WO2012091120A1

WO2012091120A1 - Fuel cell system

Info

Publication number: WO2012091120A1
Application number: PCT/JP2011/080469
Authority: WO
Inventors: 洋平水野; 修平咲間
Original assignee: Ｊｘ日鉱日石エネルギー株式会社
Priority date: 2010-12-28
Filing date: 2011-12-28
Publication date: 2012-07-05
Also published as: JPWO2012091120A1

Abstract

A fuel cell system (1) has a damper (22) that opens and closes an exhaust opening (26), and is provided in an exhaust channel for discharging FC gas emitted from a power generation unit (21). In the case that a current direction detection unit (23) detects that circulating gas flowing toward an exhaust opening (26) is flowing backward, the damper (22) is closed and the system stopped. Therefore, it is possible to minimize life-shortening, caused by the backward flow of exhaust gas to the power generation unit (21) side, for a fuel cell stack (5), various catalysts, absorbing agents, ion-exchange resins, various auxiliaries, or the like.

Description

Fuel cell system

The present invention relates to a fuel cell system.

As a technology in this type of field, for example, there is a fuel cell system described in Patent Document 1. This conventional fuel cell system includes an exhaust port for exhausting the exhaust gas after heat exchange with the heat exchanger to the outside of the case. A separate member for collecting impurities is provided in front of the exhaust port to prevent impurities from entering the heat exchanger side from the exhaust port.

JP 2009-181701 A

As an example of the installation mode of the fuel cell system, there is a case where the fuel cell system is installed indoors and the exhaust port is connected to the chimney. When the chimney is shared with other devices, the external exhaust gas that fills the chimney may contain components that are undesirable for the fuel cell system and dust in the chimney stack. At this time, if exhaust pressure rises from other devices or the chimney itself becomes blocked, the external exhaust gas in the chimney may flow into the fuel cell system.

In the conventional fuel cell system as described above, a single exhaust port is provided for the heat exchanger. However, it is difficult to sufficiently suppress exhaust gas (external exhaust gas) from other devices from flowing into the fuel cell system. When a component undesirable for the fuel cell system or external exhaust gas containing dust flows into the fuel cell system, the cell stack, various catalysts or adsorbents, ion exchange resins, various supplements, which are components of the fuel cell system. There is a risk that the machinery and the like will have a short life. Therefore, a technique for suppressing the inflow of external exhaust gas to the fuel cell system side is required.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell system capable of suppressing the inflow of external exhaust gas to the fuel cell system side.

A fuel cell system according to one aspect of the present invention includes a power generation unit including a cell stack that generates power using a hydrogen-containing gas, an exhaust port that discharges at least exhaust gas discharged from the power generation unit to the outside of the system, and power generation Disposed in the exhaust path between the exhaust section and the exhaust port, and a flow direction detecting section for detecting the flow direction of the circulating gas in the exhaust path, and disposed downstream of the flow direction detecting section in the exhaust path, A damper that switches between opening and closing; and a control unit that closes the damper and stops the system when a backflow of the flowing gas is detected by the flow direction detection unit.

In this fuel cell system, a damper for controlling the flow of the circulating gas in the exhaust path is provided in the exhaust path for exhausting the exhaust gas. Then, when the backflow of the circulating gas flowing in the exhaust path is detected by the flow direction detection unit, it is determined that there is an inflow of external exhaust gas or there is a risk, and the damper is closed to stop the system. Therefore, in this fuel cell system, it is possible to suppress the shortening of the service life of the cell stack, various catalysts or adsorbents, various auxiliary machines and the like due to the flow of external exhaust gas to the system side.

The fuel cell system according to the present invention can suppress the flow of external exhaust gas to the fuel cell system side.

1 is a diagram showing an embodiment of a fuel cell system according to the present invention. It is a figure which shows the exhaust route of the fuel cell system shown in FIG. It is a figure which shows an example of a flow direction detection part. It is a figure which shows the other example of a flow direction detection part. It is a flowchart which shows the 1st form of operation | movement of a control part. It is a flowchart which shows the 2nd form of operation | movement of a control part. It is a flowchart which shows the 3rd form of operation | movement of a control part.

Hereinafter, preferred embodiments of a fuel cell system according to the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

As shown in FIG. 1, the fuel cell system 1 includes a desulfurization unit 2, a water vaporization unit 3, a hydrogen generation unit 4, a cell stack 5, an off-gas combustion unit 6, a hydrogen-containing fuel supply unit 7, The water supply part 8, the oxidizing agent supply part 9, the power conditioner 10, the control part 11, and the heat exchange part 15 are provided. The fuel cell system 1 generates power in the cell stack 5 using a hydrogen-containing fuel and an oxidant. The type of the cell stack 5 in the fuel cell system 1 is not particularly limited, and examples thereof include a polymer electrolyte fuel cell (PEFC), a solid oxide fuel cell (SOFC), and phosphoric acid. A fuel cell (PAFC: Phosphoric Acid Fuel Cell), a molten carbonate fuel cell (MCFC: Molten Carbonate Fuel Cell), and other types can be employed. 1 may be appropriately omitted depending on the type of cell stack 5, the type of hydrogen-containing fuel, the reforming method, and the like.

As the hydrogen-containing fuel, for example, a hydrocarbon fuel is used. As the hydrocarbon fuel, a compound containing carbon and hydrogen in the molecule (may contain other elements such as oxygen) or a mixture thereof is used. Examples of hydrocarbon fuels include hydrocarbons, alcohols, ethers, and biofuels. These hydrocarbon fuels are derived from conventional fossil fuels such as petroleum and coal, and synthetic systems such as synthesis gas. Those derived from fuel and those derived from biomass can be used as appropriate. Specific examples of hydrocarbons include methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, town gas, gasoline, naphtha, kerosene, and light oil. Examples of alcohols include methanol and ethanol. Examples of ethers include dimethyl ether. Examples of biofuels include biogas, bioethanol, biodiesel, and biojet.

As the oxidizing agent, for example, air, pure oxygen gas (which may contain impurities that are difficult to remove by a normal removal method), or oxygen-enriched air is used.

The desulfurization unit 2 desulfurizes the hydrogen-containing fuel supplied to the hydrogen generation unit 4. The desulfurization part 2 has a desulfurization catalyst for removing sulfur compounds contained in the hydrogen-containing fuel. As the desulfurization method of the desulfurization unit 2, for example, an adsorptive desulfurization method that adsorbs and removes sulfur compounds and a hydrodesulfurization method that removes sulfur compounds by reacting with hydrogen are employed. The desulfurization unit 2 supplies the desulfurized hydrogen-containing fuel to the hydrogen generation unit 4.

The water vaporization unit 3 generates water vapor supplied to the hydrogen generation unit 4 by heating and vaporizing water. For the heating of the water in the water vaporization unit 3, for example, heat generated in the fuel cell system 1 such as recovering the heat of the hydrogen generation unit 4, the heat of the off-gas combustion unit 6, or the heat of the exhaust gas may be used. Moreover, you may heat water using other heat sources, such as a heater and a burner separately. In FIG. 1, only heat supplied from the off-gas combustion unit 6 to the hydrogen generation unit 4 is described as an example, but the present invention is not limited to this. The water vaporization unit 3 supplies the generated water vapor to the hydrogen generation unit 4.

The hydrogen generation unit 4 generates a hydrogen rich gas using the hydrogen-containing fuel from the desulfurization unit 2. The hydrogen generator 4 has a reformer that reforms the hydrogen-containing fuel with a reforming catalyst. The reforming method in the hydrogen generating unit 4 is not particularly limited, and for example, steam reforming, partial oxidation reforming, autothermal reforming, and other reforming methods can be employed. The hydrogen generator 4 may have a configuration for adjusting the properties in addition to the reformer reformed by the reforming catalyst depending on the properties of the hydrogen rich gas required for the cell stack 5. For example, when the type of the cell stack 5 is a polymer electrolyte fuel cell (PEFC) or a phosphoric acid fuel cell (PAFC), the hydrogen generation unit 4 is configured to remove carbon monoxide in the hydrogen-rich gas. (For example, a shift reaction part and a selective oxidation reaction part). The hydrogen generation unit 4 supplies a hydrogen rich gas to the anode 12 of the cell stack 5.

The cell stack 5 generates power using the hydrogen rich gas from the hydrogen generation unit 4 and the oxidant from the oxidant supply unit 9. The cell stack 5 includes an anode 12 to which a hydrogen-rich gas is supplied, a cathode 13 to which an oxidant is supplied, and an electrolyte 14 disposed between the anode 12 and the cathode 13. The cell stack 5 supplies power to the outside via the power conditioner 10. The cell stack 5 supplies the hydrogen rich gas and the oxidant, which have not been used for power generation, to the off gas combustion unit 6 as off gas. Note that a combustion section (for example, a combustor that heats the reformer) provided in the hydrogen generation section 4 may be shared with the off-gas combustion section 6.

The off gas combustion unit 6 burns off gas supplied from the cell stack 5. The heat generated by the off-gas combustion unit 6 is supplied to the hydrogen generation unit 4 and used for generation of a hydrogen rich gas in the hydrogen generation unit 4.

The hydrogen-containing fuel supply unit 7 supplies hydrogen-containing fuel to the desulfurization unit 2. The water supply unit 8 supplies water to the water vaporization unit 3. The oxidant supply unit 9 supplies an oxidant to the cathode 13 of the cell stack 5. The hydrogen-containing fuel supply unit 7, the water supply unit 8, and the oxidant supply unit 9 are configured by a pump, for example, and are driven based on a control signal from the control unit 11.

In the case of using a hydrogen-containing fuel that does not require a reforming process, such as pure hydrogen gas or hydrogen-enriched gas, for example, among the desulfurizer 2, the water supply unit 8, the water vaporization unit 3, and the hydrogen generation unit 4 One or more can be omitted.

The power conditioner 10 adjusts the power from the cell stack 5 according to the external power usage state. For example, the power conditioner 10 performs a process of converting a voltage and a process of converting DC power into AC power.

The control unit 11 performs control processing for the entire fuel cell system 1. The control unit 11 is configured by a device including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface, for example. The control unit 11 is electrically connected to a hydrogen-containing fuel supply unit 7, a water supply unit 8, an oxidant supply unit 9, a power conditioner 10, and other sensors and auxiliary equipment not shown. The control unit 11 acquires various signals generated in the fuel cell system 1 and outputs a control signal to each device in the fuel cell system 1.

The heat exchange unit 15 moves the heat from the combustion gas to the water by circulating the off-gas combustion gas discharged from the cell stack 5 (that is, the exhaust gas from the off-gas combustion unit 6) and water (heat medium). Heat the water. This water is stored, for example, in a hot water storage tank for supplying hot water to a facility where the fuel cell system 1 is installed, and is circulated and supplied from the hot water storage tank to the heat exchanging unit 15.

Subsequently, the exhaust path of the fuel cell system 1 will be described. FIG. 2 is a diagram showing an exhaust path of the fuel cell system 1.

As shown in FIG. 2, the exhaust path of the fuel cell system 1 includes a power generation unit 21, the heat exchange unit 15 described above, a damper 22, a flow direction detection unit 23, and a control unit 24. Housed in the housing 25. The casing 25 is provided with a circulation gas passage 27 and an exhaust port 26 through which exhaust gas (FC exhaust gas) discharged from at least the power generation unit 21 side flows. Although details are not shown, the circulation gas path 27 including the damper 22 and the flow direction detection unit 23 is airtight to the outside air. Here, the airtightness means airtightness with respect to outside air other than the gas scheduled to be discharged from the housing 25. Specifically, it means a structure in which gas is discharged from the housing 25 only from a dedicated gas discharge path.

The power generation unit 21 includes the cell stack 5 described above. The power generation unit 21 includes at least the cell stack 5, and may further include an off-gas combustion unit 6, a hydrogen generation unit 4, or the like, or may not include the off-gas combustion unit 6, the hydrogen generation unit 4, or the like. . In addition, the heat exchanging unit 15 has, as a heat recovery water system, for example, a water channel for circulating water supplied from a hot water tank into the heat exchanging unit 15 and a water channel for discharging the water from the heat exchanging unit 15. Etc. are connected through. From the heat exchange unit 15, the exhaust gas after heat exchange is discharged toward the exhaust port 26 of the housing 25.

The damper 22 is for controlling the flow of the circulating gas (FC exhaust gas, external exhaust gas, or mixed gas thereof) in the exhaust path. For example, an impeller in which blades are attached around a rotating shaft, or a guillotine damper in which a valve body crosses at right angles to a flow path. The damper 22 is provided at a position in front of the exhaust port 26 on the downstream side of the heat exchanging unit 15 and the flow direction detecting unit 23 described later in the circulation gas flow path 27, and switches between opening and closing of the exhaust port 26. A valve can be used instead of the damper.

The flow direction detection unit 23 is a part that detects the flow direction of the flow gas flowing in the flow gas channel 27. For example, as shown in FIG. 3, the flow direction detection unit 23 is configured by a fan 28 provided in a circulation gas flow path 27 toward the exhaust port 26. Since the rotation direction of the fan 28 changes depending on the flow direction of the flow gas flowing in the flow gas flow path 27, the flow direction of the flow gas can be determined from the rotation direction of the fan 28. Then, the fan 28 outputs a signal indicating the rotation direction to the control unit 24.

Note that the flow direction detection unit 23 may be a flap 29 provided in a circulation gas flow path 27 toward the exhaust port 26, for example, as shown in FIG. The flap 29 is inclined toward the exhaust port 26 when the circulating gas is flowing toward the exhaust port 26, and is inclined toward the opposite side of the exhaust port 26 when the circulating gas is flowing backward. The inclination of the flap 29 may be determined by, for example, ON / OFF of a switch provided at the base of the flap 29, or laser detection or the like may be used. Alternatively, image detection by a camera or the like may be performed, and detection by a strain gauge may be performed in a state where the base of the flap 29 is fixed.

The control unit 24 is a part that performs diagnosis processing of the flow direction of the circulating gas in the discharge path. In FIG. 2, the control unit 24 is disposed in the housing 25, but may be configured such that the function of the control unit 24 is added to the control unit 11 of the fuel cell system 1. The diagnosis process by the control unit 24 is repeatedly performed at predetermined intervals, for example, during operation of the fuel cell system 1.

FIG. 5 is a flowchart showing a first mode of operation of the control unit 24. In the example of the figure, when the diagnostic process is started, a signal indicating the flow direction of the flowing gas is output from the flow direction detection unit 23 to the control unit 24. The control unit 24 that has received the signal determines whether or not a backflow of the flowing gas has been detected (step S101), and if the backflow of the flowing gas is not detected, step S101 is repeatedly executed. On the other hand, when the backflow of the circulating gas is detected in step S101, the damper 22 is closed (step S102). Then, after the damper 22 is closed, a stop process of the fuel cell system is executed (step S103).

In this embodiment, in the exhaust path for exhausting the FC exhaust gas, when the backflow of the circulating gas is detected by the flow direction detector 23, the damper 22 is closed and the system is stopped. Accordingly, it is possible to suppress the shortening of the service life of various catalysts or adsorbents, ion exchange resins, various auxiliary machines and the like mounted on the cell stack 5 and the fuel cell system 1 due to the backflow of the flowing gas to the fuel cell system 1 side. it can.

FIG. 6 is a flowchart showing a second mode of operation of the control unit 24. In the example of the figure, when the diagnostic process is started, a signal indicating the flow direction of the flowing gas is output from the flow direction detection unit 23 to the control unit 24. The control unit 24 that has received the signal determines whether or not a backflow of the flowing gas has been detected (step S201). If the backflow of the circulating gas is not detected, step S201 is repeatedly executed.

In step S201, when the backflow of the circulating gas is detected, the damper 22 is closed (step S202). After the damper 22 is closed, it is determined whether or not the backflow of the circulating gas is still detected (step S203). When the backflow of the circulating gas is detected, it is determined that there is an abnormality in the flow direction detection unit 23 or there is an abnormality in the damper 22 and the flowing gas flowing back is not completely closed, and the damper 22 is opened. After that (step S204), the fuel cell system 1 is stopped through a predetermined first stop step (step S205). Note that the first stop step here refers to the fuel cell system 1 that has been subjected to predetermined procedures such as stopping the supply of hydrogen-containing fuel, purging the gas filling the power generation unit, and cooling the cell stack 5. It means stopping.

If the backflow of the circulating gas is not detected in step S203, the damper 22 is kept closed (step S206). In this case, it is determined that external exhaust gas is inflow or inflow, and the fuel cell system 1 is stopped through a second stop process in which at least a part of the first stop process is omitted (step S207). .

Also in this embodiment, when the backflow of the circulating gas is detected by the flow direction detector 23 in the exhaust path for exhausting the FC exhaust gas, the damper 22 is closed and the system is stopped. Accordingly, it is possible to suppress the shortening of the service life of various catalysts or adsorbents, ion exchange resins, various auxiliary machines and the like mounted on the cell stack 5 and the fuel cell system 1 due to the backflow of the flowing gas to the fuel cell system 1 side. it can. Further, in this embodiment, after the first backflow gas flow detection is performed, the exhaust path abnormality is determined by the second backflow gas flow detection with the damper 22 closed as a provisional measure. Thereby, the stop process of the fuel cell system 1 can be selected according to the presence or absence of abnormality in the exhaust path.

Specifically, when an abnormality is detected in step S303, a failure in one or both of the flow direction detection unit 23 and the damper 22 is suspected. When only the flow direction detection unit 23 has failed, the backflow of the flowing gas does not occur, so the damper 22 is opened and the first stop process is executed. In addition, when only the damper 22 or both the flow direction detection unit 23 and the damper 22 are out of order, even if a closing signal is sent to the damper 22, the backflow of the circulating gas cannot be blocked. The stop process is executed. By stopping the operation of the fuel cell system 1 and securing an opportunity to repair the defective part at an early stage, it is possible to suppress the backflow of the flowing gas that may occur in the future. At this time, it is preferable that the first stopping step includes a purge process of gas filling the reactor inside the power generation unit 21 or various catalysts, an air cooling process of each part of the fuel cell system 1, and the like. Thereby, the backflow of the circulation gas can be reduced by the FC exhaust gas discharged from the fuel cell system 1 during the stop process.

FIG. 7 is a flowchart showing a third mode of operation of the control unit 24. In the example of the figure, when the diagnostic process is started, a signal indicating the flow direction of the flowing gas is output from the flow direction detection unit 23 to the control unit 24. The control unit 24 that has received the signal determines whether or not a backflow of the flow gas has been detected (step S301). If the backflow of the circulating gas is not detected, step S301 is repeatedly executed.

In step S301, when the backflow of the circulating gas is detected, the damper 22 is closed (step S302). After the damper 22 is closed, it is determined whether or not the backflow of the circulating gas is still detected (step S303). When the backflow of the circulating gas is detected, it is determined that there is an abnormality in the flow direction detection unit 23 or that the damper 22 is abnormal and the flowing gas flowing backward is not completely closed, and the damper 22 is opened. After that (step S304), the fuel cell system 1 is stopped through the first stop process (step S305).

On the other hand, when the backflow of the circulating gas is not detected in step S303, the damper 22 is once opened (step S306). Then, it is determined again whether the backflow of the flowing gas is detected (step S307). When the backflow of the circulating gas is detected, after closing the damper 22 (step S308), the fuel cell system 1 is stopped through the second stop process (step S309). If no backflow of the circulating gas is detected in step S307, it is determined that the backflow of the circulating gas has not occurred, and the operation of the fuel cell system 1 is continued (step S310).

Also in this embodiment, when the backflow of the circulating gas is detected by the flow direction detector 23 in the exhaust path for exhausting the FC exhaust gas, the damper 22 is closed and the system is stopped. Accordingly, it is possible to suppress the shortening of the service life of various catalysts or adsorbents, ion exchange resins, various auxiliary machines and the like mounted on the cell stack 5 and the fuel cell system 1 due to the backflow of the flowing gas to the fuel cell system 1 side. it can. Further, after the first flow gas backflow detection is performed, an abnormality in the exhaust path is determined by the second flow gas backflow detection with the damper 22 closed as a provisional measure. Thereby, the stop process of the fuel cell system 1 can be selected according to the presence or absence of abnormality in the exhaust path.

Furthermore, in this embodiment, after the abnormality of the exhaust path is determined by the second detection of the backflow of the circulating gas, the presence or absence of the backflow of the circulating gas is detected again with the damper 22 opened again. As a result, it is possible to avoid the stop process of the fuel cell system 1 every time an instantaneous backflow of the flowing gas occurs, and to reduce the frequency of stop of the fuel cell system 1. Therefore, the life of the fuel cell system 1 can be extended and stable power generation can be performed.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 5 ... Cell stack, 21 ... Electric power generation part, 22 ... Damper, 23 ... Flow direction detection part, 24 ... Control part, 26 ... Exhaust port, 27 ... Exhaust gas flow path, 28 ... Fan, 29 ... Flap .

Claims

A power generation unit including a cell stack that generates power using a hydrogen-containing gas;
An exhaust port for discharging exhaust gas discharged from at least the power generation unit to the outside of the system;
A flow direction detection unit that is disposed in an exhaust path between the power generation unit and the exhaust port and detects a flow direction of the flow gas in the exhaust path;
A damper that is arranged on the downstream side of the flow direction detection unit in the exhaust path, and switches the opening and closing of the exhaust port;
A fuel cell system comprising: a control unit that closes the damper and stops the system when a backflow of the circulation gas is detected by the flow direction detection unit.
The control unit determines whether the flow direction detection unit or the damper is abnormal when the flow direction detection unit detects a backflow of the flow gas, and determines the first stop step or the first step, 2. The fuel cell system according to claim 1, wherein one of the second stop processes in which at least a part of the stop process is omitted is executed.
3. The fuel cell system according to claim 2, wherein when the control unit determines that the flow direction detection unit or the damper is abnormal, the control unit opens the damper and executes the first stop step.
4. The fuel cell system according to claim 2, wherein, when it is determined that the flow direction detection unit and the damper are not abnormal, the control unit continuously closes the damper and executes the second stop step. 5.
When the control unit determines that the flow direction detection unit or the damper is abnormal, the control unit determines whether the flow direction detection unit detects a backflow of the flow gas in a state where the damper is once opened. 4. The fuel cell system according to claim 2, wherein when the determination is made and the backflow of the flow gas is detected, the damper is closed again and the second stop step is executed. 5.
6. The fuel cell system according to claim 5, wherein when the backflow of the circulation gas is not detected, the control unit continues the operation of the system by continuously opening the damper.
The flow direction detection unit includes a fan provided in the flow path of the fuel gas toward the exhaust port, and detects the flow direction of the combustion gas based on the rotation direction of the fan. The fuel cell system according to claim 1.
The flow direction detection unit has a flap provided in the flow path of the fuel gas toward the exhaust port, and detects the flow direction of the combustion gas based on the inclination of the flap. The fuel cell system according to any one of claims.