JP2011159585A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system that can start power generation early by a solid oxide fuel cell (SOFC) when starting up. <P>SOLUTION: The fuel cell system includes: a reformer 1; an SOFC 2; an engine 3 that sucks in off-gas exhausted from the SOFC 2 as part of its fuel; exhaust path control valves 4a and 4b for controlling a destination of an exhaust gas in such a manner that the exhaust gas from the engine 3 may be led to the reformer 1 and/or the SOFC 2 in order to use the exhaust gas from the engine 3 to heat the reformer 1 and/or the SOFC 2; and a control unit 5 for controlling the exhaust path control valves 4a and 4b. The control unit 5, by controlling the exhaust path control valves 4a and 4b, selectively leads the exhaust gas to the SOFC 2 during a period until the temperature of the SOFC 2 rises to a predetermined complete warm-up temperature when the fuel cell system starts up, and then leads the exhaust gas to the reformer 1 after the temperature of the SOFC 2 reaches the complete warm-up temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system including a solid oxide fuel cell (SOFC) and an internal combustion engine.

  The following Patent Document 1 describes a conventional combined power generation facility including an SOFC and an internal combustion engine. In this combined power generation facility, as shown in FIG. 14 of Patent Document 1, the SOFC off-gas is used as part of the fuel of the internal combustion engine, and the exhaust gas of the internal combustion engine is led to the reformer and the SOFC. The reformer and SOFC are preheated.

JP 2008-180131 A

  In general, the SOFC has a power generation efficiency (for example, 45 to 65%) higher than that of a polymer electrolyte fuel cell (PEFC) (for example, 30 to 40%). Furthermore, SOFC has the advantage of being able to control a wider variety of fuels than PEFC. However, since SOFC requires an operating temperature (for example, 600 to 1000 ° C.) higher than that of PEFC (for example, 70 to 90 ° C.), there has been a problem that start-up is slow.

  In the combined power generation facility described in Patent Document 1, the exhaust gas of the internal combustion engine is guided to the reformer and the SOFC, and the reformer and the SOFC are preheated. For this reason, it is considered that the combined power generation facility can be started quickly.

  By the way, when a fuel cell system including an SOFC and an internal combustion engine is used as a power source for an electric vehicle, for example, it is desirable that electricity is supplied from the fuel cell as soon as possible at the time of startup. For this reason, in the fuel cell system, it is desired that power generation by SOFC be started earlier at the time of startup.

  Accordingly, an object of the present invention is to provide a fuel cell system capable of starting power generation at an early stage using a solid oxide fuel cell at the time of startup.

  In order to achieve the above object, a fuel cell system of the present invention is supplied with a reformer that reforms a fuel gas containing a hydrocarbon compound to generate hydrogen gas, and a hydrogen gas generated by the reformer. Solid oxide fuel cell, an internal combustion engine that sucks off-gas discharged from the solid oxide fuel cell as part of the fuel, a reformer and a solid oxide fuel that exhaust gas discharged from the internal combustion engine An exhaust path control valve for controlling a destination of the exhaust gas so as to guide the exhaust gas to at least one of the reformer and the solid oxide fuel cell, and an exhaust path control valve for use in heating at least one of the cells; Control means for controlling, and the control means controls the exhaust path control valve to solidify the exhaust gas during the start of the fuel cell system while the temperature of the solid oxide fuel cell rises to a predetermined set temperature. Type fuel Selectively leads to the pond, and, after the temperature of the solid oxide fuel cell has reached the set temperature, guiding the exhaust gas to the reformer, characterized in that.

  In the present invention configured as described above, the control means controls the exhaust path control valve while the temperature of the solid oxide fuel cell (SOFC) rises to a predetermined set temperature when the fuel cell system is started. The exhaust gas is selectively directed to the SOFC. As a result, the exhaust gas is selectively guided to the SOFC immediately after startup, and the SOFC is preferentially warmed up. As a result, the temperature of the SOFC immediately rises immediately after startup.

  Immediately after startup, the exhaust gas is selectively guided to the SOFC and not to the reformer. For this reason, immediately after startup, the temperature of the reformer is low, and the fuel gas is not sufficiently reformed in the reformer. However, if the temperature of the SOFC rises to some extent, so-called internal reforming becomes possible in the SOFC. Internal reforming refers to a phenomenon in which when unreformed fuel gas is supplied to a high-temperature SOFC, a part of the fuel gas is heated and decomposed in the SOFC to generate hydrogen gas. As a result, even if fuel gas that has not been sufficiently reformed is supplied to the SOFC, a power generation reaction starts in the SOFC by performing internal reforming in the SOFC. Once the power generation reaction is started, the power generation reaction is an exothermic reaction, so the SOFC is warmed up autonomously.

  Therefore, according to the present invention, the SOFC is warmed up preferentially by selectively leading the exhaust gas of the internal combustion engine to the SOFC while the temperature of the SOFC immediately after startup rises to a predetermined set temperature. Thus, the internal reforming is performed, so that it is possible to start power generation at an early stage using SOFC.

In the present invention, the set temperature is preferably a complete warm-up temperature that is an operating temperature during steady operation of the solid oxide fuel cell.
If the temperature of the SOFC quickly rises to the complete warm-up temperature, the power generation reaction can be performed efficiently in the SOFC.

In the present invention, the set temperature is preferably a semi-warm temperature that is lower than the operating temperature during steady operation of the solid oxide fuel cell by a predetermined temperature.
If the temperature of the SOFC quickly rises to the half warm-up temperature, the SOFC can be warmed up to some extent by the power generation reaction by internal reforming. In addition, when the temperature of the SOFC rises to the half warm-up temperature before the temperature rises to the full warm-up temperature, the warm-up of the reformer by the exhaust gas can be started early. As a result, reforming of the fuel gas in the reformer is started early. Thereby, efficient power generation by SOFC is started at an early stage.

  In the present invention, preferably, the control means controls the exhaust path control valve so that the exhaust gas is solid-oxidized while the temperature of the solid oxide fuel cell rises to a semi-warm temperature when the fuel cell system is started. After the temperature of the solid oxide fuel cell reaches a semi-warm temperature and further rises to the full warm temperature, the exhaust gas is supplied to the solid oxide fuel cell and the reformer. Both, and after the solid oxide fuel cell temperature reaches full warm-up temperature, the exhaust gas is selectively directed to the reformer.

  Thus, first, while the temperature of the SOFC rises to the half warm-up temperature, the exhaust gas is selectively guided to the SOFC, and the SOFC is preferentially warmed up. As a result, the power generation reaction utilizing internal reforming at SOFC starts early. The exhaust gas is then directed to both the SOFC and the reformer while the SOFC temperature reaches a semi-warm temperature and then rises to a full warm temperature. As a result, the temperature of the SOFC further rises, and the reformer is warmed up to start reforming the fuel gas. As a result, the reformed fuel gas is supplied to the SOFC, and the power generation reaction efficiency of the SOFC is improved. Furthermore, after the temperature of the SOFC reaches the complete warm-up temperature, the SOFC warms up autonomously by a power generation reaction. Therefore, the reformer is efficiently warmed up by introducing the exhaust gas to the reformer. In this way, the entire fuel cell system is warmed up early by controlling the destination of the exhaust gas in accordance with the temperature of the SOFC.

  In the present invention, preferably, the control means controls the exhaust path control valve so that the exhaust gas is solid-oxidized while the temperature of the solid oxide fuel cell rises to a semi-warm temperature when the fuel cell system is started. Select the exhaust gas to the reformer while the reformer temperature rises to the preset temperature after the temperature of the solid oxide fuel cell reaches the judgment device temperature. If the temperature of the solid oxide fuel cell does not reach the complete warm-up temperature after the reformer temperature reaches the set temperature, the exhaust gas is changed into the solid oxide fuel cell and the reformer. Lead to both of the genitalia.

  Thus, first, while the temperature of the SOFC rises to the half warm-up temperature, the exhaust gas is selectively guided to the SOFC, and the SOFC is preferentially warmed up. As a result, the power generation reaction utilizing internal reforming at SOFC starts early. Then, after the SOFC temperature reaches the semi-warm temperature, the exhaust gas is selectively guided to the reformer. As a result, the reformer is efficiently warmed up and fuel gas reforming starts early. As a result, the reformed fuel gas is supplied to the SOFC, and the power generation reaction efficiency of the SOFC is improved. Further, after the temperature of the reformer reaches a predetermined set temperature, if the temperature of the SOFC does not reach the complete warm-up temperature, the exhaust gas is guided to both the SOFC and the reformer. As a result, warming up of the SOFC is promoted while continuing warming up of the reformer. In this way, the entire fuel cell system is warmed up early by controlling the destination of the exhaust gas in accordance with the temperature of the SOFC and the reformer.

  According to the fuel cell system of the present invention, it is possible to start power generation at an early stage using a solid oxide fuel cell at the time of startup.

1 is a schematic diagram showing a basic configuration of a fuel cell system according to a first embodiment of the present invention. It is a block diagram which shows the input-output relationship of the control unit of the fuel cell system by 1st Embodiment of this invention. 2 is a flowchart showing basic control of the fuel cell system according to the first embodiment of the present invention. 3 is a flowchart showing control of the flow of exhaust gas in the fuel cell system according to the first embodiment of the present invention. It is a graph explaining the complete warm-up temperature and semi-warm-up temperature of a solid oxide fuel cell. (A) And (B) is the schematic which shows control of the flow of the exhaust gas in the fuel cell system by 1st Embodiment of this invention. 6 is a flowchart showing control of an exhaust gas flow in a fuel cell system according to a second embodiment of the present invention. (A)-(C) are schematic which shows control of the flow of the exhaust gas in the fuel cell system by 2nd Embodiment of this invention. 6 is a flowchart showing control of an exhaust gas flow in a fuel cell system according to a third embodiment of the present invention. (A)-(D) are the schematic which shows control of the flow of the exhaust gas in the fuel cell system by 3rd Embodiment of this invention.

Hereinafter, embodiments of a fuel cell system of the present invention will be described with reference to the accompanying drawings.
First, the configuration of the fuel cell system according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the basic configuration of the fuel cell system according to the first embodiment.

  As shown in FIG. 1, the fuel cell system according to the first embodiment is a power source for driving an electric vehicle and reforms a fuel gas containing a hydrocarbon compound to generate hydrogen gas during operation. A solid oxide fuel cell (SOFC) 2 to which hydrogen gas generated by the reformer is supplied, an engine 3 as an internal combustion engine that sucks off-gas discharged from the SOFC as part of the fuel, In order to use the exhaust gas discharged from the internal combustion engine for heating at least one of the reformer 1 and the SOFC 2, the destination of the exhaust gas is controlled so as to guide the exhaust gas to at least one of the reformer 1 and the SOFC 2. Exhaust path control valves 4a and 4b and control means 5 for controlling the exhaust path control valves 4a and 4b are provided.

  As the reformer 1, any conventionally known suitable one can be used. In the reformer 1, for example, by adding water vapor to a fuel gas containing a hydrocarbon compound such as methane at a high temperature of 600 to 800 ° C., the hydrocarbon compound is decomposed to generate hydrogen. In the present embodiment, liquefied petroleum gas (LPG) is used as the fuel gas.

  In FIG. 1, the path of the fuel gas supplied to the reformer 1 is indicated by a solid line 10a. Further, the illustration of the path of water supplied to the reformer 1 is omitted. 1 are guided by pipes (not shown) provided according to the paths.

  The reformer 1 is provided with a heat exchange mechanism (not shown) in order to heat the reformer 1 with the heat of the exhaust gas and off-gas. Any suitable structure can be adopted as the heat exchange mechanism. For example, as a heat exchange mechanism, the periphery of the reformer 1 may be covered with a jacket that allows exhaust gas and off gas to pass separately, and a plurality of pipes that allow exhaust gas and off gas to pass separately inside the reformer 1. It may be provided.

  The hydrogen gas generated in the reformer 1 and the unreformed fuel gas that has passed through the reformer 1 are supplied to the SOFC 2. Air (Air) is also supplied to the SOFC 2. In FIG. 1, the path of hydrogen gas and unreformed fuel gas supplied from the reformer 1 to the SOFC 2 is indicated by a solid line 10b, and the path of air supplied to the SOFC 2 is indicated by a broken line 11a.

  As the SOFC2, any conventionally known suitable one can be used. The SOFC 2 in this embodiment also includes a fuel electrode (anode) 21 and an air electrode (cathode) 22, as in the conventionally known one. Fuel gas or the like from the reformer 1 is supplied to the fuel electrode 21. Air is supplied to the air electrode 22.

  In the SOFC 2, hydrogen in the fuel gas supplied to the fuel electrode 21 and oxygen in the air supplied to the air electrode 22 react to generate water, and a power generation reaction that generates electricity is performed. The electricity generated by the power generation reaction is sent to a secondary battery (not shown) and a drive motor (not shown) connected to the ceramic electrodes of the fuel electrode 21 and the air electrode 22, respectively.

  Further, the SOFC 2 is provided with a heat exchange mechanism (not shown) in order to heat the SOFC 2 with the heat of the exhaust gas. Any suitable structure can be adopted as the heat exchange mechanism. For example, as the heat exchange mechanism, the periphery of SOFC 2 may be covered with a jacket through which exhaust gas passes, or a plurality of pipes through which exhaust gas passes may be provided inside SOFC 2.

  Conventional SOFC has conventionally required a high operating temperature of 800 to 1000 ° C. in order to perform a power generation reaction. However, in recent years, an SOFC having an operating temperature lowered to, for example, about 650 ° C. has been developed. Since the power generation reaction is an exothermic reaction, when the power generation reaction starts, the SOFC is heated independently, and the operating temperature of the SOFC is maintained. Therefore, the heating of the SOFC 2 by the exhaust gas is particularly useful for warming up at the time of starting the SOFC.

  The off gas discharged from the SOFC 2 is supplied to the intake port 31 of the engine 3 via a heat exchange mechanism (not shown) of the reformer 1. In the present embodiment, both the gas discharged from the fuel electrode 21 of the SOFC 2 and the gas discharged from the air electrode 22 are supplied to the engine 3 as off-gas. In FIG. 1, the path of gas containing unreacted fuel gas supplied from the fuel electrode 21 to the engine 3 is indicated by a solid line 10 c, and the path of air supplied from the air electrode 22 to the engine 3 is indicated by a broken line 11 b.

  Since the operating temperature of the SOFC 2 is high, the off-gas discharged from the SOFC 2 is usually as high as several hundred degrees Celsius. Such high temperature off gas is heat exchanged with the reformer 1 in the heat exchange mechanism of the reformer 1. As a result, the reformer 1 is heated while the off-gas is cooled. Then, the cooled off gas is supplied to the engine 3. Thereby, the effective utilization of the exhaust heat of off gas can be aimed at.

  As the engine 3, any conventionally known internal combustion engine having an intake / exhaust cycle can be used. For example, a reciprocating engine may be employed as the engine 3 or a rotary engine may be employed. In FIG. 1, the example of the reciprocating engine provided with the piston 33 is shown typically. When driving the engine 3 as an internal combustion engine, in order to optimize the combustion in the engine 3, fuel (LPG) and air (Air) are supplied to the intake port 31 of the engine 3 together with off-gas.

  The engine 3 is not a driving source for running the vehicle, and the piston rod 34 of the engine 3 is connected to the motor / generator 6. As a result, the engine 3 can be driven as an internal combustion engine using off-gas as part of the fuel, and can be supplementarily generated by the motor / generator 6. In addition, the piston 33 of the engine 3 can be moved by driving the motor / generator 6 as a motor by using electricity charged in the secondary battery.

  By using the off gas as a part of the fuel in the engine 3, high unreacted hydrogen contained in the off gas can be burned, and unreformed hydrocarbon compounds contained in the off gas can also be burned. In this way, by burning off-gas in the engine 3, it is possible to avoid releasing highly flammable hydrogen gas into the atmosphere, and to reduce exhaust gas purification by reducing hydrocarbon compounds in the off-gas. Can be planned.

  Furthermore, the engine 3 fulfills the function of a blower required in a fuel cell unit such as a normal SOFC. Specifically, the engine 3 sucks off gas from the intake port 31 in the intake cycle. As a result, fuel gas or the like is sucked from the reformer 1 at the fuel electrode 21 of the SOFC 2, and air is sucked at the air electrode 22. Further, in the reformer 1, the fuel gas is sucked. Therefore, the fuel cell unit according to the present embodiment does not require a blower for sending fuel gas to the reformer and the SOFC, nor a blower for sending air to the SOFC.

  The engine 3 exhausts exhaust gas having a high temperature of several hundred degrees Celsius from the exhaust port 32. The exhaust gas is guided to the heat exchange mechanism of at least one of the reformer 1 and the SOFC 2 and used for heating them. Thereby, the effective use of the exhaust heat of exhaust gas can be aimed at.

  The exhaust path control valves 4a and 4b are provided on the exhaust gas path, and control the destination of the exhaust gas so as to guide the exhaust gas to at least one of the reformer 1 and the SOFC 2. Specifically, the exhaust gas is guided to the reformer 1 when the exhaust path control valve 4a is open and the exhaust path control valve 4b is closed. On the other hand, when the exhaust path control valve 4a is closed and the exhaust path control valve 4b is open, the exhaust gas is guided to the SOFC 2. Further, when both the exhaust path control valves 4a and 4b are open, the exhaust gas is guided to both the reformer 1 and the SOFC 2. The ratio of the exhaust gas led to the reformer 1 and the SOFC 2 is adjusted by the opening degree of the exhaust path control valves 4a and 4b.

  In FIG. 1, during steady operation of the fuel cell system, the exhaust path control valve 4 a is opened and the exhaust path control valve 4 b is closed, and the exhaust gas path that is led from the engine 3 to the reformer 1 and is exhausted. Is indicated by a thick line 12. Further, in FIG. 1, a part of a path of gas exhausted from the engine 3 to the SOFC 2 is indicated by a two-dot chain line.

  The control means 5 is provided as a control unit 5. FIG. 2 is a block diagram showing the input / output relationship of the control unit 5. As shown in FIG. 2, the control unit 5 includes an ignition switch (IG SW) on information 51, an engine speed 52, a vehicle speed 53, an accelerator opening 54, and a state of charge of the secondary battery. : SOC) 55, SOFC temperature 56, and reformer temperature 57 are input. These pieces of information are detected by sensors (not shown).

  The control unit 5 controls the opening and closing of the exhaust path control valves 4a and 4b when the fuel cell system is activated, and the exhaust gas exhausted from the engine 3 is supplied to the SOFC2 while the temperature Ts of the SOFC2 rises to a predetermined set temperature. Then, after the temperature Ts of the SOFC 2 reaches the set temperature, the exhaust gas is guided to the reformer 1. The detailed control contents of the exhaust path control valves 4a and 4b at the time of activation will be described later.

  Further, the control unit 5 not only controls the opening and closing of the exhaust path control valves 4a and 4b, but also controls the opening and closing of the fuel cell fuel control valve 4c that controls the amount of fuel gas supplied to the reformer 1. In addition to the off-gas, the control unit 5 also controls the air control valve 4d and the fuel control valve 4e for controlling the amount of air and fuel supplied to the engine 3 and the opening and closing of each valve in the fuel cell unit. . Further, the control unit 5 controls the operation of the motor / generator 6.

Next, basic control during operation of the fuel cell system by the control unit 5 will be described with reference to the flowchart of FIG.
First, information on the vehicle speed, the accelerator opening, and the SOC of the secondary battery is read into the control unit 5 (S31).

Next, electric power required for traveling is calculated from the vehicle speed and the accelerator opening (S32).
Next, the charging power to be generated by the SOFC 2 is calculated from the SOC of the secondary battery (S33).

Next, the amount of fuel and the amount of air to be supplied to the SOFC 2 are calculated according to the calculated charging power (S34).
Next, the opening degree of the fuel cell fuel control valve 4c is controlled according to the calculated fuel amount to be supplied (S35).

Next, a target engine speed is set according to the calculated air amount to be supplied (S36). Since the engine 3 also functions as a blower, the air supply amount is adjusted according to the engine speed.
Next, the engine 3 is controlled so that the engine 3 reaches the target rotational speed (S37). In controlling the engine, the opening degrees of the air control valve 4d and the fuel control valve 4e are adjusted.
In this way, appropriate electric power is generated by the SOFC 2 while the vehicle is traveling.

  Next, with reference to the flowchart of FIG. 4, the control for leading the exhaust gas when starting the fuel cell system in the first embodiment will be described. The destination of the exhaust gas is controlled by opening / closing the exhaust control valves 4a and 4b by the control unit 5.

First, when the ignition switch (IG SW) is turned on (in the case of “Yes” in S41), the control unit 5 reads the engine speed Ne, the secondary battery SOC, and the SOFC temperature Ts (S42).
Next, the control unit 5 sets the target engine speed and controls the engine (S43).

  Next, the control unit 5 controls the exhaust path so as to selectively guide the exhaust gas to the heat exchange mechanism of the SOFC 2 while the temperature Ts of the SOFC 2 rises to the complete warm-up temperature T1 (in the case of “Yes” in S44). The opening and closing of the control valves 4a and 4b is controlled (S45). Specifically, the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened.

  Here, as shown in the graph of FIG. 5, the complete warm-up temperature T1 is the operating temperature during the steady operation of the SOFC 2. FIG. 5 is a graph schematically showing a change over time in the temperature Ts of the SOFC 2 from when the fuel cell system is activated until steady operation is performed. As shown by the curve I in the graph of FIG. 5, the temperature Ts of the SOFC 2 at the time of startup rises from, for example, the same temperature T0 as the outside temperature of the electric vehicle, and becomes substantially constant at the operating temperature T1 during steady operation. The operating temperature T1 is, for example, 650 ° C.

  FIG. 6A schematically shows an exhaust gas path when the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened. In FIG. 6A, the path of the exhaust gas that is led from the engine 3 to the SOFC 2 and exhausted is indicated by a thick line 12. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4a to the reformer 1 as indicated by a two-dot chain line.

  6, 8, and 10, in order to facilitate understanding of the invention, the route through the reformer 1 is omitted, and the off-gas is sent directly to the engine 3 without going through the reformer 1. The exhaust gas path is illustrated as shown.

  By the way, while the SOFC 2 rises to the warm-up temperature T1, the exhaust passage valve 4a is closed, and no exhaust gas is led to the reformer 1. For this reason, immediately after startup, the temperature of the reformer 1 is low, and the fuel gas is not sufficiently reformed in the reformer 1. However, if the temperature of the SOFC 2 is increased to some extent, internal reforming is performed in the SOFC 2, so that the power generation reaction can be started with the SOFC. In addition, once the power generation reaction starts, the SOFC is warmed up autonomously because the power generation reaction is an exothermic reaction. Therefore, if the temperature Ts of the SOFC 2 immediately after startup is quickly raised to the complete warm-up temperature T1, an efficient power generation reaction can be started early in the SOFC 2.

  Then, after the temperature Ts of the SOFC 2 reaches the complete warm-up temperature T1 (in the case of “No” in S44), the controller 5 exhausts the exhaust gas so as to selectively guide the exhaust gas to the heat exchange mechanism of the reformer 1. The opening and closing of the path control valves 4a and 4b is controlled (S46). Specifically, the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed.

  FIG. 6B schematically shows an exhaust gas path when the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed. In FIG. 6B, the path of the exhaust gas that is led from the engine 3 to the reformer 1 and exhausted is indicated by a thick line 12. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4b to the SOFC 2 as indicated by a two-dot chain line.

  After the SOFC 2 is warmed up to the complete warm-up temperature T1, the temperature Ts of the SOFC 2 is independently maintained at the operating temperature. On the other hand, the reformer 1 is warmed up by selectively introducing the exhaust gas to the heat exchange mechanism of the reformer 1. When the temperature Tr of the reformer 1 rises and reforming of the fuel gas is started, the power generation reaction is performed more efficiently in SOFC 2 than in the case of internal reforming.

  Further, in the first embodiment, the exhaust path is selectively guided to the heat exchange mechanism of the SOFC 2 while the temperature Ts of the SOFC 2 rises to the half warm-up temperature T2 instead of the complete warm-up temperature T1. The opening and closing of the control valves 4a and 4b may be controlled. As shown in FIG. 5, the semi-warm-up temperature T2 is a temperature lower than the warm-up temperature T1 by a predetermined temperature ΔT. For example, when the complete warm-up temperature T1 is 650 ° C. and ΔT is 150 ° C., the semi-warm-up temperature T2 is 400 ° C.

  If the temperature Ts of the SOFC2 rises quickly to the semi-warm-up temperature T2, the SOFC2 can be warmed up to some extent by the power generation reaction by internal reforming. In addition, the warm-up of the reformer 1 by the exhaust gas can be started at an early stage when the temperature Ts of the SOFC 2 rises to the half warm-up temperature T2 before the temperature Ts rises to the full warm-up temperature T1. As a result, reforming of the fuel gas in the reformer is started early. Thereby, efficient power generation with SOFC2 can be started at an early stage.

Next, a second embodiment of the present invention will be described.
The basic configuration and basic control of the fuel cell unit according to the second embodiment are the same as those of the first embodiment. For this reason, in the second embodiment, with reference to the flowchart of FIG. 7, a description will be given of the control for leading the exhaust gas when starting the fuel cell system in the second embodiment. Also in the second embodiment, the destination of the exhaust gas is controlled by opening and closing the exhaust control valves 4a and 4b by the control unit 5.

First, when the ignition switch (IG SW) is turned on (in the case of “Yes” in S71), the control unit 5 sets the engine speed Ne, the secondary battery SOC, the SOFC temperature Ts, and the reformer temperature Tr. Read (S72).
Next, the control unit 5 sets the target engine speed and controls the engine (S73).

  Next, while the temperature Ts of the SOFC 2 rises to the semi-warm-up temperature T2 (in the case of “Yes” in S74), the control unit 5 causes the exhaust path to selectively guide the exhaust gas to the SOFC 2 heat exchange mechanism. The opening and closing of the control valves 4a and 4b is controlled (S75). Specifically, the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened.

  FIG. 8A schematically shows an exhaust gas path when the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened. In FIG. 8A, the path of exhaust gas that is led from the engine 3 to the SOFC 2 and exhausted is indicated by a thick line 12. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4a to the reformer 1 as indicated by a two-dot chain line.

  Thus, first, while the temperature of the SOFC 2 rises to the semi-warm-up temperature T2, the exhaust gas is selectively guided to the SOFC 2 and the SOFC 2 is preferentially warmed up. As a result, the power generation reaction utilizing the internal reforming in SOFC2 starts early.

Then, after the temperature Ts of the SOFC2 reaches the half warm-up temperature T2 (in the case of “No” in S74), the temperature Ts of the SOFC2 further rises to the complete warming temperature T1 (in the case of “No” in S76). The controller 5 controls the opening and closing of the exhaust path control valves 4a and 4b so as to guide the exhaust gas to both the heat exchanger of the SOFC 2 and the heat exchange mechanism of the reformer 1 (S77). Specifically, both the exhaust path control valves 4a and 4b are opened.
Note that the flow ratio of the exhaust gas led to the SOFC 2 and the reformer 1 is adjusted by the opening degree of the exhaust control valves 4a and 4b. This flow ratio can be any suitable value, for example 1: 1.

  FIG. 8B schematically shows an exhaust gas path when the exhaust path control valves 4a and 4b are opened. In FIG. 8B, the path of the exhaust gas that is led from the engine 3 to the SOFC 2 and the reformer 1 and exhausted is indicated by a thick line 12.

  As described above, in the second embodiment, after the temperature Ts of the SOFC 2 reaches the semi-warm temperature T2, the exhaust gas is guided to both the SOFC 2 and the reformer 1 while the temperature rises to the complete warm temperature T1. As a result, the temperature Ts of the SOFC 2 further rises, the reformer 1 is warmed up, and fuel gas reforming starts. As a result, the reformed fuel gas is supplied to the SOFC 2 and the power generation reaction efficiency of the SOFC 2 is improved.

  Then, after the temperature Ts of the SOFC 2 reaches the complete warm-up temperature T1 (in the case of “Yes” in S76), the controller 5 controls the exhaust path control valve 4a and the exhaust path control valve 4a so as to selectively guide the exhaust gas to the reformer 1. The opening / closing of 4b is controlled (S78). Specifically, the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed.

  FIG. 8C schematically shows an exhaust gas path when the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed. In FIG. 8C, a path of exhaust gas that is led from the engine 3 to the reformer 1 and exhausted is indicated by a thick line 12. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4b to the SOFC 2 indicated by a two-dot chain line.

  After the temperature Ts of the SOFC 2 reaches the complete warm-up temperature T1, the SOFC 2 independently maintains the operating temperature by the power generation reaction. Therefore, the reformer 1 is efficiently warmed up by introducing the exhaust gas to the reformer 1 for selection. Thus, in the second embodiment, the entire fuel cell system is warmed up early by controlling the destination of the exhaust gas in accordance with the temperature Ts of the SOFC 2.

Next, a third embodiment of the present invention will be described.
The basic configuration and basic control of the fuel cell unit according to the third embodiment are the same as those of the first embodiment described above. For this reason, in the third embodiment, with reference to the flowchart of FIG. 9, a description will be given of the control for leading the exhaust gas when starting the fuel cell system in the third embodiment. Also in the third embodiment, the destination of the exhaust gas is controlled by opening and closing the exhaust control valves 4 a and 4 b by the control unit 5.

First, when the ignition switch (IG SW) is turned on (in the case of “Yes” in S91), the control unit 5 sets the engine speed Ne, the secondary battery SOC, the SOFC temperature Ts, and the reformer temperature Tr. Read (S92).
Next, the control unit 5 sets the target engine speed and controls the engine (S93).

  Next, while the temperature Ts of the SOFC 2 rises to the semi-warm-up temperature T2 (in the case of “Yes” in S94), the control unit 5 causes the exhaust path to selectively guide the exhaust gas to the SOFC 2 heat exchange mechanism. The opening and closing of the control valves 4a and 4b is controlled (S95). Specifically, the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened.

  FIG. 10A schematically shows an exhaust gas path when the exhaust path control valve 4a is closed and the exhaust path control valve 4b is opened. In FIG. 10A, the path of the exhaust gas that is led from the engine 3 to the SOFC 2 and exhausted is indicated by a thick line 12. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4a to the reformer 1 as indicated by a two-dot chain line.

  Thus, first, while the temperature of the SOFC 2 rises to the semi-warm-up temperature T2, the exhaust gas is selectively guided to the SOFC 2 and the SOFC 2 is preferentially warmed up. As a result, the power generation reaction utilizing the internal reforming in SOFC2 starts early.

Then, after the temperature Ts of the SOFC 2 reaches the half warm-up temperature T2 (in the case of “No” in S94), the temperature Tr of the reformer 1 rises to the predetermined set temperature T3 (“Yes” in S96). ), The controller 5 controls the opening and closing of the exhaust path control valves 4a and 4b so as to selectively guide the exhaust gas to the heat exchange mechanism of the reformer 1 (S97). Specifically, the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed.
The predetermined set temperature T3 of the reformer may be, for example, the operating temperature of the reformer 1 when the reforming reaction of the fuel gas is performed in the reformer 1. Such an operating temperature is, for example, 600 ° C.

  FIG. 10B schematically shows an exhaust gas path when the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed. In FIG. 10B, a thick line 12 indicates the path of exhaust exhausted from the engine 3 to the reformer 1 and exhausted. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4b to the SOFC 2 indicated by a two-dot chain line.

  In this way, after the temperature Ts of the SOFC 2 reaches the semi-warm temperature T2, the exhaust gas is selectively guided to the reformer 1. As a result, the reformer 1 is efficiently warmed up and fuel gas reforming starts early. As a result, the reformed fuel gas is supplied to the SOFC, and the power generation reaction efficiency of the SOFC is improved.

Then, after the temperature T4 of the reformer 1 reaches the set temperature T3 (in the case of “No” in S96), the temperature Ts of the SOFC 2 does not reach the complete warm-up temperature T1 (in the case of “No” in S98). ), The controller 5 controls the opening and closing of the exhaust path control valves 4a and 4b so as to guide the exhaust gas to both the SOFC 2 and the reformer 1 (S99). Specifically, both the exhaust path control valves 4a and 4b are opened.
Note that the flow ratio of the exhaust gas led to the SOFC 2 and the reformer 1 is adjusted by the opening degree of the exhaust control valves 4a and 4b. This flow ratio can be any suitable value, for example 1: 1.

  FIG. 10C schematically shows an exhaust gas path when the exhaust path control valves 4a and 4b are opened. In FIG. 10C, the path of the exhaust gas that is led from the engine 3 to the SOFC 2 and the reformer 1 and exhausted is indicated by a thick line 12.

  Thus, in the third embodiment, after the temperature Tr of the reformer 1 has reached the predetermined set temperature T3, the exhaust gas is SOFC2 and the exhaust gas when the temperature Ts of the SOFC2 has not reached the complete warm-up temperature T1. Guided to both reformers 1. As a result, the warm-up of the SOFC 2 is promoted while the warm-up of the reformer 1 is continued.

  Further, when the temperature Ts of the SOFC 2 reaches the complete warm-up temperature T1 (in the case of “Yes” in S98), the controller 5 controls the exhaust path control valve so as to selectively guide the exhaust gas to the reformer 1 again. The opening / closing of 4a and 4b is controlled (S100). Specifically, the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed.

  FIG. 10D schematically shows an exhaust gas path when the exhaust path control valve 4a is opened and the exhaust path control valve 4b is closed. In FIG. 10 (D), a thick line 12 indicates the route of exhaust exhausted from the engine 3 to the reformer 1 and exhausted. Note that the exhaust gas is not guided to the path guided from the exhaust path control valve 4b to the SOFC 2 indicated by a two-dot chain line.

  Thus, in the third embodiment, the whole fuel cell system is warmed up early by controlling the destination of the exhaust gas in accordance with the temperatures of the SOFC 2 and the reformer 1.

  In each embodiment mentioned above, although the example which constituted the present invention on specific conditions was explained, the present invention can perform various change and combination, and is not limited to this. For example, in the above-described embodiment, the example in which the off gas is supplied to the internal combustion engine after passing through the heat exchange mechanism of the reformer 1 has been described, but in the present invention, the off gas is directly passed without passing through the reformer 1. You may make it supply to an internal combustion engine.

  In the above-described embodiment, the example in which the fuel cell unit of the present invention is a fuel cell unit for driving an electric vehicle has been described. However, the use of the fuel cell unit of the present invention is not limited to an electric vehicle.

  In the above-described embodiment, the example in which the gas discharged from both the fuel electrode and the air electrode of the SOFC is supplied to the internal combustion engine as an off-gas has been described. However, in the present invention, the gas discharged from the fuel electrode of the SOFC Only off-gas may be supplied to the internal combustion engine. In other words, in the present invention, the SOFC off-gas includes at least exhaust gas from the fuel electrode and may include exhaust gas from the air electrode.

  Moreover, although the above-mentioned embodiment demonstrated the example which uses LPG as a use fuel, in this invention, it is not limited to this, For example, you may use other fuels, such as ethanol.

  The fuel cell system of the present invention can be used, for example, as a power source mounted on an electric vehicle.

1 Reformer 2 SOFC
3 Engine 4a, 4b Exhaust path control valve 4c Fuel cell fuel control valve 4d Air control valve 4e Fuel control valve 5 Control unit 6 Motor / generator 21 Fuel electrode (anode)
22 Air electrode (cathode)
31 Intake port 32 Exhaust port 33 Cylinder 34 Piston rod

Claims (5)

A reformer that generates hydrogen gas by reforming a fuel gas containing a hydrocarbon compound;
A solid oxide fuel cell to which hydrogen gas generated by the reformer is supplied;
An internal combustion engine that sucks off-gas discharged from the solid oxide fuel cell as part of the fuel;
In order to use the exhaust gas discharged from the internal combustion engine for heating at least one of the reformer and the solid oxide fuel cell, the exhaust gas is used at least one of the reformer and the solid oxide fuel cell. An exhaust path control valve for controlling the destination of the exhaust gas so as to lead to
Control means for controlling the exhaust path control valve,
The control means controls the exhaust path control valve to allow the exhaust gas to flow into the solid oxide fuel while the temperature of the solid oxide fuel cell rises to a predetermined set temperature when starting the fuel cell system. A fuel cell system, wherein the exhaust gas is selectively led to a battery and the exhaust gas is led to the reformer after the temperature of the solid oxide fuel cell reaches the set temperature.   2. The fuel cell system according to claim 1, wherein the set temperature is a complete warm-up temperature that is an operating temperature during steady operation of the solid oxide fuel cell.   2. The fuel cell system according to claim 1, wherein the set temperature is a semi-warm temperature that is lower by a predetermined temperature than an operating temperature during steady operation of the solid oxide fuel cell.   The control means controls the exhaust path control valve to allow the exhaust gas to flow into the solid oxide fuel while the temperature of the solid oxide fuel cell rises to the semi-warm temperature when the fuel cell system is started. After the temperature of the solid oxide fuel cell reaches the semi-warm temperature, and further rises to the full warm temperature, the exhaust gas is led to the solid oxide fuel cell and the modified gas. The exhaust gas is selectively guided to the reformer after the temperature of the solid oxide fuel cell reaches the complete warm air temperature. The fuel cell system described.   The control means controls the exhaust path control valve to allow the exhaust gas to flow into the solid oxide fuel while the temperature of the solid oxide fuel cell rises to the semi-warm temperature when the fuel cell system is started. After selectively leading to a battery and the temperature of the solid oxide fuel cell reaches the judgment device temperature, the exhaust gas is passed through the reformer while the temperature of the reformer rises to a predetermined set temperature. And when the temperature of the solid oxide fuel cell has not reached the complete warm-up temperature after the reformer temperature has reached the set temperature, the exhaust gas is The fuel cell system according to claim 3, wherein the fuel cell system leads to both a solid oxide fuel cell and the reformer.

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