WO2018051759A1 - Fuel cell system and method for operating same - Google Patents

Fuel cell system and method for operating same Download PDF

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Publication number
WO2018051759A1
WO2018051759A1 PCT/JP2017/030395 JP2017030395W WO2018051759A1 WO 2018051759 A1 WO2018051759 A1 WO 2018051759A1 JP 2017030395 W JP2017030395 W JP 2017030395W WO 2018051759 A1 WO2018051759 A1 WO 2018051759A1
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Prior art keywords
fuel cell
gas
gas flow
flow rate
solid oxide
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PCT/JP2017/030395
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French (fr)
Japanese (ja)
Inventor
慎弥 宇井
邦幸 高橋
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富士電機株式会社
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Publication of WO2018051759A1 publication Critical patent/WO2018051759A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a fuel cell system and an operation method thereof.
  • SOFC solid oxide fuel cells
  • the SOFC has the characteristics that the power generation operating temperature is the highest (for example, 900 ° C. to 1000 ° C.) and the power generation efficiency is the highest among the currently known fuel cell configurations.
  • the conversion efficiency is increased by making the direct current portion high voltage and low current. This is realized by increasing the number of stacked fuel cell stacks and connecting the cells in series.
  • the reason why the power generation efficiency of the SOFC is high is that the direct current portion can be made high voltage and low current.
  • Patent Document 1 discloses a fuel cell system for the purpose of quickly warming up a fuel cell.
  • the fuel cell system includes a fuel cell, fuel gas supply means, oxidant gas supply means, oxidant gas supply flow path, oxidant off-gas discharge flow path, diluter, branch gas flow path, pressure
  • An adjustment unit, an OCV determination unit, and an IV characteristic reduction unit are included.
  • the fuel cell has a fuel gas channel through which fuel gas is supplied and an oxidant gas channel through which oxidant gas is supplied.
  • the fuel gas supply means supplies fuel gas to the fuel gas flow path, and the oxidant gas supply means supplies oxidant gas to the oxidant gas flow path.
  • the oxidant gas supply channel the oxidant gas flowing from the oxidant gas supply means to the oxidant gas channel flows.
  • the oxidant off-gas discharge channel passes the oxidant off-gas discharged from the oxidant gas channel.
  • the diluter is provided in the oxidant off-gas discharge channel and dilutes the fuel off-gas discharged from the fuel gas channel with the oxidant off-gas.
  • the branch gas flow path connects the oxidant gas supply flow path or the oxidant off-gas discharge flow path upstream from the diluter and the diluter, and allows the branch gas toward the diluter to flow.
  • the pressure adjusting means adjusts the pressure of the branch gas.
  • the OCV determination means determines whether the OCV of the fuel cell is greater than or equal to a predetermined OCV when the system is activated.
  • the IV characteristic reduction means starts the power generation of the fuel cell after the OCV determination means determines that the OCV of the fuel cell is equal to or higher than the predetermined OCV, and reduces the stoichiometric ratio of the oxidant gas to reduce the IV characteristic of the fuel cell. Reduce.
  • the pressure adjusting means reduces the pressure of the branch gas introduced into the diluter when the IV characteristic of the fuel cell is lowered by the IV characteristic reducing means.
  • the present invention has been made in view of such a point, and a fuel cell system capable of realizing stable operation by suppressing open circuit voltage with a simple configuration and low cost while maintaining high power generation efficiency, and One of the purposes is to provide the operation method.
  • the fuel cell system of the present embodiment is a solid oxide fuel cell that generates power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel that supplies the fuel gas to the solid oxide fuel cell.
  • a gas flow rate control unit that controls a flow rate of the fuel gas in the fuel gas flow channel and a flow rate of the recycle gas in the recycle gas flow channel, and the calculation unit is configured to Based on the temperature and hydrogen concentration within the oxide fuel cell, and calculates the target open circuit voltage of the solid oxide fuel cell is characterized in that.
  • the operating method of the fuel cell system of the present embodiment is a solid oxide fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and the fuel gas is supplied to the solid oxide fuel cell.
  • An operation method of a fuel cell system comprising: a fuel gas channel to be supplied; and a recycle gas channel that recirculates the fuel gas discharged from the solid oxide fuel cell as a recycle gas to the fuel gas channel.
  • a calculation step of calculating a target open circuit voltage of the solid oxide fuel cell an acquisition step of acquiring a measured open circuit voltage of the solid oxide fuel cell, and the target of the solid oxide fuel cell Based on the differential voltage between the open circuit voltage and the measured open circuit voltage, the flow rate of the fuel gas in the fuel gas channel and the recycling in the recycle gas channel
  • a gas flow rate control step for controlling a flow rate of gas, and in the calculation step, the target opening of the solid oxide fuel cell is determined based on a temperature and a hydrogen concentration inside the solid oxide fuel cell. The circuit voltage is calculated.
  • the present invention it is possible to provide a fuel cell system and a method for operating the fuel cell system capable of realizing stable operation by suppressing open circuit voltage with a simple configuration and low cost while maintaining high power generation efficiency. it can.
  • FIG. 3 is a block diagram showing a control system of a fuel cell system for controlling the flow rate of fuel gas in the fuel gas channel, the flow rate of oxidant gas in the oxidant gas channel, and the flow rate of recycle gas in the recycle gas channel.
  • a solid line (outside the SOFC 10) and a broken line (inside the SOFC 10) indicate the flow of a fluid such as gas or water, and the alternate long and short dash line indicates the flow of electricity (current, power).
  • a fuel cell system 1 includes a solid oxide fuel cell (SOFC) 10, a DC / AC converter 20, a system power network 30, a combustor 40, and exhaust heat. And a recovery circulation system 50.
  • SOFC solid oxide fuel cell
  • the SOFC 10 has a cell stack in which a plurality of cells are stacked or assembled. Each cell has a basic configuration in which an electrolyte is sandwiched between an air electrode and a fuel electrode, and a separator is interposed between the cells. Each cell of the cell stack is electrically connected in series.
  • the SOFC 10 is a power generation mechanism that generates electric energy when oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions react with hydrogen or carbon monoxide at the fuel electrode. .
  • the SOFC 10 has an anode gas channel 11 and a cathode gas channel 12.
  • a fuel gas passage 13 is connected (communication) to the anode gas passage 11, and an oxidant gas passage 14 is connected (communication) to the cathode gas passage 12.
  • the fuel gas channel 13 supplies the anode gas channel 11 with the fuel gas supplied from a fuel gas supplier (not shown).
  • the oxidant gas channel 14 supplies the oxidant gas supplied from the oxidant gas supply device (not shown) to the cathode gas channel 12.
  • a direct current is generated by causing an electrochemical reaction between the fuel gas supplied to the anode gas passage 11 and the oxidant gas supplied to the cathode gas passage 12.
  • the fuel gas and oxidant gas that have not caused an electrochemical reaction are discharged from the SOFC 10 as exhaust gas.
  • a part of the fuel gas discharged from the anode gas flow path 11 of the SOFC 10 is recirculated to the fuel gas flow path 13 through the recycle gas flow path 15 as a recycle gas.
  • the fuel gas flow path 13 is provided with a fuel gas flow rate adjustment valve (gas flow rate adjustment valve) 16 that increases or decreases the flow rate of the fuel gas in the fuel gas flow path 13.
  • the oxidant gas flow path 14 is provided with an oxidant gas flow rate adjustment valve (gas flow rate adjustment valve) 17 that increases or decreases the flow rate of the oxidant gas in the oxidant gas flow path 14.
  • the recycle gas flow path 15 is provided with a recycle gas flow rate adjustment valve (gas flow rate adjustment valve) 18 that increases or decreases the flow rate of the recycle gas in the recycle gas flow path 15.
  • the fuel gas flow rate adjustment valve 16 is provided upstream of the junction with the recycle gas channel 15 in the fuel gas channel 13.
  • a gas flow rate adjusting valves 16, 17, 18 it is also possible to provide a gas flow rate adjusting blower or compressor for increasing or decreasing the gas flow rate in the gas flow paths 13, 14, 15.
  • the fuel gas flow rate adjustment valve 16 includes a fuel gas flow rate control unit (gas flow rate control unit) 16C that controls the flow rate of the fuel gas in the fuel gas flow path 13 by controlling the degree of opening and closing of the fuel gas flow rate adjustment valve 16. It is connected.
  • the oxidant gas flow rate adjustment valve 17 includes an oxidant gas flow rate control unit (a gas flow rate) that controls the flow rate of the oxidant gas in the oxidant gas flow path 14 by controlling the degree of opening and closing of the oxidant gas flow rate adjustment valve 17. Control unit) 17C is connected.
  • the recycle gas flow rate adjustment valve 18 includes a recycle gas flow rate control unit (gas flow rate control unit) 18C that controls the flow rate of the recycle gas in the recycle gas flow path 15 by controlling the degree of opening and closing of the recycle gas flow rate adjustment valve 18. It is connected.
  • the “flow rate of the fuel gas in the fuel gas passage 13” means the flow rate of the fuel gas upstream of the junction with the recycle gas passage 15 in the fuel gas passage 13. . That is, the sum of “the flow rate of the fuel gas in the fuel gas flow path 13” and “the flow rate of the recycle gas in the recycle gas flow path 15” is the flow rate of the fuel gas supplied to the anode gas flow path 11 of the SOFC 10.
  • the DC / AC converter 20 converts the direct current generated (generated) by the SOFC 10 into an alternating current.
  • the generated power of the SOFC 10 passes through the DC / AC converter 20 and is connected to the grid power network 30 via the grid interconnection relay 25.
  • the generated power of the SOFC 10 is connected to the grid power network 30 when the grid connection relay 25 is in an on state, and is disconnected from the grid connection relay 25 when the grid connection relay 25 is in an off state.
  • the generated power of the SOFC 10 is supplied to the system, and during the independent operation, the generated power is consumed in the apparatus with a load smaller than the rated maximum power.
  • another power transmission path may be branched from the power transmission path between the DC / AC converter 20 and the grid interconnection relay 25 (not shown).
  • This branched power transmission path is connected to devices mounted on the fuel cell system 1 such as the DC / AC converter 20, a pump (not shown), a blower, and a radiator (not shown) provided in the exhaust heat recovery circulation system. You may connect. These devices are driven by being supplied with power from either the SOFC 10 or the grid power network 30 via the branched power transmission path.
  • the combustor 40 removes the fuel component remaining in the exhaust gas by burning the exhaust gas discharged from the SOFC 10.
  • the exhaust heat recovery circulation system 50 has an exhaust heat recovery circulation line (not shown) for recovering the heat of the combustion gas (exhaust gas) from the combustor 40. Water (hot water) as a heat medium for exhaust heat recovery is circulated in the exhaust heat recovery circulation line.
  • the gas after exhaust heat recovery by the exhaust heat recovery circulation system 50 (exhaust heat recovery circulation line) is exhausted to the outside of the fuel cell system 1.
  • the exhaust heat recovery circulation line may be provided with various reactors (all not shown) such as an exhaust heat recovery heat exchanger, a hot water heat exchanger, a heater, a radiator, and a pump.
  • FIG. 2 shows the fuel cell system 1 for controlling the flow rate of the fuel gas in the fuel gas flow channel 13, the flow rate of the oxidant gas in the oxidant gas flow channel 14, and the flow rate of the recycle gas in the recycle gas flow channel 15. It is a block diagram which shows a control system.
  • the control system of the fuel cell system 1 in FIG. 2 has the above-described fuel gas flow rate control unit 16C, oxidant gas flow rate control unit 17C, and recycle gas flow rate control unit 18C.
  • the control system of the fuel cell system 1 of FIG. 2 includes a temperature detection unit 60, a target OCV calculation unit (calculation unit) 70, and an actually measured OCV acquisition unit (acquisition unit) 80.
  • the temperature detector 60 detects the internal temperature of the SOFC 10 (internal temperature of the cell stack) and outputs it to the oxidant gas flow rate controller 17C.
  • the oxidant gas flow rate control unit 17 ⁇ / b> C controls the flow rate of the oxidant gas in the oxidant gas flow channel 14 based on the temperature inside the SOFC 10 input from the temperature detection unit 60.
  • the oxidant gas flow rate control unit 17C is configured so that the oxidant gas flow rate in the oxidant gas flow path 14 is higher when the temperature inside the SOFC 10 exceeds a temperature range suitable for rated operation (eg, 900 ° C. ⁇ 50 ° C.). By increasing the flow rate, the temperature inside the SOFC 10 is lowered.
  • the oxidant gas flow rate control unit 17C reduces the flow rate of the oxidant gas in the oxidant gas flow path 14 when the internal temperature of the SOFC 10 is below the temperature range suitable for rated operation, so that the SOFC 10 Increase the temperature inside.
  • the temperature detector 60 and the oxidant gas flow rate control unit 17C cooperate to control the flow rate of the oxidant gas in the oxidant gas flow path 14, so that the temperature inside the SOFC 10 is suitable for the rated operation. Temperature range.
  • the target OCV calculation unit 70 calculates a target OCV that is a target value of the open circuit voltage (OCV) of the SOFC 10.
  • the target OCV of the SOFC 10 avoids a high voltage (for example, about 750 V to 950 V DC) calculated from, for example, the IV characteristics when the SOFC 10 is started (no load), and the deterioration of the cell stack and thus the auxiliary equipment And a value that can prevent damage.
  • the target OCV calculation unit 70 calculates the target OCV of the SOFC 10 by differential calculation based on the temperature inside the SOFC 10 and the hydrogen concentration. As described above, the temperature inside the SOFC 10 is detected by the temperature detector 60.
  • the hydrogen concentration inside SOFC 10 is obtained as follows. By performing a differential calculation based on the temperature inside the SOFC 10 and the flow rate of the fuel gas in the fuel gas flow path 13, “differential calculation value 1” is obtained.
  • a differential operation value 2 is obtained by performing a differential operation based on the temperature inside the SOFC 10 and the flow rate of the recycle gas in the recycle gas flow path 15.
  • This “differential calculation value 2” is a “circulation hydrogen amount” indicating the amount of hydrogen in the recycle gas.
  • “Addition calculation value 1” is obtained by adding and calculating “differentiation calculation value 1” and “differentiation calculation value 2 (circulation hydrogen amount)”. By performing a differential calculation based on “addition calculation value 1” and the flow rate of the recycle gas in the recycle gas flow path 15, “differentiation calculation value 3” is obtained. This “differential calculation value 3” corresponds to the hydrogen concentration inside the SOFC 10.
  • the actual OCV acquisition unit 80 acquires an actual OCV that is an actual measured value of the open circuit voltage (OCV) of the SOFC 10.
  • OCV open circuit voltage
  • the offset amount (differential voltage) between the target OCV of the SOFC 10 calculated by the target OCV calculation unit 70 and the actual OCV of the SOFC 10 acquired by the actual OCV acquisition unit 80 is supplied to the fuel gas flow control unit 16C and the recycle gas flow control unit 18C. Each is output.
  • the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are configured so that the flow rate of the fuel gas in the fuel gas flow channel 13 and the recycle gas flow rate in the recycle gas flow channel 15 are determined based on the offset amount (differential voltage) between the target OCV of the SOFC 10 and the actually measured OCV. Control the flow of recycle gas. That is, the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are arranged in the fuel gas flow path 13 so that the actual OCV of the SOFC 10 follows the target OCV (so as to cancel the offset amount between the target OCV and the actual OCV). The flow rate of the fuel gas and the flow rate of the recycle gas in the recycle gas flow path 15 are controlled.
  • the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are configured so that the flow rate of the fuel gas in the fuel gas flow path 13 and the recycle gas when the measured OCV at the start of the SOFC 10 reaches a predetermined threshold voltage (for example, 600V). Control of the flow rate of the recycle gas in the flow path 15 is started.
  • a predetermined threshold voltage for example, 600V
  • the recycle gas flow rate control unit 18C uses the recycle gas in the recycle gas flow path 15. Reduce the flow rate. Conversely, when the fuel gas flow rate control unit 16C decreases the flow rate of the fuel gas in the fuel gas flow channel 13 during a certain control period after the start of the gas flow rate control, the recycle gas flow rate control unit 18C Increase the flow rate of recycle gas.
  • the flow rate of the recycle gas in the recycle gas flow path 15 tends to increase. Accordingly, the flow rate of the fuel gas in the fuel gas flow path 13 is decreased accordingly.
  • the hydrogen partial pressure inside the SOFC 10 is adjusted to prevent the hydrogen partial pressure from becoming too high, and the measured OCV of the SOFC 10 follows the target OCV with high accuracy. As a result, the fuel cell system 1 is stable. Driving becomes feasible.
  • the hydrogen partial pressure in the SOFC 10 is not limited to the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15, but the oxidant in the oxidant gas flow channel 14. It is affected by the flow rate of gas and the amount of water vapor supplied from a boiler (not shown). However, if the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15 are appropriately controlled as in the present embodiment, the disturbance factor can be ignored, and the inside of the SOFC 10 The hydrogen partial pressure in can be adjusted appropriately. Alternatively, the hydrogen partial pressure inside the SOFC 10 can be further increased by controlling the flow rate of the fuel gas in the fuel gas passage 13 and the flow rate of the recycle gas in the recycle gas passage 15 in consideration of the disturbance factors. Can be adjusted.
  • Controlling (increasing / decreasing) the flow rate of the fuel gas in the fuel gas flow path 13 and the flow rate of the recycle gas in the recycle gas flow path 15 drives the internal reactor of the SOFC 10 to increase heat.
  • the temperature detector 60 monitors the temperature inside the SOFC 10, and the oxidant gas flow rate controller 17C controls the flow rate of the oxidant gas in the oxidant gas flow path 14 accordingly, so that the inside of the SOFC 10 The temperature is not too high. Also in this respect, stable operation of the fuel cell system 1 can be realized.
  • the solid line indicates the voltage applied to the SOFC 10 when the gas flow rate control according to the present embodiment is performed
  • the broken line indicates the voltage applied to the SOFC 10 when the gas flow rate control according to the present embodiment is not performed.
  • step ST1 an air blower (not shown) for sending fuel gas and oxidant gas into the SOFC 10 is turned on.
  • an air heating mechanism (not shown) for heating the fuel gas and the oxidant gas is turned on.
  • step ST3: Yes it is determined whether or not the temperature of the SOFC 10 is equal to or higher than a predetermined value. If the temperature of the SOFC 10 is equal to or higher than a predetermined value (step ST3: Yes), the process proceeds to step ST4. If the temperature of the SOFC 10 is less than the predetermined value (step ST3: No), the process waits for the temperature of the SOFC 10 to be equal to or higher than the predetermined value.
  • step ST4 the supply of fuel gas and oxidant gas to the SOFC 10 is started, and the OCV of the SOFC 10 starts to rise (see FIG. 3).
  • the gas flow rate control according to the present embodiment is not performed (see the solid line and the broken line in FIG. 3).
  • step ST5 it is determined whether or not the actual OCV at the time of activation of the SOFC 10 is equal to or higher than a predetermined threshold voltage (for example, 600V). If the measured OCV at the time of activation of the SOFC 10 is equal to or higher than a predetermined threshold voltage (step ST5: Yes), the process proceeds to step ST6. If the measured OCV at the time of starting up the SOFC 10 is less than the predetermined threshold value (step ST5: No), it waits for the measured OCV at the time of starting up the SOFC 10 to be equal to or higher than the predetermined threshold voltage.
  • a predetermined threshold voltage for example, 600V
  • step ST6 the target OCV calculation unit 70 starts calculating the target OCV of the SOFC 10.
  • step ST7 the actual OCV acquisition unit 80 starts acquiring the actual OCV of the SOFC 10.
  • step ST8 the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C perform the fuel gas flow rate and the recycle gas in the fuel gas flow channel 13 based on the offset amount (differential voltage) between the target OCV and the actual OCV of the SOFC 10. Control of the flow rate of the recycle gas in the flow path 15 is started.
  • the OCV when the SOFC 10 is started (no load) is controlled to be kept lower than the OCV when the gas flow rate control according to the present embodiment is not performed (the solid line in FIG. 3).
  • step ST8 the oxidant gas flow rate control unit 17C starts controlling the flow rate of the oxidant gas in the oxidant gas flow channel 14 based on the internal temperature of the SOFC 10 input from the temperature detection unit 60.
  • the processes in steps ST6 to ST8 may be executed substantially simultaneously or may be executed while being shifted in time.
  • step ST9 it is determined whether or not the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are equal to or greater than a predetermined value. If the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are greater than or equal to the predetermined values (step ST9: Yes), the process proceeds to step ST10. If the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are less than the predetermined values (step ST9: No), it waits for the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 to be equal to or greater than the predetermined values.
  • step ST10 the power generated by the SOFC 10 is started to be input to a power generation load (for example, various auxiliary machines). Thereby, the current flowing through the power generation load starts to rise.
  • a power generation load for example, various auxiliary machines
  • step ST11 it is determined whether or not the SOFC 10 is close to rated operation (whether or not the actual OCV of the SOFC 10 is close to rated operating power). If it is determined that the SOFC 10 is close to the rated operation (step ST11: Yes), the process proceeds to step ST12. If it is determined that the SOFC 10 is not close to the rated operation (step ST11: No), it waits for the SOFC 10 to be close to the rated operation.
  • step ST12 the target OCV calculation unit 70 ends the calculation of the target OCV of the SOFC 10.
  • step ST13 the actual OCV acquisition unit 80 ends the actual OCV acquisition of the SOFC 10.
  • step ST14 the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C end the control of the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15.
  • the OCV of the SOFC 10 converges so as to coincide with the OCV when the gas flow rate control according to the present embodiment is not performed (the solid line and the broken line in FIG. 3 are reference).
  • step ST14 the oxidant gas flow rate control unit 17C ends the control of the oxidant gas flow rate in the oxidant gas flow path 14.
  • the processes in steps ST12 to ST14 may be executed substantially simultaneously or may be executed while being shifted in time.
  • step ST15 the rated operation in which the generated power of the SOFC 10 converges to the rated maximum power is executed.
  • the flow control of the fuel gas, the recycle gas, and the oxidant gas is terminated at the timing when the SOFC 10 is close to the rated operation.
  • the flow control of the fuel gas, the recycle gas, and the oxidant gas may be terminated.
  • the fuel gas flow rate adjustment valve 16 and the recycle gas flow rate adjustment valve 18 are provided in the fuel gas flow path 13 and the recycle gas flow path 15 while maintaining the high power generation efficiency of the SOFC 10, and the fuel cell system 1
  • the OCV of the SOFC 10 (especially the OCV at the time of start-up) is simply configured and low in cost by simply controlling the gas flow rate adjustment valve 16 and the recycle gas flow rate adjustment valve 18 by the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C. Stable operation can be realized with suppression.
  • the case where the flow rate of the fuel gas in the fuel gas flow path 13 and the flow rate of the recycle gas in the recycle gas flow path 15 are controlled in order to adjust the hydrogen partial pressure inside the SOFC 10 has been described as an example.
  • the flow rate of the oxidant gas in the oxidant gas passage 14 may be controlled.
  • the hydrogen partial pressure inside the SOFC 10 may be adjusted by increasing or decreasing the amount of water vapor supplied from a boiler (not shown) or the like.
  • the combustor 40 is provided between the SOFC 10 and the exhaust heat recovery circulation system 50.
  • the combustor 40 is omitted, and the exhaust gas exhausted from the SOFC 10 is directly exhausted heat recovery and circulation. You may lead to the system 50.
  • the fuel cell system and the operation method thereof according to the present invention are suitable for application to fuel cell systems for household use, business use, and other industrial fields.

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Abstract

Provided are a fuel cell system and a method for operating the same which maintain high power generation efficiency while achieving stable operation by minimizing open circuit voltage using a simple configuration while keeping costs low. Thus, a calculation unit (70) calculates a target open circuit voltage for a solid oxide fuel cell (10). An acquisition unit (80) acquires the actually measured open circuit voltage of the solid oxide fuel cell (10). Gas flow control units (16C, 18C) control the flow of fuel gas in a fuel gas channel (13) and the flow of recycled gas in a recycled gas channel (15), on the basis of the voltage difference between the target open circuit voltage of the solid oxide fuel cell (10) and the actually measured open circuit voltage thereof. The calculation unit (70) calculates the target open circuit voltage of the solid oxide fuel cell (10) on the basis of the hydrogen concentration and the temperature inside the solid oxide fuel cell (10).

Description

燃料電池システム及びその運転方法Fuel cell system and operation method thereof
　本発明は、燃料電池システム及びその運転方法に関する。 The present invention relates to a fuel cell system and an operation method thereof.
　近年、固体酸化物形燃料電池（ＳＯＦＣ：Solid　Oxide　Fuel　Cell）の開発が進められている。ＳＯＦＣは、空気極で生成された酸化物イオンが電解質を透過して燃料極に移動し、燃料極で酸化物イオンが水素又は一酸化炭素と反応することにより電気エネルギーを発生する発電メカニズムである。ＳＯＦＣは、現在知られている燃料電池の形態の中では、発電の動作温度が最も高く（例えば９００℃～１０００℃）、発電効率が最も高いという特性を持つ。 In recent years, solid oxide fuel cells (SOFCs) have been developed. SOFC is a power generation mechanism in which oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, where the oxide ions react with hydrogen or carbon monoxide to generate electrical energy. . The SOFC has the characteristics that the power generation operating temperature is the highest (for example, 900 ° C. to 1000 ° C.) and the power generation efficiency is the highest among the currently known fuel cell configurations.
　一般的に、燃料電池が発電した直流電流を交流電流に変換して系統電力網との連系運転を行う場合、直流部を高電圧低電流にすることで、変換効率が上昇する。これは、燃料電池のセルスタックの積層数を増やして各セルを直列に接続することで実現される。直流部を高電圧低電流にできることがＳＯＦＣの発電効率が高い理由である。 Generally, when the direct current generated by the fuel cell is converted into an alternating current and connected to the grid power network, the conversion efficiency is increased by making the direct current portion high voltage and low current. This is realized by increasing the number of stacked fuel cell stacks and connecting the cells in series. The reason why the power generation efficiency of the SOFC is high is that the direct current portion can be made high voltage and low current.
　特許文献１には、燃料電池を速やかに暖機することを目的とした燃料電池システムが開示されている。この燃料電池システムは、燃料電池と、燃料ガス供給手段と、酸化剤ガス供給手段と、酸化剤ガス供給流路と、酸化剤オフガス排出流路と、希釈器と、分岐ガス流路と、圧力調整手段と、ＯＣＶ判定手段と、ＩＶ特性低下手段とを有する。 Patent Document 1 discloses a fuel cell system for the purpose of quickly warming up a fuel cell. The fuel cell system includes a fuel cell, fuel gas supply means, oxidant gas supply means, oxidant gas supply flow path, oxidant off-gas discharge flow path, diluter, branch gas flow path, pressure An adjustment unit, an OCV determination unit, and an IV characteristic reduction unit are included.
　燃料電池は、燃料ガスが供給される燃料ガス流路と、酸化剤ガスが供給される酸化剤ガス流路とを有する。燃料ガス供給手段は、燃料ガス流路に燃料ガスを供給し、酸化剤ガス供給手段は、酸化剤ガス流路に酸化剤ガスを供給する。酸化剤ガス供給流路は、酸化剤ガス供給手段から酸化剤ガス流路に向かう酸化剤ガスが通流する。酸化剤オフガス排出流路は、酸化剤ガス流路から排出された酸化剤オフガスが通流する。 The fuel cell has a fuel gas channel through which fuel gas is supplied and an oxidant gas channel through which oxidant gas is supplied. The fuel gas supply means supplies fuel gas to the fuel gas flow path, and the oxidant gas supply means supplies oxidant gas to the oxidant gas flow path. In the oxidant gas supply channel, the oxidant gas flowing from the oxidant gas supply means to the oxidant gas channel flows. The oxidant off-gas discharge channel passes the oxidant off-gas discharged from the oxidant gas channel.
　希釈器は、酸化剤オフガス排出流路に設けられると共に、燃料ガス流路から排出された燃料オフガスを、酸化剤オフガスで希釈する。分岐ガス流路は、酸化剤ガス供給流路又は希釈器よりも上流の酸化剤オフガス排出流路と、希釈器とを接続すると共に、希釈器に向かう分岐ガスが通流する。圧力調整手段は、分岐ガスの圧力を調整する。ＯＣＶ判定手段は、システム起動時に燃料電池のＯＣＶが所定ＯＣＶ以上であるか否かを判定する。ＩＶ特性低下手段は、ＯＣＶ判定手段が燃料電池のＯＣＶが所定ＯＣＶ以上であると判定した後、燃料電池の発電を開始すると共に、酸化剤ガスのストイキ比を低下させることで燃料電池のＩＶ特性を低下させる。圧力調整手段は、ＩＶ特性低下手段による燃料電池のＩＶ特性の低下時、希釈器に導入される分岐ガスの圧力を低下させる。 The diluter is provided in the oxidant off-gas discharge channel and dilutes the fuel off-gas discharged from the fuel gas channel with the oxidant off-gas. The branch gas flow path connects the oxidant gas supply flow path or the oxidant off-gas discharge flow path upstream from the diluter and the diluter, and allows the branch gas toward the diluter to flow. The pressure adjusting means adjusts the pressure of the branch gas. The OCV determination means determines whether the OCV of the fuel cell is greater than or equal to a predetermined OCV when the system is activated. The IV characteristic reduction means starts the power generation of the fuel cell after the OCV determination means determines that the OCV of the fuel cell is equal to or higher than the predetermined OCV, and reduces the stoichiometric ratio of the oxidant gas to reduce the IV characteristic of the fuel cell. Reduce. The pressure adjusting means reduces the pressure of the branch gas introduced into the diluter when the IV characteristic of the fuel cell is lowered by the IV characteristic reducing means.
特開２０１４－１０９１４号公報JP 2014-10914 A
　しかしながら、特許文献１を含む従来の燃料電池システムは、燃料電池の開回路電圧（ＯＣＶ：Open　Circuit　Voltage）が高くなりすぎて、燃料電池のセルスタックひいては補機の劣化及び損傷を誘発する結果、燃料電池システムの安定的な運転が困難になるという問題がある。また、特許文献１の燃料電池システムは、燃料電池を暖機するための構成要素が大掛かりで複雑であるため高コスト化を招いてしまう。 However, in the conventional fuel cell system including Patent Document 1, the open circuit voltage (OCV) of the fuel cell becomes too high, and as a result of inducing deterioration and damage of the cell stack of the fuel cell and thus the auxiliary machine, There is a problem that stable operation of the fuel cell system becomes difficult. Further, the fuel cell system of Patent Document 1 is costly because the components for warming up the fuel cell are large and complex.
　本発明はかかる点に鑑みてなされたものであり、高い発電効率を維持しつつ、簡単な構成かつ低コストで開回路電圧を抑制して安定的な運転を実現することができる燃料電池システム及びその運転方法を提供することを目的の１つとする。 The present invention has been made in view of such a point, and a fuel cell system capable of realizing stable operation by suppressing open circuit voltage with a simple configuration and low cost while maintaining high power generation efficiency, and One of the purposes is to provide the operation method.
　本実施形態の燃料電池システムは、その一態様では、燃料ガスと酸化剤ガスの電気化学反応により発電する固体酸化物形燃料電池と、前記固体酸化物形燃料電池に前記燃料ガスを供給する燃料ガス流路と、前記固体酸化物形燃料電池から排出された前記燃料ガスをリサイクルガスとして前記燃料ガス流路に還流するリサイクルガス流路と、前記固体酸化物形燃料電池の目標開回路電圧を演算する演算部と、前記固体酸化物形燃料電池の実測開回路電圧を取得する取得部と、前記固体酸化物形燃料電池の前記目標開回路電圧と前記実測開回路電圧の差分電圧に基づいて、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量を制御するガス流量制御部と、を有し、前記演算部は、前記固体酸化物形燃料電池の内部の温度と水素濃度に基づいて、前記固体酸化物形燃料電池の前記目標開回路電圧を演算する、ことを特徴としている。 In one aspect, the fuel cell system of the present embodiment is a solid oxide fuel cell that generates power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel that supplies the fuel gas to the solid oxide fuel cell. A gas flow path, a recycle gas flow path for recirculating the fuel gas discharged from the solid oxide fuel cell to the fuel gas flow path as a recycle gas, and a target open circuit voltage of the solid oxide fuel cell. Based on a calculation unit for calculating, an acquisition unit for acquiring a measured open circuit voltage of the solid oxide fuel cell, and a differential voltage between the target open circuit voltage and the measured open circuit voltage of the solid oxide fuel cell A gas flow rate control unit that controls a flow rate of the fuel gas in the fuel gas flow channel and a flow rate of the recycle gas in the recycle gas flow channel, and the calculation unit is configured to Based on the temperature and hydrogen concentration within the oxide fuel cell, and calculates the target open circuit voltage of the solid oxide fuel cell is characterized in that.
　本実施形態の燃料電池システムの運転方法は、その一態様では、燃料ガスと酸化剤ガスの電気化学反応により発電する固体酸化物形燃料電池と、前記固体酸化物形燃料電池に前記燃料ガスを供給する燃料ガス流路と、前記固体酸化物形燃料電池から排出された前記燃料ガスをリサイクルガスとして前記燃料ガス流路に還流するリサイクルガス流路と、を有する燃料電池システムの運転方法であって、前記固体酸化物形燃料電池の目標開回路電圧を演算する演算ステップと、前記固体酸化物形燃料電池の実測開回路電圧を取得する取得ステップと、前記固体酸化物形燃料電池の前記目標開回路電圧と前記実測開回路電圧の差分電圧に基づいて、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量を制御するガス流量制御ステップと、を有し、前記演算ステップでは、前記固体酸化物形燃料電池の内部の温度と水素濃度に基づいて、前記固体酸化物形燃料電池の前記目標開回路電圧を演算する、ことを特徴としている。 In one aspect, the operating method of the fuel cell system of the present embodiment is a solid oxide fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and the fuel gas is supplied to the solid oxide fuel cell. An operation method of a fuel cell system, comprising: a fuel gas channel to be supplied; and a recycle gas channel that recirculates the fuel gas discharged from the solid oxide fuel cell as a recycle gas to the fuel gas channel. A calculation step of calculating a target open circuit voltage of the solid oxide fuel cell, an acquisition step of acquiring a measured open circuit voltage of the solid oxide fuel cell, and the target of the solid oxide fuel cell Based on the differential voltage between the open circuit voltage and the measured open circuit voltage, the flow rate of the fuel gas in the fuel gas channel and the recycling in the recycle gas channel A gas flow rate control step for controlling a flow rate of gas, and in the calculation step, the target opening of the solid oxide fuel cell is determined based on a temperature and a hydrogen concentration inside the solid oxide fuel cell. The circuit voltage is calculated.
　本発明によれば、高い発電効率を維持しつつ、簡単な構成かつ低コストで開回路電圧を抑制して安定的な運転を実現することができる燃料電池システム及びその運転方法を提供することができる。 According to the present invention, it is possible to provide a fuel cell system and a method for operating the fuel cell system capable of realizing stable operation by suppressing open circuit voltage with a simple configuration and low cost while maintaining high power generation efficiency. it can.
本実施形態の燃料電池システムを示すブロック図である。It is a block diagram which shows the fuel cell system of this embodiment. 燃料ガス流路における燃料ガスの流量、酸化剤ガス流路における酸化剤ガスの流量、及び、リサイクルガス流路におけるリサイクルガスの流量を制御するための燃料電池システムの制御系統を示すブロック図である。FIG. 3 is a block diagram showing a control system of a fuel cell system for controlling the flow rate of fuel gas in the fuel gas channel, the flow rate of oxidant gas in the oxidant gas channel, and the flow rate of recycle gas in the recycle gas channel. . 本実施形態の燃料電池システムの起動時から定格運転開始までのＳＯＦＣに掛かる電圧を示すタイミングチャートである。It is a timing chart which shows the voltage concerning SOFC from the time of starting of the fuel cell system of this embodiment to the start of rated operation. 本実施形態の燃料電池システムの起動時から定格運転開始までの動作を示すフローチャートである。It is a flowchart which shows the operation | movement from the time of starting of the fuel cell system of this embodiment to the start of rated operation.
　図１～図４を参照して、本実施形態の燃料電池システム１について詳細に説明する。図１中において、実線（ＳＯＦＣ１０の外部）と破線（ＳＯＦＣ１０の内部）は、例えばガスや水等の流体の流れを示しており、一点鎖線は電気（電流、電力）の流れを示している。 The fuel cell system 1 of the present embodiment will be described in detail with reference to FIGS. In FIG. 1, a solid line (outside the SOFC 10) and a broken line (inside the SOFC 10) indicate the flow of a fluid such as gas or water, and the alternate long and short dash line indicates the flow of electricity (current, power).
　図１に示すように、燃料電池システム１は、固体酸化物形燃料電池（ＳＯＦＣ：Solid　Oxide　Fuel　Cell）１０と、ＤＣ／ＡＣ変換部２０と、系統電力網３０と、燃焼器４０と、排熱回収循環系５０とを有している。 As shown in FIG. 1, a fuel cell system 1 includes a solid oxide fuel cell (SOFC) 10, a DC / AC converter 20, a system power network 30, a combustor 40, and exhaust heat. And a recovery circulation system 50.
　ＳＯＦＣ１０は、複数のセルを積層または集合体として構成したセルスタックを有している。各セルは空気極と燃料極で電解質を挟んだ基本構成を有しており、各セルの間にはセパレータが介在している。セルスタックの各セルは電気的に直列に接続されている。ＳＯＦＣ１０は、空気極で生成された酸化物イオンが電解質を透過して燃料極に移動し、燃料極で酸化物イオンが水素又は一酸化炭素と反応することにより電気エネルギーを発生する発電メカニズムである。 The SOFC 10 has a cell stack in which a plurality of cells are stacked or assembled. Each cell has a basic configuration in which an electrolyte is sandwiched between an air electrode and a fuel electrode, and a separator is interposed between the cells. Each cell of the cell stack is electrically connected in series. The SOFC 10 is a power generation mechanism that generates electric energy when oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions react with hydrogen or carbon monoxide at the fuel electrode. .
　ＳＯＦＣ１０は、アノードガス流路１１と、カソードガス流路１２とを有している。アノードガス流路１１には燃料ガス流路１３が接続（連通）しており、カソードガス流路１２には酸化剤ガス流路１４が接続（連通）している。燃料ガス流路１３は、燃料ガス供給器（図示略）から供給された燃料ガスをアノードガス流路１１に供給する。酸化剤ガス流路１４は、酸化剤ガス供給器（図示略）から供給された酸化剤ガスをカソードガス流路１２に供給する。アノードガス流路１１に供給された燃料ガスとカソードガス流路１２に供給された酸化剤ガスとが電気化学反応を起こすことにより、直流電流が発生する。電気化学反応を起こさなかった燃料ガスと酸化剤ガスは、排出ガスとして、ＳＯＦＣ１０から排出される。ＳＯＦＣ１０のアノードガス流路１１から排出された燃料ガスの一部は、リサイクルガスとして、リサイクルガス流路１５を介して、燃料ガス流路１３に還流される。 The SOFC 10 has an anode gas channel 11 and a cathode gas channel 12. A fuel gas passage 13 is connected (communication) to the anode gas passage 11, and an oxidant gas passage 14 is connected (communication) to the cathode gas passage 12. The fuel gas channel 13 supplies the anode gas channel 11 with the fuel gas supplied from a fuel gas supplier (not shown). The oxidant gas channel 14 supplies the oxidant gas supplied from the oxidant gas supply device (not shown) to the cathode gas channel 12. A direct current is generated by causing an electrochemical reaction between the fuel gas supplied to the anode gas passage 11 and the oxidant gas supplied to the cathode gas passage 12. The fuel gas and oxidant gas that have not caused an electrochemical reaction are discharged from the SOFC 10 as exhaust gas. A part of the fuel gas discharged from the anode gas flow path 11 of the SOFC 10 is recirculated to the fuel gas flow path 13 through the recycle gas flow path 15 as a recycle gas.
　燃料ガス流路１３には、当該燃料ガス流路１３における燃料ガスの流量を増減させる燃料ガス流量調整弁（ガス流量調整弁）１６が設けられている。酸化剤ガス流路１４には、当該酸化剤ガス流路１４における酸化剤ガスの流量を増減させる酸化剤ガス流量調整弁（ガス流量調整弁）１７が設けられている。リサイクルガス流路１５には、当該リサイクルガス流路１５におけるリサイクルガスの流量を増減させるリサイクルガス流量調整弁（ガス流量調整弁）１８が設けられている。燃料ガス流量調整弁１６は、燃料ガス流路１３のうちリサイクルガス流路１５との合流点よりも上流側に設けられている。なお、ガス流量調整弁１６、１７、１８に代えて、ガス流路１３、１４、１５におけるガスの流量を増減させるためのガス流量調整用のブロアやコンプレッサを設けることも可能である。 The fuel gas flow path 13 is provided with a fuel gas flow rate adjustment valve (gas flow rate adjustment valve) 16 that increases or decreases the flow rate of the fuel gas in the fuel gas flow path 13. The oxidant gas flow path 14 is provided with an oxidant gas flow rate adjustment valve (gas flow rate adjustment valve) 17 that increases or decreases the flow rate of the oxidant gas in the oxidant gas flow path 14. The recycle gas flow path 15 is provided with a recycle gas flow rate adjustment valve (gas flow rate adjustment valve) 18 that increases or decreases the flow rate of the recycle gas in the recycle gas flow path 15. The fuel gas flow rate adjustment valve 16 is provided upstream of the junction with the recycle gas channel 15 in the fuel gas channel 13. Instead of the gas flow rate adjusting valves 16, 17, 18 it is also possible to provide a gas flow rate adjusting blower or compressor for increasing or decreasing the gas flow rate in the gas flow paths 13, 14, 15.
　燃料ガス流量調整弁１６には、当該燃料ガス流量調整弁１６の開閉度合いを制御することで燃料ガス流路１３における燃料ガスの流量を制御する燃料ガス流量制御部（ガス流量制御部）１６Ｃが接続されている。酸化剤ガス流量調整弁１７には、当該酸化剤ガス流量調整弁１７の開閉度合いを制御することで酸化剤ガス流路１４における酸化剤ガスの流量を制御する酸化剤ガス流量制御部（ガス流量制御部）１７Ｃが接続されている。リサイクルガス流量調整弁１８には、当該リサイクルガス流量調整弁１８の開閉度合いを制御することでリサイクルガス流路１５におけるリサイクルガスの流量を制御するリサイクルガス流量制御部（ガス流量制御部）１８Ｃが接続されている。 The fuel gas flow rate adjustment valve 16 includes a fuel gas flow rate control unit (gas flow rate control unit) 16C that controls the flow rate of the fuel gas in the fuel gas flow path 13 by controlling the degree of opening and closing of the fuel gas flow rate adjustment valve 16. It is connected. The oxidant gas flow rate adjustment valve 17 includes an oxidant gas flow rate control unit (a gas flow rate) that controls the flow rate of the oxidant gas in the oxidant gas flow path 14 by controlling the degree of opening and closing of the oxidant gas flow rate adjustment valve 17. Control unit) 17C is connected. The recycle gas flow rate adjustment valve 18 includes a recycle gas flow rate control unit (gas flow rate control unit) 18C that controls the flow rate of the recycle gas in the recycle gas flow path 15 by controlling the degree of opening and closing of the recycle gas flow rate adjustment valve 18. It is connected.
　本明細書で「燃料ガス流路１３における燃料ガスの流量」とは、燃料ガス流路１３のうち、リサイクルガス流路１５との合流点よりも上流側における燃料ガスの流量を意味している。すなわち、「燃料ガス流路１３における燃料ガスの流量」と「リサイクルガス流路１５におけるリサイクルガスの流量」の総和が、ＳＯＦＣ１０のアノードガス流路１１に供給される燃料ガスの流量となる。 In this specification, the “flow rate of the fuel gas in the fuel gas passage 13” means the flow rate of the fuel gas upstream of the junction with the recycle gas passage 15 in the fuel gas passage 13. . That is, the sum of “the flow rate of the fuel gas in the fuel gas flow path 13” and “the flow rate of the recycle gas in the recycle gas flow path 15” is the flow rate of the fuel gas supplied to the anode gas flow path 11 of the SOFC 10.
　ＤＣ／ＡＣ変換部２０は、ＳＯＦＣ１０が発生（発電）した直流電流を交流電流に変換する。 The DC / AC converter 20 converts the direct current generated (generated) by the SOFC 10 into an alternating current.
　ＳＯＦＣ１０の発電電力はＤＣ/ＡＣ変換部２０を通り、系統連系リレー２５を介して、系統電力網３０に接続されている。ＳＯＦＣ１０の発電電力は、系統連系リレー２５がオン状態のとき、系統電力網３０と連系状態となり、系統連系リレー２５がオフ状態のとき、解列状態となり、ＳＯＦＣ１０は自立運転を行う。 The generated power of the SOFC 10 passes through the DC / AC converter 20 and is connected to the grid power network 30 via the grid interconnection relay 25. The generated power of the SOFC 10 is connected to the grid power network 30 when the grid connection relay 25 is in an on state, and is disconnected from the grid connection relay 25 when the grid connection relay 25 is in an off state.
　連系運転時には、ＳＯＦＣ１０の発電電力が系統に給電され、自立運転時には、定格最大電力よりも小さい負荷で発電電力が装置内で消費される。 During the interconnected operation, the generated power of the SOFC 10 is supplied to the system, and during the independent operation, the generated power is consumed in the apparatus with a load smaller than the rated maximum power.
　また、ＤＣ／ＡＣ変換部２０と系統連系リレー２５の間の電力伝送路からは、別の電力伝送路を分岐してもよい（図示略）。この分岐した電力伝送路は、ＤＣ／ＡＣ変換部２０や、図示していないポンプ、ブロワ、排熱回収循環系に設けられたラジエータ（図示略）などの燃料電池システム１に搭載された機器に接続してもよい。これらの機器は、分岐した電力伝送路を介して、ＳＯＦＣ１０または系統電力網３０のいずれかから電力を供給されて駆動する。 Further, another power transmission path may be branched from the power transmission path between the DC / AC converter 20 and the grid interconnection relay 25 (not shown). This branched power transmission path is connected to devices mounted on the fuel cell system 1 such as the DC / AC converter 20, a pump (not shown), a blower, and a radiator (not shown) provided in the exhaust heat recovery circulation system. You may connect. These devices are driven by being supplied with power from either the SOFC 10 or the grid power network 30 via the branched power transmission path.
　燃焼器４０は、ＳＯＦＣ１０から排出された排出ガスを燃焼させることで、当該排出ガス中に残留している燃料成分を除去する。 The combustor 40 removes the fuel component remaining in the exhaust gas by burning the exhaust gas discharged from the SOFC 10.
　排熱回収循環系５０は、燃焼器４０からの燃焼ガス（排出ガス）の熱を回収する排熱回収循環ライン（図示略）を有している。この排熱回収循環ラインには、排熱回収のための熱媒体としての水（温水）が循環される。排熱回収循環系５０（排熱回収循環ライン）による排熱回収後のガスは、燃料電池システム１の外部に排気される。なお、排熱回収循環ラインには、排熱回収熱交換器、温水熱交換器、ヒータ、ラジエータ、ポンプ等の各種の反応器（いずれも図示略）が設けられていてもよい。 The exhaust heat recovery circulation system 50 has an exhaust heat recovery circulation line (not shown) for recovering the heat of the combustion gas (exhaust gas) from the combustor 40. Water (hot water) as a heat medium for exhaust heat recovery is circulated in the exhaust heat recovery circulation line. The gas after exhaust heat recovery by the exhaust heat recovery circulation system 50 (exhaust heat recovery circulation line) is exhausted to the outside of the fuel cell system 1. The exhaust heat recovery circulation line may be provided with various reactors (all not shown) such as an exhaust heat recovery heat exchanger, a hot water heat exchanger, a heater, a radiator, and a pump.
　図２は、燃料ガス流路１３における燃料ガスの流量、酸化剤ガス流路１４における酸化剤ガスの流量、及び、リサイクルガス流路１５におけるリサイクルガスの流量を制御するための燃料電池システム１の制御系統を示すブロック図である。 FIG. 2 shows the fuel cell system 1 for controlling the flow rate of the fuel gas in the fuel gas flow channel 13, the flow rate of the oxidant gas in the oxidant gas flow channel 14, and the flow rate of the recycle gas in the recycle gas flow channel 15. It is a block diagram which shows a control system.
　図２の燃料電池システム１の制御系統は、上述した燃料ガス流量制御部１６Ｃと、酸化剤ガス流量制御部１７Ｃと、リサイクルガス流量制御部１８Ｃとを有している。加えて、図２の燃料電池システム１の制御系統は、温度検出部６０と、目標ＯＣＶ演算部（演算部）７０と、実測ＯＣＶ取得部（取得部）８０とを有している。 The control system of the fuel cell system 1 in FIG. 2 has the above-described fuel gas flow rate control unit 16C, oxidant gas flow rate control unit 17C, and recycle gas flow rate control unit 18C. In addition, the control system of the fuel cell system 1 of FIG. 2 includes a temperature detection unit 60, a target OCV calculation unit (calculation unit) 70, and an actually measured OCV acquisition unit (acquisition unit) 80.
　温度検出部６０は、ＳＯＦＣ１０の内部の温度（セルスタックの内部温度）を検出してこれを酸化剤ガス流量制御部１７Ｃに出力する。酸化剤ガス流量制御部１７Ｃは、温度検出部６０から入力したＳＯＦＣ１０の内部の温度に基づいて、酸化剤ガス流路１４における酸化剤ガスの流量を制御する。例えば、酸化剤ガス流量制御部１７Ｃは、ＳＯＦＣ１０の内部の温度が定格運転に適した温度範囲（例えば９００℃±５０℃）を上回っているときに、酸化剤ガス流路１４における酸化剤ガスの流量を増やすことで、ＳＯＦＣ１０の内部の温度を下げる。逆に、酸化剤ガス流量制御部１７Ｃは、ＳＯＦＣ１０の内部の温度が定格運転に適した温度範囲を下回っているときに、酸化剤ガス流路１４における酸化剤ガスの流量を減らすことで、ＳＯＦＣ１０の内部の温度を上げる。このように、温度検出部６０と酸化剤ガス流量制御部１７Ｃが協働して、酸化剤ガス流路１４における酸化剤ガスの流量を制御することで、ＳＯＦＣ１０の内部の温度が定格運転に適した温度範囲に維持される。 The temperature detector 60 detects the internal temperature of the SOFC 10 (internal temperature of the cell stack) and outputs it to the oxidant gas flow rate controller 17C. The oxidant gas flow rate control unit 17 </ b> C controls the flow rate of the oxidant gas in the oxidant gas flow channel 14 based on the temperature inside the SOFC 10 input from the temperature detection unit 60. For example, the oxidant gas flow rate control unit 17C is configured so that the oxidant gas flow rate in the oxidant gas flow path 14 is higher when the temperature inside the SOFC 10 exceeds a temperature range suitable for rated operation (eg, 900 ° C. ± 50 ° C.). By increasing the flow rate, the temperature inside the SOFC 10 is lowered. Conversely, the oxidant gas flow rate control unit 17C reduces the flow rate of the oxidant gas in the oxidant gas flow path 14 when the internal temperature of the SOFC 10 is below the temperature range suitable for rated operation, so that the SOFC 10 Increase the temperature inside. As described above, the temperature detector 60 and the oxidant gas flow rate control unit 17C cooperate to control the flow rate of the oxidant gas in the oxidant gas flow path 14, so that the temperature inside the SOFC 10 is suitable for the rated operation. Temperature range.
　目標ＯＣＶ演算部７０は、ＳＯＦＣ１０の開回路電圧（ＯＣＶ：Open　Circuit　Voltage）の目標値である目標ＯＣＶを演算する。ＳＯＦＣ１０の目標ＯＣＶは、例えば、ＳＯＦＣ１０の起動時（無負荷時）のＩＶ特性より算出される高電圧（例えば直流で７５０Ｖ～９５０Ｖ程度）となることを回避して、セルスタックひいては補機の劣化及び損傷を防止できるような値に設定される。 The target OCV calculation unit 70 calculates a target OCV that is a target value of the open circuit voltage (OCV) of the SOFC 10. The target OCV of the SOFC 10 avoids a high voltage (for example, about 750 V to 950 V DC) calculated from, for example, the IV characteristics when the SOFC 10 is started (no load), and the deterioration of the cell stack and thus the auxiliary equipment And a value that can prevent damage.
　目標ＯＣＶ演算部７０は、ＳＯＦＣ１０の内部の温度と水素濃度に基づく微分演算により、ＳＯＦＣ１０の目標ＯＣＶを演算する。上述したように、ＳＯＦＣ１０の内部の温度は、温度検出部６０により検出される。 The target OCV calculation unit 70 calculates the target OCV of the SOFC 10 by differential calculation based on the temperature inside the SOFC 10 and the hydrogen concentration. As described above, the temperature inside the SOFC 10 is detected by the temperature detector 60.
　ＳＯＦＣ１０の内部の水素濃度は、次のようにして求められる。ＳＯＦＣ１０の内部の温度と、燃料ガス流路１３における燃料ガスの流量とに基づく微分演算を行うことで、「微分演算値１」を得る。ＳＯＦＣ１０の内部の温度と、リサイクルガス流路１５におけるリサイクルガスの流量とに基づく微分演算を行うことで、「微分演算値２」を得る。この「微分演算値２」は、リサイクルガス中の水素の量を示す「循環水素量」である。「微分演算値１」と「微分演算値２（循環水素量）」を加算演算することで、「加算演算値１」を得る。「加算演算値１」と、リサイクルガス流路１５におけるリサイクルガスの流量とに基づく微分演算を行うことで、「微分演算値３」を得る。この「微分演算値３」が、ＳＯＦＣ１０の内部の水素濃度に相当する。 The hydrogen concentration inside SOFC 10 is obtained as follows. By performing a differential calculation based on the temperature inside the SOFC 10 and the flow rate of the fuel gas in the fuel gas flow path 13, “differential calculation value 1” is obtained. A differential operation value 2 is obtained by performing a differential operation based on the temperature inside the SOFC 10 and the flow rate of the recycle gas in the recycle gas flow path 15. This “differential calculation value 2” is a “circulation hydrogen amount” indicating the amount of hydrogen in the recycle gas. “Addition calculation value 1” is obtained by adding and calculating “differentiation calculation value 1” and “differentiation calculation value 2 (circulation hydrogen amount)”. By performing a differential calculation based on “addition calculation value 1” and the flow rate of the recycle gas in the recycle gas flow path 15, “differentiation calculation value 3” is obtained. This “differential calculation value 3” corresponds to the hydrogen concentration inside the SOFC 10.
　実測ＯＣＶ取得部８０は、ＳＯＦＣ１０の開回路電圧（ＯＣＶ：Open Circuit Voltage）の実測値である実測ＯＣＶを取得する。 The actual OCV acquisition unit 80 acquires an actual OCV that is an actual measured value of the open circuit voltage (OCV) of the SOFC 10.
　目標ＯＣＶ演算部７０が演算したＳＯＦＣ１０の目標ＯＣＶと、実測ＯＣＶ取得部８０が取得したＳＯＦＣ１０の実測ＯＣＶとのオフセット量（差分電圧）は、燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃにそれぞれ出力される。 The offset amount (differential voltage) between the target OCV of the SOFC 10 calculated by the target OCV calculation unit 70 and the actual OCV of the SOFC 10 acquired by the actual OCV acquisition unit 80 is supplied to the fuel gas flow control unit 16C and the recycle gas flow control unit 18C. Each is output.
　燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃは、ＳＯＦＣ１０の目標ＯＣＶと実測ＯＣＶのオフセット量（差分電圧）に基づいて、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を制御する。すなわち、燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃは、ＳＯＦＣ１０の実測ＯＣＶが目標ＯＣＶに追従するように（目標ＯＣＶと実測ＯＣＶのオフセット量を打ち消すように）、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を制御する。 The fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are configured so that the flow rate of the fuel gas in the fuel gas flow channel 13 and the recycle gas flow rate in the recycle gas flow channel 15 are determined based on the offset amount (differential voltage) between the target OCV of the SOFC 10 and the actually measured OCV. Control the flow of recycle gas. That is, the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are arranged in the fuel gas flow path 13 so that the actual OCV of the SOFC 10 follows the target OCV (so as to cancel the offset amount between the target OCV and the actual OCV). The flow rate of the fuel gas and the flow rate of the recycle gas in the recycle gas flow path 15 are controlled.
　燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃは、ＳＯＦＣ１０の起動時の実測ＯＣＶが所定の閾値電圧（例えば６００Ｖ）に到達したときに、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量の制御を開始する。 The fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C are configured so that the flow rate of the fuel gas in the fuel gas flow path 13 and the recycle gas when the measured OCV at the start of the SOFC 10 reaches a predetermined threshold voltage (for example, 600V). Control of the flow rate of the recycle gas in the flow path 15 is started.
　ガス流量制御開始後のある制御期間において、燃料ガス流量制御部１６Ｃが、燃料ガス流路１３における燃料ガスの流量を増加させる場合、リサイクルガス流量制御部１８Ｃが、リサイクルガス流路１５におけるリサイクルガスの流量を減少させる。逆に、ガス流量制御開始後のある制御期間において、燃料ガス流量制御部１６Ｃが、燃料ガス流路１３における燃料ガスの流量を減少させる場合、リサイクルガス流量制御部１８Ｃが、リサイクルガス流路１５におけるリサイクルガスの流量を増加させる。 When the fuel gas flow rate control unit 16C increases the flow rate of the fuel gas in the fuel gas flow path 13 during a certain control period after the start of the gas flow rate control, the recycle gas flow rate control unit 18C uses the recycle gas in the recycle gas flow path 15. Reduce the flow rate. Conversely, when the fuel gas flow rate control unit 16C decreases the flow rate of the fuel gas in the fuel gas flow channel 13 during a certain control period after the start of the gas flow rate control, the recycle gas flow rate control unit 18C Increase the flow rate of recycle gas.
　例えば、ＳＯＦＣ１０の起動時には、リサイクルガス流路１５におけるリサイクルガスの流量が増加する傾向となるので、これに合わせて、燃料ガス流路１３における燃料ガスの流量を減少させる。これにより、ＳＯＦＣ１０の内部における水素分圧が調整されて当該水素分圧が高くなりすぎるのが防止され、ＳＯＦＣ１０の実測ＯＣＶが目標ＯＣＶに高精度に追従する結果、燃料電池システム１の安定的な運転が実現可能となる。 For example, when the SOFC 10 is activated, the flow rate of the recycle gas in the recycle gas flow path 15 tends to increase. Accordingly, the flow rate of the fuel gas in the fuel gas flow path 13 is decreased accordingly. As a result, the hydrogen partial pressure inside the SOFC 10 is adjusted to prevent the hydrogen partial pressure from becoming too high, and the measured OCV of the SOFC 10 follows the target OCV with high accuracy. As a result, the fuel cell system 1 is stable. Driving becomes feasible.
　ここで、ＳＯＦＣ１０の内部における水素分圧は、厳密には、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量に加えて、酸化剤ガス流路１４における酸化剤ガスの流量、さらにはボイラ（図示略）などから供給される水蒸気の量などの影響を受ける。しかし、本実施形態のように、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を適切に制御すれば、上記外乱要因は無視できる程度であり、ＳＯＦＣ１０の内部における水素分圧を適切に調整することができる。あるいは、上記外乱要因を考慮に入れた上で、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を制御すれば、ＳＯＦＣ１０の内部における水素分圧をさらに高精度に調整することができる。 Here, strictly speaking, the hydrogen partial pressure in the SOFC 10 is not limited to the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15, but the oxidant in the oxidant gas flow channel 14. It is affected by the flow rate of gas and the amount of water vapor supplied from a boiler (not shown). However, if the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15 are appropriately controlled as in the present embodiment, the disturbance factor can be ignored, and the inside of the SOFC 10 The hydrogen partial pressure in can be adjusted appropriately. Alternatively, the hydrogen partial pressure inside the SOFC 10 can be further increased by controlling the flow rate of the fuel gas in the fuel gas passage 13 and the flow rate of the recycle gas in the recycle gas passage 15 in consideration of the disturbance factors. Can be adjusted.
　燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を制御（増減）させることは、ＳＯＦＣ１０の内部の反応器を駆動させて熱が籠ることを助長する。しかし、温度検出部６０がＳＯＦＣ１０の内部の温度をモニタリングして、これに応じて、酸化剤ガス流量制御部１７Ｃが酸化剤ガス流路１４における酸化剤ガスの流量を制御するので、ＳＯＦＣ１０の内部の温度が高くなりすぎることがない。この点でも、燃料電池システム１の安定的な運転が実現可能となる。 Controlling (increasing / decreasing) the flow rate of the fuel gas in the fuel gas flow path 13 and the flow rate of the recycle gas in the recycle gas flow path 15 drives the internal reactor of the SOFC 10 to increase heat. However, the temperature detector 60 monitors the temperature inside the SOFC 10, and the oxidant gas flow rate controller 17C controls the flow rate of the oxidant gas in the oxidant gas flow path 14 accordingly, so that the inside of the SOFC 10 The temperature is not too high. Also in this respect, stable operation of the fuel cell system 1 can be realized.
　図３のタイミングチャート及び図４のフローチャートを参照して、燃料電池システム１の起動時から定格運転開始までの動作について説明する。図３のタイミングチャートにおいて、実線は本実施形態によるガス流量制御を行った場合にＳＯＦＣ１０に掛かる電圧を示し、破線は本実施形態によるガス流量制御を行わなかった場合にＳＯＦＣ１０に掛かる電圧を示している。 Referring to the timing chart of FIG. 3 and the flowchart of FIG. 4, the operation from the start of the fuel cell system 1 to the start of the rated operation will be described. In the timing chart of FIG. 3, the solid line indicates the voltage applied to the SOFC 10 when the gas flow rate control according to the present embodiment is performed, and the broken line indicates the voltage applied to the SOFC 10 when the gas flow rate control according to the present embodiment is not performed. Yes.
　ステップＳＴ１では、燃料ガスと酸化剤ガスをＳＯＦＣ１０に送り込むための空気ブロア（図示略）がオンされる。ステップＳＴ２では、燃料ガスと酸化剤ガスを加熱するための空気加熱機構（図示略）がオンされる。ステップＳＴ３では、ＳＯＦＣ１０の温度が所定値以上であるか否かが判定される。ＳＯＦＣ１０の温度が所定値以上であれば（ステップＳＴ３：Ｙｅｓ）、ステップＳＴ４に進む。ＳＯＦＣ１０の温度が所定値未満であれば（ステップＳＴ３：Ｎｏ）、ＳＯＦＣ１０の温度が所定値以上になるのを待つ。 In step ST1, an air blower (not shown) for sending fuel gas and oxidant gas into the SOFC 10 is turned on. In step ST2, an air heating mechanism (not shown) for heating the fuel gas and the oxidant gas is turned on. In step ST3, it is determined whether or not the temperature of the SOFC 10 is equal to or higher than a predetermined value. If the temperature of the SOFC 10 is equal to or higher than a predetermined value (step ST3: Yes), the process proceeds to step ST4. If the temperature of the SOFC 10 is less than the predetermined value (step ST3: No), the process waits for the temperature of the SOFC 10 to be equal to or higher than the predetermined value.
　ステップＳＴ４では、ＳＯＦＣ１０への燃料ガスと酸化剤ガスの供給が開始され、ＳＯＦＣ１０のＯＣＶが立ち上がり始める（図３参照）。この段階では、本実施形態によるガス流量制御を行っていない（図３の実線と破線を参照）。 In step ST4, the supply of fuel gas and oxidant gas to the SOFC 10 is started, and the OCV of the SOFC 10 starts to rise (see FIG. 3). At this stage, the gas flow rate control according to the present embodiment is not performed (see the solid line and the broken line in FIG. 3).
　ステップＳＴ５では、ＳＯＦＣ１０の起動時の実測ＯＣＶが所定の閾値電圧（例えば６００Ｖ）以上であるか否かが判定される。ＳＯＦＣ１０の起動時の実測ＯＣＶが所定の閾値電圧以上であれば（ステップＳＴ５：Ｙｅｓ）、ステップＳＴ６に進む。ＳＯＦＣ１０の起動時の実測ＯＣＶが所定の閾値未満であれば（ステップＳＴ５：Ｎｏ）、ＳＯＦＣ１０の起動時の実測ＯＣＶが所定の閾値電圧以上になるのを待つ。 In step ST5, it is determined whether or not the actual OCV at the time of activation of the SOFC 10 is equal to or higher than a predetermined threshold voltage (for example, 600V). If the measured OCV at the time of activation of the SOFC 10 is equal to or higher than a predetermined threshold voltage (step ST5: Yes), the process proceeds to step ST6. If the measured OCV at the time of starting up the SOFC 10 is less than the predetermined threshold value (step ST5: No), it waits for the measured OCV at the time of starting up the SOFC 10 to be equal to or higher than the predetermined threshold voltage.
　ステップＳＴ６では、目標ＯＣＶ演算部７０が、ＳＯＦＣ１０の目標ＯＣＶの演算を開始する。ステップＳＴ７では、実測ＯＣＶ取得部８０が、ＳＯＦＣ１０の実測ＯＣＶの取得を開始する。ステップＳＴ８では、燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃが、ＳＯＦＣ１０の目標ＯＣＶと実測ＯＣＶのオフセット量（差分電圧）に基づいて、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量の制御を開始する。このガス流量制御により、ＳＯＦＣ１０の起動時（無負荷時）のＯＣＶが、本実施形態によるガス流量制御を行わなかった場合のＯＣＶよりも低く維持されるように制御される（図３の実線と破線を参照）。またステップＳＴ８では、酸化剤ガス流量制御部１７Ｃが、温度検出部６０から入力したＳＯＦＣ１０の内部の温度に基づいて、酸化剤ガス流路１４における酸化剤ガスの流量の制御を開始する。ステップＳＴ６～ステップＳＴ８の処理は、略同時に実行してもよいし、時間的にずらして実行してもよい。 In step ST6, the target OCV calculation unit 70 starts calculating the target OCV of the SOFC 10. In step ST7, the actual OCV acquisition unit 80 starts acquiring the actual OCV of the SOFC 10. In step ST8, the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C perform the fuel gas flow rate and the recycle gas in the fuel gas flow channel 13 based on the offset amount (differential voltage) between the target OCV and the actual OCV of the SOFC 10. Control of the flow rate of the recycle gas in the flow path 15 is started. By this gas flow rate control, the OCV when the SOFC 10 is started (no load) is controlled to be kept lower than the OCV when the gas flow rate control according to the present embodiment is not performed (the solid line in FIG. 3). (See dashed line). In step ST8, the oxidant gas flow rate control unit 17C starts controlling the flow rate of the oxidant gas in the oxidant gas flow channel 14 based on the internal temperature of the SOFC 10 input from the temperature detection unit 60. The processes in steps ST6 to ST8 may be executed substantially simultaneously or may be executed while being shifted in time.
　ステップＳＴ９では、ＳＯＦＣ１０への燃料ガスと酸化剤ガスの供給量が所定値以上であるか否かが判定される。ＳＯＦＣ１０への燃料ガスと酸化剤ガスの供給量が所定値以上であれば（ステップＳＴ９：Ｙｅｓ）、ステップＳＴ１０に進む。ＳＯＦＣ１０への燃料ガスと酸化剤ガスの供給量が所定値未満であれば（ステップＳＴ９：Ｎｏ）、ＳＯＦＣ１０への燃料ガスと酸化剤ガスの供給量が所定値以上となるのを待つ。 In step ST9, it is determined whether or not the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are equal to or greater than a predetermined value. If the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are greater than or equal to the predetermined values (step ST9: Yes), the process proceeds to step ST10. If the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 are less than the predetermined values (step ST9: No), it waits for the supply amounts of the fuel gas and the oxidant gas to the SOFC 10 to be equal to or greater than the predetermined values.
　ステップＳＴ１０では、ＳＯＦＣ１０の発電電力が発電負荷（例えば各種の補機）に投入開始される。これにより、発電負荷に流れる電流が上昇を開始する。 In step ST10, the power generated by the SOFC 10 is started to be input to a power generation load (for example, various auxiliary machines). Thereby, the current flowing through the power generation load starts to rise.
　ステップＳＴ１１では、ＳＯＦＣ１０が定格運転に近いか否か（ＳＯＦＣ１０の実測ＯＣＶが定格運転電力に近いか否か）が判定される。ＳＯＦＣ１０が定格運転に近いと判定されれば（ステップＳＴ１１：Ｙｅｓ）、ステップＳＴ１２に進む。ＳＯＦＣ１０が定格運転に近くないと判定されれば（ステップＳＴ１１：Ｎｏ）、ＳＯＦＣ１０が定格運転に近くなるのを待つ。 In step ST11, it is determined whether or not the SOFC 10 is close to rated operation (whether or not the actual OCV of the SOFC 10 is close to rated operating power). If it is determined that the SOFC 10 is close to the rated operation (step ST11: Yes), the process proceeds to step ST12. If it is determined that the SOFC 10 is not close to the rated operation (step ST11: No), it waits for the SOFC 10 to be close to the rated operation.
　ステップＳＴ１２では、目標ＯＣＶ演算部７０が、ＳＯＦＣ１０の目標ＯＣＶの演算を終了する。ステップＳＴ１３では、実測ＯＣＶ取得部８０が、ＳＯＦＣ１０の実測ＯＣＶの取得を終了する。ステップＳＴ１４では、燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃが、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量の制御を終了する。燃料ガスとリサイクルガスの流量制御を終了することにより、ＳＯＦＣ１０のＯＣＶが、本実施形態によるガス流量制御を行わなかった場合のＯＣＶと一致するように収束していく（図３の実線と破線を参照）。またステップＳＴ１４では、酸化剤ガス流量制御部１７Ｃが、酸化剤ガス流路１４における酸化剤ガスの流量の制御を終了する。ステップＳＴ１２～ステップＳＴ１４の処理は、略同時に実行してもよいし、時間的にずらして実行してもよい。 In step ST12, the target OCV calculation unit 70 ends the calculation of the target OCV of the SOFC 10. In step ST13, the actual OCV acquisition unit 80 ends the actual OCV acquisition of the SOFC 10. In step ST14, the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C end the control of the flow rate of the fuel gas in the fuel gas flow channel 13 and the flow rate of the recycle gas in the recycle gas flow channel 15. By ending the flow control of the fuel gas and the recycle gas, the OCV of the SOFC 10 converges so as to coincide with the OCV when the gas flow rate control according to the present embodiment is not performed (the solid line and the broken line in FIG. 3 are reference). In step ST14, the oxidant gas flow rate control unit 17C ends the control of the oxidant gas flow rate in the oxidant gas flow path 14. The processes in steps ST12 to ST14 may be executed substantially simultaneously or may be executed while being shifted in time.
　ステップＳＴ１５では、ＳＯＦＣ１０の発電電力が定格最大電力に収束した定格運転が実行される。 In step ST15, the rated operation in which the generated power of the SOFC 10 converges to the rated maximum power is executed.
　図３のタイミングチャート及び図４のフローチャートでは、ＳＯＦＣ１０が定格運転に近くなったタイミングで、燃料ガスとリサイクルガスと酸化剤ガスの流量制御を終了させたが、ＳＯＦＣ１０が定格運転になった後のタイミングで、燃料ガスとリサイクルガスと酸化剤ガスの流量制御を終了させてもよい。 In the timing chart of FIG. 3 and the flowchart of FIG. 4, the flow control of the fuel gas, the recycle gas, and the oxidant gas is terminated at the timing when the SOFC 10 is close to the rated operation. At the timing, the flow control of the fuel gas, the recycle gas, and the oxidant gas may be terminated.
　以上説明した燃料電池システム１によれば、ＳＯＦＣ１０の高い発電効率を維持しつつ、燃料ガス流路１３とリサイクルガス流路１５に燃料ガス流量調整弁１６とリサイクルガス流量調整弁１８を設け、燃料ガス流量調整弁１６とリサイクルガス流量調整弁１８を燃料ガス流量制御部１６Ｃとリサイクルガス流量制御部１８Ｃにより制御するだけの簡単な構成かつ低コストで、ＳＯＦＣ１０のＯＣＶ（特に起動時のＯＣＶ）を抑制して安定的な運転を実現することができる。 According to the fuel cell system 1 described above, the fuel gas flow rate adjustment valve 16 and the recycle gas flow rate adjustment valve 18 are provided in the fuel gas flow path 13 and the recycle gas flow path 15 while maintaining the high power generation efficiency of the SOFC 10, and the fuel cell system 1 The OCV of the SOFC 10 (especially the OCV at the time of start-up) is simply configured and low in cost by simply controlling the gas flow rate adjustment valve 16 and the recycle gas flow rate adjustment valve 18 by the fuel gas flow rate control unit 16C and the recycle gas flow rate control unit 18C. Stable operation can be realized with suppression.
　なお、本発明は上記実施の形態に限定されず、種々変更して実施することが可能である。上記実施の形態において、添付図面に図示されている構成要素の大きさや形状、機能などについては、これに限定されず、本発明の効果を発揮する範囲内で適宜変更することが可能である。その他、本発明の目的の範囲を逸脱しない限りにおいて適宜変更して実施することが可能である。 It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above-described embodiment, the size, shape, function, and the like of the components illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.
　上記実施の形態では、ＳＯＦＣ１０の内部における水素分圧を調整するために、燃料ガス流路１３における燃料ガスの流量とリサイクルガス流路１５におけるリサイクルガスの流量を制御する場合を例示して説明したが、これに加えて／代えて、酸化剤ガス流路１４における酸化剤ガスの流量を制御してもよい。さらには、ボイラ（図示略）などから供給される水蒸気の量を増減させることで、ＳＯＦＣ１０の内部における水素分圧を調整してもよい。 In the above embodiment, the case where the flow rate of the fuel gas in the fuel gas flow path 13 and the flow rate of the recycle gas in the recycle gas flow path 15 are controlled in order to adjust the hydrogen partial pressure inside the SOFC 10 has been described as an example. However, in addition to / alternatively, the flow rate of the oxidant gas in the oxidant gas passage 14 may be controlled. Furthermore, the hydrogen partial pressure inside the SOFC 10 may be adjusted by increasing or decreasing the amount of water vapor supplied from a boiler (not shown) or the like.
　上記実施の形態では、ＳＯＦＣ１０と排熱回収循環系５０の間に燃焼器４０を設けているが、この燃焼器４０を省略して、ＳＯＦＣ１０から排出された排出ガスを直接的に排熱回収循環系５０に導いてもよい。 In the above embodiment, the combustor 40 is provided between the SOFC 10 and the exhaust heat recovery circulation system 50. However, the combustor 40 is omitted, and the exhaust gas exhausted from the SOFC 10 is directly exhausted heat recovery and circulation. You may lead to the system 50.
　本発明の燃料電池システム及びその運転方法は、家庭用、業務用、その他のあらゆる産業分野の燃料電池システムに適用して好適である。 The fuel cell system and the operation method thereof according to the present invention are suitable for application to fuel cell systems for household use, business use, and other industrial fields.
１　燃料電池システム
１０　固体酸化物形燃料電池（ＳＯＦＣ：Solid Oxide Fuel Cell）
１１　アノードガス流路
１２　カソードガス流路
１３　燃料ガス流路
１４　酸化剤ガス流路
１５　リサイクルガス流路
１６　燃料ガス流量調整弁（ガス流量調整弁）
１６Ｃ　燃料ガス流量制御部（ガス流量制御部）
１７　酸化剤ガス流量調整弁（ガス流量調整弁）
１７Ｃ　酸化剤ガス流量制御部（ガス流量制御部）
１８　リサイクルガス流量調整弁（ガス流量調整弁）
１８Ｃ　リサイクルガス流量制御部（ガス流量制御部）
２０　ＤＣ／ＡＣ変換部
２５　系統連系リレー
３０　系統電力網
４０　燃焼器
５０　排熱回収循環系
６０　温度検出部
７０　目標ＯＣＶ演算部（演算部）
８０　実測ＯＣＶ取得部（取得部） 1 Fuel Cell System 10 Solid Oxide Fuel Cell (SOFC)
11 Anode gas flow path 12 Cathode gas flow path 13 Fuel gas flow path 14 Oxidant gas flow path 15 Recycle gas flow path 16 Fuel gas flow rate adjustment valve (gas flow rate adjustment valve)
16C Fuel gas flow control unit (gas flow control unit)
17 Oxidant gas flow rate adjustment valve (gas flow rate adjustment valve)
17C Oxidant gas flow control unit (gas flow control unit)
18 Recycle gas flow control valve (Gas flow control valve)
18C Recycled gas flow control unit (gas flow control unit)
20 DC / AC conversion unit 25 Grid interconnection relay 30 Grid power network 40 Combustor 50 Waste heat recovery circulation system 60 Temperature detection unit 70 Target OCV calculation unit (calculation unit)
80 Actual OCV acquisition unit (acquisition unit)

Claims (5)

  1. 　燃料ガスと酸化剤ガスの電気化学反応により発電する固体酸化物形燃料電池と、
    　前記固体酸化物形燃料電池に前記燃料ガスを供給する燃料ガス流路と、
    　前記固体酸化物形燃料電池から排出された前記燃料ガスをリサイクルガスとして前記燃料ガス流路に還流するリサイクルガス流路と、
    　前記固体酸化物形燃料電池の目標開回路電圧を演算する演算部と、
    　前記固体酸化物形燃料電池の実測開回路電圧を取得する取得部と、
    　前記固体酸化物形燃料電池の前記目標開回路電圧と前記実測開回路電圧の差分電圧に基づいて、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量を制御するガス流量制御部と、
    　を有し、
    　前記演算部は、前記固体酸化物形燃料電池の内部の温度と水素濃度に基づいて、前記固体酸化物形燃料電池の前記目標開回路電圧を演算する、
    　ことを特徴とする燃料電池システム。     A solid oxide fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas;
    A fuel gas flow path for supplying the fuel gas to the solid oxide fuel cell;
    A recycle gas flow path for recirculating the fuel gas discharged from the solid oxide fuel cell to the fuel gas flow path as a recycle gas;
    A calculation unit for calculating a target open circuit voltage of the solid oxide fuel cell;
    An acquisition unit for acquiring a measured open circuit voltage of the solid oxide fuel cell;
    Based on the differential voltage between the target open circuit voltage and the measured open circuit voltage of the solid oxide fuel cell, the flow rate of the fuel gas in the fuel gas flow channel and the flow rate of the recycle gas in the recycle gas flow channel are determined. A gas flow rate control unit to be controlled;
    Have
    The calculation unit calculates the target open circuit voltage of the solid oxide fuel cell based on the temperature and hydrogen concentration inside the solid oxide fuel cell.
    A fuel cell system.
  2. 　前記ガス流量制御部は、前記固体酸化物形燃料電池の起動時の実測開回路電圧が所定の閾値電圧に到達したときに、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量の制御を開始することを特徴とする請求項１に記載の燃料電池システム。 The gas flow rate controller controls the flow rate of the fuel gas in the fuel gas flow path and the recycle gas flow path when the measured open circuit voltage at the start of the solid oxide fuel cell reaches a predetermined threshold voltage. 2. The fuel cell system according to claim 1, wherein control of the flow rate of the recycle gas is started.
  3. 　前記ガス流量制御部は、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量の一方を増加させるとともに他方を減少させることを特徴とする請求項１または請求項２に記載の燃料電池システム。 2. The gas flow rate control unit increases one of the flow rate of the fuel gas in the fuel gas flow channel and the flow rate of the recycle gas in the recycle gas flow channel, and decreases the other. Item 3. The fuel cell system according to Item 2.
  4. 　前記固体酸化物形燃料電池に酸化剤ガスを供給する酸化剤ガス流路をさらに有し、
    　前記ガス流量制御部は、前記固体酸化物形燃料電池の内部の温度に基づいて、前記酸化剤ガス流路における前記酸化剤ガスの流量を制御することを特徴とする請求項１から３のいずれかに記載の燃料電池システム。     An oxidant gas flow path for supplying an oxidant gas to the solid oxide fuel cell;
    The said gas flow rate control part controls the flow volume of the said oxidant gas in the said oxidant gas flow path based on the temperature inside the said solid oxide fuel cell, The any one of Claim 1 to 3 characterized by the above-mentioned. A fuel cell system according to claim 1.
  5. 　燃料ガスと酸化剤ガスの電気化学反応により発電する固体酸化物形燃料電池と、前記固体酸化物形燃料電池に前記燃料ガスを供給する燃料ガス流路と、前記固体酸化物形燃料電池から排出された前記燃料ガスをリサイクルガスとして前記燃料ガス流路に還流するリサイクルガス流路と、を有する燃料電池システムの運転方法であって、
    　前記固体酸化物形燃料電池の目標開回路電圧を演算する演算ステップと、
    　前記固体酸化物形燃料電池の実測開回路電圧を取得する取得ステップと、
    　前記固体酸化物形燃料電池の前記目標開回路電圧と前記実測開回路電圧の差分電圧に基づいて、前記燃料ガス流路における前記燃料ガスの流量と前記リサイクルガス流路における前記リサイクルガスの流量を制御するガス流量制御ステップと、
    　を有し、
    　前記演算ステップでは、前記固体酸化物形燃料電池の内部の温度と水素濃度に基づいて、前記固体酸化物形燃料電池の前記目標開回路電圧を演算する、
    　ことを特徴とする燃料電池システムの運転方法。     A solid oxide fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a fuel gas flow path for supplying the fuel gas to the solid oxide fuel cell, and an exhaust from the solid oxide fuel cell A recycle gas flow path for recirculating the fuel gas as a recycle gas to the fuel gas flow path, and a method for operating a fuel cell system,
    A calculation step of calculating a target open circuit voltage of the solid oxide fuel cell;
    An obtaining step of obtaining the measured open circuit voltage of the solid oxide fuel cell;
    Based on the differential voltage between the target open circuit voltage and the measured open circuit voltage of the solid oxide fuel cell, the flow rate of the fuel gas in the fuel gas flow channel and the flow rate of the recycle gas in the recycle gas flow channel are determined. A gas flow control step to control;
    Have
    In the calculation step, the target open circuit voltage of the solid oxide fuel cell is calculated based on the temperature and hydrogen concentration inside the solid oxide fuel cell.
    A method for operating a fuel cell system.
PCT/JP2017/030395 2016-09-16 2017-08-24 Fuel cell system and method for operating same WO2018051759A1 (en)

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JP2021128876A (en) * 2020-02-14 2021-09-02 三菱重工業株式会社 Power generation system, control device of the same, control method, and control program
JP7383515B2 (en) 2020-02-14 2023-11-20 三菱重工業株式会社 Power generation system, its control device, control method, and control program

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