JP4917756B2 - Fuel cell system startup method, reformer, and fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system startup method, a reformer, and a fuel cell system, and more particularly to a method for safely starting a fuel cell system including a reformer in which a raw material gas is sealed when stopped, and a raw material gas sealed when stopped. In particular, the present invention relates to a reforming apparatus that can be safely started, and a fuel cell system including such a reforming apparatus.

  With the recent increase in awareness of global environmental conservation, fuel cell systems that generate power with fuel cells that contribute to the suppression of carbon dioxide emissions are attracting attention. The fuel cell system includes a fuel cell stack that introduces hydrogen and oxygen and generates electricity through these electrochemical reactions, and a reformer that reforms the hydrocarbon raw material gas to generate a reformed gas. Is known. The reformed gas contains a large amount of hydrogen and is supplied to the fuel cell stack.

The reformer has a reforming section for reforming the raw material gas and a carbon monoxide reduction section for reducing the carbon monoxide concentration from the gas reformed in the reforming section. Since the quality reaction is an endothermic reaction, it generally has a combustion section that generates the heat of reforming necessary for the reaction. In addition, the raw material gas is generally introduced into the reforming section and is also introduced into the combustion section as a combustion fuel for generating reforming heat. The reforming section and the carbon monoxide reduction section are each filled with a catalyst that promotes the reaction. When the reformer is stopped, it is necessary to prevent oxidation of the catalyst in the reforming section and the carbon monoxide reduction section. In order to prevent this catalytic oxidation, a technique is known in which raw material gas is enclosed in a reformer and the pressure in the reformer is maintained higher than the external pressure to prevent air from entering from the outside (for example, a patent) Reference 1). By enclosing the source gas, there is an advantage that management and replenishment are easier than in the case of enclosing an inert gas such as nitrogen.
JP 2003-288930 A

  In order to start the fuel cell system in a stopped state in the above-described state, particularly the reformer, it is necessary to purge the enclosed raw material gas. It is sufficient if the enclosed raw material gas can be guided to the combustion section and used as a fuel for combustion. However, if it is sent to the combustion section under high pressure, it is difficult to adjust the air-fuel ratio, causing misfire or incomplete combustion. It will be. Therefore, it is realistic to discharge the enclosed source gas outside the fuel cell system until the pressure in the reformer is reduced to a pressure at which the amount of source gas having an air-fuel ratio suitable for combustion can be supplied to the combustion section. It is.

  However, some raw material gases have an explosion limit, and when discharging such a raw material gas, it is necessary to dilute and discharge it below the lower limit of the explosion limit. However, it is not realistic to provide a large-capacity blower for diluting the discharged source gas.

  In view of the above-described problems, the present invention provides a fuel cell system for safely starting a fuel cell system by discharging a source gas for lowering the pressure in a reformer in which the source gas is sealed without causing an explosion. Provided are a start-up method, a reformer that can be safely started by discharging a raw material gas for lowering the pressure in the reformer without causing an explosion, and a fuel cell system including such a reformer The purpose is to do.

  In order to achieve the above object, a fuel cell system start-up method according to the invention described in claim 1 is a reformed gas rich in hydrogen by reforming a raw material gas m as shown in FIGS. 1 and 2, for example. a method of starting a fuel cell system 1 having a reformer 2 that generates g, and a fuel cell stack 3 that generates power by introducing an oxidant gas k1 containing oxygen and the reformed gas g; A step (S4) of discharging the raw material gas m enclosed in the quality device 2 to the outside of the enclosed portion of the reformer 2, and air k2 to the raw material gas m discharged outside the enclosed portion of the reformer 2; a step (S5) of mixing k3; and a step (S6) of discharging the raw material gas m mixed with the air k2, k3 to the outside of the fuel cell system 1; air discharged to the outside of the fuel cell system 1 The concentration of the raw material gas m mixed with k2 and k3 is not lower than the explosion limit. And it is configured such that.

  With this configuration, since the concentration of the raw material gas mixed with air discharged outside the fuel cell system is less than the lower limit of the explosion limit, the pressure in the reformer in which the raw material gas is sealed is reduced. Source gas can be discharged safely without causing an explosion. Note that the raw material gas is sealed in the reformer, for example, when the reformer is stopped, the catalyst used for the reaction for reforming the raw material gas into the reformed gas, the reforming device, or the like. This is to prevent oxidation of the catalyst provided for reducing the carbon monoxide concentration in the gas, so that the raw material gas only needs to be sealed in at least a portion where these catalysts are installed. In this sense, the “reformer” in which the raw material gas is enclosed in the present specification typically means a portion provided with these catalysts and a gas flow path communicating with this portion when the raw material gas is sealed. Say.

Further, method of starting a fuel cell system according to the first aspect of the present invention, for example, as shown in FIGS. 1 and 2, the step of sensing the pressure of the raw material gas m is sealed reforming apparatus 2 ( S7) is provided; the flow rate of the raw material gas m discharged outside the sealed portion of the reformer 2 is controlled based on the detected pressure.

  With this configuration, the flow rate of the raw material gas discharged outside the reformer is controlled based on the detected pressure, so that the amount of the raw material gas discharged outside the fuel cell system can be calculated. The concentration of the raw material gas discharged out of the fuel cell system can be surely made lower than the lower limit of the explosion limit.

Further, method of starting a fuel cell system according to the invention of claim 2, for example, as shown in FIGS. 1 and 2, in the method of starting the fuel cell system 1 according to claim 1, reforming a raw material gas m The step (S4) of discharging out of the sealed portion of the quality device 2 discharges the raw material gas m intermittently and controls the interval at which the raw material gas m is discharged, whereby the raw material gas m mixed with the air k2, k3 is controlled. The concentration of is less than the lower limit of the explosion limit.

  If comprised in this way, since source gas is discharged | emitted intermittently and the space | interval which discharge | releases this source gas is controlled, it becomes the same as controlling the discharge | emission amount per unit time. Therefore, for example, the flow rate per unit time can be adjusted without fine adjustment of the opening degree of the control valve or the like. Further, it is possible to shorten the interval for discharging the raw material gas as the pressure in the reformer decreases, and it is possible to shorten the time required to reduce the pressure in the reformer to a predetermined pressure. .

Further, method of starting a fuel cell system according to the invention of claim 3, for example, as shown in FIGS. 1 and 2, in the method of starting the fuel cell system 1 according to claim 1, reforming a raw material gas m The raw material mixed with the air k2 and k3 by controlling the time during which the step (S4) of discharging outside the sealed portion of the quality device 2 discharges the raw material gas m intermittently and discharges the raw material gas m. The concentration of the gas m is configured to be less than the lower limit of the explosion limit.

  If comprised in this way, since source gas is discharged | emitted intermittently and the time which has discharged | emitted source gas is controlled, it becomes the same as controlling the discharge | emission amount per unit time. Therefore, for example, the flow rate per unit time can be adjusted without fine adjustment of the opening degree of the control valve or the like. In addition, it is possible to lengthen the time during which the source gas is discharged as the pressure in the reformer decreases, and shorten the time required to reduce the pressure in the reformer to a predetermined pressure. Can do.

In order to achieve the above object, a reformer according to a fourth aspect of the present invention is a reformer that reforms a raw material gas m to produce a reformed gas g rich in hydrogen as shown in FIG. The apparatus 2 includes: a gas blocking unit 53s for enclosing the source gas m therein; and a discharge passage 53 for discharging the source gas m enclosed therein to the outside through the gas blocking unit 53s. Here, “inside” typically corresponds to the above-described enclosure portion, a portion in the reformer in which a catalyst to be subjected to oxidation prevention is provided, and a gas communicating with this portion when the raw material gas is enclosed. The flow path.

  If comprised in this way, since the discharge flow path which discharges | emits the raw material gas enclosed inside is provided outside, it reforms the raw material gas enclosed in the reformer so that the inside of a reformer may fall to predetermined pressure It can be discharged out of the device.

The reformer according to the invention of claim 4, for example, as shown in FIG. 1, discharge to the overhead stream passage 53 and the air introduction passage 58A, 54 for introducing air k2, k3; raw material gas m encapsulation A pressure detector 42 for detecting the pressure in the reformer 2, and the concentration of the raw material gas m flowing through the discharge passage 53 is mixed with the air k2 and k3. A control device 4 that opens the gas blocking means 53s based on the pressure detected by the pressure detector 42 is provided so as to be less than the lower limit of the explosion limit.

  If comprised in this way, since the control apparatus which opens | releases a gas interruption | blocking means is provided so that the density | concentration of the raw material gas discharged | emitted from a discharge flow path may be less than the lower limit of an explosion limit, in the reformer in which the raw material gas was enclosed The discharge of the raw material gas for lowering the pressure can be performed safely without causing an explosion.

Further, the fuel cell system according to the invention described in claim 5 includes, for example, as shown in FIG. 1, the reformer 2 according to claim 4 ; the reformed gas g and oxygen generated by the reformer 2. A fuel cell stack 3 that generates electricity by introducing an oxidant gas k1 containing the.

  If comprised in this way, the fuel cell system provided with the reformer which can discharge | emit the raw material gas enclosed inside so that the inside of a reformer may fall to a predetermined | prescribed pressure can be supplied.

  According to the present invention, the raw material gas sealed in the reformer can be discharged out of the reformer so that the inside of the reformer is reduced to a predetermined pressure. When the concentration of the raw material gas mixed with air discharged outside the fuel cell system is less than the lower limit of the explosion limit, the raw material gas for lowering the pressure in the reformer in which the raw material gas is sealed is used. The discharge can be performed safely without causing an explosion.

Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same or similar code | symbol is attached | subjected to the mutually same or equivalent apparatus or member, and the overlapping description is abbreviate | omitted. In FIG. 1, a broken line represents a control signal.
FIG. 1 is a schematic block diagram illustrating a fuel cell system according to an embodiment of the present invention. The fuel cell system 1 includes a reformer 2 and a fuel cell stack 3.

  First, the structure of the reformer 2 and the flow path around it will be described. The reformer 2 is an apparatus that introduces a hydrocarbon-based source gas m and process water w and reforms the source gas m to generate a reformed gas g rich in hydrogen. The reformed gas g rich in hydrogen is a gas supplied to the fuel cell stack 3 containing hydrogen in an amount of 40% by volume or more, typically about 70 to 80% by volume. The hydrogen concentration in the reformed gas g may be 80% by volume or higher, that is, any concentration that allows power generation by an electrochemical reaction with the oxidant gas k1 when supplied to the fuel cell stack 3. The reformer 2 as an apparatus includes a reforming unit 21, a shift conversion unit 22, a selective oxidation unit 23, a steam generation unit 24, and a combustion unit 25. Here, each of these parts constituting the reformer 2 will be described.

  The reforming unit 21 is configured to introduce the raw material gas m and the reforming steam v and reform the raw material gas m into the mixed reformed gas n1 by a steam reforming reaction. The mixed reformed gas n1 contains hydrogen, carbon monoxide, and carbon dioxide. The mixed reformed gas n1 typically contains about 40 to 70% by volume of hydrogen and about 8 to 15% by volume of carbon monoxide. The reforming unit 21 is filled with a reforming catalyst, and is configured to promote a steam reforming reaction. Typically, a nickel-based reforming catalyst or a ruthenium-based reforming catalyst is used as the reforming catalyst. The reformer 21 and the shifter 22 are connected so that the mixed reformed gas n1 generated in the reformer 21 is sent to the shifter 22. In the following description, “connected” includes the case of being connected via a flow path or the like. On the other hand, a raw material gas supply pipe 51 for introducing the raw material gas m is connected to the reforming unit 21.

  The shift converter 22 introduces the mixed reformed gas n1 from the reforming section 21, causes the carbon monoxide contained in the mixed reformed gas n1 to undergo a shift reaction with the water contained in the mixed reformed gas n1, and produces carbon dioxide. And hydrogen. The metamorphic gas n2 typically contains about 40-80% by volume of hydrogen and about 70-80% by volume of hydrogen, and about 1000-10,000 volume ppm of carbon monoxide. The shift unit 22 is filled with a shift catalyst and is configured to promote the shift reaction. As the shift catalyst, typically, an iron-chromium shift catalyst, a copper-zinc shift catalyst, a platinum shift catalyst, or the like is used. The shift unit 22 and the selective oxidation unit 23 are connected so that the shift gas n2 is sent to the selective oxidation unit 23 in the shift unit 22.

  The selective oxidation unit 23 introduces the conversion gas n2 from the conversion unit 22, introduces the selective oxidation air k4 from outside the system, and performs the selective oxidation reaction between the carbon monoxide remaining in the conversion gas n2 and the selective oxidation air k4. The carbon monoxide concentration is further reduced from the modified gas n2, and the reformed gas g rich in hydrogen is generated. As described above, the reformed gas g is a gas containing hydrogen by 40% by volume or more, typically about 70-80% by volume. The carbon monoxide concentration in the reformed gas g is about 10 ppm by volume or less, and more preferably about 1 ppm by volume. The selective oxidation unit 23 is filled with a selective oxidation catalyst. Typically, a platinum-based selective oxidation catalyst, a ruthenium-based selective oxidation catalyst, a platinum-ruthenium-based selective oxidation catalyst, or the like is used as the selective oxidation catalyst. The selective oxidation unit 23 is connected to a selective oxidation air supply pipe 56 for introducing the selective oxidation air k4 and a reformed gas supply line 61 for sending the reformed gas g to the fuel cell stack 3. The metamorphic unit 22 and the selective oxidation unit 23 are collectively referred to as a “carbon monoxide reduction unit”.

  The steam generation unit 24 is configured to introduce process water w and evaporate it with heat to generate steam. As heat for evaporating the process water w, it is preferable to use heat generated during the shift reaction in the shift unit 22 or heat generated during the selective oxidation reaction in the selective oxidation unit 23. A heating means such as an electric heater may be provided to use heat generated therefrom. A process water supply pipe 55 for introducing the process water w from outside the fuel cell system 1 is connected to the water vapor generating unit 24. In addition, a reforming steam supply line 24 a for sending the reforming steam v generated by the steam generating section 24 to the reforming section 21 is connected to the steam generating section 24. When the reforming steam supply line 24a on the reforming section 21 side is connected to the source gas supply pipe 51 in the immediate vicinity of the reforming section 21, the reforming steam supply line 24a is modified in a state where the source gas m and the reforming steam v are mixed. It is preferably introduced into the mass part 21. However, the reforming steam supply line 24 a may be directly connected to the reforming unit 21.

  The combustion unit 25 is configured to introduce part of the raw material gas m as fuel and the combustion air k <b> 3, burn the raw material gas m, and generate reformed heat to be supplied to the reforming unit 21. . Since the reforming reaction in the reforming unit 21 is an endothermic reaction, the reforming unit 21 requires reforming heat. The combustion unit 25 has a burner for burning the raw material gas m. The combustion unit 25 is also configured to be able to introduce and burn the anode off gas p discharged from the fuel cell stack 3. The anode off gas p contains hydrogen that has not been used for the electrochemical reaction in the fuel cell stack 3. Typically, the combustion unit 25 introduces the raw material gas m when the fuel cell power generation system 1 is started up, burns this to generate reforming heat, and the fuel cell stack 3 is operated to remove the fuel cell stack 3 from the fuel cell stack 3. When the anode off gas p is discharged, the anode off gas p is introduced and combusted to generate reforming heat. The combustion exhaust gas generated after combustion in the combustion unit 25 is discharged from the combustion unit 25 through the combustion exhaust gas discharge pipe 54. A fuel supply pipe 52 for introducing the raw material gas m, an anode offgas line 62 for introducing the anode offgas p, and a combustion air supply pipe 57 for introducing the combustion air k3 are connected to the combustion section 25. Yes. In addition, a combustion exhaust gas discharge pipe 54 for discharging combustion exhaust gas is connected to the combustion unit 25.

  As the raw material gas m introduced into the reforming unit 21, a gaseous hydrocarbon fuel such as city gas, LPG, digestion gas, etc. is typically used. However, liquid hydrocarbon fuels such as methanol, GTL (Gas to Liquid) and kerosene may be used. When a liquid hydrocarbon fuel is used as the raw material gas m, it is preferable to vaporize it before introducing it into the reforming section 21. Therefore, the “raw gas” includes a raw material that was originally liquid. The source gas m introduced into the reforming unit 21 and the fuel introduced into the combustion unit 25 may be the same type or different types.

  The source gas supply pipe 51 is a flow path that guides the source gas m to the reforming unit 21. In the raw material gas supply pipe 51, a raw material gas blower 51b is provided on the upstream side, and a mass flow controller 51c having a function of a flow meter and a function of a flow control valve is provided on the downstream side. A signal cable is laid between the mass flow controller 51 c and the control device 4. The mass flow controller 51c can transmit the flow rate of the raw material gas m passing through the mass flow controller 51c as the signal i1 to the control device 4, and can receive the signal i2 from the control device 4 and adjust the valve opening degree. It is configured.

  The fuel supply pipe 52 branches off from the source gas supply pipe 51 between the source gas blower 51b and the mass flow controller 51c. The fuel supply pipe 52 is connected to the combustion unit 25, and is thereby configured to supply the raw material gas m as fuel to the combustion unit 25. A mass flow controller 52 c is provided in the fuel supply pipe 52, and a signal cable is laid between the mass flow controller 52 c and the control device 4. The mass flow controller 52c can transmit the flow rate of the raw material gas m passing through the inside thereof to the control device 4 as a signal i3, and can receive the signal i4 from the control device 4 and adjust the valve opening degree. It is configured.

  The sealed gas discharge pipe 53 as a discharge flow path branches from the source gas supply pipe 51 on the downstream side of the mass flow controller 51c. The sealed gas discharge pipe 53 is a flow path for discharging the gas sealed to prevent oxidation of the catalyst when the reformer 2 is stopped. A combustion exhaust gas discharge pipe 54 is connected to the sealed gas discharge pipe 53. The sealed gas discharge pipe 53 is provided with a sealed electromagnetic valve 53s as a gas blocking means capable of closing the flow path. A signal cable is laid between the sealed electromagnetic valve 53 s and the control device 4. The enclosing electromagnetic valve 53s is configured to receive an open / close signal i5 from the control device 4 and to open / close the valve.

  The combustion exhaust gas discharge pipe 54 is a flow path for discharging the combustion exhaust gas generated after the fuel is burned to generate reforming heat to the outside of the fuel cell system 1. The combustion exhaust gas discharge pipe 54 can also discharge the air sent by the combustion air blower 57b to the outside of the fuel cell system 1 through the combustion unit 25 where combustion is not performed. That is, the combustion exhaust gas discharge pipe 54 also serves as an air introduction path. The combustion exhaust gas discharge pipe 54 is connected to the sealed gas discharge pipe 53. A dilution air supply pipe 58 </ b> A is connected to the combustion exhaust gas discharge pipe 54 before joining the sealed gas discharge pipe 53. In addition, the heat exchanger 41 may be provided in the combustion exhaust gas discharge pipe 54 and the fuel supply pipe 52 so as to exchange heat between the combustion exhaust gas flowing in the combustion exhaust gas discharge pipe 54 and the fuel m flowing in the fuel supply pipe 52. .

  The dilution air supply pipe 58A is branched from the air supply pipe 58 via a three-way valve 58c. The dilution air supply pipe 58A is an air introduction path that guides air for diluting the raw material gas m discharged from the sealed gas discharge pipe 53 to a concentration below the explosion limit to the combustion exhaust gas discharge pipe. In addition to the dilution air supply pipe 58A, an oxidant gas line 64 is branched from the air supply pipe 58 via a three-way valve 58c. That is, the air supply pipe 58 branches into the dilution air supply pipe 58A and the oxidant gas line 64 via the three-way valve 58c. A signal cable is laid between the three-way valve 58 c and the control device 4. The three-way valve 58c receives the signal i6 from the control device 4, and can switch the valve so that the air flowing through the air supply pipe 58 flows into either the dilution air supply pipe 58A or the oxidant gas line 64. It is configured as follows.

  The process water supply pipe 55 is a flow path that guides the process water w to the water vapor generating unit 24. The process water supply pipe 55 is provided with a process water pump 55p that pumps the process water w on the upstream side, and a process water electromagnetic valve 55s that shuts off the supply of the process water w to the water vapor generating unit 24 on the downstream side. Is provided. A signal cable is laid between the process water electromagnetic valve 55 s and the control device 4. The process water electromagnetic valve 55s is configured to receive an open / close signal i7 from the control device 4 and to open / close the valve.

  The selective oxidation air supply pipe 56 is a flow path that guides the selective oxidation air k <b> 4 to the selective oxidation unit 23. The selective oxidation air supply pipe 56 is provided with a selective oxidation air blower 56b on the upstream side and a mass flow controller 56c on the downstream side. A signal cable is laid between the mass flow controller 56 c and the control device 4. The mass flow controller 56c can transmit the flow rate of the selectively oxidized air k4 passing through the inside to the control device 4 as the signal i8, and can receive the signal i9 from the control device 4 and adjust the valve opening degree. It is configured.

  The combustion air supply pipe 57 is a flow path that guides the combustion air k <b> 3 for burning the fuel m to the combustion unit 25. The combustion air supply pipe 57 is provided with a flow rate detector 57e on the upstream side and a combustion air blower 57b on the downstream side. A signal cable is laid between the flow rate detector 57e and the control device 4. The flow rate detector 57e is configured to be able to transmit the flow rate of the combustion air k3 flowing through the combustion air supply pipe 57 to the control device 4 as a signal i10. The combustion air blower 57b is configured to be able to send the amount of air necessary for combustion in the combustion section 25. When the fuel cell stack 3 is a 1 kW class solid polymer fuel cell, about 30 L / min. It is common to have a blast volume of. The combustion air blower 57b is configured to be able to adjust the amount of air pumped to the combustion unit 25 by changing the rotation speed based on the signal i11 from the control device 4. Typically, the rotational speed control of the combustion air blower 57b is performed by sending a rotational speed instruction signal from the control device 4 to a power board (not shown) and adjusting the power sent from the power board to the combustion air blower 57b. However, in this embodiment, for convenience, the signal i11 is transmitted from the control device 4 to the combustion air blower 57b.

  The air supply pipe 58 allows air introduced from outside the fuel cell system 1 to flow through the dilution air supply pipe 58 </ b> A or the oxidant gas line 64. The air supply pipe 58 is provided with a flow rate detector 58e on the upstream side and an oxidant gas blower 58b on the downstream side. A signal cable is laid between the flow rate detector 58e and the control device 4. The flow rate detector 58e is configured to be able to transmit the flow rate of the air k flowing through the air supply pipe 58 to the control device 4 as a signal i12. The oxidant gas blower 58b is configured to be able to adjust the amount of air flowing through the air supply pipe 58 by changing the rotational speed based on the signal i13 from the control device 4. Typically, the rotational speed control of the oxidant gas blower 58b is performed by adjusting the electric power sent from the power panel to the oxidant gas blower 58b by sending a rotational speed instruction signal from the control device 4 to the power panel (not shown). In this embodiment, for convenience, the signal i13 is transmitted from the control device 4 to the oxidant gas blower 58b.

Next, the fuel cell stack 3 and the control device 4 will be described.
The fuel cell stack 3 introduces the reformed gas g and the oxidant gas k1, and generates water and heat by generating an electric power by an electrochemical reaction between hydrogen in the reformed gas g and oxygen in the oxidant gas k1. Is configured to do. The fuel cell stack 3 is typically a polymer electrolyte fuel cell. The fuel cell stack 3 includes a fuel electrode 31 for introducing the reformed gas g, an air electrode 32 for introducing the oxidant gas k1, and a cooling unit 33 for removing heat generated by the electrochemical reaction. Yes.

  The fuel electrode 31 is connected to the selective oxidation unit 23 of the reformer 2 via the reformed gas supply line 61, and is configured so that the reformed gas g can be introduced into the fuel electrode 31. The reformed gas supply line 61 is provided with a reformed gas solenoid valve 61s that can close the flow path. A signal cable is laid between the reformed gas solenoid valve 61s and the control device 4. The reformed gas electromagnetic valve 61s is configured to receive an open / close signal i15 from the control device 4 and to open / close the valve. A pressure detector 42 is provided in the reformed gas supply line 61 on the upstream side of the reformed gas electromagnetic valve 61s. A signal cable is laid between the pressure detector 42 and the control device 4 so that the pressure detected by the pressure detector 42 can be transmitted to the control device 4 as a signal i14. Further, the fuel electrode 31 is connected to the combustion unit 25 via the anode offgas line 62, and the anode offgas p containing the reformed gas g that has not been used for the electrochemical reaction can be discharged from the fuel electrode 31. It is configured to be able to. The anode off gas line 62 is provided with an anode off gas electromagnetic valve 62s that can close the flow path. A signal cable is laid between the anode off-gas electromagnetic valve 62 s and the control device 4. The anode off-gas electromagnetic valve 62s is configured to receive an open / close signal i16 from the control device 4 and to open / close the valve. Further, the reformed gas supply line 61 on the upstream side of the reformed gas electromagnetic valve 61 s and the anode offgas line 62 on the downstream side of the anode offgas electromagnetic valve 62 s are connected via a bypass line 63. The bypass line 63 is provided with a bypass electromagnetic valve 63s that can close the flow path. A signal cable is laid between the bypass electromagnetic valve 63 s and the control device 4. The bypass electromagnetic valve 63s is configured to receive an open / close signal i17 from the control device 4 and to open / close the valve.

Connected to the air electrode 32 is an oxidant gas line 64 for introducing the oxidant gas k1 branched by the three-way valve 58c. The cathode 32 is connected to a cathode offgas line 65 for discharging a cathode offgas q containing an oxidant gas k1 that has not been used for the electrochemical reaction.
A cooling water line 66 through which the cooling water r flows is connected to the cooling unit 33, and a circulation channel through which the cooling water r circulates is formed.
The DC power generated by the fuel cell stack 3 is transmitted to the power conditioner 43 and converted into AC power, and then transmitted toward the power demand.

  The control device 4 is configured to be able to control the start / stop and operating state of the fuel cell system 1 including the reformer 2 and the fuel cell stack 3. Specifically, the flow rate signals i1, i3, i8, i10, i12 and the pressure signal i14 are received to understand the operating state of the fuel cell system 1, and control each valve and blower to achieve the intended operating state. Signals i2, i4 to i7, i9, i11, i13, i15 to i17 can be transmitted to each valve and blower. In particular, the control of the enclosed electromagnetic valve 53s will be described in detail later.

  Next, with reference to FIG. 2, a method for starting the fuel cell system 1 including the reformer 2 according to the embodiment of the present invention will be described. Note that FIG. 1 is referred to as appropriate for the reference numerals of the apparatus. When the fuel cell system 1 is stopped, the reformed gas g is purged, and the raw material gas m is sealed in the reformer 2 (S1). By enclosing the raw material gas m, oxidation of the reforming catalyst, the shift catalyst, and the selective oxidation catalyst is prevented. The sealing pressure is typically 120 to 200 kPa · abs. During the operation of the reformer 2, the temperature of the reforming unit 21 is about 600 ° C., but when the operation is stopped, the temperature gradually decreases and the water vapor inside condenses, and the pressure in the reformer 2 decreases. come. If the internal pressure of the reformer 2 becomes lower than the outside, air may be mixed in. Therefore, the internal pressure is maintained at atmospheric pressure or higher by sealing the raw material gas m while the reformer 2 is stopped. In addition, by enclosing the raw material gas m instead of an inert gas such as nitrogen, an inert gas cylinder, separate piping, and the like are not required, and the management of the enclosed gas is facilitated.

  The material gas m is sealed in the reformer 2 by closing the mass flow controllers 51c and 56c, the sealed solenoid valve 53s, the process water solenoid valve 55s, the reformed gas solenoid valve 61s, and the bypass solenoid valve 63s. That is, while the reforming apparatus 2 is stopped, the mass flow controllers 51c and 56c, the enclosed electromagnetic valve 53s, the process water electromagnetic valve 55s, the reformed gas electromagnetic valve 61s, and the bypass electromagnetic valve 63s are closed. In the present embodiment, the “reforming apparatus” in which the raw material gas m is sealed includes the reforming unit 21, the transformation unit 22, the selective oxidation unit 23, and the raw material gas supply pipe to the mass flow controller 51c communicating with them. 51, sealed gas discharge pipe 53 to sealed electromagnetic valve 53s, process water supply pipe 55 to process water solenoid valve 55s, selective oxidized air supply pipe 56 to mass flow controller 56c, reformed gas to reformed gas solenoid valve 61s The bypass pipe 63 extends to the line 61 and the bypass solenoid valve 63s. In other words, the concept of the reformer includes the range up to the enclosed pressure when the raw material gas m is enclosed when the operation is stopped.

  In a state where the fuel cell system 1 is stopped, the control device 4 determines whether or not there is an activation command for the fuel cell system 1 from the outside (S2). If there is no start command, the process of enclosing the raw material gas m in the reformer 2 is maintained (S1). When the activation command is issued, the control device 4 transmits a signal i11 to the combustion air blower 57b and a signal i13 to the oxidant gas blower 58b to activate each blower, and causes the air to flow toward the dilution air supply pipe 58A. The signal i6 is transmitted to the three-way valve 58c to operate the valve (S3). In the following description, when a device or valve in which a signal cable is laid between the control device 4 and the valve operates, it operates in response to a signal from the control device 4 even if not specifically described. . When the combustion air blower 57b is activated, the air flowing through the combustion air supply pipe 57 flows through the combustion unit 25 and the combustion exhaust gas discharge pipe 54. At this time, the fuel gas m is not introduced into the combustion section 25 and the burner is not ignited in the combustion section 25, so that no combustion exhaust gas is generated. That is, the exhaust from the combustion section 25 is almost air, although the combustion exhaust gas remaining in the combustion section 25 may be slightly contained. On the other hand, when the oxidant gas blower 58b is activated with the three-way valve 58c communicating with the air supply pipe 58 and the dilution air supply pipe 58A, air flows through the air supply pipe 58 and the dilution air supply pipe 58A, and the combustion exhaust gas discharge pipe Join 54.

  With the air flowing in the combustion exhaust gas discharge pipe 54, the sealed electromagnetic valve 53s is opened to discharge the raw material gas m enclosed in the reformer 2 to the outside of the reformer 2 (S4). The raw material gas m discharged out of the reformer 2 flows through the sealed gas discharge pipe 53 and is mixed with the air flowing through the combustion exhaust gas discharge pipe 54 (S5). At this time, the sealing pressure of the raw material gas m sealed in the reformer 2 is higher than the static pressure in the sealed gas discharge pipe 53 on the secondary side of the sealed electromagnetic valve 53s where the raw material gas m merges with air. The raw material gas m is discharged out of the reformer 2. The raw material gas m mixed with air in the sealed gas discharge pipe 53 is discharged out of the fuel cell system 1 (S6).

Here, the means for discharging the raw material gas m from the reformer 2, in other words, the control of the enclosed electromagnetic valve 53s will be described in more detail.
The reason why the material gas m enclosed in the reformer 2 is discharged to the outside of the reformer 2 by opening the sealed electromagnetic valve 53s is because the enclosed pressure is high, and is sent as it is to the combustion unit 25 as fuel for combustion. It is because it is not suitable for. Since the raw material gas m and the combustion fuel are typically the same (see paragraph 0028), the raw material gas m sealed in the reformer 2 is opened by opening the bypass solenoid valve 63s. However, if the raw material gas m is sent to the combustion section 25 with the enclosed pressure in the present embodiment, the amount of fuel will be excessive and the ignition will be ignited. The problem of failure occurs. Moreover, even if the material gas m is sent to the combustion section 25 at an enclosed pressure after ignition is performed once under appropriate combustion conditions, there is a problem that the fuel becomes excessive and misfires occur. Such a phenomenon must be avoided because it induces carbon monoxide emissions due to incomplete combustion. Therefore, at the beginning of the start of the fuel cell system 1, an enclosed pressure (hereinafter referred to as “predetermined pressure”) that provides an appropriate air-fuel ratio when the raw material gas m enclosed in the reformer 2 is introduced into the combustion unit 25. It is realistic to discharge the raw material gas m in the reformer 2 to the outside of the fuel cell system 1 until it becomes “pressure”.

  However, the raw material gas m generally has an explosion limit. Hereinafter, in the present embodiment, description will be made assuming that the source gas m is methane. When the raw material gas m is methane, the explosion limit is 5.3 to 14% by volume. Therefore, when the raw material gas m sealed in the reformer 2 is discharged out of the fuel cell system 1, it is preferable that the concentration of the raw material gas m is at least less than the explosion limit. It is more preferable to dilute with air so that the concentration of m is about 2% by volume.

The flow rate Q (L / min) of the raw material gas m passing therethrough by opening the enclosing electromagnetic valve 53s is α, the coefficient inherent to the enclosing electromagnetic valve 53s used, S (mm ² ), the primary sectional area of the valve. When the pressure on the side is P ₁ (kPa · abs) and the pressure on the secondary side is P ₂ (kPa · abs), it is expressed by the following equation (1).
Q = α × S × 1.35 × {P ₂ (P ₁ −P ₂ )} ^1/2 (1)
The numerical value “1.35” in the equation (1) is a correction coefficient associated with the fact that the gas flowing through the valve is methane. As apparent from the equation (1), when the sealed electromagnetic valve 53s is opened for t seconds, the maximum source gas m of tQ / 60 (L) flows.

  At this time, the enclosed electromagnetic valve 53s has a small effective cross-sectional area (the value of S in the above equation (1)), that is, the flow rate of the raw material gas m passing through the enclosed electromagnetic valve 53s and the air flowing through the combustion exhaust gas discharge pipe 54 An encapsulated electromagnetic valve 53s having an effective cross-sectional area such that the concentration of the raw material gas m becomes less than the explosion limit when mixed can be employed. However, when the enclosed electromagnetic valve 53s having a small effective cross-sectional area is used, the raw material gas m discharged due to a decrease in the differential pressure between the primary side and the secondary side of the enclosed electromagnetic valve 53s as the pressure in the reformer 2 decreases. Therefore, it takes a long time to reduce the pressure in the reformer 2 to a predetermined pressure. Therefore, the sealed electromagnetic valve 53s having an effective cross-sectional area that does not extremely decrease the flow rate even when the differential pressure is reduced is adopted, and the fuel cell system 1 is discharged by controlling the opening and closing of the sealed electromagnetic valve 53s. The concentration of the raw material gas m is preferably set to be less than the explosion limit.

  In the case of controlling the opening / closing of the valve using the enclosed electromagnetic valve 53s having an effective cross-sectional area that does not extremely decrease the flow rate even if the differential pressure decreases, the time for opening the enclosed electromagnetic valve 53s is the exhaust gas emission time. It is a time during which the flow rate can be discharged so that the concentration of the raw material gas m (methane gas) is at least less than the explosion limit and more preferably about 2% by volume with respect to the flow rate of the air flowing through the pipe 54. The opening / closing operation of the enclosing electromagnetic valve 53s performed in such an opening time is maintained at a concentration of at least less than the explosion limit, more preferably about 2% by volume when the source gas m is discharged out of the fuel cell system 1. It may be performed at predetermined intervals (in other words, intermittently) that can be performed. Alternatively, based on the opening / closing operation of the enclosed electromagnetic valve 53s, the discharge flow rate of the raw material gas m calculated from the differential pressure before and after the enclosed electromagnetic valve 53s grasped from the pressure detected by the pressure detector 42 is taken into account. The interval in which the valve 53s is opened or the opening time of the enclosed electromagnetic valve 53s may be adjusted so that the pressure in the reformer 2 decreases to a predetermined pressure more quickly. Needless to say, even if the opening interval or opening time of the enclosed electromagnetic valve 53s is adjusted, the concentration of the raw material gas m discharged from the fuel cell system 1 is kept at least below the explosion limit. At this time, the opening interval or opening time t of the encapsulated electromagnetic valve 53s is such that the source gas m and air are discharged so that the concentration becomes less than the explosion limit when the source gas m is discharged out of the fuel cell system 1. From the viewpoint of being sufficiently mixed in the pipe 53, the effective cross-sectional area of the sealed electromagnetic valve 53s and the capacity of the sealed gas discharge pipe 53 may be determined. That is, when the opening interval of the enclosed electromagnetic valve 53s is too short or the opening time t is too long with respect to the capacity of the enclosed gas discharge pipe 53, the source gas m has a concentration below the explosion limit in the enclosed gas discharge pipe 53. The opening interval or opening time t of the enclosed electromagnetic valve 53s may be determined so as to avoid the inconvenience of being discharged out of the fuel cell system 1 without being diluted. Note that the control of the opening interval and the opening time t of the enclosed electromagnetic valve 53s may be performed simultaneously.

  The opening / closing operation of the enclosing electromagnetic valve 53s is continued until the pressure in the reformer 2 reaches a predetermined pressure. The control device 4 receives the signal i14 from the pressure detector 42, and determines whether or not the pressure in the reforming device 2 is equal to or lower than a predetermined pressure (S7). If the pressure is not lower than the predetermined pressure, the process returns to the step (S4) of opening and closing the enclosed electromagnetic valve 53s. If the pressure is equal to or lower than the predetermined pressure, the bypass solenoid valve 63s is opened while the sealed solenoid valve 53s is closed (S8). When the bypass electromagnetic valve 63 s is opened, the raw material gas m enclosed in the reformer 2 is introduced into the combustion unit 25. Here, the burner of the combustion section 25 is ignited to burn the raw material gas m as fuel, and the reforming heat necessary for the reforming reaction in the reforming section 21 is generated. At this stage, since it is not necessary to introduce dilution air into the combustion exhaust gas discharge pipe 54, the oxidant gas blower 58b is stopped (S9).

  When combustion in the combustion section 25 is started, the raw material gas blower 51b is started and the valve of the mass flow controller 52c is opened to introduce the raw material gas m as fuel into the combustion section 25 (S10). Subsequently, the valve of the mass flow controller 51c is opened, and the raw material gas m is introduced into the reforming unit 21 (S11). In addition, the process water pump 55p is started and the process water electromagnetic valve 55s is opened to introduce the process water w into the water vapor generating unit 24 (S12). In the steam generation part 24, the process water w receives heat and becomes steam v. The steam v is introduced into the reforming unit 21 and used to reform the raw material gas m.

  The raw material gas m is reformed in the reforming unit 21 to become a mixed reformed gas n1, and is sent to the shift unit 22 and the selective oxidation unit 23, and the carbon monoxide concentration is gradually reduced. In the process, the selective oxidation air blower 56b is activated and the valve of the mass flow controller 56c is opened to introduce the selective oxidation air into the selective oxidation unit 23 (S13). The reformed gas g whose carbon monoxide concentration has been reduced in the selective oxidation unit 23 is not sent to the fuel electrode 31 until the composition is stabilized to be suitable for power generation in the fuel cell stack 3, and the bypass line 63 It is sent to the combustion section 25 and used as a fuel for combustion. That is, it is determined whether or not the composition of the reformed gas g is stable (S14). If it is not stable, the process does not proceed to the next step.

  When the composition of the reformed gas g becomes stable, the oxidant gas blower 58b is activated and the three-way valve 58c is operated to open toward the oxidant gas line 64, so that the oxidant gas k1 is introduced into the air electrode 32 (S15). ). Further, the reformed gas solenoid valve 61s and the anode off-gas solenoid valve 62s are opened, and the bypass solenoid valve 63s is closed (S16). As a result, the reformed gas g is introduced into the fuel electrode 31. The fuel cell stack 3 into which the reformed gas g and the oxidant gas k1 have been introduced starts power generation (S17). Since the fuel cell stack 3 generates heat along with power generation, a cooling water pump (not shown) is activated to flow the cooling water r to the cooling unit 33. Further, the anode off-gas p is discharged from the fuel electrode 31 and guided to the combustion unit 25 and used as a fuel for combustion. On the other hand, the cathode off gas q is discharged from the air electrode 32 and discharged outside the fuel cell system 1. In this way, the fuel cell system 1 enters a steady operation and continues to operate until a stop command is issued. When a command to stop the fuel cell system 1 is received, the reformer 2 is sealed with the raw material gas m and stopped.

  In the above description, the reformer 2 has been described as having the shift unit 22 (paragraphs 0023 and 0025), but the carbon monoxide concentration in the reformed gas g is reduced to a predetermined concentration only by the selective oxidation unit 23. If possible, the metamorphic portion 22 may not be provided. If the transformation unit 22 is not provided, the reformer 2 can be made compact.

  In the above description, the fuel cell stack 3 has been described as a polymer electrolyte fuel cell (paragraph 0039), but may be a fuel cell other than a polymer electrolyte fuel cell such as a phosphoric acid fuel cell.

  In the above description, the pressure detector 42 is described as being provided in the reformed gas supply line 61 (paragraph 0040). However, if the pressure in the reformer 2 in which the raw material gas m is enclosed can be detected, the reformed gas can be detected. You may provide in places other than the supply line 61. FIG.

  In the above description, the blowers 57b and 58b are provided to guide the diluted air to the air introduction path (paragraph 0045). However, when there is an air source such as a compressed air line in a factory, for example, the air is used. Just introduce it.

  In the above description, the fuel cell system considers the discharge flow rate of the raw material gas m calculated from the differential pressure before and after the enclosed electromagnetic valve 53s, which is grasped from the pressure detected by the pressure detector 42, for the opening / closing operation of the enclosed electromagnetic valve 53s. Although the control was performed so that the concentration of the raw material gas m discharged from the fuel cell 1 is less than the explosion limit (paragraph 0051), the concentration of the raw material gas m discharged from the fuel cell system 1 is directly measured by the concentration detector. It may be detected and the opening / closing operation of the enclosed electromagnetic valve 53s may be controlled based on the detected concentration.

Examples of controlling the enclosed electromagnetic valve 53s are shown below (S4 to S7 in FIG. 2). In the following examples, the parameters in the above-described equation (1) (see paragraph 0049) were α = 0.2264, S = 1.33, P ₂ = 100, and P ₁ −P ₂ = 50. Note that methane was used as the source gas m. The amount of air mixed with methane is 30 (L / min).

Example 1
In the present embodiment, the opening interval and opening time of the enclosed electromagnetic valve 53s are made constant regardless of the pressure fluctuation in the reformer 2. Specifically, the enclosed electromagnetic valve 53s is opened every 0.1 second at intervals of 5 seconds. The amount of methane gas discharged when the sealed electromagnetic valve is opened for 0.1 second is (0.1 / 60) × 0.2264 × 1.33 × 1.35 × {100 × 50} ^1/2 ≈0 0.048 (L), and the amount of air flowing in the other 5 seconds is 30 × (5/60) = 2.5 (L). Accordingly, the concentration of methane gas discharged in 5 seconds is 0.048 / (0.048 + 2.5) ≈0.019, that is, about 1.9% by volume. This concentration is below the lower limit of methane explosion limit and is approximately equal to the preferred concentration of 2% by volume.
FIG. 3A shows a timing chart showing the relationship between the opening / closing of the sealed electromagnetic valve 53s of this embodiment and the pressure fluctuation in the reformer 2 (the differential pressure D1 inside and outside the reformer 2). As is clear from the figure, in this example, the pressure in the reformer 2 reached the predetermined pressure P _{0 in} about 20 seconds.

(Example 2)
In this embodiment, the opening interval of the enclosed electromagnetic valve 53s is controlled to be shortened as the pressure in the reformer 2 decreases (the opening time is constant). The control of the opening interval is performed by calculating the flow rate of methane discharged by the control device 4 based on the pressure detected by the pressure detector 42 from the differential pressure, and setting 30 (L / min) which is the flow rate of air to be diluted. This is performed by transmitting a signal i5 for opening for 0.1 second to the sealed electromagnetic valve 53s at an interval at which the concentration of methane can maintain about 2% by volume when mixed. When the sealed electromagnetic valve 53s is opened for 0.1 seconds when the differential pressure P ₁ -P ₂ = 50, 0.048 L of methane is discharged, and the pressure in the reformer 2 decreases accordingly. That is, the differential pressure _P 1 -P ₂ decreases. In this embodiment, since the differential pressure P ₁ −P ₂ = 30, the control device 4 corrected the opening interval of the enclosed electromagnetic valve 53s to 4 seconds. The amount of methane discharged when the differential pressure P ₁ −P ₂ = 30 is (0.1 / 60) × 0.2264 × 1.33 × 1.35 × {100 × 30} ^1/2 ≈0 0.037 (L). On the other hand, the amount of air flowing in 4 seconds is 30 × (4/60) = 2 (L). Accordingly, the concentration of methane at this time is 0.037 / (0.037 + 2) ≈0.018, that is, about 1.8% by volume. Since the pressure in the reformer 2 further decreased due to the second discharge of methane gas, the controller 4 set the next opening interval to 2 seconds. Thereafter, as the differential pressure decreased, the opening interval of the enclosed electromagnetic valve 53s was shortened.
FIG. 3B is a timing chart showing the relationship between the opening / closing of the enclosed electromagnetic valve 53s of this embodiment and the pressure fluctuation in the reformer 2 (differential pressure D2 inside and outside the reformer 2). As is clear from the figure, in this example, the pressure in the reformer 2 reached the predetermined pressure P _{0 in} about 12 seconds.

(Example 3)
In this embodiment, the opening time of the enclosed electromagnetic valve 53s is controlled to be longer as the pressure in the reformer 2 decreases (the opening interval is constant). The control of the opening time is carried out by calculating the flow rate of methane discharged by the control device 4 based on the pressure detected by the pressure detector 42 from the differential pressure, and setting 30 (L / min) which is the flow rate of the air to be diluted. This is done by sending a signal i5 to the enclosing electromagnetic valve 53s so as to open a time for flowing a flow rate that can maintain a methane concentration of about 2% by volume when mixed. Is methane emissions differential pressure _P 1 _-P 2 = 50 inclusion solenoid valve 53s is opened for 0.1 second at 0.048 (L), the pressure of the reforming apparatus 2 is decreased with this , the differential pressure _P 1 -P ₂ is reduced. In this embodiment, the differential pressure P ₁ −P ₂ = 30. When the opening interval is fixed at 5 seconds, the amount of methane discharged is maintained at 0.048 (L) when the differential pressure P ₁ -P ₂ = 50 even if the differential pressure is reduced. The concentration can be maintained at about 1.9% by volume. The control device 4 to correct the opening time of the encapsulated solenoid valve 53s when the decreased pressure difference _P 1 _-P 2 = 30 to 1.3 seconds. Since the pressure in the reformer 2 further decreased due to the second discharge of methane gas, the controller 4 further extended the next opening time.
FIG. 3C is a timing chart showing the relationship between the opening / closing of the enclosed electromagnetic valve 53s of this embodiment and the pressure fluctuation in the reformer 2 (the differential pressure D3 inside and outside the reformer 2). As is apparent from the figure, in this example, the pressure in the reformer 2 reached the predetermined pressure P _{0 in} about 10 seconds.

(Comparative example)
As a comparative example, a case where the enclosed electromagnetic valve 53s is kept open until the pressure in the reformer 2 reaches a predetermined pressure is shown. At this time, the flow rate Q of methane discharged through the enclosed electromagnetic valve is Q = 0.2264 × 1.33 × 1.35 × {100 × 50} ^1/2 ≈28 (L / min), The ratio to the amount of air mixed is 28 / (30 + 28) ≈0.48, that is, about 48% by volume. This is not far from 2% by volume, which is the preferred concentration of methane to be discharged, but far below 5.3% by volume, which is the lower limit of the explosion limit. If methane is discharged out of the fuel cell system 1 at this concentration, it will eventually be diluted to air in the atmosphere and explode, and this comparative example cannot be employed.

1 is a schematic block diagram illustrating a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining the starting method of the fuel cell system which concerns on embodiment of this invention. It is a timing chart explaining the opening timing of the gas interruption | blocking means which discharges | emits the enclosed raw material gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Reformer 3 Fuel cell stack 4 Control device 53 Filled gas discharge pipe (discharge flow path)
53s sealed solenoid valve (gas shut-off means)
54 Combustion exhaust gas discharge pipe (air introduction path)
58A dilution air supply pipe (air introduction path)
g Reformed gas m Raw material gas k1 Oxidant gas k2 Diluted air k3 Combustion air (also dilution air)

Claims (5)

A fuel cell system comprising a reformer that reforms a raw material gas to produce a reformed gas rich in hydrogen, an oxidant gas containing oxygen, and a fuel cell stack that generates electricity by introducing the reformed gas How to start;
Discharging the source gas sealed in the reformer out of the sealed portion of the reformer;
Mixing air with the source gas discharged out of the enclosed portion of the reformer;
Discharging the source gas mixed with the air out of the fuel cell system;
A concentration of the raw material gas mixed with the air discharged out of the fuel cell system is less than a lower limit of explosion limit ;
Detecting a pressure in the reformer in which the source gas is sealed;
Controlling the flow rate of the source gas discharged out of the enclosed portion of the reformer based on the detected pressure;
How to start a fuel cell system. The step of discharging the raw material gas out of the enclosed portion of the reformer, the raw material gas is intermittently discharged, and the raw material mixed with the air is controlled by controlling an interval of discharging the raw material gas. Configured so that the gas concentration is below the lower limit of explosion;
The method for starting the fuel cell system according to claim 1 . The step of discharging the source gas out of the enclosed portion of the reformer is mixed with the air by intermittently discharging the source gas and controlling the time during which the source gas is discharged. Configured so that the concentration of the source gas is less than the lower limit of the explosion limit;
The method for starting the fuel cell system according to claim 1 . A reformer for reforming a source gas to produce a reformed gas rich in hydrogen;
A gas shut-off means for enclosing the source gas therein;
A discharge flow path for discharging the source gas sealed inside to the outside via the gas blocking means ;
An air introduction path for introducing air into the discharge flow path;
A pressure detector for detecting the pressure in the reformer in which the source gas is sealed;
The pressure detection is performed so that the source gas flowing through the discharge passage is mixed with air introduced from the air introduction passage, and the concentration of the source gas discharged from the discharge passage is less than a lower limit of explosion limit. A control device that opens the gas shut-off means based on the pressure detected by the vessel ;
Reformer. A reformer according to claim 4 ;
A fuel cell stack that generates electricity by introducing the reformed gas generated in the reformer and an oxidant gas containing oxygen;
Fuel cell system.

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