Fuel battery system

Abstract

To provide a fuel battery system capable of stabilizing combustion.SOLUTION: A fuel cell system 100 comprises: a hot module 10 including a cell stack 14, a reforming unit 13, a combustion unit 15, an anode off-gas supply line L14, a cathode off-gas supply line L15, and a combustion exhaust gas line L16; and a heat exchanger 51 for performing heat exchange between coolant and combustion exhaust gas circulating through the combustion exhaust gas line L16. The fuel cell system comprises at least one of a raw fuel bypass line LB1 for supplying raw fuel to the anode off-gas supply line L14 after bypassing the reforming unit 13 and the cell stack 14, an oxidant gas bypass line LB2 for supplying oxidant gas to the cathode off-gas supply line L15 after bypassing the cell stack 14; and a combustion exhaust gas bypass line LB3 for supplying combustion exhaust gas from the combustion unit 15 to the combustion exhaust gas line L16 after bypassing the heat exchanger 51.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a solid electrolyte fuel cell system including a solid electrolyte fuel cell stack made up of a plurality of stacked solid electrolyte (solid oxide) fuel cells, a gas reforming unit that reforms the fuel gas supplied to the solid electrolyte fuel cell stack, and a burner that heats the gas reforming unit to promote the gas reforming reaction by the gas reforming unit. In the solid electrolyte fuel cell system disclosed in Patent Document 1, the gas reforming unit is located at the lower end in the stacking direction of the solid electrolyte fuel cell stack, and the burner is located below the gas reforming unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-21596 Summary of the Invention [Problem to be solved by the invention]

[0004] In some fuel cell systems, such as the solid oxide fuel cell system disclosed in Patent Document 1, pressure loss in the gas supplied to the combustion section (the burner in Patent Document 1) or the gas discharged from the combustion section can become large, causing combustion oscillations due to pressure fluctuations in the space (combustion chamber) where combustion takes place and fluctuations in the combustion rate. When combustion oscillations occur, combustion in the combustion section becomes unstable (particularly at the time of ignition), which can lead to incomplete combustion and the generation of carbon monoxide. For this reason, there is a demand for a fuel cell system that can stabilize combustion in the combustion section.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fuel cell system capable of stabilizing combustion. [Means for solving the problem]

[0006] The fuel cell system according to the present invention, which achieves the above object, has the following characteristic configuration: a hot module having a container, the container containing a cell stack having a plurality of fuel cells each having an anode and a cathode, a reforming section which generates fuel gas by steam reforming a raw fuel, a fuel gas supply channel which supplies the fuel gas from the reforming section to the anode, an oxidant gas supply channel which supplies oxidant gas to the cathode, a combustion section which combusts anode off-gas and cathode off-gas discharged from the cell stack, an anode off-gas supply channel which supplies the anode off-gas discharged from the cell stack to the combustion section, a cathode off-gas supply channel which supplies the cathode off-gas discharged from the cell stack to the combustion section, and a combustion exhaust gas channel which 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 oxidant gas supply unit that supplies the oxidant gas from outside 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; a heat exchanger that exchanges heat between the combustion exhaust gas flowing through the combustion exhaust gas passage and a refrigerant to cool the combustion exhaust gas, The system is characterized in that it comprises at least one of a raw fuel bypass path that supplies the raw fuel from the raw fuel supply unit to the anode off-gas supply path, bypassing the reforming unit and the cell stack; an oxidant gas bypass path that supplies the oxidant gas from the oxidant gas supply unit to the cathode off-gas supply path, bypassing the cell stack; and a combustion exhaust gas bypass path that supplies the combustion exhaust gas from the combustion unit to the combustion exhaust gas path, bypassing the heat exchanger.

[0007] According to the above-described characteristic configuration, the raw fuel and / or oxidant gas is supplied to the combustion section bypassing the cell stack. Alternatively, the combustion exhaust gas discharged from the combustion section is supplied to the combustion exhaust gas passage bypassing the heat exchanger. This reduces the pressure loss of the gas supplied to the combustion section and / or the gas discharged from the combustion section, thereby stabilizing combustion by the combustion section.

[0008] Another characteristic configuration of the fuel cell system according to the present invention is: a raw fuel switching unit that can switch between a normal state in which the raw fuel is supplied from the raw fuel supply unit to the reforming unit and a bypass state in which the raw fuel is supplied from the raw fuel supply unit to the raw fuel bypass path; an oxidant gas switching unit that can switch between a normal state in which the oxidant gas is supplied from the oxidant gas supply unit to the cell stack and a bypass state in which the oxidant gas is supplied from the oxidant gas supply unit to the oxidant gas bypass path; a combustion exhaust gas switching unit that is switchable between a normal state in which the combustion exhaust gas is supplied from the combustion unit to the heat exchanger and a bypass state in which the combustion exhaust gas is supplied from the combustion unit to the combustion exhaust gas bypass path, The fuel cell system further includes an operation control unit that controls the operations of the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit.

[0009] According to the above-described characteristic configuration, by controlling the operation of at least one of the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit, the gas route can be switched, the pressure loss of the gas supplied to the combustion unit and / or the gas discharged from the combustion unit can be reduced, and combustion by the combustion unit can be stabilized.

[0010] Another characteristic feature of the fuel cell system of the present invention is that, when the cell stack is started up, the operation control unit switches at least one of the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit to the bypass state, and performs an ignition process to activate an igniter provided inside the combustion unit.

[0011] According to the above characteristic configuration, combustion by the combustion unit tends to become unstable during ignition processing. Therefore, by bypassing at least one of the raw fuel switching unit, oxidizer gas switching unit, and combustion exhaust gas switching unit during ignition processing, the pressure loss of at least one of the raw fuel, oxidizer gas, and combustion exhaust gas can be reduced, thereby stabilizing combustion by the combustion unit.

[0012] Another characteristic configuration of the fuel cell system according to the present invention is that, after performing the ignition process, if the operation control unit determines that the combustion state of the combustion unit is stable and satisfies predetermined stability conditions, it switches the raw fuel switching unit, the oxidant gas switching unit and the combustion exhaust gas switching unit that have been switched to the bypass state back to the normal state.

[0013] According to the above characteristic configuration, when the combustion state by the combustion unit becomes stable, the raw fuel switching unit, the oxidant gas switching unit and the combustion exhaust gas switching unit that are in the bypass state can be switched to the normal state.

[0014] Another characteristic configuration of the fuel cell system according to the present invention is: the hot module has an oxidant gas preheating heat exchanger that is disposed in the oxidant gas supply channel and the combustion exhaust gas channel and that exchanges heat between the oxidant gas flowing through the oxidant gas supply channel and the combustion exhaust gas flowing through the combustion exhaust gas channel; When the oxidant gas switching unit is in the bypass state, the oxidant gas is supplied from the oxidant gas supply unit to the oxidant gas bypass path, bypassing the oxidant gas preheating heat exchanger and the cell stack, When the combustion exhaust gas switching unit is in the bypass state, the combustion exhaust gas is supplied from the combustion unit to the combustion exhaust gas bypass path, bypassing the oxidant gas preheating heat exchanger and the heat exchanger.

[0015] According to the above characteristic configuration, when an oxidant gas preheating heat exchanger is installed, the oxidant gas preheating heat exchanger can be bypassed, the pressure loss of the oxidant gas supplied to the combustion section and the combustion exhaust gas discharged from the combustion section can be reduced, and combustion by the combustion section can be stabilized. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing the configuration of a fuel cell system according to an embodiment; [Figure 2] FIG. 4 is a diagram showing the flows of raw fuel, oxidizing agent, and combustion exhaust gas in a bypass route according to the embodiment. [Figure 3] FIG. 2 is a diagram showing the flows of raw fuel, oxidizing agent, and combustion exhaust gas in a normal route according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] A fuel cell system 100 according to an embodiment of the present invention will be described below with reference to the drawings. FIG.

[0018] [Fuel cell system] As shown in FIG. 1, the fuel cell system 100 includes a control unit 1 (an example of an operation control unit), a reforming water supply unit 2, a raw fuel supply unit 3, an oxidizing gas supply unit 4, an external heat exchange unit 5, and a hot module 10.

[0019] [Control Unit] The control unit 1 is composed of a microcontroller including a processor, a semiconductor memory, etc. The control unit 1 controls the operation of each of the reforming water supply unit 2, the raw fuel supply unit 3, the oxidant gas supply unit 4, the external heat exchange unit 5, and the hot module 10. In this embodiment, as will be described later, the control unit 1 switches the path of the gas flowing inside the hot module 10 (hereinafter referred to as the gas route) between a normal route and a bypass route. The control unit 1 also has a storage unit 101 composed of a semiconductor memory, etc.

[0020] [Reformed Water Supply Department] The reforming water supply unit 2 supplies reforming water to the hot module 10. The reforming water is, for example, tap water from which impurities have been removed. The reforming water supply unit 2 includes a reforming water supply path L2 through which the reforming water can flow, a pump 21 that can pump the reforming water, a water tank (not shown) that can store the reforming water, and a flow meter (not shown) that can measure the flow rate of the reforming water flowing through the reforming water supply path L2.

[0021] [Raw and fuel supply department] The raw fuel supply unit 3 supplies raw fuel (raw fuel gas) from the outside of the inner container 10H to the hot module 10. The raw fuel contains hydrocarbons, such as city gas and LP gas.

[0022] The raw fuel supply unit 3 includes a raw fuel supply path L3 through which the raw fuel can flow, a blower 31 capable of supplying the raw fuel to the hot module 10, and a flow meter (not shown) capable of measuring the flow rate of the raw fuel flowing through the raw fuel supply path L3.

[0023] [Oxidant gas supply unit] The oxidizing gas supply unit 4 supplies an oxidizing gas (oxidizer) from the outside of the inner vessel 10H to the hot module 10 (cell stack 14). The oxidizing gas contains oxygen and is, for example, air.

[0024] The oxidant gas supply unit 4 includes an oxidant gas supply path L4 through which the oxidant gas can flow, a blower 41 capable of supplying the oxidant gas to the hot module 10, and a flow meter (not shown) capable of measuring the flow rate of the oxidant gas flowing through the oxidant gas supply path L4.

[0025] [External heat exchange section] The external heat exchanger 5 includes an external flue gas passage L5 through which the flue gas discharged from the hot module 10 can flow, and a first heat exchanger 51 (an example of a heat exchanger) capable of exchanging heat between the flue gas flowing through the external flue gas passage L5 and the refrigerant. The first heat exchanger 51 is disposed midway along the external flue gas passage L5. The first heat exchanger 51 exchanges heat between the flue gas discharged from the hot module 10 and flowing through the external flue gas passage L5 and the refrigerant. This decreases (cools) the temperature of the flue gas and increases the temperature of the refrigerant. The refrigerant is, for example, a heat medium such as hot water supplied to homes, etc. The hot water is stored in a tank (not shown) and circulates through a hot water circulation passage (not shown).

[0026] [Hot Module] The hot module 10 is a fuel cell module that generates electricity by reacting hydrogen and oxygen. The hot module 10 includes an inner container 10H (an example of a container), a desulfurization section 11, a vaporization section 12, a reforming section 13, a cell stack 14, a combustion section 15, a second heat exchanger 16 (an example of an oxidant gas preheating heat exchanger), a combustion catalyst section 17, a bypass section 18, a raw fuel flow passage L11, a first fuel gas flow passage L12 (an example of a fuel gas supply passage), a first oxidant gas flow passage L13 (an example of an oxidant gas supply passage), a second fuel gas flow passage L14 (an example of an anode offgas supply passage), a second oxidant gas flow passage L15 (an example of a cathode offgas supply passage), and a combustion exhaust gas flow passage L16 (an example of a combustion exhaust gas passage).

[0027] A reforming water supply unit 2 (reforming water supply channel L2), a raw fuel supply unit 3 (raw fuel supply channel L3), and an oxidant gas supply unit 4 (oxidant gas supply channel L4) are connected to the hot module 10, and reforming water, raw fuel, and oxidant gas are supplied to the hot module 10. In this embodiment, when the gas route is the normal route, the raw fuel is supplied to the vaporization unit 12, the reforming unit 13, and the cell stack 14 via the desulfurization unit 11, and the oxidant gas is supplied to the cell stack 14 via the second heat exchanger 16. On the other hand, when the gas route is the bypass route, the raw fuel is supplied to the combustion unit 15 via the desulfurization unit 11, and the oxidant gas is supplied directly to the combustion unit 15. The reforming water is supplied to the vaporization unit 12.

[0028] The inner container 10H has thermal insulation properties and houses the desulfurization section 11, the vaporization section 12, the reforming section 13, the cell stack 14, the combustion section 15, the second heat exchanger 16, the combustion catalyst section 17, the raw fuel flow passage L11, the first fuel gas flow passage L12, the first oxidant gas flow passage L13, the second fuel gas flow passage L14, the second oxidant gas flow passage L15, and the combustion exhaust gas flow passage L16.

[0029] [Desulfurization section] The raw fuel is supplied to the desulfurization unit 11 via the raw fuel supply passage L3. The desulfurization unit 11 removes sulfur contained in the raw fuel. The desulfurization method used by the desulfurization unit 11 is, for example, a hydrodesulfurization method.

[0030] In addition, the desulfurization unit 11 is connected to the vaporization unit 12 via a raw fuel flow passage L11 through which the raw fuel can flow, and the raw fuel after desulfurization by the desulfurization unit 11 is supplied to the vaporization unit 12 via the raw fuel flow passage L11.

[0031] [Vaporization section] In addition to the raw fuel and reforming water, combustion heat generated in the combustion unit 15 (described later) is supplied to the vaporization unit 12. The vaporization unit 12 vaporizes the reforming water by utilizing the combustion heat to generate steam. The vaporization unit 12 supplies a mixed gas obtained by mixing the generated steam and raw fuel to the reforming unit 13.

[0032] [Modification section] The reforming unit 13 generates fuel gas by steam reforming the mixed gas (raw fuel). The reforming unit 13 generates fuel gas by steam reforming the mixed gas by utilizing the combustion heat generated in the combustion unit 15.

[0033] The reforming section 13 is connected to the cell stack 14 via a first fuel gas flow passage L12 through which fuel gas can flow, and the fuel gas generated in the reforming section 13 is supplied to the cell stack 14 via the first fuel gas flow passage L12.

[0034] [Cell stack] The cell stack 14 generates electricity based on the fuel gas and the oxidant gas. The cell stack 14 is configured by stacking a plurality of cells C (an example of a fuel cell), and each cell C generates electricity by chemically reacting hydrogen contained in the fuel gas with oxygen contained in the oxidant gas. In this embodiment, the cells C are solid oxide fuel cells and have an anode (combustion electrode), a cathode (air electrode), and an electrolyte. For this reason, the fuel cell system in this embodiment is also referred to as a solid oxide fuel cell system.

[0035] A first fuel gas flow passage L12 is connected to the anode, and fuel gas is supplied through the first fuel gas flow passage L12. The anode is also connected to the combustion section 15 through a second fuel gas flow passage L14, through which anode off-gas can flow. Fuel gas not used for power generation at the anode (anode off-gas) is supplied to the combustion section 15 through the second fuel gas flow passage L14.

[0036] The cathode is connected to a first oxidant gas flow channel L13 through which an oxidant gas can flow, and the oxidant gas is supplied via the first oxidant gas flow channel L13. In this embodiment, a second heat exchanger 16 is disposed midway through the first oxidant gas flow channel L13. That is, the cathode is connected to the oxidant gas supply channel L4 via the second heat exchanger 16, and the oxidant gas is supplied to the cathode after heat exchange in the second heat exchanger 16.

[0037] The cathode is connected to the combustion section 15 via a second oxidant gas flow passage L15 through which cathode offgas can flow. The oxidant gas (cathode offgas) not used for power generation at the cathode is supplied to the combustion section 15 via the second oxidant gas flow passage L15. Note that, hereinafter, the fuel gas (anode offgas) and oxidant gas (cathode offgas) not used for power generation may be collectively referred to as offgas (excess gas).

[0038] [Combustion section] The combustion unit 15 generates combustion heat by combusting the anode off-gas and the cathode off-gas (the combustible components contained in the anode off-gas and the oxygen contained in the cathode off-gas). In this embodiment, when the gas route is the bypass route, the combustion unit 15 generates combustion heat by combusting the raw fuel and the oxidant gas (the combustible components contained in the raw fuel and the oxygen contained in the oxidant gas).

[0039] The combustion unit 15 has an ignition unit 151 (an example of an igniter) that can be ignited. The combustion unit 15 is ignited by the ignition unit 151 and starts combustion. When the combustion unit 15 starts combustion, it generates combustion heat to raise the temperature of the internal space of the hot module 10 (the vaporization unit 12 and the reforming unit 13) and generate combustion exhaust gas.

[0040] The combustion exhaust gas is led to the outside of the hot module 10 via a combustion exhaust gas flow passage L16. The combustion exhaust gas flow passage L16 is connected to the combustion section 15 (or a combustion vessel 11H that houses the combustion section 15).

[0041] A second heat exchanger 16 is disposed in the combustion exhaust gas flow passage L16, and a combustion catalyst unit 17 is disposed at the downstream end of the combustion exhaust gas flow passage L16 (the downstream end in the flow direction of the combustion exhaust gas). Therefore, the combustion exhaust gas flowing through the combustion exhaust gas flow passage L16 passes through the second heat exchanger 16 and the combustion catalyst unit 17 and is discharged to the outside of the inner container 10H.

[0042] [Second heat exchanger] In the second heat exchanger 16, heat is exchanged between the combustion exhaust gas discharged from the combustion section 15 and the oxidant gas supplied from the oxidant gas supply section 4. As a result, the temperature of the combustion exhaust gas decreases and the temperature of the oxidant gas increases.

[0043] [Combustion catalyst section] The combustion catalyst section 17 uses oxygen to catalytically combust hydrogen, carbon monoxide, and the like contained in the combustion exhaust gas, thereby discharging the catalytically combusted combustion exhaust gas to the outside of the inner container 10H.

[0044] [Bypass section] The bypass section 18 is provided to stabilize combustion by the combustion section 15. More specifically, the bypass section 18 is configured to be able to switch the gas route through which at least one of the supply gas (raw fuel and / or oxidant gas) supplied to the combustion section 15 and the exhaust gas (combustion exhaust gas) discharged from the combustion section 15 flows between a normal route and a bypass route which has a lower pressure loss than the gas route.

[0045] The normal route is a gas route that is set when combustion by the combustion unit 15 is stable, and the bypass route is a gas route that is set when combustion by the combustion unit 15 is unstable. By switching the gas route from the normal route to the bypass route, combustion by the combustion unit 15 becomes stable. When the control unit 1 determines that a predetermined (preset) stability condition is satisfied, it determines that combustion by the combustion unit 15 has transitioned to a stable state, and switches the gas route from the bypass route to the normal route.

[0046] In this embodiment, the start timing of the bypass route is when the cell stack 14 is started (when operation starts or shortly before operation starts). In this embodiment, the start timing is the point in time when the ignition unit 151 starts ignition and the combustion unit 15 ignites. The start timing may not be at the time of start-up, but may be at the time of ignition after a misfire. The end timing is the point in time when the control unit 1 determines that combustion by the combustion unit 15 has transitioned to a stable state.

[0047] The stable condition may be, for example, (1) a condition that the elapsed time from the time of ignition or ignition exceeds a predetermined first threshold time, (2) a condition that the temperature indicated by a temperature sensor (not shown) configured to be able to acquire the temperature of the combustion unit 15 exceeds a predetermined threshold temperature, (3) a condition that the amount of change (slope) of the temperature indicated by the temperature sensor (not shown) is equal to or greater than a predetermined first set amount of change and less than a predetermined second set amount of change, (4) a condition that the value indicated by a flame detector (not shown) configured to be able to detect a flame of the combustion unit 15 (flame detection result) is stable (the duration of the current supply during which the output signal (power) of the flame detector is equal to or greater than a predetermined power threshold (a state indicating a high level) is equal to or greater than a predetermined second threshold time), (5) a condition that the inside of the inner container 10H, the combustion unit 15, and / or the upstream side of the combustion unit 15 (the raw fuel supply path L3 outside the inner container 10H, the oxygen outside the inner container 10H) is stable, or (6) a condition that the inside of the inner container 10H, the combustion unit 15, and / or the upstream side of the combustion unit 15 (the raw fuel supply path L3 outside the inner container 10H, the oxygen outside the inner container 10H) is stable, or (7) a condition that the inside of the inner container 10H, the combustion unit 15, and / or the upstream side of the combustion unit 15 (the raw fuel supply path L3 outside the inner container 10H, the oxygen outside the inner container 10H) is stable, or (8) a condition that the inside of the inner container 10H, the combustion unit 15, and / or the upstream side of the combustion unit 15 (the raw fuel supply path L4 outside the inner container 10H, the oxygen outside the inner container 10H) is stable, or (9) a condition that the inside of the inner container 10H, the combustion unit The conditions include (5) that the pressure indicated by a pressure sensor (not shown) configured to be able to measure the pressure in the vicinity of the oxidizing agent gas supply path L4, etc. is stable (the pressure duration during which the pressure is within a predetermined threshold pressure range and / or the standard deviation of the pressure over a certain period of time is below the threshold is a predetermined third threshold time or longer), (6) that the flow rate of the raw fuel and / or oxidizing gas is stable (the flow rate is within a predetermined flow rate threshold range and / or the flow rate duration during which the standard deviation of the flow rate over a certain period of time is below the threshold is a predetermined fourth threshold time or longer), and (7) that the power consumption (duty ratio) of auxiliary equipment (e.g., blower 31 and / or blower 41) is stable (the power consumption is within a predetermined power consumption threshold range and / or the power consumption duration during which the standard deviation of the power consumption over a certain period of time is below the threshold is a predetermined fifth threshold time or longer).

[0048] Information indicating the threshold temperature, the first set amount of change, the second set amount of change, the power threshold, the threshold pressure, the flow rate threshold, the power consumption threshold, the first to fifth threshold times, etc. is stored in the storage unit 101. The elapsed time is measured by a timer included in the control unit 1.

[0049] In this embodiment, when the control unit 1 determines that at least one of the conditions (1) to (7) is satisfied, it determines that the combustion by the combustion unit 15 has transitioned to a stable state. Note that the control unit 1 may also determine that the combustion by the combustion unit 15 has transitioned to a stable state based on a stability condition that is a combination of one or more of the conditions (1) to (7).

[0050] The bypass unit 18 is configured to allow the raw fuel, oxidant gas, and / or combustion exhaust gas to bypass the cell stack 14 and / or the second heat exchanger 16 inside the hot module 10. In detail, the bypass unit 18 includes a raw fuel bypass path LB1, an oxidant gas bypass path LB2, a combustion exhaust gas bypass path LB3, a first adjustment valve 181 (an example of a raw fuel switching unit), a second adjustment valve 182 (an example of an oxidant gas switching unit), and a third adjustment valve 183 (an example of a combustion exhaust gas switching unit). In this embodiment, each of the first adjustment valve 181, the second adjustment valve 182, and the third adjustment valve 183 is an electromagnetic valve.

[0051] The control unit 1 controls the operation of each of the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183 to switch the state of each of the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183. This switches the gas route between the normal route and the bypass route. Hereinafter, the state of each of the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183 when the gas route is the normal route will be referred to as the normal state (in this embodiment, the valve closed state), and the state of each of the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183 when the gas route is the bypass route will be referred to as the bypass state (in this embodiment, the valve open state). In this embodiment, when starting up the cell stack 14, the control unit 1 switches at least one of the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183 to the bypass state, and performs an ignition process to activate the ignition unit 151 for ignition.

[0052] The raw fuel bypass channel LB1 allows the raw fuel supplied from the desulfurization unit 11 to flow through. The raw fuel bypass channel LB1 is connected to the raw fuel flow channel L11 and the second fuel gas flow channel L14. Specifically, the upstream end of the raw fuel bypass channel LB1 in the flow direction of the raw fuel is connected to the raw fuel flow channel L11 upstream of the vaporization unit 12, and the downstream end is connected to the second fuel gas flow channel L14. The raw fuel bypass channel LB1 is a flow path for bypassing (short-cutting) the raw fuel to the second fuel gas flow channel L14 (before the combustion unit 15). The raw fuel flowing through the raw fuel bypass channel LB1 is led to the combustion unit 15, bypassing the vaporization unit 12, the reforming unit 13, and the cell stack 14 (without passing through the vaporization unit 12, the reforming unit 13, and the cell stack 14). It is sufficient that the raw fuel flowing through the raw fuel bypass channel LB1 is led to the combustion unit 15, bypassing at least the cell stack 14.

[0053] The oxidant gas bypass channel LB2 allows the oxidant gas supplied from the oxidant gas supply unit 4 to flow through. In the flow direction of the oxidant gas, the upstream end of the oxidant gas bypass channel LB2 is connected to the first oxidant gas flow channel L13, and the downstream end is connected to the second oxidant gas flow channel L15. More specifically, in the flow direction of the oxidant gas, the upstream end of the oxidant gas bypass channel LB2 is connected upstream of the second heat exchanger 16 arranged in the middle of the first oxidant gas flow channel L13, and the downstream end is connected to the second oxidant gas flow channel L15. In other words, the oxidant gas bypass channel LB2 is a flow path for bypassing (short-cutting) the oxidant to the second oxidant gas flow channel L15 (before reaching the combustion unit 15), and the oxidant gas flowing through the oxidant gas bypass channel LB2 is guided to the combustion unit 15, bypassing the second heat exchanger 16 and the cell stack 14 (without passing through the second heat exchanger 16 and the cell stack 14). The oxidant gas flowing through the oxidant gas bypass passage LB2 only needs to be guided to the combustion section 15 while bypassing at least the cell stack .

[0054] The combustion exhaust gas bypass channel LB3 allows the combustion exhaust gas generated in the combustion section 15 to flow through. The combustion exhaust gas bypass channel LB3 is connected to the combustion exhaust gas flow channel L16 and guides the combustion exhaust gas to the outside of the hot module 10. More specifically, in the flow direction of the combustion exhaust gas, the upstream end of the combustion exhaust gas bypass channel LB3 is connected to the combustion exhaust gas flow channel L16 upstream of the second heat exchanger 16, and the downstream end is connected to the external combustion exhaust gas channel L5 downstream of the first heat exchanger 51. In other words, the combustion exhaust gas bypass channel LB3 is a flow path for bypassing (short-cutting) the combustion exhaust gas from the combustion section 15 to the outside of the hot module 10, and the combustion exhaust gas flowing through the combustion exhaust gas bypass channel LB3 is guided from the combustion section 15 to the outside of the hot module 10, bypassing the second heat exchanger 16 and the first heat exchanger 51 (without passing through the second heat exchanger 16 and the first heat exchanger 51). The combustion exhaust gas flowing through the combustion exhaust gas bypass passage LB3 only needs to bypass at least the first heat exchanger 51 and be guided to the outside of the hot module 10 (fuel cell system 100).

[0055] The first adjustment valve 181 is disposed in the raw fuel bypass passage LB1, and switches the destination of the raw fuel flowing through the raw fuel bypass passage L11 between the raw fuel bypass passage L11 (vaporization section 12) and the raw fuel bypass passage LB1 (combustion section 15). More specifically, in the bypass state, the first adjustment valve 181 is controlled (opened) so that the raw fuel flows through the raw fuel bypass passage LB1 and the second fuel gas passage L14 to the combustion section 15, and in the normal state, the first adjustment valve 181 is controlled (closed) so that the raw fuel flows through the raw fuel passage L11 to the vaporization section 12, the reforming section 13, the first fuel gas passage L12, the cell stack 14, the second fuel gas passage L14, and the combustion section 15.

[0056] The second adjustment valve 182 is disposed in the oxidant gas bypass passage LB2, and switches the destination of the oxidant gas flowing through the first oxidant gas passage L13 between the first oxidant gas passage L13 (second heat exchanger 16) and the second oxidant gas passage L15 (combustion section 15). More specifically, in the bypass state, the second adjustment valve 182 is controlled (opened) so that the oxidant gas flows through the oxidant gas bypass passage LB2 and the second oxidant gas passage L15 to the combustion section 15, and in the normal state, the oxidant gas flows through the first oxidant gas passage L13 to the second heat exchanger 16, and then flows through the cell stack 14, the second oxidant gas passage L15, and the combustion section 15.

[0057] The third adjustment valve 183 is disposed in the combustion exhaust gas bypass passage LB3, and switches the destination of the combustion exhaust gas flowing through the combustion exhaust gas flow passage L16 between the second heat exchanger 16 and the outside of the hot module 10 (downstream of the first heat exchanger 51). More specifically, in the bypass state, the third adjustment valve 183 is controlled (opened) so that the combustion exhaust gas flows via the combustion exhaust gas bypass passage LB3 to the external combustion exhaust gas passage L5 downstream of the first heat exchanger 51, and in the normal state, the third adjustment valve 183 is controlled (closed) so that the combustion exhaust gas flows via the combustion exhaust gas flow passage L16 to the second heat exchanger 16.

[0058] [Gas flow] Next, the gas flows within the hot module 10 in the bypass route (bypass state) and the normal route (normal state) will be described with reference to Figures 2 and 3. Figure 2 is a diagram showing the flows of the raw fuel, oxidant gas, and combustion exhaust gas in the bypass route, and Figure 3 is a diagram showing the flows of the raw fuel, oxidant gas, and combustion exhaust gas in the normal route. When the ignition unit 151 is ignited (when the hot module 10 starts operating), the control unit 1 sets the gas route to the bypass route (performs ignition processing) by opening each of the first adjustment valve 181, the second adjustment valve 182, and the third adjustment valve 183.

[0059] [Bypass route] 2, in the bypass route (bypass state), the raw fuel desulfurized in the desulfurization unit 11 flows through the raw fuel flow passage L11 to a position where it connects with the raw fuel bypass passage LB1, and then flows through the raw fuel bypass passage LB1 and the second fuel gas flow passage L14, and is then led to the combustion unit 15. At the same time, the oxidant gas flows through the first oxidant gas flow passage L13 to a position where it connects with the oxidant gas bypass passage LB2, and then flows through the oxidant gas bypass passage LB2 and the second oxidant gas flow passage L15, and is then led to the combustion unit 15.

[0060] The combustion exhaust gas generated by burning the raw fuel and the oxidant gas in the combustion section 15 flows through the combustion exhaust gas flow passage L16 to a position where it connects with the combustion exhaust gas bypass passage LB3, then flows through the combustion exhaust gas bypass passage LB3 and is led to a position downstream of the first heat exchanger 51 of the external combustion exhaust gas passage L5.

[0061] After performing the ignition process, when the control unit 1 determines that the combustion in the combustion unit 15 has transitioned to a stable state, it switches the adjustment valves (first adjustment valve 181, second adjustment valve 182, and third adjustment valve 183) that are in the bypass state to a closed state (normal state).

[0062] [Normal Route] As shown in FIG. 3 , in the normal route (normal state), the raw fuel desulfurized in the desulfurization unit 11 flows through the raw fuel flow channel L11, then flows through the vaporization unit 12, the reforming unit 13, and the first fuel gas flow channel L12, and is supplied to the cell stack 14 as fuel gas. Of the fuel gas supplied to the cell stack 14, the fuel gas (anode off-gas) that was not used in the reaction is guided to the combustion unit 15 via the second fuel gas flow channel L14. At the same time, the oxidant gas flows through the first oxidant gas flow channel L13, exchanges heat with the combustion exhaust gas in the second heat exchanger 16, is heated, and is supplied to the cell stack 14. Of the oxidant gas supplied to the cell stack 14, the oxidant gas (cathode off-gas) that was not used in the reaction is supplied to the combustion unit 15 via the second oxidant gas flow channel L15.

[0063] The combustion exhaust gas generated by combusting the anode off-gas and the cathode off-gas in the combustion section 15 flows through the combustion exhaust gas flow passage L16, exchanges heat with the oxidant gas supplied from the oxidant gas supply section 4 in the second heat exchanger 16 to lower its temperature, then passes through the combustion catalyst section 17 and is discharged to the outside of the hot module 10. The combustion exhaust gas discharged to the outside of the hot module 10 flows into the external combustion exhaust gas passage L5, exchanges heat with a refrigerant in the first heat exchanger 51 arranged midway through the external combustion exhaust gas passage L5 to further lower its temperature, and is then discharged to the outside of the fuel cell system 100.

[0064] As described above, according to this embodiment, the raw fuel, oxidant gas, and / or combustion exhaust gas bypass at least the cell stack 14 and / or the first heat exchanger 51, thereby reducing the pressure loss of the gas supplied to the combustion section 15 and / or the gas discharged from the combustion section 15, and stabilizing combustion by the combustion section 15.

[0065] <Another embodiment> 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.

[0066] (1) The configuration of the hot module 10 in the above embodiment is an example, and the configuration within the hot module 10 can be changed as appropriate. For example, the raw fuel may be supplied directly to the reforming unit 13 from the raw fuel supply unit 3 without going through the vaporization unit 12. Furthermore, the desulfurization unit 11 may be arranged outside the hot module 10, and the raw fuel may be supplied to the vaporization unit 12 after being desulfurized by the desulfurization unit 11 arranged outside the hot module 10.

[0067] (2) In the above embodiment (FIG. 2), the case where all of the gas routes for the raw fuel, oxidant gas, and combustion exhaust gas are set as bypass routes has been described, but it is sufficient that at least one of the gas routes for the raw fuel, oxidant gas, and combustion exhaust gas is set as a bypass route. In other words, it is sufficient that at least one of the first adjustment valve 181, the second adjustment valve 182, and the third adjustment valve 183 is set to a bypass state.

[0068] In the case of (3)(2), the bypass unit 18 may omit at least one of the raw fuel bypass channel LB1, the oxidant gas bypass channel LB2, and the flue gas bypass channel LB3. That is, the bypass unit 18 may include at least one of the raw fuel bypass channel LB1, the oxidant gas bypass channel LB2, and the flue gas bypass channel LB3. Because the amount (flow rate) of oxidant gas supplied to the combustion unit 15 is greater than that of the raw fuel, it is preferable that the bypass unit 18 include the oxidant gas bypass channel LB2 rather than the raw fuel bypass channel LB1. Furthermore, when the bypass unit 18 is configured to include only one bypass line, it is preferable that the bypass unit 18 include the flue gas bypass channel LB3. This allows the gas to flow smoothly into the combustion unit 15 and the gas to be discharged from the combustion unit 15, making combustion by the combustion unit 15 more stable. For example, when the raw fuel bypass path LB1 is omitted, the bypass unit 18 may have a first buffer tank that is arranged between the blower 31 of the raw fuel supply unit 3 and the combustion unit 15, preferably between the cell stack 14 and the combustion unit 15, and that is capable of storing the raw fuel or fuel gas. This allows the raw fuel or fuel gas to be smoothly supplied to the combustion unit 15. For example, when the oxidant gas bypass path LB2 is omitted, the bypass unit 18 may have a second buffer tank that is arranged between the blower 41 of the oxidant gas supply unit 4 and the combustion unit 15, preferably between the cell stack 14 and the combustion unit 15, and that is capable of storing the oxidant gas. This allows the oxidant gas to be smoothly supplied to the combustion unit 15.

[0069] (4) In the above embodiment, the regulating valve is a solenoid valve. However, the regulating valve may be a thermostatic expansion valve that closes when the temperature reaches or exceeds a threshold value.

[0070] (5) The regulating valves may further include regulating valves other than the first regulating valve 181, the second regulating valve 182, and the third regulating valve 183. For example, the regulating valve may further include a regulating valve that is arranged downstream of the connection point of the raw fuel flow passage L11 with the raw fuel bypass passage LB1 and that closes when the flow route is switched to the bypass route. Alternatively, the regulating valve may further include a regulating valve that is arranged downstream of the connection point of the first oxidant gas flow passage L13 with the oxidant gas bypass passage LB2 and that closes when the flow route is switched to the bypass route. Alternatively, the regulating valve may further include a regulating valve that is arranged downstream of the connection point of the combustion exhaust gas flow passage L16 with the combustion exhaust gas bypass passage LB3 and that closes when the flow route is switched to the bypass route.

[0071] (6) After switching the regulating valves (first regulating valve 181, second regulating valve 182, and third regulating valve 183) that are in the bypass state among first regulating valve 181, second regulating valve 182, and third regulating valve 183 to the closed state (normal state), if combustion by combustion unit 15 is unstable, control unit 1 may switch at least one of first regulating valve 181, second regulating valve 182, and third regulating valve 183 to the bypass state. If control unit 1 determines that combustion is unstable (the above stability condition is not satisfied) even after switching between the normal state (normal route) and the bypass state (bypass route) multiple times, control unit 1 may notify of an error via a notification unit (display, speaker, etc.) provided in fuel cell system 100.

[0072] (7) The present invention is also applicable to fuel cells other than solid oxide fuel cells. [Industrial Applicability]

[0073] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0074] 1: Control unit (operation control unit) 2: Reformed water supply section 3: Raw fuel supply section 4: Oxidant gas supply section 10: Hot Module 10H:Inner container (container) 12: Vaporization section 13: Modification section 14: Cell stack 15: Combustion section 16: Second heat exchanger (oxidant gas preheating heat exchanger) 51: 1st heat exchanger (heat exchanger) 100: Fuel cell system 151: Ignition part (igniter) 181: First adjusting valve (raw fuel switching section) 182: Second adjusting valve (oxidizer gas switching section) 183: Third adjusting valve (combustion exhaust gas switching section) C: Cell (fuel cell) L11: Raw fuel distribution path (raw fuel supply path) L12: First fuel gas flow passage (fuel gas supply passage) L13: First oxidant gas flow passage (oxidant gas supply passage) L14: Second fuel gas flow passage (anode off-gas supply passage) L15: Second oxidant gas flow passage (cathode off-gas supply passage) L16: Combustion exhaust gas flow passage (combustion exhaust gas passage) LB1: Raw fuel bypass LB2: Oxidant gas bypass path LB3: Combustion exhaust gas bypass

Claims

1. a hot module having a container, the container containing a cell stack having a plurality of fuel cells each having an anode and a cathode, a reforming section which generates fuel gas by steam reforming a raw fuel, a fuel gas supply channel which supplies the fuel gas from the reforming section to the anode, an oxidant gas supply channel which supplies oxidant gas to the cathode, a combustion section which combusts anode off-gas and cathode off-gas discharged from the cell stack, an anode off-gas supply channel which supplies the anode off-gas discharged from the cell stack to the combustion section, a cathode off-gas supply channel which supplies the cathode off-gas discharged from the cell stack to the combustion section, and a combustion exhaust gas channel which 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 oxidant gas supply unit that supplies the oxidant gas from outside 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; a heat exchanger that exchanges heat between the combustion exhaust gas flowing through the combustion exhaust gas passage and a refrigerant to cool the combustion exhaust gas, a raw fuel bypass passage that supplies the raw fuel from the raw fuel supply unit to the anode offgas supply passage, bypassing the reforming unit and the cell stack; an oxidant gas bypass passage that supplies the oxidant gas from the oxidant gas supply unit to the cathode offgas supply passage, bypassing the cell stack; and a combustion exhaust gas bypass passage that supplies the combustion exhaust gas from the combustion unit to the combustion exhaust gas passage, bypassing the heat exchanger.

2. a raw fuel switching unit that can switch between a normal state in which the raw fuel is supplied from the raw fuel supply unit to the reforming unit and a bypass state in which the raw fuel is supplied from the raw fuel supply unit to the raw fuel bypass path; an oxidant gas switching unit that can switch between a normal state in which the oxidant gas is supplied from the oxidant gas supply unit to the cell stack and a bypass state in which the oxidant gas is supplied from the oxidant gas supply unit to the oxidant gas bypass path; a combustion exhaust gas switching unit that is switchable between a normal state in which the combustion exhaust gas is supplied from the combustion unit to the heat exchanger and a bypass state in which the combustion exhaust gas is supplied from the combustion unit to the combustion exhaust gas bypass path, 2. The fuel cell system according to claim 1, further comprising an operation control unit that controls operations of the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit.

3. 3. The fuel cell system according to claim 2, wherein the operation control unit switches at least one of the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit to the bypass state when the cell stack is started up, and performs an ignition process to ignite an igniter provided inside the combustion unit.

4. 4. The fuel cell system of claim 3, wherein, when the operation control unit determines that the combustion state of the combustion unit is stable and satisfies a predetermined stability condition after performing the ignition process, the operation control unit switches the raw fuel switching unit, the oxidant gas switching unit, and the combustion exhaust gas switching unit that have been switched to the bypass state back to the normal state.

5. the hot module has an oxidant gas preheating heat exchanger that is disposed in the oxidant gas supply channel and the combustion exhaust gas channel and that exchanges heat between the oxidant gas flowing through the oxidant gas supply channel and the combustion exhaust gas flowing through the combustion exhaust gas channel; When the oxidant gas switching unit is in the bypass state, the oxidant gas is supplied from the oxidant gas supply unit to the oxidant gas bypass path, bypassing the oxidant gas preheating heat exchanger and the cell stack, 4. The fuel cell system according to claim 2, wherein when the combustion exhaust gas switching unit is in the bypass state, the combustion exhaust gas is supplied from the combustion unit to the combustion exhaust gas bypass path, bypassing the oxidant gas preheating heat exchanger and the heat exchanger.

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