogen electrode inlet 11A of the electric furnace 2 is connected to the steam line 3A, and a gas containing steam as a main component is supplied to the hydrogen electrode inlet 11A. Further, the hydrogen electrode outlet 11B of the electric furnace 2 is connected to the hydrogen line 3B, and a gas containing hydrogen as a main component generated by electrolyzing water vapor is discharged from the hydrogen electrode outlet 11B. Further, the oxygen electrode inlet 12A of the electric furnace 2 is connected to the air line 4A, and air is supplied to the oxygen electrode inlet 12A. Further, the oxygen electrode outlet 12B of the electric furnace 2 is connected to the oxygen line 4B, and air containing oxygen generated by electrolysis of water vapor is discharged from the oxygen electrode outlet 12B.

Each of the cell stacks 1 in the electric furnace 2 is connected in parallel to the steam introduction flow path 13A communicating with the hydrogen electrode inlet 11A and the hydrogen recovery flow path 13B communicating with the hydrogen electrode outlet 11B. Further, each of the cell stacks 1 is connected in parallel to the air introduction flow rate 14A communicating with the oxygen electrode inlet 12A and the oxygen discharge flow path 14B communicating with the oxygen electrode outlet 12B. Each cell stack 1 in the electric furnace 2 is connected in parallel to the steam introduction flow path 13A and the hydrogen recovery flow path 13B, and the air introduction flow path 14A and the oxygen discharge flow path 14B as described above. The water vapor and air supplied to the cell stack 1 are evenly distributed in flow rate, and the pressure loss of the water vapor-hydrogen line 3 and the air-oxygen line 4 is reduced as compared with the pressure loss of the cell stack 1.

Further, for example, 24 cell stacks 1 installed in the electric furnace 2 are electrically connected in series with 8 cells each in the first embodiment to form a series A, a series B, and a series C, respectively. .. Each of these three series (series A, series B, series C) is independently connected to the cell power supply device 8, and each series A, B, and C is electrolyzed from the cell power supply device 8. Electrolytic power is supplied.

When the series A, the series B, and the series C are electrically connected in parallel, three series (series A, B, C), two series (for example, series A, B), and one series (for example, series A) are obtained. When the connection is switched, the total combined resistance changes according to the number of switched series, making it difficult to maintain the SOEC thermal neutral point voltage in the cell stack 1. Therefore, the power is independently supplied to the series A, the series B, and the series C.

FIG. 3 shows a control device 20 for a hydrogen production plant using SOEC according to the first embodiment. The cell stack 1 and the electric furnace 2 for accommodating the cell stack 1 are shown on the right side of FIG. An electrolytic current is supplied to the cell stack 1 from the cell power supply device 8 via the power supply line 17. A voltage measuring instrument 21 as a voltage measuring means is installed in the power supply line 17, and the voltage measuring instrument 21 measures the voltage value of the electrolytic current supplied to the cell stack 1. Further, electric power is supplied from the heater control device 22 to the electric heater 15 installed in the electric furnace 2. Further, a temperature measuring device 23 as a temperature measuring means is installed in the electric furnace 2, and the temperature measuring device 23 measures the temperature of the atmosphere in which the cell stack 1 is placed, that is, the temperature of the cell stack 1.

As described above, the control device 20 of the hydrogen production plant is a hydrogen production plant that produces hydrogen by high-temperature steam electrolysis using high-temperature steam at 500 ° C. or higher (for example, 700 ° C.) using a cell stack 1 composed of SOEC. 10 control devices, a voltage measuring device 21, a temperature measuring device 23, a PLC (Programmable Logical Controller) 24 as a second control means, and a plant control device 25 as a first control means which is an upstream control system of the PLC 24. Consists of having.

The plant control device 25 outputs the current set value m and the voltage set value o of the electrolytic current supplied to the cell stack 1 to the PLC 24. The voltage set value o is a voltage value corresponding to a thermal neutral point voltage of about 1.3 V of a single SOEC constituting the cell stack 1. The current set value m is, for example, a current value corresponding to a current density of 0.5 A / cm ² . The plant control device 25 includes a temperature set value change logic 30 that changes and sets the temperature set value s of the cell stack 1 and outputs the temperature set value to the PLC 24.

That is, the temperature set value change logic 30 sets the temperature set value s to a temperature lower than the maximum operating temperature (for example, 700 ° C.) of the SOEC (for example, 600 ° C.) at the initial stage of operation of the hydrogen production plant 10, and is a voltage measuring instrument. Each time the voltage measurement value p of the electrolytic current measured by 21 increases by a specified value from the thermal neutral point voltage (about 1.3 V) of the SOEC unit, the temperature set value s is sequentially increased and set by a predetermined value. .. Further, the temperature set value change logic 30 sequentially increases the temperature set value s by a predetermined value when the temperature measurement value t of the cell stack 1 (SOEC) measured by the temperature measuring device 23 reaches the operating maximum temperature of the SOIC. The above-mentioned temperature setting value change is stopped, and the temperature setting value s is fixedly set to the maximum operating temperature of SOC (for example, 700 ° C.).

The PLC 24 obtains the current operation signal n from the current set value m from the plant control device 25, and outputs the current operation signal n to the cell power supply device 8 via the a contact of the switch 26 to obtain this cell power supply. The current value of the electrolytic current supplied from the apparatus 8 to the cell stack 1 is controlled. Further, the PLC 24 performs a temperature control calculation using the temperature controller 29 so that the temperature measurement value t of the cell stack 1 (SOEC) measured by the temperature measuring instrument 23 matches the temperature set value s, and operates the temperature. By obtaining the signal u and outputting the temperature operation signal u to the heater control device 22, the current value supplied from the heater control device 22 to the electric heater 15 is controlled, and the temperature of the cell stack 1 (SOEC) is controlled. Control.

Further, when the temperature measurement value t of the cell stack 1 (SOEC) measured by the temperature measuring device 23 reaches the maximum operating temperature of the SOIC, the PLC 24 provides a current operation signal based on the current set value m from the plant control device 25. Instead of finding n, the voltage measurement value p (voltage measurement value p measured by the voltage measuring device 21) of the electrolytic current supplied from the cell power supply device 8 to the cell stack 1 matches the voltage set value o. A voltage control calculation is performed using the voltage controller 27, a current operation signal q is obtained from this calculated value by a proportional gain 28, and this current operation signal q is output to the cell power supply device 8 via the b contact of the switch 26. By doing so, the current value of the electrolytic current supplied from the cell power supply device 8 to the cell stack 1 is controlled.

The control operation of the PLC 24 and the plant control device 25 described above will be described more specifically below.
The current set value m for steam electrolysis is output from the plant control device 25 to the PLC 24, and is output to the cell power supply device 8 as a current operation signal n via the a contact of the switch 26. Here, the a contact of the switch 26 outputs the current operation signal n obtained from the current set value m by the PLC 24 to the cell power supply device 8. The voltage set value o is also output from the plant control device 25 to the PLC 24. The PLC 24 compares the voltage set value o with the voltage measurement value p measured by the voltage measuring device 21, performs a voltage control calculation by the voltage controller 27, and performs a voltage control calculation via the proportional gain 28 and the b contact of the switch 26. Then, the current operation signal q is output to the cell power supply device 8. Here, the b contact of the switch 26 outputs the current operation signal q from the voltage controller 27 side to the cell power supply device 8.

The temperature set value s of the SOEC constituting the cell stack 1 is output to the PLC 24 from the temperature set value changing logic 30 (described later) of the plant control device 25. The PLC 24 compares the temperature set value s with the temperature measured value t measured by the temperature measuring device 23, performs a temperature control calculation by the temperature controller 29, and outputs a temperature operation signal u to the heater control device 22. do.

The voltage measurement value p is also input to the plant control device 25. The plant control device 25 has a temperature set value changing logic 30 that increases the temperature set value s by a predetermined value when the voltage measurement value p increases by a specified value from the thermal neutral point voltage of the SOEC unit of about 1.3 V. The temperature set value change logic 30 outputs the changed temperature set value s to the PLC 24. Further, the temperature setting value changing logic 30 increases the above-mentioned temperature setting value s by a specified value when the temperature measurement value t measured by the temperature measuring device 23 reaches the maximum operating temperature (about 700 ° C.) of SOC. It has a function to stop changing the temperature set value and fix the temperature set value s to the maximum operating temperature of SOC.

When the temperature measured value t reaches the maximum operating temperature of SOC, the PLC 24 performs a voltage control calculation by the voltage controller 27 so that the voltage measured value p is maintained at the thermal neutral point voltage of about 1.3 V of the SOIC alone. The current operation signal q is output to the cell power supply device 8 via the proportional gain 28 and the b contact of the switch 26. The temperature set value changing logic 30 also has a function of transmitting a switching signal c for switching the contact of the switching device 26 to the switching device 26.

Here, the characteristics of the solid oxide electrolyzer cell (SOEC) will be described. FIG. 4 shows the heat absorption and heat generation characteristics of SOEC. Since water electrolysis is an endothermic reaction, the SOEC temperature (cell temperature) decreases as the current density increases, but when the current density is further increased, the exothermic reaction due to the ohm loss of the SOIC exceeds the endothermic reaction, and the cell The temperature starts to rise. The part marked with a circle is a heat neutral point where endothermic heat and heat generation are equal, and SOEC is operated near the heat neutral point from the viewpoint of improving hydrogen generation efficiency.

The current-voltage (IV) characteristics of the SOEC are shown in FIG. The voltage (cell voltage) of the SOIC is theoretically about 1.3V for the SOEC alone at the heat neutral point where the endothermic and heat generation are balanced. The voltage at which the current starts to flow is called the open circuit voltage. The open circuit voltage of the SOIC alone is about 0.9V, and the cell voltage of the SOIC gradually increases as the current density increases.

FIG. 6 shows an example of the initial deterioration characteristics of the SOEC after the start of operation. Deterioration of SOEC depends on operating temperature, voltage and current density. That is, the higher the operating temperature and the higher the voltage and current density, the higher the deterioration rate and the higher the resistance value of the SOIC. The causes of deterioration of SOEC are the formation of a high resistance phase due to the diffusion of elements between each constituent layer (hydrogen electrode layer, oxygen electrode layer, etc.) during the production of SOEC, and the formation of Co in the oxygen electrode layer during electrolytic operation. Localization and morphological changes of Ni particles in the hydrogen electrode layer are considered.

The initial deterioration characteristics of SOEC vary depending on the structure of SOEC, operating conditions, etc., but FIG. 6 is an example of typical high temperature deterioration characteristics. The X-axis is the time, and the Y-axis is the percent display of the SOEC voltage (cell voltage). At 2500 hours, the cell voltage increased to 120% due to the increase in the resistance value of SOEC. Even in the stable period after 2500 hours, the deterioration of SOEC progresses, but the deterioration rate becomes small.

FIG. 7 shows the characteristics of the temperature, voltage, and current of the SOEC controlled by the control device 20 of the hydrogen production plant. The operation of the control device 20 will be described with reference to FIGS. 9 and 10. There was a problem that the current at the initial stage of operation was very large when performing constant voltage operation, but as shown in FIG. 7, the operation is started from, for example, 600 ° C., and the temperature of the SOIC increases as the resistance value of the SOIC increases. The set value s is gradually increased. Here, SOEC has a negative resistance temperature characteristic in which the cell resistance decreases as the cell temperature rises, as shown in FIG. Therefore, by starting the operation from 600 ° C. and gradually increasing the temperature set value s of the SOIC according to the increase of the resistance value of the SOIC, the increase of the resistance value of the SOIC is suppressed and the resistance value is substantially constant ( Cell resistance), for example, the current density flowing through the SOEC is maintained at 0.5 A / cm ² . This control is realized by taking advantage of the bold lines in FIG.

First, a case where the switch is used as the a contact will be described. The temperature set value change logic 30 sets the current set value m to a value equivalent to 0.5 A / cm ² , and the PLC 24 causes the current operation signal n based on the current set value m to pass through the a contact of the switch 26 to the cell power supply device 8. Is output to, and an electrolytic current having a constant current value is supplied from the cell power supply device 8 to the cell stack 1. The SOIC deteriorates due to the continuation of the high temperature operation (600 ° C.) of the cell stack 1, and the resistance value of the SOIC gradually increases. This increase in the resistance value is caused by the voltage measuring instrument 21 of the power supply line 17. It is detected and measured as an ascent.

The temperature set value changing logic 30 of the plant control device 25 inputs the voltage measured value p from the voltage measuring device 21 to increase the temperature set value s. The PLC 24 compares the temperature set value s with the temperature measurement value t measured by the temperature measuring device 23, performs a temperature control calculation by the temperature controller 29, and outputs a temperature operation signal u to the heater control device 22. Then, the temperature of the cell stack 1 is raised. Since the resistance value of the SOEC of the cell stack 1 decreases as the temperature rises due to the negative resistance temperature characteristic, the measured voltage value p returns to the equivalent of the thermal neutral point voltage of 1.3V of the SOEC alone.

As a result of trial calculation, the voltage V of each series A, B, and C in FIG. 2 is 260V (= 1.3V × 25 × 8) when, for example, eight cell stacks 1 in which 25 SOECs are stacked are connected in series. Therefore, the time until the a / b switching point (700 ° C.) in FIG. 7 in which the switch 26 switches from the a contact to the b contact is about 300 days. Therefore, the temperature set value s may be increased at a rate of about 1 ° C. every 3 days by the temperature set value change logic 30. When the increase in the resistance value of the initial deterioration of the SOEC is measured by the voltage measuring instrument 21 as an increase in the voltage value, it is necessary to measure it as a significant change in consideration of the accuracy of the voltage measurement and the like. Therefore, if a voltage rise of, for example, 3 V from the above-mentioned voltage 260 V corresponding to the heat neutral point is used as a criterion for determining the temperature set value change logic 30, the temperature set value s is increased by 2 ° C. from 600 ° C. to 602 ° C. at each time point. do it.

Approximately from the initial deterioration characteristics of SOEC in FIG. 6, the voltage measured value p rises by 3 V in about 6 days. Therefore, the temperature setting value changing logic 30 sets the temperature set value s to 2 ° C. once every 6 days. The temperature setting value will be changed by increasing it little by little. By repeating this temperature setting value change 50 times, the temperature setting value s increases from 600 ° C. to 700 ° C. in 300 days. The above estimation is an example, and different results will be obtained if the SOEC used or the system configuration is changed.

Next, a case where the switch of FIG. 10 is used as the b contact will be described. The SOEC temperature (cell temperature) reaches 700 ° C., which is the maximum operating temperature, at the a / b switching point in FIG. 7, but the temperature set value s cannot be further increased due to the characteristics of the SOIC. Therefore, the temperature set value change logic 30 sets the temperature set value s by fixing it to the maximum operating temperature of 700 ° C. At the same time, the temperature set value change logic 30 outputs the switching signal c to switch the switch 26 from the a contact to the b contact. The PLC 24 compares the temperature set value s with the temperature measured value t measured by the temperature measuring device 23, performs a temperature control calculation by the temperature controller 29, and outputs a temperature operation signal u to the heater control device 22. do. As a result, the cell stack 1 is maintained at a constant temperature of 700 ° C., which is the maximum operating temperature.

At this time, the deterioration of the SOIC progresses and the resistance value increases, and this increase in the resistance value is detected and measured as an increase in the voltage value by the voltage measuring instrument 21 of the power supply line 17. Therefore, the PLC 24 compares the voltage set value o of 260 V (corresponding to the single unit voltage of SOIC of 1.3 V) with the voltage measured value p, performs a voltage control calculation by the voltage controller 27, and performs the proportional gain 28 and the switch 26. The current operation signal q is output to the cell power supply device 8 via the b contact of. As for voltage control, the increased voltage is reduced to 260V (equivalent to the single unit voltage of SOIC, 1.3V). As a result, as shown in FIG. 7, the current value (current density) of the electrolytic current is due to the deterioration of SOIC. It gradually decreases as the resistance value increases, and the amount of hydrogen produced decreases by that amount.

Here, the effect of using the control device 20 dedicated to the SOEC instead of applying the standard conventional power supply device as the control device of the hydrogen production plant 10 will be described.

Standard conventional power supplies operate in constant current mode or constant voltage mode. In the constant current mode, the resistance value of the cell stack (SOEC), which is a load, is fixed to a certain value, so the voltage applied to the SOIC is changed to constantly adjust the current flowing through the SOIC. Therefore, when the deterioration of the SOIC progresses and the resistance value of the SOIC increases and the temperature of the SOIC reaches the maximum operating temperature, the voltage applied to the SOIC is reduced according to the subsequent increase in the resistance value of the SOIC. Reset to the value. Therefore, in SOEC, the voltage becomes low and it becomes difficult to maintain the thermal neutral point voltage.

On the other hand, in the control device 20 of the first embodiment, as shown in FIGS. 7 and 9, when the switch 26 is an a contact, the current supplied to the cell stack 1 is 0.5 A / /. It is a control to increase the temperature of the SOIC by controlling the temperature of the SOIC so that the voltage applied to the SOIC becomes equivalent to 1.3V in a constant operation equivalent to cm ² , and the temperature of the SOIC is the maximum operating temperature of 700 ° C. Even when the temperature reaches, the single-unit voltage of the SOIC is maintained at the thermal neutral point voltage of 1.3 V.

Next, in the case of the constant voltage mode of a standard conventional power supply, the resistance value of the SOIC of the cell stack, which is the load, is fixed to a certain value, so the current flowing through the SOIC is changed to change the voltage applied to the SOIC. Adjust to a constant level. Therefore, when the deterioration of the SOIC progresses and the resistance value of the SOIC increases and the SOIC reaches the maximum operating temperature, the current flowing through the SOIC is reset to a small value according to the subsequent increase in the resistance value of the SOIC. do. Therefore, the simple substance voltage of the SOIC is maintained at the thermal neutral point voltage, but the current flowing through the SOIC becomes small and the amount of hydrogen produced decreases.

Further, in the case of a standard conventional power supply device, although it is in the constant voltage mode, a large current flows through the SOIC at the time of startup when the deterioration of the SOIC has not progressed and the resistance value is small at the initial stage of operation. The power supply may trip overcurrent. In this case, the supply of steam is insufficient with respect to the current supplied to the SOIC, and the cell stack may be damaged by steam withering.

On the other hand, in the control device 20 of the first embodiment, as shown in FIGS. 7 and 10, when the switch 26 is a b-contact, the SOEC temperature is a constant operation of 700 ° C., and the SOIC is a single unit. This is a control in which the current supplied to the SOIC is controlled so that the voltage corresponds to 1.3 V, and the current flowing through the SOIC is reduced by the increase in the resistance value due to the deterioration of the SOIC. In this control, even if the SOIC reaches the maximum operating temperature of 700 ° C., the SOEC voltage is maintained at the thermal neutral point voltage of 1.3 V.

Further, in the control device 20, when the deterioration of the SOIC has not progressed at the initial stage of operation and the resistance value is small, the current flowing through the SOIC is equivalent to 0.5 A / cm ² with the switch 26 as the a contact. Since it is operated at a constant current, there is no concern that a large current will flow, and there is no risk that the cell stack will wither and be damaged due to insufficient supply of steam due to the large current flowing.

As described above, in the control device 20 of the first embodiment, in the initial stage of operation, the switch 26 is used as the a contact, and the temperature of the SOIC is kept constant while supplying a constant current to the cell stack 1. Is gradually increased from a temperature lower than the maximum operating temperature to control the temperature so that the resistance value of the SOIC is substantially constant. Further, in the stable operation period when the SOEC reaches the maximum operating temperature of 700 ° C., the switch 26 is used as the b contact, and the resistance value of the SOIC is set in order to keep the voltage constant while keeping the SOEC temperature at the maximum operating temperature. Current control is performed to gradually reduce the current supplied to the SOEC according to the increase. As a result, the control device 20 of the first embodiment is a highly reliable and safe control device dedicated to SOEC.

Since it is configured as described above, according to the first embodiment, the following effects (1) and (2) are obtained.
(1) In a hydrogen production plant 10 by high-temperature steam electrolysis using SOIC, when standard conventional constant voltage control is performed, the resistance value of SOIC increases due to deterioration of SOIC due to the passage of operating time, which causes SOIC. The current to hydrogen is reduced and the amount of hydrogen produced is reduced. In addition, when standard conventional constant voltage control is performed, the resistance value of the SOIC is small only at the initial stage of operation, so the current supplied to the SOIC at the initial stage of operation becomes extremely large, and large-capacity power supply equipment and steam supply equipment become available. You will need it. Furthermore, when standard conventional constant current control is performed, the voltage increases sharply due to the increase in resistance due to deterioration of SOIC, and when the current is reduced to suppress this voltage increase, the amount of hydrogen produced decreases. It ends up.

On the other hand, according to the control device 20 of the hydrogen production plant in the first embodiment, the temperature set value change logic 30 of the plant control device 25 causes the SOIC to start from a temperature lower than the maximum operating temperature at the initial stage of operation of the plant. It is started and the temperature of the SOIC is sequentially increased according to the increase in the resistance value due to the deterioration of the SOIC. As a result, the SOIC suppresses the increase in the resistance value due to its own negative resistance temperature characteristic and becomes an almost constant resistance value, and the voltage value and the current value of the electrolytic current supplied to the SOIC become almost constant, and the electrolysis is performed. Can produce hydrogen. As a result, even if there is a large change in the SOEC characteristics as an initial deterioration, hydrogen can be efficiently and stably produced without increasing the scale of the hydrogen production plant 10.

(2) When the SOIC reaches the maximum operating temperature, the temperature set value changing logic 30 of the plant control device 25 complies with the temperature limit of the SOIC by fixing the temperature set value s to the above maximum operating temperature. Therefore, the soundness of the SOC can be ensured.

Further, in the PLC 24, when the SOIC reaches the maximum operating temperature, the voltage controller 27 sets the voltage so that the voltage value of the electrolytic current supplied to the cell stack 1 (SOEC) matches the thermal neutral point voltage of the SOIC alone. The control calculation is performed to control the current value of the electrolytic current. As described above, by keeping the SOEC voltage at the thermal neutral point voltage, the SOEC temperature can be stabilized and the hydrogen production efficiency by the SOEC can be improved.

[B] Second embodiment (FIG. 11)
FIG. 11 is a block diagram showing a control device of the hydrogen production plant according to the second embodiment. In this second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The control device 40 of the hydrogen production plant of the second embodiment is different from the first embodiment in that the PLC 41 as the second control means has the voltage measurement value p measured by the voltage measuring instrument 21 and the temperature measuring instrument 23. A point configured to add a delay element to at least one of the measured temperature measurement value t, that is, a delay element adder 42 that adds a delay element DV to the _voltage measurement value p, and a delay element t of the temperature measurement value t. The point is that the PLC 41 has at least one of the delay element adder 43 for adding the element _DT .

In the control device 20 of the hydrogen production plant according to the first embodiment, the temperature set value change logic 30 of the plant control device 25 changes the temperature set value s based on the voltage measurement value p. Further, the voltage controller 27 of the PLC 24 performs a voltage control operation based on the voltage measured value p and outputs the current operation signal q to the cell power supply device 8. Further, the temperature controller 29 of the PLC 24 performs a temperature control calculation based on the temperature measurement value t and outputs the temperature operation signal u to the heater control device 22. Therefore, when external noise or the like is superimposed on the voltage measurement value p or the temperature measurement value t, the above-mentioned temperature setting value change, voltage control, and temperature control can be performed based on the erroneous signal, and the hydrogen production plant 10 is stabilized. I can't drive.

On the other hand, in the second embodiment, the PLC 41 adds the delay element DV to the _voltage measured value p by the delay element adder 42, and adds the delay element _DT to the temperature measurement value t by the delay element adder 43. .. As the delay elements _DV and _DT , a primary delay filter or the like is installed to reduce sudden disturbance. The first-order lag filter can be configured as hardware using a resistor, a capacitor, or the like, or can be configured as software using a digital filter or the like.

Since it is configured as described above, according to the second embodiment, in addition to the same effects as those of the first embodiment (1) and (2), the following effect (3) is obtained.

(3) A delay element adder 42 that adds a delay element DV to the _voltage measurement value p measured by the voltage measuring instrument 21, and a delay element _DT are added to the temperature measurement value t measured by the temperature measuring instrument 23. By providing the PLC 41 with at least one of the delay element adder 43, it is possible to reduce a sudden disturbance of either one or both of the voltage measurement value p and the temperature measurement value t. As a result, the hydrogen production plant 10 can be stably operated by the control device 40 of the hydrogen production plant.

[C] Third Embodiment (FIG. 12, FIG. 13)
FIG. 12 is a block diagram showing a part of the control device of the hydrogen production plant according to the third embodiment omitted. Further, FIG. 13 is a block diagram showing an omitted portion of FIG. 12 and 13 have a configuration in which the symbol X in FIG. 12 is connected to the symbol X in FIG. 13 and the symbol Y in FIG. 13 is connected to the symbol Y in FIG. Further, in the third embodiment shown in FIGS. 12 and 13, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the control device 50 of the hydrogen production plant in the third embodiment and the first embodiment is that the PLC 51 as the second control means is a current operation for supplying an electrolytic current to the cell stack 1 composed of the SOC. The steam flow rate set value d is obtained by the proportional gain 52 based on the signals n and q, and the steam flow rate measurement value e of the steam measured by the steam flow meter 57 as the steam flow rate measuring means is paired with the steam flow rate set value d. As described above, the steam flow control calculation is performed by the steam flow controller 53 to control the steam flow rate of the steam supplied to the cell stack 1, and the current set value of the electrolytic current is set by the proportional gain 54 based on the steam flow rate measurement value e. The current is determined by the current controller 55 so that the current measured value h of the electrolytic current measured by the current measuring device 58 as the current measuring means is paired with the current set value g based on the steam flow rate measured value e. It is a point configured to control the current value of the electrolytic current by performing a control calculation.

First, the lower half of FIG. 13 is the steam line 3A of the steam-hydrogen line 3, and the boiler 7, the steam flow rate control valve 56, the steam flow meter 57, and the heat exchanger 5 are sequentially installed in the steam line 3A from the upstream side. Has been done. That is, steam is generated in the boiler 7 by supplying water. The supply flow rate of steam to the cell stack 1 is adjusted by the steam flow rate control valve 56, and the adjusted flow rate of steam is measured by the steam flow meter 57. The steam is heated by the hydrogen gas discharged from the cell stack 1 in the heat exchanger 5 and supplied to the cell stack 1 held at a high temperature in the electric furnace 2.

Next, the function of the PLC 51 will be described. The steam flow rate set value d is calculated by multiplying the current operation signals n and q by a constant with the proportional gain 52. The steam flow rate set value d and the steam flow rate measurement value e measured by the steam flow rate meter 57 are compared, and the steam flow rate controller 53 performs a PI control calculation to obtain a steam flow rate operation signal f, and this steam flow rate is obtained. The steam flow rate control valve 56 is opened and closed by the operation signal f to adjust the steam flow rate supplied to the cell stack 1.

Further, the proportional gain 54 multiplies the steam flow rate measurement value e measured by the steam flow meter 57 by a constant to calculate the current set value g. The current set value g is compared with the current measured value h measured by the current measuring device 58, the current controller 55 performs a PI control calculation to obtain the current operating signal i, and the current operating signal i is used as a cell. Output to the power supply device 8. The cell power supply device 8 supplies an electrolytic current (direct current) based on the current operation signal i to the cell stack 1 held at a high temperature in the electric furnace 2, thereby performing electrolysis of water vapor.

Here, the boiler 7 adjusts the amount of steam generated by a combination of pressure control and water level control (local control of the boiler). When the steam flow rate control valve 56 is opened in order to increase the amount of steam supplied to the cell stack 1, the pressure in the boiler 7 decreases. This pressure drop is detected by a pressure gauge (not shown), and the electric heater for the boiler 7 is turned on by pressure control to increase the amount of steam generated in the boiler 7. When the amount of steam generated increases and the water level in the boiler 7 drops, the water level control turns on the water supply pump for the boiler 7 (not shown) to supply water to the boiler 7.

The proportional gain 52 sets the steam flow rate set value d of steam according to the current operation signals n and q, and the steam flow rate controller 53 performs steam flow control calculation based on the steam flow rate set value d and the steam flow rate measurement value e. The steam flow rate operation signal f is output, and the steam flow rate control valve 56 adjusts the opening degree based on the steam flow rate operation signal f. The required amount of steam can be supplied from the boiler 7 to the cell stack 1. Further, after confirming that the steam flow rate has been changed by the steam flow rate measurement value e by the steam flow meter 57, the proportional gain 54 sets the current set value g corresponding to the steam flow rate measurement value e, and the current controller. 55 determines the current operation signal i to be output to the cell power supply device 8 based on the current set value g and the current measurement value h measured by the current measuring device 58, and the cell power supply device 8 determines the current operation signal i based on the current operation signal i. The electrolytic current is supplied to the cell stack 1.

Here, the proportional gain 52, the steam flow controller 53, the proportional gain 54, and the current controller 55 shown in FIG. 13 are connected to the PLC 51 in the same manner as the voltage controller 27, the proportional gain 28, and the temperature controller 29 shown in FIG. It is a stored software.

Since it is configured as described above, according to the third embodiment, in addition to the same effects as the effects (1) and (2) of the first embodiment, the following effects (4) and (5) are obtained. ) Is played.

(4) In the control device 20 of the hydrogen production plant according to the first embodiment, when the temperature of the SOIC reaches the maximum operating temperature, the temperature set value change logic 30 fixes and sets the temperature set value s, so that the SOIC deteriorates. As the resistance value increases due to the above, the measured voltage value p increases. Therefore, the voltage controller 27 of the PLC 24 performs a voltage control calculation so that the measured voltage value p is maintained at the thermal neutral point voltage (about 1.3 V) of the SOC alone, and the current operation signal q is performed via the proportional gain 28. Therefore, the amount of hydrogen produced is slightly reduced. However, since the amount of steam supplied is constant, surplus steam is supplied from the viewpoint of steam utilization rate, and the efficiency is low.

On the other hand, in the control device 50 of the hydrogen production plant according to the third embodiment, when the temperature of SOE reaches the maximum operating temperature, the voltage control of the voltage controller 27 and the reduced current operation signal q due to the proportional gain 28 The proportional gain 52 and the steam flow controller 53 output a steam flow rate operation signal f that reduces the steam flow rate supplied to the cell stack 1. Therefore, it is possible to prevent the generation of excess steam, eliminate the waste of boiler power and pump power due to the generation of excess steam, and improve the hydrogen production efficiency.

(5) In the control device 20 of the hydrogen production plant according to the first embodiment, when the current value of the electrolytic current to the cell stack 1 is reduced by the voltage control calculation by the voltage controller 27 of the PLC 24 or the like, the control device 20 is moved to the cell stack 1. Since the amount of water vapor supplied from the cell stack 1 is maintained, there is no problem that the cell stack 1 causes water vapor withering. However, when the current value of the electrolytic current to the cell stack 1 increases, the amount of steam supplied to the cell stack 1 is insufficient, and the cell stack 1 may be damaged due to steam withering.

On the other hand, in the control device 50 of the hydrogen production plant according to the third embodiment, the proportional gain 52 of the PLC 51 and the steam flow rate controller 53 determine the steam flow rate operation signal f according to the current operation signals n and q. The flow rate of steam supplied to the cell stack 1 is changed by the steam flow rate control valve 56. Then, the steam flow meter 57 measures the steam flow rate to the changed cell stack 1, the proportional gain 54 sets the current set value g based on the steam flow rate measurement value e, and the current controller 55 sets the current operation signal. i is determined and output to the cell power supply device 8. As a result, since the current value of the electrolytic current supplied to the cell stack 1 is determined according to the steam flow rate supplied to the cell stack 1, it is possible to provide a highly reliable control device that does not cause steam withering in the cell stack 1.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and their replacements and changes can be made. Is included in the scope and gist of the invention, as well as the invention described in the claims and the equivalent scope thereof.

1 ... cell stack, 10 ... hydrogen production plant, 20 ... hydrogen production plant control device, 21 ... voltage measuring instrument (voltage measuring means), 23 ... temperature measuring instrument (temperature measuring means), 24 ... PLC (second control means) ), 25 ... Plant control device (first control means), 30 ... Temperature set value change logic, 40 ... Hydrogen production plant control device, 41 ... PLC (second control means), 50 ... Hydrogen production plant control device, 51 ... PLC (second control means), 57 ... steam flow meter (steam flow rate measuring means), 58 ... current measuring instrument (current measuring means), _DV , _DT ... delay element, m ... current set value, n ... Current operation signal, o ... Voltage setting value, p ... Voltage measurement value, q ... Current operation signal, s ... Temperature setting value, t ... Temperature measurement value, u ... Temperature operation signal, d ... Steam flow rate setting value, e ... Steam Flow measurement value, g ... current set value, h ... current measurement value, i ... current operation signal

Claims (9)

In the control device of a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell
A voltage measuring means for measuring the voltage value of the electrolytic current supplied to the electrolytic cell, and
A temperature measuring means for measuring the temperature of the electrolytic cell and
A first control means that outputs the current set value of the electrolytic current and is provided with a temperature set value changing logic, and changes and outputs the temperature set value of the electrolytic cell by the temperature set value changing logic.
The current value of the electrolytic current is controlled based on the current operation signal obtained from the current set value from the first control means, and the temperature measured value measured by the temperature measuring means matches the temperature set value. It has a second control means for controlling the temperature of the electrolytic cell by performing a temperature control calculation as described above.
The temperature set value changing logic sets the temperature set value to a temperature lower than the maximum operating temperature of the electrolytic cell at the initial stage of operation, and the voltage measured value measured by the voltage measuring means is the heat of the electrolytic cell alone. A control device for a hydrogen production plant, characterized in that the temperature set value is sequentially increased by a predetermined value when the temperature is increased by a specified value from the neutral point voltage. The control device for a hydrogen production plant according to claim 1, wherein the electrolytic cell is a solid oxide electrolytic cell, and the steam electrolysis is high-temperature steam electrolysis using steam at a high temperature of 500 ° C. or higher. When the temperature measurement value reaches the maximum operating temperature of the electrolytic cell, the temperature setting value change logic stops the temperature setting value change by increasing the temperature setting value by a predetermined value and sets the temperature setting value. The control device for a hydrogen production plant according to claim 1 or 2, wherein the control device is configured to be fixedly set to the maximum operating temperature. The first control means outputs the thermal neutral point voltage of the electrolytic cell alone to the second control means as a voltage set value of the electrolytic current supplied to the electrolytic cell.
When the temperature measurement value reaches the maximum operating temperature of the electrolytic cell, the second control means does not obtain a current operation signal based on the current set value from the first control means, but the voltage measurement value is the voltage measurement value. Claims 1 to 3 are configured to perform a voltage control calculation so as to match a voltage set value to obtain a current operation signal, and to control the current value of the electrolytic current based on this current operation signal. The control device for the hydrogen production plant according to any one of the above items. The hydrogen production plant according to any one of claims 1 to 4, wherein the second control means is configured to add a delay element to at least one of a voltage measurement value and a temperature measurement value. Control device. The second control means obtains a steam flow rate set value based on a current operation signal for supplying an electrolytic current to the electrolytic cell, and the steam flow rate measurement value of steam measured by the steam flow rate measuring means is the steam flow rate set value. The steam flow rate control calculation is performed so as to match with, and the steam flow rate of the steam supplied to the electrolytic cell is controlled, and at the same time.
The current set value of the electrolytic current is obtained based on the steam flow rate measurement value, and the current is adjusted so that the current measurement value of the electrolytic current measured by the current measuring means matches the current set value based on the steam flow rate measurement value. The control device for a hydrogen production plant according to any one of claims 1 to 5, wherein the control calculation is performed to control the current value of the electrolytic current supplied to the electrolytic cell. In the control method of a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell,
At the initial stage of operation, the temperature set value of the electrolytic cell is set to a temperature lower than the maximum operating temperature of the electrolytic cell, and the temperature of the electrolytic cell is controlled based on this temperature set value.
When the voltage value of the electrolytic current supplied to the electrolytic cell increases by a specified value from the thermal neutral point voltage of the electrolytic cell alone, the temperature set value is sequentially increased by a predetermined value and increased. A method for controlling a hydrogen production plant, which comprises controlling the temperature of the electrolytic cell based on a set temperature value. In the control method of a hydrogen production plant that produces hydrogen by steam electrolysis using an electrolytic cell,
When the temperature measurement value reaches the maximum operating temperature of the electrolytic cell, the temperature set value is fixedly set to the maximum operating temperature.
A control method for a hydrogen production plant, which comprises performing a voltage control calculation so that a voltage measurement value matches a voltage set value, obtaining a current operation signal, and controlling the current value of an electrolytic current. The control method for a hydrogen production plant according to claim 7 or 8, wherein the electrolytic cell is a solid oxide electrolytic cell, and the steam electrolysis is high-temperature steam electrolysis using steam at a high temperature of 500 ° C. or higher.

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