Fuel battery system

Abstract

To provide a fuel battery system capable of suppressing an accumulation of a foreign matter such as soot in a combustion exhaust gas passage.SOLUTION: When it is necessary to stop an operation of a cell stack 7 in a start-up process of starting the operation of the cell stack 7 and the foreign matter deposition condition indicating that a possibility that the deposition of the foreign matter generated along with a combustion of an off-gas in a combustion exhaust gas passage 18 is progressing is high is not satisfied, a fuel battery system performs a cooling process of stopping the supply of a raw fuel to a reformer 8 and continuing the supply of an air to the cell stack 7. When the foreign matter deposition condition is satisfied, the combustion continuation process of continuing the supply of the raw fuel to the reforming section 8 and continuing the supply of the air to the cell stack 7 to continue the combustion of the off-gas in a combustion section 9 is performed. When the state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is equal to or higher than the predetermined temperature by performing the combustion continuation process continues for a predetermined time, the combustion continuation process is stopped and the cooling process is performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] Patent document 1 (Japanese Patent Publication No. 2002-83620) describes a fuel cell system having a combustion section (4) that burns offgas discharged from a cell stack (fuel cell G), and a combustion exhaust gas path (combustion gas path 27) that guides the combustion exhaust gas generated in the combustion section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-83620 Summary of the Invention [Problem to be solved by the invention]

[0004] In a fuel cell system such as that described in Patent Document 1, incomplete combustion of off-gas in the combustion section generates CO, which can easily cause soot to adhere to the flue gas passage. In a fuel cell system with a reforming section, when the temperature is sufficiently high, the reforming reaction, for example, from hydrocarbons to hydrogen, proceeds smoothly. The hydrogen produced by the reforming reaction is burned in the combustion section, resulting in almost no soot being produced. Even soot adhering to the flue gas passage at low temperatures, such as during startup, is burned. However, if the startup process is interrupted before the temperature reaches a sufficient level during the startup process, soot remains adhering to the flue gas passage. This creates a problem: the CO concentration increases during the subsequent startup process as the soot adhering to the flue gas passage burns.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a fuel cell system that can suppress the accumulation of foreign matter such as soot in the combustion exhaust gas passage. [Means for solving the problem]

[0006] The fuel cell system according to the present invention for achieving the above object comprises a hot module having a container, a cell stack in which a plurality of fuel cell units, each having an anode and a cathode, are provided inside the container, a reforming unit that steam reforms a raw fuel to produce a fuel gas, a fuel gas supply path that supplies the fuel gas from the reforming unit to the anode, a combustion unit that combusts off-gas discharged from the cell stack, and a combustion exhaust gas path that leads the combustion exhaust gas generated in the combustion unit to the outside of the container; a raw fuel supply unit that supplies the raw fuel from outside the container to the reforming unit; an air supply unit that supplies air from the outside of the container to the cell stack; a reforming water supply unit that supplies reforming water from the outside of the container to the reforming unit; An operation control unit, an exhaust gas temperature measuring device for measuring the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage; The operation control unit If it becomes necessary to stop the operation of the cell stack during the startup process of starting the operation of the cell stack, while the raw fuel is being supplied to the reforming section and the air is being supplied to the cell stack and the off-gas discharged from the cell stack is being combusted in the combustion section, If a foreign matter accumulation condition indicating that there is a high possibility that accumulation of foreign matter occurring in the combustion exhaust gas path due to combustion of the off-gas is progressing is not satisfied, a cooling process is performed in which the supply of the raw fuel to the reforming section is stopped and the supply of the air to the cell stack is continued; When the foreign matter accumulation condition is satisfied, a combustion continuation process is performed to continue the supply of the raw fuel to the reforming section and the supply of air to the cell stack, thereby continuing the combustion of the off-gas in the combustion section, and when the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path remains above a predetermined temperature for a predetermined period of time as a result of the combustion continuation process, the combustion continuation process is stopped and the cooling process is performed.

[0007] According to the above characteristic configuration, if it becomes necessary to stop the operation of the cell stack while the off-gas is being combusted in the combustion section during the startup process that starts the operation of the cell stack, and if the foreign matter accumulation condition is not satisfied, the operation control section performs a cooling process that stops the supply of raw fuel to the reforming section and continues the supply of air to the cell stack. As a result, it is possible to proceed with cooling the inside of the hot module while maintaining a state in which it is unlikely that foreign matter is being accumulated in the combustion exhaust gas path due to the combustion of the off-gas. Furthermore, if it becomes necessary to stop the operation of the cell stack while the off-gas is being combusted in the combustion unit during the startup process that starts the operation of the cell stack, and if the foreign matter accumulation condition is met, the operation control unit performs a combustion continuation process in which the supply of raw fuel to the reforming unit and the supply of air to the cell stack are continued to continue the combustion of the off-gas in the combustion unit. As a result, the temperature of the combustion exhaust gas flowing through the combustion exhaust gas conduit rises. Then, if the combustion continuation process causes the temperature of the combustion exhaust gas flowing through the combustion exhaust gas conduit to be equal to or higher than a predetermined temperature for a predetermined period of time, the operation control unit stops the combustion continuation process and performs the cooling process. In other words, by maintaining the temperature of the combustion exhaust gas flowing through the combustion exhaust gas conduit at or higher for a predetermined period of time, the possibility of foreign matter accumulation occurring in the combustion exhaust gas conduit due to the combustion of the off-gas is reduced, and the interior of the hot module can be cooled. Therefore, it is possible to provide a fuel cell system that can suppress the accumulation of foreign matter such as soot in the combustion exhaust gas passage.

[0008] Another characteristic configuration of the fuel cell system of the present invention is that when it becomes necessary to stop the operation of the cell stack, the operation control unit determines that the foreign matter deposition condition is not satisfied if the state is either a first state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is below a low temperature set temperature, or a second state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is equal to or higher than a high temperature set temperature that is higher than the low temperature set temperature, and determines that the foreign matter deposition condition is satisfied if it becomes necessary to stop the operation of the cell stack and the state is neither the first state nor the second state.

[0009] If the combustion section has not yet combusted much of the off-gas during the startup process of starting the cell stack, i.e., if little soot is generated, the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is low. In other words, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is below the low-temperature set temperature in the first state, it may be determined that the foreign matter accumulation condition is not met. Also, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is high during the startup process of starting the cell stack, it is considered that even if soot had previously adhered to the combustion exhaust gas passage, the soot would be combusted. In other words, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is above the high-temperature set temperature, which is higher than the low-temperature set temperature, it may be determined that the foreign matter accumulation condition is not met in the second state. Therefore, in this characteristic configuration, when it becomes necessary to stop the operation of the cell stack, the operation control unit determines that the foreign matter deposition condition is not satisfied if the cell stack is in either the first state or the second state, and can determine that the foreign matter deposition condition is satisfied if it becomes necessary to stop the operation of the cell stack and the cell stack is neither in the first state nor the second state.

[0010] Another characteristic configuration of the fuel cell system according to the present invention is to include at least one of a raw fuel pressure measuring device that measures the pressure of the raw fuel supplied to the reforming unit by the raw fuel supply unit and an air pressure measuring device that measures the pressure of the air supplied to the cell stack by the air supply unit, When it becomes necessary to stop the operation of the cell stack, the operation control unit determines that the foreign matter deposition condition is met if the pressure of the raw fuel measured by the raw fuel pressure measuring instrument is equal to or greater than a predetermined reference raw fuel pressure, or if the pressure of the air measured by the air pressure measuring instrument is equal to or greater than a predetermined reference air pressure, and otherwise determines that the foreign matter deposition condition is not met.

[0011] If foreign matter such as soot has accumulated in the flue gas passage, the foreign matter will obstruct the flow of gas from the reformer, cell stack, and combustion section to the flue gas passage downstream thereof. Therefore, in this characteristic configuration, the operation control unit can determine that the foreign matter deposition condition is met if the pressure of the raw fuel supplied to the reforming unit is equal to or greater than the reference raw fuel pressure, or if the pressure of the air supplied to the cell stack is equal to or greater than the reference air pressure, and can otherwise determine that the foreign matter deposition condition is not met.

[0012] Another characteristic configuration of the fuel cell system according to the present invention is to include a reforming section temperature measuring device that measures the temperature of the reforming section, The operation control unit adjusts the amount of raw fuel supplied to the reforming unit per unit time and the amount of air supplied to the cell stack per unit time so that, during the combustion continuation process, the temperature of the reforming unit measured by the reforming unit temperature measuring device is within a predetermined combustion continuation temperature range that includes the predetermined temperature.

[0013] If the temperature of the reforming section rises more than necessary, the members that make up the reforming section may be deformed or damaged. In this characteristic configuration, the amount of raw fuel supplied to the reforming section per unit time and the amount of air supplied to the cell stack per unit time are adjusted so that the temperature of the reforming section is within a predetermined combustion continuation temperature range while the combustion continuation process is being performed, thereby preventing the temperature of the reforming section from rising more than necessary. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a fuel cell system according to a first embodiment. [Figure 2] 4 is a flowchart illustrating the operation of a startup process of the fuel cell system. [Figure 3] FIG. 4 is a diagram illustrating the configuration of a fuel cell system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment A fuel cell system according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram illustrating the configuration of the fuel cell system according to the first embodiment.

[0016] The fuel cell system has a container 1, inside which is provided a cell stack 7 having a plurality of fuel cell cells 3 each having an anode 4 and a cathode 6, a reforming section 8 that generates fuel gas by steam reforming a raw fuel containing hydrocarbons such as city gas, a fuel gas supply path 15 that supplies fuel gas from the reforming section 8 to the anode 4, a combustion section 9 that combusts off-gas discharged from the cell stack 7, and a hot module 2 that has a combustion exhaust gas path 18 that leads the combustion exhaust gas generated in the combustion section 9 to the outside of the container 1.

[0017] The fuel cell system also includes a raw fuel supply unit 10 that supplies raw fuel to the reforming unit 8 from outside the container 1, an air supply unit 11 that supplies air to the cell stack 7 from outside the container 1, a reforming water supply unit 12 that supplies reforming water to the reforming unit 8 from outside the container 1, and an operation control unit 21.

[0018] Reforming water is supplied to the reforming section 8 via a reforming water supply channel 14. The reforming water supply channel 14 is provided with a reforming water supply unit 12, which is realized using a pump, a flow meter, etc. and supplies reforming water. The reforming water supply unit 12 can adjust the flow rate of reforming water per unit time supplied to the reforming section 8. In the reforming section 8, combustion heat generated in a combustion section 9, which will be described later, is transferred to vaporize the reforming water supplied from the reforming water supply unit 12. Note that a vaporizer that vaporizes the reforming water supplied by the reforming water supply unit 12 may be provided separately from the reforming section 8. In this case, the water vapor vaporized by the vaporizer is supplied to the reforming section 8. The operation of the reforming water supply unit 12 is controlled by an operation control unit 21 .

[0019] Furthermore, a raw fuel containing hydrocarbons is supplied to the reforming unit 8 via a raw fuel supply path 13. A raw fuel supply path 13 is provided with a raw fuel supply unit 10 that supplies the raw fuel and is realized using a blower, a flow meter, or the like. The raw fuel supply unit 10 can adjust the flow rate of the raw fuel per unit time that is supplied to the reforming unit 8. When a vaporization unit as described above is provided, the raw fuel may be supplied to the vaporization unit, and the steam generated in the vaporization unit and the supplied raw fuel may be mixed in the vaporization unit. The operation of the raw fuel supply unit 10 is controlled by an operation control unit 21 .

[0020] Combustion heat generated in a combustion unit 9, which will be described later, is transferred to the reforming unit 8. Then, in the reforming unit 8, raw fuel supplied from a raw fuel supply unit 10 is steam reformed to generate fuel gas containing hydrogen. The fuel gas generated in the reforming unit 8 flows toward the cell stack 7 via a fuel gas supply path 15. Note that when fuel gas is not being generated in the reforming unit 8, the raw fuel flows through the fuel gas supply path 15.

[0021] The cell stack 7 includes a plurality of fuel cells 3 each having an anode 4, a cathode 6, and an electrolyte 5. For example, the fuel cells 3 are solid oxide fuel cells that use a solid electrolyte.

[0022] Each fuel cell 3 generates power using the fuel gas produced in the reforming unit 8 and air (oxygen) supplied from the air supply unit 11. Specifically, fuel gas is supplied to the anode 4 via a fuel gas supply path 15, and air (oxygen) is supplied to the cathode 6 via an air supply path 19. The air supply path 19 is provided with an air supply unit 11 that supplies air and is realized using a pump, a flow meter, etc. The air supply unit 11 can adjust the flow rate of air per unit time that is supplied to the cell stack 7. The operation of the air supply unit 11 is controlled by an operation control unit 21 .

[0023] Note that not all of the hydrogen and other components contained in the fuel gas supplied to the anode 4 are used for power generation; the anode off-gas discharged from the anode 4 also contains hydrogen and other components. When fuel gas is not being generated in the reforming unit 8, the raw fuel flows through the fuel gas supply path 15. In this case, the anode off-gas discharged from the anode 4 contains the raw fuel. The cathode off-gas discharged from the cathode 6 also contains oxygen. The anode off-gas is supplied from the cell stack 7 to the combustion unit 9 via the anode off-gas path 16, and the cathode off-gas is supplied from the cell stack 7 via the cathode off-gas path 17. In the combustion unit 9, the off-gas (anode off-gas) discharged from the cell stack 7 is ignited and combusted by the igniter 20. The combustion heat generated in the combustion unit 9 increases the temperature of the internal space of the container 1 and is transferred to the reforming unit 8. The combustion exhaust gas discharged from the combustion unit 9 is discharged to the outside of the container 1 via the combustion exhaust gas path 18. The operation of the igniter 20 is controlled by an operation control unit 21 .

[0024] Additionally, the fuel cell system includes a reforming section temperature measuring device 22 that measures the temperature of the reforming section 8. The fuel cell system also includes a combustion section temperature measuring device 23 that measures the temperature inside the combustion section 9. The fuel cell system also includes a stack temperature measuring device 24 that measures the temperature of the cell stack 7. The fuel cell system also includes an exhaust gas temperature measuring device 27 that measures the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18. The measurement results of the reforming section temperature measuring device 22, combustion section temperature measuring device 23, stack temperature measuring device 24, and exhaust gas temperature measuring device 27 are transmitted to the operation control unit 21.

[0025] Next, the operation of the start-up process of the fuel cell system will be described. During the startup process, which starts the operation of the cell stack 7, the operation control unit 21 supplies raw fuel and reforming water to the reforming unit 8 and supplies air to the cell stack 7. Then, during startup of the cell stack 7, the operation control unit 21 performs an ignition process to activate the igniter 20 while supplying raw fuel to the reforming unit 8 and air to the cathode 6 of the cell stack 7, and combusts the off-gas discharged from the cell stack 7 in the combustion unit 9. Note that during the startup process, while steam reforming of the raw fuel is not sufficiently performed in the reforming unit 8, the anode off-gas contains a large amount of raw fuel. By burning this off-gas in the combustion unit 9, combustion heat is transferred to the inside of the hot module 2, and the temperature inside the hot module 2 rises.

[0026] If the temperature inside combustion unit 9 measured by combustion unit temperature measuring device 23 shows a predetermined temperature change trend after performing the ignition process, operation control device 21 determines that normal ignition has occurred in combustion unit 9, and if the temperature inside combustion unit 9 measured by combustion unit temperature measuring device 23 does not show the above-mentioned temperature change trend, operation control device 21 determines that normal ignition has not occurred in combustion unit 9 and repeats the ignition process of activating igniter 20. For example, if normal ignition has occurred in combustion unit 9, the temperature inside combustion unit 9 measured by combustion unit temperature measuring device 23 will monotonically increase and then reach a predetermined temperature.

[0027] If a predetermined error occurs inside the fuel cell system, the operation control unit 21 determines that it is necessary to stop the operation of the fuel cell system. Alternatively, if a user of the fuel cell system instructs the operation to be stopped, the operation control unit 21 also determines that it is necessary to stop the operation of the fuel cell system. However, if the start-up process is stopped midway through the start-up process before the temperature of the flue gas passage 18 has yet to become sufficiently high (i.e., if the combustion of off-gas in the combustion unit 9 is stopped), soot will remain attached to the flue gas passage 18. Then, in the next start-up process, the soot attached to the flue gas passage 18 will burn, causing a problem of an increase in the CO concentration.

[0028] Therefore, in the fuel cell system of this embodiment, if it becomes necessary to stop the operation of the cell stack 7 during the startup process in which the operation of the cell stack 7 is initiated, while raw fuel is supplied to the reforming section 8 and air is supplied to the cell stack 7 and the off-gas discharged from the cell stack 7 is combusted in the combustion section 9, the system is configured to change the processing to be performed thereafter depending on whether or not a foreign matter accumulation condition is met, which indicates that there is a high possibility that foreign matter generated by the combustion of the off-gas is being accumulated in the combustion exhaust gas path 18.

[0029] Specifically, when a foreign matter accumulation condition, which indicates that there is a high possibility that accumulation of foreign matter occurring due to the combustion of off-gas in the combustion exhaust gas path 18 is progressing, is not met, the operation control unit 21 performs a cooling process to stop the supply of raw fuel to the reforming unit 8 and continue the supply of air to the cell stack 7; when the foreign matter accumulation condition is met, the operation control unit 21 performs a combustion continuation process to continue the supply of raw fuel to the reforming unit 8 and the supply of air to the cell stack 7 to continue the combustion of off-gas in the combustion unit 9; and when the combustion continuation process causes the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18 to be above a predetermined temperature for a predetermined period of time, the combustion continuation process is stopped and a cooling process is performed.

[0030] If the combustion unit 9 has not yet combusted most of the off-gas during the startup process in which the cell stack 7 starts operating, i.e., if little soot is generated, the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is low. In other words, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is below the low-temperature set temperature, it may be determined that the foreign matter accumulation condition is not satisfied. Also, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is high during the startup process in which the cell stack 7 starts operating, it is considered that soot will be combusted even if it was previously attached to the combustion exhaust gas passage 18. In other words, if the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is at or above the high-temperature set temperature, which is higher than the low-temperature set temperature, it may be determined that the foreign matter accumulation condition is not satisfied.

[0031] In this embodiment, whether or not the foreign matter accumulation condition is satisfied is determined based on the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18, which is measured by the exhaust gas temperature measuring instrument 27. Specifically, when it becomes necessary to stop the operation of the cell stack 7, the operation control unit 21 determines that the foreign matter accumulation condition is not satisfied if the state is either a first state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is below a low temperature set temperature, or a second state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is equal to or higher than a high temperature set temperature that is higher than the low temperature set temperature, and determines that the foreign matter accumulation condition is satisfied if the state is neither the first state nor the second state when it becomes necessary to stop the operation of the cell stack 7.

[0032] The low temperature setting corresponds to a temperature in the low temperature range where soot as a foreign matter does not form, such as 40° C. Therefore, in the first state where the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is lower than the low temperature setting temperature, it can be determined that soot does not adhere to the combustion exhaust gas passage 18 and that accumulation of foreign matter in the combustion exhaust gas passage 18 is not progressing.

[0033] The high-temperature set temperature corresponds to a temperature in the high-temperature range at which soot as foreign matter does not form, such as 200° C. Therefore, in the second state where the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 is equal to or higher than the high-temperature set temperature, it can be determined that soot does not adhere to the combustion exhaust gas passage 18 and that accumulation of foreign matter in the combustion exhaust gas passage 18 is not progressing.

[0034] 2 is a flowchart illustrating the operation of the startup process of the fuel cell system. The operation control unit 21 starts this flowchart when it is time to start the startup process of the fuel cell system. That is, the operation control unit 21 starts this flowchart by supplying raw fuel to the reforming unit 8 and air to the cell stack 7, and combusting the off-gas discharged from the cell stack 7 in the combustion unit 9.

[0035] In step #10, the operation control unit 21 determines whether or not it is necessary to stop the operation of the cell stack 7. If it is necessary to stop the operation, the operation control unit 21 proceeds to step #11, and if it is not necessary to stop the operation, the operation control unit 21 proceeds to step #12.

[0036] In step #12, the operation control unit 21 determines whether the temperature of a predetermined portion inside the hot module 2 has reached a predetermined target temperature. The predetermined portion is, for example, the reformer 8 or the cell stack 7, and when the temperature of the predetermined portion reaches the target temperature, the startup process is considered to have ended and this flowchart ends. In this embodiment, the temperature of the reformer 8 can be measured using the reformer temperature measuring device 22, and the temperature of the cell stack 7 can be measured using the stack temperature measuring device 24.

[0037] In step #11, the operation control unit 21 determines whether a foreign matter accumulation condition is satisfied, which indicates that there is a high possibility that foreign matter generated as a result of the combustion of off-gas is being accumulated in the combustion exhaust gas passage 18. If the operation control unit 21 determines that the foreign matter accumulation condition is satisfied in step #11, it proceeds to step #13, and if it determines that the foreign matter accumulation condition is not satisfied in step #11, it proceeds to step #15.

[0038] In step #15, the operation control unit 21 performs a cooling process to stop the supply of raw fuel to the reforming unit 8 and continue the supply of air to the cell stack 7. In other words, based on the determination that the accumulation of foreign matter is not progressing in the combustion exhaust gas path 18, the operation control unit 21 performs the above-mentioned cooling process to promote a decrease in the temperature inside the hot module 2, and when the temperature of a predetermined part inside the hot module 2 (e.g., the reforming unit 8, the cell stack 7, etc.) reaches a cooling stop temperature (e.g., 100°C, etc.), the cooling process is terminated, and this flowchart is ended.

[0039] In this way, if the foreign matter accumulation conditions are not met, a cooling process is performed in which the supply of raw fuel to the reforming section 8 is stopped and the supply of air to the cell stack 7 is continued, thereby allowing the cooling of the inside of the hot module 2 to proceed while maintaining a state in which there is a low possibility that foreign matter accumulation occurring due to the combustion of off-gas in the combustion exhaust gas path 18 is progressing.

[0040] In step #13, the operation control unit 21 performs a combustion continuation process to continue supplying raw fuel to the reforming unit 8 and air to the cell stack 7, thereby continuing the combustion of off-gas in the combustion unit 9. The operation control unit 21 performs this combustion continuation process until the state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage 18 remains at or above a predetermined temperature as a result of the combustion continuation process continues for a predetermined time (step #14). In other words, the combustion continuation process is performed until the soot is combusted.

[0041] If the temperature of the reforming section 8 rises more than necessary, deformation or damage may occur to the members that make up the reforming section 8. Therefore, during the combustion continuation process, it is preferable that the operation control section 21 adjusts the amount of raw fuel supplied per unit time to the reforming section 8 and the amount of air supplied per unit time to the cell stack 7 so that the temperature of the reforming section 8 measured by the reforming section temperature measuring device 22 is within a predetermined combustion continuation temperature range that includes the predetermined temperature.

[0042] Then, the operation control unit 21 performs the combustion continuation process until the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18 remains at or above a predetermined temperature for a predetermined period of time, and then proceeds to step #15, where the combustion continuation process is stopped and a cooling process is performed.

[0043] In this way, if the foreign matter accumulation condition is satisfied, a combustion continuation process is performed in which the supply of raw fuel to the reforming unit 8 and the supply of air to the cell stack 7 are continued to continue, and the combustion of off-gas in the combustion unit 9 is continued. As a result, the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18 rises. Then, when the combustion continuation process causes the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18 to be equal to or higher than a predetermined temperature for a predetermined period of time, the operation control unit 21 stops the combustion continuation process and performs the cooling process. In other words, by causing the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path 18 to be equal to or higher than the predetermined temperature for a predetermined period of time, the possibility of the accumulation of foreign matter occurring in the combustion exhaust gas path 18 due to the combustion of off-gas is reduced, and then the cooling of the inside of the hot module 2 can be promoted.

[0044] Second Embodiment The fuel cell system of the second embodiment differs from the above-described embodiments in the method for determining whether the foreign matter accumulation condition is satisfied. The fuel cell system of the second embodiment will be described below, but a description of the same configuration as the above-described embodiments will be omitted.

[0045] 3 is a diagram illustrating the configuration of a fuel cell system according to a second embodiment. As shown in the figure, the fuel cell system includes a raw fuel pressure measuring device 25 that measures the pressure of the raw fuel supplied to the reforming unit 8 by a raw fuel supply unit 10, and an air pressure measuring device 26 that measures the pressure of the air supplied to the cell stack 7 by an air supply unit 11. The raw fuel pressure measuring device 25 is provided in the raw fuel flow path. The air pressure measuring device 26 is provided in the air supply path 19.

[0046] If foreign matter such as soot has accumulated in the flue gas passage 18, the foreign matter will obstruct the flow of gas from the reformer 8, the cell stack 7, and the combustor 9 to the flue gas passage 18 downstream thereof.

[0047] Therefore, when it becomes necessary to stop the operation of the cell stack 7, the operation control unit 21 determines that the foreign matter deposition condition is met if the raw fuel pressure measured by the raw fuel pressure measuring instrument 25 is equal to or greater than the reference raw fuel pressure, or if the air pressure measured by the air pressure measuring instrument 26 is equal to or greater than the reference air pressure, and if not, determines that the foreign matter deposition condition is not met.

[0048] <Another embodiment> In the above embodiment, a specific example of the configuration of the fuel cell system of the present invention has been described, but the configuration can be modified as appropriate.

[0049] In the second embodiment, an example was described in which the fuel cell system was equipped with both the raw fuel pressure measuring device 25 and the air pressure measuring device 26, but it is sufficient if the fuel cell system is equipped with at least one of the raw fuel pressure measuring device 25 and the air pressure measuring device 26.

[0050] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0051] The present invention can be used in a fuel cell system that can suppress the accumulation of foreign matter such as soot in a combustion exhaust gas passage. [Explanation of symbols]

[0052] 1: Container 2: Hot module 3: Fuel cell 4: Anode 6: Cathode 7: Cell stack 8: Modification section 9: Combustion section 10: Raw fuel supply department 11: Air supply section 12: Reformed water supply section 15: Fuel gas supply line 18: Combustion exhaust gas passage 21: Operation control section 22: Reforming section temperature measuring instrument 25: Raw fuel pressure measuring instrument 26: Air pressure measuring instrument 27: Exhaust gas temperature measuring instrument

Claims

1. a hot module having a container, the hot module including a cell stack in which a plurality of fuel cells each having an anode and a cathode are provided inside the container, a reforming section that generates fuel gas by steam reforming a raw fuel, a fuel gas supply path that supplies the fuel gas from the reforming section to the anode, a combustion section that combusts off-gas discharged from the cell stack, and a combustion exhaust gas path that leads combustion exhaust gas generated in the combustion section to the outside of the container; a raw fuel supply unit that supplies the raw fuel from outside the container to the reforming unit; an air supply unit that supplies air from the outside of the container to the cell stack; a reforming water supply unit that supplies reforming water from the outside of the container to the reforming unit; An operation control unit, an exhaust gas temperature measuring device for measuring the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage; The operation control unit If it becomes necessary to stop the operation of the cell stack during the startup process of starting the operation of the cell stack, while the raw fuel is being supplied to the reforming section and the air is being supplied to the cell stack and the off-gas discharged from the cell stack is being combusted in the combustion section, If a foreign matter accumulation condition indicating that there is a high possibility that accumulation of foreign matter occurring in the combustion exhaust gas path due to combustion of the off-gas is progressing is not satisfied, a cooling process is performed in which the supply of the raw fuel to the reforming section is stopped and the supply of the air to the cell stack is continued; When the foreign matter accumulation condition is satisfied, a combustion continuation process is performed to continue the supply of the raw fuel to the reforming section and the supply of air to the cell stack, thereby continuing the combustion of the off-gas in the combustion section, and when the temperature of the combustion exhaust gas flowing through the combustion exhaust gas path remains above a predetermined temperature for a predetermined period of time as a result of the combustion continuation process, the combustion continuation process is stopped and the cooling process is performed.

2. The operation control unit When it becomes necessary to stop the operation of the cell stack, if the state is either a first state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is lower than a low temperature set temperature, or a second state in which the temperature of the combustion exhaust gas flowing through the combustion exhaust gas passage is equal to or higher than a high temperature set temperature that is higher than the low temperature set temperature, it is determined that the foreign matter accumulation condition is not satisfied; 2. The fuel cell system according to claim 1, wherein when it becomes necessary to stop the operation of the cell stack, if the cell stack is not in the first state and not in the second state, it is determined that the foreign matter accumulation condition is satisfied.

3. a raw fuel pressure measuring device that measures the pressure of the raw fuel supplied to the reforming unit by the raw fuel supply unit, and / or an air pressure measuring device that measures the pressure of the air supplied to the cell stack by the air supply unit, The fuel cell system of claim 1, wherein the operation control unit determines that the foreign matter deposition condition is met when it becomes necessary to stop the operation of the cell stack if the pressure of the raw fuel measured by the raw fuel pressure measuring instrument is equal to or greater than a predetermined reference raw fuel pressure, or if the pressure of the air measured by the air pressure measuring instrument is equal to or greater than a predetermined reference air pressure, and otherwise determines that the foreign matter deposition condition is not met.

4. a reforming section temperature measuring device for measuring the temperature of the reforming section; A fuel cell system as described in any one of claims 1 to 3, wherein the operation control unit adjusts the amount of raw fuel supplied to the reforming unit per unit time and the amount of air supplied to the cell stack per unit time so that the temperature of the reforming unit measured by the reforming unit temperature measuring device during the combustion continuation process is within a predetermined combustion continuation temperature range including the predetermined temperature.

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