JP2015185538A - fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing influence on equipment when suppressing a pressure rise around a desulfurizer.SOLUTION: A fuel cell system 1 comprises: a desulfurizer 11; a reformer 51; a fuel cell 53; a raw material line 18 to be desulfurized; a first cutoff valve 21 provided in the raw material line 18 to be desulfurized; a desulfurized raw material line 19; a second cutoff valve 22 provided in the desulfurized raw material line 19; a desulfurizer inner pressure detector 23 which detects an inner pressure of the desulfurizer 11; an air supply unit 31 for reforming which supplies an air AR for reforming to the reformer 51; and a control unit 60. When the pressure detected by the desulfurizer inner pressure detector 23 becomes more than or equal to a first prescribed value, the control unit 60 operates the second cutoff valve 22 and the air supply unit 31 for reforming so as to guide the amount of raw materials D which can be adsorbed by a reforming catalyst 51c to the reformer 51 by opening or closing the second cutoff valve 22, supply the air AR for reforming to the reformer 51, and discharge the raw materials D adsorbed to the reforming catalyst 51c to the outside.

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that suppresses the influence on equipment when performing a process of suppressing a pressure increase around a desulfurizer.

  When installing a fuel cell that generates electricity by introducing a hydrogen-containing gas and an oxygen-containing gas, in view of the lack of infrastructure to obtain the hydrogen-containing gas, the hydrocarbon-based raw material is reformed to produce a hydrogen-containing gas. In many cases, a reformer (fuel processor) is attached. When the hydrogen-containing gas supplied to the fuel cell is produced by reforming a hydrocarbon-based raw material, it is generally reformed after desulfurizing the hydrocarbon-based raw material in a desulfurizer.

  The pressure compensation processing for the space including the fuel processor, which is necessary due to the difference in pressure change due to the difference in temperature change after the shutdown of the desulfurizer and fuel processor with different temperatures during operation, is performed as follows. Fuel processing devices are known. The fuel processing apparatus includes a first valve provided in a raw material gas flow path upstream of a desulfurizer, a second valve provided in a raw material gas flow path between the desulfurizer and the fuel processor, a fuel A third valve provided downstream of the processor, and in a state in which the pressure in the space including the desulfurizer is pressurized to a pressure equal to or higher than the first pressure threshold, the space is supplemented in the space including the fuel processor. When processing is performed, the second valve is opened while the first valve and the third valve are closed (see, for example, Patent Document 1).

JP 2009-217952 A (paragraph 0030, FIG. 1, etc.)

  However, in the fuel processor described in Patent Document 1, when the raw material gas sealed between the first valve and the third valve is discharged, the fuel processor is installed on the downstream side of the fuel processor. There is a risk of malfunctioning of devices such as gas detectors constituting the fuel cell system.

  In view of the above-described problems, an object of the present invention is to provide a fuel cell system that suppresses the influence on devices when performing a process of suppressing a pressure increase around a desulfurizer.

  In order to achieve the above object, the fuel cell system according to the first aspect of the present invention provides a desulfurized raw material Df by desulfurizing a raw material Dr to be desulfurized, which is a hydrocarbon-based raw material, for example, as shown in FIG. A desulfurizer 11 to be generated; a reforming unit 51 that reforms the desulfurized raw material Df to generate a fuel gas E containing hydrogen, and has a reforming catalyst 51c that promotes reforming of the desulfurized raw material Df. A reforming unit 51; a fuel cell 53 for generating power by introducing the fuel gas E and power generation air AG; a desulfurized raw material line 18 for introducing the desulfurized raw material Dr to the desulfurizer 11; and a desulfurized raw material line 18 A first shut-off valve 21; a desulfurized raw material line 19 for introducing the desulfurized raw material Df from the desulfurizer 11 to the reforming unit 51; a second shut-off valve 22 provided in the desulfurized raw material line 19; To detect the pressure inside the vessel 11 directly or indirectly An internal pressure detector 23; a reforming air supply unit 31 that supplies the reforming air AR to the desulfurized raw material line 19 on the downstream side of the second shut-off valve 22 or to the reforming unit 51; When the shutoff valve 21 and the second shutoff valve 22 are closed and the pressure detected by the desulfurizer internal pressure detector 23 exceeds the first predetermined value, the second shutoff valve 22 is opened and closed. The amount of the raw material D that can be adsorbed by the reforming catalyst 51c is guided to the reforming unit 51, and then the reforming air AR is supplied toward the reforming unit 51 to thereby feed the raw material D adsorbed on the reforming catalyst 51c. The control part 60 which act | operates the 2nd cutoff valve 22 and the reforming air supply part 31 is provided so that it may discharge | emit outside.

  With this configuration, the hydrocarbon-based raw material that has flowed down after passing through the second shut-off valve is diluted to an appropriate concentration with reforming air and discharged to the outside, thereby suppressing the influence on the equipment. can do.

  Further, the fuel cell system according to the second aspect of the present invention supplies power generation air AG to the fuel cell 53 in the fuel cell system 1 according to the first aspect of the present invention as shown in FIG. The control unit 60 supplies the power generation air AG toward the fuel cell 53 when the pressure detected by the desulfurizer internal pressure detector 23 is equal to or higher than the first predetermined value. The power generation air supply unit 41 is operated so as to be supplied.

  If comprised in this way, a raw material will be diluted also with power generation air in addition to reforming air, and the influence on equipment can be suppressed more.

  Further, the fuel cell system according to the third aspect of the present invention is, for example, as shown in FIG. 1, in the fuel cell system 1 according to the first aspect or the second aspect of the present invention. A combustion section 55 for combusting the raw material is provided on the downstream side of the portion where the raw material D that flows out and the power generation air AG that flows out from the fuel cell 53 can be mixed.

  If comprised in this way, it will become possible to make it discharge | emit outside after combusting the discharged | emitted raw material, and can reduce an environmental load.

  Further, the fuel cell system according to the fourth aspect of the present invention is, for example, as shown in FIG. 1, in the fuel cell system 1 according to any one of the first to third aspects of the present invention. Then, the control unit 60 opens and closes the reforming catalyst 51c by opening and closing the second shut-off valve 22 until the pressure detected by the desulfurizer internal pressure detector 23 decreases to a second predetermined value that is smaller than the first predetermined value. The material D is adsorbed on the reforming unit 51 and the reforming air AG is supplied to the reforming unit 51 alternately.

  If comprised in this way, the inside of a desulfurizer can be made into a suitable pressure, diluting the raw material discharged | emitted outside to a suitable density | concentration.

  Moreover, as a desulfurizer overpressure elimination method according to the fifth aspect of the present invention, for example, referring to FIGS. 1 and 2, a raw material D present in a desulfurizer 11 for desulfurizing a hydrocarbon-based raw material A raw material sealing step (S1) for sealing the raw material; a desulfurizer internal pressure detection step (S2) for directly or indirectly detecting the pressure inside the desulfurizer 11 in which the raw material D is sealed; and a desulfurizer internal pressure detection step (S2) The amount that can be adsorbed by the reforming catalyst 51c that promotes the reforming of the raw material D accommodated in the reforming unit 51 that can communicate with the desulfurizer 11 when the pressure detected in step S1 becomes equal to or higher than the first predetermined value. After the raw material D is fed to the reforming unit 51, the raw material adsorption step (S5); and after the raw material adsorption step (S5), the reforming air AR is supplied to the reforming unit 51 and adsorbed on the reforming catalyst 51c And a raw material discharge step (S6) for discharging the raw material D being discharged to the outside .

  If comprised in this way, a raw material will be diluted to a suitable density | concentration with reforming air, and will be discharged | emitted outside, and the influence on apparatus can be suppressed.

  According to the present invention, the raw material is diluted to an appropriate concentration with the reforming air and discharged to the outside, and the influence on the equipment can be suppressed.

1 is a schematic system diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart of the overpressure elimination control of the desulfurizer in the fuel cell system which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of the fuel cell system 1. The fuel cell system 1 includes a desulfurizer 11 that desulfurizes the raw material D, a reformer 51 as a reforming unit that reforms the raw material D desulfurized by the desulfurizer 11 into a fuel gas E rich in hydrogen, and a fuel cell 53. And a control unit 60 as main components.

  The raw material D can be made into a gas rich in hydrogen (hydrogen-rich gas) that can be used for power generation in the fuel cell 53 by reforming, and a hydrocarbon-based fuel is used. Specific examples include hydrocarbons, alcohols, ethers, biofuels, and these hydrocarbon fuels are derived from fossil fuels such as petroleum and coal, those derived from synthetic fuels such as synthesis gas, Those derived from biomass can be used as appropriate. Examples of hydrocarbons include methane, ethane, propane, butane, natural gas, LPG, 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. In the following description, the raw material D before being desulfurized by the desulfurizer 11 is referred to as a pre-desulfurized raw material Dr, and the raw material D after being desulfurized by the desulfurizer 11 is referred to as a desulfurized raw material Df. This is collectively referred to as raw material D. The raw material Dr before desulfurization corresponds to the raw material to be desulfurized.

  The desulfurizer 11 has therein a desulfurization catalyst 11c that adsorbs a sulfur content contained in the raw material Dr before desulfurization. As the desulfurization catalyst 11c, a zeolite catalyst or a metal catalyst is used. The desulfurizer 11 includes a pre-desulfurization raw material pipe 18 that leads the raw material Dr before desulfurization to the desulfurizer 11 and a desulfurized raw material pipe as a desulfurized raw material line that leads the desulfurized raw material Df to the reformer 51. 19 is connected. A "... line" is a fluid flow path, typically a tube that exclusively guides the fluid, but is a space formed between objects used for other purposes. There may be. The raw material pipe 18 before desulfurization is provided with a first shut-off valve 21 as a first shut-off valve capable of shutting off the flow path. An upstream shut-off valve 29 is disposed on the pre-desulfurization raw material pipe 18 upstream of the first shut-off valve 21. The desulfurized raw material pipe 19 is provided with a second shutoff valve 22 as a second shutoff valve capable of shutting off the flow path. In the present embodiment, electromagnetic valves are used for the first cutoff valve 21 and the second cutoff valve 22. A raw material blower 13 that pumps the desulfurized raw material Df toward the reformer 51 is disposed in the desulfurized raw material pipe 19 downstream of the second shut-off valve 22. A pre-desulfurization raw material pipe 18 between the desulfurizer 11 and the first shut-off valve 21 is provided with a pressure gauge 23 as a desulfurizer internal pressure detector. The pressure gauge 23 only needs to be able to detect the pressure inside the desulfurizer 11, and may be provided in the desulfurized raw material pipe 19 or the desulfurizer 11 upstream of the second shutoff valve 22.

  The reformer 51 includes a reforming catalyst 51c that promotes reforming of the desulfurized raw material Df. In the present embodiment, a self-heat reforming catalyst is accommodated in the reformer 51 as the reforming catalyst 51c. Connected to the reformer 51 are a desulfurized raw material pipe 19, a reforming air pipe 32 as a reforming air line for introducing the reforming air AR, and a reforming water introduction pipe (not shown). ing. The reforming air pipe 32 is provided with a reforming air blower 33 that pumps the reforming air AR toward the reformer 51. A reforming air supply unit 31 is configured including the reforming air pipe 32 and the reforming air blower 33. The reformer 51 introduces the desulfurized raw material Df, the reforming air AR, and the reforming water, burns a part of the hydrocarbons in the desulfurized raw material Df with the reforming air AR, and generates heat. Thus, the hydrocarbon in the desulfurized raw material Df and the reformed water (steam) are reformed under the reforming catalyst 51c to generate the fuel gas E. Also connected to the reformer 51 is a fuel gas pipe 52 as a fuel gas line for leading the generated fuel gas E. The reformer 51 is configured to be able to adsorb an amount of the raw material D corresponding to the filling amount of the reforming catalyst 51c when the reforming air AR and the reforming water are not introduced.

  The fuel cell 53 is connected to the reformer 51 through a fuel gas pipe 52. The fuel cell 53 is also connected with a power generation air pipe 42 as a power generation air line for introducing the power generation air AG. The power generation air pipe 42 is provided with a power generation air blower 43 that pumps the power generation air AG toward the fuel cell 53. A power generation air supply unit 41 is configured including the power generation air pipe 42 and the power generation air blower 43. The fuel cell 53 is configured to introduce the fuel gas E and the power generation air AG and generate DC power by an electrochemical reaction between hydrogen or the like in the fuel gas E and oxygen in the power generation air AG. In some cases, it is generally called a cell stack. As the fuel cell 53, in this embodiment, a solid oxide fuel cell (SOFC) of a cylindrical type (including a flat plate cylindrical type) is used, but a SOFC such as a solid polymer fuel cell (PEFC) is used. Other fuel cells may be used. The fuel gas E and power generation air AG supplied to the fuel cell 53 for power generation in the fuel cell 53 are not all used for power generation, but the amount corresponding to the power generation current of the fuel cell 53 is used. The portion not used for power generation is derived as off-gas F. In the present embodiment, a burner (not shown) for burning off gas F derived from the fuel cell 53 is provided on the downstream side of the fuel cell 53, and the off gas F is burned by the burner (not shown). The reformer 51 can be heated by the generated heat.

  The fuel cell system 1 includes a combustion unit 55 downstream of the fuel cell 53. The combustion unit 55 introduces the off-gas F after being discharged from the fuel cell 53 and burned by a burner (not shown), and burns unburned combustible components contained in the off-gas F after the primary combustion. It is configured. The combustion unit 55 is mainly for burning unburned components in the off-gas F after the primary combustion, but is disposed adjacent to the reformer 51 and serves as a reforming catalyst 51c in the reformer 51. You may be comprised so that heat can be given. The combustion unit 55 includes a combustion catalyst (not shown) that burns combustible components in the off-gas F after the primary combustion, and a heater 55h that raises the temperature of the combustion catalyst to an activation temperature. The combustion catalyst is composed of a substance that promotes oxidation of the combustible component in the off-gas F after the primary combustion. For example, a noble metal catalyst such as platinum or palladium or a base metal catalyst such as manganese or iron is used. be able to. The heater 55h is configured to have a calorific value that can quickly raise the combustion catalyst (not shown) to the activation temperature when the fuel cell system 1 is started. The combustion unit 55 is configured to discharge the exhaust gas G generated by the combustion of the off gas F after the primary combustion. An exhaust gas pipe 59 as an exhaust gas line through which the exhaust gas G flows is connected to the combustion unit 55.

  The control unit 60 is a device that controls the operation of the fuel cell system 1. The control unit 60 is connected to the first shut-off valve 21 and the second shut-off valve 22 via signal cables, respectively, and is configured to be able to open and close the first shut-off valve 21 and the second shut-off valve 22. Yes. The control unit 60 is connected to the pressure gauge 23 via a signal cable, and is configured to receive a value detected by the pressure gauge 23 as a signal. The control unit 60 is connected to the raw material blower 13, the reforming air blower 33, and the power generation air blower 43 by signal cables, respectively, so that the start and stop of each of the blowers 13, 33, 43 can be controlled. It is configured. The control unit 60 is connected to the heater 55h via a signal cable, and is configured to be able to control on / off of the heater 55h.

  With continued reference to FIG. 1, the operation of the fuel cell system 1 will be described. When the control unit 60 receives a command to start the fuel cell system 1, the control unit 60 opens the first cutoff valve 21 and the second cutoff valve 22 and starts the raw material blower 13. The upstream shut-off valve 29 is normally open when the fuel cell system 1 is in operation. When the raw material blower 13 is activated, the raw material Dr before desulfurization is introduced into the desulfurizer 11 through the raw material pipe 18 before desulfurization. The raw material Dr before desulfurization becomes a desulfurized raw material Df that is desulfurized so that the sulfur content is adsorbed by the action of the desulfurization catalyst 11 c in the desulfurizer 11 and does not adversely affect the reformer 51 and the fuel cell 53. The desulfurizer 11 in which the raw material Dr before desulfurization is desulfurized is approximately 50 ° C. The desulfurized raw material Df is introduced into the reformer 51 through the desulfurized raw material pipe 19.

  When the desulfurized raw material Df is introduced into the reformer 51, the control unit 60 activates the reforming air blower 33. When the reforming air blower 33 is activated, the reforming air AR is introduced into the reformer 51 through the reforming air pipe 32. Further, reforming water is also introduced into the reformer 51 via a reforming water introduction pipe (not shown). In the reformer 51 into which the desulfurized raw material Df, the reforming air AR, and the reforming water are introduced, a self-thermal reforming reaction is performed and the fuel gas E is generated. The reformer 51 in which the autothermal reforming reaction is performed is approximately 600 ° C. When the temperature of the reformer 51 rises and the fuel gas E is stably generated, the reforming air blower 33 is stopped and the supply of the reforming air AR to the reformer 51 is stopped. The fuel gas E is generated by steam reforming with steam changed from the reformed water. The fuel gas E generated by the reformer 51 is supplied to the fuel cell 53 via the fuel gas pipe 52.

  When the fuel gas E is supplied to the fuel cell 53, the control unit 60 activates the power generation air blower 43. When the power generation air blower 43 is activated, the power generation air AG is introduced into the fuel cell 53 via the power generation air pipe 42. In the fuel cell 53 into which the fuel gas E and the power generation air AG are introduced, power generation is performed by an electrochemical reaction between hydrogen or the like in the fuel gas E and oxygen in the power generation air AG. The electric power generated in the fuel cell 53 is supplied to electric devices (each blower 13, 43, etc.) in the fuel cell system 1 and / or an electric power load (not shown) outside the fuel cell system 1. After the fuel gas E and the power generation air AG introduced into the fuel cell 53 are used for power generation, they are discharged as off-gas F, and are first burned by a burner (not shown) to give heat to the reformer 51. To the combustion section 55.

  In the combustion unit 55, since the combustion catalyst does not reach the activation temperature at the initial start of the fuel cell system 1, the control unit 60 operates the heater 55h to quickly raise the combustion catalyst to the activation temperature. When the combustion catalyst reaches the activation temperature, the controller 60 stops energizing the heater 55h. The off-gas F after the primary combustion introduced into the combustion unit 55 is combusted by the combustion catalyst. The combustion heat generated by the combustion of the off-gas F after the primary combustion in the combustion unit 55 may be used for the reforming reaction in the reformer 51. The exhaust gas G generated by the combustion of the off-gas F after the primary combustion in the combustion unit 55 flows through the exhaust gas pipe 59 and is discharged from the fuel cell system 1.

  In the fuel cell system 1 that operates as described above, when the power generation of the fuel cell 53 is stopped, the control unit 60 stops the material blower 13 and closes the first cutoff valve 21 and the second cutoff valve 22. . Thereby, the supply of the desulfurized raw material Df to the reformer 51 is stopped, and the supply of the fuel gas E to the fuel cell 53 is stopped. In addition, the control unit 60 stops the power generation air blower 43. Thereby, the supply of the power generation air AG to the fuel cell 53 is stopped. The portions of the desulfurizer 11 between the first shut-off valve 21 and the second shut-off valve 22 that are closed and the pre-desulfurization raw material pipe 18 and the desulfurized raw material pipe 19 that are in communication with the desulfurizer 11 are sealed inside. Therefore, the internal pressure fluctuates according to changes in the temperature of the surrounding environment. Typically, when the temperature of the desulfurizer 11 increases, the internal pressure increases, and when the temperature of the desulfurizer 11 decreases, the internal pressure decreases.

  In order to avoid an excessive increase in the pressure in the desulfurizer 11, the desulfurization is performed by opening the second shut-off valve 22 when the value detected by the pressure gauge 23 exceeds the first predetermined value. The pressure in the vessel 11 can be released. Here, the first predetermined value is an upper limit value of the pressure set from the viewpoint of protection of the desulfurizer 11, and may be, for example, 65 kPa (gauge pressure). By opening the second shut-off valve 22, the pressure in the desulfurizer 11 can be released. However, if the raw material D enclosed around the desulfurizer 11 flows out to the downstream side as it is, the fuel cell system 1 enters the fuel cell system 1. A malfunction of auxiliary equipment such as installed gas detectors may occur. In the fuel cell system 1, the following measures are taken to suppress the pressure increase in the desulfurizer 11 while avoiding malfunctions of auxiliary machinery.

  FIG. 2 is a flowchart of the overpressure elimination control of the desulfurizer 11 in the fuel cell system 1. In the following description, when referring to the configuration of the fuel cell system 1, FIG. 1 will be referred to as appropriate. During the stoppage of power generation, the fuel cell system 1 closes the first shutoff valve 21 and the second shutoff valve 22 to seal around the desulfurizer 11, and encloses the raw material D present in the desulfurizer 11. (Raw material encapsulation step: S1). And the control part 60 has received the value which the pressure gauge 23 detected suitably, and judges whether the value which the pressure gauge 23 detected is more than a 1st predetermined value (desulfurizer internal pressure detection process: S2). ). If the value detected by the pressure gauge 23 is not equal to or greater than the first predetermined value, the process returns to the desulfurizer internal pressure detection step (S2) again.

  On the other hand, in the desulfurizer internal pressure detection step (S2), when the value detected by the pressure gauge 23 is equal to or greater than the first predetermined value, the control unit 60 activates the power generation air blower 43 (S3). When the power generation air blower 43 is activated, the power generation air AG is supplied to the fuel cell 53. However, in the fuel cell system 1 in which power generation is stopped, the fuel gas E is not supplied to the fuel cell 53. For this reason, the power generation air AG supplied to the fuel cell 53 passes through the fuel cell 53 and flows through the exhaust gas pipe 59. When the power generation air blower 43 is activated or simultaneously with the activation of the power generation air blower 43, the control unit 60 activates the heater 55h (S4). When the heater 55h is activated, the temperature of the combustion section 55 starts to rise.

  Next, the control unit 60 closes the second shut-off valve 22 after opening for a first predetermined time, thereby introducing the raw material D enclosed in the desulfurizer 11 to the reformer 51 to reform the reforming catalyst. It is made to adsorb | suck to 51c (raw material adsorption | suction process: S5). The first predetermined time is the time required to introduce the amount of the raw material D that can be adsorbed by the reforming catalyst 51c filled in the reformer 51 into the reformer 51, and the filling amount of the reforming catalyst 51c. Or a value detected by the pressure gauge 23 or the like. The control unit 60 takes into account the charging amount of the reforming catalyst 51c and the characteristics of the second shut-off valve 22, the value detected by the pressure gauge 23, the time for which the second shut-off valve 22 is open, the reforming The relationship with the amount of raw material D introduced into the vessel 51 is stored in advance. In the raw material adsorption step (S5), the control unit 60 opens the second shut-off valve 22 so that the raw material D exceeding the amount that the reforming catalyst 51c can be adsorbed is not introduced into the reformer 51. The predetermined time is determined.

  After performing the raw material adsorption step (S5), the control unit 60 activates the reforming air blower 33 for a second predetermined time to supply the reforming air AR to the reformer 51, and the reforming catalyst. The raw material D adsorbed on 51c is separated from the reforming catalyst 51c and discharged to the outside of the fuel cell system 1 (raw material discharge step: S6). By discharging the raw material D from the reformer 51 by the reforming air AR, the adsorption ability of the reforming catalyst 51c is regenerated. Further, by discharging the raw material D from the reformer 51 by the reforming air AR, the raw material D is diluted and discharged, and the malfunction of auxiliary equipment that may occur when the raw material D is discharged as it is. Can be avoided. Further, in the present embodiment, since the power generation air AG is supplied to the fuel cell 53, the raw material D discharged from the reformer 51 by the reforming air AR passes through the fuel gas pipe 52 and the fuel cell 53. When it is discharged from the vehicle, it is also diluted by the power generation air AG, and it is possible to more reliably avoid malfunctions of the auxiliary machinery.

  In the raw material discharge step (S6), the raw material D adsorbed on the reforming catalyst 51c flows through the exhaust gas pipe 59 together with the reforming air AR and the power generation air AG, is diluted, and is then removed from the fuel cell system 1. Discharged. Since the amount of the raw material D discharged at one time is an amount that can be adsorbed by the reforming catalyst 51c, if the internal pressure of the desulfurizer 11 is equal to or higher than the first predetermined value and the second shutoff valve 22 is kept open. It can be avoided that the flow rate of the discharged raw material D instantaneously becomes excessive and enters the combustion range (more than the lower combustion limit). At this time, the temperature of the combustor 55 is increased by the heater 55h in the time after the pressure gauge 23 detects the first predetermined value or more. Therefore, when the raw material D passes the combustion part 55, it is burned by the combustion catalyst in the combustion part 55 (S7). Since the raw material D is discharged to the outside after being burned, even when a city gas containing methane having a large greenhouse effect coefficient is used as the raw material D, the load on the environment can be reduced.

  When the raw material D adsorbed on the reforming catalyst 51c is discharged from the reformer 51, the control unit 60 determines whether or not the value detected by the pressure gauge 23 is equal to or less than a second predetermined value (desulfurizer). Internal pressure drop confirmation step: S8). Here, the second predetermined value is a pressure that can prevent the desulfurizer 11 from becoming a negative pressure even if the temperature drops after the overpressure of the desulfurizer 11 is eliminated, for example, 40 kPa (gauge pressure). It can be. At this time, even if the value detected by the pressure gauge 23 falls below the second predetermined value, the value detected by the pressure gauge 23 has decreased from the first predetermined value in the process so far. , It does not deviate greatly from the second predetermined value. When the value detected by the pressure gauge 23 is not less than or equal to the second predetermined value, the process returns to the raw material adsorption step (S5), and the process following the above-described raw material adsorption step (S5) is performed again. On the other hand, in the desulfurizer internal pressure drop confirmation step (S8), when the value detected by the pressure gauge 23 is equal to or smaller than the second predetermined value, the control unit 60 stops the power generation air blower 43 (S9). When the power generation air blower 43 is stopped, the control unit 60 determines whether or not the fuel cell system 1 has started power generation (S10). When the power generation is not started, the process returns to the desulfurizer internal pressure detection step (S2), and the above-described flow is performed. On the other hand, in the step (S10) of determining whether or not the fuel cell system 1 has started power generation, when power generation is started, the overpressure elimination control of the desulfurizer 11 ends.

  As described above, according to the fuel cell system 1 according to the present embodiment, the pressure is released when the internal pressure of the desulfurizer 11 becomes equal to or higher than the first predetermined value in the overpressure elimination control. The raw material D discharged by opening and closing the second shut-off valve 22 is once adsorbed to the reforming catalyst 51c, and then diluted with the reforming air AR and the power generation air AG and discharged to the outside of the fuel cell system 1. Therefore, it is possible to avoid the malfunction of auxiliary equipment that may occur when the raw material D is discharged as it is. Moreover, since the raw material D is combusted and discharged to the outside, the load on the environment can be reduced.

  In the above description, the power generation air AG is supplied in the overpressure elimination control, but the raw material D is diluted to a desired concentration by supplying the reforming air AR without supplying the power generation air AG. If this is possible, it is not necessary to supply the power generation air AG in the overpressure elimination control. In this case, the step (S3) of starting the power generation air blower 43 is omitted in the flow shown in FIG.

  In the above description, the fuel cell system 1 includes the combustion unit 55. However, if the raw material D need not be burned, the combustion unit 55 may be omitted. In this case, the step of starting the heater 55h (S4) is omitted in the flow shown in FIG.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 11 Desulfurizer 18 Predesulfurization raw material pipe 19 Desulfurized raw material pipe 21 First shutoff valve 22 Second shutoff valve 23 Pressure gauge 31 Reforming air supply unit 33 Reforming air blower 41 Power generation air supply unit 43 Power generation air blower 51 Reformer 51c Reforming catalyst 53 Fuel cell 55 Combustion section 60 Control section D Raw material Dr Raw material Df before desulfurization Df Desulfurized material E Fuel gas AG Power generation air AR Reforming air

Claims (4)

A desulfurizer for producing a desulfurized raw material by desulfurizing a raw material to be desulfurized which is a hydrocarbon-based raw material;
A reforming section for reforming the desulfurized raw material to generate a hydrogen-containing fuel gas, the reforming section having a reforming catalyst that promotes reforming of the desulfurized raw material;
A fuel cell for generating electricity by introducing the fuel gas and air for power generation;
A desulfurization raw material line for guiding the desulfurization raw material to the desulfurizer;
A first shut-off valve provided in the raw material line for desulfurization;
A desulfurized raw material line for guiding the desulfurized raw material from the desulfurizer to the reforming section;
A second shut-off valve provided in the desulfurized raw material line;
A desulfurizer internal pressure detector for directly or indirectly detecting the pressure inside the desulfurizer;
A reforming air supply unit that supplies reforming air to the desulfurized raw material line downstream of the second shutoff valve or to the reforming unit;
When the pressure detected by the desulfurizer internal pressure detector is equal to or higher than a first predetermined value with the first shut-off valve and the second shut-off valve closed, the second shut-off valve is By opening and closing, an amount of the raw material that can be adsorbed by the reforming catalyst is guided to the reforming unit, and then the reforming air is supplied to the reforming unit and adsorbed on the reforming catalyst. A control unit that operates the second shutoff valve and the reforming air supply unit so as to discharge the raw material to the outside;
Fuel cell system. A power generation air supply unit configured to supply the power generation air to the fuel cell;
The control unit is configured to supply the power generation air to the fuel cell when the pressure detected by the desulfurizer internal pressure detector becomes equal to or higher than the first predetermined value. Actuate the supply;
The fuel cell system according to claim 1. A combustion section provided on the downstream side of a portion where the raw material flowing out from the reforming section and the power generating air flowing out from the fuel cell can be mixed;
The fuel cell system according to claim 1 or 2. The control unit is configured to open and close the second shut-off valve until the pressure detected by the desulfurizer internal pressure detector decreases to a second predetermined value that is smaller than the first predetermined value. The raw material adsorption to the reforming unit and the supply of the reforming air to the reforming unit are alternately repeated;
The fuel cell system according to any one of claims 1 to 3.

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